JPS61235350A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent thrusting jam from taking place by switching a change-over section to a sheet correction path so as to correct warpage of the sheet by means of a sheet correction member in accordance with a copying mode set in a printed image forming device. CONSTITUTION:A sheet correction path 41, which is connected to a sheet convey recommencing path 36 and is equiped with sheet correction section 40, is formed. In addition, a conveying direction change-over section 42 is arranged at a junction point where correction path 41 meets a direct lead path 42 for recommencing sheet convey. Then, the conveying direction change-over section is switched to the sheet correction path in accordance with the specified copying mode. Therefore, the sheet which is conveyed on the sheet convey recommencing path 36, is guided by the conveying direction change-over section 42, and is conveyed to the sheet correction path 41. Thus, the sheet is corrected of its warpage through the sheet correction member 40, and then, is inducted into a printed image forming section. This configuration enables image carriers such as sensitizer of the sheet to be favorably separated, preventing thrusting jam from taking place, and enables both reliability and durability to be augmented.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Industrial Application The present invention relates to an image forming apparatus such as a copying machine or a laser beam printer, and more specifically, to an image forming apparatus including a sheet straightening path for correcting sheet warping. Regarding equipment.

(b) Conventional technology Generally, when performing multiple copying or double-sided copying with an image forming apparatus, such as a copying machine, a sheet on which an image has been formed in an image forming section is fixed in a fixing device, and the copied sheet is then reused as a sheet. The image is then introduced into the image forming section via the conveyance path, and multiple copies or double-sided copies are made.

Q→ Problems to be solved by the invention However, since the sheet passing through the fixing device of the copying machine is heated and pressurized by the fixing device to perform fixing, upward warping occurs at the leading edge of the sheet. In many cases, the curled sheet becomes a curled sheet, and when the curled sheet is reintroduced to the image forming section via the sheet re-conveying path to perform multiple copying, the curled sheet is curled upward. Due to the warpage, the sheet tends to wrap around the photoreceptor of the image forming section, and the separability of the sheet from the photoreceptor is significantly reduced.

For this reason, the sheet is not separated from the photoreceptor and hits the cleaner of the image forming section, which may damage the photoreceptor or the rubber blade of the cleaner or cause a jam.

Therefore, it has been considered to improve the separation of the sheet on the photoreceptor by bringing separation claws into contact with the photoreceptor, but the separation claws may damage the photoreceptor, and the photoreceptor's durability is The lifespan will be reduced.

Furthermore, in order to correct the warpage of the sheet, there is a device in which a correction member is placed in the ejection roller part of the fixing device, but the correction member cannot sufficiently correct the warpage and the curled sheet is still sent to the image forming unit. was introduced.

B.) Means for Solving the Problems The present invention aims to solve the above-mentioned problems, and as shown in FIG.
A sheet straightening path 41 having a sheet straightening member 40 is formed in communication with
A conveyance direction switching member 42 is disposed at the branch point 6', and the switching member 42 is switched to the sheet straightening path 41 side in accordance with the copy mode set in the main body of the image forming apparatus U. It is characterized by correcting warpage.

(E) Effect Based on the above-described configuration, the conveying direction switching member 42 is switched to the sheet straightening path 41 side in accordance with a predetermined copy mode, and the sheet conveyed along the sheet re-transfer path @36 is transferred to the conveying direction switching member 42. The sheet is guided and conveyed to the sheet correction path 41. As a result, the sheet is corrected for its warp by the sheet correction member 40, and then introduced into the image forming section again.

(F) Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

As shown in FIG. 1, the copying machine U includes a document table 7, a light source 9,
The copying machine includes a lens system 10, two cassettes 11 and 12, and a cylindrical photoreceptor 13 disposed within the main body of the copying machine. Further, near the periphery of the photoreceptor 13, there are two current +1 units 15 and 16 each containing toner of a different color, a cleaner 17 and a primary charger 19, and a transfer charger at the tip of the transport bag W20. 21 and a separation charger 22 are provided. Further, paper feed rollers 23 and 25 are arranged in the cassette 11 and 12 portions, and are guided to a pair of registration rollers 29 via paths 26 and 27, respectively. Also,
A fixing device 30 is disposed at the rear end portion of the conveyance device 20, a first flapper 31 and a twenty-seventh flapper 32 are disposed downstream of the fixing device 30, and a roller pair 33 is disposed downstream of the first flapper 31 and a twenty-seventh flapper 32. A sheet trailing edge detection sensor 35 is installed near the pair of discharge rollers 33 to detect the trailing edge of the sheet discharged from the pair of rollers 33.

Further, a sheet re-conveyance path 36 is formed by being branched and selected by the first flapper 31, and the sheet re-conveyance path 36 includes a pair of conveyance rollers 37, 39 and a pair of lateral registration rollers 1.
are arranged, and are further branched in two directions from the downstream side of the pair of registration rollers 1 to form a direct portion 3 of the sheet re-conveying path 36.
6' and a sheet correction path 41 are formed and communicate with the registration rollers 29, respectively.

As shown in FIGS. 2 and 3, a third flapper 4 is installed at the two-way branch point on the downstream side of the pair of lateral registration rollers 1.
The flapper 42 is connected to an arm 43a of a solenoid 43, and the end of the arm 43a is biased by a spring 45 in the direction of the arrow to normally switch the third flapper 42 in two directions. 42 is switched and held on the sheet re-conveyance direct path 36' side (the solid line portion in FIG. 3). Further, the sheet correction path 41 is formed to have a larger curvature than the sheet re-conveyance direct path 36',
Further, a pair of sheet straightening rollers 40 is arranged in the straightening path 41. The straightening roller pair 40 is composed of an upper roller 40a made of a non-elastic material such as resin or metal, and a lower roller 40b made of an elastic material such as silicon sponge rubber or urethane, and the upper roller 40a is fixed. An upper roller shaft 40a' is rotatably supported by the side frame 38, and is driven by a driving means (not shown). Further, a lower roller shaft 40b' fixing the lower roller 40b is rotatably supported by the side frame 38 and slidably in the direction of the upper roller 40a. Wrapped around;
Both ends thereof are pressed and biased against the upper roller 40a by a spring 46 fixed to the side frame 38, and are driven into pressure contact with the upper roller 40a.

Since the present embodiment has the above-described configuration, when the light source 9 moves, the document M placed on the document table 7 is irradiated by the light source 9, and the reflected light passes through the lens system 10 and is pre-charged by the charger 19. An image is formed on the uniformly charged surface of the photoreceptor 13 to form an electrostatic latent image, and as the photoreceptor 3 rotates in the direction of the arrow, the electrostatic latent image is transferred to the toner at the developing device 16 position. form an image. On the other hand, the sheet S loaded in the cassette 11 or 12 is sent to the paper feed roller 23 or 25, aligned with the toner image on the surface of the photoreceptor by the registration roller 29, and further transferred to the transfer charger 21. The toner image is transferred to the sheet surface. Further, the sheet S carrying the toner image is separated from the photoreceptor 13 by a separation charger 22, sent to a fixing device 30 by a conveying device 20, and fixed there. At that time, the sheet S is
The sheet is heated and pressurized at 0 to form a curled sheet S' having an upward warp at the leading edge of the sheet.

When the double-sided copying mode is selected, the curled sheet S' fixed by the fixing device 30 is guided to the first flapper 31, and is directed toward the outside of the main body of the copying machine U by the forward rotation of the discharge roller pair 33. transported to. At this time, the second flapper 32 is in a state blocking the sheet conveyance path, but since the second flapper 32 is made of a light member and is supported rotatably in the direction of arrow F, the curled sheet S'
As it passes, it is pushed up by the leading edge of the sheet and is retracted from the curl sheet S', and the curl sheet S
′ will not be a hindrance to passage. Further, a pair of discharge rollers 33
The curled sheet S' is conveyed by the forward rotation of the sheet S', and when the trailing edge of the sheet S' is detected by the sheet trailing edge detection sensor 35, the discharge roller pair 33 is rotated in the reverse direction, and the sheet S' is transferred to the second flapper. 35 and the first flapper 31, and is guided to the sheet re-conveying path 36. Further, the sheet S' is conveyed forward by the stopped tank registration roller pair 1 due to the rotation of the conveyance roller pair 37, 39, and after the leading edge of the sheet S hits the registration roller pair 1, the sheet S' is conveyed forward by the rotation of the conveyance roller pair 37, 39. 39 is stopped, and the curl sheet S' is stopped in a state where it forms a loop in front of the pair of lateral registration rollers 1. Then, when a copy signal is sent from the copying machine main body to the other side, the horizontal registration roller pair 1 is rotated, and further,
With the pair of lateral registration rollers 1 biting into the curl sheet S', the pair of lateral registration rollers 1 are moved in a direction perpendicular to the sheet conveyance direction until the side edge of the sheet is detected by an optical sensor (not shown), and the curl sheet S' is moved in a direction perpendicular to the conveyance direction of the curl sheet S'. The position is adjusted.

Furthermore, the curled sheet S' is guided to the third flapper 42 (solid line in FIG. 3) which has been switched to the sheet re-conveying path 36 side, and is guided to the pair of registration rollers 29 via the direct portion 36' of the re-conveying path 36. transported.

Furthermore, the sheet S' is conveyed by a pair of registration rollers 29, and a toner image is transferred to the back surface (the non-copied surface) of the sheet by the photoreceptor 13, transfer charger 21, etc. in the same manner as described above. At this time, since the back surface of the curled sheet S' having an upward curvature comes into contact with the photoreceptor 13, the separation of the sheet S' from the photoreceptor 13 is good.

After the sheet s' is fixed by the fixing unit M30, the sheet copied on both sides is discharged to the outside of the copying machine main body by a pair of discharge rollers 33.

In addition, when the multiple copying mode is selected, the first flapper 31 is switched to the sheet re-conveying path @36 side, and the solenoid 43 is energized so that the third flapper 42
is switched to the sheet correction path 41 side (dotted line in Figure 3),
Copied curl sheet S' fixed with fixing@s30
is guided by the first flapper 31 to the sheet re-conveying path 3
6. Then, as in the case of double-sided copying described above, the lateral position of the sheet S' is adjusted by the pair of lateral registration rollers 1, and the third flapper 42 (dotted in the third figure) is further switched to the sheet correction path 41 side. The curled sheet S' is conveyed through a sheet straightening path 41 with a large curvature, and the curl is corrected by being held between a pair of sheet straightening rollers 40, and the straightened sheet S is conveyed through a pair of registration rollers 29. Furthermore, the sheet S is transported by a pair of registration rollers 29, and a second image is superimposed and copied on the surface of the sheet S that has been copied once. Since the sheet S that has been corrected comes into contact with the photoconductor 13, the separation of the sheet S from the photoreceptor 13 is good.Furthermore, after the sheet on which multiple copies have been copied is fixed in the fixing device 30, it is switched to the ejection roller pair 33 side. It is guided by the first flapper 31 and discharged to the outside of the copying machine main body by a pair of discharge rollers 33.

In this embodiment, a sheet straightening roller pair 40 consisting of an upper roller 40a and a lower roller 40b was used as the sheet straightening member, but as shown in FIG. Pressure the rollers 40c and 40d.
A similar effect can be obtained even if it is energized.

(G) As described in detail, according to the present invention, a sheet straightening path is formed which communicates with the sheet re-conveyance path and has a sheet straightening member, and furthermore, at a branch point between the straightening path and the direct re-conveyance path. Electricity is distributed to the conveyance direction switching member, the switching member is switched to the sheet straightening path side in accordance with the copy mode set in the main body of the image forming apparatus, and the sheet straightening member corrects the warpage of the sheet, so the copy mode can be selected. When it is necessary to correct the warpage of the sheet, for example, only in the case of multiple copying, the curled sheet with the warp can be conveyed to the sheet correction path and the warp can be corrected by the sheet correction member, and the photoreceptor of the sheet It is possible to maintain good separability from the image carrier, such as the like, and to construct a reliable and durable image forming apparatus without causing jamming.

[Brief explanation of the drawing]

1 is a side view showing the image forming apparatus according to the present invention, FIG. 2 is a perspective view showing the area around the sheet correction path, FIG. 3 is a side view thereof, and FIG. 4 is the area around the sheet correction path of another embodiment. FIG. 36...Sheet re-conveyance path, 36'...Sheet re-conveyance direct path, 40...Sheet correction member (sheet correction roller pair), 41...Sheet correction path,
42...Conveyance direction switching member (third flapper),
U...image forming device.

Claims (2)

[Claims] (1) In order to perform multiple image formation or double-sided image formation on the same transfer sheet, the transferred sheet that has been carried out through the image forming section and the fixing section is reintroduced to the image forming section via the sheet re-conveying path. In an image forming apparatus configured to an image forming apparatus, wherein the switching member is switched to a sheet straightening path side in accordance with a copy mode set in an image forming apparatus main body, and the sheet straightening member corrects warping of the sheet. (2) The image forming apparatus according to claim 1, wherein the copy mode is a multiple copy mode.