JP2001063844A - Sheet conveying device, image forming device, and image reading device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately monitor a sheet conveying state even when paper sheets are conveyed gaplessly by providing a separation roller rotation/stop detecting means detecting the rotation/stop state of a separation roller and outputting the detection result as the information on the sheet conveying state. SOLUTION: If paper sheets S1, S2 with a prescribed lap quantity K are continuously fed by the operation of a paper feed section, a drive roller 50 is rotated in advance, and the signal wave-form from a photo-interrupter is switched to an L-signal when the tip of the sheet S1 reaches a sheet detection section 2. When the lap section (k) of the sheets S1, S2 reaches the sheet detection section 2, a separation roller 55 is stopped, and the second sheet S2 is separated. When the rear end of the sheet S1 passes through a nip, the separation roller 55 corotates in the sheet conveying direction, and the signal wave- form of the photo-interrupter 58 is set to H and L repeatedly, thereby the arrival of the sheet S2 at the nip position is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image forming apparatus or an image reading apparatus such as a copying machine or a printer, and a sheet conveying apparatus applied to these apparatuses.

[0002]

2. Description of the Related Art In a conventional sheet conveying apparatus applied to an image forming apparatus, an image reading apparatus, or the like, the functions of various apparatuses at a sheet conveying destination cannot be sufficiently exhibited due to a sheet conveying delay or the like. In order to prevent fatal damage and to synchronize image formation or image reading with sheet conveyance, it is necessary to monitor or detect the sheet conveyance state.

In a conventional sheet conveying apparatus, as shown in a schematic diagram of a sheet path of the sheet conveying apparatus in FIG. 9, a sheet 105 conveyed in a conveying direction e by a roller 106 is flagged in order to monitor a sheet conveying state. It was detected by the detecting means 101 such as a type sensor. A predetermined interval L (hereinafter, referred to as “sheet interval”) is provided between the sheets 105 that are continuously conveyed.
And the sheet conveyance state is monitored by detecting the sheet interval L based on the detection result of the detection unit 101.

Here, the configuration and operation of the conventional flag type sensor will be described. Flag sensor 101
Is generally configured as shown in FIG. 8, where 111 is a sensor flag, 112 is a photo interrupter, and 113 is a spring serving as a biasing means. The sensor flag 111 is urged by a spring 113. When the sheet is not at the position of the flag sensor 101, the sensor flag 111 is at the position shown in FIG. The sheet (not shown) is conveyed between the guide plates 115 in the direction of arrow e and abuts on the sensor flag 111.
Is tilted in the direction g in FIG. When the sensor flag 111 falls in the g direction, the presence or absence of a sheet is detected by the photo interrupter 112. here,
The time required for the fall of the sensor flag 111 to be returned by the spring 113, the time required for the position of the sensor flag 111 to stabilize, the time required for the potential of the sensor 101 to stabilize, etc. 1
The minimum required paper interval for the 01 to operate properly was determined.

In a conventional analog type image forming apparatus or image reading apparatus, for example, a copying machine, when a plurality of copies of the same original are continuously made, an optical device for exposing the original is required for the number of copies. Because of the time required for the reciprocating operation, the interval between sheets for transporting the image recording sheet is inevitably determined, and the sheet transport as described above is performed based on the interval. I was monitoring the condition.

However, in recent years, reading of a document and image formation thereof have been digitized, so that once a document is read, its image information can be electrically encoded and stored in a memory. . At the time of image formation, the image information in the memory is read out for each sheet on which the image is to be recorded, and an image corresponding to the image information of the document is formed on the photoconductor by an exposure device such as a laser beam or an LED array. It is sufficient that the mechanical movement of the optical device or the like is performed only once even when copying a plurality of sheets. As described above, since the operation time of the optical device and the like can be omitted, the space between the sheets to be conveyed can be reduced, and a large number of sheets can be processed in a short time.

For example, in the case of an image forming apparatus, the image forming speed has been substantially improved without increasing the image forming process speed. In an image forming apparatus, it is better to convey a sheet at a speed as low as possible, and to form an image at a process speed as low as possible.
It is known to be advantageous in various aspects, such as durability, stability of sheet conveyance, noise of the device, and power consumption of the device. In addition, the above advantages can be exhibited without lowering the sheet processing speed.

[0008]

As described above, with the recent digitization, it is very important to reduce the space between sheets, but furthermore, it is necessary to completely eliminate the space between sheets. Therefore, it is desired to further improve efficiency and increase productivity.

However, in the above-described conventional example, the sheet to be conveyed is detected by using a flag type sensor and a photo interrupter. Therefore, as described above, the return time of the sensor flag and the photo interrupter are detected. The minimum required amount of sheet space is determined by the operation time of the sensor, such as the electric reaction time, which hinders the reduction of the sheet space.

Further, there is a method of further reducing the paper interval by using an optical sensor such as a reflection type sensor or a transmission type sensor in which the operation time of the sensor is short, but the above optical sensor is very expensive. Further, there is a disadvantage that the method cannot be applied to a transparent sheet such as an OHP film. Furthermore, since there is no gap between sheets when the sheet interval is completely eliminated, it is impossible to detect the sheet conveyance state using either the flag type sensor or the optical type sensor.

In view of the above circumstances, it is an object of the present invention to provide a sheet conveying apparatus, an image forming apparatus, and an image recording apparatus capable of monitoring or detecting a sheet conveying state even in a sheet conveying state where there is no space between sheets. And

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a sheet feeding means for continuously feeding sheets at a predetermined overlap amount, a transport roller which can be driven to rotate, and a roller which rotates at a predetermined return torque. And a roller pair composed of a separation roller that has been driven and pressed so that the sheet is supplied by the sheet supply unit and nipped by the roller pair.
In a sheet conveying apparatus for conveying one sheet by the conveying roller and returning the other sheet by the separating roller, a rotation / stop state of the separation roller is detected, and the detection result is used as a sheet conveying state. And a separation roller rotation stop detecting means for outputting the information as information on the rotation of the separation roller.

Further, the separation roller rotation stop detecting means has an encoder.

Further, the sheet conveyance control is performed based on a detection result from the separation roller rotation stop detection means.

Further, according to the present invention, there is provided the above-mentioned sheet conveying device, wherein an image forming means is provided on the downstream side of the pair of rollers of the sheet conveying device, and the image forming means is provided based on a detection result from the separation roller rotation stop detecting means. Control the forming means,
It is characterized by the following.

Further, according to the present invention, there is provided the above-mentioned sheet conveying device, wherein an image reading means is provided downstream of the pair of rollers of the sheet conveying device, and the image is read based on a detection result from the separation roller rotation stop detecting means. Control the reading means,
It is characterized by the following.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a copying machine to which one embodiment of the present invention is applied. The copying machine is an image forming apparatus. In this figure, a copying machine 100 has a scanner section 38 as image reading means for reading image information such as a book document and a sheet document disposed at an upper inside thereof.

The scanner section 38 includes a scanning system light source 30c,
A document glass 31 a, a document pressure plate 32 that can be opened and closed with respect to the apparatus main body 27, an automatic document feeder 33 integrally formed with the document pressure plate 32, a document discharge tray 34, and a mirror base 3
0a, a lens, a light receiving element (photoelectric conversion element) 30, an image processing unit IP, and the like.

Then, an original composed of a book or a sheet is placed on the original glass 31a with the original surface facing downward, and the original pressing plate 32
By pressing the reading start key on the operation panel (not shown) by pressing the back surface by pressing the button, the mirror table 30a moves the lower part of the original table glass 31a to the arrow 30b in FIG.
The image information on the document surface is read by scanning in the direction. The image information of the document read by the light receiving element 30 by the reflected light of the light 37 from the scanning light source 30c is processed by the image processing unit IP, electrically encoded, and stored in the memory M.

An image forming section 7 serving as an image forming means is disposed below the scanner section 38, and a sheet cassette 29 is mounted below the image forming section 7 to supply a sheet as will be described later in detail. The paper unit 28 is configured to be able to feed the sheets S stacked in the sheet cassette 29. Note that the upper sheet cassette is 29a, the sheet feeding section is 28a, the lower sheet cassette is 29b, the sheet feeding section is 28b, and the reference numerals of parts related to the upper one are a, and the parts related to the lower one are a. The symbol "b" was added to the symbol.

The sheet S fed from the sheet feeding section 28 is guided by conveying paths 33 and 70 formed by guide plates and the like, is conveyed by conveying rollers 71 and 72, and the like. 2 and is conveyed to the image forming section 7. The transport rollers 71 and 72 are respectively connected to a drive source (not shown) via a clutch (not shown) so that the transport rollers 71 and 72 can be driven and stopped at a predetermined timing. It is configured.

The image forming section 7 of the apparatus main body 27 includes a photosensitive drum 9, a charger 9b for uniformly charging the surface of the photosensitive drum 9, and a photosensitive drum 9 charged by the charger 9b. A laser scanner 35 for irradiating the above-mentioned image information from the memory M with laser light at a predetermined timing, and developing the electrostatic latent image formed on the photosensitive drum 9 with the irradiated laser light to form a toner image And a transfer / separation charger 8 for transferring the toner image on the photosensitive drum 9 to the sheet S and separating the sheet S from the photosensitive drum 9, and removing the residual toner on the photosensitive drum 9. And a cleaner 9c.

On the downstream side of the image forming section 7, a transport section 41 for transporting the sheet S to which the toner image has been transferred, and the toner image on the sheet S transported by the transport section 41 is fixed as a permanent image. A fixing device 42 is provided for performing the fixing. Further, a discharge roller 43 for discharging the sheet S on which the image is fixed by the fixing device 42 from the apparatus main body 27 is provided. Further, on the downstream side, a sorter 4 that performs sheet post-processing such as sorting of the sheets S discharged from the apparatus main body 27 is provided.
4 is attached.

Next, a detailed description will be given of the sheet feeding section 28 (the same configuration is used for both the sheets 28a and 28b). The action of the pickup roller 10 as shown in FIG.
The sheet 15 following the fourth sheet is always conveyed to the vicinity of the nip of the retard roller 11 (by the distance C). Here, the operation of the paper feed mechanism using the pickup roller 10 will be schematically described. The distance C in the drawing represents the distance from the leading end of the sheet S stored in the sheet cassette 29 to the nip between the sheet feeding roller 12 and the retard roller 11, and the pickup roller 10 is moved by the distance C from the rear of the sheet S. It is located at the front and is fixed at the sheet feeding surface height h. The pickup roller 10 is always rotatably supported at the position of the sheet feeding surface height h during the continuous sheet feeding operation, is always rotated during the sheet feeding operation, and always feeds the uppermost sheet to the vicinity of the nip of the sheet feeding roller 12. Works like that.

Even if a plurality of sheets S are conveyed to the vicinity of the paper feed roller 12, the retard roller 11
Of the paper feed roller 12, the paper is conveyed one by one. If the sheet S has already been conveyed to the vicinity of the nip of the paper feed roller 12, the pick-up roller 10 does not touch the sheet S below that has not yet been conveyed. Never. Further, a paper surface detection sensor (not shown) monitors the uppermost sheet in the sheet cassette 29, and after the preceding sheet 14 has been conveyed by the paper supply roller 12 and has passed through the paper surface detection sensor, the uppermost sheet is at the paper supply surface height. h
If it is lower than this, the sheet supporting portion 16 is raised by lifting means (not shown), and the uppermost sheet in the sheet cassette 29 is brought into contact with the pickup roller 10.
The next sheet 15 is conveyed to the vicinity of the nip of the sheet feeding roller 12, and continuous sheet feeding is realized.

FIG. 3 shows an example of a method of driving the pickup roller 10. Further, as long as the next sheet 15 is conveyed to the vicinity of the nip between the sheet feeding roller 12 and the retard roller 11, other configurations may be used.

Now, as shown in FIG. 2, until the previously fed sheet 14 is conveyed by a fixed amount d,
When a drive that rotates in the opposite direction to the conveyance direction is input to the retard roller rotation shaft 11A through the drive input belt 12A and the electromagnetic clutch 23, and if a portion other than the preceding sheet 14 to be conveyed is conveyed to the vicinity of the nip of the paper feed roller 12, The sheet S other than the top sheet is separated by the operation of the torque limiter 13. Then, after the precedingly fed sheet 14 is conveyed by a predetermined amount d, the drive of the electromagnetic clutch 23 is cut off, and the retard roller 11 is rotated by the sheet feeding roller 12. In this way, the preceding sheet 14 and the next sheet 15 to be fed are fed with a desired overlapping amount and are transferred to the downstream side. The overlapping amount K in this case is expressed by the following equation.

K = (paper length) -d (Equation 1) In this manner, the sheet S having the predetermined overlap amount K is used to detect the sheet S on the downstream side as shown in FIG. 2
It is transported to.

Next, the sheet detecting section 2 will be described in detail.
FIG. 4A is a cross-sectional view of the sheet detection unit 2, and FIG. 4B is a plan view thereof. In this figure, a transport roller 50 is rotatably supported by a side plate (not shown) or the like, and is rotatably provided to transport the sheet S in a transport direction by a drive source (not shown). The transport roller 50
A separation roller 55 supported by a bearing (not shown) abuts and presses with a predetermined pressing force at a position opposed to the separation roller 55. The separation roller 55 is rotatably supported by a separation roller drive shaft 53 via a torque limiter 54 that generates a predetermined return torque. A drive input pulley 52 is attached to the shaft end of the separation roller drive shaft 53. Has been fixed. An output pulley 51 provided at an end of the shaft 50a of the transport roller 50 is disposed at a position facing the drive input pulley 52, and a drive belt 59 is stretched between the input / output pulleys 51 and 52. The rotation driving force of the transport roller 50 is transmitted to the separation roller shaft 53.

Note that these rotational directions are all the same as those in FIG.
7A, the separation roller driving shaft 53 is driven to rotate in the direction opposite to the sheet conveyance direction while the conveyance roller 50 is rotating. The pressing force of the separation roller 55 and the return force by the torque limiter 54 described above are such that the sheet S does not exist in the nip between the transport roller 50 and the separation roller 55, or that only one sheet S exists. In this case, the separation roller 55 rotates with the rotation of the conveyance roller 50 (in this case, the separation roller 55 rotates clockwise in FIG. 4A), and two or more sheets exist in the nip. In such a case, the separation roller 55 is set to rotate in the direction of returning the sheet S (the counterclockwise direction in FIG. 4A) by the rotation of the separation roller drive shaft 53, and to stop the sheet S. .

Further, a detection plate 57 having a plurality of holes 57a arranged at equal intervals is coaxially fixed to the separation roller 55 via a shaft 56. A photo interrupter 58 is provided at a position corresponding to the hole 57a of the detection plate 57.
In a state where the detection unit of the photo interrupter 58 is located at a position facing the hole 57a of the detection plate 57, the photo interrupter 58 outputs a high signal, and the
The photointerrupter 58 is provided in a portion (light shielding portion) other than 7a.
When the detecting section is present, a low signal is output (encoder). Further, a sensor flag 61 and a photo interrupter 60 are provided near the nip between the transport roller 50 and the separation roller 55, and when a sheet S exists near the nip, the sensor flag 61 is pushed by the sheet S to 4 (a), the photo interrupter 60 detects this and sends a low signal, and when the sheet S does not exist, the sensor flag 61 changes to the solid line state in FIG. 4 (a). It is configured to return and the photo interrupter 60 transmits a high signal.

The above two photo interrupters 58 and 60
, The state of sheet conveyance near the nip can be detected. That is,
As described above, when there is no sheet S in the nip between the driving roller 50 and the separation roller 55, the separation roller 5
5 rotates along with the driving roller 50, and as shown in FIG. 5A, the signal waveform W1
Takes a form of repetition of high and low, and the signal waveform W2 of the photointerrupter 60 maintains a high state. When only one sheet S is present in the nip, as shown in FIG. 5B, the signal waveform W1 of the photointerrupter 58 repeats high and low similarly, and the signal of the photointerrupter 60. The waveform W2 maintains a low state. Further, when two or more sheets S are conveyed into the nip, the separation roller 5
5 starts the separation operation and stops the rotation.
Alternatively, as shown in (d), the signal waveform W1 of the photointerrupter 58 maintains a high state while the signal waveform W1 of the photointerrupter 58 maintains either a high state or a low state.

In this way, it is possible to detect whether the sheet S is not present in the nip between the separation roller 55 and the conveyance roller 50, whether only one sheet is present, or whether a plurality of sheets S are present and the separation operation is being performed. It has become.

Next, the sheet S is fed from the sheet feeding section 28 described above.
The signal waveforms of the photo-interrupters 58 and 60 in the sheet detection unit 2 when the sheets are conveyed in a state where they overlap by a predetermined amount will be described with reference to FIGS.

A paper feeding operation is started by the paper feeding unit 28,
When sheets having a predetermined overlap amount K are continuously fed, before the leading edge of the first sheet S1 reaches the sheet detection unit 2 (the state in FIG. 6A), the drive roller 50 The signal waveforms W1 and W2 of the photointerrupters 58 and 60 are as shown in section A in FIG. 7 because the sheet has been rotated in advance and no sheet exists in the sheet detection section 2. Then, when the leading end of the first sheet S1 reaches the sheet detection unit 2 (the state of FIG. 6B), the signal waveform W2 from the photointerrupter 60 is switched to a low signal as indicated by B in FIG. . When the overlapping portion of the sheets (accordingly, the leading end of the second sheet S2) reaches the sheet detecting portion 2 (the state shown in FIG. 6C), the separation roller 55 moves to the second position.
Since the separation operation of the second sheet S2 is performed, the separation roller 55 stops, whereby the second sheet S2 stops (the state of FIG. 6D), as shown by C and D in FIG. To
The signal waveform W1 of the photointerrupter 58 maintains either a low state or a high state.

When the rear end of the first sheet S1 has passed through the nip (the state shown in FIG. 6E), only one sheet is present in the nip. , The conveyance operation of the second sheet S2 is restarted, so that the signal waveform W1 of the photointerrupter 58 takes a form of high-low repetition again as shown by E to C in FIG. . Therefore, by detecting that the photo interrupter 58 has been switched from a state in which the photo interrupter 58 maintains either high or low to a state in which the photo interrupter 58 repeatedly repeats high and low during the continuous sheet feeding operation, the second sheet S2 is nipped. The arrival at the position can be detected. At the same time, this is the same as detecting the rear end of the first sheet S1.

As described above, when the rollers 72 on the upstream side of the sheet detection unit 2 are rotated at the time when the first and second overlapping portions come to the nip, the second and subsequent sheets S2, Since S3 buckles in the transport path, during the separating operation, that is, while the signal form of the photointerrupters 58 and 60 is in the state of D in FIG. 7, that is, while maintaining the high signal or the low signal, The upstream roller 72 is temporarily stopped by using a clutch or the like (not shown), and is stopped by E in FIG.
If the driving of the roller 72 on the upstream side is restarted at the time point when the state (1) is detected, the problem of the buckling does not occur. Further, after detecting the separating operation, the stop time of the roller 72 due to the clutch or the like slightly shifts, and the second sheet S
In some cases, a loop may be formed in the sheet detection unit 2, but in order to avoid such a situation, as shown in FIG. A loop reservoir (so-called hood) 62 may be formed so that the sheet S2 is not buckled by the loop.

As described above, the position of the leading edge (or the trailing edge) of each sheet (the time it takes to reach the sheet detecting section 2) can be detected while reliably and stably forming a sheet-free state. With this configuration, it is possible to synchronize the toner image on the photosensitive drum 9 and each sheet S in the image forming unit 7 based on the detection signal obtained by the sheet detecting unit 2. That is, the distance from the sheet detection unit 2 to the image transfer unit 8a and the photosensitive drum 9 by the laser scanner 35
Since the distance from the irradiation position of the sheet to the image transfer section 8a is predetermined, the laser scanner 3 is moved a predetermined time after the sheet leading edge passage timing obtained by the sheet detection section 2.
By starting the irradiation of the laser beam from 5, each sheet S and each image can be synchronized.

In the above-described embodiment, the description has been made in such a manner that the leading edge of each sheet is detected. However, only the trailing edge of each sheet is detected from the signal waveform W1 of the photointerrupter 58, and the calculation is performed based on the sheet length information. Then, the leading edge of the sheet may be detected. Also, the sensor flag 61
Alternatively, a configuration in which the photo interrupter 60 is omitted can be employed, and a simpler configuration can be obtained.

Further, the sheet conveying device according to the present invention can be employed in an image reading device such as a scanner. That is, this is realized by regarding the image recording sheet in the above embodiment as a document to be read, and constructing a similar document (sheet) conveyance structure. The necessary changes and modifications in design in this case can be easily realized by those skilled in the art based on the description of the above embodiment.

[0041]

As described above, according to the present invention, a sheet is continuously supplied with a predetermined overlapping amount and separated and conveyed by a pair of rollers including a conveying roller and a separation roller, so that a stable paper interval is obtained. And the arrival of the leading edge or the trailing edge of the sheet (sheet transport state) can be known based on the detection result of the separation roller rotation stop detecting means. As a result, productivity can be efficiently improved without causing a shift between the sheet and the image. Therefore, it is possible to improve image quality, durability, and sheet transportability, reduce noise, suppress power consumption, and provide an image forming apparatus and the like with stable quality. In addition, an image reading device with high productivity can be provided efficiently.

Of course, the information on the sheet conveyance state
This is convenient because it can be used not only for determining the image forming timing but also for controlling other image forming means and controlling the sorter 44 and the like.

[Brief description of the drawings]

FIG. 1 is a sectional view of a copying machine to which an embodiment of the present invention is applied.

FIG. 2 is a perspective view showing a sheet feeding unit.

FIG. 3 is a perspective view of a sheet feeding drive unit.

FIG. 4 is a diagram illustrating a sheet detection unit.

FIG. 5 is a diagram illustrating a signal waveform from a sheet detection unit.

FIG. 6 is a diagram illustrating a sheet conveyance state.

FIG. 7 is a diagram showing a signal waveform from a sheet detection unit.

FIG. 8 is a sectional view of a conventional flag type sensor.

FIG. 9 is a schematic diagram of a conveying path in a conventional sheet conveying apparatus.

[Explanation of symbols]

 S sheet 2 sheet detection unit 7 image forming unit 28 paper feeding unit 29 paper feeding cassette 50 transport roller 54 torque limiter 55 separation roller 58 photo interrupter 60 photo interrupter 61 sensor flag

Claims (5)

[Claims] 1. A sheet feeding means for continuously feeding sheets at a predetermined overlap amount, a roller pair comprising a rotatable driving roller and a separation roller rotatably pressed against the conveying roller with a predetermined return torque, A sheet transporting apparatus that transports one sheet among the sheets supplied by the sheet supply unit and nipped by the pair of rollers by the transporting roller, and returns the other sheets by the separation roller. And a separation roller rotation stop detecting means for detecting a rotation / stop state of the separation roller and outputting the detection result as information on a sheet conveyance state. 2. The sheet conveying apparatus according to claim 1, wherein said separation roller rotation stop detecting means has an encoder. 3. The sheet conveying device according to claim 1, wherein the sheet conveying control is performed based on a detection result from the separation roller rotation stop detecting unit. 4. A sheet conveying device according to claim 1, further comprising: an image forming unit provided downstream of said roller pair of said sheet conveying device, based on a detection result from said separation roller rotation stop detecting unit. An image forming apparatus for controlling the image forming means. 5. The sheet conveying device according to claim 1, further comprising: an image reading unit provided downstream of the pair of rollers of the sheet conveying device, based on a detection result from the separation roller rotation stop detecting unit. An image reading device for controlling the image reading means.