JP4340406B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a color image forming apparatus such as a copying machine, a facsimile machine, and a printer. More specifically, the present invention relates to a plurality of image carriers and primary transfer means for primarily transferring an image formed on the image carrier onto an intermediate transfer member. The present invention also relates to an image forming apparatus having secondary transfer means for secondary transfer of a primary transfer image on the intermediate transfer body onto an image holding body.
[0002]
[Prior art]
2. Description of the Related Art Today, image forming apparatuses that can form color images, such as color copiers and color printers, are increasing in response to market demands.
Color image forming apparatuses include a one-drum type and a tandem type. The one-drum type includes a plurality of color developing devices around one photoconductor as an image carrier, forms toner images of each color with these developing devices, and superimposes them on the photoconductor. A color image is obtained by transferring a color image onto a transfer material as an image carrier. The tandem type has a plurality of photoconductors each provided with a developing device, forms a single color toner image on each photoconductor, and sequentially transfers the single color toner images onto a transfer material. To obtain a color image.
Comparing the one-drum type and the tandem type, the one-drum type has a single photoconductor, so that the image forming apparatus can be made relatively small and the cost can be reduced. Since a full-color image is formed by performing image formation (usually four times), it is difficult to speed up image formation. The tandem type, on the other hand, has the advantage that it is easy to increase the speed of image formation, although it is large and expensive. In recent years, a tandem type has attracted attention because full-color image formation is required to be as fast as monochrome image formation.
[0003]
Further, the tandem type image forming apparatus includes a direct transfer method and an indirect transfer method.
FIG. 9 is an explanatory view of a tandem type image forming apparatus of a direct transfer type, and FIG. 10 is an explanatory view of a tandem type image forming apparatus of an indirect transfer type. In the direct transfer method, as shown in FIG. 9, images formed on the respective photosensitive members are sequentially transferred onto a transfer material conveyed by a transfer material conveyance belt by a transfer device. In the indirect transfer method, as shown in FIG. 10, the image formed on each photoconductor is temporarily transferred to the intermediate transfer member once by the primary transfer device, and the primary transfer image on the intermediate transfer member is transferred to the transfer material by the secondary transfer device. Secondary transfer on top.
[0004]
Of these two types of tandem type image forming apparatuses, in the direct transfer system, a sheet feeding device and a fixing device are not arranged on the upstream side in the transfer material conveyance direction of a plurality of photoconductors arranged side by side. In other words, there is a drawback that the size of the transfer material increases in the conveyance direction. On the other hand, in the indirect transfer method, the position of the paper feeding device and the fixing device can be set relatively freely. For example, if the paper feeding device and the fixing device are disposed below the photosensitive member, the transfer material can be moved in the transfer material conveying direction. There is a merit that it is possible to downsize.
[0005]
In the direct transfer method, the fixing device is disposed close to the tandem image forming apparatus so as not to increase the size in the transfer material conveyance direction, so that from the transfer position of the last color to the fixing position. It is not possible to give enough margin to the distance. For this reason, the leading edge of the image carrier enters the fixing nip without allowing sufficient margin for the image carrier to bend, thereby increasing the impact when the leading edge of the image carrier enters the fixing nip, If there is a difference between the transfer material conveyance speed when passing through the fixing nip and the transfer material conveyance speed when passing through the fixing nip, the speed difference may cause an unexpected influence on primary transfer or image formation. . On the other hand, in the indirect transfer method, the fixing nip can be arranged with a sufficient margin that the transfer material can be bent, and therefore, there is an unexpected influence on the fixing nip and the primary transfer and image formation as described above. It doesn't reach.
In view of the above, in recent years, an indirect transfer type of tandem type image forming apparatus has attracted attention.
[0006]
[Problems to be solved by the invention]
However, among the tandem type image forming apparatuses, the intermediate transfer type has a secondary transfer member for pressing the transfer material against the intermediate transfer member during the secondary transfer, and is in contact with and separated from the intermediate transfer member. It is like that. When the contact / separation operation of the secondary transfer member is performed during the primary transfer of the image to the intermediate transfer member, the impact such as vibration received by the intermediate transfer member due to the contact / separation is transmitted to the primary transfer nip portion, and on the intermediate transfer member. The primary transfer image may be disturbed. The disturbance of the primary transfer image is a so-called banding phenomenon in which fine streaks appear on the image by receiving vibration during the primary transfer. Further, when the primary transfer image is disturbed, image disturbance such as banding and image misalignment occurs in the secondary transfer image finally formed on the transfer material.
[0007]
The present invention has been made in view of the above problems, and an object of the present invention is to prevent the transfer image from being disturbed due to an impact when the secondary transfer member comes in contact with or separates from the intermediate transfer member. It is an object of the present invention to provide an image forming apparatus capable of performing the above.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, an image forming apparatus according to any one of claims 1 to 3 includes a plurality of image carriers, a plurality of toner image forming units that form toner images on the plurality of image carriers, and the plurality of image carriers. A primary transfer means for sequentially transferring a toner image on the image bearing member to the intermediate transfer member at a position in contact with the intermediate transfer member to form a superimposed toner image; and a superimposed toner image on the intermediate transfer member. A secondary transfer unit that performs secondary transfer on the image holding member, the secondary transfer unit pressing the image holding member against the intermediate transfer member, and the secondary transfer member. In an image forming apparatus having a secondary transfer member contact / separation unit that contacts and separates from the intermediate transfer member at a predetermined timing, the predetermined timing of the contact / separation operation by the secondary transfer member contact / separation unit is The primary transfer of the first toner image among the toner images on a plurality of image carriers is performed. During the primary transfer operation from being started until the primary transfer of the last toner image is completed, and is the ash and other in the secondary transfer operation of the superimposed toner image on the intermediate transfer member.
[0009]
4. The image forming apparatus according to claim 1, wherein at least all of the toner images on the image carrier are primarily transferred to the intermediate transfer member during the primary transfer operation and the superimposed toner image on the intermediate transfer member is the image carrier. During the secondary transfer operation during the secondary transfer, the secondary transfer member contacting / separating means does not contact or separate the secondary transfer member from the intermediate transfer member. As a result, during the operations of the primary transfer and the secondary transfer, an impact formed when the secondary transfer member comes in contact with and separates from the intermediate transfer member is not exerted on each transfer portion, and the image formed on the image holding member. To prevent banding and misalignment.
In particular, in the image forming apparatus of claim 1, the toner image forming means forms an electrostatic latent image on a plurality of image carriers and develops the electrostatic latent image to form a toner image. After the development of the electrostatic latent image corresponding to the first toner image among the toner images on the image bearing member is started and before the primary transfer of the first toner image is started, It is determined whether or not the secondary transfer member is in contact with the intermediate transfer member. If not, the secondary transfer member is brought into contact with the intermediate transfer member by the secondary transfer member contacting / separating means. It is something to be made.
According to a second aspect of the present invention, the image forming apparatus includes a document reading device, and the secondary transfer member is disposed after receiving an operator's reading start instruction for the document reading device and before starting the reading. It is determined whether or not it is in contact with the intermediate transfer member, and if not, the secondary transfer member is brought into contact with the intermediate transfer member by the secondary transfer member contacting / separating means.
Here, when the secondary transfer member is separated from the intermediate transfer member, the timing for starting the toner image formation is immediately after turning on the power of the image forming apparatus, and after the secondary transfer of the previous image is completed. Alternatively, it may be immediately after the image carrier is jammed and the jam is resolved, and each is determined by the setting of the apparatus.
[0010]
According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect , from the start of primary transfer of the first toner image to the intermediate transfer body among the toner images on the plurality of image carriers. , during the transfer operation to the completion of the secondary transfer to the image-bearing member of the superimposed toner image on the intermediate transfer member is always also to the secondary transfer member that kept in contact with the intermediate transfer member.
[0011]
4. The image forming apparatus according to claim 3, wherein the secondary transfer member is brought into contact with the intermediate transfer member before the primary transfer of the first toner image is started, and the secondary transfer is performed until the secondary transfer to the image holding member is completed. Continue to maintain the contact state of the members. This eliminates the need for the image carrier to come into contact with the intermediate transfer member after the primary transfer is completed and before the secondary transfer is started, and from the end of the primary transfer of the last toner image to the start of the secondary transfer of the superimposed toner image. In addition, it is not necessary to spend time for the secondary transfer member contact operation.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to a printer which is a tandem indirect transfer type electrophotographic apparatus will be described.
FIG. 1 is a schematic configuration diagram of a printer to which the present invention is applicable. In the figure, reference numeral 100 is a copying apparatus main body, 200 is a paper feed table on which the copying apparatus is placed, 300 is a scanner mounted on the copying apparatus main body 100, and 400 is an automatic document feeder (ADF) mounted thereon. The copying machine main body 100 is provided with an endless belt-shaped intermediate transfer member 10 at the center. As shown in FIG. 2, the intermediate transfer member 10 is formed by forming a base layer 11 made of a base material 11 made of a material that is not easily stretched, such as canvas, on a less stretched fluororesin or a stretched rubber material, and an elastic layer 12 thereon. Is provided. The elastic layer 12 is made of, for example, fluorine-based rubber or acrylonitrile-butadiene copolymer rubber. The surface of the elastic layer 12 is coated with, for example, a coating layer 13 having good smoothness by coating a fluorine resin.
[0015]
As shown in FIG. 1, the intermediate transfer member is wound around three support rollers 14, 15, and 16 so as to be able to rotate and convey clockwise in the drawing. In this illustrated example, an intermediate transfer body cleaning device 17 for removing residual toner remaining on the intermediate transfer body 10 after image transfer is provided on the left of the second support roller 15 among the three. Further, among the three images, four images of cyan, magenta, yellow, and black are arranged on the intermediate transfer member 10 stretched between the first support roller 14 and the second support roller 15 along the conveyance direction. The tandem image forming unit 20 is configured by arranging the forming units 18 side by side.
[0016]
An exposure device 21 is further provided on the tandem image forming unit 20 as shown in FIG. On the other hand, a secondary transfer device 22 as a secondary transfer unit is provided on the side opposite to the tandem image forming unit 20 with the intermediate transfer body 10 interposed therebetween. In the illustrated example, the secondary transfer device 22 is configured by spanning a secondary transfer belt 24 that is an endless belt between two rollers 23 a and 23 b, and the intermediate transfer body 10 and the third support roller 16. The image on the intermediate transfer member 10 is secondarily transferred to a sheet as an image holding member. A fixing device 25 for fixing the transferred image on the sheet is provided beside the secondary transfer device 22. The fixing device 25 is configured by pressing a pressure roller 27 against a fixing belt 26 that is an endless belt.
[0017]
The secondary transfer device 22 described above is also provided with a sheet transport function for transporting the image-transferred sheet to the fixing device 25. Of course, a transfer roller or a non-contact charger may be arranged as the secondary transfer device 22, and in such a case, it is difficult to provide this sheet conveyance function together. In the illustrated example, a sheet reversing device 28 for reversing the sheet so as to record an image on both sides of the sheet is provided below the secondary transfer device 22 and the fixing device 25 in parallel with the tandem image forming unit 20 described above. Is provided.
[0018]
Now, when making a copy using this color electrophotographic apparatus, a document is set on the document table 30 of the automatic document feeder 400. Alternatively, the automatic document feeder 400 is opened, a document is set on the contact glass 32 of the scanner 300, and the automatic document feeder 400 is closed and pressed by it.
When a start switch (not shown) is pressed, when the document is set on the automatic document feeder 400, the document is transported and moved onto the contact glass 32, and then the document is set on the other contact glass 32. At that time, the scanner 300 is immediately driven to travel the first traveling body 33 and the second traveling body 34. Then, the first traveling body 33 emits light from the light source and further reflects the reflected light from the document surface toward the second traveling body 34, and is reflected by the mirror of the second traveling body 34 and passes through the imaging lens 35. The document is placed in the reading sensor 36 and the original content is read.
[0019]
When a start switch (not shown) is pressed, one of the support rollers 14, 15 and 16 is rotationally driven by a drive motor (not shown), the other two support rollers are driven to rotate, and the intermediate transfer member 10 is rotated and conveyed. To do. At the same time, the individual image forming means 18 rotates the photoconductors 40 to form monochrome images of cyan, magenta, yellow, and black on the photoconductors 40, respectively. Then, along with the conveyance of the intermediate transfer member 10, the single color images are sequentially transferred to form a composite color image on the intermediate transfer member 10.
[0020]
On the other hand, when a start switch (not shown) is pressed, one of the paper feed rollers 42 of the paper feed table 200 is selectively rotated, and the sheet is fed out from one of the paper feed cassettes 44 provided in multiple stages in the paper bank 43, and the separation roller 45. Then, the sheets are separated one by one into the paper feed path 46, transported by the transport roller 47, guided to the paper feed path 48 in the copying machine main body 100, and abutted against the registration roller 49 and stopped. Alternatively, the sheet feed roller 50 is rotated to feed out the sheets on the manual feed tray 51, separated one by one by the separation roller 52, put into the manual feed path 53, and abutted against the registration roller 49 and stopped.
[0021]
Then, the registration roller 49 is rotated in synchronization with the composite color image on the intermediate transfer member 10, the sheet is fed between the intermediate transfer member 10 and the secondary transfer device 22, and transferred by the secondary transfer device 22. A color image is recorded on the sheet. The image-transferred sheet is conveyed by the secondary transfer device 22 and sent to the fixing device 25. The fixing device 25 applies heat and pressure to fix the transferred image, and then the switching roller 55 is used to switch the discharge image. The paper is discharged at 56 and stacked on the paper discharge tray 57. Alternatively, it is switched by the switching claw 55 and put into the sheet reversing device 28, where it is reversed and guided again to the transfer position, and an image is recorded also on the back surface, and then discharged onto the discharge tray 57 by the discharge roller 56. On the other hand, the intermediate transfer body 10 after the image transfer is removed by the intermediate transfer body cleaning device 17 to remove residual toner remaining on the intermediate transfer body 10 after the image transfer, so that the tandem image forming unit 20 can prepare for another image formation.
[0022]
Here, the registration roller 49 is generally used while being grounded, but it is also possible to apply a bias for removing paper dust from the sheet. For example, a bias is applied using a conductive rubber roller. The surface is a conductive NBR rubber having a diameter of 18 mm and a thickness of 1 mm. The electric resistance is about 10E9 Ωcm in volume resistance of the rubber material, and the applied voltage is a voltage of about −800 V on the toner transfer side (front side). Further, a voltage of about +200 V is applied to the back side of the paper.
[0023]
In general, in the intermediate transfer method, it is difficult for paper dust to move to the photoconductor, so that it is not necessary to consider paper dust transfer and may be grounded. Further, a DC bias is applied as the applied voltage, but this may be an AC voltage having a DC offset component in order to more uniformly charge the sheet.
[0024]
The paper surface after passing through the registration roller 49 to which a bias is applied in this way is slightly charged on the negative side. Therefore, in the transfer from the intermediate transfer body 10 to the sheet, there are cases where the transfer conditions are changed and the transfer conditions are changed as compared with the case where no voltage is applied to the registration roller 49.
[0025]
FIG. 3 is a partially enlarged view of the tandem image forming unit 20. In the tandem image forming unit 20 described above, each image forming unit 18 includes a charging device 60, a developing device 61, and a primary transfer unit around a photosensitive member 40 as a drum-shaped image carrier as shown in FIG. Primary transfer device 62, photoconductor cleaning device 63, static eliminator 64, and the like.
[0026]
Further, the process cartridge may be formed by all or a part of the parts constituting the image forming unit 18 and may be detachable from the copying machine main body 100 at once so as to improve the maintainability. Of the portions constituting the image forming unit 18, the charging device 60 is formed in a roller shape in the illustrated example, and charges the photosensitive member 40 by applying a voltage in contact with the photosensitive member 40. Of course, charging can be performed with a non-contact scorotron charger.
[0027]
The developing device 61 may use a one-component developer. However, in the illustrated example, a two-component developer composed of a magnetic carrier and a nonmagnetic toner is used. Then, the two-component developer is conveyed while being agitated to supply and adhere the two-component developer to the developing sleeve 65, and the toner of the two-component developer attached to the developing sleeve 65 is transferred to the photosensitive member 40. The developing unit 67 is transferred to the position where the stirring unit 66 is positioned lower than the developing unit 67.
[0028]
The stirring unit 66 is provided with two parallel screws 68. FIG. 6 is an explanatory diagram of the stirring unit. As shown in FIG. 6, the two screws 68 are partitioned by a partition plate 69 except for both ends. A toner concentration sensor 71 is attached to the developing case 70.
[0029]
On the other hand, the developing portion 67 is provided with a developing sleeve 65 facing the photoreceptor 40 through the opening of the developing case 70, and a magnet 72 is fixedly provided in the developing sleeve 65. Further, a doctor blade 73 is provided with the tip approaching the developing sleeve 65. In the illustrated example, the distance at the closest portion between the doctor blade 73 and the developing sleeve 65 is set to 500 μm.
[0030]
Then, the two-component developer is conveyed and circulated while being stirred by the two screws 68 and supplied to the developing sleeve 65. The developer supplied to the developing sleeve 65 is pumped and held by the magnet 72 to form a magnetic brush on the developing sleeve 65. The magnetic brush is trimmed to an appropriate amount by the doctor blade 73 as the developing sleeve 65 rotates. The developer that has been cut off is returned to the stirring unit 66.
On the other hand, of the developer on the developing sleeve 65, the toner is transferred to the photoreceptor 40 by the developing bias voltage applied to the developing sleeve 65, and the electrostatic latent image on the photoreceptor 40 is visualized. After the visualization, the developer remaining on the developing sleeve 65 leaves the developing sleeve 65 and returns to the stirring unit 66 where there is no magnetic force of the magnet 72. When the toner concentration in the stirring unit 66 becomes light by this repetition, it is detected by the toner concentration sensor 71 and the stirring unit 66 is replenished with toner.
[0031]
Incidentally, in the illustrated example, the linear velocity of the photosensitive member 40 is 200 mm / s, and the linear velocity of the developing sleeve 65 is 240 mm / s. The developing process is performed with the diameter of the photoconductor 40 being 50 mm and the diameter of the developing sleeve 65 being 18 mm. The charge amount of the toner on the developing sleeve 65 is preferably in the range of −10 to −30 μC / g. The development gap GP, which is the gap between the photoconductor 40 and the development sleeve 65, can be set in the range of 0.8 mm to 0.4 mm as in the conventional case, and the development efficiency can be improved by reducing the value. . The thickness of the photoreceptor 40 is 30 μm, the beam spot diameter of the optical system is 50 × 60 μm, and the light quantity is 0.47 mW. Further, the developing process is performed with the charging (pre-exposure) potential V0 of the photoreceptor 40 being -700V, the post-exposure potential VL being -120V, and the developing bias voltage being -470V, that is, the developing potential 350V.
[0032]
Next, the primary transfer device 62 is formed in a roller shape and is pressed against the photoconductor 40 with the intermediate transfer body 10 interposed therebetween. Separately, it is not limited to a roller shape, and may be a conductive brush shape or a non-contact corona charger.
[0033]
The photoconductor cleaning device 63 includes a cleaning blade 75 made of polyurethane rubber, for example, with its tip pressed against the photoconductor 40. In order to improve the cleaning property, a contact brush is used together with the photoreceptor 40 at the outer periphery. In this explanatory diagram, the outer periphery is provided on the photosensitive member 40 and a contact conductive fur brush 76 is rotatably provided in the direction of the arrow. Further, a metal electric field roller 77 for applying a bias to the fur brush 76 is rotatably provided in the direction of the arrow, and the tip of the scraper 78 is pressed against the electric field roller 77. Further, a collection screw 79 for collecting the removed toner is provided.
[0034]
Then, residual toner on the photoconductor 40 is removed by a fur brush 76 that rotates in the counter direction with respect to the photoconductor 40. The toner adhering to the fur brush 76 is removed by the electric field roller 77 to which a bias that rotates in contact with the fur brush 76 in the counter direction is applied. The toner attached to the electric field roller 77 is cleaned by a scraper 78. The toner collected by the photoconductor cleaning device 63 is brought to one side of the photoconductor cleaning device 63 by a collection screw 79, and returned to the developing device 61 by a toner recycling device 80, which will be described in detail, for reuse.
The static eliminator 64 is a lamp, for example, and initializes the surface potential of the photoreceptor 40 by irradiating light.
[0035]
Then, along with the rotation of the photosensitive member 40, the surface of the photosensitive member 40 is first uniformly charged by the charging device 60, and then the writing light L by the laser, the LED, or the like is emitted from the above-described exposure device 21 according to the reading content of the scanner 300. Irradiation forms an electrostatic latent image on the photoreceptor 40.
Thereafter, toner is attached by the developing device 61 to visualize the electrostatic latent image, and the visible image is transferred onto the intermediate transfer body 10 by the primary transfer device 62. The surface of the photoconductor 40 after the image transfer is cleaned by removing residual toner with the photoconductor cleaning device 63, and is neutralized with the static eliminator 64 to prepare for another image formation.
[0036]
FIG. 4 is an enlarged view of a main part of the printer shown in FIG. In the figure, each image forming unit 18 of the tandem image forming unit 20, each photoconductor 40 of the image forming unit 18, each developing device 61, each photoconductor cleaning device 63, and each photoconductor 40 of each image forming unit 18. After the respective symbols of the primary transfer devices 62 provided opposite to each other, BK is indicated for black, Y is indicated for yellow, M is indicated for magenta, and C is indicated for cyan.
4 is a conductive roller provided in contact with the base layer 11 side of the intermediate transfer body 10 between the primary transfer devices 62, although not shown in FIGS. The conductive roller 74 prevents a bias applied by each primary transfer device 62 at the time of transfer from flowing into the adjacent image forming means 18 through the intermediate resistance base layer 11.
[0037]
The printer of this embodiment is provided with a secondary transfer member contacting / separating means (not shown), and the secondary transfer member composed of the secondary transfer belt 24 and the roller 23a is attached to the intermediate transfer member in the secondary transfer nip N. It is configured to be able to contact and separate at a predetermined timing. The contact / separation mechanism is configured by supporting a roller 23a on which the secondary transfer belt 24 is stretched on the secondary transfer nip N side so as to be able to contact and separate from the support roller 16. The contact / separation mechanism of the roller 23a can be configured so that the position of the roller 23a relative to the support roller can be moved using a clutch, but is not limited to this configuration. The timing of contact / separation of the secondary transfer member is related to the characterizing portion of this embodiment and will be described in detail later.
[0038]
Next, FIG. 5 is an explanatory view of attachment of the toner recycling apparatus 80, and FIG. 6 is an overall explanatory view. As shown in FIG. 5, the recovery screw 79 of the photoconductor cleaning device 63 is provided with a roller portion 82 having a pin 81 at one end. Then, one side of the belt-like collected toner conveying member 83 of the toner recycling device 80 is hung on the roller portion 82, and a pin 81 is inserted into the long hole 84 of the collected toner conveying member 83. The outer periphery of the collected toner conveying member 83 is provided with blades 85 at regular intervals, and the other side is hung on the roller portion 87 of the rotating shaft 86.
[0039]
The collected toner conveyance member 83 is placed in the conveyance path case 88 shown in FIG. The conveyance path case 88 is formed integrally with the cartridge case 89, and one of the above-described two screws 68 of the developing device 61 is placed at the end of the developing device 61 side. Then, a driving force is transmitted from the outside to rotate the collecting screw 79, rotate and convey the collected toner conveying member 83, and develop the toner collected by the photoconductor cleaning device 63 through the conveying path case 88 by the rotation of the screw 68. Transport to device 61. Thereafter, as described above, the two screws 68 are conveyed and circulated while being stirred together with the developer already in the developing device 61, supplied to the developing sleeve 65 and cut off by the doctor blade 73, and then the photoreceptor 40. And the latent image on the photoreceptor 40 is developed.
[0040]
By the way, in the tandem type printer of the intermediate transfer type as in the present embodiment, the secondary transfer member composed of the secondary transfer belt 24 and the roller 23a by the secondary transfer contact / separation means is impacted by the contact / separation operation with respect to the intermediate transfer body 10. In some cases, banding occurs in the primary transfer image, and banding or misalignment occurs in the secondary transfer image. Therefore, in the present embodiment, it is possible to prevent the transfer image from being disturbed due to an impact when the secondary transfer member contacts and separates from the intermediate transfer body 10. Below, the characteristic part of this embodiment is demonstrated.
[0041]
[Example 1]
FIG. 7 is a flowchart according to the apparatus operation of the first embodiment.
First, when a user sets a document on the contact glass 32 of the scanner 300 and presses a start switch (step 1), the content of the document is read (step 2). An electrostatic latent image is formed on the photoreceptors 40C, 40M, 40Y, and 40BK in accordance with the read image (step 3). Then, development of the electrostatic latent image formed on the photoreceptors 40C, 40M, 40Y, and 40BK is started (step 4). Among the four color toner images formed on the photosensitive member, before the cyan toner image, which is the first toner image at which the primary transfer onto the intermediate transfer member 10 is started, reaches the primary transfer nip, It is determined whether the secondary transfer member is in contact with the intermediate transfer body 10 (step 5). If not in contact (N in step 5), the roller 23a is supported by the secondary transfer member contacting / separating means (not shown). Then, the secondary transfer member is brought into contact with the intermediate transfer member 10 (step 6), and then primary transfer to the intermediate transfer member 10 is started (step 7). On the other hand, when the secondary transfer member is in contact with the intermediate transfer member 10 (Y in Step 5), primary transfer to the intermediate transfer member 10 is started as it is (Step 7). Then, a superimposed toner image is formed on the intermediate transfer member 10, and the secondary transfer is performed on the sheet that enters the secondary transfer nip in a timely manner (step 8). When the secondary transfer to the sheet is completed, the secondary transfer member is moved away from the intermediate transfer body 10 by moving the roller 23a away from the support roller 16 by the secondary transfer member contacting / separating means (step 9). . On the other hand, the toner image is fixed on the sheet carrying the toner image by the fixing device 25 (step 10), and the sheet is discharged outside the apparatus to complete the image forming operation.
[0042]
According to the first embodiment, the toner image on the photosensitive member is primarily transferred to the intermediate transfer member 10 during the primary transfer operation, and the superimposed toner image primarily transferred onto the intermediate transfer member 10 is secondarily transferred to the sheet. During the secondary transfer operation, the secondary transfer member is kept in contact with the intermediate transfer body 10 and is not contacted or separated during the transfer operation. Therefore, during the primary transfer and secondary transfer operations, No impact due to contact and separation. As a result, it is possible to obtain a good transfer image on which the image is not disturbed such as banding or displacement.
Further, as in the first embodiment, the secondary transfer member is brought into contact with the intermediate transfer body 10 before the primary transfer of the first toner image to the intermediate transfer body 10 is started, and the secondary transfer to the sheet is completed. Thus, it is not necessary to provide time for the secondary transfer member contact operation between the end of the primary transfer of the last toner image and the start of the secondary transfer of the toner image. Accordingly, it is possible to prevent the transfer operation time from the start of the primary transfer to the end of the secondary transfer from being prolonged.
[0043]
[Example 2]
Next, the operation of the apparatus according to the second embodiment when the secondary transfer member is separated from the intermediate transfer member 10 at the start of toner image formation will be described.
[0044]
FIG. 8 is a flowchart according to the apparatus operation of the second embodiment.
First, the user sets a document on the contact glass 32 of the scanner 300 and presses the start switch (step 1), determines whether the secondary transfer member is in contact with the intermediate transfer body 10 (step 2), and is in contact state. If not (N in step 2), the secondary transfer member contacting / separating means (not shown) moves the roller 23a toward the support roller 16 to bring the secondary transfer member into contact with the intermediate transfer member 10 (step 3), and then the document The contents are read (step 4). On the other hand, when the secondary transfer member is in contact with the intermediate transfer member 10 (Y in step 5), the document content is read as it is (step 4). An electrostatic latent image is formed on the photoreceptors 40C, 40M, 40Y, and 40BK in accordance with the read image (step 5). The electrostatic latent images formed on the photoconductors 40C, 40M, 40Y, and 40BK are developed (step 6). Among the four color toner images formed on the photosensitive member, when the cyan toner image that is the first toner image on the intermediate transfer member 10 that starts the primary transfer first reaches the primary transfer nip, the intermediate transfer is performed. The primary transfer to the body 10 is started (step 7). Then, a superimposed toner image is formed on the intermediate transfer member 10, and the secondary transfer is performed on the sheet that enters the secondary transfer nip in a timely manner (step 8). When the secondary transfer to the sheet is completed, the secondary transfer member is moved away from the intermediate transfer body 10 by moving the roller 23a away from the support roller 16 by the secondary transfer member contacting / separating means (step 9). . On the other hand, the toner image is fixed on the sheet carrying the toner image by the fixing device 25 (step 10), and the sheet is discharged outside the apparatus to complete the image forming operation.
[0045]
Here, when the secondary transfer member is separated from the intermediate transfer body 10 immediately after the start switch is pressed (N in Step 2), the start timing of the operation of the apparatus is immediately after the printer is turned on. In this case, a case where the separation operation is performed after the secondary transfer of the previous image is completed, or a case where the separation operation of the secondary transfer member is performed after the jamming of the sheet and the jamming is removed is considered. . Among these, when the configuration in which the separation operation of the secondary transfer member is performed when the printer power is turned off or after the secondary transfer is completed, contact pressure is applied to the intermediate transfer member 10 and the secondary transfer member. It is desirable to avoid both deformation and surface modification that may occur due to being left for a long time. Also in the printer of this embodiment, the secondary transfer member contacting / separating means is configured to perform the contacting / separating operation for such a purpose.
[0046]
According to the second embodiment, when the secondary transfer member is separated from the intermediate transfer body 10 at the start of the toner image forming operation, that is, at the start of the latent image formation, the second process is started prior to the start of the latent image formation. The secondary transfer member is brought into contact with the intermediate transfer member 10 by the next transfer member contacting / separating means. Then, development, primary transfer, and subsequent secondary transfer are all continuously performed while the secondary transfer member is in contact with the intermediate transfer member 10. Accordingly, even when the secondary transfer member is separated from the intermediate transfer member 10 at the start of toner image formation, the contact of the secondary transfer member with the intermediate transfer member 10 can be completed without fail before the primary transfer starts. . In addition, it is not necessary to provide a time for the secondary transfer member contact operation that is required between the end of the primary transfer of the last toner image and the start of the secondary transfer of the toner image. Therefore, it is possible to obtain a good transfer image on which the image is not disturbed such as banding or displacement, and to prevent the transfer operation time from the start of the primary transfer to the end of the secondary transfer from being prolonged. it can.
[0047]
In the first and second embodiments, the case where the image to be formed is full color has been described. However, the present invention can also be applied to the case of the black monochrome mode in which only the black image forming means 18 is used. In this case, the first toner image when performing the primary transfer is a black toner image.
[0048]
【The invention's effect】
According to the image forming apparatus of the first to third aspects, an image formed on the image holding member can be obtained by not contacting or separating the secondary transfer member with respect to the intermediate transfer member during the primary transfer and the secondary transfer. Since banding and displacement are prevented from occurring, there is an excellent effect that it is possible to prevent the transfer image from being disturbed due to an impact when the secondary transfer member comes in contact with and separates from the intermediate transfer member.
[0049]
In particular, according to the image forming apparatus of the third aspect , it is not necessary to devote time for the contact operation of the secondary transfer member between the primary transfer and the secondary transfer. Therefore, the primary transfer and the secondary transfer are continuously performed. Or secondary transfer in parallel with primary transfer. Therefore, there is an excellent effect that the transfer operation time from the start of the primary transfer to the end of the secondary transfer can be shortened.
[0051]
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a printer according to an embodiment.
FIG. 2 is a cross-sectional view of an intermediate transfer member.
FIG. 3 is a partially enlarged view of a tandem image forming unit.
4 is an enlarged view of a main part of the printer shown in FIG. 1. FIG.
FIG. 5 is an explanatory diagram of installation of a toner recycling apparatus.
FIG. 6 is an overall explanatory diagram of a toner recycling apparatus.
FIG. 7 is a flowchart according to the apparatus operation of the first embodiment.
FIG. 8 is a flowchart according to the apparatus operation of the second embodiment.
FIG. 9 is an explanatory diagram of a direct transfer type tandem image forming apparatus.
FIG. 10 is an explanatory diagram of an indirect transfer tandem image forming apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Intermediate transfer body 18 Image forming means 20 Tandem image forming part 22 Secondary transfer device 23a, b Roller 24 Secondary transfer belt 25 Fixing device 26 Fixing belt 40 Photoconductor 60 Charging device 61 Developing device 62 Primary transfer device 63 Photoconductor cleaning Device 65 Developing sleeve 67 Developing unit 70 Developing case 80 Toner recycling device 100 Copier body 200 Feeding table 300 Scanner 400 Automatic document feeder

Claims (3)

A plurality of image carriers;
A plurality of toner image forming means for forming an electrostatic latent image on the plurality of image carriers and developing the electrostatic latent image to form a toner image;
Primary transfer means for sequentially transferring the toner images on the plurality of image bearing members to the intermediate transfer member at a position where they are in contact with the intermediate transfer member to form a superimposed toner image;
Secondary transfer means for secondary transfer of the superimposed toner image on the intermediate transfer member onto the image carrier,
A secondary transfer member for pressing the image carrier against the intermediate transfer member, and a secondary transfer member for contacting and separating the secondary transfer member with respect to the intermediate transfer member at a predetermined timing. In an image forming apparatus having contact and separation means,
The predetermined timing of the contact / separation operation by the secondary transfer member contacting / separating means is the primary timing of the first toner image after the start of the primary transfer of the first toner image among the toner images on the plurality of image carriers. Other than during the primary transfer operation until the transfer is completed and during the secondary transfer operation of the superimposed toner image on the intermediate transfer member ,
After the development of the electrostatic latent image corresponding to the first toner image among the toner images on the plurality of image carriers is started, and before the primary transfer of the first toner image is started. Determining whether or not the secondary transfer member is in contact with the intermediate transfer member, and if not, the secondary transfer member is separated by the secondary transfer member contacting / separating means. An image forming apparatus that is brought into contact with the image forming apparatus.   A document reader;
A plurality of image carriers;
A plurality of toner image forming means for forming toner images on the plurality of image carriers in accordance with images read by the document reading device;
Primary transfer means for sequentially transferring the toner images on the plurality of image bearing members to the intermediate transfer member sequentially at a contact position with the intermediate transfer member to form a superimposed toner image;
Secondary transfer means for secondary transfer of the superimposed toner image on the intermediate transfer member onto the image carrier,
A secondary transfer member for pressing the image holding member against the intermediate transfer member, and a secondary transfer member for contacting and separating the secondary transfer member with respect to the intermediate transfer member at a predetermined timing. In an image forming apparatus having contact and separation means,
  The predetermined timing of the contact / separation operation by the secondary transfer member contacting / separating means is the primary timing of the first toner image from the start of the first toner image among the toner images on the plurality of image carriers. Other than during the primary transfer operation until the transfer is completed and during the secondary transfer operation of the superimposed toner image on the intermediate transfer member,
After accepting an operator's reading start instruction to the document reading apparatus and before starting reading, it is determined whether or not the secondary transfer member is in contact with the intermediate transfer body, and contact is made If not, the secondary transfer member is brought into contact with the intermediate transfer member by the secondary transfer member contacting / separating means. The image forming apparatus according to claim 1 or 2 ,
From the start of primary transfer of the first toner image to the intermediate transfer member among the toner images on the plurality of image carriers, the secondary transfer of the superimposed toner image on the intermediate transfer member to the image carrier is completed. The image forming apparatus, wherein the secondary transfer member is always kept in contact with the intermediate transfer member during the transfer operation up to .

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