Image reading device and image forming device

Abstract

To suppress an image at a tip side of a read-out image from being missed and a margin from occurring.SOLUTION: An image reading device 1005 comprises: size information obtaining means 163 that obtains size information about a size of a manuscript in a width direction which is orthogonal to a conveying direction in which the manuscript is conveyed; a manuscript conveyance path 240 having a guide shape formed so that movement distances of the manuscript differ depending on sizes of the manuscript; reading means 101 that reads out an image of the manuscript being conveyed through manuscript conveyance path; manuscript sensing means 216 that senses the manuscript being conveyed through the manuscript conveyance path; and control means 164 that makes the reading means start to read out the image of the manuscript when a predetermined time elapses after the manuscript sensing means senses the manuscript. The control means determines the predetermined time on the basis of the size information obtained by the size information obtaining means.SELECTED DRAWING: Figure 10

Description

Technical Field

[0001] The present invention relates to an image reading apparatus that conveys a document and reads an image of the document, and an image forming apparatus including the same.

Background Art

[0002] In an automatic document feeder (hereinafter referred to as ADF) that constitutes an image reading apparatus, the ability to read a wide variety of documents greatly affects the appeal of the product. In recent years, there has been an increasing demand for scanning documents that are narrower than the conventional product specification sizes such as business cards and checks. Therefore, in order to stably convey various types of documents in the image reading apparatus, various measures have been taken for the guides that constitute the document conveyance path inside the image reading apparatus. For example, documents such as business cards and checks tend to have a strong stiffness of the paper because of their large basis weight, and it is difficult to bend the paper. Due to such document characteristics, loop growth and speed fluctuations of the document occur during reading, resulting in image blurring. It is known that image blurring occurs when the posture of the document changes, such as a sagging document stretching (loop reduction, hereinafter referred to as the sag of the document as a loop) or a stretched document sagging (loop growth), and the resulting speed fluctuations occur during reading. In Patent Document 1, projections are provided on the inner guide of the bent portion downstream of the reading unit to restrain the document and suppress the above-described changes in the posture of the document, thereby reducing image blurring.

[0003] In addition to the above, there are other devices that, not limited to image reading devices, use shocks and vibrations inside and outside the device that transports paper (transport medium) to generate collision noises of the transport medium, or that incorporate diverse shapes into the mechanical structure on the transport path to improve transport accuracy. For example, in the image forming apparatus described in Patent Document 2, the shape of the ribs on the transport path is different in the center and on the outside to prevent the leading edge of the transported document from getting caught, with the central part being recessed compared to the outer part. In Patent Document 3, rubber is attached only to the central part to suppress image blur. In this case, in order to suppress the skew difference of document transport, constraints are imposed such as limiting the attachment of additional members to only the central part in the main scanning direction. Thus, in various transport countermeasures such as image blur and snagging, measures such as adding guides inside the transport path are taken, but depending on the conditions and constraints, measures such as changing the shape or attaching separate members are taken only in part of the main scanning direction, rather than the entire direction. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2006-86957 [Patent Document 2] Japanese Patent Publication No. 2019-135188 [Patent Document 3] Japanese Patent Publication No. 2017-1761 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, depending on the shape of the transport guide that forms the transport path, the location within the transport path where the document passes (its position when viewed from the width direction within the transport path) may differ depending on the size of the document. In such cases, the time it takes for the document to reach the reading position differs depending on the size of the document, and depending on the timing of when the document reading starts, image loss or margins may occur at the leading edge of the image. Therefore, the present invention aims to suppress the occurrence of image loss or margins at the leading edge of the scanned image. [Means for solving the problem]

[0006] An image reading device according to one embodiment of the present invention is A size information acquisition means for acquiring size information about the size of the document in the width direction perpendicular to the transport direction in which the document is transported, before The manuscript was transported. re The manuscript transport path and A reading means for reading the image of the document being transported along the document transport path, A document detection means for detecting the document being transported along the document transport path, A control means that starts reading the image of the document by the reading means after a predetermined time has elapsed since the document detection means detected the document, Equipped with, The document transport path is formed such that the distance a first-width document travels from the time it is detected by the document detection means until it reaches the reading means via the first transport trajectory is different from the distance a second-width document travels from the time it is detected by the document detection means until it reaches the reading means via the second transport trajectory. The control means is characterized in that it determines the predetermined time based on the size information acquired by the size information acquisition means. [Effects of the Invention]

[0007] According to the present invention, it is possible to suppress the occurrence of image defects and margins at the leading edge of the read image. [Brief explanation of the drawing]

[0008] [Figure 1] Cross-section of a printer. [Figure 2] Cross-sectional view of an image reading device. [Figure 3] Block diagram of the image reading device and controller. [Figure 4] Perspective view of the inner guide section. [Figure 5] An explanatory diagram showing different transport trajectories depending on the size of the document. [Figure 6] A diagram illustrating the distance traveled from the read sensor to the surface document reading position. [Figure 7] Flowchart of the document reading start operation in Example 1. [Figure 8]A diagram showing the relationship between size information and timer values. [Figure 9] An explanatory diagram of the remaining timer value. [Figure 10] A diagram showing the timer value set in the timer during the original document reading start operation. [Figure 11] A diagram showing the internal structure of the ADF when viewed from above in Example 2. [Figure 12] A diagram showing the internal structure of the ADF of a modification of Example 2 when viewed from above. [Figure 13] An explanatory diagram of the movement of different conveyance trajectories and the surface original document reading position according to the size of the original document. [Figure 14] A flowchart of the original document reading start operation in Example 3. [Figure 15] A cross-sectional view of the surface reading unit located at the standby position.

Modes for Carrying Out the Invention

[0009] Hereinafter, modes for carrying out the present invention will be described with reference to the accompanying drawings.

Examples

[0012] The printer body 1001A includes an image forming unit 1033 for forming an image on a sheet P, and a sheet feeding unit 1006 for feeding the sheet P to the image forming unit 1033. The sheet feeding unit 1006 includes sheet storage units 1037a, 1037b, 1037c, and 1037d that can store sheets of different sizes. The sheets P stored in the sheet storage units 1037a, 1037b, 1037c, and 1037d are fed out by pickup rollers 1002a, 1002b, 1002c, and 1002d. The sheets P are separated one by one by feed rollers 1003a, 1003b, 1003c, and 1003d and retard rollers 1004a, 1004b, 1004c, and 1004d, and fed to transport roller pair 1031. The sheet P is transported to the registration roller pair 1036 by a plurality of transport roller pairs 1031 arranged along the sheet transport path 1007.

[0013] A manual feed tray 1037e is located on the side of the printer body 1001A. A sheet P placed on the manual feed tray 1037e by the user is fed into the inside of the printer body 1001A by the feed roller 1038 and transported to the registration roller pair 1036. The leading edge of the sheet P contacts the nip of the stationary registration roller pair 1036, correcting the skew of the sheet P. The registration roller pair 1036 starts rotating in accordance with the progress of the toner image formation operation by the image forming unit 1033, and transports the sheet P to the image forming unit 1033.

[0014] The image forming unit 1033 forms a toner image on the sheet P using an electrophotographic method. The image forming unit 1033 includes a photosensitive drum 1021, which is a photoreceptor. The photosensitive drum 1021 is rotatable along the transport direction of the sheet P. Around the photosensitive drum 1021 are a charger 1018, an exposure unit 1023, a developer 1024, a transfer charger 1025, a separation charger 1026, and a cleaner 1027. The charger 1018 uniformly charges the surface of the rotating photosensitive drum 1021. The exposure unit 1023 exposes the photosensitive drum 1021 based on image data input from the image reading unit 1005 or an external device (e.g., a personal computer) and forms an electrostatic latent image on the photosensitive drum 1021.

[0015] The developer unit 1024 contains a two-component developer including toner and carrier, and supplies charged toner to the photosensitive drum 1021 to develop an electrostatic latent image into a toner image on the photosensitive drum 1021. The toner image formed on the photosensitive drum 1021 is transferred onto a sheet P, which is transported by a registration roller pair 1036, by a bias electric field formed by a transfer charger 1025. The sheet P, on which the toner image has been transferred, is separated from the photosensitive drum 1021 by a bias electric field formed by a separation charger 1026 and transported towards the fuser unit 1029 by a pre-fixing transport unit 1028. Toner remaining on the photosensitive drum 1021 that was not transferred to the sheet P is removed by a cleaner 1027.

[0016] The sheet P, transported to the fuser unit 1029, is held between roller pairs, pressurized, and heated, causing the toner to melt and adhere to the sheet P, thereby fixing the image to the sheet P. In the case of single-sided printing, the sheet P with the image formed on the surface is discharged by the discharge roller pair 1010 to the discharge tray 1030 which protrudes to the outside of the printer body 1001A. In the case of double-sided printing, the sheet P with the image formed on the surface is reversed by the inversion unit 1039, and the front and back sides are swapped, and the sheet is transported by the double-sided transport unit 1040 to the registration roller pair 1036. The image forming unit 1033 forms a toner image on the back side (second side) opposite to the front side (first side) of the sheet P. The sheet P with the toner image formed on the back side is heated and pressurized by the fuser unit 1029, and an image is formed on the back side of the sheet P. The sheet P with images formed on both sides is discharged by the discharge roller pair 1010 to the discharge tray 1030.

[0017] In Example 1, the image forming unit 1033 forms an image on the sheet P using an electrophotographic method, but the image forming unit 1033 is just one example of an image forming means. The image forming unit 1033 may also form an image on the sheet P using an inkjet method, an offset printing method, or other methods.

[0018] <Image reading device> Figure 2 is a cross-sectional view of the image reading device 1005. The scanner unit 100 includes a surface reading unit 101 (reading means), a surface flow reading glass 106, a white reference member 108, a document glass 109, a reading movement guide 110, a timing belt 151, and a document motor 169. The image reading device 1005 can operate in two modes: a fixed document reading mode that reads the image (document image) of a document placed on the document glass 109, and a flow reading mode that reads the image of a document transported by the ADF 200. In the fixed document reading mode, the scanner unit 100 drives the document motor 169 and moves the surface reading unit 101 along the reading movement guide 110 by the timing belt 151. The surface reading unit 101 reads the image of the surface of the document placed on the document glass 109 line by line while moving along the reading movement guide 110 to read the document image. In document scanning mode, the surface reading unit 101 is located at the surface document scanning position 107 and reads the image of the document being transported on the surface scanning glass 106 by the ADF 200. The surface reading unit 101 includes, for example, a contact image sensor (CIS).

[0019] The ADF200 includes a document tray 201 and a pair of document width regulating plates 202. The document tray 201 is configured to hold stacks of documents consisting of one or more documents. A document sensor 17 detects documents stacked in the document tray 201. The pair of document width regulating plates 202 are mounted on the document tray 201 so as to be movable in a direction perpendicular to the document transport direction CD (main scanning direction), and restrict the movement of documents in the main scanning direction. The ADF200 also includes a separation roller 211 and a pick roller 210. The separation roller 211 prevents the stack of documents from protruding from the document tray 201 and moving downstream before document transport begins. When the ADF200 receives a command to start document transport, it transports the top document of the stack by dropping the pick roller 210 onto the top surface of the stack of documents stacked in the document tray 201 and rotating it. The documents conveyed by the pick roller 210 are separated one by one by the action of the separation roller 211, which acts as a separation mechanism, and then conveyed. The separation of documents by the separation roller 211 is achieved by known separation techniques.

[0020] When the document separated by the separation roller 211 turns on the separation sensor 212, the timer 171 (Figure 3) starts counting. The count value of the timer 171 is used to calculate the timing for starting double-feed detection by the double-feed sensor 213 and to calculate the length of the document. When the document reaches the vicinity of the double-feed sensor 213, double-feed detection by the double-feed sensor 213 begins. The document is transported to the registration roller 215. The registration sensor 214 detects that the document has reached the registration roller 215. The leading edge of the document is struck against the nip of the stopped registration roller 215, causing the document to bend in a loop shape and correcting its skew. After that, the registration roller 215 starts rotating and transports the document.

[0021] The original document is transported through the document transport path 240 from the registration roller 215 to the front-side scanning glass 106. When the original document being transported through the document transport path 240 turns on the lead sensor 216, this triggers a timer 171 (described later) to set a first timer value (predetermined time) until the leading edge of the original document reaches the front-side reading position 107. In the case of simultaneous double-sided scanning, a second timer value is also set in the timer 171 until the leading edge of the original document reaches the back-side reading position 220. After that, the original document is transported to the front-side reading position 107 by the first lead roller 217. The separation roller 211, registration roller 215, document transport path 240, and first lead roller 217 are covered by the ADF cover 204.

[0022] When the timer 171 completes counting the first timer value for reading the image on the surface of the document, the surface reading unit 101 starts reading the image on the surface of the document. Specifically, the document being transported on the surface reading glass 106 is illuminated from below the surface reading glass 106 by the surface LED 102 in the surface reading unit 101. The reflected light from the surface of the document is read by the surface line sensor 103 (CIS) through the surface lens array 104. This reads the image on the surface of the document. While the image on the surface of the document is being read by the surface reading unit 101, the document is transported by the second lead roller 219 from the surface document reading position 107 to the back document reading position 220.

[0023] When the timer 171 completes counting the second timer value for reading the image on the back of the document, the back-side reading unit 230 (reading means) starts reading the image on the back of the document. In the case of double-sided reading, the document, which is transported on the back-side white opposing member provided integrally with the back-side reading glass 234, is illuminated from above the back-side reading glass 234 by the back-side LED 231 in the back-side reading unit 230. The reflected light from the back of the document is read by the back-side line sensor 232 (CIS) through the back-side lens array 233. This reads the image on the back of the document. While the image on the back of the document is being read by the back-side reading unit 230, the document is transported by the third lead roller 221 from the back-side document reading position 220 to the discharge roller 223. The discharge sensor 222 detects the document when it reaches the third lead roller 221. The document is discharged by the discharge roller 223 through the discharge port 224 to the discharge tray 225.

[0024] As shown in Figure 2, the front reading unit 101 and the back reading unit 230 include a front line sensor 103 (CIS) and a back line sensor 232 (CIS), respectively. However, instead of CIS, the front reading unit 101 and the back reading unit 230 may use a CCD configured with a reduction optical system using mirrors.

[0025] <Control Unit> Figure 3 is a block diagram of the image reading device 1005 and controller 500. The image reading device 1005 includes a control unit 160 and a surface LED 102, a surface line sensor 103, a back surface LED 231, a back surface line sensor 232, a document feed motor 169, and a document transport motor 170, all electrically connected to the control unit 160. The control unit 160 includes a CPU 164 as a central processing unit, a ROM 165 as read-only memory, and a RAM 166 as random access memory. The ROM 165 stores a control program for realizing document reading. The RAM 166 stores input data and work data. The control unit 160 further includes a lighting control unit 167, a scanning control unit 168, a timer 171, a surface image reading control unit 172, a back surface image reading control unit 173, a transport detection unit 174, an A / D conversion unit 161, and an image processing unit 162. The control unit 160 further includes a document main scan size acquisition unit 163, a non-volatile memory 257, and an image processing unit 275.

[0026] The lighting control unit 167 controls the on / off switching of the illumination of the front LED 102 and the back LED 231. The scanning control unit 168 controls the drive of the document feeder motor 169. The document feeder motor 169 is connected to the front reading unit 101 via a timing belt 151. By rotating the document feeder motor 169, the front reading unit 101 can move in the sub-scanning direction SS along the reading movement guide 110. The scanning control unit 168 controls the drive of the document transport motor 170 built into the ADF 200. The document transport motor 170 rotates the pick roller 210, separation roller 211, registration roller 215, first lead roller 217, second lead roller 219, third lead roller 221, and discharge roller 223 to transport the document.

[0027] The surface line sensor 103 is built into the surface reading unit 101. The surface line sensor 103 receives reflected light from the document illuminated by the surface LED 102. The amount of light (analog data) received by the surface line sensor 103 is converted into digital data by the A / D conversion unit 161. The image processing unit 162 performs image processing on the digital data from the A / D conversion unit 161 to generate image data. The back surface line sensor 232 is built into the back surface reading unit 230. The back surface line sensor 232 receives reflected light from the document illuminated by the back surface LED 231. The amount of light (analog data) received by the back surface line sensor 232 is similarly converted into image data by the A / D conversion unit 161 and the image processing unit 162.

[0028] The document main scan size acquisition unit 163, which serves as a means for acquiring size information, acquires size information input from the operation unit 506 provided on the printer body 1001A to the CPU 164 via the controller 500. The document main scan size acquisition unit 163 can also acquire size information based on a combination of detection results from the reflective large-size main scan width sensor 205, the medium-size main scan width sensor 206, and the reflective sensors 207 and 208 provided on the ADF 200.

[0029] The image processing unit 275 includes a shading RAM 254 and a shading correction circuit 253. The shading RAM 254 includes an arithmetic memory 255 and a coefficient memory 256. The CPU 164 can access the shading RAM 254 to read data from it and write data to it.

[0030] The non-volatile memory 257 is a memory (storage unit) that can retain values ​​(data) even when the power to the image reading device 1005 is turned off. The non-volatile memory 257 stores values ​​such as the shading target value used by the shading correction circuit 253 to perform shading correction, and alarm and error information that occurred during the job.

[0031] Timer 171 counts pulse signals emitted from the document transport motor 170. A pulse signal is emitted from the document transport motor 170 each time the document is transported a predetermined distance by the document transport motor 170. When the number of pulse signals counted by Timer 171 reaches a preset count value, Timer 171 sends a count completion signal to the CPU 164. By receiving the count completion signal from Timer 171, the CPU 164 can measure the distance the document has traveled.

[0032] The surface image reading control unit 172 controls the surface reading unit 101 to perform image reading processing on the surface of the document. When the timer 171 completes counting the first timer value set in the timer 171, it outputs a first count completion signal to the CPU 164. When the CPU 164 receives the first count completion signal, it sends a trigger signal to the surface image reading control unit 172. When the surface image reading control unit 172 receives the trigger signal, it starts acquiring the document image by the surface reading unit 101. The back side image reading control unit 173 controls the back side reading unit 230 to perform image reading processing on the back side of the document. When the timer 171 completes counting the second timer value set in the timer 171, it outputs a second count completion signal to the CPU 164. When the CPU 164 receives the second count completion signal, it sends a trigger signal to the back side image reading control unit 173. When the back side image reading control unit 173 receives the trigger signal, it starts acquiring the document image by the back side reading unit 230.

[0033] The transport detection unit 174 acquires the ON / OFF states of the separation sensor 212, double feed sensor 213, registration sensor 214, lead sensor 216, and ejection sensor 222, which are provided on the document transport path 240. When the leading edge of the document reaches each sensor and when the trailing edge of the document leaves each sensor, signals from each sensor are transmitted to the transport detection unit 174. The CPU 164 receives the signals received by the transport detection unit 174 from each sensor as interrupts, and the CPU 164 outputs an instruction signal to the timer 171 without delay.

[0034] <Controller> The control unit 160, located in the image reading device 1005, is electrically connected to the controller 500, located in the printer body 1001A, via a communication line 180. The controller 500 converts the image data read by the image reading device 1005 into image data in a format that can be output to the printer 1001, which forms images on a sheet (recording medium). The controller 500 also converts the image data read by the image reading device 1005 into image data in a format that can be output to a personal computer (PC). The controller 500 also handles user operation reception and overall management of the printer 1001. The controller 500 transmits and receives various data signals to and from the control unit 160 of the image reading device 1005 via the communication line 180.

[0035] The controller 500 includes a central processing unit (CPU) 501, read-only memory (ROM) 502, and random access memory (RAM) 503. ROM 502 stores control programs for image conversion and overall management of the printer 1001. RAM 503 stores input data and working data.

[0036] The controller 500 further includes an image processing unit 504 and an image memory 505. The image processing unit 504 converts the image data read by the image reading device 1005 into an image data format that can be output to the printer 1001. The image memory 505 temporarily stores this image data. The CPU 501 of the controller 500 is electrically connected to the operation unit 506. The operation unit 506 is equipped with a display and buttons. The CPU 501 accepts button operations from the user via the operation unit 506. The CPU 501 outputs various information to the user to the display of the operation unit 506.

[0037] In Embodiment 1, the image reading device 1005 has a CPU 164, ROM 165, and RAM 166, and the controller 500 also has a CPU 501, ROM 502, and RAM 503. However, for example, the image reading device 1005 may not have a CPU 164, ROM 165, and RAM 166, and may instead share the CPU 501, ROM 502, and RAM 503 of the controller 500. In that case, the various components electrically connected to the CPU 164 in Figure 3 may be directly connected to the CPU 501 of the controller 500 without going through the communication line 180. Embodiment 1 describes a configuration in which the image reading device 1005 and the controller 500 are provided with a CPU 164 and a CPU 501, respectively, but a configuration in which the CPU 164 is omitted and the CPU 501 is shared can be implemented by appropriately reinterpreting the description.

[0038] <Manuscript transport path> The document transport path 240 of the ADF200 will be described below. The document transport path 240 has a curved section that curves in a curved shape when viewed from the width direction (front to back direction of the device). The curved section is formed by an inner guide section 250 and an outer guide section 260 (see Figure 5, described later). Figure 4 is a perspective view of the inner guide section 250. The inner guide section 250, which is the first guide, constitutes the inner part of the document transport path 240 of the ADF200. The outer guide section 260, which is the second guide, constitutes the outer part of the document transport path 240 of the ADF200. Figure 4 shows an inner guide section 250 used in an ADF200 that feeds A4 size sheets vertically as an example. In Example 1, the ADF200 has three pairs of first lead rollers 217a, 217b and 217c. As shown in Figure 4, the inner guide section 250 is provided with the inner first lead rollers 217a, 217b, and 217c of the three pairs of first lead rollers 217a, 217b, and 217c, respectively. The outer first lead rollers 217a, 217b, and 217c of the three pairs of first lead rollers 217a, 217b, and 217c are provided on the ADF cover 204. In this application, the three pairs of first lead rollers 217a, 217b, and 217c are collectively referred to as the first lead roller 217. Because the ADF200 is a small machine, there are constraints on the transport guides and component shapes in order to arrange components within the small housing, and the guide shape in the main scanning direction MS is complex.

[0039] First, the basic guide shape is that of the end-side transport guides 280, which are provided at the left and right ends of the main scanning direction MS. The end-side transport guides 280 have a curved shape so that the document is transported smoothly with minimal resistance along the document transport path 240. As a result, an A4 width (210 mm) document is pulled by three rotating first lead rollers 217a, 217b, and 217c, and the left and right ends of the document are transported along the respective end-side transport guides 280. If guides with the same shape as the end-side transport guides 280 were provided near the first lead rollers 217a, 217b, and 217c, the height of the document contact surface of the guide and the contact surfaces of the first lead rollers 217a, 217b, and 217c would be almost the same. Therefore, smooth document transport would not be possible. Also, considering interference with other parts, the transport guides 281 near the first lead rollers 217a, 217b, and 217c have a linear shape. In other words, the inner guide portion 250 has a shape in which the end-side transport guide 280, which is a second region outside the transport guide 281 in the width direction, protrudes toward the outer guide portion 260 relative to the first region, the transport guide 281, which is a first region including the center in the width direction.

[0040] Downstream of the first lead roller 217b, a Mylar sheet 282 made of film material is attached to the inner guide section 250 to reduce image blur caused by document transport. To improve the ease of attaching the Mylar sheet 282 and to prevent the Mylar sheet 282 from getting caught on the document, the guide shape is further recessed inward by the length of the Mylar sheet 282 in the main scanning direction MS. The Mylar sheet 282 is made of film material, and when a document is pressed down, the Mylar sheet 282 bends accordingly, allowing the document to pass over the Mylar sheet 282. On the other hand, the Mylar sheet 282 exerts a downward force on the document, which helps to suppress document blur during transport.

[0041] <Reading start timing> The following describes the timing at which the image data of the document read by the front reading unit 101 begins to be read (hereinafter referred to as the reading start timing). As mentioned above, the document transport path 240 of the ADF 200 has a complex shape, so in the document transport path 240 of the ADF 200, the document passes through different transport paths (hereinafter referred to as transport trajectories) according to the size of the document. Figure 5 is an explanatory diagram showing the different transport trajectories according to the size of the document. First, referring to Figure 5(a), the control of the timing at which the image data begins to be read from the front reading unit 101 is explained. Note that the control of the timing at which the image data begins to be read from the back reading unit 230 is the same as that of the front reading unit 101, so the explanation of the back reading unit 230 is omitted below.

[0042] Figure 5(a) is a cross-sectional view of the vicinity of the first lead roller 217 and the surface reading unit 101, viewed from the front to the back. Here, we will describe the case where the widest A4 size document that can be transported by the ADF200 of Embodiment 1 is transported. The lead sensor 216 has a sensor flag 216a, a photointerrupter 216b having a light-emitting part and a light-receiving part, and a pivot axis 216c of the sensor flag 216a. The sensor flag 216a is rotatable about the pivot axis 216c. When the sensor flag 216a blocks the optical path between the light-emitting part and the light-receiving part of the photointerrupter 216b, the lead sensor 216 outputs an ON signal. When the leading edge of the document S being transported pushes one end of the sensor flag 216a, the sensor flag 216a rotates about the pivot axis 216c, and the other end of the sensor flag 216a blocks the optical path of the photointerrupter 216b. Thus, the read sensor 216 functions as a document detection means.

[0043] The transport detection unit 174 transmits the ON signal from the read sensor 216 as an interrupt signal to the CPU 164. The CPU 164 uses the interrupt signal as a trigger to set the first timer value (predetermined time) until the reading start timing in the timer 171. The timer 171 receives a pulse signal from the document transport motor 170 and is configured to increment the count value by 1 each time a pulse is received. Since the amount by which the first lead roller 217 rotates per pulse of the document transport motor 170 is preset, the amount of document traveled per pulse is predetermined. Therefore, the distance the document is transported is calculated from the count value × (amount traveled per pulse). Since the transport of A4-sized documents is restricted by the edge-side transport guide 280 as shown in Figure 5(a), A4-sized documents are transported along the first transport trajectory 241. Therefore, the first timer value, which is the timing for starting reading, is the number of pulses obtained by dividing the distance from the position where the leading edge of the document is detected by the lead sensor 216 to the surface document reading position 107 via the first transport trajectory 241 by the amount of advance per pulse.

[0044] Timer 171 compares the count value with the first timer value. When the count value reaches the first timer value, Timer 171 sends a count completion signal (timer expiration signal) as an interrupt signal to CPU 164. At this time, the leading edge of the document reaches the surface document reading position 107. As a control means, CPU 164, upon receiving the interrupt signal, sends a read start command to surface image reading control unit 172. Upon receiving the read start command, Surface Image Reading Control Unit 172 starts the image data acquisition process via the surface line sensor 103. In this way, Timer 171 starts counting the first timer value in response to the ON signal of the read sensor 216, and when the count of the first timer value is completed, it sends a count completion signal as an interrupt signal to CPU 164. CPU 164 sends a read start command to Surface Image Reading Control Unit 172 in response to the interrupt signal, and upon receiving the read start command, Surface Image Reading Control Unit 172 starts reading the image data of the document to be read by the surface reading unit 101. By starting the acquisition of image data from the surface line sensor 103 based on the first timer value (reading start timing) set in this manner, image data can be accurately acquired from the leading edge position of the document.

[0045] As shown in Figure 5(a), when an A4-sized document is transported, the timing at which the timer 171 completes counting the first timer value (the elapsed time) coincides with the timing at which the leading edge of the document reaches the front document reading position 107. Therefore, by setting the first timer value to the timer 171, image data can be acquired with high accuracy from the leading edge position of the document. However, as explained with reference to Figure 4, the guide shape of the document transport path 240 is complex, so the position at which the document passes through the internal space of the document transport path 240 differs depending on whether the document is wide or narrow.

[0046] For example, Figure 5(a) shows the first transport trajectory 241 of a document S having a wide width (first width), such as an A4 size document. Figure 5(a) is a cross-sectional view of the document transport path 240 taken along the VA-VA line in Figure 4. Documents with a wide width (first width) are transported with both ends of the document in the main scanning direction MS being restricted by the end-side transport guides 280. Therefore, the document passes through the outermost part of the internal space of the document transport path 240. Consequently, the distance (travel distance) that the leading edge of the document travels from the lead sensor 216 through the first transport trajectory 241 to the surface document reading position 107 is the longest.

[0047] For example, Figure 5(b) shows the second transport trajectory 242 of a document S having a narrow width (second width), such as an A6 size document or a business card. Figure 5(b) is a cross-sectional view of the document transport path 240 taken along the VB-VB line in Figure 4. For documents with a narrow width (second width), the entire area of ​​the document in the main scanning direction MS passes between the two end-side transport guides 280. The document comes into contact with the linearly shaped transport guide 281 and Mylar sheet 282 and passes through the innermost part of the internal space of the document transport path 240. Therefore, the distance (travel distance) that the leading edge of the document travels from the lead sensor 216 through the second transport trajectory 242 to the surface document reading position 107 is the shortest.

[0048] If the first timer value for a wide document transported along the first transport trajectory 241 is set to timer 171 for reading a narrow document transported along the second transport trajectory 242, document reading will not start even when the leading edge of the narrow document reaches the surface document reading position 107. This will be explained with reference to Figure 6. Figure 6 is an explanatory diagram of the travel distance from the read sensor 216 to the surface document reading position 107. As shown in Figure 6, the travel distance corresponding to the first timer value for a wide document matches the travel distance of the wide document along the first transport trajectory 241. However, since the travel distance corresponding to the first timer value for a wide document is longer than the travel distance of the narrow document along the second transport trajectory 242, by the time the count of the first timer value is completed, the leading edge of the narrow document will have passed the surface document reading position 107. As a result, image reading starts from the middle of the narrow document, and image data is generated in which the leading edge of the narrow document is missing.

[0049] Therefore, in Example 1, the timer value to be set in the timer 171 is determined according to the size of the document in the main scanning direction MS. When the ADF 200 is a small machine, there are constraints on the components that can be installed in order to reduce manufacturing costs. For example, the ADF 200 may omit a size sensor that detects the size of the document placed on the document tray 201. In this case, for example, the size of the document can be determined from the output size selected by the user on the copy screen displayed on the display unit of the operation unit 506. Alternatively, the size of the document can be determined from the scan size selected by the user on the scan screen displayed on the display unit of the operation unit 506. The determined size information is transmitted from the controller 500 to the CPU 164 of the image reading device 1005 via the communication line 180 at any time. The CPU 164 determines the size of the document based on the received size information and determines a timer value appropriate for the determined size of the document.

[0050] (Start of document scanning operation) Figure 7 is a flowchart of the document reading start operation in Embodiment 1. The CPU 164, acting as a control means, executes the document reading start operation according to the program stored in the ROM 165. In the document reading start operation of Embodiment 1, the CPU 164 determines a timer value (predetermined time) to set in the timer 171 based on the size information of the document in the main scanning direction MS (width direction). After the timer value count is completed (after the predetermined time has elapsed), the CPU 164 starts reading the image of the document.

[0051] When a document is placed in the document tray 201 and the job starts, the CPU 164 determines whether the read sensor 216 is ON or OFF (S701). If the read sensor 216 is not ON (NO in S701), the CPU 164 waits until the read sensor 216 is ON. If the read sensor 216 is ON (YES in S701), the CPU 164 starts counting using the timer 171 and determines whether the size information of the document in the main scanning direction MS (width direction) has been acquired (S702). If the size information acquired from the user input information has been sent from the printer 1001's controller 500 to the image reader 1005's CPU 164 (YES in S702), the CPU 164 proceeds to S703. If the size information has not been acquired (NO in S702), the CPU 164 proceeds to S711.

[0052] In S703, the CPU 164 determines a timer value according to the acquired size information and sets the determined timer value to the timer 171. Figure 8 shows the relationship between size information and timer value. In Embodiment 1, the size of the document is determined to be either wide or narrow based on the size information. A wide document is a document with a width such that both ends in the main scanning direction MS are restricted by the end-side transport guides 280 while it is being transported. For example, an A4 size document with a first width. A narrow document is a document with a width such that the entire area in the main scanning direction MS passes between the two end-side transport guides 280. For example, an A6 size document with a second width.

[0053] For wide documents, the document moves from the lead sensor 216 through the first transport trajectory 241 to the surface document reading position 107. Therefore, the distance traveled from the detection position of the lead sensor 216 to the surface document reading position 107 for wide documents is 50 mm. Assuming that the advance amount per pulse of the document transport motor 170 is 0.1 mm, the timer value is 500 counts (first time). On the other hand, for narrow documents, the document moves from the lead sensor 216 through the second transport trajectory 242 to the surface document reading position 107. Therefore, the distance from the detection position of the lead sensor 216 to the surface document reading position 107 is 48 mm. The timer value is 480 counts (second time).

[0054] The CPU 164 sets the timer value to timer 171 according to the size information (S703), and then determines whether the timer count has been completed (S751). Specifically, timer 171 compares the count value that has been counted since the read sensor 216 was turned ON with the timer value. When the count value reaches the timer value, timer 171 sends a count completion signal (timer expiration signal) to CPU 164 as an interrupt signal. When CPU 164 receives the count completion signal from timer 171, it determines that the timer count has been completed (YES in S751) and proceeds to S752. CPU 164 sends a read start command to surface image reading control unit 172 to start reading the document (S752), and then finishes the document reading start operation.

[0055] On the other hand, if S702 determines that size information for the main scanning direction MS (width direction) of the document has not been acquired (NO in S702), the CPU 164 proceeds to S711. For example, even when a job has started, the controller 500 may be slow to notify the image reader 1005 of the size information due to the relationship between processing such as preparing the image to be accepted and the document transport speed. In such cases, the CPU 164 may not be able to acquire size information from the controller 500 when the read sensor 216 is turned ON. In this case, the CPU 164 sets the temporary timer value (provisional time) to timer 171 (S711). The reason for setting the temporary timer value to timer 171 is that, as mentioned above, in order to acquire image data accurately from the leading edge position of the document, various interrupt signals and motor pulse counts need to be connected in a series of steps. Here, the distance traveled by an A4-sized document (wide document), which is frequently used with the ADF200, from the read sensor 216 through the first transport trajectory 241 to the surface document reading position 107 is converted into pulses and set as a temporary timer value for timer 171. Note that the temporary timer value may be the timer value for any size document.

[0056] Subsequently, the CPU 164 determines whether the leading edge of the document has reached the judgment limit position 283 (S712). The judgment limit position 283 is the position of the leading edge of the document at the limit of the time at which the CPU 164 can wait for size information to be acquired. The judgment limit position 283 is the downstream point at which the transport of the document is temporarily stopped if size information is not sent from the controller 500. In Embodiment 1, the judgment limit position 283 is the position obtained by subtracting the distance for deceleration + acceleration + behavior stabilization of the document transport motor 170 from the distance traveled from the lead sensor 216 through the first transport trajectory 241 to the surface document reading position 107. Even if the leading edge of the document reaches the judgment limit position 283, if the CPU 164 has not yet acquired size information from the controller 500, the document is temporarily stopped. This prevents the leading edge of the document from reaching the surface document reading position 107 before the size of the document is determined. In S712, if CPU 164 determines that the leading edge of the document has not reached the judgment limit position 283 (NO in S712), it determines whether or not size information has been acquired by polling at arbitrary intervals (S721). If size information has not been acquired (NO in S721), CPU 164 returns to processing S712. If size information has been acquired (YES in S721), CPU 164 proceeds to processing S722.

[0057] In S722, the CPU 164 determines whether the document is narrow or not based on the acquired size information. If the document is wide, i.e., not narrow (NO in S722), the timer value to be set in timer 171 can remain the temporary timer value set in timer 171 in S711, so the CPU 164 proceeds to S751. On the other hand, if the document is narrow (YES in S722), the CPU 164 sets the remaining timer value corresponding to the size in timer 171 (S723).

[0058] Refer to Figure 9 to explain the remaining timer value. Figure 9 is an explanatory diagram of the remaining timer value. The timer count elapsed value is the count value corresponding to the distance the leading edge of the document has advanced from the position of the lead sensor 216 when the CPU 164 acquires size information from the controller 500. The timer value corresponding to the difference distance between the wide document and the narrow document is the value obtained by subtracting the timer value of the narrow document from the timer value of the wide document. The remaining timer value is expressed by the following equation (1). Remaining timer value = Provisional timer value - (Timer count elapsed + (Timer value corresponding to the difference in distance between the wide and narrow original documents)) ... Equation 1 CPU 164 sets the remaining timer value calculated using Equation 1 to Timer 171 (S723), and proceeds to S751.

[0059] The following describes the case in S712 when the leading edge of the document reaches the judgment limit position 283. When the leading edge of the document reaches the judgment limit position 283 (YES in S712), the CPU 164 temporarily suspends document transport (S713). Then, the CPU 164 waits for size information to arrive from the controller 500 (S714). When the CPU 164 obtains the size information from the controller 500 (YES in S714), it sets the remaining timer value corresponding to the size to timer 171 (S715). The calculation of the remaining timer value in S715 is the same as in S723 described above, so the explanation is omitted. After that, the CPU 164 resumes document transport (S716) and proceeds to S751. When the CPU 164 has finished counting the remaining timer value (YES in S751), it starts reading the document (S752) and ends the document reading start operation.

[0060] Figure 10 shows the timer value set in timer 171 during the document scanning start operation. When the document is wide, timer 171 is set to a value corresponding to the distance from the lead sensor 216 to the surface document scanning position 107 along the first transport trajectory 241. When the document is narrow, timer 171 is set to a value corresponding to the distance from the lead sensor 216 to the surface document scanning position 107 along the second transport trajectory 242. Therefore, it is possible to acquire image data with high accuracy from the leading edge position of the document according to the document size.

[0061] According to Example 1, document transport control and the timing of the start of reading the document image can be controlled according to the size information, so image data can be acquired with high accuracy. According to Example 1, the occurrence of image loss or margins at the leading edge of the read image can be suppressed. [Examples]

[0062] The following describes Example 2. In Example 2, structures similar to those in Example 1 are given the same reference numerals and their descriptions are omitted. The printer 1001, image reader 1005, control unit 160, controller 500, and document transport path 240, which serve as the image forming apparatus in Example 2, have the same structure as in Example 1, so their descriptions are omitted. The ADF 200 in Example 1 was not provided with a means for acquiring size information, but the ADF 1200 in Example 2 is provided with a means for acquiring size information.

[0063] Figure 11 shows the internal structure of the ADF1200 of Embodiment 2 as viewed from above. The size information acquisition means includes a reflective main scan width sensor 205 for large size (first size detection means) and a reflective main scan width sensor 206 for medium size (first size detection means). The main scan width sensor 205 for large size and the main scan width sensor 206 for medium size are positioned on the document passage surface of the document transport path 240 of the ADF1200 between the separation roller 211 and the registration roller 215 in the document transport direction CD. In the main scan direction MS perpendicular to the transport direction CD, the main scan width sensor 205 for large size is positioned outside the main scan width sensor 206 for medium size, and the main scan width sensor 206 for medium size is positioned closer to the center than the main scan width sensor 205 for large size.

[0064] Each of the large-size main scan width sensor 205 and the medium-size main scan width sensor 206 has a transmitter and a receiver that are exposed on the document passage surface. When a document passes over the large-size main scan width sensor 205 or the medium-size main scan width sensor 206, the signal from the transmitter is reflected by the document, and the reflected signal is incident on the receiver. When the receiver receives the reflected signal, it outputs an ON signal. The large-size main scan width sensor 205 and the medium-size main scan width sensor 206 are electrically connected to the document main scan width acquisition unit 163 of the control unit 160 of the image reading device 1005. The ON / OFF signal (detection signal) from the receiver is input to the CPU 164 via the document main scan width acquisition unit 163. When the CPU 164 receives the ON signal from the receiver, it detects that a document is passing over the large-size main scan width sensor 205 or the medium-size main scan width sensor 206.

[0065] The CPU 164 receives ON / OFF signals from the large-size main scan width sensor 205 and the medium-size main scan width sensor 206 during document transport. The CPU 164 detects the size of the document in the main scan direction MS based on the combination of the ON / OFF signals from the large-size main scan width sensor 205 and the medium-size main scan width sensor 206. If both the output of the large-size main scan width sensor 205 and the output of the medium-size main scan width sensor 206 are ON signals, the CPU 164 determines that the document being transported is a wide document, such as an A4 size document. If the output of the large-size main scan width sensor 205 is OFF and the output of the medium-size main scan width sensor 206 is ON signals, the CPU 164 determines that the document being transported is a medium-width document, such as an A5 size document. When a document passes through, if both the output of the main scanning width sensor 205 for large size and the output of the main scanning width sensor 206 for medium size are OFF signals, the CPU 164 determines that the document being transported is an A6 size document or a narrow document such as a business card.

[0066] The size information acquisition means for detecting the document width is not limited to the large-size main scanning width sensor 205 and the reflective-type medium-size main scanning width sensor 206. The size information acquisition means may include, for example, a flag protruding from the document passage surface of the document transport path 240 and a reflective-type sensor whose optical path is blocked by the flag. The flag is knocked over when the document being transported along the document transport path 240 hits it, blocking the optical path of the reflective-type sensor, which then outputs an ON signal. It may also be a type of sensor that blocks light. Furthermore, the size information acquisition means may be a reading sensor such as a CIS embedded in the document passage surface of the document transport path 240 and extending in the main scanning direction MS. The reading sensor reads image data of the edge of the document being transported along the document transport path 240. The size of the document in the main scanning direction MS may be calculated from the read image data.

[0067] Hereinafter, with reference to Figure 12, another example of the size information acquisition means will be described. Figure 12 is a diagram showing the internal structure of the ADF2200 as viewed from above, which is a modified example of Embodiment 2. The pair of document width regulating plates 202 are configured to move along a pair of slide grooves 209 in the main scanning direction MS. The pair of document width regulating plates 202 are configured to operate in conjunction with each other by a rack and pinion 270. The rack and pinion 270 consists of a pair of racks 270a and 270b and a pinion 270c that meshes with the pair of racks 270a and 270b. Rack 270a is attached to one of the document width regulating plates 202. Rack 270b is attached to the other document width regulating plate 202. When one of the document width regulating plates 202 is slid, the rack and pinion 270 causes the other document width regulating plate 202 to slide closer to or further away from each other.

[0068] Below rack 270a, reflective sensors 207 and 208 (second size detection means) are installed. Based on the combination of ON / OFF signals (detection signals) from reflective sensors 207 and 208, the size of the document placed on the document tray 201 in the main scanning direction MS can be detected. For example, when an A4-sized document placed on the document tray 201 is restricted by a pair of document width restriction plates 202, the distance between the pair of document width restriction plates 202 in the main scanning direction MS becomes the widest, and the output of both reflective sensors 207 and 208 becomes an OFF signal. In this case, it is determined that the document placed on the document tray 201 is a wide document. When an A5-sized document placed on the document tray 201 is restricted by a pair of document width restriction plates 202, the distance between the pair of document width restriction plates 202 in the main scanning direction MS becomes narrower than the width of an A4-sized document. The output of reflective sensor 207 becomes an ON signal, and the output of reflective sensor 208 becomes an OFF signal. In this case, the document placed on the document tray 201 is determined to be a medium-width document. When an A6-sized document or business card placed on the document tray 201 is restricted by a pair of document width restriction plates 202, the distance between the pair of document width restriction plates 202 in the main scanning direction MS becomes narrower, and the outputs of both reflective sensors 207 and 208 become ON signals. In this case, the document placed on the document tray 201 is determined to be a narrow-width document.

[0069] Note that the detection means for detecting the position of rack 270a is not limited to reflective sensors 207 and 208. The detection means for detecting the position of rack 270a may be, for example, a variable resistor whose resistance value changes according to the movement of rack 270a. The width MS in the main scanning direction of the document placed on the document tray 201 may be detected by detecting the resistance value of the variable resistor. In Embodiment 2, the document reading start operation, which starts reading the document using the acquired size information, is the same as in Embodiment 1, so the explanation will be omitted.

[0070] According to Example 2, since document transport control and the timing of starting to read the document image can be controlled according to the size information, image data can be acquired with high accuracy. According to Example 2, the occurrence of image loss or margins at the leading edge of the read image can be suppressed. [Examples]

[0071] The following describes Example 3. In Example 3, structures similar to those in Example 1 are given the same reference numerals and their description is omitted. The printer 1001, image reader 1005, control unit 160, controller 500, and document transport path 240, which serve as the image forming apparatus in Example 3, have the same structure as in Example 1, so their description is omitted. In Examples 1 and 2, a method for setting the optimal timer value from the read sensor 216 to the surface document reading position 107 based on the size information of the document was described. However, instead of changing the timer value, the reading position of the surface reading unit 101 may be changed. In Example 3, the reading movement guide 110, timing belt 151, and document feeder motor 169 constitute a reading position moving means for moving the reading position of the surface reading unit 101.

[0072] Figure 13 is an explanatory diagram illustrating the different transport trajectories and the movement of the surface document reading position 107 according to the size of the document. Figure 13(a) shows the first transport trajectory 241 for a wide document such as A4 size. Figure 13(b) shows the second transport trajectory 242 for a narrow document such as an A6 size document or a business card. The distance that the leading edge of a wide document travels from the detection position of the lead sensor 216 through the first transport trajectory 241 to the surface document reading position 107 is different from the distance that the leading edge of a narrow document travels from the detection position of the lead sensor 216 through the second transport trajectory 242 to the surface document reading position 107. Therefore, when transporting a narrow document, the surface reading unit 101 is moved from the surface document reading position 107 (first position) to the surface document reading position 107a (second position), which is shifted downstream by the difference between the distance of the first transport trajectory 241 and the distance of the second transport trajectory 242. As a result, the distance the leading edge of a narrow document travels from the lead sensor 216 through the second transport trajectory 242 to the surface document reading position 107a is the same as the distance the leading edge of a wide document travels from the lead sensor 216 through the first transport trajectory 241 to the surface document reading position 107. Here, the distance the leading edge of a wide document travels from the detection position of the lead sensor 216 through the first transport trajectory 241 to the surface document reading position 107 is defined as the first distance. The distance the leading edge of a narrow document travels from the detection position of the lead sensor 216 through the second transport trajectory 242 to the surface document reading position 107a is defined as the second distance. By moving the surface reading unit 101 from the surface document reading position 107 (first position) to the surface document reading position 107a (second position), the second distance becomes the same as the first distance. Therefore, when the width of the document in the main scanning direction MS changes, the surface reading unit 101 can be moved along the transport direction CD according to the document size information without changing the timer value, thereby enabling accurate acquisition of image data from the leading edge position of the document.

[0073] (Start of document scanning operation) Figure 14 is a flowchart of the document reading start operation in Embodiment 3. The CPU 164, acting as a control means, executes the document reading start operation according to the program stored in the ROM 165. In the document reading start operation of Embodiment 3, the CPU 164 determines the surface document reading position 107 of the surface reading unit 101 based on the size information of the main scanning direction MS of the document.

[0074] When a document is placed on the document tray 201 and the job starts, the CPU 164 determines whether the document main scan size acquisition unit 163 has acquired size information (S1301). The document main scan size acquisition unit 163, as a means for acquiring size information, may acquire size information input to the CPU 164 via the controller 500 from the operation unit 506 provided on the printer body 1001A, as in Embodiment 1. Alternatively, the document main scan size acquisition unit 163 may acquire size information based on a combination of detection results from the reflective large-size main scan width sensor 205, the medium-size main scan width sensor 206, and the reflective sensors 207 and 208 provided on the ADF 200, as in Embodiment 2.

[0075] If size information is obtained (YES in S1301), the CPU 164 determines the reading position based on the size information and moves the surface reading unit 101 to the determined reading position using the reading position moving means (110, 151, 169) (S1302). Figure 15 is a cross-sectional view of the surface reading unit 101 located at the standby position WP. Before the job starts, the surface reading unit 101 is located at the standby position WP below the white reference member 108. For example, if the document is determined to be wide based on the size information, the surface document reading position 107 is determined as the reading position. The surface reading unit 101 is moved by the reading position moving means (110, 151, 169) by the travel distance for wide documents and moved to the surface document reading position 107 located upstream below the surface reading opposing unit 218. Also, if the document is determined to be narrow based on the size information, the surface document reading position 107a is determined as the reading position. The surface reading unit 101 is moved by the reading position moving means (110, 151, 169) by a distance corresponding to the movement distance for narrow documents, and is moved to the surface document reading position 107a located downstream of the surface reading opposing unit 218.

[0076] If size information is not obtained (NO in S1301), the CPU 164 moves the surface reading unit 101 to a temporary reading position using the reading position moving means (110, 151, 169) (S1303). In Embodiment 3, the temporary reading position is set to the surface document reading position 107 for A4 size documents (wide documents), which are frequently used.

[0077] The CPU 164 determines whether the read sensor 216 is ON or OFF (S1304). If the read sensor 216 is not ON (NO in S1304), the CPU 164 waits for the read sensor 216 to be turned ON by the document. If the read sensor 216 is ON (YES in S1304), the CPU 164 sets the fixed timer value to timer 171 (S1305). In Embodiment 3, the fixed timer value is the distance traveled by a frequently used A4-sized document (wide document) from the read sensor 216 along the first transport trajectory 241 to the surface document reading position 107, converted into the number of pulses.

[0078] The CPU 164 determines whether the document main scanning size acquisition unit 163 has acquired size information (S1306). If size information has been acquired (YES in S1306), the CPU 164 determines whether the surface reading unit 101 has moved to the confirmed reading position (S1307). The confirmed reading position is the reading position determined based on the size information acquired in S1306. The CPU 164 determines whether the reading position where the surface reading unit 101 is currently located matches the confirmed reading position. For example, suppose the surface reading unit 101 is currently located at the surface document reading position 107 for wide documents. In this case, if the confirmed reading position determined based on the size information acquired in S1306 is the surface document reading position 107 for wide documents, the CPU 164 determines that the surface reading unit 101 has moved to the confirmed reading position (YES in S1307). On the other hand, if the confirmed reading position determined based on the size information acquired in S1306 is the surface document reading position 107a for narrow documents, the CPU 164 determines that the surface reading unit 101 has not yet moved to the confirmed reading position (NO in S1307).

[0079] If it is determined that the surface reading unit 101 has moved to the confirmed reading position (YES in S1307), the surface reading unit 101 can remain in its current surface document reading position 107, and the CPU 164 proceeds to S1331. The CPU 164 determines whether the fixed timer count has been completed (S1331). If the fixed timer count has not been completed (NO in S1331), the CPU 164 waits for the fixed timer count to be completed. If the fixed timer count has been completed (YES in S1331), the CPU 164 sends a read start command to the surface image reading control unit 172 to start reading the document (S1332), and then terminates the document reading start operation.

[0080] On the other hand, if it is determined in S1306 that size information has not been acquired (NO in S1306), the CPU 164 determines whether the leading edge of the document has reached the judgment limit position 283 (S1321). If it is determined that the leading edge of the document has not reached the judgment limit position 283 (NO in S1321), the CPU 164 returns the process to S1306. If it is determined that the leading edge of the document has reached the judgment limit position 283 (YES in S1321), the CPU 164 determines whether the document transport has been stopped (S1322). If the document transport has not been stopped (NO in S1322), the CPU 164 stops the rotation of the document transport motor 170 and temporarily stops the document transport (S1323). The CPU 164 returns the process to S1306. If the document transport has been stopped (YES in S1322), the CPU 164 returns the process to S1306 as is.

[0081] If, in S1307, it is determined that the surface reading unit 101 has not yet moved to the confirmed reading position (NO in S1307), then the reading position where the surface reading unit 101 is currently located does not coincide with the confirmed reading position. In this case, the CPU 164 moves the surface reading unit 101 to the confirmed reading position using the reading position moving means (110, 151, 169) (S1311). For example, suppose the surface reading unit 101 is currently located at the surface document reading position 107 for wide documents. If the confirmed reading position determined based on the size information acquired in S1306 is the surface document reading position 107a for narrow documents, then the surface reading unit 101 is moved downstream by the difference movement distance shown in Figure 15 using the reading position moving means (110, 151, 169).

[0082] The CPU 164 determines whether or not the document transport is temporarily stopped (S1312). If the document transport is temporarily stopped (YES in S1312), the CPU 164 restarts the rotation of the document transport motor 170 and resumes document transport (S1313). The CPU 164 proceeds to S1331. If the document transport is not temporarily stopped (NO in S1312), the CPU 164 proceeds to S1331. The CPU 164 determines whether or not the fixed timer count has finished (S1331), and if the fixed timer count has finished (YES in S1331), it starts reading the document (S1332) and ends the document reading start operation.

[0083] According to Example 3, the reading position of the surface reading unit 101 can be controlled according to the size information, so image data can be acquired with high accuracy. According to Example 3, the occurrence of image loss or margins at the leading edge of the read image can be suppressed.

[0084] <Other> Although embodiments 1 to 3 of the present invention have been described above, the present invention is not limited to embodiments 1 to 3 described above. For example, embodiments 1 and 2 described controlling the start timing of reading the image of the document by setting a timer value according to size information. Embodiment 3 described moving the reading position according to size information. However, instead of performing only one of the timer value setting or the reading position movement, both may be performed in combination. Also, although embodiments 1 to 3 were described using the front reading unit 101, the same can be applied to the back reading unit 230. Furthermore, although the transport trajectories for two types of documents, wide and narrow, were described, if the transport trajectories for documents of other widths, such as medium width documents, are also different, the control may be applied in a way that is suitable for those transport trajectories. [Explanation of Symbols]

[0085] 163...Main document scanning size acquisition unit 101...Surface reading section 164...CPU 216... Reed Sensor 230...Reverse side reading section 240... Manuscript transport path 1005...Image reading device

Claims

1. A size information acquisition means for acquiring size information about the size of the document in the width direction perpendicular to the transport direction in which the document is transported, The document transport path through which the aforementioned document is transported, A reading means for reading the image of the document being transported along the document transport path, A document detection means for detecting the document being transported along the document transport path, A control means that starts reading the image of the document by the reading means after a predetermined time has elapsed since the document detection means detected the document, Equipped with, The document transport path is formed such that the distance a first-width document travels from the time it is detected by the document detection means until it reaches the reading means via the first transport trajectory is different from the distance a second-width document travels from the time it is detected by the document detection means until it reaches the reading means via the second transport trajectory. The image reading device is characterized in that the control means determines the predetermined time based on the size information acquired by the size information acquisition means.

2. Equipped with a timer, The image reading device according to claim 1, characterized in that the control means sets the predetermined time determined based on the size information to the timer after the original document is detected by the original document detection means.

3. The image reading device according to claim 2, characterized in that, even after the document has been detected by the document detection means, if the size information is not acquired by the size information acquisition means, the control means sets a provisional time in the timer.

4. The image reading device according to claim 3, characterized in that, if the size information is acquired by the size information acquisition means after the provisional time has been set in the timer, the control means sets the predetermined time determined based on the size information in the timer.

5. The image reading device according to any one of claims 1 to 4, characterized in that the size information is set by the user via the operating unit.

6. The system includes a first size detection means for detecting the size of the document being transported along the document transport path, The image reading device according to any one of claims 1 to 5, characterized in that the size information acquisition means acquires the size information based on the detection signal of the first size detection means.

7. A document tray on which the aforementioned document is placed, A second size detection means for detecting the size of the document placed on the document tray, Equipped with, The image reading device according to any one of claims 1 to 6, characterized in that the size information acquisition means acquires the size information based on the detection signal of the second size detection means.

8. The document transport path includes a curved portion that is curved when viewed from the width direction, The curved portion is composed of an inner guide portion that forms the inner part of the curve and an outer guide portion that forms the outer part of the curve. The image reading device according to any one of claims 1 to 7, characterized in that the inner guide portion includes a first region including the center of the document transport path in the width direction, and a second region that is outside the first region in the width direction and protrudes toward the outer guide portion from the first region.

9. The curved portion is formed such that the first width of the original document passes through the first transport trajectory and the second width of the original document passes through the second transport trajectory. The image reading device according to claim 8, characterized in that the control means determines the predetermined time to be the first time when the size information is the first width, and determines the predetermined time to be the second time when the size information is the second width.

10. The aforementioned first width is larger than the aforementioned second width. The image reading device according to claim 9, characterized in that the first time is longer than the second time.

11. The image reading device according to any one of claims 8 to 10, characterized in that the curved portion is formed such that the second transport trajectory is inside the first transport trajectory.

12. A size information acquisition means for acquiring size information about the size of the document in the width direction perpendicular to the transport direction in which the document is transported, The document transport path through which the aforementioned document is transported, A reading means for reading the image of the document being transported along the document transport path, A document detection means for detecting the document being transported along the document transport path, A control means that starts reading the image of the document by the reading means after a predetermined time has elapsed since the document detection means detected the document, A reading position moving means moves the reading means along the transport direction based on the size information acquired by the size information acquisition means, Equipped with, The control means moves the reading means to the first position when the size information is a first width, and moves the reading means to the second position when the size information is a second width. An image reading device characterized in that the first distance the first width of the original document travels from the detection position of the original document detection means to the first position via a first transport trajectory is the same as the second distance the second width of the original document travels from the detection position to the second position via a second transport trajectory.

13. The document transport path includes a curved portion that is curved when viewed from the width direction, The curved portion is composed of an inner guide portion that forms the inner part of the curve and an outer guide portion that forms the outer part of the curve. The image reading device according to claim 12, characterized in that the inner guide portion includes a first region including the center of the document transport path in the width direction, and a second region that is outside the first region in the width direction and protrudes toward the outer guide portion more than the first region.

14. The image reading device according to claim 12 or 13, characterized in that the size information is set by the user via the operating unit.

15. The system includes a first size detection means for detecting the size of the document being transported along the document transport path, The image reading device according to any one of claims 12 to 14, characterized in that the size information acquisition means acquires the size information based on the detection signal of the first size detection means.

16. A document tray on which the aforementioned document is placed, A second size detection means for detecting the size of the document placed on the document tray, Equipped with, The image reading device according to any one of claims 12 to 15, characterized in that the size information acquisition means acquires the size information based on the detection signal of the second size detection means.

17. An image reading device according to any one of claims 1 to 16, An image forming unit that forms an image on a recording medium based on image data read by the aforementioned image reading device, An image forming apparatus equipped with the following features.

18. Equipped with an image forming apparatus body, The image forming apparatus according to claim 17, characterized in that the control means is provided in the main body of the image forming apparatus.

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