JP7077040B2 - Image forming device - Google Patents

Description

The present invention relates to an image forming apparatus such as a copier, a printer, and a facsimile machine using an electrophotographic method or an electrostatic recording method.

Conventionally, as an image forming apparatus using an electrophotographic method or the like, an image forming apparatus adopting the following intermediate transfer method is known. The intermediate transfer type image forming apparatus has, for example, a plurality of image forming portions arranged in a line along the moving direction of the surface of the intermediate transfer body, each having an image carrier. Then, the toner images of different colors formed on the image carrier of each image forming portion are sequentially primary-transferred so as to be superimposed on the intermediate transfer body, and then collectively secondary-transferred to the transfer material. Toner.

In such an image forming apparatus, it has been proposed to increase the peripheral speed difference between the image carrier and the intermediate transfer body, for example, for the purpose of improving the quality of a character image (Patent Document 1). Further, in recent years, in order to expand the color space reproduction range, for example, an image forming apparatus capable of performing image formation in a special image forming mode for increasing the amount of toner on the image carrier has been proposed. Here, in order to distinguish from this image formation mode, a normal image formation mode that is not set as an operation setting for expanding the color space reproduction range is referred to as a "normal mode". Further, the image formation mode in which the operation settings for expanding the color space reproduction range are changed with respect to this normal mode is called "wide color gamut mode".

Japanese Unexamined Patent Publication No. 2015-227952

However, according to the studies by the present inventors, in the wide color gamut mode in which the amount of toner loaded on the image carrier is set to be larger than in the normal mode, the primary transferability is deteriorated and the image quality is deteriorated. It turned out that there was a possibility.

Therefore, an object of the present invention is to provide an image forming apparatus capable of suppressing a decrease in primary transferability in a wide color gamut mode.

The above object is achieved by the image forming apparatus according to the present invention. In summary, the present invention comprises a rotatable image carrier that carries a toner image, a developing means that supplies toner to the image carrier to form a toner image, and a toner that is primarily transferred from the image carrier. Correlate with the amount of the developing means, the intermediate transfer body rotatable for secondary transfer of the image to the transfer material, the control means capable of changing at least the peripheral speed difference between the image carrier and the intermediate transfer body, and the development means. An image is formed by a first mode in which the amount of toner on the image portion on the image carrier is the first amount, or an image on the image carrier. It is possible to select image formation by the second mode in which the amount of toner on the portion is larger than the first amount , and when the second mode is selected, the circumference of the image carrier and the intermediate transfer body is selected. An image forming apparatus in which the speed difference is made larger than the peripheral speed difference between the image carrier and the intermediate transfer body when the first mode is selected, and the control means is the detection result of the detection means. It is configured to change the peripheral speed difference between the image carrier and the intermediate transfer body at the time of image formation, and the amount of the developing means used indicated by the detection result of the detecting means is first. The change of the peripheral speed difference is made so that the peripheral speed difference in the case of the second value where the usage amount is larger than the first value is larger than the peripheral speed difference in the case of the value of. In addition, the control means is in the second mode with respect to the peripheral speed difference in the first mode when the usage amount of the developing means indicated by the detection result of the detection means is the first value. The change amount of the peripheral speed difference in the second mode with respect to the peripheral speed difference in the first mode when the usage amount is the second value, rather than the change amount of the peripheral speed difference. It is an image forming apparatus characterized in that the peripheral speed difference is changed so that the peripheral speed difference becomes smaller .

According to the present invention, it is possible to suppress a decrease in primary transferability in the wide color gamut mode.

It is a schematic cross-sectional view of an image forming apparatus. It is a schematic block diagram which shows the control mode of the main part of an image forming apparatus. It is a graph which shows the relationship between the primary transferability and the peripheral speed difference between an image carrier and an intermediate transfer body. It is a flowchart which shows the outline of the control procedure of Example 1. FIG. It is a schematic block diagram which shows the control mode of the main part of the image forming apparatus of another example. It is a graph which shows the relationship between the primary transferability and the peripheral speed difference between an image carrier and an intermediate transfer body for each cartridge life. It is a flowchart which shows the outline of the control procedure of Example 2. FIG. It is a schematic diagram which shows the driving mode of the main part of the image forming apparatus of another example.

Hereinafter, the image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

[Example 1]
1. 1. Overall Configuration and Operation of the Image Forming Device FIG. 1 is a schematic cross-sectional view of the image forming device 100 of the present embodiment. The image forming apparatus 100 of this embodiment is a tandem type laser beam printer that employs an intermediate transfer method and is capable of forming a full-color image using an electrophotographic method.

The image forming apparatus 100 has a plurality of image forming units (stations) PY, PM, PC, and PK that form images of each color of yellow (Y), magenta (M), cyan (C), and black (K), respectively. .. For elements having the same or corresponding functions or configurations in each image forming unit PY, PM, PC, PK, Y, M, C, K at the end of the code indicating that the element is for any color is omitted. And there is a general explanation. In this embodiment, the image forming unit P includes a photosensitive drum 1, a charging roller 2, an exposure device 3, a developing device 4, a primary transfer roller 5, a drum cleaning device 6, and the like, which will be described later.

The image forming apparatus 100 has a photosensitive drum 1 which is a drum-shaped (cylindrical) photosensitive member (electrophotographic photosensitive member) as a rotatable image carrier that supports a toner image. The photosensitive drum 1 is rotationally driven in the direction of arrow R1 (clockwise) in the drawing at a predetermined peripheral speed (moving speed of the surface). The surface of the rotating photosensitive drum 1 is uniformly charged to a predetermined potential of a predetermined polarity (negative electrode property in this embodiment) by a charging roller 2 which is a roller-type charging member (contact charging member) as a charging means. It is processed. During the charging step, a charging voltage (charging voltage) including a negative DC component is applied to the charging roller 2 by the charging power supply E1 (FIG. 2). The surface of the charged photosensitive drum 1 is scanned and exposed by an exposure device (laser scanner) 3 as an exposure means according to an image signal, and an electrostatic image (electrostatic latent image) is formed on the photosensitive drum 1. To.

The electrostatic image formed on the photosensitive drum 1 is developed (visualized) by supplying toner as a developer by the developing apparatus 4 as a developing means, and a toner image (developer image) is formed on the photosensitive drum 1. It is formed. The developing apparatus 4 has a developing roller 41 as a developing agent carrier and a developing container 42 for accommodating toner. In this embodiment, the developing roller 41 is rotationally driven in a direction in which the surface thereof moves in the forward direction with the surface of the photosensitive drum 1 at the portion facing the photosensitive drum 1, and conveys the toner to the portion facing the photosensitive drum 1. .. Further, during the developing step, a developing voltage (development bias) including a negative DC component is applied to the developing roller 41 by the developing power supply E2 (FIG. 2). As a result, in this embodiment, the image portion (exposed portion) on the photosensitive drum 1 whose absolute potential value is lowered by being exposed after being uniformly charged has the same polarity as the charging polarity of the photosensitive drum 1. (Negative property in this embodiment) charged toner adheres (reversal development). That is, in this embodiment, the normal charging polarity of the toner, which is the charging polarity of the toner at the time of development, is the negative electrode property.

The image forming apparatus 100 has an intermediate transfer belt 8 arranged to face the four photosensitive drums 1. The intermediate transfer belt 8 is an example of a rotatable intermediate transfer body for secondary transfer of a toner image primaryly transferred from an image carrier to a transfer material. The intermediate transfer belt 8 is composed of a flexible, endless belt. The intermediate transfer belt 8 is stretched on a drive roller 9 and a driven roller 10 as a plurality of tension rollers (support rollers). The intermediate transfer belt 8 is rotationally driven by the drive roller 9 to rotate (rotate) in the direction of arrow R2 (counterclockwise) in the figure at a peripheral speed corresponding to the peripheral speed of the photosensitive drum 1. In this embodiment, the peripheral speed of the intermediate transfer belt 8 corresponding to the process speed of the image forming apparatus 100 is 210 mm / sec. Specifically, the peripheral speed of the intermediate transfer belt 8 is obtained from a value obtained by measuring the moving speed of the surface of the intermediate transfer belt 8 during rotation using a laser Doppler velocimeter. On the inner peripheral surface side of the intermediate transfer belt 8, a primary transfer roller 5 which is a roller type primary transfer member as a primary transfer means is arranged corresponding to each photosensitive drum 1. The primary transfer roller 5 is pressed toward the photosensitive drum 1 via the intermediate transfer belt 8 to form a primary transfer portion (primary transfer nip portion) N1 in which the photosensitive drum 1 and the intermediate transfer belt 8 come into contact with each other. The toner image formed on the photosensitive drum 1 as described above is transferred (primary transfer) on the rotating intermediate transfer belt 8 by the action of the primary transfer roller 5 in the primary transfer unit N1. During the primary transfer step, the primary transfer power supply E3 (FIG. 2) applies a primary transfer voltage (primary transfer bias), which is a DC voltage opposite to the normal charging polarity of the toner, to the primary transfer roller 5. For example, at the time of forming a full-color image, the toner images of each color of yellow, magenta, cyan, and black formed on each photosensitive drum 1 are sequentially transferred so as to be superimposed on the intermediate transfer belt 8.

On the outer peripheral surface side of the intermediate transfer belt 8, a secondary transfer roller 11 which is a roller type secondary transfer member as a secondary transfer means is arranged at a position facing the drive roller 9 which also serves as a secondary transfer facing roller. ing. The secondary transfer roller 11 is pressed toward the drive roller 9 via the intermediate transfer belt 8 to form a secondary transfer portion (secondary transfer nip portion) N2 in which the intermediate transfer belt 8 and the secondary transfer roller 11 come into contact with each other. Form. The toner image formed on the intermediate transfer belt 8 as described above is sandwiched and conveyed between the intermediate transfer belt 8 and the secondary transfer roller 11 by the action of the secondary transfer roller 11 in the secondary transfer unit N2. It is transferred (secondary transfer) to a transfer material (recording material, sheet) S such as paper. During the secondary transfer step, the secondary transfer roller 11 is subjected to the secondary transfer voltage (secondary transfer bias), which is a DC voltage opposite to the normal charging polarity of the toner, by the secondary transfer power supply E4 (FIG. 2). Is applied. The transfer material S is loaded and stored in the transfer material cassette 13, and is fed from the transfer material cassette 13 by the feed / transport device 12. The feed / transport device 12 includes a feed roller 14, a transport roller pair 15, and the like. The transfer material S fed by the feed / transport device 12 is supplied to the secondary transfer unit N2 at the same timing as the toner image on the intermediate transfer belt 8 by the resist roller pair 16.

The transfer material S to which the toner image is transferred is conveyed to the fixing device 17 as a fixing means. The fixing device 17 heats and pressurizes the transfer material S carrying the unfixed toner image to fix (melt, fix) the toner image on the transfer material S. The transfer material S on which the toner image is fixed is discharged (output) by the discharge roller pair 18 onto the discharge tray 19 provided outside the device main body 110 of the image forming apparatus 100.

On the other hand, the toner (primary transfer residual toner) remaining on the surface of the photosensitive drum 1 without being transferred to the intermediate transfer belt 8 in the primary transfer step is removed from the surface of the photosensitive drum 1 by the drum cleaning device 6 as a photoconductor cleaning means. And collected. The drum cleaning device 6 scrapes the primary transfer residual toner from the surface of the rotating photosensitive drum 1 by the drum cleaning blade 61 as a cleaning member, and stores the toner in the drum cleaning container 62. Further, on the outer peripheral surface side of the intermediate transfer belt 8, a belt cleaning device 20 as an intermediate transfer body cleaning means is arranged at a position facing the driven roller 10. The toner (secondary transfer residual toner) remaining on the surface of the intermediate transfer belt 8 without being transferred to the transfer material S in the secondary transfer step is removed from the surface of the intermediate transfer belt 8 by the belt cleaning device 20 and recovered. .. The belt cleaning device 20 scrapes the secondary transfer residual toner from the surface of the rotating intermediate transfer belt 8 by the belt cleaning blade 21 as a cleaning member and stores it in the belt cleaning container 22.

Here, in the present embodiment, in each image forming unit P, the photosensitive drum 1 and the charging roller 2, the developing device 4, and the drum cleaning device 6 as process means acting on the photosensitive drum 1 are integrated into the device main body 110. On the other hand, a detachable process cartridge 7 is configured.

2. 2. Control mode FIG. 2 is a schematic block diagram showing a control mode of a main part of the image forming apparatus 100 in this embodiment. The image forming apparatus 100 is provided with a control unit (control circuit) 25 as a control means. The control unit 25 includes a CPU 26 which is an arithmetic control unit, a memory 27 which is a storage unit, and the like. In this embodiment, the image forming apparatus 100 is independently provided with drum drive motors 51Y, 51M, 51C, 51K as drive sources for driving the photosensitive drums 1Y, 1M, 1C, and 1K for each color. Further, in the present embodiment, the image forming apparatus 100 is driven by development as a drive source for driving the developing apparatus 4Y, 4M, 4C, 4K (more specifically, the developing rollers 41Y, 41M, 41C, 41K) for each color. Motors 52Y, 52M, 52C, 52K are independently provided. Further, in the present embodiment, the image forming apparatus 100 has a belt as a drive source for driving the intermediate transfer belt 8 (more specifically, the drive roller 9) independently of the drum drive motor 51 and the development drive motor 52. A drive motor 53 is provided.

Each drive motor 51, 52, 53, each power source E1, E2, E3, E4, an exposure device 3, and the like are connected to the control unit 25. Then, the control unit 25 comprehensively controls each unit of the image forming apparatus 100 by the CPU 26 controlling according to the programs and data stored in the memory 27. In this embodiment, the control unit 25 can control the drum drive motors 51Y, 51M, 51C, and 51K to independently control the peripheral speeds of the photosensitive drums 1Y, 1M, 1C, and 1K for each color. Is. Further, in this embodiment, the control unit 25 controls each developing drive motor 52Y, 52M, 52C, 52K to independently control the peripheral speeds of the developing rollers 41Y, 41M, 41C, 41K for each color. Is possible. Further, in this embodiment, the control unit 25 can control the belt drive motor 53 to control the peripheral speed of the intermediate transfer belt 8 independently of the peripheral speed of the photosensitive drum 1 and the developing roller 41. be.

In this embodiment, the image forming apparatus 100 can form an image in a "normal mode" and a "wide color gamut mode" as an image forming mode. In the "wide color gamut mode", for the purpose of improving color reproducibility, in order to expand the color space reproducibility range, image formation in which the amount of toner on the image portion on the photosensitive drum 1 is increased as compared with the "normal mode". The mode. In this embodiment, the control unit 25 controls to select and switch between the "normal mode" and the "wide color gamut mode". The control unit 25 responds to mode designation information input by an operator such as a user from an operation unit 30 provided in the image forming apparatus 100 or an external device such as a personal computer communicably connected to the image forming apparatus 100. Then, the control is performed. Then, in this embodiment, as will be described in detail later, the control unit 25 controls to change the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 in the "normal mode" and the "wide color gamut mode". I do.

3. 3. Wide color gamut mode In this embodiment, the peripheral speed of each photosensitive drum 1Y, 1M, 1C, 1K in the normal mode is 210 mm / sec. The peripheral speeds of the photosensitive drums 1Y, 1M, 1C, and 1K are specifically obtained from the values obtained by measuring the moving speed of the surface of the photosensitive drum 1 during rotation using a laser Doppler speedometer. Further, in this embodiment, the peripheral speed of each developing roller 41Y, 41M, 41C, 41K in the normal mode is 144% of the peripheral speed of each photosensitive drum 1Y, 1M, 1C, 1K, that is, It is 302.4 mm / sec. In this embodiment, with this setting, the toner loading amount of the image portion on each photosensitive drum 1Y, 1M, 1C, 1K in the normal mode is about 0.45 mg / cm ² . Here, the toner loading amount is defined as M / S (mg / cm ² ) and can be measured by the following method. That is, the toner developed on the photosensitive drum 1 is sucked from the photosensitive drum 1 and peeled off before the primary transfer. Then, the weight M (mg) of the peeled toner is measured by an electronic balance or the like. Further, the weight M (mg) is standardized by the area S (cm ² ) of the region on the photosensitive drum 1 from which the toner is peeled off, and the toner loading amount M / S (mg / cm ² ) is obtained.

On the other hand, in this embodiment, the peripheral speed of each photosensitive drum 1Y, 1M, 1C, 1K in the wide color gamut mode is 210 mm / sec (that is, the same as in the normal mode). Further, in this embodiment, the peripheral speed of each developing roller 41Y, 41M, 41C, 41K in the wide color gamut mode is 290% of the peripheral speed of each photosensitive drum 1Y, 1M, 1C, 1K. That is, it is 609 mm / sec. In this embodiment, with this setting, the amount of toner on each photosensitive drum 1Y, 1M, 1C, and 1K in the wide color gamut mode is about 0.90 mg / cm ² . That is, in this embodiment, the amount of toner loaded on the photosensitive drum 1 in the wide color gamut mode is increased more than the amount of toner loaded on the photosensitive drum 1 in the normal mode. As a result, in the wide color gamut mode, the amount of toner on the transfer material S can be increased and the color space reproduction range of the printed matter can be expanded as compared with the normal mode.

In this embodiment, the non-exposed portion (non-image portion) potential Vd of the photosensitive drum 1 is -465 V, and the exposed portion (image portion) potential Vl of the photosensitive drum 1 is set in the wide color range mode and the normal mode. -115V, DC component of development voltage (also referred to as "development DC voltage" here) Vdc is fixed at -295V. That is, in this embodiment, the development contrast, which is the potential difference between the development DC voltage Vdc and the exposure unit potential Vl, is fixed at 180V (= | Vdc | − | Vl |) between the wide color gamut mode and the normal mode. ing. In this embodiment, in the wide color gamut mode, the peripheral speed of the developing roller 41 is increased as compared with the normal mode, and the peripheral speed difference between the photosensitive drum 1 and the developing roller 41 is increased. However, the present invention is not limited to this, and the amount of toner loaded on the photosensitive drum 1 in the wide color gamut mode can be increased as compared with the normal mode, for example, as follows. That is, the peripheral speed of the developing roller 41 is fixed at 609 mm / sec, which is 290% of the peripheral speed of the photosensitive drum 1 in the wide color gamut mode and the normal mode. In the wide color gamut mode, the non-exposed part potential Vd is -465V, the exposed part potential Vl is -115V, the developing DC voltage Vdc is -295V, and the developing contrast is 180V, and the toner is placed on the photosensitive drum 1. The amount is about 0.90 mg / cm ² . On the other hand, in the normal mode, the exposure intensity of the exposure apparatus 3 is weakened and the exposure potential Vl is set to -195V, so that the development contrast is 100V and the toner loading amount on the photosensitive drum 1 is about 0.45 mg / cm. It should be about ² .

4. Difference in peripheral speed between the photosensitive drum and the intermediate transfer belt in the wide color gamut mode Fig. 3 shows the concentration of the primary transfer residual toner in the normal mode (▲ in the figure) and the wide color gamut mode (■ in the figure). Is a graph showing the relationship between the photosensitive drum 1 and the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8. In FIG. 3, the horizontal axis shows the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8, and the vertical axis shows the concentration of the primary transfer residual toner. The concentration (amount) of the primary transfer residual toner was measured by collecting the primary transfer residual toner with a tape (polyester tape No. 5511 manufactured by Nichiban) and measuring the concentration with a white photometer (TC-6DS manufactured by Tokyo Denshoku). Expressed as a value (%).

In this embodiment, the peripheral speed of the photosensitive drum 1 is slowed down with respect to the peripheral speed of the intermediate transfer belt 8, so that a peripheral speed difference is provided between the photosensitive drum 1 and the intermediate transfer belt 8. However, the present invention is not limited to this, and by increasing the peripheral speed of the intermediate transfer belt 8 with respect to the peripheral speed of the photosensitive drum 1, the peripheral speed between the photosensitive drum 1 and the intermediate transfer belt 8 is increased. A speed difference may be provided. Further, in this embodiment, the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 is changed by fixing the peripheral speed of the intermediate transfer belt 8 and changing the peripheral speed of the photosensitive drum 1. However, the present invention is not limited to this, and by fixing the peripheral speed of the photosensitive drum 1 and changing the peripheral speed of the intermediate transfer belt 8, the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 May be changed.

As shown in FIG. 3, when the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 is 0% (that is, constant speed), the concentration of the primary transfer residual toner in the normal mode is 6.4%. On the other hand, the concentration of the primary transfer residual toner in the wide color gamut mode is as high as 13.7%. This is because the amount of toner loaded on the photosensitive drum 1 is larger in the wide color gamut mode than in the normal mode.

According to the studies by the present inventors, the concentration of the primary transfer residual toner that is acceptable without deteriorating the image quality is 6%. That is, it is desired that the concentration of the primary transfer residual toner is 6% or less as a threshold value. Therefore, in this embodiment, the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 is controlled so that the concentration of the primary transfer residual toner is 6% or less, which is the target. When a peripheral speed difference is provided between the photosensitive drum 1 and the intermediate transfer belt 8, the toner on the photosensitive drum 1 is easily transferred to the intermediate transfer belt 8 by the shearing force, and the residual primary transfer toner can be reduced. In the normal mode, the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 is 0.1%, so that the concentration of the primary transfer residual toner is 6%. Therefore, in this embodiment, in the normal mode, the peripheral speed of the intermediate transfer belt 8 is set to 210 mm / sec, the peripheral speed of the photosensitive drum 1 is set to 209.7 mm / sec, and the peripheral speed of the developing roller 41 is set to 302.0 mm / sec. did. On the other hand, in the wide color gamut mode, the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 is 1.9%, so that the concentration of the primary transfer residual toner is 6%. Therefore, in this embodiment, in the wide color gamut mode, the peripheral speed of the intermediate transfer belt 8 is 210 mm / sec, the peripheral speed of the photosensitive drum 1 is 206.0 mm / sec, and the peripheral speed of the developing roller 41 is 597.4 mm / sec. Was set to.

In the wide color gamut mode, the amount of toner loaded on the transfer material S increases as compared with the normal mode. Therefore, in order to ensure fixability, for example, the process speed in the normal mode (corresponding to the peripheral speed of the intermediate transfer belt 8) is 210 mm / sec, while the process speed in the wide color gamut mode is 70 mm / sec. It may be as slow as sec. In this case, for example, in order to make the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 1.9%, the peripheral speed of the intermediate transfer belt 8 is 70 mm / sec and the peripheral speed of the photosensitive drum 1 is 68.7 mm. The peripheral speed of the developing roller 41 can be set to 199.1 mm / sec.

FIG. 4 is a flowchart showing an outline of the procedure for controlling the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 in this embodiment. Upon receiving the print signal, the control unit 25 determines whether the image formation mode is the normal mode or the wide color gamut mode (S101). Next, the control unit 25 sets the peripheral speed difference between each photosensitive drum 1Y, 1M, 1C, 1K and the intermediate transfer belt 8 based on the image formation mode information acquired in S101 (S102). Next, the control unit 25 executes image formation with the peripheral speed difference between each photosensitive drum 1Y, 1M, 1C, 1K set in S102 and the intermediate transfer belt 8 (S103).

As described above, in the present embodiment, the image forming apparatus 100 can select the image forming by the first mode (“normal mode”) or the image forming by the second mode (“wide color gamut mode”). be. In the first mode, the amount of toner on the image portion on the image carrier is the first amount, and in the second mode, the amount of toner on the image portion on the image carrier is greater than the first amount. Is also a large mode. Then, in this embodiment, the image forming apparatus 100 determines the difference in peripheral speed between the image carrier 1 and the intermediate transfer member 8 when the second mode is selected, and the image carrier when the first mode is selected. It is made larger than the peripheral speed difference between the body 1 and the intermediate transfer body 8. In this embodiment, the developing means 4 has a rotatable developer carrier 41 that carries and conveys toner. When the second mode is selected, the peripheral speed difference between the image carrier 1 and the developer carrier 41 is made larger than that when the first mode is selected, and the image portion on the image carrier 1 is formed. The amount of toner loaded on the surface is larger than that when the first mode is selected. Further, in this embodiment, the image forming apparatus 100 has at least a control means 25 capable of changing the peripheral speed difference between the image carrier 1 and the intermediate transfer body 8. Further, in the present embodiment, the image forming apparatus 100 independently drives a plurality of image forming portions PY, PM, PC, PK and image carriers 1Y, 1M, 1C, and 1K of the plurality of image forming portions. It has a plurality of first drive sources 51Y, 51M, 51C, 51K and the like. Further, in this embodiment, the image forming apparatus 100 has a second driving source 53 for driving the intermediate transfer body 8. Then, the control means 25 independently controls the peripheral speed of each image carrier 1 of the plurality of image forming portions, and causes each of the image carrier 1 and the intermediate transfer body 8 of the plurality of image forming portions. The peripheral speed difference of is controlled independently. The image carrier 1 is an electrostatic image composed of an image unit to which toner constituting a toner image is supplied by the developing means 4 and a non-image unit to which the toner constituting the toner image is not supplied by the developing means 4. Is formed. In particular, in this embodiment, the image portion on the image carrier 1 is a portion exposed by the exposure means 3, and the non-image portion is a portion not exposed by the exposure means 3. The amount of toner on the image portion on the image carrier 1 in the first mode and the second mode forms an image of a predetermined area in which the density level of the image signal is the same (for example, the maximum density level). The values measured by the above method may be used for comparison.

As described above, according to the present embodiment, the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 in the wide color gamut mode is the peripheral speed between the photosensitive drum 1 and the intermediate transfer belt 8 in the normal mode. Make it larger than the difference. This makes it possible to suppress a decrease in primary transferability in the wide color gamut mode.

[Example 2]
Next, other examples of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the first embodiment. Therefore, in the image forming apparatus of the present embodiment, the elements having the same or corresponding functions or configurations as those of the first embodiment are designated by the same reference numerals as those of the first embodiment, and detailed description thereof will be omitted.

In this embodiment, the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 is changed according to the life of the process cartridge 7 (developerable device 4) (here, referred to as “cartridge life”).

FIG. 5 is a schematic block diagram showing a control mode of a main part of the image forming apparatus 100 in this embodiment. In this embodiment, the process cartridges 7Y, 7M, 7C, and 7K for each color are provided with cartridge memories 61Y, 61M, 61C, and 61K as storage means, respectively. In this embodiment, the cartridge memory 61 is a non-volatile read / write device such as EEPROM. When the process cartridge 7 is attached to the device main body 110, the cartridge memory 61 is electrically connected to the device main body 110 by a connector (not shown), and information can be exchanged with the control unit 25. .. That is, the information in the cartridge memory 61 can be read and written by the control unit 25. As the cartridge memory 61, a read-write non-contact memory such as an electromagnetic coupling type that can transmit and receive signals in a non-contact state may be used. Further, as the cartridge memory 61, a non-volatile readable memory (ROM) may be used. In this embodiment, each cartridge memory 61 stores at least cartridge life information for each corresponding process cartridge 7.

In this embodiment, the cartridge life is the state of the developing device 4 itself (referred to here as “development life”) and the state of the toner stored in the developing device 4 (here referred to as “toner life”). Determined from two factors.

First, in this embodiment, the image forming apparatus 100 has a counter 62 as a counting means as a developing life detecting means for detecting the developing life of each process cartridge 7Y, 7M, 7C, 7K. The counter 62 counts the number of rotations of each of the developing rollers 41Y, 41M, 41C, and 41K. The control unit 25 calculates the cumulative rotation speed (total rotation speed) of the developing rollers 41 from the new state of each process cartridge 7Y, 7M, 7C, 7K based on the counting result of the counter 62, and the corresponding cartridge. The memory 61 is sequentially stored. In this embodiment, the development life of the process cartridge 7 when it is new, that is, when the total rotation speed of the developing roller 41 is zero, is set to 100%. Then, the development life at the time when the total rotation speed of the developing roller 41 reaches a predetermined threshold value is set to 0%. This predetermined threshold value is determined in advance from the viewpoint of determining the life of the process cartridge 7 before various image defects occur due to an increase in the amount of the developing apparatus 4. The developing life detecting means may be configured to count the operating time of the developing apparatus 4 from a new state, for example.

Further, in the present embodiment, the image forming apparatus 100 uses the remaining amount sensor 63Y for detecting the remaining amount of toner in the developing container 42 as the toner life detecting means for detecting the toner life of each process cartridge 7Y, 7M, 7C, 7K. , 63M, 63C, 63K. In this embodiment, as the remaining amount sensor 63, a sensor that detects the toner contained in the developing container 42 by using an optical detection method is used. In this embodiment, the toner life of the process cartridge 7 when it is new, that is, when the toner consumption is zero, is set to 100%. Then, the toner life at the time when the remaining amount of toner reaches a predetermined threshold value is set to 0%. This predetermined threshold value is determined in advance from the viewpoint of determining the life of the process cartridge 7 before various image defects occur due to the remaining amount of toner becoming low. The toner life detecting means may be configured to detect the amount of toner consumed or to determine the remaining amount of toner from the amount of toner consumed.

Then, in this embodiment, the cartridge life is determined from the two factors of the toner life and the development life as described above. Specifically, of the above two factors, the factor having the smaller value (that is, the one having the shorter remaining life) is defined as the cartridge life. The life of the cartridge is 100% when it is new and 0% when it reaches the end of its life. For example, when the toner life is 30% and the development life is 50%, the cartridge life is 30%, and when the toner life is 40% and the cartridge life is 15%, the cartridge life is 15%.

Regardless of whether the value of the toner life or the development life is small, the toner deterioration causes the toner fluidity to decrease, the amount of negative charge of the toner to decrease, or the toner to become non-uniform. Therefore, the primary transferability is lowered and the amount of toner remaining in the primary transfer is increased. Therefore, in this embodiment, the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 is changed according to the life of the cartridge.

The cartridge memory 61 may sequentially store the development life, the toner life, or the cartridge life. Further, in this embodiment, the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 is changed according to the life (remaining life) of the developing device 4. However, the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 may be changed according to the detection result of the detection means that detects the index value that correlates with the usage amount of the developing device 4. The index value that correlates with the usage amount of the developing device 4 is typically, but is not limited to, the number of rotations of the developing roller 41, the operating time, the remaining amount of toner, and the like as described above, but is not limited to these. It may be any index value that increases or decreases as the amount of the device 4 used increases.

FIG. 6 shows the concentration of the residual primary transfer toner and the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 in the normal mode (▲ in the figure) and the wide color gamut mode (■ in the figure). It is a graph which shows the relationship of. FIG. 6 shows the relationship separately for the case where the cartridge life is 100% (solid line in the figure) and the case where the cartridge life is 10% (dotted line in the figure). The method for measuring the concentration of the primary transfer residual toner is the same as that described in Example 1.

As shown in FIG. 6, in both the normal mode and the wide color gamut mode, the amount of primary transfer residual toner increases when the cartridge life is 10% than when the cartridge life is 100%. This is because the toner deteriorates as described above. In order to achieve the target concentration of 6% of primary transfer residual toner, the difference in peripheral speed between the photosensitive drum 1 and the intermediate transfer belt 8 is when the cartridge life is 10% rather than when the cartridge life is 100%. Needs to be larger.

Table 1 shows the normal mode and the wide color gamut mode for achieving the target primary transfer residual toner concentration of 6% in the case where the cartridge life in this embodiment is 100% and the case where the cartridge life is 10%. The target value of the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 is shown. Table 1 also shows the difference in the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 between the normal mode and the wide color gamut mode (“Δ wide color gamut mode-normal mode”). When the cartridge life is 10%, the difference in peripheral speed difference between the normal mode and the wide color gamut mode is smaller than when the cartridge life is 100%. This is because the effect of toner deterioration on the primary transferability is greater than the effect of the difference in the amount of toner loaded on the photosensitive drum 1 between the normal mode and the wide color gamut mode on the primary transferability. Is.

The target value of the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 shown in Table 1 is obtained in advance so as to achieve the target concentration of 6% of the primary transfer residual toner, and is stored in the memory 27 of the control unit 25. Has been done. Further, in this embodiment, the control unit 25 sets the target value of the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 in the case of the cartridge life between 100% and 10% as the cartridge life shown in Table 1. The target value when is 100% and the target value when is 10% are linearly interpolated and set.

FIG. 7 is a flowchart showing an outline of the procedure for controlling the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 in this embodiment. Upon receiving the print signal, the control unit 25 determines whether the image formation mode is the normal mode or the wide color gamut mode (S201). Next, the control unit 25 acquires information on the cartridge life of each process cartridge 7Y, 7M, 7C, 7K based on the information stored in each cartridge memory 61 and the detection result of each remaining amount sensor 63. (S202). Next, the control unit 25 sets the photosensitive drums 1Y, 1M, 1C, 1K and the intermediate transfer belt 8 based on the image formation mode information acquired in S201 and the cartridge life information acquired in S202. The peripheral speed difference is set (S203). Next, the control unit 25 executes image formation with the peripheral speed difference between each photosensitive drum 1Y, 1M, 1C, 1K set in S203 and the intermediate transfer belt 8 (S204).

As described above, in this embodiment, the image forming apparatus 100 has the detecting means 62 and 63 for detecting the index value that correlates with the usage amount of the developing means 4. Then, the control means 25 changes the peripheral speed difference between the image carrier 1 and the intermediate transfer body 8 at the time of image formation according to the detection results of the detection means 62 and 63. In this embodiment, the control means 25 uses more than the peripheral speed difference when the usage amount of the developing means 4 indicated by the detection results of the detection means 62 and 63 is the first value, and the usage amount is more than the first value. The peripheral speed difference is changed so that the peripheral speed difference in the case of the second value having a large value is larger. Further, in the present embodiment, the control means 25 is larger than the change amount of the peripheral speed difference in the second mode with respect to the peripheral speed difference in the first mode when the usage amount is the first value. The peripheral speed difference is changed so that the changed amount when the used amount is the second value is smaller.

As described above, according to the present embodiment, the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 is changed according to the life of the cartridge. More specifically, in this embodiment, as the value of the cartridge life decreases, the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 increases. In this embodiment, the change in the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 according to the cartridge life is performed in both the normal mode and the wide color gamut mode. Further, in this embodiment, the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 in the wide color gamut mode is changed with respect to the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 in the normal mode according to the cartridge life. Change the amount. More specifically, in this embodiment, as the value of the cartridge life decreases, the photosensitive drum 1 and the intermediate transfer belt in the wide color gamut mode with respect to the peripheral speed difference between the photosensitive drum 1 and the intermediate transfer belt 8 in the normal mode. The amount of change in the peripheral speed difference from 8 is reduced. As a result, it is possible to suppress a decrease in primary transferability in the wide color gamut mode throughout the life of the cartridge.

[Example 3]
Next, other examples of the present invention will be described. The basic configuration and operation of the image forming apparatus of this embodiment are the same as those of the first embodiment. Therefore, in the image forming apparatus of the present embodiment, the elements having the same or corresponding functions or configurations as those of the first embodiment are designated by the same reference numerals as those of the first embodiment, and detailed description thereof will be omitted.

In this embodiment, in order to simplify the configuration of the image forming apparatus 100 and reduce the cost, a drive motor for driving a plurality of photosensitive drums 1, a plurality of developing devices 4 (developing rollers 41), and an intermediate transfer belt 8 is provided. Partially standardized.

FIG. 8 is a schematic showing a driving mode of a main part of the image forming apparatus 100 in this embodiment. In this embodiment, the photosensitive drums 1Y, 1M, and 1C for three colors of yellow, magenta, and cyan are driven by the first drive motor 71. Further, in this embodiment, the developing devices 4Y, 4M, 4C, and 4K (developing rollers 41Y, 41M, 41C, 41K) for the three colors of yellow, magenta, and cyan are driven by the second drive motor 72. Further, the intermediate transfer belt 8, the photosensitive drum 1K for black, and the developing device 4K (developing roller 41K) for black are driven by the third drive motor 73. As a result, in the present embodiment, the number of drive motors used is reduced as compared with the first and second embodiments, and the configuration of the image forming apparatus 100 is simplified and the cost is reduced.

In this embodiment, the black photosensitive drum 1K and the developing roller 41 are driven by the same third drive motor 73. Therefore, in this embodiment, the difference in peripheral speed between the photosensitive drum 1K for black and the developing roller 41K cannot be changed between the normal mode and the wide color gamut mode as in the first and second embodiments. Therefore, in this embodiment, with respect to the black color, the amount of toner loaded on the photosensitive drum 1K is the same in the wide color gamut mode as in the normal mode. However, the black color has little effect on the expansion of the color gamut, so there is no problem.

Further, in this embodiment, the intermediate transfer belt 8, the photosensitive drum 1K for black, and the developing roller 41K are driven by the same third drive motor 73. Therefore, as in the first and second embodiments, by slowing down the rotation speed of the first drive motor 71 for driving the photosensitive drums 1Y, 1M, and 1C for each color of yellow, magenta, and cyan, these photosensitive drums 1Y, A peripheral speed difference is provided between 1M and 1C and the intermediate transfer belt 8. If the rotational speed of the third drive motor 73 that drives the intermediate transfer belt 8 is changed in order to provide a peripheral speed difference between these photosensitive drums 1Y, 1M, 1C and the intermediate transfer belt 8, the color is black. This is not preferable because the image formation speed of the above changes. Further, in this embodiment, as described above, the intermediate transfer belt 8, the photosensitive drum 1K for black, and the developing roller 41K are driven by the same third drive motor 73. Therefore, regarding the black color, the peripheral speed difference between the photosensitive drum 1K and the intermediate transfer belt 8 cannot be changed. However, in this embodiment, as for the black color, as described above, the amount of toner loaded on the photosensitive drum 1K is the same in the normal mode and the wide color gamut mode, so that the primary transferability is high in the wide color gamut mode. There is no problem of deterioration. In consideration of toner deterioration at the end of the cartridge life, for the black color, the peripheral speed difference between the photosensitive drum 1K and the intermediate transfer belt 8 should be about 1.0% from the beginning of the cartridge life (when new). It is preferable to set it.

As described above, in the present embodiment, the image forming apparatus 100 is the common first one that drives the plurality of image forming portions PY, PM, PC and the image carriers 1Y, 1M, 1C of the plurality of image forming portions. It has a drive source 71 and a second drive source 73 for driving the intermediate transfer body 8. Then, the control means 25 controls the peripheral speed of the image carrier 1 of the plurality of image forming portions to control the peripheral speed difference between the image carrier 1 of the plurality of image forming portions and the intermediate transfer body 8. .. Further, in this embodiment, the image forming apparatus 100 has an image forming unit PK which is provided with an image carrier 1K and a developing means 4K, and is different from the plurality of image forming units PY, PM, and PC. Then, the image carrier 1K of the other image forming unit PK is driven by the second drive source 73 common to the intermediate transfer body 8, and the image carrier 1K and the intermediate transfer body 8 of the other image forming unit PK are combined with each other. The difference in peripheral speed is substantially the same between the first mode and the second mode.

In this embodiment as well, as in the first embodiment, for each of the yellow, magenta, and cyan colors, the circumference of the photosensitive drums 1Y, 1M, and 1C and the intermediate transfer belt 8 in the normal mode and the wide color gamut mode. The speed difference can be changed. As a result, it is possible to suppress a decrease in primary transferability for each of the yellow, magenta, and cyan colors in the wide color gamut mode. Further, also in this embodiment, similarly to the second embodiment, the peripheral speed difference between the photosensitive drums 1Y, 1M, 1C for three colors of yellow, magenta, and cyan and the intermediate transfer belt 8 is changed according to the cartridge life. Can be done. As a result, it is possible to suppress a decrease in primary transferability for each of the yellow, magenta, and cyan colors in the wide color gamut mode throughout the life of the cartridge.

[others]
Although the present invention has been described above with reference to specific examples, the present invention is not limited to the above-mentioned examples.

For example, although the tandem type (in-line method) image forming apparatus has been described in the above-described embodiment, the present invention is not limited to such an image forming apparatus. The present invention is, for example, a so-called one-drum system in which a plurality of developing devices are provided for one image carrier, and each time a toner image is formed on the image carrier, the toner image is first transferred to an intermediate transfer body. It can also be applied to an image forming apparatus.

1 Photosensitive drum 4 Developing device 8 Intermediate transfer belt 100 Image forming device

Claims (6)

A rotatable image carrier that supports a toner image, a developing means that supplies toner to the image carrier to form a toner image, and a secondary transfer of a toner image that is primarily transferred from the image carrier to a transfer material. An intermediate transfer body that can be rotated , a control means that can change at least the peripheral speed difference between the image carrier and the intermediate transfer body, and a detection means that detects an index value that correlates with the amount of the developing means used. The image is formed by the first mode in which the amount of toner on the image portion on the image carrier is the first amount, or the amount of toner on the image portion on the image carrier is the first. Image formation by a second mode larger than the amount of 1 can be selected , and when the second mode is selected, the peripheral speed difference between the image carrier and the intermediate transfer body is set to the first. It is an image forming apparatus that makes it larger than the peripheral speed difference between the image carrier and the intermediate transfer body when the mode is selected.
The control means is configured to change the peripheral speed difference between the image carrier and the intermediate transfer body at the time of image formation according to the detection result of the detection means, and the detection result of the detection means. The peripheral speed difference when the used amount is larger than the first value is larger than the peripheral speed difference when the used amount of the developing means is the first value. The peripheral speed difference is changed so as to be.
The control means has the peripheral speed in the second mode with respect to the peripheral speed difference in the first mode when the usage amount of the developing means indicated by the detection result of the detecting means is the first value. The change amount of the peripheral speed difference in the second mode is smaller than the change amount of the difference with respect to the peripheral speed difference in the first mode when the usage amount is the second value. As described above, the image forming apparatus is characterized in that the peripheral speed difference is changed . The developing means has a rotatable developer carrier that carries and conveys toner, and when the second mode is selected, the peripheral speed difference between the image carrier and the developer carrier. Is larger than when the first mode is selected, and the amount of toner on the image portion on the image carrier is larger than when the first mode is selected. The image forming apparatus according to 1. A plurality of image forming portions each including the image carrier and the developing means, and a plurality of first driving sources for independently driving the image bearings of the plurality of image forming portions. The control means has a second drive source for driving the intermediate transfer body, and the control means independently controls the peripheral speed of each of the image carriers of the plurality of image forming portions to control the plurality of image carriers. The image forming apparatus according to claim 1 or 2 , wherein the peripheral speed difference between the image carrier and the intermediate transfer body of the image forming portion is independently controlled. A plurality of image forming portions each including the image carrier and the developing means, a common first driving source for driving the image carrier of the plurality of image forming portions, and the intermediate transfer body. The control means controls the peripheral speed of the image carrier of the plurality of image forming portions to and the image carrier of the plurality of image forming portions. The image forming apparatus according to claim 1 or 2 , wherein the difference in peripheral speed from the intermediate transfer body is controlled. The plurality of image forming units provided with an image carrier that carries a toner image that is primarily transferred to the intermediate transfer body, and a developing means that supplies toner to the image carrier to form a toner image. The image-bearing body of the other image-forming unit has another image-forming unit, and the image-bearing body of the other image-forming unit is driven by the second drive source common to the intermediate transfer body, and has the image-supporting body of the other image-forming unit. The image forming apparatus according to claim 4 , wherein the difference in peripheral speed from the intermediate transfer body is substantially the same in the first mode and in the second mode. An electrostatic image is formed on the image carrier, consisting of an image portion to which the toner constituting the toner image is supplied by the developing means and a non-image portion to which the toner constituting the toner image is not supplied by the developing means. The image forming apparatus according to any one of claims 1 to 5 , wherein the image forming apparatus is used.

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