JP4782087B2 - Sheet conveying apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a sheet conveying apparatus and an image forming apparatus including the sheet conveying apparatus.

  In a sheet conveying device provided in a conventional image forming apparatus or document reading apparatus, a light emitting unit and a light receiving unit are provided as detection means for detecting the presence or absence of a sheet of recording paper or a document conveyed in a sheet conveying path, It is known to use an optical sensor that detects the presence or absence of a conveyed sheet according to the amount of light of a light receiving unit that receives light from a light emitting unit.

  In such an optical sensor, the amount of light emitted from a light emitting unit (for example, a light emitting diode (infrared LED) that emits infrared light) may decrease with time. Then, although the sheet is being conveyed (there is a sheet), an erroneous detection may occur as the sheet is not conveyed (no sheet).

  Considering the decrease in the light emission amount due to the change over time, it is conceivable to increase the light amount of the light emitting unit from the beginning. However, in this case, the drive current to the light emitting unit increases, leading to a reduction in the life of the light emitting unit. .

On the other hand, Patent Document 1 below discloses an image forming apparatus that determines whether or not the sheet conveyance count has reached a predetermined value and adjusts the light amount of the light emitting unit.
JP 2003-267589 A

  However, in the image forming apparatus described in Patent Document 1, since the light amount of the light emitting unit is adjusted when the sheet conveyance count reaches a predetermined value, the light emitting unit is adjusted before the sheet conveyance count reaches the predetermined value. When the amount of light emission decreases, sensor misdetection occurs.

  Therefore, the present invention is capable of adjusting the light amount of the light emitting unit regardless of the sheet conveyance count, and thereby reliably preventing erroneous detection of the sensor accompanying a change with time, and an image forming apparatus including the same. The purpose is to provide.

In order to solve the above problems, the present invention provides the following sheet conveying apparatus and image forming apparatus.
(1) Sheet conveying device A sheet conveying path for conveying a sheet in a predetermined conveying direction, a light emitting unit, and a light receiving unit, and the irradiation light from the light emitting unit is reflected on the sheet conveyed to the sheet conveying path. A reflection type optical sensor that receives reflected light from the sheet by the light receiving unit and detects the presence or absence of the sheet, an irradiation light adjustment unit that adjusts the light amount of the light emitting unit, and a control unit, The control unit irradiates at least a non-image area of the conveyed sheet with light from the light-emitting unit, measures reflected light received by the light-receiving unit from the non-image area, and based on a measurement value by the measurement, the irradiation light A sheet conveying apparatus that controls an adjustment unit to adjust a light amount of the light emitting unit.
(2) Image forming apparatus An image forming apparatus comprising the sheet conveying apparatus according to the present invention.

  Here, the non-image area refers to an area where no image is formed on the sheet. For example, when the background color of the sheet is white, the non-image area is a white area.

  According to the sheet conveying apparatus and the image forming apparatus according to the present invention, the control unit irradiates light from the light emitting unit to at least a non-image region of the conveyed sheet, and receives light reflected from the non-image region by the light receiving unit. Since the light is measured and the irradiation light adjusting unit is controlled based on the measured value to adjust the light amount of the light emitting unit, the light amount of the light emitting unit can be adjusted regardless of the sheet conveyance count. Accordingly, it is possible to reliably prevent erroneous detection of the sensor accompanying a change with time.

In the sheet conveying apparatus according to the present invention, it is preferable that the control unit measures reflected light from a non-image area provided at an end portion of the conveyed sheet when adjusting the light amount of the light emitting unit. In this case, the following specific aspect can be illustrated. That is,
(A) A mode in which the control unit measures reflected light from a non-image area provided at a downstream end portion of the transported sheet in the transport direction when adjusting the light amount of the light emitting unit;
(B) The control unit is an aspect that measures reflected light from a non-image area provided at an upstream end of the transported sheet in the transport direction when adjusting the light amount of the light emitting unit.

  When measuring the reflected light from the non-image area provided at the edge of the conveyed sheet, the control unit adjusts the light amount of the light emitting unit from the central part of the non-image area in the conveyance direction. It is preferable to measure the reflected light.

  In the sheet conveying apparatus according to the present invention, a guide member for guiding the sheet so as to flatten the sheet conveyed toward the reflective optical sensor may be provided in the sheet conveying path.

  As described above, according to the present invention, the amount of light emitted from the light emitting unit can be adjusted regardless of the number of sheet conveyance counts. An image forming apparatus can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the following embodiment is an example which actualized this invention, Comprising: The thing of the character which limits the technical scope of this invention is not.

  FIG. 1 is a schematic configuration diagram of an image forming apparatus 100 including a sheet conveying device according to an embodiment of the present invention.

  First, the overall configuration of the image forming apparatus 100 shown in FIG. 1 will be described. In this embodiment, an image forming apparatus 100 shown in FIG. 1 forms an image by an electrophotographic image forming process. The image forming apparatus 100 includes an image carrier (here, a photosensitive drum) 21, a charging device (here, a charger) 22 for charging the surface of the photosensitive drum 21, and an electrostatic latent image on the photosensitive drum 21. And a developing device (here, a developing device) 24 for developing the electrostatic latent image with a developer to form a toner image on the photosensitive drum 21. A transfer device (here, a transfer unit) 25 for transferring the toner image on the photosensitive drum 21 to the recording paper P (an example of a sheet), and fixing the transfer image on the recording paper P to the recording paper P. A fixing device (here, a fixing unit) 27 for cleaning, and a cleaning device (here, a cleaner unit) 2 for removing residual toner not transferred by the transfer unit 25 but remaining on the surface of the photosensitive drum 21. When the control unit 50 and a (not shown in FIG. 1, refer to FIG. 3 to be described later).

  Specifically, the image forming apparatus 100 forms a monochrome image on the recording paper P based on image data read from a document or image data received from an external device (not shown). The image forming apparatus 100 is roughly divided into a document reading apparatus 200, an image forming unit 103, a recording paper transport path 40, a recording paper reverse discharge path 104, and a paper feeding unit 105. The recording paper conveyance path 40 and the recording paper reverse discharge path 104 constitute a sheet conveyance path.

  The document reading apparatus 200 includes a document transport unit (ADF) 101 and a document reading unit 102. When at least one document is set on the document set tray 11, the document transport unit 101 pulls out the documents one by one from the document set tray 11 and transports them. The document conveying unit 101 guides and passes the document to the document reading window 102 a of the document reading unit 102, and discharges the document to the document discharge tray 12.

  A CIS (Contact Image Sensor) 13 is disposed above the document reading window 102a. The CIS 13 repeatedly reads an image on the back side of the document in the main scanning direction when the document passes through the document reading window 102a, and converts an optically read optical signal on the back side of the document into an electrical signal.

  The document reading unit 102 exposes the document surface by the lamp of the first scanning unit 15 when the document passes through the document reading window 102a. The document reading unit 102 guides reflected light from the document surface to the imaging lens 17 by the mirrors of the first and second scanning units 15 and 16, and the imaging lens 17 converts the image on the document surface to a CCD (Charge Coupled). Device) 18 is imaged. The CCD 18 repeatedly reads an image on the surface of a document in the main scanning direction, and converts an optical signal of the document image optically read into an electrical signal.

  Further, when the document is placed on the platen glass on the upper surface of the document reading unit 102, the document reading unit 102 moves the first and second scanning units 15 and 16 while maintaining a predetermined speed relationship with each other. The first scanning unit 15 exposes the document surface on the platen glass. The document reading unit 102 guides reflected light from the document surface to the imaging lens 17 by the first and second scanning units 15 and 16, and forms an image of the document surface on the CCD 18 by the imaging lens 17. It is like that.

  The electrical signal output from the CIS 13 or the CCD 18 is converted into a digital signal as image data, and then subjected to various image processing under the control of the control unit 50 including the microcomputer 56 and the like, and then output to the image forming unit 103. The

  The image forming unit 103 records an image on the recording paper P based on the image data. The image forming unit 103 includes the photosensitive drum 21, the charger 22, the exposure unit 23, the developing unit 24, the transfer unit 25, and the cleaner unit. 26 and a fixing unit 27.

  The charger 22 is a charging means for uniformly charging the surface of the photosensitive drum 21 to a predetermined potential. In the present embodiment, the charger 22 is of a charger type. The charger 22 may be of a roller type or a brush type that contacts the photosensitive drum 21.

  In the present embodiment, the exposure unit 23 is a laser scanning unit (LSU) including two laser irradiation units 28a and 28b and two mirror groups 29a and 29b. The exposure unit 23 emits laser light from the laser irradiation units 28a and 28b in accordance with input image data. Further, the exposure unit 23 irradiates the surface of the photosensitive drum 21 uniformly charged by the charger 22 by irradiating the photosensitive drum 21 with these laser beams via the mirror groups 29a and 29b. ing. Thereby, an electrostatic latent image can be formed on the surface of the photosensitive drum 21. In the present embodiment, the exposure unit 23 employs a two-beam system including two laser irradiation units 28a and 28b in order to cope with high-speed image forming processing, so that the burden associated with increasing the irradiation timing can be reduced. It has become. As the exposure unit 23, an EL writing head or LED writing head in which light emitting elements are arranged in an array can be used instead of the laser scanning unit.

  The developing unit 24 supplies toner to the surface of the photosensitive drum 21 to develop the electrostatic latent image, and forms a toner image (also referred to as a visible image) on the surface of the photosensitive drum 21.

In the present embodiment, the transfer unit 25 includes a transfer belt 31, a driving roller 32, a driven roller 33, and an elastic conductive roller 34. The transfer belt 31 is stretched around these rollers 32 to 34 and other rollers. The surface of the transfer belt 31 is moved by the rotation of these rollers, so that the recording paper P placed on the surface is conveyed. The transfer belt 31 has a predetermined resistance value (for example, 1 × 10 ⁹ to 1 × 10 ¹³ Ω / cm). The elastic conductive roller 34 is pressed against the surface of the photosensitive drum 21 via the transfer belt 31. Thereby, the recording paper P on the transfer belt 31 can be pressed against the surface of the photosensitive drum 21. A transfer electric field having a polarity opposite to the charge of the toner image on the surface of the photosensitive drum 21 is applied to the elastic conductive roller 34. The toner image on the surface of the photosensitive drum 21 can be transferred onto the recording paper P on the transfer belt 31 by the transfer field having the reverse polarity. For example, when the toner image has a charge of (−) polarity, the polarity of the transfer electric field applied to the elastic conductive roller 34 is (+) polarity. In the transfer unit 25, the elastic conductive roller 34 has elasticity, so that the photosensitive member 21 and the transfer belt 31 are not in line contact but in surface contact having a predetermined width (referred to as a transfer nip). Thereby, the transfer efficiency to the conveyed recording paper P can be improved.

  On the downstream side of the transfer region in the transfer direction of the transfer belt 31, the recording paper P charged by the voltage applied when passing through the contact portion with the photosensitive drum 21 is discharged, and the transfer to the next process is smoothly performed. A neutralizing roller 51 is provided for this purpose. The charge removal roller 51 is disposed in contact with the back surface of the transfer belt 31 (the surface opposite to the conveyance surface of the recording paper P). The transfer unit 25 is also provided with a belt cleaning unit 54 that removes toner on the transfer belt 31 and a static elimination mechanism 55 that neutralizes the transfer belt 31. The neutralization mechanism 55 includes a method of grounding the transfer belt 31 or a method of positively applying a polarity opposite to the polarity of the transfer electric field to the transfer belt 31.

  The fixing unit 27 heats and presses the recording paper P to heat and fix the toner image on the recording paper P. Specifically, the fixing unit 27 includes a heating roller 35 and a pressure roller 36. A recording paper peeling claw 64, a roller surface temperature detection member (thermistor) 65, and a roller surface cleaning member 66 are disposed on the outer peripheral surface of the heating roller 35. A heat source 67 for heating the surface of the heating roller 35 to a predetermined temperature (fixing temperature: approximately 160 to 200 ° C.) is provided inside the heating roller 35. Further, pressure members (not shown) are arranged at both ends of the pressure roller 36 so that the pressure roller 36 is pressed against the heating roller 35 with a predetermined pressure. Similar to the outer peripheral surface of the heating roller 35, a recording paper peeling claw 64 and a roller surface cleaning member 66 are disposed on the outer peripheral surface of the pressure roller 36.

  In the fixing unit 27, when the recording paper P is conveyed to a pressure contact portion (referred to as a fixing nip portion) between the heating roller 35 and the pressure roller 36, the recording paper P is conveyed by these rollers 35 and 36. At the same time, the unfixed toner image on the recording paper P is heated and melted and pressed. As a result, the toner image can be fixed on the recording paper P.

  The cleaner unit 26 has a cleaning blade 26A that removes and collects toner remaining on the surface of the photosensitive drum 21 after development and transfer.

  In the present embodiment, the recording paper conveyance path 40 constituting the sheet conveyance path leads the recording paper P from the plurality of paper supply trays 60,. Specifically, the recording paper transport path 40 is provided with a plurality of pairs of transport rollers 41 for transporting the recording paper P and a pair of registration rollers 42. The pair of registration rollers 42 conveys the recording paper P from a plurality of pairs of conveyance rollers 41 in synchronization with the electrostatic latent image on the photosensitive drum 21. The pair of registration rollers 42 are disposed on the upstream side of the photosensitive drum 21 and on the downstream side of the plurality of pairs of conveyance rollers 41 in the recording paper conveyance direction (X direction in the drawing). Specifically, the pair of registration rollers 42 are disposed in the vicinity of the upstream side of the photosensitive drum 21 in the recording paper conveyance direction X.

  In the recording paper transport path 40, a plurality of pairs of transport rollers 41 receives the recording paper P from the paper feed trays 60,... Via the paper feeding mechanism 70, and the recording paper P until the leading edge of the recording paper P reaches the registration roller 42. P is conveyed. That is, the plurality of pairs of conveying rollers 41 convey the recording paper P until the leading edge of the recording paper P reaches and contacts the temporarily stopped registration roller 42 and the recording paper P bends. ing. Due to the elastic force of the bent recording paper P, the leading end of the recording paper P can be aligned parallel to the registration roller 42. Thereafter, the registration roller 42 is rotated to convey the recording paper P to the transfer unit 25 of the image forming unit 103.

  In this embodiment, the recording paper reverse discharge path 104 constituting the sheet transport path includes a transport path 43 and reverse transport paths 44a and 44b. The recording paper reverse discharge path 104 is provided with a plurality of branching claws 45 and a pair of paper discharge rollers 46.

  The recording paper reverse discharge path 104 is configured to convey the recording paper P on which the image is formed by the image forming unit 103 to the paper discharge tray 47 through the conveyance path 43 by the paper discharge roller 46. Further, when an image is also formed on the back side of the recording paper P, the recording paper reverse discharge path 104 selectively switches the plurality of branch claws 45 so that the recording paper P is transported from the transport path 43 to the reverse transport path 44b. Then, the conveyance of the recording paper P is temporarily stopped. Further, the recording paper reverse discharge path 104 is configured to guide the recording paper P from the reverse conveyance path 44b to the reverse conveyance path 44a by selectively switching each branch claw 45 again. As a result, the recording paper P is turned upside down and returned to the registration roller 42 through the reverse conveying path 44a and the recording paper conveying path 40, and an image is also formed on the back surface.

  In the recording paper conveyance path 40 and the recording paper reverse discharge path 104, sensors (for example, reflection type optical sensors S (S1 to S4) described later) for detecting the position of the recording paper P and the like are arranged at various places. . Thus, the transport roller 41 and the registration roller 42 are driven and controlled based on the position of the recording paper P detected by each sensor, and the recording paper P is transported and positioned.

  The sheet feeding unit 105 includes a plurality of sheet feeding trays 60,... And a plurality of sheet feeding mechanisms 70 provided corresponding thereto. Each paper feed tray 60 is for accumulating a plurality of recording papers P, and is provided in the lower part of the image forming apparatus 100 in this embodiment.

  Since the image forming apparatus 100 is intended for high-speed image forming processing in this embodiment, each paper feed tray 60 can accommodate 500 to 1500 sheets of standard size recording paper P such as A4, A3, and B4. A sufficient volume is secured.

  Further, on the side surface of the image forming apparatus 100, a large-capacity paper feed cassette (LCC) 52 capable of storing a large amount of a plurality of types of recording paper P and mainly an irregular size and / or a small amount of recording paper P are supplied. A manual feed tray 53 is provided.

  The paper discharge tray 47 is disposed on the side surface opposite to the manual feed tray 53. In this image forming apparatus 100, instead of the paper discharge tray 47, a post-processing device for discharged recording paper (for example, a post-processing device such as stapling and punching processing) and a plurality of paper discharge trays are arranged as options. Is also possible.

   Since the recording paper transport path 40 shares a transport path for transporting the recording paper P from each paper feed tray 60 to the image forming unit 103, the recording paper transport path 40 includes a single main transport path 40a and a plurality of paper feed trays 60,. A plurality of sub-conveying paths 40b for conveying the recording paper P to the main conveying path 40a. That is, the main transport path 40a is configured such that the recording paper P from the plurality of paper feed trays 60,... Is guided through the corresponding sub transport path 40b.

  A reflective optical sensor S is provided in the sheet conveyance path. The reflective optical sensor S detects the presence / absence of the sheet P conveyed to the sheet conveyance path, and can be disposed at any position where the presence / absence of the sheet P in the sheet conveyance path is to be detected. . For example, the reflective optical sensor S may be disposed between the paper feed tray 60 or the manual feed tray 53 in the recording paper conveyance path 40 and the registration roller 42 (see S1 and S2 in FIG. 1) or recording. It may be arranged in the paper reverse discharge path 104 (see S3 and S4 in FIG. 1). The reflective optical sensor S will be described in detail later.

  The control unit 50 controls the overall operation of the image forming apparatus 100 and includes, for example, a microcomputer 56 and a storage unit 57. The storage unit 57 includes a ROM (Read Only Memory), a RAM (Random Access Memory), and a nonvolatile memory.

The ROM stores a control program that is a procedure of processing executed by the microcomputer 56. The RAM provides a work area for work. The nonvolatile memory backs up and holds data necessary for control.
The controller 50 controls the timing of members such as motors, solenoids, and lamps connected to the output system based on input signals from various sensors and switches connected to the input system. Yes.

  The image forming apparatus 100 has a copier mode, a printer mode, and a facsimile (FAX) mode as image forming modes for forming an image on the recording paper P, and each mode is selected by the user.

  The control unit 50 is configured to include means for controlling a conveyance method from the fixing unit 27 to the paper discharge tray 47 in accordance with an image forming mode and a printing processing method (for example, single-sided printing / double-sided printing).

  In the copier mode, since the user normally operates near the image forming apparatus 100, the conveyance of the recording paper P is often controlled so that the recording paper P is discharged with the image forming surface facing upward. This is called “face-up discharge”. On the other hand, in each mode of the printer and the FAX, since the user is not usually in the vicinity of the image forming apparatus 100, the “face-down discharge” method for aligning the page order of the discharged recording paper P is often used.

  Therefore, the image forming apparatus 100 has a mechanism capable of switching between face-up discharge and face-down discharge according to the image forming mode. The switching mechanism is responsive to the print mode by a plurality of conveyance paths 44a and 44b and a plurality of branching claws 45 arranged until the recording paper P that has passed through the fixing unit 27 is discharged to the paper discharge tray 47. The recording paper is discharged.

  Next, the recording paper conveyance operation of the image forming apparatus 100 shown in FIG. 1 will be described. The recording paper conveyance operation is performed under the control of the control unit 50. That is, the recording paper P that meets the print request selected from the plurality of paper feed trays 60 is conveyed to the registration roller 42 by the conveyance roller 41 in the recording paper conveyance path 40, reaches the registration roller 42, and stops temporarily. To do.

  The image forming apparatus 100 rotates the registration roller 42 together with the conveying roller 41 at the timing when the toner image formed on the photosensitive drum 21 and the recording paper P are synchronized by the operation control of the control unit 50, thereby recording paper P is conveyed to the transfer unit 25. Then, the image forming apparatus 100 transfers the toner image on the photosensitive drum 21 to the recording paper P conveyed to the transfer unit 25 by the operation control of the control unit 50, and then guides the recording paper P to the fixing unit 27. Then, the transferred toner image is fixed, and is further discharged to the paper discharge tray 47.

  FIG. 2 is a schematic side view showing a state in which the recording paper P is detected by the reflective optical sensor S in the sheet conveyance path (for example, the recording paper conveyance path 40 and the recording paper reverse discharge path 104). 2 (a) shows a state in which the recording paper P being conveyed does not pass through the sensor S (no recording paper P is present), and FIG. 2 (b) shows that the recording paper P being conveyed is the sensor. A state where the sheet passes through S (there is recording paper P) is shown. In FIG. 2, an example in which the reflective optical sensor S is provided between the first transport roller 41 and the second transport roller 41 disposed on the downstream side in the recording paper transport direction X of the first transport roller 41. Is shown.

  The reflective optical sensor S includes a light emitting unit Sa and a light receiving unit Sb, and reflects the irradiation light La from the light emitting unit Sa on the conveyed recording paper P to receive the reflected light Lb from the recording paper P. The unit Sb receives light and detects whether or not the recording paper P is conveyed. As a result, the reflection type optical sensor S irradiates the recording paper P being conveyed with the light La from the light emitting portion Sa and receives the reflected light Lb from the recording paper P according to the amount of light of the light receiving portion Sb. The presence or absence of the paper P can be detected.

  In the present embodiment, the sheet conveying path is provided with a guide member 80 for guiding the recording paper P so that the recording paper P conveyed toward the reflective optical sensor S is flattened. That is, the guide member 80 guides the recording paper P so that the recording paper P is flat at least at a position facing the detection surface of the reflective optical sensor S. Here, the guide member 80 is provided with an opening 81 at a position facing the detection surface of the reflective optical sensor S (that is, a position where the light La from the light emitting section Sa is directed). The opening 81 serves to escape the light La from the light emitting portion Sa so that the light La from the light emitting portion Sa is reflected and not received by the light receiving portion Sb when the recording paper P is not present.

  FIG. 3 is a schematic block diagram mainly showing the control unit 50 and the reflective optical sensor S in the image forming apparatus 100 shown in FIG.

  As shown in FIG. 3, the light emitting unit Sa of the reflective optical sensor S is connected to the output system of the control unit 50 via the D / A converter 61. The D / A converter 61 functions as an irradiation light adjusting unit, and can adjust the irradiation light La light amount of the light emitting unit Sa under the instruction of the control unit 50. Thereby, the light emission part Sa is driven by the output of the D / A converter 61 to adjust the amount of light. Here, the light emitting unit Sa is an infrared LED that emits infrared light.

  The light receiving unit Sb outputs an analog signal (voltage value at α in FIG. 3) that receives the reflected light Lb from the recording paper P as a measured value. The light receiving unit Sb is connected to the input system of the control unit 50 by two systems. That is, the light receiving unit Sb is directly connected to the input system of the control unit 50 in one system, and is connected to the input system of the control unit 50 in the other system via the A / D converter 62. The A / D converter 62 converts the analog output from the light receiving unit Sb into a digital value. Here, the light receiving unit Sb is an infrared phototransistor that receives the infrared light from the light emitting unit Sa.

  The sheet conveying apparatus according to the embodiment of the present invention includes the sheet conveying path, the reflective optical sensor S, the irradiation light adjusting unit 61, and the control unit 50.

  Then, the control unit 50 irradiates at least a non-image area (an area where no image is formed) of the transported recording paper P from the light emitting unit Sa and receives light from the non-image area of the recording paper P by the light receiving unit Sb. The reflected light Lb is measured, and the irradiation light adjusting unit 61 is controlled based on the measurement value by the measurement to adjust the light amount of the irradiation light La of the light emitting unit Sa.

  According to the image forming apparatus 100 including the sheet conveying apparatus according to the embodiment of the present invention, the reflection type optical sensor S that detects the presence or absence of the recording paper P by the reflected light Lb from the recording paper P is the recording paper being conveyed. The light quantity of the light emitting portion Sa can be adjusted by the reflected light Lb from the non-image area of P. Thereby, the light quantity of the light emitting portion Sa can be adjusted regardless of the conveyance count number of the recording paper P, and it is possible to surely prevent erroneous detection of the sensor S accompanying a change with time.

  Further, it is possible to adjust the light amount of the light emitting unit Sa during the operation of the apparatus without stopping the operating device for adjusting the light amount of the light emitting unit Sa.

  Incidentally, when an image is formed on the recording paper P, the end P ′ of the recording paper P (that is, the upstream and downstream ends of the recording paper P in the transport direction X and the width direction of the recording paper P (the transport direction X)). In many cases, a non-image area where no image is formed is present at one end and the other end) in the direction orthogonal to the other.

  From this point of view, in the present embodiment, the control unit 50 adjusts the light amount of the light emitting unit Sa to the end portion P ′ of the recording paper P being conveyed (here, the downstream side in the conveyance direction X of the recording paper P). The reflected light received by the light receiving portion Sb from the non-image area provided at the end portion or the upstream end portion is measured.

  4 is a perspective view showing a state immediately before measuring the reflected light from the non-image area P0 of the recording paper P, and FIG. 5 is a downstream direction end P1 ′ of the recording paper P being conveyed in the conveyance direction X. It is a perspective view which shows the detection state. In FIGS. 4 and 5, hatched portions indicate image areas. The same applies to FIG. 6 described later.

  The image forming apparatus 100 according to the present embodiment does not form an image (here, a toner image) in at least both ends of the four-side peripheral area of the rectangular recording paper P in the conveyance direction X (in this example, the peripheral areas of all four sides). An image is formed on the recording paper P so as to provide the non-image area P0.

  In the state shown in FIG. 4, since the light La from the light emitting portion Sa passes through the opening 81 of the guide member 80, the reflection type optical sensor S does not receive the light La from the light emitting portion Sa at the light receiving portion Sb. Although the reflected light Lb is not detected by the light receiving unit Sb, in the state shown in FIG. 5, the first non-image area where the light La from the light emitting unit Sa is provided at the downstream end portion P1 ′ in the conveyance direction X of the recording paper P (Front end void) P1 or reflected light Lb received by the light receiving portion Sb is detected by being reflected on the second non-image area (rear end void) P2 provided at the upstream end P2 ′. .

  Specifically, when adjusting the light amount of the light emitting unit Sa, the control unit 50 measures the reflected light received by the light receiving unit Sb from the central portion in the transport direction X of the first non-image region P1 or the second non-image region P2. It is configured as follows.

  FIG. 6 is a diagram illustrating a measurement state of the light amount of the reflected light Lb from the central portion in the transport direction X of the first non-image area P1 of the recording paper P.

  For example, when the widths d1 and d2 in the transport direction X of the first non-image area P1 or the second non-image area P2 are 4 mm, the central portion C1 in the transport direction X of the first non-image area P1 or the second non-image area P2 , C2 are located 2 mm inside from the downstream end or upstream end in the conveyance direction X of the recording paper P, respectively.

  In this way, by measuring the reflected light Lb received by the light receiving unit Sb from the transport direction X center portions C1 and C2 of the first non-image region P1 or the second non-image region P2, the light amount of the reflected light Lb is stabilized. Can be detected.

  Next, detection control of the reflective optical sensor S by the control unit 50 will be described. FIG. 7 is a diagram illustrating an example of a flowchart for performing detection control of the reflective optical sensor S by the control unit 50 of the image forming apparatus 100 illustrated in FIG. 1.

  The flowchart shown in FIG. 7 is executed in parallel when the image forming apparatus 100 forms an image. In this flowchart, the control operation is started at the timing of the start of feeding the recording paper P (for example, pickup from the paper feed tray 60).

  First, it waits until the reflection type optical sensor S detects the arrival of the edge in the conveyance direction X downstream side of the recording paper P (the leading edge of the recording paper P) (step S110: No), and when this is detected (step S110: Yes). ) After waiting for a predetermined time T0 (step S120), the process proceeds to step S130.

  This predetermined time T0 is the central portion C1 in the transport direction X of the first non-image area P1 from the leading edge of the recording paper P, or the first non-image area P1 from the leading edge of the recording paper P in the second non-image area P2. This is the time to the central part C2 in the transport direction X.

  Specifically, when the width d1 in the transport direction X of the first non-image area P1 is 4 mm and the transport speed of the recording paper P is 300 [mm / sec], the first non-image area P1 from the leading edge of the recording paper P is assumed. Since the length d1 ′ up to the central portion C1 is 2 [mm], the standby time T0 = (2 [mm] ÷ 300 [mm / sec]) is set to 0.0067 [sec].

  Further, the length d3 of the recording paper P in the transport direction X is 210 [mm], the width d2 of the second non-image area in the transport direction X is 4 [mm], and the transport speed of the recording paper P is 300 [mm / sec], the length d2 ′ from the leading edge of the recording paper P to the central portion C2 of the second non-image area P2 is 210 mm−2 mm = 208 mm, so the standby time T0 = (208 [mm] ÷ 300 [mm / sec). ]) Is set to 0.6933 [sec].

  Next, the light amount of the reflected light Lb from the first non-image region P1 or the second non-image region P2 is measured by the light receiving unit Sb (step S130).

  FIG. 8 is a diagram showing a temporal change in the output voltage (voltage value at α in FIG. 3) of the light receiving unit Sb in the reflective optical sensor S detected during conveyance of the recording paper P.

  As shown in FIG. 8, since the voltage value is the lowest in the first non-image area P1 (front end void) and the second non-image area P2 (rear end void), the amount of light is corrected by the measured value at this time. That's fine.

  That is, the analog output of the light receiving unit Sb that receives the reflected light Lb from the first non-image region P1 or the second non-image region P2 is converted into a digital output value by the A / D converter 62, and the digital output value (Value in β in FIG. 3) is stored in the storage unit 57 (for example, the RAM) (step S140).

  The digital output value (value at β in FIG. 3) stored in the storage unit 57 is compared with a preset reference value (step S150), and the current value to the light emitting unit Sa is corrected based on the comparison result. In this manner, the digital output value (value at γ in FIG. 3) is output to the D / A converter 61 (step S160). The correction amount of the current value to the light emitting unit Sa will be described later.

  The D / A converter 61 converts the digital output value (value at γ in FIG. 3) from the control unit 50 into an analog signal (current value to the light emitting unit Sa) and adjusts the light amount of the light emitting unit Sa (step). S170).

  Next, the correction amount of the current value to the light emitting unit Sa will be described. FIG. 9 is a diagram showing the output voltage (voltage value at α in FIG. 3) of the light receiving unit Sb when the reflected light Lb from the non-image area P0 of the recording paper P is received. The thick broken line indicates the output voltage before adjustment, and the thick solid line in FIG. 9B indicates the output voltage after adjustment.

  In FIG. 9, the threshold value is a value that is determined to be L (Low level) when a voltage equal to or lower than this value is input to the control unit 50, and is a control in which the output voltage of the light receiving unit Sb is input. The threshold value of the input part of the part 50 is shown. In FIG. 9A, the measured value (initial time) indicates the measured value immediately after the start of use of the reflective optical sensor S (initial time), and the measured value (after change with time) indicates the reflective optical sensor S. The measured value after using for a long time is shown. After the time-dependent change of the reflective optical sensor S, the output value of the light receiving portion Sb increases due to the light amount reduction of the light emitting portion Sa. In FIG. 9B, the measured value (after adjustment) indicates the measured value of the light receiving unit Sb by adjusting the light amount by increasing the current supplied to the light emitting unit Sa. The measured value after this adjustment is reduced to the same level as the initial value.

  If the initial current value of the light emitting part Sa is Io, the initial measured value of the output voltage of the light receiving part Sb (voltage value at α in FIG. 3) is Ao, and the measured value after change over time is A, then corrected The current value I to the light emitting portion Sa can be obtained by the following equation (1).

I = Io × A / Ao (1)
Then, the control unit 50 outputs a voltage value corresponding to the current value I of the light emitting unit Sa after the correction of Expression (1) to the D / A converter 61.

  In the image forming apparatus 100 described above, the image forming unit 103 is applied to a sheet conveying apparatus that conveys the recording paper P. However, the sheet conveying apparatus according to the present invention is not limited thereto, and the document reading apparatus 200 can The present invention can also be applied to a sheet conveying apparatus that conveys a document.

1 is a schematic configuration diagram of an image forming apparatus including a sheet conveying device according to an embodiment of the present invention. FIG. 5 is a schematic side view showing a state in which recording paper is detected by a reflective optical sensor in a sheet conveyance path, and FIG. (A) is a diagram showing a state in which the recording paper being conveyed does not pass through the sensor. FIG. 5B is a diagram showing a state in which the recording paper being conveyed passes through the sensor. FIG. 2 is a schematic block diagram mainly showing a control unit and a reflective optical sensor in the image forming apparatus shown in FIG. 1. It is a perspective view which shows the state just before measuring the reflected light from the non-image area | region of a recording paper. FIG. 6 is a perspective view illustrating a detection state at a downstream end portion in a conveyance direction of a recording sheet to be conveyed. It is a figure which shows the measurement state of the light quantity of the reflected light from the center part in the conveyance direction of the 1st non-image area | region of a recording paper. FIG. 2 is a diagram illustrating an example of a flowchart for performing detection control of a reflective optical sensor by a control unit of the image forming apparatus illustrated in FIG. 1. It is a figure which shows the time change of the output voltage of the light-receiving part in the reflection type optical sensor detected during conveyance of a recording paper. FIG. 7 is a diagram illustrating an output voltage of a light receiving unit when reflected light from a non-image area of a recording sheet is received, and FIG. (A) is a diagram illustrating an output voltage before adjustment (see a thick broken line); (B) is a figure which shows the output voltage (refer thick line) after adjustment.

Explanation of symbols

40 Sheet transport path (recording paper transport path)
50 Control unit 61 Irradiation light adjustment unit 80 Guide member 100 Image forming apparatus 104 Sheet conveyance path (recording paper reverse discharge path)
C1, C2 Center portion La in the conveyance direction of the non-image area La Irradiation light Lb Reflected light P Sheet (recording paper)
P0 sheet non-image area P1 first non-image area (tip void)
P2 Second non-image area (rear edge void)
P ′ Sheet edge P1 ′ Downstream edge in the sheet conveyance direction (sheet leading edge)
P2 'Upstream end in the sheet conveyance direction (sheet rear end)
S Reflective optical sensor Sa Light emitting part Sb Light receiving part X Sheet transport direction

Claims (7)

A sheet conveyance path for conveying the sheet in a predetermined conveyance direction;
A light-emitting unit and a light-receiving unit, and reflects the irradiation light from the light-emitting unit on the sheet conveyed to the sheet conveying path, and receives the reflected light from the sheet by the light-receiving unit to determine the presence or absence of the sheet A reflective optical sensor to detect;
An irradiation light adjusting unit for adjusting the light amount of the light emitting unit;
A control unit,
The control unit irradiates at least a non-image area of the conveyed sheet with light from the light-emitting unit, measures reflected light received by the light-receiving unit from the non-image area, and based on a measurement value by the measurement, the irradiation light A sheet conveying apparatus that controls an adjustment unit to adjust a light amount of the light emitting unit. In the sheet conveying apparatus according to claim 1,
The control unit measures reflected light from a non-image area provided at an end of the conveyed sheet when adjusting the light amount of the light emitting unit. In the sheet conveying apparatus according to claim 2,
The control unit measures reflected light from a non-image area provided at a downstream end portion of the transported sheet in the transport direction when adjusting the light amount of the light emitting unit. . In the sheet conveying apparatus according to claim 2,
The control unit measures reflected light from a non-image area provided at an upstream end portion of the transported sheet in the transport direction when adjusting the light amount of the light emitting unit. . In the sheet conveying apparatus according to any one of claims 2 to 4,
The control unit measures reflected light from a central portion of the non-image area in the transport direction when adjusting the light amount of the light emitting unit. In the sheet conveying apparatus according to any one of claims 1 to 5,
The sheet conveying apparatus, wherein the sheet conveying path is provided with a guide member for guiding the sheet conveyed toward the reflective optical sensor so as to be flat.   An image forming apparatus comprising the sheet conveying device according to claim 1.

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