JP3223007B2 - Image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic apparatus.

[0002]

2. Description of the Related Art In an electrophotographic apparatus, there is a step of uniformly charging a photoreceptor, and the uniformity of the charge determines the uniformity of image density. It is very important in printing the image quality. Further, even if charging can be performed uniformly on one image, there is a problem that the charging potential changes and the image density changes due to the environment or repeated printing. In other words, the environment and the stability of charging for repeated printing are also very important in performing high-quality printing.

[0003] In recent years, scorotron charging devices having good charging uniformity and stability have been widely used. The scorotron charging device causes the photoconductor to become fatigued by repetition,
Even if the corona discharge becomes somewhat unstable due to the environment and contamination of the wire, it has a characteristic that the surface potential of the photoconductor is made equal to the potential of the grid. However, the scorotron charger uses corona discharge, and has a problem that a large amount of ozone is generated because an excess charging current flows. Increased concentrations of ozone in the air can harm the respiratory system of the human body.

On the other hand, a charging roller as disclosed in JP-A-63-168667 and a charging roller as disclosed in JP-A-62-2699 are disclosed.
No. 75 discloses a charging method that uses a contact charging device such as a brush charging and generates an extremely small amount of ozone. The charging roller has the same charging uniformity as a scorotron charging device, but has a problem that the structure is complicated, mechanical accuracy is required, and the price is high. On the other hand, the charging brush has the same price as the scorotron charging device, but is inferior to the scorotron charging device in charging uniformity, and has a problem that a halftone image is likely to generate streak images.

[0005] In contact charging of a charging roller, a charging brush, or the like, deterioration of charging performance due to aging of the charging member often becomes a problem. FIG. 2 shows the change over time of the charging potential of the brush charger. As is clear from FIG. 2, the surface potential changes near 150 V at the start of printing and two minutes after printing, and the image density changes greatly during that time, which is a problem.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of obtaining an image of good quality by stabilizing the charging potential on the surface of an image carrier. is there. Another object of the present invention is to provide a method of manufacturing a contact charging member which can obtain a good quality image by stabilizing the charging potential on the surface of the image carrier.

[0007]

Means for Solving the Problems The present invention (claim 1) provides:
Contact charging means for charging a rotatable image carrier surface; electrostatic latent image forming means for forming an electrostatic latent image on the charged image carrier; and developing the electrostatic latent image to form a developer image Developing means for rotating the image carrier for a predetermined time during non-image formation.
Causes said by contact charging means to charge the surface of the image bearing member, Zo担 and aging means to perform an aging operation, when the contact charging means the aging operation
Charging current for detecting the charging current for charging the surface of the holding body
Detecting means, and the electric current detected by the charging current detecting means.
Current value is outside the specified reference current value range
When it is within the range, image formation is started from the aging operation.
Means for shifting to an operation .

Further, the present invention (claim 2) provides the image
In the forming apparatus (Claim 1), the contact charging unit or a unit including the contact charging unit is configured to be detachable, the mounting of the contact charging unit or the unit is performed, and the mounted contact charging unit or the unit is new. Detecting means for detecting whether or not the contact charging means or the unit attached by the detecting means is new, and further comprising means for performing an aging operation by the aging means. An image forming apparatus is provided.

Further, the present invention (claim 3) provides the above-mentioned image
The image forming apparatus according to claim 1 , further comprising means for changing a developing bias applied to the developing means in accordance with a current value detected by the charging current detecting means. .

[0010]

[0011]

[0012]

The image forming apparatus according to the present invention rotates the image carrier for a predetermined time during non-image formation and charges the surface of the image carrier by the contact charging means to perform an aging operation. Means. Therefore, especially when a new contact charging unit is used, the aging operation is performed by the aging unit during non-image formation, thereby stabilizing the charging potential in the initial state and improving the image quality of the image. Also, when the contact charging means is an age
Charging current for charging the surface of the image carrier during
Charging current detecting means for detecting the charging current;
From the outside of the specified reference current value range
When the current falls within the specified reference current range, the aging
Means for shifting from an operation to an image forming operation.
You. This is because the charging current is proportional to the surface potential of the image carrier.
Surface potential by aging operation
Stable, aging when surface potential reaches a predetermined value
This ends the operation. Therefore, it is longer than necessary
Time aging operation is prevented.

According to the image forming apparatus of the present invention, in addition to the aging means, the contact charging means or a unit including the contact charging means is detachably provided. A detecting means for detecting whether or not the mounted contact charging means or unit is new; and an aging means for detecting whether the mounted contact charging means or unit is new, by the detecting means. Means for performing a zing operation. Therefore, it is possible to automatically perform an aging operation when a new contact charging unit or a unit including the same is mounted.

[0014]

An image forming apparatus according to the present invention (claim 3 ) includes, together with the aging means and the charging current detecting means described above ,
According to the current value detected by the charging current detecting means
And means for changing a developing bias applied to the developing means. By controlling the developing bias by detecting the charging current in this manner, excessive adhesion of the developer during the aging operation and adhesion of the developer to a non-image portion during the image forming operation are prevented.

[0016]

When a machine is powered on, a charger is replaced, aging is performed for a predetermined time, or after a charging current from the charger reaches a predetermined value, printing is performed. Or by performing an energizing process in the manufacturing process of the charging member, thereby performing stable charging. High-quality images can be obtained by performing charging with stable charging potential and adjusting the bias even when the charging potential is unstable.

[0018]

FIG. 1 shows an image forming apparatus according to an embodiment of the present invention. This image forming apparatus is a laser printer having an A4 size and a resolution of 400 dpi, and has a printing speed of A4: 5 sheets / min and a process speed of 30 mm / sec. In the figure, reference numeral 100 indicates a process unit, which includes a photoconductor 1, a developing unit 2, a cleaner 3, and a charging brush 4. The diameter of the photoreceptor is 24 mm, and the developing device 3 is a non-magnetic contact one-component developing device.

A bias is applied to the charging brush 4 from a DC constant voltage power supply. The entire surface of the photoreceptor 1 is uniformly negatively charged by the charging brush 4. Thereafter, an electrostatic latent image is formed by the exposure unit 5, and toner is attached to the latent image by the developing device 2 (reversal development), whereby a toner image is formed on the photoconductor 1. The paper P is transported from the paper cassette 7 and is in close contact with the photoconductor in a contact nip between the transfer brush 6 and the photoconductor 1. Due to the bias applied to the transfer brush 6, the toner image is transferred to the sheet P in the nip. Paper P with unfixed image
Is applied heat and pressure by the fixing device 8, and the image is fixed on the paper P. The transfer residual toner remaining on the photoconductor 1 is removed from the photoconductor 1 by the cleaner 3.

Next, a non-magnetic one-component developing device will be described. The developing roller 200 is formed by forming a rubber layer having a predetermined resistance value on a φ6 mm metal shaft and using a φ12 mm roller. Rubber hardness is 28 degrees ~
By setting the angle at 50 degrees (JIS-A; the same applies hereinafter), a stable development nip without permanent distortion can be obtained. Further, the resistance value of the rubber material is set to 10 ⁴ Ω · c.
By setting m to ^{10 10} Ω · cm, a clear image can be obtained without bias leak. The surface of the roller is coated with a urethane paint having a good toner release property.
It is applied to a thickness of about 0 to 150 [mu] m to prevent toner from sticking without impairing the elasticity of the roller. The rubber hardness of the roller after applying the surface layer is 30 degrees to 55 degrees.
Degree. In addition, in order not to impair the developing characteristics, the surface layer must have a resistance of about 10 ⁵ to 10 ¹⁰ Ω · cm. Further, a charge control agent is dispersed in consideration of the frictional charging performance of the toner.

The layer forming member 201 is in contact with the developing roller 200 at a pressure of 300 g to 1500 g, and charges the toner while regulating the amount of the toner layer formed on the developing roller. The configuration of the layer regulating member 201 is φ1
A layer similar to the surface layer of the developing roller is formed on the surface of a 0-mm metal rod to ensure charging performance and toner criterion. In the embodiment, the layer regulating member 201 is fixed, but may be rotated with a peripheral speed difference with respect to the developing roller. Further, in the present embodiment, the layer regulating member 201 has the same potential as the developing roller 200, but a potential difference is provided to control the amount of toner formed on the developing roller,
The toner can be charged by charge injection.

The toner supply roller 202 has a volume resistance of 10
Hardness (ASKER-C) 20 to ⁵ to 10 ¹¹ Ω · cm
35 degree firing roller (shaft φ6mm, roller diameter 12
mm), and supplies the toner to the surface of the developing roller 200. In this embodiment, the toner supply roller 202
Is in contact with the developing roller 200 with a bite amount of 0.7 mm, and simultaneously supplies toner, peels off the toner on the developing roller, and charges the toner.

As the toner, a toner having a negative charge polarity using a polyester resin as a binder is used. The toner particle size is 10.2 μm (average accumulation particle size). When the toner is used in the developing device configured as described above, the toner layer formed on the developing roller 200 has a charge amount of −8.2 μc / g and a layer formation amount of 0.73 mg.
/ Cm ² .

As shown in FIG. 2, the transfer brush 6 has a volume resistance of 10 ⁵ to 10 ¹² Ω · cm and a brush diameter of 3 to 1.
In this configuration, a brush having 0D and a density of 10,000 to 400,000 brushes / inch is sandwiched between sheet metals. The bias applied to the transfer brush 6 is +500 to +2000 V, which is opposite to the charging polarity of the toner. Further, the transfer brush 6 is configured to be able to move away from the photoconductor 1 in order to prevent contamination.

The charging brush 4 is an L-shaped sheet metal (having a thickness of 1 to
3 mm aluminum), the specific resistance of the material is 10 ³ -10 ¹¹ Ω
cm, fiber diameter 2D-10D, brush flock density 10,000
The brush is provided with up to 400,000 brushes / inch. If the resistance of the brush is too low, a portion having a high surface potential is locally generated by charge injection, the uniformity of density is impaired, and white stripes are generated in halftone. On the other hand, if the resistance is too high, partial charging is not performed, and black streaks occur in halftone. Table 1 below shows the relationship between brush resistance and image quality. In this case, the brush fiber diameter is 6D, and the brush flock density is 20,000 fibers / inch.

Table 1 Brush resistance and halftone streaks (50% coverage) Brush resistance (Ω · cm) White streaks Black streaks 10 ³ × ○ 10 ⁵ ○ ○ 10 ⁷ ○ ○ 10 ⁹ ○ ○ 10 ¹¹ ○ ○ 10 ¹² ○ ○ 10 ¹³ △ ×

From Table 1 above, it can be seen that good images were obtained at 10 ⁵ to 10 ¹² Ω · cm. Table 2 below shows the relationship between the brush fiber diameter and the occurrence of streaks in halftone. In this case, the brush resistance is 10 ⁶ Ω · c
m, the brush flock density is 20,000 brushes / inch.

Table 2 Brush fiber diameter and halftone streaks (coverage 50%) Brush fiber diameter (D) Halftone streaks 1 × Brush breakage 2 × 4 ○ 6 ○ 8 ○ 10 ×

From Table 2 above, it can be seen that when the fiber diameter is 10D or more, the image streaks in halftone become thick and conspicuous. As for the image quality, the smaller the brush diameter is, the better. However, when the brush diameter becomes 2D or less, the brush fibers are broken or cut, and these break into the developing device, thereby causing image defects. Table 3 below shows the relationship between the brush flock density and the ground fogging. In this case, the brush fiber diameter is 6D and the brush resistance is 10 ⁶ Ω · cm.

Table 3 Brush Flocking Density and Ground Fogging Brush Flocking Density (Thousands / inch) Ground Fogging 5 × 8 × 10 ○ 50 ○ 100 ○ 200 ○ 400 ○ 500 × Cannot be manufactured

As shown in Table 3 above, 10000 pieces / i
If it is less than nch, a portion where the brush does not contact the photoreceptor 1 becomes defective in charging, and fog occurs. On the other hand, 400
A brush density of 000 brushes / inch or more is difficult to realize from the viewpoint of manufacturing.

It should be noted that the disorder of the bristle at the end of the brush in the rotation direction of the photoreceptor causes a local rise in charge due to abnormal discharge and a white streak in halftone. It is preferable to provide a mylar guide so that the hair does not protrude. However, if the bristle of the brush is too long, the bristle easily protrudes even if the guide is provided. Therefore, the bristle length is preferably 7 mm or less.

In the present embodiment, the charging of the photosensitive member is performed by applying a bias of -1000 V to the charging brush member from a DC constant voltage power supply. In addition, as an applied bias,
It is also possible to use an AC / DC superimposed bias. When contact charging is used as in the present embodiment, stability of charging in an initial state of use becomes a problem. FIG. 4 shows a change in the charging potential when charging is performed with a completely new brush. From FIG. 4, especially in a high-temperature and high-humidity environment, the initial surface potential is extremely high, and it takes an average of one minute to stabilize. When printing is performed in such a state in which the potential is high, there is a problem that the halftone density is low. Further, in such a state where the surface potential is high, a high potential portion due to partial charge injection exists, and this high potential portion causes a white streak in halftone.

However, once the potential has been stabilized, the surface potential is slightly higher at the start even if it is left in a humid environment again. Absent. Therefore, in the embodiment, when the process unit is mounted on the machine, it is determined whether the process unit is new, and when it is determined that the process unit is new, the charging operation of the photosensitive member by the charging brush is performed as an initialization operation. . Here, the initialization operation is performed for about one minute.

Note that the initialization operation is an operation of applying a predetermined bias to the charging member while rotating at least the photosensitive member. In this embodiment, a normal bias of -200 V is applied to the developing device, and the developing roller also rotates. FIG. 5 shows a sequence of an initialization operation when the machine is powered on.

Next, a method of determining whether the currently mounted process unit is new or not will be described. The process unit has a substrate including a memory in which the manufacturing members of the process unit are recorded, and when the power is turned on while the process unit is mounted, or when the process unit is mounted while the power is turned on, the main unit is turned off. Controller reads the manufacturing members of the process unit. The manufacturing unit of the mounted process unit is stored in the storage unit on the main body side, and it is determined whether the unit is new by comparing with the number of the mounted process unit. If it is judged as new,
A one-minute initialization operation is performed; otherwise, a normal warm-up operation is started.

Other methods for determining whether a process unit is new include a part of the photoconductor of the new unit,
Alternatively, there is a method in which the whole is covered with black paper, and this is read by an optical sensor to determine whether or not it is new. At this time, the black paper is automatically wound up and collected inside the process unit. In addition, the production number is indicated by a bar code at a predetermined position of the process unit, and is read by a bar code reader on the main body side.
There is also a method to determine whether a process unit is new.

In this embodiment, the instability of the initial surface potential of the new brush is eliminated by performing the initialization operation for a predetermined time. As shown in FIG. 6, in the fixed type charging brush as in this embodiment,
The time Ts until the potential stabilizes has little difference between the brushes, and there is often no problem with a uniform initialization time. However, when a rotary type charging brush is used, the individual difference of the brush becomes a problem.

Next, as another embodiment, as shown in FIG. 7, an example in which the fixed brush 4 of the above-described embodiment is changed to a rotating brush 4 will be described. Other than changing the charging brush,
The configuration is exactly the same as the embodiment shown in FIG.
First, the rotating brush will be described. The appropriate resistance value, flocking density, and fiber thickness of the brush fibers are not different from the fixed type shown in FIG. In the case of the example shown in FIG.
A brush of 0 ⁸ Ω · cm, a flocking density of 100,000 fibers / inch, and a fiber thickness of 6D is used. In addition, as shown in FIG. 8, the rotary type brush is formed by spirally winding a band-shaped fiber around a base shaft (φ6 mm) and molding it. When printing with a molded brush as it is,
Oblique density unevenness as shown in FIG. 9 occurs in a halftone image or the like.

Therefore, in the example shown in FIG. 7, FIG.
As shown in FIG. 10 (b), the brush formed into a straight hair shape is rotated in a cylinder through steam for a predetermined time as shown in FIG. 10 (b). I have. In this manner, the portion having a low brush density at the seam can be made inconspicuous by making the hair beveled. Here, a straight-haired brush once molded to φ14 mm is obliquely furnished to φ12 mm.

The rotating speed of the rotating brush is 1.5 to 3 times the moving speed (process speed) of the photoreceptor in the case of the width rotation, and 1 to 3 times in the case of the opposite rotation. Thereby, a good image without halftone streaks or the above-mentioned winding marks can be obtained.

Even in the rotating brush described above, there is a problem that the initial surface potential of the new brush becomes high. In the embodiment shown in FIG. 1, the time for performing the initializing operation used the time for stabilizing the average, but the rotating brush has a large individual difference due to the brush in the time until the stabilization.
This is difficult.

FIG. 6 shows a rotating brush and a stationary brush,
The results obtained by measuring zero initial surface potentials are shown. The fixed brushes (under hot and humid conditions) showed a very small difference in potential variation due to the fixed difference, and all brushes had stable charging potentials after aging for 1 minute. However, among rotating brushes, some brushes can stabilize the electric potential in about one minute, while others have three.
Some require minutes. If the initialization time is set to 1.5 minutes, the potential stabilizes to almost no problem with most brushes, but depending on the object, it may be higher than the stable potential by 15 minutes.
Something close to 0V will come out. In such a case,
When considering aging of all units as shown in FIG. 1 for a certain period of time, some units may not be stable in one minute, and image defects may occur. Aging is too long from a user's point of view.

Therefore, in the example using the rotating brush shown in FIG. 7, it was considered to perform an initialization operation in consideration of the individual difference between the brushes. FIG. 11 shows the relationship between the current flowing from the power supply to the brush and the surface potential of the photoconductor. FIG.
It can be seen from FIG. 1 that the two have a substantially proportional relationship. Therefore, the surface potential of the photoreceptor can be known by detecting the current flowing into the brush using a detection circuit as shown in FIG. Therefore, it has been considered that the initialization operation is terminated when the surface potential becomes lower than a certain potential in the process of stabilizing the surface potential during the initialization operation.

FIG. 13 shows the relationship between the photoconductor surface potential and the halftone density at a printing rate of 50% when the developing bias is -200 V. If the photoconductor potential has an absolute value smaller than -550 V, the halftone density difference from the standard surface potential -500 V becomes 0.1 or less, and there is no problem in image quality. From FIG. 11, the current value I at the surface potential of −500 V is −8 μm.
m, and the current value I at −550 V is 8.8 μA. Therefore, during the initialization operation, the current value is 8.8 μm.
When the value becomes A or less, the initialization operation is terminated. FIG.
FIG. 4 shows a flowchart of an initialization operation in an example using a rotary charging brush.

As shown in FIG. 15, the brush which has been used once does not show a remarkable increase in the surface potential even when left again in a high-temperature and high-humidity environment. However, since a slight increase is observed, it is desirable to perform the aging operation every time the power is turned on when using the brush charging for an apparatus requiring high image quality such as a color printer. in this way,
Aging is performed until the current value to the charging brush becomes equal to or less than a predetermined value, so that good printing can be performed without initializing operation more than necessary and without being affected by changes in image density due to initial surface potential fluctuation. I can do it.

Next, it was considered that high-definition printing was performed using a toner having a small particle diameter. It is known that when printing is performed using a toner particle diameter of 6.2 μm (accumulated average particle diameter), resolution, halftone density, and the like are improved. But,
Several adverse effects occur when the toner particle size is reduced. FIG. 16 shows the relationship between the photoconductor surface potential and the amount of toner adhering to the non-image area (that is, the amount of fogging toner) when the developing bias is -200 V. In the non-image area, fog is suppressed by an electric field caused by a difference between a developing bias and a photoconductor surface potential. However, even if this potential difference is too large, fogging is likely to occur.
This tendency is due to the contact one-component development as described above, and
This is remarkable when a small particle size toner is used.

The amount of toner adhered to the non-image area is 0.01 m
If it exceeds g / cm ² , problems such as an increase in toner consumption and a curling of the cleaning blade occur. As described above, when a new charging brush is used, the surface potential is high during the initialization operation. At this time, the surface potential may exceed -700 V, and the amount of toner attached to the non-image area exceeds 0.01 mg / cm ² .

Therefore, at this time, the developing bias is set to -200.
When the voltage is changed from V to −300 V, as shown in FIG. 16, the toner adhesion amount in the non-image area can be 0.01 mg / cm ² or less. Then, when the initializing operation is completed and a normal printing operation is performed, since the surface potential is at the set potential of about -500 V, the developing bias may be set to -200 V. As described above, by controlling the developing bias, it is possible to prevent excessive toner consumption, turning over of the cleaning blade, and the like during the initialization operation of the new brush.

In the above description, the toner adhesion to the non-image area is prevented by controlling the developing bias. However, during the initialization operation, the adhesion of the toner can be prevented by stopping the rotation of the developing device. it can. Further, the method of detecting the charging current and controlling the developing bias is also effective in a normal printing mode. When toner or the like adheres to the brush, the surface potential easily rises in a humid environment.
Then, as described above, extra toner adheres to the non-image area, and the toner consumption increases and the halftone density decreases. Then, it was considered that the charging current I was detected and the developing bias was controlled according to the current value.

When the surface potential fluctuated from -500 V to -700 V, no change was made in the developing bias, and -2
When the voltage is kept at 00 V, the developing bias is set to -20 by I.
The toner adhesion amount to the non-image area when the voltage is changed from 0 V to -300 V, and the halftone (coverage 50)
%) Are shown in Table 4 below.

Table 4 Surface potential Developing bias -200 V Developing bias control Halftone Non-image area toner Halftone Non-image area toner Concentration Amount (mg / cm ² ) Concentration Amount (mg / cm ² ) ² ) -500V 0.72 0.02 0.72 0.02 -600V 0.58 0.035 0.70 0.02 -700V 0.51 0.012 0.69 0.03

From Table 4 above, by controlling the developing bias, the fog on the drum is always 0.01 mg / cm ^2.
It is understood that the density fluctuation of the halftone can be made 0.1 or less.

Next, a method for preventing an increase in the surface potential of a new brush by devising a brush manufacturing process will be described. When a new brush is used, the phenomenon in which the surface potential is initially high, gradually lowers and stabilizes is considered to be caused by oil and the like adhering to the brush in the brush manufacturing process adhering to the photoreceptor. Therefore, in the brush manufacturing process, the following phenomena are considered by preventing the above phenomenon by removing the components.
Prototypes of these three brushes.

(A) After completing the beveled hair process as shown in FIG. 10, the brush is energized by an apparatus as shown in FIG. The treatment is performed in the final step after the steps such as brush slanting and drying are completed. First, the metal cylinder 3
02, the brush roller 300 is inserted into the
Electric current was applied between the brush shaft and the metal cylinder 302 while rotating at a speed of rpm to perform an energization process. The brush 300 was energized by changing the energizing current and energizing time, and the initial surface potential of the brush 300 and the surface potential after 5 minutes were measured. FIG. 18 shows the result.

In the drawing, Is indicates the amount of current per unit area of the contact surface of the brush. In the apparatus shown in FIG. 17, when the amount of current detected by the ammeter 303 is I (μA), the width of the brush is L (cm), and the radius of the brush is R (cm), Is is represented by the following equation. I can do it. Is = I / 2πRL (μA / cm ² )

From FIG. 18, it is possible to reduce the initial surface potential to 30 V or less by setting the processing conditions so that Is × T> 150. Above is a brushro
As for La, even for fixed type brushes,
Similarly, by setting the processing conditions so that Is × T> 150, it is possible to suppress an increase in the initial surface potential.

(B) After completing the beveled hair process as shown in FIG. 10, the brush is subjected to a charging process by an apparatus as shown in FIG. That is, in the final step of the brush manufacturing,
The brush 300 was brought into contact with the discharge tube 310, a bias was applied, and discharge was performed. The discharge tube 310 is formed by coating a resin layer having a thickness of 20 μm on the surface of a base tube made of aluminum, and rotates at a peripheral speed of about 20 to 100 mm / sec. The brush 300 rotates in a direction against the discharge tube 310 at a speed of about 1 to 3 times the peripheral speed of the discharge tube 310. In the figure, reference numeral 311 denotes an apparatus for removing a substance attached to the discharge tube 310 from the brush 300.

In the example shown in FIG. 19, two sets are set for one discharge tube 310, a negative bias is applied to one, and a positive bias is applied to the other. By doing so, there is no need to discharge the discharge tube with a corona discharger or the like, and the processing apparatus shown in FIG. 19 can be made inexpensive and safe. Further, when reprocessing is performed by switching (inverting) the two bias polarities, better results can be obtained.

FIG. 20 shows a discharge current is (i / i /
L) and a characteristic diagram showing an increase in the initial surface potential when the treatment is performed while changing the discharge time. In addition, is
It is a current value per unit length in the brush longitudinal direction. Since the discharge is not performed on the entire surface of the contact nip, unlike the energization treatment, the value per unit area of the contact nip is meaningless.

It is understood from FIG. 20 that the rise of the initial potential can be suppressed to 50 V or less by satisfying is × T> 10. In the example shown in FIG. 19, an example is shown in which a brush roller is used and the bias is a DC bias. However, the present invention can also be applied to a fixed type brush, and the applied bias at the time of discharge processing is AC. Even if is × T> 10
By satisfying the above condition, good results can be obtained.

(C) As shown in FIG. 21, at the time of performing the slant hair processing, the energization processing is performed simultaneously. FIG. 21 shows FIG.
In the beveling process shown in FIG. 0, a bias is applied between the brush shaft and the outer cylinder, and the energization process is performed while performing the beveling.

FIG. 22 shows initial fluctuations in the potential of the photosensitive member between the brush processed by the above-described methods (a) to (c) and the normal brush. From FIG. 22, (a) to
Each of the treatments (c) was effective, and in particular, the treatment (b), in which discharge was performed by charging, showed a remarkable effect on the initial potential stability. Therefore, it is understood that charging (discharging) is more effective than conducting electricity.

[0064]

As described above, according to the present invention,
Since the aging operation has been performed for a predetermined time when the power of the apparatus is turned on or the charger is replaced, the image forming operation is performed after the charging current from the charger has reached a predetermined value, or the charging current value The development bias is changed in accordance with the above, so that it is possible to prevent the halftone density fluctuation, the increase in toner consumption, etc. due to the instability of the initial potential of the contact charging, especially the charging using the brush, and the favorable Image formation can be performed. Further, in the manufacturing process of the charging member, a charging member having a stable initial charging potential can be obtained by performing a charging process by conducting or discharging.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating an entire printer using a fixed charging brush according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a transfer brush.

FIG. 3 is a diagram showing prevention of halftone streaks by Mylar support.

FIG. 4 is a characteristic diagram showing a change in an initial surface potential of a new fixed brush.

FIG. 5 is a diagram showing an initialization operation of the fixed charging brush according to one embodiment of the present invention.

FIG. 6 is a characteristic diagram showing a difference in initial surface potential fluctuation between a fixed brush and a rotating brush.

FIG. 7 is a diagram schematically illustrating an entire printer using a rotary charging brush according to another embodiment of the present invention.

FIG. 8 is a view showing a method of molding a rotary charging brush.

FIG. 9 is a view showing a halftone winding mark of a rotary charging brush.

FIG. 10 is a view for explaining a beveling step of the rotary charging brush.

FIG. 11 is a characteristic diagram showing a relationship between a charging current and a surface potential.

FIG. 12 is a diagram showing a circuit for detecting a charged potential.

FIG. 13 is a characteristic diagram showing a relationship between a surface potential and a halftone density.

FIG. 14 is a diagram showing an initialization operation of a rotary charging brush according to another embodiment of the present invention.

FIG. 15 is a characteristic diagram showing a difference in surface potential fluctuation between a new brush and a used brush.

FIG. 16 is a characteristic diagram illustrating a relationship between a surface potential and a non-image portion toner adhesion amount (fogging on a drum).

FIG. 17 is a diagram showing a brush energization processing device.

FIG. 18 is a characteristic diagram showing a relationship between an energization treatment time and an increase in an initial surface potential.

FIG. 19 is a diagram showing a brush charging apparatus.

FIG. 20 is a characteristic diagram showing a relationship between a charging time and an increase in initial surface potential.

FIG. 21 is a diagram showing a method of performing energization processing while oblique hairs

FIG. 22 is a characteristic diagram showing a relationship between aging time and surface potential of a brush treated by various treatment methods.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Photoconductor 2 ... Developing device 3 ... Cleaner 4 ... Charging brush 5 ... Exposure means 6 ... Transfer brush 7 ... Paper cassette 8 ... Fixing device 201 ... Developing roller 201 ... Layer forming member 201 ... Toner supply roller 300 ... Brush roller Reference numeral 301: power supply 302: cylindrical body 303: ammeter 310: discharge tube 311: blade

────────────────────────────────────────────────── (5) Continuation of the front page (56) References JP-A-5-107834 (JP, A) JP-A-64-50070 (JP, A) JP-A-54-154334 (JP, A) JP-A-7-107 43966 (JP, A) JP-A-6-266208 (JP, A) JP-A-6-51585 (JP, A) JP-A-5-119552 (JP, A) JP-A-6-274000 (JP, A) JP-A-5-281874 (JP, A) JP-A-6-186815 (JP, A) JP-A-4-366863 (JP, A) JP-A-4-369661 (JP, A) JP-A-62-157066 (JP, A) JP-A-4-37776 (JP, A) JP-A-5-181351 (JP, A) JP-A-5-165306 (JP, A) JP-A-3-107957 (JP, A) ( 58) Investigated fields (Int.Cl. ⁷ , DB name) G03G 15/00 303 G03G 15/02 102 G03G 21/14 G03G 21/00 370-512

Claims (3)

(57) [Claims] A contact charging means for charging a rotatable image carrier surface; an electrostatic latent image forming means for forming an electrostatic latent image on the charged image carrier; and a developing means for developing the electrostatic latent image. Developing means for forming a developer image, a predetermined time during non-image formation, while rotating the image carrier, charging the image carrier surface by the contact charging means, aging means for performing an aging operation, A charging current detecting means for detecting a charging current for charging the surface of the image carrier during the aging operation by the contact charging means; and a current value detected by the charging current detecting means being a predetermined value from outside a predetermined reference current value range. Means for shifting from the aging operation to the image forming operation when the current value falls within the reference current value range. 2. The contact charging means or a unit including the contact charging means is configured to be detachable, and the mounting of the contact charging means or unit and whether the mounted contact charging means or unit is new. 2. The apparatus according to claim 1, further comprising: a detecting unit for detecting, and a unit for performing an aging operation by the aging unit when the contact charging unit or the unit mounted by the detecting unit detects that the unit is new. An image forming apparatus according to claim 1. 3. The apparatus according to claim 1, further comprising: means for changing a developing bias applied to said developing means in accordance with a current value detected by said charging current detecting means.
An image forming apparatus according to claim 1.