JPH11327282A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a high-quality image by using a silicone resin foamed body as the component member of a supply roller. SOLUTION: The supply roller 42 constituted of the silicone resin foamed body is rotated in a direction shown by an arrow C with the shaft 42a of the roller 42 formed of metal such as stainless steal as a center. Besides, a required bias voltage is applied on the roller 42. By the rotation of the roller 42, toner 40 filling the cells of the roller 42 is transferred to a developing roller 43 side. Then, the toner 40 is attached to the surface of the roller 43 by potential difference between both rollers 42 and 43 at a press-contact part between the rollers 42 and 43. Since the roller 43 is made to press-contact with a photoreceptor drum 1, the toner 40 attached to the surface of the roller 43 is carried to the drum 1 side by the rotation of the roller 43 in a direction shown by an arrow B. On the way to the drum 1, the layer thickness of the toner 40 attached to the surface of the roller 43 is uniformized by a toner film thickness regulation blade.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a supply roller between a toner hopper for storing toner and a developing roller,
The present invention relates to an image forming apparatus in which the supply roller and the developing roller are rotated in the same direction and the toner is charged by rubbing the developing roller with a blade.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus using an electrophotographic system, a supply roller is provided between a toner hopper for storing toner and a developing roller, and the supply roller and the developing roller are rotated in the same direction. In addition, an image forming apparatus of a type in which toner is charged by rubbing a developing roller with a blade is known. The supply roller in such an image forming apparatus uses a urethane foam as a constituent member.

[0003]

However, the supply roller made of urethane foam has an electric resistance value of one.
0 ⁴ Omega has a following low value, the toner filled in the bubble of the supply roller is not sufficient charge amount can be obtained, toner charging failure may occur. As a result, the attraction of the toner transferred from the supply roller to the developing roller to the developing roller is weakened, and the toner easily adheres to the portion of the photosensitive drum where the electrostatic latent image is not formed, There has been a problem that the formed image is stained with halftone and the image quality is reduced, and the image density is increased.

[0004]

The present invention uses the following means to solve the above-mentioned problems in the image forming apparatus. That is, in the first aspect, a developing device unit of a type in which a supply roller is provided between a toner hopper for storing toner and a developing roller, and the supply roller and the developing roller are rotated in the same direction to charge the toner. In the provided image forming apparatus, a silicone resin foam is used as a constituent member of the supply roller.

According to a second aspect of the present invention, the silicone resin foam has a roller state of 10 ^5.5 Ω to 10 ^8.5 Ω.
A silicone resin foam having an electric resistance value in the range of Ω is used.

According to a third aspect of the present invention, the toner is formed as a non-magnetic single component.

[0007]

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a side sectional view showing the inside of the image forming apparatus of the present invention, FIG. 2 is a side sectional view showing a developing unit and a drum unit, and FIG. 3 shows a relationship between an electric resistance value of a supply roller and a charge amount of toner. FIG.

The schematic structure of the image forming apparatus of the present invention will be described with reference to FIGS. This image forming apparatus
For example, the present invention is applied to an electrophotographic image forming apparatus such as a facsimile machine. A process unit 9 is disposed above an image forming apparatus 8. The process unit 9 includes a drum unit 10, a developing unit 4, and the like. I have. A photosensitive drum 1 is disposed in the drum unit 10, and a charger 2, an optical writing unit (LED head array) 3, and a developing device are provided around the photosensitive drum 1 along the rotation direction (arrow A). The unit 4, the transfer unit 5, the memory removing member 51, and the insulating member 52 are arranged in this order.

The photosensitive drum 1, the charger 2, the memory removing member 51 and the insulating member 52 are unitized as a drum unit 10, and the photosensitive drum 1 of the drum unit 10
Drum shaft 1a is detachably engaged with the developing unit 4. The process unit 9 is detachably mounted on the main body frame 21. When the process unit 9 is mounted on the main body frame 21, the developing unit 4 is supported by the main body frame 21 and the drum shaft 1a of the drum unit 10 is It is supported by a U-shaped groove formed in the main body frame 21. Then, the drum unit 10 and the developing unit 4 can be integrally removed, and only the drum unit 10 can be removed above the main body frame 21, so that when a paper jam occurs in the process unit 9, the paper can be easily taken out. I have to.

A fixing unit 6 for fixing the toner image transferred to the sheet is disposed downstream of the drum unit 10. The fixing unit 6 includes a heating roller 61 and a pressure roller 62 pressed against each other. It is configured. On the upstream side of the drum unit 10, sheet transport rollers 71 and 72 are provided.
A recording paper supply / conveyance system 7 including a 72 ′, pickup rollers 73/73 ′, and paper feed cassettes 74/74 ′ is provided. The charger 2 is a brush roller type charger in which a roller surface is covered with a conductive fiber brush, and a bias voltage is applied to the charger 2 to uniformly rotate the peripheral surface of the photosensitive drum 1 while rotating. It is charged to approximately -750V. The transfer unit 5 is made of a conductive foam made of urethane resin or the like, and a constant current bias voltage (for example, +600 V to +3.5 kV) is applied to the transfer unit 5.

The developing unit 4 includes a developing device main body 41 serving as a toner hopper for storing toner 40, a supply roller 42 disposed below the developing device main body 41, the supply roller 42 and the photosensitive drum 1. And a stirring member 44 for stirring the toner 40 stored and arranged in the developing device main body 41, Toner thickness regulating blade 45 elastically provided on the peripheral surface on the downstream side in the transport direction
The toner 40 is composed of a non-magnetic single component.

The developing roller 43 is formed of a rubber member or the like.
Developing roller shaft 43a made of metal such as stainless steel
2, the developing roller 43 is applied with a bias voltage of, for example, about -300 V. Further, the toner film thickness regulating blade 45 is provided with the toner 40 adhered to the outer peripheral surface of the developing roller 43.
The blade is a blade that regulates the film thickness, and is made of an elastic stainless member or the like. Then, a bias voltage of, for example, about −400 V is applied to the toner thickness regulating blade 45. The supply roller 42 is made of a silicone resin foam, and is centered on a supply roller shaft 42a formed of a metal such as stainless steel as viewed from an arrow C in FIG.
, And the supply roller 42 has, for example, -500.
A bias voltage of about V is applied.

The center distance between the supply roller 42 and the developing roller 43 is set to be slightly smaller than the sum of the respective roller radii when the supply roller 42 and the developing roller 43 are driven. As a result, the contact portions of the two rollers are brought into a pressure contact relationship. The frictional action between the supply roller 42 and the developing roller 43 due to this pressure contact relationship and the rotation direction of the arrows B and C in the same direction,
In combination with the bias voltage applied to the roller 43, the toner 40 existing near the rollers 42 and 43 is charged. That is, the toner 40 composed of one non-magnetic component is charged by static electricity generated by the frictional force and an applied voltage,
The charge amount of the toner 40 changes according to the magnitude of the electric resistance value of the supply roller 42.

The rotation of the supply roller 42 in the direction indicated by arrow C transfers the toner 40 filled in the bubbles of the supply roller 42 to the developing roller 43 side.
The toner 40 adheres to the surface of the developing roller 43 due to a potential difference between the two rollers 42 and 43 at the pressure contact portion between the developing roller 43 and the developing roller 43. The developing roller 43 is in pressure contact with the photosensitive drum 1, and the toner 40 adhered to the surface of the developing roller 43 is
The rotation of the developing roller 43 in the direction of arrow B is conveyed to the photosensitive drum 1 side. On the way, for example, -400
The layer thickness of the toner 40 adhered to the surface of the developing roller 43 becomes uniform by the toner film thickness regulating blade 45 applied to about V.

Next, an image forming process in the image forming apparatus configured as described above will be briefly described. The photoreceptor drum 1 rotates in the direction of arrow A, and the outer peripheral surface of the photoreceptor drum 1 is uniformly charged to approximately -750 V by the charger 2 composed of a conductive fiber brush. Thereafter, the light writing unit 3 irradiates the surface of the photosensitive drum 1 with light based on the image information. Photoconductor drum 1
Is made of a grounded photoconductor, the potential of the portion irradiated with light, that is, the portion of the image information corresponding to black is -30 V
And a potential difference occurs between the light-irradiated portion (the portion corresponding to the black of the image information) and the non-irradiated portion (the portion corresponding to the white of the image information). An electrostatic latent image corresponding to the image information is formed on the side surface.

This electrostatic latent image reaches the developing unit 4 and
When the electrostatic latent image and the negatively charged toner 40 attached to the outer peripheral surface of the developing roller 43 come into contact with each other, the toner 40 contacts the light-irradiated portion on the surface of the photosensitive drum 1 due to a potential difference from the light-irradiated portion. The toner image is transferred by suction, and a toner image is formed on the surface of the photosensitive drum 1. The toner image reaches a contact portion between the photosensitive drum 1 and the transfer device 5 by rotation of the photosensitive drum 1, and the contact portion is provided with the pickup roller in synchronization with the rotation of the photosensitive drum 1. The recording paper fed one by one from the paper feed cassette 74 (74 ') by 73
It is introduced via the conveying rollers 72 (72 ') and 71. Since a bias voltage of +600 V to 3.5 kV is applied to the transfer unit 5, the toner image on the surface of the photosensitive drum 1 is sucked by the transfer unit 5 and adheres to the recording paper and is transferred.
The recording paper onto which the toner image has been transferred is further conveyed by the rotation of the photosensitive drum 1 and the transfer device 5, and the fixing unit 6
Leads to.

The recording paper that has reached the fixing unit 6 is introduced into a pressure contact portion between the heating roller 61 and the pressure roller 62.
Here, the resin component contained in the toner 40 is
The recording sheet is melted by the heating / pressing action of 1.62 and fused to the sheet to form a permanent image, and the recording sheet is discharged out of the apparatus. After the transfer of the toner image onto the recording paper, the surface of the photosensitive drum 1 is positively charged by the operation of the transfer device 5, and a small amount of untransferred toner remains. The photoreceptor drum 1 continues to rotate thereafter, the surface thereof is uniformly charged by the charger 2 as described above, and the subsequent process is repeated.

On the other hand, the untransferred toner remaining on the surface of the photosensitive drum 1 is transferred to a memory removing member 51 provided separately from the charger 2.
When the voltage is applied to the photosensitive drum 1, it is disturbed by the action of the memory removing member 51 and is dispersed and charged on the surface of the photosensitive drum 1. Then, the dispersed residual toner reaches the developing unit 4, and unnecessary toner is sucked by the potential difference from the developing roller 43, and the developing unit 4
Collected in 1.

In the present image forming apparatus, an image is formed by the above-described image forming process. The image quality of the formed image depends on the charge amount of the toner 40 charged by the supply roller 42. As a result, the density of the formed image increases as the charge amount of the toner 40 decreases, and the image density decreases as the charge amount increases. That is, the toner 4
When the charge amount of 0 is small, the attraction force of the toner 40 transferred from the supply roller 42 to the developing roller 43 to the developing roller 43 is weakened, and the amount of the toner 40 adhered to the photosensitive drum 1 is increased, so that the image density is reduced. Will be higher. If the charge amount of the toner 40 becomes too small, the toner 40 easily adheres to a portion of the photoconductor drum 1 where the electrostatic latent image is not formed, and a halftone stain is formed on the formed image. And other image defects. Conversely, toner 4
0, the developing roller 43 of the toner 40
As a result, the toner 4 adheres to the photosensitive drum 1
Since the amount of 0 is reduced, the image density is reduced. If the charge amount of the toner 40 becomes too large in this case, the amount of the toner 40 attached to the photosensitive drum 1 becomes too small, and image defects such as insufficient density occur. As described above, if the charge amount of the toner 40 is too small or too large, it causes image failure. Therefore, in order to form a high-quality image, the charge amount of the toner 40 is controlled within a certain range. There is a need.

FIG. 3 shows the electric resistance value of the supply roller 42 and
The relationship with the charge amount of the toner 40 charged by the supply roller 42 is shown by a graph 71. Toner 40
Varies depending on the electric resistance value of the supply roller 42,
As the electric resistance value of the supply roller 42 is lower, the charge amount of the toner 40 is smaller, and as the electric resistance value of the supply roller 42 is higher, the charge amount of the toner 40 is larger. When the charge amount of the toner 40 is within the appropriate range 72,
The charge amount is appropriate for forming a high-quality image, and in order to keep the charge amount within the appropriate range 72, the electric resistance value must be within the range from the lower limit 73 to the upper limit 74. It is necessary to use the rollers 42.

Therefore, in the present image forming apparatus, the supply roller 42 is formed of a silicone resin foam having a high electric resistance value in order to regulate the charge amount of the toner 40 within the appropriate range 72. Feed roller 42 of the silicon resin foam has an electrical resistance value in the range from the lower limit value 73 to the upper limit 74, in this case, the lower limit value 73 is, for example, 10 ^{5. 5} Omega, The upper limit 74 is, for example, 10 ^8.5 Ω. That is, 10 in the roller state
^{5.5 Ω~10 8.5 Ω} constitute a supply roller 42 with a silicon resin foam showing an electrical resistance value in the range of, since the charge amount of toner 40 is controlled such that the charge amount of the proper range 72 is there. As a result, 10 ⁴
As in the case where the supply roller 42 is formed of a urethane foam having an electric resistance value of not more than Ω, the charge amount of the toner 40 becomes smaller than the appropriate range 72 and image failure does not occur. Partially charged toner 40
Is charged to a charge amount within the appropriate range 72, and a high-quality image can be formed.

[0022]

According to the present invention, the following effects can be obtained by employing the above-described configuration in the image forming apparatus.
First, by using a silicone resin foam as a constituent member of the supply roller, the electric resistance value of the supply roller can be made high, and a urethane foam having a low electric resistance value can be obtained. As in the case where the supply roller is configured, the charge amount of the toner does not become smaller than the appropriate range, and the toner charged at the portion of the supply roller is charged to the charge amount within the appropriate range. As a result, a high-quality image could be formed.

Further, the electric resistance value of the supply roller of the silicone resin foam is set to 10 ^5.5 Ω to 10 ^5.5 Ω.
By setting the range to ^8.5 Ω, an appropriate charge amount can be given to the toner charged at the supply roller portion made of the silicone resin foam, and a high-quality image can be formed.

Further, by configuring the toner as a non-magnetic single component, the charge amount of the toner can be controlled by the electric resistance value of the supply roller, and the electric resistance value of the supply roller can be reduced. By setting the value within a certain range, an appropriate charge amount could be given to the toner to form a high-quality image.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing the inside of an image forming apparatus of the present invention.

FIG. 2 is a side sectional view showing a developing unit and a drum unit.

FIG. 3 is a diagram illustrating a relationship between an electric resistance value of a supply roller and a charge amount of toner.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photosensitive drum 4 developing unit 8 image forming apparatus 9 process unit 10 drum unit 40 toner 42 supply roller 43 developing roller 72 appropriate range (of charge amount) 73 lower limit 74 upper limit

Claims (3)

[Claims] An image is provided with a developing unit of a type in which a supply roller is provided between a toner hopper for storing toner and a developing roller, and the supply roller and the developing roller are rotated in the same direction to charge the toner. An image forming apparatus, wherein a silicon resin foam is used as a constituent member of the supply roller. 2. The image according to claim 1, wherein said silicone resin foam is a silicone resin foam having an electric resistance value in a range of 10 ^5.5 Ω to 10 ^8.5 Ω in a roller state. Forming equipment. 3. The image forming apparatus according to claim 1, wherein the toner is formed as a non-magnetic single component.