JP2002328552A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the number of parts small so as to reduce assembly man-hour and further to surely ground a member to be grounded or a destaticization needle. SOLUTION: A carrying guide 3 is covered with a carrying sheet metal 1, and the carrying rib 3a of the guide 3 is made to project from the slit 1b of the sheet metal 1. Recording material to which a toner image has been transferred is carried to a fixing device by the rib 3a. The fixing device has a conductive fixing frame (for example, made of metal), and the fixing frame is grounded through the electric chassis of an electric part. The sheet metal 1 is provided with an elastic spring contact 1a and brought into contact with the fixing frame, and then grounded through the fixing frame and the electric chassis. A machine screw for attaching the sheet metal 1 to the electric chassis is not required differently from the conventional manner, so that the number of parts is decreased and the assembly man-hour is reduced. Then, grounding is ensured.

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 a printer, a copying machine, a facsimile, and the like.

[0002]

2. Description of the Related Art An example of a conventional image forming apparatus of a roller transfer type will be described.

FIG. 14 is a longitudinal sectional view showing a schematic configuration of a conventional image forming apparatus.

In FIG. 1, a photosensitive drum 37 is indicated by an arrow a.
After the surface is charged by a charger (not shown), an electrostatic latent image is formed by an exposure device (for example, a laser scanner) 45. The electrostatic latent image is developed as a toner image by attaching toner by a developing unit (not shown).

On the other hand, the recording material P, such as paper, loaded on the main body cassette 31 is fed by the feed roller 32 at the uppermost position, and is separated one by one by the separation pad 33. The separated recording material P is conveyed along a guide 34 to a pair of registration rollers 35a and 35b. Thereafter, the recording material P is conveyed by a pair of registration rollers 35a and 35b in accordance with the rotation of a photosensitive drum 37 disposed in a process cartridge 36 serving as an image forming unit (recording unit). The toner image on the drum 37 is transferred. Thereafter, the recording material P is guided by a synthetic resin conveyance guide (body frame) 39 and conveyed to a fixing device (fixing unit) 47, and is heated and pressed by a fixing roller 40 and a pressure roller 41 of the fixing device 47. Then, the toner image is fixed on the surface as a permanent image. After that, the recording material P is conveyed along the paper discharge conveyance guide rib 42, and the face-down tray 4
4 and loaded. The process cartridge 36 can be easily attached and detached by opening the cover 10 at the top of the image forming apparatus main body.

The transfer system of the above-described image forming apparatus is a roller charging system. In the roller charging method, a transfer roller 38 is brought into contact with a photosensitive drum 37 to form a transfer nip portion (contact nip portion) N, and the recording material P is formed by the transfer nip portion N.
While transferring the toner image (transferable image) on the photosensitive drum 37 side to the recording material surface side by applying a transfer bias to the transfer roller 38 while nipping and transporting the sheet. Transfer roller 38
Is composed of a cored bar 38a and a medium resistance sponge layer 38b formed concentrically and integrally on the outer periphery thereof. The sponge layer 38b is brought into contact with the photosensitive drum 37 with a predetermined pressing force to form a transfer nip portion N. As the photosensitive drum 37 rotates in the direction of the arrow a, it rotates in the direction of the arrow b (forward).

The recording material P is supplied to the transfer nip N, and a positive transfer bias of 1 to 10 kV is applied to the transfer roller 38 while the recording material P is nipped and conveyed by the transfer nip N. . As a result, the recording material P passing through the transfer nip N is given a positive charge, and the toner image on the photosensitive drum 37 is transferred to the surface of the recording material P by electrostatic attraction. The recording material P that has passed through the transfer nip N is separated from the surface of the photosensitive drum 37 and
7, where the toner image is fixed on the surface. The fixing device 47 is a conductive fixing frame (chassis).
Fixing roller 40 and pressure roller 41 attached to
And a fixing unit as a whole.

In order to separate the recording material P from the surface of the photosensitive drum 37 through the transfer nip N, a so-called curvature separation method utilizing the curvature of the photosensitive drum 37 is often used. The curvature separation method does not require application of a separation bias or the like, so that the device configuration can be easily simplified and the cost can be reduced. In the case of the curvature separation method, a metal static elimination needle 50 is disposed immediately after the recording material exit side of the transfer nip portion N as auxiliary means for separation, and the extra transfer charge is eliminated to smooth the separation, thereby facilitating the separation. P also enables separation.

In the image forming apparatus employing the curvature separation method, when the trailing edge of the recording material P passes through the transfer nip portion N, a so-called "rear end jump" occurs, and the unfixed toner image on the surface of the recording material P is removed. When touching a structure in the apparatus, edge of the recording material P may be stained at the rear end, and rubbing of the toner image at the rear end may occur.

In addition, when the trailing edge of the recording material is generated, the charge is not sufficiently removed because the trailing edge of the recording material is far from the static elimination needle 50, and the excessive transfer charge at the trailing edge of the recording material causes a low resistance between transfer and fixing. There is a possibility that an abnormal image called "polka dots" that discharges the toner to the conveyance guide 39 and blows the toner in a circular shape may occur.

[0011] The above-mentioned trailing edge bouncing occurs when the trailing edge of the recording material P passes through the transfer nip N and is not separated from the photosensitive drum 37 by the electrostatic attraction force of the photosensitive drum 37 but is attracted in the rotation direction of the photosensitive drum 37. It occurs because it moves and jumps up.

In the conventional roller transfer method, a transfer bias is applied from the metal core 38a of the transfer roller 38 to the sponge layer 38b having a medium resistance to supply the transfer charge onto the recording material P. In this case, the transfer is performed. Since the electric field on the roller surface is uniform, the photosensitive drum 37 is located at a position upstream of the transfer nip N where the photosensitive drum 37 contacts the transfer roller 38 (upstream along the conveying direction of the recording material P). A force acts to attract the toner image formed thereon to the transfer roller 38 side, so that the toner flies in the direction of the transfer roller, so that a faithful transfer is not performed, and a so-called “scattering” image in which the toner is scattered around characters occurs.

For this reason, in the conventional transfer type image forming apparatus, a guide member for bringing the recording material P into close contact with the photosensitive drum 37 at a position upstream of the transfer nip N is provided so that the recording material P is not affected by the transfer electric field. The recording material P is brought into contact with the toner image on the photosensitive drum 37 to prevent scattering.
Further, there is also known one provided with a transfer sheet metal (necessary ground member) 51 as shown in FIGS. 15 and 16 on the downstream side of the transfer nip portion N. The sheet metal member 51 can stably convey the recording material P separated from the photosensitive drum 37. Therefore, the recording material P has a "rear end bouncing", an image disturbance due to the "bounce", and a "polka dot" due to poor static elimination.
It is possible to prevent “scattering” due to the influence of the transfer electric field on the upstream side of the transfer nip portion, and to prevent the recording material P from being stained on the back.

The transport metal sheet 51 is for attracting the recording material P after transfer separation from the non-image forming surface (back surface) side to the lower part of the transport path by electrostatic attraction, thereby performing stable transport. Is disposed on the upper surface of the transport guide 39 on the downstream side of the static elimination needle 50, that is, over the entire sheet passing width of the surface facing the structural member such as the process cartridge 36, which easily attracts the recording material P electrostatically. And is grounded and has a potential of 0. In order to reduce the transport resistance to the recording material P, the recording material P directly contacts or approaches the low-resistance transport path suction member on the surface of the transport sheet metal 51 facing the recording material, and the transfer charge leaks and discharges. In order to prevent the occurrence of an abnormal image, the transport rib 39a is projected. The transport rib 39a is formed integrally with the transport guide 39 made of resin. Here, the transport rib 39a shows an example in which a member for fixing the static elimination needle 50 and a member for fixing the transport sheet metal 51 are integrally formed. Of course, each may be separate.

As shown in FIG. 14 to FIG.
1 is provided with an arm 51a for ground connection.
Are fixed to the fixing portion 60 of the electric component portion 46 extending upward from the electric component chassis 52 by a screw 62 and grounded. Also, an arm 5 for ground connection is provided on the static elimination needle 50.
0a is provided. Similarly, the electrical component chassis 5 of the electrical component portion 46 is provided.
A fixing portion 61 extending upward from 2 is screwed by a screw 63 and grounded. The fixing frame 53 holding the fixing device 47 is also fixed to the electrical chassis 52 by screws 54.

[0016]

In the image forming apparatus having the above-described structure, the transfer sheet metal 51 and the static elimination needle 50 are screwed and attached to the electrical equipment chassis 52. Therefore, the number of parts is increased by the amount of the screw, and The number of assembly steps also increases. In addition, when the screws are not sufficiently fastened, an effective ground may not be obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide an image forming apparatus capable of reducing the number of parts, reducing the number of assembling steps, and enabling reliable grounding. Is what you do.

[0018]

According to the present invention, there is provided a transfer device for transferring a toner image formed on an image carrier onto a recording material, and a fixing device for fixing the toner image on the recording material. An image forming apparatus comprising: a guide unit for guiding a recording material conveyed from the transfer unit to the fixing unit; and an electrical unit connected to ground, wherein the fixing unit includes a conductive unit connected to the electrical unit. Fixing means, the guide means has a grounding member required grounding,
An elastic spring contact is provided on the grounding member, and the elastic spring contact is brought into contact with the fixing frame of the fixing unit to ground the grounding member via the fixing frame and the electrical unit. Features.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, on the downstream side of the transfer unit and the upstream side of the guide unit in a recording material conveying direction,
A static elimination needle for static elimination of the recording material after the transfer of the toner image, an elastic spring contact provided on the static elimination needle, and the elastic spring contact being brought into contact with the grounding required member, thereby setting the static elimination needle to the grounding required member; The fixing frame is grounded via the electrical unit.

According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the grounding member and the static elimination needle are integrally formed.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. It is to be noted that components denoted by the same reference numerals in the drawings have the same configuration or operation, and redundant description thereof will be omitted as appropriate.

<First Embodiment> FIG. 5 shows a schematic configuration of an image forming apparatus according to the present invention. The image forming apparatus shown in FIG. 1 is an electrophotographic laser beam printer, and FIG. 1 is a longitudinal sectional view showing a schematic configuration thereof.

In a laser beam printer (hereinafter, referred to as an "image forming apparatus") shown in FIG. 1, a drum-type electrophotographic photosensitive member (hereinafter, referred to as a "photosensitive drum") as an image carrier has an arrow a. After the surface is charged by a charger (not shown), an electrostatic latent image is formed by an exposure device (for example, a laser scanner) 45. The electrostatic latent image is developed as a toner image by attaching toner by a developing unit (not shown).

On the other hand, the recording material P, such as paper, loaded in the main body cassette 31 is fed by the feed roller 32 at the top, and is separated one by one by the separation pad 33. The separated recording material P is transported along a guide 34 to a pair of registration rollers 35a and 35b. Thereafter, the recording material P is conveyed by a pair of registration rollers 35a and 35b in accordance with the rotation of the above-described photosensitive drum 4 disposed in a process cartridge 36 serving as an image forming unit (recording unit). Is transferred onto the photosensitive drum 5. After that, the recording material P is guided by a synthetic resin conveyance guide (main body frame) 3 and conveyed to the fixing device 47, where the recording material P is heated and pressed by the fixing roller 40 and the pressure roller 41 of the fixing device 47, and the surface thereof is formed. The toner image is fixed as a permanent image. After that, the recording material P is conveyed along the discharge conveyance guide ribs 42, and a pair of discharge rollers 43.
The sheets are discharged and stacked on the face down tray 44 by a and 43b. The process cartridge 36 can be easily attached to and detached from the image forming apparatus main body by opening the cover 10 on the upper part of the image forming apparatus main body.

The transfer system of the above-described image forming apparatus is a roller charging system. In the roller charging method, the transfer nip portion (contact nip portion) is obtained by bringing the transfer roller 5 into contact with the photosensitive drum 4.
A transfer bias is applied to the transfer roller 5 and the toner image (transferable image) on the photosensitive drum 4 is electrostatically applied to the surface of the recording material while the recording material P is held and conveyed by the transfer nip N. This is a transfer method. The transfer roller 5 includes a core metal 5a.
And a sponge layer 5b of a medium resistance formed concentrically and integrally with the outer periphery thereof. The sponge layer 5b is brought into contact with the photosensitive drum 4 with a predetermined pressing force to form a transfer nip portion N. With the rotation in the direction of arrow a, the rotation is driven in the direction of arrow b (forward).

The recording material P is supplied to the transfer nip N, and a positive transfer bias of 1 to 10 kV is applied to the transfer roller 5 while the recording material P is nipped and conveyed by the transfer nip N. . As a result, the recording material P passing through the transfer nip portion N is given a positive charge, and the toner image on the photosensitive drum 37 is electrostatically attracted to the recording material P.
Is transferred to the surface of The recording material P that has passed through the transfer nip N is separated from the surface of the photosensitive drum 4 and
Is transported to a fixing device 47 having a fixing roller 40 and a pressure roller 41 held by a conductive fixing frame 53, and is fixed there.

In order to separate the recording material P from the surface of the photosensitive drum 4 through the transfer nip N, a so-called curvature separation method utilizing the curvature of the photosensitive drum 4 is employed. The curvature separation method does not require application of a separation bias or the like, so that the device configuration can be easily simplified and the cost can be reduced. In the case of the curvature separation method, a metal static elimination needle 2 is disposed immediately after the recording material exit side of the transfer nip N as auxiliary means for separation, and the extra transfer charge is eliminated to smooth the separation, thereby facilitating the separation. P also enables separation.

As shown in FIG. 5, below the transport guide 3, there is an electrical unit 46 having a substrate and the like.
Is housed in a metal electrical chassis 52 having a box shape with an open top. The electrical chassis 52 includes:
A conductive (for example, metal) fixing frame 53 holding the above-described fixing device 47 is fixed by screws 54.

FIG. 1 is a perspective view of a transfer section after a transfer sheet metal (necessary ground member) 1 according to the present invention, a static elimination needle 2, and a main body frame (transport guide) 3 having a transfer rib 3a are assembled. is there. FIG. 2 shows an exploded perspective view of these. 3 and 4 are perspective views of the static elimination needle 2 and the transfer sheet metal 1 as a single unit. In the present embodiment, a guide unit is configured by the transport sheet metal 1 and the body frame (transport guide) 3.

As shown in FIGS. 6 and 9, the above-described fixing device 47 can be attached to and detached from the image forming apparatus main body together with the fixing frame 53. As shown in FIG. 6, in order to mount the fixing frame 53 on the image forming apparatus main body, a part of the fixing frame 53 is screwed with an electric chassis 52 on the image forming apparatus main body side.
Fixed to. On the other hand, to take it out, as shown in FIG.
The screw 54 is removed, and the fixing frame 53 is pulled out to the right in FIG.

As shown in FIG. 1, FIG. 2, and FIG. 4, the transport sheet metal 1 has an elasticity so as to come into contact with a part of the fixing frame 53 when the fixing device 47 is mounted on the image forming apparatus main body. A spring contact 1a is provided. Further, a similar elastic spring contact 2a is provided on the static elimination needle 2 as shown in FIGS.

As shown in the vertical sectional view of the image forming apparatus after the fixing device 47 is mounted in FIG.
3 and the electrical chassis 52 are fastened by screws 54, and the electrical chassis 52 is connected to a ground on the electrical equipment.

As shown in FIG. 9, when the fixing device 47 which has been taken out is mounted on the main body of the image forming apparatus as shown in FIG. 6, the elastic spring contacts 1 of the sheet metal 1 are fed as shown in FIG.
a makes spring contact with the fixing frame of the fixing device 47 made of metal, whereby the conveying sheet metal 1 and the fixing frame 53
Are electrically connected. After that, the fixing frame 53 of the fixing device 47 is fastened to the electrical component chassis 52 of the electrical component part 46 by a screw 54. As a result, the transport sheet metal 1 is electrically connected to the ground (not shown) on the board of the electric unit 46 via the fixing frame 53 of the fixing unit 47 and the electric chassis 52.

The transport metal sheet 1 is located on the surface side of the recording material P (on the surface side on which the toner image is formed) downstream of the static elimination needle 2.
For example, when there is a structural member such as the process cartridge 36 which easily attracts the recording material P electrostatically, the recording material P is disposed over the entire sheet passing width facing the structural member. Then, the potential of the transfer sheet metal 1 becomes 0 by being grounded as described above. As a result, the recording material P after transfer separation is attracted from the back surface side (the surface side on which the toner image is not formed) to the lower part of the conveyance path by electrostatic attraction, thereby performing stable conveyance of the recording material P.
The transport metal sheet 1 is provided with a number of slits 1b in the transport direction of the recording material P. From this slit 1b, as shown in FIG.
Is protruding. The transport rib 3a is used for the main frame 3
And is formed of, for example, a synthetic resin. The transport ribs 3a reduce the transport resistance of the recording material P, and prevent an abnormal image caused by the transfer charge leaking and discharging when the recording material P directly contacts or approaches the low-resistance transport metal sheet 1. It is provided for. Here, the transport rib 3a shows an example in which a member for fixing the static elimination needle 2 and a member for fixing the transport sheet metal 1 are also integrally formed as the main body frame 3, but, of course, each is separately provided. It may be a body.

As shown in FIG. 13, the static elimination needle 2 is similarly provided with an elastic spring contact 2a, and the fixing frame 53 of the fixing device 47, the electric chassis 52, Grounded via board ground.

FIG. 7 is an enlarged view of a contact portion between the static elimination needle 2 and the transfer sheet metal 1. Now, when the static elimination needle 2 is assembled to the main body frame 3, the elastic spring contact 2 a of the static elimination needle 2 is elastically deformed and comes into contact with the transfer sheet metal 1 to be electrically connected. Thereby, the static elimination needle 2 is connected to the substrate ground.

By grounding the static elimination needle 2 disposed immediately after the recording material exit side of the transfer nip N as auxiliary means for separation, excess transfer charge can be eliminated, so that the recording material P is exposed to light. The separation from the drum 4 is made smooth, and even the thin recording material P can be separated.

In the above description, the case where the elastic spring contact 1a is formed on the sheet metal 1 is described as an example. However, as shown in FIG. 10, the contact 53a is projected from the fixing frame 53, and the contact 53a and the sheet metal 1 and the elastic spring contact 55
The same effect can be obtained by disposing another spring member 55 having a and 55b. Such a configuration is effective when, for example, a roller for transporting a small-sized recording material is provided at an intermediate portion of the transport sheet metal 1 and the transport sheet metal 1 cannot be formed as a single component. Note that the spring member 55 may directly contact the fixing frame 53 without providing the contact point 53a.

In the same manner as the transfer sheet metal 1,
An elastic spring contact 2a may be provided to contact the static elimination needle 2 and the transfer sheet metal 1 by elastic contact, and may be connected to the electrical ground by mounting the fixing device 47.

FIGS. 11 and 12 show an example in which the transfer sheet metal 1A and the static elimination needle 2A are integrally formed. The transfer sheet metal 1A is integrated with the static elimination needle 2A,
The elastic spring contact 1a is provided in the same manner as described above. Also in this case, similarly to the above, the fixing device 47 is mounted on the image forming apparatus main body and screwed, so that the static elimination needle 2A and the transport sheet metal 1A are connected to the electrical ground via the fixing frame 53 and the electrical chassis 52. Can be electrically connected.

[0041]

As described above, according to the present invention,
The number of parts can be reduced, the number of assembling steps can be reduced, and the grounding member and the static elimination needle can be reliably grounded.

[Brief description of the drawings]

FIG. 1 is an assembled perspective view showing the configuration of guide means (transportation sheet metal, transport guide) and a static elimination needle.

FIG. 2 is an exploded perspective view showing the configuration of guide means (transfer sheet metal, transport guide) and a static elimination needle.

FIG. 3 is a perspective view showing a configuration of a static elimination needle.

FIG. 4 is a perspective view illustrating a configuration of a transport sheet metal.

FIG. 5 is a longitudinal sectional view illustrating a configuration of an image forming apparatus according to the present invention.

FIG. 6 is a longitudinal sectional view showing a state where the fixing device is mounted on the image forming apparatus main body.

FIG. 7 is an enlarged vertical sectional view showing a contact portion between a transfer sheet metal and a static elimination needle.

FIG. 8 is an enlarged vertical cross-sectional view showing a contact portion between a transport sheet metal and a fixing frame of a fixing device.

FIG. 9 is a longitudinal sectional view showing a state where the fixing device is taken out of the image forming apparatus main body.

FIG. 10 is an enlarged vertical cross-sectional view showing an example in which a conveying sheet metal and a fixing frame of a fixing device are brought into contact with another member.

FIG. 11 is a perspective view showing a member in which a transfer sheet metal and a static elimination needle are integrally formed.

FIG. 12 is a longitudinal sectional view showing a schematic configuration of an image forming apparatus provided with a member in which a transport sheet metal and a static elimination needle are integrally formed.

FIG. 13 is a perspective view showing a contact state between a static elimination needle and a transfer sheet metal.

FIG. 14 is a longitudinal sectional view illustrating a configuration of a conventional image forming apparatus.

FIG. 15 is an assembled perspective view of a conventional guide means (conveyance sheet metal, conveyance guide) and a static elimination needle.

FIG. 16 is an exploded perspective view showing the configuration of a conventional guide means (transfer sheet metal, transfer guide) and a static elimination needle.

DESCRIPTION OF SYMBOLS 1, 1A Grounding member required (transfer sheet metal) 1a Elastic spring contact 2, 2A Static elimination needle 2a Elastic spring contact 4 Image carrier (photosensitive drum) 5 Transfer unit (transfer roller) 46 Electrical unit 47 Fixing unit ( Fixing device) 53 Fixing frame P Recording material

Claims (3)

[Claims] A transfer unit configured to transfer a toner image formed on an image carrier onto a recording material; a fixing unit configured to fix the toner image on the recording material; and a recording medium conveyed from the transfer unit to the fixing unit. An image forming apparatus comprising: a guide unit for guiding a material; and an electrical unit connected to ground, wherein the fixing unit includes a conductive fixing frame connected to the electrical unit, and the guide unit includes a ground. The required earth member is provided, and an elastic spring contact is provided on the earth required member, and the elastic spring contact is brought into contact with the fixing frame of the fixing means. An image forming apparatus, which is grounded via an electrical unit. 2. A static elimination needle for neutralizing a recording material after a toner image has been transferred, downstream of the transfer means and upstream of the guide means in a recording material conveyance direction, wherein the static elimination needle has an elastic spring. The contact is provided, and by contacting the elastic spring contact with the grounding member, the static elimination needle is grounded via the grounding member, the fixing frame, and the electrical unit. 4. The image forming apparatus according to claim 1. 3. The image forming apparatus according to claim 2, wherein the grounding required member and the static elimination needle are integrally formed.