JPH086352A - Charging device - Google Patents

Abstract

PURPOSE:To suppress the generation of ozone by an electric discharge and prevent the occurrence of toner filming by covering the tip of a charging member with an insulating member, and charging a charged member from only a charge section located nearby. CONSTITUTION:The charging blade 21 of the charging device 20 of this electrostatic recording device is provided with an elastic plate-like insulation section 212 made of insulating urethane rubber and a charge section 214 made of a high-resistance body via a plate-like conducting member 211 made of a conducting resin or conducting rubber on the surface of an insulating substrate 212A by a support member 213. The insulation section 212 is provided at the tip of the charging blade 21 to be first brought into contact with the photoreceptor layer 10a of a photoreceptor drum 10. The photoreceptor layer 10a is charged by the charge section 214 located nearby while the insulation section 212 is kept in contact with the photoreceptor layer 10a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging device for an image forming apparatus using an electrostatic transfer process such as an electrophotographic copying machine or an electrostatic recording device, and more particularly to a proximity charging device.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus, a charging device using a corona charger is generally used for charging an image forming body such as a photosensitive drum. This corona charger applies a high voltage to the discharge wire to generate a strong electric field around the discharge wire to perform gas discharge, and the charged ions generated at that time are adsorbed to the image forming body to charge. Done.

Since the corona charger used in such a conventional image forming apparatus can be charged without mechanical contact with the image forming body, it is said that the image forming body is not damaged during charging. Have advantages. However, since this corona charger uses a high voltage, there is a risk of electric shock or leakage, and ozone generated by gas discharge is harmful to the human body, which shortens the life of the charged body. Had. Further, the charging potential of the corona charger is unstable because it is strongly affected by temperature and humidity. Further, the corona charger generates noise due to high voltage, which causes electrophotographic image formation as a communication terminal or an information processing device. This is a major drawback when using the device.

Many drawbacks of such corona chargers are:
The cause is that gas discharge is involved in charging.

Therefore, charging is performed by rubbing the surface of an image-receiving member, which is an image forming member, with a charging roller composed of a conductive member and a plate-shaped charging blade without performing high-pressure gas discharge unlike a corona charger. A charging device adapted to perform the above is disclosed in JP-A-63-149668 and JP-A-1-191161. 14 (a) and 14 (b) are cross-sectional views showing the charging device disclosed in Japanese Patent Laid-Open No. 1-191161.

FIG. 14A shows a charging member having a roller shape. The charging roller 40, which is a charging member, includes a lower layer portion 42 and a cored bar 41 made of a material having elasticity and conductivity, and an object to be charged as necessary. And a thin upper layer portion 43 made of a high resistance material that is in contact with the photoconductor drum 10. A bias voltage obtained by superimposing an alternating current component Va on a direct current component Vd from a bias power source 24 is passed through a core metal 41 to a lower layer portion 42. The photoconductor drum 10 is brought into contact with the photoconductor drum 10 at a predetermined pressure and is rotated by the rotation of the photoconductor drum 10 to charge the photoconductive layer of the photoconductor drum 10 with a discharge phenomenon. The upper layer portion 43 is a protective layer used to prevent overcurrent.

FIG. 14B shows a charging member having a plate shape. A charging blade 50, which is a charging member, includes a supporting member 51 made of a metal and a lower layer having a rectangular cross section and having elasticity and conductivity. The photosensitive member is composed of a portion 52 and an upper layer portion 53 made of a high resistance material, and a bias voltage similar to that of the embodiment of FIG. 14A is supplied to the supporting member 51 from a bias power source (not shown). The photosensitive drum 10 is brought into contact with the body drum 10 at a predetermined pressure in the forward direction with respect to its rotation,
To charge the photosensitive layer of.

[0008]

The image forming apparatus using the above-mentioned contact charging device still has a problem that ozone is generated. It is shown in Figure 14 (a) and (b).
2 of the photosensitive drum 10 and the charging member 40, which are indicated by the broken line circle in FIG.
This is because gas discharge is performed and ozone is generated in the proximity portion 45 of the location. In particular, discharge easily occurs at the edge portion of the tip of the plate-shaped charging blade 50, and ozone is often generated.
Further, discharge unevenness is likely to occur in the separated portion.

In the contact charging section, the toner that cannot be completely removed in the cleaning section or the toner coming from the developing unit is pressed by the charging section and further fixed to the charging member 40 by charging to form a filming layer. As a result, uniform charging cannot be performed. Further, when the proximity charging is used instead of the contact charging, it is difficult to determine the size of the gap, and good charging cannot be obtained.

An object of the present invention is to solve these problems and to provide a charging device in an image forming apparatus capable of performing stable charging with extremely little ozone generation.

[0011]

This object is achieved by any one of the following technical means a, b, c, d and e.

(A) In a charging device for charging by charging a charging member to an object to be charged, the charging member has an insulating part and a charging part on a support, and the insulating part is a surface to be charged. The charging device is characterized in that the charging unit is placed in proximity to the charging surface of the body to be charged while being brought into contact with the charging unit.

(B) In a charging device for charging a charging member by bringing the charging member into contact with the charging member, the charging member having an insulating portion and a charging portion on a support has the insulating portion contacting the charging member. A charging device characterized in that the contact position where it contacts can be moved.

(C) A charging device characterized in that the charging member has an insulating portion and a high resistance portion formed on a conductive support.

(D) The charging device according to item (a), wherein the charging member is plate-shaped or rod-shaped.

(E) The charging device as described in the item (b), wherein the pressing force of the charging member on the member to be charged can be changed.

Further, when the charging member is a plate-shaped member, the charging device of the image forming apparatus provided with the charging device is characterized by not having an insulating free end, which is a preferred embodiment.

[0018]

In the present invention, as described above, the charging member and the member to be charged are brought into contact with each other by the insulating member, and charging is not performed from this contact portion. Since the charging is performed, the discharge is extremely small, the ozone generation is small, and the toner filming does not occur. Therefore, it can be said that the charging of the present charging device is not the contact type but the proximity type. It is appropriate that the proximity distance at which good charging is performed in the charging portion is 5 to 500 μm, and when discharge is made from this distance, ozone generation is slight,
It does not deteriorate the photosensitive surface of the photosensitive drum or impair the health of the human body.

It is difficult for toner filming to occur due to the fact that the charging section does not come into contact with the member to be charged and this discharge phenomenon is small, but toner from the developing unit and the cleaning section is blocked. By surrounding the charging member with a shield member for preventing the occurrence of toner filming, a good result is produced.

As the charging member, in addition to the blade-shaped member described above, a cylindrical member is also effective, and it is assumed that the charging member is fixed without rotating around as the photosensitive member rotates. The charging ability is almost the same as that of a blade.

In such a close proximity charging device of the present invention, the charging portion and the charged body are separated on the downstream side of the rotation of the charged body from the position where the plate-shaped or cylindrical charging member contacts the surface of the charged body. Discharge is more stable when the area is the charged area,
There is little influence of toner from the cleaning section, and toner filming of the charging section does not easily occur.

[0022]

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

FIG. 1 is a sectional view showing the outline of the construction of an electrostatic recording apparatus which is an image forming apparatus of the present invention. In the figure,
Reference numeral 10 is a photoconductor drum composed of (-)-charged OPC, which is an image forming body that rotates in the direction of the arrow (clockwise) and is a charged body
A charging device 20, which will be described later, an exposure part 12 on which the image light L from the exposure device is incident, a developing device 30, a transfer roller 13, a cleaning device 150, and the like are provided on the peripheral portion thereof.

The basic operation of the copy process of this embodiment is as follows.
When a copy start command is sent from an operation unit (not shown) to a control unit (not shown), the control unit controls the photosensitive drum.
10 starts rotating in the direction of the arrow. As the photosensitive drum 10 rotates, its peripheral surface is uniformly charged by a charging blade 21 as a charging member, which will be described later, and passes through. An image is written on the photosensitive drum 10 by the image writing device or the like from the image writing device or the like on the photoconductor drum 10 to form an electrostatic latent image corresponding to the image.

There is a two-component developer consisting of magnetic particles and toner in the developing device 30, which is agitated by agitating screws 33A and 33B, and then adhered to the outer circumference of the developing sleeve 31 which is outside the magnet roller 32. Then, a magnetic brush of developer is formed, and a predetermined AC bias voltage is applied to the developing sleeve 31, and regular or reversal development is performed in the developing area facing the photoconductor drum 10 to form a toner image.

From the paper feed cassette 40, the recording papers P are fed one by one by a first paper feed roller 41. The fed recording paper P is sent onto the photosensitive drum 10 by the second paper feed roller 42 which operates in synchronization with the toner image on the photosensitive drum 10. Then, by the action of the transfer roller 13, the toner image on the photoconductor drum 10 is transferred onto the recording paper P and separated from the photoconductor drum 10. The recording paper P on which the toner image has been transferred is sent to a fixing device (not shown) via the conveying means 80, is nipped by a heat fixing roller and a pressure bonding roller, melted and fixed, and then discharged outside the apparatus. Recording paper P
The surface of the photoconductor drum 10 that has toner remaining without being transferred to the surface of the photosensitive drum 10 is scraped off and cleaned by the cleaning device 150 including the blade 151 and the like, and waits for the next image recording.

FIG. 2 is a sectional view showing an embodiment of the charging device 20 used in the image forming apparatus of FIG. In the figure,
21 is a charging blade as a charging member, 211 is a plate-shaped conductive member made of metal, conductive resin, conductive rubber or the like (the resistance of this member is preferably 10 ⁶ Ω · cm or less), and 212 is An elastic plate-shaped insulating portion made of insulating urethane rubber or the like, and 213 is a support member that holds the base portion of the charging blade 21 via an insulating material 213a. A conductive member on the surface of the charging blade 21 that contacts the photosensitive drum 10.
There should be no step at the boundary between the insulating portion 212 provided outside the 211 and the charging portion 214 covered with a high resistance body of 10 ⁶ to 10 ¹⁰ Ω · cm or less, which is further connected to the insulating member. The tip of the charging blade 21 may be a free end having an insulating property, but is preferably in contact with the surface of the photosensitive layer of the photosensitive drum 10 if possible. The photoconductor drum 10 includes a conductive base material 10b and a photoconductor layer 10a covering the surface thereof.
And the conductive base material 10b is grounded.

The charging blade 21 is supported by the support member 213.
The tip portion 212a of the insulating portion (insulator layer) 212 has the photosensitive drum 10
It is supported so as to come into contact with the photoconductor layer 10a at a predetermined pressure.

Reference numeral 24 denotes a conductive member 211 of the charging blade 21.
The conductive member 211 is grounded via the bias power source 24, which is a bias power source that applies a bias voltage between the conductive member 211 and the conductive base material 10b of the photosensitive drum 10.

With the above-described structure, the insulating portion 212 formed on the conductive member 211 of the charging blade 21 has a surface region which is in pressure contact with the photosensitive layer 10a of the photosensitive drum 10, and further the photosensitive drum is formed. In a surface area gradually separated from the surface of the photoconductor layer 10a while forming a charged area by forming an oscillating electric field by the bias power source 24 which is gradually separated toward the downstream side of the high resistance body (charging portion). Is designed to be charged. Then, a non-charged region is formed at the pressure contact portion of the insulating portion 212.

The bias power supply 24 is a power supply for supplying an AC bias voltage in which the AC component Va is superimposed on the DC component Vd set to the same value as the voltage to be charged, and is approximately the same as the voltage to be charged, -500 to -1,000. An AC bias voltage in which a peak-to-peak voltage (V _C ^PP ) 200 to 3,500 V and an AC component Va having a frequency of 0.3 to 10 kHz are superimposed on the DC component Vd of V is supplied through a protective resistor. As a result, an oscillating electric field is formed in the charging region, and the charging portion of the high-resistivity material coated on the conductive member 211 and the photosensitive layer 10a are gradually separated from each other in the proximity separation distance. In the range, the surface of the photoconductor is efficiently and stably charged. It was found that if the separation distance is 5 to 500 μm, there is little uneven discharge and uniform charging is performed.

In the present invention, the contact between the charging blade 21 as the charging member and the photosensitive layer 10a of the photosensitive drum 10 is performed by the insulating portion (insulating layer) 212, and the high resistance layer, that is, the charging portion and the photosensitive portion A close distance is maintained between the body layer 10a and the body layer 10a, and charging is performed during this distance.

The close spacing at this time is made by adjusting the pressing amount of the charging blade 21 as a charging member to the photosensitive drum 10, that is, by moving the positional relationship of the charging portion, and the adjustment amount thereof is adjusted. You can decide. The positional relationship can also be moved by sliding the blade 21 horizontally.

Next, a method of manufacturing the charging blade 21 as the charging member used in the present invention will be described with reference to the sectional views of FIGS.

A metal plate of conductive member 211 or a plate of conductive rubber or conductive resin is laminated on an insulating base 212A such as ceramics such as alumina, glass, plastic, silicon rubber or urethane, rubber, etc. Of the elastic member 211 is covered with a high-resistivity layer serving as the charging portion 214, leaving a region near the tip end thereof, and an insulating portion (insulating layer) 212 of urethane rubber or silicon rubber is covered and joined to the region considerably near the tip end. Then, scrape off the upper part at the dotted line in FIG.
The state shown in the sectional view of FIG.

FIG. 5 shows the conductive member in FIG.
Do not extend 211 to the region of the tip of the insulating portion 212, but extend and cover the high resistance layer 214 on that portion, and cut the dotted line portion of the surface similar to FIG. 4 to show it in FIG. 5B. Is finished.

Although the insulating substrate 212A is shown as an insulating layer in FIGS. 4 and 5 as described above, the one shown in FIG.
The base is a conductive member 211 instead of an insulator layer, and a high resistance layer 214 is covered on the conductive member 211 except the tip region thereof, and the insulator is formed in the tip region. Layer 2
12 is covered, and as shown in FIG. 6 (a), the portion indicated by the dotted line is scraped off to finish as shown in FIG. 6 (b).

In any case, in the embodiment of the charging blade 21 as the above three types of charging members, even if the tip of the charging blade 21 is in contact with the photoconductor drum 10, the contact portion is insulated. The body layer 212 and the high resistance layer 214 are in contact with each other, but when the high resistance layer 214 is in contact, the conductive member 211 is not arranged under the contact.

The charging of the photoconductor layer 10a of the photoconductor drum 10 does not occur from the above-mentioned contact portion, but from the high resistance layer coated on the conductive layer at the near portion gradually separated from the contact portion. It is done by electric discharge.

As a result, the charging portion is not affected by toner filming and generates less ozone, and the distance between the charging blade 21 and the photosensitive drum 10 can be stably set to a value of 5 to 500 μm. . The gap adjusting means is changed from the state shown in FIG. 11A to the state shown in FIG. 11B, that is, the charging blade 21.
By appropriately adjusting the pressing force of, the contact position is moved so that proper charging is performed. Further, as another means, although not shown, the charging blade 21 may be horizontally slid horizontally.

In the toner filming, the tip of the blade type charging member as described above is not pressed against the belly as shown in FIG. 10 (b), but the tip is exposed as shown in FIG. 10 (a). If the toner is pressed against the body, the residual toner is blocked, so that the toner passes under the blade and is pressed against the photoconductor by the contact pressure of the blade to cause toner filming to improve the photoconductor performance. It is possible to prevent the phenomenon of deterioration and the phenomenon of deterioration of the charging performance due to the adhesion of toner to the charging portion.

In order to prevent toner filming on the photosensitive member or the charging portion, as shown in the partial sectional views of FIGS. 7A, 7B and 7C, the toners of FIGS. The insulating portion 212 or the high resistance layer 214 at the tip portion of the charging blade 21 shown in each partial cross-sectional view is slightly higher and a step is formed between the charging portion and the charging portion, which has a great effect, and the occurrence of toner filming is practical. It will not become the upper support, and stable charging will continue.

As means for preventing toner filming, as shown in FIG. 8, a blade type shield member 223 made of a PET material is provided in front of and behind the contact portion with the photosensitive drum, and its tip is provided at the photosensitive drum 10. It is possible to prevent the residual toner on the photoconductor from coming into contact with the toner and to prevent the toner scattered from the cleaning portion and the developing portion from being attached to the charging portion, so that the occurrence of toner filming can be prevented.

The above is the description of the embodiment of the blade type charging member, that is, the charging blade 21, but the following embodiment of the columnar (rod-shaped) charging member will be described.

As shown in the sectional view of FIG. 3, the cylindrical charging member 21R of the columnar charging device 20R is a conductive member 211R.
A portion of the insulator layer 212R and a charging layer portion of the high resistance layer 214 are provided around and are in pressure contact with the photoconductor layer 10a of the photoconductor drum 10. The insulation layer 212R is pressed against the surface of the photoreceptor layer 10a. Then, the conductive member 211R
Between the conductive layer (conductive base material) 10b of the photoconductor drum 10 and the conductive layer 10b, a bias power source 24
Therefore, a high voltage is applied. The conductive layer (conductive base material) 10b of the photosensitive drum 10 is grounded.

Then, as shown in the sectional view of FIG. 12, the charging of the photosensitive drum 10 is changed from the state (a) to the state (b), so that the cylindrical columnar charging member 21R is pressed and deformed. Then, it becomes possible to adjust by adjusting the proximity distance between the high resistance layer 214R and the photoconductor drum 10.

To prevent toner filming on the photosensitive drum 10 in this case, as shown in FIG.
It is made by surrounding and contacting with a blade-shaped shield member 223 made of PET before and after R so that stable charging can be maintained.

Incidentally, the charging blade 21 or the cylindrical charging member 21R as the charging member is further increased in the movement shown in FIGS. 11 and 12, and the charging portion is rubbed with the surface of the rotating photosensitive drum 10, It is possible to remove contaminants such as toner from the charging unit.

Further, as shown in FIG. 13, the charging blade 21 or the cylindrical charging member 21R as a charging member can be brought into contact with the cleaning member 220 at any time to clean the charging portion. The cleaning member 220 is inserted between the charging blade 21 or the cylindrical charging member 21R and the photosensitive member, and resists the elasticity of the charging member to move the charging member to the photosensitive drum.
By separating it from the surface of 10, it can be pressed and rotated to scrape off contaminants such as toner.

It is also possible to use the charging device 20 of this embodiment to eliminate the charge on the photosensitive drum 10. The static elimination can be performed by setting only the DC component of the bias voltage to zero. After the image formation, only the AC component is applied to rotate the photoconductor drum 10 to eliminate the charge on the photoconductor drum 10.

[0051]

According to the present invention, with the configuration described above, the proximity charging area is formed only at the downstream side of the rotation of the charged body from the position where the plate-shaped or cylindrical charging member contacts the surface of the charged body, and the edge is formed. -Shaped electrode part is covered with an insulating member or high-resistor, so discharge does not occur at the edge part, ozone and charge unevenness are extremely small, and toner filming causes damage to the photoconductor surface It is possible to provide a charging device for an image forming apparatus in which the photosensitive layer is less likely to deteriorate and which is subjected to stable and uniform charging without any trouble.

[Brief description of drawings]

FIG. 1 is a sectional view showing the outline of the configuration of an image forming apparatus equipped with an embodiment of the present invention.

FIG. 2 is a sectional view showing an embodiment of the proximity charging device of the present invention.

FIG. 3 is a sectional view showing another embodiment of the proximity charging device of the present invention.

FIG. 4 is a cross-sectional view showing a manufacturing method and a configuration of an embodiment of a charging member used in the present invention.

FIG. 5 is a cross-sectional view showing a manufacturing method and a configuration of another embodiment of the charging member used in the present invention.

FIG. 6 is a cross-sectional view showing a manufacturing method and a structure of another embodiment of the charging member used in the present invention.

FIG. 7 is a cross-sectional view of an embodiment of a charging member having a stepped portion according to the present invention.

FIG. 8 is a cross-sectional view of a charging blade used in the present invention provided with a shield member.

FIG. 9 is a cross-sectional view in which a shield member is provided on a cylindrical charging member used in the present invention.

FIG. 10 is a cross-sectional view showing a contact state between a charging blade and a photosensitive drum used in the present invention.

FIG. 11 is a cross-sectional view showing a moving state of a close distance between a charging layer of a charging blade used in the present invention and a photoconductor layer.

FIG. 12 is a cross-sectional view showing a moving state of a close distance between a charging layer of a cylindrical charging member used in the present invention and a photoconductor layer.

FIG. 13 is a cross-sectional view showing a cleaning unit for the charging blade.

FIG. 14 is a sectional view showing a conventional contact charging device.

[Explanation of symbols]

 10 Photosensitive drum (charged body) 10a Photosensitive layer 10b Conductive substrate 20 Charging device 21 Charging blade (plate-shaped member) 21R Cylindrical charging member 211 Conductive member 212, 212R Insulator layer (insulating part) 212A Insulation Substrate 214, 214R High resistance layer (charging part) 220 Cleaning member 223 Shield member 24 Bias power supply

Claims (5)

[Claims] 1. A charging device for charging by charging a charging member to an object to be charged, wherein the charging member has an insulating part and a charging part on a support, and the insulating part is a surface to be charged. A charging device, characterized in that the charging part is disposed close to the charging surface of the body to be charged while being brought into contact with each other. 2. A charging device for charging a charging member by bringing the charging member into contact with the member to be charged. In the charging member having an insulating portion and a charging portion on a support, the insulating portion contacts the member to be charged. A charging device having a movable contact position. 3. The charging device according to claim 1, wherein the charging member has an insulating portion and a high resistance portion formed on a support having conductivity. 4. The charging device according to claim 1, wherein the charging member is plate-shaped or rod-shaped. 5. The charging device according to claim 2, wherein the pressing force of the charging member against the member to be charged can be changed.