JP4212208B2 - Belt unit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a belt unit applied to a transfer belt driving mechanism in an image forming apparatus such as a copying machine.
[0002]
[Prior art]
In this type of belt unit, as a measure for preventing meandering of the belt stretched around the driving and driven rollers, for example, as disclosed in Japanese Patent Laid-Open No. 10-240033, the roller axis direction of the belt (both in the width direction) is used. Or a crown shape in which the outer diameter of the roller is changed in the length direction of the roller or an inverted crown shape. It is common.
[0003]
However, these are only used to resist the tension of the belt against the meandering force. For example, the belt tension is short and the belt meandering force is relatively small. If the tension is long and a large belt meandering force is generated (in particular, a tandem transfer belt or the like), it becomes difficult to suppress meandering.
[0004]
For this reason, conventionally, the inner surfaces of the thrust rods provided respectively on the both axial ends of the driving and driven rollers are set to be slidable on the meandering movement restricting surface composed of the end surfaces of the belt in the axial direction of the belt, Alternatively, as shown in FIG. 10, thrust collars 103 and 103 are provided on both ends in the axial direction of the driving and driven rollers 101 and 102 on which the belt 100 is stretched, respectively, while both ends in the roller axial direction on the back surface of the belt 100 are provided. Convex guide bodies 104, 104 are provided on the entire circumference of the belt, and inner surfaces 104a, 104a in the axial direction of the convex guide bodies 104, 104 are used as belt meandering movement restricting surfaces. Each outer surface 103a of 103, 103 is set to be slidable on the meandering movement restricting surface 104a, and the belt meander is widened. Mechanically measures to suppress have been taken from the outside.
[0005]
[Problems to be solved by the invention]
However, these measures can prevent the meandering of the belt 100 even if the belt stretch is relatively long. However, the meandering force is suppressed because the meandering movement is suppressed by both the driving and driven rollers 101 and 102. If it is large, there is a problem that the drive roller 101 that receives the meandering force vibrates or causes uneven rotation, and as a result, the circular movement of the belt 100 itself becomes unstable.
[0006]
The present invention has been made to solve the above problem, and can effectively prevent the meandering of the belt, avoid the influence of the meandering force on the driving roller, and obtain a stable belt rotation state. It is an issue to provide.
[0007]
[Means for Solving the Problems]
Above-mentioned problems is provided in the image forming apparatus, an outer diameter of 50mm or less, comprising a plurality of rows la, the endless belt stretched over the roller of the multiple including drive and driven rollers, The belt is provided with convex guide bodies over the entire circumference of the belt on the back surfaces of both end portions in the roller axis direction, and each has a meandering movement restricting surface composed of an inner surface in the roller axis direction of the convex guide body, The driving and driven rollers have meandering prevention means made of thrust collars provided on both end faces in the axial direction of the rollers, and the outer diameter of the driving roller or driven roller is the free curvature diameter of the belt × the belt winding is set to more than the angle / 360 °, the spaced thrust collar of the drive roller and the meandering movement restricting surface of the belt, snake thrust collar and the belt of the driven roller Belt units and the movement restricting surface and having a belt drive state Ryakusuri dynamic, and provided in the image forming apparatus, an outer diameter of 50mm or less, and a plurality of rollers including a drive and a driven roller, An endless belt stretched around the plurality of rollers, the belt having meandering movement restricting surfaces each consisting of both end surfaces of the belt in the roller axial direction, and the driving and driven rollers are the rollers. The outer diameter of the driving roller or the driven roller is set to a belt free curvature diameter × belt winding angle / 360 degrees or more, and a thrust roller of the driving roller is provided. The belt has a belt drive state in which the flange and the meandering movement restricting surface of the belt are separated from each other, and the thrust rod of the driven roller and the meandering movement restricting surface of the belt slide substantially. It is solved by a belt unit according to claim.
[0008]
According to this belt unit, when the driving roller rotates, the belt rotates around the driving roller and the driven roller by the rotational force.
[0009]
If the drive roller that drives the belt is separated from the meandering movement restricting surface of the belt and the driven roller and the meandering movement restricting surface of the belt slide, the meandering occurs in the belt. The meandering force is received by the driven roller instead of the driving roller. As a result, the meandering force of the belt is suppressed and the meandering force does not act on the drive roller. Operation is retained.
Further, the outer diameter of the driving roller or the driven roller is set to be a belt free curvature diameter × belt wrapping angle / 360 degrees or more, so that the belt is repeatedly bent by the belt and the meandering is further suppressed. This reduces the local stress on the belt.
[0010]
Further, convex guide bodies are provided on both ends of the belt back surface in the roller axial direction, and the belt meandering movement restricting surface is an inner surface of the convex guide body in the roller axial direction. When the prevention means is provided on both end surfaces of the roller in the axial direction, and the outer surface in the roller axial direction is a thrust collar facing the meandering movement regulating surface of the belt, the belt end surface is directly on the roller side. There is no contact, and the belt itself is not worn by the meandering force, so that it can be used for a long period of time.
[0011]
Furthermore, the meandering movement restricting surface of the belt is composed of an end surface in the roller axial direction of the belt, the meandering preventing means is provided on both end surfaces of the roller in the axial direction, and the inner side surface in the roller axial direction is the surface of the belt. When the thrust rod is opposed to the meandering movement regulating surface, it is not necessary to provide a guide body on the belt, and the belt structure is simplified.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0014]
FIG. 1 is a schematic diagram showing a tandem color digital copying machine (hereinafter simply referred to as a copying machine) provided with a belt unit according to an embodiment of the present invention.
[0015]
In FIG. 1, the copying machine A includes an image reader unit 200 that reads a document image, and a printer unit 300 that prints and reproduces the read image on a recording sheet.
[0016]
The image reader unit 200 is a known unit that reads an image of a document placed on a document glass plate (not shown) by moving the scanner, and is irradiated by an exposure lamp installed on the scanner. The obtained document image is imaged by a condenser lens, and is further spectrally divided into light of three wavelengths of red (R), green (G), and blue (B) by a spectroscope. The image is incident on a CCD image sensor for green, a CCD image sensor for green, and a CCD image sensor for blue. An output signal from each CCD image sensor (hereinafter referred to as a CCD sensor) is AD-converted to obtain R, G, B image data of the document.
[0017]
The image data for each color component obtained by the image reader unit 200 is subjected to various data processing in the control unit 45, and further, cyan (C), magenta (M), yellow (Y ), Converted into image data of each reproduction color of black (BK) (hereinafter, reproduction colors of cyan, magenta, yellow, and black are represented as C, M, Y, and BK, and are related to each reproduction color) The C, M, Y, and BK are added as subscripts to the number of the component to be performed).
[0018]
The image data is stored in the image memory in the control unit 45 for each reproduction color, subjected to a necessary image correction for positional deviation correction, and then one scanning line in synchronism with the recording sheet supply. It is read out every time and becomes a laser diode drive signal.
[0019]
The printer unit 300 forms an image by a well-known electrophotographic system. The photosensitive drums 31C to 31BK are charged by the charging chargers 33C to 33BK, and then from the laser diodes 32C to 32BK. A latent image is formed on the surface by receiving the beam irradiation and developed by the developing devices 34C to 34BK.
[0020]
At each transfer position, the images are sequentially transferred onto the belt 2 by electrostatic action of transfer chargers 25C to 25BK disposed on the back side of an intermediate transfer belt (hereinafter simply referred to as a belt) 2. At this time, the image forming operation for each color is executed while shifting the timing toward the upstream side so that the toner image is superimposed and transferred at the same position of the rotating belt 2.
[0021]
In this manner, the toner images on the surfaces of the photosensitive drums 31C to 31BK carrying the toner images of the respective colors are transferred onto the belt 2 as the drums 31C to 31BK rotate. The belt 2 carries a toner image of each color as a full color image, and transfers the toner image to the recording medium 37 at a secondary transfer portion where the drive roller 8 is in pressure contact with the secondary transfer roller 36.
[0022]
The recording medium 37 is sent one by one by a pickup roller 38 and conveyed to the secondary transfer unit by a conveyance roller 39 or the like. The recording medium 37 onto which the toner image has been transferred by the secondary transfer unit is fixed to the toner image by a fixing device comprising a fixing roller 40 and is discharged onto the tray 42 by discharge rollers 41 and 41.
[0023]
The transfer belt unit 1 including the belt 2 can be detached from the printer unit 300 by opening and closing the operation cover 43.
[0024]
Next, the configuration of the transfer belt unit 1 will be described with reference to FIGS.
[0025]
The transfer belt unit 1 includes a pair of driving and driven rollers 8 and 3, for example, a tension roller (shown only in FIG. 1) 6 provided as necessary, and an endless shape stretched around the rollers 3, 6, and 8. The belt 2 is provided.
[0026]
The roller shaft 11 of the driven roller 3 is rotatably supported at one end portion of an elongated support frame 5 in the longitudinal direction of the belt, and the roller of the driving roller 8 is supported at the other end portion of the support frame 5. The shaft 12 is rotatably supported. Further, a long hole 9 is provided in the longitudinal direction of the support portion of the support roller 5 where the drive roller 8 is supported, and the roller shaft 12 of the drive roller 8 is fitted into the long hole 9. The drive roller 8 is rotatably supported with respect to the support frame 5 and is set to be movable in the longitudinal direction of the support frame 5.
[0027]
Further, inside the endless belt 2, one end side of the subframe 7 is rotatably connected to and supported by the roller shaft 11 of the driven roller 3, and the other end portion of the subframe 7. The tension roller 6 is rotatably supported with respect to the sub-frame 7. By urging the sub-frame 7 with the spring force of the compression coil spring 4 inserted between the support frame 5 and the sub-frame 7, the tension roller 6 applies a tension force to the belt 2. Yes.
[0028]
On the other hand, on the back surface of the belt 2, as shown in FIG. 2 to FIG. 5, convex guide bodies 21 and 21 that are located at both ends in the roller axial direction and are provided over the entire circumference of the belt are provided. Each inner side surface 21 a in the roller axis direction of the convex guide bodies 21 and 21 is configured as a meandering movement restricting surface of the belt 2.
[0029]
Thrust collars 80 and 80 having substantially the same outer diameter as that of the driving roller 8 are provided on both end surfaces of the driving unit 8 in the roller axis direction of the belt unit 1 as meandering prevention means. Thrust collars 30 and 30 having substantially the same outer diameter as the driven roller 3 are also provided on both end surfaces in the roller axis direction as meandering preventing means. The outer surfaces 30a and 80a of the thrust collars 30 and 80 in the roller axis direction respectively oppose the meandering movement restricting surfaces 21a and 21a of the belt 2 as shown in FIGS.
[0030]
When the width dimension of the driving roller 8 including the thrust collars 80 and 80 is Ld and the width dimension of the driven rollers 3 and 3 including the thrust collars 30 and 30 is Lf, Lf> Ld, and when the belt 2 meanders, The outer surface 80a of the thrust collar 80 on the drive roller 8 side is separated from the meandering movement restricting surface 21a of the belt 2, and the outer surface 30a of the thrust collar 30 on the driven roller 3 side is substantially slid. It is set to be possible.
[0031]
In the above configuration, when the driving roller 8 is rotated by a rotation driving device (not shown), the belt 2 is rotated between the driving roller 8, the tension roller 6 and the driven roller 3 by the rotational driving force.
[0032]
The belt 2 meanders during the circular movement of the belt 2, and the meandering movement restricting surface (the inner surface of the convex guide body 21 in the roller axial direction) 21 a is likely to hit the outer surface 80 a of the thrust collar 80 on the drive roller 8 side. However, prior to this, the meandering movement restricting surface 21a slides substantially on the outer surface 30a of the thrust collar 30 on the driven roller 3 side. For this reason, the thrust collars 30 and 30 on the driven roller 3 side mechanically restrict the meandering force from the width direction of the belt 2, thereby suppressing the meandering in the initial stage.
[0033]
Thus, since the meandering force is received on the driven roller 3 side instead of the driving roller 8, even if the meandering force of the belt 2 is large, the driving roller 8 is not affected by the meandering force. That is, there is no possibility that the driving roller 8 vibrates due to the meandering force or causes uneven rotation, and the stable movement state of the belt 2 is ensured.
[0034]
The thrust collar 80 on the side of the driving roller 8 may remain from the viewpoint of protecting both end surfaces of the driving roller 8 in the roller axial direction, but there is no fear that the meandering force is not exerted at all. This may be omitted.
[0035]
In this embodiment, the belt 2 is provided with the convex guide body 21 that slides on the outer surface 30a of the thrust collar 30 on the driven roller 3 side during belt meandering. There is no risk of wear, and the belt has excellent durability.
[0036]
6 and 7 show a deformation structure of the main part of the belt unit 1.
[0037]
6 and 7, a meandering movement restricting surface of the belt 2 is constituted by the end surface 2a of the belt 2 in the roller axial direction.
[0038]
Thrust rods 90, 90 having a diameter larger than that of the roller 8 are provided on both end surfaces of the driving roller 8 in the roller axial direction as meandering preventing means, and both ends of the driven roller 3 in the roller axial direction are provided. Thrust rods 50 and 50 having a diameter larger than that of the roller 3 are also provided on the surface as meandering preventing means. Inner side surfaces 50a and 90a of the thrust rods 50 and 90 in the roller axial direction respectively face the meandering movement restricting surface 2a of the belt 2.
[0039]
When the width dimension of the driving roller 8 including the thrust rods 90 and 90 is Ld and the width dimension of the driven rollers 3 and 3 including the thrust rods 40 and 40 is Lf, Lf <Ld, and when the belt 2 meanders, The inner surface 90a of the thrust rod 90 on the drive roller 8 side is separated from the meandering movement restricting surface 2a of the belt 2, and the inner surface 50a of the thrust rod 50 on the driven roller 3 side is in relation to the meandering movement restricting surface 2a. It is set to be slidable.
[0040]
Also in this case, even if the belt 2 meanders during the circular movement of the belt 2 and the belt movement restricting surface 2a of the belt 2 hits the inner surface 90a side of the thrust rod 90 on the drive roller 8 side, The meandering movement regulating surface 2a of the belt 2 is in a state of sliding substantially on the inner side surface 50a of the thrust rod 50 on the driven roller 3 side. For this reason, the thrust rods 40, 40 on the driven roller 3 side mechanically restrict the meandering force from the width direction of the belt 2, and as a result, meandering can be suppressed at the initial stage as described above.
[0041]
Thus, since the meandering force is received on the driven roller 3 side instead of the driving roller 8, even if the meandering force of the belt 2 is large, the driving roller 8 is not affected by the meandering force. The drive roller 8 is prevented from vibrating or rotating unevenly, so that the belt 2 can be stably moved.
[0042]
In this example, since it is not necessary to provide the guide bodies 21 and 21 on the back surface of the belt 2, the configuration for exhibiting the above meandering prevention effect is simplified.
[0043]
Also in this case, the thrust rod 90 on the side of the driving roller 8 may remain from the viewpoint of protecting both end surfaces of the driving roller 8 in the roller axial direction, but there is a possibility that the meandering force acts at all. If not, this may be omitted.
[0044]
By the way, the belt 2 tends to be stressed around the belt around the driving and driven rollers 8 and 3, and particularly, the driven roller 3 side that receives the meandering force tends to generate a large stress.
[0045]
In order to cope with this, the relationship between the outer diameters Rd and Rf of the driving roller 8 and the driven roller 3 and the winding angle of the belt 2 is preferably set as follows.
[0046]
Rd ≧ free curvature diameter × winding angle / 360 degrees Rf ≧ free curvature diameter × winding angle / 360 degrees In the above equation, the free curvature diameter means that the belt 2 is supported by a roller as shown in FIG. The curvature diameter R formed when left in a natural state. Further, as shown in FIG. 8B, the winding angle of the belt 2 is an angle θ in a range where the belt 2 is in contact with the roller outer peripheral surface with respect to the roller axis O of the driven roller 3 or the driving roller 8. Say.
[0047]
As a proof of the above equation, the experimental results with the free curvature diameter R of the belt 2 as a parameter are shown in FIG. In this experiment, four types of belts 2 having free curvature diameters R of 20 mm, 40 mm, 60 mm, and 80 mm, respectively, are prepared, and the thrust collar 30 of the guide body 21 and the driven roller 3 shown in FIGS. In the meandering prevention mechanism in combination with the above, the presence or absence of occurrence of belt abnormality (belt cracking) over time when the outer diameter of the driven roller 3 is changed and the belt 2 is run is examined. In FIG. 9, straight lines a, b, c, and d are characteristics when the free curvature diameter R is 20 mm, 40 mm, 60 mm, and 80 mm.
[0048]
As can be seen from the graph of FIG. 9, when the winding angle θ of the driven roller 3 is 180 degrees, for a belt having a free curvature diameter R of 20 mm, if the outer diameter Rf of the driven roller 3 is 10 mm or more, the belt There was no abnormality, and for each belt having a free curvature diameter R of 40 mm, 60 mm, and 80 mm, no belt abnormality occurred if the outer diameter Rf was 20 mm, 30 mm, or 40 mm, respectively.
[0049]
When the winding angle θ of the driven roller 3 is 80 degrees, the outer diameter Rf is 5 mm or more, 10 mm or more, 15 mm or more, 20 mm or more for each belt having a free curvature diameter R of 20 mm, 40 mm, 60 mm, or 80 mm. Then, no belt abnormality occurred.
[0050]
That is, it was found that by setting the outer diameter Rf of the driven roller 3 to each free curvature diameter R × winding angle θ / 360 degrees or more, it is possible to suppress occurrence of belt abnormality such as belt cracking or creep deformation due to belt elongation. .
[0051]
Further, the outer diameter Rd of the main driving roller 8 and the outer diameters of the other rollers were not shown, but the same experimental results were shown.
[0052]
In the above embodiment, the drive roller 8 and the driven roller 3 are provided one by one. However, the number of rollers is not limited thereto.
[0053]
In the above embodiment, the transfer belt unit 1 of the copying machine has been described as an example. However, the transfer belt unit 1 can be applied to various belt transmission mechanisms having driving and driven rollers.
[0054]
【The invention's effect】
As described above, according to the present invention, the drive roller for driving the belt and the belt meandering movement restricting surface are separated from each other, and the driven roller and the belt meandering restricting surface are in a sliding state. When meandering occurs, the meandering force is received on the driven roller side instead of the driving roller side, and the meandering is suppressed. In addition, since the meandering force does not act on the driving roller, the possibility that the driving roller may vibrate or cause uneven rotation is eliminated even if the meandering force increases, and the belt rotation is stably maintained.
In addition, since the outer diameter of the driving roller or the driven roller is set to a belt free curvature diameter × belt winding angle / 360 degrees or more, the belt can be repeatedly bent and the meandering force can be suppressed by passing the roller. The associated local stress is reduced.
[0055]
Further, convex guide bodies are provided over the entire circumference at both ends in the roller axial direction on the back surface of the belt, and the inner side surface of each of the convex guide bodies in the roller axial direction is used as a meandering movement regulating surface of the belt, thereby preventing the meandering. If the means is provided on each axial end surface of the roller and the outer surface in the roller axial direction is a thrust collar facing the meandering movement regulating surface of the belt, the belt end surface directly contacts the roller side. Thus, it is possible to avoid the belt itself from being worn by the meandering force as much as possible.
[0056]
Furthermore, the meandering movement restricting surface of the belt is constituted by the end surface of the belt in the roller axial direction, the meandering preventing means is provided on both end surfaces in the axial direction of the roller, and the inner side surface in the roller axial direction is the belt. In the case of the thrust rod facing the meandering movement restricting surface, there is no need to provide a guide body on the belt, and the structure becomes simple.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing a copying machine to which a belt unit according to an embodiment of the present invention is applied.
FIG. 2 is a schematic plan view showing a belt unit in the copying machine with a tension roller omitted.
FIG. 3 is a perspective view of the essential part of the belt unit, partly broken away.
4 is a longitudinal sectional view taken along line IV-IV in FIG.
5 is a longitudinal sectional view taken along line VV in FIG. 2. FIG.
FIG. 6 is a longitudinal sectional view showing a driving roller side in a modified example of the main part of the belt unit.
FIG. 7 is a longitudinal sectional view showing a driven roller side in a modified example of the main part of the belt unit.
FIGS. 8A and 8B are explanatory views of a belt free curvature diameter, and FIG. 8B is an explanatory view of a belt winding angle.
FIG. 9 is a characteristic diagram showing the relationship between the outer diameter of the driven roller and the belt winding angle.
FIG. 10 is a schematic perspective view showing a conventional belt unit.
[Explanation of symbols]
1 ············ Belt Unit 2 ······················· Belts 2a, 21a ... Surface 3 ············· Followed roller 8 ············································ Roller shaft 30 ... Thrust collar (Meandering prevention means)
50 ··························· Thrust cage
30a ··················································· Outside surface 50a of the thrust collar Outer diameter R ········· Free curvature diameter θ

Claims (2)

Provided in the image forming apparatus,
Outer diameter of 50mm or less, a plurality of rows la, including a drive and a driven roller,
And an endless belt stretched over the roller of the multiple,
The belt is provided with convex guide bodies over the entire circumference of the belt on the back surfaces of both end portions in the roller axis direction, and each has a meandering movement restricting surface composed of an inner surface in the roller axis direction of the convex guide body,
The driving and driven rollers have meandering prevention means composed of thrust collars provided on both end faces in the axial direction of the rollers,
The outer diameter of the driving roller or the driven roller is set to a belt free curvature diameter × belt winding angle / 360 degrees or more,
Belt and meandering movement restricting surface of the thrust collar and the belt of the drive roller is separated, and the meandering movement restricting surface of the thrust collar and the belt of the driven roller and having a belt drive state to Ryakusuri dynamic unit. Provided in the image forming apparatus,
A plurality of rollers including driving and driven rollers having an outer diameter of 50 mm or less;
An endless belt stretched around the plurality of rollers,
The belts each have meandering movement restricting surfaces composed of both end surfaces of the belt in the roller axial direction,
The driving and driven rollers have thrust rods provided on both end surfaces in the axial direction of the rollers,
The outer diameter of the driving roller or the driven roller is set to a belt free curvature diameter × belt winding angle / 360 degrees or more,
The belt has a belt driving state in which the thrust rod of the driving roller and the meandering movement regulating surface of the belt are separated from each other, and the thrust rod of the driven roller and the meandering movement regulating surface of the belt slide substantially. unit.

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