JP3508413B2 - Image forming device - 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 using a cleanerless system in which cleaning is performed simultaneously with development in an electrophotographic apparatus or an electrostatic recording apparatus.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic apparatus mainly uses equipment using dry toner, and has been put into practical use as an image forming apparatus for many copying machines, laser printers, plain paper facsimiles, etc., and has made remarkable progress. This electrophotographic apparatus is an apparatus to which electrophotographic process technology is applied, and visualizes an electrostatic latent image formed on a photoconductor with toner particles.

In this image forming apparatus, recently, from the viewpoints of downsizing, cost reduction and environmental protection of the apparatus, a cleaning device for removing the toner remaining on the photoconductor after transfer is abolished and the image forming apparatus remains at the same time as development. Those using a so-called cleanerless system for cleaning toner are becoming popular.

The structure and operation of a conventional image forming apparatus will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a conventional image forming apparatus using a cleanerless system.
In FIG. 1, reference numeral 1 denotes a photoconductor, which has a metal drum made of aluminum or the like as a base material, and a photoreceptive layer such as selenium (Se) or an organic photoconductor (hereinafter referred to as OPC) formed in a thin film on the outer peripheral surface thereof. It is formed by coating. The charger 2 arranged in proximity to the photoreceptor 1 which is an electrostatic latent image carrier is composed of a charging wire 2a such as a tungsten wire, a metal shield plate 2b and a grid plate 2c. The charging line 2a causes corona discharge to uniformly charge the photoconductor 1 through the grid plate 2c. The exposure light beam 4 emitted from the exposure optical system 3 is obtained by light intensity modulation or pulse width modulation of an image signal by a laser driving circuit (not shown), and forms an electrostatic latent image on the photoconductor 1.

Reference numeral 6 denotes a toner supply roller for supplying the toner 10 agitated and conveyed by the toner agitating member 11 whose both ends are rotatably supported by the developing hopper 9 to the surface of the developing roller 5 as a toner carrier. Supply bias power supply 2
5, the toner supply bias voltage is applied. The developing roller 5 and the toner supplying roller 6 are made of metal such as stainless steel as a base material, and elastic members such as urethane and silicon are formed in layers on the outer peripheral surfaces thereof, and are rotatably supported at both ends of the developing hopper 9. 5a and 6a are shafts.

The toner 10 supplied by the toner supply roller 6 is triboelectrically charged by the toner regulating blade 7 and forms a thin layer on the outer peripheral surface of the developing roller 5.
The developing roller 5 is in contact with the photoconductor 1, and the bias voltage applied from the developing bias power source 12 causes the photoconductor 1 to move.
The toner 10 is transferred and attached to the portion where the electrostatic latent image is formed to visualize the electrostatic latent image, and at the same time, the residual toner after transfer is collected in the developing device.

The toner regulating blade 7 comprises a metal spring plate member 7a and a toner regulating member 7b which contacts the developing roller 5, and the toner regulating member 7b has an elastic member such as silicone or urethane at one end of the metal spring plate member 7a. It is integrally formed. Reference numeral 8 denotes a blade holder for fixing the toner regulation blade 7, which is attached by screwing. The toner stirring member 11 draws a circular locus along with the rotation of the toner supply roller 6, prevents the toner 10 stored in the developing hopper 9 from aggregating, and conveys the toner 10 to the toner supply roller 6.

Paper 1 stored in paper cassette 14
The reference numeral 5 designates a half-moon-shaped feed roller 16 from the paper cassette 14.
Then, the sheets are sent one by one to the transport roller 17. The sheet 15, which is the recording sheet that has been sent out, is transported in the direction indicated by arrow A by the transport roller 17. 18 is paper 1
5 is a registration roller for temporarily stopping and waiting the paper 15 in order to match the toner image formed on the photosensitive member 1 with the toner image, and is in contact with the driven roller 19. The transfer roller 20 is made of a metal such as stainless steel as a base material, and an elastic member is formed in layers on the outer peripheral surface of the transfer roller 20. When the toner image reaches the contact portion between the transfer roller 20 and the photosensitive member 1 as the photoreceptor 1 rotates, the paper 15 also reaches this contact portion at the same timing as the toner image. By applying a high voltage from the transfer bias power source 24 to the metal shaft 20a, a charge having a polarity opposite to that of the toner 10 is applied to the back surface of the paper 15, and the toner image on the photoconductor 1 is transferred onto the paper 15. Next, the sheet 15 is sent to the left side in the drawing, and the toner image transferred onto the sheet 15 is transferred to the heat roller 22 by the fixing device 21 including a heat roller 22 and a pressure roller 23 having a heat source inside. With the pinching rotation of the pressure roller 23, it is fixed by pressure and heat. On the other hand, the photoconductor 1 after the toner image is transferred onto the paper 15 is irradiated with light by the static eliminator 13 to be neutralized, and is prepared for the next process.

The image forming apparatus using such a cleanerless system is advantageous in terms of downsizing, cost reduction and environmental protection.

[0010]

In the case of the image forming apparatus having the above-mentioned structure, generally, there is no cleaning blade arranged in contact with the photosensitive member 1 to remove the residual toner after the transfer, so that the photosensitive member 1 is not present. The surface of the photoconductor is less likely to be abraded, and the image deterioration is likely to occur due to a chemical change of the photoconductor 1 mainly due to ozone or NO _x generated in charging or transfer means, or filming of the surface of the photoconductor 1 Had a point.

As a means for solving this problem, there is a means for increasing the peripheral speed of the developing roller 5 and reducing the toner adhesion amount on the developing roller during non-developing. However, when the peripheral speed of the developing roller 5 is increased, the stress on the developing roller 5, the toner 10 and the like increases, and the life of the developing unit is shortened.

The present invention solves the above-mentioned conventional problems, and provides an image forming apparatus using a cleanerless system which is capable of forming a high-quality image over time without shortening the life of the developing unit. The purpose is to do.

[0013]

In order to achieve the above-mentioned object, the present invention provides a peripheral speed difference between a photoreceptor and a developing roller at the time of non-developing which is larger than that at the time of developing, and a peripheral speed of a developing roller at the time of developing. It is designed to be smaller than the peripheral speed of the ozone gas in the image forming apparatus using the cleanerless system.
It is possible to prevent chemical change of the photoconductor due to _{X and the} like and filming of the photoconductor surface.

If the developing bias voltage applied to the developing roller during non-developing is V _B and the toner supply bias voltage applied to the toner supplying roller during non-developing is V _SR , then V _B
Is the same as the charging polarity of the toner, and is | V _SR | <| V
_B | or V _SR satisfies the relationship of the opposite polarity to the charge polarity of the toner, and in an image forming apparatus using a cleanerless system, exposure to ozone or NO _x does not occur without shortening the life of the developing unit. It is possible to prevent chemical changes in the body and filming on the surface of the photoconductor.

If the developing bias voltage applied to the developing roller during non-developing is V _B and the toner supply bias voltage applied to the toner supplying roller during non-developing is V _SR , then V _B
Is the polarity opposite to the charging polarity of the toner, and is | V _SR |> | V
_B | which was to satisfy the relation, fill ozone and NO _X, such as by chemical transformation or a photosensitive surface of the photoreceptor without causing the reduction of the service life of the developing unit in an image forming apparatus using the cleanerless method It is possible to prevent mingling.

When the developing bias voltage applied to the developing roller during non-developing is V _B and the toner supply bias voltage applied to the toner supplying roller during non-developing is V _SR , V _{B is}
= 0, and V _SR has a polarity opposite to the charging polarity of the toner. In an image forming apparatus using a cleanerless system, ozone or N is used without shortening the life of the developing unit.
It is possible to prevent chemical changes of the photoconductor and filming of the photoconductor surface due to O _{X and the} like.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The invention according to claim 1 of the present invention comprises a charging means for charging a photoreceptor, an exposing means for forming an electrostatic latent image on the photoreceptor, and an electrostatic means formed on the photoreceptor. A developing roller that forms a layer of toner for forming a latent image into a toner image, a toner supply roller that is arranged in contact with the developing roller and supplies toner, and a toner regulating blade that regulates the toner on the developing roller to form a thin layer and developing It has a developing means having a means for applying a developing bias voltage to the roller and a means for applying a toner supplying bias voltage to the toner supplying roller, and a transferring means for transferring the toner image formed on the photoconductor to a recording medium. An image forming apparatus in which toner remaining on a photoconductor after transfer by a transfer unit is cleaned at the same time as development by a developing unit, and a peripheral speed difference between a non-developed photoconductor and a developing roller is Ri is large, and it is the peripheral speed of the developing roller which is made smaller than at the time of development, the photosensitive member surface photoconductor chemical due likely ozone and NO _X worn without increasing the stress on the developing roller and toner Change and filming on the surface of the photoconductor can be prevented.

According to the second aspect of the present invention, when the developing bias voltage applied to the developing roller during non-developing is V _B and the toner supply bias voltage applied to the toner supplying roller during non-developing is V _SR , V _B is toner. Is the same as the charging polarity of, and | V _SR | <| V _B | or V _SR satisfies the relationship of the opposite polarity to the charging polarity of the toner. Have.

According to the third aspect of the present invention, when the developing bias voltage applied to the developing roller during non-developing is V _B and the toner supply bias voltage applied to the toner supplying roller during non-developing is V _SR , V _B is the toner. It has a polarity opposite to the charging polarity of No. 1 and satisfies the relationship of | V _SR |> | V _B |, and has the same effect as in claim 1.

[0020] According to a fourth aspect of the invention, the non-development when applied to the developing roller developing bias voltage V _B, the toner supply bias voltage applied to the toner supply roller at the time of non-development and V _SR, V _B = 0 However, V _SR has a polarity opposite to the charging polarity of the toner, and has the same effect as in claim 1.

Embodiments of the present invention will be described below. Here, the basic structure of the image forming apparatus is the same as the conventional one shown in FIG. The photoconductor 1, the developing roller 5, and the toner supply roller 6 rotate in the directions of the arrows shown in FIG. 1, and the respective contact portions are in frictional contact.

The photoreceptor 1 is a negative charging type OPC, and is uniformly charged to -700V by the charger 2.

The developing roller 5 has a single layer structure in which a metal shaft 5a is used as a base material and silicon rubber which is a conductive elastic member is formed on the outer peripheral surface thereof, and has a resistance value of 10 ⁶ Ω. A developing bias power source 12, which is a constant voltage power source, is connected to the shaft 5 a of the developing roller 5. This developing roller 5
The rubber hardness is preferably in the range of 30 to 60 degrees, and the surface roughness is preferably 7 μmRz or less because the higher the surface smoothness is, the more uniform the toner thin layer can be formed. In the present embodiment, the developing roller 5 has a rubber hardness of 40 degrees and a surface roughness of 3 μmRz.

The toner supply roller 6 has a conductive shaft formed around a metal shaft 6a and has a resistance value of 10
^The toner supply bias power supply 25, which is a constant voltage power supply, is connected to the shaft 6a. The toner supply roller 6 has a function of supplying the toner 10 supplied from the developing hopper 9 to the developing roller 5 and scraping off the toner 10 remaining on the developing roller 5 without being developed. The nip width between the toner supply roller 6 and the developing roller 5 is 2 mm.

The toner regulating blade 7 is a stainless steel plate,
An elastic metal spring plate member 7a such as a phosphor bronze plate and urethane elastic rubber having a rubber hardness of 60 degrees, which is an elastic member, is integrally formed at one end thereof as a toner regulating member 7b and is screwed to the blade holder 8. . Toner regulating member 7
b presses the developing roller 5 with a linear pressure of 80 g / cm to form a toner layer of 0.5 mg / cm ^{2 on} the surface of the developing roller 5. In the non-magnetic one-component contact developing method as in this embodiment, the toner layer on the developing roller 5 has a thickness of 0.3 to 0.6.
The range of mg / cm ² is preferred.

Toner 10 is a non-magnetic one-component toner, which is a polyester resin in which carbon, wax, a charge control agent and the like are uniformly dispersed, and a negatively chargeable toner is used.

The transfer roller 20 is a metal shaft 20.
A conductive foam is formed around a and has a resistance value of 10 ⁷
Ω, and the transfer bias power source 24 is connected to the shaft 20a. The transfer bias power source 24 is a constant current power source of 4 μA.

The process speed was 76 mm / sec, the peripheral speed of the developing roller 5 during development was 106 mm / sec, and the peripheral speed of the toner supply roller 6 was 75 mm / sec.

The following printing operation was performed on the image forming apparatus using the cleanerless system configured as described above. First, the photosensitive member 1 is uniformly charged to -700V, then exposed by the exposure optical system 3 to reduce the surface potential of the exposed photosensitive member 1 to -100V, and a developing bias of -300V is applied to the developing roller 5 to expose it. Forming a toner image on the body 1,
A toner image was transferred from the transfer roller 20 to the paper 15 by applying a current of 4 μA, and a toner image was obtained on the paper 15 through a fixing step generally known as an electrophotographic process.

When the chemical change of the photosensitive member 1 due to ozone or NO _x or filming of the surface of the photosensitive member 1 occurs over time, the charging potential of the photosensitive member 1 tends to decrease. Developing bias V _B of -300V, 0V,
The peripheral speed v _d of the developing roller 5 at the time of non-developing is set to 300 V, 26 mm / sec, 46 mm / sec, 106 mm / s.
As ec, the result of measuring the charging potential of the photoconductor 1 after printing 500 sheets by the above printing operation while changing the toner supply bias V _SR during non-developing is shown in (Table 1).

[0031]

[Table 1]

As is clear from (Table 1),
The peripheral speed difference between the photoconductor 1 and the developing roller 5 is larger than that during development.
And the peripheral speed of the developing roller 5 is smaller than that during development
The developing bias voltage applied to the developing roller 5 during non-developing
Pressure V_B, The toner applied to the toner supply roller 6 at the time of non-development
The bias voltage supplied to the gate_SRThen, V_BThe toner 1
0 as the same polarity as the charging polarity of 0_SR│ <│V_B| Or
V_SRSatisfies the relationship of the polarity opposite to the charging polarity of the toner 10.
Or V_BTo the opposite polarity to the charging polarity of the toner 10.
Then | V_SR｜ ＞ ｜ V_BMust satisfy the | relationship, or
V_BV as = 0 _SRIs the polarity opposite to the charging polarity of the toner 10.
By doing so, ozone and NO_XPhotoconductor 1 by
Prevents chemical changes in the film and filming on the surface of the photoconductor 1
However, there is almost no change from the initial charging value of -700V.
The charging potential of the body 1 could be obtained.

In this case, no change in the surface of the developing roller 5 was observed, and there was no change in image quality, so it is considered that the stress on the toner 10 did not increase, and the life of the developing unit does not decrease. Conceivable.

[0034]

[0035]

As described above, according to the present invention, the peripheral speed difference between the photoconductor and the developing roller during non-developing is larger than that during developing, and the peripheral speed of the developing roller is smaller than during developing.
By moving the toner to the toner supply roller side and generating an electric field that reduces the toner adhesion amount on the developing roller,
High quality images prevent filming of chemical changes and the photosensitive member surface, such as by a photoreceptor ozone and NO _X without increasing the stress on the developing roller and the toner can be obtained.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a conventional image forming apparatus using a cleanerless system.

[Explanation of symbols]

1 photoconductor 5 developing roller 6 Toner supply roller 10 toner 12 Development bias power supply 25 Toner supply bias power supply

─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Kazuhiko Noda 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Yukinori Hara 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd. (58) Fields surveyed (Int.Cl. ⁷ , DB name) G03G 15/08 501 G03G 15/08 507 G03G 15/06 101

Claims (4)

(57) [Claims] 1. A charging device for charging a photoconductor, an exposing device for forming an electrostatic latent image on the photoconductor, and a toner layer for forming an electrostatic latent image formed on the photoconductor into a toner image. And a toner supply roller arranged in contact with the developing roller to supply toner, a toner regulating blade for regulating the toner on the developing roller to form a thin layer, and a means for applying a developing bias voltage to the developing roller. And a transfer unit for transferring the toner image formed on the photoconductor onto a recording medium, and a transfer unit for transferring the toner image formed on the photoconductor to the recording medium. An image forming apparatus for cleaning toner remaining on the photoconductor at the same time as development by the developing means, wherein the peripheral speed of the photoconductor and the developing roller during non-developing. An image forming apparatus comprising greater than at the time of development, and the peripheral speed of the developing roller less than that during the development that the. 2. When a developing bias voltage applied to the developing roller during non-developing is V _B and a toner supply bias voltage applied to the toner supplying roller during non-developing is V _SR , V
_B has the same polarity as the toner charging polarity, and | V _SR | <|
The image forming apparatus according to claim 1, wherein V _B | and V _SR satisfy a relationship of a polarity opposite to a charging polarity of the toner. 3. When the developing bias voltage applied to the developing roller during non-developing is V _B and the toner supply bias voltage applied to the toner supplying roller during non-developing is V _SR , V
_B has a polarity opposite to the charging polarity of the toner, and is | V _SR |> |
The image forming apparatus according to claim 1, wherein the relationship of V _B | is satisfied. 4. When the developing bias voltage applied to the developing roller during non-developing is V _B and the toner supply bias voltage applied to the toner supplying roller during non-developing is V _SR , V
The image forming apparatus according to claim 1, wherein _B = 0 and V _SR has a polarity opposite to the charging polarity of the toner.