JP2016109976A - Image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation device capable of accurately creating end shape data, which represents a position in a width direction of an end over the circumference of an endless belt, for a shorter period of time than a conventionally required time.SOLUTION: An arithmetic unit 80 includes an image formation controller 81 and data creation controller 82. The data creation controller 82 performs steering control in a data creation mode, controls a signal with a lower gain than the image formation controller 81 does so as to cope with a phase shift quantity, and thus drives a steering motor. Namely, the data creation controller 82 reduces a high-frequency gain, and outputs a control input signal, which has an adverse effect of a high-frequency component reduced, to a drive unit 90. Accordingly, an intermediate transfer belt is caused to meander during a cycle longer than one rotation cycle of the belt, and end shape data is created.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an image forming apparatus using electrophotographic technology, such as a printer, a copying machine, a facsimile machine, or a multifunction machine. In particular, the present invention relates to an image forming apparatus that performs steering control to position a belt member at a predetermined position in the width direction by tilting a steering roller.

  Conventionally, various image forming apparatuses that perform image formation using an endless belt member have been put into practical use. For example, an intermediate transfer type image forming apparatus forms an image using an intermediate transfer belt, a recording material conveyance type image forming apparatus forms an image using a recording material conveyance belt, and a photosensitive belt type image forming apparatus Image formation is performed using a photosensitive belt. In addition, an image forming apparatus using a transfer belt, an image forming apparatus equipped with a belt-type fixing device, and the like have been put into practical use.

  An image forming apparatus that performs steering control for tilting a steering roller in order to position and rotate these endless belt members (hereinafter referred to as endless belts) at a predetermined position in the width direction without causing deviation or meandering. Widely used. In the steering control, the steering roller is tilted every moment based on the output of the edge sensor that detects the position in the width direction of the end portion of the endless belt, and the rotation position of the endless belt is dynamically positioned in the width direction. 2. Description of the Related Art Conventionally, there has been known an image forming apparatus that performs steering control by correcting the contour position of an endless belt detected by an edge sensor based on contour shape data that has been created in advance around one end of the endless belt (patent) References 1, 2).

Japanese Patent Laid-Open No. 11-72980 Japanese Patent Laid-Open No. 11-295948

  By the way, if the endless belt is meandering when creating the contour shape data, the contour position detected by the edge sensor includes the meandering amount of the endless belt, so that it is difficult to create accurate contour shape data. Therefore, Patent Document 1 discloses that steering control is performed until the meandering of the endless belt substantially converges, and thereafter, contour shape data is created based on the contour position detected by the edge sensor. Further, Patent Document 2 discloses that steering control is performed until the meandering amount of the endless belt becomes a predetermined level or less, and then contour shape data is created.

  However, it takes time until the meandering of the endless belt is almost converged by performing the steering control. That is, the end portion of the endless belt is not formed straight, and the detection error of the contour position of the endless belt caused thereby is reflected in an input signal for steering control (hereinafter referred to as a control input signal). As long as the detection error of the contour position is reflected in the control input signal, the meandering of the endless belt cannot be accommodated. Therefore, it has been necessary to rotate the endless belt over a certain period of time until the detection error of the contour position is not reflected in the control input signal. As described above, conventionally, since the contour shape data cannot be created unless the meandering of the endless belt is substantially converged, it has been time consuming until then. Further, since it is difficult to perform steering control so that the endless belt is hardly meandered, the generated contour shape data includes errors and is not accurate.

  The present invention has been made in view of the above problems, and is capable of accurately creating end shape data indicating the position in the width direction of the end portion of the endless belt in a shorter time than in the past. An object is to provide a forming apparatus.

  An image forming apparatus according to the present invention includes a rotating endless belt, a steering roller that is provided so as to support the endless belt and tilts to move the endless belt in a width direction perpendicular to the rotation direction, and the endless belt Detecting means capable of detecting the position in the width direction of the end portion of the belt, and control means for controlling the tilting of the steering roller. When the image forming is performed, the control means is the endless belt prepared in advance. 1st steering control which controls tilting of the steering roller is performed based on the end shape data indicating the width direction position of one circumference and the detection signal of the detection means, and the end shape data is generated In this case, the tilting of the steering roller is controlled based on a signal having a cycle component longer than one cycle of rotation of the endless belt included in the detection signal of the detection means. Performing a second steering control which is characterized in that.

  ADVANTAGE OF THE INVENTION According to this invention, the edge shape data which show the width direction position of the edge part over the circumference | surroundings of an endless belt can be produced more correctly in a shorter time than before.

1 is a schematic configuration diagram illustrating a configuration of an image forming apparatus. The perspective view which shows a belt drive device. The conceptual diagram which shows an example of an edge sensor. The conceptual diagram which shows another example of an edge sensor. FIG. 3 is a control block diagram showing a steering control system of the image forming apparatus. The block diagram of the steering control part of embodiment. The Bode diagram which shows the frequency characteristic of the steering control part of embodiment. The Bode diagram showing the frequency characteristic when the steering control unit is configured by an open loop control system. It is a figure which shows the time change of the control input signal at the time of using the data preparation controller, and a belt position detection signal, (a) is a control input signal, (b) is a belt position detection signal. The figure which shows the belt position detection signal detected at the time of data creation mode. The figure which shows the edge part shape data obtained by embodiment and each conventional steering control part. FIG. 12 is a diagram showing a belt position detection signal detected when each end shape data shown in FIG. 11 is used in the image forming mode. It is a block diagram which shows a steering control part at the time of using a low-pass filter, (a) is a signal control of a difference signal, (b) is a signal control of a belt position detection signal.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. It should be noted that in the following, the general matters related to the image forming apparatus and the steering control at the time of image formation disclosed in Patent Document 1 and Patent Document 2 are not illustrated and description thereof is omitted.

<Image forming apparatus>
First, the image forming apparatus will be described with reference to FIG. FIG. 1 is a schematic diagram illustrating a configuration of an image forming apparatus. An image forming apparatus 1 shown in FIG. 1 is an intermediate transfer tandem type color image forming apparatus in which four color image forming units 1Y, 1M, 1C, and 1K are arranged to face an intermediate transfer belt 20 in the apparatus main body. .

  An outline of the recording material conveyance process of the image forming apparatus 1 will be described. The recording material S is stored so as to be stacked in a paper cassette 8 that can be inserted into and removed from the apparatus main body, and is fed by the paper feed roller 10 in accordance with the image formation timing. For paper feeding from the paper cassette 8, for example, a friction separation method is used. The recording material S sent out by the paper supply roller 10 is conveyed to a registration roller 11 disposed in the middle of the conveyance path 70. Then, after the skew correction and timing correction of the recording material S are performed by the registration roller 11, the recording material S is sent to the secondary transfer portion T2. The secondary transfer portion T2 is a transfer nip portion formed by the opposing driving roller 17 and the secondary transfer outer roller 12, and a toner image is formed on the recording material S by applying a predetermined pressure and an electrostatic load bias. To adsorb.

  A process of forming an image sent to the secondary transfer portion T2 at the same timing as the above-described transport process of the recording material S to the secondary transfer portion T2 will be described. First, the image forming units 1Y to 1K will be described. The image forming units 1Y to 1K are configured substantially the same except that the colors of toner used in the developing devices 5Y to 5K are different from yellow, magenta, cyan, and black. Hereinafter, the image forming unit 1Y will be described, and the other image forming units 1M, 1C, and 1K will be described by replacing “Y” at the end of the reference code with “M”, “C”, and “K”.

  In the image forming unit 1Y, a primary charging device 3Y, an exposure device 4Y, a developing device 5Y, a primary transfer roller 6Y, and a drum cleaning device 7Y are arranged around the photosensitive drum 2Y. The photosensitive drum 2Y has a photosensitive layer formed on the outer peripheral surface thereof, and rotates in the arrow M direction at a predetermined process speed. The surface of the rotationally driven photosensitive drum 2Y is uniformly charged in advance by a primary charging device 3Y, and then an electrostatic latent image is formed by an exposure device 4Y driven based on image information signals. The exposure device 4Y scans the scanning line image data obtained by developing the separation color image of each color with a rotating mirror, and writes an electrostatic latent image of the image on the surface of the charged photosensitive drum 2Y.

  The electrostatic latent image formed on the surface of the photosensitive drum 2Y is visualized through toner development by the developing device 5Y. Thereafter, a predetermined pressing force and an electrostatic load bias are applied by the primary transfer roller 6Y disposed opposite to the photosensitive drum 2Y with the intermediate transfer belt 20 interposed therebetween, and the toner image formed on the photosensitive drum 2Y is transferred to the intermediate transfer belt. 20 is first transferred onto 20. The drum cleaning device 7Y removes the primary transfer residual toner remaining on the photosensitive drum 2Y after the primary transfer.

  The intermediate transfer belt 20 is an endless belt that rotates in contact with the photosensitive drum 2Y, and rotates in the direction of arrow R2 in the figure. The intermediate transfer belt 20 is formed endlessly using a resin material, and is provided so that the driving roller 17, the driven roller 18, and the tension roller 19 are in contact with the inner peripheral side thereof. The intermediate transfer belt 20 is stretched around the driving roller 17, the driven roller 18, and the tension roller 19 with a constant tension. For example, a force that pushes the intermediate transfer belt 20 from the back surface to the front surface is applied to the tension roller 19 by the elastic member 9 such as a spring, and the intermediate transfer belt 20 is stretched with a predetermined tension. As will be described in detail later, the intermediate transfer belt 20 rotates in response to the driving roller 17 being rotationally driven by a belt driving device (see FIG. 2 described later).

  The image forming process of each color that is processed in parallel by the image forming units 1Y to 1K is performed at the timing of sequentially superposing the toner image of the upstream color that is primarily transferred onto the intermediate transfer belt 20. As a result, a full-color toner image is finally formed on the intermediate transfer belt 20 and conveyed to the secondary transfer portion T2. As described above, with the conveyance process and the image forming process described above, the timing of the recording material S and the full-color toner image coincide with each other in the secondary transfer portion T2, and the secondary transfer is performed. The recording material S that has been secondarily transferred is conveyed to the fixing device 13, and the toner image is melted and fixed on the recording material S by a predetermined pressure and heat amount. The recording material S on which the image has been fixed is discharged onto the discharge tray 15 as the discharge roller 14 rotates. The secondary transfer residual toner remaining on the intermediate transfer belt 20 after passing through the secondary transfer portion T2, that is, after the secondary transfer, is removed by the belt cleaning device 16.

  In general, in a belt driving device that rotates an endless belt such as the intermediate transfer belt 20 supported by a plurality of rollers, the rotating endless belt moves in the width direction (a direction perpendicular to the belt rotation direction). Can occur. This may occur due to a shape error of the roller supporting the endless belt or the endless belt, for example, a variation in the surface shape of the roller, the width direction or the circumferential direction of the endless belt, or a shift in the arrangement position of the roller. In the image forming apparatus shown in FIG. 1, when the endless belt meandering phenomenon occurs, when the toner images of the respective colors are transferred and superimposed on the intermediate transfer belt 20, the relative positional shifts of the toner images of the respective colors, and consequently This causes color shift and color unevenness in the fixed image. Alternatively, the endless belt may exceed the range that can be stretched by the roller, and the endless belt may come into contact with other parts and break. Therefore, it is necessary to suppress the meandering phenomenon of the endless belt.

  A steering system is known as one of typical techniques for converging the meandering of an endless belt. In the steering system, one or two of a plurality of rollers that support the endless belt are tilted as a steering roller, and the endless belt is moved in the width direction, thereby suppressing the meandering phenomenon of the endless belt. Such a steering system has the advantage that the force applied to the endless belt is small and high reliability and a long life can be obtained as compared with the system in which the meandering of the endless belt is physically suppressed by a rib or a guide.

<Belt drive device>
Therefore, a belt driving device having a steering mechanism that can suppress meandering of the intermediate transfer belt 20 based on the steering system will be described with reference to FIG. Here, a belt driving device capable of tilting the tension roller 19 as a steering roller will be described as an example. In FIG. 2, the illustration of the elastic member 9 and the driven roller 18 is omitted.

  As shown in FIG. 2, the belt driving device includes a driving roller 17, a tension roller 19 (steering roller), an intermediate transfer belt 20, a driving motor 21, and a steering mechanism 37. As the drive motor 21 rotates the drive roller 17, the intermediate transfer belt 20 is rotated according to the rotation of the drive roller 17. The steering mechanism 37 includes a steering arm 23, an eccentric cam 24, and a steering motor 25. The steering arm 23 rotatably supports the tension roller 19. The steering arm 23 is formed in a long shape, and an eccentric cam 24 is in contact with the side surface of the other end opposite to the one end on which the tension roller 19 is pivotally supported. The eccentric cam 24 is rotated by a steering motor 25. The steering arm 23 is supported by an apparatus main body (not shown) or the like so that the side on which the tension roller 19 is pivotally supported can swing greatly as the eccentric cam 24 rotates. That is, by driving the steering motor 25, the arrangement angle of the tension roller 19 with respect to the drive roller 17 can be changed steplessly. Thereby, the alignment (parallelism) of the tension roller 19 is adjusted, and the intermediate transfer belt 20 can move in the width direction orthogonal to the rotation direction.

  The steering mechanism 37 is often provided on the tension roller 19. This is because the tension roller 19 can eliminate sagging or distortion of the intermediate transfer belt 20 that may be caused by alignment adjustment by adjusting the elastic force of the elastic member 9 (see FIG. 1). If the steering mechanism 37 is provided on the drive roller 17, the feed amount in the rotational direction of the intermediate transfer belt 20 is affected according to the alignment adjustment of the drive roller 17 by the steering mechanism 37. Then, it becomes difficult to control the feed amount in the rotation direction of the intermediate transfer belt 20 by the drive motor 21. Therefore, the drive roller 17 is not suitable for providing the steering mechanism 37.

<Edge sensor>
As shown in FIG. 2, the belt driving device is provided with an edge sensor 26 for detecting the position in the width direction of the end of the intermediate transfer belt 20 at one place in the rotation path of the intermediate transfer belt 20. Based on the detection signal of the edge sensor 26, the position in the width direction of the rotating intermediate transfer belt 20 (hereinafter simply referred to as the width direction position) is detected, and the tension as described above is based on the detection result. Adjustment of the alignment of the roller 19 is performed. An example of the edge sensor 26 as detection means is shown in FIGS.

  FIG. 3 shows a light transmission type edge sensor 26. The edge sensor 26 shown in FIG. 3 is provided such that the end portion of the intermediate transfer belt 20 is inserted between the light emitting portion 27 and the light receiving portion 28 that are opposed to each other. The light emitting unit 27 emits light toward the light receiving unit 28, and the light receiving unit 28 receives light emitted from the light emitting unit 27. In this edge sensor 26, since a part of the light 38 emitted from the light emitting unit 27 is blocked by the intermediate transfer belt 20, the position in the width direction is detected based on the amount of light received by the light receiving unit 28. That is, the light amount of the light 38 reaching the light receiving portion 28 that changes in accordance with the amount of the intermediate transfer belt 20 inserted into the edge sensor 26 is detected, and the width direction position is determined based on this.

  FIG. 4 shows a mechanical contact type edge sensor 26. The edge sensor 26 shown in FIG. 4 is provided so that the end portion of the intermediate transfer belt 20 can come into contact with the arm portion 30 elastically biased by the spring 33. The edge sensor 26 is provided with an arm portion 30, a spring 33, and a distance sensor 34 on a sensor main body portion 26a. The spring 33 is provided on the surface opposite to the surface with which the end of the intermediate transfer belt 20 contacts. The arm portion 30 is formed in an elongated shape, and one end side thereof is swingably supported by the sensor main body portion 26a by a support portion 31, and a distance sensor 34 for detecting a distance to the sensor main body portion 26a is provided on the other end side. Is provided. When the intermediate transfer belt 20 is displaced toward the arm portion 30, the arm portion 30 is pushed by the intermediate transfer belt 20, and the arm portion 30 swings against the elastic force of the spring 33. On the other hand, when the intermediate transfer belt 20 in a state where the arm portion 30 is pushed is displaced away from the arm portion 30, the arm portion 30 is pushed back by the elastic force of the spring 33 and swings toward the intermediate transfer belt 20 side. . Since the distance to the sensor main body 26a changes with such swinging of the arm portion 30, the distance sensor 34 detects the amount of displacement of the arm portion 30. Since the displacement amount of the arm part 30 reflects the displacement of the position in the width direction of the intermediate transfer belt 20, the position in the width direction is determined based on this.

<Rotational position sensor>
Incidentally, since it is difficult to form the end of the intermediate transfer belt 20 in a straight line, the detection value of the edge sensor 26 described above includes a forming error of the intermediate transfer belt 20. Therefore, if the tension roller 19 (steering roller) is controlled so that the detection value of the edge sensor 26 is constant, the intermediate transfer belt 20 may meander instead. Therefore, in order to rotate the intermediate transfer belt 20 stably, it is necessary to compare the detection value of the edge sensor 26 for each rotation of the intermediate transfer belt 20. Therefore, a rotational position sensor 36 that detects that the intermediate transfer belt 20 has reached a predetermined rotational position is provided in the rotational path of the intermediate transfer belt 20 (see FIG. 2).

  The rotation position sensor 36 shown in FIG. 2 detects a rotation reference mark 35 attached to one place on the intermediate transfer belt 20 and outputs a rotation reference signal for each rotation of the intermediate transfer belt 20. For example, the rotational position sensor 36 is a reflective sensor that can detect the amount of light reflected from the intermediate transfer belt 20. The rotational position sensor 36 differs in the amount of received light when it passes through a place where the rotation reference mark 35 is attached and when it passes through other places. The position of the intermediate transfer belt 20 in the rotational direction can be detected by this change in the amount of received light.

<Steering control system>
FIG. 5 is a control block diagram showing a steering control system of the image forming apparatus 1 that can adjust the alignment of the tension roller 19 (steering roller) based on the detection value of the edge sensor 26. When the intermediate transfer belt 20 starts to rotate, a detection signal is output from the edge sensor 26. The detection signal of the edge sensor 26 is input to the belt side edge detection circuit 51, where a belt position detection signal indicating the width direction position of the intermediate transfer belt 20 is generated by comparison with a predetermined threshold. The generated belt position detection signal is sequentially read into the steering control unit 100. The rotation position sensor 36 outputs a rotation reference signal to the steering control unit 100 in accordance with the detection of the rotation reference mark 35 (see FIG. 2) attached to the intermediate transfer belt 20. The steering control unit 100 as control means includes a belt meandering amount calculation circuit 52, a steering amount calculation circuit 53, a motor driver 54 for the steering motor 25, and a belt shape storage memory 55.

  The belt meandering amount calculation circuit 52 calculates a meandering amount of the intermediate transfer belt 20 by comparing a number of belt position detection signals obtained for each rotation of the intermediate transfer belt 20 with those of the previous rotation. Based on the calculated meandering amount of the intermediate transfer belt 20, the steering amount calculating circuit 53 calculates how much the meandering of the intermediate transfer belt 20 can be accommodated by changing the arrangement angle of the tension roller 19. Then, a drive signal corresponding to the calculated change amount of the arrangement angle is output to the motor driver 54 of the steering motor 25. As a result, the steering motor 25 rotates the eccentric cam 24 (see FIG. 2), so that the arrangement angle of the tension roller 19 changes. Thus, the meandering of the intermediate transfer belt 20 can be gradually converged by appropriately changing the arrangement angle of the tension roller 19 based on the detection signal of the edge sensor 26 and tilting the tension roller 19. As a result, the intermediate transfer belt 20 rotates stably without causing meandering.

  When the intermediate transfer belt 20 is stably rotated, the belt position detection signal of the belt side edge detection circuit 51 does not include the meandering amount of the intermediate transfer belt 20. That is, the belt position detection signal represents the correct shape of the end of the intermediate transfer belt 20. Accordingly, the belt position detection signal indicating the width direction position is stored in the belt shape storage memory 55 as end shape data indicating the width direction position of the circumference of the intermediate transfer belt 20. Thereafter, it is determined whether or not meandering has occurred in the intermediate transfer belt 20 based on the stored end shape data.

  In this manner, end shape data called a belt end profile is stored in the belt shape storage memory 55 based on the belt position detection signal acquired when the intermediate transfer belt 20 is rotating stably without meandering. Remembered. In the image forming mode, the image forming apparatus 1 reads the stored end shape data from the belt shape storage memory 55, and executes first steering control for suppressing meandering of the intermediate transfer belt 20 based on the read end shape data. The image forming mode is a mode in which an image forming job is executed and image formation is performed. Here, the image forming job is a series of operations from the start of image formation to the completion of the image forming operation based on a print signal for forming an image on a recording material. Specifically, it refers to the period from pre-rotation (preparation operation before image formation) after receiving a print signal (input of an image formation job) to post-rotation (operation after image formation). , Including paper space.

  As described above, the end shape data needs to be created and stored in advance in the belt shape storage memory 55 before the start of the image forming mode. However, as already described, since the end shape data was created after the meandering of the intermediate transfer belt 20 was almost converged, it took time. Therefore, in the present invention, in view of the above points, the second steering control different from that in the image formation mode is performed in the data creation mode in which the edge shape data is created, and the waiting for the meandering of the intermediate transfer belt 20 to converge is not performed. The edge shape data can be created. This will be described below.

  FIG. 6 is a block diagram of the steering control unit 100 according to the embodiment. As shown in FIG. 6, the steering control unit 100 according to the present embodiment is configured by a feedback control system (closed loop control system), and realizes a partial function of the above-described steering control system (see FIG. 5). The calculation unit 80 generates a control input signal for driving the drive unit 90, that is, the steering mechanism 37 to be controlled (see FIG. 2). As the calculation unit 80, for example, a PI controller or a PID controller is used. In the case where a PID controller is used as the calculation unit 80, the differential gain is set to 0, and the same processing as that of the PI controller described below may be performed. Therefore, the description of the PID controller is omitted here.

  The calculation unit 80 is configured to detect the difference between the reference position of the intermediate transfer belt 20 as a target value signal and the belt position detection signal of the edge sensor 26, that is, the actually measured position in the width direction of the intermediate transfer belt 20, as a difference signal. And the PI calculation is performed based on these. Thereby, a control input signal for controlling the steering mechanism 37 (see FIG. 2) is obtained at that time, and the steering motor 25 is driven in accordance with the control input signal. That is, in the drive unit 90, the steering motor 25 is driven in accordance with the control input signal, and the tension roller 19 (steering roller) is tilted accordingly.

  The calculation unit 80 includes an image forming controller 81 and a data creation controller 82. However, when the calculation unit 80 is configured by one PI controller, the PI parameter is set to a different value each time in the image forming mode and in the data creation mode, so that the image forming controller is changed. 81 and a data creation controller 82 are realized. Of course, the present invention is not limited to this. For example, by using two PI controllers in which different PI parameters are set in advance, one can be switched according to the mode, with one as an image forming controller 81 and the other as a data creation controller 82. It may be.

  The image forming controller 81 performs the first steering control in the image forming mode, and drives the steering motor 25 by performing signal control with a high gain with respect to the displacement amount. On the other hand, the data creation controller 82 performs second steering control in the data creation mode, and performs signal control with a gain lower than that of the image forming controller 81 with respect to the phase shift amount to drive the steering motor 25. .

  FIG. 7 shows a Bode diagram representing the frequency characteristics of the steering control unit 100 according to the embodiment. On the other hand, FIG. 8 shows a Bode diagram representing frequency characteristics when the steering control unit 100 (see FIG. 5) is configured by an open loop control system. In FIG. 7, the case where the image forming controller 81 is used is indicated by a dotted line, and the case where the data creation controller 82 is used is indicated by a solid line. The input is a control input signal, and the output is a belt position detection signal. In the present specification, one cycle of rotation of the intermediate transfer belt 20 refers to one cycle of rotation of the intermediate transfer belt 20 during image formation.

  As can be understood from FIG. 7, the data creation controller 82 has a characteristic of reducing the gain at a frequency higher than the frequency corresponding to one rotation period of the intermediate transfer belt 20 compared to the image forming controller 81. In other words, the intermediate transfer belt 20 has a characteristic of reducing a signal having a period component equal to or less than one period of rotation. The belt position detection signal of the edge sensor 26 includes a frequency component corresponding to the molding error at the end of the intermediate transfer belt 20. The frequency component corresponding to this forming error is higher than the frequency corresponding to one rotation period of the belt. When steering control is performed by feeding back the belt position detection signal including the high-frequency component, the high-frequency component is reflected in the amount of positional deviation and thus in the control input signal, and it takes time to converge the meandering of the intermediate transfer belt 20. Cause. Therefore, the data creation controller 82 can reduce the high frequency gain and output a control input signal in which the influence of the high frequency component is reduced to the steering mechanism 37.

  In the image forming controller 81, the gain of the frequency corresponding to one rotation period of the belt is close to 0 dB which is the maximum gain, and the gain gradually decreases as the frequency becomes higher. In this case, a frequency (for example, about 0.2 Hz) corresponding to one rotation period of the belt is included in a frequency band having a high gain. When the image forming controller 81 is used in the data forming mode, a high frequency component corresponding to a molding error at the end of the intermediate transfer belt 20 is easily amplified. Therefore, a frequency component higher than a frequency corresponding to one rotation period of the belt is used. Including control input signals are easily generated.

  On the other hand, in the data creation controller 82, the gain of the frequency corresponding to one rotation period of the belt is -30 dB or less, that is, considerably lower than that of the image forming controller 81, and the gain gradually decreases as the frequency increases. doing. In other words, the gain curve of the image forming controller 81 has a gain curve shifted to the low frequency side. For this reason, in the steering control in the data formation mode, it is difficult to amplify high frequency components that may be caused by molding errors at the end of the intermediate transfer belt 20. Therefore, it is difficult for the data creation controller 82 to generate a control input signal including a frequency component higher than one rotation period of the belt.

  FIG. 9 shows a control input signal and a belt position detection signal when the data creation controller 82 is used. 9A shows the time change of the control input signal output from the calculation unit 80 to the steering mechanism 37, and FIG. 9B shows the time change of the belt position detection signal fed back to the calculation unit 80.

  As shown in FIG. 9A, the control input signal does not contain a frequency component higher than the frequency corresponding to one cycle of the belt rotation. This is because, as described above, it is difficult for the data creation controller 82 to generate a control input signal including a frequency component higher than the frequency corresponding to one rotation period of the belt. In the case of this control input signal, as shown in FIG. 9B, the belt position detection signal includes a high-frequency component that may be caused by a molding error at the end of the intermediate transfer belt 20. It can be seen that the intermediate transfer belt 20 meanders with a period longer than one period of rotation of the belt.

  How to implement the image forming controller 81 and the data creation controller 82 when one PI controller is used as the arithmetic unit 80 will be described. In the data creation controller 82, the proportional gain is set to, for example, 1/100 or less as compared with the image forming controller 81. In particular, when the molding error at the end of the intermediate transfer belt 20 is fine and small, the proportional gain may be set to “0”. The integral gain is set to, for example, 1/10 or less as compared with the image forming controller 81.

  The data creation controller 82 may be set to a PI parameter in which the gain of the frequency corresponding to one rotation of the belt is at least 20 dB lower than that of the image formation controller 81. As long as the meandering of the intermediate transfer belt 20 is accommodated without divergence, the smaller the gain of the frequency corresponding to one rotation period of the belt, the better. If the gain can be reduced, it is desirable because the time required for the meandering of the intermediate transfer belt 20 to converge can be further shortened. The PI parameter is set to the above-described parameter value in the image forming mode or the data creation mode by a CPU (not shown) or the like. Thus, the PI controller functions as either the image forming controller 81 or the data creation controller 82.

Here, PI parameters capable of realizing the image forming controller 81 and the data creation controller 82 will be described using specific examples. Here, the case where the transfer function in the open loop control system is given by (−0.05 * s ² + 0.0887 * s + 0.00234) / (s ² + 0.022 * s) will be described as an example. The Bode diagram in this case is as shown in FIG. The frequency corresponding to one rotation period of the belt is 0.2 Hz.

  For example, when the PI controller performs the steering control with a sampling period of 0.1 second, in the image forming mode, the PI parameter proportional gain is set to 3 and the integral gain is set to 0.015. And The Bode diagram in this case is as shown by the dotted line in FIG. As shown in FIG. 7, a frequency (0.2 Hz) corresponding to one rotation period of the belt is included in a frequency band with a gain of approximately 0 dB, that is, a control band with a high gain. This indicates that the frequency corresponding to one rotation period of the belt is sufficiently within the control band.

  On the other hand, in the data creation mode, the proportional gain of the PI parameter is set to 0.03, and the differential gain is set to 0.0005 to provide the data creation controller 82. That is, the proportional gain is set to 1/100 and the differential gain is set to 1/30 compared with the image forming mode. The Bode diagram in this case is as shown by the solid line in FIG. As shown in FIG. 7, the gain is reduced to about -35 dB at a frequency (0.2 Hz) corresponding to one rotation period of the belt. This indicates that the signal is approximately 1/50 or less compared to the image forming controller 81. That is, in the case of the data creation controller 82, the meandering amount of the intermediate transfer belt 20 accompanying the steering control becomes 1/50 or less compared to the image forming controller 81 and is reflected in the belt position detection signal. Then, the intermediate transfer belt 20 meanders with a period longer than one period of the belt rotation (see FIG. 9B).

  FIG. 10 shows a belt position detection signal detected in the data creation mode. When creating the end portion shape data, it is necessary to transport the intermediate transfer belt 20 over several cycles. FIG. 10 shows belt position detection when the intermediate transfer belt 20 is rotated over several cycles. Signal was shown.

  As shown in FIG. 10, the belt position detection signal includes a constant fluctuation component in substantially the same manner for each rotation period of the belt. When the intermediate transfer belt 20 meanders with a period longer than one rotation of the belt, the belt position detection signal reflects the position in the width direction of the intermediate transfer belt 20 almost correctly. This is because the intermediate transfer belt 20 meanders at a period longer than one rotation of the belt, and even if the intermediate transfer belt 20 meanders while rotating several cycles, the position in the width direction of the intermediate transfer belt 20 is between them. This is because it cannot be displaced much compared to the conventional case. Thus, the edge shape data can be created by averaging the belt position detection signal acquired when the intermediate transfer belt 20 is rotated over several cycles and removing the inclination as in the conventional case.

  FIG. 11 shows end shape data obtained by the steering control system of the data creation controller 82. For comparison, end shape data obtained by the steering control system of the image forming controller 81, that is, the conventional steering control system, is indicated by a dotted line in the drawing. As can be understood from FIG. 11, the end shape data obtained by the steering control system of the data creation controller 82 and the end shape data obtained by the steering control system of the image forming controller 81 have greatly different waveform shapes. . The difference between the two corresponds to the error of the belt position detection signal that has conventionally caused time to converge the intermediate transfer belt 20. That is, in the conventional steering control system, the intermediate transfer belt 20 is moved by an amount corresponding to this error, and as a result, it takes time to converge the intermediate transfer belt 20.

  FIG. 12 shows a belt position detection signal detected when each end shape data shown in FIG. 11 is used in the image forming mode. The upper row shows the case where the end portion shape data obtained by the steering control system of the image forming controller 81 is used, and the lower portion shows the case where the end portion shape data obtained by the steering control system of the data creation controller 82 is used. In FIG. 12, the proportional gain of the PI parameter is set to 3 and the integral gain is set to 0.015 to form the image forming controller 81, and the belt position detection signal detected when only the end shape data is changed and the steering control is performed. showed that. As can be understood from FIG. 12, when the end shape data obtained by the steering control system of the data creation controller 82 is used, compared to the case where the end shape data obtained by the conventional steering control system is used. The meandering amount of the intermediate transfer belt 20 is suppressed. That is, the end shape data obtained by the steering control system of the data creation controller 82 correctly reflects the molding error at the end of the intermediate transfer belt 20 as compared with the end shape data obtained by the conventional steering control system. It is data.

  As described above, in the data creation mode, the intermediate transfer belt 20 is meandered at a cycle longer than one rotation of the belt by the data creation controller 82 that performs steering control different from the image formation controller 81. If the intermediate transfer belt 20 is meandered at a cycle longer than one rotation of the belt, the position in the width direction of the intermediate transfer belt 20 during the rotation of the intermediate transfer belt 20 for several cycles is not displaced much compared to the conventional case. Therefore, a belt position detection signal indicating the position in the width direction almost correctly is obtained over one belt rotation period. Therefore, in the data creation mode, the end of the intermediate transfer belt 20 can be formed within a short time that the intermediate transfer belt 20 is rotated for several cycles without waiting for the meandering of the intermediate transfer belt 20 to converge. Edge shape data that correctly reflects the error can be created.

<Other embodiments>
In the above-described embodiment, the PI controller and the PID controller are used as the data creation controller 82, but the present invention is not limited to this. For example, a low-pass filter of a transfer function that can realize the Bode diagram shown in FIG. FIG. 13 is a block diagram showing a steering control system when a low-pass filter is used.

  FIG. 13A shows a case where a low-pass filter 85 and an amplifier 86 are used instead of the PI controller described above. In this case, the low-pass filter 85 as a filter unit has the same high-frequency component reduction function as the data creation controller 82 (see FIG. 6). The amplifier 86 is a signal amplifier, and uniformly amplifies the signal output from the low-pass filter 85 over a wide range of frequencies, and outputs this to the drive unit 90 as a control input signal. However, in this case, it is necessary to be able to switch between a steering control system using a PI controller or a PID controller and a steering control system using a low-pass filter depending on the mode. That is, it is necessary to input a belt detection signal to the low-pass filter 85 in the data creation mode while no belt detection signal is input to the low-pass filter 85 in the image forming mode.

  FIG. 13B shows a case where the low-pass filter 85 is arranged in the middle of returning the belt detection signal. Even in this case, the low-pass filter 85 as the filter unit has the same high-frequency component reduction function as the data creation controller 82 (see FIG. 6). The amplifier 86 is a signal amplifier and amplifies a differential signal, which is a difference between the signal output from the low-pass filter 85 and the target value signal, over a wide range of frequencies, and outputs the amplified signal to the drive unit 90 as a control input signal. .

  Even in this manner, end shape data that correctly reflects the forming error of the end of the intermediate transfer belt 20 can be generated without waiting for the meandering of the intermediate transfer belt 20 to converge in the data generation mode. .

  Further, from the viewpoint of meandering the intermediate transfer belt 20 with a period longer than one rotation period of the belt, the steering mechanism is driven by a predetermined control input signal for causing the intermediate transfer belt 20 to meander with a period longer than one period of rotation of the belt. 37 may be controlled. In this case, the steering mechanism 37 is controlled to move the intermediate transfer belt 20 to the center side of the steering roller when the position in the width direction of the intermediate transfer belt 20 enters a predetermined range from the end of the steering roller. That's fine. Then, end shape data may be created based on a belt position detection signal detected while the intermediate transfer belt 20 is moving toward the center of the steering roller. However, in this case, since the control mode differs greatly between the image forming mode and the data creation mode, a steering control system using the PI controller or PID controller as described above is simple and desirable.

  The present invention can be implemented in another embodiment in which a part or all of the configuration of the embodiment is replaced with the alternative configuration as long as the data generation mode for performing steering control different from that in the image forming mode is executed. . In other words, any image forming apparatus equipped with an endless belt that is controlled by steering can be implemented without distinction between a tandem type / 1 drum type, an intermediate transfer type, a recording material conveyance type, and a transfer belt type. The image forming apparatus can also be implemented with an endless belt such as a photosensitive belt, a transfer belt, and a fixing belt. In this embodiment, only the main part related to the formation / transfer of the toner image has been described. However, the present invention adds a printer, various printing machines, a copying machine, a FAX, and a necessary apparatus, equipment, and housing structure. It can be implemented in various applications such as a multifunction machine.

DESCRIPTION OF SYMBOLS 1 ... Image formation apparatus, 19 ... Steering roller (tension roller), 20 ... Endless belt (intermediate transfer belt), 26 ... Detection means (edge sensor), 37 ... Steering mechanism, 80 ... Calculation part, 81 ... Controller for image formation , 82 ... Data creation controller, 85 ... Filter unit (low-pass filter), 90 ... Drive unit, 100 ... Control means (steering control unit)

Claims (5)

A rotating endless belt, a steering roller which is provided to support the endless belt and tilts to move the endless belt in a width direction orthogonal to the rotation direction, and detects the position in the width direction of the end of the endless belt. Possible detection means, and control means for controlling the tilting of the steering roller,
When the image forming is performed, the control means tilts the steering roller based on the end shape data indicating the position in the width direction of one circumference of the endless belt and the detection signal of the detection means. When the first steering control to be controlled is performed and the end shape data is created, based on a signal having a cycle component longer than one cycle of rotation of the endless belt included in the detection signal of the detection means. Executing a second steering control for controlling the tilting of the steering roller;
An image forming apparatus. The control means includes an arithmetic unit to which a detection signal of the detection means is fed back and a difference signal between the detection signal and a predetermined target value signal is input.
When creating the end shape data, the calculation unit reduces a signal of a period component equal to or less than one cycle of rotation of the endless belt than when the calculation unit performs the image formation from the difference signal.
The image forming apparatus according to claim 1. The arithmetic unit is a PI controller,
When the end shape data is created, the proportional gain of the PI controller is lower than that when image formation is performed.
The image forming apparatus according to claim 2. When the end shape data is created, the integral gain of the PI controller is lower than that when image formation is performed.
The image forming apparatus according to claim 3. The control unit includes a filter unit that extracts a signal having a cycle component longer than one cycle of rotation of the endless belt from the detection signal of the detection unit,
When the image formation is performed, the detection signal of the detection unit is not input to the filter unit, while when the end shape data is generated, the detection signal of the detection unit is input to the filter unit.
The image forming apparatus according to claim 1.

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