JP2907756B2 - 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 roller transfer system in an electrophotographic apparatus or an electrostatic recording apparatus.

[0002]

2. Description of the Related Art Electrophotographic apparatuses which use toner as a dry developer have occupied the mainstream, and have been remarkably developed for practical use as many copiers, laser printers, plain paper facsimile machines and the like.

[0003] This type of electrophotographic apparatus is an apparatus to which electrophotographic process technology is applied, in which an electrostatic latent image formed on a photoconductor, which is an electrostatic latent image body, is visualized by toner particles. is there.

The configuration and operation of the electrophotographic apparatus will be described below with reference to the drawings. FIG. 2 is a sectional view of an electrophotographic apparatus using a conventional roller transfer method. In FIG. 2, a photosensitive member 1 serving as an electrostatic latent image carrier has a metal drum such as aluminum as a base material, and selenium (S)
e) or a photosensitive receiving layer such as an organic photoconductor (hereinafter referred to as OPC) is applied in a thin film form. The charger 2 disposed close to the photoreceptor 1 includes a charging wire 2a such as a tungsten wire, a metal shield plate 2b, and a grid plate 2c. The charging line 2a causes a corona discharge to uniformly charge the photoconductor 1 via the grid plate 2c. The exposure light beam 4 emitted from the exposure optical system 3 converts the image signal into a laser drive circuit (not shown).
The exposure light beam 4 forms an electrostatic latent image on the charged photoreceptor 1.

The toner supply roller 6 supplies the toner 10 stirred and conveyed by a toner stirring member 11 rotatably supported at both ends to a developing hopper 9 to the surface of the developing roller 5 which is a toner carrier. is there.

The developing roller 5 and the toner supply roller 6 are made of a 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 surface. The developing roller 5 and the toner supply roller 6 are rotatably supported at both ends of the developing hopper 9 by shafts 5a and 5b.

The toner 10 supplied by the toner supply roller 6 is frictionally charged by the toner regulating blade 7 to form a thin layer on the outer peripheral surface of the developing roller 5.
Thereafter, the developing roller 5 comes into contact with or close to the photoconductor 1, and the toner 10 is transferred and adhered to a portion of the photoconductor 1 on which the electrostatic latent image is formed by a bias voltage applied from the developing bias power supply 12. Visualize the electrostatic latent image.

The toner regulating blade 7 includes a metal spring plate member 7a and a toner regulating member 7b that comes into contact with the developing roller 5.
The toner regulating member 7b is formed by integrally forming an elastic member such as silicon or urethane at one end of a metal spring plate member 7a. The blade holder 8 fixes the toner regulating blade 7 and is attached by screwing. Toner stirring member 11
Draws a circular locus with the rotation of the toner supply roller 6,
The toner 10 contained in the developing hopper 9 is prevented from aggregating, and the toner 10 is conveyed to the toner supply roller 6.

The recording paper 15 stored in the recording paper cassette 14 is sent from the recording paper cassette 14 to a transport roller 17 one by one by a half-moon-shaped paper feed roller 16. The fed recording paper 15 is transported by a transport roller 17.
Is transported in the direction indicated by arrow A. The registration roller 18 is provided for temporarily stopping the recording paper 15 in order to match the recording paper 15 with the toner image formed on the photoconductor 1, 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 has an elastic member formed in a layer on the outer peripheral surface thereof. When the toner image reaches the contact portion between the transfer roller 20 and the photosensitive member 1 with the rotation of the photosensitive member 1, the recording paper 15 also reaches the contact portion in synchronization with the toner image. By applying a high voltage from the transfer bias power supply 24 to the metal shaft 20 a of the recording medium 20, a charge having a polarity opposite to that of the toner 10 is applied to the back surface of the recording paper 15, and the toner image on the photoconductor 1 Transfer to Next, the recording paper 15 is sent to the left, and a heat roller 22 having a heat source therein and a pressure roller 23 formed inside a fixing device 27.
Is fixed by pressurization and heat with the holding rotation of.

[0011] Such an image forming apparatus of the roller transfer system is different from a corona transfer system conventionally used in practice.
Since a high voltage power supply is not required, it is advantageous in terms of cost, and since there is no generation of ozone due to high voltage discharge, there is also an environmental advantage.

[0012]

However, in the case of the roller transfer system as in the conventional example, the transfer roller 20 is not used.
It is known that the relationship between the voltage and the current applied to the resistance greatly varies because the resistance value of the resistance varies greatly depending on the environment and the manufacturing process.

The resistance value of the transfer roller 20 is increased by several orders of magnitude in a low-temperature and low-humidity (hereinafter referred to as L / L) environment compared with a normal temperature and normal humidity (hereinafter referred to as N / N), and becomes high-temperature and high humidity (hereinafter referred to as H / H). ) Under an environment, it is reduced by one to two digits. In the manufacturing process,
It fluctuates by about 10 ⁶ Ω to 10 ⁹ Ω. These transfer rollers 2
It is technically possible to reduce the variation in the resistance value of 0 due to the manufacturing process, but this is because
It is not preferable because the cost is increased.

FIGS. 3 and 4 show variations in the relationship between the voltage applied to the transfer roller and the current due to the above environment and the manufacturing process. According to the experiment, a transfer current of 3 to 5 μA during paper passing is required to perform good transfer.
It has been found that a transfer loss occurs at 3 μA or less, and scattering of a toner image occurs at 5 μA or more. From this, for example, when the transfer roller 20 having a resistance value of 10 ⁷ Ω is used, an appropriate transfer voltage is 300 in an L / L environment.
0 to 4000V, 1000 to 1500 under N / N environment
In a V / H / H environment, the voltage is 500 to 800V.

In such an apparatus, a transfer bias power supply 2 is provided so that transfer in an N / N environment is properly performed.
4 is controlled at a constant voltage of, for example, 1000 V, toner image scattering occurs under an H / H environment, and transfer omission occurs under an L / L environment. When the transfer voltage is set so as to improve the transferability under the H / H environment, L / L, N /
Transfer failure occurs under the N environment, and the same applies when the setting is made in accordance with the L / L environment. Thus, with the constant voltage control of the transfer bias power supply, it is impossible to obtain satisfactory transferability in all environments.

When the constant current control of the transfer bias power supply 24 is performed to cope with such a situation, the following problem occurs. For example, when the transfer bias power supply is controlled at a constant current of 4 μA, under the L / L environment, 3500 V and N / N
A transfer voltage of 1300 V is applied to the transfer roller 20 under an environment and 680 V is applied under an H / H environment. Although there is no problem under the N / N or H / H environment, a voltage of as high as 3500 V is applied under the L / L environment, so that problems such as an increase in the cost of a high-voltage power supply and a withstand voltage of the photoconductor occur. This is the resistance value 1 of the transfer roller 20.
In this case, the resistance value is 0 ⁷ Ω, and when the resistance value is 10 ⁹ Ω, the voltage value further increases.

As described above, in the conventional image forming apparatus, there is a problem in each of the constant voltage control and the constant current control of the transfer bias power supply. Accordingly, the present invention provides a transfer bias power supply 2 in a roller transfer method.
4 is a constant current control, and an object of the present invention is to provide an image forming apparatus which prevents a transfer voltage from increasing without impairing transferability even if the transfer roller 20 has a high resistance due to the environment and manufacturing process.

[0018]

Images forming apparatus of the present invention According to an aspect of the exposure to form a latent electrostatic image bearing member, an electrostatic latent image by irradiating the exposure light beam on the surface of the electrostatic latent image bearing member And a developing unit for forming a toner image of the electrostatic latent image by contacting or arranging a thin layer of toner formed on the surface of the developing roller on the surface of the electrostatic latent image carrier, and a transfer member such as recording paper for transferring the toner image A transfer unit that transfers the electrostatic latent image to a toner image in the developing unit, and the transfer unit that transfers the toner image on the electrostatic latent image carrier onto recording paper, a roller transfer method using a transfer roller, also, the transfer bias applied to the transfer roller is an image forming apparatus in which a constant current control of the constant current source, and the front or the rear recording sheet of the transfer roller only set a conductive member to a position in contact, the resistance of the transfer roller
If the value is R ₁ and the resistance value of the conductive member is R ₂ , R
_1> satisfy the relationship of R _2, the conductive member, the constant
It is the one to which the current power supply is directly connected.

[0019]

[0020]

[0021]

According to this construction, the transfer section for forming the electrostatic latent image into a toner image in the developing section and transferring the toner image on the electrostatic latent image carrier onto recording paper uses a transfer roller. In the roller transfer method, the transfer bias applied to the transfer roller is a constant current control, and a conductive member is provided at a position in contact with the recording paper on the front side or the rear side of the transfer roller,
Assuming that the resistance value of the transfer roller is R ₁ and the resistance value of the conductive member is R ₂ , a transfer bias is applied to the conductive member so as to satisfy the relationship of R ₁ > R ₂ , thereby obtaining a transfer bias current. Flows on the recording paper not only from the transfer roller but also from the conductive member.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of an electrophotographic apparatus using a roller transfer system according to one embodiment of the present invention. The same elements as those in the related art shown in FIG.

The rotation directions of the photosensitive member 1, the developing roller 5, and the toner supply roller 6 are in the directions of the arrows shown in FIG. 1, and the respective contact portions are in frictional contact. The transfer roller 20 is formed by forming a conductive foam around a metal shaft 20a and has a resistance value of 10 ⁷ Ω. The transfer bias power supply 24 which is a constant current power supply is connected to the metal shaft 20a. I have.

The conductive member 25 is a metal member, and has a resistance value sufficiently smaller than that of the transfer roller 20, and is provided downstream of the transfer roller 20 so as to come into contact with the recording paper 15 when the paper is passed. Further, a transfer bias power supply 24 is connected to the conductive member 25.

The toner supply roller 6 includes a metal shaft 6.
resistance 10 in which to form a conductive foam around a ⁶
And the toner supply roller 6 is connected to the developing hopper 9
Has a function of supplying the toner 10 supplied from the developing roller 5 to the developing roller 5 and scraping off the toner 10 on the developing roller 5 remaining without being developed.

The developing roller 5 has a single-layer structure in which a metal shaft 5a is used as a base material and silicon rubber as a conductive elastic member is formed on an outer peripheral surface thereof, and has a resistance value of 10 ⁶ Ω.
Further, a developing bias power supply 12 is connected to the metal shaft 5 a of the developing roller 5.

The rubber hardness of the developing roller 5 is 30 to 60.
The range of the degree is preferable, and the higher the surface roughness of the surface is, the more uniform the toner thin layer can be formed.
7 μmRz or less is preferable. In this embodiment, the developing roller 5 has a rubber hardness of 40 degrees and a surface roughness of 43 μmRz.

The toner regulating blade 7 includes a stainless steel plate,
An elastic metal spring plate member 7a such as a phosphor bronze plate, and urethane rubber having a rubber hardness of 60 degrees, which is an elastic member, is integrally formed at one end as a toner regulating member 7b. ing.

The toner regulating member 7b presses the developing roller 5 at a linear pressure of 80 g / cm, and applies 0.5 m to the surface of the developing roller 5.
g / cm ² of toner layer is formed. In the non-magnetic one-component contact developing system as in this embodiment, the toner layer on the developing roller 5 preferably has a range of 0.3 to 0.6 mg / cm ² .

The electrophotographic process conditions for printing are as follows: process speed is 76 mm / sec, photosensitive member 1 is negatively charged OPC, and peripheral speed of developing roller 5 is 152 mm / s.
In ec, the peripheral speed ratio for the photosensitive zone 1 is twice. The transfer roller 20 is driven to rotate with the photosensitive member 1, the peripheral speed of the toner supply roller 6 is 105 mm / sec, the toner 10 is a non-magnetic one-component toner, and carbon, wax, a charge control agent, etc. are uniformly dispersed in a polyester resin. And a negatively chargeable toner was used. The photoreceptor 1 is uniformly charged to -700 V, and the bias voltage value of the developing bias power supply 12 is -300.
V, the transfer bias power supply 24 is a 4 μA constant current power supply.

Under the above conditions, the photosensitive member 1 is set at -700.
V, and thereafter, the photosensitive member 1 is exposed to an exposure optical system 3
The photosensitive member 1 is exposed to an exposure light beam 4 such as a laser scanning beam, and the surface potential of the exposed photosensitive member 1 is attenuated to -100 V. A toner image is formed on the recording paper 15 from the transfer roller 20 and the conductive member 25.
And a toner image was transferred to the recording paper 15 through a fixing step generally known as an electrophotographic process.

This printing operation was performed under three environments of L / L, N / N and H / H, and the output voltage of the transfer bias power supply 24 was measured to evaluate the printing quality. As a result, the output voltage was 1800 V under the L / L environment, and 1000 V under the N / N environment.
Under a V / H / H environment, the output voltage was 600 V. The printing quality is good in all three environments. This is because when the resistance value of the transfer roller 20 increases due to the environment, the current flowing from the conductive member 25 to the recording paper 15 increases, thereby suppressing an increase in the output voltage of the transfer bias power supply 24. Therefore, since the current flowing through the recording paper 15 does not change, the transferability is improved in all three environments.

The conductive member 25 of the above embodiment is provided on the rear side of the transfer roller 20.
May be provided in front of. Further, the conductive member 25 is provided at only one place.
, Two places on the front side, two places on the rear side, and so on.

Further, in the above-described embodiment, the operation is performed by using a system using a negatively charged photosensitive member and a negatively charged toner. Although urethane rubber as an elastic member was used as the toner regulating member 7b, various rubber materials such as silicon rubber, fluorine rubber, acrylic rubber, butadiene rubber, and EPDM rubber, various resin materials as rigid members, and Alternatively, a metal member may be used. However, in order to prevent a change in the amount of toner adhering on the developing roller with time, it is preferable that the abrasion resistance is excellent.

Further, the developing roller 5 and the transfer roller 20 need not be limited to elastic rollers, but may be metal rollers or resin rollers. Further, the developing roller 5
The photoconductor 1 may be in non-contact.

[0036]

As described above, according to the present invention , in the developing section
The electrostatic latent image is formed into a toner image, and the electrostatic latent image carrier is
The transfer section that transfers the toner image on the recording paper
Roller transfer method using a roller, and the transfer roller
The transfer bias to be applied to the
And makes contact with the recording paper on the front side or the rear side of the transfer roller.
A conductive member at a position where the resistance value of the transfer roller is reduced.
Assuming that R ₁ and the resistance value of the conductive member are R ₂ , R ₁ >
Satisfy the relationship of R _2, the conductive member, the constant current
By connecting the power directly, even if the transfer roller is high resistance by the environment and the manufacturing process, while suppressing an increase in transfer voltage for the transfer current flows through the conductive member <br/> or Ramoki recording paper quality Image can be obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an electrophotographic apparatus using a roller transfer method according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of an electrophotographic apparatus using a conventional roller transfer method.

FIG. 3 is a diagram illustrating a relationship between a voltage applied to a transfer roller and a current under a conventional L / L, N / N, H / H environment.

FIG. 4 is a diagram showing a relationship between a voltage applied to a transfer roller and a current due to a change in resistance value of a conventional transfer roller.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 3 Exposure optical system 4 Exposure light beam 5 Developing roller 6 Toner supply roller 9 Developing hopper 10 Toner 15 Recording paper 20 Transfer roller 24 Transfer bias power supply 25 Conductive member

──────────────────────────────────────────────────の Continued on the front page (72) Inventor Kazuhiko Noda 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. (56) References JP-A-57-67968 (JP, A) JP-A-6-124004 (JP, A) JP-A-57-67969 (JP, A) (58) Fields investigated (Int. ⁶ , DB name) G03G 15/16

Claims (1)

(57) [Claims] An electrostatic latent image carrier, an exposure section for irradiating an exposure light beam on the surface of the electrostatic latent image carrier to form an electrostatic latent image, and a developing roller on the surface of the electrostatic latent image carrier A developing unit for contacting or disposing a thin toner layer formed on the surface to form an electrostatic latent image into a toner image, and a transfer unit for transferring the toner image to a transfer member such as recording paper; The transfer unit that converts the electrostatic latent image into a toner image with a toner image and transfers the toner image on the electrostatic latent image carrier onto recording paper is a roller transfer method using a transfer roller, transfer bias applied to the transfer roller is an image forming apparatus in which a constant current control of the constant current power supply, only setting the conductive member to a position in contact with the front or rear of the recording paper of the transfer roller, the transfer B
The resistance of the roller is R ₁ and the resistance of the conductive member is R ₂ .
Then, the relationship of R ₁ > R ₂ is satisfied, and the conductive member
Wherein the constant current power supply is directly connected .