JPH06191705A - Image forming device - Google Patents

Abstract

PURPOSE:To provide an image forming device having good operability, when the skew of a transfer paper occurs, without the wasteful consumption of the transfer paper. CONSTITUTION:The skew of a transfer paper carried from a paper feeding part is detected by a skew detecting sensor 13, and when skew quantity is judged having a value larger than a given set value, a carrying path switching claw 15, circuit-opening a normal carrying path 16 side, is rotated in a counterclockwise direction to circuit-open a skew sheet path 16' for carrying a skew transfer paper in a skew paper housing tray direction.

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, and more particularly to detecting a skew of a transfer sheet on a transfer sheet conveying path and causing a trouble such as a paper jam of the conveyed transfer sheet. The present invention relates to an image forming apparatus configured to prevent the above.

[0002]

2. Description of the Related Art As is well known, in an image forming apparatus, a transfer sheet transferred from a sheet feeding unit is abutted against a stopped registration roller and loosened upstream of the registration roller to transfer the transfer sheet. The skew of the transfer paper is prevented at the same time when the feeding timing to the position is determined. However, the skew feeding operation at the registration roller position does not necessarily eliminate the skew of the conveyed transfer sheet, and the larger the skew of the transfer sheet, the more
The skew of the transfer paper occurs downstream of the registration roller. Therefore, conventionally, for example, as disclosed in Japanese Patent Application Laid-Open No. 64-43435, a method for detecting skew of the transfer paper, or as disclosed in Japanese Patent Application Laid-Open No. 55-53360, It has been proposed to provide a means for stopping the conveyance of the transfer paper after detecting the skew of the paper. In addition, JP-A-56
As disclosed in JP-A-8163 and JP-A-57-115567, after detecting the skew of the transfer paper, an image is formed according to a normal electrostatic photography process, and the skewed transfer paper is sorted. The method of doing is also considered.

[0003]

However, the first prior art only detects the skew of the transfer paper, and the second prior art detects the skew of the transfer paper and stops the machine. However, in both cases, the subsequent processing is entrusted to the operator, so if the operator makes a mistake in processing, the device may be damaged. On the other hand, in all of the last conventional techniques, an image is formed on the transfer paper, and thus the discharged transfer paper is wasted. SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art, and to provide an image forming apparatus that has good operability when skew of the transfer sheet occurs and does not waste the transfer sheet.

[0004]

In order to achieve this object, the present invention provides a skew detecting means for detecting skew of a transfer sheet conveyed from a sheet feeding means in the middle of a transfer sheet conveying path, and a skew detecting means. It is provided on the downstream side of the line detection means, at the branch portion of the normal conveyance path conveyance path reaching the image forming means and the skewed paper conveyance path reaching the skewed paper accommodating device. The conveyance path switching means for switching to, the skew amount determining means for comparing the skew amount of the transfer sheet detected by the skew detecting means with a predetermined set value, and outputting the skew presence / absence signal, and the skew amount determining means. According to the output skew presence / absence signal, when the skew amount of the transfer paper is smaller than a predetermined set value, the normal transport path is set, and when the skew amount of the transfer paper is larger than the predetermined set value, the skew sheet transport path is set to It has a transport path selecting means for selecting as a transport path.

[0005]

When the transfer sheet is conveyed from the sheet feeding means by the start of the image forming operation, the skew detecting means detects the skew of the conveyed transfer sheet. The skew amount determining means compares the skew amount of the transfer sheet detected by the skew detecting means with a predetermined set value, and outputs a skew presence / absence signal. According to the skew presence / absence signal output from the skew amount determination means, the transport path selection means uses the normal transport path as the transport sheet transport path when the skew amount of the transfer sheet is smaller than a predetermined set value, and the skew amount of the transfer sheet. Is larger than a predetermined set value, the skewed paper transport path is selected, and the transport path switching means switches the transport path of the transfer paper to the normal transport path side or the skewed paper transport path side according to the selection result of the transport path selection means.

[0006]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a configuration diagram showing the overall configuration of a copying machine according to the first embodiment of the present invention. FIG. 2 is an enlarged view of the conveyance path near the transfer section. The image of the document is read by the image reading unit 1, and the reflected light of the document is guided onto the photosensitive drum 2 by the optical system. The electrostatic latent image of the original image is formed on the photosensitive drum 2 uniformly charged by the charging device 3 by exposing the original to the reflected light. After the latent image is processed by the developing device 4 as a visible image, the transfer / separation device 5 transfers the electrostatic latent image to a transfer sheet conveyed from a sheet feeding unit 6 described later. The transfer sheet conveyed to the transfer position is fed from the sheet feeding section 6 and conveyed to the transfer position of the transfer / separation device 5. That is, the transfer paper stored in the paper feeding tray 7 is fed by the feeding roller 81 of the feeding paper feeding unit 8 and is fed downstream by the paper feeding roller 82. After that, the transfer sheet conveyed to the position of the registration roller 9 is set by the registration roller 9 at the timing of feeding to the transfer position, and the skew of the transfer sheet is corrected. The transfer paper on which the image is transferred by the transfer / separation device 5 is separated from the photoconductor drum 2, and then is transferred further downstream by the transfer belt 10 arranged downstream of the transfer position. Thereafter, the transferred transfer paper is subjected to a fixing process in the process of being nipped and carried by the fixing roller 11, and is eventually discharged onto the paper discharge tray 12. The above description describes the transfer sheet conveyance process when the transfer sheet is normally conveyed and does not skew, but when the transfer sheet is skewed and conveyed, the above-described conveyance process is performed. Follow a different transport process.

The transfer paper stored in the paper feeding tray 7 is conveyed from the paper feeding / separating portion 8 and abutted against the registration roller 9 and the registration roller 9 to stop, and thereafter the paper feeding timing is set by the registration roller 9. At the same time, the skew is corrected. The skew of the transfer sheet whose skew has not been corrected or the skew of the transfer sheet which has been skewed thereafter is detected by a skew detection sensor 13 (a, b) described later. When the skew is detected, the control unit 14 described later makes a comparison with a skew amount set value, and when the skew amount of the transfer sheet is larger than the skew amount set value, the shift amount will be described immediately before the photosensitive drum 2. The transport path switching claw 15 switches the transport direction of the transfer paper to the skewed paper transport path 16 ′ side, and the transfer paper transported along the skewed paper transport path 16 ′ is transported to the skewed paper storage tray 17. Is discharged. FIG. 3 shows how the skew detection sensor 13 detects skew of the transfer sheet. Two skew detection sensors 13 (a, b) are arranged in the direction perpendicular to the transfer paper conveyance direction, and each detects the transfer paper passing therethrough. The skew detection sensors 13a and 13b are connected to a control unit 14 which will be described later, and when each of them detects a transfer sheet, it sends a detection signal to the control unit 14. In addition,
As described above, in this embodiment, the two skew detection sensors 13 are arranged in the direction perpendicular to the transfer paper conveyance direction. However, the skew detection sensor 13 may be moved according to the width size of the transfer paper, or the width size of the transfer paper may be changed. In addition, a large number may be provided in the direction perpendicular to the transfer paper conveyance direction.

FIG. 4 is a partially cutaway view showing the peripheral portion of the transport path switching claw 15. When the normal copying operation is performed on the transport path switching claw 15 and the skew amount of the transported transfer paper is smaller than the skew amount set value, the rotation shaft to which it is attached by the elastic force of the spring 21 is shown in FIG. It is in a position to open the normal conveyance path 16 under the biasing force of rotating it in the clockwise direction. On the other hand, when the skew amount of the transferred transfer paper is larger than the skew amount set value, the rotation shaft to which the transport path switching claw 15 is attached is rotated by a control signal sent from the control unit 14 described later. The solenoid 20 receives an urging force that rotates counterclockwise in FIG. 4 against the elastic force of the spring 21, and the transport path switching claw 15 is oriented to the upper position for opening the skewed paper transport path 16 '. . FIG. 5 shows the control unit 1.
4 is a block diagram showing a configuration relating to transport path switching of No. 4, and FIG. 6 is a flowchart showing a transport path switching operation of the control unit 14. The control unit 14 is composed of a microcomputer. The skew detection sensor 13 is connected to the input side of the control unit 14 and the solenoid 20 of the transport path switching claw 15 is connected to the output side thereof. Then, the control unit 14 controls the sequence of the copying machine. The transport path switching operation of the transport path switching claw 15 will be described with reference to the flowchart of FIG. First, when the control unit 14 receives the transfer paper detection signal of the skew detection sensor 13, the control unit 14 calculates the amount of the skew according to the passage time of the transfer paper, and the skew of the transferred transfer paper is less than the skew set value. It is determined whether it is larger (S-1). When the skew amount of the transfer sheet is smaller than the skew amount set value, nothing is done, and when the skew amount of the transfer sheet is larger than the skew amount set value, the solenoid 20 of the transport path switching claw 15 is urged to convey the sheet. The path switching claw 15 rotates counterclockwise in FIG. 4 to open the skewed paper conveyance path 16 '(S-2). Therefore, when the skew amount of the transfer sheet to be conveyed is larger than the skew amount set value, the transfer sheet is conveyed to the skew sheet accommodating tray 17 via the skew sheet conveying path 16 ′ without forming an image. It

FIG. 21 is a flow chart of the operation of the same sheet skew processing. First, the value of the skewed sheet number counter M is reset (S-26). Next, the skewed paper is re-fed and the value of the skewed paper number counter M is incremented (S-
27). After that, it is determined whether or not the skewed paper is detected a predetermined number of times (X), that is, whether X = M (S-28). If the set number of times of skew feeding X has not been reached, it is judged whether or not skew paper is detected (S-29), and whether or not skew paper is detected is set by the judgment of step S-28. When the number of times of skew feeding X is reached, normal image formation is performed on the transferred transfer paper and the paper is discharged to the paper discharge tray 12 (S-30). When the skewed sheet is detected in the determination in step S-29, the process returns to step S-27. In the present embodiment, when the skewed sheet is detected a predetermined number of times (X) or more, it is determined that the transfer sheet to be conveyed has a skewing tendency, and normal image formation is performed on the skewed sheet. To discharge.

In this embodiment, the transfer paper temporary stop mode can be selected. When the transfer paper temporary stop mode is selected, the operator can eject the skewed paper to the outside or directly perform image formation. Select whether to continue to output as a copy. 16 is a plan view showing the transfer sheet temporary stop mechanism, FIG. 17 is a plan view showing the vicinity of the transfer sheet stop detection sensor, and FIG. 18 is a plan view showing the main part of the operation section 34. As shown in FIG. 16, the transfer sheet temporary stop mechanism is a transfer motor (M) 4 that drives a transfer roller on the transfer sheet transfer path.
2, the electromagnetic clutch 43, and gears 44a and 44 for transmitting the driving force of the carry motor (M) 42 to the electromagnetic clutch 43.
b, 44c group. Gears 44d, 4
The 4e pair transmits the driving force from the electromagnetic clutch 43 to the conveyance rollers on the conveyance path. The transfer paper stop detection sensor 45 detects a temporary stop of the transfer paper on the conveyance path. As shown in FIG. 18, the operation unit 34 is provided with a display screen 46, a transport path instruction button 47, and a restart button 48. In addition,
The skew detection sensor 13 (a, b) can also be used as the transfer sheet stop detection sensor 45. Further, instead of the display screen 46 as the transfer paper stop display means, an audio device may be used to notify by voice. FIG. 19 is a block diagram showing a control circuit for temporarily stopping the transfer sheet, and FIG. 20 is a flow chart showing an operation of the transfer sheet transport restart processing. A transfer paper stop detection sensor 45, a conveyance path instruction button 47, and a restart button 48 are connected to the input side of the control unit 14, and a solenoid 20 for driving the conveyance path switching claw 15 and an electromagnetic clutch are connected to the output side. 43 is connected. When the controller 14 detects the skew of the transfer sheet, the electromagnetic clutch 43 is detected.
A stop signal is sent to and the transfer paper conveyance is temporarily stopped. Figure 20
The operation of the transfer paper conveyance restart process will be described with reference to the flowchart of FIG. First, after the skew of the transfer sheet conveyed on the normal conveyance path 16 is detected, the urging of the electromagnetic clutch 43 is cut off by the stop signal sent from the control unit 14 to the electromagnetic clutch 43, and the transfer path is on the way. The driving force to the transport roller is cut off (S-19). As a result, the transferred transfer paper is temporarily stopped. After that, the transfer paper stop detection sensor 45 determines whether or not the transfer paper is stopped (S-2).
0). As a result, when the transfer paper is stopped, the transfer paper is temporarily stopped on the display screen 46, the skew amount of the transfer paper, and the operator's operation of the operation unit 34 to prompt the operator to select the transport path. The sentence is displayed (S-21). When the operator inputs the conveyance path instruction button 47 and the restart button 48 (S-22), it is determined whether or not the skew of the transfer sheet is ignored (S-23). When a signal for ignoring skew of the transfer sheet is input, or when the transfer sheet is not stopped as a result of the determination in step S-20, the conveyance is restarted as it is, and normal image formation is performed and the sheet is discharged. Discharge to paper tray 12 (S-
25). Solenoid 2 when not skewing transfer paper
0 to send a transport path switching signal to transport path switching claw 15
And the restart signal is sent to the electromagnetic clutch 43 to convey the transfer sheet to the side of the skewed sheet conveying path 16 '(S-24). After that, the normal copy operation is restarted. As described above, in the present embodiment, the operator can select whether to resume the transport as it is or to discharge the paper to the paper discharge tray 12 depending on the size of the skew amount of the transfer paper and the importance of the copied image.

Next, a second embodiment of the present invention having a double-sided device will be described. FIG. 10 is a configuration diagram showing the overall configuration of a copying machine according to the second embodiment of the present invention. Double-sided tray 28
Is equipped with an end fence 31, a bottom plate 32, and a side fence (not shown).
8. A paper feed roller 30 is arranged on the downstream side. During double-sided image formation, the image is formed on the surface and the fixing roller 11
The transfer sheet that has passed through is conveyed to the side of the double-sided conveyance path 18 without being discharged to the discharge tray 12, and the bottom plate 32 of the double-sided tray 28 is conveyed.
Deposited on top. When a predetermined amount of transfer paper is accumulated, the end fence 31 and the side fence move to gather the transfer paper bundle. The collated transfer paper is re-fed by the paper feed roller 30. In the present embodiment, the skewed paper feed path 1
6'is merged in the middle of the double-sided transport path 18, and the skew path is detected to detect the skew by the transport path switching claw 15.
The skewed paper conveyed to 6 ′ is conveyed in the double-sided conveyance path 18 from the middle. Then, during the above-mentioned double-sided image forming operation, an image is formed on the front surface and is piled up on the double-sided tray 28 in the same manner as the conveyed transfer paper, and then collected by the end fence 31 and the side fence and re-supplied by the paper feed roller 30. To be paper. Further, as described above, since the double-sided tray 28 is also used as the skewed sheet storage tray 17 in the first embodiment and the skewed sheets can be collected and re-fed, the number of parts can be reduced. , Skew paper can be automatically re-fed. Note that the control unit 14 immediately re-feeds the skewed paper stored in the double-sided tray 28 when the number of copies is one, and does not re-feed during the copying operation when the number of copies is multiple. Then, control is performed so that the paper is re-fed after all the number of copies has been fed. FIG. 11 is a block diagram showing the control configuration of the refeed control according to the present embodiment, and FIG. 12 is a flowchart showing the operation of the skew paper refeed processing. The operation unit 34 is connected to the input side of the control unit 14, and the paper feed motor 26 that drives the transport roller near the double-sided transport path 28 and the paper feed roller 30 is connected to the output side. The operation of the skew paper re-feeding process will be described with reference to the flowchart of FIG. First, the operator sets the input of the copy number counter N on the operation unit 34 (S-7). Next, it is determined whether or not the value of the copy number counter N is 0 (S-
8). If the determination result is No, the transfer paper is fed and the value of the copy number counter N is decremented (S
-9). The skew detection sensor 13 calculates the skew amount of the transported transfer sheet, and determines whether the skew amount of the transported transfer sheet is larger than the skew amount set value (S-10). When the skew amount of the transfer sheet is smaller than the skew amount set value, the process returns to step S-8, and when the skew amount of the transfer sheet is larger than the skew amount set value, the conveyance path switching claw 15 is switched to skew the transfer sheet. The sheet is conveyed to the line paper conveying path 16 'and accommodated in the double-sided tray 28, and the process returns to step S-8 (S-11). Step S-
If the determination result of 8 is Yes, it is determined whether there is a transfer sheet accommodated in the double-sided tray 28 (S-12). If the determination result is Yes, the transfer paper stored in the double-sided tray 28 is re-fed (S-13). If the transfer sheet is skewed when the number of copies is one, the skewed sheet is the double-sided tray 28.
However, if the transfer paper is skewed when the number of copies is more than one, it will not be immediately re-fed and will be re-fed after all feeding is completed. Therefore, the transfer paper does not remain on the double-sided tray 28.

FIG. 13 is a block diagram showing the overall structure of a copying machine according to the third embodiment of the present invention, which is equipped with a tandem paper feeding device. The tandem paper feeding device 35 includes a first transfer paper container 36 for stacking a plurality of transfer papers, and a first transfer paper container 36.
A feeding unit 38 for feeding the transfer sheets one by one from the
A second transfer paper container 37 arranged substantially parallel to and parallel to the transfer paper container 36, and the transfer papers housed in the second transfer paper container 37 are collectively stored in the first transfer paper container 36. It has a transfer mechanism 39 for transferring. When the copy operation is started,
The feeding paper feed unit 38 feeds the transfer papers stacked in the first transfer paper storage unit 36 one by one, and when the transfer papers stacked on the transfer papers run out, the transfer mechanism 39 causes the second transfer paper storage unit 37 to move. The transfer paper stored in the first transfer paper storage unit 36 is collectively transferred to the first transfer paper storage unit 36 to replenish the lost transfer paper. FIG. 14 is a block diagram showing the configuration of the skewed sheet accommodation control circuit according to the present embodiment, and FIG. 15 is a flowchart showing the operation of the skewed sheet accommodation processing. The operation section 14 is connected to the input side of the control section 14, and the solenoid 20 for driving the transport path switching claw 15 is connected to the output side. When the size of the skewed paper is the same as the size of the transfer paper stored in the first transfer paper storage unit 36 and the second transfer paper storage unit 37, the control unit 14 sets the second position of the tandem paper feeding device 35.
When the size of the skew paper stored in the transfer paper storage unit 37 is different from the size of the transfer paper stored in the first transfer paper storage unit 36 and the second transfer paper storage unit 37, normal image formation is performed and the discharge is performed. It is controlled so that the paper is discharged to the paper tray 12. The transfer sheet fed from the tandem sheet feeding device 35 skews along the conveyance path,
When it is detected by the skew detection sensor 13, the conveyance path switching claw 15 conveys the sheet to the skewed sheet conveyance path 16 '. The skewed sheet guided to the skewed sheet transporting path 16 ′ is accumulated in the second transfer sheet accommodating section 37 after the transporting posture is corrected by the skewed sheet correcting mechanism.

The operation of the skewed paper accommodation processing will be described with reference to the flowchart of FIG. First, the operator inputs the size of the transfer paper fed by the operation unit 34 (S-
14). Next, the transfer paper is fed from the tandem paper feeding device 35 (S-15). Then, the skew amount of the transfer sheet transported on the normal transport path 16 is calculated, and it is determined whether the skew amount of the transported transfer sheet is larger than the skew amount set value (S-1).
6). When the skew amount of the transfer sheet is larger than the skew amount set value, it is determined whether or not the size of the skew sheet and the size of the transfer sheet of the tandem paper feeding device 35 are the same (S-17). If the determination result is Yes, the conveyance path switching claw 15 is switched,
The transfer sheet is conveyed to the side of the skewed sheet conveying path 16 ', and the skewed sheet is fed to the second side.
The transfer paper is stored in the transfer paper storage unit 37, and the process returns to step S-15 (S-19). If the determination result is No, or the determination result of step S-16 is No, the transfer sheet is conveyed to the normal conveyance path 16 side, normal image formation is performed, and the discharge tray 12
It is then discharged (S-18). In the present embodiment, the second transfer paper accommodating portion 37 also serves as the skewed paper accommodating tray 17 of the first embodiment, and the recovered skewed paper is tandem paper feeding device 3
Since it is made to flow through 5, the number of parts can be reduced and waste of transfer paper can be prevented. Further, a transfer paper of a size different from the size of the transfer paper stored in the tandem paper feeding device 35 is not carried in, and problems such as stacking failure do not occur.

In this embodiment, the skewed sheet correction mode can be selected, and when the skewed sheet correction mode is selected, the posture of the skewed sheet is automatically corrected. FIG. 7 is a partially cutaway plan view showing the skewed sheet correcting mechanism in the skewed sheet conveying path. The pair of skewed sheet correction rollers 23a and 23b, which are arranged in parallel in the direction perpendicular to the transfer sheet conveyance direction, are provided with a gear 25.
It is driven by drive motors 24a and 24b via a and 25b, respectively. Skewed paper correction rollers 23a, 2
3b is normally driven at the same speed as the front and rear transport rollers 22 and 27 on the left and right, but when the control unit 14 detects the skew of the transported transfer sheet by the transfer sheet detection signal of the skew detection sensor 13. The speed difference between the drive motors 24a and 24b that corrects the posture of the transfer paper is calculated, and control is performed to change the rotational speeds of the drive motors 24a and 24b.
FIG. 8 is a block diagram of skew paper correction control including the control unit 14,
FIG. 9 is a flowchart of a speed correction process for conveying skewed paper. The skew detection sensor 13 is provided on the input side of the control unit 14,
On the output side, the drive motors 24a, 24 of the skew paper correction mechanism
b is connected. According to the flowchart of FIG.
The speed correction processing for skewed sheet conveyance will be described. First, the control unit 1
A transfer paper detection signal from the skew detection sensor 13 determines which of the drive motors 24a and 24b is to be shifted based on the detection time difference between the left and right skew detection sensors 13a and 13b (S-3). Next, the drive time and the rotational speed of the drive motor (24a, 24b) on the shift side are determined (S-4). The control unit 14 includes the left and right skew detection sensors 13
During the drive time determined by the detection time difference between a and 13b,
The drive signal is sent to the drive motor on one of the drive motors (24a, 24b) on the shift side, and the skew paper correction roller 2
Either 3a or 23b is rotated at the changed speed (S-5). When a predetermined time has elapsed, this skew paper conveyance speed correction process is terminated (S-6). By correcting the skew feeding amount of the skew feeding sheet in this manner, it is possible to prevent the skew feeding sheet from being jammed due to the skew feeding in the midway conveyance path, and to prevent the second transfer of the tandem sheet feeding device 35. It is possible to prevent jamming of the skewed paper when the skewed paper is stored in the paper storage unit 37 and accumulation of the paper in an irregular state. Note that a sensor or the like for detecting the posture of the skewed paper after the skewed amount correction may be provided.

[0015]

According to the first aspect of the present invention, the skew of the transfer sheet conveyed from the sheet feeding means is detected in the middle of the transfer sheet conveying path, and the detected skew amount of the transfer sheet is predetermined. When the amount of skew of the transfer paper is smaller than the preset value, the normal transport path is selected as the transport path for the transfer paper, and when it is greater than the preset value, the skew paper transport path is selected. Conveyance path Since the conveyance path switching means provided at the branch between the conveyance path and the skewed paper conveyance path is used to switch to the normal conveyance path side or the skewed paper conveyance path side, the transfer paper is skewed in the middle of the transfer paper conveyance path. Since the image is not transferred even when the sheet is moved, the transfer sheet is not wasted and the skewed sheet can be easily handled. According to the second aspect of the invention, since the skewed sheet conveying path has skewed sheet correcting means for correcting the posture of the transfer sheet skewed by the skewed presence / absence signal to the normal posture, The skew of the transfer sheet can be corrected to the extent that no mistake occurs, and the skew sheet can be conveyed in a normal posture. According to the third aspect of the present invention, since the skewed paper is conveyed to the skewed paper stacking base on which the skewed paper is stacked for discharging to the outside of the machine,
The skewed paper can be easily taken out. According to the invention described in claim 4, since the skewed paper is conveyed to the double-sided image forming transfer paper storage device, a normal double-sided sheet re-feeding operation and a storage device for the skewed paper are separately provided. I don't need it,
The apparatus can be simplified and the skewed paper can be handled easily. According to the fifth aspect of the present invention, after the skewed paper is accommodated in the transfer paper accommodating device for double-sided image formation, if the number of copies is one, it is immediately re-fed, and if the number of copies is plural, the final sheet is finally fed. Since the sheet is re-fed after the first sheet is fed, it is possible to prevent the transfer sheet from remaining in the double-sided image forming transfer sheet container. According to the sixth aspect of the invention, since the skewed paper is conveyed to the second transfer paper storage portion of the skewed paper storage device tandem paper feeder, the skewed paper is stored in the first transfer paper storage portion. Like the transferred transfer paper, it can be re-fed. According to the invention described in claim 7, when the skewed paper is not the same size as the transfer paper accommodated in the tandem paper feeding device, the skewed paper conveyance path is not selected as the transfer paper conveyance path. Therefore, it is possible to prevent the transfer papers of different sizes from being mixed in the second transfer paper storage unit of the tandem paper feeding device by the skew detection. According to the invention of claim 8, after detecting the skew of the transfer sheet, the transfer sheet is stopped, and when the stop of the transfer sheet is detected, the fact that the transfer sheet is stopped is displayed and the transfer sheet conveying path is also displayed. When the conveyance path is instructed, the conveyance of the transfer sheet is restarted, so that the operator can choose the post-processing of the skewed sheet. According to the ninth aspect of the invention, when the same sheet is repeatedly skewed a predetermined number of times, the skewed sheet is not conveyed to the skewed sheet conveying path. It is possible to prevent the device from being continuously operated wastefully due to repeated skew detection.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an overall configuration of a copying machine according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of a conveyance path near the transfer section.

FIG. 3 is a plan view showing how skew is detected on a transfer sheet by a skew detection sensor.

FIG. 4 is a partially cutaway plan view showing a peripheral portion of a transport path switching claw.

FIG. 5 is a block diagram of a transport path switching control circuit.

FIG. 6 is a flowchart of a transport path switching operation.

FIG. 7 is a partially cutaway plan view showing a skewed sheet correction mechanism.

FIG. 8 is a block diagram of a skewed sheet correction control circuit.

FIG. 9 is a flowchart showing an operation of a skew paper conveyance speed correction process.

FIG. 10 is a configuration diagram showing an overall configuration of a copying machine according to a second embodiment of the present invention.

FIG. 11 is a block diagram of a sheet re-feeding control circuit for skewed sheets.

FIG. 12 is a flowchart showing an operation of skew paper refeed processing.

FIG. 13 is a configuration diagram showing an overall configuration of a copying machine according to a third embodiment of the present invention.

FIG. 14 is a block diagram of a skewed sheet accommodation control circuit.

FIG. 15 is a flowchart showing an operation of skew paper accommodation processing.

FIG. 16 is a plan view showing a transfer paper temporary stop mechanism.

FIG. 17 is a plan view showing the vicinity of a transfer paper stop detection sensor.

FIG. 18 is a plan view showing a main part of an operation unit.

FIG. 19 is a block diagram showing a control circuit for temporarily stopping transfer paper.

FIG. 20 is a flowchart illustrating an operation of a transfer paper transport restart process.

FIG. 21 is a flowchart of an operation of the same sheet skew processing.

[Explanation of symbols]

 1 Image Reading Section 2 Photosensitive Drum 6 Paper Feeding Section 7 Paper Feeding Tray 8, 38 Feeding Paper Feeding Section 9 Registration Roller 12 Paper Ejection Tray 13 (a, b) Skew Detection Sensor 14 Control Section 15 Transport Path Switching Claw 16 Normal Conveyance path 16 'Skewed paper conveyance path 17 Skewed paper storage tray 18 Double-sided conveyance path 23 (a, b) Skewed paper correction roller 24 (a, b) Drive motor 27 Double-sided device 28 Double-sided tray 34 Operating section 35 Tandem supply Paper device 36 First transfer paper storage unit 37 Second transfer paper storage unit 39 Transfer mechanism 42 Transport motor 43 Electromagnetic clutch 45 Transfer paper stop detection sensor 46 Display screen 47 Transport path instruction button 48 Resume first button

Claims (9)

[Claims] 1. An image forming apparatus comprising: a sheet feeding unit that feeds a transfer sheet; and an image forming unit that forms an image on the transfer sheet fed from the sheet feeding unit through a transfer sheet transport path. A skew detecting unit that detects skew of the transfer sheet conveyed in the middle of the sheet conveying path, a normal conveying path conveying path that reaches the image forming unit on the downstream side of the skew detecting unit, and a skew sheet. A conveyance path switching unit that is provided at a branch portion of the skewed paper conveyance path reaching the storage device and switches to the normal conveyance path side or the skewed paper conveyance path side, and the skew amount of the transfer sheet detected by the skew detection unit. Is compared with a predetermined set value, and the skew feed amount determination means for outputting a skew feed presence / absence signal, and the skew feed amount of the transfer paper are set to the predetermined setting according to the skew feed presence / absence signal output by the skew feed amount determination means. When the value is smaller than the value, the normal conveyance path is set, and the skew amount of the transfer paper is larger than the predetermined set value. An image forming apparatus comprising: a conveying path selecting unit that selects the skewed sheet conveying path as a transfer sheet conveying path when the transfer sheet is not in use. 2. The image forming apparatus according to claim 1,
In the skewed paper conveyance path, there is skewed paper correction means for correcting the posture of the skewed transfer paper to a normal posture, and the skewed paper correction is performed by the skew presence / absence signal output from the skew amount determination means. An image forming apparatus having a control unit for operating the unit. 3. The image forming apparatus according to claim 1,
The skewed paper accommodating device is an skewed paper stacking table for stacking skewed paper in order to discharge the skewed paper to the outside of the machine. 4. The image forming apparatus according to claim 1,
An image forming apparatus, wherein the skewed paper accommodation device is a double-sided image forming transfer paper accommodation device in which an image is formed on the front surface and the transfer paper is on standby to form an image on the back surface. 5. The image forming apparatus according to claim 4,
According to the skew presence / absence signal, after the skewed paper is accommodated in the transfer paper accommodating device for double-sided image formation, it is immediately re-fed when the number of copies is one, and when the number of copies is plural, the final sheet is transferred. An image forming apparatus having a control unit for re-feeding a sheet after the sheet is fed. 6. The image forming apparatus according to claim 1 or 2, wherein the sheet feeding means has a first transfer sheet accommodating section for accommodating a plurality of transfer sheets, and is arranged in parallel with the first transfer sheet accommodating section. A second transfer paper container arranged substantially horizontally; transfer paper feeding means for feeding the transfer papers one by one from the first transfer paper container;
It is a tandem paper feeding device provided with a transfer means for collectively transferring the transfer paper stored in the second transfer paper storage unit to the first transfer paper storage unit when the transfer paper is replenished. An image forming apparatus, which is a second transfer paper container. 7. The image forming apparatus according to claim 6,
When the transfer sheet determined to have the skew amount larger than the predetermined set value is not the same size as the transfer sheet accommodated in the tandem sheet feeding device, the conveyance path selecting unit determines that the conveyance path of the transfer sheet is inclined. An image forming apparatus characterized in that a line paper conveyance path is not selected. 8. The skew presence / absence signal according to claim 1, 2, 4 or 6, wherein the skew amount determining means determines that the skew amount of the transfer sheet conveyed is larger than a predetermined set value. According to the above, the temporary stop means for stopping the transfer paper on the transfer paper transport path, the stop detection means for detecting the stop of the transfer paper on the transfer paper transport path, and the transfer paper being stopped on the transfer paper transport path 2. An image forming apparatus comprising: a stop display unit for displaying the sound or a visual indication, a conveyance path instruction unit for instructing a conveyance path of the transfer sheet, and a conveyance resumption unit for resuming the conveyance of the transfer sheet. 9. The image forming apparatus according to claim 1, wherein a skew feed signal is output when the skew feed amount determination means determines that the skew feed amount is a predetermined number of times and the repeat feed amount is larger than a predetermined set value. If so, the image forming apparatus is characterized in that the conveying path selecting means does not select the skewed sheet conveying path as the transfer sheet conveying path.