JP2006071818A - Belt transfer device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To apply even an endless belt with relatively high rigidity to a belt transfer device and to prevent the belt from meandering with simple constitution of a small number of components. <P>SOLUTION: In the belt transfer device in which the endless belt for transferring a toner image from an image carrier is extended by a plurality of rollers such as a driving roller and an idler roller, a spiral belt roller 10 as at least one of the plurality of rollers has a roller surface where a plurality of spiral belts different in swirling direction are formed of spiral belts 12A and 12B in a V expansion shape. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a belt transfer apparatus that transfers a toner image from an image carrier.

Conventionally, for example, in an image forming system such as a high-speed copying machine, a color copying machine, and a color laser printer, a belt transfer device using an endless belt for transferring a toner image is used.
In general, the rollers are arranged parallel to each other on the inner peripheral surface of the endless belt, and the endless belt is driven to rotate by friction with the rollers.
In such a belt transfer device, for example, the outer diameter varies due to a manufacturing error of the roller, or the parallelism of the mounting is deviated due to the mounting error, and the belt meanders. In the image forming system, since such belt meandering causes an image shift at the time of transfer and affects image quality, belt meandering is regulated by various means.
For example, Patent Document 1 discloses an apparatus in which a detent guide is formed on both side edges of the back surface of a belt-shaped electrophotographic photosensitive member as an endless belt meandering prevention mechanism.
Patent Document 2 discloses a belt transport in which a crown-shaped belt tension adjusting roller whose diameter is gradually reduced from the center to the end is adopted as one of the rollers for stretching an elastic transfer belt. An apparatus is described.
Patent Document 3 describes a color image forming apparatus that performs belt meandering control by vertically moving one end side of a drive steering roller based on a detection output of a belt end position sensor.
Japanese Patent Laid-Open No. 7-179239 (second page, FIGS. 4 and 5) JP-A-11-334925 (FIGS. 2 and 3) Japanese Patent Laid-Open No. 11-272094 (FIG. 3)

However, the conventional belt transfer apparatus as described above has the following problems.
The technique described in Patent Document 1 has a problem that the manufacturing cost is high because it is necessary to stick the stopper guide to the endless belt.
In addition, the detent guide is rotated and bent repeatedly along with the endless belt, and as a result, there is a problem that it is fatigued with time and easily peels off or breaks. In order to prevent this, it is necessary to increase the radius of curvature of the bend, but in this case, there is a problem that the roller diameter becomes large and it is difficult to reduce the size of the apparatus.
In the technique described in Patent Document 2, belt meandering is corrected by a combination of a belt tension adjusting roller having a crown shape and an elastic belt. Therefore, for example, an endless belt having a relatively high rigidity such as that used in an intermediate transfer belt transfer device that accurately transfers multi-color toner images in a color superimposed manner has a problem that sufficient meandering correction cannot be performed.
The technique described in Patent Document 3 requires a sensor that detects belt meandering, a control circuit that feeds back the detection output, a moving mechanism that moves the drive steering roller up and down, etc., and has a complicated configuration and high component costs. There is a problem.

  The present invention has been made in view of the above problems, and is a belt transfer apparatus that can be applied to an endless belt having relatively high rigidity and can prevent belt meandering with a simple configuration with a small number of parts. The purpose is to provide.

In order to solve the above problems, a belt transfer apparatus in which an endless belt for transferring a toner image from an image carrier is stretched by a plurality of rollers, and at least one of the plurality of rollers is provided. This roller surface is formed by a plurality of spiral bands having different turning directions.
According to this invention, since the plurality of spiral bands having different turning directions are formed on the roller surface of at least one roller, the direction component orthogonal to the conveying direction from the roller to the endless belt according to the rotation direction of the roller. The driving force is added. Therefore, the conveying force in the width direction orthogonal to the conveying direction of the endless belt can be dynamically balanced by the spiral bands having different turning directions. As a result, meandering of the endless belt can be prevented.
In particular, if the rotational direction of the spiral band is aligned with the direction in which the widthwise conveyance force is directed toward the end in the width direction during conveyance, the conveyance force by which the endless belt is extended in the width direction can be applied. In addition, the endless belt can be transported with good flatness.

According to a second aspect of the present invention, in the belt transfer device according to the first aspect, the plurality of spiral bands provided on the at least one roller pass through the center in the width direction of the endless belt and are orthogonal to the central axis of the roller. It is set as the structure provided substantially symmetrically with respect to the surface to perform.
According to the present invention, the plurality of spiral bands are provided substantially symmetrically with respect to a plane that passes through the center of the endless belt in the width direction and is orthogonal to the roller central axis. Can be formed.

According to a third aspect of the present invention, in the belt transfer device according to the first or second aspect, a friction coefficient of the plurality of spiral bands with respect to the endless belt is variable along a roller central axis direction.
According to this invention, the magnitude of the conveying force acting on the endless belt can be changed by changing the frictional force of the spiral band against the endless belt along the roller central axis direction. In particular, if the frictional force at the center in the width direction of the roller is set to be larger than that at the end, the transportability at the center of the endless belt can be stabilized and the belt can be efficiently resisted.

According to a fourth aspect of the present invention, in the belt transfer device according to any one of the first to third aspects, the plurality of spiral bands are composed of spiral ridges having elasticity.
According to this invention, since the spiral band of the endless belt is formed of a spiral protrusion having elasticity, the conveying force can be reliably transmitted from the roller to the endless belt even if the endless belt has high rigidity.

According to a fifth aspect of the present invention, in the belt transfer device according to the fourth aspect, the depth of the spiral groove sandwiched between the spiral ridges is variable along the roller central axis direction.
According to the present invention, the conveying force transmitted to the endless belt can be varied without changing the friction coefficient of the roller by varying the depth of the spiral protrusion along the roller central axis direction.

According to a sixth aspect of the present invention, in the belt transfer device according to the fourth or fifth aspect, the cross-section including the roller central axis of the spiral ridge is at least on the roller end side, and from the roller outer peripheral surface to the spiral groove. It is set as the structure formed so that it might have the inclination which goes to a roller edge part side toward a bottom part.
According to this invention, when the spiral ridge is pressed against the endless belt, at least on the roller end side, the contact surface with the endless belt is formed by the inclined surface formed from the roller outer peripheral surface to the bottom of the spiral groove. Since it increases, the conveyance force along the spiral band from a roller can be reliably transmitted to an endless belt.

  According to the belt transfer device of the present invention, a plurality of spiral bands formed on the rollers with different turning directions can dynamically balance the conveying force in the width direction perpendicular to the conveying direction of the endless belt. Even an endless belt with high mechanical rigidity can be applied, and there is an effect that belt meandering can be prevented without using other components such as a detent guide and a belt meandering control mechanism.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
A belt transfer apparatus according to an embodiment of the present invention will be described.
FIG. 1 is a schematic front view for explaining a schematic configuration of a belt transfer apparatus according to an embodiment of the present invention. FIG. 2 is a schematic front view for explaining an example of a roller used in the belt transfer device according to the embodiment of the present invention. FIG. 3A is a partial sectional view in a sectional view including a roller central axis, showing details of the portion A in FIG.

The belt transfer apparatus 1 according to the present embodiment can be used in an image forming system such as a high-speed copying machine, a color copying machine, or a color laser printer, for example, and adsorbs a transfer sheet to transfer a toner image onto the transfer sheet. And an endless belt such as an intermediate transfer belt for transferring a plurality of toner images onto a belt and transferring them collectively onto a transfer sheet.
Hereinafter, unless otherwise specified, the belt transfer device 1 is not limited to a transfer conveying unit or an intermediate transfer unit, and a description will be given focusing on portions common to both.
As shown in FIG. 1, the schematic configuration of the belt transfer device 1 includes a belt 2 (endless belt), a driving roller 3 (roller), an idler roller 5 (roller), a transfer mechanism 4, and a cleaning mechanism 7.

In FIG. 1, reference numeral 6 denotes a photosensitive member (image carrier) that forms a toner image on the surface and is rotated in the direction indicated by the arrow. Although not shown, a charging unit, an exposure unit, and a developing unit are provided on the outer peripheral side of the photoreceptor 6 along the rotation direction in order to form a toner image. Further, a sheet feeding / conveying means for conveying a transfer sheet for finally transferring the toner image is provided as necessary.
Although the figure shows a case where there is one photoconductor 6, it goes without saying that four photoconductors 6 and a transfer mechanism 4 are provided on the belt 2 when used in a tandem color printer, for example. Yes.

The belt 2 is an endless belt having a width w in the illustrated depth direction.
The material of the belt transfer device 1 is a dielectric sheet having a smooth surface, less stretchability and high dimensional stability.

The driving roller 3 is a roller member for rotationally driving the belt 2, and the roller shaft 11 is connected to driving means (not shown), and the roller surface is in contact with the inner peripheral side of the belt 2. .
The idler roller 5 is a roller member that is supported on the inner peripheral side of the belt 2 so as to be rotatable in parallel with the drive roller 3, and is pressed against the inner peripheral surface of the belt 2 by a biasing means such as a spring (not shown). Thus, the belt 2 can be stretched with a predetermined tension and can be rotated with the belt 2.
In the present embodiment, one idler roller 5 is provided, but two or more idler rollers 5 may be provided as necessary, and the belt 2 may be stretched so that the cross section along the conveying direction of the belt 2 forms a substantially polygonal cross section. In this case, the urging means is provided in at least one of the plurality of idler rollers 5.

At least one of the drive roller 3 and idler roller 5 employs a spiral belt roller 10 as shown in FIG.
The spiral belt roller 10 is a roller member in which a roller having a width W is formed around the roller shaft 11. The roller has a cylindrical portion 15 provided in a cylindrical shape with a diameter d ₁ around the roller shaft 11 and an outer peripheral surface provided on the cylindrical portion 15 having a diameter d ₂ (where d ₂ > d. ₁ ) and the spiral protrusion 14 (see FIG. 3A).
In this embodiment, the spiral ridge 14 is spirally formed by two spiral bands 12A and 12B having a rectangular cross section (see FIG. 3A) and a developed shape having a V-shape (see FIG. 2) having an apex angle 2θ. It is the protrusion part formed in the shape. And it is set as the shape which makes a plane symmetry by making the surface P which passes through the center of the width | variety of a roller and is orthogonal to a central axis into a symmetrical surface. For this reason, the angle θ is the twist angle of each spiral formed by the spiral bands 12A and 12B.
The spiral groove 13 is a groove sandwiched between the spiral bands 12A and 12B, and in this embodiment, the U-shaped cross section is formed at equal intervals.
The spiral belt roller 10 is arranged so that the V-shaped apexes of the spiral belts 12A and 12B are directed in the rotation direction when rotating with the conveyance of the belt 2.

The material of the spiral protrusion 14 is made of an elastic material having an appropriate friction coefficient with respect to the belt 2, and for example, rubber having an appropriate hardness, synthetic resin foam, or the like can be adopted.
The cylindrical portion 15 may be made of the same material as that of the spiral ridge portion 14, but any material may be adopted as long as the cylindrical ridge portion 14 can be rotationally driven while maintaining the outer diameter of the spiral ridge portion 14. . For example, synthetic resin, metal, rubber and the like can be employed.

Examples of rubber-based materials that can be used for the spiral protrusion 14 and the cylindrical portion 15 include SBR (styrene butadiene rubber), BR (polybutadiene rubber), IR (isoprene rubber), IIR (butyl rubber), and NBR. (Nitrile butadiene rubber), H-NBR (hydrogenated NBR), EPDM, EPM (ethylene propylene rubber), NBR / EPDM blend, CR (chloroprene rubber), ACM (acrylic rubber), ECO (epic chlorohydrin rubber), VMQ (Silicone rubber), U (urethane rubber), FKM (fluorine rubber), NR (natural rubber), and an appropriate mixed rubber thereof can be employed.
These rubber materials can be adjusted to an appropriate hardness by adding a softener or a filler.
Further, for example, an additive such as an ionic conductive agent, conductive carbon, metal powder, or the like may be added to these rubber-based materials so as to have an appropriate electric resistance value. In this case, there is an advantage that the spiral belt roller 10 can be provided with an antistatic effect and a static elimination effect, and the belt 2 can be prevented from being stained and the transfer performance can be improved.

Such a spiral belt roller 10 can be manufactured by various means.
For example, the roller shaft 11 is used as a metal core, and the cylindrical portion 15 is formed of, for example, a solid body or foamed material such as synthetic rubber or synthetic resin, and two rubber sheets punched in a V shape are bonded around the cylindrical portion 15. Thus, the spiral ridge 14 may be formed by providing the spiral bands 12A, 12B.
In this case, there is an advantage that the material of the cylindrical portion 15 and the spiral ridge portion 14 can be easily changed and a cutting step is not required to form the spiral groove 13.
Further, the roller shaft 11 as the core metal, a rubber-based material to form a cylindrical roller with a diameter d _2, it is also possible to form the spiral groove 13 by cutting. In this case, there is an advantage that it becomes easy to change the width, depth, cross-sectional shape and the like of the spiral groove 13 according to the position.

The transfer mechanism 4 is a mechanism for transferring the toner image formed on the surface of the photoreceptor 6 to the belt 2 side by electromagnetically attracting the toner image from the inner peripheral side of the belt 2.
When the belt transfer device 1 is a transfer conveyance unit, the transfer paper is attracted and conveyed on the belt 2, so that the toner image can be transferred onto the transfer paper via the belt 2.
When the belt transfer device 1 is an intermediate transfer unit, a toner image can be transferred in a color superimposed manner on the surface of the belt 2.
As the transfer mechanism 4, any configuration may be adopted as long as the toner image can be transferred. For example, a configuration in which a transfer roller to which a transfer voltage is applied by a high voltage power source (not illustrated) is provided.

The cleaning mechanism 7 is a mechanism for removing unnecessary toner adhering to the belt 2 so that the belt 2 can be reused. For example, a cleaning blade method in which the belt 2 is pressed against the belt 2 in a counter posture on the downstream side of the driving roller 3 can be employed.
Here, the downstream position of the drive roller 3 is downstream of the transfer paper separating position when the belt transfer device 1 is a transfer conveyance unit, and the transfer is performed when the belt transfer device 1 is an intermediate transfer unit. It is downstream of the transfer position to the paper.
The removed unnecessary toner is collected in a waste toner tank (not shown) by appropriate means.

Next, the operation of the belt transfer apparatus 1 of the present embodiment will be described focusing on the action of the spiral belt roller 10.
FIGS. 4A and 4B are schematic explanatory views in plan view and side view for explaining the operation principle of the belt transfer apparatus according to the embodiment of the present invention.

When the belt 2 is wound around the spiral belt roller 10, a finite winding angle is generally set. However, for simplicity, the belt 2 has a winding angle of approximately 0 ° as shown in FIG. Consider a case in which the paper is conveyed in the horizontal direction on the spiral belt roller 10. That is, the spiral belt roller 10 is rotated counterclockwise as indicated by an arrow in FIG. 4B, and the belt 2 is conveyed horizontally from the right side to the left side in the drawing.
At this time, it is assumed that the belt 2 has a width w (where w <W) and is disposed so that the center in the width direction is included in the surface P of the spiral belt roller 10.
At this time, as shown in FIG. 4 (a), as the conveyance of the belt 2 proceeds, the spiral bands 12A and 12B are sequentially applied to the upstream side (the right side in the figure) of the belt 2 as indicated by the hatched portions 12a and 12b, respectively. I will touch you. The conveying force of the belt 2 is transmitted as a frictional force f acting on a tangential portion on the spiral belt roller 10 in these regions.

In order to consider the direction of the conveying force, it is assumed that the belt 2 is fixed and the spiral belt roller 10 is virtually rotated slightly. At this time, since the spiral bands 12A and 12B are inclined with respect to the plane P by an angle θ, the tangential portions of the spiral bands 12A and 12B are directed from the plane P toward the end in the width direction after a slight rotation. Each moves a very small distance. Therefore, a frictional driving force in the conveying direction due to the rotation of the spiral belt roller 10 and a tensile force are applied to the belt 2 from both tangential portions toward both ends in the width direction.
Then, these tensile forces of the left and right force F _L, F _R is always well balanced from symmetry.

Here, consider a case where the belt 2 starts to meander for some reason. For example, the cause minute distance belt offset in a direction (upper side in the figure) that acts F _R in a very short time. At this time, the belt deviation, in the illustrated upper, helical band 12A, since a small moving distance in the same direction of the tangent portion 12B, a direction to reduce or cancel the fine movement amount giving a F _R.
On the other hand, in the direction (lower side) F _L acts, since the direction of the direction and the belt deviation minute movement of the minute movement of the tangential portion giving F _L are opposite, relatively helical band 12A, and 12B minute movement This is the same as increasing the amount.
As these results, the belt 2 is, when causing belt shifting in the direction of action of F _R, F _{R <F L,} and the restoring force in the direction for eliminating the belt skew acts.
Therefore, the belt 2 is pushed back to the center in the width direction, and these processes are repeated, so that the position of the belt 2 is balanced, and even if the belt meandering starts for some reason, the meandering width is immediately suppressed and Be transported. In this way, belt meandering is prevented.

  In the above, since the case where the winding angle is approximately 0 ° is taken as an example, it has been described that the frictional force acts on the tangential portion of the contact between the spiral band and the belt. It can be generalized that the same frictional force is applied from the contact portion by lateral movement of the parallelogram-shaped spiral band in plan view.

Action of such a belt meandering preventing, or increase the frictional force against the belt 2, helical band 12A, with or increase the twist angle θ of 12B, the resultant force F _L, than by increasing the value of F _R Can be enhanced.
As a means for increasing the frictional force, a material having a large friction coefficient with respect to the belt 2 can be used as the material of the spiral bands 12A and 12B.
Further, since the spiral bands 12A and 12B have elasticity, if the contact nip width is increased by changing the hardness thereof, the same effect as when the friction force is increased by changing the material is obtained.
Further, since the spiral bands 12A and 12B are provided as projecting portions, the spiral groove 13 is formed. Since the upper end portion of the spiral groove 13 has an effect of gripping the belt 2 when pressed by the belt 2, it becomes less slippery and has the same effect as an increase in frictional force.
Therefore, it is good also as a shape which raises the anti-slip | skid effect by making it a groove | channel, such as a groove | channel of a zigzag shape or a wave shape, for example.

  In the present embodiment, the spiral band is composed of two strips of the spiral strips 12A and 13A, but it goes without saying that the number of strips of the spiral strip may be appropriately changed depending on the twist angle. In general, it is preferable to increase the number of spiral bands as the twist angle increases.

As described above, the belt meandering-preventing action of the spiral belt roller 10 is based on the fact that the frictional forces toward the both ends in the width direction of the belt 2 are balanced in the width direction by the spiral bands 12A and 12B. For this reason, as long as the frictional force is balanced, the shapes of the spiral bands 12A and 12B may not be symmetrical with respect to the plane P.
For example, by changing the material and twist angle of the spiral bands 12A and 12B with the plane P as a boundary, it is possible to balance the frictional forces on the left and right in the width direction of the belt 2 even if the shape is asymmetric with respect to the plane P. It becomes.

  Further, the number of spiral bands is not limited to two in the axial direction of the roller as in this embodiment, and any number of two or more spiral bands may be provided. For example, spiral bands having different turning directions, materials, torsion angles, and the like can be arranged at predetermined intervals in the axial direction so that the frictional force on the left and right in the width direction of the belt 2 can be balanced as a whole.

As described above, according to the belt transfer apparatus of the present embodiment, belt meandering can be prevented only by providing the spiral belt roller 10 on at least one of the plurality of rollers. Therefore, for example, it is possible to provide a simple structure with fewer parts compared to the case where a belt stopper is provided on the belt or the belt meandering control is performed by controlling the position of the roller, and the apparatus is inexpensive. Can do.
Further, according to the spiral belt roller 10 of the present embodiment, the belt meandering can be prevented even if the roller diameter is constant. Unlike a case where, for example, a crown-shaped roller is used, not only an elastic belt but also a relatively high rigidity belt is used. Even if it exists, there exists an advantage which can be conveyed favorably. For this reason, for example, it is suitable for a belt transfer device of an image forming system such as a color printer that needs to use a belt having relatively high rigidity in order to suppress color misregistration.

Next, a first modification of the present embodiment will be described.
In this modification, the frictional force generated by the spiral bands 12A and 12B is balanced at both ends in the width direction of the belt 2 and is continuously or stepwise reduced from the center in the width direction of the belt 2 toward both ends. is there. That is, the frictional force received by the belt 2 has a mountain-shaped distribution that maximizes at the central portion in the width direction.
According to this modification, the influence of the belt width direction end portion is less likely to be affected, so that the transportability at the center of the belt is stabilized and the resistance to the belt meandering is increased, so that the belt meandering can be prevented more efficiently. It can be configured.

Next, a second modification of the present embodiment will be described.
FIGS. 3B and 3C are partial cross-sectional views similar to FIG. 3A for explaining a second modification of the embodiment of the present invention.
In this modification, the spiral groove 13 has a U-shaped cross section in the above embodiment, but at least in the spiral bands 12A and 12B, as shown in FIGS. 3 (b) and 3 (c). An inclined surface 16 a that is inclined toward the roller end portion side from the outer peripheral portion of the roller toward the bottom portion of the spiral groove 13 is provided on the side surface on the end portion side. The side surface on the central side of the roller may have any shape. For example, as illustrated, an inclined surface 16b that is inclined toward the central portion of the roller from the outer peripheral portion of the roller toward the bottom of the spiral groove 13 is provided. Can do. The cross-sectional shapes of the spiral bands 12A and 12B are a trapezoidal shape, a triangular shape, or the like.
According to this modified example, when frictional force acts on both ends of the belt 2 in the width direction, the belt 2 is smoothly pressed by the inclined surface 16a, so that the belt running stability can be improved.

  In the above description, the example in which a plurality of spiral bands are provided has been described. However, if there are a plurality of spiral bands having different turning directions, the number of threads may be one.

In the above description, the example in which the spiral groove 13 is provided adjacent to each of the spiral bands 12A and 12B has been described. However, the material and frictional characteristics are different by forming the spiral bands 12A and 12B adjacent to each other. It is good also as a structure which comprises one spiral band and the spiral groove 13 was provided in the both sides.
For example, the balance between belt conveyance and belt meandering prevention is good by making one of the friction characteristics that provides a large friction force in the conveyance direction and the other friction characteristic that provides a large friction force in the direction perpendicular to the conveyance direction. Can be.
Also, for example, by using one material with good friction characteristics at high humidity and the other material with good friction characteristics at low humidity, a spiral band having good belt meandering prevention performance even when the humidity change is large. Can be formed.

1 is a schematic front view for explaining a schematic configuration of a belt transfer apparatus according to an embodiment of the present invention. It is a front view schematic explanatory drawing for demonstrating an example of the roller used for the belt transfer apparatus which concerns on embodiment of this invention. It is a fragmentary sectional view of the cross section view including the roller central axis which shows the detail of the A section of FIG. 2 in the roller which concerns on embodiment of this invention, and its 2nd modification. FIG. 3 is a schematic explanatory view in a plan view and a side view for explaining an operation principle of the belt transfer device according to the embodiment of the present invention.

Explanation of symbols

1 Belt transfer device 2 Belt (endless belt)
3 Driving roller (roller)
4 Transfer mechanism 5 Idler roller (roller)
6 Photoconductor (image carrier)
7 Cleaning mechanism 10 Spiral belt roller (roller)
12A, 12B Spiral belt 13 Spiral groove 14 Spiral ridge (spiral ridge)
15 Tubular parts 16a, 16b Inclined surface

Claims (6)

A belt transfer device in which an endless belt for transferring a toner image from an image carrier is stretched by a plurality of rollers,
A belt transfer device, wherein a roller surface of at least one of the plurality of rollers is formed by a plurality of spiral bands having different turning directions.   The plurality of spiral bands provided on the at least one roller are provided substantially symmetrically with respect to a plane passing through the center in the width direction of the endless belt and orthogonal to the roller central axis. The belt transfer device described.   The belt transfer apparatus according to claim 1 or 2, wherein a friction coefficient of the plurality of spiral bands with respect to the endless belt is varied along a roller central axis direction.   The belt transfer device according to claim 1, wherein the plurality of spiral bands are made of elastic spiral ridges.   The belt transfer device according to claim 4, wherein the depth of the spiral groove sandwiched between the spiral protrusions is varied along the roller central axis direction.   The cross section including the roller central axis of the spiral ridge is formed so as to have an inclination toward the roller end side from the roller outer peripheral surface to the bottom of the spiral groove at least on the roller end side. Item 6. The belt transfer device according to Item 4 or 5.

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