JPH05107882A - Contact electrostatic charging device - Google Patents

Abstract

PURPOSE:To prevent faulty electrostatic charging such as the irregularity of electrostatic charging caused by the contamination of the abutting part of an electrostatic charging member with a substance to be electrostatically charged by providing a contamination preventing means for preventing the contamination of the abutting part of an electrostatic charging member with the substance to be electrostatically charged or a cleaning means. CONSTITUTION:When an eccentric cam 25 is rotated, the large rise part of the cam 25 is turned upward, so that a stay 23 is turned against a spring 24 centering around a supporting shaft 22. Thus, the abutting pressure of the edge part of an electrostatic charging blade 21 to the surface of a photosensitive drum 1 is reduced. In an abutting pressure reducing period until the cam 25 finishes being driven to be rotated once, a contaminant (tc) such as toner which is accumulated and stuck to the edge part of the blade 21 and the abutting surface thereof on the surface of the drum 1 is made to drop by the rotation and rubbing of the drum 1, so that the edge part of the blade 21 and the abutting surface is cleaned. Then, by providing a cleaning auxiliary member (not shown in figure) behind a cleaning device 7, the contaminant such as the toner is removed from the surface of the drum 1 before it reaches the blade 21 to prevent the contamination of the blade 21.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a contact charging device for applying a voltage to a charging member brought into contact with a member to be charged to charge the surface of the member to be charged.

[0002]

2. Description of the Related Art For example, in an image forming apparatus such as an electrophotographic copying apparatus or a printer, a non-contact system is used as a means for charging (including destaticizing) an image carrier such as an electrophotographic photoreceptor or an electrostatic recording dielectric. The corona charging (discharging) device has been generally used, but in recent years, a charging member such as a roller type or a blade type having elasticity or flexibility is brought into contact with the surface of the image bearing member as the charged member. Then, a so-called contact charging device for charging the surface of the image bearing member by applying a voltage to the charging member has attracted attention, and its practical application has been advanced. The contact charging device has advantages such as a lower voltage, less ozone generation, and a smaller device, as compared with a corona charging device. In order to make the apparatus compact, it is advantageous to use a blade type (charging blade) as the charging member rather than a roller type (charging roller).

[0003]

One of the problems of the contact charging device is that the charging member is brought into contact with the member to be charged, so that the contact portion of the charging member with the member to be charged does not contaminate the member to be charged. Easy to pick up and get dirty. Contamination of the contact portion of the charging member with the member to be charged causes uneven charging.

For example, in a transfer type electrophotographic copying machine, in a type in which a charging blade is brought into contact with a photosensitive member to perform primary charging of the surface of the photosensitive member, the photosensitive drum is more exposed than the charging blade when the photosensitive drum is started. Since there is a small amount of developer or the like that slips through the photoconductor drum surface cleaner device disposed on the upstream side in the body drum rotation direction, the developer or the like is in front of the charging blade (the contact portion of the charging blade with the photoconductor drum). Before, the blade edge portion) gradually accumulates and contaminates the charging blade.

As described above, streak-like charging unevenness is generated on the surface of the photoconductor drum due to the developer as a deposit contaminant on the above-mentioned charge blade that has slipped under the charge blade when the photoconductor drum is started. There's a problem.

SUMMARY OF THE INVENTION It is an object of the present invention to prevent the occurrence of charging defects such as uneven charging due to contamination of the contact portion of the charging member with the member to be charged, which is a problem of the contact charging device.

[0007]

SUMMARY OF THE INVENTION The present invention is a contact charging device having the following structure.

(1) In a contact charging device for charging a surface of a member to be charged by applying a voltage to the charging member brought into contact with the member to be charged, contamination of a contact portion of the charging member with the member to be charged A contact charging device, characterized by comprising a contamination preventing means or a cleaning means for preventing the above-mentioned problems.

(2) The contamination preventing means or the cleaning means is means for releasing or reducing the pressing force of the charging member with respect to the body to be charged, or a means for separating the body from the body to be charged. Contact charging device.

(3) The contamination preventing means or the cleaning means is a charged body surface cleaning means which acts on the charged body surface upstream of the charging member in the moving direction of the charged body surface. Contact charging device.

(4) When the contamination preventing means or the cleaning means is a means for separating the charging member from the member to be charged, a contaminant acting on the contact portion of the charging member separated from the member to be charged. Characterized by having a removing means (2)
The contact charging device described.

(5) The contact charging device according to any one of (1) to (4), wherein the charging member is an elastic blade member.

(6) The charged body is an image carrier such as a photoconductor or a dielectric of an image forming apparatus such as a copying machine or a printer. (1) to (5) Contact charging device.

[0014]

With the presence of the contamination prevention means or the cleaning means for preventing the contact portion of the charging member with the charged body from being contaminated, the contact portion of the charging member with the charged body is prevented from being contaminated, and the contact charging device is charged. It is possible to prevent the occurrence of charging failure such as uneven charging due to the contamination of the contact portion of the member with the member to be charged.

[0015]

【Example】

<Embodiment 1> (FIG. 1) This embodiment is an electrophotographic copying apparatus of a moving platen type and a transfer system, which uses the contact charging device according to the present invention as a primary charging device of an image carrier as a member to be charged. is there. FIG. 1 is a schematic configuration diagram of the copying machine. Since the image forming principle / process, device configuration, etc. of the copying machine are well known, the description thereof will be briefly described.

Reference numeral 1 denotes a rotary drum type electrophotographic photosensitive member (hereinafter referred to as a photosensitive drum) as an image bearing member. The photosensitive drum 1 is rotationally driven in the clockwise direction indicated by an arrow at a predetermined peripheral speed (process speed), and in the rotating process, a. A uniform primary charging treatment with a predetermined polarity and potential by the charging device 2, b. Original image exposure processing L by the exposure device 3 (this forms an electrostatic latent image corresponding to the original image on the photosensitive drum surface), c. The toner development processing of the latent image by the developing device 4 is sequentially performed.

The toner image T formed on the surface of the photosensitive drum 1 is a recording material which is fed by a transfer device 5 from a paper feeding portion (not shown) between the photosensitive drum 1 and the transfer device 5 at a predetermined timing. The recording material transferred to the (transfer material) P and transferred with the toner image is separated from the surface of the photosensitive drum 1 by the separating device 6 and is introduced into an image fixing device (not shown) to be subjected to image fixing and output as a copy. It After the image transfer, the photoconductor drum 1 is cleaned by a cleaner device 7 to remove adhering contaminants ta such as toner remaining after transfer, and is made a clean surface to be repeatedly used for image formation.

In the exposure apparatus 3, reference numeral 31 is a reciprocating type document platen glass, 32 is a document pressure plate, and 0 is a document platen glass 3.
The original placed on the first set, 33 is an exposure lamp, 34
Indicates a bar lens array of the imaging optical system.

The cleaner device 7 of this embodiment is of a blade type in which the cleaning blade 71 is pressed against the surface of the photosensitive drum 1 to wipe the surface of the drum 1.

The charging device 2 uses a blade type (charging blade) as the charging member 21. The charging blade 21 is mainly composed of a conductive elastic rubber blade, and is electrically connected to the stay 23 by using a conductive adhesive agent or the like on one arm portion of the conductive stay 23 swingable around the support shaft 22. It is electrically connected and supported. 24 is stay 2
3 is a tension spring stretched between the end of the arm portion on the other side of 3 and the cleaner device 7 as an immovable member.
The spring 24 constantly receives a turning force in the counterclockwise direction in the drawing around the support shaft 22, and the turning force causes the charging blade 2 to rotate.
The front end of the photosensitive drum 1 is urged against the surface of the photosensitive drum 1.

Reference numeral 25 denotes an eccentric cam disposed below the other arm of the stay 23 at a position between the stay support shaft 22 and the spring 24. The eccentric cam 25 is rotationally controlled about a shaft 26 by a one-rotation control clutch (not shown) or the like, and the stay 23 is swung about the support shaft 22 during the rotation process.

In this embodiment, the eccentric cam 25 always has the large ridge downward and the small ridge upward as shown by the solid line, and the small ridge receives the lower surface of the arm on the other side of the stay 23. Alternatively, the rotation is maintained in a rotation angle posture that is not in contact with the stay 23.

In this rotation angle posture of the eccentric cam 25, the rotation angle of the spring 24 in the counterclockwise direction about the support shaft 22 of the stay 23 is the maximum, and the charging blade 21
Is kept in contact with the surface of the photosensitive drum 1 with a predetermined contact pressure necessary for stable charging.

Reference numeral 27 is a bias applying power source for the charging blade 21, and the voltage of the power source is applied to the charging blade 21 via the stay 23 at a predetermined process control timing, so that the surface of the rotary photosensitive drum 1 is contact charged. The blade 21 is charged by the contact charging method.

The charging blade 21 as a contact charging member has a contacting portion with the photosensitive drum 1 which easily picks up contaminants on the surface of the drum 1 and easily contaminates the cleaning blade of the cleaner device 7 in the copying machine of this embodiment. The contact portion 71A between the photosensitive drum 1 and the photosensitive drum 1 is slightly passed through the rotary drum 1.
Contamination tb such as toner that adheres to the surface and is carried to the charging blade 21 gradually accumulates on the edge portion of the charging blade 21 and causes the charging blade to be contaminated, and the charging unevenness resulting from the contamination is caused. As described above, the charging failure such as the above occurs.

In view of this, in this embodiment, an appropriate timing / time of the copying operation sequence of the copying machine, for example, when the rotation of the photosensitive drum 1 is started (during the drum pre-rotation period) and stopped (at the drum post-rotation period). ) And the like, the eccentric cam 25 is driven to rotate once at least once.

When the eccentric cam 25 starts to rotate, the cam 2
By turning the large ridges of No. 5 upward, the stay 23
Is rotated clockwise about the support shaft 22 against the spring 24. As a result, the contact pressure of the tip of the charging blade 21 with respect to the surface of the photosensitive drum 1 is reduced, and the eccentric cam 25 makes a half rotation and the large bulge has an upward rotation angle indicated by the two-dot chain line. The tip of the charging blade 21, which is the contact portion with respect to the photosensitive drum 1, is separated from the surface of the drum 1 in a non-contact manner, or is in contact with the surface, but the contact pressure on the surface of the drum 1 is minimized. Then, in the subsequent half-rotation process of the eccentric cam 25, the large ridge portion of the cam 25 is rotated downward, so that the stay 23 is rotated counterclockwise about the support shaft 22 by the force of the spring 24. .. As a result, the contact pressure of the tip portion of the charging blade 21 on the surface of the photosensitive drum 1 increases, and when the cam 25 completes one rotation drive, the small ridge of the cam 25 again faces upward and the charging blade 21 moves.
Returns to the state of being in contact with the surface of the photosensitive drum 1 with a predetermined contact pressure.

Thus, as described above, the contact pressure of the charging blade 21 against the surface of the photosensitive drum 1 is reduced from the start of the eccentric cam 25 to the end of the one-rotational drive. During the contact pressure reduction period, contaminants tc such as toner deposited and attached to the edge portion of the charging blade 21 and the contact surface with respect to the drum surface are removed by the rotational sliding friction of the rotating photosensitive drum 1 and the charging blade 21. The edge portion and the contact surface of are cleaned.

Contaminants tc such as toner dropped from the edge portion or contact surface of the charging blade 21 easily contact between the charging blade 21 and the surface of the photosensitive drum 1 whose contact pressure with the drum 1 is reduced. After passing through the surface of the photosensitive drum 1, it adheres to the surface of the drum 1, is carried to the cleaner device 7, and is removed from the surface of the photosensitive drum 1 by the cleaning blade 71. The cleaning blade 71 is generally longer than the charging blade 21.

Therefore, the contact portion of the charging blade 21 with respect to the surface of the photosensitive drum 1 (the tip edge portion or contact surface of the charging blade) is substantially subjected to the cleaning action described above each time the eccentric cam 25 is driven to rotate once. It is possible to maintain the state in which there is no stain for a long period of time, and it is possible to prevent the occurrence of defective charging due to the contamination of the charging blade 21.

Cleaning blade 7 of cleaner device 7
The pass-through tb of the contaminant ta such as toner from the photosensitive drum surface abutting edge portion 71A of No. 1 is caused by the rotation start shock and the rotation stop shock of the drum at the start of rotation of the photosensitive drum 1 and the stop of rotation. It will be large in quantity.

Therefore, when the eccentric cam 25 is driven to rotate once to start the above-mentioned cleaning of the charging blade 21 at the time of starting the rotation of the photosensitive drum 1, at the time when the previous rotation of the photosensitive drum is stopped and when the rotation is started. Cleaning blade 7
When the drum surface portion on which the relatively large amount of contaminant tb such as toner that has passed through 1 passes through the drum surface contact portion of the charging blade 21, the drum surface contact portion of the charging blade 21 is just right. In the process of swinging in a state of being separated from the surface of the drum 1 in a non-contact manner (state indicated by a chain double-dashed line), the above-mentioned relatively large amount of toner and other contaminants attached to the surface tb of the drum 1 is charged by the charging blade. The charging blade 21 is set to start the one-rotation driving of the eccentric cam 25 so that the charging blade 21 passes through the charging blade position without coming into contact with the charging blade 21.
It is desirable because it does not unnecessarily contaminate the edges of the.

The adhering contaminant tb such as toner on the surface of the drum 1 which has passed through the charging blade position without contacting the charging blade is conveyed to the cleaner device 7 and removed from the surface of the drum 1 by the cleaning blade 71.

In this embodiment, the cleaning of the drum surface contact portion of the charging blade 21 is performed as described above.
Since the contact pressure of the drum surface is reduced and the photosensitive drum 1 is rotated and rubbed in the reduced state, the charging blade 21 is sufficiently contacted from the surface of the drum 1 in terms of cleaning the charging blade 21. There is no particular need to rock until they are separated.

<Embodiment 2> (FIGS. 2 and 3) In order to prevent the charging blade 21 and the cleaning blade 71 from settling, the charging blade 21 and the cleaning blade 71 are
It is desirable that the contact pressure with respect to the photosensitive drum 1 be released and kept in a state of being separated from the drum 1 (or contacting with substantially no contact pressure). The present embodiment is an example in which this is taken into consideration.

In the state shown by the solid line in FIG. 2, both the charging blade 21 and the cleaning blade 71 are in contact with the surface of the photosensitive drum 1 with a predetermined contact pressure. Both blades 21 and 71 are shown.
Is a state diagram when the copying machine is held or stopped from the surface of the drum 1, and FIG. 3 is a perspective view of a main part.

The charging blade 21 is attached to and supported by one arm of one side of the conductive stay 23 which is swingable about the support shaft 22 as in the case of the first embodiment, and the other side of the stay 23 is supported. A weight 28 is attached to and supported by the arm. In the free state, the stay 23 receives a rotational force in the counterclockwise direction about the support shaft 22 by the weight 28, and the tip portion of the charging blade 21 performs stable charging on the surface of the photosensitive drum 1 by the rotational force. The contact state is maintained with a predetermined contact pressure required for the contact.

The cleaning blade 71 is attached to and supported by one arm portion of a stay 73 which is swingable about a support shaft 72, and a weight 74 is attached to the other arm portion of the stay 73.
Is attached and supported.

In the free state, the stay 73 receives a rotating force counterclockwise about the spindle 72 by the weight 74, and the tip of the cleaning blade 71 is stably cleaned with respect to the surface of the photosensitive drum 1 by the rotating force. The contact state is maintained with a predetermined contact pressure required to execute the above.

26 is a cam shaft rotatably mounted between the charging blade stay 23 and the cleaning blade stay 73, and 25 is an eccentric cam integrally provided in the middle of the cam shaft 26. Reference numeral 29 is a cam plate integrally provided at both ends of the cam shaft 26 downward at the same phase angle.

Reference numeral 80 is a lever fixed to one end of the cam shaft 26, 81 is a tension spring stretched between the tip of the lever 80 and the immovable member 82, and 83 is a tension spring 81 with the lever 80 inside. It is an electromagnetic solenoid-plunger device (SL device) arranged on the side opposite to the side. Reference numeral 84 is a forward / backward plunger of the SL device 83, and the plunger 84 is connected to the tip portion of the lever 80.

During operation of the copying machine, the SL device 83 is energized and the plunger 84 is retracted into the solenoid, whereby the lever 80 of the cam shaft 26 is rotated counterclockwise against the spring 81. 2 is maintained in the rotation angle state of the substantially upright posture shown by the solid line.

When the lever 80, that is, the cam shaft 26 is in the rotation angle state, the eccentric cam 26 and the cam plates 28, 28 are not in contact (non-acting) with the charging blade stay 23 and the cleaning blade stay 73, respectively. Both of the above-mentioned blade stays 23 and 73 are in a free state for that reason, and as described above, the charging blade 21 and the cleaning blade 71 respectively contact the surface of the photosensitive drum 1 by the action of the weights 28 and 74. The contact state is maintained with contact pressure.

When the copying machine is on standby or stopped, the SL device 83
Is turned off. This releases the plunger 84 from being pulled into the solenoid, whereby the lever 80 of the cam shaft 26 is rotated clockwise by the pulling force of the spring 81, and the rotation angle is in the diagonally right upward posture shown by the two-dot chain line. Held in.

When the lever 80, that is, the cam shaft 26 is in the rotation angle state, the large ridge of the eccentric cam 26 is rotated upward and the charging blade stay 23 is rotated about the support shaft 22 against the weight 28 in the clockwise direction. By rotating the charging blade to
Are held in a state of being separated from the surface of the photosensitive drum 1.

The lower ends of the downward cam plates 29, 29 come into contact with the cleaning blade stay 73 and rotate the stay 73 clockwise around the support shaft 72 against the weight 74. Photoconductor drum 1
It is kept separated from the surface.

Thus, the state shown by the solid line during the operation of the copying machine, in which both the charging blade 21 and the cleaning blade 71 are in contact with the surface of the photosensitive drum 1 with a predetermined contact force by the on / off control of the energization of the SL device 83. And both blades 21 and 71
Of the blades 21 and 71 in the waiting period and the stopping period of the copying machine are alternately switched to the state indicated by the two-dot chain line when the copying machine is held or stopped from the surface of the photoconductor drum.
Sag is prevented.

In this embodiment, the SL device 83 is energized to charge the charging blade 21 and the cleaning blade 7.
When 1 contacts the surface of the photosensitive drum 1, first, the cleaning blade 71 contacts the surface of the drum 1, and then the charging blade 21 contacts the surface of the drum 1.
The phase angle between the eccentric cam 25 and the cam plates 29, 29 is set.

The timing for separating and contacting the charging blade 21 with respect to the surface of the photosensitive drum 1 is the same as in the first embodiment. Since the charging blade stay 23 is swung by the eccentric cam 25 as in the first embodiment, the tip end of the charging blade 21 is completely in contact with the surface of the drum 1 at a predetermined contact pressure from the state shown by the solid line. The contact pressure of the charging blade 21 with respect to the drum 1 surface is reduced until it is separated, and conversely until the tip of the charging blade 21 returns to the contact state with the predetermined contact pressure on the drum 1 surface from the separated state. In this contact pressure reduction period, cleaning of the drum surface contact portion of the charging blade 21 by the rotational rubbing of the drum 1 is performed in this contact pressure reduction period.

The charging blade 21 and the cleaning blade 71 may be independently configured to perform a swinging motion with respect to the surface of the drum 1 by a plunger or the like.

<Embodiment 3> (FIG. 4) In this embodiment, as shown in FIG. 4A, the charging blade 21 of the charging device 2 and the cleaning blade 7 of the cleaner device 7 are used.
A cleaning assisting member 85 in the form of a rotating roller is disposed in contact with the surface of the drum 1 at the surface portion of the photosensitive drum between the cleaning auxiliary member 85 and the photosensitive drum 1.

The cleaning assisting member 85 removes contaminants tb such as toner that has passed through the cleaner device 7 and is carried to the charging blade 21 from the surface of the photosensitive drum 1 before reaching the charging blade 21 and removing the charging blade 21. Prevent dirt from getting on.

Cleaning assisting member 85 in the form of a rotating roller
Then, contaminants such as toner picked up from the surface of the photosensitive drum 1 and attached thereto are scraped off by the blade member 86, and the member 85 is recleaned.

The rotating roller-shaped cleaning assisting member 85 may be a fur brush or a felt roller, but is contaminated with toner or the like that has slipped past the cleaning blade 71 and is pressed against the surface of the photosensitive drum 1 to some extent. In order to remove the object tb well, it is desirable that the surface of the drum 1 has an elastic body such as urethane rubber or silicon rubber so that a sufficient sliding effect with the surface of the drum 1 can be expected. Further, if the rotation of the roller 85 is in the forward direction with respect to the rotation of the drum 1, it is effective to drive the roller 85 at a high speed or a slow speed different from the rotation speed of the drum 1, or to rotate in the reverse direction. Alternatively, the fixed felt pad 87 may be brought into contact with the surface of the drum 1 as a cleaning assisting member so that it can be easily replaced (FIG. 4B).

<Embodiment 4> (FIG. 5) In this embodiment, the charging blade stay 23 is made swingable around a shaft 22 by a swinging means (not shown) so that the charging blade 21 can be moved relative to the surface of the photosensitive drum 1. The contact and separation can be controlled freely. Further, as shown by the broken line in FIG. 5, a cleaning member 88 for contacting the tip of the charging blade 1 and cleaning the tip of the charging blade 1 is provided in a state where the charging blade 21 is separated from the surface of the drum 1. ..

The cleaning member 88 of this embodiment has a shaft 89.
It is a brush-like member or an elastic member that is driven to rotate around.

Thus, for example, by moving the charging blade 21 away from the surface of the drum 1 just before the end of the copying operation, the drum surface contact portion at the tip of the charging blade is cleaned by contact with the rotary cleaning member 88. Cleaning member 88
Further rotating, the adhered contaminants are scraped off and re-cleaned by the hammer 90, and the scraped contaminants are collected in the container 91.

[0058]

As described above, according to the present invention, it is possible to prevent occurrence of charging failure such as uneven charging due to contamination of the contact portion of the charging member with the member to be charged, which is a problem in the contact charging device. be able to.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an example of a copying machine using a contact charging device according to the present invention as a primary charging device of an image carrier.

FIG. 2 is a schematic configuration diagram of a second embodiment device.

FIG. 3 is a perspective view of a main part

4A and 4B are schematic configuration diagrams of a third embodiment apparatus, respectively.

FIG. 5 is a schematic configuration diagram of a fourth embodiment device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Photosensitive drum as a charged body 2 Contact charging device 21 Charging blade as a charging member 25/26 Releasing or reducing the pressing force of the charging blade, or separating means 85/87 Cleaning auxiliary member for the surface of the photosensitive drum 88 Charging blade Cleaning member

Claims (6)

[Claims] 1. A contact charging device for charging a surface of a member to be charged by applying a voltage to a charging member brought into contact with the member to be charged, whereby contamination of a contact portion of the charging member with the member to be charged is prevented. A contact charging device comprising a pollution preventing means or a cleaning means for preventing. 2. The pollution preventing means or the cleaning means,
2. The contact charging device according to claim 1, wherein the contact charging device is means for releasing or reducing the pressing force of the charging member with respect to the body to be charged, or means for separating from the body to be charged. 3. The pollution prevention means or the cleaning means,
2. The contact charging device according to claim 1, further comprising cleaning means for cleaning the surface of the body to be charged on the upstream side of the charging member in the moving direction of the surface of the body to be charged. 4. A contaminant removing device which acts on a charging member contact portion of a charging member, which is separated from the charging member, when the pollution preventing unit or the cleaning unit is a unit for separating the charging member from the charging member. The contact charging device according to claim 2, further comprising means. 5. The contact charging device according to claim 1, wherein the charging member is an elastic blade member. 6. The contact according to claim 1, wherein the member to be charged is an image carrier such as a photoconductor or a dielectric of an image forming apparatus such as a copying machine or a printer. Charging device.