JP2000194191A - Developing device, process cartridge and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively prevent an image from becoming faulty because density is changed in a longitudinal direction by uniformizing a gap between a photreceptor drum and a developing sleeve in the longitudinal direction. SOLUTION: By estimating that the developing sleeve 5 is deflected because it is pressed by a supply roller 7, the sleeve 5 is molded in an inverted crown state. Thus, since the gap between the photoreceptor drum and the sleeve 5 is uniformized in the longitudinal direction, the image is effectively prevented from becoming faulty because the density is changed in the longitudinal direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic image forming apparatus such as a copying machine or a page printer, a developing device used in the image forming apparatus, and a process cartridge.

[0002]

2. Description of the Related Art First, a general electrophotographic image forming apparatus will be described with reference to FIG.

The image forming apparatus of this embodiment has a photosensitive drum 20 as a latent image carrier, and a charging device 21 for uniformly charging the photosensitive drum 20 around the photosensitive drum 20, and an electrostatic charge on the photosensitive drum 20. An exposure device 22 for forming a latent image, a developing device 1 for converting an electrostatic latent image formed on the photosensitive drum 20 into a visible image, and a transfer material 25 for converting the visible image formed on the photosensitive drum 20 to a transfer material 25 Transfer device 27 and transfer material 25 for transferring to
A cleaning device 29 for removing the toner not transferred to the photosensitive drum 20 from the photosensitive drum 20 is provided.

The developing device 1 is a storage container 3 for storing a toner 6 as a developer, and is provided at an opening of the storage container 3. The developing device 1 is a developer carrier that transports the toner 3 to the photosensitive drum 20. Sleeve 5, toner 3 on developing sleeve 5
And a supply roller 7 that is a developer supply member that removes and supplies the toner 6 on the developing sleeve 5.

The toner 6 is a non-magnetic toner, a magnetic toner, or a mixture of a magnetic carrier and a magnetic or non-magnetic toner.

When the toner 6 is conveyed to the developing unit by the magnetic force of the magnet 23 which is a magnetic field generating means provided inside the developing sleeve 5 and the rotational force of the developing sleeve 5,
In a state where an appropriate amount of toner coat is formed by the developer regulating member 4, the toner is supplied to a developing unit facing the photosensitive drum 20. At this time, a bias is applied to the developing sleeve 5 from the high voltage generation circuit 24.

The transfer material 25 is fed to the transfer section by a feed roller 26, and a visible image (toner image) on the photosensitive drum 20
Is transferred to the transfer material 25 by the operation of the transfer device 27. Thereafter, the transfer material 25 is conveyed to a fixing device 28, where the visible image is fixed, and is discharged outside the apparatus.

On the other hand, after the transfer, the photosensitive drum 20 is removed by a cleaning device 29 with a cleaning blade 30 to remove the remaining toner, is stored in a waste toner container 31, and is used for the next image formation. You.

FIG. 6 shows the developing device 1 and the photosensitive drum 2
FIG. 2 is a diagram of the “0” viewed from directly above. The developing sleeve 5 is rotatably supported at both ends by bearings (not shown).
The developing sleeve 5 is disposed in contact with the photosensitive drum 20 at both ends via SD rollers 8 as gap holding members, and is pressed in the direction of the photosensitive drum 20 by a spring (not shown). The gap between the drum 20 and the developing sleeve 5 (hereinafter, referred to as “SD gap”) is always kept constant.

[0010]

However, the conventional developing device has the following problems.

A contact-type elastic blade, that is, a developer regulating member 4 and a developer supply roller 7 made of, for example, urethane foam, are in strong contact with the developing sleeve 5.

Both ends of the developing sleeve 5 are bearings or SD rollers 8
However, since the central portion is constantly exerted by the elastic blade 4 and the developer supply roller 7 from the inside to the outside (toward the photosensitive drum 20) of the developing device 1, the shape and material of the developing sleeve 5 In some cases, the developing sleeve 5 may be bent toward the photosensitive drum 20. In particular, when a small-diameter developing sleeve is used for the purpose of miniaturization of A3-size paper or a device having a larger size in the longitudinal direction, the bending becomes more remarkable.

When the developing sleeve 20 bends in this manner, the developing sleeve 20 comes closer to the photosensitive drum 20 from the end at the center, so that the SD gap is not uniform in the longitudinal direction of the developing area. When the SD gap is not uniform,
Naturally, the electric field intensity of the developing bias applied for developing the toner is different between the center and the end, so that the density at the center becomes higher than at the end, or the fog is deteriorated at the center. Problems may occur.

Accordingly, an object of the present invention is to provide an image forming apparatus in which the gap between the latent image carrier and the developer carrier is made uniform in the longitudinal direction, and image defects due to density changes in the longitudinal direction can be effectively prevented. To provide.

[0015]

The above object is achieved by a developing device, a process cartridge and an image forming apparatus according to the present invention. In summary, the present invention relates to a developer carrier for conveying a developer, which is disposed opposite a latent image carrier for carrying an electrostatic latent image, and a developer for supplying the developer to the developer carrier. A supply member, and a developer regulating member that regulates an amount of developer carried by the developer carrier, wherein the developer carrier is disposed at a predetermined distance from the latent image carrier, and In the developing device, the developer supply member is disposed so as to substantially face the developer carrier, and the developer carrier has an inverted crown shape.

According to another aspect of the present invention, at least one of the latent image carrier, the charging device, and the cleaning device is integrated with the developing device, and is configured to be detachable from the main body of the electrophotographic image forming apparatus. In the process cartridge, the developing device is disposed to face a latent image carrier for carrying an electrostatic latent image, and a developer carrier for transporting the developer, and a developing device for supplying the developer to the developer carrier. A developer supply member, and a developer regulating member that regulates an amount of developer carried by the developer carrier, wherein the developer carrier is disposed at a predetermined distance from the latent image carrier, and A process cartridge is provided in which a developer supply member is disposed so as to substantially face the developer carrier, and the developer carrier has an inverted crown shape.

According to another aspect of the present invention, there is provided a latent image carrier for carrying an electrostatic latent image, the developer carrier being opposed to the latent image carrier, and for transporting the developer, A developer supply member that supplies a developer to the developer carrying member; and a developer regulating member that regulates an amount of developer carried by the developer carrying member. An image forming apparatus which is disposed at a predetermined distance from the developer carrying member, and wherein the developer supply member is disposed so as to substantially face the developer carrying member. An image forming apparatus having a crown shape is provided.

In the above invention, the developer carrying member has a configuration in which a resin coat layer is provided on a metal sleeve tube, and a coating thickness at an end portion of the resin coat layer is made thicker than a center. It is preferable that the shape of the developer carrying member is formed in an inverted crown shape. Preferably, the developer supply member has a crown shape. It is preferable that the developer regulating member regulates the developer by coming into contact with the developer carrying member, and the pressing force of the developer regulating member against the developer carrying member is reduced at an end. The developer regulating member regulates the developer by coming into contact with the developer carrier, and the distance from the nip portion to the free end of the developer regulating member with the developer carrier is uniform in the longitudinal direction. It is preferred that

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a developing device, a process cartridge and an image forming apparatus according to the present invention will be described in more detail with reference to the drawings. In the following description, the present invention is described as being embodied in the image forming apparatus of FIG. Therefore, description of the overall configuration and functions of the image forming apparatus will be omitted, and only the features of the present invention will be described. The same members as those described above are denoted by the same reference numerals.

Embodiment 1 A first embodiment of the present invention will be described with reference to FIG. 1 and FIG.

As shown in FIG. 6, the photosensitive drum 20 as an image carrier and the developing sleeve 5 as a developer carrier are arranged in parallel and close to each other. In this embodiment, the distance (SD gap) between the photosensitive drum 20 and the developing sleeve 5 is 290.
μm. The developing sleeve 5 has an outer diameter of about 16 mm and an inner diameter of 1
It is a 4.5 mm long, 330 mm long hollow aluminum sleeve base tube.

A developer supply roller 7, which is provided with urethane foam around a cored bar and is substantially opposed to the photosensitive drum 20, is in contact with the developing sleeve 5. The amount of penetration of the developer supply roller 7 into the developing sleeve 5 is 1.5 mm, and the contact pressure per unit length is about 80 g / cm.

In this configuration, the amount of deflection at the center of the developing sleeve 5 (the SD gap between the end and the center) is about 60.
It is about μm. For this reason, the image density is high at the center,
Fogging tended to be worse at the center.

Therefore, two developing sleeves 5 each having an inverted crown shape as shown in FIG. 1 are prepared, and one of the developing sleeves 5 has an inverted crown amount (difference between the maximum outer diameter and the minimum outer diameter) of 100 μm and the other has a reverse crown amount of 20 μm.
It was 0 μm. Note that these developing sleeves 5 were obtained in a desired shape by grinding a straight aluminum sleeve tube.

These developing sleeves 5 were mounted on the developing device 1 shown in FIG. 6, and the amount of deflection (μm) was measured, an image was formed, and the density unevenness in the longitudinal direction and fog at the center were observed. However, the results shown in Table 1 below were obtained.

[0026]

[Table 1] From Table 1, by making the developing sleeve 5 an inverted crown shape, the SD gap is kept almost uniform in the longitudinal direction.
It was found that the unevenness in the longitudinal direction of density and fog can be improved.

The amount of deflection of the developing sleeve 5 is substantially determined by the structure of the developing device. The most appropriate inverse crown amount is most preferably a value that can correct the amount of deflection when a straight developing sleeve is inserted, that is, a value close to a multiple of the amount of deflection. If the amount of the inverse crown is too small, the desired effect is reduced, and if the amount is larger than necessary, the S at the center is reversed.
Since the D gap is opened, the density unevenness in the longitudinal direction tends to be worse again.

In this embodiment, the case where the amount of deflection of the developing sleeve is about 60 μm is described by taking a developing device of A4 horizontal size as an example, but the present invention is not limited to the numerical value of this embodiment. The amount of deflection of the developing sleeve varies depending on the configuration of the developing device, the length in the longitudinal direction, the material of the sleeve, and the like, and the effect of the present invention can always be obtained by appropriately selecting the amount of reverse crown of the developing sleeve. it can.

Embodiment 2 In the second embodiment, the inverse crown-shaped developing sleeve 5 described in the first embodiment is used, and a crown-shaped developer supply roller (developer (Member) 7 is brought into contact. FIG. 2 shows the developer supply roller 7 of this embodiment.

According to the structure of this embodiment, the developing sleeve 5
The developer supply roller 7 comes into contact along the surface shape of the developer supply roller, so that the contact pressure of the developer supply roller 7 does not change between the central portion and the end portion, and stable performance is exhibited. Can be.

Embodiment 3 In the third embodiment, when the developing sleeve 5 having the inverted crown shape described in the first embodiment is used, the contact pressure of the developing blade 4 as the developer regulating member is reduced at the central portion. The end is configured to be larger than the end.

According to this embodiment, even when the developing sleeve 5 has an inverted crown shape and the contact distance with the developing blade 4 slightly changes in the longitudinal direction, the blade contact pressure is uniform in the longitudinal direction. , And stable toner coating can be performed.

The free length of the developing blade 4, that is, the length from the nip portion to the developing sleeve 5 to the free end, may be configured such that the central portion is longer than the end portion. Since the developing blade 4 comes into contact with the surface shape of the developing sleeve 5, the length of the nip end (NE) does not change between the central portion and the end portion, and more stable toner coating can be performed. Can be.

Embodiment 4 In the fourth embodiment, an inverted crown shape of a developing sleeve is realized by adjusting the coating thickness of a coating layer in a developing sleeve having a surface coated with a resin.

Specifically, the surface of a straight aluminum sleeve tube was coated with a phenol resin sprinkled with carbon and graphite with a dispersant.
FIG. 3 shows a configuration of the developing sleeve 5 according to the present embodiment. The coating thickness of the coating layer 5a is 10 μm at the center and 60 μm at the end.
μm, and finally a developing sleeve 5 having an inverse crown amount of 100 μm was obtained.

In this embodiment, all the effects described in the first embodiment can be realized, and there is a merit that the manufacturing can be performed more easily and inexpensively since a straight sleeve tube can be used.

Embodiment 5 In the fifth embodiment, the developing sleeve 5 described in the fourth embodiment is used.
When an inverted crown-shaped sleeve molded by adjusting the coating thickness of the surface resin coat layer 5a is used, the crown-shaped supply roller 7 is brought into contact with the sleeve.

The crown amount of the supply roller 7 is desirably about the same as the reverse crown amount of the developing sleeve 5.

According to this embodiment, since the developer supply roller 7 comes into contact with the surface of the developing sleeve 5, the contact pressure of the developer supply roller changes between the center and the end. It is possible to exhibit a stable performance without being lost.

Embodiment 6 In the sixth embodiment, the developing sleeve 5 described in the fourth embodiment is used.
When the reverse crown-shaped developing sleeve 5 formed by adjusting the coating thickness of the surface resin coat layer 5a is used, the contact pressure of the developing blade is higher at the center than at the ends. It is characterized by having done.

According to the structure of this embodiment, even if the developing sleeve 5 has an inverted crown shape and the contact distance with the developing blade 4 slightly changes in the longitudinal direction, the blade contact pressure is uniform in the longitudinal direction. , And stable toner coating can be performed.

The free length of the developing blade 4 may be configured such that the central portion is longer than the end portion. Since the developing blade 4 comes into contact with the surface shape of the developing sleeve 5, the length of the nip end (NE) does not change between the central portion and the end portion, and more stable toner coating can be performed. Can be.

Embodiment 7 In the seventh embodiment, at least the developing device described in the first to sixth embodiments, the electrophotographic photosensitive member (photosensitive drum) 7, and the charging as a process means acting on the electrophotographic photosensitive member 20 are described. A process cartridge in which at least one of the device 21 and the cleaning device 29 is integrally formed is detachable from the image forming apparatus main body.

FIG. 5 is a sectional view of the process cartridge according to this embodiment.

The developing unit (developing device) 1 includes a developing blade 4 as a developer regulating member, a developing sleeve 5 as a developer carrier, a hopper 3 for storing toner 6 as a developer, and a developing sleeve. And a supply roller 7 for stripping and supplying the toner 6 on the supply roller 5.

The charging cleaning unit 2 includes an electrophotographic photosensitive member 20 serving as a latent image carrier, a charging device 21 for uniformly charging the electrophotographic photosensitive member 20, and an electrophotographic photosensitive member 20. The cleaning device includes a cleaning blade 30 for removing the toner from the photoconductor 20 and a waste toner container 31.

According to this embodiment, by employing the above-described structure, the effects described in the first and second embodiments can be obtained. This can be easily performed without soiling the surroundings with the toner.

Accordingly, the maintainability of the image forming apparatus is significantly improved. Further, by replacing the process cartridge, important components of the electrophotography are replaced with new ones, so that a high-quality image can always be obtained.

[0049]

As is apparent from the above description, according to the developing device, the process cartridge and the image forming apparatus of the present invention, the developer carrying member of the developing device has an inverted crown shape so that the latent image can be carried. By making the gap between the developer and the developer carrying member uniform in the longitudinal direction, it is possible to effectively prevent image defects due to a change in density in the longitudinal direction, and to obtain a high-quality image.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a developing sleeve according to a first embodiment.

FIG. 2 is an explanatory diagram illustrating a supply roller according to a second embodiment.

FIG. 3 is an explanatory diagram illustrating a developing sleeve according to a fourth embodiment.

FIG. 4 is a configuration diagram illustrating a process cartridge according to a seventh embodiment.

FIG. 5 is a configuration diagram illustrating an example of a conventional image forming apparatus in which the present invention is embodied.

FIG. 6 is a plan view showing an example of a conventional developing device in which the present invention is embodied.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 developing device 4 developing blade (developer regulating member) 5 developing sleeve (developer carrying member) 7 supply roller (developer supplying member) 20 photosensitive drum (electrophotographic photosensitive member / latent image carrying member) 21 charging device 27 transfer device 29 Cleaning device

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasunari Watanabe 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Kazuhisa Tsurugimo 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon F term in the company (reference) 2H077 AC04 AD06 AD13 AD17 BA07 BA09 EA13 FA22 FA26

Claims (15)

[Claims] 1. A developer carrying member which is arranged opposite to a latent image carrying member for carrying an electrostatic latent image and carries a developer, and a developer supply member which supplies a developer to the developer carrying member. A developer regulating member that regulates the amount of developer carried by the developer carrying member, wherein the developer carrying member is disposed at a predetermined interval from the latent image carrying member, and the developer supply member is A developing device arranged so as to be substantially opposed to a developer carrier, wherein the developer carrier has an inverted crown shape. 2. The developing device according to claim 1, wherein the developer carrier has a structure in which a resin coat layer is provided on a metal sleeve tube. 2. The developing device according to claim 1, wherein the developer carrier is formed in an inverted crown shape. 3. The developing device according to claim 1, wherein said developer supply member has a crown shape. 4. A structure in which the developer regulating member regulates the developer by contacting the developer carrier, and the pressing pressure of the developer regulating member against the developer carrier is reduced at an end. The developing device according to claim 1 or 2, wherein 5. The developer regulating member regulates the developer by coming into contact with the developer carrying member, and a distance from a nip portion of the developer regulating member to the developer carrying member to a free end is equal to 3. The developing device according to claim 1, wherein the developing device is uniform in the longitudinal direction. 6. A process cartridge wherein at least one of a latent image carrier, a charging device, and a cleaning device is integrated with a developing device and is configured to be detachable from an electrophotographic image forming apparatus main body. A developer carrying member arranged to face a latent image carrying member for carrying an electrostatic latent image and transporting a developer, a developer supplying member for supplying a developer to the developer carrying member, and the developer A developer regulating member that regulates an amount of developer carried by the carrier, wherein the developer carrier is arranged at a predetermined distance from the latent image carrier, and the developer supply member is A process cartridge, which is disposed so as to be substantially opposed to a carrier, wherein the developer carrier has an inverted crown shape. 7. The developer carrier has a configuration in which a resin coat layer is provided on a metal sleeve base tube, and the coating thickness of an end portion of the resin coat layer is made thicker than the center, whereby the development is performed. 7. The process cartridge according to claim 6, wherein the shape of the agent carrier is formed into an inverted crown shape. 8. The process cartridge according to claim 6, wherein said developer supply member has a crown shape. 9. A structure in which the developer regulating member regulates the developer by coming into contact with the developer carrying member, and a pressing pressure of the developer regulating member against the developer carrying member is reduced at an end. The process cartridge according to claim 6 or 7, wherein . 10. The developer regulating member regulates the developer by coming into contact with the developer carrying member, and a distance from a nip portion of the developer regulating member to the developer carrying member to a free end is equal to 7. Uniform in the longitudinal direction.
Or 7 process cartridge. 11. A developer carrier having a latent image carrier for carrying an electrostatic latent image, disposed opposite to the latent image carrier, for transporting a developer, and a developer provided on the developer carrier. And a developer regulating member that regulates the amount of developer carried by the developer carrier, wherein the developer carrier is disposed at a predetermined distance from the latent image carrier. Wherein the developer supply member is provided with a developing device disposed so as to substantially face the developer carrier, wherein the developer carrier has an inverted crown shape. Image forming apparatus. 12. The developer carrier has a configuration in which a resin coat layer is provided on a metal sleeve base tube, and the coating thickness of an end portion of the resin coat layer is made thicker than the center.
The image forming apparatus according to claim 11, wherein the developer carrier is formed into an inverted crown shape. 13. The image forming apparatus according to claim 11, wherein said developer supply member has a crown shape. 14. A structure in which the developer regulating member regulates the developer by coming into contact with the developer carrier, and the pressure of the developer regulating member against the developer carrier is reduced at the end. The image forming apparatus according to claim 11, wherein: 15. The developer regulating member regulates the developer by coming into contact with the developer carrier, and a distance from a nip portion of the developer regulating member to the developer carrier to a free end is equal to 2. The method according to claim 1, wherein the first layer is uniform in the longitudinal direction.
The image forming apparatus according to 1 or 12.