JP4358086B2 - Paper transport device and image forming apparatus using the same - Google Patents

Description

  The present invention relates to a sheet conveying apparatus and an image forming apparatus using the same, and more particularly, to a sheet conveying apparatus capable of reducing variation between sheets in a sheet feeding operation and reducing the sheet interval, and an image forming apparatus using the same. .

FIG. 19 shows a cross section of a conventional paper transport device (using the FRR separation method). The sheet conveying device functions as a sheet feeding / conveying unit of an image forming apparatus such as a copier or a printer. In the figure, the leading edge of the paper 2a stacked on the paper stacking unit 1a is at the position A. The pickup roller 3 descends and rotates with a paper feed signal that tells the paper transport device to start feeding paper as a trigger, and sends the uppermost paper to the separating section B. The feed roller 4 and the reverse roller 5 are driven simultaneously with the driving of the pickup roller to separate the paper into one sheet.
In this embodiment, the pickup roller 3, the feed roller 4, and the reverse roller 5 are driven by one motor. When the leading edge of the sheet 2a separated into one sheet reaches the sheet sensor a (C), the pickup roller 3 rises and the drive is cut off, so that the sheet is not conveyed by the pickup roller 3. Thereafter, the sheet is conveyed by the conveying force of the feed roller 4 and reaches the first conveying roller pair 1 (E). The drive of the feed roller 4 is cut off after a predetermined time t1 after the start of the drive of the feed roller 4, but the leading edge of the sheet at this time is set to be after the leading edge of the sheet reaches the first conveying roller pair 1 (E). Yes.
After the drive of the feed roller 4 is cut off, the paper is fed by the first transport roller pair 1 (E). Thereafter, the leading edge of the paper passes through the paper sensor b (G), the second transport roller pair 2 (E ′), and the paper sensor F. Image writing to the photosensitive member is triggered by the fact that the leading edge of the sheet has passed the sheet sensor F (= sensor F has detected the leading edge of the sheet) (such as starting image writing 20 msec after the sensor F is turned on). It is by the control.)
The first transport roller pair 1 (E) and the second transport roller pair 2 (E ′) are driven by separate motors (not shown). After time t2 has elapsed since the leading edge of the sheet reached the sheet sensor C (I) (at this time, t2 is set so that the leading edge of the sheet reaches the registration roller (J), and at this time, the registration roller is stopped. By setting the time t2, the leading edge of the sheet forms a slack in front of the registration roller and performs skew correction (in this example, t2 = 37.5 msec), the conveyance roller motor is turned off, and the first conveyance roller pair 1 (E), 2 (E ′) is driven off.
Thereafter, simultaneously with the driving of the registration roller J, the conveyance roller motor is turned on, the first conveyance roller pair 1 (E) and the second conveyance roller pair 2 (E ′) begin to rotate, and the sheet is in contact with the photosensitive member 6. The image is transferred to a transfer portion comprising the transfer roller 7. The registration roller ON timing is set to be ON after time t3 after the paper sensor F is turned ON. As a result, the image written on the photosensitive member 6 is aligned with the paper position.

Conventionally, in an image forming apparatus such as a copy or printer, when continuously transporting paper, an interval is provided when the next paper is fed after feeding one sheet (hereinafter, this spacing is referred to as a paper gap). Most are paper and transported. Due to reasons such as detecting the leading edge of the sheet with a sensor and triggering image writing, stopping the leading edge of the sheet at the registration roller section to perform skew correction, aligning with the image, etc. It is necessary, and it is easy to leave the paper when the paper is sent out by the paper feed unit to feed the paper. It has become a method.
However, there is a problem due to a gap between sheets in the sheet feeding unit. That is, in recent years, there has been an increasing need to shorten the sheet gap as much as possible for reasons such as productivity improvement in image forming apparatuses such as copying and printers. And it is well-known that an attempt is made to improve productivity by shortening the interval between sheets of conveyed paper (see Patent Document 1 and Patent Document 2).
This is because if the same linear speed (paper feed speed) is used, the shorter the distance between papers, the faster the copying and printing speeds. Therefore, lower costs have been sought in the past (if the same printing speed is aimed, the number of rotations of the rollers). Because it is not necessary to increase the motor speed, it is possible to use motors and other parts that are one rank lower in price.) Noise reduction (If the same print speed is aimed, the motor noise can be reduced because there is no need to increase the rotation speed of the roller) The purpose is to improve the durability (durability can be improved because it is not necessary to rotate the motor extra between papers).
Japanese Patent Laid-Open No. 05-085644 JP 2003-176045 A

Conventionally, however, the following problem has been encountered in the method in which the paper feed unit provides a gap between papers.
1. Inter-paper variation due to variations in paper slip at the time of paper feeding The paper is transported while causing slippage due to the relationship between the transport force of the roller that transports the paper and the load when transporting the paper. At this time, if the conveying force is sufficiently large with respect to the load, the slip is small and is fed at a stable linear speed. However, in general, in the sheet conveyance by the sheet feeding roller, the load on the separation unit is often relatively large with respect to the conveyance force of the sheet feeding roller, and the load varies depending on the separation state, the type of sheet, and the like. . In addition, the conveying force tends to vary due to the influence of the deterioration of the rubber over time, the reduction of the friction coefficient due to the adhesion of paper dust, dirt and the like. For this reason, the slip is larger than that of other conveying rollers, and the variation is likely to increase.
As a result, the line speed of the sheet is likely to vary from the start of paper feeding until the leading edge of the sheet is sent to the first conveying roller pair 1, resulting in a large variation between the sheets (the leading edge of the sheet is the first conveying roller). Since the conveying force of the conveying roller is applied after the pair 1 is bitten, the conveying force of the sheet becomes sufficiently large with respect to the load, and the variation in the linear velocity due to the slip is reduced. In order to ensure the required paper gap when the paper gap varies, the median value between the papers is set to a large value so that the required paper gap can be secured even if the paper gap varies. There was a need to do. For this reason, in order to reduce the gap between the sheets, it is necessary to reduce the variation between the sheets.
2. Variation in distance between sheets due to variation in paper standby position The leading edge of the paper to be fed waits from the paper standby position ((A) in FIG. 19) to the separation unit ((B) in FIG. 19). ing. When the paper is continuously fed by the conventional paper feeding unit with a gap between the papers, the variation in the front end position of the paper becomes the variation in the distance between the papers. For this reason, in the same way as in 1 above, when the variation between the papers becomes large, in order to secure the necessary paper space in the state where the paper space varies, the median value between the papers is set to be large, and it is necessary even if the paper space varies. It was necessary to be able to secure a gap between papers.
That is, with the conventional configuration, it is difficult to reduce the gap between the sheets.
Accordingly, the present invention has been made in consideration of the above-described circumstances, and provides a paper transport device that can reduce paper-to-paper variations in a paper feeding operation and can reduce the paper-to-paper space, and an image forming apparatus using the same. The purpose is to do.

In order to solve the above-described problem, the invention according to claim 1 includes: a paper feed roller for feeding paper from a paper stacking unit; a separation unit for separating paper into one sheet; and the paper feed roller. A first conveying roller pair that is provided in a downstream conveying path and conveys a sheet, a second conveying roller pair that is disposed in a conveying path downstream of the first conveying roller pair and conveys a sheet, and the first conveying roller A sheet sensor positioned between the pair and the second transport roller pair, and in the case of continuous sheet feeding, the sheet is continuously fed without feeding the sheet when the sheet is fed from the sheet stacking unit. Then, at the timing after the trailing edge of the preceding sheet passes through the first conveying roller pair, the first conveying roller pair is not turned off and the first sheet is continuously conveyed without being turned off. By stopping the conveyance roller pair and stopping the conveyance of the following paper It is detected that the trailing edge of the preceding sheet has been removed from the position of the sheet sensor by the sheet sensor after transporting after a distance between the first transport roller pair and the second transport roller pair. As a trigger, the drive of the first conveying roller pair is started after a predetermined time T1 (≧ 0) after the trailing edge of the preceding paper sheet has passed, and the trailing sheet is conveyed, and the trailing edge of the preceding paper sheet passes through the sheet sensor. The paper interval time t1 until the leading edge of the line paper reaches the paper sensor is measured, and the trailing paper after the leading edge of the succeeding paper reaches the first conveying roller pair according to the measured value of the paper interval time t1. The main feature is a paper transport device that determines transport timing such as a time for transporting the paper at a speed of the paper linear speed V2 or a time for stopping the succeeding paper.
In the second aspect of the present invention, it is detected that the leading edge of the succeeding sheet has reached the position of the sheet sensor, and the conveying speed and timing of the trailing sheet after the sheet interval time t1 is measured is the sheet interval. When time t1 ≧ set time Ta (where Ta = a constant value), after the leading edge of the succeeding paper reaches the paper sensor position, the normal speed is increased by increasing the rotation speed of the first conveying roller pair during time Tb. After the succeeding sheet is conveyed at a faster sheet linear velocity V2, and the leading edge of the succeeding sheet reaches the sheet sensor position, the rotation speed of the first conveying roller pair is returned to the normal rotation speed after the time Tb has elapsed. A main feature is a paper conveyance device set to convey the following paper at a normal paper linear velocity V1.

According to a third aspect of the present invention, it is detected that the leading edge of the succeeding sheet has reached the position of the sheet sensor, and the conveying speed and timing of the succeeding sheet after the sheet interval time t1 is measured is the sheet interval. When time t1 <set time Ta (where Ta = constant value), after the leading edge of the succeeding sheet reaches the position of the sheet sensor, the rotation of the first conveying roller pair is stopped for a period of time Tc. After the conveyance of the paper is stopped and the leading edge of the succeeding paper reaches the position of the paper sensor, after the time Tc elapses, the rotation speed of the first conveyance roller pair is returned to the normal rotation speed, so that the normal sheet linear velocity is reached. The main feature is a paper transporting device set to transport subsequent paper at V1.
According to a fourth aspect of the present invention, it is detected that the leading edge of the succeeding sheet has reached the position of the sheet sensor, and the conveying speed and timing of the succeeding sheet after the sheet interval time t1 is measured is the sheet interval. When time t1 <set time Ta (where Ta = constant value), after the leading edge of the succeeding sheet reaches the position of the sheet sensor, the rotation of the first conveying roller pair is stopped for a period of time Tc. After the paper conveyance is stopped and the leading edge of the succeeding paper has reached the position of the paper sensor, after the time Tc has elapsed, the rotation speed of the first conveyance roller pair is increased until the time Td has elapsed. The succeeding paper is conveyed at a paper linear speed V2 that is faster than the speed, and after the time Td, the following paper is conveyed at the normal paper linear speed V1 by returning the rotation speed of the first conveying roller pair to the normal rotation speed. A main feature is a sheet conveying apparatus set to convey.
In the invention according to claim 5, the time Tb is Tb = (t1−Ta) × V1 / (V2−V1) where Ta = L / V1, L = target inter-paper distance after correction, V1 = Normal paper linear velocity, V2 = paper linear velocity during acceleration, time Tc is a calculated value obtained from the relationship of Tc = Ta-t1, or a data table is obtained in advance so as to obtain the same effect as when the calculated value is used. The main feature is a sheet conveying device which is a value obtained by referring to data set in the inside.

In the invention described in claim 6, the time Tb is Tb = (t1−Ta) × V1 / (V2−V1) + Td, where Ta = {L + Td × (V2−V1)} / V1, L = after correction V1 = normal paper linear velocity, V2 = paper linear velocity at the time of acceleration, Td = a fixed time, and a calculated value obtained from the relationship of Tc = Ta−t1 or the calculated value is used. In order to obtain the same effect as in the case of the paper transporting apparatus, the main feature is a sheet transporting apparatus having values obtained by referring to data set in the data table in advance.
According to a seventh aspect of the present invention, the position of the sheet sensor is larger than the distance from the position of the first conveying roller pair to the position of the separating means from the leading end position of the sheets stacked on the sheet stacking unit. A main feature is a sheet conveying apparatus provided on the downstream side of a separated conveying path.
In the invention according to claim 8, a certain time T1 (≧ 0) after the trailing edge of the preceding paper sheet is triggered by the fact that the trailing edge of the preceding sheet has been detected by the sheet sensor as being detected by the sheet sensor. ) When the first conveying roller pair starts to be driven later, the sheet linear velocity of the succeeding sheet sent by the first conveying roller pair is determined from the start of driving the first conveying roller pair to the sheet sensor. The rotation speed of the first conveying roller pair is controlled so that the following paper sheet linear velocity is fed at a speed increasing linear velocity V2 that is higher than the normal linear velocity V1 in a part or all of the interval until reaching The main feature is a paper transport device.
In the invention according to claim 9, an image forming unit for forming an image on a sheet;
An image forming apparatus including the sheet conveying device according to claim 1 that conveys a sheet to the image forming unit is a main feature.
According to a tenth aspect of the present invention, the image forming unit mainly includes an image forming apparatus that transfers a toner image formed by an electrophotographic method onto a sheet to form an image on the sheet.

According to the present invention, the position where the space between the papers is sufficiently large in relation to the transport load (separation load, transport stiffness due to the stiffness of the paper, sliding with the guide plate, etc.) Therefore, it is possible to suppress the variation between papers as compared to the conventional paper feeding unit where the paper linear speed is unstable. In addition, the paper interval is measured by the paper sensor, the acceleration time and timing of the succeeding paper are determined based on the measured values, and correction between the papers is performed, so that it is possible to reduce the variation between the corrected papers. . As a result, it is possible to reduce the set value between sheets that has been set in consideration of the variation between sheets.
Further, when the measured paper interval time is large, the subsequent paper linear velocity is increased (V2) by transporting the paper interval by Tb for a certain time Tb, and then the normal paper linear velocity V1 is restored. It becomes possible to reduce the variation of the.
Further, when the measured paper interval time is small, the following paper is stopped for a certain time Tc to clear the paper interval, and then the conveyance is resumed at the normal paper linear velocity V1 to reduce the variation between the papers. Is possible.
Further, when the measured paper interval time is small, the succeeding paper is stopped for a certain time Tc to clear the paper interval, and thereafter the conveyance is resumed at a constant time Td speed increase V2, and then returned to the normal paper linear speed V1. This makes it possible to reduce the variation between the papers.
Also, the times Tb and Tc are Tb = (t1−Ta) × V1 / (V2−V1) where Ta = L / V1, L = target inter-paper distance after correction, V1 = normal sheet linear velocity, V2 By setting = paper linear velocity during acceleration and Tc = Ta-t1, the corrected inter-paper distance≈the target inter-paper distance L can be achieved, and the variation between the papers can be effectively reduced. It becomes possible.
Further, the times Tb and Tc are set to Tb = (t1−Ta) × V1 / (V2−V1) + Td, where Ta = {L + Td × (V2−V1)} / V1, L = target inter-paper distance after correction, By setting V1 = normal sheet linear velocity, V2 = accelerated sheet linear velocity, Td = predetermined time, and Tc = Ta−t1, the corrected inter-paper distance≈target inter-paper distance L can be set. It is possible to effectively reduce the variation between the papers.

Even if there is variation in the standby position of the paper, the leading edge of the succeeding paper when the trailing paper is stopped even if the paper is partially overlapped when the paper is continuously fed without gaps due to the variation in the standby position. Since the paper sensor does not reach the paper sensor, the paper sensor can detect the sensor removal timing of the preceding paper and measure the paper interval time t1 even when the paper is overlapped, thereby correcting the paper interval. As a result, it is possible to suppress the variation between the papers, and thereby it is possible to reduce the set value between the papers set in consideration of the variation between the papers.
Further, by increasing the sheet linear speed of the succeeding sheet before the sheet interval time measurement by the sheet sensor, it is possible to further reduce the sheet interval at the time of measurement. As a result, the measurement paper interval time t1 and the variation thereof can be made smaller in advance, so that it is possible to cope with a larger variation in the paper interval in combination with the effect of the correction of the inter paper interval by the subsequent paper linear speed and the conveyance timing.
In addition, by providing the image forming apparatus with a paper conveyance device that performs this paper gap correction, it is possible to keep the paper gap small, thereby improving productivity due to small paper gaps, low cost, increased durability, calming, etc. The effect of can be obtained.
In addition, since the electrophotographic image forming apparatus is provided with a paper conveyance device for correcting the paper gap, it is possible to keep the paper gap small, thereby improving productivity due to small paper gaps, low cost, and improving durability. Effects such as calming can be obtained.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best mode (an image forming apparatus using a sheet conveying apparatus) for carrying out a sheet conveying apparatus and an image forming apparatus using the same according to the present invention will be described in detail with reference to the drawings. In this example, the image forming apparatus has functions such as a copy function, a fax function, a printer function, and a scanner function. Moreover, the same part as FIG. 19 used by description of a prior art is demonstrated using the same figure.
In FIG. 19, a paper sensor b (G) is a sensor that detects the presence or absence of paper. In the prior art, the behavior of paper between the first transport roller pair 1 and the second transport roller pair 2 (the front end of the paper is the paper sensor b). For example, the timing at which the trailing edge passes through the paper sensor b). If these timings are values that are significantly larger than the specified value, for example, if the paper sensor b remains on all the time, it is determined that the paper is stopped (JAM) at the sensor portion, It is used for the purpose of displaying abnormalities on the panel, or if the sensor does not turn on even after the specified time has passed, it is judged that the paper is not fed and the abnormalities are displayed on the panel as well. ing. In addition to this function, in the best mode for carrying out the present invention, the sheet is fed without a gap and used to leave a certain gap between the fed sheets.
The position of the paper sensor b (G) is provided at a distance of LE-G (hereinafter, L is used as a symbol indicating distance) from the first transport roller pair 1 (E), and the front end of the paper is the first transport roller. The sensor is turned on when the distance LE-G is reached from the roller pair 1, and the sensor is turned off when the trailing edge of the paper reaches the distance LE-G from the first conveying roller pair 1. At this time, the distance LE-G has a relationship of LE-G> LA-B with respect to the distance LA-B from the paper leading edge standby position (A) to the separating portion (B) when setting the paper.
In the case of the FRR separation type paper feed mechanism shown in this example, the standby position of the paper leading edge varies between the paper leading edge standby position (A) and the separating portion (B) when the paper is set. Due to the variation in the standby position, when the paper feeding unit continuously feeds paper without leaving a gap between the papers, the rear part of the preceding paper and the front part of the succeeding paper are fed with a maximum distance LA-B. There is a case. In the best mode for carrying out the present invention, the position of the sheet sensor b is provided in a relationship of LE-G> LA-B, which is the overlap between the rear part of the preceding paper and the front part of the succeeding paper. When the amount is D and the maximum value is Dmax, the sheet sensor b is intended to be provided at a location downstream from the distance Dmax (= LA−B) from the first conveying roller pair 1.
If the paper feed is continuous paper feed at the start of paper feed (determined by an instruction from the printer controller, an instruction from the number of copies of the PPC, etc.), the paper feed unit does not leave a gap between the papers. Start continuous feeding.

The first embodiment will be described with reference to the flowchart of FIG. 1 and FIGS. 2 to 16 and 19. In the first embodiment, the following three cases will be described.
1: Example in which the trailing edge of the preceding paper and the leading edge of the succeeding paper are overlapped and fed by continuous feeding (FIGS. 1, 19, and 2 to 6)
2: An example in which the leading edge of the preceding sheet and the leading edge of the succeeding sheet are fed with zero gap between continuous sheets (FIGS. 1, 19, and 7 to 11).
3: An example in which the leading edge of the preceding sheet and the leading edge of the succeeding sheet are conveyed with a slight gap between them in continuous feeding (FIGS. 1, 19, and 12 to 16).
1: An example in which the trailing edge of the preceding paper and the leading edge of the succeeding paper are overlapped and fed in continuous feeding FIGS. 2 to 6 show the paper when continuous feeding is performed without leaving a gap in the paper feeding unit. FIG. 10 is a schematic cross-sectional view when sheets are fed in overlapping due to variations in the standby position. In the figure, the numerical values written beside the rollers, sensors, etc. are the distance (mm) from the paper stacking position in this example. First, as shown in FIG. 2, the paper continuously fed by the paper feeding unit is fed with the trailing edge of the preceding paper P1 and the leading edge of the trailing paper P2 overlapped, and the trailing edge of the leading paper is the first conveying roller pair 1. When the first conveying roller pair 1 stops at a timing after passing through (the timing when 10 mm is fed from the first conveying roller pair 1 in this example), the conveyance of the succeeding paper is stopped (steps S1 to S1 in FIG. 1). Step S5).
The maximum value Dmax of the overlap amount at this time is the distance LA-B (24.5 mm in this example) from the paper leading edge standby position (A) to the separating portion (B) when setting paper, and the position of the paper sensor b. Is the distance LE-G from the conveying roller 1 and is larger than the maximum overlap amount Dmax = LA-B, so that the leading edge of the succeeding sheet stops at a position where it does not reach the sheet sensor b.

Next, as shown in FIG. 3, when it is detected that the trailing edge of the preceding paper P1 has passed through the paper sensor b, the conveyance of the succeeding paper P2 is resumed. The sheet linear velocity at this time is the increased linear velocity V2 = 500 mm / s. At the same time, measurement of the sheet interval time t1 is started by a timer (not shown) in response to the detection signal of the sheet sensor b (steps S6 to S8 in FIG. 1).
Next, as shown in FIG. 4, when the leading edge of the succeeding paper reaches the paper sensor b, the measurement of the paper interval time t1 is completed (step S9 to step S10 in FIG. 1), and the measured value of t1 and thereafter are thereafter. The subsequent paper conveyance speed and timing are determined by the control unit (see FIG. 5). In this example, Ta = L / V1 = 15 mm / (362 mm / s) = 41.4 ms, Tb = V1 / (V2−V1) × (t1−Ta), Tc = Ta−t1, corrected paper The distance target value = 15 mm.
In this example, the conveyance speed and timing of the succeeding paper are determined by calculating from the paper interval time t1 in the control unit (in FIG. 5, since t1 = 11 ms and Ta = 41.4 ms, t1 <Ta, so from here There is also a method in which the succeeding paper is stopped for the time Tc (Tc = Ta−t1 = 41.4−11 = 30.4 ms) is determined by referring to the data table stored in the control unit.
In this example, the measured inter-paper time t1 = 11 ms, which is smaller than the set value Ta = 41.4 ms, and t1 <Ta. For this reason, for the succeeding paper, the driving of the first transport roller pair 1 is stopped at the timing when the leading edge of the succeeding paper reaches the paper sensor b, and after the time Tc elapses after the transport of the succeeding paper is stopped, The conveyance is resumed at the speed V1 (see FIG. 6). When the number of fed sheets reaches the set value, the operation is terminated (Step S11, Step S15 to Step S17 in FIG. 1).
The stop time Tc is a value obtained by a calculation formula of Tc = Ta−t1, where Ta = L / V1, and L = target inter-paper distance after correction.
The distance between the sheets when the conveyance of the succeeding sheet is resumed at the normal sheet linear velocity V1 after the stop time Tc has elapsed is:
Corrected inter-paper distance = (t1 + Tc) × V1 = {t1 + (Ta−T1)} × V1 = Ta × V1, From the above formula Ta = L / V1, the inter-paper time after correction = L / V1 × V1 = L , The target inter-paper distance L is corrected. In this example, the corrected inter-paper distance = L by setting the stop time Tc.

2: An example in which the leading edge of the preceding sheet and the leading edge of the succeeding sheet are fed with zero gap in continuous feeding FIGS. 7 to 11 show the case where continuous feeding is performed without leaving a gap in the feeding section. FIG. 6 is a schematic cross-sectional view when sheets are fed overlapping due to variations in the sheet standby position. First, as shown in FIG. 7, the paper continuously fed by the paper feeding unit is fed with the leading paper and the trailing paper at a sheet interval of 0, and the trailing edge of the leading paper P1 is the nip of the first conveying roller pair 1. At the timing after exiting the section (in this example, the timing when 10 mm is fed from the first transport roller pair 1), the transport of the succeeding paper P2 is stopped by stopping the first transport roller pair 1 (FIG. 1). Steps S1 to S5).
Next, as shown in FIG. 8, when it is detected that the trailing edge of the preceding sheet has passed through the sheet sensor b, the conveyance of the trailing sheet P2 is resumed. The sheet linear velocity at this time is the increased linear velocity V2 = 500 mm / s. At the same time, the paper sensor b starts measuring the paper interval time t1 (steps S6 to S8 in FIG. 1).
Next, as shown in FIG. 9, when the leading edge of the succeeding paper reaches the paper sensor b, the measurement of the paper interval time t1 is completed (step S9 to step S10 in FIG. 1), and from the measured value of t1 onward. The subsequent paper transport speed and timing are determined by the control unit (see FIG. 10). In this example, Ta = L / V1 = 15 mm / (362 mm / s) = 41.4 ms, Tb = V1 / (V2−V1) × (t1−Ta), Tc = Ta−t1, corrected paper The distance target value = 15 mm.

In this example, the conveyance speed and timing of the succeeding paper are determined by calculating from the paper interval time t1 in the control unit (in FIG. 10, since t1 = 60 ms and Ta = 41.4 ms, t1 ≧ Ta. The subsequent sheet is accelerated at the time Tb from the time Tb = V1 / (V2−V1) × (t1−Ta) = 362 / (500−362) × (0.060−0.0414) = 48. .8 ms) can be determined by referring to a data table stored in the control unit.
In this example, the measured paper interval time t1 = 60 ms, which is larger than the set value Ta = 41.4 ms, and t1 ≧ Ta. For this reason, the succeeding paper is transported at a speed increasing linear velocity V2 higher than the normal paper linear velocity V1 in a section from the time when the leading edge of the succeeding paper reaches the paper sensor b until the time Tb elapses. Then, the number of rotations of the first conveying roller pair 1 is controlled, and the sheet is conveyed at the normal sheet linear velocity V1 after the elapse of time Tb (see FIG. 11). When the number of fed sheets reaches the set value, the operation is terminated (Step S11, Step S12 to Step S17 in FIG. 1).
The acceleration time Tb is Tb = (t1-Ta) × V1 / (V2-V1), where Ta = L / V1, L = target inter-paper distance after correction, V1 = normal sheet linear velocity, V2 = The value obtained from the calculation formula of the paper linear velocity during acceleration. The distance between the sheets when the conveyance of the succeeding sheet is switched to the normal sheet linear speed V1 after the acceleration time Tb has elapsed is:
Corrected inter-paper distance = t1 × V1−Tb × (V2−V1), and after the above equation Tb = (t1−Ta) × V1 / (V2−V1), corrected inter-paper time = t1 × V1 − {(t1 -Ta) * V1 / (V2-V1)} * (V2-V1) = Ta * V1 = L
Thus, the target inter-paper distance L is corrected. In this example, the corrected inter-paper distance = L is set by setting the acceleration time Tb.

3: Example in which the leading edge of the preceding sheet and the leading edge of the succeeding sheet are transported with a slight gap between them in continuous feeding. In this example, the sheet feeding unit performs continuous feeding operation aiming at zero sheet spacing. However, this is a case where the sheet is conveyed with a slight gap between the sheets due to slipping of the sheet (the same operation as the above example 2 is performed except that there is a gap between sheets). In FIGS. 12 to 16, when continuous feeding is performed without a gap between the papers in the paper feeding unit, the paper feeding unit continuously feeds paper with no paper gap (= 0 mm between papers). Then, due to the paper slip of the subsequent paper P2 (the subsequent paper is likely to cause a delay in conveyance due to the slip because of the load on the separation unit), and is a schematic cross-sectional view when the paper is fed with a slight paper gap is there.
First, as shown in FIG. 12, the paper continuously fed by the paper feeding unit is sent with a slight paper gap A (A = 10 mm in this case) between the preceding paper P1 and the following paper P2, and the preceding paper P1 When the first conveying roller pair 1 stops at the timing after the trailing edge of the paper has passed through the nip portion of the first conveying roller pair 1 (in this example, the timing when 10 mm is fed from the first conveying roller pair 1), Paper conveyance stops (steps S1 to S5 in FIG. 1).
Next, as shown in FIG. 13, when it is detected that the trailing edge of the preceding sheet has passed through the sheet sensor b, the conveyance of the succeeding sheet is resumed by the start of driving of the first conveying roller pair 1. The sheet linear velocity at this time is the increased linear velocity V2 = 500 mm / s. At the same time, the paper sensor b starts measuring the paper interval time t1 (steps S6 to S8 in FIG. 1).
Next, as shown in FIG. 14, when the leading edge of the succeeding paper reaches the paper sensor b, the measurement of the paper interval time t1 is completed (step S9 to step S10 in FIG. 1), and from the measured value of t1 onward. The subsequent paper transport speed and timing are determined by the control unit (see FIG. 15). In this example, Ta = L / V1 = 15 mm / (362 mm / s) = 41.4 ms, Tb = V1 / (V2−V1) × (t1−Ta), Tc = Ta−t1, corrected paper The distance target value = 15 mm.

In this example, the conveyance speed and timing of the succeeding paper are determined by calculation from the paper interval time t1 in the control unit (in FIG. 15, since t1 = 80 ms and Ta = 41.4 ms, t1 ≧ Ta. The subsequent paper is accelerated and conveyed by Tb). Tb = V1 / (V2-V1) * (t1-Ta) = 362 / (500-362) * (0.080-0.0414) = 101.3 ms) refers to the data table stored in the control unit There is also a way to decide.
In this example, the measured paper interval time t1 = 80 ms, which is larger than the set value Ta = 41.4 ms, and t1 ≧ Ta. For this reason, the succeeding sheet is fed so that the succeeding sheet is conveyed at a speed increasing linear velocity V2 higher than the normal sheet linear velocity V1 in a section from the leading edge of the trailing sheet reaching the sheet sensor b to the lapse of time Tb. The number of rotations of the one conveying roller pair 1 is controlled, and the sheet is conveyed at the normal sheet linear velocity V1 after the time Tb has elapsed (see FIG. 16). When the number of fed sheets reaches the set value, the operation is terminated (Step S11, Step S12 to Step S17 in FIG. 1).
The acceleration time Tb is Tb = (t1-Ta) × V1 / (V2-V1), where Ta = L / V1, L = target inter-paper distance after correction, V1 = normal sheet linear velocity, V2 = The value obtained from the calculation formula of the paper linear velocity during acceleration. The distance between the sheets when the conveyance of the succeeding sheet is switched to the normal sheet linear speed V1 after the acceleration time Tb has elapsed is:
Corrected inter-paper distance = t1 × V1−Tb × (V2−V1), and after the above equation Tb = (t1−Ta) × V1 / (V2−V1), corrected inter-paper time = t1 × V1 − {(t1 -Ta) * V1 / (V2-V1)} * (V2-V1) = Ta * V1 = L
Thus, the target inter-paper distance L is corrected. In this example, the corrected inter-paper distance = L is set by setting the acceleration time Tb.
Therefore, in the first embodiment, the position where the space between the sheets is spaced is sufficiently large with respect to the conveyance load (separation load, sheet stiffness, conveyance load due to sliding with the guide plate, etc.), That is, since it is a position where the sheet linear speed is stable (downstream from the nip of the first conveying roller pair 1), conventionally, a sheet feeding section with an unstable sheet linear speed has been used. On the other hand, in the present invention, the variation between the papers can be suppressed small. In addition, the paper interval is measured by the paper sensor, the acceleration time and timing of the succeeding paper are determined based on the measured values, and correction between the papers is performed, so that it is possible to reduce the variation between the corrected papers. . As a result, it is possible to reduce the set value between sheets that has been set in consideration of the variation between sheets.

Also, when the measured inter-paper time is large (examples 1 and 3 above), the trailing paper linear velocity is increased (V2), and the paper interval is reduced by transporting the paper for a certain time Tb, and then normal paper is used. By returning to the linear velocity V1, it is possible to reduce the variation between the sheets.
When the measured paper interval time is small (example 1 above), the subsequent paper is stopped by stopping for a certain time Tc, and then the conveyance is resumed at the normal paper linear velocity V1. It becomes possible to reduce the variation of the.
The above times Tb and Tc are set to Tb = (t1−Ta) × V1 / (V2−V1), where Ta = L / V1, L = target inter-paper distance after correction, V1 = normal paper line By setting the speed, V2 = speed paper linear speed, and Tc = Ta−t1, it is possible to make the corrected inter-paper distance≈the target inter-paper distance L, and effectively reduce the variation between the papers. It becomes possible to make it.
Also, even if there is variation in the standby position of the paper before feeding, even if some of the paper is fed overlapped when the paper is fed continuously without gaps due to the variation in the standby position, when the trailing paper stops Since the leading edge of the succeeding paper does not reach the paper sensor b, the paper sensor b can detect the sensor missing timing of the preceding paper and measure the paper interval time t1 even when the paper is overlapped. Correction between papers is possible. As a result, it is possible to suppress the variation between the papers, and thereby it is possible to reduce the set value between the papers set in consideration of the variation between the papers.
Further, by increasing the sheet linear speed of the succeeding sheet before the sheet interval time measurement by the sheet sensor b, it is possible to further reduce the sheet interval at the time of measurement. As a result, the measurement paper interval time t1 and its variation can be made smaller in advance, so that it is possible to cope with a larger variation between the papers in addition to the effect of the subsequent sheet linear velocity and the paper interval correction by the conveyance timing.
By providing a paper conveyance device that corrects this paper gap in the image forming apparatus, it is possible to keep the paper gap small, so productivity is improved by small paper gaps (short paper gaps), low cost, and durability is increased. Effects such as calming can be obtained.
In addition, by providing a paper conveyance device having a function for correcting the paper gap in the electrophotographic image forming apparatus, it is possible to keep the paper gap small, thereby improving productivity due to the small paper gap and low cost. In addition, effects such as improved durability and calming can be obtained.

The second embodiment differs from the first embodiment only in the setting contents of the times Ta, Tb, and Tc, and the subsequent sheet operation after stopping the subsequent sheet at the time Tc. Constituent elements such as a paper feed roller, a transport roller, and a sensor are the same and are disposed at the same place. In FIG. 19, there is no structural difference. The second embodiment will be described with reference to the flowchart of FIG. 18 and FIGS. 2 to 16, 17 and 19. In the second embodiment, the following three cases will be described.
4: Examples in which the trailing edge of the preceding paper and the leading edge of the succeeding paper are overlapped and fed in continuous paper feeding (FIGS. 18, 19, 2 to 4, 17, and 6)
5: An example in which the leading edge of the preceding sheet and the leading edge of the succeeding sheet are fed with zero gap between continuous sheets (FIGS. 18, 19, and 7 to 11).
6: Example in the case where the leading edge of the preceding sheet and the leading edge of the succeeding sheet are conveyed with a slight gap between them in continuous feeding (FIGS. 18, 19, and 12 to 16).
4: Example in which the leading edge of the preceding sheet and the leading edge of the succeeding sheet are overlapped and fed in continuous feeding FIGS. 2 to 4, 17, and 6 show that the sheet feeding unit continuously feeds the sheet without gaps FIG. 10 is a schematic cross-sectional view when sheets are overlapped and fed due to variations in the sheet standby position when performed. First, as shown in FIG. 2, the paper continuously fed by the paper feeding unit is fed with the trailing edge of the preceding sheet and the leading edge of the trailing sheet overlapping, and the trailing edge of the leading sheet passes through the first conveyance roller pair 1. At the subsequent timing (in this example, the timing when 10 mm is fed from the first conveying roller pair 1), the conveyance of the succeeding paper is stopped by stopping the first conveying roller pair 1 (step S21 to step S21 in FIG. 18). S25).
The maximum value Dmax of the overlap amount at this time is the distance LA-B (24.5 mm in this example) from the paper leading edge standby position (A) to the separating portion (B) when setting paper, and the position of the paper sensor b. Is the distance LE-G from the conveying roller 1 and is larger than the maximum overlap amount Dmax = LA-B, so that the leading edge of the succeeding sheet stops at a position where it does not reach the sheet sensor b.

Next, as shown in FIG. 3, when it is detected that the trailing edge of the preceding sheet has passed through the sheet sensor b, the conveyance of the succeeding sheet P2 is resumed. The sheet linear velocity at this time is the increased linear velocity V2 = 500 mm / s. At the same time, the paper sensor b starts measuring the paper interval time t1 (steps S26 to S28 in FIG. 18).
Next, as shown in FIG. 4, when the leading edge of the succeeding paper reaches the paper sensor b, the measurement of the paper interval time t1 is completed (step S29 to step S30 in FIG. 18), and the measured value of t1 is used thereafter. The subsequent paper conveyance speed and timing are determined by the control unit (see FIG. 5). In this example, Ta = {L + Td * (V2-V1)} / V1 = {15 + 0.02 * (500-362)} / 362 = 49 ms, Tb = V1 / (V2-V1) * (t1-Ta ) + Td, Tc = Ta−t1, Td = 20 ms (fixed time), and the corrected inter-paper distance target value L = 15 mm.
In this example, the conveyance speed and timing of the succeeding paper are determined by calculation from the paper interval time t1 in the control unit (in FIG. 5, since t1 = 11 ms and Ta = 49 ms, t1 <Ta, and therefore after this time Tc. There is also a method in which the line paper is stopped (Tc = Ta−t1 = 49−11 = 38 ms) by referring to the data table stored in the control unit.
In this example, the measured inter-paper time t1 = 11 ms, which is smaller than the set value Ta = 49 ms, and t1 <Ta. For this reason, in the succeeding sheet, the driving of the first conveying roller pair 1 is stopped at the timing when the leading end of the succeeding sheet reaches the sheet sensor b, and the state of FIG. Then, the conveyance is resumed at the increased linear velocity V2 (step S31, step S35 to step S37 in FIG. 18).
Stop time Tc is Tc = Ta−t1, where Ta = {L + Td × (V2−V1)} / V1, L = target inter-paper distance after correction, V1 = normal sheet linear velocity, V2 = acceleration Hour sheet linear velocity, Td = a value obtained by a calculation formula of a fixed time.
The distance between the sheets when the conveyance of the succeeding sheet is resumed at the normal sheet linear velocity V1 after the stop time Tc has elapsed is:
Distance between paper = (t1 + Tc) × V1 = {t1 + (Ta−T1)} × V1 = Ta × V1
It becomes.
Thereafter, after the acceleration time Td elapses, the succeeding paper is returned to the normal linear velocity V1 as shown in FIG. 6 (steps S38 and S34 in FIG. 18).
The inter-paper distance at this time is corrected inter-paper distance = Ta * V1-Td * V2 + Td * V1 = Ta * V1-Td * (V2-V1). From the above formula Ta = {L + Td × (V2−V1)} / V1,
Distance between paper after correction = {L + Td × (V2−V1)} / V1 × V1−Td × (V2−V1) = L
Thus, the target inter-paper distance L is corrected. In this example, the corrected inter-paper distance = L by setting the stop time Tc. When the number of fed sheets reaches the set value, the operation is terminated (step S39 in FIG. 18).

5: Example in which the leading edge of the preceding paper and the leading edge of the succeeding paper are fed with zero paper in continuous paper feeding FIGS. 7 to 11 show the case where the paper feeding unit performs continuous paper feeding without leaving a paper gap. FIG. 6 is a schematic cross-sectional view when sheets are fed overlapping due to variations in the sheet standby position. First, as shown in FIG. 7, the paper continuously fed by the paper feeding unit is fed between the preceding paper and the succeeding paper with a sheet interval of 0, and the trailing edge of the preceding paper has passed through the first conveying roller pair 1. Subsequent sheet conveyance is stopped by stopping the first conveyance roller pair 1 at the subsequent timing (in this example, the timing when 10 mm is fed from the first conveyance roller pair 1) (steps S21 to S25 in FIG. 18). ).
Next, as shown in FIG. 8, when it is detected that the trailing edge of the preceding sheet has passed through the sheet sensor b, the conveyance of the succeeding sheet is resumed. The sheet linear velocity at this time is the increased linear velocity V2 = 500 mm / s. At the same time, the paper sensor b starts measuring the paper interval time t1 (steps S26 to S28 in FIG. 18).
Next, as shown in FIG. 9, when the leading edge of the succeeding paper reaches the paper sensor b, the measurement of the paper interval time t1 is completed (step S29 to step S30 in FIG. 18), and the measured t1 value and thereafter are thereafter. The subsequent paper transport speed and timing are determined by the control unit. (See FIG. 10). In this example, Ta = {L + Td * (V2-V1)} / V1 = {15 + 0.02 * (500-362)} / 362 = 49 ms, Tb = V1 / (V2-V1) * (t1-Ta ) + Td, Tc = Ta−t1, Td = 20 ms (fixed time), and the corrected inter-paper distance target value L = 15 mm.

In this example, the conveyance speed and timing of the succeeding paper are determined by calculation from the paper interval time t1 in the control unit (in FIG. 10, since t1 = 60 ms and Ta = 49 ms, t1 ≧ Ta, and therefore only the time Tb from here. The following paper is accelerated and conveyed: Tb = V1 / (V2−V1) × (t1−Ta) + Td = 362 / (500−362) × (0.060−0.049) + 0.02 = 48 .9 ms) can be determined by referring to a data table stored in the control unit.
In this example, the measured inter-paper time t1 = 60 ms, which is larger than the set value Ta = 49 ms, and t1 ≧ Ta. For this reason, the succeeding sheet is fed so that the succeeding sheet is conveyed at a speed increasing linear velocity V2 higher than the normal sheet linear velocity V1 in a section from the leading edge of the trailing sheet reaching the sheet sensor b to the lapse of time Tb. The number of rotations of the one conveying roller pair 1 is controlled, and the sheet is conveyed at the normal sheet linear velocity V1 after the time Tb has elapsed (see FIG. 11). When the number of fed sheets reaches the set value, the operation is terminated (steps S31 and S32 to S39 in FIG. 18).
The acceleration time Tb is Tb = (t1−Ta) × V1 / (V2−V1) + Td, where Ta = {L + Td × (V2−V1)} / V1, L = target inter-paper distance after correction. , V1 = normal sheet linear velocity, V2 = accelerated sheet linear velocity, and Td = a constant time. The distance between the sheets when the conveyance of the succeeding sheet is switched to the normal sheet linear speed V1 after the acceleration time Tb has elapsed is:
Corrected distance between sheets = t1 × V1−Tb × (V2−V1), the above formula Tb = (t1−Ta) × V1 / (V2−V1) + Td, Ta = {L + Td × (V2−V1)} / V1 Thus, the inter-sheet time after correction = t1 × V1 − {(t1−Ta) × V1 / (V2−V1) + Td} × (V2−V1) = Ta × V1−Td × (V2−V1) = {L + Td × (V2−V1)} / V1 × V1−Td × (V2−V1) = L, and the target inter-paper distance L is corrected. In this example, the corrected inter-paper distance = L is set by setting the acceleration time Tb.

6: Example of transporting paper with the trailing edge of the preceding paper and the leading edge of the succeeding paper with a slight gap between them in this example. However, this is a case where the sheet is conveyed with a slight gap between the sheets due to slipping of the sheet (the same operation as the above example 5 is performed except that there is a gap between sheets). In FIGS. 12 to 16, when continuous paper feeding is performed without a gap between papers in the paper feeding unit, the paper feeding unit continuously feeds paper with no paper gap (= 0 mm between papers). FIG. 6 is a schematic cross-sectional view when the paper is fed in a state where there is a slight gap between papers due to subsequent paper slip (following paper is likely to cause a delay in conveyance due to slip because a load is applied to the separation unit).
First, as shown in FIG. 12, the paper continuously fed by the paper feed unit is sent with a slight space A (here A = 10 mm) between the preceding paper and the following paper, and after the preceding paper. The conveyance of the succeeding paper is stopped by stopping the first conveyance roller pair 1 at the timing after the end passes through the first conveyance roller pair 1 (in this example, the timing when 10 mm is sent from the first conveyance roller pair 1). (Steps S21 to S25 in FIG. 18).
Next, as shown in FIG. 13, when it is detected that the trailing edge of the preceding sheet has passed through the sheet sensor b, the conveyance of the succeeding sheet is resumed. The sheet linear velocity at this time is the increased linear velocity V2 = 500 mm / s. At the same time, the paper sensor b starts measuring the paper interval time t1 (steps S26 to S28 in FIG. 18).
Next, as shown in FIG. 14, when the leading edge of the succeeding paper reaches the paper sensor b, the measurement of the paper interval time t1 is completed (Step S29 to Step S30 in FIG. 18), and from the measured value of t1, The subsequent paper transport speed and timing are determined by the control unit (see FIG. 15). In this example, Ta = {L + Td * (V2-V1)} / V1 = {15 + 0.02 * (500-362)} / 362 = 49 ms, Tb = V1 / (V2-V1) * (t1-Ta ) + Td, Tc = Ta−t1, Td = 20 ms (fixed time), and the corrected inter-paper distance target value L = 15 mm.

In this example, the conveyance speed and timing of the succeeding paper are determined by calculation from the paper interval time t1 in the control unit (in FIG. 15, since t1 = 80 ms and Ta = 49 ms, t1 ≧ Ta, so only the time Tb from here. The following paper is accelerated and conveyed: Tb = V1 / (V2−V1) × (t1−Ta) + Td = 362 / (500−362) × (0.080−0.049) + 0.02 = 101 .3 ms) can be determined by referring to the data table stored in the control unit.
In this example, the measured paper interval time t1 = 80 ms, which is larger than the set value Ta = 49 ms, and t1 ≧ Ta. For this reason, the succeeding sheet is fed so that the succeeding sheet is conveyed at a speed increasing linear velocity V2 higher than the normal sheet linear velocity V1 in a section from the leading edge of the trailing sheet reaching the sheet sensor b to the lapse of time Tb. The number of rotations of the one conveying roller pair 1 is controlled, and the sheet is conveyed at the normal sheet linear velocity V1 after the time Tb has elapsed (see FIG. 16). When the number of fed sheets reaches the set value, the operation is terminated (steps S31 and S32 to S39 in FIG. 18).
The acceleration time Tb is Tb = (t1−Ta) × V1 / (V2−V1) + Td, where Ta = {L + Td × (V2−V1)} / V1, L = target inter-paper distance after correction, This is a value obtained by the following equation: V1 = normal sheet linear velocity, V2 = accelerated sheet linear velocity, and Td = constant time. The distance between the sheets when the conveyance of the succeeding sheet is switched to the normal sheet linear speed V1 after the acceleration time Tb has elapsed is:
Corrected distance between sheets = t1 × V1−Tb × (V2−V1), the above formula Tb = (t1−Ta) × V1 / (V2−V1) + Td, Ta = {L + Td × (V2−V1)} / V1 Thus, the inter-sheet time after correction = t1 × V1 − {(t1−Ta) × V1 / (V2−V1) + Td} × (V2−V1) = Ta × V1−Td × (V2−V1) = {L + Td × (V2−V1)} / V1 × V1−Td × (V2−V1) = L, and the target inter-paper distance L is corrected. In this example, the corrected inter-paper distance = L is set by setting the acceleration time Tb.
Therefore, in the second embodiment, the position where the space between the sheets is spaced is sufficiently large with respect to the conveyance load (separation load, conveyance of the sheet, conveyance load due to sliding with the guide plate, etc.) ( Therefore, it is possible to suppress the variation between papers as compared to the conventional paper feeding unit where the paper linear speed is unstable. In addition, since the time between sheets is measured by a sensor, the acceleration time, timing, etc. of the succeeding paper are determined based on the measured values, and correction between the papers is performed, so that variation between the corrected papers can be reduced. As a result, it is possible to reduce the set value between sheets that has been set in consideration of the variation between sheets.

Also, when the measured paper interval time is large (examples 5 and 6 above), the subsequent paper linear velocity is increased (V2) and the paper interval is reduced by transporting for a certain time Tb, and then the normal paper By returning to the speed V1, it is possible to reduce the variation between the sheets.
Also, when the measured paper interval time is small (example 4 above), the succeeding paper is stopped for a certain time Tc to clear the paper interval, and thereafter the conveyance is resumed at a speed increase V2 for a fixed time Td. By returning to the normal sheet linear velocity V1, it is possible to reduce variations between sheets.
The above times Tb and Tc are set to Tb = (t1−Ta) × V1 / (V2−V1) + Td, where Ta = {L + Td × (V2−V1)} / V1, L = target paper after correction By setting the distance, V1 = normal sheet linear velocity, V2 = accelerated sheet linear velocity, Td = constant time, and Tc = Ta−t1, the corrected inter-paper distance≈the target inter-paper distance L This makes it possible to effectively reduce the variation between the papers.
Even if there is variation in the standby position of the paper, the leading edge of the succeeding paper when the trailing paper is stopped even if the paper is partially overlapped when the paper is continuously fed without gaps due to the variation in the standby position. Since the sheet sensor b does not reach the sheet sensor b, the sheet sensor b can detect the timing of sensor removal of the preceding sheet and measure the sheet interval time t1 even when the sheets overlap. Correction is possible. As a result, it is possible to suppress the variation between the papers, and thereby it is possible to reduce the set value between the papers set in consideration of the variation between the papers.
Further, by increasing the sheet linear speed of the succeeding sheet before the sheet interval time measurement by the sheet sensor b, it is possible to reduce the sheet interval at the time of measurement. As a result, the measurement paper interval time t1 and its variation can be made smaller in advance, so that it is possible to cope with a larger variation between the papers in addition to the effect of the subsequent sheet linear velocity and the paper interval correction by the conveyance timing.
By providing a paper transport device that corrects this gap in the image forming device, it is possible to keep the gap between the papers small, thereby improving productivity, reducing costs, improving durability, and calming. Obtainable.
In addition, by providing a paper conveyance device for correcting the paper gap in the electrophotographic image forming apparatus, it is possible to keep the paper gap small, thereby improving productivity due to small paper gaps, low cost, and improving durability. Effects such as calming can be obtained.

3 is a flowchart illustrating an operation in the first embodiment. FIG. 2 is a schematic cross-sectional view of a paper transport device (paper overlap when paper is fed, part 1). FIG. 3 is a schematic cross-sectional view of a paper transport device (paper overlap when paper is fed, Part 2). FIG. 3 is a schematic cross-sectional view of a paper transport device (with paper overlap during paper feeding, part 3). FIG. 4 is a schematic cross-sectional view of a paper transport device (with paper overlap during paper feeding, part 4). FIG. 6 is a schematic cross-sectional view of a paper conveying apparatus (with paper overlap during paper feeding, part 5). FIG. 3 is a schematic cross-sectional view of the sheet transport device (no sheet space when feeding, part 1). FIG. 3 is a schematic cross-sectional view of the paper transport device (No paper during feeding, part 2). FIG. 3 is a schematic cross-sectional view of a paper transport device (no paper space during paper feeding, part 3). FIG. 4 is a schematic cross-sectional view of a paper transport device (No space during paper feeding, part 4). FIG. 6 is a schematic cross-sectional view of the paper transport device (no paper gap during paper feeding, part 5). FIG. 2 is a schematic cross-sectional view of a paper transport device (there is a paper gap during paper feeding, part 1). FIG. 3 is a schematic cross-sectional view of the paper transport device (there is a paper gap during paper feeding, part 2). FIG. 4 is a schematic cross-sectional view of the paper transport device (there is a paper gap during paper feeding, part 3). FIG. 6 is a schematic cross-sectional view of the paper transport device (there is a paper gap at the time of paper feeding, part 4). FIG. 5 is a schematic cross-sectional view of the paper transport device (there is a paper gap during paper feeding, part 5). FIG. 4 is a schematic cross-sectional view of a paper conveying apparatus according to a second exemplary embodiment (paper overlap at the time of paper feeding, 4 ′). 10 is a flowchart illustrating an operation in the second embodiment. It is a cross-sectional view of a conventional paper transport device (using the FRR separation method).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st conveyance roller pair 1a Paper stacking part 2 2nd conveyance roller pair 2a Paper 3 Pickup roller 4 Feed roller 5 Reverse roller 6 Photoconductor 7 Transfer roller a, b, c, F Paper sensor

Claims (10)

A paper feed roller for feeding paper from the paper stacking unit;
Separating means for separating the paper into one sheet;
A first conveyance roller pair provided in a conveyance path downstream of the paper feed roller and configured to convey paper;
A second conveying roller pair that is provided in a conveying path downstream from the first conveying roller pair and conveys paper;
A paper sensor positioned between the first transport roller pair and the second transport roller pair;
A control unit,
When continuously feeding paper from the paper stacking unit, the control unit continuously feeds paper with no gap between the papers, and the trailing edge of the preceding paper is the first paper. By stopping driving the first conveying roller pair while continuing to convey the preceding paper without stopping the driving of the second conveying roller pair at the timing after passing through the conveying roller pair, , After the distance between the first transport roller pair and the second transport roller pair, and then transported,
Drive of the first transport roller pair is started after a certain time T1 (≧ 0) after the trailing edge of the preceding paper sheet is detected, triggered by the detection of the trailing edge of the preceding sheet by the sheet sensor. Then, the succeeding sheet is conveyed, and the sheet interval time t1 from when the trailing end of the preceding sheet passes through the sheet sensor to when the leading end of the succeeding sheet reaches the sheet sensor is measured. Depending on the value of the sheet, the conveyance timing such as the time for conveying the trailing sheet at a linear velocity V2 after the leading edge of the trailing sheet reaches the first conveying roller pair or the time for stopping the trailing sheet is set. A paper conveying apparatus characterized by determining. In the paper conveyance device according to claim 1,
The control unit detects that the leading edge of the succeeding sheet has reached the position of the sheet sensor, and the transporting speed and timing of the succeeding sheet after the sheet spacing time t1 is measured is the sheet spacing time t1 ≧ the set time Ta. (Ta = constant value), after the leading edge of the succeeding paper reaches the paper sensor position, the paper linear speed is higher than the normal speed by increasing the rotation speed of the first conveying roller pair for a time Tb. After the trailing paper is conveyed at V2 and the leading edge of the succeeding paper reaches the paper sensor position, after the time Tb has elapsed, the rotation speed of the first conveying roller pair is returned to the normal rotation speed, so that the normal line speed is reached. A paper transporting device, which is set to transport subsequent paper at V1. In the paper conveyance device according to claim 1,
When it is detected that the leading edge of the succeeding sheet has reached the position of the sheet sensor and the sheet interval time t1 is measured, the conveyance speed and timing of the succeeding sheet satisfy the condition of the sheet interval time t1 <the set time Ta (where Ta = The constant value), after the leading edge of the succeeding sheet reaches the position of the sheet sensor, the conveyance of the succeeding sheet is stopped by stopping the rotation of the first conveying roller pair for a time Tc, and the sheet sensor After the leading edge of the succeeding paper has reached the position of, the time of passing the time Tc is such that the following paper is transported at the normal paper linear speed V1 by returning the rotational speed of the first transport roller pair to the normal rotational speed. A sheet conveying device characterized in that the control is performed. In the paper conveyance device according to claim 1,
The control unit detects that the leading edge of the succeeding sheet has reached the position of the sheet sensor and measures the sheet conveying time t1 after the sheet spacing time t1 is measured. (Ta = constant value) After the leading edge of the succeeding sheet reaches the position of the sheet sensor, the transport of the succeeding sheet is stopped by stopping the rotation of the first conveying roller pair for a time Tc. Then, after the leading edge of the succeeding paper reaches the position of the paper sensor, after the time Tc elapses, the paper is faster than the normal speed by increasing the rotation speed of the first conveying roller pair until the time Td elapses thereafter. The succeeding sheet is conveyed at the linear speed V2, and after the time Td, the following sheet is conveyed at the normal sheet linear speed V1 by returning the rotation speed of the first conveying roller pair to the normal rotation speed. A paper conveying device characterized by controlling. In the paper conveyance device according to claim 2 or 3,
Time Tb is Tb = (t1−Ta) × V1 / (V2−V1) (where Ta = L / V1, L = target inter-paper distance after correction, V1 = normal sheet linear velocity, V2 = (Paper speed at the time of acceleration) and time Tc are calculated values obtained from the relationship of Tc = Ta-t1, or data set in the data table in advance so as to obtain the same effect as the case where the calculated values are used. A sheet conveying apparatus characterized in that the value is obtained with reference to FIG. In the paper conveyance device according to claim 2 or 4,
Time Tb is Tb = (t1−Ta) × V1 / (V2−V1) + Td (where Ta = {L + Td × (V2−V1)} / V1, L = target inter-paper distance after correction, V1 = Normal sheet linear velocity, V2 = Increased paper linear velocity, Td = Constant time), Time Tc is a calculated value obtained from the relationship of Tc = Ta-t1, or the same effect as when using the calculated value A sheet conveying device characterized in that the value is obtained by referring to data set in advance in a data table so as to be obtained. In the paper conveyance device according to any one of claims 1 to 6,
The paper transport apparatus according to claim 1, wherein a distance between the paper sensor and the first transport roller pair is set to be larger than a distance from a front end position of the paper stacked on the paper stacking unit to the separation unit. In the paper conveyance device according to any one of claims 1 to 7,
The control unit uses the first transport roller after a predetermined time T1 (≧ 0) after the trailing edge of the preceding paper sheet as a trigger when the sheet sensor detects that the trailing edge of the preceding sheet has been removed from the paper sensor position. The sheet linear speed of the succeeding sheet sent by the first conveying roller pair when the pair driving is started is a part from the start of driving of the first conveying roller pair until the leading edge of the succeeding sheet reaches the sheet sensor. The sheet conveyance is characterized in that the rotation speed of the first conveyance roller pair is controlled so that the subsequent sheet linear velocity is fed at a speed increasing linear velocity V2 higher than the normal linear velocity V1 in this section or all sections. apparatus. An image forming unit for forming an image on paper;
An image forming apparatus comprising: the sheet conveying apparatus according to claim 1, which conveys a sheet to the image forming unit. The image forming apparatus according to claim 9.
An image forming apparatus, wherein the image forming unit transfers a toner image formed by an electrophotographic method onto a sheet to form an image on the sheet.

Images