JP3652222B2 - Sheet conveying apparatus and image forming apparatus - Google Patents

Description

[0001]
BACKGROUND 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 provided with a registration unit that feeds a sheet to an image forming unit.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an image forming apparatus such as a copying machine, a printer, a facsimile, or a complex machine of these, an image forming unit that forms an image on a sheet, a sheet feeding unit that feeds a sheet to the image forming unit, and an image forming unit In order to form an image on both sides of the sheet, the sheet formed by the image forming unit is reversed. There is known a type having a sheet reversal conveyance path and the like for feeding again to the image forming unit.
[0003]
Hereinafter, a conventional example of such an image forming apparatus will be described with reference to FIGS. FIG. 7 is a schematic sectional view of an electrophotographic copying machine as a conventional image forming apparatus. The electrophotographic copying machine (hereinafter simply referred to as a copying machine) includes a document reading unit 4 that reads an image of a document, and an image that forms an image on a sheet by an electrophotographic method based on image information read by the document reading unit 4. It has a forming unit and a plurality of sheet feeding units, and a plurality of sheets can be continuously fed from each sheet feeding unit to the image forming unit.
[0004]
In FIG. 7, reference numeral 1 denotes a copying machine main body, and an original table 2 made of a transparent glass plate is fixedly provided on the upper portion of the copying machine main body 1. Reference numeral 3 denotes a document feeder, which conveys a document to a predetermined position on the document table 2.
[0005]
In this copying machine, an image of a document on the document table 2 is read by the document reading unit 4, and based on the data, the writing laser unit 5 emits a laser beam to uniformly charge the photosensitive drum 12. By scanning the top, an electrostatic latent image is formed on the photosensitive drum 12.
[0006]
In the copying machine, as a sheet feeding unit, a deck feeding unit for feeding sheets stacked on the decks 30 and 31 and the sheet cassettes 32 and 33 built in the copying machine main body 1 to the image forming unit. 34 and 35 and cassette feeding sections 36 and 37 are provided.
[0007]
The image forming unit develops the photosensitive drum 12, the charger 13 for uniformly charging the surface of the photosensitive drum 12, and the electrostatic latent image formed on the surface of the photosensitive drum 12 charged by the charger 13. From the developing device 14 for forming a toner image to be transferred to the sheet S, the transfer charger 19 for transferring the toner image developed on the surface of the photosensitive drum 12 to the sheet S, and the photosensitive drum 12. A separation charger 20 for separating the sheet S to which the toner image is transferred, and a cleaner 26 for removing the toner remaining on the photosensitive drum 12 after the toner image is transferred.
[0008]
On the downstream side of the image forming unit, a conveyance unit 21 for conveying the sheet S to which the toner image is transferred, and a fixing device for fixing the toner image on the sheet S conveyed by the conveyance unit 21 as a permanent image. 22 is provided. Further, a discharge roller 24 for discharging the sheet S on which the toner image is fixed by the fixing device 22 from the copying machine main body 1 is provided. Further, the discharge roller 24 is discharged outside the copying machine main body 1. A discharge tray 25 for receiving the sheet S is provided.
[0009]
In this copier, the conveying rollers 105, 107, 108, 109, 110, 111, 112, and 123, and the leading and trailing edges of the sheet are placed on the conveying path for conveying the sheet from the sheet feeding unit to the image forming unit. Sheet path sensors 104, 116, 117, and 118 for detection are arranged. The sheet fed by each conveying roller is sent to the image forming unit by the registration roller 106. A registration sensor 120 for detecting the leading edge of the sheet is disposed near the upstream side of the registration roller 106 in the sheet conveyance direction.
[0010]
Here, the conveyance roller 107 is a pre-registration roller for feeding the sheet sent from each sheet feeding unit to the registration roller 106. The first conveyance roller 105, the sheet path sensor 104, the second conveyance roller 108, the third conveyance roller 109, the sheet path sensor 116, and the fourth conveyance roller 110 are disposed on the upstream sheet conveyance path of the pre-registration roller 107. , The sheet path sensor 117 is arranged in this order.
[0011]
Further, a sheet conveyance path connected to the deck feeding unit 35 is branched from the conveyance path between the pre-registration roller 107 and the first conveyance roller 105, and the fifth conveyance is performed from the downstream side to the sheet conveyance path. A roller 111, a sheet path sensor 104, a sixth transport roller 112, a sheet path sensor 118, and a seventh transport roller 123 are arranged in this order.
[0012]
Further, a sheet reversing path is branched from the conveying path between the sixth conveying roller 112 and the seventh conveying roller 123, and the sheet reversing path includes a sheet path sensor 119 and a double-sided right roller 113 from the downstream side. , The double-sided left roller 114, the reverse roller 115 rotating in the forward and reverse directions, and the sheet reverser 121 are arranged in this order. In this copying machine, in order to perform image formation on both sides of the sheet, the sheet on which the image is formed by the image forming unit is reversed by the sheet reversing unit 121 and the reversing roller 115 and sent to the sheet reversing path. The sheet is fed again to the image forming section through a path from the right roller 113 to the sixth conveyance roller 112 to the fifth conveyance roller 111 to the pre-registration roller 107 to the registration roller 106.
[0013]
Each roller described above is driven to rotate by transmitting a driving force of a driving motor (not shown). The rotation operation of each roller is controlled by a control unit (not shown) based on the detection result of each sheet path sensor.
[0014]
Next, the operation at the time of sheet feeding in this conventional copying machine will be described with reference to FIG. 8 by taking as an example the case of feeding from the deck feeding unit 34. Here, FIG. 8 is a diagram showing the positional relationship between the leading edge and the trailing edge of the sheet when the sheet is fed from the deck feeding unit 34.
[0015]
At the start of sheet feeding, the drive motor drives the pickup roller 101, the feeding roller 102, the separation roller 103, the first conveying roller 105, and the pre-registration roller 107 to rotate. At this time, the registration roller 106 is still in a stopped state.
[0016]
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 into only the uppermost sheet by a separation roller 103 provided opposite to the feeding roller 102 and applied with a force that rotates in a direction opposite to the conveying direction with a constant torque.
[0017]
The uppermost sheet is detected by the sheet path sensor 104 and conveyed by the first conveying roller 105.
[0018]
At this time, in the copying machine, the first conveying roller 105 is rotated based on the detection timing of the leading edge of the sheet by the sheet path sensor 104 in order to perform a so-called pre-registration operation that adjusts the interval between sheets (paper interval). By temporarily stopping, the leading edge of the sheet being nipped and conveyed by the first conveyance roller 105 is stopped at a predetermined position on the conveyance path, and the rotation of the first conveyance roller 105 is started again after a predetermined time has elapsed.
[0019]
That is, in the sheet feeding unit, not only the sheet at the front stacking position of the sheet deck 30 but also the sheet that is returned to the sheet deck 30 by the separation roller 103 and the sheet leading end is in the vicinity of the feeding roller 102, etc. Therefore, there is a variation in the position of the leading end of the sheet at the start of feeding, and it is necessary to eliminate this variation on the front side of the registration roller 106.
[0020]
Specifically, as shown in FIGS. 7 and 8, the first conveying roller 105 is temporarily moved at a timing when the leading end of the sheet comes to a predetermined position (pre-registration position) A on the conveying path after the sheet path sensor 104 detects it. Stop and confirm the stop position of the leading edge of the sheet. The time B at which the leading edge of the sheet is expected to arrive at the registration roller 106 (B = (distance C to the registration roller 106) / (sheet conveyance speed β of the first conveyance roller 105 until the registration roller 106 is reached)). As a result, control for restarting the first conveying roller 105 was performed.
[0021]
Thereafter, the sheet reaches the stopped registration roller 106 via the pre-registration roller 107. In this case, a predetermined amount of the sheet is fed by the pre-registration roller 107 with the leading edge of the sheet abutting against the stopped registration roller 106, and the entire sheet is looped to correct the skew of the sheet. . Thereafter, when the registration roller 106 starts to rotate at a constant speed (process speed) α, the sheet is fed to the above-described image forming unit in time with the image forming operation, and the toner image is transferred to the upper surface.
[0022]
Then, the sheet that has passed the image forming unit is sent to the fixing unit 22 by the conveying unit 21 to fix the toner image. In the case of single-sided copying, the sheet is placed on the discharge tray 25 via the discharge roller 24, and double-sided copying is performed. In this case, after the reversing operation is performed by the sheet reversing unit 121, the sheet reversing path is sequentially conveyed by the reversing roller 115, the double-sided left roller 114, and the double-sided right roller 113, and sent again to the image forming unit. ing.
[0023]
Here, the timing for starting feeding of the second and subsequent sheets at the time of continuous feeding is started after a predetermined time has elapsed since the previous sheet restarted the first conveying roller 105, and is the same as described above. The feeding was controlled.
[0024]
Note that the same pre-registration operation as described above is also performed when sheets are continuously fed from the other deck feeding unit 35 and cassette feeding units 36 and 37. In addition, when performing double-sided copying by continuously feeding sheets from any of the sheet feeding units, the double-sided right roller 113 is rotated based on the detection timing of the sheet leading edge by the sheet path sensor 119 on the double-sided conveyance path. A pre-registration operation is performed in which the sheet sensor 119, the deck feeding unit 35, and the joining part of the double-sided conveyance path are temporarily stopped, and rotation is started again after a predetermined time has elapsed.
[0025]
As described above, in the conventional copying machine, the variation in the sheet front end position in the sheet feeding unit is removed by performing the pre-registration operation as described above, the sheet front end position is determined, and the registration roller is stably provided. I was trying to send it to 106. Further, even when the sheet is temporarily stopped in the conveyance path by the pre-registration operation, in order to catch up with the previous sheet, the sheet conveyance speed (process speed α of the registration roller 106) in the image forming unit is more than The conveyance speed β in the conveyance path from the sheet feeding unit to the registration roller 106 is set to be faster.
[0026]
[Problems to be solved by the invention]
By the way, in order to perform continuous sheet feeding in the image forming apparatus and form an image on a large number of sheets in a short time, there is a limit to the laser writing speed in the image forming unit. Therefore, it is necessary to shorten the timing of the sheet to be fed to the image forming unit. For this reason, it is necessary to accurately abut the leading end of the sheet against the nip portion of the registration roller 106 at a slightly given sheet interval time. It is coming.
[0027]
However, in the conventional copying machine, the following problems have occurred when transporting thick paper or when the transport roller is increasingly worn and slipping easily occurs. It was difficult to set the
[0028]
That is, when transporting thick paper or when the wear of the transport roller has advanced, the sheet transport time B from the pre-registration position A to the registration roller 106 after the first transport roller 105 is restarted during the pre-registration operation. However, cpm (copy per minute) was lowered, and variations in the sheet stop position with respect to the pre-registration position A occurred. As a result, the sheet conveyance time of each sheet 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 narrow, the trailing edge of the previous sheet does not pass through the registration roller 106. In this state, the leading edge of the next sheet enters the registration roller 106 and the sheet conveyance becomes unstable.
[0029]
Further, in the conventional copying machine, the first is performed based on the detection result of the sheet path sensor 118 when the sheet feeding is performed from the deck feeding unit 35 arranged on the left side of FIG. The pre-registration position of the seventh conveyance roller 123 is between the sheet path sensor 118 and the junction of the double-side conveyance path, and the double-sided right roller is performed based on the detection result of the sheet path sensor 119 when performing double-sided copying. Since the position of the pre-registration 113 is different from each other, the structure of software (control program) for controlling the rotation operation of the transport rollers 123 and 113 is complicated.
[0030]
SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet conveying apparatus and an image forming apparatus equipped with the sheet conveying apparatus that can stably and accurately cause a sheet to enter a registration unit and increase throughput.
[0031]
[Means for Solving the Problems]
The first configuration of the sheet conveying apparatus according to the present invention is one sheet by the sheet feeding means. Z In the sheet conveying apparatus that conveys the separately fed sheets to the image forming unit, the sheet is arranged on the upstream side in the sheet conveying direction of the image forming unit, and the image forming operation of the image forming unit and the timing of sheet conveyance are matched. A registration unit that feeds the sheet to the image forming unit, a first sheet detection unit that is provided upstream of the registration unit in the sheet conveyance direction, and that detects the leading edge of the sheet, and a sheet conveyance of the first sheet detection unit A second sheet detecting unit that is disposed upstream of the direction and detects the leading edge of the sheet that has been separated and fed from the sheet feeding unit, and the sheet that has been separated and fed from the sheet feeding unit, Based on the detection result of the second sheet detecting means, after pre-stop in the conveying path, the pre-registration operation for conveying toward the register means is performed. A pre-registration operation timing of a subsequent sheet based on a conveyance time from when the previous sheet is temporarily stopped until it is detected by the first sheet detection unit. Make corrections The correction of the pre-registration operation timing is performed when the transport time from when the previous sheet is temporarily stopped until the sheet is detected by the first sheet detecting unit is longer than a predetermined time. The temporary stop position of the sheet is corrected so as to be closer to the registration means than the stop position of the previous sheet, and if the position is shorter, the temporary stop position of the subsequent sheet is corrected from the stop position of the previous sheet. Keep away from It is characterized by that.
[0036]
The sheet conveying apparatus according to the present invention 2 The configuration of the second 1 In this configuration, the pre-registration transport unit is configured to detect a deviation time with respect to a time when the previous sheet should arrive at the registration unit from the sheet transport timing after the previous sheet is temporarily stopped and the sheet detection timing of the first sheet detection unit. A correction unit that calculates a value and corrects the pre-registration operation timing of the next sheet so that the next sheet arrives at the registration unit within a predetermined time based on the value of the shift time;
[0037]
The first main configuration of the image forming apparatus according to the present invention is as follows. Or 2 And an image forming unit that forms an image on the sheet conveyed by the sheet conveying apparatus.
[0038]
A second main configuration of the image forming apparatus according to the present invention includes a sheet feeding unit that separates and feeds sheets one by one, an image forming unit that forms an image on the sheet, and a sheet conveyance direction of the image forming unit. Is located upstream of the image forming unit, and a registration unit that feeds the sheet into the image forming unit in synchronization with the image forming operation of the image forming unit and the sheet conveyance timing, and is provided upstream of the registration unit in the sheet conveyance direction. A first sheet detecting unit that is disposed upstream of the first sheet detecting unit in the sheet conveying direction, and a second sheet detecting unit that detects the leading edge of the sheet that has been separated and fed from the sheet feeding unit. The sheet separated and fed from the sheet feeding unit is temporarily stopped in the conveyance path based on the detection result of the second sheet detection unit, and then conveyed toward the registration unit. A first pre-registration conveyance unit that performs a pre-registration operation; a sheet reversal conveyance unit that conveys an image of the sheet that has been image-formed by the image forming unit; and a sheet conveyance direction of the first sheet detection unit A third sheet detecting means for detecting the leading edge of the sheet conveyed from the sheet reversing and conveying means disposed on the upstream side; and a sheet reversing and conveying means disposed on the upstream side in the sheet conveying direction of the third sheet detecting means. Second pre-resist conveying means for performing a pre-registration operation for conveying the sheet conveyed from the sheet toward the resist means after temporarily stopping the sheet in the conveying path based on the detection result of the third sheet detecting means. The first and second pre-resist conveying means share a predetermined position in the conveying path to be temporarily stopped, and the first sheet after the previous sheet is temporarily stopped Based on the conveying time to be detected in the knowledge unit, performs sheet pre-registration operation timing correction of the post.
[0039]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described in detail with reference to the drawings.
[0040]
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, parts that are the same as conventional ones are given the same reference numerals, and descriptions thereof are omitted.
[0041]
FIG. 1 is a schematic cross-sectional view of a copying machine to which the present invention is applied. In this embodiment, the sheet conveyance speed of each roller provided in the sheet conveyance path and the double-side conveyance path is controlled by the control unit 130 as follows. It is controlled so that it can be switched.
[0042]
That is, the pre-registration roller 107 of FIG. 1, the first conveyance roller 105 as a pre-registration conveyance means upstream of the pre-registration roller 107 in the sheet conveyance direction, and the second conveyance of the first conveyance roller 105 upstream of the sheet conveyance direction. The roller 108 can be switched between a process speed α that is the sheet conveyance speed of the registration roller 106 and a first speed β that is faster than the process speed α. Here, when the rotation of the registration roller 106 is started, since the sheet is still nipped by the pre-registration roller 107, the pre-registration roller 107 is rotationally driven at the same process speed α as the registration roller 106.
[0043]
Further, the third conveying roller 109 upstream of the second conveying roller 108 in the sheet conveying direction, the fourth conveying roller 110 upstream of the third conveying roller 109 in the sheet conveying direction, the fifth conveying roller 111, and the fifth conveying roller. The sixth conveyance roller 112 on the upstream side in the sheet conveyance direction of the roller 111 and the seventh conveyance roller 123 on the upstream side in the sheet conveyance direction of the sixth conveyance roller 112 are rotationally driven at the first speed β.
[0044]
Furthermore, the double-sided right roller 113, the double-sided left roller 114, and the reverse roller 115 arranged in the sheet reverse path can be switched between the first speed β and the second speed γ for sheet reverse. ing.
[0045]
The arrangement of the sheet path sensors 104, 116, 117, 118, and 119 is the same as the conventional one, and a sheet detection signal from each of the sheet path sensors is supplied to the control unit 130. And the control part 130 controls rotation of each conveyance roller based on the detection timing by each of these sheet path sensors. In addition, when the sheet is continuously fed, the control unit 130 corrects the pre-registration conveyance, which will be described later in detail.
[0046]
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. However, the present invention is limited to this value. It is not something.
[0047]
Next, the conveyance operation at the time of sheet feeding in the copying machine according to the embodiment will be described with reference to FIG. 2 by taking as an example the case of continuously feeding sheets from the deck feeding unit 34. Here, FIG. 2 shows a diagram representing the positional relationship between the leading edge and the trailing edge of each sheet during continuous feeding of sheets from the deck feeding unit 34.
[0048]
In this embodiment, in order to keep the distance between the trailing edge of the previous sheet and the leading edge of the next sheet within a predetermined range at the position of the registration roller 106, as shown in FIG. Time t after exiting the registration roller 106 ₈ The control is performed so that the leading edge of the next sheet reaches the registration roller 106 within a predetermined time (between a preset time B1 and time B2). Details of this control will be described later.
[0049]
At the start of continuous feeding of sheets from the deck feeding unit 34, the pickup motor 101, the feeding roller 102, the separation roller 103, the first conveying roller 105, and the pre-registration roller 107 are rotationally driven by the drive motor. At this time, the registration roller 106 is still in a stopped state.
[0050]
First, the pickup roller 101 sends the sheet S set on the deck 30 to the feeding roller 102. Here, the sheet S is separated from the uppermost sheet only by the separation roller 103 provided facing the feeding roller 102 and applied with a force that rotates in a direction opposite to the conveying direction with a constant torque.
[0051]
The top end of the uppermost sheet is detected by the sheet path sensor 104 as the second sheet detecting means (t ₁ ), And is sent to a first conveyance roller 105 as a pre-registration conveyance unit disposed near the downstream side of the sheet path sensor 104 in the sheet conveyance direction, and is conveyed by the first conveyance roller 105 as follows.
[0052]
That is, the control unit 130 determines the timing t at which the leading edge of the sheet reaches a predetermined position (pre-registration position) A on the downstream side of the sheet path sensor 104 in the sheet conveyance direction. ₂ Thus, the control for temporarily stopping the rotation of the first conveying roller 105 is performed. As a result, the stop position of the sheet front end is determined, and the variation in the sheet front end position at the start of feeding from the sheet deck 30 is removed as described above. Next, after a predetermined time has elapsed, the first conveying roller 105 starts to rotate again at the first speed β (t _Three ), The pre-registration roller 107 is also rotated at the first speed β, and as shown in FIG. Be transported.
[0053]
When the leading edge of the sheet is detected by the registration sensor 120 disposed in the vicinity of the upstream side of the registration roller 106 in the sheet conveyance direction (t _Four As shown in FIG. 2, the pre-registration roller 107 stops rotating after a predetermined time has elapsed (t _Five ), And then after a predetermined time t6 when the registration roller 106 starts rotating (t ₇ ) At the same process speed α as the registration roller 106.
[0054]
By this operation, the sheet is conveyed by the pre-registration roller 107 in a state where the leading edge of the sheet reaches the nip portion of the registration roller 106 that is stopped and the leading edge is prevented from moving, thereby forming a predetermined loop. To correct skew. Then, the pre-registration roller 107 is moved to t in FIG. _Five At this timing, the registration roller 106 moves from this state to t ₆ , The loop formed on the sheet is eliminated by rotating at the process speed α, and the pre-registration roller 107 is t ₇ , The sheet is fed into the image forming unit while maintaining a state without a loop.
[0055]
Next, the control when the sheet is continuously fed will be described in detail. When continuously feeding sheets, as described above, feeding of the next sheet is started after a lapse of a predetermined time from the restart of pre-registration conveyance by the first conveyance roller 105. The Specifically, as shown in FIG. 2, the timing t at which the leading edge of the previous sheet starts to move toward the image forming unit due to the rotation of the registration roller 106 at the process speed α. ₆ The timing t at which the trailing edge of the preceding sheet exits the registration roller 106 ₈ Time (t ₈ -T ₆ = After the sheet length (L1) / process speed α) and at a timing between time B1 and time B2 when the sheet interval between the trailing edge of the previous sheet and the leading edge of the next sheet is not too wide. Then, control is performed so that the leading edge of the next sheet reaches the registration roller 106.
[0056]
Further, the pre-registration conveyance of the next sheet by the first conveyance roller 105 is restarted by dividing 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. In consideration of the calculated time (numerical value) and the stop time (fixed value) of the registration roller 106, the control by the control unit 130 is performed so that the first conveying roller 105 is restarted at the sheet conveying speed β. Do. As a result, the next sheet can reach the registration roller 106 between the predetermined times B1 and B2.
[0057]
Here, the times B1 and B2 are in consideration of inevitable errors, and the time B1 is an allowable limit value with a narrower sheet interval between the trailing edge of the previous sheet and the leading edge of the next sheet, Time B2 is an allowable limit value in which the sheet interval between the trailing edge of the previous sheet and the leading edge of the next sheet is wider.
[0058]
On the other hand, when a sheet having a large conveyance resistance, such as thick paper, is conveyed, the time required to reach the registration roller 106 (registration sensor 120) from the pre-registration position A is calculated as shown in FIG. May take longer. As shown in FIG. 4, when the actual time is closer to B2 than a certain threshold Y, the interval between the sheets may exceed the allowable limit value of time B2 due to variations.
[0059]
In this embodiment, even in such a case, the following correction is performed by the control unit 130, so that the interval between the trailing edge of the previous sheet and the leading edge of the next sheet is changed to the registration roller 106. It is designed to be within a predetermined range before and after.
[0060]
In the present embodiment, as shown in FIG. 3, the controller 130 calculates the time C / β (known value) until the leading edge of the sheet is detected by the registration sensor 120 from the pre-registration position A. Detection timing t by registration sensor 120 _Four Whether or not the time actually taken based on is deviated is monitored, and when it deviates, a correction value is calculated as follows.
[0061]
That is, the control unit 130 calculates the calculation time C / β until the sheet front end is detected by the registration sensor 120 from the pre-registration position A and the detection timing t by the registration sensor 120. _Four When the time taken from the actual time deviates, this deviation time X is calculated, and further, the speed X is multiplied by a time X / 2 that is half the deviation time X, and the value of (X / 2) β The distance is calculated as a correction value.
[0062]
Here, the reason for halving the deviation time X is that if the value of Xβ obtained by multiplying the deviation time X by the speed β is used as the correction value, the next sheet is corrected by Xβ when a sudden and large deviation occurs. If this occurs, there is a risk that problems such as the trailing edge of the previous sheet and the leading edge of the next sheet overlap. Therefore, in order to cause the next sheet leading edge to reach the registration roller 106 within a predetermined range with respect to any deviation, correction is made with reference to a half value of the deviation time X. The reason for multiplying X by 1/2 is that the deviation distribution is a normal distribution, and the population average of the normal distribution is approximately at the center of the distribution.
[0063]
Although the correction values are set as described above in the present embodiment, the present invention is not limited by the correction value calculation method.
[0064]
The control unit 130 performs the first conveyance so that the stop position (pre-registration position) in the pre-registration operation of the next sheet by the first conveyance roller 105 is shifted from the A by the correction value (X / 2) β. The rotation of the roller 105 is controlled. As a result, the stop position in the pre-registration operation of the next sheet by the first conveying roller 105 is closer to or farther from the registration roller 106 than A by (X / 2) β.
[0065]
In the example of FIG. 3, the time from when the previous sheet is temporarily stopped to the time when the registration sensor 120 detects the leading edge of the sheet is longer than the calculated time C / β. Is also shifted closer to the registration roller 106 by (X / 2) β. When the time from the conveyance after the temporary stop of the previous sheet to the detection of the leading edge of the sheet by the registration sensor 120 is shorter than the calculated time C / β by the deviation time X, the stop position is set to A It is sufficient to correct the distance to the registration roller 106 by (X / 2) β.
[0066]
The next sheet conveyed by the first conveyance roller 105 and the pre-registration roller 107 rotated at the conveyance speed of the first speed β after performing such correction of the stop position is a distance from the stop position to the registration roller 106. Therefore, as shown in FIG. 5, the registration roller 106 is reached in a time close to the center of the times B1 and B2.
[0067]
FIG. 6 shows another embodiment of correction control during pre-registration conveyance. As shown in FIG. 6, the same effect can be obtained by leaving the pre-registration position A as it is and starting by shifting the restart timing by the first conveying roller 105 by half of the shift time X.
[0068]
That is, the control unit 130 calculates the calculation time C / β until the sheet front end is detected by the registration sensor 120 from the pre-registration position A and the detection timing t by the registration sensor 120. _Four When the time actually taken based on is deviated, this deviation time X is calculated, and a time X / 2 that is half of the deviation time X is calculated as a correction value. Then, the control unit 130 controls the operation of the first conveyance roller 105 so that the restart timing of the pre-registration operation of the next sheet by the first conveyance roller 105 is advanced or delayed by the correction value X / 2. To do.
[0069]
In the example of FIG. 6, since the time from the conveyance after the temporary stop of the previous sheet to the detection of the sheet leading edge by the registration sensor 120 is longer than the calculated time C / β, the first conveyance roller 105 Is restarted by a correction value X / 2. If the time from the conveyance after the temporary stop of the previous sheet to the detection of the leading edge of the sheet by the registration sensor 120 is shorter than the calculated time C / β by the deviation time X, the first conveyance roller 105 The restart timing may be delayed by the correction value X / 2.
[0070]
As described above, according to the copying machine of the embodiment, the distance between the trailing edge of the previous sheet and the leading edge of the next sheet is always within a certain range before and after the nip portion of the registration roller 106 during continuous feeding of the sheet. Therefore, each sheet enters the registration roller 106 stably and accurately.
[0071]
Next, in the copying machine of the embodiment, pre-registration when performing duplex copying and when continuously feeding sheets from the deck feeding unit 35 arranged on the left side of the deck feeding unit 34 in FIG. The operation will be described.
[0072]
When performing double-sided copying, the sheet on which the image is formed on the first side by the image forming unit enters the sheet reversing unit 121, is reversed by the reversing roller 115, and is disposed on the reversing path. It is sent to the registration roller 106 via the double-sided right roller 113, the sixth conveyance roller 112, the fifth conveyance roller 111, and the pre-registration roller 107, and is again sent to the image forming unit by the registration roller 106. After the image is formed, the image is discharged to the discharge tray 25 as described above.
[0073]
At this time, the control unit 130 temporarily stops the rotation of the double-sided right roller 113 at the timing when the leading end of the sheet reaches a predetermined position (pre-registration position) P on the downstream side in the sheet conveyance direction of the sheet path sensor 119, and again after a predetermined time has elapsed. Control to start rotation. As a result, the stop position of the sheet front end on the reversal path is determined, and variations in the sheet front end position during reversal by the reversing roller 115 are removed.
[0074]
Here, during the pre-registration operation, the control unit 130 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. .
[0075]
In other words, the control unit 130 determines that when the calculated time until the sheet leading edge is detected by the registration sensor 120 from the pre-registration position P and the time actually taken based on the detection timing by the registration sensor 120 deviate, A correction value is calculated based on the deviation time, and the operation of the double-sided right roller 113 is controlled so that the pre-registration position P or the restart timing in the pre-registration operation of the next sheet becomes a deviation amount according to the correction value. To do.
[0076]
When sheets are continuously fed from the deck feeding unit 35, the sheets stacked on the deck 31 are separated into one sheet by the same mechanism as that of the deck feeding unit 34 described above, and the After being sent to the seventh transport roller 123 which is the resist transport means and pre-registration operation is performed by the seventh transport roller 123, it passes through the sixth transport roller 112, the fifth transport roller 111, and the pre-registration roller 107. The image is sent to the registration roller 106 and sent to the image forming unit by the registration roller 106.
[0077]
At this time, the control unit 130 temporarily stops the rotation of the seventh conveyance roller 123 at a timing when the leading edge of the sheet reaches a predetermined position (pre-registration position) P on the downstream side in the sheet conveyance direction of the sheet path sensor 118, and after a predetermined time has elapsed. Control to start rotation again. Thereby, the variation of the sheet leading end position at the start of feeding from the sheet deck 31 is removed.
[0078]
Here, at the time of the pre-registration operation, the control unit 130 calculates a correction value in the same manner as described above, and controls to shift the pre-registration position P or the restart timing by the seventh transport roller 123 based on the calculated correction value. Do.
[0079]
In other words, the control unit 130 determines that when the calculated time until the sheet leading edge is detected by the registration sensor 120 from the pre-registration position P and the time actually taken based on the detection timing by the registration sensor 120 deviate, The correction value based on the deviation time is calculated, and the operation of the seventh transport roller 123 is performed so that the pre-registration position P or the restart timing in the pre-registration operation of the next sheet becomes the deviation amount according to the correction value. Control.
[0080]
As described above, in the copying machine of the embodiment, the pre-registration operation performed by the double-sided right roller 113 during duplex copying and the pre-registration performed by the seventh transport roller 123 during continuous feeding of sheets from the deck feeding unit 35. Since the pre-registration position with respect to the operation is set to the same P position, the reference for the operation control of the double-sided right roller 113 and the seventh transport roller 123 by the control unit 130 can be shared, and the control program can be simplified. Figured.
[0081]
In addition, sheet conveyance to the registration roller 106 can be performed with high accuracy between small paper sheets, and throughput and apparatus reliability can be improved.
[0082]
The present invention has been described in detail above. However, the present invention is not limited to an electrophotographic copying machine, and may be any recording method. It may be.
[0083]
【The invention's effect】
As described above in detail, according to the present invention, a sheet conveying apparatus capable of stably and accurately causing a sheet to enter the registration means, and having high reliability and improved throughput, and an image forming apparatus including the sheet conveying apparatus. Can be provided.
[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 for explaining a sheet continuous feeding operation when a sheet having a large conveyance resistance is conveyed.
FIG. 4 is a diagram for explaining an operation when a sheet having a large conveyance resistance is conveyed.
FIG. 5 is a diagram for explaining a case where the next sheet is corrected so as to shift the pre-registration position toward the registration roller.
FIG. 6 is a diagram for explaining the case of correcting the timing for starting sheet conveyance again after stopping the pre-registration without changing the pre-registration position for the next sheet.
FIG. 7 is a schematic cross-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]
1 Copier body
2 Document table
3 Document feeder
4 Document reader
5 Writing laser part
12 Photosensitive drum
13 Charger
14 Developer
19 Transfer charger
20 Separation charger
21 Transport section
22 Fixing device
24 discharge roller
25 Discharge tray
26 Cleaner
30, 31 decks
32, 33 sheet cassette
34,35 Deck feeding section
36, 37 Cassette feeding section
101 Pickup roller
102 Feeding roller
103 Separation roller
104 Sheet path sensor (second sheet detecting means)
116, 117, 118 Sheet path sensor
105 First transport roller (pre-resist transport means)
106 Registration roller (registration means)
107 Roller before registration (registration means)
108 Second conveying roller
109 Third transport roller
110 Fourth transport roller
111 Fifth transport roller
112 Sixth transport roller
113 Double-sided right roller (second pre-resist conveyance means)
114 Double-sided left roller
115 Reverse roller
118 Sheet path sensor (second sheet detecting means)
119 Sheet path sensor (third sheet detecting means)
120 Registration sensor (first sheet detecting means)
121 Sheet reversing part
123 Seventh transport roller (first pre-resist transport means)
130 Control unit (correction means)
A, P Pre-resist position

Claims (9)

In the sheet conveying device for conveying the image forming means one not a One separating and feeding sheets by the sheet feeding means is disposed upstream of the sheet conveyance direction of said image forming means, the image forming operation of said image forming means A registration unit that feeds the sheet to the image forming unit at the same timing as the sheet conveyance, a first sheet detection unit that is provided upstream of the registration unit in the sheet conveyance direction, and that detects the leading edge of the sheet; A second sheet detecting unit that is disposed upstream of the sheet detecting direction of the first sheet detecting unit and that detects the leading edge of the sheet that has been separated and fed from the sheet feeding unit; and the separation feeding from the sheet feeding unit. Based on the detection result of the second sheet detection unit, the fed sheet is temporarily stopped in the conveyance path and then conveyed toward the registration unit. A pre-registration conveyance unit that performs a re-registration operation, and the pre-registration conveyance unit performs the subsequent sheet based on the conveyance time until the first sheet detection unit detects the first sheet after being temporarily stopped. stomach line correction of pre-registration operation timing, correction of the pre-registration operation timing, the transport time to the after temporarily stopping the previous sheet sheet is detected in said first sheet detecting means, predetermined If it is longer than the time, the position where the subsequent sheet is temporarily stopped is corrected to be closer to the registration means than the position where the previous sheet is stopped, and if it is shorter, the position where the subsequent sheet is temporarily stopped is corrected. A sheet conveying apparatus characterized in that the sheet conveying apparatus is located farther from the registration means than the sheet stop position . The pre-registration conveying means is a value of a deviation time with respect to a time when the previous sheet should arrive at the registration means from a sheet conveyance timing after the previous sheet is temporarily stopped and a sheet detection timing of the first sheet detection means. And a correction means for correcting the pre-registration operation timing of the next sheet so that the next sheet arrives at the registration means within a predetermined time based on the value of the deviation time. The sheet conveying apparatus according to claim 1 . A sheet conveying apparatus according to claim 1 or 2, the image forming apparatus characterized by having the said image forming means for forming an image to the conveyed sheet by the sheet conveying device.   A sheet feeding unit that separates and feeds the sheets one by one; an image forming unit that forms an image on the sheet; and an image forming operation of the image forming unit that is disposed upstream of the image forming unit in the sheet conveying direction. A registration unit that feeds the sheet to the image forming unit in synchronization with a sheet conveyance timing; a first sheet detection unit that is provided upstream of the registration unit in the sheet conveyance direction; A second sheet detecting unit that is disposed upstream of the sheet detecting unit in the sheet conveying direction and detects the leading edge of the sheet that has been separated and fed from the sheet feeding unit, and is separated and fed from the sheet feeding unit. A pre-registration motion for conveying the sheet toward the registration means after being temporarily stopped in the conveyance path based on the detection result of the second sheet detection means. A first pre-registration conveyance unit that performs image processing, a sheet reversal conveyance unit that conveys an image surface of the sheet formed by the image formation unit, and an upstream of the first sheet detection unit in the sheet conveyance direction. A third sheet detecting means for detecting the leading edge of the sheet conveyed from the sheet reversing and conveying means, and an upstream side of the third sheet detecting means in the sheet conveying direction, and the sheet reversing A second resist performing a pre-registration operation in which the sheet conveyed from the conveying unit is temporarily stopped in the conveying path based on the detection result of the third sheet detecting unit, and then conveyed toward the registration unit. Pre-registration conveyance means, and the first and second pre-registration conveyance means share a predetermined position in the conveyance path to be temporarily stopped, and temporarily stop the previous sheet. An image forming apparatus comprising: performing the first based on the transfer time until the sensed sheet detecting means, the sheet pre-registration operation correction timing after later. The correction of the pre-registration operation timings of the first and second pre-registration conveyance means is based on the conveyance time from when the previous sheet is temporarily stopped until the sheet is detected by the first sheet detection means. The image forming apparatus according to claim 4, wherein the position where the subsequent sheet is temporarily stopped is changed. The correction of the pre-registration operation timings of the first and second pre-registration transport means is performed when a transport time from when the previous sheet is temporarily stopped until the sheet is detected by the first sheet detection means is predetermined. If it is longer than the time, the position where the subsequent sheet is temporarily stopped is corrected to be closer to the registration means than the position where the previous sheet is stopped, and if it is shorter, the position where the subsequent sheet is temporarily stopped is corrected. 6. The image forming apparatus according to claim 5 , wherein the correction is performed so that the position is farther from the registration means than the stop position of the sheet. The correction of the pre-registration operation timings of the first and second pre-registration conveyance units is performed based on the conveyance time from when the previous sheet is temporarily stopped until the first sheet detection unit detects the sheet. 5. The sheet conveying apparatus according to claim 4 , wherein the sheet conveying timing after the sheet is temporarily stopped is changed. The correction of the pre-registration operation timings of the first and second pre-registration conveyance means is performed by a predetermined time after the previous sheet is temporarily stopped until the sheet of the first sheet detection means is detected. If it is longer, the sheet conveyance timing 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 it is shorter, the temporary stop of the subsequent sheet is corrected. The sheet conveying apparatus according to claim 7 , wherein the timing of the subsequent conveyance is corrected so as to be delayed from the timing of sheet conveyance after the previous sheet is temporarily stopped. The first and second pre-registration conveying units should arrive at the registration unit based on the sheet conveyance timing after the previous sheet is temporarily stopped and the sheet detection timing of the first sheet detection unit. A correction for calculating a deviation time value with respect to time and correcting the pre-registration operation timing of the next sheet so that the next sheet arrives at the registration means within a predetermined time based on the deviation time value. sheet conveying apparatus according to any one of claims 4 to 8, characterized in that it has means.

Images