Tension roll and belt conveying device and image forming system using the same

Abstract

To provide a crown-shaped tension roll around which a belt is rotatably stretched, and to prevent generation of noise depending on a difference in a speed between the belt and the tension roll.SOLUTION: A crown-shaped tension roll 2 around which a belt 7 is rotatably stretched, comprises: a large diameter part 4 having a large outer diameter, having a circular cross-sectional surface, and provided at a center in an axial direction of a roll body 3, and small diameter parts 6 having a small outer diameter, and provided at the ends of diameter reduction parts 5 whose diameter is gradually reduced from the large diameter part 4 toward both ends in the axial direction, with the diameter reduction parts 5 therebetween. Slippage between the large diameter part 4 and the belt 7 is defined as SLa, slippage between the diameter reduction parts 5 and the belt 7 as SLb, and an allowable boundary value is SLa that is not a slippage causing noise as TH, and a difference in a radius dR between the large diameter part 4 and small diameter parts 6 is set so as to satisfy |SLb|≤TH. The tension roll can be applied to a belt conveying device and an image forming system.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a tension roll for tensioning a belt, and a belt conveying device and an image forming system using the same. [Background technology]

[0002] As conventional belt conveying devices, for example, those described in Patent Documents 1 to 3 are already known. Patent Document 1 discloses an image forming apparatus that solves the problem of suppressing the generation of abnormal noise caused by stick-slip vibration by making the arithmetic mean roughness of the inner peripheral surface of the belt greater in the direction of movement of the belt than in the width direction of the belt, and by making the maximum height Rz of either the tension roller or the backup roller in the direction of the rotation axis 3.0 μm or more. Patent Document 2 discloses an image forming apparatus in which an uneven shape is imparted to the back surface of a belt in order to suppress abnormal noise generated when the belt is in motion, the maximum dynamic friction coefficient of the back surface of the belt is set to 0.73 or less, and the amplitude represented by the difference between the maximum dynamic friction coefficient and the minimum dynamic friction coefficient is set to 0.51 or less. Patent Document 3 discloses an image forming device in which, in order to suppress belt chatter vibration, a primary transfer member is arranged opposite a photosensitive drum with an intermediate transfer belt in between, and convex portions are formed in each of the physical nip area A that contacts the back surface of the intermediate transfer belt when the photosensitive drum is in contact, and in the tension nip area B that contacts the back surface of the intermediate transfer belt when a space is secured between the photosensitive drum and the intermediate transfer belt, and a first ratio of convex portions to the physical nip area A and a second ratio of convex portions to the tension nip area B are made different. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2021-81645 A (Form for implementing the invention, FIG. 9) [Patent Document 2] JP 2015-132799 A (Form for carrying out the invention, FIG. 1) [Patent Document 3] JP 2011-237664 A (Form for carrying out the invention, FIG. 2) Summary of the Invention [Problem to be solved by the invention]

[0004] The technical problem to be solved by the present invention is to suppress the generation of abnormal noise that depends on the speed difference between a belt and a crown-shaped tension roll around which a belt is rotatably stretched. [Means for solving the problem]

[0005] A first technical feature of the present invention is a crown-shaped tension roll around which a belt is rotatably tensioned, the tension roll comprising a large diameter portion having a large outer diameter provided at the axial center of a roll body having a circular cross-section surface, and a small diameter portion having a small outer diameter provided at an end of the large diameter portion via a tapered diameter portion that gradually taperes in diameter from the large diameter portion toward both axial ends, the tension roll being characterized in that the radius difference between the large diameter portion and the small diameter portion is set so as to satisfy |SLb|≦TH, where SLa is the amount of slippage between the large diameter portion and the belt, SLb is the amount of slippage between the tapered diameter portion and the belt, and TH is an allowable boundary value of SLa that is not the amount of slippage that would cause abnormal noise.

[0006] A second technical feature of the present invention is a tension roll having the first technical feature, characterized in that the allowable boundary value TH is 0.03 mm in absolute value. A third technical feature of the present invention is a tension roll having the second technical feature, characterized in that the slippage amount SLb is within the allowable boundary value of 0.03 mm in absolute value. A fourth technical feature of the present invention is a tension roll having the first technical feature, characterized in that, for a plurality of tension rolls having different outer diameters of the large diameter portion, a relationship between the radius difference between the large diameter portion and the small diameter portion and a slippage amount SLb between the reduced diameter portion and the belt is obtained in advance, and the radius difference between the large diameter portion and the small diameter portion is set so as to satisfy |SLb|≦tolerable boundary value TH. A fifth technical feature of the present invention is a tension roll having the fourth technical feature, characterized in that for tension rolls having different outer diameters of the large diameter portion, the radius difference between the large diameter portion and the small diameter portion is changed, a slippage amount SLb between each of the reduced diameter portions and the belt is obtained, the outer diameter of the large diameter portion and the radius difference where the slippage amount SLb is at the allowable boundary value TH are plotted, and a characteristic line that is a linear approximation of the plotted points is used as a boundary, and the radius difference between the large diameter portion and the small diameter portion is set so as to satisfy |SLb|≦allowable boundary value TH. A sixth technical feature of the present invention is a tension roll having the fifth technical feature, characterized in that, when the allowable boundary value TH is 0.03 (mm), the outer diameter of the large diameter portion is D (mm), and the radius difference is dR (mm), the characteristic line is expressed by the following (Equation 1). dR≦-0.0155×D+0.346 (Formula 1)

[0007] A seventh technical feature of the present invention is a belt conveying device comprising a plurality of tension rolls and a belt that is stretched across the plurality of tension rolls in a tensioned state and rotates in a circular motion, wherein at least one of the tension rolls uses a tension roll having the first technical feature. An eighth technical feature of the present invention is a belt conveying device having the seventh technical feature, characterized in that the belt is hung at an angle of more than 20 degrees with respect to the crown-shaped tension roll. A ninth technical feature of the present invention is a belt conveying device having the seventh technical feature, characterized in that, when the axial length of the large diameter portion is L1 and the axial length of the reduced diameter portion is L2, L1 / L2≦1 / 2.

[0008] A tenth technical feature of the present invention is an image forming system comprising a medium transport means for transporting a medium and an image creating means for forming an image on the medium, and characterized in that a belt transport device having any of the seventh to ninth technical features is used as part of the medium transport means or as part of the image creating means. An eleventh technical feature of the present invention is an image forming system having the tenth technical feature, characterized in that, in a mode in which the belt conveying device is used as part of the imaging means and the image is held on the belt, the image forming system has a detection means that is provided opposite the surface of the belt and detects information of the image held on the belt, and when the detection means is arranged near the crown-shaped tension roll of the belt, the detection means is arranged immediately before or immediately after the area that is stretched over the crown-shaped tension roll. Effect of the Invention

[0009] According to a first technical feature of the present invention, it is possible to suppress the generation of abnormal noise that depends on the speed difference between a belt and a crown-shaped tension roll around which a belt is rotatably stretched. According to a second technical feature of the present invention, by focusing on the amount of slippage between the large diameter portion and the belt, and taking into consideration that this amount of slippage does not result in abnormal noise up to 0.03 mm, the crown shape of the tension roll can be easily selected. According to a third technical feature of the present invention, by focusing on the amount of slippage between the reduced diameter portion and the belt and suppressing this amount of slippage to within 0.03 mm, the crown shape of the tension roll can be easily selected. According to a fourth technical feature of the present invention, by grasping in advance the relationship between the radius difference between the large diameter portion and the small diameter portion and the amount of slippage between the reduced diameter portion and the belt for each tension roll having a different outer diameter of the large diameter portion, it is possible to easily set the radius difference between the large diameter portion and the small diameter portion in order to suppress the generation of abnormal noise in the tension roll. According to a fifth technical feature of the present invention, by creating a characteristic line that is the boundary between the allowable range and the non-allowable range for each tension roll having a different outer diameter of the large diameter portion, taking into account the relationship between the radius difference between the large diameter portion and the small diameter portion and the amount of slippage between the reduced diameter portion and the belt, it is possible to easily set the radius difference between the large diameter portion and the small diameter portion in order to suppress the generation of abnormal noise in the tension roll. According to the sixth technical feature of the present invention, from the characteristic line when the allowable boundary value is set to 0.03 mm, in order to suppress the generation of abnormal noise from the tension roll, the radius difference between the large diameter portion and the small diameter portion can be easily set using the outer diameter of the large diameter portion as a parameter. According to a seventh technical feature of the present invention, it is possible to provide a belt conveying device capable of suppressing the generation of abnormal noise that depends on the speed difference between a belt and a crown-shaped tension roll around which a belt is rotatably tensioned. According to an eighth technical feature of the present invention, even if the belt wrap angle with respect to the crown-shaped tension roll is increased, the generation of abnormal noise that depends on the speed difference between the belt and the tension roll can be effectively suppressed. According to a ninth technical feature of the present invention, it is possible to suppress the generation of abnormal noise that depends on the speed difference between the belt and the tension roll, while simultaneously suppressing the bending deformation of the crown-shaped tension roll and maintaining the flatness of the tensioned belt. According to a tenth technical feature of the present invention, it is possible to provide an image forming system including a belt conveying device capable of suppressing the generation of abnormal noise that depends on the speed difference between a belt and a crown-shaped tension roll around which a belt is rotatably tensioned. According to an eleventh technical feature of the present invention, by disposing a detection means near a crown-shaped tension roll of the belt, it is possible to accurately detect image information while maintaining the flatness of the belt and suppressing the generation of vibrations and abnormal noise between the belt and the tension roll. [Brief description of the drawings]

[0010] [Figure 1]FIG. 1A is an explanatory diagram showing an overview of an embodiment of an image forming system including a belt conveying device using a tension roll to which the present invention is applied; FIG. 1B is an explanatory diagram showing an example of the configuration of a tension roll to which the present invention is applied; and FIG. 1C is an explanatory diagram showing the characteristics of the tension roll shown in FIG. [Diagram 2] FIG. 11 is an explanatory diagram of an analysis of the causes of abnormal noise in a belt conveying device using a crown-shaped tension roll, in which (a) is an explanatory diagram showing the location where slippage occurs between the crown-shaped tension roll and the belt, (b) is an explanatory diagram showing how belt slippage leads to the generation of abnormal noise, (c) is an arrow view seen from the direction C in (b), and (d) is an explanatory diagram showing the relationship between belt slippage and the generation of abnormal noise. [Diagram 3] FIG. 1 is an explanatory diagram showing an overall configuration of an image forming system according to a first embodiment. [Figure 4] 4 is an explanatory diagram showing a belt conveying device used in the image forming system shown in FIG. 3. [Diagram 5] FIG. 2A is an explanatory diagram showing a configuration example of a crown-shaped tension roll used in the first embodiment, and FIG. 2B is an explanatory diagram showing a state in which a belt is stretched over the crown-shaped tension roll. [Figure 6] 4 is a graph showing the relationship between the amount of slippage between a crown-shaped tension roll used in the present embodiment and a belt and the axial position of the tension roll. FIG. [Figure 7] FIG. 11 is a graph showing the relationship between the amount of slippage between the tension roll and the belt and the axial position of the tension roll for a plurality of crown-shaped tension rolls having different radius differences between the large diameter portion and the small diameter portion as Example 1. [Figure 8] FIG. 8 is a graph plotting the relationship between the radius difference and the amount of slippage shown in FIG. [Figure 9] 9 is a graph showing an example of a characteristic line representing a radius difference that satisfies an allowable range in which abnormal noise does not occur, based on the graph shown in FIG. 8. [Figure 10] FIG. 11 is an explanatory diagram showing the relationship between the amount of slippage between a crown-shaped tension roll and a belt and the axial position of the tension roll in Example 2, in a mode in which a belt with a friction coefficient of 0.2 μ is used. [Figure 11] FIG. 10 is an explanatory diagram showing the relationship between the amount of slippage between a crown-shaped tension roll and a belt and the axial position of the tension roll in an embodiment using a belt with a friction coefficient of 0.14 μm. [Figure 12] FIG. 1 is an explanatory diagram showing the relationship between the amount of slippage between a crown-shaped tension roll and a belt and the axial position of the tension roll in an embodiment using a belt with a friction coefficient of 0.3 μm. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Overview of the embodiment FIG. 1(a) shows an outline of an embodiment of a belt conveying device to which the present invention is applied. In the figure, a belt conveying device 10 includes a plurality of tension rolls 1 (1a to 1d in this example) and a belt 7 that is stretched around the plurality of tension rolls 1 in a tensioned state and rotates in a circular fashion. In this example, at least one of the multiple tension rolls 1 (1a to 1d), in this example, the two tension rolls 1a and 1b, are configured as a crown-shaped tension roll 2. The tension rolls 1c and 1d are configured to have a straight shape with the same outer diameter. As shown in Figures 1(b) and (c), the crown-shaped tension roll 2 is a crown-shaped tension roll around which a belt 7 is rotatably tensioned, and includes a large diameter portion 4 having a large outer diameter provided in the axial center of a roll body 3 having a circular cross-section surface, and a small diameter portion 6 having a small outer diameter provided at an end of the contracted diameter portion 5, through which a diameter gradually decreases from the large diameter portion 4 toward both ends in the axial direction. If the slippage between the large diameter portion 4 and the belt 7 is SLa, the slippage between the contracted diameter portion 5 and the belt 7 is SLb, and an allowable boundary value of SLa that does not lead to abnormal noise is TH, the radius difference dR between the large diameter portion 4 and the small diameter portion 6 is set so as to satisfy |SLb|≦TH.

[0012] In such a technical means, the tension roll 1 means a roll around which the belt 7 is stretched. In addition, the "crown" in "crown shape" refers to a shape in which the center of the roll is thicker, and the crown-shaped tension roll 2, as described above, has a large diameter portion 4 that increases the outer diameter of the roll body 3 having a circular cross-section, and has reduced diameter portions 5 that gradually reduce in diameter toward both ends in the axial direction, sandwiching the large diameter portion 4 of the roll body 3, and both ends of this reduced diameter portion 5 are formed as small diameter portions 6 with the smallest outer diameter. Here, the roll body 3 may be either hollow or solid. The cross-sectional shape of the reduced diameter portion 5 of the roll body 3 along the axial direction includes either a tapered shape (linearly inclined shape) or an R shape (curved shape having a curvature). Furthermore, compared to a straight-shaped tension roll, the crown-shaped tension roll 2 can correct unevenness of the belt surface caused by bending deformation, and is effective in preventing meandering / deviation of the belt 7. For this reason, it is preferable to use a crown-shaped tension roll 2, particularly when a tension roll 1 with a small diameter is used.

[0013] -Relationship between slippage between tension roll and belt and abnormal noise- Generally, when a crown-shaped tension roll 2 is used, as shown in FIG. 2(a), a difference in peripheral speed occurs between the large diameter portion 4 and the reduced diameter portion 5 of the tension roll 2. This causes the belt 7 to slip against the reduced diameter portion 5 of the tension roll 2, resulting in a stick-slip phenomenon, which may cause abnormal noise W. Here, further examining the cause of the abnormal sound W, as shown in Figures 2(b) and (c), the area where the straight-shaped tension roll 1d and the belt 7 are passed over maintains a contact point CN over the entire axial area of ​​the tension roll 1d, and no speed difference occurs in the peripheral speed in the area where the tension roll 1d and the belt 7 are passed over, so the stick-slip phenomenon does not occur and no abnormal sound W is generated.

[0014] In contrast, in the region where the crown-shaped tension roll 2 and the belt 7 are stretched over each other, as shown in Figures 2(b) and (c), a contact point CN is maintained between the large diameter portion 4 of the tension roll 2 and the belt 7. However, a speed difference is geometrically generated between the reduced diameter portion 5 of the tension roll 2 and the belt 7. At this time, the presence or absence of slippage between the large diameter section 4 of the tension roll 2 and the belt 7 was verified. As a result, it was confirmed that, as shown in FIG. 2(d), slippage occurred due to the speed difference, but the amount of slippage was not enough to cause abnormal noise W. On the other hand, when the amount of slippage between the reduced diameter portion 5 of the tension roll 2 and the belt 7 was verified by simulation, it was confirmed that the amount of slippage increases toward the end of the reduced diameter portion 5 of the tension roll 2, as shown in Fig. 2(d), and the amount of slippage at the small diameter portion 6, which is the end of the reduced diameter portion 5 of the tension roll 2, is greater in absolute value than the amount of slippage at the large diameter portion 4. In this state, the amount of slippage increases due to the speed difference between the reduced diameter portion 5 of the tension roll 2 and the belt 7, and it is presumed that a stick-slip phenomenon occurs as a result, resulting in the generation of the abnormal sound W. Based on these results, the inventors of the present application have discovered that if the amount of slippage between the reduced diameter portion 5 of the crown-shaped tension roll 2 and the belt 7 can be sufficiently reduced, it is possible to suppress the generation of abnormal noise W.

[0015] In this example, the amount of slippage between the crown-shaped tension roll 2 and the belt 7 was verified by simulation. As a result, a method was devised to set the radius difference dR between the large diameter portion 4 and the small diameter portion 6 of the tension roll 2 so as to keep the amount of slippage |SLb| between the reduced diameter portion 5 of the tension roll 2 and the belt 7 within the allowable boundary value TH, as shown in Figure 1(c), based on the allowable boundary value TH that is not the amount of slippage that would result in abnormal noise W. According to this method, the slippage SLb varies depending on the radius difference dR, and by specifying the variation characteristic as a function f(dR), it is possible to select a radius difference dR at which the slippage |SLb| is within the allowable boundary value TH. By selecting the radius difference dR in this way, the slippage |SLb| caused by the speed difference between the reduced diameter portion 5 of the crown-shaped tension roll 2 and the belt 7 is suppressed to within the allowable boundary value TH, so that the slippage |SLb| caused by the speed difference between the reduced diameter portion 5 of the tension roll 2 and the belt 7 does not reach a slippage amount that leads to abnormal noise W, and the generation of abnormal noise W is suppressed. Regarding whether the surface roughness of the tension roll 2 or the belt 7 affects the generation of the abnormal noise W, it has been confirmed that there is no change in the sliding behavior between the tension roll 2 and the belt 7 even if the surface roughness of the tension roll 2 and the belt 7 is changed, as shown in the examples described later.

[0016] Next, a representative or preferred embodiment of the crown-shaped tension roll 2 according to the present embodiment will be described. First, a typical embodiment of the crown-shaped tension roll 2 is one in which the allowable boundary value TH is 0.03 mm in absolute value. Although this allowable boundary value TH varies depending on the outer diameter of the large diameter portion 4 of the tension roll 2, it has been confirmed that the minimum value is 0.03 mm. Therefore, a typical embodiment of the tension roll 2 is one in which the slippage amount SLb is within the allowable boundary value of 0.03 mm in absolute value.

[0017] In addition, a preferred method for constructing a tension roll 2 with a desired crown shape is to previously determine the relationship between the radius difference between the large diameter portion 4 and the small diameter portion 6 and the slippage amount SLb between the reduced diameter portion 5 and the belt 7 for multiple tension rolls 2 having different outer diameters of the large diameter portion 4, and to set the radius difference between the large diameter portion 4 and the small diameter portion 6 so that |SLb|≦the allowable boundary value TH is satisfied. In this example, for tension rolls 2 having different outer diameters of the large diameter portion 4, the radius difference between the large diameter portion 4 and the small diameter portion 6 is changed, the slippage SLb between each reduced diameter portion 5 and the belt 7 is obtained, and the outer diameter and radius difference of the large diameter portion 4 where the slippage SLb is at the allowable boundary value TH are plotted. The characteristic line obtained by linearly approximating these plotted points is used as the boundary, and the radius difference between the large diameter portion 4 and the small diameter portion 6 is set so as to satisfy |SLb|≦allowable boundary value TH. Here, if the allowable boundary value TH is 0.03 (mm), the outside diameter of the large diameter portion 4 is D (mm), and the radius difference is dR (mm), the above-mentioned characteristic line is expressed by the following (Equation 1). dR≦-0.0155×D+0.346 (Formula 1)

[0018] In addition, in this type of belt conveying device 10, the angle at which the belt 7 is hung on the crown-shaped tension roll 2 may be appropriately selected, but it has been confirmed that no abnormal noise W is generated between the crown-shaped tension roll 2 and the belt 7 even if the angle exceeds 20 degrees. Furthermore, the shape of this type of crown-shaped tension roll 2 may be appropriately selected, but from the viewpoint of both suppressing the bending deformation of the crown-shaped tension roll 2 and maintaining the flatness of the tensioned belt 7, it is preferable that L1 / L2≦1 / 2, where L1 is the axial length of the large diameter portion 4 and L2 is the axial length of the reduced diameter portion 5. In this case, a shorter L2 is more effective in making the surface of the belt 7 uniform.

[0019] This type of belt conveying device 10 can be applied to various processing systems, such as the image forming system shown in FIG. This type of image forming system 11 includes a medium transport means 12 for transporting a medium S, and an image creating means 13 for forming an image on the medium S, and uses the belt transport device 10 described above as part of the medium transport means 12 or as part of the image creating means 13. In this embodiment, a preferred embodiment of the image forming system 11 is one in which the belt conveying device 10 is used as part of the image creating means 13, and in an embodiment in which an image is held on the belt 7, the system has a detection means (not shown) that is provided opposite the surface of the belt 7 and detects the image information held on the belt 7, and when the detection means is arranged in the vicinity of the crown-shaped tension roll 2 described above on the belt 7, the detection means may be arranged immediately before or immediately after the area that is stretched over the crown-shaped tension roll 2. In this example, by devising a configuration for the crown-shaped tension roll 2, a slippage amount SLb occurs between the tension roll 2 and the belt 7 due to a speed difference, but the absolute value of the slippage amount SLb is suppressed to be equal to or less than the allowable boundary value TH. Therefore, the slippage amount SLb that leads to abnormal sound W does not occur between the tension roll 2 and the belt 7, and the belt 7 is prevented from generating abnormal sound W due to the stick-slip phenomenon in the vicinity of the tension roll 2. Therefore, even if a detection means is disposed in the vicinity of the tension roll 2, the belt 7 facing the detection means does not vibrate minutely due to the stick-slip phenomenon, and the detection means stably detects image information on the belt 7.

[0020] Hereinafter, the present invention will be described in more detail based on the embodiments shown in the accompanying drawings. First embodiment -Overall configuration of image forming apparatus- FIG. 3 shows the overall configuration of the image forming system according to the first embodiment. In the figure, the image forming system 20 is equipped with an image creating engine 30 that forms images of multiple colors (in this embodiment, four colors: yellow, magenta, cyan, and black) within an apparatus housing 21, and below this image creating engine 30 is disposed a medium supply device 50 in which media such as paper is stored, and a medium transport path 55 is disposed extending approximately vertically from this media supply device 50.

[0021] -Imaging engine- In this example, the image creation engine 30 has image forming units 31 (specifically 31a to 31d) that form images of multiple colors arranged in a substantially horizontal direction, and above them is disposed a transfer module 40 including, for example, a belt-like intermediate transfer body 45 that circulates along the arrangement direction of the image forming units 31, and transfers images of each color formed in each image forming unit 31 to a medium via the transfer module 40. In this example, the image creation engine 30 corresponds to the image creation means in Fig. 1(a), the intermediate transfer body 45 corresponds to the belt 7 in Fig. 1(a), and the transfer module 40 corresponds to the belt conveying device 10 in Fig. 1(a).

[0022] <Image forming section> In this embodiment, as shown in Figures 3 and 4, each image forming unit 31 (31a to 31d) forms toner images, for example, for yellow, magenta, cyan, and black (the arrangement is not necessarily in this order), in order from the upstream side in the circulation direction of the intermediate transfer body 45, and is equipped with a photoconductor 32, a charging device (a charging roll in this example) 33 that pre-charges the photoconductor 32, an exposure device (an LED writing head in this example) 34 that writes an electrostatic latent image on each photoconductor 32 charged by the charging device 33, a developing device 35 that develops the electrostatic latent image formed on the photoconductor 32 with a corresponding color component toner (negative polarity in this embodiment, for example), and a cleaning device 36 that cleans off residual matter on the photoconductor 32. Incidentally, reference numeral 37 (specifically, 37a to 37d) denotes a toner cartridge for replenishing each developing device 35 with a toner of each color component.

[0023] <Transcription module> In the present embodiment, as shown in FIGS. 3 and 4, the transfer module 40 has a belt-shaped intermediate transfer body 45 made of, for example, polyimide resin stretched across a plurality of tension rolls 41 (specifically, 41a to 41d). In this example, the intermediate transfer body 45 is configured to move in a circulating manner while being tensioned, for example, by using the fourth tension roll 41d as a drive roll that can be driven by a drive source 43, and the third tension roll 41c as a tension-applying roll to which tension is applied by a spring 44. Furthermore, in this example, two of the tension rolls 41 (41a to 41d), specifically the first and second tension rolls 41a and 41b, are configured as crown-shaped tension rolls 42. Since the crown-shaped tension roll 42 can make the surface of the intermediate transfer body 45 uniform, in this example, the multiple image forming units 31 (31a to 31d) are disposed facing the straight portion 45a of the intermediate transfer body 45 stretched between the crown-shaped tension rolls 42. The third and fourth tension rolls 41c and 41d are configured in a straight shape with the same outer diameter.

[0024] A transfer device (transfer roll in this example) 46 for primary transfer is disposed on the rear surface of the intermediate transfer body 45 corresponding to the photoconductor 32 of each image forming section 31, and by applying a transfer voltage of the opposite polarity to the charging polarity of the toner to this transfer device 46, the toner image on the photoconductor 32 is electrostatically transferred to the intermediate transfer body 45 side. Furthermore, a cleaning device 47 for the intermediate transfer body is disposed upstream of the most upstream image forming section 31a of the intermediate transfer body 45. In this example, the cleaning device 47 is provided facing the area of ​​the intermediate transfer body 45 that is stretched over the third tension roll 41c, and is configured to clean off residual matter on the intermediate transfer body 45 by bringing, for example, a plate-shaped cleaning member 47a into contact with the intermediate transfer body 45.

[0025] 4 and 5(b), an image sensor 48 for detecting image information is disposed facing the surface of the intermediate transfer body 45. The image sensor 48 has a light emitting element and a light receiving element, and the light emitting element irradiates light toward the surface of the intermediate transfer body 45, and the light receiving element detects the reflected light from the surface of the intermediate transfer body 45. Here, the detection target of the image sensor 48 includes image information (image density and position information) held on the intermediate transfer body 45. In this example, the image sensor 48 is disposed immediately before the moving direction of the intermediate transfer body 45 in the region of the intermediate transfer body 45 that is hung around the first tension roll 41a, which is the crown-shaped tension roll 42. The installation position of the image sensor 48 may be immediately after the moving direction of the intermediate transfer body 45 in the region that is hung around the first tension roll 41a.

[0026] <Secondary transfer device> In addition, in this embodiment, as shown in FIG. 3, a transfer device 60 for secondary transfer is arranged at a position corresponding to the tension roll 41d downstream of the most downstream image forming section 31d of the intermediate transfer body 45, so that the primary transfer image on the intermediate transfer body 45 is secondarily transferred (collectively transferred) to a medium. In this example, the transfer device 60 includes a secondary transfer roll 61 arranged in pressure contact with the toner image bearing surface side of the intermediate transfer body 45, and a backup roll (also serving as the fourth tension roll 41d in this example) arranged on the back side of the intermediate transfer body 45 and serving as an opposing electrode of the secondary transfer roll 61. For example, the secondary transfer roll 61 is grounded, and a secondary transfer voltage of the same polarity as the charging polarity of the toner is applied to the backup roll (fourth tension roll 41d).

[0027] -Media transport system / fixing device- In addition, the medium supply device 50 is provided with a supply roll 51 that supplies the medium, and a transport roll (not shown) is arranged in the medium transport path 55, which is located immediately before the secondary transfer site, and a position alignment roll 56 that supplies the medium to the secondary transfer site at a predetermined timing is arranged in the medium transport path 55, which is located immediately before the secondary transfer site. Furthermore, a fixing device 70 is provided in the medium transport path 55 located downstream of the secondary transfer portion, and this fixing device 70 includes, for example, a heating fixing roll 71 with a built-in heater (not shown), and a pressure fixing roll 72 that is placed in pressure contact with the heating fixing roll 71 and rotates following the heating fixing roll 71. Also, downstream of the fixing device 70, a discharge roll 57 is provided for discharging the medium in the device housing 21, which clamps and transports the medium to discharge it, and stores the medium in a medium storage receptacle 58 formed in the upper part of the device housing 21. Although not shown in the figure, it goes without saying that a manual medium feed device and a double-sided recording module that enables double-sided recording on a medium may be additionally provided.

[0028] -Configuration of crown-shaped tension roll- In this embodiment, as shown in Fig. 5(a), the crown-shaped tension roll 42 includes a large diameter portion 81 having a large outer diameter D provided at the axial center of a roll body 80 having a circular cross section, a reduced diameter portion 82 having a radius R gradually reduced from the large diameter portion 81 toward both axial ends, and a small diameter portion 83 having a small outer diameter D provided at an end of the reduced diameter portion 82. Here, the roll body 80 may be either hollow or solid, and the material of the roll body 80 may be appropriately selected from steel or the like, but in this embodiment, the roll body 80 is manufactured using a SUM material which is superior in machinability and processability to steel.

[0029] In this example, the crown-shaped tension roll 42 is configured to satisfy L1 / L2≦1 / 2, where L1 is the axial length of the large diameter portion 81 and L2 is the axial length of the reduced diameter portion 82. Therefore, in this example, the intermediate transfer body 45 stretched over the tension roll 42 is effectively prevented from meandering or shifting by the tension roll 42, and maintains flatness in the vicinity of the tension roll 42. In addition, in this example, as shown in FIG. 5(b), the wrap angles θ1 and θ2 of the intermediate transfer body 45 relative to the first tension roll 41a and the second tension roll 41b, which are crown-shaped tension rolls 42, are both selected to exceed 20 degrees. Furthermore, in this example, ribs (not shown) are provided at both ends of the intermediate transfer body 45 in the width direction, and rib guides (not shown) are provided at both ends of the tension roll 41 to regulate bias of the intermediate transfer body 45.

[0030] -Verification of the amount of slippage between the crown-shaped tension roll and the intermediate transfer body- In this embodiment, for example, as shown in FIG. 5(a), for a crown-shaped tension roll 42 having a large diameter portion 81 with a predetermined outer diameter D, the radius of the large diameter portion 81 is Ra, and the radius of the small diameter portion 83 is Rb. When the radius difference dR (Ra-Rb) between the large diameter portion 81 and the small diameter portion 83 was changed, the slippage amount SL was verified by simulation, and the result shown in FIG. 6 was obtained. In the same figure, when the slippage amount SL was verified by simulation for model I (e.g., dR = 200 μm) of a crown-shaped tension roll 42 having a large diameter portion 81 with an outer diameter D (e.g., φ14) and a large radius difference dR, the result shown by the solid line I was obtained.

[0031] Looking at the solid line I, at the location corresponding to the large diameter portion 81 of the tension roll 42, the slippage amount SL is a slippage in which the intermediate transfer body 45 side leads (indicated by + in Figure 6), and at the location corresponding to the narrowed diameter portion 82 of the tension roll 42, the slippage amount SL is a slippage in which the intermediate transfer body 45 is pulled in the opposite direction due to the slower peripheral speed of the tension roll 42 side (indicated by - in Figure 6), and increases toward the end of the tension roll 42. At this time, it was confirmed that the slippage amount SLb at the small diameter portions 83, which are both ends of the tension roll 42, was greater in absolute value than the slippage amount SLa at the large diameter portion 81. In addition, when checking for the presence or absence of abnormal noise, although abnormal noise was confirmed to be generated near both ends of the crown-shaped tension roll 42, no abnormal noise was observed near the center of the tension roll 42.

[0032] -Selection of radius difference of crown-shaped tension roll- Therefore, in this example, the maximum value of the slippage SLa at the large diameter portion 81 of model I is selected as the allowable boundary value TH, and a tension roll 42 having a radius difference dR such that the absolute value of the slippage SLb at the small diameter portion 83 of the tension roll 42 falls within the allowable boundary value TH is selected. Now, when the slippage SL was verified by simulation for model II with a small radius difference dR (e.g., dR = 70 μm), the result shown by the dotted line II was obtained. At this time, it was confirmed that the slippage SLa at the large diameter portion 81 of the tension roll 42 was smaller than that of model I, and the slippage SLb at the small diameter portion 83 of the tension roll 42 was equal to or less than the allowable boundary value TH in absolute value.

[0033] Furthermore, when the slippage amount SL was verified by simulation for model III (e.g., dR=100 μm) in which the radius difference dR was larger than that of model II, the result shown by the dashed dotted line III was obtained. At this time, it was confirmed that the slippage amount SLa at the large diameter portion 81 of the tension roll 42 was smaller than that of model I and larger than that of model II, and the slippage amount SLb at the small diameter portion 83 of the tension roll 42 was equal to or smaller than the allowable boundary value TH in absolute value. In this example, when a similar slippage simulation was performed on a tension roll 42 having a larger radius difference dR than that of model III, it was confirmed that the absolute value of the slippage amount SLb at the small diameter portion 83 of the tension roll 42 exceeded the allowable boundary value TH, which was a cause of abnormal noise.

[0034] In this embodiment, when using a crown-shaped tension roll 42 having a large diameter portion 81 with an outer diameter D (for example, φ14), it is understood that by selecting the radius difference dR between the large diameter portion 81 and the small diameter portion 83 of the tension roll 42 to be equal to or less than the allowable boundary value TH, it is possible to provide a transfer module 40 in which the amount of slippage that would cause abnormal noise between the intermediate transfer body 45 and the crown-shaped tension roll 42 is not reached. In this example, from the viewpoint of preventing the generation of abnormal noise, it is necessary to suppress the radius difference dR of the tension roll 42 to 100 μm or less. Also, when using a crown-shaped tension roll 42 having a large diameter portion 81 with a different outer diameter D, the allowable boundary value TH is selected as described above, and then the radius difference dR of the tension roll 42 is selected to be equal to or less than the allowable boundary value TH.

[0035] -Detection operation using image sensors- In addition, in this embodiment, the image sensor 48 is disposed immediately before the moving direction of the intermediate transfer body 45 in the area of ​​the intermediate transfer body 45 that is stretched over the first tension roll 41a. At this time, the first tension roll 41a is a crown-shaped tension roll 42, and is designed not to have an amount of slippage between the intermediate transfer body 45 and the first tension roll 41a that would cause abnormal noise. Therefore, the intermediate transfer body 45 generates minute vibrations due to the stick-slip phenomenon near the first tension roll 41a, and does not generate abnormal noise. For this reason, in this example, even if the image sensor 48 is disposed near the first tension roll 41a, which is the crown-shaped tension roll 42 of the intermediate transfer body 45, there is no concern that the image detection operation by the image sensor 48 will be hindered. EXAMPLES

[0036] Example 1 The transfer module 40 according to the first embodiment was embodied, and a slippage simulation was performed on the crown-shaped tension roll 42. In Example 1, the tension roll 42 had a large diameter portion 81 and a tapered reduced diameter portion 82, and the ratio of the axial length of the large diameter portion 81 to the reduced diameter portion 82 was 5:12. The conditions for simulating slippage between the intermediate transfer body 45 and the tension roll 42 (the tension rolls 41a and 41b) are as follows. - Friction coefficient μ between the two: 0.2 -Intermediate transfer tension: 40N Intermediate transfer material: Polyimide resin - Tension roll material: SUM material Angle of intermediate transfer body hanging on first tension roll 41a: 72° Angle of intermediate transfer body passing over second tension roll 41b: 21°

[0037] For a crown-shaped tension roll 42 having a large diameter portion 81 with an outer diameter D (φ14 in this example), the radius difference dR (Ra-Rb) between the large diameter portion 81 and the small diameter portion 83 was changed, and the slippage amount SL was verified by simulation. The results shown in Figure 7 were obtained. In this example, tension rolls with dR (μm) of 0, 50, 70, 100, 130, 150, and 200 were prepared, and slip simulations were performed showing changes in the slip amount SL with respect to the axial position of the tension roll 42 for each tension roll. According to the results shown in FIG. 7, it can be seen that the allowable boundary value TH that does not result in abnormal noise is 0.03 mm, and the radius difference dR that satisfies the condition that the absolute value of the slippage amount SLb at the small diameter portion 83 of the tension roll 42 is less than the allowable boundary value TH (0.03 mm in this example) is 100 μm or less.

[0038] In addition, when selecting a radius difference dR that does not cause abnormal noise for a crown-shaped tension roll 42 having large diameter portions 81 with different outer diameters D, a slippage simulation is performed by changing the radius difference dR for each tension roll 42 with each outer diameter D, and the relationship between the slippage amount SLb and the radius difference dR is plotted, the result shown in FIG. 8 is obtained. In the figure, the outer diameter D of the large diameter portion 81 used was a tension roll of φ10, φ12, φ14, φ16, or φ18. In Figure 8, the allowable boundary value TH is set to 0.03 mm, and for each tension roll 42 having a large diameter portion 81 with a different outer diameter D, when the outer diameter D and the radial difference dR of the large diameter portion 81 where the slippage SLb is at the allowable boundary value TH (0.03 mm in this example) are plotted, the result shown in Figure 9 is obtained. In FIG. 9, the characteristic line J, which is a linear approximation of each plot point, is used as the boundary, and the radius difference dR is set so as to satisfy |SLb|≦the allowable boundary value TH. In this example, the characteristic line J is expressed by the following (Equation 1). dR≦-0.0155×D+0.346 (Formula 1)

[0039] Example 2 A slippage simulation was performed for a crown-shaped tension roll 42 having the same outer diameter D (φ12 in this example) of the large diameter portion 81 and the same radius difference dR (150 μm in this example) by changing the friction coefficient μ between the belt-like intermediate transfer body 45 made of polyimide resin and the tension roll 42. The results shown in Figures 10 to 12 were obtained. FIG. 10 shows the results of a sliding simulation for the friction coefficient μ=0.2. In this figure, similarly to Figure 7, slippage occurs in the direction in which the intermediate transfer body 45 moves forward at the location corresponding to the large diameter portion 81 of the tension roll 42, and slippage occurs in the direction in which the intermediate transfer body 45 moves backward at the location corresponding to the narrow diameter portion 82 of the tension roll 42. Moreover, FIG. 11 shows the results of a slip simulation when the friction coefficient μ=0.14. In the same figure, the simulation results of Figure 11 (represented by a solid line) and the simulation results of Figure 10 (represented by a dotted line) are superimposed, and it can be seen that the change in the slippage amount SL with respect to the axial position of the tension roll 42 is approximately similar.

[0040] Furthermore, FIG. 12 shows the results of a slip simulation for the friction coefficient μ=0.3. In the same figure, the simulation results of Figure 12 (represented by a solid line) and the simulation results of Figure 10 (represented by a dotted line) are superimposed, and it can be seen that the change in the slippage amount SL with respect to the axial position of the tension roll 42 is approximately similar. From this, it is presumed that the change in the friction coefficient μ between the intermediate transfer body 45 and the tension roll 42 does not affect the sliding characteristics between the intermediate transfer body 45 and the tension roll 42 . Furthermore, when a similar sliding simulation was performed for a tension roll 42 having a large diameter portion 81 of the same outer diameter D (φ12) but with different radius differences dR, and further for a tension roll 42 having a large diameter portion 81 with a different outer diameter D, the friction coefficient μ between the intermediate transfer body 45 and the tension roll 42 was changed, and it was confirmed that the friction coefficient μ does not affect the sliding characteristics between the intermediate transfer body 45 and the tension roll 42.

[0041] (Additional Note) (((1))) A crown-shaped tension roll around which a belt is rotatably tensioned, a large diameter portion having a large outer diameter and provided at the axial center of a roll body having a circular cross section on a surface thereof, and a small diameter portion having a small outer diameter and provided at an end of the reduced diameter portion, the reduced diameter portion gradually reducing in diameter from the large diameter portion toward both ends in the axial direction; Let SLa be the amount of slippage between the large diameter portion and the belt, SLb be the amount of slippage between the small diameter portion and the belt, and TH be the allowable boundary value of SLa that is not the amount of slippage that leads to abnormal noise. A tension roll, characterized in that a radius difference between the large diameter portion and the small diameter portion is set so as to satisfy |SLb|≦TH. (((2))) In the tension roll according to (((1)), A tension roll characterized in that the tolerance boundary value TH is 0.03 mm in absolute value. (((3))) In the tension roll according to (((2)), A tension roll, characterized in that the slippage amount SLb is within the allowable boundary value of 0.03 mm in absolute value. (((4))) In the tension roll according to any one of (((1))) to (((3))), A tension roll characterized in that, for a plurality of tension rolls each having a different outer diameter of the large diameter portion, a relationship between the radius difference between the large diameter portion and the small diameter portion and a slippage amount SLb between the reduced diameter portion and the belt is obtained in advance, and the radius difference between the large diameter portion and the small diameter portion is set so as to satisfy |SLb|≦tolerable boundary value TH. (((5))) In the tension roll according to (((4))), A tension roll characterized in that, for tension rolls having different outer diameters of the large diameter portion, the radius difference between the large diameter portion and the small diameter portion is changed, a slippage amount SLb between each of the reduced diameter portions and the belt is obtained, the outer diameter of the large diameter portion and the radius difference at which the slippage amount SLb is at the allowable boundary value TH are plotted, and the radius difference between the large diameter portion and the small diameter portion is set so as to satisfy |SLb|≦allowable boundary value TH, using a characteristic line that is a linear approximation of the plotted points as a boundary. (((6))) In the tension roll according to (((5))), A tension roll characterized in that, when the allowable boundary value TH is 0.03 (mm), the outer diameter of the large diameter portion is D (mm), and the radius difference is dR (mm), the characteristic line is expressed by the following (Equation 1). dR≦-0.0155×D+0.346 (Formula 1) (((7))) The present invention comprises a plurality of tension rolls and a belt that is stretched around the plurality of tension rolls and rotates in a circulating manner, A belt conveying device, characterized in that at least one of the tension rolls is a tension roll described in any one of ((1)) to (((6))). (((8))) In the belt conveying device according to (((7))), A belt conveying device, characterized in that the belt is hung at an angle of more than 20 degrees with respect to the crown-shaped tension roll. (((9))) In the belt conveying device according to (((7))) or (((8)), A belt conveying device, wherein, when the axial length of the large diameter portion is L1 and the axial length of the reduced diameter portion is L2, L1 / L2≦1 / 2. (((10))) A medium transport means for transporting a medium; an imaging means for forming an image on the medium; 2. An image forming system comprising the belt transport device according to claim 1, wherein the belt transport device is a part of the medium transport means or a part of the image forming means. (((11))) In the image forming system described in (((10))), in an aspect in which the belt conveying device is used as a part of the image forming means and the image is held on the belt, An image forming system comprising a detection means disposed opposite the surface of the belt for detecting image information held on the belt, and when the detection means is disposed near the crown-shaped tension roll of the belt, the detection means is disposed immediately before or immediately after the area of ​​the belt that is stretched over the crown-shaped tension roll.

[0042] According to the tension roll of (((1))), the generation of abnormal noise that depends on the speed difference between the belt and the tension roll can be suppressed for the crown-shaped tension roll around which the belt is rotatably stretched. With the tension roll according to (((2))), the crown shape of the tension roll can be easily selected by focusing on the amount of slippage between the large diameter portion and the belt, and taking into consideration that the amount of slippage does not lead to abnormal noise up to 0.03 mm. According to the tension roll of (((3))), by focusing on the amount of slippage between the reduced diameter portion and the belt and suppressing this amount of slippage to within 0.03 mm, the crown shape of the tension roll can be easily selected. According to the tension roll of (((4))), by grasping in advance the relationship between the radius difference between the large diameter portion and the small diameter portion and the amount of slippage between the reduced diameter portion and the belt for each tension roll having a different outer diameter of the large diameter portion, the radius difference between the large diameter portion and the small diameter portion can be easily set to suppress the generation of abnormal noise in the tension roll. According to the tension roll of (((5))), by creating a characteristic line that is the boundary between the allowable range and the non-allowable range for each tension roll having a different outer diameter of the large diameter portion, taking into account the relationship between the radius difference between the large diameter portion and the small diameter portion and the amount of slippage between the reduced diameter portion and the belt, it is possible to easily set the radius difference between the large diameter portion and the small diameter portion in order to suppress the generation of abnormal noise in the tension roll. According to the tension roll of (((6))), from the characteristic line when the allowable boundary value is set to 0.03 mm, in order to suppress the generation of abnormal noise in the tension roll, the radius difference between the large diameter portion and the small diameter portion can be easily set using the outer diameter of the large diameter portion as a parameter. According to the belt conveying device of (((7))), it is possible to provide a belt conveying device that can suppress the generation of abnormal noise that depends on the speed difference between the belt and the tension roll, for a crown-shaped tension roll around which a belt is rotatably tensioned. According to the belt conveying device of (((8))), even if the belt hook angle with respect to the crown-shaped tension roll is increased, the generation of abnormal noise that depends on the speed difference between the belt and the tension roll can be effectively suppressed. According to the belt conveying device of (((9))), it is possible to suppress the occurrence of abnormal noise that depends on the speed difference between the belt and the tension roll, while simultaneously suppressing the bending deformation of the crown-shaped tension roll and maintaining the flatness of the tensioned belt. According to the image forming system relating to (((10))), it is possible to provide an image forming system including a belt conveying device that is capable of suppressing the generation of abnormal noise that depends on the speed difference between the belt and the crown-shaped tension roll around which the belt is rotatably tensioned. According to the image forming system of (((11))), when the detection means is disposed near the crown-shaped tension roll of the belt, the flatness of the belt is maintained and image information can be accurately detected while suppressing the generation of vibrations and abnormal noise between the belt and the tension roll. [Explanation of symbols]

[0043] 1 (1a to 1d)... tension roll, 2... crown-shaped tension roll, 3... roll body, 4... large diameter portion, 5... reduced diameter portion, 6... small diameter portion, 7... belt, 10... belt conveying device, 11... image forming system, 12... medium conveying means, 13... imaging means, S... medium, SLa... slippage between the large diameter portion and the belt, SLb... slippage between the reduced diameter portion and the belt, Ra... radius of the large diameter portion, Rb... radius of the small diameter portion, TH... allowable boundary value, dR... radius difference between the large diameter portion and the small diameter portion

Claims

1. A crown-shaped tension roll around which a belt is rotatably tensioned, a large diameter portion having a large outer diameter and provided at the axial center of a roll body having a circular cross section on a surface thereof, and a small diameter portion having a small outer diameter and provided at an end of the reduced diameter portion, the reduced diameter portion gradually reducing in diameter from the large diameter portion toward both ends in the axial direction; Let SLa be the amount of slippage between the large diameter portion and the belt, SLb be the amount of slippage between the reduced diameter portion and the belt, and TH be an allowable boundary value of SLa that is not the amount of slippage that leads to abnormal noise. A tension roll, characterized in that a radius difference between the large diameter portion and the small diameter portion is set so as to satisfy |SLb|≦TH.

2. In the tension roll according to claim 1 , A tension roll characterized in that the allowable boundary value TH is 0.03 mm in absolute value.

3. In the tension roll according to claim 2, A tension roll characterized in that the slippage amount SLb is within the allowable boundary value of 0.03 mm in absolute value.

4. In the tension roll according to claim 1 , A tension roll characterized in that, for a plurality of tension rolls each having a different outer diameter of the large diameter portion, the relationship between the radius difference between the large diameter portion and the small diameter portion and the amount of slippage SLb between the reduced diameter portion and the belt is determined in advance, and the radius difference between the large diameter portion and the small diameter portion is set so as to satisfy |SLb|≦tolerable boundary value TH.

5. In the tension roll according to claim 4, A tension roll characterized in that for tension rolls having different outer diameters of the large diameter portion, the radius difference between the large diameter portion and the small diameter portion is changed, a slippage amount SLb between each of the reduced diameter portions and the belt is obtained, the outer diameter of the large diameter portion and the radius difference where the slippage amount SLb is the allowable boundary value TH are plotted, and a characteristic line that is a linear approximation of the plotted points is used as a boundary, and the radius difference between the large diameter portion and the small diameter portion is set so as to satisfy |SLb|≦allowable boundary value TH.

6. The tension roll according to claim 5, A tension roll characterized in that, when the allowable boundary value TH is 0.03 (mm), the outer diameter of the large diameter portion is D (mm), and the radius difference is dR (mm), the characteristic line is expressed by the following (Equation 1). dR≦-0.0155×D+0.346 (Formula 1)

7. The present invention comprises a plurality of tension rolls and a belt that is stretched around the plurality of tension rolls and rotates in a circulating manner, 2. A belt conveying device, comprising the tension roll according to claim 1 as at least one of said tension rolls.

8. 8. The belt conveying device according to claim 7, A belt conveying device, characterized in that the belt is hung at an angle of more than 20 degrees with respect to the crown-shaped tension roll.

9. 8. The belt conveying device according to claim 7, A belt conveying device, wherein, when the axial length of the large diameter portion is L1 and the axial length of the reduced diameter portion is L2, L1 / L2≦1 / 2.

10. A medium transport means for transporting a medium; an imaging means for forming an image on the medium; 10. An image forming system comprising the belt conveying device according to claim 7 as a part of the medium conveying means or as a part of the image forming means.

11. 11. The image forming system according to claim 10, wherein the belt conveying device is used as a part of the image forming means, and the image is held on the belt, An image forming system comprising a detection means disposed opposite the surface of the belt for detecting image information held on the belt, and when the detection means is disposed near the crown-shaped tension roll of the belt, the detection means is disposed immediately before or immediately after the area of ​​the belt that is stretched over the crown-shaped tension roll.

Images