JPH05313527A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent toner from sticking to the surface of a transfer roller and to achieve satisfactory transfer free of soiling of the back of a recording carrier by making the surface of the transfer roller rough. CONSTITUTION:In an image forming device which is provided with an image carrier 1 and a transfer roller which comes into pressure-contact with the image carrier 1, and which carries out transfer by passing the recording carrier 6 between both the rollers, the surface of the transfer roller is made rough compared to the average grain diameter of toner, and the foam member of the transfer roller is made of closed-cell foam. Even if toner on the image carrier 1 is brought into direct contact with the transfer roller, the area where the transfer roller is in contact with toner is small and it is a linear contact, so that the surface of the transfer roller is hardly soiled. Therefore, the satisfactory transfer where the back of the recording carrier 6 is not soiled and transfer efficiency is stable can be achieved in the simple structure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus utilizing an electrophotographic process in a copying machine, a printer or the like.

[0002]

2. Description of the Related Art A printing apparatus using an electrophotographic process is
In order to form a toner image on the image carrier, a charging device including a charging roller having a conductive member on the outer circumference of the shaft and a charging bias controller for applying a bias is provided.

Further, in order to transfer the toner image formed on the image carrier to the recording medium, there is provided a transfer device including a transfer roller having a conductive member on the outer periphery of the shaft and a transfer bias controller for applying a bias. There is.

Further, in order to fix the record carrier on which the toner image is transferred, there is provided a fixing device including a heating roller having a heating source and a pressure roller having an elastic body on the outer circumference of the shaft.

Further, in order to convey the record carrier,
A record carrier conveying roller made of an elastic body is provided in the front part of the transfer device and immediately after the fixing device.

The elastic roller of the charging device, the transfer device, and the fixing device is formed of a solid elastic member made of rubber or the like.

[0007]

However, the transfer roller of such a transfer device is used when a paper jam occurs, when a record carrier smaller than the size of the original image is used, or when the record carrier is used. In a region such as a space where the record carrier does not exist, the toner on the image carrier is transferred to the transfer roller, which causes a back stain on the record carrier to be passed next.

Further, since the toner attached to the transfer roller is higher than the resistance value in the thickness direction of the record carrier, the transfer electric field tends to be insufficient, and there is a problem that the image is cut off only in that part. It was

In order to avoid such a problem, there is a method of preventing the toner from adhering to the transfer roller by forming an electric field having the same polarity as that of the toner between the transfer roller and the image carrier during non-transfer. There has been proposed a means for cleaning a transfer roller having toner attached thereto by using a cleaning blade or a cleaning roller.

However, in the former method, the pressure of the transfer roller and the image carrier significantly increases the toner adhesion force, and an extremely high electric field is formed to prevent the adhesion due to the electric field of the same polarity as the toner. There is a need to. For that purpose, it is necessary to apply a high voltage between the transfer roller and the image carrier, and there is a problem that a pinhole is formed in the image carrier.

In the latter method, since the transfer roller has a relatively low hardness, the pressure of the cleaning blade is lowered, and the cleaning action is not sufficiently exerted, so that there is a problem that cleaning failure easily occurs. .. Further, due to friction with the cleaning blade, there are problems such as abrasion of the transfer roller and increase of rotation torque.

Further, the charging roller of the charging device has a drawback that toner due to transfer residue, background fog toner and the like are transferred and soiled when they cannot be completely cleaned by the cleaning means.

Since the toner attached to the charging roller is higher than the resistance value of the charging roller, the charging current tends to be insufficient, and the potential decreases only in that portion. There is a problem that toner adheres.

In order to avoid such a problem, there has been proposed a means for cleaning the charging roller attached with toner with a cleaning blade or a cleaning roller.

However, in this method, as with the transfer roller, since the charging roller has a relatively low hardness, the pressure of the cleaning blade is lowered, and the cleaning action is not sufficiently exerted. There is a problem. Further, due to friction with the cleaning blade, there are problems such as wear of the charging roller and increase of rotation torque.

Furthermore, in the fixing device, toner due to defective fixing once adheres to the heating roller, and thereafter,
There is a defect that when transferred between recording carriers or during idle rotation, they transfer to the surface of the pressure roller, which is inferior in releasability to the heating roller, and become dirty.

This causes the back surface of the recording medium to be passed next time to be soiled, and in a severe case, the toner adhering to the surface of the pressure roller adheres to the recording medium and wraps around the pressure roller to cause a paper jam. There was a problem of doing.

In order to avoid such problems, there have been proposed means such as applying oil to the surface of the pressure roller and forming a fluorine material having good releasability on the surface.

However, the former method has a drawback that the oil adheres to the back surface of the record carrier to deteriorate the print quality, and the outer shape accuracy and hardness of the elastic body are changed by the oil, causing wrinkles of the record carrier. There was a problem such as occurrence.

In the latter method, the surface hardness increases due to the fluorine material on the surface of the pressure roller. Therefore, in order to ensure optimum fixing conditions, the fixing pressure must be increased or the fixing set temperature must be increased. I have to. As a result, there is a problem in that curls and wrinkles occur on the record carrier.

In the record carrier carrying roller, when the unfixed image left in the image forming apparatus is taken out by a paper jam or the like, the surface of the record carrier carrying roller may be erroneously soiled. As a result, the rear surface of the record carrier on the next page is soiled, and there is a problem that the paper carrier cannot be recovered until several sheets are passed.

The present invention has been made in view of the above circumstances, and includes a transfer roller, a charging roller, a pressure roller,
An image forming apparatus for forming a recording carrier conveying roller with an elastic body, which has a simple structure, improves the toner releasability of the surface of the elastic body, and can obtain a good image without back stains. Is in the place of providing. Still another object is to provide an image forming apparatus that is easy to manufacture and low cost.

[0023]

In order to solve such a problem, the present invention comprises an image carrier and an elastic transfer roller which is in pressure contact with the image carrier, and recording is performed between the image carrier and the transfer roller. In an image forming apparatus that transfers images through a carrier, the surface roughness of the transfer roller elastic body is set to be larger than the average particle size of the toner used for image formation.

Further, the image forming apparatus of the present invention comprises an image carrier and an elastic charging roller which is pressed against the image carrier, and the image carrier and the charging roller are contact-rotated to charge the image forming apparatus. The surface roughness of the roller elastic body is
The size of the toner used was larger than the average particle size of the toner used for image formation.

Further, the image forming apparatus of the present invention comprises a heating roller and an elastic pressure roller which is in pressure contact with the heating roller, and the image is fixed by passing the recording medium between the heating roller and the pressure roller. In the forming apparatus, the surface roughness of the pressure roller elastic body is formed to be larger than the average particle diameter of the toner used for image formation.

Further, the image forming apparatus of the present invention is an image forming apparatus in which at least one of a pair of rollers is provided with a record carrier transporting roller made of an elastic body, and the record carrier is transported between both rollers. The surface roughness of the record carrier transport roller made of an elastic material is set to be larger than the average particle diameter of the toner used for image formation. Further, in the image forming apparatus of the present invention, the transfer roller elastic body and the charging roller elastic body are formed of a foamed member made of soft foam, and polyurethane foam, polystyrene foam, polyethylene foam, polyester foam, elastomer foam, silicon foam, synthetic It was made of either rubber foam.

Further, in the image forming apparatus of the present invention, the pressure roller elastic body is formed of soft rubber or soft foam,
It is made of silicone rubber, silicone foam or the like.

Further, in the image forming apparatus of the present invention, the foaming members of the transfer roller elastic body, the charging roller elastic body, and the pressure roller elastic body are single bubbles.

[0029]

【Example】

(Embodiment 1) Therefore, details of the present invention will be described below based on illustrated embodiments.

FIG. 1 is a schematic sectional view showing a main part of an electrophotographic printing apparatus using a transfer roller, a charging roller, a pressure roller and a record carrier conveying roller according to the present invention. The image carrier is an optical signal generator 2 which rotates in the direction of arrow D in the figure, that is, in the direction of moving the record carrier 6 to the left, and which generates an optical beam at the upper part.
A charging device 3, a developing device 4, and an erase unit 5 are arranged around the image carrier 1. Below the image carrier 1, a transfer device 7 for transferring the toner image onto the recording carrier 6 is arranged. Further, on the left side of the transfer device 7, a fixing device 11 for transferring and fixing the record carrier 6 by the transfer device 7 is arranged. Further, at the exit of the fixing device and upstream of the transfer device 7, a pair of record carrier transport rollers 18 for transporting the record carrier 6 is arranged.

FIG. 2 is a transfer device showing an embodiment of the image forming apparatus of the present invention, in which reference numeral 8 is a transfer roller,
A transfer bias controller 14 applies a bias to the transfer roller and is connected to the transfer roller shaft 9. The transfer roller 8 is held by a bearing 15, and a pressure spring 16 is arranged so as to press the transfer roller 8 against the image carrier 1 via the bearing 15. Further, the transfer roller 8 is configured to be connected to a drive source via a drive gear 17. The average particle size of the toner used in this embodiment is 12 μm.
m.

Next, the elastic body forming the transfer roller will be described. A foam member is formed around the transfer roller shaft 9. The surface roughness Rz is set to 12 μm or more so as to be larger than the average particle diameter of the toner used for image formation.

Such an elastic body is formed so that the foamed cell diameter is 12 μm or more by adjusting the foaming rate during the foaming process, and is further formed on the outer circumference of the elastic body by the molding die surface. By polishing the skin layer, the foamed surface can be exposed and a predetermined surface roughness can be obtained.

It is well known that the skin layer surface can be formed to have a predetermined surface roughness without completely polishing the skin layer.

Further, it is also well known that the inner surface of the mold is made to have a predetermined surface roughness to obtain an elastic body surface.

The foaming portion can be used in the form of either single bubbles or continuous bubbles. However, from the viewpoint of the adhesion and deposition of toner, in the case of continuous bubbles, in the case of continuous bubbles, the toner can be used. Is not good because it tends to deposit from the surface toward the axis. Moreover, the phenomenon that hardness increases due to the accumulation occurs. As a result, the transfer pressure rises, causing the well-known hollow phenomenon. Therefore, the structure of the foaming member is preferably a single foam.

As the method for producing the foamed member, besides the reaction injection molding method, a gas mixing method, a foaming agent decomposition method, a solvent vaporization method, a chemical reaction method, a sintering method, an elution method or the like can be used. .. With either manufacturing method, it is possible to manufacture a light-weight and low-cost transfer roller.

Furthermore, since the foam member is preferably a low hardness member that does not cause hollowing out, polyurethane foam, polystyrene foam, polyethylene foam, which is a material that can be manufactured to have a relatively low hardness even when a conductive agent is dispersed, is used. Polyester foam, elastomer foam, silicone foam, synthetic rubber foam and the like can be used.

The foam member is made conductive by dispersing conductive fine powder such as carbon black or metal.

It has been confirmed that the same effect can be obtained even if a low hardness solid rubber elastic body is used as the elastic body.

In this embodiment, when a print command is input, the record carrier 6 is sent from a stacker (not shown) to the pair of record carrier transport rollers 18, and then to the image carrier 1. On the image carrier 1, charging by the charging device 3, electrostatic latent image formation by the optical signal generating device 2, and developing device 4
The toner images are formed in the order of toner adhesion to the electrostatic latent image by. The toner image on the image carrier 1 and the recording carrier 6 sent from the recording carrier carrying roller 18 are transferred to the transfer roller 8
And moves to the nip portion formed by the image carrier 1.

Next, by the transfer bias controller 14,
A bias is applied to the transfer roller shaft 9 in order to form an electric field required for transfer between the toner image and the record carrier 6. The applied bias is applied from the transfer roller shaft 9 to the elastic body 10 made of a conductive member. As a result, a constant transfer electric field is obtained between the recording carrier 6 and the toner layer, and good transfer can be performed.

FIG. 3 shows a paper passing test of the image forming apparatus using three kinds of transfer rollers having different surface roughness, and the transfer roller elasticity by the background fog toner on the image carrier between the papers is shown. This shows the relationship between the difference in surface roughness and the back stain. The transfer roller has a diameter of 6
The transfer roller surface roughness Rz is 7 mm thick and has a resistance value of 10 ⁵ Ωcm and is made of conductive foamed silicon.
5s, 14s and 20s were used. These transfer rollers were installed in the image forming apparatus to perform printing, and the number of sheets on which back stain started to be generated was evaluated. The average particle diameter of the toner at this time was the above-mentioned 12 μm.

As a result, as can be seen from FIG. 3, in the case of the Rz5s roller whose transfer roller surface roughness is smaller than the toner average particle diameter, back stain occurs, but the surface roughness is larger than the toner average particle diameter. The transfer roller did not stain the back.

In addition, FIG. 4 shows the toner adhesion to the transfer roller when the toner is once adhered to the surface of the transfer roller to the three kinds of the transfer rollers, and then black solid printing is performed, assuming that a paper jam occurs. It shows the relationship between the difference in the roughness of the transfer roller elastic body surface and the image loss.

As a result, as can be seen from FIG. 4, with the roller having the transfer roller surface roughness Rz5s smaller than the toner average particle diameter, the missing image is not recovered until about 10 sheets are printed, but it is larger than the toner average particle diameter. It can be seen that the transfer roller having a rough surface has recovered after several sheets. This is because the resistance value of the toner adhering to the surface of the transfer roller is higher than the resistance in the thickness direction of the record carrier, so that the transfer electric field tends to be insufficient and the image comes out. Is a difference in toner adhesion amount.

That is, it can be seen from the above two tests that the transfer roller having a surface roughness smaller than the average particle diameter of the toner has a large contact area with the toner image surface, and therefore has a large adhesive force with the toner. Toner from the image carrier easily adheres. On the other hand, the transfer roller, which has a surface roughness larger than the average particle diameter of the toner, has a small contact area with the toner image surface, and in any state, the toner and the roller surface make a line contact, so that the adhesive force between the toner and the toner is large. Is reduced, and it is difficult to adhere.

Even if the toner adheres to the transfer roller surface by line contact, it is not a lump in which the toner particles are combined, but is dispersed because the transfer roller surface roughness is larger than the average particle diameter of the toner. Since the toner adheres, it does not stand out even if it adheres to the back surface of the record carrier, and the influence on the transfer electric field is small. Therefore, stable and good transfer can be realized with a simple configuration.

(Embodiment 2) Next, FIG. 5 shows a charging device according to another embodiment of the image forming apparatus of the present invention, in which reference numeral 19 is a charging roller and 20 is a bias applied to the charging roller. The charging bias control device is connected to the charging roller shaft 21. Further, the charging roller 19 is held by the charging bearing 22, and the charging pressure spring 23 is further held by the charging bearing 2.
The charging roller 19 is disposed so as to come into pressure contact with the image carrier 1 via the pressure roller 2. Further, the charging roller 19 is configured to be connected to a driving source via a driving gear (not shown). Next, the elastic body forming the charging roller 19 will be described. A foam member is formed around the charging roller shaft 9. The surface roughness Rz is set to 12 μm or more so as to be larger than the average particle diameter of the toner used for image formation.

Since the charging roller has the same structure as the transfer roller in the sense that a conductive elastic roller is used, the structure and the manufacturing method are the same as those shown in the first embodiment. .. Further, from the viewpoint of the function of uniformity, the charging roller 19 is conventionally known to be a solid rubber elastic body, or a surface of which is covered with a tubular material so as to make stable contact with the image carrier 1. However, also with respect to such a charging roller, the same effect can be obtained by making the surface roughness larger than the average particle diameter of the toner.

In this embodiment, the charging bias controller 20 applies a bias to the charging roller shaft 21 to form an electric field required for charging between the charging roller 19 and the image carrier 1. The applied bias is the charging roller shaft 21.
Is applied to the elastic body made of a conductive member. As a result, a constant charging electric field is obtained between the charging roller 19 and the image carrier 1, and good charging can be performed.

FIG. 6 shows an image carrier 1 using three types of charging rollers having different surface roughness in the image forming apparatus.
FIG. 4 is a diagram showing a difference in surface roughness and a change in surface potential of the charging roller when toner is once attached to the surface of the charging roller and subsequently charged during the measurement of the surface potential.

As the charging roller, one made of conductive urethane foam having a diameter of 6 mm and a thickness of 5 mm and a resistance value of 10 ⁴ Ωcm was used.
The ones of 3s and 30s were used.

As a result, as can be seen from FIG. 6, the roller having a surface roughness Rz5s of which the charging roller surface roughness is smaller than the toner average particle diameter has a surface roughness larger than the toner average particle diameter of 13s and 3s.
It can be seen that the decrease range of the surface potential is larger than that of the charging roller of 0 s. This is because the toner having a higher resistance value than the resistance value of the charging roller adheres to the roller surface, which is caused by poor charging.The difference due to the roller surface roughness is the difference in the toner adhesion amount. is there.

That is, like the transfer roller of the first embodiment,
The charging roller, whose surface roughness is smaller than the average particle diameter of the toner,
Since the contact area with the toner is large, the adhesive force with the toner is also large, and the toner from the image carrier easily adheres.
On the other hand, the charging roller, whose surface roughness is coarser than the average particle diameter of the toner, has a small contact area with the toner image surface. Is reduced, and it is difficult to adhere.

Even if the toner adheres to the surface of the charging roller by line contact, it is dispersed because the surface roughness of the charging roller is larger than the average particle diameter of the toner, and not the lumps in which the toners are combined. Since the toner adheres, the influence on the charging electric field can be small. It should be noted that if the surface roughness of the charging roller is too rough, charging unevenness will occur, but in this embodiment, it has been confirmed that charging unevenness does not occur up to about Rz200s. Therefore, stable and good charging can be realized with a simple configuration.

(Embodiment 3) Next, FIG. 7 is a fixing device showing another embodiment of the image forming apparatus of the present invention, in which reference numeral 12 is a heating roller having a heat source 27 therein, and 13 is a heating roller. It is a pressure roller that rotates in pressure contact with a heating roller. The pressure roller 13 is held by the fixing bearing 24, and the fixing pressure spring 25 presses the fixing bearing 24.
Further, the heating roller 12 is configured to be connected to a drive source via a drive gear (not shown).

Next, the elastic body forming the pressure roller will be described. Around the pressure roller shaft 26, a foam member having heat resistance or a solid elastic member having low hardness is formed. Specifically, it is made of silicon foam or silicon rubber. The surface roughness Rz is set to 12 μm or more so as to be larger than the average particle diameter of the toner used for image formation.

Since the pressure roller 13 is similar to a transfer roller and a charging roller in the sense that an elastic body is used, its manufacturing method is the same as that shown in the first embodiment. In order to prevent the pressure roller 13 from being offset from the heating roller 12, the surface of the foamed member or the solid elastic member should be coated with a material having good toner releasability such as a fluorine material, or processed into a tube. However, it has been confirmed that a similar effect can be obtained also on the surface of such a pressure roller by making the surface roughness larger than the toner average particle diameter.

In this embodiment, the surface of the heating roller 12 is set to the fixing temperature necessary for fixing by the heat source 27. Next, the transferred record carrier is passed through a nip formed by a heating roller and a pressure roller, and is heated and pressed, whereby good fixing can be performed.

In FIG. 8, a paper passing test was conducted on the image forming apparatus using three types of pressure rollers having different surface roughness, and the difference in the roughness of the surface of the pressure roller elastic body due to the fixing failure. And the number of back stains generated.

The pressure roller is made of silicone rubber and has a diameter of 6 mm and a thickness of 12 mm.
A pressure roller having a surface roughness of Rz8s, 13s, 60s was used.

As a result, as can be seen from FIG. 8, the roller having the surface roughness Rz8s of which the surface roughness of the pressure roller is smaller than the average particle diameter of the toner is 13s and 6 whose surface roughness is larger than the average particle diameter of the toner.
It can be seen that the number of back stains is larger than that of the 0 s pressure roller, and the number of printed sheets is less than about 200, which causes the paper to jam around the pressure roller.

That is, similar to the transfer roller of the first embodiment,
The pressure roller whose surface roughness is smaller than the average particle diameter of the toner is
Since the contact area with the toner is large, the adhesive force with the toner is also large, and the toner from the fixing roller easily adheres. Further, since the area of contact with the toner is large, the amount of adhered toner also increases. Therefore, the toner agglomerated on the surface of the pressure roller eventually becomes a force for sticking the record carrier. On the other hand, a pressure roller having a surface roughness larger than the average particle diameter of the toner has a small contact area with the toner image surface. Adhesion is reduced and it is difficult to adhere. Therefore, stable and good fixing can be realized with a simple structure.

(Embodiment 4) Next, a record carrier conveying roller of another embodiment of the image forming apparatus of the present invention will be described.
Reference numeral 18 shown in FIG. 1 is a record carrier conveying roller composed of a pair of elastic bodies, and is configured to be connected to a drive source via a drive gear (not shown) on one roller.

Next, the elastic body which constitutes the record carrier conveying roller will be described. A solid elastic member is formed around the transport roller shaft 28. Although the elastic body may be formed of a foamed member, a solid elastic member having a large friction coefficient with the record carrier is preferable for stable transportation. Further, the surface roughness is formed to be Rz 12 μm or more so as to be larger than the average particle diameter of the toner used for image formation.

The record carrier transport roller 18 is similar to the transfer roller and the charging roller in the sense that an elastic body is used, and therefore the manufacturing method thereof is the same as that shown in the first embodiment.

In this embodiment, the record carrier 6 sent out from a stacker (not shown) is sent to the transfer device 7 by the record carrier carrying roller 18, transferred, and further fixed, and then another pair of record carrier is carried. The roller 18 discharges the paper.

FIG. 9 shows a paper passing test of the image forming apparatus using three kinds of record carrier conveying rollers 18 having different surface roughnesses, and shows that the record carrier conveying rollers are contaminated during paper jam processing. It shows the relationship between the difference in roughness of the elastic surface of the recording carrier transport roller and the back stain.

As the record carrier carrying roller, one made of chloroprene rubber and having a diameter of 6 mm and a thickness of 7 mm was used, and the surface roughness Rz7s, 15 of the record carrier carrying roller was used.
s, 40s.

As a result, as can be seen from FIG. 9, the surface roughness of the recording carrier carrying roller is Rz7 smaller than the average particle diameter of the toner.
The roller of s has a surface roughness 1 which is larger than the average particle diameter of the toner.
It can be seen that the number of back stains is larger than that of the 5 s and 40 s record carrier transport rollers.

That is, similar to the transfer roller of the first embodiment,
The recording carrier conveying roller having a surface roughness smaller than the average particle diameter of the toner has a large contact area with the toner, and therefore has a large adhesive force with the toner, and the toner from the recording carrier 6 easily adheres. On the other hand, the transfer roller, which has a surface roughness larger than the average particle diameter of the toner, has a small contact area with the toner image surface, and in any state, the toner and the roller surface make a line contact, so that the adhesive force between the toner and the toner is large. Is reduced, and it is difficult to adhere. Therefore, the backside stain is quickly recovered in the recording carrier carrying roller having a small adhered amount and larger than the toner average particle diameter. Therefore, stable and good transportation can be realized with a simple configuration.

[0073]

As described above, according to the present invention,
In an image forming apparatus that includes an image carrier and an elastic transfer roller that is in pressure contact with the image carrier and transfers a recording carrier between the image carrier and the transfer roller by transferring the surface roughness of the transfer roller elastic body. Since the average particle diameter of the toner used for image formation is made larger, the transfer roller surface comes into line contact with the toner, making it difficult for the toner to adhere to the transfer roller. Good transfer with stable transfer efficiency can be configured with a simple structure.

Further, in an image forming apparatus including an image carrier and an elastic charging roller which is in pressure contact with the image carrier and charging the image carrier and the charging roller in contact with each other, the surface roughness of the elastic body of the charging roller is Since the size of the toner used for image formation is larger than the average particle size of the toner, the surface of the charging roller comes into line contact with the toner, making it difficult for the toner to adhere to the charging roller. Stable and good charging can be configured with a simple structure.

Further, in the image forming apparatus including a heating roller and an elastic pressure roller in pressure contact with the heating roller, wherein the recording carrier is passed between the heating roller and the pressure roller for fixing, the pressure roller elasticity is used. Since the surface roughness of the body is formed to be larger than the average particle size of the toner used for image formation, the pressure roller surface comes into contact with the toner in line contact, which makes it difficult for the toner to adhere to the pressure roller. There is no stain on the back of the record carrier, and good fixing can be configured with a simple structure.

Further, in the image forming apparatus in which at least one of the pair of rollers is provided with a record carrier transporting roller made of an elastic body and the record carrier is transported by passing between the rollers, the record carrier made of an elastic body is used. Since the surface roughness of the transport roller is set to be larger than the average particle size of the toner used for image formation, the surface of the record carrier transport roller comes into line contact with the toner, which makes it difficult for toner to adhere to the record carrier transport roller. As a result, the back surface of the record carrier is not stained, and good transport can be configured with a simple structure.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an image forming apparatus of the present invention.

FIG. 2 is a front view and a cross-sectional view of the transfer device according to the first embodiment of the present invention.

FIG. 3 is a diagram showing a relationship between a difference in surface roughness of the transfer roller elastic body of the present invention and back stain.

FIG. 4 is a diagram showing the relationship between the difference in surface roughness of the transfer roller elastic body of the present invention and image loss.

FIG. 5 is a schematic sectional view of a charging device in Embodiment 2 of the image forming apparatus of the invention.

FIG. 6 is a diagram showing a difference in surface roughness and a change in surface potential of the charging roller elastic body of the present invention.

FIG. 7 is a schematic sectional view of a fixing device in Embodiment 3 of the image forming apparatus of the invention.

FIG. 8 is a diagram showing the relationship between the difference in surface roughness of the pressure roller elastic body of the present invention and the number of back stains.

FIG. 9 is a diagram showing the relationship between the difference in surface roughness of the elastic body of the recording carrier carrying roller of the present invention and the back stain.

[Explanation of symbols]

 1 Image Carrier 2 Optical Signal Generator 3 Charging Device 4 Developing Device 5 Erase Unit 6 Record Carrier 7 Transfer Device 8 Transfer Roller 9 Transfer Roller Shaft 10 Elastic Body 11 Fixing Device 12 Heating Roller 13 Pressure Roller 14 Transfer Bias Control Device 15 Bearing 16 Pressure spring 17 Drive gear 18 Record carrier transport roller 19 Charging roller 20 Charging bias control device 21 Charging roller shaft 22 Charging bearing 23 Charging pressure spring 24 Fixing bearing 25 Fixing pressure spring 26 Pressure roller shaft 27 Heat source 28 Transport Roller shaft

Claims (7)

[Claims] 1. An image forming apparatus comprising: an image carrier and an elastic transfer roller that is in pressure contact with the image carrier; and an image forming apparatus for transferring a record carrier between the image carrier and the transfer roller. The image forming apparatus is characterized in that the surface roughness of the toner is larger than the average particle diameter of the toner used for image formation. 2. An image forming apparatus comprising: an image carrier and an elastic charging roller in pressure contact with the image carrier; and an image forming apparatus for charging by rotating the image carrier and the charging roller in contact with each other. An image forming apparatus characterized in that the toner is formed to have a size larger than the average particle size of the toner used for image formation. 3. An image forming apparatus comprising a heating roller and an elastic pressure roller in pressure contact with the heating roller, wherein the recording carrier is fixed between the heating roller and the pressure roller by fixing the elasticity of the pressure roller. An image forming apparatus characterized in that a surface roughness of a body is formed to be larger than an average particle diameter of a toner used for image formation. 4. An image forming apparatus for transporting a record carrier, wherein at least one of a pair of rollers is made of an elastic body, said record carrier being made of an elastic body. An image forming apparatus characterized in that a surface roughness of a conveying roller is formed to be larger than an average particle diameter of toner used for image formation. 5. The transfer roller elastic body and the charging roller elastic body are formed of a foam member made of a soft foam, and any of polyurethane foam, polystyrene foam, polyethylene foam, polyester foam, elastomer foam, silicone foam, and synthetic rubber foam. The image forming apparatus according to claim 1 or 2, wherein 6. The pressure roller elastic body is made of heat resistant soft rubber or heat resistant soft foam, and is made of silicone rubber,
The image forming apparatus according to claim 3, wherein the image forming apparatus is made of silicon foam. 7. The foaming member of the transfer roller elastic body, the charging roller elastic body, and the pressure roller elastic body is a single bubble, and the foaming member is a single foam. Image forming apparatus.