JP2008174358A - Image forming apparatus and image forming method - Google Patents

Abstract

An object of the present invention is to accurately perform conveyance control and jam detection even when a sheet is not detected at a design-intended timing due to a sensor mounting position, aging deterioration, or the like.
In an image forming apparatus including rollers 6, 7, and 9 for transporting a sheet of paper 14 at a transport speed V through a transport path R, and transport control means for controlling them, a leading edge detection position in the transport path R is provided. The registration roller 6 that detects the leading edge of the paper 14 and outputs a detection signal, a timer that measures the measurement time T1 from the start of conveyance until the registration roller 6 outputs the detection signal, and the paper in the paper feed tray 2. And a calculator for calculating the distance S1 from the reference position where the tip of 14 is located to the tip detection position by the calculation formula S1 = T1 × V.
[Selection] Figure 1

Description

  The present invention relates to an image forming apparatus such as a printer, a copying machine, and a FAX, and an image forming method.

  In an image forming apparatus such as a printer, a registration sensor is arranged in a conveyance path for conveying a sheet to form an image, and the leading edge of the sheet is detected by the range sensor. Various paper transport controls and jam detection are performed based on a design premise that a paper discharge sensor is provided downstream by a predetermined distance from the registration sensor.

  However, due to circumstances such as variations in the sensor mounting position in the manufacturing process, individual differences among sensors, and deterioration of the sensor over time, it may not be possible to detect the paper at the intended timing in the design. . If the paper cannot be detected at the intended timing, there is a risk that the paper conveyance operation such as paper deflection creation or switchback, or jam detection may fail.

  In particular, in an image forming apparatus, a filler-type sensor is preferably used as a sensor for detecting entry and passage of paper, and therefore, the influence of individual differences and aging deterioration is large. This is because the filler-type sensor is made up of a light-blocking detection piece that is actuated by being pressed by the conveyed paper, and a photo interrupter that detects light-blocking by this detection piece, so the detection timing is the behavior of the detection piece. Depends on. Further, the return operation of the detection piece after being operated by being pressed by the paper is generally delayed due to aging deterioration, and the timing for detecting that the rear end of the paper has passed is often later than the intended timing. Therefore, if print control is performed based on the position of the sensor in the design specifications, the paper will be ejected too much and the flexure creation will fail, the switchback operation will fail, or the paper will not pass through the sensor. Judgment error may be detected.

In order to solve this problem, for example, Patent Document 1 proposes that a filler-type sensor and a reflective-type sensor are arranged in order so that jam detection is not performed by the filler-type sensor under certain conditions. This only restricts jam detection by a filler type sensor, and does not realize accurate conveyance control or jam detection.
JP 2000-337449 A

  The present invention has been invented in view of the above-mentioned problems, and even if the paper is not detected at the timing intended by the design due to the mounting position of the sensor, individual differences, aging deterioration, etc., there is no problem and accurate conveyance is performed. An object of the present invention is to provide an image forming apparatus and an image forming method capable of performing control and jam detection.

  In order to solve the above-described problems, the present invention provides an image forming apparatus including a transport unit that transports a sheet at a predetermined transport speed through a transport path for image formation, and a transport control unit that controls the transport unit. Detecting the leading edge of the paper at the leading edge detection position and outputting a detection signal, and measuring the time from when the conveying means starts conveying the paper until the leading edge detection means outputs the detection signal A time measuring means for obtaining a measuring time; and a distance calculating means for calculating a distance from a reference position where the leading edge of the sheet is located at the start of conveyance to the leading edge detection position. The distance calculating means includes a distance S1 and a measuring time T1. The distance is calculated using the arithmetic expression S1 = T1 × V when the conveyance speed V is set.

  By using the image forming apparatus having the above-described configuration (hereinafter referred to as “first image forming apparatus”), the leading edge detection unit actually detects the leading edge of the sheet from the reference position where the leading edge of the sheet is positioned at the start of conveyance. It is possible to calculate the distance to the leading edge detection position with high accuracy. By using the distance calculated here, there is no problem even if the paper is not detected at the timing designed by the mounting position of the sensor installed as the tip detection means, individual differences, aging degradation, etc., and accurate conveyance Control and jam detection can be performed.

  According to another aspect of the present invention, there is provided an image forming apparatus including a conveyance unit that conveys a sheet at a predetermined conveyance speed through a conveyance path for image formation, and a conveyance control unit that controls the conveyance unit. Leading edge detecting means for detecting the leading edge of the paper and outputting a detection signal; trailing edge detecting means for detecting the trailing edge of the paper at the trailing edge detection position in the transport path and outputting a detection signal; Measure the time from when one of the edge detection means outputs a detection signal until the other outputs the detection signal to obtain the measurement time, and calculate the distance between the leading edge detection position and the trailing edge detection position It is also preferable that the distance calculation means includes a distance calculation means, and the distance calculation means calculates the distance by a predetermined calculation formula using the distance S2, the measurement time T2, the transport speed V, and the paper length L.

  By using the image forming apparatus having the above-described configuration (hereinafter referred to as “second image forming apparatus”), a leading edge detection position where the leading edge detection unit actually detects the leading edge of the sheet during conveyance, and a trailing edge detection unit actually. Can accurately calculate the distance from the trailing edge detection position for detecting the trailing edge of the sheet. By using the distance calculated here, there is a problem even if the paper is not detected at the timing intended by the design due to the mounting position of the sensors installed as the leading edge detecting means and trailing edge detecting means, individual differences, aging deterioration, etc. Therefore, accurate conveyance control and jam detection can be performed.

  In the second image forming apparatus, the distance calculating unit corresponds to the arrangement of the leading end detecting unit and the trailing end detecting unit in the conveyance path and the order in which the leading end detecting unit and the trailing end detecting unit output the detection signal. Thus, it is preferable that an arithmetic expression is selected and used. In this way, the distance can be calculated with high accuracy corresponding to the sheet length of the actually conveyed sheet and the arrangement of the leading edge detecting means and the trailing edge detecting means.

  Specifically, the distance calculation means is configured such that the rear end detection means outputs a detection signal after the front end detection means outputs a detection signal when the rear end detection means is arranged upstream of the front end detection means. Uses the arithmetic expression S2 = L−T2 × V, and when the leading edge detection means outputs the detection signal after the trailing edge detection means outputs the detection signal, the distance is calculated using the arithmetic expression S2 = L + T2 × V. Further, when the front end detection unit is arranged on the upstream side of the rear end detection unit, the distance is calculated using the arithmetic expression S2 = T2 × V−L.

  Further, the second image forming apparatus includes a distance determination unit that determines the distance based on a plurality of calculation results obtained by the distance calculation unit each time a plurality of sheets are conveyed, and the distance When the trailing edge detection means outputs a detection signal after the leading edge detection means outputs a detection signal when the trailing edge detection means is arranged upstream of the leading edge detection means, the determination means calculates multiple times. When the maximum value of the results is a deterministic value and the leading edge detection means outputs a detection signal after the trailing edge detection means has output a detection signal, the minimum value among the multiple calculation results is the definite value It is preferable that If slip occurs on a roller etc. provided as a transport means, it takes time to transport and the measurement time becomes long. Can be a definite value.

  Further, in the second image forming apparatus, the distance calculation means includes a front end detection means and a rear end detection means, a photo interrupter having a light projecting section and a light receiving section, and a light interrupt section from a light projecting section of the photo interrupter. It is preferable that the distance is calculated using an arithmetic expression S2 = T2 × V−L in the case where the detection sensor includes a light-shielding member that is installed so as to freely move forward and backward in the optical path to It is. In this way, the distance between the leading edge detection position and the trailing edge detection position in one filler-type sensor can be calculated with high accuracy.

  Further, in the second image forming apparatus, the distance calculating means calculates the distance from the reference position where the leading edge of the sheet is positioned at the start of conveyance to the upstream position of the leading edge detection position and the trailing edge detection position. It is preferable to determine the distance based on the distance obtained using the arithmetic expression of the first image forming apparatus. In this way, the distance from the reference position where the leading edge of the sheet is located at the start of conveyance to any leading edge detection position or trailing edge detection position during conveyance can be accurately calculated by appropriately adding the calculation result. . By using the distance calculated here, there is a problem even if the paper is not detected at the timing intended by the design due to the mounting position of the sensors installed as the leading edge detecting means and trailing edge detecting means, individual differences, aging deterioration, etc. Therefore, accurate conveyance control and jam detection can be performed.

  In the first and second image forming apparatuses described above, it is preferable that the conveyance control unit performs a sheet conveyance operation during image formation based on the distance calculated by the distance calculation unit.

  In order to solve the above-described problems, the present invention provides a leading edge detection step for detecting the leading edge of a sheet at a leading edge detection position in the middle of conveyance through the conveyance path for image formation, and the leading edge of the sheet after the conveyance of the sheet is started. A time measurement step for measuring the time until the detection of the paper and obtaining a measurement time, and a distance calculation step for calculating the distance from the reference position where the front end of the paper is positioned to the front end detection position at the start of conveyance. In the calculation step, it is also preferable to use an image forming method in which the distance is calculated using the calculation formula S1 = T1 × V when the distance S1, the measurement time T1, and the conveyance speed V are set.

  By using the image forming method with the above configuration (hereinafter referred to as “first image forming method”), the leading edge detection unit actually detects the leading edge of the paper during the transportation from the reference position where the leading edge of the paper is located at the beginning of the transportation. It is possible to calculate the distance to the leading edge detection position with high accuracy. By using the distance calculated here, there is no problem even if the paper is not detected at the timing designed by the mounting position of the sensor installed as the tip detection means, individual differences, aging degradation, etc., and accurate conveyance Control and jam detection can be performed.

  The present invention also provides a leading edge detection step for detecting the leading edge of the sheet at a leading edge detection position in the middle of conveyance through the conveyance path for image formation, and a trailing edge of the sheet at the trailing edge detection position in the middle of conveyance through the conveyance path. A trailing edge detecting step for detecting, a time measuring step for measuring a time between a point at which the leading edge of the sheet is detected and a point at which the trailing edge of the sheet is detected, and obtaining a measuring time; and a leading edge detecting position and a trailing edge detecting position The image forming method may include a distance calculation step for calculating a distance, and the distance calculation step may calculate the distance using a predetermined calculation formula using the distance S2, the measurement time T2, the conveyance speed V, and the paper length L. Is preferred.

  By using the image forming method with the above configuration (hereinafter referred to as “second image forming method”), a leading edge detection position for actually detecting the leading edge of the sheet during conveyance and a trailing edge for actually detecting the trailing edge of the sheet. The distance to the detection position can be calculated with high accuracy. By using the distance calculated here, there is a problem even if the paper is not detected at the timing intended by the design due to the mounting position of the sensors installed as the leading edge detecting means and trailing edge detecting means, individual differences, aging deterioration, etc. Therefore, accurate conveyance control and jam detection can be performed.

  Further, in the second image forming method, the distance calculation step corresponds to the arrangement of the leading edge detection position and the trailing edge detection position in the transport path and the order in which the leading edge and the trailing edge of the sheet are detected. It is preferable to select and use an arithmetic expression. In this way, the distance can be calculated with high accuracy corresponding to the sheet length of the actually conveyed sheet and the arrangement of the leading edge detection position and the trailing edge detection position.

  Specifically, in the distance calculation step, when the trailing edge detection means outputs a detection signal after the leading edge detection means outputs a detection signal when the trailing edge detection means is arranged upstream of the leading edge detection means. Uses the arithmetic expression S2 = L−T2 × V, and when the leading edge detection means outputs the detection signal after the trailing edge detection means outputs the detection signal, the distance is calculated using the arithmetic expression S2 = L + T2 × V. Further, when the front end detection unit is arranged on the upstream side of the rear end detection unit, the distance is calculated using the arithmetic expression S2 = T2 × V−L.

  Further, the second image forming method includes a distance determination step for determining the distance based on a plurality of calculation results obtained in the distance calculation step every time a plurality of sheets are conveyed, and the distance In the confirmation process, if the trailing edge detection position is located upstream of the leading edge detection position, and the trailing edge of the sheet is detected after detecting the leading edge of the sheet, the maximum value among the multiple calculation results is confirmed. When the leading edge of the sheet is detected after the trailing edge of the sheet is detected, it is preferable that the minimum value among a plurality of calculation results is set as the final value. If a slip occurs on a roller, etc., provided as a paper transport unit, it takes time to transport and increases the measurement time. By doing this, the optimum value is the least affected by the slip. Can be used as a definite value of distance.

  Further, in the second image forming method, the distance from the reference position where the leading edge of the sheet is positioned at the start of conveyance to the upstream position of the leading edge detection position and the trailing edge detection position is defined as the first image formation. It is preferable to make a determination based on a calculation result obtained by using an arithmetic expression of the method. In this way, the distance from the reference position where the leading edge of the sheet is located at the start of conveyance to any leading edge detection position or trailing edge detection position during conveyance can be accurately calculated by appropriately adding the calculation result. . By using the distance calculated here, there is a problem even if the paper is not detected at the timing intended by the design due to the mounting position of the sensors installed as the leading edge detecting means and trailing edge detecting means, individual differences, aging deterioration, etc. Therefore, accurate conveyance control and jam detection can be performed.

  In the first and second image forming methods described above, it is preferable to perform the sheet conveying operation during image formation based on the distance calculated in the distance calculating step.

  Each configuration described above can be appropriately combined without departing from the gist of the present invention.

  The present invention has an effect that accurate conveyance control and jam detection can be performed without any problem even if a sheet is not detected at a design-intended timing due to a sensor mounting position, individual difference, aging deterioration, and the like. Play.

  An image forming apparatus and an image forming method of the present invention will be described based on embodiments shown in the accompanying drawings. FIG. 1 schematically shows a basic configuration of an image forming apparatus of the present invention. The image forming apparatus of the illustrated example is a laser color printer using an electrophotographic process, and the apparatus main body 1 is roughly divided into functions, and includes a paper supply / discharge section, a paper transport section, an image forming section, and a paper detection section.

  The paper supply / discharge unit includes a paper feed tray 2, a manual paper feed port 3, and a paper discharge port 4. The paper transport unit includes a paper feed roller 5, a registration roller 6, and a paper discharge roller 7. The image forming unit includes a transfer belt 8, a secondary transfer roller 9, black, magenta, cyan, and yellow image forming units, a fixing device 10, and the like. The paper detection unit includes a registration sensor 11, a paper discharge sensor 12, and a double-sided sensor 13, all of which are filler-type sensors. This will be described in more detail below.

  The paper feed tray 2 is housed in the lower part of the apparatus main body 1, and the uppermost one of the papers 14 having the paper length L stacked in the paper feed tray 2 is used for image formation by the paper feed roller 5. It is sent out at a predetermined transport speed V in the transport path R. Similarly, paper can be fed from the manual paper feed port 3, and the paper 14 transported in the transport path R passes through the image forming unit, and is then discharged by the paper discharge roller 7 to the paper discharge port 4 at the top of the apparatus main body 1. The paper is discharged from. A registration roller 6 disposed between the paper feed roller 5 and the image forming unit in the transport path R is for holding the transported paper 14 for a predetermined time and then transporting it downstream. . Here, downstream and upstream are based on the transport direction of the paper 14 in the transport path R.

  The transfer belt 8 is driven to rotate counterclockwise in FIG. 1, and image forming portions for black, magenta, cyan, and yellow are arranged in parallel from the upstream side to the downstream side in the rotational direction. Since each of these image forming units has a common structure except that the color of the toner image to be formed is different, only the black image forming unit using the toner cartridge 15Bk will be described in detail in the following description, and other toners will be described. For the magenta, cyan, and yellow image forming units using the cartridges 15M, 15C, and 15Y, the reference numerals with M, C, and Y are shown instead of the Bk added to the reference numerals of the components of the black image forming section. Keep on.

  In addition to the toner cartridge 15Bk, the black image forming unit includes a drum-type photoreceptor 16Bk, a charger 17Bk disposed around the photoreceptor 16Bk, an exposure unit 18, a developing unit 19Bk, a cleaner blade 20Bk, and the like. ing. The exposure device 18 is configured to irradiate laser beams 21Bk, 21M, 21C, and 21Y that are exposure lights corresponding to image colors formed by the toner cartridges 15Bk, 15M, 15C, and 15Y.

  At the time of image formation, that is, printing, the outer peripheral surface of the photoreceptor 16Bk is uniformly charged by the charger 17Bk in the dark, and then exposed by the black image laser beam 21Bk emitted from the exposure device 18, thereby electrostatically A latent image is formed. The developing device 19Bk visualizes the electrostatic latent image with black toner supplied from the toner cartridge 15Bk. As a result, a black toner image is formed on the outer surface of the photoreceptor 16Bk.

  The transfer belt 8 that comes into contact with the photosensitive member 16Bk is an endless belt wound between the secondary transfer drive roller 22 and the transfer belt tension roller 23. The transfer belt 8 is driven by the secondary transfer drive roller 22. 8 is driven to rotate. The toner images formed on the outer surface of the photoconductor 16Bk at the primary transfer position where the photoconductor 16Bk and the transfer belt 8 are in contact are sequentially transferred onto the transfer belt 8 that is rotationally driven, and black on the transfer belt 8. Form an image. After the transfer, the photoreceptor 16Bk removes unnecessary toner remaining on the outer peripheral surface by the cleaner blade 20Bk, and then waits for the next image formation.

  The toner image transferred onto the transfer belt 8 by the black image forming unit is conveyed to the magenta image forming unit using the toner cartridge 15M. In the magenta image forming unit, a magenta toner image is formed on the photoconductor 16M through a process similar to that in the black image forming unit, and the toner image is superimposed and transferred onto the black image on the transfer belt 8. The Subsequently, the transfer belt 8 is sequentially conveyed to a cyan image forming unit using the toner cartridge 15C and a yellow image forming unit using the toner cartridge 15Y, and each image forming unit undergoes the same process to obtain cyan toner. The image and the yellow toner image are further superimposed and transferred. In this way, a full color image is transferred onto the transfer belt 8 by superimposing and transferring the black, magenta, cyan, and yellow toner images, and the full color image is conveyed to the position of the secondary transfer roller 9. Is done.

  In synchronization with the timing at which the toner image transferred onto the transfer belt 8 reaches the position of the secondary transfer roller 9, the paper 14 in the transport path R is at a secondary transfer position where the transfer belt 8 and the secondary transfer roller 19 are in contact. The toner image on the transfer belt 8 is transferred to the paper 14 at the secondary transfer position. Thereafter, the toner image transferred onto the paper 14 by the fixing device 10 is fixed by applying heat and pressure, and the paper 14 after printing is discharged by the paper discharge roller 7 provided upstream of the paper discharge port 4. As a result, the print control ends.

  The registration sensor 11 is a paper end detection unit disposed between the paper feed roller 5 and the registration roller 6 in the transport path R, and reaches the front end of the paper 14 transported by the rotation of the paper feed roller 5. Is detected by the registration sensor 11, the rotation is stopped for a predetermined time, and then the rotation is stopped, so that the sheet 14 is put on standby in a state where the leading end is abutted against the registration roller 6 to create a bend. At this time, the conveyance start position and orientation of the paper 14 are corrected. The paper discharge sensor 12 is paper end detection means disposed between the fixing device 10 and the paper discharge roller 7 in the transport path R so as to detect arrival and passage of the paper 14 to be discharged. It has become. When performing double-sided printing, the paper discharge roller 7 is reversely rotated based on the detection of the paper discharge sensor 12 to perform a switchback operation for transporting the paper 14 into the reverse transport path R ′. A double-sided sensor 13 is arranged in the reverse conveyance path R ′ so as to detect the arrival and passage of the paper 14 during the reverse conveyance.

  FIG. 2 shows a basic electrical configuration of the image forming apparatus of the present invention. The image forming apparatus includes a CPU 25, an image memory 26, an I / O (input / output unit) 27, an I / O as control means for performing various controls such as a conveyance operation of the paper 14, a printing operation, and a distance calculation operation described later. An F (interface unit) 28, a ROM 29, and a RAM 30 are provided.

  The CPU 25 interprets and executes program instructions, and includes an arithmetic unit 31 and a timer 32 inside the CPU 25. The computing unit 31 is a distance computing unit that computes a distance by processing each data sent to the CPU 25, and the timer 32 measures time by using the exchange with the I / O 27 as a trigger, and measures this. It is a time measuring means for outputting as time.

  The image memory 26 is a memory that temporarily stores data to be printed by the image forming unit. The I / O 27 controls input / output of electrical components such as sensors, motors, and clutches, the I / F 28 is an interface between the apparatus main body 1 and a terminal that issues a print request thereto, and the ROM 29 is executed by the CPU 25. The RAM 30 is a read-only semiconductor memory storing an image forming program to be read and written by designating an arbitrary address.

  The basic configuration of the image forming apparatus of the present invention has been described above. In the following, each embodiment to which a characteristic configuration is added by the image forming apparatus of the present invention will be described.

  In the image forming apparatus according to the present exemplary embodiment, the leading edge detection process in which the registration sensor 11 detects the leading edge of the paper 14 while it is being conveyed through the printing conveyance path R, and the conveyance of the paper 14 is started. From the time measurement step of measuring and outputting the time until the leading edge of the paper 14 is detected and the leading edge position of the paper 14 at the start of conveyance (hereinafter referred to as “reference position”), the leading edge of the paper 14 is detected by the registration sensor 11. A distance calculation step of calculating a distance S1 to the leading edge position of the paper 14 (hereinafter referred to as “leading edge detection position”) at the time of detecting the printing, and performing printing control based on the calculated distance S1. Is a feature. Hereinafter, it will be described in detail with reference to FIGS.

  3A is a schematic diagram of the entire transport path R, and FIG. 3B is a schematic diagram of the main part of the transport path R. In the transport path R, the leading edge of the paper 14 at the start of transport is at the reference position in the paper feed tray 2, from which the paper feed roller 5, registration roller 6, secondary transfer roller 9, and paper discharge roller 7 rotate. It is conveyed downstream at a predetermined conveying speed V by driving. The registration sensor 11 is a front end detection unit including a filler type sensor that detects and outputs the arrival of the front end of the paper 14 at a position between the paper feed roller 5 and the registration roller 6 in the transport path R.

  FIG. 4 is a flowchart showing the processing control executed by the CPU 25 when calculating the distance. First, the conveyance of the paper 14 at a predetermined conveyance speed V is started by rotating the paper feed roller 5, and the timer 32 starts timing simultaneously with the start of the conveyance. When the leading edge of the conveyed paper 14 reaches the registration sensor 11, the registration sensor 11 detects the leading edge of the paper 14 and turns on, and outputs a detection signal. Upon receiving this detection signal, the CPU 25 stops the timer 32 and causes the calculator 31 to calculate the measurement time T1 up to this point. The arithmetic unit 31 uses the arithmetic expression S1 = T1 × V to calculate the distance S1 from the reference position in the paper feed tray 2 to the leading edge detection position of the registration sensor 11.

  FIG. 5 shows a control for creating a bend on the paper 14 as an example of the print control performed based on the distance S1 calculated in the distance calculation step. Since the distance D from the reference position to the registration roller 6 is obtained as a design specification, a value obtained by subtracting the distance S1 from the distance D, that is, (D−S1), is from the tip detection position of the registration sensor 11 to the registration roller 6. It becomes the distance. Therefore, when the predetermined conveyance distance B for creating the deflection is set, the sheet feed roller 5 is moved for a predetermined time obtained by (D−S1 + B) / V from the time when the registration sensor 11 detects the arrival of the leading edge of the paper 14. If the rotation is controlled so as to be stopped, a desired deflection can be created in the paper 14. The distances D and B are values stored in the ROM 29.

  In this way, by using the distance S1 calculated based on the actual detection timing of the registration sensor 11, for example, when the attachment position of the registration sensor 11 varies, or when the detection timing of the registration sensor 11 varies. Even if there is a shift in the detection timing of the registration sensor 11 due to deterioration over time, or further deterioration over time, it is possible to create a desired deflection on the paper 14. Needless to say, the failure based on the distance S1 is also prevented in other sheet transport operations and jam detection.

  On the other hand, conventionally, the distance from the reference position to the registration sensor 11 and the distance from the registration sensor 11 to the registration roller 6 are determined by design specifications, and printing control is always performed based on this determined value. If the paper 14 is not detected at the timing intended in the design, the creation of the deflection may fail.

  The distance calculation step is preferably set to be executed at the first printing after the apparatus main body 1 is activated. In this case, the distance S1 in the conveyance path R is calculated when the first sheet 14 is printed, and during the subsequent activation, the sheet conveyance control based on the calculated distance S1 is performed. .

  In the image forming apparatus according to the present exemplary embodiment, a leading edge detection step of detecting the leading edge of the sheet 14 conveyed through the conveyance path R for image formation at the leading edge detection position of the registration sensor 11, and the sheet 14 conveyed through the conveyance path R. Time measurement for measuring and outputting the time between the trailing edge detection step of detecting the trailing edge at the trailing edge detection position of the paper discharge sensor 12 and the time point when the leading edge of the paper 14 is detected and the time point when the trailing edge is detected. And a distance calculating step for calculating a distance S2 between the leading edge detection position and the trailing edge detection position, and printing control is performed based on the distance S2 calculated here. Hereinafter, it will be described in detail with reference to FIGS.

  As schematically shown in FIG. 6, in the transport path R, the paper 14 is downstream at a predetermined transport speed V by the rotational drive of the paper feed roller 5, the registration roller 6, the secondary transfer roller 9, and the paper discharge roller 7. It is conveyed to. A registration sensor 11 installed at a position between the paper feed roller 5 and the registration roller 6 in the transport path R detects and outputs the leading edge and the trailing edge of the paper 14. That is, the registration sensor 11 here functions as a rear end detection means in addition to the front end detection means. The paper discharge sensor 12 disposed between the secondary transfer roller 9 and the paper discharge roller 7 in the transport path R is a front end detection unit that detects and outputs the front end of the paper 14.

  FIG. 7 is a flowchart showing the processing control executed by the CPU 25 when calculating the distance. First, the conveyance of the paper 14 at the conveyance speed V is started by rotating the paper feed roller 5. If the leading edge of the conveyed paper 14 reaches the registration sensor 11, the registration sensor 11 moves the leading edge of the paper 14. Detects and turns on, and outputs a detection signal for tip detection. Upon receiving this detection signal, the CPU 25 stops the paper feed roller 5 with the leading end of the paper 14 abutting against the registration roller 6 after a predetermined time from turning on. At this time, a toner image is formed on the transfer belt 8, and the rotation of the paper feeding roller 5 and the registration roller 6 that have been stopped at the timing of matching the position of the toner image with the image forming position of the paper 14. And the conveyance of the paper 14 is resumed.

  When the paper 14 is conveyed to the downstream side, the paper discharge sensor 12 is turned on by detecting the front end of the paper 14 at the front end detection position, and outputs a detection signal for detecting the front end. Further, the registration sensor 11 detects the trailing edge of the paper 14 at the trailing edge detection position and is turned off, and outputs a detection signal for trailing edge detection. Here, the order of detection signal output from the paper discharge sensor 12 and detection signal output from the registration sensor 11 is the size of the distance S2 between the leading edge detection position and the trailing edge detection position and the sheet length L in the conveyance direction of the sheet 14. Depends on the relationship. As shown in FIG. 6A, when the distance S2 <paper length L, the paper discharge sensor 12 outputs a detection signal for detecting the leading edge before the registration sensor 11, and as shown in FIG. 6B. When the distance S2> the paper length L, the registration sensor 11 outputs a detection signal for detecting the trailing edge before the paper discharge sensor 12.

  Then, in accordance with the detection signal output order, different calculation formulas are used for calculating the distance S2. That is, when the paper discharge sensor 12 detects the leading edge of the paper 14 after the paper discharge sensor 12 detects the leading edge of the paper 14, the timer 32 is first detected when the paper discharge sensor 12 detects the leading edge of the paper 14. Then, when the registration sensor 11 detects the trailing edge of the paper 14, the time measurement is stopped, and the calculator 31 calculates the measurement time T2 up to this time. Here, the CPU 25 determines that the distance S2 <the paper length L as shown in FIG. 6A, selects the arithmetic expression S2 = L−T2 × V, and uses this arithmetic expression to set the distance S2 to the arithmetic unit 31. Let it be calculated.

  On the other hand, when the registration sensor 11 detects the trailing edge of the paper 14 after detecting the trailing edge of the paper 14, the timer 32 is first detected when the registration sensor 11 detects the trailing edge of the paper 14. Then, when the paper discharge sensor 12 detects the leading edge of the paper 14, the time measurement is stopped, and the calculator 31 calculates the measurement time T2 up to this time. Here, the CPU 25 determines that the distance S2> the paper length L as shown in FIG. 6B, selects the arithmetic expression S2 = L + T2 × V, and causes the arithmetic unit 31 to calculate the distance S2 using this arithmetic expression. .

  With the above processing, the calculation of the distance S2 is completed. When distance S2 = paper length L, that is, when the leading edge of the paper 14 is detected by the paper discharge sensor 12 and at the same time the trailing edge of the paper 14 is detected by the registration sensor 11, either of the above is used. An expression may be used. Therefore, the distance S2 can be calculated regardless of the magnitude relationship with the paper length L.

  Here, when the paper 14 is transported, the paper feed roller 5 and the registration roller 6 constituting the paper transport unit may slip. When slipping occurs, it takes extra time to transport the paper 14, and the measurement time T2 becomes longer than normal. Therefore, the distance S2 cannot be accurately calculated by performing the above process only once.

  In order to cope with this situation, the distance S2 is calculated in the distance calculation step each time a plurality of sheets 14 are conveyed, and the distance S2 is determined based on a plurality of calculation results obtained here. It is preferable to provide a confirmation step. In the distance determination step, an optimum value is determined from a plurality of calculation results, and this is determined as the distance S2. The determination method of the optimum value is the following method depending on the magnitude relationship between the distance S2 and the paper length L.

  As shown in FIG. 6A, when the distance S2 <paper length L, the distance S2 is calculated using the arithmetic expression S2 = L−T2 × V, and when slip occurs, T2 is greater than normal. In consideration of the fact that the value becomes larger, the maximum value among the calculation results of a plurality of times is determined as the optimum value, and this is set as the final value of the distance S2. On the other hand, when the distance S2> the paper length L, the distance S2 is calculated using the arithmetic expression S2 = L + T2 × V, and T2 becomes larger than that in the normal state when a slip occurs. The minimum value among the calculation results of a plurality of times is determined as the optimum value, and this is set as the final value of the distance S2. By passing through the distance determination step, the distance S2 can be calculated with high accuracy even when slipping may occur.

  As described above, the distance S2 is calculated based on the actual detection timing of the registration sensor 11 and the paper discharge sensor 12, so that, for example, the distance S2 is calculated at the first printing after the apparatus main body 1 is activated. During the subsequent start-up, by providing paper conveyance control and jam detection based on the distance S2 calculated here, variations in the mounting positions of the sensors 11 and 12, individual differences in detection timing, Thus, the desired sheet conveyance control and jam detection can be realized without any problem without being affected by a shift in detection timing due to deterioration over time.

  Note that the calculation of the distance S2 by the above processing is not limited to the case where the distance S2 is performed between the registration sensor 11 and the paper discharge sensor 12, and the front end detection unit is disposed on the downstream side of the rear end detection unit in the transport path R. If so, the distance S2 between the two detection means can be calculated by the same process.

  The image forming apparatus according to the present embodiment is the same as the second embodiment in that the distance S2 is calculated using the front end detection unit and the rear end detection unit. However, the front end detection unit is included in the transport path R. The second embodiment is different from the second embodiment in that it is arranged on the upstream side. Hereinafter, the configuration different from the second embodiment will be described in detail with reference to FIG.

  Both the registration sensor 11 and the paper discharge sensor 12 arranged in the transport path R are filler-type sensors and serve as both a front end detection unit and a rear end detection unit. Reference numeral 11 functions as a leading edge detection unit, and a downstream paper discharge sensor 12 functions as a trailing edge detection unit. In this case, the leading edge detection position where the registration sensor 11 as the leading edge detection means detects the leading edge of the paper 14 is downstream of the trailing edge detection position where the paper discharge sensor 12 as the trailing edge detection means detects the trailing edge of the paper 14. Located on the side.

  When the paper 14 is conveyed downstream, the registration sensor 11 first detects the leading edge of the paper 14 at the leading edge detection position and turns on, and outputs a leading edge detection detection signal. Next, the paper discharge sensor 12 detects the trailing edge of the paper 14 at the trailing edge detection position and turns off, and outputs a detection signal for trailing edge detection. At this time, the CPU 25 causes the timer 32 to start timing when the registration sensor 11 detects the leading edge of the paper 14, and then stops timing when the paper discharge sensor 12 detects the trailing edge of the paper 14. The calculation unit 31 is allowed to calculate the measurement time T2 until Then, by using the arithmetic expression S2 = T2 × V−L, the calculator 31 calculates the distance S2 between the front end detection position and the rear end detection position.

  Also in the present embodiment, a distance determination step of conveying a plurality of sheets 14 and calculating the distance S2 in the distance calculation step each time, and determining the distance S2 based on a plurality of calculation results obtained here. Is preferably provided. In the distance determination process, considering that the distance S2 is calculated using the arithmetic expression S2 = T2 × V−L, and that T2 becomes larger than normal when a slip occurs, Among these, the smallest value is determined as the optimum value, and this is set as the final value of the distance S2. By passing through the distance determination step, the distance S2 can be calculated with high accuracy even when slipping may occur.

  The calculation of the distance S <b> 2 by the above processing is not limited to the case where the distance S <b> 2 is performed between the registration sensor 11 and the paper discharge sensor 12. If so, the distance S2 between the two detection means can be calculated by the same processing.

  The image forming apparatus according to the present exemplary embodiment is characterized in that a distance S2 is calculated from a front end detection position of a filler type sensor that serves as both a front end detection unit and a rear end detection unit to a rear end detection position of the filler type sensor. Yes. Hereinafter, description will be made based on FIGS. 9 and 10.

  FIG. 9 schematically shows a filler sensor. This filler type sensor has a configuration common to the sensors 11, 12, and 13 forming the paper detection unit, and receives light from a light interrupter (not shown) having a light projecting unit and a light receiving unit, and from a light projecting unit of the photo interrupter. And a plate-shaped light-shielding member 33 installed so as to freely advance and retreat in the optical path leading to the section.

  FIG. 10 is a flowchart showing processing control executed by the CPU 25 when calculating the distance S2 in the registration sensor 11. When the paper 14 is conveyed downstream, the registration sensor 11 first detects the leading edge of the paper 14 and turns it on, and outputs a detection signal for detecting the leading edge. Upon receiving the output signal, the CPU 25 causes the timer 32 to start counting at this point. The CPU 25 always monitors the conveyance of the paper 14, and stops the timer 32 while the conveyance is stopped, and restarts the measurement when the conveyance is started again, whereby the paper 14 is conveyed to the timer 32. Only time is counted.

  Next, when the registration sensor 11 detects the trailing edge of the paper 14 and is turned off and outputs a detection signal for trailing edge detection, the CPU 25 that has received the output signal terminates the timer 32 at this time, and the measuring time T2 Is calculated. That is, the calculated measurement time T2 represents only the time during which the paper 14 is transported, and does not include the time during which transport is stopped. Then, the distance S2 from the leading edge detection position of the registration sensor 11 to the trailing edge detection position of the registration sensor 11 is calculated by using the arithmetic expression S2 = T2 × VL.

  The image forming apparatus according to the present embodiment combines the calculation of the distance S1 described in the first embodiment and the calculation of the distance S2 described in the second to fourth embodiments. Thereby, the distance from the reference position at the start of conveyance to the leading edge detection position or trailing edge detection position of the paper discharge sensor 12 can be calculated.

  For example, when calculating the distance S from the reference position at the start of conveyance to the leading edge detection position of the paper discharge sensor 12, the distance S1 calculated by the arithmetic expression of the first embodiment and the calculation of the second embodiment are used. Using the distance S2 calculated by the equation and the distance S2 calculated by the arithmetic expression of the fourth embodiment (hereinafter referred to as S ′), it can be calculated by S = S1 + S2 + S2 ′.

  Further, when calculating the distance S ′ from the reference position at the start of conveyance to the rear end detection position of the paper discharge sensor 12, the distance S1 calculated by the arithmetic expression of the first embodiment and the third embodiment are used. Using the distance S2 (hereinafter referred to as S ″) calculated by the following equation, it can be calculated by S ′ = S1 + S2 ″.

  If such a combination is appropriately performed, it is possible to calculate the distance from the reference position at the start of conveyance to the front end detection position and the rear end detection position of an arbitrary sensor such as the registration sensor 11 and the paper discharge sensor 12. Since the control is performed based on the actual position of the paper 14 at the time when each sensor outputs a detection signal instead of based on the sensor position on the design specification as in the past, failure of the deflection creation or switchback operation, Misdetection in jam detection is prevented.

  The distance calculation step is preferably set to be executed at the first printing after the apparatus main body 1 is activated. In this case, the distance in the conveyance path R is calculated when the first sheet 14 is printed, and during the subsequent activation, the sheet conveyance control based on the calculated distance is performed.

1 is an explanatory diagram schematically showing a basic configuration of an image forming apparatus of the present invention. It is explanatory drawing which shows roughly a basic electrical structure same as the above. It is explanatory drawing which shows schematically the conveyance path | route of Example 1 same as the above, (a) has shown the whole path | route, (b) has shown the principal part. It is a flowchart which shows the distance calculation process of Example 1 same as the above. It is a flowchart which shows the bending production process of Example 1 same as the above. It is explanatory drawing which shows schematically the conveyance path | route of Example 2 same as the above, (a) has shown the case where S2 <L, (b) has shown the case where S2> L. It is a flowchart which shows the distance calculation process of Example 2 same as the above. It is explanatory drawing which shows schematically the conveyance path | route of Example 3 same as the above. It is explanatory drawing which shows roughly the filler type sensor of Example 4 same as the above. It is a flowchart which shows the distance calculation process of Example 4 same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Apparatus main body 2 Paper feed tray 5 Paper feed roller 6 Registration roller 7 Paper discharge roller 9 Secondary transfer roller 11 Registration sensor 12 Paper discharge sensor 14 Paper 25 CPU
31 computing unit 32 timer 33 light-shielding member L paper length R transport path S1 distance S2 distance T1 measurement time T2 measurement time V transport speed

Claims (19)

  In an image forming apparatus comprising a transport unit that transports a sheet at a predetermined transport speed through a transport path for image formation and a transport control unit that controls the transport unit, the leading end of the sheet is detected at a leading end detection position in the transport path. Leading edge detection means for outputting a detection signal, time measuring means for measuring the time from when the conveyance means starts conveying the paper until the leading edge detection means outputs the detection signal, and obtaining a measurement time, and conveyance start Distance calculating means for calculating the distance from the reference position where the leading edge of the paper is positioned to the leading edge detection position at the time, and the distance calculating means is the calculation formula S1 when the distance S1, the measurement time T1, and the conveyance speed V are set. An image forming apparatus characterized in that a distance is calculated using T1 × V.   In an image forming apparatus comprising a transport unit that transports a sheet at a predetermined transport speed through a transport path for image formation and a transport control unit that controls the transport unit, the leading end of the sheet is detected at a leading end detection position in the transport path. One of the leading edge detecting means, the trailing edge detecting means for detecting the trailing edge of the sheet at the trailing edge detection position in the transport path and outputting the detection signal, and the leading edge detecting means. Measuring a time from when the detection signal is output until the other outputs the detection signal to obtain a measurement time, and a distance calculation means for calculating the distance between the front end detection position and the rear end detection position. An image forming apparatus comprising: a distance calculation unit that calculates a distance by a predetermined calculation formula using a distance S2, a measurement time T2, a conveyance speed V, and a sheet length L.   The distance calculation means selects and uses an arithmetic expression corresponding to the arrangement of the front end detection means and the rear end detection means in the transport path and the order in which the front end detection means and the rear end detection means output detection signals. The image forming apparatus according to claim 2, wherein the image forming apparatus is an image forming apparatus.   When the rear end detection unit outputs the detection signal after the front end detection unit outputs the detection signal when the rear end detection unit is disposed upstream of the front end detection unit, the distance calculation unit calculates the equation S2. The image forming apparatus according to claim 3, wherein the distance is calculated using = L−T2 × V.   When the rear end detection unit outputs the detection signal after the rear end detection unit outputs the detection signal when the rear end detection unit is arranged upstream of the front end detection unit, the distance calculation unit calculates the equation S2. The image forming apparatus according to claim 3, wherein the distance is calculated using L = T2 × V.   The distance calculating means calculates the distance using an arithmetic expression S2 = T2 × V−L when the leading edge detecting means is disposed upstream of the trailing edge detecting means. The image forming apparatus according to 3.   A distance determination unit for determining a distance based on a plurality of calculation results obtained by the distance calculation unit each time a plurality of sheets are conveyed, and the distance determination unit is a rear end detection unit rather than a front end detection unit; When the rear end detection means outputs the detection signal after the front end detection means outputs the detection signal, the maximum value among the calculation results of a plurality of times is determined as the final value, and the rear end 6. The method according to claim 2, wherein when the tip detection means outputs a detection signal after the detection means outputs a detection signal, a minimum value among a plurality of calculation results is set as a definite value. The image forming apparatus according to claim 1.   The distance calculation means includes a front end detection means and a rear end detection means, a photo interrupter having a light projecting part and a light receiving part, and a light shielding property installed so as to freely advance and retreat in an optical path from the light projecting part to the light receiving part of the photo interrupter. The image forming apparatus according to claim 3, wherein the distance is calculated using an arithmetic expression S2 = T2 × V−L when the sensor is constituted by a single detection sensor.   The distance calculation means obtains the distance from the reference position where the leading edge of the sheet is located at the start of conveyance to the upstream position of the leading edge detection position and the trailing edge detection position using the calculation expression according to claim 1. The image forming apparatus according to claim 2, wherein the image forming apparatus is determined based on a distance.   The image forming apparatus according to claim 1, wherein the conveyance control unit performs a sheet conveyance operation during image formation based on the distance calculated by the distance calculation unit.   The leading edge detection process that detects the leading edge of the paper at the leading edge detection position in the middle of conveyance through the image forming conveyance path, and the measurement time by measuring the time from the start of paper conveyance to the detection of the leading edge of the paper And a distance calculation step for calculating the distance from the reference position where the leading edge of the paper is positioned at the start of conveyance to the leading edge detection position. In the distance calculation step, the distance S1, the measurement time T1, the conveyance speed An image forming method, wherein the distance is calculated using an arithmetic expression S1 = T1 × V where V is V.   A leading edge detection process for detecting the leading edge of the paper at a leading edge detection position in the middle of conveyance through the conveyance path for image formation, and a trailing edge detection for detecting the trailing edge of the paper at a trailing edge detection position in the middle of conveyance through the conveyance path. Measuring the time between the process and the time when the leading edge of the paper is detected and the time when the trailing edge of the paper is detected to obtain the measurement time, and the distance for calculating the distance between the leading edge detection position and the trailing edge detection position An image forming method comprising a calculation step, and the distance calculation step calculates the distance by a predetermined calculation formula using the distance S2, the measurement time T2, the conveyance speed V, and the paper length L.   In the distance calculation step, an arithmetic expression is selected and used in accordance with the arrangement of the leading edge detection position and the trailing edge detection position in the transport path and the order in which the leading edge and the trailing edge of the sheet are detected. The image forming method according to claim 12.   In the distance calculation step, when the trailing edge detection position is arranged upstream of the leading edge detection position, and the trailing edge of the sheet is detected after the leading edge of the sheet is detected, the arithmetic expression S2 = L−T2 × V is used. The image forming method according to claim 13, wherein the distance is calculated.   In the distance calculation step, when the trailing edge detection position is located upstream of the leading edge detection position, and the leading edge of the sheet is detected after detecting the trailing edge of the sheet, the distance is calculated using the equation S2 = L + T2 × V. The image forming method according to claim 13, wherein the image forming method is calculated.   14. The distance calculation step according to claim 13, wherein the distance is calculated using an arithmetic expression S2 = T2 × V−L when the leading edge detection position is arranged upstream of the trailing edge detection position. Image forming method.   A distance determination step for determining the distance based on a plurality of calculation results obtained in the distance calculation step every time a plurality of sheets are conveyed, and the distance determination step includes a trailing edge detection position rather than a leading edge detection position. If the trailing edge of the paper is detected after detecting the leading edge of the paper, the maximum value among the multiple calculation results is determined as the final value, and the leading edge of the paper is detected after detecting the trailing edge of the paper. The image forming method according to any one of claims 12 to 16, wherein when detected, a minimum value among a plurality of calculation results is set as a definite value.   The calculation obtained using the arithmetic expression of the image forming method according to claim 11, wherein the distance from the reference position where the leading edge of the sheet is positioned at the start of conveyance to the upstream position of the leading edge detection position and the trailing edge detection position. The image forming method according to claim 12, wherein the image forming method is determined based on a result.   The image forming method according to any one of claims 11 to 18, wherein a sheet conveying operation at the time of image formation is performed based on the distance calculated in the distance calculating step.

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