JP3104421B2 - Endless belt transport device in image forming apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an endless belt conveying device used for a photoreceptor belt, a transfer belt, an intermediate transfer belt and the like in an image forming apparatus such as a copying machine, a facsimile, a printer, etc. using an electrophotographic method.

[0002]

2. Description of the Related Art In the above-described image forming apparatus, a charge corotron, an exposure device, a developing device, a transfer corotron, a cleaning device, a static elimination lamp and the like are arranged around an image carrier. After the body is uniformly charged, an exposure device forms an electrostatic latent image on the image carrier, and the electrostatic latent image is developed into a toner image by a developing device, and then the toner image is transferred. An image is formed by a series of processes in which the toner is transferred to a material by a transfer corotron, and a residual toner on the image carrier is removed by a cleaning device, and then the charge on the image carrier is removed by a charge removing lamp.

In the image forming apparatus, there is a system in which an endless belt transport device is used for an image carrier, a transfer material transporter, an intermediate transfer member, a continuous paper transporter, and the like. In this endless belt transport device, the endless belt is stretched and driven on at least a plurality of rolls having a driving roll and a tension applying roll. However, the parallelism between the rolls due to the arrangement of the rolls and the cylindrical accuracy of the rolls A phenomenon in which the belt moves in a direction perpendicular to the transport direction due to a difference in circumferential length between both side edges of the belt,
That is, when the meandering phenomenon occurs and the meandering phenomenon occurs, an image formed on the belt or an image transferred onto the belt is biased, so that there is a problem that a good image cannot be obtained.

A conventional method for solving this problem will be described with reference to FIG. In FIG. A, a roll 3 is rotatably supported between support members 1a and 1b via bearings 2a and 2b, and a belt 4 is stretched on the roll 3. Ribs 4 abutting on both ends of the roll 3 are provided at both ends of the belt 4.
a is formed, and the meandering of the belt 4 is regulated by the rib 4a. The belt 4 is driven by contact with a certain load F via the ribs 4a. If both ends of the belt 4 have irregularities, the load applied to the ribs 4a increases and decreases, and the belt 4 meanders in the axial direction of the roll 3. The load is applied until the belt 4 slips with the roll 3, and the load is extremely large, so that the rib 4a is immediately damaged and cannot be used. In order to reduce and use this load, it is necessary to improve the parallelism between the rolls, the accuracy of the roll cylinder, and the accuracy of the difference in the circumferential length between both ends of the belt.

For this purpose, in FIG. 15B, the roll 3 is formed from an elastic member, and a large number of slits 3a are formed on its surface in the axial direction, and the end of the belt 4 is guided by the support member 1a. The meandering of the belt 4 is regulated. In this case, when the load F is applied, the roll 3 is displaced in the axial direction by the slit 3a, so that the end of the belt 4 can be prevented from being damaged.

When the endless belt conveying device is used in a color image forming apparatus, unless the control of the meandering amount of the belt is performed with high accuracy of, for example, 0.1 mm, a color shift occurs, which is a serious problem. When the meandering of the belt is controlled with high accuracy, the accuracy of the meandering control depends on the shape of the belt end or the rib of the belt. However, it is impossible to completely straighten the shape of the belt end or the ribs of the belt.
A method disclosed in Japanese Patent Publication No. 11 has been proposed.

This will be described with reference to FIG.
15B, a number of slits 3a are formed in the axial direction in the same manner as in FIG. 15B. A belt guide member 6 is axially movable between a side surface of the roll 3 and the support member 1a via a thrust bearing 5. Pivotally supported, the belt guide member 6 and the support member 1
A spring 7 is provided between a and a, so that the end of the belt 4 is elastically supported by the belt guide member 6.
On the opposite side of the support member 1a, a cam 9 rotated by a motor 8 is provided to enable the roll 3 to tilt in the axial direction. The support member 1a is provided with a sensor 10 that detects the position of the belt guide member 6, detects the position of the belt guide member 6 (ie, the position of the belt 4), and tilts the roll 3 to adjust the meandering of the belt 4. ing.

[0008]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Application Laid-open No. Hei 4-15
In the system disclosed in Japanese Patent No. 9911, the belt 4 is driven by being brought into contact with an elastically supported belt guide member 6, and the belt guide member 6 moves along the unevenness of the belt end, thereby controlling the meandering of the belt. doing. Therefore, this method has a problem that high-precision meandering control cannot be performed unless the spring constant of the spring 7 that elastically supports the belt guide member 6 is set appropriately.

In the above-described tilt adjustment of the roll 3, when the average load acting on the belt guide member 6 changes, that is, the parallelism between the rolls, the cylindrical accuracy of the rolls, and the circumferential difference between both ends of the belt change. Sometimes, in general, equipment assembly,
It may be performed when replacing the belt and the roll. At this time,
When the belt is driven for the first time after the belt replacement, the belt is driven for a predetermined time until the belt guide member 6 comes to a position balanced with the load received by the belt end, and the balanced position becomes the belt position. However, conventionally, such belt meandering adjustment has not been performed separately from image formation.

Further, in the system disclosed in Japanese Patent Application Laid-Open No. 4-159911, the position of the belt guide member 6 is detected to adjust the inclination of the roll 3, but the shape of the belt end is made completely straight. It is impossible to do this, so if this is detected, the linearity of the belt end will affect the position measurement accuracy, and if this position measurement is not performed accurately, the average load acting on the belt guide member 6 will increase. It cannot be set to the predetermined value, and meandering of the belt occurs. If this occurs over a long period of time, the belt edge will be damaged and reliability will be reduced.

A first object of the present invention is to appropriately set a spring constant for elastically supporting a belt guide member and to control the meandering of the belt with high precision. The belt meandering adjustment mode is used to perform belt meandering control with high accuracy by detecting the position of the belt with high accuracy.

[0012]

According to one aspect of the present invention, there is provided an endless belt which stretches and drives an endless belt between a plurality of rolls having at least a driving roll and a tension applying roll. In an image forming apparatus having a transport device, a roll formed of an elastic member and having a plurality of slits formed on a surface thereof, a support member rotatably supporting the roll, and a rotatably supported pivot in the axial direction of the roll. A belt guide member for elastically supporting an end of the belt with respect to the support member, wherein a spring constant of the belt guide member is smaller than an axial rigidity of the belt in the endless belt conveyance device. And

According to a second aspect of the present invention, there is provided an image forming apparatus having an endless belt conveying device that stretches and drives an endless belt between a plurality of rolls having at least a driving roll and a tension applying roll. A roll having a plurality of slits formed on its surface, a support member rotatably supporting the roll, and a belt end movably supported in the axial direction of the roll, and a belt end portion with respect to the support member. A belt guide member for elastically supporting the belt, a displacement detection sensor for detecting displacement of the belt guide member or the belt, a detection unit provided on the belt, and a position of the detection unit
A position detecting sensor for detecting the position, and adjusting means for tilting the roll based on the detection value of the displacement detection sensor,
Stop the belt at a certain position and send it to the displacement detection sensor.
It is characterized by detecting the displacement of the belt guide member or the belt .

[0014] The invention according to claim 3 has at least
Multiple rolls with drive roll and tensioning roll
Endless belt conveyor that stretches and drives an endless belt between them
An image forming apparatus having an elastic member
A roll having a plurality of slits formed on its surface;
A supporting member for rotatably supporting the roller, and an axial direction of the roll
And movably supported by the support member.
A belt guide member for elastically supporting a belt end
Displacement detection sensor that detects the displacement of the
And a detection unit provided on the belt, and a position of the detection unit.
And a displacement detection sensor for detecting the displacement.
Adjusting means for tilting the roll according to the output value,
The displacement detection sensor is synchronized with the signal of the position detection sensor.
Detects belt guide member or belt displacement
It is characterized by the following.

[0015]

According to the present invention, the specifications of the belt conveying device are determined by determining the meandering control accuracy, the belt end shape, and the sliding withstand load between the belt and the belt guide member. Determine the axial rigidity of the belt transport device from the average load applied, the parallelism of the roll, the cylindricality of the roll, the difference in the circumference of both ends of the belt, the belt tension, the belt wrap angle, etc.
Finally, the spring constant of the belt guide member is determined from the relationship between the belt meandering amount and the belt end shape.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is an overall configuration diagram of a color image forming apparatus in which the present invention is applied to a transfer material conveying belt. The present invention is not limited to such an image forming apparatus,
The present invention is also applicable to a single-color image forming apparatus, and is not limited to a transfer material conveying belt.
It is also applicable to an intermediate transfer belt.

The transfer material transport belt 11 has an endless belt shape coated with a dielectric film, and is stretched around a plurality of rolls 12, 13, 14, 15 having at least a drive roll 12 and a tension applying roll 14, and is indicated by an arrow in the drawing. It is rotated in the A direction. Opposite to the upper surface of the transfer material transport belt 11, four sets of image forming units K, Y, M, and C for black, yellow, magenta, and cyan are provided.

Each of the image forming units K, Y, M, and C includes an image carrier 16 composed of a photosensitive drum, a charge corotron 17, a latent image writing unit 18, a developing machine 19, a transfer corotron 20, and an image carrier cleaner. 21 is provided downstream of the image forming units K, Y and M, and a transfer material neutralizing corotron 22 is provided, and the image carrier 16 is rotated in the direction of the arrow shown in the figure.

A peeling corotron 23 and a peeling claw 24 are provided downstream of the image forming unit C at the last stage, and a fixing device 25 is further provided. On the upstream side of the drive roll 12, a conveyor belt static elimination corotron 26 and a cleaning blade 27 are disposed. On the downstream side of the drive roll 12, a suction corotron 30 is provided inside the transfer material transport belt, and a transfer material suction roll 31a is provided facing the suction corotron 30. The transfer material in the paper feed tray 28 is transported to the transfer material transport belt 11 by the feed roll 29, and is then transferred to the transfer material transport belt 11 by the suction cotorotron 30 and the transfer material suction roll 31 a.
Is adsorbed.

In the above color image forming apparatus, the image carrier 16 is uniformly charged by the charge corotron 17, the image of the original is exposed by the latent image writing means 18, and the electrostatic latent image is placed on the image carrier 16. An image is formed. Developing machine 1
9, the toner is brought into contact with the surface of the image carrier 16 to form a toner image, and the developed toner image is transferred to the transfer corotron 2.
0, after transfer to the transfer material on the transfer material transport belt 11,
The toner remaining on the image carrier 16 is scraped off by the cleaner 21 to perform a series of image forming cycles. This cycle is performed by four image forming units K, Y,
The transfer is performed at M and C, and a plurality of toner images are sequentially superimposed and transferred onto the transfer material sucked and conveyed by the transfer material conveying belt 11.

FIG. 3 is a perspective view showing one embodiment of the endless belt conveying device of the present invention. A pair of front and rear belt frames 3
A tension applying mechanism 36 is attached to 1 and 32. The tension applying mechanism 36 includes a bracket 37 fixed to the belt frames 31 and 32, a spring 38 having one end fixed to an inner end of the bracket 37, and a bracket 3.
7 and a slide rail 39 provided outside.
Further, both ends of the tension applying roll 14 are supported by support arms 40.
The projection 41 is formed inside the support arm 40 so as to be rotatable.

The projection 41 of the support arm 40 is fitted into the slide rail 39, and the tip 40a of the support arm 40 is fixed to the spring 38. As a result, the support arm 40 is urged in the direction D in the drawing by the elastic force of the spring 37 to apply a predetermined tension to the belt.

One end of a release plate 42 is fixed to the spring 38 on the distal end 40a side of the support arm 40, and a bent portion 42a is formed at the other end of the release plate 42. The bent cam 42 is formed on the bent portion 42a. 43 and 44 are contacted. The release cams 43 and 44 are connected to the belt frame 3.
A release lever 46 is provided on the cam 43 on the front belt frame 31 side, which is attached to both ends of a cam shaft 45 penetrated between the cam shafts 1 and 32. With this structure, when the release lever 46 is in the state shown in the figure, the support arm 40 is urged to apply tension to the belt.
2 pulls the support arm 40 against the spring 38 to release the tension acting on the belt.

The bracket 37 of the tension applying mechanism 36
Are mounted on the belt frames 31 and 32 so as to be rotatable about a shaft 47, provided with cams 48 and 49 for moving the belt for controlling the rotation of the bracket 37, and provided on the shaft of the tension applying roll 14. Constitute a tilting mechanism for tilting. The two belt moving cams 48 and 49 are attached to both ends of the cam shaft 50 penetrated between the belt frames 31 and 32, and the two belt moving cams 48 and 49, for example, when the cam shaft 50 rotates in the A direction in the drawing, the support arm on the near side. The support arm 40 is arranged so as to rotate in the direction B and the support arm 40 on the far side rotates in the opposite direction C. Then, the cam shaft 50 is driven to rotate by the motor 51.

FIG. 4 is a sectional view of the tension applying roll 14 along the axial direction. The tension applying roll 14 is formed of an elastic member, and has a plurality of ring-shaped slits 14a formed in the surface thereof in the axial direction. Rotary axis 1 of tension applying roll 14
4b is supported by the support arm 40 via a bearing 52. A belt guide member 54 is axially movably supported between the side surface of the tension applying roll 14 and the support arm 40 via a bearing 53, and a spring 55 is provided between the belt guide member 54 and the support arm 40. With this configuration, the end of the belt 11 is elastically supported by the belt guide member 54. One of the support arm members 40 is provided with a displacement detection sensor 56 for detecting the displacement of the belt guide member 54. The displacement detection sensor 56 may be a non-contact type sensor such as a photo sensor or a load sensor that directly detects the load of the spring 55. In the above embodiment, the tension applying roll 14 is provided with a tilting mechanism for correcting the meandering. However, the present invention is not limited to this. You may make it control.

Next, a method of setting the spring constant of the belt guide member 54 for elastically supporting the belt 11, which is a feature of the present invention, will be described.

FIG. 5 shows a system in which the belt end described with reference to FIG. 15B is brought into contact with the belt guide member 1a.
Assuming that the position of the belt 1 in the driving direction is x and the shape of the belt end (distance from the center of the belt to the end) is E (x), the meandering amount of the belt at the position of the belt guide member 1a is B (x) = E (x ). Also, the load applied to the belt guide member from the belt is F
Assuming (x), F (x) = K _A × E (x) + F ₀ .
Here, F ₀ is an average load applied to the belt guide member,
It is determined by the configuration of the belt transport device, the difference in the circumference of the belt, the parallelism of the rolls, and the like. K _A is a constant, which indicates the axial rigidity (softness) of the endless belt conveyance device. In FIG. 5, the relationship between the displacement y of the belt 11 when a load F is applied to the belt 11 in the axial direction, That is, K _A = F / y.

Next, the belt guide member 54 supported elastically as shown in FIG. Assuming that the axial spring constant of the belt guide member is K _G , the belt guide member moves to a position y ₀ balanced with the average load F _0, and then the belt guide member is displaced by the unevenness of the belt end, and the amount is changed. y (x), the load applied from the belt to the belt guide member F (x) is _{F (x) · F 0 =} K G × y (x) = K a × (E (x) -y (x) ). Solving this becomes _{y (x) = K A ×} E (x) / (K A + K G). Meandering of the belt B (x) becomes B (x) = y (x ) -E (x) = [K G / (K A + K G)] E (x). Here, FIG. 6 shows an example in which the ratio of reducing the influence of B (x) / E (x), that is, the belt end shape on meandering, is shown in FIG. The K _A large, it can be seen that the meander by decreasing K _G decreases. However, since F ₀ is proportional to K _A , it cannot be made too large. Therefore it is necessary to select the appropriate K _A, K _G.

FIG. 1 is a diagram for explaining a method of determining the spring constant of the belt guide member according to the present invention. First,
In step S1, the specifications of the belt conveying device are determined. That is, the meandering control accuracy B _spec and the belt end shape E
(X) The sliding withstand load _Fmax between the belt 11 and the belt guide member 54 is determined. Next, in step S2, the axial stiffness K _A of the belt conveying device is determined. The average load F ₀ applied to the belt guide member is F ₀ = K _A × f (α, Cr, Cb, T, θ), where the parallelism α of the roll, the cylindricality Cr of the roll, and the circumferential length difference Cb at both ends of the belt. , in which the belt tension T, a coefficient determined by the belt wrap angle θ multiplied by K _a. Average load F
_{Since 0} must be smaller than the withstand load _Fmax ,
The axial rigidity K _A of the belt conveying device is determined by K _A <F _max / f (α, Cr, Cb, T, θ). Then, the determination of the spring constant K _G of the belt guide member 54 at step S3. Belt meandering amount B
(X), as described above, B (x) = a _{[K G / (K A +} K G)] E (x), the belt meandering amount B (x) is of the meander control accuracy B _spec
Must be smaller than the spring constant K _G
Is determined as K _G <[B _spec / (E (x) −B _spec )] × K _A ].

Next, the detection of the belt displacement in the belt meandering adjustment mode, which is the second object of the present invention, will be described. 3 and 4, the displacement detection sensor 56 detects the belt position, that is, the load applied to the belt guide member 54, and determines the cam rotation angle to be corrected.
A signal is output to the motor 51 so that the load applied to 4 is set to a predetermined value or less. By driving the motor 51, for example, as shown in FIG. 3, when the cam shaft 50 is rotated in the direction A,
By the action of the cams 48 and 49, the front support arm 40 tilts in the B direction, and the rear support arm 40 tilts in the opposite C direction. As a result, the endless belt moves in the E direction. That is, the load in the E direction increases. Thus, by controlling the inclination of the tension applying roll 14 in the axial direction,
The load applied to the guide member 54 is corrected so as to be equal to or less than a predetermined value.

In FIG. 7, the displacement of the belt guide member 54 is detected by the displacement detection sensor 56, and the inclination of the roll 14 is adjusted by driving the motor 51 by the control device 57. It is impossible to make the belt completely straight. Therefore, when this is detected, the linearity of the belt end affects the displacement measurement accuracy. The acting average load F ₀ cannot be set to a predetermined value, and the meandering of the belt occurs.

Therefore, the belt 11 is provided with a detecting portion 58 composed of a mark or a hole. The detecting portion 58 is detected by a position detecting sensor 59, and based on a signal generated once per rotation of the belt 11, a displacement detecting sensor is provided. The displacement of the belt guide member 54 is detected by 56. In order to easily perform the belt adjustment, it is also possible to stop the driving of the belt, visually measure the displacement of the belt, and manually adjust the roll 14 based on the measured displacement.

The details of the belt meandering adjustment mode will be described below with reference to FIG. The meandering adjustment of the belt is performed when the belt transport device is assembled or when the belt and the roll are replaced, but this is usually performed by a professional person and not performed by a general printer user. When the user selects the belt adjustment mode and presses the start button, the belt is driven. When the belt is driven, a sensor signal is generated once per rotation, the signal is counted, and becomes equal to a preset value N (for example, 20), and after a time T, the belt stops. This rotation speed may be set before the adjuster presses the adjustment start button. Here, the required number of rotations N must be stably driven by installing the belt, that is, the belt must be driven for a predetermined time until the belt guide member 54 reaches a position balanced with the load received from the belt end. Since the time until this stabilization is determined by the difference in the circumferential length of the belt, the degree of parallelism of the rolls, and the like, the rotational speed N must be determined in consideration of manufacturing tolerances and the like. The number of rotations N is also related to the configuration for meandering control, that is, the spring constant of the elastically supported belt guide member 54 and the spring constant of the roll having elasticity in the axial direction.

The time T may be constant as long as T = 0 is desirable, but if it cannot be set to 0, it may be set to a specified time. If there is a device for detecting the speed of the belt such as an encoder, this signal is used for a certain time T
Is more desirably a constant belt driving distance. The belt stopped in this manner can always be stopped at a fixed position. At this position, the position of the belt in the axial direction, that is, the position of the belt end is measured, and the cam 48 of the roll 14 is moved according to the measured distance. Rotate to make meandering correction. Then, the start button is pressed again to drive the belt, and the above operation is repeated until the displacement of the belt reaches a predetermined value.

The belt displacement is measured by the displacement detecting sensor 56 in synchronization with the detecting portion 58 on the belt generated by the position detecting sensor 59 without stopping the belt after the specified number of revolutions N. Alternatively, the measurement can be semi-automated if the measurement is continued for a constant belt drive distance and the average value is treated as the belt displacement. In this case, the belt meandering speed may be calculated from the belt displacement, and when the belt meandering speed falls below a specified value, the belt may be stopped, and meandering correction may be performed based on the belt displacement amount at this time.

Further, in order to use the position detecting sensor 59 as the displacement detecting sensor 56, as shown in FIG. 9, the detecting portion 58 has a trapezoidal shape or a triangular shape so that the lengths are different in the belt width direction. Thus, the displacement of the belt in the axial direction is calculated by the position detection sensor 59, and the ON time t of the position detection sensor 59 is set as the belt displacement x. Also in this embodiment, the belt meandering speed may be calculated from the belt displacement, and when the belt meandering speed falls below a specified value, the belt may be stopped, and the meandering correction may be performed based on the belt displacement amount at this time.

Next, although not directly related to the present invention, a method for controlling the belt surface speed to be constant will be described.
Conventionally, as a method of detecting the belt surface speed, a method of detecting the surface speed by an encoder on a detection roll shaft that is in contact with the belt surface is known. Such periodic fluctuation is observed. The fluctuation of the period T appears as a fluctuation in the surface speed of the belt 11 due to the eccentricity of the driving roll 12 even when the rotation speed of the shaft of the driving roll 12 is constant. When the belt surface speed is detected by the conventional speed detection method, the speed of the cycle T ′ in which the eccentricity of the detection roll is combined as shown in FIG. 10B is measured. If speed control is performed based on this, a color shift occurs in the case of a color image forming apparatus.

In order to solve this problem, for example, FIG.
In the tandem-type color image forming apparatus shown in (1), the relationship between the pitch P of the image forming unit 16 and the diameter D of the drive roll 12 is P = nπD (n is an integer), and the speed fluctuation is synchronized between the colors. Thus, the deviation between the colors is eliminated, but for that purpose, it is necessary to process and adjust the device with high precision. In a color image forming apparatus using an intermediate transfer belt, the relationship between the belt circumference L and the diameter D of the driving roll is L = nπD (n is an integer), but the belt circumference is always constant. It is difficult to maintain and manufacture. However, if this relationship cannot be maintained, the phase of the belt surface speed during the formation of each color image is shifted as shown in FIG. 10C.

Therefore, in addition to the detection unit 58 and the position detection sensor 59 described with reference to FIG. 7, an encoder for detecting the number of rotations of the driving roll is provided, and the encoder generates a reference signal once per rotation. FIG. 11 shows the relationship between the signal of the position detection sensor 59, the reference signal, and the encoder pulse when the belt surface speed is varied by the driving roll. Here, the relationship between the belt circumferential length L and the drive roll diameter D shows a case where 3L = 10πD.

In FIG. 11, the signal on time t _i of the position detection sensor 59 on the _i-th belt _rotation has a relationship with the belt surface speed, and indicates the surface speed at the moment when the belt passes the detection unit 58. That is, when the belt surface speed is high, the sensor passage time t _i is short, and when the belt surface speed is low, the sensor passage time t _i is long, which is a time proportional to the belt surface speed. The rotation angle of the drive roll at this time is
Encoder pulses from the reference signal to the signal of the sensor 59 can be determined by counting the to the count value C _i. From the above, as shown in FIG.
Position detection sensor signal ON time t for count value C _i
The relationship of _i can be obtained discretely and at regular intervals. The maximum value of the count value C _i is the number of encoder pulses between the reference signal and thus the frequency of the drive roll. As a result, the phase and amplitude of the driving roll frequency can be calculated by performing a Fourier transform on this. Further, the position detection sensor signal ON time t _i indicates the belt surface speed, and the count value C _i indicates the rotation angle of the drive roll. Therefore, the above relationship is the relationship of the belt surface speed to the drive roll rotation angle. Therefore, if the driving roll is driven in such a direction as to cancel the phase and amplitude of the calculated speed fluctuation of the driving roll frequency, the speed fluctuation can be reduced.

FIG. 13 shows a configuration diagram of the speed control circuit. When the belt is driven and the position detection sensor 59 passes through the detection unit 58, the position detection sensor 59 is turned on, and the ON time t _i is counted by the counter 61. Further, it counts the encoder pulses at another counter 62, the position detecting sensor 59 outputs the count value C _i when turned on, the counter 62 is cleared by the reference signal. This value is stored in the memory 63 as t ₀ and C ₀ , and the phase and amplitude calculation circuit 64 calculates the phase and amplitude of the speed fluctuation of the drive roll frequency by performing Fourier transform on this value. Next, the motor drive circuit 65 calculates a speed fluctuation correction value from the obtained value and outputs the corrected value to the motor. This speed control is performed only for the drive roll frequency. Specifically, a signal of a drive roll frequency having a corrected phase and amplitude based on a reference signal may be added to a normal speed feedback circuit. By repeating this, the speed fluctuation of the driving roll frequency decreases, and the correction value converges to a certain value. Since this correction value basically does not change unless the driving roll is replaced, if this value is stored in a non-volatile memory, the speed can be stabilized more quickly by correcting this value when the belt is driven again. Further, since the speed fluctuation is large until the converged correction value is obtained, image formation is not performed during this time, and the fluctuation of the sensor signal on time t _i is reduced to the specified value i.
If so, image formation is started.

In the above example, the circumference L of the belt 11 and the driving roll 1
This is an example where the relationship of the diameter D of 2 is not an integral multiple, and this relationship does not need to be an integral multiple in the tandem type color image forming apparatus shown in FIG. However, in a color image forming apparatus using an intermediate transfer belt, the color must be matched by four rotations of the intermediate transfer belt, and the speed variation for each rotation is the same. I have. In this case, in FIG.
At 1, 62, the sensor signal ON time t _i and the count value C _i
After the specified number of rotations (four rotations are preferable for four colors), if the fluctuation of the sensor ON time t _i is equal to or less than the specified value, the drive roll control continues, and the relationship between L and D Is an integer multiple, so it is not necessary to correct the phase and amplitude of the drive roll frequency. If Sensaon variation in time t _i is the specified value or higher, to continue the count of the sensor signal on-time t _i and the count value C _i performed until the count value C _i is reduced. The phase and amplitude of the speed fluctuation of the driving roll frequency are calculated by Fourier transform using the obtained values, and control is performed in the same manner as in the above example.

In the above example, if the fluctuation of the sensor ON time t _i is equal to or longer than the specified value after the specified rotation, the image forming cycle must be stopped and the correction cycle started to control the speed fluctuation of the driving roll frequency. Must. There is a disadvantage that it takes time to drive the belt many times until the correction is completed. For this purpose, as shown in FIG. 14A, detection units 38 having the same length are provided at a plurality of positions on the belt 11, and the distance d between the detection units 38 is set to have a relationship of πD = nd (n is 3 or more). Further, as shown in FIG. 14B, the intervals between the detection units 38 may not be equal intervals but may be equal intervals on the rotation angle of the drive roll 12. Therefore, the number of rotations of the belt can be reduced accordingly.

[0044]

As apparent from the above description, according to the present invention, the belt meandering control can be performed with high accuracy by appropriately setting the spring constant for elastically supporting the belt guide member. By having a belt meandering adjustment mode and performing belt position detection with high accuracy, belt meandering control can be performed with high accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a method of determining a spring constant of a belt guide member according to the present invention.

FIG. 2 is an overall configuration diagram of a color image forming apparatus in which the present invention is applied to a transfer material conveying belt.

FIG. 3 is a perspective view showing one embodiment of the endless belt conveying device of the present invention.

FIG. 4 is a cross-sectional view of the tension applying roll in FIG. 3 along the axial direction.

FIG. 5 is a diagram illustrating a method for setting a spring constant of a belt guide member according to the present invention.

FIG. 6 is a diagram showing a ratio of reducing the influence of the belt end shape on meandering.

FIG. 7 is a diagram for explaining belt displacement detection in a meandering adjustment mode according to the present invention;

FIG. 8 is a diagram for explaining a flow in a belt meandering adjustment mode.

FIG. 9 is a diagram for explaining another example of belt displacement detection.

FIG. 10 is a diagram for explaining a belt surface speed and its influence;

FIG. 11 is a diagram illustrating a relationship among a position detection sensor signal, a reference signal, and an encoder pulse when a belt surface speed fluctuation occurs.

FIG. 12 is a diagram illustrating a relationship between a belt surface speed and a driving roll rotation angle.

FIG. 13 is a configuration diagram of a speed control circuit.

FIG. 14 is a diagram showing another example of formation of the detection unit.

FIG. 15 is a cross-sectional view illustrating a conventional belt meandering prevention method.

FIG. 16 is a cross-sectional view for explaining a conventional belt meandering prevention method.

[Explanation of symbols]

11 ... Endless belt, 12 ... Drive roll, 14 ... Tension applying roll 14a ... Slit, 40 ... Support member, 54 ... Belt guide member

Claims (3)

(57) [Claims] 1. An image forming apparatus having an endless belt conveying device for stretching and driving an endless belt between a plurality of rolls having at least a driving roll and a tension applying roll, wherein a number of slits are formed on a surface of the endless belt. Roll, a support member rotatably supporting the roll, a belt guide member that is rotatably supported in the axial direction of the roll, and elastically supports a belt end portion with respect to the support member. Wherein the spring constant of the belt guide member is smaller than the rigidity of the endless belt conveying device in the axial direction of the belt. 2. An image forming apparatus having an endless belt conveying device for stretching and driving an endless belt between a plurality of rolls having at least a driving roll and a tension applying roll, wherein a number of slits are formed on a surface of the endless belt. Roll, a support member rotatably supporting the roll, a belt guide member that is rotatably supported in the axial direction of the roll, and elastically supports a belt end portion with respect to the support member. A displacement detection sensor that detects displacement of the belt guide member or the belt, and is provided on the belt.
Detecting unit, and position detecting sensor for detecting the position of the detecting unit
And an adjusting means for tilting the roll based on a detection value of the displacement detection sensor, and stopping the belt at a fixed position.
Then, the belt detection member or
An endless belt conveying device for detecting a displacement of a belt. 3. A driving roll and a tension applying row.
Endless belt is stretched between multiple rolls with
Image forming apparatus having an endless belt conveying device
Is formed from elastic material and has many slits on the surface
To be rolled and a supporting portion for rotatably supporting the roll
When the material is rotatably supported in the axial direction of the roll,
The belt end is elastically supported with respect to the support member.
A belt guide member and a change of the belt guide member or the belt;
Displacement detection sensor that detects the position, provided on the belt
Detecting unit, and position detecting sensor for detecting the position of the detecting unit
Tilt the roll according to the detection value of the displacement detection sensor.
Adjusting means for moving the position detecting sensor.
Synchronously with the belt detection member by the displacement detection sensor.
An endless belt conveying device for detecting belt displacement .