JP3190217B2 - Image forming apparatus and process cartridge - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrophotographic copying machine or a printer / facsimile machine, and a process cartridge used for the same.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus using an electrophotographic method, such as a copying machine or a printer / facsimile machine, has a photoconductor as a latent image carrier, a charging device for charging the photoconductor, and a photoconductor formed on the photoconductor. Developing device for visualizing the formed electrostatic latent image with toner as a developer, a transfer device for transferring the toner to a transfer material such as paper, and a cleaning device for cleaning residual toner remaining on the photoreceptor thereafter And a fixing device for fixing the toner on the transfer material.

In recent years, from the viewpoint of environmental protection and effective use of resources, an image forming apparatus has been developed in which transfer residual toner, so-called waste toner, collected by a cleaning device is returned to a developing device and reused. As one of the methods, there is a cleanerless method in which the cleaning device is abolished and the transfer residual toner is cleaned at the same time as the developing process in the developing device.

The cleanerless image forming apparatus will be described with reference to FIGS. FIG. 8 is a schematic configuration diagram of a conventional example, and FIG. 9 is an explanatory diagram showing an image forming process focusing on the surface potential of a photosensitive drum as a latent image carrier. In this example, a negative DC voltage is applied to the charging roller, the photosensitive drum is charged negatively, an electrostatic latent image is written by a laser beam, and the negatively charged developer is applied to an exposed portion on the photosensitive drum by a developing device. The example of the reversal development system for developing is shown.

In FIG. 8, first, the photosensitive drum 1 has an arrow A
, And is charged by the charging device 2. Thereafter, the image information is written as an electrostatic latent image by the exposure unit 3 and is visualized as a toner image by the developing device. The visualized toner image on the photosensitive drum is transferred to the transfer material 11 by the transfer device 5, and then the transfer material 11 is transported to a fixing device (not shown). After the transfer process, the residual toner remaining on the photoreceptor 1 passes through the charging process and the exposure process, and is collected in a developing container by a developing device, and is used again in the developing process. Thereafter, the above steps are repeated.

Further, referring to FIG. 9, the relationship between the surface potential of the photosensitive drum and the potential of each device and the movement of the toner in each process will be briefly described. In the charging step, the surface potential of the photosensitive drum is uniformly charged to a voltage value Vd by applying a DC voltage of Vc to the charging member. Fig. 9-
2 ') In the exposure step, the surface potential of the portion exposed by the laser light is attenuated to a voltage value V1, and an electrostatic latent image is written on the surface of the photosensitive drum by the on / off of the laser light due to the contrast between the voltage values Vd and V1. It is.

[0007] In the developing step, the developing sleeve carrying the negatively charged toner and applying a voltage value Vdev that satisfies Vd <Vdev <V1 (the positive side is increased) is
By bringing the electrostatic latent image closer to the photosensitive drum, the toner on the developing sleeve is moved to an exposed portion having a surface potential of V1 to perform a developing process.

9-4) In the transfer step, a transfer material such as paper is sandwiched between the developed photosensitive drum and a transfer roller as a transfer member, and a positive voltage Vt is applied to the transfer roller to thereby transfer the photosensitive drum. Above—the toner is attracted to the paper side to perform transfer. Untransferred untransferred toner remains on the photosensitive drum after the transfer.

FIG. 9-1) In the charging step, the surface of the photosensitive drum is charged from above the transfer residual toner. Since the amount of untransferred toner in one print is small, the influence on the surface potential of the photosensitive drum in the charging process is at a level that does not cause any problem. 9-2) In the exposure step, the exposure is performed from above the transfer residual toner.
There is no significant effect on the surface potential after exposure.

9-3) In the cleaning / developing process, first, the negative transfer residual toner of the non-exposed portion (surface potential is Vd) on the photosensitive drum is applied with a developing sleeve to which a voltage value vdev satisfying Vd <Vdev <V1 is applied. And the surface of the photosensitive drum is cleaned. Although the toner in the exposed area is not attracted to the developing sleeve, this area is an image area, so that the toner may remain. At the same time, the negative toner on the developing sleeve is attracted to the exposed portion on the photosensitive drum, and the developing process is performed. In this manner, the cleaning simultaneous development process is performed.
Hereinafter, image formation is repeatedly performed in the order of З → 4 → 1 → 2 → 3.

[0011]

However, such a cleaner-less type image forming apparatus has the following problems. This is due to the fact that + toner generated by frictional charging of the toner in the developing device adheres to the non-exposed portion of the photosensitive drum, and-toner in the image portion due to the transfer voltage. Is included, and this + toner adheres to the charging roller to cause charging failure, and is not collected by the developing device during the cleaning process and remains on the photosensitive drum. It is.

This will be described with reference to FIG. FIG.
-З ') In the development process, the negatively charged toner moves to an exposed portion having a surface potential of V1 and is subjected to a developing process. However, the positively charged toner generated on the developing sleeve has a surface potential of Vd. It adheres to the non-exposed area (called reverse fog). 10-4) In the transfer process, by applying a positive voltage Vt to the transfer roller, the − toner on the photosensitive drum is attracted to the paper side to perform transfer. At that time, some of the negative toner in the image portion is affected by the positive voltage of the transfer and is inverted to the positive toner, and remains on the photosensitive drum. 10-1) In the charging process, the surface of the photosensitive drum is charged from above the transfer residual toner. However, of the transfer residual toner, the toner charged to + will adhere to the charging roller. Although the amount of this + toner is very small, if it accumulates over a long period of time, it causes charging failure.

Further, even if the + toner passes through the charging roller without adhering to the charging roller, 10-2) the exposure process is passed and
-3) In the cleaning / development process, the positive transfer residual toner in the non-exposed portion (surface potential is Vd) on the photosensitive drum has a voltage value V
The developer is not attracted to the developing sleeve to which dev is applied, and remains on the photosensitive drum. In other words, when the toner charged to + adheres to the photosensitive drum, the toner cannot be collected by the cleaning / developing device, and the image becomes accumulated only as the printing is continued.

SUMMARY OF THE INVENTION It is an object of the present invention to solve such a problem and prevent the occurrence of fog images due to poor charging due to contamination of the charging member and poor recovery of residual toner remaining on the photosensitive drum.

[0015]

In order to achieve the object of the present onset to achieve the above purpose
Akira, charging means for charging the rotatable image carrier,
An exposure means for forming an electrostatic latent image on the charged processed image bearing member, to together when recovering the developer attached to the non-image portion of the electrostatic latent image developer to the image area of the electrostatic latent image a cleaning developing means for visualizing the supplied electrostatic latent image, a transfer unit that transfers a transfer material a developer image visualized, transfer means upstream of the downstream side and charging means of the transfer means in the rotation direction of the image bearing member a developer charging control means for aligning the charge polarity of the transfer residual developer not transferred to the transfer material to the normal charging polarity in the
The developer charging control means
Has a blade that rubs against the transfer residual developer,
The agent becomes the normal charging polarity by friction charging with the blade
It is characterized by being aligned .

[0016]

According to the present invention as described above, in the direction of rotation of the image carrier, downstream of the transfer means and upstream of the charging means,
The transfer means has a blade that rubs with the transfer residual developer as developer charge control means for aligning the charge polarity of the transfer residual developer not transferred to the transfer material to the normal charge polarity,
The residual developer has a regular band due to frictional charging with the blade.
Since the electrodes have the same electrode properties, it is possible to prevent the occurrence of fog images due to poor charging due to contamination of the charging member and poor recovery of transfer residual toner on the photosensitive drum.

[0017]

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

(Embodiment 1) FIG. 1 is a sectional view of an apparatus according to an embodiment of the present invention. In this example, similarly to the conventional example, the negative DC voltage is applied to the charging roller to
An example of the reversal development method is shown in which an electrostatic latent image is written with a laser beam, and a negatively charged developer is developed on an exposed portion on a photosensitive drum by a developing device. In the figure,
1 is a photosensitive drum as an image carrier, 2 and 12 are a charging roller and a power source as a charging device, 3 is a laser beam as an exposure unit, 4 is a developing sleeve as a developer carrier,
4M is a magnet, and 10 is a toner as a developer.
The developing device includes four developing sleeves, eight toner regulating members, nine toner containers, and thirteen power supplies. In the developing device, the toner 10 in the toner container 9 is formed in a thin layer on the developing sleeve 4 serving as a developing carrier by the toner layer regulating member 8 and is charged negatively by frictional charging. 5
And 14 transfer the toner on the photosensitive drum to a transfer material 11 such as paper.
And a power supply for the transfer roller. The fixing device 7 fixes the toner image on the transfer material.

Reference numeral 601 denotes a rubbing blade which is a developer charging control means of the present invention.

FIG. 2 is a sectional view around the photosensitive drum of the present embodiment. In the figure, first, the photosensitive drum 1 rotates in the direction of arrow A, and is charged negatively by the charging device 2. Thereafter, the image information is written as an electrostatic latent image by the exposure unit 3 and is visualized as a toner image by the developing device. The visualized toner image on the photosensitive drum is transferred to the transfer material 11 by the transfer device 5, and then the transfer material 11 is transported to a fixing device (not shown). After the transfer process, the residual toner remaining on the photoreceptor 1 is removed by a rubbing blade 6 made of polyurethane.
01, the charge polarity is adjusted to-by frictional charge. Thereafter, after passing through the charging step and the exposure step, the toner is collected in a developing container by a developing device and used again for the developing process. Thereafter, the above steps are repeated.

Further, the relationship between the surface potential of the photosensitive drum and the potential of each device and the movement of the toner in each step will be briefly described with reference to FIG. FIG. 3-1 ′) In the charging step, the surface potential of the photosensitive drum is uniformly charged to the voltage value Vd by applying a DC voltage having the voltage value Vc to the charging roller.
In the exposure step, the surface potential of the portion exposed by the laser light drops to the voltage value V1, and the voltage values Vd and V1 are applied to the surface of the photosensitive drum by turning on and off the laser light.
, An electrostatic latent image is written. Figure 3-
3 ') In the development process, the negatively charged toner is carried,
By bringing the developing sleeve 4 to which the voltage value Vdev that satisfies d <Vdev <V1 close to the photosensitive drum 1 on which the electrostatic latent image is written, the toner on the developing sleeve 4 is exposed at a surface potential of V1. And the developing process is performed. At this time, the toner that has been charged to + by the friction between the small amount of toner on the developing sleeve adheres to the non-image portion on the photosensitive drum 1.

3-4) In the transfer process, a transfer material 11 such as paper is sandwiched between the developed photosensitive drum 1 and the transfer roller 5, and a positive voltage Vt is applied to the transfer roller 5 to thereby transfer the photosensitive drum. Above—the toner is attracted to the paper side to perform transfer. On the photosensitive drum after the transfer, the remaining toner on the transfer includes negative toner in the image area, positive toner adhered to the non-exposed area, and a positive voltage Vt of transfer in a part of the negative toner in the image area. + Toner that has been affected and turned over is included.

3-5) In the toner charging control step, the toner having the positive or negative charge on the photosensitive drum is adjusted to the negative charging polarity by friction with the rubbing blade. 3-
1) In the charging step, the surface of the photosensitive drum is charged from above the transfer residual toner. Although the potential Vc of the charging roller is on the minus side of the surface potential Vd of the photosensitive drum, the charge of the untransferred toner is adjusted to minus so that the toner does not adhere to the charging roller. Further, since the amount of transfer residual toner in a single print is small, the influence of the charging process on the surface potential of the photosensitive drum is a level without any problem. З-2) In the exposure step, the exposure is performed from above the transfer residual toner. However, since the amount of the exposure is small as described above, the surface potential after the exposure does not have a significant effect. 3-З) In the cleaning / developing process, first, development is performed by applying a voltage value Vdev such that Vd <Vdev <V1 is applied to the untransferred toner (charge polarity is −) of the non-exposed portion (surface potential is Vd) on the photosensitive drum. The photosensitive drum is attracted to the sleeve, and the photosensitive drum is cleaned. Although the transfer toner (charge polarity is-) of the exposed portion is not attracted to the developing sleeve, since this is an image portion, the toner may remain. At the same time, the negative toner on the developing sleeve is attracted to the exposed portion on the photosensitive drum, and the developing process is performed. In this way, the cleaning simultaneous development process is performed, and
Image formation is repeated according to the flow of 5 → 1 → 2 → З.

In this embodiment, an experiment was conducted under the following voltage settings, and good printing without defective charging or fogging images could be performed in tens of thousands of durable prints.

Applied voltage of charging device; DC-1300V Surface potential Vd after charging process; -7OOV Surface potential V1 after exposure; -100V Applied voltage Vdev of developing sleeve; DC-40OV Applied voltage Vt of transfer roller DC + 100OV or more As described above, in the rotation direction of the photosensitive drum, on the downstream side of the transfer unit and on the upstream side of the charging unit, the developer charging for aligning the charging polarity of the untransferred toner not transferred to the transfer material by the transfer unit to the normal charging polarity. By providing the control means, the charge polarity of the transfer residual toner can be made equal to the normal charge polarity before the transfer residual toner enters the charging process. It is possible to prevent a fog image from being generated due to poor toner collection.

In addition, the material of the above-mentioned rubbing blade is
It is preferable to use a material such as cellulose or nylon that easily gives a negative charge to the toner. Further, as shown in FIG. 4, the material of the rubbing blade is given an appropriate conductivity, and a voltage of the same polarity as the normal charging polarity of the toner is applied by the power supply 15 to more stably control the charging polarity of the toner. can do.

In this embodiment, the image forming apparatus using a DC charging device for applying a DC voltage to a charging roller member as a charging device has been described. However, a voltage obtained by superimposing an AC voltage on a DC voltage is charged. The same effect can be obtained by combining an AC charging device applied to a roller, a corona charging device using corona discharge, a brush charging device using a brush, or the like.

( Reference Example ) FIG. 5 is a sectional view of a reference example of the present invention. This reference example uses an AC charging device that applies a voltage obtained by superimposing an AC voltage on a negative DC voltage to the charging roller to charge the photosensitive drum negatively, writes an electrostatic latent image with laser light, and removes the negatively charged toner. In an image forming apparatus of a reversal developing method in which a developing device develops an exposed portion on a photosensitive drum, a conductive roller 602 is used as the toner charging control means. The conductive roller 602 is made of ethylene propylene rubber, silicon rubber, urethane foam, or the like in which conductive particles are dispersed, and is widely used for a transfer roller and a charging roller.

However, since the function only needs to be able to control the charge of the toner to the normal side, surface properties and uniformity of resistance are not required as much as the transfer roller and the charging roller, and the structure may be simple. In this reference example , a silicon rubber roller having a single layer configuration was used. A negative DC voltage Vtc is applied to the conductive roller 602 by the power supply 15 so that the conductive roller 602 is discharged toward the surface of the photosensitive drum. After the transfer process, the transfer residual toner remaining on the photoreceptor 1 is charged to a regular charge polarity − by discharge from the conductive roller 602 or by rubbing and contact with the conductive roller 602, and the toner charge control process is performed. Pass through. + Toner adheres to the conductive roller,
It does not significantly affect the function of controlling the charging polarity of the toner to the normal side. The range of the voltage Vtc applied to the conductive roller 602 is the surface potential before entering the toner charging control process.
In the case of db, Vtc is on the minus side of Vdb. Vdb> Vtc The surface potential after receiving discharge in the toner charge control process is V
In the case of da, it is determined by two conditions that Vda is within a range that can be converged to a potential Vd to be obtained in a downstream charging process. The latter condition is as follows depending on the type of the charging device. In the case where the charging device is an AC charging device that applies a voltage obtained by superimposing an AC voltage on a DC voltage to the charging roller as in the present reference example , the surface potential Vda of the photosensitive drum after the toner charging control process is higher than the potential Vd to be obtained. Regardless of whether it is on the + or − side, the potential Vd
Therefore, there is no particular limitation on the applied voltage Vtc other than Vdb> Vtc. The charging device is D as in the first embodiment.
In the case of applying a C voltage to a charging roller or a charging brush or a DC charging device such as a corona charger, when the surface potential Vda of the photosensitive drum after the toner charging control process is on the lower side than the potential Vd to be obtained, The surface potential cannot be reduced to Vd. Therefore, the surface potential Vda after the toner charging control process is required to be on the + side of the potential Vd, and when the discharge start voltage of the conductive roller 602 is Vth, the applied voltage Vtc is not on the + side than Vd−10 Vth. Must not. Therefore, the range of the applied voltage Vtc is as follows: Vdb>Vtc> Vd + Vth. However, when an exposure device such as an LED is arranged after the toner charging control step, even if the surface potential Vda after the toner charging control step is − side than the potential Vd, it can be set to the + side than the potential Vd by exposure. Therefore, the range of the applied voltage Vtc is Vdb> Vtc as in the case of the AC charging device.

In the present reference example , an experiment was conducted under the following voltage settings, and good printing without defective charging and no fog image could be performed in tens of thousands of durable prints.

Voltage applied to charging device; DC-700V + A
C2OOOOVpp Surface potential Vd after charging process; -7OOV Surface potential V1 after exposure; -100V Application voltage Vdev to developing sleeve; DC-4OOV Application voltage Vt to transfer roller; DC + 1OOOOV Surface potential Vdb before toner charging control process; −
500V Applied voltage Vtc of conductive roller 602; DC-140O
V: Charge start voltage Vth of conductive roller: 600 V Surface potential Vda after toner charge control process: -80 OV As described above, toner charge control means for discharging by the conductive roller to normalize the charge polarity of the toner. To
By providing the toner downstream of the transfer means and upstream of the charging means in the direction of rotation of the photosensitive drum, the charge polarity of the transfer residual toner is set to the normal charge level before the transfer residual toner enters the charging process, as in the first embodiment. The polarity can be made uniform, and it is possible to prevent the occurrence of fog images due to poor charging due to contamination of the charging member and poor recovery of residual toner on the photosensitive drum.

(Embodiment 2 ) FIG. 6 shows Embodiment 2 of the present invention. This embodiment uses an AC charging device that applies a voltage obtained by superimposing an AC voltage on a negative DC voltage to a charging roller and charges the photosensitive drum negatively. In a regular developing type image forming apparatus in which a toner charged to + is developed on a non-exposed portion on a photosensitive drum by a developing device, a power supply for applying voltage to the rotating toner collecting roller 60 </ b>#, the rubbing blade 604, and the toner collecting roller 15 is provided after the transfer process and before the charging process. Toner collection roller 6
0 ° is made of an elastic roller such as a rubber material, a resin or metal sleeve, or the like. The collection roller 603 has a power supply 15
As a result, the voltage Vr on the + side of the surface potential Vdb before the toner charging control process is applied, and the toner remaining after the transfer on the photosensitive drum is the inverted toner (in this example, the + toner is the regular toner. , -Toner) is a collection roller 60
3 and is transferred to the collection roller.

The + toner, which is the normal toner, passes through as it is. The toner adhered to the collection roller 60 </ b># rubs against the rubbing blade 604 by the rotation of the collection roller 603,
The toner is charged again to the positive side (+) by frictional charging. The rubbing blade 604 is made of a material such as Teflon or a polyvinyl resin, which easily gives a positive charge to the toner. The toner on the collection roller 603 normalized to + is charged with the potential Vdb on the photosensitive drum and the potential Vr of the collection roller 603.
Is transferred onto the photosensitive drum again due to the relationship. In this way, only the regular + toner remains on the photosensitive drum after the toner charging control process. As a result, in the cleaning / developing process, the transfer residual toner could be surely collected, and good printing without a fog image could be performed even on tens of thousands of sheets.

The voltage setting in this embodiment is as follows.

Voltage applied to the charging device; DC−700V + AC200Vp
p Surface potential Vd after charging process; -700V Surface potential V1 after exposure; -100V Applied voltage Vdev to developing sleeve; DC-400V Applied voltage Vt to transfer roller; DC-2000V Surface potential Vdb before toner charging control process; -300 ~-
900V Applied voltage Vr of toner recovery roller 603; DC-100
V (Embodiment 3 ) FIG. 7 shows an example in which the present invention is applied to a process cartridge.

1 is a photosensitive drum, 2 is a charging member of the present invention,
З denotes a laser beam, 4 denotes a developing sleeve, 8 denotes a doctor blade for uniformly coating the toner on the developing sleeve, and 9 denotes a toner hopper. Reference numeral 11 denotes a transfer material, reference numeral 5 denotes a transfer roller, and reference numeral 6 denotes a rubbing blade which is a toner charging control unit of the present invention. In addition to the blade, various charging control units in the above embodiments can be used.

As a result, a process cartridge having the effects of the present invention can be supplied with a small, simple, and inexpensive configuration.

[0038]

As described above , according to the present invention ,
As developer charging control means for aligning the charge polarity of the untransferred developer not transferred to the transfer material in the transfer means to the regular charge polarity, downstream of the transfer means and upstream of the charging means in the rotation direction of the image carrier. A brush that rubs with the transfer residual developer
And the residual transfer developer has a friction band with the blade.
The charge polarity of the transfer residual toner can be adjusted to the charge polarity of the image carrier before the transfer residual toner enters the charging process, so that charging failure due to contamination of the charging member, This makes it possible to prevent the occurrence of a fog image due to a failure in collecting the transfer residual toner on the photosensitive drum.

[Brief description of the drawings]

FIG. 1 is a sectional view of a first embodiment of an image forming apparatus according to the present invention.

FIG. 2 is a sectional view around a photosensitive drum in the embodiment shown in FIG.

FIG. 3 is a diagram illustrating the operation of the first embodiment according to the present invention.

FIG. 4 is a sectional view of a modification of the first embodiment of the image forming apparatus according to the present invention;

FIG. 5 is a sectional view of a reference example of the image forming apparatus according to the present invention.

FIG. 6 is a sectional view of Embodiment 2 of the image forming apparatus according to the present invention.

FIG. 7 is a sectional view of Embodiment 3 of the image forming apparatus according to the present invention.

FIG. 8 is a sectional view of a conventional image forming apparatus.

FIG. 9 is a diagram illustrating the operation of a conventional example.

FIG. 10 is a diagram illustrating the operation of a conventional example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum 2 charging device 3 exposure device 4 developing sleeve 5 transfer device 6 toner charging control device 7 fixing device 10 toner 11 transfer material

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tetsuya Sano 3- 30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Michihito Yamazaki 3- 30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Hiroki Kisu 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-4-371977 (JP, A) JP-A-2-211475 ( JP, A) JP-A-5-107875 (JP, A) JP-A-2-259784 (JP, A) JP-A-5-281850 (JP, A) JP-A-2-67374 (JP, U) (58) ) Surveyed field (Int.Cl. ⁷ , DB name) G03G 21/00 G03G 21/10-21/12 G03G 15/08 507 G03G 15/02-15/02 103

Claims (2)

(57) [Claims] A charging means for charging a rotatable image carrier; an exposure means for forming an electrostatic latent image on the charged image carrier; and a charging means for adhering to a non-image portion of the electrostatic latent image. a cleaning developing means for visualizing the electrostatic latent image by supplying the developer to the developer to the image area of the electrostatic latent image on together when recovered are, a transfer unit that transfers a transfer material a developer image visualized image bearing developer charge control, which adjusts the downstream and charge polarity of the transfer residual developer not transferred to the transfer material in the rolling <br/> transcription unit on the upstream side of the charging means of the transfer means in the rotation direction of the body normal charging polarity Means for controlling the developer charge , wherein the developer charging control means comprises:
Transfer residual developer is frictionally charged with the blade.
An image forming apparatus characterized in that the charging polarity is adjusted to a regular charging polarity by the following . 2. The image forming apparatus according to claim 1, wherein
Serial and developer charging control means, the image bearing member, a charging means, developing means, at least one transfer means, and integrally housing a,
A process cartridge characterized in that it is detachable from the instrumentation Okimoto body.