JP2008044683A - Paper feeder and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a highly reliable paper feeder without using a drive cutout mechanism such as an electromagnetic clutch by stabilizing the transfer paper conveying performance of a paper feed drive part using a DC motor as a drive source the rollers of which are independent of each other and an image forming device having the paper feeder. <P>SOLUTION: This paper feeder comprises a transfer means for feeding, one by one, transfer paper loaded on a loading means, a conveying means on a conveying passage on the downstream side of the paper feed means, a paper feed means having detection means for detecting the conveyed position of the transfer paper fed by the transfer means, and DC motors as drive sources installed on the transfer means and the conveying means. The conveying means has a brake mechanism for loosening the transfer paper when the head of the transfer paper reaches a pair of register rollers installed in the conveying passage and temporarily stopped. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a paper feeding device that conveys transfer paper to an image forming unit, and an image forming device such as a copying machine, a printer, a facsimile, and a plotter equipped with the paper feeding device.

2. Description of the Related Art Conventionally, as a configuration of a paper feeding device of an image forming apparatus, a paper feeding roller that feeds paper from a paper feeding tray and a conveyance roller that is downstream of the paper feeding roller and conveys transfer paper to a pair of registration rollers What is done is common.
As a driving means, a plurality of rollers such as a paper feeding roller and a conveying roller are driven by a single motor. At this time, in order to maintain paper conveyance performance such as control between papers, double feeding, jam prevention, etc., a general method is to perform different operations on each roller by turning on and off the electromagnetic clutch (for example, (See Patent Documents 1 to 5).

Also in Patent Document 1, the paper feed roller and the transport roller receive driving force from the same motor, and the paper transport performance is ensured by controlling the timing of turning off and on the electromagnetic clutch.
However, there are many problems such as slipping and jamming of electromagnetic clutches, and the parts that are most frequently replaced on the market when regular replacement parts are removed are electromagnetic clutches. Paper that depends on whether the electromagnetic clutch is on or off The conveyance was not reliable.
Therefore, it is desirable that the sheet feeding roller and the conveying roller in the sheet feeding device are driven by independent motors and do not pass through a drive shut-off mechanism such as an electromagnetic clutch. Solutions have been proposed in the literature.

Patent Document 2 discloses that a stepping motor is used as a motor as a driving unit. However, there are problems such as step-out and noise, and the driving unit using a DC motor improves the reliability of the apparatus. .
However, when a DC motor is used as the drive source of the paper feeding means of the image forming apparatus, when the transfer paper leading edge reaches the registration roller pair, the transfer paper is sent by an additional several millimeters to the registration roller pair. It is necessary to temporarily stop with a slack between the roller and the conveying roller. This operation corrects the skew generated during paper conveyance.
JP 2003-176045 A Japanese Patent No. 3378650 Japanese Patent Laid-Open No. 10-329986 JP-A-2005-335302 Japanese Patent Laid-Open No. 08-301463 Japanese Patent Laid-Open No. 2005-144846

  However, when a strong transfer paper such as thick paper is passed, if the DC motor is used as the driving means, the sag is lost because it does not have a self-holding force, and it is impossible to maintain an appropriate sag amount. It is.

FIG. 7 is a schematic perspective view showing a paper feed drive unit for driving the paper feed device. FIG. 8 is a schematic perspective view of the sheet feeding drive unit of FIG. 7 as viewed from the opposite side to FIG. FIG. 9 is a schematic perspective view showing a state in which the attachment cover of the schematic perspective view of FIG. 8 is removed. FIG. 10 is a schematic diagram showing the relationship between the motor, the transport roller, and the paper feed clutch.
As shown in FIGS. 7 to 10, a motor 21 as a drive source drives the paper feed roller 13 and the transport roller 10 for one. An electromagnetic clutch (paper feed clutch) 16 is disposed on the paper feed roller 13 so that the paper feed roller 13 and the transport roller 10 have independent operations. The drawing further shows a reverse roller 22 and a mounting cover 23 (FIG. 8).

The pickup roller 12 is driven from the paper feed clutch 16. The pick-up solenoid (not shown) is brought into contact with or separated from the transfer paper by turning on or off. The paper feed roller 13 is driven by the FRR method to prevent double feeding. Since this FRR system is wide and general, detailed description thereof is omitted.
While the preceding sheet passes the sheet feeding roller 13 during continuous printing, the sheet feeding clutch 16 is on, but the trailing edge of the preceding transfer sheet does not feed the sheet feeding roller 13 so that the next transfer sheet is not sent out. It is necessary to turn off the paper feed clutch 16 before Xmm is removed.
The value of X is generally about 5 mm. For the next paper feeding, the paper feeding clutch 16 is turned on Ymm after the trailing edge of the preceding transfer paper passes through the paper feeding roller 13. The value of Y is generally about 20 to 30 mm.
In this way, the paper feed clutch 16 is repeatedly turned on and off during printing so that the paper spacing is kept uniform. However, electromagnetic clutches are unreliable, and problems such as non-feeding due to slipping of the clutch and jams are unending in the market.

Further, when the stepping motor is used as the motor 21 as the driving source, problems such as step-out and noise continue to occur, and the use of the DC motor improves reliability. However, when the DC motor is used as the driving source. Since the motor itself does not have a self-holding force, there are the following problems.
When the leading edge of the transfer paper reaches the registration roller pair 5, the transfer paper is sent by an extra several mm, and is temporarily stopped with a slack between the registration roller pair 5 and the conveyance roller 10. As described above, this operation corrects a skew generated during transfer paper transfer. The purpose of pausing with slack is as follows.

When the registration roller speed is slower than the target speed, the timing to reach the transfer nip is delayed, so that a positional deviation on the image occurs. Further, even when the registration roller pair 5 is transported at the target speed, if the upstream transport roller 10 is slower than the target speed, the rear end of the paper becomes a load and the paper transport speed is delayed and color misregistration occurs. End up.
If there is a slack between the registration roller pair 5 and the transport roller 10, even if the transport roller 10 is slower than the target speed, the delay is absorbed by the slack and does not become a load.
Therefore, when the leading edge of the transfer paper reaches the registration roller pair 5 and pauses, it is necessary to pause with a slack. However, when a DC motor is used as the drive source, as described above, the sag is returned due to the stiffness of the transfer paper, so that the sag cannot be maintained.

  In view of the above situation, an object of the present invention is not to use a drive shut-off mechanism such as an electromagnetic clutch, but to transfer paper transfer performance of a paper feed drive unit using each roller as an independent DC motor as a drive source. An object of the present invention is to provide a highly reliable sheet feeding apparatus and an image forming apparatus including the same.

In order to solve the above-described problems, the invention described in claim 1 is provided with a feeding unit that feeds the transfer sheets stacked on the stacking unit one by one, and on the conveyance path downstream of the sheet feeding unit. And a driving source provided in each of the feeding unit and the conveying unit. The feeding unit includes a plurality of detecting units for detecting the conveying position of the transfer sheet sent by the feeding unit. In the sheet feeding device including a DC motor, the transport unit includes a brake mechanism that forms a slack when the transfer paper leading edge reaches a registration roller pair provided in the transport path and temporarily stops. The paper feeding device is characterized by this.
The invention according to claim 2 is characterized in that the brake mechanism is a one-way clutch.

The invention described in claim 3 is characterized in that the DC motor is an inner rotor type.
The invention described in claim 4 is characterized in that the DC motor is an outer rotor type.
The invention according to claim 5 is characterized in that the DC motor is a brushless motor.
The invention according to claim 6 is characterized in that the DC motor is a brush motor.

Further, the invention according to claim 7 is provided with a sag amount detecting means for detecting a sag amount of the sag formed on the transfer paper, and based on information on the detected sag amount, the rotational speed of the DC motor is determined. 7. The sheet feeding device according to claim 1, wherein the sheet feeding device is changed.
The invention according to claim 8 is characterized in that the sag amount detecting means is in non-contact with the transfer paper.
According to a ninth aspect of the invention, the speed until the transfer paper reaches the image forming portion is faster than the speed after the transfer paper reaches the image forming portion. The sheet feeding device according to one item is characterized.
According to a tenth aspect of the present invention, there is provided an image forming apparatus including the paper feeding device according to any one of the first to ninth aspects.

  According to the present invention, the feeding means and the conveying means are driven by independent drive sources, respectively, so that the problem that the drive shut-off means such as an electromagnetic clutch slips is solved, the stable conveying performance is always maintained, and the driving is performed. By using a DC motor as the source, the reliability of the image forming apparatus can be improved. Furthermore, by having a brake mechanism in the conveying means, the slack holding for skew adjustment can be performed even on transfer paper with a strong strain on paper such as thick paper. It becomes possible.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an embodiment of a laser printer as an image forming apparatus. FIG. 2 is a schematic diagram illustrating a configuration of a sheet feeding device which is a characteristic part of the present embodiment. The present invention will be described with reference to one embodiment applied to an electrophotographic direct color transfer color laser printer (hereinafter referred to as “laser printer”) as an image forming apparatus.

In FIG. 1, the laser printer LP includes four sets of image forming units 1Y, 1M, 1C, for forming images of each color of yellow (Y), magenta (M), cyan (C), and black (K). 1K (hereinafter, the subscripts Y, M, C, and K of the respective symbols indicate yellow, magenta, cyan, and black members), respectively, along the moving direction of the transfer paper P (along arrow A in the figure). In the direction in which the belt 9 travels).
Each of the image forming units 1Y, 1M, 1C, and 1K includes photosensitive drums 11Y, 11M, 11C, and 11K as image carriers and a developing unit. The image forming units 1Y, 1M, 1C, and 1K are arranged so that the rotation axes of the photosensitive drums 11Y, 11M, 11C, and 11K are parallel and arranged at a predetermined pitch in the transfer sheet moving direction. Is set to

The laser printer LP carries the image forming units 1Y, 1M, 1C, and 1K, an optical writing unit 2, paper feed cassettes (stacking means) 3 and 4, a registration roller pair 5, and a transfer paper P to each image. A transfer unit 6 as a belt driving device having a transfer conveyance belt 9 as a transfer conveyance member that conveys the transfer position so as to pass through a transfer position of the forming unit, a belt fixing type fixing unit 7, a paper discharge tray 8, and the like are provided. Further, a manual feed tray MF and a toner supply container TC are provided, and a waste toner bottle, a duplex / reversing unit, a power supply unit, and the like are also provided in a space S indicated by a two-dot chain line.
The optical writing unit 2 includes a light source, a polygon mirror, an f-θ lens, a reflection mirror, and the like, and irradiates the surface of each of the photosensitive drums 11Y, 11M, 11C, and 11K while scanning with laser light based on image data.

An alternate long and short dash line 14 in the first paper discharge direction B shown in FIG. The transfer paper P fed from the paper feed cassettes 3 and 4 through the pickup roller 12 and the paper feed roller (paper feed means) 13 or from the manual feed tray MF is guided by a conveyance guide (not shown) while being conveyed by a conveyance roller (conveyance means). ) 10 and is sent to a temporary stop position where the registration roller pair 5 is provided.
The transfer paper P is temporarily stopped with a slack between the conveying roller 10 and the registration roller pair 5 and then sent out toward the photosensitive drum 11 by the registration roller pair 5 at a predetermined timing. The transferred transfer paper P is carried on the transfer transport belt 9, transported toward the image forming units 1Y, 1M, 1C, and 1K, and passes through the transfer nips.

The toner images developed on the image forming units 1Y, 1M, 1C, and 1K and the photosensitive drums 11Y, 11M, 11C, and 11K are superimposed on the transfer paper P at the transfer nips, respectively. Is transferred onto the transfer paper P. A full-color toner image is formed on the transfer paper P by this superposition transfer.
The surfaces of the photosensitive drums 11Y, 11M, 11C, and 11 after the toner image transfer are cleaned by a cleaning device, and are further neutralized to prepare for the formation of the next electrostatic latent image.
On the other hand, the transfer paper P on which the full-color toner image is formed is fixed in the first paper discharge direction B or the second in accordance with the rotation posture of the switching guide G after the full-color toner image is fixed by the fixing unit 7. In the paper discharge direction C.
When the paper is discharged from the first paper discharge direction B onto the paper discharge tray 8, it is stacked in a so-called face-down state with the image surface down. On the other hand, when the paper is discharged in the second paper discharge direction C, it is conveyed toward another post-processing device (sorter, binding device, etc.) (not shown), or again through the switchback unit for double-sided printing. Carried to pair 5.

  Next, the configuration of the sheet feeding device, which is a characteristic part of the present embodiment, will be described. As shown in FIG. 2, a paper feed drive unit 15 of a general paper feeder includes a paper feed clutch 16 of a paper feed clutch drive unit, a pickup roller (feeding means) 12 for picking up transfer paper, and a stacked transfer. A paper feed roller 13 that feeds out paper, a transport roller 10 provided downstream thereof, and sensors (registration sensor 17, vertical transport sensor 18, paper feed sensor 19, and pickup solenoid sensor 20) that detect the transport position of the transfer paper. ing.

FIG. 3 is a schematic view showing a driving device of the paper feeding device without using an electromagnetic clutch. In FIG. 3 corresponding to FIG. 9 referred to in the description of the prior art, the above-described electromagnetic clutch is turned on by driving the paper feed roller 13 and the transport roller 10 by independent paper feed motors 21a and 21b. As with the timing of turning off, the sheet feeding motors 21a and 21b are turned on / off to carry the transfer paper with high reliability.
Further, when a DC motor is used as a drive source of the paper feed driving device, when the leading edge of the transfer paper reaches the registration roller pair 5 (FIG. 2) and is paused with a slack, the transfer paper is stiffened. There is a risk that the slack cannot be maintained.

FIG. 4 is a schematic diagram illustrating a brake mechanism provided on the transport roller. Therefore, the conveyance roller 10 having the brake mechanism 24 can solve the problem that the slack cannot be retained due to the stiffness of the transfer paper.
FIG. 4 shows the photosensitive drum 11, the registration roller pair 5, and the like. If a one-way clutch is used as the brake mechanism 24, the slack can be reliably held at a low cost.
In this case, if the drive sources 21, 21 a, and 21 b are inner rotor type DC motors, the response of rising and falling is increased and the first print time can be shortened. Further, if the drive sources 21, 21a, and 21b are outer rotor type DC motors, the rotor inertia increases, motor speed fluctuations can be reduced, and stable paper conveyance becomes possible.

Furthermore, if the drive sources 21, 21a, 21b are brushless DC motors, the motor life is improved and the reliability of the machine can be improved. If the drive sources 21, 21a, and 21b are DC motors with brushes, the cost can be reduced.
The DC motor described above includes an inner rotor type or an outer rotor type, and generally has a commutator and a brush inside although not shown. Although not shown, the brushless motor generally includes a commutator including a magnetic pole position detector and a semiconductor element instead of the commutator and the brush.

FIG. 5 is a schematic view showing a first embodiment of a sag amount detecting means arranged between the conveying roller and the registration roller pair. If the above-mentioned sag amount is not appropriate, a problem such as a jam may occur. Therefore, a sag amount detecting means for detecting the sag amount is disposed at an appropriate position between the conveying roller and the registration roller pair.
As shown in FIG. 5, when the photo interrupter 25, which is a contact sensor, detects sagging, the timing for stopping the transport motor 10 and the paper feed motor (not shown) is advanced until the photo interrupter 25 no longer detects. To do. The detection timing may be performed every time the job is started or may be performed for each transfer sheet.
5A shows the position of the photo interrupter 25, which is a sag amount detection means when the sag amount is large, and FIG. 5B shows a photo, which is a sag amount detection means when the sag amount is appropriate. FIG. 5C shows the position of the interrupter 25, and the position of the photo interrupter 25, which is a sag amount detecting means when the sag amount is small.

FIG. 6 is a schematic diagram showing a second embodiment of the sag amount detecting means arranged between the conveying roller and the registration roller pair. In the second embodiment, a reflection type sensor 26 which is a non-contact type sensor is used as a sag amount detecting means. As described above, if the transfer paper is detected in a non-contact manner, it is possible to reduce the load and prevent the transfer paper from being stained or scratched.
6A shows the position of the non-contact type sensor 26 which is a sag amount detection means when the sag amount is large, and FIG. 5B shows a sag amount detection means when the sag amount is appropriate. The position of a certain reflection type sensor 26 is shown, and FIG. 5C shows the position of the reflection type sensor 26 which is a sag amount detecting means when the sag amount is small.

  In the present invention, the first print can be shortened and productivity can be improved by increasing the paper feeding speed while the transfer paper does not reach the image forming section (image forming section). It becomes. Furthermore, if the above-described paper feeding device is applied to an image forming apparatus, an image forming apparatus with stable image quality can be provided.

1 is a schematic configuration diagram showing an embodiment of a laser printer that is an image forming apparatus. FIG. FIG. 3 is a schematic diagram illustrating a configuration of a sheet feeding device that is a characteristic part of the embodiment. Schematic which shows the drive device of the paper feeder which does not interpose an electromagnetic clutch. Schematic explaining the brake mechanism provided in the conveyance roller. FIG. 3 is a schematic diagram illustrating a first embodiment of a sag amount detecting unit disposed between a conveyance roller and a registration roller pair. Schematic which shows 2nd Embodiment of the slack amount detection means arrange | positioned between a conveyance roller and a registration roller pair. FIG. 3 is a schematic perspective view illustrating a paper feed driving unit that drives a paper feed device. FIG. 8 is a schematic perspective view of the sheet feeding drive unit of FIG. 7 viewed from the side opposite to FIG. 7. The schematic perspective view shown in the state which removed the attachment cover of the schematic perspective view of FIG. Schematic which shows the relationship between a motor, a conveyance roller, and a paper feed clutch.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image formation part 3 Paper feed cassette 5 Registration roller pair 6 Transfer unit 7 Fixing unit 10 Conveyance roller 11 Photosensitive drum 12 Pickup roller 13 Paper feed roller 15 Paper feed drive unit 16 Paper feed clutch 17 Registration sensor 19 Paper feed sensor 21 Drive Source 21a Drive source 21b Drive source 24 One-way clutch 25 Photo interrupter 26 Reflective sensor LP Laser printer P Transfer paper

Claims (10)

A feeding means for feeding the transfer paper loaded on the loading means one by one;
A transport unit provided downstream of the paper feed unit on the transport path;
A paper feeding means having a plurality of detection means for detecting a transport position of the transfer paper sent out by the feeding means;
In a paper feeding device provided with a DC motor that is a drive source provided in each of the feeding means and the conveying means,
The sheet feeding device, wherein the conveying unit includes a brake mechanism that forms a slack when the leading edge of the transfer sheet reaches a pair of registration rollers provided in the conveying path and temporarily stops.   The sheet feeding device according to claim 1, wherein the brake mechanism is a one-way clutch.   The sheet feeding device according to claim 1, wherein the DC motor is an inner rotor type.   The sheet feeding device according to claim 1, wherein the DC motor is an outer rotor type.   The paper feeding device according to claim 1, wherein the DC motor is a brushless motor.   The paper feeding device according to claim 1, wherein the DC motor is a brush motor.   2. A sag amount detecting means for detecting a sag amount of the sag formed on the transfer paper, wherein the number of rotations of the DC motor is changed based on information on the detected sag amount. The sheet feeding device according to claim 6.   8. The paper feeding device according to claim 7, wherein the sag amount detecting means is not in contact with the transfer paper.   9. The paper feed according to claim 1, wherein a speed until the transfer paper reaches the image forming unit is faster than a speed after the transfer paper reaches the image forming unit. apparatus.   An image forming apparatus comprising the paper feeding device according to claim 1.

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