JP6195394B2 - Sheet conveying apparatus, image forming apparatus, and image reading apparatus - Google Patents

Description

  The present invention relates to a sheet conveying apparatus, an image forming apparatus, and an image reading apparatus, and more particularly to a configuration of a sensor that detects a sheet passing through a curved sheet conveying path.

  In recent years, image forming apparatuses such as copying machines, printers, facsimiles, and image reading apparatuses such as scanners have been demanded to increase the speed and accuracy of image forming operations and image reading operations. Along with this, high speed and high accuracy are also demanded in the sheet conveying apparatus provided in the image forming apparatus and the image reading apparatus for conveying sheets such as recording media and originals.

  By the way, conventionally, a sheet conveying apparatus includes a sheet conveying path through which a sheet passes, and a number of sensors for detecting the passage of the sheet are provided in the sheet conveying path. Here, as such a sensor, an inexpensive sensor having a photo interrupter and a mechanical flag is generally used (see Patent Document 1). However, in the sensor having such a configuration, chattering is likely to occur due to a shock when the sheet collides with the flag, and is not suitable for speeding up.

  Therefore, instead of such a sensor, an optical transmission type sensor including a light source for irradiating light to the sheet, a light receiving element arranged in line with the light source, and a prism disposed at a position facing the light receiving element. May be used (see Patent Document 2).

  In the case of such a transmissive sensor, the light receiving element detects light reflected from the prism when there is no sheet between the prism, but when there is a sheet, the light is blocked and does not detect light. For this reason, the presence or absence of the sheet can be detected based on whether or not the light receiving element detects the light reflected from the prism. However, in such a transmission type sensor that utilizes light blocking by a sheet, when the sheet is a sheet that transmits light, such as an OHP sheet, the sheet cannot be detected.

  On the other hand, as another optical sensor, a light source and a light receiving element arranged side by side with the light source are provided. Light is emitted from the light source to the sheet passing through the sheet conveyance path, and light reflected by the sheet is received by the light receiving element. There is a reflective sensor. In the case of a reflective sensor having such a configuration, a sheet that transmits light, such as an OHP sheet, can be detected unlike a transmissive sensor.

Japanese Patent Laid-Open No. 7-129027 JP 2003-040490 A

  Incidentally, some conventional sheet conveying apparatuses include a bent sheet conveying path. When a transmissive sensor is arranged in such a bent sheet conveyance path, the sheet is conveyed in an angled state with respect to the irradiation light from the light source when passing through the sheet conveyance path. become. Here, in the case of a reflection type sensor, when the sheet is conveyed with an angle with respect to the irradiation light, particularly in a sheet with little irregular reflection such as an OHP sheet, as shown in FIG. Thus, it becomes difficult for the light receiving element to detect the reflected light from the sheet.

  Thus, in order to easily detect such an angled OHP sheet, for example, it is necessary to diffuse irradiation light or increase illuminance. However, if the irradiating light is diffused or the illuminance is increased, the light hits and reflects not the sheet but the path member forming the sheet conveying path, and the light receiving element may detect the reflected light and erroneously detect it. There is.

  Therefore, in order to avoid such erroneous detection, that is, in order to reliably detect the sheet, for example, it is necessary to provide a relief hole in a portion where the diffused light hits the passage member. However, when the escape hole is provided in this way, when the sheet is conveyed at a high speed, the sheet may be caught in the escape hole and jammed.

  Accordingly, the present invention has been made in view of such a current situation, and provides a sheet conveying apparatus, an image forming apparatus, and an image reading apparatus that can reliably detect a sheet conveyed at a high speed along a bent sheet conveying path. It is intended to provide.

In the sheet conveying apparatus, the present invention includes a sheet conveying path through which a sheet conveyed in the sheet conveying direction passes, and a detection unit that is disposed in a curved portion in the sheet conveying path and detects a sheet in the sheet conveying path. a, the detection unit may emit light longer than the length in the direction in which the length in the sheet conveying direction of the optical axis perpendicular to cross section perpendicular to the sheet conveyance direction in the optical axis perpendicular cross-section, the curved portion And a light receiving portion for receiving light reflected from the light emitted from the light emitting portion and hitting the sheet in the sheet conveying path.

  As in the present invention, a sheet bent by emitting light whose length in the sheet conveyance direction in the cross section perpendicular to the optical axis is longer than the length in the direction perpendicular to the sheet conveyance direction in the cross section perpendicular to the optical axis. A sheet conveyed at high speed on the conveyance path can be reliably detected.

1 is a diagram illustrating a schematic configuration of an image forming apparatus including a sheet conveying device according to a first embodiment of the present invention. FIG. 4 is a diagram illustrating an example of a structure of a photosensor disposed in the sheet conveying apparatus. FIG. 4 is a diagram illustrating a state in which a sheet passes through a curved sheet conveyance path provided in the sheet conveyance device. The figure which shows the angle of the inclination with respect to the irradiation direction of a sheet | seat when a sheet | seat passes the said curved sheet conveyance path. The figure explaining the spot shape of the irradiation light of the said photosensor. The figure explaining the structure of the photosensor arrange | positioned at the said curved sheet conveyance path. The figure explaining the position of the photo sensor arrange | positioned at the said curved sheet conveyance path. The figure explaining the structure of the photosensor used for the sheet conveying apparatus which concerns on the 2nd Embodiment of this invention. The figure explaining the structure of the photosensor used for the sheet conveying apparatus which concerns on the 3rd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram illustrating a schematic configuration of an image forming apparatus including a sheet conveying device according to a first embodiment of the present invention. In FIG. 1, 100 is an image forming apparatus, 101 is an image forming unit that forms an image on a sheet by an electrophotographic method, and 102 is a sheet feeding unit. Here, the image forming unit 101 is provided with the photosensitive drum 1, the developing device 4, the laser scanner 3, and the like. Further, the sheet feeding unit 102 is provided with a cassette 5 that houses the sheet S and a feeding roller R1 that feeds the sheet stored in the cassette 5.

  Next, the operation of the image forming apparatus 100 having such a configuration will be described. When an image signal is input to the laser scanner 3 from a control device (not shown), the laser scanner 3 irradiates the photosensitive drum 1 with laser light corresponding to the image signal as indicated by an arrow. At this time, the photosensitive drum 1 is charged in advance, and an electrostatic latent image is formed by irradiation with a laser beam. Then, the electrostatic latent image is developed by the developing device 4, whereby toner is formed on the photosensitive drum. An image is formed.

  On the other hand, when a paper feed signal is output from the control device to the sheet feeding unit 102, the sheet S is fed from the cassette 5 by the feeding roller R1. Thereafter, the fed sheet S is sent to a transfer unit constituted by the photosensitive drum 1 and the transfer charger 6 at a predetermined timing. Next, the sheet S thus sent to the transfer unit is transferred with the toner image in the transfer unit, and then conveyed to the fixing unit 8. Thereafter, the unfixed transfer image is permanently fixed on the sheet S by being heated and pressed by the fixing unit 8. Then, the sheet S on which the image is fixed as described above is discharged by the transport roller R6 and the discharge roller R7.

  The image forming apparatus 100 according to the present embodiment has a double-sided image forming function and a reverse paper discharge function. In the reverse paper discharge mode, the sheet S after passing through the fixing unit 8 is first guided to the branch path P1 by switching a switching member (not shown). Next, the sheet is conveyed from the conveying rollers R8 and R9 to the reversing roller R10, and the sheet is sent to the reversing discharge path P2 by reversing the reversing roller R10 and switching a switching member (not shown), and thereafter, from the conveying rollers R15 and R16. It is conveyed to the discharge roller R7 and discharged.

  In the double-side mode in which images are formed on both sides of the sheet, the sheet S after the fixing process of the first surface by the fixing unit 8 is first guided to the branch path P1. Next, the sheet is conveyed to the double-sided path P3 by reverse rotation of the reverse roller R10 and switching of the switching member. Thereafter, the toner image is conveyed by conveying rollers R11 to 14 provided in the double-sided path P3, and after the toner image is transferred and fixed again, it is discharged by the conveying roller R6 and the discharging roller R7.

  In FIG. 1, reference numeral 103 denotes a sheet conveying apparatus that conveys a sheet. The sheet conveying apparatus 103 is configured to receive the sheet S fed by the feeding roller R1 in addition to the conveying rollers R6, R8 to R16 described above. Conveying rollers R2 to R5 for conveying to the transfer unit are provided. Further, the sheet conveying device 103 includes a conveying path P4 for conveying the sheet S fed by the feeding roller R1 to the transfer unit in addition to the branch path P1, the reverse discharge path P2, and the double-sided path P3 described above. A sheet conveyance path is provided.

  In the sheet conveying path, photosensors PS1 to 19 that are light reflection type sensors are arranged, and a control unit (not shown) passes the sheet S based on signals from the photosensors PS1 to PS19. Timing is detected and sheet conveyance control is performed. Here, as shown in FIG. 2, the photosensors PS <b> 1 to PS <b> 19 include a light emitting unit 21 that includes an LED 20 that is a light source and a light receiving unit 31 that includes a light receiving element 30.

  The light emitting unit 21 includes a perfect circular light emitting lens 22 for condensing the light from the LED 20 and irradiating the light toward the sheet S. In addition, the light receiving unit 31 includes a perfect circular light receiving lens 32 that collects light reflected from the sheet S after being irradiated from the light emitting unit 21 and directs the light toward the light receiving element 30.

  In the photosensor PS having such a configuration, the light from the LED 20 is condensed by the light emitting lens 22 and irradiated toward the sheet S. Thereafter, the reflected light that has been reflected by the sheet S is collected by the light receiving lens 32, and the light receiving element 30 receives this light to detect the sheet.

  FIG. 3 shows how the sheet S passes through the curved portion of the transport path P4. Note that a photosensor PS3 is disposed in a curved portion of the transport path P4. FIG. 3A shows a state where the leading edge of the sheet S is about to enter the curved portion of the conveyance path P4. At this time, the sheet S is conveyed in an inclined state with respect to the irradiation direction of the photosensor PS3. In this case, the irradiation light from the photosensor PS3 is not perpendicular to the sheet S but is irradiated from an oblique direction. Is done.

  FIG. 3B shows a state in which the sheet S passes through the curved portion of the conveyance path P4. At this time, the irradiation light from the photosensor PS3 is irradiated perpendicularly to the sheet S. become. FIG. 3C shows a state in which the rear end of the sheet S passes through the curved portion of the conveyance path P4. At this time, the irradiation light from the photosensor PS3 is not perpendicular to the sheet. Irradiated from an oblique direction.

  Here, as shown in FIG. 3, when the inclination angle of the sheet S with respect to the light irradiated perpendicularly from the photosensor PS3 toward the sheet is A (deg) as shown in FIG. When the sheet S passes through the curved portion of the conveyance path P4, the angle A changes sequentially. For example, as shown in FIG. 4B, the angle A was about −10 deg at the beginning of the entrance of the sheet S along the transport path P4. However, as the transport proceeds, the angle A becomes substantially zero. About +10 deg, it is in the opposite direction from the initial approach.

  By the way, when the light emitting lens 22 has a perfect circle shape as in the photosensor PS shown in FIG. 2, the spot light of the light emitted from the light emitting unit 21 is almost as shown in FIG. It becomes a circle. However, when the spot light is circular in this way, as shown in FIG. 2B, when the sheet is conveyed in a state inclined with respect to the irradiation direction of the photosensor PS, the angle A increases. The light reflected from the sheet S does not return in the direction of the light receiving lens 33 of the photosensor PS. In this case, in particular, when the sheet S is a sheet having a high reflectance, the diffuse reflection component is small and it is difficult to detect, so the photosensor PS cannot receive the reflected light.

  Therefore, in the present embodiment, an elliptical light emitting lens 23 is used as a light emitting lens and an elliptical light receiving lens is used as a light receiving lens, as shown in FIG. 6, at least in the curved portion of the conveyance path P4 where the angle A is large. A photo sensor sensor using the lens 33 is arranged. Here, when the light-emitting lens 23 has an elliptical shape, the spot light of the light emitted from the light-emitting portion 21 has an elliptical shape as shown in FIG.

  In this embodiment, as shown in FIGS. 5B and 7, the light-emitting lens 23 and the light-receiving lens 33 of the photosensor PS are arranged in a direction in which the long sides are parallel to the sheet conveying direction. doing. Here, when the elliptical light-emitting lens 23 is used as described above, as shown in FIG. 6B, the irradiation light spreads in the sheet conveyance direction, so that the sheet S is inclined even when the sheet S is inclined. Among the reflected light L from the light, a part of the reflected light L1 returns to the light receiving lens side.

  For this reason, even when the highly reflective sheet S is conveyed in an inclined state, the sheet S can be reliably detected. At this time, since the light receiving lens 33 also has an elliptical shape, the reflected light can be reliably received. Thus, by using at least the light-emitting lens 23 as an elliptical lens, the photosensor PS can receive reflected light even when the sheet S is conveyed in an inclined state along the sheet conveying direction.

  As described above, in the present embodiment, by using the elliptical light emitting lens 23, the light of the light emitting unit 21 is elongated along the sheet conveying direction, in other words, the state where the light is spread in the sheet conveying direction. In order to irradiate toward the sheet. Thereby, the light from the light emitting unit 21 can be irradiated to the sheet in a wide range in the sheet conveyance direction, and the sheet can be reliably detected even when the sheet has a small irregular reflection such as an OHP sheet. . In other words, the light is emitted from the light emitting unit 21 toward the sheet S in a state of spreading along the sheet conveying direction, and the reflected light from the sheet S is directed to the light receiving unit, thereby bending the sheet conveying path. The sheet conveyed at high speed can be reliably detected.

  Further, in this case, since the diffusion of the irradiation light can be expanded only in the necessary direction, that is, the sheet conveying direction, even when the escape hole is formed in the guide member that forms the conveyance path P4, it is necessary to enlarge the escape hole. Disappears. Thereby, even when the sheet is conveyed at a high speed on the sheet conveyance path where the sheet is bent, the occurrence of jamming of the sheet can be suppressed.

  For example, as shown in FIG. 2B, the sheet can be easily inclined in the bent direction of the sheet conveying path, but the sheet is inclined with respect to the width direction orthogonal to the sheet conveying direction. There is nothing. For this reason, it is not necessary to spread light in the width direction. On the contrary, when the light is spread in the width direction, there is a possibility that the possibility of erroneous detection due to unnecessary reflection from the guide member or the like forming the transport path P4 may be increased. Therefore, as in the present embodiment, arranging the elliptical light emitting lens 23 along the sheet conveying direction to spread the irradiation light in the sheet conveying direction ensures reliable detection of a highly reflective sheet without erroneous detection. It is effective in detecting.

  Next, a second embodiment of the present invention will be described. FIG. 8 is a diagram illustrating the structure of a photosensor used in the sheet conveying apparatus according to the present embodiment. In FIG. 8, the same reference numerals as those in FIG. 2 described above indicate the same or corresponding parts.

  In FIG. 8, reference numerals 34 to 36 denote perfect circular light emitting lenses, and these three (plurality) of light emitting lenses 34 to 36 are arranged along the sheet conveying direction. That is, in the present embodiment, three light emitting lenses 34 to 36 of the light emitting unit 21 are arranged in the sheet conveying direction. And when comprised in this way, as shown to (a) of FIG. 8, the light irradiated from LED20 which is a light emission source is three light emitting lenses 34-36 arranged along the sheet conveyance direction, In the sheet conveying direction, optical axes in three different directions are formed. Thereby, the light of the light emission part 21 can be irradiated toward a sheet | seat in the state elongated in the sheet conveyance direction, in other words, the state expanded in the sheet conveyance direction.

  As a result, even when the sheet S is inclined and has an angle A, as shown in FIG. 8B, a part of the reflected light L1 from the reflected light L from the sheet S returns to the light receiving lens side. become. For this reason, even when the highly reflective sheet S is conveyed in an inclined state, the sheet S can be reliably detected. In this embodiment, three light emitting lenses 34 to 36 are arranged. However, if there are two or more light emitting lenses, a plurality of optical axes in different directions can be formed, and the same effect can be obtained. be able to.

  Next, a third embodiment of the present invention will be described. FIG. 9 is a view for explaining the structure of a photosensor used in the sheet conveying apparatus according to the present embodiment. In FIG. 9, the same reference numerals as those in FIG. 2 described above indicate the same or corresponding parts.

  In FIG. 9, 24 to 26 are LEDs which are light emission sources, and these three (plural) LEDs 24 to 26 are arranged along the sheet conveying direction. That is, in the present embodiment, the three LEDs 24 to 26 are arranged in the sheet conveying direction. And when comprised in this way, as shown to (a) of FIG. 9, each LED 24-26 and the light emission lens 22 form a different angle, and form three optical axes from which a direction differs in a sheet conveyance direction. To do.

  As a result, even when the sheet S is inclined and has an angle A, as shown in FIG. 9B, a part of the reflected light L1 from the reflected light L from the sheet S returns to the light receiving lens side. become. For this reason, even when the highly reflective sheet S is conveyed in an inclined state, the sheet S can be reliably detected. In this embodiment, three LEDs 24 to 26, which are light sources, are arranged. However, if there are two or more light sources, a plurality of optical axes in different directions can be formed, and similar effects can be obtained. Can do.

  In the above description, the sheet conveying apparatus provided in the image forming apparatus has been described. However, the present invention is not limited to this, and is also applicable to a sheet conveying apparatus of an image reading apparatus including an image reading unit. be able to.

20, 24 to 26 ... LED, 21 ... light emitting part, 22, 23 ... light emitting lens, 30 ... light receiving element, 31 ... light receiving part, 32, 33, 34 to 36 ... light receiving lens, 100 ... image forming apparatus, 101 ... image Forming part 103 ... sheet conveying device P1 ... branch passage P2 ... reverse discharge passage P3 ... double-sided passage P4 ... conveyance passage PS1-19 ... photo sensor S ... sheet

Claims (7)

A sheet conveying path through which a sheet conveyed in the sheet conveying direction passes;
A detection unit that is disposed in a curved portion in the sheet conveyance path and detects a sheet in the sheet conveyance path;
The detector is
Emits light whose length in the sheet conveyance direction in the cross section perpendicular to the optical axis is longer than the length in the direction perpendicular to the sheet conveyance direction in the cross section perpendicular to the optical axis, and irradiates the curved sheet with light in the bending portion A light emitting unit to
And a light receiving portion that receives light reflected from the light emitted from the light emitting portion and hitting the sheet in the sheet conveying path. The light emitting unit
A light source;
A lens that is disposed between the light source and the sheet conveyance path, and that passes light from the light source toward the sheet conveyance path, and has an elliptical lens that is long in the sheet conveyance direction. The sheet conveying apparatus according to claim 1. The light emitting unit
A light source;
2. A plurality of lenses arranged between the light source and the sheet conveyance path and arranged in the sheet conveyance direction through which light traveling from the light source toward the sheet conveyance path passes. Sheet transport device. The light receiving unit includes a light receiving lens for light reflected against the sheet passes, to any one of claims 1 to 3, characterized in that it has a, a light receiving element for receiving the light transmitted through the light receiving lens The sheet conveying apparatus according to the description. Wherein the light emitting portion and the light receiving portion, the sheet conveying device according to any one of claims 1 to 4, characterized in that are arranged side by side in a width direction crossing the sheet conveying direction. A sheet conveying device according to any one of claims 1 to 5, the image forming apparatus characterized by having an image forming portion for forming an image on a sheet conveyed by the sheet conveying device. A sheet conveying device according to any one of claims 1 to 5, the image reading apparatus being characterized in that and an image reading unit for reading an image of a sheet conveyed by the sheet conveying device.

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