JP2005029376A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device capable of suppressing the occurrence of noise and vibration and increasing productivity. <P>SOLUTION: An image forming part of a digital copying machine has a fixing device 58 fixing toner image by pressurizing and heating a paper sheet which passes through a transcription part and on which toner image on a peripheral face of a photosensitive body drum is transcribed. A pair of delivery rollers 70 for delivering paper sheet onto a paper delivery tray by receiving the paper sheet in a nip and rotating in the first direction are provided. The pair of delivery rollers 70 receive paper sheet in the nip and rotate in the first direction. After a rear end of paper sheet passes through the fixing device 58, the pair of delivery rollers 70 rotate in the second direction to accelerate the paper sheet in the reverse direction and reduce speed down to the same speed as conveyance speed of a both-side conveyance unit immediately in front of a pair of conveyance rollers 74b on the most upstream side of the both-side conveyance unit. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an image forming apparatus capable of forming images on both sides of a sheet.

  2. Description of the Related Art Conventionally, as an image forming apparatus, an apparatus in which a duplex unit is externally attached to a main body having an image forming unit that forms an image on a sheet is known (for example, see Patent Document 1). The duplex unit functions to receive and convey a sheet that has been reversed after passing through the image forming unit, and re-supply the image forming unit. Also, in the image forming apparatus main body, a pair of switchback rollers is provided for reversing the paper by receiving the paper that has passed through the image forming unit in the nip, rotating it forward, and rotating it backward.

  The sheet on which the image is formed on one side through the image forming unit is reversed by the switchback roller pair and sent to the duplex unit. Then, the sheet conveyed by the duplex unit is supplied again to the image forming unit, and an image is formed on the other side of the sheet. That is, when processing a plurality of sheets continuously with the apparatus having such a structure, the next sheet is received by the switchback roller pair until the rear end in the feeding direction of the preceding sheet passes through the nip of the switchback roller pair. I can't. For this reason, productivity commensurate with the performance of the apparatus could not be obtained, and satisfactory productivity could not be obtained.

In order to increase productivity with this type of apparatus, a method of increasing the process speed and the reversal speed can be considered, but a new problem such as increase in noise and vibration occurs. In particular, when the paper is re-supplied through the duplex unit externally attached to the main body as described above, the problem of noise and vibration becomes remarkable. Moreover, in order to increase the reversal speed, it is necessary to develop a new double-sided unit, which causes a disadvantage in terms of cost.
JP 2001-147558 A (Claim 1, FIG. 1)

  An object of the present invention is to provide an image forming apparatus capable of enhancing productivity while suppressing generation of noise and vibration.

  In order to achieve the above object, an image forming apparatus of the present invention includes an image forming unit that forms an image on a sheet-like medium, and a discharge unit that discharges the medium on which at least one side has been formed through the image forming unit. And a conveyance path extending to the discharge section through the image forming section, and a medium formed on the conveyance path immediately before the discharge section and image-formed at least on one side by the image formation section. The medium is discharged to the discharge unit by rotating in the direction 1, and the medium on which the image is formed on one side by the image forming unit is received in the nip and rotated in the first direction. After passing through the image forming unit, the pair of rollers for temporarily stopping and rotating in the second direction to switch back the medium, and the medium switched back by the pair of rollers to receive the first speed A re-feeding unit that re-feeds the image forming unit by conveying, and when the medium on which the image is formed on one side is switched back by the image forming unit, the roller pair is moved in the first direction in the second direction. The medium is fed in the first direction, the rotation of the roller pair is stopped and the medium is temporarily stopped, and then the roller pair is moved at the third speed faster than the second speed. The medium that has been rotated in the direction and stopped once is sent in the second direction, and the rotation of the roller pair is decelerated so as to decelerate the conveyance speed of the medium to the first speed immediately before the refeeding unit. To do.

  According to the invention, in order to form an image on both sides of the medium, when the medium is switched back by the roller pair, the rotation speed of the roller pair is increased and decelerated to the transport speed of the resupply section immediately before the resupply section. I have to. For this reason, productivity can be improved while maintaining the conveyance speed of the medium in the resupply unit. In this case, since only the acceleration / deceleration control of the roller pair is performed without changing the conveyance speed in the resupply unit, generation of noise and vibration in the resupply unit can be suppressed, and the resupply unit can be used as a housing of the image forming apparatus. It is advantageous when it is externally attached.

  Since the image forming apparatus according to the present invention has the above-described configuration and operation, it is possible to increase productivity while suppressing the generation of noise and vibration.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 shows a schematic structure of a digital copying machine 1 as an example of an image forming apparatus according to an embodiment of the present invention. The digital copying machine 1 includes an apparatus main body 2 (housing). In the apparatus main body 2, a scanner unit 4 and a printer unit 6 (image forming unit) are provided.

  A document placing table 8 made of transparent glass is provided on the upper surface of the apparatus main body 2. A document D as a reading object is placed on the document placing table 8. An automatic document feeder 9 (hereinafter referred to as ADF) for automatically feeding the document D onto the document table 8 is disposed on the upper surface of the apparatus body 2.

  The document D placed on the document tray 9a of the ADF 9 is transported by a transport guide (not shown) and is discharged onto the paper discharge tray 9c via the platen roller 9b and the document placing table 8. In a state where the document D is set at a predetermined reading position on the document placement table 8 or in a state where the document D is conveyed through the document placement table 8, the document D is exposed and scanned by the scanner unit 4 which will be described later. The image of D is read.

  A document is set on the document tray 9 a of the ADF 9 with the reading surface of the document D facing upward. When a plurality of documents are set on the document tray 9 a of the ADF 9, the documents are taken one by one from the document D placed on top of them.

  The scanner unit 4 includes an exposure lamp 10 and a first carriage 14 on which a first mirror 12 is mounted. The exposure lamp 10 illuminates the document D conveyed by the ADF 9 or the document D placed on the document table 8. The exposure lamp 10 is composed of, for example, a halogen lamp. The first mirror 12 deflects the reflected light from the document D in a predetermined direction.

  The first carriage 14 is arranged to be movable in parallel with the document table 8. The first carriage 14 is reciprocated below the document table 8 by a scanner motor 16 via a toothed belt (not shown). The scanner motor 16 is constituted by a stepping motor or the like.

  A second carriage 18 that is movable in parallel with the document placement table 8 is disposed below the document placement table 8. Second and third mirrors 20 and 22 are attached to the second carriage 18 at right angles to each other. The second and third mirrors 20 and 22 sequentially deflect the reflected light from the document D deflected by the first mirror 12.

  The rotational force from the scanner motor 16 is transmitted to the second carriage 18 via a toothed belt or the like that drives the first carriage 14. As a result, the second carriage 18 is driven relative to the first carriage 14. That is, the second carriage 18 is moved in parallel along the document table 8 at a speed of 1/2 with respect to the first carriage 14.

  An imaging lens 24 and a CCD sensor 26 are disposed below the document placing table 8. The imaging lens 24 is disposed in a plane including the optical axis of the light deflected by the third mirror 22. The imaging lens 24 forms an image of reflected light from the third mirror 20 on the second carriage 18 at a desired magnification (main scanning direction) by moving itself.

  The CCD sensor 26 receives and photoelectrically converts the reflected light focused by the imaging lens 24 in accordance with an image processing clock supplied from a main CPU (not shown). As a result, an electrical signal corresponding to the scanned image of the document D is output.

  The magnification in the sub-scanning direction can be dealt with by changing the transport speed by the ADF 9 or the moving speed of the first carriage 14.

  When reading the document D conveyed by the ADF 9, the irradiation position by the exposure lamp 10 is fixed at the position shown in FIG. Further, when reading the document D placed on the document placing table 8, the irradiation position by the exposure lamp 10 is moved from left to right along the document placing table 8.

  On the other hand, the printer unit 6 includes a laser exposure device 28. By scanning the circumferential surface of the photosensitive drum 30 with the laser light from the laser exposure device 28 based on the electrical signal acquired by the scanner unit 4, electrostatic force corresponding to the document image is formed on the circumferential surface of the photosensitive drum 30. A latent image is formed. The photosensitive drum 30 is disposed substantially on the right side of the center of the apparatus main body 2, functions as an image carrier, and is rotatable.

  On the peripheral surface of the photosensitive drum 30, a charging charger 32, a developing device 34, a transfer charger 38, a peeling claw 40, a cleaning device 42, and a static eliminator 44 are arranged in this order. The charging charger 32 charges the peripheral surface of the photosensitive drum 30 to a predetermined charge. The developing device 34 supplies toner as a developer to the electrostatic latent image formed on the circumferential surface of the photosensitive drum 30 and develops it with a desired image density. The transfer charger 38 integrally includes a peeling charger 36 that separates copy paper P (sheet-like medium) fed from cassettes 48 and 50, which will be described later, from the photosensitive drum 30. The transfer charger 38 transfers the toner image formed on the photosensitive drum 30 onto the paper P. The peeling claw 40 peels the copy paper P from the circumferential surface of the photosensitive drum 30. The cleaning device 42 cleans the toner remaining on the circumferential surface of the photosensitive drum 30. Then, the slow charger 44 neutralizes the circumferential surface of the photosensitive drum 30.

  In the lower part of the apparatus main body 2, an upper cassette 48 and a lower cassette 50 that can be pulled out from the apparatus main body are arranged in a stacked state. Copy papers P of different sizes are loaded in the cassettes 48 and 50. A manual feed tray 54 is provided on the side of the upper cassette 48.

  In the apparatus main body 2, a conveyance path 56 is formed extending from each cassette 48, 50 through a transfer portion located between the photosensitive drum 30 and the transfer charger 38. The conveyance path 56 extends to the discharge port 60 through the fixing device 58 having the fixing lamp 58a. The discharge port 60 discharges the paper P having an image formed on at least one side through the fixing device 58 to a discharge tray 78.

  In the vicinity of the upper right portion of the upper cassette 48 and the lower cassette 50 in the drawing, a pickup roller 61 for taking out the paper P from the cassettes 48 and 50 one by one is provided, and a paper feed roller is provided downstream of each pickup roller 61. 62 and a separation roller 63 are provided. In addition, a pair of paper feed and transport rollers 64 is provided in the transport path 56. There are a plurality of paper feeding / conveying roller pairs 64, and the copy paper P taken out by the paper feeding roller 62 and the separation roller 63 is conveyed through the image forming unit via the conveyance path 56.

  A registration roller pair 66 is provided on the upstream side of the photosensitive drum 30 along the conveyance path 56. The registration roller pair 66 corrects the inclination of the taken copy paper P. At the same time, the registration roller pair 66 aligns the leading edge of the toner image on the photosensitive drum 30 with the leading edge of the copy paper P, and transfers the copy paper P to the transfer section at the same speed as the moving speed of the circumferential surface of the photosensitive drum 30. Feed paper. A pre-aligning sensor 68 that detects the arrival of the copy paper P is provided at a position in front of the registration roller pair 66, that is, on the side of the paper feeding and conveying roller pair 64.

  The copy paper P taken out one by one from the cassettes 48 and 50 by the paper feed roller 62 is sent to the registration roller pair 66 by the paper feed roller pair 64. Then, the copy paper P is fed to the transfer section after the leading edge is aligned by the registration roller pair 66. In the transfer portion, the developer image formed on the photosensitive drum 30, that is, the toner image is transferred onto the paper P by the transfer charger 38.

  The copy paper P to which the toner image is transferred is peeled from the circumferential surface of the photosensitive drum 30 by the action of the peeling charger 36 and the peeling claw 40. Then, the copy paper P is conveyed to the fixing device 58 via a conveyance belt (not shown) and a paper guide that constitute a part of the conveyance path 56. The developer image is melted and fixed on the copy paper P by the fixing device 58.

  Thereafter, the copy paper P that has passed through the printer unit 6 is discharged into the apparatus main body 2 via the discharge port 60 by a discharge roller pair 70 that functions as a roller pair of the present invention provided at the end of the conveyance path 56. The paper is discharged to a paper tray 78 (discharge unit). That is, the digital copying machine 1 according to the present embodiment has an in-body discharge type discharge tray 78.

  Further, on the right side of the conveyance path 56 extending in the substantially vertical direction through the transfer unit, a duplex conveyance unit 74 (re-supply unit) that sends the copy paper P that has been reversed and passed through the fixing device 58 to the conveyance path 56 again. ) Is provided. The duplex conveying unit 74 is detachably attached to the right side wall of the apparatus main body 2 in the drawing. The double-sided conveyance unit 74 includes a path 74a for re-supplying the copy paper P switched back by the paper discharge roller pair 70 to the conveyance path 56 on the near side of the registration roller pair 66, and a plurality of conveyance rollers on the path 74a. It has a pair 74b.

  Further, an operation panel (not shown) for instructing various copying conditions such as copy magnification and the start of copying is provided at the upper front of the apparatus body 2.

  Next, with reference to FIG. 2 and FIG. 3, the control operation of the paper discharge roller pair 70 will be described. Here, the operation when the copy paper P on which the image is formed on one side is reversed and re-supplied to the image forming unit will be described. FIG. 2 illustrates the fixing roller 58 and the conveyance roller pair 74b at the top along the path 74a of the duplex conveyance unit as a configuration in the vicinity of the paper discharge roller pair 70. FIG. 3 is a timing chart showing the acceleration / deceleration timing of the paper discharge roller pair 70.

  As shown in FIG. 2, when a copy sheet P (not shown here) that has passed through the transfer section and has an image formed on one side is conveyed in the direction of the arrow T1 in the drawing through the conveyance path 56, the copy sheet P is fed in the direction shown in FIG. The leading end is received in the nip of the paper discharge roller pair 70. At this time, the paper discharge roller pair 70 starts rotating according to the timing chart shown in FIG. 3 with the leading edge of the copy paper P passing the sensor 80 as a trigger, and when receiving the copy paper P, the copy paper P Is rotated at a constant speed (second speed) (212.8 [mm / sec] in the present embodiment) in the direction of feeding to the paper discharge tray 78 (hereinafter referred to as the first direction).

  On the other hand, the transport speed for transporting the copy paper P via the transport path 56, that is, the process speed of the digital copying machine 1, is set to be slightly higher than the second speed described above. The rotational speed of the paper discharge roller pair 70 is adjusted in accordance with the change in the process speed so that the ratio of the speed difference becomes constant even when the process speed changes according to the vertical magnification of the image.

  When the leading edge of the copy paper P is received in the nip of the paper discharge roller pair 70 in this state, the copy paper P is clamped and restrained by the paper discharge roller pair 70 and is sent toward the paper discharge tray 78 at the second speed. .

  Thereafter, the discharge roller pair 70 starts decelerating when the trailing edge of the copy paper P in the feed direction passes the sensor 80, and the trailing edge of the copy paper P in the feed direction passes through the nip of the discharge roller pair 70. Stopped at the previous predetermined timing. The predetermined timing here refers to the fastest timing at which the leading end of the copy paper P in the feeding direction can go to the duplex conveying unit 74 when the copy paper P is switched back. The timing for accelerating / decelerating the paper discharge roller pair 70 is not limited to the above-described embodiment, and can be set by calculating from the conveyance speed and conveyance time of the copy paper P without using the sensor 80.

  As described above, after the copy paper P is stopped, the paper discharge roller pair 70 starts rotating in the reverse direction (hereinafter referred to as the second direction) after a short time, and from the second speed described above. The acceleration is abruptly accelerated to the third speed (400 [mm / sec] in the present embodiment). That is, the copy paper P is fed toward the duplex conveyance unit 74 in the direction of the arrow T2 in the drawing at the increased third speed.

  A timing indicated by A in the figure (A in the figure) is triggered by the fact that the leading end of the copy paper P in the feeding direction has reached the sensor 81 disposed in front of the pair of conveyance rollers 74b on the most upstream side of the duplex conveyance unit 74. Then, the sheet discharge roller pair 70 starts decelerating, and the conveyance speed of the copy paper P is set to the first speed (250 mm in this embodiment) immediately before the leading edge of the copy paper P is received in the nip of the conveyance roller pair 74b. / Sec]). The first speed is a speed at which the copy paper P is transported by the double-sided transport unit 74, and is a speed at which noise and vibration generated from the double-sided transport unit 74 are suppressed to an acceptable level. In this case as well, the timing for accelerating / decelerating the discharge roller pair 70 is not limited to the above-described embodiment, and may be set by calculating from the conveyance speed and conveyance time of the copy paper P without using the sensor 81. it can.

  In other words, the deceleration start timing A and the deceleration of the copy paper P are the same as the speed at which the copy paper P is transported by the double-side transport unit 74 immediately before the leading end of the copy paper P in the feeding direction is received by the double-side transport unit 74. The value is set to decelerate until.

  As a result, the conveyance speed of the copy paper P after the switch-back is increased to increase productivity, and the conveyance speed of the copy paper P by the duplex conveyance unit 74 is not changed. Productivity can be increased while keeping it at a minimum. In particular, when the double-sided conveyance unit 74 is externally attached to the apparatus main body 2 as in the present embodiment, it is advantageous to suppress noise and vibration.

  Then, after the copy paper P is delivered to the duplex conveying unit 74, immediately after the trailing end of the copy paper P in the feeding direction passes through the nip of the paper discharge roller pair 70, the paper discharge roller pair 70 is rapidly decelerated. The copy paper P is stopped in preparation for reversal. In this embodiment, in order to receive the next copy sheet P into the nip, the discharge roller pair is accelerated to the second speed, and then the leading end of the next copy sheet P in the feed direction is 100 [mm / sec]. The nip of the paper discharge roller pair 70 is reached.

  As described above, according to the present embodiment, when the copy paper P is switched back for reversal, the conveyance speed of the copy paper P is set to the apparatus main body side without changing the conveyance speed of the copy paper P in the duplex conveyance unit. Productivity is increased by increasing the speed in a short section. For this reason, the noise and vibration generated from the double-sided conveyance unit externally attached to the apparatus main body can be suppressed to the conventional level, and the productivity can be enhanced.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above-described embodiments. For example, you may delete some components from all the components shown by embodiment mentioned above. Furthermore, you may combine the component covering different embodiment suitably.

  For example, in the above-described embodiment, a case has been described in which productivity is increased by increasing the conveyance speed of the copy paper P before reaching the duplex conveyance unit 74 after the copy paper P is switched back. Not only that, but immediately after the trailing edge of the copy paper P in the feeding direction passes through the fixing device 58 before the switchback, the productivity is further improved by shortening the processing time by abruptly accelerating the paper discharge roller pair 70 by a short interval. You can also.

1 is a schematic diagram showing a schematic structure of a digital copying machine as an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a schematic diagram for explaining the operation of a pair of paper discharge rollers of the digital copying machine of FIG. 1. FIG. 3 is a timing chart showing acceleration / deceleration timing of the paper discharge roller pair in FIG. 2. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Digital copying machine, 2 ... Apparatus main body, 4 ... Scanner part, 6 ... Printer part, 30 ... Photosensitive drum, 56 ... Conveyance path, 58 ... Fixing device, 60 ... Ejection port, 66 ... Registration roller pair, 70 ... Paper discharge roller pair, 74... Two-name transport unit, 74 a... Pass, 74 b.

Claims (5)

An image forming unit for forming an image on a sheet-like medium;
A discharge unit that discharges the image-formed medium that has passed through the image forming unit at least on one side;
A transport path extending through the image forming section to the discharge section;
The medium that is provided on the conveyance path immediately before the discharge unit and image-formed on at least one side by the image forming unit is received in the nip and rotated in the first direction to discharge the medium to the discharge unit, and the image The medium image-formed on one side by the forming unit is received in the nip and rotated in the first direction. After the rear end in the conveyance direction of the medium passes through the image forming unit, the medium is temporarily stopped and rotated in the second direction. A pair of rollers for switching back the medium by
A resupply unit that receives the medium switched back by the roller pair and transports the medium at a first speed to resupply the image forming unit,
When switching the image-formed medium on one side by the image forming unit, the roller pair is rotated at the second speed in the first direction and the medium is fed in the first direction to rotate the roller pair. After stopping and temporarily stopping the medium, the roller pair is rotated in the second direction at a third speed higher than the second speed, and the temporarily stopped medium is sent in the second direction, and the resupply is performed. An image forming apparatus characterized in that the rotation of a roller pair is decelerated so as to decelerate a medium conveying speed to the first speed immediately before the section.   The image forming apparatus according to claim 1, wherein only one set of the roller pair is provided on the conveyance path.   The image forming apparatus according to claim 1, wherein the discharge unit is provided in a housing of the image forming apparatus.   The image forming apparatus according to claim 1, wherein the resupply unit is a double-sided conveyance unit externally attached to a housing of the image forming apparatus.   The image forming apparatus according to claim 1, wherein when the process speed in the image forming unit changes, the second and third speeds are changed in accordance with the change.

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