JP3601211B2 - Image forming device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus using an electrostatic transfer process, and more particularly, to an electrostatic copying machine, an electrostatic printer, and the like.
[0002]
[Prior art]
As a well-known image forming apparatus for transferring a transferable toner image formed on the surface of an image carrier to a transfer material such as paper, a transfer roller, a transfer belt, or the like is used as a transfer unit. It is well known that the nip portion for contacting the two with each other and pressing each other is set as a transfer position for transferring the toner image from the image carrier to the transfer unit.
[0003]
In this image forming apparatus, the toner image on the image carrier and the transfer material are supplied to the transfer position at the same time, and a transfer bias is applied to the transfer unit to transfer the toner image on the image carrier. It is made to transfer to wood.
[0004]
Here, FIGS. 10 and 11 are schematic cross-sectional views of main parts showing portions related to transfer and transfer of a transfer material to a transfer position of an image forming apparatus using a transfer roller as a transfer unit. The prior art will be described with reference to the drawings.
[0005]
As shown in these figures, the primary charger and the image signal applying means (not shown), the developing device including the developing roller 114 and the developing housing 116, and the like have an axis perpendicular to the drawing and have an arrow. A toner image is formed on the surface of the photosensitive drum 112 that rotates in the direction. This toner image is sent to a transfer position C formed as a nip portion between the photosensitive drum 112 and the transfer roller 118 pressed against the photosensitive drum 112.
[0006]
When the toner image reaches the transfer position C, the toner image is conveyed by a pair of conveying rollers 120 in a timely manner, and is guided by a lower transfer guide 122 and an upper transfer guide 124 in the structure shown in FIG. In the structure shown in FIG. 11, a transfer material (not shown) is guided by the lower transfer guide 122 and the upper transfer guide 126, and is supplied to the transfer position C as shown by an arrow. Accordingly, a transfer bias having a polarity opposite to that of the toner is applied to the transfer roller 118, and the toner image on the photosensitive drum 112 is transferred to the transfer material.
[0007]
At this time, a method in which a toner image is formed on a bright portion potential on the photosensitive drum 112, that is, a portion where the surface potential is lowered by the image signal applying means is called a reversal developing method, and is particularly used in a laser printer. I have. However, in such a system, the charging polarity of the toner and the photosensitive drum 112 is the same, and the toner adheres to a portion having a low potential. There is a disadvantage that the toner on the drum 112 is easily scattered around.
[0008]
On the other hand, in recent years, the size of the image forming apparatus has been reduced, and members around the photosensitive drum 112 are arranged as close to the photosensitive drum 112 as possible. In particular, as shown in FIG. 10, the downstream end portion 124A of the upper transfer guide 124 located downstream in the transfer material movement direction, or the upper transfer guide 126 located downstream in the transfer material movement direction as shown in FIG. Is downstream of the photosensitive drum 112. Therefore, the toner on the photosensitive drum 112 tends to adhere to these downstream end portions 124A and 126A.
[0009]
In the case of the structure shown in FIG. 10, the charging polarity of the photosensitive drum 112 and the toner is negative and the transfer bias is positive, and the upper transfer guide 124 is mainly positive due to frictional charging with the transfer material and the transfer bias of the transfer roller 118. Charge. For this reason, an electric field acts between the toner on the photosensitive drum 112 and the toner is attracted to the upper transfer guide 124 by the electrostatic force. The toner mainly adheres and accumulates on the opposing surface 124C opposing the photosensitive drum 112, and when the opposing surface 124C is full of toner, the toner flows from the ridge line 124D to the guide surface 124B.
[0010]
The transfer material is guided and conveyed by the guide surface 124B. In such a situation, the leading end and the rear end of the transfer material scrape off the toner adhering to and depositing on the guide surface 124B from the ridgeline 124D. Toner stain occurs on the leading edge and the trailing edge of the transfer material. The same phenomenon occurs in the structure shown in FIG.
[0011]
On the other hand, Japanese Patent Application Laid-Open No. Sho 60-112082 discloses that the above-mentioned toner contamination is improved by grounding a conductive transfer guide via a resistance element and keeping the potential of the transfer guide within a predetermined range. Have been proposed.
[0012]
However, the charge distribution of the toner has a certain spread, and even if the potential of the transfer guide is suppressed to a low positive polarity, the adhesion of the negatively charged toner cannot be completely prevented. As a result, even if the structure of this publication is adopted, the toner adheres little by little to the opposing surface 124C shown in FIG. 10, and the toner deposited on the ridge line 124D goes around the guide surface 124B side, and the leading end of the transfer material and Toner contamination occurs at the rear end.
[0013]
Japanese Patent Publication No. Hei 5-79988 proposes a method in which a DC component of a developing bias is applied to a conductive transfer guide to make the same potential as the developing bias, thereby preventing toner contamination of the transfer guide. .
[0014]
In the device disclosed in this publication, the average charge amount of the toner and the potential of the transfer guide are adjusted to the same potential, so that the toner is less likely to be stained than that described above. There is a small amount of charged toner, and this positively charged toner is attracted to the guide. For this reason, the adhesion of the toner to the transfer guide gradually proceeds, albeit little.
[0015]
When the transfer guide is set to a negative potential, a transfer current leaks from the transfer guide when the resistance of the transfer material decreases in a high humidity environment. As a result, the transfer material cannot maintain the transfer potential, which causes a problem of transfer failure.
[0016]
Further, Japanese Patent Application Laid-Open No. 2-168278 discloses that an upper transfer guide is provided in a process cartridge and the amount of toner deposited on the upper transfer guide is limited by replacing the process cartridge with the life of the process cartridge. Further, there is disclosed an apparatus which reduces toner stain on the rear end. However, even when the structure of this publication is adopted, a remarkable effect cannot be obtained under severe conditions such as the above-described reversal development system and downsizing of the apparatus.
[0017]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described disadvantages of the related art, and has as its object to provide an image forming apparatus in which toner smear does not occur on a leading edge portion and a trailing edge portion of a transfer material.
[0018]
[Means for Solving the Problems]
An image forming apparatus according to claim 1, wherein an image carrier having a surface on which a toner image is formed;
A transfer charging member for electrostatically transferring the toner image of the image carrier to the transfer material by sandwiching the transfer material with the image carrier,
A guide member that guides the transfer material to a transfer position where the transfer material is sandwiched between the image carrier and the transfer charging member and the toner image is transferred;
In the image forming apparatus having
The end of the guide member, which is the downstream portion in the moving direction of the transfer material And a step in the thickness direction of the guide member and in the moving direction of the transfer material is provided at the end of the guide member located near the image carrier. It is characterized by having been formed.
[0019]
An image forming apparatus according to a second aspect is the image forming apparatus according to the first aspect, Located near the image carrier Of the plurality of steps of the guide member, the end of the step closest to the image carrier is
Located near the image carrier The transfer material is located at a position closer to the transfer position from a line connecting the most downstream end in the moving direction of the transfer material in the guide surface for guiding the transfer material of the guide member and the center point of the image carrier. In a position where it does not touch,
It is characterized by being arranged.
[0020]
An image forming apparatus according to a third aspect of the present invention is the image forming apparatus according to the first aspect, wherein the end portion of the guide member that is a portion on the downstream side in the moving direction of the transfer material. And an end portion of the guide member located near the image carrier. A plurality of depressions are provided in any of the plurality of steps formed in the first step.
[0021]
An image forming apparatus according to a fourth aspect is the image forming apparatus according to the first aspect, Located near the image carrier The most downstream end in the moving direction of the transfer material in the guide surface for guiding the transfer material of the guide member,
The image carrier is arranged at a position closer to the image carrier from a tangent line of the image carrier at the transfer position.
[0022]
The operation of the image forming apparatus according to claim 1 will be described below.
A guide member guides the transfer material to a transfer position where the toner image is transferred, sandwiches the transfer material between the image carrier and the transfer charging member, and electrostatically transfers the toner image on the image carrier to the transfer material. .
[0023]
Further, an end portion of the guide member which is a portion on the downstream side in the moving direction of the transfer material. And an end portion of the guide member located near the image carrier. However, since it is formed in a step-like shape including a plurality of steps, a portion that actively captures the toner on the image carrier is Located near the image carrier A portion formed on the guide member and in contact with the leading and trailing ends of the transfer material is formed away from the portion that actively captures the toner.
[0024]
As a result, the toner is less likely to adhere to the portion of the guide member that comes into contact with the leading and trailing edges of the transfer material, thereby preventing toner from adhering to the leading and trailing edges of the transfer material and greatly reducing toner contamination. Can be reduced.
[0025]
The operation of the image forming apparatus according to claim 2 will be described below.
The present invention has the same effect as the first embodiment. However, this claim Located near the image carrier Of the plurality of steps of the guide member, the end of the step closest to the image carrier is Located near the image carrier The transfer material is located at a position closer to the transfer position from a line connecting the most downstream end in the moving direction of the transfer material in the guide surface for guiding the transfer material of the guide member and the center point of the image carrier. It is configured to be arranged at a position where it does not touch.
[0026]
Therefore, it becomes the shadow of the step closest to the image carrier, Located near the image carrier It is possible to prevent the guide surface of the guide member from directly opposing the image carrier, and to reliably prevent toner from adhering to the guide surface that guides the transfer material by contacting the leading and trailing ends of the transfer material. , The toner stain on the leading edge portion and the trailing edge portion can be further reduced.
[0027]
The operation of the image forming apparatus according to claim 3 will be described below.
The present invention has the same effect as the first embodiment. However, the present invention is directed to an end portion of the guide member which is a portion on the downstream side in the moving direction of the transfer material. And an end portion of the guide member located near the image carrier. Is provided with a plurality of depressions in any of the plurality of steps formed in the first step.
[0028]
Therefore, even if the toner spills out, the toner can be stored in the recess, and the toner stain on the transfer material can be minimized.
[0029]
The operation of the image forming apparatus according to claim 4 will be described below.
The present invention has the same effect as the first embodiment. However, this claim Located near the image carrier The most downstream end in the moving direction of the transfer material in the guide surface for guiding the transfer material of the guide member is arranged at a position closer to the image carrier from a tangent to the image carrier at the transfer position. .
[0030]
Therefore, the rear end of the transfer material is not hit against the image carrier, and the transferred image at the rear end of the transfer material is not disturbed. The rear end of the transfer material does not hit the paper end more strongly than necessary and does not pass through, so that the unstable behavior of the rear end of the transfer material can be suppressed. Further, according to the present invention, the effect of preventing toner contamination on the trailing edge of the transfer material can be reliably improved.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
A laser beam printer as an embodiment of an image forming apparatus according to the present invention is shown in the drawings, and the present embodiment will be described below based on the drawings. First, FIG. 3 shows a simplified cross-sectional view of the laser beam printer 10 capable of printing up to A3 size paper.
[0032]
As shown in FIG. 1, a photosensitive drum 12, which is an image carrier, is rotatably arranged in a laser beam printer 10, and a charging roller 14 for charging the surface of the photosensitive drum 12, and an electrostatic latent image is visualized. A developing roller 16 and a transfer roller 18 serving as a transfer charging member are arranged in parallel with the photosensitive drum 12 while being in contact with the photosensitive drum 12. For this reason, the transfer material P is sandwiched between the photosensitive drum 12 having a toner image formed on the surface thereof and the transfer roller 18 for electrostatically transferring the toner image on the photosensitive drum 12 to the transfer material P. The image is transferred to the transfer material P. Then, a position where the transfer material P is sandwiched between the photosensitive drum 12 and the transfer roller 18 is defined as a transfer position C.
[0033]
The developing roller 16 is housed in a developing housing 24 that forms an outer frame of a developing device 22 having a portion facing the photosensitive drum 12 opened, and an image signal is applied to the developing device 22 and the photosensitive drum 12 by a laser beam. An exposure device 26 for feeding at L and a fixing device 28 for fixing the toner image transferred to the transfer material P by the photosensitive drum 12 are arranged in the laser beam printer 10.
[0034]
Further, on the lower side of the photosensitive drum 12, a plurality of types of transfer materials P, which are papers having different sizes, are installed. From the portions where the transfer materials P are installed, the transfer position C and the fixing device 28 are determined. A transfer material transport path T indicated by an arrow is formed by a transport roller and guides to the outside of the laser beam printer 10 through the like.
[0035]
On the other hand, a pair of transport rollers 36 is disposed on the upstream side in the transport direction of the transfer material P with respect to the transfer position C, and between the transfer position C and the pair of transport rollers 36, the transfer position C is set. An upper transfer guide 40 and a lower transfer guide 38, which are guide members for guiding the transfer material P, are arranged with the transfer material transport path T interposed therebetween.
[0036]
Next, an image forming process by the laser beam printer 10 will be briefly described.
[0037]
First, the surface of the photosensitive drum 12 serving as a photosensitive layer is uniformly charged by the charging roller 14, and an image signal indicated by a laser beam L is sent from the exposure device 26 to the photosensitive drum 12, and an electrostatic latent image is formed on the surface of the photosensitive drum 12. To form This electrostatic latent image is visualized by the action of the developing device 22 including the developing roller 16 and the developing housing 24, and a toner image is formed on the surface of the photosensitive drum 12.
[0038]
Along with this, the transfer material P passes through the transfer material transport path T indicated by the arrow, is guided by the upper transfer guide 40 and the lower transfer guide 38, and is sent to the transfer position C. Then, by applying a transfer bias to the transfer roller 18, the toner image is transferred to the transfer material P, and the transferred toner image is heated by the fixing device 28 and fixed to the transfer material P, thereby completing the image forming process. I do.
[0039]
Thereafter, the transfer material P is discharged out of the laser beam printer 10 through the transfer material transport path T. At this time, the remaining toner on the photosensitive drum 12 that has not been transferred to the transfer material P is scraped off by a cleaning blade 34 of a toner collecting unit 32 provided adjacent to the photosensitive drum 12, and is transferred to the toner collecting unit 32. Will be accommodated.
[0040]
As shown in FIGS. 1 and 2, which are main parts of the first embodiment, the downstream end 40 </ b> A of the upper transfer guide 40 located near the photosensitive drum 12, which is the end on the photosensitive drum 12 side, has three ends. It has the shape of a step structure. Then, among the three opposing surfaces 42A, 42B, and 42C opposing the photosensitive drum 12 at the downstream end 40A, the opposing surfaces 42A, 42B, and 42C are arranged in this order from the surface closest to the photosensitive drum 12. ing.
[0041]
Of the surfaces connecting the three opposing surfaces 42A, 42B, and 42C, the surface between the opposing surfaces 42A and 42B is a connecting surface 44A, and the surface between the opposing surfaces 42B and 42C is connected. Surface 44B. A guide surface 40B of the upper transfer guide 40 facing the lower transfer guide 38 contacts the transfer material P to guide the transfer material P to the transfer position C, and an opposing surface 42C adjacent to the guide surface 40B and the guide surface 40C. A line intersecting with the surface 40B forms a ridge line 46A.
[0042]
Next, the operation of the present embodiment will be described.
The transfer material P is transported by the transport rollers 36 to the transfer position C where the toner image is transferred to the transfer material P, and the transfer material P is guided by the upper transfer guide 40 and the lower transfer guide 38, and is transferred to the photosensitive drum 12 The toner image on the photosensitive drum 12 is electrostatically transferred to the transfer material P by sandwiching the transfer material P with the roller 18.
[0043]
Further, with the above-described structure, the upper transfer guide 40 is positively charged due to friction with the transfer material P and the influence of the transfer bias, and the toner on the photosensitive drum 12 is negatively charged. Then, the negatively charged toner on the photosensitive drum 12 can be attracted to the downstream end 40A of the positively charged upper transfer guide 40 and adhere to the downstream end 40A. The toner adheres to the facing surface 42A of the portion 40A.
[0044]
That is, since the photosensitive drum 12 is rotating in the direction of the arrow, the facing surface 42A is the surface of the upper transfer guide 40 that first faces the toner on the photosensitive drum 12 developed at the position of the developing roller 16. Further, the fact that the facing surface 42A is the surface closest to the photosensitive drum 12 among the surfaces facing the photosensitive drum 12 causes the toner to adhere to the facing surface 42A first.
[0045]
In particular, since the facing surface 42A is the surface closest to the photosensitive drum 12, the electric field acting between the upper transfer guide 40 and the photosensitive drum 12 becomes the strongest as compared with the other facing surfaces 42B and 42C. The toner on the photosensitive drum 12 having a weak adhesive force among the toners on the photosensitive drum 12 is captured and attached to the facing surface 42A of the upper transfer guide 40.
[0046]
Furthermore, when the opposing surface 42A is full of the attached toner, the toner wraps around to the connecting surface 44A adjacent to the opposing surface 42A. Separately from this, when the electric field acting between the opposing surface 42A and the photosensitive drum 12 is weakened by the negative charge of the accumulated toner, the toner having a weak adhesion to the photosensitive drum 12 is next drawn to the opposing surface 42B, It adheres and accumulates on the facing surface 42B.
[0047]
On the other hand, the transfer material P is guided by the guide surface 40B of the upper transfer guide 40 and is conveyed to the transfer position C. At this time, the leading end or the rear end of the transfer material P has a ridgeline 46A just before leaving the guide surface 40B. Contact. When the toner adheres to the ridgeline 46A and the guide surface 40B, the transfer material P comes into contact with the ridgeline 46A and the guide surface 40B when the transfer material P passes, and the toner is scraped off. Toner staining will occur.
[0048]
However, in the present embodiment, the ridge line 46A is separated from the opposing surface 42A that captures the toner, and the structure is such that the toner does not easily adhere to the ridge line 46A. It is possible to greatly reduce toner contamination on the edge portion and the rear end edge portion.
[0049]
That is, since the end portion of the upper transfer guide 40, which is a portion on the downstream side in the moving direction of the transfer material P, is formed in a step-like shape including a plurality of steps, a portion that actively captures the toner on the photosensitive drum 12 is provided. The portion formed on the upper transfer guide 40 and in contact with the front and rear ends of the transfer material P is formed away from the portion that actively captures the toner. As a result, the toner hardly adheres to the portion that comes into contact with the leading and trailing ends of the transfer material P.
[0050]
Next, a second embodiment of the present invention is shown in FIGS. 4 and 5, and the present embodiment will be described with reference to these drawings. The same members as those in the first embodiment are denoted by the same reference numerals, and duplicate description will be omitted.
[0051]
The laser beam printer 10 of the present embodiment has substantially the same structure as the first embodiment and has the same function. However, in the present embodiment, as shown in FIGS. The upper transfer guide 40 is formed by a part of the developing housing 24 of the process cartridge 22 and the downstream end 40A, which is the end on the photosensitive drum 12 side, has a tapered shape in which the front end side is expanded.
[0052]
In the case of such a structure, not only the number of components can be reduced, but also the toner stain on the leading edge portion and the trailing edge portion of the transfer material P can be prevented as in the first embodiment. In the case of this structure, the upper transfer guide 40 is successively replaced together with the process cartridge due to the life of the process cartridge, so that it is more advantageous for toner contamination than in the case of the first embodiment.
[0053]
Next, the present invention As a reference example of the embodiment, An embodiment is shown in FIG. 6, and the present embodiment will be described with reference to FIG. The same members as those in the first embodiment are denoted by the same reference numerals, and duplicate description will be omitted.
[0054]
The laser beam printer 10 according to the present embodiment has substantially the same structure as the first embodiment and performs the same function. However, in the present embodiment, as shown in FIG. The end on the photosensitive drum 12 side is constituted by a downstream end 40A of the upper transfer guide 40 and a part of the developing housing 24 of the process cartridge.
[0055]
In other words, a line intersecting the guide surface 40B with the opposing surface 42C adjacent to the guide surface 40B of the upper transfer guide 40 forms a ridge line 46A, and the distal end side of the outer wall of the developing housing 24 is bent to An opposing surface 24A is formed.
[0056]
With such a structure, the toner 24 having a weak adhesive force on the photosensitive drum 12 is captured by the facing surface 24A of the developing housing 24 facing the photosensitive drum 12, and the toner adheres to the ridge line 46A of the upper transfer guide 40. Can be prevented.
[0057]
Also, in the present embodiment, similarly to the second embodiment, the opposed surface 24A on which the toner is deposited is sequentially replaced together with the process cartridge due to the life of the process cartridge. This is advantageous for toner contamination.
[0058]
Next, a fourth embodiment of the present invention is shown in FIG. 7, and the present embodiment will be described with reference to FIG. The same members as those in the first embodiment are denoted by the same reference numerals, and duplicate description will be omitted.
[0059]
The laser beam printer 10 according to the present embodiment has substantially the same structure as the first embodiment and performs the same operation. However, in the present embodiment, as shown in FIG. The downstream end 40A has a two-stage structure, and the end of the opposing surface 42A of the upper transfer guide 40 near the transfer position C is defined as a ridgeline 46B. Further, the transfer material P is transported along the transfer material transport path T indicated by an arrow.
[0060]
Further, a distance between the center point X of the photosensitive drum 12 and a ridge line 46A which is the most downstream end in the moving direction of the transfer material P on the guide surface 40B which contacts the transfer material P and guides the transfer material P to the transfer position C. The connecting line is defined as a line segment L1.
[0061]
Then, the ridge line 46B, which is the end of the opposing surface 42A of the upper transfer guide 40, is arranged on the line L1 or on the transfer position C side of the line L1 and does not contact the transfer material transport path T. As a result, it becomes a shadow of the opposing surface 42A closest to the photosensitive drum 12, and it is possible to prevent the guide surface 40B including the ridge line 46A from directly opposing the photosensitive drum 12, and to the guide surface 40B including the ridge line 46A. Is reliably prevented, and toner contamination on the leading edge and the trailing edge of the transfer material P can be further reduced.
[0062]
Therefore, when the structure of this embodiment is applied to the first, second, and third embodiments, the effect of preventing toner from adhering to the ridge line 46A can be enhanced.
[0063]
Next, a fifth embodiment of the present invention is shown in FIG. 8, and the present embodiment will be described with reference to FIG. The same members as those in the first embodiment are denoted by the same reference numerals, and duplicate description will be omitted.
[0064]
The laser beam printer 10 according to the present embodiment has substantially the same structure as the first embodiment and performs the same operation. However, in the present embodiment, as shown in FIG. The downstream end 40A has a two-stage structure. When a tangent line of the photosensitive drum 12 at a transfer position C, which is a nip portion where the photosensitive drum 12 and the transfer roller 18 come into contact with each other, is L2, the transfer material P on the guide surface 40B of the upper transfer guide 40 at the most downstream end in the moving direction of the transfer material P A certain ridge line 46A is arranged on the tangent line L2 or at a position closer to the photosensitive drum 12 than the tangent line L2.
[0065]
That is, if the ridge line 46A is closer to the transfer roller 18 than the tangent line L2, when the rear end of the transfer material P leaves the ridge line 46A, a force is generated by the elasticity of the transfer material P to straighten the transfer material P. There is a possibility that the rear end of P is hit against the photosensitive drum 12 and the transfer image at the rear end of the transfer material P is disturbed. Further, when the ridge line 46A is closer to the transfer roller 18 than the tangent line L2, the rear end of the transfer material P hits the ridge line 46A more than necessary and passes through, so that the toner which does not normally cause a problem adheres to the ridge line 46A. Even when the transfer is performed, this is scraped to cause toner stain on the trailing edge of the transfer material P.
[0066]
However, according to the present embodiment, the behavior of the rear end of the unstable transfer material P can be suppressed. Further, if the structure of the present embodiment is applied to the first, second, and third embodiments, the effect of preventing toner stain on the trailing edge of the transfer material P can be reliably increased.
[0067]
Next, a sixth embodiment of the present invention is shown in FIG. 9, and the present embodiment will be described with reference to FIG. The same members as those in the first embodiment are denoted by the same reference numerals, and duplicate description will be omitted.
[0068]
Although the laser beam printer 10 of the present embodiment has substantially the same structure as the first embodiment and exerts the same effect, in the present embodiment, as shown in FIG. The downstream end portion 40A has a two-stage structure, and is adjacent to the guide surface 40B via a ridgeline 46A which is the most downstream end in the moving direction of the transfer material P on the guide surface 40B of the upper transfer guide 40. A plurality of depressions 48 each having a square shape are provided on the formed facing surface 42C.
[0069]
As a result, even if the toner spills out from the facing surface 42A onto the facing surface 42C, the toner can be stored in the concave portion 48, and the toner contamination of the transfer material P can be minimized. Can be.
[0070]
In the above-described embodiment, only the end of the upper transfer guide 40 in the guide member is formed in a step-like shape including a plurality of steps, but the end of the lower transfer guide 38 may also be formed in a step-like shape. .
[0071]
【The invention's effect】
As described above, according to the present invention, toner contamination on the leading edge and the trailing edge of the transfer material, which could not be solved by the conventional technology, is significantly reduced at low cost without adding any additional components. This has the effect that a good image can be obtained.
[Brief description of the drawings]
FIG. 1 is a schematic view of a main part of a first embodiment according to the present invention.
FIG. 2 is an enlarged view of a main part of FIG.
FIG. 3 is a simplified cross-sectional view of the laser beam printer according to the embodiment of the present invention.
FIG. 4 is a schematic view of a main part of a second embodiment according to the present invention.
FIG. 5 is an enlarged view of a main part of FIG. 4;
FIG. 6 is a schematic diagram of a main part of a third embodiment according to the present invention.
FIG. 7 is a schematic diagram of a main part of a fourth embodiment according to the present invention.
FIG. 8 is a schematic diagram of a main part of a fifth embodiment according to the present invention.
FIG. 9 is a schematic perspective view of a main part of a sixth embodiment according to the present invention.
FIG. 10 is a diagram illustrating an image forming apparatus according to a first related art.
FIG. 11 is a diagram illustrating an image forming apparatus according to a second related art.
[Explanation of symbols]
10 Laser beam printer (image forming device)
12 Photosensitive drum (image carrier)
18 Transfer roller (transfer charging member)
40 Upper transfer guide (guide member)
40A downstream end

Claims (4)

An image carrier on which a toner image is formed,
A transfer charging member for electrostatically transferring the toner image of the image carrier to the transfer material by sandwiching the transfer material with the image carrier,
A guide member that guides the transfer material to a transfer position where the transfer material is sandwiched between the image carrier and the transfer charging member and the toner image is transferred;
In the image forming apparatus having
An end portion of the guide member, which is a downstream portion of the transfer material in the moving direction of the transfer material, and an end portion of the guide member located closer to the image carrier is provided with a step in the thickness direction of the guide member and in the direction of movement of the transfer material. an image forming apparatus characterized by forming a. The end of the step closest to the image carrier among the plurality of steps of the guide member located near the image carrier,
From the line connecting the most downstream end of the transfer material in the guide surface, which guides the transfer material of the guide member positioned closer to the image carrier, and the center point of the image carrier, the transfer position is closer to the transfer position. In a position that does not contact the transfer material
The image forming apparatus according to claim 1, wherein the image forming apparatus is disposed. A plurality of depressions are formed in any one of a plurality of steps formed at the end of the guide member, which is a downstream portion of the transfer material in the moving direction of the transfer material, and at the end of the guide member located closer to the image carrier. The image forming apparatus according to claim 1, wherein the image forming apparatus is provided. The most downstream end in the moving direction of the transfer material in the guide surface for guiding the transfer material of the guide member located near the image carrier ,
2. The image forming apparatus according to claim 1, wherein the image forming apparatus is arranged at a position closer to the image carrier from a tangent line of the image carrier at the transfer position.

Images