JPH08220832A - Color image forming device - Google Patents

Abstract

PURPOSE: To prevent the fluctuation of color registration disturbing uniformity by eliminating the temperature dependency of color image quality, to restrain the rise of cost and to prevent the deterioration of color image quality by simple constitution. CONSTITUTION: This device is provided with a belt speed comparison part 29 comparing the speed signal of a belt speed detecting sensor 28 with previously set belt average speed and outputting a matching signal when they match with each other, an image write control part 31 controlling an image write part 9 based on reference time which is set by counting the time from outputting the reference position detection signal of a belt reference position detection sensor 22 till outputting the coincidence signal, and a memory 30 storing the belt average speed and the reference time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus, and more particularly to a color image forming apparatus for improving image quality by reducing a positional error when superposing color toner images on an image carrying belt.

[0002]

2. Description of the Related Art Conventionally, various types of color image forming apparatuses have been proposed, but a belt-shaped or drum-shaped photosensitive member is exposed by an optical signal (laser light) modulated according to a color image signal. By doing so, an electrostatic latent image is formed on the surface, and the color toner image obtained by developing the formed electrostatic latent image with the corresponding color toner is transferred to recording paper directly or through an intermediate transfer member. It is common in the configuration to be performed.

In such a color image forming apparatus, a photoconductor,
A belt is used for an image carrier such as an intermediate transfer member and a recording paper transporting device for transporting recording paper, and the belt is driven by a plurality of rolls.

When such a belt is driven by a plurality of rolls, if the roll itself is eccentric, or if a driving force transmitting member such as a gear for driving the roll is eccentric, speed fluctuations corresponding to the rotation frequency of the roll will occur. Occurs in

FIG. 9 shows a roll for driving a belt (hereinafter,
The speed fluctuation of the belt caused by the eccentricity of the driving roll) is shown, and the belt has speed fluctuation corresponding to the rotation frequency of the roll.

For example, when a belt is used as the image carrier, a speed error of the belt causes a position error of the color toner images to be color-superposed, which causes a problem of deterioration of image quality. .

FIG. 10 shows the positional error of the color toner image caused by the speed fluctuation of the belt. At the end of the first color (curve R ₁ ), there is a difference in the circumferential length between the belt and the roll, and the second color ( A position error occurs in the belt and the roll at the writing start point of the curve R ₂ ).

FIG. 11 shows the first color and the second color in FIG.
It shows the writing start points of the colors in agreement,
The registration fluctuation that occurs between the first color toner image and the second color toner image is represented by Δx, and is usually 0.1 to 0.
2 mm is generated. This registration variation includes a component that varies in one color image and a component that is substantially constant in one color image but varies between a plurality of color images. If the registration variation occurs between the color images, there is a problem that the uniformity of the color image quality cannot be obtained.

In order to prevent the deviation of the image caused by the difference in the peripheral length between the belt and the roll, the ratio of the peripheral length of the driving roller and the peripheral length of the intermediate transfer member is an integer.
A color image forming apparatus disclosed in Japanese Patent Laid-Open No. 199165;
The image forming apparatus disclosed in Japanese Patent Laid-Open No. 63-11965, in which the driving unevenness of the driving means and the cycle of the image forming medium are set to integral multiples, or the cycle of the drive shaft and the transfer member is set to integral multiples In addition, there is a transfer device disclosed in Japanese Patent Application Laid-Open No. 2-12271 in which the drive shaft and the transfer body are made to match in phase.

[0010]

However, according to the conventional color image forming apparatus, even if the peripheral length of the belt and the roll is set to an integral multiple, the peripheral length depends on the temperature dependence of the belt and the elongation caused by the change over time. It is unavoidable that a difference occurs, and as a result, a phase shift between the roll and the belt occurs, so that a registration fluctuation of the color toner images to be color-superposed occurs. Ideally, it is possible to select the material and devise the structure so that it is not affected by the temperature dependence or the change over time.
It increases costs and complicates the structure. Accordingly, it is an object of the present invention to provide a color image forming apparatus capable of eliminating the temperature dependence and preventing the variation of color registration which hinders the uniformity of color image quality.

Another object of the present invention is to provide a color image forming apparatus capable of suppressing an increase in cost and preventing deterioration of color image quality with a simple structure.

[0012]

SUMMARY OF THE INVENTION The present invention eliminates temperature dependence and prevents color registration fluctuations that hinder the uniformity of color image quality, suppresses cost increase, and provides a simple structure for color image quality control. In order to prevent deterioration, a reference position detecting means for detecting a reference position of the image carrying belt, a speed detecting means for detecting a speed of the image carrying belt, a speed detected by the speed detecting means and the image carrying belt The belt speed comparison means for detecting the timing at which the average speed matches, the holding means for holding the reference time from the detection of the reference position by the reference position detection means to the timing, and the reference position detection means After detecting the reference position, when the belt speed comparing means detects the timing, the first color image writing is executed and read from the holding means. To provide a color image forming apparatus having the image writing control means for executing an image writing 2 and subsequent colors on the basis of the reference time.

[0013]

According to the color image forming apparatus of the invention, when the reference position of the image carrying belt is detected by the reference position detecting means, the speed detecting means detects the speed of the image carrying belt based on the detection signal. The belt speed comparing means compares the speed signal of the image carrying belt detected by the speed detecting means with the average speed of the image carrying belt, and detects the timing when these match. At this timing, the image writing of the first color is executed. At the same time, the time between the reference position detection time and the coincidence timing detection time is held in the holding means as the reference time. Second
The writing of the image after the color is performed based on the reference time held by the holding means after the reference position of the image carrying belt is detected by the reference position detecting means.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A color image forming apparatus of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a first embodiment of a color image forming apparatus using an image bearing belt. This color image forming apparatus outputs an image input unit 1 that scans an original image and an image output that prints on recording paper based on an image signal that is scanned by the image input unit 1 and processed by an image processing unit (not shown). It is composed of a section 8.

The image input section 1 includes a lamp 3 for irradiating a document (not shown) placed on a transparent document table 2 with light.
It has reflecting mirrors 4 and 5 that reflect the reflected light from the original, a lens 6 that focuses the reflected light from the mirror 5, and a charge imaging device (CCD) 7 on which the light focused by the lens 6 is incident. The charge imaging device 7 simultaneously separates the incident light into R, G, and B signals and reads them.

The image output unit 8 converts the R, G and B signals obtained by the image input unit 1 into Y (yellow), M (magenta) and C signals.
IPS (Image Processing) (not shown) that separates and retains complementary colors of (cyan) and BK (black)
Image writing unit 9 which has a system) and which oscillates a laser beam modulated by a laser light source 9A based on image data obtained by performing image processing by IPS and deflects the laser beam by a polygon mirror 9B. A mirror 10 that reflects the laser light emitted from the portion 9 in the scanning direction, and a photosensitive drum 11 that is irradiated with the laser light reflected by the mirror 10.
And the Y, M, C, and BK toner developing machines in the circumferential direction 90
And a rotary type developing unit unit 12 which is arranged at an interval and rotates during development to supply toner corresponding to each color to the surface of the photoconductor drum 11. A charger is provided around the photoconductor drum 11. 13 and a photoconductor cleaner 14 for removing the toner remaining on the photoconductor drum 11 are arranged.

Below the photosensitive drum 11, the intermediate transfer belt 15 onto which the toner image formed on the drum surface is transferred.
Is provided, and the intermediate transfer belt 15 is a drive roll 1
7 and is supported by support rolls 18 and 19.

Around the intermediate transfer belt 15, a primary transfer corotron 20 provided at a primary transfer point, and a belt cleaner 21 provided adjacent to the driving roll 17 are provided.
Belt reference position detection sensor 22 for detecting a mark 27 (described later) provided at the reference position of the intermediate transfer belt 15.
A belt speed detection sensor 28 for detecting the speed of the intermediate transfer belt 15, and a secondary transfer roll 25 provided at a secondary transfer point where the support roll 19 is located,
A paper tray 23 that supplies paper by a paper feed roll 24 is provided upstream of the secondary transfer point, and a fixing device 26 is provided downstream thereof.

FIG. 2 is a partial perspective view of the intermediate transfer belt 15. A mark 27 having a reflectance different from that of the belt is provided on the side of the intermediate transfer belt 15, and the belt reference position detection sensor 22 has a mark 27. It is arranged so that the passage of can be detected. The belt speed detection sensor 28 detects the speed by irradiating the surface of the intermediate transfer belt 15 with laser light and receiving the reflected light.

FIG. 3 is a block diagram showing the control circuit of the image writing section 9. The speed signal of the belt speed detection sensor 28 is compared with a preset average speed of the belt, and when they match, a coincidence signal is output. The time from the output of the reference position signal of the belt speed comparison unit 29 and the belt reference position detection sensor 22 to the output of the coincidence signal is measured as a reference time, and the image writing unit 9 is based on this reference time. And an image writing control unit 31 for controlling the speed and a memory 30 for storing the average belt speed and the reference time.

The writing control process of the color image forming apparatus of the present invention will be described below with reference to the flow chart shown in FIG.

When the image forming start is instructed, the image input unit 1
, A document (not shown) placed on the document table 2 is illuminated by the lamp 3, and the reflected light is reflected by the reflecting mirrors 4.
The light is focused by the lens 6 via the lens 5 and is incident on the CCD 7.

In the image output section 8, the intermediate transfer belt 15 is driven along with the start of image formation, and when the belt reference position detection sensor 22 detects the mark 27 on the intermediate transfer belt 15, the image writing control section 31 receives the reference position. The detection signal is output. On the other hand, the image writing control unit 31 resets the reference time t ₁ which is the writing start timing of the color toner image when the control is started. The reference time t ₁ can also be defined as a reference position and is for specifying the image writing reference position on the belt.

The belt speed comparison unit 29 reads the average speed of the intermediate transfer belt 15 stored in the memory 30 and compares the speed with a speed detection signal output from the belt speed detection sensor 28. This speed comparison continues while the control counter (not shown) is ON. The control counter is turned on when the belt reference position detection sensor 22 detects the mark 27.

The speed difference between the average speed of the intermediate transfer belt 15 and the speed detection signal output from the belt speed detection sensor 22 becomes 0 (zero), and a coincidence signal is output. The time from the output of the detection signal to the output of the coincidence signal is stored in the memory 30 as the reference position t ₁ . At the same time, the image writing control device 31 outputs a first color writing start signal to the image writing unit 9. The control counter is turned off by the output of the coincidence signal.

On the other hand, when the speed difference between the average speed of the intermediate transfer belt 15 and the speed detection signal output from the belt speed detection sensor 22 is not 0 (zero), the control counter is turned on.
Then, the operation of comparing the belt speed detection sensor 28 and the average speed of the intermediate transfer belt 15 is repeated by continuing the time measurement at t = t + 1.

The image writing section 9 outputs a laser beam corresponding to the color image of the first color from the laser light source 9A, deflects this laser beam in the scanning direction by the polygon mirror 9B, and then reflects it by the mirror 10. The electrostatic latent image is formed by irradiating the photoconductor drum 11 charged by the charger 13 with the light. The electrostatic latent image is developed by the corresponding color toner in the developing unit 12 located in the rotation direction of the photoconductor drum 11, and the developed first color toner image is provided with the primary transfer corotron 20. It is conveyed to the transfer point and transferred to the intermediate transfer belt 15.

When the image writing of the first color is completed (n =
n + 1), when the mark 27 of the intermediate transfer belt 15 is detected by the belt reference position detection sensor 22 and the reference position detection signal is output, the image writing control device 31 causes the image writing control device 31 to store in the memory 3.
The reference time t ₁ stored in 0 is read, and this time t ₁
When has passed, a control signal is output to the image writing unit 9. The image writing unit 9 starts the image writing of the second color based on the output from the image writing control device 31. The control counter during counting of the reference time t ₁ is ON, and when t = t ₁ , it becomes O
Become FF. Thereafter, the same operation is repeated up to the fourth color so that the color toner images are superimposed.

FIG. 5 shows a timing chart in the first embodiment. After the mark 27 on the intermediate transfer belt 15 is detected by the belt reference position detection sensor 22, a speed detection signal output from the belt speed detection sensor 28. And the intermediate transfer belt 15 stored in advance in the memory 30.
The average speed is compared with the average speed, and the timing at which they match is detected and set as the reference time t ₁ . The intermediate transfer belt has a velocity fluctuation of amplitude 2aω. Here, a is the roll eccentricity amount, and ω is the angular velocity. For the writing of the second color, the writing of the first color is completed, and the mark 27 on the intermediate transfer belt 15 indicates the belt reference position detection sensor 22.
It is started after the reference time t ₁ has elapsed after being detected by.

FIG. 6 shows another embodiment of the speed detecting means. Instead of detecting the belt speed by the belt speed detecting sensor 28, for example, the rotating shaft 1 of the drive roll 17 is used.
The encoder 32 is attached to 7A, and this encoder 32
An angular velocity detection signal of the rotating shaft 17A detected by
The average angular velocity of the rotating shaft 17A, which is previously stored in the memory 30, may be compared.

Further, a mark is previously provided on the rotary shaft 17A,
Furthermore, the correlation between the axial position of the rotating shaft 17A and the belt speed fluctuation is obtained and stored in the memory 30, the mark of the rotating shaft 17A is detected by the sensor, and the mark 27 of the intermediate transfer belt 15 is detected.
Is detected by the belt reference position detection sensor 22, the timing at which the speed of the intermediate transfer belt becomes the average speed is obtained from the detection result of the mark on the rotary shaft 17A and the correlation value of the memory 30, and the rotary shaft 17A corresponding to the timing is obtained. The predetermined position may be set as the writing reference position.

As a result, the structure of the sensor, the arithmetic circuit, etc. can be simplified and the cost can be reduced.

FIG. 7 shows the second embodiment of the present invention.
A flow chart of the write control process is shown
The belt reference position detection sensor 22 and the belt speed detection sensor.
Sensor 28, belt speed comparison unit 29, reference time t₁Remember
The reference position of the memory 30 and the drive roll 17
Drive roll having a roll reference position detection sensor 33
The belt speed comparison unit 29 determines the belt speed while 17 rotates once.
From the speed detection signal output from the degree detection sensor 28
Maximum speed V of transfer belt 15_maxAnd time t at that time
_maxAnd the minimum speed V_minAnd time t at that time_minSeeking
This t_maxAnd t _minTo intermediate time t_int=
(T_max+ T_min) / 2, and the intermediate time t_int
At the time t from the belt reference position detection_maxOr t_minWell
Time [t + (t_max
+ T_min) / 2] for writing reference time t ₁Set as
Then, it is stored in the memory 30. After this, write the first color
Initialize only timing (0 → t), reference position detection signal
Is output after the reference time t₁When the first color has passed
Start writing the eyes.

The writing control process for the second and subsequent colors is as follows:
It is repeated until the fourth color based on the write reference time t ₁ stored in the memory 30. This repetition is performed in the same way as in the first embodiment.

This makes it possible to deal with the case where the average speed of the intermediate transfer belt cannot be specified due to a plurality of factors that cause a difference in circumferential difference between the roll and the intermediate transfer belt.

FIG. 8 shows a flow chart of the writing control process in the third embodiment of the present invention, in which the belt speed detecting sensor 28 and the belt speed comparing unit 2 are provided.
9, a memory 30 for storing the reference time t ₁ and a roll reference position detection sensor 33 for detecting the reference position of the drive roll 17, and the belt speed detection sensor 28 is an intermediate transfer during one rotation of the drive roll 17. The speed of the belt 15 is continuously detected, and the detected speeds are accumulated. The time t required for one rotation of the drive roll is calculated by accumulating the detected speeds thus accumulated.
The average speed V of the intermediate transfer belt 15 is divided by
Calculate ₀ . This average speed V ₀ is stored in the memory 30. Next, when the mark 27 on the intermediate transfer belt 15 is detected, the belt speed detection sensor 28 detects the speed of the intermediate transfer belt 15, and the detected speed is the average speed V.
_The timing matching ₀ is detected and set as the reference time t ₁ ,
This is stored in the memory 30 and the first writing is started. The following control process is the same as that of the first embodiment, and thus duplicated description will be omitted.

This makes it possible to deal with the case where there is a concern that the average speed of the intermediate transfer belt may be affected by changes over time or changes in temperature environment and the like.

In the writing control process described above, when the image formation start is instructed, the reference time t ₁ which is the writing start point of the color toner image is reset. For example, the reference time t ₁ is stored in the memory without being erased. Then, when the image formation start is instructed later, a new reference time t ₁ may be set with reference to the reference time t ₁ stored in the memory. As a result, the time required to set the write start point can be shortened.

In the present embodiment, the writing control process of the color image forming apparatus using the intermediate transfer belt as the image carrying belt has been described, but the present invention is not limited to this, and for example, the writing control process to the photoconductor belt. Can also be applied to. Further, in addition to the image carrier, the present invention can be applied to an image output device using a belt as a paper conveying device.

[0041]

As described above, according to the color image forming apparatus of the present invention, writing is performed at the timing when the speed detection result obtained by detecting the speed of the image carrying belt and the average speed of the image carrying belt match. Because I tried to run it,
It is possible to prevent the variation of color registration that obstructs the uniformity of color image quality by eliminating the influence of temperature dependence and change over time, and to suppress the increase in cost and prevent the deterioration of color image quality with a simple configuration. it can.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a color image forming apparatus that uses an intermediate transfer belt as an image carrier according to a first embodiment of the present invention.

FIG. 2 is an explanatory view showing a partial perspective view of an intermediate transfer belt 15.

FIG. 3 is a block diagram showing an image writing control circuit.

FIG. 4 is a flowchart of an image writing control process in the first embodiment.

FIG. 5 is a timing chart in the first embodiment.

FIG. 6 is an explanatory view showing another embodiment of the speed detecting means.

FIG. 7 is a flowchart of an image writing control process in the second embodiment.

FIG. 8 is a flowchart of an image writing control process in the third embodiment.

FIG. 9 is an explanatory diagram showing belt speed fluctuations.

FIG. 10 is an explanatory diagram showing a positional error of a color toner image caused by a belt speed fluctuation.

11 is an explanatory diagram of a positional error of a color toner image in which the writing start points of the first color and the second color in FIG. 10 are made to coincide with each other.

[Description of sign]

 1, image input unit 2, platen 3, lamp 4, reflection mirror 5, reflection mirror 6, lens 7, charge imaging device 8, image output unit 9, image writing unit 9A, laser light source 9B, polygon mirror 10, Mirror 11, photoconductor drum 12, developer unit 13, charger 14, photoconductor cleaner 15, intermediate transfer belt 17, drive roll 17A, rotating shaft 18, support roll 19, support roll 20, primary transfer corotron 21, belt Cleaner 22, belt reference position detection sensor 23, paper tray 24, supply roll 25, secondary transfer roll 26, fixing device 27, mark 28, belt speed detection sensor 29, belt speed comparison unit 30, memory 31, image writing control Part 32, encoder 33, roll reference position detection sensor

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Kozo Tagawa 2274 Hongo, Ebina City, Ebina, Kanagawa Prefecture Fuji Xerox Co., Ltd.Ebina Works (72) Inventor Kimito Omori 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd. Ebina Co., Ltd. In-house (72) Inventor Susumu Kobayashi 2274 Hongo, Ebina-shi, Kanagawa Fuji Xerox Co., Ltd.In Ebina Works (72) Inventor Junichi Murakami 2274, Hongo, Ebina-shi, Kanagawa Fuji-Xerox Co., Ltd.

Claims (3)

[Claims] 1. A color image forming apparatus for forming a color image by superposing a plurality of color toner images on an image bearing belt supported by a plurality of rolls, a reference for detecting a reference position of the image bearing belt. Position detecting means, speed detecting means for detecting the speed of the image carrying belt, belt speed comparing means for detecting the timing at which the speed detected by the speed detecting means and the average speed of the image carrying belt match, After the reference position detecting means detects the reference position,
Holding means for holding a reference time until the timing; and, when the belt speed comparison means detects the timing after the reference position detection means detects the reference position, the first color image writing is executed, and A color image forming apparatus comprising image writing control means for executing image writing for the second and subsequent colors based on the reference time read from the holding means. 2. The color image forming apparatus according to claim 1, wherein the belt speed comparison unit sets a preset speed as the average speed. 3. The color image forming apparatus according to claim 1, wherein the belt speed comparing means compares the intermediate value between the maximum value and the minimum value detected by the speed detecting means with the average speed.