JP3687743B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus employing an electrophotographic system or the like, and in particular, a plurality of image forming units are disposed along a transfer material conveyance path, and the plurality of image forming units are arranged on a transfer material moving along the transfer material conveyance path. The present invention relates to an improvement in an image forming apparatus effective for a type in which toner images are sequentially transferred from an image forming unit.
[0002]
[Prior art]
As a conventional color image forming apparatus, for example, a plurality of image forming units (for example, adopting an electrophotographic system) are arranged on a paper conveyance path along the horizontal direction, and each of the above-mentioned paper is moved along a paper conveyance path. A so-called tandem type in which toner images are sequentially transferred from an image forming unit to form a color image on a sheet is known.
In this type of color image forming apparatus, each image forming unit is provided with a transfer roll that comes into contact with the image bearing photosensitive member, and the photosensitive member and the transfer roll perform the paper conveying operation. A transfer roll transport system (see, for example, JP-A-7-319254) or a paper transport belt that circulates along a paper transport path is provided, and the paper is held on the paper transport belt, for example, by electrostatic adsorption. A belt conveying system (see, for example, Japanese Patent Laid-Open No. 5-53412) has already been proposed.
[0003]
Further, in this type of color image forming apparatus, an inlet transport roll pair is provided on the upstream side of the most upstream image forming unit, and the paper is nipped and transported by this pair of inlet transport rolls, so that at least between each image forming unit. In this case, a method of applying a conveying force to the sheet at a position where the sheet can be sequentially conveyed, specifically, a position where the leading edge of the sheet substantially reaches the transfer area of the most upstream image forming unit is employed.
Furthermore, the arrangement structure of the image forming units of this type of color image forming apparatus is also a horizontal type in which a plurality of image forming units are juxtaposed in the horizontal direction with respect to the paper conveyance path along the horizontal direction (for example, Japanese Patent Laid-Open No. Hei. No. 5-53412) or a vertical type in which a plurality of image forming units are arranged in the vertical direction with respect to a sheet conveyance path along the vertical direction (for example, see Japanese Patent Laid-Open No. 7-287455) has already been proposed. Yes.
[0004]
[Problems to be solved by the invention]
Conventionally, in this type of color image forming apparatus, a “loop control system” is usually employed in a paper bridging area between the pair of inlet transport rolls and the uppermost image forming unit. This “loop control system” is a path configuration in which the paper is bent and absorbs the acceleration / deceleration of the paper conveyance speed.
By adopting such a “loop control method”, even if paper with different stiffness depending on the paper size and paper type (plain paper, thick paper, etc.) is transported, the transportability to various papers is maintained. It becomes possible to do.
[0005]
However, in order to maintain transportability for various types of paper, the length of the loop control area (the span in the paper transport direction between the inlet transport roll pair and the uppermost image forming unit) must be set with a margin. Accordingly, it is difficult to reduce the size of the image forming apparatus.
On the other hand, if priority is given to the demand for miniaturization, a situation arises in which the length of the loop control area must be set short.
At this time, the position of the sheet that is conveyed and nipped by the pair of inlet conveyance rolls is determined, so depending on the type of the sheet, the sheet attracts or pushes, and the leading edge position of the sheet deviates from the transfer area in the most upstream image forming unit. easy. For this reason, transfer position shifts with respect to other image forming units are likely to occur, leading to a technical problem of color shift (which impairs color registration).
[0006]
The present invention has been made to solve the above technical problem, and by devising the transfer system on the inlet side of the transfer material, the apparatus is not affected by the size and type of the transfer material. An image forming apparatus capable of maintaining good color registration while satisfying the demand for downsizing.
[0007]
[Means for Solving the Problems]
That is, according to the present invention, as shown in FIG. 1, an image forming unit 2 having an image carrier 4 on which a toner image is carried, and a toner image on the image carrier 4 are transferred onto a transfer material 3. A transfer and transfer means 5 for transferring and transferring the transfer material 3, and a transfer material disposed on the upstream side of the transfer and transfer means 5 and transferred to a transfer region where the toner image on the image carrier 4 is transferred to the transfer material 3. 3 an inlet conveying means 6 for conveying the prior timing the toner image on the image bearing member 4 is transferred onto the transfer material 3, the inlet conveying means 6 transfer material transport capability to the transfer area by is made to decrease the control The inlet transport means 6 is a pair of rotatable rolls arranged in pressure contact with each other, one of which is a drive feed roll and the other is a driven pinch roll, and the control means 7 Non-contact arrangement of roll pairs In is intended to release the transfer material conveying capacity, under conditions of non-contact positioning the roll pair by the control unit 7, which is characterized in that the non-contact disposed transfer material 3 for at least the feed roll that It is.
Here, the present invention is mainly intended for a color image forming apparatus in which a plurality of image forming units are arranged in parallel. However, the present invention is also applicable to a single color image forming apparatus. To do.
[0008]
When the present invention is applied to a so-called tandem type image forming apparatus in which a plurality of image forming units are arranged in parallel, as shown in FIG. 1, the toner images are sequentially arranged along the transfer material conveyance path 1. In order to sequentially transfer a plurality of image forming units 2 (for example, 2a to 2d) having the image carrier 4 and toner images on the plurality of image carriers 4 onto the transfer material 3, the transfer material 3 is conveyed. Further, the toner image on the image carrier 4 of the image forming unit 2 a disposed on the upstream side of the transfer material transfer path 1 is transferred to the transfer material 3. the transfer member 3 in the transfer area is caused to transfer the inlet conveying means 6 for conveying, before the timing at which the toner image on the image forming units 2a image bearing member 4 which is located in the most upstream is transferred onto the transfer material 3, In the entrance conveying means 6 And control means 7 the transfer material conveying capacity is caused to decrease toward the transfer area that the inlet conveying unit 6 is a rotatable roll pair are pressed against each other, and, in one of the feed rolls for driving The other is a driven pinch roll, and the control means 7 cancels the transfer material conveying capability by disposing the roll pair in a non-contact manner. The transfer material 3 is arranged in a non-contact manner at least with respect to the feed roll .
[0009]
In such technical means, the image forming unit 2 (2a to 2d) may be appropriately selected as long as it forms a toner image of each color component and carries it on the image carrier 4. In consideration of mounting workability and the like, it is preferable that peripheral parts of the image carrier 4 are made into cartridges as much as possible.
The image carrier 4 may be any material as long as it can carry at least a toner image, and an appropriate material such as a photoreceptor or a dielectric may be selected according to the type of the latent image forming unit. The form may be a drum shape or a belt shape.
[0010]
Further, the conveyance transfer means 5 may be of any form as long as it can transfer the toner image to the transfer material 3 while applying a conveyance force to the transfer material 3, but it is simple and small. From the viewpoint of a device, it is preferable to use a transfer roll that is arranged in pressure contact with the image carrier 4 and rotates.
In this case, nothing needs to be provided in front of each image forming unit 2, but from the viewpoint of more stably transporting the transfer material 3, it is in front of each image forming unit 2 (2a to 2d). In addition, it is preferable to provide a transfer material guide for guiding the transfer material 3 to the nip portion between the image carrier 4 and the conveyance transfer means 5 of each image forming unit 2.
[0011]
Furthermore, from the viewpoint of easily transporting the transfer material 3, the transport and transfer unit 5 is arranged on a transfer material transport belt on which the transfer material 3 is held and transported, and on a transfer site facing the image carrier 4. What is provided with the transfer device provided is preferable.
Here, the transfer device may be a device such as a transfer corotron, but from the viewpoint of more stably transporting the transfer material 3, the transfer device is connected to the image carrier 4 via a transfer material transport belt. It is preferable that the transfer roll be arranged in pressure contact and rotate.
[0012]
Further, in the type in which a transfer material conveyance belt is used as the conveyance transfer unit 5, in order to stabilize the holding conveyance property of the transfer material 3, the transfer material 3 is disposed in pressure contact with the transfer material conveyance belt and downstream of the inlet conveyance unit 6. It is preferable to provide an adsorbing means 8 (indicated by a dotted line in the figure) for adhering the transfer material 3 to the transfer material conveying belt.
[0013]
Further, in the present invention, the inlet transport means 6 is intended for the one disposed immediately upstream of the transport transfer means 5 and is appropriately selected as long as it has a function of transporting the transfer material 3. However, in the present invention, a pair of rotatable rolls that are arranged in pressure contact with each other is used.
In the case of such a roll pair configuration, a drive feed roll (usually a roll with a high surface friction resistance is used) and a pinch roll driven by being pressed against the feed roll are used from the viewpoint of providing a normal conveying force. Many embodiments are used.
[0014]
Also, the control unit 7, as long as it allowed to drop enough to prevent displacement in the transfer area at least the transfer material 3 enters the transfer material transport capacity towards the transfer area by the inlet conveying means 6, For example, it is possible to appropriately select, for example, to reduce the nip pressure of the inlet-conveying means 6 having a roll pair configuration, but from the viewpoint of surely avoiding the displacement of the transfer material 3 in the transfer region, the control of the present invention. As in the case of the means 7, it is preferable to completely cancel the transfer material conveying ability of the inlet conveying means 6.
Here, as an aspect of the control means 7 for completely canceling the transfer material conveying capability of the inlet conveying means 6, for example, in the type using the inlet conveying means 6 composed of rotatable roll pairs arranged in pressure contact with each other, It is only necessary to cancel the transfer material conveying capability by disposing them in a non-contact manner.
[0015]
To describe a specific embodiment of this type, for example, an embodiment in which at least one of the rolls is moved and arranged in a non-contact manner with the other roll can be cited.
In this aspect, for example, a cam mechanism may be added to the drive system of the inlet conveyance means 6 so that the roll pair is brought into and out of contact with the timing of the cam shape of the cam mechanism, or a shift using a solenoid is performed. It is possible to change the design as appropriate, such as performing the contact / separation operation of the roll pair using an actuator.
[0016]
Further, as another specific mode of the control means 7, either one of the roll pairs is a non-circular roll in cross section, the transfer length of the transfer material 3 is regulated by the arc length of the non-circular roll, and the non-circular roll The aspect arrange | positioned non-contactingly with the other roll in a non-circular site | part is mentioned.
[0017]
Further, the inlet conveying means 6 is a pair of rotatable rolls arranged in pressure contact with each other, and one feed roll for driving and the other is a pinch roll for driven, the normal feed roll has surface friction. The one with large resistance is used.
For this reason, if the transfer material 3 passing through the release position of the inlet conveyance means 6 is placed in contact with the feed roll under the condition that the transfer material conveyance capability of the inlet conveyance means 6 is released by the control means 7, The friction resistance leads to the conveyance resistance of the transfer material 3.
From the viewpoint of avoiding such problems, it is preferable to take the following measures.
[0018]
For example, a transfer material regulating member 9 (shown by a dotted line in FIG. 1) in which the transfer material 3 is arranged in a non-contact manner with respect to the feed roll under the condition that the control means 7 arranges the roll pair in a non-contact manner , or A mode in which the transfer material 3 is arranged in a non-contact manner at least with respect to the feed roll, for example , the roll on the side where the transfer material 3 is arranged in a contact state is a pinch roll under the condition that the control means 7 arranges the roll pair in a non-contact manner If so, it can be appropriately selected .
In the case where the transfer material 3 is in contact with the feed roll under the condition that the roll pair is arranged in a non-contact manner, a measure to configure the feed roll so as to be freely rotatable with respect to the transfer direction of the transfer material 3 is taken. It is preferable to apply.
[0019]
Further, the arrangement direction of the image forming units 2 (2a to 2d) may be appropriately selected according to the arrangement relationship of the transfer material conveyance path 1. For example, if the transfer material conveyance path 1 is arranged in a substantially horizontal direction, it is necessary to arrange the image forming units 2 in the horizontal direction, while the transfer material conveyance path 1 is arranged in a substantially vertical direction. If it is, it is necessary to arrange the image forming units 2 in the vertical direction.
In this case, in consideration of downsizing of the apparatus, it is preferable to arrange the transfer material conveyance path 1 in a substantially vertical direction and vertically arrange the image forming units 2.
Further, from the viewpoint of facilitating handling of the transfer material 3 after image formation, it is preferable to convey the transfer material 3 from the bottom to the top and handle the transfer material 3 after the image formation on the upper side.
[0020]
In addition, the layout of the transfer path of the transfer material 3 before and after the entrance transfer unit 6 may be selected as appropriate. However, in a mode in which, for example, a transfer material transfer belt is used as the transfer transfer unit 5, the transfer material transfer belt and the transfer material 3 From the viewpoint of improving the adhesion, the transfer direction of the transfer material 3 in front of the entrance transfer means 6 and the transfer direction of the transfer material 3 by the transfer transfer means 5 are deviated by about 90 degrees, and the transfer material 3 It is preferable that the image printing surface is disposed inside the bent surface of the transfer material 3 in the conveyance direction.
[0021]
Next, the operation of the technical means described above will be described.
Now, taking a so-called tandem type image forming apparatus as shown in FIG. 1 as an example, the entrance conveying means 6 is provided on the image carrier 4 of the image forming unit 2 a located at the uppermost stream of the transfer material conveying path 1. The transfer material 3 is conveyed toward a transfer region where the toner image is transferred to the transfer material 3.
Then, before the timing at which the toner image on the image carrier 4 of the image forming unit 2 a located at the most upstream is transferred to the transfer material 3, the control means 7 is capable of conveying the transfer material toward the transfer region by the entrance conveyance means 6. To lower.
For this reason, at the time when the transfer operation is performed in the image forming unit 2a positioned at the most upstream, the transfer material transport capability by the entrance transport unit 6 is reduced, and the transfer material 3 is transported only by the transport transfer unit 5. .
Accordingly, when the transfer material 3 substantially reaches the transfer region of the image forming unit 2a, the transfer material 3 is not completely restrained by the entrance conveying means 6, and the position associated with the transfer material 3 being attracted or pressed in the transfer region. The shift phenomenon is avoided.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
Embodiment 1
FIG. 2 shows a first embodiment of a color image forming apparatus to which the present invention is applied.
In the figure, the color image forming apparatus arranges image forming units 22 (specifically, 22a to 22d) of four colors (in this embodiment, yellow, magenta, cyan, and black) in a vertical direction in a housing 21. A paper feed cassette 23 for storing paper for supply is disposed below the paper feed path, and a paper feed path serving as a paper feed path from the paper feed cassette 23 is provided at a position corresponding to each image forming unit 22. 24 is arranged in the vertical direction.
[0023]
In the present embodiment, the image forming units 22 (22a to 22d) form toner images for yellow, magenta, cyan, and black in order from the upstream side of the sheet conveyance path 24. A cartridge 30 and a laser exposure device 40 are provided.
Here, as shown in FIG. 3 in particular, the photosensitive member cartridge 30 includes a drum-shaped photosensitive member 31, a charging roll 32 that precharges the photosensitive member 31, and the laser exposure device on the charged photosensitive member 31. A developing device 33 that develops the electrostatic latent image formed by exposure with the corresponding color toner and a cleaner 34 that removes residual toner on the photoreceptor 31 are integrally formed into a cartridge.
[0024]
In the present embodiment, the developing device 33 is disposed on the lower side of the photoreceptor 31 and has a developing housing 331 extending in the lateral direction, and a developer containing a predetermined color toner is contained in the developing housing 331. (One-component developer composed of a non-magnetic developer or a magnetic developer) is accommodated, and a pair of developer agitating members 332 are disposed in the development housing 331, and are opposed to the photoreceptor 31 of the development housing 331. A developing roll 333 is disposed in the opening portion to be opened, and a developer supplying member 334 for supplying the developer in the developing housing 331 to the developing roll 333 side is disposed in the vicinity of the developing roll 333, and A developer layer thickness regulating member 335 that regulates the layer thickness of the developer on the developing roll 333 is provided.
On the other hand, the cleaner 34 is disposed on the upper side of the photoconductor 31 and has a cleaner housing 341 extending in the lateral direction, and a blade 342 for scraping residual toner at a location facing the photoconductor 31 of the cleaner housing 341. Is provided.
[0025]
In particular, in the present embodiment, since the developing housing 331 in which the developer is accommodated and the cleaner housing 341 in which the residual toner is collected are extended in the lateral direction, the respective accommodating spaces are secured. The vertical dimension of 30 is set to a short dimension.
[0026]
The laser exposure apparatus 40 stores a semiconductor laser (not shown), a polygon mirror 42, an imaging lens 43, and mirrors 44 and 45 in a case 41, and deflects and scans light from the semiconductor laser (not shown) with the polygon mirror 42. The optical image is guided to the exposure point on the photosensitive member 31 through the imaging lens 43 and the mirrors 44 and 45.
In the present embodiment, since the case 41 extends in the lateral direction, the vertical dimension is set to be short.
[0027]
Further, in the present embodiment, as shown in FIG. 4, a sheet conveying belt 80 that circulates and moves along the sheet conveying path 24 is disposed at a position corresponding to each photoconductor 31 of each of the image forming units 22a to 22d. Has been.
The paper transport belt 80 is made of a belt material capable of electrostatically adsorbing paper, and is stretched around a pair of tension rolls 81 and 82 (usually one is a drive roll and the other is a driven roll).
In particular, in the present embodiment, the suction roll 90 is placed in contact with the stretch roll 81 on the entrance side of the paper transport path 24 of the paper transport belt 80, and for example, a predetermined paper suction is performed on the stretch roll 81. A bias 91 is applied and the suction roll 90 is grounded.
[0028]
Furthermore, in the present embodiment, a transfer roll 50 is disposed on the back surface of the sheet conveying belt 80 corresponding to the photoreceptor 31 of each image forming unit 22 (22a to 22d). Thus, the sheet on the sheet conveying belt 80 is nipped. A predetermined transfer electric field is applied to the transfer roll 50, and a transfer force toward the transfer roll 50 is applied to the toner image on the photoconductor 31.
[0029]
In the present embodiment, as shown in FIGS. 2 and 4, the paper feed cassette 23 is provided with a paper feed roll 61 that sends out paper at a predetermined timing. An entrance transport roll 62 is provided in the paper transport path 24 positioned between the transfer portion of the forming unit 22a. Note that small-size paper such as postcards is directly supplied to the inlet transport roll 62 through a postcard manual feed tray (not shown) in FIG.
In particular, in the present embodiment, as shown in FIGS. 5 and 6, the inlet transport roll 62 is a feed roll 621 that is drivingly connected to the drive motor 623 (in this example, a pair is arranged apart from each other in the axial direction). And a pinch roll 622 (in this example, a pair spaced apart in the axial direction) that is arranged in pressure contact with the feed roll 621 and that is driven to rotate. The pinch roll has a higher frictional resistance on the surface of the feed roll 621. A sheet conveying force is applied in a nip region with 622. In FIG. 6A, reference numeral 624 denotes a driving gear for transmitting a driving force from the driving motor 623.
[0030]
Further, in the present embodiment, an approach / separation mechanism 100 for contacting / separating the feed roll 621 and the pinch roll 622 is provided.
The contact / separation mechanism 100 rotatably supports both ends of the pinch roll 622 with long hole bearings 625 that can advance and retreat in the contact / separation direction, and the long hole bearing 625 is attached to the feed roll 621 side by a biasing spring 626. Furthermore, an eccentric cam 101 having a protruding portion 102 formed on a part of a disk having the same diameter as that of the feed roll 621 is attached coaxially with the feed roll 621, and the eccentric cam 101 is attached to the long hole bearing 625. It is arranged to abut on the outer periphery.
Here, the contact / separation operation between the feed roll 621 and the pinch roll 622 is performed based on the positional relationship between the protruding portions 102 of the eccentric cam 101 by rotating the eccentric roll 101 by appropriately rotating the feed roll 621.
That is, as shown in FIG. 5A, when the portion other than the projecting portion 102 of the eccentric cam 101 is disposed opposite to the outer peripheral portion of the long hole bearing 625, the feed roll 621 and the pinch roll 622 are in a nipped state. On the other hand, as shown in FIG. 5B, the nip state between the feed roll 621 and the pinch roll 622 is released when the protruding portion 102 of the eccentric cam 101 is disposed opposite to the long hole bearing 625. It has become.
[0031]
In the present embodiment, a sheet passage sensor (not shown) is disposed at a predetermined location in the sheet conveyance path 24. When the sheet passage sensor detects the leading end position of the sheet, the detection timing is used. For example, the writing timing of the electrostatic latent image of the laser exposure device 40 of each image forming unit 22 is controlled.
[0032]
Furthermore, as shown in FIG. 4, a fixing device 64 is provided in the paper transport path 24 located on the downstream side of the most downstream image forming unit 22d.
The fixing device 64 includes a heating roll 641 and a pressure belt 642 that is in surface contact with the heating roll 641 in a wide nip area. The performance is improved.
Further, a discharge roll 66 for discharging paper is provided on the downstream side of the fixing device 64, and discharged paper is stored in a storage tray 67 formed on the upper portion of the housing 21. In FIG. 2, reference numeral 65 denotes a paper guide that guides the paper delivered from the paper transport belt 80 to the fixing device 64.
[0033]
Next, the operation of the color image forming apparatus according to this embodiment will be described.
First, when an image forming start switch (not shown) is pressed, as shown in FIG. 7A, after the paper 25 in the paper feed cassette 23 is sent out by the paper feed roll 61, the leading end of the paper 25 is moved. It reaches the entrance conveyance roll 62.
Then, at the timing when the leading end of the paper 25 reaches the entrance transport roll 62 (for example, the timing counted for a predetermined time from the feed timing of the paper 25 by the paper feed roll 61), the entrance transport roll 62 is driven in the nip state.
Then, the sheet 25 is nip-conveyed by the entrance conveyance roll 62 and is sent out toward the transfer portion of the most upstream image forming unit 22 a in the sheet conveyance path 24.
[0034]
As shown in FIG. 7B, when the leading end of the sheet 25 reaches the transfer region P of the uppermost image forming unit 22a, the eccentric cam of the contact / separation mechanism 100 shown in FIG. Since 101 rotates once, the nip state of the inlet transport roll 62 is automatically released as indicated by the solid line from the two-dot chain line by the cam action of the contact / separation mechanism 100.
At this time, the sheet 25 is not restrained by the entrance conveyance roll 62, and the sheet 25 passing through the transfer region P of the image forming unit 22a is based only on the nip conveyance force between the sheet conveyance belt 80, the photoreceptor 31, and the transfer roll 50. Be transported.
For this reason, even if the size and type of the paper 25 are different, the paper 25 is not attracted or pushed due to the restraint of the paper 25 by the entrance conveyance roll 62, and the position of the paper 25 entering the transfer region P is not shifted. The image writing position on the paper 25 in the transfer area P is always kept constant.
In the present embodiment, the entrance transport roll 62 is reset at a predetermined timing after the rear end of the sheet 25 has passed through the entrance transport roll 62 and is set again to the initial nip state position.
[0035]
Thereafter, the sheet 25 is held by the sheet conveying belt 80 and passes through the transfer portions of the image forming units 22b to 22d at a constant speed, so that the color component toner images in the image forming units 22a to 22d are predetermined on the sheet 25. Sequentially multiple transferred to the position.
When the leading end of the paper 25 enters the fixing device 64 and passes through, the paper 25 on which the unfixed toner image is fixed is discharged to the storage tray 67 (see FIG. 2) through the discharge roll 66.
In such an operation process, it was confirmed that a color image without color misregistration and color unevenness was obtained with respect to the paper 25.
[0036]
In such a paper transport process, in order to confirm the performance of the entrance transport roll 62 described above, for example, A4L (A4 longitudinal direction) paper 25 is fed, for example, from a position 20 mm from the front end of the paper to 20 mm before the rear end of the paper. An image image is formed between them, and the nip state of the entrance conveyance roll 62 is set before the time when the center position of the image image area (position of 130 mm with respect to the position of 20 mm from the front end of the sheet) passes through the transfer area P. An experiment was conducted to measure the positional error (Position Error) of both edges (In, Out) in the width direction of the paper 25 under the condition that the nip state of the entrance conveyance roll 62 is released thereafter. The result as shown in FIG. 8 was obtained.
According to the figure, in the area A where the entrance transport roll 62 is in the nip state, it can be understood that the locus lines of In and Out of the paper are greatly shifted, the entrance transport roll 62 dominates the paper speed, and the paper 25 is skewed. It is understood that
In contrast, in the area B where the nip state of the entrance transport roll 62 is released, there is almost no difference in the In and Out trajectory lines of the paper, and it can be understood that the paper 25 is transported without skew. It is confirmed that releasing the nip state of the entrance transport roll 62 improves the sheet transport stability.
[0037]
Further, in this embodiment and the comparative embodiment (using the entrance conveyance roll 62 ′ without the contact / separation mechanism 100), image misalignment does not occur using various types of paper 25 (size-specific, plain paper, thick paper, etc.). In order to satisfy the condition, an experiment was conducted in which a vertical span between the transfer region P of the most upstream image forming unit 22a and the entrance conveyance roll 62 or 62 ′ was examined.
In the comparative form, the paper 25 must be loop-controlled as shown in FIG. 9B (the loop shape of the paper 25 is shown by a one-dot chain line or two-dot chain line in FIG. 9B). Therefore, the vertical span d2 between the transfer region P of the most upstream image forming unit 22a and the entrance transport roll 62 'must be set relatively large. In the embodiment, as shown in FIG. 9A, the vertical span d1 between the transfer region P of the most upstream image forming unit 22a and the inlet transport roll 62 is set to be sufficiently smaller than d2. Confirmed to get.
[0038]
Further, in the present embodiment, the transport direction of the paper 25 in front of the entrance transport roll 62 and the transport direction of the paper 25 by the paper transport belt 80 are deviated by approximately 90 degrees, and the image printing surface of the paper 25 is the paper 25, the paper 25 is pressed against the paper transport belt 80 with the strength of the paper 25, and the adhesiveness of the paper 25 to the paper transport belt 80 is accordingly increased. Will improve.
Further, in the present embodiment, the suction roll 90 is disposed on the entrance side of the paper transport belt 80, and the paper 25 is immediately electrostatically attracted to the paper transport belt 80 via the suction roll 90. In this respect, the close contact holding property of the paper 25 with respect to the paper transport belt 80 is extremely stable.
[0039]
Furthermore, in the present embodiment, as shown in FIG. 7B, the pinch roll 622 of the entrance transport roll 62 is disposed inside the bent surface in the transport direction of the paper 25, so that the nip state of the entrance transport roll 62 When is released, the paper 25 is placed in contact with the pinch roll 622 in accordance with the stiffness of the paper 25.
However, since the pinch roll 622 is a driven roll that can freely rotate, even if the paper 25 is placed in contact with the pinch roll 622, the conveyance resistance of the paper 25 does not increase unnecessarily.
[0040]
Further, in the present embodiment, the contact / separation mechanism 100 of the entrance transport roll 62 is configured using a cam mechanism, but is not limited to this, for example, as shown in FIGS. 10 (a) and 10 (b). As described above, the pinch roll 622 is supported by one end of the link arm 111 having the center of rotation at the center, and the other end of the link arm 111 is urged by the urging spring 112 to the pinch roll 622 toward the feed roll 621. A shift actuator 113 using a solenoid may be driven and connected to the other end of the link arm 111, and the link arm 111 may be swung by the shift actuator 113 to perform the contact / separation operation of the inlet transport roll 62.
[0041]
According to this type, it is possible to perform the contact / separation operation of the entrance transport roll 62 by driving the shift actuator 113 at an appropriate timing without considering the sheet feed amount of the feed roll 621 and the like.
[0042]
In the present embodiment, the grounded suction roll 90 is used as a method for attracting the paper 25 to the paper transport belt 80. However, the present invention is not limited to this. For example, as shown in FIG. In addition, a paper suction bias 91 is applied to the suction roll 90 and the stretching roll 81 of the paper transport belt 80 is grounded, or as shown in FIG. 11B, the suction roll of FIG. Instead of 90, a flexible conductive sheet 92 that elastically contacts the surface of the paper conveying belt 80 may be disposed and grounded. In FIG. 11B, it goes without saying that the sheet suction bias 91 may be applied to the conductive sheet 92 and the stretching roll 81 may be grounded.
[0043]
◎ Reference form 1
FIG. 12 is an explanatory diagram showing a paper transport system of the image forming apparatus according to Reference Embodiment 1 .
In the figure, the basic configuration of the paper transport system is substantially the same as that of the first embodiment, but the configuration of the inlet transport roll 62 is different from that of the first embodiment. Components similar to those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and detailed description thereof is omitted here.
That is, in the present reference, inlet conveying roller 62, a feed roll 621 comprising a non-circular cross section roll which is drivingly connected to an unillustrated drive motor, pinch rolls 622 are pressed disposed arcuate surface of the feed roll 621 As shown in FIGS. 13A to 13C, by appropriately rotating the feed roll 621, the conveyance amount of the paper 25 is regulated by the arc length m of the feed roll 621, and the feed roll 621 The pinch roll 622 is disposed in a non-contact manner due to the presence of the non-circular portion 627.
According to this type, the contact / separation operation of the entrance transport roll 62 can be performed more easily without using the cam mechanism or the shift actuator as in the first embodiment as the contact / separation mechanism of the entrance transport roll 62.
In this reference embodiment, the layout of the feed roll 621 and the pinch roll 622 is opposite to that of the first embodiment. However, the same layout as that of the first embodiment is applied to the inlet transport roll 62 according to this reference embodiment. If the separation mechanism is used, when the feed roll 621 and the pinch roll 622 are not in contact with each other, the paper is arranged in a non-contact manner with respect to the feed roll 621.
[0044]
Embodiment 2
FIG. 14 is an explanatory diagram showing the main part of the paper transport system of the image forming apparatus according to the second embodiment.
In the figure, the paper transport system is substantially the same as in the first embodiment, but the configuration of the entrance transport roll 62 is different from that in the first embodiment.
That is, in this embodiment, as shown in FIGS. 14 and 15, the inlet transport roll 62 sets the layout of the feed roll 621 and the pinch roll 622 in the reverse direction of the first embodiment, and further, when the nip is released. A flexible sheet 120 on which the feed roll 621 and the paper 25 are arranged in a non-contact manner is provided.
The flexible sheet 120 is fixed to the support bracket 125 at the base end side, and the pinch roll 622 is spaced from the peripheral position of the feed roll 621 toward the pinch roll 622 in a state where the pinch roll 622 is spaced apart when the entrance conveyance roll 62 is released from the nip. For example, an appropriate number (three in this example) is arranged in the axial direction of the feed roll 621 and elastically contacts the paper 25 when the nip is released, and the feed roll 621 is an elastic sheet made of a low-resistance material. And the paper 25 are arranged in a non-contact manner.
[0045]
Therefore, according to the present embodiment, when the nip of the inlet transport roll 62 is released, the paper 25 tends to press against the feed roll 621 by its waist strength, but the paper 25 protrudes from the peripheral surface of the feed roll 621. Since the flexible sheet 120 is supported, the paper 25 is not pressed against the feed roll 621.
Therefore, when the entrance conveyance roll 62 is released from the nip, a situation in which the conveyance resistance of the paper 25 is unnecessarily increased at the entrance conveyance roll 62 is effectively avoided.
[0046]
In the present embodiment, the flexible sheet 120 is used as a method for reducing the conveyance resistance of the paper 25 when the nip is released from the entrance conveyance roll 62. However, the present invention is not limited to this, and is shown in FIG. Thus, an appropriate number (four in this example) of low-resistance guide rolls 122 that are larger than the outer diameter of the feed roll 621 are arranged in the axial direction of the feed roll 621, and the paper 25 is loaded when the nip is released from the inlet transport roll 62 The contact resistance of the paper 25 may be reduced by bringing it into contact with the circumferential surface of the guide roll 122 as compared with the case of contacting the feed roll 621.
As a reference form related to the present invention, for example, as shown in FIGS. 16 and 17, the one-way clutch bearing 121 is incorporated in the drive gear 624 of the feed roll 621, the gear drive direction and the idling rotation direction of the feed roll 621. Are set to the same, and even when the paper 25 is pressed against the feed roll 621 when the nip of the inlet transport roll 62 is released, the feed roll 621 rotates idly following the movement of the paper 25 to reduce the transport resistance of the paper 25. You may make it make it .
[0047]
Embodiment 3
FIG. 19 shows Embodiment 3 of an image forming apparatus to which the present invention is applied.
In the present embodiment, the color image forming apparatus has four color image forming units 22 (22a to 22d) as in the first embodiment, but unlike the first embodiment, the color image forming apparatus is arranged vertically. The sheet conveying belt 80 that circulates and moves along the sheet conveying path 24 is removed, and the sheet 25 is conveyed and transferred simultaneously by the transfer roll 50 that is arranged in pressure contact with the photosensitive member 31 of each image forming unit 22 and rotates. It is configured.
In the present embodiment, the transfer roll 50 is provided separately from the photoreceptor cartridge 30 and is rotationally driven in synchronization with the photoreceptor 31 by a drive transmission system (not shown). Note that the transfer roll 50 may be integrated into the photosensitive cartridge 30.
Further, in the present embodiment, the movement trajectory of each sheet 25 is regulated in front of the most upstream image forming unit 22a, between the image forming units 22a to 22d, and behind the most downstream image forming unit 22d. Paper guides 131 to 135 are provided.
Furthermore, in the present embodiment, since the other components such as the inlet conveyance roll 62 are the same as those in the first embodiment, the details thereof are denoted by the same reference numerals and the description thereof is omitted.
Needless to say , Reference Embodiment 1 and Embodiment 2 can be applied to the configuration of the entrance conveyance roll 62.
[0048]
In the present embodiment, when the sheet 25 nip transported to the entrance transport roll 62 reaches the transfer area of the uppermost image forming unit 22a, the nip state of the entrance transport roll 62 is released and the sheet 25 is a photosensitive member. The nip is transported between the photosensitive drum 31 and the transfer roll 50, and thereafter, the nip is transported between the photoreceptor 31 of each of the image forming units 22 b to 22 d and the transfer roll 50.
In such a sheet transport operation process, the entrance transport roll 62 can be disposed close to the most upstream image forming unit 22a, and color misregistration in each transfer region can be observed, as in the first embodiment. It was confirmed that it was not possible.
[0049]
Embodiment 4
FIG. 20 shows Embodiment 4 in which the present invention is applied to a monochrome image forming apparatus.
In the figure, the image forming apparatus is one in which a single color photosensitive cartridge 30 is incorporated in a housing 21, a paper feed cassette 23 is disposed on the lower side, and a fixing device 64 and a receiving tray 67 on the upper side. Further, as the paper transport system, for example, the same entrance transport roll 62, paper transport belt 80 and transfer roll 50 as those in the first embodiment are used.
Components similar to those in the first embodiment are denoted by the same reference numerals as those in the first embodiment, and detailed description thereof is omitted here.
Therefore, even in the present embodiment, the sheet 25 can be stably conveyed by appropriately controlling the nip release of the inlet conveyance roll 62, and the gap between the photoconductor 31 and the transfer roll 50 can be improved. Since the transfer operation is performed without positional deviation, a good monochromatic image can be obtained.
[0050]
【The invention's effect】
As described above, according to the present invention, in the image forming apparatus of the type that transports the transfer material by the transport transfer unit facing the image carrier, the inlet transport unit disposed on the upstream side of the transport transfer unit. As a result, the transfer material transport ability toward the transfer region by the entrance transport means is lowered before the toner image on the image carrier positioned at the most upstream is transferred to the transfer material. Even if the sizes and types differ, the transfer operation is not performed while the transfer material is constrained by the entrance conveyance means, and the transfer operation can be realized while conveying the transfer material only by the conveyance transfer means.
This eliminates the need for loop control of the transfer material between the image carrier positioned at the uppermost stream and the inlet conveying means, and accordingly, the span between the image carrier positioned at the uppermost stream and the inlet conveying means is set narrow. In addition, it is possible to avoid displacement of the transfer material due to an attracting or pushing phenomenon of the transfer material based on the difference in size and type of the transfer material.
Therefore, by devising the conveyance method on the entrance side of the transfer material, the color registration can be maintained well while satisfying the demand for downsizing of the apparatus without being affected by the size and type of the transfer material. .
In particular, in the present invention, the inlet conveyance means is constituted by a roll pair of a feed roll and a pinch roll, and when releasing the transfer material conveyance capability of the inlet conveyance means, at least under the condition that the roll pair is arranged in a non-contact manner. Since the transfer material is arranged in a non-contact manner with respect to the feed roll, the transfer resistance of the transfer material can be reduced as much as the friction resistance due to the feed roll does not act on the transfer material, and accordingly, the inlet transport means. Thus, it is possible to effectively prevent a situation in which the transfer material conveyance operation is hindered.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a configuration of an image forming apparatus according to the present invention.
FIG. 2 is an explanatory diagram showing an outline of the image forming apparatus according to the first embodiment.
3 is an explanatory diagram showing details of an image forming unit used in Embodiment 1. FIG.
FIG. 4 is an explanatory diagram showing details of a paper transport system used in the first embodiment.
FIGS. 5A and 5B are explanatory views showing a contact / separation mechanism of the inlet transport roll used in Embodiment 1, and FIG. 5B is an explanatory view showing a state when the nip of the inlet transport roll is released.
6A is an explanatory plan view of an inlet conveyance roll used in Embodiment 1, and FIG. 6B is an explanatory view of the contact / separation mechanism in FIG.
7A is an explanatory diagram illustrating a state at the time when a sheet has entered the entrance conveyance roll, and FIG. 7B is an explanatory diagram illustrating a state at the time when the sheet has entered the transfer area of the photoconductor located at the uppermost stream. It is.
FIG. 8 is a graph showing the performance test result of the nip state release method of the inlet transport roll in the present embodiment.
9A is an explanatory diagram showing an example layout of an inlet transport roll according to the present embodiment, and FIG. 9B is an explanatory diagram showing an example layout of the inlet transport roll according to a comparative embodiment.
10A is an explanatory view showing a modified form of the contact mechanism of the inlet transport roll used in Embodiment 1, and FIG. 10B is an explanatory view showing a state when the nip of the inlet transport roll is released.
11A is an explanatory view showing a modified form of the paper suction mechanism used in Embodiment 1, and FIG. 11B is an explanatory view showing another modified form of the paper suction mechanism.
FIG. 12 is an explanatory diagram illustrating a paper transport system of the image forming apparatus according to Reference Embodiment 1 ;
FIGS. 13A to 13C are explanatory views showing the nip releasing operation process of the inlet transport roll used in Reference Embodiment 1. FIGS.
FIG. 14 is an explanatory diagram illustrating a main part of a paper transport system of an image forming apparatus according to a second embodiment.
15A is an explanatory plan view of an inlet transport roll used in Embodiment 2 , and FIG. 15B is an explanatory view of the contact / separation mechanism in FIG.
FIG. 16 is an explanatory diagram showing a reference form related to the inlet transport roll used in the second embodiment.
17A is an explanatory plan view of an inlet transport roll used in the reference embodiment, and FIG. 17B is a view as viewed from the B direction in FIG.
FIG. 18 is an explanatory plan view showing an inlet transport roll used in another modification of the second embodiment.
FIG. 19 is an explanatory diagram showing an outline of an image forming apparatus according to a third embodiment.
FIG. 20 is an explanatory diagram showing an overview of an image forming apparatus according to a fourth embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Transfer material conveyance path, 2 (2a-2d) ... Image forming unit, 3 ... Transfer material, 4 ... Image carrier, 5 ... Conveyance transfer means, 6 ... Inlet conveyance means, 7 ... Control means, 8 ... Adsorption means , 9 ... Transfer material regulating member, 22 (22a to 22d) ... Image forming unit, 24 ... Paper transport path, 25 ... Paper, 31 ... Photoconductor, 50 ... Transfer roll, 62 ... Entrance transport roll, 80 ... Paper transport belt

Claims (14)

An image forming unit (2) having an image carrier (4) on which a toner image is carried;
A transfer and transfer means (5) for transferring and transferring the transfer material (3) in order to transfer the toner image on the image carrier (4) onto the transfer material (3);
An inlet conveyance means (provided upstream of the conveyance transfer means (5)) conveys the transfer material (3) to a transfer region where the toner image on the image carrier (4) is transferred to the transfer material (3). 6) and
Control means (7) in which the transfer material conveyance ability toward the transfer region by the entrance conveyance means (6) is lowered before the toner image on the image carrier (4) is transferred to the transfer material (3). And
The inlet transport means (6) is a pair of rotatable rolls arranged in pressure contact with each other, one of which is a drive feed roll and the other is a driven pinch roll,
The control means (7) releases the transfer material conveyance capability by disposing the roll pair in a non-contact manner,
An image forming apparatus, wherein the transfer material (3) is arranged in a non-contact manner at least with respect to the feed roll under the condition that the control means (7) arranges the roll pair in a non-contact manner. A plurality of image forming units (2: 2a to 2d) which are sequentially arranged along the transfer material conveyance path (1) and each have an image carrier (4) on which a toner image is carried;
Conveying transfer means (5) for conveying and transferring the transfer material (3) in order to sequentially transfer the toner images on the plurality of image carriers (4) onto the transfer material (3);
The toner image on the image carrier (4) of the image forming unit (2a), which is disposed upstream of the transport transfer means (5) and is located on the uppermost stream of the transfer material transport path (1), is transferred to the transfer material (3 Inlet transport means (6) for transporting the transfer material (3) to a transfer region to be transferred to
Before the timing at which the toner image on the image carrier (4) of the image forming unit (2a) located at the uppermost stream is transferred to the transfer material (3), the toner image is directed to the transfer region by the inlet conveying means (6). And a control means (7) capable of lowering the transfer material conveyance capability,
The inlet transport means (6) is a pair of rotatable rolls arranged in pressure contact with each other, one of which is a drive feed roll and the other is a driven pinch roll,
The control means (7) releases the transfer material conveyance capability by disposing the roll pair in a non-contact manner,
An image forming apparatus, wherein the transfer material (3) is arranged in a non-contact manner at least with respect to the feed roll under the condition that the control means (7) arranges the roll pair in a non-contact manner. The image forming apparatus according to claim 1 or 2,
2. An image forming apparatus according to claim 1, wherein the transfer material conveyance path (1) of the conveyance transfer means (5) is substantially vertical and conveys the transfer material (3) from the bottom to the top. The image forming apparatus according to claim 1 or 2,
2. An image forming apparatus according to claim 1, wherein the conveying transfer means (5) comprises a transfer roll that is arranged in pressure contact with the image carrier (4) and rotates. The image forming apparatus according to claim 1 or 2,
The conveyance transfer means (5) includes a transfer material conveyance belt on which the transfer material (3) is held and conveyed, and a transfer device disposed at a transfer portion facing the image carrier (4). An image forming apparatus. The image forming apparatus according to claim 5 .
The image forming apparatus, wherein the transfer device is a transfer roll that is arranged in pressure contact with the image carrier (4) via a transfer material conveying belt and rotates. The image forming apparatus according to claim 5 .
A transfer means (8) that is in pressure contact with the transfer material conveyance belt and that is disposed downstream of the inlet conveyance means (6) is provided on the transfer material conveyance belt. Image forming apparatus. The image forming apparatus according to claim 1 or 2,
The image forming apparatus, wherein the inlet transport means (6) is disposed immediately upstream of the transport transfer means (5). The image forming apparatus according to claim 1 or 2,
The image forming apparatus, wherein the control means (7) moves at least one of the rolls and disposes the other roll in a non-contact manner. The image forming apparatus according to claim 1 or 2,
The image forming apparatus is characterized in that the control means (7) adds a cam mechanism to the drive system of the inlet conveying means (6), and performs the contact / separation operation of the roll pair according to the cam shape timing of the cam mechanism. apparatus. The image forming apparatus according to claim 1 or 2,
The control means (7) uses either one of the roll pairs as a non-circular roll in cross section, restricts the conveyance amount of the transfer material (3) by the arc length of the non-circular roll, and controls the other at the non-circular portion of the non-circular roll. An image forming apparatus, wherein the image forming apparatus is arranged in a non-contact manner with a roll of the above. The image forming apparatus according to claim 1 or 2,
The inlet conveying means (6) is a pair of rotatable rolls arranged in pressure contact with each other, one of which is a drive feed roll and the other is a driven pinch roll, and the control means (7) An image forming apparatus comprising a transfer material regulating member (9) in which the transfer material (3) is arranged in a non-contact manner with respect to the feed roll under the condition of contact arrangement. The image forming apparatus according to claim 1 or 2,
The inlet conveying means (6) is a pair of rotatable rolls arranged in pressure contact with each other, one of which is a drive feed roll and the other is a driven pinch roll, and the control means (7) An image forming apparatus, wherein a roll on which a transfer material is placed in contact with each other under a condition of contact placement is a pinch roll. The image forming apparatus according to claim 1 or 2,
The transfer direction of the transfer material (3) before the entrance transfer means (6) and the transfer direction of the transfer material (3) by the transfer transfer means (5) are deviated by approximately 90 degrees, and the transfer material (3) An image forming apparatus, wherein the image printing surface is disposed on the inner side of the bent surface in the conveying direction of the transfer material (3).

Images