JP2699073B2 - Image forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that forms an image on both sides. [Background Art] As an apparatus of this type, an apparatus shown in FIG. 5 can be considered. In the figure, reference numeral 1 denotes an image forming unit, and 2 denotes an image processing device. The image forming unit 1 forms an image on a sheet by printing an image signal sent from the image processing device 2. 3 and 4 are the upper deck and the lower deck, respectively, on which sheets are loaded. Reference numerals 8 and 9 denote pickup rollers, which feed paper from the upper deck 3 and the lower deck 4 to print the first side of the sheet. A double-sided unit 5 feeds / conveys the sheet to the image forming unit 1 in order to print the second side of the sheet on which the first side is printed. Reference numeral 25 denotes an intermediate tray for temporarily storing sheets on which the first surface is printed, and a first sheet sent to the intermediate tray 25 is re-supplied by a re-feed roller 26 serving as re-feeding means.
The paper is re-supplied in advance. 27 is a conveyance roller. From the re-feed roller 26 to the photosensitive drum of the image forming unit 1
A second path, which is a path to 15, is longer than a first path, which is a path from the paper feeding units 3 and 4 to the photosensitive drum 15 for forming an image on the first surface of the sheet. In addition, the preceding sheet is fed from the re-feed roller 26 to a position equal to the first path, and the sheet can be made to stand by on the second path. FIG. 6 is an explanatory diagram of the sheet refeeding state of the apparatus shown in FIG. In the figure, a sheet on which an image is to be formed is sent out through a first path by a re-feed roller 26, an image is formed on the surface of the sheet, then sent to the intermediate tray 25, and the sheet is immediately re-supplied. In order to form an image on the second surface of the sheet by the paper roller 26 and the conveying roller 27, a preceding sheet is fed, and the sheet is made to stand by on a second path. Assuming that the position where the end of the sheet fed into the intermediate tray 25 on the re-feeding side falls farthest from the re-feeding roller 26 is P, the preceding feeding is performed and the sheet is made to wait on the second path. In some cases, the trailing end of the sheet is located closer to the sheet re-feeding side than the position P in the intermediate tray 25. [Problems to be Solved by the Invention] In such a state, when the second sheet S2 is fed into the intermediate tray, the end of the second sheet S2 may be caught on the rear end of the first sheet S1. (Q in FIG. 6)
When the third sheet S3 is sent to the intermediate tray, as shown in FIG. 6, the third sheet S3 reaches the sheet re-feed roller without being caught by the rear end of the sheet S1. In this state, after the first sheet S1 has been received by the image forming unit, if the second sheet S2 is to be pre-fed by the re-feeding unit, the third sheet reaching the re-feeding roller will be described. Whether the sheet S3 is fed before the second sheet S2 and the page turns around,
There has been a problem that the second sheet S2 and the third sheet S3 are fed while being partially overlapped with each other (by double feeding), thereby causing an obstacle. [Purpose of the Invention] The present invention has been made to solve such a problem, and eliminates obstacles such as rounding of pages and double feeding at the time of feeding from an intermediate tray, as well as transporting sheets. It is an object of the present invention to provide an image forming apparatus that can be reliably performed. [Means for Solving the Problems] An image forming apparatus according to the present invention is characterized in that a sheet on which an image is formed by an image forming unit is dropped onto an intermediate tray, and the sheet on the intermediate tray is sent out from a sending unit to a predetermined position. An image forming apparatus capable of dropping a next sheet onto the intermediate tray when a rear end of the waiting sheet remains in the intermediate tray. A determination is made as to whether or not the position of the trailing end of the sheet when the sheet is made to stand by at a predetermined position is between the drop position of the next sheet on the intermediate tray on the sending section side and the sending section of the intermediate tray. Means, and if the determination means makes an affirmative determination, the sheet at a position other than the predetermined position where the position of the trailing end of the sheet is outside the range from the drop position to the sending section. To wait, if a negative determination is made, which is constituted to have a control means for waiting the sheet at the predetermined position. Embodiment An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram of a configuration of a two-sided printing apparatus which is an image forming apparatus according to an embodiment of the present invention. The same / corresponding components in the apparatus shown in FIGS. 5 and 6 are denoted by the same reference numerals. In the figure, reference numeral 1 denotes an image forming unit, and 2 denotes an image processing device. The image forming means 1 prints the image signal sent from the image processing device 2. Sheets 3 and 4 are an upper deck and a lower deck, respectively, on which sheets are stacked and fed to print the first side of the sheets. 5
A duplex unit feeds and conveys the sheet to the image forming unit 1 in order to print the second side of the sheet on which the first side is printed. Reference numeral 6 denotes a vertical transport unit that sorts out the sheets output from the image forming unit 1, and 7 denotes a tray on which the output sheets are stacked. 3a and 4a are upper deck 3 and lower deck 4 respectively
The sheets 3a and 4a are located in the image processing device 2
Is selected according to the control signal from, and the paper is fed by rotating the respective pickup rollers 8 and 9. Then, the fed paper reaches the registration roller 14 through the sensors 12 and 13 by the transport rollers 10 and 11, respectively,
The registration roller 14 temporarily stops, corrects the skew, conveys again by the timing signal from the image processing device 2, and simultaneously transmits the image signal sent from the image processing device 2 on the photosensitive drum 15 by the optical system. It is formed as a latent image and is made visible. The sheet on which the image to be visualized is formed is fixed to a fixing roller by a belt-shaped paper transport mechanism 16.
The sheet is sent to a fixing unit 17, and is conveyed to a deflector 19 by a conveying roller 18. The deflector 19 divides the sheet into the vertical transport unit 6 or the duplex unit 5. For example, deflector 19
Is moved upward, the sheet is conveyed to the duplex unit 5. The sheet entering the duplex unit 5 is transported by the transport roller 20, the leading edge of the sheet is detected by the sensor 21, and is sent to the intermediate tray 25 at a timing based on this.
Until the sheet is fed to the intermediate tray 25, the sheet is conveyed by the belt-shaped conveying section 22, the leading end of the sheet is detected by the sensor 23, and delay and stay are confirmed in accordance with the timing based on the sensor 21. The sheet that has passed the sensor 23 is sent to the intermediate tray 25 by the transport roller 22. Intermediate tray
25 temporarily stores the sheet on which the first surface is printed.
The first sheet sent to the intermediate tray 25 is
The re-feed roller, which is the means for re-feeding paper as soon as it is loaded on 25
According to 26, the sheet is re-advanced. After refeeding the first sheet, the first sheet passes through the conveying roller 27 and is sent to the sensor 28. The leading edge of the sheet is detected by the sensor 28, and is conveyed to the sensor 31 based on the leading edge of the sheet.
stand by. The distance from the sensor 31 to the registration rollers 14
It is equal to the distance to the registration rollers 14 which are the feed paths 3 and 4. 29 and 30 are conveying rollers. The second and subsequent sheets fed to the intermediate tray 25 are separated one by one with an interval equal to or greater than the minimum sheet interval, and are sequentially re-fed from the lower side of the overlapping portion in the intermediate tray 25. Next, the sheet is fed in the same manner as the sheets 3a and 4a in the decks 3 and 4, and is fed to the second
Print the side (back side). Then, the sheet having passed through the fixing device 17 is transported upward by the deflector 19. Reference numerals 32 and 33 denote conveying rollers for discharging sheets to the tray 7. The configuration will be described with reference to FIG. In the figure, reference numerals 50-1 and 50-2 denote sheet size detectors for detecting the sizes of the sheets 3a and 4a set in the decks 3 and 4, which are connected to the control circuit 51, and which are supplied from the intermediate tray 25 in advance. When the previously fed sheet is stopped at the position of the sensor 31 that detects the leading edge of the sheet, the trailing edge position L of the stopped sheet satisfies the relationship of 0 <L ≦ A as described later. Information as to whether the sheet size is different is input to the control circuit 51. Here, A is the distance between the position P where the end of the sheet fed into the intermediate tray 25 on the re-feeding side is farthest away from the re-feeding roller 26 and the re-feeding roller 26. The control circuit 51 is mainly composed of a well-known microcomputer having a built-in ROM and RAM. Reference numeral 52 denotes a paper feed command input, which is input to the control circuit 51. A drive control circuit 53 controls a clutch 54 for transmitting power to the transport rollers 29 and 30. The drive control circuit 53 is connected to the control circuit 51. ON of clutch 54
Occasionally, power is transmitted to the transport rollers 29, 30 and started, and O
At the time of FF, transmission is canceled and stopped. FIG. 3 is a flowchart for explaining the operation of the duplex printing apparatus according to the embodiment of the present invention, which is performed by the control circuit 51. In order to start the apparatus and convey the re-fed sheet to the sensor 31, the clutch 54 is turned on and the conveying rollers 29 and 3 are turned on.
0 is started (S60). S61 is a step of determining the subsequent flow based on the input signal from the sensor 31, the leading edge of the sheet reaches the sensor 31,
The process waits until the tip detection signal from the sensor 31 is input to the control circuit 51, and when the tip detection signal is input, the process proceeds to S62. In S62, it is determined whether or not the sheet rear end position in the intermediate tray 25 is a sheet size satisfying 0 <L ≦ A, based on the input signal from the sheet size detector 50-1 or 50-2, as described above. I do. In response to an input signal from the sheet size detector 50-1 or 50-2, the control circuit 51 sets the sheet rear end position to 0 <L ≦ A.
If it is determined that there is a sheet size to be satisfied, S63 is executed. When the control circuit 51 determines that the rear end position of the sheet has a sheet size that does not satisfy 0 <L ≦ A, S64 is executed. In step S63, the transport rollers 29 and 30 are activated for the time T, and the clutch 54 is turned on for the time T via the drive control circuit 53 by the output signal from the control circuit 51 in order to transport the sheet by the distance L. In S64, in order to stop the transport rollers 29 and 30 and wait for the sheet, the drive control circuit 53 turns the clutch 54 off according to an output signal from the control circuit 51. In S65, the subsequent flow is determined based on the input 52 for the sheet feeding command. When a paper feed command is input from the paper feed command input 52, S66
Execute In S66, as described above, the sheet rear end position is set to 0 according to the input signal from the sheet size detector 50-1 or 50-2.
It is determined whether or not the sheet size satisfies <L ≦ A,
The subsequent flow is determined. When the control circuit 51 determines from the input signal from the sheet size detector 50-1 or 50-2 that the rear end position of the sheet is a sheet size satisfying 0 <L ≦ A, S67 is executed. The control circuit 51 determines that the rear end position of the seat is 0
If it is determined that the sheet size does not satisfy <L ≦ A
Execute S68. In S67, the drive control circuit 53 puts the clutch 54 into the OFF state for T time in response to an input signal from the control circuit 51 in order to stop the transport rollers 29 and 30 for T time and hold the sheet for T time. In S68, the drive control circuit 53 is activated by the input signal from the control circuit 51 in order to start the conveying rollers 29 and 30 and convey the sheet.
Turns on the clutch 54. FIG. 4 is a timing chart showing the operation. In the drawing, ENB is a sheet presence signal of the sensor 31, PU is a pickup signal of a standby sheet, R is L ≦ 0, where the rear end position of the sheet is ahead of the re-feed roller 26, or the rear end position of the sheet Is longer than A and is longer than L>
A roller ON signal for the re-feed roller 26 and the like at A, and a roller ON signal when the rear end position of the sheet is between the re-feed roller 26 and P and 0 <L ≦ A. First, the sheet is fed again simultaneously with the rise of the signal R,
At the same time as the rising of the signal ENB, the signal R falls after a,
The sheet waits at the sensor 31. The signal R rises in response to the signal PU, and when the waiting sheet is conveyed and reaches the registration roller 14 after b, the signal R falls. Next, in the sequence where 0 <L ≦ A as described above, the signal R ′ falls after (ca) from the rising of the signal ENB. The signal R 'falls after c from the rise. At this time, the sheet is stopped and is advanced by L from the sensor 31. Now, assuming that the speed of the sheet is v, the time required for the sheet to advance by L is represented by T = L / v, and T = ca
It is. With the signal PU, the signal R 'rises later (ca) than the signal R, the sheet starts to be conveyed, and the signal R' falls when it reaches the registration roller 14 after d. Where a + b
= C + d. Thus, when a sheet is in the intermediate tray 25, the signal indicating the sequence of R, R ', etc., regardless of whether the rear end position of the sheet is 0 <L ≦ A, L ≦ 0 or L> A. As can be seen from the figure, the shifted standby positions are made equal in the sequence. As described above, according to the embodiment of the present invention, the rear end of the sheet that has been fed earlier than the re-feeding exists in the intermediate tray, and L is in the position of 0 <L ≦ A. At this time, at least the sheet is advanced by L, the standby position is shifted, and this position is set to the same position in the sequence, so that the rear end position of the sheet existing in the intermediate tray is 0 <L ≦
An image forming apparatus can be provided which can be prevented from being out of the range A and preventing a problem such as a page turn or a double feed at the time of re-feeding without a large change depending on each sheet size in the sequence. [Other Embodiments] In one embodiment of the present invention, the stop position of the preceding sheet feeding is determined by the sheet size by the sequence processing, but the position of the re-feeding roller 26 and the position on the intermediate tray 25 are Sensors Sa and Sb (not shown) that can detect the presence or absence of a sheet are provided at a position P that is separated from the re-feed roller 26 by the distance A, and if the presence of a sheet is turned ON, the preceding sheet standby state Sa ( ON), Sb (OF
Only in the case of F), if the sheet is conveyed until it becomes Sa (OFF) and Sb (OFF) and is made to stand by, the same effect as in the above embodiment can be obtained. [Effects of the Invention] As described above, according to the present invention, a sheet on which an image is formed by an image forming unit is dropped on an intermediate tray,
The sheet on the intermediate tray is sent out from the feeding section to a predetermined position to wait for the next image formation, and when the trailing end of the waiting sheet remains in the intermediate tray, the next sheet drops to the intermediate tray. In the image forming apparatus, the position of the trailing end of the sheet when the sheet is made to stand by at a predetermined position is between the drop position on the intermediate tray on the side of the next sheet sending section and the sending section of the intermediate tray. If a positive determination is made, the sheet is made to wait at a position other than a predetermined position where the rear end position of the sheet is out of the range from the drop position to the sending unit, and a predetermined determination is made if a negative determination is made. Since the sheet is made to wait at the position, the end of the second sheet is caught at the rear end of the waiting sheet as shown in FIG. 6, and the third sheet falls closer to the sending section than the second sheet. Get lost The occurrence of page glove No multi-feeding at the time of delivery from the intermediate tray caused can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram illustrating the configuration of a two-sided printing apparatus which is an image forming apparatus according to an embodiment of the present invention, FIG. 2 is a control block diagram thereof, and FIG. FIG. 4 is a diagram showing a sequence of the same operation, FIG. 5 is a configuration diagram showing an apparatus for explaining the background art of the present invention, and FIG. 3 Upper deck 4 Lower deck 3a, 4a Sheets 8, 9 Pickup roller 15 Photosensitive drum 25 Intermediate tray 26 Re-feed roller 31 Sensor In each figure, The same reference numerals indicate the same or corresponding parts.

Claims (1)

(57) [Claims] A sheet on which an image has been formed by the image forming means is dropped onto an intermediate tray, and the sheet on the intermediate tray is sent out from a feeding unit to a predetermined position to wait for the next image formation. An image forming apparatus capable of dropping the next sheet onto the intermediate tray when the sheet remains in the intermediate tray, wherein the position of the rear end of the sheet when the sheet is made to stand by at the predetermined position is the intermediate position Determining means for determining whether or not the next sheet on the tray is located between the drop position on the side of the sending section and the sending section of the intermediate tray; The sheet is made to stand by at a position other than the predetermined position where the position is out of the range from the drop position to the sending section, and when a negative determination is made, the sheet is made to stand by at the predetermined position. Image forming apparatus characterized by and a control means for.