JP2000267439A - Spacing holding member and developing device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To diminish rolling deformation in spite of repetitive exertion of compressive stress by using annular spacing holding members (spacer rollers) formed of material consisting of polybutyrene terephthalate(PBT) as base material. SOLUTION: The spacer rollers 60 to be freely rotatably mounted at both ends of a developing roller are formed of the material prepared by adding 15 pts.wt. potassium titanate fibers to 85 pts.wt. PBT and include abutment parts 61 which abut on a photosensitive drum and position regulating parts 62 for regulating the position in the thrust direction with respect to the developing roller by colliding against the end faces of the developing roller. The developing roller is pressed in the photosensitive drum direction by the effect of compression springs and at this time, the abutment parts 61 of the spacer rollers 60 are inserted between the developing roller and the photosensitive drum to stably maintain the spacing between the developing roller and the photosensitive drum at a prescribed value. The abutment parts 61 of the spacer rollers 60 abut on the photosensitive layer of the photosensitive drum.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using an electrophotographic technique, such as a laser printer, a copying machine, and a facsimile, and more particularly to a member for maintaining a gap between an image carrier and a developer carrier.

[0002]

2. Description of the Related Art (Description of Electrophotographic Technology) In an image forming apparatus 1 using electrophotographic technology as shown in FIGS. 2 and 3, an image carrier is charged uniformly by a charging device 30. A latent image is formed on the photosensitive drum 20 by selectively exposing the photosensitive drum 20 with the exposure device 3, the latent image is developed with a developer (toner) T, and the developed image is
The image is recorded by transferring the image onto the recording medium P, such as, for example, and then fixing the transferred image on the recording medium P with heat and pressure by the fixing device 9. After completing the image transfer process, the photosensitive drum 20
After the residual toner is removed by the cleaning device 50, the cleaning device 50 is subjected to an image forming process starting from charging again.

(Description of Photosensitive Drum) As the photosensitive drum 20 used in such an image forming apparatus, a conductive base material such as aluminum as shown in FIG. 22 is known which is coated with a photoconductive material. As a photoconductive material,
Inorganic photoconductive materials such as selenium, cadmium sulfide, and zinc oxide, or organic photoconductive materials such as polyvinyl carbazole, oxadiazole, and phthalocyanine have been used. In particular, when an organic photoconductive material is used, the charge generation layer 22a and the charge transport layer 22b are used for sensitization.
It is known to use a function-separated type photosensitive layer 22 in which a layer is laminated. As the charge transport layer 22b serving as a surface layer, a layer using polycarbonate as a binder has been put to practical use.

(Description of Developing Apparatus) As the developing apparatus 40, a toner chamber 45 containing a developer (toner) T as shown in FIG. 3, a developer supply chamber 44, and a developer carrier (developing roller) ) 41 and a developer regulating member (developing blade) 42 have been put to practical use.

[0005] The developing roller 41 is formed of a conductive material such as aluminum and is rotatably held from the photosensitive drum 20 with a predetermined gap, preferably a gap of 0.2 mm to 0.5 mm. The developing roller 41 further includes a magnet roller 43 having a plurality of magnetic poles therein.
Built-in. The magnet roller 43 is non-rotatably held by the developing device frame 46 as shown in FIG.

The developing blade 42 is fixed to the developing device frame 46 such that one end of the developing blade 42 is pressed against the outer peripheral surface of the developing roller 41.

(Description of Developing Process) As shown in FIG. 3, the toner T in the toner chamber 45 is transferred from the toner chamber 45 to the developer supply chamber 4 by its own weight or by a conveying means (not shown).
4 and is attracted to the vicinity of the developing roller 41 by the magnetic force of the magnet roller 43. The toner T conveyed to the vicinity of the developing roller 41 is conveyed toward the developing blade 42 by the rotation of the developing roller 41,
Thus, the sheet is conveyed in the direction of the photosensitive drum 20 with its thickness regulated. Here, a predetermined charge is applied to the toner T of which the layer thickness is regulated when passing through the nip between the developing blade 42 and the developing roller 41.

(Explanation of Spacer Roller) In the above-described developing device 40, a means for stably holding the developing roller 41 and the photosensitive drum 20 at a predetermined interval is made of polyacetal, and is described in FIGS. As described above, for example, a substantially cylindrical interval holding member (spacer roller) 60 having a thickness of 0.2 mm to 0.5 mm is rotatably fitted to both ends of the developing roller 41, and a compression spring 54 serving as an urging means is provided. A device in which the developing roller 41 is pressed in the direction of the photosensitive drum 20 has been devised and put to practical use. FIG. 1 shows two representative examples.

(Explanation of Process Cartridge) In such an image forming apparatus 1, when the image forming apparatus 1 has been used for a long time, replenishment of the toner T and adjustment, cleaning and replacement of various process means such as the photosensitive drum 20 are required. Required. Performing such maintenance work has been practically difficult except for service personnel having specialized knowledge.

As means for solving this problem, toner T
And process means such as the photosensitive drum 20, the developing device 40, the charging device 30, and the cleaning device 50,
For example, as shown in FIG. 2, a unit having improved maintainability by decomposing the process cartridge 2 into a unit as the process cartridge 2 and making the process cartridge 2 detachable from the image forming apparatus 1 has been devised and put into practical use.

[0011]

SUMMARY OF THE INVENTION Recent image forming apparatus 1
With the widespread use of the image forming apparatus, the image forming apparatus (apparatus main body) 1 is required to be smaller, quieter, and lower in cost. Research has been made on elimination of an exhaust fan as a means of silencing and low coasting, and as another means of reducing cost, changing the main body frame 1a from one made of sheet metal to one integrally molded with resin.・ It has been put to practical use. However, in order to reduce the size and noise of the apparatus main body 1 and to reduce the cost, the image forming apparatus 1 using the conventional spacer roller 60 has the following problems.

The apparatus main body 1 includes various heat sources such as the fixing device 9 described above. If an attempt is made to reduce the size of the apparatus main body 1, the temperature inside the apparatus main body 1 tends to rise, and in particular, the exhaust fan In the main body 1 having no device, the temperature inside the main body 1 is easily increased.

On the other hand, a compressive stress is repeatedly applied to the spacer rollers 60. Therefore, when the apparatus body 1 is downsized or the exhaust fan is omitted, the spacer rollers 6
0 is repeatedly subjected to compressive stress under high temperature conditions. In the case of the apparatus using the spacer roller 60 shown in FIG. As a result, there is a possibility that an appropriate interval cannot be maintained due to long-term use.

The outer peripheral side of the spacer roller 60 is normally pressed against the photosensitive layer 22 of the photosensitive drum 20. Here, the spacer roller 60 and the photosensitive layer 22 are repeatedly brought into contact with each other.
The outer peripheral surface of the spacer roller 60 is in an environment that is easily charged due to the separation and rubbing.

On the other hand, in the photosensitive drum 20, it is preferable that the photosensitive layer 22 is short in terms of manufacturing process and cost.
As described above, it is preferable that the base material 21 of the photosensitive drum 20 be exposed without providing the photosensitive layer 22 in an end region not involved in image formation.

For this reason, the surface of the spacer roller 60 may be charged, and the charge may be discharged to the exposed substrate portion 21a of the photosensitive drum 20 to emit an electric field radiation voltage. In some cases, the electric field radiation voltage might penetrate through the resin frame and be radiated out of the apparatus main body. Therefore, depending on the combination of the spacer roller 60 and the photosensitive layer 22, in order to prevent the electric field emission voltage from being radiated to the outside of the device main body 1, the device main body 1 may be provided with a sheet metal part for shielding, etc. It is necessary to provide a shield, which hinders cost reduction of the apparatus main body 1.

An object of the present invention is to provide a spacing member that has small rolling deformation even when compressive stress is repeatedly applied.

It is another object of the present invention to provide an interval maintaining member that causes less discharge between the contact portion of the interval maintaining member and the exposed portion of the substrate of the photosensitive drum.

Another object of the present invention is to provide a developing device and a process cartridge using such a spacing member.

[0020]

The present inventors have conducted intensive studies in view of the above-mentioned circumstances, and as a result, have found that in an image forming apparatus in which a developing roller and a photosensitive drum are held at a predetermined interval, the developing roller and the photosensitive drum are separated. As a means to keep the interval constant,
By using an annular spacing member (spacer roller) formed of a material based on polybutylene terephthalate (PBT), it is possible to use a spacer roller that is not easily rolled and deformed and wear even at high temperature conditions and is not easily triboelectrically charged. As a result, the present inventors have found that the size, quietness, and low cost of the apparatus main body can be realized, and have reached the present invention.

That is, according to the present invention, the distance between the image carrier and the cylindrical portion of the developer carrier of the image forming apparatus having at least the image carrier and the developer carrier rotatably held in a cylindrical shape is maintained. The spacing member is provided with a material comprising at least a polybutylene terephthalate resin and a reinforcing material.

As the polybutylene terephthalate resin used for forming the spacing member, those commercially available as plastic molding materials can be widely used. For example, UBE PBT (trade name, manufactured by Ube Industries), Hauser (trade name, manufactured by Kuraray), Sumicon FM
(Trade name, manufactured by Sumitomo Bakelite), Planac (trade name, manufactured by Dainippon Ink), Teijin PBT (trade name, manufactured by Teijin), Krastin (trade name, manufactured by Dupont), Toray PB
T resin (trade name, manufactured by Toray), NOVADUR (trade name,
Mitsubishi Engineering Plastics), Toughpet PBT (trade name, manufactured by Mitsubishi Rayon) and the like.

The reinforcing material enhances the strength of the polybutylene terephthalate resin, and includes an organic reinforcing material and an inorganic reinforcing material.

In the present invention, the spacing member is more preferably formed of a material comprising at least a polybutylene terephthalate resin, a reinforcing material, and a lubricant.

According to the present invention, there is also provided a developing device capable of acting on an image carrier including at least a frame and a developer carrier having a cylindrical main part, wherein the developer carrier is provided near both ends of the developer carrier. And a developing device having the distance maintaining member.

According to the present invention, there is further provided a developer carrier disposed in a developer supply chamber, which is rotated to rotate the peripheral surface of the developer carrier into contact with the peripheral surface of the image carrier to thereby carry the developer carried on the peripheral surface of the developer carrier. To
A developing unit including the developing chamber, the developer carrier, and the image carrier is incorporated in a cartridge body so as to transfer to an electrostatic latent image on the peripheral surface of the image carrier, and is removably loaded into the image forming apparatus body. The process cartridge according to claim 1, wherein the spacing member is provided near both ends of the developer carrier.

[0027]

BEST MODE FOR CARRYING OUT THE INVENTION As the organic reinforcing material, the inorganic reinforcing material and the lubricant used in the above-mentioned spacing member of the present invention, a wide range can be adopted. Aramid fiber etc.
The inorganic reinforcing material is preferably mica or potassium titanate fiber, and the lubricating oil is preferably polytetrafluoroethylene, molybdenum sulfide, ultrahigh molecular weight polyethylene, or the like.

The addition amount of the above-mentioned organic and inorganic reinforcing materials is usually in the range of 5 to 50 parts by weight based on 100 parts by weight of the polybutylene terephthalate resin, and the lubricant is usually in the range of 5 to 30 parts by weight. is there. When the organic and inorganic reinforcing materials are fibers, they are used in the form of long fibers and / or short fibers.

Although any method can be used to form the spacing member from a mixture of these materials, an injection molding method is generally employed.

[0030]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First, an overall configuration of an image forming apparatus and a process cartridge according to the present invention will be described, and then a developing device will be described.

(Overall Configuration) FIG. 2 schematically shows an image forming apparatus 1 and a process cartridge 2 according to the present invention. The image forming apparatus 1 is a laser printer using an electrophotographic technique in which a process cartridge 2 is detachably mounted.

When the process cartridge 2 is mounted on the main body 1 of the image forming apparatus, an exposure device (laser scanner unit) 3 is disposed above the process cartridge 2 and is located on the inner side of the process cartridge 2 (right side in FIG. 2). Is a recording medium (sheet material) P on which an image is to be formed.
The sheet tray 4 that accommodates the sheets is arranged. further,
In the image forming apparatus main body 1, a sheet feeding roller 5, a transfer guide 6, a transfer charging roller 7, a transfer guide 8, a fixing device 9, a sheet discharge roller pair 10, a sheet discharge The tray 11 and the like are arranged on the apparatus main body frame 1a made of resin.

(Configuration of Process Cartridge) As shown in FIGS. 3 and 4, the process cartridge 2 includes an image carrier (photosensitive drum) 20, a charging device 30, and a developing device 4.
0 and a cleaning device 50 are integrally accommodated. Photosensitive drum 20 and charging device 30
Is attached to the cleaning frame 51 of the cleaning device 50. Holes 51 a are provided in the side plates at both ends of the cleaning frame 51. On the other hand, the developing device 40 has a coupling arm 48 having coupling holes 48a near both ends.

A coupling shaft 70 is provided between the hole 21a and the coupling hole 48a.
Are penetrated, and the developing device 40 is rotatably attached to the cleaning frame 51. Further, between the developing device 40 and the cleaning frame 51, a compression spring 5 serving as an urging means is provided.
4, and the developing device 40 is urged clockwise in FIG.

The process cartridge 2 may include at least the photosensitive drum 20 and the developing device 40.

(Explanation of Image Forming Process) Next, the outline of image formation will be described. Based on the print start signal, the photoconductor 20 is driven to rotate at a predetermined peripheral speed (process speed) in the direction of arrow K1. Photosensitive drum 20
A charging device 30 to which a bias voltage is applied is in contact with the outer peripheral surface of the photosensitive drum 20, and the outer peripheral surface of the photosensitive drum 20 is uniformly and uniformly charged by the charging device 30.

The laser beam L modulated in accordance with the time-series electric digital image signal of the target image information is output from the laser scanner unit 3, and is exposed through the exposure window 53 on the upper surface of the process cartridge 2.
Light enters the outer peripheral surface of the photosensitive drum 20 (photosensitive layer 22)
Is exposed by scanning. As a result, an electrostatic latent image corresponding to the target image information is formed on the outer peripheral surface (photosensitive layer) of the photosensitive drum 20. The thickness of the electrostatic latent image is regulated by a developer regulating member (developing blade) 42 of the developing device 40 and a developer (toner) T applied on a developer carrier (developing roller) 41 as a toner image. Developed.

On the other hand, the sheet material P is fed from the sheet tray 4 by the feed roller 5 at the same time as the output of the laser light L, and is transferred via the transfer guide 6 to the photosensitive drum 20 and the transfer charging roller 7. The timing is supplied to the transfer position between. At this transfer position, the toner image is sequentially transferred from the photosensitive drum 20 to the sheet material P.

The sheet material P on which the toner image has been transferred is separated from the photosensitive drum 20, conveyed to the fixing device 9 along the conveyance guide 8, and passes through the nip between the fixing roller 9a and the pressure roller 9b. The toner image is fixed on the sheet material P by performing a pressure / heat fixing process in the nip portion.
The sheet material P that has been subjected to the toner image fixing process is conveyed to the paper discharge roller pair 10 and discharged to the paper discharge tray 11.

On the other hand, the residual toner on the outer peripheral surface of the photoreceptor 20 after the transfer is removed by the cleaning device 50.
Again, it is subjected to image formation starting from charging.

(Structure of Photosensitive Drum)
It is composed of an aluminum cylindrical base material 21 and a photosensitive layer 22 coated on the outer peripheral surface of the base material 21.
The photosensitive layer 22 is formed by laminating a charge generation layer 22a using an organic photoconductive material such as polyvinyl carbazole, oxadiazole, phthalocyanine and the like, and a charge transport layer 22b using polycarbonate as a binder.

As shown in FIG. 5, the photosensitive layer 22 is applied only to the image forming area and the area including the abutting portion of the spacer roller 60.
There is.

The photosensitive drum 20 has a drum gear 23 fixed at one end and a drum flange 2 at the other end.
4 is fixed. Ground sheet metal 25 is attached to drum flange 24.
Is attached. A part of the ground sheet metal 25 is in contact with the base material 21, and is further electrically grounded to the drum shaft 26 by ground means (not shown).

(Structure of Developing Apparatus) Next, the developing apparatus 40 will be described with reference to FIG.

The developing device 40 includes a toner chamber 45 containing a developer (toner) T, a developer supply chamber 44, a developer carrier (developing roller) 41, and a developer regulating member (developing blade) 42. It consists of.

The developing roller 41 is obtained by applying a carbon coating (not shown) to an aluminum cylindrical member, and has a sleeve gear 47 attached to one end thereof.
And is rotatably held with respect to. Spacer rollers 60 are rotatably fitted to both ends of the developing roller 41. Inside the developing roller 41, a magnet roller 43 having a plurality of magnetic poles is arranged. The magnet roller 43 is held non-rotatably with respect to the developing device frame 46. On the other hand, the developing blade 42 is fixed to the developing device frame 46 such that one end side thereof is pressed against the outer peripheral surface of the developing roller 41.

(Structure of Spacer Roller) Developing Roller 41
Spacer roller 60 rotatably attached to both ends of
Is made of a material obtained by adding 15 parts by weight of potassium titanate fiber to 85 parts by weight of polybutylene terephthalate (trade name: manufactured by Polyplastics, Inc.), and as shown in FIG. The image forming apparatus includes a contact portion 61 that comes into contact therewith and a position regulating portion 62 that abuts against an end surface of the developing roller 41 and regulates a position in the thrust direction with respect to the developing roller 41. In particular, the spacer roller 60 in the embodiment is a thin molded body having an inner diameter of 12 mm, and the thickness of the contact portion 61 is, for example, 0.2 mm to 0.5 mm, and about 0.3 mm in the example.

(Detailed Description of Spacer Roller) In the state of the process cartridge 2, the developing roller 41 is pressed toward the photosensitive drum 20 by the action of the compression spring 54. At this time, the contact portion 61 of the spacer roller 60 is developed. Roller 4
1 and the photosensitive drum 20, the developing roller 4
The distance between 1 and the photosensitive drum 20 is stably maintained at a predetermined value. Here, the contact portion 61 of the spacer roller 60 contacts the photosensitive layer 22 of the photosensitive drum 20. Further, the sleeve gear 47 and the drum gear 23 mesh with each other to form a gear train.

During operation of the image forming apparatus, the photosensitive drum 20 is driven to rotate in the k1 direction by a gear (not shown), and the developing roller 41 is driven to rotate in the k2 direction by a gear train. 20 k
With the rotation in one direction and the rotation of the developing roller 41 in the k2 direction, the developing roller 41 rotates in the k2 direction. On the other hand, during operation of the image forming apparatus, the fixing unit 9, the laser scanner unit 3, the controller (not shown), and the like generate heat. This heat is stored inside the apparatus main body 1. Therefore, a compressive stress is repeatedly applied to the contact portion 61 of the spacer roller 60 under a high temperature condition (40 to 50 ° C. in the image forming apparatus of the present embodiment).

In the spacer roller 60 formed of PBT and potassium titanate fiber according to the present invention, the rolling resistance and abrasion resistance are significantly improved as compared with the conventional spacer coro formed of polyacetal (POM). Specifically, using a 1.5 mm-wide spacer roller of the contact portion 61, the image forming apparatus 1 of the present embodiment converts the letter paper to 2,
When 500 sheets were printed, the conventional POM spacer roller 60 was deformed in addition to the thickness change of 5.5 μm, whereas the spacer roller 60 formed of PBT and potassium titanate fiber of the present invention was deformed. 1.7 change in wall thickness
μ, and no deformation was observed.

On the other hand, in the image forming apparatus in which the substrate exposed portion 20a is provided at the end of the photosensitive drum 20 as in this embodiment, the contact portion 61 of the spacer roller 60 is 20 charge transport layer 22 of photosensitive layer 22
The surface of the abutting portion 61 of the spacer roller 60 is charged by abutting and rubbing against the surface b, and the charge is discharged toward the substrate exposed portion 21a of the photosensitive drum 20 to generate an electric field emission voltage. .

In this embodiment, the spacer rollers 60
The distance from the contact portion 61 to the substrate exposed portion 21a is 2.0
from 2.5 mm to 2.5 mm.
It has been found that an electric field emission voltage in a frequency band centered on 0 MHz may be generated. In this embodiment, the spacer roller 60 is made of PBT as a base material,
The field emission voltage value can be suppressed. For example, it is known that the durability of the spacer roller formed of polyphenylene sulfide (PPS) is excellent. However, the spacer roller formed of PPS is easily frictionally charged. Generates an electric field emission voltage. Specifically, the peak value of the electric field emission voltage near 560 MHz is equal to the spacer roller 6 formed of PPS.
In the case of 0, it becomes about 48 dBuV / m, while P
In the case of the spacer roller 60 formed of a material based on BT, the noise is suppressed to about 20 dBuV / m or less, which is background noise.

In this embodiment, the spacer roller is made of polybutylene terephthalate (trade name: Duranex) 7
Similar results were obtained when the material was formed by adding 15 parts by weight of mica and 10 parts by weight of polytetrafluoroethylene to 5 parts by weight.

[0054]

As described above, according to the first aspect of the present invention, at least the image carrier and the cylindrical developer carrier are provided, and the image carrier and the developer carrier are fixed to each other. In an image forming apparatus using an electrophotographic technique held at an interval, a material obtained by adding a reinforcing material to polybutylene terephthalate as a means for maintaining the interval between the image carrier and the developer carrier at a predetermined value. The formed spacing member realizes a spacing member that is less likely to undergo rolling deformation and abrasion even in a relatively high temperature environment. As a result, it is possible to reduce the size, quietness, and cost of the image forming apparatus body. I have.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a form of a spacing member, showing two typical examples (a) and (b).

FIG. 2 is a cross-sectional view illustrating the image forming apparatus.

FIG. 3 is a cross-sectional view illustrating a process cartridge.

FIG. 4 is a side view showing the process cartridge.

FIG. 5 is a longitudinal sectional view showing an image carrier and a developer carrier according to an embodiment.

Claims (7)

[Claims] 1. An image forming apparatus having at least an image carrier and a cylindrically rotatably held developer carrier maintains a distance between the image carrier and the cylindrical portion of the developer carrier. Wherein the spacing member is formed of a material comprising at least a polybutylene terephthalate resin and a reinforcing material. 2. The spacing member according to claim 1, wherein the spacing member is formed of a material comprising at least a polybutylene phthalate resin, a reinforcing material, and a lubricant. 3. The spacing member according to claim 1, wherein the reinforcing material is an aramid fiber. 4. The spacing member according to claim 1, wherein the reinforcing material is selected from the group consisting of mica and potassium titanate fiber. 5. The lubricant is polytetrafluoroethylene,
The spacing member according to claim 2, wherein the spacing member is selected from the group consisting of molybdenum sulfide and ultra-high molecular weight polyethylene. 6. A developing device comprising at least a frame and a developer carrier having a cylindrical main part, wherein the spacing member according to claim 1 or 2 is provided near both ends of the developer carrier. A developing device comprising: 7. A developer carrier disposed in a developer supply chamber is driven to rotate, and the peripheral surface thereof is rolled into contact with the peripheral surface of the image carrier, and the developer carried on the peripheral surface of the developer carrier is transferred to the developer carrier. The developing unit including the developing chamber, the developer carrier, and the image carrier is incorporated into the cartridge body so as to be transferred to the electrostatic latent image on the peripheral surface of the image carrier, and is removably mounted on the image forming apparatus body. 3. The process cartridge according to claim 1, wherein the spacing member according to claim 1 is provided near both ends of the developer carrier.