JP6365439B2 - Document reading apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a document reading device that reads an image of a document while conveying the document, and an image forming apparatus.

  Some document reading apparatuses employ a method in which reading units are provided on both sides of a document, and both sides of the conveyed document are simultaneously read. In such a document reading apparatus, generally, a CIS (Contact Image Sensor) is used as a reading unit for reading one side of a document, and a CCD (Charge coupled Device) is used as a reading unit for reading the other side of the document. There are many.

  On the other hand, in the document reading apparatus described in Patent Document 1, a common pattern formed at the same position of each document is detected by comparing images of a plurality of scanned documents, and the common pattern is excluded from the document image. Then, based on the image after the exclusion, it is determined whether the document is blank or non-blank, and thereby the blank of the document is accurately determined.

JP, 2006-160885, A

  By the way, in the document reading apparatus that reads both sides of the document by the respective reading units as described above, document edge detection that detects the leading edge and the trailing edge of the document upstream of the reading unit in the document conveying direction for each reading unit. The document reading period is set based on the detection time of the leading edge and the trailing edge of the document by the document edge detection unit.

  However, if a perforation such as a punch hole is formed on the rear edge side of the document, the inner edge of the perforation is mistaken for the rear edge of the document and is erroneously detected by the document edge detection unit. There is a case where a deviation occurs in the time point and the document reading period is set short. If erroneous detection occurs in only one of the document edge detection units, only the reading period of the document by one reading unit is set to be short. As a result, a difference occurs in each reading period by each reading unit. There has been a problem that the lengths of the images on both sides of the document read by the reading unit do not match.

  Further, the technique of excluding a common pattern from an image of a document as in Patent Document 1 applies image processing. However, when the reading period of the document is shortened as described above, perforation itself is not performed. It is not read and therefore cannot be handled by image processing.

  The present invention has been made in view of the above circumstances, and the lengths of the images on both sides of the document read by each reading unit are the same even if punched holes or the like are formed on the trailing edge side of the document. An object of the present invention is to provide an original reading apparatus and an image forming apparatus that can be used.

A document reading apparatus according to one aspect of the present invention includes a first reading unit that reads an image on one side of a document that is transported along a transport path, and an image on the other side of the document that is transported along the transport path. From the second reading unit, the first document end detecting unit that is disposed upstream of the first reading unit in the document transport direction and detects the leading edge and the trailing edge of the document, and the second reading unit. Is also arranged upstream of the document conveyance direction, and detects a leading edge and a trailing edge of the document, and a detection time of the leading edge and the trailing edge based on a detection output of the first document edge detection unit. The document reading period by the first reading unit is set based on these detection time points, and the leading edge and trailing edge detection time points are determined based on the detection output of the second document edge detecting unit. Based on these detection points, the second reading unit A control unit that sets a reading period of the document, and the first document edge detection unit and the second document edge detection unit are arranged at positions different from each other in a direction orthogonal to the document conveyance direction. The trailing edge is detected, and the control unit determines a detection point of the trailing edge based on a detection output of the second document edge detection unit, and the second document edge is detected until a predetermined time elapses from the detection point. When the trailing edge detection time point is determined again based on the detection output of the detection unit, the trailing edge detection time point determined again is used for setting the document reading period by the second reading unit . A reading unit is disposed upstream of the first reading unit in the document conveyance direction, and the control unit sets the reading period of the document by the second reading unit, and then detects the first document edge detection. Based on the detection output of the rear part When the detection time of the trailing edge is determined again based on the detection output of the first document edge detection unit before the specified time elapses from the detection time point, the first reading unit determines the output time point. The document reading apparatus sets a document reading period to the same length as the document reading period by the second reading unit .

  An image forming apparatus according to an aspect of the present invention is an image forming apparatus including the document reading device according to the present invention and an image forming unit that records an image of the document read by the document reading device on a recording sheet. is there.

  According to the present invention, even when a punch hole or the like is formed on the rear end side of the document, the lengths of the images on both sides of the document read by each reading unit can be matched.

1 is a cross-sectional view illustrating an image forming apparatus including a document reading apparatus according to a first embodiment of the present invention. 1 is a cross-sectional view showing a document reading device. It is sectional drawing which shows the 2nd reading part in a document reading device. (A), (b), and (c) are a timing chart showing a document reading operation by the second reading unit, and a timing chart showing a document reading operation by the first reading unit. (A), (b), and (c) are a timing chart showing an original reading operation by the second reading unit, and a timing chart showing an original reading operation by the first reading unit. . 6 is a flowchart illustrating a reading process by the document reading apparatus according to the first embodiment. 10 is a flowchart illustrating a reading process by the document reading apparatus according to the second embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an image forming apparatus to which the document reading apparatus according to the first embodiment of the present invention is applied. The image forming apparatus 1 is a multifunction machine having a plurality of functions such as a copy function, a printer function, a scanner function, and a facsimile function. The image forming apparatus 1 includes an operation unit 47, an image forming unit 120, a fixing unit 13, a paper feeding unit 14, a document reading unit (ISU; Image scanner unit) 5 according to the first embodiment, and the like. Composed.

  The operation unit 47 receives instructions such as an image forming operation execution instruction and an image reading operation execution instruction from the user regarding various operations and processes that can be executed by the image forming apparatus 1.

  When the image reading operation is performed, the document reading device 5 optically reads an image of the document and generates image data.

  When performing the image forming operation, the image forming unit 120 is stored in the image data generated by the image reading operation described above, the image data received from a user terminal device such as a computer or smartphone connected to the network, or the built-in HDD. A toner image is formed on a recording sheet P as a recording medium fed from the sheet feeding unit 14 based on the image data and the like.

  The image forming units 12M, 12C, 12Y, and 12Bk of the image forming unit 120 expose the surface of the photoconductive drum 122, the charging device that uniformly charges the surface of the photoconductive drum 122, and the surface of the photoconductive drum 122. An exposure device (LSU; Laser scanning units) 123 that forms an electrostatic latent image on the surface, a developing device that develops the electrostatic latent image on the surface of the photosensitive drum 122 into a toner image, and a primary transfer roller 126 Each has.

  When performing color printing, in the magenta image forming unit 12M, the cyan image forming unit 12C, the yellow image forming unit 12Y, and the black image forming unit 12Bk of the image forming unit 120, the photosensitive drum 122 is used. The surface of the photosensitive drum 122 is uniformly charged and exposed to form an electrostatic latent image corresponding to the color component image on the surface, and the electrostatic latent image on the surface of the photosensitive drum 122 is converted into the toner of the color component. The toner image is developed to form a toner image on the photosensitive drum 122, and the toner image is primarily transferred by the primary transfer roller 126 onto the intermediate transfer belt 125 stretched between the driving roller 125A and the driven roller 125B. .

  The toner images of the respective colors transferred onto the intermediate transfer belt 125 are superimposed on the intermediate transfer belt 125 by adjusting the transfer time point, and become a color toner image. The secondary transfer roller 210 records the color toner image formed on the surface of the intermediate transfer belt 125 from the paper supply unit 14 through the conveyance path 190 at the nip portion N between the secondary transfer roller 210 and the intermediate transfer belt 125. Secondary transfer is performed on the paper P. Thereafter, the fixing unit 13 fixes the toner image on the recording paper P to the recording paper P by thermocompression bonding. The recording paper P on which the color image has been formed after completion of the fixing process is discharged to a discharge tray 151.

  FIG. 2 is a sectional view showing the document reading apparatus according to the first embodiment of the present invention. As shown in FIG. 2, the document reading device 5 includes a document feeding unit 6, a first reading unit 30, and a second reading unit 40 built in the document feeding unit 6.

  The document feeder 6 pulls out the documents MS placed on the document feed tray 21 one by one, conveys the documents MS along the contact glass (not shown) of the second reading unit 40, and then continues. The original MS is conveyed through the first contact glass 31 of the first reading unit 30, and the original MS is further discharged to the original discharge tray 27. When the document MS is conveyed, the image on the back surface of the document MS is read by the second reading unit 40, and the image on the front surface of the document MS is read by the first reading unit 30.

  The document feeding unit 6 is provided on the upper surface of the first reading unit 30 so as to be opened and closed by a hinge or the like, and the document feeding the document MS placed on the second contact glass 32 of the first reading unit 30. Functions as a holding cover. In this case, the first reading unit 30 reads an image on one side of the document MS placed on the second contact glass 32.

  The document feeder 6 includes a document feed tray 21 on which a document MS is placed, a pickup roller 22, a plurality of transport roller pairs 24, a discharge roller pair 25, and a second reading unit arranged along a document transport path 23. A shading roller 26, a document discharge tray 27, a first document edge sensor 28, a second document edge sensor 29, and the like disposed to face the unit 40 are provided.

  In the document feeding unit 6, the document MS is pulled out from the document feed tray 21 by the pickup roller 22, and the document MS is transported along the document transport path 23 by the plurality of transport roller pairs 24 and the shading roller 26, and the first contact is made. The original MS passes through the glass 31 and is discharged to the original discharge tray 27 by the discharge roller pair 25.

  The second document edge sensor 29 detects the leading edge and the trailing edge of the document MS at a detection position upstream of the second reading unit 40 in the conveyance direction of the document MS. Therefore, after the leading edge of the document MS is detected by the second document edge sensor 29, the document MS reaches the reading position of the second reading unit 40, and the trailing edge of the document MS is detected by the second document edge sensor 29. Later, the document MS moves away from the reading position of the second reading unit 40. The reading period T2 of the second reading unit 40 is set according to the detection time of the leading edge and the trailing edge of the document MS by the second document edge sensor 29. In this reading period T2, the back surface of the document MS is set by the second reading unit 40. Are read.

  The first document edge sensor 28 detects the leading edge and the trailing edge of the document MS at a detection position upstream of the first contact glass 31 of the first reading unit 30 in the conveyance direction of the document MS. Therefore, after the leading edge of the document MS is detected by the first document edge sensor 28, the document MS reaches the reading position (first contact glass 31) of the first reading unit 30, and the document MS is detected by the first document edge sensor 28. After the trailing edge is detected, the document MS moves away from the reading position of the first reading unit 30. The reading period T1 of the first reading unit 30 is set according to the detection time of the leading edge and the trailing edge of the document MS by the first document edge sensor 28. In this reading period T1, the surface of the document MS is read by the first reading unit 30. Are read.

  The first document edge sensor 28 and the second document edge sensor 29 are, for example, a reflection type light sensor or a transmission type light sensor formed by combining a light emitting element and a light receiving element.

  The first reading unit 30 includes a first contact glass 31, a second contact glass 32, a white reference plate 33, a carriage 34, an optical system unit 35, a condenser lens 36, a CCD (Charge Coupled Device) sensor 37, and the like. Yes.

  The carriage 34 includes a line-shaped LED (Light Emitting Diode) array 34 </ b> A that irradiates light on the document MS and a mirror 34 </ b> C that reflects light reflected by the document MS.

  The optical system unit 35 includes a mirror 35A and a mirror 35B. The mirror 35A receives the light reflected by the mirror 34C of the carriage 34 and further changes the direction downward substantially vertically. The mirror 35B further changes the direction of the light reflected by the mirror 35A in a substantially horizontal direction and guides it to the CCD sensor 37 through the condenser lens 36.

  The carriage 34 and the optical system unit 35 are reciprocated in the sub-scanning direction orthogonal to the main scanning direction along the rails by a mechanism (not shown).

  Here, when the surface of the document MS is read by the first reading unit 30 while the document MS is conveyed by the document feeding unit 6, the carriage 34 and the optical system unit 35 are positioned as shown in FIG. In this state, in the document feeder 6, the document MS is pulled out from the document feed tray 21, passes over the first contact glass 31, and is further discharged to the document discharge tray 27.

  At this time, in the first reading unit 30, the light of the LED array 34 </ b> A of the carriage 34 is irradiated on the surface of the document MS passing on the first contact glass 31, and the light reflected on the surface of the document MS is irradiated on the carriage 34. Reflected by the mirror 34C. Further, this light is reflected by the mirror 35 </ b> A and the mirror 35 </ b> B of the optical system unit 35 and enters the CCD sensor 37 through the condenser lens 36. The condenser lens 36 forms an image of the surface of the document MS on the light receiving surface of the CCD sensor 37, and the CCD sensor 37 reads the image of the surface of the document MS.

  When reading the document MS placed on the second contact glass 32, the carriage 34 and the optical system unit 35 are moved in the sub-scanning direction while maintaining a predetermined speed relationship, and the light of the LED array 34A is emitted. The original MS on the second contact glass 32 is irradiated, and the light reflected by the original MS is sequentially reflected by the mirror 34C, the mirror 35A, and the mirror 35B, and is incident on the CCD sensor 37 through the condenser lens 36. 37 reads the image of the document MS.

  On the other hand, the second reading unit 40 is called a contact image sensor (CIS (Contact Image Sensor)), and the image on the back surface of the document MS conveyed along the surface of the contact glass is displayed as the contact. Read in the main scanning direction through glass. In the second reading unit 40, for example, light from an LED (Light Emitting Diode) is irradiated on the back surface of the document MS via a contact glass, and reflected light from the back surface of the document MS is used as a CMOS (Complementary Metal Oxide Semiconductor) image sensor. And the image on the surface of the document MS is read by the CMOS image sensor.

  The CCD sensor 37 of the first reading unit 30 and the CMOS image sensor of the second reading unit 40 convert the received reflected light into an electric signal and output an image signal indicating an image of the document MS. This image signal is D / A converted into image data, and this image data is further subjected to various image processing such as shading correction, gamma correction, chromatic aberration correction, MTF (Modulation Transfer Function) correction, and scanner color correction. The

  The first reading unit 30 is an example of a first reading unit in the claims, and the second reading unit 40 is an example of a second reading unit in the claims. The first document edge sensor 28 is an example of a first document edge detection unit in the appended claims, and the second document edge sensor 29 is an example of a second document edge detection unit in the claims.

  Next, a configuration related to the control of the image forming apparatus 1 will be described. FIG. 3 is a functional block diagram showing the main internal configuration of the image forming apparatus 1. 3, the image forming apparatus 1 includes a control unit 60, a document reading device 5, a fixing unit 13, an image forming unit 120, an operation unit 47, an image memory 62, an HDD 63, a facsimile communication unit 64, a network interface unit 66, and the like. It is prepared for. In addition, the same code | symbol is attached | subjected to the same thing as the component demonstrated using FIG.

  The control unit 60 includes a CPU (Central Processing Unit), a RAM, a ROM, a dedicated hardware circuit, and the like. The control unit 60 includes a main control unit 61.

  The main control unit 61 is connected to the control unit 60, the document reading device 5, the fixing unit 13, the image forming unit 120, the operation unit 47, the image memory 62, the HDD 63, the facsimile communication unit 64, the network interface unit 66, and the like. The overall control of the image forming apparatus 1 is controlled.

  The document reading device 5 cooperates with the document feeding unit 6, the first reading unit 30, the second reading unit 40, the first document end sensor 28, the second document end sensor 29, and the main control unit 61 of the image forming apparatus 1. A reading control unit 51 that controls the document reading device 5 while operating is provided. The reading control unit 51 is an example of a control unit in the claims.

  In such a configuration, the user can select and operate any one of the facsimile communication function, the copy function, the printer function, and the scanner function by operating the operation unit 47. For example, when the start of copying of one side (front side) of the document MS is instructed by the operation of the operation unit 47, the main control unit 61 causes the document feeding unit 6 to convey the document MS and causes the first reading unit 30 to The image on the surface of the document MS is read, and the image on the surface of the document MS is printed on one side of the recording paper by the image forming unit 120 or the like. When the start of double-sided copying of the document MS is instructed by the operation of the operation unit 47, the main control unit 61 conveys the document MS by the document feeding unit 6 and the second reading unit 40 causes the document MS to be copied. The image on the back side is read, the image on the front side of the document MS is subsequently read by the first reading unit 30, and the images on both sides of the document MS are printed on both sides of the recording paper by the image forming unit 120 or the like.

  As shown in FIG. 4A, the first document edge sensor 28 and the second document edge sensor 29 are arranged at different positions in the main scanning direction orthogonal to the conveyance direction (sub-scanning direction) of the document MS. The detection positions m1 and m2 for detecting the leading edge and the trailing edge of the document MS are also different from each other. For this reason, when a perforation h such as a punch hole is formed on the rear end side of the document MS, the perforation h on the rear end side of the document MS passes through the detection position m2 of the second document end sensor 29 and passes through the second position. The perforation h is detected by the document end sensor 29, while the perforation h on the rear end side of the document MS deviates from the detection position m1 of the first document end sensor 28, and the first document end sensor 28 does not detect the perforation h. Sometimes. In this case, the second document edge sensor 29 detects the inner peripheral edge of the perforation h on the trailing edge side of the document MS and the trailing edge of the document MS, and the first document edge sensor 28 detects only the trailing edge of the document MS. Is done.

  4B and 4C show the detection signal V2 of the second document edge sensor 29 that detects the inner peripheral edge of the perforation h on the trailing edge side of the document MS and the trailing edge of the document MS (FIG. 4B). ), The detection signal V1 of the first document edge sensor 28 that detects only the trailing edge of the document MS and (FIG. 4C) are compared. The detection signal V2 of the second document edge sensor 29 is turned on at the detection time tv21 of the leading edge of the document MS, and is turned off after being turned off once at the detection time tv2a according to the inner periphery of the perforation h on the rear end side of the document MS. Thereafter, it is turned off again at the detection time tv22 at the trailing edge of the document MS. The detection signal V1 of the first document edge sensor 28 is turned on at the detection time tv11 of the leading edge of the document MS and turned off at the detection time tv12 of the trailing edge of the document MS.

  Conventionally, the reading periods T1 and T2 ′ of the original MS corresponding to the time points tv11 and tv21 when the detection signals V1 and V2 are turned on and the first time points tv12 and tv2a when the detection signals V1 and V2 are turned off are set. Therefore, there is a difference between the reading period T1 of the image on the front side of the document MS and the reading period T2 ′ of the image on the back side of the document MS, and the length of the image on the front side and the length of the image on the back side are different. There has occurred. Specifically, the image of the perforation h is included in the image on the front surface of the document MS, and the image of the perforation h is not included in the image on the back surface of the document MS.

  5A, 5B, and 5C, the perforation h on the rear end side of the document MS deviates from the detection position m2 of the second document end sensor 29, and the second document end sensor 29 is removed. , The perforation h on the rear end side of the document MS passes through the detection position m1 of the first document end sensor 28 and the first document end sensor 28 detects the perforation h. The same problem arises due to a difference between the reading period T1 'for the front surface image and the reading period T2 for the back surface image of the document MS.

  Therefore, in the present embodiment, even if the perforation h is formed on the rear end side of the document MS, the reading period T1 of the image on the front surface of the document MS and the reading period T2 of the image on the back surface of the document MS are matched, The length of the image on the front surface of the document MS read by the first reading unit 30 and the length of the image on the back surface of the document MS read by the second reading unit 40 are matched.

  Next, a processing procedure for matching the reading periods T1 and T2 will be described with reference to the flowchart of FIG.

  First, the reading control unit 51 drives and controls the document feeding unit 6 to pull out and transport the document MS from the document feeding tray 21. The document MS is detected by the second document edge sensor 29, the reading position by the second reading unit 40, the detection position by the first document edge sensor 28, and the reading position by the first reading unit 30 (of the first contact glass 31). Position) sequentially, and is discharged to the document discharge tray 27.

  When the document MS is conveyed, the reading control unit 51 waits for the detection signal V2 of the second document end sensor 29 to be turned on (step S11 “No”), and the document MS is detected by the second document end sensor 29. When the leading edge of the document MS is detected and the detection signal V2 of the second document edge sensor 29 is turned on ("Yes" in step S11), the second reading unit 40 corresponding to the leading edge detection time tv21 of the document MS A reading start time point ts21 is set (step S12), and the synchronization signal Vsy2 indicating the reading period T2 is turned on from the reading start time point ts21 to start reading the document MS by the second reading unit 40 (step S13).

  Similarly, the reading control unit 51 waits for the detection signal V1 of the first document edge sensor 28 to be turned on ("No" in step S14), and the first document edge sensor 28 detects the leading edge of the document MS. When the detection signal V1 of the first document edge sensor 28 is turned on (step S14 “Yes”), the reading start time ts11 of the document MS by the first reading unit 30 corresponding to the detection time tv11 of the leading edge of the document MS. Is set (step S15), the synchronization signal Vsy1 indicating the reading period T1 is turned on from the reading start time ts11, and the reading of the document MS by the first reading unit 30 is started (step S16).

  For example, as shown in FIGS. 4A and 4B, a predetermined time Δtt is added to the detection time tv21 of the leading edge of the document MS by the second document edge sensor 29, and the reading start time ts2 by the second reading unit 40 is set. 4A and 4C, a predetermined time Δtt is added to the detection time tv11 of the leading edge of the document MS by the first document edge sensor 28, and the reading start time by the first reading unit 30 is set. Set ts11.

  Subsequently, the reading control unit 51 waits for the detection signal V2 of the second document edge sensor 29 to be turned off (“No” in step S17), and the detection signal V2 of the second document edge sensor 29 is turned off. When this happens (step S17 “Yes”), for example, the built-in timer starts counting from the time of turning off, and the detection signal V2 of the second document edge sensor 29 is turned on until the time counting exceeds the specified time ty. Then, it is monitored whether or not it is turned off again (steps S18 and S19).

  For example, it is assumed that the measured time exceeds the specified time ty without turning off again after the detection signal V2 of the second document edge sensor 29 is turned on (step S18 “No”, step S19 “Yes”). The reading control unit 51 regards the time when the detection signal V2 of the second document edge sensor 29 is first turned off in step S17 as the detection time tv22 of the trailing edge of the document MS by the second document edge sensor 29. A reading end time ts22 of the document MS by the second reading unit 40 corresponding to the detection time tv22 of the trailing edge of the document MS is set (step S20), and the synchronization signal Vsy2 indicating the reading period T2 is turned off at the reading end time ts22. Thus, the reading of the document MS by the second reading unit 40 is terminated (step S21).

  Here, as shown in FIG. 5 (a), the perforation h on the rear end side of the document MS deviates from the detection position m 2 of the second document end sensor 29, and the second document end sensor 29 detects the rear end side of the document MS. In the state where the punching h is not detected, the detection signal V2 of the second document edge sensor 29 is turned off at the detection time tv22 of the trailing edge of the document MS by the second document edge sensor 29 as shown in FIG. After that, it will not turn on and off. Therefore, the time when the detection signal V2 of the second document edge sensor 29 is first turned off is regarded as the detection time tv22 of the trailing edge of the document MS by the second document edge sensor 29.

  Then, a predetermined time Δtt is added to the detection time point tv22 of the trailing edge of the document MS by the second document edge sensor 29 to set the reading end time point ts22 by the second reading unit 40, and from the reading start time point ts21 to the reading end time point ts22. The reading period T2 of the back side of the document MS by the second reading unit 40 is defined as above, and the image on the back side of the document MS is read by the second reading unit 40 in the reading period T2.

  If the detection signal V2 of the second document edge sensor 29 is turned on and then turned off again before the measured time exceeds the specified time ty (step S18 “Yes”, step S19 “No”), reading is performed. The control unit 51 regards the time when the detection signal V2 is turned off again as the detection time tv22 of the trailing edge of the document MS by the second document edge sensor 29, and sets the detection time tv22 of the trailing edge of the document MS. The corresponding reading end time ts22 of the document MS by the second reading unit 40 is set (step S22), the synchronization signal Vsy2 indicating the reading period T2 is turned off at the reading end time ts22, and the document MS by the second reading unit 40 is turned off. Is finished (step S21).

  Here, as shown in FIG. 4A, the perforation h on the rear end side of the document MS passes through the detection position m2 of the second document end sensor 29, and the second document end sensor 29 causes the rear end side of the document MS to be on the rear end side. In the state in which the perforation h is detected, as shown in FIG. 4B, the detection signal V2 of the second document end sensor 29 is temporarily detected at the detection time tv2a according to the inner peripheral edge of the perforation h on the rear end side of the document MS. After being turned off, it is turned on, and then turned off again at the detection time tv22 of the trailing edge of the document MS.

  Accordingly, the detection signal V2 of the second document edge sensor 29 is turned off before the detection of the trailing edge of the document MS by the second document edge sensor 29, and this off time is the detection time of the trailing edge of the document MS. Does not correspond to tv22. However, since the perforation h is formed in a range of a certain width (for example, 20 to 30 mm) from the rear end of the document MS and the document MS is conveyed at a constant speed, the perforation h is formed on the rear end side of the document MS. In this case, the detection signal V2 of the second document edge sensor 29 is turned off again after a preset specified time ty has elapsed from the time point tv2a once turned off.

  Therefore, the detection signal V2 of the second document edge sensor 29 is temporarily turned off (step S17 “Yes”), and the detection is performed before the specified time ty has elapsed from the detection time tv2a of the off (step S19 “No”). When the signal V2 is turned on and turned off again (step S18 “Yes”), the time point when the signal V2 is turned off again is regarded as the detection time point tv22 of the trailing edge of the document MS by the second document edge sensor 29. Thus, the reading end time ts22 of the document MS by the second reading unit 40 corresponding to the detection time tv22 is set (step S22).

  Then, the period from the reading start time ts21 to the reading end time ts22 shown in FIG. 4B is defined as a reading period T2 of the back side of the document MS by the second reading unit 40. In the reading period T2, the second reading unit 40 causes the document MS to be read. The back side image is read.

As described above, the detection signal V2 of the second document edge sensor 29 is temporarily turned off ("Yes" in step S17), and before the specified time ty has elapsed from the detection time tv2a of the off (step S19 "No" )), When the detection signal V2 is turned on and turned off again (step S18 “Yes”), the reading control unit 51 first turns on the detection signal V2 of the second document end sensor 29 ( The elapsed time from the time when the detection signal V2 is turned off again (step S18 “Yes”) to one of the predetermined elapsed times for each standard paper size is determined from “Yes” in step S11). Only in the case of coincidence, the processing of step S22 and step S21 may be performed.

  In this case, it is assumed that the reading control unit 51 stores the predetermined elapsed time for each standard sheet size (A4, B5, B4, etc.). This elapsed time is detected when the second document edge sensor 29 detects the leading edge of the document MS and the trailing edge when the document MS having a standard paper size is conveyed by the document feeder 6. This is the time required for each paper size to be completed. In addition, the reading control unit 51 starts counting from the time when the detection signal V2 of the second document edge sensor 29 is first turned on by the timer (“Yes” in step S11), and the detection signal V2 is returned to the above-described time. The elapsed time until the point of turning off (step S18 “Yes”) is counted.

  In addition, the reading control unit 51 starts from the time when the detection signal V2 of the second document edge sensor 29 is first turned on (“Yes” in step S11), and when the detection signal V2 is turned off again (“step S18”). If it is determined that the elapsed time until “Yes”) does not coincide with any of the predetermined elapsed times for each standard paper size, the processing of step S20 and step S21 is performed.

  As a result, the process of step S22 is performed only when the conveyed document MS is a standard paper size, and therefore the detection of the off-state when the detection signal V2 is turned off again as described above. Thus, it is possible to improve the accuracy of showing the original trailing edge of the document MS.

  Next, the reading control unit 51 waits for the detection signal V1 of the first document edge sensor 28 to be turned off ("No" in step S23), and when the detection signal V1 of the first document edge sensor 28 is turned off (step S23). Step S23 “Yes”), whether the time is started from the time point of the off time, and the detection signal V1 of the first document edge sensor 28 is turned on again until the timed time exceeds the specified time ty. Whether or not is monitored (steps S24 and S25).

  For example, if the timing signal exceeds the specified time ty without the detection signal V1 of the first document edge sensor 28 being turned on / off (step S24 “No”, step S25 “Yes”), the reading control unit 51 performs step S23. At this point, the time when the detection signal V1 of the first document edge sensor 28 is first turned off is regarded as the detection time tv12 of the trailing edge of the document MS by the first document edge sensor 28, and the detection time of the trailing edge of the document MS. The reading end point ts12 of the document MS by the first reading unit 30 corresponding to tv12 is set (step S26), the synchronization signal Vsy1 indicating the reading period T1 is turned off at the reading end point ts12, and the first reading unit 30 The reading of the document MS is terminated (step S27).

  As shown in FIG. 4A, the perforation h on the rear end side of the document MS deviates from the detection position m1 of the first document end sensor 28, and the first document end sensor 28 forms the perforation h on the rear end side of the document MS. In the undetected state, as shown in FIG. 4C, after the detection signal V1 of the first document edge sensor 28 is turned off at the detection time tv12 of the trailing edge of the document MS by the first document edge sensor 28, It will never turn on or off. Therefore, the time point when the detection signal V1 of the first document edge sensor 28 is first turned off is regarded as the detection time point tv12 of the trailing edge of the document MS by the first document edge sensor 28.

  Then, a predetermined time Δtt is added to the detection time point tv12 of the trailing edge of the document MS by the first document edge sensor 28 to set the reading end time point ts12 by the first reading unit 30, and from the reading start time point ts11 to the reading end time point ts12. The period until the reading period T2 of the back side of the document MS by the first reading unit 30 is read, and the image on the back side of the document MS is read by the first reading unit 30 in the reading period T2.

  Accordingly, the rear end of the document MS by the second document end sensor 29 is determined regardless of whether or not the second document end sensor 29 has detected the perforation h on the rear end side of the document MS by the processing in steps S11 to S22. Is accurately identified, and the reading period T2 on the back side of the document MS is accurately set. If the first document edge sensor 28 does not detect the perforation h on the trailing edge side of the document MS, the first document edge sensor 28 detects the trailing edge of the document MS through the processes in steps S23 to S27. Are accurately identified, and the reading period T1 of the surface of the document MS is accurately set. For this reason, the reading period T1 and the reading period T2 coincide, and the length of the image on the front surface of the document MS read by the first reading unit 30 and the length of the image on the back surface of the document MS read by the second reading unit 40 Also agree.

  On the other hand, if the detection signal V1 of the first document edge sensor 28 is turned on before the time count exceeds the specified time ty (step S24 “Yes”, step S25 “No”), the reading control unit 51 performs step The time when the reading period T2 of the back side of the original MS by the second reading unit 40 is added to the reading start time ts11 of the original MS by the first reading unit 30 set in S15 is the time when the original MS of the original MS by the first reading unit 30 is added. The reading end time ts12 is obtained and set (step S28), the synchronization signal Vsy1 indicating the reading period T1 is turned off at the reading end time ts12, and the reading of the document MS by the first reading unit 30 is ended (step S27). .

  As shown in FIG. 5A, the perforation h on the rear end side of the document MS passes through the detection position m1 of the first document end sensor 28, and the first document end sensor 28 forms the perforation h on the rear end side of the document MS. In the detected state, as shown in FIG. 5C, the detection signal V1 of the first document edge sensor 28 is temporarily turned off at the detection time tv1a according to the inner peripheral edge of the perforation h on the rear end side of the document MS. After that, it is turned on, and then turned off again at the detection time tv12 of the trailing edge of the document MS. Accordingly, the detection signal V1 of the first document edge sensor 28 is turned off before the detection of the trailing edge of the document MS by the first document edge sensor 28, and the time point of this off is the detection time of the trailing edge of the document MS. It does not correspond to tv12, and this off time point cannot be used for setting the reading period.

  However, the reading of the second reading unit 40 that reads the back surface of the document MS is performed regardless of whether or not the second document edge sensor 29 has detected the perforation h on the trailing edge side of the document MS by the processing in steps S11 to S22. The period T2 is accurately set. Further, since the length of the document MS is the same on the front surface and the back surface of the document MS, the reading period T1 on the front surface of the document MS may be set equal to the reading period T2 on the back surface of the document MS.

  For this reason, as shown in FIG. 4C, the first reading unit 30 indicates a time point when the reading period T2 of the second reading unit 40 is added to the reading start time point ts11 of the surface of the document MS by the first reading unit 30. The reading period T1 of the first reading unit 30 from the reading start time ts11 to the reading end time ts12 is set as the reading end time ts12 of the original MS.

  In this case, since the reading period T1 is set equal to the reading period T2, the length of the image on the front surface of the document MS read by the first reading unit 30 and the back surface of the document MS read by the second reading unit 40 are set. The image lengths match.

Thus, in the first embodiment, the perforation h on the rear end side of the document MS passes through the detection position m2 of the second document end sensor 29, and the perforation h on the rear end side of the document MS is formed by the second document end sensor 29. If detected, the detection signal V2 of the second document edge sensor 29 is temporarily turned off, and the detection signal V2 is turned on before the specified time ty elapses from the off detection time tv2a, and further the detection signal is detected. V2 since is turned off again, the time this was again turned off is regarded as the second document-original edge sensor 29 is detected at the time tv22 of the trailing edge of the document MS, the back side of the document MS by the second reading unit 40 A reading period T2 is set. Accordingly, the reading period T1 of the image on the front surface of the document MS and the reading period T2 of the image on the back surface of the document MS are matched, and the length of the image on the surface of the document MS read by the first reading unit 30 is set to the second. The lengths of the images on the back side of the document MS read by the reading unit 40 can be matched.

Further, when the perforation h on the rear end side of the document MS passes through the detection position m1 of the first document end sensor 28, and the perforation h on the rear end side of the document MS is detected by the first document end sensor 28, The time when the reading period T2 of the second reading unit 40 is added to the reading start time ts11 of the surface of the original MS by the first reading unit 30 is obtained and set as the end time ts12 of the reading of the original MS by the first reading unit 30. ing. Therefore, the reading period T1 is set equal to the reading period T2, and the length of the image on the front surface of the document MS read by the first reading unit 30 and the length of the image on the back surface of the document MS read by the second reading unit 40 are set. Match.
Second Embodiment

  Next, a document reading apparatus according to a second embodiment of the present invention will be described. Similar to the first embodiment, the document reading device 5 of the second embodiment is applied to the image forming apparatus 1 shown in FIGS. 1 and 3 and has the configuration shown in FIG. 30 is different from the first embodiment in the setting method of the reading end time ts12 of the document MS.

  FIG. 7 is a flowchart illustrating a method for setting the reading end point ts12 of the document MS by the first reading unit 30 in the second embodiment. Note that the processing of the flowchart shown in FIG. 7 is processing subsequent to steps S11 to S22 shown in FIG. 6. Therefore, in the second embodiment, the processing of steps S11 to S22 shown in FIG. 6 is the same as in the first embodiment. Done.

  In the processing of steps S11 to S22 shown in FIG. 6, the reading start time ts21 and the reading end time ts22 of the document MS by the second reading unit 40 are set, and the second reading unit 40 sets the back side of the document MS in the reading period T2. The image is read, and the reading start time ts11 of the document MS by the first reading unit 30 is set. In the subsequent processing of the flowchart shown in FIG. 7, the reading end point ts12 of the document MS by the first reading unit 30 is set, and the image on the surface of the document MS is read by the first reading unit 30 in the reading period T1. .

  The reading control unit 51 waits for the detection signal V1 of the first document edge sensor 28 to be turned off ("No" in step S31), and when the detection signal V1 of the first document edge sensor 28 is turned off (step S31). S31 “Yes”), the time measurement is started from this time point of OFF, and whether or not the detection signal V1 of the first document edge sensor 28 is turned on again until the time measurement time exceeds the specified time ty. Is monitored (steps S32, 33).

  For example, when the detection time V1 of the first document edge sensor 28 does not turn on and off and the timed time exceeds the specified time ty (step S32 “No”, step S33 “Yes”), the reading control unit 51 performs step S31. At this point, the time when the detection signal V1 of the first document edge sensor 28 is first turned off is regarded as the detection time tv12 of the trailing edge of the document MS by the first document edge sensor 28, and the detection time of the trailing edge of the document MS. The reading end point ts12 of the document MS by the first reading unit 30 corresponding to tv12 is set (step S34), and the reading of the document MS by the first reading unit 30 is ended at the reading end point ts12 (step S35).

  That is, as shown in FIG. 4A, the perforation h on the rear end side of the document MS deviates from the detection position m1 of the first document end sensor 28, and the first document end sensor 28 perforates the rear end side of the document MS. In a state where h is not detected, as shown in FIG. 4C, a predetermined time Δtt is added to the detection time tv12 of the trailing edge of the document MS by the first document edge sensor 28, and the reading end time by the first reading unit 30 is reached. ts12 is set, and the period from the reading start time ts11 to the reading end time ts12 is defined as a reading period T1 of the back side of the document MS by the first reading unit 30.

  If the detection signal V1 of the first document edge sensor 28 is turned on and then turned off again before the measured time exceeds the specified time ty (step S32 “Yes”, step S33 “No”), reading is performed. The control unit 51 regards the time point when the detection signal V1 is turned off again as the detection time point tv12 of the trailing edge of the document MS by the first document edge sensor 28, and based on the detection time point tv12 of the trailing edge of the document MS. The reading end point ts12 of the document MS by the first reading unit 30 is set (step S36), and the reading of the document MS by the first reading unit 30 is ended at the reading end point ts12 (step S35).

  As shown in FIG. 5A, the perforation h on the rear end side of the document MS passes through the detection position m1 of the first document end sensor 28, and the first document end sensor 28 forms the perforation h on the rear end side of the document MS. In the detected state, as shown in FIG. 5C, the detection signal V1 of the first document edge sensor 28 is temporarily turned off at the detection time tv1a according to the inner peripheral edge of the perforation h on the rear end side of the document MS. After that, it is turned on, and then turned off again at the detection time tv12 of the trailing edge of the document MS. Accordingly, the detection signal V1 of the first document edge sensor 28 is turned off before the detection of the trailing edge of the document MS by the first document edge sensor 28, and the time point of this off is the detection time of the trailing edge of the document MS. It does not correspond to tv12, and this off time point cannot be used for setting the reading period.

  For this reason, the detection signal V1 of the first document edge sensor 28 is temporarily turned off (step S31 “Yes”), and the detection signal V1 is detected before the specified time ty has elapsed from the time of the off (step S32 “No”). When the signal is turned on and then turned off again (step S32 “Yes”), the time point when the signal is turned off again is regarded as the detection time point tv12 of the trailing edge of the document MS by the first document edge sensor 28. Then, in the reading period T1 from the reading start time ts11 to the reading end time ts12, the first reading unit 30 reads the image on the back surface of the document MS.

  Thus, in the second embodiment, the perforation h on the rear end side of the document MS passes through the detection position m1 of the first document end sensor 28, and the first document end sensor 28 forms the perforation h on the rear end side of the document MS. If detected, the detection signal V1 of the first document edge sensor 28 is temporarily turned off, and the detection signal V1 is turned on before the specified time ty has elapsed from the detection time point tv1a of the off, and further the detection signal V1. Assuming that the time point when is turned off again is the detection time point tv12 of the trailing edge of the document MS by the first document edge sensor 28, the reading period T1 of the back surface of the document MS by the first reading unit 30 is set. Accordingly, the reading period T1 of the front surface of the document MS by the first reading unit 30 is set in the same procedure as the setting of the reading period T2 of the back surface of the document MS by the second reading unit 40. Thereby, the length of the image on the front surface of the document MS read by the first reading unit 30 and the length of the image on the back surface of the document MS read by the second reading unit 40 can be matched.

  In the above embodiment, the processing of the flowcharts of FIGS. 6 and 7 is executed by the reading control unit 51 of the document reading device 5, but the same processing is also executed by the main control unit 61 of the image forming apparatus 1. It is possible. In this case, the main control unit 61 is an example of a control unit in the claims.

  The configuration and processing described with reference to FIGS. 1 to 7 are only one embodiment of the present invention, and the present invention is not limited to the configuration and processing.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Apparatus main body 5 Original reading apparatus 6 Original feeding part 13 Fixing part 14 Paper feeding part 47 Operation part 28 First original edge sensor 29 Second original edge sensor 30 First reading part 40 Second reading part 51 Reading Control unit

Claims (3)

A first reading unit that reads an image on one side of a document conveyed along a conveyance path;
A second reading unit that reads an image on the other side of the document conveyed along the conveyance path;
A first document edge detection unit that is disposed upstream of the first reading unit in the document conveyance direction and detects a leading edge and a trailing edge of the document;
A second document edge detection unit that is disposed upstream of the second reading unit in the document conveyance direction and detects a leading edge and a trailing edge of the document;
The leading edge and trailing edge detection time points are determined based on the detection output of the first document edge detection unit, the reading period of the document by the first reading unit is set based on these detection time points, and the second A control unit that determines detection times of the leading edge and the trailing edge based on a detection output of the document edge detection unit, and sets a reading period of the document by the second reading unit based on these detection points;
The first document edge detection unit and the second document edge detection unit detect a leading edge and a trailing edge of the document at positions different from each other in a direction orthogonal to the document conveyance direction;
The control unit determines the detection time of the trailing edge based on the detection output of the second document edge detection unit, and outputs the detection output of the second document edge detection unit until a specified time elapses from the detection time. When the trailing edge detection time point is determined again, the trailing edge detection time point determined again is used for setting the reading period of the document by the second reading unit ,
The second reading unit is disposed upstream of the first reading unit in the document transport direction;
The control unit determines a detection time of the trailing edge based on a detection output of the first document edge detection unit after setting a reading period of the document by the second reading unit, and a predetermined time from the detection time. When the trailing edge detection time point is determined again based on the detection output of the first document edge detection unit before the time elapses, the document reading period by the first reading unit is set to the second reading unit by the second reading unit. A document reading device that is set to the same length as the document reading period . The control unit determines the detection time of the trailing edge based on the detection output of the second document edge detection unit, and outputs the detection output of the second document edge detection unit until a specified time elapses from the detection time. If on the basis to determine the detection time point of the trailing edge again, the detection time point of the tip based on the detection output of the second document end detecting unit, the elapsed time until the detection time point of the trailing edge of the is determined again, The trailing edge detection time determined again is used for setting the reading period of the document by the second reading unit only when it matches one of the predetermined elapsed times for each standard paper size. The document reading device according to claim 1. An original reading apparatus according to claim 1 or 2 ,
An image forming apparatus comprising: an image forming unit that records an image of the document read by the document reading device on a recording sheet.