JP5432020B2 - Paper transport control device, paper transport control method, and printer - Google Patents

Description

  The present invention relates to a paper conveyance control device that controls a paper conveyance operation provided in an ink jet printer or the like, a paper conveyance control method, and a printer including a paper conveyance control device.

  In an ink jet printer, a DC servo motor or a stepping motor is used for transporting paper. When a DC servo motor is used, the amount of rotation is measured by an encoder attached to the motor shaft, and feedback control is performed. This is to obtain an appropriate print image quality by keeping the carry amount at an optimum value. If there is an error in the carry amount, streaks and color differences are produced in the print result, and the expected print image quality cannot be obtained. As another example of the attachment position of the encoder, the paper is sandwiched and conveyed by a grid roller and a pinch roller depending on the ink jet printer. The encoder is also attached to a shaft that rotates a mechanism called a grid roller that contacts the paper. There is. When a stepping motor is used, open loop control is possible, and control for obtaining a constant transport amount is possible without using an encoder.

  By the way, there are a wide variety of papers used in ink jet printers, and their thicknesses and surface conditions vary widely. For this reason, the pressure applied by the grid roller and the pinch roller may differ depending on the paper. This causes a phenomenon called slip, in which the movement of the paper does not follow the rotation of the grid roller. The presence of this slip means that the rotation amount of the motor shaft and the grid roller shaft does not match the conveyance amount of the paper. This appears as a carry amount error and causes the above-described deterioration in print image quality.

  For example, as in JP 2009-66871 A, the motor rotation amount is set by selecting the one with the best image quality from a plurality of test patterns printed with the motor rotation amount slightly changed in advance. There is a known technique to do this.

  In addition, some ink jet printers measure the transport amount by tracking a slight unevenness of a medium using an optical sensor (camera). According to this, since the conveyance amount of the medium can be directly measured and fed back regardless of the presence of the slip, the optimum conveyance amount can be maintained.

JP 2009-66871 A

  In the setting of the optimum motor rotation amount using the test pattern described above, a plurality of test patterns must be printed, and paper and ink are wasted and printing time is also required. In addition, this operation must be performed every time the roll-shaped paper is replaced, which is very troublesome for the user and contributes to a decrease in productivity.

  Even in the same roll, the weight of the roll is different between the vicinity of the beginning of use (the beginning of the sheet) and the vicinity of the end of use (the end of the roll), and therefore, the load state on the roll side is different during sheet conveyance. As a result, the amount of slip during conveyance changes, and the appropriate amount of rotation deviates from the initially set amount of motor rotation, leading to deterioration in print image quality.

  Furthermore, the amount of slip varies for each conveyance. For this reason, even if the optimum motor rotation amount is set as the center value, the conveyance amount actually varies for each scan printing. This variation cannot be measured by an encoder attached to the motor shaft or grid roller shaft, and as a result, improvement in print image quality cannot be expected. When a stepping motor is used, any rotation error on the axis cannot be measured unless an encoder is used.

  Since the conveyance amount measurement using the optical sensor is non-contact, false detection is inevitable. In addition, erroneous detection may appear as an extreme abnormal value. This erroneous detection is rather a factor that deteriorates the print image quality.

  The present invention has been made in view of such circumstances, and by directly measuring the transport amount of paper under any conditions, a paper transport device, a paper transport control method, It is an object to provide a paper transport control program.

  The present invention is a paper transport control device of a printing apparatus having a motor for transporting paper, the storage means for storing an optimal value of the paper transport amount that is the optimal transport amount according to the print mode of the printing apparatus, A paper conveyance amount measuring means for measuring a conveyance amount of the paper by detecting a position of the reference device before and after the conveyance of the paper by the motor is performed, and having a reference device placed on the paper; When the deviation amount between the sheet conveyance amount measured by the sheet conveyance amount measuring unit and the sheet conveyance amount optimum value read from the storage unit is a predetermined amount or more, the deviation amount is based on the deviation amount. And a correction unit that performs sheet conveyance control for conveying the sheet.

The present invention is characterized in that the sheet conveyance amount measuring means can be moved up and down in a direction perpendicular to the sheet.
According to the present invention, the paper conveyance amount measuring means is supported by a linear guide or the like so as to be freely operable in the paper conveyance direction, and includes means for detecting a position within the operation range, and the origin after paper conveyance A mechanism for returning to the position is provided.

The reference device is characterized in that a member for preventing slippage is attached to a contact surface with the paper.
The present invention is a printer including any one of the above-described sheet conveyance control devices.

In the present invention, a plurality of the transport amount measuring means are installed in the paper width direction of the paper, and the skew at the time of transporting the paper based on the transport amount of the paper measured by each of the transport amount measuring means. It is characterized by detecting.
The present invention includes a plurality of drive systems required for paper conveyance, and corrects to eliminate the skew by individually controlling the drive systems based on the paper conveyance amounts measured by the conveyance amount measurement units. It is characterized by doing.

  Further, the present invention is a paper transport device of a printing apparatus having a motor for transporting paper, and storing means for storing a paper transport amount optimum value that is an optimal transport amount according to a print mode of the printing device; A paper transport control method for a paper transport device, comprising: a reference device placed on the paper; and a paper transport amount measuring means for measuring the transport amount of the paper by detecting the position of the reference device. A step of placing the reference device on the paper, a step of transporting the paper, a step of measuring a transport amount of the paper by the paper transport amount measuring means, and a paper transport amount measuring means. A step of calculating a deviation amount between the measured conveyance amount of the sheet and the optimum value of the sheet conveyance amount read from the storage unit; and when the deviation amount is a predetermined amount or more, based on the deviation amount. For the above A sheet transport control method characterized by comprising a correction step of performing sheet conveyance control for conveying the.

  According to the present invention, the amount of paper transport can be measured equivalently by measuring the amount of movement of the reference device placed on the paper. That is, by performing the paper conveyance control again based on the difference between the actual paper conveyance amount measured when the paper conveyance control is performed and the paper conveyance amount optimum value stored according to the print mode, Any error factor associated with the paper conveyance control can be eliminated, and the effect of performing stable paper conveyance can be obtained. Accordingly, it is possible to always obtain a high print image quality regardless of the type and state of the paper. Further, by adding the present invention to an inexpensive drive system such as a stepping motor, it is possible to obtain high print image quality while suppressing the total cost.

It is a block diagram which shows the structure of one Embodiment of this invention. FIG. 2 is a configuration diagram of a paper transport mechanism 43 shown in FIG. 1. FIG. 3 is a diagram illustrating a positional relationship of sheets in FIG. 2. It is the figure which looked at the structure of FIG. 3 from the apparatus side surface. FIG. 6 is a diagram illustrating an installation example of a sheet conveyance amount measuring unit. FIG. 6 is a diagram illustrating a configuration example of a sheet conveyance amount measuring unit. It is the figure which showed an example of the origin position return means of a weight. 3 is a flowchart illustrating an operation of a sheet conveyance control unit 28 illustrated in FIG. 1. FIG. 6 is a diagram illustrating an operation of a paper conveyance amount measuring unit during printing. FIG. 10 is a diagram illustrating an example in which the lifting and lowering of the sheet conveyance amount measuring unit and the return to the origin position of the weight are performed simultaneously. FIG. 6 is a diagram illustrating an example in which a plurality of sheet conveyance amount measuring units are installed. FIG. 6 is a diagram illustrating an example in which skew is corrected by installing a plurality of sheet conveyance amount measuring units and a plurality of sheet conveyance drive systems.

  Hereinafter, a printing apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the embodiment. In this figure, description will be made using an ink jet printing apparatus 1. The printing apparatus 1 includes a control unit 20 that controls the operation of the printing apparatus 1. The control unit 20 includes a CPU 21 that collectively controls and executes processing operations such as calculation, control, determination, and setting in the control unit 20, a control program to be executed by the CPU 21 such as a program that performs a printing operation, and initial setting values. Are stored in advance, a RAM 23 used as a work storage area by each control unit during execution of a printing operation, an EEPROM 24 composed of a nonvolatile memory for storing setting values and data immediately before the power is turned off, and printing. An operation panel 44 that performs operation input and various displays on the apparatus 1, an operation panel control unit 25 that reads a state operated on the operation panel 44 and displays information on a display unit included in the operation panel 44, and a print medium The print control unit 26 for controlling the operation of printing by the print head 41 and the operation of the carriage mechanism 42 are controlled. A carriage control unit 27, a paper conveyance control unit 28 that controls the paper conveyance mechanism 43, an image memory 30 that stores image data, and an image memory write / read control unit 31 that controls reading and writing of information with respect to the image memory 30. And comprising. The print control unit 26 and the carriage control unit 27 control the print operation while coordinating the print positions based on the position of the carriage 420 read by the linear encoder 45. The RAM 23 stores information on the relationship between the conveyance amount and the motor rotation amount. The printing unit includes a print head 41, a print control unit 26, a carriage mechanism 42, a carriage control unit 27, and the like. The paper conveyance measuring unit 50 is a unit that is controlled by the CPU 21 and measures the conveyance amount of the paper.

  FIG. 2 shows an outline of the paper transport mechanism. The paper transport mechanism 43 includes a motor 435 for rotating the grid roller shaft 432 to which the grid roller 431 is attached, a motor driving circuit built in the motor 435, a driving pulley 434 for transmitting the driving force of the motor, and a driven pulley. 433, and rotary encoders 436 and 437 that detect the rotation of each axis. The rotation of the motor 435 is transmitted to the grid roller shaft 432, and the grid roller 431 is rotated. The encoders 437 and 436 are attached to the motor 435 or the grid roller shaft 432.

  FIG. 3 shows how the paper 439 is actually conveyed. A pinch roller 438 is installed above the grid roller 431, and the paper 439 is sandwiched between them. The pinch roller 438 applies a certain pressure to the grid roller 431 and sandwiches the paper 439 so that the paper 439 is conveyed following the rotation of the grid roller 431.

  FIG. 4 shows the path of the paper 439 from the paper supply side to the paper discharge side. The sheet 439 conveyed by the rotation of the grid roller 431 receives droplets discharged from the print head 41 disposed in the carriage 420 that reciprocates in the vertical direction (main scanning direction) on the print surface. . After the printing of one scan is completed, the paper 439 is conveyed and further one scan printing is performed. By repeating this, the drawing operation is performed.

  The grid roller 431 and the pinch roller 438 are arranged to face each other with the paper 439 interposed therebetween. An appropriate pressure is applied between them so that the sheet 439 can easily follow the rotation of the grid roller 431. In FIG. 4, four pairs of grid rollers 431 and pinch rollers 438 are shown, but a plurality of grid rollers 431 and pinch rollers 438 are generally installed at equal intervals according to the printing width of the printer. The paper is supplied from the roll 440 and guided to the paper discharge side along the paper guides 441 and 442. Printing is performed by causing droplets ejected from the print head 41 mounted on the carriage 420 that reciprocates in the vertical direction in FIG. 4 to land on the paper.

  FIG. 5 shows an example of an installation location of the paper conveyance amount measuring means 50 of the present invention. It is necessary to be in the vicinity of the grid roller 432, which does not hinder the reciprocating operation of the carriage 420 on the printing surface, and can easily measure the sheet conveyance amount. It is desirable to install between a plurality of pinch rollers 438.

  Here, with reference to FIG. 6, the structure of the paper conveyance amount measuring means 50 will be described. The linear guide 502 and the linear encoder 503 are fixed by a support member (not shown). A weight 501 and a linear scale 504 are also fixed separately. An anti-slip member 504 is attached to the back surface of the weight. These can be translated with respect to the linear guide 502 and the linear encoder 503, and constitute detection means capable of detecting the position of the weight 501 in the linear guide 502 with the linear encoder 503. It is desirable that the reference device is fixed to the paper 439 without slipping due to conveyance when it is placed on the paper 439. Here, a reference device in which a non-slip member 504 is disposed on the back surface of the weight 501 is used. The weight 501 and the anti-slip member 504 are fixed on the paper 439 by a frictional force.

  Next, a method for returning the weight 501 to the origin position will be described with reference to FIG. As a return means for returning the weight 501 to the origin position, the weight 501 is provided with a magnet 505, and a support member 507 that supports the linear guide 502 is also provided with a solenoid coil 506. Here, by energizing the solenoid coil 506, magnetic flux is generated, and the magnet 505 and the main weight 501 move in the direction of the solenoid coil 506. If this position is defined as the origin, the weight 501 can be returned to the origin position by energizing the solenoid coil 506. Although not shown, the sheet conveying means 50 can be raised and lowered by the same means. In this case, a magnet is installed on the support member 507 and a solenoid coil is installed on the housing side of the printer. Of course, it is also possible to configure the origin return means and the lifting means with a motor or other means.

Next, with reference to FIGS. 8 and 9, an operation for measuring the amount of paper transport accompanying the paper transport during printing will be described.
First, when the CPU 21 starts a printing operation, the sheet conveyance control unit 28 stands by while performing various initial operations such as detection of the sheet width, temperature rise of various heaters, restoration of the meniscus state of the head nozzle surface (step S1). ). In this state, the transport amount measuring means is in the raised position, and the weight is not in contact with the paper. Then, when the CPU 21 starts the printing operation, the weight 501 is returned to the origin. (Step S2). This is the state of FIG.

Next, the transport amount measuring means is lowered to bring the weight 501 into contact with the paper (step S3). Thereafter, the weight can be moved along with the conveyance of the sheet. This is the state of FIG.
Here, the CPU 21 outputs a carriage drive command to the carriage control unit 27 and also outputs a print command to the print control unit 26. As the carriage 420 moves, a one-scan printing operation is performed (step S4). Here, when all the data has been printed, the operation proceeds to an end operation (steps S5 and S11).

  If it is before the completion of printing, a drive circuit (not shown) provided in the carry amount measuring unit 50 initializes a counter obtained by accumulating the outputs of the linear encoder 503 (step S6). Although the origin should have been returned in step S2, since the subsequent lowering operation (step 3) and slight vibration accompanying the movement of the carriage 420 are also conceivable, the weight is not always at the same position every time. This error is corrected.

  Next, the CPU 21 reads the motor rotation amount based on the conveyance amount optimum value from the RAM 23 and outputs it to the sheet conveyance control unit 28. In response to this, the paper conveyance control unit 28 rotates the motor to carry the paper (step S7). This is the state of FIG. Note that a drive circuit (not shown) provided in the transport amount measuring unit 50 constantly monitors the output from the linear encoder 503 and accumulates the count while the paper transport operation is being performed. Thereby, the moving amount of the weight 501 is obtained before and after the paper conveyance.

  After the paper conveyance is completed, the CPU 21 acquires the position information of the weight 501 from the conveyance amount measuring unit 50. This value is set as dX (step S8). The CPU 21 compares the conveyance amount optimum value read in advance with dX (step S9), and if they do not match, the deviation amount, that is, the difference is set as the movement amount, and the sheet is conveyed by the movement amount. A control command is output to the conveyance control unit. That is, the operation from step 7 is performed again. By repeating this, dX is brought close to the optimum value for the sheet transport amount. It is desirable for dX to be the same value as the optimum value for the paper conveyance amount. Here, repeating the correction operation many times causes a decrease in the printing speed. Therefore, the upper limit of the number of times of performing the correction operation may be determined in advance, and the correction operation may be performed within the range of the number of times. For example, the upper limit value of the number of times of performing the correction operation is stored in the EEPROM 24, the value is written in the RAM 23 at the time of the first correction operation, and subtracted every time one correction operation is performed, and the correction operation is terminated when it becomes zero. be able to. In addition, an upper limit of the difference between dX and the optimum amount of paper conveyance may be determined in advance, and processing may be performed in which the correction operation is considered complete if the difference falls within the range. Finally, the paper is transported to a position where dX becomes the optimum value for the paper transport amount or a value that falls within a predetermined range with respect to the optimal value for the paper transport amount. This predetermined range is stored in the EEPROM 24 in advance. Further, it is desirable that the difference between dX and the optimum value of the sheet transport amount is equal to or less than the distance between dots of ink landed on the sheet 439. The inter-dot distance is a distance between the centers of the dots. More preferably, the difference between dX and the optimum amount of paper transport is a distance that is an integral number of the inter-dot distance, preferably a half distance, and more preferably a quarter distance. This is because it is possible to prevent the ink landing position from moving back and forth before the paper is transported due to the transport amount error and the formation of a gap between the dots. It is desired to transport the paper so that a transport error does not occur as much as possible. Further, since the landing position is also shifted depending on the characteristics of each nozzle of the head 41, it is better that the error in the transport amount is smaller.

  As another form, the predetermined range may be determined by the nozzle pitch of the head 41. In that case, it is necessary to consider the relationship with the conveyance stop position of the sheet 439. In the case of carrying the dots with an accuracy equal to or less than the nozzle pitch so as to form dots between the dots, the predetermined range is equal to or less than the nozzle pitch, and more preferably, equal to or less than an integer such as a half or a quarter of the nozzle pitch. It is good to decide so that it becomes. Further, since a blank portion may be formed when a dot is formed due to an error between the dot size and the carry amount, the predetermined range may be determined according to the dot size. In that case, it is preferable that the distance is equal to or less than a distance in which adjacent dots overlap in an ideal state.

Finally, after the paper conveyance is properly completed, the conveyance amount measuring means 50 is raised (step S10). Thereafter, the process returns to step 2 to move to the next scan printing.
As described above, the amount of movement of the weight 501 placed on the sheet 439 is equivalently measured as the amount of sheet conveyance for each scan of the printing operation, thereby keeping the sheet conveyance amount stable and appropriate. Can do. This has the effect of increasing the ink dot landing accuracy in the paper feed direction for each scan, and an improvement in print image quality can be expected. In addition, since it is not necessary to set the optimum motor rotation amount using a test pattern, which is done with a conventional printer, it is possible to eliminate unnecessary use of ink and paper and improve user productivity. Can also contribute.

  Note that the above-described optimum value of the sheet conveyance amount is a value determined from the number and pitch of nozzles perforated on the print surface of the print head 41 and the number of passes corresponding to the print mode. On the other hand, during printing, the motor rotation amount set at the time of the first paper conveyance in step 7 does not coincide with the optimum value of the paper conveyance amount, and is given as a slip amount added thereto. Should. Otherwise, a correction operation corresponding to the slippage amount is always included in each scan, and a decrease in printing speed is unavoidable. Conventionally, the motor rotation amount is set by using test pattern printing. However, in the present invention, the amount of paper transport during printing is directly measured and can be easily determined. In other words, in FIG. 8, the sum of the motor rotation amounts at step 7 performed in one scan is the motor rotation amount for conveying the sheet by the optimum value for the sheet conveyance amount. If this motor rotation amount is dY, the ideal motor rotation amount from which variation has been eliminated can be calculated by averaging the past dY times during the printing operation. By using it when the motor is rotating, it is possible to approach the paper conveyance amount in which the correction operation is difficult to enter. That is, the ideal motor rotation amount is calculated by the control unit 20 and stored in the RAM 23, and the motor rotation amount at the time of conveyance is read out and used.

  In addition, when the motor 435 in FIG. 3 is a DC servo motor, control is performed by feeding back the amount of rotation from the rotary encoders 436 and 437 attached to the respective axes. The rotary encoders 436 and 437 themselves are conveyed. It can be considered that the measuring means 50 is replaced. In this case, since it is possible to follow the optimum value of the sheet conveyance amount as a control target in real time, it is not necessary to perform a correction operation in principle. As a result, an improvement in print image quality can be expected without reducing the print speed.

  In addition, FIG. 10 shows an example in which the operation of returning the origin position of the weight 501 described in FIG. In this case, the support member 507 is rotatable at a fulcrum 508 on the printer side, and the sheet conveyance amount measuring means 50 is also rotated at the same time. The weight 501 moved in the direction away from the origin in the state of FIG. 10A is separated from the paper 439 by the paper transport amount measuring means 50 rotating clockwise as shown in FIG. 10B. In addition, it is possible to return to the origin position by its own weight. Thereafter, as shown in FIG. 10C, the weight 501 returned to the origin position can be placed on the paper 439 by further rotating the paper conveyance amount measuring means 50 counterclockwise. With this method, since the lifting and lowering of the sheet conveyance amount measuring means 50 and the return to the origin position of the weight 501 can be realized simultaneously with one type of actuator, the cost can be reduced and the size can be reduced.

  In this embodiment, the linear encoder 503 and the linear scale 504 are shown as an example for detecting the position of the weight 501. However, in addition to this, a sensor such as a magnetic linear encoder or a laser displacement meter is used. I think that.

  In addition, as shown in FIG. 11, it is also conceivable to install a plurality of conveyance amount measuring means 50 in the width direction of the paper and individually measure the conveyance amounts at the left and right ends in the width direction. In this case, when there is a difference between the left and right transport amounts, it means that the sheet 439 is transported obliquely, that is, a skew has occurred, which may cause a printing failure. Further, when the skew of the sheet 439 continues, the drawing area may protrude from the sheet width. By installing a plurality of conveyance amount measuring means 50, these problems can be prevented in advance. Each of the plurality of transport amount measuring means 50 is controlled by the control unit 20. The control unit 20 calculates and stores the transport amount and the deviation amount of the transport amount measuring means 50, and uses these values for calculation and control. The skew is determined in advance, and it is determined whether the skew is present or not by comparing with a value stored in the control unit 20, and in response thereto, the skew avoidance control is performed or the drawing is continued as it is.

  A plurality of pairs of grid rollers 431 and pinch rollers 438 are arranged in the width direction of the paper 349. By disposing at least between the outermost roller pair, a difference in the conveyance amount due to the skew of the paper can be remarkably detected. More preferably, the conveyance amount measuring means 50 is arranged between all roller pairs. As a result, a finer movement of the paper 439 can be detected.

  Furthermore, it is also useful when left and right individual paper transport systems as shown in FIG. 12 are installed. In FIG. 12, the grid roller shaft 432 is divided into left and right parts, which can be individually rotated by a motor or the like (not shown). Accordingly, it is possible to correct the skew of the sheet 439 by individually controlling the sheet conveyance using the conveyance amount measuring means 50 corresponding to each grid roller shaft 432. As a result, it is possible to perform highly accurate paper conveyance control with suppressed skew, and it is possible to maintain extremely good print image quality. For example, each conveyance system is controlled so that the actual conveyance amount becomes the reference value of the conveyance amount. If the value is advanced more than the reference value of the conveyance amount, the conveyance amount of the conveyance system is reduced, and if the value is advanced less, the conveyance amount of the conveyance system is increased. The controller 20 independently controls the conveyance of the sheet 439 by the roller pair of the grid roller 431 and the pinch roller 438 on the right side of the figure and the conveyance of the sheet by the roller pair of the grid roller 431 and the pinch roller 438 on the left side of the figure. The paper is conveyed so as to eliminate skew during the conveyance of the paper.

  The present invention can be used for a printer such as an inkjet printer.

  DESCRIPTION OF SYMBOLS 1 ... Printing apparatus, 20 ... Control part, 21 ... CPU, 22 ... ROM, 23 ... RAM, 24 ... EEPROM, 25 ... Operation panel control part, 26 ... Print control unit, 27 ... carriage control unit, 28 ... paper conveyance control unit, 29 ... host I / F unit, 30 ... image memory, 31 ... image memory write / read control unit , 41 ... print head, 42 ... carriage mechanism, 43 ... paper transport mechanism, 44 ... operation panel, 45 ... linear encoder

Claims (9)

A paper transport control device of a printing apparatus having a motor for transporting paper,
Storage means for storing an optimum value of a paper conveyance amount that is an optimum conveyance amount according to a printing mode of the printing apparatus;
A paper conveyance amount measuring unit which has a reference device placed on the paper and measures the conveyance amount of the paper by detecting the position of the reference device before and after the conveyance of the paper by the motor. ,
When the deviation amount between the sheet conveyance amount measured by the sheet conveyance amount measuring unit and the sheet conveyance amount optimum value read from the storage unit is a predetermined amount or more, the deviation amount is based on the deviation amount. Correction means for performing paper conveyance control for conveying paper;
A sheet conveyance control device comprising:   The paper conveyance control device according to claim 1, wherein the paper conveyance amount measurement unit includes an elevating unit that moves up and down in a direction perpendicular to the paper.   The paper conveyance amount measuring means includes a linear guide that supports the reference device movably in the paper conveyance direction, a detection means that detects a position of the reference device within a movable range of the reference device, and a paper conveyance The sheet conveyance control device according to claim 1, further comprising a return mechanism that returns the reference device to a predetermined origin position later.   The paper transport control device according to claim 3, wherein the reference device has a weight portion for applying pressure to a contact surface with the paper.   5. The sheet conveyance control device according to claim 1, wherein a member for preventing slippage is attached to a contact surface of the reference unit with the sheet. 6.   A printer comprising the paper conveyance control device according to claim 1 and a printing unit.   A plurality of the transport amount measuring means are installed in the paper width direction of the paper, and a skew during the paper transport of the paper is detected based on the transport amount of the paper measured by each of the transport amount measuring means. The printer according to claim 5.   A plurality of drive systems required for paper conveyance are provided, and correction is made to eliminate the skew by individually controlling the drive systems based on the paper conveyance amounts measured by the conveyance amount measuring means. The printer according to claim 6. A paper transport device of a printing apparatus having a motor for transporting paper, wherein the storage means stores an optimum value of the paper transport amount that is an optimal transport amount according to the printing mode of the printing device, and is placed on the paper A paper transport control method for a paper transport device, comprising a paper transport amount measuring means for measuring the transport amount of the paper by detecting the position of the reference device,
Placing the reference device on the paper;
Conveying the paper;
Measuring the paper transport amount by the paper transport amount measuring means;
Calculating a deviation amount between the sheet conveyance amount measured by the sheet conveyance amount measuring unit and the sheet conveyance amount optimum value read from the storage unit;
When the deviation amount is equal to or greater than a predetermined amount, a correction step for performing paper conveyance control for conveying the paper based on the deviation amount;
A paper conveyance control method comprising:

Images