JP2011047673A - Paper detection sensor and method of detecting paper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper detection sensor that has a simple structure and can detect paper by a simple method, and to provide a method of detecting paper. <P>SOLUTION: The paper detection sensor includes photoresistors 11a, 11b disposed in a paper detection area and a means of detecting the presence or absence of paper, based on a change in the value of resistance in the photoresistors 11a, 11b. In the paper detection sensor, the width of the paper detection area is not less than the width occupied by the paper, when the paper enters the paper detection area, the first photoresistor 11a is disposed over one end, in a direction substantially vertical with respect to the entry direction of the paper from one predetermined reference position within the paper detection area, and the second photoresistor 11b is disposed independently of the first photoresistor 11a over the other end section, in a direction substantially vertical with respect to the entrance direction of the paper from the reference position. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a paper detection sensor and a paper detection method, and more particularly to a paper detection sensor and a paper detection method that have a simple structure and can detect paper by a simple method.

  An image forming apparatus or an image reading apparatus such as a printer or a scanner conveys paper to an image forming or reading area, and forms an image on the paper in the area or reads an image from characters, drawings, and images on the paper. When transporting paper to the area, the paper detection sensor generally causes the image forming apparatus or image reading apparatus to recognize the size and position of the paper, and then forms an image on the paper or reads an image from the paper. Is. FIG. 10 shows an example of a conventional paper detection sensor.

  The paper detection sensor 101 includes a light source 102, a light projection lens 103, a grating 104, a light receiving lens 109, and light detection elements 110a, 110b, and 110c. The light source 102 emits light 105, and the light 105 is divided into three lights 105 a, 105 b, and 105 c by the grating 104 via the light projection lens 103, and to the detection points 107 a, 107 b, and 107 c for the paper 106. Irradiated. Next, the reflected light 108 a, 108 b, 108 c from the detection points 107 a, 107 b, 107 c is irradiated to the light detection elements 110 a, 110 b, 110 c through the light receiving lens 109.

  At this time, the presence / absence, size, and position of paper can be detected by detecting the presence / absence and number of reflected light emitted from the detection point.

Japanese Patent Laid-Open No. 5-58511

  By the way, when the paper detection sensor tries to detect the size of the paper, it is necessary to predict the size of the paper to be detected in advance and to arrange the detection points. Therefore, only paper of a size that conforms to the industry standard can be detected, and detection points are complicatedly arranged in parallel with the size of the paper to detect the tilt when the paper is fed. Need arises. For this reason, the paper detection sensor has a very complicated structure.

  Therefore, in view of the above, an object of the present invention is to provide a paper detection sensor and a paper detection method having a simple structure and capable of detecting paper by a simple method.

  In order to solve the above problems, the paper detection sensor according to the present invention includes a photo register disposed in the paper detection area, and includes means for detecting the presence or absence of paper based on a change in the resistance value of the photo register. In the paper detection sensor, the width of the paper detection area is equal to or larger than a width occupied when the paper enters the paper detection area, and the paper is detected from one predetermined reference position in the paper detection area. The first photoresistor is disposed over one end in a direction substantially perpendicular to the entry direction of the paper, and extends from the reference position to the other end in a direction substantially perpendicular to the entry direction of the paper. The second photoresistor is arranged independently of the first photoresistor.

  In the paper detection sensor of the present invention, it is preferable that a plurality of the paper detection areas are arranged along the paper entering direction.

  In the paper detection sensor of the present invention, the resistance value per unit length in the width direction that is substantially perpendicular to the paper entering direction of the photoresist is determined by the light irradiated to the photoresist. It is preferably uniform in a state where it is shielded by paper.

  In the paper detection sensor of the present invention, it is preferable that a fixed resistor is connected in parallel to the photoresistor.

  According to the present invention, the presence / absence, size, entry position or inclination of the paper is detected based on a change in resistance value of the first and second photoresistors arranged in the paper detection sensor. A featured paper detection method is provided.

  As described above, since the paper detection sensor according to the present invention is configured by arranging the first and second photoresistors at predetermined positions, the structure is simple. Further, since the paper is detected based on the change in the resistance value of the photoresistor, the paper can be detected by a simple method.

1 is a perspective view of an external appearance of a paper tray on which a paper detection sensor according to a first embodiment of the present invention is installed, a light source for irradiating the paper detection sensor with light, and an image forming apparatus in which the paper tray and the light source are connected. It is. BRIEF DESCRIPTION OF THE DRAWINGS It is for showing typically the structure of the light detection element part of the paper detection sensor which concerns on the 1st Embodiment of this invention, The figure (A) is a top view, The figure (B) is sectional drawing. It is a schematic diagram for demonstrating the case where a rectangular paper approached perpendicularly to the paper detection area of the paper detection sensor which concerns on the 1st Embodiment of this invention. It is a top view for demonstrating the case where rectangular paper approached diagonally into the paper detection area of the paper detection sensor which concerns on the 1st Embodiment of this invention. 6 is a schematic graph showing a change in resistance value of a photoresist when rectangular paper passes obliquely over the paper detection area of the paper detection sensor according to the first embodiment of the present invention. It is a top view for demonstrating the case where a rectangular paper approached perpendicularly to the paper detection area of the paper detection sensor which concerns on the 2nd Embodiment of this invention. It is for demonstrating the structure of the paper detection sensor which concerns on the 3rd Embodiment of this invention, The same figure (A) is a schematic diagram of the photon detection element part of a paper detection sensor, The same figure (B) is FIG. It is the circuit diagram. It is a top view which shows typically the structure of the modification of the light detection element part of the paper detection sensor by this invention. It is a top view which shows typically the structure of the other modification of the light detection element part of the paper detection sensor by this invention. It is sectional drawing which shows the conventional paper detection sensor typically.

  Embodiments of a paper detection sensor according to the present invention will be described below with reference to FIGS. In addition, the same code | symbol is attached | subjected to the same element and the overlapping description is abbreviate | omitted. Also, the positional relationship such as up / down / left / right is based on the positional relationship of the drawings.

<< First Embodiment >>
FIG. 1 is an external perspective view of an image forming apparatus provided with a paper detection sensor according to a first embodiment of the present invention. The paper detection sensor includes an optical detection element provided with a photoresistor, a detector that detects a change in the resistance value of the photoresistor, and a calculation process using a detection signal from the detector according to a predetermined arithmetic expression. A signal processing device is provided. In FIG. 1, the detector of the paper detection sensor and the signal processing device are not shown and are omitted.

  FIGS. 2A and 2B are diagrams schematically showing the configuration of the light detection element portion of the paper detection sensor according to the first embodiment of the present invention. FIG. 2A is a top view, and FIG. FIG.

  FIG. 3 is a schematic diagram for explaining a case where rectangular paper vertically enters the paper detection area of the paper detection sensor according to the first embodiment of the present invention. FIG. 3A is a top view showing a state where no paper has entered the paper detection area. FIG. 5B is a top view showing a state where the paper vertically enters the paper detection area. FIG. 3C is a graph showing changes in the resistance value of the photoresist when paper passes over the paper detection area, with the horizontal axis representing time t and the vertical axis representing resistance value R.

  FIG. 4 is a diagram for explaining a case where rectangular paper enters obliquely into the paper detection area of the paper detection sensor according to the first embodiment of the present invention.

  FIG. 5 is a graph showing changes in the resistance value of the photoresistor described in FIG. 4, with the horizontal axis representing time t and the vertical axis representing resistance value R.

  Hereinafter, an image forming apparatus provided with a paper detection sensor will be described with reference to FIG.

  On the paper tray 3 connected to the paper feed port 2 of the image forming apparatus 1, the light detection element 4 of the paper detection sensor is installed. A light source 5 for irradiating the light detecting element 4 with light is installed above the light detecting element 4. The rectangular paper 10 passes through the light detection element 4 and then is inserted into the image forming apparatus 1 through the paper feed port 2 to form an image.

  Next, the configuration of the photodetecting element 4 will be described with reference to FIG.

  On the surface of a substrate 18 made of PET (polyethylene terephthalate), a rectangular metal electrode 12a made of Al is provided in one direction perpendicular to the paper 10 entry direction from a reference position S1 which is the center of the paper detection area A1. (Right side in FIG. 2).

  Similarly, a rectangular metal electrode 12b made of Al is disposed on the surface of the substrate 18 from the reference position S1 to the other (left side in FIG. 2) independently of the metal electrode 12a. Yes.

An insulating layer 17a made of SiO ₂ is disposed on the surface of the metal electrode 12a so as not to partially cover the end surface on the reference position S1 side of the metal electrode 12a. The insulating layer 17a is disposed over one side (right side in FIG. 2) perpendicular to the paper 10 entry direction from the reference position S1.

Similarly, an insulating layer 17b made of SiO ₂ is formed on the surface of the metal electrode 12b from the reference position S1 so as not to partially cover the end surface on the reference position S1 side of the metal electrode 12b. It is arranged over the left side in FIG.

  On the surface of the insulating layer 17a, a rectangular first photo-resistor 11a made of ZnO extends from the reference position S1 to one side (right side in FIG. 2) perpendicular to the paper 10 entrance direction. Has been placed. The first photoresistor 11a is disposed so as not to be directly connected to the metal electrode 12a.

  Similarly, on the surface of the insulating layer 17b, a rectangular second photoresist 11b made of ZnO extends directly from the reference position S1 to the other (left side in FIG. 2) with the metal electrode 12b. Are arranged so as not to connect.

  The first photoresistor 11a and the second photoresistor 11b are arranged independently of each other. The distance L3 between the end portion of the first photo-resistor 11a on the reference position S1 side and the end portion of the second photo-resistor 11b on the reference position S1 side is preferably narrower. Further, it is preferable that the width of the photoregisters 11a and 11b in the entering direction of the paper 10 is narrower.

  A connection electrode 13a made of Ag is disposed on the end surface of the metal electrode 12a on the reference position S1 side that is not covered with the insulating layer 17a. The connection electrode 13a is arranged so that the metal electrode 12a and the end of the first photoresistor 11a on the reference position S1 side are electrically connected.

  Similarly, a connection electrode 13b made of Ag is disposed on the end surface of the metal electrode 12b on the reference position S1 side that is not covered with the insulating layer 17b. The connection electrode 13b is disposed so that the end portion on the reference position S1 side of the metal electrode 12b and the second photoresistor 11b is conductively connected.

  An external terminal 15a is connected to the end of the first photoresistor 11a opposite to the reference position S1 via an extraction electrode 14a made of Ag. An external terminal 16a is connected to the end of the metal electrode 12a opposite to the reference position S1 side. The external terminals 15a and 16a are connected to a detector (not shown), and the resistance value of the first photoresistor 11a is detected by the detector.

  Similarly, an external terminal 15b is connected to an end of the second photoresistor 11b opposite to the reference position S1 via an extraction electrode 14b made of Ag. An external terminal 16b is connected to the end of the metal electrode 12b opposite to the reference position S1 side. The external terminals 15b and 16b are connected to a detector (not shown), and the resistance value of the second photoresistor 11b is detected by the detector.

  Next, the case where the rectangular paper 10 vertically enters the paper detection area A1 of the paper detection sensor in the present embodiment will be described in detail with reference to FIG.

  As shown in FIG. 3A, in the paper detection area A1, the first photoresistor 11a having a width L1 in the direction perpendicular to the entry direction G of the paper 10 and the second register having a width L2. The photo-resistor 11b is arranged. The lengths of L1 and L2 are set equal (L1 = L2). The resistance value per unit length in the direction perpendicular to the entrance direction G of the paper 10 of the photo-registers 11a and 11b is a state in which light applied to the photo-registers 11a and 11b is shielded by the paper 10 Is uniform.

  In the photoresistors 11a and 11b, electrons in the valence band are excited by light irradiation and move to the conduction band, whereby carriers are generated and the resistance value is greatly reduced. That is, it corresponds to a variable resistor whose resistance value decreases as the amount of received light increases. The width (L1 + L2 + L3) of the paper detection area A1 is set to be equal to or greater than the width occupied when the paper 10 enters.

  When the paper detection area A1 is irradiated with visible light from the light source 5 in a state where the paper 10 has not entered, the resistance values of the photoresistors 11a and 11b installed in the paper detection area A1 are large. descend. Since the widths L1 and L2 of the photoregisters 11a and 11b are set equal, the resistance values of the photoregisters 11a and 11b are both R0 as shown in FIG.

  FIG. 3B is a top view showing a state in which the paper 10 enters the paper detection area A1 vertically. In this state, when visible light from the light source 5 is irradiated to the paper detection area A1, in the regions B4 and B6 irradiated with light from the photo-registers 11a and 11b installed in the paper detection area A1, The resistance value is greatly reduced. On the other hand, in the regions D5 and D7 of the photoresistors 11a and 11b that are covered with the paper 10 and are not irradiated with light, there is less movement of electrons in the valence band, so the resistance value is sufficiently larger than that of the regions B4 and B6. Become.

  For this reason, the resistance values of the photoresistors 11a and 11b are determined depending on the widths L5 and L7 of the regions D5 and D7 covered by the paper 10 in the direction perpendicular to the entrance direction G of the paper 10. As shown in FIG. 3C, the resistance values of the photo-registers 11a and 11b are R1 and R2, respectively, and the widths L5 and L7 are obtained from these values. The width P1 of the paper 10 is expressed by Equation 1.

P1 = L3 + L5 + L7 (Formula 1)
Thus, the presence / absence of the paper 10, the width P1 and the entry position can be detected by the paper detection sensor in the present embodiment.

  In FIG. 3C, the time when the paper 10 reaches the detection area A1 is t0, and the time when the paper 10 has passed through the detection area A1 is t1. When the passing speed of the paper 10 is set to a known value v, the length P2 of the paper 10 in the entering direction G is expressed by Equation 2.

P2 = (t1-t0) · v (Expression 2)
Thus, the length P2 of the paper 10 can be detected by the paper detection sensor in the present embodiment.

  Next, the case where the rectangular paper 10 enters obliquely into the paper detection area A1 of the paper detection sensor in the present embodiment will be described in detail with reference to FIGS.

  FIG. 4 is a top view showing a state in which the paper 10 has entered the paper detection area A1 with an inclination θ. In FIG. 4A, the upper right vertex 10a of the paper 10 is the first photoresistor. It is the top view which showed the state which reached | attained 11a. L8 in the figure is the distance between the vertex 10a and the end of the first photoresistor 11a on the reference position S1 side.

  FIG. 4B shows a state after the state of FIG. 1A, and a top view showing a state in which the paper 10 has reached the end on the reference position S1 side of the first photoresistor 11a. It is. L9 in the drawing is an area where the first photoresist 11a is covered with the paper 10 when the paper 10 reaches the end of the first photoresist 11a on the reference position S1 side. The width in the direction perpendicular to the entry direction G of the paper 10.

  FIG. 5C shows a state after the state shown in FIG. 5B, and is a top view showing a state in which the upper left vertex 10b of the paper 10 reaches the second photo register 11b.

  FIG. 4D shows a state after the state shown in FIG. 3C, and is a top view showing a state where the lower right vertex 10c of the paper 10 has reached the first photoresistor 11a.

  FIG. 5 shows changes in resistance values of the photo-registers 11a and 11b when the paper 10 passes through the paper detection area A1 with an inclination θ as shown in FIG. Is a resistance value R. In FIG. 5, the time at which the upper right vertex 10a of the paper 10 reaches the first photoresistor 11a is t0, and the paper 10 has reached the end of the first photoresistor 11a on the reference position S1 side. Time is t1. The time when the paper 10 reaches the end of the second photoresistor 11b on the reference position S1 side is t2, and the time when the upper left vertex 10b of the paper 10 reaches the second photoresistor 11b is t3. Further, the time when the lower right vertex 10c of the paper 10 reaches the first photoresistor 11a is t4.

  In the figure, R0 is the resistance value of the photo-registers 11a and 11b when the paper 10 does not enter the paper detection area A1, and R1 is the resistance value of the first photo-register 11a at the time t1. It is.

  When the passing speed of the paper 10 is set to a known value v, the inclination θ of the paper 10 is expressed by Equation 3.

θ = 90 ° −1 / 2 · sin ⁻¹ (2v · (t1−t0) / L9) (Expression 3)
Since the width L9 is the width of the area where the first photoresistor 11a is covered with the paper 10, it can be calculated based on the resistance value of the first photoresistor 11a. Thus, the presence / absence of the paper 10 and the inclination θ can be detected by the paper detection sensor in the present embodiment.

  The distance L8 is expressed by Equation 4.

L8 = v · (t1−t0) · tan θ (Expression 4)
Thus, the paper detection sensor in the present embodiment can detect the entry position of the paper 10.

  Further, the width P1 of the paper 10 is expressed by Equation 5.

P1 = v · (t3−t0) / cos θ (Formula 5)
Thus, the paper detection sensor in this embodiment can detect the width P1 of the paper 10.

  Further, the length P2 of the paper 10 is expressed by Equation 6.

P2 = v · (t4−t0) / sin θ (Expression 6)
Thus, the length P2 of the paper 10 can be detected by the paper detection sensor in the present embodiment.

  As described above, in the paper detection sensor according to the present embodiment, the paper 10 enters the paper detection area A1 obliquely with a simple structure in which the first and second photoresistors are arranged at predetermined positions. Even so, the presence / absence, entry position, width and length of the paper 10 can be detected, and the inclination can also be detected. Further, since the paper is detected based on the change in the resistance value of the photoresistor, the paper can be detected by a simple method.

  Note that, when the paper 10 enters the paper detection area A1 vertically, the rise time of the resistance values of the photoresistors 11a and 11b (time t0 in FIG. 3C) is the same. When the paper 10 enters the paper detection area A1 obliquely, the resistance value rise start times (time t0, t2 in FIG. 5) of the photo-registers 11a and 11b are different. Thereby, it can be detected whether the paper 10 has entered the paper detection area A1 vertically or obliquely.

<< Second Embodiment >>
FIG. 6 is a top view for explaining a case where rectangular paper vertically enters the paper detection area of the paper detection sensor according to the second embodiment of the present invention. FIG. 4A is a top view showing a state where no paper has entered the paper detection area, and FIG. 4B is a top view showing a state where the paper has vertically entered the paper detection area.

  In the paper detection areas A2, A3, and A4, a photoresistor is arranged in the same configuration as in the first embodiment, and constitutes a first, a second, and a third photodetecting element, respectively.

  In the paper detection area A2, a reference position S2 is set at the rightmost position among three positions that divide the paper detection area A2 into four equal parts in a direction perpendicular to the entry direction G of the rectangular paper 10. Yes. In the paper detection area A2, a rectangular first photoresist 11c made of ZnO extends from the reference position S2 in one direction perpendicular to the paper 10 entry direction G (to the right in FIG. 6). Has been placed.

  Similarly, in the paper detection area A2, a rectangular second photoresist 11d made of ZnO is arranged from the reference position S2 to the other (left side in FIG. 6).

  In the paper detection area A3, a reference position S3 is set at a central position among three positions that divide the paper detection area A3 into four equal parts in a direction perpendicular to the entrance direction G of the rectangular paper 10. Yes. In the paper detection area A3, a rectangular first photo-resistor 11e made of ZnO extends from the reference position S3 in one direction perpendicular to the paper 10 entry direction G (to the right in FIG. 6). Has been placed.

  Similarly, in the paper detection area A3, a rectangular second photoresist 11f made of ZnO is disposed from the reference position S3 to the other (left side in FIG. 6).

  Further, in the paper detection area A4, a reference position S4 is set at the leftmost position among three positions that divide the paper detection area A4 into four equal parts in a direction perpendicular to the entrance direction G of the rectangular paper 10. Yes. In the paper detection area A4, a rectangular first photo-resistor 11g made of ZnO extends from the reference position S4 to one side (right side in FIG. 6) perpendicular to the paper 10 entry direction G. Has been placed.

  Similarly, in the paper detection area A4, a second rectangular photoresist 11h made of ZnO is arranged from the reference position S4 to the other (left side in FIG. 6).

  The paper detection areas A2, A3, and A4 are arranged so as not to overlap along the entry direction G of the paper 10.

  FIG. 6B is a top view showing a state in which the paper 10 has entered the paper detection areas A2, A3, A4. The paper 10 is greatly displaced from the right end in the drawing, and is disposed so as not to pass over the second photoresistor 11f in the paper detection area A3 and the second photoresistor 11h in the paper detection area A4. It has become. In such a case, the position of the paper 10 cannot be detected in the paper detection areas A3 and A4. However, the reference position S2 in the paper detection area A2 is set to be at the right end of the drawing with respect to the reference positions S3 and S4. For this reason, in the paper detection area A2, the position of the paper 10 can be detected based on the principle shown in the first embodiment.

  As described above, according to the present embodiment, the same operational effects as those of the first embodiment can be obtained. Furthermore, by disposing a plurality of paper detection areas whose reference positions are shifted, it is possible to detect a paper whose entry position is greatly shifted, and it is also possible to detect a paper whose width is extremely small. For example, when the minimum size of the paper is determined, the interval in the direction perpendicular to the paper entrance direction between the reference positions of the plurality of paper detection areas is made smaller than the size of the paper. Is set. Thereby, even if the paper enters from any position in the paper detection area, it can be reliably detected.

<< Third Embodiment >>
FIG. 7 is a diagram for explaining a configuration of a paper detection sensor according to the third embodiment of the present invention. FIG. 7A is a schematic diagram of a light detection element portion of the paper detection sensor, and FIG. Is a circuit diagram thereof.

  In the paper detection area A5, the first photo register 11i and the second photo register 11j are arranged in the same configuration as in the first embodiment, and constitute a photodetecting element. A fixed resistor 19i is electrically connected to the first photoresistor 11i, and a fixed resistor 19j is electrically connected to the second photoresistor 11j in parallel. The combined resistance value of the first photoresistor 11i and the fixed resistor 19i is detected by a detector (not shown) connected to the external terminals 15i and 16i. Similarly, the combined resistance value of the second photoresistor 11j and the fixed resistor 19j is detected by a detector (not shown) connected to the external terminals 15j and 16j.

Here, the first photoresist 11i the resistance value R _11i of the and the resistance value of the fixed resistor 19i and R _19i, the composite resistance value of the first photoresist 11i and the fixed resistor 19i R _i Is represented by Equation 7.

R _i = R _19i / (1 + R _19i / R _11i ) (Formula 7)
Also, the second photoresist 11j of the resistance value R _11j, wherein when the resistance value of the fixed resistor 19j and R _19j, the combined resistance value R _j of the first photoresist 11j and the fixed resistor 19j is , Represented by Equation 8.

R _j = R _19j / (1 + R _19j / R _11j ) (Formula 8)
At this time, when the resistance value R _{11i of} the first photoresistor _{11 i} becomes larger than the resistance value R _19i of the fixed resistor 19 _i , the combined resistance value R _i becomes the resistance value R _{19i of the} fixed resistor 19 _i. To converge. Further, when the resistance value R _{11j of} the second photoresistor 11j becomes larger than the resistance value R _19j of the fixed resistor 19j, the combined resistance value R _j becomes the resistance value R _19j of the fixed resistor _19j . It will converge.

  As described above, the resistance values of the photoresistors 11i and 11j change according to the amount of received light. When the paper detection sensor is composed of only the photo-registers 11i and 11j, the amount of light received through the areas of the photo-registers 11i and 11j that is reduced by light transmitted through the paper due to deterioration of the light source is reduced. As the resistance decreases, the resistance values of the photo-resistors 11i and 11j gradually increase, which may adversely affect the paper detection accuracy.

  On the other hand, if the fixed resistors 19i and 19j are connected in parallel to the photoresistor 11i and 11j as described above, the amount of light received in the area shielded by the paper is reduced, and the photoresistor 11i, Even if the resistance value of 11j rises, the combined resistance value detected by the detector can be converged to the resistance values of the fixed resistors 19i and 19j.

  As described above, according to the present embodiment, substantially the same operational effects as those of the first embodiment can be achieved. Furthermore, even when the light source is deteriorated, the paper detection accuracy can be kept good. Also, the same effect can be obtained when the thickness of the paper is different and the amount of light received in the shielding area varies.

  The fixed resistors 19i and 19j may be formed as film elements, and may be electrically connected in parallel to the photoresistors 11i and 11j, or may be connected to the photoresistors 11i and 11j using a chip resistor or the like. They may be electrically connected in parallel.

  The invention of the present application is not limited to the above-described embodiment, and relates to the type of material constituting the paper detection sensor, the specific configuration of the paper detection sensor, the method of paper detection, and the like within the scope of the invention. Various applications and modifications can be added.

  For example, in the above embodiment, PET is used as the substrate 18. However, the present invention is not limited to this, and a flexible plastic substrate such as PEN (polyethylene naphthalate) or PC (polycarbonate) or a glass substrate is used. May be used. Further, the paper tray 3 may be used as the substrate 18.

  Al is used as the metal electrodes 12a and 12b, but Cu, Pt, Au, Ag, or the like may be used.

As the insulating layers 17a and 17b, SiO ₂ is used. However, SiN, polyimide, polyamide, polyester, polyacrylate, or the like may be used.

  ZnO was used as the photo-resistor, but in addition, electrons in the valence band such as Si, Ge, GaAs, CdTe, CdS, NiO and organic semiconductors are excited by light irradiation and move to the conduction band. The same effect can be obtained if it is a substance having properties. In particular, when ZnO is used, it becomes easy to design the reaction wavelength on the short wavelength side, and the influence of diffraction can be reduced. Moreover, the light transmittance with respect to the shielding object can be lowered, and the difference in illuminance between the area shielded by the paper and the area not shielded is increased, and the detection accuracy is increased.

  Although Ag is used as the connection electrodes 13a and 13b and the extraction electrodes 14a and 14b, Cu, solder, or the like may be used.

  Moreover, in the said embodiment, although the said photoresistor 11a is connected to the said external terminal 16a via the said metal electrode 12a, you may be connected to the said external terminal 16a not via the said metal electrode 12a.

  Similarly, the photoresistor 11b is connected to the external terminal 16b via the metal electrode 12b, but may be connected to the external terminal 16b without passing through the metal electrode 12b.

  In the above embodiment, the light source connected to the image forming apparatus is exemplified as the light source. However, room light or natural light may be used. In addition, when the image forming apparatus is provided with a light source for another purpose in advance, the image forming apparatus may be used for this purpose.

  Moreover, although the structure shown by FIG. 2 in 1st Embodiment was illustrated as a structure of the said light detection element 4, as shown in FIG. 8 and FIG.

  FIG. 8 is a top view schematically showing a configuration of a modification of the light detection element portion of the paper detection sensor according to the present invention. On the surface of the substrate 18, the rectangular first photoresistor 11 k is arranged over one side (right side in FIG. 8) perpendicular to the paper entrance direction from the reference position S 5 in the paper detection area A 6. Has been.

  Similarly, a rectangular second photoresistor 11m is disposed on the surface of the substrate 18 from the reference position S5 to the other (left side in FIG. 8).

  The first photoresistor 11k and the second photoresistor 11m are arranged independently of each other. The distance L10 between the end portion on the reference position S5 side of the first photoresistor 11k and the end portion on the reference position S5 side of the second photoresistor 11m is preferably narrower. Further, it is preferable that the width of the photoregisters 11k and 11m in the paper entering direction is narrower.

  In addition, a rectangular metal electrode 12k is formed on the surface of the substrate 18 from the reference position S5 in one direction perpendicular to the paper entering direction (rightward in FIG. 8). It is arranged in parallel with the photo-resistor 11k so as not to be directly connected.

  Similarly, on the surface of the substrate 18, a rectangular metal electrode 12m extends from the reference position S5 to the other side (left side in FIG. 8) in parallel with the second photoresistor 11m and directly. The metal electrode 12k is disposed independently so as not to be connected.

  The end on the reference position S5 side of the first photoresistor 11k and the end on the reference position S5 side of the metal electrode 12k are conductively connected by a connection electrode 13k.

  Similarly, the end on the reference position S5 side of the second photoresistor 11m and the end on the reference position S5 side of the metal electrode 12m are electrically connected by a connection electrode 13m.

  An external terminal 15k is connected to the end of the first photoresistor 11k opposite to the reference position S5 via an extraction electrode 14k. An external terminal 16k is connected to the end of the metal electrode 12k opposite to the reference position S5. The external terminals 15k and 16k are connected to a detector (not shown), and the resistance value of the first photoresistor 11k is detected by the detector.

  Similarly, an external terminal 15m is connected to the end of the second photoresistor 11m opposite to the reference position S5 via an extraction electrode 14m. An external terminal 16m is connected to the end of the metal electrode 12m opposite to the reference position S5. The external terminals 15m and 16m are connected to a detector (not shown), and the resistance value of the second photoresistor 11m is detected by the detector.

  As described above, according to the configuration of the present modification, an insulating layer for insulating the first photoresistor 11k and the metal electrode 12k, and the second photoresistor 11m and the metal electrode 12m is not necessary. . For this reason, the structure is simplified and an inexpensive paper detection sensor is provided.

  FIG. 9 is a top view schematically showing the configuration of another modification of the light detection element portion of the paper detection sensor according to the present invention. On the surface of the substrate 18, a rectangular photo-resistor 11 n ′ is arranged over one side (right side in FIG. 9) perpendicular to the paper entry direction from the reference position S 6 in the paper detection area A 7. Yes. A rectangular photoresist 11n ″ made of the same material as the photoresist 11n ′ is disposed on the surface of the substrate 18. The photo-register 11n ″ is connected in parallel to the photo-register 11n ′ from the reference position S6 in the direction perpendicular to the paper entrance direction (right side in FIG. 9) and directly. Arranged not to.

  The end portion on the reference position S6 side of the photoresistor 11n ′ and the end portion on the reference position S6 side of the photoresistor 11n ″ are a photoresistor 11n ′ ″ made of the same material as the photoresistor 11n ′. It is connected. The first photoresistor 11n is formed by integrally forming the photoresistors 11n ', 11n ", 11n".

  Similarly, on the surface of the substrate 18, a rectangular photo-resistor 11o 'is arranged from the reference position S6 in the paper detection area A7 to the other (left side in FIG. 9). Further, on the surface of the substrate 18, a rectangular photoresist 11o ″ made of the same material as the photoresist 11o ′ extends from the reference position S6 to the other side (left side in FIG. 9). It is arranged in parallel with 11o ′ and not directly connected.

  The end portion on the reference position S6 side of the photoresistor 11o ′ and the end portion on the reference position S6 side of the photoresistor 11o ″ are a photoresistor 11o ′ ″ made of the same material as the photoresistor 11o ′. It is connected. The second photoresistor 11o is formed by integrally forming the photoresistors 11o ', 11o ", 11o" ".

  The first photoresistor 11n and the second photoresistor 11o are arranged independently of each other. The distance L11 between the end of the first photo-resistor 11n on the reference position S6 side and the end of the second photo-register 11o on the reference position S6 side is preferably narrower. Further, it is preferable that the width of the photoregisters 11n ′, 11n ″, 11n ″, 11o ′, 11o ″, 11o ″ ″ in the paper entering direction is narrower. Further, it is preferable that an interval L12 between the photoregister 11n ′ and the photoregister 11n ″ and an interval L13 between the photoregister 11o ′ and the photoregister 11o ″ are narrower.

  An external terminal 15n is connected to the end of the photoresistor 11n 'opposite to the reference position S6 via an extraction electrode 14n. An external terminal 16n is connected to the end of the photoresistor 11n ″ opposite to the reference position S6 side via an extraction electrode 17n. The external terminals 15n and 16n are connected to a detector (not shown), and the resistance value of the first photoresistor 11n is detected by the detector.

  Similarly, an external terminal 15o is connected to the end of the photoresistor 11o 'opposite to the reference position S6 via an extraction electrode 14o. An external terminal 16o is connected to the end of the photoresistor 11o ″ opposite to the reference position S6 side via an extraction electrode 17o. The external terminals 15o and 16o are connected to a detector (not shown), and the resistance value of the second photoresistor 11o is detected by the detector.

  As described above, according to the configuration of this modification, in addition to the need for the insulating layer, the first photoresistor 11n and the external terminal 16n, and the second photoresistor 11o and the external terminal are used. A metal electrode for conducting connection of 16o is also unnecessary. For this reason, the structure is simplified and an inexpensive paper detection sensor is provided.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Paper feed port 3 Paper tray 4,110a, 110b, 110c Photodetection element 5,102 Light source 10,106 Paper 11a, 11c, 11e, 11g, 11i, 11k, 11n
First photoresistor 11b, 11d, 11f, 11h, 11j, 11m, 11o
Second photoresistor 11n ′, 11n ″, 11n ′ ″, 11o ′, 11o ″, 11o ′ ″
Photoresistors 12a, 12b, 12k, 12m Metal electrodes 13a, 13b, 13k, 13m Connection electrodes 14a, 14b, 14k, 14m, 14n, 14o, 17n, 17o
Extraction electrodes 15a, 15b, 15i, 15j, 15k, 15m, 15n, 15o, 16a, 16b, 16i, 16j, 16k, 16m, 16n, 16o
External terminal 17a, 17b Insulating layer 18 Substrate 19i, 19j Fixed resistor 101 Paper detection sensor 103 Projection lens 104 Grating 105, 105a, 105b, 105c Light 107a, 107b, 107c Detection point 108a, 108b, 108c Reflected light 109 Light receiving lens A1, A2, A3, A4, A5, A6, A7 Paper detection area S1, S2, S3, S4, S5, S6 Reference position

Claims (5)

In a paper detection sensor provided with a means for detecting the presence or absence of paper on the basis of a change in the resistance value of the photo-resistor, wherein a photo register is arranged in the paper detection area.
The width of the paper detection area is equal to or greater than the width occupied when the paper enters the paper detection area;
A first photoresistor is disposed from one predetermined reference position in the paper detection area to one end in a direction substantially perpendicular to the paper entering direction,
A second photoresistor is disposed independently of the first photoresistor from the reference position to the other end in a direction substantially perpendicular to the paper entering direction;
A paper detection sensor. A plurality of the paper detection areas are arranged along the paper entry direction;
The paper detection sensor according to claim 1. The resistance value per unit length in the width direction that is substantially perpendicular to the paper entrance direction of the photoresist,
The light irradiated to the photoresistor is uniform in a state where it is shielded by the paper;
The paper detection sensor according to claim 1 or 2. A fixed resistor connected in parallel to the photoresistor;
The paper detection sensor of any one of Claims 1 thru | or 3 characterized by these. 5. The presence / absence, size, entry position or the presence / absence of the paper based on a change in the resistance value of the first and second photoresistors arranged in the paper detection sensor according to any one of claims 1 to 4. Detecting tilt,
A paper detection method characterized by the above.