Medium conveying device, medium conveying method, and control program

Abstract

To provide a medium conveying device, a medium conveying method, and a control program that enable better control of a DC motor.SOLUTION: A medium conveying device includes a roller that conveys a medium, a DC motor that drives the roller, and a control unit that can control the DC motor using either open-loop control or closed-loop control, and the control unit changes the control of the DC motor from open-loop control to closed-loop control when a predetermined time has elapsed since starting to change the speed of the DC motor or roller, or when the speed of the DC motor or roller reaches a predetermined speed.SELECTED DRAWING: Figure 10

Description

[Technical Field]

[0001] The present invention relates to a medium transport device, a medium transport method, and a control program. [Background technology]

[0002] In media transport devices such as scanners and printers, direct current (DC) motors are often used to drive rollers that transport media. DC motors are low cost and consume little power, but they are susceptible to external factors such as load fluctuations, and when the speed of the DC motor or roller is changed, it takes time to reach the target speed.

[0003] A motor control device is disclosed that controls a motor based on a first current command value that depends on closed-loop control and a second current command value that depends on open-loop control (see Patent Document 1). When switching the motor control method from closed-loop control to open-loop control, this motor control device transitions the second current command value stepwise to a first target value during a predetermined switching period, and transitions the first current command value stepwise to the second target value. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-007533 Summary of the Invention [Problem to be solved by the invention]

[0005] In media transport devices that use DC motors to transport media, there is a need for better control of the DC motors.

[0006] An object of the present invention is to provide a medium transport device, a medium transport method, and a control program that are capable of better controlling a DC motor. [Means for solving the problem]

[0007] A media conveying device according to one aspect of the present invention comprises a roller for conveying a medium, a DC motor for driving the roller, and a control unit capable of controlling the DC motor using either open-loop control or closed-loop control, and the control unit changes the control of the DC motor from open-loop control to closed-loop control when a predetermined time has elapsed since starting to change the speed of the DC motor or roller, or when the speed of the DC motor or roller reaches a predetermined speed.

[0008] A media transport method according to one aspect of the present invention includes transporting a media by a roller, driving the roller by a DC motor, and controlling the DC motor using either open-loop control or closed-loop control, and in the control, when a predetermined time has elapsed since starting to change the speed of the DC motor or roller, or when the speed of the DC motor or roller reaches a predetermined speed, the control of the DC motor is changed from open-loop control to closed-loop control.

[0009] A control program according to one aspect of the present invention is a control program for a media conveying device having a roller for conveying a medium and a DC motor for driving the roller, and causes the media conveying device to control the DC motor using either open-loop control or closed-loop control, and in the control, when a predetermined time has elapsed since starting to change the speed of the DC motor or roller, or when the speed of the DC motor or roller reaches a predetermined speed, the control of the DC motor is changed from open-loop control to closed-loop control. [Effects of the Invention]

[0010] According to the present invention, the medium transport device, the medium transport method, and the control program are capable of better controlling the DC motor. [Brief explanation of the drawings]

[0011] [Figure 1]FIG. 1 is a perspective view illustrating a medium transport device according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating a transport path inside the medium transport device. [Figure 3] 1A to 1C are schematic diagrams for explaining the circuit configuration of a motor. [Figure 4] FIG. 2 is a block diagram showing a schematic configuration of a medium transport device. [Figure 5] 1A to 1C are schematic diagrams for explaining a driving device. [Figure 6] FIG. 2 is a diagram showing a schematic configuration of a storage device and a processing circuit. [Figure 7] 10 is a flowchart illustrating an example of the operation of a medium transport process. [Figure 8] 10 is a graph for explaining a change in the speed of a roller. [Figure 9] 10 is a flowchart illustrating an example of the operation of a medium ejection process. [Figure 10] 10 is a flowchart illustrating an example of a portion of the operation of a speed change process. [Figure 11] Graphs (A) to (C) are graphs for explaining changes in motor speed. [Figure 12] FIG. 10 is a diagram showing a schematic configuration of another processing circuit. DETAILED DESCRIPTION OF THE INVENTION

[0012] A medium conveying device, a medium conveying method, and a control program 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 configured as an image scanner.

[0014] The medium conveying device 100 conveys, captures an image of, and discharges a medium that is an original. The medium may be paper, cardboard, a card, a booklet, a passport, etc. The medium conveying device 100 may also be a facsimile machine, a copier, a multifunction printer (MFP), etc.

[0015] 1, arrow A1 indicates the medium transport direction, arrow A2 indicates the width direction perpendicular to the medium transport direction, and arrow A3 indicates the height direction perpendicular to the medium transport path. Hereinafter, "upstream" refers to the upstream side of the medium transport direction A1, and "downstream" refers to the downstream side of the medium transport direction A1. The width direction A2 is an example of a direction that intersects with the medium transport direction.

[0016] 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.

[0017] 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.

[0018] The loading platform 103 engages with the lower housing 101 and places media to be fed and transported on it. The ejection platform 104 engages with the lower housing 101 and places ejected media on it. The ejection platform 104 may also be engaged with the upper housing 102 by a hinge or the like.

[0019] 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.

[0020] FIG. 2 is a diagram for explaining a transport path inside the medium transport device.

[0021] The transport path inside the media transport device 100 includes a first media sensor 111, a feed roller 112, a separation roller 113, a second media sensor 114, a transport roller 115, a first opposing roller 116, a third media sensor 117, an imaging device 118, an ejection roller 119, and a second opposing roller 120, etc.

[0022] The feed roller 112, separation roller 113, transport roller 115, first opposing roller 116, discharge roller 119, and / or second opposing roller 120 are examples of rollers that transport a medium. Note that the number of each of the feed roller 112, separation roller 113, transport roller 115, first opposing roller 116, discharge roller 119, and / or second opposing roller 120 is not limited to one, and may be multiple. In this case, the multiple feed rollers 112, separation roller 113, transport roller 115, first opposing roller 116, discharge roller 119, and / or second opposing roller 120 are arranged side by side at intervals in the width direction A2.

[0023] 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. As shown in Fig. 2, the medium transport path has a so-called straight path mechanism in which the vertical positional relationship between the front and back surfaces of the medium does not change between the state before transport when the medium is placed on loading tray 103 and the state after ejection when the medium is placed on ejection tray 104. Because the medium transport path has a straight path mechanism, medium transport device 100 can be formed compactly.

[0024] The first medium sensor 111 is disposed upstream of the feed roller 112 and the separation 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. Note that the first medium sensor 111 is not limited to a contact detection sensor, and any other sensor capable of detecting the presence or absence of a medium, such as an optical detection sensor, may be used as the first medium sensor 111.

[0025] The feed roller 112 is provided in the lower housing 101, and separates and feeds the media placed on the mounting table 103, starting from the bottom. The separation roller 113 is a so-called brake roller or retard roller, and is provided in the upper housing 102, and is disposed opposite the feed roller 112. The separation roller 113 is provided so as to be rotatable or stoppable in the direction A5 opposite the medium feeding direction. Note that a separation pad may be used instead of the separation roller 113.

[0026] The second media sensor 114 is positioned downstream of the feed roller 112 and upstream of the transport roller 115, and detects the leading and trailing edges of a medium transported to that position. The second media sensor 114 includes a light emitter and a light receiver provided on one side of the medium transport path, and a light guide member provided opposite the light emitter and light receiver across the medium transport path. The light guide member is a light guide tube such as a U-shaped prism. The light emitter is an LED (Light Emitting Diode) or the like, and emits light toward the transport path. On the other hand, the light receiver is a photodiode or the like, and receives light emitted by the light emitter and guided by the light guide member. When a medium is present in a position opposite the second media sensor 114, the light emitted from the light emitter is blocked by the medium, and the light receiver does not detect the light emitted from the light emitter. Based on the intensity of the received light, the light receiver generates and outputs a second medium signal whose signal value changes depending on whether a medium is present or not at the position of second medium sensor 114. Note that a reflective member such as a mirror may be used instead of the light guiding member. Also, the light emitter and light receiver may be positioned opposite each other across the transport path. Also, second medium sensor 114 may detect the presence of a medium using a contact detection sensor or the like that passes a predetermined current when the medium is in contact or not in contact.

[0027] The conveying roller 115 and the first opposing roller 116 are disposed opposite each other downstream of the feeding roller 112 and the separation roller 113 in the medium conveying direction A1. The conveying roller 115 and the first opposing roller 116 convey the medium fed by the feeding roller 112 and the separation roller 113 to the imaging device 118.

[0028] The third media sensor 117 is located downstream of the transport roller 115 and upstream of the imaging device 118 and detects the leading and trailing edges of a medium transported to that position. The third media sensor 117 includes a light emitter and a light receiver located on one side of the media transport path, and a light guide member located opposite the light emitter and light receiver across the media transport path. The light guide member is a light guide tube such as a U-shaped prism. The light emitter is an LED or the like and emits light toward the transport path. The light receiver is a photodiode or the like and receives light emitted by the light emitter and guided by the light guide member. When a medium is present in a position opposite the third media sensor 117, the light emitted from the light emitter is blocked by the medium, and the light receiver does not detect the light emitted from the light emitter. The light receiver generates and outputs a third media signal based on the intensity of the received light. The signal value changes depending on whether a medium is present or not at the third media sensor 117. A reflective member such as a mirror may be used instead of the light-guiding member. The light emitter and the light receiver may be positioned opposite each other across the transport path. Third medium sensor 117 may detect the presence of a medium using a contact detection sensor that passes a predetermined current when the medium is in contact or when the medium is not in contact.

[0029] The imaging device 118 captures an image of the medium transported by the transport rollers 115. The imaging device 118 includes a first imaging device 118a and a second imaging device 118b that are arranged opposite each other across the medium transport path.

[0030] The first imaging device 118a has an imaging sensor based on a CIS (Contact Image Sensor) of a 1:1 optical system type having imaging elements based on CMOS (Complementary Metal Oxide Semiconductor) linearly arranged in the main scanning direction. The first imaging device 118a 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 118a captures images of the surface of the medium being transported, sequentially generating and outputting input images.

[0031] Similarly, the second imaging device 118b has a CIS imaging sensor with a life-size optical system having CMOS imaging elements linearly arranged in the main scanning direction. The second imaging device 118b 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 118b captures the back side of the medium being conveyed, sequentially generating and outputting line images.

[0032] The medium conveying device 100 may have only one of the first and second imaging devices 118a and 118b, and may read only one side of the medium. Alternatively, a CIS line sensor with a life-size optical system equipped with a CCD (Charge Coupled Device) imaging element may be used as the imaging sensor. Alternatively, a reduction optical system line sensor with a CMOS or CCD imaging element may be used as the imaging sensor.

[0033] The discharge roller 119 and the second opposing roller 120 are disposed opposite each other downstream of the imaging device 118 in the medium conveying direction A1. The discharge roller 119 and the second opposing roller 120 discharge the medium that has been conveyed by the conveying roller 115 and the first opposing roller 116 and processed (imaged) by the imaging device 118 onto the discharge tray 104.

[0034] The media placed on the mounting table 103 is transported between the lower guide 107a and the upper guide 107b in the media transport direction A1 by the rotation of the feed roller 112 in the direction of arrow A4 in Figure 2, i.e., the media feed direction. When transporting the media, the separation roller 113 rotates in the direction of arrow A5, i.e., the opposite direction to the media feed direction. When multiple media are placed on the mounting table 103, the feed roller 112 and the separation roller 113 work to separate only the media placed on the mounting table 103 that are in contact with the feed roller 112. This restricts the transport of media other than the separated media (preventing double feeding).

[0035] The medium is guided by lower guide 107a and upper guide 107b and fed between conveying roller 115 and first opposing roller 116. The medium is fed between first imaging device 118a and second imaging device 118b as conveying roller 115 and first opposing roller 116 rotate in the directions of arrows A6 and A7, respectively. The medium read by imaging device 118 is discharged onto discharge tray 104 as discharge roller 119 and second opposing roller 120 rotate in the directions of arrows A8 and A9, respectively.

[0036] Also, as shown in FIG. 2, the medium conveying device 100 has a first motor 131, a first transmission mechanism 132, a first encoder 133, a second motor 141, a second transmission mechanism 142, a second encoder 143, a third motor 151, a third transmission mechanism 152, and a third encoder 153.

[0037] The first motor 131 is a drive source for the feed roller 112 and is, for example, a DC motor, particularly a brushed DC motor. The first motor 131 may be a motor other than a DC motor, such as a stepping motor. The first motor 131 is provided in the lower housing 101 and is connected to the feed roller 112 via a first transmission mechanism 132 to drive the feed roller 112. The first motor 131 generates a drive force for rotating the feed roller 112 in response to a control signal from the processing circuit, thereby feeding the medium. The first motor 131 may be disposed in the upper housing 102.

[0038] The first transmission mechanism 132 includes one or more pulleys, belts, gears, etc. arranged between the first motor 131 and the shaft 112a, which is the rotation axis of the feed roller 112, and transmits the driving force generated by the first motor 131 to the feed roller 112.

[0039] The first encoder 133 is attached to the rotary shaft of the first motor 131 and detects the rotation of the first motor 131. The first encoder 133 has a disk with numerous slits (light-transmitting holes) formed therein and configured to rotate in accordance with the rotation of the first motor 131, and a light emitter and a light receiver configured to face each other across the disk. The light emitter is an LED or the like and emits light toward the disk (light receiver). The light receiver is a photodiode or the like and receives the light emitted by the light emitter through the disk. The light receiver detects the number of changes within a predetermined period from a state in which there is a slit between the light emitter and the light receiver to a state in which there is no slit and the light is blocked by the disk. The light receiver calculates the rotation speed of the first motor 131 from the number of changes and the number of slits for the predetermined period and outputs a rotation speed signal indicating the rotation speed of the first motor 131. The first encoder 133 may be provided on the shaft 112a of the feed roller 112, detect the rotation of the feed roller 112, and output a rotation number signal indicating the number of rotations of the feed roller 112. Furthermore, the first encoder 133 is not limited to an optical encoder, and may be any encoder such as a mechanical encoder, a magnetic encoder, or an electromagnetic induction encoder.

[0040] The second motor 141 is a drive source for the separation roller 113 and is, for example, a DC motor, particularly a brushed DC motor. The second motor 141 may be a motor other than a DC motor, such as a stepping motor. The second motor 141 is provided in the upper housing 102 separately from the first motor 131, and is connected to the separation roller 113 via a second transmission mechanism 142 to drive the separation roller 113. The second motor 141 generates a drive force for rotating the separation roller 113 in response to a control signal from the processing circuit, causing the separation roller 113 to separate, feed, and transport the medium. The second motor 141 may be disposed in the lower housing 101.

[0041] The second transmission mechanism 142 includes one or more pulleys, belts, gears, etc., provided between the second motor 141 and the shaft 113a which is the rotation axis of the separation roller 113. The second transmission mechanism 142 transmits the driving force generated by the second motor 141 to the separation roller 113.

[0042] The second encoder 143 is attached to the rotary shaft of the second motor 141 and detects the rotation of the second motor 141. The second encoder 143 includes a disk with numerous slits (light-transmitting holes) formed therein and configured to rotate in accordance with the rotation of the second motor 141, and a light emitter and a light receiver configured to face each other across the disk. The light emitter is an LED or the like and emits light toward the disk (light receiver). The light receiver is a photodiode or the like and receives the light emitted by the light emitter through the disk. The light receiver detects the number of changes within a predetermined period from a state in which there is a slit between the light emitter and the light receiver to a state in which there is no slit and the light is blocked by the disk. The light receiver calculates the rotation speed of the second motor 141 from the number of changes and the number of slits for the predetermined period and outputs a rotation speed signal indicating the rotation speed of the second motor 141. The second encoder 143 may be provided on the shaft 113a of the separation roller 113, detect the rotation of the separation roller 113, and output a rotation number signal indicating the number of rotations of the separation roller 113. Furthermore, the second encoder 143 is not limited to an optical encoder, and may be any encoder such as a mechanical encoder, a magnetic encoder, or an electromagnetic induction encoder.

[0043] The third motor 151 is a drive source for the transport rollers 115 and the discharge rollers 119, and is, for example, a DC motor, particularly a brushed DC motor. The third motor 151 may be a motor other than a DC motor, such as a stepping motor. The third motor 151 is provided in the lower housing 101 separately from the first motor 131 and the second motor 141. The third motor 151 is connected to the transport rollers 115 and the discharge rollers 119 via a third transmission mechanism 152 and drives the transport rollers 115 and the discharge rollers 119. The third motor 151 generates a drive force for rotating the transport rollers 115 and the discharge rollers 119 in response to a control signal from the processing circuit, causing the transport rollers 115 and the discharge rollers 119 to transport and discharge the medium. The third motor 151 may be disposed in the upper housing 102.

[0044] The third transmission mechanism 152 includes one or more pulleys, belts, gears, etc., provided between the third motor 151 and a shaft 115a which is the rotation shaft of the conveying roller 115 and a shaft 119a which is the rotation shaft of the discharging roller 119. The third transmission mechanism 152 transmits the driving force generated by the third motor 151 to the conveying roller 115 and the discharging roller 119.

[0045] The third encoder 153 is attached to the rotary shaft of the third motor 151 and detects the rotation of the third motor 151. The third encoder 153 includes a disk with numerous slits (light-transmitting holes) formed therein and configured to rotate in accordance with the rotation of the third motor 151, and a light emitter and a light receiver configured to face each other across the disk. The light emitter is an LED or the like and emits light toward the disk (light receiver). The light receiver is a photodiode or the like and receives the light emitted by the light emitter through the disk. The light receiver detects the number of changes within a predetermined period from a state in which there is a slit between the light emitter and the light receiver to a state in which there is no slit and the light is blocked by the disk. The light receiver calculates the rotation speed of the third motor 151 from the number of changes and the number of slits for the predetermined period and outputs a rotation speed signal indicating the rotation speed of the third motor 151. The third encoder 153 may be provided on the shaft 115a of the conveying roller 115 or the shaft 119a of the discharge roller 119, detect the rotation of the conveying roller 115 or the discharge roller 119, and output a rotation speed signal indicating the rotation speed of the conveying roller 115 or the discharge roller 119. Furthermore, the third encoder 153 is not limited to an optical encoder, and may be any encoder such as a mechanical encoder, a magnetic encoder, or an electromagnetic induction encoder.

[0046] The first opposing roller 116 is a driven roller that rotates following the conveyance roller 115, and the second opposing roller 120 is a driven roller that rotates following the discharge roller 119. The first opposing roller 116 and / or the second opposing roller 120 may be configured to be driven by a driving force from a third motor 151. In this case, the third transmission mechanism 152 further includes one or more gears provided between the shaft 115a of the conveyance roller 115 and the shaft 116a that is the rotation axis of the first opposing roller 116 and / or between the shaft 119a of the discharge roller 119 and the shaft 120a that is the rotation axis of the second opposing roller 120, and further transmits the driving force generated by the third motor 151 to the first opposing roller 116 and / or the second opposing roller 120. When the first opposing roller 116 and / or the second opposing roller 120 are configured to be driven by a driving force from the third motor 151, the third encoder 153 may be provided on the shaft 116a of the first opposing roller 116 or the shaft 120a of the second opposing roller 120 to detect the rotation of the first opposing roller 116 or the second opposing roller 120 and output a rotation speed signal indicating the rotation speed of the first opposing roller 116 or the second opposing roller 120.

[0047] The separation roller 113, the transport roller 115, and the discharge roller 119 may be driven by a common motor. Alternatively, the transport roller 115 and the discharge roller 119 may be driven by separate motors.

[0048] 3(A) to 3(C) are schematic diagrams for explaining the circuit configuration of each motor.

[0049] As shown in FIG. 3A, the circuit inside the first motor 131 includes a first motor section 131a and a first resistor section 131b. The first motor section 131a is driven to rotate in response to the voltage applied to or current flowing into terminals on both sides. The first resistor section 131b is a variable resistor. The first resistor section 131b may also be a fixed resistor. The first resistor section 131b may also be provided so as to be short-circuitable.

[0050] As shown in FIG. 3B, the circuit inside the second motor 141 includes a second motor section 141a and a second resistor section 141b. The second motor section 141a is driven to rotate in response to the voltage applied to or current flowing into terminals on both sides. The second resistor section 141b is a variable resistor. The second resistor section 141b may also be a fixed resistor. The second resistor section 141b may also be provided so as to be short-circuitable.

[0051] As shown in FIG. 3(C), the circuit inside the third motor 151 includes a third motor section 151a and a third resistor section 151b. The third motor section 151a is driven to rotate in response to the voltage applied to or current flowing into terminals on both sides. The third resistor section 151b is a variable resistor. The third resistor section 151b may also be a fixed resistor. The third resistor section 151b may also be provided so as to be short-circuitable.

[0052] FIG. 4 is a block diagram showing a schematic configuration of the medium transport device.

[0053] In addition to the above-described configuration, the medium conveying device 100 further includes a first driving device 130, a second driving device 140, a third driving device 150, an interface device 161, a storage device 170, a processing circuit 180, and the like.

[0054] The interface device 161 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 personal digital assistant, etc.) to transmit and receive input images and various information. Instead of the interface device 161, 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). The communication unit may have a wired communication interface device for transmitting and receiving signals via a wired communication line in accordance with a communication protocol such as a wired LAN.

[0055] The storage device 170 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 170 also stores computer programs, databases, tables, and the like used for various processes of the medium conveyance device 100. The computer programs may be installed into the storage device 170 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) or a DVD-ROM (Digital Versatile Disc Read Only Memory). The computer programs may also be distributed from a server or the like and installed into the storage device 170.

[0056] The processing circuit 180 operates based on a program stored in advance in the storage device 170. The processing circuit is, for example, a CPU (Central Processing Unit). The processing circuit 180 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.

[0057] The processing circuit 180 is connected to the operation device 105, the display device 106, the first medium sensor 111, the second medium sensor 114, the third medium sensor 117, the imaging device 118, the first driving device 130, the second driving device 140, the third driving device 150, the interface device 161, the storage device 170, etc., and controls each of these components. The processing circuit 180 performs drive control of the first driving device 130, the second driving device 140, and the third driving device 150, image capture control of the imaging device 118, etc., based on each medium signal acquired from each media sensor. The processing circuit 180 acquires an input image from the imaging device 118 and transmits it to the information processing device via the interface device 161.

[0058] 5(A) to 5(C) are schematic diagrams for explaining each driving device.

[0059] 5(A), the first driving device 130 includes a first motor control circuit 134 in addition to the first motor 131. The first motor control circuit 134 sets the voltage applied to the terminals on both sides of the first motor unit 131a, the current flowing through the first motor unit 131a, and / or the power consumed by the first motor unit 131a in accordance with a control signal from the processing circuit 180.

[0060] For example, the first motor control circuit 134 includes a step-up / step-down circuit that outputs a voltage applied to terminals on both sides of the first motor unit 131a. The processing circuit 180 adjusts a control signal (voltage) input to the step-up / step-down circuit of the first motor control circuit 134 to change the voltage applied to terminals on both sides of the first motor unit 131a, the current flowing through the first motor unit 131a, and / or the power consumed by the first motor unit 131a. The processing circuit 180 changes the pulse width and / or period of the control signal (voltage) input to the step-up / step-down circuit to change the duty ratio of the voltage input to the step-up / step-down circuit, thereby changing the voltage applied to terminals on both sides of the first motor unit 131a. This allows the medium conveying device 100 to easily control the first motor control circuit 134 while reducing the circuit size for controlling the first motor control circuit 134. The processing circuit 180 may change the amplitude of the control signal (voltage) input to the step-up / step-down circuit to change the voltage applied to the terminals on both sides of the first motor unit 131a. This allows the medium conveyance device 100 to appropriately control the first motor control circuit 134 while easily taking measures against EMI (Electromagnetic Interference).

[0061] Furthermore, the first motor control circuit 134 may short-circuit the terminals on both sides of the first motor unit 131a and / or change the resistance value of the first resistor unit 131b in accordance with a control signal from the processing circuit 180.

[0062] 5(B), the second driving device 140 includes a second motor control circuit 144 in addition to the second motor 141. The second motor control circuit 144 sets the voltage applied to the terminals on both sides of the second motor unit 141a, the current flowing through the second motor unit 141a, and / or the power consumed by the second motor unit 141a in accordance with a control signal from the processing circuit 180.

[0063] For example, the second motor control circuit 144 includes a step-up / step-down circuit that outputs a voltage applied to terminals on both sides of the second motor unit 141a. The processing circuit 180 adjusts the voltage input to the step-up / step-down circuit of the second motor control circuit 144 to change the voltage applied to terminals on both sides of the second motor unit 141a, the current flowing through the second motor unit 141a, and / or the power consumed by the second motor unit 141a. The processing circuit 180 changes the pulse width and / or period of the control signal (voltage) input to the step-up / step-down circuit to change the duty ratio of the voltage input to the step-up / step-down circuit, thereby changing the voltage applied to terminals on both sides of the second motor unit 141a. This allows the medium conveyance device 100 to easily control the second motor control circuit 144 while reducing the circuit size for controlling the second motor control circuit 144. The processing circuit 180 may change the amplitude of the control signal (voltage) input to the step-up / step-down circuit to change the voltage applied to the terminals on both sides of the second motor unit 141a. This allows the medium conveying device 100 to appropriately control the second motor control circuit 144 while easily taking measures against EMI.

[0064] Furthermore, the second motor control circuit 144 may short-circuit the terminals on both sides of the second motor unit 141a and / or change the resistance value of the second resistor unit 141b in accordance with a control signal from the processing circuit 180.

[0065] 5(C), the third driving device 150 includes a third motor control circuit 154 in addition to the third motor 151. The third motor control circuit 154 sets the voltage applied to the terminals on both sides of the third motor unit 151a, the current flowing through the third motor unit 151a, and / or the power consumed by the third motor unit 151a in accordance with a control signal from the processing circuit 180.

[0066] For example, the third motor control circuit 154 includes a step-up / step-down circuit that outputs a voltage applied to terminals on both sides of the third motor unit 151a. The processing circuit 180 adjusts the voltage input to the step-up / step-down circuit of the third motor control circuit 154 to change the voltage applied to terminals on both sides of the third motor unit 151a, the current flowing through the third motor unit 151a, and / or the power consumed by the third motor unit 151a. The processing circuit 180 changes the pulse width and / or period of the control signal (voltage) input to the step-up / step-down circuit to change the duty ratio of the voltage input to the step-up / step-down circuit, thereby changing the voltage applied to terminals on both sides of the third motor unit 151a. This allows the medium conveying device 100 to easily control the third motor control circuit 154 while reducing the circuit size for controlling the third motor control circuit 154. The processing circuit 180 may change the amplitude of the control signal (voltage) input to the step-up / step-down circuit to change the voltage applied to the terminals on both sides of the third motor unit 151a. This allows the medium conveying device 100 to appropriately control the third motor control circuit 154 while easily taking measures against EMI.

[0067] Furthermore, the third motor control circuit 154 may short-circuit the terminals on both sides of the first motor unit 131a and / or change the resistance value of the third resistor unit 151b in accordance with a control signal from the processing circuit 180.

[0068] FIG. 6 is a diagram showing a schematic configuration of a storage device and a processing circuit.

[0069] 6, the storage device 170 stores a control program 171, an image acquisition program 172, and the like. Each of these programs is a functional module implemented by software running on a processor. The processing circuitry 180 reads each program stored in the storage device 170 and operates in accordance with the read program. As a result, the processing circuitry 180 functions as a control unit 181 and an image acquisition unit 182.

[0070] FIG. 7 is a flowchart showing an example of the operation of the medium conveyance process of the medium conveyance device.

[0071] An example of the operation of the medium conveying process of medium conveying device 100 will be described below with reference to the flowchart shown in Fig. 7. The flow of the operation described below is executed mainly by processing circuit 180 in cooperation with each element of medium conveying device 100 based on a program stored in advance in storage device 170.

[0072] First, the control unit 181 waits until the user inputs an instruction to read a medium using the operation device 105 or the information processing device, and an operation signal instructing the reading of the medium is received from the operation device 105 or the interface device 161 (step S101).

[0073] Next, control unit 181 acquires a first medium signal from first medium sensor 111, and determines whether or not a medium is placed on mounting table 103 based on the acquired first medium signal (step S102). If no medium is placed on mounting table 103, control unit 181 ends the series of steps.

[0074] On the other hand, if a medium is placed on the placement table 103, the control unit 181 controls the first drive unit 130, the second drive unit 140, and the third drive unit 150 to rotate each roller to transport the medium (step S103). The control unit 181 changes the speeds of the first motor 131, the second motor 141, and the third motor 151 to rotate the feed roller 112, the separation roller 113, the transport roller 115, the first opposing roller 116, the discharge roller 119, and / or the second opposing roller 120. When feeding the medium, the control unit 181 changes the speed of the first motor 131 to increase the speed of the feed roller 112. This allows the medium transport device 100 to feed the medium appropriately. The speed of each motor is changed in a speed change process, which will be described later.

[0075] FIG. 8 is a graph for explaining the change in speed of each roller.

[0076] In FIG. 8, graph G1 shows the change in speed of the feed roller 112, graph G2 shows the change in speed of the separation roller 113, and graph G3 shows the change in speed of the transport roller 115. The speeds of the first opposing roller 116, discharge roller 119, and second opposing roller 120 change in the same way as the speed of the transport roller 115, so the following will explain the change in speed of the transport roller 115 as a representative. The horizontal axis of each of graphs G1, G2, and G3 represents time, and the vertical axis represents the transport speed of the medium by each roller, i.e., the moving speed of the surface of each roller. Meanwhile, graph G4 shows the change in the signal value of the third medium signal. The horizontal axis of graph G4 represents time, and the vertical axis represents the signal value. In this embodiment, when no medium is present at the position of the third medium sensor 117, the signal value of the third medium signal is L, and when a medium is present at the position of the third medium sensor 117, the signal value of the third medium signal is H.

[0077] 8, time T1 indicates the start of medium conveyance. The control unit 181 starts the rotation of the separation roller 113 and the conveyance roller 115 at time T1, and starts the rotation of the feed roller 112 at time T2, a specific time after time T1. The control unit 181 drives the first motor 131, the second motor 141, and the third motor 151 so that the speed of the feed roller 112 becomes initial speed V1, the speed of the separation roller 113 becomes initial speed U1, and the speed of the conveyance roller 115 becomes initial speed W1. The initial speed V1 is set to a speed lower (slower) than the initial speed W1.

[0078] 8, after a predetermined through-up period has elapsed since the start of driving each motor at time T1 or T2, each roller rotates at the determined speed. Similarly, if control unit 181 subsequently increases the speed of each roller, after a predetermined through-up period has elapsed since the start of driving each motor, each roller rotates at the set speed. Similarly, if control unit 181 subsequently reduces the speed of each roller, after a predetermined through-down period has elapsed since the start of driving each motor, each roller rotates at the set speed.

[0079] Next, the control unit 181 waits until the leading edge of the transported medium passes a first predetermined position (step S104). The first predetermined position is set, for example, to a position between the feed roller 112 and separation roller 113 and the transport roller 115 and first opposing roller 116 in the medium transport direction A1. In particular, the first predetermined position is set downstream of and near the nip portion between the feed roller 112 and separation roller 113 in the medium transport direction A1. For example, the control unit 181 periodically acquires a second medium signal from the second medium sensor 114, and determines that the leading edge of the medium has passed the first predetermined position when the signal value of the second medium signal changes from a value indicating that the medium is not present to a value indicating that the medium is present. The control unit 181 may also determine that the leading edge of the medium has passed the first predetermined position when a first predetermined time has elapsed since the start of feeding the medium. The first predetermined time is set to the time required for the medium to move from the upstream end to the downstream end of the nip portion between the feed roller 112 and separation roller 113, plus a margin.

[0080] Next, the control unit 181 controls the first driving device 130 to increase the speed of the feed roller 112 (step S105). The control unit 181 changes the speed of the first motor 131 to increase the speed of the feed roller 112. The change in the speed of the first motor 131 is performed by a speed change process, which will be described later.

[0081] In FIG. 8 , time T3 indicates the time when the leading edge of the medium passes through the first predetermined position. When the leading edge of the medium passes through the nip portion between the feed roller 112 and the separation roller 113, the control unit 181 changes the speed of the feed roller 112 to final speed V2. The final speed V2 of the feed roller 112 is set to a speed that is higher than the initial speed V1 of the feed roller 112 and lower than the initial speed W1 of the transport roller 115. The final speed V2 of the feed roller 112 may also be set to the same speed as the initial speed W1 of the transport roller 115. In this way, when feeding the medium, the control unit 181 gradually increases the speed of the feed roller 112 while reducing the speed of the feed roller 112 during the separation period of the medium. This allows the control unit 181 to reduce the processing time required for the medium transport process while preventing double feeding or jamming of media and loss of synchronization of the first motor 131. Therefore, the control unit 181 can achieve both feeding performance (reduction of abnormality occurrence) and processing performance (reduction of transport time).

[0082] Next, control unit 181 waits until the leading edge of the transported medium passes a second predetermined position (step S106). The second predetermined position is set, for example, to a position between transport roller 115 and first opposing roller 116 and the imaging position of imaging device 118 in medium transport direction A1. For example, the second predetermined position is set to the arrangement position of third medium sensor 117. Control unit 181 periodically acquires a third medium signal from third medium sensor 117, and determines that the leading edge of the medium has passed the second predetermined position when the signal value of the third medium signal changes from a value indicating that no medium is present to a value indicating that a medium is present.

[0083] Next, the control unit 181 controls the first driving device 130 to stop the feed roller 112 (step S107). The control unit 181 changes the speed of the first motor 131 to stop the feed roller 112. The change in the speed of the first motor 131 is performed by a speed change process, which will be described later.

[0084] In Figure 8, time T4 indicates the time when the leading edge of the medium passes the position of third medium sensor 117. As shown in Figure 8, after the leading edge of the medium passes the position of third medium sensor 117, control unit 181 stops feed roller 112 (changes the speed to 0). As a result, the medium is subsequently transported by transport roller 115, and feed roller 112 rotates along with the transported medium. By stopping feed roller 112, control unit 181 can prevent the medium from being pushed by feed roller 112 and bending between feed roller 112 and transport roller 115, which could cause a medium jam.

[0085] Next, the image acquisition unit 182 causes the imaging device 118 to start capturing an image of the medium (step S108).

[0086] Next, the control unit 181 waits until the trailing edge of the transported medium passes the first predetermined position (step S109). The control unit 181 determines that the trailing edge of the medium has passed the first predetermined position when the signal value of the second medium signal changes from a value indicating the presence of the medium to a value indicating the absence of the medium. The control unit 181 may also determine that the trailing edge of the medium has passed the first predetermined position when a second predetermined time has elapsed since the start of feeding the medium. The second predetermined time is set to the time required for the leading edge of a medium of the maximum size supported by the medium transport device 100 to move from the upstream end of the nip portion between the feed roller 112 and the separation roller 113 to the downstream end of the nip portion, plus a margin.

[0087] Next, control unit 181 determines whether or not a medium remains on mounting table 103 based on the first medium signal received from first medium sensor 111 (step S110).

[0088] If media remain on the mounting table 103, the control unit 181 controls the first drive device 130 to rotate the feed roller 112 to feed and transport the subsequent media (step S111). The control unit 181 changes the speed of the first motor 131 so that the feed roller 112 rotates at an initial speed V1. The speed change of the first motor 131 is performed in a speed change process, which will be described later.

[0089] 8, time T5 indicates the time when the trailing edge of the medium passes through the first predetermined position. When the trailing edge of the preceding medium passes through the nip portion between the feed roller 112 and the separation roller 113, the control unit 181 rotates the feed roller 112 again to start feeding the following medium.

[0090] Next, the control unit 181 returns the process to step S104 and repeats the processes from step S104 onwards. On the other hand, if there are no media remaining on the mounting table 103 in step S110, the control unit 181 ends the series of steps.

[0091] The processes of steps S104 and S105 may be omitted. In that case, in steps S103 and S111, the feed roller 112 may be set to the final speed V2 when it starts to rotate.

[0092] FIG. 9 is a flowchart illustrating an example of the operation of the medium ejection process of the medium conveyance device.

[0093] An example of the operation of the medium ejection process of medium conveying device 100 will be described below with reference to the flowchart shown in Figure 9. The flow of the operation described below is executed mainly by processing circuit 180 in cooperation with each element of medium conveying device 100 based on a program stored in advance in storage device 170. The medium ejection process is executed in parallel with the medium conveying process.

[0094] First, the control unit 181 waits until the trailing edge of the medium passes the third predetermined position (step S201). The third predetermined position is set to a position in the medium conveying direction A1 that is downstream of the imaging position of the imaging device 118 by the overscan amount and upstream of the discharge rollers 119. The overscan amount is preset to an amount (e.g., 16 mm) that is likely to capture the entire medium even if the medium is conveyed at an angle. The control unit 181 determines that the trailing edge of the medium has passed the position of the third medium sensor 117 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 181 determines that the trailing edge of the medium has passed the position of the third medium sensor 117 when a third predetermined time has elapsed since the trailing edge of the medium passed the position of the third medium sensor 117. The third predetermined time is set to the time required for the medium to move from the position of the third medium sensor 117 to the third predetermined position.

[0095] Next, the image acquisition unit 182 stops the imaging device 118 from capturing an image, and acquires an input image from the imaging device 118. The image acquisition unit 182 outputs the acquired input image by transmitting it to the information processing device via the interface device 161 (step S202).

[0096] Next, the control unit 181 controls the third driving device 150 to reduce the speed of the discharge roller 119 (step S203). The control unit 181 changes the speed of the third motor 151 to reduce the speeds of the conveying roller 115, the first opposing roller 116, the discharge roller 119, and the second opposing roller 120. The speed of the third motor 151 is changed in a speed change process, which will be described later.

[0097] In FIG. 8, time T6 indicates the time when the trailing edge of the medium passes the position of the third medium sensor 117, and time T7 indicates the time when the trailing edge of the medium passes the third predetermined position. When the trailing edge of the medium passes a position downstream of the imaging position by the overscan amount, the control unit 181 changes the speed of the conveyance rollers 115 (discharge rollers 119) to discharge speed W2. Discharge speed W2 is set to a speed lower than the initial speed W1. Discharge speed W2 is set in advance to a speed at which the discharged medium does not fly out of the discharge tray 104, does not scatter on the discharge tray 104, and does not remain around the discharge opening. In this way, the medium conveying device 100 can convey the medium at high speed before medium discharge to shorten the time required for the medium conveyance process, and discharge the medium at a low speed when discharging the medium, thereby preventing the medium from flying out of the discharge tray 104 or scattering on the discharge tray 104.

[0098] Furthermore, as described above, the third predetermined position for changing the speed of the discharge rollers 119 is set upstream of the discharge rollers 119. Therefore, the control unit 181 changes the speed of the discharge rollers 119 before the trailing edge of the medium passes the discharge rollers 119. This allows the medium conveying device 100 to reliably change the discharge speed of the medium using the discharge rollers 119.

[0099] Next, the control unit 181 waits until the trailing edge of the medium being discharged passes the position of the discharge rollers 119 (step S204). The control unit 181 determines that the trailing edge of the medium has passed the position of the discharge rollers 119 when a fourth predetermined time has elapsed since the trailing edge of the medium passed the position of the third medium sensor 117. The fourth predetermined time is set to a value obtained by adding a margin to the time required for the medium to move from the position of the third medium sensor 117 to the position of the downstream end of the nip portion between the discharge rollers 119 and the second opposing roller 120.

[0100] Next, the control unit 181 determines whether or not the subsequent medium has been fed in step S111 of FIG. 7 (step S205).

[0101] If the subsequent medium has been fed, the control unit 181 controls the third drive device 150 to increase the speed of the discharge roller 119 (step S206). The control unit 181 changes the speed of the third motor 151 so as to increase the speeds of the conveyance roller 115, the first opposing roller 116, the discharge roller 119, and the second opposing roller 120 and return them to the initial speed W1. The change in the speed of the third motor 151 is performed in a speed change process, which will be described later. Next, the control unit 181 returns the process to step S201 and repeats the processes from step S201 onwards.

[0102] In this way, the control unit 181 reduces the speed of the discharge rollers 119 when the trailing edge of the medium passes the third predetermined position or when reading of the medium is completed, and increases the speed of the discharge rollers 119 when discharge of the medium is completed. This allows the medium conveying device 100 to convey the medium at high speed, shortening the time required for the medium conveyance process, while preventing the medium from flying out of the discharge tray 104 or scattering on the discharge tray 104.

[0103] Furthermore, when the discharge of a medium is complete, the control unit 181 increases the speed of the discharge rollers 119 on the condition that the subsequent medium has been fed. This allows the medium conveying device 100 to convey the subsequent medium at high speed when a subsequent medium exists after the discharge of a medium is complete, thereby shortening the time required for the medium conveying process.

[0104] 8, time T8 indicates the time when the trailing edge of the medium passes the position of the discharge rollers 119. As shown in FIG. 8, at time T8 when the trailing edge of the medium passes the position of the discharge rollers 119, the control unit 181 returns the speed of the conveying rollers 115 (discharge rollers 119) to the initial speed W1.

[0105] Note that because the transport rollers 115 are driven by the same third motor 151 as the discharge rollers 119, the speed of the transport rollers 115 does not return to its initial speed until the speed of the discharge rollers 119 returns to its initial speed, and the following medium should not be transported by the transport rollers 115. Therefore, the initial speed, final speed, discharge speed, and / or the timing of change thereof are set in advance for each roller so that the speed of the transport rollers 115 returns to its initial speed before the leading edge of the following medium passes the position of the transport rollers 115 (time T9 in FIG. 8). By setting them in this manner, while the speed of the discharge rollers 119 is being changed, the leading edge of the following medium will not reach the position of the transport rollers 115, and the following medium will be fed by the feed rollers 112 and separation rollers 113. Therefore, even if the speed of the transport rollers 115, which are driven by the same third motor 151 as the discharge rollers 119, changes together with the discharge rollers 119, the following medium will be fed without any problems.

[0106] In this way, the control unit 181 controls the discharge roller 119 so as to reduce the speed of the discharge roller 119 before the leading edge of the succeeding medium reaches the conveyance roller 115. The medium conveying device 100 reduces the speed of the discharge roller 119 before the succeeding medium reaches the conveyance roller 115, which is driven by the third motor 151 that is also driven by the discharge roller 119. This allows the conveyance roller 115 to stably convey the succeeding medium at a speed that is the same as or higher than the feeding speed of the feed roller 112, and the medium conveying device 100 can prevent jams and wrinkles from occurring in the medium. Furthermore, the conveyance roller 115 can convey the medium at a constant speed at the imaging position, and the medium conveying device 100 can prevent distortion from occurring in the input image.

[0107] If the subsequent medium has not been fed, the control unit 181 controls the second drive device 140 and the third drive device 150 to stop the rollers (step S207). The control unit 181 changes the speed of the second motor 141 and the third motor 151 to stop the separation roller 113, the transport roller 115, the first opposing roller 116, the discharge roller 119, and the second opposing roller 120. The speed of each motor is changed in a speed change process, which will be described later. Next, the control unit 181 ends the series of steps.

[0108] 8, time T10 indicates the time when the trailing edge of the subsequent medium (the last medium transported) passes the position of the discharge roller 119. As shown in FIG. 8, the control unit 181 stops the separation roller 113, the transport roller 115, the first opposing roller 116, the discharge roller 119, and / or the second opposing roller 120 at time T10 when the trailing edge of the last medium transported passes the position of the discharge roller 119.

[0109] Note that the processing of steps S203 and S206 may be omitted, and the control unit 181 may not change the speed of the conveying roller 115, the first opposing roller 116, the discharge roller 119, and / or the second opposing roller 120 midway. Alternatively, the conveying roller 115 and the discharge roller 119 may be driven by separate drive devices. That is, the control unit 181 may increase the speed of the conveying roller 115 when starting to convey the first medium among the media placed on the mounting table 103, and may decrease the speed of the conveying roller 115 when conveying all of the media placed on the mounting table 103 has been completed. This allows the medium conveying device 100 to convey media easily and quickly.

[0110] Furthermore, the processing of step S203 may be executed before the rear end of the medium passes the third predetermined position, i.e., before reading of the medium is completed. In this case, the control unit 181 changes the reading interval of the medium by the imaging device 118 in accordance with the change in the medium ejection speed. Alternatively, the image acquisition unit 182 may execute a known thinning process or interpolation process to correct expansion or contraction that occurs in the input image.

[0111] FIG. 10 is a flowchart showing an example of the operation of the speed change process of the medium conveyance device.

[0112] An example of the speed processing operation of the medium conveying device 100 will be described below with reference to the flowchart shown in Figure 10. The flow of the operation described below is executed mainly by the processing circuit 180 in cooperation with each element of the medium conveying device 100 based on a program previously stored in the storage device 170. The speed change process is executed in parallel with the medium conveying process and the medium ejection process. The speed change process is executed individually for each of the first drive device 130, the second drive device 140, and the third drive device 150.

[0113] Hereinafter, among the first drive device 130, the second drive device 140, and the third drive device 150, the drive device whose speed is to be changed may be referred to as the target drive device. Furthermore, among the feed roller 112, the separation roller 113, the conveyance roller 115, the first opposing roller 116, the discharge roller 119, and the second opposing roller 120, the rollers driven by the target drive device may be referred to as the target roller. Furthermore, among the first motor 131, the second motor 141, and the third motor 151, the motor included in the target drive device may be referred to as the target motor. Furthermore, among the first encoder 133, the second encoder 143, and the third encoder 153, the encoder provided on the rotation shaft of the target motor or the target roller and detecting the rotation of the target motor or the target roller may be referred to as the target encoder. Furthermore, among the first motor control circuit 134, the second motor control circuit 144, and the third motor control circuit 154, the motor control circuit that controls the target motor may be referred to as the target motor control circuit.

[0114] First, the control unit 181 waits until a speed change of the target motor for the target driving device is executed (step S301). The control unit 181 waits until a speed change of the target motor is executed in step S103, S105, S107, or S111 of Fig. 7 or step S203, S206, or S207 of Fig. 9.

[0115] When the speed change of the target motor for the target drive device is executed, the control unit 181 controls the target motor by open-loop control so as to start changing (increasing or decreasing) the speed of the target roller (step S302). In open-loop control, the control unit 181 changes the speed of the target motor without using feedback of the speed of the target motor. The control unit 181 inputs a predetermined control signal to the target drive device so that the conveying speed of the target roller approaches a target conveying speed (hereinafter, sometimes referred to as a target speed).

[0116] When the control unit 181 changes the speed of the third motor 151 so as to reduce the speed of the discharge roller 119 in step S203, the control unit 181 may control the target drive device to apply a voltage reverse to the current voltage to the terminals on both sides of the third motor unit 151a. This allows the control unit 181 to rapidly reduce the speed of the discharge roller 119.

[0117] Next, the control unit 181 waits until a predetermined condition for changing the control of the target motor from open-loop control to closed-loop control is met (step S303). In closed-loop control, the control unit 181 changes the speed of the target motor using feedback of the target motor speed. That is, the control unit 181 does not change the control signal input to the target driving device based on the feedback of the target motor speed until the predetermined condition is met, and after the predetermined condition is met, the control unit 181 changes the control signal input to the target driving device based on the feedback of the target motor speed.

[0118] The predetermined condition is, for example, the passage of a predetermined time from the start of the speed change of the target motor or target roller. The predetermined time is the time it takes for the conveying speed of the target roller to change from the speed before the change to the target speed. The predetermined time may be set in advance to the time obtained by subtracting a predetermined margin from the time it takes for the conveying speed of the target roller to change from the speed before the change to the target speed, or the time obtained by adding a predetermined margin to the time it takes for the conveying speed of the target roller to change from the speed before the change to the target speed. The medium conveying device 100 stores the predetermined time corresponding to each roller in the storage device 170 in advance. The control unit 181 determines that the predetermined condition is met when the predetermined time corresponding to the target roller has passed since the start of the speed change of the target motor or target roller.

[0119] The predetermined condition may be that the speed of the target motor or roller reaches a predetermined speed. The predetermined speed is a target speed of the target motor or roller. The predetermined speed may be a speed between the current speed of the target motor or roller and a speed corresponding to the target speed. Alternatively, the predetermined speed may be preset to a speed that is a predetermined margin away from the speed corresponding to the target speed of the target motor or roller. In other words, the predetermined speed may be a speed within a predetermined range of the target speed of the target motor or roller. The medium conveying device 100 may store the predetermined speeds corresponding to each roller and the encoder rotation speeds corresponding to each predetermined speed in the storage device 170, and the control unit 181 may identify the predetermined speed corresponding to the target roller and the encoder rotation speed corresponding to the identified predetermined speed. Alternatively, the medium conveying device 100 may store the encoder rotation speeds corresponding to the predetermined speeds of each roller in the storage device 170, and the control unit 181 may identify the encoder rotation speed corresponding to the predetermined speed of the target roller. The control unit 181 periodically acquires a rotation speed signal from the target encoder, and determines that the predetermined condition is satisfied when the rotation speed indicated by the rotation speed signal reaches a specified rotation speed. Alternatively, the control unit 181 may determine that the predetermined condition is satisfied when the rotation speed indicated by the rotation speed signal reaches a rotation speed within a specified range of the specified rotation speed (for example, a rotation speed not less than the specified rotation speed minus 10 and not more than the specified rotation speed plus 10).

[0120] Next, the control unit 181 changes the control of the target motor from open-loop control to closed-loop control (step S304). The medium conveying device 100 stores in advance in the storage device 170 the encoder rotation speeds corresponding to each target speed for each roller. Thereafter, the control unit 181 periodically acquires a rotation speed signal from the target encoder and changes the control signal input to the target drive device so that the rotation speed indicated by the rotation speed signal corresponds to the target speed. Next, the control unit 181 returns to step S301 and repeats the processes from step S301 onward. That is, the control unit 181 continues to control the target motor with closed-loop control until the speed of the target motor for the target drive device is next changed. Note that the control unit 181 may stop the target motor when stopping the target roller in step S107 of FIG. 7 and step S207 of FIG. 9.

[0121] In this way, the control unit 181 can control each motor using either open-loop control or closed-loop control. The control unit 181 changes the control of each motor from open-loop control to closed-loop control when a predetermined time has elapsed since starting to change the speed of each motor or each roller, or when the speed of each motor or each roller reaches a predetermined speed.

[0122] 11(A) to 11(C) are graphs for explaining the speed change of a DC motor. Fig. 11(A) is a graph showing the speed change of a motor controlled by open-loop control. Fig. 11(B) is a graph showing the speed change of a motor controlled by closed-loop control. Fig. 11(C) is a graph showing the speed change of a motor controlled to change from open-loop control to closed-loop control.

[0123] In Figures 11(A) to 11(C), the vertical axis represents motor speed and the horizontal axis represents time. In Figures 11(A) to 11(C), graph G5 represents ideal speed change, i.e., target speed change, and graphs G6 to G8 represent actual speed change. DC motors are easily affected by external factors such as load fluctuations, and when changing the speed of a DC motor, it takes time to reach the target speed. In open-loop control, motor speed feedback is not referenced, and the motor speed is fixedly changed toward the target speed. Therefore, as shown in graph G6 in Figure 11(A), the motor speed changes ideally immediately after the change, but it takes time to settle at the target speed. In closed-loop control, motor speed feedback is referenced, and the motor speed is dynamically changed to approach the target speed. Therefore, as shown in graph G7 in Figure 11(B), the motor speed changes with a delay compared to the ideal speed change immediately after the change, but immediately settles at the target speed after approaching the target speed.

[0124] On the other hand, when control is changed from open-loop control to closed-loop control, the motor speed changes ideally immediately after the change and immediately settles at the target speed after approaching the target speed. Therefore, as shown in graph G8 in Figure 11(C), by controlling each motor with open-loop control immediately after the speed change and then switching to closed-loop control when the speed approaches the target speed, the motor speed changes ideally over the entire period. The medium conveying device 100 can ideally change the speed of each motor by controlling each motor with open-loop control when the speed is away from the target speed and controlling with closed-loop control when the speed approaches the target speed.

[0125] 10, if a change in motor speed is executed, the control unit 181 changes the motor control back to open-loop control in step S302. That is, when the control unit 181 starts changing the speed of each motor or roller, it changes the control of each motor from closed-loop control to open-loop control. This allows the medium conveying device 100 to control each motor with open-loop control immediately after the speed change, thereby ideally changing the speed of each motor.

[0126] The control unit 181 may execute the speed change process only for some of the processes in steps S103, S105, S107, and S111 of Fig. 7 and steps S203, S206, and S207 of Fig. 9, rather than for all of them. For example, the control unit 181 may execute the speed change process only when the speed of the third motor 151 is changed in step S203 to reduce the speed of the discharge roller 119. When the speed change process is not executed, the control unit 181 controls each motor using either open-loop control or closed-loop control.

[0127] As described above in detail, the medium conveying device 100 controls the DC motor using open-loop control when starting to change the speed of the DC motor or roller, and switches to closed-loop control before, when, or after reaching the target speed. Alternatively, the medium conveying device 100 controls the DC motor using open-loop control when starting to change the speed of the DC motor or roller, and switches to closed-loop control when a speed within a predetermined range of the target speed is reached. Alternatively, the medium conveying device 100 controls the DC motor using open-loop control when starting to change the speed of the DC motor or roller, and switches to closed-loop control when a predetermined time has elapsed since starting to change the speed of the DC motor or roller. This enables the medium conveying device 100 to better control the DC motor.

[0128] By transporting the medium at a constant speed from the start to the completion of medium reading, the medium transport device 100 can maintain a constant relationship between the timing of medium reading by the imaging device 118 and the speed of the medium, thereby suppressing distortion (stretching or shrinking) of the input image. Furthermore, by reducing the speed of the medium from the completion of medium reading to the completion of ejection, the medium transport device 100 can improve the alignment of the ejected medium. Furthermore, by returning the speed of the medium before starting to read the next medium, the medium transport device 100 can properly transport the next medium.

[0129] FIG. 12 is a diagram showing a schematic configuration of a processing circuit in a medium conveyance device according to another embodiment.

[0130] The processing circuit 280 is used in place of the processing circuit 180 of the medium conveying device 100, and executes medium conveyance processing, discharge control processing, speed change processing, etc. in place of the processing circuit 180. The processing circuit 280 includes a control circuit 281 and an image acquisition circuit 282. Note that each of these components may be configured as an independent integrated circuit, microprocessor, firmware, etc.

[0131] The control circuit 281 is an example of a control unit, and has the same functions as the control unit 181. The control circuit 281 receives an operation signal from the operation device 105 or the interface device 161, a first medium signal from the first medium sensor 111, a second medium signal from the second medium sensor 114, and a third medium signal from the third medium sensor 117. The control circuit 281 controls the first drive device 130, the second drive device 140, and the third drive device 150 based on the received signals.

[0132] The image acquisition circuit 282 is an example of an image acquisition unit, and has the same function as the image acquisition unit 182. The image acquisition circuit 282 acquires an input image from the imaging device 118 and outputs it to the interface device 161.

[0133] As described above in detail, the media transport device is now able to better control the DC motor when using the processing circuit 280.

[0134] Although the above has described preferred embodiments, the embodiments are not limited thereto. For example, the medium transport path of the medium transport device may have a so-called U-turn path mechanism, which feeds and transports the media placed on the loading tray from the top to the bottom and discharges them onto the discharge tray. In this case, the separation roller is disposed below the feed roller and faces the feed roller.

[0135] Furthermore, the medium transport device may have an image forming device instead of or in addition to the imaging device 118. The image forming device is an inkjet type or laser type printer, etc., and is placed at a position corresponding to the position where the imaging device 118 is placed, and forms an image (prints predetermined information) on the transported medium. [Explanation of symbols]

[0136] 100 medium conveying device, 103 placing table, 112 feeding roller, 113 separation roller, 115 conveying roller, 116 first opposing roller, 119 discharge roller, 120 second opposing roller, 131 first motor, 141 second motor, 151 third motor, 181 control section

Claims

1. a roller for transporting the medium; a DC motor for driving the roller; a control unit capable of controlling the DC motor by either open loop control or closed loop control, the control unit changes the control of the DC motor from open-loop control to closed-loop control when a predetermined time has elapsed since starting to change the speed of the DC motor or the roller, or when the speed of the DC motor or the roller reaches a predetermined speed. A medium transport device characterized by:

2. The medium conveying device according to claim 1 , wherein the control unit changes control of the DC motor from closed-loop control to open-loop control when starting to change the speed of the DC motor or the roller.

3. the roller is an ejection roller that ejects the medium, 3. The medium transport device according to claim 1, wherein the control unit reduces the speed of the roller when the trailing edge of the medium passes a predetermined position or when reading of the medium is completed, and increases the speed of the roller when ejection of the medium is completed.

4. Further, the apparatus has a mounting table, The medium transport device according to claim 3 , wherein the control unit increases the speed of the rollers on condition that a medium is placed on the placement table when the medium has been completely discharged.

5. the roller is a feeding roller that feeds a medium, The medium transport device according to claim 1 , wherein the control unit increases the speed of the roller when feeding the medium.

6. Further, the apparatus has a mounting table, the roller is a transport roller that transports a medium, 3. The media transport device of claim 1, wherein the control unit increases the speed of the roller when starting to transport the first medium among the media placed on the mounting table, and decreases the speed of the roller when transport of all media placed on the mounting table is completed.

7. The rollers transport the media. The roller is driven by a DC motor, controlling the DC motor by either open loop control or closed loop control; In the control, when a predetermined time has elapsed since the start of changing the speed of the DC motor or the roller, or when the speed of the DC motor or the roller reaches a predetermined speed, the control of the DC motor is changed from open-loop control to closed-loop control. A medium transport method comprising:

8. A control program for a medium transport device having a roller for transporting a medium and a DC motor for driving the roller, the program comprising: causing the medium conveying device to control the DC motor using either open-loop control or closed-loop control; In the control, when a predetermined time has elapsed since the start of changing the speed of the DC motor or the roller, or when the speed of the DC motor or the roller reaches a predetermined speed, the control of the DC motor is changed from open-loop control to closed-loop control. A control program comprising:

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