JP3578980B2 - Transfer material separating mechanism and image forming apparatus provided with the same - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a transfer material separating mechanism used in an image forming apparatus such as a copying machine, a printer, and a facsimile, and an image forming apparatus including the same.
[0002]
[Prior art]
2. Description of the Related Art In an image forming apparatus such as a copying machine, a printer, and a facsimile, a mechanism having a separation claw is known as a mechanism for separating a transfer material after a toner image is transferred from a photosensitive drum.
[0003]
FIG. 3 shows an example of such a transfer material separating mechanism. FIG. 1 shows a schematic configuration of a portion from a registration roller to a fixing device via a transfer unit in the image forming apparatus.
[0004]
The photoreceptor drum 101 is driven to rotate in the direction of the arrow a, and on the surface thereof, a toner image charged by an image forming process of primary charging, exposure, and development by a primary charger 102, an exposing device 103, and a developing device 104 is provided. It is formed. On the other hand, the transfer material P is supplied at a predetermined timing by a registration roller 105, guided by pre-transfer guides 106 and 107, and inserted into a transfer nip portion N1 between the photosensitive drum 101 and the transfer roller. A transfer bias is applied to the transfer roller 108 at the timing when the transfer material P is inserted into the transfer nip portion N1, whereby the toner image on the photosensitive drum 101 is transferred to the surface of the transfer material P. The transfer material P after the transfer of the toner image is separated (separated) from the surface of the photosensitive drum 101 and is conveyed to the fixing device 111. The transfer material P conveyed to the fixing nip portion N2 between the fixing roller 112 and the pressure roller 113 of the fixing device 111 is heated and pressed here to fix the toner image on the surface, and then perform image formation. The sheet is discharged to the outside of the apparatus main body, thereby completing the image formation on the transfer material P. On the other hand, the residual toner remaining on the surface of the photoreceptor drum 1 after the transfer of the toner image is removed by the cleaning device 114, and is used for the next image formation.
[0005]
During the transfer of the toner image, a transfer bias having a polarity opposite to that of the toner image on the photosensitive drum 101 is applied to the transfer roller 108 to apply a charge of a reverse polarity to the back surface of the transfer material P. The toner image on the surface is electrostatically attracted to the surface of the transfer material P and transferred. The transfer material P after the transfer of the toner image is separated from the surface of the photosensitive drum 101 using the curvature of the photosensitive drum 101 and the separation claw 109. The transfer material P after separation is transported to the fixing device 111 along the transport guide 110.
[0006]
[Problems to be solved by the invention]
As described above, when the transfer material P after separation is conveyed along the conveyance guide 110, the back surface of the transfer material P, that is, the back surface not carrying the unfixed toner image, rubs against the conveyance guide 110. Therefore, the unfixed toner image on the front side is not disturbed during conveyance to the fixing device 111 even though the electrostatic coupling force with the transfer material P is relatively weak.
[0007]
On the other hand, the rear end of the separated transfer material P may be transported along the rib 115 disposed above the separation claw 109. In this case, the unfixed toner on the surface of the transfer material P The image may be disturbed, or the separation roller 116 may be required to separate the rear end, which may lead to a complicated configuration. Such a risk is likely to occur in digital image forming apparatuses such as laser printers and LED printers. These image forming apparatuses generally employ reversal development. In the reversal development, the surface potential of the photosensitive drum 101 has the same polarity as the polarity of the toner image, and thus has the opposite polarity to the transfer material P at the time of transfer. P is electrically attracted to the surface of the photosensitive drum 101 and is hardly separated. In particular, the rear end portion of the transfer material P tends to move in the direction indicated by the arrow a while being dragged by the photosensitive drum 101 due to the concentration of the charges having the opposite polarity being concentrated. For this reason, although the rear end of the transfer material P is preferably separated along the transport guide 110 after being separated by the separation claw 109, the rear end of the transfer material P moves along the rib 115. Separated by rollers 116. In this case, since the unfixed toner image on the transfer material P is transferred to the front and back surfaces of the transfer material P, that is, to the rib 115 side, the unfixed toner image is rubbed by the rib 115 and disturbed, or the rib 115 is supported. Scattered on the member 117 that is in contact with it.
[0008]
Accordingly, the present invention provides a transfer material separating mechanism that has a simple structure and that smoothly separates a transfer material to prevent disturbance of an unfixed toner image and contamination of other members due to scattering of unfixed toner. , And an image forming apparatus provided with the same.
[0009]
[Means for Solving the Problems]
According to the first aspect of the present invention, the toner image on the photosensitive drum is transferred by being inserted into a transfer nip portion between the photosensitive drum having a toner image formed on its surface and a transfer roller to which a transfer bias is applied. The present invention relates to a transfer material separating mechanism for separating a transfer material from the surface of a photosensitive drum. The transfer material separating mechanism is disposed opposite to the surface of the photosensitive drum downstream of the transfer nip along the moving direction of the surface of the photosensitive drum, and separates the transfer material after the transfer of the toner image from the surface of the photosensitive drum. An insulating separating member is provided. The transfer material separating mechanism may be configured such that a plane including the axis of the photosensitive drum and the axis of the transfer roller is a first plane, and the fixing member is located on a conveyance path downstream of the transfer nip in a sheet conveyance direction. Assuming that a plane including the axis of the fixing roller and the axis of the pressure roller is a second plane, the first plane and the second plane are arranged in a substantially C shape, and the transport path is The transfer material sent out from the transfer nip is gently curved and supplied to a fixing nip between the fixing roller and the pressure roller. The separating member in the transfer material separating mechanism, when assuming a transfer material stretched between the fixing nip transfer nip portion, and for this assumed transfer material in a direction intersecting obliquely transfer It has a separation surface that is inclined in a direction to narrow the material conveyance path toward the downstream side. The tip edge of said separation surface, against the surface of the photosensitive drum, and is disposed at all times in a position to close a non-contact manner.
[0010]
According to the present invention having such a configuration, the transfer material separated from the photoreceptor drum surface by the separation member is moved to the rear surface side by colliding with the inclined separation surface. The unfixed toner image on the surface of the transfer material is not disturbed by being rubbed against the ribs on the surface side, and the unfixed toner does not adhere to other members disposed on the surface side. That is, smooth separation without disturbing the unfixed toner image can be realized with a simple configuration.
[0011]
According to a second aspect of the invention (transfer material separating mechanism), the separating member has a top portion located on the most downstream side of the separation surface along the transfer material transport direction, and an auxiliary separation surface continuous with the top portion. This auxiliary separation surface is characterized in that the assumed inclination angle with respect to the transfer material is smaller than the separation surface.
[0012]
According to the present invention configured as described above, the top portion is formed in a convex shape with respect to the transfer material by the separation surface and the auxiliary separation surface. Is moved to the back side by the top. By providing such a convex top portion, the separation performance of the transfer material is further improved.
[0013]
According to a third aspect of the present invention, a transfer material separating mechanism is provided between the transfer nip portion and the fixing unit, and guides the back surface of the transfer material conveyed between the transfer member and the separation member. A transport guide is provided.
[0014]
According to the present invention having such a configuration, the transfer material having the charge at the time of separation is moved to the back side by the above-described separation surface and the top portion, and is further electrostatically moved by the grounded conductive conveyance guide. The transfer material is more reliably separated from the surface of the photosensitive drum. In addition, the transfer material is discharged by the transfer guide by bringing the back surface into contact with the transfer guide at the time of separation. Then, the transfer material from which the charge has been removed is then conveyed to the fixing unit in a stable posture.
[0015]
According to a fourth aspect of the present invention, there is provided an image forming apparatus comprising: a photosensitive drum; charging means for charging the surface of the photosensitive drum; and exposing means for exposing the charged photosensitive drum surface to form an electrostatic latent image. Developing means for developing the electrostatic latent image as a toner image, transfer means for transferring the toner image on the photosensitive drum to a transfer material, and separation means for separating the transfer material after the toner image transfer from the surface of the photosensitive drum. And a fixing unit for fixing a toner image to the transfer material after separation, and a transfer material separation mechanism according to claim 1, 2, or 3.
[0016]
According to the present invention having such a configuration, since the image forming apparatus is provided with the above-described transfer separation mechanism, the transfer material after the transfer of the toner image is smoothly separated from the surface of the photosensitive drum and conveyed to the fixing unit. Is done. Therefore, it is possible to prevent an image defect due to the separation failure.
[0017]
The invention (image forming apparatus) according to a fifth aspect is characterized in that the fixing means is located above the transfer nip portion.
[0018]
According to the present invention having such a configuration, when the transfer material after the transfer of the toner image is separated from the surface of the photosensitive drum, for example, an image forming apparatus in which the transfer nip portion and the fixing unit are arranged substantially horizontally is provided. In comparison, it is difficult to expect the effect of the curvature separation due to the weight of the transfer material. The transfer material separating mechanism described above is particularly effective for such an image forming apparatus.
[0019]
The invention (image forming apparatus) according to claim 6 is characterized in that the toner image formed on the photosensitive drum is formed by reversal development.
[0020]
According to the present invention having such a configuration, since the transfer material and the photosensitive drum at the time of separation have opposite polarities to each other and have a strong electric adhesion, separation of the transfer material after transfer of the toner image is particularly performed. Have difficulty. The transfer material separating mechanism described above is extremely effective for such an image forming apparatus.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0022]
FIG. 1 shows an example of an image forming apparatus according to the present invention. The image forming apparatus shown in FIG. 1 is a copying machine having a reader unit (image reading unit) and a printing unit (printing unit), and FIG. 1 is a longitudinal sectional view showing a schematic configuration thereof.
[0023]
First, an overall configuration of the copying machine 10 will be described with reference to FIG.
[0024]
A copying machine 10 shown in FIG. 1 includes a copying machine main body 11 constituting an entire framework, and a reader unit 12 for reading image surfaces (image information) G of originals D1 and D2 is provided above the copying machine main body 11. A printing unit 13 is provided below the printing unit 13 for forming a toner image on a transfer material P such as paper in accordance with image information read by the reader unit 12.
[0025]
The former reader unit 12 includes a transparent document table 14 on which the document D1 is placed with its image surface G facing down, and an openable and closable document for bringing the image surface G of the document D1 into close contact with the upper surface of the document table 13. A scanning unit 18 having a pressing plate 15, a light source 16 for irradiating light from below onto the image surface G of the document D1 on the document table 14 and a first reflecting mirror 17, and a light reflected from the first reflecting mirror 17. Further, there are provided second and third reflecting mirrors 20 and 21 for reflecting light, a lens array 22 for forming an image of light from the third reflecting mirror 21, and a CCD 23 to which light from the lens array 22 is incident. I have. The above-described scanning unit 18 is configured to scan the image surface G of the document D1 with the light source 16 while moving rightward from the home position HP shown in FIG. 1, and to return to the home position HP after the scanning is completed. I have. The above is a configuration for performing the so-called fixed reading, in which the document D1 is fixed and the scanning unit 18 is moved to read the image surface G.
[0026]
The reader unit 12 further includes an automatic document feed mechanism 24 for moving the document D2, fixing the scanning unit 18 and reading the document surface G, that is, performing a so-called drift reading. The automatic document feeder 24 transports the document D2 on the paper feed table 25 leftward toward the scanning unit 18 disposed at the home position HP, and a paper feed table 25 that supports the leading end side of the document D2 from below. And a discharge roller pair 27 that carries out the document D2 read by the scanning unit 18 to the left from the scanning unit 18. The automatic document feed mechanism 24 conveys the document D2 to the left in FIG. 1 by the above-described paper feed roller pair 26 and paper discharge roller pair 27, and after reading the document D2, discharges the rear end of the document D2. The sheet is nipped by the roller pair 27 and discharged so as to hang down on the left side of the copying machine main body 11. Here, the document D2 is easily pulled out from between the paper discharge roller pair 27 by being pulled by a person.
[0027]
The fixed reading and the flow reading are selectively used, for example, while a document D1 such as a bound book is placed on the platen 14 to perform fixed reading, while a cut sheet-shaped document D2 is The document is placed on the paper feed table 25 and read.
[0028]
The print unit 13 includes a cylindrical photoconductor (hereinafter, referred to as a “photoconductor drum”) 30 as an electrostatic latent image carrier (subject to be charged), which is disposed substantially at the center in the vertical direction on the left side in FIG. Have. The photoreceptor drum 30 is rotatably supported by the copying machine main body 11 in the direction of the arrow (clockwise in the figure), and its primary charger (charging means) 31 is arranged around the photoconductor drum 30 substantially in the rotation direction. , An exposure unit (exposure unit) 32, a development unit (development unit) 33, a transfer charger (transfer unit) 34, and a cleaning unit 35 are provided. Further, along a transport path 36 (indicated by a two-dot chain line in FIG. 1) of a transfer material P such as paper to be image-formed, from the upstream side to the downstream side (from substantially lower to upper in FIG. 1), A paper feed cassette 37, a paper feed roller 38, a transport roller pair 40, a registration roller pair 41, a transport guide 42, a fixing device (fixing unit) 43, a paper discharge roller pair 44, and a paper discharge tray 45 are provided.
[0029]
The photosensitive drum 30 is configured by providing a photosensitive layer such as OPC (organic optical semiconductor) or amorphous silicon on the outer peripheral surface of a conductive drum base such as aluminum. The photoconductor drum 30 is driven to rotate at a predetermined process speed (peripheral speed) in the direction of the arrow by a driving unit (not shown).
[0030]
In the present embodiment, a scorotron type corona charger is used as the primary charger 31. The primary charger 31 is configured to uniformly charge the surface of the photosensitive drum 30 to a predetermined polarity / potential by applying a charging bias from a charging bias application power supply (not shown).
[0031]
The exposing device 32 has a laser oscillator, a polygon mirror, and the like (both not shown), and forms an electrostatic latent image on the surface of the photosensitive drum 30. The image information of the document D1 (or D2) read by the reader unit 12 is appropriately converted by an image processing unit (not shown) provided in the printing unit 13 into A / D conversion, density correction, shading correction, and the like. After the processing, the image signal is input to the laser oscillator as an image signal. The laser oscillator exposes the charged surface of the photosensitive drum 30 via a polygon mirror or the like with a laser beam whose ON / OFF is controlled based on the image signal, and removes the charge of the exposed portion to remove the electrostatic latent image. Is formed.
[0032]
The developing device 33 includes a developing container 46 that stores the developer and a developing roller that conveys the developer carried on the surface to a developing position facing the surface of the photosensitive drum 30 by rotating the developer in the direction of the arrow (counterclockwise). 47. A developing bias is applied to the developing roller 47 by a developing bias application power supply (not shown), whereby toner in the developer adheres to the electrostatic latent image on the surface of the photosensitive drum 30, and this electrostatic latent image is removed. It is adapted to developed as a toner image.
[0033]
The transfer charger 34 is formed by a roller-shaped member provided so as to face the surface of the photosensitive drum 30. To the transfer charger 34, a transfer bias having a polarity opposite to that of the toner image on the photosensitive drum 30 is applied by a transfer bias application power supply (not shown), whereby the toner on the photosensitive drum 30 is applied to the surface of the transfer material P. it is intended to transfer the image. Here, the transfer material P on which the toner image is transferred is stored in the paper feed cassette 37, is fed by the paper feed roller 38, is transported by the transport roller pair 40, and is temporarily transferred by the registration roller pair 41. After being stopped, the toner image is sent out from the pair of registration rollers 41 so as to match the timing with the toner image on the photosensitive drum 30.
[0034]
The cleaning device 35 has a cleaning blade 48 in contact with the surface of the photoconductor drum 30 to remove residual toner remaining on the surface of the photoconductor drum 30 without being transferred onto the transfer material P during the above-described transfer.
[0035]
A transport guide 42 that guides the transfer material P after the transfer of the toner image to the fixing device 43 is provided downstream of the transfer charger 34.
[0036]
The fixing device 43 includes a fixing roller 51 that is heated by a heater 50 disposed inside, and a pressure roller 52 that presses the transfer material P against the fixing roller 51.
The transfer material P transported with the unfixed toner image carried on the surface is heated and pressed to fix the toner image on the surface of the transfer material P.
[0037]
The discharge roller pair 44 discharges the transfer material P on which the toner image has been fixed onto a discharge tray 45 as a completed product.
[0038]
In the copying machine 10 having the configuration described above, when forming an image, first, the photosensitive drum 30 is driven to rotate in the direction of the arrow by the driving unit, and the surface thereof is set to a predetermined polarity and potential by the primary charger 31. Charged uniformly. An electrostatic latent image corresponding to the image information is formed on the surface of the charged photosensitive drum 30 by irradiation of laser light from an exposure device 32 that operates according to the image information of the document D1 (or D2) read by the reader unit 12. It is formed. The electrostatic latent image is developed with a toner by a developing device 33 as a toner image. The toner image formed on the surface of the photoconductor drum 30 is transferred to the transfer material P conveyed at a predetermined timing by the registration roller pair 41 and the like, and a transfer bias is applied to the transfer charger 34 so that the transfer material P It is transferred to the surface. The residual toner remaining on the surface of the photosensitive drum 30 after the transfer of the toner image is removed by the cleaning device 35, and the photosensitive drum 30 is provided for the next image formation. On the other hand, the transfer material P after the transfer of the toner image is transported to the fixing device 43 along the transport guide 42, where the toner image is fixed on the surface by receiving heat and pressure. The transfer material P after the toner image is fixed is discharged onto the paper discharge tray 45 by the paper discharge roller pair 44 with the image surface (the surface on which the toner image is fixed) facing downward, that is, in a face-down state. Thus, the image forming (printing) by the copying machine 10 is completed.
[0039]
In the above-described image forming apparatus, the quality of the final print quality depends on the performance of each component. Therefore, it also depends on the transfer material separating performance of a transfer material separating mechanism (described later), which is one of the constituent members.
[0040]
In the following, an example in which the effect of the transfer material separating mechanism according to the present invention is remarkable, that is, an OPC photosensitive member having a negative (negative) charging characteristic is used as the photosensitive drum 30, and the photosensitive drum 30 is inverted by a toner having a negative charge An example in which development is performed will be described.
[0041]
First, the surface of the photosensitive drum 30 is uniformly charged to a predetermined negative potential by the primary charger 31. The surface of the charged photosensitive drum 30 is subjected to image exposure in accordance with image information by an exposure device 32, and charges on exposed portions are removed to form an electrostatic latent image. A toner having a negative charge is attached to the portion from which the charge has been removed by the developing device 33, and the image is reversely developed as a toner image. On the other hand, the transfer material P conveyed from the lower sheet cassette 37 is temporarily stopped by the registration roller pair 41, and the registration roller pair 41 is rotated so as to match the timing with the toner image on the photosensitive drum 30. The transfer material P is passed through a transfer nip portion N1 (see FIG. 2) between the photosensitive drum 30 and a transfer roller (hereinafter, referred to as a "transfer roller 34") as a transfer charger (transfer member) 34. At this time, a positive charging bias having a polarity opposite to that of the toner image on the photosensitive drum 30 is applied to the transfer roller 34. By applying the charging bias, a positive charge is applied to the back surface of the transfer material P, whereby the negative toner image on the photosensitive drum 30 is transferred to the surface of the transfer material P. The transfer material P on which the toner image has been transferred by the reversal development is positively charged by the transfer bias at the time of transfer. On the other hand, the surface of the photosensitive drum 30 after the transfer of the toner image remains negative because the polarity at the time of charging is negative. Therefore, the transfer material P after the transfer of the toner image is electrically attracted to the surface of the photoconductor drum 30, so that it is difficult to perform good separation. In particular, the rear end portion of the transfer material P moves so as to be dragged by the rotation of the photosensitive drum 30 because positive charges are concentrated.
[0042]
As shown in FIG. 2, the transfer material P after the transfer of the toner image is separated from the surface of the photosensitive drum 30 by a separation member 60 which is a main component of the transfer separation mechanism. Here, a straight line L1 in FIG. 2 is formed between the transfer nip portion N1 formed between the photosensitive drum 30 and the transfer roller 34, and between the fixing roller 51 and the pressure roller 52 of the fixing device 43. The line L2 is a straight line connecting the transfer material P to the fixing nip N2, and the straight line L2 is a straight line connecting the transfer material P when the transfer material P is stretched between the transfer nip N1 and the fixing nip N2. It is a straight line indicating a position. In the present embodiment, a plane S1 including the shaft 30a of the photosensitive drum 30 and a shaft 34a of the transfer roller 34, and a plane S2 including a shaft 51a of the fixing roller 51 and a shaft 52a of the pressure roller 52 Considering the above, the latter plane S2 is arranged substantially horizontally, and the former plane S1 is arranged at the lower left in FIG. That is, the plane S1 and the plane S2 are configured such that the transfer roller 34 and the pressure roller 52 corresponding to the back side of the transfer material P spread in a substantially C shape. Therefore, when the transfer material P after the transfer of the toner image is smoothly separated from the surface of the photosensitive drum 30, the transfer material P is guided by the conveyance guide 42 and the pre-fixing guide 61 disposed above the conveyance guide 42 in FIG. As indicated by P1 in the middle, the toner is supplied to the fixing nip portion N2 in a state of being gently curved to the left.
[0043]
The above-described separating member 60 is formed of an insulating material (for example, an insulating synthetic resin or ceramic), and is attached to a frame 35 a constituting a part of the above-described cleaning device 35. The separating member 60 has a separating surface 62 on a side near the surface of the photosensitive drum 30 and an auxiliary separating surface 63 on a side farther from the surface facing the transport guide 42. The separation surface 62 is formed in a flat shape connecting a leading edge 62a close to the photosensitive drum 30 and a top portion 62b serving as a boundary between the auxiliary separation surface 63, and the separation surface 62 itself or its extension is formed by the straight line L1 described above. , And obliquely intersects the straight line L2, and further narrows the transport path of the transfer material P toward the downstream side. The position of the leading edge 62a of the separation surface 62 is set to a position on the right side of the straight line L1 and close to the surface of the photosensitive drum 30 in a non-contact manner. The position of the top 62b is set on the straight line L1 or at a position near the straight line L1. On the other hand, the auxiliary separation surface 63 is formed in a planar shape on the downstream side so as to be continuous with the top portion 62b. The inclination angle of the auxiliary separation surface 63 with respect to the straight line L1 or the straight line L2 is set to be smaller than the inclination angle of the separation surface 62. Thus, the top portion 62b is provided in a convex shape with respect to the transport guide 42. The thickness of the separation member 60 (the thickness in the direction along the axis 30a of the photoconductor drum 30) may be set appropriately on condition that sufficient mechanical strength can be secured. In addition, the number of sheets arranged in the direction along the axis 30a may be determined as needed. For example, a total of three sheets at positions corresponding to the central portion and the left and right ends of the transfer material P (length in the direction along the axis 30a) of the transfer material P, and two sheets are added between them. It can be set to five sheets.
[0044]
With this configuration, the separation member 60 can satisfactorily separate the transfer material P on which the toner image has been formed by the reversal development. That is, since the transfer material P at the time of separation has a polarity opposite to that of the photosensitive drum 30 as described above, it is generally difficult to satisfactorily separate the transfer material P. However, the above-described separation member 60 has an insulating material. The separation surface 62 is formed so as to obliquely intersect the straight line L 1, and is formed so as to narrow the transfer path of the transfer material P toward the downstream side. The transfer material P at the time of separation collides with the separation surface 62 or the top portion 62b, and is moved to the back surface side, that is, the conveyance guide 42 side. Therefore, the transfer material P is favorably separated from the surface of the photosensitive drum 30 not only at the front end but also at the rear end.
[0045]
Further, in the present embodiment, the above-described plane S1 and plane S2 are configured so as to spread in a substantially C-shape to the left in FIG. 1, and the transfer material nipped and conveyed by the fixing nip portion N2. Since P has a tendency to curve as indicated by P1 in the figure, good separation of the transfer material P is promoted by the waist (rigidity) of the transfer material P itself.
[0046]
Further, the transport guide 42 that is disposed to face the separation member 60 and contacts the back surface of the transfer material P is configured by a grounded conductive member, and is opposed to the top 62 b of the guide surface 42 a of the transport guide 42. The guide rib described below is not provided at the position M and on the upstream side of the position M, and the guide surface 42a is directly opposed. Therefore, the portion of the separated transfer material P that is moved toward the transport guide 42 by the separation surface 62 and the top 62b of the separation member 60 is likely to be electrically attracted to the position M and the upstream side thereof. . Then, when the transfer material P comes into direct contact with the transport guide 42, the charge is removed, and there is also an effect that the subsequent transport becomes smooth.
[0047]
On the downstream side of the position M on the guide surface 42a of the transport guide 42, there is provided an insulating guide rib 64 for gradually increasing the protruding amount h from the guide surface 42a toward the downstream side. The thickness of the guide rib 64 in the direction along the axis 30a of the photosensitive drum 30 is, for example, equal to that of the separation member 60, and the arrangement position thereof is set to a position facing the separation member 60. do it.
[0048]
Since such a guide rib 64 is provided on the conveyance guide 42, the transfer material P separated from the surface of the photosensitive drum 30 by the separation member 60 first contacts the upstream side of the position M in the conveyance guide 42. As the charge is removed and further conveyed downstream beyond the position M, the guide rib 64 moves away from the guide surface 42a of the conveyance guide 42. For this reason, the conveyance resistance is reduced, and the smooth conveyance of the transfer material P can be promoted.
[0049]
It can be said that the above-mentioned separating member 60 is operatively combined with the separating claw 109, the rib 115, and the separating roller 116 in the conventional example described with reference to FIG. That is, in the present embodiment, the configuration of the transfer material separating mechanism can be simplified by employing the separating member 60 as described above.
[0050]
Since the conventional separation claw 109 is arranged so as to be in contact with the surface of the photosensitive drum 30, the contact angle is greatly restricted in order not to damage the surface of the photosensitive drum 30. Was. On the other hand, in the present embodiment, the separating member 60 does not contact the surface of the photosensitive drum 30. Therefore, from the viewpoint of scratches on the surface of the photosensitive drum 30, the angle of the separation surface 62 with respect to the surface of the photosensitive drum 30 can be set arbitrarily. For this reason, in the present embodiment, the angle of the separation surface 62 can be suitably determined with the separation of the transfer material P as a main viewpoint, and a good separation can be realized accordingly.
[0051]
It is sufficient that the transfer material separating mechanism according to the present invention includes the above-described separating member 60 as a component, and the transport guide 42 and the guide rib 64 may be added as necessary. . Further, the arrangement of the photosensitive drum 30, the transfer roller 34, and the fixing device 43 (see the planes S1 and S2 in FIG. 2) for easily separating the transfer material P may be included in the transfer material separation mechanism. That is, in the present invention, the separating member 60 alone can improve the separability of the transfer material P, and the separability can be further improved each time the above-mentioned other components are added. It is.
[0052]
The transfer material separating mechanism having the above-described structure satisfactorily separates the transfer material P after the transfer of the toner image from the surface of the photosensitive drum 30, and contaminates other members due to disturbance of the unfixed toner image and scattering of the unfixed toner. Can be prevented. Moreover, these effects can be realized with a simple configuration. Therefore, the image forming apparatus provided with such a transfer material separating mechanism can simplify the entire configuration and can prevent an image defect due to a separation failure of the transfer material P beforehand.
[0053]
In the above description, an example in which the transfer material separating mechanism according to the present invention is applied to an electrophotographic image forming apparatus (copier) has been described. The present invention can also be applied to a recording type image forming apparatus. Further, the present invention can be applied not only to a monochrome image forming apparatus but also to a color image forming apparatus.
[0054]
【The invention's effect】
As described above, according to the transfer material separation mechanism of the present invention, the separation member is provided between the transfer nip portion and the fixing unit disposed on the downstream side of the transfer nip portion along the transfer direction of the transfer material. When assuming a stretched transfer material, this separation during transfer is performed by a separation surface that is inclined in a direction obliquely intersecting the assumed transfer material and in a direction to narrow the transfer material transport path toward the downstream side. Since the transfer material colliding with the surface can be moved to the back surface side, unlike the conventional example, the unfixed toner image on the transfer material surface is not disturbed by being rubbed by the ribs. That is, with a simple configuration, smooth separation without disturbing the toner image can be realized.
[0055]
Further, according to the image forming apparatus provided with the above-described transfer material separating mechanism, it is possible to simplify the overall configuration and prevent an image defect due to a separation defect.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present invention.
FIG. 2 is a schematic configuration diagram of a transfer material separating mechanism according to the present invention.
FIG. 3 is a diagram illustrating a conventional separation of a transfer material.
[Explanation of symbols]
Reference numeral 10: copying machine (image forming apparatus), 30: photosensitive drum, 31: primary charger (charging unit), 32: exposure unit (exposure unit), 33: developing unit (developing unit), 34 ... Transfer roller (transfer means, transfer charger),..., Conveyance guide, 42a guide surface, 43 fixing device (fixing means), 60 separating member, 62 separating surface, 62b Top, 63 ... Auxiliary separation surface, 64 ... Guide rib, h ... Projection amount of the guide rib from the guide surface, N1 ... Transfer nip, N2 ... Fixing nip, P ... Transfer material,

Claims (6)

The transfer material, on which the toner image on the photosensitive drum is transferred by being inserted into a transfer nip portion between a photosensitive drum having a toner image formed on its surface and a transfer roller to which a transfer bias is applied, is transferred to the photosensitive drum. In the transfer material separation mechanism that separates from the surface,
An insulating property is disposed downstream of the transfer nip portion along the moving direction of the photosensitive drum surface and opposed to the photosensitive drum surface to separate the transfer material after toner image transfer from the photosensitive drum surface. With a separating member of
A plane including the axis of the photoconductor drum and the axis of the transfer roller is defined as a first plane, and the pressure of the axis of the fixing roller of the fixing unit located in the conveyance path downstream of the transfer nip in the sheet conveyance direction is pressed. Assuming that a plane including the axis of the roller is a second plane, the first plane and the second plane are arranged in a substantially C-shape, and the transport path is sent out from the transfer nip portion. The transfer material is gently curved and supplied to a fixing nip between the fixing roller and the pressure roller,
When the transfer member is assumed to be stretched between the transfer nip portion and the fixing nip portion , the separation member is disposed in a direction obliquely intersecting the assumed transfer material and the transfer of the transfer material. Having a separating surface inclined in a direction to narrow the road toward the downstream side,
The leading edge of the separation surface, the the surface of the photosensitive drum, is placed constantly in a position adjacent a non-contact,
A transfer material separating mechanism. The separating member has a top portion located on the most downstream side of the separation surface along the transfer direction of the transfer material, and an auxiliary separation surface continuous with the top portion,
The auxiliary separation surface, the inclination angle with respect to the assumed transfer material is smaller than the separation surface,
The transfer material separating mechanism according to claim 1, wherein: A grounded conductive conveyance guide is provided between the transfer nip portion and the fixing unit, and guides a back surface of the transfer material conveyed between the transfer member and the separation member.
The transfer material separating mechanism according to claim 1, wherein: A photosensitive drum,
Charging means for charging the photosensitive drum surface,
Exposure means for exposing the photosensitive drum surface after the charging to form an electrostatic latent image,
Developing means for developing the electrostatic latent image as a toner image;
Transfer means for transferring the toner image on the photosensitive drum to a transfer material,
Separating means for separating the transfer material after the transfer of the toner image from the surface of the photosensitive drum,
Fixing means for fixing the toner image on the transfer material after the separation,
The transfer material separating mechanism according to claim 1, 2, or 3,
An image forming apparatus comprising: The fixing unit is located above the transfer nip portion,
The image forming apparatus according to claim 4, wherein: A toner image formed on the photosensitive drum is formed by reversal development,
The image forming apparatus according to claim 4, wherein:

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