JP2677566B2 - Color image forming equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a color image forming apparatus using a plurality of latent image carriers. [Prior Art] In a color image forming apparatus of a type in which a toner image formed on a plurality of photoconductors is sequentially transferred onto one sheet of transfer paper to obtain a color image, a support shaft of each photoconductor is provided. For example, a driven transmission means such as a gear is provided, and each photoconductor is rotated by driving each of these gears by the drive transmission means. In this case, due to the manufacturing relationship of these gears, eccentricity occurs in the rotation of the gears,
Due to this eccentricity, speed fluctuations occur in each photoconductor, and as a result, color misregistration occurs in each color image on the transfer paper. FIG. 3a and FIG. 3b are diagrams for explaining the speed variation of the photoconductor drum (hereinafter simply referred to as a photoconductor) which is the latent image carrier due to the eccentricity. When the angle of one tooth of the gear viewed from the correct center of the gear is 2θ ₀ , the sensitivity for one tooth when the center of rotation is eccentric by e ₁ is 2θ ₁ , and the amount by which the angular velocity fluctuates is a ( %) Becomes Here, as can be seen from Figures 3a and 3b, That is, when the rotation angle of the photosensitive member support shaft with respect to one tooth of the gear is θ, the rotation angle θ is Will vary in the range of. In order to solve such a defect, for example, Japanese Patent Laid-Open No. 61-
As described in No. 156158, a means has been proposed for mounting the gears on the support shafts of the respective photoconductors by adjusting the angles thereof so that the phases of the speed fluctuations of the respective photoconductors match each other. There is. However, even if the phases of the speed fluctuations are matched in this way, as shown in FIG. 8, when the amplitudes of the speed fluctuations of the photoconductors are different, color misregistration occurs. That is, the upper part of FIG. 8 shows the rotational speed of the photoconductor, which is equal to the rotational speed of the driven gear fixed to the support shaft on which the photoconductor is attached, and the lower part shows the ideal speed on the photoconductor. The position, that is, the amount of deviation from the position recorded on the transfer paper when the driven gear is installed without eccentricity, represents the amount of deviation, and the solid line and the dotted line respectively represent the first photoconductor and the first photoconductor belonging to different recording devices. This is for the second photoconductor. Both the photoconductors rotate in the cycle T and the average rotation speed V ₀ is equal, but the instantaneous rotation speed is not uniform due to the eccentricity of the driven gear as described above. As shown, the first photosensitive member has an average rotation speed V ₀ of ± ΔV ₁ , and the second photosensitive member has an average rotation speed V ₀ .
The rotation speed fluctuates in the range of ± ΔV ₂ with respect to V ₀ according to the rotation angle of the driven gear. The rotation speed of these photoconductors is faster than the rotation speed V ₀ averaged in the first half rotation as shown in the figure, that is, the exposure point on the photoconductor is faster than the transfer position at the average rotation speed. Since the average rotation speed is maintained, the image is transferred in a compressed state because it is transferred in front of the ideal position on the transfer paper that is transferred when the photoconductor rotates while maintaining the average rotation speed. . On the contrary, if the rotation speed is slow, the average rotation speed is maintained and the image is transferred behind the ideal position transferred when the photoconductor is rotating, and the image is obtained in a stretched state. . By the way, even if the phases of the fluctuations in the rotational speeds of the first photoconductor and the second photoconductor match as shown in the figure,
Since the fluctuation range of the rotation speed is different, the deviation amount from the ideal position when the second photosensitive member makes a half rotation is smaller than the deviation amount from the ideal position when the first photosensitive member makes a half rotation, and both If the ideal rotation speed equal to the above average rotation speed is maintained, the points (pixels) to be recorded at the same location on the transfer paper are recorded with different deviation amounts for each recording device. Therefore, the difference in the amount of deviation between the images recorded by the first photoconductor and the second photoconductor appears as a color misregistration on the transfer paper. The amount of this displacement becomes maximum at the time T / 2 in the lower part of FIG. 8, and the maximum amount of displacement from one ideal position of the first photosensitive member is ΔX ₁ , Assuming that the maximum amount of deviation from the ideal position is ΔX ₂ , the phases of these deviations match each other, and the maximum color deviation is | ΔX ₁ −ΔX ₂ |. [Object of the Invention] The present invention provides an image forming apparatus capable of obtaining a color image by superposing color toner images formed on a plurality of photoconductors, to obtain a color image without color shift on a transfer paper. It is an object of the present invention to provide a device capable of [Structure of the Invention] In order to achieve the above-mentioned object, the present invention uniformly arranges a latent image carrier having an exposure position at which image light for forming an electrostatic latent image is irradiated and the surface of the latent image carrier. A plurality of recording devices each including a charging charger that electrically charges the electrostatic latent image, a developing unit that visualizes the electrostatic latent image, and a transfer unit that transfers the developed image onto a transfer sheet are arranged, and the transfer sheet is conveyed by the transfer sheet conveying unit. In an image forming apparatus that sequentially conveys the images to each recording apparatus and transfers the images in an overlapping manner,
One driven gear is fixed to the support shaft of the latent image carrier of each recording device, and the driven gear is interlocked at each angle formed by the exposure position and the transfer position as an integral fraction of 360 °. It is characterized in that the plurality of drive transmission members are driven simultaneously. [Operation] The basic principle of the present invention is to drive all the teeth of the driven gear driven by the plurality of drive transmission members at the exposure position by the plurality of drive transmission members even at the transfer position, The latent image carrier is rotationally driven by the tooth having the highest rotational speed among these teeth at both the exposure position and the transfer position. As shown in Examples 90 ° and 120 ° to be described later, the plurality of drive transmission members are arranged at an angle of an integer fraction of 360 °, and the arrangement angle between the drive transmission members is set. 360 divided by an integer equal to
This can be achieved by arranging the exposure position and the transfer position at an angle of, and thereby matching the rotational phases of the latent image carrier at the exposure position and the transfer position. As a result, the image on the transfer paper is not distorted,
It is possible to obtain a color image without color shift on the transfer paper. Embodiment An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a color copying machine as an example of the image forming apparatus. The copier includes a scanner unit 1 for reading a document, an image processing unit 2 for electrically processing an image signal output as a digital signal from the scanner unit 1, and image recording information of each color from the image processing unit 2. And a printer unit 3 for forming an image on copy paper based on the image data. The scanner 1 has a lamp 5 for scanning and illuminating the original on the original placing table 4, for example, a fluorescent lamp. The reflected light from the original when illuminated by the fluorescent lamp 5 is reflected by the mirrors 6, 7, 8 and is incident on the imaging lens 9. By the imaging lens 9,
The image light is imaged on a dichroic prism 10 and split into light of three wavelengths, for example, red R, green G, and blue B, and a light receiver 11, for example, a red CC for each wavelength light.
It is incident on D11R, CCD11G for green, and CCD11B for blue. Each of the CCDs 11R, 11G, and 11B converts incident light into a digital signal and outputs the digital signal. The output is subjected to necessary processing in the image processing unit 2 to record color information of each color, for example, black (hereinafter, abbreviated as Bk). , Yellow (Y for short), magenta (M for short), and cyan (C for short) for recording. FIG. 1 shows an example in which four colors of Bk, C, M, and Y are formed.
A color image can be formed using only colors. In that case, the number of recording devices can be reduced by one set compared to the example of FIG. The signal from the image processing unit 2 is input to the printer unit 3 and sent to the respective color laser light emitting devices 12Bk, 12C, 12M and 12Y. In the example of the figure, the printer unit has four sets of recording devices 13Bk, 13Bk.
C, 13M, and 13Y are arranged side by side. Since the recording devices 13 are made of the same components, the recording device for C will be described for simplicity of description, and the other colors will be omitted. For each color, the same portions are denoted by the same reference numerals, and in order to distinguish the configuration of each color, a reference numeral indicating each color is added to the reference numeral. The recording device 13C has a drum lock photoconductor 14C in addition to the laser light emitting device 12C. The photoreceptor 14 as a latent image carrier has a charging charger 15
C, exposure device using laser emitting device 12C, developing device 16
C, the transfer charger 17C, etc. are energized in the same manner as in a known copying machine. Photoreceptor 14C made uniform by charging charger 15C
Forms a latent image of a cyan light image by exposure with the laser emitting device 12C, and develops it with the developing device 16C to form a visible image. The copy paper supplied from the paper feed unit 19 by the paper feed roller 18, for example, from one of the two paper feed cassettes, is fed to the transfer belt 21 which is a transfer paper conveyance unit with the leading ends aligned by the registration rollers 20 and at the same timing. To be Transfer belt
The copy paper conveyed by 21 is sequentially sent to the photoconductors 14Bk, 14C, 14M, and 14Y on which the visible images are formed, and the visible images are transferred under the action of the transfer charger 17. The transferred copy sheet is fixed by the fixing roller 22 and discharged by the discharge roller 23. The copy paper can be accurately conveyed at the speed of the transfer belt by being electrostatically attracted to the transfer belt 21. FIG. 2 shows a main part of an example of a rotary drive system for each of the photoconductors 14Bk, 14C, 14M and 14Y. The four gears 25 are the four photoconductors.
14Bk, 14C, 14M, 14Y photoconductor support shafts 30Bk, 30C, 3
It is fixed on 0M and 30Y and meshes with a worm 28 which is rotationally driven by a drive source (not shown) such as a motor. When the worm 28 rotates, the rotation of the worm 28 is transmitted through the gears 25 and the photoconductor support shafts 30Bk, 30C, 30M and 30Y to the photoconductors 14B.
It is transmitted to k, 14C, 14M and 14Y, which causes the photoconductor to rotate. In the case of this embodiment, the exposure position and the transfer position on the photoconductor are shifted by 180 °, and one support member fixed to each of the support shafts 30Bk, 30C, 30M and 30Y of the photoconductors. Gears 25Bk, 25C, 25M and 25Y as drive transmission members are provided, and two worms 28 are meshed with each gear 25 at positions shifted by 180 °. Each worm 28 is attached to two worm shafts 26, and gears 27 provided at the ends of the worm shafts 26 are connected to each other via two idle gears 29. Two idle gears 29 are arranged in order to align the rotation direction of the worm 28 with the normal direction, that is, to rotate the two worm shafts 26 in opposite directions,
In addition, the gear 27 at the end of each worm shaft 26
It has the same number of teeth in order to make 28 rotation speeds the same. As long as the transmission means is such that the two worm shafts rotate in opposite directions at the same number of rotations, it is obvious that the transmission means can be constituted by adopting other means without being limited to the embodiment. is there. In the embodiment shown in FIG. 2, since two worms 28, 28 mesh with one gear 25, when the two worms 28, 28 each make one rotation, the gears 25 are respectively rotated. The worms 28, 28 are rotated by a larger angle with respect to the rotation center of one tooth at a position facing each other. In other words, the speed fluctuation of the photosensitive member support shaft 30 is obtained by superimposing the waveforms of the speed fluctuations when driven by only one worm and having a higher speed. FIG. 4 (a) is a diagram for explaining this principle. D is a photoconductor as a latent image carrier, G is a gear.
The two teeth of the gear G are shown by a and b, and only the teeth cited in this description are shown and the other teeth are omitted. Note that, for the sake of clarity, the exposure position and the transfer position are shown by moving in the clockwise direction. O is the center of protrusion of the gear and O'is the center of rotation of the gear. The distance between the correct center O and the center of rotation O'of this gear is actually extremely short, but in this figure it is greatly exaggerated. The center of rotation O ′ of the gear G coincides with the center of rotation of the photoconductor support shaft and the photoconductor D. Note that W ₁ and W ₂ indicate the drive of the gear G by the drive transmission member. In this figure, the gear G is eccentrically attached to the photosensitive member support shaft O'by the length of O-O ', and since the rotation center O'is located below the correct center O in the figure, the rotation center O'. ′ To tooth a (0′-a) is shorter than the distance to tooth b (0′-b), so that one drive transmission member causes one of teeth a or b to be of equal length (eg worm When it is driven by one rotation), the rotation angle θa of the gear G by the tooth a is the rotation angle θ of the gear G by the tooth b.
It becomes larger than b. Thus, as shown, when the point A on the photosensitive body (actually corresponds to a line on the photoreceptor) is in the exposure position shown, the gear G and a photoreceptor D is the tooth by drive transmission member W ₁ Even if the tooth b of the gear G is driven by the drive transmitting member W ₂ at the same time as the tooth b of the gear G is driven by the drive transmission member W _{2 at a} large rotation angle θa by the drive of the tooth a, the gear b is slow. It does not affect the rotational speed of G. 4 (b) and 4 (c), as shown in FIG. 4 (a), two worms W ₁ and W ₁ are provided as drive transmission members for driving the teeth a and b of the gear G at positions separated by 180 °. W ₂ is provided, and the fluctuation of the rotation speed of the gear G is shown when the gear G is driven by only one worm. The horizontal axis indicates the gear G.
And the vertical axis represents the variation of the rotation speed in comparison with the rotation speed V ₀ when the rotation center coincides with the correct center of the gear. Incidentally, in these figures (b) and (c), the rotation angle at which the starting point is not substantially affected by the eccentricity, that is, in FIG. When b is at the position S'180 ° apart from this S (b),
In the diagram (c), the starting point is used. At this starting point, the tooth a, which is located at the position S and has the highest rotation speed, gradually increases in rotation speed as the gear G approaches the worm W ₁ by the clockwise rotation of the gear G, and the gear G rotates T / 4 rotations. When the tooth a comes to a position driven by the worm W ₁ after rotating for 90 °, which is the period, the maximum rotation speed is reached as shown in FIG. The amount becomes ΔV. At this time, the tooth b having the slowest rotation speed is the worm W ₂
It is in a position to be driven by, and this worm W ₂ alone is the gear G
If is driven, it will rotate at the slowest rotation speed (-ΔV) as shown in FIG.
The gear G rotates at the maximum rotation speed by driving the tooth a described above. FIG. 3D shows the actual rotation speed of the gear G. Further, when the gear G rotates 90 ° C. to the position of T / 2 (half rotation), the teeth a and b are not driven, and at the time of T / 4 rotation described above,
Since the teeth at the positions S and S'are driven by the _two worms W ₁ and W ₂ , respectively, the rotation speed of the gear G is the same as that at the time of rotation T / 2 in FIGS. As shown,
Similar to the case where the tooth a is in the S position, it is almost the ideal rotation speed.
It becomes V ₀ . In addition, when the gear G further rotates 90 ° and rotates 4/3,
This time the tooth a rotational speed becomes maximum is driven by a worm W ₂ moved to the position of a ', in the same manner as described above,
The gear G has its maximum rotational speed (Δ) regardless of its tooth b moving to the b ′ position and the drive by the worm W2.
V) rotates. (D) shows the rotational speed of the gear when the gear G is driven by the _two worms W ₁ and W ₂ described above. As is clear from this figure, the exposure position and the transfer position are shown. Since the rotation speed of the gear G, and hence the photoconductor, becomes the same for each half rotation equal to the interval, no distortion occurs in the exposed and transferred image. Further, if the angle between the exposure position and the transfer position is equal to the angle between the worms W ₁ and W ₂ described above, the position of the worm with respect to the exposure / transfer position may have any angular relationship. It will be clear from the above description. In the above description, the tooth a that maximizes the rotation speed of the gear G has been described as an example. However, in general, all the teeth that have been driven by the driving means that interlock with the exposure position are driven by the driving means that interlock with each other at the transfer position. If it is driven, the driving of the gear G by the tooth having the fastest rotation speed among these teeth is given priority, and the rotation speed of the photoconductor at the time of exposure becomes the same as that at the time of transfer, and the exposure / transfer is performed. There is no distortion in the image. FIG. 5 shows a recording device of an image forming apparatus according to another embodiment of the present invention, in which an exposure position for projecting an optical image from the exposure device 12 on the photoconductor 14 and the photoconductor by the transfer charger 17. The angle α between the upper toner image and the transfer position at which the toner image is transferred is 120 °. The drive section of this recording apparatus is shown in FIG. 6, and three drive gears 31, 31, 31 are provided at a position of an angle of 120 ° on the gear 25 attached to the photoconductor support shaft 30. It is meshed. The rotation of the drive pulley 33 provided on the shaft of the motor 32 is transmitted to the three drive gears 31, 31, 31 via the belt 34. FIG. 7 is for explaining the operation of the embodiment shown in FIGS. 5 and 6, and FIG. 7A is a view for explaining the operation principle of this embodiment, and FIG. ) To (d)
The three drive gears W ₂₁ , W ₂₂ and W ₂₃ are individually gear G
Is a diagram showing the fluctuation of the rotation speed when the gear G is driven, and FIG. 6 (e) shows that when the gear G is driven by three teeth r, s, t,
That is, it shows the actual fluctuation of the rotation speed. When the point A on the photoconductor D is at the exposure position as shown in the figure, the three teeth s, r, t of the gear G are respectively driven by the drive gear.
Although being driven by W ₂₁ , W ₂₂ and W ₂₃ , the gear G is rotating at the fastest speed by the drive gear W ₂₁ driving the tooth r closest to the rotation center O ′. When the gear G rotates 120 ° from the position shown in the figure and the point A on the photosensitive member reaches the transfer position, the tooth r that gives the fastest rotation speed is driven by the drive gear W _22. It rotates at the same speed as when it was exposed. The tooth r that gives the highest rotation speed is the drive gear W _22.
In a point on the exposed photosensitive member when being driven tooth r transfer is performed when it is driven by the drive gear W _23, also the teeth r is driven by the drive gear W ₂₃ transfer is performed when a point on the exposed photosensitive member tooth r is driven by the drive gear W ₂₁ that when you're. When the point A on the photoconductor is at the exposure position or the transfer position, the teeth t, s driven at the drive positions W ₂₁ , W ₂₂ , W ₂₃
Since the rotation speed due to the tooth r is slower than the rotation speed due to the tooth r, the rotation speed of the gear G is not affected, and
It is as described above that the high rotation speed is maintained. FIG. 7 (e) shows these three drive gears W ₂₁ , W ₂₂ , W _23.
When the gear G is driven by, that is, the rotation speed at the time of actual use is shown. The rotation speed becomes the same every 1/3 rotation of the gear G, which corresponds to 1/3 rotation.
If the exposure position and the transfer position are provided at an interval of °, the exposed and transferred image will not be distorted. [Advantages of the Invention] In the configuration of the present invention, since the rotational speeds of the latent image carriers at the exposure position and the transfer position are the same in each recording device to prevent distortion occurring in each monochromatic image, A particular effect is obtained in that color images having no color shift on the transfer paper are superposed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectional view showing an example of a color image forming apparatus to which the present invention is applied, and FIG. 2 is a schematic sectional view showing an embodiment of a photoconductor drive system of the present invention. FIG. 3 is a diagram for explaining speed fluctuations due to eccentricity of the drive system of the photoconductor, FIG. 4 is a graph showing speed fluctuations when driven by two worms, and FIG. 5 is an image forming apparatus of the present invention. 6 is a schematic sectional view showing another embodiment of the drive system of the photoconductor in FIG. 5, and FIG. 7 is a schematic sectional view showing the speed fluctuation of each gear in the embodiment of FIG. FIG. 8 and FIG. 8 are graphs showing the speed fluctuation and the deviation amount of two conventional photoconductors. 12 ... exposure means, 14 ... latent image carrier, 17 ... transfer means,
25 ... Driven transmission member, 28, 28, 31, 31, 31, ... Plural drive transmission members, 30 ... Support shaft.

Claims (1)

(57) [Claims] A latent image carrier having an exposure position where image light is irradiated to form an electrostatic latent image, a charger for uniformly charging the surface of the latent image carrier, and development for visualizing the electrostatic latent image. An image forming apparatus in which a plurality of recording devices each including a transfer unit and a transfer unit that transfers the visible image onto the transfer paper are arranged, and the transfer paper is sequentially transferred to each recording device by the transfer paper transfer unit to transfer the images in an overlapping manner. In the above, one driven gear is fixed to the support shaft of the latent image carrier of each recording device, and the angle formed between the exposure position and the transfer position, which is an integral fraction of 360 °, is fixed to the driven gear. A color image forming apparatus characterized in that a plurality of drive transmission members interlocking with each other are engaged with each other, and the plurality of drive transmission members in the plurality of recording devices are simultaneously driven.