JP2017052569A - Image formation device, sheet feeding method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation device capable of preventing feeding of a plurality of sheets by properly controlling rotation of a pickup roller.SOLUTION: An image formation device includes a manual tray 111 in which a sheet P is placed, a pickup roller 113 which picks up the sheet P from the manual tray for transportation, and a sheet feeding pull-out roller 119 for transporting the sheet P that is transported from the pickup roller 113 to a printing part for image formation. The image formation device detects a size of the sheet P, and after the sheet feeding pull-out roller 119 starts transportation of the sheet P, stops rotation of the pickup roller 113 at a timing corresponding to the size of the sheet P.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an image forming apparatus such as a printer, a copier, or a multifunction peripheral that forms an image on paper.

  An electrophotographic image forming apparatus forms an image on a sheet fed from a sheet feeding cassette or a manual feed tray. The manual feed tray is used when an image is formed on thick paper having a basis weight that is not supported by the paper feed cassette, coated paper, or the like.

  Japanese Patent Application Laid-Open No. 2004-228561 discloses a paper feeding device that feeds a plurality of sheets stacked on a paper feeding cassette or a manual feed tray to an image forming apparatus one by one by a pickup roller. The sheet is conveyed to the registration roller by the pickup roller, and the image is formed after the timing is adjusted by the registration roller. This paper feeding device is provided with a sensor for detecting paper in the transport path, and determines the time from when the sensor detects paper to when the pickup roller is stopped based on the image forming speed input from the operation unit. . In such a configuration, the speed of the pickup roller is the same as the image forming speed, and the faster the image forming speed input from the operation unit, the longer the time from when the sensor detects the paper until the pickup roller stops. shorten. Thus, the time from when the sensor detects the paper until the pickup roller stops is appropriately controlled according to the image forming speed. Note that since the optimum image forming speed mainly depends on the basis weight of the paper, the image forming apparatus determines the image forming speed according to the type of paper.

  When the distance from the pickup roller to the registration roller is longer than the length in the conveyance direction of the paper to be conveyed (hereinafter referred to as “paper length”), a conveyance roller is provided between the pickup roller and the registration roller. The conveyance roller and the pickup roller are driven by different driving sources. This is because when the rear end portion (hereinafter simply referred to as “paper rear end”) in the paper transport direction exceeds the position of the pickup roller, the pickup roller starts feeding the next paper before the pickup. This is because it is necessary to stop only the rollers. It is preferable to set the drive time from when the sensor detects the paper until the pickup roller stops so that the pickup roller rotates to the vicinity of the rear end of the paper by inputting the paper length from the operation unit.

JP-A-10-35910

  If the rotation of the pickup roller is not stopped before the trailing edge of the sheet exceeds the pickup roller, the pickup roller feeds the next sheet. Therefore, the pickup roller conveys the sheet by a distance shorter than the sheet length input from the operation unit and stops rotating. When the pickup roller stops during the conveyance of the sheet, the conveyance roller needs to compensate for the rotational resistance of the pickup roller applied to the sheet with the driving torque. This becomes a factor that the conveyance of the sheet to the registration roller is not stable. Therefore, it is preferable that the pickup roller is stopped immediately before the trailing edge of the sheet exceeds the pickup roller.

  However, when the sheet length set by the operation unit is longer than the actual sheet length, the pickup roller does not stop even if the trailing edge of the sheet passes the pickup roller. Therefore, the next sheet is fed, and two or more sheets are fed in one image forming process. When the actual sheet length is different from the set sheet length, it is necessary to control the rotation of the pickup roller according to the actual sheet length.

  In view of the above problems, it is a main object of the present invention to provide an image forming apparatus that appropriately controls the rotation of a paper feed roller such as a pickup roller to prevent paper feeding of a plurality of sheets.

  The image forming apparatus of the present invention includes a tray on which paper is placed, a paper feed roller that picks up and transports the paper from the tray, and a print that performs image formation on the paper that is transported from the paper feed roller. A conveyance roller that conveys the sheet, a size detection unit that detects a size of the paper, and the conveyance roller that starts conveying the paper that has been conveyed from the paper feed roller, and then the size detection unit detects the paper. Control means for stopping the rotation of the paper feed roller at a timing according to the size of the paper.

  According to the present invention, after the sheet is conveyed to the conveying roller, two or more sheets are fed at a time by stopping the rotation of the sheet feeding roller at a timing according to the size of the sheet detected by the size detecting unit. Can be prevented.

1 is a configuration diagram of an image forming apparatus. The block diagram of a control block. (A)-(d) is explanatory drawing of a manual feed tray. (A)-(c) is explanatory drawing of the selection process of paper size. (A)-(c) is explanatory drawing of sheet feeding control. (A), (b) is explanatory drawing of a size detection process. 6 is a flowchart showing a paper feed process.

  Hereinafter, embodiments will be described in detail with reference to the drawings.

(Constitution)
FIG. 1 is a configuration diagram of an image forming apparatus according to the present embodiment. The image forming apparatus includes a printer unit that performs image forming processing, a scanner unit that reads a document image from a document, and a UI (User Interface) 330 that is an operation unit that receives a user operation.

  The scanner unit includes a document table 152, a document presence / absence sensor 151, a document conveyance roller 112, a glass table 55, and an image sensor 233. A document is placed on the document table 152. Document presence / absence sensor 151 detects the presence / absence of a document on document table 152. The document transport roller 112 transports the documents placed on the document table 152 one by one to the reading position. The image sensor 233 optically reads the original image of the original conveyed to the reading position, and generates an image signal. On the glass table 55, the document is directly placed by the user without using the document table 152. The image sensor 233 can optically read a document image from a document placed on the glass table 55 and generate an image signal.

  The printer unit includes an image forming unit 120, a laser scanner unit 103, an intermediate transfer unit 140, a secondary transfer unit 118, a fixing device 170, and various rollers for conveying a sheet on which an image is formed.

  The image forming unit 120 includes photosensitive drums 101y, 101m, 101c, and 101k, charging rollers 102y, 102m, 102c, and 102k, developing devices 104y, 104m, 104c, and 104k, and cleaners 107y, 107m, 107c, and 107k. The charging rollers 102y, 102m, 102c, and 102k charge the surfaces of the photosensitive drums 101y, 101m, 101c, and 101k. The developing units 104y, 104m, 104c, and 104k develop the toner by attaching toner to the photosensitive drums 101y, 101m, 101c, and 101k. A yellow toner image is formed on the photosensitive drum 101y. A magenta toner image is formed on the photosensitive drum 101m. A cyan toner image is formed on the photosensitive drum 101c. A black toner image is formed on the photosensitive drum 101k. The cleaners 107y, 107m, 107c, and 107k remove toner remaining on the photosensitive drums 101y, 101m, 101c, and 101k.

  The laser scanner unit 103 emits light according to the video signal obtained by digitally converting the image signal generated by the scanner unit. The laser scanner unit 103 includes laser scanners 103y, 103m, 103c, and 103k. The laser scanner 103y irradiates the photosensitive drum 101y with laser light corresponding to the yellow video signal. The laser scanner 103m irradiates the photosensitive drum 101m with laser light corresponding to the magenta video signal. The laser scanner 103c irradiates the photosensitive drum 101c with laser light corresponding to the cyan video signal. The laser scanner 103k irradiates the photosensitive drum 101k with laser light corresponding to the black video signal.

  The intermediate transfer unit 140 includes an intermediate transfer belt 130 and primary transfer rollers 105y, 105m, 105c, and 105k. The primary transfer rollers 105y, 105m, 105c, and 105k are provided so as to sandwich the intermediate transfer belt 130 between the photosensitive drums 101y, 101m, 101c, and 101k. The primary transfer roller 105y transfers the yellow toner image formed on the photosensitive drum 101y to the intermediate transfer belt 130. The primary transfer roller 105m transfers the magenta toner image formed on the photosensitive drum 101m to the intermediate transfer belt 130. The primary transfer roller 105 c transfers the cyan toner image formed on the photosensitive drum 101 c to the intermediate transfer belt 130. The primary transfer roller 105k transfers the black toner image formed on the photosensitive drum 101k to the intermediate transfer belt 130. The intermediate transfer belt 130 is transferred so that the toner images of the respective colors overlap each other, thereby forming a full-color toner image.

  The secondary transfer unit 118 transfers the toner image transferred to the intermediate transfer belt 130 onto the paper P. In this embodiment, the paper P is also fed from the manual feed tray 111 in addition to the paper feed cassette (no code). The paper P placed on the manual feed tray 111 is conveyed to the secondary transfer unit 118 by the paper feed separation roller 114, the paper feed drawing roller 119, and the registration roller 116. The manual feed tray 111 is provided with a paper sensor 115 that detects the placement of the paper P on the manual feed tray 111 based on the presence or absence of the paper P on the manual feed tray 111. In the conveyance path between the paper feed separation roller 114 and the paper feed drawing roller 119, a paper feed drawing sensor 117 for detecting the paper P is provided.

  The fixing device 170 fixes the toner image on the paper P by heating and pressurizing the paper P on which the toner image is transferred by the secondary transfer unit 118. Thereby, the image formation on the paper P is completed. The paper P on which the image is formed is discharged from the fixing device 170 to the paper discharge tray 132 via the paper discharge roller 139.

  The UI 330 includes key buttons, a display, and a touch panel operated by the user.

  FIG. 2 is a configuration diagram illustrating a control block of the image forming apparatus. The control unit 100 is built in the image forming apparatus. The control unit 100 includes a main control unit 300, a scanner control unit 280, an image signal processing unit 281, an external I / F 282, a printer control unit 285, a paper transport unit 270, and an image forming unit 271. The main control unit 300 includes a CPU (Central Processing Unit) 301, a ROM (Read Only Memory) 302, a RAM (Random Access Memory) 303, and a timer 291. The CPU 301, the ROM 302, the RAM 303, and the timer 291 are communicably connected via a bus.

  The main control unit 300 controls the operation of each unit in the image forming apparatus. The CPU 301 reads a computer program from the ROM 302 and executes various processes by using the RAM 303 as a work area. The timer 291 performs time counting. The CPU 301 acquires the count value of the time count by the timer 291 and measures the time by the timer 291. The main control unit 300 acquires detection results of various sensors provided in the image forming apparatus, and performs image forming processing according to the acquired detection results.

  The main control unit 300 is also connected to the UI 330. The CPU 301 receives an instruction for setting or starting image forming processing from the UI 330. The CPU 301 stores the received setting in the RAM 303 and performs image forming processing in response to a start instruction. The settings of the image forming process are, for example, the size and type of paper used for image formation, the number of copies for image formation, and the like. Further, the CPU 301 displays various screens such as a setting screen and a status display screen on the display of the UI 330.

  For example, when the paper P is placed on the manual feed tray 111, the CPU 301 detects this by the paper sensor 115. The CPU 301 detecting that the paper P is placed on the manual feed tray 111 displays a selection screen that is a paper size setting screen on the display of the UI 330 and prompts the user to input the paper size. The CPU 301 stores the paper size selected on the selection screen in the RAM 303 together with the paper size of the paper P actually placed on the manual feed tray 111. A method for detecting the paper size of the paper P actually placed on the manual feed tray 111 will be described later.

  The scanner control unit 280 controls the operation of the scanner unit of the image forming apparatus according to the control of the main control unit 300. The scanner control unit 280 performs drive control of the document transport roller 112 and detects the presence or absence of a document on the document table 152 by the document presence / absence sensor 151. Further, the scanner control unit 280 optically reads a document image of a document with the image sensor 233 and generates an image signal. This image signal is an analog signal. The scanner control unit 280 transmits the generated image signal to the image signal processing unit 281.

  The image signal processing unit 281 performs various processes such as digital change to an analog image signal under the control of the main control unit 300, converts it into a video signal, and transmits it to the printer control unit 285. Video signals are generated for each color of yellow, magenta, cyan, and black. The image signal processing unit 281 acquires an analog image signal from the scanner control unit 280 during the copy process. The image signal processing unit 281 acquires an analog image signal from an external device 283 such as a personal computer via the external I / F 282 at the time of print processing.

  The printer control unit 285 controls the operation of the printer unit of the image forming apparatus in accordance with the control of the main control unit 300. The printer control unit 285 transmits the video signal acquired from the image signal processing unit 281 to the image forming unit 271 to instruct image forming processing. In addition, the printer control unit 285 causes the paper transport unit 270 to control the transport of the paper P placed on the manual feed tray 111. The image forming unit 271 performs image forming processing by controlling the operation of each unit in the image forming apparatus based on the video signal acquired from the printer control unit 285.

(Image formation processing)
An image forming process performed by the image forming apparatus configured as described above will be described.
When the user places, for example, A4 size paper P on the manual feed tray 111, the CPU 301 detects the size of the paper P by a size detection mechanism of the manual feed tray 111 described later, and displays a paper size selection screen on the display of the UI 330. indicate. At this time, the CPU 301 displays the size of the paper P (in this case, A4 size) detected by the size detection mechanism on the selection screen. The size of the paper P is determined by input from the selection screen by the user. The CPU 301 stores the determined paper size in the RAM 303. The CPU 301 determines the size of the paper P placed on the manual feed tray 111 by input from the selection screen.

  When the user instructs the start of image formation via the UI 330, the CPU 301 causes the scanner control unit 280 to control the operation of the scanner unit, and acquires an image signal of the document image. The scanner control unit 280 rotates and drives the document transport roller 112 to transport the document placed on the document table 152 to the reading position. The scanner control unit 280 irradiates a document conveyed to a reading position by a light emitting unit (not shown). The image sensor 233 receives reflected light from the original, reads the original image, and outputs an image signal corresponding to the read original image. The scanner control unit 280 acquires an image signal from the image sensor 233 and transmits it to the image signal processing unit 281. The scanner control unit 280 repeats such processing until the document presence / absence sensor 151 no longer detects a document.

  The image signal processing unit 281 generates a video signal from the image signal acquired from the scanner control unit 280 and transmits the video signal to the printer control unit 285. Note that the video signal may not be transmitted directly from the image signal processing unit 281 to the printer control unit 285 but may be stored in the RAM 303 and then transmitted to the printer control unit 285.

  The CPU 301 causes the printer control unit 285 to control the operation of the printer unit. The printer control unit 285 controls the image forming unit 271 to charge the surfaces of the photosensitive drums 101y, 101m, 101c, and 101k by the charging rollers 102y, 102m, 102c, and 102k. The laser scanning unit 103 acquires video signals corresponding to the respective colors from the printer control unit 285, and irradiates the photosensitive drums 101y, 101m, 101c, and 101k by the laser scanners 103y, 103m, 103c, and 103k. As a result, electrostatic latent images corresponding to the video signals are formed on the surfaces of the photosensitive drums 101y, 101m, 101c, and 101k. The developing units 104y, 104m, 104c, and 104k cause the toner to adhere to the photosensitive drums 101y, 101m, 101c, and 101k under the control of the image forming unit 271. As a result, the electrostatic latent images on the photosensitive drums 101y, 101m, 101c, and 101k are developed to form toner images.

  The printer control unit 285 controls the image forming unit 271 to transfer the toner image to the intermediate transfer belt 130. The toner images formed on the photosensitive drums 101y, 101m, 101c, and 101k are sequentially transferred to the rotating intermediate transfer belt 130 so as to overlap each other by the primary transfer rollers 105y, 105m, 105c, and 105k. The transferred toner image is conveyed to the secondary transfer unit 118 by the rotation of the intermediate transfer belt 130. The toner remaining on the photosensitive drums 101y, 101m, 101c, and 101k after the transfer is removed by the cleaners 107y, 107m, 107c, and 107k.

  The printer control unit 285 controls the paper transport unit 270 so that the paper P placed on the manual feed tray 111 is transferred to the secondary transfer unit 118 in accordance with the timing at which the toner image is transported to the secondary transfer unit 118. Transport. The paper transport unit 270 drives the pickup roller 113 to start transporting the paper P placed on the manual feed tray 111 one by one. The paper P is transported to the registration roller 116 by the paper feed separation roller 114 and the paper feed drawing roller 119 after the transport is started. The registration roller 116 temporarily stops the conveyance of the paper P, corrects the inclination with respect to the conveyance direction of the paper P, etc., and transfers the paper P to the secondary transfer unit 118 in accordance with the timing when the toner image is conveyed to the secondary transfer unit 118. Transport to.

  The printer control unit 285 controls the image forming unit 271 to cause the secondary transfer unit 118 to transfer the toner image from the intermediate transfer belt 130 to the paper P. The sheet P on which the toner image is transferred is conveyed from the secondary transfer unit 118 to the fixing device 170. The fixing device 170 fixes the toner image on the paper P at a predetermined temperature and pressure under the control of the image forming unit 271. The printer control unit 285 controls the image forming unit 271 to discharge the paper P from the fixing device 170 to the paper discharge tray 132 via the paper discharge roller 139.

  Note that such image formation processing is an example, and image formation may be performed by another method using an image processing apparatus having a similar configuration.

(Bypass tray configuration)
The configuration of the manual feed tray 111 will be described in detail. FIG. 3 is an explanatory diagram of the manual feed tray 111. As shown in the top view of FIG. 3A, the manual feed tray 111 includes a paper sensor 115, a pickup roller 113, regulation guides 212 and 213, a paper width sensor 217, a first paper length sensor 218, and a second paper length sensor. 219. The paper sensor 115, the regulation guides 212 and 213, the paper width sensor 217, the first paper length sensor 218, and the second paper length sensor 219 constitute a size detection mechanism.

  The sheet sensor 115 is a flag type sensor, detects the presence of the sheet when the sheet P is placed on the manual feed tray 111, and transmits the detection result to the main control unit 300. The pickup roller 113 is a paper feed roller that picks up the paper P from the manual feed tray 111 and feeds it to the printer unit. When a plurality of sheets P are placed on the manual feed tray 111, the pickup roller 113 separates and feeds the sheets P one by one from the uppermost sheet P. When the paper P is placed on the manual feed tray 111, the leading end portion in the transport direction (hereinafter referred to as “paper leading edge”) is abutted against the pickup roller 113.

  The two regulation guides 212 and 213 sandwich the side edges of the plurality of sheets P placed on the manual feed tray 111, and prevent the sheet P from being skewed during feeding by the pickup roller 113. The two regulation guides 212 and 213 are slidable in the directions of arrows 215 and 216, and their positions are determined in accordance with the length of the sheet P in the width direction orthogonal to the transport direction (hereinafter referred to as “sheet width”). Can do. The regulation guide 212 is connected to the paper width sensor 217 via a link (not shown). The paper width sensor 217 transmits a paper width value corresponding to the position of the regulation guide 212 to the main control unit 300. The CPU 301 detects the paper width of the paper P based on the paper width value.

  The first paper length sensor 218 and the second paper length sensor 219 are flag-type sensors, and detect the paper length that is the length in the transport direction of the paper P placed on the manual feed tray 111. The first paper length sensor 218 and the second paper length sensor 219 are provided side by side in the transport direction of the paper P. The first sheet length sensor 218 is provided at a predetermined distance upstream from the position of the pickup roller 113 in the transport direction, that is, at a position of 170 [mm] in the present embodiment. The second paper length sensor 219 is provided behind the first paper length sensor 218 in the transport direction from the position of the pickup roller 113, in the present embodiment at a position of 355 [mm]. The distance from the position of the pickup roller 113 of the first sheet length sensor 218 is represented by “L1”, and the distance from the position of the pickup roller 113 of the second sheet length sensor 219 is represented by “L2”. That is, in this embodiment, L1 = 170 [mm] and L2 = 355 [mm].

  FIG. 3B is a diagram illustrating the relationship between the sheet width value that is the detection result of the sheet width sensor 217 and the actual sheet width of the sheet P. The paper width sensor 217 outputs a paper width value represented by 10 bits. The paper width sensor 217 outputs a value “0 to 0x400” as a paper width value substantially linearly. In the example of FIG. 3B, if the paper width value is “0x320”, the paper width of the paper P is A4R (210 [mm]). If the paper width value is “0x384”, the paper width of the paper P is B4R (257 [mm]). If the paper width value is “0x3D4”, the paper width of the paper P is A4 (297 [mm]). Note that the notation with “R” after the standard size code indicates the portrait orientation in which the sheet length is longer than the sheet width, and the notation indicates the landscape orientation.

  FIG. 3C is a table for specifying the size of the paper P. This table is stored in advance in the ROM 302 or RAM 303, for example. The CPU 301 detects the size of the paper P with reference to this table based on the detection results of the paper width sensor 217, the first paper length sensor 218, and the second paper length sensor 219.

  For example, if the paper sensor 115 detects the paper P, the first paper length sensor 218 and the second paper length sensor 219 detect the paper P, and the paper width value is “0x384 ± 0x10”, the CPU 301 The size is specified as “B4R”. Further, the CPU 301 detects the paper P when the paper sensor 115 and the first paper length sensor 218 detect the paper P, the second paper length sensor 219 does not detect the paper P, and the paper width value is “0x320 ± 0x10”. Is specified as “A4R”.

  The CPU 301 detects the presence / absence of the paper P on the manual feed tray 111 by the paper sensor 115, but determines that the paper P is newly placed when the detection result of the paper sensor 115 changes from the absence of paper to the presence of paper. In this case, the CPU 301 controls paper feeding in a paper length detection mode to be described later. As for the size of the paper P, for example, the paper width may be detected using a size detection switch or the like.

  FIG. 3D shows a state where the interval between the regulation guides 212 and 213 is widened to the A4R size and the B5R paper P is placed. According to the table of FIG. 3C, the detection results of the first paper length sensor 218 and the second paper length sensor 219 are the same for the paper P sizes A4R and B5R. For this reason, the CPU 301 erroneously determines that the A4R paper P is placed even if the B5R paper P is placed. If the image forming process is performed in this state, an output result desired by the user cannot be obtained.

  Therefore, in this embodiment, the main control unit 300 detects the actual size of the paper P after feeding, stops the image forming process if the sizes do not match, and notifies the user of the size mismatch via the UI 330. To do. This prevents the output result that is not desired by the user from being continuously generated. Details of the size mismatch determination control when the sizes do not match will be described later.

(Select paper size)
FIG. 4 is an explanatory diagram of paper size selection processing. 4A and 4B are examples of screens for allowing the user to confirm the size of the paper P placed on the manual feed tray 111. FIG. This screen is displayed on the display of the UI 330.

  When the user places the paper P on the manual feed tray 111, the main control unit 300 displays the selection screen 500 of FIG. 4A on the display of the UI 330. The selection screen 500 is displayed when the size of the paper P placed on the manual feed tray 111 is detected by the size detection mechanism. The selection screen 500 includes a size display 501 of the paper P detected by the size detection mechanism. The user confirms the paper size on the selection screen 500.

  For example, when the user places the B4R paper P on the manual feed tray 111 and then moves the regulation guides 212 and 213 to the side edges of the paper P, the CPU 301 detects the size of the paper P. When detecting the size of the paper P, the CPU 301 displays a selection screen 500 on the display of the UI 330. The user confirms the size display 501 on the selection screen 500. If the size of the loaded paper P is displayed, the user presses the “OK” button 503. If the size is different from the size of the loaded paper P, the user changes “change”. A button 502 is pressed. When the “OK” button 503 is pressed, the CPU 301 stores the size of the size display 501 (in this case, “B4R”) in the RAM 303 as the confirmed size.

  When the “change” button 502 is pressed, the CPU 301 displays the size designation screen 600 in FIG. 4B on the display of the UI 330. The user can designate the size of the paper P on the size designation screen 600. The user presses the size specifying button 601 to specify the size of the paper P and presses an “OK” button 602. As a result, the CPU 301 stores the size designated by the user in the RAM 303 as the determined size.

A “free size” button 604 is a button for forming an image based on the paper size detected by the image forming apparatus without the user specifying the size. When the “OK” button 502 is pressed after the “free size” button 604 is pressed, the CPU 301 stores the free size in the RAM 303 as the determined size. When the “free size” button 604 is selected, the CPU 301 calculates the paper width Lw of the paper P by linear interpolation from the following equation.
Lw = 210 + (297-210) / {(0x3D4-0x320) x (paper width value-0x320)}

  FIG. 4C is an exemplary diagram of fixed size information representing a fixed size stored in the RAM 303. The CPU 301 stores the selected paper P size, paper width Lw, and paper length Ls in the RAM 303 as fixed size information. The fixed size information is stored in the RAM 303 until the paper P is removed from the manual feed tray 111 and the paper sensor 115 detects the absence of paper.

  The confirmed size information 701 represents a confirmed size when the paper P is B4R. In the fixed size information 701, the size of the paper P is “B4R”, the paper width Lw is “257”, and the paper length Ls is “364”. In this way, when the standard size becomes the fixed size, the paper width and paper length of the standard size are stored. The confirmed size information 702 represents a state where the paper P is not placed on the manual feed tray 111. When the paper sensor 115 does not detect the paper P on the manual feed tray 111, the CPU 301 determines that the paper P is not placed on the manual feed tray 111, and the size, the paper width Lw, and the paper length Ls are “undecided”. ”Is stored in the RAM 303.

  The fixed size information 703 represents a fixed size when a free size is selected. When the free size is selected, the CPU 301 calculates the paper width Lw corresponding to the paper width value by the above formula. In the confirmed size information 703, the size is “free size”, the paper width Lw is “257”, and the paper length Ls is “undecided”. The sheet length Ls can be determined by a size detection process described later. The confirmed size information 703 represents a state where a free size is selected and the paper length Ls is confirmed. In the confirmed size information 704, the size is “free size”, the paper width Lw is “257”, and the paper length Ls is “364”.

(Paper feed control)
FIG. 5 is an explanatory diagram of paper feed control of the paper P from the manual feed tray 111.

FIG. 5A is an explanatory diagram of a conveyance path from the manual feed tray 111 to the paper feed drawing roller 119. For convenience of explanation, the angle is different from that in FIG. The pickup roller 113 and the paper feed separation roller 114 are driven by a tray paper feed motor 122. The pickup roller 113 picks up the paper P from the manual feed tray 111. When the pickup roller 113 picks up two or more sheets P, the sheet feeding separation roller 114 separates and conveys only the uppermost sheet P. The pickup roller 113 and the paper feed separation roller 114 are configured such that a one-way clutch is sandwiched between a tray paper feed motor 122 as a driving source, and the paper P can be drawn by the paper feed drawing roller 119 when rotation stops. Is done.
The paper feed pulling sensor 117 is arranged downstream in the transport direction with respect to the paper feed separation roller 114 and detects the paper P transported by the paper feed separation roller 114. The paper feed drawing roller 119 is a transport roller driven by a paper feed drawing motor 123. The paper feed drawing roller 119 transports the paper P transported from the pickup roller 113 and the paper feed separation roller 114 to the registration roller 116. When the pickup roller 113 and the paper feed separation roller 114 stop rotating, the paper feed drawing roller 119 pulls out the paper P from the pickup roller 113 and the paper feed separation roller 114 and conveys it. When a plurality of sheets on the manual feed tray 111 are fed, the pickup roller 113 remains in contact with the sheet until the last sheet is fed after the first sheet is fed. . When all of the plurality of sheets to be fed are fed, the pickup roller 113 is moved to a position away from the sheet surface or the placement surface of the manual feed tray 113.

  FIG. 5B is a timing chart when feeding from the manual feed tray 111. FIG. 5B illustrates a timing chart in the case of feeding the paper P having the size B4R in the normal operation (normal mode) and the paper length detection mode. Each time in the timing chart is measured by the timer 291.

  In the normal mode, the paper feed pulling motor 123 starts driving at the conveyance speed Vfeed [mm / s] from the start of the image forming process before time T1. At time T1, the tray paper feed motor 122 starts driving at the transport speed Vfeed [mm / s]. As a result, the paper P is transported at a transport speed Vfeed [mm / s]. At time T <b> 2, the leading edge of the paper P reaches the detection range of the paper feed extraction sensor 117, and thereby the paper feed extraction sensor 117 detects the paper P. The paper feed pull-out sensor 117 transmits a detection result indicating that the paper P has been detected to the CPU 301. The paper feed drawing sensor 117 is provided on the pickup roller 113 side in the vicinity of the paper feed drawing roller 119, and detects the start of conveyance of the paper P by the paper feed drawing roller 119.

At time T <b> 2 when the CPU 301 obtains the detection result indicating the presence of paper from the paper feed pull-out sensor 117, the paper rear end, which is the rear end portion in the transport direction of the paper P, is a distance Lm upstream from the pickup roller 113 in the transport direction. The time to move to the position is calculated. This time is the time when the pickup roller 113 stops rotating. The CPU 301 acquires the paper length Ls of the paper P from the confirmed size information stored in the RAM 303. Based on the distance Lc from the pickup roller 113 to the paper feed drawing roller 119, the acquired paper length Ls, and the distance Lm, the CPU 301 stops driving the tray paper feed motor 122 from the following equation at time T (3-1 ) Is calculated. The distance Lm and the distance Lc are values stored in the ROM 302 in advance.
T (3-1) = T2 + (Ls−Lc−Lm) / Vfeed

  At time T (3-1), the tray paper feed motor 122 stops driving, and the pickup roller 113 and the paper feed separation roller 114 stop rotating. As a result, the next sheet is not fed. When the tray paper feed motor 122 stops driving immediately after the paper feed drawing roller 119 starts transporting the paper P, the pickup roller 113 and the paper feed separation roller 114 rotate in accordance with the transport of the paper P. For this reason, the paper feed pulling motor 123 needs to compensate for the rotational resistance of the pickup roller 113 and the paper feed separation roller 114 applied to the paper P with the driving torque. However, the tray paper feed motor 122 rotates the pickup roller 113 and the paper feed separation roller 114 until the time T (3-1), and the pickup roller 113 conveys the paper P to the vicinity of the rear end of the paper, so The amount that 123 compensates with the driving torque decreases. Therefore, the conveyance of the paper P is stably performed by the paper feed drawing roller 119.

  In FIG. 5B, the distance Lm is set to 10 [mm], and the tray paper feed motor 122 stops driving when the trailing edge of the paper reaches the position of 10 [mm] from the pickup roller 113. . The time T (3-1) is represented by {(364-Lc-10) / Vfeed} because the size of the paper P is B4R. The distance Lm may be any value as long as the rear end of the sheet is in the vicinity of the pickup roller 113. The distance Lm may be set so that the rear end of the sheet comes near the paper feed separation roller 114 beyond the pickup roller 113.

  In the paper length detection mode, the tray paper feed motor 122 and the paper feed pull-out motor 123 are driven at the same timing as in the normal mode until time T2. The paper length detection mode is a paper feed mode when the paper length Ls is unknown and the timing for stopping the rotation of the pickup roller 113 is unknown. The paper length detection mode is, for example, a paper feed mode for feeding the first paper P after the paper P is once removed from the manual feed tray 111 and placed again. By performing paper feeding in the paper length detection mode, for example, as shown in FIG. 3D, when the actual paper size is different from the set paper size, the second and subsequent sheets are prevented from being fed, Realizes stable paper feeding.

  In the example of FIG. 3D, the set paper size is A4R (paper length = 297 [mm]), and the actual paper size is B5R (paper length = 257 [mm]). When feeding in the normal mode in this state, the second sheet is fed even if the tray feeding motor is stopped at time T (3-1). This is prevented in the paper length detection mode.

In the paper length detection mode, the tray paper feed motor 122 stops driving at time T (3-2). The CPU 301 sets the paper length of the paper P to be actually fed, and calculates the time T (3-2) from the set paper length (hereinafter referred to as “paper detection length”) Lss, distance Lc, and distance Lm. To do. Time T (3-2) is calculated by the following equation.
T (3-2) = T2 + (Lss-Lc-Lm) / Vfeed

  The paper detection length Lss is set based on the detection results of the first paper length sensor 218 and the second paper length sensor 219. FIG. 5C is an example of a table for setting the paper detection length Lss, and shows the relationship between the paper detection length Lss and the detection results of the first paper length sensor 218 and the second paper length sensor 219. When the first paper length sensor 218 detects the paper P (on state) and the second paper length sensor 219 does not detect the paper P (off state), the paper length of the paper P is at least the first paper length sensor 218. It is to the position of. Therefore, the CPU 301 sets the paper detection length Lss = L1 = 170 [mm]. When neither the first paper length sensor 218 nor the second paper length sensor 219 detects the paper P (OFF state), the CPU 301 sets the shortest paper length supported by the image forming apparatus as the paper detection length Lss. . In this embodiment, in order for the image forming apparatus to support up to A5, the CPU 301 sets the paper detection length Lss = 148 [mm]. In the present embodiment, the configuration using two sheet length sensors for setting the sheet detection length has been described. However, more sheet length sensors may be used. In that case, the sheet detection length can be set with higher accuracy.

  When the tray paper feed motor 122 stops driving at time T (3-2), the pickup roller 113 stops rotating and does not feed the next paper. Further, since the pickup roller 113 is transporting the paper P that is already being fed to the vicinity of the rear end of the paper, the pick-up roller 113 can stably transport the paper P.

  Note that the CPU 301 also feeds paper in the paper length detection mode when feeding paper P for which a free size is set. In this case, the CPU 301 detects the sheet length of the first sheet P by size detection processing described later, and in the second and subsequent sheet feeding, the sheet is fed in the normal mode based on the detected sheet length.

  When a stepping motor is used for the tray paper feed motor 122 or the paper feed pulling motor 123, the position of the trailing edge of the paper may be calculated by the driving pulse of the stepping motor to determine the timing of stopping the drive of the tray paper feed motor 122. . Alternatively, the pickup roller 113 and the paper feed separation roller 114 may be provided with encoders, and the position of the trailing edge of the paper may be calculated from the number of rotations to determine the timing of stopping the tray paper feed motor 122.

(Size detection process)
FIG. 6 is an explanatory diagram of the size detection process. In the size detection process, the actual length of the fed paper P is detected based on the detection result of the paper feed pull-out sensor 117. FIG. 6A shows the relationship between the detection result of the paper feed pulling sensor 117 and the driving speed of the paper feed pulling motor 123. The paper feed pulling sensor 117 is turned on when the paper P is detected at time T11, and is turned off when the paper P passes through at time T12. From the time (T12-T11) from when the paper feed pulling sensor 117 is turned on to when it is turned off, and the conveyance speed Vfeed of the paper P by the paper feed pulling motor 123, the paper P is obtained by the following formula. The length (hereinafter referred to as “paper detection length”) Lsd is detected.
Lsd = (T12−T11) / Vfeed

  Note that the paper feed of the paper P may be temporarily stopped before the paper feed pull-out sensor 117 is turned off due to factors such as waiting for image formation. In this case, the paper detection length Lsd is calculated from the time that the paper feed pulling motor 123 is driven until it stops, regardless of the above formula. That is, T12 in the above formula is the time when the paper feed pulling motor 123 stops.

  When a free size is set as the paper size as in the confirmed size information 703 in FIG. 4C, the paper detection length Lsd detected by the size detection process is used as the paper length Ls. As a result, the second and subsequent sheets of paper P are fed in the normal mode. Time T (3-1) in FIG. 5B is calculated according to the sheet detection length Lsd.

  When the determined size is other than the free size, if the difference between the sheet detection length Lsd and the sheet length Ls included in the determined size information is greater than or equal to a predetermined threshold Lth, the CPU 301 determines that the sheet sizes do not match. In this case, the CPU 301 stops the image forming process including paper feeding. The threshold Lth is, for example, 15 [mm].

  When the paper sizes do not match, the CPU 301 displays a screen for notifying that there is a mismatch on the display of the UI 330. FIG. 6B is an illustration of such a screen. When the setting (A4R) is different from the size (B5R) of the actually loaded paper P as shown in FIG. 3D, the difference in paper length is 40 [mm]. Since this is equal to or greater than the threshold value Lth, the CPU 301 determines that the paper sizes do not match and displays the screen of FIG. This screen includes a message indicating that the paper sizes do not match and a set paper size 610 (A4R). When the user confirms the paper P placed on the manual feed tray 111 and the positions of the regulation guides 212 and 213 and presses the continue button 611, the CPU 301 resumes the image forming process. When the user presses the cancel button 621, the CPU 301 stops the image forming process.

  As described above, the image forming apparatus according to the present embodiment feeds paper in the paper length detection mode when feeding the first sheet regardless of the paper size of the paper P, and performs tray feed motors based on the paper detection length Lss. 122 stops driving. Further, the image forming apparatus feeds the second and subsequent sheets in the normal mode, and stops driving the tray sheet feeding motor 122 based on the sheet length Ls. Therefore, the image forming apparatus prevents two or more sheets P from being fed. Further, since the tray paper feed motor 122 is driven according to the paper length, the image forming apparatus can stably carry the paper.

(Paper feed processing)
FIG. 7 is a flowchart showing a paper feed process by such an image forming apparatus. This paper feed process is repeated while the image forming apparatus is powered on. The CPU 301 determines the presence or absence of the paper P on the manual feed tray 111 based on the detection result of the paper sensor 115.

  When the detection result of the paper sensor 115 changes from the state where the paper P is present in the manual feed tray 111 to the state where the paper P is not present (S1111: Y), the CPU 301 deletes the confirmed size information stored in the RAM 303 (S1112). As a result, the paper size is not set. The processing of S1111 to S1112 is processing performed when the paper P is once removed from the manual feed tray 111 and placed again by replacement of the manual feed tray 111 or the like.

  When the paper sensor 115 detects that the paper P is placed on the manual feed tray 111 (S1113: Y), the CPU 301 determines whether or not the paper size is confirmed, that is, whether or not the confirmed size information is stored in the RAM 303. Is determined (S1114). If the paper size has not been determined (S1114: N), the CPU 301 displays a selection screen 500 as shown in FIG. 4A on the display of the UI 330 (S1115). When the size of the paper P is determined by a user instruction according to the display of the selection screen 500 (S1116: Y), the CPU 301 stores determined size information indicating the determined size in the RAM 303 (S1117). In addition, the CPU 301 turns on the paper reset flag (S1119). The paper reset flag indicates whether or not the paper P has been once removed from the manual feed tray 111 and placed again after the previous paper feed. When a free size is instructed, the fixed size information 703 shown in FIG. If the paper P is removed from the manual feed tray before an instruction according to the selection screen 500 by the user (S1118: N), the CPU 301 waits until the paper P is placed on the manual feed tray 111 again (S1113). In the above processing, the paper P is placed on the manual feed tray 111 and the fixed size information is stored in the RAM 303.

  When the CPU 301 receives an instruction to start the image forming process from the UI 330 (S1121: Y), the CPU 301 starts driving the paper feed pulling motor 123. When the paper P is removed from the manual feed tray 111 after the fixed size information is stored and before the start instruction of the image forming process is input (S1121: N), the CPU 301 erases the fixed size information and the paper P is again stored. It waits until it is placed (S1112).

  After starting the driving of the paper feed pulling motor 123, the CPU 301 determines the paper feed timing according to the progress of the image forming process and the paper feed interval with the previous paper (S1131). If it is determined that it is the paper feed timing (S1131: Y), the CPU 301 starts driving the tray paper feed motor 122 (S1141). This timing corresponds to time T1 in FIG. As a result, the pickup roller 113 and the paper feed separation roller 114 start rotating, and the paper feed from the manual feed tray 111 to the printer unit is started.

  When the paper P is transported through the transport path to the position of the paper feed extraction sensor 117, the paper feed extraction sensor 117 detects the paper P and is turned on (S1151: Y). The timing when the paper feed pull-out sensor 117 is turned on corresponds to time T2 in FIG. The CPU 301 checks whether or not the paper reset flag is on after the paper feed pull-out sensor 117 is turned on (S1161).

  If the paper reset flag is on (S1161: Y), it is the first paper feed after the paper P is placed on the manual feed tray 111. In this case, the CPU 301 feeds paper in the paper length detection mode described with reference to FIG. The CPU 301 calculates time T (3-2) in FIG. 5B, which is the timing of stopping driving of the tray paper feed motor 122 in the paper length detection mode (S1162). CPU301 which calculated time T (3-2) sets a paper reset flag to an OFF state (S1163).

  If the paper reset flag is off (S1161: N), the paper P is fed from the manual feed tray 111 following the previous paper feed. In this case, the CPU 301 feeds paper in the normal mode described with reference to FIG. The CPU 301 is the drive stop timing of the tray paper feed motor 122 in the normal mode. Time T (3-1) in FIG. 5B is calculated (S1165).

  The CPU 301 stops driving the tray paper feed motor 122 when the drive stop timing of the tray paper feed motor 122 calculated in the processing of S1162 or S1165 is reached (S1171: Y) (S1181). As described above, since the one-way clutch is provided between the tray paper feed motor 122 and the pickup roller 113 and the paper feed separation roller 114 to be driven, the paper P is pulled out by the paper feed drawing roller 119. When the paper size is set to a free size, the paper length is detected and stored in the RAM 303 as described with reference to FIG. When the paper size is set to a size other than the free size, as described with reference to FIG. 6B, it is determined whether or not the paper sizes do not match, and processing according to the determination result is performed.

  The CPU 301 determines whether or not to continue the image forming process on the next sheet P, and determines whether or not to feed the next sheet (S1191). When the next sheet is fed (S1191; Y), the CPU 301 repeats the processes from S1131 onward. When the next sheet is not fed (S1191: N), the CPU 301 waits for the end of the image forming process to end the process (S1195: Y). When the series of processing ends, the CPU 301 repeats the processing from S1111 onward.

In the image forming apparatus of the present embodiment as described above, when the sheet P is placed on the manual feed tray 111 and the first sheet is fed, the sheet is fed in the sheet length detection mode, and the pickup roller 113 rotates. Control the time. By performing paper feed in the paper length detection mode, it is possible to prevent the second and subsequent sheets from being continuously fed. The image forming apparatus feeds the second and subsequent sheets in the normal mode based on the sheet length detected in the sheet length detection mode. As a result, the pickup roller 113 rotates to the vicinity of the trailing edge of the sheet and assists the sheet conveyance, so that the conveyance of the sheet P to the registration roller 116 can be performed stably.
In this embodiment, the case where paper is fed from the manual feed tray 111 has been described as an example. However, the same paper feed control may be performed in a normal paper feed cassette.

  DESCRIPTION OF SYMBOLS 300 ... Main control part 111 ... Manual feed tray, 113 ... Pick-up roller, 114 ... Paper feed separation roller, 117 ... Paper feed extraction sensor, 119 ... Paper feed extraction roller, 122 ... Tray paper feed motor, 123 ... Paper feed extraction motor

Claims (10)

A tray on which paper is placed;
A paper feed roller for picking up and transporting the paper from the tray;
A transport roller for transporting the paper transported from the paper feed roller to a printing unit for image formation;
Size detection means for detecting the size of the paper;
Control that stops the rotation of the paper feed roller at a timing according to the size of the paper detected by the size detection unit after the transport roller starts transporting the paper conveyed from the paper feed roller. Means.
Image forming apparatus. The control means stops rotation of the paper feed roller at a timing when a rear end portion in the paper transport direction is transported to the vicinity of the paper feed roller, and causes the paper to be fed to the transport roller from the paper feed roller. It is characterized by being pulled out and transported.
The image forming apparatus according to claim 1. The control means includes the size of the paper, the distance from the paper feed roller to the transport roller, the distance from the rear end portion of the paper to the paper feed roller when rotation of the paper feed roller is stopped, And the timing is determined according to the conveyance speed of the paper.
The image forming apparatus according to claim 2. The size detection means is provided side by side in the transport direction of the paper on the tray, and has a plurality of paper length sensors for detecting the presence or absence of the paper, and depending on the position of the paper length sensor for detecting the presence of paper, Detecting the paper length, which is the length in the transport direction of the paper placed on the tray,
The control means determines the timing to stop the rotation of the paper feed roller according to the detected paper length.
The image forming apparatus according to claim 1. The size detection means includes detection means for detecting the paper conveyed from the paper feed roller to the conveyance roller, and the time during which the detection means detects the paper and the paper detected by the conveyance roller. Detecting the paper length that is the length of the paper in the conveyance direction from the conveyance speed,
The control means determines the timing to stop the rotation of the paper feed roller according to the detected paper length.
The image forming apparatus according to claim 1. An operation unit for allowing a user to confirm the size of the paper detected by the size detection unit;
When the user confirms the size of the sheet by the operation unit, the control unit stores the size as a fixed size in a predetermined storage unit, and when the second and subsequent sheets are fed, The rotation of the paper feed roller is stopped at a timing according to the determined size,
The image forming apparatus according to claim 1. The size detecting means includes
The tray has a plurality of paper length sensors that are provided side by side in the conveyance direction of the paper to detect the presence of the paper, and is placed on the tray according to the position of the paper length sensor that detects the presence of the paper. First size detecting means for detecting a first paper length which is a length in the transport direction of the paper;
A detecting unit configured to detect the sheet conveyed from the sheet feeding roller to the conveying roller; a second unit based on a time during which the detecting unit detects the sheet and a conveying speed of the sheet by the conveying roller; A second size detecting means for detecting the paper length,
An operation unit for allowing a user to check the size of the sheet including the first sheet length;
When the user confirms the size of the sheet by the operation unit, the control unit stores the size as a determined size in a predetermined storage unit, and stores the second sheet length and the determined unit stored in the storage unit. The paper feeding is stopped if a difference from the first paper length included in the size is a predetermined threshold value or more.
The image forming apparatus according to claim 1. The first size detecting unit includes two restriction guides that sandwich the sheet placed on the tray and are slidable in a direction perpendicular to the conveyance direction, and the sheet corresponds to the position of the restriction guide. Detect the paper width, which is the length in the direction perpendicular to the transport direction,
The control means allows the user to confirm the size corresponding to the paper by the operation means based on the first paper length and the paper width detected by the first size detection means.
The image forming apparatus according to claim 7. When feeding a plurality of papers placed on the tray, the paper feed roller is used to feed paper from the start of feeding the first paper to the last paper of the plurality of papers. Characterized by staying in contact with the
The image forming apparatus according to claim 1. A tray on which paper is placed; a paper feed roller that picks up and transports the paper from the tray; a transport roller that transports the paper transported from the paper feed roller to a printing unit that forms an image; A method executed by an image forming apparatus comprising:
After the paper size is detected and the transport roller starts transporting the paper transported from the paper feed roller, the paper feed roller is rotated at a timing according to the detected size of the paper. Characterized by stopping,
Paper feeding method.