JP2001188454A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a photoreceptor drum from being defectively electrified and to prevent an electrifying member from being soiled at a restarting time after jam processing is executed in an image forming device for a simultaneous developing and cleaning system. SOLUTION: When the image forming device is started again after the jam processing is executed because jam is caused, bias whose polarity is identical to the electrifying polarity of toner and which is equal to or under a discharge threshold value is applied to an electrifying roller 2 in prescribed time. Thereafter, bias whose polarity is identical to the electrifying polarity of the toner and which is equal to or over the discharge threshold value is applied to the roller 2. Thus, since the bias pressing the untransfer toner to the photoreceptor drum 1 side from the roller 2 side can be applied to the untransfer toner even when large amount of untransfer toner on the drum 1 rushes in the roller 2, the toner can be excellently recovered by a developing unit 4. Besides, the drum 1 is prevented from being defectively electrified and the roller 2 is prevented from being soiled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine, a laser printer, and a facsimile.

[0002]

2. Description of the Related Art Conventionally, in a developing device for developing with a one-component developer, a developing roller for developing a toner image by attaching toner to an electrostatic latent image formed on a photosensitive drum (image carrier) is developed. Depending on whether the (developer bearing member) is in contact with or not in contact with the photosensitive drum, a distinction is made between a contact developing device and a non-contact developing device.

[0003] Among the contact developing devices, in recent years, a developing roller in which toner (developer) remaining on the photosensitive drum in the transfer process is arranged in contact with the photosensitive drum without providing a cleaning device in order to save energy and reduce running costs. A so-called simultaneous development cleaning system in which development is performed while collecting images at a time, has attracted attention.

FIG. 8 shows a schematic configuration of an image forming apparatus of a conventional simultaneous cleaning with developing method in contact development using a non-magnetic one-component toner.

As shown in FIG. 1, a conventional image forming apparatus of this type includes a charging brush (primary charger) 10 around a photosensitive drum (image carrier) 101 rotating in the direction of arrow X in FIG.
2, an exposure unit 103, a development unit 104, and a transfer roller (transfer charger) 105 are provided. Further, a fixing device 107 is provided on the downstream side of the transfer roller 105 along the transfer direction of the transfer material P (the direction of the arrow Kp).

A developing device 104 is arranged in contact with the photosensitive drum 101 and performs development while rotating in the direction of arrow Y, and supplies non-magnetic toner T to the developing roller 108 by rotating in the direction of arrow Z. Roller (developer supply means) 109, toner T on developing roller 108
Regulating blade (developer regulating means) 110 for regulating the application amount and charge amount of the toner, a stirring member 11 for supplying the toner T to the supply roller 109 and stirring the non-magnetic one-component toner
1 and the like. The toner T is a negatively charged toner, and so-called reversal development is performed in which the toner T is attached to an exposed portion.

Next, the image forming operation of the above-described image forming apparatus will be described.

An external print signal (image forming signal)
As a result, the photosensitive drum 101 starts rotating in the arrow X direction.
First, the surface of the photosensitive drum 101 is uniformly charged by the charging brush 102. The charging brush 102 has a brush shape, and is rotated in a direction of an arrow W by a driving unit (not shown). Next, an electrostatic latent image is formed on the photosensitive drum 101 by the exposure L by the exposure device 103, and the electrostatic latent image reaches a contact portion with the developing device 104 by rotation of the photosensitive drum 101.

The developing device 104 performs the following operation in conjunction with the above operation.

The toner T stirred by the stirring member 111
Is supplied onto the developing roller 108 by sliding friction between the supply roller 109 rotating in the arrow Z direction and the developing roller 108 rotating in the arrow Y direction. The toner T on the developing roller 108 is provided with a desired amount of charge by the regulating blade 110 and the amount of toner (layer thickness) is regulated, and is carried on the developing roller 108. The toner in the developing device 104 is stirred by the stirring member 111, and
9 is conveyed.

The toner T carried on the developing roller 108
Reaches a position in contact with the photosensitive drum 101, a DC developing bias is applied to the developing roller 108 by a power supply (not shown). Thus, the electrostatic latent image formed on the surface of the photosensitive drum 101 is developed (visualized) as a toner image by attaching the toner T carried on the surface of the developing roller 108. At this time, the toner remaining on the surface of the developing roller 108 without contributing to the development is collected into the developing device 104 via the supply roller 109.

In a contact developing device using a rigid photosensitive drum 101 and performing simultaneous development and cleaning by contact with a developing roller 108, the developing roller 108 is preferably a roller having an elastic body formed in a roller shape. As the elastic body, a solid rubber single layer or a solid rubber coated with a resin in consideration of the charging property to the toner is used.

In order to perform the contact development, in addition to the method of bringing the elastic developing roller 108 into contact with the rigid photosensitive drum 101, a rigid developing roller is used for a belt-shaped photosensitive belt. There are ways.

The toner on the photosensitive drum 101 reaches the opposite portion of the transfer roller 105 by the rotation of the photosensitive drum 101, and is transferred onto the transfer material P by the transfer roller 105.
The transfer material P after the transfer of the toner image is conveyed in the direction of the arrow Kp, and the toner image on the surface is melted and fixed by the fixing device 107, and then discharged out of the image forming apparatus main body.

On the other hand, the toner T (residual toner) remaining on the photosensitive drum 101 without being transferred onto the transfer material P at the time of transfer.
Passes through the charging brush 102 and reaches a contact portion with the developing roller 108. At this time, the toner is collected by the developing roller 108 by the DC developing bias applied to the developing roller 108, and the collected toner is used for development at the next image formation.

By repeating the above operation, the image formation by the simultaneous development and cleaning method is repeated.

FIG. 9 is a relative comparison diagram showing set potentials at the time of image formation in each device section in the simultaneous development cleaning method. As is clear from the figure, the set potential of each device is set as follows.

V_D<V_DC<V_L<0 <V_T  Where V_D: Charged potential on photosensitive drum surface, V_DC: Bias potential of the developing unit, V_L: The part of the photosensitive drum surface exposed by the exposure unit
Min potential, 0: Zero potential V_T: Potential of photosensitive drum surface after transfer charge elimination, development is "V_DC~ V_LIs performed by the potential difference
The photo is "V_L~ V_TIs performed by the potential difference of

[0019] Even in such a case, residual toner is generated, and the residual toner is removed as described above.

FIG. 10 is a time chart showing a printing sequence in a conventional cleanerless image forming apparatus. In the figure, the vertical axis indicates the voltage in the negative direction, and the horizontal axis indicates the elapsed time. The two-dot chain line indicates the movement of the same point on the photosensitive drum 101. For example, at time _t01 , the photosensitive drum 1
The point on 01 that faces the charging brush 102 indicates that it has reached the position facing the developing roller 108 at time t _{0 1} ′.

According to this time chart, the time t ₀₁
At the same time, the motor is turned on to rotate the photosensitive drum 101, and at the same time, the primary charger, the developing device, and the transfer charger are turned on.

The charge bias is a value obtained by adding a discharge threshold charge potential V _D, for example, the photosensitive drum 101 surface -
If it is desired to charge to 700V, a voltage of about -1300V is applied.

As the developing bias, a positive voltage is applied at time _t01 , and when the uniformly charged surface of the photosensitive drum 101 reaches the developing section, the developing bias during image formation is applied (time _t01). ').

The transfer bias, negative voltage is applied to the time _{t 01.} This is to discharge toner stains and the like in the previous image formation.

At time _t02 , the development of the image signal and the like is completed, and the temperature adjustment of the fixing device 107 and the like is completed, and the printer is ready for printing. Then, the photosensitive drum 101 is exposed to an image according to the image signal. Further, time t ₀₂ ″
Then, the toner image generated on the photosensitive drum 101 is transferred onto a transfer material P such as paper.

At time t ₀₃ , when the image formation is completed, the transfer bias is switched at time t ₀₃ ″, and at time t ₀₄ , the transfer material P passes through the fixing device 107 and is discharged outside the image forming apparatus main body. The rotation of the drum (rotation of the photosensitive drum) and each bias are stopped.

[0027]

However, in the image forming apparatus of the simultaneous cleaning system shown in the above-mentioned prior art, the main body of the image forming apparatus is forcibly stopped during image formation due to a so-called "jam (paper jam)" or the like. In such a case, a large amount of toner remains on the photosensitive drum 101 without being transferred to the transfer material P, causing the following problem. When an image defect occurs due to insufficient charging potential and an image forming operation is interrupted, a large amount of toner remains on the photosensitive drum 101 without being transferred onto the transfer material P. The user performs the processing of the transfer material P left in the image forming apparatus body, enters the preparatory operation for image formation after processing (time t ₀₁ ~ of Figure 10
Time t ₀₂ ).

Therefore, when the image forming operation is started again in this state after the jam is cleared, the charging brush 10
A large amount of untransferred toner enters the area 2. Although the toner is diffused to some extent due to the effect of the charging brush 102, for example, when a vertical band image is jammed,
The amount of toner that enters the charging brush at the longitudinal position of the charging brush 102 differs. As a result, the surface where the toner does not enter can charge the surface of the photosensitive drum 101 to a desired potential, but if a large amount of toner enters, the surface of the photosensitive drum 101 cannot be charged to the desired potential. The potential of the surface of the photosensitive drum 101 that cannot be charged is
When the _voltage becomes close to or below _{VDC in} FIG. 9, the toner carried on the developing roller 108
An electric field is created which is energized in the direction. The developing roller 1 is further provided on the portion of the photosensitive drum 101 where toner has not been charged to a desired potential due to the adhesion of the toner by the electric field.
08, the toner is supplied. As a result, the newly supplied toner stains the transfer roller 105 and the charging brush 102, and the image cannot be formed. Similarly to the case of the charger contamination, if the image forming operation is started again in this state after the jam is eliminated, a large amount of untransferred toner enters the charging brush 102. A large amount of non-transferred toner adheres and stays in the charging brush 102. As a result, the dispersion effect of the residual toner is reduced, and the charging / exposure cannot be performed satisfactorily.

Further, the toner adhered to the charging brush 102 solidifies on the charging brush 102 with the passage of time and does not easily come off, and the adhered toner is removed during the preparatory rotation operation before the start of the next image forming process. Otherwise, the surface of the photosensitive drum 101 may not be uniformly charged.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image forming apparatus in which even if a jam occurs, the quality of an image on a subsequent transfer material does not deteriorate. Is what you do.

[0031]

According to a first aspect of the present invention, there is provided a charging apparatus for uniformly charging the surface of an image carrier by a charging member in contact with the surface of the image carrier. Means, an exposing means for exposing the charged image carrier surface according to image information to form an electrostatic latent image, and a developing means for adhering toner to the electrostatic latent image and developing it as a toner image A transfer unit for transferring a toner image on the image carrier onto a transfer material, wherein the residual toner on the image carrier is passed through the charging member and collected by the developing unit. A charging bias power source for applying a charging bias to a charging member, charging the surface of the image carrier by discharging between the charging member and the image carrier, and control means for controlling the charging bias power source, The control means may be an image type Upon restarting after the operation is stopped halfway, after applying a bias having the same polarity as the toner charging polarity and a discharge threshold or less to the charging member by the charging bias power source for a predetermined time, the charging polarity of the toner is A bias having the same polarity and being equal to or greater than a discharge threshold is applied.

According to a second aspect of the present invention, in the image forming apparatus of the first aspect, a position where the toner image on the image carrier is transferred to the transfer material is a transfer position, and the surface of the image carrier is When the position charged by the transfer member is a charging position, on the image carrier, downstream of the transfer position and upstream of the charging position, along the moving direction of the surface of the image carrier. And a toner flyer for scattering the toner.

According to a third aspect of the present invention, in the image forming apparatus of the first or second aspect, the charging member is a cylindrical charging roller, and the coefficient of dynamic friction at the outermost surface is 0.0.
1 to 0.4.

The present invention according to claim 4 is based on claims 1, 2,
Or the image forming apparatus according to 3, wherein the toner is a toner for developing an electrostatic latent image containing at least a binder resin, a colorant, and a wax component, and in observation of a tomographic plane of the toner particles using a transmission electron microscope, The wax component is contained in the toner particles in a state in which the wax component is not compatible with the binder resin and is substantially spherical and / or spindle-shaped islands.

The present invention according to claim 5 is based on claims 1, 2,
In the image forming apparatus of 3 or 4, the shape factor SF1 of the toner measured by the image analyzer is 100 to 160.
And the shape factor SF2 is 100 to 140.

[0036]

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

<First Embodiment> FIG. 1 is a diagram showing a control sequence when the image forming apparatus according to the first embodiment is used. The control sequence will be described later in detail.

According to the present invention, in an image forming apparatus of a simultaneous development and cleaning system using a contact charging member, when the jam (paper jam) is recovered (restarted), the charging member discharges the same polarity as the toner for a predetermined period. In addition to applying a bias equal to or less than the threshold, a bias equal to or less than the discharge threshold having a polarity opposite to that of the toner is applied to the developing member for a predetermined period. Even if a large amount of untransferred toner (residual toner) enters the charging member at the time of recovery from a jam, defective charging and charging of the photosensitive drum can be performed by applying a bias to bias the untransferred toner toward the photosensitive drum. This is to prevent the members from being stained and to collect the toner in the developing device.

FIG. 2 shows an example of the image forming apparatus according to the present invention. The image forming apparatus shown in FIG. 1 is an image forming apparatus (for example, a copying machine or a laser beam printer) of a simultaneous development and cleaning system, and FIG.

First, a schematic configuration and an overall operation of the entire image forming apparatus will be described.

The image forming apparatus shown in FIG. 1 includes a drum type electrophotographic photosensitive member (hereinafter, referred to as "photosensitive drum") 1 as an image carrier. Around the photosensitive drum 1, a charging roller (primary charger) 2 as a charging unit, an exposing unit 3 as an exposing unit, and a developing unit ( A developing device) 4 and a transfer roller (transfer member) 5 as transfer means are provided, and on the downstream side of the transfer roller 5 along the transport direction (arrow Kp direction) of the transfer material P such as paper. Is provided with a fixing device 7 as fixing means. In the image forming apparatus shown in FIG. 1, toner (residual toner) remaining on the surface of the photosensitive drum 1 without being transferred onto the transfer material P at the time of transfer passes through the charging roller 2 and is collected by the developing device 4.

As shown in FIG. 2, the charging roller 2 uniformly charges the photosensitive drum 1 rotating in the direction of the arrow X to a predetermined polarity and a predetermined potential while rotating in the direction of the arrow W. Then, laser or LE is applied to the surface of the charged photosensitive drum 1.
Exposure L based on the information signal is performed by the exposure device 3 having the D light emitting element to form an electrostatic latent image. The electrostatic latent image is developed (visualized) as a toner image by attaching toner to the developing device 4. This toner image is transferred by the transfer roller 5 to the transfer material P conveyed by a feeding / conveying means (not shown). Transfer material P after toner image transfer
Is transported to a fixing device 7 where the toner is heated and pressed to fix the toner on the surface. On the other hand, on the photosensitive drum 1 after the transfer of the toner image, the residual toner remaining on the surface without being transferred onto the transfer material P passes through the charging roller 2 and is collected by the developing roller 8 of the developing device 4.

The description of the outline of the configuration and operation of the image forming apparatus has been completed. Then, each member etc. are explained in full detail.

The photosensitive drum 1 shown in FIG. 2, in the direction of arrow X by a driving means (not shown), is rotated at a peripheral speed V _X. In the present embodiment, and the _{V X} and 48 mm / sec.

The charging roller 2 is a contact charging roller that contacts and charges the photosensitive drum 1 and is driven to rotate in the direction of arrow W at the same speed as the photosensitive drum 1. A charging bias power supply 12 is connected to the charging roller 2 so as to uniformly charge the surface of the photosensitive drum 1. The charging bias power supply 12
During the image forming operation, approximately -1300 V is applied to the charging roller 2 to uniformly charge the surface of the photosensitive drum 1 to approximately -700 V.

The charging roller 2 used in this embodiment is
A low-resistance conductive rubber layer 2 having a thickness of 3 mm and a volume resistivity of about 10 ⁴ Ω · cm on the outer peripheral surface of a conductive metal core 2a having a diameter of 6 mm.
b, and a high-resistance layer 2c having a thickness of 20 to 50 μm and a volume resistivity of about 10 ⁸ Ω · cm is formed on the outer peripheral surface thereof.

Next, the light emitting element (laser or LE
D), the surface of the photosensitive drum 1 is exposed and scanned according to the information signal to form an electrostatic latent image. In the present embodiment, a so-called reversal developing system for forming a toner image by attaching negatively charged toner to an exposed portion on the photosensitive drum 1 will be described, but the present invention is not limited to this.

The developing device 4 includes a developing container 4A for storing a non-magnetic one-component toner T (hereinafter, simply referred to as “toner T”). The developing container 4 </ b> A has an opening at a portion facing the photosensitive drum 1.
A developing roller (developer carrier) 8 is provided. Developing roller 8 is in contact with the photosensitive drum 1, rotates in an arrow Y direction at a peripheral velocity V _Y. The developing device 4 further includes a regulating blade 10 as a toner regulating member, a supply roller 9 rotating in the arrow Z direction, and a stirring member 11 for stirring the toner T. Here developing the peripheral velocity V _X of the photosensitive drum 1 roller 8
Relationship between the peripheral velocity _{V Y} of _{is V} X <V _Y. Circumferential speed V _Y of the developing roller 8 is set to 81 mm / sec.

In order to adhere the toner T contained in the developing container 4A to the developing roller 8, the toner T
And the developing roller 8 are rubbed, and charge must be applied. As the material of the supply roller 9, a known material such as urethane foam rubber or EPDM rubber is used. In this embodiment, the feed roller 9 made of foamed urethane rubber was rotated in the counter direction (arrow Z direction) at a peripheral velocity V _Z with respect to the rotation direction of the developing roller 8 (arrow Y). As the rotation speed, _VZ is 40 mm / sec. A supply bias power supply 15 is connected to the supply roller 9, and a DC voltage of about −460 V is applied to urge the negatively charged toner T from the supply roller 9 to the developing roller 8.

Next, the toner applied to the developing roller 8 by the supply roller 9 is regulated by the regulating blade 10 to regulate the toner amount and to apply a tribo by friction. The regulating blade 10 is a thin stainless steel plate (about 0.1 m thick).
m) is bent at a position of about 2 mm from the tip of the developing roller 8 in a direction opposite to the developing roller 8.
It is arranged so that it may bite into and touch it.

The developing roller 8 has a developing bias power source 1.
3 is connected, and the photosensitive drum 1 is grounded.
The developing bias power supply 13 is a negative DC power supply. In the present embodiment, a potential of −350 V is applied as a developing bias during image formation. The toner that is charged by the regulating blade 10 and carried on the developing roller 8 is supplied onto the photosensitive drum 1 by the above-described developing bias (−350 V) and adheres to the electrostatic latent image. Is developed as a toner image.

The toner image formed on the surface of the photosensitive drum 1 is transferred to the transfer material P. The transfer material P is supplied from a feeding / conveying device, for example, a sheet feeding cassette, a sheet feeding roller, a conveying roller,
The paper is supplied to a transfer section formed between the photosensitive drum 1 and the transfer roller 5 by a feeding / conveying device (both not shown) constituted by a resist roller and the like. The transfer material P is supplied to the transfer unit in such a manner as to be synchronized with the toner image on the surface of the photosensitive drum 1, and the toner image on the photosensitive drum 1 is transferred by the transfer roller 5. The transfer roller 5 is a roller-type transfer charger in the present embodiment, and a transfer bias power supply 14 is connected to the transfer roller 5. A voltage of about 1 to 4 kV is applied to the transfer roller 5 by the transfer bias power supply 14 at the time of image transfer.

The application timings of the above-described charging bias power supply 12, developing bias power supply 13, supply bias power supply 15, and transfer bias power supply 14 are controlled by a controller (control means) 16.

Further, a jam sensor 18 for monitoring the state of the transfer material P during image formation is provided, and the state is sent to the controller 16 one by one.

The rotation of the photosensitive drum 1, the charging roller 2, the developing roller 8, the transfer roller 5, and the fixing device 7 is performed by connecting a gear from a main motor 17.

The transfer material P on which the toner image has been transferred is supplied to the fixing device 7.
Is fused by heat.

The residual toner remaining on the photosensitive drum 1 without being transferred onto the transfer material P by the transfer roller 5 is charged by the charging roller 2
And is collected by the developing roller 8.

The photosensitive drum 1, the charging roller 2, and the developing device 4 are integrated into a cartridge container (not shown) to constitute a process cartridge 6. The process cartridge 6 is detachably mounted on the image forming apparatus main body.

Next, with reference to FIGS. 1 and 3, a recovery operation in the event of a jam, which is a feature of the present invention, will be described.

FIG. 1 is a diagram showing a recovery sequence at the time of a jam in the image forming apparatus according to the present embodiment.

FIG. 3 shows a flowchart in image formation. Here, charging, development, and transfer indicate the applied bias in each. And it has a negative polarity in the upward direction. The horizontal axis indicates the passage of time. A two-dot chain line covering charging, development, and transfer indicates the same position on the photosensitive drum 1. The time t time t ₁₁ when came to a position facing the developing roller 8 after the position of the nip portion to a photosensitive drum surface of the charging roller 2 is the elapsed time at _{11 ',} in same time t ₁₁ and the charging roller 2 The time t ₁₁ ″ is set when the position of the surface of the photosensitive drum in the nip portion comes to a position facing the transfer roller 5 after a lapse of time.

First, an image signal is input to the image forming apparatus from a computer or the like (not shown) (step 1; hereinafter, described as “S1”), and the main motor 1 is turned on.
7, the photosensitive drum 1 starts rotating (time t).
₁₁ ). At the same time, a charging bias (−13) is applied to the charging roller 2 from the charging bias power supply 12 in the same manner as during image formation.
00V) is applied. Preparation rotation before the image formation during the time t ₁₁ the time t ₁₂ (hereinafter referred to as "pre-rotation".), And performs the start-up or the like of the temperature adjustment and laser scanner of the fixing device 7 during this time (S2).

In the developing bias power supply 13, the time t
_{At 11} , approximately +100 V is applied to the developing roller 8. This is because the surface potential may be near zero due to dark decay of the photosensitive drum 1 between the charging roller 2 and the developing roller 8, and if the surface potential is zero and a developing bias of 0V is applied, the developing roller 8 This is because the upper toner may be developed.

At time t ₁₁ ′, −350 V is applied from the developing bias power supply 13. At this time, since the surface of the photosensitive drum 1 is already charged to about -700 V, the toner carried on the developing roller 8 is not developed.

Then, a negative bias is applied to the transfer roller 5 as a cleaning bias. This bias is about -400 V, and is performed to remove toner contamination on the transfer roller 5.

[0066] When the time pre-rotation becomes _{t 12} is finished, the image formation is started from the time _{t 12} (S3). That is, the photosensitive drum 1 in accordance with the time t ₁₂ after the image signal
The surface is exposed and an image is formed as described above.

[0067] In this embodiment, at time _{t 13,}
The image forming operation is forcibly stopped by the jam sensor 18 in FIG. 2 (S4). Due to this forced stop, the voltage output of each power supply of the charging bias, the developing bias and the transfer bias is turned off. Then, the user is notified of the jam.

The user inputs the process cartridge 6
Is once removed from the image forming apparatus main body, and the transfer material P is removed. At this time, the surface of the photosensitive drum 1 receives bright light (exposed with external light), so that the potential becomes substantially zero.

The process cart is newly installed in the image forming apparatus main body.
The ridge 6 is attached, and the cover of the image forming apparatus main body (not shown)
Is closed, and the jam recovery operation is executed (S6, time).
Interval t ₁₄). In the jam recovery operation, the charging bias power supply 1
2 to about -300 V (V in FIG. 3_D1) Bias
The voltage is applied to the electric roller 2 (S7).

When a large amount of toner left on the surface of the photosensitive drum 1 enters the charging roller 2, if a discharge electric field is formed as in the conventional example, the surface of the photosensitive drum 1 is not exposed by the toner layer. The surface of the photosensitive drum 1 cannot be charged to a desired potential, and the charging roller 2 becomes dirty. In particular, the photosensitive drum 1
It is considered that the upper toner is also affected by the discharge and the charge polarity of the toner is partially reversed.

Therefore, in the present invention, the toner layer on the surface of the photosensitive drum 1 is applied to the charging roller 2 by applying a bias to the charging roller 2 having the same polarity as the toner (negative electrode) and less than the discharge threshold value. When passing through the charging roller 2, an undischarged electric field is formed in the direction in which the negative toner is urged from the charging roller 2 toward the photosensitive drum 1. Since the toner is not discharged, most of the toner on the photosensitive drum 1 is negatively charged (because it is a toner on which an image is appropriately formed). The surface potential of the photosensitive drum 1 becomes substantially zero by receiving bright light.

Since the surface potential of the photosensitive drum 1 is about 0 V and −300 V is applied to the charging roller 2, the negative toner passing through the charging roller 2 is urged toward the photosensitive drum 1, and It can pass through the charging roller 2 without adhering.

The lower limit of the bias to be applied at this time is that the potential difference from the photosensitive drum 1 is 50 V or more, that is,
It is preferable to apply a voltage of −50 V or less to the charging roller 2. If the potential difference is 50 V or less, the electric field for urging the toner toward the photosensitive drum is weakened, and the toner may adhere to the charging roller 2.

In the present invention, the discharge threshold means a point at which the flowing current changes abruptly when the voltage applied to the charging roller 2 is gradually increased. Generally, the discharge threshold is about 600 V at normal temperature and normal humidity.

[0075] Then, the time _{t 14,} the recovery bias of about + 100 V in order to recover the negative GokuTadashi toner coming through the charging roller 2 _{(V DC1)} is applied as a developing bias. Since the surface potential of the photosensitive drum 1 is about 0 V and +100 V is applied as a developing bias, the negative positive toner is collected by the developing roller 8.

Further, at time t ₁₄ , a negative bias (V _T1 ) is applied to the transfer roller 5 as a cleaning bias. This bias is about -400V
This is performed to remove toner stains on the transfer roller 5.

[0077] from the jam recovery operation time _{t 14} time t
_{15 is} performed. Length from time t ₁₄ time t ₁₅ is preferably take the time necessary to the photosensitive drum 1 surface passes through charging position through the transfer position from the developing position.

[0078] The time _{t 15,} to exit the recovery operation (S
8) The pre-rotation operation starts (S2). A voltage of about -1300 V is applied to the charging roller 2 so that the surface of the photosensitive drum 1 is charged to -700 V in the same manner as in image formation. Time t ₁₅ ′
Is applied with a developing bias of -350V. Thereafter, the pre-rotation ends.

[0079] Then, the time _{t 17} from the time _{t 16} is imaged as described above is made (S3), the rotation step after the after image formation (S5) enters from the time _{t 17.} And time t
_{At 18} , the transfer material P is discharged to the outside of the image forming apparatus main body, and the post-rotation operation ends, so that all operations end.

In the image forming apparatus of the simultaneous cleaning type using the contact charging member (charging roller 2) as described above, a bias having the same polarity as the toner and a discharge threshold or less is applied to the charging member for a predetermined period during recovery from a jam. At the same time, by applying a bias to the developing member (developing roller 8) for a predetermined period that is equal to or less than a discharge threshold having a polarity opposite to that of the toner,
Even if a large amount of untransferred toner enters the charging member, a bias that urges the untransferred toner toward the photosensitive drum 1 can be applied to prevent poor charging of the photosensitive drum 1 and contamination of the charging member. Then, the toner can be collected in the developing device 4.

The following are preferred as each member and toner used in the present invention.

[Surface Properties of Charging Roller] As described above, the charging roller 2 is formed by attaching a conductive metal core 2a having a diameter of 6 mm (see FIG. 2) to a thickness of 3 mm and a volume resistivity of about 10 ⁴ Ω · cm. And a surface layer 2c of a high-resistance layer having a volume resistivity of about 10 ⁸ Ω · cm and a thickness of 20 to 50 μm is formed on the outer peripheral surface thereof.

As the material of the low-resistance conductive rubber layer 2b,
Commonly used rubbers such as silicone rubber, NBR (nitrile rubber), butyl rubber, natural rubber, acrylic rubber, butyl rubber, hydrin rubber and urethane rubber can be used.

As the material of the high-resistance surface layer 2c, urethane resin, silicone resin, polyamide resin, fluorine resin and the like can be used.

By reducing the surface roughness of the surface layer of the charging roller 2, there is an effect that toner adhesion to the charging roller 2 can be reduced. The surface roughness of the charging roller 2 is preferably 0.5 to 6 μm as a ten-point average roughness Rz. If the ten-point average roughness Rz is 0.5 μm or less, it is difficult to manufacture. If the ten-point average roughness Rz is 6 μm or more, the adhesion area of the untransferred toner becomes large, so that the untransferred toner easily mechanically adheres to the charging roller 2. Because. The ten-point average roughness Rz
Used the definition shown in JIS B0601, and used a surface roughness tester "SE-30H" (manufactured by Kosaka Laboratories) for the measurement.

Dynamic friction coefficient μ on the surface of charging roller 2
Has the effect of reducing toner adhesion to the charging roller 2. The dynamic friction coefficient μ in the surface layer of the charging roller 2 is preferably from 0.01 to 0.4. Preferably it is 0.02-0.4.
If the dynamic friction coefficient μ is 0.01 or less, it is difficult to manufacture the charging roller 2. Conversely, if the dynamic friction coefficient μ is 0.4 or more, the adhesion of untransferred toner to the charging roller 2 increases, which is not preferable.

The dynamic friction coefficient μ here is the dynamic friction coefficient μ of the surface of the charging roller 2 with respect to the stainless steel plate, measured by the following method. The dynamic friction coefficient μ was determined as shown in FIG. A weight W1 is loaded on one end, and a stainless steel thin plate 31 having a thickness of 0.03 mm connected to a digital force gauge 32 on the other end is set on the surface of the charging roller 2, and θ in FIG. Set. The digital force gauge 32 is adjusted to a value of 0 when no load is applied to neither the weight W1 nor the stainless steel plate 31. After the value of the digital force gauge 32 is stabilized, the charging roller 2 is rotated in the direction of arrow R in FIG. 4, and the sliding force between the charging roller 2 and the stainless steel plate 31 at this time is measured by the digital force gauge 32. I do. The measured value is obtained by sampling the analog output value from the digital force gauge 32 with a recorder at a frequency of 10 Hz, calculating the sampled data by the computer 33 according to the following equation (1), and further calculating the data for one rotation of the charging roller 2. The calculated values were averaged.

Μ = (1 / θ) · ln (F / W) (1) where μ: dynamic friction coefficient, θ: contact between the surface of the charging roller and the stainless steel plate in the entire circumference of the charging roller Angle (90
Degrees), W: Weight W1 (100 g) and weight of stainless steel sheet (5
g, including the thin plate supporting member), and F: a measured value of a digital force gauge.

In the present embodiment, the charging roller 2 has been described among the contact charging systems. However, the present invention is not limited to this. For example, a brush-shaped charging brush can be used as the charging member. .

[Toner] The toner used in the present embodiment is a non-magnetic one-component toner, and is a transmission electron microscope (TE).
In observation of the tomographic plane of the toner particles using M), it is preferable that the wax component is substantially spherical and / or spindle-shaped and dispersed in an island shape without being compatible with the binder resin. By dispersing the wax component as described above and encapsulating it in the toner, it is possible to prevent deterioration of the toner and contamination of the image forming apparatus, etc., so that good chargeability is maintained and excellent dot reproduction is achieved. It is possible to form a toner image for a long time. In addition, since the wax component acts efficiently during heating, low-temperature fixability and offset resistance are satisfied.

In the present embodiment, as a specific method for observing the tomographic plane of the toner particles, a method in which the toner particles are sufficiently dispersed in a room temperature-curable epoxy resin and the temperature is reduced to 40 ° C.
After curing for 2 days in an atmosphere of ° C, the resulting effect is combined with ruthenium tetroxide and, if necessary, osmium tetroxide, dyed, and then sliced using a microtome with diamond teeth. Are cut out, and the tomographic morphology of the toner particles is observed with a transmission electron microscope. In the present embodiment, it is preferable to use a ruthenium tetroxide dyeing method in order to give a contrast between materials by utilizing a slight difference in crystallinity between the wax component used and the resin constituting the outer shell.

FIGS. 5A and 5B show typical examples. In the toner particles used in this embodiment, it was observed that the wax component Ta was encapsulated by the outer shell resin (binder resin) Tb. In the DSC curve measured by the differential scanning calorimeter, the wax component Ta
Those having the maximum endothermic peak in the range of 0 to 130 ° C are used. By having the maximum endothermic peak in the above-mentioned temperature range, it greatly contributes to low-temperature fixing, and also effectively develops releasability. When the maximum endothermic peak is less than 40 ° C., the self-cohesive force of the wax component becomes weak, and as a result, the hot offset resistance deteriorates and the gloss becomes too high. On the other hand, if the maximum endothermic peak exceeds 130 ° C., the fixing temperature becomes high, and it becomes difficult to appropriately smooth the surface of the fixed image. Absent.
Further, when the toner is directly obtained by a polymerization method by performing granulation and polymerization in an aqueous medium, a high maximum endothermic peak temperature is not preferable because a problem such as precipitation of a wax component mainly occurs during granulation. .

The maximum endothermic peak temperature of the wax component Ta is measured according to “ASTM D3418-8”. For the measurement, for example, DSC-
7 is used. The temperature correction of the device detection unit uses the melting points of indium and zinc, and the heat quantity correction uses the heat of fusion of indium. An aluminum pan was used as a measurement sample, an empty pan was set as a control, the temperature was raised and lowered once to obtain a pre-history, and then the measurement was performed at a heating rate of 10 ° C./min. Specific examples of the wax component include paraffin wax, polyolefin wax, Fischer-Tropsch wax, amide wax, higher fatty acid, ester wax, derivatives thereof, and graft / block compounds thereof.

The toner used in the present invention preferably has a spherical shape. The reason is that the spherical shape reduces the contact surface with the charging roller 2 and thus reduces the amount of adhered toner. Further, the spherical surface acts as a spacer between the photosensitive drum 1 and the charging roller 2. Is effective against shaving.

The toner used in the present embodiment has a shape factor SF1 value of 100 to 160 measured by an image analyzer.
It is preferable that the value of the shape factor SF2 is 100 to 140, more preferably the value of the shape factor SF1 is 100 to 140, and the value of the shape factor SF2 is 100 to 120. Further, the above condition is satisfied and (SF
2) By setting the value of / (SF1) to 1.0 or less,
Not only the various characteristics of the toner, but also the matching with the image analyzer becomes very good.

The SF1 and SF2 indicating the above-mentioned shape factors are obtained by using FE-SEM (S-800) manufactured by Hitachi, Ltd.
A sample of 100 toner particles magnified 500 times is randomly sampled, and the image information is introduced into an image analyzer (Luzex3) manufactured by Nicole via an interface, analyzed, and calculated by the following equation. These values were defined as shape factors SF1 and SF2 in the present embodiment.

SF1 = ｛(MXLNG) ² / (ARE
A) {× (π / 4) × 100 SF2 = {(PERI) ² / (AREA)} × (1/4
π) × 100 where AREA: toner projection area, MXLNG: absolute maximum length, PERI: peripheral length.

The shape factor SF1 of the toner indicates the degree of roundness of the toner particles. 100 is a perfect spherical shape, and gradually changes from a spherical shape to an irregular shape as the numerical value increases. The shape factor SF2 indicates the degree of unevenness of the toner particles. 100 is the smoothest, and the unevenness of the toner surface becomes more remarkable as the numerical value increases.

When the shape factor SF1 exceeds 160, the shape of the toner becomes indefinite, so that the charge amount distribution of the toner becomes broad and the toner easily adheres to the charging roller 2 firmly.

In order to reduce the adhesion of the toner image to the charging roller 2, the shape factor SF2 of the toner particles should be 100 to 100.
140, and the value of (SF2) / (SF1) is preferably 1.0 or less. The shape factor SF2 of the toner particles is 14
If the value is larger than 0 and the value of (SF2) / (SF1) exceeds 1.0, the surface of the toner particles is not smooth, and the toner particles have many irregularities, and the amount of adhesion to the charging roller 2 is small. To increase.

The toner particles preferably have a weight average particle size of 10 μm or less (preferably 4 to 8 μm) and a coefficient of variation A in number distribution of 35% or less. Since the toner particles having a weight average particle diameter of less than 4 μm are apt to be charged up, they tend to firmly adhere to the charging roller 2 and are not preferable. When the weight average particle diameter of the toner particles exceeds 10 μm, fusion to the surface of the photosensitive drum 1 is likely to occur. When the coefficient of variation in the number distribution of toner particles exceeds 35%, the tendency is further enhanced. The particle size distribution of the toner particles can be measured by various methods. In the present embodiment, the measurement was performed using a Coulter counter.

For example, a Coulter Counter TA-II type (manufactured by Coulter Inc.) is used as a measuring device, and an interface (manufactured by Nikkaki) that outputs a number distribution and a volume distribution.
And a personal computer, and the electrolyte is 1
Adjust 1% NaCl aqueous solution using graded sodium chloride. For example, IS0T0NII (manufactured by Coulter Scientific Japan) can be used. As a measuring method, 0.1 to 5 ml of a surfactant (preferably an alkylbenzene sulfonate) is added as a dispersing agent to 100 to 150 ml of the above-mentioned electrolytic aqueous solution, and the measurement sample is further added to 2 to 20 ml.
Add mg. The electrolyte in which the sample is suspended is approximately 1
Dispersion treatment for ~ 3 minutes and the aforementioned Coulter counter T
The A-II type uses an aperture of, for example, 100 μm as an aperture, measures the particle size distribution of particles of 2 to 40 μm based on the number, and then calculates the value according to the present embodiment.

Coefficient of variation A in the number distribution of toner particles
Is calculated from the following equation.

A = (S / D ₁ ) × 100 In the formula, S indicates a standard deviation value in the number distribution of toner particles, and D ₁ indicates a number average particle diameter (μm) of the toner particles.

Further, as the toner particles used in the present embodiment, it is preferable to use a toner particle whose surface is coated with an external additive so that a desired charge amount is imparted to the toner. This is because, by coating with the external additive, the external additive functions as a spacer and prevents adhesion to the charging roller 2. In that sense, the external additive coverage on the toner surface is
It is preferably from 5 to 99%, more preferably from 10 to 99%.

The coverage of the external additive on the toner surface was determined by using FE-SEM (S-800) manufactured by Hitachi, Ltd.
00 samples are randomly sampled, and the image information is obtained via an interface using an image analyzer manufactured by Nicole (Luze).
x3). The resulting image information, since the brightness of the toner particle surface portions and the external additive portions are different, binarized, and the area of the area (external additive portion of the area S _G and the toner particles portion of the external additive portion (Included) _ST and calculated by the following equation.

External additive coverage (%) = ( _SG / _ST ) × 100 As the external additive used in the present embodiment, the toner particles are used in view of durability when added to the toner. The particle diameter is preferably 1/10 or less of the weight average diameter. The particle size of the additive means an average particle size obtained by observing the surface of the toner particles with an electron microscope. As the external additive, for example, the following are used.

Metal oxides (aluminum oxide, titanium oxide, strontium titanate, cerium oxide, magnesium oxide, chromium oxide, tin oxide, zinc oxide, etc.), nitrides (silicon nitride, etc.), carbides (silicon carbide, etc.)
Metal salts (calcium sulfate, barium sulfate, calcium carbonate, etc.), fatty acid metal salts (zinc stearate, calcium stearate, etc.), carbon black, silica, etc.

These external additives are used in an amount of 0.01 to 10 parts by weight, preferably 0.05 to 5 parts by weight, based on 100 parts by weight of the toner particles. These external additives may be used alone or in combination. Those subjected to a hydrophobic treatment are more preferable.

When the amount of the external additive is less than 0.01 parts by weight, the fluidity of the one-component developer deteriorates, the efficiency of transfer and development decreases, and unevenness in image density occurs. Or the toner scatters around the image portion, that is, so-called scatter occurs.

On the other hand, when the amount of the external additive exceeds 10 parts by weight, an excessive amount of the external additive adheres to the photosensitive drum 1 or the developing roller 8 to deteriorate the chargeability of the toner or disturb the image. Or

As described above, in the image forming apparatus of the simultaneous cleaning type using the contact charging member (charging roller 2), the bias is applied to the charging member for a predetermined period at the time of recovery from a jam and the discharge threshold is equal to or less than the discharge threshold of the same polarity as the toner. Is applied to the developing member (developing roller 8) for a predetermined period.
Even if a large amount of untransferred toner rushes into the charging member by applying a bias that is equal to or lower than the discharge threshold of the opposite polarity to the toner, a bias that urges the untransferred toner toward the photosensitive drum 1 can be applied. As a result, defective charging of the photosensitive drum 1 and contamination of the charging member can be prevented, and the toner can be collected in the developing device 4.

<Second Embodiment> A second embodiment will be described with reference to FIG. Note that members and the like having the same configurations and functions as those in the first embodiment are denoted by the same reference numerals and description thereof will be omitted.

In the present embodiment, a case where a toner flyer 19 as an auxiliary member is provided between the transfer roller and the charging roller for the purpose of preventing ghost during image formation will be described.

FIG. 6 is a schematic configuration diagram of an image forming apparatus according to the present embodiment. Reference numeral 19 in the figure indicates a toner flyer member. In the present embodiment, the toner flyer 19 is formed of a sponge roller, and rotates in the direction of arrow R19 with respect to the photosensitive drum 1 that rotates in the direction of arrow X. A flyer bias power supply 20 is connected to the toner flyer member 19. Flyer bias power supply 2
0, charging bias power supply 21, and developing bias power supply 2
The control such as 2 is performed by a controller (control means) 23.

FIG. 7 is a diagram showing a control sequence according to the present embodiment.

[0117] For displaying on the time axis, toner flyer member (flyer member) 19 for the time, the toner flyer member after the position over time of a surface of the photosensitive drum 1 in the nip between the charging roller 2 at time t ₂₁ when came to the position facing the 19 have a time t _{3 1.}

First, an image signal is input to the image forming apparatus from a computer or the like (not shown) and the main motor 1
7, the photosensitive drum 1 starts rotating (time t).
₁₂ ). At the same time, a charging bias (−13) is applied to the charging roller 2 from the charging bias power supply 21 in the same manner as during image formation.
00V) is applied. Time period from t ₂₁ time t ₂₂ is the image forming preparatory rotation, performs startup such temperature adjustment and laser scanner of the fixing device 7 during this time. At this time,
A negative bias is applied to the toner flyer 19 to discharge the toner.

In the developing bias power supply 22, the time t
_{At 21} , approximately +100 V is applied to the developing roller 8. This is because the surface potential may be near zero due to dark decay of the photosensitive drum 1 between the charging roller 2 and the developing roller 8, and if the surface potential is zero and a developing bias of 0V is applied, the developing roller 8 This is because the upper toner may be developed.

At time t ₂₁ ′, −350 V is applied from the developing bias power supply 22. At this time, since the surface of the photosensitive drum 1 is already charged to about -700 V, the developing roller 8
Is not developed.

A negative bias is applied to the transfer roller 5 as a cleaning bias. This bias is about -400 V, and is performed to remove toner contamination on the transfer roller 5. At this time, a negative bias (−300 V) is applied to the toner flyer 19 to discharge the toner. When the time is to _{t 31,}
The toner flyer 19 has a positive bias (+300
V) is applied to collect and fly the toner.

[0122] When the pre-rotation is the time _{t 22} and ends at the time the image formation is started from the time _{t 22.} That is exposed is the surface of the photosensitive drum 1 in accordance with the time t ₂₂ after the image signals, the image formation is performed as described above.

[0123] At time _{t 23,} the image forming operation is suspended by the jam sensor 18. Due to a forced stop,
The voltage output of each power supply of the charging bias, the developing bias, the transfer bias, and the toner flyer bias is turned off. Then, the user is notified of the jam.

The process cartridge 2 is set by the user.
4 is temporarily removed from the image forming apparatus main body, and the transfer material P is removed. At this time, since the surface of the photosensitive drum 1 receives bright light, the potential on the surface of the photosensitive drum 1 becomes almost zero.

The process cartridge 24 is mounted again on the main body of the image forming apparatus, the cover (not shown) of the image forming apparatus is closed, and the jam recovery operation is executed (time t).
₂₄ ). In the jam recovery operation, a bias of about −300 V is applied to the charging roller 2 from the charging bias power supply 21.

At the same time, a negative bias is applied to the toner flyer 19 to transfer the toner accumulated during image formation to the photosensitive drum 1. Toner flyer 1
After the transfer of the toner from No. 9 ends, the untransferred toner remaining on the photosensitive drum 1 reaches the charging roller 2 next.

Since the surface potential of the photosensitive drum 1 is about 0 V and −300 V is applied to the charging roller 2, the negative polarity toner passing through the charging roller 2 is urged toward the photosensitive drum 1, and Can pass through the charging roller 2 without adhering to the charging roller 2. In the present embodiment, the bias applied to the charging roller 2 is a constant voltage. However, it is also possible to detect the amount of untransferred toner adhered and increase or decrease the applied bias in accordance with the detection result. As a method of detecting the amount of untransferred toner attached, for example, a method of integrating the number of print pixels from a computer signal can be used.

[0128] Then, the time t _24, as the developing bias, the recovery bias of about + 100 V for recovering is applied a negative polarity toner coming through the charging roller 2. The surface potential of the photosensitive drum 1 is about 0 V, and +100 V is applied as a developing bias.
The untransferred toner on the photosensitive drum 1 is collected by the developing roller 8.

[0129] Further, the time t _24, negative bias is applied as the cleaning bias to the transfer roller 5. This bias is about -400 V, and is performed to remove toner contamination on the transfer roller 5.

[0130] jam recovery operation time _{t 24} from the time t
Up to ₂₅ . Length from time t ₂₄ time t ₂₅ is preferably take the time necessary to the photosensitive drum 1 surface passes through charging position through the transfer position from the developing position.

[0131] to time _{t 25,} quit the recovery operation, entering the pre-rotation operation. In order to charge the surface of the photosensitive drum 1 to −700 V in the same manner as in image formation, the charging roller 2
00V is applied. The time _{t 25} ', applying a -350V as the developing bias. A collection bias is applied to the toner flyer member 19, and the pre-rotation ends.

[0132] Then, the time _{t 27} from the time _{t 26} is imaged as described above is made (S3), the rotation step after the after image formation (S5) enters from the time _{t 27.} And time t
_{At 28} , the transfer material P is discharged to the outside of the image forming apparatus main body, and the post-rotation operation ends, so that all operations are ended.

In the image forming apparatus of the simultaneous development and cleaning method using the contact charging member as described above, a bias having the same polarity as the toner and a discharge threshold or less is applied to the charging member (charging roller 2) for a predetermined period during recovery from a jam. At the same time, a large amount of untransferred toner and toner collected by the toner flyer rush into the charging member by applying a bias to the developing member (developing roller 8) for a predetermined period and having a polarity equal to or lower than the discharge threshold of the toner. In this case, a bias that urges the untransferred toner toward the photosensitive drum 1 can be applied, preventing defective charging of the photosensitive drum and contamination of the charging member. It is possible to do.

[0134]

As described above, in the image forming apparatus of the simultaneous cleaning type using the charging member arranged in contact with the image bearing member, the toner is applied to the charging member at the time of restart after the jam processing. After applying a bias having the same polarity as the charging polarity and equal to or lower than the discharge threshold for a predetermined time, applying a bias equal to or higher than the charging threshold and dynamic polarity of the toner and equal to or higher than the discharge threshold allows a large amount of charging to the charging member via the image carrier. Even if untransferred toner enters, a bias can be applied to the untransferred toner to bias the untransferred toner from the charging member side to the image carrier side, thereby effectively preventing poor charging of the image carrier and contamination of the charging member. can do.

[Brief description of the drawings]

FIG. 1 is a diagram showing a control sequence according to the first embodiment.

FIG. 2 is a schematic configuration diagram of the image forming apparatus according to the first embodiment.

FIG. 3 is a flowchart when a jam occurs in the image forming apparatus according to the first embodiment;

FIG. 4 is a diagram illustrating a method for measuring a dynamic friction coefficient.

FIGS. 5A and 5B are cross-sectional views of toner particles used in the present invention.

FIG. 6 is a schematic configuration diagram of an image forming apparatus according to a second embodiment.

FIG. 7 is a diagram showing a control sequence according to the second embodiment.

FIG. 8 is a schematic configuration diagram of a conventional image forming apparatus.

FIG. 9 shows a charged potential (V _D ) of a photosensitive drum surface, a bias potential (V _DC ) of a developing device, a potential (V _L ) of a portion exposed by an exposure device, and a potential of a photosensitive drum surface (V _T ) after transfer erasing. FIG.

FIG. 10 is a diagram showing a conventional control sequence.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 image carrier (photosensitive drum) 2 charging means (charging member, charging roller) 3 exposure means (exposure device) 4 developing means (developing device) 5 transfer means (transfer roller) 12, 21 charging bias power supply 16, 23 control means (Control Controller) 19 Toner Flyer P Transfer Material Ta Wax Component Tb Binder Resin

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/24 G03G 21/00 372 2H078 21/00 15/08 507B 507L F term (Reference) 2H003 AA12 BB11 CC05 DD03 EE11 2H005 AA06 AA15 CA14 2H027 DA39 DC14 EA01 EA03 EA05 ED03 ED09 ED24 EE06 GB06 ZA07 2H034 AA06 BC09 BC10 2H077 AA37 AC04 AD02 AD06 AD13 AD35 DB08 DB12 EA14 EA15 GA17 2H078 DD15 DD15

Claims (5)

[Claims] A charging unit for uniformly charging the surface of the image carrier by a charging member disposed in contact with the surface of the image carrier;
Exposing means for exposing the charged surface of the image carrier according to image information to form an electrostatic latent image; developing means for adhering toner to the electrostatic latent image to develop as a toner image; and A transfer unit for transferring a toner image on a carrier onto a transfer material, wherein the residual toner on the image carrier is passed through the charging member and collected by the developing unit. A charging bias power source that applies a charging bias and charges the surface of the image carrier by discharging between the charging member and the image carrier; and a control unit that controls the charging bias power source; When the image forming operation is restarted after being stopped halfway, after applying a bias having the same polarity as the charging polarity of the toner and less than or equal to a discharge threshold to the charging member by the charging bias power source for a predetermined time, Applying a toner having the same polarity as the charging polarity in and discharge threshold or bias, the image forming apparatus characterized by. 2. When a position where the toner image on the image carrier is transferred to the transfer material is a transfer position, and a position where the surface of the image carrier is charged by the transfer member is a charging position, A toner flyer for scattering toner on the image carrier is provided downstream of the transfer position and upstream of the charging position along a moving direction of the surface of the image carrier. The image forming apparatus according to claim 1, wherein: 3. The image forming apparatus according to claim 1, wherein the charging member is a cylindrical charging roller, and has a coefficient of kinetic friction at the outermost surface of 0.01 to 0.4. . 4. The toner for developing an electrostatic latent image containing at least a binder resin, a colorant, and a wax component, wherein the toner component is obtained by observing a tomographic plane of toner particles using a transmission electron microscope. The image according to claim 1, wherein the toner particles are contained in the toner particles in a state of being incompatible with the binder resin and in a substantially spherical and / or spindle-shaped island shape. Forming equipment. 5. The shape factor SF1 of the toner measured by an image analyzer is 100 to 160, and the shape factor SF2 is
5. The image forming apparatus according to claim 1, wherein the number is 100 to 140. 6.