JP2009091070A - Curling detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a curling detection device capable of surely detecting curling of a paper in a simple constitution having a small number of parts. <P>SOLUTION: This curling processing device comprises a light projection means 2 for radiating light approximately in parallel to a surface of one side of a paper 50 delivered by paper delivery means 32a, 32b, reflection members 4a, 4b opposed to the light projection means 2 across a paper delivery path and reflecting a radiation light 7 from the light projection means 2 approximately in parallel to the surface of the other side of the paper, reflection light receiving means 3a opposed to the reflection means 4a, 4b across the paper delivery path and receiving a reflection light 8 from the reflection members 4a, 4b, and control means 35 for detecting curling of the paper based on the detection results of the reflection light receiving means 3a. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a curl detection device that detects a curved state of a sheet discharged from an external device.

  In an image forming apparatus such as a copying machine, a printer, or a facsimile machine, an electrostatic latent image such as a toner image carried on the surface of a photosensitive member, which is a latent image carrier, is transferred to paper, and then the paper is transferred by a fixing device. It is heated and fixed and discharged. When the paper passes through the fixing device, the paper may be bent due to heat or pressure accompanying fixing, and so-called curling may occur.

  When the paper is curled in this way, there may be a conveyance failure such as the leading edge of the paper being folded. For example, when a sheet on which an image is fixed is transported to a sheet post-processing apparatus that performs predetermined post-processing, the sheet may be caught in the transport path and cause jamming. Also, in a paper post-processing apparatus, when performing a sorter process for aligning sheets to a predetermined number of sheets, a stapling process for binding a bundle of sheets, or a punching process for punching holes in a sheet, it may cause alignment failure, staple failure, punch failure, etc. There is a case. In view of this, various curl correction devices that correct the curl by applying stress to the curled paper have been proposed. In such an apparatus, for example, a paper curl is detected using a non-contact type optical sensor, and the curl correction is performed according to the detection result (see, for example, Patent Document 1).

JP 2002-326754 A Japanese Patent Laid-Open No. 05-116841

  By the way, the curl state in the paper differs depending on the paper, such as a face curl with the front surface curved inward and a back curl with the back surface curved inward. It is difficult to position the sensor where the curl is measured. In order to detect curl with certainty, there is a method in which the optical sensor is movably arranged by a sheet. However, this method requires a mechanism for moving the optical sensor and position control, and becomes a large-scale one. Although there is a method of arranging a plurality of photosensors in parallel, the cost increases due to an increase in the number of parts, and it is necessary to secure a relatively large space for arranging a plurality of photosensors.

  The present invention has been made in view of the above, and an object of the present invention is to provide a curl detection apparatus that can reliably detect curl of a sheet with a simple configuration with a small number of parts.

In order to solve the above-described problems and achieve the object, the invention according to claim 1 is a curl detection apparatus that receives a sheet to be processed and detects the curl of the sheet while conveying the sheet by the sheet conveying unit. A light projecting means for irradiating light substantially parallel to the surface of one side of the paper transported by the paper transport means, and a light projecting means disposed opposite the light projecting means across the paper transport path. Reflecting means for reflecting the irradiation light from the surface of the other side of the paper substantially in parallel;
Based on the detection result of the reflected light receiving means, the reflected light receiving means that receives the reflected light from the reflecting means, and is disposed opposite to the reflecting means across the paper conveyance path. And a control means for detecting the presence or absence of.

  According to a second aspect of the present invention, in the curl detecting device according to the first aspect, the reflecting means includes a spectroscopic member that splits incident light into transmitted light and reflected light, and a reflecting member that reflects incident light. And further comprising transmitted light receiving means for receiving the light transmitted through the spectral member, and the control means detects the curl of the paper based on the detection results of the reflected light receiving means and the transmitted light receiving means. The presence or absence is detected.

  According to a third aspect of the present invention, in the curl detection apparatus according to the first aspect, the curl detection device further includes a paper detection unit that detects the presence or absence of the paper conveyed by the paper conveyance unit, and the irradiation light from the light projecting unit and The light projecting means, the reflecting means, and the reflected light emitting means are arranged so that the reflected light from the reflecting means is inclined with respect to the transport direction of the paper, and the control means is the paper detecting means. Detecting the presence or absence of curling of the paper based on the time difference between the timing of detecting the presence or absence of paper and the timing of detecting the presence or absence of reflected light by the reflected light receiving means.

  According to a fourth aspect of the present invention, there is provided the curl detecting apparatus according to the second aspect, further comprising paper detection means for detecting the presence / absence of the paper conveyed by the paper conveyance means, and the irradiation light from the light projecting means and The light projecting means, the reflecting means, the reflected light emitting means, and the transmitted light receiving means are arranged so that the reflected light from the reflecting means is inclined with respect to the transport direction of the paper, and the control means Is based on a time difference between the timing at which the paper detection unit detects the presence of paper, the timing at which the reflected light receiving unit detects the presence of reflected light, and the timing at which the transmitted light receiving unit detects the presence of transmitted light. The presence or absence of curling of the paper is detected.

According to a fifth aspect of the present invention, in the curl detection device according to the third or fourth aspect, a direction perpendicular to a conveyance direction of the paper is used for irradiating light from the light projecting unit and reflected light from the reflecting unit. When viewed from above, the light projecting means and the reflecting means are arranged so as to intersect with the paper detection means, and the acute angle formed by the transport direction of the paper and the irradiation light and reflected light is θ, When the length in the transport direction is Lx and the length in the direction perpendicular to the transport direction is Ly, the above θ satisfies tan θ> L _y / L _x .

  According to a sixth aspect of the present invention, in the curl detection apparatus according to the first aspect, the light emitted from the light projecting means is different from the first irradiated light that is parallel to each other and has a different distance from the paper. A second spectral member that splits the second irradiation light and irradiates the first irradiation light and the second irradiation light to the surface on one side of the paper substantially in parallel is provided, and the reflecting means includes the first irradiation light. And reflecting the second irradiation light to form first reflected light and second reflected light that are parallel to each other and at different distances from the paper, and the first reflected light and the second reflected light are formed on the paper. And the reflected light receiving means includes a first reflected light receiving means for receiving the first reflected light and a second reflected light receiving means for receiving the second reflected light. The control means includes a detection result of the first and second reflected light receiving means. Based on, and detecting the presence or absence of curl of the paper.

  According to a seventh aspect of the present invention, in the curl detection apparatus according to the second aspect, the light emitted from the light projecting means is different from the first irradiated light that is parallel to each other and has a different distance from the paper. A second spectral member that splits the second irradiation light and irradiates the first irradiation light and the second irradiation light to the surface on one side of the paper substantially in parallel is provided, and the reflecting means includes the first irradiation light. And reflecting the second irradiation light to form first reflected light and second reflected light that are parallel to each other and at different distances from the paper, and the first reflected light and the second reflected light are formed on the paper. And the reflected light receiving means includes a first reflected light receiving means for receiving the first reflected light and a second reflected light receiving means for receiving the second reflected light. The transmitted light receiving means includes a first transmitted light that receives the first irradiation light. An optical means and a second transmitted light receiving means for receiving the second irradiation light, and the control means detects the first and second reflected light receiving means and the first and second transmitted light receiving means. Based on the result, the presence or absence of curling of the paper is detected.

  The invention according to claim 8 is the curl detecting apparatus according to any one of claims 1 to 7, wherein the irradiation light from the light projecting means is laser light.

  According to the curl detecting apparatus of the first aspect, the light projecting means for irradiating light substantially parallel to the surface on one side of the paper and the light projecting means with the paper conveyance path interposed therebetween are disposed. Reflecting means for reflecting the irradiation light from the means substantially parallel to the surface on the other side of the paper, and a reflected light receiving means for receiving the reflected light from the reflecting means, disposed opposite the reflecting means across the paper conveyance path Means for detecting the presence or absence of curling of the paper based on the detection result of the reflected light receiving means. For example, curls with different curling directions such as face curls and back curls can be made with a simple structure. There exists an effect that it can detect reliably.

  According to the curl detecting apparatus of the second aspect, the reflecting means is composed of the spectroscopic member and the reflecting member, and the transmitted light receiving means for receiving the light transmitted through the spectroscopic member is provided. Based on the detection result of the light receiving means, it is configured to detect the presence / absence of curling of the paper, so that the combination of detection / non-detection of the light of the two light receiving means can be used for curling such as face curl, back curl and no curling. There is an effect that the state can be determined.

  Further, according to the curl detecting apparatus of the third aspect, the sheet detecting means for detecting the presence or absence of the sheet conveyed by the sheet conveying means is provided, and the irradiation light from the light projecting means and the reflected light from the reflecting means are The light projecting means, the reflecting means and the reflected light emitting means are arranged so as to be inclined with respect to the transport direction, the timing when the paper detecting means detects the presence or absence of paper, and the reflected light receiving means detects the presence or absence of reflected light. The configuration in which the presence / absence of curling of the paper is detected based on the time difference from the above timing provides an effect that the positions of the front, back, left and right curls on the paper can be determined.

  According to the curl detecting apparatus of the fourth aspect, the sheet detecting means for detecting the presence or absence of the sheet conveyed by the sheet conveying means is provided, and the irradiation light from the light projecting means and the reflected light from the reflecting means are reflected on the sheet. The light projecting means, the reflecting means, the reflected light emitting means, and the transmitted light receiving means are arranged so as to be inclined with respect to the transport direction, and the timing when the paper detecting means detects the presence or absence of the paper, the reflected light receiving means and the transmitted light Based on the time difference from the timing at which the light receiving means detects the presence or absence of light, it is configured to detect the presence or absence of paper curl. There is an effect that the position can be determined.

According to the curl detecting apparatus of the fifth aspect, the irradiation light from the light projecting means and the reflected light from the reflecting means intersect the paper detecting means when viewed from a direction orthogonal to the paper transport direction. The light projecting means and the reflecting means are disposed on the sheet, the acute angle formed between the paper transport direction and the irradiation light and reflected light is θ, the length of the paper transport direction is Lx, and the length perpendicular to the transport direction is When Ly is set to Ly, the configuration in which θ satisfies tan θ> L _y / L _x has an effect that the positions of the front, rear, left, and right curls on the paper can be reliably detected.

  According to the curl detecting apparatus of the sixth aspect, the irradiation light from the light projecting means is split into the first irradiation light and the second irradiation light that are parallel to each other and have different distances from the paper, and the first irradiation. The first reflected light receiving means and the second reflected light receiving means for receiving the first reflected light and the second reflected light reflected from the light and the second irradiation light, respectively, and detection results of the two light receiving means By detecting whether or not the paper is curled based on the above, the curl amount (curl height) can be determined.

  According to the curl detecting apparatus of the seventh aspect, the irradiation light from the light projecting means is split into the first irradiation light and the second irradiation light that are parallel to each other and have different distances from the paper, and the first irradiation. A first transmitted light receiving means and a second transmitted light receiving means for receiving the first transmitted light and the second transmitted light transmitted through the light and the second irradiated light, respectively, and reflecting the first irradiated light and the second irradiated light. The first reflected light receiving means and the second reflected light receiving means for receiving the first reflected light and the second reflected light, respectively, and the presence or absence of curling of the paper based on the detection results of the four light receiving means By detecting this, in addition to the discrimination of face curl and back curl, there is an effect that the height of the curl can be discriminated.

  Further, according to the curl detection apparatus of the eighth aspect, by applying the laser light as the irradiation light from the light projecting means, the curl can be clearly detected from the directivity and convergence of the laser light. There is an effect.

  DETAILED DESCRIPTION Exemplary embodiments of a curl detection apparatus according to the present invention are explained in detail below with reference to the accompanying drawings. In the embodiment described below, an image forming apparatus is described as an example of an external apparatus in the present invention, but the present invention is not limited to this, and any apparatus that can discharge paper is used. The device can also be applied as an external device.

(Embodiment 1)
FIG. 1 is a cross-sectional view showing a part of an image forming apparatus equipped with a curl detection apparatus 30 according to the first embodiment. The image forming apparatus forms an image on a sheet by an image forming unit (not shown) in the apparatus main body, and then detects a curve (hereinafter, referred to as “curl”) at the end of the sheet by the curl detection apparatus 30 to detect the sheet. The post-processing device 40 executes predetermined post-processing and discharges the paper out of the image forming apparatus. An image forming apparatus is an image forming apparatus that can perform image processing of a multi-function machine in which a plurality of functions such as a copier, a printer, a facsimile, a scanner function, a copy, a fax, and a printer are housed in one casing. The invention can be applied.

  In the curl detection device 30 shown in FIG. 1, as shown in FIG. 1, the fixing unit (not shown) inside the image forming apparatus main body is subjected to fixing processing, and then is discharged from the apparatus main body and conveyed in the direction of arrow P. A sheet (not shown) is received by the guide unit 31 and conveyed in the direction of the arrow. The paper transported by the guide unit 31 is transported while being sandwiched between a pair of paper transport rollers 32a and 32b, and the presence or absence of curl is detected by a curl detection unit 20 provided in the transport process. The sheet that has passed through the curl detection unit 20 is received by the sheet receiving unit 33 and conveyed to the sheet post-processing device 40 via the guide unit 34.

  The paper sent from the curl detection device 30 to the paper post-processing device 40 is subjected to predetermined processing according to the detection result of the curl detection unit 20 in the curl processing unit 41, and then sent to the paper post-processing unit 42. A post process such as a sorting process for sorting a plurality of sheets, a stapling process for aligning a plurality of sheets and binding a bundle of sheets, and a punching process for punching holes in the sheets is performed and discharged to the discharge tray 43. In the case of straight paper discharge processing, the paper is discharged as it is without being sent to the paper post-processing section 42 after processing in the curl processing section 41.

  2 is a block diagram of the curl detection device 30 according to the present embodiment, FIG. 3 is a conceptual diagram illustrating an example of a curl detection unit in the curl detection device 30, and FIG. 4 is a diagram illustrating the curl detection unit in the direction A in FIG. FIG. 5 is a diagram for explaining detection of paper curl. In FIG. 1, the paper conveyance direction in the curl detection device 30 is vertically downward. However, the paper conveyance direction is not limited, and the conveyance direction is horizontal as shown in FIG. It can also be a direction. In the following description, an example in which the conveyance direction is the horizontal direction will be described. In the present embodiment, the paper conveyance rollers 32a and 32b shown in FIG. 1 are used to detect the curl of the paper while conveying the paper. However, the paper conveyance rollers 32a and 32b are not shown in FIG. To do. In the following description, the paper conveyance area in the curl detection unit 20 is referred to as a “conveyance path”.

  In the following description, the surface of the paper 50 on which an image is formed is referred to as a face surface, and the back surface is referred to as a back surface. A curl with the face surface curved inward is called a face curl, and a curl with the back surface curved inward is called a back curl.

  As shown in FIG. 2, the curl detection device 30 according to the present embodiment includes a curl detection unit 20, paper conveyance means (paper conveyance rollers) 32 a and 32 b, and a control unit 35. The curl detection unit 20 includes an optical transmission / reception unit 10 and a reflection unit 11.

  The light transmitting / receiving unit 10 includes a light projecting unit 2 and a reflected light receiving unit 3a. As shown in FIG. 3, the light projecting means 2 and the reflected light receiving means 3a are juxtaposed in the coaxial direction on one side of the transport path. The light projecting means 2 is disposed above the position of the paper 50 being conveyed, and irradiates light substantially parallel to the face surface of the paper 50. On the other hand, the reflected light receiving means 3a is disposed below the position of the sheet 50 being conveyed, and receives the light reflected from the light projecting means 2 by the reflecting means 11. In the present embodiment, a laser light emitting element is applied as the light projecting means 2, and a semiconductor laser is applied for light emission of the laser light.

  The reflecting means 11 is composed of a pair of reflecting members 4a and 4b. In the present embodiment, a pair of mirrors is applied as the reflecting members 4a and 4b. As shown in FIG. 3, the reflecting member 4a is disposed at a position facing the light projecting means 2 across the conveyance path, and reflects the irradiation light from the light projecting means 2 to irradiate the reflecting member 4b. On the other hand, the reflecting member 4b is disposed at a position facing the reflected light receiving means 3a across the conveyance path, and reflects the light reflected by the reflecting member 4a so as to be substantially parallel to the back surface of the paper 50, Irradiation toward the reflected light receiving means 3a. Instead of using a pair of mirrors as the reflecting members 4a and 4b, a right-angle prism mirror in which the reflecting members 4a and 4b are integrated may be used.

  In the curl detection unit 20 having the above configuration, as shown in FIG. 3, the irradiation light 7 from the light projecting means 2 goes straight in a direction orthogonal to the conveyance direction of the paper 50 and substantially parallel to the face surface of the paper 50. Then, after being reflected by the reflecting member 4a and the reflecting member 4b, the light travels straight in parallel with the back surface of the paper 50 and is received by the reflected light receiving means 3a. The reflected light receiving means 3 a outputs a detection signal when it receives the reflected light 8 from the reflecting member 4 b and transmits it to the control unit 35. On the other hand, when the reflected light 8 is not received because the irradiation light 7 from the light projecting means 2 is blocked or the reflected light 8 from the reflecting member 4b is blocked, the reflected light receiving means 3a is A non-detection signal is output and transmitted to the control unit 35.

  The control unit 35 detects the presence or absence of curling of the paper 50 based on the detection result received from the reflected light receiving unit 3a. When receiving the detection signal from the reflected light receiving unit 3a, the control unit 35 determines that the paper is not curled. On the other hand, when a non-detection signal is received from the reflected light receiving means 3a, it is determined that the paper is curled.

  The sheet conveying rollers 32a and 32b convey the sheet 50 by sandwiching and rotating the sheet 50 conveyed from the guide portion 31 shown in FIG. 1 at the nip position as described above. Note that conveyance means other than rollers may be applied as the paper conveyance means.

  Next, the curl detection operation of the curl detection device 30 will be described with reference to FIGS. The control means 35 monitors whether or not the reflected light from the reflecting member 4b is blocked through the reflected light receiving means 3a. The sheet 50 conveyed to the curl detection unit 20 by the sheet conveying rollers 32a and 32b passes between the irradiation light 7 from the light projecting unit 2 and the reflected light 8 from the reflecting member 4b. At this time, when the paper 50 is not curled (that is, in the case of flat paper), the irradiation light 7 from the light projecting means 2 and the reflected light 8 from the reflecting member 4b are not blocked. Therefore, the reflected light receiving unit 3 a transmits a detection signal to the control unit 35. The control unit 35 that has received the detection signal determines that the paper 50 is not curled.

  On the other hand, when the paper 50 is face-curled, as shown in FIG. 4, the irradiation light 7 from the light projecting means 2 is blocked by the face curl, so the irradiation light 7 does not reach the reflecting member 4a. Accordingly, the reflected light receiving means 3 a does not receive the reflected light, and therefore transmits a non-detection signal to the control unit 35. Further, when the paper 50 is back curled, as shown in FIG. 4, the irradiation light 7 from the light projecting means 2 is reflected by the reflecting members 4a and 4b, but the reflected light 8 is blocked by the back curl. The reflected light 8 does not reach the reflected light receiving means 3a. Therefore, the reflected light receiving unit 3 a transmits a non-detection signal to the control unit 35.

  The control unit 35 that has received the non-detection signal from the reflected light receiving unit 3 a determines that the paper 50 is curled, transmits a curl processing command to the curl processing unit 41, and transmits a predetermined curl through the curl processing unit 41. Perform curl processing. The curl processing performed by the curl processing unit 41 includes correcting a curl of the paper 50, or displaying a message on the display panel (not shown) that the conveyance quality, the stack quality, etc. cannot be secured due to the occurrence of the curl. Processing.

  As described above, according to the curl detection device of the present embodiment, the light projecting means 2 that irradiates light substantially parallel to the surface of one side of the paper 50 that is conveyed by the paper conveyance rollers 32a and 32b; Reflecting means 11 disposed opposite to the light projecting means 2 across the conveyance path of the paper 50 and reflecting the irradiation light 7 from the light projecting means 2 substantially parallel to the surface of the other side of the paper 50; A reflection light receiving means 3a arranged opposite to the reflection means 11 across the conveyance path and receiving the reflected light 8 from the reflection means 11, and based on the detection result of the reflection light receiving means 3a By adopting a configuration for detecting the presence or absence of curl, it is not necessary to arrange a large-scale device, and both face curl and back curl can be reliably detected with a simple configuration.

(Embodiment 2)
FIG. 5 is a conceptual diagram showing the curl detection unit 20 in the curl detection device 30 according to the second embodiment of the present invention. FIG. 4 is a diagram of the curl detection unit 20 viewed from the direction A in FIG. It is a figure for demonstrating this curl detection. In addition, the same code | symbol is attached | subjected about the structure same as Embodiment 1, and the description is abbreviate | omitted. As shown in FIG. 5, in the second embodiment, instead of the reflecting member 4 a in the first embodiment, a spectral member 4 c that splits incident light into transmitted light and reflected light is applied, and this spectral member 4 c is used. The transmitted light receiving means 3b for receiving the transmitted light is provided. That is, in the curl detecting apparatus of the second embodiment, the light transmitting / receiving unit 10 is configured by the light projecting unit 2, the reflected light receiving unit 3a, and the transmitted light receiving unit 3b, and the reflecting unit 11 is configured by the spectroscopic member 4c and the reflecting member. 4b. Other configurations are the same as those in the first embodiment. With the configuration described above, it is possible to determine whether the curl of the paper 50 is a face curl or a back curl, in addition to detecting the presence or absence of curl, as will be described below. is there.

  As the spectroscopic member 4c, a half mirror, a cube-type beam splitter, or the like is preferably used, but other optical system members can be applied as long as they have a function of separating a light beam into two. In the example shown in FIG. 5, a half mirror is applied as the spectroscopic member 4c. The transmitted light receiving means 3b has the same configuration as the reflected light receiving means 3a, and is disposed behind the spectroscopic member 4c.

  In the curl detection unit 20 having the above-described configuration, as shown in FIG. 5, light irradiated from the light projecting unit 2 in a direction orthogonal to the conveyance direction of the paper 50 and substantially parallel to the face surface of the paper 50 is spectrally separated. The member 4c is split into transmitted light and reflected light, and the transmitted light 9 is received by the transmitted light receiving means 3b. The transmitted light receiving means 3 b outputs a detection signal when transmitting the transmitted light 9 and transmits it to the control unit 35. On the other hand, when the transmitted light 9 is not received due to the irradiation light 7 from the light projecting means 2 being blocked, the transmitted light receiving means 3b outputs a non-detection signal and transmits it to the control unit 35. . The light reflected by the spectroscopic member 4c is reflected by the reflecting member 4b, travels substantially parallel to the back surface of the paper 50, and is received by the reflected light receiving means 3a. Similar to the first embodiment, the reflected light receiving unit 3 a transmits a detection signal to the control unit 35 when receiving the reflected light 8. The control unit 35 detects the presence or absence of curling of the paper 50 based on the detection results received from the reflected light receiving unit 3a and the transmitted light receiving unit 3b.

  Hereinafter, a curl detection operation of the curl detection apparatus 30 according to the second embodiment will be described with reference to FIGS. The control unit 35 monitors whether or not the reflected light from the reflecting member 4b is blocked through the reflected light receiving unit 3a, and blocks the irradiation light 9 of the light projecting member 2 through the transmitted light receiving unit 3b. Whether it is monitored. The sheet 50 conveyed to the curl detection unit 20 by the sheet conveying rollers 32 a and 32 b passes between the irradiation light 7 and the reflected light 8. At this time, if the paper 50 is not curled, neither the irradiation light 7 nor the reflected light 8 is blocked, so the reflected light receiving means 3a receives the reflected light 8, and the transmitted light receiving means 3b transmits. Light 9 is received. Accordingly, the reflected light receiving unit 3 a and the transmitted light receiving unit 3 b each transmit a detection signal to the control unit 35. The control unit 35 determines that the paper 50 is not curled when receiving detection signals from both the reflected light receiving unit 3a and the transmitted light receiving unit 3b.

  On the other hand, when the paper 50 is face curled, as shown in FIG. 6, the irradiation light 7 from the light projecting means 2 is blocked by the face curl, so the irradiation light 7 does not reach the spectral member 4c. Therefore, since neither the reflected light receiving means 3a nor the transmitted light receiving means 3b receives light, it transmits a non-detection signal to the control unit 35, respectively. When receiving the non-detection signal from both the reflected light receiving unit 3a and the transmitted light receiving unit 3b, the control unit 35 determines that the sheet 50 has a face curl.

  When the paper 50 is back curled, as shown in FIG. 6, the irradiation light 7 from the light projecting means 2 is split into transmitted light 9 and reflected light by the spectral member 4c, and the transmitted light 9 is received by the transmitted light. Light is received by means 3b. Accordingly, the transmitted light receiving means 3 b transmits a detection signal to the control unit 35. On the other hand, the light reflected from the spectroscopic member 4c is reflected by the reflecting member 4b. However, since the reflected light 8 is blocked by the back curl, it does not reach the reflected light receiving means 3a. Therefore, the reflected light receiving unit 3 a transmits a non-detection signal to the control unit 35. When the control unit 35 receives the detection signal from the transmitted light receiving unit 3b and receives the non-detection signal from the reflected light receiving unit 3a, the control unit 35 determines that the paper 50 has a back curl.

  That is, in this embodiment, three types of face curl, back curl, and no curl are discriminated by the combination of detection / non-detection (ON / OFF) of the light of the reflected light receiving unit 3a and the transmitted light receiving unit 3b. Yes. That is, when both the reflected light receiving means 3a and the transmitted light receiving means 3b are OFF, the face curl, when the reflected light receiving means 3a is OFF, and when the transmitted light receiving means 3b is ON, the back curl and the reflected light receiving means 3a. When both the transmitted light receiving means 3b are ON, it is determined that there is no curl.

  As described above, in the curl detection apparatus according to the second embodiment as well, similarly to the first embodiment, light is irradiated substantially parallel to the surface on one side of the paper 50 conveyed by the paper conveyance rollers 32a and 32b. Reflecting the light projecting means 2 and the light projecting means 2 across the conveyance path of the paper 50 and reflecting the irradiation light 7 from the light projecting means 2 substantially parallel to the surface of the other side of the paper 50. A large-scale apparatus is arranged by including the means 11 and the reflected light receiving means 3a that is disposed to face the reflecting means 11 across the paper conveyance path and receives the reflected light 8 from the reflecting means 11. There is no need, and both face curl and back curl can be reliably detected with a simple configuration.

  Furthermore, according to the curl detecting apparatus of the second embodiment, the reflecting means 11 is constituted by the spectroscopic member 4c and the reflecting member 4b, and the transmitted light receiving means 3b for receiving the light transmitted through the spectroscopic member 4c is provided. In addition, by adopting a configuration for detecting the presence or absence of curling of the paper based on the two detection results of the reflected light receiving means 3a and the transmitted light receiving means 3b, the combination of detection / non-detection of light in the two light receiving means, The curl state such as face curl, back curl or no curl can be determined.

  In the second embodiment, it is only necessary to add the light receiving means, and it is not necessary to add the light projecting means. Therefore, the power supply for driving the light projecting means can be minimized.

(Embodiment 3)
FIG. 7 is a conceptual diagram showing the curl detection unit 20 in the curl detection device 30 according to the third embodiment of the present invention. FIG. 8 is a view of FIG. 7 as viewed from above, and shows the optical transmission / reception means 10 and the reflection means 11. It is a figure for demonstrating arrangement | positioning. In addition, the same code | symbol is attached | subjected about the structure same as Embodiment 1, 2, and the description is abbreviate | omitted. In the third embodiment, similar to the second embodiment, the light transmitting / receiving means 10 including the light projecting means 2, the reflected light receiving means 3a, and the transmitted light receiving means 3b, and the reflection including the spectral member 4c and the reflecting member 4b. Means 11 are provided. In the second embodiment described above, each member is arranged so that the irradiation direction of the irradiation light 7 and the reflected light 8 is orthogonal to the conveyance direction of the paper 50, whereas in this embodiment, as shown in FIG. The members are arranged such that the irradiation directions of the irradiation light 7 and the reflected light 8 are oblique with respect to the paper transport direction. Further, the present embodiment is characterized in that the curl detection unit 20 includes the paper detection unit 5. Other configurations are the same as those in the second embodiment. With the arrangement shown in FIG. 7, it is possible to determine the position of the curl on the paper 50 in addition to the detection of the presence or absence of curl, as will be described below.

  The paper detection means 5 is for detecting the paper 50 conveyed to the detection area of the curl detection unit 20, and is disposed near the center of the conveyance path in the curl detection unit 20, as shown in FIG. is there. In the present embodiment, as shown in FIG. 8, the paper detection means 5 is arranged so that the central portion of the paper 50 passes over the paper detection means 5. As the sheet detection means 5, for example, a known detection means such as a reflection type photosensor or a transmission type photosensor that captures the movement of an actuator for detecting a sheet can be applied.

  The light projecting means 2, the spectroscopic member 4c, and the reflecting member 4b are arranged so that the irradiation light 7 and the reflected light 8 intersect the paper detecting means 5 when the curl detecting unit 20 is viewed in plan as shown in FIG. It is. As shown in FIG. 8, when the front end portion of the paper 50 passes the curl detection unit 20, the timing at which the front end corner portion A of the paper 50 passes the irradiation light 7 on the basis of the paper detection means 5, and the front end There is a difference in the timing at which the corner C passes the irradiation light 7. Similarly, when the rear end portion of the paper 50 passes through the curl detection unit 20, the timing at which the rear end corner portion F of the paper 50 passes the irradiation light 7 on the basis of the paper detection unit 5 and the rear end A difference occurs in the timing at which the corner portion D passes the irradiation light 7.

  That is, the timing at which the front edge corner A of the paper 50 passes the irradiation light 7 is earlier than the timing at which the front edge center B of the paper 50 passes through the paper detection means 5, and the front edge corner C of the paper 50 emits the irradiation light 7. The passing timing is later than the timing at which the front end center B of the sheet 50 passes the sheet detecting means 5. Similarly, the timing at which the rear end corner portion D of the paper 50 passes the irradiation light 7 is earlier than the timing at which the rear end center E of the paper 50 passes through the paper detection means 5. The timing of passing the irradiation light 7 is later than the timing of the rear end center E of the paper 50 passing through the paper detection means 5. Therefore, whether the curl is at the front edge of the sheet from the time difference between the timing at which the sheet detecting unit 5 detects or does not detect the sheet and the timing at which the reflected light receiving unit 3a and the transmitted light receiving unit 3b detect no light. It is possible to determine whether it is at the rear end.

  FIGS. 9-1 to 9-4 show the sheet detection / non-detection timing (ON / OFF timing) of the sheet detection means 5 and the light detection / non-detection timings of the reflected light receiving means 3a and the irradiated light receiving means 3b. 5 is a timing chart corresponding to (ON / OFF timing). Hereinafter, the face curl detection operation of the curl detection device 30 will be described with reference to FIGS. In the following description, a space between the irradiation light 7 including the paper detection unit 5 and the reflected light 8 is referred to as a “detection region”.

  When the paper 50 is conveyed to the curl detection unit 20, the front end corner A first reaches the detection area. Here, when the front end corner portion A of the paper 50 is face-curled, the reflected light receiving means 3a and the transmitted light receiving means 3b are turned on because the irradiation light 7 from the light projecting means 2 is blocked by the face curl. It turns off and turns on again when the front end corner A passes the detection area. Next, when the front edge center B of the paper reaches the detection area, the paper detection means 5 detects the paper and turns from OFF to ON. Therefore, when the front end corner A is curled, the OFF timing of the reflected light receiving means 3a and the irradiation light receiving means 3b is before the ON timing of the paper detecting means 5. When the control unit 35 receives the non-detection signal from the reflected light receiving unit 3a and the transmitted light receiving unit 3b before the detection signal from the sheet detection unit 5, the face curl is generated at the front end corner A of the sheet 50. Determine that there is.

  After the front end center B of the paper 50 passes the detection area, the front end corner C reaches the detection area. Here, when the front end corner portion C is face curled, the reflected light receiving means 3a and the transmitted light receiving means 3b are turned from ON to OFF by blocking the irradiation light 7 from the light projecting means 2 by the face curl, When the front end corner C passes the detection area, it is turned ON again. Therefore, when the front end corner C is curled, the OFF timing of the reflected light receiving means 3a and the irradiated light receiving means 3b is later than the ON timing of the paper detecting means 5. When the control unit 35 receives a non-detection signal from the reflected light receiving unit 3a and the transmitted light receiving unit 3b later than the detection signal from the sheet detection unit 5, the front end corner C of the sheet 50 has a face curl. Is determined.

  After the front end corner C of the paper 50 passes the detection area, the rear end corner D reaches the detection area. Here, when the rear end corner portion D is face-curled, the irradiation light 7 is blocked by the face curl, so that the reflected light receiving means 3a and the transmitted light receiving means 3b are turned from ON to OFF, and the rear end corner portion C Is turned on again after passing the detection area. Next, when the rear end center E of the paper passes the detection area, the paper detection means 5 does not detect the paper and turns from ON to OFF. Therefore, when the rear end corner portion D is curled, the OFF timing of the reflected light receiving means 3a and the irradiation light receiving means 3b is earlier than the OFF timing of the sheet detecting means 5. When the control unit 35 receives the non-detection signal from the reflected light receiving unit 3a and the transmitted light receiving unit 3b before the non-detection signal from the sheet detection unit 5, the control unit 35 applies the face curl to the front end corner C of the sheet 50. It is determined that there is.

  After the rear end center E of the paper 50 passes through the detection area, the rear end corner F reaches the detection area. When the rear end corner F is face-curled, the reflected light receiving means 3a and the transmitted light receiving means 3b are switched from ON to OFF because the irradiation light 7 from the light projecting means 2 is blocked by the face curl. When the corner F passes the detection area, it is turned on again. Therefore, when the rear end corner portion F is curled, the OFF timing of the reflected light receiving means 3a and the irradiation light receiving means 3b is later than the OFF timing of the paper detecting means 5. When the control unit 35 receives a non-detection signal from the reflected light receiving unit 3a and the transmitted light receiving unit 3b later than the non-detection signal from the paper detection unit 5, the control unit 35 applies a face curl to the rear end corner F of the sheet 50. It is determined that there is.

  In the above description, the case of detecting a face curl has been described. In Embodiment 3, it is not necessary to discriminate between the face curl and the back curl, and when only the positions of the front, rear, left and right curls are discriminated, the reflecting member 4a is applied instead of the spectroscopic member 4c, and the transmitted light The light receiving means 3b is omitted.

In the present embodiment, the time difference between the timing when the paper detection unit 5 detects or does not detect the paper and the timing when the reflected light receiving unit 3a and the transmitted light receiving unit 3b detect no light is shown in FIG. The time difference is the same in any case of -1 to 9-4. That is, as shown in FIG. 8, the angle between the conveyance direction of the paper 50 and the irradiation light 7 is θ, the length in the conveyance direction of the paper 50 is L _x , and the length perpendicular to the conveyance direction of the paper is L _y, L _y / 2 the distance from the front edge portion a to the sheet detecting means 5, the conveying speed of the sheet to is V, the time difference, are all _{L y / (2tanθ · V)} .

Depending on the magnitude of θ, the front end corner portion C and the rear end corner portion D pass through the irradiation light 7 at the same time, and thus the curl of both may not be identified. In FIG. 8, the difference between the position of the sheet 50 when the front end corner A crosses the irradiation light 7 and the position of the sheet 50 when the front end center B crosses the irradiation light 7 is as shown in FIG. , L _y / (2 tan θ). Similarly, as shown in FIG. 10, the difference between the position of the sheet 50 when the front end center B crosses the irradiation light 7 and the position of the sheet 50 when the front end corner C crosses the irradiation light 7 is L _y / (2 tan θ). On the other hand, the difference between the position of the sheet 50 when the front end corner portion A crosses the illumination light 7, the position of the sheet 50 when the rear end corner portion D crosses the illumination light 7 is L _x. Therefore, as shown in FIG. 10, when L _y / (2 tan θ) × 2 = L _x , the front end corner C and the rear end corner D pass the irradiation light 7 at the same time. The curl of both cannot be identified. Therefore, in this embodiment, it is necessary to select θ so that Ly / (2 tan θ) × 2 <L _x , that is, tan θ> L _y / L _x .

  As described above, in the curl detection apparatus according to the third embodiment, light is emitted substantially parallel to the surface on one side of the paper 50 conveyed by the paper conveyance rollers 32a and 32b, as in the first and second embodiments. Is disposed opposite to the light projecting means 2 across the conveyance path of the paper 50, and the irradiation light 7 from the light projecting means 2 is substantially parallel to the other surface of the paper 50. A large-scale apparatus is provided by including the reflecting means 11 for reflecting and the reflected light receiving means 3a that is disposed so as to face the reflecting means 11 across the paper conveyance path and receives the reflected light 8 from the reflecting means 11. Therefore, both face curl and back curl can be reliably detected with a simple configuration.

  Furthermore, according to the curl detecting apparatus of the third embodiment, the sheet detecting unit 5 that detects the presence or absence of the sheet 50 conveyed by the sheet conveying unit is provided, and the irradiation light 7 from the light projecting unit 2 and the reflection member 4b. The light projecting member 2, the spectroscopic member 4c, the reflecting member 4b, the reflected light receiving means 3a, and the irradiated light receiving means 3b are provided so that the reflected light 8 is inclined with respect to the sheet transport direction, and the sheet detecting means 5 is provided. Is configured to detect the presence or absence of paper curl based on the time difference between the timing at which the presence / absence of paper is detected and the timing at which the reflected light receiving means 3a and the irradiated light receiving means 3b detect the presence / absence of light. In addition to discrimination of face curl and back curl, the positions of front, rear, left and right curls on the paper 50 can be discriminated.

Further, according to the curl detecting apparatus of the third embodiment, when the curl detecting unit 20 is viewed in plan, the irradiation light 7 from the light projecting unit 2 and the reflected light 8 from the reflecting member 4b intersect with the sheet detecting unit 5. As shown, each member is disposed, the acute angle formed by the paper transport direction and the irradiation light 7 and the reflected light 8 is θ, the length in the paper transport direction is Lx, and the length in the direction perpendicular to the transport direction. When Ly is set to Ly, the configuration in which θ satisfies tan θ> L _y / L _x prevents the curling of the front end corner C and the rear end corner D from being made indistinguishable. Can be detected.

(Embodiment 4)
FIG. 11 is a conceptual diagram showing the curl detection unit 20 in the curl detection device 30 according to the fourth embodiment of the present invention. FIG. 12 is a diagram of the curl detection unit 20 viewed from the direction A in FIG. It is a figure for demonstrating this curl detection. In addition, about the structure same as Embodiment 1-3, the same code | symbol is attached | subjected and the description is abbreviate | omitted. As shown in FIG. 11, in the fourth embodiment, a second spectral member 6 that splits the irradiation light from the light projecting means 2 into two is added, and two sets of reflected light receiving means and transmitted light receiving means are set. The configuration is the same as that of the second embodiment except that each is provided. That is, in the curl detecting apparatus of the fourth embodiment, the light transmitting / receiving means 10 is composed of the light projecting means 2, the reflected light receiving means 3a, 3c, and the transmitted light receiving means 3b, 3d, and the reflecting means 11 is the spectral member. 4c, the reflection member 4b, and the 2nd spectroscopy member 6. With the above configuration, as described below, in addition to the detection of the presence or absence of curling, it is possible to determine the curl amount (that is, the curl height) of the paper 50 that is the detection target.

  As shown in FIG. 11, the second spectral member 6 is disposed in front of the light projecting unit 2, and the light irradiated from the light projecting unit 2 is irradiated in parallel with each other at different distances from the paper 50. The light is split into light 7a and irradiation light 7b. In the present embodiment, a beam splitter and a prism mirror are applied as the second light splitting member 6, but other optical system members may be applied.

  In the curl detection unit 20 having the above-described configuration, as shown in FIG. 11, the irradiation light from the light projecting means 2 is split into irradiation light 7 a and 7 b by the second spectral member 6, and the irradiation light 7 a and 7 b The light is irradiated in a direction orthogonal to the transport direction and substantially parallel to the face surface of the paper 50. The irradiation lights 7a and 7b are split into transmitted light and reflected light by the spectroscopic member 4c, the transmitted light 9a is received by the transmitted light receiving means 3b, and the transmitted light 9b is received by the transmitted light receiving means 3d. The transmitted light receiving means 3 b and 3 d each output a detection signal when transmitted light is received, and transmit this to the control unit 35. On the other hand, when the transmitted light 9a and 7b are not received due to the irradiation light 7a and 7b being blocked, the transmitted light receiving means 3b and 3d output non-detection signals and transmit them to the control unit 35. . The two lights reflected by the spectroscopic member 4c are reflected by the reflecting member 4b, respectively, and reflected lights 8a and 8b that are parallel to each other and have different distances from the paper 50 are formed. The reflected light 8a is received by the reflected light receiving means 3a, and the reflected light 8b is received by the reflected light receiving means 3c. The reflected light receiving means 3a and 3b transmit the detection results of the reflected light 8a and 8b to the control unit 35, respectively. The control unit 35 detects the presence or absence of curling of the paper 50 based on the detection results received from the reflected light receiving units 3a and 3c and the transmitted light receiving units 3b and 3d.

  Hereinafter, an example will be described in which the distance from the paper 50 to the irradiation light 7a is z1, and the distance from the paper 50 to the irradiation light 7b is z2, and the two-stage curl amount is detected. The sheet 50 conveyed to the curl detection unit 20 by the sheet conveying rollers 32a and 32b passes between the irradiation light 7a and the reflected light 8a. At this time, if the paper 50 is not curled, neither the irradiated light 7a, 7b nor the reflected light 8a, 8b is blocked, so the reflected light receiving means 3a, 3c receive the reflected light 8a, 8b. The transmitted light receiving means 3b and 3d receive the transmitted lights 9a and 9b and transmit detection signals to the control unit 35, respectively. The control unit 35 determines that the paper 50 is not curled when receiving a detection signal from each light receiving unit.

  On the other hand, as shown in FIG. 12, when there is a face curl having a curl height of z1 or more and z2 or less, the irradiation light 7a does not reach the spectral member 4c because the irradiation light 7a is blocked by the face curl. Therefore, since neither the reflected light receiving means 3a nor the transmitted light receiving means 3b receives light, it transmits a non-detection signal to the control unit 35, respectively. On the other hand, the irradiation light 7b is reflected by the spectral member 4c without being blocked by the face curl. Therefore, the reflected light receiving unit 3d and the transmitted light receiving unit 3c receive light and transmit detection signals to the control unit 35, respectively. When the control unit 35 receives a non-detection signal from the reflected light receiving unit 3a and the transmitted light receiving unit 3b and receives a detection signal from the reflected light receiving unit 3c and the transmitted light receiving unit 3d, the curl height of the sheet 50 is increased. It is determined that there is a face curl of z1 or more and z2.

  As shown in FIG. 12, when there is a back curl with a curl height of z1 or more and z2 or less, the irradiated light 7a, 7b is reflected by the spectroscopic member 4c and the reflecting member 4b, but the reflected light 8a is reflected by the back curl. Blocked. Accordingly, the reflected light receiving means 3 a does not receive light, and therefore transmits a non-detection signal to the control unit 35. On the other hand, the transmitted light receiving means 3 b and 3 d and the reflected light receiving means 3 c receive light and transmit a detection signal to the control unit 35. When the control unit 35 receives a non-detection signal from the reflected light receiving unit 3a and receives detection signals from the reflected light receiving unit 3c and the transmitted light receiving units 3b and 3d, the curl height of the sheet 50 is z1 or more and z2. It is determined that there is a back curl.

  That is, in the present embodiment, a face having no curl and a height of z1 or more and z2 or less is obtained by a combination of detection / non-detection (ON / OFF) of the light of the reflected light receiving units 3a and 3c and the transmitted light receiving units 3b and 3d A curl, a face curl having a height of z2 or more, a back curl having a height of z1 or more and z2 or less, and a back curl having a height of z2 or more can be discriminated. FIG. 13 shows combinations of light detection / non-detection (ON / OFF) of the light receiving means 3a, 3b, 3c, 3d in these five cases.

  In the fourth embodiment, when only the height of the curl is determined without determining the face curl and the back curl, the reflection member 4a is applied instead of the spectroscopic member 4c, and the transmitted light receiving means 3b is used. , 3d are omitted.

  As described above, also in the curl detection device according to the fourth embodiment, light is emitted substantially parallel to the surface on one side of the paper 50 conveyed by the paper conveyance rollers 32a and 32b, as in the first to third embodiments. Is disposed opposite to the light projecting means 2 across the conveyance path of the paper 50, and the irradiation light 7 from the light projecting means 2 is substantially parallel to the other surface of the paper 50. A large-scale apparatus is provided by including the reflecting means 11 for reflecting and the reflected light receiving means 3a that is disposed so as to face the reflecting means 11 across the paper conveyance path and receives the reflected light 8 from the reflecting means 11. Therefore, both face curl and back curl can be reliably detected with a simple configuration.

  Furthermore, according to the curl detecting device of the fourth embodiment, the second light splitting member that splits the irradiation light from the light projecting means into the irradiation lights 7a and 7b that are parallel to each other and have different distances from the paper, and the irradiation light 7a, Transmitted light receiving means 3b, 3d for receiving the transmitted light 9a, 9b transmitted through 7b, and reflected light receiving means 3a, 3c for receiving the reflected lights 8a, 8b reflecting the irradiated lights 7a, 7b, respectively. With the above-described configuration, the presence or absence of curling of the paper is detected based on the detection results of the four light receiving units, so that the curl height can be determined in addition to the determination of the face curl and the back curl. .

  In the fourth embodiment, only the light receiving means and the spectral member are added, and it is not necessary to add the light projecting means. Accordingly, it is possible to determine the face curl and the back curl and the height of the curl without increasing the power supply for driving the light projecting means.

1 is a cross-sectional view showing a part of an image forming apparatus equipped with a curl detection apparatus according to a first embodiment; 1 is a block diagram of a curl detection apparatus according to a first exemplary embodiment. FIG. 3 is a conceptual diagram illustrating an example of a curl detection unit in the curl detection apparatus according to the first exemplary embodiment; FIG. 4 is a diagram for explaining sheet curl detection in a curl detection unit illustrated in FIG. 3. FIG. 6 is a conceptual diagram illustrating an example of a curl detection unit in a curl detection apparatus according to a second exemplary embodiment; FIG. 6 is a diagram illustrating paper curl detection in the curl detection unit illustrated in FIG. 5. FIG. 10 is a conceptual diagram illustrating an example of a curl detection unit in a curl detection apparatus according to a third embodiment; FIG. 8 is a top view of FIG. 7. FIG. 8 is a diagram illustrating paper curl detection in the curl detection unit illustrated in FIG. 7. FIG. 8 is a diagram illustrating paper curl detection in the curl detection unit illustrated in FIG. 7. FIG. 8 is a diagram illustrating paper curl detection in the curl detection unit illustrated in FIG. 7. FIG. 8 is a diagram illustrating paper curl detection in the curl detection unit illustrated in FIG. 7. FIG. 8 is a diagram illustrating paper curl detection in the curl detection unit illustrated in FIG. 7. FIG. 10 is a conceptual diagram illustrating an example of a curl detection unit in a curl detection apparatus according to a fourth embodiment; It is a figure explaining the curl detection of the paper in the curl detection part shown in FIG. 12 is a chart showing ON / OFF combinations of light receiving units in the curl detection unit shown in FIG. 11.

Explanation of symbols

2 Light projecting means 3a, 3c Reflected light receiving means 3b, 3d Transmitted light receiving means 4a, 4b Reflecting member 4c Spectral member 5 Paper detecting means 6 Second spectral member 7, 7a, 7b Irradiated light 8, 8a, 8b Reflected light 9 , 9a, 9b Transmitted light 10 Optical transmission / reception means 11 Reflection means 20 Curl detection unit 30 Curl detection device 31 Guide units 32a, 32b Paper transport rollers (paper transport means)
33 Paper receiving unit 34 Guide unit 35 Control unit 40 Paper post-processing device 41 Curl processing unit 42 Paper post-processing unit 43 Paper discharge tray 50 Paper

Claims (8)

A curl detection device that receives paper to be processed and detects paper curl while transporting the paper by a paper transport means,
A light projecting means for irradiating light substantially parallel to the surface of one side of the paper conveyed by the paper conveying means;
Reflecting means disposed opposite to the light projecting means across the paper conveyance path, and reflecting the irradiation light from the light projecting means substantially parallel to the other surface of the paper;
A reflected light receiving means arranged to face the reflecting means across the paper conveyance path and receiving reflected light from the reflecting means;
A curl detection apparatus comprising: control means for detecting the presence or absence of curling of the paper based on a detection result of the reflected light receiving means. The reflection means includes a spectral member that splits incident light into transmitted light and reflected light, and a reflective member that reflects incident light.
Furthermore, a transmitted light receiving means for receiving the light transmitted through the spectral member is provided,
The control means includes
2. The curl detection apparatus according to claim 1, wherein the curl is detected based on detection results of the reflected light receiving unit and the transmitted light receiving unit. A paper detecting means for detecting the presence or absence of paper conveyed by the paper conveying means;
The projecting unit, the reflecting unit, and the reflected light emitting unit are disposed so that the irradiation light from the projecting unit and the reflected light from the reflecting unit are inclined with respect to the transport direction of the paper,
The control means includes
The presence or absence of curling of the paper is detected based on a time difference between the timing when the paper detection unit detects the presence or absence of paper and the timing when the reflected light receiving unit detects the presence or absence of reflected light. Item 4. The curl detection apparatus according to item 1. A paper detecting means for detecting the presence or absence of paper conveyed by the paper conveying means;
The light projecting unit, the reflecting unit, the reflected light emitting unit, and the transmitted light receiving unit so that the irradiation light from the light projecting unit and the reflected light from the reflecting unit are inclined with respect to the transport direction of the paper. Means,
The control means includes
Based on the time difference between the timing when the paper detection means detects the presence or absence of paper, the timing when the reflected light receiving means detects the presence or absence of reflected light, and the timing when the transmitted light receiving means detects the presence or absence of transmitted light, The curl detection apparatus according to claim 2, wherein the presence or absence of curling of the paper is detected. The light projection means and the reflection means are arranged in such a manner that the irradiation light from the light projection means and the reflected light from the reflection means intersect with the paper detection means when viewed from a direction orthogonal to the conveyance direction of the paper. Arranged,
The acute angle formed between the conveying direction of the paper the irradiated light and the reflected light is theta, wherein the length of the conveying direction L _x of the paper, the length of the vertical direction when the L _y to the conveying direction, The curl detection apparatus according to claim 3, wherein the θ satisfies tan θ> L _y / L _x . The light emitted from the light projecting means is split into first and second irradiation lights that are parallel to each other and at different distances from the paper, and the first and second irradiation lights are split into the paper. A second spectroscopic member that irradiates the surface of one side of the lens substantially in parallel,
The reflecting means is
By reflecting the first irradiation light and the second irradiation light, first reflected light and second reflected light that are parallel to each other and have different distances from the paper are formed, and the first reflected light and the second reflected light are formed. Irradiate the surface of the other side of the paper with the reflected light substantially parallel;
The reflected light receiving means is
A first reflected light receiving means for receiving the first reflected light; and a second reflected light receiving means for receiving the second reflected light;
The control means includes
2. The curl detection apparatus according to claim 1, wherein the curl detection unit detects the curl of the sheet based on detection results of the first and second reflected light receiving units. The light emitted from the light projecting means is split into first and second irradiation lights that are parallel to each other and at different distances from the paper, and the first and second irradiation lights are split into the paper. A second spectroscopic member that irradiates the surface of one side of the lens substantially in parallel,
The reflecting means is
By reflecting the first irradiation light and the second irradiation light, first reflected light and second reflected light that are parallel to each other and have different distances from the paper are formed, and the first reflected light and the second reflected light are formed. Irradiate the surface of the other side of the paper with the reflected light substantially parallel;
The reflected light receiving means is
A first reflected light receiving means for receiving the first reflected light; and a second reflected light receiving means for receiving the second reflected light;
The transmitted light receiving means is
A first transmitted light receiving means for receiving the first irradiation light; and a second transmitted light receiving means for receiving the second irradiation light;
The control means includes
3. The curl according to claim 2, wherein the curl is detected based on detection results of the first and second reflected light receiving units and the first and second transmitted light receiving units. Detection device.   8. The curl detection apparatus according to claim 1, wherein the irradiation light from the light projecting unit is a laser beam.

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