JP3785848B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus that forms an image (including characters) on a recording material, fixes the image, and discharges the image. The present invention relates to an image forming apparatus such as a printer, a facsimile machine, and a copying machine that forms, fixes, and discharges a toner image on a recording material mainly using an electrophotographic technique, and particularly relates to a conveyance technology for the recording material.
[0002]
[Prior art]
In general, an image forming apparatus that forms a toner image on a recording material such as paper using electrophotographic technology is a photosensitive member that is rotationally driven and an exposure that exposes the photosensitive member to form an electrostatic latent image on the surface. Means, developing means for developing the electrostatic latent image into a toner image, a transfer portion for transferring the toner image onto a recording material, and heating while passing the recording material onto which the toner image has been transferred by the transfer portion. And a fixing unit for fixing the toner image on the recording material.
[0003]
In such an image forming apparatus, if the recording material from the transfer portion to the fixing portion is not smoothly conveyed, the unfixed toner image on the recording material may be disturbed.
[0004]
Therefore, conventionally, for example, as shown in FIG. 3, a fan 3 as a suction unit is provided in the conveyance path (4) of the recording material S from the transfer unit 1 to the fixing unit 2, and the fan 3 fixes from the transfer unit 1. There is known an image forming apparatus in which the recording material S heading to the section 2 is sucked so as to be along the guide surface 4 (Japanese Patent Publication No. 1-334377). Note that the fan 3 of this image forming apparatus blows air to the stock recording material S ′ to dehumidify the recording material S ′.
[0005]
On the other hand, various image forming apparatuses capable of forming images on both sides of a recording material have been provided in recent years in order to save resources.
[0006]
Among this type of image forming apparatus, there is known a type in which the recording material that has passed through the fixing unit is reversed and turned back to the transfer unit so that an image can be formed on the back side. It has been.
[0007]
[Problems to be solved by the invention]
In an image forming apparatus in which the recording material that has passed through the fixing unit is returned to the transfer unit again so that an image can be formed on the back surface, the recording material to be returned once passes through the fixing unit and is heated. However, there is a difficulty that it is easy to curl.
[0008]
And if the curl amount at the leading edge of the recording material is different on the left and right, the biting timing to the conveying roller provided in the return path will be different on the left and right, so the recording material is skewed, and as a result, There is a problem that the image tends to be inclined with respect to the recording material.
[0009]
SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems and to provide an image forming apparatus in which the recording material from the transfer unit to the fixing unit can be smoothly moved and the image on the back surface is not easily inclined with respect to the recording material. It is to provide.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, an image forming apparatus according to claim 1 is configured to transfer a transfer unit that transfers an unfixed image onto a recording material, and to convey the recording material on which the unfixed image is transferred by the transfer unit while heating. A fixing unit that fixes the unfixed image on the recording material, a guide surface that guides the recording material from the transfer unit toward the fixing unit, and a suction unit that sucks the recording material so that the recording material is placed along the guide surface. A return path capable of returning the recording material that has passed through the fixing unit to the transfer unit again,
The suction means is provided between the guide surface and the return path, and air from the suction means is applied toward the recording material passing through the return path, and the entire surface of the guide surface. Is covered with the recording material, at least the tip of another recording material does not pass through the blowing position in the return path.
[0012]
Here, “the entire surface of the guide surface” means, more specifically, “all the suction ports formed in the guide surface for suction by the suction means”.
[0013]
[Function and effect]
According to the image forming apparatus of the first aspect, the recording material on which the unfixed image has been transferred by the transfer unit is guided by the guide surface toward the fixing unit, and is conveyed while being heated by the fixing unit. It is fixed. The recording material heading from the transfer unit to the fixing unit is sucked by the suction unit and runs along the guide surface, so that the posture thereof moves stably and smoothly. In addition, since the image forming apparatus includes a return path through which the recording material that has passed through the fixing unit can be returned to the transfer unit again, it is possible to form images on both sides of the recording material.
[0014]
According to the image forming apparatus of the first aspect, the suction unit is provided between the guide surface and the return path, and the air blown from the suction unit is recorded through the return path. Therefore, even if the recording material heated once passing through the fixing unit is curled, when the recording material passes through the return path, the curl amount is the effect of the air blowing. Will be reduced.
[0015]
Therefore, the difference in curl amount at the left and right ends of the recording material to be returned is also reduced, and the biting timing to the conveying roller provided in the return path is not so different from right to left. The skew amount of the recording material is also reduced, and the image on the back surface is less likely to be inclined with respect to the recording material.
[0016]
As described above, according to the image forming apparatus of the first aspect, the recording material is smoothly moved from the transfer portion to the fixing portion, and the image on the back surface is hardly inclined with respect to the recording material. .
[0017]
In addition, since the curl amount of the recording material to be returned is reduced, the recording material is hardly clogged.
[0018]
According to an image forming apparatus of claim 2, in the image forming apparatus of claim 1, when the entire guide surface is covered with the recording material, the blowing position in the return path is set to another recording material. At least the tip of the recording material does not pass through, that is, when at least the tip of another recording material passes through the air blowing position in the return path, at least a part of the guide surface is not covered with the recording material. Therefore, air is reliably blown to at least the tip of the recording material (the other recording material) passing through the return path.
[0019]
Accordingly, the amount of skew of the recording material to be returned is more reliably reduced, and the image on the back surface is more unlikely to be inclined with respect to the recording material.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0021]
1A and 1B are schematic views showing a main part of an embodiment of an image forming apparatus according to the present invention. FIG. 1A is a front view and FIG. 1B is a bottom view mainly showing a return path.
[0022]
In FIG. 1, reference numeral 10 denotes a transfer unit, which has an image carrier 11 and a transfer roller 12. A toner image is formed on the surface of the image carrier 11 by image forming means (not shown), and this toner image is transferred onto the recording material S passing between the image carrier 11 and the transfer roller 12.
[0023]
A fixing unit 20 includes roller pairs 21 and 22. At least one (or both) of these rollers 21 and 22 has a heat source therein, and the recording material S on which the unfixed toner image has been transferred by the transfer unit 10 is conveyed while being heated. The image is fixed on the recording material S.
[0024]
Reference numeral 30 denotes a suction unit, which has a case 31 and a fan 32 as suction means housed in the case. The suction unit 30 is disposed between the transfer unit 10 and the fixing unit 20, and the upper surface 33 of the case 31 forms a guide surface for guiding the recording material S from the transfer unit 10 toward the fixing unit 20. ing.
[0025]
Reference numeral 40 denotes a conveyance path for the recording material S. The supply path 41 for supplying the recording material S from a paper feeding device (not shown) to the transfer unit 10 and the recording material S1 on which the toner image is fixed by the fixing unit 20 are illustrated. A paper discharge path 42 for discharging paper to a paper discharge section (for example, a paper discharge tray) that is not used and a return path 43 for forming double-sided images are provided.
[0026]
In the supply path 41, a gate roller pair 51 that defines the conveyance timing of the recording material S to the transfer unit 10 is arranged.
[0027]
The paper discharge path 42 is provided with a pair of rollers 52 that can be rotated forward and backward, and a pair of paper discharge rollers (not shown) that is provided on the downstream side (upward in the drawing) of the roller pair 52 and that can be rotated forward and backward. As the roller pair 52 and the discharge roller pair continue to rotate forward (rotate in the direction of the arrow in the drawing), the recording material S1 from the fixing unit 20 is discharged to a predetermined location (for example, a discharge tray). It is like that.
[0028]
On the other hand, after the recording material S1 from the fixing unit 20 enters the paper discharge path 42 and the rear end S1a of the recording material S1 passes through the roller pair 52, the roller pair 52 and the paper discharge roller pair are reversed. The recording material S1 is fed to the return path 43 in a state where the front and back thereof are reversed (that is, the rear end S1a is the leading end). In other words, the paper discharge path 42 constitutes a switchback path for feeding the recording material S1 to the return path 43 with its front and rear reversed.
[0029]
The return path 43 passes below the suction unit 30, and its end 44 joins the supply path 41. In the return path 43, conveyance roller pairs 53, 54, 55, and 56 for the recording material S1 are provided.
[0030]
Accordingly, the recording material S1 fed from the switchback path 42 to the return path 43 is transported by the transport roller pairs 53 to 56, and the supply path 41 and the gate roller pair 51 in a state where the front and back sides are reversed. Then, the image is again supplied to the transfer unit 10 and an image is formed on the back surface thereof.
[0031]
Since the return path 43 passes below the suction unit 30, the fan 32 of the suction unit 30 is provided between the guide surface 33 and the return path 43.
[0032]
The upper and lower guide plates 45 and 46 with respect to the recording material S1 that form the return path 43 pass the air A (see FIG. 8A) blown from the suction unit 30 as shown in FIG. A large number of slit-shaped openings 47 are formed, and air blown from the suction unit 30 (that is, air blown by the fan 32) A is applied to the recording material S1 passing through the return path 43 through the openings 47. ing.
[0033]
The return path 43 is provided with a detector 48 for detecting a conveyance failure (clogging or the like) of the recording material S1 and stopping the apparatus when the conveyance failure occurs.
[0034]
The operation of the entire image forming apparatus is controlled by a control unit (not shown). The control unit records the detector 48 within a predetermined time after the gate roller pair 51 starts rotating. When the material S1 is not detected, it is determined that a conveyance failure such as a paper jam has occurred, and the operation of the apparatus is stopped.
[0035]
In addition, the control unit is configured so that all of the suction surfaces (not shown but similar to the opening opening 47) formed on the entire guide surface 33, more specifically the guide surface 33, are sucked by the fan 32. When the recording material S is covered, the recording material S is arranged such that at least the tip of another recording material S1 does not pass through the blowing position in the return path 43 (the range of the return path 43 provided with the opening 47). , The conveyance of the recording material S1 is controlled.
[0036]
According to the image forming apparatus as described above, the following effects can be obtained.
[0037]
(A) The recording material S on which the unfixed toner image is transferred by the transfer unit 10 is guided by the guide surface 33 toward the fixing unit 20 and is conveyed while being heated by the fixing unit 20 to fix the toner image. Since the recording material S heading from the transfer unit 10 toward the fixing unit 20 is sucked by the suction unit 32 and runs along the guide surface 33, the posture thereof moves stably and smoothly. In addition, since the image forming apparatus includes the return path 43 through which the recording material S1 that has passed through the fixing unit 20 can be returned to the transfer unit 10 again, it is possible to form images on both sides of the recording material S. .
[0038]
According to the image forming apparatus of this embodiment, the suction means 32 is provided between the guide surface 33 and the return path 43, and the air blow A from the suction means 32 passes through the return path 43. Therefore, even if the recording material S1 that has passed through the fixing unit 20 and is heated is curled, when the recording material S1 passes through the return path 43, the recording material S1 is applied. The curl amount is reduced by the action of the air blow A.
[0039]
This point will be specifically described with reference to FIG.
[0040]
FIG. 2 is a conceptual diagram showing a state in which the recording material S1 curled at the leading end S1a because it has once passed through the fixing unit 20 and is about to reach the conveying roller pair 55 in the return path 43. It is.
[0041]
In this figure, for easy understanding, the left end S1a1 of the leading end of the recording material S1 is greatly curled, and the right side S1a2 is not curled (the curl amount is 0).
[0042]
For example, in this situation, if no measures are taken, the curl amount of the tip S1a is different between the left and right S1a1 and S1a2 (in this case, the curl amount of the right S1a2 is 0), so that recording is performed. When the right side S1a2 of the leading end S1a of the material S1 reaches the conveyance roller pair 55, the left side S1a1 is separated from the conveyance roller pair 55 by a distance L due to the curl.
[0043]
Therefore, the left side S1a1 of the leading end S1a of the recording material S1 bites into the conveying roller pair 55 with a delay corresponding to the distance L with respect to the right side S1a2 (enters the nip portion N of the roller pair). It will be.
[0044]
Therefore, the recording material S1 is skewed (in this case, the right side S1a2 is skewed so as to precede the left side S1a1), and as a result, the image on the back surface is inclined with respect to the recording material S1. It becomes.
[0045]
If the skew amount of the recording material S1 is large, the detection timing of the recording material S1 by the detector 48 is delayed, so that the recording material S1 is not actually clogged but clogged. It may be determined by the control unit that it has occurred, and the operation of the apparatus may stop.
[0046]
On the other hand, according to the image forming apparatus of this embodiment, since the air blow A from the suction unit 32 is applied toward the recording material S1 passing through the return path 43, it passes through the fixing unit 20 once. Even if the heated recording material S1 is curled, when the recording material S1 passes through the return path 43, the curling amount is reduced by the action of the air blow A. If it is described in an easy-to-understand manner (in an extreme example) in FIG. 2, the curling of the left side S1a1 of the leading end S1a of the recording material S1 is corrected and the position relative to the conveying roller pair 55 is the right side S1a2 as indicated by the broken line S1a1 ′. Is equivalent to
[0047]
That is, the curl amount difference between the left and right ends of the recording material S1 to be returned is reduced, and the biting timing to the transport roller 55 provided in the return path 43 is not so different from right to left. As a result, the skew amount of the recording material S1 is also reduced, and the image on the back surface is less likely to be inclined with respect to the recording material S1.
[0048]
Therefore, when the recording material S1 is not actually clogged, the detection timing of the recording material S1 by the detector 48 is not delayed and the operation of the apparatus is not stopped.
[0049]
As described above, according to the image forming apparatus of this embodiment, the recording material S from the transfer unit 10 to the fixing unit 20 can be smoothly moved, and the image on the back surface is inclined with respect to the recording material. It becomes difficult. In addition, unnecessary stop of the apparatus is prevented.
[0050]
(B) Since the curl amount of the recording material S1 to be returned is reduced, the recording material S1 itself is hardly clogged.
[0051]
(C) For example, as shown in FIG. 1A, when the entire guide surface 33 is covered with the recording material S, the blowing position (see arrow A) in the return path 43 is set to another recording material S1. At least the tip S1a does not pass, that is, when at least the tip S1a of another recording material S1 passes through the blowing position in the return path 43, at least a part of the guide surface 33 (its suction port) is the recording material S. Since it is in an uncovered state, the air blow A is surely made to at least the tip S1a of the recording material (the other recording material) S1 passing through the return path 43.
[0052]
Therefore, the amount of skew of the recording material S1 returned is more reliably reduced, and the image on the back surface is more unlikely to be inclined with respect to the recording material.
[0053]
Although one embodiment of the present invention has been described above, the present invention is not limited to the above-described embodiment, and can be appropriately modified within the scope of the gist of the present invention.
[0054]
【The invention's effect】
In any of the image forming apparatuses according to the first and second aspects, the recording material can be smoothly moved from the transfer portion to the fixing portion, and the image on the back surface is hardly inclined with respect to the recording material. In addition, since the curl amount of the recording material to be returned is reduced, the recording material is hardly clogged.
[0055]
Further, according to the image forming apparatus of the second aspect, the skew amount of the recording material to be returned is more reliably reduced, and the image on the back surface is more unlikely to be inclined with respect to the recording material.
[0056]
[Brief description of the drawings]
1A and 1B are schematic views showing a main part of an embodiment of an image forming apparatus according to the present invention, in which FIG. 1A is a front view and FIG. 1B is a bottom view mainly showing a return path;
FIG. 2 is an explanatory diagram of operation.
FIG. 3 is an explanatory diagram of a conventional technique.
[Explanation of symbols]
S Recording material 10 Transfer section 20 Fixing section 30 Suction unit 32 Fan (suction means)
33 Guide surface 43 Return path A

Claims (1)

A transfer unit that transfers an unfixed image onto a recording material, a fixing unit that heats and conveys the recording material onto which the unfixed image has been transferred by the transfer unit, and fixes the unfixed image on the recording material; and the transfer unit A guide surface that guides the recording material from the fixing portion to the fixing portion, a suction means for sucking the recording material so that the recording material is along the guide surface, and the recording material that has passed through the fixing portion can be returned to the transfer portion again. With a return path,
The suction means is provided between the guide surface and the return path, and air from the suction means is applied toward the recording material passing through the return path, and the entire surface of the guide surface. Is covered with the recording material, at least the tip of another recording material does not pass through the blowing position in the return path.

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