JP2009035379A - Paper sheet conveying device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper sheet conveying device capable of effectively suppressing an increase of the charging quantity of static electricity by adjusting the humidity of a paper sheet conveying passage. <P>SOLUTION: When a large number of recording paper sheets are rapidly conveyed on a conveying path 43 one by one, a large amount of paper powder is generated by the friction between each conveying roller 41, each paper discharge roller 46 and the recording paper sheets, and a large amount of paper powder is charged with static electricity by the friction. However, a humidified air flow from a humidifier 63 flows in the conveying direction A along the conveying path 43, and the high atmospheric humidity of the conveying path 43 is maintained. Thus, paper powder is hardly charged, charges of the paper powder are rapidly discharged, and paper powder is hardly electrostatically attracted onto a detection surface 62a of an optical sensor 62. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sheet conveying apparatus that conveys a sheet by a conveying roller and an image forming apparatus including the same.

  In an image forming apparatus that performs high-speed printing, a paper transport device for transporting original paper or recording paper at high speed is indispensable. However, in such a paper transport device, the transport roller is rotated at a high speed to transport a large number of papers one after another, so that a large amount of paper dust is generated from the paper surface due to friction between the paper and the transport roller. A large amount of paper dust is charged with static electricity due to friction. Then, this electrostatically charged paper dust may adhere to various members near the paper transport path, causing problems. For example, in a configuration in which an optical sensor is provided to detect the paper transported in the paper transport path, static paper dust adheres to the detection surface of the optical sensor, and the detection sensitivity of the optical sensor deteriorates. Or false detection occurred.

  In order to prevent such static electricity, adjustment of the resistance value of the transport roller and grounding, or grounding of the paper transport path or its nearby members can be considered. However, the amount of electrostatic charge is large in the low humidity environment in the device. , Could not get enough effect.

On the other hand, in Patent Document 1, humidity is supplied to the paper cassette to reduce or prevent the curling of the paper, but the generation of static electricity is not suppressed by humidity adjustment, and there is no suggestion thereof.
JP-A-4-345447

  As described above, in order to prevent static electricity, adjustment of the resistance value of the transport roller and grounding have been conventionally performed. However, in a low-humidity environment in the apparatus, the amount of static electricity is large and sufficient effects can be obtained. I could not.

  In Patent Document 1, humidity is supplied to the paper cassette in order to reduce or prevent paper curling. However, the technical contrivance of suppressing the generation of static electricity by adjusting the humidity is not provided. Humidity is not supplied to the paper conveyance path.

  Furthermore, in the past, there has been no technical proposal for fundamentally suppressing the increase in the amount of electrostatic charge, although the amount of electrostatic charge has increased with the increase in the speed of the paper conveyance path. Technology was desired.

  Accordingly, the present invention has been made to solve the above-described problems, and provides a sheet conveying apparatus and an image forming apparatus that can effectively suppress an increase in static charge amount by adjusting the humidity of the sheet conveying path. For the purpose.

  In order to solve the above-described problems, a sheet conveying apparatus according to the present invention includes a sheet conveying path including a sheet conveying path that conveys a sheet by a conveying roller, and includes a humidifying unit that increases the atmospheric humidity of the sheet conveying path.

  In addition, the humidifying unit includes a blowing unit that blows a humidified airflow to the sheet conveyance path.

  Further, a partition wall is provided along the sheet conveyance path, and the detection surface of the optical sensor that detects the sheet conveyed on the sheet conveyance path is passed through the partition wall by flowing the humidified airflow blown from the blowing unit along the partition wall. It is provided so as to face the paper conveyance path.

  Further, the detection surface of the optical sensor is inclined so as to face the humidified airflow blown from the blowing means.

  Further, the optical sensor detects the paper through the translucent member, and the detection surface of the translucent member is inclined so as to face the humidified air flow blown from the blowing means.

  In addition, a partition wall is provided along the sheet transport path so that the humidified airflow blown from the blowing unit flows along the partition wall and is guided to the transport roller.

  Further, the blower blows a humidified airflow in a direction opposite to the paper transport direction in the paper transport path.

  On the other hand, an image forming apparatus according to the present invention includes the above-described sheet conveying device according to the present invention.

  The image forming apparatus transfers the image on the surface of the photosensitive member to the sheet while conveying the sheet along the sheet conveying path, and the humidifying unit is provided on the downstream side in the sheet conveying direction from the transfer position of the image. ing.

  According to the paper transport device of the present invention, the atmospheric humidity in the paper transport path can be increased by the humidifying means. In a high-humidity atmosphere, static electricity is unlikely to occur and is easily discharged. For this reason, if the atmospheric humidity of the paper transport path is increased by applying the present invention, even if paper dust is generated from the paper surface due to friction between the paper and the transport roller, the paper powder is difficult to be charged. The charged electric charge is quickly discharged, and the paper dust does not adhere to the detection surface of the optical sensor that detects the paper conveyed in the paper conveyance path.

  For example, a humidified airflow may be blown from the blower to the paper transport path. In this case, if a partition wall is provided along the paper conveyance path, and the humidified air current flows along the partition wall so that the detection surface of the optical sensor faces the paper conveyance path via the partition wall, the humidified air current is It flows along the detection surface, and the detection surface of the optical sensor is cleaned by the humidified airflow. Furthermore, if the detection surface of the optical sensor is inclined so as to face the humidified airflow, the humidified airflow hits the detection surface of the optical sensor, and paper dust or the like adhering to the detection surface is blown off by the humidified airflow. To be cleaned. Alternatively, in the case where the optical sensor detects paper via the translucent member, if the detection surface of the translucent member is inclined so as to face the humidified airflow, the humidified airflow of the translucent member When hitting the detection surface, the detection surface is efficiently cleaned by the humidified airflow.

  In addition, a partition along the paper transport path is provided so that the humidified air flow blown from the blowing means flows along the partition and is guided to the transport roller, so the humid air flow is generated by the friction between the paper and the transport roller. The paper powder can be directly applied, and the paper powder can be humidified to effectively suppress the charging of the paper powder.

  In addition, since the humidified airflow is blown in the direction opposite to the paper conveyance direction in the paper conveyance path, the humidified airflow and the direction of the airflow generated by the paper conveyance conflict, and the humidified airflow is weakened and gently The flow and the paper dust stay in the high atmospheric humidity for a long time, and the charging of the paper dust can be effectively suppressed.

  On the other hand, since the image forming apparatus according to the present invention includes the above-described paper conveying apparatus according to the present invention, the same effects can be obtained.

  In addition, since the humidifying means is provided downstream of the transfer position for transferring the image on the surface of the photoreceptor onto the paper, the static electricity of the paper or paper dust charged by the transfer potential can be effectively discharged. The paper dust of the paper can be effectively prevented from adhering to the detection surface of the optical sensor.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view showing an image forming apparatus to which a first embodiment of a paper conveying apparatus of the present invention is applied. The image forming apparatus 100 reads an image on a document sheet in the apparatus 100 to acquire image data, or acquires image data received from the outside, and forms a monochrome image indicated by the image data on a recording sheet. The configuration is roughly divided into an original paper transport unit (ADF) 101, an image reading unit 102, a printing unit 103, a recording paper transport unit 104, and a paper feed unit 105.

  When at least one document sheet is set on the document set tray 11 in the document sheet transport unit 101, each document on the document set tray 11 is sequentially pulled out by the pickup roller 3, and the documents are printed one by one by the roller roller 4. After the separation, the original is conveyed by each of the conveying rollers 5, 6, 7, etc., the original is guided to the original reading window 102 a of the image reading unit 102, and the original is discharged to the original 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 original paper in the main scanning direction when the original paper passes through the original reading window 102a, and outputs image data indicating the image on the back side of the original paper.

  The image reading unit 102 exposes the surface of the original paper by the lamp of the first scanning unit 15 when the original paper passes through the original reading window 102a, and the original by the mirrors of the first and second scanning units 15 and 16. Reflected light from the paper surface is guided to the imaging lens 17, and an image on the surface of the original paper is formed on a CCD (Charge Coupled Device) 18 by the imaging lens 17. The CCD 18 repeatedly reads an image on the surface of the original paper in the main scanning direction, and outputs image data indicating the image on the surface of the original paper.

  Further, when the original paper is placed on the platen glass 19 on the upper surface of the image reading unit 102, the first and second scanning units 15 and 16 are moved while maintaining a predetermined speed relationship with each other. 15, the surface of the original paper on the platen glass 19 is exposed, the reflected light from the original paper surface is guided to the imaging lens 17 by the first and second scanning units 15, 16, and the imaging lens 17 An image is formed on the CCD 18.

  The image data output from the CIS 13 or the CCD 18 is subjected to various image processing by a control circuit such as a microcomputer and then output to the printing unit 103.

  The printing unit 103 records a document indicated by image data on a sheet, and includes a photosensitive drum 21, a charger 22, an optical writing unit 23, a developing unit 24, a transfer unit 25, a cleaning unit 26, and a fixing device. 27 etc.

  The photoconductor drum 21 is an organic photoconductor whose surface layer is made of an organic photoconductive material. The photoconductor drum 21 rotates in one direction, the surface is cleaned by the cleaning unit 26, and the surface is uniformly charged by the charger 22. Is done. The charger 22 may be of a charger type or of a roller type or a brush type that contacts the photosensitive drum 21.

  The optical writing unit 23 is a laser scanning unit (LSU) including two laser irradiation units 28a and 28b and two mirror groups 29a and 29b. In the optical writing unit 23, image data is input, laser light corresponding to the image data is emitted from the laser irradiation units 28a and 28b, and the laser light is transmitted through the mirror groups 29a and 29b. The drum 21 is irradiated to expose the uniformly charged surface of the photosensitive drum 21 to form an electrostatic latent image on the surface of the photosensitive drum 21.

  The optical writing unit 23 employs a two-beam method including two laser irradiation units 28a and 28b in order to cope with high-speed printing processing, thereby reducing the burden associated with increasing the irradiation timing.

  As the optical writing unit 23, an EL writing head or an LED writing head in which light emitting elements are arranged in an array can be used instead of the laser scanning unit.

  The developing device 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. The transfer unit 25 transfers the toner image on the surface of the photosensitive drum 21 onto the recording paper conveyed by the paper conveyance unit 104. The fixing device 27 heats and pressurizes the recording paper to fix the toner image on the recording paper. Thereafter, the recording sheet is further conveyed to the sheet discharge tray 47 by the sheet conveying unit 104 and discharged. The cleaning unit 26 removes and collects the toner remaining on the surface of the photosensitive drum 21 after development and transfer.

Here, the transfer unit 25 includes a transfer belt 31, a drive roller 32, a driven roller 33, an elastic conductive roller 34, and the like, and the transfer belt 31 is stretched between the rollers 32 to 34 and other rollers. Rotating. The transfer belt 31 has a predetermined resistance value (for example, 1 × 10 ⁹ to 1 × 10 ¹³ Ω / cm), and conveys the recording paper placed on the surface thereof. The elastic conductive roller 34 is pressed against the surface of the photosensitive drum 21 via the transfer belt 31, and presses the recording paper on the transfer belt 31 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, and the toner image on the surface of the photosensitive drum 21 is transferred to the transfer belt by the transfer electric field having the opposite polarity. 31 is transferred to a recording sheet on the recording medium 31. 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 set to (+) polarity.

  The cleaning unit 26 presses the cleaning blade against the surface of the photosensitive drum 21 to remove residual toner and paper dust on the surface of the photosensitive drum 21.

  The fixing device 27 includes a heating roller 35 and a pressure roller 36. 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. When the recording paper is conveyed to a pressure contact area (referred to as a nip area) between the heating roller 35 and the pressure roller 36, the recording paper is conveyed by the rollers 35 and 36, and an unfixed toner image on the recording paper is formed. The toner image is fixed on the recording paper by being heated and melted and pressurized.

  The paper transport unit 104 includes a plurality of pairs of transport rollers 41, a pair of registration rollers 42, a transport path 43, reverse transport paths 44a and 44b, a plurality of branching claws 45, and a pair of paper discharge rollers 46 for transporting recording paper. Etc.

  In the conveyance path 43, the recording paper is received from the paper supply unit 105, and the recording paper is conveyed until the leading edge of the recording paper reaches the registration roller 42. At this time, since the registration roller 42 is temporarily stopped, the leading edge of the recording paper reaches and contacts the registration roller 42, and the recording paper is bent. The leading edge of the recording sheet is aligned parallel to the registration roller 42 by the elastic force of the bent recording sheet. Thereafter, rotation of the registration roller 42 is started, and the recording paper is conveyed to the transfer unit 25 of the printing unit 103 by the registration roller 42. Further, the recording sheet passes through the fixing device 27 and is then conveyed to the discharge tray 47 by the discharge roller 46.

  The registration roller 42 is stopped and rotated by switching on and off the clutch between the registration roller 42 and the drive shaft, or by switching on and off the motor that is the drive source of the registration roller 42.

  When an image is also recorded on the back side of the recording sheet, each branch claw 45 is selectively switched, and the recording sheet discharged from the fixing device 27 is led from the conveyance path 43 to the reverse conveyance path 44b to record. The conveyance of the paper is temporarily stopped, each branch claw 45 is selectively switched again, the recording paper is guided from the reverse conveyance path 44b to the reverse conveyance path 44a, and the recording paper is reversed. Is returned to the registration rollers 42 in the transport path 43 through the reverse transport path 44a.

  Such conveyance of the recording paper is referred to as switchback conveyance. By this switchback conveyance, the front and back of the recording paper can be reversed, and at the same time, the leading edge and the trailing edge of the recording paper are also switched. Therefore, when the recording paper is reversed and returned, the trailing edge of the recording paper comes into contact with the registration roller 42 and the trailing edge of the recording paper is aligned in parallel with the registration roller 42. Is transferred to the transfer unit 25 of the printing unit 103, and printing is performed on the back surface of the recording paper. The unfixed toner image on the back surface of the recording paper is heated and melted and pressed by the fixing device 27, and the toner image is transferred to the recording paper. After fixing on the back surface, the recording paper is conveyed to a paper discharge tray 47 by a paper discharge roller 46.

  In the transport path 43 and the reverse transport paths 44a and 44b, optical sensors (not shown) for detecting the position of the recording paper and the like are arranged in various places, and the transport roller is based on the position of the recording paper detected by each optical sensor. And the registration roller is driven and controlled to convey and position the recording paper.

  The paper feed unit 105 includes a plurality of paper feed trays 51. Each paper feed tray 51 is a tray for storing recording paper and is provided below the image forming apparatus 100. Each paper feed tray 51 is provided with a pick-up roller or the like for pulling out recording sheets one by one, and sends out the pulled recording sheets to the transport path 43 of the paper transport unit 104.

  Since the image forming apparatus 100 is intended for high-speed printing processing, each paper feed tray 51 has a capacity capable of storing 500 to 1500 standard size recording sheets.

  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 papers and a manual feed tray 53 for mainly supplying irregular-size recording papers are provided. ing.

  The paper discharge tray 47 is disposed on the side surface opposite to the manual feed tray 53. In place of the paper discharge tray 47, a post-processing device for paper discharge (such as stapling and punching) and a plurality of paper discharge trays can be arranged as options.

  In such an image forming apparatus 100, the printing process speed is increased to improve usability. For example, when A4 standard recording paper is used, the recording paper conveyance speed is set to 120 sheets / min (process speed 600 mm / sec).

  By the way, when recording paper is transported at high speed in this way, each transport roller 41, each paper discharge roller 46, and the like are rotated at high speed, and a large amount of paper dust is generated from the surface of the recording paper due to friction between the recording paper and the rollers. Or a large amount of paper dust is easily charged with static electricity. If the electrostatically charged paper dust is left unattended, the paper dust adheres to the detection surface of the optical sensor that detects the position of the recording paper in the transport path 43, and the detection sensitivity of the optical sensor is deteriorated or erroneous. Detection occurs.

  Therefore, in the present embodiment, the humidified airflow is supplied to at least a part of the transport path 43 to increase the atmospheric humidity of the transport path 43. In the region where the atmospheric humidity is increased, static electricity is unlikely to occur and discharge is easily caused. Even when paper dust is generated from the surface of the recording paper due to friction between the recording paper and the roller, the paper dust is hardly charged and the paper dust is not charged. It does not adhere to the detection surface of the optical sensor.

  2A and 2B are a cross-sectional view and a front view showing the paper conveying apparatus of the present embodiment. The sheet conveying apparatus of the present embodiment is used for supplying a humidified airflow to a part of the conveying path 43 in the image forming apparatus 100.

  In this sheet conveying apparatus, as shown in FIGS. 2A and 2B, the conveying path is in a range from a pair of conveying rollers 41 provided on the recording sheet discharging side of the fixing device 27 to a pair of discharging rollers 46. A humidified airflow is supplied to 43.

  The conveyance path 43 is formed by arranging upper and lower paper guide members 43a and 43b so as to guide the recording paper between the upper and lower paper guide members 43a and 43b. The lower paper guide member 43b is adjacent to a branch claw 45 and a branch conveyance path as shown in FIG. 1, but in FIG. 2A and FIG. 2B, these branch claw 45 and branch conveyance path. Etc. are omitted.

  The shaft 41 a of each transport roller 41 and the shaft 46 a of each paper discharge roller 46 are connected to a roller drive mechanism 61 provided on the side of the transport path 43, and the roller drive mechanism 61 causes each transport roller 41 and each transport roller 41 to be connected. The paper discharge roller 46 is driven to rotate. When the recording paper is discharged from the fixing device 27, the recording paper is guided between the transport rollers 41 and transported in the transport direction A by the transport rollers 41, and is discharged between the upper and lower paper guide members 43a and 43b. It is guided in between, conveyed by each paper discharge roller 46, and discharged to the paper discharge tray 47 in FIG.

  The optical sensor 62 is provided at a substantially central position between the transport roller 41 and the paper discharge roller 46 and above the upper paper guide member 43a, and the detection surface 62a of the optical sensor 62 is the opening 43c of the paper guide member 43a. The conveyance path 43 is faced through. As described above, since the detection surface 62a of the optical sensor 62 is disposed above the transport path 43, even if paper dust is generated in the transport path 43 as described later, the optical sensor located above the transport path 43. It is difficult for paper dust to adhere to the detection surface 62a of 62.

  The optical sensor 62 emits a light beam to the transport path 43 through the detection surface 62a, and receives the light beam reflected by the recording paper passing through the transport path 43, and is reflected by the recording paper. The presence or absence of a recording sheet is detected based on whether or not the light beam is received, and the passage of the leading and trailing ends of the recording sheet is detected.

  The humidifying device 63 blows a humidified airflow to the transport path 43 and is provided in the vicinity of the downstream side of each transport roller 41 and on the side of the transport path 43. The humidifying device 63 includes a blower fan 64 and a humidifying member 65 provided on the exhaust side of the blower fan 64. The humidifying member 65 is a fibrous or porous member, and is supplied with moisture as needed. The airflow blown from the blower fan 64 passes through the humidifying member 65, but is humidified at this time to become a high-humidity airflow (referred to as a humidified airflow), and is blown out to the transport path 43.

  This humidified airflow is blown out in a direction crossing the conveyance path 43, that is, in a direction orthogonal to the conveyance direction of the recording paper. When the recording paper passes through the conveyance path 43, the conveyance caused by the conveyance of the recording paper In response to the airflow in the direction, the flowing direction is changed to the transport direction. Therefore, the humidified airflow flows in the transport direction A together with the recording paper.

  The humidity sensor 66 is juxtaposed with the optical sensor 62 and faces the conveyance path 43 through the opening 43c of the paper guide member 43a to detect the atmospheric humidity of the conveyance path 43.

  The control unit 67 controls the amount of humidified airflow blown into the transport path 43 by controlling on / off the blower fan 64 of the humidifying device 63 according to the atmospheric humidity of the transport path 43 detected by the humidity sensor 66. The atmospheric humidity of the path 43 is adjusted. When the inside of the image forming apparatus 100 is in a low humidity environment, the blower fan 64 of the humidifier 63 is normally turned on, and the blower fan 64 is turned off when the ambient humidity rises to a specified value or higher. To do.

  In such a configuration, if a large number of recording sheets are conveyed one after another on the conveying path 43, a large amount of paper dust is generated due to friction between the conveying rollers 41 and the respective discharge rollers 46 and the recording sheet. Since the humidified airflow from the humidifier 63 flows in the transport direction A along the transport path 43 and the atmospheric humidity in the transport path 43 is kept high, the paper dust is less likely to be charged with static electricity and the charged charge of the paper powder is high. Electric discharge is quickly performed in a humidity atmosphere, and paper dust is not electrostatically adsorbed to the detection surface 62 a of the optical sensor 62. For this reason, the detection sensitivity of the optical sensor 62 does not deteriorate or erroneous detection does not occur due to adhesion of paper dust.

  Further, since the humidifying device 63 is provided on the downstream side in the transport direction from the transfer unit 25, the static electricity of the recording paper or paper dust charged by the transfer potential can be effectively discharged. Adhesion to the detection surface 62a of the optical sensor 62 can be effectively prevented.

  Furthermore, the charged paper dust easily adheres not only to the detection surface 62a of the optical sensor 62 but also to various members near the transport path 43. However, if the paper dust is not charged, Is also prevented.

  In this embodiment, the humidified airflow is supplied to the transport path 43 in the range from the transport rollers 41 on the recording paper discharge side of the fixing device 27 to the discharge rollers 46, but in other ranges. The humidified airflow may be supplied to the conveyance path 43.

  Further, the sheet conveying apparatus of the present embodiment can also be applied to the document sheet conveying unit 101 of FIG. For example, in the original paper transport unit 101 of FIG. 1, each of the roller 4 and each of the transport rollers 5 corresponds to each of the transport rollers 41 and each of the paper discharge rollers 46 of FIGS. Provided in the vicinity of the downstream side of the roller roller 4, a humidified airflow from the humidifying device 63 is blown out in a direction crossing the conveyance path of the original paper, and the humidified airflow is caused to flow in the conveyance direction along with the airflow in the conveyance direction caused by the conveyance of the original paper. It doesn't matter. As a result, the atmospheric humidity of the transport path of the manuscript paper becomes high, so even if a large amount of paper dust is generated due to friction between the roller and the manuscript paper, the paper dust is not easily charged with static electricity, and the charged charge of the paper dust quickly It is discharged and the paper dust does not adhere electrostatically to the detection surface of the optical sensor in the vicinity of the conveyance path.

  3A and 3B are a cross-sectional view and a front view showing a second embodiment of the paper conveying apparatus of the present invention. The sheet conveying apparatus of the present embodiment is used to supply a humidified airflow to at least a part of the conveying path 43 in the image forming apparatus 100, similarly to the apparatuses of FIGS.

  In this sheet conveying apparatus, a humidified air flow is supplied to the conveying path 43 in the arrangement range of the three pairs of conveying rollers 41 provided between the paper feeding unit 105 and the registration rollers 42.

  The conveyance path 43 is formed by arranging upper and lower paper guide members 43a and 43b so as to guide the recording paper between the upper and lower paper guide members 43a and 43b. A partition member 71 is provided so as to be substantially parallel to the upper guide member 43a.

  The shaft 41 a of each transport roller 41 is connected to a roller drive mechanism 72 provided on the side of the transport path 43, and each transport roller 41 is rotationally driven by this roller drive mechanism 72. The recording paper is supplied from the paper supply unit 105, guided one after another between the three pairs of transport rollers 41, transported in the transport direction A by the transport rollers 41, and registered between the upper and lower paper guide members 43 a and 43 b. It is guided to the roller 42.

  The two optical sensors 73 and 74 are provided at a substantially central position of the arrangement interval of the transport roller 41 and on the partition member 71, and the detection surfaces 73 a and 74 a of the optical sensors 73 and 74 are interposed via the partition member 71. It protrudes downward and further faces the conveyance path 43 through the openings 43c and 43d of the paper guide member 43a. As described above, the detection surfaces 73a and 74a of the optical sensors 73 and 74 are disposed above the transport path 43. Therefore, even if paper dust is generated in the transport path 43, the optical sensor 73 is located above the transport path 43. , 74 is hard to adhere paper dust to the detection surfaces 73a, 74a.

  Each of the optical sensors 73 and 74 emits a light beam to the conveyance path 43 through the detection surfaces 73a and 74a, receives the light beam reflected by the recording sheet passing through the conveyance path 43, and whether there is a recording sheet. Or the passage of the leading and trailing edges of the recording paper.

  The humidifier 75 is disposed on the upper paper guide member 43a. The humidifying device 75 includes a blower fan 76, a humidifying member 77 that is supplied with moisture as needed, and a throat portion 78 that leads to a space between the partition wall member 71 and the paper guide member 43a. The airflow blown from the blower fan 76 passes through the humidifying member 77 and is humidified to become a humidified airflow, and this humidified airflow passes through the throat portion 78 to the space between the partition wall member 71 and the upper sheet guide member 43a. Blown out.

  This humidified airflow is blown out in a direction opposite to the recording paper conveyance direction, and flows in a direction opposite to the airflow in the conveyance direction generated along with the conveyance of the recording paper in the conveyance path 43.

  The humidity sensor 79 is provided in parallel with the optical sensor 73 on the partition wall member 71, faces the space between the partition wall member 71 and the paper guide member 43 a, and detects the atmospheric humidity of this space. Since this space is connected to the conveyance path 43 through the opening 43c of the paper guide member 43a and the openings S1 and S2 at the right ends of the respective paper guide members 43a and 43b, the atmospheric humidity of this space and the atmospheric humidity of the conveyance path 43 are different. Almost equal. Therefore, it can be said that the humidity sensor 79 detects the atmospheric humidity of the conveyance path 43 by detecting the atmospheric humidity of the space between the partition wall member 71 and the paper guide member 43a.

  The control unit 80 controls the amount of humidified airflow blown into the transport path 43 by controlling on / off the blower fan 76 of the humidifying device 75 according to the atmospheric humidity of the transport path 43 detected by the humidity sensor 79. The atmospheric humidity of the path 43 is adjusted. When the inside of the image forming apparatus 100 is in a low humidity environment, the blower fan 76 of the humidifier 75 is normally turned on, and the blower fan 76 is turned off when the ambient humidity rises to a specified value or higher. To do.

  In such a configuration, the humidified air current is blown into the space between the partition wall member 71 and the paper guide member 43a through the throat portion 78 in the direction opposite to the transport direction A, and the transport path from the opening 43c of the paper guide member 43a. 43, or enters the transport path 43 from the opening S1 at the right end of each paper guide member 43a, 43b. Further, as apparent from FIG. 3B, the transport roller 41 is fixed to the shaft through a plurality of short rollers, and since these short rollers are separated from each other, the short rollers are humidified. Airflow passes through. For this reason, the humidified airflow flows to the right side via the respective central transport rollers 41, enters the transport path 43 from the opening 43d of the paper guide member 43a, and opens at the right end of the respective paper guide members 43a and 43b. It also enters the transport path 43 from the location S2. Thereby, the humidified airflow is mixed into the atmosphere of the transport path 43, and the atmospheric humidity of the transport path 43 is increased. For this reason, even if paper dust is generated due to friction between each conveying roller 41 and the recording paper, the paper dust is less likely to be charged with static electricity, and the charged charge of the paper dust is quickly discharged in a high humidity atmosphere. There is no electrostatic adsorption to the detection surfaces 73a and 74a of the optical sensors 73 and 74.

  Further, since the humidified airflow flows in the direction opposite to the conveyance direction A, the humidified airflow merges with the weak airflow in the conveyance direction A that occurs along with the conveyance of the recording paper, and the flow is weakened. For this reason, in the conveyance path 43, the flow of the humidified airflow is weak, and the paper dust remains in the high-humidity atmosphere for a long time, and the charged charge of the paper dust is more reliably discharged.

  Further, since the humidified airflow is blown into the space between the partition wall member 71 and the paper guide member 43a and enters the transport path 43 from the openings 43c and 43d and the opening locations S1 and S2, the humidified airflow is transferred to the transport path 43. Thus, it is possible to avoid a situation where only the atmospheric humidity in the vicinity of the humidifier 75 becomes high.

  Further, since the humidified airflow is blown out in the vicinity of the respective transport rollers 41 at the openings S1 and S2, the atmospheric humidity in the vicinity of the respective transport rollers 41 is reliably increased. For this reason, even if a large amount of paper dust is generated due to friction between each of the conveying rollers 41 and the recording paper, the charging of the paper dust can be effectively suppressed, and the charge of the paper dust can be discharged quickly.

  Further, since the humidified airflow quickly flows in the space between the partition wall member 71 and the sheet guide member 43a, the detection surfaces 73a and 74a of the optical sensors 73 and 74 facing this space are cleaned by the humidified airflow, and the detection surfaces thereof. The contamination of 73a and 74a is prevented.

  Note that the sheet conveying apparatus of the present embodiment can also be applied to the document sheet conveying unit 101 of FIG. For example, in the original paper transport unit 101 in FIG. 1, each of the roller 4 and each of the transport rollers 5 and 6 correspond to the three pairs of transport rollers 41 in FIGS. 3A and 3B, and the humidifier 75 is connected to each transport roller. 6 may be provided in the vicinity of the upstream side, and the humidified airflow may be blown out in the direction opposite to the conveyance direction of the original paper. As a result, the atmospheric humidity in the transport path of the original paper becomes high, so the charged charge of the paper dust is quickly discharged in a high humidity atmosphere, and the paper dust does not adhere to the detection surface of the optical sensor near the transport path. That's it.

  Further, as shown in FIGS. 4A and 4B, the detection surface 73a of the optical sensor 73 protruding downward through the partition wall member 71 may be inclined so as to face the direction of the flow of the humidified airflow. In this case, the humidified airflow hits the detection surface 73a of the optical sensor 73, and the detection surface 73a is efficiently cleaned by the humidified airflow. Further, in the configuration in which the optical sensor 74 detects the paper via the translucent member 74b, if the detection surface 74c of the translucent member 74b is inclined so as to face the humidified airflow, the humidified airflow is transmitted through the translucent member. When hitting the detection surface 74c of 74b, the detection surface 74c is efficiently cleaned by the humidified airflow.

  In addition, this invention is not limited to said each embodiment, It can deform | transform variously. For example, a known ultrasonic type or steam type device may be applied as the humidifier. Moreover, you may change suitably the number and arrangement position of a humidifier.

1 is a cross-sectional view illustrating an image forming apparatus to which a first embodiment of a paper conveying apparatus of the present invention is applied. (A) And (b) is sectional drawing and the front view which show the paper conveying apparatus of 1st Embodiment. (A) And (b) is sectional drawing and the front view which show the paper conveying apparatus of 2nd Embodiment. (A) And (b) is sectional drawing and the front view which show the modification of the paper conveying apparatus of FIG.

Explanation of symbols

41 Conveying roller 43 Conveying path 46 Discharge roller 61, 72 Roller driving mechanism 62, 73, 74 Optical sensor 63, 75 Humidifier 64, 76 Blower fan 65, 77 Humidifying member 66, 79 Humidity sensor 67, 80 Control unit 71 Partition Member 78 Throat section 100 Image forming apparatus 101 Document transport section (ADF)
102 Image Reading Unit 103 Print Processing Unit 104 Recording Paper Conveying Unit 105 Paper Feeding Unit

Claims (9)

In a paper transport device having a paper transport path for transporting paper by a transport roller,
A sheet conveying apparatus comprising humidifying means for increasing the atmospheric humidity of the sheet conveying path.   The paper transporting apparatus according to claim 1, wherein the humidifying unit includes a blowing unit that blows a humidified airflow to the paper transporting path.   A partition wall is provided along the sheet conveyance path, and a humidified airflow blown from the blowing unit is caused to flow along the partition wall, and a detection surface of an optical sensor that detects a sheet conveyed in the sheet conveyance path is provided via the partition wall. The sheet conveying apparatus according to claim 2, wherein the sheet conveying apparatus is provided so as to face the conveying path.   The sheet conveying device according to claim 3, wherein a detection surface of the optical sensor is inclined so as to face a humidified airflow blown from the blowing unit.   The optical sensor detects a sheet through a translucent member, and the detection surface of the translucent member is inclined so as to face a humidified air flow blown from the blowing means. 4. The paper conveying device according to 3.   3. A sheet conveying apparatus according to claim 2, wherein a partition wall is provided along the sheet conveying path, and the humidified air flow blown from the blowing means is caused to flow along the partition wall and be guided to the conveying roller. .   The paper conveying apparatus according to claim 2, wherein the blowing unit blows a humidified airflow in a direction opposite to a paper conveying direction in the paper conveying path.   An image forming apparatus comprising the sheet conveying device according to any one of claims 1 to 7.   The image forming apparatus transfers the image on the surface of the photosensitive member to the sheet while conveying the sheet along the sheet conveying path, and the humidifying unit is provided on the downstream side in the sheet conveying direction from the transfer position of the image. The image forming apparatus according to claim 8.

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