JP2003233253A - Image forming method and image forming device using the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent a defective image (positive ghost) due to the reduction of the electrified quantity of toner left after transfer, as for an image forming device wherein developing and cleaning are simultaneously performed by a developing device. <P>SOLUTION: A developing bias is controlled in accordance with the quantity of the toner left after transfer. In such the condition that it is difficult to recover the toner left after transfer, the developing bias is made lower, or the surface potential of the photoreceptor drum 11 is made higher, then, a potential difference working the recovery of the toner left on the white surface part of the photoreceptor drum 11 is increased. Then, the recovering efficiency of the toner left after transfer is enhanced, and then, the ghost image due to the defective recovery is prevented. <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 such as a printer, a copying machine or a facsimile, and in particular, a cleanerless system for collecting and reusing the residual toner on the image carrier after transferring the toner image at the same time as development. System) image forming apparatus.

[0002]

2. Description of the Related Art Conventionally, in image forming apparatuses such as printers, copying machines, and facsimiles, there are generally consumable items that need to be replaced or replenished at regular intervals. It keeps functioning.
It has been a goal in terms of quality and service of the image forming apparatus that the regular replacement is easy and the number of times is small. In addition, reuse of consumables is an important issue from the viewpoints of economy and environmental protection, and it is said that it is preferable not to discard consumables.

Due to recent demands for downsizing, cost reduction, and maintenance-free of the image forming apparatus, the process simplification, long life and high reliability of each unit have been promoted. As a specific example, there is no drum replacement by using an a-Si photoconductor, stabilization of the latent image potential, and a developing device that does not require carrier replacement using one-component toner. Unnecessary spherical magnetic toner and the like can be mentioned.

Particularly, in order to eliminate the replacement of the waste toner unit for storing the transfer residual toner obtained by cleaning the residual toner on the photoconductor, and to reduce the number of times of toner replenishment and the consumption thereof, a toner reusing device. Various image forming apparatuses including the following (hereinafter referred to as "reuse type image forming apparatus") have been proposed. In particular, as a reuse type image forming apparatus, there is an image forming apparatus (hereinafter, referred to as "cleanerless image forming apparatus") in which a developing device is provided with a role of cleaning transfer residual toner and development is performed at the same time as cleaning.

This cleanerless type image forming apparatus is
Usually, since an independent dedicated cleaning device for removing the residual toner after transfer provided between the transfer member and the charging member is not provided, the space advantage is large and the image forming apparatus can be significantly downsized. It will be possible.

Further, since the developing device collects and mixes the reused toner little by little, when an image defect which is often a problem in the reuse type image forming apparatus, that is, when the new toner and the reused toner are rapidly mixed, Image defects due to defective toner charging, which is called contamination, are less likely to occur.

FIG. 10 shows a schematic configuration of a conventional cleanerless image forming apparatus.

The image forming apparatus shown in FIG. 1 includes a photosensitive drum 11 as an image carrier. The surface of the photosensitive drum 11 is an organic optical semiconductor (OPC), amorphous silicon (a
-Si) has a photoconductive layer, such as arrow R1 in FIG.
Driven to rotate. The surface of the photosensitive drum 11
The primary charging device 2 such as corona charging and roller contact charging uniformly charges the battery to −500V, for example. Next, the exposure device 3 performs image exposure to form an electrostatic latent image on the photosensitive drum 11. For image exposure, for example, analog exposure, semiconductor laser, or LED array is used.

Next, the developing device 4 carries out regular development or reversal development to visualize the electrostatic latent image as a toner image. This toner image is then transferred by a transfer charger 5 onto a transfer material P such as paper that is conveyed in the direction of the arrow (from right to left in the figure), and is separated from the surface of the photosensitive drum 11 by a separation charger 6. It is separated and conveyed to the fixing device 8. The toner image of the transfer material P is heated and pressed here to be fixed on the surface thereof.

On the other hand, the toner remaining on the surface of the photosensitive drum 11 without being transferred to the transfer material P during transfer (transfer residual toner)
Are removed and collected by the developing bias applied to the developing device 4. The transfer residual toner thus collected in the developing device 4 is mixed again in the developing device 4, charged and provided for development.

According to such a configuration, it is not necessary to dispose a dedicated cleaning device (cleaner) between the transfer portion (transfer charger 5) and the charging portion (primary charger 2), and therefore, the dedicated cleaning. An image can be formed without discarding the transfer residual toner removed by the apparatus.

[0012]

However, when an image having a high density and a high image ratio is output in the image forming apparatus as described above, the photosensitive drum 11 is printed on a portion where there is no image.
The positive ghost of the previous image occurred in the rotation cycle of. This positive ghost reaches the transfer portion because the transfer residual toner of the previous image could not be collected in the developing area or was insufficiently collected, and the transfer material P is originally a white background portion. It is a phenomenon that occurs by being transferred.

A contact charging device is used as the primary charger 2, and a direct current voltage is applied to the contact charging member brought into contact with the photosensitive drum 11, so that the photosensitive drum 11 is primarily charged to a predetermined polarity and potential, and this charging is performed. Photosensitive drum 11 passing through
By aligning the above-mentioned transfer residual toner to the developing device 4 by aligning it with the normal charging polarity, the transfer residual toner becomes advantageous in the toner recoverability during the development of the developing device 4, and the above-mentioned image defect (positive ghost) can be prevented. Like

However, also in this case, the toner cannot be sufficiently aligned to the normal charge polarity due to the image output under high humidity and the toner contamination of the contact charging member due to the continuous output of a large number of sheets, and the quality of the output image is deteriorated. That is, the image quality depends on the charge amount of the transfer residual toner.

The present invention has been made in view of the above circumstances, and it is possible to effectively prevent an image defect (positive ghost) due to a decrease in the charge amount of transfer residual toner in an image forming apparatus in which simultaneous development and cleaning are performed by a developing device. It is an object of the present invention to provide an image forming apparatus according to the above.

[0016]

The invention according to claim 1 is
The surface of the image bearing member is charged by a charging unit, the surface of the image bearing member after charging is exposed by an exposing unit to form an electrostatic latent image, and toner is attached to the electrostatic latent image by a developing unit to form a toner image. In the image forming method, the toner image is transferred to another member by transfer means, and the transfer residual toner remaining on the surface of the image carrier without being transferred to the other member at the time of transfer is recovered by the developing means. The charge amount of the transfer residual toner is detected by the transfer residual toner charge amount detecting unit, and based on the detection result of the transfer residual toner charge amount detecting unit, the developing bias of the developing unit and the surface potential of the image carrier are determined. At least one of the above is controlled by the control means.

According to a second aspect of the invention, in the image forming method according to the first aspect, the charge amount of the transfer residual toner is
It is characterized in that the potential on the image carrier is obtained by a potential sensor.

According to a third aspect of the present invention, in the image forming method according to the first aspect, the charge amount of the transfer residual toner is
Humidity is measured at the time of image formation, and it is calculated from the detection result.
It is characterized by

According to a fourth aspect of the present invention, in the image forming method according to the first aspect, the charge amount of the transfer residual toner is
It is characterized in that the degree of residual toner contamination of the charging means is detected and obtained from the detection result.

According to a fifth aspect of the present invention, in the image forming method according to the first aspect, when controlling at least one of the developing bias and the surface potential of the image carrier, the developing bias AC component At least one of the frequency and the waveform is controlled at the same time.

According to a sixth aspect of the present invention, in the image forming method according to the first aspect, the charging unit is a conductive member.
And a conductive particle carried on the surface of the conductive member, a charging bias is applied to the conductive member to charge the surface of the image carrier without causing discharge through the conductive particles. Characterize.

According to a seventh aspect of the present invention, in the image forming method according to the first aspect, the image carrier is a photoconductive layer made of a non-single crystal material having silicon atoms as a matrix on a conductive substrate. And a surface layer composed of a non-single-crystal material having carbon atoms as a matrix.

According to an eighth aspect of the invention, in the image forming method according to the first aspect, the toner comprises toner particles containing at least a binder resin and a magnetic substance, and an inorganic fine powder, and has an average circularity of 0. The magnetic toner has a saturation magnetization of 10 Am ² / kg (e) under 79.6 kA / m (1000 Oersteds).
mu / g) or more and 50 Am ² / kg or less.

According to a ninth aspect of the present invention, an image carrier, a charging unit that charges the surface of the image carrier, and an exposing unit that exposes the surface of the image carrier after charging to form an electrostatic latent image. The image carrier, comprising: a developing unit that adheres toner to the electrostatic latent image to develop it as a toner image; and a transfer unit that transfers the toner image to another member, without being transferred to the other member at the time of transfer. In an image forming apparatus for collecting the transfer residual toner remaining on the surface by the developing device, a transfer residual toner charge amount detecting device for detecting the charge amount of the transfer residual toner,
Control means for controlling at least one of the developing bias of the developing means and the surface potential of the image carrier based on the detection result of the transfer residual toner charge amount detecting means;
Is provided.

According to a tenth aspect of the invention, in the image forming apparatus according to the ninth aspect, the transfer residual toner charge amount detecting means has a potential sensor for detecting the potential on the image carrier. And

According to an eleventh aspect of the invention, in the image forming apparatus according to the ninth aspect, the transfer residual toner charge amount detecting means has a humidity sensor for measuring the humidity during image formation.

According to a twelfth aspect of the present invention, in the image forming apparatus according to the ninth aspect, the transfer residual toner charge amount detecting means has a stain detecting sensor for detecting a degree of residual toner stain on the charging means. Is characterized by.

According to a thirteenth aspect of the invention, in the image forming apparatus according to the ninth aspect, the developing bias AC component of the developing bias AC component is controlled when at least one of the developing bias and the surface potential of the image carrier is controlled. At least one of the frequency and the waveform is controlled at the same time.

According to a fourteenth aspect of the present invention, in the image forming apparatus according to the ninth aspect, the charging means has a conductive member and conductive particles carried on the surface of the conductive member, A charging bias is applied to the member to charge the surface of the image carrier through the conductive particles without causing discharge.

According to a fifteenth aspect of the present invention, in the image forming apparatus according to the ninth aspect, the image carrier is a photoconductive layer made of a non-single crystal material having silicon atoms as a matrix on a conductive substrate. And a surface layer composed of a non-single-crystal material having carbon atoms as a matrix.

According to a sixteenth aspect of the present invention, in the image forming apparatus according to the ninth aspect, the toner comprises toner particles containing at least a binder resin and a magnetic substance, and an inorganic fine powder, and has an average circularity of 0. The magnetic toner has a saturation magnetization of 10 Am ² / kg (e) under 79.6 kA / m (1000 Oersteds).
mu / g) or more and 50 Am ² / kg or less.

[Operation] The operation of the above configuration will be described. As described above, the increase in the charge amount of the transfer residual toner leads to defective transfer residual toner collection. Therefore, the above-described configuration is adopted so that the developing bias can be controlled according to the transfer residual toner amount. Under conditions where it is difficult to collect the residual toner after transfer, lower the developing bias or increase the surface potential of the image carrier to increase the potential difference that affects the recovery of the toner remaining on the white background on the image carrier. By improving the collection efficiency of the transfer residual toner, a ghost image due to poor collection is prevented. Normally, the charge amount of the residual toner after transfer is high. By making the potential difference small, the applied voltage to the charging member and the exposure amount for writing a latent image can be reduced, and leakage due to the use of more voltage or current than necessary,
It is possible to prevent adverse effects such as deterioration of members and increased power consumption.

In this way, by controlling the potential difference during development by the charge amount of the transfer residual toner, it becomes possible to satisfy the transfer residual toner cleaning property without using excessive voltage and current.

[0034]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. The same reference numerals in the drawings denote the same configurations or operations, and repeated description thereof will be omitted as appropriate.

<First Embodiment> FIG. 1 shows an example of an image forming apparatus according to the present invention. It should be noted that this figure is a vertical cross-sectional view showing a schematic configuration of a digital copying machine. The copying machine (hereinafter referred to as "image forming apparatus") shown in FIG. 1 includes a drum type electrophotographic photosensitive member (hereinafter referred to as "photosensitive drum") 11 as an image bearing member. The photosensitive drum 11 is rotationally driven in the direction of the arrow by a driving unit (not shown).
Around the photosensitive drum 11, a charging roller 12, which is a primary charging device (primary charging means), an exposure device 13, a developing device (developing means) 14, and a transfer charging, are arranged substantially in order along the rotation direction (direction of arrow R1). A device (transfer device) 15 and a separation charging device (separation device) 16 are provided. Further, a fixing device 18 is disposed on the downstream side (left side in the drawing) of the separation charging device 16 in the transport direction (direction of arrow K) of the transfer material (for example, paper or transparent film) P as another member. There is.

The surface of the above-mentioned photosensitive drum 11 is uniformly charged by the charging roller 12 to a predetermined polarity and potential. Next, image exposure is performed by the laser light emitted from the exposure device 13, and the electric charge in the laser light irradiation portion is removed to form an electrostatic latent image. The electrostatic latent image on the surface of the photosensitive drum 11 is developed by the charged toner of the developing device 14. The developed toner image on the surface of the photosensitive drum 11 is transferred by the transfer charger 15 onto the transfer material P conveyed in the direction of arrow K. The transfer material P after the toner image transfer is separated from the surface of the photosensitive drum 11 by the separation charging device 16 and is conveyed to the fixing device 18. The transfer material P is heated and pressed here, and the toner image is fixed on the surface of the transfer material.

The image forming apparatus according to the present invention is not equipped with a dedicated cleaning device for removing transfer residual toner on the surface of the photosensitive drum 11 after the toner image is transferred onto the transfer material P. Photosensitive drum 1
The surface 1 reaches the contact portion A with the transfer roller 12 with the transfer residual toner adhered thereto, and the transfer residual toner is temporarily taken into the charge roller 12 by the rubbing force of the charging roller 12 and the charging bias. Be recovered. As a result, the transfer residual toner pattern on the surface of the photosensitive drum 11 is scraped off, and the transfer residual toner is subjected to frictional charging with the charged particles on the surface of the charging roller 12 so that the toner charge whose charge polarity is reversed is properly aligned, and the photosensitive drum 11 is normally charged. It will be gradually exhaled on the surface. The discharged toner (hereinafter referred to as “discharged transfer residual toner”) is collected by the developing device 14 in the developing section (cleaning at the same time as development) and reused for development.

The above-mentioned members and processes will be described in detail below.

[Image Carrier (Photosensitive Drum)] In the present embodiment, the photosensitive drum 11 which is a rotary drum type electrophotographic photosensitive member is used as the image carrier, and the reversal development is performed. The copying machine of this embodiment uses reversal development, the photosensitive drum 11 is a negative-polarity a-Si photosensitive member having a diameter of 30 mm, and is rotationally driven in the direction of arrow R1 at a peripheral speed of 210 mm / sec. The photosensitive drum 11 has on its surface a photosensitive layer made of negative-chargeable amorphous silicon (a-Si). Further, the outermost layer has a-
Amorphous carbon (a with higher hardness than Si)
-C) has a protective film. The optimum film thickness of aC can be determined from the relationship between the amount of wear of the surface layer and the life of the entire image forming apparatus, but is generally 0.01 to 10 μm, preferably 0.1 to 1 μm. The range of is desirable. When the thickness of the surface layer is 0.01 μm or less, the mechanical strength is impaired, and conversely 1
If it is 0 μm or more, the residual potential may increase. a
-Si photosensitive drums have higher durability than organic photosensitive drums against wear due to members contacting the photosensitive drums such as charging roller 12, and almost no consumable parts need to be replaced. It is consistent with the concept of free maintenance of forming equipment and less waste. Further, since the amount of scraped powder due to the scraping of the drum is small, it is also advantageous from the viewpoint of foreign matter mixing into the developing device 14, which is a problem of the cleanerless system.

[Charging] In the image forming apparatus shown in FIG. 1, as a primary charging means, a conductive elastic roller (charging) is provided as a flexible contact charging member arranged in contact with the photosensitive drum 11 with a predetermined pressing force. Roller). Reference numeral A in the figure denotes a charging nip portion between the photosensitive drum 11 and the charging roller 12. The outer peripheral surface of the charging roller 12 is coated beforehand with charging promoting particles (not shown), and the charging roller 12 has the charging promoting particles present in the charging nip portion A. In the present embodiment, the charging roller 12 is rotationally driven in the charging nip portion A in the direction opposite to the rotation direction of the photosensitive drum 11 (counter direction) at a peripheral speed of 100%, and the speed with respect to the surface of the photosensitive drum 11 is increased. Contact with a difference. Then, a predetermined charging bias is applied to the charging roller 12 from a charging bias applying power source. As a result, the outer peripheral surface of the rotating photosensitive drum 11 is uniformly contact-charged to a predetermined polarity and potential by the injection charging method. In this embodiment, the outer peripheral surface of the photosensitive drum 11 is approximately -400 in the charging roller 12.
A charging bias is applied from a charging bias applying power source so that the charging process is uniformly performed to V.

In the cleanerless system, the transfer residual toner is temporarily scraped from the surface of the photosensitive drum 11 as the charging roller 12 rotates in the counter direction with respect to the photosensitive drum 11. As a result, the transfer residual toner pattern on the surface of the photosensitive drum 11 is scraped off, and the transfer residual toner is reversed in charging polarity by frictional charging with the charge promoting particles, so that the toner charges are regularly aligned and slightly transferred to the surface of the photosensitive drum 11. It will be spit out one by one.

The charging roller 12, charging promoting particles, injection charging and the like will be described in detail below.

(1) Charging Roller The charging roller 12 as the contact charging member in the present embodiment is manufactured by forming a medium resistance layer on a core metal with rubber or foam. The medium resistance layer is made of resin (eg urethane), conductive particles (eg carbon black),
It was formulated with a sulfiding agent, a foaming agent, etc., and formed into a roller shape on a cored bar. Then, the surface was polished as needed. When the roller resistance of the charging roller 12 of the present embodiment was measured, it was 100 kΩ. The roller resistance is the charging roller 12
In a state where the charging roller 12 was pressure-bonded to an aluminum base having a diameter of 30 mm so that a total pressure of 1 kg was applied to the core, the measurement was performed by applying 100 V between the core and the aluminum base.

Here, the charging roller 1 which is a contact charging member.
It is important that 2 functions as an electrode. In other words, the photosensitive drum 1 which is movable while at the same time obtaining a sufficient contact state with the surface of the photosensitive drum 11 which has been made to be a charged member by elasticity.
One must have a low enough resistance to charge the surface. On the other hand, it is necessary to prevent voltage leakage when a low breakdown voltage defective portion such as a pinhole exists on the surface of the photosensitive drum 11. When the photosensitive drum 11 is used as the member to be charged, 10 ⁴ to 10 ⁷ are required to obtain sufficient chargeability and leak resistance.
A resistance of Ω is desirable. Further, it is desirable that the surface of the charging roller 12 has micro unevenness so as to hold the charge promoting particles. If the hardness of the charging roller 12 is too low, the shape is not stable, so the contactability with the photosensitive drum 11 deteriorates. If the hardness is too high, the charging nip portion A cannot be secured between the charging roller 12 and the charging roller 12. Since the microscopic contact property to the surface of the photosensitive drum 11 is deteriorated, the Asker C hardness is preferably in the range of 25 to 50 degrees. The material of the charging roller 12 is not limited to the elastic foam, and the material of the elastic body may be EPDM, urethane, NB.
Examples thereof include R, silicone rubber, IR, etc., a rubber material in which a conductive material such as carbon black or a metal oxide is dispersed for resistance adjustment, or a material obtained by foaming these.
It is also possible to adjust the resistance by using an ion conductive material without particularly dispersing the conductive substance. The charging roller 12 is arranged so as to be pressed against the photosensitive drum 11 as the member to be charged with a predetermined pressing force against the elasticity, and in this embodiment, the charging nip portion A having a width of several mm is formed. Has become.

(2) Charge-Promoting Particles In this embodiment, the charge-promoting particles have a resistivity of 10 or less.
Conductive zinc oxide particles having an average particle diameter of ⁷ Ω · cm and 1.5 μm were used. There is no problem that the charge-promoting particles exist not only in the state of primary particles but also in the state of agglomeration of secondary particles. Whatever the state of aggregation,
The form is not important as long as it can realize the function of the charge promoting particles as an aggregate. The particle size is defined as the average particle size of the aggregate when the particles form the aggregate. To measure the particle size, 100 or more particles were extracted from observation by an optical or electron microscope, the volume particle size distribution was calculated with the maximum chord length in the horizontal direction, and the 50% average particle size was determined. The resistance value of the charge promoting particles is 2 × 10 ¹² Ω · cm
If it is above, the charging property is impaired. Therefore, it is necessary resistance value is less than 1 × ^{10 12} Ω · cm, more preferably may not more than ^{1 × 10 1 0 Ω · cm} . In the present embodiment, the one having 1 × 10 ⁷ Ω · cm is used. The resistance was measured by the tablet method and normalized. That is, about 0.5 g of a powder sample was placed in a cylinder having a bottom area of 2.26 cm ² , 15 kg of pressure was applied to the upper and lower electrodes, and at the same time, a voltage of 100 V was applied to measure the resistance value, and then normalized. Then, the specific resistance was calculated.

The charge promoting particles are preferably white or nearly transparent so as not to interfere with the formation of the electrostatic latent image, that is, during the exposure of the surface of the photosensitive drum 11 by the exposure device 13, and thus are non-magnetic. Is preferred. Further, considering that the charge-accelerating particles are partially transferred from the photosensitive drum 11 to the recording material P, colorless or white toner is preferable when using a color toner other than black. Further, if the particle diameter is not about 1/2 or less of the particle diameter of the developer, image exposure may be blocked. Therefore, it is desirable that the particle size of the charge promoting particles is smaller than 1/2 of the particle size of the developer. The lower limit of the particle diameter is considered to be 10 nm as a particle that can be stably obtained. As the material of the electrification promoting particles, zinc oxide was used in the present embodiment, but the present invention is not limited to this. In addition, a mixture of other metal oxide such as titanium oxide or alumina with conductive inorganic particles or organic matter, Alternatively, various conductive particles such as surface-treated particles can be used.

(3) Injecting charging By interposing charging accelerating particles in the charging nip portion A between the photosensitive drum 11 which is an image carrier and the charging roller 12 which is a contact charging member, the charging accelerating particles have a lubricant effect. Even if the charging roller 12 has a large frictional resistance and it is difficult to bring the photosensitive drum 11 into contact with the photosensitive drum 11 with a speed difference, the effect can be easily and easily applied to the surface of the photosensitive drum 11. It becomes possible to bring them into contact with each other with a speed difference, and the charging roller 12 comes into close contact with the surface of the photosensitive drum 11 through the charging accelerating particles to more frequently contact the surface of the photosensitive drum 11. It comes in contact.

By providing a sufficient speed difference between the charging roller 12 and the photosensitive drum 11, the opportunity for the charging promoting particles to contact the photosensitive drum 11 at the charging nip portion A between the charging roller 12 and the photosensitive drum 11 is significantly increased. The charge promoting particles present in the charging nip portion A between the charging roller 12 and the photosensitive drum 11 rub the surface of the photosensitive drum 11 without any gaps, thereby increasing the contact property.
The charge can be directly injected into the charging roller 12
The contact charging of the photosensitive drum 11 by means of the injection charging mechanism is predominant due to the presence of the charging promoting particles.

As a structure for providing the speed difference, the charging roller 12 is rotationally driven or fixed to provide the speed difference with the photosensitive drum 11. Preferably, the charging roller 12
It is desirable to rotate and drive the surface of the photosensitive drum 11 in the opposite direction to the surface of the photosensitive drum 11.

Therefore, it is possible to obtain a high charging efficiency which has not been obtained by the conventional roller charging or the like, and it is possible to give the photosensitive drum 11 a charging potential almost equal to the voltage applied to the charging roller 12. Thus, even when the charging roller 12 is used as the contact charging member, the applied bias (charging bias) necessary for charging the charging roller 12 is sufficient to be the voltage corresponding to the charging potential required for the photosensitive drum 11, and the discharge phenomenon is used. A stable and safe contact charging method or contact charging device can be realized.

Further, by preliminarily supporting the charge accelerating particles on the surface of the charging nip portion A or the charging roller 12, the above-mentioned direct charging performance can be exhibited without any trouble from the beginning of use of the image forming apparatus.

(4) Replenishment of charging promoting particles to the charging nip A and the charging roller 12 First, a sufficient amount of charging promoting particles may be interposed in the charging nip A between the photosensitive drum 11 and the charging roller 12, or Even if the charging roller 12 is coated with a sufficient amount of the charging promoting particles, the charging promoting particles may decrease from the charging nip portion A or the charging roller 12 or the charging promoting particles may deteriorate with the use of the image forming apparatus. As a result, the chargeability is lowered.
Therefore, when the charging property is deteriorated, the charging nip A
It is necessary to replenish the charging roller 12 with charging accelerating particles.

Although charging-promoting particle supply means for supplying charging-promoting particles may be provided on the surface of the charging roller 12, in the present embodiment, by supplying the charging-promoting particles into the developing device 14,
The charging promoting particles are replenished through the surface of the photosensitive drum 11. The charge-accelerating particles are external additives as a charge auxiliary agent for the toner in the developing device 14, are charge particles in the charging section, and are supplied to the surface of the photosensitive drum 11 with a developing bias applied in the developing section. The rotation of the photosensitive drum 11 reaches the charging roller 12.

[Exposure] In the present embodiment, the exposure device 13 is a laser beam scanner including a laser diode, a polygon mirror, and the like. This exposure device 13
Outputs laser light whose intensity is modulated corresponding to the time-series electric digital pixel signal of the target image information, and scans and exposes the uniformly charged surface of the photosensitive drum 11 with this laser light.
By this scanning exposure, an electrostatic latent image corresponding to target image information is formed on the surface of the photosensitive drum 11.

The light source for forming the electrostatic latent image on the surface of the photosensitive drum 11 may be an LED array. In this case, the LE at the position corresponding to the target image information is used.
By turning on D, an electrostatic latent image is formed on the surface of the photosensitive drum 11.

Further, in the image forming apparatus of this embodiment,
No charge removing device is provided for removing the charge on the surface of the photosensitive drum 11.

The surface of the above-mentioned photosensitive drum 11 is uniformly charged to -400V by the charging roller 12. Next, a wavelength of 680 nm emitted from the semiconductor laser of the exposure device 13.
600dpi (dot / inch) by laser light
The image exposure is carried out in order to remove the electric charge in the portion irradiated with the laser beam and an electrostatic latent image is formed.

[Development] The developing device 14 includes the photosensitive drum 11
Toner is attached to the electrostatic latent image formed on the surface to develop it as a toner image. The developing device 14 includes a developing roller 14a whose surface is coated with toner in a thin layer, a stirring member which stirs the toner in the developing container and moves the toner toward the developing roller 14a, and a toner which is applied to the surface of the developing roller 14a. It has the regulation blade 14b which regulates the layer thickness. The gap between the developing roller 14a and the regulation blade 14b is set to about 200 μm. The surface of the developing roller 14a is coated with a phenol resin which is a binder and a resin which is carbon and graphite which are pigments. The composition weight ratio of these binder and pigment is set to 2.5: 1.0.

The toner in the developing device 14 is the developing roller 1
4a is applied to the surface of the developing roller 14a, and the layer thickness is regulated by the regulating blade 14b while being frictionally charged with the coating resin on the surface of the developing roller 14a so that the roller coating amount is about 1.0 mg / cm ² . The toner whose layer thickness is regulated is carried on the surface of the developing roller 14a, and is conveyed to the developing position facing the surface of the photosensitive drum 11 as the developing roller 14a rotates in the direction of arrow R4. The gap between the developing roller 14a and the photosensitive drum 11 at the developing position (hereinafter referred to as "SD gap") is 180 to 30 due to the photosensitive drum abutment roller (not shown) rotatably supported by the developing roller shaft.
It is set to 0 μm. Negative magnetic one-component toner (7 μm) was used as the toner, and the developing method was jumping development.

The toner is a spherical toner having an average circularity of 0.950 or more, which is composed of toner particles containing a binder resin and a magnetic substance and inorganic fine powder externally added thereto. This magnetic toner is 79.6 kA / m (1000 Oersted)
Saturation magnetization under 10 Am ² / kg (emu / g)
The above is 50 Am ² / kg or less. The externally added inorganic powder can mainly have a function of optimizing the charge amount of the toner, and in the present embodiment, the above-described charged particles such as zinc oxide are used. The average circularity of the toner in the present invention is used as a simple method for quantitatively expressing the shape of particles, and in the present invention, a flow type particle image analyzer “FPIA-1000” manufactured by Toa Medical Electronics is used. The circularity (Ci) of each particle measured for a group of particles having an equivalent circle diameter of 3 μm or more is obtained by the equation (1) in FIG. 3 and measured as shown in the equation (2) in the figure. A value obtained by dividing the sum of circularity of all the particles thus obtained by the total number of particles (m) is defined as the average circularity (AvC).

The average circularity in the present invention is an index of the degree of unevenness of the toner, and is 1.000 when the toner is a perfect sphere, and the more the surface shape of the toner becomes complicated, the smaller the average circularity becomes. .

Since the spherical toner having a high circularity is less likely to be caught between the toners or various members, the charging roller 12 is used.
Has a small mechanical share, and surface shape changes are minimal. In addition, since the toner base itself has high fluidity, the fluidity hardly changes significantly even if the amount of externally added inorganic powder changes. As described above, the spherical toner has a shape factor that causes less toner deterioration. Further, the transfer efficiency is excellent due to the excellent releasability from the photosensitive drum 11, so that the image density can be sufficiently secured and the transfer residual toner can be reduced. For these reasons, it is desirable to use toner with high circularity in the cleanerless reuse system.

Further, the toner is 79.6 kA / m (100
Saturation magnetization under 0 Oersted) is 10 Am ² / k
When it is g (emu / g) or more, even the reused toner has sufficient transportability on the developing roller 14a and the degree of scattering becomes good. In addition, the toner is 79.6 kA /
When the saturation magnetization under m is 50 Am ² / kg or less, the size of the toner ears due to the magnetism on the developing roller 14a and the reuse toner supply roller can be kept small, and the image quality is roughened by aggregation in the developing area. Never be.

In the image forming method of the present invention, the absolute value of the alternating bias voltage applied to the developing roller 14a is 5 or less.
00V or more, preferably 500 to 1500V in consideration of leakage to the photosensitive drum 11. However,
This leak varies depending on the setting of the gap between the developing roller 14a and the photosensitive drum 11. In the present invention, the alternating bias frequency is 1000 to 5000.
It is preferably in the range of Hz. That is, when the alternating bias frequency is less than 1000 Hz, the gradation of the obtained image is improved, but it is difficult to eliminate the background fog. In the low frequency region where the number of reciprocating movements of the toner is small, the pressing force of the toner against the photosensitive drum 11 due to the developer bias electric field becomes too strong even in the non-image portion, so that the toner is peeled off by the reverse developing side bias electric field. It is considered that this is because the toner attached to the non-image portion cannot be completely removed even by the force. On the other hand, when the frequency exceeds 5000 Hz, the toner is not transferred to the photosensitive drum 11.
Since the bias electric field on the reverse developing side is applied before the contact is sufficiently made with, the developability is deteriorated. That is,
The toner itself becomes unresponsive to the high frequency electric field. According to the study by the present applicants, it has been confirmed that in the present invention, when the frequency of the alternating bias electric field is 1500 to 3000 Hz, optimum image quality is exhibited.

In consideration of the above reason, the developing bias at the time of developing is 2000 Hz, the peak-to-peak voltage is 800 Vp.
A superimposing bias in which a direct current voltage of −250 V is superposed on an alternating current voltage of p, Duty 50% is applied to the developing roller 14. As a result, the electrostatic latent image on the surface of the photosensitive drum 11 is subjected to reversal development, toner is attached, and is visualized as a toner image. Note that, in order to suppress toner scattering, no AC voltage is applied between the paper (between the transfer material P and the transfer material P), the photosensitive drum 11 in the non-image portion at the time of pre-rotation, and the developing roller 14a. .

[Transfer] The transfer roller 15 is a medium resistance roller as a contact transfer means, and is in contact with the photosensitive drum 11 with a predetermined contact force to form a transfer nip portion with the photosensitive drum 11. ing. The transfer material P as a recording medium is fed to the transfer nip portion from a paper feeding portion (not shown) at a predetermined timing, and a predetermined transfer bias is applied to the transfer roller 15, whereby the surface of the photosensitive drum 11 is The toner image is sequentially transferred onto the surface of the transfer material P fed to the transfer nip portion by electrostatic force and pressing force. The transfer material P on which the toner image has been transferred is separated from the surface of the photosensitive drum 11 by the separation charger 16.

[Fixing] A fixing device 18 of a thermal fixing type or the like is arranged downstream of the separation charging device 16 along the transfer material conveying direction (arrow K direction). The transfer material P that has received the transfer of the toner image on the photosensitive drum 11 and is separated from the surface of the photosensitive drum 11 is introduced into the fixing device 18, and is heated and heated when passing between the fixing roller and the pressure roller. Upon receiving pressure, the toner image is fixed on the surface. The transfer material P after the toner image is fixed is discharged to the outside of the image forming apparatus main body as an image formed product (print, copy), thereby completing the image formation.

In the present embodiment, the above-described structure is used to detect the image output environment and the ability to impart charge to the discharged transfer residual toner, and to calculate the charge amount of the discharged transfer residual toner from the detection result. . The control of the potential difference Vback required to collect the discharged transfer residual toner on the non-image portion of the photosensitive drum 11 is performed by changing the value of the developing bias. The details of the control are as follows.

<Method for Detecting Discharge Transfer Residual Toner Charging Amount>
The discharge transfer residual toner charge amount from the charging roller 12 is
Temperature and humidity of image output environment, output image, transfer conditions, developing device 1
4 depends on the deterioration state of the toner in 4 and the charge imparting ability to the toner at the charging portion, but the influence of humidity during image formation and the charge imparting ability to the discharge transfer residual toner of the charging roller 12 are particularly large. Therefore, a humidity sensor (not shown) for detecting humidity and a charging roller dirt sensor 20 for detecting dirt on the charging roller 12 are provided in the image forming apparatus, and based on the result detected by the charging roller dirt sensor 20. Obtain the charge amount.

A change amount of the discharge transfer residual toner charge amount due to a difference in humidity environment is stored in advance in a recording device (not shown) in the image forming apparatus, and charging is performed in several steps according to the charge amount detected by the humidity sensor. The amount is divided into levels, and the amount of charge of the discharged transfer residual toner is output. Further, the dirt of the charging roller 12 is detected in order to detect the charge imparting ability of the charging roller 12 to the discharged transfer residual toner. For the dirt on the charging roller 12, the amount of toner adhering to the charging roller 12 is measured by the charging roller dirt sensor 20 constituted by a reflection density sensor provided above the charging roller 12, and the quantity of dirt is estimated from the density. I have to. For the degree of stain, the toner adhesion area on the surface of the charging roller 12 is obtained from the value of the reflection density, and A: toner adhesion area is less than 10% B: toner adhesion area is 10% or more and less than 30% C: toner adhesion area is 30% or more . The humidity and the dirt on the charging roller are variously changed, and the value of the charge amount of the discharged transfer residual toner is actually measured by the blow-off method. H: -5 μC / g or more, N: -5 to -2 μC / g, L : Used as an index when changing the potential difference by dividing the level into less than -2 μC / g.
FIG. 4 shows the relationship between the humidity, the dirt on the charging roller, and the discharge transfer residual toner. The potential difference is controlled according to this figure.

<Potential Difference Control Method> The potential difference in the developing area is controlled according to the above-mentioned charge amount level. A bias potential difference required when the negative toner on the photosensitive drum 11 is collected by the developing roller 14a, that is, a potential difference Vback between the photosensitive drum solid white portion potential and the developing roller 14a potential.
When the discharge amount of the transfer residual toner is large, the difference is controlled to be small, and when the charge amount is small, the potential difference is controlled to be large. As a potential difference control method, in the present embodiment, the developing bias Vdc is changed to control Vback. When the development contrast potential is changed by changing Vdc and the image density is largely changed, the exposure intensity of the exposure device 13 for writing the electrostatic latent image is increased to lower the solid black potential VL. Ensure contrast. The control values in this embodiment are shown in FIG.

FIG. 6 shows the result of evaluation showing the relationship of stains on the non-image area when the present embodiment is applied, as the first embodiment. Note that FIG. 6 also shows a conventional example (when the bias is not changed) for comparison with the first embodiment. Contamination on the non-image area is quantified as a fog by measuring the amount of reflected light with a fog reflection densitometer and expressed in%.
It was shown by a graded evaluation (good, good, good, bad, bad, and bad). When the fog value is 1.0% or less, ○, 1.0 to
1.5% for △ ○, 1.5-2.0% for △, 2.0-2.
5% was evaluated as Δx, and 2.5% or more was evaluated as x.

According to the result of FIG. 6, in the conventional image output, when the discharge transfer residual toner charge amount is N and L, the image stain in the non-image portion due to the uncollected toner can be visually confirmed. Became. This is because the transfer residual toner is once collected by the charging roller 12 and ejected uniformly little by little, and reaches the development area and is collected by the developing device 14 during image formation or non-image formation. This is because if the amount becomes large, the collection capacity of the developing device 14 will be exceeded, and uncollected toner will be transferred onto the image and stain the image.

As shown in the result of FIG. 6, by applying the present invention as in the first embodiment, the collectability of the discharged transfer residual toner is good even if the charge amount of the discharged transfer residual toner changes. The fog level no longer deteriorates. Humidity 5% (Temperature 23 ° C), 50% (Temperature 25 ° C),
Even when a high-density image was output under each environment of 80% (temperature 30 ° C.), stable image output performance could be confirmed without causing deterioration of fog due to defective collection of residual toner after transfer.

Since the development contrast is changed by changing Vdc, the potential of the solid black portion is also controlled in the present embodiment.
The pp may be changed and the frequency or waveform may be controlled.
In addition, depending on the toner image to be formed, there is a case where the stain on the image in the longitudinal direction of the developing roller 14 is large, and the discharge transfer residual toner charge amount becomes uneven. In this case, it is preferable that the charging roller 14 be shaken in the longitudinal direction (reciprocating movement), or that the dirt of the charging roller be evenly smoothed with a brush or the like.

As described above, the image output environment and the charge imparting ability to the discharge transfer residual toner are detected, the charge amount of the discharge transfer residual toner is calculated from the detection result, and the charge amount on the drum non-image portion is determined according to the charge amount. By controlling the potential difference Vback necessary to collect the discharge transfer residual toner by changing the value of the developing bias, the discharge transfer residual amount can be achieved with a simple configuration without using an excessive bias and exposure amount. It is possible to effectively prevent an image defect due to a toner recovery defect.

<Embodiment 2> In the present embodiment, as a method for measuring the discharge transfer residual toner charge amount, the potential of the discharge transfer residual toner and its amount are detected, and the toner charge amount Q / M is calculated. Vd according to the calculated Q / M value
c and the exposure amount of the exposure device at the time of writing (forming) the electrostatic latent image are changed.

In this embodiment, the discharge transfer residual toner amount and the toner potential are detected, and the charge amount of the discharge transfer residual toner discharged from the charging roller 12 is measured. It controls the developing bias and the exposure amount for writing the electrostatic latent image.

The structure of the image forming apparatus main body is almost the same as that of the first embodiment. However, in the second embodiment, as shown in FIG. 2, between the charging roller 12 and the exposure device 13,
The difference is that a toner amount detection sensor 21 and a potential sensor 22 are provided. The toner amount detection sensor 21 measures the reflection density on the drum, and is the C of the image forming apparatus main body.
The weight of the toner is calculated by referring to the reflection density and toner weight table recorded on the PU (not shown). On the other hand, the potential sensor 22 is a vibration capacitance type potential sensor using a tuning fork at its tip, and its resolution is 0.1 to 5V.

<Method for Detecting Discharge Transfer Residual Toner Charging Amount>
First, the amount of reflected light on the surface of the photosensitive drum 11 is measured in order to detect that there is no toner remaining after the transfer when the image forming apparatus main body is started up, before rotation, in a non-image forming area such as a sheet interval. The surface potential of the photosensitive drum 11 at that time is measured, and this is used as a reference potential. Next, when the residual toner after transfer after image formation is on the photosensitive drum 11, the amount of residual toner after transfer is calculated by measuring the amount of reflected light on the surface of the photosensitive drum 11, and the toner weight per unit area M / S Ask for. It should be noted that M / S is obtained from a table showing the relationship between the amount of reflected light and the toner weight M / S per unit area recorded in the CPU of the image forming apparatus main body.
The detection of the amount of residual toner after transfer is detected by the toner amount detection sensor 2 of the reflection type light on the photosensitive drum 11 as in the present embodiment.
In addition to setting 1 and calculating the toner amount from the reflected light amount,
Detection by a CCD camera, detection of the amount of residual toner after discharge by detecting the torque by contacting a roller provided with a torque converter with the photosensitive drum 11 so as to rotate, and consumption based on the number of pixels of the output image read by the scanner Toner amount is calculated and C of the image forming apparatus main body is calculated in advance.
A method such as detection by calculating from the transfer efficiency recorded in the PU and the toner consumption amount may be used.

Further, the potential on the photosensitive drum 11 at this time is measured by the potential sensor 22, the reference potential is subtracted from the potential, and the potential difference is used as the potential of the toner layer. The value of the potential difference ΔV is a difference caused by the electric potential of the discharged transfer residual toner remaining on the photosensitive drum 11, and at this time, the charge amount Q of the discharged transfer residual toner.
Is correlated with ΔV.

In general, the relationship between the charge amount and the potential is expressed by the equation of Q = C × V = (εS / d) × V. Here, ε is the relative dielectric constant of the toner layer, S is the area of the toner layer, and d is the toner layer thickness.

From this equation, Q / S is expressed as Q / S = (ε / d) × V, but in reality, since the charging roller 12 regulates the layer thickness of the discharged toner, the discharged toner layer thickness largely changes. In addition, since the relative dielectric constant of the toner layer may be measured in advance and the numerical value recorded in the storage device of the CPU of the image forming apparatus main body may be used, ε and d can be treated as substantially constant constants.

From the above process, the charge amount Q per unit area
By calculating / S and dividing Q / M by the aforementioned M / S, the charge amount Q / M of the toner particles per unit weight can be calculated.

The photosensitive drum 11 with respect to the calculated Q / M
The difference between the potential of the white background and the potential of the developing roller 14a is adjusted.

<Potential Difference Control Method> In this embodiment, since the actual charge amount of the discharged transfer residual toner can be measured, the developing bias can be finely changed according to the table shown in FIG. 7, which is more efficient. Control becomes possible. At this time, in the same manner, the light amount of the exposure device 13 that writes the electrostatic latent image in accordance with the developing bias is also changed so that the same developing contrast can be obtained.

FIG. 7 shows the fog and density when an image is output by the image forming apparatus to which this embodiment is applied. The fog level was evaluated according to the same criteria as in the first embodiment.

As shown in FIG. 7, even when the discharge transfer residual toner charge amount changes, the discharge transfer residual toner recoverability is good and the fog level does not deteriorate.

As described above, the toner amount detection sensor 2
1 and the potential sensor 22 to detect and calculate the discharge transfer residual toner charge amount, and Vdc is changed according to the toner charge amount to control the recovery potential difference Vback, so that unnecessary bias and exposure amount can be obtained. Fogging due to defective discharge toner collection when the discharge transfer residual toner amount increases can be prevented without using.

In this embodiment, since the discharge transfer residual toner charge amount with higher accuracy can be detected, the developing bias can be finely changed, and more efficient collection control can be performed. Even if the amount changes, it becomes possible to provide a sufficient recovery capacity.

<Third Embodiment> In the present embodiment, as in the first embodiment, the discharge transfer residual toner charge amount is obtained from the humidity and the detection result of dirt on the charging roller 12, and the charge is performed according to the charge amount. The voltage applied to the roller 12 is controlled to change the solid white portion potential of the photosensitive drum 11. By changing the solid white part potential, the Vback potential difference can be changed, and the toner recoverability can be controlled.

<Method for Detecting Discharge Transfer Residual Toner Charging Amount>
Since it is the same as that of the first embodiment, it is omitted.

<Potential Difference Control Method> The charging roller 1 controls the potential difference Vback that contributes to the recovery of the discharged transfer residual toner.
This is carried out by changing the bias applied to 2. FIG. 8 shows the potential control setting conditions in this embodiment.

In the above setting, the humidity is 5% (temperature 23
C.), 50% (temperature 25.degree. C.), 80% (temperature 30.degree. C.), the images were confirmed to be confirmed, and as shown in FIG. Even when a high-density image was output under each environment, there was no deterioration of fog due to defective collection of discharged transfer residual toner, and stable image output performance was confirmed.

As described above, the image output environment and the charge imparting ability to the discharge transfer residual toner are detected, the charge amount of the discharge transfer residual toner is calculated from the detection result, and the non-image of the photosensitive drum 11 is determined according to the charge amount. The control of the potential difference Vback required to collect the discharged transfer residual toner on the sheet is changed by changing the voltage applied to the charging roller 12 to change the value of the potential VD of the photosensitive drum 11, so that a bias more than necessary can be obtained. It is possible to prevent image defects due to defective recovery of the discharged transfer residual toner without applying the voltage.

In the above description, the case where the image forming apparatus according to the present invention is a monochromatic electrophotographic image forming apparatus has been described as an example. However, the present invention is not limited to this, and an image of a plurality of colors is formed. The present invention can be applied to various color image forming apparatuses. In this case, an intermediate transfer body (intermediate transfer belt or intermediate transfer drum) is used as the other member instead of the above-mentioned transfer material.

Furthermore, the present invention can be applied not only to the electrophotographic system but also to an electrostatic recording system image forming apparatus. In this case, instead of the charging roller (charging means) 12 and the exposure device (exposure means) 13, the electrostatic latent image is recorded (formed) directly on the surface of the image carrier.

[0098]

As described above, according to the present invention,
By detecting the charge amount of transfer residual toner and controlling the fog removal potential difference in the developing area according to the toner charge amount, it is possible to prevent fogging due to poor transfer residual toner collection and reduction of image density during durable output at the same time. .

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a schematic configuration of an image forming apparatus according to a first embodiment.

FIG. 2 is a vertical sectional view showing a schematic configuration of an image forming apparatus according to a second embodiment.

FIG. 3 is a diagram showing definitions of circularity and average circularity.

FIG. 4 is a diagram showing a relationship among humidity, a charging roller, and a discharging transfer residual toner residual charge level.

FIG. 5 is a diagram showing a drum potential setting change value with respect to a charge amount level.

FIG. 6 is a diagram showing a relationship between the discharge transfer residual toner charge amount and the image quality in the first embodiment and the conventional example.

FIG. 7 is a diagram showing the relationship between the discharged transfer residual toner and the image quality according to the second embodiment.

FIG. 8 is a diagram showing a potential control value in the third embodiment.

FIG. 9 is a diagram showing the relationship between the discharge transfer residual toner charge amount and the image quality in the third embodiment and the conventional example.

FIG. 10 is a vertical sectional view showing a schematic configuration of a conventional image forming apparatus.

[Explanation of symbols]

11 image carrier (photosensitive drum) 12 charging means (conductive member, charging roller) 13 exposure means (exposure device) 14 developing means (developing device) 15 transfer means (transfer charger) 20 transfer residual toner charge amount detection means ( Charge roller dirt sensor) 21 Transfer residual toner charge amount detection means (toner amount detection sensor) 22 Transfer residual toner charge amount detection means (potential sensor) P Other member (transfer material)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 15/00 303 G03G 15/06 101 2H134 15/02 101 21/00 2H200 15/06 101 15/08 507B 21/00 9/08 101 F term (reference) 2H005 AA08 AA15 EA02 EA10 FA06 2H027 DA02 DA14 DA50 DE05 DE07 EA01 EA05 EC06 EC19 2H068 CA03 DA12 DA21 2H073 AA03 AA09 BA04 BA13 BA25 CA02 CA14 2H077 AA37 AC01 AB16 AB14 AB02 AD31 AD36 DA01 DA18 DA57 DB08 EA13 EA16 GA03 2H134 GA01 GB02 HF13 JA11 KG03 KH01 MA04 2H200 FA02 GA23 GA34 GA44 GA56 GB37 HA02 HA21 HA28 HB12 HB22 HB45 HB46 JA02 MA03 MA05 MA08 MA13 MA14 MA20 MB06

Claims (16)

[Claims] 1. The surface of the image bearing member is charged by a charging means,
The electrostatic latent image is formed by exposing the surface of the image carrier after charging with an exposing unit, and toner is attached to the electrostatic latent image by a developing unit to develop it as a toner image, and the toner image is transferred by a transferring unit. In the image forming method, the transfer residual toner remaining on the surface of the image carrier without being transferred to the other member at the time of transfer is collected by the developing means. Detected by the amount detecting unit, and based on the detection result of the transfer residual toner charge amount detecting unit, at least one of the developing bias of the developing unit and the surface potential of the image carrier is controlled by the control unit. And an image forming method. 2. The image forming method according to claim 1, wherein the charge amount of the transfer residual toner is obtained by determining a potential on the image carrier by a potential sensor. 3. The image forming method according to claim 1, wherein the charge amount of the transfer residual toner is obtained by measuring humidity during image formation and detecting the humidity. 4. The image forming method according to claim 1, wherein the charge amount of the transfer residual toner is obtained from the detection result of the residual toner stain degree of the charging unit. 5. When controlling at least one of the developing bias and the surface potential of the image carrier, at least one of the frequency or the waveform of the developing bias AC component is controlled at the same time. The image forming method according to claim 1. 6. The charging means includes a conductive member and conductive particles carried on the surface of the conductive member, and a charging bias is applied to the conductive member to generate a discharge through the conductive particles. The image forming method according to claim 1, wherein the surface of the image bearing member is charged without being charged. 7. The image carrier comprises a photoconductive layer formed of a non-single-crystal material having a silicon atom as a base on a conductive substrate, and a surface layer made of a non-single-crystal material having a carbon atom as a base. The image forming method according to claim 1, comprising: 8. The magnetic toner, which is composed of toner particles containing at least a binder resin and a magnetic substance and an inorganic fine powder, has an average circularity of 0.950 or more, and is 79.6 kA of the magnetic toner. / M (1000 Oersted)
Saturation magnetization under 10 Am ² / kg (emu / g)
The image forming method according to claim 1, wherein the image forming method is 50 Am ² / kg or less. 9. An image carrier, a charging unit for charging the surface of the image carrier, an exposing unit for exposing the surface of the image carrier after charging to form an electrostatic latent image, and the electrostatic latent image. A transfer unit that transfers the toner image to another member by attaching a toner to the member and develops it as a toner image, and the transfer residue remaining on the surface of the image carrier without being transferred to the other member during transfer. In an image forming apparatus that collects toner by the developing unit, the transfer residual toner charge amount detecting unit that detects the charge amount of the transfer residual toner, and the developing unit based on the detection result of the transfer residual toner charge amount detecting unit. Control means for controlling at least one of the developing bias and the surface potential of the image carrier,
An image forming apparatus comprising: 10. The transfer residual toner charge amount detection means comprises:
The image forming apparatus according to claim 9, further comprising a potential sensor that detects a potential on the image carrier. 11. The transfer residual toner charge amount detection means comprises:
The image forming apparatus according to claim 9, further comprising a humidity sensor that measures humidity during image formation. 12. The transfer residual toner charge amount detection means comprises:
The image forming apparatus according to claim 9, further comprising a dirt detection sensor that detects a degree of dirt of the residual toner on the charging unit. 13. When controlling at least one of the developing bias and the surface potential of the image carrier, at least one of the frequency and the waveform of the developing bias AC component is controlled at the same time. The image forming apparatus according to claim 9. 14. The charging means includes a conductive member and conductive particles carried on the surface of the conductive member, and a charging bias is applied to the conductive member to generate a discharge through the conductive particles. The image forming apparatus according to claim 9, wherein the surface of the image bearing member is charged without being charged. 15. The image carrier comprises a photoconductive layer formed of a non-single-crystal material having a silicon atom as a base on a conductive substrate, and a surface layer made of a non-single-crystal material having a carbon atom as a base. The image forming apparatus according to claim 9, wherein the image forming apparatus comprises: 16. The toner is composed of toner particles containing at least a binder resin and a magnetic material, and an inorganic fine powder,
A magnetic toner having an average circularity of 0.950 or more, and the saturation magnetization of the magnetic toner at 79.6 kA / m (1000 Oersted) is 10 Am ² / kg (emu /
The image forming apparatus according to claim 9, wherein g) is 50 Am ² / kg or less.