JPH08133530A - Sheet conveying device, image reading device, and image forming device - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a sheet conveying device capable of accurately performing registration of a sheet even after being repeatedly used for a long time or repeatedly a number of times. To aim. A first skew amount detecting means for detecting the skew amount of the sheet, and a second skew amount detecting means for detecting the skew amount of the sheet corrected by the registration means. Control for controlling the registration unit based on the skew amount of the sheet detected by the first skew amount detecting unit and the skew amount of the sheet previously detected by the second skew amount detecting unit And a sheet transporting device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying device in an image forming apparatus such as a copying machine, a scanner, a printer, etc., or an image reading apparatus, and in particular, it performs sheet registration on the upstream side of the image forming section or the image reading section. The present invention relates to a sheet conveying device for the purpose.

[0002]

2. Description of the Related Art Conventionally, in a machine such as a copying machine, a scanner or a printer for forming or reading an image, a registration device for adjusting the posture and position of the sheet immediately before the image forming section or the image reading section. Is used. These registration devices include, for example, a loop resist that pushes the leading end of a sheet into a nip of a pair of rollers that are stopped to bend the sheet and causes the elasticity of the sheet to bring the leading end of the sheet into the roller nip to correct skew. System, or a shutter registration method in which a shutter member for stopping the leading edge of the sheet is provided so as to be retractable in the sheet conveying path, and the leading edge of the sheet is attached to the shutter member, and then the shutter member is retracted from the conveying path to correct skew. Is used.

However, as these image forming apparatuses and image reading apparatuses have been digitized in recent years, the distance between sheets (hereinafter referred to as "paper interval") is reduced,
By processing a large number of sheets in a short time, a substantial improvement in the image forming speed can be achieved without increasing the image forming process speed.

For example, in a conventional analog copying machine, when copying is continuously performed, an optical device for exposing an original has to reciprocate by the number of copies, so that the distance between sheets for copying the information of the original is small. It was decided inevitably. However, since the reading of the original and the image formation thereof are digitized, after the original is read once, the image information thereof is electrically encoded and stored in the memory. Then, at the time of image formation, the image information in the memory is read and an image corresponding to the image information is formed on the photoconductor of the image forming unit by an exposure device such as a laser beam or an LED array. Therefore, even when copying a plurality of sheets, mechanical movement of the optical device or the like becomes unnecessary.

Therefore, the above-described time for sheet registration is one of the major factors that determine the above-mentioned sheet interval. One of the methods that have been proposed to reduce the registration time is an active registration method that corrects skew feeding while conveying a sheet. In this method, two sensors are arranged on a coaxial line orthogonal to the sheet conveying direction in the sheet conveying path, and the inclination of the sheet tip is detected based on a signal that the sheet tip crosses each sensor. , The sheet skew correction rollers (hereinafter referred to as "registration rollers") arranged on the same axis orthogonal to the sheet conveyance direction and driven independently of each other are intended to correct the sheet skew by controlling the sheet conveyance speed. is there. According to this method, skew feeding correction can be performed while the sheet is being conveyed without being temporarily stopped, so that the above-described sheet interval can be made smaller than other methods.

[0006]

However, in the above-mentioned conventional example, when the apparatus is used in a durable manner, the rollers are gradually scraped, but the outer diameter is reduced and the desired speed can be obtained. There is also a problem that paper dust, toner, etc. are lost in the surface clearance of the roller, and the uplifting force on the roller surface is reduced, so that the initial gripping force becomes insufficient and the desired speed cannot be obtained.

Therefore, the present invention has been made in view of the above, and the registration of the sheet is as accurate as that before the durable use even after the sheet conveying device is durablely used for a long time or repeatedly many times. An object of the present invention is to provide a sheet conveying device that can perform well.

[0008]

The structure of the present invention for attaining the above-mentioned object comprises a first skew feed amount detecting means for detecting the skew feed amount of a sheet, and a registration means for correcting the skew feed of the sheet. A second skew amount detecting means for detecting the skew amount of the sheet that has been skew-corrected by the registration means; and a skew amount of the sheet detected by the first skew amount detecting means. And a control unit that controls the registration unit based on the skew amount of the sheet previously detected by the second skew amount detection unit.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, one embodiment of the sheet conveying apparatus according to the present invention will be concretely described with reference to the drawings. In the present embodiment, an embodiment in which the present invention is applied to a document image reading apparatus will be described. FIG. 1 is a cross-sectional view showing a schematic configuration of a document feeder and an image reading apparatus to which the present invention is applied, FIG. 2 is a cross-sectional view showing a contact / separation mechanism of a pair of feed rollers, and FIG. It is a perspective view.

In FIG. 1, reference numeral 1 is a document placing table,
A plurality of originals G are set with their image surfaces facing up. Two
Reference numerals a and 2b are sensors as sheet length detecting means, which detect the lengths L _s1 and L _s2 of the original G set on the original table 1 in the transport direction (L).
_s1 <L _s2 ). Reference numeral 3 denotes a pickup roller, the outer peripheral surface of which is coated with rubber or the like having a relatively high coefficient of friction, and which feeds out the original G set on the original table 1. 4 is a pair of separate feeding rollers, which are upper rollers 4A,
The original G sent by the pickup roller 3 as the lower roller 4B rotates clockwise.
It separates the sheets one by one and feeds them.

Reference numerals 5 and 6 respectively denote a first conveying roller pair as a sheet conveying means and a second conveying roller pair capable of contacting / separating. Of the second pair of conveying rollers 6, the roller 6
A is configured to contact / separate with respect to the roller 6b by the contact / separation mechanism 7 shown in FIG. The contacting / separating mechanism 7 in this embodiment is electrically turned on as shown in FIG.
It is constituted by a solenoid 7a that turns on / off, an arm 7b that connects the solenoid 7a and the roller 6a, and a spring 7c that abuts the roller 6a on the roller 6b. In this embodiment, the solenoid 7a is turned on.
In this state, the roller 6a is separated from the roller 6b. Then, when the solenoid 7a is opened, it is brought into contact with the roller 6b by the force of the spring 7c.

Further, in FIG. 1, reference numeral 8 is a registration means for correcting the skew feeding of the document G, and as shown in FIG. 3, transporting is independently driven on coaxial lines orthogonal to the document transporting direction. It has two pairs of rollers 8a and 8b as means or rotating bodies. That is, the skew feeding of the document is performed by increasing or decreasing the rotation speed of one roller pair according to the skew feeding amount of the document to make the feeding speed of the two feeding means different. still,
In this embodiment, the skew of the original is corrected by slowing the rotation speed of one roller pair (the side on which the original is leading) according to the amount of skew of the original.

Reference numeral 9 denotes a sheet skew amount detecting means for detecting the skew amount (tilt of the leading edge) of the document. As shown in FIG. 3, two sets of light transmission type sensors 9a and 9b are provided. It is arranged on a coaxial line orthogonal to the document conveyance direction via a conveyance path. The sensor 9a, the by unillustrated control means, based on the skew amount of the original detected by 9b registration roller pair 8a, the rotation of the drive motor 8b M _1, M ₂ are controlled, skew correction of the original Is done.

Further, in FIG. 1, reference numeral 10 denotes an image reading apparatus, which illuminates an illumination lamp 10a for illuminating an image surface of an original G through a transparent glass disposed in a conveyance path and reflects the emitted light. It is composed of mirrors 10b, 10c, and 10d, a lens 10e that collects the reflected light, and an image reading element 10f such as a CCD.

Reference numeral 12 denotes a discharge roller pair, which discharges the original G from which the image is read onto the discharge tray 13. A conveyance guide 14 for guiding the document G is provided between each pair of rollers.

Here, the relationship of lengths shown in FIG. 1 will be described. In FIG. 1, the transport length L _a1 from the registration means 8 to the second transport roller pair 6 is L _a1 <L _s1 with respect to the length L _s1 of the document G in the transport direction. In addition, the registration means 8 to the first conveying roller pair 5
The transport length L _{a2 up to} is L _a2 <L _s2 with respect to the length L _s2 of the document G in the transport direction.

Further, the sum of the transport lengths L _a1 and L _a2 plus the transport length L _b from the registration means 8 to the light transmission type sensor 9 is the length L of the original G in the transport direction. L _a1 + L _b > L _s1 , L _a2 + L _b for _s1 and L _s2
> L _s2 .

Next, the operation of the original image reading apparatus configured as described above will be described.

When the document G is set on the document table 1, the sensors 2a and 2b detect the lengths L _s1 and L _{s2 of the} document G in the transport direction. Here, when the detected length of the document G is L _s1 , the length L _s1 is longer than the transport length L _a1 from the registration means 8 to the second transport roller pair 6 (L _a1 <L _s1 ), and it is shorter than the length L _a1 + L _b, which is the _sum of the transport length L _b from the registration means 8 to the light transmission type sensor 9, (L _a1 + L _b + L _s1 ), and therefore is in a separated state in advance. The second conveying roller pair 6 is brought into contact with the contacting / separating mechanism 7. When the detected length of the document G is L _s2 , the length L _s2 is the transport length L _a1 from the registration means 8 to the second transport roller pair 6.
Longer than (L _a1 <L _s2), and registration longer than the length L _a1 + L _b which transport plus the length L _b from the means 8 to the light transmission sensor _{9 (L a1 + L b <} L s2) For,
The second conveying roller pair 6 is held in a separated state.

After the contact / separation of the second conveying roller pair 6 is performed, the pickup roller 3 is rotated and the uppermost document on the document mounting table 1 is fed toward the separating / feeding roller pair 4. The separated feeding roller pair 4 has 1
If the number of sheets is one, the original is fed as it is toward the first conveying roller pair 5, but when two or more originals are fed at once, the lower roller rotates in the opposite direction to the conveying direction. Only the uppermost original is fed to the first conveying roller pair 5. Since this separating mechanism is not related to the essence of the present invention, its detailed description is omitted.

When the fed original is the original having the length L _s1 , the roller pair 6 is in contact with the original. Therefore, the pair of rollers 5 and 6 are used to register the pair of registration rollers 8a along the conveyance guide 14. 8b, and in the case of a document having a length L _s2 , the roller pair 6 is in a separated state, and therefore is fed by the roller pair 5 along the conveyance guide 14 to the registration roller pairs 8a and 8b.

The pair of registration rollers 8a and 8b are rotated at the same speed as the document conveying speed of the pair of conveying rollers 5 and 6. As shown in FIG. 3, the original sandwiched by the pair of registration rollers 8a and 8b is the transparent glass 1 that serves as an image reading unit.
Although it is transported to the upper side of the sheet 1, it passes through the light transmission type sensors 9a and 9b in the middle of the transportation. The sensors 9a and 9b each emit a signal at the moment when the document passes, and an arithmetic circuit (not shown) calculates the inclination of the leading edge of the document based on these signals. Based on the calculated inclination, the skew of the original G is corrected by controlling the rotation of the drive motors M ₁ and M ₂ of the pair of registration rollers 8a and 8b by a control unit (not shown). At this time, since the trailing edge of the document G is largely rotated,
If the trailing edge is still sandwiched by the pair of transport rollers 5 and 6, the movement is restricted.

As described above, the leading edge of the document is the sensor 9
When reaching a and 9b, the trailing edge of the document having the length L _s1 has always passed the conveyance roller pair 5 and 6, and further has the length L.
_Since the trailing edge of the document of _s2 has passed the transport roller pair 5 and the transport roller pair 6 has been previously separated, it is not possible to restrain the movement of the trailing edge of the document during skew correction by the registration roller pairs 8a and 8b. Absent. Therefore, regardless of the length of the manuscript,
The skew correction is accurately performed.

Skew correction control will be described with reference to the block diagram shown in FIG. 4 and the flow chart shown in FIG.

When the leading edge of the first conveyed document passes through the light transmission type sensors 9a and 9b, the count circuit 21 outputs the count data corresponding to the skew amount due to the time difference between the output timings of the both sensors.

In the timing chart of FIG. 6, 9a is replaced by 9b.
When the sensor output of 9a changes to a high level, the counter circuit 21 starts and the sensor 9a
The counting operation is performed until b becomes a high level. On the contrary, 9
The counter circuit 21 operates similarly when b precedes.

Next, when both of the sensors become high level, an interrupt signal is sent from the counter circuit 21 to the microcomputer 22.
Is output to (flow chart: step S
1).

When the interrupt signal is input, the microcomputer 22 reads the count data and knows in which direction and how much the sheet was skewed (step S).
2).

Since the original has passed the sensor 9a first, the microcomputer 22 causes the step motor driver 23 to operate.
Thus, the motor of M1 that drives the roller 8a near the leading corner 9a of the leading edge corners Pa and Pb of the sheet P is decelerated to correct the skew amount (step S3).

This will be described with reference to (control time-driving frequency) in FIG. The drive frequency is a clock output to the motor driver of M1. Normally, when the skew feeding correction control is not performed, it is driven at 5000 Hz. When the deceleration control in step S3 starts, the step motor M1 is gradually decelerated. M for the microcomputer
The difference between the clock outputs output to 1 and M2 is counted by a counter circuit (not shown) in the microcomputer (step S4).

When the count amount becomes half of the count amount corresponding to the skew feed correction amount (when the correction of half of the detected skew feed amount is completed), the control is returned to start the acceleration control (step S5). ) (FIG. 7, turning point 1).

Simultaneously with the deceleration control, the difference between the clock outputs output to M1 and M2 is counted by a counter circuit (not shown) in the microcomputer, and the counted amount corresponds to the skew correction amount. When it becomes equal to, the skew feed correction ends (step S6) (control end 1 in FIG. 7).

That is, the delayed corner 9b has advanced more than the preceding corner 9a by the delay.

If the skew amount is large, the deceleration control time becomes long (turning point 2) and the acceleration control time also becomes long (control end 2).

Further, since the contact or separation of the conveying roller pair 6 can be selected by detecting the document size in advance (or the operator may input the size), the contact or separation of the roller pair 6 can be selected. It is not necessary to precisely control the timing of the contacting / separating mechanism 7 for performing. Further, when the originals are continuously fed, the contacting / separating operation of the roller pair 6 is not performed every time, so that the contacting / separating mechanism is not required to have a strict durability. In addition, the shock accompanying the contact and separation operation of the roller pair 6 is transmitted,
There is no fear of adversely affecting the reading of the original.

(Second Embodiment) Next, a second embodiment of the sheet conveying apparatus according to the present invention will be described with reference to FIG.

In FIG. 8, after passing through the light transmission type sensor 9 for detecting the skew amount, before the image reading section, another 1
Two sets (15a and 15b) of the light transmission type sensor of No. 5 are arranged on the coaxial line orthogonal to the document conveyance direction via the conveyance path.

If the skew feeding correction described above is completed before the 15 sensors, the sensor 15 can know the skew feeding correction result, and the image reading unit measures the skew feeding amount again. You don't have to.

Normally, in order to measure the amount of skew in the image reading section, a counter in the main running direction (reading line direction) must be provided, but if a light transmission type sensor 15 is newly installed, it is not necessary. . By using the light transmission type sensors 9 and 15 described above, the skew feed amount can be corrected accurately and durable.

Further, in the case of the second embodiment, if there is sufficient time and distance between the 15 sensors and the reading unit, further fine correction of the skew feeding amount can be performed during this time, and further better skewing is possible. Line amount can be corrected.

However, the registration roller pair 8
For a and 8b, abrasion of the outer diameter and reduction of the surface roughness cannot be avoided in a durable manner, and the desired transport speed is reduced. Therefore, the skew amount that was completely corrected at the beginning cannot be corrected correctly. Therefore, the skew amount of the image is measured again at the image reading position, and the amount is accumulated in the memory. When the skew amount after the correction performed for the latest 10,000 sheets when passing a certain number of sheets, for example, several hundred thousand sheets, is not 0 mm and is skewed to either side, for example, the registration roller 8a side Is 0.1mm after correction
If it precedes, if it makes corrections in the future, registration roller 8
0.1 mm is added to the correction amount so that the roller on the a side is delayed by 0.1 mm.

Regarding this control, the flow chart is as shown in FIG. 9 as described above.

Read value of counter data (step S
The average value of the corrected skew feeding amount of the latest 10,000 sheets is added to 2) (step S7) to perform deceleration control (step S5).

As described above, the correction amount is feedback-corrected from the latest correction result, so that the control can be performed with higher accuracy in terms of durability. In addition, even if the registration roller 8 is slightly slipped or the diameter is drastically reduced due to some other abnormality, self-feedback control is performed, so that the frequency of roller replacement by calling a service person can be reduced.

In the above-described embodiment, an example in which the sheet conveying device according to the present invention is applied to the original image reading device has been described, but the present invention is not limited to this and can be applied to an image forming device, for example. Of course. As the image forming apparatus, for example, in FIG. 1, a recording medium such as copy paper is placed instead of the original G, and the optical systems 10a to 10a.
A recording system (including a recording head, a head drive circuit, etc.) is arranged in place of 10f and 11. At this time, the size information from the copy paper cassette also corresponds to the sheet length detecting means. Furthermore, an image forming apparatus that records the image information of the read original on a copy sheet may be configured by combining the original image reading apparatus having the features of the present invention and the image forming apparatus main body.

In the above embodiment, when the sensor 9a precedes the sensor 9b and outputs a high level, the motor M1 is decelerated to correct the skew amount, but the motor M1 is temporarily stopped. It is possible to correct the skew feeding also by doing. Conversely, the motor M2 may be speed-up controlled to perform skew correction. Further, the deceleration control of the motor M1 and the motor M2
The speed increase control may be performed at the same time.

In the above embodiment, the deceleration control or acceleration control of the pulse motor changes the speed at a constant rate. However, the present invention is not limited to this, and the normal speed V _{O is changed} to a higher speed V _H.
Alternatively, the speed may be gradually switched to the low speed V _L.

In the above embodiment, the larger the sheet skew amount, the longer the deceleration control time and the larger the speed difference between the two conveying means. On the other hand, the deceleration control time may be constant, and the deceleration rate may be increased as the skew amount is increased, or the speed may be switched to a lower speed.

The above-described sheet conveying apparatus can be applied not only to the document reading apparatus but also to the image forming apparatus. In particular, the image can be formed at an accurate position on the sheet by arranging it on the upstream side of the image forming means for forming an image on the sheet.

[0050]

As described above, in the conveying apparatus for correcting the skew feeding while conveying the sheet, the skew correction result is measured after the skew correction by the registration means is completed, and the result is accumulated and fed back. Therefore, the correction accuracy can be maintained and improved in a durable manner.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a schematic configuration when a sheet conveying device according to a first embodiment of the present invention is applied to a document image reading device.

FIG. 2 is a cross-sectional view showing a contact / separation mechanism of a conveyance roller pair in the apparatus.

FIG. 3 is a top view showing a skew feeding correction portion of a document in the apparatus.

FIG. 4 is a control block diagram of the apparatus.

FIG. 5 is a control flowchart of the apparatus.

FIG. 6 is a control timing chart of the device.

FIG. 7 is a graph showing a change in drive frequency of a pulse motor during deceleration control.

FIG. 8 is a sectional view showing a schematic configuration when a sheet conveying device according to a second embodiment of the present invention is applied to a document image reading device.

FIG. 9 is a control flowchart of the apparatus.

[Explanation of symbols]

G Document M ₁ , M ₂ Motor 1 Document Plate 2a, 2b Sensor 3 Pickup Roller 4 Separation Feeding Roller Pair 5, 6 Conveying Roller Pair 6a, 6b Roller 7 Contact / Separation Mechanism 7a Solenoid 7b Arm 7c Spring 7d Motor 7e Motor Gear 7f Cam 8 Registration means 8a, 8b Registration roller pair 9 Sheet skew amount detection means 9a, 9b Light transmission type sensor 10 Image reading device 10a Illumination lamps 10b, 10c, 10d Mirror 10e Lens 10f Image reading element 11 Transparent glass 12 Ejection roller 13 to Ejection Tray 14 Transport Guide 15 Sensor

Claims (24)

[Claims] 1. A first skew amount detecting means for detecting a skew amount of a sheet, a registration means for correcting skew of the sheet, and a skew of the sheet corrected by the skew correction means. Second skew amount detecting means for detecting a line amount, sheet skew amount detected by the first skew amount detecting means, and sheet previously detected by the second skew amount detecting means And a control unit that controls the registration unit based on the skew feeding amount. 2. The control unit adds the skew amount of the sheet detected by the first skew amount detection unit and the skew amount of the sheet detected in the past by the second skew amount detection unit. The sheet conveying apparatus according to claim 1, wherein the registration unit is controlled based on the skew feeding amount. 3. The average of the sheet skew amount detected by the first skew amount detection unit and the sheet skew amount previously detected by the second skew amount detection unit. The sheet conveying apparatus according to claim 1, wherein the registration unit is controlled based on the skew amount added with the value. 4. The sheet conveying apparatus according to claim 3, further comprising a memory capable of storing the sheet skew amount detected by the second skew amount detection unit for a plurality of times. 5. The sheet skew correction is performed by the registration unit, and skew correction is performed again based on the skew amount of the sheet detected by the second skew amount detection unit. The sheet conveying apparatus according to claim 1, further comprising: controlling the registration means. 6. The sheet conveying apparatus according to claim 1, wherein the second skew amount detecting means is an image reading section. 7. An image forming apparatus having an image forming unit for forming an image on a sheet conveyed by the sheet conveying apparatus according to claim 1. 8. An image reading apparatus having an image reading unit for reading an image of a sheet conveyed by the sheet conveying apparatus according to claim 1. 9. An image forming apparatus having the image reading apparatus according to claim 8. 10. A plurality of conveying means for applying a conveying force to the sheet at the same time to correct the skew of the sheet, a first skew detecting means for detecting the skew of the sheet, and the plurality of conveying means. Second skew detecting means for detecting skew of the sheet having skew correction, sheet skew amount detected by the first skew amount detecting means, and second skew amount Based on the skew amount of the sheet detected in the past by the detection unit, in order to correct the skew, the transport speeds of at least one of the plurality of transport units are different so that the transport speeds of the plurality of transport units are different from each other. And a control unit that controls the sheet conveyance device. 11. The sheet conveying apparatus according to claim 10, wherein the plurality of conveying units include first and second conveying units arranged in a direction intersecting with a sheet conveying direction. 12. The control means corrects the skew by controlling the transport speed of the transport means on the side closer to the preceding one of the both corners of the leading edge of the sheet to be slower than the other transport means. The sheet conveying device according to claim 11. 13. The control means corrects the skew by reducing the transport speed of the transport means on the side closer to the preceding one of the both corners of the leading edge of the sheet.
The sheet conveying device described. 14. The control means corrects the skew by increasing the transport speed of the transport means on the side closer to the delayed one of the both corners of the leading edge of the sheet.
3. The sheet conveying device according to item 3. 15. The control means decelerates the carrying speed of the carrying means on the side closer to the leading one of the two corners of the leading edge of the sheet, and increases the carrying speed of the carrying means on the side closer to the trailing one. 2. The skew feeding is corrected at a high speed.
2. The sheet conveying device according to item 2. 16. The conveying means according to claim 10, wherein each of the plurality of conveying means has a rotating body that contacts a sheet and a pulse motor that drives the rotating body. Sheet conveying device. 17. The first or second skew feeding detecting means has a plurality of sheet sensors for detecting the presence or absence of sheets arranged side by side in a direction intersecting the sheet conveying direction. The sheet conveying apparatus according to any one of claims 10 to 16. 18. The sheet conveying apparatus according to claim 17, wherein the control unit calculates the sheet skew amount based on a time difference between the sheet detections of the plurality of sheet sensors. 19. The sheet conveying apparatus according to claim 18, wherein the control unit controls the speed of the conveying unit based on the calculated skew feeding amount of the sheet. 20. The control means controls the speed of at least one of the plurality of conveying means such that the larger the calculated skew feeding amount of the sheet is, the larger the difference of the conveying speeds of the plurality of conveying means becomes. 20. The sheet conveying apparatus according to claim 19, wherein: 21. The control unit controls at least one of the plurality of conveying units so that the conveying speed of the plurality of conveying units is relatively different for a longer period as the calculated skew feeding amount of the sheet is larger. 20. The sheet conveying apparatus according to claim 19, wherein speed control is performed. 22. An image forming apparatus having an image forming unit for forming an image on a sheet conveyed by the sheet conveying apparatus according to claim 10. 23. An image forming apparatus having an image reading unit for reading an image of a sheet conveyed by the sheet conveying apparatus according to claim 10. 24. An image forming apparatus having the image reading apparatus according to claim 23.