JP2004317865A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enlarge a pre-registration delay allowance without increasing the conventional accelerating speed of the registration roller in an image forming apparatus carrying out paper feeding, especially by image reference. <P>SOLUTION: In the image forming apparatus for feeding paper especially by image reference, a registration roller speed control means as follows is provided. 1. When a registration roller part is reached within a specified time from the specified reference by the means, carrying in the direction of the image forming part is started by counting the timing after inclination compensation of sheet material. 2. After inclination of the sheet material is compensated when more than the specified time is taken from the specified reference to the registration roller, carrying in the direction of the image forming apparatus is started without any standby time. The carrying speed at this time is determined according to the delayed time from the specified time. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine or a printer that forms an image by an electrophotographic method or the like, and particularly to an apparatus that feeds sheet materials on the basis of image formation and a sheet feeding interval that is small. It is effective for
[0002]
[Prior art]
For example, in an image forming apparatus such as a copying machine, a printer, and a facsimile, a sheet material (transfer material, photosensitive paper, electrostatic recording paper, 2. Description of the Related Art Apparatuses for fixing an unfixed toner image formed and carried on a paper sheet such as a printing paper) in accordance with target image information by a transfer method (indirect method) or a direct method are widely used.
[0003]
Further, an apparatus for directly forming an image on a sheet material using a liquid containing a dye or a pigment, such as an ink jet method, is also used.
[0004]
FIG. 3 is a schematic cross-sectional view of a conventional image forming apparatus. In FIG. 3, reference numeral 100 denotes a full-color image forming apparatus as an example of the image forming apparatus, and 100A denotes a full-color image forming apparatus main body (hereinafter, referred to as an apparatus main body). Reference numeral 101 denotes a digital full-color image reader unit (hereinafter, referred to as a reader unit) arranged at an upper portion of the apparatus main body 100A, and 102, a digital full-color image printer unit (hereinafter, referred to as a printer unit) arranged at a central portion of the apparatus main body 100A. ) And 103, a paper feeder disposed below the apparatus main body 100A, and 61, a manual paper feeder.
[0005]
Then, in the reader unit 101 as a reading unit, the original 30 placed on the original table glass 31 is exposed and scanned by the exposure lamp 32, and the reflected light image from the original 30 is transmitted to the full-color CCD sensor 34 by the lens 33. The light is condensed to obtain a color separation image signal. The color-separated image signal is processed by a video processing unit (not shown) through an amplification circuit (not shown), and is sent to the printer unit 102.
[0006]
On the other hand, the printer unit 102 as an image forming unit includes a photosensitive drum 1 as an image carrier, a laser exposure optical system 3, a heat roller fixing device 9, and the like. The photosensitive drum 1 is rotatably supported in the direction of the arrow, and is surrounded by a pre-exposure lamp 11, a corona charger 2, a laser exposure optical system 3, a potential sensor 12, and four developing devices 4y of different colors. , 4c, 4m, and 4Bk, a photosensitive drum light amount detecting unit 13, a transfer device 5, a cleaning device 6, and the like.
[0007]
In such a printer unit 101, an image signal from the reader unit 101 is converted into an optical signal by a laser output unit (not shown) in the laser exposure optical system 3, and the laser light converted into the optical signal is converted into a polygon. After being reflected by the mirror 3a, the light is projected onto the surface of the photosensitive drum 1 through the lens 3b and the mirror 3c.
[0008]
On the other hand, at the time of image formation, the photosensitive drum 1 is rotated in the direction of the arrow, the photosensitive drum 1 after having been neutralized by the pre-exposure lamp 11 is uniformly charged by the charger 2, and the light image E is irradiated for each of the separated colors. To form a latent image.
[0009]
Next, by operating a predetermined developing device, the latent image on the photosensitive drum 1 is developed, and a toner image having a resin and a pigment as a base is formed on the photosensitive drum 1. The developing units 4y, 4c, 4m, and 4Bk are selectively brought closer to the photosensitive drum 1 according to the respective separation colors by the operation of the eccentric cams 24y, 24c, 24m, and 24Bk.
[0010]
Next, after the toner image on the photosensitive drum 1 is fed from the sheet feeding device 103 or the manual sheet feeding device 61, the toner image is attracted to the transfer device 5 via the electrostatic attraction roller unit 5 g, and the photosensitive drum 1 The image is transferred to the sheet material supplied to the facing position.
[0011]
Here, the transfer device 5 includes a transfer drum 5a, a transfer charger 5b, an attraction roller 5g opposed to an attraction charger 5c for electrostatically attracting a sheet material, an inner charger 5d, and an outer charger 5e. A sheet supporting sheet 5f made of a dielectric material is integrally stretched in a cylindrical shape in a peripheral opening area of the transfer drum 5a which is axially supported so as to be driven to rotate. In this embodiment, a dielectric sheet such as a polycarbonate film is used as the sheet material supporting sheet 5f.
[0012]
Then, the transfer device 5 configured as above transfers the toner image on the photosensitive drum to the sheet material carried on the sheet material carrying sheet 5f by the transfer charger 5b by rotating the transfer drum 5a. . Further, thereafter, a desired number of color images are transferred to the sheet material thus electrostatically attracted to the sheet material carrying sheet 5f and conveyed, thereby forming a full color image.
[0013]
Next, when the transfer of the toner image of the desired color is completed in this way, the sheet material is separated from the transfer drum 5a by the action of the separation claw 8a, the separation push-up roller 8b, and the separation charger 5h, and the heat roller fixing unit 9 is removed. The paper is discharged to the paper discharge tray 10 through the paper tray.
[0014]
By the way, the full-color image forming apparatus 100 can form an image on both sides of a sheet material. When forming an image on both sides of the sheet material, the sheet material passes through the heat roller fixing device 9. Then, immediately after the conveyance path switching guide 19 is driven, the sheet material is once guided to the reversing path 2la via the conveyance vertical path 20, and the reversing of the reversing roller 21b causes the rear end of the fed sheet to be the leading end. The sheet is retracted in a direction opposite to the direction in which the sheet is fed, and is stored in an intermediate tray 22 which is another example of the sheet stacking unit. Thereafter, an image is formed on the other surface again by the above-described image forming step.
[0015]
After the transfer, the photosensitive drum 1 is cleaned with a cleaning device 6 to remove the residual toner on the surface, and then subjected to the image forming process again. Further, the full-color image forming apparatus 100 includes the fur brush 14 and the sheet brush to prevent the scattering and adhesion of powder such as toner on the sheet material supporting sheet 5f of the transfer drum 5a and the adhesion of oil on the sheet material. Cleaning is performed by the action of a backup brush 15 facing the fur brush 14 via the material carrying sheet 5f and a backup brush 17 facing the oil removing roller 16 via the oil removing roller 16 and the sheet material carrying sheet 5f.
[0016]
Here, such cleaning is performed before or after image formation, and at any time when a jam (paper jam) occurs.
[0017]
Further, the full-color image forming apparatus 100 arbitrarily sets the gap between the sheet supporting sheet 5f and the photosensitive drum 1 by rotating the eccentric cam 25 and operating the cam follower 5i integrated with the transfer drum 5a. The transfer drum 5a and the photosensitive drum 1 are spaced apart from each other except during image formation.
[0018]
By the way, an image position reference detection sensor 80 for detecting a reference of an image position serving as a reference when forming an image on a sheet material as described later with reference to FIG. 4 is arranged inside the transfer drum 5a. In the present embodiment, when the transfer drum 5a is pressed against the photosensitive drum 1 at the start of copying, the image position reference detection sensor 80 is driven by the rotating photosensitive drum 1 to rotate the transfer drum 5a. And when the rotation is almost stabilized (after about 1/3 rotation), a signal indicating the image position reference is generated.
[0019]
The image position reference signal (hereinafter, referred to as an Itop signal) is regularly transmitted for each rotation of the transfer drum 5a, and operations such as reading a document and conveying a sheet material are performed based on this signal.
[0020]
On the other hand, after the copy is started, the sheet feeding device 103 rotates the pickup rollers 61 and 62 and the pair of retard rollers 63 and 64 constituting the separation unit based on the Itop signal, and the first and second cassettes 72 as sheet stacking means. , 73 are picked up and separated.
[0021]
In addition, when two or more sheet materials are sandwiched between the sheet feeding rollers 63a and 64a rotating in the direction of the arrow and the sheet feeding rollers 63a and 64a, the pair of retard rollers 63 and 64 are used as the sheet feeding rollers 63a and 64a. And the separation rollers 63b and 64b sandwich the sheet together with the paper feed rollers 63a and 64a, the separation rollers 63b and 64b, and the paper feed rollers 63a and 64a. When a single sheet of material is sandwiched between the sheet feed rollers 63a and 64a, the separation rollers 63b and 64b have a torque limiter that is shown later.
[0022]
Also, when forming an image on the other surface of the sheet material (not shown) having an image formed on one surface stored in the intermediate tray 22, the pull-out roller 65 of the re-feeding unit 60 is provided at a predetermined timing. Then, the retard roller pair 66 is rotated to pull out and separate the sheet material. The retard roller pair 66 also has a paper feed roller 66a, a separation roller 66b, and a torque limiter.
[0023]
When a predetermined time t1 elapses after the input of the Itop signal, the control means 81 drives sheet feeding motors M4 and M5 shown in FIG. 5 described later to rotate the conveying rollers 50 and 51 so as to start a sheet feeding operation. Thus, the sheet material is conveyed to the stopped registration roller 54 via the conveyance rollers 41, 43, 45, 50, 51.
[0024]
The sheet material is pressed against the stopped registration rollers 54 to form a loop, thereby performing skew feeding. Thereafter, the controller 81 drives the registration roller drive motor M to rotate the registration roller 54 at the timing when an image is formed at a predetermined position on the sheet material, and transfers the sheet material to the transfer charger 5b at the image transfer position. Transport to
[0025]
Next, the sheet feeding operation of the sheet feeding device 103 having such a configuration will be described in detail with reference to FIGS. FIG. 5 shows a state in which the A4 size sheet material is continuously conveyed from the second cassette 73 farthest from the image transfer unit, and the state of movement of the sheet material to the transfer charger 5b is represented by the time axis on the horizontal axis. This is a diagram in which the vertical axis is represented by distance.
[0026]
FIG. 6 is a drive development view of a drive system relating to sheet feeding from the cassettes 72 and 73 and refeeding from the double-sided deck 22, and FIG. 7 is a drive development view of drive systems of the transport rollers 50 and 51 and the registration roller 54. is there.
[0027]
In FIG. 6, GA is a first gear train for transmitting the driving force of the paper feed motor M3 to the vertical path transport roller 40, the pull-out roller 65, the paper feed roller 66a and the separation roller 66b constituting the retard roller pair 66. , GB is a second gear train for transmitting the driving force of the paper feed motor M2 to the vertical path transport roller 42, the pickup roller 61, the paper feed roller 63a and the separation roller 63b constituting the retard roller pair 63, and GC is paper feed. This is a third gear train for transmitting the driving force of the motor M1 to the vertical path conveying roller 44, the pickup roller 62, the sheet feeding roller 64a constituting the retard roller pair 64, and the separation roller 46b.
[0028]
In the figure, G1 constitutes a first gear train GA and is a gear attached to a shaft 66a1 of the paper feed roller 66a via a clutch CL1. When turned ON, the gear G1 is connected to the shaft 66a1 of the paper feed roller 66a via the clutch CL1. Thus, when the sheet feeding operation is started, the pull-out roller 65 and the pair of retard rollers 66 rotate together with the vertical path conveying roller 40 directly driven by the driving force of the sheet feeding motor M3.
[0029]
G2 and G4 are gears that constitute the second and third gear trains GB and GC and are attached to the shafts 63a1 and 64a1 of the paper feed rollers 63a and 64a via the clutches CL2 and CL3. At this time, when the clutches CL2 and CL3 are turned ON by the control device 80, the gears G2 and G4 are connected to the shafts 63a1 and 64a1 of the paper feed rollers 63a and 64a via the clutches CL2 and CL3.
[0030]
On the other hand, G3 and G5 are gears provided rotatably with respect to the shafts 63a1 and 64a1 of the paper feed rollers 63a and 64a, and the driving force of the paper feed motors M2 and M1 passes through the gears G3 and G5 in the vertical path. The power is directly transmitted to the transport rollers 42 and 44. With this configuration, when the paper feeding operation is started, the pickup rollers 61 and 62 and the retard roller are provided together with the vertical path conveying rollers 42 and 44 driven directly by the driving force of the paper feeding motors M2 and M1. The pair 63, 64 rotates.
[0031]
In the figure, TL1, TL2, and TL3 transmit a rotational force to the separation rollers 63b, 64b, and 66b so that the transport direction is opposite to that of the paper feed rollers 63a and 64a, as described above. When two or more sheet materials are sandwiched by the rollers 63a and 64a, the second and subsequent sheet materials are returned, and when only one sheet material is sandwiched, the sheet material is rotated together with the sheet feeding rollers 63a, 64a and 66a. It is a torque limiter that acts to perform
[0032]
CL4, CL5, and CL6 are one-way clutches that operate to rotate the paper feed rollers 63a, 64a, and 66a freely when pulling out the jammed sheet material in the transport direction.
[0033]
On the other hand, in FIG. 7, GD is a fourth gear train for transmitting the driving force of the registration roller driving motor M to the registration roller 54, and GE is a fifth gear train for transmitting the driving force of the sheet feeding motor M5 to the conveyance roller 50. A gear train GF is a sixth gear train for transmitting the driving force of the paper feed motor M4 to the transport roller 51.
[0034]
G6 constitutes a fourth gear train GD and is a gear attached to a shaft 54a of the registration roller 54 via a clutch CL7. After the sheet feeding operation is started, the control device 80 controls a predetermined sheet material. When the clutch CL7 is turned on at the timing when an image is formed at the position, the gear G6 is connected to the shaft 54a of the registration roller 54 via the clutch CL7. Accordingly, the registration roller 54 rotates as described above, and the sheet material is conveyed to the transfer charger 5b.
[0035]
By configuring each drive system in this way, for example, when the sheet material S of the second cassette 73 is fed, copying starts, and the transfer drum 5a presses the photosensitive drum 1 and then moves to the image position reference. When an Itop signal is input from the detection sensor 80 and the paper feed motor M1 shown in FIG. 6 is driven by the control device 81 based on the Itop signal (this is defined as a time axis 0), the pickup roller 62 and the retard roller The paper feed roller 64a and the separation roller 64b forming the pair 64 rotate to pick up and separate the sheet material S.
[0036]
Here, in the present embodiment, the conveyance speed of the pickup and the sheet material S from the pickup to the registration roller is 400 mm / sec. This is because the separation ability of the retard roller pair 64 is a reference, and if the speed is higher than this, the life of the sheet feeding roller 64a is significantly shortened and the sheet material S is double fed.
[0037]
Next, after being separated in this way, the sheet feeding motors M2, M3, M4, M5 are driven in addition to the sheet feeding motor M1, and the sheet material is transported by the vertical path transport rollers 40, 42, 44 and the transport rollers 50, 51. S is conveyed toward the registration roller 54.
[0038]
Next, after forming a loop in the sheet material S by the registration roller 54 and performing skew feeding, the sheet feeding motor is temporarily stopped, and a signal from the pre-registration sensor 53 provided on the upstream side of the registration roller 54 is detected. Based on the detection signal, the control device 81 drives the registration roller drive motor M after a predetermined time Tr has elapsed so that the sheet material S reaches the image transfer position at the timing of Tt shown in FIG. Is rotated to start conveyance.
[0039]
Here, in the present embodiment, the conveying speed of the sheet material S by the registration rollers is set to 400 mm / sec from immediately after the start of the conveyance to a position 20 mm upstream of the image transfer position, and the subsequent portion is set to 200 mm which is substantially equal to the image forming speed. / Sec.
[0040]
After the detection signal from the pre-registration sensor 53 is input, the sheet material S is stopped until a predetermined time Tr elapses, so that the sheet material S is skewed and the sheet material S is fed in the feeding direction. Is corrected. Further, by making the initial conveying speed of the sheet material S by the registration roller faster than the image forming speed, the interval between the preceding sheet and the following sheet sent out by the registration roller can be made smaller than the interval to the registration roller. Productivity can be increased.
[0041]
Next, the sheet material S is electrostatically attracted to the transfer drum 5a and is conveyed on the transfer drum at a speed equal to the image forming speed. Thereafter, the image is transferred at the transfer charger 5b which is the image transfer position. It is transported to the fixing device. In the present embodiment, the image forming speed is 200 mm / sec.
[0042]
Here, when the Itop signal is set to 0, the time Tt is set by pressing the transfer drum and then applying toner to the image written by laser on the photosensitive drum in accordance with the Itop signal. It is almost matched with the time until it comes to the transfer position.
[0043]
The transport speed is set to 400 mm / sec and 200 mm / sec as described above so that the sheet material S can be sent from the second cassette 73 from the image transfer unit with the target of the time Tt.
[0044]
Further, when the sheet material S is conveyed from the first cassette 72 closer to the image transfer unit than the second cassette 73, if the time of the pick-up start of the sheet material S is delayed with the aim of the same time Tt, the later In this case, it is sufficient to perform sheet feeding and transport control at exactly the same timing and speed as sheet feeding from the second cassette 73.
[0045]
On the other hand, in the drive system diagrams shown in FIGS. 6 and 7, the registration roller drive motor M for driving the registration roller 54, the pickup rollers 61 and 62, the pull-out roller 65, the pair of retard rollers 63, 64 and 66, the vertical path conveyance roller 40 , 42, 44 and the sheet feeding motors M1 to M5 for driving the transport rollers 50, 51 are all stepping motors, whereby all the rollers up to the registration roller 54 are directly driven by the stepping motor, and as a result, the speed is switched. , The accuracy of rotation, STOP, etc., is extremely improved, thereby enabling the position of the sheet material S to be transported very accurately and stably.
[0046]
Next, the configuration around the registration roller 54 and the transport state of the sheet material S there will be described in detail.
[0047]
The fed sheet material S once strikes the nip of the registration roller pair 54. At this time, the sheet material detection sensor 53 disposed near the upstream of the registration roller pair detects the front end of the sheet material. After the front end abuts the registration roller, the sheet material is generally pushed by 5 to 15 mm and the registration roller is pressed at a predetermined timing. The upstream conveying rollers 40, 42, 44, 50, 51 are stopped. As a result, skew correction is performed by arranging the sheet material parallel to the nip line of the registration roller due to the waist of the sheet. After that, the registration roller is driven in synchronization with the image of the image forming means, thereby aligning the sheet material with the image.
[0048]
The sheet detection sensor is composed of a reflection type photo-interrupter in which light from a light emitting element is applied to a sheet material and reflected light or diffused light is directly detected by a light receiving element. Further, the position of the sheet detection sensor 53 in the direction perpendicular to the sheet conveyance is arranged near the center in a device that distributes the sheet to both sides based on the center of the sheet when conveying a sheet having a different width in the direction perpendicular to the sheet conveyance. In an apparatus that conveys a sheet based on one end of the largest sheet, the sheet is arranged closer to the reference side.
[0049]
In addition, it has a butting plate that does not have a registration roller and can be selectively retracted immediately before the sheet conveying roller in front of the image forming unit, and a sheet detection sensor similar to the above is arranged upstream of the butting plate to detect the same. In some cases, the conveyance roller upstream of the registration roller is stopped at a predetermined timing from a signal. Similar to the registration roller, skew correction is performed by aligning the sheet parallel to the abutment plate, and the sheet and image are aligned by evacuating the abutment plate in synchronization with the image of the image forming means. ing.
[0050]
In recent years, digitization has been advanced in image forming apparatuses such as fax machines, printers, and copiers. For example, in an electrophotographic copier, reflected light of illumination of a reader portion is read by a photoelectric element such as a CCD, and A / D converted. Then, there is a method in which a laser beam is emitted and the polygon mirror is rotated to scan in the generatrix direction of the photoreceptor to write the photoreceptor, or to write the photoreceptor using LEDs arranged at a fine pitch.
[0051]
However, in promoting the above-mentioned digitization, for example, as the number of revolutions of the polygon mirror and the driving frequency of the LED head increase, the technical problems increase, and the cost of solving the problems increases. Therefore, it is desired to improve productivity by reducing the interval between sheets as much as possible even at the same image forming speed.
[0052]
It is also desirable to reduce the image forming speed as much as possible in terms of energy and durability of all moving or rotating parts.
[0053]
However, when the intervals between sheets are shortened, for example, in a copying machine, there is a problem that the time of the back scan in the reader unit is shortened. As one of the methods for solving such a problem, there is a method having a memory for the entire surface of an image that can be read by one reader scan. In this case, it is possible to omit the back scan time of the reader by repeatedly ejecting the image once read from the memory, so that the space between the sheets can be reduced. In the past, memories were expensive, but in recent years the price has been remarkably reduced, and devices equipped with means for storing images, such as memories and hard disks, have been released. Therefore, the factor that determines the sheet interval is determined by the sheet conveyance performance of the image forming apparatus.
[0054]
Further, in a color copying machine as in the above-mentioned conventional example, the copying speed is reduced to about half at a time unless two sheets are electrostatically attracted onto the transfer drum. Therefore, it is required to adsorb two sheet materials to the transfer drum as much as possible. Therefore, as described above, a method has been adopted in which a sufficient interval is provided at the time of pickup in which the transport speed is unstable, and the interval between the sheet materials is narrowed after the registration roller whose transport speed is accurate.
[0055]
[Problems to be solved by the invention]
However, the conventional image forming apparatus has the following disadvantages. FIG. 8 is a cross-sectional view showing a state during continuous two-sheet copying operation from the lower cassette 73 in the conventional image forming apparatus shown in FIG. The details show a state in which the preceding sheet material S1 of A4 size is transferring the toner image TG1, and the succeeding sheet material S2 is being developed before the toner image TG2 transferred to the sheet material S2 after the paper is fed and before the registration rollers arrive. It is sectional drawing.
[0056]
In the conventional control, the following time is required from when the leading edge of the sheet material reaches the registration roller to when the conveyance from the registration roller to the image forming unit is started.
[0057]
Creating a loop for skew correction, generally the time required to turn off / on the transport roller before the 5 to 15 mm registration ... If high rotation is required, to drive the stepping motor accurately without step-out Requires a certain pre-excitation time between the fall / rise with the acceleration / deceleration curve and the OFF / ON.
[0058]
Adjustment time for restarting in accordance with the transfer timing: about 50 msec
This time fluctuates depending on the paper conveyance speed from the sheet material feeding to the registration roller.
[0059]
That is all. Therefore, if this time cannot be secured, that is, if the sheet material is delayed, a delay jam has to be made. Here, assuming that the image forming speed (the speed of the photosensitive drum 1 and the transfer drum 5a) is V1 and the distance between the leading ends of the toner images TG1 and TG2 is L1, the leading end of the preceding sheet arrives at the transfer position 5T and then reaches the leading end of the succeeding sheet. The time until the operation must be L1 / V1. Therefore, in the conventional image forming apparatus, at the registration roller position, the succeeding paper must arrive within t = L1 / V1 after the leading edge of the preceding paper arrives. Generating the delay jam of the pre-registration sensor 53 in the state shown in FIG. 8 wastes the toner image TG2 because the development of the toner is started before the detection of the pre-registration delay jam. This causes problems such as soiling of the transfer drum surface, an increase in waste toner recovery capacity of the transfer cleaner, and toner scattering. On the other hand, in order to increase the jam margin, there is a method of increasing the sheet feeding speed or the initial conveying speed of the registration rollers with respect to the image forming speed. In order to secure a sufficient section for increasing the speed, the size of the apparatus is increased.
[0060]
Accordingly, an object of the present invention is to increase the margin of delay jam before registration without increasing the paper feeding speed or the conveying speed of the registration rollers, and without increasing the cost or the size of the apparatus, thereby increasing the productivity at a low cost. It is to provide a configuration to realize.
[0061]
[Means for Solving the Problems]
An image forming apparatus for forming an image on a sheet, a feeding means for continuously feeding the sheet material from the sheet material tray to the image forming apparatus, and a leading end of the fed sheet material on an upstream side of the image forming means. A sheet aligning means for feeding the sheet toward the image forming means after correcting the skew in the image, timing the image, and a pre-alignment sheet disposed near the upstream of the sheet aligning means. A measuring means for measuring a time t when a sheet material reaches the pre-alignment sheet material detecting means from a predetermined reference in the image forming apparatus provided with the material detecting means; The sheet material is supplied at a first speed (V1) substantially equal to the material conveying speed, a predetermined second speed (V2) satisfying V2 ≧ V1, and an arbitrary third speed (V3) satisfying V3 <V2. Feeding speed variable means for enabling feeding and Is less than or equal to the first predetermined time T1, the skew of the sheet material is corrected by the sheet material aligning means, the timing is measured for the image, and then the sheet material is directed toward the image forming means at the second speed (V2). When the sheet material is fed and the t is longer than the first predetermined time T1, the sheet material aligning means performs only the skew correction without stopping the sheet material conveying means upstream of the sheet material aligning means. Feeding the sheet material toward the image forming unit at the third speed (V3), feeding the sheet material for a predetermined distance or for a predetermined time, and then changing the speed to the first speed (V1) so that the leading edge of the sheet material becomes the image. And speed control means for controlling so as to reach the forming means.
[0062]
BEST MODE FOR CARRYING OUT THE INVENTION
The image forming apparatus of the present invention is the same as the conventional one shown in 3 and 4, and the detailed description of the configuration and basic operation is omitted. The driving configuration is the same as that of the conventional one shown in FIGS.
[0063]
An embodiment of the present invention will be described below with reference to FIGS.
[0064]
FIG. 1 is a flowchart showing the paper transport sequence of the present invention when the second sheet cassette 73 feeds the sheet material S, and FIG. 2 is a diagram showing the actual movement of the sheet material based on the flowchart of FIG. is there.
[0065]
In FIG. 1, as in the conventional example, the sheet is fed by the pickup roller 62 based on the signal of the image position reference detection sensor, and when the sheet is fed multiple times, it is reliably separated into one sheet by the pair of retard rollers 64 (P1). Next, the leading edge of the sheet material operates the vertical path sensor lever 45 to detect the leading edge of the sheet material by a photo sensor (not shown). With this timing as the reference t = 0, measurement of the time t until the leading edge of the sheet material reaches the pre-registration sensor 53 is started thereafter (P2).
[0066]
Next, the sheet is sequentially conveyed by the vertical path rollers 44, 42, 40 and the conveying rollers 51, 50 at the sheet feeding speed Vf, and the leading edge of the sheet material is detected by the pre-registration sensor 53 (P6). Here, if t exceeds a predetermined delay margin, that is, a time T2 at which it is determined that the sheet material cannot be sent to the transfer position 5T by the transfer timing based on the signal of the image position reference detection sensor (P3), the sensor delay before registration is performed. It is determined that jam (P4) has occurred, and the copy operation is terminated. Further, a jam occurrence (P5) is displayed on a display unit (not shown) to instruct the user to remove the sheet material.
[0067]
Next, when the sheet material reaches the pre-registration sensor within T2 (P6), it is determined whether it is within the predetermined time T1 (P7). T1 is a time during which the sheet feeding motors M1 to M5 are not stopped after the skew correction by the registration roller when the skew is corrected by the registration roller.
[0068]
Next, a case where the sheet material reaches the pre-registration sensor at t ≦ T1 will be described.
[0069]
After the sheet material forms a loop between the registration roller 54 and the conveyance roller 50, the sheet feeding motors M1 to M5 are stopped, and the process waits until the sheet material can reach the transfer position at the transfer timing based on the signal of the image position reference detection sensor. Then, the conveyance is started at the maximum conveyance speed V2 of the registration rollers (P8). Here, the measurement of the time t 'is started with the reference roller transport start time as the reference t' = 0. When it is determined that the conveying time t 'of the registration roller has passed the predetermined time T3 and the sheet material conveyance distance 1 of the registration roller has reached a position 20 mm before the transfer position (distance 11) (P9), the registration roller motor M and the sheet feeding motor M1 To M5, the conveying speed of the registration roller is reduced from V2 to V1 (image forming speed) (P10). In this embodiment, V2 = 400 mm / S and V2> V1 (image forming speed: 200 mm / s). However, according to the features of the present invention, V2 = V1 may be used. In addition, the timing of deceleration of the registration roller is not limited to the time from the start of conveyance of the registration roller, and a sensor is used near the upstream side of the deceleration position from the registration roller and a predetermined time after detecting the leading edge of the sheet material. You may decelerate later.
[0070]
Next, the case where the sheet material reaches the pre-registration sensor at T1 <t ≦ T2 will be described.
[0071]
After the sheet material forms a loop of a predetermined length between the registration roller 54 and the conveyance roller 50, conveyance of the registration roller is started at a speed V3 according to the size of t without stopping the sheet feeding motors M1 to M5 (P11). ).
[0072]
V3 is a value that changes according to the time delayed with respect to t = T1, and is determined by the following calculation.
[0073]
Tr: time required for loop formation
Tw: a standby time from when the sheet material arrives at the pre-registration sensor from the vertical path sensor to T1 when the sheet material arrives at the registration roller and starts to be conveyed after forming the loop.
tl: time when the sheet material is sent from the vertical path sensor to the time before arrival at the sensor before registration T1
11: If the distance from the registration roller to the leading edge of the paper when the registration roller starts decelerating, the time from the start of conveyance of the registration roller to shifting is longer by Tw-tl than in the case of T1.
Since l1 / V3 = l1 / V2 + (Tw-tl),
V3 = 11 / (11 / V2 + Tw-tl)
It becomes. Then, the measurement of the time t ″ is started with the reference roller transfer start time t ″ = 0. If it is determined that the conveyance time t "of the registration roller has passed the predetermined time T4 and the conveyance distance l of the sheet material by the registration roller has reached 20 mm before the transfer position (distance l1), (P12) the registration is performed in the same manner as in the case of t≤T1. The conveyance speed of the registration rollers is reduced from V3 to V1 (image forming speed) by changing the roller motor M and the paper feed motors M1 to M5 (P10).
[0074]
Since the sequence (P13 to P16) after the sheet material conveyance speed of the registration roller is reduced to the image forming speed is the same as that of the conventional example, detailed description is omitted. Note that FIG. 2 shows a case in which the preceding sheet a at the time when the sheet material reaches the pre-registration sensor from the vertical path sensor is t = T1, the succeeding sheet of b is T1 <t <T2, and c is t <T1. In the diagram showing the transport state, the horizontal axis represents time, and the vertical axis represents the transport distance from sheet feeding. If the sheet material shown in b is delayed from reaching the registration roller, only the loop is created without stopping the trailing edge of the paper, and the conveyance by the registration roller is made faster than (a, c) when t ≦ T1. It can be seen that the conveyance speed V3 of the registration rollers after that is lower than V2 (= 400 mm / sec).
[0075]
As described above, in the conventional control means, when t> T1, when the pre-registration sensor delay jam occurs, the sheet material is started to be conveyed without being stopped at the registration roller portion without stopping the loop for correcting the skew feeding. By adjusting the conveyance speed of the registration rollers thereafter, the position of the sheet material and the image can be aligned even if the conveyance start timing of the registration rollers is advanced with respect to the transfer timing. In this way, even if the sheet material is delayed by the time Tl as compared with the related art, it is possible to keep up with the maximum conveyance speed by the registration roller and to catch up with the transfer timing. Therefore, the sensor delay jam before the registration can be reduced. Specifically, for example, taking the diagram shown in FIG. 2 as an example, the following time required by the conventional control means is not required, so that the delay margin is increased as compared with the conventional control means.
[0076]
{Circle around (1)} Time required for falling of the conveying rollers (50, 52) before the registration: 20 ms (assuming that the falling speed has been reduced from 400 to 200 mm / sec)
(2) Time required between OFF and ON of the motor: 20 msec
{Circle around (3)} Time required for starting the conveying rollers (50, 52) before the registration: 20 ms (assuming that the starting speed has increased from 200 to 400 mm / sec)
If (1), (2), and (3) are changed to distances, the delay of 8.0 mm can be saved when the sheet feeding speed Vf is 400 mm / s. Also, if this margin is not used as a jam margin but is used for pre-registration conveyance and for lowering the speed of the registration roller, the required torque of the motor can be reduced, and power consumption can be reduced.
[0077]
In this embodiment, an example of a color copying machine having a transfer drum supporting two sheet materials has been described. However, the control method according to the present invention can reduce the sheet material interval, so that color copying without a transfer drum can be performed. This is also effective for increasing the productivity of a copying machine and a black-and-white copying machine.
[0078]
【The invention's effect】
As described above, in the present invention, in an image forming apparatus such as a printer, a facsimile, a copying machine, or a multifunction peripheral having these functions, an image forming apparatus for forming an image on a sheet, and a sheet material from a sheet material tray to an image forming apparatus. Feeding means for continuously feeding the sheet material, and correcting the skew of the leading end of the fed sheet material upstream of the image forming means, timing the image, and then feeding the image to the image forming means. A sheet material aligning means for feeding the sheet material toward the sheet material, a sheet material detecting means arranged before the sheet material arranged upstream of the sheet material aligning means, and the sheet material reaching the sheet material detecting means before the alignment from a predetermined reference. The measuring means for measuring the time t and the sheet material aligning means are provided with a first speed (V1) substantially equal to the sheet material conveying speed in the image forming means, and a predetermined second speed (V2) satisfying V2 ≧ V1. ) And V <V2> a feeding speed varying means for enabling the sheet material to be fed at an arbitrary third speed (V3), and if t is equal to or less than the first predetermined time T1, the sheet material adjusting means After correcting the skew, the sheet is fed toward the image forming means at the second speed (V2) after timing is measured for the image, and when the t is longer than the first predetermined time T1, The sheet material aligning means performs only skew correction without stopping the sheet material conveying means upstream of the sheet material aligning means, and moves the sheet toward the image forming portion at the arbitrary third speed (V3). Speed control means for feeding the material, changing the speed to the first speed (V1) after a predetermined distance or for a predetermined time, and controlling the leading end of the sheet material to reach the image forming means. Registration speed without increasing the speed or registration roller transport speed. Increasing the delay jam margin, thereby effectively providing a configuration for realizing high productivity at low cost is obtained.
[Brief description of the drawings]
FIG. 1 is a flowchart illustrating an image forming control unit according to an embodiment.
FIG. 2 is a diagram illustrating a conveyance state of a sheet material from a paper supply to a registration roller according to the embodiment.
FIG. 3 is a schematic sectional view of a conventional image forming apparatus.
FIG. 4 illustrates a sheet conveyance control unit in a conventional image forming apparatus.
FIG. 5 is a diagram illustrating a state in which A4 size sheet materials are continuously fed from a second cassette 73;
FIG. 6 is a drive development diagram of a drive system relating to sheet feeding from cassettes 72 and 73 and sheet re-feeding from double-sided deck 22.
FIG. 7 is a drive development diagram of a drive system of conveyance rollers 50 and 51 and a registration roller 54.
FIG. 8 is a cross-sectional view showing a state in which a problem occurs particularly in a sheet material conveyance state in a conventional image forming apparatus.
[Explanation of symbols]
1 Photosensitive drum
5 Transfer drum
40, 42, 44 Vertical pass rollers
41,43,45 Vertical path sensor
50, 51 transport roller
53 Sensor before cash register
54 Registration Roller
61, 62 paper feed roller
63, 64, 66 retard roller
72, 73 paper cassette

Claims (4)

An image forming apparatus for forming an image on a sheet, a feeding means for continuously feeding the sheet material from the sheet material tray to the image forming apparatus, and a leading end of the fed sheet material on an upstream side of the image forming means. A sheet aligning means for feeding the sheet toward the image forming means after correcting the skew in the image, timing the image, and a pre-alignment sheet disposed near the upstream of the sheet aligning means. An image forming apparatus comprising:
Measuring means for measuring a time t when the sheet material reaches the pre-alignment sheet material detecting means from a predetermined reference;
The sheet material aligning means has a first speed (V1) substantially equal to the sheet material conveying speed in the image forming means, a predetermined second speed (V2) satisfying V2 ≧ V1, and an arbitrary condition satisfying V3 <V2. Feeding speed varying means for enabling the sheet material to be fed at the third speed (V3);
If the time t is equal to or less than the first predetermined time T1, the skew correction of the sheet material is performed by the sheet material aligning means, and then the timing for the image is measured, and then the image forming means is transferred to the image forming means at the second speed (V2). Sheet material toward
When the time t is greater than the first predetermined time T1, the sheet material aligning means performs only the skew correction without stopping the sheet material conveying means on the upstream side of the sheet material aligning means, and performs the third speed ( In V3), the sheet material is fed toward the image forming unit,
An image forming apparatus comprising: a speed control unit configured to change the speed to the first speed (V1) after feeding the sheet material for a predetermined distance or a predetermined time so that the leading end of the sheet material reaches the image forming unit. The third speed (V3) is equal to the second speed (V2);
When the skew of the sheet is corrected by the sheet aligning means when the time t is the first predetermined time T1, the feeding of the sheet toward the image forming means at the second speed (V2) is started. Time and
2. The image forming apparatus according to claim 1, wherein the time t is a time determined by a time transmitted with respect to a first predetermined time T <b> 1. 3. The image forming apparatus according to claim 1, wherein the sheet material aligning unit is a pair of rollers that can be selectively driven. 3. The image forming apparatus according to claim 1, wherein the sheet material aligning unit is a shutter that can be selectively moved.

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