JPH11338256A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form an excellent image by reducing frictional resistance between a developing roller and a photoreceptor drum, and reducing the leakage between the developing roller and a toner layer thickness controlling member. SOLUTION: This developing device is allowed to hold the developing roller 3 in contact with the photoreceptor drum 2, to let the toner 7 being carried by the roller 3 stuck on the electrostatic latent image carried by the photoreceptor drum 2, and to develop the same. The toner layer non-forming area on the developing roller 3 is held in non-contact with the photoreceptor drum 2 and the toner layer thickness controlling member 10. An outside diameter of the toner layer non-forming area is made smaller than the outside diameter of the toner layer forming area and held in non-contact or approximately non-contact therewith. A step being larger than a deformation quantity on the developing roller 3 as a result of contact with the photoreceptor drum 2 is disposed between the toner layer non-forming area and the toner layer forming area. On the toner layer non-forming area, the tapered part gradually becoming smaller from the center part toward the end part is disposed. The toner layer thickness controlling member 10 is provided with the notched part or the bent part. The toner sealing member is disposed in the toner hopper 6 for preventing the toner leakage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device for use in an electrophotographic apparatus, and more particularly, to a developing device carrying a one-component toner, which is brought into contact with a photosensitive drum carrying an electrostatic latent image to form an electrostatic latent image. The present invention relates to a developing device that develops with toner. In addition, the present invention particularly relates to a developing device including a toner layer thickness regulating member that regulates a toner on a developing roller to a predetermined thickness and charges the toner to a predetermined charge amount.

[0002]

2. Description of the Related Art A developing device using a one-component toner without using a carrier has a relatively simple structure, can be inexpensively reduced in size, and has advantages in cost and maintenance. In particular, when no magnetic toner is used, since a magnet roller is not used, an inexpensive device that is small and can be developed clearly can be realized.
In a developing device using a non-magnetic one-component toner, a photosensitive drum for carrying an electrostatic latent image and a developing roller for carrying toner are arranged to face each other in a non-contact state, and an alternating electric field is applied therebetween to reciprocate the toner. A non-contact type developing device that flies and develops, and a contact type developing device that opposes a developing roller and a photosensitive drum made of a conductive elastic body in a contact state and applies a voltage to the developing roller to perform development. They are roughly divided into Non-contact type devices mainly require a developing bias voltage in which an AC voltage is superimposed on a DC voltage, which complicates the power supply and increases the withstand voltage.
A simple DC developing bias voltage power supply is sufficient.

In the case of a contact type developing device, the contact nip between the developing roller having appropriate elasticity used and the photosensitive drum, that is, the width of contact between the developing roller and the photosensitive drum in the rotational direction is determined by the image quality of the image developed and formed. Has a large effect on Therefore, the contact nip is preferably constant.

Further, the toner carried on the developing roller needs to be charged to a predetermined film thickness and a predetermined charge amount.

[0005]

The toner layer on the developing roller is formed at least for the effective image forming width in the axial direction of the developing roller, but is not necessarily formed over the entire area in the axial direction. This is to make the toner layer thickness uniform on the developing roller and to prevent toner from flowing out from both ends of the developing roller. The developing roller is formed of the same material and the same outer diameter in both the toner layer forming region and the toner layer non-forming region. In a developing device of the related art in which such a developing roller is brought into contact with the photosensitive drum with a relative rotational speed difference to develop an electrostatic latent image into a visible image, a toner layer of the developing roller is not formed. The frictional resistance between the area and the photosensitive drum becomes excessive, and the load torque of the photosensitive drum and the developing roller increases and fluctuates. by this,
The rotation of the photosensitive drum and developing roller becomes unstable,
The contact nip fluctuates, and exposure deviation in an exposure part, uneven development in a development part, transfer deviation in a transfer part, and the like occur, so that the quality of an image to be formed deteriorates. In particular, image unevenness occurs in the transfer paper transport direction, which is the sub-scanning direction.

FIG. 14A is a view showing the configuration of Japanese Patent Application Laid-Open No. 3-102369.
FIG. 14B is a perspective view showing a conventional developing device disclosed in Japanese Patent Application Laid-Open Publication No. H10-209, FIG. 14B is a plan view showing a developing roller 62 and a photosensitive drum 66 of the developing device, and FIG. FIG. 3 is a plan view illustrating an end of a developing roller 62. The developing device includes a developing container 61 having an opening 65 opposed to a photosensitive drum 66, and a developing roller 62 rotatably provided inside the developing container 61 and having a part of a peripheral surface protruding from the opening 65. And a toner seal member 63 for sealing a gap between the developing roller 62 and the edge of the opening 65 at both ends of the opening 65. Tapered portions 64 are provided at both ends of the developing roller 62, and the toner seal member 63 is attached to the developing container 6.
By providing the developing roller 62 along the tapered portion 64 of the developing roller 62 from the outside, the occurrence of toner accumulation is prevented. Although a slight gap B is generated between the photosensitive drum 66 and the developing roller 62, the toner seal member 63 is formed in a portion of the toner seal member 63 which does not contact the photosensitive drum 66.
End portion 63a floats from the developing roller 62,
The occurrence of toner accumulation is prevented.

When the developing roller 62 is used, the tapered portion 64 of the developing roller 62 does not always coincide with the toner layer non-formed area. Therefore, the non-toner layer forming area of the developing roller 62 and the photosensitive drum 66 come into contact with each other, the rubbing resistance becomes excessive, and the load torque increases or fluctuates, so that the image quality may be deteriorated. Further, since the toner seal member 63 is provided outside the developing container 61, the size of the apparatus is increased.

Further, for example, Japanese Patent Application Laid-Open No. Hei 7-139541 discloses a technique for forming a tapered shape at both ends of a rubber roller used as a developing roller to obtain excellent contact with other rollers. ing. Even when the roller of this technique is used, since the tapered portion of the developing roller does not always coincide with the toner layer non-formed area, the same problem as described above may occur.

On the other hand, regarding the toner layer thickness regulating member, for example, Japanese Patent Publication No. 63-16736 and Japanese Patent Publication No.
Japanese Patent No. 3152 discloses a developing device provided with an elastic regulating plate and a plate-shaped flexible frictional charging member. Japanese Patent Application Laid-Open No. 62-182780 discloses a toner layer thickness regulating member integrally comprising a thin metal plate having a spring property and a soft elastic body disposed between the thin metal plate and a developing roller. Is disclosed.

As described in JP-B-62-31346, generally, the toner is not carried over the entire area of the developing roller in the axial direction. Only carried for a minute,
It is not carried near both ends.

On the other hand, if attention is paid to the developing roller of the prior art, the same material and the same outer diameter are used for the entire area where toner adheres and the area where toner does not adhere. Therefore, a predetermined amount of charge cannot be given to the toner due to a bias voltage leak applied to the conductive toner layer thickness regulating member, or an excessive current flows to the developing roller, and the developing roller generates heat. When the developing roller generates heat, the heat deteriorates the developing roller itself, and the toner on the developing roller is condensed and fused. Further, when the toner is fused to the toner layer thickness regulating member, there is a large problem that the toner layer on the developing roller is disturbed.

In response to such inconvenience, Japanese Patent Publication No.
In JP-A-2-31346, the volume resistivity and the hardness near both ends of the developing roller where the toner does not adhere are made higher than those at the center where the toner adheres to prevent the occurrence of excessive current. However, such a method requires complicated processing steps.

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the frictional resistance between a developing roller and a photoreceptor drum, reduce the load torque on these rollers, eliminate fluctuations, and perform development for high quality image formation. It is to provide a device. Another object of the present invention is to prevent the occurrence of leakage between the developing roller and the toner layer thickness regulating member, stably form the toner layer on the developing roller, and form a high quality image. An object of the present invention is to provide a developing device capable of developing.

[0014]

According to the present invention, there is provided a photosensitive drum rotatable to carry an electrostatic latent image, and a conductive and elastic developing roller rotatable to carry one-component toner. A developing roller that contacts a photosensitive drum with a rotational speed difference relative to the photosensitive drum to develop an electrostatic latent image into a visible image; Is a non-contact device.

According to the present invention, by rotating the developing roller and the photosensitive drum and making contact with each other, the toner carried on the developing roller is adhered along the electrostatic latent image carried on the photosensitive drum. And develop. In order to make the thickness of the toner layer uniform and prevent the toner from flowing out, a toner layer non-formation area is provided on the developing roller. Since the toner layer non-forming area is configured to be in non-contact with the photosensitive drum, the frictional resistance is reduced, the load torque on the photosensitive drum and the developing roller can be reduced, and the fluctuation can be eliminated. As a result, the rotation stability of the photosensitive drum and the developing roller is improved, and development for forming a high-quality image becomes possible.
In particular, occurrence of image unevenness in the sub-scanning direction can be suppressed.

According to another aspect of the present invention, there is provided a photosensitive drum rotatably carrying an electrostatic latent image, and a conductive and elastic developing roller rotatable carrying one-component toner. In a developing device in which a rotational speed difference is provided relative to the body drum to develop an electrostatic latent image to develop a visible image, an outer diameter of the toner layer non-formed area of the developing roller is equal to a toner layer formed area. A developing device characterized by being smaller than the outer diameter.

According to the present invention, by limiting the outer diameter as described above, even if the area where the toner layer is not formed and the photosensitive drum do not completely come into non-contact with each other, the area where the toner layer is not formed and the area where the toner Since the contact with the body drum is weakened, the rubbing resistance is reduced, the load torque on the photosensitive drum and the developing roller is reduced, and fluctuations can be eliminated, enabling development for high-quality image formation. Becomes

The present invention is further characterized in that the surface of the developing roller is exposed in the non-toner layer forming area, and the surface directly faces the photosensitive drum.

According to the present invention, the developing roller in the toner layer non-formation area is exposed, and no special member or the like is formed at all, and directly faces the photosensitive drum. Therefore, the toner layer non-forming region and the photosensitive drum can be easily configured to be in non-contact or almost non-contact.

Further, the present invention is characterized in that a step is provided between the toner layer forming area and the toner layer non-forming area of the developing roller, the step being greater than the contact depth of the developing roller with the photosensitive drum.

According to the present invention, the area where the toner layer is not formed and the photosensitive drum can be brought into non-contact or almost non-contact with each other by the above-mentioned steps, so that the rubbing resistance is reduced, and the photosensitive drum and the developing roller are reduced. In addition, the load torque applied to the substrate can be reduced and the fluctuation can be eliminated, thereby enabling development for forming a high-quality image.

Further, according to the present invention, the step is larger than an amount of deformation of the developing roller due to the contact of the developing roller with the photosensitive drum.

According to the present invention, by providing a step that is larger than the amount of deformation of the developing roller due to contact with the photosensitive drum, the toner layer non-forming region and the photosensitive drum are surely kept in non-contact or almost non-contact. Can be configured.

Further, the present invention is characterized in that the outer diameter of the developing roller in the non-toner layer forming area continuously decreases from the center to the end.

According to the present invention, the toner layer non-formation area of the developing roller is formed in a tapered shape which is continuously inclined from the center to the end. The non-contact or almost non-contact with the drum can be configured, the frictional resistance can be reduced, the load torque on the photoreceptor drum and the developing roller can be reduced, and the fluctuation can be eliminated. Development becomes possible. The continuously inclined tapered portion may be inclined linearly or curvedly.

The present invention also includes a toner seal member which is configured to contain a foamed elastic material and which comes into contact with the toner layer non-forming area of the developing roller from the side opposite to the photosensitive drum to prevent the toner layer from flowing out. It is characterized by.

According to the present invention, the outflow of toner can be prevented by the seal member. Since such a sealing member includes a foamed elastic material, it can follow a change in the shape of both ends of the developing roller and maintain high sealing properties. Further, since the device is provided on the side opposite to the photosensitive drum, it is possible to prevent the apparatus from being enlarged.

According to the present invention, there is provided a photosensitive drum rotatable to carry an electrostatic latent image, a conductive and elastic developing roller rotatable to carry one-component toner, and a toner layer forming of the developing roller. A toner layer thickness regulating member having a width larger than the region width and having conductivity and elasticity, and pressing an abdominal portion near a free end of the toner layer thickness regulating member against the developing roller to press the developing roller. By applying a bias voltage to the toner layer thickness regulating member, the toner layer on the developing roller is charged to a predetermined amount of charge and formed to a predetermined thickness, and a toner layer having a predetermined amount of charge and a predetermined thickness is formed. A developing device that develops an electrostatic latent image into a visible image by bringing the developing roller into contact with the photosensitive drum at a speed difference relative to the developing roller, the toner layer non-forming region of the developing roller A developing apparatus is characterized in that the non-contact with the toner layer thickness regulating member.

According to the present invention, by rotating the developing roller and the photosensitive drum and making contact with each other, the toner carried on the developing roller adheres along the electrostatic latent image carried on the photosensitive drum. And develop. In order to make the thickness of the toner layer uniform and prevent the toner from flowing out, a toner layer non-formation area is provided on the developing roller. Since the toner layer non-forming region is configured to be in non-contact with the toner layer thickness regulating member, it is possible to prevent the bias voltage applied to the toner layer thickness regulating member from leaking to the developing roller, thereby preventing heat generation of the developing roller. be able to. Therefore, deterioration of the developing roller due to heat,
Aggregation and fusion of the toner on the developing roller and fusion of the toner to the toner layer thickness regulating member can be prevented, and the toner layer can be stably formed on the developing roller. This enables development for high-quality image formation.

The present invention is also directed to a photosensitive drum rotatable to carry an electrostatic latent image, a conductive and elastic developing roller rotatable to carry one-component toner, and a toner layer forming of the developing roller. A toner layer thickness regulating member having a width larger than the width of the region and having conductivity and elasticity, wherein the abdomen near the free end of the toner layer thickness regulating member is brought into contact with the developing roller to form the developing roller. By pressing and applying a bias voltage to the toner layer thickness regulating member,
The toner layer on the developing roller is charged to a predetermined charge amount and formed to a predetermined thickness, and the developing roller having the toner layer of the predetermined charge amount and the predetermined film thickness is provided with a speed difference relative to the photosensitive drum. A developing device that develops the electrostatic latent image into a visible image by contacting the developing roller, wherein the outer diameter of the toner layer non-forming region of the developing roller is smaller than the outer diameter of the toner layer forming region. Is a developing device.

According to the present invention, by limiting the outer diameter as described above, even if the toner layer non-forming region of the developing roller and the toner layer thickness regulating member are not completely in non-contact,
Since the contact between the toner layer non-forming region and the toner layer thickness regulating member becomes weak, it is possible to prevent the bias voltage of the toner layer thickness regulating member from leaking to the developing roller. Therefore, it is possible to prevent deterioration of the developing roller due to heat generated by the developing roller, aggregation and fusion of the toner on the developing roller, and fusion of the toner to the toner layer thickness regulating member, and stabilize the toner layer on the developing roller. , And can be developed for high-quality image formation.

Further, the present invention is characterized in that a step is provided between the toner layer forming region and the toner layer non-forming region of the developing roller.

According to the present invention, the toner layer non-forming region of the developing roller and the toner layer thickness regulating member can be configured to be in non-contact or almost non-contact by the above-described step, and the bias voltage of the toner layer thickness regulating member can be reduced. To the developing roller can be prevented.

The present invention is also characterized in that the outer diameter of the developing roller in the non-toner layer non-forming area continuously decreases from the center to the end.

According to the present invention, the toner layer non-forming region of the developing roller is formed in a tapered shape that is continuously inclined from the center to the end. The region and the toner layer thickness regulating member can be configured to be in non-contact or almost non-contact, and leakage of the bias voltage of the toner layer thickness regulating member to the developing roller can be prevented. The continuously inclined tapered portion may be inclined linearly or curvedly.

Also, in the present invention, the toner layer thickness regulating member has a bent portion, and the bent portion is provided at a free front end portion of the developing roller facing the toner layer non-formation area. It is characterized by being bent in the opposite direction.

According to the present invention, even if the above-described bent portion is provided in the toner layer thickness regulating member, the toner layer non-formation region of the developing roller and the toner layer thickness regulating member do not come into contact with each other or almost do not contact each other. And the leakage of the bias voltage of the toner layer thickness regulating member to the developing roller can be prevented.

The present invention is also characterized in that the toner layer thickness regulating member has a notch, and the notch is provided at a free front end of the developing roller opposed to the toner layer non-formation area. And

According to the present invention, by providing the above-described notch portion in the toner layer thickness regulating member instead of the bent portion, the toner layer non-forming region of the developing roller and the toner layer thickness regulating member can be formed. Can be configured in a non-contact or almost non-contact manner, and leakage of the bias voltage of the toner layer thickness regulating member to the developing roller can be prevented.

[0040]

FIG. 1 is a sectional view showing a developing device 1a according to an embodiment of the present invention. The developing device 1a is used in an electrophotographic apparatus, and the overall configuration of the electrophotographic apparatus can be realized by a known technique, and includes steps such as charging, exposure, development, transfer, cleaning, fixing, and static elimination. .

A one-component toner 7 is accommodated in a toner hopper 6 opened toward the developing area 5 where the photosensitive drum 2 and the developing roller 3 are in contact with each other. The toner 7 is agitated by an agitator / supply member 14 such as an agitator or a screw, and is supplied near the toner supply roller 8.

The toner supply roller 8 rotating in the direction S2
Is in contact with, for example, pressed, the developing roller 3 rotating in the same direction S3 as the direction S2. Further, the toner supply roller 8
Is supplied with a predetermined bias voltage from the power supply 9. The voltage is set so as to electrically move the toner 7 toward the developing roller 3. For example, when a negative polarity toner is used, a voltage having a higher potential is applied to the negative electrode side. The toner 7 is effectively supplied to the developing roller 3 by injecting electric charge due to a potential difference between the developing roller 3 and the toner supply roller 8 and applying a charge by frictional charging at a contact portion between the two rollers 3, 8. The developing roller 3 and the toner supply roller 8 are configured in substantially the same manner, and the adjustment of the electric resistance is performed using the same adjustment material. Further, it is preferable that the toner supply roller 8 is realized by a foam, and a roller using a larger amount of a foaming agent than the developing roller 3 is used.

A toner layer 15 is formed by the toner 7 attached to the developing roller 3, and the toner 7 is applied to a toner layer thickness regulating member 10, which is a so-called blade, provided on the upstream side of the developing area 5 in the rotation direction of the developing roller. It is transported to the vicinity. For example, the toner layer thickness regulating member 10 is made of a plate-like metal material, and one end thereof or the surface near the development roller on the developing roller side is pressed against the developing roller 3, and the other end is the upper part of the toner hopper 6. 6a. Further, a predetermined bias voltage is applied from a power supply 11 to the toner layer thickness regulating member 10. By these, the developing roller 3
The toner layer 15 formed thereon is charged to a predetermined charge amount and formed to a predetermined thickness. For example, 1
It is formed in a thickness of 0 μm to 20 μm. The toner 7 attached to the developing roller 3 is conveyed to the developing area 5 to visualize the electrostatic latent image on the surface of the photosensitive drum 2.

The photosensitive drum 2 is provided so as to be rotatable in a direction S1 opposite to the directions S2 and S3. Photoconductor drum 2
Is uniformly charged to a predetermined charge amount by a corona charger or a contact roller charger (not shown), and a predetermined electrostatic latent image potential is formed by an exposure unit (not shown). Carry.
The photoconductor drum 2 includes a conductive base made of metal or resin,
It comprises an undercoat layer formed on the surface thereof and a photosensitive layer formed thereon. The photosensitive layer is composed of a relatively thin carrier generation layer (CGL) formed on the undercoat layer and a relatively thin carrier transfer layer (CTL) mainly composed of polycarbonate formed on the outermost layer. Exposure generates carriers in the carrier generation layer, and the charges on the photosensitive drum 2 are canceled by the carriers to form the electrostatic latent image potential.

The electrostatic latent image carried on the photosensitive drum 2 is
As the drum 2 rotates, it is transported to a developing area 5 that comes into contact with the developing roller 3. The developing roller 3 is pressed against the photosensitive drum 2, and the toner carried on the developing roller 3 moves and adheres according to the electrostatic latent image on the photosensitive drum 2, whereby the electrostatic latent image is visualized and developed. . A predetermined bias voltage is applied to the developing roller 3 from a power supply 4.

After the development, the toner adhered to the photosensitive drum 2 is conveyed to a predetermined transfer area. A transfer material such as paper is supplied to the transfer area by a paper supply unit (not shown), and comes into contact with the toner image on the photosensitive drum 2 in synchronization with the transfer material. The transfer unit (not shown) provided in the transfer area includes a charger type having a high-voltage power supply and a contact roller type, and applies a voltage having a polarity on the side where the toner 7 is transferred to the photosensitive drum 2. As a result, the toner 7 moves to the transfer material,
The toner image is transferred. After the transfer material is separated from the photosensitive drum 2, the toner on the transfer material is fixed by a fixing unit (not shown). For example, it is fixed by heat melting. Then, the paper is discharged outside the apparatus. Further, after the surface of the photosensitive drum 2 after the transfer is cleaned by a cleaning unit (not shown), the charge remaining on the surface is removed by a discharging unit (not shown), and the surface is electrically initialized. The static elimination means includes an optical static elimination lamp and a contact static eliminator.

The toner 7 remaining on the developing roller 3 having passed through the developing area 5 is conveyed to the vicinity of a charge removing sheet 12 provided on the downstream side of the developing area 5 in the rotation direction of the developing roller.
The charge removing sheet body 12 is fixed to, for example, a lower portion 6 b of the toner hopper 6 so as to be in pressure contact with the developing roller 3.
A predetermined bias voltage is applied to the charge removing sheet body 12 from the power supply 13. The charge of the toner 7 is removed by the charge removing sheet member 12. Further, the developing roller 3 is in pressure contact with the toner supply roller 8 whose moving direction is opposite at the point of contact with the developing roller 3.
Is separated from the developing roller 3, collected in the toner hopper 6 and reused. Through such steps, an image is repeatedly formed.

Next, detailed components and examples of setting conditions of the developing device 1a for performing contact reversal development will be described.
The photosensitive drum 2 has a conductive base as described above,
The substrate is grounded. With respect to the photosensitive drum 2, the surface potential is -550 V, the diameter Da is 65 mm, and the rotation peripheral speed V
a is 190 mm / s.

The developing roller 3 is realized by forming an elastic member having a volume resistivity of about 10 ⁶ Ωcm and a JIS A hardness of 60 to 70 degrees on a conductive shaft by adding an electric resistance adjusting agent. Is done. With respect to the developing roller 3, the diameter Db
Is 34 mm, and the rotational peripheral speed Vb is 285 mm / s. The diameter Ds of the shaft is 18 mm.
0 V is applied. The contact width between the photosensitive drum 2 and the developing roller 3 in the roller rotation direction, that is, the so-called nip is 2 mm. The developing roller contacts the photosensitive drum 2 via the toner layer 15 at a contact depth of 0.1 mm to 0.3 mm.

The conductive shaft of the developing roller 3 is realized by metal such as stainless steel or conductive resin. The elastic member formed on the shaft is realized by conductive urethane rubber or the like. Carbon black or the like can be used as the electric resistance adjusting agent.

The toner supply roller 8 has a volume resistivity of about 1
In 0 ⁵ [Omega] cm, the cell density due to foaming is a conductive urethane foam about 3 / mm, for example, realized by forming on the shaft such as stainless steel or a conductive resin having a diameter of 8 mm. The diameter of the toner supply roller 8 is 20 mm, and the rotational peripheral speed Vc is 170 mm / s. On the shaft,
-450 V or -550 as the voltage E2 from the power supply 9
V is applied. The toner supply roller 8 is 0.5 mm to
It contacts the developing roller 3 with a contact depth of 1 mm. Toner 7
Is preliminarily negatively charged by the supply roller 8, for example.

The toner layer thickness regulating member 10 has a thickness of 0.1
is a conductive plate member made of stainless steel (SUS304), phosphor bronze, aluminum, conductive resin, or the like having a thickness of 0.2 mm to 0.2 mm, and a cantilever plate beam having a free end upstream in the rotation direction of the developing roller 3. About 10 to 50 gf / cm, especially 15 to 50 gf / cm with respect to the developing roller 3.
The toner hopper 6 is brought into contact with a line pressure of 30 gf / cm.
And is supported by a blade holder 18 fixed to the upper part 6a. The power supply 1 is attached to the toner layer thickness regulating member 10.
1 to -450 V or -550 V is applied as the voltage E3. Due to the toner layer thickness regulating member 10, the amount of toner adhered to the developing roller 3 is about 0.6 mg / cm ² to
1.0 mg / cm ² , especially 0.6 mg / cm ^{2 to} 0.8 m
g / cm ² , the toner charge amount is about −10 μC / g to −1
Regulated to 5 μC / g.

The charge removing sheet member 12 is a seal member for preventing the leakage of the toner 7 from below the developing roller 3, and the toner 7 remaining on the developing roller 3 after development.
And is realized by a conductive film having a thickness of about 0.3 mm, for example. The static elimination sheet body 12
The potential of the developing roller 3 is adjusted to about +50 V or more by the same potential as that of the developing roller 3 or by a voltage from the power supply 13. The surface of the charge removing sheet body 12 is
Contacted. The sheet member 12 may be realized by a conductive member such as a film on which aluminum is deposited. In the case where it is not necessary to remove the toner charge and only to prevent toner leakage, it may be realized by a Mylar film. In this case, the power supply 13 is unnecessary.

Note that a voltage drop Vd = ir is generated inside the developing roller 3 due to the effective roller resistance r of the developing roller 3 and the developing current i flowing through the developing operation. By setting the effective roller resistance r to an appropriate value, the effective developing bias acting on the surface of the developing roller 3 is adjusted so that a binary developing characteristic having a steep inclination and a gradation characteristic having a gentle inclination are high. Development characteristics can be obtained.

The conductive shaft of the developing roller 3 is realized by a metal such as stainless steel or a resin having a relatively low electric resistance. The developing roller 3 is realized by forming a single conductive rubber layer on the shaft. As the elastic member formed on the shaft, a resin material having a relative dielectric constant of about 10 is used, and EPDM, urethane, nylon, silicone, P
VDF (polyvinylidene fluoride), natural rubber, nitrile butadiene rubber, chloroprene rubber, styrene butadiene rubber, butadiene rubber, ethylene propylene rubber, isoprene rubber, polynorbornene rubber, and the like can be used. In addition, as an electric resistance adjusting agent,
One based on a dispersion-type resistance-adjusting resin dispersed and mixed using one or more of conductive fine particles, carbon black and TiO ₂ , or an ionic conductive substance such as sodium perchlorate or perchloric acid; A material based on an electric resistance adjusting resin using one or more of inorganic ionic conductive materials such as calcium and sodium chloride can be used. When a foaming agent is used to form the elastic member, a silicone-based surfactant such as a polydialkylsiloxane or a polysiloxane-polyalkylene oxide block copolymer is optimal.

For example, a predetermined amount of a resin for an elastic member and an electric resistance adjusting agent are mixed, stirred by a mixing and injection machine, injected into an extrusion die, and heated at 80 to 120 ° C. for about 5 to 100 minutes. An elastic member is formed on the shaft by the hot blow foam molding to be injected. Further, the elastic member may be formed on the shaft by injection molding. In this case, the shaft is arranged at the center of a predetermined mold, the resin material for the elastic member is poured, and heating is performed for about 100 to 160 minutes. Sulphate.

The carbon black used as the electric resistance adjuster has a nitrogen adsorption specific surface area of 20 m ² / g or more.
0m ² / g or less, DBP oil absorption is 60ml / 100g
Those having a size of at least 120 ml / 100 g are preferred. For example, ISAF, HAF, GPF and SRF grade carbon blacks are preferred.

As the polyurethane used as the resin material for the elastic member, a flexible polyurethane foam or polyurethane elastomer is preferable, but EPDM, urethane, silicon, nitrile butadiene rubber, chloroprene rubber, butadiene rubber and the like can also be used. For example, it is preferable to mix 0.5 to 15 parts by weight, and in some cases, about 70 parts by weight of carbon black to 100 parts by weight of polyurethane.

The EPDM used as the resin material for the elastic member is a mixture of ethylene, propylene and a third component such as dichloropentadiene, ethylidene norbornene and 5-hexadiene. The propylene content is preferably 5 to 95 parts by weight, and the third component content is preferably 0 to 50 parts by weight in terms of iodine value. For example, 10
Mixing 1 to 30 parts by weight of carbon black with 0 parts by weight of EPDM is preferred from the viewpoint of dispersibility. Also, an ionic conductive substance such as sodium perchlorate and tetraethylammonium chloride, and a surfactant such as dimethylpolysiloxane and polyoxyethylene lauryl ether as an electric resistance adjuster are added to the EPDM together with carbon black. It is preferable to add 10 to 10 parts by weight for improving the uniformity of dispersion.

Examples of the ionic conductive substance used as the electric resistance adjusting agent include inorganic ionic conductive substances such as sodium perchlorate, calcium perchlorate and sodium chloride;
And one or more of organic ion conductive substances such as modified aliphatic dimethylethylammonium ethosulfate, stearylammonium acetate, laurylammonium acetate, octadecyltrimethylammonium perchlorate, and the like.

The electric resistance of the developing roller 3 is 1 × 10 ⁵ Ω to
The range of 1 × 10 ⁶ Ω is preferable, and the volume resistivity is 3.75.
The range of × 10 ⁵ Ωcm to 7.5 × 10 ⁶ Ωcm is preferable, the Asker C hardness under a 1 kgf load according to JIS K 6301 is preferably 68 degrees, and the surface roughness Rz of JIS B 0601 is 1 μm to 6 μm, particularly 3 μm to 6 μm is preferred. The rubber hardness of the developing roller 3 of this embodiment is J
The IS A hardness was about 60 to 70 degrees. The hardness of the elastic member can be selected depending on the amount of the vulcanizing agent or filler added, and the hardness can be reduced by increasing the amount, but the surface resistance decreases due to the adhesion of the low molecular weight vulcanizing agent or filler to the surface of the elastic member. I do. The method for measuring the electric resistance will be described later.

The polyurethane foam used for the toner supply roller 8 has 5 parts by weight based on 100 parts by weight of the foam.
Carbon black is mixed in an amount of not less than 15 parts by weight, and in some cases, about 70 parts by weight. The same polyurethane foam and carbon black as those used for the developing roller 3 can be used. After mixing the polyurethane foam and carbon black with a whisk to stir and foam, a sponge body is formed around the shaft by heat blow molding to form the toner supply roller 8.

The sponge body formed around the shaft is
The volume resistivity is preferably 10 ⁵ Ωcm or less.
When the thickness is 6 mm, the cell density due to foaming is 80 cells / inch to 140 cells / inch, particularly 80 cells / inch.
h ~ 100 / inch, sponge density 0.1g /
cm ³ , Asker F hardness is 68 degrees or 60 degrees,
It is preferable that Asker C hardness is 30 degrees and JIS K 6401 hardness is 24.2 kgf. In addition, thickness 6m
m, the resistance value of the toner supply roller 8 is the applied voltage 2
When the load on both ends of the shaft is 100 gf at 00 V, about 10 ⁴ Ω is suitable. As such a sponge body,
EPT urethane conductive sponge manufactured by Bridgestone Corporation can be used.

The static elimination sheet 12 is made of, for example, a resin mixture of PC (polycarbonate) and PBT (polybutylene terephthalate), nylon, PET (polyethylene terephthalate), PTFE (polytetrafluoroethylene) -containing resin, or polyurethane. It is made of a material in which one is used as a base material and an electric resistance adjuster such as carbon black is appropriately mixed. Resin material for elastic member 10
10 parts by weight or more of carbon black is mixed with 0 parts by weight. The same carbon black as that used for the developing roller 3 can be used.

The static elimination sheet body 12 is specifically made of PC + P
Extruded film of BT, Bayf manufactured by Bayer
olAS-A film (trade name) can be used. According to the film, the toner slips sufficiently, so that the toner 7 does not accumulate on the upstream side of the charge removing sheet member 12 in the rotation direction of the developing roller, so that the developing operation is not hindered and the toner 7 is efficiently removed. The toner can be collected in the toner popper 6. The film has a thickness of 0.3 mm ± 0.1 mm and an electric resistance of 10 ³ Ω to 10 ⁶ Ω. Such a film is affixed and fixed to the lower portion 6b of the toner hopper 6, for example, by an adhesive tape No. 500 manufactured by Nitto Denko Corporation.

If the effective width Lt of the toner layer 15 formed on the developing roller 3 in the axial direction and the effective width Ld of the charge removing sheet body 12 of the residual toner after the developing process are set as Ld ≧ Lt, the charge of the residual toner is obtained. Is uniformly removed, and the removal and supply of the toner by the toner supply roller 8 can be performed uniformly. When it is desired to extend the life of the developing device, the both ends of the static elimination sheet 12 fixed with an adhesive tape are sandwiched, or a conductive adhesive or a hot-melt adhesive is used. It is preferable to use a device having a small change in the temperature.

As the toner 7, a toner generally called a high-resistance toner can be used. The volume resistivity in the form of a pellet is preferably about 10 ¹⁰ Ωcm. For example, about 4 to 10 parts by weight of carbon black is kneaded with 80 to 90 parts by weight of a base resin such as a polyester resin or a styrene-acryl copolymer, and 0 to 5 parts by weight.
A charge control agent (CCA) or a small amount of a vulcanization control agent is appropriately mixed in parts by weight, and silica or the like is added as an external additive after the pulverization step.
It is preferable to add about 2 to 2 parts by weight. The volume resistivity was measured by a method in which two members obtained by curing a toner in a pellet shape were sandwiched between electrodes, and a current value was measured by applying a current.
The applied voltage depends on the thickness, but about 1 mm
00V or less is preferable. As the toner 7, AR-ST12-B manufactured by Sharp Corporation can be specifically used. This toner is an electronic copier AR manufactured by Sharp Corporation
5130 toner.

FIG. 2 is a plan view showing a specific example of the developing roller 3. In the developing roller 3a shown in FIG. 2A and the developing roller 3b shown in FIG.
Wt indicates the width of the toner layer forming area 21 in the rotation axis direction, and Ws indicates the width of the toner layer non-forming area 22 in the rotation axis direction. For example, Wt is 300 mm and Ws is 15 mm
It is.

In order to make the toner layer non-forming region 22 of the developing roller and the photosensitive drum 2 non-contact or almost non-contact, the developing roller 3a, 3b
Is made smaller than the outer diameter of the toner layer forming area 21. Further, the surfaces of the developing rollers 3a and 3b are exposed in the toner layer non-forming area 22, and the surfaces are directly opposed to the photosensitive drum 2.

Specifically, in the developing roller 3a of FIG. 2A, a step is provided between the toner layer forming area 21 and the toner layer non-forming area 22. The step has a predetermined constant height δ1 which is equal to or greater than the contact depth δ of the developing roller 3a with the photosensitive drum 2. For example, δ is set to 100 μm and δ1 is set to 200 μm.

FIG. 3 shows the developing roller 3a and the photosensitive drum 2
It is a top view which expands and shows. The contact depth δ is regulated by a contact depth setting roller 16 formed of a material having excellent rigidity, for example, polyacetal resin, with little influence of distortion or deformation and negligible influence. The roller 16
Are provided at both ends thereof coaxially with the developing roller 3a. δ
= 100 μm and δ1 = 200 μm, the photosensitive drum 2 and the developing roller 3a have a gap of δ1−δ = 100 μm in the toner layer non-forming region 22. Accordingly, the frictional resistance at both ends of the developing roller 3 due to the relative speed difference between the photosensitive drum 2 and the developing roller 3a is reduced, the load torque on the photosensitive drum 2 and the developing roller 3a is reduced, and the fluctuation is small. That is, a high-quality image without image unevenness in the sub-scanning direction can be formed.

It is preferable that the step is set to a value larger than the amount of deformation of the developing roller 3a due to the contact of the developing roller 3a with the photosensitive drum 2. For this purpose, specifically, the JIS A hardness of the developing roller 3a is set to 50 to 7
When the angle is set to 0 degrees, it is preferable that the pressing force of the developing roller 3a on the photosensitive drum 2 be 2 kgf or less. As a result, the rotation stability of the photosensitive drum 2 and the developing roller 3a can be improved, and a higher quality image without image unevenness in the sub-scanning direction can be formed.

In order to set the step to a value larger than the deformation amount of the developing roller 3a due to the contact of the developing roller 3a with the photosensitive drum 2, the JI of the developing roller 3a is set.
When the SA hardness is 50 to 70 degrees, δ1 is 50 μm
Not less than 500 μm, especially not less than 100 μm and not more than 500 μm.
It is preferable that the pressure is selected within the range of μm or less, and the pressing force of the developing roller 3 a to the photosensitive drum 2 is set to 100 gf to 2 kgf or less. Thus, the rotation stability of the photosensitive drum 2 and the developing roller 3a is further improved, and a higher quality image can be formed.

The developing roller 3b shown in FIG.
In the toner layer non-forming region 22, the outer diameter of the developing roller 3b is continuously reduced from the center to the end to form a tapered portion. The slope of the tapered section is 1 ° or more and 5 °
It is preferable to select the following range, for example, when δ is 100
μm, and the inclination height δ2 is 500 μm,
The slope is set at 1.9 °.

When the developing roller 3b and the photosensitive drum 2 come into contact with each other, there is a contact depth δ.
2, the photosensitive drum 2 does not come into contact with the photosensitive drum 2 from the boundary with the toner layer forming area 21 to a certain point. However, if it is not completely non-contact, but is almost non-contact, the contact between the developing roller 3b and the toner layer non-forming region 22 of the photosensitive drum 2 becomes weak. Therefore,
The frictional resistance at both ends of the developing roller 3b due to the relative speed difference between the photosensitive drum 2 and the developing roller 3b is reduced, and a high quality image without image unevenness in the sub-scanning direction can be formed. It should be noted that the present invention is not limited to the linearly inclined taper portion.
A tapered portion inclined in a curved manner may be provided.

FIG. 4 is an enlarged perspective view showing the developing roller 3a and the toner layer thickness regulating member 10. The toner layer thickness regulating member 10 is supported by, for example, a blade holder 18 fixed to the upper portion 6a of the toner hopper. As described above, a step δ1 of, for example, 200 μm is provided between the toner layer forming region 21 and the toner layer non-forming region 22.

Therefore, at both ends of the developing roller 3a, the developing roller 3a does not come into contact with the toner layer thickness regulating member 10, and the bias voltage applied to the toner layer thickness regulating member 10 leaks to the developing roller 3a. And the heat generation of the developing roller 3a can be prevented. Therefore, deterioration of the developing roller 3a due to heat, the developing roller 3
Thus, aggregation and fusion of the toner on the toner layer a and fusion of the toner to the toner layer thickness regulating member 10 can be prevented, and the toner layer can be stably formed on the developing roller 3a. This enables development for high-quality image formation.

The developing roller 3 shown in FIG.
In b, the non-toner layer forming region 22 is provided with, for example, a gradient of 1.9 ° as described above. Due to such a gradient, the developing roller 3b and the toner layer thickness regulating member 10 are almost in a non-contact state at both ends of the developing roller 3b, and the toner layer non-forming region and the toner layer thickness regulating member 1
0, the toner layer thickness regulating member 10
Of the bias voltage to the developing roller 3b can be prevented. Therefore, the deterioration of the developing roller 3b due to the heat generated by the developing roller 3, aggregation and fusion of the toner on the developing roller 3b, and fusion of the toner to the toner layer thickness regulating member 10 can be prevented. And a toner layer can be stably formed, and development for forming a high-quality image can be performed.

FIG. 5 shows a developing device 1b according to another embodiment of the present invention. FIG. 5A is a cross-sectional view,
FIG. 5B is a sectional perspective view. The developing device 1b is configured in substantially the same manner as the developing device 1a, but includes a toner seal member 17. The toner seal member 17 is provided inside the toner hopper 6 and
The toner hopper is elastically in contact with the toner hopper inner side of the toner layer non-forming region, and one end is fixed to the upper surface 6a of the toner hopper 6 and the other end is fixed to the lower surface 6b by adhesion. The thickness of the toner seal member 17 is constant in a free open state,
The developing roller 3 is elastically deformed along the shape of the toner layer non-formed area. The member 17 is realized by a foamed polyurethane foam having a thickness of 2 to 5 mm, for example.

FIG. 6A is a plan view showing an example in which a toner seal member 17 is provided on the developing roller 3a. FIG. 6B is a plan view showing the toner seal member 17 provided on the developing roller 3b. It is a top view which shows the example provided. By providing the toner seal member 17 in the developing device having the developing roller 3a having a step, the outflow of toner can be prevented, and the formed image can be prevented from being stained by the toner. Further, the developing roller 3b provided with a tapered portion as compared with the developing roller 3a provided with a step has a toner layer forming area 21.
And the toner layer non-forming region 22 are smoothly continuous, so that the outflow of toner can be easily and reliably prevented. Therefore, toner contamination can be further prevented.

It is preferable that the toner seal member 17 that can prevent the toner from flowing out contains a foamed elastic material. Thereby, it is possible to absorb a change in the shape of both ends of the developing roller 3 and to maintain a high sealing property. Further, since the photoconductor drum 2 is provided on the opposite side, the size of the apparatus can be prevented from increasing.

FIG. 7 is a graph showing the relationship between the contact depth δ and the amount of increase in the sliding torque. A broken line R1 shows a case where the developing roller 3a shown in FIG. 2A is used, and a solid line R2 shows a comparative example, that is, a case where a developing roller having a substantially uniform outer diameter without a step or a tapered portion is used. . Using these developing rollers, the sliding torque with the photosensitive drum 2 on the developing roller side was measured while changing the contact depth δ with the photosensitive drum 2. When the contact depth δ = 0.05 mm in the comparative example, The amount of increase in the sliding torque with respect to the contact depth δ is shown on the basis of the sliding torque of FIG.

For example, when δ = 0.1 mm, it can be understood that the sliding torque of the embodiment can be reduced by about 400 gf · cm and that of the photosensitive drum side by about 760 gf · cm compared with the comparative example. That is, by making the toner layer non-forming region of the developing roller and the photosensitive drum non-contact,
It can be seen that the rubbing resistance can be reduced and image unevenness occurring in the sub-scanning direction can be suppressed.

The sliding torque was measured using torque gauges 6BTG and 15BTG of Tonichi Seisakusho. Also,
With the photosensitive drum 2 kept still, the sliding torque on the developing roller side was measured. The developing roller used has a rubber hardness of JIS A hardness of 60 to 70 degrees. The contact depth δ measures and indicates the distance between the axes of the photosensitive drum 2 and the developing roller.

Next, a method for measuring the electric resistance of the developing roller, the amount of charged toner on the developing roller, and the amount of adhered toner will be described. 8A and 8B are diagrams showing a static electric resistance measuring device such as a toner supply roller. FIG. 8A is a front view, and FIG. 8B is a side view. The static electric resistance is such that the surface of the roller 30 is brought into contact with the electrode 33 on the base material 32, and a weight 36 of 100 g is placed on both ends of the rotating shaft 31,
A voltage of 200 V was applied from a power supply 35 connected to the rotating shaft 31, and a current was measured by an ammeter 34 connected to the electrode 33 to obtain a value. This makes it possible to measure the electric resistance value of the developing roller.

FIG. 9 is a diagram showing an apparatus for measuring the static and dynamic electric resistance of the developing roller. FIG. 9 (A) is a plan view and FIG. 9 (B) is a side view. Regarding the measurement of electric resistance, JIS K 6911 shows a method of measuring a sheet-like member having a ring electrode as a guard. However, actual development, regulation of a toner layer, toner supply, and toner charge removal after development are performed. Since a roll-shaped elastic conductive developing roller is used in the process, electric lines of force are not completely parallel.
For this reason, the actual electric resistance value is about one digit smaller than the electric resistance value measured according to JIS K 6911. In order to solve such a problem, a measuring device as shown in FIG. 9 was used.

That is, a drum electrode 41 having the same radius of curvature as the photosensitive drum is rotatably provided on the base material 40,
The roller 30 is pressed against the pressure member 42 at the same pressure as in the actual developing process. The power supply 43 connected to the rotating shaft 31 of the roller 30 can change the intensity of the applied voltage. A resistance 44 for measurement is connected to the drum electrode 41.
The potential difference between both ends is detected and amplified by the isolation amplifier 45, and an analog signal from the isolation amplifier 45 is converted into a digital signal by the AD converter 46, and is measured by the measuring computer 50.
Further, in order to check the actual behavior, the driving force of the motor 49 is transmitted to the drum electrode 41 via the coupling member 48 and the roller 47, thereby
Rotates.

When a voltage of 10 V was applied without rotating the drum electrode 41 using the roller 30 formed by heating and injection molding carbon in which polyurethane was dispersed, 1.83 × 10 3
A static electrical resistance of ⁶ Ω was measured, and during rotation, 8.02 × 10 ⁸ Ω when a voltage of 20 V was applied and 1.02 when a voltage of 40 V was applied.
A dynamic electrical resistance of 05 × 10 ⁷ Ω was measured and the dynamic electrical resistance was greater than the static electrical resistance.

The charge amount of the toner on the developing roller is obtained as follows. First, the toner layer formed on the developing roller is sucked by a nozzle provided with a toner collection filter, and the mass of the sucked toner is determined based on the difference in nozzle mass between before and after the suction. Next, a charge equivalent to the amount of the toner charge sucked is measured by an electrometer provided on the rotation shaft of the developing roller. Then, by dividing the total charge amount by the mass of the attracted toner, the charge amount (specific charge) of the toner on the developing roller is obtained.

Further, the toner adhesion amount is obtained by calculating the adhesion area of the sucked toner and dividing the suction toner weight by the area. By pressing the member having the guide groove against the developing roller and sucking the toner by the area of the guide groove, the adhesion area of the sucked toner is obtained.

FIG. 10 shows a developing roller 3c and a toner layer thickness regulating member 10 for explaining another method for bringing the developing roller and the toner layer thickness regulating member out of contact with each other as described in FIG.
FIG. FIG. 11A
FIG. 1 is a side view showing a toner layer thickness regulating member 10, and FIG.
FIG. 1B is a plan view showing the toner layer thickness regulating member 10. Here, Wt is set to 300 mm and Ws is set to 10 mm.

The toner layer thickness regulating member 10 has a bent portion 1
0a is formed. The bent portion 10a is connected to the developing roller 3c.
And is bent in a direction opposite to the developing roller 3c.
Specifically, it is provided at a corner on the free end side of the toner layer thickness regulating member 10.

It is preferable that an angle α between a line to be bent (indicated by a broken line in FIG. 11B) and a free end is set to 45 ° or less. If it is larger than this, the flexibility of the toner layer thickness regulating member 10 decreases, which is not preferable. For example, α is set to 30 °.

The bending angle β (see FIG. 11A)
In consideration of the production of the toner layer thickness regulating member 10 such as sheet metal pressing, it is preferable to set the angle to 90 ° or less so as to facilitate the processing. For example, β is set to 45 °.

FIG. 12 is an enlarged perspective view showing the developing roller 3c and the toner layer thickness regulating member 10 for explaining still another method for bringing the developing roller and the toner layer thickness regulating member into a non-contact state. It is. Here, Wt is 300 mm,
Ws is set to 10 mm.

The toner layer thickness regulating member 10 has a notch 1
0b is provided. The notch 10b is provided with the developing roller 3c.
Is provided at the free front end portion facing the toner layer non-forming region. Specifically, it is provided at a corner on the free end side of the toner layer thickness regulating member 10.

FIG. 13 is a plan view showing a specific example of the notch 10b. The notch 10b is realized by a notch 10ba cut in a rectangular shape as shown in FIG. Alternatively, as shown in FIG. 13 (B), this is realized by a cutout portion 10bb cut out in a curved shape. In this case, it is preferable that the notch 10bb be cut in an arc shape having a radius of Ws. Further alternatively, FIG.
Notch 1 cut linearly as shown in (C)
0bc. In this case, the notch 10bc
It is preferable that the notch is formed by setting the angle between the cut line and the free end to α.

By providing the bent portion 10a and the notch portion 10b, the toner layer non-forming region of the developing roller 3c and the toner layer thickness regulating member 10 can be configured to be in non-contact or almost non-contact. 10 is prevented from leaking to the developing roller 3c.
c can be prevented from generating heat. Therefore, deterioration of the developing roller 3 due to heat, aggregation and fusion of the toner on the developing roller 3c, and fusion of the toner to the toner layer thickness regulating member 10 can be prevented, and the toner layer is formed on the developing roller 3c. It can be formed stably. This enables development for high-quality image formation.

[0099]

As described above, according to the present invention, the non-toner layer forming area is configured to be in non-contact with the photosensitive drum.
The rubbing resistance is reduced, the load torque on the photosensitive drum and the developing roller can be reduced, and the fluctuation can be eliminated. Thus, the rotation of the photosensitive drum and the developing roller is stabilized, and a high-quality image can be formed. In particular, occurrence of image unevenness in the sub-scanning direction can be suppressed.

Further, according to the present invention, by making the outer diameter of the toner layer non-forming area of the developing roller smaller than the outer diameter of the toner layer forming area, the non-contact area between the toner layer non-forming area and the photosensitive drum is reduced. It can be configured almost non-contact. Even when the contact is substantially non-contact, the force of the photosensitive drum exerted on the toner layer non-formation area is weakened, so that the rubbing resistance can be reduced, the load torque can be reduced, and the fluctuation can be eliminated.

Further, according to the present invention, the developing roller in the toner layer non-formation area is exposed and no special member is formed, so that the toner layer non-formation area and the photosensitive drum can be easily brought into non-contact or non-contact. It can be configured almost non-contact.

Also, according to the present invention, the step between the toner layer forming region and the toner layer non-forming region allows the toner layer non-forming region and the photosensitive drum to be in non-contact or almost non-contact.

Further, according to the present invention, since the step is larger than the deformation of the developing roller due to the contact with the photosensitive drum, the area where the toner layer is not formed and the photosensitive drum are surely non-contact or almost non-contact. Can be configured.

Further, according to the present invention, the toner layer non-formation area of the developing roller is formed in a tapered shape which is continuously inclined from the center to the end, so that the toner layer non-formation area and the photosensitive drum are formed. Non-contact or almost non-contact can be configured.

According to the present invention, the outflow of toner can be prevented by the toner seal member. Since such a toner seal member includes a foamed elastic material, it can follow a change in the shape of both ends of the developing roller and maintain high sealing properties. Further, since the toner seal member abuts on the non-toner layer forming region of the developing roller on the photosensitive drum side, the size of the apparatus can be reduced.

Further, according to the present invention, since the toner layer non-formation region is formed so as not to contact the toner layer thickness regulating member, it is possible to prevent the bias voltage applied to the toner layer thickness regulating member from leaking to the developing roller. Thus, heat generation of the developing roller can be prevented. Therefore, deterioration of the developing roller due to heat,
Aggregation and fusion of the toner on the developing roller and fusion of the toner to the toner layer thickness regulating member can be prevented, and the toner layer can be stably formed on the developing roller. This enables development for high-quality image formation.

Further, according to the present invention, by making the outer diameter of the toner layer non-forming area of the developing roller smaller than the outer diameter of the toner layer forming area, the toner roller non-forming area of the developing roller and the toner layer thickness regulating member are reduced. Even if the toner layer does not completely come into non-contact, the contact between the toner layer non-forming region and the toner layer thickness regulating member is weakened, so that leakage of the bias voltage of the toner layer thickness regulating member to the developing roller can be prevented. Can be.

Further, according to the present invention, the step between the toner layer forming region and the toner layer non-forming region allows the non-toner layer forming region of the developing roller and the toner layer thickness regulating member to be configured to be in non-contact with each other. Leakage of the bias voltage of the layer thickness regulating member to the developing roller can be prevented.

Further, according to the present invention, the non-toner layer forming region of the developing roller and the toner layer thickness regulating member are formed by the tapered portion continuously inclined from the center to the end of the non-toner layer forming region of the developing roller. Can be configured in a non-contact or almost non-contact manner, and leakage of the bias voltage of the toner layer thickness regulating member to the developing roller can be prevented.

According to the present invention, the bent portion of the toner layer thickness regulating member can make the toner layer non-formation area of the developing roller and the toner layer thickness regulating member non-contact or almost non-contact. Leakage of the bias voltage of the regulating member to the developing roller can be prevented.

Further, according to the present invention, the notched portion of the toner layer thickness regulating member can make the toner layer non-forming region of the developing roller and the toner layer thickness regulating member non-contact or almost non-contact, so that the toner layer thickness can be reduced. Leakage of the bias voltage of the regulating member to the developing roller can be prevented.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a developing device 1a according to an embodiment of the present invention.

FIG. 2A is a plan view showing a developing roller 3a, and FIG. 2B is a plan view showing a developing roller 3b.

FIG. 3 is an enlarged plan view showing a developing roller 3a and a photosensitive drum 2;

FIG. 4 is an enlarged perspective view showing a developing roller 3a and a toner layer thickness regulating member 10.

5 is a view showing a developing device 1b according to another embodiment of the present invention, FIG. 5 (A) is a sectional view, and FIG. 5 (B) is a sectional perspective view.

FIG. 6A is a plan view showing the developing roller 3a and the toner seal member 17, and FIG. 6B is a plan view showing the developing roller 3b and the toner seal member 17.

FIG. 7 is a graph showing a relationship between a contact depth δ and a sliding torque increase amount.

FIG. 8A is a front view showing a static electric resistance measuring device such as a toner supply roller, and FIG. 8B is a side view.

FIG. 9A is a plan view showing a device for measuring static and dynamic electric resistance of a developing roller, and FIG. 9B is a side view.

FIG. 10 is an enlarged perspective view showing a developing roller 3c and a toner layer thickness regulating member 10.

FIG. 11A is a side view showing a toner layer thickness regulating member 10 having a bent portion 10a, and FIG.
Is a plan view.

FIG. 12 is an enlarged perspective view showing a developing roller 3c and a toner layer thickness regulating member 10.

FIG. 13 is a plan view showing the toner layer thickness regulating member 10 having notches 10ba, 110bb, and 10bc, respectively.

FIG. 14 is a diagram illustrating a developing device according to the related art, and FIG.
FIG. 14A is a perspective view, and FIG.
FIG. 14 is a plan view showing the photoconductor drum 66 and FIG.
FIG. 4C is a plan view showing the developing roller 62.

[Explanation of symbols]

 1a, 1b Developing device 2 Photoreceptor drum 3, 3a, 3b, 3c Developing roller 6 Toner hopper 7 Toner 10 Toner layer thickness regulating member 10a Bending portion 10b, 10ba, 10bb, 10bc Cutout portion 15 Toner layer 17 Toner seal member 21 Toner layer forming area 22 Toner layer non-forming area

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Tatsumi 22-22, Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside (72) Inventor Takashi Sakai 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka (72) Inventor Hiroshi Ishii 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation

Claims (13)

[Claims] A photosensitive drum rotatably carrying an electrostatic latent image; and a conductive and elastic developing roller rotatable carrying one-component toner, wherein the developing roller is mounted on the photosensitive drum. In a developing device for providing a relative rotational speed difference to make contact and develop an electrostatic latent image to make it a visible image, it is preferable that the toner layer non-forming region of the developing roller and the photosensitive drum are brought into non-contact. Characteristic developing device. 2. A photosensitive drum rotatably carrying an electrostatic latent image, and a conductive and elastic developing roller rotatable carrying one-component toner, wherein the developing roller is mounted on the photosensitive drum. In a developing device for providing a relative rotational speed difference and making a contact to develop an electrostatic latent image to visualize the image, the outer diameter of the toner layer non-formed area of the developing roller is larger than the outer diameter of the toner layer formed area. A developing device, which is also small. 3. The developing device according to claim 1, wherein a surface of the developing roller is exposed in the toner layer non-formation area, and the surface directly faces the photosensitive drum. 4. The method according to claim 1, wherein a step is provided between the toner layer forming area and the toner layer non-forming area of the developing roller, the step being greater than a contact depth of the developing roller with the photosensitive drum. The developing device as described in the above. 5. The developing device according to claim 4, wherein the step is larger than a deformation amount of the developing roller due to the contact of the developing roller with the photosensitive drum. 6. The developing device according to claim 1, wherein an outer diameter of the developing roller in the non-toner layer non-forming region continuously decreases from a center to an end. 7. A toner seal member comprising a foamed elastic material, wherein the toner seal member prevents the toner layer from flowing out by abutting the toner roller non-forming area of the developing roller from the side opposite to the photosensitive drum. 3. The developing device according to claim 1, wherein 8. A photosensitive drum rotatable to carry an electrostatic latent image, a conductive and elastic developing roller rotatable to carry one-component toner, and a width of a toner layer forming area of the developing roller. A toner layer thickness regulating member having conductivity and elasticity, and having an abdomen near a free end of the toner layer thickness regulating member in contact with a developing roller to press the developing roller, By applying a bias voltage to the toner layer thickness regulating member, the toner layer on the developing roller is charged to a predetermined amount of charge and formed to a predetermined thickness, and has a toner layer of a predetermined amount of charge and a predetermined thickness. A developing device that develops an electrostatic latent image into a visible image by contacting the developing roller with a photosensitive drum at a relative speed difference, wherein the toner layer non-forming region of the developing roller; Developing apparatus is characterized in that the non-contact and a layer thickness regulating member. 9. A photoreceptor drum rotatable carrying an electrostatic latent image, a conductive and elastic developing roller rotatable carrying one-component toner, and a width of a toner layer forming region of the developing roller A toner layer thickness regulating member having conductivity and elasticity, and having an abdomen near a free end of the toner layer thickness regulating member in contact with a developing roller to press the developing roller. By applying a bias voltage to the toner layer thickness regulating member, the toner layer on the developing roller is charged to a predetermined amount of charge and formed to a predetermined thickness, and has a toner layer of a predetermined amount of charge and a predetermined thickness. A developing device that develops the electrostatic latent image into a visible image by bringing the developing roller into contact with the photosensitive drum at a relative speed difference, wherein an outer diameter of the toner layer non-forming region of the developing roller Is Developing apparatus is characterized in that less than the outer diameter of the toner layer forming area. 10. The developing device according to claim 8, wherein a step is provided between the toner layer forming region and the toner layer non-forming region of the developing roller. 11. The developing device according to claim 8, wherein the outer diameter of the developing roller in the non-toner layer non-forming region continuously decreases from the center to the end. 12. The toner layer thickness regulating member has a bent portion, and the bent portion is provided at a free front end portion of the developing roller opposite to the toner layer non-forming region, and is provided in a direction opposite to the developing roller. The developing device according to claim 8, wherein the developing device is bent. 13. The toner layer thickness regulating member has a notch portion, and the notch portion is provided at a free front end portion of the developing roller facing a toner layer non-formation area. Item 10. The developing device according to Item 8.