JPH0423778B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a double-sided recording device that makes copies on both the front and back sides of copy paper.

Prior Art Conventionally, as known from Japanese Patent Publication No. 53-97843, an intermediate tray is disposed between upper and lower paper feed cassettes and a paper output tray, and a copying paper that can be copied on both the front and back sides of the copy paper is known, for example, from Japanese Patent Publication No. 53-97843. The copy sheets supplied from the paper feed section to the image forming section and copied on the front side are once stacked and stored in the intermediate tray, and after the copying on the front side is completed, the sheets are stacked and stored on the intermediate tray after copying the front side. The copy sheets are sequentially sent out and re-sent to the image forming section, and copies are made on the back side of each copy sheet, so that copies can be made on both the front and back sides.

In this case, an intermediate tray for double-sided copying must be provided between the paper feed cassette and the paper discharge tray arranged above and below, which increases the size of the copying machine. Also, in the intermediate tray, copy paper after surface copying is likely to remain due to electrostatic adsorption force caused by corona charge during the transfer process during front surface copying.
As a result of being stacked and stored in an orderly manner, even if you try to feed the copy sheets in the intermediate tray after front side copying to one sheet for back side copying, they will be electrostatically attracted to each other with almost no misalignment. Not only is it difficult to send out multiple sheets of copy paper, but it is also difficult to separate sheets of copy paper sent out in piles, and there is a risk that multiple sheets of copy paper after front-side copying will be used for back-side copying at the same time.
Furthermore, when the paper feed roller feeds the copy sheets stacked in the intermediate tray after front side copying to one sheet, the copy paper comes into pressure contact with the paper feed roller and is rubbed strongly against other copy sheets. , copy images, etc., so that they become dirty with each other.

Purpose This invention supplies a sheet from a sheet feeding means on one side to an image forming means to form an image, and discharges the sheet after image formation to the outside by a sheet discharging means on the other side. In such a recording device, the sheets having the surface image formed thereon that have reached the sheet discharging means are sequentially and continuously returned to the sheet feeding means side, and then re-fed to the image forming means in a state where the front and back sides have been reversed to form an image on the back side. a detection means for detecting that the first sheet returned by the sheet return means has reached a predetermined return position; When the previous sheet is detected, the recording progress status of the front surface image forming operation is stored, the front surface image forming operation in progress is interrupted, and the image formation on the back surface of the sheet that is re-fed by the sheet return means is started. The present invention is equipped with a control means for controlling the image forming means to perform image formation, thereby solving the above-mentioned drawbacks of the conventional technology and providing simple control for switching from image formation on the front side to image formation on the back side without slowing down for double-sided recording. The object of the present invention is to provide a double-sided recording device that can perform double-sided printing.

Embodiment FIG. 1 is an internal mechanism diagram showing an example of a double-sided electrophotographic copying machine according to the present invention. In the figure, 1
1 is a copying machine main body, and a photosensitive drum 2 is provided approximately at the center thereof so as to be driven to rotate in the direction of the arrow. Around the drum 2, there are a charger 3 for charging, a slit part 4 for exposure, a developing device 5, a charger 6 for transfer, a charger 7 for separating static electricity, a separation claw 8, a cleaning device 9, and an eraser lamp 1.
0 are sequentially arranged in the direction of rotation of the drum 2 shown by the arrow, act sequentially on the same part of the surface as the drum 2 rotates, and are conveyed in synchronization with the rotation of the drum 2. It constitutes an image forming section a where a toner image is transferred onto copy paper.

In the image forming section a, the portion of the surface of the photosensitive drum 2 that has been cleaned by the cleaning device 9 is first neutralized by the eraser lamp 10 and then charged by the charger 3 for charging. This charged surface of the drum 2 is provided with the exposure slit portion 4.
Through this, the image of the original placed on the original placing glass 12 on the top surface of the main body 1 is exposed by the scanning optical system 13 to form an electrostatic latent image. Next, this electrostatic latent image is developed with toner by a developing device 5, and the developed toner image is transferred by a transfer charger 6 onto a synchronously fed copy paper. Furthermore, the copy paper after the transfer is separated from the surface of the drum 2 by the separation charger 7 and the separation claw 8.
After the copy paper has been separated and the surface of the drum 2 has been transferred, residual toner is scraped off by the cleaning device 9, and then the drum 2 returns to the static elimination process using the eraser lamp 10 described above.

Reference numeral 14 denotes a document pressure bonding plate, which is attached to the document placement glass 1.
It is attached to the main body 1 so that it can be opened and closed with respect to 2. 15 is an imaging lens in the scanning optical system 13.

On the left side of the image forming section a, there is a paper feeding section b that feeds the copy paper into the transfer section, that is, between the photosensitive drum 2 and the transfer charger 6, and on the right side of the image forming section a, there is a paper feed section b that feeds the copy paper between the photosensitive drum 2 and the transfer charger 6, and on the right side of the image forming section a, there is a paper feed section b that feeds the copy paper between the photosensitive drum 2 and the transfer charger 6. A fixing device 17 that heats and fuses the transferred toner image on the copy paper separated from the drum 2 and a paper discharge section c that discharges the copy paper after passing through the fixing device 17 are arranged in substantially a horizontal line near the bottom of the drum 2. It is located in the 1000 yen area and serves as a normal means of copying. Paper feed section b holds two types of copy paper of different sizes.
Each paper feed cassette 18a that stores Pa and Pb,
18b are mounted on the top and bottom of the copying machine main body 1 in a state of protruding to one side, and selectively drive paper feed rollers 19a and 19b to feed one of the copy sheets Pa and Pb to the paper feed path 20. The drum 2 passes through a pair of feed/pause adjustment rollers 21 and a pair of auxiliary timing rollers 22 to a transfer section below the photosensitive drum 2.
The toner is fed in synchronization with the movement of the toner image above.
Reference numeral 11 denotes a manual insertion section for copy paper.

The paper feed rollers 19a and 19b are driven by transmitting driving force from a power source (not shown) through a clutch mechanism including a known spring clutch and a solenoid, and the paper feed timing signal is generated by the solenoid. It is given as the activation timing. Further, the temporary stop adjustment roller pair 21 is initially stopped, and the paper feed cassettes 18a and 18b are
Copy paper fed into the paper feed path 20 from one side of the
It once receives Pa or Pb to correct the skew and sends it to the auxiliary timing roller pair 22 by being driven at an appropriate timing. The auxiliary timing roller pair 22 is also initially stopped,
Once the copy paper Pa or Pb sent from the pair of temporary stop adjustment rollers 21 is received, the photosensitive drum 2
It is driven by a timing roller actuation signal that is output in final synchronization with the toner image formed above, and is sent to the transfer section.

Reference numeral 23 designates a conveyor belt that transports the copy paper sent out from the transfer unit to the fixing device 17, and 24 designates a discharge roller that discharges the copy paper sent out from the fixing device 17 to the paper discharge unit c. The paper ejection section c is provided with a paper ejection tray 25 that receives and stacks and stores ejected copy sheets.

Below the copying means, there is provided a double-sided copying auxiliary means for returning the copy sheet after the front side has been copied by the copying means to the image forming unit a side and sending it back to the image forming unit in a reversed state so that the back side is copied. ing. The double-sided copying auxiliary means includes a switchback unit d that exchanges the leading edge and trailing edge of the copy paper after front side copying and returns it to the image forming section a side, and a switchback unit d that switches the front end and rear end of the copy paper after front side copying and sends it back to the image forming section. It consists of a front and back reversal section f that sends back the paper in a reversed state.

The switchback unit d is the copying machine body 1.
It is formed in a horizontally elongated shape to be detachably attached to a lower flat space e provided below the paper feed section b, image forming section a, and fixing device 17. The paper ejection tray 2 is attached to one end of the switchback unit d that protrudes from the copying machine main body 1 toward the copy paper ejection side.
5 is removably attached, and a paper ejecting section c has a pair of ejecting rollers 34 that sends out the ejected copy paper to the tray 25, and the copy paper after the surface copy that is ejected from the ejecting roller pair 24 is switched. The copy paper discharged from the discharge roller pair 24 is moved to the paper discharge tray 25 according to a selection signal for single-sided copying or double-sided copying before copying operation.
A paper passing direction switching gate 27 is provided which has a guide claw 27a that allows the paper to pass to the side or to be received into the switchback section 26. The switchback section 26 includes a switchback passage 26a which is open at the top and slightly curved in a downwardly convex state that is shorter than the minimum number of copies used, and a pair of introduction rollers 2 for introducing the copy paper sent downward from the gate 27 section.
8, 29 and short switchback passage 26a
It has a pair of delivery rollers 29 and 30 which share the one roller 29 and send out the copy paper from the rear end after it has completely entered the paper and is stretched.

Further, a pair of delivery rollers 29, 30 of the switchback passage 26a is provided in the portion of the switchback unit d inserted into the flat space e below the copying machine main body.
The copy paper fed out from the
A return section g consists of a return belt 31 that returns the paper to the image forming section a side and a plurality of auxiliary rollers 32 in contact with the conveyance surface thereof, and a paper feed section 20 that transports the returned copy paper.
A pair of back copy paper feed rollers 33 that send the sheet toward the paper feed path 20 and return it to the image forming section a from the middle of the paper feed path 20 are sequentially arranged from the feed roller pair 29, 30 of the switchback path 26a to the sheet return section side in the middle of the paper feed path 20. has been done. From the pair of paper feed rollers 33 to the position in front of the pair of temporary stop adjustment rollers 21 in the middle of the paper feed path 20,
The reversing section f is fixedly installed in the copying machine main body 1 to guide the copy paper after front side copying sent out from the return paper feed roller pair 33 and return it to the paper feed path 20 with the front and back reversed. The reversing section f is formed by a curved passage 16 that allows the returned copy paper after front side copying to smoothly enter the paper feed path 20 toward the temporary stop adjustment roller pair 21 in a reversed state. By meshing the passive gear provided in the switchback unit d with the interlocking gear 24 on the main body 1 side when the unit d is installed, it can be driven simultaneously with the copying means.

The double-sided copying auxiliary means has a return section g at a position immediately before the back side copy paper feed roller pair 33 of the return section g, and the first one of the copy sheets after each front side copy returned to the image forming section a side. Photo sensor 3 that detects objects
5 is provided, and when the sensor 35 detects the copy paper after the front side has been copied, it stops the paper feed section b of the copying means and the return section of the double-sided copying auxiliary means at an appropriate timing, and calculates the number of copies that have been made on the front side. After memorizing the copying progress state at that time, the return section g is operated to send the copy paper after the front side copying back to the image forming section, giving priority to the back side copying with respect to the copying paper where the front side copy has already been made, and duplex copying is performed. be carried out.

Such operation control can be easily performed by sequence control by a microcomputer. Based on the flowchart of the operations shown in FIG. Paper is sequentially fed from paper feed section b to paper feed section a, and surface copying is continuously performed in the copying means. After the front side has been copied by the copying means, the copy paper is received by the switchback unit d under the guidance of the guide claw 27a, which is switched in response to the double-sided copying instruction, and is transferred to the switchback unit 26.
After the leading and trailing ends are received through the
sent to. The return section g receives the copy paper after the front side has been copied, sent out from the switchback section 26, and returns it to the image forming section a.

The front side copying is continued until the first one returned after the front side copying is detected by the photo sensor 35, unless the number of double-sided copying sets is reached. When the photo sensor 35 detects the first copy sheet to be returned after the front side has been copied, a timer is set at an appropriate timing to temporarily stop the paper feed section b in the copying means and the return section g in the double-sided copying auxiliary means. Then, the copying progress status at that time, such as the number of front side copies, is stored. This calculates and sets the remaining number of copies for the front side, and when the original is replaced for back copying or reversed for a sufficient period of time before back copying becomes possible, the number of copies already made for the front side is calculated. is set as the number of copies for the back side, and the return section g is operated to send the copy paper after the front side copy to the image forming section a to perform the back side copy.

The paper feed section b of the copying means and the return section g of the double-sided copy assisting means are temporarily stopped by the detection operation of the photo sensor 35, so that the document is not copied on the back side before priority is given to copying on the back side of the copy paper for which the front side has already been copied. This is to allow for the preparation time necessary to replace the main body 1
It is also possible to control the operation as shown by the imaginary line in FIG. 2 as an operation of stopping the entire copying means and the double-sided copying auxiliary means. In this case, the start of backside copying is performed by re-driving the parts other than the paper feed section b of the copying means.

The back side copying continues until the number of front side copies set as the number of back side copies is completed.
When the back side copying is completed, front side copying and back side copying are performed in the same manner as described above unless the set remaining number of copies is 0.

During front side copying, when the previously set number of copies is reached, the timer is activated to indicate that front side copying is complete, regardless of whether or not the photo sensor 35 detects it, and the process starts from the last front side copy to the back side copy for the last front side copy. However, when the front side copying is completed, the set number of remaining copies becomes 0, and the number of back side copies becomes the number of copies made on the front side in the last time.
As a result, back side copying is continued until the final front side copying is performed. When this last back side copying is completed, the remaining number of copies is 0, so the state returns to the state before the start of double-sided copying, and the double-sided copying for the set number of copies is completed.

In addition to the photo sensor 35, a reed switch, a microswitch, an ultrasonic sensor, or the like can be used as a means for detecting that the copy paper after surface copying has reached a predetermined position in the return section g.

Double-sided copying by automatic switching between front-side copying and back-side copying is reliably performed no matter what timing the copy paper after front-side copying reaches the position of photo sensor 35. Therefore, the duplex copying aid may simply equalize its total paper feed to the normal system speed in the copying means.

However, only the return speed of the return unit g in the double-sided copying auxiliary means, that is, the driving speed of the return belt 31, is made lower than the system speed by a reduction device such as a gear device, or
can be driven independently by various dedicated motors, clutches, solenoids, ratchets, etc., and can be driven intermittently to a distance smaller than the size of the copy paper in the feeding direction each time the surface is continuously copied in the copying means. , the return belt 31 is shown in FIG.
As shown in FIG. 4, each copy sheet after the front side has been copied is processed at the system speed and sent out from the switchback section 26, and is received in an overlapping state with a certain amount of misalignment, and is returned to the image forming section a side. As a result, the timing at which the first copy sheet after surface copying is detected by the photo sensor 35 is considerably delayed, and it is possible to set more copy sheets on the return belt 31 than the length of the paper path. can. This reduces the frequency of switching between front-side copying and back-side copying,
The number of times required to replace the original and turn the front and back sides when making double-sided copies of a large number of copies is reduced. Therefore, it would be more convenient if such a return state could be selected as needed, and if the return state could be automatically obtained in accordance with the set number of double-sided copies.

Even if the copy sheets after front side copying are returned in an overlapping state, they are misaligned by a certain amount from each other, and the earliest one is reliably bitten into the rear side copy paper feed roller pair 33 for each copying cycle. By doing so, it should be possible to copy the back side of a single sheet. However, in reality, it is difficult to pull out stacked copies from the first copy paper below without dragging the copy paper above it, so it is difficult to pull out the stacked copies one by one without dragging the copy paper above it. Therefore, it is desirable to prevent the next copy sheet from accompanying the first copy sheet. In addition, the back side copy paper feed roller pair 3
Instead of the upper roller 3, pads 41 made of polyurethane rubber or the like are provided which are in pressure contact with the lower roller 33 as shown in FIGS. A reversing roller 43, which is fixed to the support shaft 42 and has a slightly smaller diameter than the upper roller 33 and is driven in the opposite direction to the conveying direction, is provided to separate the subsequent copy paper and perform double feeding. It may also be prevented, and if used in conjunction with the gate or brake member, double feeding can be more reliably prevented.

Furthermore, as another double-feed prevention means, the distance l (FIG. 9) between the final auxiliary roller 32 and the back side copy paper feeding roller pair 33 in the return section g is set to be slightly larger than the dimension in the conveying direction of the copy paper. Short, e.g. A4
In the case of size horizontal feed, if it is set as 192 mm < l < 210 mm, until the final point when the first copy paper is bitten by the pair of paper feed rollers 33 and sent to the reversing section f,
The subsequent copy paper is transferred to the return belt 31 and the auxiliary roller 3.
2, and double feeding will never occur.

Further, as shown in FIG. 10, the distance l
is set between the back copy paper feed roller pair 33 and the temporary stop adjustment roller pair 21, and the paper feed roller pair 33 is driven at the same low speed as the return belt 31. This is done between the roller pair 33 and the temporary stop adjustment roller pair 21, while the distance between both roller pairs 33 and 21 is 192 mm<l<210
Since the length of mm can also be used as a low-speed return range for storing copy sheets after front-side copying, the maximum stock amount, that is, the maximum number of copies that can be made in one double-sided copy, is further increased.

Effects According to the present invention, the sheet on which the surface image has been formed, which has been fed from the paper feeding means on one side and reached the paper discharge section on the other side via the image forming means, is sent to the sheet return means and then fed to the paper feeding means. In order to perform double-sided recording by returning the paper to the image forming means in a reversed state and using it to form an image on the back side, the image is continuously formed by the image forming means on the front side. The sheets are sequentially fed into the sheet return means and continuously returned to form an image on the back side, so that the sheet after the front surface image is transferred from the paper ejection means on the other side to the feeder on one side for refeeding. By continuously forming images on the sheet surface with the image forming means using the time required for returning the sheet to the paper means side, the sheet return path using the sheet return means without using an intermediate tray can be realized. Continuous image formation on the front side of the sheet and continuous image formation on the back side of the sheet are performed one after another in a number of sheets up to the length of the sheet, thereby achieving double-sided recording in an efficient manner. By repeating this process a number of times, it is possible to achieve double-sided recording on an unlimited number of sheets. Furthermore, the timing for switching from image formation on the front side to image formation on the back side by refeeding is determined when the first sheet after the front side image formation, which is returned by the sheet return means for refeeding, reaches a predetermined position. This is the point at which the detection means detects this, so it is possible to achieve switching without slow speed by simple control regardless of the sheet size or the number of sheets for double-sided recording, reducing time loss due to slow switching and surface image This does not cause problems such as paper feeding for forming and paper refeeding at the same time, and depending on the set number of sheets for double-sided recording, the surface image forming operation may be interrupted by the above switching, but the surface image forming operation at the time of this interruption may be The forming state is memorized, and when the back side image forming operation by refeeding the paper is completed, the next front side image forming operation is started again.By repeating the above operation, it is possible to automatically record on both sides of a large number of sheets without any problems. can be carried out.

[Brief explanation of drawings]

Fig. 1 is an internal mechanism diagram showing an embodiment of the present invention, Fig. 2 is a flowchart showing an example of a double-sided copying operation, and Figs. 3 and 4 are a portion showing a copy paper return state after front side copying. , FIGS. 5 and 6 are a side view and a sectional view showing an example of a double feed prevention device, FIGS. 7 and 8 are a side view and a sectional view showing another double feed prevention device, FIGS. 9 and 10 are side views showing other double feed prevention devices, respectively. {a... Image forming section, b... Paper feeding section, c... Paper discharge section, } Copying means, {27... Paper feeding direction switching gate, 26... Switchback section, g... Return section,
f...Reversing section}Double-sided copying auxiliary means.

Claims (1)

[Scope of Claims] 1. A sheet is fed from a sheet feeding means on one side to an image forming means for image formation, and the sheet after image formation is discharged to the outside by a sheet discharging means on the other side. In the recording apparatus, the sheet having the surface image formed thereon reaching the sheet ejecting means is sequentially and continuously returned to the sheet feeding means side, and is re-fed to the image forming means with the front and back reversed, and an image on the back side is generated. a sheet return means for use in formation; a detection means for detecting that the first sheet returned by the sheet return means has reached a predetermined return position; When the first sheet is detected, the recording progress status of the front surface image forming operation is stored, the currently running front surface image forming operation is interrupted, and an image is formed on the back surface of the sheet that is re-fed by the sheet return means. A double-sided recording device comprising: a control means for controlling an image forming means to perform the following operations. 2. A patent characterized in that, after the recording operation on the back side of the sheet re-fed by the sheet return unit is completed, the control means restarts the front side recording based on the stored recording progress status. A double-sided recording device according to claim 1.