JP2007108259A - Charging current detecting member and process cartridge having same, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a charging current detecting member capable of measuring the value of a current flowing from a charging roller to a photoreceptor by a method which is hardly affected by an electrical supply path and an image forming unit other than static electrification, a process cartridge having the charging current detecting member, and an image forming apparatus. <P>SOLUTION: The detecting member 21 detects the value of the current flowing from the charging roller. The detecting member is arranged nearby the charging roller 2 opposite thereto and has a metal surface coated with the same material with a photoreceptor 1 to the same film thickness with the same layer constitution with the photoreceptor 1 as a surface opposed to the charging roller 2, thereby providing the charging current detecting member 21, the process cartridge having the charging current detecting member 21, and the image forming apparatus. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a charging current detection member, a process cartridge having the same, and an image forming apparatus.

In the case of a non-contact charging roller, it is necessary to apply a constant voltage corresponding to the change in the gap between the charging roller photoconductors instead of considering only the resistance variation of the charging roller as in the case of the contact charging device.
For this reason, in the prior art, control is performed by measuring the current value flowing from the charging roller to the photosensitive member and taking the average of the current values. However, as a method for measuring the value of the current flowing from the charging roller to the photosensitive member, the current output from the high-voltage power supply (power pack) is detected. However, AC interference occurs between the power supply path from the power pack to the charging roller. The current that contributes to the discharge between the charging roller and the photoconductor cannot be calculated properly.
For this reason, in the conventional machine, when AC is applied slightly more or when the AC bias is controlled to be lower as a result, an abnormal image is generated by setting the current target value to be changed. I was able to cope with it sometimes.
When AC is applied a little, there is a problem that a problem of excessive AC bias occurs. Further, in the latter case, where the setting that can change the current target value is provided, there is a problem that the problem cannot be prevented because it corresponds to the occurrence.

Therefore, in Patent Document 1, charging is performed by detecting a total current flowing from a charging roller to a power supply device that applies a constant voltage controlled DC voltage and a constant voltage controlled AC voltage to a charging member, and a charging roller. Determining the voltage applied to the roller is disclosed. As a result, a voltage is applied from the power supply device to the charging member arranged with a predetermined gap facing the surface of the image carrier to generate a discharge between the charging member and the surface of the image carrier. In the charging device for charging the surface of the image carrier, the surface of the image carrier can be charged to a predetermined constant value even if the gap changes.

However, there are many members that are close to or in contact with the photosensitive member, such as development and transfer, in addition to the charging roller. For this purpose, a charging current detection member capable of measuring a current value flowing from the charging roller to the photosensitive member by a method that is not easily influenced by the image forming unit other than the feeding path and charging, a process cartridge having the charging current detecting member, and image formation A device was sought.

In Patent Document 2, a gap holding member is pressed between the non-contact charging roller and the photosensitive member to adjust the gap between the non-contact charging roller and the photosensitive member. An image forming apparatus is disclosed in which a press-contact position of a gap holding member is set in a portion inside a press-fitting region of a flange that is partly press-fitted into an end portion. As a result, the accuracy and reliability of gap management with respect to the photoreceptor of the non-contact charging roller can be improved, charging unevenness due to abnormal discharge, charging failure, etc. can be prevented, and high image quality can be obtained.

However, the gap between the charging member and the image carrier varies periodically or randomly depending on the eccentricity of the charging member and the image carrier, vibration during operation, and the like. The above method can improve the accuracy and reliability of the gap management, but it is not sufficient for the gap management due to fluctuations during operation, and the toner image formed on the image carrier has uneven density. Could not escape.

JP 2002-108059 A JP 2004-264792 A

Accordingly, the present invention has been made in view of the above problems, and the problem is that the current value flowing from the charging roller to the photosensitive member is measured by a method that is not easily affected by the image forming unit other than the power feeding path and charging. It is an object to provide a charging current detection member that can be used, a process cartridge having the charging current detection member, and an image forming apparatus.

The features of the present invention, which is a means for solving the above problems, are listed below.
The present invention is a charging current detection member for detecting a current value flowing from a charging roller, wherein the charging current detection member is disposed opposite to the vicinity of the charging roller, and a surface facing the charging roller is exposed to a metal surface. The charging current detecting member is characterized in that the same material as that of the photosensitive member is applied with the same film thickness and the same layer structure as the photosensitive member. A charging current detection member made of the same material as that of the photosensitive member is disposed in the vicinity of the charging roller, and the current value flowing from the charging roller to the charging current detection member is detected as a substitute characteristic value of the current value flowing from the charging roller to the photosensitive member. Therefore, the charging performance of the charging roller without worrying about the influence of interference and attenuation in the power supply path from the high-voltage power supply to the charging roller, and without considering the influence of members other than the charging roller contacting the photoconductor Therefore, by determining the voltage to be applied to the charging roller during image formation based on the value, it is possible to always maintain high quality charging characteristics and prevent the occurrence of abnormal images.

The present invention is a charging current detection member for detecting the current value flowing from the charging roller,
The charging current detection member is disposed in the vicinity of the charging roller, and the surface facing the charging roller has a metal surface coated with a resin constituting the charge transport layer of the photosensitive member with the same thickness as the total thickness of the photosensitive member. A charging current detecting member. By applying only the resin that constitutes the charge transport layer to the surface layer of the charging current detection member to the same film thickness as the photoconductor, it is possible to make an inexpensive component having resistance similar to that of the photoconductor in the dark part facing the charging roller. Therefore, the current can be detected with a pseudo-photosensitive member having similar electric characteristics, so that the current value flowing from the charging roller to the photosensitive member can always be controlled to the same value, and charging failure due to insufficient charging bias is prevented. be able to.

According to the present invention, in the charging current detection member described above, the charging current detection member is characterized in that at least a surface facing the charging roller has the same shape as a surface facing the photosensitive member of the charging roller. It is a member. By making the shape of the charging current detection member a curved surface obtained by partially cutting the surface of the photoconductor facing the charging roller, a gap similar to that between the charging roller and the photoconductor can be formed. Since the current value close to the current value flowing through the body can be measured, the current value flowing from the charging roller to the photoconductor is always controlled to the same value by determining the voltage applied to the charging roller based on the current value. be able to.

The present invention is the above-described charging current detection member, characterized in that the charging current detection member can be divided and detected in the longitudinal direction of the charging roller. By dividing the current detection member in the longitudinal direction, it is not the average of the entire width, but even when there is a locally high resistance part (dirty part), a bias is set so that the current flows sufficiently in that part. Therefore, charging failure due to insufficient charging bias can be prevented.

The present invention relates to a process cartridge in which a photosensitive member, a non-contact charging roller for charging the photosensitive member by applying a constant-voltage controlled voltage to a roller disposed on the photosensitive member via a gap, and a charging roller And a charging current detecting member according to any one of claims 1 to 4 provided in the vicinity of the process cartridge. By forming the charging roller, the charging current detection member, and the photoconductor in the form of an integral cartridge, the exchangeability of components when the life is reached can be improved.

According to the present invention, in the process cartridge described above, the process cartridge is provided with a charging roller cleaning member that contacts the charging roller, and only the charging roller cleaning member member can be replaced separately. This is a featured process cartridge. Since the charging roller cleaning member can be replaced separately, the charging roller cleaning member, which seems to have the shortest life, is frequently replaced. Life can be extended. Examples of the charging roller cleaning member include a charging roller cleaner.

According to the present invention, an image forming apparatus includes a photosensitive member, a non-contact charging roller that charges the photosensitive member by applying a constant-voltage controlled voltage to a roller disposed with respect to the photosensitive member via a gap, The charging current detection member described above provided in the vicinity of the roller, a current detection unit for detecting a current flowing from the charging roller to the charging current detection member, and the charging roller during image formation based on the detected current value And a voltage control unit that determines and controls a voltage value to be applied. A charging current detection member made of the same material as that of the photosensitive member is disposed in the vicinity of the charging roller, and the current value flowing from the charging roller to the charging current detection member is detected as a substitute characteristic value of the current value flowing from the charging roller to the photosensitive member. Therefore, the charging performance of the charging roller without worrying about the influence of interference and attenuation in the power supply path from the high-voltage power supply to the charging roller, and without considering the influence of members other than the charging roller contacting the photoconductor Therefore, by determining the voltage to be applied to the charging roller during image formation based on the value, it is possible to always maintain high quality charging characteristics and prevent the occurrence of abnormal images.

According to the present invention, an image forming apparatus includes a process cartridge described above, a current detection unit that detects a current that flows from a charging roller to the charging current detection member, and a charging roller that is used during image formation based on a detected current value. An image forming apparatus having a voltage control unit for determining and controlling a voltage value to be applied, and determining a replacement timing of the charging roller cleaning member according to a current value flowing from the charging roller to the charging current detecting member. . By predicting an increase in resistance due to contamination of the charging roller from the value of the current flowing through the charging current detection member, it is possible to detect the lifetime of the charging roller cleaner due to contamination saturation, and the charging that seems to be the shortest in the cartridge By frequently exchanging the roller cleaning member, it is possible to extend the life of the charging roller and the photosensitive member, which are the main parts of the cartridge.

According to the present invention, in the image forming apparatus described above, the image forming apparatus divides the detection current value of the charging current detection member by the discharge width to obtain a detection current value at a point where the current value per unit length is the smallest. An image forming apparatus that determines a current value to be applied to a charging roller based on the image forming apparatus. By setting a bias that allows a sufficient current to flow even in a portion where the current is most difficult to flow, a necessary bias can be secured over the entire width, so that charging failure due to insufficient charging bias can be prevented.

In the image forming apparatus according to the present invention, a current detection member for measuring a current value flowing from the charging roller is provided in the vicinity of the charging roller, and the current value flowing from the charging roller is provided on the current detection member. And the voltage to be applied to the charging roller during image formation can be determined from the current value. Furthermore, in order to increase the accuracy of current measurement, the current detection member can be divided in the longitudinal direction so that variations due to location can be detected.

The best mode for carrying out the present invention will be described below with reference to the drawings. Note that it is easy for a person skilled in the art to make other embodiments by changing or correcting the present invention within the scope of the claims, and these changes and modifications are included in the scope of the claims. The following description is an example of the best mode of the present invention, and does not limit the scope of the claims.

Example 1
FIG. 1 is a cross-sectional view of the main part of the charging current detection member of the present invention.
Reference numeral 1 denotes a photosensitive member, 2 denotes a charging roller, and 21 denotes a charging current detection member used in the present invention. Since the value of the current flowing between the photosensitive member 1 and the charging roller 2 is affected by the gap, it is desirable that the charging current detection member 21 has the same gap shape as the photosensitive member 1.
Since this time, a combination of a photoconductor having a diameter of 30 mm and a charging roller having a diameter of 12 mm, the charging current detection member 21 is shaped like a part of a cylinder having a diameter of 30 mm.
With such a configuration, a gap having a shape similar to the shape of the closest gap between the charging roller and the photosensitive member can be formed between the charging roller 2 and the charging current detection member 21. The current flowing through the photosensitive member 1 can be measured in a pseudo manner.
Further, the surface of the charging current detection member 21 is coated with a resin having the same layer structure as that of the photoreceptor 1 so that a value closer to the current flowing through the photoreceptor 1 can be detected. 10 is a metal base, 11 is an undercoat layer, 12 is a charge generation layer, 13 is a charge transport layer, and 14 is a high hardness charge transport layer containing a filler. By taking the same layer structure in this way, the current value corresponding to the current value flowing to the photosensitive member 1 can be measured by measuring the current value flowing through the charging current detection member 21.
However, if the charging roller 2 is not separated from the photoreceptor 1, a current flows through both the charging current detection member 21 and the photoreceptor 1 when a voltage is applied to the charging roller 2. It is desirable that the charging roller 2 is made to float electrically from the ground, or the charging roller 2 is brought into contact with the charging current detection member 21 in a state where it is mechanically separated to a position where the charging roller 2 is not discharged to the photoreceptor 1. In this embodiment, the photosensitive member 1 side is floated.

FIG. 2 is a diagram showing the connector shape of the charging current detection member 21. If the current value is attenuated between the charging current detection member 21 and the detection unit that performs actual current detection, the effect of the present invention is reduced. Therefore, the tip of the charging current detection member 21 is processed into a connector shape, The configuration is such that it directly hits the terminal coming out of the substrate of the current detection unit. Thus, by shortening the power feeding path, the state of the charging roller 2 can be detected with higher sensitivity.
In the conventional method, since the output current from the power pack is read, the combination of the photosensitive member 1 and the charging roller 2 having the same average current value is about 5% due to the wiring of the harness. The variation of the average value of the detected current value can be suppressed to 2% or less.

(Example 2)
FIG. 3 is a diagram showing a second embodiment of the present invention. Only the polycarbonate 15 made of the same material as the base of the charge transport layer was applied to the surface of the charging current detection member 21 instead of the resin having the same configuration as that of the photoreceptor 1.
For example, in the case of the embodiment of the present invention, in the case of the photosensitive member 1 having a thickness of 32 μm, the undercoat layer 11 is ˜5 μm, the charge generating layer 12 is 1 μm, The high hardness filler layer 14 is about 5 μm, and the charge transport layer 13 is 22 μm. Since the filler layer 14 is also a mixture of fillers and the base polymer is the same resin as the charge transport layer 13, the substance is substantially the same even when the resin transport layer 13 is applied to a thickness of 32 μm. It becomes charging performance. By doing so, there is an advantage that the photogeneration of the charge generation layer 12 is eliminated. Furthermore, since only one material is applied individually, the cost can be reduced.

(Example 3)
FIG. 1 is a cross-sectional view of the main part of the charging current detection member of the present invention. FIG. 4 is a cross-sectional view of the main part of the process cartridge of the present invention.
Here, the value of the current flowing from the charging roller 2 to the photosensitive member 1 is influenced by the contamination of the charging roller 2 in addition to the gap between the photosensitive member and the charging roller in the case of the non-contact and proximity charging method. For this reason, the charging roller cleaner 22 is disposed so as to contact the charging roller 2, but the charging roller 2 is partially changed depending on the contact state of the charging roller cleaner 22 and the performance of the photosensitive member cleaning member that is upstream of the charging roller 2. May get dirty. In particular, when edge chipping or the like occurs in the cleaning blade 6 that is a photosensitive member cleaning member or uneven wear occurs, only a part of the charging roller 2 in the longitudinal direction is selectively soiled (see FIG. 5). ).
FIG. 5 is a diagram illustrating the charging roller 2 according to the third embodiment. The portion (a) in FIG. 5 is a portion with a large amount of dirt. The main components of this dirt are toner that has passed through the cleaning blade 6, silica that is an external additive of the toner, and coating resin and paper powder that comes from the transfer material. , Because they all have high resistance, they tend to make current difficult to flow.
Therefore, there is a difference in current flow between the unclean (b) portion and the dirty (a) portion. In order to discharge the portion (a) and to charge the photosensitive member 1 at a level that does not affect the image, the most dirty place is where the current is most difficult to flow. In addition, it is necessary to determine a voltage value to be applied to the charging roller 2 during image formation. However, it cannot be detected by measuring the current flowing from the power pack to the charging roller 2 or directly measuring the current flowing from the charging roller 2 to the photosensitive member 1. This is because in such a system, the current values of the part with much dirt and the part with little dirt are averaged.
Therefore, in the system in which the charging current detection member 21 is provided as in the present invention, the charging current detection member 21 can be divided and detected for each area by dividing the charging current detection member 21 in the longitudinal direction. By dividing and detecting in this way, it is possible to detect a variation in the difficulty of the current flow in the longitudinal direction due to the charging roller dirt, and to normally charge even the portion where the current hardly flows.

FIG. 6 is a diagram illustrating the charging current detection member 21 according to the third embodiment. Specifically, a charging current detection member 21 that is electrically divided into three equal parts in the longitudinal direction is installed. In this method, two masks are formed on a base made of glass or resin, and divided into three in the longitudinal direction. After applying a conductive resin, the same polycarbonate as the charge transport layer 13 is coated on the photosensitive member 1. Applied to about 30 μm.
A voltage is applied to the charging roller 2 to detect a current flowing from the charging roller 2 to the charging current detection member 21. If the charging roller 2 is not separated from the photosensitive member 1, the voltage is applied to the charging roller 2. When applied, current flows through both the charging current detection member 21 and the photosensitive member 1, so that the charging roller 2 is discharged to the charging current detection member 21 in a state where the charging roller 2 is mechanically separated to a position where it does not discharge to the photosensitive member 1. It is desirable to make it.
In addition, if the current value is attenuated between the charging current detection member 21 and the detection unit that performs actual current detection, the effect of the present invention is reduced. Therefore, the tip of the charging current detection member 21 is processed into a connector shape, The configuration is such that it directly hits the terminal coming out of the substrate of the current detection unit. Thus, by making the detection signal circuit as short as possible, the state of the charging roller 2 can be detected with higher sensitivity.

In this state, a DC + AC bias of DC = −500 V, AC = 1.8 kVpp, f = 1 kHz is applied to the charging roller 2. Then, a DC current, a current of Idc = −7 to 8 μA, and a current of Iac = 0.56 to 0.58 mA flowed from the charging roller 2 to the three charging current detection members 21 in the unstained roller. On the other hand, in the roller where the end of the roller is dirty, the same current of Idc = −7.7 μA and Iac = 0.55 mA was detected as in the roller not dirty in the center, but the end is dirty. Only a current of Idc = −6.8 μA and Iac = 0.51 mA flowed through the current detection plate corresponding to the portion. At this time, a background stain corresponding to the stain was seen on the image. Therefore, as a result of searching for a voltage at which a current equal to that of other portions flows even in a portion where current does not easily flow, a bias of DC = −500 V and AC = 1.95 kVpp was applied to the charging roller. A current of Idc = −7.8 μA and Iac = 0.62 mA flowed, whereas Idc = −7.5 μA and Iac = 0.55 mA at the end, and the image was also good.
By applying a voltage that allows a sufficient current to flow even in a portion where current does not easily flow, a voltage that sufficiently discharges even a portion that is difficult to discharge can be applied, so that uniform chargeability can be obtained.
Further, since the output current from the power pack is read in the conventional method, the combination of the photosensitive member and the charging roller having the same average current value due to the wiring of the harness from the power pack to the charging roller was about 5%. However, according to the method of the present invention, the variation in the average value of the detected current value can be suppressed to 2% or less, and a good image without background stain can be obtained even if there is a partial stain. It was.

Example 4
FIG. 4 is a sectional view of the main part of the process cartridge of the present invention.
In this embodiment, the photosensitive member 1, the charging roller 2, the charging roller cleaner 22, the charging current detection member 21, and the photosensitive member cleaning member are integrated into a process cartridge. Only the charging roller cleaner 22 can be separated from the process cartridge.
The charging roller cleaner 22 is provided to prevent the charging performance of the charging roller 2 from being deteriorated. Specifically, when the charging roller 2 is contaminated with toner or paper powder, the surface resistance is increased and the charging discharge current is increased. Decreases even at the same applied voltage.
When the cleaning performance of the charging roller cleaning member deteriorates and the charging roller 2 begins to become dirty, the resistance of the charging roller 2 increases and the flowing current decreases. Due to the AC bias, the photosensitive member 1 is electrostatically fatigued and the entire cartridge has a lifetime.
However, since the resistance value of the charging roller 2 can be maintained over a long period of time by frequently replacing the charging roller cleaner 22, the life of the cartridge can be extended. At this time, the life of the charging roller cleaner 22 can be detected from the current value of the charging current detecting member 21 by utilizing the fact that the resistance of the charging roller 2 increases when the performance of the charging roller cleaner 22 decreases.
Specifically, the current value flowing from the charging roller 2 to the charging current detection member 21 for each environment is stored in a memory, and the combination of the environment having the same current value, the same charging roller 2 and the same charging current detection member 21 is used. If it decreases, it indicates that the charging roller 2 is dirty, that is, the charging roller cleaner 22 is saturated and cannot be cleaned any more.
Therefore, when the amount of current flowing through the charging current detection member 21 has decreased by a certain level or more (in this embodiment, when a current value drop of 5% or more is observed in the same environment and the same roller), the life of the charging roller cleaner 22 is determined. Added an alert. At this time, since only the charging roller cleaner 22 can be removed separately from the process cartridge, the photosensitive member 1 and the roller can be kept stationary, so that the running cost can be reduced.

It is principal part sectional drawing of the charging current detection member of this invention. FIG. 3 is a diagram showing a connector shape of a charging current detection member 21. It is a figure which shows Example 2 of this invention. It is principal part sectional drawing of the process cartridge of this invention. FIG. 6 is a diagram illustrating a charging roller 2 according to a third embodiment. FIG. 6 is a diagram showing a charging current detection member 21 in Example 3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Charging roller 6 Cleaning blade 10 Metal base 11 Undercoat layer 12 Charge generation layer 13 Charge transport layer 14 High hardness charge transport layer 15 containing filler Polycarbonate 21 Charging current detection member 22 Charging roller cleaner

Claims (9)

A charging current detection member for detecting a current value flowing from the charging roller,
The charging current detection member is disposed in opposition to the vicinity of the charging roller, and the surface facing the charging roller is coated on the metal surface with the same material as the photoconductor with the same film thickness and the same layer configuration. A charging current detection member. A charging current detection member for detecting a current value flowing from the charging roller,
The charging current detection member is disposed in the vicinity of the charging roller, and the surface facing the charging roller has a metal surface coated with a resin constituting the charge transport layer of the photosensitive member with the same thickness as the total thickness of the photosensitive member. A charging current detection member characterized by comprising: In the charging current detection member according to claim 1 or 2,
The charging current detecting member, wherein at least a surface facing the charging roller has the same shape as a surface facing the photosensitive member of the charging roller. In the charging current detection member according to claim 1,
A charging current detection member, wherein the charging current detection member can be divided and detected in the longitudinal direction of the charging roller. Process cartridge
A non-contact charging roller for charging a photosensitive member by applying a constant voltage controlled voltage to a roller disposed through a gap with respect to the photosensitive member, and a charging roller provided near the charging roller. And a charging current detecting member according to any one of 1 to 4. The process cartridge according to claim 5,
The process cartridge is provided with a charging roller cleaning member that contacts the charging roller, and the charging roller cleaning member can be replaced separately. The image forming apparatus
A photoreceptor,
A non-contact charging roller for charging the photosensitive member by applying a constant voltage controlled voltage to a roller disposed through a gap with respect to the photosensitive member;
The charging current detection member according to any one of claims 1 to 4, which is provided in the vicinity of the charging roller;
A current detection unit that detects a current flowing from the charging roller to the charging current detection member; and a voltage control unit that determines and controls a voltage value to be applied to the charging roller during image formation based on the detected current value. An image forming apparatus. The image forming apparatus
A process cartridge according to claim 5 or 6,
A current detection unit for detecting a current flowing from the charging roller to the charging current detection member;
A voltage control unit that determines and controls a voltage value to be applied to the charging roller during image formation based on the detected current value;
An image forming apparatus, wherein a replacement timing of the charging roller cleaning member is determined according to a current value flowing from the charging roller to the charging current detecting member. The image forming apparatus according to claim 7 or 8,
The image forming apparatus determines a current value to be applied to the charging roller based on a detected current value at a position where the current value per unit length is the smallest, which is obtained by dividing the detected current value of the charging current detecting member by the discharge width. An image forming apparatus.

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