JP3511818B2 - Color image forming equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [0001] [0001] The present invention relates to an electrophotographic camera.
For color printers, color copiers, color faxes, etc.
The present invention relates to a color image forming apparatus. [0002] 2. Description of the Related Art Conventionally, an electrophotographic color image forming apparatus is used.
Various types of devices have been proposed.
Then, there are two systems of a multiple development type and a multiple transfer type. Multiple
Development type (for example, JP-A-1-195774)
Two colors
Charge, exposure, and current
There are many issues to be solved in order to repeat the image, and it is stable
It is difficult to obtain a developed color. On the other hand, the multiple transcription type
Furthermore, it is divided into two types, a 4-cycle type and a 1-cycle type.
Although both methods can be used,
Although it is necessary to prevent the displacement,
There is an advantage that the image quality can be used as it is.
Particularly, the 4-cycle type has a disadvantage that the recording speed is slow.
Nevertheless, the problem of color misregistration is relatively easy to overcome
Therefore, many products adopt this method. On the other hand, one cycle
Formula (for example, JP-A-61-79658)
The image forming apparatus has a higher recording speed than the four-cycle type.
Color misregistration is likely to occur
Need a large and precise control unit to solve this
Therefore, it is used only in some expensive products. FIG. 6 shows a conventional one-cycle multi-transfer type.
FIG. 2 is a plan view showing a schematic configuration of a color image forming apparatus,
7 is a side view thereof. As shown in FIGS. 6 and 7
In addition, this color image forming apparatus is used for cyan and magenta, respectively.
4 sets of electrophotographic printers corresponding to
Process units 2a, 2b, 2c, 2d
Four transfer devices 8a, 8b, 8c, 8d corresponding to each color
And a transfer medium transport device 9 for transporting the transfer medium 5.
ing. In addition, there is a
Transfer medium for supplying transfer medium 5 to color image forming apparatus
A supply roll 10 is provided, and a transfer device for a final color is provided at a subsequent stage.
Fixes the toner image on the transfer medium 5 sent from 8d
A fixing device 14 is provided. [0004] Electrophotographic process units 2a, 2b, 2
c and 2d rotate in the direction of the arrow and bear the toner image on the surface.
Image carriers 1a, 1b, 1 corresponding to each of the above colors
c, 1d and their image carriers 1a, 1b, 1c, 1d
Scanning exposure apparatus for forming an electrostatic latent image corresponding to each of the above colors
21a, 21b, 21c, 21d and their respective electrostatic latent images
Developing devices 22a and 22 for developing toner images to form toner images
b, 22c, 22d, four charging devices not shown, shown
Not include four cleaning devices
You. These four electrophotographic process units 2a, 2
b, 2c and 2d are transfer positions 26a and 26, respectively.
b, 26c and 26d, the toner of each color is
ー Along the conveyor belt 6 so that images can be sequentially transferred
The unit mounting side plates 7a, 7 are arranged in parallel to
b. [0005] It should be noted that the electrophotographic process in the present embodiment.
The unit 2a, 2b, 2c, 2d is an image according to the present invention.
It corresponds to a carrier and a toner image forming unit.
The transfer medium transporting device 9 includes the image carriers 1a, 1b, 1
transfer medium 5 for receiving the transfer of the toner image on c, 1d
Each of the holding bodies 1a, 1b, 1c, 1d
The transport belt 6 to be moved sequentially, and the transport belt 6 is stretched.
Belt tension rolls 3a, 3b, belt tension rolls 3a,
Roll supporting side plates 4a and 4b for supporting the 3b, a transfer bell
Or a drive device (not shown) for driving the
It is composed of A color image forming apparatus shown in FIGS. 6 and 7
As the transfer medium 5 in the above, generally, plain paper, high quality paper,
An OHP sheet or the like is used. The transfer medium 5 is a transfer medium
Placed on or adsorbed to the conveyor belt 6 of the body conveyor 9
Each of the electrophotographic process units 2a, 2b, 2c, 2
d at each transfer position 26a, 26b, 26c, 26d
When moved, each transfer position 26a, 26b, 26c, 26
d, the image is formed on each of the image carriers 1a, 1b, 1c, 1d.
The formed color toner images are sequentially superimposed on the transfer medium 5
Is transcribed. At this time, each of the image carriers 1a, 1b, 1c,
The respective color toner images formed on the transfer medium 5
Is accurately superimposed on the
It is extremely important to obtain a high quality color image. Colorless
Factors that cause this are scanning exposure devices 21a, 21b, 2
On image carriers 1a, 1b, 1c, 1d by 1c, 21d
Deviation of writing position of latent image to the printer and scanning / exposure timing
Between the four image carriers 1a, 1b, 1c, 1d.
Misalignment, eccentricity of image carriers 1a, 1b, 1c, 1d
Fluctuations in the rotational angular velocity, fluctuations in the transport speed of the transfer medium 5, and meandering
Or skew, due to temperature change in the color image forming apparatus
Many factors such as dimensional change of each component due to thermal expansion
is there. The main scanning direction of the transfer medium 5 (axial direction of the image carrier)
Direction and the axial direction of the belt tension roll)
Movement (meandering and skew) is not desirable for image formation.
In particular, the skew of the transfer medium 5 causes color misregistration.
This has a particularly serious adverse effect. FIG. 8 shows a transfer medium.
5 is a graph schematically showing the meandering and skewed states. As shown in FIG. 8A, a transfer medium 5 (see FIG.
The meandering of 6) shows a periodic change with the progress of time t.
This is mainly due to the belt of the transfer medium transport device 9.
Belt tension rolls due to eccentricity of tension rolls 3a and 3b
Of the velocity v in the main scanning direction within one rotation cycle of the rollers 3a and 3b.
This is caused by reversing the direction.
The time length is longer than the rotation cycle of the tension rolls 3a and 3b.
In terms of the degree, the position y of the transfer medium 5 in the main scanning direction is a certain constant.
Only oscillates periodically within the range. like this
In addition, the meandering of the transfer medium stays within a certain range and the displacement is
The effect on color misregistration is explained next because it is not accumulated
Smaller than skew. In addition, the belt tension roll rows 3a, 3
b, the transfer medium 5 is controlled by the image carriers 1a, 1b, 1
c, 1d the time required to move the distance G (see FIG. 6) between
By setting it to an integral number, the meandering of the transfer medium 5
Methods for making color misregistration inconspicuous have conventionally been known.
You. On the other hand, the skew of the transfer medium is caused by the image carriers 1a,
1b, 1c, 1d (see FIG. 6)
Arrangement direction of the arrangements 21a, 21b, 21c, 21d, and
Due to the inconsistency between the transfer directions of the transfer medium transfer device 9,
The transfer medium is generated as shown in FIG.
The position y of the body 5 in the main scanning direction shifts only in one direction,
Since the deviation is accumulated with the passage of time t,
The transfer medium 5 is located at the transfer position 26a of the image carrier 1a for the first color.
To the transfer position 26d of the image carrier 1d for the final color.
Large position while moving distance L (see FIG. 6)
The transfer medium 5 transferred at the transfer position 26a.
And the first color toner image transferred at the transfer position 26d.
A large color shift occurs between the toner image and the fourth color toner image. Next, referring to FIGS. 9, 10 and 11, FIG.
Color shift due to skew of the transfer medium will be described schematically.
You. FIG. 9 shows that the transfer medium is conveyed without skew and is normally transferred.
FIG. 3 is a schematic diagram illustrating a state in which an image is formed. The mosquito shown in FIG.
In the color image forming apparatus, the image carriers 1a, 1b, 1c, 1
d, the arrangement direction p, and the scanning exposure devices 21a, 21b, 21
c, 21d, scanning exposure images 25a, 25b, 25c,
25d alignment direction s and transfer direction of transfer medium transfer device 9
t (that is, the arrangement of the belt tension rolls 3a and 3b)
Direction) are parallel to each other. At this time, the image carrier
Scanning exposure images 25a, 25 on 1a, 1b, 1c, 1d
b, 25c, 25d are visualized by a developing device (not shown)
And the image bearing members 1a, 1b, 1c, 1d
Image is formed, and the image carriers 1a, 1b, 1c, 1d
The respective transfer positions 26a, 26b, 2
Proceed to 6c and 26d, and at the appropriate timing
Onto the transfer medium 5 transported by the rollers 3a and 3b.
Will be copied. This transfer is first performed at the first transfer position 26a.
The transfer image 28a of the first color is transferred by
At the position 26b, the second color is placed on the transfer image 28a of the first color.
The transferred image 28b of the color is transferred, and the third
At the transfer position 26c and the fourth transfer position 26d
Transfer image 28c of the third color and transfer image 28d of the fourth color
Is transferred. As shown in FIG. 9, the transfer medium transport device 9
Of the image carriers 1a, 1b, 1c, 1d
Direction p and scanning exposure images 25a, 25b, 25c, 25
When the transfer direction coincides with the arrangement direction s of d, the transfer medium after transfer
Transfer images 28a, 28b, 28c, 28 of each color on body 5 '
No color shift in the main scanning direction occurs between d. [0013] However, the following is a description.
Transfer media transfer device, such as a color image forming device
Feeding direction, image carrier alignment direction, and scanning exposure image alignment
If the directions are not parallel to each other,
Color shift occurs in the main scanning direction. FIG. 10 shows the transfer of the transfer medium.
The transport direction of the apparatus is the arrangement direction p of the image carrier and the scanning exposure
Color misregistration occurs when the images do not match the arrangement direction s
FIG. FIG. 10 shows the transfer direction of the transfer medium transfer device 9.
t is the direction p in which the image carriers 1a, 1b, 1c, 1d are arranged.
Of scanning and scanning exposure images 25a, 25b, 25c, 25d
Angle error θ with respect to direction s₁ Each color only
Main scanning method between the transfer images 29a, 29b, 29c, 29d
This shows how color misregistration occurs in the directions. In FIG.
Here, the scanning exposure image 25a on the image carrier 1a for the first color
To the scanning exposure image 25d on the image carrier 1d for the fourth color
Scanning exposure images for four colors are formed at normal exposure positions.
And formed on each image carrier by each developing device (not shown)
Toner image is also placed in a normal position on each image carrier.
Formed, but transferred when sequentially transferred onto the transfer medium 5.
Since the medium 5 is skewed, the transfer medium 5 '
Main scanning method like mappings 29a, 29b, 29c, 29d
The image is transferred out of alignment. In this case, maximum color shift occurs.
The transfer image 29a of the first color and the transfer image 29 of the fourth color
d and the transfer position 2 of the image carrier 1a for the first color.
6a to the transfer position 26d of the image carrier 1d for the final color
Let L be the distance between the transfer positions of₁
Is     δ₁ ＝ L ・ tanθ₁                                   ... (1) Can be expressed as According to equation (1), the distance L between the transfer positions is shorter.
Is the size of the color shift δ₁ Is small. But,
Conventional one-cycle type multi-transfer type color image forming apparatus
In this case, the distance L between the transfer positions is, for example, about 400 to 600.
mm color image forming apparatus
Adjustment of the transfer direction t of the transfer medium transfer device 9 when assembling
Even if the operation is performed satisfactorily, the color misregistration
Size δ₁ To about 0.2-0.3mm
Is at its best. So, for example, the actual color while driving
Complex optics installed in the scanning exposure device while detecting misalignment
Do not perform color misregistration correction control using a device inclination correction device.
Which measures need to be taken. The reason why such color misregistration occurs is that the transfer medium
The belt tension rolls 3a and 3b of the body transport device 9 are
This is due to the mounting being shifted from the mounting position. You
That is, in FIG. 10, the image carrier 1d for the final color and the transfer medium are shown in FIG.
It is originally a regular distance d with the belt tension roll 3b on the exit side.
Must be mounted parallel to each other
However, the upper side of the roll supporting side plate
And the shaft center of the image carrier 1d.
Is maintained at the regular distance d, while going to the drawing
, The belt tension roll axis of the lower roll supporting side plate 4a
Distance d between receiving portion 4a 'and the axis of image carrier 1d_r Is
Error e from regular distance d₁ Only short. In other words, belt stretcher
The roll 3b is attached by tilting to the left as viewed in the drawing.
ing. At this time, the belt tension rolls 3a and 3b are supported.
The distance between the centers of the roll supporting side plates 4a and 4b
Then, the arrangement direction p of the image carrier row 1 and the belt tension row
Angle θ of the row 3 with the transport direction t₁ Is     tanθ₁ = E₁ / W (2) Can be expressed as Strictly speaking, W is the belt tension roll 3b.
Should be expressed as the distance between two supporting points that are substantially supported
However, here, for convenience, both roll supporting side plates 4a, 4b
Is used as W. Where
From the equations (1) and (2), the magnitude of color shift δ₁ Is     δ₁ = E₁ × L / W (3) Can be expressed as Incidentally, the mounting position of the belt tension roll 3b
Is relative to the image carrier (that is, the distance d or
Distance d + L) instead of the transfer medium entrance side
When expressed as the distance D from the belt tension roll 3a,
Dimensional error of belt tension roll 3b with respect to image carrier 1d
e₁ Instead of using the two belt tension rolls 3a, 3b
Dimensional error e between_Two (That is, the regular distance D and the actual distance
Release D_r To express the magnitude of color misregistration using
You can also. By the way, JIS-B0405 "Normal tolerance"
-Part 1 "As shown in Table 1, the reference size is 6 m
Tolerance for length dimension from m to 400mm
Is "fine grade" and is defined as ± 0.1 to 0.2 mm.
On the other hand, the color reproduction of color images in the field of printing is
The magnitude of the color misregistration is set at 0.
It is said to be 1 to 0.15 mm or less. Therefore, on
Distance error e in equation (3) above₁ The above JIS standard
If the lower limit (0.1 mm) of the tolerance of
Is approximately 1, the size of the allowable color shift is
It is equal to the lower limit (0.1 mm) in the field. sand
That is, the first color image carrier 1a to the fourth color image carrier
The distance L between the transfer positions up to 1 d and the belt tension roll 4 a
The distance W between the centers of both roll supporting side plates 4a and 4b is substantially equal.
Color shift is within an acceptable level,
In the image forming apparatus, the value of L / W greatly exceeds 1
Therefore, if the size of the color shift exceeds the allowable level
I have no choice. Next, the scanning exposure device is arranged in the transfer medium
The transfer direction of the transfer device and the arrangement direction of the image carrier belt
When the transfer medium is skewed if they do not match
explain. FIG. 11 shows that the arrangement direction of the scanning exposure apparatus is the transfer medium.
Transport direction of the body transport device and the alignment direction of the image carrier belt
A model showing how color misregistration occurs when the
FIG. In the color image forming apparatus shown in FIG.
Scanning exposure images 25a, 25 by a scanning exposure device not shown
The arrangement direction s of b, 25c, 25d is the transfer medium transport device.
9 and the image carriers 1a, 1b, 1c, 1d
Angle θ with respect to the arrangement direction p_TwoIt is only shifted. Sand
That is, the transfer direction t of the transfer medium transfer device 9 and the image carriers 1a,
The arrangement direction p of 1b, 1c, and 1d matches. In such a color image forming apparatus, the first
The scanning exposure image 25a of the color is formed by rotating the image carrier 1a for the first color.
Angle θ to axis_Two The first color toner
-The image is transported as the image carrier 1a rotates while being tilted.
And is developed by a developing device (not shown) to form a toner image.
Formed on the transfer medium 5 and then proceeds to the transfer position 27a.
Is transferred to However, the normal transfer position 26a is
And the actual transfer position 27a and the regular transfer position 26
There is a large deviation from the value a. Similarly the second, third and fourth colors
The toner images of the normal transfer positions 26b, 26c, 26d
Transfer at shifted transfer positions 27b, 27c, 27d
The image is sequentially transferred onto the medium 5, and is transferred onto the transfer medium 5 ′ after the transfer.
Main scanning like transfer images 29a, 29b, 29c, 29d
A color shift occurs in the direction. Also in this case, the largest color shift is the first.
Color between the transfer image 29a of the color and the transfer image 29d of the fourth color
And the size of the color shift δ_Two Is the above equation (1)
the same as,     δ_Two ＝ L ・ tanθ_Two                                   ... (4) Can be expressed as That is, as shown in FIG.
The arrangement direction s is the transfer direction t of the transfer medium transfer device 9 and the image
The angle θ with respect to the arrangement direction p of the carriers_Two Just off the spot
In this case as well, the transfer direction t of the transfer medium transfer device 9 as shown in FIG.
Is the alignment direction p of the image carrier and the alignment direction of the scanning exposure device
angle s with respect to s₁ Same size as when it is shifted only
It can be seen that the following color shift occurs. The present invention has been made in view of the above circumstances, and has a complicated control.
Color images with little color shift
It is an object of the present invention to provide a color image forming apparatus that can be used. [0025] A book which achieves the above object.
The color image forming apparatus of the invention rotates in a predetermined direction,
A plurality of image carriers for carrying a toner image on the surface;
Each of the image carriers is provided based on image data.
Toner for forming toner images of different colors on an image carrier
Image forming means, and transfer of toner images on the plurality of image carriers.
A predetermined transfer medium to be copied is placed on each of the plurality of image carriers.
In the direction of transfer of the transfer medium
Transfer medium transport device with both ends in the intersecting direction supported
And a toner image on the image carrier at each of the transfer positions.
To the transfer medium, corresponding to each of the image carriers.
Transfer means, on the transfer medium on the image carrier
A professional that transfers toner images sequentially from the first color to the final color.
Process and finally fixed on the specified image recording medium.
Color image forming apparatus that forms
The first color image carrier among the plurality of image carriers.
Transfer from the transfer position to the transfer position of the image carrier for the final color
The distance between positions supports the transfer medium transport device,
The distance between the two fulcrums in the direction that intersects the transfer medium
The plurality of image carriers are arranged so that
It is characterized by. Here, the distance between the transfer positions is equal to the distance between the two supports.
The plurality of image bearing members are set so that the distance between the points is equal to or less than half of the distance between the points.
It is preferable that the holding body is arranged. Ma
Further, the plurality of image carriers and the transfer medium transport device,
It is also preferable that they are supported by a set of common side plates.
This is a preferable mode. In the present invention, the transfer
The medium and the image recording medium may be the same medium.
Alternatively, the transfer medium may be a toner on the image carrier.
-After the transfer of the image, the toner image is transferred to the image recording medium.
It may be an intermediate transfer medium for copying. [0027] DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described.
explain. FIG. 1 shows a first embodiment of the color image forming apparatus of the present invention.
It is a schematic diagram showing an embodiment. The color image shown in FIG.
The forming apparatus is a conventional one-cycle type shown in FIGS.
Has a configuration similar to the multiple transfer type color image forming apparatus
And perform almost the same image forming process.
Now, only the differences will be described below. In the present embodiment shown in FIG.
From the transfer position 26a of the image carrier 1a for the first color.
Transfer position up to transfer position 26d of image carrier 1d for final color
A transfer medium supporting the transfer medium transport device 9 has a transfer distance L.
The distance between the two fulcrums in the direction intersecting the moving direction of the body 5 is not more than W.
It is arranged so that. In addition, the rotation of the adjacent image carrier
The scanning exposure device 11a for each color is set within the distance G between the photographing positions.
11b, 11c, 11d and developing devices 12a, 12
b, 12c, and 12d are configured to fit. Was
However, the distance G between the image carriers of each color is not necessarily the same distance
You don't have to
The distance suitable for the formation of the toner image
Scanning so that the toner image is correctly superimposed on the transfer medium
Set the writing timing for each color of the exposure device
No. Further, the image carriers 1a, 1b, 1c, 1d
Are the belt tension rolls 3a, 3b of the transfer medium transport device 9.
Are supported by the roll supporting side plates 15a, 15b
Have been. Thus, the image carriers 1a, 1b, 1c, 1
d and the belt tension rolls 3a, 3b support a common roll
The transfer medium is supported by the side plates 15a and 15b.
Angle between the transport direction of the body transport device and the alignment direction of each image carrier
Deviation can be reduced. This angle shift is
Error due to the mounting position of each image carrier on the
The reason for this is as described above.
The media transport device is mounted on a separate support side plate.
You need to align the two
There is a difference in the distance on each supporting side plate.
An angle error is increased due to the addition of an error in the alignment.
So avoid the angle shift due to this alignment error
Image bearing members 1a, 1b, 1c, 1d and belt tension
Rolls 3a, 3b and a common roll supporting side plate 15a, 1
5b. In addition, the above roll support
The image carriers 1a, 1b, 1 are mounted on the side plates 15a, 15b.
c and 1d together with the scanning exposure devices 11a, 11b, 11c,
11d, developing devices 12a, 12b, 12c, 12d, etc.
Related devices that make up the electrophotographic process unit
Is defined. The developing rolls 12a, 12b, 12
c and 12d are conductive rubber rollers that carry and transport the toner.
It is. Developing rolls 12a, 12b, 12c, 12
d is not limited to only the conductive rubber roll,
Even with a magnetic roll that carries a two-component magnetic developer,
Good. Around the image carriers 1a, 1b, 1c, 1d
The charging device, transfer device and cleaning device not shown
Four of each are arranged. The charging device is, for example,
Photoreceptor layer on the surface of the image carrier
A voltage required for charging is applied. Cleaning equipment
Consists of rubber blades, rubber rolls, etc.
Voltage to separate the toner from the photoconductor
You may do so. These charging devices, cleaning devices
Are omitted or multiple depending on the process to be applied.
The functions may be combined into one shared device. Next, the color image forming apparatus of the present embodiment
The magnitude of the color misregistration will be described. FIG. 2 shows the first
FIG. 9 is a schematic diagram illustrating the occurrence of color misregistration in the embodiment.
You. FIG. 2A shows a scanning exposure apparatus, an image carrier, and a roller.
An ideal camera that has been manufactured and assembled without error
FIG. 2 is a plan view of the color image forming apparatus. This color image formation
Image carriers 1a, 1b, 1c, 1d of the apparatus,
3a, 3b and four scanning exposure devices (not shown)
Scanning exposure images 25a, 25b, 25c, 25d
Are arranged in parallel with each other.
In an ideal color image forming apparatus such as
Transfer images 28a, 28 of each color formed on the transfer medium 5 '
b, 28c and 28d have no color shift in the sub-scanning direction.
No. However, in reality, manufacturing and assembly of color image forming apparatuses
Errors in standing time are inevitable.
It is almost impossible to obtain a color image forming apparatus. For example,
In the case of an actual color image forming apparatus, as shown in FIG.
Thus, the transfer direction t of the transfer medium transfer device 9 and the image carrier 1
a, 1b, 1c, and 1d are aligned with the error angle θ_ThreeIs
They may be staggered. However, in this case,
How to arrange the image carriers 1a, 1b, 1c, 1d for the sake of clarity
The error angle between the direction p and the arrangement direction s of the scanning exposure apparatus is
It does not exist. About the difference between these two angles
Will be described later. In FIG. 2 (b), FIG.
Similarly, the scanning exposure images 25a, 25b, 25c, 25d
Are the regular on the image carriers 1a, 1b, 1c and 1d, respectively.
Position, and the toner image of each color
It is transported to the stations 26a, 26b, 26c, 26d. I
However, the transfer direction t of the transfer medium transfer device 9 is
a, 1b, 1c, 1d at an angle θ with respect to the arrangement direction p_Three Only
The toner image is transferred onto the transfer medium 5 because of the displacement.
And transfer images 29a and 29 on transfer medium 5 'after transfer.
b, 29c, and 29d in the main scanning direction as shown in the figure.
A shift occurs. The transfer of the first color shows the largest color shift
The color shift between the image 28a and the transfer image 28d of the fourth color.
From the transfer position 26a of the image carrier 1a for the first color.
Between the transfer positions up to the transfer position 26d of the color image carrier 1d
Assuming that the distance is L, the magnitude of the color shift δ_ThreeIs δ_Three = L
tanθ_Three Is represented as Also, the error angle θ_Three Is the dimension
Error e₁Or e_Two Tan θ using_Three = E₁ / W also
Is tanθ_Three = E_Two / W. here,
e₁ Or e_Two The size of the standard dimension d or D is about 10
~ 300mm, so it is about 0.1 ~ 0.2mm
You. The distance W between both fulcrums supporting the transfer medium transport device 9 (see FIG.
On the surface, between the centers of both roll supporting side plates 15a and 15b.
(Expressed as distance) is about 300 mm,
tan θ is 0.00033 to 0.00067, that is,
θ_Three Are ± 1 ′ to 2 ′, and this embodiment shown in FIG.
In the state, the distance L between the transfer positions is, for example, 60 to 220.
mm, the size of the color shift δ_Three
(= L tanθ_Three ) Is over 0.04
0.15 mm, which is within the allowable range. This figure 2
(B), the transfer direction t of the transfer medium transfer device 9
With respect to the arrangement direction p of the carriers 1a, 1b, 1c, 1d.
Compared with the conventional example (see FIG. 10), the L / W
By setting the value to 1 or less, 0.2 to 0.3 mm (Fig.
Δ at 10₁ 2), the color shift was about
Δ shown_Three : Reduced to about 0.04 to 0.15 mm
You can see that it is. As described above, the color image forming of the present embodiment
In the apparatus, the transfer position 26 of the image carrier 1a for the first color
a to the transfer position 26d of the image carrier 1d for the fourth color.
The distance L between the transfer positions is set to both supports for supporting the transfer medium conveying device 9.
By making the distance between the points shorter than W, the size of the color shift δ
_Three Can be kept below the allowable level. This is
Transfer medium when a color toner image is transferred onto transfer medium 5
The skew of the transfer medium 5 is caused by shortening the body travel distance.
Color shift due to
Are shown. This effect of reducing color shift is as described above.
Transfer due to a shift of the transfer medium transfer device 9 in the transfer direction t.
Not only when the printing medium 5 is skewed, but also
Even when the transfer medium 5 is skewed due to the deviation of p, the scanning exposure
When the transfer medium 5 is skewed due to misalignment of the optical devices,
The same is true in any case. The cause of the color shift is one of the above-mentioned causes.
If there is only one, the distance L between the transfer positions is
By setting the distance between the points smaller than W, the color shift
Color difference, but generally causes color misregistration
There are multiple causes other than the above. These causes
Color misregistration is roughly classified into
Shift, periodic color shift in the main scanning direction, steady in the sub scanning direction
Color shift and periodic color shift in the sub-scanning direction.
Therefore, the color shift due to the skew of the transfer medium is prevented in the main scanning direction.
This is one of the stationary color shifts. Like this
Error factor δ_n Work together if they work independently
Error δ is represented by the square root of the sum of squares from the additive nature of the variance, δ = √ (δ₁ ^Two+ Δ_Two ^Two+ Δ_Three ^Two+ Δ_Four ^Two) Becomes The sum of the color misregistration in the main scanning direction and the color misregistration in the sub-scanning direction
The magnitude of the generated color shift is also calculated from the geometric distance calculation.
After all, each color shift can be expressed by the square root of the sum of squares.
It can be treated like this. Each cause of color misregistration
Assuming color shifts of approximately the same size, δ = √ (4δ₁ ^Two) Ie δ₁ = Δ / 2 Becomes Therefore, there are several causes of color misregistration, for example,
Assuming that there are four major causes,
The error due to the factor must be half of the combined error.
No. Therefore, in the present invention, the image carrier for the first color is used.
From the transfer position of the image carrier to the transfer position of the image carrier for the final color.
The distance L between the photographing positions (that is,
Transfer medium travel distance), the distance
It is preferable that the distance between the fulcrums is not more than half of the distance W.
This can cause other similar causes of color shift
Keep color shifts below acceptable levels, regardless of presence
Can be. Next, the second embodiment of the color image forming apparatus of the present invention will be described.
An embodiment will be described. FIG. 3 shows a second embodiment.
FIG. 4 is a schematic diagram illustrating the occurrence of color misregistration in FIG. In FIG.
Means that the arrangement direction s of the scanning exposure apparatus is
Angle error with respect to the transport direction t and the arrangement direction p of the image carrier
θ_Four Is shown. Follow
In this embodiment, the transfer direction t of the transfer medium transfer device is
The arrangement direction p of the image carriers coincides with the arrangement direction p. In this color image forming apparatus, the scanning of the first color
The inspection exposure image 25a is opposed to the rotation axis of the image carrier 1a for the first color.
And the angle θ_Four And the first color toner image is
Angle θ to rotation axis_Four Image carrier with only tilt
1a is conveyed along with the rotation of 1a, and is sent to a developing device (not shown).
After the toner image is further developed, the toner image is transferred to the transfer position 27a.
The image is transferred onto the transfer medium 5. However, the correctness of the toner image
The reference transfer position 26a and the actual transfer position 27a
The toner images of the second, third, and fourth colors are similarly shifted.
Transfer that deviates from the normal transfer positions 26b, 26c, 26d
Transfer to the transfer medium 5 sequentially at the positions 27b, 27c and 27d
The transferred images 29a and 29 are formed on the transferred transfer medium 5 '.
Color shift in the main scanning direction occurs as shown in b, 29c, 29d
You. As described above, the color image forming apparatus of this embodiment
Main scanning similar to the above-described conventional example (see FIG. 11).
Although color misregistration occurs in the direction, in this embodiment, L / W
Is set to a small value, the size of the color shift
It is extremely smaller than the case of No. 11. Sand
In this embodiment, the image carrier 1a for the first color is used.
The transfer position of the image carrier 1d for the fourth color from the transfer position 26a
Transfer distance L up to 26d supports the transfer medium
It is configured to be shorter than the distance W between both fulcrums. This embodiment
Also, the largest color misregistration occurs between the transfer image 29a of the first color and the
This is a color shift between the transfer images 29d of the fourth color.
Size δ_Four Is the same as the above equation (1), δ_Four = L
tanθ_Four Can be expressed as Color shift magnitude θ
_Four Is ± 1 ′ to 2 ′ as described above, and is shown in FIG.
In the embodiment, the distance between both fulcrums W is shorter than about 300 mm.
The range L between the transfer positions is, for example, 60 to 260 mm.
By selecting from the following, the size of the color shift δ_Four Is
0.03 to 0.15 mm, which is below the allowable level.
On the other hand, the distance L between the transfer positions with respect to the distance W between the two fulcrums
Conventional example in which the ratio of the above is not considered (see FIG. 11)
Is the size of the color shift δ_Two Is 0.2-0.3mm
It can be seen that the effect of the present invention is great. Next, the third embodiment of the color image forming apparatus of the present invention will be described.
An embodiment will be described. FIG. 4 shows a third embodiment.
FIG. 4 is a schematic diagram illustrating the occurrence of color misregistration in FIG. In FIG.
Is a color image forming apparatus according to the first embodiment shown in FIG.
And a similar color image forming apparatus. As shown in FIG.
In the color image forming apparatus, the image carrier 1a for the first color is
The transfer position of the image carrier 1d for the fourth color from the transfer position 26a
The distance L between the transfer positions up to 26 d
Support in the direction intersecting the moving direction of the transfer medium 5
The distance is set to a half of the point-to-point distance W. Sand
That is, in the embodiment shown in FIG.
Transfer of 1/2 mm or less of distance W between both fulcrums for 0 mm
When L is set to 120 mm as the distance L between positions
Is shown below. Here, the image carrier 1 having a diameter of 16 mm
a, 1b, 1c, 1d are the distances between the respective axes 40 mm
To support the roll supporting side plates 15a, 15b in parallel with each other.
Have been. Around each image carrier 1a, 1b, 1c, 1d
, Charging devices 53a, 53b, 53c, 53d, developing
Rolls 51a, 51b, 51c, 51d, rolls not shown
A copying device and a cleaning device are
You. The charging devices 53a, 53b, 53c, 53d are, for example,
For example, a rubber blade or a rubber roll with a diameter of 10 mm or less
It is composed of Cleaning device is rubber blade
Or a rubber roll with a diameter of 10 mm or less.
It is. These charging devices and cleaning devices are applicable
May be omitted or multiple functions
They may be combined into a combined device. Developing roll 5
1a, 51b, 51c, and 51d denote distances L between transfer positions.
It is composed of a conductive rubber roll with a diameter of 10 mm for shortening.
Have been. Developing rolls 51a, 51b, 51c, 51d
Is not limited to conductive rubber rolls only,
If the diameter can be configured to about 10 mm, for example, 2
A magnetic roll for transporting the component magnetic developer may be used. The magnitude of the color shift in the third embodiment is
Approximately 0.06mm when calculated according to the above calculation example
And the magnitude of the color shift in the second embodiment described above.
δ_Four: Further color shift compared to 0.03 to 0.15 mm
It shows that it is possible to decrease. next,
Fourth Embodiment of the Color Image Forming Apparatus of the Present Invention
explain. In each of the above embodiments, both
The present invention in which the distance L between transfer positions is shorter than the distance W between points
The above is an example of a color image forming apparatus.
In which the distance W between both fulcrums is increased with respect to the distance L between the transfer positions
For wide color drawing output as a color image forming apparatus of the embodiment
Will be described. A2 size (420mm × 59
4mm) or A1 size (594mm x 840mm)
Color image forming apparatus for paper output
When the distance W between both fulcrums is 450mm and 630mm, transfer
Color shift when the distance L between positions is 300 mm
Find the size of The magnitude of the color shift is δ as described above.
Δ = e × L / W, L = 300 mm
E = 0.1 to 0.2 mm, the A2 size
Δ = 0.07-0.
13mm, and color image formation for A1 size
In the case of the device, δ = 0.05 to 0.1 mm. Therefore
Color for wide drawing output such as A2 size, A1 size
Also in the case of the image forming apparatus, the color image forming apparatus of the present invention is used.
To reduce color shift to a level that is
it can. Next, the distance L between transfer positions, that is,
The transfer medium travel distance from the start to the end of transfer is simply shortened.
Cannot reduce color misregistration below an acceptable level
For example, small size dedicated cards such as postcards, photos, cards, etc.
The case of the color image forming apparatus will be described. Now, A6
Color using paper of size (74mm x 105mm)
The distance W between both fulcrums of the transfer medium transport device of the image forming apparatus is set to 1
00 mm. The distance L between the transfer positions is set to the third embodiment.
Even if L = 120 mm, the distance between transfer positions
Since L is longer than the distance W between the fulcrums, the color shift is large.
From the above equation (3), δ is δ = 0.12 to 0.24 mm.
And exceeds the allowable level. Thus, the distance between the two fulcrums
When W is narrow, the distance L between transfer positions is set according to the present invention.
Shorter than the distance W between both fulcrums, for example, 60 to 100 mm
If not, it is impossible to achieve a color shift below the allowable level.
Absent. In each of the above embodiments, a plurality of image carriers
The transfer medium that receives the transfer of the toner image is plain paper, high-quality
Paper or OHP sheet, etc. on this transfer medium
The toner image on the image carrier is transferred and fixed
A type of image recording medium on which a color image is recorded
Although the color image forming apparatus has been described, the present invention
And the transfer medium and the image recording medium are the same medium
Is not limited to color image forming apparatuses
The transfer medium receives the transfer of the toner image on the image carrier.
And then transfer the toner image to an image recording medium
It can be applied to the color image forming device that is the medium.
You. In each of the above embodiments, the transfer medium transfer
An example in which the feeding device is an endless belt type feeding device
As described above, the present invention relates to this type of transfer medium conveyance.
It is not limited to a device, but a sheet member or a drum member
For other types of transport devices such as grippers and grippers
Can also be used. In each of the above embodiments,
Is an example where a plurality of image carriers are aligned on a straight line.
However, the present invention is limited to such an embodiment.
Instead of multiple image carriers on an arc or
It can be applied even if it is on another curve
You. FIG. 5 shows a fifth embodiment of the color image forming apparatus of the present invention.
It is a schematic diagram showing a form. As shown in FIG. 5, this color image forming apparatus
The intermediate transfer medium drum 1 rotating in the direction of arrow A
3. Four sets of electrophotographs surrounding the intermediate transfer medium drum 13
Process units 20a, 20b, 20c, 20d, middle
A power supply 16 for applying a transfer voltage to the intermediary transfer medium drum 13,
Transfers the toner image formed on the intermediate transfer medium drum 13
A secondary transfer device 18 for transferring the image onto the medium 5;
The transfer medium 5 is placed in the nip between the ram 13 and the secondary transfer device 16.
Is provided. Electrophotographic process units 20a, 20
b, 20c, and 20d represent cyan, magenta, and i, respectively.
Image carriers 1a, 1b, 1c, 1d for each color of yellow and black
According to the image information on the image carriers 1a, 1b, 1c, 1d.
Irradiating the exposed exposure light 11a, 11b, 11c, 11d
An electrostatic charge is applied on the photoreceptor layer on the surfaces of the carriers 1a, 1b, 1c, 1d.
Four sets of scanning exposure devices (not shown) for forming latent images, and
These electrostatic latent images are developed to form image carriers 1a, 1b, 1c, 1
d. Form toner images corresponding to the above colors on the photoreceptor layer on the surface.
Four developing devices 12a, 12b, 12c, 12d to be formed
And four charging devices (not shown) and four cleaning devices
And a recording device (not shown). These four sets
Electrophotographic process units 20a, 20b, 20c,
20d is an intermediate transfer at each predetermined transfer position
Each color toner image can be sequentially transferred onto the medium drum 13.
As shown in FIG. As described above, in this embodiment, the image carrier 1
a, 1b, 1c, 1d formed on the photoreceptor layer on the surface
The toner image corresponding to the color is superimposed on the intermediate transfer medium drum 13.
After the primary transfer, a large number of
The heavily primary-transferred color toner image is transferred to the secondary transfer device 16.
Is secondary-transferred onto the transfer medium 5. This implementation
In the embodiment, four image carriers 1a, 1b, 1c, 1d
Are arranged side by side on an arc on the outer periphery of the intermediate transfer medium drum 13.
ing. In this embodiment, the intermediate transfer medium drum
Reference numeral 13 corresponds to the transfer medium of the present invention.
The image carriers 1a, 1b, 1c, 1d described above are used for the image for the first color.
The transfer of the image carrier 1d for the final color from the transfer position of the carrier 1a
The distance L between the transfer positions to the transfer position (that is, the transfer medium travel
Distance) is the transfer medium transport device (the intermediate transfer medium drum 1).
The distance between the two fulcrums supporting 3) (corresponding to W in FIG. 1)
The image forming apparatus is arranged so that
You. In this case, from the transfer position of the image carrier 1a for the first color
Transfer position distance to transfer position of image carrier 1d for final color
The separation L, ie, the transfer medium travel distance, is
The value measured along the outer periphery of the program 13 may be used. What
The distance G between the transfer positions of each image carrier is not necessarily the same distance.
You don't have to do with each toner
Set the distance suitable for image formation, and adjust the toner
-Make sure that the images are correctly superimposed on the intermediate transfer medium.
The write timing for each color
No. In each of the embodiments described above, the electrophotographic
An example where the process unit is provided for four colors is shown.
However, the present invention is not limited to four-color image formation,
Can be applied when forming multi-color images using
Wear. [0050] As described above, the color image of the present invention is
According to the image forming apparatus, the transfer position of the image carrier for the first color is determined.
From the transfer position to the transfer position of the image carrier for the final color
Is less than the distance between the two fulcrums supporting the transfer medium transport device.
This effectively eliminates color shift caused by skew of the transfer medium.
Can be reduced. This effect is due to the oblique
The cause of the line is a shift in the transfer direction of the transfer medium transfer device,
Misalignment of the body alignment direction and misalignment of the scanning exposure device
The same applies to any of these cases. According to the present invention, color misregistration is detected and compensated.
Inexpensive and compact color because no control device is required
An image forming apparatus can be realized. In addition, the first color
Of image carrier for final color from transfer position of image carrier for image
Support the transfer medium transport device by the distance between the transfer positions to the position.
By setting the distance between the two fulcrums to less than half,
Even if the cause of color shift exists, the color shift is below the allowable level
To obtain high-quality color images
be able to.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic view showing a first embodiment of a color image forming apparatus of the present invention. FIG. 2 is a schematic diagram illustrating the occurrence of color misregistration in the first embodiment. FIG. 3 is a schematic diagram illustrating the occurrence of color misregistration in a second embodiment. FIG. 4 is a schematic diagram illustrating the occurrence of color misregistration in a third embodiment. FIG. 5 is a schematic view showing a fifth embodiment of the color image forming apparatus of the present invention. FIG. 6 is a plan view showing a schematic configuration of a conventional one-cycle type multi-transfer type color image forming apparatus. FIG. 7 is a side view illustrating a schematic configuration of a conventional one-cycle type multiple transfer type color image forming apparatus. FIG. 8 is a graph schematically showing the meandering and skew of the transfer medium. FIG. 9 is a schematic diagram illustrating a state in which a transfer medium is transported without skew and a transfer image is formed normally. FIG. 10 is a schematic diagram illustrating a state in which color misregistration occurs when the transfer direction of the transfer medium transfer device does not match the arrangement direction p of the image carriers and the arrangement direction s of the scanning exposure images. FIG. 11 is a schematic diagram illustrating a state in which color misregistration occurs when the arrangement direction of the scanning exposure device does not match the conveyance direction of the transfer medium conveyance device and the arrangement direction of the image carrier belt. DESCRIPTION OF SYMBOLS 1a, 1b, 1c, 1d Image carriers 2a, 2b, 2c, 2d Electrophotographic process units 3a, 3b Belt stretching rolls 4a, 4b Roll supporting side plate 5 Transfer medium 6 Transport belts 7a, 7b Unit Mounting side plate 8 Transfer device 9 Transfer medium transport device 10 Transfer medium supply rolls 11a, 11b, 11c, 11d Scanning exposure devices 12a, 12b, 12c, 12d Developing device 14 Fixing devices 15a, 15b Roll supporting side plate 16 Power supply 17 Unit mounting Side plate 18 Secondary transfer devices 21a, 21b, 21c, 21d Scanning exposure devices 22a, 22b, 22c, 22d Developing devices 25a, 25b, 25c, 25d Scanning exposure images 26a, 26b, 26c, 26d Transfer positions 27a, 27b, 27c , 27d Transfer positions 28a, 28b, 28c, 28d, 29a, 29 , 2
9c, 29d Transfer image

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/16 G03G 15/01 114 G03G 21/14

Claims (1)

(57) Claims 1. A plurality of image carriers that rotate in a predetermined direction and carry a toner image on a surface, and based on image data provided in each of the plurality of image carriers. A toner image forming means for forming toner images of different colors on each image carrier, and a predetermined transfer medium for receiving the transfer of the toner images on the plurality of image carriers; Sequentially transferring to a transfer position, a transfer medium transport device in which both ends in a direction intersecting the movement direction of the transfer medium are supported, and transferring the toner image on the image carrier to the transfer medium at each of the transfer positions; Transfer means corresponding to each of the image carriers, through a process of sequentially transferring the toner image on the image carrier from the first color to the final color on the transfer medium,
Finally, in a color image forming apparatus that forms a color image fixed on a predetermined image recording medium, a transfer position of a first color image carrier among the plurality of image carriers is transferred to a final color image carrier. The plurality of image carriers are arranged such that a distance between transfer positions of the image carriers to the transfer position is equal to or less than a distance between two fulcrums in a direction intersecting a moving direction of the transfer medium that supports the transfer medium transport device. Tomo and placed formed by
The plurality of image carriers and the transfer medium transport device,
A color image forming apparatus, which is pivotally supported by a pair of common side plates .