JP4021717B2 - Image forming apparatus - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an apparatus for constant belt speed control of equipment having a belt apparatus that requires constant speed running. There are many devices such as printers, facsimiles, and copiers that incorporate a belt driving device. In these devices, it is desired that the belt travels stably at a constant speed, and image disturbance occurs when the belt deviates from the constant speed. The present invention relates to a technique for increasing the accuracy of speed detection means for returning a belt to an original speed when the belt deviates from a target speed.
[0002]
[Prior art]
There is an increasing demand for color printers and color copiers that use electrostatic imaging technology.
Some color image forming apparatuses use an electrostatic image forming system. For example, an electrostatic latent image is formed on a dielectric by discharge or contact charging using a needle-like electrode, and this is developed, or analog or digitally on a photoconductor having a uniformly charged surface. A so-called electrophotographic system is known in which an electrostatic latent image is formed by exposure and developed. Hereinafter, for convenience of explanation, an electrophotographic method will be described as an example, but the present invention can be applied to an electrostatic image forming method in general.
[0003]
A multi-color developing device is provided around one photoconductor, and toner is adhered to these photoconductors to form a composite toner image on the photoconductor, and the toner image is transferred to record a color image on the transfer paper. A so-called one-drum type and a plurality of photoconductors arranged side by side are individually provided with a developing device, and a single color toner image is formed on each photoconductor, and the single color toner images are sequentially transferred to transfer paper. There is a so-called tandem type that records a composite color image.
[0004]
Comparing the 1-drum type and the tandem type, since the former has one photoconductor, there is an advantage that the size can be reduced relatively and the cost can be reduced. Times) Since image formation is repeated to form a full-color image, it is difficult to speed up image formation. The latter, on the contrary, has the advantage that it is easy to increase the speed of image formation, although there is a disadvantage that the size is increased and the cost is increased.
Recently, full-color and monochrome-like speeds are desired, and the tandem type has been attracting attention.
[0005]
FIG. 13 is a schematic diagram showing an example of a tandem type electrophotographic apparatus as an example of an electrostatic image forming apparatus.
FIG. 14 is a schematic view showing another example of a tandem type electrophotographic apparatus.
In FIG. 13, reference numeral 100 denotes a photoconductor, and the subscript K indicates a photoconductor for black, Y for yellow, C for cyan, and M for magenta. Reference numeral 200 denotes a belt, 400 denotes transfer paper, 700 denotes a registration roller for paper feeding, and 800 denotes a fixing device.
14, the same components as those in FIG. 13 are denoted by the same reference numerals. In FIG. 14, reference numeral 300 denotes a secondary transfer device.
[0006]
As shown in FIG. 13, the tandem type electrophotographic apparatus includes a direct transfer system in which an image on each photoconductor 100 is sequentially transferred onto a transfer paper 400 conveyed by a belt 200 by a transfer device, and FIG. As shown, an indirect transfer method in which images on each photoconductor 100 are sequentially transferred to a belt 200 once by a primary transfer device, and then the images on the belt 200 are collectively transferred to a transfer sheet 400 by a secondary transfer device 300. There are things. In this case, the belt 200 functions as a conveyance belt in the former, and functions as an intermediate transfer member in the latter. Although the secondary transfer device 300 has a roller shape, a belt shape can also be used.
[0007]
Comparing the direct transfer type and the indirect transfer type, the former requires that a paper feeding device 700 is disposed on the upstream side where the photoreceptors 100 are arranged, and a fixing device 800 is disposed on the downstream side. There is a problem that the transfer paper is enlarged in the conveyance direction.
On the other hand, the latter can set the secondary transfer position relatively freely. The sheet feeding device 700 and the fixing device 800 can be arranged so as to be vertically overlapped with the portion where the photoreceptors 100 are arranged, and there is an advantage that downsizing is possible.
[0008]
In the former case, the fixing device 800 is arranged close to the photoconductor 100 in order not to increase the size in the transfer paper conveyance direction. Therefore, the fixing device 800 cannot be arranged with a sufficient margin that the transfer paper 400 can bend, and an impact when the leading edge of the transfer paper 400 enters the fixing device 800 (particularly with a thick transfer paper). In addition, there is a problem that the fixing device 800 easily affects image formation on the upstream side due to a speed difference between the transfer paper conveyance speed when passing through the fixing device 800 and the transfer paper conveyance speed by the transfer conveyance belt.
[0009]
On the other hand, in the latter case, the fixing device 800 can be disposed with a sufficient margin that the transfer paper 400 can be bent, so that the fixing device 800 can hardly affect the image formation.
In view of the above, recently, an indirect transfer type of tandem type electrophotographic apparatus has attracted attention.
[0010]
At the same time, image color misregistration has become a concern as a quality problem of tandem electrophotographic devices. Therefore, as a means for suppressing the running unevenness of the belt 200 which causes color misregistration, a method of measuring the running state of the belt 200 and performing feedback control has been proposed. There is provided a tandem type electrophotographic apparatus free from color misregistration in which detection accuracy is not lowered by a detection sensor causing a feedback control error at this time, and running unevenness is reduced.
[0011]
[Problems to be solved by the invention]
As a method of reducing the running unevenness of the belt device, there is a method of detecting the speed of the belt surface and performing speed control so that the belt running speed becomes constant according to the detected value. When this method is used, the accuracy of the belt speed detection unit is important, and the decrease in the accuracy of speed detection appears as running unevenness of the belt that is controlled based on the data. Therefore, in the present invention, the belt speed detection unit pays attention to a change in the distance between the speed detection pattern and the detection sensor, that is, a decrease in speed detection accuracy due to a so-called gap fluctuation, and the belt speed is reduced to reduce the gap fluctuation. Configured the device.
[0012]
[Means for Solving the Problems]
  In order to solve the above-mentioned problems, in the invention according to claim 1, in the belt device, a belt having a speed detection pattern formed on the surface thereof, a motor for driving the belt, and a detection sensorWhen,The speed detection pattern is read by the detection sensor, a correction amount is output based on the read information, and the rotational speed of the motor is controlled so that the surface speed of the belt is constant. In the belt device, the movement other than the parallel movement in the vertical direction with respect to the belt surface is restricted, while the belt deviceUsing the peripheral surface as the contact surfacePressed againstA pair of rotating rollers are provided at positions that do not contact the speed detection pattern on both sides of the speed detection pattern in a direction orthogonal to the belt traveling direction.Pressing memberPreparationThe detection sensor is on the pressing member.The center portion of the pair of rotating rollersFixed toAnd having a contacted member at least at a position facing the rotating roller via the belt.It is characterized by that.
[0013]
  In the invention according to claim 2, in the belt device according to claim 1, the contact surface isCorners are curvedIt is characterized by being.
[0014]
  Claim 3In the invention described in claim 1,Or 2In the belt device described in (1), at least the contact surface of the pressing member is formed of a fluorine-based resin or a silicon-based resin.
  Claim 4In the invention according to claim 1, in the belt device according to any one of claims 1 to 3,The contacted member is formed with a curved corner at the surface that contacts the belt.It is characterized by that.
[0015]
  Claim 5In the invention described in claim 1,4In the belt device according to any one of the above,The abutted member is a plate-like member at least in contact with the beltIt is characterized by that.
  Claim 6In the invention described inAny one of claims 1 to 4The belt device according to claim 1, wherein the contacted member is the belt.Each has a rotating roller at a position facing the pair of rotating rollers viaIt is characterized by
  Claim 7In the invention described in claimAny one of 1 to 6The belt device according to claim 1, wherein the contacted member contacts at least the belt.The side surface is made of fluorine resin or silicon resinIt is characterized by that.
[0017]
  Claim 8In the invention described in claim 1,7In the belt device according to any one of the above, the speed detection patterns are provided on both sides of the belt, and the detection sensors correspond to the speed detection patterns, respectively.One by oneIt is provided.
  Claim 9In the invention described inClaim 8In the belt device described in (1), the correction amount is output based on an average value of the deviations obtained from the respective detection sensors.
[0018]
  Claim 10In the invention described in claim 1, the claims 1 to9An image forming apparatus using the belt apparatus described in any one of the above as a belt apparatus for transferring a transfer paper of an image forming apparatus of a direct transfer type.
  Claim 11In the invention described inClaims 1 to 10The belt device according to any one of the above is used as an intermediate transfer belt device of an indirect transfer type image forming apparatus.
[0019]
Claim 12In the invention described in claim10 or 12In the image forming apparatus, the speed detection pattern is provided on a surface in contact with a belt driving roller, and the contacted member is disposed outside an image forming area on the belt.
[0020]
  Claim 13In the invention described inClaims 10 to 12In the image forming apparatus according to any one of the above, the speed detection pattern is provided on a surface that does not contact the belt driving roller, and the contact surface is disposed outside the image forming area on the belt. Features.
  Claim 14In the invention described inClaims 10 to 13A color image forming apparatus in which the image forming apparatus according to any one of the above is applied to an electrostatic image forming image forming apparatus having two or more image carriers.
[0021]
[Action]
  According to the belt device of the first aspect, the distance between the speed detection pattern and the detection sensor is a predetermined distance determined by the shape of the pressing member, and does not vary even when the belt moves.. And thisAccording to the belt device, the contact surface does not contact the speed detection pattern.
[0022]
  Claim 2According to the belt device described in (1), the frictional resistance due to the contact of the corners is reduced.
  Claim 3According to the belt device described in (2), the frictional resistance between the pressing member and the belt is reduced..
[0023]
  Claim 4According to the belt device described in (1), the pressing member hits the abutted member through the belt at all times or when the belt extends over time, and prevents the belt from flapping.
  Claim 5According to the belt device described in (1), the configuration of the contacted member is simple.
  According to the belt device of the sixth aspect, the sliding between the contacted member and the belt is eliminated.
[0024]
  Claim 7According to the belt device described in (2), the frictional resistance between the contacted member and the belt is reduced..
Claim 8and9According to the image forming apparatus described in 1), the speed correction including the skew of the belt is performed.
[0025]
  Claim 10According to the image forming apparatus described in 1), an image forming apparatus capable of stably controlling the speed of the transfer paper transport belt can be obtained.
  Claim11 thru 13According to the image forming apparatus described in 1), an image forming apparatus capable of stably controlling the speed of the intermediate transfer belt is obtained.
  Claim 14According to the color image forming apparatus, a color image forming apparatus capable of stably controlling the speed of the belt device can be obtained.
[0026]
【Example】
FIG. 1 is a perspective view showing only a portion related to transfer of a direct transfer type image forming apparatus.
1, the same components as those in FIGS. 13 and 14 are denoted by the same reference numerals. In FIG. 1, reference numeral 101 denotes a photosensitive drum motor, 201 denotes a belt driving roller, 202 denotes a belt support roller, 204 denotes a belt driving motor, 210 denotes a speed detection pattern, and 211 denotes a detection sensor.
[0027]
FIG. 2 is a perspective view showing only a portion related to the transfer of the indirect transfer type image forming apparatus.
2, the same components as those in FIGS. 1, 13, and 14 are denoted by the same reference numerals. In FIG. 2, reference numeral 203 denotes a transfer receiving roller, and 301 denotes a transfer roller driving motor.
FIG. 3 is a plan view showing the relationship between the belt and the detection sensor.
In the figure, reference numeral 220 denotes a pressing member, and 223 denotes a contact surface of the pressing member with the belt.
[0028]
FIG. 4 is a front view showing the relationship between the belt and the detection sensor. For the convenience of explanation, FIGS. 1 and 2 are shown upside down. The same applies to the subsequent drawings.
In FIG. 4, reference numeral 205 denotes a contacted member, and 225 denotes a pressing spring.
[0029]
An embodiment of the present invention will be described with reference to the above drawings. The photosensitive drums 100K, 100M, 100C, and 100Y are arranged in parallel, and image formation is performed for each color of black, magenta, cyan, and yellow, respectively. As a medium for transferring the formed image, a belt 200 as an intermediate transfer belt or a transfer paper 400 on the belt 200 as a conveyance belt moves in the direction of arrow A. The formed image is transferred to the transfer paper 400 on the belt 200 or the belt 200 itself in the order of each station of the yellow drum 100Y, cyan drum 100C, magenta drum 100M, and black drum 100K, and the images are superimposed. .
[0030]
A speed detection pattern 210 provided along the belt traveling direction on the surface opposite to the image forming surface of the belt 200 is read by the detection sensor 211, and the traveling speed of the belt 200 is detected by electrical processing described later. To do. Based on the result, the motor 204 is controlled so that the speed of the belt 200 is constant.
[0031]
The detection sensor 211 is fixed on the pressing member 220. The pressing member 220 is pressed against the surface of the belt 200 only by the parallel translation in the vertical direction by the pressing spring 225, and the movement in the direction parallel to the belt surface is restricted by the member (not shown) and tilted. Is also regulated so as not to occur. The detection surface of the detection sensor 211 is opposed to the speed detection pattern at a certain predetermined distance so as not to contact the belt 200. The pressing member 220 can be made of a transparent member, and the detection surface of the detection sensor 211 can be used in close contact with the pressing member 220. Alternatively, an opening may be provided at the detection sensor contact portion of the pressing member 220 so as to directly face the speed detection pattern.
[0032]
The contact surface 223 of the pressing member 220 that contacts the belt 200 is configured to contact the belt on both sides of the speed detection pattern 210 so as not to contact the speed detection pattern 210. By doing so, it is possible to prevent the speed detection pattern 210 from being deteriorated due to wear. Since the contact surface 223 slides with the belt 200, a material having a contact area as small as possible and a friction coefficient as small as possible is selected. If necessary, the surface may be coated with a material having a small coefficient of friction. As a material having a small friction coefficient, a fluorine-based resin or a silicon-based resin is known. However, when the contact area is reduced, the belt 200 may be damaged if the pressure spring 225 is too strong. Therefore, the strength of the pressure spring 225 is the pressing member 220 even if the belt 200 is swung (so-called fluttering). It is preferable that the belt 200 is not easily separated from the belt 200.
[0033]
Since a certain amount of tension is normally applied to the belt 200, the position in the direction perpendicular to the surface of the belt 200 does not move much even when pressed by the pressing member 220. If this occurs, the belt flutters if the force pushing in the direction perpendicular to the surface is weak. With respect to the belt 200, the contacted member 205 provided on the opposite side of the pressing member 220 plays a role of suppressing such flapping. In other words, the position of the contacted member 205 is set so that the pressing member 220 can sufficiently follow even if the position of the belt 200 changes due to the extension of the belt until it comes into contact with the contacted member 205. ing. Note that at least the surface of the contacted member 205 that contacts the belt 200 is preferably made of a material having a sufficiently small coefficient of friction, like the contact surface 223.
[0034]
Therefore, the detection sensor 211 can always read the speed detection pattern 210 on the belt 200 at a constant distance. As a result, the conventional variation in the distance between the belt and the detection sensor, that is, the error due to the gap variation is eliminated, and the belt can be controlled with high accuracy.
The contact surface 223 of the pressing member 220 may be configured to always press the belt 200 against the contacted member 205. In this case, since the belt running position is always a constant position, reading by the detection sensor is very stable.
[0035]
FIG. 3 shows an example in which the speed detection patterns 210 are provided on both sides of the belt 200. Basically, the object can be achieved if there is one speed detection pattern 210. If one speed detection pattern 210 is provided on each side of the belt 200, two effects can be expected. First, since the frictional resistance between the speed detection pattern 210 and the pressing member 220 or the abutted member 205 occurs, the state in which the brake is applied to the belt traveling occurs not a little. If it is only the end of the belt, there is a possibility that a so-called skew is generated in which the belt moves to one side. However, by providing the speed detection pattern on both sides, the frictional resistance is applied almost evenly on both ends of the belt, and the running is stabilized.
[0036]
Second, there is an effect that the correction error can be reduced with respect to the skew phenomenon that often occurs during belt running without the above circumstances. When skew is generated from normal running, the detection sensors 211 on both sides detect different deviations, that is, speed changes. If the detection amounts of both the detection sensors 211 are averaged, it should substantially correspond to the speed change at the center in the width direction of the belt. Can be kept in. Therefore, there is no possibility that excessive correction is performed by only one of the detection sensors.
[0037]
FIG. 5 is a view showing a modification of the pressing member.
In the figure, the pressing member 220 is made by bending a single plate, and the parts cost can be reduced regardless of whether it is made of metal or synthetic resin.
FIG. 6 is a view showing another modification of the pressing member. In this modification, the surfaces that contact the belt 200, that is, the corners of the contact surface 223 are all curved. By doing so, the frictional resistance between the pressing member 220 and the belt 200 is further reduced, and the belt running unevenness caused by the speed detection mechanism can be reduced.
[0038]
FIG. 7 is a perspective view showing a configuration example of a contacted member when the pressing member shown in FIG. 5 is used.
FIG. 8 is a view showing a modification of the contacted member.
Although not shown in FIG. 7, the abutted member 205 is supported by a fixed member and is normally configured not to move. The drawing shows the simplest plate-shaped member having the simplest configuration, which is very effective in suppressing the flapping of the belt, but the frictional resistance tends to increase due to the larger contact area. If the contacted member 205 has only a surface opposite to the contact surface 223 of the pressing member 220, the purpose of the present time is achieved. Therefore, the other surfaces do not contact the belt 200 as shown in FIG. It can also be configured.
[0039]
In the example shown in FIGS. 1 and 2, the contact surface of the contacted member 205 is the side having the image forming surface in the case of an indirect transfer type image forming apparatus. A certain place cannot be used as an image forming area. Therefore, in the case of the indirect transfer method, the contact area of the contacted member 205 needs to be outside the image forming area, that is, the area where the image is primarily transferred.
[0040]
1 and 2 show an example in which the speed detection pattern is provided on the surface that does not contact the photosensitive member, that is, the surface that contacts the belt driving roller 201, this is not a necessary configuration. The speed detection pattern can also be provided on the side that contacts the photoconductor, that is, the side that does not contact the belt driving roller 201. In this case, it is necessary to form so that the contact surface 223 of the pressing member 220 is positioned outside the image forming area.
Although not shown in the drawings, it is natural that the contacted member 205 may be configured to reduce the frictional resistance by making the corners in contact with the belt 200 curved.
[0041]
FIG. 9 is a view showing still another modification of the pressing member.
In the figure, reference numeral 222 indicates rotating rollers provided on both sides of the detection sensor 211. The pressing member 220 is pressed against the belt 200 by the pressing spring 225. In this case, the contact surface 223 to the belt 200 is a surface facing the belt 200 of the rotating roller 222. As described above, the pressing member 220 is supported by the fixing member so as not to move. Therefore, as the belt 200 travels, the rotating roller 222 rotates, and the pressing member 220 and the belt 200 are moved. Friction resistance is hardly generated as much as rolling friction rather than sliding friction. In the drawing, the pressing springs 225 are shown as being disposed at both ends in the figure. However, as long as the balance can be maintained, only one pressing spring 225 may be used at the center.
[0042]
In this configuration, the detection sensor 211 maintains the same position and the rotating roller 222 is formed so as not to be eccentric, so that the distance between the detection sensor 211 and the surface of the belt 200 does not change. Therefore, when reading the speed detection pattern, gap variation between the detection sensor 211 and the speed detection pattern 210 does not occur, and highly accurate speed control can be performed. Although not particularly illustrated, if the outermost corner portion of the rotating roller 222 that contacts the belt 200 is formed into a curved surface, stress concentration at the corner portion does not occur, and the rolling friction resistance does not increase so much. .
[0043]
FIG. 10 is a perspective view showing an example of a contacted member when the pressing member shown in FIG. 9 is used.
As shown in the figure, the abutted member 205 can achieve its purpose if it has only a portion where the abutting surface 223 of the pressing member 220 is opposed to the abutting member 220. Therefore, the width need not be so wide. Also in this configuration, as shown in FIG. 8, portions other than the facing portion of the contact surface 223 may be separated from the belt 200.
[0044]
FIG. 11 is a perspective view showing another modification of the contacted member.
In the figure, reference numeral 206 denotes a rotating roller.
In this modification, the contacted member 205 uses a rotating roller 206 similar to the rotating roller 222 used for the pressing member 220. By doing so, the frictional resistance between the contacted member 205 and the belt 200 is almost eliminated, and there is no possibility that the speed detection mechanism may cause the belt speed fluctuation.
In order to receive the pressing member 220 stably and reliably, the rotating roller 206 may be wider than the rotating roller 222 in the rotation axis direction.
Even when the pressing member shown in FIGS. 4 to 6 is used, the present embodiment can be used as the contacted member 205. In this case, it is preferable that the width of the rotary roller 206 in the direction of the rotation axis is the same as the contact surface 223 or slightly larger. In addition, if the outermost corner portion of the rotating roller 206 that contacts the belt 200 is formed into a curved surface, stress concentration at the corner portion does not occur, and the rolling friction resistance does not increase so much.
[0045]
FIG. 12 is a block diagram showing an outline of belt speed control.
The belt device is provided with a predetermined input that can achieve the target belt speed. In the initial state, there is no correction amount output from the error calculation unit, so the belt 200 is driven by the motor rotation speed according to the input of the belt device. As the detection sensor, a normal light projecting / receiving type is used, and a current change or a voltage change generated in the light receiving element due to the movement of the speed detection pattern on the belt is sent to the error calculating unit. The error calculation unit electrically processes the obtained pulsating flow to shape it into a rectangular wave, and detects a period shift or phase shift from the wrinkle waveform obtained at a normal speed.
[0046]
There are cases where the shift in the period is on the plus side and on the minus side. In the case of the plus side, it means that the current speed of the belt is too fast than the target, so that the error calculation unit outputs a correction amount corresponding to the deviation. The correction amount is subjected to signal synthesis with the input, and the belt device returns to the target speed by driving the belt with the corrected input. If the period deviation is on the minus side, it means that the current speed of the belt is too slower than the target, and the error calculation unit outputs a correction amount corresponding to the deviation. The subsequent operation is the same.
In the case of detecting a phase shift, the correction amount can be output based on substantially the same principle.
[0047]
【The invention's effect】
  Invention of Claim 1Since the distance between the speed detection pattern and the detection sensor is kept constant, accurate speed control can be performed.. further,Since the speed detection pattern has no fear of being worn, stable speed control can be performed in the long term.
[0048]
  Inventions of Claims 2 to 4 and 6 to 7According to this, since the frictional resistance with the member in contact with the belt is reduced, there is no possibility that the speed detection device will cause the belt speed unevenness.
  Claim 5According to the invention, the contacted member can be configured with a simple configuration.
  Claims 8 and 9According to this invention, even if the belt runs temporarily at an angle, the average speed error can be detected by the two detection sensors, so that excessive correction is not performed.
[0049]
  Claims 10 to 13According to the invention, an image forming apparatus capable of performing belt speed control with high accuracy is obtained.
  Claim 14According to the invention, it is possible to obtain a color image forming apparatus capable of performing belt speed control with high accuracy.
[Brief description of the drawings]
FIG. 1 is a perspective view showing only a portion related to transfer of a direct transfer type image forming apparatus.
FIG. 2 is a perspective view showing only a portion related to transfer of an indirect transfer type image forming apparatus.
FIG. 3 is a plan view showing a relationship between a belt and a detection sensor.
FIG. 4 is a front view showing a relationship between a belt and a detection sensor.
FIG. 5 is a view showing a modified example of the pressing member.
FIG. 6 is a view showing another modification of the pressing member.
7 is a perspective view showing an example of a contacted member when the pressing member shown in FIG. 5 is used. FIG.
FIG. 8 is a view showing a modified example of the contacted member.
FIG. 9 is a view showing still another modified example of the pressing member.
10 is a perspective view showing an example of a contacted member when the pressing member shown in FIG. 9 is used.
FIG. 11 is a perspective view showing a modified example of the contacted member.
FIG. 12 is a block diagram showing an outline of belt speed control.
FIG. 13 is a schematic diagram illustrating an example of a tandem type electrophotographic apparatus.
FIG. 14 is a schematic diagram illustrating another example of a tandem type electrophotographic apparatus.
[Explanation of symbols]
100 photoconductor
200 belts
201 Belt drive roller
202 Belt support roller
204 Belt drive motor
205 Contacted member
206 Rotating roller
210 Speed detection pattern
211 Detection sensor
220 Pressing member
222 Rotating roller
223 Contact surface
225 Pressing spring
300 Secondary transfer device
400 transfer paper

Claims (14)

A belt device having a belt having a speed detection pattern formed on a surface thereof, a motor for driving the belt, and a detection sensor, wherein the speed detection pattern is read by the detection sensor, and a deviation from a target speed is obtained. In the belt device that outputs the correction amount to the belt device and controls the rotational speed of the motor so that the surface speed of the belt becomes constant, while movement other than parallel movement in the direction perpendicular to the belt surface is restricted, A pressing roller having a pair of rotating rollers pressed against the belt with the peripheral surface as a contact surface at positions not contacting the speed detection pattern on both sides of the speed detection pattern in a direction perpendicular to the belt traveling direction. against comprising a member, the detection sensor is fixed to the substantially central portion of the pair of rotary rollers on said pressing member, through the belt, small With a position opposed to the rotary roller, belt apparatus characterized by having a contacted member. The belt device according to claim 1, wherein the contact surface has a corner formed in a curved surface .   3. The belt device according to claim 1, wherein at least the contact surface of the pressing member is formed of a fluorine-based resin or a silicon-based resin. 4. The belt device according to claim 1 , wherein a corner of a surface of the contacted member that contacts the belt is formed into a curved surface . 5. 5. The belt device according to claim 1, wherein at least a portion of the contacted member that is in contact with the belt is a plate-like member . 5. The belt device according to claim 1 , wherein the contacted member has a rotating roller at a position facing the pair of rotating rollers via the belt . 6. Belt device. The belt device according to any one of claims 1 to 6 , wherein at least a surface of the contacted member that is in contact with the belt is formed of a fluorine-based resin or a silicon-based resin. Belt device. The belt device according to any one of claims 1 to 7 , wherein one speed detection pattern is provided on each side of the belt, and one detection sensor is provided corresponding to each of the speed detection patterns. A belt device characterized by being provided one by one . 9. The belt device according to claim 8 , wherein the correction amount is output based on an average value of the deviations obtained from the respective detection sensors . The belt device according to any one of claims 1 to 9, the image forming apparatus, which comprises using as a belt device for the transfer sheet conveyance of the image forming apparatus of a direct transfer system. 10. An image forming apparatus, wherein the belt apparatus according to claim 1 is used as an intermediate transfer belt apparatus of an indirect transfer type image forming apparatus. 12. The image forming apparatus according to claim 10 , wherein the speed detection pattern is provided on a surface that comes into contact with a belt driving roller, and the contacted member is disposed outside an image forming area on the belt. An image forming apparatus. 13. The image forming apparatus according to claim 10 , wherein the speed detection pattern is provided on a surface that is not in contact with a belt driving roller, and the contact surface is located outside an image forming area on the belt. An image forming apparatus that is arranged . 14. A color image forming apparatus , wherein the image forming apparatus according to claim 10 is applied to an electrostatic image forming type image forming apparatus having two or more image carriers .

Images