JP2000122436A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an excellent image being free from generating a transporting roller trace on the image by providing a notch part at a position on recording material where a rub is caused by the transporting roller in a blade shape member on the upper side opposite to the blade shape member on the lower side of transfer guide. SOLUTION: This device is allowed to leave a metal plate tip part in the position matching with the present transport roller position in the lengthwise direction of the metal plate wider than the transporting roller width by about 3 mm, completely exposing the space saving type brush 8' in the position required for at least letting respective recording material 7 enter into a transfer nip part at a desired angle, controlling the progressing direction of the recording material. Then, the device is provided with the notch part 13b against the toner soiling which is notched toward the rear side by the leading end 10 mm long on which the toner adhesion occurs in the conventional structure. Moreover, the transfer guide upper metal plate is composed of the notched metal plate 13 provided with the notch part 13a against roller trace which is notched in the transporting direction length of the recording material 7 so as to be apart by at least 5 mm from the notch trailing part.

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 such as an electrophotographic printer, a copying machine, a facsimile and the like.

[0002]

2. Description of the Related Art Conventionally, as an image forming process in an apparatus such as a printer, a copying machine, a facsimile or the like using an electrophotographic system, a surface of a photosensitive drum 2 is mainly charged by a charging roller 1 as shown in FIG. After being uniformly charged to a certain polarity, only the area where the photosensitive drum 2 is exposed by the exposure means 3 such as a laser is discharged to form a latent image, and the toner 5 of the developing device 4 is developed by the developing blade 4a and the developing sleeve 4b. Between the photosensitive drum 2 and the developing sleeve 4b, DC and AC biases are superimposed and applied, and the toner is caused to float and vibrate by the action of an electric field. While selectively adhering it to the latent image forming portion of the photosensitive drum 2, and then transferring the photosensitive drum 2 to a transfer nip formed by the transfer roller 10 and the photosensitive drum 2.
Conveyed by the rotation of.

On the other hand, a recording material 7 such as a paper on which an image is recorded is conveyed from a paper feeding section to a transfer section by a conveying roller 6, while the paper is unnecessarily charged due to rubbing with the conveying roller 6. Therefore, it is necessary to remove the charge from the surface of the recording material 7 after passing through the conveying roller 6 so that an unnecessary electric field does not act during transfer to disturb the image.

For this reason, as shown in the figure, a neutralization brush 8 provided along the width direction of the recording material 7 and grounded.
Is configured to contact the recording material 7 being conveyed from the back surface and remove the charge. Further, metal fibers are used for the static elimination brush 8, and amorphous metal fibers having particularly high flexibility and hardly bendable characteristics are preferably used. As a specific configuration example, the hair length is about 5 mm. A bundle in which about six fibers are collected and arranged in the longitudinal direction at a pitch of 2.4 mm is used.

[0005] Next, the recording material 7 thus neutralized is removed.
The transfer upper guide plate 9a and the transfer lower guide plate 9b for regulating the traveling direction of the recording material 7 are made up of two upper and lower sheet metals that are both grounded in order to make the recording medium 7 protrude into the transfer section at an optimum angle. Transfer guide 9 is provided.

The recording material 7 that has passed through the transfer guide portion 9 is transferred at a transfer nip portion with a high voltage having a polarity opposite to that of the toner so that the toner on the photosensitive drum 2 is electrostatically attracted and moved toward the recording material. The transfer charge is applied to the roller 10, and at the same time, the back surface of the recording material 7 is charged to a polarity opposite to that of the toner, so that a transfer charge for continuously holding the toner is applied to the back surface of the recording material 7.

The recording material 7 onto which the toner image has been transferred in this manner is finally conveyed to a fixing unit 12, where a fixing-side rotating body 12a composed of a roller or a film having a heating source (not shown) and the fixing unit 12a. Heat and pressure are applied at a fixing nip portion formed between the pressure roller 12b and the pressure roller 12b which is in pressure contact with the side rotator 12a, and the toner image is permanently fixed by melt pressure contact.

On the other hand, since a small amount of foreign matter such as toner having a different polarity remains on the surface of the photosensitive drum 2 after the transfer, the surface of the photosensitive drum 2 after passing through the transfer nip portion is countered on the surface of the photosensitive drum by the cleaning container 11. After the adhering substances are scraped off and cleaned by the cleaning blade 11a to be abutted, the apparatus waits for the next image formation.

Further, the charging roller 1, the photosensitive drum 2, the developing device 4, and the cleaning container 11 having the above structure are integrated into one cartridge, and when the user consumes a consumable such as toner, the cartridge is removed together. A method of easily exchanging the hands without soiling the hands is widely used.

[0010] As described above, various image forming apparatuses such as printers using the above-described image forming process have a basic principle of electrostatic action. It is important to design so as not to cause abnormal electrostatic charging itself.

Further, even in the event of electrification, it is necessary to provide a structure for quickly eliminating the charged charges. The charge eliminating brush 8 provided between the transport roller 6 and the transfer nip portion improves image quality. It is a very important member.

The image forming apparatus having the above-mentioned configuration has been widely used due to its high image quality and high processing speed, and its progress has been remarkable. Cost reduction is strongly required.

[0013] For this reason, developments are being made to further improve the fineness of the toner, the fineness of the exposure spot, the shortening of the transport path, the reduction of the number of parts, and the like.

However, if such improvements are made, many new problems that must be solved at the same time will occur, and for example, the following problems tend to occur near the transfer portion.

As one of the adverse effects, as shown in the enlarged view of the transfer entrance in FIG. 5A, first, in order to improve the image quality, the toner is made finer from about 7 μm to about 5 μm and the recording speed is increased. For this reason, when the transport speed of each transport unit is increased 1.5 times from about 60 mm per second to about 90 mm per second, the toner easily adheres to the front end side of the upper transfer sheet metal 9 a close to the photosensitive drum 2, It has been found that the toner may accumulate to a degree that cannot be ignored during the period of use.

One of the causes of the remarkable accumulation of the toner is that the toner is liable to float in the developing section due to the decrease in the mass of the toner. It is considered that the peripheral speed of the surface of the photosensitive drum 2 is increased due to the increase in the speed.
The centrifugal force acting on the toner once adhered to the photosensitive drum 2 by the development increases, and the relatively weakly adhered toner on the surface layer separates from the photosensitive drum surface and is transferred to the transfer upper guide sheet metal 9a which is also electrically grounded. It may be attracted and adhered.

Another disadvantage is to shorten the transport path and reduce the number of parts to reduce the size and space.
Static elimination brush 8 for removing unnecessary charge by the transport roller 6
When a space saving type static elimination brush 8 ′ grounded integrally with the transfer lower guide sheet metal 9 b in the transfer guide section 9 is omitted by omitting the space where the transfer section is provided, the adverse effect is as shown in FIG. As shown in FIG. 7, a defective image called a vertical belt-like transport roller trace having a high density partially corresponding to the position of the transport roller 6 occurred in the image on the recording material 7 after the transfer.

The reason for this is that, as can be seen from the cross-sectional view of FIG. 5 (A), the charge removal brush 8 'was provided at a position facing the grounded transfer upper metal plate to save space. When the recording material 7 passes while contacting the tip of the charge erasing brush 8 ', a conductor having the same potential as the charge elimination brush 8' also exists on the opposing surface close to the tip of the charge elimination brush 8 '. It is considered that it became difficult to generate a potential gradient only on the side of the discharging brush 8 '.

Such a phenomenon is exacerbated when the resistance of the conveying roller 6 and the recording material 7 is increased in a dry environment, and particularly, when a halftone image is formed, it is easily regarded as a defective image.

[0020]

SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus using an electrophotographic system, which achieves high image quality, high recording speed, and small size and space saving of the toner by making toner fine. When trying to promote
The disadvantages are that toner is contaminated at the leading end of the upper transfer guide plate in the pre-transfer area, and that the charge elimination brush lacks the charge elimination performance due to space saving, resulting in the formation of traces of the conveying rollers on the image.

An object of the present invention is to solve the above-mentioned problems, and to prevent the toner from being stained at the top of the transfer upper guide plate even if the image quality is increased and the speed is increased, and to reduce the charge removal performance of the charge removal brush to save space. An object of the present invention is to provide an image forming apparatus capable of obtaining a good image in which no trace of a conveying roller is generated on an image without performing the operation.

[0022]

According to the present invention, an object of the present invention is to provide an image carrier, a transfer device for transferring a toner image on the image carrier onto a recording material, the transfer device and the image carrier. Transfer guide means for injecting the recording material at a predetermined angle toward the transfer portion between the bodies, a transport roller for transporting the recording material to the transfer portion, and the recording material generated by rubbing with the transport roller A transfer brush for removing charge on the surface; and the transfer guide means includes two upper and lower grounded plate-like members, and the discharge brush is a lower side of the transfer guide means inside the recording material passage area. In the image forming apparatus provided on the side of the plate member, the upper plate member opposed to the lower plate member of the transfer guide means is located at a position where the recording material is rubbed by the transport roller. Characterized by having a notch

The transfer guide means is provided with a minimum necessary for guiding the traveling directions of all the recording materials which can pass through the vicinity of the image carrier at the tip of the upper plate-shaped member other than the notch. It is characterized in that a notch is provided leaving a portion.

The plate member constituting the transfer guide means is formed of a sheet metal member.

The plate member constituting the transfer guide means is
A portion other than the cutout portion is constituted by a wire-like member.

Further, the plate-like member constituting the transfer guide means uses a sheet metal or a wire-like member only on both left and right side surfaces and a rear end portion, and all other portions are constituted by a non-chargeable mesh member. It is characterized by the following.

Further, the net-like member is composed of fibers perpendicular to the recording material conveyance direction and perpendicular to the conveyance direction of the recording material, wherein the fibers parallel to the conveyance direction are on the recording material passage surface side. And

According to the present invention, even if the toner is finely divided to improve the image quality and the rotation speed of the photosensitive drum is increased to increase the speed, the plate-like member constituting the transfer guide means is, for example, a transfer upper guide. Since there is only a minimum necessary portion for restricting the angle at which the recording material enters the transfer portion as the sheet metal tip, it is possible to prevent a large amount of toner from adhering and contaminating the inside of the apparatus.

Further, even if the static elimination brush is provided in the plate member constituting the transfer guide means to save space, the plate member above the portion facing the static elimination brush in at least the area corresponding to the position of the conveying roller is present. As a result, a sufficient potential gradient can be generated between the tip of the neutralizing brush and the grounding portion that is in contact with the charged portion of the recording material, and a good image without density unevenness can be obtained by efficiently removing the charge of the recording material charged by the conveyance roller. Can be.

[0030]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) FIG. 1 shows a first embodiment of the present invention.
FIG. 3 is a top view around a transfer unit of the image forming apparatus according to the first embodiment.

In FIG. 1, the conventional example shown in FIG.
The members having the same reference numerals as (B) indicate the same components. In the present embodiment, the transfer roller 6 is replaced with a new transfer guide upper sheet metal 9a in the same position as the transfer roller 6 in place of the conventional transfer guide upper sheet metal 9a. The width of the sheet metal to be extended is about 3 mm to the left and right from the width of the transport roller at the longitudinal position of the sheet metal to be removed, and the static elimination brush 8 ′
Is completely exposed (hidden at the position indicated by the broken line on the back surface of the recording material in FIG. 1), and regulates the traveling direction of the leading end of the recording material of a size that allows the paper to pass therethrough so that each recording material 7 is formed at a desired angle. Toner which is notched rearward only in the area of 10 mm in the tip where the toner adhesion has occurred in the conventional configuration while leaving the tip of the sheet metal at the minimum necessary position to allow the toner to enter the transfer nip portion A dirt notch 13b and a recording material 7 that is at least 5 mm away from the rear end of the notch
Roller mark notch 13 cut to length in the transport direction
and a notched sheet metal 13 having a.

With such a configuration, even if the surface of the recording material 7 is charged by the transport roller 6, the neutralizing brush 8 'provided in the transfer guide portion 9 is located at a position corresponding to the sliding position of the transport roller 6. Since the transfer guide upper sheet metal 9a does not exist, a potential gradient required for static elimination is generated at the brush tip portion and the grounding portion, so that good static elimination can be performed, and good image quality in which the generation of transport roller marks is suppressed is obtained. Will be able to

Before actually using the configuration of the present embodiment, the transfer guide unit 9 of the conventional configuration was attached to the apparatus and the paper was sufficiently dried in a low-temperature and low-humidity environment. When a halftone image was printed using the image forming method, a vertical belt-like transport roller trace as shown in FIG. 5B in the conventional example was immediately generated.
The density was increased twice (the hair transplant pitch of the bundle was reduced by half), but no improvement was obtained, and no static eliminating effect was obtained.

Next, under the same conditions, the transfer guide 9
After replacing only the notched sheet metal of this embodiment,
Even with a combination of a normal brush density neutralizing brush, the transport roller traces become sufficiently inconspicuous as the density is sufficiently reduced, and when the same notched sheet metal and a double-density neutralizing brush 8 'are combined, the transport roller traces have almost completely disappeared. Was.

Thus, by using the configuration of the present embodiment, the performance of the neutralizing brush 8 'is sufficiently improved even when the position of the neutralizing brush 8' is provided in the transfer guide portion 9 for downsizing the apparatus. It can be confirmed that the brush can be extracted and that the static elimination performance can be improved in proportion to an increase in the brush density.

Next, the printing operation for 6,000 continuous pages was repeatedly performed using this apparatus with an image pattern having a printing rate of about 5%. After removing the cartridge and observing the surface of the transfer guide section 9, the notch remained. Although a small amount of toner adhered to the tip of the sheet metal, the ratio of the floating toner adhering was drastically reduced due to the small area acting as the counter electrode, and this problem was particularly problematic on the periphery and on the recording material 7. No clear toner contamination occurs (there is no transfer upper guide sheet metal 9a, so the possibility that toner adheres to the surface of transfer lower guide sheet metal 9b increases. In this case, even if it adheres, the transfer upper guide sheet metal 9a Since the distance is longer than the electric field caused by the weak electric field, there is a possibility that only a small amount of toner attracted between the sheets at the time of paper passing by the weak electric field may adhere, and these toner Since the cleaned immediately with the back surface of the recording material 7 for the next print be attached transferred on the guide sheet metal 24
As shown in FIG. 7A, the toner stain does not accumulate,
There is no practical problem at all because the amount of toner that can adhere to the back surface of the transfer sheet is very small, and there is no practical problem.) Thus, the toner contamination is clearly reduced as compared with the case where the toner is used, and a good replacement operation without soiling the user's hands or the like with the toner can be performed even when the cartridge is replaced or the jam is cleared.

(Second Embodiment) FIG. 2 shows a second embodiment of the present invention.
FIG. 3 is a top view around a transfer unit of the image forming apparatus according to the first embodiment.

In FIG. 2, members having the same reference numerals as those in FIG. 1 in the first embodiment represent the same components.
In the present embodiment, instead of the conventional transfer guide upper sheet metal 9a, a new transfer guide portion 9 is provided to regulate the advancing direction of the leading end of a recording material of a size that can be passed in the first embodiment and to a desired angle. 2 m diameter at the position where the sheet metal tip is left at the minimum necessary position to allow each recording material 7 to enter the transfer nip
A wire-like transfer guide member 14 composed of m wires is used.

By using the configuration of the present embodiment,
The same effect as that of the first embodiment can be obtained, and the degree of exposure of the charge removing brush 8 ′ is further increased, so that traces of the conveying roller can be made harder to occur, and the toner contamination around the transfer guide section 9 is further reduced. Therefore, the user's hands and the like are not stained with the toner at the time of cartridge replacement or jam clearance.

(Third Embodiment) FIGS. 3A and 3B
7A and 7B are a sectional view of a fixing device and a sectional view of a transfer guide member of an image forming apparatus according to a third embodiment of the present invention.

In FIG. 3A, members having the same reference numerals as those in FIG. 1 in the first embodiment indicate the same components, and in this embodiment, a conventional transfer guide upper metal plate 9a is used.
Instead, a metal frame is used as a new transfer guide portion 9 only at the left, right and rear end portions, and a net-like guide member 15 is used at the center portion and the front end portion, which is made of a metal fiber net having a diameter of about 0.2 mm. ing.

The mesh of the mesh-like guide member 15 has such a roughness that each bundle of static elimination brushes can be sufficiently exposed, and the positions of the holes of the mesh are matched with the brush pitch positions. 'The upper guide member does not oppose the opposing surface of the tip. Further, as shown in FIG. 3B, the cross-sectional structure of the mesh has a structure in which a horizontal fiber 15a perpendicular to the transport direction is formed on a vertical fiber 15b parallel to the transport direction of the recording material 7. Since the fibers along the conveyance direction face the passing surface of the recording material 7, there is no fear that the leading end of the recording material 7 is caught by the protrusion of the upper guide member and the conveyance is disturbed, and the recording material 7 is conveyed well. And the regulation of the angle of entry into the transfer nip.

On the other hand, by using the structure of the present embodiment, since only a net portion made of fine fibers is present at the leading end of the guide, the amount of the floating toner attracted from the developing unit and the surface of the photosensitive drum 2 adheres. Is negligible, so that toner contamination around the transfer guide section 9 is further reduced, and a good replacement operation can be performed without replacing the user's hands or the like with toner even during cartridge replacement or jam clearance.

The reticulated guide member 15 of the upper transfer guide in the configuration of the present embodiment is not necessarily made of metal fiber, and is required to have at least non-charging property such as antistatic fiber having self-discharge characteristics. May be used, and in that case, it is not necessary to ground the upper guide member.

[0046]

As described above, according to the present invention, the plate-like member constituting the transfer guide means can be formed even if the toner is finely divided for higher image quality and the rotation speed of the photosensitive drum is increased for higher speed. For example, since there is only a minimum necessary portion for restricting the angle of entry of the recording material into the transfer portion as the leading end of the upper transfer sheet metal, it is possible to prevent a large amount of toner from adhering and contaminating the inside of the apparatus.

Further, even if the static elimination brush is provided in the plate member constituting the transfer guide means to save space, the plate member above the portion opposed to the static elimination brush in at least the area corresponding to the position of the transport roller is present. As a result, a sufficient potential gradient can be generated between the tip of the neutralizing brush and the grounding portion that is in contact with the charged portion of the recording material, and a good image without density unevenness can be obtained by efficiently removing the charge of the recording material charged by the conveyance roller. Can be.

[Brief description of the drawings]

FIG. 1 is a top view around a transfer unit of an image forming apparatus according to a first embodiment of the present invention.

FIG. 2 is a top view around a transfer unit of an image forming apparatus according to a second embodiment of the present invention.

3A and 3B show an image forming apparatus according to a third embodiment of the present invention, wherein FIG. 3A is a cross-sectional view of a fixing device, and FIG. 3B is a cross-sectional view of a transfer guide member.

4A and 4B show an image forming apparatus in a conventional example, in which FIG. 4A is a schematic diagram of the configuration of the image forming apparatus, and FIG.

5A and 5B show an image forming apparatus in a conventional example, in which FIG. 5A is an enlarged view of a transfer entrance portion of the conventional example in which the image quality, speed and space are reduced, and FIG. Top view around the transfer section of the device

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Charging roller 2 Photosensitive drum 3 Exposure means 4 Developing device 4a Developing blade 4b Developing sleeve 5 Toner 6 Conveying roller 7 Recording material 8 Static elimination brush 8 'Space-saving type static elimination brush 9 Transfer guide section 9a Transfer upper guide sheet metal 9b Transfer lower guide sheet metal DESCRIPTION OF SYMBOLS 10 Transfer roller 11 Cleaning container 11a Cleaning blade 12 Fixing device 12a Fixing side rotating body 12b Pressure roller 13 Notch sheet metal 13a Notch portion for roller trace 13b Notch portion for toner stain 14 Wire-like transfer guide member 15 Net-like guide member 15a Weft fiber 15b Vertical fiber

Claims (6)

[Claims] An image carrier; a transfer unit configured to transfer a toner image on the image carrier onto a recording material; and a predetermined angle directed to a transfer unit between the transfer unit and the image carrier. Transfer guide means for injecting a recording material, a transport roller for transporting the recording material to the transfer portion, and a static elimination brush for eliminating static electricity on the recording material surface caused by rubbing with the transport roller, In the image forming apparatus, the transfer guide unit is configured by two upper and lower grounded plate members, and the discharging brush is provided on a lower plate member side of the transfer guide unit inside the recording material passage area. An image characterized in that the upper plate-shaped member facing the lower plate-shaped member of the transfer guide means has a notch at a position where the conveyance roller rubs the recording material. Forming equipment. 2. The transfer guide means according to claim 1, wherein said transfer guide means guides the traveling direction of all recording materials which can pass through the vicinity of said image carrier at the tip of said upper plate member other than the notch. 2. The image forming apparatus according to claim 1, wherein a cutout portion is provided while leaving a portion. 3. The image forming apparatus according to claim 1, wherein the plate member constituting the transfer guide unit is formed of a sheet metal member. 4. The image forming apparatus according to claim 1, wherein a portion of the plate-shaped member constituting the transfer guide unit is formed of a wire-shaped member except for the notch. 5. The plate-like member constituting the transfer guide means uses a sheet metal or a wire-like member only on both left and right side portions and a rear end portion, and all other portions are made of a non-chargeable net-like member. The image forming apparatus according to claim 1, wherein: 6. The recording medium according to claim 6, wherein the mesh member is formed of fibers perpendicular to a recording material conveyance direction and fibers perpendicular to the conveyance direction of the recording material. The image forming apparatus according to claim 5, wherein