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 device that conveys a document and reads an image on the document, and an image forming apparatus that includes the same. [Background technology]

[0002] The ability to scan a wide variety of documents in an automatic document feeder (ADF)—a component of an image reading device—has a significant impact on the product's appeal. In recent years, there has been growing demand for scanning documents narrower than the conventional product specifications, such as business cards and checks. To ensure stable transport of various types of documents, image reading devices have implemented various innovations for the guides that make up the document transport path within the device. For example, documents such as business cards and checks tend to be stiff due to their high basis weight, making it difficult to bend them. These document characteristics can lead to document loop growth and speed fluctuations during scanning, resulting in image blur. It is known that image blur can occur when a document becomes taut (loop reduction; hereinafter, document slack is referred to as "loop") or when a taut document becomes slack (loop growth)—a change in document posture and the resulting speed fluctuations. In Patent Document 1, a protrusion is provided on the inner guide of the bent portion downstream of the reading unit to restrain the document, thereby suppressing the above-mentioned change in document posture and reducing image blur.

[0003] In addition, not only in image reading devices, but also in other devices, there are cases where impacts and vibrations generated inside and outside the device transporting the paper (transport medium) cause collision noises of the transport medium, and various shapes are used for the mechanical structure of the transport path to improve transport accuracy. For example, in the image forming device described in Patent Document 2, the shape of the ribs on the transport path is different between the center and the outside to prevent the leading edge of the transported document from getting caught, with the center portion being recessed compared to the outside portion. In Patent Document 3, as a countermeasure against image blur, rubber is attached only to the center portion to suppress blur. In this case, a restriction is imposed, such as limiting the attachment of additional components to only the center portion in the main scanning direction to suppress skew differences in the document transport. As such, various transport countermeasures against image blur, snagging, etc., include adding guides inside the transport path, but depending on conditions and constraints, measures such as changing the shape or attaching additional components to only part of the transport path rather than the entire main scanning direction are also taken. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-86957 [Patent Document 2] Japanese Patent Application Publication No. 2019-135188 [Patent Document 3] Japanese Patent Application Laid-Open No. 2017-1761 Summary of the Invention [Problem to be solved by the invention]

[0005] However, depending on the shape of the transport guide that forms the transport path, the location within the transport path through which the document passes (the position within the transport path as viewed from the width direction) 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, so depending on the timing at which reading of the document begins, image clipping or blank spaces may occur on the leading edge. Therefore, an object of the present invention is to suppress the occurrence of image clipping or blank spaces on the leading edge of the scanned image. [Means for solving the problem]

[0006] An image reading device according to an embodiment of the present invention comprises: a size information acquiring means for acquiring size information about the size of the document in a width direction perpendicular to a conveying direction in which the document is conveyed; a document transport path having a guide shape such that the moving distance of the document varies depending on the size of the document; a reading unit for reading an image of the document conveyed through the document conveying path; a document detection means for detecting the document transported through the document transport path; a control means for starting reading of 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 control means 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 prevent the occurrence of image fragments or blank spaces at the leading edge of a read image. [Brief explanation of the drawings]

[0008] [Figure 1] Cross-sectional view of the printer. [Figure 2] FIG. [Figure 3] FIG. 2 is a block diagram of an image reading device and a controller. [Figure 4] FIG. [Figure 5] 10A and 10B are explanatory diagrams showing different transport trajectories according to the size of the original; [Figure 6] FIG. 10 is an explanatory diagram of the movement distance from the lead sensor to the front side document reading position. [Figure 7] 4 is a flowchart of the document reading start operation according to the first embodiment. [Figure 8] FIG. 10 is a diagram showing the relationship between size information and a timer value. [Figure 9]FIG. [Figure 10] FIG. 10 is a diagram showing timer values ​​set in a timer when a document reading start operation is performed. [Figure 11] FIG. 10 is a diagram showing the internal structure of the ADF of the second embodiment when viewed from above. [Figure 12] FIG. 10 is a diagram showing the internal structure of the ADF according to a modification of the second embodiment, as viewed from above. [Figure 13] 10A and 10B are explanatory diagrams of the movement of the transport trajectory and the front side document reading position that differ depending on the size of the document. [Figure 14] 10 is a flowchart of the document reading start operation according to the third embodiment. [Figure 15] FIG. 4 is a cross-sectional view of the front surface reading unit positioned at the standby position. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. [Example]

[0010] <Image forming device> A printer 1001 as an image forming apparatus will be described with reference to Figure 1. Figure 1 is a cross-sectional view of the printer 1001. In the following description, the position facing the operation unit 506 where the user inputs / sets various settings to the printer 1001 is defined as the "front side" of the printer 1001, and the rear side is defined as the "rear side." In other words, Figure 1 shows the internal configuration of the printer 1001 as seen from the front side.

[0011] The printer 1001 includes a printer main body 1001A and an image reading device 1005 disposed above the printer main body 1001A. An operation unit 506 is provided in the printer main body 1001A. The image reading device 1005 includes a scanner unit 100 and an ADF 200 (automatic document feeder). The scanner unit 100 optically scans a document S conveyed by the ADF 200 to read image data. The image data converted into an electrical signal by the image reading device 1005 is transferred via a control unit 160 to a controller 500 (control means) provided in the printer main body 1001A (image forming apparatus main body). The printer 1001 is controlled by the controller 500 and forms an image on a sheet P (recording medium) based on the image data read by the image reading device 1005.

[0012] The printer main body 1001A includes an image forming unit 1033 that forms an image on a sheet P, and a sheet feeding unit 1006 that feeds 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 the conveying roller pair 1031. The sheet P is conveyed to a pair of registration rollers 1036 by a plurality of pairs of conveying rollers 1031 arranged along the sheet conveying path 1007 .

[0013] A manual feed tray 1037e is disposed on the side of the printer main body 1001A. A sheet P placed on the manual feed tray 1037e by a user is fed into the printer main body 1001A by a feed roller 1038 and conveyed to a pair of registration rollers 1036. The leading edge of the sheet P abuts against the nip portion of the stopped registration roller pair 1036, correcting any skew of the sheet P. The pair of registration rollers 1036 start rotating in accordance with the progress of the toner image formation operation by the image forming unit 1033, and conveys 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 system. The image forming unit 1033 includes a photosensitive drum 1021, which is a photosensitive member. The photosensitive drum 1021 is rotatable along the conveyance direction of the sheet P. A charger 1018, an exposure device 1023, a developing device 1024, a transfer charger 1025, a separation charger 1026, and a cleaner 1027 are arranged around the photosensitive drum 1021. The charger 1018 uniformly charges the surface of the rotating photosensitive drum 1021. The exposure device 1023 exposes the photosensitive drum 1021 to light based on image data input from the image reading device 1005 or an external device (for example, a personal computer), and forms an electrostatic latent image on the photosensitive drum 1021.

[0015] The developing device 1024 contains a two-component developer containing toner and carrier, and develops the electrostatic latent image on the photosensitive drum 1021 into a toner image by supplying charged toner to the photosensitive drum 1021. The toner image formed on the photosensitive drum 1021 is transferred onto a sheet P being transported by a pair of registration rollers 1036 by a bias electric field formed by a transfer charger 1025. The sheet P with the transferred toner image is separated from the photosensitive drum 1021 by a bias electric field formed by a separation charger 1026, and transported by a pre-fixing transport section 1028 toward a fixing section 1029. Any toner remaining on the photosensitive drum 1021 without being transferred to the sheet P is removed by a cleaner 1027.

[0016] The sheet P conveyed to the fixing unit 1029 is sandwiched between a pair of rollers and heated while being pressurized, 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 its front side is discharged by a pair of discharge rollers 1010 to an output tray 1030 that protrudes outward from the printer main body 1001A. In the case of double-sided printing, the sheet P with the image formed on its front side is reversed by a reversing unit 1039 and conveyed to a pair of registration rollers 1036 by a double-sided conveying unit 1040. The image forming unit 1033 forms a toner image on the back side (second side) of the sheet P, which is opposite to the front side (first side). The sheet P with the toner image formed on its back side is heated and pressurized by the fixing unit 1029, and an image is formed on the back side of the sheet P. The sheet P with the images formed on both sides is discharged by the pair of discharge rollers 1010 to the output tray 1030.

[0017] The image forming unit 1033 in the first embodiment forms an image on the sheet P using an electrophotographic method, but the image forming unit 1033 is an example of an image forming means. The image forming unit 1033 may form an image on the sheet P using an inkjet method, an offset printing method, or other methods.

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

[0019] The ADF 200 has a document tray 201 and a pair of document width restriction plates 202. The document tray 201 is configured to accommodate a stack of documents consisting of one or more documents. The document sensor 17 detects the documents loaded on the document tray 201. The pair of document width restriction plates 202 are provided on the document tray 201 to be movable in a direction (main scanning direction) perpendicular to the document transport direction CD, and restrict movement of the documents in the main scanning direction. The ADF 200 also has a separation roller 211 and a pick roller 210. The separation roller 211 restricts the document stack from protruding from the document tray 201 and advancing downstream before the start of document transport. When the ADF 200 receives a document transport start instruction, the pick roller 210 drops onto the top of the document stack loaded on the document tray 201 and rotates, thereby transporting the topmost document of the document stack. The originals conveyed by the pick roller 210 are separated and conveyed one by one by the action of a separation roller 211 serving as a separation mechanism. Separation of the originals by the separation roller 211 is achieved by a known separation technique.

[0020] When the document separated by separation roller 211 turns on separation sensor 212, timer 171 (FIG. 3) starts counting. The count value of timer 171 is used to calculate the timing for multi-feed sensor 213 to start detecting multi-feeds and to calculate the length of the document. When the document reaches the vicinity of multi-feed sensor 213, multi-feed detection by multi-feed sensor 213 begins. The document is transported to registration roller 215. Registration sensor 214 detects that the document has reached registration roller 215. The leading edge of the document abuts against the nip of stopped registration roller 215, causing the document to bend into a loop and correcting any skew in the document. Thereafter, registration roller 215 starts rotating and transports the document.

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

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

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

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

[0025] <Control unit> FIG. 3 is a block diagram of the image reading device 1005 and the controller 500. The image reading device 1005 includes a control unit 160, a front LED 102, a front line sensor 103, a rear LED 231, a rear line sensor 232, a document table motor 169, and a document transport motor 170, all of which are electrically connected to the control unit 160. The control unit 160 includes a CPU 164, which is a central processing unit, a ROM 165, which is a read-only memory, and a RAM 166, which is a random access memory. The ROM 165 stores a control program for implementing document scanning. The RAM 166 stores input data and working data. The control unit 160 further includes a lighting control unit 167, a scanning control unit 168, a timer 171, a front image reading control unit 172, a rear 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 scanning size acquisition unit 163 , a nonvolatile memory 257 , and an image processing unit 275 .

[0026] The lighting control unit 167 controls the on / off of the illumination of the front LED 102 and the back LED 231. The scanning control unit 168 controls the drive of the platen motor 169. The platen motor 169 is connected to the front reading unit 101 via a timing belt 151. The rotation of the platen motor 169 allows the front reading unit 101 to 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, the separation roller 211, the registration roller 215, the first read roller 217, the second read roller 219, the third read roller 221, and the discharge roller 223 to transport the document.

[0027] The front surface line sensor 103 is built in the front surface reading unit 101. The front surface line sensor 103 receives light reflected from the original illuminated by the front surface LED 102. The amount of light (analog data) received by the front 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 in the back surface reading unit 230. The back surface line sensor 232 receives light reflected from the original 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 original main scanning size acquisition unit 163, which serves as a size information acquisition unit, acquires size information input from an operation unit 506 provided in the printer main body 1001A to the CPU 164 via the controller 500. The original main scanning size acquisition unit 163 can also acquire size information based on a combination of detection results from a reflective large size main scanning width sensor 205, a medium size main scanning width sensor 206, and reflective sensors 207 and 208 provided in 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 the shading RAM 254 and write data to the shading RAM 254.

[0030] The nonvolatile 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 nonvolatile memory 257 retains, for example, values ​​such as shading target values ​​used by the shading correction circuit 253 to perform shading correction, and alarm and error information that occurs during a job.

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

[0032] The front image reading control unit 172 controls the front reading unit 101 to perform image reading processing on the front side of the document. When the timer 171 completes counting a 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 front image reading control unit 172. When the front image reading control unit 172 receives the trigger signal, it starts acquiring the document image by the front reading unit 101. The back image reading control unit 173 controls the back reading unit 230 to perform image reading processing on the back side of the document. When the timer 171 completes counting a 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 image reading control unit 173. When the back image reading control unit 173 receives the trigger signal, it starts acquiring the document image by the back 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 discharge sensor 222 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, a signal from each sensor is sent to the transport detection unit 174. The CPU 164 receives the signals received by the transport detection unit 174 from each sensor as an interrupt, and the CPU 164 outputs an instruction signal to the timer 171 without delay.

[0034] <controller> The control unit 160 provided in the image reading device 1005 is electrically connected to a controller 500 provided in the printer main body 1001A via a communication line 180. The controller 500 converts 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 an image on a sheet (recording medium). The controller 500 also converts 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 accepts user operations and manages the entire 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 CPU 501, which is a central processing unit, a ROM 502, which is a read-only memory, and a RAM 503, which is a random access memory. The ROM 502 stores a control program for realizing image conversion and overall management of the printer 1001. The 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 image data read by the image reading device 1005 into image data in a format that can be output to the printer 1001. The image memory 505 temporarily stores the image data. The CPU 501 of the controller 500 is electrically connected to an operation unit 506. The operation unit 506 is provided with a display unit and buttons. The CPU 501 accepts button operations from the operation unit 506 by the user. The CPU 501 outputs various information for the user to the display unit of the operation unit 506.

[0037] In the first embodiment, the image reading device 1005 has a CPU 164, a ROM 165, and a RAM 166, and the controller 500 also has a CPU 501, a ROM 502, and a RAM 503. However, for example, the image reading device 1005 may not have the CPU 164, the ROM 165, and the RAM 166, and may share the CPU 501, the ROM 502, and the RAM 503 of the controller 500. In that case, various components electrically connected to the CPU 164 in FIG. 3 may be directly connected to the CPU 501 of the controller 500 without passing through the communication line 180. In the first embodiment, a configuration in which the image reading device 1005 and the controller 500 are provided with the CPU 164 and the CPU 501, respectively, will be described. However, a configuration in which the CPU 164 is omitted and the CPU 501 is shared can be realized by appropriately changing the description.

[0038] <Document transport path> The document transport path 240 of the ADF 200 will be described below. The document transport path 240 has a curved portion that is curved in a curved shape when viewed from the width direction (the direction from the front to the rear of the device). The curved portion is formed by an inner guide portion 250 and an outer guide portion 260 (see FIG. 5, described later). FIG. 4 is a perspective view of the inner guide portion 250. The inner guide portion 250, which is a first guide, constitutes the inner portion of the document transport path 240 of the ADF 200. The outer guide portion 260, which is a second guide, constitutes the outer portion of the document transport path 240 of the ADF 200. FIG. 4 shows, as an example, the inner guide portion 250 used in an ADF 200 that feeds A4-sized sheets vertically. In the first embodiment, the ADF 200 has three pairs of first read rollers 217a, 217b, and 217c. 4, the inner guide portion 250 is provided with three pairs of first read rollers 217a, 217b, and 217c, each of which is an inner first read roller 217a, 217b, and 217c. The outer first read rollers 217a, 217b, and 217c of the three pairs of first read rollers 217a, 217b, and 217c are provided on the ADF cover 204. In this application, the three pairs of first read rollers 217a, 217b, and 217c are collectively referred to as first read rollers 217. Because the ADF 200 is a compact device, there are restrictions on the transport guides and component shapes, etc., in order to arrange components within a small housing, and the guide shape in the main scanning direction MS is complex.

[0039] First, the basic guide shape is the shape of the edge-side transport guides 280 provided at the left and right ends in the main scanning direction MS. The edge-side transport guides 280 have a curved shape to minimize resistance and ensure smooth document transport along the document transport path 240. As a result, an A4-width (210 mm) document is pulled by the three rotating first read rollers 217a, 217b, and 217c, and the left and right edges of the document are transported along the edge-side transport guides 280. If guides with the same shape as the edge-side transport guides 280 were provided near the first read rollers 217a, 217b, and 217c, the document contact surface of the guide would be at approximately the same height as the contact surface of the first read rollers 217a, 217b, and 217c. This would prevent smooth document transport. Furthermore, taking into consideration interference with other components, the transport guides 281 near the first read rollers 217a, 217b, and 217c have a linear shape. In other words, the inner guide portion 250 has a shape in which the conveying guide 281 is a first region that includes the center in the width direction, and the end side conveying guide 280 is a second region that is outside the conveying guide 281 in the width direction and protrudes toward the outer guide portion 260.

[0040] Downstream of first lead roller 217b, a Mylar sheet 282 made of a film material is attached to inner guide portion 250 in order to reduce image blurring caused by document transport. To improve the ease of attaching Mylar sheet 282 and to prevent Mylar sheet 282 from getting caught on the document, the guide shape is recessed further inward by the length of Mylar sheet 282 in the main scanning direction MS. Mylar sheet 282 is made of a film material, and when a document is pressed into it, Mylar sheet 282 bends accordingly, allowing the document to pass over Mylar sheet 282. Meanwhile, Mylar sheet 282 applies a pressing force from above to the document, thereby reducing blurring of the document during transport.

[0041] <Reading start timing> The timing at which the reading of image data of a document read by the front side reading unit 101 starts (hereinafter referred to as the reading start timing) will be described below. As described above, the document transport path 240 of the ADF 200 has a complex shape, and therefore, in the document transport path 240 of the ADF 200, the document passes through different transport paths (hereinafter referred to as the transport trajectory) depending on the size of the document. FIG. 5 is an explanatory diagram showing different transport trajectories depending on the size of the document. First, with reference to FIG. 5(a), the control of the timing at which the reading of image data from the front side reading unit 101 starts will be described. Note that, since the control of the timing at which the reading of image data from the back side reading unit 230 starts is the same as that of the front side reading unit 101, a description of the back side reading unit 230 will be omitted below.

[0042] FIG. 5A is a cross-sectional view of the vicinity of the first read roller 217 and the front surface reading unit 101, viewed from the front to the rear. Here, a case where an A4-sized document, the widest size that can be conveyed by the ADF 200 of the first embodiment, is conveyed will be described. The read sensor 216 includes a sensor flag 216a, a photointerrupter 216b having a light-emitting unit and a light-receiving unit, and a rotation shaft 216c for the sensor flag 216a. The sensor flag 216a is rotatable around the rotation shaft 216c. When the sensor flag 216a blocks the optical path between the light-emitting unit and the light-receiving unit of the photointerrupter 216b, the read sensor 216 outputs an ON signal. When the leading edge of the document S being conveyed presses one end of the sensor flag 216a, the sensor flag 216a rotates around the rotation shaft 216c, and the other end of the sensor flag 216a blocks the optical path of the photointerrupter 216b. In this way, the lead sensor 216 functions as a document detection means.

[0043] The transport detection unit 174 transmits an ON signal from the read sensor 216 to the CPU 164 as an interrupt signal. The CPU 164, triggered by the interrupt signal, sets a 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 increments its count value by one each time it receives a pulse. The amount by which the first read roller 217 rotates per pulse of the document transport motor 170 is preset, so the advance amount of the document transported per pulse is determined in advance. Therefore, the distance the document is transported is calculated by multiplying the count value by (advance amount per pulse). The transport of an A4-sized document is restricted by the end-side transport guide 280 as shown in FIG. 5(a), so the A4-sized document is transported along the first transport trajectory 241. Therefore, the first timer value as the timing to start 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 front document reading position 107 through the first transport trajectory 241 by the advance amount per pulse.

[0044] The timer 171 compares the count value with the first timer value. When the count value reaches the first timer value, the timer 171 transmits a count completion signal (timer expiration signal) to the CPU 164 as an interrupt signal. At this timing, the leading edge of the document reaches the front document reading position 107. Upon receiving the interrupt signal, the CPU 164 as a control unit transmits a read start command to the front image reading control unit 172. Upon receiving the read start command, the front image reading control unit 172 starts acquiring image data through the front line sensor 103. In this manner, the timer 171 starts counting the first timer value in response to an ON signal from the lead sensor 216, and upon completing the counting of the first timer value, transmits a count completion signal to the CPU 164 as an interrupt signal. In response to the interrupt signal, the CPU 164 transmits a read start command to the front image reading control unit 172. Upon receiving the read start command, the front image reading control unit 172 starts reading image data of the document to be read by the front reading unit 101. By starting to acquire image data from the front surface line sensor 103 based on the first timer value (reading start timing) set in this way, image data can be acquired with high accuracy from the leading edge position of the document.

[0045] 5(a), when an A4-sized document is conveyed, the timing at which timer 171 completes counting the first timer value (after a predetermined time has elapsed) coincides with the timing at which the leading edge of the document reaches front document reading position 107. Therefore, by setting the first timer value in timer 171, it is possible to acquire image data with high accuracy from the leading edge position of the document. However, as described with reference to FIG. 4, because the guide shape of document conveyance path 240 is complex, the document passes through different positions in the internal space of document conveyance path 240 for wide and narrow documents.

[0046] For example, FIG. 5(a) is a diagram showing a first transport locus 241 of an original S having a wide width (first width), such as an A4-sized original. FIG. 5(a) is a cross-sectional view of the original transport path 240 taken along the line VA-VA in FIG. 4. An original having a wide width (first width) is transported while both ends of the original in the main scanning direction MS are regulated by end-side transport guides 280. Therefore, the original passes through the outermost part of the internal space of the original transport path 240. Therefore, the distance (travel distance) that the leading edge of the original travels from the lead sensor 216 along the first transport locus 241 to the front-side original reading position 107 is the longest.

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

[0048] If the first timer value for a wide document transported along the first transport path 241 is set in the timer 171 for reading a narrow document transported along the second transport path 242, document reading will not start even if the leading edge of the narrow document reaches the front-side document reading position 107. This will be explained with reference to FIG. 6. FIG. 6 is an explanatory diagram of the travel distance from the lead sensor 216 to the front-side document reading position 107. As shown in FIG. 6, the travel distance corresponding to the first timer value for a wide document coincides with the travel distance of the wide document along the first transport path 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 path 242, the leading edge of the narrow document will have passed the front-side document reading position 107 by the time the counting of the first timer value is completed. As a result, image reading will start midway through the narrow document, and image data will be generated that lacks the leading edge of the narrow document.

[0049] Therefore, in the first embodiment, the timer value to be set in the timer 171 is determined according to the size of the original document in the main scanning direction MS. When the ADF 200 is a compact device, there are restrictions on the components that can be installed to reduce manufacturing costs. For example, the ADF 200 may not include a size sensor that detects the size of the original document placed on the original document tray 201. In this case, for example, the original document size may be determined from the output size selected by the user on the copy screen displayed on the display of the operation unit 506. Alternatively, the original document size may be determined from the scan size selected by the user on the scan screen displayed on the display 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 timing. The CPU 164 determines the original document size based on the received size information and sets a timer value appropriate for the determined original document size.

[0050] (Original reading start operation) 7 is a flowchart of the document reading start operation in the first embodiment. The CPU 164 as a control means executes the document reading start operation in accordance with a program stored in the ROM 165. In the document reading start operation in the first embodiment, the CPU 164 determines a timer value (predetermined time) to be set in the timer 171 based on size information of the document in the main scanning direction MS (width direction). The CPU 164 starts reading the document image after the timer value has been counted (after the predetermined time has elapsed).

[0051] When a document is placed on document tray 201 and a job is started, CPU 164 determines whether or not lead sensor 216 is turned ON (S701). If lead sensor 216 is not turned ON (NO in S701), CPU 164 waits until lead sensor 216 is turned ON. If lead sensor 216 is turned ON (YES in S701), CPU 164 starts counting with timer 171 and determines whether or not size information in the main scanning direction MS (width direction) of the document has been acquired (S702). If size information acquired from information input by the user has been transmitted from controller 500 of printer 1001 to CPU 164 of image reading device 1005 (YES in S702), CPU 164 proceeds to S703. If size information has not been acquired (NO in S702), 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 in the timer 171. FIG. 8 is a diagram showing the relationship between size information and timer values. In the first embodiment, it is determined whether the size of the original is wide or narrow based on the size information. A wide original is an original having a width that allows both ends of the original in the main scanning direction MS to be conveyed while being restricted by the end-side conveying guides 280. For example, it is an A4-sized original having a first width. A narrow original is an original having a width that allows the entire area of ​​the original in the main scanning direction MS to pass between the two end-side conveying guides 280. For example, it is an A6-sized original having a second width.

[0053] Since a wide original moves from the lead sensor 216 to the front-side original reading position 107 along the first transport path 241, the movement distance of the wide original from the detection position of the lead sensor 216 to the front-side original reading position 107 is 50 mm. Assuming that the advance amount per pulse of the original transport motor 170 is 0.1 mm, the timer value is 500 counts (first time). On the other hand, a narrow original moves from the lead sensor 216 to the front-side original reading position 107 along the second transport path 242, so the distance from the detection position of the lead sensor 216 to the front-side original reading position 107 is 48 mm. The timer value is 480 counts (second time).

[0054] When the CPU 164 sets a timer value in the timer 171 in accordance with the size information (S703), it determines whether or not the timer count has been completed (S751). Specifically, the timer 171 compares the count value, which has been counted since the read sensor 216 was turned ON, with the timer value. When the count value reaches the timer value, the timer 171 transmits a count completion signal (timer expiration signal) to the CPU 164 as an interrupt signal. When the CPU 164 receives the count completion signal from the timer 171, it determines that the timer count has been completed (YES in S751), and proceeds to the process of S752. The CPU 164 transmits a reading start command to the front image reading control unit 172 to start reading the document (S752), and ends the document reading start operation.

[0055] On the other hand, if it is determined in S702 that size information in 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 been started, the controller 500 may be slow to notify the image reading device 1005 of the size information due to the relationship between the process of preparing to receive an image and the document conveyance speed. In such a case, the CPU 164 may not be able to acquire the size information from the controller 500 when the lead sensor 216 turns ON. In this case, the CPU 164 sets a temporary timer value (provisional time) in the timer 171 (S711). The reason for setting the temporary timer value in the timer 171 is that, as described above, in order to accurately acquire image data from the leading edge position of the document, a series of connections between various interrupt signals and the motor pulse count is required. Here, the moving distance of an A4 size document (wide document), which is frequently used in the ADF 200, from the lead sensor 216 through the first transport trajectory 241 to the front document reading position 107 is converted into the number of pulses and set as a temporary timer value in the timer 171. Note that the temporary timer value may be a timer value for a document of any size.

[0056] Thereafter, the CPU 164 determines whether the leading edge of the document has reached the determination limit position 283 (S712). The determination limit position 283 is the leading edge position of the document at the limit of the time that the CPU 164 can wait for the acquisition of size information. The determination limit position 283 is the most downstream point at which the document transport is temporarily stopped if size information is not received from the controller 500. In the first embodiment, the determination limit position 283 is the distance traveled from the lead sensor 216 along the first transport path 241 to the front document reading position 107, minus the distances required for deceleration, acceleration, and stabilization of the document transport motor 170. If the leading edge of the document has reached the determination limit position 283 but 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 front document reading position 107 before the document size is determined. If CPU 164 determines in S712 that the leading edge of the document has not reached determination limit position 283 (NO in S712), it determines whether size information has been acquired while polling at an arbitrary interval (S721). If size information has not been acquired (NO in S721), CPU 164 returns the process to S712. If size information has been acquired (YES in S721), CPU 164 advances the process to S722.

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

[0058] The remaining timer value will be explained with reference to Figure 9. Figure 9 is an explanatory diagram of the remaining timer value. The count value corresponding to the distance that the leading edge of the document has advanced from the position of the lead sensor 216 at the time when CPU 164 acquires size information from controller 500 is set as the timer count elapsed value. The timer value corresponding to the difference in distance between a wide document and a narrow document is the value obtained by subtracting the timer value for the narrow document from the timer value for the wide document. The remaining timer value is expressed by the following equation (1). Remaining timer value = temporary timer value - (timer count elapsed value + (timer value corresponding to the difference in distance between the wide document and the narrow document)) Formula 1 The CPU 164 sets the remaining timer value calculated using Equation 1 in the timer 171 (S723), and the process proceeds to S751.

[0059] The following describes the case where the leading edge of the document reaches the determination limit position 283 in S712. When the leading edge of the document reaches the determination limit position 283 (YES in S712), the CPU 164 temporarily stops conveying the document (S713). Then, the CPU 164 waits for size information to arrive from the controller 500 (S714). When the CPU 164 acquires the size information from the controller 500 (YES in S714), it sets a remaining timer value corresponding to the size in the timer 171 (S715). The calculation of the remaining timer value in S715 is the same as in S723 described above, and therefore a description thereof will be omitted. Thereafter, the CPU 164 resumes conveying the document (S716) and proceeds to S751. When the CPU 164 has completed counting the remaining timer value (YES in S751), it starts reading the document (S752) and ends the document reading start operation.

[0060] 10 is a diagram showing timer values ​​set in timer 171 when starting document reading. When the document is a wide document, a timer value corresponding to the distance from lead sensor 216 to front document reading position 107 along first transport path 241 is set in timer 171. When the document is a narrow document, a timer value corresponding to the distance from lead sensor 216 to front document reading position 107 along second transport path 242 is set in timer 171. Therefore, it is possible to acquire image data from the leading edge position of the document with high accuracy according to the document size.

[0061] According to the first embodiment, it is possible to control the document transport control and the timing of starting to read the document image according to the size information, so that it is possible to acquire image data with high accuracy. According to the first embodiment, it is possible to prevent the occurrence of image loss or blank space on the leading edge side of the read image. [Example]

[0062] Hereinafter, a second embodiment will be described. In the second embodiment, the same structures as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted. The printer 1001, image reading device 1005, control unit 160, controller 500, and document transport path 240 as the image forming apparatus in the second embodiment have the same structures as those in the first embodiment, and therefore the description thereof will be omitted. The ADF 200 in the first embodiment was not provided with a size information acquisition means, but the ADF 1200 in the second embodiment is provided with a size information acquisition means.

[0063] 11 is a diagram showing the internal structure of the ADF 1200 of the second embodiment when viewed from above. The size information acquisition unit includes a reflective large-size main-scanning width sensor 205 (first size detection unit) and a reflective medium-size main-scanning width sensor 206 (first size detection unit). The large-size main-scanning width sensor 205 and the medium-size main-scanning width sensor 206 are arranged on the document passing surface of the document transport path 240 of the ADF 1200 between the separation roller 211 and the registration roller 215 in the document transport direction CD. In the main scanning direction MS perpendicular to the transport direction CD, the large-size main-scanning width sensor 205 is arranged outside the medium-size main-scanning width sensor 206, and the medium-size main-scanning width sensor 206 is arranged closer to the center than the large-size main-scanning width sensor 205.

[0064] The large size main scanning width sensor 205 and the medium size main scanning width sensor 206 each have a transmitter and a receiver exposed to the document passing surface. When a document passes over the large size main scanning width sensor 205 or the medium size main scanning width sensor 206, a 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 scanning width sensor 205 and the medium size main scanning width sensor 206 are electrically connected to the document main scanning size 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 scanning size 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 scanning width sensor 205 or the medium size main scanning width sensor 206.

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

[0066] The size information acquisition unit that detects the document width is not limited to the large-size main scanning width sensor 205 and the reflective medium-size main scanning width sensor 206. The size information acquisition unit may include, for example, a flag protruding from the document passage surface of the document transport path 240 and a reflective sensor whose optical path is blocked by the flag. When a document transported along the document transport path 240 hits the flag, the flag is knocked over and blocks the optical path of the reflective sensor, causing the reflective sensor to output an ON signal. A light-blocking type sensor may also be used. The size information acquisition unit may also 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 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] Another example of the size information acquisition means will be described below with reference to FIG. 12. FIG. 12 is a diagram illustrating the internal structure of an ADF 2200 according to a modification of the second embodiment, viewed from above. The pair of document width restriction plates 202 are configured to move in the main scanning direction MS along a pair of slide grooves 209. The pair of document width restriction plates 202 are configured to move in conjunction with each other via a rack-and-pinion 270. The rack-and-pinion 270 includes a pair of racks 270a and 270b and a pinion 270c that meshes with the pair of racks 270a and 270b. The rack 270a is attached to one document width restriction plate 202. The rack 270b is attached to the other document width restriction plate 202. When one document width restriction plate 202 is slid, the other document width restriction plate 202 is also slid by the rack-and-pinion 270 so as to move closer to or farther away from each other.

[0068] Reflective sensors 207 and 208 (second size detection means) are installed below rack 270a. The size of the document in the main scanning direction MS placed on document tray 201 can be detected based on a combination of ON / OFF signals (detection signals) from reflective sensors 207 and 208. For example, when an A4-sized document placed on document tray 201 is restricted by the 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 outputs of reflective sensors 207 and 208 are both OFF signals. In this case, the document placed on document tray 201 is determined to be a wide document. When an A5-sized document placed on document tray 201 is restricted by the 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 the A4 size. The output of reflective sensor 207 is an ON signal, and the output of reflective sensor 208 is 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-size document or business card placed on the document tray 201 is restricted by the 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 the reflective sensors 207 and 208 both become ON signals. In this case, the document placed on the document tray 201 is determined to be a narrow-width document.

[0069] The detecting means for detecting the position of rack 270a is not limited to reflective sensors 207 and 208. The detecting means for detecting the position of rack 270a may be, for example, a variable resistor whose resistance value changes in accordance with the movement of rack 270a. The width of the document placed on document tray 201 in the main scanning direction MS may be detected by detecting the resistance value of the variable resistor. In the second embodiment, the document reading start operation for starting reading of the document using the acquired size information is the same as in the first embodiment, and therefore a description thereof will be omitted.

[0070] According to the second embodiment, it is possible to control the document transport control and the timing of starting to read the document image according to the size information, so that it is possible to acquire image data with high accuracy. According to the second embodiment, it is possible to prevent the occurrence of image loss or blank space on the leading edge side of the read image. [Example]

[0071] A third embodiment will be described below. In the third embodiment, the same structures as those in the first embodiment are assigned the same reference numerals, and description thereof will be omitted. The printer 1001, image reading device 1005, control unit 160, controller 500, and document transport path 240 as the image forming apparatus in the third embodiment have the same structures as those in the first embodiment, and description thereof will be omitted. In the first and second embodiments, a method for setting an optimal timer value from the lead sensor 216 to the front document reading position 107 based on document size information has been described. However, instead of changing the timer value, the reading position of the front document reading unit 101 may be changed. In the third embodiment, the reading movement guide 110, the timing belt 151, and the document table motor 169 constitute a reading position moving means for moving the reading position of the front document reading unit 101.

[0072] FIG. 13 is an explanatory diagram of the movement of the transport locus and the front document reading position 107, which differ depending on the size of the document. FIG. 13(a) is a diagram showing a first transport locus 241 for a wide document such as an A4 size document. FIG. 13(b) is a diagram showing a second transport locus 242 for a narrow document such as an A6 size document or a business card. The distance traveled by the leading edge of a wide document from the detection position of the lead sensor 216 along the first transport locus 241 to the front document reading position 107 is different from the distance traveled by the leading edge of a narrow document from the detection position of the lead sensor 216 along the second transport locus 242 to the front document reading position 107. Therefore, when transporting a narrow document, the front document reading unit 101 is moved downstream from the front document reading position 107 (first position) to the front document reading position 107a (second position) by the difference between the distances of the first transport locus 241 and the second transport locus 242. As a result, the distance that the leading edge of the narrow original moves from the lead sensor 216 to the front document reading position 107a along the second transport locus 242 becomes the same as the distance that the leading edge of the wide original moves from the lead sensor 216 to the front document reading position 107 along the first transport locus 241. Here, the moving distance that the leading edge of the wide original moves from the detection position of the lead sensor 216 to the front document reading position 107 along the first transport locus 241 is defined as a first distance. The moving distance that the leading edge of the narrow original moves from the detection position of the lead sensor 216 to the front document reading position 107a along the second transport locus 242 is defined as a second distance. By moving the front document reading unit 101 from the front document reading position 107 (first position) to the front 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 front surface reading unit 101 is moved along the conveying direction CD according to the document size information without changing the timer value, thereby enabling image data to be acquired with high accuracy from the leading edge position of the document.

[0073] (Original reading start operation) 14 is a flowchart of the document reading start operation in Example 3. The CPU 164 as a control means executes the document reading start operation in accordance with a program stored in the ROM 165. In the document reading start operation in Example 3, the CPU 164 determines the front document reading position 107 of the front reading unit 101 based on size information of the document in the main scanning direction MS.

[0074] When a document is placed on document tray 201 and a job is started, CPU 164 determines whether document main scanning size acquisition unit 163 has acquired size information (S1301). Document main scanning size acquisition unit 163, which serves as a size information acquisition unit, may acquire size information input to CPU 164 via controller 500 from operation unit 506 provided in printer main body 1001A, as in the first embodiment. Alternatively, document main scanning size acquisition unit 163 may acquire size information based on a combination of detection results from reflective large size main scanning width sensor 205, medium size main scanning width sensor 206, and reflective sensors 207 and 208 provided in ADF 200, as in the second embodiment.

[0075] If size information has been acquired (YES in S1301), the CPU 164 determines the reading position based on the size information and moves the front side reading unit 101 to the determined reading position by the reading position moving means (110, 151, 169) (S1302). FIG. 15 is a cross-sectional view of the front side reading unit 101 positioned at the standby position WP. Before a job is started, the front side reading unit 101 is positioned at the standby position WP below the white reference member 108. For example, if the document is determined to be a wide document based on the size information, the front side document reading position 107 is determined as the reading position. The front side reading unit 101 is moved by the reading position moving means (110, 151, 169) by the movement distance for a wide document to the front side document reading position 107 located upstream below the front side reading opposing unit 218. On the other hand, if the document is determined to be a narrow document based on the size information, the front side document reading position 107a is determined as the reading position. The front surface reading unit 101 is moved by the reading position moving means (110, 151, 169) by the movement distance for a narrow original to the front surface original reading position 107a located below the front surface reading opposing unit 218 on the downstream side.

[0076] If the size information has not been acquired (NO in S1301), the CPU 164 moves the front side reading unit 101 to the temporary reading position by the reading position moving means (110, 151, 169) (S1303). In the third embodiment, the temporary reading position is set to the front side document reading position 107 for A4 size documents (wide documents), which are frequently used.

[0077] The CPU 164 determines whether the lead sensor 216 is turned ON (S1304). If the lead sensor 216 is not turned ON (NO in S1304), the CPU 164 waits for the lead sensor 216 to be turned ON by the original. If the lead sensor 216 is turned ON (YES in S1304), the CPU 164 sets a fixed timer value in the timer 171 (S1305). In the third embodiment, the fixed timer value is a pulse number obtained by converting the travel distance of a frequently used A4 size original (wide original) from the lead sensor 216 to the front side original reading position 107 along the first conveyance trajectory 241.

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

[0079] If it is determined that the front surface reading unit 101 has been moved to the confirmed reading position (YES in S1307), the front surface reading unit 101 may remain at the current front surface document reading position 107, and the CPU 164 proceeds to the process at S1331. The CPU 164 determines whether or not counting of the fixed timer value has been completed (S1331). If counting of the fixed timer value has not been completed (NO in S1331), the CPU 164 waits for counting of the fixed timer value to be completed. If counting of the fixed timer value has been completed (YES in S1331), the CPU 164 issues a reading start command to the front surface image reading control unit 172 to start reading the document (S1332), and ends 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), CPU 164 determines whether the leading edge of the document has reached judgment limit position 283 (S1321). If it is determined that the leading edge of the document has not reached judgment limit position 283 (NO in S1321), CPU 164 returns the process to S1306. If it is determined that the leading edge of the document has reached judgment limit position 283 (YES in S1321), CPU 164 determines whether the transport of the document has been stopped (S1322). If the transport of the document has not been stopped (NO in S1322), CPU 164 stops the rotation of document transport motor 170 and temporarily stops the transport of the document (S1323). CPU 164 returns the process to S1306. If the transport of the document has been stopped (YES in S1322), CPU 164 returns the process to S1306.

[0081] If it is determined in S1307 that the front surface reading unit 101 has not been moved to the confirmed reading position (NO in S1307), the reading position where the front surface reading unit 101 is currently located does not match the confirmed reading position. In this case, the CPU 164 moves the front surface reading unit 101 to the confirmed reading position by the reading position moving means (110, 151, 169) (S1311). For example, assume that the front surface reading unit 101 is currently located at the front surface original reading position 107 for a wide document. At this time, if the confirmed reading position determined based on the size information acquired in S1306 is the front surface original reading position 107a for a narrow document, the front surface reading unit 101 is moved downstream by the differential movement distance shown in FIG. 15 by the reading position moving means (110, 151, 169).

[0082] CPU 164 determines whether or not the transport of the document is temporarily stopped (S1312). If the transport of the document is temporarily stopped (YES in S1312), CPU 164 restarts the rotation of document transport motor 170 and restarts the transport of the document (S1313). CPU 164 proceeds to S1331. If the transport of the document is not temporarily stopped (NO in S1312), CPU 164 proceeds to S1331 without changing the process. CPU 164 determines whether or not the counting of the fixed timer value has been completed (S1331), and when the counting of the fixed timer value has been completed (YES in S1331), starts reading the document (S1332), and ends the document reading start operation.

[0083] According to the third embodiment, the reading position of the front surface reading unit 101 can be controlled according to the size information, so that the image data can be acquired with high accuracy. According to the third embodiment, the occurrence of missing images or blank spaces at the leading edge of the read image can be suppressed.

[0084] <Other> Although the first to third embodiments of the present invention have been described above, the present invention is not limited to the first to third embodiments. For example, in the first and second embodiments, a timer value is set according to size information to control the timing for starting reading of an image of a document. In the third embodiment, a reading position is moved according to size information. However, rather than performing only one of setting a timer value and moving the reading position, both may be performed in combination. Furthermore, while the first to third embodiments have been described using the front-side reading unit 101, the same can be applied to the back-side reading unit 230. Furthermore, while the transport trajectories of two types of document widths, wide and narrow, have been described, if the transport trajectories of documents of other widths, such as medium-width documents, are different, control suitable for the transport trajectory may be applied. [Explanation of symbols]

[0085] 163 Document main scanning size acquisition unit 101 Surface reading unit 164 CPUs 216 Reed Sensor 230 Back side reading unit 240 Document transport path 1005 Image reader

Claims

1. a size information acquiring unit that acquires size information about a size of the document in a width direction perpendicular to a conveying direction in which the document is conveyed; a document transport path along which the document is transported, the document transport path including a curved portion that is curved when viewed from the width direction; a reading means for reading an image of the document conveyed through the document conveying path; a document detection means for detecting the document transported through the document transport path; a control means for starting reading of 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 curved portion of the document transport path is configured by an inner guide portion that forms an inner portion of the curve and an outer guide portion that forms an outer portion of the curve, the inner guide portion includes a first region including a center of the document transport path in the width direction, and a second region that is located outside the first region in the width direction and protrudes toward the outer guide portion more than the first region, The image reading device according to claim 1, wherein the control means determines the predetermined time based on the size information acquired by the size information acquisition means.

2. A timer is provided, 2. The image reading apparatus according to claim 1, wherein the control means sets the timer to the predetermined time period determined based on the size information after the document is detected by the document detection means.

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

4. The image reading device according to claim 3, characterized in that when 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 timer to the predetermined time determined based on the size information.

5. 5. The image reading apparatus according to claim 1, wherein the size information is set by a user via an operation unit.

6. a first size detection means for detecting the size of the document transported through the document transport path; 6. The image reading apparatus according to claim 1, wherein the size information acquiring unit acquires the size information based on a detection signal from the first size detecting unit.

7. a document tray on which the document is placed; a second size detection means for detecting the size of the document placed on the document tray; Equipped with 7. The image reading apparatus according to claim 1, wherein the size information acquiring unit acquires the size information based on a detection signal from the second size detecting unit.

8. the curved portion is formed so that the document of a first width passes along a first transport path and the document of a second width passes along a second transport path, An image reading device as described in any one of claims 1 to 7, characterized in that the control means determines the specified time to be a first time when the size information is the first width, and determines the specified time to be a second time when the size information is the second width.

9. the first width is greater than the second width; 9. The image reading apparatus according to claim 8, wherein the first time period is longer than the second time period.

10. 10. The image reading device according to claim 8, wherein the curved portion is formed so that the second transport path is on the inside of the first transport path.

11. a size information acquiring unit that acquires size information about a size of the document in a width direction perpendicular to a conveying direction in which the document is conveyed; a document transport path along which the document is transported, the document transport path including a curved portion that is curved when viewed from the width direction; a reading means for reading an image of the document conveyed through the document conveying path; a document detection means for detecting the document transported through the document transport path; a control means for starting reading of the image of the document by the reading means after a predetermined time has elapsed since the document detection means detected the document; An image reading device comprising: the curved portion of the document transport path is configured by an inner guide portion that forms an inner portion of the curve and an outer guide portion that forms an outer portion of the curve, the inner guide portion includes a first region including a center of the document transport path in the width direction, and a second region that is located outside the first region in the width direction and protrudes toward the outer guide portion more than the first region, The image reading device further includes a reading position moving unit that moves the reading unit along the transport direction based on the size information acquired by the size information acquiring unit; An image reading device comprising:

12. the curved portion is formed so that the document of a first width passes along a first transport path and the document of a second width passes along a second transport path, 12. The image reading device according to claim 11, wherein the control means moves the reading means to a first position when the size information is the first width, and moves the reading means to a second position when the size information is the second width.

13. An image reading device as described in claim 12, characterized in that a first distance from the detection position of the document detection means to the first position through the first transport locus is the same as a second distance from the detection position of the document detection means to the second position through the second transport locus.

14. 14. The image reading apparatus according to claim 11, wherein the size information is set by a user via an operation unit.

15. a first size detection means for detecting the size of the document transported through the document transport path; 15. The image reading apparatus according to claim 11, wherein the size information acquiring unit acquires the size information based on a detection signal from the first size detecting unit.

16. a document tray on which the document is placed; a second size detection means for detecting the size of the document placed on the document tray; Equipped with 16. The image reading apparatus according to claim 11, wherein the size information acquiring unit acquires the size information based on a detection signal from the second size detecting unit.

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 image reading device; An image forming apparatus comprising:

18. An image forming apparatus body, 18. The image forming apparatus according to claim 17, wherein the control means is provided in the main body of the image forming apparatus.

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