Medium conveying device, control method, and control program

Abstract

To provide a medium conveyance device, a control method and a control program which can more properly control the magnitude of a current used by a DC motor in a medium conveyance device which conveys a medium by using the DC motor.SOLUTION: A medium conveyance device 100 comprises: conveyance rollers 116 and 117 which convey a medium; an imaging unit 119 which images the medium; a DC motor 131 which drives the conveyance roller; a detection unit 154 which detects that the tip of the medium reaches a space between the conveyance rollers and the imaging unit; a setting unit 152 which sets a current limit value in the DC motor to a first limit value until the tip of the medium reaches the space between the conveyance rollers and the imaging unit and changes the current limit value to a second limit value larger than the first limit value after the tip of the medium reaches the space between the conveyance rollers and the imaging unit; and a control unit 151 which drives the conveyance rollers by rotating the DC motor on the basis of the second limit value when the imaging unit performs imaging.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a medium transport device, a control method, and a control program, and more particularly to a medium transport device that transports a medium using a DC (Direct Current) motor, a control method, and a control program. [Background technology]

[0002] In media transport devices such as scanners, DC motors are often used to transport media. While DC motors are low-cost and their speeds can be easily adjusted, the amount of current required fluctuates due to external factors such as load fluctuations. Media transport devices typically use an alternating current (AC) adapter to supply power, limiting the power supply capacity of the media transport device. Therefore, in media transport devices that use DC motors to transport media, it is necessary to appropriately control the amount of current used by the DC motor.

[0003] A paper feeding device is disclosed that performs paper feeding operations by driving a DC motor with a PWM signal of fixed duty during the first specified section, and feeds paper using position feedback control when the leading edge of the paper is detected by a registration sensor (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-291433 Summary of the Invention [Problem to be solved by the invention]

[0005] In a media transport device that transports a medium using a DC motor, it is desirable to more appropriately control the magnitude of the current used by the DC motor.

[0006] The object of the present invention is to provide a media transport device, a control method, and a control program that can more appropriately control the amount of current used by a DC motor in a media transport device that transports media using a DC motor. [Means for solving the problem]

[0007] A medium transport device according to one aspect of the present invention includes a first roller, a DC motor that drives the first roller, a second roller that is provided upstream of the first roller in a medium transport direction, a second motor that drives the second roller, and a second motor that changes a current limit value of the DC motor from a first limit value to a second limit value that is greater than the first limit value after a leading edge of a medium has passed the first roller. Stop A setting unit.

[0008] A control method according to one aspect of the present invention is a control method for a medium transport device having a first roller, a DC motor that drives the first roller, a second roller that is provided upstream of the first roller in a medium transport direction, and a second motor that drives the second roller, wherein, after a leading edge of a medium has passed the first roller, a current limit value of the DC motor is changed from a first limit value to a second limit value that is greater than the first limit value, and Stop .

[0009] A control program according to one aspect of the present invention is a control program for a medium transport device having a first roller, a DC motor that drives the first roller, a second roller that is provided upstream of the first roller in a medium transport direction, and a second motor that drives the second roller, wherein, after a leading edge of a medium has passed the first roller, a current limit value of the DC motor is changed from a first limit value to a second limit value that is greater than the first limit value, and the second motor Stop The medium transport device executes the above. [Effects of the Invention]

[0010] According to the present invention, the medium transport device, control method, and control program are capable of more appropriately controlling the magnitude of the current used by a DC motor in a medium transport device that transports a medium using a DC motor. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a perspective view showing a medium conveying device 100 according to an embodiment. [Figure 2] 2 is a diagram for explaining a transport path inside the medium transport device 100. FIG. [Figure 3] 1 is a block diagram showing a schematic configuration of a medium conveying device 100. FIG. [Figure 4] FIG. 2 is a diagram showing a schematic configuration of a storage device 140 and a processing circuit 150. [Figure 5] 10 is a flowchart illustrating an example of the operation of a medium reading process. [Figure 6] 10 is a flowchart illustrating an example of the operation of a medium reading process. [Figure 7A] FIG. 4 is a schematic diagram for explaining the magnitude of torque. [Figure 7B] FIG. 4 is a schematic diagram for explaining the magnitude of torque. [Figure 7C] FIG. 4 is a schematic diagram for explaining the magnitude of torque. [Figure 8] 10 is a flowchart illustrating an example of a part of the operation of another medium reading process. [Figure 9] 10 is a diagram for explaining a transport path inside another medium transport device 200. FIG. [Figure 10] FIG. 2 is a block diagram showing a schematic configuration of a medium conveying device 200. [Figure 11] 10 is a flowchart illustrating an example of a portion of the operation of another medium reading process. [Figure 12] FIG. 10 is a diagram showing a schematic configuration of another processing circuit 450. DETAILED DESCRIPTION OF THE INVENTION

[0012] A medium transport device according to one aspect of the present invention will be described below with reference to the drawings. However, please note that the technical scope of the present invention is not limited to the embodiments, but extends to the inventions set forth in the claims and their equivalents.

[0013] FIG. 1 is a perspective view showing a medium conveying device 100 configured as an image scanner. The medium conveying device 100 conveys a medium, which is an original document, and captures an image of the medium. The medium may be a thin medium such as paper, or a thick medium such as cardboard, a plastic card, a booklet, or a passport. The medium conveying device 100 may be a facsimile machine, a copier, a multifunction peripheral (MFP), or the like. Note that the medium being conveyed may not be an original document, but may be a print target or the like, and the medium conveying device 100 may be a printer or the like.

[0014] The medium conveying device 100 includes a lower housing 101, an upper housing 102, a loading table 103, an ejection table 104, an operation device 105, a display device 106, and the like.

[0015] The upper housing 102 is disposed in a position that covers the top surface of the medium conveying device 100, and is engaged with the lower housing 101 by a hinge so that it can be opened and closed when a medium becomes jammed or when cleaning the inside of the medium conveying device 100, for example.

[0016] The loading platform 103 is engaged with the lower housing 101 so that the medium to be transported can be placed thereon. The ejection platform 104 is engaged with the lower housing 101 so that the ejected medium can be held. The ejection platform 104 is foldable so that it faces the front surface of the medium transport device 100 (upper housing 102).

[0017] The operation device 105 has input devices such as buttons and an interface circuit for acquiring signals from the input devices, accepts input operations by a user, and outputs operation signals in response to the user's input operations. The display device 106 has a display such as a liquid crystal display, an organic EL (Electro-Luminescence) display, or the like, and an interface circuit for outputting image data to the display, and displays the image data on the display.

[0018] FIG. 2 is a diagram for explaining the transport path inside the medium transport device 100. As shown in FIG.

[0019] The transport path inside the medium transport device 100 includes a first medium sensor 111, a feed roller 112, a brake roller 113, a thickness sensor light emitter 114a, a thickness sensor light receiver 114b, an ultrasonic transmitter 115a, an ultrasonic receiver 115b, a first transport roller 116, a second transport roller 117, a second medium sensor 118, a first image capture device 119a, a second image capture device 119b, a third transport roller 120, and a fourth transport roller 121. Note that the number of each roller is not limited to one, and there may be multiple of each roller. Hereinafter, the first image capture device 119a and the second image capture device 119b may be collectively referred to as the image capture device 119.

[0020] The top surface of lower housing 101 forms lower guide 107a of the medium transport path, and the bottom surface of upper housing 102 forms upper guide 107b of the medium transport path. In Figure 2, arrow A1 indicates the medium transport direction. Hereinafter, "upstream" refers to the upstream side of medium transport direction A1, and "downstream" refers to the downstream side of medium transport direction A1.

[0021] The first medium sensor 111 is disposed upstream of the feed roller 112 and the brake roller 113. The first medium sensor 111 has a contact detection sensor and detects whether or not a medium is placed on the placement table 103. The first medium sensor 111 generates and outputs a first medium signal whose signal value changes depending on whether or not a medium is placed on the placement table 103.

[0022] The feed roller 112 and the brake roller 113 are provided upstream of the first conveyor roller 116 and the second conveyor roller 117 in the medium conveying direction A1. The feed roller 112 is provided in the lower housing 101, and feeds the media placed on the mounting table 103 from the bottom up. The brake roller 113 is provided in the upper housing 102, and is disposed opposite the feed roller 112.

[0023] The thickness sensor light emitter 114a and the thickness sensor light receiver 114b are disposed downstream of the feed roller 112 and the brake roller 113 and upstream of the first conveyor roller 116 and the second conveyor roller 117. The thickness sensor light emitter 114a and the thickness sensor light receiver 114b are disposed near the medium conveyance path, facing each other across the conveyance path. The thickness sensor light emitter 114a is an LED (Light Emitting Diode) or the like, and emits light toward the medium conveyance path. Meanwhile, the thickness sensor light receiver 114b receives light emitted by the thickness sensor light emitter 114a that has passed through the conveyed medium, and generates and outputs a thickness signal, which is an electrical signal corresponding to the intensity (amount of light) of the received light. Hereinafter, the thickness sensor light emitter 114a and the thickness sensor light receiver 114b may be collectively referred to as the thickness sensor 114.

[0024] If a medium is present between the thickness sensor light emitter 114a and the thickness sensor light receiver 114b, the light emitted by the light emitter is attenuated by the medium. The thicker the medium, the more the light emitted from the thickness sensor light emitter 114a is blocked by the medium, reducing the amount of light received by the thickness sensor light receiver 114b and resulting in a smaller thickness signal value. On the other hand, the thinner the medium, the more the light emitted from the thickness sensor light emitter 114a passes through the medium, increasing the amount of light received by the thickness sensor light receiver 114b and resulting in a larger thickness signal value. Note that if no medium is present between the thickness sensor light emitter 114a and the thickness sensor light receiver 114b, the light emitted from the thickness sensor light emitter 114a reaches the thickness sensor light receiver 114b without being blocked at all. Therefore, the signal value of the thickness signal in this case is even larger than when an extremely thin medium is present between the thickness sensor light emitter 114a and the thickness sensor light receiver 114b. That is, the thickness sensor 114 determines whether or not a medium is present at that position based on the amount of light received by the thickness sensor light receiver 114b, and also detects the thickness of the medium being transported.

[0025] Note that the thickness sensor 114 may be formed using means other than the thickness sensor light emitter 114a and the thickness sensor light receiver 114b. For example, the thickness sensor 114 may be formed using a reflected light sensor, a pressure sensor, or a mechanical sensor. The reflected light sensor detects the time between irradiating the surface of the medium with light and receiving the reflected light, and generates a signal corresponding to the detected time as a thickness signal. The pressure sensor detects pressure, which varies depending on the thickness of the medium, and generates a signal corresponding to the magnitude of the detected pressure as a thickness signal. The mechanical sensor detects the amount of movement of a roller in contact with the medium, and generates a signal corresponding to the detected amount of movement as a thickness signal.

[0026] The ultrasonic transmitter 115a and the ultrasonic receiver 115b are disposed downstream of the feed roller 112 and the brake roller 113 and upstream of the first conveyor roller 116 and the second conveyor roller 117. The ultrasonic transmitter 115a and the ultrasonic receiver 115b are disposed near the medium conveyance path, facing each other across the conveyance path. The ultrasonic transmitter 115a is capable of outputting ultrasonic waves. Meanwhile, the ultrasonic receiver 115b receives ultrasonic waves emitted by the ultrasonic transmitter 115a and that have passed through the medium, and generates and outputs an ultrasonic signal, which is an electrical signal corresponding to the received ultrasonic waves. Hereinafter, the ultrasonic transmitter 115a and the ultrasonic receiver 115b may be collectively referred to as the ultrasonic sensor 115.

[0027] The first conveying roller 116 is provided in the lower housing 101. The second conveying roller 117 is provided in the upper housing 102 and is disposed opposite the first conveying roller 116. The first conveying roller 116 and the second conveying roller 117 are examples of conveying rollers, and are provided downstream of the feed roller 112 and the brake roller 113 in the medium conveying direction A1. The first conveying roller 116 and the second conveying roller 117 convey the medium fed by the feed roller 112 and the brake roller 113 to the imaging device 119.

[0028] The second medium sensor 118 is disposed downstream of the first transport roller 116 and the second transport roller 117 and upstream of the imaging device 119 in the medium transport direction A1. The second medium sensor 118 detects whether a medium is present at that position. The second medium sensor 118 includes a light emitter and a light receiver disposed on one side of the medium transport path, and a reflecting member such as a mirror disposed opposite the light emitter and the light receiver across the transport path. The light emitter emits light toward the transport path. The light receiver receives the light emitted by the light emitter and reflected by the reflecting member, and generates and outputs a second medium signal, which is an electrical signal corresponding to the intensity of the received light. When a medium is present at the second medium sensor 118, the light emitted by the light emitter is blocked by the medium. Therefore, the signal value of the second medium signal changes depending on whether a medium is present or not at the second medium sensor 118. The light emitter and the light receiver may be disposed opposite each other across the transport path, and the reflecting member may be omitted.

[0029] The first imaging device 119a has a line sensor based on a CIS (Contact Image Sensor) of a 1:1 optical system type having CMOS (Complementary Metal Oxide Semiconductor) imaging elements arranged linearly in the main scanning direction. The first imaging device 119a also has a lens that forms an image on the imaging element and an A / D converter that amplifies and analog-to-digital (A / D) converts the electrical signal output from the imaging element. The first imaging device 119a captures an image of the surface of the transported medium under control of a processing circuit (described later), generates an input image, and outputs it.

[0030] Similarly, the second imaging device 119b has a CIS line sensor with a life-size optical system having CMOS imaging elements linearly arranged in the main scanning direction. The second imaging device 119b also has a lens that forms an image on the imaging element and an A / D converter that amplifies and analog-to-digital (A / D) converts the electrical signal output from the imaging element. The second imaging device 119b captures the back side of the transported medium under control of a processing circuit (described later) to generate and output an input image.

[0031] The first imaging device 119a and the second imaging device 119b are examples of an imaging unit. Note that the medium conveying device 100 may have only one of the first imaging device 119a and the second imaging device 119b disposed therein, and may read only one side of the medium. Also, instead of a CIS line sensor of an equal-magnification optical system type equipped with a CMOS imaging element, a CIS line sensor of an equal-magnification optical system type equipped with a CCD (Charge Coupled Device) imaging element may be used. Also, a reduction optical system type line sensor equipped with a CMOS or CCD imaging element may be used.

[0032] The medium placed on the mounting table 103 is transported between the lower guide 107a and the upper guide 107b in the medium transport direction A1 by the rotation of the feed roller 112 in the direction of arrow A2 in Figure 2. The brake roller 113 rotates in the direction of arrow A3 when transporting the medium. When multiple media are placed on the mounting table 103, the feed roller 112 and the brake roller 113 work to separate only the media placed on the mounting table 103 that are in contact with the feed roller 112. This operates to restrict the transport of media other than the separated media (preventing double feeding).

[0033] The medium is fed between first conveyor roller 116 and second conveyor roller 117 while being guided by lower guide 107a and upper guide 107b. The medium is fed between first image capture device 119a and second image capture device 119b as first conveyor roller 116 and second conveyor roller 117 rotate in the directions of arrows A4 and A5, respectively. After being scanned by image capture device 119, the medium is discharged onto discharge tray 104 as third conveyor roller 120 and fourth conveyor roller 121 rotate in the directions of arrows A6 and A7, respectively.

[0034] FIG. 3 is a block diagram showing a schematic configuration of the medium conveying device 100. As shown in FIG.

[0035] In addition to the above-described configuration, the medium conveying device 100 further includes a DC motor 131, a second motor 132, an interface device 133, a storage device 140, a processing circuit 150, and the like.

[0036] The DC motor 131 drives and rotates the first to fourth transport rollers 116, 117, 120, and 121 in response to a control signal from the processing circuit 150, thereby transporting the medium. The DC motor 131 may drive only some of the first to fourth transport rollers 116, 117, 120, and 121, including at least the first transport roller 116 or the second transport roller 117. In this case, the other transport rollers are driven by the second motor 132. The DC motor 131 may also drive and rotate the feed roller 112 and / or the brake roller 113, thereby feeding the medium.

[0037] The DC motor 131 includes a modulation circuit that PWM (Pulse Width Modulation) modulates a predetermined voltage so that the motor rotates at a speed specified by the processing circuit 150, and rotates in accordance with the voltage demodulated by the modulation circuit. The DC motor 131 controls the magnitude of the current flowing through its coil so that the motor rotates at a constant speed, regardless of the magnitude of the load on the DC motor 131, which varies depending on the type or state of the medium transported by the first to fourth transport rollers 116, 117, 120, and 121. The DC motor 131 also includes a known control circuit that can change a current limit value, which is the upper limit of the current flowing through the coil, and changes the current limit value in accordance with a control signal from the processing circuit 150.

[0038] The second motor 132 drives and rotates the feed roller 112 and the brake roller 113 in response to a control signal from the processing circuit 150, thereby feeding the medium. The second motor 132 is a stepping motor. The second motor 132 may also be a DC motor. The feed roller 112 and the brake roller 113 may also be driven by separate motors.

[0039] The interface device 133 has an interface circuit conforming to a serial bus such as USB, and is electrically connected to an information processing device (not shown) (for example, a personal computer, a mobile information terminal, etc.) to transmit and receive input images and various information. Instead of the interface device 133, a communication unit having an antenna for transmitting and receiving wireless signals and a wireless communication interface device for transmitting and receiving signals via a wireless communication line in accordance with a predetermined communication protocol may be used. The predetermined communication protocol is, for example, a wireless LAN (Local Area Network).

[0040] The storage device 140 includes a memory device such as a RAM (Random Access Memory) or a ROM (Read Only Memory), a fixed disk device such as a hard disk, or a portable storage device such as a flexible disk or optical disk. The storage device 140 also stores computer programs, databases, tables, and the like used for various processes of the medium conveying device 100. The computer programs may be installed into the storage device 140 from a computer-readable portable recording medium using a known setup program or the like. The portable recording medium is, for example, a CD-ROM (Compact Disc Read Only Memory), a DVD-ROM (Digital Versatile Disc Read Only Memory), or the like.

[0041] The processing circuit 150 operates based on a program stored in advance in the storage device 140. The processing circuit is, for example, a CPU (Central Processing Unit). The processing circuit 150 may be a DSP (Digital Signal Processor), an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or the like.

[0042] The processing circuit 150 is connected to the operation device 105, the display device 106, the first medium sensor 111, the thickness sensor 114, the ultrasonic sensor 115, the second medium sensor 118, the imaging device 119, the DC motor 131, the second motor 132, the interface device 133, the storage device 140, etc., and controls each of these components. The processing circuit 150 drives the DC motor 131 and the second motor 132 to cause the rollers to transport the medium, acquires an input image from the imaging device 119, and transmits it to the information processing device via the interface device 133. In particular, the processing circuit 150 changes the current limit value of the DC motor 131 based on the second medium signal received from the second medium sensor 118.

[0043] FIG. 4 is a diagram showing a schematic configuration of the storage device 140 and the processing circuit 150. As shown in FIG.

[0044] 4, the storage device 140 stores a control program 141, a setting program 142, a determination program 143, a detection program 144, etc. Each of these programs is a functional module implemented by software running on a processor. The processing circuit 150 reads each program stored in the storage device 140 and operates in accordance with the read program. As a result, the processing circuit 150 functions as a control unit 151, a setting unit 152, a determination unit 153, and a detection unit 154.

[0045] 5 and 6 are flowcharts showing an example of the operation of the medium reading process of the medium conveying device 100. FIG.

[0046] An example of the operation of the medium reading process of the medium conveying device 100 will be described below with reference to the flowcharts shown in Figures 5 and 6. The operation flow described below is executed mainly by the processing circuit 150 in cooperation with each element of the medium conveying device 100 based on a program stored in advance in the storage device 140. The operation flow shown in Figures 5 and 6 is executed periodically.

[0047] First, the control unit 151 waits until a user inputs an instruction to read a medium using the operation device 105 and an operation signal instructing to read a medium is received from the operation device 105 (step S101).

[0048] Next, control unit 151 acquires a first medium signal from first medium sensor 111, and determines whether or not a medium is placed on placement table 103 based on the acquired first medium signal (step S102).

[0049] If no medium is placed on the placement table 103, the control unit 151 returns the process to step S101 and waits until a new operation signal is received from the operation device 105.

[0050] On the other hand, when a medium is placed on the placement table 103, the setting unit 152 sets the current limit value of the DC motor 131 to a first limit value (step S103). The first limit value is preset to a current magnitude such that the sum of the power consumption of the DC motor 131 and the power consumption of the second motor 132 when the DC motor 131 is driven with a current of that magnitude plus a margin does not exceed the rated power consumption of the medium conveyance device 100.

[0051] Next, the control unit 151 drives and rotates the second motor 132, thereby rotating the feed roller 112 and the brake roller 113 to feed the medium. Furthermore, the control unit 151 drives and rotates the DC motor 131, thereby rotating the first to fourth transport rollers 116, 117, 120, and 121 to transport the medium (step S104).

[0052] The control unit 151 performs feedback control of the DC motor 131 so that the rotation speed of the DC motor 131 follows a command value, such as a preset voltage value. The DC motor 131 is inexpensive and allows for easy speed adjustment, but the rotation speed of the DC motor 131 changes due to external factors such as load fluctuations. However, through the above feedback control, the rotation speed of the DC motor 131 becomes the rotation speed corresponding to the command value after a predetermined period of time. Furthermore, based on the first limit value set as the current limit value in step S103, the control unit 151 rotates the DC motor 131 to drive the first to fourth conveyance rollers 116, 117, 120, and 121 so that the magnitude of the current flowing through the coil does not exceed the first limit value. This allows the control unit 151 to appropriately control the magnitude of the current used by the DC motor 131 and appropriately limit the power consumption of the medium conveyance device 100.

[0053] Next, determination unit 153 determines whether a multi-feed of media has occurred (step S105). Determination unit 153 acquires an ultrasonic signal from ultrasonic sensor 115, and determines whether the signal value of the acquired ultrasonic signal is less than a multi-feed threshold. The multi-feed threshold is set to a value between the signal value of the ultrasonic signal when one sheet of paper is being conveyed and the signal value of the ultrasonic signal when a multi-feed of paper has occurred. If the signal value of the ultrasonic signal is equal to or greater than the multi-feed threshold, determination unit 153 determines that a multi-feed of media has not occurred, and if the signal value of the ultrasonic signal is less than the multi-feed threshold, determination unit 153 determines that a multi-feed of media has occurred.

[0054] If it is determined that a multifeed of media has occurred, the control unit 151 executes abnormality processing (step S106) and ends the series of steps. As abnormality processing, the control unit 151 stops the DC motor 131 and the second motor 132 to stop feeding and transporting the media. As abnormality processing, the control unit 151 also displays a message that an abnormality has occurred on the display device 106 or sends a message to the information processing device via the interface device 133 to notify the user of a warning. Note that the medium conveying device 100 has two feeding modes for feeding media: a separation mode in which multiple media are separated and fed, and a non-separation mode in which media are fed without being separated. If the feeding mode is set to the non-separation mode, the processing of steps S105 to S106 is omitted.

[0055] On the other hand, if it is determined that a double feed of media has not occurred, the detection unit 154 determines whether the leading edge of the medium has reached between the first and second conveyance rollers 116 and 117 and the imaging device 119 (step S107). The detection unit 154 periodically acquires a second medium signal from the second medium sensor 118, and determines whether a medium is present at the position of the second medium sensor 118 based on the acquired second medium signal. The detection unit 154 determines that the leading edge of the medium has reached between the first and second conveyance rollers 116 and 117 and the imaging device 119 when the signal value of the second medium signal changes from a value indicating that a medium is not present to a value indicating that a medium is present.

[0056] The detection unit 154 may periodically acquire a thickness signal from the thickness sensor 114 and determine, based on the acquired thickness signal, whether the leading edge of the medium has reached a position between the first and second conveyor rollers 116 and 117 and the imaging device 119. In this case, the detection unit 154 determines that the leading edge of the medium has reached a position between the first and second conveyor rollers 116 and 117 and the imaging device 119 when a predetermined time has elapsed since the signal value of the thickness signal changed from a value indicating that the medium is not present to a value indicating that the medium is present. Alternatively, the detection unit 154 may determine that the leading edge of the medium has reached a position between the first and second conveyor rollers 116 and 117 and the imaging device 119 when a predetermined time has elapsed since feeding of the medium began.

[0057] If the leading edge of the medium has not yet reached the gap between the first and second conveying rollers 116 and 117 and the imaging device 119, the processing circuit 150 returns the process to step S105 and repeats the processes of steps S105 to S107.

[0058] On the other hand, when the leading edge of the medium reaches between the first conveyor roller 116, the second conveyor roller 117, and the imaging device 119, the determination unit 153 determines the type of the medium being conveyed (step S108). The determination unit 153 determines the type of the medium being conveyed based on the thickness of the medium detected by the thickness sensor 114. The determination unit 153 acquires a thickness signal from the thickness sensor 114. The medium conveying device 100 stores in advance in the storage device 140 a table that associates signal values ​​of the thickness signal with medium types, and the determination unit 153 refers to the table to identify the type of medium corresponding to the thickness signal acquired from the thickness sensor 114. For example, paper, cardboard, plastic card, booklet, passport, etc. are set as medium types in ascending order of medium thickness. By using the thickness of the medium, the determination unit 153 can determine the type of medium being conveyed with high accuracy.

[0059] The determination unit 153 may determine the type of medium being conveyed based on the ultrasonic signal generated by the ultrasonic sensor 115. The determination unit 153 acquires the ultrasonic signal from the ultrasonic sensor 115. The medium conveying device 100 pre-stores a table in the storage device 140 that associates the signal value of the ultrasonic signal with the type of medium, and the determination unit 153 references the table to identify the type of medium corresponding to the ultrasonic signal acquired from the ultrasonic sensor 115. Generally, the thicker the medium passing through, the more attenuated the ultrasonic waves emitted by the ultrasonic transmitter 115a and received by the ultrasonic receiver 115b become. Therefore, the determination unit 153 can use the ultrasonic signal to identify the thickness of the medium and determine the type of medium being conveyed with high accuracy. In this case, the thickness sensor 114 can be omitted, allowing the medium conveying device 100 to reduce device costs and weight.

[0060] Next, the setting unit 152 determines whether the type of medium determined by the determination unit 153 is a high-load medium (step S109). A high-load medium is a medium that has a certain thickness and places a high load on the transport roller when transported. A high-load medium is, for example, a medium thicker than PPC paper (cardboard, plastic cards, booklets, passports, etc.). Note that a high-load medium may also be a medium thicker than cardboard.

[0061] If the type of medium is not a high-load medium, the setting unit 152 determines not to change the current limit value (step S110), and proceeds to step S113.

[0062] On the other hand, if the type of medium is a high-load medium, the setting unit 152 determines to change the current limiting value (step S111). In this way, the setting unit 152 determines whether to change the current limiting value depending on the type of medium determined by the determination unit 153. In this way, when a medium with a small load on the conveyance roller is conveyed, the setting unit 152 can suppress an increase in the current used by the DC motor 131 and suppress an increase in power consumption of the medium conveyance device 100.

[0063] Next, the setting unit 152 changes the current limit value of the DC motor 131 to a second limit value (step S112). The second limit value is a value greater than the first limit value. The second limit value is set in advance to a current magnitude such that the power consumption of the DC motor 131 when the DC motor 131 is driven with a current of that magnitude plus a margin does not exceed the rated power consumption of the medium conveyance device 100. In particular, the second limit value is set to a value obtained by adding the magnitude (maximum value) of the current used by the second motor 132 to the first limit value.

[0064] Next, the control unit 151 stops the second motor 132 and continues to drive the DC motor 131 (step S113). That is, if the current limit value has been changed to the second limit value, the control unit 151 rotates the DC motor 131 to drive the first to fourth conveyor rollers 116, 117, 120, and 121 based on the second limit value so that the magnitude of the current flowing through the coil does not exceed the second limit value.

[0065] In this way, the setting unit 152 sets the current limit value for the DC motor 131 to the first limit value until the leading edge of the medium reaches between the first and second conveyance rollers 116 and 117 and the imaging device 119. That is, before imaging is performed by the imaging device 119, the control unit 151 rotates the DC motor 131 based on the first limit value to drive the first and second conveyance rollers 116 and 117. In this way, before imaging is performed by the imaging device 119, the control unit 151 can reduce the current used by the DC motor 131 and reduce the power consumption of the medium conveyance device 100.

[0066] On the other hand, the setting unit 152 changes the current limit value to the second limit value after the medium reaches between the first and second conveyance rollers 116 and 117 and the imaging device 119. That is, when imaging is performed by the imaging device 119, the control unit 151 rotates the DC motor 131 based on the second limit value to drive the first and second conveyance rollers 116 and 117. As a result, when imaging is performed by the imaging device 119, the control unit 151 increases the current available to the DC motor 131 to stably convey the medium and suppress distortion of the medium in the input image generated by the imaging device 119.

[0067] Furthermore, the control unit 151 rotates the second motor 132 until the leading edge of the medium reaches between the first and second conveyance rollers 116 and 117 and the imaging device 119. Then, the control unit 151 stops the second motor 132 after the leading edge of the medium reaches between the first and second conveyance rollers 116 and 117 and the imaging device 119. Therefore, while the feed roller 112 and the brake roller 113 are feeding the medium, the control unit 151 reduces the current used by the DC motor 131 so that the second motor 132 can consume sufficient power instead. On the other hand, after the first and second conveyance rollers 116 and 117 have gripped the medium, the control unit 151 reduces the power consumption by the second motor 132 so that the DC motor 131 can increase the current available for use, thereby stably conveying the medium.

[0068] Next, the control unit 151 causes the imaging device 119 to start imaging the medium (step S114).

[0069] Next, control unit 151 determines whether the trailing edge of the medium has passed imaging device 119 (step S115). For example, control unit 151 periodically acquires a second medium signal from second medium sensor 118 and determines whether a medium is present at the position of second medium sensor 118 based on the acquired second medium signal. Control unit 151 determines that the trailing edge of the medium has passed the position of second medium sensor 118 when the signal value of the second medium signal changes from a value indicating the presence of a medium to a value indicating the absence of a medium. Control unit 151 determines that the trailing edge of the medium has passed the position of second medium sensor 118 when a certain period of time has passed since it was determined that the trailing edge of the medium had passed the position of second medium sensor 118. Control unit 151 waits until the trailing edge of the medium has passed imaging device 119.

[0070] When the rear end of the medium has passed the imaging device 119, the control unit 151 acquires an input image from the imaging device 119 and transmits it to the information processing device via the interface device 133 (step S116).

[0071] Next, control unit 151 determines whether or not a medium remains on mounting table 103 based on the first medium signal obtained from first medium sensor 111 (step S117). If a medium remains on mounting table 103, control unit 151 returns the process to step S103 and repeats the processes of steps S103 to S117.

[0072] On the other hand, if there are no media remaining on the mounting table 103, the control unit 151 stops the DC motor 131 (step S118) and ends the series of steps.

[0073] The processing of steps S105 to S106 may be omitted, and the determination unit 153 may not determine whether a double feed of the transported medium has occurred. Furthermore, the processing of steps S108 to S111 may be omitted, and the setting unit 152 may change the current limit value to the second limit value after the leading edge of the medium reaches between the first transport roller 116 and the second transport roller 117 and the imaging device 119, regardless of the type of medium being transported. Furthermore, from the time imaging is started in step S114 until it is determined in step S115 that the trailing edge of the medium has passed the imaging device 119, it may be determined whether a double feed has occurred, similar to the processing of steps S105 to S106, and if a double feed has occurred, abnormality processing may be executed.

[0074] 7A, 7B, and 7C are schematic diagrams for explaining the magnitude of the torque of the second motor 132 and the DC motor 131 at each timing when the medium is transported.

[0075] 7A shows a state in which the leading edge L of the medium M has reached a position between the feed roller 112 and the brake roller 113 and the first and second conveyor rollers 116 and 117. FIG. 7B shows a state in which the leading edge L of the medium M has reached a position between the first and second conveyor rollers 116 and 117 and the imaging device 119.

[0076] FIG. 7C is a graph showing the maximum torque values ​​of the second motor 132 and the DC motor 131 at each timing. Graph 700 in FIG. 7C shows the maximum torque value of the second motor 132, and graph 701 in FIG. 7C shows the maximum torque value of the DC motor 131. The horizontal axis of FIG. 7C represents time, and the vertical axis represents torque magnitude. Time T1 is the timing when transport of the medium begins, and time T2 is the timing when the leading edge L of the medium M reaches the gap between the first transport roller 116 and the second transport roller 117 and the imaging device 119. Torque P1 is the magnitude of torque that can be generated when a first limit value of current is passed through the DC motor 131, and torque P2 is the magnitude of torque that can be generated when a second limit value of current is passed through the DC motor 131. The torque of each motor is proportional to the magnitude of the current passed through the motor. When the second limit value is set to a value obtained by adding the magnitude (maximum value) of the current used by the second motor 132 to the first limit value, the torque P2 is a value obtained by adding the torque P3 of the second motor 132 to the torque P1.

[0077] As shown in FIG. 7A, the medium M is fed by the feed roller 112 and the brake roller 113 until the leading edge L of the medium M passes the positions of the first conveyor roller 116 and the second conveyor roller 117. Therefore, even if the torque (P1) of the DC motor 131 that drives the first conveyor roller 116 and the second conveyor roller 117 is small, the medium is fed without any problems. Furthermore, when the leading edge L of the medium M passes the positions of the first conveyor roller 116 and the second conveyor roller 117, the rotation speed of the DC motor 131 fluctuates due to load fluctuations when the first conveyor roller 116 and the second conveyor roller 117 bite the medium M. However, at this time, the leading edge L of the medium M has not yet reached the imaging position of the imaging device 119, and the imaging device 119 has not yet started imaging. Therefore, even if the conveyance speed of the medium M fluctuates, distortion or the like does not occur in the input image generated by the imaging device 119. Therefore, until the leading edge L of the medium M reaches between the first and second conveying rollers 116, 117 and the imaging device 119, the medium is conveyed without any problems even if the torque (P1) of the DC motor 131 is small.

[0078] As shown in FIG. 7B , after the leading edge L of the medium M passes the positions of the first conveyor roller 116 and the second conveyor roller 117, the medium is conveyed by the first conveyor roller 116 and the second conveyor roller 117. Therefore, even if the current value used by the second motor 132 is set to zero and the drive of the feed roller 112 and the brake roller 113 by the second motor 132 is stopped, the medium is conveyed without problem by the first conveyor roller 116 and the second conveyor roller 117. Furthermore, by increasing the torque (P2) of the DC motor 131 by the amount by which the current value used by the second motor 132 is set to zero, the medium M is conveyed stably, and the imaging device 119 can generate an input image without distortion of the medium M. Furthermore, by setting the second limit value to a value obtained by adding the magnitude of the current used by the second motor 132 to the first limit value, the medium conveying device 100 can maintain a constant level of power consumption during medium conveyance and operate stably within the rated power consumption range.

[0079] As described above in detail, the medium conveying device 100 increases the current limit value of the DC motor 131 when the leading edge of the medium reaches between the first conveying roller 116 and the second conveying roller 117 and the imaging device 119. This enables the medium conveying device 100 to more appropriately control the magnitude of the current used by the DC motor 131 while stably capturing an image of the medium being conveyed.

[0080] In particular, medium conveying device 100 can sufficiently increase the torque of DC motor 131 when imaging a medium, even when a thick medium such as a passport is being conveyed, making it possible to stably image the medium. Generally, medium conveying devices that support the conveyance of passports use a carrier sheet for sandwiching and conveying the passport. The carrier sheet is colorless and transparent and has a marker at its leading edge. It is preferable that second medium sensor 118 be positioned so that the torque of DC motor 131 is sufficiently stable from the time the leading edge of the carrier sheet passes second medium sensor 118 until the leading edge of the passport sandwiched between the carrier sheet passes the imaging position of imaging device 119.

[0081] Furthermore, the medium conveying device 100 stops the feed roller 112 and the brake roller 113 after the feeding of the medium is completed, but continues to rotate the first to fourth conveying rollers 116, 117, 120, and 121 while the medium is being conveyed. By using the DC motor 131 to drive the first to fourth conveying rollers 116, 117, 120, and 121, which continue to rotate while the medium is being conveyed, the medium conveying device 100 can more appropriately limit the power consumption of the medium conveying device 100.

[0082] Furthermore, medium conveying device 100 is now able to convey and capture good images of multiple types of media with various thicknesses, including media with multiple regions of different thicknesses, such as an open passport, using low-cost DC motor 131. This allows medium conveying device 100 to generate good input images while reducing device costs.

[0083] FIG. 8 is a flowchart showing an example of a part of the operation of a medium reading process of the medium conveying device 100 according to another embodiment.

[0084] A part of the medium reading process shown in Fig. 8 is executed in place of a part of the medium reading process shown in Fig. 5. The processes of steps S201 to S208 and S211 to S212 in the flowchart shown in Fig. 8 are the same as the processes of steps S101 to S108 and S113 to S114 in the flowchart shown in Fig. 5, and therefore detailed explanations will be omitted. The processes of steps S209 to S210 will be explained below.

[0085] In step S209, the setting unit 152 changes (sets) the second limit value according to the medium type determined by the determination unit 153 (step S209). The medium conveying device 100 stores a table in advance in the storage device 140 that associates medium types with second limit values, and the setting unit 152 references the table to determine the second limit value according to the medium type. In the table, the medium type is associated with the second limit value so that the thinner the medium, the smaller the second limit value, and the thicker the medium, the larger the second limit value. This allows the setting unit 152 to reduce the current limit value of the DC motor 131 as the medium becomes thinner, thereby reducing the power consumption of the DC motor 131. Furthermore, the setting unit 152 increases the current limit value of the DC motor 131 as the medium becomes thicker, thereby increasing the torque of the first conveyor roller 116 and the second conveyor roller 117, enabling stable medium conveyance.

[0086] Next, the setting unit 152 sets the current limit value of the DC motor 131 to the second limit value changed (set) in step S209 (step S210).

[0087] As described above in detail, the medium conveying device 100 is now able to more appropriately control the magnitude of the current used by the DC motor 131, even when the second limit value is changed depending on the type of medium.

[0088] FIG. 9 is a diagram for explaining a transport path inside a medium transport device 200 according to another embodiment.

[0089] The medium conveying device 200 has all the parts of the medium conveying device 100, and further has an imprinter 300. Note that the imprinter 300 does not have to be configured separately from the lower housing 101 and the upper housing 102, but may be configured integrally with the lower housing 101 and the upper housing 102. In the medium conveying device 200, the discharge tray 104 is removed, and the lower housing 101 and the upper housing 102 are placed on the imprinter 300. The imprinter 300 is detachably engaged with the lower housing 101 and the upper housing 102. The imprinter 300 is engaged with the lower housing 101 by fitting a claw 308 on the top surface of the imprinter 300 into a recess 223 via a hole 222 provided on the bottom surface of the lower housing 101. When the imprinter 300 is engaged with the lower housing 101, the medium inlet of the imprinter 300 faces the medium outlets from the lower housing 101 and the upper housing 102. The imprinter 300 prints predetermined information on the medium transported from the lower housing 101 and the upper housing 102.

[0090] The imprinter 300 has a second discharge table 301, a third medium sensor 302, a fifth transport roller 303, a sixth transport roller 304, a printing device 305, a seventh transport roller 306, and an eighth transport roller 307. The number of each roller is not limited to one, and there may be more than one of each roller.

[0091] The second ejection table 301 is engaged with the imprinter 300 so as to be able to hold the ejected medium.

[0092] The third medium sensor 302 is positioned upstream of the fifth conveyance roller 303 and the sixth conveyance roller 304 in the medium conveyance direction A1. The third medium sensor 302 has a configuration similar to the second medium sensor 118, and detects whether or not a medium is present at that position. The third medium sensor 302 includes a light emitter, a light receiver, and a reflecting member, and generates and outputs a third medium signal, which is an electrical signal corresponding to the intensity of light emitted by the light emitter, reflected by the reflecting member, and received by the light receiver.

[0093] The fifth conveyance roller 303 and the sixth conveyance roller 304 are arranged opposite to each other. The fifth conveyance roller 303 and the sixth conveyance roller 304 are an example of second rollers, and are arranged downstream of the imaging device 119 and upstream of the printing device 305 in the medium conveyance direction A1. The fifth conveyance roller 303 and the sixth conveyance roller 304 are imaged by the imaging device 119, and convey the medium conveyed by the third conveyance roller 120 and the fourth conveyance roller 121 to the printing device 305.

[0094] The printing device 305 is an example of a printing unit, and is disposed below the medium transport path so that it can print on the surface of the transported medium, and prints predetermined information on the surface of the transported medium. The printing device 305 prints information such as characters specified by a user using an information processing device. The printing device 305 is an inkjet printer, and has a printer head with multiple ink ejection orifices formed therein, and prints predetermined information on the medium by ejecting ink onto the medium as it passes the position of the printing device 305.

[0095] The printing device 305 may be configured to print on the back side of the medium being transported. Alternatively, the printing device 305 may be configured to print on both the front and back sides of the medium being transported. The printing device 305 may also be a printer other than an inkjet type, such as a laser type.

[0096] The medium is scanned by the imaging device 119 and transported by the third transport roller 120 and the fourth transport roller 121, and is sent to the position of the printing device 305 by the rotation of the fifth transport roller 303 and the sixth transport roller 304 in the directions of arrows A8 and A9, respectively. The medium printed by the printing device 305 is discharged onto the second discharge tray 301 by the rotation of the seventh transport roller 306 and the eighth transport roller 307 in the directions of arrows A10 and A11, respectively.

[0097] FIG. 10 is a block diagram showing a schematic configuration of the medium conveying device 200. As shown in FIG.

[0098] In addition to the components and configurations of the medium conveying device 100 described above, the medium conveying device 200 further includes a third motor 311 and the like.

[0099] The third motor 311 drives and rotates the fifth to eighth transport rollers 303, 304, 306, and 307 in response to a control signal from the processing circuit 150, thereby transporting the medium. The third motor 311 is a stepping motor. The third motor 311 may also be a DC motor. The fifth to eighth transport rollers 303, 304, 306, and 307 may also be driven by separate motors.

[0100] FIG. 11 is a flowchart showing an example of a part of the operation of the medium reading process of the medium conveying device 200.

[0101] A part of the medium reading process shown in Fig. 11 is executed in place of a part of the medium reading process shown in Fig. 6. The processes of steps S315 to S316 and S325 to S326 in the flowchart shown in Fig. 11 are the same as the processes of steps S115 to S116 and S117 to S118 in the flowchart shown in Fig. 6, and therefore detailed explanations will be omitted. The processes of steps S317 to S324 will be explained below.

[0102] In step S317, the detection unit 154 determines whether the leading edge of the medium has reached a position between the imaging device 119 and the fifth and sixth conveyance rollers 303 and 304 (step S317). The detection unit 154 periodically acquires a third medium signal from the third medium sensor 302, and determines whether a medium is present at the position of the third medium sensor 302 based on the acquired third medium signal. The detection unit 154 determines that the leading edge of the medium has reached a position between the imaging device 119 and the fifth and sixth conveyance rollers 303 and 304 when the signal value of the third medium signal changes from a value indicating that a medium is not present to a value indicating that a medium is present.

[0103] The third medium sensor 302 may determine that the leading edge of the medium has reached the gap between the imaging device 119 and the fifth and sixth conveyance rollers 303 and 304 when a predetermined time has elapsed since the leading edge of the medium passed the position of the second medium sensor 118 or the thickness sensor 114. Alternatively, the third medium sensor 302 may determine that the leading edge of the medium has reached the gap between the imaging device 119 and the fifth and sixth conveyance rollers 303 and 304 when a predetermined time has elapsed since feeding of the medium began. The detection unit 154 waits until the leading edge of the medium has reached the gap between the imaging device 119 and the fifth and sixth conveyance rollers 303 and 304.

[0104] On the other hand, if the leading edge of the medium reaches the area between the imaging device 119 and the fifth conveying roller 303 and the sixth conveying roller 304, the setting unit 152 determines whether the type of medium determined by the determination unit 153 in step S108 is a high-load medium (step S318).

[0105] If the type of medium is not a high-load medium, the setting unit 152 determines not to change the current limit value (step S319), and proceeds to step S321.

[0106] On the other hand, if the type of medium is a high-load medium, the setting unit 152 determines to change the current limit value (step S320).

[0107] Next, the setting unit 152 changes the current limit value of the DC motor 131 to a third limit value (step S321). The third limit value is a value smaller than the second limit value. The third limit value is set in advance to a current magnitude such that the sum of the power consumption of the DC motor 131 and the power consumption of the third motor 311 when the DC motor 131 is driven with a current of that magnitude plus a margin does not exceed the rated power consumption of the medium conveyance device 200. In particular, the third limit value is set to a value obtained by subtracting the magnitude (maximum value) of the current used by the third motor 311 from the second limit value.

[0108] Next, the control unit 151 drives and rotates the third motor 311, and rotates the fifth to eighth conveyance rollers 303, 304, 306, and 307 to convey the medium, while continuing to drive the DC motor 131 (step S322). That is, if the current limit value has been changed to the third limit value, the control unit 151 drives the first to fourth conveyance rollers 116, 117, 120, and 121 by rotating the DC motor 131 based on the third limit value so that the magnitude of the current flowing through the coil does not exceed the third limit value.

[0109] In this way, after the leading edge of the medium reaches between the imaging device 119 and the fifth and sixth conveyance rollers 303 and 304, the setting unit 152 rotates the third motor 311 and changes the current limit value to the third limit value. That is, when the control unit 151 rotates the third motor 311 to convey the medium to the printing device 305, the control unit 151 rotates the DC motor 131 based on the third limit value to drive the first and second conveyance rollers 116 and 117. Therefore, when rotating the third motor 311, the control unit 151 reduces the current available to the DC motor 131, thereby maintaining a constant level of power consumption of the medium conveyance device 200 and enabling stable operation within the rated power consumption range. When the fifth and sixth conveyance rollers 303 and 304 convey the medium, the medium is stably conveyed by the fifth and sixth conveyance rollers 303 and 304 even if the torque of the first to fourth conveyance rollers 116, 117, 120, and 121 is reduced.

[0110] Next, the control unit 151 waits for a predetermined time until the printing position of the medium is transported to the position of the printing device 305, and causes the printing device 305 to print predetermined information on the transported medium (step S323).

[0111] Next, the control unit 151 determines whether the trailing edge of the medium has passed the printing device 305 (step S324). The control unit 151, for example, periodically acquires a third medium signal from the third medium sensor 302 and determines whether the medium is present at the position of the third medium sensor 302 based on the acquired third medium signal. The control unit 151 determines that the trailing edge of the medium has passed the position of the third medium sensor 302 when the signal value of the third medium signal changes from a value indicating the presence of the medium to a value indicating the absence of the medium. The control unit 151 determines that the trailing edge of the medium has passed the printing device 305 when a certain period of time has elapsed since determining that the trailing edge of the medium has passed the position of the third medium sensor 302. The control unit 151 waits until the trailing edge of the medium has passed the printing device 305, and when the trailing edge of the medium has passed the printing device 305, the control unit 151 proceeds to step S325.

[0112] The processing of steps S318 to S320 may be omitted, and the setting unit 152 may change the current limit value to the third limit value after the leading edge of the medium reaches between the imaging device 119 and the fifth and sixth conveying rollers 303 and 304, regardless of the type of medium being conveyed.

[0113] Alternatively, instead of steps S318 to S321, steps similar to steps S208 to S210 in FIG. 8 may be performed, with the setting unit 152 changing the third limit value depending on the medium type. In this case, the medium conveying device 100 stores a table in advance in the storage device 140 that associates medium types with third limit values, and the setting unit 152 references the table to determine the third limit value depending on the medium type. The table associates the medium type with the third limit value such that the thinner the medium, the smaller the third limit value, and the thicker the medium, the larger the third limit value. This allows the setting unit 152 to reduce the current limit value of the DC motor 131 the thinner the medium, thereby reducing power consumption by the DC motor 131. Furthermore, the setting unit 152 increases the current limit value of the DC motor 131 the thicker the medium, thereby increasing the torque of the first conveyor roller 116 and the second conveyor roller 117, enabling stable medium conveyance.

[0114] As described above in detail, the medium conveying device 200 is now able to more appropriately control the amount of current used by the DC motor 131, even when the third motor 311 drives the fifth conveying roller 303 and the sixth conveying roller 304.

[0115] 12 is a diagram showing a schematic configuration of a processing circuit 450 in a medium conveying device according to another embodiment. The processing circuit 450 is used in place of the processing circuit 150 of the medium conveying device 100 or the medium conveying device 200, and executes the medium reading process in place of the processing circuit 150. The processing circuit 450 includes a control circuit 451, a setting circuit 452, a determination circuit 453, and a detection circuit 454. Note that each of these components may be configured as an independent integrated circuit, microprocessor, firmware, or the like.

[0116] The control circuit 451 is an example of a control unit and has the same functions as the control unit 151. The control circuit 451 receives an operation signal from the operation device 105, a first medium signal from the first medium sensor 111, a second medium signal from the second medium sensor 118, and a third medium signal from the third medium sensor 302, and reads out the determination result of the medium type from the storage device 140. The control circuit 451 outputs control signals to the DC motor 131, the second motor 132, and the third motor 311 so as to control the transport of the medium in accordance with the received signals and the read out determination result. The control circuit 451 also receives an input image from the imaging device 119 and transmits it to the information processing device via the interface device 133. The control circuit 451 also outputs a control signal to the printing device 305 to instruct printing on the medium.

[0117] The setting circuit 452 receives a change instruction to change the current limit value of the DC motor 131 from the detection circuit 454, and changes the current limit value of the DC motor 131.

[0118] The determination circuit 453 receives a thickness signal from the thickness sensor 114 and an ultrasonic signal from the ultrasonic sensor 115 , determines the type of medium according to the received signals, and stores the determination result in the storage device 140 .

[0119] The detection circuit 454 receives a second medium signal from the second medium sensor 118 and a third medium signal from the third medium sensor 302, and outputs a change instruction to the setting circuit 452 to change the current limit value of the DC motor 131 according to each received signal.

[0120] As described above in detail, the medium conveying device is now able to more appropriately control the magnitude of the current used by the DC motor 131 even when using the processing circuit 450. [Explanation of symbols]

[0121] 100 medium conveying device, 112 feeding roller, 114 thickness sensor, 115 ultrasonic sensor, 116 first conveying roller, 117 second conveying roller, 119 imaging device, 131 DC motor, 132 second motor, 151 control unit, 152 setting unit, 153 determination unit, 154 detection unit, 303 fifth conveying roller, 304 sixth conveying roller, 305 printing device

Claims

1. A first roller; a DC motor that drives the first roller; a second roller provided upstream of the first roller in the medium transport direction; a second motor that drives the second roller; a setting unit that changes a current limit value of the DC motor from a first limit value to a second limit value that is greater than the first limit value and stops the second motor after the leading edge of the medium has passed the first roller; A medium transport device comprising:

2. a thickness sensor for detecting the thickness of the transported medium; 2. The medium conveying device of claim 1, wherein the setting unit determines whether to change the second limit value or change the current limit value from the first limit value to the second limit value based on the thickness of the medium detected by the thickness sensor.

3. further comprising an ultrasonic sensor for generating an ultrasonic signal; The medium conveying device according to claim 1 , wherein the setting unit determines whether to change the second limit value or change the current limit value from the first limit value to the second limit value based on the ultrasonic signal.

4. an imaging unit that images a medium; a detection unit that detects when the leading edge of the medium reaches a position between the first roller and the imaging unit, 4. The medium conveying device according to claim 1, wherein the setting unit changes the current limit value from the first limit value to the second limit value based on the detection result by the detection unit.

5. a sensor disposed between the first roller and the imaging unit; The medium transport device according to claim 4 , wherein the detection unit detects that the leading edge of the medium has reached a position between the first roller and the imaging unit based on a signal output from the sensor.

6. an imaging unit that images a medium; a printing unit that prints on the medium; a third roller that transports the medium imaged by the imaging unit to the printing unit; a third motor that drives the third roller, A medium conveying device described in any one of claims 1 to 3, wherein the setting unit changes the current limit value from the second limit value to a third limit value smaller than the second limit value after the leading edge of the medium reaches between the imaging unit and the third roller.

7. A method for controlling a medium transport device having a first roller, a DC motor that drives the first roller, a second roller that is provided upstream of the first roller in a medium transport direction, and a second motor that drives the second roller, the method comprising: After the leading edge of the medium has passed the first roller, the current limit value of the DC motor is changed from a first limit value to a second limit value that is greater than the first limit value, and the second motor is stopped. A control method comprising:

8. A control program for a medium transport device having a first roller, a DC motor that drives the first roller, a second roller that is provided upstream of the first roller in a medium transport direction, and a second motor that drives the second roller, the program comprising: After the leading edge of the medium has passed the first roller, the current limit value of the DC motor is changed from a first limit value to a second limit value that is greater than the first limit value, and the second motor is stopped. a control program for causing the medium transport device to execute the above steps;

Images