JP2000105526A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To carry out a series of image formation processing at a proper processing speed corresponding to a variety of required image formation conditions, in an image forming device interposed with an intermediate transfer body between an image carrier and a transfer material. SOLUTION: Plural kinds of linear velocities A in a imaging process for changing the write density in the sub-scanning direction of a write laser beam to change the resolution of a formed image and plural of linear velocities B in a transfer process to transfer from an intermediate transfer body to a transfer material are made to be freely combined. Selecting the linear velocities from A or B can cope with requirements of various changes in resolution, the kind of paper, etc., and properly provide a processing mode with high print efficiency. For example, the combination of the linear velocity A of 156 mm/sec and the linear velocity B of 78 mm/sec, where A is larger than B, can provide a high quality image formation on a transfer material such as pasteboard and an OHP sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color copying machine and a color printer using an electrophotographic process capable of forming a color image or the like on a transfer material by providing an intermediate transfer member capable of transferring an image on a photosensitive member a plurality of times. And the like.

[0002]

2. Description of the Related Art Generally, 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 apparatus. 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 photosensitive member as the image carrier without changing the rotation speed of the polygon motor. This means that the resolution can be changed by changing the number of rotations of the polygon mirror.However, as the resolution increases, the number of rotations of the polygon motor increases, and when the rotation becomes extremely high, the configuration of the polygon mirror increases. This is because it has to be changed drastically, which increases the cost.

For example, Japanese Patent Application Laid-Open No. 1-2224780 discloses a method in which the writing density of laser light is changed in accordance with the resolution, and the process speed is also changed. Further, it has been proposed to change the latent image forming condition, the developing condition, the transfer condition, and the fixing condition together with the change of the process speed.

On the other hand, the following is known as a conventional example for changing the linear speed of image formation on a photosensitive member and the linear speed of transfer / fixing. That is, an image in which single-color images of different colors are sequentially superimposed on the intermediate transfer body with reference to the detection of the alignment mark attached to the intermediate transfer body, and the image superimposed on the intermediate transfer body is transferred to transfer paper. In the forming device, cardboard or O
In order to prevent heat from being taken by the transfer paper when fixing the image on the transfer paper such as an HP sheet and to reduce the fixing efficiency, the speed of the intermediate transfer body is reduced after transferring the image to the intermediate transfer body. There is a type in which an image is transferred to a transfer paper such as a thick paper or an OHP sheet.

For example, according to Japanese Patent Application Laid-Open No. 4-67174, after the full-color toner image for one page of the transfer paper is completely transferred to the intermediate transfer member, the speed of the intermediate transfer member is substantially equal to the speed of the fixing device. By decelerating to a speed, a high-quality image can be obtained even in a small fixing device full-color printing. According to Japanese Patent Application Laid-Open No. Hei 6-11977, a high recording speed is maintained by lowering the speed of an intermediate transfer body when transferring and fixing an image than the speed in other processes during image formation. I have to.

[0006]

However, in the case of these prior arts, the problem of maintaining the resolution of the image or the fixing efficiency is only grasped one-sidedly and solved.
It is not always possible to maintain the resolution and the fixing efficiency or to improve the printing efficiency properly in accordance with the required various image forming conditions.

Therefore, the present invention relates to an image forming apparatus of the type in which an intermediate transfer member is interposed between an image carrier and a transfer material, and a series of images at a proper processing speed corresponding to various required image forming conditions. It is an object to provide an image forming apparatus capable of performing an image forming process.

In addition, in order to achieve the above object, when the process linear speed is changed so that the processing speed becomes appropriate in accordance with various image forming conditions required, the developer on the developing sleeve is changed to a photosensitive member. When contacting the photoconductor, the linear velocity ratio of the developing sleeve to the photoconductor is slightly changed, and a horizontal band-like background stain is generated on the photoconductor due to vibration or the like when the linear velocity is changed. The manner in which this occurs is different depending on the relationship between the driving of the developing sleeve and the driving of the photoconductor. However, even if the same driving source is used, the above-described background stain is generated. For example, in the thick paper mode, that is, the image is transferred to the intermediate transfer belt at a normal linear speed on the photoconductor, and then the linear speed of the intermediate transfer belt is reduced (1
/ 2 normal speed), when batch transfer to the transfer material, if the developing material of the developing device is in contact with the photoconductor at the time of changing the process linear speed, the background stain occurs and is transferred to the intermediate transfer belt. A background image appears on the toner image on the intermediate transfer belt and is eventually transferred to a transfer material. Accordingly, it is an object of the present invention to provide an image forming apparatus capable of obtaining a high-quality image free from abnormal images such as background contamination and carrier adhesion even when the process linear velocity is changed.

[0009]

According to the first aspect of the present invention,
An image is formed by irradiating the 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. A plurality of types of linear velocities A of the image forming process for changing the writing density of the writing laser light in the sub-scanning direction to change the resolution of an image to be formed, A plurality of types of linear velocities B of the transfer process for transferring from the intermediate transfer member to the transfer material can be freely combined. Therefore, by selecting the linear velocity A or B, it is possible to respond to various requests for changing the resolution or changing the paper type and the like, and to adopt a processing mode with high printing efficiency as appropriate.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, a plurality of developing means for bringing a developer into contact with the image carrier to develop the image, and the developer for the image carrier. Switching means for switching between contact and non-contact with the image bearing member when the linear velocities A and B are changed. Therefore, when the process linear velocities A and B are changed, the developer is not in contact with the image carrier, so that a high-quality image free of abnormal images such as background contamination and carrier adhesion can be obtained.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, a combination of linear velocity conditions of linear velocity A> linear velocity B is included. Therefore, even if various resolution changes are made, it is possible to form an image on a transfer material such as a cardboard or an OHP sheet with high quality.

According to a fourth aspect of the present invention, in the image forming apparatus according to the first or second aspect, a combination of linear velocity conditions such that linear velocity A <linear velocity B is included. Therefore, printing efficiency can be improved especially at a high resolution. That is, at the time of high resolution, the processing of the image forming process is slow and the linear speed A, that is, the rotation of the image carrier is slow, but at the time of transfer from the intermediate transfer member to the transfer material, the linear speed B of the transfer process is increased accordingly. Therefore, it is possible to improve the printing efficiency as a whole while securing a high resolution.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings. The present embodiment is applied to a full-color copying machine using KCMY (black, cyan, magenta, and yellow) toners. FIG. 1 shows a schematic configuration of the entire system, and includes a printer 1, a scanner 2, a paper feed unit 3, a document feeder 4, and a sorter 5.

Here, 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 is provided as an image carrier. Around the photoreceptor 10, according to an electrostatographic 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 body And a cleaning device 17 are provided in this order.

The writing optical system 13 includes a polygon mirror 18 that deflects and scans a writing laser beam emitted from a semiconductor laser (not shown) modulated according to image data toward the photoconductor 10, and the polygon mirror 18. Is constituted by a polygon motor 19 for rotating the lens at high speed, an fθ lens 20, and the like. The full-color developing device 15 is a black K
And a developing unit 15C for cyan C, a developing unit 15M for magenta M, and a developing unit 15Y for yellow Y are arranged in a cylindrical revolver unit 21 into four equal parts. By rotating the revolver unit 21 by the revolver motor 22 (see FIG. 4), a developing device facing the photoconductor 10 is selected. Also,
When the revolver unit 22 is rotated by the revolver motor 22, the developing sleeve in each of the developing devices is regulated to a position where the developing sleeve does not face the photoconductor 10 by switching means (not shown). Are configured to be able to appropriately take a state where they do not contact each other (non-contact state).

The intermediate transfer belt 16 is formed to be longer than the peripheral length of the photoconductor 10 (having a length capable of forming at least two A4 size screens simultaneously) and is supported by a plurality of rollers 23 and the like. Drum motor 24 with 10
(See FIG. 4). Such an intermediate transfer belt 16 is a member to which an image (toner image) formed on the photoreceptor 10 is once transferred. In the case of full color, a toner image of four colors is transferred and then the toner image 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, the intermediate transfer belt 16 is provided with 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, and is provided on the downstream side thereof. A cleaning device 29 is provided at a position upstream of the photoconductor 10.

The intermediate transfer belt 16 is provided with alignment marks 30x and 30y at predetermined positions. The mark 30x is a mark used to align the toner image formed on the photoreceptor 10 on the intermediate transfer belt 16 with the toner image of each color. Roller 27
This mark is used for alignment with the leading end of the transfer material 25 conveyed from the printer. A mark sensor 31 for detecting such marks 30x and 30y is provided at a predetermined position in the intermediate transfer belt 16. 32 is a transferred transfer material 2
5 is a transport belt for transporting the fixing belt 5 to the fixing unit 33 (see FIG. 4).

The printer 1 is mainly controlled by the printer controller 41. As shown in FIG. 3, the printer control unit 41 is provided together with the 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 sheet feeding. The processing, the document transport processing, and the sorting processing are controlled.

FIG. 4 shows an example of the configuration of the printer control unit 41. The printer control unit 41 includes a CPU 51, a ROM 5,
The microcomputer 51 is mainly controlled by a microcomputer including a serial communication controller 54, a write control IC 55, and a laser light source control unit 5 according to a control program stored in a ROM 52 in advance.
6, IO controller 57, main motor 58, drum motor 24, developing motor 59, revolver motor 22, supply motor 60, polygon motor 19, mark sensor 3
1. It controls the revolver home position sensor 61, the fixing unit 33, the power supply unit 62, the electrometer circuit 63, and the toner adhesion amount sensor (so-called P sensor) circuit 64.

The CPU 51 has functions of a relative position detecting means 51a, a mark detection time predicting means 51b, and a time comparing means 51c. As a result, Japanese Patent Application Laid-Open
As shown in Japanese Patent Application Laid-Open No. 185271, the relative position detection means 51a is a relative position between the position of the mark for alignment and the position of the mark sensor 31 for detecting the marks 30x and 30y for alignment shown in FIG. Detect relationships. The mark detection time estimating means 51b calculates the position of the mark detected by the relative position detecting means 51a at the start of image formation and the position of the mark sensor 31 for detecting the marks 30x and 30y. Mark sensor 31
Predicts the time required for detecting the alignment marks 30x and 30y. The time comparing means 51c reduces the time to reach the detection position of the mark sensor 31 for detecting the marks 30x and 30y on the intermediate transfer belt 16 predicted by the mark detection time prediction means 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 stabilizes in that case is obtained. The writing control IC 55 controls exposure of image data via the laser light source control unit 56 and the polygon motor 19. The drum motor 24 rotationally drives the photoconductor 10 and the intermediate transfer belt 16 as described above.

Here, in the present embodiment, a line of an image forming process for changing the writing density of the writing laser light on the photosensitive member 10 in the sub-scanning direction to change the resolution of an image to be formed. As the speed A, three types of scanning line density, polygon rotation speed, process speed (linear speed A) 400 dpi 24566.9 rpm 156 mm / sec 600 dpi 24566.9 rpm 104 mm / sec 800 dpi 24566.9 rpm 78 mm / sec (half speed), and three types are prepared. Two types of linear speeds B of a plurality of types of transfer processes for transferring from the transfer belt 16 to the transfer material 25 are prepared: paper type process speed (linear speed B) plain paper 156 mm / sec cardboard / OHP 78 mm / sec (half speed). (Stored in the ROM 52 or the RAM 53), and these 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.

That is, 400 dpi plain paper mode (A = B = 156 mm / sec) 400 dpi thick paper / OHP mode (A = 156 mm / sec, B = 78 mm / sec) 600 dpi plain paper mode (A = 104 mm / sec, B = 156 mm) / dpi) 600 dpi cardboard / OHP mode (A = 104 mm / sec, B = 78 mm / sec) 800 dpi plain paper mode (A = 78 mm / sec, B = 156 mm / sec) 800 dpi cardboard / OHP mode (A = B = 78 mm / sec) sec) can be selected freely.

In such a configuration, a full-color image is converted to a 400 dpi cardboard / OHP mode (A = 156 mm / sec,
FIG. 5 is a time chart showing sequence control in the printer control unit 43 when forming in the mode (B = 78 mm / sec) mode (assuming that images for two screens are formed continuously on the intermediate transfer belt 16). This will be described with reference to FIG. When an image forming start command is received, the charge removing lamp 11 and the drum motor 24 are turned on, and an image forming cycle is started.
As a result, the photoconductor 10 rotates counterclockwise, and the intermediate transfer belt 16 rotates clockwise. At this time, the linear velocity A of the photoconductor 10 and the intermediate transfer belt 16 is 156 mm / sec.
It is. Here, when the portion on the photosensitive member 10 that is in contact with the charge removing lamp 11 at the time when the charge removing lamp 11 is turned on reaches the charging position, the charging charger 12 is turned on. When the portion where the charger 12 is in contact with the photoreceptor 10 at the time when the charger 12 is turned on reaches the developing position, the developing bias DC, the developing bias AC, and the developing motor 59 are turned on. Further, when the developing bias on the photoreceptor 10 is turned on, the developing devices 15K, 15C, 15M
Alternatively, when the portion in contact with 15Y reaches the image transfer position on the intermediate transfer belt 16, the belt transfer charger 26
Turn on. The developing device 15 stopped at the developing position
When the color of K, 15C, 15M or 15Y is different from the designated developing color (for example, black K), after turning on the developing bias, the revolver unit 21 is rotated to bring the developing device of the designated developing color to the developing position. Move.

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. The electrostatic latent images of the first color (black) for two screens on the photoconductor 10 are continuously developed, and when the transfer to the intermediate transfer belt 16 is completed, the developing device 15C for the second color (for example, cyan C) is moved to the development position. The revolver unit 21 is rotated to come to the position. 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 is released so that the image on the intermediate transfer belt 16 is not erased. Thereafter, when an interruption due to the detection of the mark 30x by the mark sensor 31 is input again, the scan start command for the second color (cyan C) is transmitted. An untransferred image is superimposed on the intermediate transfer belt 16 for two screens in the same manner as the first color (black). Then, the third color (for example, magenta M)
The revolver unit 21 is rotated so that the developing device 15M of the second position comes to the developing position. Images for two screens of the third color (magenta M) and the fourth color (yellow Y) are similarly developed, and an untransferred image is superimposed on the intermediate transfer belt 16. On the other hand, when the image formation is started, the transfer material (thick paper) 25 is
Paper is being fed from the paper cassette inside. When the leading end 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 end of the transfer material 25 coincides with the leading end of the toner image. Thus, the 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. At this time, the linear velocity B of the photoconductor 10 and the intermediate transfer belt 16 becomes 78 mm after the transfer to the intermediate transfer belt 16 is completed. / sec has been switched. When the linear velocity B is switched, any of the developing devices 15K, 15C, 15M, 15
Y is also restricted to the non-contact position. Thus, the transfer material 2
When the toner image 5 passes through the paper transfer charger 28 connected to a positive potential power supply while being superimposed on the toner image on the intermediate transfer belt 16, the transfer material 25 is charged with a positive charge by a corona discharge current, and the toner image is transferred. You. The electric charge on the transfer material 25 is eliminated when passing through the position of a static elimination core (not shown) provided slightly downstream of the paper transfer charger 28. The transfer material 25 carrying the toner image is sent to the fixing unit 33 by the conveyor belt 32. The fixing unit 33 heats and presses the transfer material 25 to fix the toner image on the transfer material 25. The fixed transfer material 25 is discharged to the outside. In the transfer process including the series of paper transfer and fixing, since the linear velocity B is as low as 78 mm / sec, the transfer material 25 is a thick paper. A quality image can be formed. Further, since the developer is not in contact with the photoconductor 10 when the linear velocity is changed, a high-quality image free of abnormal images such as background contamination and carrier adhesion can be obtained.

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 portion of the photoconductor 10 that is in contact with the belt transfer charger 26 when the belt transfer charger 26 is turned off reaches the position of the charger 12, the 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 charger 12 at the time when the charging charger 12 on the photoconductor 10 is turned off reaches the developing position. From this point, a standby state for mark detection by the mark sensor 31 attached to the intermediate transfer belt 16 is established. After the detection of the mark 30x, the drum motor 24 is turned on until the mark 30x advances to a predetermined position. The discharge lamp 11 is turned off simultaneously with the turning off.

Next, a case where a full-color image is formed in a 600 dpi plain paper mode (A = 104 mm / sec, B = 156 mm / sec) mode (however, an image for two screens is continuously formed on the intermediate transfer belt 16) Will be described with reference to a time chart shown in FIG. When an image forming start command is received, the charge removing lamp 11 and the drum motor 24 are turned on, and an image forming cycle is started. As a result, the photoconductor 10 rotates counterclockwise, and the intermediate transfer belt 16 rotates clockwise. At this time, the linear velocity A of the photoconductor 10 and the intermediate transfer belt 16 is 104 mm / sec. Here, when the portion on the photosensitive member 10 that is in contact with the charge removing lamp 11 at the time when the charge removing lamp 11 is turned on reaches the charging position, the charging charger 12 is turned on. When the portion where the charger 12 is in contact with the photoreceptor 10 at the time when the charger 12 is turned on 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 device 15K, 15C, 15M or 15Y at the time when the developing bias on the photoreceptor 10 is turned on reaches the image transfer position to the intermediate transfer belt 16, the belt transfer charger 26 is turned on. I do. If the color of the developing device 15K, 15C, 15M or 15Y stopped at the developing position is different from the designated developing color (for example, black K), after turning on the developing bias, the revolver unit 21 is rotated to rotate the designated developing color. The developing device for the developing color is moved to the developing position.

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. The electrostatic latent images of the first color (black) for two screens on the photoconductor 10 are continuously developed, and when the transfer to the intermediate transfer belt 16 is completed, the developing device 15C for the second color (for example, cyan C) is moved to the development position. The revolver unit 21 is rotated to come to the position. 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 is released so that the image on the intermediate transfer belt 16 is not erased. Thereafter, when an interruption due to the detection of the mark 30x by the mark sensor 31 is input again, the scan start command for the second color (cyan C) is transmitted. An untransferred image is superimposed on the intermediate transfer belt 16 for two screens in the same manner as the first color (black). Then, the third color (for example, magenta M)
The revolver unit 21 is rotated so that the developing device 15M of the second position comes to the developing position. Images for two screens of the third color (magenta M) and the fourth color (yellow Y) are similarly developed, and an untransferred image is superimposed on the intermediate transfer belt 16.

On the other hand, when the image formation is started, the transfer material (plain paper) 25 has begun to be fed from the paper feed cassette in the paper feed unit 3. When the leading end 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 end of the transfer material 25 coincides with the leading end of the toner image. Thus, the registration of the transfer material 25 and the toner image is performed. The registration is performed based on the detection of the alignment mark 30y by the mark sensor 31. At this time, the linear velocity B of the photoconductor 10 and the intermediate transfer belt 16 is 156 mm after the transfer to the intermediate transfer belt 16 is completed. / sec has been switched. When the linear velocity B is switched, any of the developing units 15K, 15C, 15M, and 15Y of the full-color developing device 15 is regulated to the non-contact position with respect to the photoconductor 10. Thus, the transfer material 25 is transferred to the intermediate transfer belt 16.
When passing through the paper transfer charger 28 connected to the positive potential power supply while being superposed on the upper toner image, the transfer material 25 is charged with a positive charge by the corona discharge current, and the toner image is transferred. The charge on the transfer material 25 is transferred to a paper transfer charger 28.
Is removed when passing through the position of a charge removal core (not shown) provided slightly downstream of the. Transfer material 2 with toner image
5 is sent to the fixing unit 33 by the conveyor belt 32. The fixing unit 33 heats and presses the transfer material 25 to fix the toner image on the transfer material 25. Fixed transfer material 2
5 is discharged outside. In the transfer process including a series of paper transfer and fixing, the linear speed B is increased to 156 mm / sec.
Although the processing up to image transfer to 6 is high resolution and slow, the processing speed of transfer from the intermediate transfer belt 16 to the transfer material 25 is increased, and overall printing efficiency can be improved. That is, the printing efficiency can be improved while utilizing the high resolution. When the linear velocity is changed, the developer is
Since no contact is made, a high quality image free of abnormal images such as background contamination and carrier adhesion can be obtained.

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 portion of the photoconductor 10 that is in contact with the belt transfer charger 26 when the belt transfer charger 26 is turned off reaches the position of the charger 12, the 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 charger 12 at the time when the charging charger 12 on the photoconductor 10 is turned off reaches the developing position. From this point, a standby state for mark detection by the mark sensor 31 attached to the intermediate transfer belt 16 is established. After the detection of the mark 30x, the drum motor 24 is turned on until the mark 30x advances to a predetermined position. The discharge lamp 11 is turned off simultaneously with the turning off.

[0030]

According to the first aspect of the present invention, a plurality of types of linear velocities in an image forming process for changing the writing density of a writing laser beam in the sub-scanning direction to change the resolution of an image to be formed. A can be freely combined with a plurality of types of linear velocities B of a transfer process for transferring from an intermediate transfer member to a transfer material. , And a processing mode with high printing efficiency can be appropriately adopted.

According to the second aspect of the present invention, in the image forming apparatus according to the first aspect, when the linear velocities A and B are changed, the developer is brought into a non-contact state with the image carrier by the switching means. When the process linear velocities A and B are changed, the developer is not in contact with the image carrier, and a high-quality image free of abnormal images such as background contamination and carrier adhesion can be obtained.

According to the third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the linear velocity A> the linear velocity B
Since a combination of the linear velocity conditions is included, even if various resolution changes are made, it is possible to form a high quality image particularly on a transfer material such as a thick paper or an OHP sheet.

According to the fourth aspect of the present invention, in the image forming apparatus according to the first or second aspect, the linear velocity A <the linear velocity B
Since the combination of the linear velocity conditions is included, the printing efficiency can be improved particularly at a high resolution.

[Brief description of the drawings]

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

FIG. 2 is a schematic configuration diagram illustrating a configuration of a printer unit.

FIG. 3 is a schematic block diagram illustrating a configuration of an 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.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Image carrier 15 Developing means 16 Intermediate transfer body 25 Transfer material

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (reference) G03G 15/16 F term (reference) 2C362 AA03 CB14 2H027 EB06 ED02 ED04 ED08 ED16 ED24 EE03 2H030 AD17 BB16 BB24 BB33 BB42 BB53 BB71 2H03 CA13 2H076 AB05 AB68

Claims (4)

[Claims] 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. In an image forming apparatus for transferring onto a transfer material in accordance with a transfer process, a plurality of lines of the image forming process for changing a writing density of the writing laser light in a sub-scanning direction to change a resolution of an image to be formed. An image forming apparatus, wherein a speed A and a plurality of types of linear velocities B of the transfer process for transferring the image from the intermediate transfer member to the transfer material can be freely combined. 2. A developing device comprising: a plurality of developing means for bringing a developer into contact with the image carrier to develop the image; and a switching means for switching contact / non-contact of the developer with the image carrier. Wherein the developer is brought into a non-contact state with the image carrier by the switching means when changing the image forming apparatus and the image forming apparatus. 3. The image forming apparatus according to claim 1, wherein a combination of linear velocity conditions of linear velocity A> linear velocity B is included. 4. The image forming apparatus according to claim 1, wherein a combination of linear velocity conditions such that linear velocity A <linear velocity B is included.