JP3221255B2 - Image forming device - Google Patents

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 copying machine or a printer having a structure for transferring a toner image formed on an image carrier to a sheet at a transfer position, and more particularly, to a sheet forming apparatus at the transfer position. The present invention relates to an image forming apparatus in which a transfer drum is used to convey an image and a charge removing corotron for removing charges before cleaning is arranged along the surface of the image carrier downstream of the transfer position.

[0002]

2. Description of the Related Art In an image forming apparatus of this type, a sheet for transferring a toner image is attached to a transfer drum and conveyed to a transfer position. The image is being transferred to a sheet. The sheet to which the toner image has been transferred is peeled off from the transfer drum at a predetermined peeling position, and after the toner image is fixed by the fixing device, the sheet is discharged to a sheet discharge tray. In such an image forming apparatus, the sheet on the transfer drum may adhere to the image carrier at the transfer position depending on the charged state of the sheet. In this case, the sheet adheres to the surface of the image carrier and is conveyed. In this case, POP jam (Paper On the Photoresepter Jam) occurs. On the surface of the image carrier, a corotron, a cleaner and the like for static elimination are arranged downstream of the transfer position.
When a jam occurs, the sheet adhered to the surface of the image carrier is dragged between those elements and the image carrier.

[0003]

FIG. 5 is a view showing a state where the transfer drum is pulled out in order to remove the jammed sheet when the POP jam occurs. FIG. 6 is an explanatory diagram of a conventional static elimination corotron. FIG.
In FIG. 1, a transfer drum 02, a cleaner sonic unit 03, a pre-cleaning static elimination corotron 04 and the like are arranged around the image carrier 01. The static elimination corotron 04
Has a shield case 05 having a U-shaped cross section. An insulating block 06 is fixed to both ends of the shield case 05, and both ends of the corotron wire 07 are supported by the insulating block 06.

In FIG. 5, when the sheet S on the transfer drum 02 adheres to the image carrier 01, the entire apparatus may stop at a position where the leading end of the sheet S has entered the cleaner unit 03. In this case, when the transfer drum is pulled out, the sheet S may be caught and broken. Since the jam after transfer is not in a controlled state, there are various types of jams. However, when the sheet S is torn when the transfer drum 02 is pulled out, it has been found that the following cases are common.

That is, as shown in FIG. 5, the slightly bent sheet S is hooked on the rear side surface of the front insulating block 06 of the static elimination corotron 04 and bent. As a result, the sheet S is twisted and further torn. If the leading edge of the sheet breaks before it leaves the cleaning device, and the unremovable sheet fragments remain in the main body of the image forming apparatus, the image carrier and the cleaning device will be used when the image forming apparatus is operated next time. It is necessary to remove the jammed sheet without leaving any debris in order to cause problems such as damage.

The following techniques are conventionally known as techniques for detecting the POP jam. (J01) Technology described in Japanese Patent Application Laid-Open No. 2-156270.
A sensor for detecting P jam is described. If a POP jam is detected, the operation of the image forming apparatus is stopped before the leading edge of the sheet enters the cleaning device, and the jammed sheet is removed, and the jammed sheet is removed without leaving any debris. Is possible. However,
When an image is formed on both sides of the sheet, when the transfer drum sheet adheres to the image carrier during image formation on the back side of the sheet,
In some cases, the POP jam sensor cannot distinguish between untransferred toner on the image carrier or an image formed on the sheet surface, and cannot detect POP jam.

When the POP jam cannot be detected as described above, or because of the high speed, even if the POP jam is detected and then the brake is applied to the image carrier, the leading end of the sheet S enters the downstream side of the static elimination corotron. In such a case, the jammed sheet must be taken out by pulling out the transfer drum. The present invention has been made in view of the above circumstances, and has the following content as an object. (O01) To prevent the sheet from being torn when the POP jammed sheet is pulled out.

[0008]

Next, the present invention devised to solve the above-mentioned problems will be described. Elements of the present invention are used to facilitate correspondence with elements of the embodiments described later. , The reference numerals of the elements of the embodiment are enclosed in parentheses. The reason why the present invention is described in correspondence with the reference numerals of the embodiments described below is to facilitate understanding of the present invention and not to limit the scope of the present invention to the embodiments.

In order to solve the above problems, an image forming apparatus according to the present invention has the following requirements.
(Y01) a charger (10) for uniformly charging the surface of the moving image carrier (9); (Y02) means (8) for writing an electrostatic latent image on the surface of the image carrier (9); (Y03) A developing device (11) for developing the electrostatic latent image to form a toner image on the surface of the moving image carrier (9); (Y04) applying the toner image on the surface of the image carrier (9) to a sheet (S) A transfer drum (12) that conveys the sheet (S) to a transfer position (Po) for transfer to the image carrier (9), which is disposed downstream from the transfer position (Po) in the moving direction of the surface of the image carrier (9). A cleaning device (15a), (Y06) a static elimination corotron (14) arranged between the transfer position (Po) and the cleaning device (15a) and extending along the surface of the image carrier (9) in the axial direction thereof; Corotron wire (33), (Y07)
The image bearing member supports the front end of the corotron wire (33) and prevents the sheet (S) from being caught when the sheet (S) having entered the space between the image carrier (9) and the sheet (S) is dragged forward. The front insulating block (3) formed on a smooth inclined guide surface that moves away from the surface of the image carrier (9) as the surface facing the body (9) moves backward.
2).

[0010]

Next, the operation of the present invention having the above-mentioned features will be described. In the image forming apparatus of the present invention having the above-described features,
The surface of the moving image carrier (9) is uniformly charged by the charger (10). The means (8) for writing an electrostatic latent image writes an electrostatic latent image on the surface of the image carrier (9). The developing device (11) develops the electrostatic latent image to form a toner image on the surface of the moving image carrier (9). Transfer drum (1
2) The sheet (S) is placed at a transfer position (Po) at which the toner image on the surface of the image carrier (9) is transferred to the sheet (S).
Is transported. The front end of the corotron wire (33) of the static elimination coroton arranged in the axial direction along the surface of the image carrier (9) downstream of the transfer position (Po) is supported by the front insulating block (32). ing. Image carrier (9)
The surface is neutralized by the neutralizing corotron (14),
The cleaning is performed by a cleaning device (15a) arranged on the downstream side.

When a POP jam occurs in the image forming apparatus and the leading end of the sheet (S) is conveyed downstream of the neutralizing corotron (14), the sheet (S) is pulled out forward. In this case, the front-side insulating block (32) prevents the sheet (S) from being caught when the sheet (S) having entered between the front-side insulating block (32) and the image carrier (9) is dragged forward. Is formed on an inclined guide surface that moves away from the surface of the image carrier (9) as it goes backward. For this reason, the jammed sheet (S) does not get caught in the leading edge block of the static elimination corotron (14) and break.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to an embodiment of the present invention will be described below with reference to the drawings, but the present invention is not limited to the following embodiment. In order to facilitate the understanding of the following description, coordinate axes X orthogonal to each other in the drawing.
An axis, a Y axis, and a Z axis are defined, and the arrow X direction is forward, the arrow Y direction is left, and the arrow Z direction is upward. In this case, the direction opposite to the X direction (−X direction) is backward, and the direction opposite to the Y direction (−Y
Direction) is to the right, and the opposite direction to the Z direction (-Z direction) is downward. In addition, the front-rear direction including X direction and -X direction or X direction
The term “axial direction” refers to the left-right direction or the Y-axis direction including the Y direction and the −Y direction, and the up-down direction or the Z-axis direction includes the Z direction and the −Z direction. Furthermore, in the figure, "○"
The symbol with “•” in it means an arrow pointing from the back of the paper to the front, and the symbol with “X” in “○” means an arrow pointing from the front to the back of the paper. Shall be.

FIG. 1 is an overall explanatory view of a digital color copying machine having a transfer drum as an image forming apparatus according to an embodiment of the present invention. FIG. 2 is an enlarged view of a main part of FIG. 1, in which a sheet adhered to a transfer drum and conveyed adheres to an image carrier side, and the leading end of the sheet protrudes into a cleaner arranged around the image carrier. It is a front view of (POP jam state). FIG. 3 is a perspective view of the static elimination corona of the embodiment. FIG. 4 is an explanatory view of a front insulating block that supports a corotron wire of a static elimination corona. FIG. 4A is a perspective view of a front insulating block mounted on a shield case.
4B is a perspective view of the front insulating block taken out of the shield case, FIG. 4C is an exploded perspective view of the front insulating block, and FIG. 4D is an exploded sectional view of the front insulating block.

In FIG. 1, light emitted from a document illumination lamp 2 moving along the lower surface of a document (not shown) placed on a platen 1 and reflected by the document is reflected by a moving mirror unit 3 and a lens. 4. The light is converged on the image reading unit 6 via the fixed mirror 5. The image reading unit 6 is a color CCD having a large number of photoelectric conversion elements and R, G, and B filters.
It is composed of a sensor. The image reading unit 6 converts the original image into an electric signal for each color, and the electric signal is input to the optical writing control device 7.

The optical writing control device 7 converts a document image reading signal input for each color into a digital signal, stores the digital signal, reads the signal at a predetermined timing, and writes a light beam as a means for writing an electrostatic latent image. Output to the writing device 8. The light beam writing device 8 writes an electrostatic latent image corresponding to each color on the image carrier 9. Around the image carrier 9, a charging charger 10 for uniformly charging the surface of the image carrier 9, and a developing device for developing an electrostatic latent image written on the image carrier 9 into a toner image of each color. 11, a transfer drum 12, a charge removing corotron 14, and a cleaner unit 15 are arranged. Cleaner unit 1
5 supports a cleaning device 15a, the charging charger 10, and a static eliminator 16 composed of a red LED. The developing device 11 is Y (yellow),
M (magenta), C (cyan), and K (black) color developing devices are provided, and the electrostatic latent image is developed with toner of each color.

The sheet suction surface on the surface of the transfer drum 12 rotates, and the transfer drum 12 has a suction corotron 17 inside.
And the transfer corotron 18 is arranged in a fixed state. The transfer corotron 18 is arranged at a transfer position Po where the surface of the transfer drum 12 and the surface of the image carrier 9 are in contact with each other. The sheet S supplied from the paper tray 19 is suctioned at a suction position where the suction corotron 17 is arranged, with the leading end of the sheet S positioned at a predetermined position in the circumferential direction of the transfer drum 12. The transfer drum 12 rotates four times while the sheet S is being sucked. And 1
Each time the transfer corotron 18 is rotated, the toner images of the respective colors Y (yellow), M (magenta), C (cyan), and K (black) are sequentially transferred to the sheet S at the transfer position Po where the transfer corotron 18 is disposed. You.

In FIG. 1, a sheet S on the transfer drum 12 is separated by a separation claw 21 after the toner images of the respective colors on the image carrier 9 are transferred at a transfer position Po, and passes through a fixing unit 22. And is discharged to the discharge tray 23. Around the transfer drum 12, a post-transfer jam sensor 26, a charge eliminating corotron 27, and a cleaner 28 are arranged. The post-transfer jam sensor 26 is disposed downstream of the transfer position Po, and detects the presence or absence of the sheet S based on the amount of light reflected from the surface of the transfer drum 12. If there is no sheet after the transfer to the sheet S, a jam signal is output.

Next, the neutralizing corotron 14 will be described with reference to FIGS. The static elimination corotron 14 has a shield case 31 extending in the front-rear direction and having a U-shaped cross section.
In FIG. 4, insulating blocks 32, 32 (only the front insulating block is shown) are fixed to both front and rear ends of the shield case 31, respectively.
A corotron wire 33 is supported by 32.
At both ends of the shield case 31, a plurality of cut-and-raised portions 31a for fixing the insulating block are provided. The insulating block 32 is made of an elastic plastic detachable lower case 34 and upper case 3.
5. The lower case 34 has a wire fixing portion 34a, a lower connecting hole 34b, and an upper connecting hole 34c.
Is provided. Further, a plurality of locking holes 34 d for fixing to the shield case 31 are formed in the lower case 34. The insulating block 32 is fixed to the shield case 31 by locking the cut-and-raised portion 31 in the locking hole 34d.

The upper case 35 has a wire through groove 35a,
A lower connection projection 35b and an upper connection projection 35c are formed. The lower connection protrusion 35b is engaged with the lower connection hole 34b, and the upper connection protrusion 35c is connected to the upper connection hole 34b.
By engaging with c, the lower case 34 and the upper case 35 are integrally connected.
When the static elimination corotron 14 is installed along the surface of the image carrier 9 as shown in FIGS. 2 and 3, as can be seen from FIGS. Are formed on a smooth curved inclined guide surface which moves away from the surface of the image bearing member 9 as going toward. For this reason, when the sheet S that has entered between the charge removing corotron 14 and the image carrier 9 and is jammed is drawn forward, the sheet S
Is guided by the smooth curved inclined surface of the insulating block, so that it is not caught on the rear side surface of the front insulating block.

(Operation of First Embodiment) Next, the operation of the image forming apparatus of the first embodiment having the above-described configuration will be described. In FIG. 2, the sheet S is normally attracted to the transfer drum 12, but the attracting force is reduced for some reason, such as distortion of the transfer film forming the surface of the transfer drum 12 and a decrease in the water content of the sheet S. When the sheet S becomes weaker, the force of the sheet S attracted to the static electricity of the image carrier 9 may become stronger than the force of the sheet S being attracted to the transfer drum 12. At this time, the sheet S on the transfer drum 12 is attracted to the image carrier 9 and is conveyed as it is to the cleaner unit 15 to cause a jam. This jam is detected by the post-transfer jam sensor 26, and the rotation of the image carrier 9 and the transfer drum 12 is braked.

In FIG. 2, although the sheet S is stopped by the brake, the position of the stopped end of the sheet S may enter the cleaner unit 15 depending on the high-speed image forming apparatus. Further, even in an image forming apparatus which is normally configured so that the front end of the sheet S is stopped at a position before entering the cleaner unit 15 by the brake, the front end of the sheet S is not detected without detecting the jam. May enter 15. In this case, it is necessary to pull out the transfer drum 12 forward and the jammed sheet S.

As described with reference to FIG. 5, conventionally, when the jammed sheet is pulled out, the sheet may be caught on the rear side surface of the front insulating block of the static elimination corotron and may be broken. However, as can be seen from FIG. 4, the insulating block 32 of this embodiment shown in FIG. 4 has a smooth curved inclined guide in which the surface facing the image carrier 9 moves away from the surface of the image carrier 9 as going backward. Formed on the surface. For this reason, when the jammed sheet S that has entered between the static elimination corotron 14 and the image carrier 9 is pulled out forward, the sheet S is guided by the smooth curved inclined surface of the insulating block. It does not catch on the rear side of the insulation block. Therefore, when the sheet S that has been jammed by the jam after the transfer is pulled out, the sheet S does not get caught on the front insulating block 32 and is not broken.

(Modifications) Although the embodiments of the present invention have been described in detail, the present invention is not limited to the above-described embodiments, but falls within the scope of the present invention described in the appended claims. Thus, various changes can be made. Modified embodiments of the present invention will be exemplified below.

(H01) The inclined guide surface moving away from the image carrier surface 9 toward the rear of the front insulating block 32 of the charge removing corotron 14 can be an inclined plane instead of a curved surface. (H02) The rear side surface of another member on which the sheet is easily caught may be formed as a smooth inclined surface.

[0025]

The above-described seat guide device of the present invention can provide the following effects. (E01) When the POP jammed sheet is pulled out, the sheet can be prevented from tearing and remaining.

[Brief description of the drawings]

FIG. 1 is an overall explanatory diagram of a digital color copying machine having a transfer drum as an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of FIG. 1, in which a sheet adhered to a transfer drum and conveyed adheres to an image carrier side, and the leading end of the sheet is arranged inside the image carrier; FIG. 4 is a front view of a state (POP jammed state) in which the vehicle enters the state shown in FIG.

FIG. 3 is a perspective view of a charge removing corona according to the embodiment.

FIG. 4 is an explanatory view of a front insulating block that supports corotron wires of a static elimination corona, FIG. 4A is a perspective view of a front insulating block mounted on a shield case, and FIG. FIG. 4C is an exploded perspective view of the front insulating block, and FIG. 4D is an exploded sectional view of the front insulating block.

FIG. 5 is a diagram illustrating a state where the transfer drum is pulled out to remove a jammed sheet when the POP jam occurs.

FIG. 6 is an explanatory view of a conventional static elimination corotron.

[Explanation of symbols]

Po: transfer position, S: sheet, 8: means for writing an electrostatic latent image (light beam writing device), 9: image carrier, 10: charger, 11: developing device, 14: static elimination corotron, 12 ... Transfer drum, 15a cleaning device, 32 front insulating block, 33 corotron wire,

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03G 21/06 G03G 15/02 103 G03G 15/16 102

Claims (1)

(57) [Claims] 1. An image forming apparatus having the following requirements: (Y01) a charger for uniformly charging the surface of a moving image carrier; and (Y02) an electrostatic latent surface on the image carrier. Means for writing an image, (Y03) a developing device for developing the electrostatic latent image to form a toner image on the surface of the moving image carrier;
(Y04) a transfer drum that transports the sheet to a transfer position where the toner image on the surface of the image carrier is transferred to the sheet, (Y0
5) a cleaning device disposed downstream of the transfer position in the direction of movement of the surface of the image carrier; (Y06) a cleaning device disposed between the transfer position and the cleaning device; A corotron wire of a static elimination corotron extending in a direction, (Y07) supporting a front end of the corotron wire and preventing the sheet from being caught when the sheet that has entered between the image carrier and the sheet is dragged forward; A front insulating block formed on an inclined guide surface that moves away from the surface of the image carrier as the surface facing the carrier moves rearward;