JP2013033132A - Belt conveyor, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need for reducing a range of belt scale detection that is used for belt conveyance control, and maintain the belt scale detection when a skew direction of the belt is not stable.SOLUTION: An edge position of an endless belt is obtained when the endless belt is moved to the limit in two directions that are orthogonal to the conveying direction. A target position within the two edge positions is calculated on the basis of the obtained edge positions, and then a steering control roller is controlled to be within a predetermined range of the target position.

Description

  The present invention relates to a belt conveyance device and an image forming apparatus that control conveyance of an endless belt.

  2. Description of the Related Art Conventionally, in image forming apparatuses such as copying machines and printers, an endless belt (endless belt; hereinafter, also simply referred to as “belt”) uses, for example, an intermediate transfer belt, a photosensitive belt, a paper conveyance belt, and the like to make a multicolor. There are color image forming apparatuses that form (color) images. In addition, this type of color image forming apparatus is individually provided with, for example, an image forming unit corresponding to each color of yellow (Y), magenta (M), cyan (C), and black (Bk) on an intermediate transfer belt. There is also a tandem color image forming apparatus.

  Generally, the endless belt is supported by a predetermined number of rollers. Then, any one of these rollers functions as a driving roller, whereby the endless belt is conveyed (traveled). An image forming apparatus including an endless belt is provided with a belt conveyance device that controls conveyance of the endless belt.

  By the way, in an image forming apparatus provided with an endless belt, the endless belt being transported gradually moves in the width direction (a direction perpendicular to the transport direction of the endless belt; also referred to as main scanning direction or depth direction). "Slip" may occur. When this belt shift occurs when an image of each color is transferred onto an endless intermediate transfer belt in a tandem type color image forming apparatus, for example, the relative position shift of the image of each color, and the color shift or Causes uneven color. For this reason, in order to obtain a high-quality output image (color image), it is necessary to appropriately correct the deviation of the belt.

  In this specification, the speed of the belt shift, that is, the speed at which the endless belt being conveyed gradually moves in the width direction is referred to as “shift speed”. In the measurement of the shifting speed, the position in the width direction is measured at a predetermined point on the endless belt. For example, when the endless belt moves 50 μm per second, it is expressed as 50 μm / s. Further, when the control for the belt shift is not performed, the shift speed changes in proportion to the conveyance speed of the endless belt. The deviation of the belt is geometrically determined by the parallelism of each roller.

  Further, in this specification, a direction toward the belt, that is, a direction in which the endless belt being conveyed approaches in the width direction is referred to as a “shift direction”. As the shifting direction, for example, in the double-headed arrow y in FIGS. 3, 5, and 6, the direction indicating the side where the belt 1 exists is referred to as “right direction”, and indicates the side where the belt 1 does not exist. The direction in which it is present is called the “left direction”.

  It has been found that when the position of the roller on which the endless belt is hung is changed near the belt, the shifting speed changes and it takes a certain time to stabilize. Therefore, when the contact / separation operation for switching between monochrome image formation and full-color image formation is performed by changing the tension posture of the endless belt, the belt shift direction and shift speed change.

  Therefore, when switching from single-color (for example, Bk) image formation to full-color image formation, the primary transfer position is shifted in the main scanning direction due to the shift of the intermediate transfer belt, resulting in a color-shifted abnormal image. End up.

  For this reason, several techniques for correcting the deviation of the belt have been proposed. As a typical technique, a steering system (steering control mechanism) is known in which a roller supporting an endless belt is tilted to control the deviation of the belt. This steering method has a smaller force applied to the belt and higher reliability than the side guide method in which the belt side is forcibly suppressed by ribs or guides.

  Incidentally, a belt scale FB system is known as a technique for conveying the belt itself at a stable speed. This is because the belt itself is equipped with a scale (referred to as a belt scale or encoder; for example, shown in 1-1 in FIG. 5), and the belt thickness deviation and drive roller runout are controlled based on the result of reading it with a sensor. In this technique, the belt conveyance speed on the primary transfer surface is controlled. An example of such a technique is disclosed in Patent Document 1, for example.

  By the way, in the belt scale FB system, it is necessary to provide the belt scale at an image forming range and a position (range) that does not interfere with the transfer paper. The reason is that when the belt scale is made of aluminum vapor deposition, if the belt scale is in a position where it comes into contact with the primary transfer roller, a problem of discharging occurs. Further, even if the belt scale is not aluminum vapor deposition, if the belt scale is thick, the quality of the image to be formed is affected.

  Then, the belt scale provided at a limited position on the belt, for example, as shown in FIG. 2, greatly changes to the left and right in the width direction (meanders) when the belt shift direction is not stable. At this time, if the belt moves to a position where the belt scale cannot be detected, there is a problem that the belt scale FB system is not established. It supplements below about the above-mentioned "the direction in which a belt slips is not stable." As the number of rollers that make up the posture of the belt changes, the belt begins to move in a different direction. For example, if the number of rollers is switched while the belt is moving in the right direction in the width direction, the belt starts to move in the left direction. Therefore, the position of the roller that can stabilize the shifting direction changes greatly. When controlling the belt deviation, the end of the belt is detected by a sensor, but the sensor controls the belt deviation because of the badness of the straightness component of the edge and layout restrictions on the design. Since it is provided at some distance, the detection response is slow. Therefore, immediately after the posture of the roller is changed, the belt position is largely changed without being stabilized. This large fluctuation is referred to as “belt direction is not stable”.

  In order to solve the problem that the belt moves to a position where the belt scale cannot be detected as described above, the range in which the sensor can detect the belt scale is simply considered in consideration of mechanical variations (for each part). It is possible to set. However, if this is done, there is a problem that the range in which the sensor can detect the belt scale becomes very narrow, and it is not possible to cope with a case where the belt greatly fluctuates immediately after the posture of the roller is changed as shown in FIG.

  The present invention has been made in view of the above circumstances, and in belt conveyance control using belt scale detection, it is not necessary to narrow the range in which the belt scale can be detected, and the belt shift direction is not stable. It is another object of the present invention to provide a belt conveyance device and an image forming apparatus that can maintain detection of a belt scale.

  In order to achieve this object, a belt conveyance device of the present invention is an endless belt conveyance device that controls conveyance of an endless belt stretched around a plurality of rollers, and the edge of the endless belt is conveyed during conveyance of the endless belt. Edge position detection means for detecting the position, belt scale detection means for detecting a belt scale provided along the conveyance direction of the endless belt during conveyance of the endless belt, and edge position detection during conveyance of the endless belt And a control means for controlling the conveyance of the endless belt based on the detection result. The control means tilts the endless belt and is orthogonal to the conveyance direction. When the belt scale detecting means cannot obtain a predetermined detection result, the edge position detecting hand is moved. Is obtained as a first edge position, and the endless belt is tilted and moved in a direction opposite to one of the directions orthogonal to the conveying direction, and predetermined from the belt scale detecting means. When the obtained detection result is no longer obtained, the detection result obtained from the edge position detection means is acquired as the second edge position, and those positions are obtained based on the first edge position and the second edge position. The target position within the range is calculated, and the inclination of the endless belt is controlled so that the detection result by the edge position detection means falls within the predetermined range of the target position.

  According to the present invention, in belt conveyance control using belt scale detection, it is not necessary to narrow the range in which the belt scale can be detected, and belt scale detection can be maintained when the belt shift direction is not stable.

1 is a diagram illustrating a configuration example of an image forming apparatus according to an embodiment of the present invention. 6 is a graph showing an example of a position of a sutecon roller control motor, a position of an endless belt, and a shifting speed when a belt shift occurs during image forming mode switching. It is a figure which shows an example of the edge sensor which concerns on one Embodiment of this invention. It is a figure which shows an example of the edge sensor which concerns on one Embodiment of this invention. It is a figure which shows the example of arrangement | positioning of the edge sensor which concerns on one Embodiment of this invention, and a belt scale FB sensor. It is a figure which shows the example of arrangement | positioning of the edge sensor which concerns on one Embodiment of this invention, and a belt scale FB sensor. 6 is a flowchart illustrating an operation example of the image forming apparatus according to the embodiment of the present disclosure. It is a figure which shows an example of a pulse when the belt scale FB sensor which concerns on one Embodiment of this invention has detected the belt scale signal. It is a figure which shows an example of a pulse when the belt scale FB sensor which concerns on one Embodiment of this invention is becoming impossible to detect a belt scale signal. It is a figure which shows the example which has arrange | positioned the edge sensor and belt scale FB sensor which concern on one Embodiment of this invention to the photoreceptor belt. It is a figure which shows the example which has arrange | positioned the edge sensor and belt scale FB sensor which concern on one Embodiment of this invention to the fixing belt. It is a figure which shows the example which has arrange | positioned the edge sensor and belt scale FB sensor which concern on one Embodiment of this invention to a paper conveyance belt.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments (embodiments) for carrying out the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic diagram illustrating a configuration example of an image forming apparatus according to an embodiment of the present invention. In the example of FIG. 1, an example of an endless belt to be controlled is an intermediate transfer belt. First, FIG. 1 will be described.

  The intermediate transfer belt 1 (an example of an image carrier) as an endless belt is supported with a predetermined tension by a driving roller 2, a secondary transfer roller 4, and driven rollers 51, 52, 53, and 54 (supported by a tension). The state that has been done is called "tension").

  Further, on the intermediate transfer belt 1, image forming units 8 and 9 corresponding to yellow (Y), magenta (M), cyan (C), and black (Bk) colors according to the conveyance direction (traveling direction) x. 10, 11 are arranged in order. The order of these colors does not matter for Y, M, and C.

  Each of the image forming units 8, 9, 10, and 11 includes a photosensitive drum (an example of an image carrier) 8a, 9a, 10a, and 11a that is rotatably supported by a main body frame of the image forming apparatus, and each photosensitive member. Image writing units 8b, 9b, 10b, and 11b that expose and scan the surfaces of the drums 8a, 9a, 10a, and 11a with a laser beam or the like.

  Around each of the photosensitive drums 8a, 9a, 10a, and 11a, the chargers 8c, 9c, 10c, and 11c, and the developing units 8d, 9d, and the developing units 8d, 9d, are arranged in accordance with the rotation direction of the photosensitive drum (counterclockwise direction in the drawing). 10d, 11d, primary transfer rollers 8e, 9e, 10e, 11e, cleaners 8f, 9f, 10f, 11f are arranged in this order.

  Of the primary transfer rollers 8e, 9e, 10e, and 11e, the three primary transfer rollers 8e, 9e, and 10e for color image formation on the upstream side in the transport direction x are held by the color bracket 7 provided below them. Is done. A contact / separation mechanism 6 is provided below the color bracket 7. When the contact / separation mechanism 6 is driven by a contact / separation mechanism drive motor (not shown), the positions of the primary transfer rollers 8e, 9e, 10e held by the color bracket 7 are the distances from the photosensitive drums 8a, 9a, 10a. Change. That is, as the contact / separation mechanism 6 is driven, the primary transfer rollers 8e, 9e, and 10e are brought into contact with and separated from the photosensitive drums 8a, 9a, and 10a. In this way, a contact / separation operation for switching between monochromatic imaging (monochromatic imaging mode) and full-color imaging (full-color imaging mode) is realized. As described above, the belt is shifted by this contact / separation operation.

  In the image forming apparatus of the present embodiment, an example of a recording medium that is an object of image formation (image formation) will be described as paper, but the material is not limited to paper. The sheets 14 are accommodated in a sheet feeding cassette 50 and are fed out one by one by a pickup roller 15 provided on the sheet feeding side of the sheet feeding cassette 50. The fed paper 14 is transported by a predetermined number of roller pairs 16 along a path (paper transport path) indicated by a broken line in the drawing, and is sent to the pressure contact position of the secondary transfer roller 4.

  Next, an outline of an operation procedure when a color image is formed in the image forming apparatus configured as described above will be described.

  First, image writing is started in order by the image forming units 8, 9, 10, and 11, and then each color image of yellow, magenta, cyan, and black is sequentially superimposed and transferred onto the intermediate transfer belt 1 (primary transfer). Is done. In this way, one color image is formed.

  Thereafter, the color image is fed to the secondary transfer roller 4 as the intermediate transfer belt 1 travels, and the color image on the intermediate transfer belt 1 is collectively transferred (secondary transfer) onto the paper 14.

  The sheet 14 on which the color image has been transferred is sent to a fixing unit 18 by a sheet transport system 17 where the image is fixed (heating, pressing, etc.) and then discharged to a tray (not shown).

  In such a series of image forming operations, when the above-described deviation of the intermediate transfer belt 1 occurs, relative to the position of the image transferred onto the intermediate transfer belt 1 by each of the image forming units 8, 9, 10, 11. A shift occurs, and this appears as a color shift or uneven color in the output image (color image).

  Therefore, the image forming apparatus according to the present embodiment detects the position of the intermediate transfer belt 1 in the width direction (a direction orthogonal to the conveyance direction x; also referred to as a depth direction or a main scanning direction) in order to correct the belt misalignment. The sensor includes an edge sensor 13 and control means (for example, a central processing unit, not shown) that controls the steering roller 3 to tilt based on the detection result of the edge sensor 13.

  The edge sensor 13 (an example of edge position detection means) is disposed on the conveyance path of the intermediate transfer belt 1 and detects the edge position of the intermediate transfer belt 1 (the end in the width direction of the intermediate transfer belt 1). . Examples of the edge sensor 3 include a sensor that can measure the distance itself and a sensor that can detect the edge position of the belt based on the amount of received light as shown in FIG. The edge sensor 3 is disposed at a predetermined location between the driven roller 51 and the secondary transfer roller 4 in the transport direction (transport path) X of the intermediate transfer belt 3, for example.

  As described above, when steering control is performed in the image forming apparatus of the present embodiment, a control unit (not shown) uses the steering roller 3 (or drive roller 2) based on the edge position of the intermediate transfer belt 1 detected by the edge sensor 13. Control the tilt of the. As a result, the intermediate transfer belt 1 tilts, and the deviation of the belt is corrected (adjusted). Examples of the control means include a CPU (Central Processing Unit).

  Here, an example of the edge sensor 13 will be described. FIG. 3 is a schematic diagram illustrating a configuration example of the edge sensor 13.

  In FIG. 3, at one end of the intermediate transfer belt 1, one end side of the contact 13b is held in a pressure contact state by the tensile force of the spring 13a. In this case, the pressure contact force of the contact 13 b by the spring 13 a is set to an appropriate magnitude that does not deform the intermediate transfer belt 1. The contact 13b is rotatably supported by a support shaft 13c at an intermediate portion thereof, and a displacement sensor 13d is disposed in an opposed state on the other end side of the contact 13b with the support shaft 13c as a boundary. Yes.

  In the edge sensor 13 shown in FIG. 3, the movement in the width direction y of the intermediate transfer belt 1 when the belt is deviated is replaced with the movement (swinging movement) of the contact 13 b in pressure contact with the belt edge. At this time, since the output level of the displacement sensor 13d varies in accordance with the movement (displacement) of the contact 13b, the variation in the edge position of the intermediate transfer belt 1 can be detected based on the sensor output. The sensor output is output to the control means. When the control means detects a change in the edge position of the intermediate transfer belt 1 based on the sensor output, the control means executes the steering control.

  As the edge sensor 13, any configuration may be adopted as long as it generates an output corresponding to the position change (belt shift) of the intermediate transfer belt 1. For example, the configuration shown in FIG. In the configuration example of FIG. 4, an LED (Light Emitting Diode) 13 e and a light amount sensor 13 f are arranged in an opposing state via an edge portion of the intermediate transfer belt 1. And a sensor output level changes according to the light quantity in which the light radiate | emitted from LED13e injects into the light quantity sensor 13f. This sensor output is output to the control means. When the control unit detects a change in the edge position of the intermediate transfer belt 1 based on the sensor output, the control unit executes steering control.

  Further, the above-described belt scale FB system is applied to the image forming apparatus of the present embodiment illustrated in FIG. That is, the intermediate transfer belt 1 is provided with a belt scale (encoder) along the conveyance direction of the intermediate transfer belt 1 at a position (range) where the image forming range and the transfer paper do not interfere. The belt scale is provided, for example, as 1-1 shown in FIG.

  As a sensor (encoder sensor) for detecting the belt scale, a belt scale FB sensor 20 (an example of a belt scale detection unit) is disposed on the conveyance path of the intermediate transfer belt 1.

  Although the arrangement position of the belt scale FB sensor 20 is different between FIG. 1 and FIG. 5, any arrangement position may be adopted. However, as shown in FIG. 1, the belt scale FB sensor 20 is disposed between the rollers 51 and 55, while the edge sensor 13 is disposed between the driving roller 2 and the secondary transfer roller 4. When the belt scale FB sensor 20 and the edge sensor 13 are between different rollers, there are the following problems. That is, each roller (the roller between the sensors 20 and 13) has a difference in parallelism with the intermediate transfer belt 1. In other words, each roller is basically held by the front and rear bearings, but because the mounting holes are shifted and the coaxiality between the shafts at both ends of the roller is not zero, it should be straight. It is attached with some inclination with respect to the belt conveying direction. For this reason, the occurrence of the belt deviation cannot be prevented due to the variation of parts. For this reason, “parallelism” means inclination. Due to the difference in parallelism (inclination) between the rollers, the intermediate transfer belt 1 is distorted and stretched obliquely, and therefore the distance in the width direction from the belt scale FB sensor 20 to the edge sensor 13 varies. For this reason, there is a problem that there is a high possibility that the intermediate transfer belt 1 is outside the detectable range of the belt scale FB sensor 20.

  Because of the above problem, it is preferable that the belt scale FB sensor 20 and the edge sensor 13 are arranged between the same rollers (between the rollers 21 and 22) as shown in FIG. Here, “between the same rollers” means that the rollers stretching the belt are shifted so that the sensors are arranged between two adjacent rollers. Such an arrangement can solve the above problem.

  That is, the variation in the distance in the width direction in the belt between the sensor 20 and the sensor 13 can be reduced.

  Further, it is possible to perform control aiming at the center of the belt scale. In other words, the belt is displaced by the amount of the roller between the sensors, but this also occurs over time. Although the median value is calculated by performing the control flow of FIG. 7 (details will be described later) due to the wear of the roller and the wear of the bearing portion over time, the value may be shifted over time. It is possible to suppress such variation with time.

  FIG. 6 shows an arrangement example of the belt scale FB sensor 20 and the edge sensor 13 below the intermediate transfer belt 1 shown in FIG. In FIG. 5, the belt scale FB sensor 20 and the belt scale 1-1 are shown as being on the upper surface of the intermediate transfer belt 1, but actually, as shown in FIG. In other words, it exists on the side where the rollers 21 and 22 are present.

  Based on the detection result of the belt scale FB sensor 20, the control means described above controls the thickness deviation of the intermediate transfer belt 1 and the deflection of the drive roller 2, and controls the belt conveyance speed on the primary transfer surface. That is, in addition to the steering control function described above, the control means also has a belt running control function for controlling the conveyance speed of the intermediate transfer belt 1 by controlling the driving of the driving roller 2.

  As described above, the control means, the belt scale FB sensor 20 and the driving roller 2, the edge sensor 13 and the steering roller 3 can be called a “belt conveying device” for controlling the conveyance of the intermediate transfer belt 1. Note that the control means may be separate or integrated (common) with the control means of the image forming apparatus (controlling the entire image forming apparatus such as control of image forming operation).

  As described above, the image forming apparatus of the present embodiment realizes the steering control function and the belt scale FB system (belt travel control function). However, these functions alone have the following problems.

  Here, in FIG. 2, the output result of the edge sensor 13 (position of the intermediate transfer belt 1) and the drive source of the sutecon roller 3 when the belt is shifted due to the contact / separation operation at the time of switching the image forming mode An example showing the position of a stepping motor used as a steering roller control motor) in time series is shown in the graph. FIG. 2 shows that even if the steering control is performed, it is difficult to sufficiently control the sudden change in the position of the intermediate transfer belt 1 due to the switching of the image forming mode (contact / separation operation). It can be said that. In addition, it is obvious that an abnormal image such as color misregistration occurs in an image formed during such a rapid belt position change.

  Further, the belt scale is often drawn at the end of the intermediate transfer belt 1 as shown in FIGS. 5 and 6 (in order not to interfere with the image forming range and transfer paper). Therefore, when the belt is deviated (for example, when the belt is shifted in the right direction indicated by the arrow y in FIG. 6), the scale signal is detected when the belt scale FB sensor 20 is out of the focal position. It becomes difficult.

  Therefore, in the image forming apparatus of the present embodiment, the above-described problem is solved by performing the control flow (adjustment mode for adjusting the conveyance of the belt) shown in FIG. Hereinafter, FIG. 7 will be described.

  First, the control means starts driving of the driving roller 2 by a motor (not shown) to start the conveyance of the intermediate transfer belt 1 and changes the angle of the steering roller 3 to be inclined (S1). As the intermediate transfer belt 1 starts to be conveyed, the edge sensor 13 and the belt scale FB sensor 20 each start outputting the detection result to the control means.

  The intermediate transfer belt 1 approaches one direction (one side) in the width direction (S2). Here, as an example, in FIG. 6, the intermediate transfer belt 1 moves in the right direction in the drawing in the direction indicated by the arrow y.

  Examples of detection results of the belt scale FB sensor 20 at the time of S2 are shown in FIGS. For example, as shown in FIG. 6, the belt scale FB sensor 20 can detect the scale signal at the time when the belt shift is generated in S2, so that the pulses are at regular intervals as shown in FIG. Thereafter, when the belt further moves, the belt scale deviates from the detection (reading) range by the sensor, so that the belt scale FB sensor 20 gradually cannot detect the scale signal. At this time, as shown in FIG. 9, a missing pulse (missing pulse of either High or Low) occurs. For this reason, in the present embodiment, it is necessary to set the limit of the detectable range of the belt scale when a certain number of missing pulses as shown in FIG. 9 occur. This predetermined number is acquired in advance by experiment and verification (an ideal number of pulses proportional to the conveyance speed is acquired), and is used as a “predetermined number” in S3 and S5 described later.

  When the detection result as shown in FIGS. 8 and 9 is input from the belt scale FB sensor 20, the control means determines whether the number of missing pulses exceeds a predetermined number (a predetermined number) (S3). At this time, the control means inputs the detection result of the belt scale FB sensor 20, but makes the above determination based on the detection result, and does not perform control using the belt scale. That is, in the flow of FIG. 7, the conveyance control of the intermediate transfer belt 1 using the belt scale is not performed. This is because if the control using the belt scale is performed in the flow of FIG. 7, the pulse is missing = the control means detects that the conveyance speed is low. Therefore, in the adjustment mode of FIG. 7, for example, when another encoder wheel is provided on the same axis as the drive roller 2, a normal DC brushless motor with an FG, or a motor such as an STM determined to rotate by the number of pulses. Control without using a belt scale is performed.

  When the number of missing pulses exceeds a predetermined number (when the belt scale reaches the limit of the detectable range of the sensor 20) (S3 / YES), the control means detects the detection result (from the edge sensor 13 at that time) ( The edge position of the intermediate transfer belt 1) is stored in a predetermined storage unit as an edge sensor read value A (an example of the first edge position) (S4). An example of the predetermined storage means is a main storage device such as a RAM (Random Access Memory).

  Next, the control means changes the angle of the steering roller 3 so as to tilt the steering roller 3 in the direction opposite to that in S2 (S5). Thereby, the intermediate transfer belt 1 approaches one direction (one side) in the width direction (S6). Here, as an example, in FIG. 6, the intermediate transfer belt 1 moves to the left in the direction indicated by the arrow y.

  After S5, the control means inputs the detection result from the belt scale FB sensor 20, and determines whether the pulse has returned to a normal value (a predetermined number) (S7).

  When the pulse returns to the normal value (S7 / YES), the control means inputs the detection results as shown in FIGS. 8 and 9 from the belt scale FB sensor 20 in the same manner as S3, and the pulse It is determined whether the number of omissions exceeds a predetermined number (a predetermined number) (S8).

  When the number of missing pulses exceeds a predetermined number (when the belt scale reaches the limit of the detectable range of the sensor 20) (S8 / YES), the control means detects the detection result (from the edge sensor 13 at that time) ( The edge position of the intermediate transfer belt 1) is stored in a predetermined storage unit as an edge sensor read value B (an example of a second edge position) (S9).

  The control means calculates (sensor reading value A + sensor reading value B) / 2, and sets the result as a target value (the median value of two sensor reading values. An example of a target position), and performs steering control (S10). That is, the control unit controls the inclination of the sutecon roller 3 so that the detection result from the edge sensor 13 keeps the target value. Note that after the adjustment mode in FIG. 7 is finished, the steering control (inclination control of the steering roller 3) is performed so as to maintain the target value obtained in S10 in the subsequent image formation. The adjustment mode of FIG. 7 is performed again when the edge sensor 13 or the belt scale FB sensor 20 is replaced or when the belt is replaced.

  Thereafter, the control means satisfies target value−predetermined value (predetermined value) <edge sensor read value <target value + predetermined value (predetermined value) for a predetermined time (predetermined value). (S11). Here, the “edge reading value” is a value detected by the edge sensor 13 after the start of the stacon control in S10.

  The determination at S11 is made for the following reason. In other words, if the edge reading value does not reach the target value, there is a possibility that the belt conveyance will not stop indefinitely under the control that the belt conveyance does not stop. For example, in the case of PID control, since the overshoot is not performed only by the P control, the edge read value does not reach the target value forever. Therefore, in this embodiment, when the edge sensor reading value reaches the vicinity of the target value after the start of the steering control in S10 (S11 / YES), the conveyance of the belt is stopped (S12). Since the vicinity of the target value is a numerical value determined so that the belt scale cannot be detected even if a sudden belt position fluctuation occurs as shown in FIG. The predetermined value used in S11 varies depending on whether it is a unit.

  In addition, the “predetermined time” is provided in S11 because the overshoot may become very large depending on how the control is made. is there.

  As a result of the determination in S11, when the edge sensor read value is larger than the target value−predetermined value and smaller than the target value + predetermined value for a predetermined time (S11 / YES), the control means drives the drive roller 2. Is stopped, the conveyance of the intermediate transfer belt 1 is stopped, the angle of the steering roller 3 is returned to the default value, and the inclination is stopped (S12). As a result, the series of adjustment modes ends normally. Thereafter, the intermediate transfer belt 1 is controlled in accordance with the target value (at this time, control using a belt scale is also performed).

  As a result of the determination in S11, when the edge sensor read value is larger than the target value−predetermined value and not smaller than the target value + predetermined value for a predetermined time (S11 / NO), the control means notifies an error. (S13). That is, the adjustment mode is an abnormal process. The error notification may be performed, for example, via a display unit or a sound emitting unit of the image forming apparatus.

  As described above, according to the present embodiment, in belt conveyance control using belt scale detection, it is not necessary to narrow the range in which the belt scale can be detected and the belt shift direction is not stable. Scale detection can be maintained.

  In other words, if the range where the sensor can detect the scale is simply set in consideration of mechanical variation, the belt scale can be detected only in a very narrow range in the belt width direction, and control becomes difficult. It is impossible to cope with a case where a large fluctuation occurs during the mode switching as shown in FIG. However, in this embodiment, the belt scale can be read by setting a range in which the belt scale can be detected for each belt and for each machine, and setting the median value as a control target value instead of such mechanical variation. A wide range can be set, and control becomes simple (it is possible to create more stable control, such as eliminating the need to correct belt misalignment due to sudden movements), preventing problems such as inability to detect scale signals. (Because of the behavior as shown in FIG. 2, the belt scale is less likely to be read.)

  Further, when the belt or sensor is replaced, the target value can be set each time by performing the control flow of FIG.

  In the above description, the example of the endless belt to be controlled by the flow of FIG. 7 has been described as the intermediate transfer belt 1 in FIG. 1, but is not limited thereto. Examples of other endless belts are shown in FIGS. 10, 11, and 12, respectively.

  FIG. 10 shows an example in which the photosensitive belt 29-1 of the photosensitive member 29 is a control target. As shown in FIG. 10, the edge sensor 13 and the belt scale FB sensor 20 are arranged on the conveyance path of the photosensitive belt 29-1. The steering roller is one of the rollers that stretch the photosensitive belt 29-1. Basically, steering control can be realized with two pairs of rollers. The photoreceptor belt 29-1 is provided with a belt scale as shown in FIG. In such a configuration, a control unit (not shown) can execute the control flow of FIG. 7 to obtain the same effect as that of the above-described intermediate transfer belt.

  FIG. 11 shows an example in which the fixing belt 18-1 of the fixing device 18 is controlled. As shown in FIG. 11, the edge sensor 13 and the belt scale FB sensor 20 are arranged on the conveyance path of the fixing belt 18-1. The steering roller is one of the rollers that stretch the fixing belt 18-1. Further, the fixing belt 18-1 is provided with a belt scale as shown in FIG. In such a configuration, a control unit (not shown) can execute the control flow of FIG. 7 to obtain the same effect as that of the above-described intermediate transfer belt.

  FIG. 12 illustrates an example in which the paper conveyance belt 30 (an example of a recording medium conveyance belt) is a control target in a system that directly transfers to transfer paper (an example of a recording medium) instead of the intermediate transfer method illustrated in FIG. ing. As shown in FIG. 12, the edge sensor 13 and the belt scale FB sensor 20 are arranged on the conveyance path of the paper conveyance belt 30. The steering roller is one of the rollers that stretch the paper conveyance belt 30. Further, the paper transport belt 30 is provided with a belt scale as shown in FIG. In such a configuration, a control unit (not shown) can execute the control flow of FIG. 7 to obtain the same effect as that of the above-described intermediate transfer belt.

  Further, in the image forming apparatus of the present embodiment, the following modifications are also conceivable.

  For example, when the linear expansion coefficient of the material constituting the endless belt is high, the width direction of the endless belt changes as the temperature rises, and there is a high possibility that the endless belt will be outside the detectable range of the belt scale FB sensor. In order to solve this problem, in this modification, the target value used for the endless belt conveyance control can be set for each temperature, so that control aiming at the center of the belt scale (maintenance of belt scale detection is maintained). Control).

  Therefore, for example, a thermistor or the like is provided on the substrate of the belt scale FB sensor 20, and a control unit (not shown) sets the target value based on the temperature detected by the thermistor. The setting of the target value by the control means is performed as follows, for example.

The target value changes during steering control. Basically, the distance changes depending on the linear expansion coefficient.
Belt linear expansion coefficient: α1
Linear expansion coefficient of intermediate frame (iron): α2
Distance between encoder sensor and steering sensor in depth direction: L
Thermistor temperature when the target value is set: T0
Current thermistor temperature: T
Target value at T0: β0
If the target value at T is β,
The target value for each temperature can be calculated by the equation: β = β0 + (α2−α1) × L × (T−T0). The control means sets the value calculated by the above formula as a target value, and controls the conveyance of the endless belt based on the target value.

  From the above, according to this modification, when the temperature change is large and the linear expansion coefficient is large, it is possible to perform control aiming at the center of the belt scale by setting a target value for each temperature. Become.

  As mentioned above, although embodiment of this invention was described, it is not limited to the said embodiment, A various deformation | transformation is possible in the range which does not deviate from the summary.

  For example, the operation in the above-described embodiment can be executed by hardware, software, or a combined configuration of both.

  When executing processing by software, a program in which a processing sequence is recorded may be installed and executed in a memory in a computer incorporated in dedicated hardware. Or you may install and run a program in the general purpose computer which can perform various processes.

  For example, the program can be recorded in advance on a hard disk or a ROM (Read Only Memory) as a recording medium. Alternatively, the program is stored on a removable recording medium such as a CD-ROM (Compact Disc Read Only Memory), an MO (Magneto Optical) disc, a DVD (Digital Versatile Disc), a USB (Universal Serial Bus) memory, a magnetic disc, and a semiconductor memory. It is possible to store (record) temporarily or permanently. Such a removable recording medium can be provided as so-called package software.

  The program may be wirelessly transferred from the download site to the computer in addition to being installed on the computer from the removable recording medium as described above. Or you may wire-transfer to a computer via networks, such as LAN (Local Area Network) and the internet. The computer can receive the transferred program and install it on a recording medium such as a built-in hard disk.

  In addition to being executed in time series in accordance with the processing operations described in the above embodiment, the processing capability of the apparatus that executes the processing, or a configuration to execute in parallel or individually as necessary Is also possible.

DESCRIPTION OF SYMBOLS 1 Intermediate transfer belt 1-1 Belt scale 2 Driving roller 3 Stecon roller 4 Secondary transfer roller 6 Contact / separation mechanism 7 Color bracket 8, 9, 10, 11 Image forming unit 8a, 9a, 10a, 11a, 29 Photoconductor 8b, 9b, 10b, 11b Image writing unit 8c, 9c, 10c, 11c Charger 8d, 9d, 10d, 11d Developer 8e, 9e, 10e, 11e Primary transfer roller 13 Edge sensor 13a Spring 13b Contact 13c Support shaft 13d Displacement Sensor 13e LED
13f Light quantity sensor 14 Paper 15 Pickup roller 16 Roller pair 17 Paper transport system 18 Fixing device 18-1 Fixing belt 20 Belt scale FB sensor 21, 22, 51, 52, 53, 54, 55 Roller 29 Photosensitive belt 30 Paper transport belt 50 Paper cassette

JP 2010-217301 A

Claims (5)

An endless belt conveyance device that controls conveyance of an endless belt stretched around a plurality of rollers,
Edge position detecting means for detecting an edge position of the endless belt during conveyance of the endless belt;
Belt scale detection means for detecting a belt scale provided along the conveyance direction in the endless belt during conveyance of the endless belt;
A control unit that acquires a detection result from each of the edge position detection unit and the belt scale detection unit during conveyance of the endless belt, and controls conveyance of the endless belt based on the detection result;
The control means includes
When the endless belt is tilted and moved in one of the directions orthogonal to the conveying direction, and the predetermined detection result cannot be obtained from the belt scale detecting means, the edge position detecting means The detection result obtained from is acquired as the first edge position,
When the endless belt is tilted and moved in a direction opposite to the one direction out of the directions orthogonal to the conveying direction, when a predetermined detection result cannot be obtained from the belt scale detecting means, The detection result obtained from the edge position detection means is acquired as the second edge position,
Based on the first edge position and the second edge position, a target position that is within the range of those positions is calculated,
An endless belt conveying apparatus, wherein the inclination of the endless belt is controlled so that a detection result by the edge position detecting means falls within a predetermined range of the target position. The edge position detection means and the belt scale detection means are:
The belt conveyance device according to claim 1, wherein the belt conveyance device is disposed between the same rollers of the plurality of rollers. The control means includes
The belt conveyance device according to claim 1 or 2, wherein the target position is set for each temperature detected at a predetermined position in the conveyance path of the endless belt. The endless belt is
The belt conveyance device according to any one of claims 1 to 3, wherein the belt conveyance device is any one of an intermediate transfer belt, a photosensitive belt, a fixing belt, and a recording medium conveyance belt.   An image forming apparatus comprising the belt conveyance device according to claim 1.

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