JP4456851B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus that transfers an image formed on an image carrier onto a transfer material conveyed by a conveying unit.

Conventionally, in an image forming apparatus such as a copying machine, a printer, a plotter, and a facsimile, an image is formed on an image carrier such as a photosensitive member by an image forming unit such as an electrophotographic method or an electrostatic recording method, and then the image is formed. The image on the carrier is transferred to a transfer material (recording paper or the like) conveyed by the conveying means and fixed to form an image.
In such an image forming apparatus, when a wide and long sheet is used as a transfer material and long conveyance is performed, a back tension is applied to the sheet, and the sheet is conveyed without being skewed. In many cases, omission, image blurring, and the like are prevented. In addition, a technique is known in which the linear speed of the transfer paper in the image transfer unit is made equal to the linear velocity of the photosensitive member by controlling the linear speed of the image fixing unit and the paper feed resist unit for the purpose of suppressing variation in magnification. (See, for example, Patent Document 1).

On the other hand, in an electrophotographic or electrostatic recording type image forming apparatus using dry toner, for example, a photoconductor is used as an image carrier, and a toner image formed on the photoconductor through charging, latent image formation, and development processes. The toner is transferred to a transfer material conveyed by a conveying means and fixed to form an image. The toner remaining on the photoconductor after transfer is removed and collected by a cleaning device, but the photoconductor is used repeatedly. In the meantime, toner that cannot be removed even by the cleaning device gradually accumulates on the surface of the photoconductor to cause toner filming, which deteriorates the image quality and ultimately shortens the life of the photoconductor. There's a problem.
In order to solve this problem, a cleaning operation instruction means is provided for instructing an operation for removing the toner adhering to the surface of the photosensitive member that cannot be removed by the cleaning device, and the normal recording operation is suspended by the instruction of the cleaning operation instruction means. In this state, an image forming apparatus that performs a toner filming removal operation has been proposed (see, for example, Patent Document 2). In this prior art, during the cleaning operation, the cleaning paper is fed into the apparatus in the same manner as the recording paper, and when it is brought into contact with the surface of the photoconductor, the conveyance is stopped or decelerated. Thus, for the purpose of cleaning, the photosensitive member is rotated a certain number of times to wipe off the toner adhering to the surface of the photosensitive member, and after the wiping is completed, the cleaning paper is discharged from the apparatus in the same manner as the recording paper.

JP 2002-287444 A Japanese Patent Publication No. 6-48415

  In an image forming apparatus that performs long conveyance, by setting the linear velocity of the fixing device arranged after the image transfer unit to be larger than the linear velocity of the paper feeding / registration roller arranged in front of the image transfer unit, In many cases, back tension is applied to the paper to suppress the skew feeding of the paper in the fixing device, preventing wrinkles, image transfer omission, and image blurring. In this state, the sheet is conveyed while slipping slightly, and the respective line speeds at this time are “feeding / registration roller linear speed” <“paper linear speed” <“fixing apparatus linear speed”. Further, since the “feeding / registration roller linear velocity” is set to be substantially equal to the “photosensitive member linear velocity” of the image carrier (for example, a photosensitive member) that is a transfer medium to the paper when not in a tension state, When the tension starts, “paper linear velocity”> “photosensitive linear velocity”.

  Since the slip state in the fixing device slightly changes depending on the type and surface state of the paper and rollers, the paper linear speed fluctuates slightly. Further, the adhesion between the photosensitive member and the paper in the transfer portion is extremely strong, and if the linear speed of the paper is higher than the linear speed of the photosensitive material, the photosensitive member is pulled on the paper. That is, minute fluctuations in the sheet linear velocity due to slipping in the fixing device are transmitted to the photosensitive member, and rotation unevenness occurs in the photosensitive member. Further, the fluctuation of the sheet linear velocity at the moment when the sheet changes from the initial slack state to the tension state also affects the photosensitive member, resulting in rotation unevenness.

  An image forming apparatus that performs long conveyance is often a wide-width machine. In addition, the market for wide machines is small compared to popular machines that process A3 and A4 and below, and it is difficult to reduce costs due to the lot effect, and it is possible to reduce costs by using inexpensive parts of common machines in common. Has been done. As for devices that form images on photoreceptors, wide-width machines use optical writing devices (for example, optical writing heads (LPH) using light emitting diode (LED) arrays or liquid crystal shutter arrays) in the main scanning direction. There are cases where multiple devices are used. Since the optical writing device does not emit light to the end in the main scanning direction, it is arranged in a staggered manner when a plurality of optical writing devices are connected. When optical writing devices arranged in a staggered pattern are used to form a line across the optical writing device in the main scanning direction on the photosensitive member, the photosensitive member moves the distance in the sub-scanning direction between adjacent optical writing devices. Draw the same line. With this configuration, if rotation irregularity occurs in the photoconductor due to the previous cause, a step is generated in the line. Even if this configuration is not used, a jitter image will be formed on the sheet if rotation irregularity occurs on the photosensitive member.

  In the invention described in the above-mentioned patent document 1, the purpose is not to cope with the step or the jitter image but to ensure the same magnification, but “feeding / registration roller linear velocity” and “fixing device linear velocity”. By changing this during paper conveyance, the “paper linear velocity” and “photosensitive linear velocity” are always controlled to be equal to each other, which is one of the solutions to this problem. Basically, at the moment when the slack state of the paper changes to the tensioned state, the “paper feed / registration roller linear velocity” and the “fixing device linear velocity” are decelerated, and the “paper linear velocity” and “photoconductor linear velocity” are reduced. Although the speed is maintained at a constant speed, the slip state at the fixing device varies depending on the surface condition of each paper, or the time for the leading edge of the paper to reach the fixing device varies depending on the curl condition of the paper. In some cases, variations occur in the timing of decelerating, the start of deceleration is deviated, and the linear speed fluctuation of the paper is transmitted to the photosensitive member, resulting in uneven rotation. In addition, since “paper linear velocity” and “photosensitive linear velocity” are basically maintained at a constant velocity, the “paper linear velocity”> “photosensitive” is instantaneously caused by minute fluctuations in the paper linear velocity due to the slip state. In some cases, the “body speed” may occur, and rotation unevenness may occur in the photosensitive member.

  The present invention has been made in view of the above circumstances, and prevents the speed fluctuation of the paper from being transmitted to the photoconductor, and is difficult to cause rotation unevenness in the photoconductor. An object of the present invention is to provide an image forming apparatus having a configuration in which a seam level difference is unlikely to occur.

Further, the invention described in Patent Document 2 requires a special toner filming removal operation and a complicated mechanism in order to remove toner filming of the photosensitive member. is there.
Therefore, in addition to the above object, the present invention does not require a special toner filming removal operation or a complicated mechanism, and can easily prevent toner filming without causing an increase in cost. An object is to provide a forming apparatus.

As means for achieving the above object, the present invention employs the following configuration.
According to a first aspect of the present invention, there is provided an image forming apparatus for forming an image on an image carrier and transferring the image formed on the image carrier to a transfer material conveyed by a conveyance unit. And a registration roller pair on the upstream side in the transfer material transport direction with respect to the transfer portion that transfers the image on the image carrier to the transfer material, and a fixing roller on the downstream side in the transfer material transport direction with respect to the transfer portion. A fixing unit that includes a pressure roller and sandwiches and conveys the transfer material to fix the image transferred to the transfer material; the linear velocity of the pair of registration rollers is Vr; and the fixing roller and the pressure roller of the fixing unit Is Vf, the linear velocity of the image carrier is Vd, and the linear velocity of the transfer material in the transfer portion is Vp.
Vr <Vf, Vp <Vd, Vr <Vp <Vf
The linear velocity of the image carrier is always higher than the linear velocity of the transfer material at the transfer position, and the image carrier can be driven at a plurality of linear velocities. Is set to change the writing timing in the sub-scanning direction by a writing device that forms a latent image on the image carrier in response to a change in the linear velocity of the image carrier , and the transfer material After the leading edge reaches the fixing portion, the linear velocity of the image carrier is set to be increased by a predetermined ratio .

According to the second configuration of the present invention, a charging unit, a latent image forming unit, a developing unit, a transfer unit, a cleaning unit, and a charge eliminating unit are sequentially arranged around the rotating image carrier along the moving direction. In an image forming apparatus for transferring an image formed on an image carrier through an image formation and development process onto a transfer material conveyed by a conveyance unit, the image on the image carrier is transferred as the conveyance unit. And a registration roller pair on the upstream side in the transfer material transport direction from the transfer portion to which the transfer material is transferred to the transfer material. The transfer material includes a fixing roller and a pressure roller on the downstream side in the transfer material transport direction from the transfer portion. A fixing unit that fixes the image transferred to the transfer material by sandwiching and conveying the image, Vr is a linear velocity of the registration roller pair, Vf is a linear velocity of the fixing roller and the pressure roller of the fixing unit, and the image The linear velocity in the rotation direction of the carrier d, when the linear velocity of the transfer material in the transfer section and the Vp,
Vr <Vf, Vp <Vd, Vr <Vp <Vf
The linear velocity of the image carrier is always higher than the linear velocity of the transfer material at the transfer position, and the image carrier can be driven at a plurality of linear velocities. Is set so as to change the writing timing in the sub-scanning direction by the writing device as the latent image forming means in response to the change in the linear velocity of the image carrier , and the leading edge of the transfer material is After reaching the fixing unit, the linear velocity of the image carrier is set to be increased by a predetermined ratio .

In the image forming apparatus of the first configuration of the present invention, the conveying unit has a pair of registration rollers on the upstream side in the transfer material conveyance direction from the transfer unit that transfers the image on the image carrier to the transfer material by the transfer unit, A fixing unit that includes a fixing roller and a pressure roller and sandwiches and conveys the transfer material to fix the image transferred to the transfer material downstream of the transfer unit in the transfer material conveyance direction. Vr is the linear velocity of the fixing roller and the pressure roller of the fixing unit, Vf is the linear velocity in the rotation direction of the image carrier, and Vp is the linear velocity of the transfer material in the transfer unit.
Vr <Vf, Vp <Vd, Vr <Vp <Vf
Set so that, by the linear velocity of the image bearing member than the linear speed of the transfer material is set to always be faster at the transfer position, without the image bearing member is pulled to the transfer material, Since the speed variation of the transfer material is not transmitted to the image carrier, rotation unevenness is unlikely to occur in the image carrier, and a seam step is less likely to occur when a jitter or writing device is used in a staggered arrangement.

In the image forming apparatus of the second configuration, the transfer unit includes a registration roller pair on the upstream side in the transfer material conveyance direction as compared with the transfer unit that transfers the image on the image carrier onto the transfer material by the transfer unit, and the transfer unit A fixing unit that is composed of a fixing roller and a pressure roller and sandwiches and conveys the transfer material to fix the image transferred to the transfer material, and has a linear velocity of the resist roller pair. Is Vr, the linear velocity of the fixing roller and the pressure roller of the fixing unit is Vf, the linear velocity of the image carrier in the rotation direction is Vd, and the linear velocity of the transfer material in the transfer unit is Vp,
Vr <Vf, Vp <Vd, Vr <Vp <Vf
Set so that, by the linear velocity of the image bearing member than the linear speed of the transfer material is set to always be faster at the transfer position, without the image bearing member is pulled to the transfer material, Since the speed variation of the transfer material is not transmitted to the image carrier, rotation unevenness is unlikely to occur in the image carrier, and a seam step is less likely to occur when a jitter or writing device is used in a staggered arrangement.
Also, the toner filming problem of the image bearing member surface that occurs when using dry toner in the developer of the current image means, than the conveying speed of the transfer material at the transfer position, to the extent that the image can be maintained well By increasing the rotational speed of the image carrier, a difference in speed occurs between the surface of the image carrier and the surface of the transfer material, and the surface of the image carrier is rubbed by the transfer material. The occurrence of filming can be prevented.

In the image forming apparatus of the first or second configuration, before Kizo bearing member, by which can be driven in a plurality of linear velocity, optimal image carrier linear speed in a plurality of sheet type can be set Therefore, a higher quality image can be obtained with respect to rear end equal magnification.

In the image forming apparatus having the first or second configuration , after the leading edge of the transfer material reaches the fixing unit, the linear velocity of the image carrier is set to be increased at a predetermined ratio. Even when the transfer material is pulled by the part and the linear speed of the transfer material is increased, the linear speed of the image carrier is increased, so that it always exceeds the linear speed (conveyance speed) of the transfer material at the transfer position. Since the linear velocity (rotational speed) of the image carrier can be increased, the image carrier is not pulled by the transfer material, and fluctuations in the speed of the transfer material are not transmitted to the image carrier. It is difficult to cause a seam step when a jitter or a writing device is used in a staggered arrangement. Even after the leading edge of the transfer material reaches the fixing portion, the linear velocity of the image carrier is increased to cause a speed difference between the surface of the image carrier and the transfer material, and the surface of the image carrier is slid by the transfer material. Since it is rubbed, toner filming can be easily prevented without increasing the cost.

  Hereinafter, the configuration, operation and action of the present invention will be described in detail based on the embodiments shown in the drawings.

  FIG. 1 is a schematic configuration diagram of an image forming apparatus showing an embodiment of the present invention. In FIG. 1, reference numeral 1 is a document, 2 is a pair of document transport rollers (A) for transporting a document, 3 is a pair of document transport rollers (B) for transporting a document, and 4 is an imaging element (microlens array, rod not shown). Document reading unit comprising a lens array or the like and an image sensor such as a CCD, 5 is a drum-shaped photosensitive member as an image carrier, and 6 is an optical writing head using two writing devices (for example, an LED array or a liquid crystal shutter array). (LPH), etc.) 6a, 6b, a writing device (latent image forming means) for forming a latent image on the photoreceptor, and 7 a developer (for example, dry toner) to develop the latent image on the photoreceptor to be a visible image. 8 is a paper roll wound as a transfer material, 9a and 9b are a pair of paper feed rollers (A), 10a and 10b are a pair of paper feed rollers (B), and 11a and 11b are a pair of registration rollers. , 12 is feeling A transfer unit for transferring the toner image on the body to the paper; 13 a cleaning device for removing residual toner and the like on the photoconductor 5; 14 a fixing unit comprising a fixing roller 14a and a pressure roller 14b; and 15a and 15b for paper discharge A roller pair 16 is a cutter for cutting paper. Incidentally, the charging means and the charge eliminating means of the photoconductor 5 are not shown. As the writing device (latent image forming means) 6, in addition to the optical writing method, an electrostatic recording method using a needle electrode array or the like can also be adopted.

  In FIG. 1, a document 1 is transported by a document transport roller pair (A) 2 and a document transport roller pair (B) 3, and an image is read by a document reading unit 4. The image read by the document reading unit 4 is written on the rotating photoconductor 5 by the writing devices 6a and 6b of the writing device 6 to form an electrostatic latent image. This electrostatic latent image is developed with a developer (for example, dry toner) of the developing device 7 to be visualized. On the other hand, the paper 8 wound in a roll is fed and conveyed by a pair of paper feed rollers (A) 9a and 9b and a pair of paper feed rollers (B) 10a and 10b, and is cut to a predetermined length by a cutter 16. Are sent to the registration roller pair 11a, 11b and conveyed to the transfer unit 12 by the registration roller pair 11a, 11b in time with the above image forming operation. The transfer unit 12 aligns the image with the image on the photoconductor 5. Thus, the image is transferred to the paper 8. The sheet 8 on which the image has been transferred is conveyed to the fixing unit 14, and the image is fixed while being nipped and conveyed by the fixing roller 14 a and the pressure roller 14 b, and is discharged to a discharge unit such as a stacker (not shown) by the discharge roller pairs 15 a and 15 b. Discharged. Further, the toner remaining on the surface of the photoreceptor 5 after the image transfer is removed by the cleaning device 13.

In this embodiment, in the image forming apparatus configured as described above, the linear velocity of the registration roller pair 11a and 11b is Vr, the linear velocity of the fixing roller 14a and the pressure roller 14b of the fixing unit 14 is Vf, and the photosensitive member 5 If the linear velocity is Vd and the linear velocity of the paper 8 in the transfer unit 12 is Vp,
Vr <Vf, Vp <Vd
Is set to be.
Vp is
Vr <Vp <Vf
It is.

  Thus, by setting the linear velocity Vd of the photosensitive member 5 faster than the linear velocity Vp of the paper 8 in the transfer unit 12, the photosensitive member 5 is not pulled by the paper 8, and the linear velocity fluctuation of the paper 8 is changed. Is not transmitted to the photosensitive member 5, so that the rotation unevenness of the photosensitive member 5 is less likely to occur, and the generation of jitter and the like can be prevented.

In order to simplify the explanation here, the speed relationship of the drive roller is shown only for the registration roller, the fixing roller, and the pressure roller, but in actuality in the example of FIG. The sheet feeding roller pair (A) 9a, 9b and the sheet feeding roller pair (B) 10a, 10b and the registration roller pair 11a, 11b, which are conveying means, are sheet conveying speeds determined by the combination of linear velocities, and Vf is downstream of the photoconductor. The sheet conveyance speed is determined by the combination of the linear speeds of the fixing / pressure rollers 14a and 14b and the paper discharge roller pairs 15a and 15b.
Further, when Vp <Vd, a slight slip occurs at the contact point when the image on the photoconductor 5 is transferred to the paper 8, but the linear velocity difference (velocity difference) of Vd with respect to Vp is as follows. It is 1% or less and does not cause a problem on the image.

  By the way, as described in the above-mentioned Patent Document 1, the appropriate linear velocity difference of Vf with respect to Vr varies depending on the paper type in consideration of the transportability of the long paper and the paper shrinkage rate due to thermal fixing. . For this reason, if an appropriate Vf is set for each paper type, Vp in this embodiment also changes. Therefore, it is desirable that a plurality of photosensitive member linear speeds Vd can be set correspondingly. In this case, there is no problem if Vd exceeding the maximum Vp at the maximum Vf is set. However, if Vd is extremely increased, the isotropic property is obtained after the trailing edge of the sheet 8 passes through the registration roller pairs 11a and 11b. However, since it may vary slightly toward the contraction side, it becomes possible to obtain a higher quality image by setting Vd corresponding to each Vf.

  When a plurality of writing devices 6a and 6b are used in a staggered arrangement in the writing device 6, when a plurality of photosensitive member linear velocities Vd are set, the space between the writing devices 6a and 6b is determined by Vd. Since the time required to move in the sub-scanning direction (rotation direction) changes, a plurality of writing timings in the sub-scanning direction can be set corresponding to a plurality of photosensitive member linear velocities Vd. Specifically, if the setting values of the write timing in the sub-scanning direction are previously stored in a data table corresponding to a plurality of setting values of the photosensitive member linear velocity Vd and stored in the memory of the control unit, the photosensitive member Corresponding to the change of the linear velocity Vd, the writing timing can be changed to an appropriate timing, and the occurrence of a seam step when the writing device is used in a staggered arrangement can be prevented.

  Next, a more specific configuration example of the image forming apparatus according to the present invention will be shown. FIG. 2 is a schematic diagram showing the main part of an image forming apparatus according to the second embodiment of the present invention. This image forming apparatus includes a drum-shaped photosensitive member 101 that is an example of an image carrier, a charging device 102 that includes a main charger and a grid that is an example of a charging unit that charges the photosensitive member 101, and a charged photosensitive member. A writing device (latent image forming means) 103 for forming an electrostatic latent image by irradiating the body 101 with light according to image information, and an electrostatic latent image on the photosensitive member having a function of applying and changing a developing voltage. A developing device 104 that develops an image with toner of a two-component developer (dry toner 115 and carrier 116) and visualizes the image, and a transfer material (for example, a toner image on the photosensitive member conveyed from a paper feeding unit not shown) A transfer unit 105 that transfers to the transfer sheet 118, a separation unit 106 that separates the transferred transfer sheet 118 from the photosensitive member 101, and a transfer residual toner that is not transferred to the transfer sheet 118 but remains on the photosensitive member. The And Ningu device 107, and a charge removing device 108 for removing charges remaining on the photoreceptor for the next charging. Further, as shown in FIG. 3, a fixing unit 120 is disposed downstream of the separation unit 106 in the transfer material conveyance direction 119, and the fixing unit 120 includes a fixing roller 121 and a pressure roller 122. Yes.

A specific example of the configuration and operation of the image forming apparatus shown in FIGS.
A drum-shaped photoconductor 101 as an example of an image carrier rotates in a clockwise direction indicated by an arrow in the drawing. A charging device 102 as an example of a means for charging the photosensitive member 101 starts discharging, and charges the image area of the photosensitive member 101 to a predetermined charging potential. Then. Image data of a document read by a document reading unit (not shown) on the photoconductor 101 (or image information transmitted from an external device such as a personal computer or image information transmitted via a telephone line). Based on this, exposure by the writing device (latent image forming means) 103 is performed, and an electrostatic latent image based on the image information is formed in the image area. As the writing device 103, for example, an optical writing method using an LED array or a liquid crystal shutter array, an optical writing method using a laser scanning device, or the like is used. In addition, a needle electrode array or the like is used. An electrostatic recording method can also be adopted.

  In synchronism with the rotation of the photosensitive member 101, the developing roller 109 of the developing device 104 rotates in the direction of the arrow in the drawing. Although not shown, the developing roller 109 includes a cylindrical sleeve and a non-rotating magnet fixedly disposed inside the sleeve, and the magnet is provided with, for example, six magnetic poles. By the magnetic force of this magnet, the two-component developer (dry toner 115 and carrier 116) is carried on the sleeve of the developing roller 109, and is conveyed to the developing position by the rotation of the sleeve, and the two-component developer spikes at the developing position, A so-called magnetic brush is formed. The latent image in the image area on the photoconductor is developed and visualized by the toner in the magnetic brush. In addition, a predetermined developing bias is applied to the developing roller 109 during the visualization.

The image visualized in the image area on the photoconductor is transferred to the transfer paper 118 by the transfer unit 105, and the transfer paper 118 on which the image has been transferred is separated from the photoconductor 101 by the separation unit 106, as shown in FIG. The image is fixed by the fixing roller 121 and the pressure roller 122 of the fixing unit 120 and discharged to a paper discharge unit (not shown).
Further, the transfer residual toner remaining on the photoreceptor 101 after the transfer is removed and cleaned by the cleaning device 107, and the residual charge is removed by the charge removal device 108 to prepare for the next image forming operation.

  The developing device 104 of the developing unit 110 includes a developing container 111 and a toner container 112. In the toner container 112, a replenishment paddle 113 for supplying the toner 115 in the container into the developing container 111 is disposed. In the developing container 111, a stirring paddle 114 and a developing roller 109 are provided. Reference numeral 109 denotes a proximity to the photoconductor 101. Although the toner 115 and the carrier 116 are mixed in the developing container 111, only the toner is consumed by the developing operation. Accordingly, only the toner 115 is accommodated in the toner container 112, and the toner 115 is appropriately replenished into the developing container 111 by the rotation of the replenishment paddle 113.

In this embodiment, in the image forming apparatus having the above-described configuration, the relationship between the rotation speed (linear speed Vd) of the photosensitive member 101 in the transfer unit 105 and the conveyance speed (linear speed Vp) of the transfer paper 118 is as follows. When the image on the body 101 is transferred to the transfer paper 118, the photosensitive member 101 is set to rotate faster to the extent that the image is not affected. That is, as in the first embodiment, the rotational speed (linear speed Vd) of the photoconductor 5 is made faster (Vp <Vd) than the transfer speed (linear speed Vp) of the transfer paper 118 in the transfer unit 105. By setting, the photosensitive member 101 is not pulled by the transfer paper 118, and fluctuations in the linear speed of the transfer paper 118 are not transmitted to the photosensitive member 101. Therefore, rotation unevenness of the photosensitive member 101 is less likely to occur, and jitter is generated. Etc. can be prevented.
Further, by making the rotation speed of the photoconductor 101 faster than the transfer speed of the transfer paper so as not to affect the image in this way, when transferring the image on the photoconductor 101 to the transfer paper 118, a minute amount at the contact point. Although slipping occurs, the surface of the photoconductor 101 is slightly slid with respect to the surface of the transfer paper 118 in this way, so that the surface of the photoconductor 101 is rubbed with the transfer paper 118 to cause toner filming. Occurrence can be prevented. That is, no special toner filming removal operation or complicated mechanism is required, and toner filming can be easily prevented without increasing costs.

By the way, for the purpose of preventing the transfer sheet 118 from being wrinkled, the fixing unit 120 is such that the linear velocity of the fixing roller 121 and the pressure roller 122 is a registration roller (not shown) on the upstream side of the transfer unit 105 in the transport direction. Therefore, when the transfer paper 118 reaches the fixing unit 120, the transfer paper 118 is pulled by the fixing roller 121 and the pressure roller 122, as shown in FIG. Speed up. Therefore, in this embodiment, after the leading edge of the transfer paper 118 reaches the fixing unit 120, the rotation speed (linear speed) of the photosensitive member 101 is set to increase at a predetermined ratio.
As described above, after the leading edge of the transfer paper 118 reaches the fixing unit 120, the transfer paper 118 is pulled by the fixing unit 120 by increasing the rotational speed (linear speed) of the photosensitive member 101 at a predetermined ratio. Even when the conveyance speed (linear speed) is increased, the rotation speed (linear speed) of the photoconductor 101 is increased, so that the rotation of the photoconductor 101 always exceeds the transfer speed of the transfer paper 118 at the transfer position. The speed can be increased, the photosensitive member 101 is not pulled by the transfer paper 118, and the fluctuation in the speed of the transfer paper 118 is not transmitted to the photosensitive member 101. Less likely to occur.
Further, even after the leading edge of the transfer paper reaches the fixing unit 120, the rotational speed of the photosensitive member 101 is increased to cause a speed difference between the photosensitive member surface and the transfer paper surface, and the photosensitive member surface is rubbed by the transfer paper. Therefore, it is possible to easily prevent toner filming without causing an increase in cost.

  The image forming apparatus of the present invention can be used in a copying machine, a printer, a plotter, a facsimile, and a printing apparatus that perform image formation using an electrophotographic system or an electrostatic recording system.

1 is a schematic configuration diagram of an image forming apparatus showing an embodiment of the present invention. FIG. 3 is a schematic configuration diagram of a main part of an image forming apparatus showing a second embodiment of the invention. FIG. 3 is a diagram illustrating a configuration example of a fixing unit of the image forming apparatus illustrated in FIG. 2.

Explanation of symbols

1: Document 2: Document transport roller pair (A)
3: Document transport roller pair (B)
4: Document reading unit 5: Photoconductor (image carrier)
6: Writing device (latent image forming means)
7: Developing device 8: Paper (transfer material)
9a, 9b: Paper feed roller pair (A)
10a, 10b: Paper feed roller pair (B)
11a, 11b: Registration roller pair 12: Transfer unit 13: Cleaning device 14: Fixing unit 14a: Fixing roller 14b: Pressure roller 15a, 15b: Paper discharge roller pair 16: Cutter 101: Photoconductor (image carrier)
102: Charging unit 103: Writing device (latent image forming means)
104: Development device 105: Transfer unit 106: Separation unit 107: Cleaning device 108: Static elimination device 109: Development roller 110: Development unit 111: Development container 112: Toner container 113: Replenishment paddle 114: Stir paddle 115: Toner 116: Carrier 117: Reflective sensor 118: Transfer paper (transfer material)
119: Transfer material conveyance direction 120: Fixing unit 121: Fixing roller 122: Pressure roller

Claims (2)

In an image forming apparatus that forms an image on an image carrier and transfers the image formed on the image carrier to a transfer material conveyed by a conveying unit.
As the conveying means, a registration roller pair is provided on the upstream side in the transfer material conveyance direction with respect to the transfer portion for transferring the image on the image carrier to the transfer material, and on the downstream side in the transfer material conveyance direction with respect to the transfer portion. A fixing unit that includes a fixing roller and a pressure roller, and sandwiches and conveys the transfer material to fix the image transferred to the transfer material;
When the linear velocity of the registration roller pair is Vr, the linear velocity of the fixing roller and the pressure roller of the fixing unit is Vf, the linear velocity of the image carrier is Vd, and the linear velocity of the transfer material in the transfer unit is Vp. ,
Vr <Vf, Vp <Vd, Vr <Vp <Vf
Set so that the linear velocity of the image carrier is always faster than the linear velocity of the transfer material at the transfer position,
The image carrier can be driven at a plurality of linear velocities, and writing in the sub-scanning direction by a writing device that forms a latent image on the image carrier in response to a change in the linear velocity of the image carrier. The timing is set to be changed , and the linear velocity of the image carrier is increased at a predetermined ratio after the leading edge of the transfer material reaches the fixing unit. Forming equipment. A charging unit, a latent image forming unit, a developing unit, a transferring unit, a cleaning unit, and a neutralizing unit are sequentially arranged around the rotating image carrier along the moving direction, and the image is subjected to charging, latent image forming, and developing processes. In an image forming apparatus for transferring an image formed on a carrier to a transfer material conveyed by a conveying unit,
As the conveying means, a registration roller pair is provided on the upstream side in the transfer material conveyance direction with respect to the transfer portion for transferring the image on the image carrier to the transfer material by the transfer means, and the transfer material conveyance direction with respect to the transfer portion On the downstream side, there is a fixing unit composed of a fixing roller and a pressure roller, which sandwiches and conveys the transfer material and fixes the image transferred to the transfer material,
The linear velocity of the registration roller pair is Vr, the linear velocity of the fixing roller and the pressure roller of the fixing unit is Vf, the linear velocity of the rotation direction of the image carrier is Vd, and the linear velocity of the transfer material in the transfer unit is Vp. When
Vr <Vf, Vp <Vd, Vr <Vp <Vf
Set so that the linear velocity of the image carrier is always faster than the linear velocity of the transfer material at the transfer position,
Further, the image carrier can be driven at a plurality of linear speeds, and the writing timing in the sub-scanning direction by the writing device as the latent image forming means is changed corresponding to the change of the linear speed of the image carrier. An image forming apparatus, wherein the linear velocity of the image carrier is increased by a predetermined ratio after the leading edge of the transfer material reaches the fixing unit .

Images