Image reading device and image forming apparatus including the same

Abstract

To provide an image reading device that can appropriately acquire white reference data, while preventing a reduction in reading efficiency and damage to a document in continuous double-sided reading, and an image forming apparatus including the same.SOLUTION: An image reading device comprises a contact glass, a document conveying device, a first reading module, a second reading module, a white reference member, a swinging mechanism, one motor, and a control unit. The swinging mechanism swings the second reading module or the white reference member in a direction orthogonal to a conveyance direction. The control unit rotates the motor in a regular direction, and thereby drives a conveying member to convey a document, and rotates the motor in a reverse direction, and thereby drives the swinging mechanism to swing the second reading module or the white reference member, with the conveying member being stopped, during which acquires white reference data. When continuously executing double-sided reading processing on a plurality of documents to be conveyed, the control unit acquires the white reference data, with the documents being stopped at a position immediately near the upstream side of the second reading module with respect to the conveyance direction.SELECTED DRAWING: Figure 15

Description

Technical Field

[0001] The present invention relates to an image reading apparatus that scans and reads a document, which is used in a digital copying machine, an image scanner, etc., and an image forming apparatus including the same.

Background Art

[0002] Conventionally, among image reading apparatuses mounted on multifunction devices using an electrophotographic process, there are those equipped with a document conveyance device (Automatic Document Feeder) that sequentially feeds a sheet-like document onto a document placement table (contact glass) to read it and discharges it from the document placement table after reading. In such an image reading apparatus, there are two types of reading methods: a sheet-through method in which the document is automatically conveyed and read by the document conveyance device with the reading module fixed at the image reading position, and a document fixing method in which the document presser is opened and closed for each document reading to replace the documents on the document placement table one by one, and the reading module is scanned and moved to read the documents placed on the document placement table.

[0003] In recent years, in the above sheet-through method, a double-sided simultaneous reading method in which the front and back surfaces of a double-sided document are simultaneously read using different reading modules in one document conveyance operation by the document conveyance device has become mainstream. The reading module for reading the back surface of the double-sided document is arranged on the document conveyance device side. Also, in the image reading apparatus, there are various processes necessary for initial setting and adjustment of the reading module, etc. One of these processes is a white reference data acquisition process and a black reference data acquisition process in which, when the light source mounted on the reading module is turned on and off, the light amount data of the reflected light from the white reference plate arranged opposite the reading module is acquired as white reference data and black reference data.

[0004] When a plurality of originals are continuously read by an image reading apparatus equipped with an original conveying device, as described in Patent Document 1, the image density may vary or density unevenness may occur due to the reading module being affected by temperature. Therefore, by re-acquiring white and black reference data between originals and properly performing shading correction, a good image can be obtained. Further, as described in Patent Document 2, in consideration of dirt or damage to the white reference member, a configuration in which the white reference member is a rotating member and white reference data is acquired while rotating it is common.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0006] In an image reading apparatus, in order to achieve cost reduction and miniaturization, instead of the method of rotating the white reference member as in Patent Document 2, a configuration in which the white reference member or the reading module is swung in a direction orthogonal to the original conveying direction is conceivable. In this case, there is a problem that providing a dedicated drive source and drive mechanism for swinging the white reference member or the reading module leads to an increase in the cost and size of the image reading apparatus.

[0007] Also, when the original is conveyed while the white reference member or the reading module is swung, the original may be damaged. Therefore, it is necessary to stop the conveyance of the original during the acquisition of the swung white reference data, and there is also a problem that the reading efficiency (productivity) is reduced.

[0008] In view of the above problems, an object of the present invention is to provide an image reading apparatus capable of appropriately acquiring white reference data while suppressing as much as possible a decrease in reading efficiency and damage to a document during double-sided continuous reading, and an image forming apparatus including the same.

Means for Solving the Problems

[0009] To achieve the above object, a first configuration of the present invention is an image reading apparatus including a contact glass, a document conveying device, a first reading module, a second reading module, a white reference member, a swing mechanism, one motor, and a control unit. The contact glass has a document placed thereon. The document conveying device is provided on the upper surface of the contact glass so as to be openable and closable, and has a conveying member that conveys the document to the automatic reading position of the contact glass. The first reading module is arranged below the contact glass so as to be reciprocally movable in the sub-scanning direction, and can read the images on the surface sides of the fixed document placed on the contact glass and the conveyed document conveyed to the automatic reading position by the document conveying device. The second reading module is arranged in the document conveying device and can read the image on the back side of the conveyed document conveyed by the conveying member. The white reference member is arranged opposite to the second reading module. The swing mechanism swings the second reading module or the white reference member in a direction perpendicular to the conveying direction of the conveyed document. The motor drives the conveying member and the swing mechanism. The control unit controls the second reading module, the swing mechanism, and the motor. The second reading module includes a light source and a sensor that reads the reflected light of the light irradiated from the light source to the conveyed document as image light. The control unit drives the conveying member by rotating the motor forward to convey the conveyed document, and while driving the swing mechanism to swing the second reading module or the white reference member with the conveying member stopped by rotating the motor backward, reads the reflected light of the light irradiated from the light source to the white reference member by the sensor to execute a white reference data acquisition process for acquiring white reference data. As a conveyance reading process for reading the image of the conveyed document, a double-sided reading process for reading the images on the front and back sides of the conveyed document at once is continuously executed for a plurality of conveyed documents, and when the white reference data acquisition process is executed during the interval of the conveyed documents, the white reference data is acquired with the conveyed document stopped in the immediate upstream side of the second reading module with respect to the conveying direction.

Effect of the Invention

[0010] According to the first configuration of the present invention, by rotating the motor forward, the document is conveyed, and by rotating the motor backward, the second reading module or the white reference member can be swung to obtain white reference data. Therefore, a dedicated motor for swinging the second reading module or the white reference member is not required, and the cost reduction and space saving of the document conveying device can be achieved. Further, when performing double-sided reading processing continuously on a plurality of documents, by obtaining white reference data with the document stopped immediately upstream of the second reading module, it is possible to appropriately obtain white reference data while suppressing a decrease in reading efficiency and damage to the document due to reverse conveyance of the document.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Figure 14

Figure 15

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an image forming apparatus 100 including an image reading unit 6 of the present invention. In FIG. 1, in the image forming apparatus 100 (here, a digital multi-functional device is shown as an example), when performing a copying operation, the image reading unit 6 described later reads the image data of the document and converts it into an image signal. On the other hand, in the image forming unit 3 in the multi-functional device main body 2, the photosensitive drum 5 that rotates in the clockwise direction in FIG. 1 is uniformly charged by the charging unit 4. Then, an electrostatic latent image based on the document image data read by the image reading unit 6 is formed on the photosensitive drum 5 by the laser beam from the exposure unit (such as a laser scanning unit) 7. The developer (hereinafter referred to as toner) is attached to the formed electrostatic latent image by the developing unit 8 to form a toner image. The supply of toner to the developing unit 8 is performed from the toner container 9.

[0013] Towards the photoreceptor drum 5 on which the toner image is formed as described above, the paper is conveyed from the paper feed mechanism 10 to the image forming unit 3 via the paper conveyance path 11 and the registration roller pair 12. The conveyed paper passes through the nip portion of the photoreceptor drum 5 and the transfer roller 13 (image transfer unit), and the toner image on the surface of the photoreceptor drum 5 is transferred. Then, the paper with the toner image transferred is separated from the photoreceptor drum 5, conveyed to the fixing unit 14 having the fixing roller pair 14a, and the toner image is fixed. The paper that has passed through the fixing unit 14 is conveyed to the paper conveyance path 15 that branches in multiple directions. The conveyance direction of the paper is sorted by the path switching mechanisms 21 and 22 having a plurality of path switching guides provided at the branch points of the paper conveyance path 15, and is discharged to the paper discharge unit composed of the first discharge tray 17a and the second discharge tray 17b as it is (or after being sent to the reverse conveyance path 16 and double-sided copied).

[0014] Also, although not shown, a charge removing device for removing the residual charge on the surface of the photoreceptor drum 5 is provided on the downstream side of the cleaning device 18 with respect to the rotation direction of the photoreceptor drum 5. Further, the paper feed mechanism 10 is detachably attached to the multifunction machine main body 2, and includes a plurality of paper feed cassettes 10a and 10b for storing paper, and a stack bypass (manual feed tray) 10c provided above them, and these are connected to the image forming unit 3 including the photoreceptor drum 5 and the developing unit 8 etc. by the paper conveyance path 11.

[0015] An image reading unit 6 is arranged above the multifunction machine main body 2, and a document conveyance device 27 is attached to the upper surface of the multifunction machine main body 2. The lower surface of the document conveyance device 27 also serves as a platen (document presser) that presses and holds the document placed on the contact glass 25 (see FIG. 2) of the image reading unit 6 when the document conveyance device 27 is in the closed state.

[0016] An operation unit 80 is provided on the front surface of the image reading unit 6. The operation unit 80 is provided with a liquid crystal display unit and LEDs, and is configured to indicate the state of the image forming apparatus 100, display the image forming status and the number of printed sheets, etc. In addition, the operation unit 80 is provided with a start button for the user to instruct to start image formation, a stop / clear button used when aborting image formation, a reset button used when setting various settings of the image forming apparatus 100 to the default state, etc.

[0017] Specifically, the paper conveyance path 15 branches into two first on the downstream side of the fixing roller pair 14a. One path (the path that branches to the right in FIG. 1) is configured to communicate with the first discharge tray 17a. Then, the other path (the path that branches to the left in FIG. 1) branches into two via the conveyance roller pair 19. One path (the path that branches to the left in FIG. 1) is configured to communicate with the second discharge tray 17b. On the other hand, the other path (the path that branches downward in FIG. 1) is configured to communicate with the reverse conveyance path 16.

[0018] Furthermore, a control unit (CPU) 90 that controls the operations of the image forming unit 3, the image reading unit 6, the document conveyance device 27, etc. is arranged inside the multifunction machine main body 2.

[0019] FIG. 2 is a side cross-sectional view showing the internal structure of the image reading unit 6 according to an embodiment of the present invention provided with the document conveyance device 27. A contact glass 25 composed of an automatic reading glass 25a and a manual document glass 25b is arranged on the upper surface of the image reading unit 6.

[0020] A surface reading module 50 is arranged inside the image reading unit 6. The surface reading module 50 reads the document image placed on the manual document glass 25b while moving in the sub-scanning direction (the left-right direction in FIG. 2). In addition, the surface reading module 50 reads the image on the surface side (lower surface side) of the document conveyed by the document conveyance device 27 while stopped directly below the automatic reading glass 25a.

[0021] Between the automatic reading glass 25a and the manual document glass 25b, a conveyance guide 54 for scooping up the leading edge of the document conveyed by the document conveyance device 27 is disposed. Below the conveyance guide 54, a surface white reference plate 55 for shading correction of the surface reading module 50 is disposed.

[0022] The cover member 31 of the document conveyance device 27 is supported so as to be openable and closable with the device side surface side (the left side in FIG. 2) as a fulcrum with respect to the frame (not shown) of the document conveyance device 27. Inside the cover member 31, a document conveyance path d from the document feed tray 29 to the document discharge tray 32 is formed, and along the document conveyance path d, conveyance members including a pickup roller 33, a feed belt 34, a separation roller 35, a registration roller pair 36, a conveyance roller pair 37, a discharge roller pair 43, etc., and a back surface reading module 51 for reading an image on the back surface side of the document are provided.

[0023] The document conveyance path d is curved so as to invert between the registration roller pair 36 and the automatic reading glass 25a. Further, in the document conveyance path d, a plurality of paper detection sensors (not shown) including a paper feed sensor and a discharge sensor for detecting the presence or passage of the document are provided at appropriate positions. Further, at a position facing the back surface reading module 51 with the document conveyance path d interposed therebetween, a back surface white reference plate 57 for shading correction of the back surface reading module 51 is disposed.

[0024] The feed belt 34 is wound around a drive roller 44a and a driven roller 44b, and the separation roller 35 is in contact with it from below with a predetermined pressure. A torque limiter is built into the separation roller 35, and it is configured to rotate driven by the feed belt 34 only when the rotational load exceeds a predetermined torque.

[0025] Inside the cover member 31, an opening / closing detection sensor 58 for detecting the opening and closing of the cover member 31 is arranged. The opening / closing detection sensor 58 is a PI (photo interrupter) sensor provided with a detection unit having a light emitting unit and a light receiving unit. As shown in FIG. 2, when the cover member 31 is in the closed position, the opening / closing detection sensor 60 is shielded from light by a light shielding plate (not shown) provided on the cover member 31 side, and the light receiving signal level of the detection unit is in the LOW state. When the cover member 31 rotates in the opening direction (upward) from the state of FIG. 2, the light shielding plate retracts upward from the detection unit of the opening / closing detection sensor 58, and the light receiving signal level of the detection unit becomes the HIGH state. The opening and closing of the cover member 31 are detected by transmitting the light receiving signal of the opening / closing detection sensor 60 to the control unit 90 (see FIG. 6).

[0026] Next, the sheet-through type document conveyance operation using the document conveyance device 27 will be described. In the sheet-through type, with the document conveyance device 27 in the closed state in contact with the contact glass 25, a plurality of documents are set on the document feed tray 29 with the image surface facing upward. Then, when the copy start button on the operation unit 80 (see FIG. 1) of the image forming apparatus 100 is turned on, a lift plate (not shown) lifted by a lifting mechanism (not shown) pushes up the pickup roller 33 through the document. As a result, the weight of the frame body (not shown) including the pickup roller 33 is applied to the lift plate, and the upper surface of the document is pressed against the pickup roller 33 with a predetermined pressure (paper feed pressure).

[0027] Here, the pickup roller 33, the driving roller 44a, the driven roller 44b, and the paper feed belt 34 are arranged on a frame body (not shown). Further, the pickup roller 33 is connected to the driving roller 44a by a gear (not shown). When the driving roller 44a rotates by a roller driving motor (not shown), the paper feed belt 34 stretched between the driving roller 44a and the driven roller 44b is rotationally driven, and the pickup roller 33 is also rotationally driven.

[0028] The original document set on the original document paper feed tray 29 is usually sent by the pickup roller 33 to the nip between the paper feed belt 34 and the separation roller 35 for multiple sheets in the upper layer. Then, only the top sheet of the multiple sheets of the original document is separated by the separation roller 35 and conveyed toward the registration roller pair 36. At this time, after the leading edge of the original document is detected by the paper feed sensor and the original document is conveyed by a predetermined distance, the rotational drive of the pickup roller 33 and the paper feed belt 34 is stopped by stopping the operation of the roller drive motor, and the primary paper feed is completed. The originally fed document stops at the nip of the registration roller pair 36 with a bend formed and the leading edge thereof.

[0029] After a predetermined time has elapsed since the primary paper feed is completed, the secondary paper feed is started. That is, the registration roller pair 36 is rotationally driven by the operation of a secondary paper feed drive motor (not shown). The original document is conveyed toward the automatic reading glass 25a by the registration roller pair 36 and the conveyance roller pair 37. The original document conveyed to the automatic reading glass 25a is pressed against the automatic reading glass 25a from above by contacting a document pressing member (not shown) disposed opposite to the automatic reading glass 25a. Then, the image on the front side (the automatic reading glass 25a side) of the original document is read by the front side reading module 50 through the automatic reading glass 25a.

[0030] Thereafter, the original document that has passed through the automatic reading glass 25a is conveyed through the conveyance guide 54 toward the conveyance roller pair 37 and the discharge roller pair 43, and finally discharged onto the original document discharge tray 32 by the discharge roller pair 43. At this time, when the passage of the trailing edge of the original document is detected by the discharge sensor, the completion of the image reading of one original document is detected. Here, the discharge sensor has a counting function of counting the number of original documents for each completion of the conveyance of the original document. If the paper feed sensor detects a subsequent original document, the conveyance of the second and subsequent original documents continues in the same manner as described above.

[0031] When reading a double-sided original document, after the back surface reading module 51 provided on the upstream side of the automatic reading glass 25a reads the image of the back surface of the original document, the front surface reading module 50 reads the image of the front surface of the original document.

[0032] FIG. 3 and FIG. 4 are enlarged views around the front surface reading module 50 and the front surface white reference plate 55 in FIG. 2, showing the states where the front surface reading module 50 is in the reference position (home position) and the automatic reading position, respectively. The front surface reading module 50 is a reading module of the CIS sensor (Contact Image Sensor) type.

[0033] As shown in FIG. 3, inside the front surface reading module 50, there are provided a light source 70a, a condenser lens 71a composed of a plurality of lenses, and a CMOS (Complementary MOS) sensor 73a as a reading means. The CMOS sensor 73a is supported by a substrate 75a. After the light irradiated from the light source 70a is reflected by the original document (not shown), it is condensed by the condenser lens 71 and guided to the CMOS sensor 73a. The front surface reading module 50 is in contact with the back surface of the contact glass 25 via a slider 60.

[0034] Here, as the reading method of the front surface reading module 50, an equal magnification optical system using a CMOS sensor 73 for the imaging device without using a mirror is exemplified. However, it is also possible to use a reduction optical system that uses a plurality of mirrors and optical lenses, uses a charge coupled device called a CCD (Charge Coupled Devices) for the imaging device, and forms a reduced image by the optical lens to read the image.

[0035] In the above configuration, when reading a document image in the document fixing method, first, the document conveyance device 27 is opened, and a document (not shown) is placed face down on the manual document glass 25b. Then, the document conveyance device 27 is closed, and while irradiating the image surface of the document with light from the light source 70a, the front surface reading module 50 is moved from the scanner home side (the left side in FIG. 2) to the scanner return side (the right side in FIG. 2) at a predetermined speed. As a result, the light reflected by the image surface becomes image light and is imaged on the CMOS sensor 73a. The imaged image light is pixelated by the CMOS sensor 73a and converted into an electrical signal corresponding to the density of each pixel, and the image is read.

[0036] On the other hand, when reading a document image in the sheet-through method, the document conveyance device 27 is closed, and as shown in FIG. 4, the front surface reading module 50 is moved to the automatic reading position (directly below the automatic reading glass 25a). Then, the document is sequentially conveyed toward the automatic reading glass 25a by the document conveyance device 27, the surface of the document passing through the automatic reading glass 25a is irradiated with light from the light source 70a, and the image light reflected by the image surface is imaged on the CMOS sensor 73a to read the image. In any reading method, the image signal read by the front surface reading module 50 is converted into a digital signal and then sent to the temporary storage unit 94 (see FIG. 6).

[0037] FIG. 5 is an enlarged view around the back surface reading module 51 in FIG. 2. The back surface reading module 51 is a reading module of the same CIS sensor (Contact Image Sensor, close contact type image sensor) method as the front surface reading module 50. As shown in FIG. 5, inside the back surface reading module 51, a light source 70b, a condenser lens 71b composed of a plurality of lenses, and a CMOS (Complementary MOS) sensor 73b as a reading means are provided. The CMOS sensor 73b is supported by a substrate 75b.

[0038] The back surface of the document passing through the back surface reading module 51 is irradiated with light from the light source 70b, and the reflected light (image light) reflected on the image surface is condensed again by the condenser lens 71b and imaged on the CMOS sensor 73b. The imaged image light is pixelated by the CMOS sensor 73b and converted into an electrical signal corresponding to the density of each pixel, and the image is read.

[0039] FIG. 6 is a block diagram showing an example of a control path used in the image forming apparatus 100 of the present embodiment. Note that since various controls of each part of the image forming apparatus 100 are performed when using the image forming apparatus 100, the control path of the entire image forming apparatus 100 is complicated. Therefore, here, the parts necessary for the implementation of the present invention in the control path will be mainly described.

[0040] The operation unit 80 is provided with a liquid crystal display unit 81 and LEDs 82 indicating various states, and is configured to indicate the state of the image forming apparatus 100, display the image forming status and the number of printed sheets. Various settings of the image forming apparatus 100 are made from the printer driver of the personal computer.

[0041] In addition, the operation unit 80 is provided with a start button for the user to instruct to start image formation, a stop / clear button used when aborting image formation, a reset button used when setting various settings of the image forming apparatus 100 to the default state, and the like.

[0042] The module drive motor 83 reciprocates the front surface reading module 50 in the sub-scanning direction (the left-right direction in FIG. 2) when reading a document image in the document fixing method. Further, the module drive motor 83 moves the front surface reading module 50 to the automatic reading position when reading a document image in the sheet-through method. The module drive motor 83 is a stepping motor, and the control unit 90 can detect the position of the front surface reading module 50 based on the number of drive pulses of the module drive motor 83.

[0043] The control unit 90 includes at least a CPU (Central Processing Unit) 91 as a central processing unit, a ROM (Read Only Memory) 92 which is a read-only storage unit, a RAM (Random Access Memory) 93 which is a readable and writable storage unit, a temporary storage unit 94 that temporarily stores image data and the like, a plurality (here two) of I / F (interfaces) 96 that transmit control signals to each device within the image forming apparatus 100 and receive input signals from the operation unit 80, and a reading processing unit 97. Also, the control unit 90 can be arranged at any location within the image forming apparatus 100.

[0044] Further, the control unit 90 transmits control signals from the CPU 91 to each part and device in the image forming apparatus 100 through the I / F 96. Also, signals indicating the state and input signals from each part and device are transmitted to the CPU 91 through the I / F 96. Examples of the parts and devices controlled by the control unit 90 include the image forming unit 3, the image reading unit 6, the original document conveying device 27, the operation unit 80, and the like.

[0045] The ROM 92 stores data such as a control program for the image forming apparatus 100 and numerical values necessary for control, which are not to be changed during the use of the image forming apparatus 100. The RAM 93 stores necessary data generated during the control of the image forming apparatus 100 and data temporarily required for the control of the image forming apparatus 100. The temporary storage unit 94 receives the image data transmitted from the image reading unit 6 through an image input unit (not shown), and temporarily stores the image signal converted into a digital signal.

[0046] The reading processing unit 97 executes a reading process of the original document fixing method (fixed reading process) for reading image data from the original document placed on the original document glass 25b for hand-placed originals using the surface reading module 50. Also, the reading processing unit 97 executes a reading process of the sheet-through method (conveying reading process) for reading image data on the front and back sides of the original document automatically conveyed by the original document conveying device 27 using the surface reading module 50 and the back surface reading module 51.

[0047] Incidentally, when the image forming apparatus 100 is powered on, when resuming from the power saving state (sleep mode), when there is a predetermined temperature and humidity change, or at various timings such as when starting the image reading process, etc., processes necessary for the initial setting and adjustment of the front surface reading module 50 and the back surface reading module 51 are performed. One of the processes is a white reference data acquisition process in which the light source of the front surface reading module 50 or the back surface reading module 51 is turned on, and white reference data from the front surface white reference plate 55 or the back surface white reference plate 57 is acquired.

[0048] When performing the white reference data acquisition process of the back surface reading module 51, by turning on the light source while swinging the back surface white reference plate 57, the light irradiated from the light source is reflected by the back surface white reference plate 57, condensed by the condenser lens, and guided to the CMOS sensor. The output voltage (output level) of the CMOS sensor at this time is acquired as light amount data (white reference data).

[0049] More specifically, in a state where the back surface white reference plate 57 is swung, the output level of the CMOS sensor is detected a plurality of times to acquire a plurality of light amount data. Then, extremely low values (abnormal values) are discarded, and the average value of the available light amount data is calculated. Thereby, the influence of abnormal data caused by variations in the surface state of the back surface white reference plate 57 can be reduced.

[0050] FIG. 7 is a perspective view showing the configuration around the swing mechanism 510 of the back surface reading module 51 in the image reading unit 6 of the present embodiment. FIG. 8 is a perspective view of the module holding member 514 that constitutes the swing mechanism 510. FIG. 9 is a perspective view showing a state where the module holding member 514 is attached to the frame 270 of the document conveying device 27. FIG. 10 is an enlarged view of the swing member 511 in FIG. 7. Hereinafter, the configuration and operation of the swing mechanism 510 will be described in detail.

[0051] The swing mechanism 510 includes a swing member 511, a locked gear 512, a locking member 513, a holding member 514, and a coil spring 515. The swing mechanism 510 swings the back surface reading module 51 in a direction (main scanning direction) perpendicular to the conveyance direction and horizontal by the rotational driving force of the conveyance motor 85.

[0052] The conveyance motor 85 is connected to conveyance members such as a resist roller pair 36, a conveyance roller pair 37, and a discharge roller pair 43 via a pinion gear (not shown) fixed to the output shaft of the conveyance motor 85 and a drive transmission gear train 87. The drive transmission gear train 87 has a plurality of gears 87a to 87f. The rotational driving force of the conveyance motor 85 is transmitted in the order of the gears 87a to 87f.

[0053] The conveyance motor 85 is connected to the swing member 511 via the gears 87a to 87c, the drive input gear 88, and the locked gear 512 that constitute the drive transmission gear train 87. More specifically, the rotational driving force of the conveyance motor 85 is transmitted from a pinion gear (not shown) fixed to the output shaft of the conveyance motor 85 to the gears 87a, 87b, 87c, the drive input gear 88, and the locked gear 512 in that order. That is, the conveyance member and the swing mechanism 510 are driven by one conveyance motor 85.

[0054] FIG. 11 is an exploded perspective view of the swing member 511. The swing member 511 has a main body portion 511a and a swing portion 511b. The swing member 511 is arranged coaxially with the locked gear 512.

[0055] The main body portion 511a has a first cam 520a and a first through hole 521. The first cam 530a meshes with the second cam 530b of the swing portion 511b. The first through hole 521 is penetrated by the rotation shaft 525 (see FIG. 12(a)) of the sun gear portion 512a. The rotation shaft 525 rotatably holds the main body portion 511a and meshes with the planetary gear 512c. The main body portion 511a is in a hollow cylindrical shape, and gear teeth (not shown) that mesh with the planetary gear 512c (see FIG. 12(b)) are formed on the inner peripheral surface.

[0056] The swing part 511b includes a second cam 520b, a shaft 522, and a connecting part 523. The shaft 522 is held by a bearing member (not shown) supported by the housing of the document conveying device 4 so as to be axially movable. The connecting part 523 is supported by the guide part 514a of the module holding member 514. A rib-shaped rotation restricting part 524 protruding in the radial direction is formed on the outer peripheral surface of the connecting part 523. The rotation restricting part 524 engages with an engaging part (not shown) of the guide part 514a to restrict the rotation of the swing part 511b about the shaft 522.

[0057] FIG. 12 is an exploded perspective view of the locked gear 512. The locked gear 512 includes a sun gear part 512a (FIG. 12(a)), a planetary gear holding part 512b (FIG. 12(c)), and a planetary gear 512c (FIG. 12(b)).

[0058] The sun gear part 512a has a rotation shaft 525. Gear teeth 525a that mesh with the locking member 513 are formed on the outer peripheral surface of one side (the lower right side in FIG. 12(a)) of the rotation shaft 525. Gear teeth (not shown) that mesh with the planetary gear 512c are formed on the outer peripheral surface of the other side (the upper left side in FIG. 12(a)) of the rotation shaft 525. The rotation shaft 525 has a second through hole 525b. The shaft 522 of the swing part 511b passes through the second through hole 525b. The shaft 522 rotatably holds the sun gear part 512a.

[0059] The planetary gear holding part 512b includes a pair of support shafts 526 and a third through hole 527. The support shafts 526 rotatably support the planetary gear 512c. The third through hole 527 allows the rotation shaft 525 of the sun gear part 512a to pass through. The rotation shaft 525 rotatably holds the planetary gear holding part 512b. Gear teeth that mesh with the drive input gear 88 and the conveying gear 89 are formed on the outer peripheral surface of the planetary gear holding part 512b.

[0060] The planetary gear 512c is disposed between the rotation shaft 525 of the sun gear part 512 and the inner peripheral surface of the main body part 511a. The planetary gear 512c meshes with the gear teeth formed on the outer peripheral surface of the rotation shaft 525 and the gear teeth formed on the inner peripheral surface of the main body part 511a.

[0061] The locking member 513 has a locking gear 513a and a locking claw 513b. The locking gear 513a is connected to the planet gear holding portion 512b of the locked gear 512 via a conveying gear 89. The conveying gear 89 inputs a rotational driving force to a conveying shaft and a conveying roller (both not shown) fixed to the conveying shaft.

[0062] The locking claw 513b is swingable between a regulating position where it engages with the gear teeth 525a of the sun gear portion 512a to regulate the rotation of the sun gear portion 512a and a retracted position where it is separated from the gear teeth 525a. The locking claw 513b is arranged at the regulating position or the retracted position as the locking gear 513a rotates. More specifically, when the conveying motor 85 rotates forward, the locking claw 513b is arranged at the retracted position, and when the conveying motor 85 rotates reversely, the locking claw 513b is arranged at the regulating position.

[0063] A washer (not shown) is built into the locking gear 513a. The washer functions as a resistance (rotational load) of the locking gear 513a against the locking claw 513b.

[0064] The module holding member 514 holds the back surface reading module 51. The module holding member 514 is swingably supported in a direction orthogonal to the conveying direction by a frame 270 (see FIG. 9) of the document conveying device 27. The module holding member 514 has a guide portion 514a and a regulating projection 514b. The guide portion 514a supports the connecting portion 523 of the swinging portion 511b. The regulating projection 514b engages with an opening 270b of the frame 270 to regulate the movement of the module holding member 514 when it is pressed by a coil spring 515.

[0065] The coil spring 515 is disposed at one longitudinal end (the left end in FIG. 8) of the module holding member 514. As shown in FIG. 9, one end of the coil spring 515 is fixed to the spring holding portion 514c of the module holding member 514. The other end of the coil spring 515 is in contact with the restricting portion 270a of the frame 270. Thereby, the module holding member 514 is always pressed toward the rear side (the direction of arrow A in FIG. 9) of the document conveying device 27 by the resistance force received from the frame 270 against the biasing force acting from the coil spring 515 on the frame 270.

[0066] Next, the relationship between the rotation direction of the conveyance motor 85 and the operation of the swing mechanism 510 will be described. When the conveyance motor 85 is rotated forward to convey a document, the lock member 513 is disposed at the retracted position. Therefore, the rotation of the sun gear portion 512a of the locked gear 512 is not restricted.

[0067] By the forward rotation of the conveyance motor 85, a rotational driving force is transmitted to the drive gear 88 via the gears 87a to 87c, and the drive gear 88 rotates forward. By the forward rotation of the drive gear 88, the planetary gear holding portion 512b rotates. At this time, the main body portion 511a of the swing member 511 is engaged with the second cam 520b of the swing portion 511b by the first cam 520a, and the rotation is restricted. On the other hand, the rotation of the sun gear portion 512a of the locked gear 512 is not restricted because the lock claw 513b is disposed at the retracted position.

[0068] Therefore, the rotational driving force of the planetary gear holding portion 512b is transmitted to the sun gear portion 512a via the planetary gear 512c. That is, the sun gear portion 512a, the planetary gear holding portion 512b, and the planetary gear 512c are rotating. On the other hand, the main body portion 511a is stationary without rotating by the rotational driving force of the planetary gear holding portion 512b.

[0069] As a result, the state where the second cam portion 520b of the swing portion 511b and the first cam portion 520a of the main body portion 511a are engaged is maintained. Therefore, the module holding member 514 does not swing, and the document is conveyed.

[0070] When the conveyance motor 85 rotates in the reverse direction, the locking claw 513b is disposed at the restricting position, so the rotation of the sun gear portion 512a is restricted. Therefore, the rotational driving force of the planetary gear holding portion 512b attempts to rotate the main body portion 511a via the planetary gear 512c. As a result, the main body portion 511a rotates from the state where the first cam 520a of the main body portion 511a meshes with the second cam 520b of the swing portion 511b. Thereby, the state where the first cam 520a of the main body portion 511a meshes with the second cam 520b of the swing portion 511b and the state where the meshing is displaced are repeated, and the swing portion 511b swings in the axial direction.

[0071] And, the module holding member 514 connected to the swing portion 511b is pressed by the swing portion 511b when the meshing between the first cam 520a and the second cam 520b is displaced, and moves to one side while compressing the coil spring 515. Further, when the first cam 520a and the second cam 520b mesh with each other, it moves to the other side by the biasing force (restoring force) of the coil spring 515.

[0072] That is, the module holding member 514 swings in the direction orthogonal to the document conveyance direction. Therefore, the white reference data can be acquired while swinging the back surface reading module 51, and the influence of dirt and scratches on the back surface white reference plate 57 can be reduced. The swing stroke w (see FIG. 10) of the module holding member 514 can be adjusted by the distance from the valley portion to the peak portion of the first cam 520a and the second cam 520b.

[0073] FIG. 13 is a perspective view showing the drive transmission gear train 87 and the gears constituting the swing mechanism 510, and is a perspective view showing the gear train constituting the swing mechanism 510. Note that FIG. 13 and FIG. 14 described later are perspective views seen from the back side of FIG. 7, and the arrangement of each gear is reversed left and right from FIG. 7. In the following description, the gear 87c to which the drive input gear 88 is connected is referred to as the branch gear 87c.

[0074] As shown in FIG. 13, the branch gear 87c to which the drive input gear 88 is connected is a two-stage gear composed of a first gear portion 871 and a second gear portion 872. The gear 87b and the drive input gear 88 are engaged with the first gear portion 871. The gear 87b is engaged with the second gear portion 872.

[0075] FIG. 14 is a diagram showing a state in which the second gear portion 872 of the branch gear 87c in FIG. 13 is removed. As shown in FIG. 14, engaging convex portions 873 are formed on the opposing surface of the first gear portion 871 with the second gear portion 872. Two engaging convex portions 873 are formed at positions point-symmetrical with respect to the rotation center of the first gear portion 871.

[0076] Also, engaging convex portions (not shown) are formed on the opposing surface of the second gear portion 872 with the first gear portion 871. Similar to the engaging convex portion 813 of the first gear portion 871, two engaging convex portions of the second gear portion 872 are formed at positions point-symmetrical with respect to the rotation center of the second gear portion 872. In a state where the first gear portion 871 and the second gear portion 872 are combined as shown in FIG. 13, the engaging convex portions of the second gear portion 872 are arranged between the engaging convex portions 813 of the first gear portion 871.

[0077] With the above configuration, the first gear portion 871 and the second gear portion 872 are connected with a play of a predetermined angle d in the rotation direction. As a result, after the gear 87c rotates forward and then rotates reversely, when the first gear portion 871 rotates reversely by the angle d, the second gear portion 872 starts to rotate reversely. In other words, while the first gear portion 871 rotates reversely by the angle d, the second gear portion 872 remains stationary.

[0078] That is, when the conveyance motor 85 rotates reversely, during the period (idle region) in which the branch gear 87c rotates by the angle d, the rotational driving force of the conveyance motor 85 is not transmitted to the gears 87d to 87f. Therefore, the document stops without moving in the reverse direction with respect to the conveyance direction within the document conveyance path d. While the document is stopped, the back surface reading module 51 swings in a direction orthogonal to the conveyance direction by the swing mechanism 510, so that the back surface white reference data is reacquired.

[0079] According to the above configuration, by rotating the conveyance motor 85 forward, the document is conveyed, and by rotating the conveyance motor 85 backward, the reading module 51 for the back side can be swung to obtain white reference data. Therefore, a dedicated motor for swinging the reading module 51 for the back side is not required, and the cost reduction and space saving of the document conveyance device 27 can be achieved.

[0080] Also, when the conveyance motor 85 is rotated backward, by configuring the first gear portion 871 and the second gear portion 872 of the branch gear 87c to idle by a predetermined angle d, it is possible to prevent the document from moving in the direction opposite to the conveyance direction. As a result, the reading module 51 for the back side can be swung with the document stopped immediately before the reading module 51 for the back side to re-acquire the white reference data for the back side. Therefore, the image density can be appropriately maintained without causing a decrease in document reading efficiency (productivity) or damage to the document due to its movement in the reverse direction.

[0081] FIG. 15 is a flowchart showing a control example of the white reference data acquisition process for the reading module 51 for the back side in the double-sided reading process. With reference to FIGS. 1 to 14 as necessary, the acquisition procedure of the white reference data for the back side in the double-sided reading process will be described along the steps of FIG. 15.

[0082] When the double-sided reading process is requested (step S1), the control unit 90 acquires the black reference data for the back side (step S2). Specifically, the output level of the CMOS sensor 73b with the light source 70b of the reading module 51 for the back side turned off is acquired as the black reference data for the back side.

[0083] Next, the control unit 90 turns on the light source 70b of the reading module 51 for the back side (step S3). Then, the control unit 90 starts swinging the reading module 51 for the back side by the swinging mechanism 60 (step S4). Specifically, the reading module 51 for the back side is swung one or more reciprocations in the direction orthogonal to the conveyance direction by rotating the conveyance motor 85 backward by a predetermined angle.

[0084] Then, while the back - side reading module 51 is swinging, the back - side white reference data is acquired (step S5). Specifically, the output level of the CMOS sensor 73b with the light source 70b of the back - side reading module 51 turned on is acquired as the back - side white reference data. After the acquisition of the back - side white reference data, the rotation of the conveyance motor 85 is stopped to end the swinging of the back - side reading module 51 (step S6).

[0085] Next, the control unit 90 moves the front - side reading module 50 directly below the automatic - reading glass 25a (reading position) to start the conveyance of the document (step S7), and reads the document (step S8). Then, it is determined whether or not the required number of double - sided reading processes has been completed (step S9). If the double - sided reading process has been completed (Yes in step S9), the process ends.

[0086] On the other hand, if the double - sided reading process continues (No in step S9), the control unit 90 determines whether or not the continuous reading time has elapsed for a predetermined time (step S10). If the continuous reading time has not elapsed for the predetermined time (No in step S10), the process returns to step S7 to continue the conveyance of the document and the double - sided reading process (steps S7, S8).

[0087] If the continuous reading time has elapsed for the predetermined time (Yes in step S10), the control unit 90 stops the conveyance of the document upstream of the back - side reading module 51 (step S11). Then, the light source 70b of the back - side reading module 51 is turned off (step S12). Then, the process returns to step S2 to acquire the back - side black reference data, swing the back - side reading module 51 to acquire the back - side white reference data, and then start the conveyance of the document and the double - sided reading process again (steps S2 - S8).

[0088] According to the control example shown in FIG. 15, when double-sided reading is requested, after obtaining the backside black reference data with the light source 70b of the backside reading module 51 turned off, the light source 70b is turned on and the oscillation of the backside reading module 51 is started to obtain the backside white reference data, and the image reading preparation is executed in the procedure of ending the oscillation of the backside reading module 51. Then, the conveyance of the document is started and the document image is read.

[0089] After reading the first document, in the case of continuous reading processing, the conveyance and reading of the next document are continued without obtaining the black and white reference data. When the continuous reading time has elapsed for a predetermined time, the document is stopped immediately upstream of the backside reading module 51, the light source 70b is turned off to obtain the black reference data, the light source 70b is turned on again to start the oscillation of the backside reading module 51 to obtain the white reference data, and the black and white reference data are re-obtained in the procedure of ending the oscillation of the backside reading module 51. Then, the conveyance and reading of the document are resumed.

[0090] As the trigger conditions for re-acquiring the black and white reference data during the continuous reading process, different reading times (number of read sheets) are set according to the line speed (conveyance speed) of the document for each reading condition, such as color reading, monochrome reading, or reading resolution. For example, in color reading, the three colors of R, G, and B are read in order with one CIS sensor, but in monochrome reading, for one reading, the line speed of the document is faster in monochrome. Therefore, even if the continuous reading time is the same, the number of read sheets is larger in monochrome than in color. Also, the number of read sheets serving as the trigger condition is set to the number of sheets that can be read in a certain time (for example, 2 minutes).

[0091] Thereby, the waiting time for document conveyance can be shortened and a decrease in reading efficiency can be suppressed. Also, damage to the document due to reverse conveyance of the document can be suppressed. Image density correction after resuming reading can effectively eliminate image density fluctuations and density unevenness by using the re-acquired black and white reference data.

[0092] The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the swing mechanism 510 is configured to swing the back surface reading module 51 in a direction orthogonal to the conveyance direction. However, the swing mechanism 510 may be configured to swing the white reference plate 57 for the back surface in a direction orthogonal to the conveyance direction instead of the back surface reading module 51. The mechanism for swinging the white reference plate 57 for the back surface is the same as the swing mechanism 510 of the present embodiment.

[0093] Further, in the above-described embodiment, as a mechanism for switching the swing state and the stationary state of the back surface reading module 51 by the forward rotation and the reverse rotation of the conveyance motor 85, a locked gear 512 having a planetary gear mechanism including a sun gear portion 512a, a planetary gear holding portion 512b, and a planetary gear 512c is used. Instead of the above-described planetary gear mechanism, other configurations can be used to switch the forward rotation and the reverse rotation of the conveyance motor 85 and the swing state and the stationary state of the back surface reading module 51. Examples of other configurations include a configuration using a one-way gear that transmits a driving force to the swing member 511 only when the conveyance motor 85 rotates in the reverse direction.

[0094] Further, in the above-described embodiment, an image reading apparatus including an image reading unit 6 and a document conveyance apparatus 27, having a front surface reading module 50 disposed in the image reading unit 6 and a back surface reading module 51 disposed in the document conveyance apparatus 27, was described as an example. However, the present invention can be similarly applied to an image scanner used separately from the image forming apparatus 100, which includes two reading modules corresponding to the above-described front surface reading module 50 and back surface reading module 51.

Industrial Applicability

[0095] The present invention can be used in an image reading apparatus including a reading module disposed in a document conveyance apparatus. By using the present invention, it is possible to provide an image reading apparatus capable of appropriately acquiring white reference data while suppressing as much as possible a decrease in reading efficiency and damage to a document during double-sided continuous reading, and an image forming apparatus including the same.

Explanation of Reference Numerals

[0096] 6 Image reading unit (image reading device) 25 Contact glass 27 Original document conveying device 31 Cover member 50 Backside reading module (first reading module) 51 Frontside reading module (second reading module) 55 Frontside white reference plate 57 Backside white reference plate (white reference member) 70a, 70b Light sources 71a, 71b Condensing lenses 73a, 73b CMOS sensors 85 Conveying motor (motor) 87 Drive transmission gear train 87c Branching gear 90 Control unit 100 Image forming device 510 Oscillation mechanism 511 Oscillation member 511a Main body part 511b Oscillation part 512 Locked gear 513 Locking member 514 Module holding member (holding member) 515 Coil spring (biasing member)

Claims

1. A contact glass on which a document is placed, a document conveying device that is provided on the upper surface of the contact glass so as to be openable and closable and has a conveying member that conveys the document to the automatic reading position of the contact glass, a first reading module that is disposed below the contact glass so as to be reciprocally movable in the sub-scanning direction and is capable of reading an image on the front surface side of a fixed document placed on the contact glass and a conveyed document conveyed to the automatic reading position by the document conveying device, a second reading module that is disposed in the document conveying device and is capable of reading an image on the back surface side of the conveyed document conveyed by the conveying member, a white reference member disposed opposite to the second reading module, a swing mechanism that swings the second reading module or the white reference member in a direction perpendicular to the conveying direction of the conveyed document, one motor that drives the conveying member and the swing mechanism, a control unit that controls the second reading module, the swing mechanism, and the motor, In an image reading apparatus comprising: the second reading module includes a light source and a sensor that reads reflected light of light irradiated from the light source to the conveyed document as image light, the control unit: drives the conveying member to convey the document by rotating the motor forward, and drives the swing mechanism to swing the second reading module or the white reference member while stopping the conveying member by rotating the motor backward, and reads reflected light of light irradiated from the light source to the white reference member by the sensor to execute white reference data acquisition processing for acquiring white reference data; As conveyance reading processing for reading an image of the conveyed document, double-sided reading processing for reading images on the front surface side and the back surface side of the conveyed document at once is continuously executed for a plurality of the conveyed documents, and when the white reference data acquisition processing is executed during an interval of the conveyed documents, the white reference data is acquired with the conveyed document stopped at a position closest to the upstream side of the second reading module with respect to the conveying direction. An image reading apparatus characterized by this.

2. The conveying member is connected to the motor via a drive transmission gear train composed of a plurality of gears, The swing mechanism is connected to the motor via a locked gear connected to a branch gear that is one of the gears constituting the drive transmission gear train, The branch gear is, A first gear portion connected to the gear upstream of the branch gear in the drive transmission gear train and the locked gear with respect to the drive transmission direction; A second gear portion connected to the gear downstream of the branch gear in the drive transmission gear train with respect to the drive transmission direction; and having The image reading apparatus according to claim 1, wherein the second gear portion idles until the first gear portion rotates by a predetermined angle after the motor starts reverse rotation.

3. The swing mechanism includes A swing member including a main body portion and a swing portion disposed coaxially with the locked gear and having chevron gear teeth formed on respective sliding surfaces; A lock member that separates from the locked gear and allows rotation of the locked gear when the motor rotates forward, and engages with the locked gear and restricts rotation of the locked gear when the motor rotates in reverse; A holding member that is reciprocally movable in the swing direction and holds the second reading module or the white reference member; A biasing member that biases the holding member to one side in the swing direction; and having The main body portion does not rotate when the motor rotates forward and the locked gear rotates, and rotates when the motor rotates in reverse and the rotation of the locked gear is restricted by the lock member. The swing portion is non-rotatable and axially movable, and is disposed to abut against the holding member from the side opposite to the biasing member. The image reading apparatus according to claim 2, wherein by rotating the motor in reverse, the main body portion rotates, the gear teeth slide against each other, and the swing portion reciprocates in the axial direction to swing the holding member.

4. The image reading apparatus according to claim 2, wherein the swing mechanism swings the second reading module or the white reference member one or more times while the second gear portion of the branch gear idles.

5. The image reading apparatus according to claim 1, wherein the control unit starts the white reference data acquisition process at the timing when the motor starts reverse rotation and ends the white reference data acquisition process before the motor stops reverse rotation.

6. An image forming apparatus equipped with the image reading apparatus according to any one of claims 1 to 5.

Images