Media transport device, control method, and control program

Abstract

To provide a medium conveying device, a control method, and a control program that can better control medium feeding.SOLUTION: A medium conveying device has a mounting table on which media are placed, a feeding roller that separates and sequentially feeds the media placed on the mounting table, a conveying roller that conveys the media fed by the feed roller, a sensor that is disposed between the feeding roller and conveying roller and detects the media, a motor that drives the feeding roller, and a control part which, when feeding the first medium among the media placed on the mounting table, controls the motor to rotate the feeding roller at a constant speed during the separation period from the time when the feeding roller starts feeding the media to the time when the sensor detects the leading edge of the media, and, when feeding the second or subsequent media, controls the motor to rotate the feeding roller at a first speed and then at a second speed higher than the first speed.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present disclosure relates to a medium conveying apparatus, a control method, and a control program, and particularly relates to a medium conveying apparatus, a control method, and a control program that separate media and sequentially feed the same.

Background Art

[0002] In a medium conveying apparatus such as a scanner that sequentially feeds and images a plurality of media while separating the media, there is a demand for further reducing the time required for feeding media. On the other hand, the medium conveying apparatus needs to temporarily stop feeding media when the free capacity of a storage device that stores images obtained by imaging media is insufficient, or when the distance between consecutively fed media is short. In such a case, the medium conveying apparatus is required to appropriately control the stop and restart of medium feeding.

[0003] A sheet feeding apparatus is disclosed that controls a feeding roller to a low speed when starting feeding of a succeeding sheet by the feeding roller after the arrival of the trailing edge of a preceding sheet is detected by a post-registration sensor (see Patent Document 1). This sheet feeding apparatus controls the feeding roller to a high speed when the leading edge of the succeeding sheet exceeds the nip position between the feeding roller and a separation roller.

Prior Art Literature

Patent Literature

[0004]

Patent Document 1

Summary of Invention

[0005] In medium conveying apparatuses, there is a demand for better control of medium feeding.

[0006] An object of the medium conveying apparatus, the control method, and the control program is to enable better control of medium feeding.

[0007] A media transport device according to one aspect of the embodiment includes a platform on which media are placed, and a feed roller that separates and sequentially feeds the media placed on the platform. , salary A motor that drives the feed roller, and a sensor that detects the medium and is positioned downstream of the feed roller in the medium transport direction. , published When feeding the first medium among the media placed on the stand, From the time the feed roller starts feeding the first medium until the sensor detects the leading edge of the first medium Feed roller 1st speed Rotate it Furthermore, after the sensor detects the leading edge of the first medium, the feed roller is rotated at a second speed higher than the first speed. The motor is controlled in this way, and when supplying the second and subsequent media, From the start of feeding the second and subsequent media by the feed roller until the sensor detects the leading edge of the second and subsequent media Feed roller The feed roller rotates at a third speed that is higher than the first speed and lower than the second speed, and after the sensor detects the leading edge of the second or subsequent media, the feed roller is set to the second speed. A control unit that controls the motor to rotate, and do .

[0008] Furthermore, relating to one aspect of the embodiment Control method teeth, A control method for a media transport device, wherein a feed roller separates and sequentially feeds media placed on a platform, a motor drives the feed roller, a sensor positioned downstream of the feed roller in the media transport direction detects the media, and when feeding the first medium from among the media placed on the platform, the motor is controlled to rotate the feed roller at a first speed from the start of feeding the first medium by the feed roller until the sensor detects the leading edge of the first medium, and then to rotate the feed roller at a second speed higher than the first speed after the sensor detects the leading edge of the first medium, and when feeding the second and subsequent media, the motor is controlled to rotate the feed roller at a third speed higher than the first speed and lower than the second speed from the start of feeding the second and subsequent media by the feed roller until the sensor detects the leading edge of the second and subsequent media, and then to rotate the feed roller at a second speed after the sensor detects the leading edge of the second and subsequent media. .

[0009] Ma Furthermore, a control program relating to one aspect of the embodiment is a control program for a media transport device having a mounting table on which a medium is placed, a feed roller that separates and sequentially feeds the medium placed on the mounting table, a motor that drives the feed roller, and a sensor that is positioned downstream of the roller in the medium transport direction and detects the medium. , published When feeding the first medium among the media placed on the stand, From the time the feed roller starts feeding the first medium until the sensor detects the leading edge of the first medium Feed roller 1st speed Rotate it Furthermore, after the sensor detects the leading edge of the first medium, the feed roller is rotated at a second speed higher than the first speed. Yo ni mo When controlling the feeder and feeding the second and subsequent media, From the start of feeding the second and subsequent media by the feed roller until the sensor detects the leading edge of the second and subsequent media Feed roller The feed roller rotates at a third speed that is higher than the first speed and lower than the second speed, and after the sensor detects the leading edge of the second or subsequent media, the feed roller is set to the second speed. Rotate it ni mo The medium transport device is made to control the data.

[0010] According to this embodiment, the media transport device, control method, and control program can more effectively control the feeding of the media.

[0011] The objects and effects of the present invention will be appreciated and attained by particularly using the components and combinations pointed out in the claims. Both the foregoing general description and the following detailed description are exemplary and explanatory, and do not limit the present invention described in the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] [Figure 1] FIG. 1 is a perspective view illustrating a medium conveying apparatus 100 according to an embodiment. [Figure 2] FIG. 2 is a diagram for explaining a conveying path inside the medium conveying apparatus 100. [Figure 3] FIG. 3 is a schematic diagram for explaining a driving source. [Figure 4] FIG. 4 is a schematic diagram for explaining the third medium sensor 116 and the like [Figure 5] FIG. 5 is a schematic diagram for explaining the third medium sensor 116 and the like [Figure 6] FIG. 6 is a block diagram illustrating a schematic configuration of the medium conveying apparatus 100. [Figure 7] FIG. 7 is a diagram illustrating a schematic configuration of a storage device 140 and a processing circuit 150. [Figure 8] FIG. 8 is a flowchart illustrating an example of the operation of medium reading processing. [Figure 9] FIG. 9 is a flowchart illustrating an example of the operation of medium reading processing. [Figure 10] FIG. 10 is a graph for explaining a change in roller speed. [Figure 11] FIG. 11 is a graph for explaining a change in roller speed. [Figure 12] FIG. 12 is a graph for explaining a change in roller speed. [Figure 13] FIGS. 13(a) and 13(b) are schematic diagrams for explaining technical significance. [Figure 14] FIG. 14 is a schematic diagram for explaining technical significance. [Figure 15] FIG. 15 is a schematic diagram for explaining another driving source. [Figure 16]This flowchart shows some examples of how other media reading processes work. [Figure 17] This graph illustrates the change in the roller's speed. [Figure 18] Furthermore, the flowchart shows some examples of the operation of other media reading processes. [Figure 19] This graph illustrates the change in the roller's speed. [Figure 20] Furthermore, the flowchart shows examples of the operation of other media reading processes. [Figure 21] Furthermore, the flowchart shows examples of the operation of other media reading processes. [Figure 22] This graph illustrates the change in the roller's speed. [Figure 23] This is a schematic diagram illustrating other power sources. [Figure 24] Furthermore, the flowchart shows examples of the operation of other media reading processes. [Figure 25] Furthermore, the flowchart shows examples of the operation of other media reading processes. [Figure 26] This graph illustrates the change in the roller's speed. [Figure 27] This is a schematic diagram illustrating other power sources. [Figure 28] This is a schematic diagram illustrating other power sources. [Figure 29] Furthermore, the flowchart shows some examples of the operation of other media reading processes. [Figure 30] This graph illustrates the change in the roller's speed. [Figure 31] This is a schematic diagram illustrating other power sources. [Figure 32] Furthermore, the flowchart shows some examples of the operation of other media reading processes. [Figure 33] This graph illustrates the change in the roller's speed. [Figure 34]Furthermore, the flowchart shows examples of the operation of other media reading processes. [Figure 35] Furthermore, the flowchart shows examples of the operation of other media reading processes. [Figure 36] This graph illustrates the change in the roller's speed. [Figure 37] This figure shows the schematic configuration of the other processing circuit 250. [Modes for carrying out the invention]

[0013] The following describes a media transport device, control method, and control program relating to one aspect of this disclosure with reference to the figures. However, it should be noted that the technical scope of the present invention is not limited to these embodiments, but extends to the invention described in the claims and its equivalents.

[0014] Figure 1 is a perspective view showing a media transport device 100 configured as an image scanner. The media transport device 100 transports and images a medium, which is the original document. The medium can be paper, cardboard, card, booklet, or passport, etc. The media transport device 100 may also be a facsimile, copier, printer / multifunction device (MFP, Multifunction Peripheral), etc. Note that the transported medium may not be an original document but a print target, etc., and the media transport device 100 may be a printer, etc.

[0015] The media transport device 100 includes a lower housing 101, an upper housing 102, a mounting table 103, a discharge table 104, an operating device 105, and a display device 106, etc.

[0016] The upper housing 102 is positioned to cover the top surface of the media transport device 100 and is engaged with the lower housing 101 by a hinge so that it can be opened and closed when the media jams, when cleaning the inside of the media transport device 100, etc.

[0017] The mounting platform 103 engages with the lower housing 101 and places the medium to be fed and transported on it. The discharge platform 104 engages with the upper housing 102 and places the discharged medium on it. The discharge platform 104 may also engage with the lower housing 101.

[0018] The operating device 105 has input devices such as buttons and an interface circuit that acquires signals from the input devices, accepts input operations from the user, and outputs an operation signal corresponding to the user's input operation. The display device 106 has a display including liquid crystal, organic EL (Electro-Luminescence), etc. and an interface circuit that outputs image data to the display, and displays the image data on the display.

[0019] Figure 2 is a diagram illustrating the transport path inside the media transport device 100.

[0020] The transport path inside the media transport device 100 includes a first media sensor 111, a feeding roller 112, a brake roller 113, a second media sensor 114, an ultrasonic sensor 115, a third media sensor 116, a fourth media sensor 117, a fifth media sensor 118, a transport roller 119, a first opposing roller 120, a sixth media sensor 121, an imaging device 122, a discharge roller 123, and a second opposing roller 124, among others.

[0021] Note that the number of each of the feed roller 112, brake roller 113, transport roller 119, first opposing roller 120, discharge roller 123 and / or second opposing roller 124 is not limited to one, but may be multiple. In that case, the multiple feed rollers 112, brake roller 113, transport roller 119, first opposing roller 120, discharge roller 123 and / or second opposing roller 124 are arranged side by side with spacing between them in the width direction perpendicular to the media transport direction A1.

[0022] The upper surface of the lower housing 101 forms the lower guide 101a of the media transport path, and the lower surface of the upper housing 102 forms the upper guide 102a of the media transport path. In Figure 2, arrow A1 indicates the media transport direction. Hereafter, "upstream" refers to the upstream of the media transport direction A1, and "downstream" refers to the downstream of the media transport direction A1.

[0023] The first medium sensor 111 is positioned 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 mounting base 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 mounting base 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 a light detection sensor, may be used as the first medium sensor 111.

[0024] The feed roller 112 is provided on the lower housing 101 and feeds the media placed on the mounting table 103 sequentially from the bottom. The brake roller 113 is provided on the upper housing 102 and is positioned opposite to the feed roller 112, and rotates in the opposite direction to the media feeding direction. Alternatively, the feed roller 112 may be provided on the upper housing 102 and the brake roller 113 on the lower housing 101, and the feed roller 112 may feed the media placed on the mounting table 103 sequentially from the top.

[0025] The second medium sensor 114 is an example of a second sensor and is positioned downstream of the feed roller 112 and upstream of the transport roller 119 to detect the medium transported to that position. In particular, the second medium sensor 114 is positioned between the feed roller 112 and the fifth medium sensor 118 in the medium transport direction A1, near the nip region of the feed roller 112 and the brake roller 113. The second medium sensor 114 includes a light emitter and a light receiver provided on one side of the medium transport path, and a light guide tube provided at a position opposite the light emitter and light receiver across the medium transport path. The light emitter is an LED (Light Emitting Diode) or the like, and emits light toward the medium transport path. On the other hand, the light receiver is a photodiode or the like, and receives the light emitted by the light emitter and guided by the light guide tube. When medium is present at a position opposite the second medium sensor 114, the light emitted from the light emitter is blocked by the medium, so the light receiver does not detect the light emitted from the light emitter. The second medium sensor 114 generates and outputs a second medium signal whose signal value changes depending on whether a medium is present or absent at the location of the second medium sensor 114, based on the intensity of the light received by the photodetector.

[0026] The ultrasonic sensor 115 is positioned downstream of the feed roller 112 and upstream of the transport roller 119. The ultrasonic sensor 115 includes an ultrasonic transmitter 115a and an ultrasonic receiver 115b. The ultrasonic transmitter 115a and ultrasonic receiver 115b are positioned near the transport path of the medium, facing each other across the transport path. The ultrasonic transmitter 115a emits ultrasonic waves. On the other hand, the ultrasonic receiver 115b receives ultrasonic waves emitted by the ultrasonic transmitter 115a and transmitted through the medium, and generates and outputs an ultrasonic signal, which is an electrical signal corresponding to the received ultrasonic waves. When multiple media are transported overlapping, the ultrasonic waves transmitted through the media are attenuated by the air layer between the overlapping media. Therefore, the media transport device 100 can detect overlapping transport of media based on the ultrasonic signal. In addition, the ultrasonic waves transmitted through the medium are also attenuated by the medium itself, and the thicker the medium through which the ultrasonic waves are transmitted, the greater the attenuation. Therefore, the media transport device 100 can detect the thickness of the transported media based on the ultrasonic signal.

[0027] The fifth medium sensor 118 is an example of a sensor, and is positioned downstream of the feed roller 112 and upstream of the transport roller 119 to detect the medium transported to that position. That is, the fifth medium sensor 118 is positioned between the feed roller 112 and the transport roller 119. The fifth medium sensor 118 includes a light emitter and a light receiver provided on one side of the medium transport path, and a light guide tube provided opposite the light emitter and light receiver across the medium transport path. The light emitter is an LED or the like, and emits light toward the medium transport path. On the other hand, the light receiver is a photodiode or the like, and receives the light emitted by the light emitter and guided by the light guide tube. The fifth medium sensor 118 generates and outputs a fifth medium signal whose signal value changes depending on whether medium is present or absent at the position of the fifth medium sensor 118, based on the intensity of the light received by the light receiver.

[0028] The transport roller 119 and the first opposing roller 120 are positioned downstream of the feed roller 112 and facing each other, and transport the medium fed by the feed roller 112 and the brake roller 113 to the imaging device 122. The transport roller 119 is provided on the upper housing 102, and the first opposing roller 120 is provided on the lower housing 101, below the transport roller 119.

[0029] The sixth medium sensor 121 is positioned downstream of the transport roller 119 and upstream of the imaging device 122, and detects the medium being transported to its position. The sixth medium sensor 121 includes a light emitter and a light receiver provided on one side of the medium transport path, and a light guide tube provided opposite the light emitter and light receiver across the medium transport path. The light emitter is an LED or the like, and emits light toward the medium transport path. The light receiver, on the other hand, is a photodiode or the like, and receives the light emitted by the light emitter and guided by the light guide tube. The sixth medium sensor 121 generates and outputs a sixth medium signal whose signal value changes depending on whether a medium is present or absent at the position of the sixth medium sensor 121, based on the intensity of the light received by the light receiver.

[0030] The imaging device 122 is an example of an imaging unit and is located downstream of the transport roller 119, and images the medium transported by the transport roller 119. The imaging device 122 includes a first imaging device 122a and a second imaging device 122b, which are located opposite each other across the medium transport path. The first imaging device 122a has a line sensor using a 1:1 optical system type CIS (Contact Image Sensor) with image sensors made of CMOS (Complementary Metal Oxide Semiconductor) arranged linearly in the main scanning direction. The first imaging device 122a also has a lens that forms an image on the image sensor and an A / D converter that amplifies the electrical signal output from the image sensor and performs analog / digital (A / D) conversion. The first imaging device 122a generates and outputs an input image by imaging the surface of the transported medium according to control from a processing circuit described later.

[0031] Similarly, the second imaging device 122b has a line sensor with a CIS of the 1:1 optical system type, which has CMOS image sensors arranged linearly in the main scanning direction. The second imaging device 122b also has a lens that forms an image on the image sensor and an A / D converter that amplifies the electrical signal output from the image sensor and performs analog-to-digital (A / D) conversion. The second imaging device 122b generates and outputs an input image by imaging the back surface of the transported medium according to the control from the processing circuit described later.

[0032] Furthermore, the media transport device 100 may have only one of the first imaging device 122a and the second imaging device 122b, and may read only one side of the media. Also, instead of a CIS line sensor of the 1:1 optical system type equipped with a CMOS image sensor, a CIS line sensor of the 1:1 optical system type equipped with a CCD (Charge Coupled Device) image sensor may be used. Alternatively, a reduction optical system type line sensor equipped with a CMOS or CCD image sensor may be used.

[0033] The discharge roller 123 and the second opposing roller 124 are positioned downstream of the imaging device 122, facing each other, and are transported by the transport roller 119 and the first opposing roller 120 to discharge the medium imaged by the imaging device 122 to the discharge table 104. The discharge roller 123 is provided on the upper housing 102, and the second opposing roller 124 is provided on the lower housing 101, below the discharge roller 123.

[0034] The medium placed on the mounting table 103 is transported between the lower guide 101a and the upper guide 102a toward the medium transport direction A1 as the feed roller 112 rotates in the direction of arrow A2 in Figure 2, i.e., the medium transport direction. The brake roller 113 rotates in the direction of arrow A3, i.e., the opposite direction to the medium transport direction, during medium transport. Due to the action of the feed roller 112 and the brake roller 113, when multiple media are placed on the mounting table 103, only the media in contact with the feed roller 112 are separated from the media placed on the mounting table 103. This restricts the transport of media other than the separated media (preventing double feeding).

[0035] The medium is fed between the transport roller 119 and the first opposing roller 120, guided by the lower guide 101a and the upper guide 102a. The medium is then fed between the first imaging device 122a and the second imaging device 122b as the transport roller 119 and the first opposing roller 120 rotate in the directions of arrows A4 and A5, respectively. The medium read by the imaging device 122 is then discharged onto the discharge platform 104 as the discharge roller 123 and the second opposing roller 124 rotate in the directions of arrows A6 and A7, respectively.

[0036] Figure 3 is a schematic diagram illustrating the drive sources for the feed roller 112, brake roller 113, transport roller 119, first opposing roller 120, discharge roller 123 and / or second opposing roller 124.

[0037] As shown in Figure 3, the media transport device 100 has a first motor 131 and a second motor 132 as drive sources for each roller.

[0038] The first motor 131 is an example of a motor, and is provided in the lower housing 101. It is connected to the feed roller 112 via the first transmission mechanism 131a and drives the feed roller 112. The first motor 131 generates a driving force to drive the feed roller 112 in response to a control signal from the processing circuit. The first transmission mechanism 131a includes one or more pulleys, belts, gears, etc., provided between the first motor 131 and the shaft 112a of the feed roller 112, and transmits the driving force generated by the first motor 131 to the feed roller 112. As a result, the first motor 131 rotates the feed roller 112 and feeds the medium.

[0039] The second motor 132 is provided separately from the first motor 131 in the upper housing 102 and is connected to the transport roller 119, discharge roller 123, and brake roller 113 via the second transmission mechanism 132a, driving the transport roller 119, discharge roller 123, and brake roller 113. The second motor 132 generates driving force to drive the transport roller 119, discharge roller 123, and brake roller 113 in response to a control signal from the processing circuit. The second transmission mechanism 132a includes one or more pulleys, belts, gears, etc., provided between the second motor 132 and the shaft 119a of the transport roller 119, the shaft 123a of the discharge roller 123, and the shaft 113a of the brake roller 113. In particular, one or more gears are provided between the shaft 119a of the conveyor roller 119 and / or the shaft 123a of the discharge roller 123 and the shaft 113a of the brake roller 113 to make the rotation direction and rotation speed of each roller different. The second transmission mechanism 132a transmits the driving force generated by the second motor 132 to the conveyor roller 119, the discharge roller 123 and the brake roller 113. As a result, the second motor 132 rotates the conveyor roller 119, the discharge roller 123 and the brake roller 113, supplying, conveying and discharging the medium to the conveyor roller 119, the discharge roller 123 and the brake roller 113. The second motor 132 is an example of a drive source for the brake roller 113.

[0040] The first opposing roller 120 is a driven roller that rotates in accordance with the conveying roller 119, and the second opposing roller 124 is a driven roller that rotates in accordance with the discharge roller 123. The first opposing roller 120 and / or the second opposing roller 124 may be provided to be driven by the driving force from the second motor 132. In that case, one or more gears are further provided between the shaft 119a of the conveying roller 119 and the shaft 120a of the first opposing roller 120, and / or between the shaft 123a of the discharge roller 123 and the shaft 124a of the second opposing roller 124. The second transmission mechanism 132a further transmits the driving force generated by the second motor 132 to the first opposing roller 120 and / or the second opposing roller 124.

[0041] Figures 4 and 5 are schematic diagrams illustrating the third medium sensor 116 and the fourth medium sensor 117. Figure 4 is a schematic diagram of the lower guide 101a of the lower housing 101 viewed from above, and Figure 5 is a schematic diagram of the upper guide 102a of the upper housing 102 viewed from below.

[0042] As shown in Figures 4 and 5, the third medium sensor 116 and the fourth medium sensor 117 are positioned downstream of the feed roller 112 and upstream of the transport roller 119 to detect the medium being transported to their respective positions. In particular, the third medium sensor 116 and the fourth medium sensor 117 are positioned between the second medium sensor 114 and the fifth medium sensor 118 in the medium transport direction A1. The third medium sensor 116 and the fourth medium sensor 117 may also be positioned at approximately the same location as the fifth medium sensor 118 in the medium transport direction A1. Furthermore, the third medium sensor 116 and the fourth medium sensor 117 are positioned side by side with a gap between them in the width direction A8, which is perpendicular to the medium transport direction.

[0043] The third medium sensor 116 includes a light emitter and a light receiver provided on one side of the medium transport path, and a light guide tube provided opposite the light emitter and light receiver across the medium transport path. The light emitter is an LED or the like, and emits light toward the medium transport path. The light receiver, on the other hand, is a photodiode or the like, and receives the light emitted by the light emitter and guided by the light guide tube. The third medium sensor 116 generates and outputs a third medium signal whose signal value changes depending on whether a medium is present or absent at the position of the third medium sensor 116, based on the intensity of the light received by the light receiver.

[0044] The fourth medium sensor 117 includes a light emitter and a light receiver provided on one side of the medium transport path, and a light guide tube provided opposite the light emitter and light receiver across the medium transport path. The light emitter is an LED or the like, and emits light toward the medium transport path. The light receiver, on the other hand, is a photodiode or the like, and receives the light emitted by the light emitter and guided by the light guide tube. The fourth medium sensor 117 generates and outputs a fourth medium signal whose signal value changes depending on whether a medium is present or absent at the position of the fourth medium sensor 117, based on the intensity of the light received by the light receiver.

[0045] Furthermore, in the second medium sensor 114, third medium sensor 116, fourth medium sensor 117, fifth medium sensor 118 and / or sixth medium sensor 121, a reflective member such as a mirror may be used instead of a light guide tube. Also, in the second medium sensor 114, third medium sensor 116, fourth medium sensor 117, fifth medium sensor 118 and / or sixth medium sensor 121, the light emitter and light receiver may be provided facing each other across the medium transport path. In addition, the second medium sensor 114, third medium sensor 116, fourth medium sensor 117, fifth medium sensor 118 and / or sixth medium sensor 121 may detect the presence of a medium by using a contact detection sensor or the like that which supplies a predetermined current when the medium is in contact or when the medium is not in contact.

[0046] Furthermore, as shown in Figure 4, the medium transport device 100 has a first electromagnetic clutch 133. The first electromagnetic clutch 133 is an example of a shutoff mechanism and is provided on the shaft 112a of the feed roller 112, that is, in the drive force transmission path from the first motor 131 to the feed roller 112. The first electromagnetic clutch 133 is provided so as to be able to shut off the drive force from the first motor 131 to the feed roller 112 by a control signal from the processing circuit.

[0047] Furthermore, as shown in Figure 5, the media transport device 100 has a second electromagnetic clutch 134. The second electromagnetic clutch 134 is an example of an electromagnetic clutch and is provided on the shaft 113a of the brake roller 113, that is, in the power transmission path from the second motor 132, which is the drive source for the brake roller 113, to the brake roller 113. The second electromagnetic clutch 134 is provided so that the magnitude of the torque applied to the brake roller 113 can be changed by a control signal from the processing circuit.

[0048] Figure 6 is a block diagram showing the schematic configuration of the media transport device 100.

[0049] In addition to the configuration described above, the media transport device 100 further includes an interface device 135, a storage device 140, and a processing circuit 150.

[0050] The interface device 135 has an interface circuit similar to a serial bus such as USB, and electrically connects to an information processing device (not shown) (e.g., a personal computer, a portable information terminal, etc.) to transmit and receive input images and various types of information. Alternatively, instead of the interface device 135, a communication unit may be used that has an antenna for transmitting and receiving wireless signals and a wireless communication interface device for transmitting and receiving signals via a wireless communication line according to a predetermined communication protocol. The predetermined communication protocol is, for example, a wireless LAN (Local Area Network). The communication unit may also have a wired communication interface device for transmitting and receiving signals via a wired communication line according to a communication protocol such as a wired LAN.

[0051] The storage device 140 includes memory devices such as RAM (Random Access Memory) and ROM (Read Only Memory), fixed disk devices such as hard disks, or portable storage devices such as flexible disks and optical disks. The storage device 140 also stores computer programs, databases, tables, etc., used for various processes of the media transport 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. Examples of portable recording media include CD-ROMs (compact disc read-only memory) and DVD-ROMs (digital versatile disc read-only memory).

[0052] The processing circuit 150 operates based on a program pre-stored in the memory device 140. The processing circuit is, for example, a CPU (Central Processing Unit). A DSP (digital signal processor), LSI (large scale integration), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), etc., may be used as the processing circuit 150.

[0053] The processing circuit 150 is connected to the operating device 105, display device 106, first medium sensor 111, second medium sensor 114, ultrasonic sensor 115, third medium sensor 116, fourth medium sensor 117, fifth medium sensor 118, sixth medium sensor 121, imaging device 122, first motor 131, second motor 132, first electromagnetic clutch 133, second electromagnetic clutch 134, interface device 135, and storage device 140, and controls each of these parts. Based on the medium signals received from each sensor, the processing circuit 150 controls the drive of the first motor 131, controls the imaging of the imaging device 122, acquires an input image from the imaging device 122, and transmits it to the information processing device via the interface device 135.

[0054] Figure 7 shows a schematic configuration of the storage device 140 and the processing circuit 150.

[0055] As shown in Figure 7, the storage device 140 stores control programs 141 and determination programs 142, etc. Each of these programs is a functional module implemented by software running on the processor. The processing circuit 150 reads each program stored in the storage device 140 and operates according to each program it has read. In this way, the processing circuit 150 functions as a control unit 151 and a determination unit 152.

[0056] Figures 8 and 9 are flowcharts illustrating examples of the operation of the media reading process of the media transport device 100.

[0057] The following describes an example of the operation of the media reading process of the media transport device 100, referring to the flowcharts shown in Figures 8 and 9. The operation flow described below is mainly executed by the processing circuit 150 in cooperation with each element of the media transport device 100, based on a program pre-stored in the storage device 140.

[0058] First, the control unit 151 waits until the user inputs an instruction to read the medium using the operating device 105 or the information processing device, and receives an operation signal instructing the reading of the medium from the operating device 105 or the interface device 135 (step S101).

[0059] Next, the control unit 151 acquires a first medium signal from the first medium sensor 111 and determines whether or not a medium is placed on the mounting table 103 based on the acquired first medium signal (step S102). If no medium is placed on the mounting table 103, the control unit 151 terminates the series of steps.

[0060] On the other hand, when a medium is placed on the mounting table 103, the control unit 151 sets the surface movement speed of the feed roller 112, brake roller 113, transport roller 119, first opposing roller 120, discharge roller 123 and / or second opposing roller 124 (step S103). The surface movement speed is the speed at which the surface of each roller that is in contact with the medium moves. That is, the surface movement speed of the feed roller 112, transport roller 119, first opposing roller 120, discharge roller 123 and / or second opposing roller 124 is the transport speed of the medium by the feed roller 112, transport roller 119 and discharge roller 123. The surface movement speed of the brake roller 113 is the speed at which the surface of the brake roller 113 that is in contact with the medium moves in the direction opposite to the medium feeding direction. Hereafter, the surface movement speed of each roller may be simply referred to as speed.

[0061] Furthermore, the media transport device 100 has three transport modes for transporting the media: a high-speed mode, a medium-speed mode, and a low-speed mode. The transport mode is set by the user using the operating device 105 or the information processing device before the media reading process is executed.

[0062] Figures 10 to 12 are graphs illustrating the speed changes of the feed roller 112, brake roller 113, transport roller 119, first opposing roller 120, discharge roller 123, and second opposing roller 124. Figure 10 shows the speed change of each roller in high-speed mode, Figure 11 shows the speed change of each roller in medium-speed mode, and Figure 12 shows the speed change of each roller in low-speed mode.

[0063] In Figures 10 to 12, graphs G11, G21, and G31 show the speed change of the feed roller 112, graphs G12, G22, and G32 show the speed change of the brake roller 113, and graphs G13, G23, and G33 show the speed change of the transport roller 119. The speeds of the first opposing roller 120, discharge roller 123, and second opposing roller 124 change in the same way as the speed of the transport roller 119, so below we will explain the speed change of the transport roller 119 as a representative example. In each graph G11 to G13, G21 to G23, and G31 to G33, the horizontal axis represents time and the vertical axis represents speed.

[0064] Meanwhile, graph G14 shows the change in the signal value of the fifth medium sensor 118, and graph G15 shows the change in the signal value of the sixth medium sensor 121. In graphs G14 and G15, the horizontal axis represents time, and the vertical axis represents the signal value. In this embodiment, when there is no medium at the position of each sensor, the signal value of the corresponding signal becomes L, and when there is a medium at the position of each sensor, the signal value of the corresponding signal becomes H.

[0065] In Figures 10 to 12, time T1 indicates the start of media feeding. As shown in Figures 10 to 12, regardless of whether the transport mode is set to high-speed mode, medium-speed mode, or low-speed mode, at the start of media feeding, the control unit 151 sets the speed of the feed roller 112 to an initial speed V1. Furthermore, when the transport mode is set to high-speed mode, the control unit 151 sets the speed of the brake roller 113 to an initial speed U1 and the speed of the transport roller 119 to an initial speed W1. The initial speed U1 of the brake roller 113 is set to a speed higher than half the initial speed V1 of the feed roller 112. In addition, the initial speed U1 of the brake roller 113 may be set to a speed lower than the initial speed V1 of the feed roller 112.

[0066] On the other hand, when the transport mode is set to medium speed mode, the control unit 151 sets the speed of the brake roller 113 to the final speed U3b and the speed of the transport roller 119 to the final speed W3b. The final speed U3b of the brake roller 113 is set to a lower (slower) speed than the final speed U3a of the brake roller 113 in high speed mode, which will be described later. The final speed W3b of the transport roller 119 is set to a lower speed than the final speed W3a of the transport roller 119 in high speed mode, which will be described later. Also, when the transport mode is set to low speed mode, the control unit 151 sets the speed of the brake roller 113 to the final speed U3c and the speed of the transport roller 119 to the final speed W3c. The final speed U3c of the brake roller 113 is set to a lower speed than the final speed U3b of the brake roller 113 in medium speed mode. The final speed W3c of the transport roller 119 is set to a lower speed than the final speed W3c of the transport roller 119 in medium speed mode.

[0067] Next, the control unit 151 drives the first motor 131 and the second motor 132. This causes the control unit 151 to rotate the feed roller 112, brake roller 113, transport roller 119, first opposing roller 120, discharge roller 123 and / or second opposing roller 124 to feed and transport the medium (step S104).

[0068] The control unit 151 controls the first motor 131 and the second motor 132 to rotate each roller at the set speed. As shown in Figures 10 to 12, after a predetermined thru-up period has elapsed since the start of driving each motor at time T1, each roller rotates at the set speed. Similarly, if the control unit 151 increases the speed of each roller, each roller rotates at the set speed after a predetermined thru-up period has elapsed since the start of driving each motor. Similarly, if the control unit 151 decreases the speed of each roller, each roller rotates at the set speed after a predetermined thru-down period has elapsed since the start of driving each motor.

[0069] Next, the control unit 151 waits until the leading edge of the transported medium passes the position of the fifth medium sensor 118 (step S105). The control unit 151 periodically acquires a fifth medium signal from the fifth medium sensor 118, and determines that the leading edge of the medium has passed the position of the fifth medium sensor 118 when the signal value of the fifth medium signal changes from a value indicating the absence of medium to a value indicating the presence of medium.

[0070] Next, the control unit 151 changes the speed of the feed roller 112 and the brake roller 113 (step S106).

[0071] In Figures 10 to 12, time T2 indicates the time when the signal value of the fifth medium signal changes from L to H, that is, when the leading edge of the medium passes the position of the fifth medium sensor 118. As shown in Figures 10 to 12, the speed of the feed roller 112, which is changed when the leading edge of the medium passes the position of the fifth medium sensor 118, differs depending on the transport mode.

[0072] If the transport mode is set to high-speed mode, the control unit 151 changes the speed of the feed roller 112 to the final speed V3a. The final speed V3a of the feed roller 112 is set to be higher than the initial speed V1 of the feed roller 112 and less than or equal to the final speed W3a of the transport roller 119, which will be described later. The final speed V3a of the feed roller 112 may also be set to be the same speed as the final speed W3a of the transport roller 119. If the transport mode is set to medium-speed mode, the control unit 151 changes the speed of the feed roller 112 to the final speed V3b. The final speed V3b of the feed roller 112 in medium-speed mode is set to be higher than the initial speed V1 and lower than the final speed V3a in high-speed mode. If the transport mode is set to low-speed mode, the control unit 151 changes the speed of the feed roller 112 to the final speed V3c. In low-speed mode, the final speed V3c of the feed roller 112 is set to be higher than the initial speed V1 and lower than the final speed V3b in medium-speed mode.

[0073] Furthermore, if the transport mode is set to high-speed mode, the control unit 151 changes the speed of the brake roller 113 to the final speed U3a and the speed of the transport roller 119 to the final speed W3a. The final speed U3a of the brake roller 113 is set to a speed higher than the initial speed U1 of the brake roller 113. The final speed W3a of the transport roller 119 is set to a speed higher than the initial speed W1 of the transport roller 119. On the other hand, if the transport mode is set to medium-speed mode, the speeds of the brake roller 113 and the transport roller 119 are already set to the final speeds U3b and W3b, so the control unit 151 does not change the speeds of the brake roller 113 and the transport roller 119. Similarly, if the transport mode is set to low-speed mode, the speeds of the brake roller 113 and the transport roller 119 are already set to the final speeds U3c and W3c, so the control unit 151 does not change the speeds of the brake roller 113 and the transport roller 119.

[0074] Next, the control unit 151 waits until the leading edge of the conveyed medium passes the position of the conveying roller 119 (step S107). The control unit 151 periodically acquires a sixth medium signal from the sixth medium sensor 121, and determines that the leading edge of the medium has passed the position of the sixth medium sensor 121 when the signal value of the sixth medium signal changes from a value indicating the absence of medium to a value indicating the presence of medium. When the leading edge of the medium has passed the position of the sixth medium sensor 121, the control unit 151 determines that the leading edge of the medium has passed the position of the conveying roller 119.

[0075] Next, the control unit 151 controls the first motor 131 to stop the feed roller 112 (step S108).

[0076] In Figures 10 to 12, time T3 indicates the time when the signal value of the sixth medium signal changes from L to H, that is, when the leading edge of the medium passes the position of the sixth medium sensor 121. As shown in Figures 10 to 12, after the leading edge of the medium passes the position of the sixth medium sensor 121, the control unit 151 stops the feed roller 112 (changes its speed to 0). As a result, the medium is then transported by the transport roller 119, and the feed roller 112 is carried along by the transported medium. By stopping the feed roller 112, the control unit 151 can suppress the occurrence of medium jamming, which would occur if the medium were pushed by the feed roller 112 and bent between the feed roller 112 and the transport roller 119.

[0077] Next, the control unit 151 instructs the imaging device 122 to start imaging the medium (step S109).

[0078] Next, the control unit 151 waits until the trailing end of the transported medium passes the position of the fifth medium sensor 118 (step S110). The control unit 151 periodically acquires a fifth medium signal from the fifth medium sensor 118, and determines that the trailing end of the medium has passed the position of the fifth medium sensor 118 when the signal value of the fifth medium signal changes from a value indicating the presence of medium to a value indicating the absence of medium.

[0079] Next, the control unit 151 determines whether or not there is any medium remaining on the mounting tray 103 based on the first medium signal received from the first medium sensor 111 (step S111).

[0080] If there is still media remaining on the mounting table 103, the control unit 151 sets the speed of the feed roller 112 for feeding the subsequent media (step S112).

[0081] In Figures 10 to 12, time T4 indicates the time when the signal value of the fifth medium signal changes from H to L, that is, when the trailing end of the medium passes the position of the fifth medium sensor 118. As shown in Figures 10 to 12, the speed of the feed roller 112 set to feed the subsequent medium when the trailing end of the medium passes the position of the fifth medium sensor 118 differs depending on the transport mode. When the transport mode is set to high-speed mode or medium-speed mode, the control unit 151 sets the speed of the feed roller 112 to a first intermediate speed V2a. The first intermediate speed V2a is an example of a first speed, and is set to be higher than the initial speed V1 and lower than the final speeds V3a and V3b. The first speed is the first stage speed of the feed roller 112 when feeding the second and subsequent media. Note that the first intermediate speed V2a may be set to approximately the same speed as the final speed V3c. On the other hand, if the transport mode is set to low-speed mode, the control unit 151 sets the speed of the feed roller 112 to the final speed V3c.

[0082] Next, the control unit 151 drives the first motor 131 to rotate the feed roller 112, thereby feeding and transporting the subsequent medium (step S113). The control unit 151 controls the first motor 131 to rotate the feed roller 112 at a set speed.

[0083] Next, the control unit 151 waits until the leading edge of the subsequent medium passes the position of the second medium sensor 114 (step S114). The control unit 151 periodically acquires a second medium signal from the second medium sensor 114, and determines that the leading edge of the medium has passed the position of the second medium sensor 114 when the signal value of the second medium signal changes from a value indicating the absence of medium to a value indicating the presence of medium.

[0084] Next, the control unit 151 changes the speed of the feed roller 112 (step S115).

[0085] As shown in Figures 10 to 12, the speed of the feed roller 112, which is changed when the leading edge of the subsequent medium passes the position of the second medium sensor 114, differs depending on the transport mode. When the transport mode is set to high-speed mode, the control unit 151 changes the speed of the feed roller 112 to the second intermediate speed V2b. The second intermediate speed V2b is an example of a second speed and is set to a speed higher than the first intermediate speed V2a and lower than the final speed V3a. The second speed is the second speed of the feed roller 112 when transporting the second and subsequent media. Note that the second intermediate speed V2b may be set to approximately the same value as the final speed V3b. On the other hand, when the transport mode is set to medium-speed mode, the control unit 151 changes the speed of the feed roller 112 to the final speed V3b. Furthermore, when the transport mode is set to low-speed mode, the control unit 151 does not change the speed of the feed roller 112.

[0086] Next, the control unit 151 waits until the rear end of the preceding medium passes the imaging position of the imaging device 122 (step S116). The control unit 151 periodically acquires a sixth medium signal from the sixth medium sensor 121, and determines that the rear end of the preceding medium has passed the position of the sixth medium sensor 121 when the signal value of the sixth medium signal changes from a value indicating the presence of medium to a value indicating the absence of medium. The control unit 151 determines that the rear end of the preceding medium has passed the imaging position when a first predetermined time has elapsed since the rear end of the preceding medium passed the position of the sixth medium sensor 121. The first predetermined time is set to a value that includes a margin over the time required for the medium to move from the position of the sixth medium sensor 121 to the imaging position.

[0087] Next, the control unit 151 acquires an input image from the imaging device 122 and stores the acquired input image in the storage device 140. The control unit 151 outputs the input image stored in the storage device 140 by transmitting it to the information processing device via the interface device 135 and deletes it from the storage device 140 (step S117).

[0088] Next, the control unit 151 waits in the same manner as in step S105 until the leading edge of the subsequent medium passes the position of the fifth medium sensor 118 (step S118).

[0089] Next, the control unit 151 changes the speed of the feed roller 112 (step S119).

[0090] In Figures 10 to 12, time T5 indicates the time when the signal value of the fifth medium signal changes from L to H, that is, when the leading edge of the subsequent medium passes the position of the fifth medium sensor 118. As shown in Figures 10 to 12, when the transport mode is set to high-speed mode, the control unit 151 changes the speed of the feed roller 112 to the final speed V3a when the leading edge of the subsequent medium passes the position of the fifth medium sensor 118. On the other hand, when the transport mode is set to medium-speed mode or low-speed mode, the control unit 151 does not change the speed of the feed roller 112.

[0091] Next, the control unit 151 returns the process to step S107 and repeats the process from step S107 onward for the subsequent medium. In this case, in step S107, the control unit 151 waits until the leading edge of the subsequent medium passes the position of the transport roller 119 (time T6 in Figure 10), and in step S108, controls the first motor 131 to stop the feed roller 112.

[0092] On the other hand, if no medium remains on the mounting table 103 in step S111, the control unit 151 waits in the same manner as in step S116 until the rear end of the transported medium passes the imaging position of the imaging device 122 (step S120).

[0093] Next, the control unit 151 acquires an input image from the imaging device 122 and outputs the acquired input image by transmitting it to the information processing device via the interface device 135 (step S121).

[0094] Next, the control unit 151 waits until the rear end of the conveyed medium passes the position of the discharge roller 123 (step S122). The control unit 151 determines that the rear end of the medium has passed the position of the discharge roller 123 when a second predetermined time has elapsed since the rear end of the medium passed the position of the sixth medium sensor 121. The second predetermined time is set to a value that includes a margin over the time required for the medium to move from the position of the sixth medium sensor 121 to the position of the discharge roller 123.

[0095] Next, the control unit 151 controls the second motor 132 to stop the brake roller 113, the transport roller 119, the first opposing roller 120, the discharge roller 123 and / or the second opposing roller 124 (step S123), and ends the series of steps.

[0096] In step S117, the control unit 151 may execute the processing from step S118 onward even if the transmission of the input image has not been completed. In that case, in step S118, the control unit 151 may temporarily stop the feeding of the subsequent medium if the free capacity of the storage device 140 is less than a predetermined amount when the leading edge of the subsequent medium passes the position of the fifth medium sensor 118. The control unit 151 controls the first motor 131 to stop the feeding roller 112 until the free capacity of the storage device 140 is equal to or greater than a predetermined amount. This enables the medium transport device 100 to efficiently transport the medium while reliably transmitting the input image.

[0097] Furthermore, in step S118, the control unit 151 may temporarily stop feeding the subsequent medium if the distance between the rear end of the preceding medium and the front end of the subsequent medium is short when the front end of the subsequent medium passes the position of the fifth medium sensor 118. For example, the control unit 151 detects the time from when the rear end of the preceding medium passes the position of the fifth medium sensor 118 or the sixth medium sensor 121 until the front end of the subsequent medium passes the position of the fifth medium sensor 118. If the measured time is less than the third predetermined time, the control unit 151 controls the first motor 131 to stop the feeding roller 112 until the third predetermined time has elapsed since the rear end of the preceding medium passed the position of the fifth medium sensor 118 or the sixth medium sensor 121. This enables the medium transport device 100 to efficiently transport the medium while suppressing the occurrence of medium jams.

[0098] Figures 13(a) and 13(b) are schematic diagrams illustrating the technical significance of feeding media according to the media reading process shown in Figures 8 and 9.

[0099] Figures 13(a) and (b) are schematic diagrams of the feed roller 112 and brake roller 113 viewed from the side. Figure 13(a) shows the feeding of the first medium M1 from a state in which the medium group M is placed on the mounting table 103, and Figure 13(b) shows the feeding of the second and subsequent mediums M2 from a state in which the medium group M is placed on the mounting table 103.

[0100] As shown in Figure 13(a), when a certain amount of media group M is placed on the mounting table 103, the leading edges of the media group M are usually aligned by the user or by an alignment member (not shown). Therefore, the leading edge of the first media M1, which is placed at the bottom, does not reach the nip area of ​​the feed roller 112 and the brake roller 113. In this case, the frictional force between each media increases due to the weight of the media group placed on top of the first media M1. Due to this frictional force, the media group placed on top of the first media M1 tries to move downstream together with the first media M1 being fed and is pressed against the brake roller 113. If the speed of the feed roller 112 is too high at this time, the brake roller 113 may be lifted upward by the media group placed on top of the first media M1, and the media group may enter between the feed roller 112 and the brake roller 113, potentially causing double feeding of media.

[0101] Furthermore, if the speed of the feed roller 112 is too high at this time, the leading edge of the first medium M1 may lift up before reaching the nip area between the feed roller 112 and the brake roller 113, potentially causing the medium M1 to buckle and resulting in a medium jam.

[0102] As shown in steps S103 to S105 of Figure 8, when the control unit 151 feeds the first medium from among the media placed on the mounting table 103, it controls the first motor 131 to rotate the feed roller 112 at a constant speed during the separation period from when the feed roller 112 starts feeding the medium until the fifth medium sensor 118 detects the leading edge of the medium. The separation period when feeding the first medium is the period from time T1 to time T2 in Figures 10 to 12. In particular, when feeding the first medium, the control unit 151 controls the first motor 131 to rotate the feed roller 112 at an initial speed V1 that is lower than the first intermediate speed V2a when feeding the second and subsequent media. By reducing the speed of the feed roller 112 during the separation period of the first medium, the control unit 151 can suppress the occurrence of double feeding or jamming of the medium.

[0103] On the other hand, as shown in Figure 13(b), when the first medium M1 is fed, the second and subsequent mediums M2 are separated by the brake roller 113, and the leading edge of each medium M2 comes into contact with the brake roller 113. Similar to when the first medium M1 is fed, if the speed of the feed roller 112 is too high, double feeding or jamming of the medium may occur when the second and subsequent mediums M2 are fed. However, compared to when the first medium M1 is fed, the possibility of double feeding or jamming of the medium is lower when the second and subsequent mediums M2 are fed. On the other hand, if the feed speed is too low during the separation period of the second and subsequent mediums M2, a considerable amount of time will be required to complete the transport of all the mediums. However, if the speed of the stationary feed roller 112 is rapidly increased when feeding the second and subsequent mediums M2, the first motor 131 may lose step.

[0104] As shown in steps S112 to S115 and S118 of Figure 9, when the transport mode is set to high-speed mode, the control unit 151 controls the first motor 131 to rotate the feed roller 112 at a first intermediate speed V2a and a second intermediate speed V2b, which are higher than the initial speed V1 when feeding the first medium, during the separation period when feeding the second and subsequent media. The separation period when feeding the second and subsequent media is the period from time T4 to time T5 in Figures 10 to 12. In particular, when feeding the second and subsequent media from among the media placed on the mounting table 103, the control unit 151 controls the first motor 131 to rotate the feed roller 112 at a first intermediate speed V2a and then at a second intermediate speed V2b. In this way, the control unit 151 gradually increases the speed of the feed roller 112 to a speed higher than the speed during the separation period of the first medium, while decreasing the speed of the feed roller 112 during the separation period of the second and subsequent media. As a result, the control unit 151 can reduce the processing time required for media reading while suppressing double feeding or jamming of the media and loss of synchronization of the first motor 131, thereby achieving both feeding performance (reduction of abnormal occurrences) and processing performance (reduction of transport time).

[0105] Figure 14 is a schematic diagram illustrating the technical significance of feeding the media according to the media reading process shown in Figures 8 and 9. Figure 14 is a schematic diagram of the lower guide 101a of the lower housing 101 viewed from above.

[0106] Figure 14 shows a state in which the leading edge of a medium M3 being transported at an angle is in contact with only one of the two transport rollers 119 (first opposing roller 120). If the speed of the transport roller 119 is approximately the same as the speed of the feed roller 112, the medium M3 will then be transported downstream while maintaining its current angle. However, if the speed of the transport roller 119 is higher than the speed of the feed roller 112, the medium M3 will then be pulled by the transport roller 119 on the side it is in contact with and rotate in the direction of arrow A9. Consequently, the angle of the medium M3 increases, and the medium M3 may collide with the side wall of the transport path, potentially causing a medium jam. The greater the difference between the speed of the transport roller 119 and the speed of the feed roller 112, the higher the likelihood of a medium jam occurring.

[0107] As described above, if the storage device 140 has insufficient free space or the distance between media is short when the leading edge of the media passes the position of the fifth media sensor 118, the control unit 151 may temporarily stop feeding the media. However, if the control unit 151 temporarily stops feeding the media, a certain amount of pass-through time is required for the speed of the feeding roller 112 to reach the set speed after resuming feeding. If the speed of the feeding roller 112 has not increased sufficiently when the leading edge of the media reaches the position of the transport roller 119, skew of the media may occur. Therefore, if the control unit 151 temporarily stops feeding the media, it is necessary to stop the media sufficiently upstream of the transport roller 119. However, a certain amount of pass-down time is required from the time the control unit 151 stops the first motor 131 until the rotation of the feeding roller 112 completely stops. For example, the above problem can be avoided by making the distance between the feed roller 112 and the transport roller 119 sufficiently large, but in that case, the overall size of the device will increase.

[0108] As shown in steps S106 and S119 of Figures 8 and 9, in high-speed mode, the control unit 151 controls the first motor 131 to rotate the feed roller 112 at a final speed V3a that is higher than the second intermediate speed V2b after the fifth medium sensor 118 detects the leading edge of the medium. Therefore, when the leading edge of the medium passes the position of the fifth medium sensor 118, the speed of the feed roller 112 is set to the second intermediate speed V2b, which is lower than the final speed V3a, and the control unit 151 can completely stop the rotation of the feed roller 112 in a sufficiently short time. In medium-speed mode and low-speed mode, when the leading edge of the medium passes the position of the fifth medium sensor 118, the speed of the feed roller 112 is set to the final speed V3b and final speed V3c. However, since the final speeds V3b and V3c are lower than the final speed V3a, the control unit 151 can completely stop the rotation of the feed roller 112 in a sufficiently short time.

[0109] Therefore, when the control unit 151 temporarily stops the feeding of the medium, it is possible to stop the medium at a position well upstream of the transport roller 119. As a result, when the control unit 151 resumes feeding the medium, it is possible to sufficiently increase the speed of the feed roller 112 before the leading edge of the medium reaches the position of the transport roller 119, thereby suppressing an increase in the tilt of the medium and preventing the occurrence of medium jams.

[0110] Furthermore, as shown in steps S114 and S115 of Figure 9, during the separation period when feeding the second and subsequent media, the control unit 151 controls the first motor 131 to rotate the feed roller 112 at a second intermediate speed V2b when the second media sensor 114 detects the leading edge of the media. After the leading edge of the media passes the position of the second media sensor 114, that is, after passing the nip region between the feed roller 112 and the brake roller 113, the leading edge of the media will not collide with the brake roller 113 and lift up. Therefore, the possibility of the media buckling and causing a media jam is low. When the second media sensor 114 detects the leading edge of the media, the control unit 151 considers that the leading edge of the media has passed the nip region between the feed roller 112 and the brake roller 113 and increases the speed of the feed roller 112. This makes it possible for the control unit 151 to reduce the media feeding time while suppressing the occurrence of media jams.

[0111] In particular, the period during which the feed roller 112 rotates at the first intermediate speed V2a is shortened, and the period during which it rotates at the second intermediate speed V2b is lengthened, so that even if the second intermediate speed V2b is low, the total feed speed of the medium can be increased. That is, the control unit 151 can lower the second intermediate speed V2b, and when the feed of the medium is temporarily stopped as described above, it is possible to stop the medium at a position sufficiently upstream of the transport roller 119. Note that in steps S114 and S115 of Figure 9, the control unit 151 may change the speed of the feed roller 112 not when the leading edge of the medium passes the position of the second medium sensor 114, but when a fourth predetermined time has elapsed since the start of medium feed. The fourth predetermined time is set by prior experimentation to the time required from the start of medium feed until the leading edge of the medium passes the nip region of the feed roller 112 and the brake roller 113. In that case, the second medium sensor 114 may be omitted. Furthermore, if the second medium sensor 114 is omitted, the fifth medium sensor 118 may be placed in the position of the second medium sensor 114.

[0112] Furthermore, the control unit 151 may increase the amount of current supplied to the first motor 131 and / or the second motor 132 during the through-up period of the first motor 131 and / or the second motor 132. This reduces the possibility of motors losing step even when the speed of each motor is increased in a short period of time, and makes it possible to reduce the distance required for through-up. In addition, by limiting the period during which the amount of current is increased to the through-up period, the media transport device 100 can suppress an increase in overall power consumption.

[0113] Furthermore, as shown in Figure 13(b), media that enters the nip region between the feed roller 112 and the brake roller 113 are pushed back by the brake roller 113, which rotates in the opposite direction to the media feeding direction. The larger the ratio of the speed of the brake roller 113 to the speed of the feed roller 112, the better the media is pushed back. In particular, as shown in Figure 13(a), when feeding the first medium M1 begins, the leading edges of each medium positioned above the first medium M1 have not yet reached the nip region between the feed roller 112 and the brake roller 113. Therefore, when feeding the first medium M1 begins, each medium enters the nip region between the feed roller 112 and the brake roller 113 with force. Consequently, when feeding the first medium M1, the ratio of the speed of the brake roller 113 to the speed of the feed roller 112 needs to be set to a reasonably large value in order to effectively return the other media to the upstream side.

[0114] On the other hand, as shown in Figure 13(b), when the second and subsequent media M2 are fed, the leading edge of each media M2 is already in contact with the brake roller 113. Therefore, when feeding the second and subsequent media M2, even if the ratio of the speed of the brake roller 113 to the speed of the feeding roller 112 is set to a relatively small value, media other than the media being fed are effectively pushed back.

[0115] Furthermore, as described above, the brake roller 113 is driven by the same second motor 132 as the transport roller 119 and discharge roller 123. This allows the media transport device 100 to reduce the number of motors, thereby reducing the device cost and size. However, if the speed of the brake roller 113 is reduced, the speeds of the transport roller 119 and discharge roller 123 are also reduced, resulting in a decrease in the media processing performance.

[0116] Furthermore, the higher the speed of the brake roller 113, the greater the vibration of the brake roller 113, resulting in a loud vibration noise (so-called rattling noise). When starting the feeding of the second and subsequent media, the media is in contact with the brake roller 113, suppressing vibration. However, when starting the feeding of the first media M1, the media is not in contact with the brake roller 113, and vibration is not suppressed. Therefore, it is desirable to reduce the speed of the brake roller 113, especially when starting the feeding of the first media M1.

[0117] As shown in steps S103 and S106 of Figure 8, the control unit 151 sets the rotational speed of the brake roller 113 during the separation period when feeding the first medium placed on the mounting table 103 to a lower speed than the rotational speed of the brake roller 113 during the separation period when feeding the second and subsequent media. This allows the control unit 151 to suppress vibration of the brake roller 113 when feeding the first medium and suppress the generation of vibration noise. During the separation period when feeding the first medium, the transport roller 119 has not yet transported the medium, so reducing the rotational speed of the brake roller 113 does not increase the medium transport time. On the other hand, by increasing the rotational speed of the brake roller 113 during the separation period when feeding the second and subsequent media, the control unit 151 can maintain a high rotational speed of the transport roller 119. Therefore, the medium transport device 100 can improve processing performance (reduction of transport time) while suppressing increases in device cost and device size.

[0118] Furthermore, as shown in step S103 of Figure 8, the control unit 151 sets the speed of the feed roller 112 to a sufficiently low initial speed V1 when media feeding begins, and sets the initial speed U1 of the brake roller 113 to a speed higher than half the initial speed V1 of the feed roller 112. That is, the control unit 151 sets the rotational speed of the brake roller 113 such that the speed of the brake roller 113 during the separation period when feeding the first medium of the media placed on the mounting table 103 is higher than half the speed of the feed roller 112 during the separation period when feeding the first medium. As a result, the brake roller 113 can effectively push back the media that has entered the nip area between the feed roller 112 and the brake roller 113 when media is being fed.

[0119] As detailed above, the media transport device 100 gradually increases the rotational speed of the feed roller 112 during the period from the start of media feeding until the leading edge of the media passes the feed roller 112. This allows the media transport device 100 to reduce the media feeding time while appropriately controlling the stopping and restarting of media feeding when the available capacity of the storage device 140 is insufficient or when the distance between media being fed continuously is short. Therefore, the media transport device 100 is able to control media feeding more effectively.

[0120] In particular, by devising a motor control method, the media transport device 100 is able to more effectively control the feeding of the media without using a motor or media sensor with a special configuration. Therefore, the media transport device 100 can more effectively control the feeding of the media while suppressing increases in equipment cost and equipment size.

[0121] Furthermore, the media transport device 100 rotates the feed roller 112 at a low speed while the media is being separated, and rotates the feed roller 112 at a high speed when the media is not being separated, thereby enabling efficient separation of the media while transporting it in a short amount of time.

[0122] Figure 15 is a schematic diagram illustrating the drive sources for the feed roller 112, brake roller 113, transport roller 219, first opposing roller 220, discharge roller 223 and / or second opposing roller 224 in a media transport device according to another embodiment.

[0123] As shown in Figure 15, the media conveying device according to this embodiment has a conveying roller 219, a first opposing roller 220, a discharge roller 223, and a second opposing roller 224 instead of a conveying roller 119, a first opposing roller 120, a discharge roller 123, and a second opposing roller 124. In addition, the media conveying device has a second motor 232 instead of a second motor 132.

[0124] The conveying roller 219 is provided on the lower housing 101, and the first opposing roller 220 is provided on the upper housing 102 above the conveying roller 219. The discharge roller 223 is provided on the lower housing 101, and the second opposing roller 224 is provided on the upper housing 102 above the discharge roller 223.

[0125] The second motor 232 is provided separately from the first motor 131 in the lower housing 101 and is connected to the transport roller 219, discharge roller 223 and brake roller 113 via the second transmission mechanism 232a, driving the transport roller 219, discharge roller 223 and brake roller 113. The second motor 232 generates driving force to drive the transport roller 219, discharge roller 223 and brake roller 113 in response to a control signal from the processing circuit 150. The second transmission mechanism 232a includes one or more pulleys, belts, gears, etc., provided between the second motor 232 and the shaft 219a of the transport roller 219, the shaft 223a of the discharge roller 223 and the shaft 113a of the brake roller 113. In particular, one or more gears are provided between the shaft 219a of the conveyor roller 219 and / or the shaft 223a of the discharge roller 223 and the shaft 113a of the brake roller 113 to cause each roller to rotate in a different direction and at a different speed. These gears are positioned outside the medium conveying path in the width direction A8 so as to transmit driving force across the medium conveying path. The second transmission mechanism 232a transmits the driving force generated by the second motor 232 to the conveyor roller 219, the discharge roller 223 and the brake roller 113. As a result, the second motor 232 rotates the conveyor roller 219, the discharge roller 223 and the brake roller 113, thereby supplying, conveying and discharging the medium to the conveyor roller 219, the discharge roller 223 and the brake roller 113. The second motor 232 is an example of a drive source for the brake roller 113.

[0126] The first opposing roller 220 is a driven roller that rotates in accordance with the conveying roller 219, and the second opposing roller 224 is a driven roller that rotates in accordance with the discharge roller 223. The first opposing roller 220 and / or the second opposing roller 224 may be provided to be driven by the driving force from the second motor 232. In that case, one or more gears are further provided between the shaft 219a of the conveying roller 219 and the shaft 220a of the first opposing roller 220, and / or between the shaft 223a of the discharge roller 223 and the shaft 224a of the second opposing roller 224. The second transmission mechanism 232a further transmits the driving force generated by the second motor 232 to the first opposing roller 220 and / or the second opposing roller 224.

[0127] As detailed above, even when the transport roller 219 is mounted on the lower housing 101 and both the transport roller 219 and the brake roller 113 are driven by the same second motor 232, the transport device can now more effectively control the feeding of the medium.

[0128] Figure 16 is a flowchart showing some examples of the operation of the media reading process of a media transport device according to another embodiment.

[0129] The flowchart shown in Figure 16 is executed instead of the flowchart shown in Figure 9. The processes in steps S211-S213 and S216-S223 in Figure 16 are the same as the processes in steps S111-S113 and S116-S123 in Figure 9, so their explanation is omitted, and only steps S214-S215 will be explained below.

[0130] In step S213, after the control unit 151 drives the feed roller 112, the determination unit 152 determines whether or not skew has occurred in the conveyed medium (step S214). The determination unit 152 periodically acquires the third medium signal and the fourth medium signal from the third medium sensor 116 and the fourth medium sensor 117, and determines whether or not skew has occurred in the medium based on the acquired third medium signal and fourth medium signal. The determination unit 152 determines that the leading edge of the medium has passed the position of the third medium sensor 116 when the signal value of the third medium signal changes from a value indicating the absence of medium to a value indicating the presence of medium. The determination unit 152 also determines that the leading edge of the medium has passed the position of the fourth medium sensor 117 when the signal value of the fourth medium signal changes from a value indicating the absence of medium to a value indicating the presence of medium.

[0131] The determination unit 152 determines that skew has occurred in the medium if the leading edge of the medium does not pass through the position of the third medium sensor 116 or the position of the fourth medium sensor 117 within a fifth predetermined time after passing through one of the positions. The fifth predetermined time is set by prior experiments to a value between the difference in the time it takes to pass through each sensor position when no medium jam occurs and the difference in the time it takes to pass through each sensor position when a medium jam occurs. On the other hand, the determination unit 152 determines that skew has not occurred in the medium if the leading edge of the medium passes through the position of the third medium sensor 116 or the position of the fourth medium sensor 117 within a fifth predetermined time after passing through one of the positions.

[0132] Next, the control unit 151 changes the speed of the feed roller 112 (step S215). Similar to the process in step S115, if the transport mode is set to medium speed mode, the control unit 151 changes the speed of the feed roller 112 to the final speed V3b, and if the transport mode is set to low speed mode, it does not change the speed of the feed roller 112. On the other hand, if the transport mode is set to high speed mode, the control unit 151 changes the speed of the feed roller 112 based on the result of determining the skew of the medium.

[0133] Figure 17 is a graph illustrating the speed change of the feed roller 112 in high-speed mode.

[0134] In Figure 17, graph G41 shows the speed change of the feed roller 112. The horizontal axis of graph G41 represents time, and the vertical axis represents speed. The speeds of the brake roller 113 and the transport roller 119 change in the same way as graphs G12 and G13 shown in Figure 10. Graphs G14 and G15 show the changes in the signal values ​​of the fifth medium sensor 118 and the sixth medium sensor 121, and change in the same way as graphs G14 and G15 shown in Figure 10. Also, times T1 to T6 represent the same times as times T1 to T6 shown in Figure 10.

[0135] If skew occurs in the medium, the control unit 151 changes the speed of the feed roller 112 to the second intermediate speed V2b, as shown in graph G11 in Figure 10. On the other hand, if skew does not occur in the medium, the control unit 151 changes the speed of the feed roller 112 to the final speed V3a, as shown in graph G41 in Figure 17. In this case, the final speed V3a is an example of the second speed. The final speed V3a is set to the same speed as the feed roller 112. That is, if the determination unit 152 determines that skew has occurred in the medium, the control unit 151 sets the second intermediate speed V2b as the second speed so that the speed of the feed roller 112 is lower than the speed of the transport roller 119. On the other hand, if the determination unit 152 does not determine that skew has occurred in the medium, the control unit 151 sets the final speed V3a as the second speed so that the speed of the feed roller 112 is the same as the speed of the transport roller 119.

[0136] As described above, if the storage device 140 has insufficient free space, or if the distance between media is short, the control unit 151 may temporarily stop feeding the media. However, if the media is tilted and the speed of the transport roller 119 is higher than the speed of the feed roller 112, the tilt of the media will increase, and the media may collide with the side wall of the transport path, causing a jam. When skew occurs in the media, the control unit 151 sets the speed of the feed roller 112 to the second intermediate speed V2b, making it possible to stop the media well upstream of the transport roller 119 when temporarily stopping the feeding of the media. As a result, when the control unit 151 resumes feeding the media, it is possible to sufficiently increase the speed of the feed roller 112 before the leading edge of the media reaches the position of the transport roller 119, thereby suppressing the increase in the tilt of the media and preventing the occurrence of a jam.

[0137] On the other hand, if the medium is not tilted, even if the speed of the transport roller 119 is higher than the speed of the feed roller 112, the likelihood of the medium tilting increasing and causing a medium jam is low. When no skew occurs in the medium, the control unit 151 can reduce the medium feeding time by setting the speed of the feed roller 112 to the final speed V3a. Therefore, the control unit 151 can reduce the medium transport time while suppressing the occurrence of medium jams.

[0138] As detailed above, the media transport device can now more effectively control the feeding of the media even when the speed of the feed roller 112 is changed depending on whether or not skew occurs in the media.

[0139] Figure 18 is a flowchart showing some examples of the operation of the media reading process of a media transport device according to yet another embodiment.

[0140] The flowchart shown in Figure 18 is executed instead of the flowchart shown in Figure 8. The processes in steps S301-S306 and S308-S311 in Figure 18 are the same as the processes in steps S101-S106 and S107-S110 in Figure 8, so their explanation is omitted, and only steps S307 and S312 will be explained below.

[0141] In step S305 or S118, the control unit 151 waits until the leading edge of the medium passes the position of the fifth medium sensor 118, that is, after the leading edge of the medium passes the position of the ultrasonic sensor 115, and then detects the thickness of the medium being transported (step S307). The control unit 151 detects the thickness of the medium based on the ultrasonic signal received from the ultrasonic sensor 115. The ultrasonic waves emitted by the ultrasonic transmitter 115a and transmitted through the medium are attenuated by the medium, and the thicker the medium, the greater the attenuation of the ultrasonic waves. The medium transport device 100 stores in the storage device 140 a table that defines the relationship between the magnitude of the ultrasonic waves received by the ultrasonic receiver 115b, i.e., the signal value of the ultrasonic signal, and the thickness of the medium. The control unit 151 refers to the table stored in the storage device 140 and identifies the thickness of the medium corresponding to the signal value of the received ultrasonic signal.

[0142] The control unit 151 may further determine whether or not a double feed of media has occurred based on the ultrasonic signal received from the ultrasonic sensor 115. When multiple media are transported overlapping, the ultrasonic waves that penetrate the media are attenuated by the air layer between the overlapping media. Therefore, the control unit 151 can determine whether or not a double feed of media has occurred by checking whether or not the signal value of the ultrasonic signal is below the double feed threshold. The double feed threshold is set to a value between the signal value of the ultrasonic signal when one sheet of paper is transported and the signal value of the ultrasonic signal when two sheets of paper are transported. If it is determined that a double feed of media has occurred, the control unit 151 stops the first motor 131 and the second motor 132 to stop transporting and discharging the media. The control unit 151 may also discharging the media currently being transported before stopping the media reading process. Alternatively, the control unit 151 may drive each motor and control each roller to reverse-fly the media remaining on the transport path back to the mounting table 103 before re-feeding (separating) it. This eliminates the need for users to re-place the medium on the loading tray 103 and re-feed it, allowing the control unit 151 to improve user convenience. The control unit 151 may also notify the user by displaying information indicating that a double feed of the medium has occurred on the display device 106 or by transmitting it to the information processing device via the interface device 135.

[0143] Furthermore, the control unit 151 may detect the thickness of the medium using a thickness sensor other than the ultrasonic sensor 115. The thickness sensor is positioned at the same location as the ultrasonic sensor 115. The thickness sensor may be positioned at any location on the medium transport path. The thickness sensor is, for example, a reflected light sensor including a pair of light emitters and receivers provided on one side of the medium transport path and a pair of light emitters and receivers provided on the other side. The reflected light sensor detects the distance between each pair and each surface of the medium from the time it takes for one pair to irradiate one surface of the medium with light and receive the reflected light, and the time it takes for the other pair to irradiate the other surface of the medium with light and receive the reflected light. The reflected light sensor generates a thickness signal that shows the thickness as a subtracted value obtained by subtracting the detected distances from the distance between the two pairs. The medium transport device 100 stores in the storage device 140 a table that defines the relationship between the signal value of the thickness signal and the thickness of the medium. The control unit 151 refers to a table stored in the storage device 140 and identifies the thickness of the medium corresponding to the signal value of the received thickness signal. Note that the thickness sensor is not limited to one that uses light; any other sensor capable of detecting the thickness of the medium, such as a pressure sensor or a thickness sensor using a contact piece, may be used as the thickness sensor.

[0144] On the other hand, in step S311, after waiting until the rear end of the medium passes the position of the fifth medium sensor 118, the control unit 151 detects the size of the medium being transported (step S312). The control unit 151 detects the length of the medium in the medium transport direction A1 as the size of the medium. The control unit 151 detects the length of the medium in the medium transport direction A1 based on the fifth medium signal received from the fifth medium sensor 118. The control unit 151 calculates the distance the medium is moved by the feed roller 112 by driving the first motor 131 from the time the fifth medium sensor 118 detects the front end of the medium until the rear end of the medium is detected, as the length of the medium in the medium transport direction A1. That is, the control unit 151 calculates the length of the medium in the medium transport direction A1 as a value obtained by multiplying the time from the time the fifth medium sensor 118 detects the front end of the medium until the rear end of the medium is detected by the transport speed of the medium.

[0145] The control unit 151 may also detect the length of the medium in the width direction A8 as the size of the medium. In that case, the medium transport device 100 arranges a number of fifth medium sensors 118 in the width direction A8 at intervals and stores the spacing between each fifth medium sensor 118 in advance. The control unit 151 detects the length of the medium in the width direction A8 based on the distance between the outermost fifth medium sensors 118 that have detected the medium being transported.

[0146] Furthermore, when imaging of the medium is completed, the control unit 151 may detect the length of the medium in the medium transport direction A1 or the length of the medium in the width direction A8 based on the input image generated by the imaging device 122. In this case, the control unit 151 uses known image processing techniques to detect the edges of the medium from the input image and detects the length of the medium in the medium transport direction A1 or the width direction A8 based on the distance between the upper and lower ends of the medium, or the distance between the left and right ends.

[0147] When the flowchart shown in Figure 18 is executed, in steps S115 and / or S119 of the flowchart shown in Figure 9, the control unit 151 changes the speed of the feed roller 112 based on the length of the medium.

[0148] Figure 19 is a graph illustrating the speed change of the feed roller 112 in high-speed mode.

[0149] In Figure 19, graphs G51 and G52 show an example of the speed change of the feed roller 112. The horizontal axis of graphs G51 and G52 represents time, and the vertical axis represents speed. The speeds of the brake roller 113 and the transport roller 119 change in the same way as graphs G12 and G13 shown in Figure 10. Graphs G14 and G15 show the changes in the signal values ​​of the fifth medium sensor 118 and the sixth medium sensor 121, and change in the same way as graphs G14 and G15 shown in Figure 10. Also, times T1 to T6 represent the same times as times T1 to T6 shown in Figure 10.

[0150] In step S115, if the size of the medium is less than or equal to the first size threshold and greater than the second size threshold, the control unit 151 changes the speed of the feed roller 112 to the second intermediate speed V2b, as shown in graph G11 in Figure 10. For example, the first size threshold is set to a value between A4 portrait and A3 portrait when the size of the medium is the length of the medium in the medium transport direction A1, and to a value between A4 landscape and A3 landscape when the size of the medium is the length of the medium in the width direction A8. The second size threshold is set to a value smaller than the first size threshold. For example, the second size threshold is set to a value between A5 portrait and A4 portrait when the size of the medium is the length of the medium in the medium transport direction A1, and to a value between A5 landscape and A4 landscape when the size of the medium is the length of the medium in the width direction A8. The first and second size thresholds are examples of size thresholds.

[0151] On the other hand, if the size of the medium is greater than the first size threshold, the control unit 151 changes the speed of the feed roller 112 to the second intermediate speed V2c, as shown in graph G51. The second intermediate speed V2c is set to be higher than the second intermediate speed V2b, which is used when the size of the medium is less than or equal to the first size threshold and greater than the second size threshold, and lower than the final speed V3a. Also, if the size of the medium is less than or equal to the second size threshold, the control unit 151 changes the speed of the feed roller 112 to the second intermediate speed V2d, as shown in graph G52. The second intermediate speed V2d is set to be lower than the second intermediate speed V2b, which is used when the size of the medium is less than or equal to the first size threshold and greater than the second size threshold, and higher than the first intermediate speed V2a.

[0152] Furthermore, in step S119, if the size of the medium is less than or equal to the first size threshold and greater than the second size threshold, the control unit 151 changes the speed of the feed roller 112 to the final speed V3a, as shown in graph G11 in Figure 10. On the other hand, if the size of the medium is greater than the first size threshold, the control unit 151 changes the speed of the feed roller 112 to the final speed V3d, as shown in graph G51. The final speed V3d is set to a higher speed than the final speed V3a when the size of the medium is less than or equal to the first size threshold and greater than the second size threshold. Note that if the control unit 151 changes the speed of the feed roller 112 to the final speed V3d, it may change the speed of the feed roller 112 to the final speed V3a before the leading edge of the subsequent medium passes the position of the fifth medium sensor 118, as shown by the dotted line D1 in graph G51. Specifically, the control unit 151 reduces the speed of the feed roller 112 to the final speed V3a before the leading edge of the subsequent medium passes the position of the transport roller 119. This prevents the control unit 151 from causing the medium to be pushed by the feed roller 112, causing it to bend between the feed roller 112 and the transport roller 119 and resulting in a jam. Furthermore, if the size of the medium is below the second size threshold, the control unit 151 changes the speed of the feed roller 112 to the second intermediate speed V2b, as shown in graph G52.

[0153] Furthermore, if the size of the medium is greater than the first size threshold, the control unit 151 may change the speed of the feed roller 112 to the same speed as when the size of the medium is less than or equal to the first size threshold and greater than the second size threshold. Alternatively, if the size of the medium is less than or equal to the second size threshold, the control unit 151 may change the speed of the feed roller 112 to the same speed as when the size of the medium is less than or equal to the first size threshold and greater than the second size threshold.

[0154] Thus, when the size of the preceding medium is small, the control unit 151 lowers the speed of the feed roller 112 after the leading edge of the following medium has passed through the nip region of the feed roller 112 and the brake roller 113 compared to the speed when the size of the preceding medium is large. In other words, the control unit 151 sets the second speed when the size of the preceding medium is less than or equal to the size threshold to a lower speed than the second speed when the size of the preceding medium is greater than the size threshold.

[0155] Generally, the shorter the length of the medium, the shorter the distance between continuously transported mediums tends to be. The control unit 151 can suppress collisions between continuously transported mediums by setting the speed of the feed roller 112 lower when the size of the preceding medium is small than the speed of the feed roller 112 when the size of the preceding medium is large.

[0156] Furthermore, if the flowchart shown in Figure 18 is executed, in steps S115 and / or S119 of the flowchart shown in Figure 9, the control unit 151 may change the speed of the feed roller 112 based on the thickness of the medium.

[0157] In step S114, if the thickness of the medium is less than or equal to the first thickness threshold and greater than the second thickness threshold, the control unit 151 changes the speed of the feed roller 112 to the second intermediate speed V2b, as shown in graph G11 in Figure 10. For example, the first thickness threshold is set to a value between the thickness of PPC (Plain Paper Copier) paper and the thickness of a typical business card. The second thickness threshold is set to a value smaller than the first thickness threshold. For example, the second thickness threshold is set to a value between the thickness of typical thin paper and the thickness of PPC paper. The first and second thickness thresholds are examples of thickness thresholds.

[0158] On the other hand, if the thickness of the medium is greater than the first thickness threshold, the control unit 151 changes the speed of the feed roller 112 to the second intermediate speed V2c, as shown in graph G51. Also, if the thickness of the medium is less than or equal to the second thickness threshold, the control unit 151 changes the speed of the feed roller 112 to the second intermediate speed V2d, as shown in graph G52.

[0159] Furthermore, in step S119, if the thickness of the medium is less than or equal to the first thickness threshold and greater than the second thickness threshold, the control unit 151 changes the speed of the feed roller 112 to the final speed V3a, as shown in graph G11 in Figure 10. On the other hand, if the thickness of the medium is greater than the first thickness threshold, the control unit 151 changes the speed of the feed roller 112 to the final speed V3d, as shown in graph G51. Also, if the size of the medium is less than or equal to the second thickness threshold, the control unit 151 changes the speed of the feed roller 112 to the second intermediate speed V2b, as shown in graph G52.

[0160] Furthermore, if the thickness of the medium is greater than the first thickness threshold, the control unit 151 may change the speed of the feed roller 112 to the same speed as when the thickness of the medium is less than or equal to the first thickness threshold and greater than the second thickness threshold. Alternatively, if the thickness of the medium is less than or equal to the second thickness threshold, the control unit 151 may change the speed of the feed roller 112 to the same speed as when the thickness of the medium is less than or equal to the first thickness threshold and greater than the second thickness threshold.

[0161] Thus, when the preceding medium is thin, the control unit 151 lowers the speed of the feed roller 112 after the leading edge of the following medium has passed through the nip region of the feed roller 112 and the brake roller 113 compared to the speed when the preceding medium is thick. In other words, the control unit 151 sets the second speed when the thickness of the preceding medium is below the thickness threshold to a lower speed than the second speed when the thickness of the preceding medium is greater than the thickness threshold.

[0162] Generally, the thinner the medium, the more likely it is to jam. The control unit 151 can suppress the occurrence of medium jams by setting the speed of the feed roller 112 when the preceding medium is thin to be lower than the speed of the feed roller 112 when the preceding medium is thick.

[0163] Note that either step S307 or S311 may be omitted. Also, the control unit 151 may change the speed of the feed roller 112 based on both the size and thickness of the medium. In that case, the control unit 151 will lower the speed of the feed roller 112 the shorter the preceding medium is, and lower the speed of the feed roller 112 the thinner the preceding medium is.

[0164] As detailed above, the media conveying device can now more effectively control the feeding of the media even when the speed of the feed roller 112 is changed based on the size or thickness of the media.

[0165] Figures 20 and 21 are flowcharts illustrating examples of the operation of the media reading process of a media transport device according to yet another embodiment.

[0166] The flowcharts shown in Figures 20 and 21 are executed instead of the flowcharts shown in Figures 8 and 9. The processes in steps S401-S407, S409-S411, S413-S417, and S422-S426 in Figures 20 and 21 are the same as the processes in steps S101-S107, S109-S111, S114-S118, and S119-S123 in Figures 8 and 9, so their explanation is omitted. Below, only steps S408, S412, and S418-S421 will be explained.

[0167] In step S407, the control unit 151 waits until the leading edge of the medium passes the position of the transport roller 119, and then controls the first motor 131 to reduce the speed of the feed roller 112 without stopping it (step S408). That is, when the leading edge of the medium passes the transport roller 119, the control unit 151 controls the first motor 131 to continue rotating the feed roller 112 while reducing its rotational speed.

[0168] Figure 22 is a graph illustrating the speed change of the feed roller 112 in high-speed mode.

[0169] In Figure 22, graph G61 shows an example of the speed change of the feed roller 112. The horizontal axis of graph G61 represents time, and the vertical axis represents speed. The speeds of the brake roller 113 and the transport roller 119 change in the same way as graphs G12 and G13 shown in Figure 10. Graphs G64 and G65 show the changes in the signal values ​​of the fifth medium sensor 118 and the sixth medium sensor 121. The horizontal axis of each graph G64 and G65 represents time, and the vertical axis represents the signal value. Also, times T1 to T6 are the same as times T1 to T6 shown in Figure 10. However, in the examples shown in graphs G61, G64, and G65, the distance between the trailing end of the preceding medium and the leading end of the following medium is shorter, and the time between time T4 and time T5 is shorter, compared to the examples shown in the graphs in Figure 10.

[0170] As shown in graph G61, between time T3 and time T4, when the leading edge of the medium passes the transport roller 119, the speed of the feed roller 112 decreases, but does not become zero. This allows the control unit 151 to reduce the distance between continuously fed media while suppressing the occurrence of jams between the feed roller 112 and the transport roller 119, thereby reducing the media transport time.

[0171] In step S410, the control unit 151 waits until the trailing end of the medium passes the position of the fifth medium sensor 118. If it determines in step S411 that there is still medium remaining on the mounting table 103, the control unit 151 changes the speed of the feed roller 112 (step S412). Similar to step S112 in Figure 9, if the transport mode is set to high-speed mode, the control unit 151 sets the speed of the feed roller 112 to the first intermediate speed V2a.

[0172] In step S417, the control unit 151 waits until the leading edge of the medium passes the position of the fifth medium sensor 118. Then, in step S418, the control unit 151 calculates the time from when the trailing edge of the preceding medium passes the first position until the leading edge of the following medium passes the second position. Hereinafter, the time from when the trailing edge of the preceding medium passes the first position until the leading edge of the following medium passes the second position may be referred to as the medium interval. The first and second positions are set to, for example, the position of the fifth medium sensor 118. In that case, the control unit 151 calculates the time from when the trailing edge of the preceding medium passes the position of the fifth medium sensor 118 in step S410 until when the leading edge of the following medium passes the position of the fifth medium sensor 118 in step S417 as the medium interval. Note that the first and second positions may be any other positions, such as the position of the second medium sensor 114. Also, the first and second positions are not limited to the same position, but may be different positions from each other.

[0173] Next, the control unit 151 determines whether the calculated media interval is less than or equal to a predetermined time (step S418). If the media interval is greater than the predetermined time, the control unit 151 proceeds to step S422.

[0174] On the other hand, if the media interval is less than or equal to a predetermined time, the control unit 151 determines the deceleration time for decelerating the feed roller 112 based on the media interval (step S419). The deceleration time is the time from when the feed roller 112 is stopped until its rotation is resumed, or the time from when the feed roller 112 is decelerated until it is accelerated.

[0175] The control unit 151 determines the deceleration time such that the shorter the distance between media, the longer the deceleration time, and the longer the distance between media, the shorter the deceleration time. The media transport device 100 stores a table that defines the relationship between the distance between media and the deceleration time in the storage device 140 in advance, and the control unit 151 refers to the table stored in the storage device 140 to identify the deceleration time corresponding to the distance between media.

[0176] Next, the control unit 151 reduces the speed of the feed roller 112 (step S420).

[0177] As shown in graph G61 of Figure 22, when the media interval (time from time T4 to time T5) is short, at time T5, when the leading edge of the subsequent media passes the position of the fifth media sensor 118, the control unit 151 reduces the speed of the feed roller 112 to a predetermined speed. For example, as shown by the solid line L2 in graph G61, the control unit 151 changes the speed of the feed roller 112 to a speed at least lower than the second intermediate speed V2b, thereby decelerating the feed roller 112. Alternatively, as shown by the dotted line D2 in graph G61, the control unit 151 may change the speed of the feed roller 112 to 0 and stop the feed roller 112.

[0178] Next, the control unit 151 waits until the deceleration time determined in step S420 has elapsed (step S421).

[0179] Next, the control unit 151 changes the speed of the feed roller 112 (step S422).

[0180] As shown in Figure 22, the control unit 151, similar to the process in step S119 of Figure 9, changes the speed of the feed roller 112 to the final speed V3a when the transport mode is set to high-speed mode.

[0181] In this way, the control unit 151 stops or slows down the feed roller 112 when the interval between media is less than or equal to a predetermined time. This allows the control unit 151 to suppress the occurrence of collisions between continuously fed media.

[0182] Furthermore, the control unit 151 temporarily stops or decelerates the feed roller 112 when the leading edge of a following medium passes the fifth medium sensor 118 over the preceding medium. Then, based on the medium spacing, the control unit 151 determines the timing to temporarily stop the feed roller 112 and then restart its rotation, or the timing to decelerate the feed roller 112 and then accelerate it. In this way, the control unit 151 can appropriately set the time for decelerating the feed roller 112, suppressing collisions between continuously fed media while preventing the media transport time from increasing too much.

[0183] In step S408, the control unit 151 may control the first motor 131 to stop the feed roller 112, similar to step S108 in Figure 8. In that case, in step S412, the control unit 151 sets the speed of the feed roller 112 and restarts the rotation of the feed roller 112 by restarting the first motor 131, similar to steps S112 and S113 in Figure 9.

[0184] As detailed above, the media transport device can now better control the feeding of media even when the speed of the feed roller 112 is changed based on the interval between the continuously fed media.

[0185] Figure 23 is a schematic diagram illustrating the drive sources for the feed roller 112, brake roller 113, transport roller 119, first opposing roller 120, discharge roller 123 and / or second opposing roller 124 in a media transport device according to yet another embodiment.

[0186] As shown in Figure 23, the media transport device according to this embodiment has a first motor 231 instead of the first motor 131. Furthermore, the media transport device has a second transmission mechanism 132b instead of the second transmission mechanism 132a of the second motor 132.

[0187] The first motor 231 is mounted in the upper housing 102 and connected to the feed roller 112 and the brake roller 113 via the first transmission mechanism 231a, driving the brake roller 113 together with the feed roller 112. The first motor 231 generates driving force to drive the feed roller 112 and the brake roller 113 in response to a control signal from the processing circuit 150. The first transmission mechanism 231a includes one or more pulleys, belts, gears, etc., provided between the first motor 231 and the shaft 113a of the brake roller 113 and the shaft 112a of the feed roller 112. The first transmission mechanism 231a transmits the driving force generated by the first motor 231 to the feed roller 112 and the brake roller 113. In particular, one or more gears are provided between the shaft 113a of the brake roller 113 and the shaft 112a of the feed roller 112 to make the rotation direction and rotation speed of each roller different. These gears are positioned outside the medium transport path in the width direction A8 so as to transmit driving force across the medium transport path. As a result, the first motor 231 rotates the feed roller 112 and the brake roller 113 to feed the medium. The first motor 231 is an example of a drive source for the brake roller 113.

[0188] Furthermore, by providing the first motor 231 in the housing on the brake roller 113 side (upper housing 102), it is possible to reliably transmit driving force to the brake roller 113 before the feed roller 112. As a result, the first motor 231 can start rotating the brake roller 113 before the feed roller 112 starts rotating, enabling stable separation of the medium. It is also preferable that the first motor 231 and the shaft 113a of the brake roller 113 are directly connected by a belt. As a result, the first motor 231 can more reliably start rotating the brake roller 113 before the feed roller 112 starts rotating.

[0189] The second motor 132 is provided separately from the first motor 231 in the upper housing 102 and is connected to the transport roller 119 and discharge roller 123 via the second transmission mechanism 132b, driving the transport roller 119 and discharge roller 123. The second motor 132 generates a driving force to drive the transport roller 119 and discharge roller 123 in response to a control signal from the processing circuit 150. The second transmission mechanism 132b includes one or more pulleys, belts, gears, etc., provided between the second motor 132 and the shaft 119a of the transport roller 119 and the shaft 123a of the discharge roller 123. The second transmission mechanism 132b transmits the driving force generated by the second motor 132 to the transport roller 119 and discharge roller 123. As a result, the second motor 132 rotates the transport roller 119 and discharge roller 123, causing the medium to be transported and discharged by the transport roller 119 and discharge roller 123.

[0190] Figures 24 and 25 are flowcharts illustrating examples of the operation of the media reading process of a media transport device according to yet another embodiment.

[0191] The flowcharts shown in Figures 24 and 25 are executed instead of the flowcharts shown in Figures 8 and 9. The processes in steps S501-S507, S509-S511, S514, S516-S518, and S520-S523 in Figures 24 and 25 are the same as the processes in steps S101-S107, S109-S111, S114, S116-S118, and S120-S123 in Figures 8 and 9, so their explanation is omitted. Below, only steps S508, S512-S513, S515, and S519 will be explained.

[0192] In step S507, after waiting until the leading edge of the medium has passed the position of the transport roller 119, the control unit 151 controls the first motor 231 to stop or decelerate the brake roller 113 together with the feed roller 112 (step S508). The medium transport device 100 has a first mode that prioritizes ensuring distance between media and a second mode that prioritizes preventing double feeding of media. The first and second modes are set by the user using the operating device 105 or the information processing device.

[0193] Figure 26 is a graph illustrating the speed changes of the feed roller 112, brake roller 113, and conveyor roller 119 in high-speed mode.

[0194] In Figure 26, graph G71 shows an example of speed change of the feed roller 112, graph G72 shows an example of speed change of the brake roller 113, and graph G73 shows an example of speed change of the transport roller 119. In each of graphs G71 to G73, the horizontal axis represents time and the vertical axis represents speed. Graphs G14 and G15 show the changes in signal values ​​of the fifth medium sensor 118 and the sixth medium sensor 121, and change in the same way as graphs G14 and G15 shown in Figure 10. Also, times T1 to T6 represent the same times as times T1 to T6 shown in Figure 10.

[0195] When set to the first mode, the control unit 151 controls the first motor 231 to stop the feed roller 112 and the brake roller 113. In this case, as shown by the solid line L3 in graph G71 and the solid line L4 in graph G72, the speeds of the feed roller 112 and the brake roller 113 become 0 between time T3 and time T4. This makes it possible for the control unit 151 to reliably prevent the occurrence of a medium jam between the feed roller 112 and the transport roller 119.

[0196] On the other hand, when set to the second mode, the control unit 151 controls the first motor 231 to keep the feed roller 112 and brake roller 113 rotating while reducing their rotational speed (without stopping them). In this case, as shown by the dotted line D3 in graph G71 and the dotted line D4 in graph G72, the speed of the feed roller 112 and brake roller 113 is reduced, but not zero, between time T3 and time T4. This allows the control unit 151 to suppress the reduction in separation performance caused by stopping the brake roller 113 and to suppress the occurrence of double feeding of the medium.

[0197] In step S510, the control unit 151 waits until the trailing end of the medium passes the position of the fifth medium sensor 118. If it determines in step S511 that there is still medium remaining on the mounting table 103, the control unit 151 sets the speed of the feed roller 112 for feeding the subsequent medium (step S512).

[0198] When set to the first mode, the control unit 151 sets the speed of the feed roller 112 to the first intermediate speed V2a at time T4, as shown in graph G71 of Figure 26. Also, the control unit 151 sets the speed of the brake roller 113 to the first intermediate speed U2a at time T4, as shown in graph G72. The first intermediate speed U2a is set to be higher than the initial speed U1 and lower than the final speed U3a.

[0199] Next, the control unit 151 controls the first motor 231 to rotate the feed roller 112 and the brake roller 113 at a set speed (step S513). If the system is set to the first mode and the feed roller 112 and the brake roller 113 are stopped, the control unit 151 restarts the rotation of the feed roller 112 and the brake roller 113 to feed and transport the subsequent medium.

[0200] On the other hand, if the system is set to the second mode and the feed roller 112 and brake roller 113 are not stopped, the control unit 151 changes the speeds of the feed roller 112 and brake roller 113. The control unit 151 increases the speed of the feed roller 112 to the first intermediate speed V2a and increases the speed of the brake roller 113 to the first intermediate speed U2a.

[0201] In step S514, the control unit 151 waits until the leading edge of the subsequent medium passes the position of the second medium sensor 114, and then changes the speed of the feed roller 112 and the brake roller 113 (step S515).

[0202] As shown in graph G71 of Figure 26, the control unit 151 changes the speed of the feed roller 112 to the second intermediate speed V2b. Also, as shown in graph G72, the control unit 151 changes the speed of the brake roller 113 to the second intermediate speed U2b. The second intermediate speed U2b is set to be higher than the first intermediate speed U2a and lower than the final speed U3a.

[0203] In step S518, the control unit 151 waits until the leading edge of the subsequent medium passes the position of the fifth medium sensor 118, and then changes the speed of the feed roller 112 and the brake roller 113 (step S519).

[0204] As shown in graph G71 of Figure 26, at time T5, the control unit 151 changes the speed of the feed roller 112 to the final speed V3a. Also, as shown in graph G72, the control unit 151 changes the speed of the brake roller 113 to the final speed U3a.

[0205] In step S508, the control unit 151 may stop the feed roller 112 by controlling the first electromagnetic clutch 133 to cut off the driving force from the first motor 231 to the feed roller 112 while decelerating the brake roller 113. That is, when the leading edge of the medium passes the transport roller 119, the control unit 151 controls the first electromagnetic clutch 133 to cut off the driving force from the first motor 231 to the feed roller 112 while continuing to transmit the driving force from the first motor 231 to the brake roller 113. In that case, in step S513, the control unit 151 controls the first electromagnetic clutch 133 to transmit the driving force from the first motor 231 to the feed roller 112 and restarts the rotation of the feed roller 112. As a result, the control unit 151 can suppress the reduction in separation performance caused by stopping the brake roller 113 while suppressing the narrowing of the distance between continuously fed mediums.

[0206] In this embodiment, since the feed roller 112 and the brake roller 113 are driven by the same first motor 231, the speed of the feed roller 112 and the speed of the brake roller 113 are proportional. The speed of the brake roller 113 is set to be lower than the speed of the feed roller 112 and higher than half the speed of the feed roller 112.

[0207] Furthermore, the media transport device may operate in a fixed mode, either the first mode or the second mode.

[0208] As detailed above, the media transport device can now control the feeding of the media more effectively, even when the feed roller 112 and the brake roller 113 are driven by the same first motor 231.

[0209] Figure 27 is a schematic diagram illustrating the drive sources for the feed roller 112, brake roller 113, transport roller 219, first opposing roller 220, discharge roller 223 and / or second opposing roller 224 in a media transport device according to yet another embodiment.

[0210] As shown in Figure 27, the media conveying device according to this embodiment has a conveying roller 219, a first opposing roller 220, a discharge roller 223, and a second opposing roller 224 instead of a conveying roller 119, a first opposing roller 120, a discharge roller 123, and a second opposing roller 124. The configuration of the conveying roller 219, the first opposing roller 220, the discharge roller 223, and the second opposing roller 224 is the same as the configuration of the conveying roller 219, the first opposing roller 220, the discharge roller 223, and the second opposing roller 224 in the media conveying device shown in Figure 15. Furthermore, the media conveying device has a second motor 232 instead of a second motor 132. The configuration of the second motor 232 is the same as the configuration of the second motor 232 in the media conveying device shown in Figure 15. Furthermore, the media conveying device has a first motor 231 instead of a first motor 131. The configuration of the first motor 231 is the same as the configuration of the first motor 231 in the media conveying device shown in Figure 23.

[0211] In other words, in the media conveying device according to this embodiment, similar to the media conveying device shown in Figure 23, the first motor 231 drives the brake roller 113 together with the feed roller 112, and the second motor 232 drives the conveying roller 219 and the discharge roller 223.

[0212] As detailed above, even when the media transport device has the transport roller 219 mounted on the lower housing 101 and drives the feed roller 112 and brake roller 113 with the same first motor 231, it is possible to control the feeding of the media more effectively.

[0213] Figure 28 is a schematic diagram illustrating the drive sources for the feed roller 112, brake roller 113, transport roller 119, first opposing roller 120, discharge roller 123 and / or second opposing roller 124 in a media transport device according to yet another embodiment.

[0214] As shown in Figure 28, the media transport device according to this embodiment has a third motor 336 in addition to the first motor 131. Furthermore, the media transport device has a first transmission mechanism 131b instead of the first transmission mechanism 131a of the first motor 131, and a second transmission mechanism 132b instead of the second transmission mechanism 132a of the second motor 132. The configuration of the second motor 132 is the same as the configuration of the second motor 132 shown in Figure 23.

[0215] The first motor 131 is connected to the feed roller 112 via the first transmission mechanism 131b and drives the feed roller 112. The first motor 131 generates a driving force to drive the feed roller 112 in response to a control signal from the processing circuit 150. The first transmission mechanism 131b includes one or more pulleys, belts, gears, etc., provided between the first motor 131 and the shaft 112a of the feed roller 112, and transmits the driving force generated by the first motor 131 to the feed roller 112. As a result, the first motor 131 rotates the feed roller 112 and feeds the medium.

[0216] The third motor 336 is provided in the upper housing 102 separately from the first motor 131 and the second motor 132, and is connected to the brake roller 113 via the third transmission mechanism 336a to drive the brake roller 113. The third motor 336 generates a driving force to drive the brake roller 113 in response to a control signal from the processing circuit 150. The third transmission mechanism 336a includes one or more pulleys, belts, gears, etc., provided between the third motor 336 and the shaft 113a of the brake roller 113, and transmits the driving force generated by the third motor 336 to the brake roller 113. As a result, the third motor 336 rotates the brake roller 113 to feed the medium. The third motor 336 is an example of a drive source for the brake roller 113.

[0217] Figure 29 is a flowchart showing some examples of the operation of the media reading process of a media transport device according to yet another embodiment.

[0218] The flowchart shown in Figure 29 is executed instead of the flowchart shown in Figure 9. The processes in steps S611, S614-S615, S616, S618, S620, and S622-S625 in Figure 29 are the same as the processes in steps S111, S112-S113, S116, S117, S118, and S120-S123 in Figure 9, so their explanation is omitted. Below, only steps S612-S613, S617, S619, and S621 will be explained.

[0219] In step S110, the control unit 151 waits until the rear end of the medium passes the position of the fifth medium sensor 118. If it determines in step S611 that there is still medium remaining on the mounting table 103, the control unit 151 controls the second motor 132 to reduce the speed of the transport roller 119 (step S612). That is, the control unit 151 reduces the rotational speed of the transport roller 119 when the rear end of the medium passes the fifth medium sensor 118.

[0220] Figure 30 is a graph illustrating the speed changes of the feed roller 112, brake roller 113, and transport roller 119 in high-speed mode.

[0221] In Figure 30, graph G81 shows an example of speed change of the feed roller 112, graph G82 shows an example of speed change of the brake roller 113, and graph G83 shows an example of speed change of the transport roller 119. In each of graphs G81 to G83, the horizontal axis represents time and the vertical axis represents speed. Graphs G14 and G15 show the changes in the signal values ​​of the fifth medium sensor 118 and the sixth medium sensor 121, and change in the same way as graphs G14 and G15 shown in Figure 10. Also, times T1 to T6 represent the same times as times T1 to T6 shown in Figure 10. The control unit 151 may reduce the rotational speed of the transport roller 119 when the trailing end of the medium passes through the second medium sensor 114 instead of the fifth medium sensor 118.

[0222] As shown in graph G83, at time T4, when the rear end of the medium passes the fifth medium sensor 118, the control unit 151 reduces the speed of the transport roller 119. During separation, a force acts on the medium, pushing it upstream by the feed roller 112 and the brake roller 113. When the rear end of the medium leaves the feed roller 112 and the brake roller 113, this force disappears, and the transport speed of the medium tends to increase. By reducing the speed of the transport roller 119 when the rear end of the medium passes the feed roller 112 and the brake roller 113, the control unit 151 makes it possible to transport the medium at a stable speed.

[0223] Next, the control unit 151 waits until the sixth predetermined time has elapsed (step S613). The sixth predetermined time is set to allow the feeding of the medium by the feeding roller 112 to be delayed by the amount by which the transport of the medium is delayed due to the deceleration of the transport roller 119. As a result, the control unit 151 can delay the feeding of the medium by the feeding roller 112 by the amount by which the transport of the medium by the transport roller 119 is delayed, making it possible to transport the medium at a stable speed. Note that the process in step S613 may be omitted.

[0224] After waiting in step S616 until the rear end of the medium has passed the imaging position, the control unit 151 controls the second motor 132 to increase the speed of the transport roller 119 (step S617). That is, when the rear end of the medium has passed the imaging position of the imaging device 122, the control unit 151 increases the rotational speed of the transport roller 119.

[0225] As shown in graph G83 of Figure 30, the control unit 151 increases the speed of the transport roller 119 when the rear end of the medium passes the imaging position between time T4 and time T5. By changing the speed of the transport roller 119 after the rear end of the medium has passed the imaging position, the control unit 151 can suppress the occurrence of stretching or shrinking of the medium included in the input image. Also, when the rear end of the medium passes the transport roller 119 and the first opposing roller 120, the transport force on the medium decreases, and the transport speed of the medium tends to decrease. After the rear end of the medium has passed the transport roller 119 and the first opposing roller 120, the control unit 151 increases the speed of the discharge roller 123, making it possible to transport the medium at a stable speed.

[0226] After acquiring the input image in step S618, the control unit 151 controls the first motor 131 to increase the speed of the feed roller 112 (step S619). That is, the control unit 151 increases the rotational speed of the feed roller 112 when the rear end of the medium has passed the transport roller 119.

[0227] As shown by the solid line L5 in graph G81 of Figure 30, the control unit 151 increases the speed of the feed roller 112 to the second intermediate speed V2b after the trailing end of the medium has passed the position of the transport roller 119 (after the signal value in graph G15 changes from H to L). In particular, the control unit 151 increases the speed of the feed roller 112 after increasing the speed of the transport roller 119. This allows the control unit 151 to suppress the occurrence of medium jamming, which would occur if the medium were pushed by the feed roller 112 and bent between the feed roller 112 and the transport roller 119.

[0228] Furthermore, as shown by the dotted line D5 in graph G81, the control unit 151 may increase the speed of the feed roller 112 to a final speed V3a, which is higher than the second intermediate speed V2b, after the trailing end of the medium has passed the position of the transport roller 119. This allows the control unit 151 to recover from any delay in the transport of the medium by the transport roller 119 and the feed roller 112.

[0229] After waiting in step S620 until the leading edge of the medium passes the fifth medium sensor 118, the control unit 151 controls the first motor 131 to increase the speed of the feed roller 112 (step S621).

[0230] As shown by the solid line L6 in graph G81 of Figure 30, the control unit 151 increases the speed of the feed roller 112 to the final speed V3a at time T5. Alternatively, as shown by the dotted line D6 in graph G81, the control unit 151 may increase the speed of the feed roller 112 to a final speed V3d, which is higher than the final speed V3a, at time T5. This allows the control unit 151 to recover from the delay in transporting the medium by the transport roller 119 and the feed roller 112. If the control unit 151 changes the speed of the feed roller 112 to the final speed V3d, it may change the speed of the feed roller 112 to the final speed V3a before the leading edge of the subsequent medium passes the position of the fifth medium sensor 118, as shown by the dotted line D7 in graph G81. This allows the control unit 151 to suppress the occurrence of medium jams caused by the medium being pushed by the feed roller 112 and bending between the feed roller 112 and the transport roller 119.

[0231] In this embodiment, the drive source for the feed roller 112, the drive source for the brake roller 113, and the drive sources for the transport roller 119 and the discharge roller 123 are provided separately, so that the speed of each roller can be changed at an independent timing. Therefore, the control unit 151 can flexibly control the feeding and transport of the medium.

[0232] As shown by the dotted line D8 in graph G82, the control unit 151 may temporarily stop the brake roller 113 while the trailing end of the medium is passing through the nip region between the feed roller 112 and the brake roller 113, and then resume the rotation of the brake roller 113 after it has passed through that nip region. Alternatively, as shown by the dotted line D9 in graph G82, the control unit 151 may reduce the speed of the brake roller 113 while the trailing end of the medium is passing through that nip region, and then increase the speed of the brake roller 113 after it has passed through that nip region to return to the final speed U3a. When the trailing end of the preceding medium passes through the nip region between the feed roller 112 and the brake roller 113, the load on the brake roller 113 in the medium feeding direction is reduced by the medium, and the brake roller 113 may rotate vigorously in the opposite direction to the medium feeding direction. Also, at that time, the elastically deformed parts of the feed roller 112 and the brake roller 113 may return to their original shape, and the following medium may be pushed back to the upstream side. In that case, the leading edge of the subsequent medium may be pushed up (curled up) by the brake roller 113, potentially causing a medium jam. The control unit 151 can suppress the curling up of the leading edge of the subsequent medium and the occurrence of a medium jam by reducing the speed of the brake roller 113 when the trailing edge of the medium passes through the nip region.

[0233] Furthermore, the control unit 151 may start the rotation of the brake roller 113 before the rotation of the feed roller 112. This allows the control unit 151 to prevent multiple media placed on the mounting table 103 from collapsing between the feed roller 112 and the brake roller 113, thereby suppressing the occurrence of double feeding of media.

[0234] As detailed above, the media transport device drives the feed roller 112, brake roller 113, and transport roller 219 with separate motors, and even when changing the speed of the transport roller 119, it is possible to control the feeding of the media more effectively.

[0235] Furthermore, when changing the speed of the transport roller 119, the media transport device may also drive the brake roller 113 with either the first motor or the second motor. In that case, the control unit 151 synchronizes the timing of changing the speed of the brake roller 113 with the timing of changing the speed of the feed roller 112 or the transport roller 119. The control unit 151 may also change the speed of the feed roller 112 or the brake roller 113 by controlling the first electromagnetic clutch 133 or the second electromagnetic clutch 134. In addition, the media transport device may have a drive force interruption mechanism such as an electromagnetic clutch between the transport roller 119 and the second motor, and the control unit 151 may change the speed of the transport roller 119 by controlling the drive force interruption mechanism.

[0236] Figure 31 is a schematic diagram illustrating the drive sources for the feed roller 112, brake roller 113, transport roller 219, first opposing roller 220, discharge roller 223 and / or second opposing roller 224 in a media transport device according to yet another embodiment.

[0237] As shown in Figure 31, the media conveying device according to this embodiment has a conveying roller 219, a first opposing roller 220, a discharge roller 223, and a second opposing roller 224 instead of a conveying roller 119, a first opposing roller 120, a discharge roller 123, and a second opposing roller 124. The configuration of the conveying roller 219, the first opposing roller 220, the discharge roller 223, and the second opposing roller 224 is the same as the configuration of the conveying roller 219, the first opposing roller 220, the discharge roller 223, and the second opposing roller 224 in the media conveying device shown in Figure 15. In addition, the media conveying device has a second motor 232 instead of a second motor 132. The configuration of the second motor 232 is the same as the configuration of the second motor 232 in the media conveying device shown in Figure 15. In addition, the media conveying device has a third motor 336 in addition to the first motor 131. The configuration of the first motor 131 and the third motor 336 is the same as the configuration of the first motor 131 and the third motor 336 in the media conveying device shown in Figure 28.

[0238] In other words, in the media transport device according to this embodiment, similar to the media transport device shown in Figure 28, the first motor 131 drives the feed roller 112, the third motor 336 drives the brake roller 113, and the second motor 232 drives the transport roller 219 and the discharge roller 223.

[0239] As detailed above, even when the media transport device has the transport roller 219 mounted on the lower housing 101 and the feed roller 112, brake roller 113, and transport roller 219 are driven by separate motors, it is possible to control the feeding of the media more effectively.

[0240] Figure 32 is a flowchart showing some examples of the operation of the media reading process of a media transport device according to yet another embodiment. The media transport device according to this embodiment has the drive source shown in Figure 28 or the drive source shown in Figure 31.

[0241] The flowchart shown in Figure 32 is executed instead of the flowchart shown in Figure 9. The processes in steps S711, S714-S716, S719-S721, S724, and S727-S731 in Figure 32 are the same as the processes in steps S111, S112-S114, S115-S117, S118, and S119-S123 in Figure 9, so their explanation is omitted. Below, only steps S712-S713, S717-S718, S722-S723, and S725-S726 will be explained. Also, when the flowchart shown in Figure 32 is executed, steps S301-S312 of the flowchart shown in Figure 18 are executed instead of steps S101-S110 of the flowchart shown in Figure 8.

[0242] In step S311, the control unit 151 waits until the trailing end of the medium passes the position of the fifth medium sensor 118, and then determines whether the size of the preceding medium is greater than the first size threshold and whether it is greater than the second size threshold (step S712). If the size of the preceding medium is less than or equal to the first size threshold and greater than or equal to the second size threshold, the control unit 151 proceeds to step S714 without performing any special processing.

[0243] On the other hand, if the size of the preceding medium is greater than the first size threshold or less than the second size threshold, the control unit 151 waits until the seventh predetermined time has elapsed (step S713). The seventh predetermined time is set to, for example, the time obtained by subtracting the time required for medium transport from the time required for image processing when a medium larger than the first size threshold is transported. Alternatively, the seventh predetermined time may be set to the maximum value of the stop time when a medium collision occurs in a prior experiment in which medium smaller than the second size threshold is continuously transported while changing the stop time of the feed roller 112. Alternatively, the seventh predetermined time may be set to a time that allows for delaying the feeding of the medium by the feed roller 112 by the amount by which the discharge of the medium is delayed by decelerating the discharge roller 123 in the processing described later.

[0244] Specifically, in step S308, when the leading edge of the medium passes the transport roller 119, the control unit 151 stops the feed roller 112 in step S309. Also, in step S311, after the rear end of the medium passes the position of the fifth medium sensor 118, the control unit 151 resumes feeding by the feed roller 112 in step S715. The control unit 151 delays the timing of resuming feeding by the feed roller 112 when the size of the medium whose rear end has passed the position of the fifth medium sensor 118 is greater than the timing of resuming feeding by the feed roller 112 when the size of the medium whose rear end has passed the position of the fifth medium sensor 118 is less than or equal to the first size threshold. Similarly, the control unit 151 delays the timing at which feeding by the feeding roller 112 is resumed when the size of the medium whose rear end has passed the position of the fifth medium sensor 118 is smaller than the second size threshold, compared to the timing at which feeding by the feeding roller 112 is resumed when the size of the medium whose rear end has passed the position of the fifth medium sensor 118 is equal to or greater than the second size threshold.

[0245] Figure 33 is a graph illustrating the speed changes of the feed roller 112, brake roller 113, and transport roller 119 in high-speed mode when the size of the preceding medium is greater than the first size threshold or less than the second size threshold.

[0246] In Figure 33, graph G91 shows an example of speed change of the feed roller 112, graph G92 shows an example of speed change of the brake roller 113, and graph G93 shows an example of speed change of the transport roller 119. In each of graphs G91 to G93, the horizontal axis represents time and the vertical axis represents speed. Graphs G14 and G15 show the changes in signal values ​​of the fifth medium sensor 118 and the sixth medium sensor 121, and change in the same way as graphs G14 and G15 shown in Figure 10. Also, times T1 to T6 represent the same times as times T1 to T6 shown in Figure 10.

[0247] As shown in graph G91, if the size of the preceding medium is greater than the first size threshold or less than the second size threshold, the control unit 151 delays the timing of restarting feeding by the feed roller 112 at time T4. When a large medium is being transported, the size of the input image becomes large, which may require a significant amount of time for image processing. By delaying the restart timing of feeding when a large medium is being transported, the control unit 151 makes it possible to transport the medium smoothly without stopping it for image processing and to acquire a good image. Also, as mentioned above, generally, the shorter the length of the medium, the shorter the distance between continuously transported mediums tends to be. By delaying the restart timing of feeding when a small medium is being transported, the control unit 151 can suppress collisions between continuously transported mediums. Furthermore, when a large or small medium is being transported, the control unit 151 reduces the speed of the discharge roller 123 in the processing described later. In that case, by delaying the restart timing of feeding, the control unit 151 makes it possible to transport the medium at a stable speed.

[0248] In step S716, the control unit 151 waits until the leading edge of the medium passes the position of the second medium sensor 114, and then determines whether the size of the preceding medium is greater than or equal to the first size threshold and whether it is less than or equal to the second size threshold (step S717). If the size of the preceding medium is less than or equal to the first size threshold and greater than or equal to the second size threshold, the control unit 151 proceeds to step S719 without performing any special processing.

[0249] On the other hand, if the size of the preceding medium is greater than the first size threshold or less than the second size threshold, the control unit 151 waits until the seventh predetermined time has elapsed (step S718).

[0250] As shown in graph G91 of Figure 33, if the size of the preceding medium is greater than the first size threshold or less than the second size threshold, the control unit 151 delays the timing of increasing the speed of the feed roller 112 between times T4 and T5. This allows the control unit 151 to smoothly transport larger mediums without stopping them for image processing, thereby acquiring good images. Furthermore, the control unit 151 can suppress collisions between smaller mediums and other mediums when transporting them. In addition, the control unit 151 can transport the mediums at a stable speed.

[0251] After acquiring the input image in step S721, the control unit 151 determines whether the size of the preceding medium is greater than or equal to the first size threshold and whether it is less than or equal to the second size threshold (step S722). If the size of the preceding medium is less than or equal to the first size threshold and greater than or equal to the second size threshold, the control unit 151 proceeds to step S724 without performing any special processing.

[0252] On the other hand, if the size of the preceding medium is greater than the first size threshold or less than the second size threshold, the control unit 151 controls the second motor 132 to reduce the speed of the transport roller 119 and the discharge roller 123 (step S723).

[0253] Specifically, the control unit 151 sets the rotation speed of the discharge roller 123 to a lower speed when the size of the medium is greater than the first size threshold than when the size of the medium is less than or equal to the first size threshold. Furthermore, the control unit 151 sets the rotation speed of the discharge roller 123 to a lower speed when the size of the medium is less than the second size threshold than when the size of the medium is greater than or equal to the second size threshold.

[0254] As shown in graph G93 of Figure 33, if the size of the preceding medium is greater than the first size threshold or less than the second size threshold, the control unit 151 reduces the speed of the discharge roller 123 between time T4 and time T5. When a large medium is discharged, the leading edge of the medium may exceed the leading edge of the discharge platform 104, and the weight of the leading edge exceeding the platform 104 may cause the medium to fly off the platform 104. By reducing the speed of the discharge roller 123 when a large medium is discharged, the control unit 151 can suppress the medium from flying off the platform 104. Also, when multiple mediums of different sizes are discharged, only the smaller medium may be discharged with force, and the trailing edges of the mediums may not be aligned. By reducing the speed of the discharge roller 123 when a small medium is discharged, the control unit 151 can improve the alignment of the mediums.

[0255] In step S724, the control unit 151 waits until the leading edge of the medium passes the position of the fifth medium sensor 118, and then determines whether the size of the preceding medium is greater than or equal to the first size threshold and whether it is less than or equal to the second size threshold (step S725). If the size of the preceding medium is less than or equal to the first size threshold and greater than or equal to the second size threshold, the control unit 151 proceeds to step S727 without performing any special processing.

[0256] On the other hand, if the size of the preceding medium is greater than the first size threshold or less than the second size threshold, the control unit 151 waits until the seventh predetermined time has elapsed (step S727).

[0257] Specifically, in step S724, after the fifth medium sensor 118 detects the leading edge of the medium, the control unit 151 increases the rotational speed of the feed roller 112 in step S727. The control unit 151 delays the timing of increasing the rotational speed of the feed roller 112 when the size of the preceding medium is greater than the first size threshold, compared to the timing of increasing the rotational speed of the feed roller 112 when the size of the preceding medium is less than or equal to the first size threshold. Similarly, the control unit 151 delays the timing of increasing the rotational speed of the feed roller 112 when the size of the preceding medium is less than the second size threshold, compared to the timing of increasing the rotational speed of the feed roller 112 when the size of the preceding medium is greater than or equal to the second size threshold.

[0258] As shown in graph G91 of Figure 33, if the size of the preceding medium is greater than the first size threshold or less than the second size threshold, the control unit 151 delays the timing of increasing the speed of the feed roller 112 at time T5. This allows the control unit 151 to smoothly transport larger mediums without stopping them for image processing, thereby acquiring good images. Furthermore, the control unit 151 can suppress collisions between smaller mediums and other mediums when transporting them. In addition, the control unit 151 can transport the mediums at a stable speed.

[0259] Note that any of the processes in steps S712-S713, S717-S718, S722-S723, or S725-S726 may be omitted. Also, in steps S712, S717, S722, or S725, the control unit 151 may determine only one of the following: whether the size of the medium is greater than the first size threshold, or whether the size of the medium is less than the second size threshold. In that case, the control unit 151 executes the processes in steps S713, S718, S723, or S726 regardless of whether the size of the medium is less than the second size threshold, or regardless of whether the size of the medium is greater than the first size threshold.

[0260] Furthermore, in steps S712, S717, or S725, the control unit 151 may determine whether the size of the medium preceding the medium whose rear end has passed the position of the fifth medium sensor 118 is greater than or equal to the first size threshold, and whether or not it is less than or equal to the second size threshold. That is, the control unit 151 delays the restart timing of feeding by the feeding roller 112 when the size of the medium preceding the medium whose rear end has passed the position of the fifth medium sensor 118 is greater than the first size threshold, compared to the restart timing of feeding by the feeding roller 112 when the size of the medium preceding the medium whose rear end has passed the position of the fifth medium sensor 118 is equal to or less than the first size threshold. Similarly, the control unit 151 delays the timing at which feeding by the feeding roller 112 is resumed when the size of the preceding medium is smaller than the second size threshold for the medium whose rear end has passed the position of the fifth medium sensor 118, compared to the timing at which feeding by the feeding roller 112 is resumed when the size of the preceding medium is equal to or greater than the second size threshold for the medium whose rear end has passed the position of the fifth medium sensor 118.

[0261] In these cases as well, the control unit 151 enables smooth transport of larger media without stopping for image processing, thereby acquiring good images. Furthermore, the control unit 151 can suppress collisions between smaller media and other media when they are being transported.

[0262] As shown by the dotted line D8 of G92 in Figure 33, the control unit 151 may temporarily stop the brake roller 113 while the rear end of the medium is passing through the nip region between the feed roller 112 and the brake roller 113, and then restart the rotation of the brake roller 113 after it has passed through that nip region. Alternatively, as shown by the dotted line D9 of G92, the control unit 151 may reduce the speed of the brake roller 113 while the rear end of the medium is passing through that nip region, and then increase the speed of the brake roller 113 after it has passed through that nip region to return to the final speed U3a. This allows the control unit 151 to suppress the curling of the leading edge of the subsequent medium and prevent medium jamming.

[0263] Further, the control unit 151 may start rotation of the brake roller 113 before starting rotation of the feeding roller 112. Accordingly, the control unit 151 can suppress a plurality of media placed on the placement table 103 from sliding between the feeding roller 112 and the brake roller 113, thereby suppressing the occurrence of multi-feed of media.

[0264] As described in detail above, the medium conveying device can better control the feeding of media even when changing the speed of the discharge roller 123 based on the size of the medium.

[0265] Note that, even when changing the speed of the discharge roller 123, the medium conveying device may drive the brake roller 113 by either the first motor or the second motor. In such a case, the control unit 151 matches the timing for changing the speed of the brake roller 113 with the timing for changing the speed of the feeding roller 112 or the discharge roller 123. Further, the control unit 151 may change the speed of the feeding roller 112 or the brake roller 113 by controlling the first electromagnetic clutch 133 or the second electromagnetic clutch 134. Further, the medium conveying device has a driving force cutoff mechanism such as an electromagnetic clutch between the discharge roller 123 and the second motor, and the control unit 151 may change the speed of the conveying roller 119 by controlling the driving force cutoff mechanism.

[0266] FIG. 34 and FIG. 35 are flowcharts illustrating an example of the operation of a medium reading process of a medium conveying device according to still another embodiment. The medium conveying device according to the present embodiment includes the drive source shown in FIG. 28 or the drive source shown in FIG. 31.

[0267] The flowcharts shown in FIG. 34 and FIG. 35 are executed in place of the flowcharts shown in FIG. 8 and FIG. 9. The processes of steps S801 to S805, S810 to S821, and S823 to S826 in FIG. 34 and FIG. 35 are the same as the processes of steps S101 to S105, S107 to S118, and S120 to S123 in FIG. 8 and FIG. 9, and thus descriptions thereof are omitted. Only steps S806 to S809 and S822 are described below.

[0268] In step S805, the control unit 151 waits until the leading edge of the medium passes the position of the fifth medium sensor 118, and then controls the first motor 131 to either temporarily stop the feed roller 112 or reduce the speed of the feed roller 112 (step S806).

[0269] Figure 36 is a graph illustrating the speed changes of the feed roller 112, brake roller 113, and transport roller 119 in high-speed mode.

[0270] In Figure 36, graph G101 shows an example of speed change of the feed roller 112, graph G102 shows an example of speed change of the brake roller 113, and graph G103 shows an example of speed change of the transport roller 119. In each of graphs G101 to G103, the horizontal axis represents time and the vertical axis represents speed. Graphs G14 and G15 show the changes in signal values ​​of the fifth medium sensor 118 and the sixth medium sensor 121, and change in the same way as graphs G14 and G15 shown in Figure 10. Also, times T1 to T6 represent the same times as times T1 to T6 shown in Figure 10.

[0271] As shown by the solid line L10 in graph G101, the control unit 151 stops the feed roller 112 at time T2. Alternatively, as shown by the dotted line D10 in graph G101, the control unit 151 decelerates the feed roller 112 at time T2.

[0272] Next, the control unit 151 detects the thickness of the transported medium in the same manner as the process in step S307 of Figure 18 (step S807).

[0273] Next, the control unit 151 sets and changes the speed of the transport roller 119 based on the detected thickness of the medium (step S808). The speed of the transport roller 119 is set within a range that is greater than or equal to the initial speed W1 and less than or equal to the final speed W3a. In particular, the control unit 151 sets the rotational speed of the transport roller 119 so that its speed is greater than or equal to the speed of the feed roller 112. This allows the control unit 151 to suppress the occurrence of medium jams, which would result from the medium being pushed by the feed roller 112 and bending between the feed roller 112 and the transport roller 119.

[0274] Furthermore, the speed of the transport roller 119 is set to increase as the thickness of the medium decreases and decrease as the thickness of the medium increases. Alternatively, the speed of the transport roller 119 may be set to increase as the thickness of the medium increases and decrease as the thickness of the medium decreases. The medium transport device 100 stores a table in the storage device 140 in advance that defines the relationship between the thickness of the medium and the speed of the transport roller 119. The control unit 151 refers to the table stored in the storage device 140 and identifies the speed corresponding to the detected thickness.

[0275] In this way, the control unit 151 sets the speed of the transport roller 119 based on the detected thickness of the medium. This allows the control unit 151 to transport the medium at an appropriate speed according to its thickness.

[0276] As shown in graph G103 of Figure 36, the control unit 151 changes the speed of the transport roller 119 to the speed set in step S808 when the feed roller 112 is stopped or decelerating.

[0277] Next, the control unit 151 restarts the rotation of the feed roller 112 and changes the speed of the brake roller 113. Alternatively, the control unit 151 changes the speeds of both the feed roller 112 and the brake roller 113. (Step S809)

[0278] As shown in graph G101 of Figure 36, the control unit 151 sets the speed of the feed roller 112 to the final speed V3a, and then restarts the rotation of the feed roller 112, or changes the speed of the feed roller 112 to increase it to the final speed V3a. Also, as shown in graph G102, the control unit 151 changes the speed of the brake roller 113 to increase it to the final speed U3a.

[0279] In this manner, when the leading edge of the medium passes the fifth medium sensor 118, the control unit 151 temporarily stops or decelerates the feed roller 112 to detect the thickness of the medium and sets the rotation speed of the transport roller 119 based on the thickness of the medium. After that, the control unit 151 resumes the rotation of the feed roller 112 or accelerates the feed roller 112. If the thickness of the medium is detected while the medium is being fed, detection errors may occur due to the shaking of the medium, etc. By detecting the thickness of the medium while the feed roller 112 is temporarily stopped or decelerated, the control unit 151 can detect the thickness of the medium with greater accuracy.

[0280] Meanwhile, in step S821, the control unit 151 waits until the leading edge of the medium passes the position of the fifth medium sensor 118, and then controls the first motor 131 to either temporarily stop the feed roller 112 or reduce the speed of the feed roller 112 (step S822). Subsequently, the processes in steps S807 to S809 are executed, and the control unit 151 detects the thickness of the next medium and sets the rotation speed of the transport roller 119 based on the thickness of the medium, and then restarts the rotation of the feed roller 112 or accelerates the feed roller 112.

[0281] As shown in graph G101 of Figure 36, the control unit 151 stops or slows down the feed roller 112 at time T5. Subsequently, as shown in graph G103, the control unit 151 changes the speed of the transport roller 119 to the speed newly set in step S808, and restarts the rotation of the feed roller 112 or accelerates the feed roller 112, as shown in graph G101.

[0282] As detailed above, the media conveying device can now more effectively control the feeding of the media even when the speed of the conveying rollers 119 is changed based on the thickness of the media.

[0283] Furthermore, the media conveying device may change the speed of the conveying roller 119 based on the thickness of the media, or it may drive the brake roller 113 with either the first motor or the second motor. In that case, the control unit 151 synchronizes the timing of changing the speed of the brake roller 113 with the timing of changing the speed of the feed roller 112 or the conveying roller 119. The control unit 151 may also change the speed of the feed roller 112 or the brake roller 113 by controlling the first electromagnetic clutch 133 or the second electromagnetic clutch 134. In addition, the media conveying device may have a drive force interruption mechanism such as an electromagnetic clutch between the conveying roller 119 and the second motor, and the control unit 151 may change the speed of the conveying roller 119 by controlling the drive force interruption mechanism.

[0284] Figure 37 shows a schematic configuration of the processing circuit 250 in a media transport device according to another embodiment. The processing circuit 250 is used in place of the processing circuit 150 of the media transport device 100 and performs media reading processing, etc., instead of the processing circuit 150. The processing circuit 250 includes a control circuit 251 and a determination circuit 252, etc. Each of these parts may be composed of an independent integrated circuit, microprocessor, firmware, etc.

[0285] The control circuit 251 is an example of a control unit and has the same functions as the control unit 151. The control circuit 251 receives an operation signal from the operation device 105 or the interface device 135. The control circuit 251 also receives a first medium signal, a second medium signal, an ultrasonic signal, a fifth medium signal, and a sixth medium signal from the first medium sensor 111, the second medium sensor 114, the ultrasonic sensor 115, the fifth medium sensor 118, and the sixth medium sensor 121, respectively. Further, the control circuit 251 receives a determination result of medium skew from the determination circuit 252. The control circuit 251 controls the first motor 131, the second motor 132, the third motor 336, the first electromagnetic clutch 133, and the second electromagnetic clutch 134 based on each received piece of information, acquires an input image from the imaging device 122, and outputs the input image to the interface device 135.

[0286] The determination circuit 252 is an example of a determination unit and has the same functions as the determination unit 152. The determination circuit 252 receives a third medium signal, a fourth medium signal, and a fifth medium signal from the third medium sensor 116, the fourth medium sensor 117, and the fifth medium sensor 118, respectively. The determination circuit 252 determines whether skew of the medium has occurred based on each received signal, and outputs the determination result to the control circuit 251.

[0287] As described in detail above, even when the processing circuit 250 is used, the medium conveying device can still better control the feeding of the medium.

[0288] Preferred embodiments have been described above, but the embodiments are not limited thereto. For example, the medium conveying device 100 may have a thin paper conveying mode for conveying thin paper as a medium, and a normal mode for conveying other media. In that case, the control unit 151 sets the rotational speed of the feeding roller 112 such that the speed of the feeding roller 112 in the normal mode is higher than the speed of the feeding roller 112 in the thin paper conveying mode. Accordingly, since thin paper is conveyed at a lower speed than other media, the control unit 151 can suppress the occurrence of damage to thin paper caused by conveyance.

[0289] Furthermore, similar to the embodiments described above, the control unit 151 sets the rotational speed of the feed roller 112 and the rotational speed of the transport roller 119 so that the speed of the transport roller 119 is greater than the speed of the feed roller 112 in both the normal mode and the thin paper transport mode. This allows the control unit 151 to suppress the occurrence of jams in both the normal mode and the thin paper transport mode, where the medium is pushed by the feed roller 112 and bends between the feed roller 112 and the transport roller 119. In addition, the control unit 151 sets the rotational speed of the feed roller 112 and the rotational speed of the transport roller 119 so that the ratio of the speed of the feed roller 112 to the speed of the transport roller 119 in the normal mode is smaller than the ratio of the speed of the feed roller 112 to the speed of the transport roller 119 in the thin paper transport mode. As a result, in the thin paper transport mode, the speed of the feed roller 112 approaches the speed of the transport roller 119, and the thin paper is transported more stably.

[0290] Furthermore, the media transport device may have a separation mode in which the media is fed while being separated, and a non-separation mode in which the media is fed without being separated. In this case, the control unit 151 executes the media reading processes described above when operating in separation mode. On the other hand, when operating in non-separation mode, the control unit 151 controls each motor so that the brake roller 113 rotates in the media feeding direction, or so that it rotates along with the feeding roller 112. In this case, the control unit 151 controls the second electromagnetic clutch 134 to change the magnitude of the torque applied to the brake roller 113. As a result, the control unit 151 can appropriately feed the media in both separation mode and non-separation mode.

[0291] Furthermore, the media transport device may not have high-speed mode, medium-speed mode, and low-speed mode, and may operate fixed in high-speed mode.

[0292] Furthermore, when determining whether to use the fifth medium sensor 118, the control unit 151 may use the second medium sensor 114 instead of the fifth medium sensor 118. That is, the control unit 151 may perform each of the above-described processes, which are executed when the leading or trailing end of the medium passes the position of the fifth medium sensor 118, when the leading or trailing end of the medium passes the position of the second medium sensor 114.

[0293] Furthermore, the size or thickness of the medium may not be detected using a sensor, but may be set by the user using the operating device 105 or the information processing device. Alternatively, the size or thickness of the medium may be determined from the type of medium (paper, postcard, business card, etc.) set by the user using the operating device 105 or the information processing device. In this case, the medium transport device stores a table in the storage device 140 in advance that defines the relationship between the type of medium and the size or thickness of the medium. The control unit 151 refers to the table stored in the storage device 140 and determines the size or thickness of the medium to be transported. With regard to the embodiments described above, the following additional information is disclosed. (Note 1) A mounting platform on which the media is placed, A feeding roller that separates and sequentially feeds the medium placed on the aforementioned mounting platform, A motor that drives the feed roller, A conveying roller for transporting the medium supplied by the aforementioned supply roller, A sensor for detecting the medium is positioned between the feeding roller and the conveying roller, During the separation period from the start of feeding the medium by the feeding roller until the sensor detects the leading edge of the medium, when feeding the first medium from among the medium placed on the aforementioned stand, the control unit controls the motor to rotate the feeding roller at a constant speed, and when feeding the second and subsequent media, the control unit controls the motor to rotate the feeding roller at a first speed and then at a second speed higher than the first speed. A media transport device characterized by having the following features. (Note 2) The media transport device according to Appendix 1, wherein the control unit controls the motor to continue rotating the feed roller while reducing the rotational speed of the feed roller when the leading edge of the medium passes the transport roller. (Note 3) The media transport device according to any one of the appendices 1 to 2, wherein the control unit reduces the rotational speed of the transport roller when the rear end of the medium passes the sensor. (Note 4) In the media transport direction, the system further includes an imaging unit positioned downstream of the transport roller and for imaging the media transported by the transport roller. The media transport device according to any one of the appendices 1 to 3, wherein the control unit increases the rotational speed of the transport roller when the rear end of the medium passes the imaging position of the imaging unit. (Note 5) The media transport device according to any one of the appendices 1 to 4, wherein the control unit increases the rotational speed of the feeding roller when the rear end of the media passes the transport roller. (Note 6) The control unit, Detect the size of the medium, A media transport device according to any one of the appendices 1 to 5, wherein the second speed when the size of the preceding medium is less than or equal to the size threshold is set to a lower speed than the second speed when the size of the preceding medium is greater than the size threshold. (Note 7) The control unit, The thickness of the medium is detected, A media transport device according to any one of the appendices 1 to 6, wherein the second speed when the thickness of the preceding medium is less than or equal to a thickness threshold is set to a lower speed than the second speed when the thickness of the preceding medium is greater than the thickness threshold. (Note 8) The system further includes a discharge roller for discharging the medium conveyed by the aforementioned conveying roller. The control unit, Detect the size of the medium, A media conveying device according to any one of the appendices 1 to 7, wherein the rotational speed of the discharge roller when the size of the media is greater than a first size threshold is set to a speed lower than the rotational speed of the discharge roller when the size of the media is less than or equal to the first size threshold. (Note 9) The system further includes a discharge roller for discharging the medium conveyed by the aforementioned conveying roller. The control unit, Detect the size of the medium, A media conveying device according to any one of the appendices 1 to 7, wherein the rotation speed of the discharge roller when the size of the media is smaller than the second size threshold is set to a speed lower than the rotation speed of the discharge roller when the size of the media is equal to or greater than the second size threshold. (Note 10) The control unit, Detect the size of the medium, After the sensor detects the leading edge of the medium, the rotational speed of the feeding roller is increased. A media conveying device according to any one of the appendices 1 to 9, wherein the timing for increasing the rotational speed of the feed roller when the size of the preceding medium is greater than a first size threshold is delayed compared to the timing for increasing the rotational speed of the feed roller when the size of the preceding medium is less than or equal to the first size threshold. (Note 11) The control unit, Detect the size of the medium, The feeding roller is stopped when the leading edge of the medium passes the transport roller, and feeding by the feeding roller is resumed after the trailing edge of the medium has passed a predetermined position. A media conveying device according to any one of the appendices 1 to 10, wherein the timing for restarting feeding by the feeding roller when the size of the medium whose rear end has passed the predetermined position or the medium preceding the said medium is greater than the first size threshold timing for restarting feeding by the feeding roller when the size of the medium whose rear end has passed the predetermined position or the medium preceding the said medium is less than or equal to the first size threshold. (Note 12) The control unit, The thickness of the medium is detected, A media conveying device according to any one of the appendices 1 to 11, wherein the rotation speed of the conveying roller is set based on the thickness of the media. (Note 13) The media conveying device according to Appendix 12, wherein the control unit temporarily stops or decelerates the feed roller when the leading edge of the medium passes the sensor, detects the thickness of the medium, sets the rotation speed of the conveying roller, and then resumes the rotation of the feed roller or accelerates the feed roller. (Note 14) The media conveying device according to any one of the appendices 1 to 13, wherein the control unit sets the rotational speed of the conveying roller such that the surface movement speed of the conveying roller is equal to or greater than the surface movement speed of the feeding roller. (Note 15) The media transport device has a normal mode and a thin paper transport mode. The media transport device according to Appendix 14, wherein the control unit sets the rotational speed of the feed roller and the transport roller such that the ratio of the surface movement speed of the feed roller to the surface movement speed of the transport roller in the normal mode is smaller than the ratio of the surface movement speed of the feed roller to the surface movement speed of the transport roller in the thin paper transport mode, and the surface movement speed of the feed roller in the normal mode is greater than the surface movement speed of the feed roller in the thin paper transport mode. (Note 16) The media transport device according to any one of the appendices 1 to 15, wherein the control unit temporarily stops or decelerates the feed roller when the time from when the trailing end of the preceding medium passes the first position until when the leading end of the following medium passes the second position is less than or equal to a predetermined time. (Note 17) A media transport device according to any one of the appendices 1 to 16, wherein the control unit temporarily stops or decelerates the feed roller when the leading edge of the following medium passes the sensor after the preceding medium, and determines the timing to restart the rotation of the feed roller or to accelerate the feed roller based on the time from when the trailing edge of the preceding medium passes the first position until the leading edge of the following medium passes the second position. [Explanation of Symbols]

[0294] 100 Medium transport device, 103 Mounting platform, 112 Feeding roller, 113 Brake roller, 114 Second medium sensor, 118 Fifth medium sensor, 119, 219 Transport roller, 122 Imaging device, 123, 223 Discharge roller, 131, 231 First motor, 132, 232 Second motor, 133 First electromagnetic clutch, 134 Second electromagnetic clutch, 151 Control unit, 152 Determination unit, 336 Third motor

Claims

1. A mounting platform on which the media is placed, A feeding roller that separates and sequentially feeds the medium placed on the aforementioned mounting platform, A motor that drives the feed roller, A sensor for detecting the medium is positioned downstream of the feed roller in the medium transport direction, When feeding the first medium among the media placed on the mounting platform, the motor is controlled to rotate the feeding roller at a first speed from the start of feeding the first medium by the feeding roller until the sensor detects the leading edge of the first medium, and then to rotate the feeding roller at a second speed higher than the first speed after the sensor detects the leading edge of the first medium; when feeding the second and subsequent media, the motor is controlled to rotate the feeding roller at a third speed higher than the first speed and lower than the second speed from the start of feeding the second and subsequent media by the feeding roller until the sensor detects the leading edge of the second and subsequent media, and then to rotate the feeding roller at a second speed after the sensor detects the leading edge of the second and subsequent media; A media transport device characterized by having the following features.

2. The media conveying device according to claim 1, wherein the control unit controls the motor to rotate the feed roller at a fourth speed that is higher than the third speed and lower than the second speed before rotating the feed roller at the second speed when feeding the second and subsequent media.

3. The control unit, Get the size of the media, The medium conveying device according to claim 1, wherein when feeding the second and subsequent media, if the size of the preceding media is less than or equal to a first size threshold and greater than a second size threshold that is smaller than the first size threshold, the motor is controlled to rotate the feeding roller at a fourth speed that is higher than the third speed and lower than the second speed before rotating the feeding roller at the second speed.

4. It further has an discharge roller for discharging the medium, The control unit, Get the size of the media, The media conveying device according to claim 1 or 2, wherein the rotational speed of the discharge roller when the size of the media is greater than a first size threshold is set to a speed lower than the rotational speed of the discharge roller when the size of the media is less than or equal to the first size threshold.

5. It further has an discharge roller for discharging the medium, The control unit, Get the size of the media, The media conveying device according to claim 1 or 2, wherein the rotational speed of the discharge roller when the size of the media is smaller than a second size threshold is set to a speed lower than the rotational speed of the discharge roller when the size of the media is equal to or greater than the second size threshold.

6. The control unit, Get the size of the media, A media conveying device according to claim 1 or 2, wherein the timing for increasing the rotational speed of the feed roller when the size of the preceding medium is greater than a first size threshold is delayed compared to the timing for increasing the rotational speed of the feed roller when the size of the preceding medium is less than or equal to the first size threshold.

7. The system further includes a conveying roller for transporting the medium supplied by the aforementioned supply roller, The control unit, Get the size of the media, The feeding roller is stopped when the leading edge of the medium passes the transport roller, and feeding by the feeding roller is resumed after the trailing edge of the medium has passed a predetermined position. A media conveying device according to claim 1 or 2, wherein the timing for restarting feeding by the feeding roller when the size of the medium whose rear end has passed the predetermined position or the medium preceding the said medium is greater than a first size threshold is delayed compared to the timing for restarting feeding by the feeding roller when the size of the medium whose rear end has passed the predetermined position or the medium preceding the said medium is less than or equal to the first size threshold.

8. The media transport device according to any one of claims 1 to 7, wherein the control unit controls the motor to stop the feed roller during transport of the medium and then restart the feed roller.

9. A method for controlling a media transport device, The feed roller separates the media placed on the mounting platform and feeds them sequentially. The motor drives the feed roller, A sensor positioned downstream of the feed roller in the medium transport direction detects the medium. When feeding the first medium from among the media placed on the mounting platform, the motor is controlled to rotate the feeding roller at a first speed from the start of feeding the first medium by the feeding roller until the sensor detects the leading edge of the first medium, and then to rotate the feeding roller at a second speed higher than the first speed after the sensor detects the leading edge of the first medium. When feeding the second and subsequent media, the motor is controlled to rotate the feeding roller at a third speed higher than the first speed and lower than the second speed from the start of feeding the second and subsequent media by the feeding roller until the sensor detects the leading edge of the second and subsequent media, and then to rotate the feeding roller at a second speed after the sensor detects the leading edge of the second and subsequent media. A control method characterized by the following:

10. A control program for a media transport device comprising: a platform on which media are placed; a feed roller for separating and sequentially feeding the media placed on the platform; a motor for driving the feed roller; and a sensor positioned downstream of the feed roller in the media transport direction for detecting the media, wherein When feeding the first medium from among the media placed on the mounting platform, the motor is controlled to rotate the feeding roller at a first speed from the start of feeding the first medium by the feeding roller until the sensor detects the leading edge of the first medium, and then to rotate the feeding roller at a second speed higher than the first speed after the sensor detects the leading edge of the first medium. When feeding the second and subsequent media, the motor is controlled to rotate the feeding roller at a third speed higher than the first speed and lower than the second speed from the start of feeding the second and subsequent media by the feeding roller until the sensor detects the leading edge of the second and subsequent media, and then to rotate the feeding roller at a second speed after the sensor detects the leading edge of the second and subsequent media. A control program characterized by causing the media transport device to perform the above action.

Images