JP2001034030A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device where registration shift is accurately corrected, even in the case of the start time or the like when the temp. in the device is rapidly changed. SOLUTION: This image forming device 10 forms the image in plural colors by successively transferring images formed on plural photoreceptor drums 16 by the optical scanning device 12 and the developing device 14 onto an intermediate transfer belt 19. Moreover, the image forming device is provided with the computing device 35 computing the value of registration shift at the time of detecting a registration mark 42 by a registration mark detecting sensor 30, and a predictive computing device 50 computing a registration shift predictive value based on the predicted temp. of the intermediate transfer belt 19 by temp. sensors 32A and 32B, and moreover based on these computed result, the image formation timing by an optical scanning device 12 is corrected by a correcting device 52.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a laser beam printer and a digital copier,
The present invention relates to color shift correction of an image forming apparatus that forms a color image.

[0002]

2. Description of the Related Art Conventionally, a plurality of photosensitive drums (image carriers)
For example, Japanese Patent Application Laid-Open (JP-A) No. 1-14
Japanese Patent Application Laid-Open No. 2567 and Japanese Patent Application Laid-Open No. 61-2221764 are known. Hereinafter, description will be made with reference to FIG.

FIG. 7 shows a schematic configuration of a four-tandem (serial) type full-color laser beam printer. The image forming apparatus 100 includes an optical scanning device 12 as an image forming unit that is independently arranged for each color of cyan (C), magenta (M), yellow (Y), and black (K) in a frame 11. , A developing device 14, a photosensitive drum 16, an intermediate transfer belt 18 on which an image formed for each color is transferred, a belt driving roll 20, an intermediate transfer belt cleaner 22, and a transfer roll 24. Registration mark detection sensor 30
And a temperature sensor 32 and an arithmetic unit 34.

The optical scanning device 12 of each color modulates a laser beam in accordance with image data, deflects the laser beam by an optical deflector 36 comprising a laser beam irradiation device and a rotating polygon mirror (each not shown), and further deflects the mirror. Via 38, scanning exposure is performed on each photosensitive drum 16 whose surface is charged. As a result, an electrostatic latent image is formed on the photosensitive drum 16, and the electrostatic latent image is toner-developed (C, M, Y, K) into each color by each developing device 14 and is visualized.

The visualized image of each color is visualized at a predetermined timing from above each photosensitive drum 16 onto an intermediate transfer belt 18 (endless belt) which moves in the direction of arrow A in the figure by the driving force of a belt driving roll 20. Are sequentially transferred and superimposed, thereby forming a full-color image.

The color image is transferred from a transfer sheet 40 fed from a paper feed tray or an auxiliary tray (not shown).
The transfer paper 40 on which the color image is transferred electrostatically by the transfer roll 24 is subjected to a heat fixing process in an image fixing unit (not shown), and is discharged to an output tray (not shown). Further, the toner remaining on the intermediate transfer belt 18 without being transferred to the transfer paper 40 is removed by the intermediate transfer belt cleaner 22.

As described above, the four-tandem tandem-type image forming apparatus 100 forms the images of each color individually and continuously, sequentially transfers the images onto the intermediate transfer belt 18 and combines them in one process. Print processing.

However, since the superposition accuracy of each image at the time of this transfer affects the image quality, that is, the problem of registration deviation (color deviation) due to each image being superimposed and shifted from the normal transfer position. Therefore, improvements have been made to improve the transfer position accuracy.

Here, main types of the registration deviation will be described with reference to FIG.

FIG. 8 shows that the intermediate transfer belt 18 has an arrow A in FIG.
This schematically shows a state where the transfer position of black (K) is shifted with respect to yellow (Y) when moving in the direction.

FIG. 8A shows a state in which the Y and K images have been transferred to correct positions, and both lines having a line length L are located in parallel at an interval M.

FIG. 8B shows that the image of K with respect to Y is perpendicular to the direction of movement of the intermediate transfer belt 18 (hereinafter, referred to as “K”).
(Referred to as “X direction”).
This is a displacement called a margin. Here, the X margin is represented by “ΔX” in the figure.

FIG. 8C shows a state in which the K image is shorter than a predetermined length, which is a positional deviation called a magnification deviation. Here, the X-direction magnification of the K image is represented by “a” in the figure.

FIG. 8D shows a state in which the K image is tilted, which is a positional shift called skew. Here, K
Is represented by “θ” in the figure.

FIG. 8E shows a state in which an image of K with respect to Y is transferred with a shift in the moving direction of the intermediate transfer belt 18 (hereinafter, referred to as "Y direction"). It is. Here, the Y margin is represented by “ΔY” in the figure.

One of the causes of the registration deviation is that the relative position between the optical scanning device 12 and the photosensitive drum 16 shown in FIG. 3 is deviated from a predetermined positional relationship. In addition to the initial mounting error of each block, expansion and contraction due to heat of the frame 11 supporting the optical scanning device 12, the photosensitive drum 16, the belt driving roll 20 (the intermediate transfer belt 18) and the like are caused. .

In the four-tandem type image forming apparatus as shown in FIG. 7, since the photosensitive drums are arranged in series, the installation distance between the photosensitive drums located at both ends is particularly small. It is a long configuration. Further, in the case of a configuration in which heating is performed at a high temperature in the fixing process during printing, the amount of displacement in the arrangement direction of the photosensitive drums, that is, the longitudinal direction (Y direction) of the intermediate transfer belt 18 is affected by this heat. Is thought to be larger. Therefore, the deviation amount of the Y margin (Δ
Y) becomes larger than the X margin or the like.

Further, the main cause of the Y margin is not only the relative displacement between the optical scanning device 12 and the photosensitive drum 16 described above, but also the driving speed unevenness of the intermediate transfer belt 18 and the like.

The driving unevenness of the intermediate transfer belt 18 is caused by driving the belt driving roll 20 (not shown), a drive motor (not shown), the eccentricity of the belt driving roll 20 itself, and a driving force from the driving motor to the belt driving roll 20. This is caused by rattling (backlash) of the transmitting gear.

In view of the above, conventionally, the following reduction measures have been taken against registration deviation due to these factors.

First, feedback control is performed on the eccentricity and the like of the belt drive roll 20 and its drive motor by monitoring the rotation speed and the like of the drive motor using an encoder or the like. The unevenness is reduced.

On the other hand, the optical scanning device 12 and the photosensitive drum 16
With respect to the transfer deviation due to the relative position deviation, a registration mark 42 (toner image) for detecting the position deviation of each image is transferred from each photosensitive drum 16 onto the intermediate transfer belt 18 and formed. Then, the registration mark 42 of each color is read by the registration mark detection sensor 30. Based on the information obtained by the mark detection, the arithmetic unit 34 calculates the displacement of the photosensitive drum 16 and the like, and corrects the position of the optical scanning device 12 and the scanning timing of the laser beam to thereby transfer the transfer position of each color image. Increases accuracy.

The above is the method of reducing the registration deviation in a steady state, that is, when there is no change over time due to heat or the like.

However, when the temperature inside the machine rapidly rises, for example, when the printer machine is started up or when the machine is not used for a long time, or when the machine is used for a long period of time, each part in the machine changes over time due to a change in heat. . Therefore, as described above, especially in the case of the quadruple tandem type in which the change in the Y margin due to heat is large, the method of reducing the registration deviation alone cannot always sufficiently correct the temporal change in the Y margin.

On the other hand, for example, Japanese Patent Application Laid-Open No. 63-307
481, JP-A-1-96665, JP-A-2-304
465, JP-A-8-286566, JP-A-3051
No. 08 proposes a measure against a change with time due to heat.

JP-A-63-307481, JP-A-Hei.
No. 96665 is to detect the temperature inside the machine such as a frame by a temperature sensor and adjust the irradiation position of the optical member and the writing timing of the optical writing means according to the difference between the initial reference temperature and the current temperature.

However, simply correcting the misregistration of each part in the apparatus based on the temperature change, when there are a large number of high-temperature heat sources such as an image fixing unit and a drive motor, the heat interferes with each other, thereby causing each part to interfere with each other. Temperature changes in a complicated manner,
Variations occur in the relative position shift and the like due to the temperature change of the portion that affects the registration shift.

Therefore, even if the initial reference temperature or the current temperature of a specific location in the machine shows the same value, the registration deviation at that time does not always become the same amount, and it is difficult to perform accurate correction.

Further, JP-A-2-304465, JP-A-8-286566, and JP-A-305108 have the registration mark detection sensor 30, the temperature sensor 32, the arithmetic unit 34 and the like shown in FIG. The temperature in the apparatus is detected, and when the temperature change exceeds a certain level, a registration mark is formed to correct the positional deviation.

In this case, even if the positional deviation of each part in the apparatus varies due to the thermal interference of the heat source, the total positional deviation at that time can be measured by detecting the registration deviation. For this reason, misregistration correction within a short period of time during which the registration mark is formed and detected can be accurately performed.

However, for example, when the equipment is initially started in a low-temperature environment, the temperature rises more rapidly than in a normal-temperature environment. Therefore, if the correction is performed based on the registration deviation at the time of detection, the temperature must be corrected. However, there is a problem that the correction cannot follow the shift amount that changes rapidly depending on the temperature, and the correction up to such a temperature change is not considered.

[0032]

SUMMARY OF THE INVENTION In consideration of the above fact, the present invention provides an image forming apparatus capable of accurately correcting a registration error even at the time of startup when the temperature in the apparatus changes rapidly. That is the task.

[0033]

According to a first aspect of the present invention, there is provided an image forming apparatus comprising: a plurality of image carriers arranged in a housing; a light beam modulated according to an image; A plurality of optical scanning means for forming a latent image on each of the image carriers by scanning, a plurality of developing means for developing each latent image with toner to form a visible image of each color; An intermediate transfer member on which a visible image is sequentially transferred from each of the image carriers to form a composite image, and a registration mark formed on the image carrier at a predetermined timing and transferred to the intermediate transfer member are detected. Mark detection means, calculation means for calculating the value of registration deviation of the composite image from the detection signal of the registration mark by the mark detection means, and temperature measurement means for measuring the temperature in the housing, An image forming apparatus comprising: a prediction value calculation unit configured to calculate the predicted value of the registration deviation based on a temperature measured by the temperature measurement unit; and a registration deviation value calculated by the calculation unit and the predicted value calculation unit. Correction means for correcting the formation position of each latent image based on the calculated registration deviation predicted value.

That is, in the present invention, a plurality of image carriers are arranged side by side in the housing, and the light deflector of the light scanning means corresponding to each image carrier scans each image carrier with a light beam. By doing so, latent images are respectively formed. Each of the latent images is developed with toner by developing means corresponding to each image carrier to become a visual image of each color, and each of the visual images is sequentially transferred from each image carrier to the intermediate transfer body to form a plurality of latent images. An image composed of colors (synthesized image) is formed.

Here, the calculating means calculates the value of the registration deviation in the composite image based on the detection signal when the registration mark on the intermediate transfer member is detected by the mark detecting means.

The predicted value calculating means calculates a predicted value of a registration shift in the composite image based on the measured temperature when the temperature in the housing is measured by the temperature measuring means. The predicted value of the registration deviation is a value obtained by calculating a change amount of the registration deviation depending on the temperature change based on the degree of the temperature change.

The amount of registration deviation change due to temperature change is usually unique to each apparatus, and can be set by a function or the like, for example, by examining the relationship in advance by measurement or the like. Thus, when the temperature changes at a certain rate, it is possible to calculate the registration deviation prediction value based on the degree of change in the temperature.

The correcting means corrects the formation position of each latent image formed on each image carrier based on the predicted value of the registration deviation and the registration deviation value calculated by the calculating means.

Therefore, even when the temperature inside the housing rises rapidly, for example, when the apparatus is started up, the registration deviation can be corrected accurately.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the correction of the formation position of each of the latent images is performed by using the light scanning unit to start irradiation of the light beam and the light deflection. It is characterized by adjustment with the phase of the vessel.

According to the second aspect of the present invention, when the correction of the formation position of each latent image is the adjustment of the light beam irradiation start timing by the light scanning means, the light beam for scanning the image carrier is moved in the main scanning direction (X ), The X margin of the registration deviation can be corrected.

Similarly, when the latent image formation position is corrected by adjusting the phase of the optical deflector, the Y margin can be corrected by shifting the light beam in the sub-scanning direction (Y direction). .

According to a third aspect of the present invention, in the image forming apparatus of the first aspect, a plurality of the temperature measuring means are provided.

That is, in the third aspect of the present invention, since a plurality of temperature measuring means for measuring the temperature inside the housing are provided,
Temperature information can be obtained at a plurality of locations in the housing, and a more accurate average temperature and the like can be obtained even when temperature variations in the housing are large. Further, when the correcting means corrects the position of forming the latent image on each image carrier, it is possible to adjust the latent image forming position for each image carrier in accordance with the variation in temperature, thereby further improving the accuracy. Correction becomes possible.

According to a fourth aspect of the present invention, in the image forming apparatus according to the first or third aspect, the temperature measuring means is configured to transfer the respective visible images from the respective image carriers to the intermediate transfer member. It is characterized in that it is arranged in the vicinity of a transfer position to be transferred.

In other words, according to the fourth aspect of the present invention, since the temperature measuring means is disposed near the transfer position where each visual image is transferred from each image carrier to the intermediate transfer member, the image is transferred onto the intermediate transfer member. It is possible to detect the thermal expansion and contraction of the member around the transfer position, which affects the positional deviation when the transfer is performed.

According to a fifth aspect of the present invention, in the image forming apparatus according to the fourth aspect, the temperature measuring means measures the temperature of the intermediate transfer member instead of the temperature in the housing. I have.

That is, according to the fifth aspect of the present invention, since the temperature measuring means measures the temperature of the intermediate transfer member instead of the temperature in the housing, the thermal expansion and contraction of the intermediate transfer member can be directly detected.

According to a sixth aspect of the present invention, in the image forming apparatus of the first aspect, the registration mark is formed at a position on the intermediate transfer body that does not overlap with the composite image. And

That is, in the sixth aspect of the present invention, the registration mark is formed at a position that does not overlap with the composite image on the intermediate transfer member, so that registration deviation can be detected even during normal image formation.

According to a seventh aspect of the present invention, in the image forming apparatus according to the first or sixth aspect, the registration mark is formed near an end of the intermediate transfer body. .

That is, since the registration mark is formed near the end of the intermediate transfer member, the X margin due to thermal expansion and contraction of the intermediate transfer member and the housing can be detected with high accuracy.

According to an eighth aspect of the present invention, in the image forming apparatus according to the seventh aspect, a plurality of the registration marks are formed on a line substantially orthogonal to a moving direction of the intermediate transfer member. A plurality of registration marks are arranged corresponding to each of the plurality of registration marks.

That is, in the invention of claim 8, a plurality of registration marks are formed on a line substantially orthogonal to the moving direction of the intermediate transfer member, and the mark detecting means is arranged corresponding to each of the plurality of registration marks. Therefore, the X margin can be detected with higher accuracy.

Furthermore, if registration marks are formed at both ends in the width direction (X direction) of the intermediate transfer body, the positional deviation of both ends in the moving direction of the intermediate transfer body, that is, the inclination in the width direction is detected. This can be used for skew correction information for misregistration.

According to a ninth aspect of the present invention, in the image forming apparatus of the first aspect, the registration deviation is calculated based on a plurality of detection results by the mark detecting means. .

In other words, in the ninth aspect of the present invention, the registration deviation is calculated based on the detection results of the mark detection means a plurality of times, and thus is caused by eccentricity of the image carrier, uneven thickness of the intermediate transfer body, and the like. It is possible to remove a fluctuation component due to a position shift having a relatively short cycle change.

According to a tenth aspect of the present invention, in the image forming apparatus of the first aspect, the predicted value of the registration deviation is calculated based on a plurality of measurement results by the temperature measuring means. And

According to the tenth aspect of the present invention, the predicted value of the registration deviation is calculated based on the results of a plurality of measurements made by the temperature measuring means. Even in such a configuration, a more accurate registration deviation prediction value is obtained.

According to an eleventh aspect of the present invention, in the image forming apparatus according to the first aspect, the mark detecting means is a reflection type sensor.

That is, according to the eleventh aspect of the present invention, in the intermediate transfer member usually made of a transparent material, a transmission type sensor is used for detecting a registration mark. Here, a reflection type sensor is used as the mark detecting means. This makes it possible to detect a registration mark other than a transparent material. Therefore, the range of selection of the material of the intermediate transfer member is widened.

[0062]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an image forming apparatus 10 (four-tandem image forming apparatus) according to an embodiment of the present invention. In the image forming apparatus 10, the same components as those described in the conventional image forming apparatus 100 (FIG. 7) are denoted by the same reference numerals.

The image forming apparatus 10 includes:
The optical scanning device 12, the developing device 14, the photosensitive drum 16 and the intermediate transfer belt 19, the belt driving roll 20, the intermediate transfer belt cleaner 22, and the transfer roll 24 for each of the colors cyan, magenta, yellow, and black are respectively provided. A registration mark detection sensor 30 for detecting a registration mark formed on the intermediate transfer belt 19; temperature sensors 32A and 32B for measuring the temperature in the frame 11; 35,
A predicted value calculation device 50 and a correction device 52 are provided.

The photosensitive drums 16 are arranged in the order of cyan, magenta, yellow, and black from the upstream side in the moving direction of the intermediate transfer belt 19.
Accordingly, the respective color images formed on the respective photosensitive drums 16 are transferred onto the intermediate transfer belt 19 in the arrangement order.

The intermediate transfer belt 19 has a belt surface made of a black material having a low reflectance. The registration mark 42 formed on the intermediate transfer belt 19 has a reflectance higher than that of the black belt surface. Are formed with colors such as yellow, magenta, and cyan.

It should be noted that the material color of the intermediate transfer belt 19 may be any color that reduces the reflectance with respect to the color of the registration mark, and is not limited to black.

FIG. 2 shows the registration marks formed on the intermediate transfer belt and the positional relationship between the registration mark detection sensors.

Registration marks 42A, 42B
Is the moving direction of the intermediate transfer belt 19 (the direction of arrow A in the figure)
Are formed on both ends in the width direction on a line substantially orthogonal to the image forming portion and outside the image forming portion 19A of the intermediate transfer belt 19.

Registration mark detection sensor 30
A, 30B are the registration marks 42A,
42B.

As a result, it is possible to detect a registration deviation even during normal image formation, and it is not necessary to interrupt the image formation by providing an operation mode or the like dedicated to position deviation correction, and to achieve high productivity by an interlocking operation with the image formation. Is possible.

The registration mark detecting sensors 30A and 30B are reflection type sensors, for example, irradiating the intermediate transfer belt 19 with infrared light and detecting the reflected light from the registration marks 42A and 42B with a photodiode. To take the form.

The signals detected by the photodiodes are signals having different levels due to the difference between the reflectance of the registration marks 42A and 42B and the reflectance of the intermediate transfer belt 19. For example, the mark detection unit outputs Hi and the non-detection unit outputs Low. TTL signals can be obtained. Such a mark detection signal is input to the arithmetic unit 35.

On the other hand, the temperature sensors 32A and 32B are connected to the intermediate transfer belt 19 of the photosensitive drum 16 (here, Y and K).
It is arranged in the vicinity of the transfer position to the printer.

As the temperature sensors 32A and 32B, it is desirable to use a radiation type thermometer (non-contact type) which can measure the surface temperature of the intermediate transfer belt 19 and does not damage the surface of the intermediate transfer belt 19. However, a contact type thermocouple or the like may be used due to a problem such as cost.

The temperature information measured by the temperature sensors 32A and 32B is input to the arithmetic unit 35 and transmitted to the predicted value arithmetic unit 50.

Next, how the positional deviation due to temperature changes over time will be described in detail.

FIG. 3 shows an image forming apparatus 10 according to this embodiment.
2 shows an example in which a change from the initial value of the Y margin during continuous printing is measured when the positional deviation is not corrected. What is plotted in the figure is the Y margin of each color on the basis of cyan. The vertical axis in the figure is the Y margin, and the positive and negative signs indicate the direction of deviation of the Y margin. The horizontal axis in the figure is the number of prints (cycle).

From the measurement results, the Y margin was determined for each color.
The change is the largest at the start of printing, and gradually becomes saturated.

Note that the Y margin here is shifted to the minus side, which is similar to the state shown in FIG.
This indicates that the position is shifted from the normal position in the direction of delay. Therefore, this change in the Y margin is caused by
It is considered that the portion affected by the heat expanded due to the rise in the temperature inside 1. For this reason, in the black where the position of the photosensitive drum 16 is farthest from cyan, the degree of change in the Y margin is the largest.

FIG. 5 shows a simulation result when the Y margin is continuously corrected using the result. From the figure, it can be seen that the displacement correction cannot follow the change of the Y margin at the start of printing (for example, in the range of about 2 to 10 cycles).

FIG. 4 shows the relationship between the change in the Y margin in FIG. 3 and the temperature measurement result of the intermediate transfer belt 19 at that time. From this figure, it can be seen that there is a high correlation between the change in the Y margin and the temperature of the intermediate transfer belt 19 for each color.

From these results, the next positional deviation can be predicted by including a function term of the difference between the temperature of the previous cycle and the current temperature in the correction amount during the positional deviation correction.

In this embodiment, the Y margin at the nth cycle is Y (n), the temperature of the intermediate transfer belt 19 at that time is T (n), and the temperature at the (n-1) th cycle is T (n-1). Where, correction amount = Y (n) + α · (T (n) −T (n−1)) (1) Here, α is a proportional constant for each color, and is a value obtained from the thermal expansion characteristics of the intermediate transfer belt 19, the distance between the photosensitive drums 16, and the like.

The term of Y (n) in the equation (1), that is, the Y margin is calculated by the arithmetic unit 35, and further, the function term of α · (T (n) −T (n−1)), that is, The change in the Y margin due to the temperature change is calculated by the predicted value calculation device 50 to which the measured temperature information of the temperature sensors 32A and 32B is input via the calculation device 35. The calculation result of the predicted value calculation device 50 is returned to the calculation device 35.

Therefore, here, the correction amount represented by the equation (1) is obtained by adding the calculation result by the predicted value calculation device 50 to the calculation result by the calculation device 35. This correction amount (electric signal) is input to a correction device 52 connected to the arithmetic device 35.

The correction device 52 is connected to each of the optical scanning devices 12 and, from the reference optical writing start signal of the optical scanning device 12 to the actual start of laser beam irradiation, based on the input correction amount. And the control for adjusting the rotational phase of a polygon mirror (not shown) in the optical deflector 36 is performed.

Thus, the X margin shown in FIG. 4B can be corrected by adjusting the laser beam irradiation start timing.

The Y margin shown in FIG. 4E can be corrected by adjusting the rotation phase of the polygon mirror so that the black line is advanced from the true position by a time corresponding to ΔY. The gap disappears.

FIG. 8 shows a simulation result in the case where the predicted value of the registration error is obtained from the temperature information and the registration error is corrected.

FIG. 8 shows that the change in the Y margin at the start of printing is suppressed to less than half as compared with the result shown in FIG. 7 in which the correction based on the registration deviation predicted value is not performed.

Note that, in the result of FIG.
Although the simulation was performed based on the temperature measurement result at one point in FIG. 9, it is also possible to calculate the correction amount from the temperature difference between the upstream and downstream portions of the intermediate transfer belt 19 and the average using the temperature sensors 32A and 32B. Thus, more accurate correction can be performed.

Further, the temperature sensors 32A and 32B can be arranged near the transfer position where each visual image is transferred from each photosensitive drum 16 to the intermediate transfer belt 19, and the temperature near the transfer position can be measured. In this case, the thermal expansion and contraction of a member around the transfer position is detected, which affects the displacement when the image is transferred onto the intermediate transfer belt 19, and is included in the correction amount represented by the above equation (1). Thus, the correction accuracy can be further improved.

As described above, in the image forming apparatus 10 of this embodiment, the arithmetic unit 35 detects the registration marks 42A and 42B on the intermediate transfer belt 19 by the registration mark detection sensors 30A and 30B. The value of the registration deviation in the composite image is calculated based on the detection signal at that time, and the predicted value calculation device 50 calculates the value of the registration error in the composite image based on the measured temperature when the temperature of the intermediate transfer belt 19 is measured by the temperature sensor 32. The predicted value of the registration deviation is calculated.

Further, the correcting device 52 corrects the formation position of each latent image formed on each photosensitive drum 16 based on the registration deviation value and the registration deviation prediction value.

As a result, even when the temperature in the frame 11 rapidly rises, for example, when the apparatus is started up, the registration deviation can be accurately corrected.

The correction of the formation position of each latent image by the correction device 52 is performed by adjusting the laser beam irradiation start timing by the optical scanning device 12 and the phase of the optical deflector. The X margin and the Y margin can be corrected.

The temperature sensors 32A and 32B measure the temperature of the intermediate transfer belt 19,
9 can be detected directly, and the registration deviation due to the intermediate transfer belt 19 can be accurately corrected.

Further, a plurality of registration marks are arranged near the end of the intermediate transfer belt 19 and formed on a line substantially perpendicular to the moving direction of the belt (registration marks 42A and 42B), and the registration mark detection sensors 30A and 30B are formed. Are arranged corresponding to the respective marks, so that the X margin due to the thermal expansion and contraction of the intermediate transfer belt 19, the frame 11, and the like can be detected more accurately. In addition, it is also possible to detect a displacement of both ends in the moving direction of the intermediate transfer belt 19, that is, a tilt in the width direction, which can be used for correcting skew.

The registration marks 42A,
Since 42B is formed at a position on the intermediate transfer belt 19 that does not overlap with the image forming section 19A, registration deviation can be detected even during normal image formation.

Further, the registration deviation can be calculated based on a plurality of detection results by the registration mark detection sensor 30. In this case, the eccentricity of the photosensitive drum 16 and the thickness of the intermediate transfer belt 19 can be calculated. It is possible to remove a fluctuation component due to a position shift having a relatively short cycle change due to unevenness or the like.

Further, the predicted value of the registration deviation is:
It is also possible to calculate based on the results of a plurality of measurements by the temperature sensor 32. In this case, even in a configuration having a large number of heat source sections and in which the temperature of each section in the machine varies in a complicated manner, more accurate registration can be performed. It is possible to obtain the estimated value of the deviation of the ratio.

Further, in this embodiment, since the registration mark detection sensor 30 is a reflection type sensor, the registration mark 42 can be detected even if the intermediate transfer belt 19 is made of a material other than a transparent material.
The selection range of the material used for the intermediate transfer belt 19 is expanded.

[0104]

Since the image forming apparatus of the present invention has the above-described configuration, it is possible to accurately correct the registration deviation even at the time of startup when the temperature in the apparatus changes rapidly.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a plan view showing a positional relationship between a registration mark and a mark detection sensor according to one embodiment of the present invention.

FIG. 3 is a diagram illustrating an example of Y during continuous printing in a case where registration misalignment is not corrected in the image forming apparatus of the present invention.
FIG. 4 is an explanatory diagram showing a change in a margin.

FIG. 4 is an explanatory diagram showing a relationship between a change in a Y margin in FIG. 3 and a temperature measurement result of the intermediate transfer belt at that time.

FIG. 5 is an explanatory diagram showing a simulation result when a Y margin is continuously corrected by a conventional correction method.

FIG. 6 is an explanatory diagram showing a simulation result when a Y margin is continuously corrected by a correction method according to an embodiment of the present invention.

FIG. 7 is a schematic configuration diagram of a conventional image forming apparatus.

FIG. 8 is an explanatory diagram of a registration shift.

[Explanation of symbols]

Reference Signs List 10 image forming apparatus 11 frame (housing) 12 optical scanning device (optical scanning unit) 14 developing device (developing unit) 16 photoconductor drum (image carrier) 19 intermediate transfer belt (intermediate transfer member) 30A, 30B registration mark Detection sensor (mark detection means) 32A, 32B Temperature sensor (temperature measurement means) 35 Calculation device (calculation means) 36 Optical deflector 42A, 42B Registration mark 50 Predicted value calculation device (predicted value calculation means) 52 Correction device (correction) means)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H027 DA13 DA38 DA50 DE02 EB04 EC03 EC06 EC20 ED06 ED24 EE02 EE07 EF09 JA11 JA12 JB30 JC05 2H030 AA01 AB02 AD12 AD17 BB02 BB16 BB23 BB42 BB56

Claims (11)

[Claims] 1. A plurality of image carriers arranged side by side in a housing;
A plurality of light scanning means for forming a latent image on each of the image carriers by irradiating a light beam modulated according to an image and scanning with an optical deflector, and developing each latent image with toner A plurality of developing means for forming a visual image of each color; an intermediate transfer body on which each of the visual images is sequentially transferred from each of the image carriers to form a composite image; and a predetermined timing on the image carrier. Mark detection means for detecting a registration mark formed and transferred to the intermediate transfer member, calculation means for calculating a value of the registration deviation of the composite image from a detection signal of the registration mark by the mark detection means, A temperature measuring unit for measuring a temperature in the housing, wherein the registration deviation is based on a temperature measured by the temperature measuring unit. Predictive value calculating means for calculating the predicted value of, and the formation position of each latent image based on the registration error value calculated by the calculating means and the registration error predicted value calculated by the predicted value calculating means. An image forming apparatus, comprising: a correction unit configured to perform correction. 2. The image according to claim 1, wherein the correction of the formation position of each of the latent images is performed by adjusting a timing at which the light scanning unit starts irradiation of the light beam and a phase of the light deflector. Forming equipment. 3. The image forming apparatus according to claim 1, wherein a plurality of the temperature measuring units are provided. 4. The image forming apparatus according to claim 1, wherein the temperature measuring unit is arranged near a transfer position at which the visualized images are transferred from the image carriers to the intermediate transfer body. 4. The image forming apparatus according to 3. 5. The image forming apparatus according to claim 4, wherein the temperature measuring unit measures a temperature of the intermediate transfer body instead of a temperature in the housing. 6. The image forming apparatus according to claim 1, wherein the registration mark is formed at a position on the intermediate transfer member that does not overlap with the composite image. 7. The image forming apparatus according to claim 1, wherein the registration mark is formed near an end of the intermediate transfer body. 8. A plurality of the registration marks are formed on a line substantially perpendicular to a moving direction of the intermediate transfer body,
The image forming apparatus according to claim 7, wherein the mark detection unit is arranged corresponding to each of the plurality of registration marks. 9. The image forming apparatus according to claim 1, wherein the registration deviation value is calculated based on a plurality of detection results by the mark detection unit. 10. The image forming apparatus according to claim 1, wherein the registration deviation prediction value is calculated based on a plurality of measurement results by the temperature measurement unit. 11. The image forming apparatus according to claim 1, wherein said mark detecting means is a reflection type sensor.