JP2002029649A - Sheet carrying device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably and precisely rush a sheet into a resister roller. SOLUTION: This sheet carrying device comprises resist means 106 and 107 arranged on the carrying directional upstream side of an image forming means 12 to send the sheet into the image forming means at a sheet carrying timing matched to the image forming motion of the image forming means; a first sheet detecting means 120 provided on the sheet carrying directional upstream side of the resist means to detect the tip of the sheet; a second sheet detecting means 104 arranged on the sheet carrying directional upstream side of the first sheet detecting means to detect the tip of the sheet separately fed from a sheet feeding means ; and a pre-resist carrying means 105 performing a pre-resist operation of temporarily stopping the sheet separately fed from the sheet feeding means in the middle of a carrying passage on the basis of the detection result by the second sheet detecting means and then carrying it toward the resist means. The pre-resist carrying means corrects the pre-resist operation timing of the following sheet on the basis of the carrying time from the temporary stop of the former sheet to its detection by the first sheet detecting means 120.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet conveying apparatus and an image forming apparatus, and more particularly, to a sheet conveying apparatus in an image forming apparatus having a registration unit for feeding a sheet to the image forming unit.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, a printer, a facsimile, or a multifunction peripheral thereof, an image forming section for forming an image on a sheet, and a sheet feeding for feeding the sheet to the image forming section. And a sheet discharge unit that discharges a sheet on which an image has been formed by the image forming unit to the outside of the apparatus. Further, in order to form an image on both sides of the sheet, an image forming unit is used. A known type is provided with a sheet reversal conveyance path for reversing a reconstructed sheet and sending it to the image forming unit again.

Hereinafter, a conventional example of such an image forming apparatus will be described with reference to FIGS. 7 and 8. FIG. FIG. 7 is a schematic sectional view of an electrophotographic copying machine as a conventional image forming apparatus. This electrophotographic copying machine (hereinafter simply referred to as a copying machine) includes a document reading unit 4 for reading an image of a document.
An image forming unit that forms an image on a sheet by an electrophotographic method based on image information read by the document reading unit 4, and a plurality of sheet feeding units, and a plurality of sheets from each sheet feeding unit. Can be continuously fed to the image forming unit.

In FIG. 7, reference numeral 1 denotes a copying machine main body, and a document table 2 made of a transparent glass plate is fixedly provided on an upper portion of the copying machine main body 1. An original feeder 3 conveys the original to a predetermined position on the original table 2.

In this copying machine, an image of a document on a document table 2 is read by a document reading unit 4, and based on the data, a writing laser unit 5 emits a laser beam and is uniformly charged. By scanning on the photosensitive drum 12, an electrostatic latent image is formed on the photosensitive drum 12.

In a copying machine, a sheet feeding unit includes
Deck feeding units 34 and 35 and cassette feeding units 36 and 37 for feeding the sheets stacked on the decks 30 and 31 and the sheet cassettes 32 and 33 incorporated in the copying machine body 1 to the image forming unit are provided. Is provided.

The image forming section includes a photosensitive drum 12 and a charger 13 for uniformly charging the surface of the photosensitive drum 12.
A developing unit 14 for developing the electrostatic latent image formed on the surface of the photosensitive drum 12 charged by the charger 13 to form a toner image to be transferred to the sheet S; Charger 19 for transferring the toner image developed on the sheet S to the sheet S, and a separation charger 20 for separating the sheet S on which the toner image has been transferred from the photosensitive drum 12
And a cleaner 26 for removing the toner remaining on the photosensitive drum 12 after transferring the toner image.

On the downstream side of the image forming section, a conveying section 21 for conveying the sheet S on which the toner image has been transferred, and a fixing section for fixing the toner image on the sheet S conveyed by the conveying section 21 as a permanent image. Is provided. Further, a discharge roller 24 for discharging the sheet S on which the toner image has been fixed by the fixing device 22 from the copying machine main body 1 is provided. A discharge tray 25 for receiving the sheet S is provided.

In this copying machine, conveying rollers 105, 107, 108, 109, 110, 111, and 110 are provided on a conveying path for conveying a sheet from a sheet feeding section to an image forming section.
112, 123 and sheet path sensors 104, 116, 117, 118 for detecting the leading and trailing edges of the sheet.
Is arranged. The sheet fed by each transport roller is sent to the image forming unit by the registration roller 106. Registration roller 10
A registration sensor 120 for detecting the leading edge of the sheet is disposed near the upstream side in the sheet conveyance direction of No. 6.

Here, the transport roller 107 is a pre-registration roller for feeding the sheet sent from each sheet feeding unit to the registration roller 106. In the sheet conveyance path on the upstream side of the pre-registration roller 107,
The first transport roller 105, the sheet path sensor 104, the second transport roller 108, the third transport roller 109, the sheet path sensor 116, the fourth transport roller 110, and the sheet path sensor 117 are arranged in this order.

Further, a sheet conveying path connected to the deck feeding section 35 branches from a conveying path between the pre-registration roller 107 and the first conveying roller 105, and the sheet conveying path is connected to the sheet conveying path from the downstream side. The fifth transport roller 111, the sheet path sensor 104, the sixth transport roller 112, the sheet path sensor 118, and the seventh transport roller 123 are arranged in this order.

Further, a sheet reversing path branches off from the conveying path between the sixth conveying roller 112 and the seventh conveying roller 123. The sheet reversing path includes a sheet path sensor 119, A right roller 113, a double-sided left roller 114, a reversing roller 115 rotating in the forward and reverse directions, and a sheet reversing unit 121 are arranged in this order. In this copier, in order to form images on both sides of a sheet,
The sheet on which the image is formed by the image forming unit is
The sheet is reversed by the reversing roller 115 and sent to the sheet reversing path, and the image is formed again on the path of the double-sided left roller 114, the double-sided right roller 113, the sixth conveying roller 112, the fifth conveying roller 111, the pre-registration roller 107, and the registration roller 106 Department.

Each of the above-mentioned rollers is driven to rotate by transmitting a driving force of a driving motor (not shown). The rotation of each roller is controlled by a control unit (not shown) based on the detection result of each sheet path sensor described above.

Next, the operation of the conventional copier when feeding a sheet will be described with reference to FIG. 8, taking the case of feeding from the deck feeding section 34 as an example. Here, FIG. 8 is a diagram illustrating a positional relationship between the leading end and the trailing end of the sheet when the sheet is fed from the deck feeding unit 34, and the like.

At the start of sheet feeding, the pickup motor 101 and the feeding roller 10 are driven by the drive motor.
2. The separation roller 103, the first transport roller 105, and the pre-registration roller 107 are rotationally driven. At this time, the registration roller 106 is still in a stopped state.

At the time of sheet feeding, first, the pickup roller 101 sends the sheet S set on the sheet deck 30 to the feeding roller 102. Here, the sheet S is separated only into the uppermost sheet by a separation roller 103 provided opposite to the feeding roller 102 and applied with a force rotating in a direction opposite to the conveyance direction with a constant torque.

The uppermost sheet is conveyed by a first conveying roller 105 when the leading end of the sheet is detected by a sheet path sensor 104.

At this time, in the copying machine, in order to perform a so-called pre-registration operation of adjusting the interval (sheet interval) between the sheets, the first conveying roller 105 is controlled based on the detection timing of the leading edge of the sheet by the sheet path sensor 104. By temporarily stopping the rotation of the first conveying roller 105,
The control is performed to stop the leading edge of the sheet being nipped and conveyed at a predetermined position on the conveyance path, and to restart the rotation of the first conveyance roller 105 after a predetermined time has elapsed.

That is, in the sheet feeding section, not only the sheet whose leading end is at the regular stacking position of the sheet deck 30 but also the sheet leading end is returned to the sheet deck 30 by the separation roller 103 and is located near the feed roller 102. Sheet is also fed, there is a variation in the sheet leading end position at the start of feeding, and it is necessary to eliminate this variation on the front side of the registration roller 106.

Specifically, as shown in FIGS. 7 and 8,
The first conveying roller 105 is temporarily stopped at a timing at which it reaches a predetermined position (pre-registration position) A on the conveying path after the sheet leading edge is detected by the sheet path sensor 104, and the stop position of the sheet leading end is determined. The time B at which the leading edge of the sheet is expected to arrive at the registration roller 106
(B = (distance C to registration roller 106) / (first transport roller 10 until reaching registration roller 106)
Assuming a sheet transport speed β)) of 5, the control for restarting the first transport roller 105 was performed.

Thereafter, the sheet is transferred to the pre-registration roller 10.
7, reaches the stopped registration roller 106. Here, a predetermined amount of the sheet is fed by the pre-registration roller 107 in a state where the leading end of the sheet abuts against the stopped registration roller 106, and a loop is formed on the entire sheet, thereby correcting the skew of the sheet. . afterwards,
The registration roller 106 has a constant speed (process speed)
By starting rotation at α, the sheet is sent to the above-described image forming unit at the same timing as the image forming operation,
The toner image is transferred to the upper surface.

The sheet that has passed through the image forming section is
The toner image is fixed by being sent to the fixing unit 22 by the transport unit 21, and is placed on a discharge tray 25 via a discharge roller 24 in the case of one-sided copying, and is reversed by the sheet reversing unit 121 in the case of double-sided copying. Roller 1
The sheet reversing path is sequentially conveyed by 15, a double-sided left roller 114, and a double-sided right roller 113, and is again sent to the image forming section.

Here, the timing for starting the feeding of the second and subsequent sheets during continuous feeding is as follows.
The control is started after a lapse of a predetermined time from the time when the previous sheet restarts the first transport roller 105, and the feeding is controlled in the same manner as described above.

When the sheets are continuously fed from the other deck feeding sections 35 and cassette feeding sections 36 and 37, the same pre-registration operation as described above is performed.
Further, when performing double-sided copying by continuously feeding sheets from any of the sheet feeding units, the rotation of the double-sided right roller 113 is controlled based on the detection timing of the leading edge of the sheet by the sheet path sensor 119 on the double-sided conveyance path. Sheet sensor 11
A pre-registration operation has been performed in which the image forming apparatus is temporarily stopped between the position 9, the deck feeding section 35, and the junction of the two-sided conveyance path, and starts rotating again after a predetermined time has elapsed.

As described above, in the conventional copying machine, variations in the position of the leading edge of the sheet in the sheet feeding section are eliminated by performing the above-described pre-registration operation, and the leading edge position of the sheet is determined. To the registration roller 106. Further, even when a sheet is temporarily stopped in the conveyance path by the pre-registration operation, the sheet conveyance speed (the process speed α of the registration roller 106) in the image forming unit is set to be higher than the sheet conveyance speed in order to catch up with the previous sheet. The conveying speed β in the conveying path from the sheet feeding unit to the registration roller 106 is set to be faster.

[0026]

By the way, in order to continuously feed a sheet in an image forming apparatus and to form an image on many sheets in a short time, it is necessary to reduce a writing speed of a laser in an image forming section. Since there is a limit, it is necessary to shorten the timing of the sheet to be sent to the image forming unit by the registration roller 106, and therefore, the sheet is accurately transferred to the nip portion of the registration roller 106 at a slightly given sheet interval. It is becoming necessary to hit the tip.

However, in the conventional copying machine, when the thick paper is conveyed or when the conveyance rollers are worn out and slipping is likely to occur, the following problem occurs, and the sheet in the sheet conveyance path It was difficult to reduce the distance between the two.

That is, when the thick paper is conveyed or when the wear of the conveyance roller is advanced, the sheet from the pre-registration position A to the registration roller 106 after the restart of the first conveyance roller 105 during the pre-registration operation is performed. The transfer time B is delayed, and cpm (copy per mi
nute) decreased, and the sheet stop position varied with respect to the pre-resist position A. This allows
The sheet conveyance time of each sheet up to the registration roller 106 varies, and in this case, if the interval between the sheets in the sheet conveyance path is set to be narrowed, the next sheet in the state where the trailing edge of the previous sheet does not pass through the registration roller 106 is set. The sheet conveyance was unstable, for example, the leading edge of the sheet entered the registration roller 106.

In the conventional copying machine, a deck feeding unit 35 arranged on the left side of FIG.
The pre-registration position of the seventh conveyance roller 123, which is performed based on the detection result of the sheet path sensor 118 when the sheet is fed from the sheet path, is between the sheet path sensor 118 and the confluence of the two-sided conveyance path, as described above. Since the pre-registration position of the right side roller 113 is different from the pre-registration position of the right side roller 113 based on the detection result of the sheet path sensor 119 in the case of performing double side copying, each of the transport rollers 123, 11
The structure of software (control program) for controlling the rotation operation of No. 3 was complicated.

An object of the present invention is to provide a sheet conveying apparatus capable of stably and accurately inserting a sheet into a registration means and increasing a throughput, and an image forming apparatus having the same.

[0031]

A first structure of a sheet conveying apparatus according to the present invention is a sheet conveying apparatus for conveying sheets separated and fed one by one by a sheet feeding means to an image forming means. A registration unit that is disposed upstream of the forming unit in the sheet conveyance direction and that feeds the sheet to the image forming unit in synchronization with the image forming operation of the image forming unit and the timing of sheet conveyance; and a registration unit upstream of the registration unit in the sheet conveyance direction. A first sheet detecting unit for detecting a leading edge of the sheet, and a first sheet detecting unit disposed upstream of the first sheet detecting unit in the sheet conveying direction to detect a leading edge of the sheet separated and fed from the sheet feeding unit. The sheet separated and fed from the second sheet detecting unit and the sheet feeding unit is
Based on the detection result of the second sheet detection means, after temporarily stopping in the conveyance path, a pre-registration conveyance means for performing a pre-registration operation to convey toward the registration means, the pre-registration conveyance means, The pre-registration operation timing of the subsequent sheet is corrected based on the transport time from the temporary stop of the previous sheet to the detection by the first sheet detection means.

According to a second configuration of the sheet transport apparatus according to the present invention, in the first configuration, the correction of the pre-registration operation timing of the pre-registration transport unit is performed after the first sheet is temporarily stopped and the first sheet is stopped. The position where the subsequent sheet is temporarily stopped is changed based on the transport time until the detection is performed by the detection unit.

According to a third configuration of the sheet transport apparatus according to the present invention, in the second configuration, the correction of the pre-registration operation timing of the pre-registration transport means is performed after the first sheet is temporarily stopped and the first sheet is stopped. If the conveyance time until the detection is detected by the detection means is longer than a predetermined time, the position where the subsequent sheet is temporarily stopped is corrected so as to be closer to the registration means than the stop position of the previous sheet. Corrects the position where the subsequent sheet is temporarily stopped so that it is farther from the registration means than the stop position of the preceding sheet.

According to a fourth configuration of the sheet transport apparatus according to the present invention, in the first configuration, the pre-registration operation timing of the pre-registration transport unit is corrected by temporarily stopping the first sheet after the first sheet is temporarily stopped. The timing of sheet conveyance after the temporary stop of the subsequent sheet is changed based on the conveyance time until the sheet is detected.

According to a fifth configuration of the sheet transport apparatus according to the present invention, in the fourth configuration, the pre-registration operation timing of the pre-registration transport unit is corrected by temporarily stopping the first sheet from the first sheet detection unit. If the transport time until the sheet is detected is longer than the predetermined time, the timing of the sheet transport after the temporary stop of the subsequent sheet is corrected to be earlier than the sheet transport timing after the temporary stop of the previous sheet. However, if the time is short, the timing of sheet conveyance after the temporary stop of the subsequent sheet is corrected so as to be later than the timing of sheet conveyance after the temporary stop of the preceding sheet.

According to a sixth configuration of the sheet transport apparatus according to the present invention, in any one of the first to fifth configurations, the pre-registration transport unit includes a sheet transport timing after the previous sheet is temporarily stopped and the first transport timing. From the sheet detection timing of the sheet detection means, the value of the shift time with respect to the time at which the previous sheet should arrive at the registration means is calculated, and based on the value of the shift time, the next sheet is set within the predetermined time. And a correction means for correcting the pre-registration operation timing of the next sheet so as to arrive at the registration means.

A first main structure of the image forming apparatus according to the present invention is a sheet conveying apparatus having any one of the first to sixth structures, and an image forming apparatus for forming an image on a sheet conveyed by the sheet conveying apparatus. Means.

A second main configuration of the image forming apparatus according to the present invention includes a sheet feeding unit for separating and feeding sheets one by one, an image forming unit for forming an image on a sheet, and an image forming unit. A registration unit that is disposed upstream in the sheet conveyance direction and feeds the sheet to the image forming unit in synchronization with the image forming operation of the image forming unit and the sheet conveyance timing; and a sheet that is provided upstream of the registration unit in the sheet conveyance direction. First sheet detecting means for detecting the leading end;
A second sheet detecting unit that is disposed upstream of the sheet detecting unit in the sheet conveying direction and detects a leading end of the sheet separated and fed from the sheet feeding unit; and a second sheet detecting unit that is separated and fed from the sheet feeding unit. A first pre-registration conveying means for performing a pre-registration operation of temporarily stopping the sheet in the conveyance path based on the detection result of the second sheet detection means and then conveying the sheet toward the registration means; Sheet reversing and conveying means for reversing the image surface and conveying the sheet on which the image is formed by the means, and a sheet which is disposed upstream of the first sheet detecting means in the sheet conveying direction and conveyed from the sheet reversing and conveying means. A third sheet detecting unit that detects the leading edge of the sheet, and a sheet that is disposed upstream of the third sheet detecting unit in the sheet conveying direction and conveyed from the sheet reversing and conveying unit. And a second pre-registration conveying means for performing a pre-registration operation of temporarily stopping in the conveyance path based on the detection result of the sheet detection means, and then conveying to the registration means. The pre-registration conveyance means has a common position in the conveyance path to be temporarily stopped, and based on the conveyance time from the temporary stop of the previous sheet to the detection by the first sheet detection means, the subsequent sheet The pre-registration operation timing is corrected.

[0039]

Embodiments of the present invention will be described in detail with reference to the drawings.

First, a copying machine as an image forming apparatus to which the present invention is applied will be described with reference to the drawings. here,
The same parts as those in the related art are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 1 is a schematic sectional view of a copying machine to which the present invention is applied. In this embodiment, the control section 130 controls the sheet conveying speed of each roller provided in the sheet conveying path and the double-sided conveying path. Is controlled to be switchable as follows.

That is, the pre-registration roller 107 shown in FIG.
And a first transport roller 105 as a pre-registration transport unit upstream of the pre-registration roller 107 in the sheet transport direction.
The second transport roller 108 on the upstream side of the first transport roller 105 in the sheet transport direction can be switched between a process speed α, which is a sheet transport speed of the registration roller 106, and a first speed β, which is faster than the process speed α. Has become. Here, when the registration roller 106 starts rotating, the sheet is still held between the registration rollers 107, so that the registration roller 107 is rotated at the same process speed α as the registration rollers 106.

A third transport roller 109 upstream of the second transport roller 108 in the sheet transport direction, and a fourth transport roller 110 upstream of the third transport roller 109 in the sheet transport direction.
The fifth transport roller 111, the sixth transport roller 112 upstream of the fifth transport roller 111 in the sheet transport direction, and the seventh transport roller 123 upstream of the sixth transport roller 112 in the sheet transport direction. At the speed β.

Further, both right-side rollers 113, left-side left rollers 114, and reverse rollers 11
5 is switchable between the first speed β and the second speed γ for sheet reversal.

Each sheet path sensor 104, 116, 11
The arrangement of 7, 118, and 119 is the same as in the related art, and a sheet detection signal of each of these sheet path sensors is supplied to the control unit 130. Then, the control unit 130
Controls the rotation of each transport roller based on the detection timing of each sheet path sensor. In addition, the control unit 130 is configured to perform correction for pre-registration conveyance when performing continuous sheet feeding, and the details will be described later.

In this embodiment, the first speed β
Is 1.5 times the process speed α, and the second speed γ
Is 2.3 times the process speed α, but the present invention is not limited to this value.

Next, the conveyance operation of the copying machine according to the embodiment during sheet feeding will be described with reference to FIG. 2 by taking a case where sheets are continuously fed from the deck feeding section 34 as an example. Here, FIG. 2 is a diagram illustrating a positional relationship between the leading end and the trailing end of each sheet when the sheets are continuously fed from the deck feeding unit 34, and the like.

In this embodiment, as shown in FIG. 2, the distance between the trailing edge of the previous sheet and the leading edge of the next sheet is within a predetermined range at the position of the registration roller 106. Time t ₈ at which the trailing edge passes through the registration roller 106
The control is performed such that the leading edge of the next sheet reaches the registration roller 106 within a predetermined time (between the time B1 and the time B2 set in advance). The details of this control will be described later.

When continuous feeding of sheets from the deck feeding section 34 is started, the pickup motor 101, the feeding roller 102, the separating roller 103, the first conveying roller 105, and the pre-registration roller 107 are rotationally driven by the driving motor. You. At this time, the registration roller 106 is still in a stopped state.

The sheet S set on the deck 30 is first picked up by the pickup roller 101 by the feed roller 10.
Send to 2. Here, the sheet S is provided to face the feeding roller 102, and the separation roller 103 is provided with a force for rotating the sheet S in a direction opposite to the conveying direction with a constant torque.
Only the top sheet is separated.

The leading edge of the uppermost sheet is detected by the sheet path sensor 104 as the second sheet detecting means (t ₁ ), and the pre-registration disposed near the downstream side of the sheet path sensor 104 in the sheet conveying direction. It is sent to the first transport roller 105 as a transport unit, and is transported by the first transport roller 105 as a pre-register as follows.

That is, the control unit 130 determines the timing t _{2 when the} leading edge of the sheet reaches the predetermined position (pre-registration position) A on the downstream side of the sheet path sensor 104 in the sheet conveying direction.
The control for temporarily stopping the rotation of the first transport roller 105 is performed. Thereby, the stop position of the sheet leading edge is determined, and the variation in the sheet leading edge position at the start of feeding from the sheet deck 30 is removed as described above. Next, after a lapse of a predetermined time, the first transport roller 105 starts rotating again at the first speed β (t ₃ ), and the pre-registration roller 107 also rotates at the first speed β, as shown in FIG. First, the sheet is moved from the pre-registration position A to the registration roller 106.
(Registration sensor 120) at a transport speed β.

Then, the leading end of the sheet is
Once detected by the sheet conveyance direction upstream side registration sensor 120 disposed in the vicinity of 6 (t _4), as shown in FIG. 2, the pre-registration rollers 107, the rotation is stopped after a predetermined time has elapsed (t ₅₎ And then the registration roller 106
After a predetermined time (t ₇ ) after the rotation start time t 6, the rotation is started at the same process speed α as that of the registration roller 106.

By this operation, the front end of the sheet is transferred to the pre-registration roller 10 in a state where the front end of the sheet reaches the nip portion of the registration roller 106 whose rotation is stopped and the front end movement is prevented.
The skew is corrected by forming a predetermined loop by being conveyed by. Then, the pre-registration roller 107 stops at the timing of t ₅ in FIG. 2, and from this state, the registration roller 106 rotates at the process speed α from t ₆ to eliminate the loop formed on the sheet. the roller 107 is rotated at a process speed α from t _7, the sheet is to be fed to the image forming portion while maintaining a state there is no loop.

Next, the control for continuous sheet feeding will be described in detail. When the sheets are continuously fed, as described above, the previous sheet is
After a lapse of a predetermined time from the restart of the pre-registration conveyance in step 05, the feeding of the next sheet is started.
Specifically, as shown in FIG.
Time trailing edge of the preceding sheet leading end of the sheet before the start of rotation of the process speed α from the timing t ₆ to start to move to the image forming portion side from the timing t ₈ exiting the registration roller 106 of the (t ₈ - t ₆ = sheet length (L
1) / After the process speed α) and at a timing between the times B1 and B2 during which the sheet interval between the trailing edge of the previous sheet and the leading edge of the next sheet is not too wide, the next sheet Control is performed so that the leading end reaches the registration roller 106.

The first transport roller 105 for the next sheet
Restarts the pre-registration conveyance by the length C from the pre-registration position A to the registration roller 106 for the previous sheet by the sheet conveyance speed β of the first conveyance roller 105.
The controller 130 controls the first transport roller 105 to restart at the sheet transport speed β in anticipation of the time (numerical value on calculation) calculated by dividing by the formula (1) and the stop time (fixed value) of the registration roller 106. Perform control. This allows
The next sheet can reach the registration roller 106 between the predetermined times B1 and B2.

Here, the times B1 and B2 take account of errors that are inevitably generated, and the time B1 is a time when the sheet interval between the rear end of the previous sheet and the front end of the next sheet is smaller. The limit value, time B2, is a permissible limit value in which the sheet interval between the rear end of the previous sheet and the front end of the next sheet is wider.

On the other hand, when a sheet such as thick paper having a large conveyance resistance is conveyed, as shown in FIG. 3, the time required to reach the registration roller 106 (registration sensor 120) from the pre-registration position A is calculated. It may take longer than the above numbers. As shown in FIG. 4, when the actual time is closer to B2 than a certain threshold value Y, the interval between the sheets may exceed the allowable limit of time B2 due to variation.

In this embodiment, even in such a case, the following correction is performed by the control unit 130 so that the distance between the rear end of the previous sheet and the front end of the next sheet is reduced. It falls within a predetermined range before and after the registration roller 106.

In the present embodiment, the control unit 130
As shown in FIG. 7, the calculated time C from the time when the leading edge of the sheet is detected by the resist sensor 120 to the position of the pre-resist position A is calculated.
/ Β (known value) is monitored to determine whether or not the time actually taken based on the detection timing t ₄ by the registration sensor 120 is shifted. If the time is shifted, a correction value is calculated as follows. I do.

That is, the control unit 130 calculates the calculated time C / β until the leading edge of the sheet is detected by the registration sensor 120 from the pre-registration position A and the registration sensor 120
In the case where the actual time based on the detection timing t ₄ is shifted, the shift time X is calculated, and the time β is multiplied by half the time X / 2 of the shift time X (X / 2 ) The distance of the value of β is calculated as a correction value.

Here, the reason why the shift time X is halved is that if the value of Xβ obtained by multiplying the shift time X by the speed β is used as the correction value, when a sudden and large shift occurs, the next sheet is changed to Xβ. If the correction is made in step (1), there may be a problem that the trailing edge of the previous sheet overlaps the leading edge of the next sheet. Therefore, in order to make the next sheet leading edge reach the registration roller 106 within a predetermined range with respect to any deviation, the correction is performed based on a half value of the deviation time X. The reason for multiplying X by １ ／ is selected because the distribution of the deviation is a normal distribution and the population mean of the normal distribution is substantially at the center of the distribution.

Although the correction values are set as described above in the present embodiment, the present invention is not limited by the method of calculating the correction values.

The control unit 130 sets the stop position (pre-registration position) in the pre-registration operation of the next sheet by the first conveying roller 105 to this correction value (X / X)
2) The rotation of the first transport roller 105 is controlled so as to be shifted by β. As a result, the stop position of the next sheet in the pre-registration operation by the first transport roller 105 becomes closer to or farther from the registration roller 106 by (X / 2) β than A.

In the example shown in FIG. 3, the time from the time when the previous sheet is temporarily stopped and conveyed to the time when the registration sensor 120 detects the leading edge of the sheet is longer than the calculated time C / β. Is shifted closer to the registration roller 106 by (X / 2) β than A. If the time from the conveyance of the previous sheet after the temporary stop and the detection of the sheet leading edge by the registration sensor 120 is shorter than the calculated time C / β by the shift time X, the stop position is set to A. It may be corrected so as to be farther than the registration roller 106 by (X / 2) β.

By correcting the stop position as described above, the next sheet conveyed by the first conveying roller 105 rotating at the first speed β and the pre-registration roller 107 is moved from the stop position to the registration roller 106. As shown in FIG. 5, the distance to the registration roller 106 comes to a point near the center between the times B1 and B2.

FIG. 6 shows another embodiment of the correction control during pre-registration conveyance. As shown in FIG. 6, a similar effect can be obtained by leaving the pre-registration position A as it is, and starting the restart by the first transport roller 105 by shifting the timing by half the shift time X.

That is, the control unit 130 calculates the calculated time C / β until the leading edge of the sheet is detected from the pre-registration position A by the registration sensor 120 and the registration sensor 120
If the displaced and the detection timing t actually time taken based on ₄ by calculates the deviation time X, calculates the time X / 2 of half the deviation time X as a correction value. Then, the control unit 130 controls the first transport roller 1 for the next sheet.
The operation of the first transport roller 105 is controlled so that the restart timing in the pre-registration operation by 05 is earlier or later by this correction value X / 2.

In the example shown in FIG. 6, the time from the time when the previous sheet is temporarily stopped and conveyed to the time when the registration sensor 120 detects the leading edge of the sheet is longer than the calculated time C / β. The restart timing of the transport roller 105 is advanced by the correction value X / 2. In addition,
If the time from the conveyance of the previous sheet after the temporary stop and the detection of the leading edge of the sheet by the registration sensor 120 is shorter than the calculated time C / β by the shift time X,
What is necessary is just to delay the restart timing of the first transport roller 105 by the correction value X / 2.

As described above, according to the copying machine of the embodiment, the interval between the trailing edge of the previous sheet and the leading edge of the next sheet is always set before and after the nip portion of the registration roller 106 during continuous feeding of the sheet. Each sheet can stably and accurately enter the registration roller 106.

Next, in the copying machine according to the embodiment, a case where double-sided copying is performed and a case where sheets are continuously fed from the deck feeding unit 35 disposed on the left side of FIG. Will be described.

When performing double-sided copying, 1
The sheet on which the image has been formed on the first side enters the sheet reversing unit 121, is reversed by the reversing roller 115, and is a double-sided left roller 114, a double-sided right roller 113 which is a pre-registration conveying unit, and a sixth conveying roller 112. After being sent to the registration roller 106 via the fifth conveyance roller 111 and the registration pre-roller 107, sent again to the image forming unit by the registration roller 106, and forming an image on the second surface, the discharge tray is used as described above. It is discharged to 25.

At this time, the control unit 130 temporarily stops the rotation of the right and left rollers 113 at the timing when the leading end of the sheet comes to a predetermined position (pre-registration position) P on the downstream side of the sheet path sensor 119 in the sheet conveying direction, and then for a predetermined time. After the elapse, control to start rotation again is performed. As a result, the stop position of the leading end of the sheet on the reversing path is determined, and the reversing roller 115
The variation in the position of the leading end of the sheet at the time of reversal or the like is removed.

Here, during the pre-registration operation, the control unit 1
The control unit 30 calculates a correction value in the same manner as described above, and performs control to shift the pre-registration position P or the restart timing by the double-sided right roller 113 based on the calculated correction value.

That is, the control unit 130 determines whether the calculated time from the pre-registration position P to the registration sensor 120 detecting the leading edge of the sheet is different from the actual time based on the detection timing by the registration sensor 120. The correction value based on this shift time is calculated, and the pre-registration position P in the pre-registration operation of the next sheet or the timing of restart is adjusted to the shift amount according to the correction value. Control behavior.

When the sheets are continuously fed from the deck feeding section 35, the sheets stacked on the deck 31 are transferred to the deck feeding section 34 by the same mechanism as the deck feeding section 34 described above.
After being separated into sheets and sent to a seventh conveying roller 123 which is a pre-registration conveying means, and a pre-registration operation is performed by the seventh conveying roller 123, the sixth conveying roller 112, the fifth conveying roller 111, and the resist The sheet is sent to the registration roller 106 via the front roller 107, and is sent to the image forming unit by the registration roller 106.

At this time, the control unit 130 temporarily stops the rotation of the seventh transport roller 123 at the timing when the leading edge of the sheet reaches a predetermined position (pre-registration position) P on the downstream side of the sheet path sensor 118 in the sheet transport direction, and After the elapse of time, control is performed to start rotation again. As a result, the variation in the position of the leading edge of the sheet when feeding from the sheet deck 31 is started is removed.

Here, during the pre-registration operation, the control unit 1
The control unit 30 calculates a correction value in the same manner as described above, and performs control to shift the pre-registration position P or the restart timing by the seventh transport roller 123 based on the calculated correction value.

That is, the control unit 130 determines whether the calculated time from when the leading edge of the sheet is detected by the registration sensor 120 from the pre-registration position P to the actual time based on the detection timing by the registration sensor 120 is different. The seventh transport roller 123 calculates a correction value based on the shift time, and adjusts the pre-registration position P or restart timing in the pre-registration operation of the next sheet to a shift amount according to the correction value. Control the operation of.

As described above, in the copying machine according to the embodiment, the pre-registration operation performed by the right-sided double roller 113 at the time of double-sided copying and the seventh conveyance roller 123 performs the continuous feeding of the sheet from the deck feeding unit 35. Since the pre-registration position for the pre-registration operation to be performed is set to the same P position, the control unit 130 controls the two-sided right
The standard of operation control of the thirteenth and seventh transport rollers 123 can be shared, and the control program can be simplified.

Further, the sheet can be conveyed to the registration roller 106 between small sheets and with high accuracy, and the throughput and the reliability of the apparatus can be mutually increased.

Although the present invention has been described in detail above, the present invention is not limited to an electrophotographic copying machine, but may be any recording system, and is not limited to a copying machine. It may be a printer or a facsimile.

[0083]

As described above in detail, according to the present invention, a sheet conveying apparatus capable of stably and accurately injecting a sheet into a resist means, having high reliability and improving throughput, and a sheet conveying apparatus capable of improving throughput. It is possible to provide an image forming apparatus provided with.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a configuration of a copying machine as an image forming apparatus to which the present invention is applied.

FIG. 2 is a diagram for explaining an operation during sheet conveyance in the copying machine.

FIG. 3 is a diagram illustrating a continuous sheet feeding operation when a sheet having a large conveyance resistance is conveyed.

FIG. 4 is a diagram illustrating an operation when a sheet having a large conveyance resistance is conveyed.

FIG. 5 is a diagram for explaining a case in which a pre-registration position of a next sheet is corrected so as to be shifted to a registration roller side.

FIG. 6 is a diagram for describing a case where the timing of restarting sheet conveyance after stopping the pre-registration without changing the pre-registration position is corrected for the next sheet.

FIG. 7 is a schematic sectional view showing a configuration of a copying machine as a conventional image forming apparatus.

FIG. 8 is a diagram for explaining an operation during sheet conveyance in a conventional image forming apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Copier main body 2 Document table 3 Document feeder 4 Document reading section 5 Writing laser section 12 Photosensitive drum 13 Charger 14 Developing device 19 Transfer charger 20 Separate charger 21 Transport section 22 Fixing device 24 Discharge roller 25 Discharge tray 26 Cleaner 30, 31 Deck 32, 33 Sheet cassette 34, 35 Deck feeding unit 36, 37 Cassette feeding unit 101 Pickup roller 102 Feeding roller 103 Separation roller 104 Sheet path sensor (second sheet detecting unit) 116, 117, 118 Sheet path sensor 105 First conveyance roller (pre-registration conveyance means) 106 Registration roller (registration means) 107 Pre-registration roller (registration means) 108 Second conveyance roller 109 Third conveyance roller 110 Fourth conveyance roller 111 Fifth conveyance roller 112 Sixth conveyor R 113 Double-sided right roller (second pre-registration conveying unit) 114 Double-sided left roller 115 Reverse roller 118 Sheet path sensor (second sheet detecting unit) 119 Sheet path sensor (third sheet detecting unit) 120 Register sensor (second 1 sheet detecting means) 121 sheet reversing unit 123 seventh conveying roller (first pre-registration conveying means) 130 control unit (correction means) A, P pre-registration position

Claims (13)

[Claims] 1. A sheet conveying device for conveying sheets separated and fed one by one by a sheet feeding unit to an image forming unit, wherein the image forming unit is disposed upstream of the image forming unit in a sheet conveying direction. Register means for feeding the sheet to the image forming means at the same timing as the image forming operation and sheet conveyance, and first sheet detecting means provided upstream of the resist means in the sheet conveying direction and detecting the leading edge of the sheet A second sheet detecting unit disposed upstream of the first sheet detecting unit in the sheet conveying direction and detecting a leading end of a sheet separated and fed from the sheet feeding unit; and the sheet feeding. Sheets separated and fed from the means
A pre-registration conveying means for performing a pre-registration operation of temporarily stopping in a conveyance path based on a detection result of the second sheet detection means and then conveying the pre-registration toward the registration means; Means for correcting a pre-registration operation timing of a subsequent sheet based on a transport time from a temporary stop of the preceding sheet to a detection by the first sheet detecting means. . 2. The pre-registration operation timing of said pre-registration conveyance means is corrected based on a conveyance time from a temporary stop of a previous sheet to a detection of said sheet by said first sheet detection means. 2. The sheet conveying apparatus according to claim 1, wherein the position at which the sheet is temporarily stopped is changed. 3. The correction of the pre-registration operation timing of the pre-registration conveyance means is performed by setting a conveyance time from a temporary stop of a previous sheet to a detection of the sheet by the first sheet detection means being a predetermined time. If it is longer than the stop position of the subsequent sheet, the stop position of the preceding sheet is corrected so as to be closer to the registration means, and if it is shorter, the position of the subsequent sheet is temporarily stopped. 3. The sheet conveying apparatus according to claim 2, wherein the correction is performed so as to be farther from the registration unit than the stop position of the sheet. 4. The pre-registration operation timing of the pre-registration conveyance means is corrected based on a conveyance time from a time when the previous sheet is temporarily stopped to a time when the first sheet detection means detects the sheet. 2. The method according to claim 1, wherein the timing of sheet conveyance after the sheet is temporarily stopped is changed.
The sheet conveying device as described in the above. 5. The correction of the pre-registration operation timing of the pre-registration conveying means is such that the conveyance time from the temporary stop of the previous sheet to the detection of the sheet by the first sheet detection means is longer than a predetermined time. If the length is long, the timing of the sheet conveyance after the temporary stop of the subsequent sheet is corrected so as to be earlier than the timing of the sheet conveyance after the temporary stop of the preceding sheet. 5. The sheet conveying apparatus according to claim 4, wherein the sheet conveying timing is corrected so as to be delayed from the sheet conveying timing after the previous sheet is temporarily stopped. 6. The pre-registration conveying means determines a time at which the previous sheet should arrive at the registration means based on a sheet conveyance timing after the previous sheet is temporarily stopped and a sheet detection timing of the first sheet detection means. Correction means for calculating a shift time value for the next sheet and correcting the pre-register operation timing of the next sheet based on the shift time value so that the next sheet arrives at the registration means within a predetermined time. The sheet conveying device according to any one of claims 1 to 5, further comprising: 7. An image, comprising: the sheet conveying device according to claim 1; and the image forming unit that forms an image on a sheet conveyed by the sheet conveying device. Forming equipment. 8. A sheet feeding means for separating and feeding one sheet at a time, an image forming means for forming an image on a sheet, and an image forming means arranged upstream of the image forming means in a sheet conveying direction. Register means for feeding the sheet to the image forming means at the same timing as the image forming operation and sheet conveyance, and first sheet detection means provided upstream of the resist means in the sheet conveyance direction to detect the leading edge of the sheet. A second sheet detecting unit disposed upstream of the first sheet detecting unit in a sheet conveying direction and detecting a leading end of a sheet separated and fed from the sheet feeding unit; and the sheet feeding unit. Sheet that has been separated and fed from
A first pre-registration conveyance unit that performs a pre-registration operation of temporarily stopping in a conveyance path based on a detection result of the second sheet detection unit and then conveying the conveyance unit toward the registration unit; A sheet reversing and conveying means for reversing the image surface and conveying the sheet on which the image is formed, and being disposed upstream of the first sheet detecting means in the sheet conveying direction and conveyed from the sheet reversing and conveying means. A third sheet detecting unit for detecting a leading edge of the sheet, a sheet disposed upstream of the third sheet detecting unit in a sheet conveying direction, and conveying the sheet conveyed from the sheet reversing conveying unit to the third sheet. A second pre-registration transport that performs a pre-registration operation of temporarily stopping in the transport path based on the detection result of the detection unit and then transporting the same toward the registration unit The first and second pre-registration conveyance means share a predetermined position in the conveyance path to be temporarily stopped, and the first and second pre-registration conveyance means communicate with the first sheet detection means after the previous sheet is temporarily stopped. An image forming apparatus that corrects a pre-registration operation timing of a subsequent sheet based on a transport time until the detection is performed. 9. The correction of the pre-registration operation timing of the first and second pre-registration conveyance means is performed after the previous sheet is temporarily stopped until the first sheet is detected by the first sheet detection means. 9. The image forming apparatus according to claim 8, wherein a position at which a subsequent sheet is temporarily stopped is changed based on time. 10. The correction of the pre-registration operation timing of the first and second pre-registration conveyance means is performed after the previous sheet is temporarily stopped until the first sheet is detected by the first sheet detection means. If the time is longer than a predetermined time, the temporarily stopped position of the subsequent sheet is corrected so as to be closer to the registration means than the stopped position of the previous sheet. 10. The stop position is corrected so as to be farther from the registration means than the stop position of the preceding sheet.
The image forming apparatus as described in the above. 11. The correction of the pre-registration operation timing of the first and second pre-registration conveyance means is performed by a conveyance time from a temporary stop of the previous sheet to a detection of the sheet by the first sheet detection means. 9. The sheet conveying apparatus according to claim 8, wherein a timing of conveying the sheet after temporarily stopping the subsequent sheet is changed based on the timing. 12. The correction of the pre-registration operation timing of the first and second pre-registration conveyance means is performed by a conveyance time from a stop of a previous sheet to a detection of the sheet by a first sheet detection means. However, if the time is longer than a predetermined time, the timing of the sheet conveyance after the temporary stop of the subsequent sheet is corrected to be earlier than the sheet conveyance timing after the temporary stop of the previous sheet, and if the time is short, the subsequent sheet is corrected. 12. The sheet conveying apparatus according to claim 11, wherein a timing of conveying the sheet after the temporary stop is corrected so as to be later than a timing of conveying the previous sheet after the temporary stop of the sheet. 13. The first and second pre-registration conveyance units determine whether a previous sheet is in the registration mode based on a sheet conveyance timing after the previous sheet is temporarily stopped and a sheet detection timing of the first sheet detection unit. Calculating the value of the shift time with respect to the time to arrive at the means, and based on the value of the shift time, the pre-register operation of the next sheet so that the next sheet arrives at the registration means within a predetermined time. The sheet conveying apparatus according to claim 8, further comprising a correction unit configured to correct a timing.