JP2020020920A - Image forming device - Google Patents

Abstract

To provide an image forming device capable of minimizing reduction in transferability regardless of surrounding environments when operating in a mode that increases the amount of toner per unit area carried by a photosensitive drum.SOLUTION: A controller 102 is capable of switching to a wide color gamut mode, in which a rotational speed ratio of a developer roller to a photosensitive drum is controlled to be a second speed ratio greater than a first speed ratio in a standard mode, to form images. When operating in the wide color gamut mode, the controller 102 controls voltage outputted to a secondary transfer roller by a secondary transfer power supply 41 according to humidity surrounding an image forming device 100.SELECTED DRAWING: Figure 2

Description

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

  2. Description of the Related Art As an electrophotographic image forming apparatus, a configuration of a tandem type image forming apparatus in which a plurality of image forming units are arranged in a moving direction of an intermediate transfer body such as an intermediate transfer belt is known. Each color image forming unit has a drum-shaped photosensitive member (hereinafter, referred to as a photosensitive drum) as an image carrier. In such an image forming apparatus, an image is formed on a transfer material such as paper or an OHP sheet through a charging step, an exposure step, a development step, a transfer step, and a fixing step.

  Here, in the developing step, a voltage is applied to a developing roller as a developing member provided in the developing means, so that the toner image is developed on the photosensitive drum by the toner carried on the developing roller. In the transfer step, first, a toner image is primarily transferred from each photosensitive drum to an intermediate transfer belt. Thereafter, a voltage (hereinafter, referred to as a secondary transfer voltage) is applied to the secondary transfer member at a secondary transfer portion where the secondary transfer member and the intermediate transfer belt face each other, so that toner is transferred from the intermediate transfer belt to the transfer material. The image is secondarily transferred.

  Patent Document 1 discloses a configuration of an image forming apparatus capable of executing a mode (wide color gamut mode) for expanding a color reproduction range of an image formed on a transfer material. In the wide color gamut mode of Patent Document 1, the color reproduction range is expanded by setting the rotation speed of the developing roller higher than the rotation speed of the photosensitive drum and increasing the amount of toner carried on the photosensitive drum per unit area. are doing.

JP 2017-173465 A

  In the wide color gamut mode disclosed in Patent Document 1, the toner amount per unit area carried on the photosensitive drum is larger than the toner amount per unit area carried on the photosensitive drum in the normal mode in which the color reproduction range is not expanded. Many. That is, the toner amount per unit area of the toner image primarily transferred from the photosensitive drum of each color to the intermediate transfer belt is larger than that in the normal mode. Therefore, if the secondary transfer voltage in the wide color gamut mode is set to be the same as the secondary transfer voltage in the normal mode, the toner image carried on the intermediate transfer belt cannot be sufficiently transferred to the transfer material P, and May decrease.

  In order to solve such a problem, when the value of the secondary transfer voltage in the wide color gamut mode is set to be larger than that in the normal mode, a decrease in transferability can be suppressed. However, if the secondary transfer voltage is set too high, a local discharge may occur in the secondary transfer portion. In this case, at the position where the local discharge has occurred, a phenomenon occurs in which the toner is not transferred to the transfer material P and the surface of the transfer material P is exposed, so that the image becomes white (hereinafter, referred to as white spot). There is a risk.

  As described above, the setting of the secondary transfer voltage when executing the wide color gamut mode needs to be appropriately set in consideration of the transferability and the occurrence of white spots in accordance with the increased toner amount. However, the amount of toner per unit area carried on the photosensitive drum in the wide color gamut mode varies depending on the humidity of the surrounding environment in which the image forming apparatus is used. That is, when the toner image is transferred at a uniform secondary transfer voltage irrespective of the surrounding environment, there is a possibility that current transfer in the secondary transfer portion may be excessive or insufficient, thereby deteriorating transferability.

  Accordingly, an object of the present invention is to suppress a decrease in transferability regardless of the surrounding environment when executing a mode in which the amount of toner per unit area carried on a photosensitive drum is increased.

  The present invention has an image carrier for carrying a toner image, and a developing means for developing an electrostatic latent image formed on the image carrier with a toner, the developing device having a developing member arranged to face the image carrier. An intermediate transfer member on which the toner image carried on the image carrier is primarily transferred, and a transfer section formed by contacting the intermediate transfer member, and a primary transfer from the image carrier to the intermediate transfer member A transfer member for secondarily transferring the transferred toner image from the intermediate transfer member to a transfer material, a transfer power source for applying a voltage to the transfer member, and a rotation speed of the developing member with respect to a rotation speed of the image carrier. A first mode in which image formation is performed by controlling the speed ratio to be a first speed ratio, and a speed ratio of a rotation speed of the developing member to a rotation speed of the image carrier is the first speed ratio. Control so that the second speed ratio is larger than An image forming apparatus comprising: a second mode for performing the image forming operation; and a control unit capable of executing the second mode. The value of the current flowing from the transfer member toward the intermediate transfer member when the environment is the environment is the same as that when the surrounding environment is the second environment where the humidity is lower than the first environment. A voltage applied from the transfer power supply to the transfer member is controlled so as to be larger than a value of a current flowing toward the transfer member.

  According to the present invention, it is possible to suppress a decrease in transferability regardless of the surrounding environment when executing a mode in which the amount of toner per unit area carried on the photosensitive drum is increased.

FIG. 2 is a schematic sectional view illustrating a configuration of an image forming apparatus. FIG. 3 is a block diagram of a control unit of the image forming apparatus. FIG. 2 is a schematic diagram illustrating a configuration of an image forming unit. FIG. 3 is a schematic diagram illustrating a layer configuration of a photosensitive drum. FIG. 3 is a schematic diagram illustrating a potential formed on a photosensitive drum in a normal mode and a wide color gamut mode. FIG. 4 is a schematic diagram illustrating an image defect that occurs in a secondary transfer unit. 5 is a timing chart illustrating control of a secondary transfer power supply according to the first exemplary embodiment. FIG. 11 is a schematic diagram illustrating a charge amount supplied to a rear end of a transfer material in a secondary transfer unit in a modified example. 9 is a timing chart illustrating control of a secondary transfer power supply in Embodiment 2.

  Hereinafter, preferred embodiments of the present invention will be illustratively described in detail with reference to the drawings. However, dimensions, materials, shapes, relative arrangements, and the like of the components described in the following embodiments should be appropriately changed depending on the configuration of the apparatus to which the present invention is applied and various conditions. Therefore, the scope of the present invention is not limited unless otherwise specified.

(Example 1)
[Configuration of Image Forming Apparatus]
FIG. 1 is a schematic configuration diagram of an image forming apparatus 100 according to the present embodiment. FIG. 2 is a block diagram of a control unit of the image forming apparatus 100 according to the present embodiment. As shown in FIG. 2, the image forming apparatus 100 is connected to a host computer 101. An operation start command and an image signal from the host computer 101 are transmitted to a controller 102 as a control unit, and the image forming is performed in the image forming apparatus 100 by the controller 102 controlling various units.

  As shown in FIG. 1, an image forming apparatus 100 of the present embodiment is an intermediate transfer type color image forming apparatus using an electrophotographic method, and includes first, second, and third image forming units. , Fourth image forming units SY, SM, SC, and SK. The first, second, third, and fourth image forming units SY, SM, SC, and SK form images of yellow (Y), magenta (M), cyan (C), and black (Bk), respectively. It is for doing. These four image forming units SY, SM, SC, and SK are arranged in a line at regular intervals. Further, in this embodiment, each of the image forming units SY, SM, SC, and SK is , With respect to the direction of gravity. In this embodiment, the configurations of the first to fourth image forming units SY, SM, SC, and SK are substantially the same except that the colors of the toners used are different. Therefore, unless otherwise specified, the suffixes Y, M, C, and K given to the reference numerals to indicate that the element is provided for any color will be omitted, and the description will be made generally.

  FIG. 3 is a schematic diagram illustrating the configuration of the image forming unit S according to the present embodiment. As shown in FIG. 3, the image forming unit S is rotatable in a direction indicated by an arrow B in response to a driving force from a first driving source (shown in FIG. 2), and an image carrier on which a toner image is formed is formed. A drum-type electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum) 1 as a body is provided. Around the photosensitive drum 1, a charging roller 2 as a charging member for charging the photosensitive drum 1, a developing unit 9, and a cleaning unit 10 are provided. Further, with respect to the rotation direction of the photosensitive drum 1, an exposure unit to which laser light from an exposure unit 20 (laser scanner) is irradiated is provided downstream of the charging roller 2 and upstream of the developing unit 9. Have been.

  The developing unit 9 includes a developing roller 3 as a developing member, a toner T as a developer, a supply roller 6 for supplying the toner T to the developing roller 3, a stirring member 307 rotating in a direction indicated by an arrow E in FIG. And a developing blade 8 as regulating means. The developing roller 3 is rotatable in a direction indicated by an arrow C by receiving a driving force from a second driving source (shown in FIG. 2). The cleaning unit 10 has a cleaning blade 4 as a cleaning member that comes into contact with the photosensitive drum 1 and a waste toner container 5 that stores toner collected by the cleaning blade 4.

  Next, the overall configuration of the image forming apparatus 100 will be described. As shown in FIG. 1, an intermediate transfer belt 25, which is an endless belt-shaped intermediate transfer member, is disposed to face the photosensitive drum 1 of the image forming unit S. The intermediate transfer belt 25 is stretched around a plurality of support members, and is movable in the direction of arrow A by the drive roller 12.

  At a position facing the photosensitive drum 1 via the intermediate transfer belt 25, a primary transfer roller 26 as a primary transfer member (transfer member) is disposed. The primary transfer roller 26 is urged at a predetermined pressure to the photosensitive drum 1 via the intermediate transfer belt 25, and a primary transfer unit (primary transfer) where the intermediate transfer belt 25 and the photosensitive drum 1 are in contact with each other. Nip) N1 is formed. Further, a primary transfer power supply 40 is connected to the primary transfer roller 26, and the primary transfer power supply 40 can apply a positive or negative voltage to the primary transfer roller 26.

  On the outer peripheral surface side of the intermediate transfer belt 25, a secondary transfer roller 11 as a secondary transfer member is disposed at a position facing the drive roller 12. The secondary transfer roller 11 is urged at a predetermined pressure against the drive roller 12 via the intermediate transfer belt 25, and the secondary transfer unit (2) where the intermediate transfer belt 25 and the secondary transfer roller 11 come into contact with each other. Next transfer nip) N2 is formed. A secondary transfer power supply 41 is connected to the secondary transfer roller 11, and the secondary transfer power supply 41 can apply a positive or negative voltage to the secondary transfer roller 11.

  With respect to the moving direction of the intermediate transfer belt 25, the toner remaining on the intermediate transfer belt 25 after the secondary transfer (hereinafter referred to as residual toner) is located on the upstream side of each photosensitive drum 1 and on the downstream side of the secondary transfer portion N2. ) Is provided. The cleaning unit 16 has a cleaning blade 16a that contacts the intermediate transfer belt 25.

  On the upstream side of the secondary transfer portion N2 with respect to the transfer direction of the transfer material P, a paper feed cassette 28 for storing the transfer material P, and a feeding unit 29 for feeding the transfer material P stored in the paper feed cassette 28 And a transport roller 30 for transporting the fed transfer material P to the secondary transfer portion N2. Further, a fixing unit 13 having a heat source and a toner image fixed by the fixing unit 13 on the downstream side of the secondary transfer unit N2 in the transport direction of the transfer material P, and the transfer discharged from the image forming apparatus 100. And a paper discharge tray 15 on which the materials P are stacked.

[Image forming operation]
As shown in FIG. 3, when the image forming operation is started, each photosensitive drum 1, the intermediate transfer belt 25, the developing roller 3, and the supply roller 6 are rotated at a predetermined rotational speed in the directions of arrows A to D in the figure. Start spinning. The surface of the rotating photosensitive drum 1 is charged substantially uniformly to a predetermined polarity (negative in this embodiment) by the charging roller 2. At this time, a predetermined charging voltage is applied to the charging roller 2 from a charging power source 42. Thereafter, the photosensitive drum 1 is exposed by the exposure unit 20 in accordance with image information corresponding to each image forming unit, so that an electrostatic latent image is formed on the surface of the photosensitive drum 1 according to the image information.

  The developing roller 3 carries the toner supplied by the supply roller 6 and charged by the developing blade 8 to the normal charging polarity (negative in this embodiment) of the toner. A development voltage is applied. As a result, the latent image formed on the photosensitive drum 1 is visualized by the negative toner at a portion (developing portion) between the photosensitive drum 1 and the developing roller 3, and a toner image is formed on the photosensitive drum 1.

  Next, the toner image formed on the photosensitive drum 1 is rotationally driven by a current (hereinafter, referred to as a primary transfer current) flowing from the primary transfer roller 26 to the photosensitive drum 1 in the primary transfer portion N1. The image is transferred (primary transfer) to the intermediate transfer belt 25. At this time, a voltage having a polarity (positive in this embodiment) opposite to the normal charging polarity of the toner is applied to the primary transfer roller 26 from the primary transfer power supply 40. That is, in the configuration of the present embodiment, constant current control is performed to control the output of the primary transfer power supply 40 so that a predetermined primary transfer current flows from the primary transfer roller 26 toward the photosensitive drum 1. The primary transfer of the toner image to the intermediate transfer belt 25 is performed.

  At the time of forming a full-color image, an electrostatic latent image is formed on each photosensitive drum 1 in each image forming unit S, and this is developed into a toner image of each color. Then, the toner images of the respective colors formed on the respective photosensitive drums 1 of the respective image forming sections S are transferred so as to be sequentially superimposed on the intermediate transfer belt 25 in the respective primary transfer sections N1Y, N1M, N1C, N1K. Four color toner images are formed on the transfer belt 25.

  Further, the transfer material P loaded on the sheet cassette 28 serving as a storage unit is fed to the transport roller 30 by the feeding unit 29, and is transported to the secondary transfer unit N2 by the transport roller 30. Then, the multicolor toner image of four colors carried on the intermediate transfer belt 25 is caused by a current (hereinafter, referred to as a secondary transfer current) flowing from the secondary transfer roller 11 to the intermediate transfer belt 25 in the secondary transfer portion N2. Is transferred (secondary transfer) to the transferred transfer material P. At this time, a secondary transfer voltage having a polarity opposite to the normal charge polarity of the toner (positive in this embodiment) is applied to the secondary transfer roller 11 from the secondary transfer power supply 41. That is, in the configuration of the present embodiment, the intermediate transfer belt is controlled by a constant current control that controls the output of the secondary transfer power supply 41 so that a predetermined secondary transfer current flows from the secondary transfer roller 11 toward the intermediate transfer belt 25. From 25, the toner image is secondarily transferred to the transfer material P.

  Thereafter, the transfer material P on which the toner image has been transferred is conveyed to the fixing unit 13, where the toner image is fixed on the surface of the transfer material P, and then discharged outside the apparatus main body of the image forming apparatus 100. To be loaded.

  The toner remaining on the photosensitive drum 1 after the primary transfer is removed from the surface of the photosensitive drum 1 by the cleaning blade 4. The transfer residual toner remaining on the intermediate transfer belt 25 after passing through the secondary transfer portion N2 is removed from the surface of the intermediate transfer belt 25 by the cleaning blade 16a.

[Image formation in wide color gamut mode]
In the image forming apparatus of this embodiment, in addition to the normal mode (first mode) as the reference image forming mode, a wide color gamut mode (second mode) for expanding the color reproduction range of the image formed on the transfer material P Mode). In the wide color gamut mode, the speed ratio between the rotation speed of the photosensitive drum 1 and the rotation speed of the developing roller 3 is set to be larger than the speed ratio between the photosensitive drum 1 and the developing roller 3 in the normal mode. Thus, the color reproduction range is expanded by increasing the amount of toner per unit area carried on the photosensitive drum 1. When the wide color gamut mode is executed, the speed ratio between the photosensitive drum 1 and the developing roller 3 is changed from that in the normal mode, and the setting of the surface potential of the photosensitive drum 1 is also changed. Hereinafter, various settings in the normal mode and the wide color gamut mode will be described.

<Various settings in normal mode and wide color gamut mode>
FIG. 4 is a schematic diagram illustrating the layer configuration of the photosensitive drum 1. As shown in FIG. 4, the photosensitive drum 1 includes, from the lower layer, a base 31 made of a conductive material, an undercoat layer 32 for suppressing interference of light and improving the adhesiveness of an upper layer, and a charge generating layer 33 for generating carriers. And a charge transport layer 34 for transporting generated carriers.

  The base 31 is grounded, and an electric field is formed from the inside to the outside of the photosensitive drum 1 by charging the photosensitive drum 1 by the charging roller 2 to which a negative voltage is applied. When the photosensitive drum 1 is irradiated with light from the exposure unit 20, carriers are generated in the charge generation layer 33. The carriers generated in the charge generation layer 33 move from the inside to the outside of the photosensitive drum 1 by the above-described electric field, and form a pair with the charges on the surface of the photosensitive drum 1 charged by the charging roller 2. As a result, the surface potential of the photosensitive drum 1 changes.

  FIG. 5 is a schematic diagram illustrating potentials formed on the photosensitive drum 1 in the normal mode and the wide color gamut mode. In FIG. 5, the potential formed on the photosensitive drum 1 by being charged by the charging roller 2 is a background potential Vd, and the potential formed on the photosensitive drum 1 by being exposed by the exposure means 20 is a latent image potential Vl. The voltage applied to the developing roller 3 is defined as a developing voltage Vdc. In FIG. 5, the description will be made with the suffix n added to the potential for the normal mode and the suffix w for the potential for the wide color gamut mode.

As shown in FIG. 5, the developing voltage Vdc _n in the normal mode, it is set between the latent image potential Vl _n and the background potential Vd _n, similarly, the developing voltage Vdc _w in wide color gamut mode, the latent image It is set between the potential Vlw and the background potential Vd _w. For this reason, in both the normal mode and the wide color gamut mode, the negative toner carried on the developing roller 3 electrostatically moves to the exposed portion exposed by the exposure unit 20 and is exposed by the exposure unit 20. It does not electrostatically move to a non-exposed portion that has not been exposed.

  Here, when the development is performed by moving the toner from the developing roller 3 to the exposed portion of the photosensitive drum 1, the potential at the exposed portion of the photosensitive drum 1 changes to the negative polarity side due to the negatively charged toner. As a result, the electric field formed between the developing roller 3 and the photosensitive drum 1 is weakened. That is, when the wide color gamut mode is executed, even if the speed ratio between the photosensitive drum 1 and the developing roller 3 is increased to increase the amount of toner per unit area on the photosensitive drum 1, the predetermined speed ratio is required. The amount of toner that can be carried on the photosensitive drum 1 is saturated.

To widen more increased so by the color reproduction range of the toner amount per unit area to be carried on the photosensitive drum 1, the potential difference Vcont _w between the developing voltage Vdc _w and the latent image potential Vl _w to form on the photosensitive drum 1 Must be set large enough. Even if the exposure amount by the exposure unit 20 is further increased in a state where the potential charged by the charging roller 2 has sufficiently disappeared, the carrier generated in the charge generation layer 33 is reduced because the electric field inside the photosensitive drum 1 is weakened. It does not move to the surface, and the potential of the exposed portion does not change. Therefore, in order to set a higher potential difference Vcont _w , it is necessary to control charging by the charging roller 2 so that the value of the background potential Vd _w increases.

In the present embodiment, in order to widen the color reproduction range in the wide color gamut mode not only greater than in the normal mode and a speed ratio of the photosensitive drum 1 and the developing roller 3, the potential difference Vcont _w wide color gamut mode The potential difference Vcont _{n in the} normal mode is set to be larger. More specifically, in the normal mode of this embodiment, 140% of the speed ratio of the rotational speed of the developing roller 3 (first speed ratio) relative to the rotational speed of the photosensitive drum 1, -500 V a background potential Vd _n, development voltage -350V the Vdc _n, a latent image potential Vl _n was set to -100V. In the wide color gamut mode, the speed ratio (second speed ratio) of the rotation speed of the developing roller 3 to the rotation speed of the photosensitive drum 1 is 280%, the background potential Vd _w is -850 V, and the development voltage Vdc _w is -600 V. It was set a latent image potential Vl _w to -120V. In this embodiment, when the wide color gamut mode is executed, the speed ratio of the rotation speed of the developing roller 3 to the rotation speed of the photosensitive drum 1 is set to 280% regardless of the surrounding environment.

[Secondary transfer control in wide color gamut mode]
As described above, in the wide color gamut mode, the toner amount per unit area carried on the photosensitive drum 1 is larger than the toner amount per unit area carried on the photosensitive drum 1 in the normal mode. That is, the toner amount per unit area of the toner image primarily transferred from the photosensitive drums 1Y, 1M, 1C, and 1K to the intermediate transfer belt 25 also becomes larger than that in the normal mode. Therefore, in the wide color gamut mode, a voltage (hereinafter, referred to as a secondary transfer voltage) applied from the secondary transfer power supply 41 to the secondary transfer roller 11 to secondary transfer the toner image from the intermediate transfer belt 25 to the transfer material P. Must be set appropriately according to the increased amount of toner.

  More specifically, if the secondary transfer voltage is set to the same value as the secondary transfer voltage in the normal mode, the toner image primarily transferred to the intermediate transfer belt 25 in the wide color gamut mode cannot be sufficiently transferred to the transfer material P. Second, the transfer efficiency of the secondary transfer may be reduced. On the other hand, if the secondary transfer voltage is set too high, the charging polarity of the toner carried on the intermediate transfer belt 25 may be inverted due to the discharge generated in the secondary transfer portion N2. In this case, at the position where the local discharge has occurred, a phenomenon occurs in which the toner is not transferred to the transfer material P and the surface of the transfer material P is exposed, so that the image becomes white (hereinafter, referred to as white spot). There is a risk.

  Therefore, it is necessary to appropriately set the secondary transfer voltage in the wide color gamut mode according to the amount of toner carried on the photosensitive drum 1. However, the amount of toner carried on the photosensitive drum 1 is affected by the speed ratio of the rotation speed of the developing roller 3 to the rotation speed of the photosensitive drum 1 and the temperature and humidity of the surrounding environment where the image forming apparatus 100 is used. In this embodiment, when the wide color gamut mode is executed, the speed ratio of the rotation speed of the developing roller 3 to the rotation speed of the photosensitive drum 1 is set to a constant value regardless of the surrounding environment. The amount of toner carried on the drum 1 is affected by the ambient temperature and humidity.

  Therefore, in the configuration of the present embodiment, the temperature and the humidity are detected by the detection sensor 103 as the detection means for detecting the surrounding environment, and the optimum secondary transfer voltage is determined based on the absolute weight of the weight obtained from the detection result. Set. More specifically, in the configuration of the present embodiment, the value of the secondary transfer current is set in advance based on the value of the weight absolute humidity, and the secondary transfer power supply 41 An appropriate secondary transfer voltage is applied to the secondary transfer roller 11.

  Table 1 is a table showing the value of the secondary transfer current based on the value of the weight absolute humidity. In the present embodiment, the values of the weight absolute humidity and the value of the secondary transfer current are stored in a look-up table (LUT) in advance as a controller. 102 is stored in the storage means. As shown in Table 1, for example, when the absolute humidity is 3.0 (g / kg), the controller 102 causes the secondary transfer current of 27 μA to flow from the secondary transfer roller 11 to the intermediate transfer belt 25. Then, the voltage applied from the secondary transfer power supply 41 to the secondary transfer roller 11 is controlled.

Next, with respect to Comparative Example 1 and this example, the wide color gamut mode was executed at each absolute weight of humidity, and the transfer efficiency and the occurrence of white spots were evaluated. In Comparative Example 1, the secondary transfer current is 29 μA, which is the optimum secondary transfer current when the absolute humidity in Table 1 is 5 (g / kg) or more and less than 15 (g / kg) in any environment. The voltage applied from the secondary transfer power supply 41 to the secondary transfer roller 11 was controlled such that The configuration of Comparative Example 1 is the same as that of the present embodiment except that the secondary transfer current is not changed based on the absolute weight of the weight. The description is omitted. Further, as the transfer material P for the evaluation, a high-white paper GF-C081 (basis weight 81.4 g / m ² ) manufactured by Canon Inc. was used, and the evaluation was performed with the image forming unit S being almost new. Was.

  Table 2 is a table showing the evaluation results of this example and Comparative Example 1. Regarding the transfer efficiency, since the difference between the colors was small, the transfer efficiency at the time of secondary transfer of the toner image primarily transferred to the intermediate transfer belt 25 in the image forming unit SC to the transfer material P was evaluated. More specifically, “○” indicates that the transfer efficiency when the toner image formed in the image forming unit SC is secondarily transferred to the transfer material P is 96% or more, and “場合” indicates that the transfer efficiency is 92% or more and less than 96%. "△", and the case of less than 92% are indicated as "x" in Table 2. The evaluation of white spots is shown in Table 10 as “場合” when no white spots were generated and “×” when white spots were generated.

  As shown in Table 2, according to the configuration of the present embodiment, when image formation is performed using the wide color gamut mode, image formation can be performed with good transfer efficiency in any environment. White spots could also be suppressed. On the other hand, in Comparative Example 1, sufficient transfer efficiency could not be obtained in an environment where the absolute humidity was 15 (g / kg) or more, and in an environment where the absolute humidity was less than 5 (g / kg). White spots occurred.

  The amount of toner carried on the photosensitive drum 1 from the developing roller 3 (hereinafter, simply referred to as toner applied amount) varies depending on the amount of charge per unit mass of toner (hereinafter, referred to as tribo). When the amount is small and the tribo is low, the amount of applied toner increases. Further, the value of the tribo varies depending on the surrounding environment, and becomes higher on the side where the absolute weight of humidity is low, and becomes lower on the side where the absolute weight of humidity is high. That is, when the absolute weight of the toner is higher than 5 (g / kg) and less than 15 (g / kg), the amount of the applied toner is higher on the side where the absolute weight of the weight is higher, and the absolute weight of the weight is lower. On the side, the amount of applied toner is reduced.

  Therefore, in the configuration of Comparative Example 1, the amount of applied toner is greater in an environment where the absolute humidity is 15 (g / kg) or more than in an environment where the absolute humidity is 5 (g / kg) or more and less than 15 (g / kg). , The secondary transfer current was insufficient, and sufficient transfer efficiency could not be obtained. Further, in an environment where the absolute humidity is less than 5 (g / kg), the amount of applied toner is smaller than in an environment where the absolute humidity is not less than 5 (g / kg) and less than 15 (g / kg). The next transfer current became excessive, and white spots occurred due to generation of discharge.

  As described above, according to the configuration of the present embodiment, the secondary transfer is performed when the toner image is transferred from the photosensitive drum 1 to the intermediate transfer belt 25 in the wide color gamut mode based on the surrounding environment of the image forming apparatus 100. The secondary transfer voltage applied from the power supply 41 to the secondary transfer roller 11 is controlled. Thus, regardless of the surrounding environment, it is possible to suppress a decrease in transfer efficiency by suppressing a decrease in transfer efficiency and the occurrence of white spots.

(Example 2)
In the first embodiment, the configuration in which the secondary transfer voltage in the wide color gamut mode is set based on the surrounding environment of the image forming apparatus 100 has been described. On the other hand, in the second embodiment, a configuration in which the secondary transfer voltage in the wide color gamut mode is set based on the surrounding environment of the image forming apparatus 100 and the durability of the image forming unit S will be described. The configuration of the present embodiment has the same configuration as that of the first embodiment except that the secondary transfer voltage is set based on the surrounding environment of the image forming apparatus 100 and the durability of the image forming unit S. Therefore, in the following description, the same parts as those in the first embodiment are denoted by the same reference numerals, and description thereof will be omitted.

[Secondary transfer control in wide color gamut mode]
As described in the first embodiment, it is necessary to appropriately set the secondary transfer voltage in the wide color gamut mode according to the amount of applied toner, and the applied amount of toner fluctuates due to tribo. The tribo of the toner also varies depending on the durability of the image forming unit S. More specifically, in the later stage of use of the image forming unit S, the tribo of the toner tends to be lower than in the early stage of use. Therefore, in the present embodiment, an optimal secondary transfer voltage is set based on the absolute weight of the humidity obtained from the surrounding environment of the image forming apparatus 100 and the durability of the image forming unit S. More specifically, in the configuration of the present embodiment, the value of the secondary transfer current is set in advance based on the absolute weight of the weight and the durability of the image forming unit S. , An appropriate secondary transfer voltage is applied to the secondary transfer roller 11 from the secondary transfer power supply 41.

  Here, in the present embodiment, the controller 102 integrates the integrated drive time of each image forming unit S from the time of brand-new operation, and sets the integrated drive time for determining the life as 100%. Calculate the degree. That is, the durability of each image forming unit S is 0% when new, increases as image formation is performed, and reaches 100% during the life. In this embodiment, the integrated driving time of the image forming unit S is calculated by the controller 102 every time image formation is completed, and is sequentially written to a nonvolatile memory (not shown) provided in the image forming unit S.

  Table 3 is a table showing values of the secondary transfer current based on the durability and the absolute humidity of the image forming unit S. In the present embodiment, the value of the secondary transfer current based on the durability and the absolute humidity of the image forming unit S is stored in advance in a storage unit of the controller 102 as a look-up table (LUT). As shown in Table 3, for example, when the durability of the image forming apparatus S is 40% and the weight absolute humidity is 3.0 (g / kg), the controller 102 sets the secondary transfer current to 27 μA. And a secondary transfer voltage applied from the secondary transfer power supply 41 to the secondary transfer roller 11.

  Next, for Comparative Example 2 and this example, the wide color gamut mode was executed at each absolute weight of the image forming unit S for each durability, and the transfer efficiency and white spots were evaluated. In Comparative Example 2, the voltage applied from the secondary transfer power supply 41 to the secondary transfer roller 11 was controlled such that the secondary transfer current was 29 μA in any durability and any environment. Here, 29 μA set as the secondary transfer current is the optimum value in Table 3 when the durability of the image forming portion S is 40% and the absolute humidity is 5 (g / kg) or more and less than 15 (g / kg). Is the value of the secondary transfer current. In the following description, the same reference numerals are given to the same components as those of the present embodiment in the configuration of Comparative Example 2, and the description is omitted. Further, the transfer material P and each evaluation criterion at the time of the evaluation are the same as those of the first embodiment, and thus the description is omitted.

  Table 4 is a table showing the evaluation results of the transfer efficiency in the present example and Comparative Example 2, and Table 5 is a table showing the evaluation results of white spots in the present Example and Comparative Example 2.

  As shown in Table 4, according to the configuration of the present embodiment, when image formation is performed using the wide color gamut mode, image formation can be performed with good durability and good transfer efficiency in any environment. Was completed. On the other hand, in Comparative Example 2, the transfer efficiency could not be obtained in an environment where the absolute weight of the weight was 15 (g / kg) or more, and the transfer efficiency was increased as the durability of the image forming unit S was increased. Tended to further decrease. This is because, in an environment where the absolute humidity is 15 (g / kg) or more, the amount of applied toner increases due to a decrease in tribo, and the current becomes insufficient with the set value of the secondary transfer current in Comparative Example 2. It is considered that sufficient transfer efficiency could not be obtained. Regarding a decrease in transfer efficiency due to an increase in durability, as the durability of the image forming unit S increases, the tribo becomes lower, and the amount of applied toner further increases, so that the secondary transfer current becomes more insufficient, It is considered that sufficient transfer efficiency could not be obtained.

  As shown in Table 5, according to the configuration of the present embodiment, when performing image formation using the wide color gamut mode, the occurrence of white spots can be suppressed in any durability and any environment. Was. On the other hand, in Comparative Example 2, it was difficult to suppress white spots in an environment where the absolute humidity was less than 5 (g / kg). The occurrence of white spots in Comparative Example 2 is considered to be due to an excessive secondary transfer current due to a reduced amount of applied toner in an environment where the absolute weight of humidity is less than 5 (g / kg).

  As described above, according to the configuration of the present embodiment, based on the durability of the image forming unit S and the surrounding environment of the image forming apparatus 100, the secondary transfer power supply 41 and the secondary transfer roller in the wide color gamut mode. 11 is controlled. Thereby, regardless of the surrounding environment, it is possible to suppress a decrease in the transferability in the secondary transfer by suppressing a decrease in the secondary transfer efficiency and white spots.

  In the present embodiment, the durability of the image forming unit S is obtained by integrating the integrated driving time of each image forming unit S from the time of a new product. However, the present invention is not limited to this. For example, the configuration may be such that the durability of the image forming unit S is obtained from the integrated value of the number of rotations of the developing roller 3 and the amount of toner stored in the developing unit 9. In addition, the durability of the image forming unit S can be obtained from the thickness of the photosensitive drum 1, the accumulated rotation time of the photosensitive drum 1, the amount of movement of the surface of the photosensitive drum 1, and the like.

(Example 3)
In the third embodiment, in addition to the control of the second embodiment, when the wide color gamut mode is executed, the secondary transfer voltage applied to the rear end of the transfer material P in the transport direction of the transfer material P is changed. A configuration for setting a value higher than the secondary transfer voltage applied to the central portion will be described. The third embodiment has the same configuration as the second embodiment except that the secondary transfer voltage is different between the rear end portion and the central portion of the transfer material P in the transport direction of the transfer material P. Therefore, in the following description, portions common to the second embodiment are denoted by the same reference numerals, and description thereof is omitted.

  In the case of executing the wide color gamut mode, a phenomenon in which the toner image secondarily transferred to the image portion at the rear end of the transfer material P scatters to the non-image portion depending on the electric resistance value of the transfer material P (hereinafter, simply referred to as scatter May occur). Hereinafter, the scattering in the wide color gamut mode will be described with reference to FIGS. FIG. 6A is a schematic diagram illustrating a toner image carried on the rear end of the transfer material P at the time of the secondary transfer in the normal mode, and FIG. 6B is a diagram illustrating scattering in the wide color gamut mode. FIG. 4 is a schematic diagram illustrating a toner image carried on a rear end of a transfer material when the toner image is generated.

  As shown in FIGS. 6A and 6B, a positive voltage is applied to the secondary transfer roller 11 from the secondary transfer power supply 41 in order to secondary transfer the toner image from the intermediate transfer belt 25 to the transfer material P. Then, a positive charge is supplied to the back surface of the transfer material P facing the secondary transfer roller 11. At this time, if the electric charge supplied to the back surface of the transfer material P is larger than the electric charge held by the toner image to be secondarily transferred, no scattering occurs. However, when a large amount of toner is carried on the intermediate transfer belt 25 by executing the wide color gamut mode, the charge supplied to the transfer material P may be smaller than the charge held by the toner image. There is. When the charge supplied to the transfer material P becomes smaller than the charge held by the toner image, the phenomenon in which the toner secondary-transferred onto the transfer material P scatters to the non-image portion as shown in FIG. (Hereinafter, referred to as scattering). In particular, the scattering easily occurs in a low-temperature and low-humidity environment where the electric resistance of the transfer material P is high.

  Therefore, in the present embodiment, in addition to the control of the second embodiment, when the wide color gamut mode is executed in a low-temperature and low-humidity environment, the secondary transfer applied to the rear end of the transfer material P in the transport direction of the transfer material P The voltage is set to a value higher than the secondary transfer voltage applied to the central portion of the transfer material P. More specifically, as shown in FIG. 7, based on the absolute weight of the weight and the durability of the image forming unit S, with respect to the transport direction of the transfer material P, 2 at the rear end (first region) of the transfer material P. The next transfer current is set to a value larger than the secondary transfer current in the central portion (second region) of the transfer material P. FIG. 7 is a schematic timing chart illustrating control of the secondary transfer power supply 41 in the present embodiment.

As shown in FIG. 7, in the normal mode and the wide color gamut mode of the present embodiment, at time T11 before the leading end of the toner image secondary-transferred onto the transfer material P reaches the secondary transfer portion N2, A secondary transfer voltage is applied from the secondary transfer power supply 41 to the secondary transfer roller 11. At this time, the controller 102 controls the output value of the secondary transfer power supply 41 so that the secondary transfer current flowing from the secondary transfer roller 11 toward the intermediate transfer belt 25 becomes the current In in the normal mode. Further, in the wide color gamut mode, the output value of the secondary transfer power supply 41 is controlled so as to be the current Iw _c (second current value).

Subsequently, in the wide color gamut mode, at time T12 the trailing edge of the toner image is secondarily transferred onto the transfer material P reaches the secondary transfer portion N2, the secondary transfer current, than the value of the current Iw _c controlling the value of the output of the secondary transfer power supply 41 so it becomes large current Iw e _(first current value). Thereafter, at time T13, the application of the voltage from the secondary transfer power supply 41 to the secondary transfer roller 11 is stopped, and the image formation on the transfer material P in the normal mode and the wide color gamut mode is completed.

  In the configuration of the present embodiment, the value of the secondary transfer current at the center of the transfer material P and the value of the secondary transfer current at the rear end of the transfer material P are set in advance. When executing the wide color gamut mode, the controller 102 controls the secondary transfer power supply 41 based on the value of each secondary transfer current, and applies an appropriate secondary transfer voltage to the secondary transfer roller 11. Further, in the present embodiment, in an environment where scattering is more likely to occur, that is, in an environment where the absolute humidity of the weight is less than 5 (g / kg), the secondary transfer current between the central portion and the rear end portion of the transfer material P is reduced. The value is made different.

Table 6 is a table showing the value of the current Iw _c based on the durability and weight absolute humidity of the image forming unit S, the table 7, a current based on the durability and weight absolute humidity of the image forming unit S Iw _e Is a table showing values. As shown in Tables 6 and 7, for example, when the durability of the image forming apparatus S is 40% and the absolute weight of the weight is 3 (g / kg), the controller 102 makes the secondary transfer power supply 41 as follows. To control the secondary transfer voltage applied to the secondary transfer roller 11. That is, as the transfer material P current Iw _c in a central portion which is corresponding secondary transfer current 27Myuei, current Iw _e on the rear end portion of the corresponding secondary transfer current of the transfer material P is 32Myuei, 2 The secondary transfer voltage applied to the next transfer roller 11 is controlled. Here, in the present embodiment, switching of the secondary transfer voltage from the second region to the first region in the wide color gamut mode is performed 5 mm before the rear end of the transfer material P passes through the secondary transfer portion N2. The configuration was adopted.

Next, for Comparative Example 3 and this example, the wide color gamut mode was executed at each absolute weight of the image forming unit S for each durability level, and white spots and scattering were evaluated. As the transfer time P, high white paper GF-C081 (basis weight: 81.4 g / m ² ) manufactured by Canon Inc. was used. The area mode was executed to evaluate white spots and scattering.

Comparative Example 3 has a configuration in which the value of the secondary transfer current is not switched between the central portion and the rear end portion of the transfer material P in an environment where the weight absolute humidity is less than 5 (g / kg). That is, in Comparative Example 3, the weight even in the absolute humidity 5 (g / kg) than the environmental, secondary transfer current in the central portion and the rear end portion of the transfer material P, 2 so that the current Iw _c order The voltage applied from the transfer power supply 41 to the secondary transfer roller 11 was controlled. In the following description, the same reference numerals are given to the same components as those of the present embodiment in the configuration of Comparative Example 3, and the description is omitted.

  Table 8 is a table showing evaluation results of white spots in this example and Comparative Example 3, and Table 9 is a table showing evaluation results of scattering in this Example and Comparative Example 3. Regarding white spots and splatters, Table 8 or Table 9 shows "O" when no occurrence occurred and "X" when occurrence occurred.

  As shown in Table 8, in any of the configurations of the present embodiment and Comparative Example 3, the occurrence of white spots was not confirmed when image formation was performed using the wide color gamut mode. This is because, in the present embodiment and Comparative Example 3, the secondary transfer current in the wide color gamut mode is set based on the durability of the image forming unit S and the surrounding environment of the image forming apparatus 100, and This is because the current applied from 41 to the secondary transfer roller 11 is controlled. With this configuration, it is possible to suppress a decrease in transferability in the secondary transfer by suppressing a decrease in the secondary transfer efficiency and white spots regardless of the surrounding environment.

  As shown in Table 9, in Comparative Example 3, scattering occurred at the rear end of the transfer material P in an environment where the absolute humidity was less than 5 (g / kg). This is because the electric resistance of the transfer material P increases due to being left for 4 days in an environment where the absolute humidity is less than 5 (g / kg), and the electric charge supplied to the transfer material P from the secondary transfer roller 11 is reduced. This is probably because the charge of the toner image became smaller than that of the toner image. On the other hand, in an environment where the absolute humidity is less than 5 (g / kg), the value of the secondary transfer current corresponding to the rear end of the transfer material P is changed to the value of the secondary transfer current corresponding to the center of the transfer material P. In the configuration of the present embodiment in which the value is larger than the value, the occurrence of scattering can be suppressed.

  In the present embodiment, the value of the secondary transfer current corresponding to the rear end of the transfer material P is increased in an environment where the absolute humidity is less than 5 (g / kg). No white spots occurred due to the following. This is because the first area where the secondary transfer current is increased includes the rear end of the image forming area where the toner image is secondarily transferred in the transport direction of the transfer material P, but the first area increases from the rear end of the transfer material P. It is considered that the area is relatively narrow, that is, an area within 5 mm.

  As described above, in the configuration of the present embodiment, the secondary transfer current is set based on the durability of the image forming unit S and the surrounding environment, and the transfer direction of the transfer material P is The secondary transfer current at the end is set to a value larger than the secondary transfer current at the center. Thereby, not only the same effect as in the second embodiment is obtained, but also the occurrence of scattering at the rear end of the transfer material P can be suppressed.

  Although the description has been made on the assumption that the secondary transfer current is set based on the durability of the image forming unit S and the surrounding environment, the configuration is not limited to this. In order to suppress the scattering in the secondary transfer portion N2, at least the secondary transfer current at the rear end of the transfer material P in the transport direction of the transfer material P is made smaller than the secondary transfer current at the central portion of the transfer material P. May be set to a large value. Further, in contrast to the configuration in which the secondary transfer current is set based on the surrounding environment of the first embodiment, the secondary transfer current at the rear end of the transfer material P is larger than the secondary transfer current at the center of the transfer material P. It may be configured to set to a value. Thereby, not only the same effect as in the first embodiment can be obtained, but also the scattering in the configuration of the first embodiment can be suppressed.

  Further, in the present embodiment, the configuration in which the value of the secondary transfer current is switched in an area within 5 mm from the rear end of the transfer material P has been described, but the present invention is not limited to this. At least the rear end of the image forming area where the toner image is secondarily transferred, and the upstream side where the toner image transferred to the rear end of the image forming area may be scattered in the transport direction of the transfer material P. If the area is included, it is possible to suppress the occurrence of scattering. That is, the value of the secondary transfer current may be switched downstream of the rear end of the image forming area in the transport direction of the transfer material P. However, if the first area is set too wide, white spots may occur due to a large value of the secondary transfer current. It is preferable that the first area includes the rear end of the image forming area and is set such that the width of the first area is smaller than the width of the second area in the transport direction of the transfer material P.

  In the present embodiment, the durability of the image forming unit S is obtained by integrating the integrated driving time of each image forming unit S from the time of a new product. However, the present invention is not limited to this. For example, the configuration may be such that the durability of the image forming unit S is obtained from the integrated value of the number of rotations of the developing roller 3 and the amount of toner stored in the developing unit 9. In addition, the durability of the image forming unit S can be obtained from the thickness of the photosensitive drum 1, the accumulated rotation time of the photosensitive drum 1, the amount of movement of the surface of the photosensitive drum 1, and the like.

<Modification>
In the present embodiment, a configuration in which the value of the secondary transfer current is switched between the central portion and the rear end portion of the transfer material P in an environment in which the electrical resistance of the transfer material P is high and the absolute humidity of the weight is less than 5 (g / kg). Was explained. This is because when the electric resistance of the transfer material P is high, the possibility that the scattering occurs due to a decrease in the amount of charge supplied from the secondary transfer roller 11 to the transfer material P is increased. Here, the amount of electric charge supplied from the secondary transfer roller 11 to the transfer material P also depends on the attitude of the rear end of the transfer material P in the secondary transfer portion N2. This will be described in detail below.

  FIG. 8A is a schematic diagram illustrating a state in which the rear end of the transfer material P comes off toward the intermediate transfer belt 25 in the transport direction of the transfer material P when the transfer material P passes through the secondary transfer portion N2. is there. FIG. 8B illustrates a state in which, when the transfer material P passes through the secondary transfer portion N <b> 2, the rear end of the transfer material P comes off toward the secondary transfer roller 11 in the transport direction of the transfer material P. It is a schematic diagram.

  In an environment with a low absolute weight humidity (low-temperature, low-humidity environment), discharge is dominant in supplying electric charge from the secondary transfer roller 11 to the transfer material P. That is, as shown in FIG. 8A, in a state where the rear end of the transfer material P moves toward the intermediate transfer belt 25, discharge from the secondary transfer roller 11 to the back surface of the transfer material P increases. The amount of charge supplied from the secondary transfer roller 11 to the transfer material P also increases. On the other hand, as shown in FIG. 8B, in a state where the rear end of the transfer material P moves toward the secondary transfer roller 11, the discharge from the secondary transfer roller 11 to the back surface of the transfer material P decreases. As a result, the amount of charge supplied from the secondary transfer roller 11 to the transfer material P also decreases.

  When the transfer material P is transported in a posture as shown in FIG. 8B, there is a possibility that scattering occurs at the rear end of the transfer material P. Specifically, after the toner image is secondarily transferred onto the first surface in the secondary transfer portion N2 and the toner image is fixed on the first surface by the fixing means 13, the secondary transfer portion N2 is again passed through the double-sided conveyance path. The transfer material P conveyed to is easily in the posture of FIG. This is because the transfer material P may curl when passing through the double-sided conveyance path.

Here, in the present embodiment, regardless of the first surface or the second surface of the transfer material P, when the wide color gamut mode is executed in an environment where the absolute humidity is less than 5 (g / kg), large current Iw _e than the value of the current Iw _c to control the secondary transfer power supply 41 to flow to the rear end portion of the P. However, not limited to this, only when the secondary transfer of the toner image on the second surface of the transfer material P in the case to perform a wide color gamut mode, the value of the current Iw _c on the rear end portion of the transfer material P it may be controlled secondary transfer power supply 41 to flow a large current Iw _e than. Even in such a configuration, it is possible to obtain the same effects as in the present embodiment.

(Example 4)
In the third embodiment, in the transport direction of the transfer material P, the secondary transfer current at the rear end of the transfer material P is set to a value larger than the secondary transfer current at the central portion of the transfer material P. The configuration for suppressing the scattering at the rear end portion has been described. On the other hand, in the fourth embodiment, when the wide color gamut mode is executed in an environment where the weight absolute humidity is low (low temperature and low humidity environment), the timing of turning off the output of the secondary transfer power supply 41 is later than in the normal mode. The configuration will be described. Note that the fourth embodiment is different from the fourth embodiment in that the timing of turning off the output of the secondary transfer power supply 41 is different without switching the secondary transfer current between the central portion and the rear end portion of the transfer material P. 3 has the same configuration. Therefore, in the following description, portions common to the second embodiment are denoted by the same reference numerals, and description thereof is omitted.

  FIG. 9 is a schematic timing chart illustrating control of the secondary transfer power supply 41 in the present embodiment. As shown in FIG. 9, in the normal mode and the wide color gamut mode of the present embodiment, at time T21 before the leading end of the toner image secondary-transferred onto the transfer material P reaches the secondary transfer portion N2, A secondary transfer voltage is applied from the secondary transfer power supply 41 to the secondary transfer roller 11. Subsequently, in the normal mode, at time T22 after the trailing end of the toner image secondary-transferred onto the transfer material P has passed through the secondary transfer portion N2, the secondary transfer power supply 41 transfers the toner image to the secondary transfer roller 11. Is stopped, and the image formation on the transfer material P is completed. On the other hand, in the wide color gamut mode, the application of the voltage from the secondary transfer power supply 41 to the secondary transfer roller 11 is stopped at time T23 later than time T22, and the image formation on the transfer material P is completed. I do.

  As described in the third embodiment, in a low-temperature and low-humidity environment where the weight absolute humidity is low, the discharge is dominant in the charge supply from the secondary transfer roller 11 to the transfer material P. In this case, the amount of electric charge supplied to the transfer material P also decreases due to a decrease in discharge to the back surface of the transfer material P. In view of this point, in the present embodiment, the timing of turning off the output of the secondary transfer power supply 41 in the wide color gamut mode is set later than in the normal mode, so that the rear end of the transfer material P Make up for the amount of charge supplied to the

  The value of the secondary transfer current in the wide color gamut mode in the present embodiment is set in advance based on the absolute weight of the weight and the durability of the image forming unit S. Since the value of the secondary transfer current is the same as the value shown in Table 6 in the third embodiment, the description is omitted. When executing the wide color gamut mode, the controller 102 controls the secondary transfer power supply 41 based on the value of each secondary transfer current, and applies an appropriate secondary transfer voltage to the secondary transfer roller 11. In the present embodiment, the control for switching the value of the secondary transfer current between the central portion and the rear end portion of the transfer material P as described in the third embodiment is not performed.

Next, for Comparative Example 4 and this example, the wide color gamut mode was executed at each absolute weight of the image forming unit S for each durability of the image forming unit S, and white spots and scattering were evaluated. As the transfer time P, high white paper GF-C081 (basis weight: 81.4 g / m ² ) manufactured by Canon Inc. was used. The area mode was executed to evaluate white spots and scattering.

  In the configuration of Comparative Example 4, the timing of turning off the output of the secondary transfer power supply 41 at the rear end of the transfer material P in the transport direction of the transfer material P is the same in the normal mode and the wide color gamut mode. The secondary transfer power supply 41 is controlled by the controller 102 so as to be as follows. In the following description, the same reference numerals are given to the same components as those of the present example in the configuration of Comparative Example 4, and the description is omitted.

  Table 10 is a table showing the evaluation results of white spots in this example and Comparative Example 4, and Table 11 is a table showing the evaluation results of scattering in this Example and Comparative Example 3. Regarding white spots and splatters, Table 8 or Table 9 shows "O" when no occurrence occurred and "X" when occurrence occurred.

  As shown in Table 10, in the present embodiment, the timing for turning off the output of the secondary transfer power supply 41 in the wide color gamut mode is set later than in the normal mode, but the secondary transfer current becomes excessive. No white spots were found. Also in the configuration of Comparative Example 4, the occurrence of white spots was not confirmed when performing image formation using the wide color gamut mode. In the present embodiment and Comparative Example 4, the secondary transfer current in the wide color gamut mode is set based on the durability of the image forming unit S and the surrounding environment of the image forming apparatus 100, and the secondary transfer power supply 41 The current applied to the next transfer roller 11 is controlled. With this configuration, it is possible to suppress a decrease in transferability in the secondary transfer by suppressing a decrease in the secondary transfer efficiency and white spots regardless of the surrounding environment.

  As shown in Table 11, in Comparative Example 4, scattering occurred at the rear end of the transfer material P in an environment where the absolute humidity was less than 5 (g / kg). This is because the electric resistance of the transfer material P is increased by being left for four days in an environment where the absolute humidity is less than 5 (g / kg), and the electric charge supplied to the transfer material P from the secondary transfer roller 11 is This is probably because the charge of the toner image became smaller than that of the toner image. On the other hand, in the configuration of the present embodiment in which the timing of turning off the output of the secondary transfer power supply 41 in the case of executing the wide color gamut mode is later than in the case of executing the normal mode, the occurrence of scattering is suppressed. Was completed.

  Here, in the wide color gamut mode, the timing at which the output of the secondary transfer power supply 41 is turned off is at the position of the rear end of the transfer material P in the transport direction of the transfer material P, or downstream of the rear end of the transfer material P. It is preferable to set. In a configuration in which the output of the secondary transfer power supply 41 is turned off after the rear end of the transfer material P has passed through the secondary transfer portion N2, the secondary transfer roller 11 travels toward the intermediate transfer belt 25 without passing through the transfer material P. Current will flow. At this time, since an electrostatic history due to the secondary transfer current remains in the intermediate transfer belt 25, an image defect may occur at the time of the next image formation. Further, when toner or the like that has passed through the cleaning unit remains on the intermediate transfer belt 25, the secondary transfer current flows without passing through the transfer material P, and the toner adheres to the secondary transfer roller 11. During the next image formation, the back surface of the transfer material P may be stained.

  As described above, in the configuration of the present embodiment, the secondary transfer current is set based on the durability of the image forming unit S and the surrounding environment, and the output of the secondary transfer power supply 41 in the wide color gamut mode is set. The turning off timing is set later than the normal mode. Thereby, not only the same effect as in the second embodiment is obtained, but also the occurrence of scattering at the rear end of the transfer material P can be suppressed.

  In the present embodiment, the description has been given on the premise of the configuration of the second embodiment in which the secondary transfer current is set based on the durability of the image forming unit S and the surrounding environment. However, the present invention is not limited to this. In contrast to the configuration of the first embodiment in which the secondary transfer current is set based on the surrounding environment, the timing for turning off the output of the secondary transfer power supply 41 in the wide color gamut mode may be configured to be later than in the normal mode. Thereby, not only the same effect as in the first embodiment can be obtained, but also the scattering in the configuration of the first embodiment can be suppressed.

  In the present embodiment, the durability of the image forming unit S is obtained by integrating the integrated driving time of each image forming unit S from the time of new product. However, the present invention is not limited to this. For example, the configuration may be such that the durability of the image forming unit S is obtained from the integrated value of the number of rotations of the developing roller 3 and the amount of toner stored in the developing unit 9. In addition, the durability of the image forming unit S can be obtained from the thickness of the photosensitive drum 1, the accumulated rotation time of the photosensitive drum 1, the amount of movement of the surface of the photosensitive drum 1, and the like.

  In the above embodiment, when the toner image is secondarily transferred to the transfer material P, a predetermined current is set to flow from the secondary transfer roller 11 toward the photosensitive drum 1 based on the surrounding environment. The configuration of the constant current control for controlling the output of the next transfer power supply 41 has been described. However, the present invention is not limited to this, and the secondary transfer of the toner image from the intermediate transfer belt 25 to the transfer material P is performed by the constant voltage control that applies a predetermined voltage from the secondary transfer power supply 41 to the secondary transfer roller 11 based on the surrounding environment. Even with this configuration, it is possible to obtain the same effect as that of the present embodiment.

  When the secondary transfer of the toner image is performed by the constant voltage control, an appropriate secondary transfer voltage can be set by performing a voltage setting control as described below in a pre-rotation operation before the image forming operation is performed. It is possible to set. First, the controller 102 controls the output of the secondary transfer power supply 41 so that a predetermined target current flows through the secondary transfer roller 11 in the pre-rotation operation. Is obtained. After that, an appropriate secondary transfer voltage is set based on the surrounding environment by calculation in the controller 102 or a voltage value look-up table (LUT) stored in the controller 102 in advance.

  Further, the second speed ratio provided between the rotation speed of the photosensitive drum 1 and the rotation speed of the developing roller 3 in the wide color gamut mode of the first to fourth embodiments is larger than the first speed ratio in the normal mode. If it is a value, either the developing roller 3 or the photosensitive drum 1 may be changed. For example, by setting the rotation speed of the photosensitive drum 1 in the wide color gamut mode to be lower than the rotation speed of the photosensitive drum 1 in the normal mode without changing the rotation speed of the developing roller 3, the second speed ratio May be set. Also, by setting the rotation speed of the developing roller 3 in the wide color gamut mode higher than the rotation speed of the developing roller 3 in the normal mode without changing the rotation speed of the photosensitive drum 1, the second speed ratio May be set.

  In the first to fourth embodiments, the configuration has been described in which the absolute weight of the weight is obtained from the detection result of the temperature and humidity of the surrounding environment by the detection sensor 103, and the secondary transfer voltage is set based on the obtained absolute humidity. However, it is not limited to this. For example, the configuration may be such that the secondary transfer voltage is set based on the detection result of the temperature and humidity of the surrounding environment by the detection sensor 103. In this case, a lookup table (LUT) of the secondary transfer voltage based on the temperature and humidity of the surrounding environment may be stored in the controller 102 in advance. In addition, regarding the method of obtaining information on the temperature and humidity of the surrounding environment, the detection sensor 103 does not necessarily need to be used. For example, a configuration may be adopted in which information on the temperature and humidity of the surrounding environment is obtained from image forming conditions and the like input from the host computer 101 to the controller 102, and a configuration in which the temperature and humidity of the surrounding environment is input to the image forming apparatus 100 by the user. May be.

REFERENCE SIGNS LIST 1 photosensitive drum 3 developing roller 11 secondary transfer roller 25 intermediate transfer belt 41 secondary transfer power supply 102 controller

Claims (20)

An image carrier that carries the toner image;
A developing unit that has a developing member disposed to face the image carrier, and develops an electrostatic latent image formed on the image carrier with toner;
An intermediate transfer member on which a toner image carried on the image carrier is primarily transferred;
A transfer member for forming a transfer section in contact with the intermediate transfer body, and for secondary-transferring the toner image primarily transferred from the image carrier to the intermediate transfer body from the intermediate transfer body to a transfer material; ,
A transfer power supply for applying a voltage to the transfer member,
A first mode of performing image formation by controlling a speed ratio of a rotation speed of the developing member to a rotation speed of the image carrier to be a first speed ratio, and the developing mode with respect to a rotation speed of the image carrier. A second mode for performing image formation by controlling the speed ratio of the rotation speeds of the members to be a second speed ratio having a value greater than the first speed ratio. And an image forming apparatus comprising:
In the second mode, in the second mode, a value of a current flowing from the transfer member toward the intermediate transfer body when the surrounding environment of the image forming apparatus is the first environment is such that the surrounding environment is The transfer power supply applies a voltage from the transfer power source to the transfer member such that the current flows from the transfer member toward the intermediate transfer member in a second environment having a lower humidity than the first environment. An image forming apparatus comprising:   In the same surrounding environment, a value of a current flowing from the transfer member toward the intermediate transfer member in the second mode is changed from the transfer member in the first mode to the intermediate transfer member in the same surrounding environment. 2. The image forming apparatus according to claim 1, wherein a voltage applied from the transfer power supply to the transfer member is controlled so as to be larger than a value of a current flowing toward the transfer member. Comprising a detecting means for detecting temperature and humidity in the surrounding environment,
3. The control unit according to claim 1, wherein when executing the second mode, the control unit controls a voltage applied from the transfer power supply to the transfer member based on a detection result by the detection unit. An image forming apparatus according to claim 1.   The control unit, when executing the second mode, so that a current set based on the absolute humidity obtained from the detection result by the detection unit flows from the transfer member toward the intermediate transfer body, 4. The image forming apparatus according to claim 3, wherein a voltage applied from the transfer power supply to the transfer member is controlled.   The control means controls a voltage applied from the transfer power supply to the transfer member based on information on durability obtained from at least one of the image carrier and the developing means and the surrounding environment. The image forming apparatus according to claim 1, wherein: A charging member for charging the image carrier, a charging power source for applying a voltage to the charging member, and a position for forming the electrostatic latent image by exposing the image carrier charged by the charging member. Exposing means for forming a latent image potential, and a developing power supply for applying a developing voltage for developing the electrostatic latent image with toner to the developing member,
The control means may be configured such that a second potential difference formed between the latent image potential and the developing voltage in the second mode is between the latent image potential and the developing voltage in the first mode. The image forming apparatus according to claim 1, wherein an output of the charging power supply is controlled so as to have a value larger than a first potential difference to be formed.   An absolute value of a voltage applied to the charging member from the charging power supply in the second mode is larger than an absolute value of a voltage applied to the charging member from the charging power supply in the first mode. The image forming apparatus according to claim 6.   When executing the second mode, the control unit performs the transfer in a first area including a rear end of a toner image that is secondarily transferred from the intermediate transfer body to the transfer material with respect to a transfer direction of the transfer material. A first current value flowing from the member to the intermediate transfer body is transferred in a second area provided upstream of the leading end of the transfer material and downstream of the first area in the transport direction. 8. The apparatus according to claim 1, wherein a voltage applied from the transfer power supply to the transfer member is controlled so as to be larger than a second current value flowing from the member to the intermediate transfer member. Item 10. The image forming apparatus according to item 1.   The image forming apparatus according to claim 8, wherein a width of the first area is smaller than a width of the second area in the transport direction.   The control unit is configured to control the transfer power from the transfer power supply to the transfer member after a rear end of a toner image that is secondarily transferred from the intermediate transfer body to a transfer material passes through the transfer member when the second mode is executed. When the output of the applied voltage is stopped, the transfer is performed after the rear end of the toner image secondarily transferred from the intermediate transfer body to the transfer material passes through the transfer member when the first mode is executed. 8. The image forming apparatus according to claim 1, wherein the transfer power supply is controlled so as to be later than a timing at which output of a voltage applied to the transfer member from the power supply is stopped. 9. An image carrier that carries the toner image;
A developing unit that has a developing member disposed to face the image carrier, and develops an electrostatic latent image formed on the image carrier with toner;
An intermediate transfer member on which a toner image carried on the image carrier is primarily transferred;
A transfer member for forming a transfer section in contact with the intermediate transfer body, and for secondary-transferring the toner image primarily transferred from the image carrier to the intermediate transfer body from the intermediate transfer body to a transfer material; ,
A transfer power supply for applying a voltage to the transfer member,
A first mode of performing image formation by controlling a speed ratio of a rotation speed of the developing member to a rotation speed of the image carrier to be a first speed ratio, and the developing mode with respect to a rotation speed of the image carrier. A second mode for performing image formation by controlling the speed ratio of the rotation speeds of the members to be a second speed ratio having a value greater than the first speed ratio. And an image forming apparatus comprising:
When executing the second mode, the control unit performs the transfer in a first area including a rear end of a toner image that is secondarily transferred from the intermediate transfer body to the transfer material with respect to a transfer direction of the transfer material. A first current value flowing from the member to the intermediate transfer body is transferred in a second area provided upstream of the leading end of the transfer material and downstream of the first area in the transport direction. An image forming apparatus, wherein a voltage applied from the transfer power supply to the transfer member is controlled so as to be larger than a second current value flowing from the member to the intermediate transfer body.   The image forming apparatus according to claim 11, wherein a width of the first area is smaller than a width of the second area in the transport direction.   12. The image forming apparatus according to claim 11, wherein the control unit controls a voltage applied from the transfer power supply to the transfer member based on a surrounding environment of the image forming apparatus when executing the second mode. 13. The image forming apparatus according to claim 12.   In the second mode, in the second mode, a value of a current flowing from the transfer member toward the intermediate transfer body when the surrounding environment of the image forming apparatus is the first environment is such that the surrounding environment is The transfer power supply applies a voltage from the transfer power source to the transfer member such that the current flows from the transfer member toward the intermediate transfer member in a second environment having a lower humidity than the first environment. The image forming apparatus according to claim 13, wherein a voltage to be applied is controlled.   In the same surrounding environment, a value of a current flowing from the transfer member toward the intermediate transfer member in the second mode is changed from the transfer member in the first mode to the intermediate transfer member in the same surrounding environment. 15. The image forming apparatus according to claim 13, wherein a voltage applied from the transfer power supply to the transfer member is controlled so as to be larger than a value of a current flowing toward the transfer member. Comprising a detecting means for detecting temperature and humidity in the surrounding environment,
16. The control unit according to claim 13, wherein when executing the second mode, a voltage applied from the transfer power supply to the transfer member is controlled based on a detection result by the detection unit. The image forming apparatus according to claim 1.   The control unit, when executing the second mode, so that a current set based on the absolute humidity obtained from the detection result by the detection unit flows from the transfer member toward the intermediate transfer body, 17. The image forming apparatus according to claim 16, wherein a voltage applied from the transfer power supply to the transfer member is controlled.   When executing the second mode, the control unit is configured to transfer the transfer power from the transfer power supply based on information on durability obtained from at least one of the image carrier and the developing unit and the surrounding environment. 18. The image forming apparatus according to claim 13, wherein a voltage applied to the member is controlled. A charging member for charging the image carrier, a charging power source for applying a voltage to the charging member, and a position for forming the electrostatic latent image by exposing the image carrier charged by the charging member. Exposing means for forming a latent image potential, and a developing power supply for applying a developing voltage for developing the electrostatic latent image with toner to the developing member,
The control means may be configured such that a second potential difference formed between the latent image potential and the developing voltage in the second mode is between the latent image potential and the developing voltage in the first mode. The image forming apparatus according to any one of claims 11 to 18, wherein an output of the charging power source is controlled so as to have a value larger than the first potential difference to be formed. 20. The control device according to claim 1, wherein the control unit performs control by setting the second speed ratio to a constant value regardless of the surrounding environment when executing the second mode. The image forming apparatus according to claim 1.

Images