JP2012035953A - Sheet type discriminating device, sheet feeder, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet type discriminating device capable of accurately discriminating types of sheets being hardly influenced by changes in sheet thickness and surface reflection intensity.SOLUTION: The sheet type discriminating device includes: a light emitting part 41 irradiating the sheet P with light; a plurality of light receiving parts 42a-42f receiving reflected light from the sheet P and disposed so that light receiving axes M1-M6 are inclined in different directions with respect to an irradiation light axis L from the light emitting part 41; a sheet information storage part for storing the type information of the sheet P associated with the directivity of reflected light from the sheet P; and a sheet type discriminating part for discriminating the type of the sheet P based on light receiving intensity at the light receiving parts 42a-42f receiving the reflected light and on the information stored in the sheet information storage part.

Description

  The present invention relates to a sheet type discriminating apparatus that discriminates the type of a sheet, a sheet feeding apparatus including the same, and an image forming apparatus.

  2. Description of the Related Art Conventionally, as described in Patent Document 1 below, a sheet supply device that supplies a sheet such as a recording sheet or a document has a sheet type determination device that determines the type of the sheet for the purpose of detecting double feeding of sheets. There is something with.

  The sheet type discriminating apparatus described in Patent Document 1 is made by paying attention to the fact that the reflected light of the light irradiated onto the paper differs when the paper type is different. When the light receiving element receives the reflected light, The type of sheet is determined based on the amount of received light.

  However, even with the same type of paper, if the unevenness of the surface or the light reflection intensity changes due to the difference in paper thickness, the amount of reflected light received will change, so a sheet using a conventional reflective sensor There is a problem that the type discrimination device cannot accurately discriminate the paper type.

  In view of such circumstances, the present invention is less susceptible to changes in sheet thickness and surface reflection intensity, and can accurately determine a sheet type, and a sheet supply apparatus and an image forming apparatus including the same Is to provide.

  According to the first aspect of the present invention, the light emitting unit that emits light to the sheet and the reflected light from the sheet are received, and the light receiving axis is inclined in a different direction with respect to the optical axis of the light emitted from the light emitting unit. A plurality of light receiving units disposed on the sheet, a sheet information storage unit that stores sheet type information associated with directivity of reflected light from the sheet, and light reception by the light receiving unit that receives the reflected light. The sheet type discrimination device includes a sheet type discrimination unit that discriminates the type of the sheet based on strength and information stored in the sheet information storage unit.

  When the sheet is irradiated with light from the light emitting unit, the irradiated light is radially spread around the irradiation optical axis and reflected, and the reflected light is received by a plurality of light receiving units. Since the directivity of the reflected light that spreads radially varies depending on the type of sheet, the sheet type determination unit determines the received light intensity of the reflected light received by each light receiving unit and the direction of the reflected light stored in the sheet information storage unit. The sheet type can be determined based on the sheet type information associated with the property. As described above, the sheet type discriminating apparatus according to the present invention is configured to discriminate the type of the sheet based on the directivity of the reflected light from the sheet. Compared to what is determined, it is less susceptible to changes in sheet thickness and surface reflection intensity. For this reason, the discrimination accuracy of the sheet type can be improved, and the sheet type can be accurately discriminated.

  According to a second aspect of the present invention, there is provided a sheet supply apparatus comprising: a sheet storage unit that stores a sheet; and a sheet feeding unit that feeds the sheet from the sheet storage unit. It is equipped with.

  Since the sheet supply device includes the sheet type determination device according to the first aspect, the above-described effects of the sheet type determination device can be obtained.

  A third aspect of the present invention is the sheet feeding apparatus according to the second aspect, further comprising a sheet thickness determining device that determines the thickness of the sheet, wherein the sheet thickness determining device is a thickness of the sheet from an oblique direction with respect to the sheet. A light emitting unit that irradiates light toward the part, and a plurality of light receiving elements that receive reflected light from the thickness part of the sheet and that are arranged side by side in a direction in which the reflected light width increases or decreases according to the thickness of the sheet The light receiving intensity obtained from the comparison result in the comparison part, the comparison part comparing the received light intensity at the light receiving part that receives the reflected light from the thickness part of the sheet and the reference part with the reference intensity, and the reference light intensity A sheet thickness discriminating unit that discriminates the thickness of the sheet according to the number of the light receiving units larger than the intensity is provided.

  When light is irradiated from the light emitting unit to the thickness portion of the sheet, the reflected light is reflected on any one or a plurality of the light receiving units according to the reflected light width (the width of the light receiving region) which varies depending on the thickness of the sheet. Is received. Then, in the comparison unit, the received light intensity of the reflected light received by the light receiving unit is compared with the reference intensity, and the sheet thickness is obtained according to the number of the light receiving units with the received light intensity greater than the reference intensity obtained from the comparison result The determination unit determines the thickness of the sheet. In this way, the sheet thickness determining apparatus irradiates light toward the thickness portion of the sheet and determines the thickness according to the width of the light receiving area of the reflected light, so that double feeding occurs. In this case, it is possible to prevent erroneous detection, and it is possible to accurately determine the thickness of a sheet that has high light transmittance and hardly changes its transmittance according to its thickness.

  According to a fourth aspect of the present invention, in the sheet feeding apparatus according to the third aspect, a reference strength changing unit that changes the reference strength for determining the thickness of the sheet according to the type of the sheet.

  Since the reference strength varies depending on the type of sheet, the thickness of many types of sheets can be determined by changing the reference strength to a reference strength suitable for the type of sheet in the reference strength changing unit.

  According to a fifth aspect of the present invention, in the sheet feeding apparatus according to the third or fourth aspect, an enlarged projection member is provided for enlarging reflected light from the thickness portion of the sheet and projecting the reflected light on the light receiving unit.

  By enlarging and projecting the reflected light by the magnifying projection member, it becomes possible to receive the light with high accuracy by the light receiving unit having a limited size.

  A sixth aspect of the present invention is the sheet feeding apparatus according to the fifth aspect, wherein the magnifying projection member is a Fresnel lens.

  By using a Fresnel lens as the magnifying projection member, the thickness can be reduced, and space can be saved.

  A seventh aspect of the present invention is the sheet feeding apparatus according to the fifth or sixth aspect, wherein the plurality of light receiving portions and the enlarged projection member of the sheet thickness determining device are accommodated in a housing member, and the sheet of the housing member A guide surface for guiding the sheet being conveyed is provided on a surface facing the conveyance path.

  In this case, the sheet can be smoothly conveyed by the guide surface.

  The invention according to claim 8 is the sheet supply apparatus according to claim 7, wherein a dustproof member for preventing dust and dirt from entering the housing member is provided.

  In this case, dust and dust can be prevented from entering the housing member by the dust-proof member, and the light receiving accuracy can be maintained well.

  The invention according to claim 9 is the sheet feeding device according to any one of claims 3 to 8, wherein unnecessary light is prevented from entering the light receiving portion that receives the reflected light from the thickness portion of the sheet. The aperture is provided.

  In this case, unnecessary light can be prevented from entering each light receiving portion by the diaphragm, so that the light receiving accuracy at each light receiving portion can be improved.

  A tenth aspect of the present invention is the sheet feeding apparatus according to any one of the second to ninth aspects, further comprising a double feed detection device that detects the presence or absence of the double feed of the sheet, wherein the double feed detection device includes: A first light-emitting unit and a first light-receiving unit disposed on one surface side of the sheet; and a second light-emitting unit and a second light-receiving unit disposed on the other surface side of the sheet. The unit receives the reflected light of the light irradiated on the sheet from the first light emitting unit and the transmitted light of the light irradiated on the sheet from the second light emitting unit, and the second light receiving unit receives the second light emission Configured to receive the reflected light of the light irradiated on the sheet from the unit and the transmitted light of the light irradiated on the sheet from the first light emitting unit, and further, the multifeed detection device includes the transmitted light and the light Receiving intensity of each of the first light receiving part and the second light receiving part that has received the reflected light A comparator for comparing the reference intensity, those having a double feed determination unit for determining multifeed whether on the basis of the result of comparison by the comparison unit.

  When the sheet is irradiated with light from the first and second light emitting units, the reflected light of the light emitted from the first light emitting unit and the transmitted light of the light emitted from the second light emitting unit are received by the first light receiving unit, The reflected light of the light emitted from the two light emitting units and the transmitted light of the light emitted from the first light emitting unit are received by the second light receiving unit. Then, the comparison unit compares the received light intensity information of the transmitted light and the reflected light at each light receiving unit with the reference intensity, and based on the comparison result, the multi-feed discriminating unit discriminates the presence or absence of double feed. Thus, the multifeed detection device does not include a light emitting unit and a light receiving unit separately for each application of the transmission type sensor and the reflection type sensor, but includes one light emitting unit and one light receiving unit. And a reflective sensor, it is less affected by unevenness on the same sheet surface and variations in the light transmission of each type of sheet. It is possible to improve.

  The invention according to claim 11 is the sheet feeding apparatus according to claim 10, further comprising a reference strength changing unit that changes the reference strength for determining the presence or absence of double feeding according to the type of the sheet. .

  Since the reference strength varies depending on the type of sheet, it is possible to detect the presence or absence of double feeding in many types of sheets by changing the reference strength to a reference strength suitable for the type of sheet at the reference strength changing unit. It becomes.

  According to a twelfth aspect of the present invention, in the sheet feeding apparatus according to the tenth or eleventh aspect, the first light emitting unit and the second light receiving unit are disposed so as to face each other, and the respective centers are coaxially arranged. The second light emitting unit and the first light receiving unit are disposed so as to face each other, and the centers of the second light emitting unit and the first light receiving unit are disposed coaxially.

  The center of the light emitting part has the highest light emission intensity, and the light receiving part has the highest light receiving sensitivity at the center, so that the first light emitting part and the second light receiving part, and the second light emitting part and the first light receiving part are opposed to each other. By arranging them at the same center and coaxially, the influence of noise due to unevenness on the sheet surface, sheet powder, etc. can be reduced and the SN ratio (signal / noise ratio) can be improved. Can be detected with high accuracy.

  A thirteenth aspect of the present invention is an image forming apparatus including the sheet type determining device according to the first aspect or the sheet feeding device according to any one of the second to twelfth aspects.

  Since the image forming apparatus includes the sheet type determination device according to claim 1 or the sheet supply device according to any one of claims 2 to 12, the above-described effects of these devices can be obtained.

  Since the sheet type discriminating apparatus according to the present invention is configured to discriminate the sheet type based on the directivity of the reflected light from the sheet, it is possible to discriminate the paper type based on the received light amount of the conventional reflected light. In comparison, it is less susceptible to changes in sheet thickness and surface reflection intensity. Thus, according to the present invention, it is possible to improve the discrimination accuracy of the sheet type, and it is possible to accurately discriminate the sheet type.

1 is a schematic configuration diagram of a color image forming apparatus according to the present invention. FIG. 2 is a side view showing a schematic configuration of a paper feeding device mounted on the color image forming apparatus. FIG. 3 is a plan view of FIG. 2. It is a front view which shows schematic structure at the time of seeing the paper type discrimination | determination apparatus provided in the said paper feeding apparatus from the paper conveyance direction. It is a block diagram which shows the structure of the control system of the said paper kind discrimination | determination apparatus. FIG. 3 is a front view illustrating a schematic configuration when a double feed detection device provided in the paper feeding device is viewed from a paper conveyance direction. It is a perspective view which shows schematic structure of the said double feed detection apparatus. It is a block diagram which shows the structure of the control system of the said double feed detection apparatus. It is a side view which shows schematic structure of the paper thickness discrimination | determination apparatus provided in the said paper feeding apparatus. It is a block diagram which shows the structure of the control system of the said paper thickness discrimination | determination apparatus. FIG. 6 is a timing chart showing ON / OFF of a paper feed signal, ON / OFF of each drive signal of a paper type discriminating device, a double feed detecting device, and a paper thickness discriminating device, and presence / absence of a light reception signal in those devices. (A) is coated paper, (B) is plain paper, (C) is a figure which shows typically the intensity distribution of the reflected light in each of mylar paper. It is a figure which shows an example of the table | surface used for paper type discrimination | determination. It is a figure which shows an example of the table | surface used for the detection of the presence or absence of double feeding. It is a figure for demonstrating the effect | action and effect of the said double feed detection apparatus. It is the figure which represented typically the image of the rear focal plane of the Fresnel lens at the time of receiving the reflected light from the thickness part of a paper through a Fresnel lens, and reflected light intensity distribution. It is a figure which shows an example of the table | surface used for paper thickness discrimination | determination. Although the paper type is the same plain paper, it is a diagram showing a comparison between the amount of light received when a single thick sheet is conveyed and when a thin sheet is double-fed. It is side surface sectional drawing which shows the structure of other embodiment of the said paper thickness discrimination | determination apparatus. It is side surface sectional drawing which shows the structure which provided the dust-proof member in the paper thickness discrimination | determination apparatus shown in FIG. It is side surface sectional drawing which shows the structure which provided the aperture_diaphragm | restriction in the paper thickness discrimination | determination apparatus shown in FIG.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to an embodiment of the present invention.
The image forming apparatus shown in FIG. 1 includes four process units 1Y, 1C, 1M, and 1Bk as image forming units. Each of the process units 1Y, 1C, 1M, and 1Bk is configured to be detachable from the image forming apparatus main body 100. Each process unit 1Y, 1C, 1M, 1Bk contains toners of different colors of yellow (Y), cyan (C), magenta (M), and black (Bk) corresponding to the color separation components of the color image. The configuration is the same except that.

  Specifically, each of the process units 1Y, 1C, 1M, and 1Bk is a drum-shaped photosensitive member 2 as an electrostatic latent image carrier (or an image carrier) and charging means for charging the surface of the photosensitive member 2. A charging roller 3, a developing roller 4 as a developing unit for developing an electrostatic latent image on the photosensitive member 2, a cleaning blade 5 as a cleaning unit for cleaning the surface of the photosensitive member 2, and the like. In FIG. 1, only the photoconductor 2, the charging roller 3, the developing roller 4, and the cleaning blade 5 included in the yellow process unit 1 </ b> Y are denoted by reference numerals, and the other process units 1 </ b> C, 1 </ b> M, and 1 </ b> Bk are denoted by reference numerals. Omitted.

  In FIG. 1, an exposure device 6 as an exposure means for exposing the surface of the photoreceptor 2 is disposed above each process unit 1Y, 1C, 1M, 1Bk. On the other hand, a transfer device 7 is disposed below the process units 1Y, 1C, 1M, and 1Bk. The transfer device 7 has an intermediate transfer belt 8 constituted by an endless belt member as a transfer body. The intermediate transfer belt 8 is supported around a driving roller 9 and a driven roller 10. The driving roller 9 is configured so as to obtain a driving force from a driving means (not shown) and rotationally drive it counterclockwise in the figure. By the rotation of the driving roller 9, the intermediate transfer belt 8 is moved in the direction of the arrow in the figure. It can be rotated. The driven roller 10 is urged toward the intermediate transfer belt 8 by an urging means (not shown), whereby a predetermined tension is applied to the intermediate transfer belt 8.

  Four primary transfer rollers 11 as primary transfer means are disposed at positions facing the four photoconductors 2 via the intermediate transfer belt 8. Each primary transfer roller 11 presses the inner peripheral surface of the intermediate transfer belt 8 at each position, and a primary transfer nip is formed at a location where the pressed portion of the intermediate transfer belt 8 and each photoconductor 2 are in contact with each other. ing. A secondary transfer roller 12 as a secondary transfer unit is disposed at a position facing the drive roller 9 with the intermediate transfer belt 8 interposed therebetween. The secondary transfer roller 12 presses the outer peripheral surface of the intermediate transfer belt 8, and a secondary transfer nip is formed at a location where the secondary transfer roller 12 and the intermediate transfer belt 8 are in contact with each other.

  A belt cleaning device 13 for cleaning the surface of the intermediate transfer belt 8 is disposed on the outer peripheral surface of the intermediate transfer belt 8 on the right end side in the drawing. A waste toner transfer hose (not shown) is attached from the belt cleaning device 13, and the tip of the toner transfer hose is connected to an inlet portion of a waste toner container 14 disposed below the transfer device 7.

  A sheet feeding device 23 as a sheet feeding device for feeding sheets is provided at the lower part of the image forming apparatus main body 100. Here, the sheet includes not only plain paper generally used for copying or the like, but also an OHP sheet, cardboard, cardboard, or other thick paper, an envelope, or the like. The sheet feeding device 23 is provided with a sheet feeding tray 15 as a sheet accommodating portion that accommodates sheets P that are sheets, a sheet feeding roller 16 as sheet feeding means for feeding sheets P from the sheet feeding tray 15, and the like. It has been. On the other hand, a pair of paper discharge rollers 17 for discharging the paper to the outside and a paper discharge tray 18 for stocking the discharged paper are disposed on the upper portion of the image forming apparatus main body 100.

  In the image forming apparatus main body 100, a paper transport path R for guiding paper from the lower paper feed tray 15 to the upper paper discharge tray 18 is formed. A pair of registration rollers 19 is disposed in the middle of the paper transport path R from the paper feed roller 16 to the secondary transfer roller 12. In addition, a fixing device 20 for fixing an image on the sheet is disposed on the way from the secondary transfer roller 12 to the paper discharge roller 17. The fixing device 20 includes a fixing roller 21 as a fixing member that is heated by a heat source, and a pressure roller 22 as a pressure member that presses the fixing roller 21. A fixing nip as a fixing unit is formed at a position where the fixing roller 21 and the pressure roller 22 are in pressure contact with each other.

The basic operation of the image forming apparatus will be described below with reference to FIG.
When the image forming operation is started, the photoconductors 2 of the process units 1Y, 1C, 1M, and 1Bk are rotationally driven clockwise by a driving device (not shown), and the surface of each photoconductor 2 is predetermined by the charging roller 3. It is uniformly charged to the polarity. The surface of each charged photoreceptor 2 is irradiated with laser light from the exposure device 6 to form an electrostatic latent image. At this time, the image information to be exposed on each photoconductor 2 is monochromatic image information obtained by separating a desired full-color image into color information of yellow, cyan, magenta, and black. The electrostatic latent image formed on the photoreceptor 2 in this way is supplied with toner by each developing roller 4 so that the electrostatic latent image is visualized (visualized) as a toner image.

  By driving the drive roller 9 counterclockwise in the figure, the intermediate transfer belt 8 is driven to rotate in the direction indicated by the arrow in the figure. Further, a constant voltage or a constant current controlled voltage having a polarity opposite to the toner charging polarity is applied to each primary transfer roller 11. As a result, a transfer electric field is formed at the primary transfer nip between each primary transfer roller 11 and each photoconductor 2. The toner images of the respective colors formed on the photoreceptors 2 of the process units 1Y, 1C, 1M, and 1Bk are sequentially transferred onto the intermediate transfer belt 8 by the transfer electric field formed in the primary transfer nip. The Thus, the intermediate transfer belt 8 carries a full-color toner image on its surface. After the transfer of the toner image, the toner remaining on the surface of each photoconductor 2 is removed by the cleaning blade 5. Next, the surface of the photoconductor 2 is subjected to a static elimination action by a static eliminator (not shown), and the surface potential is initialized to prepare for the next image formation.

  When the image forming operation is started, the sheet feeding roller 16 starts rotating, and the sheet P stored in the sheet feeding tray 15 is sent out to the sheet conveying path R by the sheet feeding roller 16. The paper P sent to the paper transport path R is temporarily stopped by the registration roller 19. Thereafter, the driving of the registration roller 19 is resumed, and the paper P is sent to the secondary transfer nip between the secondary transfer roller 12 and the drive roller 9 in synchronization with the toner image on the intermediate transfer belt 8. At this time, a transfer voltage having a polarity opposite to the toner charging polarity of the toner image on the intermediate transfer belt 8 is applied to the secondary transfer roller 12, thereby forming a transfer electric field in the secondary transfer nip. When the paper P and the toner image on the intermediate transfer belt 8 reach the secondary transfer nip, the toner image on the intermediate transfer belt 8 is collectively put on the paper P by the transfer electric field formed in the secondary transfer nip. And transferred. Further, the toner remaining on the intermediate transfer belt 8 after the transfer is removed by the belt cleaning device 13, and the removed toner is conveyed to the waste toner container 14 and collected. The paper P on which the toner image has been transferred is conveyed to the fixing unit 20, and the paper P is heated and pressed by the fixing roller 21 and the pressure roller 22 to fix the toner image. Thereafter, the paper P is discharged to the paper discharge tray 18 by the paper discharge roller 17.

  The above description is an image forming operation when a full-color image is formed on a sheet. A single-color image is formed using any one of the four process units 1Y, 1C, 1M, and 1Bk, and 2 Two or three process units can be used to form a two or three color image.

FIG. 2 is a side view showing a schematic configuration of the paper feeding device 23, and FIG. 3 is a plan view of FIG.
As shown in FIG. 2, the paper feeding device 23 is provided with a pickup roller 25, a reverse roller 26, and a conveyance roller 27 in addition to the paper feeding tray 15 and the paper feeding roller 16 described above. The uppermost sheet P of the sheet bundle accommodated in the sheet feeding cassette 15 is separated from the sheet bundle by the frictional conveying force of the pickup roller 25, and the sheet feeding roller 16 that rotates in the direction in which the sheet P is conveyed, and the sheet feeding roller The sheet is reliably separated and conveyed into one sheet by a reverse roller 26 that rotates at a predetermined torque in a direction opposite to the rotation of 16 and further conveyed by a conveyance roller 27.

  As shown in FIG. 3, the paper feed roller 16, the pip-up roller 25, the reverse roller 26, and the transport roller 27 are driven by two drive motors 28 and 29 provided in the paper feed device 23. Specifically, the rotation shaft 28a of the drive motor 28 and the rotation shaft 16a of the paper feed roller 16 shown in the left side of FIG. 3 are interlocked and connected via the transmission belt 30, and when the drive motor 28 rotates, the driving force However, the driving force is transmitted to the paper feed roller 16 via the transmission belt 30 so that the paper feed roller 16 rotates. Further, a gear 31 provided integrally with the rotation shaft 16a of the supply roller 16 and a gear 32 provided integrally with the rotation shaft 25a of the pickup roller 25 are connected via a gear 33 disposed therebetween. When the paper feed roller 16 rotates, the rotational force is transmitted to the pickup roller 25 through the gears 31, 32, 33, and the pickup roller 25 rotates. Further, the rotation shaft 29a of the drive motor 29 and the rotation shaft 27a of the transport roller 27 shown in the right side of FIG. 3 are interlocked and connected via a transmission belt 34. When the drive motor 29 is driven to rotate, the driving force is transmitted. A driving force is transmitted to the conveying roller 27 via the belt 34 so that the conveying roller 27 rotates. Further, a gear 35 provided integrally with the rotation shaft 27a of the transport roller 27 and a gear 36 (see FIG. 2) provided integrally with the rotation shaft 26a of the reverse roller 26 are disposed therebetween. When the conveying roller 27 rotates, the rotation force is transmitted to the reverse roller 26 through the gears 35, 36, and 37, and the reverse roller 26 rotates.

  Further, a sheet type discriminating device 40 (hereinafter referred to as “paper type discriminating device”) for discriminating the type of the paper P at a position between the paper feed roller 16 and the transport roller 27 and whether or not the paper P is double-fed. A double feed detection device 50 for detecting, and a sheet thickness determination device 60 (hereinafter referred to as “paper thickness determination device”) for determining the thickness of the paper P are provided.

FIG. 4 is a front view illustrating a schematic configuration when the paper type identification device 40 is viewed from the paper conveyance direction.
As illustrated in FIG. 4, the paper type determination device 40 includes a light emitting unit 41 that emits light to the paper P, a plurality of light receiving units 42 a to 42 f that receive reflected light from the paper P, and a light emitting unit. 41 and a semicircular support member 43 that supports the light receiving portions 42a to 42f. The light emitting part 41 and the light receiving parts 42a to 42f are disposed on the inner peripheral surface side of the support member 43, the light emitting part 41 is disposed at the center part of the support member 43, and the light receiving parts 42a to 42f emit light. It is arrange | positioned at equal intervals or unequal intervals on the both sides of the part 41. FIG. In other words, the light receiving parts 42a to 42f are arranged such that the light receiving axes M1 to M6 are inclined in different directions with respect to the irradiation optical axis L from the light emitting part 41. The support member 43 is fixed to a frame (not shown) of the image forming apparatus main body by mounting members such as a plurality of set screws 44.

FIG. 5 is a block diagram showing the configuration of the control system of the paper type discrimination device 40.
As shown in FIG. 5, the paper type determination device 40 includes a drive unit 45, a sheet information storage unit 46, and a sheet type determination unit 47 in addition to the light emitting unit 41 and the light receiving units 42 a to 42 f. The drive unit 45 drives (turns on) the light emitting unit 41 and the light receiving units 42a to 42f based on the drive start signal of the control unit 101 that controls various devices provided in the image forming apparatus. The sheet information storage unit 46 stores paper type information associated with the directivity of reflected light from the paper. The sheet type discriminating unit 47 is a unit that discriminates the type of paper based on the received light intensity of the reflected light received by each of the light receiving units 42a to 42f and the information stored in the sheet information storage unit.

FIG. 6 is a front view showing a schematic configuration when the multifeed detection device 50 is viewed from the sheet conveyance direction.
As shown in FIG. 6, the double feed detection device 50 includes a first light emitting unit 51 and a first light receiving unit 52 disposed on one side (upper side in the drawing) of the conveyed paper P, and the paper P. The second light emitting unit 53 and the second light receiving unit 54 are provided on the other surface side (the lower side of the figure). The first light receiving unit 52 receives the reflected light of the light irradiated on the paper P from the first light emitting unit 51, and the second light receiving unit 54 receives the reflected light of the light irradiated on the paper P from the second light emitting unit 53. It has become. Further, the first light emitting unit 51 and the second light receiving unit 54 are disposed at positions facing each other with the paper P interposed therebetween, and the second light emitting unit 53 and the first light receiving unit 52 are also disposed with the paper P interposed therebetween. It is arrange | positioned in the position which opposes. By arranging the light emitting units 51 and 53 and the light receiving units 52 and 54 in this way, the second light receiving unit 54 receives the transmitted light of the light emitted from the first light emitting unit 51 to the paper P, and the second light receiving unit 54 receives the second light. The first light receiving unit 52 receives the transmitted light of the light emitted from the light emitting unit 53 to the paper P. In the present embodiment, the first light emitting unit 51 and the first light receiving unit 52, and the second light emitting unit 53 and the second light receiving unit 54 are integrally configured, respectively.

Further, the center of the light emitting part has the highest emission intensity, and the center of the light receiving part has the highest light receiving sensitivity. Therefore, as shown in FIG. 7, in the first light-emitting part 51 and the second light-receiving part 54, the first light-receiving part 52 and the second light-emitting part 53 facing each other, the respective centers O ₅₁ and O ₅₄ , O ₅₂ and O It is desirable to arrange ₅₃ on the same axis. As a result, it is possible to improve the SN ratio (signal / noise ratio) by reducing the influence of noise caused by unevenness on the paper surface, paper dust, etc., and to detect with high accuracy.

FIG. 8 is a block diagram showing the configuration of the control system of the double feed detection device 50.
As shown in FIG. 8, in addition to the first light emitting unit 51, the first light receiving unit 52, the second light emitting unit 53, and the second light receiving unit 54, the double feed detection device 50 includes a driving unit 55, a comparison unit 56, , A reference strength changing unit 57 and a double feed discriminating unit 58. The drive unit 55 drives the first light emitting unit 51, the first light receiving unit 52, the second light emitting unit 53, and the second light receiving unit 54 based on the drive start signal of the control unit 101 that controls the various devices (ON). To do). The comparison unit 56 compares the received light intensity of the transmitted light and the reflected light from the first and second light receiving units 52 and 54 with a preset reference intensity. Further, the reference strength in the comparison unit 56 can be changed to a reference strength corresponding to the type of paper by the reference strength changing unit 57. The double feed discriminating unit 58 is a means for discriminating the presence / absence of double feed based on the comparison result in the comparison unit 56.

FIG. 9 is a side view showing a schematic configuration of the paper thickness discrimination device 60.
As shown in FIG. 9, the paper thickness determination device 60 includes a light emitting unit 61 that irradiates light toward the thickness portion of the paper P from an oblique direction with respect to the paper P, and a thickness from the thickness portion of the paper P. A plurality of light receiving parts 62a to 62d that receive the reflected light and a Fresnel lens 63 as an enlargement projection member that enlarges and projects the reflected light until the reflected light reaches each of the light receiving parts 62a to 62d. The plurality of light receiving portions 62 a to 62 d are arranged side by side in a direction in which the reflected light width increases or decreases in accordance with the thickness of the paper P.

FIG. 10 is a block diagram showing the configuration of the control system of the paper thickness discrimination device 60.
As shown in FIG. 10, in addition to the light emitting unit 61 and the light receiving units 62a to 62d, the paper thickness determining device 60 includes a driving unit 64, a comparing unit 65, a reference intensity changing unit 66, and a sheet thickness determining unit 67. Is provided. The drive unit 64 drives (turns on) the light emitting unit 61 and the light receiving units 62a to 62d based on the drive start signal of the control unit 101 that controls the various devices. The comparison unit 65 compares the received light intensity of the reflected light from each of the light receiving units 62a to 62d with a preset reference intensity. The reference strength in the comparison unit 65 is configured to be changed to a reference strength corresponding to the type of paper by a reference strength changing unit 66. The sheet thickness determining unit 67 is a unit that determines the sheet thickness according to the number of the light receiving units 62 a to 62 d whose received light intensity is larger than the reference intensity based on the comparison result in the comparing unit 65.

FIG. 11 shows ON / OFF of a control signal (paper feed signal) of the drive motor 28 for driving the paper feed roller and the like, and respective drive signals of the paper type discriminating device 40, the double feed detecting device 50, and the paper thickness discriminating device 60. It is a figure which shows the timing chart of ON / OFF of these, the presence or absence of the light reception signal in those apparatuses.
As shown in FIG. 11A, first, when the paper feed signal is turned ON and rotation of the paper feed roller or the like is started by the drive motor 28, the paper P is drawn from the paper feed tray 15 shown in FIG. Sent to the right. Next, as shown in FIGS. 11B, 11C, and 11D, the drive signals of the paper type determination device 40, the double feed detection device 50, and the paper thickness determination device 60 are turned ON. Specifically, the drive units 45, 55, and 64 shown in FIGS. 5, 8, and 10 receive a drive start signal from the control unit 101, and turn on each light emitting unit and each light receiving unit. Thereafter, the sheet P passes through the irradiation position of the light emitting unit of each device, and the reflected light at that time is received by the light receiving unit of each device, as shown in FIGS. 11 (E), 11 (F), and 11 (G). The light receiving signal is emitted in the order of the double feed detecting device 50, the paper type determining device 40, and the paper thickness determining device 60.

Hereinafter, the operations of the paper type determination device 40, the double feed detection device 50, and the paper thickness determination device 60 will be described in detail.
First, in the paper type identification device 40, as shown in FIG. 4, when the paper P is conveyed below the light emitting unit 41 and light is emitted from the light emitting unit 41 to the paper P, the irradiated light is applied to the paper P. Reflected by. In general, the reflected light on the paper P has a directivity that spreads not only in the vertical direction but also in the radial direction with respect to the surface of the paper P, so that the reflected light is received by each of the light receiving portions 42a to 42f. The received light intensity information of the reflected light received by each of the light receiving units 42a to 42f is sent to the sheet type determining unit 47 shown in FIG. 5, and the sheet type determining unit 47 receives the light received from each of the light receiving units 42a to 42f. The paper type is determined based on the intensity information and the information stored in the sheet information storage unit 46.

FIG. 12 schematically shows the intensity distribution of reflected light in coated paper (A), plain paper (B), and mylar paper (C).
In FIG. 12, the intensity distribution of each reflected light is indicated by a circle or an ellipse. As described above, when the vertical direction with respect to the surface of the paper P is set to 0 °, the intensity for each radiation angle of the reflected light is different for each paper type. For this reason, the received light intensity of the reflected light received by the plurality of light receiving units 42a to 42f is an intensity corresponding to the directivity (intensity distribution pattern) of the reflected light for each paper type.

  From the directivity of the reflected light as described above, in this embodiment, as shown in the table of FIG. 13, the amount of light received (light reception intensity) at each of the light receiving portions 42a to 42f is large, medium, or small for each paper type. This information is stored in the sheet information storage unit 46. Then, the paper type is determined by collating the sheet type information associated with the directivity of the reflected light shown in FIG. 13 and the received light intensity information. In FIG. 13, for example, in the case of Mylar paper, based on the directivity of the reflected light, the amount of light received by the two light receiving portions 42a and 42d arranged on the innermost side (near the center) is large, one lighter than them. The light receiving amounts of the two light receiving portions 42b and 42e provided are set to be small, while the light receiving amounts of the two light receiving portions 42c and 42f provided on the outermost side are set to be small.

  As described above, in the paper type discriminating device 40, the received light intensity obtained from each of the light receiving units 42a to 42f is collated with the table of FIG. 13, and the directivity (intensity distribution pattern) of the reflected light is identical or similar. By selecting, it is possible to determine the paper type. If the detected light reception amount pattern is not similar to the light reception amount patterns of the three paper types shown in FIG. 13, it is determined that the paper type cannot be determined.

Next, the operation of the double feed detection device 50 will be described.
As shown in FIG. 6, when the paper P is transported between the first light emitting unit 51 and the second light emitting unit 53 and light is emitted from the respective light emitting units 51 and 53 to the paper P, The transmitted light and the reflected light are received by the first light receiving unit 52 and the second light receiving unit 54. Then, the received light intensity information of the transmitted light and the reflected light at each of the light receiving parts 52 and 54 is sent to the comparison part 56 shown in FIG. When the first light emitting unit 51 irradiates the paper P with light, the comparison unit 56 processes the received light signal at the first light receiving unit 52 as reflected light, and the received light signal at the second light receiving unit 54 as processed light. Is done. Further, when the second light emitting unit 53 irradiates the paper P with light, the comparison unit 56 processes the light reception signal at the first light receiving unit 52 as transmitted light, and the light reception signal at the second light receiving unit 54 is reflected light. Is processed as Then, the comparison unit 56 compares the received light intensity information obtained from each of the light receiving units 52 and 54 with a preset reference intensity, and based on the comparison result, the double feed determination unit 58 determines the presence or absence of double feed.

  As shown in the table of FIG. 14, the reference intensity is set in three patterns of large, medium, and small with respect to the amounts of light transmitted and reflected by the light receiving portions 52 and 54. For example, in the case of Mylar paper, when the paper is normally conveyed (when there is no double feed), the amount of light received by each of the light receiving units 52 and 54 is large, and the amount of light received by reflected light is small. However, when double feed occurs (when double feed is present), the amount of transmitted light is small because the sheets are overlapped, making it difficult for light to pass therethrough. Note that since the surface state of the sheet does not change even if double feeding occurs, the amount of received reflected light remains small as in the case where there is no double feeding.

  Therefore, as shown in FIG. 14, in Mylar paper, by setting the reference intensity of transmitted light to two patterns, large and small, the received light intensity (the amount of received light) is compared with each reference intensity, and the received light intensity is high.・ It is possible to detect the presence or absence of double feeding by determining which of the two corresponds to small. The reference intensity of the reflected light is used for discriminating the paper type. As shown in FIG. 14, by setting the reference intensity of the reflected light of the Mylar paper to be small and setting the reference intensity of the reflected light of the coated paper and the plain paper to be respectively medium, by receiving the reflected light, the paper It can be determined whether the seed is Mylar paper, coated paper or plain paper. When it is determined that the determined paper type is coated paper or plain paper, the reference strength changing unit 57 shown in FIG. 8 changes the reference strength according to the paper type. Referring to the example shown in FIG. 14, when the paper type is coated paper or plain paper, the reference intensity of transmitted light is set to medium or small, and it is determined whether the received light intensity is medium or small. Thus, the presence or absence of double feeding is detected. In this way, by changing to the reference strength suitable for the paper type, it is possible to detect the presence or absence of double feeding in many types of paper.

  The reference strength changing unit 57 may change the reference strength based on the paper type information input by the user. When the paper type determination device 40 is also provided, the reference strength changing unit 57 may change the reference strength based on the paper type information determined by the paper type determination device 40. Here, when the paper type discriminating device 40 and the double feed detecting device 50 are controlled at the timing shown in FIG. 11, after the light receiving signal is generated in the double feed detecting device 50 (see FIG. 11E), the paper type discriminating device. A light reception signal is generated at 40 (see FIG. 4F). In this case, the double feed detection device 50 once stores the light reception signal, and after the paper type discrimination device 40 discriminates the paper type information, the reference strength is changed based on the discriminated paper type information and stored. The double feed can be detected using the received light signal.

Further, the multifeed detection device 50 of the present embodiment does not include a light emitting unit and a light receiving unit separately for each use of the transmission type sensor and the reflection type sensor, but transmits one light emitting unit and one light receiving unit. Since it is equipped as a sensor that can be used as both a type sensor and a reflection type sensor, it is less affected by unevenness on the same paper surface and variations in light transmission between types, and improves double feed detection accuracy for each type of paper. It is possible.
Specifically, as shown in FIG. 15A, reflected light and transmitted light with respect to light emitted from one light emitting unit can be received simultaneously by two light receiving units, so the ratio of the reflected light amount to the transmitted light amount is highly accurate. Can be detected. In addition, as shown in FIG. 15B, since the reflected light of the light emitted from one light emitting unit and the transmitted light of the light emitted from the other light emitting unit are received by one light receiving unit, the surface state is It is excellent in detecting the presence or absence of double feeding in similar paper types. Furthermore, as shown in FIG. 15C, the transmitted light of the light emitted from the two light emitting units is received by the two light receiving units, so that the transparency of the paper is averaged and detected accurately. Excellent. Further, as shown in FIG. 15D, the reflected light of the light emitted from the two light emitting units is received by the two light receiving units, so that the reflectivity of the paper is averaged and accurately detected. Is also excellent.

The operation of the paper thickness discrimination device 60 will be described.
As shown in FIG. 9, when the paper P is conveyed and the light from the light emitting unit 61 is irradiated on the thickness portion of the leading end of the paper P, the reflected light of the irradiated light passes through the Fresnel lens 63 and expands. The light is projected and received by one or more of the plurality of light receiving portions 62a to 62d. Then, the received light intensity information of the reflected light from the light receiving units 62a to 62d is sent to the comparing unit 65 shown in FIG. 10, and the comparing unit 65 receives the received light intensity information obtained from the light receiving units 62a to 62d and the preset reference intensity. The sheet thickness determination unit 67 determines the sheet thickness based on the comparison result.

FIG. 16 is a diagram schematically showing the image (x) of the rear focal plane of the Fresnel lens and the reflected light intensity distribution (y) when the reflected light from the thickness portion of the paper is received through the Fresnel lens 63. .
As shown in FIG. 16A, when the paper is thin, the reflected light is received by only one light receiving portion 62a. On the other hand, FIG. 16B shows a case where reflected light is received from a sheet having an intermediate thickness that is thicker than that in the case of (A). As shown in FIG. 16B, when the reflected light from the intermediate thickness paper is received, the reflected light is received by the two light receiving portions 62a and 62b adjacent to each other. Although not shown, reflected light from a thick paper sheet is received by three light receiving units adjacent to each other. As described above, the number of light receiving portions that receive reflected light from the thick portion varies depending on the thickness of the paper. Further, the received light intensity obtained from the reflected light intensity distribution shown in (y) of FIG. 16 varies depending on the paper type. For example, when the level of received light intensity is divided into three patterns of large, medium and small, the relative received light intensity of Mylar paper, coated paper and plain paper is small for Mylar paper and medium for coated paper and plain paper.

  In the present embodiment, as shown in the table of FIG. 17, the reference intensity is set to one of large, medium, and small for each paper type because of the characteristics of the reflected light as described above. Then, the set reference intensity is compared with the received light intensity (received light amount), and the thickness of the sheet is determined according to the number of light receiving portions whose received light intensity is greater than the reference intensity. For example, in the case of Mylar paper, the reference intensity is set to a small value, and the reference intensity and the received light intensity are compared. If there are three light receiving parts having a received light intensity greater than the reference intensity, the thickness is determined to be thick. If it is two, it is determined that the thickness is intermediate, and if it is one, it is determined that the thickness is thin.

  In addition, as shown in FIG. 17, when the paper type is coated paper or plain paper, the reference intensity is set to medium, and the number of light receiving portions whose received light intensity is larger than the reference intensity as in the case of the Mylar paper. The thickness of the paper is determined according to the above. The reference strength change according to the paper type is performed by a reference strength changing unit 66 shown in FIG. In this way, by changing the reference strength to be suitable for the paper type, it is possible to determine the thickness of many types of paper.

  The reference strength changing unit 66 may change the reference strength based on the paper type information input by the user. When the paper type determining device 40 is provided, the paper determined by the paper type determining device 40 is used. The reference strength may be changed based on the seed information. Furthermore, when the double feed detection device 50 is also provided, the reference strength may be changed based on the paper type information determined by the double feed detection device 50 (see FIG. 14).

  By the way, as a device for discriminating the thickness of a paper, a transmissive sensor is generally used, and the paper thickness is discriminated by detecting the amount of transmitted light passing through the paper. However, when the transmission type sensor is used, the amount of transmitted light when a plurality of thin papers are conveyed in a stack and the amount of transmitted light when a single sheet of thick paper is conveyed are detected with the same or approximate values. The two cannot be distinguished from each other, and there is a possibility that the cardboard is erroneously detected as being transported normally when a double feed occurs. Further, with respect to a paper type having a high light transmittance, there is a problem in that the amount of received light does not change greatly even if the thickness changes, and therefore the transmission type sensor cannot accurately detect the paper thickness.

  On the other hand, the paper thickness discrimination device 60 of the present embodiment irradiates light toward the thickness portion of the paper and discriminates the paper thickness based on the width of the light receiving area of the reflected light. In the case of a paper type that has high light transmission and does not easily change in accordance with the thickness, it is possible to accurately determine the paper thickness. In the present embodiment, since the reflected light is enlarged and projected by the Fresnel lens 63, the light receiving units 62a to 62d having a limited size can receive light with high accuracy. In addition, space saving can be achieved by using the Fresnel lens 63 that is thinner than other magnifying projection lenses (plano-convex lenses). For this reason, as shown in FIG. 2, it is possible to secure the installation space for the full-lens 63 even in a narrow space between the paper feed roller 16 and the transport roller 27. However, in the present invention, it is also possible to use an enlarged projection member other than the Fullel lens 63.

Further, the table shown in FIG. 18 is obtained by extracting a part of the tables shown in FIG. 14 and FIG.
In FIG. 18, the paper type is the same plain paper, but the amount of light received is compared when the thick paper is transported by one sheet (without double feed) and when the thin paper is double fed (with double feed). It shows. As can be seen from this table, the amount of transmitted light in the first light receiving unit and the second light receiving unit is the same in the case of heavy paper and no multi-feeding and in the case of thin paper and multi-feeding. In this way, the presence / absence of double feeding cannot be detected because the amount of transmitted light alone cannot be distinguished from each other. However, comparing the received light amount of the paper thickness discriminating device, when there is no double feed with thick paper, there are three light receiving parts with a light reception intensity greater than the medium level reference intensity, and with double paper with thin paper Since there is one light receiving portion having a light receiving intensity greater than the medium level reference intensity, it is possible to distinguish between them. That is, in this embodiment, by using the received light amount information of the paper thickness determination device 60 in addition to the double feed detection device 50, it is possible to detect the presence or absence of double feed with higher accuracy.

  The paper type information determined by the paper type determination device 40 and the paper thickness information determined by the paper thickness determination device 60 are sent to the control unit 101, and the control unit 101 sets the control conditions of various devices. Set the conditions suitable for the paper thickness. For example, fixing accuracy, writing accuracy, etc. are improved by changing the fixing temperature of the fixing device, the conveyance speed of the paper passing through the fixing unit, or the image writing conditions based on the paper type information and paper thickness information. It is possible to make it. When the double feed is detected by the double feed detection device 50, the information is sent to the control unit 101, and the control unit 101 stops the paper feeding operation or displays an error.

FIG. 19 is a side cross-sectional view showing the configuration of another embodiment of the paper thickness discrimination device 60.
As shown in FIG. 19, in this embodiment, the Fresnel lens 63 and the plurality of light receiving portions 62a to 62d are housed in a cylindrical housing member 68, and are configured as one light receiving unit. Specifically, the fullnel lens 63 is sandwiched and fixed by a stepped portion 68 a formed on the inner surface of the housing member 68 and a cylindrical pressing member 69. The light receiving portions 62a to 62d are accommodated in the hole portions 70a to 70d of the holding member 70 having four hole portions 70a to 70d accommodated in the accommodation member 68. Further, the base end portions of the light receiving portions 62 a to 62 d are fixed to a plate-like fixing member 71 accommodated in the accommodating member 68.

  The accommodating member 68 has a cylindrical outer distal end member 72 having a wedge-shaped cross section on the distal end side (light incident side), and is accommodated in the outer distal end member 72 and has a wedge-shaped cross section. And a cylindrical inner end member 73. The inner tip member 73 is in contact with the presser member 69, whereby the presser member 69 is fixed in the housing member 68. Further, a surface 72 a of the outer front end member 72 that faces the sheet conveyance path R (sheet conveyance path) is disposed so as to be parallel to the sheet conveyance path R. As a result, when the sheet is conveyed, the sheet 72 can be smoothly conveyed by the surface 72a parallel to the sheet conveyance path R. In other words, in the present embodiment, the guide surface 72a for guiding the sheet being conveyed is provided on the surface of the accommodation member 68 that faces the sheet conveyance path R.

  In addition, as shown in FIG. 20, a dustproof member 74 may be provided on the distal end side of the housing member 68. In this case, the dust-proof member 74 prevents dust and dirt from entering the housing member 68, so that it is possible to maintain good light receiving accuracy.

  Further, as shown in FIG. 21, a diaphragm 75 may be provided in the housing member 68. In this case, since the diaphragm 75 can prevent unnecessary light from entering each of the light receiving portions 62a to 62d, the light receiving accuracy at each of the light receiving portions 62a to 62d can be improved.

  As described above, the paper type discrimination device 40 according to the present invention is configured to discriminate the paper type based on the directivity of the reflected light from the paper. It is less susceptible to changes in the thickness of the paper and the reflection intensity on the surface, compared to those that determine the seed. As a result, according to the present invention, the paper type discrimination accuracy can be improved, and the paper type can be accurately discriminated. In the above-described embodiment, the paper type discriminating apparatus 40 irradiates light on the paper being conveyed. However, the paper type is discriminated by irradiating light on the paper that is stopped or stacked. It is also possible to do so.

  Further, the present invention is not limited to the above-described embodiment, and it is needless to say that various modifications can be made without departing from the gist of the present invention. For example, the configuration of the present invention is applied to a sheet feeding device for feeding a document mounted on an image forming apparatus such as a printer, a copying machine, a facsimile, or a multifunction machine thereof, or a sheet feeding device for feeding other types of sheets. It is also possible to apply.

23 Paper Feeder (Sheet Feeder)
40 Paper type discriminating device (sheet type discriminating device)
41 Light Emitting Units 42a to 42f Light Receiving Unit 46 Sheet Information Storage Unit 47 Sheet Type Discriminating Unit 50 Double Feed Detection Device 51 First Light Emitting Unit 52 First Light Receiving Unit 53 Second Light Emitting Unit 54 Second Light Receiving Unit 56 Comparison Unit 57 Reference Strength Change Section 58 Double feed discrimination section 60 Paper thickness discrimination device (sheet thickness discrimination device)
61 Light Emitting Unit 62a to 62d Light Receiving Unit 63 Fresnel Lens (Enlarged Projection Member)
65 Comparison Unit 66 Reference Strength Change Unit 67 Sheet Thickness Discrimination Unit 68 Housing Member 72a Guide Surface 74 Dustproof Member 75 Aperture P Paper (Sheet)

JP 2003-137457 A

Claims (13)

A light emitting unit that emits light to the sheet;
A plurality of light receiving units arranged to receive the reflected light from the sheet and to be inclined in different directions with respect to the irradiation optical axis from the light emitting unit;
A sheet information storage unit that stores sheet type information associated with directivity of reflected light from the sheet;
A sheet type comprising: a sheet type determining unit configured to determine the type of the sheet based on light reception intensity at the light receiving unit that has received the reflected light and information stored in the sheet information storage unit Discriminator. In a sheet supply apparatus including a sheet storage unit that stores a sheet, and a sheet feeding unit that feeds the sheet from the sheet storage unit,
A sheet supply apparatus comprising the sheet type determination apparatus according to claim 1. A sheet thickness determining device for determining the thickness of the sheet;
The sheet thickness determining device, a light emitting unit that irradiates light toward the thickness portion of the sheet from an oblique direction with respect to the sheet;
A plurality of light-receiving portions that are arranged side by side in a direction in which the reflected light width increases or decreases according to the thickness of the sheet, while receiving the reflected light from the thickness portion of the sheet;
A comparison unit that compares the received light intensity at the light receiving unit that receives reflected light from the thickness portion of the sheet with a reference intensity;
The sheet thickness determination unit according to claim 2, further comprising: a sheet thickness determination unit configured to determine the thickness of the sheet according to the number of the light reception units having the light reception intensity larger than the reference intensity, obtained from the comparison result in the comparison unit. Sheet feeding device.   The sheet feeding apparatus according to claim 3, further comprising a reference strength changing unit that changes the reference strength for determining the thickness of the sheet according to the type of the sheet.   The sheet supply apparatus according to claim 3, further comprising an expansion projection member that expands reflected light from a thickness portion of the sheet and projects the light on the light receiving unit.   The sheet supply apparatus according to claim 5, wherein the enlarged projection member is a Fresnel lens.   The plurality of light receiving portions and the enlarged projection member of the sheet thickness determining device are accommodated in an accommodating member, and a guide surface for guiding the sheet being conveyed is provided on a surface facing the sheet conveying path of the accommodating member. The sheet supply apparatus according to claim 5 or 6.   The sheet supply apparatus according to claim 7, further comprising a dustproof member that prevents dust and dust from entering the housing member.   The sheet feeding apparatus according to any one of claims 3 to 8, further comprising a diaphragm that prevents unnecessary light from entering the light receiving unit that receives reflected light from a thickness portion of the sheet. A double feed detection device for detecting the presence or absence of double feed of the sheet,
The multifeed detection device includes a first light emitting unit and a first light receiving unit disposed on one surface side of the sheet, and a second light emitting unit and a second light receiving unit disposed on the other surface side of the sheet. Part
The first light receiving unit receives reflected light of the light applied to the sheet from the first light emitting unit and transmitted light of the light applied to the sheet from the second light emitting unit, and the second light receiving unit includes: It is configured to receive reflected light of light irradiated on the sheet from the second light emitting unit and transmitted light of light irradiated on the sheet from the first light emitting unit,
Further, the multifeed detection device includes a comparison unit that compares the received light intensity of the first light receiving unit and the second light receiving unit that have received the transmitted light and the reflected light with a reference intensity, and the comparison unit. The sheet feeding apparatus according to any one of claims 2 to 9, further comprising a double feed discriminating unit that discriminates the presence or absence of double feed based on the comparison result.   The sheet feeding apparatus according to claim 10, further comprising a reference strength changing unit that changes the reference strength for determining presence / absence of double feeding according to a type of the sheet.   The first light emitting unit and the second light receiving unit are disposed so as to face each other, and the centers of the first light emitting unit and the second light receiving unit are arranged coaxially, and the second light emitting unit and the first light receiving unit are opposed to each other. The sheet feeding device according to claim 10 or 11, wherein the sheet feeding devices are arranged in such a manner that their centers are arranged coaxially.   An image forming apparatus comprising the sheet type determination device according to claim 1 or the sheet supply device according to any one of claims 2 to 12.

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