JP4025966B2 - Image forming apparatus - Google Patents

Description

[0001]
[Industrial application fields]
The present invention provides a flexible endless sleeve-like image transfer / conveying means, and a latent image formed on the image carrier by a latent image forming means arranged in parallel with an image carrier contacting the image transfer / conveying means. The present invention relates to an image forming apparatus comprising a plurality of image forming means for developing an image by a developing means and configured to sequentially transfer the developed toner images of the image forming means to an image transfer conveying means.
[0002]
[Prior art]
The tandem type image forming apparatus is roughly classified as follows.
A plurality of image forming stations are arranged in a line, the recording paper is electrostatically attracted to the transport belt, and the recording paper is sequentially brought into contact with each station and transported between the stations and the recording paper. A paper conveying system that applies a transfer force and superimposes colors while directly transferring a plurality of color toner images to a recording paper; and
A plurality of image forming stations are arranged in a row, and the toner image formed at each station is transferred between the station and the intermediate transfer belt while the intermediate transfer belt formed of a dielectric is brought into contact with each station and conveyed. An intermediate transfer method in which electrostatic transfer force is sequentially applied to the image, primary transfer is performed, color is superimposed on the intermediate transfer belt, and secondary transfer is performed collectively from the intermediate transfer belt to the recording paper;
The following two methods are adopted.
[0003]
The above paper transport method requires means (rollers and brushes) for adsorbing the recording paper to the transport belt and a high voltage power supply, but the intermediate transfer method does not require these means and power supply, and the paper transport method. However, it is necessary to strictly control the transfer bias applied to each image transfer unit according to the size, thickness, and type of the recording paper.In the intermediate transfer method, the resistance and thickness are independent of these factors of the recording paper. Transfer conditions such as transfer voltage, transfer current, and contact pressure are only performed when a primary transfer of a toner image is performed on an intermediate transfer belt with a constant surface roughness, and then secondary transfer is performed collectively on a recording sheet. Therefore, the intermediate transfer method has many advantages.
[0004]
On the other hand, when divided by the arrangement method of each image forming station, there are a method in which each station is arranged in a horizontal direction and a method in which each station is arranged in a vertical direction. Has a drawback that it is difficult to install on a desk.
[0005]
For this purpose, conventionally, Japanese Patent Application Laid-Open No. 11-95520 and Japanese Patent Application Laid-Open No. 8-305115 have known a method in which image forming stations are arranged in an oblique direction. The former is provided with an exposure device corresponding to each image forming station, and the latter is provided with an exposure device common to each image forming station.
[0006]
[Problems to be solved by the invention]
However, in an image forming apparatus using an image transfer / conveying means composed of a conveyance belt or an intermediate transfer belt that forms and conveys an image by sequentially transferring toner images in contact with a plurality of image carriers, the first image carrier The conditions for transferring the first toner image in step 1, the conditions for transferring the second toner image on the next second image carrier onto the first toner image, and the next on the n-1 toner image. The conditions for transferring the nth toner image on the nth image carrier are often different due to the influence of the attributes of the previously transferred toner image. In particular, the contact pressure and contact mode between each image carrier and the image transfer conveying means, the transfer bias application mode for transferring the toner image, and the like, the toner images are sequentially stacked in contact with the plurality of image carriers as described above. This is an important requirement that determines the transfer conditions for transfer.
[0007]
Further, in the above conventional method, since each image forming station is arranged above the belt surface arranged in an oblique manner, whether it is a paper conveyance belt or an intermediate transfer belt, development at the image forming station is performed. The toner spills from the means, and the belt and other image forming means are soiled to cause image quality deterioration. Further, since the exposure means must be disposed above the apparatus main body, there is a problem that the vibration of the apparatus main body is increased and the image quality is deteriorated.
[0008]
[Means for Solving the Problems]
The present invention solves the above-described conventional problems, and without providing a special contact pressure applying means, it is possible to stabilize transfer conditions with an inexpensive configuration, to prevent image quality deterioration, and to achieve high-quality images. A forming apparatus is provided.
[0009]
For this purpose, the present invention provides a flexible endless sleeve-like image transfer / conveying means and an image carrier that is arranged in parallel along an oblique arch-like line below the image transfer / conveying means. A plurality of image forming means for developing a latent image formed on the image carrier by a developing means, and laser beams from a plurality of laser light sources disposed in a space formed obliquely below the plurality of image forming means A latent image formed on the image carrier of each of the plurality of image forming means by reflecting the light on a common reflecting surface of a common rotary polygon mirror and reflecting the light back by an optical system including a plurality of reflecting mirrors. Forming means, and adjusting the winding angle of the image transfer conveying means with respect to the image carrier of each image forming means by the arch-shaped curvature, and adjusting the nip width and contact with the winding angle and tension. Adjust the pressure, and is characterized in that said constituted the developed toner images of the respective image forming means to sequentially superposed transferred to the image transfer conveying means.
[0010]
In addition, the wrapping angle of the image transfer conveyance unit with respect to the image carrier of each image forming unit is substantially the same, the image carrier of each image formation unit and the image transfer conveyance unit have a speed difference, and The image transfer / conveying means is stretched by at least two rollers, and the driving roller is selected on the upstream side or the downstream side in accordance with the speed difference from the image carrier. A conductive biasing roller, a conductive elastic member, and a conductive brush, which are rotated by the movement of the image transfer conveying means, are disposed on the back side of the contact portion with the body, and the image transfer conveying means includes: It is an intermediate transfer medium.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic cross-sectional view of the overall configuration showing an embodiment of an image forming apparatus according to the present invention, and FIG. 2 explains the contact pressure applied by the wrapping angle and tension of the image transfer conveying means to the image carrier. FIG. 3 is a diagram showing a configuration example of the primary transfer bias applying means. In the figure, 1 is an image forming apparatus, 2 is a housing, 3 is a door, 6 is an exposure unit, 7 is an image forming unit, 9 is a transfer belt unit, 10 is a paper feeding unit, 11 is a paper transport unit, and 15 is cleaning. Means 17, an image carrier, 18 an image transfer and conveyance means, 20 a developing means, 21 a scanner means, 21 b a rotary polygon mirror, and 40 a fixing means.
[0012]
In FIG. 1, an image forming apparatus 1 according to the present embodiment includes a housing 2, a paper discharge tray 2 a formed on the top of the housing 2, and a door body 3 that can be opened and closed on the front surface of the housing 2. An exposure unit (exposure unit) 6, an image forming unit 7, a transfer belt unit 9 having an image transfer / conveyance unit, and a paper feed unit 10 are disposed in the housing 2, and a paper conveyance unit 11 is disposed in the door 3. It is arranged. Each unit has a configuration that can be attached to and detached from the main body, and can be removed and repaired or replaced integrally during maintenance or the like.
[0013]
The image forming unit 7 includes a plurality (four in this embodiment) of image forming stations Y (for yellow), M (for magenta), C (for cyan), and K (for black) that form images of different colors. I have. In each of the image forming stations Y, M, C, and K, an image carrier 17 that is a photosensitive drum, a charging unit 19 that is a corona charging unit and a developing unit that are disposed around the image carrier 17 are provided. Means 20 are included. Each of these image forming stations Y, M, C, and K is arranged in parallel on the lower side of the transfer belt unit 9 so that the image carrier 17 faces upward along an oblique arched line. The order of arrangement of the image forming stations Y, M, C, and K is arbitrary.
[0014]
The transfer belt unit 9 is disposed below the housing 2 and is driven to rotate by a drive source (not shown), a driven roller 13 disposed obliquely above the drive roller 12, and a backup roller (tension roller). ) 14, an image transfer conveyance means 18 comprising an intermediate transfer belt that is stretched between these three or at least two rollers and driven to circulate in the direction indicated by the arrow (counterclockwise direction X), and an image transfer conveyance means 18 And a cleaning means 15 that abuts against the surface. The driven roller 13, the backup roller 14, and the image transfer / conveying means 18 are disposed in a direction inclined to the left in the drawing with respect to the driving roller 12, so that the belt conveying direction X when driving the image transfer / conveying means 18 is downward. The belt surface 18a is positioned below, and the belt surface 18b whose transport direction is upward is positioned above.
[0015]
Accordingly, the image forming stations Y, M, C, and K are also arranged in a direction inclined to the left in the drawing with respect to the driving roller 12. Then, the image carrier 17 is brought into contact with the belt surface 18a facing downward in the transport direction of the image transfer transport unit 18 along the arched line, and is rotationally driven in the transport direction of the image transfer transport unit 18 as indicated by the arrows in the drawing. The The flexible endless sleeve-shaped image transfer / conveyance means 18 is brought into contact with the image carrier 17 from substantially the same wrapping angle so as to be covered from above, so that the image carrier 17 and the image transfer / conveyance means 18 are in contact with each other. The contact pressure and the nip width can be adjusted by controlling the tension applied to the image transfer / conveying means 18 by the tension roller 14, the arrangement interval of the image carrier 17, the winding angle (arch curvature), and the like. .
[0016]
The drive roller 12 also serves as a backup roller for the secondary transfer roller 39. The circumferential surface of the drive roller 12 has a thickness of about 3 mm and a volume resistivity of 10 for example. ^Five A rubber layer of Ω · cm or less is formed, and a conductive path for a secondary transfer bias supplied via the secondary transfer roller 39 is grounded through a metal shaft. As described above, by providing the driving roller 12 with a rubber layer having high friction and shock absorption, it is difficult for the impact when the recording medium enters the secondary transfer portion to be transmitted to the image transfer conveying means 18 and the image quality is deteriorated. Can be prevented. Further, by making the diameter of the driving roller 12 smaller than the diameters of the driven roller 13 and the backup roller 14, the recording paper after the secondary transfer can be easily separated by the elastic force of the recording paper itself. Further, the driven roller 13 is also used as a backup roller for the cleaning means 15 described later.
[0017]
Note that the image transfer conveying means 18 is disposed in a direction inclined to the right in the drawing with respect to the driving roller 12, and correspondingly, each of the image forming stations Y, M, C, K is also illustrated with respect to the driving roller 12. In FIG. 1, it may be arranged along the oblique arch shape in the direction inclined to the right side, that is, on the left and right objects in FIG.
[0018]
Next, the contact pressure applied by the winding angle and tension of the image transfer / conveying means 18 with respect to the image carrier 17 will be described. For example, as shown in FIG. 2, when the tension P is applied to the image transfer / conveying means 18 by the urging force F of the illustrated roller using the backup roller 14 as a tension roller, the winding angle α of the image transfer / conveying means 18 with respect to the image carrier 17 is set. Accordingly, the contact pressure f is a component of the tension P.
f = P · sin α
Is required. This contact pressure f is applied between the image carrier 17 and the lower surface 18 a of the image transfer / conveying means 18. Accordingly, the contact pressure f can be adjusted by adjusting the tension P by the urging force F of the roller, and the contact pressure can also be adjusted by adjusting the winding angle α of the image transfer conveying means 18 with respect to the image carrier 17. f can be adjusted. At the same time, the nip width L can also be adjusted by adjusting the winding angle α of the image transfer conveying means 18 with respect to the image carrier 17. Further, when the winding angle α of the image transfer / conveying means 18 is different from each other with respect to the image carrier 17, different contact pressures f and nip widths L can be realized according to the angles.
[0019]
For example, the tension P is set to a desired value required for stable running of the image transfer conveyance means 18, and the contact pressure f acting on the nip portion is an angle (winding angle) formed by lines provided at the centers of the image carrier 17. A desired value can be obtained by adjusting α. The tension P required for stable running of the flexible endless sleeve-like image transfer / conveying means 18 may be set depending on the material characteristics. However, in the case of a material having high rigidity, the tension P is increased to stabilize the tension state. However, it is desirable to set the tension within a range that does not leave permanent distortion or creep at the portion wound around the roller. On the other hand, a material with low rigidity can easily stabilize the stretched state even if the tension is reduced, and has a large allowable range for permanent distortion and creep at the portion wound around the roller. However, it is desirable to set the tension according to the driving force that is stably driven when the roller is stretched and driven.
[0020]
Suitable materials for the image transfer / conveyance means include PC resin, PET resin, polyimide resin, urethane resin, silicon resin, polyether resin, polyester resin, etc. Of course, conductivity, rigidity, etc. For the purpose of setting the degree, friction coefficient and the like to desired characteristics, a corresponding additive or the like may be added, and the rigidity can be set to a desired rigidity by setting the thickness.
[0021]
In the embodiment, the image transfer / conveying means is formed of urethane resin and polyether resin having relatively small rigidity, permanent distortion, and no creep, and the tension P is 40 N by the urging force F of the roller, and the winding angle α of the image carrier Was set to 4 °, and a stable transfer condition was set as 2.8 N (= 40 N × sin 4 °) for burning the contact pressure f acting on the nip portion. However, in consideration of the above materials, the desired transfer condition can be obtained by setting the combination of the tension P of 10N to 100N and the winding angle α of the image carrier 0.5 ° to 15 ° by the urging force F of the roller. It was confirmed that the setting is possible.
[0022]
The primary transfer member 16 is disposed at a position in contact with the inner side of the image transfer conveying means as a transfer bias applying means for forming an image by sequentially superimposing and transferring the toner images. By the application, it is not necessary to apply a pressing force for forming the transfer nip. Since it is only necessary to be in contact with the image transfer / conveying means as a means capable of ensuring energization, for example, as shown by 16a to 16c in FIG. 3, a conductive roller or a rigid contactor that rotates in contact with the image transfer / conveying means, or A conductive elastic member such as a leaf spring, a conductive brush formed of a group of fibers such as resin, and the like can also be configured. Accordingly, the sliding resistance with the image transfer / conveying means is small, and not only can the lifetime of each other be improved, but also it can be constructed at low cost.
[0023]
As described above, in the image forming apparatus according to the present embodiment, a plurality of image carriers 17 are arranged in parallel, and the endless sleeve-like shape is flexible with a posture having substantially the same winding angle with respect to each image carrier 17. The image transfer / conveying means 18 is placed in contact and is stretched and rotated around at least two rollers 12 and 13. The image transfer / conveying means 18 is tensioned by any of the rollers 12 and 13 to carry the image. The toner image on the body 17 is configured to be transferred in a superimposed manner. In this way, substantially the same nip is easily formed at the contact portion between the image carrier 17 and the image transfer conveying means 18 according to substantially the same winding angle, and the contact pressure at the contact portion is also substantially the same. Composed.
[0024]
On the other hand, in the image transfer member 17 and the image transfer / conveying means 18 driven in contact therewith, it is preferable that the moving peripheral speeds of the contact portions coincide with each other. It is not realistic to set the speed to be completely constant due to variations in the outer diameter of 17 or eccentricity or the eccentricity of the driving means, the diameter of the driving roller 12 of the image transfer / conveying means 18, or variations in the driving means.
[0025]
Therefore, when these variations are taken into consideration, the moving speed of the image transfer / conveying means 18 becomes relatively fast or slow with respect to the moving speed of the image carrier 17, and the transfer conditions are set. This is not preferable. Rather, it is preferable to provide a relative speed difference that is shifted to one of the image carrier 17 and the relative speed. However, if an extreme speed difference is provided, the toner image transported by the image carrier 17 is transferred to the image transfer transport means 18, and the position of the toner image is shifted to cause image disturbance. It is preferable to provide a speed difference.
[0026]
When the speed difference caused by the above contents is set to a relative speed difference shifted to one of the plurality of image carriers 17, the speed difference is calculated in consideration of the ability from mass production and the limit of image disturbance. The speed of the image transfer / conveying means 18 with respect to the moving speed of the image carrier 17 is preferably about ± (direction) 3 ± (variation) 2%.
[0027]
Further, when the moving speed of the image carrier 17 and the moving speed of the image transfer / conveying means 18 are constant, the toner image is transferred by the electric energy action of the transfer bias, but when the above speed difference is provided. Since the mechanical scraping action is added in addition to the electric energy action to improve the transfer efficiency, the process of cleaning the transfer residual toner on the image carrier 17 can be eliminated or simplified.
[0028]
Further, if a relative speed difference is provided between the moving speed of the image carrier 17 and the moving speed of the image transfer / conveyance means 18, the flexible image transfer / conveyance means 18 is connected between the drive rollers 12 or to the image carrier 17. It is not preferable because slack occurs between the contact nips. Therefore, when the speed of the image transfer / conveyance means 18 is shifted in the fast direction with respect to the image carrier 17, the drive roller 12 of the image transfer / conveyance means 18 is disposed on the downstream side, and the image carrier 17 is imaged. When shifting the speed of the transfer / conveyance means 18 in the slow direction, if the drive roller 12 of the image transfer / conveyance means 18 is arranged on the upstream side, the occurrence of the slack can be prevented, and a preferable transfer condition can be set.
[0029]
The cleaning unit 15 is provided on the side of the belt surface 18a facing downward in the transport direction, and a cleaning blade 15a that removes toner remaining on the surface of the image transfer transport unit 18 after the secondary transfer, and a toner transport that transports the collected toner A member 15b is provided. The cleaning blade 15 a is in contact with the image transfer / conveyance means 18 at a portion where the image transfer / conveyance means 18 is wound around the driven roller 13. Further, a primary transfer member 16 is brought into contact with the back surface of the image transfer conveying unit 18 so as to face an image carrier 17 of each of the image forming stations Y, M, C, and K described later. A transfer bias is applied.
[0030]
The exposure means 6 is disposed in a space formed obliquely below the image forming unit 7 disposed in an oblique direction. A paper feeding unit 10 is disposed below the exposure unit 6 and at the bottom of the housing 2. The exposure means 6 is entirely housed in a case, and the case is disposed in a space formed obliquely below the belt surface facing downward in the transport direction. A single scanner means 21 comprising a polygon mirror motor 21a and a polygon mirror (rotating polygon mirror) 21b is horizontally disposed at the bottom of the case, and a plurality of laser light sources 23 modulated by image signals of respective colors. In the optical system B that reflects and scans the image beam by the polygon mirror 21 b and deflects and scans the image carrier, a single f-θ lens 22 and scanning light paths y, m, c, and k of the respective colors are provided on the image carrier 17. A plurality of reflecting mirrors 24 are arranged so as to be folded in parallel with each other.
[0031]
In the exposure means 6 having the above configuration, an image signal corresponding to each color is emitted from the polygon mirror 21b with a laser beam modulated and formed based on a common data clock frequency, and the f-θ lens 22 and the reflection mirror 24 are passed through. After that, the image carrier 17 of each image forming station Y, M, C, K is irradiated to form a latent image. By providing the reflecting mirror 24, the scanning light paths y, m, c, and k can be bent, the height of the case can be lowered, and the optical system can be made compact. In addition, the reflection mirror 24 is arranged so that the scanning optical path lengths to the image carrier 17 of the image forming stations Y, M, C, and K are the same. In this way, the length of the optical path (optical path length) from the polygon mirror 21b of the exposure unit 6 to the image carrier 17 with respect to each image forming unit 7 is set to be substantially the same, thereby scanning in each optical path. The scanning widths of the emitted light beams are also substantially the same, and no special configuration is required for image signal formation. Therefore, the laser light source can be modulated and formed based on a common data clock frequency even though it is modulated corresponding to images of different colors by different image signals, and uses a common reflecting surface. Color misregistration caused by a relative difference in the sub-scanning direction can be prevented, and a simple and inexpensive color image forming apparatus can be configured.
[0032]
Further, in this embodiment, by arranging the scanning optical system below the apparatus, the vibration of the scanning optical system due to the vibration that the drive system of the image forming means gives to the frame that supports the apparatus can be minimized. Degradation of image quality can be prevented. In particular, by arranging the scanner means 21 at the bottom of the case, the vibration that the polygon motor 21a itself gives to the entire case can be minimized, and deterioration of the image quality can be prevented. Further, by making the number of polygon motors 21a, which are vibration sources, one, vibration applied to the entire case can be minimized.
[0033]
In this embodiment, the image stations Y, M, C, and K are arranged in an oblique direction, and the image carrier 17 is arranged in parallel upward along an oblique arch-shaped line. The toner storage container 26 is disposed obliquely downward so as to be in contact with the belt surface 18a facing downward in the conveying direction. Therefore, a special configuration is adopted for the developing means 20. FIG. 4 is an enlarged cross-sectional view of the image forming unit comprising the developing means and the image carrier shown in FIG.
[0034]
As shown in FIG. 4, the developing means 20 includes a toner storage container 26 that stores toner (mesh portion in the figure), a toner storage section 27 formed in the toner storage container 26, and a toner storage section 27. A provided toner agitating member 29, a partition member 30 partitioned on the toner reservoir 27, a toner supply roller 31 disposed above the partition member 30, and a toner supply roller provided on the partition member 30 31 includes a flexible blade 32 that contacts the developing roller 31, a developing roller 33 that contacts the toner supply roller 31 and the image carrier 17, and a regulation blade 34 that contacts the developing roller 33. Has been.
[0035]
The image carrier 17 is rotated in the conveyance direction of the image transfer conveyance means 18, and the developing roller 33 and the supply roller 31 are driven to rotate in the direction opposite to the rotation direction of the image carrier 17 as shown by the arrows in the figure. The stirring member 29 is driven to rotate in the direction opposite to the rotation direction of the supply roller 31. The toner stirred and carried up by the stirring member 29 in the toner reservoir 27 is supplied to the toner supply roller 31 along the upper surface of the partition member 30, and the supplied toner is supplied by being rubbed with the flexible blade 32. The roller 31 is supplied to the surface of the developing roller 33 by the mechanical adhesion force on the surface irregularities and the adhesion force due to the frictional band power. The toner supplied to the developing roller 33 is regulated to a coating layer having a predetermined thickness by the regulating blade 34, and the thinned toner layer is conveyed to the image carrier 17 so that the developing roller 33 and the image carrier 17 are in contact with each other. The latent image portion of the image carrier 17 is developed at the nip portion configured as described above and in the vicinity thereof.
[0036]
In this embodiment, the developing roller 33, the toner supply roller 31, and the contact portion between the developing roller 33 and the regulating blade 34 on the side facing the image carrier 17 are not buried in the toner in the toner storage unit 27. With this configuration, it is possible to prevent fluctuations in the contact pressure of the regulating blade 34 against the developing roller 33 due to a decrease in the stored toner, and surplus toner scraped off from the developing roller 33 by the regulating blade 34 falls into the toner reservoir 27. Therefore, filming of the developing roller 33 can be prevented.
[0037]
Further, the contact portion between the developing roller 33 and the regulating blade 34 is positioned below the contact position between the supply roller 31 and the developing roller 33, and the surplus that has been supplied to the developing roller 33 by the supply roller 31 and has not shifted to the developing roller 33. A path is provided for returning the toner and excess toner regulated and removed from the developing roller 33 by the regulating blade 34 to the toner reservoir 27 below the developing means. The toner returning to the toner reservoir 27 is contained in the toner reservoir 27 by the stirring member 29. The toner is agitated and supplied again to the toner introduction portion near the supply roller 31 by the agitating member 29. Therefore, the excess toner is dropped to the lower part without being jammed on the sliding part of the supply roller 31 and the developing roller 33 or the contact part of the developing roller 33 and the regulating blade 34, and the toner in the toner storing part 27 is stirred. It is possible to prevent the toner in the developing unit from gradually deteriorating and a sudden change in image quality occurring immediately after the replacement of the developing unit.
[0038]
Further, the developing means 20 has a developing roller exposed portion 20 a formed in the vicinity of the developing roller 33, while the corona charging means 19, which is a charging means, has an upward opening 19 a facing the image carrier 17. Is formed. At this time, when the upward opening 19a of the corona charging unit 19 is positioned below the developing roller exposed portion 20a, toner spills from the developing roller exposed portion 20a due to gravity, and the corona charging unit 19 from the upward opening 19a of the corona charging unit 19 A problem arises that the corona charging means 19 is contaminated by entering the inside 19.
[0039]
Therefore, in the present embodiment, the upward opening 19a is offset toward the image transfer transport unit 18 so that the upward opening 19a of the corona charging unit 19 does not overlap the developing roller exposed portion 20a of the developing unit 20. I am doing so. Accordingly, it is possible to solve the problem that the toner spills from the developing roller exposed portion 20a due to gravity and enters the corona charging means 19 from the upward opening 19a, thereby contaminating the corona charging means 19.
[0040]
The paper feed unit 10 includes a paper feed cassette 35 in which the recording media P are stacked and held, and a pickup roller 36 that feeds the recording media from the paper feed cassette 35 one by one. The paper transport unit 11 includes a gate roller pair 37 (one roller is provided on the housing 2 side) that defines the timing of feeding the recording medium P to the secondary transfer unit, a drive roller 12 and an image transfer transport unit. 18 is provided with a secondary transfer roller 39 as a secondary transfer unit that is pressed against 18, a main recording medium conveyance path 38, a fixing unit 40, a discharge roller pair 41, and a duplex printing conveyance path 42.
[0041]
The fixing means 40 includes at least one heating element such as a halogen heater incorporated therein and a rotatable fixing roller pair 40a, and at least one roller of the fixing roller pair 40a is pressed and urged to the other side. The secondary image secondarily transferred to the recording medium P is pressed to the recording medium P, and the secondary image secondarily transferred to the recording medium is at a predetermined temperature at the nip portion formed by the fixing roller pair 40a. It is fixed on the recording medium. In the present embodiment, the fixing unit 40 is disposed in a space formed obliquely above the belt surface 18b facing upward in the transfer belt conveyance direction, in other words, in a space opposite to the image forming station with respect to the transfer belt. Therefore, heat transfer to the exposure unit 6, the image transfer conveyance unit 18, and the image formation unit can be reduced, and the frequency of performing the color misregistration correction operation for each color can be reduced. In particular, the exposure unit 6 is located farthest from the fixing unit 40, can minimize the displacement of the scanning optical system component due to heat, and can prevent color misregistration.
[0042]
In the present embodiment, since the image transfer conveying means 18 is arranged in a direction inclined with respect to the driving roller 12, a large space is generated in the right space in the figure, and the fixing means 40 can be arranged in that space. In addition, downsizing can be realized, and heat generated by the fixing unit 40 is transmitted to the exposure unit 6, the image transfer conveyance unit 18 and the image forming stations Y, M, C, and K located on the left side. Can be prevented. Further, since the exposure unit 6 can be arranged in the space on the lower left side of the image forming unit 7, the vibration of the scanning optical system of the exposure unit 6 due to the vibration applied to the housing 2 by the drive system of the image forming means is minimized. The image quality can be suppressed and deterioration of the image quality can be prevented.
[0043]
In this embodiment, the use of the spherical toner increases the primary transfer efficiency (approximately 100%), and each image carrier 17 is provided with a cleaning means for collecting the primary transfer residual toner. Not done. Thereby, it becomes possible to arrange each image carrier 17 composed of a photosensitive drum having a diameter of 30 mm or less close to each other, and the apparatus can be miniaturized.
[0044]
Further, the corona charging means 19 is adopted as the charging means in accordance with the absence of the cleaning means. When the charging unit is a roller, a small amount of primary transfer residual toner existing on the image carrier 17 accumulates on the roller to cause a charging failure, but the corona charging unit 19 which is a non-contact charging unit. Can prevent toner from adhering and can prevent charging failure.
[0045]
FIG. 5 is a view showing another embodiment of the present invention in which the cooling means is arranged on the scanner means, and FIG. 6 is an illustration of the present invention in which the cooling means is arranged together with the storage space for the control unit and the power supply unit above the scanner means. FIG. 7 is a view showing another embodiment, and FIG. 7 is a view showing another embodiment of the present invention in which the image transfer / conveyance means is a sheet material conveyance medium.
[0046]
When the frame for fixing the exposure apparatus and the plurality of image carriers expands due to temperature fluctuations, and the relative position of the exposure apparatus and the image forming station changes, each laser beam is not parallel, so that depending on the relative angle between the scanning lines There arises a problem that the pitch of the scanning line also fluctuates. The variation in the scanning line pitch results in a variation in the scanning position on the image carrier, and the image position is shifted depending on the color, resulting in a color shift and greatly degrading the image quality.
[0047]
In particular, with the recent increase in speed and resolution of image forming apparatuses, the rotational speed of rotating polygon mirrors tends to increase to reach an area of tens of thousands of RPM, increasing the burden on rotating polygon mirror bearings. Yes. However, when the rotating polygonal mirror is arranged obliquely as in the conventional device, a radial force acts only in the direction of gravity of the bearing portion, and friction increases at that portion. Heat generation in the vicinity of these also increases. Naturally, such heat generation increases the temperature fluctuation of the entire apparatus, and also causes image deterioration due to the color shift.
[0048]
Therefore, in the above-described embodiment, the single scanner unit 21 including the polygon mirror motor 21a and the polygon mirror 21b is disposed horizontally, and the optical system including the f-θ lens 22 and the reflection mirror 24 in the vertical direction together with the laser light source 23. It is arranged at a position apart from. Since the polygon mirror motor 21a and the polygon mirror 21b are horizontally arranged in this way, the force acting in the radial direction of the bearing can be eliminated, so that the number of rotations increases as the image forming apparatus increases in speed and resolution. Even if the load on the bearing increases, the heat generation of the bearing portion can be reduced.
[0049]
Further, as shown in FIG. 5, a cooling means 8 comprising a blower fan is provided above the scanner means 21 by separating from the heat generating parts such as the polygon mirror motor 21a, the bearing part, and the laser light source 23 in the vertical direction. By providing the control unit 5 as a space for disposing the control unit and the power supply unit in the space above the side surface of the exposure unit 6 above the scanner unit 21 as shown in FIG. The internal air can be guided in the direction of the arrow in the figure, and heat from the exposure means 6 and other heat generating portions can be released. By doing so, heat is dissipated by avoiding the arrangement space of the optical system to reduce the thermal influence, the temperature increase of the polygon motor 21a is suppressed, the deterioration of the image quality is prevented, and the life of the polygon motor 21a and the bearing is extended. Therefore, the temperature variation in the apparatus can be reduced, and a high-quality image forming apparatus can be provided.
[0050]
In the above-described embodiment, the intermediate transfer belt is configured to contact the image carrier 17 as the image transfer and conveyance means 18, but the embodiment shown in FIG. A sheet material conveying belt for forming and conveying an image by sequentially superimposing and transferring toner images on the surface of the sheet material is configured to contact the image carrier 17 as an image transfer conveying means 18. In this case, the difference from each of the above embodiments is that the belt conveyance direction of the sheet material conveyance belt which is the image transfer conveyance means 18 is upward in the opposite direction on the lower surface in contact with the image carrier 17.
[0051]
Therefore, in each of the above-described embodiments, the toner image is transferred from the upper image carrier 17 to the intermediate transfer belt as the image transfer conveyance means 18 in a superimposed manner. However, in this embodiment, the lower image carrier is reversed. From 17, the toner image is transferred onto the sheet material that is attracted to the surface of the sheet material conveyance belt as the image transfer conveyance means 18 and conveyed and transferred one after another.
[0052]
In this case, in the above embodiment, the driven roller 13 is also used as a backup roller for the cleaning unit 15. However, the roller 13 is a driving roller, the roller 12 is a driven roller, and the roller 14 is a backup roller for the cleaning unit 15. It is also used as. Also in this embodiment, since the fixing unit 40 is disposed on the upper side of the image forming unit and can dissipate heat upward, the temperature variation in the apparatus can be reduced, and a high-quality image forming apparatus can be provided.
[0053]
The outline of the operation of the entire image forming apparatus as described above is as follows.
(1) When a print command signal (image forming signal) from a host computer (not shown) (personal computer or the like) is input to the control unit of the image forming apparatus 1, the image of each image forming station Y, M, C, K is displayed. The carrier 17, the rollers of the developing unit 20, and the image transfer / conveying unit 18 are driven to rotate.
(2) The outer peripheral surface of the image carrier 17 is uniformly charged by the charging means 19.
(3) The exposure unit 6 selectively exposes the outer peripheral surface of the image carrier 17 uniformly charged in each image forming station Y, M, C, K according to the image information of each color, for each color. An electrostatic latent image is formed.
(4) The toner image is developed by the developing means 20 from the electrostatic latent image formed on each image carrier 17.
(5) The primary transfer member 16 of the image transfer conveying means 18 is applied with a primary transfer voltage having a polarity opposite to the charged polarity of the toner, so that the toner image formed on the image carrier 17 is transferred to the primary transfer portion. As the conveying means 18 moves, the images are sequentially transferred onto the image transfer conveying means 18.
(7) The recording medium P stored in the paper feed cassette 35 is fed to the secondary transfer roller 39 through the registration roller pair 37 in synchronization with the movement of the image transfer conveying means 18 that has primarily transferred the primary image. Sent.
(8) The primary transfer image is a secondary transfer roller 39 that is joined to the recording medium at the secondary transfer portion and is pressed toward the driving roller 12 of the image transfer conveyance unit 18 by a pressing mechanism (not shown). A bias having a polarity opposite to that of the next transfer image is applied, and the primary transfer image formed on the image transfer conveying means 18 is secondarily transferred to the recording medium fed synchronously.
(9) The transfer residual toner in the secondary transfer is conveyed in the direction of the driven roller 13 and scraped off by the cleaning means 15 disposed opposite to the roller 13, and the image transfer conveying means 18 is It is refreshed and the cycle can be repeated again.
(10) The toner image on the recording medium is fixed by passing the recording medium through the fixing unit 40, and then the recording medium is directed toward a predetermined position (or double-sided printing toward the paper discharge tray 2a if not double-sided printing). In this case, the paper is conveyed toward the conveyance path 42 for double-sided printing.
[0054]
Although the embodiment of the present invention has been described above, the present invention is not limited to this, and a conventionally known or well-known technique can be replaced or added as necessary. For example, in the present embodiment, a plurality of image carriers 17 are arranged in parallel along an oblique arch-shaped line and these are in contact with the image transfer / conveying means 18. The line may be a line, or the line may be a straight line. Also in this case, the position of the polygon mirror motor 21 a can be selected from a position that is thermally advantageous by the arrangement of the reflection mirror 24. Alternatively, the backup roller 14 may be omitted, and the image transfer conveying means 18 may be stretched only by the driving roller 12 and the driven roller 13. Further, although the drive roller 12 is disposed below the driven roller 13, the driven roller 13 may be disposed below and the drive roller 12 may be disposed above. In the present invention, the image transfer / conveying means is collectively defined as an intermediate transfer belt and a paper conveying belt.
[0055]
As the latent image forming means, the exposure means for deflecting and scanning the laser beam from each laser light source using one polygon mirror to each image carrier has been described. However, the present invention is not limited to this and the present invention is not limited to this. It is of course applicable to exposure means having a polygon mirror corresponding to the above, means for forming a latent image by selective light irradiation by arranging LED elements or EL elements in a line-like manner, and scanning optical system. Also in the latent image forming means and other latent image forming means in which write electrode portions having the same shape as the latent image shape having no electrode are arranged in a multi-sequential arrangement and are slid on the image carrier so that voltage can be selectively applied to the electrode portions. It goes without saying that the same applies.
[0056]
【The invention's effect】
As is apparent from the above description, according to the present invention, an endless sleeve-like image transfer / conveying means having flexibility, and a latent image forming means in which an image carrier is in contact with the image transfer / conveying means and arranged in parallel. A plurality of image forming means for developing the latent image formed on the image carrier by the developing means, and the contact pressure is applied to the image carrier of each image forming means by the winding angle and tension of the image transfer conveying means. Since the toner images developed by the respective image forming units are sequentially superimposed and transferred onto the image transfer conveyance unit, a unit for applying a predetermined contact pressure between the image carrier and the image transfer conveyance unit is provided. Even if it is not specially provided, the contact pressure can be easily applied with a simple configuration based on the winding angle and tension of the image transfer / conveying means.
[0057]
By substantially equalizing the wrapping angle of the image transfer conveyance means with respect to the image carrier of each image forming means, it is possible to apply substantially the same contact pressure, and the contact pressure can be individually adjusted depending on the wrapping angle. It becomes. The image carrier of each image forming unit and the image transfer / conveying unit have a speed difference, the image transfer / conveying unit is stretched by at least two rollers, and the drive roller corresponds to the speed difference with the image carrier. By selecting on the upstream side or the downstream side, it is possible to achieve a uniform speed due to variations in the outer diameter and eccentricity of the image carrier or the eccentricity of the driving means, the driving roller diameter of the image transfer conveying means, or the driving means and the like. Even if it cannot be set, it is possible to provide a relative speed difference shifted to either one with respect to the image carrier, and to reduce the occurrence of image disturbance due to deviation in the position of the toner image during transfer. In addition to the electrical energy action, a mechanical scraping action is also added to improve the transfer efficiency, and the process of cleaning the transfer residual toner on the image carrier can be eliminated or simplified. Even if there is a relative speed difference between the moving speed of the image carrier and the moving speed of the image transfer / conveyance means, the drive roller of the flexible image transfer / conveyance means or the contact nip with the image carrier It is possible to prevent slack from occurring.
[0058]
The image transfer / conveying means includes a conductive roller that rotates following the movement of the image transfer / conveying means, a transfer bias means including a conductive elastic member, and a conductive brush on the back side of the contact portion with each image carrier. Since it is not necessary to apply a pressing force for forming the transfer nip, the sliding resistance with the image transfer / conveying means is small, the service life of each other can be improved, and the structure can be configured at low cost.
[0059]
Each image forming unit and image transfer conveying unit are arranged at a position where the image carrier is in contact with the lower surface of the image transfer conveying unit, and the image transfer conveying unit conveys and moves the intermediate transfer medium and the surface by adsorbing the sheet material. Since the sheet material is a sheet material conveyance medium that forms and conveys an image by sequentially transferring and transferring toner images on the surface of the sheet material, the toner images are eliminated and the toner images are sequentially superimposed and transferred to form and convey the image. can do.
[0060]
As described above, according to the present invention, it is possible to stabilize the transfer conditions with an inexpensive configuration without providing a special contact pressure application unit, to prevent image quality deterioration, and to provide a high-quality image forming apparatus. Can do.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of an overall configuration showing an embodiment of an image forming apparatus according to the present invention.
FIG. 2 is a diagram for explaining a contact pressure applied by a winding angle and tension of an image transfer / conveying unit with respect to an image carrier.
FIG. 3 is a diagram illustrating a configuration example of a primary transfer bias applying unit.
4 is an enlarged cross-sectional view of an image forming unit including a developing unit and an image carrier shown in FIG.
FIG. 5 is a diagram showing another embodiment of the present invention in which cooling means is arranged on the scanner means.
FIG. 6 is a view showing another embodiment of the present invention in which a cooling unit is disposed together with a storage space for a control unit and a power supply unit above the scanner unit.
FIG. 7 is a diagram showing another embodiment of the present invention in which the image transfer conveyance means is a sheet material conveyance medium.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 2 ... Housing, 3 ... Door body, 6 ... Exposure unit, 7 ... Image forming unit, 9 ... Transfer belt unit, 10 ... Paper feed unit, 11 ... Paper conveyance unit, 15 ... Cleaning means, 17 DESCRIPTION OF SYMBOLS ... Image carrier, 18 ... Image transfer conveyance means, 20 ... Developing means, 21 ... Scanner means, 21b ... Rotary polygon mirror, 40 ... Fixing means

Claims (9)

  A flexible endless sleeve-shaped image transfer and conveyance means, and an image carrier is arranged in parallel along the oblique arched line below the image transfer and conveyance means, and is arranged in parallel on the image carrier. A plurality of image forming means for developing the formed latent image by the developing means, and a common rotating polygon mirror that is disposed in a space formed obliquely below the plurality of image forming means and that emits laser beams from a plurality of laser light sources. A latent image forming unit that forms a latent image on each of the image bearing members of the plurality of image forming units by reflecting on the common reflecting surface of the plurality of image forming units and reflecting back by an optical system using a plurality of reflecting mirrors. Adjusting the wrapping angle of the image transfer / conveying means by the arch-shaped curvature with respect to the image carrier of each image forming means, and adjusting the nip width and the contact pressure by the wrapping angle and tension; An image forming apparatus comprising superimposed sequentially by being configured so as to transfer it to the image transfer conveying means the developed toner image of the image forming means.   2. The image forming apparatus according to claim 1, wherein the wrapping angle of the image transfer / conveying unit with respect to the image carrier of each of the image forming units is substantially the same.   2. The image forming apparatus according to claim 1, wherein the image carrier of each of the image forming units and the image transfer conveying unit have a speed difference.   4. The image transfer / conveying means is stretched by at least two rollers, and the driving roller is selected on the upstream side or the downstream side according to the speed difference from the image carrier. Image forming apparatus.   The transfer bias means comprising a conductive roller that rotates following the movement of the image transfer conveyance means is disposed on the back side of the contact portion with each image carrier. The image forming apparatus according to 1.   2. The image forming apparatus according to claim 1, wherein the image transfer conveying unit includes a transfer bias unit made of a conductive elastic member on a back side of a contact portion with each image carrier.   2. The image forming apparatus according to claim 1, wherein the image transfer conveying unit includes a transfer bias unit made of a conductive brush on a back side of a contact portion with each of the image carriers.   The image forming apparatus according to claim 1, wherein the image transfer conveyance unit is an intermediate transfer medium.   A flexible endless sleeve-shaped image transfer conveyance means that adsorbs and conveys a sheet material, and an image carrier is in contact with the image carrier along an oblique arch-like line below the image transfer conveyance means. A plurality of image forming means for developing the latent images formed in parallel and formed on the image carrier by developing means, and a space formed obliquely below the plurality of image forming means, and arranged from a plurality of laser light sources The laser beam is reflected by a common reflecting surface of a common rotary polygon mirror and reflected by an optical system using a plurality of reflecting mirrors to form a latent image on each of the image carriers of the plurality of image forming means. A latent image forming unit that adjusts a winding angle of the image transfer conveying unit based on a curvature of the arch with respect to an image carrier of each of the image forming units and a nip by the winding angle and tension. And the contact pressure is adjusted so that the developed toner image of each of the image forming units is transferred to the surface of the sheet material that is attracted to and conveyed by the image transfer conveyance unit in order and transferred. Forming equipment.

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