JPH0954504A - Image forming device - Google Patents

Abstract

(57) [Summary] [Object] To improve the detection accuracy of an identification unit in an image forming apparatus that detects the identification unit provided on an intermediate transfer member to determine the timing of forming a latent image on a latent image carrier. [Structure] Mark 53 formed on intermediate transfer belt 10
The mark detection using the signal from the optical mark detection device 54 for detecting the is detected when the vibration of the intermediate transfer belt or the detection device due to the operation of the actuators is sufficiently attenuated. The detection device 54 is provided for the roller 11 of the belt 10.
It is desirable to dispose it so as to face the winding portion around the.

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 copying machine, a facsimile and a printer.

[0002]

In Japanese Patent Laid-Open No. 5-150574, an endless belt or drum-shaped photosensitive member having a photosensitive layer on its surface, a photosensitive member position detecting means for detecting the position of the photosensitive member in the rotating direction, and the photosensitive member A latent image forming unit that scans the body to form a latent image, a developing unit of a plurality of colors that visualizes the latent image, and an intermediate transfer member that temporarily holds the visualized image on the photoconductor. And an intermediate transfer member position detection means for detecting the position of the intermediate transfer member in the rotation direction, and one position detection mark is provided on the photosensitive member, and a plurality of position detection marks are provided on the intermediate transfer member. Such an electrophotographic apparatus has been proposed.

[0003]

This type of rotatable latent image carrier, and latent image forming means for sequentially forming a plurality of latent images corresponding to a plurality of image information on the latent image carrier, A developing unit that visualizes the latent image formed on the image carrier, a movable intermediate transfer member that sequentially transfers the visible images on the latent image carrier, and an intermediate transfer member. An identification member that is provided to indicate the moving position of the intermediate transfer member, a detector that is provided near the movement path of the intermediate transfer member and that detects the identification member, and a latent image forming unit of the latent image forming means based on the detection result of the detector. In an image forming apparatus having a latent image forming control means for controlling the latent image forming time, when the detection accuracy of the detector is insufficient,
There is a problem that a timing shift of latent image formation occurs, and for example, a position shift between the visible images when the visible images are superposed on the intermediate transfer body may occur.

The present invention has been made in view of the above problems, and an object thereof is an image forming apparatus of this type, which is capable of accurately detecting an identification means provided on an intermediate transfer member. It is to provide an image forming apparatus capable of performing the above.

[0005]

An image forming apparatus according to any one of claims 1 to 21 sequentially forms a rotatable latent image carrier and a plurality of latent images corresponding to a plurality of image information on the latent image carrier. Latent image forming means, developing means for visualizing the latent image formed on the image carrier, and a movable intermediate transfer body for sequentially transferring the visible image on the latent image carrier. And an identification member that is provided on the intermediate transfer member and indicates a moving position of the intermediate transfer member,
A detector provided in the vicinity of the moving path of the intermediate transfer member for detecting the identification member, and a latent image forming control means for controlling the latent image forming timing of the latent image forming means based on the detection result of the detector. It has the following basic configuration.

In the image forming apparatus according to the first aspect of the invention, in the above basic structure, the timing of detection by the detector varies depending on the position of at least one of the intermediate transfer member and the detector due to the operation of the drive section in the apparatus. Is set at a time when is less than a predetermined amount.

An image forming apparatus according to a second aspect of the present invention is the image forming apparatus according to the first aspect, wherein the developing means accommodates toners of a plurality of colors separately and is rotatably provided with respect to the latent image carrier. The operation of the in-apparatus drive unit is a rotation operation of the developing unit.

An image forming apparatus according to a third aspect of the present invention is the image forming apparatus according to the first aspect, further comprising cleaning means for cleaning the surface of the intermediate transfer body, the cleaning means being in contact with or separated from the intermediate transfer body. The operation of the in-apparatus drive section is provided freely, and is characterized in that it is a contact / separation operation of the cleaning unit with respect to the intermediate transfer member.

An image forming apparatus according to a fourth aspect of the present invention is the image forming apparatus according to the first aspect, further comprising a sheet feeding device that feeds the transfer material in order to transfer the visible image carried on the intermediate transfer member to the transfer material. The operation of the in-apparatus drive section has means, and is characterized in that the transfer material is fed by the paper feeding means.

An image forming apparatus according to a fifth aspect of the present invention is characterized in that, in the above basic configuration, the image forming apparatus has a control means for prohibiting the start or end of the operation of the drive section in the apparatus during the detection period of the identification member by the detector. To do.

An image forming apparatus according to a sixth aspect of the present invention is the image forming apparatus according to the fifth aspect, wherein the developing means separately accommodates toners of a plurality of colors and is rotatably provided with respect to the latent image carrier. The operation of the drive unit in the apparatus is a rotation operation of the developing unit.

An image forming apparatus according to a seventh aspect is the image forming apparatus according to the fifth aspect, further comprising cleaning means for cleaning the surface of the intermediate transfer body, the cleaning means being in contact with or separated from the intermediate transfer body. The operation of the in-apparatus drive section is provided freely, and is characterized in that it is a contact / separation operation of the cleaning unit with respect to the intermediate transfer member.

An image forming apparatus according to an eighth aspect of the present invention is the image forming apparatus according to the fifth aspect, further comprising a sheet feeding device for feeding a transfer material in order to transfer the visible image carried on the intermediate transfer member onto the transfer material. The operation of the in-apparatus drive section has means, and is characterized in that the transfer material is fed by the paper feeding means.

According to a ninth aspect of the present invention, in the image forming apparatus having the above-mentioned basic structure, the intermediate transfer member is constituted by a belt member which is stretched over a plurality of supporting rollers, and the detector is wound around the supporting roller of the belt member. Then, it is provided so as to perform the detection.

An image forming apparatus according to a tenth aspect of the present invention is the image forming apparatus according to the ninth aspect, wherein the detector drives the intermediate transfer member among a plurality of supporting rollers that support the belt-shaped intermediate transfer member. It is characterized in that it is provided so as to detect the identification member at the winding portion of the belt-shaped intermediate transfer member around the roller.

An image forming apparatus according to an eleventh aspect of the present invention is the image forming apparatus according to the ninth aspect, wherein a plurality of the identification members are provided on the belt-shaped intermediate transfer member, and the intervals between the plurality of identification members are the same as those of the detector. It is characterized in that it is the same as the peripheral length of the opposing support roller or is an integral multiple of the peripheral length.

According to a twelfth aspect of the present invention, in the image forming apparatus according to the above-mentioned basic configuration, the intermediate transfer member is constituted by a belt member that is stretched over a plurality of supporting rollers, and a plurality of the identifying members are provided on the belt member. The space between the identification members is the same as the circumference of the support roller or an integral multiple of the circumference.

According to a thirteenth aspect of the present invention, there is provided the image forming apparatus of the thirteenth aspect.
In the above image forming apparatus, the detector is provided so as to detect the identification member at the winding portion of the belt-shaped intermediate transfer member around the support roller.

An image forming apparatus according to a fourteenth aspect is the image forming apparatus according to the thirteenth aspect.
In the image forming apparatus, the supporting roller is a driving roller that drives the belt-shaped intermediate transfer member.

In the image forming apparatus according to the fifteenth aspect of the present invention, in the basic configuration, the identification member uses a mark formed on the intermediate transfer member, and the detector causes the mark on the intermediate transfer member at a predetermined time interval. When the mark is detected and the detection signal is continuously output a predetermined number of times, it is determined that the mark has been detected, and when the output of the detection signal is less than the predetermined number of times, it is not determined that the mark has been detected. It is characterized by that.

According to a fifteenth aspect of the present invention, there is provided the image forming apparatus according to the fifteenth aspect.
In the image forming apparatus, the mark detection determination based on the detection signal is not performed for a predetermined period after the detection signal is continuously output a predetermined number of times by the detector.

The image forming apparatus according to claim 17 is the same as that according to claim 16.
In the image forming apparatus, the predetermined period is shorter than the time required to move the intermediate transfer body from the first mark formed on the intermediate transfer body to the second mark immediately after. .

In the image forming apparatus of the eighteenth aspect of the present invention, in the basic configuration, the identifying member uses a plurality of marks formed on the intermediate transfer member, and a second mark is output after a first mark detection signal is output. It is characterized by further comprising control means for comparing a time interval until the output of the mark detection signal of the second time with a range of a predetermined time interval and judging whether or not the detection timing is within the range of the time interval. To do.

An image forming apparatus according to a nineteenth aspect is the eighteenth aspect.
In the image forming apparatus, the control means operates the notifying means for notifying the operator of the abnormal state when the detection timing is out of the specified value.

The image forming apparatus according to claim 20 is the same as that according to claim 18.
In the image forming apparatus, the operation of the apparatus is stopped by the control unit when the detection timing is out of the specified value.

An image forming apparatus according to a twenty-first aspect is the eighteenth aspect.
In the image forming apparatus, the second mark detection signal is canceled when the detection timing is out of a specified value and the detection timing is within a predetermined time interval.

In the image forming apparatus according to any one of claims 1 to 21, the latent image forming means sequentially forms a plurality of latent images corresponding to a plurality of image information on the rotatable latent image carrier.
Based on the detection result of the detector, the detector detects the identifying means provided on the intermediate transfer body, which is provided on the intermediate transfer body to which the visualized image formed by the developing means is transferred onto the latent image carrier. ,
The latent image formation control means determines the latent image formation timing. As a result, each latent image can be formed at a predetermined position in the rotation direction of the intermediate transfer body.

Further, in the image forming apparatus according to any one of claims 1 to 4, the detection by the detector is such that the positional fluctuation caused in at least one of the intermediate transfer member and the detector by the operation of the drive unit in the apparatus is less than a predetermined amount. Will be done when. As a result, erroneous detection of the detector and deterioration of detection accuracy due to such a position change are prevented.

In the image forming apparatus of the fifth to eighth aspects, the control means prohibits the start or end of the operation of the in-apparatus drive section during the detection period of the identification member by the detector. As a result, the position variation of at least one of the intermediate transfer member and the detector, which occurs at the start or end of the operation of the drive unit in the apparatus, is prevented from occurring during the detection period, and the detection by the position variation is performed. Prevent erroneous detection of detectors and decrease in detection accuracy.

In the image forming apparatus according to the ninth to eleventh aspects, the detection is carried out at the winding portion of the belt member which constitutes the intermediate transfer member which is wound around a plurality of supporting rollers with respect to the supporting rollers. Thereby, unlike the case where the detection is performed at the stretched portion of the belt member, it is possible to suppress the variation in the detection accuracy due to the distance variation between the identification member on the intermediate transfer member and the detector, which is caused by the slack or the shake of the belt member. You can

Particularly, in the image forming apparatus of the tenth aspect, since the winding portion of the belt-shaped intermediate transfer member is the drive roller for driving the intermediate transfer member among the plurality of supporting rollers, a tension roller or the like is used. Unlike the driven roller described above, the drive shaft does not move, so that the variation in the detection accuracy can be further suppressed.

According to the twelfth to fourteenth aspects of the present invention, the interval between the plurality of identification members on the belt member forming the intermediate transfer member is equal to or is an integer of the peripheral length of the supporting roller supporting the belt. By doubling, the influence of the support roller eccentricity on the distance between the identification member on the belt member and the detector is suppressed, and the identification member can be detected by the detector while keeping the distance substantially constant. .

Particularly, in the image forming apparatus according to claim 13, the detector is provided so as to detect the identification member at the winding portion of the belt-shaped intermediate transfer member around the supporting roller. As in the case of No. 9, it is possible to suppress variation in detection accuracy due to variation in the distance between the identification member on the intermediate transfer member and the detector, which is caused by slackening or shaking of the belt member.

Further, particularly in the image forming apparatus of claim 14, the winding portion of the belt-shaped intermediate transfer member is for a driving roller for driving the intermediate transfer member among the plurality of supporting rollers. Similar to the item 10, it is possible to suppress the variation in the detection accuracy due to the fluctuation of the roller axis of the winding target.

In the image forming apparatus according to any one of claims 15 to 17, the mark as the identification means formed on the intermediate transfer member is detected by the detector that detects the intermediate transfer member at a predetermined time interval, and the mark is detected. When the signal is continuously output a predetermined number of times, it is determined that the mark is detected, and when the output of the detection signal is less than the predetermined number of times, it is not determined that the mark is detected. This prevents erroneous detection of toner stains or scratches on the intermediate transfer member as marks.

Particularly, in the image forming apparatus according to the sixteenth aspect, the mark detection determination based on the detection signal is not performed for a predetermined period after the detection signal is continuously output a predetermined number of times by the detector. Thus, it is possible to prevent erroneous detection of two marks when one mark is partially soiled. In addition, as the predetermined period, a period during which one mark may be erroneously detected as two marks when partial stain occurs is used.

In the image forming apparatus according to the eighteenth to twenty-first aspects, the detector detects a plurality of marks formed on the intermediate transfer member as the identifying means. And
The control means compares the time interval from the output of the first mark detection signal to the output of the second mark detection signal with a range of a predetermined time interval to detect the detection timing. Determine if it is within the time interval. The result of this determination is used for control when a detection signal is generated at an incorrect timing due to stains or scratches on the mark.

[0038]

Embodiments of the present invention will be described below with reference to the drawings. [Embodiment 1] FIG. 1 shows a schematic configuration of a color image forming apparatus (color laser printer) according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a flexible belt-shaped photosensitive member which is a belt-shaped image carrier, and the belt-shaped photosensitive member 1 is provided between rotating rollers 2 and 3 and is driven by the rotating roller to drive a timepiece. Is rotated in the direction. Reference numeral 4 is a charging member as a charging means, reference numeral 5 is a laser writing system unit as an image exposure means, and reference numeral 60 is a rotary developing device having a plurality of developing means, that is, developing devices each containing a developer of a specific color.

The laser writing system unit 5 is incorporated in the main body of the apparatus by being housed in a holding case having a slit-shaped exposure opening on the upper surface. In addition to the illustrated optical system, the laser writing system unit 5 may be an optical system in which a light emitting unit and a converging optical transmission body are integrated.
The charging position by the charging member 4 and the optical writing position by the laser writing system unit 5 are set on one roller 2 of the plurality of rollers that bridge the belt-shaped photosensitive member 1. Each of the developing devices contains, for example, each of yellow, magenta, cyan, and black developers, and is provided with each developing sleeve that comes close to or in contact with the belt-shaped photoreceptor 1 at a predetermined position. Has the function of developing the latent image of No. 1 by non-contact development or contact development.

Reference numeral 10 denotes an intermediate transfer belt which is a transfer image carrier, and the intermediate transfer belt 10 is installed between a driving roller 11 and a driven roller 12, and is rotated counterclockwise by the driving of a rotating roller. To be done. This intermediate transfer belt 1
0 and the belt-shaped photoconductor 1 are in contact with each other at the rotating roller 3, and the first-time visible image on the belt-shaped photoconductor 1 is intermediated by the bias roller 13 provided in the intermediate transfer belt. The image is transferred onto the transfer belt 10. Then, by repeating the same process, the second visible image, the third visible image, and the fourth visible image,
Each of them is sequentially superposed on the intermediate transfer belt 10 and transferred so as not to cause positional deviation. A transfer roller 14 is provided so as to come into contact with and separate from the intermediate transfer belt 10.

Reference numeral 15 is a cleaning device for the belt-shaped photosensitive member 1 provided on the rotating roller 2, and reference numeral 16 is a cleaning device for the intermediate transfer belt 10. The blade 16A of the cleaning device 16 is used during image formation. The intermediate transfer belt 10 is kept at a position separated from the surface of the intermediate transfer belt 10 and only during cleaning after image transfer as shown in the figure.
Is pressed against the surface of

The color image forming process by this color image forming apparatus is performed as follows. First, the formation of a multicolor image according to the present embodiment is performed according to the following image forming system. That is, in the color image data input section, which is a separate image reading apparatus from the color image forming apparatus (not shown), the image sensor scans the original image to obtain data, and this data is processed by the image data processing section. Then, the image data is created. This image data is
Once stored in the image memory. The image data in the image memory is taken out at the time of recording and input to the color image forming apparatus of FIG. 1 which is a recording unit. That is, a color signal output from an image reading device that is separate from the color image forming device is input to the laser writing system unit 5. Then, in the laser writing system unit 5, the laser beam generated by the semiconductor laser (not shown)
A belt-shaped photosensitive member which is rotationally scanned by a polygon mirror 5B rotated by a drive motor 5A, has its optical path bent by a mirror through an fθ lens 5C, is previously discharged by a discharging lamp 21, and is uniformly charged by a charging member 4. The peripheral surface of the body 1 is exposed and an electrostatic latent image is formed. Here, the image pattern to be exposed is a monochromatic image pattern when the desired full-color image is separated into yellow, magenta, cyan, and black. Each formed electrostatic latent image is developed by a rotary developing device by a yellow, magenta, cyan, and black developing device to form a monochromatic image. The monochromatic image formed on the belt-shaped photoreceptor 1 is transferred onto the intermediate transfer belt 10 which rotates counterclockwise while contacting the belt-shaped photoreceptor 1. The yellow, magenta, cyan, and black monochromatic images formed on the photosensitive belt 1 are sequentially superposed on the surface of the intermediate transfer belt 10. Intermediate transfer belt 1
The yellow, magenta, cyan, and black images superposed on 0 are transferred by the transfer roller 14 to the transfer paper conveyed from the paper feed table 17 through the paper feed roller 18 and the registration roller 19 to the transfer section. After the transfer is completed, the transfer paper is fixed by the fixing device 20 to complete a full-color image.

FIG. 2 is an enlarged view of a part of the color image forming apparatus. In FIG. 2, the rotary roller 2 is rotationally driven by the rotary drive motor 25, and the photosensitive belt 1 is rotated by the rotary roller 2 at a constant speed. A pulley 22 is provided between the rotary drive motor 25 and the rotary roller 2. The pulley 22 drives a timing belt 23, and a gear 24 provided at one end of the timing belt 23.
Drive. The gear 24 is connected to the rotating roller 11 via a rotation shaft, and the gear 24 rotationally drives the rotating roller 11, and the rotating roller 11 rotates the intermediate transfer belt 10 at a constant speed. A mark 53 having a reflectance different from that of the intermediate transfer belt 10 is provided on the intermediate transfer belt 10, and the output timing of the write signal is determined by detecting the mark 53 with an optical mark detection device 54.

In this embodiment, as the mark 53,
It is assumed that eight marks having a width of 10 mm are provided at equal intervals in the circumferential direction of the intermediate transfer belt 10 having a circumferential length of 400 mm. The linear velocity of the intermediate transfer belt 10 is 100 mm / se.
Let be c.

In this embodiment, the optical mark detection device 54
Are arranged so as to detect a portion where the intermediate transfer belt 10 is wound around the driving roller 11, as shown in FIG. By arranging in this way, the intermediate transfer belt 1
It is possible to eliminate the inaccuracy of mark detection due to zero fluctuation and deflection. That is, the above-mentioned JP-A-5-1505
In the device disclosed in Japanese Patent Laid-Open No. 74, the position of the detector for detecting the mark on the intermediate transfer belt is between the rollers that stretch the intermediate transfer belt and faces the belt portion where the roller does not exist. Therefore, the distance between the mark and the detector is likely to fluctuate due to the deterioration of the flatness of the belt (waviness), etc., and if the height at the time of detection changes for each color, the detection timing will vary and the image formation timing for each color will change. Since there are variations, there is a positional shift between colors. On the other hand, in the present embodiment, the optical mark detection device 54 is arranged at a position facing the roller 11, and the intermediate transfer belt 10 is
The upper mark 53 is detected at a position corresponding to the winding position of the roller 11 around which the belt 10 is stretched.
This detection position is not a position where the property of the belt surface becomes unstable like the technique described in JP-A-5-150574, but a portion where the belt is tightly wound around the roller. The positional relationship between the detector and the mark is more stable than that of the above device. Therefore, the inaccuracy of detection can be eliminated as described above.

The optical mark detecting device 54 may be installed at a place where the intermediate transfer belt 10 is wound around the driven roller 12. Further, the arrangement of such a mark detection device is not limited to the case where the optical mark and the optical mark detection device are used, and is effective as long as the detection output and the like change depending on the distance between the mark and the mark detection device. Is. For example, it is effective when using a mark detecting device that detects a mark magnetically or electrically as well as using a magnetic or electrical mark.

FIG. 4 shows the relationship between the mark recognition signal and the image writing start signal. As described above, there are eight marks on the intermediate transfer belt, and the image writing start signal for each color is generated by recognizing a common mark among the eight.

The mark recognition operation for generating the image writing start signal is performed by a revolver rotation motor (not shown), a paper feed clutch (not shown) for operating the paper feed roller 18, and a cleaning blade. When the operation of actuators such as a belt cleaning solenoid (not shown) for operating 16A is started or immediately after the operation is started, vibration at the start of operation of the actuators causes the drive roller 11 and the optical mark to be detected. There is a possibility that the positional relationship of the device 54 may change and a defect may occur in mark detection. For example, as shown in FIG.
Depending on the state of the cleaning blade 16A that appropriately abuts on the drive roller 1, the normal drive roller 1 as shown in FIG.
1 from the positional relationship between the optical mark detecting device 54 and the optical mark detecting device 54.
If the positional relationship as shown in (b) is deviated, mark detection cannot be performed, and accurate color superposition cannot be performed. Even if the positional relationship between the drive roller 11 and the optical mark detection device 54 does not change, the speed of the intermediate transfer belt 10 may change due to the operation of the actuators.

Therefore, in the present embodiment, as shown in FIG. 6, it is assumed that the vibration due to the start and end of the operation of the actuators is attenuated at 0.08 (sec), and the distance from 10 mm before the mark detection to the rear end of the mark is reduced. Does not start or end the operation of the actuators during the actuator mask period. The mask period does not have to be the same between the eight marks. In the present embodiment, the intermediate transfer member is not limited to the belt shape and may be the drum shape. The developing device is one in which a plurality of developing devices containing multi-color toners integrally and linearly reciprocate in a horizontal or vertical direction with respect to the photoconductor, and a plurality of developing devices containing multi-color toners with respect to the photoconductor. It may be fixedly arranged. The cleaning device is not only a blade,
It may have a roller shape or a brush shape.

FIG. 7 shows an example of a mark recognition flow chart, and FIG. 8 shows an explanatory diagram of signal processing in the mark recognition. here,
Sampling operation for mark detection is assumed to be 1 KHz. In this embodiment, after the mark outside portion on the intermediate transfer belt 10 is continuously detected a predetermined number of times (for example, 5 times), the mark portion is similarly continuously detected a predetermined number of times (5 times), and if a detection signal is output, it is recognized as a mark. . As a result, even if any mark is detected on the intermediate transfer belt, if the detection signal is not continuously output for the predetermined number of times or more (for example, only once), it is not determined that the identification mark is detected, and the toner is not detected. It is possible to prevent erroneous detection of belt stains and other belt scratches due to the identification mark.

A predetermined period (for example, 0.1 sec) after the mark recognition is a mark detection mask period in which the mark detection judgment based on the mark detection signal is not performed. As a result, it is possible to prevent the mark stain section from being generated in the mark as shown in FIG. 9 and to generate the mark detection signal twice for one mark. The mark detection mask period is
It is set to a period that is at least shorter than the moving time of the intermediate transfer member from the first mark formed on the intermediate transfer member 10 to the second mark immediately thereafter.

Further, since a plurality of marks are formed on the intermediate transfer belt 10, if the mark portions become soiled or damaged with toner over time, the output timing of the mark detection signal will shift for each color, and color superimposition will be successful. Since there is a possibility that it will not go, the suitability of the detection timing of each mark is determined.

That is, when the operation of the color laser printer is started, the counting operation by the CPU is started, and the CPU reads and stores the count value at the time of outputting the first mark detection signal by the optical mark detection device 54. Next, the count value at the time of outputting the second mark detection signal continuous to the first mark is read, and the count value at the time of outputting the first mark detection signal and the count value at the time of outputting the second mark detection signal are read. Is calculated and compared with a predetermined value range, and whether or not the detection timing is appropriate is determined by whether or not the difference between the count values is out of the predetermined value range. For example, in the present embodiment, the distance from the tip of the first mark to the tip of the next second mark is 50.
Since it is mm, if the count interval of the counter is 1 KHz, the difference between the count values must be between 400 and 600 counts.

When the difference between the count values is out of the predetermined value, it is determined that the mark detection is abnormal,
A message is displayed on the operation display section of the laser printer main unit to inform the user of the abnormality. As a result, image formation is continued with abnormal detectors, etc., and it is possible to prevent misalignment between visible images when overlapping the images on the intermediate transfer body due to the latent image formation timing deviation. it can.

Instead of reporting such an abnormality, or
In addition, when the difference between the count values is out of the predetermined value range, the image forming operation of the laser printer device may be stopped. Further, instead of reporting the above abnormality, even if the difference between the count values is out of a predetermined value range, if the difference between the count values is extremely small (for example, about 20 counts), it is treated as noise. -The image forming operation of the laser printer may be continued after the judgment. According to this, it is possible to prevent the convenience from being deteriorated due to the detection of the minute noise as the detection accuracy is improved.

FIG. 10 is a block diagram showing a schematic structure of an electric component section for executing each of the above controls. FIG.
At 0, an optical mark detection device 54, a drive unit 60 for latent image formation, a drive unit 61 for development, a drive unit 62 for an intermediate transfer belt cleaning device, a drive unit 63 for paper feeding, an operation display. The drive unit 64, the intermediate transfer belt, and the drive unit 65 for the photoconductor are connected to the main controller 66. The main controller 66 includes a central processing unit (CPU) 67 and a read-only memory (ROM) 6
8. Readable and writable memory (RAM) 69
It is composed of This read-only memory (RO
In M) 68, the programs for the above respective controls are written. Then, in this main control device, in accordance with a control program read from the memory 68, in response to an input signal from the optical mark detection device 54, and while performing various recognition / judgment including operation timings of various drive parts. , Outputs operation commands to various drive units to perform predetermined operations.

[Second Embodiment] Next, a color image forming apparatus (color laser printer) according to another embodiment of the present invention.
Will be described. As in Embodiment 1 above,
Even if the optical mark detection device 54 is disposed at a position facing the belt supporting roller 11 so that the positional relationship between the detector and the mark is stable, in reality, the intermediate transfer belt 1
Since the roller 11 inside 0 has a certain amount of eccentricity due to parts accuracy, assembly accuracy, etc., the surface of the intermediate transfer belt at the detection position and the optical mark detection device 5
The positional relationship with 4 must be changed in synchronization with the rotation of the roller 11. FIG. 11 shows such a situation.
11 (a) shows a state in which the distance between the belt surface and the optical mark detection device 54 has become small due to eccentricity, and FIG.
(B) shows a state in which the distance is increased due to eccentricity. Due to such a distance variation between the mark 53 on the belt surface and the optical mark detection device 54 due to the eccentricity of the roller, the mark detection timing differs for each color, and there is a possibility that a positional deviation between colors of the color image occurs. Remaining. Further, such a mark detection defect due to the roller eccentricity is not limited to the case where the optical mark and the optical mark detection device are used, and the detection output changes depending on the distance between the marks and the mark detection device. It can occur as long as there is. For example, it may occur when using a mark detecting device that detects a mark magnetically or electrically as well as using a magnetic or electrical mark.

The color image forming apparatus of the present embodiment, in order to prevent the positional displacement due to such a cause,
A latent image forming unit that forms an electrostatic latent image on the photoconductor for each color based on the color-separated image data, and visualizes each electrostatic latent image with toner of a color corresponding to the image data of each color. Developing means, and first transfer means for sequentially transferring the visualized toner images on the photoconductor to an endless intermediate transfer belt,
The toner image transferred for each color on the intermediate transfer belt is superposed on the intermediate transfer belt with a control means for controlling the process of repeating the step of aligning the image position and transferring for the number of separated colors. Second transfer means for collectively transferring the toner image onto the transfer paper, fixing means for fixing the toner image transferred onto the transfer paper, and a detector for detecting a plurality of marks provided on the intermediate transfer belt. In the force-line image forming apparatus in which the control unit controls the start of writing the image data of the latent image forming unit based on the output of the detector, the detector stretches the intermediate transfer belt. The plurality of marks on the intermediate transfer belt, which are provided so as to face one of the rotating rollers to be provided, are spaced at the same interval as the circumference of the rotating roller facing the detector, or An integer multiple of the circumference And it is characterized in Rukoto.

FIG. 12 is a schematic block diagram of the color image forming apparatus according to this embodiment. In FIG. 12, reference numeral 1 is an endless belt-shaped photoconductor as a belt-shaped image carrier, and the belt-shaped photoconductor 1 is installed between rotating rollers 2 and 3 and is driven by the rotating roller. Transported in the clockwise direction. Reference numeral 4 denotes a charging member serving as a charging means disposed in contact with the belt-shaped photoreceptor 1, 5 denotes a laser writing system unit serving as an image exposing means (latent image forming means), and 6 to 9 each include a plurality of developers containing a specific color developer. This is a developing means, that is, a developing device, and the developing devices 6, 7, 8 and 9 are arranged in the circumferential direction on the outer diameter side around the axis S and rotate integrally. The laser writing system unit 5 is housed in a holding housing 5E having a slit-shaped exposure opening on the upper surface and incorporated in the apparatus body.

As the laser writing system unit 5, in addition to the optical system having the structure shown in the figure, an optical system in which a light emitting section and a convergent light transmitting body are integrated can be used. The photoconductor cleaning device 15 including the charging member 4, the laser writing 5D, and the cleaning blade 15A is
All of them are provided on the side of one roller 2 out of a plurality of rollers that bridge the belt-shaped photoreceptor 1. The developing units 6, 7, 8 and 9 contain, for example, yellow, magenta, cyan, and black developers, respectively, and come into contact with or come into contact with the surface of the belt-shaped photoreceptor 1 at a predetermined position. Each developing sleeve 6A, 7A, 8A, 9A is provided, and has a function of forming a frame image of the melted image on the belt-shaped photoreceptor 1 by a non-contact developing method or a contact developing method.

Reference numeral 10 is an intermediate transfer belt which is a transfer image carrier, and the intermediate transfer belt 10 includes a rotating roller 11 and
It is erected endlessly between 12 and the rotating roller 1
It is conveyed counterclockwise by driving 1 and 12. The belt-shaped photoreceptor 1 and the intermediate transfer belt 10 are composed of a rotating roller 3
Of the transfer bias from the bias roller (first transfer unit) 13 provided in the intermediate transfer belt. It is transferred onto the intermediate transfer belt 10 by application. By repeating the same process, the second visible image (for example, magenta toner image), the third
The fourth visible image (e.g., cyan toner image) and the fourth visible image (e.g., black toner image) are sequentially superimposed on the intermediate transfer belt 10 and transferred without causing positional deviation.

The transfer roller (second transfer means) 14 is arranged so as to come into contact with and separate from the intermediate transfer belt 10 at a position on the outer diameter side of the rotating roller 11, and the transfer roller (second transfer means) 14 is moved four times on the intermediate transfer belt 10. It is a means for transferring the visualized image that has been transferred onto the transfer paper. Reference numeral 15 is a cleaning device for the belt-shaped photoreceptor, 16 is a cleaning device for the intermediate transfer belt 10, and the blade 16A of the cleaning device 16 is kept at a position apart from the surface of the intermediate transfer belt 10 during image formation. At the time of cleaning after the image transfer, the toner and the like adhering to the surface of the intermediate transfer belt 10 are removed by pressure contact as shown in the figure. Note that in the example of FIG. 12, the number of rotary rollers that support the intermediate transfer belt 10 is two, but as in the embodiment of FIG. 13 described later, it is possible to support three or more rotary rollers. It doesn't matter.

A mark detector 22 (not shown in FIG. 12) composed of a photosensor is provided at a position facing any of the rotating rollers 11, 12, and 21 in the intermediate transfer belt 10. Therefore, the mark on the intermediate transfer belt 10 is detected, and the control means that receives the detection signal controls the image forming timing of each color (writing timing of each color).

The process of forming a color image by the color image forming apparatus (printer) having the above configuration is carried out as follows. First, the formation of a multicolor image according to this embodiment is performed according to the following image forming procedure. That is, for example, image data obtained by scanning an original document image by an image reading device (not shown) separate from the image forming device is imaged on an image sensor provided in the image reading device or the like, and A / D converted. After performing other required processing, the image data processing unit performs arithmetic processing to create image data and stores it in the image memory.

Next, image recording is performed. Particularly, the control means of the image reading apparatus or the control means of the image forming apparatus retrieves the image data stored in the image memory and records it in the recording apparatus, for example, the embodiment of FIG. It is output to the image forming unit of the color image forming apparatus indicated by. That is, for example, when a color signal output from an image reading apparatus separate from the color image forming apparatus is input to the laser writing system unit 5, the laser writing system unit 5 corresponds to each color signal from a semiconductor laser (not shown). The laser beam is emitted, the laser beam is rotationally scanned by the polygon mirror 5B rotated by the drive motor 5A, the optical path is bent by the mirror through the fθ lens 5C, and the belt-shaped photoconductor 1 is irradiated with the laser beam. The belt-shaped photoconductor 1 is preliminarily discharged by the lamp 35 and then uniformly charged by the charging member 4 serving as a charging means. By exposing the laser beam on the peripheral surface of the photoconductor in the charged state, an electrostatic latent image is formed. An image is formed. Here, the image pattern to be exposed is a monochromatic image pattern when a desired full-color image is separated into yellow, magenta, cyan, and black. Each of the formed electrostatic latent images is developed by each of the yellow, magenta, cyan and black developing devices by the rotary developing device, visualized and made into a monochromatic image to form a monochromatic image. The yellow, magenta, cyan, and black images formed on the belt-shaped photosensitive member 1 are fed from the paper feed table 17 to the paper feed roller 18 and the registration roller 1.
Transfer roller 1 on the transfer paper that is conveyed to the transfer unit via 9
4 is transferred. A transfer bias is applied to the transfer roller 14 from a bias applying means (not shown), so that the force image on the photoconductor 1 is transferred onto the transfer paper.
After the transfer is completed, the transfer sheet is fixed by the fixing device 20 including the fixing roller 20A and the pressure roller 20C, and a full color image is completed. The intermediate transfer belt and the belt-shaped photoreceptor are seamless. In the illustrated example, the photoconductor has a belt shape, but may have a drum shape.

The characteristic configuration of this embodiment is that the optical mark detection device 54 is provided so as to face one of the rotating rollers 11, 12, 21 that stretches the intermediate transfer belt 10, and the optical mark detection device 54 is provided on the intermediate transfer belt. The distance between the plurality of marks 53 is the same as the circumference of the rotary roller of the intermediate transfer belt facing the optical mark detection device 54 or an integral multiple of the circumference.

13 and 14 are explanatory views of the characteristic structure. As shown in this figure, one of a plurality of rotating rollers that stretches the intermediate transfer belt 10
An optical mark detecting device 54 for the mark is provided opposite to. The distance L1 between the marks on the intermediate transfer belt 10 is
It is an integral multiple of the circumferential length (πxd1) of the rotating roller 11 having a diameter of d1 as shown in the following equation. L1 = A × (π × d1) A: integer In this way, the distance between the marks 53 on the intermediate transfer belt 10 is an integral multiple of the circumferential length of the rotating roller 11 facing the optical mark detecting device 54. The rotating roller 1
Even if the positional relationship between the surface of the intermediate transfer belt and the optical mark detecting device 54 changes in synchronization with the rotation of the roller due to the amount of eccentricity of 1, the image forming timing start for each color is started at the time of forming the four-color image. Since the distance between the mark and the detector is almost constant at all times, the image forming timing can be controlled to be constant, and a color image with less positional deviation can be formed. In other words, by setting the mark spacing as described above, the positions where the respective mark portions are wound around the rotating roller 11 are always the same, so that even if the rotating roller 11 is eccentric, the distance between the mark and the detector can be increased. The distance is always constant. As a result, when forming a four-color image, it is possible to keep the distance between the mark for starting the image formation timing of each color and the detector substantially constant, and as a result, the image formation timing can be controlled to be constant so that there is little positional deviation. A color image can be formed.

FIG. 15 and FIG. 16 are explanatory views of a more preferable arrangement of the optical mark detecting device 54. As shown in the figure, a characteristic feature is that the drive roller 11 is selected as a rotating roller that opposes the optical mark detection device 54. That is, in this embodiment, the optical mark detection device 54 for the mark is provided at a position facing the drive roller 11 of the intermediate transfer belt 10. Further, the distance L2 between the marks 53 on the intermediate transfer belt 10 is, as shown in the following equation, the peripheral length (π
It is an integral multiple of xd2). L2 = B × (π × d2) B: integer In addition, the rotation roller (tension roller) other than the drive roller may move its position, but the shaft center of the drive roller is supported by the drive shaft. Since it does not move, it is possible to realize stable mark detection by disposing the detector facing the drive roller.

It is needless to say that the present invention is not limited to the above-mentioned respective embodiments, and is included in the present invention as long as the technical idea of the present invention is utilized. Position of the position detection mark provided on the intermediate transfer member,
The shape and the number are changed as necessary, and the mark detection member may be a transmission type, a reflection type, or other than the optical type, and the number and arrangement position of the rollers that support the intermediate transfer belt may be changed appropriately. The image carrier is not only belt-shaped,
It may have a drum shape, and the present invention can be applied not only to a color laser printer but also to a copying machine and a facsimile.

[0070]

According to the image forming apparatus of the first aspect of the present invention, the position fluctuation occurring in at least one of the intermediate transfer member and the detector due to the operation of the drive unit in the apparatus causes erroneous detection of the detector and deterioration of detection accuracy. Since it is possible to prevent the occurrence of a timing error in latent image formation due to such erroneous detection or deterioration in accuracy,
For example, it is possible to prevent the positional deviation between the visible images when the visible images are superposed on the intermediate transfer member.

According to the image forming apparatus of the second aspect, when the intermediate transfer member is constituted by the belt member wound around the plurality of support rollers, it is possible to suppress the variation in the detection accuracy due to the slack or the shake of the belt member. Therefore, even when the intermediate transfer member is configured in this way, a visible image is superimposed on the intermediate transfer member, for example, due to the timing deviation of the latent image formation due to the decrease in the detection accuracy due to the slack of the belt member. It is possible to prevent the occurrence of positional deviation between the visible images when they are aligned.

According to the twelfth to fourteenth aspects of the present invention, the support roller is set with respect to the distance between the identification member of the belt member and the detector by setting the distance between the plurality of identification members on the belt member that constitutes the intermediate transfer member. Since the influence of the eccentricity is suppressed, even when the intermediate transfer member is configured in this way, the timing deviation of the latent image formation due to the decrease in the detection accuracy due to the eccentricity of the support roller of the belt member causes a delay in, for example, the intermediate transfer member. It is possible to prevent positional deviation between the visible images when the visible images are superimposed on each other.

According to the image forming apparatus of the fifteenth to seventeenth aspects, when the mark formed on the intermediate transfer member is used as the identifying means, even if one mark is partially soiled, two marks are formed. In order to prevent erroneous detection as a mark, a latent image formation timing shift caused by erroneously detecting one mark as two marks in this way, for example, superimposes a visible image on an intermediate transfer body. It is possible to prevent the occurrence of positional deviation between the visible images when they are aligned.

According to the image forming apparatus of the eighteenth to twenty-first aspects, when a plurality of marks formed on the intermediate transfer body are used as the identifying means, the mark detection timing is determined by the time intervals at which the marks are continuously detected. Since it is determined whether or not it is appropriate, it is possible to take appropriate action when the detection signal is generated at an incorrect timing due to stains or scratches on the mark.

For example, according to the image formation of claim 19,
It is possible to notify the operator that the generation timing of the detection signal is abnormal. According to the image forming apparatus of claim 20, the operation of the apparatus is stopped and the latent image forming timing is shifted by the latent image forming control based on the detection signal generated at the wrong timing. It is possible to prevent the occurrence of misalignment between the visible images when the images are superimposed.

Particularly, according to the image forming apparatus of the twenty-first aspect, even if the detection timing is outside the range of the predetermined time interval, if the detection timing is within the predetermined time interval, the second Since the device operation can be continued only by canceling the mark detection signal for the second time, it is possible to prevent the convenience from being deteriorated due to the detection of the minute noise, which is accompanied by the improvement in the detection accuracy.

[Brief description of drawings]

FIG. 1 is a front view illustrating a schematic configuration of a color image forming apparatus according to an embodiment.

FIG. 2 is a partially enlarged perspective view of the color image forming apparatus.

FIG. 3 is a partially enlarged front view of the color image forming apparatus.

FIG. 4 is an explanatory diagram of a relationship between a mark recognition signal and an image writing start signal in the color image forming apparatus.

5A and 5B are optical mark detection devices 54. FIG.
Explanatory drawing of a defect due to a positional relationship between the roller and the roller 11.

FIG. 6 is an explanatory diagram of mark detection in the color image forming apparatus.

FIG. 7 is a flow chart of mark recognition control in the color image forming apparatus.

FIG. 8 is an explanatory diagram of signal processing in the mark recognition control.

FIG. 9 is an explanatory diagram of a defect in mark recognition control.

FIG. 10 is a block diagram of an electric component section of the color image forming apparatus.

11A and 11B are explanatory views of a detection defect of the optical mark detection device 54 due to roller eccentricity.

FIG. 12 is a schematic configuration diagram of a color image forming apparatus according to another embodiment.

FIG. 13 is a schematic configuration diagram around an intermediate transfer belt applicable to the color image forming apparatus.

14 is a perspective view of the intermediate transfer belt of FIG.

FIG. 15 is a schematic configuration diagram of the periphery of another intermediate transfer belt applicable to the color image forming apparatus.

16 is a perspective view of the intermediate transfer belt of FIG.

[Explanation of symbols]

 1 Photoconductor Belt 2 Rotating Roller 3 Rotating Roller 4 Charging Member 5 Laser Writing System Unit 5A Drive Motor 5B Polygon Mirror 5C fθ Lens 60 Rotating Developing Device 6 Y Developing Unit 7 M Developing Unit 8 C Developing Unit 9 Black Developing Unit 10 intermediate transfer belt 11 drive roller (rotating roller) 12 driven roller (rotating roller) 12A driven roller (rotating roller) 13 bias roller 14 transfer member 15 photoconductor belt cleaning device 16 intermediate transfer belt cleaning device 16A cleaning Blade 17 Paper feed table (paper feed cassette) 18 Paper feed roller 19A Upper registration roller 20 Fixing device 20A Fixing roller 20C Pressure roller 21 Static elimination lamp 35 Static elimination lamp 22 Pulley 23 Timing belt 24 Gear 25 Rotation drive motor 53 mark 54 optical mark detection device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location G03G 21/14 G03G 21/00 372

Claims (21)

[Claims] 1. A rotatable latent image carrier, latent image forming means for sequentially forming a plurality of latent images corresponding to a plurality of image information on the latent image carrier, and a latent image carrier formed on the image carrier. Developing means for visualizing the latent image, a movable intermediate transfer body to which the visible images on the latent image carrier are sequentially transferred, and a moving position of the intermediate transfer body provided on the intermediate transfer body. And an identification member indicating
A detector provided near the movement path of the intermediate transfer member for detecting the identification member; and a latent image forming control means for controlling a latent image forming timing of the latent image forming means based on a detection result of the detector, An image having control means for setting the detection timing of the identification member by the detector to a timing at which the positional fluctuation caused in at least one of the intermediate transfer member and the detector due to the operation of the drive section in the apparatus becomes a predetermined amount or less. Forming equipment. 2. The image forming apparatus according to claim 1, wherein the developing means is provided rotatably with respect to the latent image carrier and separately accommodates toners of a plurality of colors. The operation is an image forming apparatus that is a rotation operation of the developing unit. 3. The image forming apparatus according to claim 1, further comprising:
The cleaning means has a cleaning means for cleaning the surface of the intermediate transfer body, and the cleaning means is provided so as to be able to come into contact with and separate from the intermediate transfer body. An image forming apparatus that is a contact / separation operation with respect to a body. 4. The image forming apparatus according to claim 1, further comprising:
In order to transfer the visible image carried on the intermediate transfer member to the transfer material, the apparatus has a paper feeding means for feeding the transfer material, and the operation of the in-apparatus drive section means the operation of the transfer material by the paper feeding means. An image forming apparatus that is a paper feeding operation. 5. A rotatable latent image carrier, latent image forming means for sequentially forming a plurality of latent images corresponding to a plurality of image information on the latent image carrier, and a latent image carrier formed on the image carrier. Developing means for visualizing the latent image, a movable intermediate transfer body to which the visible images on the latent image carrier are sequentially transferred, and a moving position of the intermediate transfer body provided on the intermediate transfer body. And an identification member indicating
A detector provided near the movement path of the intermediate transfer member for detecting the identification member; and a latent image forming control means for controlling a latent image forming timing of the latent image forming means based on a detection result of the detector, An image forming apparatus having: a control unit that prohibits the start or end of the operation of the in-apparatus drive unit during the detection period of the identification member by the detector. 6. The image forming apparatus according to claim 5, wherein said developing means is provided rotatably with respect to said latent image carrier and separately accommodates toners of a plurality of colors. The image forming apparatus is operated by rotating the developing unit. 7. The image forming apparatus according to claim 5, further comprising:
The cleaning means has a cleaning means for cleaning the surface of the intermediate transfer body, and the cleaning means is provided so as to be able to come into contact with and separate from the intermediate transfer body, and the operation of the drive unit in the apparatus means the intermediate transfer of the cleaning means. An image forming apparatus that is a contact / separation operation with respect to a body. 8. The image forming apparatus according to claim 5, further comprising:
In order to transfer the visible image carried on the intermediate transfer member to the transfer material, the apparatus has a paper feeding means for feeding the transfer material, and the operation of the in-apparatus drive section means the operation of the transfer material by the paper feeding means. An image forming apparatus that is a paper feeding operation. 9. A rotatable latent image carrier, latent image forming means for sequentially forming a plurality of latent images corresponding to a plurality of image information on the latent image carrier, and the latent image carrier formed on the image carrier. A developing means for visualizing the latent image, a movable belt-shaped intermediate transfer member which is hung over a plurality of supporting rollers and sequentially transfers the visible images on the latent image carrier, An identification member that is provided on the intermediate transfer member and indicates a moving position of the intermediate transfer member, and a winding portion of the belt-shaped intermediate transfer member with respect to the support roller,
An image forming apparatus comprising: a detector provided so as to detect the identification member; and a latent image forming control means for controlling a latent image forming timing of the latent image forming means based on a detection result of the detector. 10. The image forming apparatus according to claim 9, wherein the detector includes a plurality of support rollers that support the belt-shaped intermediate transfer member, and the belt-shaped intermediate member to a drive roller that drives the intermediate transfer member. An image forming apparatus provided so as to detect the identification member at a winding portion of a transfer body. 11. The image forming apparatus according to claim 9, wherein a plurality of the identifying members are provided on the belt-shaped intermediate transfer member,
An image forming apparatus in which the interval between the plurality of identification members is the same as the circumference of the support roller facing the detector or an integral multiple of the circumference. 12. A rotatable latent image carrier, latent image forming means for sequentially forming a plurality of latent images corresponding to a plurality of image information on the latent image carrier, and a latent image carrier formed on the image carrier. A developing means for developing the latent image into a visible image; a movable belt-shaped intermediate transfer member that is hung over a plurality of support rollers and sequentially transfers the visible image on the latent image carrier; A plurality of discriminating members provided on the belt-shaped intermediate transfer member and indicating the moving position of the intermediate transfer member at intervals equal to the peripheral length of the support roller or an integer multiple of the peripheral length, and in the vicinity of the moving path of the intermediate transfer member. An image forming apparatus having a detector provided for detecting the identification member, and a latent image forming control means for controlling a latent image forming time of the latent image forming means based on a detection result of the detector. 13. The image forming apparatus according to claim 12, wherein the detector is provided at a portion where the belt-shaped intermediate transfer member is wound around the supporting roller so as to detect the identification member. 14. The image forming apparatus according to claim 13, wherein the supporting roller is a driving roller that drives the belt-shaped intermediate transfer member. 15. A rotatable latent image carrier, latent image forming means for sequentially forming a plurality of latent images corresponding to a plurality of image information on the latent image carrier, and a latent image carrier formed on the image carrier. And a developing unit that visualizes the latent image, a movable intermediate transfer body on which the visualized images on the latent image carrier are sequentially transferred, and a moving position of the intermediate transfer body formed on the intermediate transfer body. Mark indicating
A detector provided near the moving path of the intermediate transfer member to detect the mark and output a detection signal thereof, and a latent image forming timing control unit for controlling the latent image forming time of the latent image forming means based on the detection result of the detector. Image forming control means, and detects the mark on the intermediate transfer member at a predetermined time interval by the detector,
When the detection signal is obtained a predetermined number of times consecutively, it is determined that the mark is detected, and if the output of the detection signal is less than the predetermined number of times, the image is configured not to be determined that the mark is detected. Forming equipment. 16. The image forming apparatus according to claim 15, further comprising an image in which a mark detection judgment based on the detection signal is not made for a predetermined period after the detection signal is continuously output a predetermined number of times by the detector. Forming equipment. 17. The image forming apparatus according to claim 16, wherein the predetermined period is shorter than a time required for moving the intermediate transfer member from a first mark formed on the intermediate transfer member to a second mark immediately after the first mark. Image forming apparatus. 18. A rotatable latent image carrier, latent image forming means for sequentially forming a plurality of latent images corresponding to a plurality of image information on the latent image carrier, and a latent image carrier formed on the image carrier. And a developing unit that visualizes the latent image, a movable intermediate transfer body on which the visualized images on the latent image carrier are sequentially transferred, and a moving position of the intermediate transfer body formed on the intermediate transfer body. Indicating a plurality of marks, a detector provided in the vicinity of the moving path of the intermediate transfer member to detect the mark and outputting a detection signal thereof, and a latent image forming means based on the detection result of the detector. Latent image formation control means for controlling the image formation timing, a time interval from the output of the first mark detection signal to the output of the second mark detection signal, and a range of a predetermined time interval And a control hand that determines whether or not the detection timing is within the range of the time interval. An image forming apparatus having and. 19. The image forming apparatus according to claim 18, wherein the control means operates a notifying means for notifying an operator of an abnormal state when the detection timing is out of a specified value. 20. The image forming apparatus according to claim 18, wherein the control means stops the operation of the apparatus when the detection timing is out of a specified value. 21. The image forming apparatus according to claim 18, wherein when the detection timing is outside a specified value and the detection timing is within a predetermined time interval, the image for canceling the second mark detection signal. Forming equipment.