JP4106995B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus, and in particular, reverses the front and back sides by exchanging the leading edge and the trailing edge of a transfer sheet while conveying the transfer sheet on which an image is formed by an image forming unit while accelerating to a second conveyance speed. The present invention relates to an image forming apparatus provided with a reverse conveying unit.
[0002]
[Prior art]
In an image forming apparatus such as a printer, a copying machine, or a facsimile machine, transfer paper for image formation is stored in a paper feed cassette, and the transfer paper is transferred from the paper feed cassette by a paper feed means such as a paper feed roller. It is structured to send out towards the.
[0003]
Then, the image forming unit executes image formation by transferring and fixing the toner image while conveying the transfer paper at the first conveying speed. Further, while the transfer paper on which the image is formed by the image forming means is accelerated to the second transport speed and transported, the front and back sides are reversed by switching the front end and the rear end of the transfer paper by the reverse transport means.
[0004]
The second transport speed is generally twice as fast as the first transport speed. The reverse conveyance is used for reverse paper discharge or for double-sided image formation.
[0005]
[Problems to be solved by the invention]
In recent image forming apparatuses, in order to improve productivity, image formation is executed while continuously transferring transfer paper with the transfer paper interval as narrow as possible. For this reason, if a deviation occurs in the conveyance speed (conveyance time) due to the slip of the transfer paper, there is a possibility that the delayed transfer paper and the rear transfer paper collide.
[0006]
Such a problem is likely to occur in the reverse conveying means that performs high-speed conveyance at the second conveyance speed. In other words, since it is conveyed at high speed, it is in a state where it is more susceptible to the influence of deviation in conveyance.
[0007]
Therefore, in order to avoid the above problems, conventionally, image formation is performed in a state where there is a margin in the transfer sheet interval. For this reason, there has been a limit to improving productivity. Further, even if the transfer paper interval has a margin, if the amount of slip is large, it is inevitable that the transfer paper will collide.
[0008]
Accordingly, an object of the present invention is to realize an image forming apparatus capable of performing reverse conveyance at the second conveyance speed in a stable state regardless of fluctuations in the transfer paper conveyance speed.
[0009]
[Means for Solving the Problems]
  That is, the present invention for solving the above problems is as described below.
  (1) According to the first aspect of the present invention, there is provided an image forming unit that forms an image by transferring and fixing a toner image while conveying a transfer sheet at a first conveying speed, and a transfer sheet on which an image is formed by the image forming unit. Reversing and conveying means for inverting the front and back by switching the leading and trailing edges of the transfer paper while accelerating to the second conveying speed and measuring the time required for image formation by the image forming means Means and said time measuring meansBymeasurementIf the time required for the image formation is longer than a predetermined range, the acceleration start timing in the reverse conveying means is advanced, and if it is shorter than the predetermined range, the acceleration start timing is delayed.An image forming apparatus comprising: a control unit that performs control to change.
[0010]
The present invention forms an image by transferring and fixing a toner image while conveying a transfer sheet at a first conveyance speed, and accelerates the image-formed transfer sheet to a second conveyance speed while conveying the transfer sheet. When the front and back sides are reversed by reversing the front and back, the time required for image formation is measured, and the control result for changing the acceleration timing in reverse conveyance is performed by referring to the measurement result. ing.
[0011]
For this reason, it is possible to perform reverse conveyance at the second conveyance speed in a stable state regardless of fluctuations in the conveyance speed due to slippage of the transfer paper during image formation, and the transfer paper interval is kept constant. It becomes possible.
[0012]
  (2) The invention according to claim 2 includes an image forming unit that forms an image by transferring and fixing a toner image while conveying the transfer paper at a first conveying speed, and a transfer sheet on which an image is formed by the image forming unit. While accelerating and transporting to the second transport speed, the front and back sides of the transfer paper are reversed to reverse the front and back and decelerated to the first transport speed to refeed the image forming means. Reversing conveying means, time measuring means for measuring the time required for reversing conveying by the reversing conveying means, and the time measuring meansBymeasurementIf the time required for the reverse conveyance is longer than a predetermined range, the deceleration start timing in the reverse conveyance means is delayed, and if it is shorter than the predetermined range, the deceleration start timing is advanced.An image forming apparatus comprising: a control unit that performs control to change.
[0013]
The present invention forms an image by transferring and fixing a toner image while conveying a transfer sheet at a first conveyance speed, and accelerates the image-formed transfer sheet to a second conveyance speed while conveying the transfer sheet. When the front and back sides are reversed by reversing the front and back and decelerating to the first transport speed for re-feeding the image, measure the time required for reverse transport. With reference to this, control for changing the deceleration timing in the reverse conveyance is performed.
[0014]
For this reason, it is possible to perform reverse conveyance and re-feeding in a stable state regardless of fluctuations in the conveyance speed due to slippage of transfer paper during reverse conveyance, and to maintain a constant transfer paper interval. It becomes possible.
[0015]
(3) The invention according to claim 3 is characterized in that the reversing and conveying means performs reversing and conveying when the transfer paper having the image formed on one surface by the image forming means is discharged. The image forming apparatus according to 1.
[0016]
According to the present invention, the control (1) is performed when the image forming unit performs the reverse conveyance when the transfer sheet having the image formed on one surface is discharged.
For this reason, regardless of fluctuations in the conveyance speed due to slippage of the transfer paper during image formation, the paper is reversed and conveyed at the second conveyance speed in a stable state, and the transfer paper is kept at a constant interval. The paper can be discharged while being discharged.
[0017]
(4) The invention according to claim 4 is characterized in that the reverse conveying means performs reverse conveyance when the image forming means forms an image on both sides of the transfer paper. The image forming apparatus according to any one of the above.
[0018]
According to the present invention, the control (1) or (2) is performed when the image forming unit performs the reverse conveyance when the image is formed on both surfaces of the transfer paper.
Therefore, regardless of fluctuations in the conveyance speed due to slippage of the transfer paper during image formation and reverse conveyance, the reverse conveyance is performed at the second conveyance speed in a stable state, and the transfer paper interval is kept constant. Thus, it is possible to form a double-sided image while being conveyed.
[0019]
(5) In the invention according to claim 5, a plurality of transfer sheets being conveyed are retained in the image forming unit and the reverse conveying unit, and the control unit changes the acceleration timing or the deceleration timing, 5. The image forming apparatus according to claim 1, wherein the control is performed so that intervals between the plurality of transfer sheets are constant.
[0020]
  According to the present invention, in the above (1) to (4), when a plurality of transfer sheets being conveyed stays in the image forming unit and the reversing conveyance unit, the acceleration timing or the deceleration timing is changed. Control is performed so that the interval between transfer sheets is constant. For this reason, it is possible to carry out paper discharge and double-sided image formation while transporting with the transfer paper interval kept constant.
  (6) In the invention according to claim 6, the reversing and conveying means accelerates the transfer paper image-formed by the image forming means to the second conveyance speed, Is a reversing conveyance unit that reverses the front and back and decelerates to the first conveying speed in order to refeed the image forming unit, and measures the time required for reversing conveyance by the reversing conveyance unit And a timing for starting the reverse in the reverse conveying means when the time required for the reverse conveyance measured by the time measuring means is longer than a predetermined range, and start the deceleration when the time is shorter than the predetermined range. The image forming apparatus according to claim 1, further comprising a control unit that performs control to change the timing so as to advance the timing.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing an electrical configuration example of an image forming apparatus according to an embodiment of the present invention, and FIG. 2 is a side sectional view showing a mechanical configuration of the image forming apparatus according to the embodiment of the present invention.
[0022]
First, the entire image forming apparatus will be described with reference to FIG. In this embodiment, an electrophotographic image forming apparatus will be described as a specific example as an image forming apparatus.
[0023]
In FIG. 2, when there is an image formation instruction from an operation unit (not shown) or an external computer, the transfer paper p is fed out from the paper feed cassette 30 on which the transfer paper is stacked by the paper feed roller 31 to form an image. It is fed toward the section 50.
[0024]
Further, a loop is formed between the transfer paper p fed to the image forming unit 50 and the registration roller 33 by the loop forming roller 32 driven by the loop motor 524. The transfer paper p is synchronized by the registration roller 33 near the entrance to the photosensitive drum 51 and then approaches the photosensitive drum 51 serving as an image carrier. At this time, the leading edge of the transfer paper p is detected by the leading edge detection sensor 501.
[0025]
Here, image data is input from the image processing unit 30 (see FIG. 1) to the image writing unit 40, and a laser beam corresponding to the image data is irradiated onto the photosensitive drum 51 from a laser diode in the image writing unit 40, An electrostatic latent image is formed. The electrostatic latent image is developed by the developing unit 53 to form a toner image on the photosensitive drum 51.
[0026]
This toner image is transferred onto the transfer paper p conveyed in synchronization with the rotation of the photosensitive drum 51 by the transfer section 54 below the photosensitive drum 51. Then, the transfer paper p in contact with the photosensitive drum 51 is separated by the separation unit 55. The transfer paper p separated from the photosensitive drum 51 enters a fixing unit 59 via a belt conveyor-like transport mechanism 58, and the toner image is fixed by heat and pressure. In this way, an image is formed on the transfer paper p. Note that image formation and fixing are performed while being conveyed at the first conveyance speed.
[0027]
Here, when it is necessary to perform reversal paper discharge or reversal re-feeding at the time of double-sided image formation, the transfer paper p on which the toner image is fixed is reversed by a guide 61 and a reverse acceleration / deceleration motor 521. It is conveyed downward via the acceleration / deceleration roller 63 and enters the reversing unit 64. At this time, the passing state of the transfer paper p is detected by the reverse acceleration / deceleration sensor 502. Note that when the trailing edge of the transfer paper p leaves the fixing roller of the fixing unit 59, the reverse acceleration / deceleration motor 521 accelerates the first conveying speed to the second conveying speed and is driven.
[0028]
In the case of reverse paper discharge, the transfer paper p contained in the reversing unit 64 is fed out in the reverse direction by the reverse paper discharge roller 65 and discharged outside the apparatus toward the paper discharge roller 69.
[0029]
In the case of double-sided image formation, the transfer paper p contained in the reversing unit 64 is transported at a second transport speed by a reversing paper discharge roller 65 driven by a reversing paper discharge motor 522, and the ADU reversing unit. It is conveyed in 68 directions.
[0030]
In the ADU reversing unit 68, the front and back are reversed by switching the leading edge and the trailing edge of the transfer paper by the ADU reversing roller 67 driven by the ADU reversing motor 523. At this time, the passing state of the transfer paper is detected by the ADU reverse sensor 503.
[0031]
Then, the transfer paper reversely conveyed at the second conveyance speed is sent to the image forming unit 50 again while being decelerated to the first conveyance speed by the loop forming roller 32 driven by the loop motor 524. At this time, the passing state of the transfer paper p is detected by the resist portion acceleration / deceleration sensor 504. Then, in the same manner as the image formation on the first surface (front surface) described above, image formation on the second surface (back surface: a surface on which no image is formed yet) is also executed.
[0032]
Here, referring to the block diagram of FIG. 1, image formation that can be reversed and conveyed at the second conveyance speed in a stable state regardless of fluctuations in the conveyance speed of the transfer paper by appropriate conveyance control. The configuration of the apparatus will be described.
[0033]
In FIG. 1, reference numeral 10 denotes a control unit configured by a CPU or the like for controlling each part of the image forming apparatus and controlling the reverse conveyance of the transfer paper p in the present embodiment. The control means includes an overall control unit 11 that controls each part of the image forming apparatus, a first timing control unit 12 that performs first timing control of the reverse conveyance of the transfer paper p in the present embodiment, and the present embodiment. And a second timing control unit 13 that performs second timing control of the reverse conveyance of the transfer paper p in the embodiment.
[0034]
Reference numeral 20 denotes an operation display unit for displaying the status of the image forming apparatus and inputting various information. The operation display unit 20 includes an operation unit for inputting information by an operator and a display unit for displaying the status of the image forming apparatus. .
[0035]
An image processing unit 30 executes predetermined image processing in response to an instruction from the control unit 10. Reference numeral 40 denotes an image writing unit that receives image data from the image processing unit 30 and performs exposure (writing) with a laser beam on the photosensitive drum 51 of FIG.
[0036]
  Reference numeral 501 denotes a registration roller.3Reference numeral 502 denotes a leading edge detection sensor that detects the leading edge of the transfer paper that has passed through 3, and a reverse acceleration / deceleration sensor that detects the transfer paper that has passed through the reverse acceleration / deceleration roller 63. The detection results of the tip detection sensor 501 and the reverse acceleration / deceleration sensor 502 are transmitted to the first timing control unit 12, and the time required for image formation is detected from these detection results.
[0037]
Reference numeral 503 denotes an ADU inversion sensor that detects the transfer paper that has passed through the ADU inversion roller 67, and reference numeral 504 denotes a registration unit acceleration / deceleration sensor that detects the transfer paper that has reached the loop forming roller 32 via the inversion conveyance path. The detection results of the ADU reversal sensor 503 and the registration unit acceleration / deceleration sensor 504 are transmitted to the second timing control unit 13, and the time required for the reverse conveyance is detected from these detection results.
[0038]
Reference numeral 521 denotes a reverse acceleration / deceleration motor that drives the reverse acceleration / deceleration roller 63, and is driven by a driver 511 controlled by the first timing control unit 12. Reference numeral 522 denotes a reverse paper discharge motor that drives the reverse paper discharge roller 65, and is driven by a driver 512 controlled by the first timing control unit 12.
[0039]
Reference numeral 523 denotes an ADU reverse motor that drives the ADU reverse roller 67, and is driven by a driver 513 controlled by the second timing control unit 13. A loop motor 524 drives the loop forming roller 32 and is driven by a driver 514 controlled by the second timing control unit 13.
[0040]
Here, in addition to the above drawings, the operation of the present embodiment will be described with reference to the flowchart of FIG. 3 and the time charts of FIGS. 4 and 5. FIG. 3 is a flowchart showing mainly the control of the control unit 10 for performing reverse conveyance at the second conveyance speed in a stable state regardless of fluctuations in the conveyance speed of the transfer paper.
[0041]
First, with the start of image formation based on an image formation instruction from an operation unit (not shown) or an external computer, the transfer paper p is fed out from the paper feed cassette 30 by the paper feed roller 31 under the control of the control unit 10. It is fed (conveyed) toward the image forming unit 50 (S1 in FIG. 3).
[0042]
At this time, a loop (deflection) is formed between the transfer paper p fed to the image forming unit 50 and the registration roller 33 whose rotation is stopped by the loop forming roller 32 driven by the loop motor 524. The The transfer paper p is synchronized by the registration roller 33 near the entrance to the photosensitive drum 51 and then approaches the photosensitive drum 51 serving as an image carrier. At this time, the leading edge of the transfer paper p is detected by the leading edge detection sensor 501 (FIG. 3 S2, FIG. 4 (a) (1)).
[0043]
When the transfer paper p passes through the leading edge detection sensor 501 (Y in FIG. 3S), the first timing control unit 12 starts a timer count (FIG. 3S3, FIG. 4 (b) (2)).
[0044]
Then, the toner image is transferred to the first surface (front surface) of the transfer paper p by a known electrophotographic process, and the toner image is fixed on the transfer paper p by the heat and pressure of the fixing unit 59 ( FIG. 3S4).
[0045]
The transfer and fixing of the toner image are performed while being conveyed at the first conveyance speed. Also, at this first transport speed, the toner image is not stable between the transfer and fixing, and therefore it is not preferable because the image may be misaligned when sandwiched by a roller or the like. It is moved by the transport mechanism 58. Note that when the transfer mechanism 58 is transported, the transfer paper p is not sandwiched by rollers or the like, so that slipping or the like is likely to occur.
[0046]
Then, the transfer paper p on which the toner image is fixed is conveyed downward through the guide 61 and the reverse acceleration / deceleration roller 63 driven by the reverse acceleration / deceleration motor 521 and enters the reversing unit 64. At this time, the passing state of the transfer paper p is detected by the reverse acceleration / deceleration sensor 502 (S5 in FIG. 3). Here, when the transfer sheet p passes through the reverse acceleration / deceleration sensor 502 (Y in FIG. 3, FIG. 4 (b) (3)), the first timing control unit 12 ends the count of the timer and forms an image. The time T1 ((4) (4) in FIG. 4) required for the calculation is calculated (S6 in FIG. 3).
[0047]
If the time T1 required for image formation is within a predetermined range (appropriate in FIG. 3 S7), a predetermined timing after the trailing edge of the transfer paper p leaves the fixing roller of the fixing unit 59 is determined. Then (FIG. 3 S8), the reverse acceleration / deceleration motor 521 accelerates the first conveyance speed to the second conveyance speed and reversely conveys the transfer paper p (FIG. 3 S11, S12).
[0048]
Further, if the time T1 required for image formation is larger than the predetermined range (large in S7 in FIG. 3), a delay occurs due to slip or the like, so that the rear end of the transfer paper p causes the fixing roller of the fixing unit 59 to move. After the separation, the reverse acceleration / deceleration motor 521 accelerates the transfer paper p from the first transport speed to the second transport speed at an earlier timing at a predetermined timing (FIG. 3 S9). The paper is reversed and conveyed (S11 and S12 in FIG. 3).
[0049]
Further, if the time T1 required for image formation is smaller than the predetermined range (small in FIG. 3 S7), the advance has occurred for some reason, so that the trailing edge of the transfer paper p causes the fixing roller of the fixing unit 59 to move. After the separation, the reverse acceleration / deceleration motor 521 accelerates the transfer sheet p from the first transport speed to the second transport speed at a later timing at a predetermined timing (FIG. 3 S10). The paper is reversed and conveyed (S11 and S12 in FIG. 3).
[0050]
As described above, when the image-formed transfer sheet is conveyed while being accelerated to the second conveyance speed and the front and back sides are reversed by exchanging the leading edge and the trailing edge of the transfer sheet, the time T1 required for image formation. By referring to the measurement result T1 and changing the acceleration timing in the reverse conveyance (FIG. 4 (c) (5)), it is caused by slip of the transfer paper at the time of image formation. Regardless of the fluctuation of the conveyance speed, it is possible to carry out the reverse conveyance at the second conveyance speed in a stable state, and it is possible to keep the transfer paper interval constant.
[0051]
The transfer paper p reversely conveyed at the second conveyance speed enters the ADU reversing unit 68, and the passage is detected by the ADU reversal sensor 503 (FIG. 3S13, FIG. 5 (a) (1)).
[0052]
When the transfer paper p passes through the ADU inversion sensor 503 (Y in FIG. 3), the second timing control unit 13 starts counting of the timer (FIG. 3S14, FIG. 5 (b) (2)).
[0053]
Then, the ADU reversing unit 68 reverses the front and back by replacing the leading end and the trailing end of the transfer paper p ((c) (3) in FIG. 5). At this time, the ADU reverse motor 523 is driven from the second transport speed (forward rotation) to the second transport speed (reverse rotation).
[0054]
The reversal conveyance of the transfer paper p is performed while being conveyed at the second conveyance speed. However, depending on how the ADU reversal roller 67 of the ADU reversing unit 68 is sandwiched, the grip is too good for thick paper thicker than the standard. In some cases, the sheet is reversely conveyed at a timing earlier than usual. Further, depending on how the ADU reversing roller 67 is sandwiched by the ADU reversing unit 68, the thin paper that is thinner than the standard and the special paper that has been subjected to surface treatment that is slippery may have a poor grip and may be reversed and conveyed at a later timing than usual.
[0055]
Then, the reversely conveyed transfer paper p passes through the resist portion acceleration / deceleration sensor 504 (S15 in FIG. 3) and then reaches the loop forming roller 32. In other words, the passage state of the transfer paper p is detected by the resist portion acceleration / deceleration sensor 504. Here, when the transfer paper p passes through the registration portion acceleration / deceleration sensor 504 (Y in FIG. 3, FIG. 5B), the second timing control unit 13 ends the count of the timer and inverts it. Time T2 (FIG. 5 (b) (5)) required for conveyance is calculated (S16 in FIG. 3).
[0056]
  AndReverse transferIf the time T2 required for the time is within a predetermined range (appropriate in FIG. 3 S17), the loop forming motor 524 changes the second transport speed to the first transport speed at a predetermined timing (FIG. 3 S18). And the reverse conveyance of the transfer paper p is completed (S21 in FIG. 3).
[0057]
  Also,Reverse transferIf the time T2 required for the time is larger than the predetermined range (large in FIG. 3 S17), a delay occurs due to slip or the like, and at a later timing at a predetermined timing (FIG. 3 S19), The loop forming motor 524 decelerates from the second conveyance speed to the first conveyance speed and ends the reverse conveyance of the transfer paper p (S21 in FIG. 3).
[0058]
  Also,Reverse transferTime T required for2If it is smaller than the predetermined range (small in FIG. 3 S17), the advance has occurred for some reason. Therefore, the loop forming motor 524 causes an earlier timing at a predetermined timing (FIG. 3 S20). The reversal conveyance of the transfer paper p is terminated by decelerating from the second conveyance speed to the first conveyance speed (S21 in FIG. 3).
[0059]
Then, the transfer paper p decelerated to the first conveyance speed as described above is re-fed toward the image forming unit, and image formation on the second side (back side) is executed (S22 in FIG. 3).
In this way, the image-formed transfer paper is accelerated and conveyed to the second conveyance speed, and the front and back sides of the transfer paper are reversed by reversing the front and back of the transfer paper for image re-feeding. When the speed is reduced to the first transport speed, the time T2 required for the reverse transport is measured, and the control for changing the deceleration timing in the reverse transport is performed with reference to the measurement result T2 (FIG. 5C) 6)), it becomes possible to perform reverse conveyance and re-feeding in a stable state regardless of fluctuations in the conveyance speed due to slip or grip of the transfer paper during reverse conveyance, and the transfer paper interval. Can be kept constant.
[0060]
In the above description, the control of the reverse acceleration / deceleration roller 64 is the reverse conveyance acceleration timing change control for double-sided image formation based on the time T1 required for image formation. It can also be used as timing control.
[0061]
In addition, the control of the acceleration timing and the control of the deceleration timing in each of the above descriptions is that the intervals between the plurality of transfer sheets are constant when the plurality of transfer sheets staying during the image formation and the reverse conveyance are staying. It is preferable to control as described above. By such control, it becomes possible to perform paper discharge and double-sided image formation while transporting with the transfer paper interval kept constant.
[0062]
【The invention's effect】
As described above in detail, the present invention provides the following effects.
(1) According to the first aspect of the present invention, an image is formed by transferring and fixing the toner image while the transfer paper is conveyed at the first conveyance speed, and the image-formed transfer paper is accelerated to the second conveyance speed. When the front and back sides of the transfer paper are reversed by reversing the front and back edges of the transfer paper, measure the time required for image formation and refer to this measurement result to determine the acceleration timing for reverse conveyance. The control to change is performed. For this reason, it is possible to perform reverse conveyance at the second conveyance speed in a stable state regardless of fluctuations in the conveyance speed due to slippage of the transfer paper during image formation, and the transfer paper interval is kept constant. It becomes possible.
[0063]
(2) According to the second aspect of the present invention, an image is formed by transferring and fixing the toner image while the transfer paper is being conveyed at the first conveyance speed, and the image-formed transfer paper is accelerated to the second conveyance speed. Measure the time required for reverse conveyance when the front and back sides of the transfer paper are reversed by reversing the front and back edges and decelerated to the first conveyance speed for re-feeding the image. In addition, referring to the measurement result, control for changing the deceleration timing in the reverse conveyance is performed. For this reason, it is possible to perform reverse conveyance and re-feeding in a stable state regardless of fluctuations in the conveyance speed due to slippage of transfer paper during reverse conveyance, and to maintain a constant transfer paper interval. It becomes possible.
[0064]
(3) In the invention described in claim 3, the control of the above (1) is performed when the image forming unit performs the reverse conveyance when discharging the transfer sheet on which the image is formed on one surface. . For this reason, regardless of fluctuations in the conveyance speed due to slippage of the transfer paper during image formation, the paper is reversed and conveyed at the second conveyance speed in a stable state, and the transfer paper is kept at a constant interval. The paper can be discharged while being discharged.
[0065]
(4) In the invention described in claim 4, the control of (1) or (2) is performed when the image forming means performs reverse conveyance when forming an image on both sides of the transfer paper. Therefore, regardless of fluctuations in the conveyance speed due to slippage of the transfer paper during image formation and reverse conveyance, the reverse conveyance is performed at the second conveyance speed in a stable state, and the transfer paper interval is kept constant. Thus, it is possible to form a double-sided image while being conveyed.
[0066]
  (5) In the invention described in claim 5, in the above (1) to (4), when a plurality of transfer sheets being conveyed are retained in the image forming means and the reverse conveying means, the acceleration timing or the deceleration timing is set. By changing, the interval between the plurality of transfer sheets is controlled to be constant. For this reason, it is possible to carry out paper discharge and double-sided image formation while transporting with the transfer paper interval kept constant.
  (6) In the invention according to claim 6, by combining the above (1) and (2), it is stable regardless of the fluctuation of the conveyance speed due to the slip of the transfer paper at the time of image formation or reverse conveyance. In this state, it is possible to perform reverse conveyance and refeeding, and it is possible to keep the transfer sheet interval constant.
[Brief description of the drawings]
FIG. 1 is a functional block diagram showing an electrical configuration of an image forming apparatus according to an embodiment of the present invention.
FIG. 2 is a configuration diagram illustrating a mechanical configuration of an image forming apparatus according to an exemplary embodiment of the present invention.
FIG. 3 is a flowchart illustrating an operation of the image forming apparatus according to the exemplary embodiment of the present invention.
FIG. 4 is a time chart showing the operation of the image forming apparatus according to the embodiment of the present invention.
FIG. 5 is a time chart illustrating an operation of the image forming apparatus according to the exemplary embodiment of the present invention.
[Explanation of symbols]
10 Control means
11 Overall control unit
12 First timing control unit
13 Second timing control unit
20 Operation display
30 Image processing unit
40 Image writer
501 Tip detection sensor
502 Reverse acceleration / deceleration sensor
503 ADU reversing sensor
504 Resistor acceleration / deceleration sensor
521 Reverse acceleration / deceleration motor
522 Reverse paper discharge motor
523 ADU reversing motor
524 loop motor

Claims (6)

An image forming means for forming an image by transferring and fixing a toner image while conveying the transfer paper at a first conveying speed;
Reversing conveying means for inverting the front and back by replacing the leading edge and the trailing edge of the transfer paper while accelerating and conveying the transfer paper image-formed by the image forming means to the second conveying speed;
Time measuring means for measuring time required for image formation in the image forming means;
Changed to the earlier time required for image formation, which is measured by the timer means the acceleration start timing in said reversing transport means is longer than the predetermined range, if less than a predetermined range, delaying the acceleration start timing Control means for performing control,
An image forming apparatus comprising: An image forming means for forming an image by transferring and fixing a toner image while conveying the transfer paper at a first conveying speed;
While transferring the transfer paper image-formed by the image forming means to the second transfer speed, the front and back sides of the transfer paper are reversed by reversing the front and back edges of the transfer paper, and the transfer paper is re-transferred to the image forming means. Reversing conveying means that decelerates to the first conveying speed for feeding paper,
Time measuring means for measuring the time required for the reverse conveyance in the reverse conveyance means;
Changes as time required for reversing transport measured by said time measuring means is longer than a predetermined range delaying the deceleration start timing in said reversing transport means, is shorter than the predetermined range to speed the deceleration start timing Control means for performing control,
An image forming apparatus comprising: The reversing conveyance unit performs reversal conveyance when discharging the transfer paper on which one image is formed by the image forming unit.
The image forming apparatus according to claim 1. The reverse conveying unit performs reverse conveyance when forming an image on both surfaces of the transfer paper by the image forming unit.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. A plurality of transfer sheets being conveyed are retained in the image forming unit and the reverse conveying unit,
The control means controls the intervals between the plurality of transfer sheets to be constant by changing the acceleration timing or the deceleration timing.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The reversing and conveying means reverses the front and back by replacing the leading edge and the trailing edge of the transferring paper while accelerating and conveying the transfer paper on which the image is formed by the image forming means to the second conveying speed. Reversing conveying means that decelerates to the first conveying speed in order to refeed the forming means,
Time measuring means for measuring the time required for the reverse conveyance in the reverse conveyance means;
Changed to delay the deceleration start timing in the reverse conveyance means if the time required for the reverse conveyance measured by the time measuring means is longer than a predetermined range, and to advance the deceleration start timing if it is shorter than the predetermined range Control means for performing control,
The image forming apparatus according to claim 1, further comprising:

Images