JP2006085030A - Belt driving device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a belt driving device capable of correcting meandering of a belt in its early stage and an image forming apparatus capable of stably forming an image of high image quality. <P>SOLUTION: A travel distance of the belt in non-steady mode wherein the belt is made to travel not at a steady speed is acquired and the actual travel distance of the belt is found by using a travel time in steady mode and the travel distance in the non-steady mode. Further, the actual position shift of the belt along the width is found from a position in the belt-width direction detected by an edge position sensor and a shape of a part, corresponding to the travel distance of the belt, of the prestored shape of the edge of the belt. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a belt driving device that makes a belt travel along a predetermined traveling route, and an image forming apparatus that includes the belt driving device and forms an image on a recording medium.

  Conventionally, the surface of a charged photoreceptor is exposed to form a latent image, the latent image is developed to form a toner image, the toner image is transferred to an intermediate transfer belt, and finally recorded. Image forming apparatuses that transfer onto a medium are known. In such an image forming apparatus, an annular intermediate transfer belt is generally supported by a plurality of rolls and travels along a predetermined circulation path. There is a risk of so-called meandering of the belt that moves in a direction (perpendicular to the belt traveling direction). When this belt meandering occurs, image blurring or color misregistration occurs in the image formed on the belt, and ultimately the image quality of the image formed on the recording medium is degraded. is there.

  With respect to such a problem, a method of detecting the position of the belt edge with an edge position sensor and tilting the roll supporting the belt according to the detection result to correct the belt running position is widely known. According to this method, compared to the method of forcibly suppressing the meandering of the belt using a guide or the like, it is possible to reduce the meandering of the belt by avoiding the trouble that the belt is damaged, but the shape of the belt edge is Since the belt is not constant over the entire circumference and is distorted, an error due to the distortion is included in the detected position of the belt edge, and the traveling position of the belt cannot be accurately corrected. In a color image forming apparatus, the allowable range of belt meandering is 20 μm or less, and it is difficult to achieve this allowable range by this method.

  Further, in Patent Document 1, a reference mark is attached on the belt, the shape of the belt edge is stored in advance, and the detection result of the position of the belt edge and the shape of the belt edge are used. A method for accurately correcting the positional deviation of the belt is described. According to the method described in Patent Document 1, first, it is detected that the reference mark on the belt has passed a predetermined measurement position, and the travel distance of the belt is determined based on the elapsed time after the reference mark is detected. Calculated. Subsequently, based on the stored edge shape, the original edge position at the position where the belt has advanced by the travel distance calculated from the reference mark is acquired. Then, the position deviation in the width direction of the belt is accurately calculated by subtracting the original edge position from the detected position of the belt edge.

Here, the method described in Patent Document 1 is based on the premise that the belt travels at a stable steady speed. For example, when the image formation is interrupted, the belt travel is stopped. Then, when the traveling of the belt is resumed, the belt speed is gradually accelerated until the predetermined speed is reached, or the belt is run in the reverse direction in order to fly the adhered paper dust, etc. With the method described in Patent Document 1, the meandering of the belt cannot be corrected. In this regard, Patent Document 2 discloses a method of keeping the belt meandering as small as possible by tilting the roll supporting the belt to a predetermined inclination until the reference mark is detected. Are listed.
Japanese Patent Laid-Open No. 11-295948 JP 2002-287591 A

  However, even in the method described in Patent Document 2, the meandering of the belt is only suppressed until the reference mark is detected for the first time. There is a problem that the image quality of the image is degraded. At present, it is generally about 8 seconds for the belt to make one circuit around the circuit route. In the method described in Patent Document 2, the image is not captured until the belt makes one circuit on the circuit route at the maximum. Since the state of unstable image quality continues, development of an image forming apparatus that can stably form high-quality images is desired.

  In view of the above circumstances, an object of the present invention is to provide a belt driving device capable of correcting belt meandering at an early stage and an image forming apparatus capable of stably forming a high-quality image. .

The belt driving device of the present invention that achieves the above object includes an annular belt, a belt driving unit that causes the belt to travel along a predetermined circulation path, and a displacement detection that determines a displacement in the belt width direction during belt traveling. A belt position correction unit that corrects a position in the belt width direction in belt travel based on the positional deviation obtained by the positional deviation detection unit,
The belt is provided with a reference mark at a predetermined part of the entire circumference,
An edge position sensor for detecting the position of the belt edge in the belt width direction at a predetermined edge monitoring point on the circulation path;
A reference sensor that detects the passage of a reference mark at a predetermined reference monitoring point on the patrol route;
A shape storage unit that stores the shape of the edge of the belt in relative coordinates based on the location of the reference mark;
The belt drive unit has a steady mode in which the belt travels at a predetermined steady speed and an unsteady mode in which the belt travels in a travel state other than the travel state at the steady speed,
A mileage obtaining unit for obtaining a mileage in the traveling direction of the belt in the unsteady mode is provided.
The misalignment detection unit uses the detection result of the reference sensor, the travel time in the steady mode, and the travel distance obtained by the travel distance acquisition unit, and the traveling direction from the reference mark passing through the reference monitoring point to the present The belt travel distance is obtained, the position in the belt width direction detected by the edge position sensor is associated with the relative coordinates of the shape stored in the shape storage unit, and the relative coordinate is subtracted from the position to determine the position. It is characterized in that the deviation is obtained.

  According to the belt driving device of the present invention, after the travel distance in the traveling direction of the belt in the unsteady mode is obtained and the reference mark passes through the reference monitoring point based on the travel distance and the detection result by the reference sensor. The belt travel distance in the traveling direction up to now is determined. Further, the relative coordinates of the belt edge shape with respect to the reference mark position at the position where the belt has advanced from the reference mark position by the belt travel distance are acquired, and the position in the belt width direction detected by the edge position sensor is acquired. The relative coordinate of the shape is subtracted from the belt to determine the belt position shift, and the position in the belt width direction is corrected based on the position shift. For this reason, for example, when the stopped belt is restarted, even before the reference mark is detected, the belt travel distance from the previous reference mark passing through the reference monitoring point to the present time. Therefore, the belt misalignment is promptly corrected.

  In the belt drive device of the present invention, it is preferable that the travel distance obtaining unit is an encoder that measures the travel distance of the belt in the traveling direction in the unsteady mode.

  By measuring the traveling distance of the belt in the unsteady mode, the belt positional deviation can be obtained with high accuracy and the belt meandering can be reliably corrected.

The belt drive device of the present invention includes a travel distance storage unit that stores a travel distance of the belt in the traveling direction in the unsteady mode,
It is also preferable that the travel distance acquisition unit acquires the travel distance stored in the travel distance storage unit.

  By preliminarily storing the traveling distance of the belt in the traveling direction in the unsteady mode, the positional deviation of the belt can be easily obtained with a simple mechanism.

The image forming apparatus of the present invention that achieves the above object is an image forming apparatus for forming an image on a recording medium by forming a toner image, and finally transferring and fixing the toner image on the recording medium.
An annular belt, a belt driving unit that causes the belt to travel along a predetermined traveling path, a positional deviation detection unit that determines positional deviation in the belt width direction during belt traveling, and a positional deviation that is obtained by the positional deviation detection unit A belt drive device including a belt position correction unit that corrects the position in the belt width direction in belt running based on
The belt drive is
The belt is provided with a reference mark at a predetermined part of the entire circumference,
An edge position sensor for detecting the position of the belt edge in the belt width direction at a predetermined edge monitoring point on the circulation path;
A reference sensor that detects the passage of a reference mark at a predetermined reference monitoring point on the patrol route;
A shape storage unit that stores the shape of the belt edge in relative coordinates with respect to the location of the reference mark;
The belt drive unit has a steady mode in which the belt travels at a predetermined steady speed and an unsteady mode in which the belt travels in a travel state other than the travel state at the steady speed,
A mileage obtaining unit for obtaining a mileage in the traveling direction of the belt in the unsteady mode is provided.
The misalignment detection unit uses the detection result of the reference sensor, the travel time in the steady mode, and the travel distance obtained by the travel distance acquisition unit, and the traveling direction from the reference mark passing through the reference monitoring point to the present The belt travel distance is obtained, the position in the belt width direction detected by the edge position sensor is associated with the relative coordinates of the shape stored in the shape storage unit, and the positional deviation is calculated by subtracting the relative coordinate from the position. It is what is required.

  According to the image forming apparatus of the present invention, even when the driving of the belt is resumed, the meandering of the belt is corrected quickly and with high accuracy, and a high-quality image can be stably formed.

  Note that the image forming apparatus according to the present invention is only shown in its basic form here, but this is only for avoiding duplication, and the image forming apparatus according to the present invention has only the above basic form. Instead, various forms corresponding to each form of the belt driving device described above are included.

  ADVANTAGE OF THE INVENTION According to this invention, the belt drive device which can correct | amend the meander of a belt at an early stage, and the image forming apparatus which can form a high quality image stably can be provided.

  Hereinafter, embodiments of the present invention will be described.

  FIG. 1 is a schematic configuration diagram showing a main part of a printer to which an embodiment of the present invention is applied.

  As shown in FIG. 1, the printer 1 includes four image forming units 10Y, 10M, 10C, and 10K that form toner images based on image data. Members 11Y, 11M, 11C, 11K, chargers 12Y, 12M, 12C, 12K, exposure devices 13Y, 13M, 13C, 13K, developing devices 14Y, 14M, 14C, 14K, primary transfer members 15Y, 15M, 15C, 15K, Photoconductor cleaners 16Y, 16M, 16C, and 16K are provided. The printer 1 is capable of full-color printing, and the symbols Y, M, C, and K added to the end of each of the above components are yellow, magenta, cyan, and black images, respectively. It is a component for formation.

  Further, the printer 1 includes a control unit 20, a storage unit 21, an intermediate transfer belt 30, a drive roll 31, slave rolls 32 and 35, an intermediate transfer belt cleaner 33, a steering roll 34, a secondary transfer body 36, and a transfer body cleaner 37. A fixing device 38, a reference mark sensor 41, and an edge position sensor 42 are also provided.

  The intermediate transfer belt 30 travels in the direction of arrow B by the drive roll 31 and the inclination of the steering roll 34 is adjusted, so that the movement in the width direction (direction perpendicular to the travel direction) is corrected. The drive roll 31 includes an intermediate transfer belt 30 such as a steady mode in which the intermediate transfer belt 30 is circulated at a predetermined steady speed, and at the start of driving before the running speed of the intermediate transfer belt 30 reaches the steady speed. An unsteady mode for running 30 at a running speed other than the steady speed is prepared. The intermediate transfer belt 30 corresponds to an example of a belt according to the present invention, the drive roll 31 corresponds to an example of a belt drive unit according to the present invention, and the steering roll 34 corresponds to a belt position correction unit according to the present invention. It corresponds to an example.

  Further, a reference mark is attached to the back side of the intermediate transfer belt 30. The reference mark sensor 41 detects that the reference mark of the intermediate transfer belt 30 has passed, and the edge position sensor 42 detects the intermediate transfer belt 30. The running position of the edge is detected. In the present embodiment, the reference mark sensor 41 and the edge position sensor 42 are provided so as to face each other with the intermediate transfer belt 30 interposed therebetween. Hereinafter, the position where the reference mark sensor 41 and the edge position sensor 42 are provided is referred to as a monitoring location. The reference mark sensor 41 corresponds to an example of a reference sensor according to the present invention, and the edge position sensor 42 corresponds to an example of an edge position sensor according to the present invention. In addition, this monitoring location corresponds to an example of the edge monitoring location according to the present invention and corresponds to an example of a reference monitoring location.

The storage unit 21 includes an edge shape table in which the edge shape of the intermediate transfer belt 30 is indicated by relative coordinates (coordinates in the traveling direction and coordinates in the width direction) with respect to the location where the reference mark is attached. distance (hereinafter, referred to as non-stationary distance R _n) the intermediate transfer belt 30 travels between the steady mode is stored. As for the coordinates in the travel direction, the travel distance from the location with the reference mark is used, the coordinate value of the location with the reference mark is set to 0, and the coordinate value increases in the direction opposite to the arrow B. The storage unit 21 corresponds to an example of a shape storage unit referred to in the present invention and corresponds to an example of a travel distance storage unit referred to in the present invention.

The control unit 20 controls various elements shown in FIG. Further, the control unit 20 determines the intermediate transfer belt 30 based on the edge shape table and the unsteady distance R _n stored in the storage unit 21, the detection result of the reference mark sensor 41, and the detection result of the edge position sensor 42. Detects misalignment in the width direction. This positional deviation detection method will be described in detail later. The control unit 20 corresponds to an example of a misregistration detection unit referred to in the present invention.

  A basic operation of the printer 1 in image formation will be described.

  First, as preparation for forming an image, the photoconductors 11Y, 11M, 11C, and 11K for the respective colors are rotated in the direction of the arrow A, and contact type chargers are formed on the surfaces of the photoconductors 11Y, 11M, 11C, and 11K. Predetermined charges are applied by 12Y, 12M, 12C, and 12K, respectively.

  Subsequently, image data representing a color separation image obtained by separating the image into yellow, magenta, cyan, and black is given to the corresponding image forming units 10Y, 10M, 10C, and 10K by the control unit 20.

  Next, toner image formation by the yellow image forming unit 10Y is started, and exposure light corresponding to a yellow color separation image is irradiated onto the surface of the photoconductor 11Y by the exposure device 13Y, so that an electrostatic latent image (electrostatic potential) is generated. Latent image) is formed. The electrostatic latent image is developed by a developing voltage applied to a developing position between the developing device 14Y and the photosensitive member 11Y with yellow toner contained in the developer circulated and supplied by the developing device 14Y. A yellow toner image is formed on the body 11Y. The toner image is transferred to the intermediate transfer belt 30 by the primary transfer body 15Y.

  The intermediate transfer belt 30 circulates in the direction of arrow B, and is synchronized with the timing at which the yellow toner image transferred onto the intermediate transfer belt 30 reaches the primary transfer body 15M of the next color image forming unit 10M. The magenta image forming unit 10M forms a toner image so that the next color magenta toner image reaches the primary transfer body 15M. The magenta toner image formed in this way is transferred onto the yellow toner image on the intermediate transfer belt 30 so as to be superimposed on the primary transfer body 15M. Here, when the toner images on the photoconductors 11Y, 11M, 11C, and 11K are transferred onto the intermediate transfer belt 30, the photoconductor cleaners 16Y, 16M, 16C, and 16K use the photoconductors 11Y, 11M, 11C, and 16K, respectively. Waste toner remaining on 11K is removed.

  Subsequently, toner images are formed by the cyan and black image forming units 10C and 10K at the same timing as described above, and are sequentially superimposed on the yellow and magenta toner images of the intermediate transfer belt 30 in the primary transfer members 15C and 15K. Is transcribed.

  In this way, the multicolor toner image transferred onto the intermediate transfer belt 30 is secondarily transferred onto the paper 100 by the secondary transfer body 36, and the multicolor toner image is conveyed along with the paper 100 in the direction of arrow C, and the fixing device 38. As a result, the color image is formed by being fixed on the paper 100. Waste toner remaining on the secondary transfer body 36 is removed by the transfer body cleaner 37, and waste toner remaining on the intermediate transfer belt 30 after transfer is removed by the intermediate transfer belt cleaner 33 for the next image formation. All preparations are made.

  Here, the feature of the present invention in the printer 1 lies in the process of detecting the positional deviation of the intermediate transfer belt 30 in the width direction and correcting the running position of the intermediate transfer belt 30.

  FIG. 2 is a flowchart showing the control of the steering roll 34 in a series of image forming processes in the printer 1. Hereinafter, a method for correcting the meandering of the intermediate transfer belt 30 by controlling the steering roll 34 will be described in detail according to this flowchart. The printer 1 is provided with a transmitter that generates a clock having a predetermined frequency, and various elements constituting the printer 1 are driven in synchronization with the clock.

  First, the printer 1 is powered on, and various elements constituting the printer 1 are driven (step S1 in FIG. 2).

  In the state where the power is turned on, the reference mark sensor 41 does not recognize where the reference mark attached to the intermediate transfer belt 30 is on the circulation path (step S2: No in FIG. 2). The intermediate transfer belt 30 is circulated until it is detected that the mark has passed the monitoring point. When the power is turned on, a certain amount of waiting time is required to stabilize the driving state of the entire printer 1, so the time until the reference mark is detected does not matter.

  When the driving state of the printer 1 is stabilized and the reference mark is detected by the reference mark sensor 41 (step S2 in FIG. 2: Yes), the detection result is transmitted from the reference mark sensor 41 to the control unit 20, and in the steady mode. Steering control is performed (step S3 in FIG. 2).

  FIG. 3 is a flowchart showing a steering control process in the steady mode. Here, the description of FIG. 2 is temporarily interrupted, and the steady steering control process will be described with reference to FIG.

When the control unit 20 is notified that the reference mark has been detected, the control unit 20 acquires the running position of the edge of the intermediate transfer belt 30 from the edge position sensor 42 (step S11 in FIG. 3). In this embodiment, the edge position sensor 42 detects the coordinate value in the width direction of the edge of the intermediate transfer belt 30. Further, the edge position sensor 42 detects the running position of the belt edge every predetermined clock (p clock), and an average of q detection results is used as the detection result. That is, the edge position sensor 42 generates an averaged detection result every predetermined clock time T _pq (= time T ₁ × p × q per clock). Thus, by using the averaged detection results, errors due to noise or the like can be reduced.

Subsequently, the control unit 20 acquires the travel distance R ₁ of the intermediate transfer belt 30 from when the reference mark is detected by the reference mark sensor 41 to the present (step S12 in FIG. 3). In this example, since the reference mark is detected immediately, the travel distance R ₁ = 0 is acquired.

When the travel distance R ₁ is acquired, the control unit 20 refers to the edge shape table stored in the storage unit 24 and the intermediate transfer belt 30 at the position where the belt has advanced by the travel distance R ₁ from the reference mark. The shape of the edge is acquired (step S13 in FIG. 3). That is, the width when the coordinate value in the traveling direction is the traveling distance R ₁ among the relative coordinates (coordinates in the traveling direction, coordinates in the width direction) of the edge shape of the intermediate transfer belt 30 shown in the edge shape table. The coordinate value of the direction is acquired.

Further, the control unit 20 detects the position shift in the width direction of the intermediate transfer belt 30 based on the running position of the edge of the intermediate transfer belt 30 detected by the edge position sensor 42 and the acquired edge shape of the intermediate transfer belt 30. The amount is calculated (step S14 in FIG. 3). For example, the relative coordinates of the acquired edge shape of the intermediate transfer belt 30 are (coordinates in the running direction, coordinates in the width direction) = (R ₁ , W ₁ ), and the intermediate transfer belt 30 detected by the edge position sensor 42 is used. When the edge travel position is W ₂ (coordinates in the width direction), the positional deviation amount in the width direction is calculated as W = W ₂ −W ₁ .

  When the positional deviation amount W is calculated, the control unit 20 calculates the inclination S of the steering roll 34 for correcting the positional deviation amount W. In this example, when the positional deviation amount W> 0, this indicates that the intermediate transfer belt 30 has been displaced toward the front side, and the steering roll 34 is tilted so that the front side is lowered. Further, when the positional deviation amount W <0, it indicates that the intermediate transfer belt 30 has shifted to the back side, and the steering roll 34 is tilted so that the front side is raised. When the inclination of the steering roll 34 is adjusted, the position in the width direction of the intermediate transfer belt 30 is corrected by the displacement amount W (step S15 in FIG. 3).

  Steady steering control is performed in the above procedure.

  Returning to FIG.

  When the steering control is executed after the power is turned on and the running position deviation in the width direction is corrected, the above-described series of image forming processes is performed. The intermediate transfer belt 30 is cyclically driven in the steady mode (step S4 in FIG. 2: No), and at a predetermined control timing (step S6 in FIG. 2) even during a series of processes in which an image is formed. Yes), steady steering control similar to the above is executed (step S7 in FIG. 2). In the present embodiment, steady steering control is performed each time the intermediate transfer belt 30 advances a control interval E (clock portion: one clock portion travels at a steady speed for one clock).

When the predetermined control timing, first, similarly to the steering control after the power is turned on, (step S11 in FIG. 3) travel position W ₂ of the edge of the intermediate transfer belt 30 is obtained, followed by the last reference mark is detected The travel distance R ₁ of the intermediate transfer belt 30 from the current to the present is acquired (step S12 in FIG. 3). Here, since the intermediate transfer belt 30 travels at a steady speed, the number of clocks t after the reference mark is detected is acquired, and the travel distance R ₁ = t (for clocks) is obtained using the number of clocks t. Calculated.

Using the calculated travel distance R ₁ , the edge shape table is referred to (step S 13 in FIG. 3), and the positional deviation amount W in the width direction of the intermediate transfer belt 30 is calculated (step S 14 in FIG. 3). The inclination S of the steering roll 34 is adjusted according to the positional deviation amount W, and the running positional deviation of the intermediate transfer belt 30 is corrected (step S15 in FIG. 3).

  Further, for example, when the image forming process is interrupted and restarted after a while, the intermediate transfer belt 30 is in the unsteady mode until the intermediate transfer belt 30 reaches the cyclic running in the steady mode. Traveling is performed (step S4 in FIG. 2: Yes). At this time, in the same manner as after the power is turned on, when waiting for the reference mark to be detected by the reference mark sensor 41 and performing an image forming process after performing steady steering control, various elements other than the intermediate transfer belt 30 are Although the image forming process can be executed immediately, the intermediate transfer belt 30 is allowed to wait for the time required to make one round of the circulation path, resulting in a reduction in processing efficiency. . In addition, if an image is formed without performing the steering control until the reference mark is detected by the reference mark sensor 41, color misregistration or image blurring occurs in the formed image, and the image quality deteriorates. There is a problem of end. In the printer 1 of this embodiment, when the intermediate transfer belt 30 is driven again, steering control in the unsteady mode is executed even before the reference mark is detected by the reference mark sensor 41 (FIG. 2 step S5).

  FIG. 4 is a flowchart showing a steering control process in the unsteady mode. Here, the non-steady steering control when the running of the intermediate transfer belt 30 is temporarily stopped and the intermediate transfer belt 30 is run again after a while will be described.

  FIG. 5 is a diagram illustrating a state of the intermediate transfer belt when the intermediate transfer belt 30 is stopped and the intermediate transfer belt 30 is rerun. In this example, when the intermediate transfer belt 30 stops running and re-runs, reverse running is performed for a predetermined time in order to remove paper dust and the like attached to the intermediate transfer belt 30.

  Part (A) of FIG. 5 shows a detection signal transmitted from the reference mark sensor 41 to the control unit 20. One reference mark is provided on the back side of the intermediate transfer belt 30. When the intermediate transfer belt 30 is traveling in a steady mode, the intermediate transfer belt 30 makes one round of the circulation path when the detection signal is received. It takes a long time (about 8 seconds).

Part (B) of FIG. 5 shows a drive signal transmitted from the control unit 20 to the motor attached to the intermediate transfer belt 30, and part (C) shows an intermediate traveled according to the drive signal. The traveling speed of the transfer belt 30 is shown. In this example, after traveling in the steady mode after the reference mark is detected (movement distance A), the motor drive signal is turned off at time t ₁ and the intermediate transfer belt 30 is decelerated (movement distance B ₁ ). . Thereafter, motor preparation for the intermediate transfer belt 30 is driven again, the intermediate transfer belt 30 by the drive signal is transmitted to the drive in the reverse direction to the motor is running in the reverse direction (moving distance C), at time t ₂ And the intermediate transfer belt 30 is accelerated (moving distance B ₂ ), and the traveling speed of the intermediate transfer belt 30 reaches a steady speed at time t ₃ . Further, after the travel in the steady mode is continued for the moving distance F, the steering roll 34 is controlled at time t ₄ .

Part (D) of FIG. 5 shows the belt position of the intermediate transfer belt 30 when it passes through the monitoring position. As shown in this part (D), since the intermediate transfer belt 30 travels in the reverse direction or accelerates and the traveling speed is not constant, the total number of clocks is simply calculated from the number of clocks as in the traveling distance R ₁ in the steady mode. The travel distance (movement distance A + movement distance B ₁ −movement distance C + movement distance B ₂ + movement distance F) cannot be calculated.

When such unsteady mode travel is performed, first, the control unit 20 first detects the previous travel distance of the intermediate transfer belt 30 from when the reference mark is detected last time until the travel in the steady mode ends. R ₀ is acquired (step S111 in FIG. 4). This previous travel distance R ₀ corresponds to the travel distance A shown in Part (C) of FIG. During this time, since the intermediate transfer belt 30 travels at a steady speed, the travel distance A is determined by using the number of clocks t ₁ from the last detection of the reference mark to the end of travel in the steady mode. A = t ₁ (for clock) is calculated.

Subsequently, the control unit 20 obtains the unsteady distance R _n = movement distance B ₁ -movement distance C + movement distance B ₂ of the intermediate transfer belt 30 in the unsteady mode (step S112 in FIG. 4). When the intermediate transfer belt 30 is accelerated and decelerated in the same manner every time, the unsteady distance R _n is constant. In the present embodiment, the unsteady distance R _n is stored in advance in the storage unit 24 shown in FIG. 2, and the stored unsteady distance R _n is acquired by the control unit 20.

Here, a calculation method for calculating the unsteady distance R _n will be described.

The movement distance B ₁ of the intermediate transfer belt 30 at the time of deceleration and the movement distance B ₂ of the intermediate transfer belt 30 at the time of acceleration are almost constant each time, and these movement distance B ₁ and movement distance B ₂ are given as constants.

Further, the moving distance C of the intermediate transfer belt 30 during reverse rotation varies depending on the reverse running time of the intermediate transfer belt 30 and the number of reverse rotations. If the time T ₁ (ms / clock) per clock and the reverse running time T _r (ms) of the intermediate transfer belt 30 are calculated, the movement distance C (clock portion) = T _r ÷ T. In the case where the reverse running is not performed, the moving distance C = 0 (for the clock).

Using these movement distance B ₁ , movement distance B ₂ , and movement distance C, an unsteady distance R _n is obtained.

Subsequently, the estimated travel distance R _p from the last detection of the reference mark to the steady mode, the unsteady mode, and the steady mode until the first control timing is calculated (step S113 in FIG. 4).

Predicted travel distance R _p = movement distance A + movement distance B ₁ −movement distance C + movement distance B ₂ + movement distance F
= Last travel distance R ₀ + unsteady distance R _n + travel distance F
Since the previous travel distance R ₀ and the unsteady distance R _n have already been calculated, the travel distance F is calculated here.

First, how many times the control timing is determined during the travel distance R ′ (= previous travel distance R ₀ + unsteady distance R _n ) from when the last reference mark is detected to when the travel in the unsteady mode ends. It is calculated whether there was. In this embodiment, since the steady steering control is performed every time the intermediate transfer belt 30 advances the control interval E (clock), the quotient a of travel distance R ′ ÷ control interval E is calculated, and finally the reference mark is It is determined that the steering control is performed at the (a + 1) th control timing after the detection.

  The movement distance F for adjusting the control timing for the (a + 1) th time is calculated by using the travel distance R ′ ÷ the remainder b of the control interval E by the movement distance F = the control interval E−the remainder b.

When the predicted travel distance R _p is acquired, the travel of the intermediate transfer belt 30 is continued until the control timing (Step S114 in FIG. 4: No).

When the control timing comes (step S114 in FIG. 4: Yes), the running position of the belt edge that has passed the monitoring position is acquired in the same manner as in step S11 in FIG. 3 (step S115 in FIG. 4). Actually, it is not detected that the intermediate transfer belt 30 has traveled the estimated travel distance R _p and the control timing is determined, but the control timing is determined by the number of clocks (t ₄ −t ₂ ). . For example, if the acceleration time (t ₃ −t ₂ = constant) until the intermediate transfer belt 30 reaches a steady speed is b ₂ (clock) and the moving distance F = f (clock portion), the intermediate transfer belt 30 is After running for (b ₂ + f) clocks, the running position of the belt edge is acquired.

Subsequently, the travel distance R ₁ of the intermediate transfer belt 30 from the last detection of the reference mark to the present is acquired (step S116 in FIG. 4). This travel distance R ₁ is the predicted travel distance R _p calculated in step S113.

Further, the edge shape table is referred to using the travel distance R ₁ acquired in step S116 (step S117 in FIG. 4), and the amount of positional deviation in the width direction of the intermediate transfer belt 30 is calculated (step S118 in FIG. 4). ), The travel position of the intermediate transfer belt 30 is corrected (step S119 in FIG. 4).

  As described above, according to the printer 1 of the present embodiment, even when the vehicle travels in the unsteady mode, the steering control is performed before the reference mark is detected, so a stable and high-quality image is formed. can do.

  Above, description of 1st Embodiment in this invention is complete | finished, and 2nd Embodiment in this invention is described. Since the first embodiment and the second embodiment have substantially the same configuration, FIG. 1 is used as a schematic configuration diagram of the printer 1 ′ of the second embodiment, and only the differences will be described.

  In the printer 1 ′ of this embodiment, an encoder 31 ′ that measures the travel distance of the intermediate transfer belt 30 is provided instead of the drive roll 31 of the first embodiment. This encoder 31 'corresponds to an example of an encoder according to the present invention.

  In the present embodiment, the storage unit 24 stores an edge shape table in which the shape of the edge of the intermediate transfer belt 30 is indicated by relative coordinates, as in the storage unit 24 of the first embodiment. The travel distance that the intermediate transfer belt 30 travels in the unsteady mode is not stored.

In the encoder 31 ′, the traveling distance is measured while the intermediate transfer belt 30 is traveling around. For example, when the intermediate transfer belt 30 is stopped and re-driven, the control unit 20 acquires the travel distance at the time when the intermediate transfer belt 30 is stopped from the encoder 31 ′, and the intermediate transfer belt 30 is When shifting to the steady mode, the travel distance is acquired again from the encoder 31 ′, and the difference between the travel distances is used as the unsteady distance R _n in the unsteady mode.

  As described above, by providing the encoder 31 ′, the travel distance in the unsteady mode can be accurately calculated, the meandering of the intermediate transfer belt 30 can be reliably corrected, and the printer 1 can form a high-quality image. Can do.

  Here, in the above description, an example in which only one total travel distance in the unsteady mode is stored in the storage unit has been described. However, the travel distance storage unit according to the present invention is, for example, a total when performing reverse travel once. A plurality of total travel distances such as a travel distance and a total travel distance in the case where the reverse travel is performed twice may be stored. You may acquire the thing according to the driving state.

  In the above description, the example of storing the total travel distance in the unsteady mode in the storage unit has been described. However, the travel distance storage unit according to the present invention includes the travel distance in reverse travel, the travel distance during acceleration, and the like. It may be stored separately, and the travel distance obtaining unit referred to in the present invention may calculate the total travel distance from the travel distance stored separately.

  In the above description, an example in which the reference sensor and the edge position sensor are provided facing each other across the belt has been described. However, the reference monitoring point where the reference sensor according to the present invention is provided and the edge position sensor according to the present invention are provided. The edge monitoring points provided may be at positions separated from each other.

1 is a schematic configuration diagram illustrating a main part of a printer to which an embodiment of the present invention is applied. 4 is a flowchart showing control of a steering roll 34 in a series of image forming processes in the printer 1. It is a flowchart which shows the process of the steering control in a normal state. It is a flowchart which shows the process of the steering control in unsteady mode. FIG. 3 is a diagram illustrating a state of the intermediate transfer belt when the intermediate transfer belt is stopped and the intermediate transfer belt is re-run.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printer 10Y, 10M, 10C, 10K Image formation part 11Y, 11M, 11C, 11K Photoconductor 12Y, 12M, 12C, 12K Charger 13Y, 13M, 13C, 13K Exposure device 14Y, 14M, 14C, 14K Developing device 15Y, 15M, 15C, 15K Primary transfer member 16Y, 16M, 16C, 16K Photoconductor cleaner 20 Control unit 21 Storage unit 30 Intermediate transfer belt 31 Drive roll 32, 35 Subordinate roll 33 Intermediate transfer belt cleaner 34 Steering roll 36 Secondary transfer member 47 Transfer body cleaner 38 Fixing device 41 Reference mark sensor 42 Edge position sensor

Claims (4)

An annular belt, a belt driving unit that causes the belt to travel along a predetermined circulation route, a positional deviation detection unit that determines positional deviation in the belt width direction during belt traveling, and the positional deviation detection unit. In a belt drive device comprising a belt position correction unit that corrects a position in the belt width direction in the belt running based on a positional deviation,
The belt is provided with a reference mark at a predetermined portion of the entire circumference,
An edge position sensor for detecting the position of the belt edge in the belt width direction at a predetermined edge monitoring point on the patrol path;
A reference sensor for detecting passage of the reference mark at a predetermined reference monitoring point on the patrol route;
A shape storage unit that stores the shape of the edge of the belt in relative coordinates based on the location of the reference mark;
The belt drive unit has a steady mode in which the belt travels at a predetermined steady speed and an unsteady mode in which the belt travels in a traveling state other than a traveling state at the steady speed;
A travel distance obtaining unit for obtaining a travel distance of the belt in the traveling direction in the unsteady mode;
The positional deviation detection unit uses the detection result of the reference sensor, the travel time in the steady mode, and the travel distance obtained by the travel distance acquisition unit, so that the reference mark passes through the reference monitoring point. The belt travel distance in the traveling direction from the present to the present is obtained, the position in the belt width direction detected by the edge position sensor is associated with the relative coordinates of the shape stored in the shape storage unit, and the position A belt driving device characterized in that the positional deviation is obtained by subtracting the relative coordinate component from the belt driving device.   The belt driving device according to claim 1, wherein the travel distance obtaining unit is an encoder that measures a travel distance of the belt in a traveling direction in the unsteady mode. A travel distance storage unit that stores the travel distance of the belt in the traveling direction in the unsteady mode;
The belt driving device according to claim 1, wherein the travel distance acquisition unit acquires a travel distance stored in the travel distance storage unit. In an image forming apparatus for forming an image on a recording medium by forming a toner image, and finally transferring and fixing the toner image on the recording medium.
An annular belt, a belt driving unit that causes the belt to travel along a predetermined circulation route, a positional deviation detection unit that determines positional deviation in the belt width direction during belt traveling, and the positional deviation detection unit. A belt driving device including a belt position correcting unit that corrects a position in the belt width direction in the belt traveling based on a positional deviation;
The belt drive device
The belt is provided with a reference mark at a predetermined portion of the entire circumference,
An edge position sensor for detecting the position of the belt edge in the belt width direction at a predetermined edge monitoring point on the patrol path;
A reference sensor for detecting passage of the reference mark at a predetermined reference monitoring point on the patrol route;
A shape storage unit that stores the shape of the edge of the belt in relative coordinates based on the location of the reference mark;
The belt drive unit has a steady mode in which the belt travels at a predetermined steady speed and an unsteady mode in which the belt travels in a traveling state other than a traveling state at the steady speed;
A travel distance obtaining unit for obtaining a travel distance of the belt in the traveling direction in the unsteady mode;
The positional deviation detection unit uses the detection result of the reference sensor, the travel time in the steady mode, and the travel distance obtained by the travel distance acquisition unit, so that the reference mark passes through the reference monitoring point. The belt travel distance in the traveling direction from the present to the present is obtained, the position in the belt width direction detected by the edge position sensor is associated with the relative coordinates of the shape stored in the shape storage unit, and the position An image forming apparatus characterized in that the positional deviation is obtained by subtracting the relative coordinate component from the image forming apparatus.

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