JP2008001450A - Printer and method for determining existence or absence of printing medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printer provided with a constitution capable of suppressing wearing of a take-in roller and determining existence or absence of a printing medium set to a front surface paper feeding cassette by a simple constitution. <P>SOLUTION: The printer for performing printing on printing paper is provided with the front surface paper feeding cassette 14 set with the printing paper fed from a front surface side to the inside and mounted with a friction member for preventing overlapped-feeding of the printing paper to a bottom surface; the take-in roller 15 arranged so as to be opposed to the friction member and taking in the printing paper set to the front surface paper feeding cassette 14 to the inside of the printer; an ASF motor 29 for driving the take-in roller 15; and a control part 35 having a determination means for determining existence or absence of the printing paper set to the front surface paper feeding cassette 14 based on load of the ASF motor 29 on and after passing of a predetermined time or on and after rotation of a predetermined amount from starting of activation of the ASF motor 29. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a printer and a method for determining the presence or absence of a print medium.

  As an ink jet printer that performs printing on a predetermined printing medium such as printing paper, a so-called rear paper feed type printer in which printing paper is supplied from the rear side of the printer to the inside is known (for example, see Patent Document 1). The printer described in Patent Document 1 includes a paper detection device for determining whether or not printing paper is supplied inside. This paper detection device is disposed between a carriage on which a print head is mounted and a paper feed roller for supplying printing paper to the inside. Further, the presence or absence of printing paper set in the paper feeding hopper arranged on the rear side is detected by this paper detection device. That is, if the paper detection device does not detect printing paper within a predetermined time after the rotation of the paper feeding roller starts, it is determined that there is no printing paper on the paper feeding hopper.

  Also, as an inkjet printer that performs printing on printing paper, a so-called front feed type printer configured to be able to supply printing paper from the front side of the printer is known (see, for example, Patent Document 2). The printer described in Patent Document 2 is configured to be able to supply printing paper from the rear side. Then, the printing paper supplied from the front side is once conveyed toward the rear side, and then the conveyance direction is reversed and conveyed along the same path as the printing paper supplied from the rear side. In general, in a front feed type printer, printing paper supplied from the front side is set in a front side paper feeding cassette (front feeding paper cassette), and the printing paper set in the paper feeding cassette is predetermined. It is taken in by the take-in roller pressed by the force of.

JP-A-2005-212101 JP 2006-89147 A

  As described above, in a front feed type printer, in general, printing paper supplied from the front side is once conveyed toward the rear side, and then the conveyance direction is reversed and conveyed toward the front side. . Therefore, when the paper detection device described in Patent Document 1 arranged between the carriage and the paper feed roller is used in a front-side paper feed type printer, the printing paper is conveyed from the paper feed hopper on the rear side to the paper detection device. Compared to the distance, the conveyance distance of the printing paper from the front sheet feeding cassette to the paper detection device becomes longer. Accordingly, when the paper detection device described in Patent Document 1 is used to determine whether or not there is print paper in the front paper feed cassette, the loading until it is determined that there is no print paper in the front paper feed cassette. The rotation time of the roller is longer than the rotation time of the paper feed roller until it is determined that there is no printing paper in the rear paper feed hopper.

  As described above, when the paper detection device described in Patent Document 1 is used in a front-feed type printer, and this paper detection device is configured to detect the presence or absence of printing paper in the front-feed cassette, the front-feed cassette When there is no printing paper, the take-in roller rotates for a longer time without printing paper. Further, when there is no printing paper, the take-in roller rotates while being pressed against the bottom surface of the front sheet feeding cassette. Therefore, wear of the take-in roller becomes a problem.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a printer having a configuration capable of suppressing the wear of a take-in roller and determining the presence or absence of a print medium set in a front sheet feeding cassette with a simple configuration. Another object of the present invention is to provide a method for determining the presence or absence of a print medium that can suppress the wear of the take-in roller and can determine the presence or absence of a print medium set in the front sheet feeding cassette with a simple configuration. .

  In order to solve the above problems, the present invention provides a printer that prints on a print medium, in which a print medium supplied from the front side of the printer to the inside of the printer is set and prevents double feeding of the print medium. Front friction cassette attached to the bottom of the paper feed cassette, a take-up roller that is arranged to face the friction member and that is set in the front paper feed cassette, and takes in the drive roller And a control unit having a determination unit that determines whether or not there is a print medium set in the front sheet feeding cassette based on the load of the motor after a predetermined time has elapsed since the start of the motor start or after a predetermined amount of rotation. It is characterized by providing.

  In the printer of the present invention, the friction member facing the take-in roller is attached to the front paper feed cassette, and whether or not there is a print medium set in the front paper feed cassette based on the load of the motor that drives the take-in roller is determined. Judgment. Therefore, when there is no print medium in the front paper feed cassette, there is no print medium in the front paper feed cassette at an early stage based on the motor load that fluctuates greatly as the take-in roller presses against the friction member and rotates. Can be detected. Therefore, when there is no print medium in the front paper feed cassette, the take-in roller can be stopped early. As a result, it is possible to determine the presence or absence of the print medium set in the front sheet feeding cassette while suppressing the wear of the take-in roller. In addition, it is easy to use the motor load without using a complicated configuration such as attaching a torque limiter to the wear roller to suppress wear or providing a separate detection device for detecting the presence or absence of print media. With this configuration, it is possible to determine whether or not there is a print medium set in the front paper feed cassette.

  In the printer according to the present invention, the determination unit determines whether or not there is a print medium set in the front sheet feeding cassette after a predetermined time has elapsed from the start of motor activation or after a predetermined amount of rotation. Therefore, for example, in order to increase the take-in speed of the print medium taken from the front sheet cassette, the motor immediately after start-up is suddenly accelerated. As a result, even when the motor load increases, The presence / absence of the print medium in the front paper feed cassette can be prevented from being determined. Therefore, the motor can be accelerated rapidly, and the throughput (number of printed sheets per unit time) can be improved.

  In the present invention, the determination means compares the load value of the motor with a predetermined set value at a predetermined time interval, and the load value reaches or reaches the set value N times continuously (N is an integer of 2 or more). If it exceeds, it is preferable to determine that there is no print medium in the front paper feed cassette. With this configuration, even when there is only one print medium in the front paper feed cassette, it is possible to take in the print medium. That is, when a plurality of print media are set in the front paper feed cassette, the frictional resistance generated in the print media taken in by the take-in roller is the friction coefficient between the print media and the print media. In contrast, when there is only one print medium in the front sheet cassette, the frictional resistance generated in the print medium taken in is based on the coefficient of friction between the print medium and the friction member. Arises. For this reason, when there is only one print medium in the front sheet cassette, the load value of the motor may be temporarily increased. With this configuration, the load value of the motor is temporarily increased. Even if it becomes higher, it is not immediately determined that there is no print medium. As a result, even when there is only one print medium in the front paper feed cassette, the print medium can be taken in.

  In the present invention, the control unit includes a speed control unit that performs PID control, which is control for converging the current rotational speed of the motor to the target rotational speed by combining proportional control, integral control, and differential control. The determination of the presence or absence of a print medium set in the front paper feed cassette may be started after a predetermined time has elapsed or after a predetermined amount of rotation has occurred during acceleration control for accelerating the printing. If comprised in this way, the presence or absence of the printing medium set to a front sheet feeding cassette can be determined at an early stage, and wear of a taking-in roller can be controlled more effectively. In the present invention, the control unit includes a speed control unit that performs PID control, which is control for converging the current rotational speed of the motor to the target rotational speed by combining proportional control, integral control, and differential control. At the time of deceleration control for decelerating the motor, it may be determined whether or not there is a print medium set in the front sheet feeding cassette. With this configuration, even a print medium having a large friction coefficient can be taken into the printer.

  Further, in order to solve the above-described problem, according to the method for determining the presence / absence of a print medium according to the present invention, the print medium supplied from the front side to the inside of the printer has a friction member for preventing double feed of the print medium on the bottom surface. In order to load the print medium set in the front paper feed cassette to the inside, the load of the motor that drives the take-in roller arranged to face the friction member is set. On the basis of this, the method includes a determination step of determining whether or not there is a print medium set in the front paper feed cassette after a predetermined time has elapsed since the start of motor activation or after a predetermined amount of rotation.

  The method for determining the presence or absence of a print medium according to the present invention includes a motor that drives a take-in roller based on the presence or absence of a print medium set in a front paper feed cassette having a friction member facing the take-in roller attached to the front paper feed cassette And a determination step for determining after a predetermined time has elapsed or after a predetermined amount of rotation since the start of the motor. Therefore, wear of the take-in roller can be suppressed, and the presence / absence of a print medium set in the front sheet feeding cassette can be determined with a simple configuration using a motor load. In addition, it is possible to improve the throughput of a printer using this determination method.

  Hereinafter, a printer and a method for determining the presence or absence of a print medium according to an embodiment of the present invention will be described with reference to the drawings.

(Schematic configuration of the printer)
FIG. 1 is a side view showing a schematic configuration of a main part of a printer 1 according to an embodiment of the present invention. FIG. 2 is a perspective view showing the configuration of the front sheet feeding cassette 14 shown in FIG. FIG. 3 is a diagram schematically showing a configuration of a portion related to the take-in roller 15 shown in FIG.

  The printer 1 of the present embodiment is an ink jet printer that performs printing by ejecting ink droplets onto a printing paper P or the like as a printing medium. As shown in FIG. 1, the front side (the left side in FIG. 1) and the rear side The printing paper P can be supplied from both sides (right side in FIG. 1). As shown in FIG. 1, the printer 1 includes a carriage 3 on which a print head 2 that ejects ink droplets is mounted, a PF driving roller 5 and a PF driven roller 6 for conveying the printing paper P in the sub-scanning direction SS. , A paper discharge driving roller 7 and a paper discharge driven roller 8, and a platen 9 facing the ink discharge surface (the lower surface in FIG. 1) of the print head 2. In addition to the printing paper P such as plain paper used for normal document printing, photographic paper used for photo printing, thick paper thicker than plain paper or photographic paper, etc. And transparent films such as OHP sheets.

  The carriage 3 is connected to a CR motor (not shown). The carriage 3 is driven by the CR motor and is guided by the guide shaft 4 to move in the main scanning direction (the direction perpendicular to the plane of FIG. 1). The PF drive roller 5 and the paper discharge drive roller 7 are connected to a PF motor (not shown). The PF driven roller 6 and the paper discharge driven roller 8 are urged so as to come into contact with the PF drive roller 5 and the paper discharge drive roller 7, respectively.

  Further, as shown in FIG. 1, the printer 1 according to the present embodiment is configured to supply the printing paper P from the rear side, and has a rear paper feeding hopper 10 on which the printing paper P supplied from the rear side is placed. A paper feed roller 11 that supplies the printing paper P placed on the rear paper feeding hopper 10 to the inside of the printer 1 and a double feed of the printing paper P (a plurality of printing papers P into the printer 1 at a time). And a retard roller 12 for preventing the paper from being fed). These structures are arranged on the rear side of the carriage 3 as shown in FIG. Further, as shown in FIG. 1, the retard roller 12 is pressed against the paper feed roller 11 when paper is fed from the rear side, and when the paper is not fed from the rear side, as shown in FIG. Get away from.

  Further, the printer 1 is configured to supply the printing paper P from the front side, and the front paper feeding cassette 14 in which the printing paper P supplied from the front side is set, and the printing set in the front paper feeding cassette 14. A take-in roller 15 that takes the paper P into the printer 1, an arm 16 that rotatably holds the take-in roller 15, a conveyance path 17 through which the print paper P that is taken in by the take-in roller 15 passes, and a conveyance path 17 A transport driving roller 18 and a transport driven roller 19 for transporting the printing paper P passing through the transport paper 19 are provided. As shown in FIG. 1, these components are arranged below the carriage 3 and the rear sheet feeding hopper 10.

  In this embodiment, as shown in FIG. 1, the printing paper P supplied from the rear side is conveyed toward the front side as it is. Further, the printing paper P supplied from the front side is first transported toward the rear side, and then the transport direction is reversed by the transport path 17 formed in a substantially arc shape, and is supplied from the rear side. The paper is conveyed toward the front surface along a common path with the printing paper P.

  As shown in FIG. 2, the front paper feed cassette 14 includes end guides 22 and 23 for guiding the width direction end and the length direction end of the printing paper P, respectively. The front end of the printing paper P set in the front paper feeding cassette 14 abuts on the rear side of the front paper feeding cassette 14 and the sliding contact portion 24 with which the front end of the printing paper P taken into the printer 1 comes into sliding contact. Two friction members 25 made of a material having a relatively large friction coefficient such as cork are attached to the bottom surface of the front sheet feeding cassette 14. The friction member 25 is attached to the rear surface side of the front sheet feeding cassette 14 and functions to prevent double feeding of the printing paper P.

  The take-in roller 15 is attached to the tip of the arm 16. The arm 16 can swing around a swing shaft 16a attached to the base end side. When the paper is fed from the front side, as shown by the solid line in FIG. 1, the take-in roller 15 is pressed against the upper surface of the printing paper P, and when the paper is not fed from the front side. As shown by a two-dot chain line in FIG. In this embodiment, the take-in roller 15 conveys the printing paper P into the printer 1 until the leading edge of the printing paper P reaches the PF driving roller 5 and the PF driven roller 6. When the leading edge of the printing paper P reaches the PF driving roller 5 or the like, the take-in roller 15 is in a state indicated by a two-dot chain line in FIG. That is, the printing paper P at the time of printing is conveyed by the PF drive roller 5 and the like, and the take-in roller 15 is not in pressure contact with the upper surface of the printing paper P at the time of printing. The take-in roller 15 is disposed at a position where it can be pressed against the friction member 25 when there is no print paper P in the front paper feed cassette 14.

  Further, as shown in FIG. 3, the take-in roller 15 is connected to an ASF motor 29 through a planetary gear train 26, a plurality of belts 27, and a plurality of pulleys 28. The paper feed roller 11 is also connected to the ASF motor 29 via the planetary gear train 26 and the like (illustration of the paper feed roller 11 is omitted in FIG. 3). In this embodiment, when the ASF motor 29 rotates in one direction, the take-in roller 15 is rotated by the action of the planetary gear train 26 and the printing paper P is taken into the printer 1 from the front side. When the ASF motor 29 rotates in the other direction, the paper feed roller 11 is rotated by the action of the planetary gear train 23 and the printing paper P is taken into the printer 1 from the rear side.

  As shown in FIG. 3, a rotary scale 32 is attached to the rotation shaft of the ASF motor 29. The rotary encoder 34 composed of the rotary scale 32 and the photosensor 33 detects the rotational speed and rotational position of the ASF motor 29. The output signal from the rotary encoder 34 is input to the control unit 35. Note that the ASF motor 29 of this embodiment is a DC (direct current) motor. In this embodiment, PWM (Pulse Width Modulation) control, which is one of voltage control, is adopted as a control method of the ASF motor 29, and the ASF motor 29 is combined with proportional control, integral control, and differential control. PID control, which is control for converging the current rotation speed to the target rotation speed, is employed.

  The transport driving roller 18 is connected to a motor (not shown). Further, when the printing paper P is taken in from the front side by the take-in roller 15, the transport driven roller 19 is pressed against the transport driving roller 18 and is fed from the front side as shown by the solid line in FIG. 1. When there is not, it leaves | separates from the conveyance drive roller 18, as shown with the dashed-two dotted line of FIG.

  Furthermore, the printer 1 of this embodiment includes a paper detection device 37 for detecting the passage of the printing paper P taken in the inside. The paper detection device 37 of the present embodiment is an optical detection device that includes a light emitting element and a light receiving element (not shown), and detects one end portion of the printing paper P in the width direction. Further, the paper detection device 37 is disposed between the PF drive roller 5 and the paper feed roller 11 disposed on the rear side of the carriage 3.

(Schematic configuration of control unit)
FIG. 4 is a block diagram showing a schematic configuration of the control unit 35 and its peripheral portion shown in FIG. FIG. 5 is a diagram illustrating an example of a waveform of the control signal SG output from the PID control unit 43 illustrated in FIG. 6A and 6B are diagrams for explaining the relationship between the rotational speed and the duty value of the ASF motor 29 shown in FIG. 3, wherein FIG. 6A shows an example of a target speed curve of the ASF motor 29, and FIG. An example of a change in the duty value of the ASF motor 29 when the printing paper P is not set in the paper feeding cassette 14 is shown, and (C) shows an ASF motor when the printing paper P is not set in the front paper feeding cassette 14. An example of the change of 29 current rotational speeds is shown. FIG. 7 is a diagram illustrating a state in which the printing paper P illustrated in FIG. 1 is not properly set in the front paper feeding cassette 14. In FIG. 4, only the configuration of the control unit 35 related to the ASF motor 29 is shown.

  As shown in FIG. 4, the control unit 35 drives the ASF motor 29 and a speed control unit 37 that performs speed control (specifically, PID control) of the ASF motor 29 as a configuration related to the ASF motor 29. And an ASF motor drive unit 38. Further, the control unit 35 of the present embodiment includes a sheet presence / absence determination unit 39 as a determination unit that determines the presence / absence of the print sheet P set in the front sheet feeding cassette 14 based on the load of the ASF motor 29. In addition, a control command unit 40 is connected to the control unit 35 via input / output means (not shown). Note that the speed control unit 37 and the paper presence / absence determination unit 39 are actually a calculation unit such as a CPU, a storage unit such as a ROM, a RAM, and a nonvolatile memory, and an input / output such as an IO port. It is realized by means and the like.

  As described above, the ASF motor 29 of this embodiment is PID-controlled. Therefore, the speed control unit 37 includes a speed calculation unit 41, a position calculation unit 42, and a PID control unit 43. The speed calculation unit 41 calculates the current rotation speed (current rotation speed) of the ASF motor 29 based on the signal input from the rotary encoder 34 and outputs a signal corresponding to this rotation speed to the PID control unit 43. The position calculation unit 42 calculates the current rotational position of the ASF motor 29 based on the signal input from the rotary encoder 34 and outputs a signal corresponding to this rotational position to the PID control unit 43. The signal output from the position calculation unit 42 is also input to the paper presence / absence determination unit 39.

  The PID control unit 43 performs a predetermined calculation based on signals input from the speed calculation unit 41 and the position calculation unit 42 and outputs a control signal SG based on the calculation result to the ASF motor drive unit 38. Specifically, since the ASF motor 29 of the present embodiment is PWM-controlled, the control signal SG is a pulse-like signal that repeatedly turns on and off at the switching period T as shown in FIG. That is, the ASF motor drive unit 38 applies a voltage to the ASF motor 29 only during the on-time T1. Here, in this specification, the ratio of the on-time T1 to the switching period T is defined as “duty”.

  The ASF motor 29 is speed controlled so as to follow the target speed curve shown in FIG. That is, it is controlled by PID control that converges the current rotational speed to the target rotational speed at each rotational position. Therefore, if the difference between the target rotational speed and the current rotational speed is large, the duty increases. If the difference between the target rotational speed and the current rotational speed is small, the duty decreases. That is, if the load on the ASF motor 29 is large and the difference between the target rotational speed and the current rotational speed is large, the duty increases, and if the load on the ASF motor 29 is light and the difference between the target rotational speed and the current rotational speed is small. , The duty is reduced. In other words, in this embodiment, the duty value (duty value) indirectly indicates the load value of the ASF motor 29.

  As shown in FIG. 6A, the target speed curve includes an acceleration region where acceleration control for accelerating the ASF motor 29 is performed and constant speed control for rotating the ASF motor 29 at a constant speed. And a deceleration region in which deceleration control for decelerating the ASF motor 29 is performed.

  The paper presence / absence determination unit 39 receives the output signal of the position calculation unit 42 and the control signal SG. Based on these signals, the paper presence / absence determination unit 39 determines whether or not there is a printing paper P set in the front sheet feeding cassette 14. Determine. Specifically, in the paper presence / absence determination unit 39, as shown in FIG. 6B, an upper limit value U of the duty value for determining the presence / absence of the printing paper P is set in advance. This upper limit value U is calculated based on the duty value when the ASF motor 29 is driven in a state where there is no printing paper P in the front paper feed cassette 14. Then, the sheet presence / absence determination unit 39 compares the duty value of the control signal SG input at each control period of the PID control with the upper limit value U (that is, the duty value and the upper limit value at the control period of the PID control). U is compared), and when the duty value reaches the upper limit value U continuously for N times (N is an integer of 2 or more), it is determined that there is no printing paper P in the front paper feed cassette 14. That is, when there is no printing paper P in the front paper feed cassette 14, the take-in roller 15 and the friction member 25 are in pressure contact with each other, so the load on the ASF motor 29 increases, and as a result, the duty value increases. . Therefore, by comparing the duty value with the upper limit value U, it is possible to determine the presence or absence of the printing paper P. Note that the control period of the PID control of this embodiment is 150 μsec, for example. Moreover, it is preferable that the continuous arrival frequency N is about 50 times, and the continuous arrival frequency N of this embodiment is 50 times.

  Here, in the sheet presence / absence determination unit 39 according to the present embodiment, when the duty value reaches the upper limit value U consecutively N times, it is determined that there is no printing sheet P in the front sheet feeding cassette 14. This is because even if there is only one printing paper P in 14, the printing paper P can be taken in. That is, when a plurality of printing sheets P are set in the front sheet feeding cassette 14, the frictional resistance generated in the printing sheet P taken in by the take-in roller 15 is the friction coefficient between the printing sheets P. In contrast, when there is only one print sheet P in the front paper feed cassette 14, the frictional resistance generated in the print sheet P taken in is between the print sheet P and the friction member 25. It occurs based on the friction coefficient. Therefore, when there is only one print sheet P in the front paper feed cassette 14, the duty value may temporarily increase. However, when the duty value reaches the upper limit value U continuously N times, By determining that there is no print paper P in the front paper feed cassette 14, even if the duty value temporarily increases, it is not immediately determined that there is no print paper P. As a result, the last printing sheet P can be taken in.

  Further, in this embodiment, as shown in FIG. 7, the printing paper P is not properly set in the front paper feeding cassette 14, and only a part on the leading end side of the last printing paper P is in the take-in roller 15. The upper limit value U and the continuous arrival count N are set so that the printing paper P can be taken in even when it is in contact. In this embodiment, if the ratio between the contact area between the take-in roller 15 and the print paper P and the contact area between the take-in roller 15 and the friction member 25 is about 3 to 7, the print paper P is taken in. However, if the ratio of the contact area between the take-in roller 15 and the friction member 25 is larger than this, it is difficult to take in the printing paper P.

  In addition, the sheet presence / absence determination unit 39 according to the present embodiment is configured to print the print sheet P set in the front sheet feeding cassette 14 until the ASF motor 29 starts to rotate for a predetermined amount (that is, until a predetermined time elapses). Without the presence / absence determination, the presence / absence of the printing paper P is determined after a predetermined amount of rotation from the start of activation of the ASF motor 29. That is, as shown in FIG. 6B, the paper presence / absence determination unit 39 does not determine in advance whether or not the print paper P is present until the ASF motor 29 starts to rotate by a predetermined amount. Is set. In the non-determination area R11, the presence / absence of the printing paper P is not determined, and the presence / absence of the printing paper P is determined in the determination area R21 after the predetermined amount of rotation. Specifically, as shown in FIG. 6B, in the non-determination region R11, even when the duty value reaches the upper limit value U, the number of times of arrival is not counted, and the duty value is determined in the determination region R21. When the upper limit value U is reached N times consecutively, it is determined that there is no printing paper P in the front paper feed cassette 14. In this embodiment, as shown in FIG. 6B, a non-determining region R11 is set in the acceleration region. That is, in the present embodiment, the determination of the presence or absence of the printing paper P is started after entering the determination region R21 after the predetermined amount of rotation during acceleration control for accelerating the ASF motor 29. FIG. 6B shows a change in the duty value when the ASF motor 29 stops after the duty value reaches the upper limit value U for N times in the determination region R21. FIG. 6C shows a change in the current rotational speed of the ASF motor 29 corresponding to the change in the duty value shown in FIG. 6B.

(Judgment method for the presence of printing paper)
FIG. 8 is a flowchart illustrating a method for determining the presence / absence of printing paper P in the paper presence / absence determination unit 39 shown in FIG. Hereinafter, a method for determining the presence / absence of the printing paper P in the front paper feed cassette 14 in the paper presence / absence determination unit 39 will be described.

  As shown in FIG. 8, first, the ASF motor 29 is driven to take the printing paper P set in the front paper feeding cassette 14 into the printer 1 (step S0). Thereafter, it is determined whether or not the ASF motor 29 is rotating (step S1). Specifically, the determination is made based on a signal input from the position calculation unit 42. If the ASF motor 29 is not rotating, the determination flow for the presence or absence of the printing paper P in the front paper feed cassette 14 ends. On the other hand, when the ASF motor 29 is rotating, it is determined whether or not it is the control period of the PID control (step S2). Specifically, the determination is made based on whether or not the control signal SG is input to the sheet presence / absence determination unit 39. If it is not the control cycle, the process returns to step S2, and if it is the control cycle, it is determined whether or not the rotational position of the ASF motor 29 is in the determination region R21 (step S3). Specifically, the determination is made based on a signal input from the position calculation unit 42.

  If it is determined in step S3 that the rotational position of the ASF motor 29 is in the non-determined region R11, the process returns to step S2. On the other hand, when the rotational position of the ASF motor 29 is in the determination region R21, it is determined whether or not the duty value has reached the upper limit value U (step S4). If the duty value has not reached the upper limit value U, it is determined whether or not the number n of times the duty value reaches the upper limit value U is zero (step S5). If the number of arrivals n is 0, the process directly returns to step S1. If the number of arrivals n is not 0, the number of arrivals n is reset to 0 (step S6), and then the process returns to step S1.

  If it is determined in step S4 that the duty value has reached the upper limit value U, 1 is added to the number n of times that the duty value reaches the upper limit value U to obtain a new number of times n (step S7). Thereafter, it is determined whether or not the new arrival number n is the continuous arrival number N (step S8). If the new arrival number n is not the continuous arrival number N, the process returns to step S1. On the other hand, as shown in FIG. 6B, when the new arrival number n is the continuous arrival number N (that is, when the duty value reaches the upper limit value N consecutively in the determination region R21), It is determined that there is no printing paper P in the front paper feed cassette 14 (step S9), the ASF motor 29 is stopped, and a no-paper signal is output (step S10). Specifically, the paper presence / absence determination unit 39 outputs a stop signal of the ASF motor 29 to the ASF motor driving unit 38 and outputs a paper out signal to the control command unit 40. In response to a control command from the control command unit 40 to which a paper-out signal has been input, for example, a paper-free display is performed on a predetermined display unit.

  In this embodiment, steps S1 to S10 constitute a determination step for determining the presence or absence of the printing paper P set in the front sheet feeding cassette 14.

(Main effects of this form)
As described above, in this embodiment, the friction member 25 that can face the take-in roller 15 is attached to the front sheet feeding cassette 14, and the front sheet feeding cassette is based on the load (specifically, duty) of the ASF motor 29. The presence or absence of the printing paper P set to 14 is determined. For this reason, when there is no printing paper P in the front paper feed cassette 14, the front paper feed cassette 14 is quickly transferred to the front paper feed cassette 14 based on a duty value that varies greatly as the take-in roller 15 is pressed against the friction member 25 and rotates. The absence of the printing paper P can be detected, and the take-in roller 15 can be stopped early. As a result, it is possible to determine the presence or absence of the printing paper P set in the front sheet feeding cassette 14 with a simple configuration using the duty value while suppressing the wear of the take-in roller 15. In addition, wear of the friction member 25 that is in pressure contact with the take-in roller 15 can be suppressed.

  In the present embodiment, the presence / absence of the printing paper P set in the front sheet feeding cassette 14 is determined in the determination region R21 after a predetermined amount of rotation from the start of activation of the ASF motor 29 (that is, after a predetermined time has elapsed). ing. Therefore, in order to increase the take-in speed of the printing paper P taken in from the front paper feed cassette 14, the ASF motor 29 after the start of activation is accelerated rapidly, and as a result, the duty value reaches the upper limit value U in the non-determining region R11. Even in this case, the presence / absence of the print medium P is not determined in the non-determined region R11. Accordingly, the ASF motor 29 can be accelerated rapidly, and the throughput of the printer 1 can be improved.

  In this embodiment, the sheet presence / absence determination unit 39 compares the duty value with the upper limit value U in the control cycle of PID control, and when the duty value reaches the upper limit value N consecutively, the front sheet feeding cassette 14 It is determined that there is no printing paper P. Therefore, as described above, even when there is only one printing sheet P in the front sheet feeding cassette 14, the printing sheet P can be taken in. In particular, as shown in FIG. 7, even when the last sheet of printing paper P is not properly set in the front sheet feeding cassette 14, the printing paper P can be taken in.

  In this embodiment, the determination of the presence or absence of the printing paper P is started after entering the determination region R21 after a predetermined amount of rotation during acceleration control of the ASF motor 29. Therefore, the presence or absence of the printing paper P set in the front paper feeding cassette 14 can be determined at an early stage. As a result, wear of the take-in roller 15 and the friction member 25 can be more effectively suppressed.

(Other embodiments)
The above-described embodiment is an example of a preferred embodiment of the present invention. However, the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention. That is, in the above-described form, the sheet presence / absence determination unit 39 compares the duty value with the upper limit value U in the control period of PID control, but is provided in the control unit 35 as shown in FIG. The clock generator 50 may be used to compare the duty value and the upper limit value U with the period of the periodic clock signal generated from the clock generator 50. In the above-described form, the control signal SG output from the PID control unit 43 is input to the paper presence / absence determination unit 39. However, as indicated by a two-dot chain line in FIG. 4, the output from the ASF motor driving unit 38. A signal may be input to the sheet presence / absence determination unit 39, and the duty value may be calculated based on the output signal.

  Further, in the above-described form, when the duty value reaches the upper limit value U continuously for N times, it is determined that there is no printing paper P in the front paper feed cassette 14, but the duty value is N even if it is not continuous. When the upper limit value U is reached, it may be determined that there is no printing paper P in the front paper feed cassette 14. Alternatively, a setting value lower than the upper limit value U may be set, and when the duty value exceeds the setting value N times consecutively, it may be determined that there is no printing paper P in the front sheet feeding cassette 14.

  Furthermore, in the above-described embodiment, the presence or absence of the printing paper P set in the front sheet feeding cassette 14 is determined based on the duty value. However, based on the substitute characteristics of the load value of the ASF motor 29 other than the duty value. The presence or absence of the print paper P set in the front paper feed cassette 14 may be determined. For example, when the ASF motor 29 is current-controlled instead of voltage-controlled, the presence or absence of the printing paper P set in the front sheet feeding cassette 14 may be determined from the current value supplied to the ASF motor 29.

  In the embodiment described above, the boundary between the non-determination area R11 and the determination area R21 is set as an acceleration area, and the determination of the presence or absence of the printing paper P is started during acceleration control, as shown in FIG. In addition, the boundary between the non-determination region R12 and the determination region R22 may be set as a constant speed region, and the determination of the presence or absence of the printing paper P may be started during the constant speed control. Further, the boundary between the non-determination area R13 and the determination area R23 may be set as a deceleration area, and the determination of the presence or absence of the printing paper P may be started during deceleration control. When the determination of the presence or absence of the printing paper P is started during the deceleration control, it is difficult to determine that there is no printing paper P. For example, the printing paper P or other printing medium that has a large friction coefficient and is difficult to take in is used. Even if it exists, it becomes possible to take in the inside of the printer 1.

  Further, the configuration of this embodiment can be applied to various apparatuses including a paper feed mechanism such as a laser printer in addition to an ink jet printer.

1 is a side view showing a schematic configuration of a main part of a printer according to an embodiment of the present invention. FIG. 2 is a perspective view illustrating a configuration of a front sheet feeding cassette in FIG. 1. The figure which shows typically the structure of the part relevant to the taking-in roller of FIG. The block diagram which shows schematic structure of the control part of FIG. 3, and its peripheral part. The figure which shows an example of the waveform of the control signal output from the PID control part of FIG. The figure for demonstrating the relationship between the rotational speed of the ASF motor of FIG. 3, and a duty value. The figure which shows the state in which the printing paper of FIG. 1 is not set appropriately. 5 is a flowchart illustrating a determination method in a sheet presence / absence determination unit in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Printer, 14 Front sheet cassette, 15 Take-in roller, 25 Friction member, 29 ASF motor (motor), 35 Control part, 37 Speed control part, 39 Paper presence determination part (determination means), P Printing paper (printing medium) ), S1 to S10 determination step, U upper limit value (set value).

Claims (5)

In a printer that prints on print media,
A front paper feed cassette in which the print medium supplied from the front side of the printer to the inside of the printer is set and a friction member for preventing double feeding of the print medium is attached to the bottom surface; A take-in roller that is disposed so as to face the friction member and is set in the front paper feed cassette, takes in the printer, a motor that drives the take-in roller, and a predetermined time from the start of the motor. And a control unit having a determination unit for determining the presence or absence of the print medium set in the front sheet feeding cassette based on the load of the motor after the elapse or after a predetermined amount of rotation. .   The determination means compares the load value of the motor with a predetermined set value at predetermined time intervals, and the load value reaches the set value for N consecutive times (N is an integer of 2 or more) or the set value. The printer according to claim 1, wherein when the value exceeds the value, it is determined that the print medium does not exist in the front paper feed cassette. The control unit includes a speed control unit that performs PID control, which is control for converging the current rotational speed of the motor to a target rotational speed by combining proportional control, integral control, and differential control.
The determination means determines whether or not there is the print medium set in the front sheet feed cassette at the time of acceleration control for accelerating the motor and after the predetermined time has elapsed or after the predetermined amount of rotation. 3. The printer according to claim 1, wherein the printer is started. The control unit includes a speed control unit that performs PID control, which is control for converging the current rotational speed of the motor to a target rotational speed by combining proportional control, integral control, and differential control.
3. The printer according to claim 1, wherein the determination unit starts determining whether or not the print medium is set in the front sheet feeding cassette during deceleration control for decelerating the motor. When the print medium supplied to the inside of the printer from the front side is set in a front sheet feed cassette having a friction member for preventing double feeding of the print medium attached to the bottom surface,
A predetermined time elapses from the start of the start of the motor based on the load of the motor that drives the take-in roller arranged to face the friction member in order to take in the print medium set in the front paper feed cassette. A determination method for presence / absence of a print medium, comprising: a determination step of determining the presence / absence of the print medium set in the front paper feed cassette after the time or after a predetermined amount of rotation.

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