JP2007197177A - Image forming device and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming device capable of further highly accurately detecting a double feeding state. <P>SOLUTION: This image forming device has a light emitting part 15 oppositely arranged by sandwiching a paper carrying passage and a light receiving part 16 for receiving the light emitted by the light emitting part 15; and detects the double feeding state of multily overlapped sheets on the paper carrying passage based on acquired carrying time information, by acquiring information on a light receiving quantity in the light receiving part 16 when emitting the light by the light emitting part 15 as the carrying time information, by emitting the light by the light emitting part 15 while changing a quantity of light, during carrying of the paper on the paper carrying passage. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image on a sheet, such as a printer or a multifunction peripheral, and a control method thereof.

  In an image forming apparatus such as a printer or a multifunction peripheral, paper placed on a paper feed tray is transported one by one by a transport roller or the like, and an image such as a toner image is transferred onto the transported paper. Form. However, such an image forming apparatus may cause a malfunction in which a plurality of sheets are mistakenly conveyed when conveying the sheets.

In order to cope with such a problem, a technique has been proposed in which an optical sensor is used to detect a multi-feed state in which a plurality of sheets are conveyed on the sheet conveyance path (see Patent Document 1). In this technology, a light receiving unit and a light emitting unit that constitute an optical sensor are arranged to face each other across a paper conveyance path, and a predetermined amount of light is emitted from the light emission unit, and the light is conveyed on the paper conveyance path. The amount of light that reaches the light-receiving unit through the printed paper and reaches the light-receiving unit, and compares the data obtained by this measurement with preset reference data Thus, double feed detection for determining whether or not the paper is in a double feed state is performed.
JP 2000-172897 A

  However, when double feed detection is performed using an optical sensor as described above, the amount of received light varies depending on the type of paper, the degree of paper overlap, the change in sensitivity of the sensor due to dirt and changes over time, and the like. For this reason, it is not possible to detect double feeding with sufficient accuracy by simply causing the light emitting unit to emit light with a predetermined light amount and measuring the amount of received light. In Patent Document 1, in order to prevent erroneous detection due to a change in the sensitivity of the sensor, the amount of received light is measured in a state where there is no sheet in the optical path between the light emitting unit and the light receiving unit, and the amount of received light is overlapped. A method of adjusting the light emission amount of the light emitting unit in the feed detection has been proposed. However, in this technique, there is a risk of erroneous detection depending on the type of paper and the degree of paper overlap.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of detecting a double-feed state with higher accuracy and a control method thereof.

  An image forming apparatus according to the present invention for solving the above-described problems includes a light-emitting unit and a light-receiving unit that receive light emitted from the light-emitting unit. While transporting the paper, the light emitting unit emits light while changing the amount of light, and information on the amount of light received by the light receiving unit when the light emitting unit emits light is acquired as information at the time of conveyance. And multi-feed detection means for detecting a multi-feed state in which a plurality of sheets are transported on the paper transport path based on the acquired transport time information.

  According to the above configuration, the light emitting unit emits light while changing the light emission amount during paper conveyance, and when the light amount is changed, the change in the amount of light received through the paper is acquired. Then, based on the change in the amount of received light, it is determined whether or not the paper is in a double feed state. Thereby, the precision of double feed detection can be further improved.

  Further, the image forming apparatus is configured to emit the light emitting unit by causing the light emitting unit to emit light while changing a light amount in a state where there is no paper in an optical path between the light emitting unit and the light receiving unit. Paper out time information acquisition means for acquiring information related to the amount of light received by the light receiving unit as paper out time information, and double feed detection as a reference when detecting the double feed state based on the acquired paper out time information Reference information generating means for generating reference information may be further included.

  Alternatively, the image forming apparatus is configured to cause the light emitting unit to emit light while changing a light amount in a state in which an image forming operation is stopped and there is no sheet in the optical path between the light emitting unit and the light receiving unit. Stoppage information acquisition means for acquiring information on the amount of light received by the light receiving section when the light emitting section emits light as stoppage information, and an optical path between the light emitting section and the light receiving section during an image forming operation In-operation information acquisition for causing the light-emitting unit to emit light while changing the amount of light in a state where there is no paper inside, and to acquire information on the amount of light received by the light-receiving unit when the light-emitting unit emits light as operating information And a reference for correcting the in-stop information based on the value of the in-operation information and generating double feed detection reference information serving as a reference for detecting a double feed state based on the corrected in-stop information Information generating means; It is also possible to include further.

  Further, in the image forming apparatus, the reference information generating unit generates a plurality of double feed detection reference information corresponding to the paper type of the paper, and the double feed detection unit is configured to detect the paper transported on the paper transport path. The double feed state may be detected using the double feed detection reference information corresponding to the paper type.

  Alternatively, when the image forming apparatus causes the light emitting unit to emit light while changing the amount of light in a state where a sheet exists in the optical path between the light emitting unit and the light receiving unit, the light emitting unit emits light. Specific sheet information acquisition means for acquiring information on the amount of light received by the light receiving unit as specific sheet information, and a sheet of the same sheet type as the sheet type of the sheet existing in the optical path based on the acquired specific sheet information Further, it is possible to further include reference information generating means for generating double feed detection reference information that serves as a reference for detecting the double feed state.

  Further, in the image forming apparatus, the transport time information acquisition unit may determine the maximum light amount and the minimum light amount based on the maximum light amount and the minimum light amount determined according to the paper type of the paper transported on the paper transport path. The light emitting unit may emit light while changing the amount of light.

  In the image forming apparatus, the transport time information acquisition unit may change the light amount based on a change amount per unit time determined according to the size of the paper transported on the paper transport path. The light emitting unit may emit light.

  The image forming apparatus control method according to the present invention is a control method for an image forming apparatus including a light emitting unit and a light receiving unit that receives light emitted from the light emitting unit, which are disposed to face each other with a paper conveyance path interposed therebetween. The information on the amount of light received by the light receiving unit when the light emitting unit emits light while changing the amount of light while the paper is being conveyed on the paper conveying path. And a step of detecting a multi-feed state in which a plurality of sheets are conveyed on the sheet conveyance path based on the acquired conveyance information.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, an image forming apparatus 10 according to an embodiment of the present invention includes a paper feed tray 11, an image forming unit 12, a transfer roll 13, a fixing unit 14, a control unit 18, and a storage unit 19. Has been. Further, the light emitting unit 15 and the light receiving unit 16 as shown in FIG.

  The paper transported from the paper feed tray 11 is transported along the paper transport path and guided to the image forming unit 12. Here, the conveyance timing is controlled so that the sheet reaches the transfer roll 13 at the timing when the image formed in the image forming unit 12 arrives at the transfer roll 13.

  Here, the paper transport path is provided with a reverse path (C) for transporting the paper to the transfer roll 13 again at the time of backside printing.

  The image forming unit 12 shown in FIG. 1 transfers the image formed on the drum D directly to a sheet. However, the image forming unit 12 transfers the image from the drum D to the intermediate transfer belt, and the image on the intermediate transfer belt. May be transferred onto a sheet sandwiched between the intermediate transfer belt and the transfer roll 13.

  In the transfer roll 13, a voltage that attracts the toner image formed on the drum D to the paper side is applied, and the toner image is transferred to the paper. Thereafter, the sheet is conveyed to the fixing unit 14 and heated and pressed by the fixing unit 14 to fix the image. The sheet on which the image has been fixed is further transported along the sheet transport path and is discharged to the outside of the image forming apparatus 10.

  The light emitting unit 15 emits light based on the control of the control unit 17. The light receiving unit 16 receives the light emitted from the light emitting unit 15, converts the detection level of the received light amount into a digital value, and outputs it to the control unit 17 as information related to the received light amount. Here, as shown in FIG. 2, the light emitting unit 15 and the light receiving unit 16 are disposed to face each other with the paper conveyance path interposed therebetween. In other words, the light emitting unit 15 and the light receiving unit 16 are arranged so that the light emitted from the light emitting unit 15 reaches the light receiving unit 16 across the paper conveyance path. In addition, the arrow by the broken line in FIG. 2 represents the optical path of the light radiated | emitted from the light emission part 15. FIG.

  In the present embodiment, the light emitting unit 15 and the light receiving unit 16 are used to detect a multi-feed state based on the amount of light transmitted through the paper, but the image forming apparatus 10 uses the light emitting unit 15 and the light receiving unit 16. May be used to determine the paper type based on the amount of light transmitted through the paper. That is, in the present embodiment, it is possible to detect the double feed state using an optical sensor for paper type discrimination, and it is not necessary to add a new sensor for double feed detection.

  The control unit 17 is a CPU or the like, and operates according to a program stored in the storage unit 18. The control unit 17 controls the image forming unit 12 and also controls the conveyance of the paper. In addition, the control unit 17 performs light emission control of the light emitting unit 15, acquires information regarding the amount of received light received by the light receiving unit 16, and detects a multifeed state based on the acquired information regarding the amount of received light. Execute double feed detection processing. The specific processing contents of the control unit 17 will be described in detail later.

  The storage unit 18 includes a RAM, an NVRAM (nonvolatile RAM), and the like. The storage unit 18 operates as a work memory for the control unit 17. Further, the storage unit 18 stores parameters relating to the light amount control and information related to the received light amount that is a determination criterion in the double feed detection process.

  Here, an example of the double feed detection process by the control unit 17 will be described. As shown in FIG. 3, the program of the control unit 17 that executes this processing functionally acquires information on the light amount control unit 21 that controls the light emission amount of the light emitting unit 15 and the amount of light received by the light receiving unit 16. The received light amount detection unit 22 and the comparison unit 23 are included.

  The light amount control unit 21 performs light emission control for causing the light emitting unit 15 to emit light while changing the light amount between the maximum light amount and the minimum light amount determined by a predetermined method. As a specific example, the light quantity control unit 21 is predetermined as a parameter relating to light quantity control, and the initial light quantity setting value X (corresponding to the minimum light quantity) and the final light quantity setting value Y (corresponding to the maximum light quantity) stored in the storage unit 18. ) And the light quantity change value Z are read from the storage unit 18. Then, the process shown in FIG. 4 is executed. That is, the light emission amount P is set to the initial light amount setting value X (S1), and the light emitting unit 15 is controlled to emit light having a light amount corresponding to the light emission amount P at a predetermined timing (S2). Then, a signal indicating that the detection should be executed is output to the received light amount detection unit 22 (S3). Next, the light amount change value Z is added to the light emission amount P (S4), and it is checked whether or not the light emission amount P after the addition exceeds the final light amount setting value Y (S5). Here, if the light emission amount P after the addition does not exceed the final light amount setting value Y, the process returns to the process S2 to continue the process. If the added light emission amount P exceeds the final light amount setting value Y in process S5, the process ends.

  When the light reception amount detection unit 22 receives a signal indicating that the detection should be performed from the light amount control unit 21, the light reception amount detection unit 22 acquires information on the light reception amount output by the light reception unit 16, and the light emission amount of the light emission unit 15 at that time In association with the information regarding the received light amount, the received light amount change information is accumulated and stored in the storage unit 18. Thereby, the received light amount detection unit 22 can acquire information on the received light amount in the light receiving unit 16 when the light emitting unit 15 emits light while changing the emitted light amount. This information is a value related to the amount of light emission (here, for example, it is assumed that the light emission unit 15 emits light when the light emission unit 15 emits light, and the light emission unit 15 emits light having a light amount proportional to the drive current). This is information representing the level of light received by the light receiving unit 16.

  In the example of a certain light receiving unit 16, as illustrated in FIG. 5, until the amount of light received from the light emitting unit 15 reaches a certain value Imin, the received light amount information (for example, resistance value) is almost close to the maximum value MAX. It changes in. The amount of light exceeding Imin up to a predetermined value Imax is approximately proportional to the amount of light received, and if it exceeds Imax, the information regarding the amount of light received becomes the minimum value MIN and is saturated.

  Here, assuming that the light emission amount of the light emitting unit 15 when the light amount after passing through the paper is Imin is the lower limit light emission amount R1, and the light emission amount of the light emitting unit 15 when Imax is the upper limit light emission amount R2, the light emission. The change in the information regarding the amount of received light accompanying the change in the amount can be schematically represented by determining these R1, MAX, R2, and MIN parameters. For example, according to a plurality of paper types, information regarding the amount of received light according to the amount of light obtained by transmitting through each paper can be represented as schematically shown in FIG.

  The comparison unit 23 uses the change in the amount of received light accompanying the change in the amount of emitted light, and changes the amount of emitted light by changing the amount of emitted light by the process shown in FIG. 4 while the sheet is being conveyed on the sheet conveyance path. Based on the received light amount change information (information at the time of conveyance) acquired by emitting light, it is determined whether or not the sheet in the optical path between the light emitting unit 11 and the light receiving unit 12 is in a double feed state, and the determination result is output. . Based on the information of the determination result, for example, the control unit 17 executes processing such as stopping the sheet conveyance and displaying message information that prompts the user to remove the overlapped sheets on a display unit (not shown). .

  As a specific example, the comparison unit 23 includes the i-th conveyance time information and the (i−1) -th conveyance time information among the plurality of conveyance time information acquired by the received light amount detection unit 22 while the paper is being conveyed. Is determined to be in the double feed state. Also, when the actual i-th transport time information differs by a predetermined value or more from the predicted value calculated as the value that the i-th transport time information can take based on the (i-1) -th transport time information May be determined to be in a double feed state.

  Further, the comparison unit 23 uses the double feed detection reference information stored in the storage unit 18 and compares the double feed detection reference information with the information at the time of conveyance by using the double feed detection reference information as a reference so that the paper in the optical path is in the double feed state. It may be determined whether or not there is. Here, the double feed detection reference information is information representing a schematic change amount of the received light amount that is assumed with respect to a change in the light emission amount. For example, the above-described lower limit light emission amount R1, upper limit light emission amount R2, and light reception amount. Is defined by four parameters, a maximum value MAX and a minimum value MIN.

  Specifically, for example, the comparison unit 23 determines whether or not it is in the double feed state using the double feed detection reference information as follows. That is, a difference value between each of the acquired plurality of pieces of transport information and the double feed detection reference information associated with the same light emission amount is calculated. Then, when the difference value is equal to or greater than a predetermined value for all the information at the time of conveyance acquired at the time of paper conveyance, it is determined that a plurality of sheets are in close contact multi-feeding state in which they are conveyed in close contact. Further, when the difference between the difference value for the i-th transport information and the difference value for the (i-1) -th transport information is equal to or greater than a predetermined value, the multi-feed in which the leading ends of the sheets are shifted and overlapped It is determined that it is in a state.

  As a specific example, FIG. 7 schematically illustrates an example of a correspondence relationship between the acquired conveyance time information and the state of the sheet on the sheet conveyance path when the leading end of the sheet is shifted and overlapped. FIG. Here, the broken line in the graph represents the double feed detection reference information. In the example of FIG. 7, the conveyance time information deviates from the double feed detection reference information from the time when the light emitting unit 15 is caused to emit light with the light emission amount Rs, and the comparison unit 23 causes the paper to pass through the optical path after this time. It can be determined that it has passed in the double feed state.

  Note that a plurality of double feed detection information may be prepared for each of a plurality of paper types. In this case, the double feed detection reference information corresponding to each paper type is information representing a change in information regarding the amount of received light according to a change in the light emission amount for each paper type as shown in FIG. When the paper type of the paper in the optical path is known in advance by the paper type discrimination processing or the like, the comparison unit 23 uses the double feed detection reference information corresponding to the paper type of the paper in the optical path to determine whether the paper is in the double feed state. By performing the determination, it is possible to perform highly accurate double feed detection corresponding to various paper types.

  The double feed detection reference information may be determined in advance based on the characteristics of the optical sensor at the time of shipment and stored in the storage unit 18. However, in the light emitting unit 15 and the light receiving unit 16 that are optical sensors, the correspondence between the light emission amount and the light reception amount may differ depending on the mounting accuracy and individual differences. Further, the correspondence relationship may change depending on the dust caused by the paper generated in the vicinity of the paper conveyance path or the temperature change between when the paper is conveyed and when it is not.

  Therefore, in order to correct these fluctuations, it is possible to newly generate double feed detection reference information or correct existing double feed detection reference information. For example, the control unit 17 of the present embodiment executes the operation of the light amount control unit 21 (the process shown in FIG. 4) in a state where there is no paper in the optical path between the light emitting unit 15 and the light receiving unit 16. Received light amount change information when there is no paper (information when no paper is present) is acquired.

Then, based on the no-sheet-time information acquired here, for example, the lower limit emission amount Rj1 and the upper limit emission amount Rj2 included in the double feed detection reference information for the j-th sheet type are corrected. A specific example of this correction is as follows. That is, the light emission amount at the lower limit in the information when there is no paper is Ro1, and the light emission amount at the upper limit is Ro2. For each paper type, the ratio rj1 between the light emission amount at the lower limit Rj1 and the light emission amount at the upper limit Rj2 and the light emission amount at the lower limit Ro1 and the light emission amount at the upper limit Ro2 in the information when there is no paper, based on the transmitted light quantity of the paper. , Rj2 are predetermined and stored in the storage unit 18. And
Rj1 = rj1 × Ro1
Rj2 = rj2 × Ro2
As described above, the lower limit light emission amount Rj1 and the upper limit light emission amount Rj2 for the jth sheet are determined and stored in place of the information included in the double feed detection reference information stored in the storage unit 18.

  Here, an example in which correction is performed using information on a predetermined ratio has been shown, but the present invention is not limited to this, and it may be calculated by a predetermined function. Further, although the lower limit light emission amount Rj1 and the upper limit light emission amount Rj2 are set here, the present invention is not limited thereto, and the lower limit light emission amount Rj1 and the rate of change in the proportional change portion may be determined.

  Here, in order to correct the change in the amount of received light due to the occurrence of paper dust and temperature change during paper conveyance, the information on the change in the amount of light received when there is no paper while the image forming operation is stopped (while the paper is not being conveyed). (In-stop information) and received light amount change information (in-operation information) when there is no paper during the image forming operation (while the paper is being conveyed), and the in-stop information is the value of the in-operation information The lower limit light emission amount Rj1 and the upper limit light emission amount Rj2 for each paper type included in the double feed detection reference information may be corrected based on the information during stop after the correction.

Here, the correction of the stopped information by the operating information is performed as follows, for example. That is, the lower limit light emission amount and the upper limit light emission amount are obtained from the operating information and the stop information (hereinafter, the lower limit light emission amount for the operating information is Rop1, and the upper limit light emission amount is Rop2. The lower limit light emission amount for the stopped information is Rnop1 and the upper limit light emission amount is Rnop2), and the difference between the operating information and the stopped information (corresponding to the amount of change in the light amount due to paper dust or the like) is obtained. That is,
ΔR1 = Rop1-Rnop1,
ΔR2 = Rop2-Rnop2,
Ask for.

Then, the lower limit light emission amount Rj1 and the upper limit light emission amount Rj2 for each paper type included in the double feed detection reference information,
Rj1 = rj1 × Rop1-ΔR1
Rj2 = rj2 × Rop2-ΔR2
Asking. Thereby, the double feed detection reference information corresponding to the change in the amount of received light under the operating condition can be generated.

  Further, the light amount control unit 21 has a lower limit light emission amount Ro1 and an upper limit light emission amount Ro2 in the received light amount change information when there is no paper (these may be in operation or stopped). On the basis of the above, the initial light amount setting value X, the final light amount setting value Y, and the light amount change value Z may be set to perform light emission control on the light emitting unit 15. The light quantity change value Z may be determined based on the size of the paper to be transported and the transport speed of the paper.

For example, the light amount control unit 21 sets the initial light amount setting value X to the lower limit light emission amount Ro1 or a value Ro1-ΔL that is lower than the lower limit light emission amount Ro1 by a predetermined value ΔL, and sets the final light amount setting value Y to the upper limit. A value obtained by adding a predetermined value ΔH to the hourly light emission amount Ro2 is set. Then, based on the period T in which the sheet is in the optical path between the light emitting unit 15 and the light receiving unit 16, the number N of times during which the light emitting unit 15 can be controlled to emit light is calculated, and a value n equal to or smaller than N is calculated. The light intensity change value Z is
Z = (Y−X) / n
It is determined. This period T is determined according to the size (feed length) of the sheet to be conveyed and the conveyance speed of the sheet. Alternatively, conversely, the light quantity change value Z may be a fixed value, and the number n of times of light emission of the light emitting unit 15 during the period T may be determined based on X, Y, and Z.

  When the paper type of the paper in the optical path is known in advance by the paper type discrimination process or the like, the light quantity control unit 21 sets the lower-limit light emission amount Ro1 and the upper-limit light emission amount Ro2 in the above-described no-paper information. Instead, the initial light amount setting value X and the final light amount setting value Y may be set based on the lower limit light emission amount Rj1 and the upper limit light emission amount Rj2 in the double feed detection reference information corresponding to the paper type.

  As a result, the amount of light emitted from the light-emitting unit 15 is changed from the leading edge to the trailing edge of the paper during the conveyance of the paper so as to be as close as possible to the section in which the information regarding the amount of received light changes proportionally. The detection accuracy can be increased. When acquiring the received light amount change information when there is no paper, for example, when acquiring operating information or stopping information, the initial light amount setting value X is the minimum light amount that can be emitted by the light emitting unit 15. The final light amount setting value Y is set to the maximum light amount that can be emitted by the light emitting unit 15. The light amount change value Z may be the unit change amount if there is a unit change amount of the light amount in the light emitting unit 15.

  In addition, the light quantity change value Z when acquiring information during operation may be increased compared with information during stoppage to reduce the number of times the amount of received light amount change information is acquired.

  Further, the control unit 17 determines the operating state of the light receiving unit 16 based on the received light amount change information when there is no paper (they may be operating or stopped). Processing may be executed. For example, when the light emission amount Ro1 at the lower limit exceeds a predetermined determination reference threshold value, it is determined that there is some failure in the light emitting unit 15 or the light receiving unit 16, and that is notified to the user. . This notification may be performed, for example, by displaying that fact on a display unit (not shown).

  Further, in the above description, the double feed detection reference information is predetermined or generated based on the received light amount change information when there is no paper. It is also possible to generate double feed detection reference information for a sheet of a specific sheet type used by. That is, in accordance with an instruction from the user, the control unit 17 acquires the received light amount change information as the specific sheet information while conveying the sheet provided by the user along the sheet conveyance path. Then, the double feed detection reference information generated based on the specific paper information is stored in the storage unit 18 in association with the information specifying the paper type of the paper input from the user. In this case, the comparison unit 23 performs comparison with the double feed detection reference information regarding the paper provided by the user.

  Further, the double feed detection process by the operation of the control unit 17 in the above description is performed after the printing is performed (the inner side of the image forming apparatus 10 to print the back paper or the back side and the back side already printed. If the process is performed on a sheet that is being re-conveyed in step (b), there is a possibility that the received light amount change information may be affected by the content of the printing. Therefore, the light emitting unit 15 and the light receiving unit 16 are placed at the end of the paper transport locus (the end of the paper) so that the optical path from the light emitting unit 15 to the light receiving unit 16 is a place where printing is not performed, such as the end of the paper. It may be installed close to the (part side). Further, the light emitting unit 15 and the light receiving unit 16 of the present embodiment may not be provided on the re-conveyance path at the time of printing on the back side. As a specific example, it may be provided near the paper feed tray 11 (position A in FIG. 1). Further, when the light emitting unit 15 and the light receiving unit 16 are provided on the conveyance path through which the sheet is conveyed in both front side printing and back side printing (refer to position B in FIG. 1), the processing content of the image forming unit 12 is referred to. Thus, it is determined whether or not the printing on the back side is being performed. If the printing on the back side is being performed, the above process may not be performed. As a result, the above-described processing is performed only when printing on the front side (first printing), and it is possible to detect double feed on a sheet before printing.

  As described above, in this embodiment, the amount of light emitted from the leading edge to the trailing edge of the sheet is changed stepwise or continuously when the sheet is conveyed, and the amount of light transmitted through the sheet is received when the amount of light is changed. Obtain changes in detection results. Then, based on the change in the light reception detection result, it is determined whether or not the paper is in a double feed state. Thereby, the detection accuracy of the double feed state can be further improved.

  In step S4 in FIG. 4, the light emission amount is changed in the increasing direction. On the other hand, the initial light amount setting value X is set larger than the final light amount setting value Y, and the light emission amount is changed in step S4. It may be gradually decreased.

1 is a schematic diagram illustrating a configuration example of an image forming apparatus 10 according to an embodiment of the present invention. 3 is an explanatory diagram illustrating an arrangement example of a light emitting unit and a light receiving unit in the image forming apparatus 10. FIG. 3 is a functional block diagram relating to paper detection of the image forming apparatus 10; FIG. FIG. 4 is a flowchart illustrating an operation related to sheet detection of the image forming apparatus 10. 4 is an explanatory diagram illustrating an example of a summary of received light amount change information measured in the image forming apparatus 10. FIG. 4 is an explanatory diagram illustrating an example of an outline of double feed detection reference information set in the image forming apparatus. FIG. FIG. 6 is an explanatory diagram illustrating an example of conveyance time information acquired by the image forming apparatus in a double feed state.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 Image forming apparatus, 11 Paper feed tray, 12 Image forming part, 13 Transfer roll, 14 Fixing part, 15 Light emitting part, 16 Light receiving part, 17 Control part, 18 Storage part, 21 Light quantity control part, 22 Light reception amount detection part, 23 Comparison unit.

Claims (8)

A light emitting unit disposed opposite to the paper conveyance path, and a light receiving unit that receives light emitted by the light emitting unit;
While the paper is transported on the paper transport path, the light emitting unit emits light while changing the amount of light, and information on the amount of light received by the light receiving unit when the light emitting unit emits light is acquired as transport time information. Conveying information acquisition means for
Based on the acquired transport time information, a multi-feed detection means for detecting a multi-feed state in which a plurality of sheets of paper are transported on the paper transport path;
An image forming apparatus comprising: The image forming apparatus according to claim 1.
The amount of light received by the light receiving unit when the light emitting unit emits light by changing the amount of light in a state where there is no paper in the optical path between the light emitting unit and the light receiving unit. An out-of-paper information acquisition means for acquiring information as out-of-paper information;
A reference information generating unit configured to generate double feed detection reference information serving as a reference when detecting a double feed state based on the acquired no-sheet-time information;
An image forming apparatus further comprising: The image forming apparatus according to claim 1.
When the image forming operation is stopped and there is no paper in the optical path between the light emitting unit and the light receiving unit, the light emitting unit emits light while changing the amount of light, and the light emitting unit emits light. Stopping information acquisition means for acquiring information on the amount of light received by the light receiving unit as stopping information;
When the image forming operation is being performed and there is no paper in the optical path between the light emitting unit and the light receiving unit, the light emitting unit emits light while changing the amount of light, and the light emitting unit emits light. In-operation information acquisition means for acquiring information on the amount of light received at the light receiving unit as in-operation information;
Reference information generating means for correcting the information during stop based on the value of the information during operation and generating double feed detection reference information serving as a reference when detecting a double feed state based on the corrected stop information. When,
An image forming apparatus further comprising: The image forming apparatus according to claim 2 or 3,
The reference information generating means generates a plurality of double feed detection reference information according to the paper type of the paper,
The image forming apparatus, wherein the double feed detection unit detects a double feed state by using double feed detection reference information corresponding to a paper type of the paper transported on the paper transport path. The image forming apparatus according to claim 1.
The amount of light received by the light receiving unit when the light emitting unit emits light while changing the amount of light in a state where a sheet exists in the optical path between the light emitting unit and the light receiving unit. Specific paper information acquisition means for acquiring information on specific paper as specific paper information;
Based on the acquired specific sheet information, reference information for generating double feed detection reference information that serves as a reference for detecting a double feed state for a paper of the same paper type as that of the paper existing in the optical path Generating means;
An image forming apparatus further comprising: The image forming apparatus according to any one of claims 1 to 5,
The transport time information acquisition means changes the light amount between the maximum light amount and the minimum light amount based on the maximum light amount and the minimum light amount determined according to the paper type of the paper transported on the paper transport path. An image forming apparatus characterized by causing a light emitting unit to emit light. The image forming apparatus according to any one of claims 1 to 6,
The transport time information acquisition means causes the light emitting unit to emit light while changing the amount of light based on the amount of change per unit time determined according to the size of the paper transported on the paper transport path. An image forming apparatus. A control method of an image forming apparatus including a light emitting unit and a light receiving unit that receive light emitted from the light emitting unit, which are arranged to face each other with a paper conveyance path interposed therebetween,
While the paper is transported on the paper transport path, the light emitting unit emits light while changing the amount of light, and information on the amount of light received by the light receiving unit when the light emitting unit emits light is acquired as transport time information. And steps to
Detecting a multi-feed state in which a plurality of sheets of paper are transported on the paper transport path based on the acquired transport time information; and
A control method for an image forming apparatus.

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