JP5839982B2 - Sheet transport device - Google Patents

Description

  The present invention relates to a sheet conveying apparatus that conveys a sheet drawn from a roll sheet wound in a roll shape.

  In a recording apparatus such as a printer, a facsimile machine, and a copying machine, a sheet is transported by using a sheet that is drawn out from a roll sheet wound in a roll shape, cut to a predetermined length, and used. A device may be used. In such a sheet conveying apparatus, for the purpose of improving the sheet conveying accuracy, a constant tension is applied to the sheet between the pair of conveying rollers for conveying the sheet drawn from the roll sheet and the roll sheet. Sometimes. Thereby, it is possible to remove or correct the sheet misalignment, slackness, skew, curl, etc. during conveyance.

  A sheet conveying apparatus that applies a certain tension to such a sheet is disclosed in Patent Document 1. The sheet conveying device drives a first motor that applies a driving force for rotating the roll body around which the sheet is wound to pull out the sheet, and a conveyance driving roller provided on the downstream side in the conveying direction from the roll body. A second motor for providing a driving force. Furthermore, the sheet conveying apparatus has load measuring means for measuring the relationship between the load acting on the first motor and the driving speed when only the first motor is driven without driving the second motor. Then, by giving an interpolation output based on the result measured by the load measuring means and the driving speed of the second motor to the first motor, a desired tension is applied when the roll sheet is conveyed at a certain conveying speed. Is given to.

JP 2009-242048 A

  However, in Patent Document 1, the relationship between “current to the sheet feeding motor” and “predetermined speed of the roll sheet” is used for tension adjustment. Since this method does not consider the moment of inertia around the rotation axis of the roll sheet (hereinafter sometimes referred to as inertia), the tension applied to the roll sheet deviates from a predetermined value due to the influence of inertia during the acceleration / deceleration of the roll motor. There is a possibility, and at that time, there is a concern about a decrease in the conveyance accuracy.

  Therefore, it is necessary to apply a torque according to the fluctuation of the inertia to the roll sheet, and to perform control to always keep the tension acting on the drawn sheet constant. For that purpose, it is necessary to obtain the inertia generated in the roll sheet. Inertia has several calculation methods, and the advantages and disadvantages differ depending on the calculation method. Therefore, control that compensates for the disadvantages of each calculation method is required.

  A sheet conveying apparatus according to an aspect of the present invention is a sheet conveying apparatus that pulls out a sheet from a roll sheet wound in a roll shape and conveys the sheet, and generates a driving force that rotates the roll sheet around a rotation axis. A first driving source to be driven, a second driving source for generating a driving force for pulling the sheet drawn from the roll sheet and conveying the sheet, and the second driving source being operated. First inertia calculating means for calculating a moment of inertia about the rotation axis of the roll sheet by measuring the rotational movement of the roll sheet, and based on the width, density and radius of the roll sheet, A second inertia calculating means for calculating an inertia moment about the rotation axis; and an inertia moment about the rotation axis of the roll sheet. Is calculated by the first inertia calculating means or the second inertia calculating means, and the first inertia calculating means or the second inertia calculating means. And a controller that controls the first drive source so that a predetermined tension acts on the sheet being conveyed based on the moment of inertia.

  An image forming apparatus according to the present invention includes the above-described sheet conveying device and an image forming unit that forms an image on a sheet fed from the sheet conveying device.

  According to the present invention, when the conveyance accuracy needs to be improved, the inertia is directly measured from the measurement of the rotational movement of the roll sheet. In other cases, the second inertia calculation means is used to improve the throughput. The inertia is calculated by Thereby, the conveyance accuracy of the sheet pulled out from the roll sheet can be improved while suppressing a decrease in throughput.

1 is a perspective view illustrating a schematic configuration of a printer as an image forming apparatus which is an example of the present invention. FIG. 3 is a block diagram illustrating a control configuration of a paper feeding / conveying mechanism of a printer that is an example of the present invention. It is a conceptual diagram of the detection means of the radius of a roll sheet. It is a conceptual diagram of the inertia calculation of the 1st inertia calculation means E1. It is a conceptual diagram of the inertia calculation of the 2nd inertia calculation means E2. 6 is a graph showing a driving operation during printing of a printer which is an example of the present invention. It is a conceptual diagram of the drive operation at the time of printing of the printer which is an example of this invention. It is a flowchart which shows the operation | movement procedure which switches an inertia calculation means according to printing mode. It is a flowchart which shows the operation | movement procedure which switches an inertia calculation means according to a paper type. It is a flowchart which shows the operation | movement procedure which switches an inertia calculation means according to temperature and humidity. It is a flowchart which shows the operation | movement procedure which switches an inertia calculation means according to whether the radius of a roll sheet is 45 mm or more. It is a flowchart which shows the operation | movement procedure which switches an inertia calculation means according to whether the radius of a roll sheet is less than 35 mm. 6 is a flowchart illustrating an operation procedure of a printer according to a second embodiment. It is a table for judging the implementation timing of the 1st inertia calculation means which concerns on 3rd Embodiment. 10 is a flowchart illustrating an operation procedure of a printer according to a third embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. Hereinafter, a printer (image forming apparatus) including a sheet conveying apparatus that pulls out and conveys a sheet from a roll sheet wound in a roll shape will be described. However, the present invention is not limited to this, and can be applied to all devices including a sheet conveying apparatus that pulls out and conveys a sheet from a roll sheet, such as a copying machine or a facsimile. Further, a single sheet conveying apparatus is also included in the present invention.

(First embodiment)
FIG. 1 is a perspective view illustrating a schematic configuration of a printer including a sheet conveying apparatus according to a first embodiment of the present invention, and FIG. 2 is a block diagram illustrating a control configuration of a paper feeding / conveying mechanism of the printer. A configuration of a printer provided with the sheet conveying apparatus of the present invention will be described with reference to FIGS. 1 and 2.

  The roll sheet 1 is rotatably held by the paper feed unit 3 with the spool 2 as a rotation axis. The sheet M is fed out from the roll sheet 1 as the roll sheet 1 rotates. Further, the spool 2 is provided with a paper feed encoder 4 that coaxially detects the rotation angle of the spool 2. The spool 2 is provided with a gear 5 coaxially. The gear 5 is connected to a paper feed motor (first drive source) 6 that generates a driving force for rotating the spool 2, that is, rotating the roll sheet, and transmits the driving torque of the paper feed motor 6 to the spool 2. .

  The image forming unit 7 is located downstream of the roll sheet 1 in the sub-scanning direction H in which the sheet M drawn from the roll sheet 1 is conveyed. The image forming unit 7 includes an ink jet print head and a carriage on which the print head is mounted. The carriage reciprocates in the main scanning direction orthogonal to the sub-scanning direction H by a drive mechanism such as a motor, and prints on the sheet M facing the print head at the print position. The transport roller 8 is positioned upstream of the print position in the sub-scanning direction H. In addition, a plurality of pinch rollers 9 that rotate following the rotation of the conveying roller 8 are provided. The conveyance roller 8 and the pinch roller 9 rotate while sandwiching the sheet M, and convey the sheet M. The conveyance roller 8 and the pinch roller 9 divided into a plurality constitute a part of a conveyance mechanism that conveys the sheet M. A transport encoder 10 that detects the amount of rotation of the transport roller 8 is provided coaxially with the transport roller 8. A gear 11 is provided coaxially with the transport roller 8, and the gear 11 transmits the driving torque of the transport motor (second drive source) 12 to the transport roller 8. The sheet M is conveyed in the sub-scanning direction H by the conveyance roller 8 rotated by the driving torque of the conveyance motor 12. The platen 13 facing the print head at the printing position holds the drawn sheet M in a flat shape while sucking it.

  The control unit P3 mainly controls the paper feed motor 6 and the transport motor 12. The control unit P3 includes a CPU, a ROM, a RAM, a motor driver, and the like (not shown), and includes a main control unit 100, a paper feed motor control unit 120, and a transport motor control unit 130. The main control unit 100 further includes a roll size detection unit P1 and a calculation unit P2.

The roll size detection unit P1 includes means for detecting the radius of the roll sheet 1 that is cylindrical. Here, the detection method of the radius of the roll sheet 1 is demonstrated using FIG. When the sheet is conveyed by rotating the conveyance roller 8 by a predetermined amount, the rotation angle of the spool 2 detected by the paper feed encoder 4, that is, the rotation angle of the roll sheet 1 is θ0 [rad], and the conveyance roller detected by the conveyance encoder 10 A rotation angle of 8 is θ1 [rad]. When the radius of the roll sheet 1 is R0 [m] and the radius of the transport roller 8 is R1 [m],
“R0 · θ0 = R1 · θ1 (1)”
Is obtained. The relational expression (1) is derived on the assumption that the sheet M is not slackened and the sheet is conveyed without slipping in a state where the sheet M is strongly held between the conveying roller 8 and the pinch roller 9. Further, it was assumed that the rotation angle is relatively small and the radius of the roll sheet does not change at this rotation angle. Since the radius R1 of the conveying roller 8 is constant, from the above relational expression (1), the radius R0 [m] of the roll sheet 1 is
“R0 = R1 · θ1 / θ0 (2)”
Can be calculated as

  The roll size detection unit P1 also includes means for detecting the paper width B [m] of the roll sheet 1. Here, the paper width B refers to the width of the sheet M in the main operation direction. The means for detecting the paper width B is disposed in the image forming unit 7 and detects the paper width B by detecting both ends of the sheet M with an optical sensor that can move in the main scanning direction.

  The print information storage unit P4 stores the print contents and print mode set by the user. The print mode (image formation mode) is a print quality selected when the user forms an image. In this example, the print mode is divided into four stages. The print mode 4 has the highest print quality, and “highest” is displayed on the panel provided in the printer. The print mode 3 is displayed as “beautiful”, the print mode 2 is displayed as “standard”, and the print mode 1 is displayed as “fast”. The feeding amount (number of passes) of the sheet M by the conveyance roller 8 varies depending on these printing modes. The higher the print quality mode is, the smaller the feed amount is. As the one-time feed amount of the conveying roller 8 is smaller, unevenness when printed on the sheet M becomes less conspicuous, and high-quality printing becomes possible.

  The temperature / humidity detector P5 detects the temperature and humidity around the printer. For example, a digital thermometer using a thermistor is used for measuring the temperature, and a digital hygrometer using a moisture sensitive agent is used for measuring the humidity. In addition, a thermometer and a hygrometer can use various things not only in these.

  The data storage unit P6 stores the torque coefficient Kt of the paper feed motor 6, the density and paper tube diameter of the fed roll sheet, the sheet level, and the like. The sheet level is a level indicating whether the fed sheet is suitable for high-definition printing. As the determination of the sheet level, the degree of reproducibility of the dot diameter of the ink applied from the print head to the sheet can be used. It is determined that the higher the reproducibility of the ink dot diameter (that is, the less the bleeding at the time of ink landing), the higher the resolution of printing and the higher the sheet level. Specifically, a sheet used for printing a line drawing or the like (for example, a sheet called plain paper or tracing paper) has a relatively low sheet level. Compared with them, a sheet whose surface has been processed (for example, a sheet called coated paper or glossy paper) has a higher reproducibility of the ink dot diameter and a higher sheet level. In addition, the user may be allowed to set the sheet mode when feeding a sheet. In this embodiment, the sheet level is divided into three stages.

  The calculation unit P2 calculates the inertia of the roll sheet 1, that is, the moment of inertia around the rotation axis. The calculation unit P2 includes two calculation units, a first inertia calculation unit E1 and a second inertia calculation unit E2. FIG. 4 shows a conceptual diagram of the first inertia calculating means E1, and FIG. 5 shows a conceptual diagram of the second inertia calculating means.

  The first inertia calculation means E1 stores the angular acceleration θ "of the roll sheet obtained from the paper feed encoder 4, the current i of the paper feed motor 6 detected from the current detection unit 14, and the data storage unit P6. The inertia J is calculated from the torque coefficient Kt of the paper feed motor that is present, and a specific calculation method will be described later.The second inertia calculation means E2 is the density ρ of the roll sheet stored in the data storage unit P6 and The inertia J is calculated from the paper tube diameter rc, the roll sheet radius r detected by the roll size detection unit P1, and the paper width B. A specific calculation method will be described later.

  The main control unit P3 determines which calculation means E1 and E2 to execute based on information obtained from the roll size detection unit P1, the print information storage unit P4, the temperature / humidity detection unit P5, and the sheet data storage unit P6. select. Further, the main control unit P3 controls the paper feed motor 6 according to the fluctuation of the inertia calculated by the calculation unit P2.

  FIG. 6 is a graph showing a driving operation at the time of printing of a printer provided with the sheet conveying apparatus of the present invention. FIG. 7 is a conceptual diagram of the driving operation. The drive operation of the printer provided with the sheet conveying apparatus of the present invention will be described with reference to FIGS. In a printer equipped with a sheet conveying apparatus of the present invention, in order to obtain a stable image during a printing operation, tension (tension) that is pulled out and acts on the sheet being conveyed in a range that does not affect the image with respect to the roll sheet. ) To control the paper feed motor 6. As described above, in order to convey the sheet M with high accuracy, it is preferable to perform torque control of the sheet feeding motor so as to apply a constant tension F [N] to the sheet M. Therefore, a calculation method of the paper feeding motor torque for generating the tension F [N] will be described by dividing it into a constant speed section (A3, A7), an acceleration section (A2, A6), and a deceleration section (A4, A8). .

In the constant velocity section (A3, A7) shown in FIG. 6, the feed motor torque for generating a predetermined tension F on the roll sheet is Ta [N · m], and the torque generated on the roll sheet shaft is T _roll. [N · m]. At this time, since Ta = T _roll [N · m] in the constant speed section, if the radius of the current roll sheet 1 is R0 [m],
“Ta = T _roll = F × R0 (3)”
It becomes. Since F [N] is a force in a negative direction, the paper feed motor torque Ta [N · m] also works in a negative direction.

Next, the feed motor torques Tb and Tc [N · m] that generate the desired tension F [N] in the acceleration section (A2, A6) and the deceleration section (A4, A8) will be described. The inertia of the roll sheet 1 is J [kg · m ² ], the acceleration of the sheet drawn from the roll sheet is a [m / s ² ] (positive during acceleration, negative during deceleration), and the radius of the roll sheet is Let R0 [m]. At this time, the torque generated by the inertia J [kg · m ² ] of the roll sheet (corresponding to the amount obtained by converting the angular acceleration of rotation into torque) Ti [N · m] is negative in acceleration and positive in deceleration. To work,
“Ti = −J × a / R0 (4)”
It becomes. Here, “a / R0” corresponds to the angular acceleration of the roll sheet. The torque T _roll [N · m] generated on the roll sheet axis in the acceleration / deceleration section is the sum of the torque Ti [N · m] generated by the inertia and the feed motor torque Tb or Tc in the acceleration or deceleration section. . Therefore,
“T _roll = Tb + Ti = Tb− (J × a / R0) [a> 0] (5)”
“T _roll = Tc + Ti = Tc− (J × a / R0) [a <0] (6)”
Is expressed as That is, the feeding motor torques Tb to Tc in the acceleration section / deceleration section are expressed by the above equations (3), (5), and (6).
“Tb = T _roll −Ti = (F × R0) + (J × a / R0) [a> 0] (7)”
“Tc = T _roll −Ti = (F × R0) + (J × a / R0) [a <0] (8)”
It becomes.

In the above formula (6), it is desirable that the tension F [N] is constant as described above. When the tension is constant, if the roll sheet acceleration a [m / s ² ] is constant, the sheet is fed in accordance with the inertia J [kg · m ² ] and the radius R0 in the acceleration / deceleration section. It can be seen that it is necessary to control the motor torques Tb and Tc.

Next, the relationship between the above-described inertia J [kg · m ² ] and radius R0 and the paper feeding motor torque Tb during acceleration will be described. The load torque T _roll [N · m] on the roll sheet shaft increases in proportion to the radius R0 [m] in order to keep the back tension F [N] constant from the equation (3). Further, since the inertia J [kg · m ² ] is proportional to the square of the radius of the roll sheet, the torque Ti [N · m] is also proportional to the square of the radius from the equation (4). Therefore, torque control corresponding to the radius R0 is also performed for the paper feed motor torque Tb being accelerated from the equation (7). Actually, the change in the tension F [N] is allowed as long as it does not affect the conveyance accuracy. Therefore, T _roll [N · m] has an upper limit value Tr1 and a lower limit value Tr2, and Tb [N · m] is set so that T _roll maintains a range between the upper limit value Tr1 and the lower limit value Tr2. Will be controlled.

From the above description, control based on the inertia J [kg · m ² ] is necessary for controlling the feed motor torque Tb [N · m] or Tc [N · m] in the acceleration zone / deceleration zone. I understand that. Accordingly, the inertia calculation performed by the calculation unit P2 will be described below with reference to FIGS. 2, 4, and 5. FIG. 4 is a conceptual diagram showing the first inertia calculating means E1, and FIG. 5 is a conceptual diagram showing the second inertia calculating means E2.

The first inertia calculation means E1 in the calculation unit P2 drives the paper feed motor 6, and calculates the inertia J of the roll sheet 1 from the torque coefficient and current of the paper feed motor 6 and the angular acceleration of the roll sheet. Here, the angular acceleration of the roll sheet obtained from the paper feed encoder 4 is θ ″ [rad / s ² ], the current obtained from the current detection unit 14 of the paper feed motor 6 is i [A], and the data storage unit P6. Kt is the torque coefficient of the paper feed motor 6 stored in the roll sheet, and the inertia J [kg · m ² ] of the roll sheet is
“J = (Kt × i) / θ” (9) ”
And is calculated using the above equation (9) in the calculation unit P2. The angular acceleration θ ″ [rad / s ² ] is the second-order time derivative of the rotation amount θ [rad] of the paper feed encoder 4.

Next, the second inertia calculation means E2 will be described. The second inertia calculation means E2 calculates the inertia based on the sheet information stored in the data storage unit P6 and the sheet information measured by the roll size detection unit P1. The roll sheet inertia J [kg · m ² ] is determined in advance in the roll sheet density ρ [kg / m ³ ] and the paper tube diameter rc [m] stored in the data storage unit P6 and the roll size detection unit P1. Using the detected roll sheet radius R0 [m] and paper width B [m],
^{"J = πρB × (R0 2 -rc} 2) 2/8 ··· (10) "
And is calculated using the above equation (10) in the calculation unit P2. Note that a plurality of pieces of data such as the density ρ [kg / m ³ ] and the paper tube diameter rc [m] of the roll sheet stored in the data storage unit P6 are stored in the sheet type. These pieces of information are sequentially called based on the sheet type information input by the user via the operation panel or printer driver.

  Next, which inertia calculation means E1, E2 calculates the inertia of the roll sheet will be described. As described above, since the first inertia calculation unit E1 drives the paper feed motor 6, the throughput slightly decreases. However, since the inertia J is directly measured from the rotation angle of the roll sheet at a predetermined time, the inertia calculation accuracy is high. Since the second inertia calculating means E2 does not need to drive the paper feed motor 6, there is no decrease in throughput. However, the second inertia calculation means E2 may cause an error in the calculated inertia J due to various factors.

  For example, the roll size detection unit P1 calculates the radius of the roll sheet on the assumption that the sheet M is not slack and the conveyance roller 8 can convey the sheet M without slipping. However, in reality, in the case of a roll sheet having a large radius, the sheet M slips between the conveying roller 8 and the pinch roller 9, and there is a possibility that “θ1 · r1 ≠ θ0 · r0”. For this reason, an error may occur in the calculated radius r0, an error may occur in the mass m calculated therefrom, and an error may occur in the inertia J as a result. Therefore, it is better to calculate the inertia J by the first inertia calculation means E1 until the radius of the paper tube is equal to or more than the first predetermined amount (for example, in the case of a roll sheet having a length of 30 m, the radius is 45 mm or more).

  In addition, in a high temperature and high humidity environment, the roll sheet absorbs moisture, and the density of the roll sheet may deviate from an assumed value measured in advance. If the density deviates from the assumed value, an error may occur in the mass m calculated therefrom, and as a result, an error may occur in the inertia J. Therefore, in an environment where the density deviates from the assumed value (for example, temperature 30 ° C. or higher and humidity 80% or higher), it is better to calculate the inertia J by the first inertia calculating means E1.

  The second inertia calculation means E2 must use the density and paper tube diameter information of the sheet data storage unit P6. Therefore, when the user uses a roll sheet whose information is not stored in the sheet data storage unit P6, a value different from the actual roll sheet inertia may be calculated. As described above, when the paper tube diameter information is different from the actual value, the inertia J calculated based on the information may greatly deviate from the actual value. In particular, the influence tends to be remarkable near the core. Therefore, when the radius of the paper tube is less than a second predetermined value smaller than the first predetermined amount (for example, a radius of 35 mm or less), the first inertia calculation means E1 is executed once to calculate the inertia Ja, and at the same time, the second inertia calculation is performed. Inertia Jb is calculated by means E2, and the difference between the two is compared. When the difference between Ja and Jb is very large, it may be determined that the paper tube diameter information is different from the actual one. Thereby, the correct paper tube diameter can be calculated.

  In addition, by storing the information of the roll sheet in which information is not stored in this manner in the sheet data storage unit P6, when the user sets the same roll sheet again in the sheet conveying device, the roll sheet The paper tube diameter can be set to a correct value. For example, there is a method for determining whether or not the roll sheets are the same, for example, by having the user input whether or not the roll sheets are the same when setting the roll sheets.

  For users who are demanding high print quality, it is better to increase the frequency of calculating the inertia by the first inertia calculation means E1 than the second inertia calculation means E2 in which an error is likely to occur in the inertia. . Whether or not the user is demanding high print quality can be determined by determining the print mode stored in the print information storage unit P4. As described above, in this embodiment, the print mode is divided into four stages. In print mode 4, the highest-definition printing can be performed, and “highest” is displayed on the panel. Hereinafter, the printing mode 3 is displayed as “beautiful”, the mode 2 is displayed as “standard”, and the mode 1 is displayed as “fast”. That is, when the print mode is high, it is better to increase the frequency of inertia calculation by the first inertia calculation means E1.

  As another method for knowing whether or not the user is demanding high print quality, there is a method for judging based on the type of fed sheet. As described above, the sheet level is determined in three stages depending on the type of the sheet. The higher the sheet level, the higher the reproducibility of the ink dot diameter, and the higher the precision printing is possible. That is, when the seat level is high, it is better to increase the inertia calculation frequency by the first inertia calculation means E1.

  In addition, if there is a method that can be used as a determination as to whether or not the user is seeking a high print quality, a determination may be made to increase the frequency of inertia calculation by the first inertia calculation means E1 based on the method. Good.

  8 to 12 show flowcharts of the printing operation in the printer of this embodiment. FIG. 8 is a flowchart for determining which inertia calculation means E1, E2 measures the inertia according to the print mode. When the roll sheet is fed to the sheet conveying apparatus (S001), the radius of the roll sheet is detected from the rotation amount ratio between the conveyance encoder 10 and the sheet feeding encoder 4. Further, the paper width is detected by detecting both ends of the sheet with an optical sensor movable in the main scanning direction (S002). Thereafter, the print mode stored in the print information storage unit is read (S003). When the print mode is “fine” or higher (S004), the first inertia calculation means E1 calculates the inertia of the roll sheet (S005). If the print mode is less than “pretty”, the inertia of the roll sheet is calculated by the second inertia calculation means E2 (S006). When the calculation of the inertia is completed, as described above, the paper feed motor 6 is controlled according to the calculated inertia value so that a desired tension is applied to the roll sheet during printing. Note that the sheet conveying apparatus may include a memory (determination unit) in which a program for performing processing as illustrated in FIG. 8 is stored.

  For users who require high print quality, it is necessary to further improve the sheet conveyance accuracy. In the flowchart shown in FIG. 8, which inertia calculation means E <b> 1, E <b> 2 calculates inertia is switched according to the type of print mode. That is, when the user is demanding high print quality, the inertia is calculated by the first inertia calculating means E1 in order to improve the sheet conveyance accuracy, and in other cases, the second is calculated in order to improve the throughput. The inertia calculation means E2 calculates the inertia.

  That is, the inertia calculation means E1 and E2 are switched appropriately so that the first inertia calculation means E1 for directly calculating the inertia from the rotational movement of the roll sheet by driving the paper feed motor 6 is executed only when necessary. . Thereby, the conveyance accuracy can be improved while suppressing a decrease in throughput.

  FIG. 9 is a flowchart for determining which inertia calculation means E1, E2 calculates inertia according to the paper type of the roll sheet. When the roll sheet is fed to the sheet conveying device (S101), the roll sheet radius and paper width are detected (S102). Thereafter, the sheet mode (information such as sheet type) stored in the sheet data storage unit P6 is read (S103). When the sheet mode is “3”, that is, a high-quality sheet type (S104), inertia is calculated by the first inertia calculation means E1 (S105). If the sheet mode is not “3”, inertia is executed by the second inertia calculation means E2 (S106). When the inertia calculation is completed, as described above, the paper feed motor 6 is controlled in accordance with the calculated inertia value so that a desired tension is applied during printing. Note that the sheet conveying apparatus may include a memory (determination unit) in which a program for performing processing as illustrated in FIG. 9 is stored.

  In this way, depending on the type of the roll sheet, which inertia calculation means E1, E2 calculates the inertia is switched. Thus, when using a high-quality sheet, the first inertia calculating unit is used for improving the conveyance accuracy, and in other cases, the second inertia calculating unit is used for improving the throughput. Thereby, the conveyance accuracy can be improved while suppressing a decrease in throughput.

  FIG. 10 is a flowchart for determining which inertia calculation means E1, E2 calculates inertia according to temperature and humidity. When the roll sheet is fed (S201), the radius and paper width of the roll sheet are detected (S202). Thereafter, the temperature and humidity are detected by the temperature / humidity detector P5 (S203). For example, when the temperature is 30 ° C. or higher and the humidity is 80% or higher (S204), the inertia of the roll sheet is calculated by the first inertia calculating means E1 (S205). When the temperature is less than 30 ° C. or the humidity is less than 80%, the inertia is calculated by the second inertia calculation means E2 (S206). When the calculation of the inertia is completed, as described above, the paper feed motor 6 is controlled in accordance with the inertia value so as to apply a desired tension during printing. Note that the sheet conveying apparatus may include a memory (determination unit) in which a program for performing processing as illustrated in FIG. 10 is stored.

  If the roll sheet absorbs moisture due to environmental changes such as temperature and humidity, the density of the roll sheet may deviate from the assumed value. If the density deviates from the assumed value, an error occurs in the inertia value calculated based on the expression (10) by the second inertia calculating means E2, and the torque control of the paper feeding motor 6 controlled based on the error also includes an error. Therefore, there is a possibility that improvement in sheet conveyance accuracy cannot be expected. In the flowchart shown in FIG. 10, when the temperature and humidity of the roll sheet exceed predetermined values, the inertia of the roll sheet is calculated by the first inertia calculation means E1. That is, in an environment where the density of the roll sheet is likely to deviate from the assumed value, the inertia calculation accuracy is improved using the first inertia calculation means E1. In other cases, the second inertia calculation means E2 is used to improve the throughput. Thereby, the conveyance accuracy can be improved while suppressing a decrease in throughput.

  FIG. 11 is a flowchart for determining which inertia calculation means E1, E2 calculates the inertia according to the radius of the roll sheet. When the roll sheet is fed (S301), the radius and paper width of the roll sheet are detected (S302). For example, when the radius is 45 mm or more (S303), the inertia of the roll sheet is calculated by the first inertia calculation means E1 (S304). Thereafter, the sheet feeding motor 6 is driven to operate the sheet feeding roller, and the angular acceleration θ ″ of the roll sheet is calculated (S305). If the radius is less than 45 mm, the second inertia calculating unit E2 performs the roll sheet. (S306) When the calculation of the inertia is completed, the paper feed motor 6 is controlled in accordance with the calculated inertia value so as to apply a desired tension during printing as described above. The sheet conveying apparatus may include a memory (determination unit) in which a program for performing processing as illustrated in FIG. 11 is stored.

  When the radius of the roll sheet is large, the measurement accuracy of the radius may be reduced due to disturbance or the like depending on the method of measuring the radius of the roll sheet. If an error occurs in the radius, an error occurs in the inertia value calculated based on the equation (10) by the second inertia calculation means E2, and the paper feed motor 6 is controlled based on the error. There is a possibility that the improvement of the transport accuracy that has been expected cannot be expected. In the free chart shown in FIG. 11, when the radius of the roll sheet exceeds the first predetermined value, the inertia of the roll sheet is calculated by the first inertia calculation means E1. That is, when the measured value of the radius of the roll sheet is likely to deviate from the assumption, the inertia calculation accuracy is improved by using the first inertia calculation means E1. In other cases, the second inertia calculation means E2 is used to improve the throughput. Thereby, the conveyance accuracy can be improved while suppressing a decrease in throughput.

  FIG. 12 is a flowchart for determining whether to perform an inertia measurement operation in the vicinity of the core and determining a paper tube. When the roll sheet is fed (S401), the radius and paper width of the roll sheet are detected (S402). When the radius is less than 35 mm (S403), the first inertia calculation means E1 calculates the inertia Ja of the roll sheet (S404). Subsequently, the inertia Jb of the roll sheet is calculated by the second inertia calculating means E2 (S405). If Ja and Jb are compared and if they are substantially the same (S406), the calculation of the inertia is terminated, and the paper feed motor 6 is controlled in accordance with the inertia so as to apply a desired tension during printing. If there is a difference between Ja and Jb that exceeds a predetermined value, the paper tube diameter of the sheet data storage unit P6 is updated (S407). If the radius is 35 mm or more, the inertia of the roll sheet is calculated by the second inertia calculation means E2 (S408), and the paper feed motor 6 is controlled based on the value. Note that the sheet conveying apparatus may include a memory (determination unit) in which a program for performing processing as illustrated in FIG. 12 is stored.

  When the paper tube diameter of the roll sheet set by the user is not known, when the second inertia calculation means E2 tries to calculate the roll sheet inertia, the sheet is conveyed by the torque control of the paper feed motor 6 based on the inertia. There is a concern that the accuracy will decrease. In particular, when the remaining amount of the roll sheet is reduced and the radius of the roll sheet is in the vicinity of the core, the influence is likely to be significant. In the flowchart shown in FIG. 12, when the radius of the roll sheet detected by the radius measuring means for measuring the radius of the roll sheet becomes equal to or smaller than the second predetermined value, the first inertia calculating means E1 Calculate inertia. That is, the inertia is calculated by the first inertia calculation means E1 only when an error is likely to occur in the inertia calculation by the second inertia calculation means E2 and there is a concern about a decrease in the conveyance accuracy. As a result, the first inertia calculation means E1 can be executed only when necessary, so that the conveyance accuracy can be improved while suppressing a decrease in throughput.

  Note that the flowchart shown in FIG. 12 can be implemented in combination with the flowchart shown in FIG. 11 or can be implemented alone. When combined with the flowchart shown in FIG. 11, when the radius of the roll sheet exceeds the first predetermined value and becomes equal to or smaller than the second predetermined value smaller than the first predetermined value, the first The inertia of the roll sheet may be calculated by the inertia calculating means E1.

(Second Embodiment)
In the first embodiment, the case where the first inertia calculation unit E1 and the second inertia calculation unit E2 are switched based on a certain threshold value is shown. However, the first inertia calculation unit E1 is based on a plurality of threshold values. And the second inertia calculation means E2.

  FIG. 13 shows a flowchart of the printing operation in the printer of this embodiment. FIG. 13 shows a case where the same image is continuously printed, and is a flowchart for determining which inertia calculation means E1, E2 calculates inertia according to the print mode. When the roll sheet is fed (S501), the radius of the roll sheet is detected from the ratio of the rotation amounts of the transport encoder 10 and the feed encoder 4, and both ends of the sheet are detected by optical sensors that can move in the main scanning direction. Is detected to detect the paper width (S502). Thereafter, the print mode stored in the print information storage unit is read (S503). When the print mode is “3” (“clean”) or more (S504), the inertia of the roll sheet is calculated by the first inertia calculation means E1 before each printing (S505). If the print mode is less than “3”, it is next determined whether or not the print mode is “2” (“standard”) or more (S506). The inertia of the roll sheet is calculated by the first inertia calculation means E1 only before (S507). If the print mode is less than “2”, the inertia of the roll sheet is calculated by the second inertia calculation means E2 (S508). When the calculation of the inertia is completed, as described above, the paper feed motor 6 is controlled in accordance with the inertia so as to apply a desired tension during printing. Note that the sheet conveying apparatus may include a memory (determination unit) in which a program for performing processing as illustrated in FIG. 13 is stored.

  In this flowchart, the print mode is divided into a plurality of threshold values, and processing to determine which inertia calculation means E1, E2 is used according to the plurality of threshold values. In addition, even with the sheet type, radius, temperature, humidity, and the like as shown in the first embodiment, the operation can be similarly performed by dividing into a plurality of threshold values. According to the present embodiment, since the first inertia calculation unit E1 can be executed more finely, the conveyance accuracy can be improved while suppressing a decrease in throughput.

(Third embodiment)
In the first and second embodiments, the execution timing of the first inertia calculation means E1 is determined by a single factor. However, the execution timing of the first inertia calculation means E1 is determined by combining a plurality of factors. You can also FIG. 14 is a table for determining the execution timing of the first inertia calculation means E1 of the printer of this embodiment from the print mode and the roll sheet radius value. This table is divided into three regions Z1, Z2, and Z3 according to the print mode and the roll sheet radius value. This table is stored in the calculation unit P2.

  FIG. 15 shows a flowchart of the printing operation in the printer of this embodiment. FIG. 15 is a flowchart for determining which inertia calculation means E1, E2 calculates inertia according to the print mode and the value of the radius of the roll sheet, when the same image is printed continuously. . When the roll sheet is fed (S601), the roll sheet radius is detected from the ratio of the rotation amounts of the transport encoder 10 and the paper feed encoder 4, and both ends of the sheet are detected by an optical sensor that can move in the main scanning direction. Then, the paper width is detected (S602). Thereafter, the print mode stored in the print information storage unit is read (S603). Then, the print mode and the radius of the roll sheet are compared with a table (see FIG. 14) stored in the calculation unit P2, and the current area ZX determined from the print mode and the roll sheet radius is any area in the table. It is determined whether it belongs to Z1 to Z3 (S604). The sheet conveying apparatus may include a table (determination unit) in which a table as illustrated in FIG. 14 and a program for performing processing as illustrated in FIG. 15 are stored.

  When the current area ZX belongs to the area Z1 in the table (S605), the inertia of the roll sheet is calculated by the first inertia calculating means E1 before each printing (S606). If the current area ZX does not belong to the area Z1 in the table, it is next determined whether or not the current area ZX belongs to the area Z2 in the table (S607). If it belongs to Z2, the inertia of the roll sheet is calculated by the first inertia calculation means E1 only before printing the first sheet (S608). If the current area ZX does not belong to the area Z2 in the table, the inertia of the roll sheet is calculated by the second inertia calculation means E2 (S609). When the calculation of the inertia is completed, as described above, the paper feed motor 6 is controlled in accordance with the inertia so as to apply a desired tension during printing.

  The flowchart shown in FIG. 15 shows a case where these values are divided into a plurality of areas using the printing mode and the roll sheet radius, and the inertia calculation means E1, E2 are switched according to the areas. However, as shown in the first embodiment, the inertia calculation means E1 and E2 may be similarly switched using a plurality of elements such as the sheet type, temperature, and humidity.

  According to the present embodiment, it is possible to determine whether or not it is necessary to calculate the inertia of the roll sheet by the first inertia calculating unit E1 using a plurality of elements. Therefore, the first inertia calculation means E1 can be executed only when it is required more finely. In other cases, the second inertia calculation means E2 is used while suppressing a decrease in throughput. The conveyance accuracy can be improved.

M sheet 1 roll sheet 6 paper feed motor (first drive source)
12 Conveyor motor (second drive source)
P3 control unit E1 first inertia calculation means E2 second inertia calculation means

Claims (14)

A sheet conveying apparatus that pulls out a sheet from a roll sheet wound in a roll shape and conveys the sheet,
A first driving source for generating a driving force for rotating the roll sheet around a rotation axis;
A second driving source for generating a driving force for pulling the sheet drawn from the roll sheet and conveying the sheet;
First inertia calculation means for calculating a moment of inertia about the rotation axis of the roll sheet by measuring a rotational movement of the roll sheet in a state where the second drive source is operated;
Second inertia calculating means for calculating the moment of inertia about the rotation axis of the roll sheet based on the width, density and radius of the roll sheet;
A determination unit that determines which of the first inertia calculation unit and the second inertia calculation unit calculates the moment of inertia about the rotation axis of the roll sheet;
A control unit that controls the first drive source so that a predetermined tension acts on the sheet being conveyed based on the moment of inertia calculated by the first inertia calculating unit or the second inertia calculating unit. A sheet conveying device.   The sheet conveying apparatus according to claim 1, wherein the determination unit determines whether to use the first inertia calculation unit or the second inertia calculation unit according to a type of the roll sheet. It has a temperature / humidity detector that measures temperature and humidity,
When the temperature and humidity measured by the temperature / humidity detection unit exceed a predetermined value, the determination unit determines the moment of inertia around the rotation axis of the roll sheet to the first inertia calculation unit. The sheet conveying apparatus according to claim 1, which is calculated. Radius measuring means for measuring the radius of the roll sheet,
When the radius of the roll sheet measured by the radius measurement unit exceeds a predetermined first predetermined value, the determination unit sends the first inertia calculation unit around the rotation axis of the roll sheet. The sheet conveying apparatus according to claim 1, wherein the moment of inertia is calculated.   When the radius of the roll sheet measured by the radius measuring unit becomes equal to or smaller than a second predetermined value that is smaller than the first predetermined value, the determination unit causes the first inertia calculating unit to transfer the roll to the first inertia calculating unit. The sheet conveying apparatus according to claim 4, wherein a moment of inertia about the rotation axis of the sheet is calculated. Radius measuring means for measuring the radius of the roll sheet,
When the radius of the roll sheet measured by the radius measuring unit is equal to or less than a second predetermined value, the determination unit sends the inertia moment about the rotation axis of the roll sheet to the first inertia calculating unit. The sheet conveying apparatus according to claim 1, wherein: A radius measuring means for measuring the radius of the roll sheet, and a temperature and humidity detector for measuring temperature and humidity,
The determination unit determines the moment of inertia about the rotation axis of the roll sheet according to at least two values of temperature and humidity, the type of the roll sheet, and the radius of the roll sheet. The sheet conveying apparatus according to claim 1, wherein it is determined which of the calculating means and the second inertia calculating means calculates.   The determination unit causes the second inertia calculation unit to calculate the inertia moment when the first inertia calculation unit does not calculate the moment of inertia around the rotation axis of the roll sheet. The sheet conveying apparatus according to any one of the above. The first inertia calculating means has an encoder for measuring a rotation angle of the roll sheet,
The first inertia calculating means is based on a rotation angle of the roll sheet at a predetermined time when a constant current is passed through the second drive source and a torque coefficient of the second drive source. The sheet conveying apparatus according to claim 1, wherein a moment of inertia of the roll sheet is calculated.   An image forming apparatus comprising: the sheet conveying apparatus according to claim 1; and an image forming unit that forms an image on a sheet fed from the sheet conveying apparatus.   The determination unit calculates the moment of inertia about the rotation axis of the roll sheet according to the type of image forming mode indicating the quality of image formation by the image forming unit, and the second inertia calculating unit and the second inertia calculating unit. The image forming apparatus according to claim 10, wherein it is determined which of the inertia calculation means calculates.   12. The image forming apparatus according to claim 11, wherein the image forming apparatus has at least two image forming modes in which a single feed amount of the sheet by the second driving source is different.   The determination unit causes the first inertia calculation unit to calculate an inertia moment about the rotation axis of the roll sheet in an image forming mode in which a single feed amount of the sheet is relatively large. 12. The image forming apparatus according to 12. 2. The sheet conveying apparatus according to claim 1, an image forming unit that forms an image on a sheet sent from the sheet conveying apparatus, a radius measuring unit that measures a radius of the roll sheet, and a temperature and humidity that measures temperature and humidity. A detection unit;
The determination unit includes the temperature and humidity, the type of the roll sheet, the radius of the roll sheet, and at least two values among the types of image forming modes indicating the quality of image formation by the image forming unit. An image forming apparatus that determines which of the first inertia calculation unit and the second inertia calculation unit calculates the moment of inertia of the roll sheet around the rotation axis.