JPH06161177A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device preventing the attachment of both normal-charged and reverse-charged toner to an optical device such as a toner attachment quantity measuring instrument and an exposure optical system so as to make possible the formation of desirable images. CONSTITUTION:An image forming device is provided with a conductive transparent member 58 provided between a photosensitive body drum 1 and a laser optical system 13 for exposing the photosensitive body drum 1, and this conductive transparent member 58 is connected to a bias supply 56. The bias supply 56 applies voltage between charging voltage and developing bias voltage to the conductive transparent member 58 in reverse development and applies voltage between ground and developing bias voltage to the conductive transparent member 58 in normal development.

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 such as an electrophotographic printer or a copying machine.

[0002]

2. Description of the Related Art Image forming apparatuses such as printers and copying machines are equipped with a measuring device for measuring the amount of toner adhering to an image carrier in order to correct and control changes in image density due to environmental changes and changes over time. It is known that As a measuring device, the image carrier is irradiated with light from a light source,
It is known that the reflected light from the image carrier is received to measure the toner adhesion amount. In this type of measuring device, toner scattered from the image carrier may adhere to optical members such as a cover glass and a lens provided adjacent to the image carrier. There is a problem that it is impossible to perform accurate measurement.

Further, not only the above-mentioned toner adhesion amount measuring device, but also a device having a light emitting portion and a light receiving portion such as a laser optical system or a solid-state scanning head, the mirror disposed in the optical path thereof. -, Cover glass, optical members such as lenses,
The scattered toner adheres, causing a change in exposure amount and scattering of emitted light. In this case, these devices cannot fully exhibit their functions, making accurate image formation difficult.

Therefore, the inventor of the present invention has filed Japanese Patent Application No. 3-282.
601 (US Patent Application No. 935,276), a conductive transparent member that transmits light is provided on a light projecting / receiving surface facing the image carrier, and a bias voltage having the same polarity as that of the toner is applied to the conductive transparent member. We propose a structure that prevents the adhesion of scattered toner.

[0005]

However, if a high bias voltage is applied to the conductive transparent member when the bias voltage is applied to the conductive transparent member, the adhesion of the normally charged toner does not occur, but the oppositely charged toner is applied. Adheres to the conductive transparent member. Therefore, in this case, the measuring device is an accurate toner.
The amount of adhesion cannot be detected, resulting in deterioration of measurement accuracy.

Similarly, in an optical device such as a laser optical system or a solid-state scanning head, a reversely-charged toner is conductively transparent only by providing a conductive transparent member in the optical path and applying a bias voltage thereto. It adheres to the member and changes in the amount of light or scattering of light occurs.

The present invention has been made in view of the above points, and an object thereof is to provide both polarities of a toner that is normally charged and an oppositely charged toner to an optical means such as a toner adhesion amount measuring device and an exposure optical system. Another object of the present invention is to provide an image forming apparatus capable of preventing the toner from adhering to the image forming apparatus and capable of forming an excellent image.

[0008]

In order to achieve the above object, an image forming apparatus according to the present invention has a conductive transparent member between an optical unit that functions by irradiating an image bearing member with light and the image bearing member. In reverse development, a voltage between the charging voltage and the developing bias voltage is applied to the conductive transparent member, and in regular developing, a voltage between the ground and the developing bias voltage is applied to the conductive transparent member. There is provided a voltage supply means for operating.

According to the image forming apparatus of the present invention,
In the reversal development, the conductive transparent member is electrically connected to a power supply for charging voltage or a power supply for developing bias,
In regular development, the conductive transparent member is electrically connected to the ground or a power source for developing bias.

[0010]

In the reversal development, a voltage between the charging voltage and the developing bias voltage is applied to the conductive transparent member to generate an electric field between the image carrier and the conductive transparent member. It prevents the scattered developer from adhering to the conductive transparent member. In regular development, an electric field is generated between the image carrier and the conductive transparent member by applying a voltage between the ground and the developing bias voltage to the conductive transparent member. It prevents the scattered developer from adhering to the transparent member. As a result, both the normally charged developer and the oppositely charged developer are prevented from adhering to the optical means, and good image formation is possible.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment in which the image forming apparatus according to the present invention is applied to a color laser printer. A photoconductor drum 1 as an image carrier that rotates in a counterclockwise direction (direction of arrow A shown in FIG. 1) is provided in a substantially central portion of a main body 100 of the color laser printer. Around the photosensitive drum 1, a charger 2 as a charging unit, a first developing unit 4, a second developing unit 5, a third developing unit 6, a fourth developing unit 7, and a photosensitive unit, which are developing units, are provided. A toner adhesion amount measuring device 8 as a reflected light amount measuring means for measuring the adhesion amount of toner on the body drum 1, a transfer drum 9, a pre-cleaning static eliminator 10, a cleaner 11, and a static elimination lamp 12 are sequentially arranged. Has been done.

The photosensitive drum 1 rotates in the direction of arrow A in the figure, and the surface of the photosensitive drum 1 is uniformly charged by the charger 2. Charger 2
The laser beam light 14 emitted from the laser optical system 13 which is the exposure means is applied to the surface of the photoconductor drum 1 between the first developing device 4 and the first developing device 4, and electrostatic charges corresponding to the image data are generated. A latent image is formed on the photosensitive drum 1.

The first to fourth developing devices 4 to 7 visualize the electrostatic latent image on the photoconductor drum 1 corresponding to each color into a color toner image, for example, the first developing device. 4, magenta, the second developing device 5 is cyan, the third developing device 6 is yellow,
The fourth developing device 7 is designed to develop black.

On the other hand, a transfer sheet as a transfer material is sent out from a paper feed cassette 15 by a paper feed roller 16, once aligned by a registration roller 17, and then sent to a predetermined position on a transfer drum 9. . Then, the transfer paper is a suction roller 18
And the electrostatic charger 19 electrostatically attracts the outer peripheral surface of the transfer drum 9. The transfer sheet is attracted to the transfer drum 9 while the transfer sheet is in the clockwise direction (arrow B shown in FIG. 1).
(Direction) and is conveyed.

The developed toner image on the photosensitive drum 1 is transferred onto a transfer sheet by the transfer charger 20 at a position where the photosensitive drum 1 and the transfer drum 9 face each other. In the case of printing a plurality of colors, the step of making one rotation of the transfer drum 9 for one cycle is performed a plurality of times by switching the developing device, and the toner images of a plurality of colors are multiply transferred onto the transfer paper.

The transfer sheet on which the toner image has been transferred is further conveyed as the transfer drum 9 rotates, and the internal static eliminator 21,
After being discharged by the external static eliminator 22 and the separate static eliminator 23,
The separation claw 24 separates the transfer drum 9. The peeled transfer sheet is fixed to the fixing device 2 by the conveyor belts 25 and 26.
It is transported to 7. The toner on the transfer sheet heated by the fixing device 27 is melted and fixed on the transfer sheet immediately after being discharged from the fixing device 27, and the transfer sheet after the fixing is discharged to the tray 28.

FIG. 2 is a block diagram of a charging device, an exposure device, a developing device and a control circuit for the color laser printer having the above structure. The configuration and operation of the color laser printer will be described in more detail with reference to FIG.

The photosensitive drum 1 is rotated counterclockwise. As the charger 2, a non-contact type charger having a charging wire 31, a conductive case 32, and a grid electrode 33 is mainly used. The charging wire 31 is connected to a high voltage power supply 34 for corona, and charges the surface of the photoconductor drum 1 by corona discharge. Grid electrode 33
Is connected to a high voltage power supply 35 for grid bias, and the amount of charge on the surface of the photosensitive drum 1 is determined by the grid bias voltage. In addition, the high voltage power supplies 34, 3
5 is connected to the control circuit 45, and the control circuit 45
The output voltage is controlled by.

The surface of the photosensitive drum 1 uniformly charged by the charger 2 is exposed to the modulated laser beam light 14 from the laser optical system 13 to form an electrostatic latent image on the drum surface. To be done. The gradation data buffer 36 stores gradation data from an external device (not shown) or a controller,
The tone characteristics of the printer are corrected and converted into laser exposure time (pulse width) data. The laser drive circuit 37 is controlled by the control circuit 45 so as to synchronize with the scanning position of the laser beam light 14 in accordance with the laser exposure time data from the gradation data buffer 36. -The drive current (light emission time) is modulated. Then, by the modulated laser drive current,
A semiconductor laser oscillator (not shown) in the laser optical system 13 is driven. As a result, the semiconductor laser oscillator
It emits light according to the exposure time data.

Further, the laser drive circuit 37 compares the output of a monitor light receiving element (not shown) in the laser optical system 13 with a set value, and sets the output light quantity of the semiconductor laser oscillator by the drive current. Control to keep the value.

On the other hand, the pattern generation circuit 38 generates the test pattern of the printer alone and the gradation data of the pattern for measuring the toner adhesion amount under the control of the control circuit 45, and the laser. It is designed to be sent to the drive circuit 37.

Here, the laser exposure time data from the gradation data buffer 36 and the pattern gradation data for measuring the toner adhesion amount from the pattern generation circuit 38 are used. Is switched by the control circuit 45, and the data selected by the control circuit 45 is sent to the laser drive circuit 37.

The photosensitive drum 1 on which the electrostatic latent image is formed is
It is developed by a developing device. In the color laser printer of this embodiment, as described above, the four developing devices 4, 5,
Although there are 6 and 7, the case of the first developing device 4 will be described here. The developing roller 43 of the first developing device 4
Is formed of a conductive member, is connected to a high voltage power source 44 for developing bias, and rotates in a state where a developing bias voltage is applied. Thereby, the developing roller 43
Attaches a toner to the image corresponding to the electrostatic latent image on the photosensitive drum 1. The toner image in the image area thus developed is transferred to the transfer sheet supported and conveyed by the transfer drum 9. The transfer charger 20 is connected to a high-voltage power supply 21, and applies a voltage having a reverse bias to the grid bias voltage and the developing bias voltage to transfer the toner image onto the transfer sheet. The high voltage power supplies 44 and 21 are controlled by the control circuit 45.
The developing bias voltage and the transfer bias voltage are controlled by the control circuit 45.

The control circuit 45 outputs data supplied from the gradation data buffer 36 to the laser drive circuit 37 in synchronization with the non-image area on the photosensitive drum 1 reaching the exposure position. The laser exposure time data is switched to the gradation data from the pattern generating circuit 38. Thereby, the photosensitive drum 1
A gradation pattern for measuring the toner adhesion amount is exposed in the upper non-image area, and a gradation pattern for measurement is formed on the photosensitive drum 1 by developing the exposed portion. When the gradation pattern comes to a position facing the toner adhesion amount measuring device 8,
The toner adhesion amount measuring device 8 measures the toner adhesion amount on the photosensitive drum 1. The configuration of the toner adhesion amount measuring device 8 will be described in detail later.

Output of the toner adhesion amount measuring device 8 (measured value)
Is digitized by the A / D converter 46 and is converted into the control circuit 45.
Entered in. The control circuit 45 uses the toner adhesion amount measuring device 8
Of the toner adhesion amount and the reference value of the toner adhesion amount which is preset and stored in the memory 49 are compared, and according to the comparison result, the grid bias voltage of the charger 2 and the developing device 4 which are image forming conditions. Development bias voltage, laser optical system 13
Processing for converting at least one of the exposure amount, the toner concentration of the developer, the emission time of the area gradation, and the like.

Further, the control circuit 45 is a pattern for tone data from an external device or a controller (not shown), a test pattern for the printer alone, and a pattern for a toner adhesion meter.
Tone gradation data switching control, taking in the output of the toner adhesion amount measuring device 8, controlling the output amount of the high voltage power supplies 21, 34, 35, 44, setting the target value of the laser drive current, and setting the toner density. Various controls such as target value setting, toner replenishment control, correction processing of the gradation characteristics of the gradation data of the printer are also performed. further,
The control circuit 45 has a memory 49 whose contents can be rewritten.
Are connected, and the memory 49 stores the above-mentioned reference value of the toner adhesion amount and the like.

Next, the construction and operation of the toner adhesion amount measuring device 8 will be described with reference to FIGS. 3 and 4. The toner adhesion amount measuring device 8 is provided between the developing device 4 and the transfer charging device 20 so as to face the photoconductor drum 1. The measuring instrument 8 has a box-shaped main body 83 made of an insulating material, and a pair of support sleeves 50 made of an insulating material in the main body 83.
51 is fixed. The main body 83 has a bottom wall 83a facing the photoconductor drum 1 at a predetermined interval, and a pair of through holes are formed in the bottom wall 83a. Sleeves 50, 51
In each of the above, the upper end is closed and the lower end is fitted into the through hole and opens toward the photosensitive drum 1. A light source 81 such as an LED is arranged in the sleeve 50, and the light source 81 is a driving circuit 9
Connected to 1. Further, a photoelectric conversion unit 82 is arranged in the sleeve 51, and the photoelectric conversion unit 82 is provided in the transmission circuit 9
Connected to 2. And the sleeves 50 and 51 are
The light emitted from the light source 81 is arranged at an appropriate angle so that the light enters the surface of the photosensitive drum 1 through the through hole, is reflected by the surface of the photosensitive drum 1, and then enters the photoelectric conversion unit 82 through the through hole. There is.

A plate-shaped conductive transparent member 54 having the same size as the bottom wall is fixed to the lower surface of the bottom wall 83a of the main body 83 to close the through hole formed in the bottom wall. The conductive transparent member 54 is connected to the bias power supply 56. Then, as described later, when a predetermined voltage is applied to the conductive transparent member 54 from the bias supply power source 56, an electric field is generated between the conductive transparent member and the surface of the photosensitive drum 1. When the toner scattered from the photoconductor drum 1 or the like enters the electric field, the toner receives a force toward the outside of the electric field. Therefore, the scattered toner is prevented from adhering to the conductive transparent member 54, the light source 81 of the toner adhesion amount measuring device 8 and the photoelectric conversion section 82. Here, the light source 81 and the photoelectric conversion unit 82
Is supported by the insulative main body 83 and the support sleeves 50 and 51, and is not affected by the high voltage applied to the conductive transparent member 54.

The light emitted from the light source 81 passes through the optical path 86 and is applied to the surface of the photosensitive drum 1 to
The surface itself or the surface of the photosensitive drum is reflected by the toner developed and attached. The reflected light reaches the photoelectric conversion unit 82 through the optical path 86, is converted into a current according to the light amount of the reflected light by the photoelectric conversion unit 82, and is further converted into current / voltage. The reflected light from the photosensitive drum 1 converted into the voltage value is A / D by the transmission circuit 92.
The signal is transmitted to the converter 46, where it is converted into a digital signal and taken into the control circuit 45. In addition, the light source drive circuit 91 that drives the light source 81 is a control circuit 4.
On / off control is performed by 5 or by a signal for adjusting the amount of drive current to the light source 81.

As shown in FIG. 2, the laser optical system 1
A conductive transparent member 58 is provided at the exit of the optical path of 3, and is adjacently opposed to the photosensitive drum 1. The conductive transparent member 58 is connected to the bias supply power source 56, and like the conductive transparent member 54 described above, the bias supply power source 56.
Is applied with a predetermined voltage. By applying a voltage, an electric field is formed between the conductive transparent member 58 and the surface of the photosensitive drum 1, and this electric field prevents the scattered toner from adhering to the conductive transparent member 58. Therefore, toner is prevented from adhering to optical members such as mirrors and lenses arranged in the optical path of the laser optical system 13.

Next, the developing process in the color laser printer configured as described above will be described. Normal,
The surface potential of the photosensitive drum 1 charged by the charger 2 is the potential VO at the unexposed portion and changes to the potential VL at the exposed portion exposed by the laser optical system 13. Developing device 4
Of the developing bias voltage VD applied to the developing roller 43 of
It is set to have a size between O and VL.

FIG. 5 shows the potential relationship between the photosensitive drum 1 and the toner when reversal development is performed. In reverse development, the toner is negatively charged with the developing bias voltage VD as a reference. Therefore, the toner is VD like VL
There is a tendency to move to a site having a potential on the positive side of Vd and not to a site having a potential on the negative side of Vd such as Vo. Therefore, in the developing device 4, the toner adheres to the exposed portion of the surface of the photosensitive drum 1 where the surface potential is between the developing bias voltage VD and the potential VL of the exposing portion due to the exposure, and the toner is developed.

On the other hand, FIG. 6 shows the potential relationship between the photosensitive drum and the toner when the normal development is performed. In normal development, the toner is positively charged with the developing bias voltage VD as a reference. Therefore, the toner is V
It tends to move to a portion having a potential on the negative side of D, and does not tend to move to a portion having a potential on the positive side of VD such as VL. Therefore, in the developing device 4, the photosensitive drum 1
Of the surface, the surface potential is the developing bias voltage VD due to exposure.
Toner is adhered to a portion between the unexposed portion and the potential V0 of the unexposed portion to be developed. Next, the surface potential of the photosensitive drum 1 and the conductive transparent member 5 in the reversal development and the regular development.
The relationship with the voltage VCG applied to Nos. 4 and 58 will be described.

As shown in FIG. 7, in the reversal development, the difference (VO-V) between the potential VO of the unexposed portion and the development bias voltage VD.
D) is the background potential VBG, and the difference (VD-VL) between the developing bias voltage VD and the exposed portion potential VL is the contrast potential VC.

In the reversal development, the development bias voltage VD
Is in the range of VO ≧ VD ≧ VL, and the toner is negatively charged.
Tends to adhere to the potential on the VC side. Therefore,
By setting the voltage VCG applied to the conductive transparent members 54 and 58 within the range of VBG (VO to VD), it becomes possible to prevent toner from adhering to the conductive transparent members. Normally, when developing an electrostatic latent image on the photosensitive drum 1, in reverse development, each bias value has a negative charge that is normally charged in a portion having a potential between the developing bias voltage and the unexposed portion potential. It is set so that neither the toner nor the reverse charging toner adheres. This is because if toner adheres to the above-mentioned portion, fog occurs in printed matter or copied matter. From this, it is understood that the scattered toner also does not adhere to the toner to which the bias voltage between the developing bias voltage and the unexposed portion potential is applied. Therefore, in the reversal development, by setting the applied voltage VCG within the range of VO ≧ VCG ≧ VD, it is possible to prevent all the scattered toners from adhering to the conductive transparent members 54 and 58.

Further, as shown in FIG. 8, in the normal development, the potential relationship on the photosensitive drum surface 1 is the same as in the case of the reversal development, but the relationship between the contrast potential and the background potential becomes opposite, and VO − VD is the contrast potential VC, VD-
VL becomes the background potential VBG. The developing bias voltage VD is also in the range of VO ≥VD ≥VL.

However, in the case of normal development, the positively charged toner tends to adhere to the potential on the VC side, and it is possible to prevent the toner from adhering to the portion to which the potential on the VBG side is applied. is there.

Normally, when developing the electrostatic latent image on the photosensitive drum 1, in the normal development, a portion having a potential between the developing bias voltage and the exposed portion potential or the ground (0 V) is normally charged. Each bias value is set so that neither the positive charging toner nor the reverse charging toner adheres. this is,
This is because when toner adheres to the above-mentioned portion, fog occurs in a printed matter or a copied matter. From this, scattered toner
Similarly, it can be seen that there is no adhesion to those to which a bias voltage between the developing bias voltage and the exposed portion potential or the ground (0 V) is applied. Therefore, in the normal development, by setting the applied voltage VCG in the range of VD ≧ VCG ≧ 0V, it is possible to prevent all the scattered toners from adhering to the conductive transparent members 54 and 58.

As described above, with respect to the rotation direction of the photosensitive drum 1, the component arranged between the upstream side of the charging device 2 and the downstream side of the transfer charging device 20, that is, the optical system 13.
By providing conductive transparent members 58 and 54 facing the toner adhesion amount measuring device 8 and the toner adhesion amount measuring device 8, respectively, the optical system 13
Further, it is possible to effectively prevent the toner from adhering to the measuring device 8. That is, for example, when measuring the toner adhesion amount in reversal development, the photosensitive drum 1 negatively charged with the voltage V0.
The optical system 13 exposes the gradation pattern for detecting the toner adhesion amount on the surface at the potential VL, and the development bias voltage VD
And is developed with a negatively charged toner. Then, the area on the drum 1 to which the developed gradation pattern is attached is re-exposed by the measuring instrument 8 for measuring the toner attachment amount, and the potential VLS of this area is exposed by the optical system 13. Is closer to the ground than the potential VL. Therefore, the negatively charged toner on the drum 1 has the potential VLS.
It is easy to move to the area of, and is easily scattered to the outside of the drum when moving. Therefore, by providing the conductive transparent member 54 on the toner adhesion amount measuring device 8, it is possible to effectively prevent such scattered toner from adhering to the measuring device.

On the other hand, the toner remaining on the photosensitive drum 1 without being cleaned is negatively charged by the charger 2 and has a negative polarity. Therefore, when such negatively charged residual toner moves to a position where the optical system 13 opposes in accordance with the rotation of the photoconductor drum 1, the optical system is in an electrically floating state or the potential of the drum surface is high. If it has a lower potential, the residual toner is scattered from the drum and adheres to the optical system. Therefore, as described above, when the conductive transparent member 58 is provided between the photoconductor drum 1 and the optical system 13, the adhesion of toner to the optical system can be prevented, which is very effective.

An optical device such as the toner adhesion amount measuring device 8 is provided between the upstream side of the transfer charging device 20 and the downstream side of the charging device 2, and a conductive material is provided between the optical device and the photosensitive drum 1. It may be possible to provide a transparent member, but in this case, it is difficult to effectively prevent the toner from adhering. That is, when the toner image on the photosensitive drum 1 is transferred onto the transfer sheet at the transfer position, the transfer sheet and the toner have the potentials VO and V.
A reverse bias voltage is applied to L and VD. for that reason,
The toner remaining on the drum 1 is a mixture of positively charged toner and negatively charged toner, and the polarity of the toner becomes unstable. Therefore, even when the above-mentioned predetermined bias voltage is applied to the conductive transparent member, the residual toner scattered from the photosensitive drum 1 may adhere to the conductive transparent member. From the above, with respect to the rotation direction of the photoconductor drum 1, the conductive transparent member is provided so as to face the components arranged between the upstream side of the charger 2 and the downstream side of the transfer charger 20. It can be seen that the adhesion of toner can be effectively prevented when a predetermined bias voltage is applied to this conductive transparent member.

On the other hand, as described above, the toner remains on the surface of the photosensitive drum 1 without being cleaned and remains attached to the drum surface. Therefore, the conductive transparent member 54,
When a bias is applied to 58 at the same time as a bias is applied to the charger 2, the residual toner of the drum house may adhere to the conductive transparent member. Therefore, as shown in FIG. 9, the conductive transparent members 54, 5 are connected from the bias power supply 56.
It is necessary to control the timing of applying a predetermined bias voltage to each of 8 in accordance with the image forming process. That is, when the front end of the charging area on the photosensitive drum 1 negatively charged by the charger 2 reaches the exposure position, the conductive transparent member 5
The bias application to the conductive transparent member 54 needs to be started when the front end of the charging area reaches the measurement position of the toner adhesion amount measuring device 8. Further, when the end of the charged area on the drum 1 reaches the exposure position, application of the bias to the conductive transparent member 58 is stopped, and when the end of the charged area reaches the measurement position, the conductive transparent member 54 is transferred. It is necessary to stop the bias application.

Therefore, according to the present embodiment, as shown in FIG. 10, the conductive transparent members 54 and 58 are connected to the bias supply power source 56 via the switches 70 and 72 as timing adjusting means, respectively. . These switches 70 and 72 are connected to the control circuit 45, and are switched by the control circuit according to the image forming process, that is, according to the position of the charging area on the photosensitive drum 1.

According to the color laser printer configured as described above, the conductive transparent member 54 provided between the light source 81 and the photoelectric conversion unit 82 of the toner adhesion amount measuring device 8 and the photosensitive drum 1, and By applying a predetermined voltage to the conductive transparent member 58 provided facing the photoconductor drum in the optical path of the laser optical system 13 at the same time in the image forming process, the conductive transparent members 54 and 58 are supplied. Prevents the adhesion of scattered toner. In particular, the voltage VCG applied to the conductive transparent members 54 and 58 is set in the range of VO ≧ VCG ≧ VD in the reversal development and in the range of VD ≧ VCG ≧ 0V in the normal development. In both cases of reversal development and regular development, it is possible to reliably prevent the positively charged, negatively charged, and oppositely charged scattered toner from adhering to the conductive transparent members 54 and 58.

Therefore, in the toner adhesion amount measuring device 8, it is possible to prevent the scattered toner from adhering to the light source 81 and the photoelectric conversion portion 82, and it is possible to maintain high detection accuracy for a long period of time. Further, in the laser optical system 13, scattered toner can be prevented from adhering to optical members such as glass, lenses, mirrors, etc. arranged in the optical path for guiding the laser light to the photosensitive drum 1, and the laser optical system 13 can be accurately operated. Image data can be guided to the photosensitive drum 1. Therefore, according to the present color laser printer, a high-quality image can be stably formed over a long period of time. Further, it is possible to save labor or reduce maintenance of the measuring instrument 8 and the laser optical system 13, and it is possible to reduce the overall running cost.

In the above embodiment, the bias is applied to the conductive transparent members 54 and 58 by using the single bias supply power source 56. However, as shown in FIG. 11, the transparent members 54 and 58 are used. It is also possible to use two bias supply power sources 56a and 56b which are separately provided for this purpose. In this case, the control circuit 45 directly controls the bias power supply 5
By controlling the operation timing of 6a and 56b,
Conductive transparent member 5 in time with the image forming process
It is configured to apply a bias voltage to 4, 58.

In the above embodiment, the conductive transparent member 5 is provided by the bias supply power source 56 provided independently.
Although a predetermined voltage is applied to 4, 58, the means for applying such a voltage may be configured as follows.

As described above, in the reversal development, the applied voltage VCG to the conductive transparent members 54 and 58 is VO ≧ VCG ≧ VD.
In this case, it is possible to prevent the toner from scattering.

Therefore, as shown in FIG. 12, a high voltage power source 44 for developing bias for supplying a bias voltage to the developing roller 43 is electrically connected to the conductive transparent members 54 and 58 via the switches 70 and 72. However, the developing bias voltage VD may be applied to these conductive transparent members. Since it is necessary to continuously apply the bias voltage to the conductive transparent members 54 and 58 even after the application of the bias voltage to the developing roller 43 is stopped, a control circuit is provided between the developing roller and the high voltage power source 44. A switch 73 whose opening and closing is controlled by 45 is provided.

In this case, as shown in FIG. 13, a resistor R1 is interposed between the high voltage power source 44 and the conductive transparent members 54 and 58 to connect the high voltage power source 44 to the conductive transparent member. It is possible to avoid a risk such as a leak that occurs.

As shown in FIG. 14, the high voltage power source 35 for supplying the grid bias voltage to the grid electrode 33 and the electrically conductive transparent members 54, 58 are electrically connected to each other through the switches 70, 72. A voltage may be applied from 35 to the conductive transparent members 54 and 58.

In this case, as shown in FIG. 15, a resistor R2 is interposed between the high voltage power source 35 and the conductive transparent members 54 and 58 to connect the high voltage power source 35 to the conductive transparent member. It is possible to avoid a risk such as a leak that occurs.

Further, as shown in FIG. 16, the voltage from the high voltage power source 35 is changed to a resistance R3 having a high resistance value so that the range of the voltage applied to the conductive transparent member 51 is VO ≧ VCG ≧ VD. , R4, and the conductive transparent member 5
You may make it apply to each of 4 and 58.

On the other hand, as described above, in the regular development, the applied voltage VCG to the conductive transparent members 54 and 58 is VD.
If ≧ VCG ≧ 0V is set, it is possible to prevent the scattering of toner particles.

Therefore, as shown in FIGS. 12 and 13, as in the case of the reversal development, the conductive transparent members 54 and 58 are connected to the high voltage power source 44 for the developing bias directly or through a resistor, and this high voltage power source is connected. 44 to conductive transparent members 54, 5
Alternatively, a voltage may be applied to 8.

In this case, as shown in FIG. 17, the range of the voltage applied to the conductive transparent members 54 and 38 is VD ≧ VCG ≧
The voltage from the high-voltage power supply 44 may be divided by the resistors R6 and R7 having a high resistance value so as to be 0 V, and the divided voltages may be applied to the conductive transparent members 54 and 58, respectively.

In the case of regular development, the conductive transparent member 5
Since the voltage applied to 4, 58 is within a predetermined range even if it is 0 V, the conductive transparent members 54, 58 may be electrically connected to the ground as shown in FIG.

In the above embodiment, as the charger 2,
Although a non-contact type charger having a grid electrode is used, a contact type charger 2 having a charging roller, a charging brush, a charging blade or the like that contacts the photosensitive drum 1 may be used. 19 and 20 show examples in which a charging roller is used as the charger 2 and conductive transparent members 54 and 55 are connected to a high-voltage power supply 35 that supplies a bias voltage to the charging roller. Further, in the embodiment shown in FIG. 19, as the high voltage power source 35, a high voltage power source in which an AC power source 35a and a DC power source 35b are combined is used. Figure 2
In the embodiment shown in FIG. 0, only the DC power supply is used as the high voltage power supply 35.

On the other hand, the charging characteristics of the high-voltage power supply in which the AC power supply 35a and the DC power supply 35b are combined and the high-voltage power supply including only the DC power supply are different as shown in FIG.
That is, in the case of using the high-voltage power supply 35 in which the AC power supply 35a and the DC power supply 35b are combined, if the AC component (amplitude) is increased to some extent, as shown by the characteristic line A in FIG.
The photosensitive drum 1 is charged with a charging potential V0 equivalent to the DC component. Therefore, as shown in FIG. 19, by connecting these so that a voltage is applied from the DC power source 35b of the high-voltage power source 35 to the conductive transparent members 54, 58, the conductive transparent members 54, 58 are charged with a charging potential. Equal bias voltages can be applied.

Further, the high voltage power supply 35 consisting of only DC power supply
In the case of using, the applied voltage VDC and the charging potential V0 are different as shown by the characteristic line B in FIG. The difference between the applied potential VDC and the charging potential V0 is almost constant with respect to the applied voltage. Therefore, the high voltage power source 35 is directly connected to the conductive transparent member 54,
When connected to 58, a voltage higher than the charging potential V0 is applied to the transparent member, causing problems such as toner adhesion. Therefore, as shown in FIG. 20, resistors R3 and R4 having a high resistance value are provided between the high voltage power source 35 and each of the conductive transparent members 54 and 58, and the supply voltage VDC from the high voltage power source is set to the charging potential V0. And the developing bias voltage VL.

12 to 17 and FIG. 1 described above.
According to the configurations shown in FIG. 9 and FIG. 20, respectively, a high voltage power source 44 for developing bias and a high voltage power source 35 for supplying charging voltage are provided.
It is possible to apply a predetermined voltage to the conductive transparent members 54 and 58 by using the above-mentioned embodiment, and the above-mentioned embodiment without providing a dedicated power supply for applying a voltage to these conductive transparent members 54 and 58. The same effect can be obtained.
Therefore, the structure can be simplified and the manufacturing cost can be reduced.

Further, the high voltage power source 44 or the high voltage power source 35
When a predetermined voltage is applied to the conductive transparent members 54 and 58 by using, the following operational effects can be obtained in addition to the operational effects of the above-described embodiment.

That is, generally, the developing characteristics, for example, the density (toner adhesion amount) of the toner image formed on the photosensitive drum 1 changes with environmental changes or changes over time.
Therefore, normally, the toner adhesion amount measuring device 8 detects the toner adhesion amount on the surface of the photoconductor drum 1, and the control circuit 45 follows the detection values to determine the grid bias voltage, the developing bias voltage, the exposure amount of the laser optical system 13, and the developing amount. At least one of the light emission time of the toner density area gradation of the agent is changed to cope with the change in the developing characteristics. In particular, in this embodiment,
The toner adhering amount measuring device 8 detects a change in the developing characteristic and changes the bias conditions of the grid bias voltage and the developing bias voltage.

That is, the laser optical system 13 is driven based on the test pattern output from the pattern generating circuit 38 to the laser driving circuit 37, and the laser beam light 14 emitted from the laser optical system 13 causes the surface of the photosensitive drum 1 to be exposed. A latent image pattern is formed. This latent image pattern is developed by the developing device 4.
To develop a test pattern visualized as a toner image. Then, the toner adhesion amount of the formed test pattern is detected by the toner adhesion amount measuring device 8,
Based on the detection result, the control circuit 45 controls the output voltages of the high-voltage power supplies 44 and 45 to supply the developing bias voltage to the developing device 4 and the grid electrode 33 to control the charging characteristics of the charger 2. The optimum image condition is set by varying the bias voltage.

Here, conductive transparent provided on the surface of the toner adhesion amount measuring device 8 facing the photosensitive drum 1 and the optical path of the laser beam light 14 output from the laser optical system 13 to the photosensitive drum 1, respectively. The members 54 and 58 are connected to a high voltage power source 44 for developing bias via a resistor R1 or to a high voltage power source 35 for charging via a resistor R2.

Therefore, when the developing bias voltage or the grid bias voltage (charging voltage) is changed by the above-mentioned control, the conductive transparent member 5 follows the changed voltage value.
Bias values of 4, 58 change equally.

22 and 23 show changes in the bias voltage due to control under different environments. 22 shows control under a low temperature and low humidity environment (10 ° C., 20% RH), and FIG. 23 shows control under a high temperature and high humidity environment (35 ° C., 90% RH).

Under a low temperature and low humidity environment, both the grid bias voltage (charging voltage) and the developing bias voltage are increased, and under a high temperature and high humidity environment, both the grid bias voltage (charging voltage) and the developing bias voltage are decreased. There is. In this control, the interval between the grid bias voltage (charging voltage) and the developing bias voltage is also variable.

In the case of reversal development, toner or carriers are less likely to adhere to the member to which a voltage between the grid bias voltage (charging voltage) and the development bias voltage is applied in the case of two-component development.

When the voltage applied to the conductive transparent member is fixed, the applied voltage may deviate from the range in which toner or carriers are hard to adhere due to changes in the grid bias voltage (charging voltage) and the developing bias voltage. Occurs.
When the applied voltage becomes lower than the developing bias voltage, the toner easily adheres. Further, when the applied voltage becomes higher than the grid bias voltage (charging voltage), the reversely charged toner or carrier easily adheres.

As described above, the electrically conductive transparent member is electrically connected to the power source for charging or the power source for developing bias, so that the conductive material is electrically conductive according to the change of the developing bias voltage or the grid bias voltage (charging voltage). The voltage applied to the transparent member is also changed automatically. Therefore, it is possible to prevent the toner from adhering to the conductive transparent member or the carrier in the case of a two-component developer. Therefore, it is not necessary to provide a special applied voltage control device, and the configuration can be simplified and the manufacturing cost can be reduced.

In the above-described embodiment, the switch 7 is used as an adjusting means for adjusting the start and stop of voltage application to the conductive transparent members 54 and 58 at the timing of the image forming process.
Although 0, 72, and 73 are used, a voltage control unit having a delay circuit may be used as the adjusting unit. For example, in FIG.
According to the configuration shown in FIG. 3, the conductive transparent member 54 is connected to the high voltage power source 35 for charging via the first voltage control unit 76, and the conductive transparent member 58 is connected via the second voltage control unit 78. And is connected to a high voltage power supply 35 for charging. As shown in FIG. 25, the first voltage control circuit 76 includes resistors Ri and Rj and diodes Di and Dj connected in parallel with each other.
And these diodes are connected to ground via a capacitor C. As a result, the voltage control circuit 76 of the stand 1 constitutes a delay circuit having a predetermined time constant, and the voltage V applied to the conductive transparent member 54 is kept at the predetermined time t2 after the high voltage power supply 35 is turned on. The supply voltage V0 from the high voltage power source 35 is controlled so that the voltage VD equal to the developing bias voltage rises after ON, and the voltage V applied to the conductive transparent member 54 is changed to the high voltage power source 35.
After the predetermined time t2OFF has passed since the power was turned off, the high voltage power supply 3
The supply voltage V0 from 5 is controlled.

Therefore, the delay circuit of the first control circuit 76 has, for example, a rising time-voltage characteristic expressed by the following equation (1) and a falling time time expressed by the following equation (2). -It has voltage characteristics.

[0075]

[Equation 1]

[0076]

[Equation 2]

Here, VCG is the voltage supplied to the conductive transparent member 54, TON is the time constant at the time of rising, tON is the time from when the high-voltage power supply 35 is turned on until the supply voltage VCG reaches VD, and TOFF is The time constant, tOFF, at the time of falling represents the time from when the high-voltage power supply 35 is turned off until the supply voltage VCG decreases to VD. The time constant T
The relationship between ON and TOFF is TON = C · Rj, TOFF = C ·
It is Ri.

Rise and fall times tON, t
OFF is defined by the following formula (3), where d1 is the distance between the charging position and the toner adhesion amount measuring position along the outer peripheral surface of the photosensitive drum 1, and v is the peripheral speed of the photosensitive drum 1. (4)
Respectively indicated by. tON = d1 / v (3), tOFF = d1 / v ...
(4) Then, from these equations (1) and (3), and also from equations (2) and (4), the time constants TON and TOFF are determined as in the following equations (5) and (6).

[0079]

[Equation 3]

[0080]

[Equation 4]

Since tON = tOFF here, the charging voltage and the developing bias voltage are V0 / VD = 1 /
When the relationship of 2 is satisfied, TON and TOFF are expressed by the following formula (7).
As shown in, the values are equal to each other. When TON and TOFF are equal to each other, the circuit configuration becomes easy.

[0082]

[Equation 5]

Similarly, the second voltage control circuit 78 has a delay circuit having a predetermined time constant, and the conductive transparent member 58.
The voltage VCG applied to the high voltage power source 35 is controlled so that it rises to a voltage VD equal to the developing bias voltage after a predetermined time ton has passed since the high voltage power source 35 was turned on. The voltage VCG applied to the member 58 is a voltage VD equal to the developing bias voltage after a predetermined time tOFF has passed since the high voltage power supply 35 was turned off.
Supply voltage V0 from the high-voltage power supply 35
To control. The delay circuit of the second voltage control circuit 78 has, for example, the time-voltage characteristics at the time of rising and falling shown by the above equations (1) and (2), and its time constants TON and TOFF are as described above. It is defined by the equations (5) and (6).

Even when the adjusting means constructed as described above is used, a predetermined bias voltage is applied to the conductive transparent members 54 and 58 at the timing of the image forming process, as in the above-described embodiment. In both cases of reversal development and regular development, the conductive transparent member 5
It is possible to reliably prevent the positively charged toner, the negatively charged toner, and the oppositely charged scattered toner from adhering to the toner particles 4, 58.

The present invention is not limited to the above-mentioned embodiments, but can be variously modified within the scope of the present invention. For example, the conductive transparent member does not have to be configured as a plate-shaped independent member, and the photosensitive drum 1 is one of the components of the laser optical system 13 and the toner adhesion amount measuring device 8.
Components adjacent to, for example, glass, lenses, mirrors
It is also possible to form a conductive transparent member on the surface of, for example, and apply a voltage thereto.

The optical means that functions by irradiating the photosensitive drum 1 with light is not limited to the toner adhesion amount measuring device 8 and the laser optical system 13 described above, and a solid head as shown in FIG. 13 may be used. Good.

This solid head is used in place of the laser optical system 13 and exposes the surface of the photosensitive drum 1 to form an electrostatic latent image on the surface of the photosensitive drum. Here, a fluorescent head, which is one of the solid heads and uses a fluorescent substance as a light emitting portion, will be described as an example. Fluorescent head
It has a supporting member 62 made of an insulating member, and a glass substrate 63 is attached to the supporting member. Glass substrate 6
3 is provided with a light emitting portion 66 including a phosphor dot (anode) 64 and a cathode 65 facing the phosphor dot 64, and a plurality of driving ICs 67 for driving the fluorescent head. Further, the support member 62 is provided with a rod lens array 68 that collects the light emitted from the light emitting unit 66 and guides it to the surface of the photosensitive drum 1. A conductive transparent member 69 is attached to the exit surface of the rod lens array 68 facing the surface of the photosensitive drum 1, and a bias power supply 56 for applying a voltage is connected to the conductive transparent member 69. ing.

In the fluorescent head having the above structure, a signal corresponding to the image data is output from the driving IC 67 to the cathode 65, and the fluorescent dots 64 are coated with the thermoelectrons emitted from the cathode. It stimulates the body to emit light. The emitted light passes through the glass substrate 63, is condensed through the rod lens array 68, and exposes the photosensitive drum 1.

Even when the solid head as described above is used, the conductive transparent member 69 provided on the exit surface of the rod lens array 68 is applied with a voltage in the range of VO ≥VD ≥VL during reversal development, and a normal voltage. In development, VD is V0 ≥VD ≥V
By applying a voltage in the range of L, the scattering toner to the conductive transparent member 69 and the rod lens array 68 is scattered.
Can be prevented from adhering.

[0090]

As described above, according to the present invention, the conductive transparent member is provided between the image carrier and the optical means such as the toner adhesion amount measuring device and the exposure optical system, and the conductive transparent member is provided. An image forming apparatus capable of forming an excellent image by preventing a toner having both polarities of a normally charged toner and an oppositely charged toner from adhering is provided because it is provided with a voltage supply means for applying a predetermined voltage. can do.

[Brief description of drawings]

FIG. 1 is a sectional view of a color laser printer according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a charging device, an exposure device, a developing device of the color laser printer, and a control circuit thereof.

FIG. 3 is a sectional view of a toner adhesion amount measuring device.

FIG. 4 is a block diagram of a toner adhesion amount measuring device.

FIG. 5 is a diagram schematically showing the relationship between the surface potential of the photosensitive drum and the potential of toner during reversal development.

FIG. 6 is a diagram schematically showing the relationship between the surface potential of a photosensitive drum and the potential of toner during normal development.

FIG. 7 is a diagram schematically showing a relationship between a surface potential of a photosensitive drum and an applied voltage during reversal development.

FIG. 8 is a diagram schematically showing the relationship between the surface potential of the photosensitive drum and the potential of toner during normal development.

FIG. 9 is a timing chart showing the timing of applying voltage to the charging device, the conductive transparent member of the exposure optical system, the developing device, the conductive transparent member of the measuring device, and the transfer charging device.

FIG. 10 is a diagram schematically showing a connection state between a power supply and a conductive transparent member.

FIG. 11 is a diagram schematically showing a connection state between a power supply and a conductive transparent member when two power supplies are used.

FIG. 12 is a diagram showing a configuration in which a high voltage power source for developing bias is connected to a conductive transparent member.

FIG. 13 is a diagram showing a configuration in which a high-voltage power supply for developing bias is connected to a conductive transparent member via a resistor.

FIG. 14 is a diagram showing a configuration in which a high voltage power source for grid bias is connected to a conductive transparent member.

FIG. 15 is a diagram showing a configuration in which a high voltage power supply for grid bias is connected to a conductive transparent member via a resistor.

FIG. 16 is a diagram showing a configuration in which a high voltage power supply for grid bias is connected to a conductive transparent member via a plurality of resistors.

FIG. 17 is a diagram showing a configuration in which a high-voltage power supply for developing bias is connected to a conductive transparent member via a plurality of resistors.

FIG. 18 is a diagram showing a configuration in which a conductive transparent member is connected to the ground.

FIG. 19 is a diagram showing a configuration using a charging roller and a high voltage power source in which an AC power source and a DC power source are combined.

FIG. 20 is a diagram showing a configuration using a charging roller and a DC power source.

FIG. 21 is a diagram showing a relationship between a power supply voltage and a supply voltage.

FIG. 22 is a graph showing a bias voltage control method under a low temperature and low humidity environment.

FIG. 23 is a graph showing a method of controlling a bias voltage under a high temperature and high humidity environment.

FIG. 24 is a diagram showing a configuration in which a conductive transparent member and a high voltage power source are connected via a voltage control unit.

FIG. 25 is a circuit diagram showing a configuration of a voltage control unit.

FIG. 26 is a charger when a power control unit is used,
6 is a timing chart showing the timing of applying a voltage to the conductive transparent member of the exposure optical system, the developing device, the conductive transparent member of the measuring device, and the transfer charger.

FIG. 27 is a sectional view showing a solid head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photosensitive drum, 2 ... Charging device, 4 ... Developing device, 8 ... Toner adhesion amount measuring device, 13 ... Laser optical system, 33 ... Grid electrode, 34, 35, 44 ... High voltage power supply, 43 ... Developing roller, 54 , 58, 70 ... Conductive transparent member, 56 ... Bias supply power source.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI Technical indication location G03G 15/04 120 9122-2H 15/06 101 15/08 7810-2H 115 9222-2H

Claims (23)

[Claims] 1. An image forming apparatus for forming an image on an image carrier, wherein a charging means for charging the image carrier to a predetermined charging voltage and a developer are supplied to the image carrier at a predetermined developing bias voltage. Developing means, an optical means for irradiating the image bearing member with light, a conductive transparent member provided facing the image bearing member and transmitting light from the optical means, and the conductive transparent member. An image forming apparatus comprising: a voltage supply unit that applies a voltage between the charging voltage and the developing bias voltage to generate an electric field between the conductive transparent member and the image carrier. apparatus. 2. The image forming apparatus according to claim 1, wherein the optical unit has an exposing unit that exposes the image bearing member to form a latent image. 3. The optical means comprises detection means for detecting the reflected light from the image carrier to measure the amount of the developer attached to the image carrier by the developing means. The image forming apparatus according to claim 1. 4. A transfer means for transferring the developer image formed on the image bearing member by the developing means to a transfer member, wherein the optical means is provided in an area between the charging means and the transfer means. The image forming apparatus according to claim 1, wherein the image forming apparatus is provided. 5. The operation of the voltage supply means is started when the start end of the charged area of the image carrier charged by the charging means reaches a position facing the optical means, and the end of the charged area is changed. The image forming apparatus according to claim 1, further comprising an adjusting unit that stops the voltage supply unit when a position facing the optical unit is reached. 6. An image forming apparatus for forming an image on an image carrier, applying means for applying a voltage to the image carrier to form the image on the image carrier, and light for the image carrier. Optical means for irradiating, and a conductive transparent member provided facing the image carrier and transmitting light from the optical means, wherein the conductive transparent member is electrically connected to the applying means. An image forming apparatus characterized by the above. 7. The applying means comprises: a charging means for applying a predetermined charging voltage to the image bearing member; and a power source connected to the charging means. Image forming apparatus. 8. The charging means comprises a charger having a grid electrode provided to face the image carrier, and the applying means has a power source for applying a grid bias voltage to the grid electrode. 7. The method according to claim 7, wherein
The image forming apparatus according to item 1. 9. The image forming apparatus according to claim 6, further comprising a developing unit that supplies a developing agent to the image carrier, and the applying unit includes a power source that applies a developing bias voltage to the developing unit. Image forming device. 10. The grid bias voltage supplied from the power supply is provided between a developing means for supplying a developer to the image carrier at a predetermined development bias voltage, the conductive transparent member and the power supply. The image forming apparatus according to claim 8, further comprising: a voltage dividing unit that divides the voltage into a voltage between a bias voltage and the developing bias voltage. 11. An image forming apparatus for forming an image on an image carrier, comprising: a developing unit that supplies a developer to the image carrier at a predetermined developing bias voltage; and an optical unit that irradiates the image carrier with light. A conductive transparent member which is provided to face the image bearing member and transmits light from the optical means, and a voltage between a ground and the developing bias voltage is applied to the conductive transparent member, An image forming apparatus, comprising: a voltage supply unit that generates an electric field between a conductive transparent member and the image carrier. 12. The image forming apparatus according to claim 11, wherein the optical unit has an exposing unit that exposes the image bearing member to form a latent image. 13. The optical means comprises detection means for detecting reflected light from the image carrier to measure the amount of the developer adhered to the image carrier by the developing means. The image forming apparatus according to claim 11. 14. A transfer means for transferring the developer image formed on the image carrier by the developing means to a transfer member, wherein the optical means is provided in an area between the charging means and the transfer means. The image forming apparatus according to claim 11, wherein the image forming apparatus is provided. 15. The operation of the voltage supply means is started when the start end of the charging area of the image carrier charged by the charging means reaches a position facing the optical means, and the end of the charging area is changed. The image forming apparatus according to claim 11, further comprising an adjusting unit that stops the voltage supply unit when a position facing the optical unit is reached. 16. An image forming apparatus for forming an image on an image bearing pair, a developing means for supplying a developer to the image bearing member, a power source means for applying a predetermined developing bias voltage to the developing means, and the image as described above. Optical means for irradiating the carrier with light, and a conductive transparent member which is provided so as to face the image carrier and transmits light from the optical means are provided, wherein the conductive transparent member is the power supply means and An image forming apparatus, which is electrically connected to one of the grounds. 17. The conductive transparent member is connected to the power source means, and the developing bias voltage supplied from the power source is supplied between the conductive transparent member and the power source to the ground and the developing bias voltage. The image forming apparatus according to claim 16, further comprising a voltage dividing unit that divides a voltage between the two. 18. An image forming apparatus for forming an image on an image carrier, comprising: charging means for charging the image carrier to a predetermined charging voltage; and developing for supplying a developer to the image carrier at a predetermined developing bias voltage. Means, an optical means for irradiating the image carrier with light, and an optical means electrically connected to one of the charging means and the developing means and provided so as to face the image carrier, An image forming apparatus comprising: a conductive transparent member that transmits light; and a control unit that is connected to the charging unit and the developing unit and that changes a gradation characteristic of at least one of a charging voltage and a developing bias. . 19. An image forming apparatus for forming an image on an image carrier, comprising: a developing unit for supplying a developer to the image carrier at a predetermined developing bias voltage; and an optical unit for irradiating the image carrier with light. A conductive transparent member electrically connected to the developing means and facing the image carrier and transmitting light from the optical means; and a developing bias connected to the developing means. An image forming apparatus comprising: a control unit that changes a tonality characteristic. 20. An image forming apparatus for forming an image on an image bearing member, comprising: a charging member in contact with the image bearing member, for applying a predetermined charging voltage to the image bearing member, and the image bearing member. And an electrically conductive transparent member that is electrically connected to the charging unit and that is provided to face the image carrier and that transmits the light from the optical unit. An image forming apparatus characterized in that 21. The charging means applies AC to the charging member.
21. A power supply unit for supplying a voltage and a DC voltage, and a unit for guiding the DC voltage to the conductive transparent member is provided between the power supply unit and the conductive transparent member. The image forming apparatus according to item 1. 22. The charging means applies DC to the charging member.
21. A power supply unit for supplying a voltage, and a unit for lowering the DC voltage to a predetermined voltage is provided between the power supply unit and the conductive transparent member.
The image forming apparatus according to item 1. 23. An image forming apparatus for forming an image on an image carrier, a charging means for charging the image carrier to a predetermined charging voltage, and a developing device for supplying a developer to the image carrier at a predetermined developing bias voltage. Means, an optical means for irradiating the image carrier with light, and an optical means electrically connected to one of the charging means and the developing means and provided so as to face the image carrier, Is provided between the conductive transparent member and the conductive transparent member and the one of the charging means and the developing means, and the voltage supplied to the conductive transparent member is charged by the charging means. When the start end of the charged area of the image carrier reaches a position facing the optical means, a predetermined voltage is reached, and when the end of the charged area reaches the position facing the optical means. In the above To decrease the voltage lower than the voltage,
An image forming apparatus comprising: a voltage control unit that controls a voltage supplied from the charging unit to the conductive transparent member.