JP3126602B2 - Sheet conveying device, image reading device, and image forming device - Google Patents

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 and the like and an image reading apparatus, and more particularly, to a sheet registration in an image forming section or an upstream side of 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 for forming an image or reading an image, such as a copying machine, a scanner, or a printer, a registration device for adjusting the position and position of a sheet immediately before the image forming unit or the image reading unit. Is used. These registration devices include, for example, a loop registration device that protrudes a sheet tip into a nip of a pair of stopped rollers to bend the sheet, and adjusts the skew by attaching the sheet tip to the roller nip by the elasticity of the sheet. A shutter registration method that corrects the skew by retracting the shutter member from the conveyance path after the shutter member is provided in the sheet conveyance path so that it can be retracted, and the shutter member is stopped in the sheet conveyance path. Is used.

However, in recent years, as these image forming apparatuses and image reading apparatuses have been digitized, the distance between sheets (hereinafter, referred to as “sheet interval”) has been reduced.
By processing a large number of sheets in a short period of 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 performing continuous copying, an optical device for exposing a document must reciprocate by the number of copies, so that the space between copies of the document information is limited. Inevitably decided. However, since the reading of the document and the image formation thereof are digitized, the image information is electrically encoded and stored in the memory after the document is read once. At the time of image formation, the image information in the memory is read out, and an image corresponding to the image information is formed on a photoconductor of an image forming unit by an exposure device such as a laser beam or an LED array. For this reason, a mechanical movement of an optical device or the like is not required even when copying a plurality of sheets.

[0005] Therefore, the time for the above-mentioned sheet registration is one of the major factors for determining the sheet interval. One of the methods proposed to shorten the registration time is an active registration method for correcting skew while conveying a sheet. In this method, two sensors are arranged on a coaxial line orthogonal to the sheet conveyance direction in the sheet conveyance path, and the inclination of the sheet front is detected based on a signal that the front end of the sheet crosses each sensor. The skew feeding correcting rollers (hereinafter referred to as “registration rollers”), which are arranged coaxially perpendicular to the sheet feeding direction and are independently driven, attempt to correct the skew feeding of the sheet. is there. According to this method, the skew correction can be performed while the sheet is conveyed without being temporarily stopped, so that the above-mentioned sheet interval can be reduced as compared with other methods.

[0006]

However, in the above-mentioned conventional example, when the apparatus is used in a durable manner, the rollers are slightly but slightly scraped off, the outer diameter becomes small, and a desired speed can be obtained. There is a problem that the desired speed cannot be obtained due to lack of the initial clamping force due to a decrease in the rubbing force on the roller surface due to paper powder, toner, or the like clogging in the gap between the roller surfaces.

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

[0008]

In order to achieve the above object, the present invention comprises a first skew amount detecting means for detecting a skew amount of a sheet and a registration means for correcting the skew amount of the sheet. Second skew amount detecting means for detecting the skew amount of the sheet corrected for skew by the registration means, and skew amount of the sheet detected by the first skew amount detecting means And a control unit for controlling the registration unit based on the skew amount of the sheet detected in the past by the second skew amount detection unit.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the sheet conveying apparatus according to the present invention will be specifically described with reference to the drawings. In this 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 mechanism for moving a pair of feed rollers, and FIG. FIG.

In FIG. 1, reference numeral 1 denotes a document table,
A plurality of originals G are set with their image surfaces facing up. 2
Reference numerals a and 2b denote sensors as sheet length detecting means for detecting the lengths L _s1 and L _s2 of the document G set on the document table 1 in the transport direction, respectively (L
_s1 < _Ls2 ). Reference numeral 3 denotes a pickup roller whose outer peripheral surface is covered with rubber or the like having a relatively high coefficient of friction, and which feeds out the original G set on the original mounting table 1. Reference numeral 4 denotes a separation feeding roller pair, and upper rollers 4A,
The document G sent out by the pickup roller 3 when the lower roller 4B rotates clockwise together.
Are separated and fed one by one.

Reference numerals 5 and 6 denote a first pair of conveying rollers as sheet conveying means and a second pair of conveying rollers capable of contacting / separating. Roller 6 of the second transport roller pair 6
a is configured to be brought into contact with / separated from the roller 6b by the contact / separation mechanism 7 shown in FIG. The contact / separation mechanism 7 in this embodiment is electrically turned on as shown in FIG.
The solenoid 7a is turned on / off, an arm 7b for connecting the solenoid 7a to the roller 6a, and a spring 7c for contacting the roller 6a with the roller 6b. In this embodiment, the solenoid 7a is ON.
In this state, the roller 6a is separated from the roller 6b. When the solenoid 7a is released, the solenoid 7a comes into contact with the roller 6b by the force of the spring 7c.

In FIG. 1, reference numeral 8 denotes registration means for correcting skew of the original G. As shown in FIG. 3, conveyance means which are independently driven to rotate on coaxial lines orthogonal to the original conveyance direction. It has two roller pairs 8a, 8b as means or rotating bodies. That is, the skew of the document is corrected by increasing or decreasing the rotation speed of one roller pair in accordance with the amount of skew of the document to make the transport speeds of the two transport units different. still,
In the present embodiment, the rotation speed of one roller pair (the leading side of the document) is reduced according to the amount of skew of the document to correct the skew of the document.

Reference numeral 9 denotes sheet skew amount detecting means for detecting the skew amount (tilt of the leading edge) of the document. As shown in FIG. 3, two sheet light-transmitting sensors 9a and 9b are provided. They are arranged on a coaxial line orthogonal to the document conveyance direction via a conveyance path. The rotation of the drive motors M ₁ and M ₂ of the pair of registration rollers 8 a and 8 b is controlled by control means (not shown) based on the skew amount of the document detected by the sensors 9 a and 9 b, thereby correcting the skew of the document. Is performed.

In FIG. 1, reference numeral 10 denotes an image reading device, which is an illumination lamp 10a for irradiating the image surface of the original G through a transmission glass disposed in a conveyance path, and reflecting the irradiation light. It is composed of mirrors 10b, 10c, 10d, a lens 10e for condensing 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 whose image has been read onto a discharge tray 13. A transport guide 14 for guiding the document G is provided between each pair of rollers.

Here, the relationship between the lengths shown in FIG. 1 will be described. In Figure 1, the transport length L _a1 from the registration unit 8 to the second conveying roller pair 6 has a L _a1 <L _s1 with respect to the conveying direction of the length L _s1 of the document G. In addition, the first conveying roller pair 5
The length L _a2 of the document G with respect to the length L _s2 of the document G in the direction of conveyance is L _a2 <L _s2 .

Further, the conveying length L _a1, conveying length L _b of the length obtained by adding from L _a2 the registration means 8 to the light transmission sensor 9, the length of the conveying direction of each of the original G L _s1, for the _{L s2 L a1 + L b>} L s1, L a2 + L b
> _Ls2 .

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

When the document G is set on the document table 1, the lengths L _s1 and L _{s2 of the} document G in the transport direction are detected by the sensors 2a and 2b. If the length of the detected document G is L _s1 , the length L _s1 is longer than the transport length _{La 1} from the registration means 8 to the second transport roller pair 6 (L _a1 <L _s1 ) and is shorter than (L _a1 + L _b + L _s1 ) which is shorter than the length L _a1 + L _{b obtained} by adding the transport length L _b from the registration means 8 to the light transmission type sensor 9. The second transport roller pair 6 is contacted by the contact / separation mechanism 7. When the length of the detected document G is L _s2 , the length L _s2 is the transport length _{La a1} from the registration means 8 to the second transport roller pair 6.
(L _a1 <L _s2 ) and longer than the length L _a1 + L _b (L _a1 + L _b <L _s2 ), which is the _sum of the transport length L _b from the registration means 8 to the light transmission type sensor 9. For,
The second transport 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 rotates to feed the uppermost document on the document table 1 toward the separation / feed roller pair 4. The separation feeding roller pair 4 is configured to feed the original 1
If the original is fed, the original is fed toward the first transport roller pair 5 as it is, but if two or more originals are fed at once, the lower roller rotates in the direction opposite to the transport direction and Only the uppermost document is fed to the first transport roller pair 5. Since the separation mechanism does not relate to the essence of the present invention, a detailed description thereof will be omitted.

When the fed document is a document of length L _s1 , since the roller pair 6 is in a contact state, the registration roller pair 8 a, In the case of an original having a length L _{s2, since} the roller pair 6 is in a separated state, the original is sent to the registration roller pair 8 a, 8 b by the roller pair 5 along the transport guide 14.

The pair of registration rollers 8a and 8b rotate at the same speed as the document transport speed of the pair of transport rollers 5 and 6. As shown in FIG. 3, the document sandwiched between the pair of registration rollers 8a and 8b is a transparent glass 1 serving as an image reading unit.
1, and passes through the light transmitting sensors 9a and 9b on the way. The sensors 9a and 9b respectively emit signals at the moment when the document passes, and the inclination of the leading edge of the document is calculated by an arithmetic circuit (not shown) based on those signals. On the basis of the calculated inclination, the rotation of the drive motors M ₁ and M ₂ of the registration roller pairs 8 a and 8 b is controlled by a control unit (not shown) to correct the skew of the original G. At this time, the rear end of the original G is largely rotated and moved.
In a state where the rear end is held between the conveying roller pairs 5 and 6, the movement is restricted.

As described above, the leading edge of the original is
a and 9b, the trailing edge of the document having the length L _s1 always passes through the pair of transport rollers 5 and 6, and 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 separated in advance, it is not possible to restrict the movement of the trailing edge of the document during the skew correction by the registration roller pairs 8a and 8b. Absent. Therefore, regardless of the length of the original,
The skew correction is performed with high accuracy.

The skew correction control will be described with reference to the block diagram shown in FIG. 4 and the flowchart shown in FIG.

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

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

Next, when both sensors become high level, an interrupt signal is sent from the counter circuit 21 to the microcomputer 22.
(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 skew has occurred at this time (step S).
2).

Here, since the original has passed the sensor 9a first, the microcomputer 22
Thus, the skew amount is corrected by controlling the speed of the motor of M1 that drives the roller 8a closer to the preceding corner 9a of the front corners Pa and Pb of the sheet P (step S3).

This will be described with reference to (control time-drive frequency) in FIG. The drive frequency is a clock output to the motor driver of M1. Normally, the motor is driven at 5000 Hz when the skew feed correction control is not performed. When the deceleration control of step S3 starts, the step motor of M1 is gradually decelerated. M in 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 correction amount (when the correction of half the detected skew amount is completed), the acceleration control is started again (step S5). ) (Turning point 1 in FIG. 7).

At the same time as the deceleration control, the difference between the clock outputs outputted to M1 and M2 is counted by a counter circuit (not shown) in the microcomputer, and the counted amount is equal to the skew correction amount. When it becomes equal to, the skew feeding correction ends (step S6) (control end 1 in FIG. 7).

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

If the skew amount is large, the deceleration control time becomes longer (return point 2) and the acceleration control time becomes longer (control end 2).

Further, by detecting the document size in advance (or by inputting the size by the operator), the contact or separation of the pair of transport rollers 6 can be selected. It is not necessary to precisely control the timing of the contact / separation mechanism 7 that performs the above. Further, when the document is continuously fed, since the contact / separation operation of the roller pair 6 is not performed every time, it is not necessary to strictly demand the durability of the contact / separation mechanism. Further, a shock accompanying the contact / separation operation of the roller pair 6 is transmitted,
There is no risk of adversely affecting document reading.

(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 amount of skew, an additional one is provided before the image reading unit.
Two sets (15a and 15b) of the five light-transmitting sensors are disposed on a coaxial line orthogonal to the document conveyance direction via a conveyance path.

If the skew correction described above is completed before the 15 sensors, the result of the skew correction can be known by the sensor 15, and the skew amount is measured again by the image reading unit. No need to do.

Usually, the skew amount measurement in the image reading unit requires the provision of a counter in the main running direction (reading line direction). However, if the light transmission type sensor 15 is newly provided, the necessity is eliminated. . By using the light transmission type sensors 9 and 15, the skew amount correction can be performed with high accuracy and durability.

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

However, the registration roller pair 8
In a and 8b, the desired conveyance speed is reduced, since the outer diameter and the surface lashing force cannot be avoided in a durable manner. For this reason, the skew amount that could be completely corrected initially 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. If a certain number of sheets, for example, hundreds of thousands, are corrected, and the skew amount after correction performed for the last 10,000 sheets is not 0 mm, but is skewed to either side, for example, the registration roller 8a side Is 0.1mm after correction
In the case of preceding, in the case of performing correction in the future, the 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 more.

FIG. 9 is a flowchart of this control, as described above.

The read value of the counter data (step S
The average value of the corrected skew amount of the recent 10,000 sheets is added to 2) (step S7), and deceleration control is performed (step S5).

As described above, by performing feedback correction of the correction amount based on the latest correction result, more accurate control can be performed in a durable manner. Even if the diameter of the registration roller 8 is slightly reduced and the diameter is sharply reduced due to other abnormalities, the 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 is described in which the sheet conveying apparatus according to the present invention is applied to a document image reading apparatus. However, the present invention is not limited to this, and is applicable to, for example, an image forming apparatus. Of course. As an image forming apparatus, for example, in FIG. 1, a recording medium such as copy paper is placed instead of the original G, and
In this configuration, a recording system (including a recording head, a head driving circuit, and the like) 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 image information of a read original on a copy sheet may be configured by combining the original image reading apparatus having the features of the present invention with the image forming apparatus main body.

In the above embodiment, when the sensor 9a outputs a high level signal before the sensor 9b, the motor M1 is decelerated to correct the amount of skew, but the motor M1 is temporarily stopped. By doing so, the skew can be corrected. Conversely, the skew may be corrected by controlling the speed of the motor M2. Further, the deceleration control of the motor M1 and the motor M2
May be simultaneously performed.

The deceleration control or speed increasing control of the pulse motor in the above embodiments had varying the speed at a constant rate but not limited to, the faster V _H from the normal velocity V _O,
Alternatively, it may be switched stepwise to a low-speed _VL .

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

The above-described sheet conveying apparatus can be applied not only to a document reading apparatus but also to an image forming apparatus. In particular, an 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 which performs skew correction while conveying a sheet, the skew correction result is measured after the skew correction is completed by the registration means, and the result is accumulated and fed back. Thus, the correction accuracy can be maintained and improved in a durable manner.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating 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 mechanism for moving a pair of conveyance rollers in the apparatus.

FIG. 3 is a top view illustrating a skew feeding correction unit of the document in the apparatus.

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

FIG. 5 is a control flowchart of the device.

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 cross-sectional view illustrating 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 device.

[Explanation of symbols]

G Documents M ₁ , M ₂ Motor 1 Document Placement Table 2a, 2b Sensor 3 Pickup Roller 4 Separation Feeding Roller Pair 5, 6 Transport 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 lamp 10b, 10c, 10d mirror 10e lens 10f image reading element 11 transmission glass 12 discharge roller Pair 13 Eject tray 14 Transport guide 15 Sensor

Claims (24)

(57) [Claims] A first skew amount detecting means for detecting a skew amount of the sheet; a registration means for correcting the skew of the sheet; and a skew correction of the skew of the sheet corrected by the registration means. A second skew amount detecting means for detecting a line amount, a skew amount of the sheet detected by the first skew amount detecting means, and a sheet detected in the past by the second skew amount detecting means. And a control unit for controlling the registration unit based on the skew amount of the sheet. 2. The control means adds the skew amount of the sheet detected by the first skew amount detecting means and the skew amount of the sheet detected in the past by the second skew amount detecting means. 2. The sheet conveying apparatus according to claim 1, wherein the registration unit is controlled based on the skew amount. 3. The skew amount of a sheet detected by the first skew amount detecting means and the skew amount of a sheet detected in the past by the second skew amount detecting means. 2. The sheet conveying device according to claim 1, wherein the registration unit is controlled based on the skew amount obtained by adding the value. 4. The sheet conveying apparatus according to claim 3, further comprising a memory capable of storing a plurality of skew amounts of the sheet detected by said second skew amount detecting means. 5. A skew correction is performed again on a sheet whose skew has been corrected by the registration means, based on the skew amount of the sheet detected by the second skew amount detection means. 2. A sheet conveying apparatus according to claim 1, wherein said registration means is controlled in advance. 6. The sheet conveying device according to claim 1, wherein the second skew amount detecting unit is an image reading unit. 7. An image forming apparatus comprising: an image forming unit configured to form an image on a sheet conveyed by the sheet conveying apparatus according to claim 1. 8. An image reading apparatus having an image reading means for reading an image of a sheet conveyed by the sheet conveying apparatus according to claim 1. 9. An image forming apparatus comprising the image reading device according to claim 8. 10. A plurality of conveying means for simultaneously applying a conveying force to a sheet to correct skew of the sheet, a first skew detecting means for detecting skew of the sheet, and a plurality of conveying means. Second skew detecting means for detecting skew of the sheet subjected to skew correction, skew amount of the sheet detected by the first skew amount detecting means, and the second skew amount Based on the skew amount of the sheet detected in the past by the detection means, in order to correct the skew, the conveyance speed of at least one of the plurality of conveyance means such that the conveyance speeds of the plurality of conveyance means are different from each other. And a control unit for controlling the sheet feeding device. 11. The sheet conveying apparatus according to claim 10, wherein said plurality of conveying units include first and second conveying units arranged side by side in a direction intersecting a sheet conveying direction. 12. The control device according to claim 1, wherein, of the two corners at the leading end of the sheet, the conveying speed of the conveying unit closer to the preceding one is controlled to be slower than the other conveying units to correct the skew. The sheet conveying device according to claim 11, wherein: 13. The skew correction device according to claim 12, wherein the control unit reduces the conveying speed of the conveying unit closer to the preceding one of the two corners at the leading end of the sheet to correct the skew.
The sheet conveying device as described in the above. 14. The skew correction according to claim 1, wherein the control unit increases the conveying speed of the conveying unit on the side closer to the delayed one of the two corners at the leading end of the sheet to correct the skew.
3. The sheet conveying device according to 3. 15. The control device according to claim 1, wherein, of the two corners at the leading end of the sheet, the conveying speed of the conveying unit closer to the preceding one is reduced, and the conveying speed of the conveying unit closer to the delayed one is increased. 2. The method according to claim 1, wherein the skew is corrected at a high speed.
3. The sheet conveying device according to 2. 16. The apparatus according to claim 10, wherein each of the plurality of conveying units includes a rotating body that contacts a sheet, and a pulse motor that drives the rotating body. Sheet conveying device. 17. The apparatus according to claim 17, wherein the first or second skew detecting means has a plurality of sheet sensors for detecting the presence or absence of a sheet arranged in a direction intersecting with the sheet conveying direction. The sheet conveying apparatus according to claim 10, wherein 18. The sheet conveying apparatus according to claim 17, wherein said control means calculates a skew amount of the sheet based on a time difference between sheet detections of said 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 amount of the sheet. 20. The control means controls the speed of at least one of the plurality of transport means so that the difference in transport speed between the plurality of transport means increases as the calculated skew amount of the sheet increases. The sheet conveying device according to claim 19, wherein: 21. The control unit may control at least one of the plurality of transport units so that the transport speed of the plurality of transport units is relatively different for a longer period as the calculated skew amount of the sheet is larger. 20. The sheet conveying device according to claim 19, wherein the speed is controlled. 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 device according to claim 23.