JP3989156B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a color copying machine, a facsimile, a printer, and the like using an electrophotographic process that includes an intermediate transfer member capable of transferring an image on an image carrier such as a photosensitive member a plurality of times and can form a color image on a transfer material. The present invention relates to an image forming apparatus.
[0002]
[Prior art]
In general, in an image forming apparatus using an electrophotographic process, several methods have been proposed as means for changing the resolution of an image using a single image forming device. As one of the methods, a method is known in which the resolution is changed by changing the laser writing density and the rotation speed of the photoconductor as an image carrier without changing the rotation speed of the polygon motor. The resolution can be changed by changing the rotation speed of the polygon mirror. However, if the resolution is increased, the rotation speed of the polygon motor will be increased. This is because it has to be drastically changed and the cost is high.
[0003]
For example, Japanese Laid-Open Patent Application No. 1-224780 discloses a method of changing the writing speed of laser light according to the resolution and changing the process speed. Furthermore, it has also been proposed to change the latent image forming conditions, the developing conditions, the transfer conditions, and the fixing conditions as the process speed is changed.
[0004]
On the other hand, the following are known as conventional examples for changing the image forming linear velocity on the photosensitive member and the transfer / fixing linear velocity. That is, an image in which monochromatic images of different colors are sequentially superimposed on the intermediate transfer body on the basis of detection of an alignment mark attached to the intermediate transfer body, and the image superimposed on the intermediate transfer body is transferred onto a transfer sheet. In the forming apparatus, in order to prevent heat from being lost to the transfer paper when fixing the image on transfer paper such as cardboard or OHP sheet, after the image is transferred to the intermediate transfer body, There is one in which the speed of the transfer body is lowered and the image is transferred to a transfer paper such as a thick paper or an OHP sheet.
[0005]
For example, according to Japanese Patent Laid-Open No. 4-67174, after all color toner images for one page of transfer paper have been completely transferred to the intermediate transfer body, the speed of the intermediate transfer body becomes substantially the same as the speed of the fixing device. By decelerating in this manner, a high-quality image can be obtained even during full-color printing of a small fixing device. Further, according to Japanese Patent Laid-Open No. 6-11977, a higher recording speed is maintained by making the speed of the intermediate transfer member when transferring and fixing the image slower than the speed in other processes during image formation. I have to.
[0006]
[Problems to be solved by the invention]
As described above, in an image forming apparatus using an electrophotographic process, the process line speed is changed in order to change the image resolution at a low cost, and the process line is compatible with various types of paper from thick paper and OHP sheets to thin paper. The thing which changed speed was proposed and put into practical use.
[0007]
However, due to the difference in the process linear velocity, the stop position of the photosensitive member (image carrier) and the intermediate transfer member differs depending on the process linear velocity after all image forming processes are completed. As a result, there is a problem in that it takes time to align the image during the next image formation for a full-color image and the like, and it takes time for the first copy. In particular, many types of paper models are equipped with an intermediate transfer member. In this case, an alignment mark is provided at a predetermined position on the intermediate transfer member, and this mark is detected. On the basis of the above, there is one in which the writing signal to the image carrier is turned on to start writing. In the case of such a control method, if the position of the mark at the time of stoppage shifts, the time required to turn on the write signal at the next image formation also shifts, and as a result, at the time of the next image formation The first copy of will be delayed.
[0008]
An example of actual measurement will be described. For example, after each image is formed at a process linear velocity of 156 mm / s (resolution 400 dpi) and a process linear velocity of 104 mm / s (resolution 600 dpi), the image formation process is completed, and then 156 mm / s (resolution 400 dpi) at the next image formation. The time between the on timing of the image forming motor (drum motor) that rotates and drives the photosensitive member and the intermediate transfer member and the mark detection timing for image alignment on the intermediate transfer member when image formation is started When T1 (see FIG. 9) was measured,
Stop at linear velocity of 156 mm / s: T1 = 210, 208, 209 ms
Stop at linear velocity 104mm / s: T1 = 328, 330, 328ms
It has become. That is, there is a difference of about 118 to 122 ms in the time T1, and this affects the first copy time required for starting the next image formation. Here, if the difference in time T1 is on the order of several tens of ms, it can be said to be an acceptable range. End up.
[0009]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus capable of obtaining a stable first copy time at the start of the next image formation based on detection of a mark for image alignment even under a condition having a plurality of process linear velocities. To do.
[0010]
More specifically, an image forming apparatus capable of obtaining a stable first copy time at the start of the next image formation based on mark detection for image alignment while responding to various resolution changes and paper type changes. Objective.
[0011]
Another object of the present invention is to provide an image forming apparatus capable of always obtaining the same first copy time which is stable at the start of the next image formation based on detection of a mark for image alignment even when the process linear velocity is changed.
[0012]
[Means for Solving the Problems]
According to the first aspect of the present invention, an image is formed by irradiating an image carrier with a writing laser beam in accordance with an image forming process, and the image on the image carrier is temporarily transferred to an intermediate transfer member, and then the intermediate transfer member. A plurality of the image forming processes for changing the writing density of the writing laser beam in the sub-scanning direction in order to change the resolution of the formed image in an image forming apparatus that transfers the image on the transfer material according to the transfer process An image alignment mark provided at a predetermined position of the intermediate transfer body, in which various types of linear speed A and a plurality of types of linear speeds B of the transfer process for transferring from the intermediate transfer body to the transfer material can be freely combined. Writing timing control means for controlling the writing timing of the writing laser beam to the image carrier by detecting the image line, and the process linear velocity at the stop after completion of the image forming process and the transfer process Depending on In order to stop the image carrier and the intermediate transfer member at substantially the same position when operating at any process linear velocity, A stop timing control unit that changes a stop timing of a driving unit that rotationally drives the image carrier and the intermediate transfer member.
[0013]
each Under the condition that there are multiple types of process linear velocities that can cope with various types of resolution changes and paper type changes, the stop timing to stop the drive means for the image carrier etc. according to the process linear velocity at the time of stop is set as the process linear velocity By changing it in consideration of the actual deviation etc. Even when operating at any process linear velocity, the image carrier and the intermediate transfer member can be stopped at substantially the same position. Therefore, Image carrier as well as Intermediate transfer the body's Stop position Place It can be stabilized. Therefore, a stable first copy time can be maintained at the start of the next image formation based on the detection of the mark for image alignment on the intermediate transfer member.
[0014]
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the stop timing control unit performs change control so that the stop timing of the driving unit becomes earlier as the process linear velocity at the time of stop increases.
[0015]
Therefore, even when the process linear velocity is changed, the operation of the invention according to claim 1 can be maintained.
[0016]
According to a third aspect of the present invention, an image is formed by irradiating an image carrier with a writing laser beam in accordance with an image forming process, the image on the image carrier is once transferred to an intermediate transfer member, and then the intermediate transfer member A plurality of the image forming processes for changing the writing density of the writing laser beam in the sub-scanning direction in order to change the resolution of the formed image in an image forming apparatus that transfers the image on the transfer material according to the transfer process An image alignment mark provided at a predetermined position of the intermediate transfer body, in which various types of linear speed A and a plurality of types of linear speeds B of the transfer process for transferring from the intermediate transfer body to the transfer material can be freely combined. Writing timing control means for controlling the writing timing of the writing laser beam to the image carrier by detection of Whether operating at any process linear speed, Process linear velocity when stopping after completion of image forming process and transfer process After approximately the same speed, the driving means for rotating the image carrier and the intermediate transfer member is stopped. Stopping process linear velocity control means.
[0017]
each Under the condition that there are multiple types of process linear velocities that can cope with various resolution changes and paper type changes, Whether operating at any process linear speed, The process linear velocity at that stop Stop the image carrier and the intermediate transfer member after almost the same speed control I do Therefore, the image carrier can be used regardless of changes in the process linear velocity such as the image forming process and transfer process. as well as Intermediate transfer the body's Stop position Place It can be stabilized. Therefore, a stable first copy time can be maintained at the start of the next image formation based on the detection of the mark for image alignment on the intermediate transfer member.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
A first embodiment of the present invention will be described with reference to FIGS. This embodiment is applied to a full-color copying machine using each color toner of KCMY (black, cyan, magenta, yellow). FIG. 1 shows a schematic configuration of the whole, and includes a printer 1, a scanner 2, a paper feed unit 3, a document feeder 4, and a sorter 5.
[0019]
An example of the configuration of the main part of the printer 1 will be described with reference to FIG. First, a drum-shaped photoconductor 10 that is driven to rotate counterclockwise as an image carrier is provided. Around this photoreceptor 10, in accordance with an electrostatic photographic process, a static elimination lamp 11, a charging charger 12 using a charging scotron charger, a writing optical system 13, an eraser 14, a full color developing device 15, and an intermediate transfer belt 16 as an intermediate transfer member. A cleaning device 17 is sequentially provided.
[0020]
The writing optical system 13 is a polygon mirror 18 that deflects and scans a writing laser beam emitted from a semiconductor laser (not shown) that is modulated and driven in accordance with image data toward the photoconductor 10, and the polygon mirror 18 is rotated at high speed. The polygon motor 19 and the fθ lens 20 are used. The full-color developing device 15 divides a black K developing device 15K, a cyan C developing device 15C, a magenta M developing device 15M, and a yellow Y developing device 15Y into four equal parts into a cylindrical revolver unit 21. The revolver system is an arrayed revolver, and a revolver unit 21 is rotated by a revolver motor 22 (see FIG. 4) to select a developing device that faces the photoreceptor 10. Further, when the revolver unit 21 is rotated by the revolver motor 22, the switching sleeve (not shown) restricts the developing sleeve in each developing device to a position where the developing sleeve does not face the photosensitive member 10. A state in which the developer is not in contact (non-contact state) can be appropriately taken.
[0021]
The intermediate transfer belt 16 is formed longer than the circumferential length of the photoreceptor 10 (supported by a plurality of rollers 23 having a length capable of simultaneously forming at least two A4 size screens) and is driven together with the photoreceptor 10. It is rotationally driven by a drum motor 24 (see FIG. 4) as a source. Such an intermediate transfer belt 16 is an image to which an image (toner image) formed on the photoconductor 10 is once transferred. When full-color, the toner image for four colors is transferred and then the toner is transferred. The image is transferred to the transfer material 25. For this reason, a belt transfer charger 26 is disposed on the inner peripheral side facing the photoconductor 10. Further, a paper transfer charger 28 for transferring the toner image on the intermediate transfer belt 16 to the transfer material 25 timed by the registration roller 27 is provided for the intermediate transfer belt 16, and on the downstream side thereof. A cleaning device 29 is provided at a position upstream of the photoconductor 10.
[0022]
Further, alignment marks 30x and 30y are provided at predetermined positions on the intermediate transfer belt 16. The mark 30x is a mark used to align the toner image of each color on the intermediate transfer belt 16 with the toner image formed on the photoconductor 10, and the mark 30y is a registration mark between the front end of the toner image on the intermediate transfer belt 16 and the resist. This mark is used for alignment with the tip of the transfer material 25 conveyed from the roller 27. A mark sensor 31 for detecting such marks 30x and 30y is disposed at a predetermined position in the intermediate transfer belt 16. Reference numeral 32 denotes a conveyance belt for conveying the transferred transfer material 25 to the fixing unit 33 (see FIG. 4).
[0023]
Such a printer 1 is mainly controlled by the printer control unit 41. Here, as shown in FIG. 3, the printer control unit 41 is provided together with control units 42, 43, 44, 45, and 46 for each unit such as the scanner 2, and the system control unit 47 performs printing processing, image writing processing, and paper feeding. Processing, document conveyance processing, and sorting processing are controlled.
[0024]
A configuration example of the printer control unit 41 is shown in FIG. The printer control unit 41 is mainly controlled by a microcomputer including a CPU 51, a ROM 52, and a RAM 53. The CPU 51 follows a control program stored in advance in the ROM 52, a serial communication controller 54, a write control IC 55, a laser light source control unit 56, IO controller 57, main motor 58, drum motor 24, development motor 59, revolver motor 22, replenishment motor 60, polygon motor 19, mark sensor 31, revolver home position sensor 61, fixing unit 33, power supply unit 62, electrometer circuit 63 And a toner adhesion amount sensor (so-called P sensor) circuit 64 is controlled.
[0025]
Further, the CPU 51 has functions of a relative position detection unit 51a, a mark detection time prediction unit 51b, and a time comparison unit 51c. As a result, as disclosed in Japanese Patent Laid-Open No. 9-185271, the relative position detecting means 51a detects the position of the alignment mark and the position of the mark sensor 31 for detecting the alignment marks 30x and 30y shown in FIG. The relative positional relationship with the position is detected. The mark detection time predicting means 51b is based on the relative positional relationship between the alignment mark position detected by the relative position detection means 51a at the start of image formation and the position of the mark sensor 31 that detects the alignment marks 30x and 30y. The time until the mark sensor 31 detects the alignment marks 30x and 30y is predicted. The time comparison unit 51c sets the time to reach the detection position of the mark sensor 31 that detects the marks 30x and 30y on the intermediate transfer belt 16 predicted by the mark detection time prediction unit 51b and the speed of the intermediate transfer belt 16 to, for example, half speed. The difference from the time until the speed of the intermediate transfer belt 16 is stabilized is obtained. The write control IC 55 performs exposure control of image data via the laser light source control unit 56 and the polygon motor 19. As described above, the drum motor 24 rotationally drives the photoreceptor 10 and the intermediate transfer belt 16.
[0026]
In this embodiment, the linear velocity A of the image forming process for changing the writing density of the writing laser beam in the sub-scanning direction with respect to the photoconductor 10 in order to change the resolution of the formed image. ,
Scanning line density Polygon rotation speed Process speed (Linear speed A)
400dpi 24566.9rpm 156mm / s
600 dpi 24566.9 rpm 104 mm / s
800dpi 24566.9rpm 78mm / s (half speed)
Are prepared, and as a plurality of types of linear velocities B in the transfer process of transferring from the intermediate transfer belt 16 to the transfer material 25
Paper type Process speed (Linear speed B)
Plain paper 156mm / s
Cardboard / OHP 78mm / s (half speed)
These two types are prepared (stored in the ROM 52 or the RAM 53) and can be freely combined. According to the scanning line density (resolution) on the operation panel and the paper type selection, 3 × 2 = 6 types of image forming modes can be selected.
[0027]
That is,
400 dpi plain paper mode (A = B = 156 mm / s)
400 dpi cardboard / OHP mode (A = 156 mm / s, B = 78 mm / s)
600 dpi plain paper mode (A = 104 mm / s, B = 156 mm / s)
600 dpi cardboard / OHP mode (A = 104 mm / s, B = 78 mm / s)
800 dpi plain paper mode (A = 78mm / s, B = 156mm / s)
800 dpi cardboard / OHP mode (A = B = 78 mm / s)
The six types are selectable.
[0028]
In the present embodiment, the CPU 51 executes the functions of the write timing control means and the stop timing control means.
[0029]
In such a configuration, when a full-color image is formed in a 400 dpi cardboard / OHP (A = 156 mm / s, B = 78 mm / s) mode (however, two screen images are continuously formed on the intermediate transfer belt 16. The sequence control in the printer control unit 43 will be described with reference to the time chart shown in FIG. When the image formation start command is received, the static elimination lamp 11 and the drum motor 24 are turned on to start an image formation cycle. As a result, the photoreceptor 10 rotates counterclockwise, and the intermediate transfer belt 16 rotates clockwise. At this time, the linear velocity A of the photoreceptor 10 and the intermediate transfer belt 16 is 156 mm / s. Here, when the portion in contact with the charge removal lamp 11 at the time when the charge removal lamp 11 on the photosensitive member 10 is turned on reaches the charging position, the charge charger 12 is turned on. When the charging charger 12 on the photoconductor 10 is in contact with the charging charger 12 and reaches the developing position, the developing bias DC, the developing bias AC, and the developing motor 59 are turned on. Further, when the portion in contact with the developing devices 15K, 15C, 15M or 15Y reaches the image transfer position to the intermediate transfer belt 16 when the developing bias on the photosensitive member 10 is turned on, the belt transfer charger 26 is turned on. To do. If the color of the developing unit 15K, 15C, 15M or 15Y stopped at the development position is different from the designated development color (for example, black K), the revolver unit 21 is rotated and designated after the development bias is turned on. The developing unit for the developing color is moved to the developing position.
[0030]
When the intermediate transfer belt 16 rotates and the mark sensor 31 detects the alignment mark 30x, a scan start command for the first color (black) is transmitted. When the electrostatic latent images of the first color (black) for two screens on the photoreceptor 10 are continuously developed and transferred to the intermediate transfer belt 16, the developing device 15C for the second color (for example, cyan C) is moved to the development position. The revolver unit 21 is rotated so that When the transfer to the intermediate transfer belt 16 is completed, the cleaning device 29 that has been in contact with the intermediate transfer belt 16 until then is released so that the image on the intermediate transfer belt 16 is not erased. After that, when an interrupt due to detection of the mark 30x of the mark sensor 31 occurs again, a scan start command for the second color (cyan C) is transmitted. Similar to the first color (black), the untransferred images are superimposed on the intermediate transfer belt 16 for two screens. Thereafter, the revolver unit 21 is rotated so that the developing device 15M for the third color (for example, magenta M) comes to the developing position. The image for two screens of the third color (magenta M) and the fourth color (yellow Y) is similarly developed, and an untransferred image is superimposed on the intermediate transfer belt 16. In this manner, the writing timing control means controls the writing timing of the writing laser to the photoconductor 10 based on the detection of the mark 30x.
[0031]
On the other hand, when the image formation is started, the transfer material (thick paper) 25 starts to be fed from the paper feed cassette in the paper feed unit 3. When the leading edge of the toner image on the intermediate transfer belt 16 approaches the paper transfer charger 28 for transferring the image on the intermediate transfer belt 16 to the transfer material 25, the leading edge of the transfer material 25 coincides with the leading edge of the toner image. In this way, registration of the transfer material 25 and the toner image is performed. This registration is performed based on the detection of the alignment mark 30y by the mark sensor 31. The linear velocity B of the photosensitive member 10 and the intermediate transfer belt 16 at this time is 78 mm after the transfer to the intermediate transfer belt 16 is completed. / S. When the linear velocity B is switched, any of the developing devices 15K, 15C, 15M, and 15Y of the full-color developing device 15 with respect to the photoreceptor 10 is restricted to the non-contact position. In this way, when the transfer material 25 is superimposed on the toner image on the intermediate transfer belt 16 and passes through the paper transfer charger 28 connected to the positive potential power source, the transfer material 25 is charged with a positive charge by the corona discharge current. The toner image is transferred. The charge charged on the transfer material 25 is neutralized when it passes through the position of a neutralization core (not shown) provided slightly after the paper transfer charger 28. The transfer material 25 on which the toner image is placed is sent to the fixing unit 33 by the transport belt 32. The fixing unit 33 heats and pressurizes the transfer material 25 to fix the toner image on the transfer material 25. The fixed transfer material 25 is discharged to the outside. With regard to this series of paper transfer / fixing transfer processes, the linear velocity B is set to a low speed of 78 mm / s, so that even if the transfer material 25 is thick paper, the fixing efficiency is not lowered and it is good on the thick paper. Can be formed. In addition, since the developer is not in contact with the photosensitive member 10 when the linear velocity is changed, a high-quality image without occurrence of abnormal images such as background contamination or carrier adhesion can be obtained.
[0032]
When all the images have been transferred to the transfer material 25, the process proceeds to an end sequence. That is, when the belt transfer charger 26 is turned off and the belt transfer charger 26 on the photosensitive member 10 is turned off, the portion that is in contact with the belt transfer charger 26 reaches the position of the charge charger 12 and the charge charger 12 is turned off. To. Further, the developing bias and the developing motor 59 are turned off when the portion in contact with the charging charger 12 at the time when the charging charger 12 on the photosensitive member 10 is turned off reaches the developing position. From this point, the mark sensor 31 attached to the intermediate transfer belt 16 enters a standby state for mark detection, and after the mark 30x is detected, the drum motor 24 is turned on until the mark 30x advances to a predetermined position. The static elimination lamp 11 is turned off simultaneously with the turning off.
[0033]
Next, when a full color image is formed in a 600 dpi plain paper mode (A = 104 mm / s, B = 156 mm / s) mode (however, two screen images are continuously formed on the intermediate transfer belt 16). The sequence control in the printer control unit 43 will be described with reference to the time chart shown in FIG. When the image formation start command is received, the static elimination lamp 11 and the drum motor 24 are turned on to start an image formation cycle. As a result, the photoreceptor 10 rotates counterclockwise, and the intermediate transfer belt 16 rotates clockwise. At this time, the linear velocity A of the photoreceptor 10 and the intermediate transfer belt 16 is 104 mm / s. Here, when the portion in contact with the charge removal lamp 11 at the time when the charge removal lamp 11 on the photosensitive member 10 is turned on reaches the charging position, the charge charger 12 is turned on. When the charging charger 12 on the photoconductor 10 is in contact with the charging charger 12 and reaches the developing position, the developing bias DC, the developing bias AC, and the developing motor 59 are turned on. Further, when the portion in contact with the developing devices 15K, 15C, 15M or 15Y reaches the image transfer position to the intermediate transfer belt 16 when the developing bias on the photosensitive member 10 is turned on, the belt transfer charger 26 is turned on. To do. If the color of the developing unit 15K, 15C, 15M or 15Y stopped at the development position is different from the designated development color (for example, black K), the revolver unit 21 is rotated and designated after the development bias is turned on. The developing unit for the developing color is moved to the developing position.
[0034]
When the intermediate transfer belt 16 rotates and the mark sensor 31 detects the alignment mark 30x, a scan start command for the first color (black) is transmitted. When the electrostatic latent images of the first color (black) for two screens on the photoreceptor 10 are continuously developed and transferred to the intermediate transfer belt 16, the developing device 15C for the second color (for example, cyan C) is moved to the development position. The revolver unit 21 is rotated so that When the transfer to the intermediate transfer belt 16 is completed, the cleaning device 29 that has been in contact with the intermediate transfer belt 16 until then is released so that the image on the intermediate transfer belt 16 is not erased. After that, when an interrupt due to detection of the mark 30x of the mark sensor 31 is received again, a scan start command for the second color (cyan C) is transmitted. Similar to the first color (black), the untransferred images are superimposed on the intermediate transfer belt 16 for two screens. Thereafter, the revolver unit 21 is rotated so that the developing device 15M for the third color (for example, magenta M) comes to the developing position. The image for two screens of the third color (magenta M) and the fourth color (yellow Y) is similarly developed, and an untransferred image is superimposed on the intermediate transfer belt 16. In this manner, the writing timing control means controls the writing timing of the writing laser to the photoconductor 10 based on the detection of the mark 30x.
[0035]
On the other hand, when the image formation is started, the transfer material (plain paper) 25 starts to be fed from the paper feed cassette in the paper feed unit 3. When the leading edge of the toner image on the intermediate transfer belt 16 reaches the paper transfer charger 28 for transferring the image on the intermediate transfer belt 16 to the transfer material 25, the leading edge of the transfer material 25 coincides with the leading edge of the toner image. In this way, registration of the transfer material 25 and the toner image is performed. This registration is performed based on the detection of the alignment mark 30y by the mark sensor 31. The linear velocity B of the photosensitive member 10 and the intermediate transfer belt 16 at this time is 156 mm after the transfer to the intermediate transfer belt 16 is completed. / S. Further, when the linear velocity B is switched, any of the developing devices 15K, 15C, 15M, and 15Y of the full-color developing device 15 with respect to the photoreceptor 10 is restricted to the non-contact position. In this way, when the transfer material 25 is superimposed on the toner image on the intermediate transfer belt 16 and passes through the paper transfer charger 28 connected to the positive potential power source, the transfer material 25 is charged with a positive charge by the corona discharge current. The toner image is transferred. The charge charged on the transfer material 25 is neutralized when it passes through the position of a neutralization core (not shown) provided slightly after the paper transfer charger 28. The transfer material 25 on which the toner image is placed is sent to the fixing unit 33 by the transport belt 32. The fixing unit 33 heats and pressurizes the transfer material 25 to fix the toner image on the transfer material 25. The fixed transfer material 25 is discharged to the outside. Regarding this series of paper transfer / fixing transfer processes, the linear velocity B is increased to 156 mm / s, so the processing from the photosensitive member 10 side to the image transfer to the intermediate transfer belt 16 is high resolution and slow. However, the transfer processing speed from the intermediate transfer belt 16 to the transfer material 25 is increased, and the overall printing efficiency can be improved. That is, it is possible to improve printing efficiency while utilizing high resolution. In addition, since the developer is not in contact with the photosensitive member 10 when the linear velocity is changed, a high-quality image without occurrence of abnormal images such as background contamination or carrier adhesion can be obtained.
[0036]
When all the images have been transferred to the transfer material 25, the process proceeds to an end sequence. That is, when the belt transfer charger 26 is turned off and the belt transfer charger 26 on the photosensitive member 10 is turned off, the portion that is in contact with the belt transfer charger 26 reaches the position of the charge charger 12 and the charge charger 12 is turned off. To. Further, the developing bias and the developing motor 59 are turned off when the portion in contact with the charging charger 12 at the time when the charging charger 12 on the photosensitive member 10 is turned off reaches the developing position. From this point, the mark sensor 31 attached to the intermediate transfer belt 16 enters a standby state for mark detection, and after the mark 30x is detected, the drum motor 24 is turned on until the mark 30x advances to a predetermined position. The static elimination lamp 11 is turned off simultaneously with the turning off.
[0037]
In this way, a stop sequence (end) controlled by the stop timing control means after completion of the image forming process and transfer process under the condition that there are a plurality of process linear velocities that can cope with various resolution changes and paper type changes. Sequence) control will be described with reference to FIG. In this embodiment, the stop timing of the drum motor 24 that rotationally drives the photosensitive member 10 and the intermediate transfer belt 16 is basically changed according to the process linear velocity at the time of stop. More specifically, the change control is performed so that the stop timing of the drum motor 24 is earlier as the process linear velocity at the time of stop is higher.
[0038]
Now, in the configuration of the printer 1 as shown in FIG. 2, the circumferential length DL of the drum-shaped photoreceptor 10 is 282.74 mm, and the circumferential length BL of the intermediate transfer belt 16 is 565.49 mm. Further, the position of the static elimination lamp 11 is set as a reference position (origin), a length L1 from the reference position to the charging charger 12 is 23.67 mm, a length L4 from the reference position to the developing position is 86.50 mm, and the belt from the reference position The length L7 to the entrance of the transfer charger 26 is 179.85 mm, and the length L9 from the reference position to the paper transfer charger 28 is 225.87 mm.
[0039]
FIG. 7A shows an example of an end sequence when the process linear velocity at stop is 156 mm / s (= 400 dpi), and FIG. 7B shows that the process linear velocity at stop is 104 mm / s (= 600 dpi). An example of the end sequence is shown. In both cases, after detecting the mark 30x, the charging charger 12 is turned off at a timing advanced by 277 mm, and further, the developing bias DC and the developing motor 59 are turned off at a timing advanced by 435 mm. Is set so that the off-timing (time until off) is different (basically, the case of FIG. 7 (b) where the linear velocity is slower is set to 1.5 times the time). The off timing of the belt transfer charger 26 and the paper transfer charger 28 is set in the same manner. Furthermore, regarding the off timing of the drum motor 24 that rotationally drives the photosensitive member 10 and the intermediate transfer belt 16, 365 ms has passed after the paper transfer charger 28 is turned off in the case of the linear velocity 156 mm / s shown in FIG. In the case of the linear velocity of 104 mm / s shown in FIG. 7B, the ratio of the linear velocity is 1.5 times, that is, 365 × 1.5. = 547.5 ms, as described in FIG. 9, the average value of actual deviation 120 ms (400 dpi conversion) → 180 ms (600 dpi conversion) is added to obtain 547.5 + 180 = 727.5 ms. The timing is set. That is, in the case of the actual measurement value described with reference to FIG. 9, when the linear velocity is stopped at 104 mm / s, the linear velocity is 156 mm / s at the stop position when the linear velocity is stopped at 104 mm / s. There is a delay of 118 to 122 ms = 120 ms on average (actual deviation), so when stopping at a linear velocity of 104 mm / s, this deviation is converted to a linear velocity of 104 mm / s and stopped when it is sent extra. In this way, the stop timing is changed. Since such an actual deviation varies depending on the load of the machine (due to the moment of inertia), optimization is necessary.
[0040]
As illustrated in FIGS. 7A and 7B, the stop timing control unit changes and controls the stop timing of the drum motor 24 in accordance with the process linear velocity at the time of stop, so that the process linear velocity at the time of stop is controlled. Even if they are different, the stop position relationship between the photoconductor 10 and the intermediate transfer belt 16 can always be stabilized. Therefore, a stable first copy time can be maintained at the start of the next image formation based on the detection of the image alignment mark 30x on the intermediate transfer belt 16.
[0041]
A second embodiment of the present invention will be described with reference to FIG. The same parts as those shown in the first embodiment are denoted by the same reference numerals, and description thereof is also omitted. In the present embodiment, instead of the stop timing control means, the function of the stop process linear speed control means executed by the CPU 51 is added so that the process linear speed at the time of stop is always constant. .
[0042]
In this embodiment, the process linear velocity at the time of stop is made constant at 156 mm / s (= 400 dpi) regardless of the process linear velocity during the image forming process or the transfer process. Therefore, when the process linear velocity during the transfer process is 156 mm / s (= 400 dpi), the stop process is performed at the process linear velocity 156 mm / s (= 400 dpi) as it is even in the end sequence at the time of stop. That is, it is the same as the case shown in FIG.
[0043]
On the other hand, when the process linear velocity during the transfer process is 104 mm / s (= 600 dpi), the process linear velocity is changed to a constant value of 156 mm / s (= 400 dpi) as shown in FIG. The stop process similar to that shown in FIG. 7A is performed.
[0044]
Therefore, according to the present embodiment, the process linear velocity at the time of stoppage is controlled to be constant under the condition that there are plural types of process linear velocity that can cope with various resolution changes and paper type changes. Regardless of changes in the process linear velocity such as the image forming process and the transfer process, the stop position relationship between the photoconductor 10 and the intermediate transfer belt 16 can always be stabilized. Therefore, a stable first copy time can be maintained at the start of the next image formation based on the detection of the image alignment mark 30x on the intermediate transfer belt 16.
[0045]
【The invention's effect】
According to the invention of claim 1 ,image Carrier as well as Intermediate transfer the body's Stop position Place Therefore, a stable first copy time can be maintained at the start of the next image formation based on the detection of the mark for image alignment on the intermediate transfer member.
[0046]
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the stop timing control means performs change control so that the stop timing of the drive means becomes earlier as the process linear velocity at the time of stop increases. Therefore, even when the process linear velocity is changed, the effect of the invention of claim 1 can be reliably maintained.
[0047]
According to invention of Claim 3, , Product Regardless of changes in process linear velocity such as image process and transfer process, image carrier as well as Intermediate transfer the body's Stop position Place Therefore, a stable first copy time can be maintained at the start of the next image formation based on the detection of the mark for image alignment on the intermediate transfer member.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a basic configuration of an image forming apparatus according to a first embodiment of the present invention.
FIG. 2 is a schematic configuration diagram illustrating a configuration of a printer portion.
FIG. 3 is a schematic block diagram showing the configuration of the entire control system.
FIG. 4 is a block diagram illustrating a configuration of a printer control unit.
FIG. 5 is a time chart showing sequence control in a 400 dpi thick paper / OHP mode.
FIG. 6 is a time chart showing sequence control in a 600 dpi plain paper mode.
FIG. 7 is a time chart showing end sequence control when process linear velocities are different.
FIG. 8 is a time chart showing end sequence control according to the second embodiment of the present invention.
FIG. 9 is a time chart showing a deviation time T1 between the on-timing of the image forming motor and the mark detection timing.
[Explanation of symbols]
10 Image carrier
16 Intermediate transfer member
25 Transfer material
30 mark

Claims (3)

According to an image forming process, an image is formed by irradiating an image carrier with a writing laser beam, and the image on the image carrier is temporarily transferred to an intermediate transfer member. In the image forming apparatus to be transferred onto
A plurality of types of linear velocities A of the image forming process for changing the writing density in the sub-scanning direction of the writing laser light to change the resolution of the formed image, and transfer from the intermediate transfer member to the transfer material A plurality of types of linear velocities B of the transfer process can be freely combined,
Writing timing control means for controlling the writing timing of the writing laser beam to the image carrier by detecting an image alignment mark provided at a predetermined position of the intermediate transfer member;
The image carrier and the intermediate transfer member are stopped at substantially the same position regardless of the process linear velocity depending on the process linear velocity at the stop after the image forming process and the transfer process. An image forming apparatus comprising: a stop timing control unit that changes a stop timing of a driving unit that rotationally drives the carrier and the intermediate transfer member.   The image forming apparatus according to claim 1, wherein the stop timing control unit performs change control so that the stop timing of the drive unit becomes earlier as the process linear velocity at the time of stop increases. According to an image forming process, an image is formed by irradiating an image carrier with a writing laser beam, and the image on the image carrier is temporarily transferred to an intermediate transfer member. In the image forming apparatus to be transferred onto
A plurality of types of linear velocities A of the image forming process for changing the writing density in the sub-scanning direction of the writing laser light to change the resolution of the formed image, and transfer from the intermediate transfer member to the transfer material A plurality of types of linear velocities B of the transfer process can be freely combined,
Writing timing control means for controlling the writing timing of the writing laser beam to the image carrier by detecting an image alignment mark provided at a predetermined position of the intermediate transfer member;
Regardless of the process linear velocity, the drive means for rotationally driving the image carrier and the intermediate transfer member after setting the process linear velocity at the stop after completion of the image forming process and the transfer process to substantially the same speed. an image forming apparatus comprising: a, a stop process linear velocity control means for stopping.

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