JP2019053217A - Image forming device - Google Patents

Abstract

To enable an intermediate transfer belt to be stably circled without increasing the complexity of composition or control of an image forming device.SOLUTION: An image forming device of the present invention is characterized by comprising an image carrier, an intermediate transfer belt 5 coming in contact with the image carrier, a primary transfer member for primarily transferring a toner image on the image carrier to the intermediate transfer belt 5, a secondary transfer member 15 for secondarily transferring a toner image on the intermediate transfer belt 5 to a transfer material, and a driver roller 21 for sandwiching the intermediate transfer belt 5 together with the secondary transfer member 15 and causing the intermediate transfer belt 5 to circle. The image forming device is further characterized in that the drive roller 21 is provided with an elastic layer 21B, the ASKER-A hardness of the elastic layer 21B is 50° to 80° inclusive, the thickness of the elastic layer 21B is 0.3 mm to 0.8 mm inclusive, the elastic layer 21B is composed of rubber vulcanized using a peroxide, and polishing marks Q formed on the outer circumferential surface of the elastic layer 21B are reverse to the direction of rotation of the drive roller 21.SELECTED DRAWING: Figure 3

Description

  The present invention relates to an electrophotographic image forming apparatus.

  Conventionally, an electrophotographic image forming apparatus includes an image carrier that carries a toner image, an intermediate transfer belt that contacts the image carrier, and a primary transfer member that primarily transfers the toner image on the image carrier to the intermediate transfer belt. And a secondary transfer member that secondarily transfers the toner image on the intermediate transfer belt to a transfer material, and a drive roller that rotates in a predetermined rotation direction and rotates the intermediate transfer belt.

  For example, there is a drive roller manufactured by applying an alumite treatment to the surface of an aluminum tube. Such a driving roller can be manufactured at low cost, but the intermediate transfer belt cannot be stably circulated in a high-temperature and high-humidity environment or in an initial stage of use of the image forming apparatus. There is a risk of image misalignment) and the same size defect (the length of the output image deviates from the original length).

  Therefore, there is a drive roller manufactured by providing an elastic material such as EPDM rubber on the surface of the core metal (see Patent Document 1).

JP 2005-338403 A

  When the driving roller is manufactured by providing an elastic material on the surface of the core metal as described above, if the elastic material is too thick, the outer diameter of the driving roller changes greatly with the thermal expansion of the elastic material. When the outer diameter of the driving roller changes greatly as described above, the linear speed of the intermediate transfer belt also changes greatly with this, and there is a possibility that color misregistration or equal magnification defect may occur.

  In addition, when the driving roller is manufactured by providing an elastic material on the surface of the core metal as described above, when the driving roller is left in a high temperature environment for a long period of time, there is a risk that bleeding occurs on the surface of the driving roller. is there. When the bleed occurs in this manner, the frictional resistance of the surface of the driving roller decreases, and there is a possibility that the intermediate transfer belt cannot be stably circulated by the driving roller.

  In order to suppress the above problems, it is conceivable to estimate the change in the outer diameter of the driving roller based on the surface temperature of the driving roller and correct the linear velocity of the intermediate transfer belt. However, when such a configuration is adopted, a sensor for measuring the surface temperature of the driving roller is required, and the configuration of the image forming apparatus may be complicated. In addition, in order to correct the linear velocity of the intermediate transfer belt, complicated control may be required.

  SUMMARY OF THE INVENTION An object of the present invention is to stably rotate an intermediate transfer belt without complicating the configuration and control of an image forming apparatus.

  An image forming apparatus according to the present invention includes an image carrier that carries a toner image, an intermediate transfer belt that contacts the image carrier, and a primary transfer that primarily transfers the toner image on the image carrier to the intermediate transfer belt. A member, a secondary transfer member that secondary-transfers the toner image on the intermediate transfer belt onto a transfer material, and the intermediate transfer belt is wound around, sandwiching the intermediate transfer belt together with the secondary transfer member, and a predetermined rotation A driving roller that rotates in the direction and rotates the intermediate transfer belt, and the driving roller includes a base material layer and an elastic layer provided around the base material layer, and the ASKER of the elastic layer. -A hardness is 50 ° or more and 80 ° or less, the thickness of the elastic layer is 0.3 mm or more and 0.8 mm or less, and the elastic layer is made of rubber vulcanized using a peroxide. The elastic The polishing marks formed on the outer peripheral surface of the layer are opposite to the rotation direction of the driving roller.

The image forming apparatus includes a tension roller around which the intermediate transfer belt is wound, and a tension spring that applies tension to the intermediate transfer belt by urging the tension roller toward a side opposite to the drive roller side. The pressure applied to the contact portion between the intermediate transfer belt and the driving roller in a state where tension is applied to the intermediate transfer belt may be 0.005 N / mm ² or more.

  The elastic layer may be made of conductive ethylene propylene rubber vulcanized using a peroxide.

  The linear velocity of the outer peripheral surface of the secondary transfer member may be set faster than the linear velocity of the outer peripheral surface of the intermediate transfer belt.

  According to the present invention, it is possible to stably rotate the intermediate transfer belt without complicating the configuration and control of the image forming apparatus.

1 is a schematic diagram illustrating an image forming apparatus according to an embodiment of the present invention. 1 is a cross-sectional view showing an intermediate transfer belt and its peripheral part in an image forming apparatus according to an embodiment of the present invention. In the image forming apparatus according to an embodiment of the present invention, it is a cross-sectional view showing a driving roller and its peripheral portion. 6 is a graph showing the results of Experiment 1. 10 is a graph showing the results of Experiment 2. 10 is a cross-sectional view showing a pressure measuring instrument in Experiment 3. FIG. 10 is a graph showing the results of Experiment 3. 10 is a graph showing the results of Experiment 5. 10 is a graph showing the results of Experiment 6.

  Hereinafter, an image forming apparatus 1 according to an embodiment of the present disclosure will be described with reference to the drawings. Arrows L, R, U, and Lo attached to FIGS. 1 to 3 indicate the left side, right side, upper side, and lower side of the image forming apparatus 1, respectively.

  First, the overall configuration of the image forming apparatus 1 will be described. The image forming apparatus 1 is, for example, a complex machine that is provided with a print function, a copy function, a fax function, and the like.

  Referring to FIG. 1, the image forming apparatus 1 includes a box-shaped apparatus main body 2. An image reading device 3 for reading a document image is provided at the upper end of the apparatus body 2. A paper discharge tray 4 is provided on the upper part of the apparatus main body 2.

  An intermediate transfer belt 5 is accommodated in the central portion of the apparatus main body 2 in the vertical direction. A cleaning unit 6 is provided on the left side of the intermediate transfer belt 5. Four image forming portions 7Y, 7C, 7M, and 7K are provided below the intermediate transfer belt 5 at the center in the vertical direction of the apparatus main body 2. Each of the image forming units 7Y, 7C, 7M, and 7K corresponds to yellow, cyan, magenta, and black, respectively. Each of the image forming units 7Y, 7C, 7M, and 7K includes a photosensitive drum 8 (an example of an image carrier), a charging device 9, a developing device 10, a primary transfer roller 11 (an example of a primary transfer member), and a cleaning. The apparatus 12 is provided. The photosensitive drum 8 is in contact with the intermediate transfer belt 5, and a primary transfer nip N <b> 1 is formed between the photosensitive drum 8 and the intermediate transfer belt 5. The intermediate transfer belt 5 is sandwiched between the primary transfer roller 11 and the photosensitive drum 8.

  An exposure device 13 is accommodated in the lower part of the apparatus body 2. A paper feed cassette 14 is accommodated at the lower end of the apparatus main body 2. A sheet S (an example of a transfer material) is stored in the sheet feeding cassette 14.

  A conveyance path P for the sheet S is provided on the right side of the apparatus main body 2. A secondary transfer roller 15 (an example of a secondary transfer member) is provided in the middle portion of the conveyance path P. The secondary transfer roller 15 is in contact with the intermediate transfer belt 5, and a secondary transfer nip N <b> 2 is formed between the secondary transfer roller 15 and the intermediate transfer belt 5. A fixing device 16 is provided in the downstream portion of the transport path P.

  Next, the operation of the image forming apparatus 1 will be described.

  First, the charging device 9 charges the surface of the photosensitive drum 8. Next, the exposure device 13 exposes the surface of the photosensitive drum 8 to form an electrostatic latent image on the surface of the photosensitive drum 8 (see the dotted arrow in FIG. 1). Next, the developing device 10 supplies toner to the photosensitive drum 8 to develop the electrostatic latent image. As a result, a toner image is carried on the photosensitive drum 8. Next, the primary transfer roller 11 primarily transfers the toner image on the photosensitive drum 8 to the intermediate transfer belt 5 in the primary transfer nip N1. The image forming operation as described above is executed in each of the image forming units 7Y, 7C, 7M, and 7K, so that a full-color toner image is formed on the intermediate transfer belt 5. The toner remaining on the photosensitive drum 8 after the primary transfer is removed by the cleaning device 12.

  On the other hand, the paper S taken out from the paper feed cassette 14 enters the secondary transfer nip N2. When the sheet S enters the secondary transfer nip N2 in this way, the secondary transfer roller 15 secondarily transfers the full-color toner image on the intermediate transfer belt 5 to the sheet S. The toner remaining on the intermediate transfer belt 5 after the secondary transfer is removed by the cleaning unit 6.

  The sheet S on which the toner image is secondarily transferred enters the fixing device 16. When the paper S enters the fixing device 16 in this way, the fixing device 16 fixes the toner image on the paper S. The paper S on which the toner image is fixed is discharged onto the paper discharge tray 4.

  Next, the intermediate transfer belt 5 will be further described.

  Referring to FIG. 2, the intermediate transfer belt 5 is endless in the circumferential direction. The intermediate transfer belt 5 is provided so as to be capable of rotating in a predetermined rotating direction A. The primary transfer pitch (interval of the primary transfer nip N1) on the intermediate transfer belt 5 is set to 85 mm, for example.

  Referring to FIG. 3, the intermediate transfer belt 5 includes a base layer 5A, an elastic layer 5B provided around the base layer 5A, and a coat layer 5C that covers the elastic layer 5B. The base material layer 5A is made of, for example, PVDF (polyvinylidene fluoride). The elastic layer 5B is made of, for example, urethane resin. The coat layer 5C is made of, for example, PTFE (polytetrafluoroethylene).

  Next, the secondary transfer roller 15 will be further described.

  Referring to FIG. 3, the secondary transfer roller 15 rotates in a predetermined rotation direction B and conveys the sheet S to the downstream side of the conveyance path P together with the intermediate transfer belt 5 that rotates in the rotation direction A. The linear velocity of the outer peripheral surface of the secondary transfer roller 15 is set faster than the linear velocity of the outer peripheral surface of the intermediate transfer belt 5.

  The secondary transfer roller 15 includes a base material layer 15A and an elastic layer 15B provided around the base material layer 15A. The base material layer 15A is made of metal, for example. The elastic layer 15B is made of rubber having ion conductivity, for example. The ASKER-C hardness of the elastic layer 15B is, for example, 40 °.

  Referring to FIG. 2, in addition to the above-described members, the image forming apparatus 1 includes a drive roller 21 around which the right end (one end in the width direction) of the intermediate transfer belt 5 is wound, and a left end ( A tension roller 22 around which the other end in the width direction is wound, and an auxiliary roller 23 around which the lower left portion of the intermediate transfer belt 5 is wound are further provided.

  Referring to FIG. 3, drive roller 21 sandwiches intermediate transfer belt 5 together with secondary transfer roller 15. The drive roller 21 is connected to a drive source 25 configured by a motor or the like. When the drive source 25 rotates the drive roller 21 in a predetermined rotation direction C, the intermediate transfer belt 5 rotates following the rotation. Circulate in direction A. That is, the driving roller 21 rotates in the rotation direction C, and the intermediate transfer belt 5 rotates in the rotation direction A.

  The drive roller 21 includes a base material layer 21A and an elastic layer 21B provided around the base material layer 21A.

  The base material layer 21A of the driving roller 21 is made of, for example, metal. The base material layer 21A includes an inner peripheral portion A1, an outer peripheral portion A2 provided around the inner peripheral portion A1, and three connecting portions A3 that connect the inner peripheral portion A1 and the outer peripheral portion A2. I have.

  The diameter of the elastic layer 21B of the driving roller 21 is 27 mm, for example. The outer peripheral surface of the elastic layer 21 </ b> B is in contact with the inner peripheral surface of the intermediate transfer belt 5. The ASKER-A hardness of the elastic layer 21B is not less than 50 ° and not more than 80 °, for example, 60 °. The elastic layer 21B has a thickness of 0.3 mm to 0.8 mm, preferably 0.3 mm to 0.5 mm.

  The elastic layer 21B of the drive roller 21 is formed by mixing a conductive material into EPDM (ethylene propylene rubber). That is, the elastic layer 21B is made of conductive EPDM. This conductive EPDM is vulcanized using a peroxide.

  The outer peripheral surface of the elastic layer 21 </ b> B of the drive roller 21 is subjected to a polishing process. Thus, a large number of polishing marks Q are formed on the outer peripheral surface of the elastic layer 21B. A number of polishing marks Q are reversed with respect to the rotation direction C of the drive roller 21. In other words, the leading ends of the many polishing marks Q face the downstream side in the rotation direction C of the drive roller 21. Therefore, a large number of polishing marks Q are in contact with the inner peripheral surface of the intermediate transfer belt 5 in the counter direction.

Referring to FIG. 2, the outer peripheral surface of tension roller 22 is in contact with the inner peripheral surface of intermediate transfer belt 5. The tension roller 22 is biased toward the left side (the side opposite to the driving roller 21) by a pair of front and rear tension springs 27 (only the rear tension spring 27 is shown in FIG. 2). As a result, tension is applied to the intermediate transfer belt 5 spanned between the drive roller 21, the tension roller 22, and the auxiliary roller 23. The pressure P applied to the contact portion between the inner peripheral surface of the intermediate transfer belt 5 and the outer peripheral surface of the elastic layer 21B of the driving roller 21 in the state where the tension is applied to the intermediate transfer belt 5 is 0.005 N / mm ^2. That's it. Here, the force that the pair of front and rear tension springs 27 urge the tension roller 22 toward the left side is F, and the contact area between the inner peripheral surface of the intermediate transfer belt 5 and the outer peripheral surface of the elastic layer 21B of the drive roller 21 is S. Then, the pressure P = F / S.

  In the present embodiment, as described above, the ASKER-A hardness of the elastic layer 21 </ b> B of the drive roller 21 is 50 ° or more and 80 ° or less. If the ASKER-A hardness of the elastic layer 21 </ b> B is less than 50 ° during manufacturing, the manufacturing accuracy cannot be maintained. On the other hand, if the above numerical range is adopted, the change in the linear velocity of the outer peripheral surface of the intermediate transfer belt 5 accompanying the change in the outer diameter of the elastic layer 21B is suppressed, and the linear velocity of the outer peripheral surface of the photosensitive drum 8 is suppressed. Therefore, it is possible to suppress the occurrence of color misregistration (deviation of the superposition positions of the toner images of the respective colors) due to the deviation of the linear velocity of the outer peripheral surface of the intermediate transfer belt 5. In addition, since the amount of change in the outer diameter of the elastic layer 21B can be reduced as described above, it is possible to suppress the occurrence of equal magnification defects (a phenomenon in which the length of the output image deviates from the original length). . Further, by setting the ASKER-A hardness of the elastic layer 21B to 80 ° or less as described above, the width of the secondary transfer nip N2 can be increased as compared with the case where the ASKER-A hardness of the elastic layer 21B exceeds 80 °. It can be widened. As a result, the toner image can be reliably secondary transferred from the intermediate transfer belt 5 to the sheet S at the secondary transfer nip N2.

  As described above, in the present embodiment, the ASKER-A hardness of the elastic layer 21 </ b> B of the drive roller 21 is set to 50 ° or more and 80 ° or less, thereby suppressing occurrence of color misregistration or equal magnification failure with respect to the paper S. It is possible to improve the transferability of the toner image.

  Moreover, the thickness of the elastic layer 21B of the drive roller 21 is 0.3 mm or more and 0.8 mm or less. As described above, by setting the thickness of the elastic layer 21B to 0.3 mm or more, the undulation at the time of inserting the elastic layer 21B is suppressed as compared with the case where the thickness of the elastic layer 21B is less than 0.3 mm. Is possible. In addition, by setting the thickness of the elastic layer 21B to 0.8 mm or less, the thermal expansion of the elastic layer 21B accompanying the increase in the ambient temperature of the drive roller 21 compared to the case where the thickness of the elastic layer 21B exceeds 0.8 mm. And the amount of change in the outer diameter of the elastic layer 21B can be reduced. Accordingly, the change in the linear velocity of the outer peripheral surface of the intermediate transfer belt 5 due to the change in the outer diameter of the elastic layer 21B is suppressed, and the linear velocity of the outer peripheral surface of the photosensitive drum 8 and the outer peripheral surface of the intermediate transfer belt 5 are reduced. It is possible to suppress the occurrence of color misregistration due to linear velocity deviation. Further, as described above, since the amount of change in the outer diameter of the elastic layer 21B can be reduced, it is possible to suppress the occurrence of equal magnification defects.

  As described above, in the present embodiment, by setting the thickness of the elastic layer 21B of the driving roller 21 to 0.3 mm or more and 0.8 mm or less, the outer peripheral surface of the elastic layer 21B is damaged or the elastic layer 21B is wavy. It is possible to simultaneously suppress the occurrence of color misregistration and equal magnification defects.

  The elastic layer 21B of the drive roller 21 is made of rubber vulcanized using a peroxide. By adopting such a configuration, it is more elastic when the driving roller 21 is left in a high-temperature and high-humidity environment for a long period of time than when the elastic layer 21B is made of rubber vulcanized using sulfur. Bleeding is less likely to occur on the outer peripheral surface of the layer 21B, and it is possible to suppress a decrease in frictional resistance on the outer peripheral surface of the elastic layer 21B caused by the bleed. Therefore, even if the driving roller 21 is left in a high temperature and high humidity environment for a long period of time, slip is unlikely to occur between the driving roller 21 and the intermediate transfer belt 5, and the intermediate transfer belt 5 is reliably circulated by the driving roller 21. Is possible.

  Further, a large number of polishing marks Q formed on the outer peripheral surface of the elastic layer 21 </ b> B of the driving roller 21 are opposite to the rotation direction C of the driving roller 21. By adopting such a configuration, the slip between the driving roller 21 and the intermediate transfer belt 5 is less than that in the case where a large number of polishing marks Q are in order with respect to the rotation direction C of the driving roller 21. Is less likely to occur, and the intermediate transfer belt 5 can be reliably rotated by the drive roller 21.

  As described above, in the present embodiment, the intermediate transfer belt 5 can be stably circulated by optimizing various parameters of the elastic layer 21 </ b> B of the drive roller 21. Therefore, it is not necessary to employ a complicated configuration and control in order to stably rotate the intermediate transfer belt 5, and the configuration and control of the image forming apparatus 1 are not complicated.

Further, the pressure P is 0.005 N / mm ² or more in a state where the tension is applied to the intermediate transfer belt 5. By adopting such a configuration, compared with the case where the pressure P is less than 0.005 N / mm ² , slip is less likely to occur between the driving roller 21 and the intermediate transfer belt 5, and the driving roller 21 The intermediate transfer belt 5 can be reliably rotated.

  The elastic layer 21B of the drive roller 21 is made of EPDM vulcanized using a peroxide. By adopting such a configuration, the elastic layer 21B of the drive roller 21 can be manufactured at low cost.

  Further, the linear velocity of the outer peripheral surface of the secondary transfer roller 15 is set to be higher than the linear velocity of the outer peripheral surface of the intermediate transfer belt 5. By adopting such a configuration, the sheet S can be smoothly conveyed by the secondary transfer roller 15 and the intermediate transfer belt 5.

<Experiment>
An experiment for demonstrating the effect of the image forming apparatus 1 according to the embodiment was performed as follows.

<Experiment 1>
In Experiment 1, the thickness of the elastic layer 21B of the driving roller 21 according to the example was 0.5 mm, and the thickness of the elastic layer 21B of the driving roller 21 according to the comparative example was 1.2 mm. In Experiment 1, the ambient temperature of the driving roller 21 was changed from the reference temperature (22 ° C.), and the outer diameter change amount of the elastic layer 21B of the driving roller 21 was measured. The result of Experiment 1 is shown in FIG.

  As shown in FIG. 4, in the driving roller 21 according to the example, the outer diameter change amount of the elastic layer 21 </ b> B of the driving roller 21 due to the change in the ambient temperature of the driving roller 21 compared to the driving roller 21 according to the comparative example. Is getting smaller. From this, by setting the thickness of the elastic layer 21B to 0.8 mm or less, the elastic layer 21B has a change in the ambient temperature of the driving roller 21 as compared with the case where the thickness of the elastic layer 21B exceeds 0.8 mm. It has been demonstrated that the outer diameter change is small.

<Experiment 2>
In Experiment 2, as in Experiment 1, the thickness of the elastic layer 21B of the driving roller 21 according to the example was 0.5 mm, and the thickness of the elastic layer 21B of the driving roller 21 according to the comparative example was 1.2 mm. In Experiment 2, after color registration (color misregistration correction) was performed, the temperature around the driving roller 21 was increased by 10 ° C., and the color misregistration amount of the comparative colors (yellow, cyan, magenta) with respect to the reference color (black) was measured. did. The reason why the ambient temperature of the drive roller 21 is increased by 10 ° C. is that the ambient temperature of the drive roller 21 is increased by approximately 10 ° C. during continuous printing. In Experiment 2, the allowable upper limit value of the color misregistration amount was set to 100 μm. The result of Experiment 2 is shown in FIG.

  As shown in FIG. 5, the driving roller 21 according to the example has a smaller color misregistration amount than the driving roller 21 according to the comparative example. From this, it was demonstrated that there is a correlation between the thickness of the elastic layer 21B and the amount of color shift. Further, in the driving roller 21 according to the example, the color misregistration amount does not reach 100 μm (allowable upper limit value) in any of the comparative colors. On the other hand, in the driving roller 21 according to the comparative example, the color misregistration amount exceeds 100 μm (allowable upper limit value) in yellow and cyan. From this, it was demonstrated that the color misregistration amount is suppressed by setting the thickness of the elastic layer 21B to 0.8 mm or less as compared with the case where the thickness of the elastic layer 21B exceeds 0.8 mm.

<Experiment 3>
In Experiment 3, a peroxide was used as the vulcanizing agent for the elastic layer 21B of the driving roller 21 according to Examples 1 and 2, and the sulfur was used as the vulcanizing agent for the elastic layer 21B of the driving roller 21 according to Comparative Examples 1 and 2. It was used. In Experiment 3, the driving roller 21 was left in a high temperature and high humidity environment (temperature 45 ° C./humidity 90%), and the friction coefficient μ between the outer peripheral surface of the elastic layer 21B of the driving roller 21 and the paper S was calculated. The calculation method of the friction coefficient μ is as follows.

  With reference to FIG. 6, a pressure gauge 31 is connected to one end of the paper S in the transport direction with the central portion in the transport direction of the paper S being in contact with the outer peripheral surface of the elastic layer 21 </ b> B of the drive roller 21. A 100 g weight 32 was connected to the other end in the transport direction. In this state, the driving roller 21 was rotated in the rotation direction C, and the pressure when the rotation stopped was measured with the pressure gauge 31. The friction coefficient μ was calculated by dividing the measured pressure by the weight of the weight 32. The experimental result of Experiment 3 is shown in FIG.

  As shown in FIG. 7, in the driving roller 21 according to the first and second embodiments, the maximum change amount of the friction coefficient μ is less than 0.5 (about 0.2). On the other hand, in the driving roller 21 according to Comparative Examples 1 and 2, the maximum change amount of the friction coefficient μ is 0.5 or more (about 0.6). From this, by using a peroxide as the vulcanizing agent for the elastic layer 21B, the amount of change in the friction coefficient μ is smaller than when using sulfur as the vulcanizing agent for the elastic layer 21B. Proven.

<Experiment 4>
In Experiment 4, a peroxide is used for the vulcanizing agent of the elastic layer 21 </ b> B of the driving roller 21 according to the example, and the polishing mark Q of the driving roller 21 according to the example is set to the rotation direction C of the driving roller 21. I turned the other way around. In Experiment 4, a peroxide was used as the vulcanizing agent for the elastic layer 21B of the driving roller 21 according to Comparative Example 1, and the polishing mark Q of the driving roller 21 according to Comparative Example 1 was used as the rotational direction C of the driving roller 21. In order. In Experiment 4, sulfur is used as the vulcanizing agent for the elastic layer 21 </ b> B of the driving roller 21 according to the comparative example 2 and the polishing marks Q of the driving roller 21 according to the comparative example 2 are set to the rotational direction C of the driving roller 21. I turned the other way around. In Experiment 4, sulfur is used as the vulcanizing agent for the elastic layer 21 </ b> B of the driving roller 21 according to the comparative example 3, and the polishing mark Q of the driving roller 21 according to the comparative example 3 is set to the rotational direction C of the driving roller 21. I was in order. In Experiment 4, the friction coefficient μ was calculated for the driving roller 21 according to Example and Comparative Examples 1 to 3 by the same method as in Experiment 3. The results of Experiment 4 are shown in Table 1.

  As shown in Table 1, in the driving roller 21 according to the example, the friction coefficient μ is 1.5 or more. On the other hand, in the driving roller 21 according to Comparative Examples 1 to 3, the friction coefficient μ is less than 1.5. From this, the peroxide is used as the vulcanizing agent for the elastic layer 21B, and the polishing marks Q are reversed with respect to the rotational direction C of the driving roller 21, thereby making the elastic layer 21B a vulcanizing agent. It has been proved that the friction coefficient μ is smaller than when sulfur is used or when the polishing marks Q are in order with respect to the rotation direction C of the drive roller 21.

<Experiment 5>
In Experiment 5, for the image forming apparatus 1 (new one) according to the above embodiment, the pressure P applied to the contact portion between the inner peripheral surface of the intermediate transfer belt 5 and the outer peripheral surface of the elastic layer 21B of the drive roller 21 is calculated. The idling torque T corresponding to the pressure P was measured. The calculation method of the pressure P is as described in the above embodiment. The measuring method of the idling torque T is as follows. That is, the driving roller 21 was rotated with the intermediate transfer belt 5 fixed, and the torque when the driving roller 21 started to slide with respect to the intermediate transfer belt 5 was measured with a torque gauge. The result of Experiment 5 is shown in FIG.

As shown in FIG. 8, as the pressure P increases, the idling torque T also increases. From this, it was proved that there is a correlation between the pressure P and the idling torque T. Further, it was demonstrated that when the pressure P is 0.005 N / mm ² or more, the slope of the curve indicating the relationship between the pressure P and the idling torque T becomes very gentle.

<Experiment 6>
In Experiment 6, using the image forming apparatus 1 according to the above-described embodiment (thickness of the elastic layer 21B of the driving roller 21 is 0.5 mm), a printing operation is performed on the paper S with a printing rate of 5%. The idling torque T for each 50K sheets (K sheets = 1000 sheets) was measured by the same method as in Experiment 5. In Experiment 6, the allowable lower limit value of the idling torque T was set to 5 kgf · cm. The experimental result of Experiment 6 is shown in FIG.

  As shown in FIG. 9, in the image forming apparatus 1 according to the above-described embodiment, the idling torque T becomes higher than the allowable lower limit value (5 kgf · cm) even when the printing operation is performed on 300K sheets S. Yes. From this, it was proved that the image forming apparatus 1 according to the embodiment can suppress the decrease in the idling torque T.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 5 Intermediate transfer belt 8 Photosensitive drum (an example of an image carrier)
11 Primary transfer roller (an example of a primary transfer member)
21 Drive roller 21A (Drive roller) base material layer 21B (Drive roller) elastic layer 22 Tension roller 27 Tension spring Q Polishing eye S Paper (an example of transfer material)

Claims (4)

An image carrier for carrying a toner image;
An intermediate transfer belt in contact with the image carrier;
A primary transfer member that primarily transfers a toner image on the image carrier to the intermediate transfer belt;
A secondary transfer member for secondary transfer of the toner image on the intermediate transfer belt to a transfer material;
A drive roller around which the intermediate transfer belt is wound, sandwiching the intermediate transfer belt together with the secondary transfer member, and rotating the intermediate transfer belt in a predetermined rotation direction;
The drive roller is
A base material layer;
An elastic layer provided around the base material layer,
The ASKER-A hardness of the elastic layer is 50 ° or more and 80 ° or less,
The elastic layer has a thickness of 0.3 mm or more and 0.8 mm or less,
The elastic layer is composed of rubber vulcanized using a peroxide,
The image forming apparatus according to claim 1, wherein the polishing eyes formed on the outer peripheral surface of the elastic layer are opposite to the rotation direction of the drive roller. A tension roller around which the intermediate transfer belt is wound;
A tension spring that applies tension to the intermediate transfer belt by urging the tension roller toward the side opposite to the driving roller; and
^2. The image formation according to claim 1, wherein a pressure applied to a contact portion between the intermediate transfer belt and the driving roller in a state where tension is applied to the intermediate transfer belt is 0.005 N / mm ² or more. apparatus.   The image forming apparatus according to claim 1, wherein the elastic layer is made of conductive ethylene propylene rubber vulcanized using a peroxide.   The image forming apparatus according to claim 1, wherein a linear velocity of the secondary transfer member is set higher than a linear velocity of the intermediate transfer belt.

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