JP2006080768A - Paper detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To allow a threshold to be changed without a threshold changing operation of a serviceman or the like with respect to a paper detector wherein compares an output value of a sensor for paper detection with the threshold to detect a paper for use in image forming processing. <P>SOLUTION: A paper detector 1 wherein an output value of a sensor 16 for detecting the presence or the absence of a paper 23 is compared with a threshold stored in a storage means 10 to judge whether the paper 23 exists or not is provided with a threshold calculation means 2 for not only acquiring an output value Vp at the time of paper detection of the sensor 16 and an output value Vb at the time of paper non-detection in response to an automatic adjustment start trigger but also calculating a threshold Vs on the basis of both acquired output values Vp and Vb and a threshold change means 2 for rewriting the threshold stored in the storage means 10 with the threshold Vs calculated by the threshold calculation means 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sheet detection apparatus, and more particularly to a sheet detection apparatus that detects a sheet used in an image forming process of a recording unit included in a facsimile machine, a copying machine, or a multifunction machine thereof.

  A facsimile machine, a copying machine, and the like are provided with a paper detection device that detects a paper used for image forming processing, and for example, a reflective sensor is used for paper detection. FIG. 11 is a perspective view schematically showing the reflection type sensor and a sheet to be detected. As shown in the figure, the reflective sensor 101 includes a light emitting element 103 such as a light emitting diode that emits light toward one surface of the paper 102 conveyed in the direction of the arrow in the figure, and the paper 102 emitted from the light emitting element 103. And a light receiving element 104 such as a phototransistor that is energized by receiving light reflected from the light source. In the paper detection device, the output value of the reflective sensor 101 that changes according to the energization state of the light receiving element 103 ( It is determined whether or not the reflective sensor has detected the sheet 102 based on whether or not the output voltage exceeds a prestored threshold value.

  As described above, the paper detection device determines whether or not a paper is detected based on the output value of the sensor such as a reflective sensor and the threshold value, that is, the presence or absence of the paper. Due to variations in sensitivity, there is a problem that the detection sensitivity of the paper varies depending on the apparatus. There is also a problem that even in one apparatus, the detection sensitivity changes with the passage of time due to aging of the sensor. Therefore, in general, the variation in the sensitivity of the sensor is corrected by changing the above-described threshold used as a reference for paper detection to an appropriate value.

As described above, as an apparatus that corrects variations in the sensitivity of the sensor by changing the threshold value, for example, there is a sensor signal processing apparatus disclosed in Patent Document 1. The sensor signal processing apparatus of Patent Document 1 is used as a sensor for detecting a sheet, an A / D converter that converts an output value of the sensor into a digital signal, and a reference for determining whether or not a sheet is detected. Storage means for storing the first threshold value and the second threshold value as digital data. As described above, since the sensor signal processing apparatus of Patent Document 1 stores the threshold value used for the paper detection determination process as digital data, rewriting from the outside through a predetermined operation from the operation unit, a communication line, or the like. The threshold value can be easily changed based on the instruction.
JP 2001-267903 A

  However, the threshold value for correcting variations in the sensitivity of the sensor may be changed by any operation by a service person such as a predetermined operation from the operation unit or an operation for transmitting a rewrite instruction in the service center device as described above. And the threshold value could not be changed automatically.

  The present invention has been made in view of the problems as described above, and compares the output value of a sensor for detecting a sheet with a threshold value to detect a sheet used for image forming processing. It is an object of the present invention to provide a paper detection device that can change a threshold without a serviceman performing an operation for changing the threshold.

  In order to achieve the above object, the paper detection apparatus according to claim 1 compares the output value of a sensor for detecting the presence or absence of paper with a threshold value stored in a storage means to determine the presence or absence of the paper. In response to the automatic adjustment start trigger, the threshold calculation means for acquiring the output value at the time of paper detection of the sensor and the output value at the time of non-detection of the paper and calculating a threshold based on both acquired output values; Threshold value changing means for changing the threshold value stored in the storage means to the threshold value calculated by the threshold value calculating means.

  3. The paper detection device according to claim 2, wherein the paper detection device for determining the presence or absence of the paper by comparing the output value of the sensor for detecting the presence or absence of the paper and the threshold value stored in the storage means responds to the automatic adjustment start trigger. Then, based on a first virtual threshold stored in advance, a first acquisition unit that acquires an output value when the sensor detects a sheet or when a sheet is not detected, and when the sensor detects a sheet detected by the unit The second virtual threshold is calculated based on the output value and the voltage value of the power supply for detection, or the output value and the reference voltage value when the sheet is not detected by the sensor acquired by the first acquisition means, and based on the second virtual threshold Second acquisition means for acquiring an output value when the paper is not detected or detected by the sensor, an output value when the sensor is detected by the first acquisition means, and the second acquisition means When the sensor is not detecting paper Threshold value calculation means for calculating a threshold value based on the force value or the output value obtained when the paper is not detected by the sensor acquired by the first acquisition means and the output value obtained when the paper is detected by the sensor acquired by the second acquisition means. And a threshold value changing means for changing the threshold value stored in the storage means to the threshold value calculated by the threshold value calculating means.

  In the paper detection device that determines the presence or absence of the paper by comparing the output value of the sensor that detects the presence or absence of the paper and the threshold value stored in the storage means, in response to the automatic adjustment start trigger, the first stored in advance A first acquisition unit configured to acquire an output value at the time of paper detection or non-detection of the paper by the sensor based on a virtual threshold; The second virtual threshold value is calculated based on the voltage value of the power source or the output value and the reference voltage value of the sensor acquired by the first acquisition means and the sensor is not detected based on the second virtual threshold value. Alternatively, a second acquisition unit that acquires an output value at the time of paper detection, an average value of output values at the time of paper detection of the sensor acquired by the first acquisition unit, and the second acquisition unit acquired by the second acquisition unit. Output value when sensor paper is not detected Alternatively, the threshold value is calculated based on the output value of the sensor when the sheet is not detected acquired by the first acquisition unit and the average value of the output values of the sensor when the sheet is detected by the second acquisition unit. And a threshold value changing means for changing the threshold value stored in the storage means to the threshold value calculated by the threshold value calculating means.

  According to a fourth aspect of the present invention, in the paper detection apparatus according to any one of the first to third aspects, the threshold value calculation means calculates an average value by performing an averaging process.

  According to the paper detection apparatus of claim 1 or 2, since the threshold value is changed in response to an automatic adjustment start trigger (for example, the power supply of its own apparatus is turned on), the serviceman or the like changes the threshold value. There is an advantage that there is no need to perform an operation for this.

  According to the paper detection device of the third aspect, since the average value of the plurality of output values when the sensor detects the paper is used as the output value when the sensor detects the paper, the output value when the sensor detects the paper is obtained. Even if the sheet fluctuates due to sheet chattering or the like, the influence can be reduced and an appropriate threshold value can be calculated.

  According to the paper detection device of the fourth aspect, since the threshold value is calculated by performing the averaging process between the output value when the sensor detects the paper and the output value when the paper is not detected, the threshold value is changed to an optimum value. be able to.

  An embodiment in which a sheet detection apparatus according to an embodiment of the present invention is embodied in a copying machine that reads image data of a document and records the image data on a sheet (thermal paper) by a thermal recording method will be described with reference to the drawings. As illustrated in FIG. 1, the copier (paper detection device) 1 includes a control unit (MPU: Microprocessing Unit) 2, a ROM (Read Only Memory) 3, a document reading unit 4, a codec 5, an image memory 6, and an operation unit. 7, a display unit 8, a recording unit 9, and a RAM (Random Access Memory) 10. The units 2 to 10 are communicably connected via a bus 11.

  The control unit 2 controls each unit constituting the copying machine 1 in accordance with a control program stored in the ROM 3. The document reading unit 4 reads image data of a document and outputs it to a predetermined output destination.

  The codec 5 encodes and decodes image data. Here, the image data output from the document reading unit 4 is converted into JPEG (Joint Photographic Experts Group), MH (Modified Huffman), MR (Modified Read), MMR (Modified Modified Read), JBIG (Joint Bi-level Image Group). Encoding is performed by a method or the like, and the encoded image data is decoded. The image memory 6 stores image data directly output from the document reading unit 4, image data encoded by the codec 5, and the like.

  Although not shown, the operation unit 7 is linked to the display unit 8 such as a start key for instructing the document reading unit 4 to start reading a document, a numeric keypad for inputting the number of copies, a cursor key for performing various settings, and the like. Various operation keys are provided. The display unit 8 includes a liquid crystal display (LCD) that displays various setting states, operation states of the copying machine 1 and the like in characters and graphics.

  The recording unit 9 records an image of the image data read from the image memory 6 on a sheet, and includes a recording head 12, a recording unit interface 13, a cover open / close sensor 14, a sheet conveyance control unit 15, and a sheet detection sensor 16. And an A / D converter 17. The recording head 12 is configured by arranging heating elements for each recording pixel, and the heating elements generate heat according to image data transmitted from the image memory 6 via the recording unit interface 13 to heat the paper. Then, an image is recorded on the paper (image forming process). The cover opening / closing sensor 14 detects opening / closing of a cover (not shown) for accessing the recording unit 9 provided in the main body of the apparatus 1.

  The paper transport control unit 15 controls the transport of paper used in the image forming process. FIG. 2 is a diagram illustrating a sheet used in the image forming process of the recording unit 9. As shown in the figure, the recording unit 9 includes a paper folder 18, a transport motor 19, a rubber roller 20, a cutter motor 21, and a cutter 22 in order to supply paper used in the image forming process to the recording head 12. is doing. The paper folder 18 is for storing the paper 23 wound in a roll shape. The transport motor 19 and the rubber roller 20 transport the paper 23 in a direction toward the recording head 12 (hereinafter referred to as “forward direction”) or in a direction opposite to the forward direction (hereinafter referred to as “reverse direction”). Then, the rotation of the conveyance motor 19 is controlled by the sheet conveyance control unit 15, and the sheet 23 is conveyed in the forward direction or the reverse direction. The cutter motor 21 and the cutter 22 are for cutting the paper 23. When the cutter motor 21 is controlled by the paper conveyance control unit 15 to rotate, the cutter 22 moves in the direction of arrow A in the figure. The paper 23 is moved and cut. The cutter motor 21 and the cutter 22 cut a sheet 23 (recording sheet) on which an image is recorded by the recording head 12 by a predetermined length. Further, when the power of the apparatus 1 is turned on, the paper conveyance control unit 15 records one of the papers 23 on the recording head 12 side from the cutting position of the cutter 22 in order to record an image at an appropriate position on the paper 23. A process (hereinafter referred to as “initial cut”) is performed by cutting the portion (front end portion) and aligning the front end of the sheet 23 with a predetermined position.

  The paper detection sensor 16 detects the presence or absence of the paper 23, and is on a light absorbing plate (not shown) provided at a position facing the paper detection sensor 16 with respect to the paper 23 to be transported or the transport path of the paper 23. A light emitting element (light emitting diode) 24 that emits light toward the light source, and a light receiving element (phototransistor) 25 that is energized by receiving light emitted from the light emitting element 24 and reflected from the paper 23. When the paper 23 is not on the paper detection sensor 16, the light emitted from the light emitting element 24 is absorbed by the light absorbing plate, so that the light receiving element 25 cannot receive the light emitted from the light emitting element 24 and is not energized. .

  FIG. 3 is a diagram showing a circuit configuration around the paper detection sensor 16. As shown in the figure, the light emitting element 24 has one end connected to the driving power supply 26 and the other end connected to the GND 27, and emits light by the power supply Vo supplied from the driving power supply 26. The light receiving element 25 has one end connected to the detection power supply 29 and the other end connected to the GND 27 via a resistor 28 having a predetermined resistance value. The A / D converter 17 is connected to a connection point a between the light receiving element 25 and the resistor 28 via a signal line 30.

  The A / D converter 17 performs A / D conversion on the voltage value at the connection point a as the output value of the paper detection sensor 16 and outputs the result to the control unit 2 as digital data. The control unit 2 acquires the output value of the paper detection sensor 16 A / D converted by the A / D converter 17 and compares the acquired output value of the paper detection sensor 16 with the threshold value stored in the RAM 10. Thus, it is determined whether or not the paper detection sensor 16 has detected the paper 23, that is, the presence or absence of the paper 23 at the detection point of the paper detection sensor 16. Specifically, in a state where the light receiving element 25 receives light reflected from the paper 23 and is energized, the voltage value at the connection point a is substantially equal to the voltage value (reference voltage value) of the GND 27 that is zero voltage. Therefore, the voltage value of the connection point a (output value of the sheet detection sensor 16) A / D converted by the A / D converter 17 is smaller than the threshold value stored in the normal RAM 10. Accordingly, the control unit 2 can determine that the paper detection sensor 16 has detected the paper 23, that is, the paper 23 is at the detection point of the paper detection sensor 16.

  On the other hand, in a state where the light receiving element 25 is not energized because it cannot receive the light emitted from the light emitting element 24, the voltage value at the connection point a is substantially equal to the voltage value Vcc (here, 5V) of the power supply 29 for detection. Therefore, the voltage value of the connection point a (output value of the sheet detection sensor 16) A / D converted by the A / D converter 17 is larger than the threshold value stored in the normal RAM 10. Accordingly, the control unit 2 can determine that the paper detection sensor 16 has not detected the paper 23, that is, the paper 23 is not present at the detection point of the paper detection sensor 16.

  The RAM 10 functions as a main memory, a work area, and the like of the control unit 2 and stores various setting information and the like. The threshold used for the paper detection determination process and the sensitivity of the paper detection sensor 16 as described above. The first virtual threshold value Vsimi1 set in advance according to is stored. Therefore, the RAM 10 functions as a storage unit that stores a threshold value.

  The copying machine 1 having the above configuration compares the output value of the paper detection sensor 16 with the threshold value stored in the RAM 10 and determines the presence or absence of the paper 23. The copying machine 1 also has an automatic threshold adjustment function. When the power of the apparatus 1 is turned on, the copying machine 1 performs the above-described initial cut and a process of changing the threshold. This threshold value changing process is a process of changing the threshold value based on the output value when the paper detection sensor 16 detects the paper and the output value when the paper is not detected. Hereinafter, processing operations performed in the copying machine 1 when the power of the apparatus 1 is turned on will be described with reference to the flowcharts shown in FIGS. FIG. 6 is a diagram showing a change in the output value (voltage value at the connection point a) of the paper detection sensor 16 after the power of the apparatus 1 is turned on. The vertical axis indicates the output of the paper detection sensor 16. The value represents the value, and the horizontal axis represents the time.

  The control unit 2 is provided in the main body of the apparatus 1 based on the detection signal of the cover opening / closing sensor 14 in order to prevent the appropriate threshold value changing process from being performed by external light when the power of the apparatus 1 is turned on. It is determined whether the covered cover is closed (S1). Here, if it is determined that the cover is closed (S1: YES), the output value of the paper detection sensor 16 (voltage value at the connection point a), that is, the paper A / D converted by the A / D converter 17. The output value of the detection sensor 16 is acquired (S2).

  Next, the control unit 2 determines whether or not the output value of the paper detection sensor 16 acquired in S2 is smaller than the first virtual threshold value Vsimi1 stored in the RAM 10 (S3). That is, it is determined whether or not the sheet detection sensor 16 detects the sheet 23 (the presence or absence of the sheet 23 at the detection point of the sheet detection sensor 16) based on the first virtual threshold value Vsimi1. The first virtual threshold value Vsimi1 is a threshold value unique to the paper detection sensor 16, and in the present embodiment, the first virtual threshold value Vsimi1 is set to 3.5 V from the performance of the paper detection sensor 16.

In the S3, as the output value of the paper detection sensor 16 at time t ₁ from the time t ₀ in FIG. 6, the output value of the paper detection sensor 16 is large, the control unit 2 than the first virtual threshold Vsimi1 determines In the case (S3: NO), that is, when the paper detection sensor 16 has not detected the paper 23, a message indicating that there is no paper 23 is displayed on the display unit 8 to notify the user of a paper out error, The process returns to S1 (S4). In the present embodiment, when the paper 23 is correctly set at a predetermined position in the paper folder 18 and the cover is closed, the paper detection sensor 16 detects the paper 23.

On the other hand, in the S3, as the output of the paper detection sensor 16 at time t ₂ in FIG. 6, when the output value of the paper detection sensor 16 the control unit 2 to be smaller than the first virtual threshold Vsimi1 determines (S3 : YES), that is, when the sheet detection sensor 16 detects the sheet 23, the sheet conveyance control unit 15 rotates the conveyance motor 19 (S5). As shown in FIG. 7, the sheet conveyance control unit 15 controls the rotation of the conveyance motor 19 to convey the sheet 23 in the forward direction, and at the time of detection of the sheet by the sheet detection sensor 16 (when the sheet is detected). ) Are obtained at predetermined time intervals (S6). The output value from the time t ₂ to time t ₃ in FIG. 6 shows the change in the output value Vp of the sheet detection sensor 16 during the processing of S6, the control unit 2 that functions as a first obtaining unit, the It acquires a plurality of output values Vp between the time t ₂ to time t ₃ at predetermined time intervals.

  By the way, since the first virtual threshold value Vsimi1 which is a reference for determining whether or not the sheet detection sensor 16 detects the sheet in S3 is a temporary threshold value, the determination process in S3 is accurately performed. There is a risk of not. That is, there is a possibility that the sheet 23 is not actually detected when an affirmative determination is made in S3. Accordingly, in S6, the paper detection sensor 16 determines that it is during paper detection based on the first virtual threshold Vsimi1 that is a temporary threshold, and then acquires the output value Vp while further transporting the paper 23. The output value Vp at the time of paper detection is acquired in a state where the paper 23 is reliably detected.

Next, the control unit 2 calculates an average value Vpave of the output values Vp at the time of paper detection of the paper detection sensor 16 acquired in S6 (S7). In S6, one output value Vp at the time of paper detection by the paper detection sensor 16 is acquired, and the single output value Vp may be used as an output value at the time of paper detection without performing the processing of S7. Is possible. However, during the process of S6 is performed, i.e., between time t ₃ from the time t ₂ in FIG. 6, since the sheet 23 is being conveyed, the output value Vp is slightly changed. Therefore, by obtaining a plurality of output values Vp and averaging them, a more accurate output value at the time of paper detection of the paper detection sensor 16 can be obtained.

  The control unit 2 calculates the second virtual threshold value Vsimi2 based on the average value Vpave of the plurality of output values Vp at the time of paper detection of the paper detection sensor 16 calculated in S7 and the voltage value Vcc of the power supply 29 for detection. (S8). Specifically, an average value between the average value Vpave and the voltage value Vcc of the detection power supply 29 is calculated as the second virtual threshold value Vsimi2. As described above, the output value of the paper detection sensor 16 when the paper is not detected is substantially equal to the voltage value Vcc of the power supply 29 for detection. Therefore, as an ideal output value when the paper detection sensor 16 does not detect the paper, A second virtual threshold value Vsimi2 is calculated using the voltage value Vcc of the detection power source 29.

  Next, when the number of steps of the conveyance motor 19 rotated in S5 reaches a predetermined number of steps, the sheet conveyance control unit 15 stops the rotation of the conveyance motor 19 and, as shown in FIG. The motor 21 is rotated and the leading end portion of the paper 23 is cut by the cutter 22 (S9). In this state, the paper detection sensor 16 detects the paper 23. After the front end portion of the paper is cut by the cutter 22, as shown in FIG. 9, the rotation of the transport motor 19 is controlled to transport the paper 23 in the reverse direction (S10). In parallel with the processing operation of S10, the control unit 2 determines whether or not the output value of the paper detection sensor 16 is greater than the second virtual threshold value Vsimi2 (S11). That is, it is determined whether or not the paper detection sensor 16 has detected the paper 23 with reference to the second virtual threshold value Vsimi2.

  In S11, when the control unit 2 determines that the output value of the paper detection sensor 16 is smaller than the second virtual threshold Vsimi2 (S11: NO), that is, when the paper detection sensor 16 detects the paper 23. The paper transport control unit 15 controls the rotation of the transport motor 19 to transport the paper 23 in the reverse direction until the output value of the paper detection sensor 16 becomes larger than the second virtual threshold value Vsimi2 (S10).

On the other hand, the control unit 2, in the S11, as in the output value of the paper detection sensor 16 at time t ₄ in FIG. 6, the output value of the paper detection sensor 16 is determined to become larger than the second virtual threshold Vsimi2 If (S11: YES), that is, when the paper detection sensor 16 no longer detects the sheet 23, and detects the sheet non-detection time (paper 23 of the paper detection sensor 16 shown in time _{t 5} from time _{t 4} in FIG. 6 Output value Vb is acquired (S12). As described above, the control unit 2 functioning as the second acquisition unit obtains the average value Vpave of the output values Vp at the time of paper detection of the plurality of paper detection sensors 16 and the voltage value Vcc of the detection power supply 29 of the paper detection sensor 16. Based on the second virtual threshold value Vsimi2 calculated based on the output value Vb when the paper detection sensor 16 detects no paper. Incidentally, as shown at time t ₅ from time t ₄ in FIG. 6, the output value Vb of the paper is not detected when the paper detection sensor 16, the variation does not occur as the output value Vp during sheet detection, a constant value It becomes.

  Next, the control unit 2 functioning as a threshold value calculation unit calculates the average value Vpave of the plurality of output values Vp at the time of paper detection of the paper detection sensor 16 calculated in S7 and the non-paper of the paper detection sensor 16 acquired in S12. A threshold value Vs is calculated based on the output value Vb at the time of detection (S13). Specifically, an averaging process is performed based on the average value Vpave and the output value Vb, and the average value of the average value Vpave and the output value Vb is calculated as a threshold value. The threshold value is most preferably an average value of the average value Vpave and the output value Vb, but may be a value around the average value. Next, the control unit 2 functioning as a threshold value changing unit changes the threshold value stored in the RAM 10 to the threshold value Vs calculated in S13 (S14). Specifically, the threshold value stored in the RAM 10 is rewritten to the threshold value Vs calculated in S13. When the threshold value is not stored in the RAM 10 at the time of factory shipment, the threshold value Vs is stored as it is.

  Next, as shown in FIG. 10, the paper transport control unit 15 controls the rotation of the transport motor 19 to transport the paper 23 in the forward direction (S15). In parallel with the processing operation of S15, the control unit 2 determines whether or not the output value of the paper detection sensor 16 is smaller than the threshold value Vs (S16). That is, based on the threshold value Vs, it is determined whether or not the paper detection sensor 16 has detected the paper 23. In S15, when the control unit 2 determines that the output value of the paper detection sensor 16 is larger than the threshold value Vs (S16: NO), that is, when the paper detection sensor 16 has not detected the paper, the paper transport control unit 15 controls the rotation of the conveyance motor 15 to convey the sheet 23 in the forward direction until the output value of the sheet detection sensor 16 becomes smaller than the threshold value Vs (S15).

On the other hand, in the S16, as in the output value of the paper detection sensor 16 at time t ₆ in FIG. 6, if a control unit 2 output value is smaller than the threshold value Vs of the paper detection sensor 16 is determined (S16: YES In other words, when the paper detection sensor 16 detects the paper 23, the paper transport control unit 15 stops the rotation of the transport motor 19 and ends the process (S17). In this state, the leading edge of the paper 23 is positioned on the paper detection sensor 16. As described above, the copying machine 1 performs the processing operations of S1 to S17 to perform the threshold changing process together with the initial cut.

  The copying machine 1 according to the embodiment of the present invention changes the threshold value to an appropriate value by performing the processing operations of S1 to S17 each time the power of the apparatus 1 is turned on. Therefore, the copying machine 1 can always perform the paper detection determination process with an appropriate threshold value.

  In the present embodiment, after obtaining the output value Vp when the paper detection sensor 16 detects the paper, the output value Vb when the paper detection sensor 16 does not detect the paper is obtained, and the threshold value Vs based on the obtained both output values. However, the order of obtaining the output value Vp when the paper detection sensor 16 detects the paper and the output value Vb when the paper is not detected is not limited to this. That is, after obtaining the output value Vb when the paper detection sensor 16 does not detect the paper, the output value Vp when the paper non-detection sensor 16 detects the paper is obtained, and the threshold value Vs is calculated based on both the obtained output values. You may do it. Specifically, first, based on the first virtual threshold value Vsimi1, an output value Vb when no paper is detected is acquired. Next, based on the obtained output value Vb of the sheet detection sensor 16 when no sheet is detected and the voltage value (reference voltage value) of the GND 27, that is, the output value Vb and the voltage value of the GND 27 are averaged. The second virtual threshold value Vsimi2 is calculated. Next, based on the calculated second virtual threshold value Vsimi2Vsimi2, the output value Vp at the time of paper detection of the paper detection sensor 16 is acquired. Then, the threshold value Vs is acquired based on the acquired output value Vp of the paper detection sensor 16 when the paper is not detected and the output value Vb when the paper is not detected.

  In the present embodiment, the description has been given of the paper detection sensor 16 having a configuration in which the light receiving element 25 receives the light emitted from the light emitting element 24 and reflected from the paper 23 and energizes the light (reflection type). The configuration is not limited to this, and a so-called transmissive sensor may be used. When this transmission type sensor is used, the output value when the paper is detected and the output value when the paper is not detected are opposite to those in the present embodiment. Further, although the case where the paper detection device is embodied in a copying machine has been described, the paper detection device can also be applied to a facsimile machine, a copying machine, a multifunction machine of a facsimile machine, and the like. Further, the recording method in the recording unit 9 may be a recording method other than the thermal recording method, for example, an ink jet method or an electrophotographic method.

  The present invention can be applied to, for example, a copying machine, a facsimile machine, and a complex machine thereof.

1 is a block diagram illustrating a configuration example of a copier according to an embodiment of the present invention. FIG. 6 is a diagram illustrating a sheet used in an image forming process of a recording unit. FIG. 3 is a diagram illustrating a circuit configuration around a sheet detection sensor. 6 is a flowchart showing processing operations executed when the copying machine according to the embodiment of the present invention is turned on. 5 is a flowchart showing processing operations executed when the power of the copying machine according to the embodiment of the present invention is turned on. FIG. 6 is a diagram illustrating a change in an output value of a paper detection sensor. FIG. 6 is a diagram illustrating a state in which a sheet is conveyed in a forward direction. FIG. 6 is a diagram illustrating a state where a leading end portion of a sheet is cut. FIG. 6 is a diagram illustrating a state in which a sheet is conveyed in a reverse direction. FIG. 6 is a diagram illustrating a state in which a sheet is conveyed in a forward direction. It is the perspective view which showed roughly the reflection type sensor and the paper which is a detection target.

Explanation of symbols

1 Copying machine (paper detection device)
2 Control unit 3 ROM
10 RAM (storage means)
16 Paper detection sensor
23 Paper 29 Detection power supply

Claims (4)

In the paper detection device for judging the presence or absence of the paper by comparing the output value of the sensor for detecting the presence or absence of the paper and the threshold value stored in the storage means,
In response to an automatic adjustment start trigger, threshold value calculating means for acquiring an output value when the paper is detected and an output value when no paper is detected by the sensor and calculating a threshold value based on both acquired output values; and the storage And a threshold value changing means for changing the threshold value stored in the means to the threshold value calculated by the threshold value calculating means. In the paper detection device for judging the presence or absence of the paper by comparing the output value of the sensor for detecting the presence or absence of the paper and the threshold value stored in the storage means,
In response to the automatic adjustment start trigger, first acquisition means for acquiring an output value at the time of paper detection or paper non-detection of the sensor based on a first virtual threshold stored in advance, and the means Based on the output value of the sensor when the paper is detected and the voltage value of the power supply for detection, or the output value of the sensor when the paper is not detected and the reference voltage value acquired by the first acquisition means, A second acquisition unit that calculates and outputs an output value of the sensor at the time of non-detection or detection of the paper, and an output value of the sensor at the time of paper detection acquired by the first acquisition unit; The output value of the sensor when the paper is not detected acquired by the second acquisition means, or the output value of the sensor when the paper is not detected acquired by the first acquisition means and the paper of the sensor acquired by the second acquisition means Threshold value is calculated based on the output value at the time of detection That the threshold value calculating means, the storage means paper detection apparatus characterized by comprising a threshold value changing means for changing the threshold value of the threshold for storing the calculated the threshold value calculating means. In the paper detection device for judging the presence or absence of the paper by comparing the output value of the sensor for detecting the presence or absence of the paper and the threshold value stored in the storage means,
In response to the automatic adjustment start trigger, a first acquisition means for acquiring an output value at the time of paper detection or paper non-detection of the sensor based on a first virtual threshold stored in advance, and a plurality of the means acquire Based on the average value of the output value of the sensor when the paper is detected and the voltage value of the power supply for detection, or based on the output value of the sensor when the paper is not detected and the reference voltage value acquired by the first acquisition unit. And a second acquisition unit that calculates an output value at the time of non-detection or detection of the sheet by the sensor, and a plurality of the first acquisition units at the time of detection of the sheet of the sensor acquired by the sensor. The average value of the output values and the output value obtained when the sensor is not detected by the sensor acquired by the second acquisition means, or the output value obtained when the sensor is not detected by the first acquisition means and the second value. The sensor paper acquired by a plurality of acquisition means A threshold value calculation unit that calculates a threshold value based on an average value of output values at the time of departure; and a threshold value change unit that changes a threshold value stored in the storage unit to a threshold value calculated by the threshold value calculation unit. Paper detection device.   The sheet detection apparatus according to claim 1, wherein the threshold value calculation unit calculates the threshold value by performing an averaging process.

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