JP2000211774A - Sheet material feeder and picture forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten a space between continuously fed sheet materials, by providing a sheet material rear end detection means detecting a rear end of the sheet material in the vicinity of the downstream in a sheet material conveying direction of an oblique feed correction rotary body pair, and controlling its rotation based on a detection result of the sheet material rear end detection means. SOLUTION: When picture forming is started, a register roller 5 as an oblique feed correction rotary body pair starts rotation synchronously with a picture, by the timing T1 detecting a rear end of the leading sheet material 1 to pass a register after sensor 70 as a sheet material rear end detection means, the register roller 5 is stopped. The following sheet material, conveyed to the register roller 5 similarly to the sheet material 1, makes a tip end thereof collide against the stopped register roller 5, and the same feed sequence to the leading sheet material is executed. By performing this feed sequence unchangeably on and after a sheet material 3, a continuous sheet material feed is realized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a laser printer, a copying machine, and a facsimile.
The present invention relates to a sheet material feeding device that continuously feeds a cut sheet material, and an image forming apparatus including the sheet material feeding device.

[0002]

2. Description of the Related Art FIG. 6 shows a sheet feeding apparatus using an FRR type feeding mechanism as an example of a conventional sheet feeding apparatus. The sheet material P in the cassette 7 is sent to the feed roller 52 by the rotation of the pickup roller 51 provided in the vicinity of the cassette under pressure contact, and further from the feed roller 52.
It is sent out to 4. At this time, in order to prevent double feeding, a predetermined torque is applied to the separation roller 53 facing the feed roller 52 in the direction of the arrow that pushes back the sheet material.

When the leading end of the sheet material P is nipped by the transport roller 54, the pickup roller 51 is retracted to a position where it does not come into contact with the uppermost sheet material (in the direction of the arrow in the figure).

Further, the feed roller 52 is cut off and driven to rotate, and the sheet material is conveyed by the driving force of the conveying roller 54. Thereafter, the leading end of the sheet material P is abutted against the stopped registration roller 5, and from this state, the start of image formation is synchronized based on the timing at which the leading end is detected by the pre-registration sensor 60. Therefore, wait temporarily. In addition, the transport roller 54 is a sheet material P
The sheet material P continues to move between the guides 56 and stops until a loop is formed in order to perform the tip correction (skew feeding correction) of the above.

[0005] When the image formation is started, the registration roller 5 rotates, and the sheet material P is sent to a transfer section composed of a photoconductor and a transfer / separation section.

By the way, in a conventional analog type copying machine,
Each time an image is formed on a sheet material, a scan time of the document is required, so that a large sheet material interval is inevitably required. Further, since a page printer and a plain paper facsimile take an image processing time to perform the next print, there has been little study on shortening the interval between sheet materials. In recent years, with the advent of digital copying machines and the speeding up of image processing apparatuses installed in printers and facsimile machines, it has been desired to minimize the sheet material interval as much as possible.

[0007]

However, when the sheet interval is reduced, the conventional method has the following problems.

FIG. 7 shows the problem with reference to a diagram when the continuous sheet material is fed. FIG. 7 shows two continuous diagrams. In the conventional method, the registration roller 5 starts rotating in synchronization with image formation ((a) in the figure), and the trailing end of the preceding sheet material 1 , The time t1 for sufficiently passing through the registration roller 5 is set to the sheet material length L.
Then, the calculation is performed from the transport speed, the control is performed by a timer, and the registration roller 5 is temporarily stopped ((a) in the figure).

The leading sheet material strikes the leading edge against the stopped registration roller 5 and executes the same feeding sequence as the preceding sheet material. By performing this invariably, continuous sheet material feeding is realized.

At this time, the interval between sheets during image formation (the interval between the trailing edge of the preceding sheet material and the leading edge of the next sheet material) is represented by L1 in the figure. It is conceivable that reducing L1 can be achieved by reducing the time t2 from the rear end of the sheet material 1 to the leading end of the sheet material 2 at the feed / separation rollers 52 and 53, but it is actually t3. When the feeding of the sheet material 2 is started, the rotation of the registration rollers for the preceding sheet material 1 is not completed, and the sheet material 2 cannot be synchronized with the image.

In other words, in order to reduce the above-mentioned sheet interval during image formation, it is important to stop the registration roller as soon as the rear end of the preceding sheet material 1 passes through the registration roller 5. However, actually, the transport speed v1 of the registration roller has an error due to a rotation speed error of the driving motor, a roller diameter error of the registration roller, and the like.

If the registration roller is stopped before the trailing edge of the sheet material completely passes through the registration roller, a jam occurs. Therefore, L2 in the drawing is represented by the following equation.

L2> (L + α) / (1−β) · v1 × v
1−L = (Lβ + α) / (1−β) where α is the margin length and β is the transport speed error.

For example, L = 436 mm, α = 15 mm,
When β = 2% = 0.02, L2> 24 mm. Particularly, α takes into account the sequence due to the delay due to the slippage of the sheet material at the registration roller, the variation in the position of the leading edge of the sheet at the registration roller, and the variation in the length of the sheet.

As described above, L2 always exists in the related art, has a large specific gravity with respect to the sheet interval L1, and has been a major problem for reducing the sheet material interval.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide a sheet feeding apparatus capable of shortening an interval between continuously fed sheet members. It is to provide a device.

[0017]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a sheet material feeding apparatus which continuously feeds a cut sheet material to a processing unit which performs a predetermined process on the sheet material. An apparatus, comprising: a pair of rotating bodies that are in contact with each other, wherein a skew correction rotating body pair that corrects a skew of the sheet material by abutting a tip of the sheet material against a nip portion of the rotating body, In a sheet material feeding device provided upstream of a processing unit in a sheet material conveying direction, a sheet material rear end detecting means for detecting a rear end of the sheet material in the vicinity of a downstream side of the skew correction rotating body pair in the sheet material conveying direction. And controlling the rotation of the skew feeding correcting rotary member pair based on a detection result of the sheet material rear end detecting means.

In this case, it is necessary to perform the rotation control of the skew feeding correcting rotary member so as to increase the interval between the preceding sheet material and the succeeding sheet material in consideration of the conveyance speed error of the sheet material. Since there is no sheet material, the interval between continuously fed sheet materials can be reduced.

The skew correction rotating member is rotated by rotating the skew correction rotating member pair to convey the preceding sheet material, and the skew correction rotating member pair is detected by detecting the trailing edge of the preceding sheet material by the sheet material trailing edge detecting means. May be stopped, and the leading end of the following sheet material may be abutted against the nip portion.

In this manner, the conveyance by the skew correction rotating body pair can be reliably performed, and it is necessary to delay the stop of the skew feeding correction rotating body pair in consideration of the conveyance speed error of the sheet material and the like. Since there is no paper jam, it is possible to reduce the interval between sheet materials that are continuously fed while suppressing the occurrence of jam.

At least one of the skew-correction rotators may be configured such that a nip portion is formed between the rotator and the other rotator on an outer peripheral surface of the skew correcting rotator, and a rotation center is formed from the outer peripheral surface of the transport portion. A retracting portion having an outer peripheral surface retracted in the direction, and the sheet material rear end detecting means may detect a rear end of the sheet material via the retracting portion.

According to this configuration, when the rear end of the sheet material is conveyed to a position facing the retracting portion of the rotating body, the sheet material can be detected by the rear end detecting means.
Detection can be performed at a position closer to the nip portion, and the interval between continuously fed sheet materials can be further reduced. The sheet material trailing edge detecting means may be arranged in such a retracting section, or only the sheet material trailing edge detecting means arranged outside the retracting section may perform detection through the retracting section.

Further, the transport section is a plurality of transport rotators spaced apart in a direction perpendicular to the rotation direction, and the retracting section is an area between the transport rotators adjacent in the direction perpendicular to the rotation direction. May be used.

Also in this case, the rear end of the sheet material can be detected at a position closer to the nip portion of the skew correction rotating body pair, so that the interval between continuously fed sheet materials can be further reduced. Can be. Further, the sheet material trailing edge detection means may be an optical reflection type or transmission type detection means having a light emitting portion and a light receiving portion.

Further, a plurality of pairs of the skew correction rotating bodies may be provided.

Further, in an image forming apparatus provided with an image forming means for forming an image on a sheet material and a sheet material feeding means for feeding the sheet material to the image forming means, A sheet material feeding device according to the present invention for feeding a sheet material to the image forming unit as the processing unit may be provided.

With this configuration, by reducing the interval between the sheet materials continuously fed to the image forming means,
Since the number of sheets fed per unit time increases, it is possible to provide an image forming apparatus capable of performing image forming processing at higher speed.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] An embodiment of the present invention will be specifically described below with reference to the drawings.

FIG. 5 shows a digital copying machine which is an image forming apparatus using a sheet feeding apparatus according to an embodiment of the present invention.

In FIG. 5, the image of the original placed on the platen glass of the reader section is composed of an illumination lamp, a reflection mirror,
The light is guided to the CCD 20 by the optical system 1 including a lens, and is converted into an electric signal. The converted image signal is temporarily stored in a memory (not shown), and then sent to a lower printer unit.

In the printer section, laser light is emitted based on the image signal, and the scanning system 21 irradiates the photosensitive drum 2. The electrostatic latent image formed by irradiating the photosensitive drum 2 uniformly charged by the primary charger 3 with the laser beam is visualized by the toner supplied from the developing device 4 to become a toner image.

On the other hand, the sheet material P stored in the cassette 7a is sent to a feed roller 52 by a pickup roller 51, and further sent out therefrom to a conveying roller 54 and a registration roller 5 as a skew correction rotating body pair. Then, the leading end is abutted against the stopped registration roller 5,
The skew is corrected and the system temporarily waits.

The sheet material that has been on standby is synchronized with the above-described toner image, and is sent to the transfer unit 6 with the rotation of the registration roller 5.

In the transfer section 6, the toner image is transferred onto the sheet material P by electrostatically attracting the toner on the photosensitive drum 2 from the back side of the sheet material P by a corona charger 22 or the like. Here, the image forming means includes the photosensitive drum 2, the primary charger 3, the developing device 4, the corona charger 22, and the like.

The sheet material P to which the toner has been transferred is removed from the electrostatic attraction force with the drum by the separation charger 23, and then conveyed to the fixing unit 9 by the suction belt conveying unit 8. The suction belt conveying unit 8 is configured to adsorb the sheet material P by the fan 801 while the rubber belt 8 made of chloroprene or the like.
02 conveys the sheet material P.

The sheet material P on which the toner image is fixed by heat fixing in the fixing section 9 or other means is supplied to the sheet discharging section 1.
0 to the tray 12 outside the machine. Alternatively, the sheet is sent to the re-feeding path 11 for double-sided copying, or sent to a post-process such as sorting and stapling.

Next, the operation of the main sheet feeding apparatus of the present invention will be described with reference to FIGS.

FIG. 2 is a diagram showing continuous sheet feeding, FIG. 1 is a timing chart, and FIG. 3 is a detailed view of a sheet feeding section.

When a copy start is instructed (FIG. 1
(A)), the sheet material P in the cassette 7a is fed to the feed roller 52 by the rotation of the pickup roller 51 provided near the cassette under pressure, and further from there.
The paper is sent out toward the transport roller 54.

At this time, in order to prevent double feeding, a predetermined torque is applied to the separation roller 53 facing the feed roller 52 in the direction of the arrow that pushes back the sheet material.

When the leading end of the sheet material P is nipped by the transport roller 54 (FIG. 1A), the pickup roller 51 slightly retracts to a position where it does not come into contact with the uppermost sheet material (FIG. 3). Arrow direction).

Further, the feed roller 52 is cut off and driven to rotate, and the sheet material is conveyed by the driving force of the conveying roller 54. Thereafter, the sheet material P is abutted against the registration roller 5 whose leading end is stopped (FIG. 1).
(A)) From this state, based on the timing at which the leading end of the sensor 60 is detected by the pre-registration sensor 60, the system temporarily waits to synchronize the start of image formation. Also, the transport roller 55
Is stopped until the sheet material P forms a loop between the guides 56 in order to perform the tip correction (skew correction) of the sheet material P.

When the image formation is started, the registration roller 5 starts rotating in synchronization with the image (FIG. 1 (c)).
The registration roller 5 is stopped at the timing T1 at which the trailing edge of the preceding sheet material 1 passes through the post-registration sensor 70 as the sheet material trailing edge detecting means. The succeeding sheet material is conveyed to the registration roller 5 in the same manner as the sheet material 1, and its leading end is abutted against the stopped registration roller 5 to execute the same feeding sequence as the preceding sheet material. By performing this invariably after the sheet material 3, continuous sheet material feeding is realized.

Here, as the post-registration sensor 70, a reflection type photo sensor having a light emitting portion and a light receiving portion is used.
L2 in FIG. 3 is equal to L2 in FIG. 3, and as in the prior art, there is a delay due to an error in the conveyance speed of the registration roller 5, slippage of the sheet material at the registration roller portion, variation in the position of the sheet material tip at the registration roller portion, It is not necessary to set a large value in consideration of variations in length. The reason is that immediately after the registration roller 5, the trailing edge of the sheet material is detected by the post-registration sensor 70 and the registration roller 5 is stopped. This is because the increase in the paper interval is determined by the physical distance L2 between the nip of the registration roller 5 and the post-registration sensor 70. In the embodiment, L2 is set to 15 mm. Conventional example (Paper interval 2)
As a result, the distance between sheets can be shortened by 9 mm.

Although the reflection type photosensor is used as the post-registration sensor here, the same effect can be obtained with a transmission type photosensor. In the combination of the photointerrupters described above, there are some restrictions on the reduction of L2, but it is needless to say that the same effect can be achieved with an inexpensive configuration.

[Second Embodiment] Next, a second embodiment of the registration roller 5 and the post-registration sensor 70 will be described with reference to FIG. The other configuration is the same as that of the first embodiment, and the description is omitted.

In the figure, the registration roller 5 is composed of a rotating shaft 5C penetrating in the thrust direction and conveyance roller portions (conveyance portions) 5a and 5b divided into two in the thrust direction. Photo sensor (post-register sensor 7
0) is disposed between the transport roller sections 5a and 5b as a retracting section. With this configuration, the post-registration sensor 70
As compared with the previous embodiment, it is possible to dispose it near the nip of the registration roller, and as a result, it is possible to further reduce L2. In the present embodiment, the diameter φD of the transport roller portions 5a and 5b is φ18, and the diameter φd of the rotating shaft 5C is φd = φ18.
As L6, L2 = 7 mm could be achieved. This is L2
= 15 mm, L2 can be further reduced by 8 mm, and as a result, the sheet interval can be further reduced by 8 mm.

[0048]

As described above, according to the present invention,
Near the downstream of the skew correction rotating body pair in the sheet material conveying direction, there is provided a sheet material rear end detecting means for detecting the rear end of the sheet material, and based on the detection result of the sheet material rear end detecting means, The rotation of the skew correction rotator pair needs to be controlled so as to increase the distance between the preceding sheet material and the succeeding sheet material in consideration of the sheet material conveyance speed error, etc. Therefore, the interval between sheet materials fed continuously can be reduced.

Further, at least one of the skew correction rotating body pairs has a transport portion forming a nip portion between the outer circumferential surface and the other rotary body, and a rotation center direction from the outer circumferential surface of the transport portion. And a retracting portion having an outer peripheral surface retracted to the sheet member. The sheet material rear end detecting means detects the rear end of the sheet material via the retracting portion. At the time when the sheet is conveyed to the position where the sheet material is conveyed, and by detecting at a position closer to the nip portion, the interval between continuously fed sheet materials is further reduced. be able to.

[Brief description of the drawings]

FIG. 1 is a timing chart when a continuous sheet material is fed according to the present invention.

FIG. 2 is a diagram when a continuous sheet material is fed according to the present invention.

FIG. 3 is a detailed view of a sheet material feeding section according to the present invention.

FIG. 4 is a detailed view of the vicinity of a registration roller according to the present invention.

FIG. 5 is an image forming apparatus using the sheet material feeding device of the present invention.

FIG. 6 is a schematic cross section of a conventional sheet material feeding device.

FIG. 7 is a diagram illustrating the operation of a conventional sheet material feeding device.

[Explanation of symbols]

 Reference Signs List 2 photosensitive drum 3 primary charger 4 developing device 5 registration roller 22 corona charger 51 pickup roller 52 feed roller 53 separation roller 60 pre-registration sensor 70 post-registration sensor L1

Claims (7)

[Claims] 1. A sheet material feeding device that continuously feeds a sheet material cut to a processing unit that performs a predetermined process on the sheet material, comprising a pair of rotating bodies that abut against each other, A sheet material feeder provided with a skew correction rotating body pair that abuts the leading end of the sheet material on the nip portion of the rotator to correct skew of the sheet material, and is provided upstream of the processing unit in the sheet material transport direction; In the device, near the downstream of the skew feeding correction rotating body pair in the sheet material conveyance direction,
A sheet material comprising sheet material rear end detecting means for detecting a rear end of the sheet material, and controlling rotation of the skew feeding correcting rotating body pair based on a detection result of the sheet material rear end detecting means. Feeding device. 2. The skew correction rotating body pair is conveyed by rotating the skew correction rotating body pair, and the skew correction rotating body pair is detected by detecting the trailing end of the preceding sheet material by the sheet material trailing edge detecting means. 2. The sheet feeding apparatus according to claim 1, wherein the stop of the sheet is stopped, and the leading end of the succeeding sheet is abutted against the nip portion. 3. The skew-correction rotator pair of at least one of the rotators includes a transport unit that forms a nip between the outer peripheral surface and the other rotator, and a rotation center from the outer peripheral surface of the transport unit. A retracting portion having an outer peripheral surface retracted in a direction, wherein the sheet material rear end detecting means detects a rear end of the sheet material via the retracting portion. Feeder. 4. The transport section is a plurality of transport rotators arranged apart from each other in a direction perpendicular to the rotation direction, and the retreating section is an area between transport rotators adjacent in a direction perpendicular to the rotation direction. The sheet feeding device according to claim 3, wherein: 5. The sheet material rear end detecting means according to claim 1, wherein said sheet material rear end detecting means is an optical reflection type or transmission type detecting means having a light emitting portion and a light receiving portion. Sheet material feeding device. 6. The sheet feeding apparatus according to claim 1, wherein a plurality of pairs of the skew feeding correcting rotary members are provided. 7. An image forming apparatus comprising: an image forming unit that forms an image on a sheet material; and a sheet material feeding unit that feeds the sheet material to the image forming unit. An image forming apparatus comprising the sheet material feeding device according to claim 1, wherein the sheet material is fed to the image forming means as the processing unit.