JP2004177508A - Image carrier driving device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a good image by carrying out phase matching so that periodic components are not caused as color deviation. <P>SOLUTION: The total of the time from the engaging point of a driven gear 110C positioned on the downstream side in the moving direction of an intermediate transfer belt 200 and an idler gear 120B engaged with it until the engaging point of the idler gear 120B with a driven gear 110M on the upstream side by a rotational movement on a pitch circle of the idler gear 120B, the time until a photoreceptor drum 110M which is on the same axis with the driven gear 110M is brought into contact with the intermediate transfer belt 200 by a rotational movement on the pitch circle of the driven gear 110M, and the time from the contact point of the photoreceptor drum 100M on the upper stream side with the intermediate transfer belt 200 to the contact point of a photoreceptor drum 100C on the downstream side with the intermediate transfer belt 200 is the same as the total of the time which is the integral multiple of 1 rotational period of the idler gear 120B and the time from the engaging point of the driven gear 110C and the idler gear 120B to the contact point with the photoreceptor drum 110C. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a so-called tandem-type image carrier driving device for forming a multi-color image by sequentially transferring toner images formed for each color by arranging a plurality of image carrier drums, and the image carrier. The present invention relates to an image forming apparatus provided with a body driving device.
[0002]
[Prior art]
2. Description of the Related Art Many image forming apparatuses, such as electrophotographic copying machines and printers, are color-compatible in response to market demands. In such a color image forming apparatus, a plurality of developing devices are arranged around a single photoreceptor so as to correspond to a plurality of colors, and an image is written for each color and developed by the developing device. A so-called one-drum type in which toner is formed on a photoconductor by forming a composite toner image by transferring the composite toner image to an image forming medium, and a plurality of photoconductors arranged side by side. A so-called tandem type in which a single-color toner image is formed on each photoreceptor, the single-color toner images are sequentially transferred, and a composite color image is finally recorded on an image forming medium, provided with a developing device individually. There are things.
[0003]
Comparing the one-drum type image forming apparatus and the tandem type image forming apparatus, the former has a single photosensitive member, and therefore has the advantage that it can be relatively small in size and can be provided at low cost. Since a full-color image is formed by repeating image formation a plurality of times (four times in the case of full color) using a body, it is difficult to speed up image formation. On the other hand, the latter requires a photoreceptor, a writing device, a developing device, and a transfer device for each color, so the device must be increased in size, and although there is a disadvantage of increasing the cost, the image forming operation is not performed. Since it is performed in parallel, there is an advantage that the speed of image formation can be easily increased. Recently, tandem-type image forming apparatuses have been receiving attention because full-color image formation is required to be as fast as monochrome image formation.
[0004]
The tandem type image forming apparatus includes a direct transfer type in which images on a plurality of photosensitive members are sequentially transferred onto a transfer sheet conveyed by a transfer belt by a transfer device, and a primary transfer method in which images on each photosensitive member are transferred. There is an indirect transfer type in which an image on the intermediate transfer body is once transferred to an intermediate transfer body by an apparatus and then collectively transferred to a transfer sheet by a secondary transfer apparatus. Here, an example of a conventional tandem type image forming apparatus is shown in FIGS. FIG. 5 is a diagram showing a schematic configuration of a conventional direct transfer type tandem type image forming apparatus, and FIG. 6 is a diagram showing a schematic configuration of a conventional indirect transfer type tandem type image forming apparatus. Note that substantially the same components are denoted by the same reference numerals, and redundant description will be omitted.
[0005]
As shown in FIG. 5, the tandem image forming apparatus of the direct transfer type uses an image carrier on which toner images of black (K), magenta (M), cyan (C), and yellow (Y) are formed. Of photosensitive drums 100K, 100M, 100C, and 100Y are arranged side by side on a sheet transport belt 250 that transports a sheet 400 as a transfer medium. The rotation axes of the photosensitive drums 100K, 100M, 100C, and 100Y are provided in parallel with the rotation axes of the driving roller 251 and the driven roller 252 that drive the sheet conveyance belt 250, and are orthogonal to the conveyance direction of the sheet conveyance belt 250. Are arranged. Each of the photoconductor drums 100K, 100M, 100C, and 100Y is driven to rotate by a motor and gears (not shown). The sheet conveying belt 250 is stretched between the driving roller 251 driven by a motor (not shown) and the driven roller 252.
[0006]
The sheet 400 is fed onto the sheet conveying belt 250 from the sheet feeding device 700, is electrostatically attracted to the sheet conveying belt 250, and moves integrally with the sheet conveying belt 250. When the sheet 400 reaches the nip position between the photosensitive drums 100K, 100M, 100C, and 100Y of black (K), magenta (M), cyan (C), and yellow (Y) and the sheet conveying belt 250, each color The images of the respective colors are sequentially transferred to each other, and when the transfer of the yellow image is completed, a full-color image is formed. Next, the sheet 400 on which the toners of the four colors are superimposed to form the full-color toner image is fixed by the fixing device 800 and is discharged.
[0007]
On the other hand, an indirect transfer type tandem type image forming apparatus is an intermediate transfer material, as shown in FIG. 6, by a primary transfer device (not shown) for images on the respective photosensitive drums 100Y, 100C, 100M, 100K. After the images are sequentially transferred to the intermediate transfer belt 200, the image on the intermediate transfer belt 200 is transferred by a secondary transfer device 300 including rollers along a transport path indicated by a dotted line by a paper feeding device 300 by a paper feeding device 300. Batch transfer. The intermediate transfer belt 200 is stretched between a driving roller 201 and a driven roller 202, and the intermediate transfer belt 200 is pressed by a pressure roller 203 in the direction of the secondary transfer device 300. In the illustrated example, the secondary transfer device 300 has a roller shape, but an endless transfer belt shape is also available.
[0008]
Comparing the former direct transfer type and the latter indirect transfer type, the former shows that the paper feeding device 700 is located upstream on the photosensitive drums 100K, 100M, 100C and 100Y, and the downstream is located downstream. The fixing device 800 must be arranged, and there is a disadvantage that the size is increased in the sheet conveyance direction. In the latter case, on the other hand, the secondary transfer position can be set relatively freely. Further, the sheet feeding device 700 and the fixing device 800 can be disposed so as to overlap with the portion where the photosensitive drums 100K, 100M, 100C, and 100Y are arranged, which is advantageous in that the size can be reduced.
[0009]
Further, in the former, the fixing device 800 is arranged close to the photosensitive drum 100Y in order not to increase the size in the sheet conveying direction. For this reason, the fixing device 800 cannot be arranged with a sufficient margin to allow the sheet 400 to bend, and the impact when the leading end of the sheet 400 enters the fixing device 800 (particularly remarkable in a thick sheet) and the fixing There is a disadvantage that the fixing device 800 tends to affect the image formation on the upstream side due to the speed difference between the sheet conveyance speed when passing through the apparatus 800 and the sheet conveyance speed by the transfer conveyance belt. On the other hand, in the latter, since the fixing device 800 can be arranged with a sufficient margin to allow the sheet 400 to bend, the fixing device 800 can hardly affect the image formation. From the above, recently, indirect transfer type tandem image forming apparatuses have attracted attention.
[0010]
As described above, attention has been paid to the tandem-type image forming apparatus, and the quality requirements for the image have been increased, and image deterioration such as color shift and jitter has been concerned. For this purpose, it is necessary to prevent a frequency fluctuation component of a drive system of a plurality of photosensitive drums, which is one of the causes of image deterioration, from occurring on an image. It is considered that image deterioration due to such a frequency fluctuation component is inevitable. To reduce this, for example, Japanese Patent Application Laid-Open No. 6-161205 discloses an intermediate transfer belt or a transfer belt from a writing position of each photosensitive drum. There is disclosed an invention in which color shift is reduced by focusing on a phase of a distance to a transfer position on a sheet on a sheet conveying belt.
[0011]
In the known example, one photosensitive motor of each of the four image forming units and a belt drive roller for driving a recording material carrying belt are respectively driven by one drive motor, and the drive unevenness period of the drive motor is T1, The time required for each photosensitive drum to move from the image writing position to the image transfer position is T2, the movement unevenness period of the recording material when the recording material is conveyed by the recording material carrying belt 40 is T3, and the recording materials are adjacent to each other. T1 to T4 are set so that T2 / T1, T3 / T1, and T4 / T3 are substantially integers, respectively, when the time required to advance between the image transfer positions of the photosensitive drums is T4. is there. As described above, in this known example, the relationship of the cycle and time by the driving of each unit is set.
[0012]
[Patent Document 1]
JP-A-6-161205
[0013]
[Problems to be solved by the invention]
As is clear from the above-mentioned known examples, various periodic components accompanying the drive transmission can be cited as a cause of the color shift which is one of the causes of the image deterioration of the tandem type color image forming apparatus. Due to the occurrence of the periodic variation, a position shift, which is an integrated value of the variation, occurs at each station for transferring an image. However, the fluctuation of the periodicity is inherent to the system, and it is impossible to completely eliminate the fluctuation even if T1 to T4 are set as in the above-mentioned known example.
[0014]
The present invention has been made in view of such circumstances of the related art, and has as its object to provide an image carrier driving device and a periodic component capable of performing phase adjustment so that a periodic component does not occur as a color shift on an image. An object of the present invention is to provide an image forming apparatus capable of performing phase adjustment such that color shift does not occur on an image, thereby reducing color shift and obtaining a good image.
[0015]
[Means for Solving the Problems]
In order to achieve the above object, a first means includes a plurality of image carriers having a rotation axis parallel to a direction orthogonal to a transfer medium moving direction and arranged in parallel along the transfer medium moving direction; A driven gear provided coaxially and integrally rotatable with respect to the rotation axis of the carrier, and an idler gear provided between the driven gears,
An image carrier driving device that drives one gear train connected by the idler gear by one motor, wherein the driven gear positioned downstream in the moving direction of the transfer medium and the idler gear meshing with the driven gear From the point of engagement, the idler gear rotates on the pitch circle of the idler gear, and the idler gear rotates on the pitch circle of the upstream driven gear for a first time until the idler gear meshes with the driven gear on the upstream side. A second time until the image carrier, which is coaxial with the driven gear, contacts the transfer medium, and the contact point between the upstream image carrier and the transfer medium is the downstream image carrier. A fourth time that is an integral multiple of one rotation cycle of the idler gear; and a third time that is an integral multiple of one rotation cycle of the idler gear, and a third time that is downstream of the driven gear and the idler gear. The driven gear and the idler gear are adjusted so that the sum of the fifth time when the image carrier on the downstream side where the joint point is coaxial with the driven gear reaches the point where the image carrier contacts the transfer medium is equal. The relationship is set.
[0016]
According to a second aspect, in the first aspect, the driven gear and the idler gear are such that a gear having a large number of teeth has an integral multiple of the number of teeth of a gear having a small number of teeth.
[0017]
The third means is the first or second means, wherein the driven gear and the thickness of the idler gear are adjusted so that the driven gear fits within the thickness shape of the idler gear at a meshing portion with the idler gear. The meshing position in the direction is set.
[0018]
A fourth means is the first to third means, wherein the driven gear is formed of a resin having slidability, and a plurality of driven gears used in one gear train are of the same type and the same cabinet. It is characterized by being molded.
[0019]
According to a fifth aspect, in the first to third aspects, the drive transmission of the gear train from the output gear of the motor is performed from a gear having a large number of teeth among the driven gear and the idler gear.
[0020]
A sixth means is the fifth means, wherein the number of teeth of the idler gear is an integral multiple of the number of teeth of the output gear of the motor.
[0021]
The seventh means is the first to fifth means, wherein the first gear means is provided on one driven gear of the gear train, and detects the rotational position of the driven gear; An image carrier driven by a gear train including a driven gear driven by one motor, separately provided for the image carrier driven by the motor, and a driven member for driving the separately provided image carrier A second detecting means provided on one of the gears for detecting the rotational position of the driven gear.
[0022]
Eighth means is the seventh means, further comprising a control device for controlling the phases of both gear trains based on the detection outputs of the first and second detection means.
[0023]
A ninth means is a transfer medium transporting means for transporting a transfer medium in place of the transfer medium in the first to eighth means.
[0024]
A tenth means is an image carrier driving device according to the first to ninth means, an image forming means for forming a toner image on an image carrier driven by the image carrier driving device, and The image forming apparatus comprises a transfer unit for transferring an image.
[0025]
According to the first means, the time passed through the image carrier driven gear and the image carrier on the upstream side in the moving direction of the transfer of the transfer medium from the meshing position of the driven gear and the idler gear coaxial with the carrier to the transfer position. Since the sum of the integral multiple time of one rotation cycle of the idler gear and the time of rotational movement on the driven gear is equalized, it is possible to match the cycle of expansion and contraction of the pixel of the transfer image by one rotation cycle of the idler gear. No color shift appears on the image.
[0026]
According to the second means, one rotation cycle of the driven gear is an integral multiple of one rotation cycle of the idler gear, and the phases of the periodic fluctuation components match on the image. Can be reduced.
[0027]
According to the third means, since the driven gear falls within the thickness shape of the idler gear at the meshing portion with the idler gear, adverse effects due to disturbance of the tooth surface at the end of the idler gear may affect the driven gear. As a result, the rotation unevenness of the image carrier can be reduced.
[0028]
According to the fourth means, it is possible to suppress the variation in the shape of the driven gears in the gear train, thereby reducing the variation in the rotational unevenness phase characteristic and the color shift due to the phase shift.
[0029]
According to the fifth means, it is possible to increase the speed reduction ratio, to obtain a high torque even with a motor having a small output, and to realize a reduction in size and energy saving of the motor.
[0030]
According to the sixth means, one rotation cycle of the idler gear can be made an integral multiple of one rotation cycle of the output gear of the motor, and the speed fluctuation unevenness of one rotation of the output gear of the motor is synchronized with the one rotation fluctuation unevenness of the idler gear. As a result, it is possible to prevent an increase in image degradation elements on the image, and to reduce color misregistration.
[0031]
According to the seventh means, the home position can be set by detecting the rotational position of the driven gear by the first and second detecting means, and phase control can be performed on the sheet.
[0032]
According to the eighth means, it is possible to always adjust the rotation start position based on the rotation position detected by the first and second detection means, and to keep the rotation unevenness phase characteristic constant between the separated gear trains. Thus, color shift can be reduced.
[0033]
According to the ninth means, the same effect can be obtained even if the transfer medium functioning as the intermediate transfer medium is replaced with, for example, a transport belt that transports a recording sheet. That is, the first to ninth means can be applied to a tandem type image carrier driving device of an indirect transfer type and a tandem type image carrier driving device of a direct transfer type.
[0034]
According to the tenth means, it is possible to provide a tandem type image forming apparatus of an indirect transfer type and a tandem type image forming apparatus of a direct transfer type capable of reducing color shift.
[0035]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same reference numerals are given to the same portions in the above-described conventional example and the embodiments, and the overlapping description will be appropriately omitted.
[0036]
FIG. 1 is a diagram illustrating a schematic configuration of a transfer unit of an indirect transfer type tandem image forming apparatus according to a first embodiment. FIG. 2A is a plan view illustrating a relationship between a driven gear and an idler gear. ) Is a side view thereof, and FIG. 3 is a diagram showing a positional relationship between a driven gear and an idler gear.
[0037]
1, in the tandem-type image forming apparatus according to the present embodiment, four photosensitive drums 100Y, 100C, 100M, and 100K are arranged in the same manner as in the conventional example shown in FIG. An image forming station constituting an electrophotographic process of a unit, a developing unit, a transfer unit, a cleaning unit, and a charge removing unit is provided. In this order, yellow (Y), cyan (C), magenta (M), and black (K) are provided. An imaging station is located. An intermediate transfer belt 200 is arranged between the photosensitive drums 100Y, 100C, 100M, and 100K of the respective colors and transfer units of the respective colors (not shown). The intermediate transfer belt 200 is wound around a driving pulley 201 and a driven pulley 202 by a pressure pulley 203 so as to obtain a predetermined tension. A secondary transfer roller 300 as a secondary transfer device is disposed on the pressure pulley 203 so as to sandwich the intermediate transfer roller 200 between the nips. Then, a sheet 400 as a recording medium is fed between the secondary transfer roller 300 and the intermediate transfer belt 200, a full-color toner image on the sheet is transferred, fixed by the fixing device 800, and discharged out of the device. Paper.
[0038]
The intermediate transfer belt 200 is conveyed in the direction of arrow 200a, and the toner is transferred in the order of yellow (Y), cyan (C), magenta (M), and black (K) photosensitive drums 100Y, 100C, 100M, and 100K. The image is transferred, and the images are superimposed. Driven gears 110Y, 110C, 110M, 110K are coaxially mounted on the photosensitive drums 100Y, 100C, 100M, 100K, respectively. The output gears 140A and 140B of the drive motors 130A and 130B are meshed with the driven gears 110Y and 110K at the forefront and last stages, respectively, as viewed from the image forming direction, and are driven to rotate by the drive motors 130A and 130B. . The driven gears 110Y, 110C, and 110M mesh with the driven gears 110Y and 110C adjacent to the idler gear 120A and the driven gears 110C and 110M adjacent to the idler gear 120B, respectively, to form one gear train. 130C is a motor for driving the driving roller 201 of the intermediate transfer belt 200, and 130D is a motor for driving the secondary transfer device 300. The driven gear 110K is independently driven by the drive motor 130B without the intermediary of the idler gear. However, when a black-and-white image is obtained, only the black photosensitive drum 100K needs to be rotationally driven. is there.
[0039]
FIG. 2 is a diagram showing the relationship between driven gears 110C and 110M and idler gear 120A. Formed on the two photosensitive drums 100C and 100M from a point A which is a meshing point between the driven gear 110M and the idler gear 120B, which is coaxial with the photosensitive drum 100M on the downstream side with respect to the moving direction of the intermediate transfer belt 200. The path from the point A to the point D ′ where the image to be superimposed on the intermediate transfer belt 200 is rotated from the point A on the pitch circle of the idler gear 120B in the direction of arrow D0 at an angular velocity ω0, and is driven via the point B. The path involved in the formation of an image of the photoconductor 100C on the upstream side that rotates on the pitch circle of the gear 110C at the angular velocity ω1 in the direction of arrow D1 at point C and moves on the intermediate transfer belt 200 from point C ′ to point D ′. And a path related to the formation of an image on the downstream photosensitive drum 100M that rotates at the angular velocity ω2 in the direction of arrow D2 from point A to point D on the pitch circle of the driven gear 110C. There is a path.
[0040]
Here, looking at the influence on the transfer image due to the rotation unevenness of one rotation cycle of the idler gear 120B, it is assumed that the peripheral speed on the pitch circle of the idler gear 120B at the point A at the time T0 becomes the maximum, and from the point A to the point B Is θ0, the time T1 to reach point B is
T1 = θ0 / ω0
When the time T1 is reached, the peripheral speed transmitted to the driven gear 110C by the idler gear 120B becomes maximum.
[0041]
Also, the maximum value of the peripheral speed on the pitch circle at point C, which is the contact point of the driven gear 110C with the intermediate transfer belt 200, caused by the rotation unevenness of the idler gear 120 in one rotation cycle is as follows:
T2 = θ1 / ω1 + T1
Is the largest. This time T2 is the time when the maximum value of the pixel expansion caused by the idler gear 120B at the point C ′ at which the image is transferred from the photosensitive drum 100C to the intermediate transfer belt 200 is obtained. The time T3 at which the image transferred from the photoconductor drum 100C to the intermediate transfer belt 200 at the time T2 reaches the point D 'where the image transferred from the photoconductor drum 100M is superimposed is C'. When the distance from the point to the point D ′ is L and the moving speed of the intermediate transfer belt is V,
T3 = L / V + T2
It becomes.
[0042]
Similarly, when the images are superimposed at the point D ', the peripheral speed at the point D' of the contact point with the intermediate transfer belt 200 of the photosensitive drum 100M caused by the rotation unevenness of the idler gear 120B in one rotation cycle at the point D '. If the maximum time is T4, the period of one rotation of the idler gear 120B is 2π / ω0, and if the rotation angle (movement angle) from the point A to the point D is θ2,
T4 = 2π / ω0 × N + θ2 / ω2 (N is a natural number)
At time T4, the peripheral speed unevenness of the photosensitive drum 100M caused by the rotation unevenness of one rotation of the idler gear 120B becomes the maximum value at the transfer point D ', and the elongation of the pixel caused by the relative speed difference with the intermediate transfer belt 200 Is the maximum value.
[0043]
Therefore
T3 = T4
With such a configuration, it is possible to match the expansion of the transferred image due to one rotation cycle unevenness of the idler gear 110B, and it is possible to reduce the color shift caused by the expansion and contraction of the pixel. In the above description, the driven gears 110C and 110M and the idler gear 120B therebetween have been described, but the same applies to the driven gears 110Y and 110C and the idler gear 120A therebetween.
[0044]
If the number of teeth of the driven gears 110Y, 110C, 110M, and 110K is an integral multiple of the number of teeth of the idler gears 120A and 120B, one rotation cycle of the driven gears 110Y, 110C, 110M, and 110K is one of the idler gears 120A and 120B. An image having a plurality of frequency components can be obtained by synchronizing the speed fluctuation unevenness of one rotation of the idler gears 120A and 120B with the one rotation fluctuation unevenness of the driven gears 110Y, 110C and 110M. The above fluctuation can be prevented from occurring, and the color shift caused by the fluctuation can be reduced.
[0045]
In FIG. 2B, Rg is the radius of the idler gear 120B, Rd is the radius of the driven gear 110M, RD is the radius of the photosensitive drum 100M, and the path length is calculated by multiplying the rotation angles θ0 and θ2, respectively. Easy to do.
[0046]
Further, as shown in FIG. 2 (a), at the meshing portion between the driven gears 110Y, 110C, 110M and the idler gears 120A, 120B, the driven gears 110Y, 110C, 110M fall within the thickness of the idler gears 120A, 120B. Set the gear thickness and the axial meshing position. As a result, it is possible to prevent the rotation of the driven gears 110Y, 110C, and 110M from being uneven due to burrs at the end portions of the idler gears 120A and 120B due to burrs at the time of gear formation and torn tooth surfaces due to chipped end surfaces. Rotational unevenness of each of the photosensitive drums 100Y, 100C, 100M can be reduced.
[0047]
Further, the driven gears 110Y, 110C, 110M, and 110K are formed of a molded product made of a highly slidable resin such as a polyamide resin (PA), a polyacetal resin (POM), or an oil-impregnated resin material. 110C and 110M are molded with the same mold and the same cabinet. Thus, it is possible to suppress the variation in shape among the driven gears 110Y, 110C, and 110M in the gear train, reduce the variation in the rotation unevenness phase characteristic, and reduce the color shift due to the phase shift.
[0048]
The motor 130A that drives the photoconductor drums 100Y, 100C, and 100M has a greater number of teeth than the idler gears 120A and 120B in the gear train formed by the driven gears 110Y, 110C and 110M and the idler gears 120A and 120B. It is connected to the drive gear 110Y. As a result, the reduction ratio becomes larger than when the driving force is transmitted using the idler gear 120 as a driving gear, so that a high-speed motor can be used, and the motor can be used efficiently.
[0049]
As shown in FIG. 3, the driven gear 110Y for driving the photoconductor drum 100Y and the driven gear 110K for driving the photoconductor drum 110K are provided with position detection patterns (not shown), respectively. The position detection patterns are read by 111A and 111B, respectively. The read result is input to a control device (not shown), and the control device detects the rotational positions of the driven gears 110Y and 110K. Then, based on this detection result, the control device performs an initialization operation so that the rotation start positions at the time of image formation of the driven gears 110Y and 110K are always at the same position, and sets the home position. This makes it possible to always make the phase between the gear train including the driven gears 110Y, 110C, and 110M and the driven gear 110K the same, and to prevent the color shift on the image from fluctuating for each image formation. Can be prevented. The control device includes a CPU serving as a main control unit, a ROM storing a control program, and a RAM used by the CPU as a work area and storing information necessary for control. Runs.
[0050]
Further, if the number of teeth of the idler gears 120A and 120B is set to an integral multiple of the number of teeth of the output gear 140A of the motor 130A, one rotation cycle of the idler gears 120A and 120B is set to an integral multiple of one rotation cycle of the output gear 140A of the motor 130A. This makes it possible to synchronize the speed fluctuation unevenness of one rotation of the output gear 140A of the motor 130A with the one rotation fluctuation unevenness of the idler gears 120A and 120B. As a result, it is possible to prevent a change in an image having a plurality of frequency components from occurring, and it is possible to reduce a color shift caused by a change in an image having a plurality of frequency components.
[0051]
FIG. 4 is a diagram showing a schematic configuration of a direct transfer type tandem image forming apparatus according to a second embodiment of the present invention. In the case of the tandem-type image forming apparatus of the direct transfer type as well, similarly to the conventional example shown in FIG. 5, yellow (Y), yellow (Y), The photosensitive drums 100Y, 100C, 100M, and 100K that form toner images of cyan (C), magenta (M), and black (K) are placed on the sheet transport belt 250 in a direction perpendicular to the transport direction of the sheet transport belt. The photoconductor drums 100Y, 100C, 100M, and 100K are arranged so that their rotation axes are parallel. The sheet 400 is set so as to pass between the photosensitive drums 100Y, 100C, 100M, and 100K and the sheet conveying belt 250. In addition, a drive mechanism including driven gears 110Y, 110C, 110M, 110K, idler gears 120A, 120B, drive motors 130A, 130B, and output gears 140A, 140B is configured the same as in the first embodiment.
[0052]
With this configuration, even in the tandem-type image forming apparatus of the direct transfer type, color misregistration on an image can be prevented in the same manner as in the tandem-type image forming apparatus of the indirect transfer type.
[0053]
【The invention's effect】
As described above, according to the present invention, an image carrier driving device capable of performing phase adjustment so that a periodic component does not occur as a color shift on an image, and an image carrier driving device that does not generate a periodic component as a color shift on an image It is possible to provide an image forming apparatus capable of performing phase adjustment, thereby reducing color misregistration and obtaining a good image.
[Brief description of the drawings]
FIG. 1 is a diagram for explaining a schematic configuration of a transfer unit according to a first embodiment of the present invention.
FIGS. 2A and 2B are diagrams for explaining a relationship between a driven gear and an idler gear according to the first embodiment, wherein FIG. 2A is a plan view and FIG. 2B is a side view.
FIG. 3 is a diagram for explaining a positional relationship between a driven gear and an idler gear according to the first embodiment.
FIG. 4 is a diagram illustrating a schematic configuration of a transfer unit according to a second embodiment of the present invention.
FIG. 5 is a view for explaining a schematic configuration of a conventional direct transfer type tandem type image forming apparatus.
FIG. 6 is a diagram for explaining a schematic configuration of a conventional indirect transfer type tandem image forming apparatus.
[Explanation of symbols]
100Y yellow photoconductor drum
100C Photoconductor drum for cyan
100M photoconductor drum for magenta
100K photoreceptor drum for black
110Y, 110C, 110M, 110K Driven gear
111A, 111B sensor
120A, 120B Idler gear
130A, 130B drive motor
140A, 140B output gear
200 Intermediate transfer belt
250 sheet transport belt

Claims (10)

A plurality of image carriers having a rotation axis parallel to a direction orthogonal to the transfer medium moving direction, and arranged in parallel along the transfer medium moving direction;
A driven gear provided coaxially and integrally rotatable with respect to the rotation axis of each image carrier,
An idler gear provided between the driven gears,
An image carrier driving device that drives one gear train connected by the idler gear by one motor,
The idler gear meshes with the driven gear on the upstream side by rotating on the pitch circle of the idler gear from the meshing point of the driven gear located on the downstream side in the movement direction of the transfer medium and the idler gear meshing with the driven gear. A first time until it fits, a second time until the image carrier coaxial with the driven gear by rotating on the pitch circle of the driven gear on the upstream side comes into contact with the transfer medium, And the sum of a third time when the contact point between the image carrier on the upstream side and the transfer medium reaches the contact point between the image carrier on the downstream side and the transfer medium,
A fourth time that is an integral multiple of one rotation cycle of the idler gear, and the downstream image carrier in which the mesh point between the downstream driven gear and the idler gear is coaxial with the driven gear. Wherein the relationship between the driven gear and the idler gear is set such that the sum of the first time and the fifth time until the point of contact with the transfer medium is equal. 2. The image carrier driving device according to claim 1, wherein the driven gear and the idler gear are such that a gear having a large number of teeth has an integral multiple of the number of teeth of a gear having a small number of teeth. The meshing position of the driven gear and the idler gear in the axial direction is set so that the driven gear fits within the thickness of the idler gear at a meshing portion with the idler gear. Item 3. The image carrying driving device according to Item 1 or 2. 4. The driven gear according to claim 1, wherein said driven gear is formed of a resin having slidability, and a plurality of driven gears used in one gear train are formed of the same mold and the same cabinet. The image carrier driving device according to claim 1. The image carrier according to any one of claims 1 to 3, wherein the drive transmission of the gear train from the output gear of the motor is performed from a gear having a large number of teeth among the driven gear and the idler gear. Drive. 6. The image carrier driving device according to claim 5, wherein the number of teeth of the idler gear is an integral multiple of the number of teeth of the output gear of the motor. First detection means provided on one driven gear of the gear train for detecting a rotational position of the driven gear;
An image carrier that is separately provided for the image carrier driven by the gear train and is driven by a gear train including a driven gear driven by one motor;
A second detection means provided on one of the driven gears for driving the separately provided image carrier, for detecting a rotational position of the driven gear;
The image carrier driving device according to any one of claims 1 to 5, further comprising: 8. The image carrier driving device according to claim 7, further comprising a control device for controlling the phases of both gear trains based on the detection outputs of said first and second detection means. 9. The image carrier driving device according to claim 1, wherein a transfer medium transport unit that transports the transfer medium instead of the transfer medium is used. An image carrier driving device according to any one of claims 1 to 9,
Image forming means for forming a toner image on an image carrier driven by the image carrier driving device;
Transfer means for transferring an image to the transfer medium,
An image forming apparatus comprising:

Images