JP4096517B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus that employs an image forming method such as an electrophotographic recording method, an electrostatic recording method, an ionography, or a magnetic recording method, and forms a latent image such as an electrostatic latent image on an image carrier. The present invention relates to an image forming apparatus that develops a latent image with toner to form a toner image, and transfers and fixes the toner image onto a recording sheet such as paper or an OHP sheet to form a recorded image.
[0002]
[Prior art]
In general, in an image forming apparatus, after a toner image formed on an image carrier is transferred onto a recording sheet, residual toner remaining on the image carrier is collected by a cleaning device, and the collected toner is temporarily collected. It is accumulated in the collection container and discarded when the collected toner amount reaches a certain amount.
[0003]
In a full-color image forming apparatus, image data is received from a host device such as a personal computer or a workstation, and color separation is performed into four colors, yellow, magenta, cyan, and black, based on this image data. A toner image of each color is formed on the image carrier by the image information obtained, and the toner images of each color are superimposed on an intermediate transfer body such as an intermediate transfer roll or an intermediate transfer belt, and then transferred onto a recording sheet all at once. In some cases, a full-color image is obtained. In this case as well, the residual toner remaining on the image carrier or intermediate transfer member is collected by a cleaning device, and the collected toner is temporarily stored in a collection container. The accumulated toner is discarded when the amount of collected toner reaches a certain amount.
[0004]
In such an image forming apparatus, the cleaning process for removing the residual toner remaining on the image bearing member or the intermediate transfer member is performed by using the residual toner as it is as a result of contamination such as ghosting or fogging in the recorded image or color mixing due to color mixing. This is a very important process because it causes unevenness.
[0005]
However, in recent years, as the problem of environmental protection has been highlighted, it is required to reduce the collected amount of residual toner collected and discarded in this way as much as possible. Is required to be reused.
[0006]
Further, the problem of reducing the amount of waste for environmental protection and the reuse of waste is not limited to the residual toner collected from the image carrier or the intermediate transfer member. There is a demand for components, but if a cleaning device is attached to the image carrier or intermediate transfer member, the cleaning blade or cleaning brush of this cleaning device will come into sliding contact with the surface of the image carrier or intermediate transfer member, which will wear out. This is an obstacle to extending the life of the image bearing member and the intermediate transfer member.
[0007]
In view of this, various proposals have conventionally been made. For example, in Japanese Patent Laid-Open No. 8-314,231, an image in which a toner image formed on an image carrier is primarily transferred onto an intermediate transfer member and then the toner image on the intermediate transfer member is secondarily transferred onto a recording sheet. In the forming apparatus, a voltage having a polarity opposite to that of the residual toner remaining on the intermediate transfer member during the secondary transfer is applied to the intermediate transfer member, whereby the residual toner on the intermediate transfer member is moved onto the transfer roll to be removed. Thus, it is described that cleaning with an intermediate transfer member is unnecessary and wear is suppressed.
[0008]
Japanese Patent Laid-Open No. 9-197,750 discloses an image in which a toner image formed on an image carrier is primarily transferred onto an intermediate transfer member, and then the toner image on the intermediate transfer member is secondarily transferred onto a recording sheet. In the forming apparatus, a toner collecting member that temporarily collects the residual toner is disposed on the intermediate transfer member, and at the start of the secondary transfer, the toner collecting member is brought into contact with the intermediate transfer member to collect the residual toner, and the secondary transfer is performed. After completion, the remaining toner collected on the toner collecting member is moved onto the intermediate transfer member, and further, the toner collecting member is moved away from the intermediate transfer member to move the remaining toner from the intermediate transfer member onto the image bearing member. It is described that the residual toner moved onto the body is collected by a cleaning device attached to the image carrier.
[0009]
Further, Japanese Patent Laid-Open No. 10-161,425 discloses that at least two different fine particles having a particle diameter smaller than that of the toner and having a charge polarity opposite to the toner are added to the toner. Various types of fine particles are left on the image carrier, and in the development process, a toner image is formed on the image carrier through the fine particles, thereby reducing the adhesion between the toner image and the image carrier. It is described that the transfer efficiency of an image is remarkably improved and a recorded image free from ghosting and fogging is formed without using a cleaning device.
[0010]
However, in the methods described in JP-A-8-314,231 and JP-A-9-197,750, a cleaning device around the image carrier cannot be omitted, and from the image carrier or intermediate transfer member. There is also a problem that the amount of collected residual toner cannot be reduced.
[0011]
Accordingly, the present inventors configured a color image forming apparatus as shown in FIG. 19, and significantly improved the transfer efficiency of the toner image as described in Japanese Patent Laid-Open No. 10-161,425, thereby generating residual toner. A method of reducing the amount as much as possible and omitting a cleaning device around the image carrier, for example, a so-called tandem type full color having four image carriers as disclosed in JP-A-10-78,686 An attempt was made to apply it to an image forming apparatus.
[0012]
That is, in the tandem type full-color image forming apparatus shown in FIG. 19, the two image carriers 10 and 20 for yellow (Y) and magenta (M) are in contact with one first intermediate transfer roll 51, and The other two image carriers 30, 40 for cyan (C) and black (K) are in contact with the other first intermediate transfer roll 52, and further, the pair of first intermediate transfer rolls 51, 52. Is in contact with the second intermediate transfer roll 53, and the four image carriers 10, 20, 30, 40 shown here have a common tangent. The four image carriers 10, 20, 30, 40 are respectively provided with charging rolls (contact type charging devices) 11, 21, 31, 41, exposure devices 12, 22, 32, 42, and The developing devices 13, 23, 33, and 43 are arranged in the same positional relationship with each other, and parts are shared for each type of each device. Each of the developing devices 13, 23, 33, and 43 includes a developing roll 131, a developer amount regulating member 132, a developer conveying member 133, and an auger 134 that conveys and stirs the developer.
[0013]
Therefore, in this tandem full-color image forming apparatus, each single color toner image formed by the two image carriers 10 and 20 is transferred to the first intermediate transfer roll 51 and then transferred to the second intermediate transfer roll 53. In addition, each single color toner image formed by the two image carriers 30 and 40 is transferred to the first intermediate transfer roll 52 and then transferred to the second intermediate transfer roll 53, and this second intermediate transfer The paper is superposed on the roll 53, and then transferred in a lump onto the paper (recording sheet) P conveyed between the conveyance roll 91 and the final transfer roll 61 in contact with the second intermediate transfer roll 53. The toner image transferred onto the paper P is fixed by the fixing device 70. In this method, a plurality of image carriers 10, 20, 30, 40, charging rolls 11, 21, 31, 41, exposure devices 12, 22, 32, 42, and developing devices 13, 23, 33, 43, The first intermediate transfer rolls 51, 52, etc. have the advantage that the parts are made common and high-precision positioning is possible, so that each single-color toner image can be aligned with high precision.
[0014]
However, each single color toner image formed on each image carrier 10, 20, 30, 40 is transferred to the image carrier 30 until the single color toner image formed on the image carrier 30 is transferred onto the paper P. A total of three times between the first intermediate transfer roll 52, between the first intermediate transfer roll 52 and the second intermediate transfer roll 53, and between the second intermediate transfer roll 53 and the paper P In addition, each monochrome toner image formed on the image carrier 10, 40 is a total of 4 times, and each monochrome toner image formed on the image carrier 20 is a total of 5 times. The transfer electric field is received 5 times.
[0015]
For this reason, the toner that forms the toner image is charged with a reverse polarity slightly by Paschen discharge before and after the transfer nip and charge injection in the transfer nip when receiving a transfer electric field. The toner moves in a direction opposite to that of the positive toner during image formation, and finally accumulates in the image carrier or a contact charger that contacts the image carrier. In particular, when a contact-type charger is used, the contact-type charger adsorbs reverse polarity residual toner that has flowed back to the image carrier and causes problems such as uneven charging due to long-term use. Causes uneven color.
[0016]
Therefore, in the method of significantly improving the transfer efficiency of the toner image and omitting the cleaning device around the image carrier, the amount of residual toner can be reduced as much as possible, and the cleaning device is omitted. Thus, it is possible to extend the life of the image carrier and the like, but there is another problem that it is difficult to prevent the occurrence of image defects when the reverse polarity residual toner is generated.
[0017]
Therefore, the present applicant has already disclosed in Japanese Patent Application No. 11-250108 an image carrier, a contact-type charging device that contacts and charges the image carrier, and an exposure device that forms a latent image on the surface of the charged image carrier. And a developing device that develops a latent image formed on the surface of the image carrier to form a toner image, and at least one transfer body, and is formed on the surface of the image carrier in contact with the image carrier. An image forming apparatus including a contact type transfer device that transfers a toner image onto a recording sheet. A cleaning device is attached to one transfer body constituting the contact type transfer device, and a cleaning mode of the image forming apparatus is set. In this case, a potential gradient is formed between the transfer device with the cleaning device provided with the cleaning device and the contact-type charging device, and remains in the contact-type charging device, the image carrier, and the contact-type transfer device. Collected toner to the cleaning device with the transfer member, and recovered collectively residual toner collected in the cleaning device with transfer member by the cleaning device, it proposes an image forming apparatus.
[0018]
According to such an image forming apparatus, even if a reverse polarity residual toner is generated in the image forming apparatus, it can be effectively recovered by performing simple system control.
[0019]
[Problems to be solved by the invention]
However, this image forming apparatus is provided with a cleaning mode for cleaning the reverse polarity residual toner separately from the image forming mode, and gives a potential gradient corresponding to each mode. When switching to the potential gradient corresponding to each mode, In addition, the potential difference between the transfer members becomes excessive, and it may be difficult to set the surface potential of each transfer member to a desired value. Variations in the surface potential of each transfer body result in image defects such as transfer failure and transfer unevenness.
[0020]
The present invention has been made in view of such technical problems, and the object thereof is to prevent the potential difference between the transfer bodies from becoming excessive even when the voltage applied to each transfer body is changed, and to prevent the surface of the transfer body from being changed. An object of the present invention is to provide an image forming apparatus capable of stably setting a potential to a desired value and obtaining a good image.
[0021]
[Means for Solving the Problems]
That is, the present invention includes a plurality of stages of transfer bodies that are in contact with each other from the upstream side to the downstream side in the toner image transfer direction. In an image forming apparatus having a second mode that provides a potential gradient opposite to the first mode, there is a transition from the first mode to the second mode and / or a transition from the second mode to the first mode. Control means for controlling the change timing of the voltage applied to the transfer body at each stage so that the potential difference between the transfer body and the transfer body adjacent to the transfer body becomes small.
[0022]
Here, “adjacent to the transfer member” includes (1) the case adjacent to the upstream side of the transfer member and (2) the case adjacent to the downstream side of the transfer member.
[0023]
As a more specific mode of controlling the change timing of the voltage applied to the transfer body at each stage so that the potential difference between a transfer body and a transfer body adjacent to the transfer body becomes small, the first mode can be changed to the second mode. When the mode is shifted, the voltage is changed in order from the upstream transfer body, and when the mode is shifted from the second mode to the first mode, the voltage is changed in order from the downstream transfer body. Here, “change the voltage in order” means that the voltage value of a certain transfer body (I) is the voltage value V of the first mode._IVoltage value V in the second mode from (1)_IAfter the change to (2), the voltage value of the transfer body (I + 1) adjacent to the downstream side of the transfer body is the voltage value V of the first mode._{I + 1}Voltage value V in the second mode from (1)_{I + 1}It means the case where it is changed to (2).
[0024]
Specifically, for example, in the case of an image forming apparatus including a two-stage transfer body (upstream transfer body (1) and downstream transfer body (2)), when transferring from the first mode to the second mode, the upstream transfer is performed. Applied voltage V to body (1)₁V₁(1) to V₁After changing to (2), the applied voltage V to the downstream transfer body (2)₂V₂(1) to V₂Change to (2). On the other hand, when the mode is shifted from the second mode to the first mode, the applied voltage V to the downstream transfer body (2).₂V₂(2) to V₂After changing to (1), the applied voltage V to the upstream transfer body (1)₁V₁(2) to V₁Change to (1). In addition, V between each voltage₁(1) <V₁(2), V₂(1) <V₂(2) holds.
[0025]
In addition, in the case of an image forming apparatus including a three-stage transfer body (upstream transfer body, midstream transfer body, and downstream transfer body), the voltage applied to the upstream transfer body (1) when shifting from the first mode to the second mode. V₁V₁(1) to V₁After changing to (2), the applied voltage V to the midstream transfer body (2)₂V₂(1) to V₂Change to (2). The applied voltage V to the midstream transfer body (2)₂V₂(1) to V₂After changing to (2), the applied voltage V to the downstream transfer body (3)_ThreeV_Three(1) to V_ThreeChange to (2). On the other hand, when shifting from the second mode to the first mode, the applied voltage V to the downstream transfer body (3) is as follows._ThreeV_Three(2) to V_ThreeAfter changing to (1), the applied voltage V to the midstream transfer body (2)₂V₂(2) to V₂Change to (1). The applied voltage V to the midstream transfer body (2)₂V₂(2) to V₂After changing to (1), the applied voltage V to the upstream transfer body (1)₁V₁(2) to V₁Change to (1). In addition, V between each voltage₁(1) <V₁(2), V₂(1) <V₂(2), V_Three(1) <V_Three(2) holds.
[0026]
As a more specific aspect of controlling the change timing and voltage value of the voltage applied to the transfer body at each stage so that the potential difference between a transfer body and a transfer body adjacent to the transfer body is small, the first mode When shifting from the second mode to the second mode, the voltage is changed sequentially and stepwise from the upstream transfer body, and when shifting from the second mode to the first mode, the voltage is sequentially and stepwise from the downstream transfer body. The thing which changes is mentioned. Here, “change the voltage stepwise” means that the voltage value of a certain transfer body (I) is the voltage value V of the first mode._IVoltage value V in the second mode from (1)_ISimultaneously with the change to (2), the voltage value of the transfer body (I + 1) adjacent to the downstream side of the transfer body becomes the voltage value V of the first mode._{I + 1}(1) to first mode voltage value V_{I + 1}(1) and voltage value V in the second mode_{I + 1}Voltage value V intermediate between (2)_{I + 1}Then, the voltage value of the transfer body (I + 1) is changed to the voltage value V (after a predetermined time has elapsed)._{I + 1}From (m), voltage value V of the second mode_{I + 1}It means the case where it is changed to (2).
[0027]
Furthermore, this intermediate voltage value V_{I + 1}(M) = V_I(2). That is, the voltage of the transfer body (I) at the time of transition from the first mode to the second mode is a certain value V._IAt the same time, the voltage of the transfer body (I + 1) on the downstream side of the transfer body is also the value V_IThe voltage of the transfer body (J) when changing from the second mode to the first mode is a certain value V_JAt the same time, the voltage of the transfer body (J-1) upstream of the transfer body is also the value V._JIt may be changed to.
[0028]
Specifically, for example, in the case of an image forming apparatus including a two-stage transfer body (upstream transfer body and downstream transfer body), when the first mode is switched to the second mode, the transfer to the upstream transfer body (1) is performed. Applied voltage V₁V₁(1) to V₁Simultaneously with the change to (2), the applied voltage V to the downstream transfer body (2)₂V₂(1) to V₁(2) (= V₂Change to (m)). Thereafter, the applied voltage V to the downstream transfer body (2)₂V₁(2) (= V₂(M)) to V₂Change to (2). On the other hand, when the mode is shifted from the second mode to the first mode, the applied voltage V to the downstream transfer body (2).₂V₂(2) to V₁(2) (= V₂Change to (m)). Thereafter, the applied voltage V to the downstream transfer body (2)₂V₁(2) (= V₂(M)) to V₂Simultaneously with the change to (1), the applied voltage V to the upstream transfer body (1)₁V₁(2) to V₁Change to (1). In addition, V between each voltage₁(1) <V₁(2), V₂(1) <V₁(2) (= V₂(M)) <V₂(2) holds.
[0029]
In addition, in the case of an image forming apparatus including a three-stage transfer body (upstream transfer body, midstream transfer body, and downstream transfer body), the voltage applied to the upstream transfer body (1) when shifting from the first mode to the second mode. V₁V₁(1) to V₁At the same time as changing to (2), the applied voltage V to the midstream transfer body (2)₂V₂(1) to V₁(2) (= V₂(M)), the applied voltage V to the downstream transfer member (3)._ThreeV_Three(1) to V₁(2) (= V_ThreeChange to (m)). Next, the applied voltage V to the midstream transfer body (2)₂V₁(2) (= V₂(M)) to V₂Simultaneously with the change to (2), the applied voltage V to the downstream transfer body (3)_ThreeV₁(2) (= V_Three(M)) to V₂(2) (= V_Three(M ′)). Finally, the applied voltage V to the downstream transfer body (3)_ThreeV₂(2) (= V_Three(M ') to V_ThreeChange to (2).
[0030]
On the other hand, when shifting from the second mode to the first mode, the applied voltage V to the downstream transfer body (3) is as follows._ThreeV_Three(2) to V₂(2) (= V_ThreeChange to (m '). Next, the applied voltage V to the downstream transfer body (3)_ThreeV₂(2) (= V_Three(M ') to V₁(2) (= V_Three(M)) and the applied voltage V to the midstream transfer member (2) at the same time₂V₂(2) to V₁(2) (= V₂Change to (m)). Finally, the applied voltage V to the downstream transfer body (3)_ThreeV₁(2) (= V_Three(M) to V_ThreeAt the same time as changing to (1), the applied voltage V to the midstream transfer body (2)₂V₁(2) (= V₂(M)) to V₂Similarly to (1), the applied voltage V to the upstream transfer body (1)₁V₁(2) to V₁Change to (1). In addition, V between each voltage₁(1) <V₁(2), V₂(1) <V₁(2) (= V₂(M)) <V₂(2), V_Three(1) <V₁(2) (= V_Three(M)) <V₂(2) (= V_Three(M ′)) <V_Three(2) holds.
[0031]
By the way, the voltage value (from the upstream side) V applied to the transfer body at each stage in the first mode.₁(1), V₂(1) ... V_N(1) The voltage value (from the upstream side) V applied to the transfer body at each stage in the second mode₁(2), V₂(2), V_N(2) V₁(1) <V₁(2), V₂(1) <V₂(2), V_N(1) <V_N(2) holds. Where each voltage value V₁(1), V₂(1) ... V_N(1) and V₁(2), V₂(2), V_NCan take different values. And, for example, V₁(1)> V₂(1)> ...> V_N(1) and V₁(2) <V₂(2) <... <V_NAs (2), a potential gradient can be formed by each voltage value. The difference in voltage value applied to the transfer body at each stage | V₁(2) -V₁(1) |, | V₂(2) -V₂(1) |, ..., | V_N(2) -V_N(1) Between ||₁(2) -V₁(1) | <| V₂(2) -V₂(1) | <... <| V_N(2) -V_N(1) Each voltage value can also be set so that |
[0032]
Such setting of each voltage value can be appropriately changed according to the state of the image forming apparatus, the charging polarity of the toner to be used, and the like. For example, in an image forming apparatus using negatively charged toner, in the image forming mode or the positive (−) residual toner cleaning mode (described later), these are set as the second mode.₁(2) <V₂(2) <... <V_NIn the case of the reverse polarity (+) residual toner cleaning mode (described later), the potential gradient of (2) is formed, and this is set as the first mode.₁(1)> V₂(1)> ...> V_NThe potential gradient of (1) is formed, and in the case of the pause or stop mode, this is used as the first mode.₁(1) = V₂(1) = ... = V_N(1) = 0 [V]. These can also be combined.
[0033]
In an image forming apparatus using positively charged toner, in the image forming mode or the positive (+) residual toner cleaning mode (described later), these are set as the first mode.₁(1)> V₂(1)> ...> V_NThe potential gradient of (1) is formed, and in the case of the reverse polarity (-) residual toner cleaning mode (described later), this is set as the second mode.₁(2) <V₂(2) <... <V_NThe potential gradient of (2) is formed, and in the case of the pause or stop mode, this is set as the second mode V₁(2) = V₂(2) = ... = V_N(2) = 0 [V].
[0034]
The present invention can be applied to an image forming apparatus that the applicant has already proposed in Japanese Patent Application No. 11-250108.
[0035]
That is, as a first aspect of the image forming apparatus to which the present invention can be applied, an image carrier, a contact type charging device that contacts and charges the image carrier, and a latent image is formed on the surface of the charged image carrier. The image forming apparatus is composed of an exposure device, a developing device that develops a latent image formed on the surface of the image carrier to form a toner image, and a plurality of transfer members, and is formed on the surface of the image carrier in contact with the image carrier. And a contact transfer device for transferring the toner image onto a recording sheet. A cleaning device is attached to one transfer body constituting the contact transfer device, and the image forming device is cleaned. During the mode, a potential gradient is formed between the transfer member with the cleaning device provided with the cleaning device and the contact type charging device, and remains in the contact type charging device, the image carrier, and the contact type transfer device. Left over Over the collected cleaning device with transfer member, the image forming apparatus and the like to recover collectively residual toner collected to the cleaning device with transfer body cleaning device.
[0036]
In addition, as a second aspect of the image forming apparatus to which the present invention can be applied, an image carrier, a contact type charging device that contacts and charges the image carrier, and a latent image is formed on the surface of the charged image carrier. An exposure device for developing, a developing device for developing a latent image formed on the surface of the image carrier to form a toner image, and a toner image formed on the surface of the image carrier in contact with the image carrier. An image forming apparatus comprising an intermediate transfer member and a final transfer member that contacts the intermediate transfer member and transfers a toner image on the surface of the intermediate transfer member onto a recording sheet. The final transfer member is provided with a cleaning device. At the same time, a temporary holding member is attached to the intermediate transfer member, and a part or all of the positive and / or reverse polarity residual toner is temporarily held by the temporary holding member during image formation of the image forming apparatus. When the forming device is in cleaning mode A potential gradient is formed between the contact-type charging device, the image carrier, the intermediate transfer member, the temporary holding member, and the final transfer member, and the remaining toner including the residual toner held on the temporary holding member An image forming apparatus that collects on the transfer body and collects the residual toner collected on the final transfer body with the above-described cleaning device may be used.
[0037]
Further, as a third aspect of the image forming apparatus to which the present invention can be applied, there are an image carrier, a charging device for charging the surface of the image carrier, and an exposure device for forming a latent image on the surface of the charged image carrier. A developing device that develops a latent image formed on the surface of the image carrier to form a toner image, and an intermediate transfer member on which the toner image formed on the surface of the image carrier is transferred in contact with the image carrier And a final transfer member that contacts the intermediate transfer member and transfers the toner image on the surface of the intermediate transfer member onto a recording sheet. The intermediate transfer member is provided with a temporary holding member. A cleaning device is attached to the final transfer body, and a part or all of the positive polarity and / or reverse polarity residual toner is temporarily held by the temporary holding member during image formation of the image forming apparatus. In the cleaning mode, the above A potential gradient is formed between the final transfer member, the intermediate transfer member, and the temporary holding member, and residual toner including residual toner temporarily held on the temporary holding member is collected on the final transfer member. An image forming apparatus that collects the residual toner collected on the transfer body with the above-described cleaning device may be used.
[0038]
[Regarding First Aspect] In the first aspect, the configurations of the image carrier and the contact-type transfer device are not particularly limited, but typically have the following configurations:
[0039]
(1) The image carrier is composed of one image carrier, and the contact type transfer device is in contact with the image carrier, the intermediate transfer body (first stage) and the final transfer body in contact with the intermediate transfer body (second stage). The toner image transferred from the image carrier onto the intermediate transfer member while the recording sheet passes between the intermediate transfer member and the final transfer member is transferred onto the recording sheet. Of the type,
[0040]
(2) The image carrier is composed of three image carriers for cyan, magenta and yellow, or four image carriers in which black is added to these, and a contact type transfer device is used for these three or four image carriers. The intermediate transfer member is in contact with the intermediate transfer member (first stage) and the final transfer member (second step) is in contact with the intermediate transfer member, and the recording sheet passes between the intermediate transfer member and the final transfer member. A second type in which a toner image transferred from an image carrier onto an intermediate transfer member is transferred onto a recording sheet;
[0041]
(3) The image carrier is composed of four image carriers for cyan, magenta, yellow, and black, and the contact-type transfer device contacts two of these four image carriers. A pair of first intermediate transfer members (first stage), a second intermediate transfer member (second stage) contacting the pair of first intermediate transfer members, and a contact of the second intermediate transfer member And a final transfer member (third stage). While the recording sheet passes between the second intermediate transfer member and the final transfer member, the second intermediate transfer member passes through the first intermediate transfer member. And a third type in which the toner image transferred onto the intermediate transfer member is transferred onto the recording sheet.
[0042]
In the configuration of these three types of image carrier and contact type transfer device, the first and second types have the number of developing devices attached to the image carrier and the type of transfer member used, that is, roll ( Alternatively, it can be configured as an image forming apparatus for black-and-white images depending on whether a transfer roll of a drum) type is used, or as an image forming apparatus for multi-color images such as for two colors of red and black. Further, the image forming apparatus may be configured as a full-color image forming apparatus including three developing devices for cyan, magenta, and yellow, or four developing devices in which a developing device for black is added to these. You can also.
[0043]
In the first aspect, as for the means for forming a potential gradient between the transfer body with a cleaning device and the contact-type charging device, the cleaning device constituting the contact-type charging device, the image carrier, and the contact-type transfer device. A predetermined potential is applied to each transfer member constituting the contact-type charging device, the image carrier, and the contact-type transfer device so that the residual toner remaining on the transfer member other than the attached transfer member can be collected on the transfer member with the cleaning device. Anything can be used.
[0044]
Specifically, as the potential gradient applying means, in the case where the configuration of the image carrier and the contact type transfer device is the first and second types, the transfer body with a cleaning device is used as the final transfer body. In addition to applying a voltage to the contact-type charging device, the intermediate transfer member, and the final transfer member, the intermediate transfer member between the image carrier and the grounded image carrier can be electrically applied while applying a voltage to the final transfer member. It is possible to apply voltage applying means that floats and forms a potential gradient between the relationship between the resistance value of the final transfer member, the intermediate transfer member, and the image carrier and the voltage applied to the contact-type charging device. . Further, when the transfer body with a cleaning device is an intermediate transfer body, means for applying a voltage to the contact charging device, the intermediate transfer body, and the final transfer body can be applied.
[0045]
Further, in the case where the configuration of the image carrier and the contact type transfer device is the third type, when the transfer body with the cleaning device is used as the final transfer body, as in the case of the first and second types. In addition to applying a voltage to each contact-type charging device, each first intermediate transfer member, second intermediate transfer member, and final transfer member, the image is grounded while applying a voltage to the final transfer member. The first intermediate transfer member and the second intermediate transfer member are electrically floated between the first transfer member, the final transfer member, the second intermediate transfer member, the first intermediate transfer member, and the image carrier. A means for forming a potential gradient between the relationship between the resistance value and the voltage applied to the contact charging device can be applied. When the transfer device with a cleaning device is the second intermediate transfer member, a voltage is applied to each contact-type charging device, each first intermediate transfer member, the second intermediate transfer member, and the final transfer member. In addition to applying the voltage, a voltage is applied to the second intermediate transfer member and each first intermediate transfer member positioned between the second intermediate transfer member and the grounded image carrier is electrically floated. A potential gradient is formed between the relationship between the resistance values of the first intermediate transfer member and the image carrier and the individual voltages applied to the second intermediate transfer member and the final transfer member. Means can be applied.
[0046]
Here, as a means for applying a voltage, an image forming apparatus using a contact-type charging device and a power source connected to supply a voltage for each purpose to a transfer body constituting the contact-type transfer device as it is, In the control system (control means), it may be possible to supply a voltage necessary for the cleaning mode, or a dedicated power supply for supplying a voltage may be provided separately from this power supply. .
[0047]
As for means for applying a voltage and electrically floating to use the relationship of resistance, for example, an image carrier or a transfer member constituting a contact transfer device (transfer member other than a transfer member with a cleaning device) When manufacturing the device, the relationship between the resistance values is designed in advance, and a power source connected to supply a voltage for each purpose between the transfer body with the cleaning device and the contact type charging device is used. Alternatively, a dedicated power source different from this power source may be provided to apply a predetermined voltage.
[0048]
Further, in this first aspect, the image carrier may be a drum type image carrier drum or a belt type image carrier belt, and the image forming apparatus is for monochrome images. It is determined depending on whether it is for a multi-color image or a full-color image.
[0049]
In addition, a roll-type charging roll, a film-type charging film, a brush-type charging brush, or the like can be appropriately used as the contact-type charging device, and the charging system is of a type that applies only DC. However, it may be of a type in which DC + AC is applied.
[0050]
In the first aspect, the transfer body of the contact type transfer device is such that the entire surface is charged to a substantially uniform potential (not only a part of the surface is charged to a predetermined potential). Specifically, a roll type transfer roll, a drum type transfer drum, and the like can be given. Further, for example, an intermediate transfer drum may be used as an intermediate transfer member, and a transfer roll may be used as a final transfer member. What type of transfer member is used may be selected as necessary when designing the image forming apparatus.
[0051]
In this first aspect, the cleaning device attached to one transfer body constituting the contact type transfer device is a brush type having a cleaning brush even if it is a blade type having a cleaning blade. However, a cleaning scraper made of a metal such as a cleaning blade or stainless steel having a certain degree of elasticity is preferable.
[0052]
The developing device used in the first aspect is not particularly limited, and may be a magnetic brush contact type two-component development type, a non-contact type development type using magnetic toner, or the like.
[0053]
For this developing device, in particular, in the case of a contact type, a predetermined potential is applied to the image carrier in the cleaning process, so that a plurality of developing devices are mounted particularly in an image forming apparatus for a multi-color image or a full-color image. In this case, a retraction mechanism is provided for the image carrier so that the reverse polarity residual toner does not flow backward in the developing device, and a shutter mechanism for shielding the image carrier from the image carrier. It is desirable to use the one provided, the one provided with the control mechanism for stopping the developing roll in the cleaning process, the one equipped with the control mechanism for changing the potential of the developing roll in accordance with the potential displacement of the image carrier in the cleaning process, etc. .
[0054]
[Second Aspect] Next, in the second aspect, in the image forming apparatus including the contact-type charging device, the image bearing member, the exposure device, the developing device, the intermediate transfer member, and the final transfer member, the final transfer A cleaning device is attached to the body, a temporary holding member is attached to the intermediate transfer member, a means for applying a predetermined potential gradient between the final transfer member and the contact-type charging device is provided, and the temporary transfer member is provided. The holding member is provided with means for applying a potential gradient between the holding member and the intermediate transfer member.
[0055]
Here, the contact-type charging device, the image carrier, the exposure device, the developing device, the intermediate transfer member, the final transfer member, the cleaning device, the means for applying a potential gradient, and the image carrier, the intermediate transfer member, and the final transfer. The structure of the body (the structure of the image carrier and the contact type transfer device) can be considered in the same manner as in the case of using the intermediate transfer member in the first invention and using the transfer member with the cleaning device as the final transfer member. The temporary holding member attached to the intermediate transfer member may be a brush-type brush cleaning device or a roll-type roll cleaning device that can temporarily hold the positive or reverse polarity residual toner.
[0056]
The intermediate transfer member is composed of, for example, a pair of first intermediate transfer members that are in contact with two image carriers and a second intermediate transfer member that is in contact with the pair of first intermediate transfer members. In this case, the temporary holding member may be attached to all of the pair of first intermediate transfer members and the second intermediate transfer member, or may be attached only to the pair of first intermediate transfer members, It may be provided only on the second intermediate transfer member side, or may be provided only on one first intermediate transfer member.
[0057]
In addition, whether the brush cleaning device or the roll cleaning device is used as a temporary holding member attached to the intermediate transfer member depends on whether the residual toner to be cleaned is positive polarity or reverse polarity, cleaning property, toner retention property, Determined in consideration of resistance value selectivity and the like.
[0058]
For example, when a transfer voltage that does not generate reverse polarity (+) toner is applied to the intermediate transfer member, the remaining toner has a positive polarity (-), so the temporary holding member has a reverse polarity (+) side from the transfer voltage. It is necessary to apply a high voltage. At this time, if the resistance value on the temporary holding member side becomes lower than the resistance value on the intermediate transfer member side, the temporary holding member charges the intermediate transfer member and changes a desired transfer electric field. The potential difference with the body is reduced and the cleaning property is also lowered. Therefore, it is necessary to set the resistance value on the temporary holding member side to be higher than the resistance value on the intermediate transfer member side. In such a case, a roll cleaning device or a (rotating) brush cleaning device is preferably used as the temporary holding member. The amount of residual toner held on the roll or brush at this time is determined by the circumferential surface area (that is, the outer diameter) of the roll. For example, in the case of a 13 mmφ cleaning roll, about 200 A4-sized images are continuous. It can respond even if it prints.
[0059]
On the other hand, when reverse polarity (+) toner is generated by applying a transfer voltage, it is necessary to apply a positive (−) side voltage from the intermediate transfer member to the temporary holding member. In this case, since the temporary holding member is charged to the reverse polarity (+) side by the intermediate transfer member and the cleaning property is lowered, it is necessary to set the resistance value on the temporary holding member side lower than the resistance value on the intermediate transfer member side. However, in such a case, it is preferable to use a brush cleaning device having a low resistance and an excellent cleaning property as the temporary holding member.
[0060]
Further, for example, a pair of first intermediate transfer members that contact two of the four image carriers as an intermediate transfer member, and a second contact that contacts the pair of first intermediate transfer member and final transfer member. When the combination with the intermediate transfer member is used, the second intermediate transfer member may transfer the toner images for four colors, and the transfer rate may vary. Tends to generate positive (-) residual toner. Further, when the first intermediate transfer member and the second intermediate transfer member are used in combination as described above, each single color toner image is exposed to a transfer electric field many times (3 to 5 times), and has a reverse polarity (+ ) The toner is likely to be generated as a residual toner, but the residual toner having the reverse polarity (+) returns from the second intermediate transfer member to the first intermediate transfer member. Therefore, in such a case, it is preferable that a temporary holding member for reverse polarity is attached to the first intermediate transfer member, and a temporary holding member for positive polarity is attached to the second intermediate transfer member.
[0061]
In the second aspect, part or all of the positive or reverse polarity residual toner remaining on the surface of the intermediate transfer member is temporarily held by the temporary holding member during image formation of the image forming apparatus, and then image formation is performed. In the cleaning mode of the apparatus, a potential gradient is applied to the contact-type charging device, the image carrier, the intermediate transfer member, the temporary holding member, and the final transfer member, and the residual toner including the residual toner held on the temporary holding member remains. The residual toner is collected on the final transfer member, and the residual toner collected on the final transfer member is collected by the cleaning device.
[0062]
For example, a positive-type temporary holding member is attached to the intermediate transfer member, and in order to finally collect the positive-polarity residual toner temporarily collected on the positive-polarity temporary holding member with the final transfer member, a contact type A high potential gradient may be applied to the (+) side in the direction of charging device → image carrier → intermediate transfer member → final transfer member and temporary holding member → intermediate transfer member → final transfer member. Similarly, a temporary holding member for reverse polarity is attached to the intermediate transfer member, and in order to finally collect the reverse polarity residual toner temporarily collected on the temporary holding member for reverse polarity with the final transfer member, contact is required. It is only necessary to apply a high potential gradient on the (+) side in the direction of the mold charging device ← image carrier ← intermediate transfer member ← final transfer member and temporary holding member ← intermediate transfer member ← final transfer member. Then, two temporary holding members for positive polarity and reverse polarity are attached to the intermediate transfer body, and the residual toner of positive polarity and reverse polarity temporarily collected on these temporary holding members is finally transferred to the final transfer body. In order to recover, the above-described two operations may be repeated.
[0063]
  Also this secondAspectIn this case, the image carrier may be provided with a temporary holding member such as a brush cleaning device or a roll cleaning device that cleans and temporarily holds the residual toner remaining on the surface of the image carrier. The residual toner temporarily held by the temporary holding member for the image carrier is finally collected on the final transfer body and collected by the cleaning device, as in the case of the temporary holding member attached to the intermediate transfer member. be able to.
[0064]
[Third Aspect] Further, in the third aspect, the image forming apparatus including the charging device, the image carrier, the exposure device, the developing device, the intermediate transfer member, and the final transfer member is temporarily held on the intermediate transfer member. A member is attached and a cleaning device is attached to the final transfer member, and at the time of image formation of the image forming apparatus, the temporary holding member temporarily holds a part or all of the positive and / or reverse polarity residual toner, In the cleaning mode of the forming device, a residual toner that forms a potential gradient between the final transfer member, the intermediate transfer member, and the temporary holding member, and includes the residual toner temporarily held on the temporary holding member. Are collected on the final transfer member, and the residual toner collected on the final transfer member is collected by the cleaning device.
[0065]
  Where this thirdAspectIn the image carrier, the exposure device, the developing device, the intermediate transfer member, the final transfer member, the temporary holding member, the cleaning device, the means for applying a potential gradient, the image carrier, the intermediate transfer member, and the final transfer member. The configuration (the configuration of the image carrier and the contact type transfer device) is the same as that of the second invention, but the charging device is a contact type charging device as in the first and second inventions. Or a non-contact charging device such as corotron.
[0066]
  [When to enter the cleaning mode]
  The above first to thirdAspectIn regard to the timing for performing cleaning by the cleaning device attached to the transfer member, for example,(1)When power is turned on,(2)When the interlock switch (I / L) is on,(3)At cycle-in / cycle-out,(4)During continuous image formation (every number of sheets),(5)During process control, and(6)For example, when a cleaning command is input.
[0067]
Here, regarding the cleaning operation {circle around (1)} when the power is turned on, the main motor is rotated immediately after the power is turned on to operate the positive residual toner cleaning mode (hereinafter referred to as “positive cleaning”), and then the reverse polarity residual toner. The cleaning mode (hereinafter referred to as “reverse electrode cleaning”) is operated. The remaining toner remaining on the charging device, image carrier, contact-type transfer device (intermediate transfer member and final transfer member) without being able to perform the worst cleaning by this operation is positive, and causes problems such as fogging during subsequent image formation. It can be prevented from happening.
[0068]
As for the cleaning operation {circle around (3)} at the time of cycle-in / cycle-out, at the start of image formation, reverse polarity cleaning may be operated after the main motor rotation is started, and then the normal image forming process is operated. In this case, if a predetermined time is taken from the start of the normal image forming process to the start of the actual image formation, the positive electrode cleaning is performed during this time. Further, after the image forming process is completed, the reverse polarity cleaning is performed again, the reverse polarity residual toner generated during the image forming process is cleaned, and the main motor is stopped to end the process.
[0069]
Furthermore, with regard to the cleaning operation (4) during continuous image formation (every constant number of sheets), reverse polarity residual toner accumulates in the contact-type charging device and causes image defects such as fog when performing continuous image formation of a large number of sheets. When the number of image formation reaches a predetermined number, the image forming process is temporarily interrupted, and reverse polarity cleaning → positive electrode cleaning → reverse polarity cleaning is operated. Thus, continuous image formation can be performed while preventing image defects such as fogging caused by accumulation of reverse polarity residual toner in the contact-type charging device.
[0070]
Furthermore, for the cleaning operation (5) during the process control, the same operation as the cleaning for the continuous image formation (every constant number of sheets) is performed during the process control, and image defects such as fogging due to the reverse polarity residual toner are removed. To prevent.
[0071]
Furthermore, the cleaning operation (6) when the cleaning command is input is a command to be executed when an image defect such as fog occurs even if the cleaning operations (1) to (5) are performed. Operate positive electrode cleaning → reverse electrode cleaning.
[0072]
The above cleaning operations (1) to (6) do not necessarily have to be operated, but only one of them may be selected and operated, and two or more may be performed as necessary. The operation may be performed by appropriately combining them, but it is preferable to combine two or more types.
[0073]
[Regarding potential difference (potential gradient) required between each member] In the present invention, a potential difference to be applied between each member such as a contact charging device, an image carrier, and a contact transfer device (intermediate transfer member and final transfer member). Regarding (potential gradient), there is a need for a potential difference that allows the residual toner to move at a rate close to approximately 100% between the members. If the transfer electric field in the transfer process is within a specified range {necessary transfer electric field (having a certain range)}, a transfer rate close to 100% can be obtained and developed on the image carrier. The charge of the toner is normally distributed on both sides of the high charge side / low stagnant side with respect to the center value.
[0074]
For example, when the charge of the toner is −25 ± 20 μC / g, the remaining toner that remains due to insufficient transfer electric field in the transfer process is usually a high-charge toner, and has a charge of −35 μC / g or more. In addition, the residual toner that remains due to an excess transfer electric field in the transfer process is usually a low-charge toner, has a charge of approximately -5 to +10 μC / g, and is further produced due to a paper jam or the like. The residual toner remaining on the image carrier or the contact transfer device after the machine is forcibly stopped in the image is normally -25 ± 20 μC / g without any change in charge.
[0075]
Therefore, the relationship between the potential difference between the members for each charge of the remaining toner and the toner movement (cleaning rate) between the members is as shown in FIG. 1. In the case of the toner with the charge of −25 ± 20 μC / g, It can be seen that the cleaning rate reaches almost 100% when there is a potential difference of 300-800V.
[0076]
Therefore, in the present invention, the charge of the toner used in the image forming apparatus is examined, and the relationship between the potential difference between the members and the toner movement (cleaning rate) between the members for each remaining toner charge is examined. It is possible to easily design what kind of potential difference (potential gradient) should be applied between the members such as the carrier and the contact transfer device (intermediate transfer member and final transfer member).
[0077]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be specifically described.
[0078]
Embodiment 1 FIG. 2 shows a tandem type full-color image forming apparatus according to Embodiment 1 of the present invention.
[0079]
The full-color image forming apparatus according to the first embodiment has the same configuration as that of FIG. 19 described above, and is for yellow (Y), magenta (M), cyan (C), and black ( K) four photoconductors (image carriers) 10, 20, 30, 40 for charging, and charging rolls (contact type charging devices) 11, 21, 31, 41 in contact with these photoconductors 10, 20, 30, 40 And the exposure devices 12, 22, 32, 42, the developing devices 13, 23, 33, 43, and one of the four photoconductors 10, 20, 30, 40 in contact with the two photoconductors 10, 20 The first intermediate transfer roll 51 and the other first intermediate transfer roll 52 in contact with the other two photoreceptors 30 and 40, and the second intermediate transfer roll 51 and 52 in contact with the pair of first intermediate transfer rolls 51 and 52. An intermediate transfer roll 53, a final transfer roll 61 in contact with the second intermediate transfer roll 53, a transport roll 91, and a fixing device 70 are provided.
[0080]
Also in the first embodiment, as in the case of FIG. 19 described above, the single color toner images formed by the two photoconductors 10 and 20 are transferred to the first intermediate transfer roll 51 and then the first toner image is transferred. Each single color toner image formed by the two photoconductors 30 and 40 is transferred to the first intermediate transfer roll 53 and then transferred to the second intermediate transfer roll 53. On the sheet (recording sheet) P, which is superposed on the second intermediate transfer roll 53 and then conveyed between the final transfer roll 61 contacting the second intermediate transfer roll 53 by the conveyance roll 91. The toner images transferred in a batch and transferred onto the paper P are fixed by the fixing device 70.
[0081]
In the first embodiment, the photoreceptors 10, 20, 30, and 40 are applied with a DC voltage of about −840V by the charging rolls 11, 21, 31, and 41, and are thereby charged to about −300V. Further, when the electrostatic latent image is written by the exposure apparatus 12, 22, 32, 42, the surface potential is neutralized to about −60V.
[0082]
In the first embodiment, the developing devices 13, 23, 33, and 43 include a developing roll 131, a developer amount regulating member 132, a developer conveying member 133, and an auger 134 that conveys and stirs the developer. A magnetic brush contact type two-component developing type developing device. The amount of developer regulated by the developer amount regulating member 132 and conveyed to the developing section is about 30 to 40 g / m @ 2, and the charge amount of the toner existing on the developing roll 131 at this time is approximately -20 to -30 .mu.C. / G or so. The developing devices 13, 23, 33, and 43 are developed by applying an AC + DC developing voltage. The developing voltage is 4 kHz for AC, 1.6 kVpp, and about −230 V for DC.
[0083]
Furthermore, the first intermediate transfer rolls 51 and 52 used in the first embodiment are formed by providing a silicon rubber layer on a metal pipe and further coating a high release layer thereon, and the resistance value thereof. Usually about 10^Five -10⁹ The one in the range of Ω can be used, but here 10⁸ It is supposed to be about Ω. The surface potential required to transfer the toner image from the photoconductors 10, 20, 30, 40 to the first intermediate transfer rolls 51, 52 is usually in the range of about +250 to 500 V, and the charging of the toner The optimum value is set according to the state, ambient temperature, humidity, etc., but here it is set to about surface potential + 380V.
[0084]
The second intermediate transfer roll 53 used in the first embodiment is also provided with a silicon rubber layer on the metal pipe, and further on the high release layer, similarly to the first intermediate transfer rolls 51 and 52. The resistance value is usually 10⁸ -10¹²The one in the range of Ω can be used, but here 10¹¹It is supposed to be about Ω. The surface potential required to transfer the toner image from the first intermediate transfer rolls 51 and 52 to the second intermediate transfer roll 53 is usually in the range of about +600 to 1200 V, the charged state of the toner, The optimum value is set according to the ambient temperature, humidity, and the like, but here the surface potential is set to about + 880V, and the potential difference from the first intermediate transfer rolls 51 and 52 is about + 500V.
[0085]
Further, in the first embodiment, the final transfer roll 61 is provided with a urethane rubber layer on a metal pipe and further coated thereon, and the resistance value is usually 10.⁶ -10⁹ The one in the range of Ω can be used, but here 10⁸ It is supposed to be about Ω. Further, a PI tube can be coated instead of the urethane rubber layer. The transfer voltage applied to the final transfer roll 61 for transferring the toner image from the second intermediate transfer roll 53 onto the paper (recording sheet) is usually in the range of about +1200 to 5000 V, the ambient temperature, The optimum value will be set depending on the humidity, the type of paper P (resistance value, etc.), etc. Here, a constant current method is adopted, and about +6 μA is applied in a room temperature and normal humidity environment, and an almost appropriate transfer voltage + 1600 About 2000V is obtained.
[0086]
In the full-color image forming apparatus of Embodiment 1, unlike the full-color image forming apparatus shown in FIG. 19, a blade cleaning device 71 having a cleaning blade 72 is attached to the final transfer roll 61. A predetermined voltage is applied to each charging roll 11, 21, 31, 41, each first intermediate transfer roll 51, 52, second intermediate transfer roll 53, and final transfer roll 61 to apply each charging roll 11, 21, 31, 41, photoreceptors 10, 20, 30, 40, first intermediate transfer rolls 51, 52, second intermediate transfer roll 53, and final transfer roll 61 to form a predetermined potential gradient Let me.
[0087]
In the first embodiment, in the cleaning mode by the blade cleaning device 71, in the positive electrode cleaning, the charging rolls 11, 21, 31, 41 are −840V, the photoconductors 10, 20, 30, 40 are −300V, The first intermediate transfer rolls 51, 52 are + 380V, the second intermediate transfer roll 53 is + 880V, and the final transfer roll 61 is + 1600V. In the reverse polarity cleaning, the charging rolls 11, 21, 31, 41 is 0V, each photoconductor 10, 20, 30, 40 is -300V, each first intermediate transfer roll 51, 52 is -800V, second intermediate transfer roll 53 is -1300V, and final transfer roll 61 is- It is set to be 2000V. In the first embodiment, voltage supply to the charging rolls 11, 21, 31, 41, the first intermediate transfer rolls 51, 52, the second intermediate transfer roll 53, and the final transfer roll 61 is as follows. This is performed by supplying a voltage to the metal part (shaft or pipe) of each member by a control means (not shown).
[0088]
Next, a rough timing sequence of an image forming job in the full-color image forming apparatus according to the first embodiment will be described. In the description of the timing sequence, the reference numerals of the members indicate only representative examples.
[0089]
In FIG. 3, a region A shows a cleaning mode at the time of cycle-in / cycle-out, and here, reverse polarity cleaning is performed. An area B indicates an image forming mode, and 30 continuous images are formed. Further, the region C is a cleaning mode that is inserted every constant sheet (here, 30 sheets) during continuous image formation, and reverse polarity cleaning → positive electrode cleaning → reverse polarity cleaning is performed.
[0090]
Here, the positive electrode cleaning and the reverse electrode cleaning will be described based on the cleaning implementation diagrams shown in FIGS. 4 to 6. In the positive electrode cleaning shown in FIG. 4, the charging roll 11 is −840 V as in the normal transfer process. The photosensitive member 10 is set to -300V, the first intermediate transfer roll 51 is set to + 380V, the second intermediate transfer roll 53 is set to + 880V, and the final transfer roll 61 is set to + 1600V. The positive polarity (−) residual toner remaining on each member with a potential gradient between them is charged roll 11 → photoconductor 10 → first intermediate transfer roll 51 → second intermediate transfer roll 53 → final transfer roll Then, as shown in FIG. 5, it is removed by a blade cleaning device 71 attached to the final transfer roll 61.
[0091]
At this time, the reverse polarity (+) residual toner remaining in each member moves in the opposite direction to the positive polarity (−) residual toner and collects on the charging roll 11 as shown in FIG.
[0092]
6, as described above, the charging roll 11 is set to 0V, the photosensitive member 10 is set to −300V, the first intermediate transfer roll 51 is set to −800V, and the second intermediate transfer roll is used. 53 is set to -1300V, and the final transfer roll 61 is set to -2000V. A potential gradient is applied between these members, and the reverse polarity (+) attached to each member, particularly the charging roll 11. The remaining toner moves from the charging roll 11 → the photoconductor 10 → the first intermediate transfer roll 51 → the second intermediate transfer roll 53 → the final transfer roll 61, and is attached to the final transfer roll 61 as shown in FIG. The blade cleaning device 71 is removed.
[0093]
Therefore, according to the full-color image forming apparatus of Embodiment 1, not only positive polarity residual toner but also reverse polarity residual toner can be efficiently and reliably obtained by appropriately performing positive electrode cleaning and reverse polarity cleaning in an image forming job. Can be removed.
[0094]
By the way, during such an image forming job, each transfer body (first intermediate transfer roll 51 (52), second intermediate transfer roll 53, final transfer roll 61) in order from the upstream side in the normal transfer direction of the toner image). The voltage applied to is changed at a predetermined timing (see FIG. 3). That is, (1) when shifting from the stopped state to the cycle A in the area A, the voltage applied to each transfer body is lowered (second mode → first mode), and (2) the cycle A in the area A is completed. Thus, it becomes high when the image forming mode shifts to the area B (first mode → second mode), and (3) low when the image forming mode ends and the area C shifts to the reverse polarity cleaning mode. (2nd mode → 1st mode), (4) High when the reverse polarity cleaning mode ends and shifts to the positive electrode cleaning mode (1st mode → 2nd mode), (5) Positive electrode cleaning mode ends Thus, it becomes low when the reverse polarity cleaning mode is shifted again (second mode → first mode), and (6) becomes high when the reverse polarity cleaning mode is completed and the region B image forming mode is shifted again. (first (Second mode → second mode), (7) Low when the image forming mode ends and the cycle shifts to the area A (second mode → first mode), and (8) the cycle out ends and is stopped. It becomes higher when shifting to (first mode → second mode).
[0095]
In the present invention, when shifting from the first mode to the second mode and / or when shifting from the second mode to the first mode, the potential difference between a certain transfer body and the transfer body adjacent to the transfer body is reduced. In this way, the timing of changing the voltage applied to the transfer body at each stage is controlled. Hereinafter, a specific voltage control method will be described based on the first and second embodiments. The present invention can be provided for all of the above (1) to (8) in which the mode shifts, but the present invention can also be provided for a part of the above (1) to (8).
[0096]
FIG. 8 is a timing chart showing voltage control timing of the image forming apparatus according to the first embodiment. The timing shown in FIG. 8 may be understood to indicate the timing of, for example, the region A → the region B → the region C, or the timing of the reverse polarity cleaning mode → the positive polarity cleaning mode → the reverse polarity cleaning mode in the region C. It may be understood that this indicates a cleaning mode of the region C (reverse polarity) → image forming mode of the region B → cycle out of the region A. Hereinafter, the voltage control timing shown in FIG. 8 will be described in time series.
[0097]
As shown in FIG. 8, when shifting from the first mode to the second mode, first the time t₁→₂The applied voltage V to the first intermediate transfer roll 51 (and the first intermediate transfer roll 52: the same applies hereinafter)₅₁V₅₁(1) (in this example -800 [V]) to V₅₁(2) Change to (+380 [V] in this embodiment). Then time Δt₁After the lapse of time, the applied voltage V to the second intermediate transfer roll 53₅₃V₅₃(1) (-1300 [V] in this embodiment) to V₅₃(2) Change to (+880 [V] in this embodiment). And then the time Δt₂After the lapse of time, the applied voltage V to the final transfer roll 61₆₁V₆₁(1) (in this example -2000 [V]) to V₆₁(2) Change to (+1600 [V] in this embodiment). These procedures complete the transition from the first mode to the second mode.
[0098]
On the other hand, when shifting from the second mode to the first mode, first the time t₂→₁The applied voltage V to the final transfer roll 61 in FIG.₆₁V₆₁(2) to V₆₁Change to (1). Then time Δt₂ ^'After the lapse of time, the applied voltage V to the second intermediate transfer roll 53₅₃V₅₃(2) to V₅₃Change to (1). And then the time Δt₁'After the lapse of time, the applied voltage V to the first intermediate transfer roll 51₅₁V₅₁(2) to V₅₁Change to (1). These procedures complete the transition from the second mode to the first mode.
[0099]
Note that time Δt₁, Δt₂, Δt₁', Δt₂'Can be set as appropriate, but is preferably set in consideration of the rise time and fall time of the voltage when the voltage is changed. For example, when shifting from the first mode to the second mode, the applied voltage V to the first intermediate transfer roll 51 is₅₁V₅₁(1) to V₅₁Change to (2), surely applied voltage V₅₁Is V₅₁Considering the time to reach (2), time Δt₁Is preferably set. Other time Δt₂, Δt₁', Δt₂The same applies to '.
[0100]
By controlling the timing of voltage change to each transfer member in this way, the potential difference between a transfer member and a transfer member adjacent to the transfer member can be reduced.
[0101]
For example, when shifting from the first mode to the second mode, the applied voltage is changed in the order of the first intermediate transfer roll 51 → the second intermediate transfer roll 53 → the final transfer roll 61 as in this embodiment. The potential difference between the final transfer roll 61 and the second intermediate transfer roll 53 is maximum | V₅₃(2) -V₆₁(1) | = | 880 − (− 2000) | = 2880 [V], the potential difference between the second intermediate roll 53 and the first intermediate transfer roll 51 is maximum | V₅₁(2) -V₅₃(1) | = | 380 − (− 1300) | = 1680 [V]. On the other hand, when shifting from the first mode to the second mode, unlike the present embodiment, the applied voltage is changed in the order of the final transfer roll 61 → the second intermediate transfer roll 53 → the first intermediate transfer roll 51. The potential difference between the final transfer roll 61 and the second intermediate transfer roll 53 is maximum | V₆₁(2) -V₅₃(1) | = | 1600 − (− 1300) | = 2900 [V], and the potential difference between the second intermediate roll 53 and the first intermediate transfer roll 51 is maximum | V₅₃(2) -V₅₁(1) | = | 880 − (− 800) | = 1680 [V]. The same applies when shifting from the second mode to the first mode. In this way, the potential difference between the transfer members can be reduced.
[0102]
Further, if either the first mode or the second mode is the stop mode (not shown in FIG. 8) and the voltage applied to each transfer member in the stop mode is 0 [V], this is the case. The effect is more prominent. For example, when the first mode is the stop mode, the final transfer roll 61 when the applied voltage is changed in the order of the first intermediate transfer roll 51 → the second intermediate transfer roll 53 → the final transfer roll 61 as in the present embodiment. And the potential difference between the second intermediate transfer roll 53 and the maximum | V₅₃(2) -V₆₁(1) | = | 880−0 | = 880 [V], and the potential difference between the second intermediate roll 53 and the first intermediate transfer roll 51 is maximum | V₅₁(2) -V₅₃(1) | = | 380-0 | = 380 [V]. On the other hand, when shifting from the first mode to the second mode, unlike the present embodiment, the applied voltage is changed in the order of the final transfer roll 61 → the second intermediate transfer roll 53 → the first intermediate transfer roll 51. The potential difference between the final transfer roll 61 and the second intermediate transfer roll 53 is maximum | V₆₁(2) -V₅₃(1) | = | 1600-0 | = 1600 [V], and the potential difference between the second intermediate roll 53 and the first intermediate transfer roll 51 is maximum | V₅₃(2) -V₅₁(1) | = | 880-0 | = 880 [V]. The same applies when shifting from the second mode to the first mode. Thus, the potential difference between the transfer bodies can be greatly reduced. In this embodiment, V₆₁(1) <V₅₃(1) <V₅₁(1) <V₅₁(2) <V₅₃(2) <V₆₁The relationship (2) is established.
[0103]
Example 2 This example relates to the improvement of Example 1. Hereinafter, the present embodiment will be described focusing on differences from the first embodiment.
[0104]
As shown in FIG. 9, when shifting from the first mode to the second mode, first, the time t₁→₂The applied voltage V to the first intermediate transfer roll 51 in FIG.₅₁V₅₁(1) to V₅₁Change to (2). At the same time, the applied voltage V to the second intermediate transfer roll 53₅₃V₅₃(1) to V₅₁(2) (= V₅₃Change to (m)). At the same time, the applied voltage V to the final transfer roll 61₆₁V₆₁(1) to V₅₁(2) (= V₆₁Change to (m)). Then time Δt₁After the lapse of time, the applied voltage V to the second intermediate transfer roll 53₅₃V₅₁(2) to V₅₃Change to (2). At the same time, the applied voltage V to the final transfer roll 61₆₁V₅₁(2) to V₅₃(2) (= V₆₁(M ′)). And then the time Δt₂After the lapse of time, the applied voltage V to the final transfer roll 61₆₁V₅₃(2) to V₆₁Change to (2). These procedures complete the transition from the first mode to the second mode.
[0105]
On the other hand, when shifting from the second mode to the first mode, first the time t₂→₁The applied voltage V to the final transfer roll 61 in FIG.₆₁V₆₁(2) to V₅₃(2) (= V₆₁(M ′)). Then time Δt₂ ^'After the lapse of time, the applied voltage V to the second intermediate transfer roll 53₅₃V₅₃(2) to V₅₁(2) (= V₅₃Change to (m)). At the same time, the applied voltage V to the transfer roll 61₆₁V₅₃(2) to V₅₁(2) (= V₆₁Change to (m)). And then the time Δt₁'After the lapse of time, the applied voltage V to the first intermediate transfer roll 51₅₁V₅₁(2) to V₅₁Change to (1). At the same time, the applied voltage V to the second intermediate transfer roll 53₅₃V₅₁(2) to V₅₃Change to (1). At the same time, the applied voltage V to the transfer roll 61₆₁V₅₁(2) to V₆₁Change to (1). These procedures complete the transition from the second mode to the first mode.
[0106]
In this way, by controlling the voltage change timing and voltage value for each transfer member in stages, the potential difference between a transfer member and a transfer member adjacent to the transfer member can be further reduced.
[0107]
For example, when shifting from the first mode to the second mode, in this embodiment, the potential difference between the final transfer roll 61 and the second intermediate transfer roll 53 is maximum | V₅₃(2) -V₆₁(2) | = | 880-1600 | = 720 [V], and the potential difference between the second intermediate roll 53 and the first intermediate transfer roll 51 is maximum | V₅₁(2) -V₅₃(2) | = | 380−880 | = 500 [V]. On the other hand, as described above, in Example 1, the potential difference between the final transfer roll 61 and the second intermediate transfer roll 53 is maximum | V₅₃(2) -V₆₁(1) | = | 880 − (− 2000) | = 2880 [V], the potential difference between the second intermediate roll 53 and the first intermediate transfer roll 51 is maximum | V₅₁(2) -V₅₃(1) | = | 380 − (− 1300) | = 1680 [V]. Thus, the potential difference between the transfer bodies can be further reduced.
[0108]
That is, by applying Example 1 and Example 2 to the tandem type full-color image forming apparatus according to Embodiment 1, the potential difference between the transfer members does not become excessive even if the voltage applied to each transfer member is changed. It is possible to stably set the surface potential of the transfer body to a desired value and obtain a good image.
[0109]
Second Embodiment Next, a tandem full-color image forming apparatus according to a second embodiment of the present invention will be described. In the following description, the reference numerals for the members indicate only representative examples.
[0110]
The tandem full-color image forming apparatus according to the second embodiment has the same basic configuration as that of the first embodiment shown in FIG. 2, but includes each charging roll 11, each first intermediate transfer roll 51, and a second intermediate. The means for applying a potential gradient to the transfer roll 53 and the final transfer roll 61 is different from that in the first embodiment, and a predetermined voltage is applied to the final transfer roll 61 and the respective photoreceptors 10 are grounded. The first intermediate transfer roll 51 and the second intermediate transfer roll 53 that are positioned between them are electrically floated, and the final transfer roll 61, the second intermediate transfer roll 53, the first intermediate transfer roll 51, and Each charging roll 11, each photoconductor 10, each first intermediate transfer roll 51, and each second intermediate transfer roll 53 according to the relationship between the resistance value of each photoconductor 10 and the voltage applied to each charging roll 11. , And a predetermined potential gradient between the final transfer roll 61 It is adapted to growth.
[0111]
Also in the case of the second embodiment, in the same manner as in the first embodiment, in the cleaning mode by the blade cleaning device 71, in the positive electrode cleaning, each charging roll 11 is −840V, each photoconductor 10 is −300V, The first intermediate transfer roll 51 is +380 V, the second intermediate transfer roll 53 is +880 V, and the final transfer roll 61 is +1600 V. In reverse cleaning, each charging roll 11 is 0 V, and each photoreceptor 10 Is set to −300V, each first intermediate transfer roll 51 is set to −800V, second intermediate transfer roll 53 is set to −1300V, and final transfer roll 61 is set to −2000V.
[0112]
Here, the positive electrode cleaning and the reverse electrode cleaning will be described with reference to the cleaning execution diagrams shown in FIGS. 10 to 13. When the positive electrode cleaning shown in FIG. 10 is performed, each of them is exactly the same as in the first embodiment shown in FIG. A potential is set on the members to apply a potential gradient between these members, and the positive (−) residual toner remaining on each member finally moves to the final transfer roll 61, as shown in FIG. As shown, the blade is removed by a blade cleaning device 71 attached to the final transfer roll 61. At this time, the reverse polarity (+) residual toner remaining in each member moves in a direction opposite to that of the positive polarity (−) residual toner and collects on the charging roll 11 as shown in FIG.
[0113]
In the reverse polarity cleaning shown in FIG. 12, -2000V DC is applied to the final transfer roll 61, the second intermediate transfer roll 53 with respect to the grounded photoconductor 10 is set to -1300V, and the first The intermediate transfer roll 51 is settled to −800V, and the photosensitive member 10 in contact with the first intermediate transfer roll 51 is charged by the first intermediate transfer roll 51 and set to −300V. 0V is applied by grounding. Therefore, in exactly the same manner as in the first embodiment, a potential gradient is present between the final transfer roll 61, the second intermediate transfer roll 53, the first intermediate transfer roll 51, the photoconductor 10, and the charging roll 11. The reverse polarity (+) residual toner adhering to each member, especially the charging roll 11, finally moves to the final transfer roll 61, and is attached to the final transfer roll 61 as shown in FIG. The blade cleaning device 71 is removed.
[0114]
Therefore, in the case of the full-color image forming apparatus according to the second embodiment, as in the first embodiment, not only the positive residual toner but also the positive polarity cleaning and the reverse polarity cleaning are appropriately included in the image forming job. The reverse polarity residual toner can also be efficiently and reliably removed.
[0115]
By applying Example 1 and Example 2 described above to this embodiment, Example 1 and Example 2 are applied to the tandem-type full-color image forming apparatus according to Embodiment 1 to each transfer body. Even if the voltage to be applied is changed, the potential difference between the transfer members does not become excessive, the surface potential of the transfer member can be stably set to a desired value, and a good image can be obtained.
[0116]
[Third Embodiment] Next, FIG. 14 shows a tandem full-color image forming apparatus according to a third embodiment. In the following description, the reference numerals for each member may indicate only representative examples.
[0117]
In the case of the third embodiment, unlike the case of the first embodiment, the pair of first intermediate transfer rolls 51 and 52 and the second intermediate transfer roll 53 are each a brush type first that is a temporary holding member. The cleaning members 81 and 82 and the second cleaning member 83 are provided so that a high voltage can be applied to the first cleaning members 81 and 82 in the range of 300 to 800 V on the + side of the first intermediate transfer rolls 51 and 52. In addition, a high voltage in the range of 300 to 800 V can be applied to the second cleaning member 83 on the + side of the second intermediate transfer roll 53 as well.
[0118]
In the third embodiment, at the time of image formation of an image forming job, each charging roll 11 is −840V, each photoconductor 10 is −300V, each first intermediate transfer roll 51, 52 is + 380V, and the second intermediate transfer. The roll 53 is set to + 880V, the final transfer roll 61 is set to + 1600V, the first cleaning members 81 and 82 are set to + 880V, and the second cleaning member 83 is set to + 1380V. The positive (−) residual toner generated in the first cleaning members 81 and 82 and the second intermediate transfer roll 53 is immediately held by the first cleaning members 81 and 82 and the second cleaning member 83, respectively. .
[0119]
For this reason, according to the full-color image forming apparatus of the third embodiment, the positive (−) remaining on the first intermediate transfer rolls 51 and 52 and the second intermediate transfer roll 53 during image formation, particularly during continuous image formation. Even if toner is generated, the first cleaning members 81 and 82 and the second cleaning member 83 attached to the first intermediate transfer rolls 51 and 52 and the second intermediate transfer roll 53 can temporarily hold them. Can do.
[0120]
In the third embodiment, in the cleaning mode by the blade cleaning device 71, each charging roll 11, each photoconductor 10, each first intermediate transfer roll 51, 52, second intermediate transfer roll 53, and The same potential gradient as that of the first embodiment is applied to the final transfer roll 61, and the first cleaning members 81 and 82 are set to 0V and the second cleaning member 83 is set to + 380V during positive electrode cleaning. At the time of pole cleaning, the first cleaning members 81 and 82 are set to −300V, and the second cleaning member 83 is set to −800V.
[0121]
Therefore, in the case of the third embodiment, in the cleaning mode of the image forming job, in the positive electrode cleaning, each charging roll 11 is −840V, each photoconductor 10 is −300V, each first intermediate transfer roll 51, 52 is set to + 380V, the second intermediate transfer roll 53 is set to + 880V, the final transfer roll 61 is set to + 1600V, the first cleaning members 81 and 82 are set to 0V, and the second cleaning member 83 is set to + 380V. At the time of reverse polarity cleaning, each charging roll 11 is 0V, each photoconductor 10 is -300V, each first intermediate transfer roll 51, 52 is -800V, and the second intermediate transfer roll 53 is -1300V. And the final transfer roll 61 is set to −2000V, the first cleaning members 81 and 82 are set to −300V, and the second cleaning member 83 is − It is set to 00V.
[0122]
Therefore, according to the third embodiment, at the time of positive electrode cleaning, as shown in FIG. 15, the above-described potential is set to each member, and a potential gradient is applied between these members, thereby remaining on each member. As shown in FIG. 16, the positive (−) residual toner that has been collected, including the positive (−) residual toner collected by the second cleaning member 83 of the second intermediate transfer roll 53, is the final one. Then, the process proceeds to the final transfer roll 61 and is removed by a blade cleaning device 71 attached to the final transfer roll 61 as shown in FIG. At this time, the reverse polarity (+) residual toner remaining in each member moves in the opposite direction to the positive polarity (−) residual toner, and the first intermediate transfer is performed as shown in FIG. The first cleaning members 81 and 82 of the rolls 51 and 52 and the charging roll 11 gather.
[0123]
Therefore, according to the full-color image forming apparatus of the third embodiment, in an actual image forming job, the optimum transfer potential and voltage are set due to factors such as changes in the ambient temperature, humidity, toner charge amount, developer amount, and the like. Not only can image defects such as transfer ghosts due to positive (−) residual toner occurring due to this occur, but also positive electrode cleaning can be performed appropriately in an image forming job, as in the first and second embodiments. By performing reverse polarity cleaning, not only the positive polarity residual toner but also the reverse polarity residual toner can be efficiently and reliably removed.
[0124]
By applying Example 1 and Example 2 described above to this embodiment, Example 1 and Example 2 are applied to the tandem-type full-color image forming apparatus according to Embodiment 1 to each transfer body. Even if the voltage to be applied is changed, the potential difference between the transfer members does not become excessive, the surface potential of the transfer member can be stably set to a desired value, and a good image can be obtained.
[0125]
[Fourth Embodiment] Further, unlike the third embodiment, the tandem full-color image forming apparatus according to the fourth embodiment is provided with first cleaning members 81 and 82 attached to the pair of first intermediate transfer rolls 51 and 52. Is set to be approximately −100 to −500 V lower than the potential applied to the first intermediate transfer rolls 51 and 52, and the second cleaning member 83 attached to the second intermediate transfer roll 53 is the first one. It is set to about +100 to +500 V higher than the potential applied to the second intermediate transfer roll 53.
[0126]
For this reason, in the full-color image forming apparatus according to the fourth embodiment, the optimum transfer potential and voltage are set in an actual image forming job due to factors such as variations in ambient temperature, humidity, toner charge amount, developer amount, and the like. The positive (−) residual toner generated due to this is held by the second cleaning member 83 attached to the second intermediate transfer roll 53, and also between the first intermediate transfer rolls 51, 52 and the second intermediate transfer roll 53. When the secondary transfer with the transfer roll 53 or the tertiary transfer between the second intermediate transfer roll 53 and the final transfer roll 61 is performed, charging is performed with respect to the reverse polarity (−) residual toner generated due to the influence of pash-on discharge or the like. Before being accumulated back to the roll 11, it is held by the second cleaning member 83 attached to the first intermediate transfer rolls 51 and 52, thereby preventing the charging roll 11 from being contaminated as much as possible. Can do.
[0127]
Also in the fourth embodiment, the same cleaning mode by the blade cleaning device 71 as in the third embodiment is applied, and the positive (−) residual toner remaining on each member by the positive electrode cleaning is finally transferred to the final transfer roll. 61, and is removed by the blade cleaning device 71. Also, by reverse polarity cleaning, it adheres to each member, especially the charging roll 11, and the reverse polarity (+ ) The residual toner can be finally transferred to the final transfer roll 61 and removed by the blade cleaning device 71.
[0128]
By applying Example 1 and Example 2 described above to this embodiment, Example 1 and Example 2 are applied to the tandem-type full-color image forming apparatus according to Embodiment 1 to each transfer body. Even if the voltage to be applied is changed, the potential difference between the transfer members does not become excessive, the surface potential of the transfer member can be stably set to a desired value, and a good image can be obtained.
[0129]
【The invention's effect】
According to the image forming apparatus of the present invention, even if the voltage applied to each transfer body is changed, the potential difference between the transfer bodies does not become excessive, the surface potential of the transfer body is stably set to a desired value, and good Can be obtained.
[Brief description of the drawings]
FIG. 1 shows a relationship between a potential difference between members for each charge of residual toner and toner movement between members.
FIG. 2 is a schematic cross-sectional view of the full-color image forming apparatus according to the first embodiment.
FIG. 3 shows a basic timing sequence of an image forming job in the full-color image forming apparatus according to the first embodiment.
FIG. 4 shows a state immediately after the start of positive polarity cleaning of the full-color image forming apparatus according to the first embodiment.
FIG. 5 shows a state at the end of positive polarity cleaning of the full-color image forming apparatus according to the first embodiment.
FIG. 6 shows a state immediately after the start of reverse polarity cleaning of the full-color image forming apparatus according to the first embodiment.
FIG. 7 illustrates a state at the end of reverse polarity cleaning of the full-color image forming apparatus according to the first embodiment.
FIG. 8 is a timing chart illustrating potential control of the full-color image forming apparatus according to the first embodiment.
FIG. 9 is a timing chart illustrating potential control of the full-color image forming apparatus according to the second embodiment.
FIG. 10 shows a state immediately after the start of positive polarity cleaning of the full-color image forming apparatus according to the second embodiment.
FIG. 11 shows a state at the end of positive polarity cleaning of the full-color image forming apparatus according to the second embodiment.
FIG. 12 shows a state immediately after the start of reverse polarity cleaning of the full-color image forming apparatus according to the second embodiment.
FIG. 13 illustrates a state at the end of reverse polarity cleaning in the full-color image forming apparatus according to the second embodiment.
FIG. 14 is a schematic cross-sectional view of a full-color image forming apparatus according to Embodiment 3.
FIG. 15 shows a state immediately after the start of positive polarity cleaning of the full-color image forming apparatus according to the third embodiment.
FIG. 16 illustrates a state at the end of positive polarity cleaning of the full-color image forming apparatus according to the third embodiment.
FIG. 17 illustrates a state immediately after the start of reverse polarity cleaning in the full-color image forming apparatus according to the third embodiment.
FIG. 18 illustrates a state at the end of reverse polarity cleaning of the full-color image forming apparatus according to the third embodiment.
FIG. 19 illustrates a conventional image forming apparatus.
[Explanation of symbols]
10, 20, 30, 40 ... photoconductor, 11, 21, 31, 41 ... charge roll, 12, 22, 32, 42 ... exposure device, 13, 23, 33, 43 ... developing device, 51, 52 ... first Intermediate transfer roll, 53 ... second intermediate transfer roll, 61 ... final transfer roll, 71 ... cleaning device, 72 ... cleaning blade, P ... paper

Claims (4)

A multi-stage transfer body that contacts each other from the upstream side to the downstream side in the transfer direction of the toner image,
The normal charge polarity Ru electrodeposition position gradient is moved to the transfer body on the downstream side of the opposite polarity remaining toner from the upstream side of the transfer body remaining is charged to the opposite polarity to the Oite the toner image on the transfer member in each stage The first mode to give,
A second mode for applying a potential gradient Before moving the positive polarity residual toner from the upstream side of the transfer member to the transfer member downstream remaining is charged to the normal charging polarity of Oite the toner image on the transfer member in each stage In an image forming apparatus having
When shifting from the first mode to the second mode , a predetermined time is shifted in the order from the upstream transfer member to the downstream transfer member among the transfer members of the respective steps, and the transfer members of the respective steps are transferred to the transfer members of the respective steps. While changing the voltage to be applied from the voltage value in the first mode to the voltage value in the second mode,
When shifting from the second mode to the first mode, a predetermined time is shifted in the order from the downstream transfer body to the upstream transfer body among the transfer bodies of the respective stages, and the transfer bodies of the respective stages are transferred to the transfer bodies of the respective stages. An image forming apparatus comprising control means for changing a voltage to be applied from a voltage value in the second mode to a voltage value in the first mode . The control means includes
In the transition from the first mode to the second mode is the transfer member downstream of the transfer member even if the voltage is higher than the transfer member a second mode when it is changed to the voltage value V _I applied during the same time that the transfer of the also the voltage after changing its value V _I, repeating a pattern of changing the voltage of the downstream side of the transfer member after a predetermined time has elapsed voltage applied to the second mode of the transfer member,
When shifting from the second mode to the first mode, the voltage of a certain transfer body is changed to a voltage value V _J applied in the first mode of the transfer body, and at the same time, the transfer on the upstream side of the transfer body. The pattern in which the voltage of the downstream transfer body is changed to the voltage applied during the first mode of the transfer body after a predetermined time has elapsed after the body voltage is also changed to the value V _J is repeated. The image forming apparatus according to 1. V ₁ (1), V ₂ (1),..., V _N (1) are applied to the transfer body at each stage in the first mode from the upstream side , and the transfer body at each stage in the second mode. , V ₁ (2), V ₂ (2),..., V _N (2) from the upstream side ,
Difference of voltage value applied to transfer member at each stage | V ₁ (2) −V ₁ (1) |, | V ₂ (2) −V ₂ (1) |,... | V _N (2) − Between V _N (1) |, | V ₁ (2) −V ₁ (1) | <| V ₂ (2) −V ₂ (1) | <... <| V _N (2) −V _N (1) The image forming apparatus according to claim 1 or 2, wherein | 4. The image forming apparatus according to claim 1, further comprising a cleaning device that removes and collects residual toner remaining on the most downstream transfer body among the plurality of stages of transfer bodies .

Images