JP4517658B2 - Development device - Google Patents

Description

The present invention relates to a developing device such as a copying machine or a printer, and more particularly to an improvement of a developing device using a flexible layer regulating member that includes a developer carrying member and regulates a developer layer on the developer carrying member.

In general, in an image forming apparatus employing an electrophotographic method, a hard photosensitive drum having a photosensitive layer formed on the outer peripheral surface and an image forming apparatus having a photosensitive layer formed on the surface as an image bearing member that supports an electrostatic latent image. A photosensitive belt having flexibility is known.
When a hard photosensitive drum is used as the image bearing member and a hard developing roll is used as the image bearing member, for example, there is a limit to manufacturing the photosensitive drum and the hard developing roll with high accuracy. In order to produce an error, it is difficult to make both contact uniformly. For this reason, there is a problem in that local gaps are generated between the contact surfaces of the two, resulting in uneven development, and scratches on the photosensitive drum and the developing roll.
Therefore, when a hard photosensitive drum is used as the image carrier, the developing roll is made of an elastic member made of soft rubber, for example.
However, in the method in which the soft rubber is brought into contact with the photosensitive drum, the hardness varies due to the distribution of the amount of carbon normally dispersed in the rubber, and when used for a long time, the plasticizer moves (bleeds) in the rubber. ) May impair the photosensitive characteristics of the photosensitive drum or increase the rubber hardness.

JP-A-9-160274 (column of embodiment of the invention, FIG. 4) Japanese Laid-Open Patent Publication No. 10-222010 (column of the first embodiment, FIG. 2) JP-A-11-352835 (column of embodiment of the invention, FIG. 1) JP 63-106766 (Structure column, Fig. 1) Japanese Patent Laid-Open No. 10-153910 (column of the first embodiment, FIG. 4) JP 2000-131944 (column of embodiment of the invention, FIG. 2)

Therefore, various methods using a photosensitive member using a flexible substrate as an image carrier have been proposed (see, for example, Patent Documents 1 to 3).
In Patent Document 1, a roll smaller than the inner diameter is arranged inside a photosensitive belt formed on a flexible substrate, and the inner surface of the end portion of the photosensitive belt is held by an elastic layer. A system is proposed in which the cleaning blade is brought into contact with the surface of the photosensitive belt, the photosensitive belt and the roll are brought into contact with each other, and the photosensitive belt is rotated by a frictional force acting on the contact surface. Further, it is stated that the axial contact length of the cleaning blade has a predetermined value for the distance between the elastic layer and the blade contact end in order to prevent abnormal deformation of the photosensitive belt.
However, no consideration is given to the length relationship between the developing roll and the cleaning blade.

Further, in Patent Document 2, a supported portion (a portion where the photosensitive member is supported by another supporting member) at the end of a flexible thin cylindrical photosensitive member having a photosensitive layer formed on the outer peripheral surface thereof; As for the axial distance between the charging roll and the end of the developing roll that are in pressure contact with the photoconductor, the charging roll and the developing roll come into contact with the photoconductor to cause the photoconductor to bend so that this bending does not cause permanent deformation. A method of setting a long length is proposed. The cleaning blade is used by pressing the photoconductor until the outer circumferential surface of the photoconductor comes into contact with the outer circumferential surface of the cylindrical member inserted in the photoconductor. It is supposed to be cleaned.
However, no particular consideration is given to the width of the cleaning blade on the photoreceptor, and no consideration is given to the relationship between the length of the developing roll and the cleaning blade.

Further, Patent Document 3 proposes a method of finally forming a flexible thin cylindrical substrate as a drum-shaped image carrier by drawing. In this case, since the image carrier is formed by drawing, a so-called crown shape in which the central portion of the image carrier swells (the central portion becomes thicker than the periphery in a drum shape), even on a hard developing roll. It is said that reliable contact can be maintained.
However, no consideration is given to the relationship between the length of the developing roll and the cleaning blade on the image carrier.

In the above-described method, at the time of cleaning on the flexible image carrier, a hard member such as a roll is disposed inside the image carrier, so that the cleaning blade is strongly applied to ensure cleaning. I am doing so.
However, disposing a member such as a roll inside the image carrier requires a member such as a roll and a mounting member thereof as compared to a configuration in which no member is provided inside, leading to an increase in apparatus cost. is there. Further, when assembling them, it is necessary to fix a member such as a roll in a predetermined position without damaging the flexible image carrier, and it is difficult to handle the flexible image carrier. There is also a concern of damaging both ends.

The present inventors have studied the case where a member such as a roll is not provided inside the flexible image carrier, and have obtained the following knowledge.
In order to clean the toner remaining on the flexible image carrier, it is necessary to press the elastic rubber cleaning blade with a pressing force within a range in which the flexible image carrier does not deform abnormally. There are many toners that pass through the cleaning blade and there is a concern that sufficient cleaning performance cannot be obtained.
Therefore, the toner that has passed through the cleaning blade may be scraped and collected by an electric or simple mechanical rubbing force with a developing roll that is in contact with the image carrier. At this time, when a contact charger is used as a member for charging the image carrier between the cleaning blade and the developing roll, a voltage having the same polarity as the toner is applied to the contact charger so that the toner does not adhere to the contact charger. It is better to apply.

However, it has also been found that when the toner is collected by such a method, the following another problem occurs. That is, in order to clean the image carrier with a sufficient margin, the cleaning blade is in contact with the image carrier outside the width of the developing roll when the cleaning blade is larger than the developing roll, particularly when used for a long period of time. There was a problem that the toner adhered to the portion.
Since the fixed toner is fixed with a small adhesive force, it eventually falls on the paper conveyance path or the intermediate transfer member, resulting in smearing of the image front and back surfaces.

  The occurrence mechanism of this problem is considered as follows. That is, since the inside of the flexible image bearing member is hollow, it is deformed by the pressing of the cleaning blade, and the force that stops the toner sufficiently by the cleaning blade does not work. Some of the toner slips through the cleaning blade, and most of the slipped toner is collected by the developing roll. However, in the region outside the width of the developing roll, the toner remaining on the image carrier repeatedly passes through the cleaning blade over a long period of time, and the toner partially melts due to the frictional heat. It will stick to. This phenomenon remarkably occurs particularly in an apparatus using a toner having a low glass transition point and easily melted, for example, a color toner pursuing more vividness.

Here, the present inventors further indicate that the relationship between the above-described flexible image carrier and the developing roll is flexible as a member that regulates the layer of the developing roll and the developer on the developing roll. It was predicted that the same relationship was obtained when the layer regulating member having the same was used.
Therefore, the present inventors have made a similar study on the developing device.
In general, in a one-component developing device, a configuration is known in which a toner regulating roll is used as a layer regulating member for forming and charging a thin toner layer on a developing roll, and a scraper scrapes off excess toner on the toner regulating roll. (For example, refer to Patent Documents 4 to 6).

In Patent Document 4, a scraper width Ws for scraping off excess toner on a toner regulation roll and a toner regulation roll width Wm are illustrated in a relationship of Wm <Ws.
In Patent Document 5, a rotating toner layer regulating member (toner regulating roll) that contacts the surface of the elastic developing roll and rotates at the contact portion in the direction opposite to the rotating direction of the developing roll to regulate the layer of nonmagnetic toner; A developing device having a scraper that contacts the toner regulating roll and scrapes off the nonmagnetic toner on the toner regulating roll is proposed. Further, although it is shown that the toner regulating roll width Wm is wider than the developing roll width Wd (Wd <Wm), there is no description about the width Ws of the scraper.
Furthermore, in Patent Document 6, a metal roll shorter than the developing roll is pressed against the developing roll to thin the toner, and a scraper longer than the metal roll and shorter than the developing roll is pressed against the metal roll to be placed on the metal roll. A structure for scraping off toner is presented. Further, regarding the relationship between these widths, it is shown that the regulation roll width Wm <the scraper width Ws <the developing roll width Wd.
In any of the examples, a rigid roll or a rubber elastic roll is used as the toner regulating roll.

The inventors of the present invention examined a method of pressing the developing roll with a flexible toner regulating member instead of the above-described toner regulating roll to regulate the toner layer on the developing roll.
As shown in FIG. 11, a flexible and rotatable toner regulating member 52 that controls the toner layer on the developing roll 51 facing the developing roll 51, and the toner regulating member 52. A configuration including a scraper 53 disposed in contact with the toner and scraping off the toner on the toner regulating member 52 will be considered. At this time, when the width Wm of the toner regulating member 52 is larger than the width Wd of the developing roll 51, the width Ws of the scraper 53 is larger than the width Wd of the developing roll 51 (Ws> Wd). Thus, in the area A inside the scraper 53, the toner that could not be scraped off by the scraper 53 stays, and when used for a long period of time, the toner is fixed to the surface of the toner regulating member 52. This phenomenon is particularly noticeable when a toner having a low glass transition point is used.
The adhered toner eventually peels off from the surface of the toner regulating member 52, for example, clogs between the developing roll 51 and the toner regulating member 52, and a uniform thin toner layer on the developing roll 51. Formation is impaired, and image defects such as white stripes occur. Further, for example, the developing roll 51 is scratched with a lump of separated toner, and an image defect such as a black stripe is generated.

  The present invention is to solve the technical problems as described above, and an image forming apparatus capable of suppressing the adhesion of a developer on a flexible image carrier and forming a stable image. It is to provide. Furthermore, it is an object of the present invention to provide a developing device that suppresses developer sticking on a flexible developer layer regulating member and ensures stable development characteristics.

That is, as an aspect of the image forming apparatus according to the reference invention related to the present invention, as shown in FIG. 1A, a flexible image carrier having a visible image by a developer and having flexibility. 1, a scraping member 3 that contacts the flexible image carrier 1 and scrapes off the developer on the flexible image carrier 1, and is placed in contact with the flexible image carrier 1 and has a developer on the surface. And a rotatable developer carrier 2 that collects the developer on the flexible image carrier 1 that has not been scraped off by the scraping member 3. the axial effective length W _a, an axial effective length of the developer carrying member 2 W _B, the effective length of scraping member 3 when the W _C, set to satisfy W _C ≦ W _{B <W a} It is characterized by that.

Further, as shown in FIG. 1B, the developing device according to the present invention includes a developer carrying body 2 carrying and transporting a developer on the surface, and a developer arranged in contact with the developer carrying body 2 for development. A rotatable hollow flexible layer regulating member 4 which performs layer regulation of the developer on the developer carrier 2 and at least a contact portion with the developer carrier 2 is flexible, and this flexible layer a developing apparatus comprising a scraping member 3 to the regulating member 4 scraping contact flexible layer regulating member 4 on the developer, the axial effective length of the flexible layer regulating member 4 and W _D, intended to axially effective length of the developer carrying member 2 when W _E, the effective length of the scraping member 3 and W _F, characterized in that it is set to satisfy W _F ≦ W _{E <W D} is there.

In such technical means, the present invention includes an image forming apparatus having a flexible image carrier and a developing apparatus having a flexible developer layer regulating member. Moreover, the effective length as used in this application shows the length of the area | region which has a function instead of the full length of a mere member.
Further, the developer carrier 2 may be any one that supports and conveys a developer (or toner in the case of a two-component developer), and includes a roll shape and a belt shape, and is either elastic or rigid. There is no problem.
Furthermore, the scraping member 3 is preferably an elastic member from the viewpoint of coming into contact with the flexible image carrier 1 or the flexible layer regulating member 4, thereby causing deformation of the flexible portion or generation of scratches. Can be deterred.

Then, in the image forming apparatus definitive reference invention relating to the present invention, a flexible image bearing member 1, as long as it has a carrying and flexible a visible image by a developer, representative Specifically, an image forming area that carries an electrostatic latent image for visualization with a developer and at least the image forming area has flexibility can be mentioned. In this case, as long as the flexible portion covers at least the image forming area, the shape may be either a roll shape or a belt shape. As an aspect which has this flexibility, a resin film-like aspect, such as PET, may be sufficient, for example, a metal foil-like aspect may be sufficient.
Further, as the flexible image carrier 1, a hollow cylindrical shape is more preferable from the viewpoint of cost because it is not necessary to have other components such as a roll in the flexible image carrier 1, and this At this time, an aspect including a circular rigid support that supports the inner surfaces of both ends is preferable because stable rotation performance can be secured.
Furthermore, by providing a conductive layer in at least the flexible portion of the flexible image carrier 1, the conductive layer provides conductivity even if the base material of the flexible cylindrical body does not have conductivity. For example, an electric field can be effectively applied as a flexible image carrier.
According to this aspect, the flexible image bearing member, the scraping member for scraping off the developer on the flexible image bearing member, and the flexible image bearing member in contact with the developer are carried on the surface. In an image forming apparatus comprising a rotatable developer carrier that transports and collects a developer on a flexible image carrier that has not been scraped off by a scraping member, the width of the developer carrier can be reduced. By making the width smaller than the width of the flexible image carrier and making the width of the scraping member equal to or less than the width of the developer carrier, the residual developer that has passed through the scraping member can be recovered by the developer carrier. The fixing of the developer to the flexible image bearing member can be suppressed, and the image smear can be suppressed.

On the other hand, in the developing device according to the present invention, the flexible layer regulating member 4 may have a roll shape or a belt shape as long as the flexible region covers at least the image region. Absent. As an aspect which has this flexibility, a resin film-like aspect, such as PET, may be sufficient, for example, a metal foil-like aspect may be sufficient.
Further, as the flexible layer regulating member 4, a hollow cylindrical shape is more preferable from the viewpoint of cost because it does not have other components such as a roll inside, and at this time, the inner surfaces of both end portions The aspect provided with the circular rigid support body which supports is preferable because stable rotation performance can be secured.
Furthermore, by providing a conductive layer in at least the flexible portion of the flexible layer regulating member 4, the conductive layer provides conductivity even if the base material of the flexible cylindrical body does not have conductivity. For example, an electric field can be effectively applied as a regulating member for regulating the developer layer on the developer carrier 2.

According to the present invention, a developer carrying member that carries and conveys a developer, a hollow flexible layer regulating member that regulates the layer of the developer on the developer carrying member, and the flexible layer regulating member In a developing device having a scraping member that scrapes off the developer above, the width of the developer carrying member is made smaller than the width of the flexible layer regulating member, and the width of the scraping member is equal to or less than the width of the developer carrying member. By doing so, image defects such as white stripes and black stripes can be suppressed.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
Embodiment 1
FIG. 2 shows a first embodiment of an image forming apparatus to which a reference invention related to the present invention is applied. In the figure, the image forming apparatus according to the present embodiment uses an image forming unit 10 (specifically, 10a to 10d) of four colors (in this embodiment, yellow, magenta, cyan, and black) as an intermediate transfer drum. 20 and a sheet conveyance path 22 from the sheet supply cassette 21 are arranged in the vertical direction.

In the present embodiment, each image forming unit 10 (10a to 10d) forms, for example, toner images for yellow, magenta, cyan, and black along the rotation direction of the intermediate transfer drum 20. In addition, each image forming unit includes a photoconductor unit, a developing unit, and an exposure unit.
The photoconductor unit includes a photoconductor 11 as an image carrier made of a flexible hollow cylindrical body, a charger 12 for charging the photoconductor 11, and a cleaning as a scraping member for scraping off toner on the photoconductor 11. It consists of a blade 13. The developing unit is composed of a developing roll 14 as a developer carrying member disposed facing the photoconductor 11 and a developing device 15 for supplying a thin toner layer onto the developing roll 14. Further, the exposure unit is not limited as long as it can form an electrostatic latent image on the photoconductor 11, and an exposure device 16 using an LED array is used in this embodiment.

  On the other hand, the intermediate transfer drum 20 is constituted by, for example, an aluminum sleeve covered with a semiconductive resin layer having a thickness of about 20 μm, and sequentially transfers toner images on the photoreceptor 11 of each image forming unit 10 (10a to 10d). Transfer. The toner images superimposed on the color on the intermediate transfer drum 20 are secondarily collected by the secondary transfer roll 23 onto a sheet as a recording material conveyed from the sheet supply cassette 21 through the sheet conveyance path 22. It is designed to be transcribed. Note that reference numeral 24 in the drawing denotes a cleaning unit that cleans residual toner on the intermediate transfer drum 20.

FIG. 3 schematically shows a main part of the image forming unit 10 of FIG. 2, and shows only the photoconductor 11, the developing roll 14, and the cleaning blade 13 in the image forming unit 10.
The photoconductor 11 in the present embodiment has a structure as shown in FIG. An aluminum thin film is formed on a surface of a base made of a PET (polyethylene terephthalate) resin tube having a thickness of 100 μm and having flexibility, for example, by physical plating such as vapor deposition. Further, an organic photoconductive layer is coated on the surface to constitute the flexible tube 111. A pair of rigid flanges 112 and 113 are fitted and fixed to both ends of the flexible tube 111. The rigid flanges 112 and 113 are connected by a shaft 114.

Further, the developing roll 14 shown in FIG. 3 may be any one that can carry and convey a developer (in this embodiment, a non-magnetic one-component toner). In this embodiment, the surface of the aluminum sleeve is sandblasted. What was done was used. Further, on the surface of the developing roll 14, a regulating blade made of, for example, SUS plate, which is not shown, is attached with a regulating blade so that a toner layer having a predetermined thickness and a predetermined charge amount is formed on the developing roll 14. It has become.
In this embodiment, the rotational speeds are set between the developing roll 14 and the photoconductor 11 so as to have a peripheral speed difference.
As the developing roll 14, a metal roll is used in the present embodiment. However, the developing roll 14 is not limited to this. For example, a semiconductive resin roll or a semiconductive rubber roll may be used. Further, although the regulating blade is used as the layer regulating member, any material may be used as long as it can regulate and charge the toner layer thickness such as roll, brush or film.

  The cleaning blade 13 is disposed so that a 150 μm-thick PET thin plate hits the photoconductor 11 in the counter direction, and pushes the residual toner on the photoconductor 11 to the photoconductor 11 with a small pressing force that almost scrapes off the residual toner. It has been applied. The cleaning blade 13 may be an elastic member, for example.

  In this embodiment, in particular, the effective length of the photoconductor 11 (the length excluding the rigid flanges 112 and 113 from the entire length of the photoconductor 11) is Wm, and the length (width) of the developing roll 14 is Wd. When the length (width) of the cleaning blade 13 is Ws, the length (width) of each part is set so as to satisfy the relationship of Ws ≦ Wd <Wm.

Next, the operation of the image forming apparatus according to the present embodiment will be described, particularly focusing on the collection of residual toner on the photoreceptor 11.
In the present embodiment, negatively charged toner is used as a developer, and the photosensitive member 11 is negatively and uniformly charged by the charger 12 to perform reverse development. On the photosensitive member 11, after being charged by the charger 12, an electrostatic latent image is formed by the exposure device 16, and this electrostatic latent image is developed in a developing region at a portion facing the developing roll 14 and the photosensitive member 11. A toner image is formed.
The toner image formed on the photoconductor 11 is primarily transferred onto the intermediate transfer drum 20 at a portion where the photoconductor 11 and the intermediate transfer drum 20 face each other.
At this time, residual toner that is not transferred onto the intermediate transfer drum 20 and remains on the photoconductor 11 is scraped off by the cleaning blade 13, but a part of the toner remains on the photoconductor 11 and proceeds to the charger 12 side. . Here, the toner of normal polarity (negatively charged) proceeds on the photoconductor 11 as it is without being attracted by the negative voltage of the charger 12 and reaches a portion facing the developing roll 14. Then, due to the potential difference between the developing bias applied to the developing roller 14 and the surface potential of the photosensitive member 11, the toner on the photosensitive member 11 is collected on the developing roller 14 side.
Even if the charge amount of the toner is small, there is a peripheral speed difference between the developing roll 14 and the photoconductor 11, so that the toner remains on the photoconductor 11 due to the frictional force generated between them. A low charge amount of toner is also collected on the developing roll 14.
The toner remaining on the photoconductor 11 without being transferred to the intermediate transfer drum 20 includes toner of reverse polarity (positive charge). For example, the toner remaining on the photoconductor 11 before and after the cleaning blade 13 is included. It is also possible to separately provide a charging member that positively injects negative charges (regular charged charges) into the toner.

  In this embodiment, in particular, since the photosensitive member 11 has a flexible tube configuration having rigid flanges 112 and 113 at both ends, the photosensitive member 11 can rotate smoothly, and the intermediate transfer drum 20 and Even the opposite part of the film is deformed slightly flexibly. Also, the contact pressure is usually set to be small (compared to the case of a rigid photoconductor) at the contact portion with the developing roll 14, so that the toner image on the photoconductor 11 immediately after development is disturbed in a so-called development nip. This is much smaller, and it is possible to suppress degradation of image resolution and toner scattering. Further, even if a circumferential speed difference is provided between the developing roll 14 and the photoconductor 11, they are less likely to wear each other, and there is an effect that the life of the member is extended.

Furthermore, in the present embodiment, the length (width) of the photoconductor 11, the developing roll 14, and the cleaning blade 13 is set as described above, so that residual toner that has passed through the cleaning blade 13 is collected by the developing roll 14. As a result, it is possible to prevent toner from adhering to the photoconductor 11. Therefore, it is possible to prevent image contamination due to the fixed toner.
In this embodiment, the configuration in which the rigid flanges 112 and 113 are provided at both ends of the photoconductor 11 is used. However, for example, an elastic member having such a hardness that the photoconductor 11 is not twisted during rotation. In this case, the effective length of the photoconductor 11 having flexibility is increased, and the apparatus can be miniaturized.

Further, in the present embodiment, the flexible tube 111 of the photoconductor 11 has been shown in which an aluminum thin film is formed on a PET resin tube. However, the present invention is not limited to this, for example, an electrode such as nickel electroforming or SUS. A thin metal tube may be used. Further, for example, a transparent conductive layer made of ITO (Indium Tin Oxide) may be formed on a PET resin tube by, for example, a dip coating method.
And especially in the structure provided with the transparent conductive layer like ITO, the structure as shown in FIG. 5 is also possible.
In the figure, a flexible tube 111 of the photoreceptor 11 is obtained by forming a transparent conductive film 111b of ITO by dip coating on a PET resin tube 111a and forming a photoconductive layer 111c as a photosensitive layer thereon. is there. An LED array 27 formed on the substrate 26 along the axial direction of the photosensitive member 11 is provided inside the flexible tube 111, and the condensing lens surface thereof hits the inner wall of the flexible tube 111. It is like that. The substrate 26 is connected to a shaft 29 via a support 28.
In such a configuration, the flexible tube 111 is rotated by a pair of rigid flanges (not shown), but the shaft 29 does not rotate. Therefore, the LED array 27 can expose the photoconductor 11 at the same position. .
Therefore, it is not necessary to provide an exposure device outside the photoconductor 11 as in the first embodiment, and exposure from the inside of the photoconductor 11 is possible, and ITO can be manufactured by an inexpensive manufacturing method called a dip coating method. Therefore, a small and inexpensive image forming apparatus can be realized.

Embodiment 2
Unlike the first embodiment, the present embodiment is characterized in that a flexible tube is used as a toner regulating member on the developing roll.
FIG. 6 shows a developing device according to an embodiment to which the present invention is applied. In the figure, a developing housing 32 is provided to face a photosensitive drum 31 made of a rigid base material. At the opening of the developing housing 32 facing the photosensitive drum 31, a developing roll 33 for carrying and transporting the developer (in this embodiment, non-magnetic one-component toner) is disposed at a predetermined distance from the photosensitive drum 31. It is installed. Around the developing roll 33, a supply roll 34 made of a foaming roll such as semiconductive foamed urethane for supplying toner to the developing roll 33 is disposed to face the downstream side of the supply roll 34. The toner regulating roll 35 having flexibility is disposed. Reference numeral 39 denotes a bias power source connected to the developing roll 33.
In the present embodiment, the developing roll 33 and the toner regulating roll 35 rotate in different directions (Against direction) at the opposed portions. In addition, a bias power source 41 is connected to the toner regulating roll 35 so that a DC electric field for applying a predetermined charge amount to the toner is applied at a portion facing the developing roll 33 and the toner regulating roll 35. Further, a scraper 36 as a scraping member that scrapes off the toner on the toner regulating roll 35 is provided in contact with the toner regulating roll 35, and one end thereof is fixed to the developing housing 32 via a bracket (not shown). .
Further, a toner hopper 37 for storing toner is provided behind the supply roll 34 in the developing housing 32, and the agitator 38 agitates the toner.

FIG. 7 schematically shows the main part of FIG. 6, and shows the relationship between the developing roll 33, the toner regulating roll 35 and the scraper 36.
In the present embodiment, the developing roll 33 is a mirror finished surface of a stainless steel (SUS) sleeve. For example, an aluminum sleeve can be used, and a semiconductive resin roll, a semiconductive rubber roll, etc. Can also be used.
As the toner regulating roll 35 having flexibility, a flexible tube 351 made of semiconductive polyamide (PA) having an outer diameter of 15 mm, a thickness of 150 μm, and a volume resistivity of 10E + 5 Ω · cm is used. Rigid flanges 352 and 353 are fitted into both ends of the flexible tube 351 and bonded to the flexible tube 351. As the flexible tube 351, in addition to polyamide (PA), semiconductive such as polyimide (PI), polyetherimide (PEI), polyvinylidene fluoride (PVdF), polytetrafluoroethylene (PTFE), PFA, etc. A sex tube can be used.
Furthermore, as the flexible tube 351, for example, a metal tube such as nickel electroforming or stainless steel (SUS) can be used.
The scraper 36 is a thin sheet of PET having a thickness of 150 μm applied to the movement of the toner regulating roll 35 in the counter direction, and the toner regulating roll with a small pressing force enough to scrape off the toner on the toner regulating roll 35. 35 is pressed against. In the present embodiment, the scraper 36 is attached to the developing housing 32 via a bracket. However, for example, by providing a foam between the scraper 36 and the bracket, the scraper 36 is attached to the toner regulating roll 35 of the scraper 36. It is more preferable that the pressure can be made more uniform.

  In particular, in this embodiment, the length (width) of the developing roll 33 is Wd, and the effective length of the toner regulating roll 35 (the length excluding the rigid flanges 352 and 353 from the total length of the toner regulating roll 35). Is Wm, and the length (width) of the scraper 36 is Ws, the length (width) of each part is set so as to satisfy the relationship of Ws ≦ Wd <Wm.

Next, the operation in the present embodiment will be described with reference to FIGS.
The toner stirred by the agitator 38 is conveyed on the supply roll 34 toward the developing roll 33 as the supply roll 34 rotates. Since the portions facing the supply roll 34 and the developing roll 33 are rotated in different directions (Against direction), the toner on the supply roll 34 is supplied onto the developing roll 33 by the rubbing force at this portion. Is done. On the other hand, the toner remaining on the developing roll 33 is collected on the supply roll 34 side.
Further, the toner supplied from the supply roll 34 onto the developing roll 33 is sufficiently layer-regulated in a wide nip region formed by the developing roll 33 and the toner regulating roll 35, and the effect of the bias power source 41 is added to the predetermined level. The amount of charge is charged.
A thin toner layer having a predetermined layer thickness and charge amount is formed on an electrostatic latent image on the photosensitive drum 31 by a developing bias from a bias power source 39 in a developing nip region at a position where the developing roll 33 and the photosensitive drum 31 face each other. Visualize the image.

On the other hand, since the toner regulating roll 35 rotates while regulating the toner on the developing roll 33, the toner adheres to the outer periphery thereof. The adhered toner is scraped off by the scraper 36. At this time, since the toner regulating roll 35 has flexibility, the toner on the toner regulating roll 35 cannot be completely scraped off by the scraper 36, and a part of the toner is conveyed on the toner regulating roll 35. Is done. However, the conveyed toner is collected to the developing roll 33 side by electrostatic force or simple rubbing force.
Therefore, toner does not accumulate or adhere to both ends of the toner regulating roll 35, and the occurrence of white and black lines on the image can be prevented.

In the present embodiment, a configuration in which a DC electric field is applied to the toner regulating roll 35 by the bias power supply 41 is shown. However, for example, an AC electric field superimposed on DC can be applied. The amount is further improved. Further, for example, the supply roll 34 is provided with a bias power supply, and the toner power is applied to the toner by the bias power supply so that the toner restriction roll 35 is not provided with a bias power supply. Both rolls 35 can be provided with a bias power source. In this case, the toner supply performance and the charging performance are further improved.
Further, in the present embodiment, the developing roll 33 and the toner regulating roll 35 are configured to rotate in different directions (Against direction) at the opposed portions, but are configured to rotate in the same direction (With direction). However, since a wide nip region can be constructed, the same layer regulation and charging effect can be obtained.

Embodiment 3
FIG. 8 shows an image forming apparatus according to a third embodiment to which the present invention is applied. This embodiment includes the image forming apparatus according to the first embodiment and the developing apparatus according to the second embodiment. It is a combination. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1 or Embodiment 2, and the detailed description is abbreviate | omitted.
FIG. 9 shows a flexible photosensitive member 11 according to the present embodiment, a cleaning blade 13 disposed on the photosensitive member 11, a developing roller 33, a toner regulating roller 35, and the toner. The relationship with the scraper 36 that scrapes off the toner on the regulating roll 35 is schematically shown.

In this embodiment, as shown in FIG. 9, the effective length (width) of the toner regulating roll 35 is Wm1, the length (width) of the developing roll 33 is Wd, and the width of the scraper 36 on the toner regulating roll 35 is Ws1. , The length (width) of each part is configured to satisfy the relationship of Ws1 ≦ Wd <Wm1.
Further, when the effective length (width) of the flexible photoconductor 11 is Wm2, and the width of the cleaning blade 13 disposed on the photoconductor 11 is Ws2, Ws2 ≦ Wd <Wm2 The length (width) of each part is configured so as to satisfy the above relationship.
Due to the configuration described above, the toner attached on the toner regulating roll 35 is collected by the developing roll 33, and the toner attached on the photoreceptor 11 is also collected by the developing roll 33.
Therefore, it is possible to form an image free from image stains, white stripes, and black stripes.

Example 1
In this example, specific reliability evaluation is performed in the configuration of the first embodiment.
In this embodiment, the effective length Wm of the flexible photoconductor is 240 mm, the width Wd of the developing roll is 220 mm, the width Ws of the scraper is 215 mm, and the apparatus is operated for a time corresponding to 50,000 printed sheets. Thereafter, the printed image and the photoreceptor surface were visually confirmed, but no image defect was confirmed, and no toner adhered to the photoreceptor surface.

Example 2
In this example, specific reliability evaluation is performed in the configuration of the second embodiment.
In this embodiment, as a flexible toner regulating roll, an effective length Wm is 230 mm, a developing roll width Wd is 220 mm, and a scraper width Ws is 215 mm using a polyamide (PA) tube having a volume resistivity of 1 × 10E + 5 Ω · cm. In addition, as the toner, a color toner for two-component developer having a volume center particle diameter of 7.5 μm, a glass transition point of 69 ° C., and a wax internally added was used.
In this embodiment, the developing device is intermittently operated for a time corresponding to the number of printed sheets 50,000, and then the printed image and the surface of the toner regulation roll are visually checked. However, image defects such as white stripes and black stripes are detected. Also, no toner sticking occurred on the surface of the toner regulating roll.

Comparative Example This comparative example was performed as a comparison with Example 2, and the reliability evaluation similar to that of Example 2 was performed with a dimensional configuration as shown in FIG.
In this comparative example, an effective length Wm is 230 mm, a developing roll width Wd is 220 mm, a scraper width Ws is 230 mm with a volume resistivity of 1 × 10E + 5 Ω · cm, and a scraper width Ws is 230 mm. This was carried out using a color toner for a two-component developer having a particle diameter of 7.5 μm, a glass transition point of 69 ° C., and a wax internally added. Therefore, the width Ws of the scraper is wider than the width Wd of the developing roll.
In this comparative example, before reaching the time corresponding to 10,000 printed sheets, the toner regulating roll is placed on the outside of both ends of the developing roll and within the range of the scraper (corresponding to the area A in FIG. 11). The toner flakes adhered to the toner.

Example 3
In this example, the configuration of the developing device in the second embodiment is applied, and the effect of bias application on the toner charge amount between the toner regulating roll and the developing roll (evaluated by a DC electric field and a partial DC electric field superimposed AC electric field) and This is a comparative study of the effects of materials.
FIG. 10 shows the evaluation results. It was confirmed that the toner charge amount increases by biasing the toner regulating roll side to be negative between the toner regulating roll and the developing roll. In terms of material, a large charge amount was obtained when the toner regulating roll was a nickel electroformed tube and the developing roll was a semiconductive rubber.
According to this embodiment, it was confirmed that a predetermined charge amount can be obtained by selecting the material of the toner regulating roll and the developing roll and the bias condition.
Furthermore, the present inventors examined the material of the toner regulating roll and the developing roll, and evaluated the charge amount at that time. As a result, the resistance value range of the toner regulating roll was within the range of 10E + 12 Ω · cm from the conductive region. For example, it was confirmed that charging with a toner regulating roll was possible.
In this case, the conductive region indicates that a metal tube such as nickel electroforming or SUS can be applied. However, in order to apply the conductive region, the developing roll needs to be semiconductive, which allows a bias to be applied between the two, and charging can be performed.

(A) is explanatory drawing which shows the outline | summary of the image forming apparatus which concerns on this invention, (b) is explanatory drawing which shows the outline | summary of the image development apparatus concerning this invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram illustrating an image forming apparatus according to a first embodiment to which a reference invention related to the present invention is applied. 2 is a schematic diagram of a main part of the first embodiment. FIG. FIG. 3 is an explanatory diagram showing a flexible photosensitive member according to the first embodiment. FIG. 6 is an explanatory view showing a photoconductor as a modification of the first embodiment. It is explanatory drawing which shows the developing device which concerns on Embodiment 2 to which this invention was applied . FIG. 6 is a schematic diagram of a main part of a second embodiment. 5 is an explanatory diagram illustrating an image forming apparatus according to Embodiment 3. FIG. FIG. 10 is a schematic diagram of a main part of a third embodiment. 10 is a table showing evaluation results of Example 3. It is explanatory drawing which shows the conventional developing device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Flexible image carrier, 2 ... Developer carrier, 3 ... Scraping member, 4 ... Flexible layer control member

Claims (4)

A developer carrying member for carrying and carrying the developer on the surface;
A rotatable hollow flexible layer regulating member disposed in contact with the developer carrying member to regulate the layer of the developer on the developer carrying member and having at least a contact portion with the developer carrying member having flexibility. When,
A developing device comprising a scraping member that contacts the flexible layer regulating member and scrapes off the developer on the flexible layer regulating member;
Axially effective length W _D of the flexible layer regulating _member, an axial effective length of the developer carrying member when W _E, the effective length of the scraping member and _{W F, W F ≦ W E} <W D A developing device set to satisfy The developing device according to claim 1 ,
The developing device according to claim 1, wherein the scraping member is made of an elastic member. The developing device according to claim 1 ,
The developing device according to claim 1, wherein the flexible layer regulating member includes a circular rigid support that supports inner surfaces of both ends. The developing device according to claim 1 ,
The developing device according to claim 1, wherein the flexible layer regulating member includes a conductive layer at least in a flexible portion.

Images