JP3317748B2 - Roller charging device and image forming apparatus using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roller charging device having at least a charging roller which is driven to rotate in contact with a photosensitive drum, and a cleaning blade for removing foreign matter such as toner adhered to the surface of the charging roller. The present invention relates to an apparatus and an image forming apparatus using the same.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, a corona discharger has been widely used as a charging means for uniformly charging the entire surface of a photoreceptor. This corona discharger is effective as a means to uniformly charge the photoreceptor to a certain potential. Conversely, charging by corona discharge requires a high-voltage power supply, Ozone is generated. The generation of a large amount of ozone not only adversely affects the environment, but also causes the problem that the charging member and the photoconductor are deteriorated by the ozone.

[0005] As shown in FIG. 5, the charging roller 501 is brought into contact with the photosensitive drum 502 and is driven to rotate with respect to the corona discharger, and a voltage is applied from a power source 504 to a metal core 503 of the charging roller 501. A charging roller for charging the surface of the photosensitive drum 502 has been put to practical use. The charging roller 501 as the charging means has the advantage that the voltage of the power supply 504 can be reduced and the amount of ozone generated due to the charging process is small. In addition, there is an advantage that there is no electrostatic adsorption of dust due to the use of the corona electrode wire, and a high voltage power supply is not required.

[0004] However, the charging roller has a drawback that charging unevenness easily occurs and the charging potential fluctuates greatly due to a change in environment.
At present, it is considerably inferior to charging treatment by a corona discharger.

Therefore, in order to improve the uniformity of charging, the "contact charging method" disclosed in Japanese Patent Application Laid-Open No. 63-149668 discloses a method for controlling the peak-to-peak voltage which is twice or more the charging start voltage (V _TH ) when a DC voltage is applied. It discloses that by superimposing an AC voltage having a voltage, charging uniformity can be considerably improved.

As a device for removing toner stains on the charging roller, for example, a "roller charging device" disclosed in Japanese Patent Application Laid-Open No. 58-194061 is disclosed. This device removes toner contamination on the surface of the charging roller by providing a cleaning element near the surface of the charging roller made of a conductive elastic body and coating the surface of the conductive elastic body with a non-adhesive film. It is like that.

[0007]

However, in the "contact charging method" of Japanese Patent Application Laid-Open No. 63-149668, the peak-to-peak voltage which is twice or more the charging start voltage (V _TH ) when a DC voltage is applied. To superimpose AC voltage
An AC power source is required separately from the DC power source, which leads to an increase in the cost of the apparatus itself. Further, a large amount of useless AC current that does not contribute to the charging position of the photoconductor is consumed, thereby increasing the power source cost. In addition, a large amount of ozone is generated, and as a result, the charging member and the photoreceptor are deteriorated.

For this reason, in order to enable the voltage to be applied to the charging roller by using only the DC power supply without using the AC power supply, the present inventor uses a medium-resistance synthetic rubber (epichlorohydrin rubber) for the elastic layer. A charging roller to be used has been proposed. The present inventor has studied the cause of the occurrence of charging unevenness when only the DC voltage is applied, and as a result, it has been found that the elastic layer is a dispersion layer of synthetic rubber and carbon. It was discovered that this was due to the electrical non-uniformity of the conductive elastic layer due to poor dispersion of the synthetic rubber, and by replacing the carbon / synthetic rubber elastic layer of the charging roller with a medium-resistance synthetic rubber (epichlorohydrin rubber), Eliminates electrical non-uniformity and reduces DC
This is to eliminate charging unevenness that occurs when only voltage is applied.

When only a DC voltage is applied, the withstand voltage of the roller layer becomes a problem. However, by using a medium-resistance epichlorohydrin rubber for the elastic layer, a conventional carbon / synthetic rubber based conductive elastic material is used. The withstand voltage is significantly improved as compared with the case of the layer. Further, epichlorohydrin rubber has a relatively high rubber hardness of 40 (JISA) and little elastic deformation, and therefore has good mechanical strength.

However, even when a charging roller having excellent electrical and mechanical characteristics and capable of being uniformly charged only by applying a DC voltage is used, the durability as a roller charging device is good depending on the copying machine used. There is a problem that there is no case.

Specifically, in a high-speed copying machine, the photosensitive drum is not completely cleaned. That is,
If a small amount of residual toner still exists on the photosensitive drum even after the photosensitive drum cleaning step is completed, the residual toner is transferred to the charging roller that is in contact with the photosensitive drum and is driven to rotate. There is a problem that charging unevenness occurs due to toner contamination, and a problem that the charging roller has substantially poor durability.

On the other hand, according to the "roller charging device" disclosed in Japanese Patent Application Laid-Open No. 58-194061, the cleaning element is used to remove toner stains on the surface of the charging roller, but the surface of the charging roller is higher than the surface of the photosensitive drum. When a rubber blade is used as a cleaning element, the rotation of the charging roller becomes unstable and uneven charging may occur due to the soft and rough surface and the rotation of the charging roller following the photosensitive drum. There was a problem. Further, when a felt, a sponge, or the like is used as the cleaning element, foreign substances such as toner clog the cleaning element and stick to the cleaning element.

The present invention has been made in view of the above, and it is an object of the present invention to prevent the occurrence of charging unevenness due to toner contamination of a charging roller and uneven rotation, and to improve the substantial durability of the charging roller. Aim.

[0014]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention removes at least a charging roller which is driven to rotate in contact with a photosensitive drum and foreign matters such as toner adhered to the surface of the charging roller. in the roller charging apparatus having a cleaning blade for the charging roller before
Serial contact with the photosensitive drum pressure P ₁ and friction coefficient mu ₁
When the relationship between the contact pressure P ₂ and friction coefficient mu ₂ between the charging roller and the cleaning blade, P _1> P
_2, and Ri mu ₁ <mu ₂ der, rubber hardness of the charging roller
Degree is higher than the rubber hardness of the cleaning blade.
It is characterized by having.

[0015]

Further, since the present invention is to achieve the above object, in the roller charging apparatus according to claim 1, wherein the band <br/> conductive roller, a rubber hardness of 40 (JISA) or more epichlorohydrin rubber becomes, the cleaning blade is characterized in that the rubber hardness of from 40 (JISA) or less of the synthetic rubber.

Further, since the present invention is to achieve the above object, in the roller charging apparatus according to claim 1 or 2, the friction between the charging roller and the cleaning blade, the charging roller surface developer toner It has the same polarity as the above.

According to a third aspect of the present invention, there is provided an image forming apparatus using the roller charging device according to the third aspect.
A forming device, which is negatively charged by the charging roller.
Exposure means for exposing the surface of the photosensitive drum,
Reversal development of the latent image formed on the drum with negative polarity toner
Developing means, and a visible image formed by the developing means on a recording paper.
Transfer means for transferring the image to the printer and after the transfer by the transfer means is completed
Then, the surface of the photosensitive drum is cleaned with a cleaning member.
Cleaning means for cleaning the roller,
Charging roller has a surface covered with fluorine resin, the <br/> cleaning blade is characterized in that it consists of ethylene propylene rubber or urethane rubber.

According to a third aspect of the present invention, there is provided an image forming apparatus using the roller charging device according to the third aspect.
A forming device, which is negatively charged by the charging roller.
Exposure means for exposing the surface of the photosensitive drum,
Development of latent images formed on drums with positive polarity toner
Image means and the visible image formed by the developing means are transferred to recording paper.
Transfer means for transferring the image, and before and after the end of the transfer by the transfer means.
Clean the surface of the photosensitive drum with a cleaning member.
And a cleaning unit that, strips <br/> conductive roller of the charging roller has a surface covered with a polyamide resin, the <br/> cleaning blade, characterized in that it consists of urethane rubber or ethylene propylene rubber And

According to a fourth aspect of the present invention, there is provided an image forming apparatus comprising:
The photosensitive drum and the charging roller during non image forming, characterized in regular be idling.

[0021]

According to the roller charging device of the present invention, the relationship between the contact pressure P ₁ and the friction coefficient μ ₁ between the charging roller and the photosensitive drum and the contact pressure P ₂ and the friction coefficient μ ₂ between the charging roller and the cleaning blade are determined. , P ₁ > P ₂ , and μ ₁ <μ
₂ and the rubber hardness of the charging roller.
Is higher than the rubber hardness of the cleaning blade, thereby removing toner contamination of the charging roller and ensuring uniform rotation of the charging roller.

Further, the roller charging apparatus of the present invention, the strip conductive roller rubber hardness and 40 (JISA) or more epichlorohydrin rubber, a cleaning blade rubber hardness 4
By using a synthetic rubber of 0 (JISA) or less, toner contamination of the charging roller is removed and uniform rotation of the charging roller is ensured.

Further, the roller charging device of the present invention makes the surface of the charging roller have the same charging polarity as that of the developer toner by friction between the charging roller and the cleaning blade, thereby removing toner stains on the charging roller. Remove
In addition to ensuring uniform rotation of the charging roller, toner is less likely to adhere to the surface of the charging roller and is easily removed, so that toner can be efficiently removed with a small blade pressure.

Further, the image forming apparatus of the present invention comprises a photosensitive drum.
Reverse development of latent image formed on ram with negative toner
If the surface of the charging roller is covered with fluorine resin, and, by forming the cleaning blade with ethylene propylene rubber or urethane rubber, toner charging roller
-To remove dirt and ensure uniform rotation of the charging roller
In both cases, the negative toner hardly adheres to the charging roller surface,
And easily removed, toner removal can be performed efficiently with a small blade pressure.

Further, the image forming apparatus of the present invention comprises a photosensitive drum.
When developing the latent image formed on the ram with positive polarity toner
The surface of the charging roller is covered with polyamide resin, and
By forming the cleaning blade with urethane rubber or ethylene propylene rubber, the charging roller
Removes toner stains and ensures uniform rotation of the charging roller
At the same time , the positive polarity toner does not easily adhere to the surface of the charging roller and is easily removed, so that the toner can be efficiently removed with a small blade pressure.

Further, the image forming apparatus of the present invention, by periodically idle rotation of the photosensitive drum and the charging roller during non image forming, the toner contamination of the charging roller is further removed
To ensure uniform rotation of the charging roller,
The roller surface makes it difficult for toner to adhere and is
Toner removal efficiently with small blade pressure
I can do it.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a roller charging device of the present invention and an image forming apparatus using the same will be described in detail in the order of [Embodiment 1], [Embodiment 2], [Embodiment 3] with reference to the drawings. .

First, an outline of the present invention will be described prior to the first to third embodiments. As one of the methods for removing foreign matters such as toner adhered to the surface of the charging roller, there is a method of performing cleaning by bringing a cleaning member into contact with the charging roller. Felt,
A sponge, a rubber blade or the like is conceivable. However, when a felt, sponge, or the like is used as a cleaning member, foreign substances such as toner clog the cleaning member,
It is not good because it sticks as it is.

On the other hand, when a thin and soft rubber blade is used, the rubber blade is evenly and lightly applied to the surface of the charging roller to lower the toner adhering to the charging roller surface (on the photosensitive drum). Although it can be dropped, the surface of the charging roller is softer and rougher than the surface of the photoreceptor drum, and the charging roller rotates with the photoreceptor drum. With such a blade cleaning method, the rotation of the charging roller becomes unstable.

In order to prevent the occurrence of uneven charging due to toner contamination and uneven rotation of the charging roller and to improve the substantial durability of the charging roller, the present inventors have proposed the following methods (1) to (4). And good results were obtained in blade cleaning of the charging roller.

As the cleaning member, a rubber blade having a rubber hardness lower than that of the charging roller is used. Since the friction coefficient between the charging roller and the rubber blade is larger than the friction coefficient between the charging roller and the photosensitive drum,
The contact pressure between the charging roller and the rubber blade is much smaller than the contact pressure between the charging roller and the photosensitive drum. The charging roller surface material and the blade material are selected so that the frictional charging polarity of the charging roller surface due to the friction between the charging roller and the cleaning blade becomes the same as the polarity of the toner. In order to clean the charging roller, the photosensitive drum and the charging roller are periodically idled during non-image formation.

Next, according to the first to third embodiments,
1 shows a roller charging device and an image forming apparatus of the present invention using the above method.

Embodiment 1 In Embodiment 1, the contact pressure P between the charging roller and the photosensitive drum is set.
₁ and friction coefficient mu _1, the relationship between the contact pressure P ₂ and friction coefficient mu ₂ between the charging roller and the cleaning blade, P _1> P _2, and, by setting the range of mu ₁ <mu _2, This is to remove toner contamination of the charging roller and to ensure uniform rotation of the charging roller. Further, by making the rubber hardness of the charging roller higher than that of the cleaning blade, for example, the charging roller is made of epichlorohydrin rubber having a rubber hardness of 40 (JISA) or more, and the cleaning blade is made of a rubber hardness of 40 (JIS).
A) By using the following synthetic rubber, toner contamination of the charging roller is removed and uniform rotation of the charging roller is ensured.

FIG. 1 shows a roller charging device 101 according to the first embodiment.
The reference numeral 102 denotes a charging roller, and 103 denotes a cleaning blade. Reference numeral 104 denotes a photosensitive drum. Here, the charging roller 102 is formed by molding an epichlorohydrin rubber elastic layer (thickness: 3 mm) on a core of 8φ so that the outer diameter of the roller is 14φ. The electric resistance of this elastic layer is 3 × 10 ⁸ Ω · cm, and the rubber hardness is 40 (J
ISA). Next, a thin layer (about 5 μm)
m) Providing a coating of polyamide resin. The roller surface hardness is 41 (JISA).

On the other hand, the cleaning blade 103 is an ethylene propylene rubber blade (0.5 mm thick) adjusted to have a rubber hardness of 35 (JISA) by adding a plasticizer.

The photoconductor drum 104 is an OPC photoconductor, and a CGL of about 0.3 μm
(Elastic layer) and then hydrazone (C
TM) A dispersion of 1 part by weight of polycarbonate resin and 1 part by weight of polycarbonate resin in tetrahydrofuran is applied on a CGL by dipping, dried and dried to a CTL of about 28 μm thickness.
(Surface layer).

FIG. 2 is an explanatory diagram showing a method of measuring the friction coefficient between the charging roller 102 and the photosensitive drum 104 and the friction coefficient between the charging roller 102 and the cleaning blade 103 in FIG. First, a sheet material 201 obtained by applying a CTL material of the photosensitive drum 104 to a mylar film on the surface of the charging roller 102 is pressed by a weight 202 by a pressure P.
Then, the friction coefficient μ ₁ when pressed against the charging roller 102 and pulled by the tension F was measured, and μ ₁ = 0.5 was obtained. Next, the cleaning blade 103 is replaced with a CTL material.
Was pressed against the charging roller 102 with the pressure P by the weight 202 and the friction coefficient μ ₂ when the sheet material 203 was pulled by the tension F was measured, and μ ₂ = 1.5 was obtained.
Therefore, the friction coefficient is μ ₁ (0.5) <μ ₂ (1.5)
It can be seen that the relationship is as follows.

Next, as described above, the friction coefficient is μ ₁ <μ ₂
In the roller charging device 101 of FIG. 1 in the state shown in FIG.
0 g each, charging roller 102 and photosensitive drum 1
If the contact pressure P ₁ = 34g / cm and 04, observation of the state of the toner contamination of the charging roller 102 surface while changing the contact pressure P ₂ of the cleaning blade 103 to the charging roller 102, the contact pressure P ₂ = 2 ~ 5g
/ Cm, the cleaning performance is good, and the toner stain can be sufficiently removed. Particularly in this case (μ ₁ = 0.
5, μ ₂ = 1.5 contact pressure P ₁ = 34 g / cm)
For example, when the contact pressure P _{2 is} 3 g / cm, the toner stain can be removed most efficiently.

FIG. 3 shows a part of a copying machine equipped with the roller charging device 101 of FIG. In the figure, reference numeral 301 denotes a DC power supply (Va) for applying a voltage to the charging roller 102 and the photosensitive drum 104; 302, a charge removing lamp for erasing residual charges on the photosensitive drum 104; A drum cleaner 304 for removing the residual toner is an electrometer for measuring the charged potential Vs on the surface of the photosensitive drum 104.

Evaluation of the durability of the roller charging device 101 in the above configuration will be described. First, the initial charging characteristics of the charging roller 102 were measured using an electrometer 304. As a result, the applied voltage Va was -1.5 KV.
Charge potential Vs = −800 V, variation width of charge potential Vs is 1
At 0 V, the uniformity of charging was good.

Next, after forming an image of 10K sheets, the charging characteristics of the charging roller 102 were measured using an electrometer 304. The charged potential Vs = −750 to −780 V, and the variation width of the charged potential Vs was measured. The voltage was 30 V, and the charged position of the photosensitive drum 104 at that portion was lowered in accordance with the dirt on the surface of the charging roller 102. However, the image quality was not much different from the initial level, and there was no problem in image formation.

Further, after forming an image of 30K sheets,
When the charging characteristics of the charging roller 102 were measured using the electrometer 304, the charging potential Vs = −740 to −760V,
The variation width of the charged potential Vs is 20 V, and the charging roller 102
The surface dirt was fairly uniform, and the durability of the roller charging device 101 of the present invention was good.

This is because the toner adhering to the surface of the charging roller 102 is completely removed by making the cleaning blade 103 having a rubber hardness lower than that of the charging roller 102 lightly and uniformly contact the surface of the charging roller 102. Rather, the fact that the surface of the charging roller 102 was evenly contaminated to substantially improve the durability led to a favorable result (improved durability).

Further, at the time of non-image formation, the photosensitive drum 10
4 and the charging roller 102, the photosensitive drum 104 and the charging roller 102 are cleaned, and the cleaning blade 103 of the charging roller 102 is cleaned.
Foreign matter such as toner adhered to the photosensitive drum 104 is dropped on the photosensitive drum 104 and collected by a developing unit (not shown). At the same time, the surface of the charging roller 102 is charged by friction with the cleaning blade 103. At this time, the friction between the charging roller 102 and the cleaning blade 103 causes the surface of the charging roller 102 to have the same charging polarity as the toner, so that the toner hardly adheres to the surface of the charging roller 102 and is removed. Therefore, toner can be efficiently removed with a small blade pressure.

Here, for example, the cleaning blade 1
03 is made of polyurethane rubber or ethylene propylene rubber, and if the surface layer of the charging roller 102 is made of polyamide resin, the charging roller 1
02 is positively charged, and the cleaning blade 1
03 is negatively charged. Alternatively, the charging roller 10
When the surface layer of No. 2 is formed of a fluororesin, the surface of the charging roller 102 is negatively charged, and the cleaning blade 103 is positively charged.

On the other hand, the toner on the photosensitive drum 104, which cannot be removed by the drum cleaner 303, receives a reverse charge during the transfer process, and loses its normal charging polarity or charges to the opposite polarity. May be. In this case, the toner easily adheres to the surface of the charging roller 102.
Further, when the surface of the charging roller 102 is subjected to toner filming, the frictional charging of the surface of the charging roller 102 is changed, so that the above effect may not be expected in some cases. However, recently, in the transfer process, the conventional corona transfer / corona separation has been replaced with a belt (roller) transfer. In the case of the belt (roller) transfer, the residual toner on the photosensitive drum maintains a regular charging polarity. Toner tends not to adhere to the surface of the charging roller 102, and
The toner can be easily removed, and a sufficient effect that the toner can be efficiently removed with a small blade pressure can be obtained.

Embodiment 2 FIG. 4 shows a configuration of a roller charging device 401 and an image forming apparatus (digital copying machine) according to a second embodiment.
In No. 02A, an epichlorohydrin rubber elastic layer having a thickness of 4 mm was formed on a core having a diameter of 8 mm, and a surface layer of a fluororesin (containing 4 wt% of carbon) having a thickness of 15 μm was provided thereon.

In the figure, reference numeral 402 denotes a charge removing lamp for erasing residual charges on the photosensitive drum 104; 403, a drum cleaner for removing residual toner on the photosensitive drum 104 after completion of the transfer process; and 404, exposure light. Reference numeral 405 denotes a laser beam, reference numeral 405 denotes a developing device for developing a latent image on the photosensitive drum 104 with toner, and reference numeral 406 denotes a transfer belt. The cleaning blade 103 and the photosensitive drum 104 are
The description is omitted because it is common to the first embodiment.

The operation of the above configuration will be described. The photosensitive drum 104 cleaned by the drum cleaner 403 and the static elimination lamp 402 is charged by the charging roller 102A.
It is charged to 800 V, and the image is exposed by the laser beam 404.
The latent image is reverse-developed with a negative polarity toner to be a visible image, and thereafter, the image is transferred to a recording sheet by a transfer belt 406.
At this time, transfer residual toner is present on the photosensitive drum 104, and most of the transfer residual toner is removed by the drum cleaner 403.

The toner that cannot be removed by the drum cleaner 403 adheres to the charging roller 102A.
The surface of the charging roller 102A is a cleaning blade 103
The toner is negatively charged due to friction with the toner, and the negative polarity toner does not easily adhere. Roller charging device 4 in this digital copying machine
No. 01 had good durability, the surface of the charging roller 102A after forming 30K sheets of image was little stained, and the charging characteristics were reduced by about 10 to 30 V.

As a comparative example, the charging roller 1 shown in FIG.
A similar experiment was performed using a charging roller having a surface layer formed of a 10 μm-thick polyamide resin (the surface of the charging roller had a positive triboelectric charging polarity) in place of 02A. Charging roller 1 of Embodiment 2
The charge characteristics were much lower than that of 02A, and the deterioration of the charging characteristics was also large. From this comparative example, the effect of forming the surface layer of the charging roller with a fluororesin (containing 4% by weight of carbon) is apparent.

Example 3 Next, as Example 3, an epichlorohydrin rubber elastic layer having a thickness of 4 mm was formed on a core having a diameter of 8 mm, and a 10 mm thick elastic layer was formed thereon.
charging roller with a surface layer formed of μm polyamide resin,
Using a cleaning blade made of ethylene propylene rubber (or urethane rubber), and exposing the photosensitive drum charged to -800 V using an image forming apparatus having the same other configuration as that of the second embodiment. The resulting latent image was developed with a positive polarity toner, and 30
When the image formation of K sheets was performed and the durability of the roller charging device was examined, it was as good as in Example 2.

[0053]

As described above, according to the present invention, the roller charging apparatus of the present invention, the contact pressure P ₁ between the charging roller and the photosensitive drum
And the friction coefficient mu _1, the relation between the contact pressure P ₂ and friction coefficient mu ₂ between the charging roller and the cleaning blade,
When setting so that P ₁ > P ₂ and μ ₁ <μ ₂ ,
In both cases, the rubber hardness of the charging roller is
Since the hardness is higher than the rubber hardness, the occurrence of charging unevenness due to toner contamination of the charging roller and uneven rotation can be prevented, and the substantial durability of the charging roller can be improved.

[0054] The roller charging apparatus of the present invention, the rubber hardness of the strip conductive roller and 40 (JISA) or more epichlorohydrin rubber, the rubber hardness of the cleaning blade 4
Since synthetic rubber of 0 (JISA) or less is used, it is possible to prevent the occurrence of charging unevenness due to toner contamination of the charging roller and uneven rotation, and to improve the substantial durability of the charging roller.

Further, the roller charging device of the present invention is arranged so that the surface of the charging roller has the same charging polarity as the developer toner due to friction between the charging roller and the cleaning blade.
To prevent toner from adhering to the surface of the charging roller.
And easily removed, toner removal with a small blade pressure efficiently performed, thereby preventing the occurrence of charging unevenness due to the toner contamination and uneven rotation of the charging roller, to improve the substantial durability of the charging roller be able to.

Further, the image forming apparatus of the present invention comprises a photosensitive drum.
Reverse development of latent image formed on ram with negative toner
When covering the surface of the charging roller with fluorine resin, and, due to the cleaning blade so as to form an ethylene-propylene rubber or urethane rubber, the charge roller table
The negative polarity toner does not easily adhere to the surface and is easily removed.
The toner can be removed efficiently with a small blade pressure,
It is possible to prevent the occurrence of charging unevenness due to toner contamination and uneven rotation of the charging roller, and to improve the substantial durability of the charging roller.

Further, the image forming apparatus of the present invention comprises a photosensitive drum.
When developing the latent image formed on the ram with positive polarity toner
The surface of the charging roller is covered with polyamide resin, and
Because of the cleaning blade to form a urethane rubber or ethylene propylene rubber, a charging roller
Positive polarity toner hardly adheres to the surface and is easily removed
And toner removal can be performed efficiently with a small blade pressure.
In addition, it is possible to prevent the occurrence of charging unevenness due to toner contamination and uneven rotation of the charging roller, and to improve the substantial durability of the charging roller.

Further, the image forming apparatus of the present invention is a non-image type
Periodically idle the photoconductor drum and charging roller during formation
The surface of the charging roller with more toner.
It is difficult to adhere and easy to remove.
Thus, the toner can be efficiently removed by the pressure, and the occurrence of charging unevenness due to toner contamination and uneven rotation of the charging roller can be prevented, and the substantial durability of the charging roller can be improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a configuration of a roller charging device according to a first exemplary embodiment.

FIG. 2 is an explanatory view showing a method of measuring a friction coefficient between a charging roller and a photosensitive drum and a friction coefficient between a charging roller and a cleaning blade in FIG. 1;

FIG. 3 is an explanatory view showing a part of a copying machine equipped with the roller charging device of FIG. 1;

FIG. 4 is an explanatory diagram illustrating a configuration of a roller charging device and an image forming apparatus according to a second embodiment.

FIG. 5 is an explanatory diagram showing a conventional method of using a charging roller.

[Explanation of symbols]

 101 Roller Charging Device 102, 102A Charging Roller 103 Cleaning Blade 104 Photoconductor Drum 401 Roller Charging Device

Continuation of the front page (56) References JP-A-3-100676 (JP, A) JP-A-2-173677 (JP, A) JP-A-5-2312 (JP, A) JP-A-4-145463 (JP) JP-A-3-39771 (JP, A) JP-A-6-202447 (JP, A) JP-A-1-93762 (JP, A) JP-A-58-194061 (JP, A) 58-142368 (JP, A) JP-A-63-235977 (JP, A) JP-A-6-83165 (JP, A) JP-A-5-188738 (JP, A) JP-A-58-115761 (JP, A) U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) G03G 15/02 G03G 21/10

Claims (6)

(57) [Claims] 1. A roller charging device having at least a charging roller that is driven to rotate in contact with a photosensitive drum and a cleaning blade for removing foreign matter such as toner attached to the surface of the charging roller, wherein the charging roller is The relationship between the contact pressure P ₁ and the friction coefficient μ ₁ between the charging roller and the cleaning drum and the contact pressure P ₂ and the friction coefficient μ ₂ between the charging roller and the cleaning blade is P ₁ > P ₂ and μ. Ri ₁ <mu ₂ der, the cleaning blade rubber hardness of the charging roller
A roller charging device characterized by having a hardness higher than the rubber hardness of the roller. 2. The charging roller has a rubber hardness of 40 (J).
ISA) or more of epichlorohydrin rubber, and the cleaning blade has a rubber hardness of 40 (JIS).
A) A synthetic rubber comprising:
3. The roller charging device according to claim 1. 3. The cleaning roller according to claim 1 , wherein
Due to friction with the developer, the surface of the charging roller
Having the same polarity as the toner.
3. The roller charging device according to 1 or 2 . 4. A roller charging device according to claim 3,
An image forming apparatus comprising: a photosensitive drum surface negatively charged by the charging roller;
Exposure means for exposing the photosensitive drum, and a latent image formed on the photosensitive drum with a negative polarity toner.
Developing means for reversal development, and transfer for transferring the visible image formed by the developing means to recording paper
Means and a surface of the photosensitive drum after transfer by the transfer means is completed.
Cleaning means for cleaning a surface with a cleaning member
The charging roller of the roller charging device has a
The surface is covered with a fluororesin, and the cleaning blade is
Is from ethylene propylene rubber or urethane rubber
An image forming apparatus comprising: 5. The roller charging device according to claim 3,
An image forming apparatus using the negatively charged by the charging roller of the photosensitive drum surface
Exposure means for exposing the photosensitive drum, and a latent image formed on the photosensitive drum with a positive toner.
Developing means for developing, and transfer for transferring the visible image formed by the developing means to recording paper
Means and a surface of the photosensitive drum after transfer by the transfer means is completed.
Cleaning means for cleaning a surface with a cleaning member
The charging roller of the roller charging device has a
The surface is covered with polyamide resin and the cleaning
The image forming apparatus is made of urethane rubber or ethylene propylene rubber . 6. The photosensitive drum and a photosensitive drum during non-image formation.
Characterized in that the charging roller is periodically idled.
The image forming apparatus according to claim 4, wherein: