JP5907604B2 - Sheet transport device - Google Patents

Description

  The present invention relates to a sheet conveying apparatus that pulls out and conveys a sheet from a roll sheet in which the sheet is wound in a roll shape.

  Conventionally, paper is rolled from roll paper (hereinafter referred to as “roll body” where the paper is wound in roll form, and “sheet body” is the portion pulled out from the roll body). In a sheet conveying apparatus that pulls out and conveys, improvement in conveying accuracy is required. Therefore, by applying a constant tension between the roll body and the pair of transport rollers that pulls out the sheet body from the roll body, it is possible to remove and correct misalignment, slack, skew, curl, etc. that adversely affect print quality. Has been done.

  As a mechanism for applying a constant tension to such a sheet body, a mechanism disclosed in Patent Document 1 is known. This mechanism includes a first motor that provides a driving force for rotating the roll body, a second motor that provides a driving force for driving the conveyance driving roller, and a relationship between a load and a driving speed that act on the first motor in advance. Load measuring means for measuring By giving an interpolation output based on the measurement result of the load measuring means and the driving speed of the second motor to the first motor, a desired tension is applied to the sheet body when the sheet body is conveyed at a certain conveyance speed. It has become.

JP 2009-242048 A

  However, in the method described in Patent Document 1, the tension is adjusted using the relationship between “the current to the sheet feeding motor (first motor)” and “the predetermined speed of the sheet member”. That is, in this method, the moment of inertia around the rotation axis (hereinafter referred to as “inertia”) generated when the roll body rotates is not taken into consideration. For this reason, during acceleration / deceleration of the sheet feeding motor, there is a possibility that the tension applied to the sheet member may deviate from a predetermined value due to the influence of inertia, and there is a concern that the conveyance accuracy may be deteriorated.

  Therefore, in order to maintain the conveyance accuracy, it is necessary to apply control to keep the tension constant by applying rotational torque corresponding to the fluctuation of inertia to the roll body. To that end, it is necessary to calculate the inertia of the roll body There is.

  By the way, as a method of calculating inertia, there are a method of calculating from kinetic energy, a method of calculating from the equation of motion, and the like, but each calculation method has advantages and disadvantages. For this reason, depending on the calculation method, there is a case where throughput is lowered in order to accurately calculate the inertia. On the other hand, it is possible to calculate the inertia without reducing the throughput, but in that case, maintaining the conveyance accuracy becomes a problem.

  SUMMARY An advantage of some aspects of the invention is that it provides a sheet conveying apparatus that maintains high conveyance accuracy while minimizing a decrease in throughput.

In order to achieve the above-described object, a sheet conveying apparatus according to the present invention includes a sheet feeding motor that rotates and rolls a sheet of paper wound in a roll shape, and a conveyance that conveys the sheet drawn from the rolled sheet in a predetermined direction A roller, a conveyance motor that rotationally drives the conveyance roller, and a control unit that controls driving of the paper feed motor and the conveyance motor . In one aspect, the control unit detects a current value of the conveyance motor, a calculation unit that calculates the moment of inertia of the roll paper, and whether the calculated moment of inertia value by the calculation unit is within a predetermined range. And a recalculation unit that recalculates the moment of inertia of the roll paper when the determination unit determines that the calculated moment of inertia value is outside a predetermined range . When the current value detected by the current detection unit is within a predetermined range, it is determined that the calculated moment of inertia value is within the predetermined range, and the control unit determines the calculated moment of inertia value by the calculation unit or the recalculation unit. Based on this, the torque generated by the paper feed motor is controlled to generate a predetermined tension on the paper between the transport roller and the roll paper. In another aspect, the control unit calculates a moment of inertia of the roll paper using the first calculation method that does not require driving of the paper feed motor, and the moment of inertia calculated by the calculator is within a predetermined range. And a second calculation method that requires driving of the paper feed motor when the determination means does not determine that the calculated moment of inertia value is outside the predetermined range. Re-calculating means for re-calculating the moment of inertia of the roll paper, and when the determining means determines that the calculated moment of inertia is outside a predetermined range, the control section Based on the calculated value, when the determining means determines that the calculated moment of inertia is outside the predetermined range, the generated torque of the paper feeding motor is calculated based on the calculated recalculated moment of inertia. And your, characterized in that to generate a predetermined tension in the sheet between the conveying roller and the roll paper.

  As described above, according to the present invention, since the inertia moment (inertia) of the roll paper is calculated and the reliability of the calculated value is determined, it is possible to always obtain the calculated value of the inertia with high accuracy. In addition, since the inertia recalculation is limited only when it is determined that the reliability is low, the influence on the throughput is also limited. In this way, it is possible to provide a sheet conveying apparatus that maintains high conveyance accuracy while minimizing a decrease in throughput.

1 is a schematic perspective view illustrating an embodiment of a printer including a sheet conveying device of the present invention. FIG. 3 is a block diagram illustrating a configuration of a control system of the sheet conveying apparatus of the present embodiment. It is the schematic for demonstrating the detection method of the radius of a roll body. 6 is a graph illustrating a sheet conveyance speed and a generated torque of a sheet feeding motor. It is the schematic showing the relationship between the generated torque of a paper feed motor, and the torque which acts on a roll body. It is a graph which shows the relationship between the radius of a roll body, and torque. It is a conceptual diagram for demonstrating the 1st inertia calculation method. It is a conceptual diagram for demonstrating the 2nd inertia calculation method. It is a flowchart which shows the 1st determination method of an inertia calculated value. 6 is a graph illustrating a relationship between a duty value of a conveyance motor and a tension acting on a sheet member. It is a flowchart which shows the 2nd determination method of an inertia calculated value.

  Embodiments of the present invention will be described below with reference to the drawings. In this specification, the sheet conveying apparatus of the present invention is described as an example applied to a printer. However, the present invention is not limited to this, and for example, a roll paper such as a copying machine or a facsimile is used. Applicable to various devices used.

  FIG. 1 is a schematic perspective view showing an embodiment of a printer provided with a sheet conveying apparatus of the present invention.

  The printer 20 according to the present embodiment includes a sheet conveying device 30 that pulls out and conveys a sheet from a roll sheet in which the sheet is wound in a roll shape. Hereinafter, a portion where the paper is wound in a roll shape is referred to as a “roll body”, and a portion pulled out from the roll body is referred to as a “sheet body”.

  The sheet conveying device 30 includes a paper feed unit 3 that rotatably supports a spool 2 that holds the roll body 1, and a paper feed motor 6 that rotationally drives the roll body 1 via a gear 5 provided on the spool 2. Have. In addition, the sheet conveying device 30 cooperates with the opposing pinch roller 9 to convey the conveying roller 8 that conveys the sheet body M drawn from the roll body 1 in a predetermined direction (sub-scanning direction) H, and the conveying roller 8. It has a conveyance roller (not shown in FIG. 1) that rotates.

  On the downstream side of the conveying roller 8 in the sub-scanning direction H, a printing unit 7 including an inkjet print head and a carriage on which the print head is mounted is provided. In addition, a platen 13 that holds the sheet body M in a substantially planar shape by being in contact with the back surface of the sheet body M during the printing operation is provided at a position facing the printing unit 7. The printing operation is performed by causing the carriage to reciprocate in the main scanning direction intersecting the sub-scanning direction H by a drive mechanism such as a motor, and the print head to eject ink onto the sheet member M. During this printing operation, the conveyance operation of the sheet body M is stopped, and when printing for one line is completed by the printing unit 7, the sheet conveyance device 30 conveys the sheet body M by a predetermined amount, and then again for one line. Is printed. Thus, in this embodiment, every time the sheet body M is intermittently conveyed, printing for each line is performed.

  Next, the configuration of the control system of the sheet conveying apparatus of the present embodiment will be described with reference to FIG. FIG. 2 is a block diagram illustrating a configuration of a control system of the sheet conveying apparatus of the present embodiment.

  The sheet conveying apparatus 30 of the present embodiment includes a control unit P3 that controls driving of the paper feeding motor 6 and the conveying motor 12, a data storage unit P6 that stores various data, and current values of the paper feeding motor 6 and the conveying motor 12. Current detectors 14 and 15 for detecting the current.

  The data storage unit P6 stores the density and paper tube diameter for each paper type as data, and when paper type information is selected on an operation panel (not shown) or the like, the density and paper tube diameter of the corresponding paper type are selected. Output information. Information such as the torque coefficient of the paper feed motor 6 is also stored and output as necessary.

  The control unit P3 includes a main control unit 110, a paper feed motor control unit 120, and a transport motor control unit 130, and also includes a CPU, a ROM, a RAM, a motor driver, and the like (not shown). .

  The paper feed motor control unit 120 controls the drive of the paper feed motor 6 based on the detection result of the physical quantity related to the rotation of the roll body 1 by the paper feed encoder (roll paper rotation detection unit) 4 provided in the spool 2. . Further, the transport motor control unit 130 performs drive control of the transport motor 12 based on the detection result of the physical quantity related to the rotation of the transport roller 8 by the transport encoder (transport roller rotation detection unit) 10 provided on the transport roller 8. .

  The main control unit 110 includes a roll size detection unit P1, a calculation unit P2, a determination unit P7, and a recalculation unit P8.

  The roll size detection unit P1 has a function of detecting the radius of the sheet body 1. Here, with reference to FIG. 3, the detection method of the radius of the roll body 1 by the roll size detection part P1 is demonstrated. FIG. 3 is a diagram for explaining a method of detecting the radius of the roll body 1, and is a schematic side view showing the roll body 1 and the transport roller 8.

The rotation angle of the spool 2 detected by the paper feed encoder 4 (that is, the rotation angle of the roll body 1) when the conveyance roller 8 rotates by a predetermined amount is θ ₀ , and the rotation angle of the conveyance roller 8 detected by the conveyance encoder 10 Is θ ₁ and the radius of the transport roller 8 is R ₁ . Further, it is assumed that the sheet body M is strongly sandwiched between the transport roller 8 and the pinch roller 9 and transported without slipping, and the sheet body M has no slack. At that time, the radius R ₀ of the roll body 1 is
R ₀ = R ₁ (θ ₁ / θ ₀ ) (1)
It is represented by

  The roll size detection unit P1 further has a function of detecting the paper width B. The print unit 7 moves in the main scanning direction, and an optical sensor (not shown) provided in the print unit 7 crosses each end of the sheet, so that the end position of the sheet is grasped. Then, the paper width B is calculated from the position information of both ends.

  The calculation unit P2 calculates the moment of inertia (hereinafter referred to as “inertia”) of the roll body 1 based on the paper information output from the data storage unit P6 and the paper information detected by the roll size detection unit P1. Done. The calculated inertia (inertia calculated value) is output from the calculation unit P2 to the determination unit P7.

  In the determination unit P7, the reliability of the inertia calculated value input from the calculation unit P2 is determined. If it is determined that the reliability is low, the recalculation unit P8 performs recalculation of the inertia. Detailed operations of the determination unit P7 and the recalculation unit P8 will be described later.

  In addition, the main control unit 110 has a function of simultaneously giving commands to the paper feed motor control unit 120 and the transport motor control unit 130 in order to realize correlation driving between the paper feed motor 6 and the transport motor 12. ing. Accordingly, the sheet can be conveyed in a state where the predetermined tension F is generated on the sheet body M. This tension F acts as a back tension on the transport roller 8. Therefore, by controlling the tension F to be constant, the slip amount between the transport roller 8 and the sheet member M can be kept constant, and the sheet member M can be transported with high accuracy.

  Next, with reference to FIGS. 4 and 5, a specific correlation operation between the paper feed motor 6 and the transport motor 12 will be described. FIG. 4 is a graph showing the sheet conveyance speed and the torque generated by the sheet feeding motor 6. FIG. 5 is a schematic diagram showing the relationship between the torque generated by the paper feed motor 6 and the torque acting on the roll body 1.

  As described above, in order to convey the sheet body M with high accuracy, a constant tension is applied to the sheet body M by controlling the torque generated by the sheet feeding motor 6 (hereinafter referred to as “sheet feeding motor torque”). F needs to act. Therefore, regarding the paper feed motor torque for generating the predetermined tension F, in the case of the constant speed section (A3, A7), the acceleration section (A2, A6), and the deceleration section (A4, A8) shown in FIG. Separately described.

First, the case of the constant velocity section (A3, A7) will be described. The paper feed motor torque for producing a desired tension F on the sheet member M and T _a, when the torque applied to the roll body 1 (the spool 2) and T _roll, constant speed section (A3, A7) in T _a = T _roll . Therefore, if the radius of the roll body 1 at this time is R _0, the paper feed motor torque T _a at constant speed section (A3, A7) is
T _a = T _roll = F · R ₀ (2)
It is represented by If the paper transport direction is positive, the tension F is a force acting in the negative direction, and therefore the paper feed motor torque _Ta also works in the negative direction. In the following, similarly, the sheet conveyance direction is positive.

Next, the feed motor torques T _b and T _c that generate a predetermined tension F in the acceleration section (A2, A6) and the deceleration section (A4, A8) will be described. When the inertia of the roll body 1 is J, the acceleration of the sheet body M is a, and the radius of the roll body 1 is R ₀ , the torque T _i based on the inertia J of the roll body 1 is
T _i = −J · a / R ₀ (3)
It is represented by Here, the acceleration a of the sheet body M takes a positive value during acceleration, and takes a negative value during deceleration. The torque T _roll acting on the spool 2 in the acceleration (deceleration) section is the sum of the torque T _i based on the inertia and the paper feed motor torque T _b (T _c ) in the acceleration (deceleration) section. That is,
T _roll = T _b + T _i = T _b − (J · a / R ₀ ) (4)
T _roll = T _c + T _i = T _c − (J · a / R ₀ ) (5)
Given in. Therefore, Equation (2), Equation (4), and from equation (5), a paper feed motor torque T _b in the acceleration section, the paper feed motor torque T _c in the deceleration section, respectively given by: It is done. That is,
T _b = T _roll −T _i = (F · R ₀ ) + (J · a / R ₀ ) (6)
T _c = T _roll −T _i = (F · R ₀ ) + (J · a / R ₀ ) (7)
It becomes.

In the equations (6) and (7), it is desirable that the tension F is constant as described above. Therefore, assuming that the acceleration a of the sheet M is always constant as the acceleration of the conveying roller 8, the sheet feeding motor torque T _b (T _c ) in the acceleration (deceleration) section is in accordance with the inertia J and the radius R _0. It turns out that it needs to be controlled.

Next, with reference to FIG. 6, the relationship between the inertia J and the radius R ₀ and the paper feed motor torque T _b in the acceleration section will be described. FIG. 6 shows a torque T _i based on the inertia J of the roll body 1 in the acceleration section (a negative value from the expression (3) in the acceleration section), the feed motor torque T _b, and the load torque T _roll acting on the spool 2. Is a graph showing a radius R ₀ . The horizontal axis is the radius and the vertical axis is the torque.

As can be seen from the equation (2), the load torque T _roll acting on the spool 2 increases in proportion to the radius R ₀ in order to keep the back tension F constant. Further, since the inertia J is proportional to the square of the radius of the roll body 1, the torque T _i based on the inertia J is also proportional to the radius from the equation (3). Therefore, from equation (6), as shown in FIG. 6, torque control corresponding to the radius R ₀ is also performed for the paper feed motor torque T _b in the acceleration section. Actually, since the change in the tension F is allowed within a range that does not affect the conveyance accuracy, the feed motor torque T _b in the acceleration section is such that the load torque T _roll is lower _{than the} predetermined upper limit value T _roll1. It is controlled to be in a range up to T _roll2 .

From the above description, it can be seen that control in consideration of the inertia J is indispensable for controlling the feed motor torque T _b (T _c ) in the acceleration (deceleration) section. In order to calculate the inertia J, the calculation unit P2 uses a plurality of (two in the present embodiment) inertia calculation methods. Hereinafter, the inertia calculation method of the calculation unit P2 will be described with reference to FIGS. FIG. 7 is a conceptual diagram for explaining the first inertia calculation method, and FIG. 8 is a conceptual diagram for explaining the second inertia calculation method.

The first inertia calculation method is a method for calculating the inertia J of the roll body 1 based on a physical quantity related to driving of the paper feed motor 6. The inertia J of the roll body 1 is determined from the angular acceleration θ ″ of the roll body 1, the current I flowing through the paper feed motor 6, and the torque coefficient K _t of the paper feed motor 6.
J = (K _t · I) / θ ”(8)
And is calculated by the calculation unit P2 based on the equation (8). The angular acceleration θ ″ is obtained by second-order differentiation of the rotation angle θ detected by the paper feed encoder 4 with respect to time. The current I is detected by the current detection unit 14 of the paper feed motor 6 and the torque coefficient K _t is stored in the data storage unit P6.

On the other hand, the second inertia calculation method is a method for calculating the inertia based on the paper information stored in the data storage unit P6 and the paper information obtained from the roll size detection unit P1. Inertia J of the roll body 1, and density ρ of the sheet, and Kamikan径r _c, the radius R ₀ of the roll body 1, and a sheet width B,
^{_{J = πρB (R 0 2 -r}} c 2) 2/8 (9)
And is calculated by the calculation unit P2 based on the equation (9). Here, the density ρ and Kamikan径r _c of the paper is information stored in advance in the data storage unit P6, the plurality of information on the paper type is stored, which is input through the operation panel or printer driver Based on the paper type information, information to be adapted is sequentially called up. Further, the radius R ₀ and the sheet width B of the roll body 1 are information detected by the roll size detection unit P1 as described above.

Although the above-described first inertia calculation method can accurately calculate the inertia, if it is performed before every printing, there is a problem that the throughput is lowered. Therefore, when the once calculated inertia J with a first inertia calculation method, a conversion equation of Equation (9) ρ = 8J / ( πB (R 0 2 -r c 2) 2) (10)
From this, the density ρ is calculated. Then, the value can be temporarily stored in the data storage unit P6, and the inertia can be calculated by the second inertia calculation method (that is, the equation (9)) according to the subsequent change in the radius _R0 .

However, in the second inertia calculation method, it is not necessary to drive the paper feed motor, so that there is no demerit of a decrease in throughput, but if the radius R ₀ or the density ρ includes an error, the calculated inertia J May deviate from the actual value. That is, the radius R ₀ obtained from the equation (1) is calculated on the assumption that the sheet body M is transported without slipping on the transport roller 8, and therefore, if the sheet body M slips, R ₀ ≠ R _1. (Θ ₁ / θ ₀ ), which includes an error. In addition, if the paper absorbs moisture in a high humidity environment, an error may occur between the density ρ of the paper stored in the data storage unit P6 and the actual value. As described above, since the density ρ and the radius R ₀ may include an error, it is important to accurately grasp the reliability of the calculated inertia.

  Therefore, in this embodiment, as described above, the determination unit P7 determines the reliability of the inertia calculated by the calculation unit P2. Therefore, when it is determined that the reliability of the calculated inertia is low, the recalculation unit P8 recalculates the inertia. The determination unit P7 uses two determination methods, and the recalculation unit P8 also uses two recalculation methods.

  First, the first determination method of the determination unit P7 will be described with reference to the flowchart shown in FIG.

  As described above, when the inertia of the roll body 1 is calculated in the calculation unit P2 (step S1), the calculated inertia (inertia calculation value) J is output to the determination unit P7.

Here, assuming that the target value of the torque acting on the spool 2 is T _roll , the difference ΔT _roll between the torque target value T _roll and the actually acting torque is the difference ΔJ between the calculated value J of the inertia and the actual value J ′. From the equation (4), it is expressed as follows. That is, torque deviation ΔT _ro
ll
ΔT _roll = (T _b −J · a / R ₀ ) − (T _b −J ′ · a / R ₀ )
= (J'-J) .a / R ₀
= ΔJ · a / R ₀ (11)
It is represented by As described with reference to FIG. 6, even if the actually applied torque is shifted by ΔT _{roll with} respect to the torque target value, if it is in the range from the upper limit value T _roll1 to the lower limit value T _roll2 , It is assumed that control is performed within a range that does not affect the conveyance accuracy. And the tension F is obtained from the equation (2):
F = T _roll / R ₀ (12)
For given, the upper limit value T _Roll1 and a lower limit value T _Roll2 described above can be replaced, respectively to the upper limit value F ₁ and the lower limit value F ₂ tension F.

Further, the tension F applied to the sheet M and the current value (duty value) D of the conveyance motor 12 controlled by PWM (pulse width modulation) are in a proportional relationship as shown in FIG. FIG. 10 is a graph showing the relationship between tension F (vertical axis) and duty value D (horizontal axis). For this reason, the upper limit value F ₁ and the lower limit value F ₂ of the tension F can be replaced with the upper limit value D ₁ and the lower limit value D ₂ of the duty value D of the transport motor 12, respectively.

Thus, the duty value D of the transport motor 12 is used to determine the reliability of the calculated inertia value J (step S2). That is, if the duty value D of the transport motor 12 is within a predetermined range (D ₁ <D <D ₂ ), it is determined that the deviation ΔJ of the calculated inertia value is a range that does not affect the transport accuracy. In this case, the inertia is not recalculated, and the conveyance control is performed based on the calculated inertia value J at that time (step S3). Therefore, since there is no need to recalculate the inertia, the throughput does not naturally decrease.

On the other hand, when the duty value D of the transport motor 12 is outside the predetermined range (D ₁ ≦ D, D ₂ ≦ D), it is determined that the deviation ΔJ of the calculated inertia value is deviated to the extent that the transport accuracy is affected. That is, it is determined that the reliability of the inertia calculated value J is low. Therefore, in this case, it is necessary to recalculate the inertia. As shown in FIG. 10, the relationship between the duty value D and the tension F varies depending on the paper type. Therefore, it is possible to set the upper limit value D ₁ and the lower limit value D ₂ to the paper type, to set the upper limit value D ₁ and the lower limit value D ₂ of the most severe determination condition from the upper and lower limit values of all paper types You can also.

  Next, the second determination method of the determination unit P7 will be described with reference to the flowchart shown in FIG. The second determination method is a method for performing determination from information obtained by the paper feed encoder 4 and the transport encoder 10.

  Similar to the first determination method, the calculation unit P2 calculates the inertia of the roll body 1 (step S11), and the calculated inertia (inertia calculation value) J is output to the determination unit P7.

When the deviation between the calculated value J of the inertia and the actual value J ′ is extremely large by the calculation unit P2, the torque deviation ΔT _roll becomes extremely large from the equation (11), and a large positive value is obtained in the acceleration section. Value. That is, the torque acts on the roll body 1 (spool 2) in the positive direction, so that the tension F is not generated. As a result, the roll body 1 is slackened. In the second determination method, the reliability of the inertia is determined using this fact.

That is, first, the linear velocity V ₁ of the conveyance roller 8 and the linear velocity V of the roll body 1 are determined from an angular velocity θ ′ that is a time derivative of the rotation amount θ of each roller detected by the conveyance encoder 10 and the paper feed encoder 4. ₀ is required. Then, the magnitude relation between the linear velocities V ₁ and V ₀ is compared (step S12). If the linear velocity V ₀ of the roll body 1 is equal to or lower than the linear velocity V _{1 of the} conveying roller (V ₁ ≧ V ₀ ), inertia is not recalculated, and conveyance control is performed based on the calculated inertia value J at that time. (Step S13). On the other hand, when the linear velocity V ₀ of the roll body 1 exceeds the linear velocity V ₁ of the conveying roller (V ₁ <V ₀ ), inertia is recalculated (step S14).

  In such a second determination method, the inertia recalculation is performed when the deviation of the calculated inertia value is large enough to affect the conveyance accuracy, so that the conveyance accuracy can be maintained without reducing the throughput as much as possible. .

  Next, two recalculation methods performed in the recalculation unit P8 will be described.

  First, the first recalculation method is the same method as the first inertia calculation method, that is, a method of calculating the inertia J of the roll body 1 based on a physical quantity related to driving of the paper feed motor 6. As described above, this method causes a decrease in throughput, but is limited only when it is determined by the determination unit P7 that the conveyance accuracy is affected, so that the influence on the throughput is minimized. The conveyance accuracy can be maintained.

On the other hand, the second recalculation method is a method in which the inertia calculated value J is corrected and recalculated based on the difference ΔD between the actual duty value D ′ of the transport motor 12 and the target value D. FIG.
As shown, the duty value difference ΔD is proportional to the tension difference ΔF. Further, from the equations (9) and (10), since the tension difference ΔF is proportional to the torque deviation ΔT _roll and the torque deviation ΔT _roll is proportional to the inertia calculated value deviation ΔJ, the duty difference ΔD Is proportional to the deviation ΔJ of the calculated inertia value. That is, ΔD and Δ
By grasping the proportional relationship with J, it is possible to correct the inertia calculation value J by ΔJ according to ΔD and recalculate the inertia. From the graph shown in FIG. 10, the proportional relationship between the difference ΔD in duty value and the difference ΔF in tension is
ΔD = βΔF + ω (13)
It is represented by Here, β and ω are constants obtained experimentally, and have different values depending on the paper type as shown in FIG. In these constants, the friction coefficient of the paper type is dominant, and if the friction coefficient is low, the conveyance roller 8 is likely to slip, and therefore the proportionality constant β of the duty value D of the conveyance motor 12 tends to be small. . By knowing the constants corresponding to β and ω as paper types, ΔJ can be obtained from ΔD according to the paper type selected by the user. Furthermore, since there is no need to operate the paper feed motor as in the first recalculation method, the throughput does not decrease. In this respect, the second recalculation method is more advantageous than the first recalculation method. However, as described above, β and ω in Expression (13) are obtained experimentally and are selectively determined based on the paper information input by the user. For this reason, it should be noted that correction for recalculation is difficult to function for an arbitrary medium prepared by the user, which may affect the conveyance accuracy.

Note that as a method approximate to the second determination method, there is also a method of directly correcting the duty value D ₀ ′ of the paper feed motor 6 so that the duty value D of the transport motor 12 becomes the target value D ′. However, since the radius of the roll body 1 always decreases and the inertia constantly changes, torque control that predicts the inertia change is necessary. Therefore, in reality, it is difficult to generate the optimum tension F on the sheet body M. Therefore, it is desirable to correct the inertia calculated value J as in the second determination method described above.

  As described above, according to the present embodiment, since the inertia moment (inertia) of the roll paper is calculated and the reliability of the calculated value is determined, a highly accurate calculated value of inertia can always be obtained. In addition, since the inertia recalculation is limited only when it is determined that the reliability is low, the influence on the throughput is also limited. In this way, it is possible to maintain the conveyance accuracy with high accuracy while minimizing a decrease in throughput.

6 Feeding motor 8 Conveying roller 12 Conveying motor P3 Control unit

Claims (13)

A paper feed motor that rotationally drives a roll of paper wound in a roll, a transport roller that transports the paper drawn from the roll paper in a predetermined direction, a transport motor that rotationally drives the transport roller, and In a sheet conveying apparatus having a sheet feeding motor and a control unit that controls driving of the conveying motor,
The control unit is
A current detection unit for detecting a current value of the transport motor;
Calculating means for calculating the moment of inertia of the roll paper;
Determining means for determining whether or not the calculated moment of inertia value by the calculating means is within a predetermined range;
Re-calculating means for re-calculating the moment of inertia of the roll paper when the determining means determines that the calculated moment of inertia value is outside a predetermined range;
Have
The determination means determines that the calculated moment of inertia value is within a predetermined range when the current value detected by the current detection unit is within a predetermined range;
The control unit controls a torque generated by the paper feeding motor based on a calculated moment of inertia value by the calculating unit or the recalculating unit, and applies a predetermined amount to the paper between the transport roller and the roll paper. A sheet conveying device that generates tension. The sheet conveying apparatus according to claim 1, wherein the calculating unit calculates the moment of inertia of the roll paper using a first calculation method that does not require driving of the paper feed motor. 3. The sheet according to claim 1, wherein the recalculation unit recalculates the moment of inertia of the roll paper using a second calculation method that requires driving of the paper feed motor. Conveying device. The recalculation means, as the second method for calculating the, on the basis of the physical quantity related to the driving of the paper feed motor, characterized by re-calculating the moment of inertia of the paper roll, the sheet conveying according to claim 3 apparatus. 5. The sheet conveyance according to claim 4, wherein the recalculation unit recalculates the moment of inertia of the roll paper based on a current value of the paper feed motor detected by another current detection unit. apparatus. The sheet conveying apparatus according to claim 1, further comprising a printing unit that performs printing. A paper feed motor that rotationally drives a roll of paper wound in a roll, a transport roller that transports the paper drawn from the roll paper in a predetermined direction, a transport motor that rotationally drives the transport roller, and In a sheet conveying apparatus having a sheet feeding motor and a control unit that controls driving of the conveying motor,
The control unit is
Calculating means for calculating the moment of inertia of the roll paper using a first calculation method that does not require driving of the paper feed motor;
Determining means for determining whether or not the calculated moment of inertia value by the calculating means is within a predetermined range;
When the inertia moment calculation value is determined to be out of a predetermined range by the determination means, the inertia moment of the roll paper is regenerated using a second calculation method that requires driving of the paper feed motor. Recalculating means for calculating,
Have
When the determination unit does not determine that the calculated moment of inertia is out of a predetermined range, the control unit determines that the calculated moment of inertia is determined by the determination unit based on the calculated inertia moment. If it is determined that the value is out of the range, the torque generated by the paper feeding motor is controlled based on the recalculated moment of inertia value by the recalculating means, and the paper between the transport roller and the roll paper is controlled. A sheet conveying apparatus that generates a predetermined tension on a sheet. The sheet conveying apparatus according to claim 7, wherein the second calculation method is a method of calculating a moment of inertia of the roll paper based on a physical quantity relating to driving of the paper feed motor. 9. The method according to claim 8, wherein the second calculation method is a method of calculating a moment of inertia of the roll paper based on a current value of the paper feed motor detected by a current detection unit. Sheet conveying device. A roll paper rotation detection unit that detects a physical quantity related to the rotation of the roll paper;
10. The method according to claim 8, wherein the second calculation method is a method of calculating a moment of inertia of the roll paper based on the physical quantity detected by the roll paper rotation detection unit. Sheet conveying device. An acquisition means for acquiring information on the radius of the roll paper;
11. The method according to claim 7, wherein the first calculation method is a method of calculating a moment of inertia of the roll paper based on the information acquired by the acquisition unit. The sheet conveying apparatus according to the description. 12. The sheet conveyance according to claim 7, wherein the first calculation method is a method of calculating an inertia moment of the roll paper based on a width of the roll paper. 13. apparatus. The sheet conveying apparatus according to claim 7, further comprising a printing unit that performs printing.

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