JPH11100135A - Sheet conveyance device and picture image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain a proper interval between a preceding sheet and a following sheet and convey sheet efficiently when sheet is separated and conveyed from a loading means on which a plurality of sheets are loaded. SOLUTION: This device has a loading means 120 on which sheets are loaded, a feeding means 110 which feeds sheet from the loading means, a separation means 113 which separates a preceding sheet from a following sheet, conveyance means 114, 116 which convey sheet from the separation means, and sheet detection means 115, 117 which detect sheet. In this case, when the preceding sheet passes the detection means 115 and a tip of the following sheet is detected by the detection means 115, the drive of the separation means 113 and the conveyance means 114 which convey the following sheet is temporarily stopped. When a rear end part of the preceding sheet is detected by the detection means 117 and an interval between papers is detected by the detection means 115, the separation means 113 and the conveyance means 114 are driven again, and they are driven again by delaying the timing for restart by a predetermined time if the interval between papers is not detected.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the conveyance so as to maintain a predetermined sheet interval on a conveyance path when there is a variation between the preceding sheet and the succeeding sheet in a sheet feeding operation during continuous printing. And an image forming apparatus such as a printer, a copying machine, a facsimile, etc., which achieves the maximum throughput.

[0002]

2. Description of the Related Art A prior art example of a printer in an image forming apparatus will be described with reference to FIG. 1 according to an embodiment of the present invention. In FIG. 1, 101 is a photosensitive drum as a carrier on which an electrostatic latent image is formed, 102 is a semiconductor laser as a light source for forming the latent image,
Reference numeral 103 denotes a rotating polygon mirror rotated by a scanner motor 104, and reference numeral 105 denotes a laser beam emitted from the semiconductor laser 102 and scanning the photosensitive drum 101.

Reference numeral 106 denotes a charging roller for uniformly charging the photosensitive drum 101, and 107 denotes a photosensitive drum 101.
This is a developing device for developing the electrostatic latent image formed thereon with toner as a developer. Reference numeral 108 denotes a transfer roller as a transfer unit that transfers the toner image developed by the developing unit 107 onto a sheet (hereinafter, referred to as recording paper) such as paper, and 109 fixes the toner transferred to the recording paper by heating and fusing. This is a fixing roller as a means.

A cassette feed roller 110 feeds paper from a cassette 120 having a function of discriminating the size of a plurality of sheets of recording paper that can be stacked by rotating once, and feeds the sheet to a conveyance path. This is a manual paper feed roller that feeds a sheet to a conveyance path from a manual paper feed port that does not have a function of identifying a size. A transport roller 114 transports the paper fed from the cassette.

Reference numeral 115 denotes a pre-feed sensor for detecting the leading edge and the trailing edge of the fed paper. 116 denotes a pre-transfer roller for feeding the transported paper to the photosensitive drum 101.
Reference numeral 17 denotes a top sensor for synchronizing image writing (recording / printing) on the photosensitive drum 101 with the fed paper and feeding the fed paper, and measuring the length of the fed paper in the feeding direction. It is. Reference numeral 118 denotes a discharge sensor for detecting the presence or absence of a sheet after fixing, and reference numeral 119 denotes a discharge roller for discharging the sheet after fixing outside the apparatus.

FIG. 2 is a block diagram of a circuit configuration of a control system for controlling such a mechanism. In FIG.
Reference numeral 201 denotes a printer controller for expanding image code data sent from an external device such as a host computer (not shown) into bit data necessary for printing by a printer, reading information inside the printer, and displaying the read information.

Reference numeral 202 denotes a printer engine control unit for controlling the operation of each unit of the printer engine in accordance with an instruction from the printer controller 201 and for notifying the printer controller 201 of printer internal information. 2
Reference numeral 03 denotes a paper transport control unit that drives / stops a motor and rollers for transporting recording paper in accordance with an instruction from the printer engine control unit 202. Reference numeral 204 denotes a printer that controls output of each high voltage in each process such as charging, development, and transfer. Engine control unit 2
02 is a high-pressure control unit performed according to the instruction of 02. 205
Reference numeral denotes an optical system control unit that controls driving / stop of the scanner motor 104 and lighting of the laser beam in accordance with an instruction from the engine control unit 202. Reference numeral 206 denotes a sensor input unit for inputting a detection signal from each sensor. Reference numeral 207 denotes a fixing temperature control unit for adjusting the temperature of the fixing unit to a temperature designated by the printer engine control unit 202.

In FIG. 1, a sheet feeding operation from a cassette as a sheet stacking means capable of recognizing a sheet size is performed by pushing a predetermined number or less of sheets of paper into a conveying path by a separating claw 112 with rotation of a sheet feeding roller 110, and The roller (retard roller) 113 controls such that only one sheet of paper extruded from the separation claw is separated and sent to the conveyance path.

[0009]

However, in the above-described image forming apparatus, in the conventional sheet feeding configuration, when there is a type in which the leading end of the sheet loaded in the cassette exceeds the separation claw, the image forming apparatus stands by. The position of the leading end of the sheet varies from the separating claw to the FR roller. Therefore, when continuous printing is performed, a certain interval between the preceding sheet and the succeeding sheet may not be maintained due to the position of the leading end of the scattered subsequent sheet.

That is, the following two cases can be considered depending on the setting of the feed timing of the succeeding paper during continuous printing.

1. When the feeding operation of the succeeding sheet is performed at a timing assuming that the leading end of the succeeding sheet is located at the FR roller, the gap between the leading sheet and the preceding sheet occurs when the actual leading end is at the position of the separation claw. When the maximum throughput (processing) cannot be achieved due to being too long.

2. When the feeding operation of the succeeding paper is performed at a timing assuming that the leading end of the sheet is located at the separation claw, when the actual leading end of the sheet is at the FR roller, the gap between the leading sheet and the preceding sheet is small or overlaps.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to secure a necessary minimum sheet interval between a preceding sheet and a succeeding sheet during continuous printing. Another object of the present invention is to maintain a constant interval between sheets regardless of the position of the leading end of the sheets stacked on the cassette, thereby improving the maximum throughput.

[0014]

In order to achieve the above object, a typical configuration of the present invention is a sheet stacking means capable of stacking a plurality of sheets, and feeding sheets from the stacking means. Feeding means; separating means for separating a sheet fed by the feeding means from a succeeding sheet; at least two conveying means for feeding the sheet separated from the succeeding sheet by the separating means; A sheet conveying device having at least two sheet detecting means for detecting a sheet on a conveying path formed by a feeding means and the conveying means, wherein a preceding sheet is detected on the conveying path based on detection information of the sheet detecting means; So that the interval between the next sheet and the subsequent sheet is constant, independently of the conveying means downstream of the sheet detecting means at the most upstream in the sheet conveying direction, and above the sheet detecting means. Characterized in that it has a control means for controlling driving and stopping of said separating means and conveying means.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) Hereinafter, an embodiment of an image forming apparatus provided with a paper feed / conveyance control device to which the present invention is applied will be described with reference to the drawings. FIG. 1 is a schematic diagram of a printer provided with a paper feeder according to the present invention, FIG. 2 is a block diagram showing a circuit configuration of a control system of the printer, and FIG. 3 shows a sequence of a paper feeding operation by the control system. It is a flowchart. Since FIGS. 1 and 2 have been described in the section of the conventional example, detailed description is omitted here.

FIG. 3 shows a flowchart of a control sequence of the sheet feeding and conveyance according to the present embodiment. This is a sequence in a case where the engine control unit 202 performs printing on a plurality of sheets according to an instruction from the printer controller 201. In FIG. 3, the feeding of the second and subsequent sheets of continuous printing is performed in step S301.
, And waits until a paper feed timing is reached such that a predetermined paper interval is set between the preceding paper. When the timing at which paper can be fed is reached, the paper feed roller 110 as a feeding means is rotated once in S302, and the paper feeding operation of the paper loaded on the cassette capable of recognizing the paper size is started. The above operation is the same as the conventional operation.

From the start of the paper feeding operation, the presence / absence of paper of the pre-feed sensor 115 as the first sheet detecting means is monitored (S302). This is because the time is measured from the leading edge of the preceding sheet, which is a sheet, and the trailing edge of the sheet is the pre-feed sensor 1.
15 until it is determined that it has passed (S306). Although a mechanical sensor may be used as the pre-feed sensor and the top sensor in the present invention, an optical photo sensor is preferable.

During this period, the pre-feed sensor 115
Detects that there is no paper (the trailing edge of the preceding paper),
In step 4, the leading edge of the succeeding sheet fed is detected. When the leading edge of the succeeding paper is detected, the transport rollers 114 and F
The driving of the R roller 113 is stopped, and the succeeding sheet is set in a standby state (S305).

If the pre-feed sensor 115 cannot detect the interval between the preceding sheet and the succeeding sheet within the predetermined time set in step S306, it is determined in step S307 that the sheet interval has not been detected, and the first transport unit of the sheet feeding mechanism is determined. Then, the driving of the conveying roller 114 and the retard roller as the separating means, that is, the FR roller 113 is stopped (S305).

Then, the trailing edge of the preceding sheet is detected by the top sensor 117 as the second sheet detecting means (S3).
08). If the trailing edge of the paper has been detected, it is determined in S307 whether the paper interval has been detected (S309). If the sheet interval has been detected, at the same time or after a predetermined period of time after the detection of the top sensor 117, in step S311 the driving of the transport rollers 114 and the FR roller 113 serving as the sheet feeding mechanism is restarted, and the subsequent sheet is transported in the second transport mode. It is fed to a pre-transfer roller 116 as a means. If it is detected in S307 that the paper interval has not been detected, the top sensor 117 detects the trailing edge of the preceding paper (S307).
308), a predetermined time (from the detection by the top sensor when the sheet interval is detected,
4. Time longer than drive restart time of FR roller 113)
After the interval (S310), the driving of the conveying roller 114 and the FR roller 113 as the sheet feeding mechanism is started in S311, and the succeeding sheet is fed to the pre-transfer roller 116.

As described above, when the prefeed sensor 115 cannot detect the interval between the preceding sheet and the succeeding sheet (when the trailing edge of the preceding sheet and the leading edge of the succeeding sheet overlap), the sheet interval cannot be detected. In this case, the restart timing of the sheet feeding mechanism is delayed by a predetermined time, thereby making it possible to surely open the space between the preceding sheet and the succeeding sheet by a predetermined distance. If the sheet interval can be detected, the trailing edge of the preceding sheet is detected by the top sensor 117.
By starting conveyance of the succeeding paper when passing through
The distance between sheets can be set to a predetermined distance.

(Embodiment 2) Next, Embodiment 2 of the present invention
Will be described with reference to FIG. The same printer and control system as those shown in FIGS. 1 and 2 are used. FIG. 4 is a flowchart showing a sequence of the sheet feeding operation of this embodiment performed by the control system.

In the present embodiment, the feed interval when the space between the preceding sheet and the succeeding sheet cannot be detected by the pre-feed sensor 115 during continuous printing is made variable, and the pre-feed sensor 115 starts the next succeeding sheet. This is to ensure that the sheet interval can be detected. When the sheet interval is detected, the same operation as in the above embodiment is performed.

FIG. 4 illustrates a control sequence of the sheet feeding and conveyance realized in the present embodiment. This is the engine control unit 20
Reference numeral 2 denotes a sequence when printing a plurality of sheets according to an instruction from the printer controller 201. In FIG.
For the second and subsequent sheets of the continuous printing, the process waits until the sheet feeding timing is reached such that a predetermined sheet interval is set between the preceding sheet in S401. If it is time to feed paper, S4
At 02, the paper feed roller 110 is rotated once to start the paper feed operation of the paper loaded on the cassette capable of recognizing the paper size.

From the start of the sheet feeding operation, the pre-feed sensor 1
The presence or absence of the 15 sheets is monitored (S403). this is,
The time is measured from the leading edge of the preceding paper, and the time is measured until it is determined that the trailing edge of the paper has passed the pre-feed sensor 115 (S40).
4).

If the pre-feed sensor 115 detects that there is no paper (the trailing edge of the preceding paper) during this period, it is determined that the paper interval has been detected in S405, and the leading edge of the succeeding paper fed in S406 is detected. . Then, when the pre-feed sensor 115 detects the leading edge of the succeeding paper (S406), the driving of the conveying roller 114 and the FR roller 113 of the paper feeding mechanism is stopped (S409).

If the pre-feed sensor 115 cannot detect the interval between the preceding sheet and the succeeding sheet within the predetermined time detected in step S404, it is determined in step S408 that the sheet interval has not been detected.
At 09, the conveying roller 114 of the sheet feeding mechanism and the FR roller 11
3 is stopped.

Thereafter, the trailing edge of the preceding sheet is detected by the top sensor 117 (S410). When the trailing edge of the preceding paper is detected, in S411, the transport rollers 11
4. The driving of the FR roller 113 is started, and the succeeding paper is fed to the pre-transfer roller 116. Thereafter, in step S412, a request for feeding the succeeding paper (print request) by the printer controller 201 is confirmed, and if there is no request, the sequence ends. If there is a request, the time until the paper feeding operation of the succeeding paper is started is set in S413, and the paper feeding operation from S401 is repeated.

The setting of the time until the feeding of the succeeding paper set in S413 is changed between when it is determined that the paper interval is detected in S405 and when it is determined that the paper interval is not detected in S408. . When it is determined in S408 that the paper interval has not been detected, a time longer than the case where it is determined in S405 that the paper interval has been detected is set to a predetermined time. As this time, a time obtained by dividing at least the distance from the separation claw 112 to the nip of the FR roller 113 by the transport speed is set.

By performing such time setting, the pre-feed sensor 115 can detect the interval between the next succeeding sheet and the preceding sheet, and a stable sheet feeding operation can be performed.

Further, such a time setting is made because the leading end of the paper loaded in the cassette capable of recognizing the paper size and capable of loading a plurality of sheets is waiting between the separation claw 112 and the FR roller 113. Make such settings. In other words, when the pre-feed sensor 115 cannot detect the sheet interval during the continuous printing, the standby position of the leading end of the paper stacked in the cassette is the position of the FR roller, so However, even if the timing of starting the feeding operation of the succeeding paper is delayed, a desired paper interval can be obtained. Therefore, it is not impossible to achieve the throughput.

In this embodiment, when the pre-feed sensor 115 cannot detect the sheet interval, the start of the sheet feeding operation for only one succeeding sheet is delayed. Needless to say, it is good.

Embodiment 3 Hereinafter, Embodiment 3 according to the present invention will be described mainly with reference to FIG. The same printer and control system as those shown in FIGS. 1 and 2 are used.

In the present embodiment, the feed interval when the space between the preceding sheet and the succeeding sheet cannot be detected by the pre-feed sensor 115 during continuous printing is made variable, and the pre-feed sensor 115 starts from the next succeeding sheet. To make sure that the sheet interval can be detected.

In the second embodiment, when the paper interval cannot be detected by the pre-feed sensor 115 during continuous printing,
The timing of starting the feeding operation of the next succeeding paper or a predetermined number of papers from the next succeeding paper is delayed. This makes it possible to always detect the sheet interval by the pre-feed sensor 115, thereby enabling a stable sheet feeding operation.

On the other hand, in the present embodiment, if the sheet interval cannot be detected by the pre-feed sensor 115 during continuous printing, the start timing of the feeding operation of the next succeeding sheet is delayed, and the feeding time at that time is delayed. Is measured, and when it is detected that the predetermined paper feeding time is reached, the timing of starting the paper feeding operation of the succeeding paper is returned to the default, that is, the initial setting.

FIG. 5 illustrates a control sequence of the sheet feeding and conveyance realized in the present embodiment. This is the engine control unit 20
Reference numeral 2 denotes a sequence when printing a plurality of sheets according to an instruction from the printer controller 201. However, steps S501 to S511 in FIG. 5 correspond to steps S401 to S4 in FIG.
Since this is the same as that described in Embodiment 12, and has been described in Embodiment 2, the detailed description is omitted here.

In FIG. 5, in step S511, a request for feeding a succeeding sheet (print request) by the printer controller 201 is confirmed. If there is no request, the sequence is terminated.
If there is a request, the time until the paper feeding operation of the succeeding paper is started is set in S512, and the paper feeding operation from S501 is repeated.

The setting of the time until the feeding of the succeeding paper set in S512 is changed between the case where it is determined that the paper interval is detected in S505 and the time when it is determined that the paper interval is not detected in S507. . When it is determined in S507 that the paper interval has not been detected, a time longer than the case where it is determined that the paper interval has been detected in S505 is set. This is at least the separation claw 1
A time obtained by dividing the distance from 12 to the nip of the FR roller 113 by the transport speed is set.

In step S513, it is determined whether the sheet interval has been detected in step S505 or not. In step S507, it is determined whether the sheet interval has not been detected.
From 01, the sheet feeding operation is repeated. Conversely, if it is determined in S507 that the sheet interval has not been detected, the following sheet feed time detection sequence is executed.

In step S514, the process waits until the timing for starting the feeding of the succeeding sheet set in step S512 is reached.
0 is rotated once, and the paper feeding operation of the paper loaded in the cassette capable of recognizing the paper size is started. S at the same time as the paper feeding operation starts
At 515, the timer for measuring the paper feed time is cleared, and the timer counter is started to increment.

Thereafter, in step S516, the pre-feed sensor 1
At 15, the leading end of the paper that has been fed is detected. This is detected until the trailing edge of the preceding sheet passes through the pre-feed sensor 115. If the pre-feed sensor 115 cannot detect the sheet interval between the preceding sheet and the succeeding sheet during this time, it is determined that the sheet interval has not been detected in S518, and the sheet feeding and conveying operation is repeated from S508 again. If the sheet interval at the trailing edge of the preceding sheet is detected in S516, it is determined that the sheet interval is detected in S519. Thereafter, in S520, the leading edge of the succeeding sheet is detected. S520
If the leading edge of the succeeding paper is detected in step S521, the processing proceeds to step S521.
The increment operation of the timer counter started at 515 ends, and at step S522, the conveying roller
14. The driving of the FR roller 113 is stopped.

In step S523, similarly to step S509, it is detected whether or not the trailing edge of the preceding sheet has passed the top sensor 117. At the time when the trailing edge of the preceding paper has passed the top sensor 117, in S524, the transport rollers 114,
The driving of the roller 113 is restarted.

In step S525, a paper feed request (print request) from the printer controller 201 is checked. If there is no request, the paper feed operation sequence ends. Conversely, when a request is made, the timing for starting the feeding operation of the succeeding paper is set in S526. The paper feed operation start timing is based on the value of the timer counter that stopped the increment operation in S520, and the standby position of the leading end of the preceding paper is determined by the separation claw 112 or FR.
The position of the roller 113 is calculated. When the paper feed operation is started, the standby position of the leading edge of the paper is set to
The setting is made according to the position of each of the rollers 113.

If it is determined that the standby state is at the separation claw 112, the paper feed control is performed from S501. If it is determined that the standby state is at the position of the FR roller 113, the process proceeds to S51.
Then, the paper feed control from step 4 is performed.

As described above, when the paper interval cannot be detected by the pre-feed sensor 115, the start of the feeding operation of the succeeding paper is delayed, the feeding time of the paper is measured, and the standby position of the paper is recognized. . Then, when it is determined that the standby position is located at the separation claw 112 which is the default, the paper feeding operation start time is returned to the default, thereby enabling a stable paper feeding operation. When the paper feed operation start timing is delayed, the standby position of the paper is at the position of the FR roller 113, and even if the paper feed operation start timing is delayed, the throughput does not decrease.

In this embodiment, the stop position of a specified sheet is estimated from the measured sheet feeding time.
The paper feed permission timing may be set linearly from the paper feed time. Also, it has been described that the paper feeding time is measured only when the pre-feed sensor 115 cannot detect the paper interval during continuous printing. Needless to say, there is no problem if you give feedback to. The sheet conveying device according to the above embodiment can efficiently convey the sheet while properly maintaining the sheet interval, and the image forming apparatus for the sheet conveyed by the sheet conveying device secures the sheet interval. Thereby, the operability and reliability are improved.

[0048]

As described above, according to the present invention,
In the case of continuous image formation, when the sheet interval between the preceding sheet and the succeeding sheet cannot be detected by the first sheet detecting unit,
The required interval between sheets is ensured by delaying the restart timing from the normal time. In this case, control is performed such that the sheet interval can be detected at the first sheet detecting unit by delaying the start timing of the sheet feeding operation of the subsequent sheet. In addition, when the timing is delayed, the sheet interval required for sheet feeding and conveyance is secured by returning to the default based on a predetermined number of sheets to be conveyed thereafter or the measurement result of the sheet feeding time of the succeeding sheet. However, sheet conveyance can be performed efficiently without reducing the maximum processing amount.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an embodiment of a sheet conveying apparatus and an image forming apparatus according to the present invention.

FIG. 2 is a diagram showing a control unit in the image forming apparatus.

FIG. 3 is a diagram showing one embodiment of a control sequence of the transport device according to the present invention.

FIG. 4 is a second diagram illustrating a control sequence of the transport apparatus according to the present invention.
Showing an embodiment of

FIG. 5 is a third control sequence of the transport device according to the present invention.
Showing an embodiment of

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 ... Photoreceptor drum 102 ... Semiconductor laser 106 ... Charge roller 107 ... Developer 108 ... Transfer roller 109 ... Fixing roller 110 ... Paper feeding roller 112 ... Separation claw 113 ... FR roller 114 ... Conveying roller 115 ... Pre-feed sensor 116 ... Transfer Front roller 117: Top sensor 120: Cassette

Claims (7)

[Claims] 1. A sheet stacking means capable of stacking a plurality of sheets, a feeding means for feeding sheets from the stacking means, and a sheet fed by the feeding means being separated from a subsequent sheet. Separating means for conveying a sheet separated from a succeeding sheet by the separating means.
A sheet conveying device having two conveying units, and at least two sheet detecting units for detecting a sheet on a conveying path formed by the feeding unit and the conveying unit, based on detection information of the sheet detecting unit. The separation means upstream of the sheet detection means independently of the conveyance means downstream of the sheet detection means at the most upstream in the sheet conveyance direction so that the interval between the preceding sheet and the succeeding sheet on the conveyance path is constant. A sheet conveying apparatus comprising a control unit for controlling driving and stopping of the conveying unit. 2. The sheet detecting device according to claim 1, wherein the sheet detecting device comprises: a first sheet detecting device disposed on an upstream side in a sheet conveying direction; and a second sheet detecting device disposed on a downstream side. A sheet separating unit and a first conveying unit are arranged upstream of the first sheet detecting unit, and a second conveying unit is arranged downstream of the first sheet detecting unit. Sheet conveying device. 3. The separation means for conveying a succeeding sheet when the first sheet detecting means determines that the interval between the preceding sheet and the succeeding sheet is short at the rear end of the preceding sheet. The driving of the conveying means is stopped, and the interval between the preceding sheet and the succeeding sheet is detected by the first sheet detecting means. When the second sheet detecting means detects the rear end of the preceding sheet, A sheet conveying apparatus comprising: a control unit that re-drives the separating unit and the first conveying unit in response to the timing to start a feeding operation of a subsequent sheet. 4. The apparatus according to claim 3, wherein when the first sheet detecting means detects the interval between the preceding sheet and the succeeding sheet, the second sheet detecting means detects the trailing edge of the preceding sheet almost simultaneously. Control for re-driving the separation means and the first conveyance means, and when the interval has not been detected, re-driving the separation means and the first conveyance means at a timing later by a predetermined correction time than in the case of the detection of the interval. A sheet conveying device having a means. 5. The sheet conveyance device according to claim 4, wherein the correction time is a time obtained by dividing at least a distance from a separation claw of the sheet stacking means to a nip of the separation means by a conveyance speed. 6. The feeding method according to claim 3, wherein a feeding time from a start of feeding of the succeeding sheet by the feeding means to a detection of a leading end of the succeeding sheet by the first sheet detecting means is measured. A sheet conveying device, comprising: a control unit that sets re-driving timing of the separation unit and the first conveying unit according to a feeding time. 7. An image forming apparatus comprising: the sheet conveying apparatus according to claim 1; and an image forming unit that forms an image on a sheet conveyed by the conveying apparatus.