JP2006139217A - Drive controller for endless moving member, image forming apparatus and method for controlling moving velocity of endless moving member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly accurately control the moving velocity of an endless moving member without being affected by the moving velocity of the endless moving member, the attachment error of a sensor, the mark pitch error and the contraction/expansion, etc. <P>SOLUTION: Many marks continuously formed at equal intervals on the surface of the intermediate transfer belt 10 as the endless moving member are detected by mark sensors 6A and 6B, and the phase difference of the detection signal is calculated by a phase difference calculating means 13. The profile of the mark pitch error by the amount of one rotation is formed by a profile forming means 14 based on the phase difference Cab successively calculated when the intermediate transfer belt 10 is previously rotated once, and then, the mark pitch correction data by the amount of one rotation is formed and stored by a correction data storing means 37 based on the profile. At the following normal operation, the feedback control of the moving velocity of the intermediate transfer belt 10 driven by the driving means 80 is performed by a control means 70 while correcting target position data based on the successively calculated phase difference Cab and the mark pitch correction data successively read from the correction data storing means 37. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a belt-shaped or drum-shaped endless moving member, in particular, various endless moving member drive control devices used in an image forming apparatus such as a copying machine or a printer, an image forming apparatus including the same, and an endless moving member thereof The present invention relates to a moving speed control method.

In recent years, for example, copiers and printers, which are image forming apparatuses using an electrophotographic system, are increasingly capable of forming full-color images in accordance with market demands.
A color image forming apparatus capable of forming such a color image is provided with a plurality of developing devices that perform development with toner of each color around one photosensitive member, and a latent image on the photosensitive member is formed by these developing devices. There is a so-called one-drum type in which a toner is attached to form a full-color synthetic toner image, and the toner image is sequentially superimposed and transferred onto a recording material sheet or a transfer belt to obtain a color image.

  Further, the image forming units for the respective colors including the photoconductor and the developing device are arranged in a straight line, and the toner images of the respective colors formed by the respective image forming units are carried on the sheet conveying belt and conveyed. A direct transfer system that forms a full-color image directly on the sheet (paper) by transferring the image on the sheet (paper), and a toner image of each color formed by the image forming unit for each color on the intermediate transfer belt. There is also an indirect transfer type tandem type color image forming apparatus in which a full-color image is formed by sequentially superimposing and transferring, and the color image is collectively transferred onto a sheet (paper) by a secondary transfer device.

  In any of these color image forming apparatuses, toner images of a plurality of colors (for example, four colors of yellow, cyan, magenta, and black) are created, and the toner images are formed on a sheet or a transfer belt (also referred to as an intermediate transfer belt). Since the color image is formed by sequentially superimposing and transferring the image on the upper side, if the overlapping positions of the toner images of the respective colors are deviated, the color deviation and the hue are changed, and the image quality is deteriorated. Accordingly, it has been an important problem to prevent a shift (color shift) in the transfer position of each color toner image.

It is known that the main cause of the color misregistration is uneven movement speed of the photosensitive drum (or photosensitive belt), the sheet conveying belt, the transfer belt (intermediate transfer belt), and the like.
Therefore, for example, as seen in Patent Document 1, in a one-drum type color image forming apparatus, the amount of movement of a rotating body such as a transfer belt can be accurately detected, and this is used for controlling the moving speed of the rotating body. Thus, it has been proposed to prevent deterioration in image quality such as color misregistration.

In Patent Document 1, toner images of four colors of cyan, magenta, yellow, and black are sequentially formed on the outer peripheral surface of a photosensitive drum for each rotation, and are sequentially superimposed on the surface of an endless transfer belt. A one-drum type color copying machine is described which forms a full-color image by transferring.
The transfer belt is then provided with a scale consisting of marks (scales) that are continuous in the direction of movement in the direction of movement, and the scale is read with an optical detector to detect the amount of movement of the transfer belt directly and accurately. Then, the detected moving amount is fed back by a feedback control system to accurately control the moving speed of the transfer belt. Furthermore, a scale is also provided on the surface of the photosensitive drum or other rotating body so that the same movement amount can be detected and the movement speed can be controlled.

According to this method, since the amount of movement of the surface of the rotating body such as the transfer belt is directly detected, the actual amount of movement of the surface of the rotating body should be able to be detected with high accuracy. However, in reality, there is a random variation in the interval (pitch) between the marks on the scale, so that the detected movement amount includes this and is not necessarily highly accurate.
Thus, for example, Patent Document 2 proposes a belt conveyance device that improves this point.
JP 11-24507 A Japanese Patent No. 3344614

  The belt conveyance device described in Patent Document 2 repeatedly provides a plurality of marks at a predetermined pitch in the conveyance direction on a carrier made of an endless belt such as an intermediate transfer belt that carries paper or a toner image, Two photoelectric sensors for sequentially reading the marks are provided with their positions shifted in the carrying direction of the carrier, and when the carrier is driven by the driving means, based on the outputs of the two sensors, The time difference at which the two sensors detect the same mark is calculated. Further, an average value is obtained for a plurality of time difference calculation results, and the control means controls the driving speed of the carrier by the driving means based on the calculation result of the average value and the time difference calculation result.

  In this case, the average value of the time difference during which the same mark passes through the two sensors is obtained over the integral rotation of the drive roll that drives the carrier, and this is used as the average speed of the carrier. This average speed is substantially equal to the rotational speed of the drive source, and is based on the recognition that the rotational speed of the drive source is suppressed to a fluctuation of a few percent of commas. Therefore, this average value is a highly accurate reference, and if the rotational speed of the drive source is controlled based on this reference, the speed of the carrier such as the intermediate transfer belt can be controlled to a stable and constant speed.

  However, it is difficult to form the scales and marks on the belt-like or drum-like endless moving members with high accuracy, and the temperature and humidity of the environment, and in the case of a belt, it expands and contracts due to roller tension. (Pitch) changes. Further, since the interval between the two sensors is also affected by an attachment error or expansion / contraction of the attachment member due to temperature, it is difficult to manage at an absolute position.

  For this reason, the method described in Patent Document 1 is directly affected by variations in the interval (pitch) of the scale marks as described above, so that it is difficult to control the transfer belt or the like with high accuracy. Also in the method described in Patent Document 2, the time difference during which the same mark passes through the two sensors is not only influenced by the fluctuation of the mark pitch and the interval between the two sensors, but also by the moving speed of the transfer belt or the like. Also changes. Therefore, even if the average value is taken, it cannot be said that it is an accurate reference value, and it is difficult to control the speed or position with high accuracy even if the drive speed of the transfer belt or the like is controlled based on the average value. It was not possible to eliminate color misregistration and density unevenness and to always obtain a high-quality image.

  The present invention has been made to solve such problems, and is a drive control device or a moving speed of various belt-like or drum-like endless moving members including a transfer belt and a photosensitive drum in an image forming apparatus. In the control method, the endless moving member is reliably corrected for the error in the pitch of the mark formed on the endless moving member and the pitch variation due to expansion and contraction without being affected by the moving speed of the endless moving member or the mounting error of the plurality of sensors. The moving speed of the image forming apparatus can be controlled with high accuracy, and thereby high quality image formation (not limited to a full color image) by the image forming apparatus can always be guaranteed.

An endless moving member drive control device according to the present invention is an endless moving member drive control device comprising a belt-like or drum-like endless moving member and a driving means for rotating the endless moving member, To achieve the goal,
A plurality of marks are provided on the front or back surface of the endless moving member so as to be continuous at predetermined intervals in the moving direction, and the marks are detected at predetermined intervals along the moving direction of the endless moving member. A plurality of mark sensors are provided, and a phase difference calculating means is provided for sequentially calculating the phase difference of signals detected by the plurality of mark sensors as the endless moving member moves.

Furthermore, when the endless moving member is rotated once in advance, a profile creating unit that creates a pitch error profile of the mark for the endless moving member around the end by the phase difference sequentially calculated by the phase difference calculating unit;
Correction data storage means for creating and storing mark pitch correction data for one round of the endless moving member from the mark pitch error profile created by the profile creation means;
During normal operation, the endless moving member by the driving unit while correcting the target position data based on the phase difference sequentially calculated by the phase difference calculating unit and the mark pitch correction data sequentially read from the correction data storage unit And a control means for feedback-controlling the moving speed.

In addition, when the endless moving member is rotated once in advance, a profile for creating and storing a mark pitch error profile for the endless moving member around by the phase difference sequentially calculated by the phase difference calculating means is stored. Storage means;
During normal operation, the pitch error data is sequentially read from the profile creation storage means to create mark pitch correction data, and based on the mark pitch correction data and the phase difference sequentially calculated by the phase difference calculation means. Further, there may be provided control means for feedback-controlling the moving speed of the endless moving member by the driving means while correcting the target position data.

  Alternatively, an error extracting unit that extracts an error between the phase difference sequentially calculated by the phase difference calculating unit and a preset initial phase difference, and position correction data are generated according to the error extracted by the error extracting unit. Correction data generating means for performing the feedback control of the moving speed of the endless moving member by the driving means while correcting the target position data based on the position correction data generated by the correction data generating means. Also good.

In that case, when the control means feedback-controls the moving speed of the endless moving member by the driving means and the endless moving member is moved by a preset distance, the phase difference sequentially calculated by the phase difference calculating means is calculated. It is desirable to provide an initial phase difference setting means for calculating an average value and setting the average value as the subsequent initial phase difference.
At that time, the preset distance may be set to be equal to or more than a distance corresponding to one round of the endless moving member.

Alternatively, a plurality of mark pattern forming means are provided at predetermined intervals in the moving direction of the endless moving member, and the downstream end of the plurality of mark pattern forming means in the moving direction of the endless moving member is at the same position on the downstream side. The same number of mark pattern sensors as the plurality of mark pattern forming means are arranged by shifting the position in a direction perpendicular to the moving direction,
The endless moving member is moved at a predetermined speed, and the endless moving member is sequentially moved from the mark pattern forming means located on the most upstream side in the moving direction to the front or back surface of each of the plurality of mark pattern forming means. The endless moving member on which the plurality of mark patterns are formed is formed by shifting the timing by the predetermined time at the predetermined speed and forming the plurality of mark patterns by shifting the position in the direction orthogonal to the moving direction. A plurality of mark patterns are detected by the mark pattern sensors by moving in the moving direction at the predetermined speed, and a phase difference between the detection signals or an average value of the phase differences is set as a subsequent initial phase difference. An initial phase difference setting means may be provided.

In these endless moving member drive control devices, the plurality of mark sensors may be held on a common glass substrate.
Further, it is possible to provide mark defect / joint detection means for detecting a plurality of mark defects or joints continuous at the predetermined interval based on the phase difference calculated by the phase difference calculation means.
Further, when the mark defect / joint detection means detects that the mark defect or joint is located between a plurality of mark sensors, the control means performs feedback control of the moving speed of the endless moving member. It is desirable to stop.

  An image forming apparatus according to the present invention includes the endless moving member drive control device, and the endless moving member is at least one of a transfer belt, an intermediate transfer belt, a photosensitive belt, a paper transport belt, an intermediate transfer drum, and a photosensitive drum. One.

  A moving speed control method for an endless moving member according to the present invention comprises a belt-shaped or drum-shaped endless moving member and a driving means for rotating the endless moving member, and the endless moving member has a front surface or a back surface thereof. An endless moving member drive control device in which a plurality of marks are provided so as to be continuous at a predetermined interval in the moving direction, and a plurality of mark sensors for detecting the marks are provided at different positions in the moving direction of the endless moving member. And a moving speed control method for controlling the moving speed of the endless moving member.

And in order to achieve the above-mentioned object, the endless moving member is rotated once in advance, and the phase difference of signals for detecting marks by the plurality of mark sensors is sequentially calculated with the movement of the endless moving member, A profile of a pitch error of the mark for one turn of the endless moving member is created by each phase difference.
Then, mark pitch correction data for one round of the endless moving member is created and stored from the pitch error profile of the mark.

  During normal operation thereafter, the phase difference of the signals for detecting the marks by the plurality of mark sensors is sequentially calculated with the movement of the endless moving member, and the phase difference corresponds to one end of the endless moving member. Based on the mark pitch correction data stored for the position to be moved, the moving speed of the endless moving member by the driving means is feedback controlled while correcting the target position data.

Further, a similar movement speed control method is provided in which the endless moving member is rotated once in advance and the phase difference of signals for detecting marks by the plurality of mark sensors is sequentially calculated as the endless moving member moves. Then, a pitch error profile of the mark for one round of the endless moving member is created and stored by each phase difference.
During normal operation thereafter, the phase difference of the signals for detecting the marks by the plurality of mark sensors is sequentially calculated with the movement of the endless moving member, and at the corresponding position of the profile of the circumference of the endless moving member. The stored pitch error is read to generate mark pitch correction data. Based on the mark pitch correction data and the phase difference, the moving speed of the endless moving member by the driving means is feedback controlled while correcting the target position data. May be.

Alternatively, in accordance with the movement of the endless moving member, a phase difference of signals for detecting the marks by the plurality of mark sensors is sequentially calculated, and the sequentially calculated phase difference and a preset initial phase difference are calculated. Extract the error, create position correction data according to the extracted error,
The moving speed of the endless moving member by the driving means may be feedback controlled while correcting the target position data with the position correction data.

In that case, when the moving speed of the endless moving member is feedback controlled by the driving means and the endless moving member is moved by a preset distance, an average value of phase differences calculated sequentially is calculated, and the average The value may be set as the subsequent initial phase difference.
At this time, the preset distance may be set to be equal to or more than a distance corresponding to one round of the endless moving member.

  Further, the endless moving member is moved at a predetermined speed, and a plurality of mark pattern forming means provided on the front or back surface of the endless moving member at predetermined intervals in the moving direction of the endless moving member, In order from the mark pattern forming means located on the most upstream side, the endless moving member is shifted in time by the predetermined interval at the predetermined speed, and a plurality of marks are shifted in the direction orthogonal to the moving direction. A pattern is formed. Then, the endless moving member on which the plurality of mark patterns are formed is moved in the moving direction at the predetermined speed, and the same number as the mark pattern forming means arranged so as to be shifted in the direction orthogonal to the moving direction. The plurality of mark patterns may be detected by a mark pattern sensor, and the phase difference between the detection signals or the average value of the phase differences may be set as the initial phase difference thereafter.

  According to the endless moving member drive control device and the endless moving member moving speed control method according to the present invention, the pitch of the scale-like marks provided on the endless moving member on the belt or the drum has a slight variation, or the endless moving Even if the pitch changes due to the expansion and contraction of the member, the error is accurately detected by the phase difference of the mark detection signals by a plurality of mark sensors that are not affected by the moving speed of the endless moving member, and marks for one endless moving member in advance Can be stored as a pitch error profile, or mark pitch correction data for one round can be created from the profile and stored.

Then, during normal operation, mark pitch correction data is created based on the stored mark pitch correction data or pitch error from the stored profile, and the target position is corrected based on the sequentially calculated phase difference and the correction data, The moving speed of the endless moving member can be controlled with high accuracy.
Therefore, the absolute speed can be detected by the phase difference between the mark detection signals, the pitch of a large number of marks (to form a scale) provided on the endless moving member is uneven, and the endless moving member due to changes in temperature and humidity. Even if there is expansion and contraction of the end, it is possible to measure the linear velocity of the endless moving member with high accuracy, and always to easily perform highly accurate speed control with a small control load.

Alternatively, an error between the phase difference sequentially calculated during normal operation and a preset initial phase difference is extracted, position correction data is created according to the extracted error, and the target position data is corrected by the position correction data. However, the same effect as described above can be obtained by feedback controlling the moving speed of the endless moving member. In that case, more accurate control can be realized by appropriately setting the initial phase value.
Further, by integrating a plurality of sensors with a material having a low linear expansion coefficient, the absolute position of the sensor interval can be managed, and the phase difference due to expansion and contraction of the endless moving member can be calculated more accurately.
It is also possible to prevent the feedback control of the moving speed from being disturbed due to defective marks or joints.

  According to the image forming apparatus of the present invention, it is possible to accurately control the moving speed of an endless moving member related to image formation such as a transfer belt, an intermediate transfer belt or a drum, a photosensitive drum or a belt, a paper conveying belt, etc. It is always possible to guarantee high-quality image formation without distortion.

The best mode for carrying out the present invention will be described below with reference to the drawings.
1 to 3 are block diagrams showing configurations of first to third embodiments of an endless moving member drive control device and an endless moving member speed control method according to the present invention, respectively. FIG. 4 schematically shows an internal structure of an example of a color image forming apparatus that includes the endless moving member drive control device according to the present invention and performs the speed control method of the endless moving member.
First, the image forming apparatus will be described.

In this color image forming apparatus, an apparatus main body 1 is placed on a paper feed table 2. A scanner 3 is mounted on the apparatus body 1 and an automatic document feeder (ADF) 4 is mounted thereon.
In the apparatus main body 1, a transfer device 20 having an intermediate transfer belt 10 that is a belt-like endless moving member is provided at substantially the center thereof. The intermediate transfer belt 10 includes a driving roller 9 and two driven rollers 15 and 16. It is stretched between them and is rotated clockwise in FIG.

  The intermediate transfer belt 10 is configured so that residual toner remaining on the surface after image transfer is removed by a cleaning device 17 provided on the left side of the driven roller 15. Above the linear portion spanned between the driving roller 9 and the driven roller 15 of the intermediate transfer belt 10, yellow (Y), cyan (C), magenta along the moving direction of the intermediate transfer belt 10. Four drum-shaped photoconductors 40Y, 40C, 40M, and 40K (hereinafter simply referred to as photoconductors 40 if not specified) of (M) and black (K) are arranged at predetermined intervals. . Then, four primary transfer rollers 62 are provided inside the intermediate transfer belt 10 so as to oppose the respective photoreceptors 40 and sandwich the intermediate transfer belt 10 therebetween.

Each of the four photoconductors 40 can be rotated counterclockwise in FIG. 2, and around each photoconductor 40, a charging device 60, a developing device 61, the primary transfer roller 62 described above, respectively. A photoconductor cleaning device 63 and a charge removal device 64 are provided, and each constitutes an image forming unit 18. A common exposure device 21 is provided above the four image forming units 18.
Each image (toner image) formed on each photoconductor is successively transferred onto the intermediate transfer belt 10 in a superimposed manner.

  On the other hand, on the lower side of the intermediate transfer belt 10, a secondary transfer device 22 serving as a transfer unit that transfers an image on the intermediate transfer belt 10 to a sheet P that is a recording sheet is provided. The secondary transfer device 22 has a secondary transfer belt 24, which is an endless belt, spanned between two rollers 23, 23, and the secondary transfer belt 24 is driven by the driven roller 16 via the intermediate transfer belt 10. It comes to be pressed against.

The secondary transfer device 22 collectively transfers the toner images on the intermediate transfer belt 10 onto a sheet P fed between the secondary transfer belt 24 and the intermediate transfer belt 10.
A fixing device 25 for fixing the toner image on the sheet P is provided downstream of the secondary transfer device 22 in the sheet conveying direction. A pressure roller 27 is pressed against the fixing belt 26 which is an endless belt. Yes.

The secondary transfer device 22 also functions to convey the sheet after image transfer to the fixing device 25. Further, the secondary transfer device 22 may be a transfer device using a transfer roller or a non-contact charger. A sheet reversing device 28 is provided below the secondary transfer device 22 for reversing the sheet when images are formed on both sides of the sheet.
As described above, the apparatus main body 1 constitutes an indirect transfer tandem color image forming apparatus.

  When making a color copy with this color image forming apparatus, the document is set on the document table 30 of the automatic document feeder 4. When the document is manually set, the automatic document feeder 4 is opened, the document is set on the contact glass 32 of the scanner 3, and the automatic document feeder 4 is closed and pressed.

  When a start key (not shown) is pressed, when the document is set on the automatic document feeder 4, the document is fed onto the contact glass 32. When the document is manually set on the contact glass 32, the scanner 3 is immediately driven, and the first traveling body 33 and the second traveling body 34 start traveling. Then, light is emitted from the light source of the first traveling body 33 toward the document, and reflected light from the document surface is directed to the second traveling body 34, and the light is reflected by the mirror of the second traveling body 34. The light enters the reading sensor 36 through the imaging lens 35 and the content of the original is read.

  Further, when the start key is pressed, the intermediate transfer belt 10 starts to rotate. At the same time, the photoconductors 40Y, 40C, 40M, and 40K start to rotate, and yellow (Y), cyan (C), magenta (M), and black (K) monochromatic toners on the photoconductors. The operation for forming an image is started. The toner images of the respective colors formed on the respective photoconductors are sequentially transferred while being superimposed on the intermediate transfer belt 10 that rotates in the clockwise direction in FIG. 2, and a full-color composite color image is formed there. It is formed.

  On the other hand, when the start key described above is pressed, the paper feed roller 42 of the selected paper feed stage in the paper feed table 2 rotates, and the sheet P is fed from one selected paper feed cassette 44 in the paper bank 43. The paper is fed out, separated into one sheet by the separation roller 45, and conveyed to the paper feed path 46. The sheet P is transported to the paper feed path 48 in the apparatus main body 1 by the transport roller 47, hits the registration roller 49, and temporarily stops.

In the case of manual sheet feeding, the sheet P set on the manual tray 51 is fed out by the rotation of the sheet feeding roller 50, and is separated into one sheet by the separation roller 52 and conveyed to the manual sheet feeding path 53. Then, it hits the registration roller 49 and temporarily stops.
The registration roller 49 starts to rotate at an accurate timing in accordance with the composite color image on the intermediate transfer belt 10, and temporarily stops the sheet P between the intermediate transfer belt 10 and the secondary transfer device 22. Send it in. Then, a color image is transferred onto the sheet P by the secondary transfer device 22.

The sheet P on which the color image has been transferred is conveyed to a fixing device 25 by a secondary transfer device 22 that also functions as a conveying device, where the transferred color image is fixed by applying heat and pressure. . Thereafter, the sheet P is guided to the discharge side by the switching claw 55, is discharged onto the discharge tray 57 by the discharge roller 56, and is stacked there.
When the double-sided copy mode is selected, the sheet P on which an image is formed on one side is conveyed to the sheet reversing device 28 side by the switching claw 55, reversed there and guided again to the transfer position, and this time the image on the back side. Is discharged onto the discharge tray 57 by the discharge roller 56.

A portion corresponding to the endless moving member drive control device according to the present invention in this image forming apparatus will be described with reference to FIG.
The intermediate transfer belt, which is an endless moving member, is stretched between the driving roller 9 and the driven roller 15, and is tensioned by the driven roller 16. Then, when the driving roller 9 is rotated by the motor 7 via the speed reducer 8, the motor 7 rotates in the direction indicated by the arrow F.
The intermediate transfer belt 10 is a belt formed of, for example, a fluorine-based resin, a polycarbonate resin, a polyimide resin, or the like, and an elastic belt in which all layers or a part of the belt is formed of an elastic member is often used. .

  A plurality of marks 5 are provided along one side edge of the outer peripheral surface of the intermediate transfer belt 10 so as to be continuous at a predetermined interval (pitch) in the moving direction. In this example, a large number of marks 5 are provided over the entire circumference of the intermediate transfer belt 10 so that the scale 250 is formed with extremely small bits (equal intervals). In the figure, the mark 5 is shown in a black scale, but in actuality, the mark 5 is printed with ink having a higher reflectance than the surface of the intermediate transfer belt 10, or the mark 5 having a reflectance different from the reflectance of the ground is printed. A tape is attached to the entire circumference of the intermediate transfer belt 10.

A plurality of (in this example, two) mark sensors 6A, 6 are provided at different positions in the moving direction above the side edge of the intermediate transfer belt 10 where the marks 5 are provided. 6B is provided.
An example of the arrangement relationship between the mark 5 and the two mark sensors 6A and 6B is shown in an enlarged manner in FIG.
Assuming that the design value of the interval (pitch) of the marks 5 forming the scale 250 is P0, the interval D of the detection points of the mark sensors 6A and 6B is an integral multiple of the pitch P0 of the marks 5, that is, D = N · P0 ( N is preferably 1.2, 3,. In this embodiment, the mark sensor 6A is disposed downstream of the moving direction of the intermediate transfer belt 10 (direction indicated by arrow F), and the mark sensor 6B is disposed upstream.

  Then, the motor 7 is driven by the motor drive circuit 81, and the motor 7 rotates the drive roller 9 via the speed reducer 8, thereby rotating the intermediate transfer belt 10 in the direction indicated by the arrow F. The movement of the intermediate transfer belt 10 causes the two mark sensors 6A and 6B to input a signal for detecting the mark 5 of the scale 250 to the control device 71, which controls the motor based on the phase difference between the input signals. The drive circuit 81 is feedback controlled to control the moving speed of the intermediate transfer belt 10 with high accuracy. Details of the control device 71 will be described later.

  FIG. 7 is a configuration diagram showing an example of a scale 250 and a mark sensor 6 (6A and 6B are the same since 6A and 6B are the same) provided on the outer peripheral surface of the intermediate transfer belt. a) is a plan view of a part of the scale 250 as viewed from above, and (b) is a side perspective view showing the configuration and optical path of the optical system of the mark sensor 6, which are shown upside down for convenience. (C) is a plan view of the detection surface of the mark sensor 6.

The scale 250 is a reflective scale, and is formed by alternately forming marks (reflecting portions) 5 and light shielding portions 58 along the rotation direction on the outer peripheral surface (or inner peripheral surface) of the intermediate transfer belt 10. is there.
The mark sensor 6 includes a light emitting element 111 such as an LED, a collimating lens 112, a light receiving window 114 provided with a slit mask 113 and a transparent cover such as glass or a transparent resin film as clearly shown in FIG. A light receiving element 115 such as a transistor is fixed to the housing 110.

  In the mark sensor 6, the light emitted from the light emitting element 111, which is a light source, passes through the collimator lens 112 to become a parallel light flux, and passes through a slit mask 113 in which a plurality of slits 113 a arranged in parallel with the scale 250 is formed. The light beam LB is divided into a plurality of light beams LB and irradiated on the scale 250 on the intermediate transfer belt. A part of the reflected light is reflected by the mark 5, and the reflected light is received by the light receiving element 115 through the light receiving window 114. The light receiving element 115 converts the change in brightness of the reflected light into an electric signal.

Therefore, the light receiving element 115 of the housing 110 of the mark sensor detects the mark 5 of the scale 250 by receiving the reflected light, and is continuously analog-modulated by the presence or absence of the reflecting portion 251 due to the rotation of the intermediate transfer belt. Output a signal. When the signal is waveform-shaped, a rectangular wave pulse signal as shown in FIG. 8 is obtained.
FIG. 8 is a diagram (timing chart) showing the relationship between the waveform obtained by shaping the output signals of the two mark sensors 6A and 6B and the phase difference.

In this figure, (a) shows the waveform of the detection signal from the mark sensor 6A, Ca (1), Ca (2), Ca (n) are their respective periods, and (b) is the detection signal from the mark sensor 6B. Where Cb (1), Cb (2), and Cb (n) indicate their respective periods. (C) shows the waveform of the phase difference between the detection signals of the mark sensors 6A and 6B, and Cab (1), Cab (2), and Cab (n) are the phase differences.
Here, an area composed of the slit mask 113 and the light receiving window 114 on the detection surface of the mark sensor 6 shown in FIG. 7C is defined as a mark detection area SA. Here, the positional relationship between the mark detection areas SA of the two mark sensors 6A and 6B and the marks 5 detected thereby will be described with reference to FIG.

As shown in FIG. 6, if the pitch P0 of the mark 5 remains at the design value (initial value) and the distance D between the two mark sensors 6A and 6B is exactly N · P0, the right side of FIG. When the center line CLa of the mark detection area SA of the mark sensor 6A shown in FIG. 5 coincides with the center of the width of the mark 5 being detected, the mark 5 corresponding to the mark detection area SA of the mark sensor 6B shown on the left side is also indicated by a broken line. The center of the width coincides with the center line CLb of the mark detection area SA.
Therefore, the rising and falling timings of the waveforms obtained by shaping the output signals of the mark sensors 6A and 6B coincide with each other, and the phase difference Cab = 0.

In practice, however, the intermediate transfer belt 10 expands and contracts due to the temperature and humidity in the machine and the tension applied to the intermediate transfer belt 10, thereby shifting the position of the mark 5 on the scale 250.
Therefore, when the center line CLa of the mark detection area SA of the mark sensor 6A shown on the right side of FIG. 9 coincides with the center of the width of the mark 5 being detected, the mark corresponding to the mark detection area SA of the mark sensor 6B shown on the left side 5 shifts as indicated by a solid line, and the center of its width deviates from the center line CLb of the mark detection area SA (when the pitch of the mark 5 increases, the movement direction of the intermediate transfer belt 10 indicated by an arrow F). It will be late.) Thereby, as shown in FIG. 8, the rising and falling timings of the waveforms obtained by shaping the output signals of the mark sensors 6A and 6B are shifted from each other, and a phase difference Cab is generated.

The pitch elongation amount ΔL of the mark 5 at this time is δt = ΔL / V, where δt is the delay time and V is the linear velocity of the intermediate transfer belt 10, and the period of the detection signal by the mark sensors 6A and 6B. Is Ca = Cb = T, the phase difference Cab is calculated by the following equation.
Cab = δt / T = ΔL / V · T (1)
Therefore, the phase difference Cab changes in proportion to the pitch extension amount (change amount) ΔL.

The elongation change rate R is obtained by the following equation, where L is the distance between the mark sensors 6A and 6B.
R = ΔL / L = δt · V / L (2)
The actual belt linear velocity Vreal obtained by P / T using the pitch (scale pitch) P of the mark 5 is calculated by the following equation in consideration of the elongation of the scale.
Vreal = P (1 + R) / T (3)

The cumulative movement distance Lreal is calculated by multiplying the count value “N” of the detection signal by the mark sensor 6A or 6B by the scale pitch “P”.
Lreal = N · P + Σ {ΔL (k)} = N · P + Σ {P · R (k)}
= N · P {1 + Σ (P (k)} (4)
Thus, the amount obtained by adding the integral value of the elongation amount can be calculated as the actual cumulative moving distance.

In the control that does not consider the scale pitch error, the difference between the pulse interval Ca (n) or Cb (n) of the detection signal of one mark sensor 6 and the standard pulse interval C0 is feedback-controlled. A difference ΔV between the target speed Vref to be fed back and the actual speed Vreal is calculated by the following equation.
ΔV = Vref−Vreal
= Fc · P0 / C0−fc · Pa (n) / Ca (n) (5)
fc: counter clock P0: standard scale pitch C0: standard clock count of one cycle of detection signal of mark sensor,
Pa (n): Scale pitch with error added Ca (n): Real clock count of one cycle of detection signal of mark sensor

Next, on the basis of the above description, first to third embodiments of the endless moving member drive control device and the speed control method of the endless moving member according to the present invention will be described with reference to FIGS. .
[First embodiment]
FIG. 1 is a block diagram showing the configuration of the first embodiment, which corresponds to an embodiment of the invention according to claims 1 and 11. In FIG. 1, parts corresponding to those in FIG. 5 and the like described so far are denoted by the same reference numerals, and description thereof is omitted.

In FIG. 1, the phase counters 11 </ b> A and 11 </ b> B, the mark counter 12, the phase difference calculation means 13, the profile creation means 14, the correction data storage means 37, and the control means (control circuit) 70 are used to control the control device 71 shown in FIG. 5. Is configured. Further, the motor 7 and the motor drive circuit 81 constitute drive means 80 for rotating the intermediate transfer belt 10 that is an endless moving member.
A large number of marks 5 are provided on the outer peripheral surface of the intermediate transfer belt 10 so as to be continuous at a predetermined initial pitch P0 in the moving direction indicated by arrow F as shown in FIGS. Is forming. The two mark sensors 6A and 6B have an interval D that is an integral multiple of the initial pitch P0 of the mark 5 with respect to the scale 250 on the intermediate transfer belt 10 as shown in FIG. In order to prevent this, the image forming apparatus is fixed to a fixed portion.

Then, when the driving roller 9 is rotated by the motor 7 and the intermediate transfer belt 10 is rotated in the direction indicated by the arrow F, the two mark sensors 6A and 6B detect the mark 5 on the scale 250, thereby detecting the mark 5 in FIG. The detection signals shown in (a) and (b) are output as Sa and Sb, the detection signal Sa is used as the gate input of the phase counter 11A, the detection signal Sb is used as the gate input of the phase counter 11B, and the mark counter 12 is input as a count pulse. The mark counter 12 may be input with the detection signal Sa as a count pulse.
As a source input of the two phase counters 11A and 11B, a clock pulse CK (generated at a very short constant period) serving as a reference for the operation of a microcomputer (not shown) that performs overall control of the entire control device 71 is input. To do.

Then, the phase counter 11A resets the count value at the rising edge of the detection signal Sa, returns it to 0, starts counting the clock pulse CK again, and outputs the count value to the phase difference calculation means 13. The phase counter 11B also resets the count value at the rising edge of the detection signal Sb to return it to 0, starts counting the clock pulse CK again, and outputs the count value to the phase difference calculation means 13.
The phase difference calculating means 13 watches the count value of the phase counter that is reset earlier among the phase counters 11A and 11B, and then stores the count value when the other phase counter is reset. The count value corresponds to the delay time δt in the above equation (1).

Thereafter, the count value immediately before the count value of the phase counter that was reset earlier is reset again is stored. The count value at this time corresponds to the cycle T of the detection signal Sa or Sb. Therefore, the phase difference Cab described with reference to FIG.
The phase difference between the detection signals Sa and Sb can be easily calculated by calculating Cab = δt / T. When calculating the phase difference Cab as the advance / delay of the detection signal Sa of the mark sensor 6A with respect to the detection signal Sb of the mark sensor 6B, the phase difference counter 11A resets earlier when the pitch of the mark 5 increases. Thus, when the lead phase difference is reached and the pitch of the mark 5 is reduced, the phase counter 11B is reset earlier and becomes a delayed phase difference.

  The intermediate transfer belt 10 is rotated at predetermined timings before actual image formation (factory shipment, installation, immediately after power-on, preparation for image formation operation, etc.), and the mark sensors 6A and 6B Each time the mark 5 is detected, this phase difference Cab is calculated by the phase difference calculating means 13, and when the advance / delay is determined, the information is sent to the profile creating means 14.

  At the same time, the mark counter 12 counts the rising edge of the detection signal Sb from the mark sensor 6B and sends the count value to the profile creating means 14. When the mark sensor 6B detects a seam (described later) of the scale 250, or when a home position mark provided on the intermediate transfer belt 10 is detected by a home position sensor (not shown), the mark counter 12 Then, the count value N of the mark 5 for one rotation of the intermediate transfer belt 10 is sequentially counted up at the rising edge of the detection signal Sb and output.

The phase counters 11A and 11B are reset at the falling edges of the detection signals Sa and Sb by the mark sensors 6A and 6B, and the phase difference calculation means 13 calculates the phase difference between the falling edges of the detection signals Sa and Sb. You may make it do.
The phase counters 11A and 11B may be included in the phase difference calculation means 13. Further, the phase difference between the detection signals Sa and Sb may be directly calculated (detected) using a phase comparator.
When the intermediate transfer belt 10 that is an endless moving member is rotated once in advance in this way, the profile creating unit 14 marks one round of the intermediate transfer belt 10 based on the phase differences sequentially calculated by the phase difference calculating unit 13. A pitch error profile of 5 is created. This is data indicating the characteristic characteristic of the mark pitch error of the scale for one rotation of the intermediate transfer belt 10 at this time.

For example, the cumulative movement distance Lreal from the home position due to the rotation of the intermediate transfer belt 10 is equal to the count pitch N (the count value of the mark 5) of the detection signal Sa or Sb detected by the mark sensor 6A or 6B as described above. (Interval of the mark 5) is multiplied by P, and since the scale pitch P actually changes, if the elongation amount (change amount) is ΔL, it is obtained by the above-described equation (4),
Lreal = N · P + Σ {ΔL (k)}
It becomes. That is, a value obtained by adding the integral value of the change amount ΔL of the scale pitch P to N · P can be calculated as the actual accumulated movement distance. The change amount ΔL of the scale pitch is proportional to the phase difference Cab as described above.

  Therefore, the cumulative movement distance Lreal with respect to the count value N in the ideal case where the scale pitch P is constant and the variation ΔL = 0 is proportional to the count value N of the mark counter 12 as shown by a straight line a in FIG. When the distance increases and reaches the distance of one turn of the intermediate transfer belt 10, the count value N is reset. However, since the scale pitch P actually varies somewhat, the amount of change ΔL is not 0, but is a value proportional to the phase difference Cab calculated by the phase difference calculating means 13. When this is sequentially integrated and added to the value of N · P, the actual cumulative movement distance Lreal with respect to the count value N is the phase difference Cab and its difference with respect to the straight line a as shown by the curve b in FIG. The characteristic increases or decreases according to the advance / delay.

  The profile creating means 14 thus calculates the actual cumulative moving distance Lreal with respect to the count value N of the mark counter 12 by the above formula, and stores the characteristic indicated by the curve b in FIG. 10 as the pitch error profile of the mark 5. Memorize temporarily. This pitch error is often caused by a gradual shift in the interval between the marks 5 when the scale is printed. Therefore, the pitch error often changes little by little as shown by the curve b in FIG. The cumulative moving distance does not change abruptly due to the increment.

  Alternatively, the profile creating means 14 temporarily associates the phase differences Cab sequentially calculated by the phase difference calculating means 13 with the count value N as they are, and temporarily stores them in the sequential memory for one round of the intermediate transfer belt 10 as shown by a curve in FIG. The pitch error profile of the mark 5 can also be stored. The constant phase difference indicated by the one-dot chain line in FIG. 11 indicates the phase difference corresponding to the interval between the mark sensors 6A and 6B, but this is not stored, and only the pitch error of the mark 5 may be stored as a profile. .

  Then, the correction data storage unit 37 generates mark pitch correction data for one rotation of the intermediate transfer belt 10 corresponding to the count value N from the pitch error profile of the mark 5 generated by the profile generation unit 14 and stores it in the memory. Remember. This is data that is corrected so as to subtract the pitch error due to the profile created in advance from the actually calculated phase difference or the fluctuation of the cumulative movement distance proportional thereto.

  During the subsequent normal image operation, when the intermediate transfer belt 10 is rotated, the phase difference calculating unit 13 sequentially calculates the phase difference Cab as described above. Mark pitch correction data sequentially read according to the count value of the mark counter 12 is input from the storage means 37, and a control signal (for example, a torque command) is output to the motor drive circuit 81 while correcting target position data using them. The moving speed of the intermediate transfer belt 10 by the driving unit 80 is feedback controlled.

  Here, the phase difference Cab newly calculated by the phase difference calculating means 13 includes not only the pitch error of the mark 5 but also the expansion and contraction due to the change in the temperature and humidity of the environment and the change of the tension related to the intermediate transfer belt 10. Further, fluctuations due to changes in the moving speed of the intermediate transfer belt 10 are included, and correction is performed by subtracting the mark pitch error inherent to the scale of the intermediate transfer belt 10 stored in advance from the calculated phase difference. become.

Therefore, even if there is an error in the mark pitch of the scale, feedback control of the speed of the intermediate transfer belt 10 is realized with respect to the drive unit 80 so that the expansion and contraction of the intermediate transfer belt 10 and fluctuations in the moving speed are accurately compensated. be able to.
The functions of the phase difference calculating means 13, the profile creating means 14, the correction data storage means 37, and the control means 70 in this control device can also be realized by software processing by a microcomputer (not shown).

[Second Embodiment]
Next, a second embodiment of the endless moving member drive control device and the speed control method of the endless moving member according to the present invention will be described. FIG. 2 is a block diagram showing the configuration of the second embodiment, which corresponds to an embodiment of the invention according to claims 2 and 12. In FIG. 2, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.
The second embodiment differs from the first embodiment described above in that the control device 72 replaces the profile creation means 14 and the correction data storage means 37 in the control device 71 of the first embodiment with a profile creation storage means. 38, and the control means 70 uses the same reference numerals as those in the first embodiment for the sake of convenience, but only the functions are somewhat different.

  According to the second embodiment, when the intermediate transfer belt 10 is rotated once in advance at a predetermined timing, the profile creation storage unit 38 is operated by the phase difference Cab sequentially calculated by the phase difference calculation unit 13. In accordance with the count value N from the mark counter 12, the mark pitch error of one rotation of the intermediate transfer belt 10, such as the fluctuation of the cumulative movement distance indicated by the curve b in FIG. A profile is created and stored in the memory as unique characteristic data at this point.

  In the subsequent normal image forming operation, the mark pitch error data sequentially read from the profile creation storage means 38 is input to the control means 70 based on the count value N from the mark counter 12 to create mark pitch correction data. The control means 70 outputs a control signal (for example, a torque command) to the motor drive circuit 81 while correcting the target position data based on the mark pitch correction data and the phase difference Cab sequentially calculated by the phase difference calculation means 13. Then, the moving speed of the intermediate transfer belt 10 by the driving unit 80 is feedback controlled.

Also according to the second embodiment, the same effect as that of the first embodiment can be obtained. Even if there is an error in the mark pitch of the scale, it is possible to realize feedback control of the speed of the intermediate transfer belt 10 with respect to the drive unit 80 so that the expansion and contraction of the intermediate transfer belt 10 and fluctuations in the moving speed are accurately compensated. it can.
The function of the profile creation storage means 38 in this embodiment can also be realized by software processing by a microcomputer (not shown).

[Third embodiment]
Next, a description will be given of a third embodiment of the endless moving member drive control device and the endless moving member speed control method according to the present invention. FIG. 3 is a block diagram showing the configuration of the third embodiment, which corresponds to an embodiment of the invention according to claims 3 and 13. 3, parts corresponding to those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.
The third embodiment differs from the first embodiment described above in that the control device 73 replaces the profile creation means 14 and the correction data storage means 37 in the control device 71 of the first embodiment with the initial phase difference setting. The means 66, the error extracting means 67, and the correction data creating means 68 are provided, and the control means 70 uses the same reference numerals as those in the first embodiment for convenience, but only the functions are slightly different.

According to the third embodiment, during the normal image forming operation, the phase difference Cab sequentially calculated by the phase difference calculating unit 13 as the intermediate transfer belt 10 rotates is input to the error extracting unit 67. Then, the error extraction unit 67 extracts an error between the phase difference Cab and the initial phase difference preset in the initial phase difference setting unit 66.
Then, the correction data creation means 68 creates position correction data according to the error extracted by the error extraction means 67, and the control means 70 corrects the target position data with the position correction data, while driving the motor drive circuit 81. A control signal (for example, a torque command) is output to the feedback control of the moving speed of the intermediate transfer belt 10 by the driving unit 80.
The moving speed of the endless moving member by the driving means is feedback controlled.

  The initial phase difference setting means 66 sets a reference phase difference (initially may be zero) such as a design value in advance, but preferably the set value is updated as follows. That is, the control unit 70 feedback controls the moving speed of the intermediate transfer belt 10 by the driving unit, and the phase difference sequentially calculated by the phase difference calculating unit 13 when the intermediate transfer belt 10 is moved by a preset distance. The average value of Cab is calculated, and the average value is set as the initial phase difference thereafter.

  In this case, it is desirable that the preset distance is equal to or more than the distance of one turn of the intermediate transfer belt 10. If the number of rotations of the intermediate transfer belt 10 at this time is increased, the average value of a large number of phase differences can be set so that the accuracy is improved, but it takes time to set the initial phase difference. ~ Several revolutions are sufficient.

Here, another example of the initial phase difference setting means will be described with reference to FIGS.
This is suitable for implementation in a tandem type color image forming apparatus as described with reference to FIG.
FIG. 12 shows a simplified arrangement example of the photoconductors of the four color image forming units, the intermediate transfer belt, and the newly shown mark pattern sensor in the image forming apparatus shown in FIG.

  As shown in FIG. 4, the yellow, cyan, magenta, and black photoconductors 40Y, 40C, 40M, and 40K are sequentially arranged on the intermediate transfer belt 10 from the upstream side in the moving direction. An image forming unit 18 including each device necessary for each image formation such as a developing device (which will be simply described as “photosensitive member” in the following description for convenience) is arranged at a constant interval Ps. Each of the photoconductors is used as a plurality of mark pattern forming means provided at predetermined intervals in the moving direction (arrow direction) of the intermediate transfer belt 10.

Then, in the moving direction of the intermediate transfer belt 10, the moving direction (as shown in FIG. The same number of mark pattern sensors 75Y, 75C, 75M, and 75K as the plurality of mark pattern forming means (40Y, 40C, 40M, 40K) are disposed by shifting the position in a direction orthogonal to the direction indicated by the arrow.
Each of the mark pattern sensors 75Y, 75C, 75M, and 75K uses the same configuration as the mark sensor 6 with high detection accuracy described with reference to FIG. However, other reflective photosensors may be used.

  Therefore, when setting the initial phase difference, the intermediate transfer belt 10 is moved at a predetermined linear velocity V0 in the direction indicated by the arrow in FIG. As shown in FIG. 13, the photosensitive drums 40Y, 40C, 40M, and 40K sequentially cause the intermediate transfer belt 10 to move to a predetermined linear velocity as shown in FIG. The timing is shifted by the time T0 (T0 = Ps / V0) for moving by the interval Ps at V0, and the positions are shifted in the direction orthogonal to the moving direction as shown in FIG. M and K are formed.

Thereafter, the intermediate transfer belt 10 on which the mark patterns Y, C, M, and K are formed is moved in the same direction at the same linear velocity V0, and each mark pattern sensor 75Y, 75C, 75M, and 75K respectively Mark patterns Y, C, M, and K are detected.
When the linear velocity of the intermediate transfer belt 10 is exactly constant and the writing timing of the mark pattern by each photoconductor is accurately shifted by T0 = Ps / V0, each mark pattern Y, C, M, K is moved. The mark patterns Y, C, M, and K are slightly displaced in the moving direction as shown in FIG. 14 due to fluctuations in the linear velocity of the intermediate transfer pel 10 and expansion and contraction.

Therefore, the detection pulse signals SY, SC, SM, and SK obtained by shaping the signals obtained by detecting the corresponding mark patterns Y, C, M, and K by the mark pattern sensors 75Y, 75C, 75M, and 75K are shown in FIG. As shown in FIG.
The actual moving speed V of the intermediate transfer belt 10 at this time is
V = (Ps + δt · V) / T0
Therefore, if this is transformed and arranged for V, it is calculated by the following equation.
V = Ps / (T0 + δt)

  When δt is positive, the belt speed is fast, so control is performed so as to slow down by V−V0. Then, the phase difference corresponding to V−V0: δt / (T0 + δt) is set as the initial phase difference by the initial phase difference setting means 66 in FIG. 3, and the control based on the phase difference Cab is performed. If the detection pulse deviations δt by the mark pattern sensors 75Y, 75C, 75M, and 75K shown in FIG. 15 are different, the phase difference: δt / (T0 + δt) is also different. What is necessary is just to set as a phase difference.

[Other Examples]
In the endless moving member drive control device of each of these embodiments, if the plurality of mark sensors 6A and 6B are held by a common glass substrate, the distance between them can be kept constant, and the phase difference can be kept constant. Detection accuracy is improved.

Further, when the mark sensor 6A, 6B has a position corresponding to a portion where the mark 5 is missing or a mark discontinuous portion such as a joint of scales, the mark detection signal is spaced as shown in FIG. As a result, the phase difference pulse becomes abnormally large and the phase comparison output increases rapidly. Means for detecting this can be provided to detect defects or joints in the mark 5.
In the example shown in FIG. 16, the phase difference is calculated by the time difference between the falling edges of the detection signals of the mark sensors 6A and 6B. If the phase difference pulse is viewed as a signal whose duty changes as a PWM signal, it is monitored by analog input. be able to. If the phase difference between the detection signals of the two mark sensors 6A and 6B is monitored, a mark discontinuity can be detected.

  When the defect or the joint of the mark 5 is located between the two mark sensors 6A and 6B, the detection signal of the mark sensor 6A or 6B is sequentially lost and the phase difference pulse is abnormally large as shown in FIG. Or will not be output. Therefore, during this period after detecting this state, the control means 70 in FIGS. 1 to 3 stops the feedback control of the moving speed of the intermediate transfer belt 10 by the phase difference (referred to as “phase difference control stop section” in FIG. 17). As shown). Thereby, control due to an abnormal phase difference is prevented, and the control state can be maintained by continuing the control state immediately before that.

  It should be noted that three or more mark sensors can be provided so that even if a defect or joint of the mark 5 is located between the two mark sensors, it cannot be located between the other mark sensors. Accordingly, in the mark discontinuous portion, the mark sensor to be used can be switched, and the accurate phase difference can be continuously detected so that the feedback control of the moving speed of the intermediate transfer belt 10 does not have to be stopped.

Here, although not an embodiment of the present invention, as an application example, when two mark sensors 6A and 6B are provided as shown in FIG. 6, the two mark sensors 6A and 6B are identical to each other. By measuring the time difference for detecting the passage of the toner, the speed of the intermediate transfer belt 10 can be calculated with high accuracy.
As an example of the configuration, when the mark sensor 6B is on the upstream side in the moving direction (arrow F direction) of the intermediate transfer belt 10, the count value of the mark detection signal of the mark sensor 6B by the phase counter 11B shown in FIG. The multi-stage register is used as a delay memory to count the time for the number of marks between the two mark sensors 6A and 6B to pass.

When there are N marks between the mark sensors 6A and 6B, an N-stage register is used, and by a time T obtained by integrating N count values of detection signals from the mark sensor 6B,
V = (distance between sensors) / T
The speed V can be calculated by the following calculation.

In this case, the optimum value of the interval between the two mark sensors will be examined.
(1) Detection amplitude and reproducibility If the mark sensor interval is reduced, the observed phase difference is reduced. However, if the interval is increased, the measurable frequency is reduced by averaging the phase difference, and oscillation due to phase rotation occurs. Possibility occurs. In order to correct the third-order component of the belt period, the interval between the mark sensors is preferably 50 mm or less.

(2) Detection sensitivity Even if the scale error is several tens of μm per rotation of the belt, the fluctuation that occurs within one pitch of the mark is 1 / number of marks (about 7000), so high sensitivity detection is required. Thus, the sensitivity increases as the interval between the mark sensors is increased.
The detection sensitivity x can be calculated by the following equation.
x = 7.85 / Nab (Nab: number of marks between mark sensor intervals)
When the interval is 20 mm, Nab = 118
x = 0.067 μm
Therefore, if there is an interval of 20 mm, the sensitivity is sufficient. Therefore, if the distance between the two mark sensors is D, it is appropriate to set the following range.
10mm <D <50mm

Although the embodiment in which the present invention is applied to the speed control of the intermediate transfer belt 10 of the tandem type color image forming apparatus shown in FIG. 4 has been described, the secondary transfer belt 24 and the photoreceptors 40Y, 40C, 40M, The present invention can be similarly applied to speed control of other belt-shaped or drum-shaped endless moving members such as 40K.
Also, images of transfer belts, intermediate transfer belts, photosensitive belts, paper transport belts, intermediate transfer drums, photosensitive drums, etc. in image forming apparatuses such as other electrophotographic color or monochrome copying machines, printers, facsimile machines, etc. The present invention can be similarly applied to the speed control of a belt-like or drum-like endless moving member related to formation.
Furthermore, the present invention can also be applied to speed control of an endless moving member in the form of a belt or drum that requires high-accuracy speed control in an inkjet color printer or other various devices.

  The present invention can be used for speed control of a belt-like or drum-like endless moving member that requires high-precision speed control in various devices. In particular, it is suitable for high-speed speed or position control of an endless moving member such as a belt-shaped or drum-shaped transfer belt or a photoreceptor, which is used for image formation of various image forming apparatuses. When applied to a color image forming apparatus, it is possible to prevent color misregistration and the like and always form a high-quality full-color image.

It is a block diagram which shows the structure of 1st Example of the endless moving member drive control apparatus by this invention and the speed control method of an endless moving member. It is a block diagram which similarly shows the structure of the 2nd Example. It is a block diagram which similarly shows the structure of the 3rd Example. 1 is an overall configuration diagram of a mechanism unit showing an example of an image forming apparatus to which the present invention is applied. FIG. 5 is a schematic configuration diagram of a portion corresponding to the endless moving member drive control device according to the present invention in the image forming apparatus shown in FIG. 4.

It is explanatory drawing which expands and shows the example of the arrangement | positioning relationship between the mark 5 shown in FIG. 5, and the two mark sensors 6A and 6B. FIG. 6 is a diagram illustrating a configuration example of a scale and a mark sensor including a large number of marks provided on the outer peripheral surface of the intermediate transfer belt. It is a figure which shows the relationship between the waveform which shape | molded the output signal of two mark sensors 6A and 6B, and its phase difference. It is a figure for demonstrating the positional relationship of the mark detection area | region of two mark sensors 6A, 6B, and the mark detected by it. It is a diagram which shows an example of the profile of the mark pitch error by cumulative movement distance.

It is a diagram which shows an example of the profile of the mark pitch error by a phase difference. FIG. 5 is a diagram illustrating a simplified arrangement example of each photoconductor, an intermediate transfer belt, and a mark pattern sensor in the image forming apparatus illustrated in FIG. 4. 13 is a timing chart showing mark pattern writing timing by an image forming unit having each photoconductor shown in FIG. 12. FIG. 6 is a plan view showing an example of the arrangement of mark patterns of respective colors on the intermediate transfer belt and mark pattern sensors for detecting the same.

It is a timing chart which shows the shift | offset | difference of the signal which detected the mark pattern respectively corresponding by four mark pattern sensors. It is a timing chart for demonstrating a means to detect a mark discontinuity part from a phase difference pulse. It is a timing chart for demonstrating the case where control is stopped in a mark defective part.

Explanation of symbols

1: Main body 2: Paper feed table 3: Scanner 4: Automatic document feeder (ADF)
5: Mark (composing a scale) 6, 6A, 6B: Mark sensor 7: Motor 8: Reducer 9: Drive roller 10: Intermediate transfer belt (endless moving member)
11A, 11B: Phase counter 12: Mark counter 13: Phase difference calculation means
14: Profile creation means 15, 16: Driven roller 18: Image forming unit 20: Transfer device 21: Exposure device 22: Secondary transfer device 24: Secondary transfer belt
37: Correction data storage means 38: Profile creation storage means
40Y, 40M, 40C, 40K: photoconductor 58: light shielding unit 60: charging device
61: Developing device 62: Primary transfer roller 66: Initial phase difference setting means
67: Error extraction means 68: Correction data creation means 70: Control means (control circuit)
71, 72, 73: Control devices 75Y, 75C, 75M, 75K: Mark pattern sensors 80: Driving means
81: Motor drive circuit
110: Case of mark sensor 111: Light emitting element 112: Collimating lens
113 slit mask 114: light receiving window 115: light receiving element 250: scale

Claims (16)

An endless moving member drive control device comprising a belt-shaped or drum-shaped endless moving member and a driving means for rotating the endless moving member,
A plurality of marks are provided on the front or back surface of the endless moving member so as to be continuous at a predetermined interval over the moving direction,
A plurality of mark sensors for detecting the marks are disposed at predetermined intervals along the moving direction of the endless moving member,
A phase difference calculating means for sequentially calculating a phase difference between signals detected by the marks by the plurality of mark sensors as the endless moving member moves;
A profile creating means for creating a pitch error profile of the mark for one turn of the endless moving member by the phase difference sequentially calculated by the phase difference calculating means when the endless moving member is rotated once in advance;
Correction data storage means for creating and storing mark pitch correction data for one round of the endless moving member from the pitch error profile of the mark created by the profile creation means;
During normal operation, the endless movement by the driving unit while correcting target position data based on the phase difference sequentially calculated by the phase difference calculating unit and the mark pitch correction data sequentially read from the correction data storage unit An endless moving member drive control device comprising: control means for feedback controlling the moving speed of the member. An endless moving member drive control device comprising a belt-shaped or drum-shaped endless moving member and a driving means for rotating the endless moving member,
A plurality of marks are provided on the front or back surface of the endless moving member so as to be continuous at a predetermined interval over the moving direction,
A plurality of mark sensors for detecting the marks are disposed at predetermined intervals along the moving direction of the endless moving member,
A phase difference calculating means for sequentially calculating a phase difference between signals detected by the marks by the plurality of mark sensors as the endless moving member moves;
Profile creation storage for creating and storing a pitch error profile of the mark for one end of the endless moving member based on the phase difference sequentially calculated by the phase difference calculating means when the endless moving member is rotated once in advance. Means,
During normal operation, the pitch error data is sequentially read from the profile creation storage means to create mark pitch correction data, and based on the mark pitch correction data and the phase difference sequentially calculated by the phase difference calculation means. And an endless moving member drive control apparatus comprising: a control unit that feedback-controls a moving speed of the endless moving member by the driving unit while correcting target position data. An endless moving member drive control device comprising a belt-shaped or drum-shaped endless moving member and a driving means for rotating the endless moving member,
A plurality of marks are provided on the front or back surface of the endless moving member so as to be continuous at a predetermined interval over the moving direction,
A plurality of mark sensors for detecting the marks are disposed at predetermined intervals along the moving direction of the endless moving member,
A phase difference calculating means for sequentially calculating a phase difference between signals detected by the plurality of mark sensors as the endless moving member;
An error extracting means for extracting an error between a phase difference sequentially calculated by the phase difference calculating means and a preset initial phase difference;
Correction data creation means for creating position correction data according to the error extracted by the error extraction means;
Control means for feedback-controlling the moving speed of the endless moving member by the driving means while correcting the target position data by the position correction data created by the correction data creating means. Drive control device. In the endless moving member drive control device according to claim 3,
When the control means feedback-controls the moving speed of the endless moving member by the driving means to move the endless moving member by a preset distance, the average of the phase differences sequentially calculated by the phase difference calculating means An endless moving member drive control device comprising an initial phase difference setting means for calculating a value and setting the average value as the initial phase difference thereafter. In the endless moving member drive control device according to claim 4,
The endless moving member drive control device, wherein the preset distance is equal to or more than a distance of one round of the endless moving member. In the endless moving member drive control device according to claim 3,
A plurality of mark pattern forming means are provided at predetermined intervals in the moving direction of the endless moving member,
The same number of marks as the plurality of mark pattern forming means are shifted to the same position on the downstream side with respect to all of the plurality of mark pattern forming means in the moving direction of the endless moving member and shifted in a direction perpendicular to the moving direction. A pattern sensor,
The endless moving member is moved to the front or back surface of the endless moving member at a predetermined speed, and the endless moving member is sequentially moved from the mark pattern forming means located on the most upstream side in the moving direction by the plurality of mark pattern forming means. The endless moving member on which the plurality of mark patterns are formed after forming the plurality of mark patterns by shifting the timing by the time of moving the predetermined interval at a predetermined speed and shifting the position in a direction orthogonal to the moving direction. Is moved in the moving direction at the predetermined speed, and each of the mark patterns is detected by each of the mark pattern sensors, and a phase difference between the detection signals or an average value of the phase differences is determined as the initial position thereafter. An endless moving member drive control device comprising an initial phase difference setting means for setting as a phase difference. In the endless moving member drive control device according to any one of claims 1 to 6,
The endless moving member drive control device, wherein the plurality of mark sensors are held on a common glass substrate. In the endless moving member drive control device according to any one of claims 1 to 7,
An endless moving member drive control device comprising mark defect / joint detection means for detecting a plurality of mark defects or joints that are continuous at the predetermined interval based on the phase difference calculated by the phase difference calculating means. In the endless moving member drive control device according to claim 8,
When the mark defect / joint detection means detects that the mark defect or joint is located between the plurality of mark sensors, the control means performs feedback control of the moving speed of the endless moving member. An endless moving member drive control device characterized by stopping.   An endless moving member drive control device according to claim 1, wherein the endless moving member is a transfer belt, an intermediate transfer belt, a photosensitive belt, a paper transport belt, an intermediate transfer drum, or a photosensitive drum. An image forming apparatus characterized by being at least one of the above. A belt-shaped or drum-shaped endless moving member, and a drive means for rotating the endless moving member, and a plurality of marks so as to be continuous at a predetermined interval in the moving direction on the front or back surface of the endless moving member In the endless moving member drive control device, a movement for controlling the moving speed of the endless moving member is provided, wherein a plurality of mark sensors for detecting the marks are provided at different positions in the moving direction of the endless moving member. A speed control method,
The endless moving member is rotated once in advance, and a phase difference of signals for detecting the marks is sequentially calculated by the plurality of mark sensors as the endless moving member is moved. Create a pitch error profile for the mark in minutes,
Create and store mark pitch correction data for one round of the endless moving member from the generated pitch error profile of the mark,
During normal operation, a phase difference of signals for detecting the marks by the plurality of mark sensors is sequentially calculated with the movement of the endless moving member, and stored in a corresponding position on the circumference of the endless moving member. A moving speed control method for an endless moving member, wherein the moving speed of the endless moving member by the driving means is feedback-controlled while correcting target position data based on the mark pitch correction data. A belt-shaped or drum-shaped endless moving member, and a drive means for rotating the endless moving member, and a plurality of marks so as to be continuous at a predetermined interval in the moving direction on the front or back surface of the endless moving member In the endless moving member drive control device, a movement for controlling the moving speed of the endless moving member is provided, wherein a plurality of mark sensors for detecting the marks are provided at different positions in the moving direction of the endless moving member. A speed control method,
The endless moving member is rotated once in advance, and a phase difference of signals for detecting the marks is sequentially calculated by the plurality of mark sensors as the endless moving member is moved. Create and store a pitch error profile for the mark in minutes,
During normal operation, the phase difference of signals for detecting the marks by the plurality of mark sensors is sequentially calculated along with the movement of the endless moving member, and stored in a corresponding position in the profile of the circumference of the endless moving member. The pitch error is read to generate mark pitch correction data, and the moving speed of the endless moving member by the driving means is feedback controlled while correcting the target position data based on the mark pitch correction data and the phase difference. A moving speed control method for an endless moving member. A belt-shaped or drum-shaped endless moving member and a driving means for rotating the endless moving member, and a plurality of marks so as to be continuous at a predetermined interval on the front or back surface of the endless moving member in the moving direction In the endless moving member drive control device, a plurality of mark sensors for detecting the marks are arranged at different positions in the moving direction of the endless moving member, and the moving speed of the endless moving member is controlled. A moving speed control method,
With the movement of the endless moving member, the phase difference of signals for detecting the marks by the plurality of mark sensors is sequentially calculated,
Extract the error between the sequentially calculated phase difference and the preset initial phase difference,
Create position correction data according to the extracted error,
A moving speed control method for an endless moving member, wherein the moving speed of the endless moving member by the driving means is feedback controlled while correcting the target position data with the position correction data. A moving speed control method for an endless moving member according to claim 13,
When the endless moving member is moved by a predetermined distance by feedback control of the moving speed of the endless moving member by the driving means, an average value of the phase differences calculated sequentially is calculated, and the average value is calculated. A moving speed control method for an endless moving member, which is set as the initial phase difference thereafter. A moving speed control method for an endless moving member according to claim 13,
The moving speed control method for an endless moving member, wherein the preset distance is equal to or more than a distance of one round of the endless moving member. In the moving speed control method of the endless moving member according to claim 13,
The endless moving member is moved at a predetermined speed, and a plurality of mark pattern forming means provided at predetermined intervals in the moving direction of the endless moving member on the front surface or the back surface of the endless moving member most upstream in the moving direction. The mark pattern forming means positioned on the side sequentially shifts the timing of the endless moving member by the predetermined interval at the predetermined speed, and shifts the position in a direction orthogonal to the moving direction to form a plurality of mark patterns. Form,
The endless moving member on which the plurality of mark patterns are formed is moved in the moving direction at the predetermined speed, and the same number of marks as the mark pattern forming means disposed in a direction perpendicular to the moving direction. A plurality of mark patterns are detected by a pattern sensor, and a phase difference between the detection signals or an average value of the phase differences is set as the initial phase difference thereafter. Method.

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