JP7066104B2 - Conveyor device, image forming device - Google Patents

Description

The present invention relates to a transport device and an image forming device.

In a transport device for transporting a sheet, positional deviation such as skewing of the sheet or displacement in the width direction during transport becomes a problem. For example, in an image forming apparatus that forms an image on a recording medium, there is a problem that the image position formed on the recording medium is deviated from the ideal position due to the positional deviation during transportation of the recording medium.

Then, an invention has already been made in which such a misalignment of the sheet is detected and the misalignment is corrected. For example, in the sheet matching device of Patent Document 1 (Japanese Unexamined Patent Publication No. 4-251058), a sheet skew detector and an edge detector are provided, and these detectors detect sheet skew and lateral displacement. However, the misalignment of the seat is corrected.

In Patent Document 1, a dedicated detection mechanism is provided for detecting the positional deviation of the seat, but there is a problem that the provision of these detection mechanisms leads to an increase in cost and an increase in size of the entire device.

From such a problem, it is an object of the present invention to provide a transport device capable of detecting a misalignment of a seat without providing a dedicated detection mechanism.

In order to solve the above problems, the present invention comprises a first holding roller and a second holding roller for transporting the sheet, which are juxtaposed in the width direction of the sheet in the transport device for transporting the sheet. The first drive mechanism for driving the first pinch roller, the second drive mechanism for driving the second pinch roller, the detection unit capable of detecting the rotational speeds of the first pinch roller and the second pinch roller, and the said. Based on the detection result by the detection unit, the first drive mechanism and the control unit capable of recognizing the drive load of the second drive mechanism are included, and the control unit includes the first drive mechanism and the second drive mechanism. By inputting a current command value to, the first pinching roller and the second pinching roller are rotationally driven, and the control unit receives the drive load of the first drive mechanism required to drive the first pinching roller. Recognizing that the sheet has reached the first pinching roller or the second pinching roller due to an increase or an increase in the driving load of the second driving mechanism required to drive the second pinching roller, the said The increase in the drive load due to the pinching of the first pinching roller or the second pinching roller is estimated by the current command value and the rotational speed detected by the detection unit, and the control unit controls the first. It is characterized in that the skew amount of the sheet is calculated based on the difference in the arrival time of the sheet to the one pinching roller and the second pinching roller.

In the present invention, the amount of skew of the sheet can be calculated by increasing the drive load of the first sandwiching roller and the second sandwiching roller that convey the sheet. Therefore, the amount of skew of the sheet can be calculated without providing a dedicated detection mechanism.

It is a schematic block diagram of an image forming apparatus. It is a figure which shows the transport device, (a) is a plan view, (b) is a side view. It is a top view which shows the state which the paper reached the 2nd CIS. It is a top view which shows the state which the paper reached the 3rd holding roller. It is a figure explaining the skew correction of a paper. It is a figure which shows the method of calculating the skew amount of a paper based on the detection result of CIS. It is a flow chart which shows the operation which the transport device transports and corrects a paper. It is a block diagram which shows the structure of the control part of the transfer device of this embodiment. It is a block diagram which shows the estimated part of the load torque by a disturbance observer. It is a schematic block diagram which shows the image forming apparatus of a different embodiment.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In each figure, the same or corresponding parts are designated by the same reference numerals, and the duplicated description thereof will be appropriately simplified or omitted.

The color image forming apparatus 1 shown in FIG. 1 is provided with an image forming unit 2 to which four process units 9Y, 9M, 9C, and 9Bk are detachably provided. Each process unit 9Y, 9M, 9C, 9Bk accommodates developers of different colors of yellow (Y), magenta (M), cyan (C), and black (Bk) corresponding to the color separation components of the color image. It has the same configuration except that it is.

Specific process units 9 include a photoconductor drum 10 which is a drum-shaped rotating body capable of supporting toner as a developer on the surface, and a charging roller 11 which uniformly charges the surface of the photoconductor drum 10. It also includes a developing device 12 that supplies toner to the surface of the photoconductor drum 10, a cleaning device, and the like.

An exposure unit is arranged above the process unit 9. The exposed unit is configured to emit laser light based on the image data.

The transfer unit 4 is arranged directly below the image-creating unit 2. The transfer unit 4 includes a drive roller 13, a secondary transfer facing roller 15, a plurality of tension rollers, an endless intermediate transfer belt 16 stretched so as to be able to travel around by these rollers, and a photoconductor drum of each process unit 9. It is composed of primary transfer rollers 17 and the like arranged at positions facing the intermediate transfer belt 16 with respect to 10. Each primary transfer roller 17 presses the inner peripheral surface of the intermediate transfer belt 16 at each position, and a primary transfer nip is formed at a position where the pressed portion of the intermediate transfer belt 16 and each photoconductor drum 10 come into contact with each other. Has been done.

Further, the drive roller 13 of the intermediate transfer belt 16 and the secondary transfer roller 18 are arranged at positions facing the drive roller 13 with the intermediate transfer belt 16 interposed therebetween. The secondary transfer roller 18 presses the outer peripheral surface of the intermediate transfer belt 16, and a secondary transfer nip is formed at a position where the secondary transfer roller 18 and the intermediate transfer belt 16 come into contact with each other.

The paper feed unit 5 is located at the lower part of the image forming apparatus 1, and is a paper feed cassette 19 as a sheet loading unit that accommodates the paper P as a sheet, and a paper feed roller that carries out the paper P from each paper feed cassette. It consists of 20 mag.

The transport path 6 is a transport path for transporting the paper P carried out from the paper feeding unit 5. A plurality of transport roller pairs are appropriately arranged on the transport path 6 up to the paper ejection portion described later.

On the transport path 6, on the downstream side in the paper transport direction from the paper feed unit 5, and on the upstream side from the secondary transfer nip position, the misalignment of the paper P on the transport path 6 is corrected, and the paper P is moved to the downstream side. A transport device 30 for transport is provided.

The fixing device 7 has a fixing roller 22 heated by a heating source, a pressure roller 23 capable of pressurizing the fixing roller 22, and the like.

The paper ejection unit is arranged at the most downstream of the transport path 6 of the image forming apparatus 1, and a pair of paper ejection rollers 24 for discharging the paper P to the outside are provided.

The transport path 6 is provided with an inverted transport path 6a that divides the flow downstream of the fixing device 7, in addition to the path leading to the paper ejection unit 8. The inverted transport path 6a joins the transport path 6 continuing from the paper feed section 5 at the end thereof.

Hereinafter, the basic operation of the image forming apparatus 1 will be described with reference to FIG.

When the image forming operation is started in the image forming apparatus 1, an electrostatic latent image is formed on the surface of the photoconductor drum 10 of each process unit 9Y, 9C, 9M, 9Bk. The image information exposed by the exposure unit 3 on each photoconductor drum 10 is monochromatic image information obtained by decomposing a desired full-color image into yellow, cyan, magenta, and black color information. An electrostatic latent image is formed on each photoconductor drum 10, and the toner stored in each developing device is supplied to the photoconductor drum 10 by a drum-shaped developing roller, so that the electrostatic latent image is visualized. It is visualized as a toner image (developer image).

In the transfer unit 4, the intermediate transfer belt 16 is driven to travel in the direction of the arrow A1 in the figure by the rotational drive of the drive roller 13. Further, a constant voltage or a constant current controlled voltage having a polarity opposite to the charging polarity of the toner is applied to each primary transfer roller 17. As a result, a transfer electric field is formed at the primary transfer nip, and the toner images formed on each photoconductor drum 10 are sequentially superimposed and transferred on the intermediate transfer belt 16 at the primary transfer nip. As described above, for example, the image forming unit 2, the exposure unit, the transfer unit 4, and the like function as an image forming unit that forms an image on the paper P.

On the other hand, when the image forming operation is started, in the lower part of the image forming apparatus 1, the paper feeding roller 20 of the paper feeding unit 5 is rotationally driven, so that the paper P accommodated in the paper feeding cassette 19 is moved to the transport path 6. Be sent out.

The paper P sent out to the transport path 6 is transported to the downstream side by the transport device 30 on the transport path 6, the roller pair 40, and the like, and the misalignment is corrected by the transport device 30, so that the paper P is combined with the secondary transfer roller 18. It is sent to the secondary transfer nip formed between the secondary transfer facing roller 15. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the intermediate transfer belt 16 is applied, and a transfer electric field is formed in the secondary transfer nip. The toner image on the intermediate transfer belt 16 is collectively transferred onto the paper P by the transfer electric field formed in the secondary transfer nip.

When double-sided printing is performed on the paper P, the paper P is conveyed to the paper ejection roller 24, and the paper ejection roller 24 rotates in the reverse direction until the rear end of the paper P passes through the paper ejection roller 24, and the paper is printed. P is conveyed in the opposite direction and sent out to the reverse transfer path 6a. After that, the paper P is conveyed on the reverse transfer path 6a by the reverse transfer roller, and is fed to the upstream side of the transfer device 30 of the transfer path 6 again in a state of being turned upside down. Then, after the misalignment of the paper P is corrected by the transport device 30, the image is transferred and fixed on the back surface, and the paper P is discharged to the paper output tray by the paper discharge roller 24.

The paper P on which the toner image is transferred is conveyed to the fixing device 7, and the paper P is heated and pressed by the fixing roller 22 and the pressure roller 23 to fix the toner image on the paper P. Then, the paper P on which the toner image is fixed is separated from the fixing roller 22 and conveyed to the downstream paper ejection unit, and is ejected to the outside of the apparatus.

The above description is an image forming operation when forming a full-color image on paper P, but a single-color image can be formed by using any one of four process units 9Y, 9C, 9M, and 9Bk. It is also possible to use two or three process units 9 to form a two-color or three-color image.

As shown in FIGS. 2A and 2B, the transfer device 30 of the present embodiment includes a first sandwiching roller 31, a second sandwiching roller 32, and a third sandwiching roller that sandwich and convey the paper P. A (conveying member) 33, a first CIS (detection mechanism) 34 for detecting the paper P, and a second CIS (detection mechanism) 35 are provided.

The first holding roller 31, the second holding roller 32, and the third holding roller 33 are each composed of a pair of rollers. Each sandwiching roller conveys the paper P to the downstream side in the transport direction (on the downstream side in the arrow direction in FIG. 2) by rotating the rollers in a state where the paper P is sandwiched between the nip portions of the roller pair. In the following description, this direction is also referred to simply as a transport direction, and the upstream and downstream sides of the paper transport direction are also simply referred to as upstream and downstream sides. Further, the first holding roller 31 and the second holding roller 32 are arranged side by side in the width direction of the paper P. In the following description, this direction is also simply referred to as the width direction.

The first CIS34 and the second CIS35 are contact image sensors in which a plurality of photosensors including a light emitting element such as an LED and a light receiving element such as a photodiode are arranged side by side in the width direction of the paper P.

Next, a method of correcting the misalignment of the paper P while the transport device 30 conveys the paper P will be described. This will be described with reference to the flow charts of FIGS. 2 to 6 and 7.

First, as shown in FIG. 2A, the paper P conveyed to the transfer device 30 by the roller pair on the upstream side reaches the first sandwiching roller 31 and the second sandwiching roller 32 (step S1 in FIG. 8). ). Then, the paper P is sandwiched by the first sandwiching roller 31 and the second sandwiching roller 32, and is further conveyed to the downstream side. Examples of the roller pair arranged on the upstream side of the transport device 30 include a roller pair 40 (see FIG. 1). However, a different roller pair may be arranged between the roller pair 40 and the transfer device 30, and the paper P may be conveyed to the transfer device 30 by the roller pair.

When the first sandwiching roller 31 or the second sandwiching roller 32 sandwiches the paper P, frictional resistance is generated between the paper P and the roller pair at the nip portion of each roller pair, and the rollers are rotationally driven. The drive load increases. That is, the drive load of the holding roller is greatly increased before and after holding the paper P. In the present embodiment, by recognizing the increase in the drive load, it is possible to recognize the arrival of the paper P on the first pinching roller 31 or the second pinching roller 32.

Further, in the present embodiment, the skew amount of the paper P can be calculated by using the difference in the arrival times of the first sandwiching roller 31 and the second sandwiching roller 32 (step S2). That is, as shown in FIG. 2A, when the paper P is conveyed in an oblique state, the time when the tip P1 of the paper P reaches the first holding roller 31 and the second holding roller 32 is deviated. Occurs. From this time difference, the amount of skew of the paper P can be obtained.

Specifically, as shown in FIG. 5, the pinching position K1 and the pinching position K2 of the first pinching roller 31 are defined at a certain point, and the distance between the pinching position K1 and the pinching position K2 in the width direction is L. Then, let v be the transport speed of the paper P by the transport roller on the upstream side of the transport device 30, and let t be the time difference between the time when the paper P reaches the first pinching roller 31 and the time when the paper P reaches the second pinching roller 32. , The skew amount θ1 of the paper P is
tan θ1 = vt / L ... (1)
It can be expressed as. Here, the distance L and the velocity v are measurable values. Further, as described above, the arrival time to the sandwiching roller can be known from the drive load of each sandwiching roller, and the time difference t can be calculated. Therefore, the angle θ1 can be calculated by the above equation (1). As described above, the skew amount of the paper P can be calculated from the change in the drive load of the first holding roller 31 and the second holding roller 32.

When the paper P reaches the first holding roller 31 and the second holding roller 32, the paper P is conveyed by these holding rollers. At this time, the relative transfer speeds of the first pinching roller 31 and the second pinching roller 32 are changed based on the obtained skewing amount (angle θ1), and the skewing of the paper P is corrected (step S3). ..

For example, as shown in FIG. 5, at the tip P1 of the paper P, the side of the second pinching roller 32 is on the upstream side in the transport direction as compared with the side of the first pinching roller 31 (the transport on the side of the second pinching roller 32 is). Consider the case (being late). In this case, by increasing the transport speed V2 of the second pinching roller 32 to be higher than the transport speed V1 of the first pinching roller 31, the skew of the paper P can be gradually corrected in the transporting process.

A specific method for obtaining the transport speeds V1 and V2 will be described. First, the target position for completing the skew correction is defined as a vertical line N perpendicular to the transport direction, and the distance between the vertical line N and the pinch position K1 or the pinch position K2 in the transport direction is M1. Then, as shown in FIG. 5, at the timing when the tip P1 of the paper P reaches the holding position of the second holding roller (the holding position K2 of the holding roller 32 in the figure), the paper P is on the side of the holding roller 32. The distance between the tip portion P1b and the vertical line N is M1. On the other hand, when the above-mentioned arrival time difference t is used, the tip portion P1a is conveyed downstream of the tip portion P1b by vt on the side of the holding roller 31. Therefore, the distance between the tip portion P1a and the vertical line N can be expressed as M1-vt. Further, when the transport speed of the second pinching roller 32 is set to V2 and the transport speed of the first pinching roller 31 is set to V1, the time until the tip portion P1b reaches the vertical line N is set.
M1 / V2 ... (2)
It can be expressed as.
Then, the time until the tip portion P1a reaches the vertical line N is
(M1-vt) / V1 ... (3)
It can be expressed as. Then, by setting the velocities V1 and V2 so that the equations (2) and (3) are equal, the tip portion P1a and the tip portion P1b can reach the vertical line N at the same timing. That is, the skew of the paper P can be corrected. As a specific example of the correction, the skew of the paper P can be corrected from the dotted line portion to the solid line portion in FIG. Hereinafter, this correction is also referred to as the first correction of the skew of the paper.

From FIG. 2A to FIG. 3, the first pinching roller 31 and the second pinching roller 32 correct the skew of the paper P for the first time while the paper P is further conveyed to the downstream side. Then, as shown in FIG. 3, when the paper P reaches the first CIS34 and the second CIS35 (step S4), the detection operation is performed by the first CIS34 and the second CIS35, and the paper P is based on the detection result. The amount of skew is calculated again (step S5).

Specifically, as shown in FIG. 6, the width direction position of the side end P2 detected by the first CIS 34 is La, and the width direction position of the side end P2 detected by the second CIS 35 is the width direction position. Assuming that Lb is used and the distance between the first CIS34 and the second CIS35 in the transport direction is M2, the inclination angle θ2 is
TANθ2 = (La-Lb) / M2 ... (4)
Can be obtained by. Further, the positional deviation of the paper P, which will be described later, in the width direction can be obtained from the average value of the two CIS.

In the present embodiment, the skew of the paper P is corrected again based on the detection result by the CIS (step S5). Hereinafter, this correction is referred to as re-correction of the skew of the paper.

As described above, when the paper P reaches the second CIS 35, the skew re-correction is started based on the detection result by the CIS, so that the first skew correction is completed before that. Therefore, the vertical line N (see FIG. 3), which is the target position, is provided at the position of the second CIS35 or on the upstream side of the position.

The re-correction of the skew of the paper P is performed by changing the relative transfer speed (rotational speed) of the first sandwiching roller 31 and the second sandwiching roller 32, as in the case of the first correction of the skew amount. Will be done. The difference from the first correction is that it is performed based on the detection result of CIS, and the position of the vertical line N, which is the target position, is different. That is, the skew re-correction needs to be performed until the paper P is sandwiched by the third sandwiching roller 33 and the first sandwiching roller 31 and the second sandwiching roller 32 are separated from the paper P. Therefore, the vertical line N at the time of re-correction is provided at the position of the third sandwiching roller 33 or on the upstream side of the position.

In the present embodiment, the skew recorrection is performed by feedback control. That is, the amount of skew calculated from the first CIS34 and the second CIS35 is fed back from moment to moment, and the transport speed V1 and the transport speed V2 are corrected each time. In this way, the skew of the paper P can be corrected with high accuracy by performing the re-correction after the first skew correction and performing the re-correction by the feedback control.

Then, as shown in FIG. 4, when the paper P reaches the third holding roller 33, the first holding roller 31 and the second holding roller 32 are separated from the paper P, and the skew re-correction is completed (step S6). ).

The third holding roller 33 conveys the paper P to the downstream side and corrects the positional deviation of the paper P in the width direction by moving in the width direction (step S7).

The amount of misalignment in the width direction of the paper P is detected by the first CIS34 and the second CIS35. As for the amount of positional deviation in the width direction, as described above, the position of the side edge P2 of the paper P is detected by each CIS, and the average value thereof is calculated. However, the result detected by one CIS may be used as the amount of positional deviation of the paper P in the width direction. In the present embodiment, the momentary positional deviation amount in the width direction detected by the first CIS34 and the second CIS35 is fed back, and the movement amount in the width direction of the third holding roller 33 is corrected.

The correction operation in the width direction is completed until the paper P is delivered to the roller on the downstream side and the paper P passes through the third holding roller 33 (step S8). When the paper P is delivered to the roller on the downstream side, the sandwiching roller 33 is separated from the transport path, and the transport of the paper P by the transport device 30 is completed.

With the above flow, the transport device 30 corrects the skew amount of the paper P and the position shift amount in the width direction. Then, with the misalignment of the paper P corrected, the paper P is conveyed to the transfer process further downstream. As a result, the image is transferred to the paper P with the misalignment of the paper P corrected. Further, the transport device 30 that has completed the transport and correction operations shifts to the preparatory operation for transporting the next paper.

As described above, in the transport device 30 of the present embodiment, the first pinching roller 31 and the second pinching roller 32 have a transport function of transporting the paper P to the downstream side, and the increase in the drive load causes the paper P by the control unit. It also has a function of enabling the calculation of the skew amount of the paper P and a correction function of correcting the skew of the paper P based on the skew amount of the paper P. Therefore, it is possible to detect that the paper P has reached the first pinching roller 31 or the second pinching roller 32 without providing a tip detection sensor or the like of an optical system that detects the arrival of the paper P. Further, it is possible to calculate the skew amount without providing a detection sensor such as CIS that detects the position of the paper P. As a result, the number of parts of the entire transport device 30 can be reduced, and the device can be downsized and the cost can be reduced.

Further, in the transport device 30 of the present embodiment, after the skew correction is performed by the first holding roller 31 and the second holding roller 32, the correction in the width direction is performed by the third holding roller 33. In this way, by independently performing the skew correction and the position deviation correction in the width direction, each correction operation can be further simplified and the correction accuracy can be improved. That is, when the skew correction and the correction in the width direction are performed at the same time, it is necessary to consider that the paper P is displaced in the width direction due to the skew correction, which complicates the correction method. In particular, in the case of the method of correcting the skew of the paper by changing the transport speed of the first holding roller 31 and the second holding roller 32 as in the present embodiment, (these holding rollers are also moved in the width direction). If the correction in the width direction is performed at the same time, the movement path tends to be complicated. Therefore, as in the present embodiment, it is preferable to first correct only the skew of the paper and then correct it in the width direction by the third holding roller 33 provided downstream.

FIG. 8 is a block diagram showing a configuration of a control unit that controls each operation of the above transport device 30.
As shown in FIG. 8, the control unit 60 includes a first motor control unit 61, a second motor control unit 62, a third motor control unit 63, a first position recognition unit 64, and a second position recognition unit 65. A first disturbance observer (first disturbance estimation unit) 66 and a second disturbance observer (second disturbance estimation unit) 67 are provided.

The first motor control unit 61 controls the rotational drive operation of the first holding roller 31. The first motor driver 611 drives the first motor (first drive mechanism) 612 to rotate the first holding roller 31 by the signal (first command value) from the first motor control unit 61. Then, the rotation amount of the first holding roller 31 is detected by the first motor encoder 613.

The second motor control unit 62 controls the rotational drive operation of the second holding roller 32. The second motor driver 621 drives the second motor (second drive mechanism) 622 to rotate the second holding roller 32 by the signal (second command value) from the second motor control unit 62. Then, the rotation amount of the second holding roller 32 is detected by the second motor encoder 623.

The third motor control unit 63 controls the movement operation of the third sandwiching roller 33 in the width direction. The third motor driver 631 drives the third motor 632 to move the third holding roller 33 in the width direction by the signal (third command value) from the third motor control unit 63. Then, the third motor encoder 633 detects the amount of movement of the third sandwiching roller 33 in the width direction.

The first motor control unit 61 and the second motor control unit 62 are the rotation speeds of the holding rollers determined by the first position recognition unit 64 and the second position recognition unit 65, which will be described later (rotational speeds required for each motor). Therefore, each current command value is input to each motor driver. This current command value is also transmitted to each disturbance observer.

In the present embodiment, as a method of estimating the increase in the external load, that is, the increase in the drive load due to the sandwiching of the paper P, among the increase in the drive load of the first pinch roller 31 and the second pinch roller 32, the disturbance Observers (details below) are used. The amount of rotation detected by the first motor encoder 613 and the second motor encoder 623 is transmitted to the first disturbance observer 66 and the second disturbance observer 67, respectively.

The first disturbance observer 66 and the second disturbance observer 67 estimate their respective disturbance torques from the current command value transmitted from the motor control unit and the actual rotation amount of the motor, and calculate the estimated disturbance torque. Input to the first position recognition unit 64.

The first position recognition unit 64 detects whether or not the paper P has reached each holding roller, that is, the timing at which the paper P has reached, and calculates the skew amount of the paper P based on the input estimated disturbance torque. can. Then, based on the calculated skew amount, the rotation speeds (each paper transport speed) of the first pinching roller 31 and the second pinching roller 32 are determined, and the first motor control unit 61 and the second motor control are performed. Information on the determined rotation speed is input to the unit 62. As a result, each motor control unit can rotate each sandwiching roller at a determined speed to perform the first skew correction of the paper P.

The detection information of the first CIS34 and the second CIS35 is input to the second position recognition unit 65. The second position recognition unit 65 can calculate the skew amount of the paper P and the position deviation amount in the width direction based on the input detection information.

The second position recognition unit 65 determines the rotation speeds of the first pinching roller 31 and the second pinching roller 32 based on the calculated skew amount of the paper P, and controls the first motor control unit 61 and the second motor. Information on the determined rotation speed is input to the unit 62. As a result, each motor control unit can rotate each holding roller at a determined speed to re-correct the skew of the paper P.

Further, the second position recognition unit 65 determines the movement amount of the third holding roller 33 based on the calculated position deviation amount in the width direction of the paper P, and the movement amount determined by the third motor control unit 63. Enter the information. As a result, the third motor control unit 63 can move the third holding roller 33 in the width direction to correct the positional deviation of the paper P in the width direction.

Next, a method of estimating the increase in the drive load due to the sandwiching of the paper P in the first sandwiching roller 31 and the second sandwiching roller 32 by using the disturbance observer will be described with reference to FIG. Although FIG. 9 shows the case of the first motor control unit 61, the second motor control unit 62 also has the same configuration.

As shown in FIG. 9, when the target rotation speed of the first pinching roller 31 is input to the first motor control unit 61, the first motor control unit 61 causes the first motor driver 611 according to the input target value. Enter the current command value. Then, a current is passed from the first motor driver 611 to the first motor 612, and the first motor 612 rotationally drives the first holding roller 31. Further, the current command value input by the first motor driver 611 to the first motor 612 is input to the first disturbance observer 66.

When the first motor encoder 613 detects the actual rotation speed of the first motor 612, the detected rotation speed is input to the first disturbance observer 66. The first disturbance observer 66 is the disturbance torque of the first motor 612 from the difference between the input torque calculated from the input current command value and the output torque calculated from the actual rotation speed of the first motor 612. Is estimated (calculated). This disturbance estimation is performed for each control cycle of the first motor control unit 61. As a method of calculating the input torque from the current command value, a method of multiplying the current command value by the torque constant of the motor can be mentioned. Further, as a method of calculating the output torque from the rotational speed, there is a method of differentiating the rotational speed to obtain the rotational acceleration and multiplying the rotational acceleration by the inertia of the controlled target system of the first motor.

The estimated disturbance torque is input to the first position recognition unit 64. When the input estimated disturbance torque greatly increases, the first position recognition unit 64 recognizes that the paper P is sandwiched by the first sandwiching roller 31 at that timing. That is, it is determined that the increase in the disturbance torque is an increase in torque due to the holding roller 31 holding the paper P. By the above method, it is possible to detect the timing at which the paper P reaches the first holding roller 31.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

The third sandwiching roller 33 described in the present embodiment may be a timing roller that conveys the paper P to the secondary transfer roller 18 (see FIG. 1). In this case, the paper P conveyed to the third holding roller 33 is conveyed to the secondary transfer position at the right timing.

As the detection mechanism provided on the downstream side of the first pinching roller 31 and the second pinching roller 32, a known sensor can be appropriately used in addition to the contact image sensor as in the present embodiment.

The image forming apparatus according to the present invention is not limited to the color image forming apparatus shown in FIG. 1, and may be a monochrome image forming apparatus, a copying machine, a printer, a facsimile, or a combination machine thereof.

Further, in the embodiment described above, the present invention has been applied to the transport device 30 installed in the electrophotographic image forming apparatus 1, but to the transport device installed in the inkjet type image forming apparatus. The present invention can also be applied. Hereinafter, an inkjet type image forming apparatus will be described with reference to FIG.

As shown in FIG. 10, the inkjet type image forming apparatus 100 includes a feeding unit 110, a conveying device 120, an image forming unit 130, a drying unit 140, and a paper ejection unit 150.

The paper P sent out from the paper feeding unit 110 is conveyed by the conveying device 120 and sent out to the image forming unit 130.

In the image forming unit 130, the paper P is positioned on the cylindrical drum 131 and is conveyed in the direction of the arrow in the figure by the rotation of the cylindrical drum 131. Then, the paper P is conveyed to the lower part of the ejection head 132 of each color (the position where the image is formed on the paper P) at a predetermined timing, the ink of each color is discharged to the paper P, and the image is formed on the surface of the paper P. ..

The paper P on which the image is formed by the image forming unit 130 is conveyed to the drying unit 140 to evaporate the moisture in the ink, and then is discharged to a position where the operator can take it out by the paper ejection unit 150.

When double-sided printing is performed, after the drying step, the paper P is sent to the reverse transfer path 160, and the paper P is sent to the transfer device 120 again with the front and back sides inverted.

By applying the configuration of the transport device of the present invention described above to the transport device 120 described above, the same effects as those of the present embodiment described above can be obtained. That is, the transport device 120 corrects the skew of the paper P and the positional deviation in the width direction. Then, the paper P is conveyed to the downstream image forming unit 130 in a state where the positional deviation of the paper P is corrected.

Sheets include paper P (plain paper), thick paper, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper, transparencies, plastic films, prepregs, copper foil, etc. Is done.

1 Image forming device 30 Conveying device 31 First pinching roller 32 Second pinching roller 33 Third pinching roller (conveying member)
34 First CIS (Detection Mechanism)
35 Second CIS (Detection Mechanism)
60 Control unit 61 First motor control unit 612 First motor (first drive mechanism)
613 First motor encoder (detector)
62 Second motor control unit 622 Second motor (second drive mechanism)
623 Second motor encoder (detector)
P paper (sheet)

Japanese Unexamined Patent Publication No. 4-251058

Claims (8)

In a transport device that transports sheets
A first sandwiching roller and a second sandwiching roller for transporting the sheet, which are juxtaposed in the width direction of the sheet,
The first drive mechanism that drives the first holding roller and
The second drive mechanism that drives the second holding roller and
A detector capable of detecting the rotational speeds of the first pinching roller and the second pinching roller, and
It has a control unit capable of recognizing the drive load of the first drive mechanism and the second drive mechanism based on the detection result by the detection unit.
The control unit rotationally drives the first pinching roller and the second pinching roller by inputting current command values to the first driving mechanism and the second driving mechanism.
The control unit increases the drive load of the first drive mechanism required to drive the first pinching roller, or increases the drive load of the second drive mechanism required to drive the second pinching roller. As a result, it is recognized that the sheet has reached the first pinching roller or the second pinching roller, and the increase in the drive load due to pinching the first pinching roller or the second pinching roller is the current. Estimated from the command value and the rotation speed detected by the detection unit,
The control unit is a transport device, characterized in that the skewing amount of the sheet is calculated based on the difference in the arrival time of the sheet to the first pinching roller and the second pinching roller. The control unit is provided so that the rotation speeds of the first holding roller and the second holding roller can be adjusted.
The first aspect of the present invention, wherein the control unit corrects the skew of the sheet by changing the relative rotation speed between the first pinching roller and the second pinching roller based on the skewing amount of the sheet. Conveyor device. Further having a detection mechanism for detecting the positional deviation in the width direction of the sheet,
The transport device according to claim 2, further comprising a transport member for transporting the sheet while correcting a positional deviation in the width direction of the sheet based on the detection result of the detection mechanism. The transport device according to claim 3, wherein the position deviation in the width direction of the sheet is corrected by the feedback control. It has multiple detection mechanisms,
At least one of the detection mechanisms is provided on the downstream side of the first pinching roller and the second pinching roller in the sheet transport direction.
The plurality of detection mechanisms detect the skew of the sheet, and based on the detection result, the relative rotation speeds of the first pinch roller and the second pinch roller are changed to correct the skew of the sheet. The transport device according to any one of claims 3 or 4. The transport device according to claim 5, wherein the skew correction of the sheet based on the detection results by the plurality of detection mechanisms is performed by feedback control. The transport device according to claim 5 or 6, wherein the plurality of detection mechanisms are contact image sensors. An image forming apparatus including the transport device according to any one of claims 1 to 7 .

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