JP2004018194A - Paper conveying device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable alignment of paper and images with accuracy in the direction crossing the conveying direction of the paper. <P>SOLUTION: In this paper conveying device provided with a conveying roller, an edge sensor 40 for sensing the side end of the paper in conveyance by this conveying roller, a sensor moving means for moving the edge sensor 40 in the direction crossing the paper conveying direction, a home sensor 39 for sensing whether the edge sensor 40 exists or not at a home position to be a reference when moving the edge sensor 40, and a controller 46 for controlling movement of the edge sensor 40 by the sensor moving means based on an output signal ϕS1 of a home sensor 39, a sampling cycle T1 when the controller 46 samples the output signal ϕS1 of the home sensor 39 is set shorter than a pulse cycle T3 at input of a pulse signal ϕM3 by the controller 46 in a sensor moving motor 41 to be a driving source of the sensor moving means. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile, and more particularly, to a sheet conveying device used in the image forming apparatus.
[0002]
[Prior art]
2. Description of the Related Art Image forming apparatuses such as copiers, printers, and facsimile machines incorporate a paper transport device that transports paper along a predetermined transport path. A plurality of transport rollers are disposed on a transport path of the paper transport device. Each transport roller is rotationally driven by a motor or the like as a drive source, and the paper is transported according to the rotational drive of the transport roller.
[0003]
In an image forming apparatus provided with such a sheet transport device, alignment with an image is performed in a direction orthogonal to the sheet transport direction (hereinafter also referred to as a side direction) with a predetermined position of the sheet as a transport reference. In order to accurately align the position of the image with the sheet in the side direction, the sheet in the side direction must be located before (the image transfer position) the image is actually transferred to the sheet (upstream in the transport direction). , That is, the side registration needs to be corrected.
[0004]
As a method for correcting the position of the sheet in the side direction, an edge sensor for detecting one side edge (side edge) of the sheet is provided, and the sheet is integrated with the conveyance roller in the side direction based on an output signal of the edge sensor. A method is known in which the side edge of the sheet is adjusted to the sensing position of the edge sensor in the side direction by moving (side shifting).
[0005]
In addition, the above-described conveyance reference may be adopted as a center reference method using the center position of the sheet in the side direction as a conveyance reference, or a side reference method using one side edge (side edge) of the sheet in the side direction as the conveyance reference. There is. Among them, when the side reference method is adopted, the arrangement condition of the conveying rollers in the side direction is restricted to a minimum sheet size, so it becomes difficult to apply a uniform conveying force to sheets of various sizes. When the center reference method is adopted, by uniformly arranging the transport rollers from the center position in the side direction to the left and right, a uniform transport force can be applied to paper of various sizes. This is advantageous in that it is difficult to generate.
[0006]
However, when the side reference method is used, the edge sensor does not need to be moved in the side direction. However, when the center reference method is used, the distance from the center position of the paper width in the side direction to the paper side end is the side position. Therefore, it is necessary to move the edge sensor in the side direction in accordance with the width of the paper actually conveyed (paper size in the side direction).
[0007]
Therefore, conventionally, the edge registration is stopped at a preset home position, and the edge sensor is moved in the side direction from the home position by a movement amount corresponding to the sheet width, so that the side registration using the center reference method is performed. Correction has been realized. Conventionally, a stepping motor is used as a drive source for moving the edge sensor in the side direction, and whether or not the edge sensor is at the home position is detected by the home sensor, and based on the output signal of the home sensor, By controlling the driving of the stepping motor, the edge sensor is stopped at the home position.
[0008]
[Problems to be solved by the invention]
However, in the conventional paper conveyance device and the image forming apparatus, the sensor stop position when stopping the edge sensor at the target position in the side direction may vary, which may cause the correction of the paper position in the side direction. Was inappropriate, and there was a problem that an image was formed on a sheet in a shifted state.
[0009]
More specifically, in general, when controlling the rotation angle of the stepping motor with high accuracy, it is effective to shorten the cycle of the pulse signal input to the stepping motor. The pulse signal period (hereinafter also referred to as pulse period) becomes shorter as the number of input pulses per unit time increases, so if this pulse period is shortened, the rotation angle of the stepping motor can be more finely controlled within a certain time. It is possible to do.
[0010]
However, if the pulse cycle of the pulse signal input to the stepping motor is shortened, the relationship with the sampling cycle when sampling the sensor output signal referred to when controlling the stepping motor becomes inappropriate, and the The stop position accuracy may vary. As a specific example, when the edge sensor is set as a control target and the edge sensor is moved to a home position, extra power is supplied to the stepping motor after the edge sensor reaches the target home position and the output signal of the home sensor is switched. When a pulse signal is input and the edge sensor overruns due to the input, a variation may occur in the sensor stop position at the home position. The variation in the sensor stop position at the home position appears as a variation in the sensor stop position at the side register position when the edge sensor is moved from the home position to a position corresponding to the sheet width (hereinafter also referred to as a side register position). .
[0011]
Also, when the edge sensor is moved from the home position to the side registration position by driving the stepping motor, the number of input pulses to the stepping motor is an integer value. It is limited to a value obtained by multiplying the amount of movement by the number of input pulses (integer value). That is, assuming that the moving amount of the edge sensor based on the input of the pulse signal to the stepping motor is L (mm), the moving amount of the sensor per pulse is Lp (mm), and the number of input pulses to the stepping motor is M (pulse). , “L = P × M” holds. In such a case, the movement amount (actual sensor movement amount) L of the edge sensor cannot be accurately matched with the appropriate movement amount of the edge sensor corresponding to the width of the actually conveyed paper, and an error between the two. This may cause variations in the stop position of the edge sensor.
[0012]
If the stop position of the edge sensor varies as described above, even if the position of the sheet in the side direction is corrected using the edge sensor, the position of the sheet and the image cannot be accurately adjusted at the image transfer position.
[0013]
The present invention has been made to solve the above-described problem, and an object of the present invention is to enable accurate alignment of a sheet and an image in a direction (side direction) orthogonal to a sheet conveying direction. It is in.
[0014]
[Means for Solving the Problems]
A paper transport device according to the present invention includes a transport roller that transports a sheet, an edge sensor that detects a side edge of the sheet being transported by the transport roller, and moves the edge sensor in a direction orthogonal to the transport direction of the sheet. Sensor moving means, detecting means for detecting whether or not the edge sensor exists at a home position which is a reference when moving the edge sensor, and movement of the edge sensor by the sensor moving means based on an output signal of the detecting means And a control unit for controlling the sampling period when the control unit samples the output signal of the detection unit, and a pulse period when the control unit inputs a pulse signal to a stepping motor serving as a driving source of the sensor moving unit. It is set shorter.
[0015]
In this paper transport apparatus, the sampling period when the control unit samples the output signal of the detection unit is shorter than the pulse period when the control unit inputs a pulse signal to the stepping motor serving as the driving source of the sensor moving unit. With this setting, when the control means inputs a pulse signal to the stepping motor and moves the edge sensor to the home position, the control means recognizes the switching of the output signal of the detection means by sampling, and then sends the signal to the stepping motor. Until the input of the pulse signal is stopped, no extra pulse signal is input. Therefore, overrun of the edge sensor can be prevented. Further, in the image forming apparatus provided with the sheet transport device, it is possible to improve the accuracy of the alignment between the sheet and the image in the direction orthogonal to the sheet transport direction.
[0016]
Another sheet conveying device according to the present invention includes a conveying roller that conveys a sheet, a roller moving unit that moves the conveying roller in a direction orthogonal to a sheet conveying direction, and a side end of the sheet being conveyed by the conveying roller. An edge sensor for detecting, and a control unit for controlling the movement of the conveying roller by the roller moving unit based on the output signal of the edge sensor, and a sampling period when the control unit samples the output signal of the edge sensor, The pulse period is set shorter than the pulse period when the control unit inputs a pulse signal to the stepping motor serving as the driving source of the roller moving unit.
[0017]
In this paper transport device, the sampling period when the control unit samples the output signal of the edge sensor is shorter than the pulse period when the control unit inputs a pulse signal to the stepping motor serving as the driving source of the roller moving unit. With this setting, when the control means inputs a pulse signal to the stepping motor and moves the sheet together with the transport roller, the control means recognizes, by sampling, the switching of the output signal of the edge sensor by sampling, and then sends the signal to the stepping motor. Until the input of the pulse signal is stopped, no extra pulse signal is input. Therefore, it is possible to prevent the paper from overrun. Further, in the image forming apparatus provided with the sheet transport device, it is possible to improve the accuracy of the alignment between the sheet and the image in the direction orthogonal to the sheet transport direction.
[0018]
The image forming apparatus according to the present invention conveys a sheet on which an image is to be formed via an image transfer position where an image is transferred to the sheet, and a side of the sheet being conveyed upstream of the image transfer position. A sheet conveying means having an edge sensor for detecting an edge, a sensor moving means for moving the edge sensor from a preset home position in a direction perpendicular to the conveying direction with a moving amount corresponding to the sheet width, and forming an image. An image forming means for transferring the formed image to a sheet at an image transfer position, and an edge sensor corresponding to the amount of movement of the edge sensor and the sheet width based on the input of a pulse signal to a stepping motor serving as a driving source of the sensor moving means The difference from the proper moving amount of the image is used as correction data, and according to the correction data, the image Position is obtained by an image forming control means for variably controlling.
[0019]
In this image forming apparatus, the difference between the moving amount of the edge sensor based on the input of the pulse signal to the stepping motor serving as the driving source of the sensor moving unit and the appropriate moving amount of the edge sensor corresponding to the paper width is used as correction data. By providing image forming control means for variably controlling the image forming position of the image forming means in a direction orthogonal to the transport direction according to the correction data, when transferring an image to a sheet at the image transfer position, It is possible to accurately adjust the position of the sheet and the image in the direction orthogonal to the transport direction without depending on the sensor movement amount.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0021]
FIG. 1 is a schematic diagram illustrating a configuration example of a full-color image forming apparatus to which the present invention is applied. The illustrated image forming apparatus 1 is mainly composed of an image reading unit 2, an image forming unit 3, and a sheet conveying device 4.
[0022]
The image reading section 2 reads an image of a document set on a transparent platen (platen glass). The image reading unit 2 includes, for example, an optical scanning system including a lamp, a mirror, and a carriage, a lens system that forms an optical image read and scanned by the optical scanning system, and an optical image that is formed by the lens system. And an image reading sensor (for example, a three-line CCD sensor) that receives light and converts it into an electric signal.
[0023]
The image forming unit 3 includes four photosensitive drums 5, 6, 7, and 8 corresponding to K (black), Y (yellow), M (magenta), and C (cyan) colors, and each photosensitive drum. A quadruple tandem type configuration including four corresponding primary transfer rollers 9, 10, 11, 12, an intermediate transfer belt 13, a secondary transfer roller 14, a vacuum transport unit 15, and a fixing device 16. ing.
[0024]
A charger, a laser writing device (laser ROS), a developing device, a cleaner, and the like are disposed around each of the photosensitive drums 5, 6, 7, and 8, respectively. The charger uniformly charges the surface of the photosensitive drum, and the laser writing device forms an electrostatic latent image on the surface of the photosensitive drum charged by the charger by laser irradiation. The developing device supplies toner as a developer to the surface of the photosensitive drum to visualize (develop) the electrostatic latent image to form a toner image. The cleaner is an unnecessary cleaner remaining on the photosensitive drum. This is to remove toner.
[0025]
On the other hand, the respective primary transfer rollers 9, 10, 11, and 12 are disposed in the vicinity of the corresponding photosensitive drums 5, 6, 7, and 8 via the intermediate transfer belt 13 so as to face each other. . These primary transfer rollers 9, 10, 11, 12 transfer (primary transfer) the toner images formed on the photosensitive drums 5, 6, 7, 8 to the intermediate transfer belt 13 as described above. . The intermediate transfer belt 13 is stretched in a loop by a plurality (five in the illustrated example) of belt support rollers.
[0026]
The secondary transfer roller 14 is arranged to face the intermediate transfer belt 13. The secondary transfer roller 14 transfers (secondarily transfers) the toner image formed on the intermediate transfer belt 13 to the paper as described above, and the transfer position (secondary transfer position) of the toner image is determined by image formation. This is the image transfer position in the section 3. The vacuum transport unit 15 transports the sheet on which the toner image has been transferred by the secondary transfer roller 14 to the fixing unit 16. The fixing device 16 fixes a toner image on a sheet by heating and pressing.
[0027]
On the other hand, the paper transporting device 4 is configured to use the paper of the tray selected by the user operation or the automatic selection function from the respective papers stored in the first tray 17, the second tray 18, and the third tray 19. The sheets on the selected tray are conveyed along respective predetermined routes. In the vicinity of each of the trays 17, 18, and 19, corresponding delivery rollers 20, 21, and 22 are provided. Each of the feed rollers 20, 21, and 22 separates one by one from the corresponding trays 17, 18, and 19, and pinches (nips) the called paper to feed the paper downstream in the paper transport direction. is there. An operation panel 23 operated by a user is provided near the image reading unit 2.
[0028]
Here, a series of paper transport paths R1 to R5 each extending from a paper feed position by each of the feed rollers 20, 21 and 22 to an output tray 24 via an image transfer position in the image forming unit 3 are respectively provided. Rollers for conveyance are appropriately arranged. The sheet stored in the first tray 17 is sent out by the sending-out roller 20, and then sent to the merging and conveying section 25 via the first sheet conveying path R1. Further, the sheet stored in the second tray 18 is sent out by the sending-out roller 21 and is then sent to the merging and conveying section 25 via the first sheet conveying path R1. On the other hand, the sheets stored in the third tray 19 are directly sent to the conveyer 25 by the feed roller 22.
[0029]
Further, the sheet sent to the merged conveying section 25 is sent to the image transfer position of the image forming section 3 via the second sheet conveying path R2. Further, the sheet that has passed the image transfer position is sent to the fixing device 16 by the vacuum transfer unit 15 and then discharged to the discharge tray 24 via the third sheet transfer path R3. On the other hand, a sheet on which images are formed on both sides (first and second sides) passes through the fixing device 16 and is then sent to the two-side reversing unit 28 via the fourth sheet conveying path R4. Then, after being turned upside down, the sheet is fed again to the merging and conveying section 25 via the fifth sheet conveying path R5.
[0030]
In such a paper transport path R1 to R5, a registration roller 27 is disposed on the second paper transport path R2 from the merge transport section 25 to the image transfer position, located before (upstream) the image transfer position. Have been. The registration roller 27 is one of transport rollers for transporting the sheet, and is configured by a pair of rollers (drive roller, pinch roller) held in pressure contact with each other. The registration roller 27 feeds the sheet to the image transfer position by rotating the pair of rollers while nipping the sheet between the pair of rollers.
[0031]
When the sheet is fed by the registration roller 27, the timing at which the sheet arrives at the image transfer position is adjusted by a timing adjusting unit (not shown). The timing adjusting unit varies the speed at which the registration roller 27 conveys the sheet based on the timing at which the sheet passage sensor (not shown) provided before (upstream) the registration roller 27 detects the passage of the sheet. Thus, the arrival timing of the sheet at the image transfer position is adjusted in accordance with the arrival timing of the toner image at the image transfer position.
[0032]
On the other hand, the paper transport paths R3 and R5 are provided with curl correction units 29 and 30, respectively. Each of the curl correction units 29 and 30 is for correcting the curl (warpage) of the sheet that occurs when the fixing unit 16 fixes the toner image.
[0033]
Next, the operation of the full-color image forming apparatus 1 having the above configuration will be described. First, when an image of a document is read by the image reading unit 2, a toner image is formed by the image forming unit 3 based on the image signal obtained thereby. In the image forming section 3, while rotating the four photosensitive drums 5, 6, 7, and 8, the respective photosensitive drums 5, 6, and 6 are respectively driven by a corresponding charger, laser writing device (laser ROS), and developing device. , 7, and 8 are sequentially formed with K, Y, M, and C toner images.
[0034]
The toner images of the respective colors thus formed are sequentially transferred onto the intermediate transfer belt 13 by the primary transfer rollers 9, 10, 11 and 12. As a result, a multicolor (full color) toner image in which four color toners are superimposed is formed on the intermediate transfer belt 13. The toner image thus formed on the intermediate transfer belt 13 is carried on the intermediate transfer belt 13 and sent to an image transfer position (secondary transfer position).
[0035]
On the other hand, the paper on the tray selected by the user using the operation panel 23 or the paper on the tray selected by the automatic selection function is fed by the registration roller 27 in accordance with the timing at which the toner image reaches the image transfer position. For example, assuming that the tray selected as described above is the first tray 17, the sheet sent out by the sending-out roller 20 is sent to the merging and conveying section 25 via the first sheet conveying path R1. The sheet is sent to the image transfer position by the registration roller 27 via the second sheet conveyance path R2.
[0036]
Thus, at the image transfer position of the image forming unit 3, the toner image (full color image) carried on the intermediate transfer belt 13 is collectively transferred (secondarily transferred) to the sheet by the secondary transfer roller 14. Thereafter, the paper is sent to the fixing device 16 by the vacuum transport unit 15, where the toner image is subjected to a fixing process, and then discharged to the discharge tray 24 via the third paper transport path R <b> 3.
[0037]
The paper on which image formation is performed on both sides (paper to be copied on both sides) is sent to the double-sided reversing unit 28 via the fourth paper conveyance path R4, where it is turned over to the fifth paper conveyance path. Sent to R5. Thereafter, the sheet is conveyed along the fifth sheet conveying path R5, and then is re-sent to the merging and conveying section 25 with the timing adjusted by the rotation of the sending-out roller 31. Thereafter, after the toner image is transferred and fixed to the paper in the same manner as described above, the paper is discharged to the discharge tray 24 via the third paper conveyance path R3.
[0038]
FIG. 2 is a schematic diagram illustrating a mechanical configuration of a sheet position correcting device provided in the sheet conveying device 4 according to the embodiment of the present invention. The illustrated paper position correcting device sandwiches the paper 26 conveyed from the upstream side along the paper conveyance direction Y by the registration rollers 27, and places the registration rollers 27 in a direction orthogonal to the conveyance direction Y (X1 direction or The position (side registration) of the sheet 26 in the side direction is corrected by moving the sheet 26 in the side direction (X2 direction).
[0039]
The registration rollers 27 are provided in a plurality (four in the illustrated example) in a direction orthogonal to the transport direction Y. Each of the registration rollers 27 is constituted by a pair of rollers, one of which is a drive roller and the other is a pinch roller. The registration rollers 27 are arranged in a left-right uniform positional relationship with respect to a designed paper width center reference position K at which the center position of the paper width should be aligned in a direction (side direction) orthogonal to the transport direction Y. In each of the registration rollers 27, the drive roller on the rotation drive side is attached to the rotation shaft 32, and the pinch roller on the rotation driven side is attached to another rotation shaft arranged parallel to the rotation shaft 32. I have. Each rotating shaft is rotatably supported by bearing means (not shown) and is movably supported in an axial direction (a direction orthogonal to the transport direction Y).
[0040]
A gear 33 is provided at one end of the rotating shaft 32, and a rack 34 is provided at the other end of the rotating shaft 32. The gear 33 is mounted coaxially with the rotating shaft 32, and is provided so as to be rotatable integrally with the rotating shaft 32 using, for example, a locking means using a key and a key groove. On the other hand, the rack 34 is attached along the axial direction of the rotating shaft 32, and is provided so as to be movable integrally with the rotating shaft 32 in the axial direction of the rotating shaft 32. The orientation of the rack 34 about the rotation shaft 32 is held in a fixed direction by a guide means (not shown), and the rack 34 is free to rotate with respect to the rotation shaft 32. Further, the gear 33 meshes with a drive gear 36 which is axially mounted on a motor shaft of the paper transport motor 35, and the rack 34 meshes with a pinion 38 which is axially mounted on a motor shaft of the side shift motor 37.
[0041]
The paper transport motor 35 is configured by a stepping motor capable of switching between normal rotation and reverse rotation, and the side shift motor 37 is also configured by a stepping motor capable of switching between normal rotation and reverse rotation. Then, when the sheet conveying motor 35 is rotated by the input of the pulse signal, the rotating force is transmitted by the engagement of the driving gear 36 and the gear 33, so that the rotating shaft 32 rotates integrally with the registration roller 27. When the side shift motor 37 is rotated by the input of the pulse signal, the rotational force is transmitted by the engagement of the pinion 38 and the rack 34, so that the rotating shaft 32 is orthogonal to the conveyance direction Y integrally with the registration roller 27. Move in the direction. In this case, the rotation direction and the rotation amount of the registration roller 27 correspond to the rotation direction and the rotation amount of the paper transport motor 35, respectively, and the movement direction and the movement amount of the registration roller 27 correspond to the rotation direction of the side shift motor 37 respectively. This corresponds to the rotation amount.
[0042]
A home sensor 39 and an edge sensor 40 are provided in front (upstream side) of the registration roller 27. The home sensor 39 serves as a detecting unit for detecting whether or not the edge sensor 40 is at the home position HP. The home sensor 39 is provided in a fixed state. The edge sensor 40 detects one side edge of the sheet 26. The edge sensor 40 is provided so as to be movable in a direction (side direction) orthogonal to the transport direction Y by a sensor moving unit described later. The sensor moving motor 41 is a drive source of the sensor moving means.
[0043]
The home position HP of the edge sensor 40 is a reference position when the edge sensor 40 is moved in a direction orthogonal to the transport direction Y. Here, when the edge sensor 40 is moved in the side direction according to the sheet width. Is the home position of the edge sensor 40. The home sensor 39 is configured by a transmission type optical sensor, and the edge sensor 40 is configured by a reflection type optical sensor. Further, the sensor moving motor 41 is configured by a stepping motor capable of switching between forward rotation and reverse rotation.
[0044]
FIG. 3 is a schematic diagram showing a specific configuration example of the sensor moving means. 3, the edge sensor 40 is attached to an endless timing belt 42. The timing belt 42 is stretched by a drive pulley 43 and a pair of idle pulleys 44A and 44B. The drive pulley 43 is mounted on the motor shaft of the sensor moving motor 41. On the other hand, the edge sensor 40 is fixedly attached to the timing belt 42 between the pair of idle pulleys 44A and 44B. A detection piece 45 is attached to the edge sensor 40. The mounting position of the detection piece 45 is adjusted so that the detection piece 45 blocks the optical axis of the home sensor 39 when the edge sensor 40 exists at the preset home position HP.
[0045]
When the sensor moving motor 41 is driven in the sensor moving means having the above-described configuration, the timing belt 42 moves around by the rotation of the drive pulley 43 and the rotation of the pair of idle pulleys 44A and 44B driven by the motor. At this time, the edge sensor 40 moves in a direction (X1 direction or X2 direction) orthogonal to the sheet conveyance direction according to the rotation of the timing belt 42 between the pair of idle pulleys 44A and 44B. In this case, the movement direction and the movement amount of the edge sensor 40 correspond to the rotation direction and the rotation operation amount of the sensor movement motor 41, respectively.
[0046]
FIG. 4 is a block diagram showing a control configuration of the sheet position correcting device employed in the sheet conveying device 4 according to the embodiment of the present invention. In FIG. 4, the controller 46 individually controls the driving (rotation direction, rotation operation amount, rotation start timing, rotation stop timing) of the sheet conveyance motor 35, the side shift motor 37, and the sensor movement motor 41. In this case, since each of the motors 35, 37, and 41 is constituted by a stepping motor, the controller 46 supplies the motors 35, 37, and 41 with pulse signals φM1, φM2, By inputting (applying) φM3 at a predetermined pulse cycle, the driving of each of the motors 35, 37, 41 is individually controlled.
[0047]
A paper size sensor 47 and a paper passage sensor 48 are connected to the controller 46 in addition to the home sensor 39 and the edge sensor 40 described above. The paper size sensor 47 detects the size of the paper actually conveyed, and the paper passage sensor 48 detects the passage of the paper on the paper conveyance path (passage of the front end / rear end). The output signal (on / off signal) φS1 of the home sensor 39 is switched depending on whether or not the edge sensor 40 is present at the home position HP, and the output signal (on / off signal) φS2 of the edge sensor 40 is Is switched depending on whether or not a sheet is present at the sensing position.
[0048]
On the other hand, the controller 46 repeatedly samples the output signal φS1 of the home sensor 39 and the output signal φS2 of the edge sensor 40 at a predetermined sampling cycle. Incidentally, in the present embodiment, when the edge sensor 40 is at the home position HP, the output signal φS1 of the home sensor 30 is turned on. It is also assumed that the output signal φS2 of the edge sensor 40 is turned on when a sheet is present at the sensing position of the edge sensor 40.
[0049]
Here, the sampling period when sampling the output signal φS1 of the home sensor 39 is “T1”, the sampling period when sampling the output signal φS2 of the edge sensor 40 is “T2”, and the pulse signal input to the sensor moving motor 41 Assuming that the pulse period of φM3 is “T3” and the pulse period of the pulse signal φM2 input to the side shift motor 37 is “T4”, as shown in FIG. 5, the sampling period T1 and the pulse period T3 satisfy “T1 <T3”. The relationship is set such that the sampling period T2 and the pulse period T4 have a relationship of “T2 <T4”.
[0050]
As long as the relationship between the sampling period and the pulse period (T1 <T3, T2 <T4) is satisfied, the sampling periods T1 and T2 may be set to the same period or may be set to different periods. May be. Further, the sampling periods T1 and T2 may be synchronized with each other or may be asynchronous. This is the same for the pulse periods T3 and T4.
[0051]
Next, a description will be given of a paper position correction process performed based on the control of the controller 46. First, in a state where the edge sensor 40 is stopped at the home position HP, when the sheet 26 is conveyed from the upstream side in the conveying direction Y toward the registration roller 27, the controller 46 sets the leading end of the sheet 26 to the registration roller 27. Before reaching, the pulse signal φM3 is input to the sensor movement motor 41, and the edge sensor 40 is moved from the home position to the side registration position corresponding to the size of the sheet 26 (sheet width) by driving the sensor movement motor 41. At the same time, the pulse signal φM1 is input to the paper conveyance motor 35, and the registration roller 27 is rotated by driving the paper conveyance motor 35 (see FIGS. 6A and 6B).
[0052]
At that time, the timing of inputting the pulse signal φM3 to the sensor moving motor 41 (in other words, the timing of starting the driving of the sensor moving motor 41) is controlled based on the output signal of the paper passage sensor 48. The number of pulses of the pulse signal φM3 input to the sensor moving motor 41 is set according to the size (paper width) of the paper 26 detected by the paper size sensor 47. The correspondence between the sheet width and the set pulse number is given to the controller 46 as control data in advance.
[0053]
Thereafter, when the leading end of the sheet 26 advances downstream of the edge sensor 40 in front of the registration roller 27, the controller 46 recognizes the direction of the position shift of the sheet 26 in the side direction based on the output signal φS2 of the edge sensor 40. . Then, when the leading end of the sheet 26 reaches the registration roller 27, the controller 46 drives the side shift motor 37 to move the registration roller 27 in the direction for correcting the above-described positional deviation.
[0054]
More specifically, as shown in FIG. 6C, when the sheet 26 is present at the sensing position of the edge sensor 40 and the output signal φS2 of the edge sensor 40 is in the ON state, As shown in D), when the leading edge of the paper 26 reaches the registration roller 27, a pulse signal φM2 is input to the side shift motor 37, and the side shift motor 37 is driven to move the registration roller 27 in the X1 direction in the drawing. Move. As a result, the sheet 26 moves in the X1 direction integrally with the registration roller 27 while being held by the registration roller 27. During this movement, the controller 46 samples the output signal φS2 of the edge sensor 40. When the side edge of the sheet 26 moving in the X1 direction reaches the sensing position of the edge sensor 40, and thereby recognizes that the output signal φS2 of the edge sensor 40 has been switched from the on state to the off state, the controller at that time 46 stops the input of the pulse signal φM2 to stop driving the side shift motor 37.
[0055]
On the other hand, as shown in FIG. 7A, when the sheet 26 is not present at the sensing position of the edge sensor 40 and the output signal φS2 of the edge sensor 40 is turned off, As shown in (B), when the leading edge of the paper 26 reaches the registration roller 27, a pulse signal φM2 is input to the side shift motor 37, and the side shift motor 37 is driven to move the registration roller 27 in the X2 direction in the drawing. Move to As a result, the sheet 26 moves in the X2 direction integrally with the registration roller 27 while being held by the registration roller 27. During this movement, the controller 46 samples the output signal φS2 of the edge sensor 40. Then, when the side edge of the sheet 26 moving in the X2 direction reaches the sensing position of the edge sensor 40 and thereby recognizes that the output signal φS2 of the edge sensor 40 has been switched from the off state to the on state, the controller at that point in time 46 stops the input of the pulse signal φM2 to stop driving the side shift motor 37.
[0056]
Thus, the side edge of the sheet 26 is aligned with the sensing position of the edge sensor 40, and in this state, the sheet 26 is fed to the image transfer position as the registration roller 27 rotates. Thereafter, when the trailing edge of the sheet 26 passes through the registration roller 27 and the subsequent sheet is conveyed toward the registration roller 27, the controller 46 outputs the next sheet based on the output signal of the sheet size sensor 47. It is determined whether the size (sheet width) of the sheet is the same as the size (sheet width) of the sheet 26 conveyed before. Then, when it is determined that the size is the same, the edge sensor 40 is maintained at a state where it is stopped at the previous side registration position, and when it is determined that the size is different, the edge sensor 40 is temporarily returned to the home position HP. Is moved to the side registration position corresponding to the size of the succeeding sheet. If there is no succeeding sheet following the sheet 26 (all sheets have been sent to the image transfer position), the edge sensor 40 is returned to the home position HP.
[0057]
In returning the edge sensor 40 to the home position HP, the controller 46 inputs the pulse signal φM3 to the sensor movement motor 41 and moves the edge sensor 40 toward the home position HP by driving the sensor movement motor 41. During this movement, the controller 46 samples the output signal φS1 of the home sensor 39. When the controller 46 recognizes that the output signal φS1 of the home sensor 39 has been switched from the off state to the on state, the controller 46 stops the input of the pulse signal φM3 and stops driving the sensor moving motor 41 at that time.
[0058]
In the above-described paper position correction processing, the relationship between the sampling cycle T1 corresponding to the home sensor 39 and the pulse cycle T3 corresponding to the sensor moving motor 41 is set to “T1 <T3”, so that the edge sensor in the side direction. It is possible to accurately stop at the position where the target 40 is aimed. In addition, by setting the relationship between the sampling period T2 corresponding to the edge sensor 40 and the pulse period T4 corresponding to the side shift motor 37 to "T2 <T4", the sheet 26 accurately stops at the position where the sheet 26 is aimed in the side direction. It is possible to do.
[0059]
More specifically, when the sampling period T1 is set shorter than the pulse period T3, a plurality of pulse signals φM3 are not input to the sensor movement motor 41 within the sampling period T1. Therefore, when the edge sensor 40 is moved to the home position HP, the controller 46 recognizes by sampling that the output signal φS1 of the home sensor 39 has been switched from the off state to the on state, and then sends the signal to the sensor movement motor 41. Until the input of the pulse signal φM3 is cut off, no extra pulse signal φM3 is input to the sensor movement motor 41. Thus, it is possible to eliminate the variation in the position due to the overrun of the edge sensor 40 and to improve the stop position accuracy of the edge sensor 40 with respect to the home position HP.
[0060]
As a result, when the edge sensor 40 is moved from the home position HP to the side registration position by the input of the pulse signal φM3 to the sensor movement motor 41, the edge sensor 40 can always be moved from a fixed position. At this time, the amount of movement of the edge sensor 40 is uniquely determined by the number of pulses of the pulse signal φM3 input to the sensor movement motor 41. Therefore, if the movement start position of the edge sensor 40 is always constant, the edge sensor 40 can be stopped at a constant position even at the side registration position.
[0061]
When the sampling period T2 is set shorter than the pulse period T4, a plurality of pulse signals φM2 are not input to the side shift motor 37 within the sampling period T2. Therefore, when moving the paper 26 to the side registration position, the controller 46 recognizes by sampling that the output signal φS2 of the edge sensor 40 has been switched from the on state to the off state or from the off state to the on state, and then the side signal is output. Until the input of the pulse signal φM2 to the shift motor 37 is cut off, no extra pulse signal φM2 is input to the side shift motor 37. As a result, it is possible to eliminate the variation in the position due to the overrun of the sheet 26 and to improve the accuracy of the stop position of the sheet 26 with respect to the side registration position.
[0062]
As a result, when the side edge of the sheet 26 is moved in a direction approaching the side registration position (the sensing position of the edge sensor 40) by the input of the pulse signal φM2 to the side shift motor 37, the side edge of the sheet 26 The movement of the paper 26 can be stopped at the same time when the target side registration position is reached. Therefore, the side edge of the sheet 26 can be accurately matched with the side registration position.
[0063]
By the way, the form of paper conveyance is classified into vertical conveyance (SEF; Short Edge feed) and horizontal conveyance (LEF; Long Edge feed) depending on the direction of the paper when the paper is conveyed. The vertical conveyance refers to a form in which the short side of the paper is conveyed in the conveyance direction (in other words, the long side of the paper is directed in the side direction), and the horizontal conveyance is the long side of the paper In the transport direction (in other words, with the short side of the paper facing the side direction). Therefore, even if the paper is the same size, the paper size (paper width) in the side direction differs depending on whether the paper is transported vertically or horizontally.
[0064]
Therefore, as shown in FIG. 8A, the home position HP of the edge sensor 40 in the case where the center reference method is adopted is set to the width of the A3 size paper transported vertically or the width of the A4 size paper transported horizontally. When the corresponding side registration position is set, when the A3 size paper is transported vertically or the A4 size paper is transported horizontally, the home position HP remains the side registration position, so the edge sensor 40 is moved from the home position HP. There is no need to make it.
[0065]
On the other hand, when the paper width in the side direction is smaller than the A3 size paper is vertically conveyed, that is, when the B4 size, A4 size, and B5 size papers are respectively conveyed vertically, or when the B5 size paper is In the case of conveyance, it is necessary to move the edge sensor 40 from the home position HP to the side registration position corresponding to each sheet width.
[0066]
At this time, when the A3 size paper is conveyed vertically or the A4 size paper is conveyed horizontally, the paper width W1 is 297 mm, whereas when the B4 size paper is conveyed vertically or when the B5 size paper is conveyed. Is 257 mm when the sheet is conveyed sideways. Therefore, when the B4 size paper is conveyed vertically or the B5 size paper is conveyed horizontally, the appropriate movement amount of the edge sensor 40 in the side direction is 20 mm from the calculation formula of “(W1−W2) / 2”. Become. Further, when the A4 size paper is transported in the vertical direction, the paper width W3 is 210 mm. Therefore, in this case, the appropriate movement amount of the edge sensor 40 in the side direction is calculated from the formula of “(W1−W3) / 2”. 43.5 mm. Further, when the B5 size paper is transported in the vertical direction, the paper width W4 is 182 mm. Therefore, in this case, the appropriate movement amount of the edge sensor 40 in the side direction is obtained from the calculation formula of “(W1−W4) / 2”. 57.5 mm.
[0067]
On the other hand, when the pulse signal φM3 is input to the sensor movement motor 41, the sensor movement amount per pulse is, for example, 0.6 mm as shown in FIG. The number of pulses of the pulse signal φM3 input when the paper is transported vertically or when the B5 size paper is transported horizontally is “33”, and the pulse signal φM3 that is input when the A4 size paper is transported vertically. It is assumed that the number of pulses is set to “72” and the number of pulses of the pulse signal φM3 input when vertically conveying B5 size paper is set to “95”.
[0068]
In such a case, as shown in FIG. 8B, the actual sensor movement amount corresponding to the set pulse number “33” is 19.8 mm from the calculation formula of “0.6 × 33”. Also, the actual sensor movement amount corresponding to the set pulse number “72” is 43.2 mm from the calculation formula of “0.6 × 72”, and the actual sensor movement amount corresponding to the set pulse number “95” is “0”. 0.6 × 95 ”is 57 mm.
[0069]
Here, comparing the above-described appropriate movement amount of the sensor and the sensor movement amount corresponding to the set pulse number, when the B4 size paper is conveyed vertically or the B5 size paper is conveyed horizontally, both sensor movements are detected. The difference (20-19.8) in the amount is +0.2 mm, and when the A4 size paper is conveyed in the vertical direction, the difference (43.5-43.2) in both sensor movement amounts is +0.3 mm, and B5 When a paper sheet of a size is conveyed vertically, the difference (57.5-57) between the two sensor movement amounts is +0.5 mm. The difference between the sensor movement amounts is a positional error when the edge sensor 40 is stopped at the side registration position where the side edge of the sheet 26 should be aligned.
[0070]
Therefore, in the image forming apparatus according to another embodiment of the present invention, the difference (error) of the above-described sensor movement amount is used as correction data at the time of image formation, and the image forming unit is moved in a direction orthogonal to the transport direction according to the correction data. 3 has an image forming control function for variably controlling the image forming position. More specifically, in the image forming apparatus 1, control data in which the paper widths of various sizes are associated with the correction data is stored (stored) in a memory or the like of a main control unit (not shown) in advance. When the paper size sensor 47 detects the paper size actually conveyed, the main control unit reads out the correction data associated with the paper size (paper width), and the main control unit uses the laser writing device (ROS) in the main scanning direction. The image writing timing is controlled (adjusted).
[0071]
The laser writing device scans laser light emitted from a semiconductor laser or the like in the axial direction of the photosensitive drum by rotation of a polygon mirror (rotating polygon mirror) to write an image (electrostatic latent image). Therefore, if the writing timing of the image in the main scanning direction by the laser writing device is advanced, the image forming position on the sheet is displaced to one side in the side direction, and if the writing timing of the image in the main scanning direction by the laser writing device is delayed, The image forming position is displaced to the other side in the side direction. Whether the image writing timing by the laser writing device is advanced or delayed is appropriately switched and controlled depending on whether the correction data is a positive (+) value or a negative (-) value. Further, how fast or how late the image writing timing is to be controlled is appropriately controlled by the size of the correction data (the value of the absolute error).
[0072]
As described above, by controlling the image writing timing (the image writing position corresponding to the side direction) by the laser writing device using the correction data associated with the sheet width as described above, even if the edge sensor 40 Even if the movement amount of the image has an error with respect to the appropriate movement amount, the image writing position can be appropriately corrected according to the correction data corresponding to the error. Thereby, when the side edge of the sheet is aligned with the side registration position using the edge sensor 40, and the image is transferred to the aligned sheet at the image transfer position, the side edge is not dependent on the sensor movement amount per pulse. It is possible to accurately align the position of the sheet with the image in the direction.
[0073]
In the above example, the set pulse number of the pulse signal φM3 input when the B5 size paper is conveyed in the vertical direction is set to “95”, and the correction data corresponding to the error of the sensor movement amount at this time is set to 0. However, when the number of input pulses is set to “96”, the correction data may be set to −0.1 mm. Similarly, when the number of input pulses when the A4 size paper is transported in the vertical direction is set to “73”, the correction data is set to −0.3 mm, and when the B4 size paper is transported in the vertical direction or the B5 size paper is transported. When the number of input pulses when the paper is conveyed horizontally is set to “34”, the correction data may be set to −0.4 mm.
[0074]
Further, in the above example, the home position of the edge sensor 40 is set to the side registration position corresponding to the width of the A3 size paper conveyed in the vertical direction. However, other than this, for example, as shown in FIG. In addition, the present invention can be similarly applied to a case where the designed paper width center reference position K in which the center position of the paper width should be aligned in the side direction is set to the home position HP of the edge sensor 40.
[0075]
That is, when the home position HP of the edge sensor 40 is set to the above-described paper width center reference position K in the design, the paper width W1 when the A3 size paper is transported vertically or the A4 size paper is transported horizontally. = 297 mm, the appropriate amount of movement of the edge sensor 40 in the side direction is 148.5 mm, which is half of the paper width W1. Similarly, when the B4 size paper is transported vertically or the B5 size paper is transported horizontally, the appropriate movement amount of the edge sensor 40 corresponding to the paper width W2 = 257 mm is 128.5 mm, and the A4 size paper is transported. The appropriate movement amount of the edge sensor 40 corresponding to the paper width W3 = 210 mm when the paper is transported vertically is 105 mm, and the edge sensor corresponding to the paper width W4 = 182 mm when the B5 size paper is transported vertically. The appropriate moving distance of the forty is 91 mm.
[0076]
On the other hand, when the pulse signal φM3 is input to the sensor movement motor 41, the sensor movement amount per pulse is, for example, 0.6 mm as shown in FIG. The pulse number of the pulse signal φM3 input in the case of conveying vertically or the size of A4 size paper is set to “247”, and in the case of conveying the size of B4 size paper or the size of B5 size paper horizontally. In this case, the pulse number of the pulse signal φM3 to be input is “214”, the pulse number of the pulse signal φM3 to be input when the A4 size paper is vertically conveyed is “175”, and the B5 size paper is It is assumed that the number of pulses of the pulse signal φM3 input when the paper is transported in the direction is set to “151”.
[0077]
In such a case, as shown in FIG. 9B, the actual sensor movement amount corresponding to the set pulse number “247” is 148.2 mm, and the actual sensor movement amount corresponding to the set pulse number “214” is 128. 0.4 mm. Further, the actual sensor movement amount corresponding to the set pulse number “175” is 105 mm, and the actual sensor movement amount corresponding to the set pulse number “151” is 90.6 mm.
[0078]
Therefore, the difference (error) between the above-described proper movement amount of the sensor and the sensor movement amount corresponding to the set number of pulses is +0. 0 when the A3 size paper is transported vertically or the A4 size paper is transported horizontally. 3 mm, +0.1 mm when transporting B4 size paper vertically or B5 size paper horizontally, ± 0 mm when transporting A4 size paper vertically, and B5 size paper. It becomes +0.4 mm when conveying vertically. Therefore, as a configuration of the image forming apparatus, the image forming control function of variably controlling the image forming position in the side direction according to the correction data using the difference of the sensor movement amount as the correction data at the time of image formation as described above is provided. Thus, the position of the sheet and the image can be accurately adjusted in the side direction without depending on the sensor movement amount per pulse.
[0079]
In the above embodiment, the tandem type image forming apparatus 1 including a plurality of photosensitive drums has been described as an example. However, the present invention is not limited to this, and the present invention is not limited thereto. Alternatively, the present invention is similarly applicable to an image forming apparatus that forms a color image.
[0080]
Further, regarding the configuration in which the sampling period T2 when the controller 46 samples the output signal of the edge sensor 40 is set shorter than the pulse period T4 when the controller 46 inputs the pulse signal φM2 to the side shift motor 37, The present invention is also applicable to a sheet conveying device that corrects a sheet position in a side direction according to a side reference method that does not need to move the sensor 40 and an image forming apparatus including the same.
[0081]
【The invention's effect】
As described above, according to the paper transporting apparatus of the present invention, the control unit samples the output signal of the detection unit when the control unit samples the pulse signal to the stepping motor serving as the driving source of the sensor moving unit. By setting the pulse period shorter than the input pulse period, it is possible to prevent the input of an extra pulse signal to the stepping motor and the overrun of the edge sensor due to this, and to improve the stop position accuracy of the edge sensor at the home position. Can be. Therefore, in the image forming apparatus provided with the sheet conveying device, it is possible to enhance the accuracy of the alignment between the sheet and the image in the direction orthogonal to the sheet conveying direction.
[0082]
According to another aspect of the present invention, the control unit inputs a pulse signal to a stepping motor serving as a driving source of the roller moving unit, the sampling period when the control unit samples the output signal of the edge sensor. By setting the pulse period to be shorter than the pulse period at the time of inputting, it is possible to prevent the input of an extra pulse signal to the stepping motor and the overrun of the sheet due to the input, thereby improving the accuracy of the stop position of the sheet at the side registration position. Therefore, in the image forming apparatus provided with the sheet conveying device, it is possible to enhance the accuracy of the alignment between the sheet and the image in the direction orthogonal to the sheet conveying direction.
[0083]
Further, according to the image forming apparatus of the present invention, the difference between the moving amount of the edge sensor based on the input of the pulse signal to the stepping motor serving as the driving source of the sensor moving unit and the proper moving amount of the edge sensor corresponding to the sheet width is obtained. The difference is used as correction data, and image forming control means for variably controlling an image forming position by the image forming means in a direction orthogonal to the transport direction according to the correction data is provided, which depends on a sensor movement amount per pulse. Thus, the position of the sheet and the image can be accurately adjusted in the direction orthogonal to the transport direction.
[Brief description of the drawings]
FIG. 1 is a schematic diagram illustrating a configuration example of a full-color image forming apparatus to which the present invention is applied.
FIG. 2 is a schematic diagram illustrating a mechanical configuration of a sheet position correcting device provided in the sheet conveying device according to the embodiment of the present invention.
FIG. 3 is a schematic diagram showing a specific configuration example of a sensor moving unit.
FIG. 4 is a block diagram illustrating a control configuration of a sheet position correcting device employed in the sheet conveying device according to the embodiment of the present invention.
FIG. 5 is a diagram showing a relationship between a sampling period of a sensor and a pulse period of a motor.
FIG. 6 is a diagram (part 1) illustrating a basic operation example of the paper position correction device.
FIG. 7 is a diagram (part 2) illustrating a basic operation example of the paper position correction device.
FIG. 8 is a diagram (part 1) for describing the configuration of an image forming apparatus according to another embodiment of the present invention.
FIG. 9 is a diagram (part 2) for describing the configuration of an image forming apparatus according to another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 3 ... Image forming part, 4 ... Paper conveyance apparatus, 27 ... Registration roller, 37 ... Side shift motor, 39 ... Home sensor (detection means), 40 ... Edge sensor, 41 ... Sensor moving motor, 46 …controller

Claims (6)

A transport roller that transports the paper, an edge sensor that detects a side edge of the paper being transported by the transport roller, a sensor moving unit that moves the edge sensor in a direction orthogonal to the transport direction of the paper, and the edge sensor. Detecting means for detecting whether or not the edge sensor is present at a home position serving as a reference when moving, and controlling means for controlling movement of the edge sensor by the sensor moving means based on an output signal of the detecting means And with
A sampling period when the control unit samples the output signal of the detection unit is set shorter than a pulse period when the control unit inputs a pulse signal to a stepping motor serving as a driving source of the sensor moving unit. A paper transport device, comprising: A transport roller that transports the paper, a roller moving unit that moves the transport roller in a direction perpendicular to the transport direction of the paper, an edge sensor that detects a side edge of the paper being transported by the transport roller, and an edge sensor. And control means for controlling the movement of the transport roller by the roller moving means based on the output signal,
A sampling period when the control unit samples the output signal of the edge sensor is set shorter than a pulse period when the control unit inputs a pulse signal to a stepping motor serving as a driving source of the roller moving unit. A paper transport device, comprising: A transport roller that transports the paper, a roller moving unit that moves the transport roller in a direction orthogonal to the transport direction of the paper, an edge sensor that detects a side edge of the paper being transported by the transport roller, and the edge sensor. A sensor moving unit for moving the edge sensor in a direction orthogonal to the sheet conveying direction, a detecting unit for detecting whether or not the edge sensor exists at a home position which is a reference when the edge sensor is moved, And control means for controlling the movement of the transport roller by the roller moving means based on the output signal, and controlling the movement of the edge sensor by the sensor moving means based on the output signal of the detecting means.
A sampling period when the control unit samples the output signal of the detection unit is set shorter than a pulse period when the control unit inputs a pulse signal to a stepping motor serving as a driving source of the sensor moving unit. The sampling period when the control unit samples the output signal of the edge sensor is set shorter than the pulse period when the control unit inputs a pulse signal to a stepping motor serving as a driving source of the roller moving unit. A sheet transport device comprising: An image forming apparatus comprising the sheet conveying device according to claim 1. An edge sensor that conveys a sheet to be subjected to image formation via an image transfer position where an image is transferred to the sheet and detects a side edge of the sheet being conveyed upstream of the image transfer position, Paper transport means having a sensor moving means for moving the edge sensor in a direction perpendicular to the transport direction with a travel amount corresponding to the paper width from a preset home position,
Image forming means for forming an image and transferring the formed image to a sheet at the image transfer position;
The difference between the movement amount of the edge sensor based on the input of the pulse signal to the stepping motor serving as the driving source of the sensor movement means and the appropriate movement amount of the edge sensor corresponding to the paper width is used as correction data, and the correction data And an image forming control means for variably controlling an image forming position of the image forming means in a direction orthogonal to the transport direction in accordance with the following. The image forming unit includes an image writing unit that writes an image on a photoconductor,
The image forming control unit variably controls an image forming position in a direction orthogonal to the transport direction by adjusting an image writing timing in the main scanning direction by the image writing unit. 6. The image forming apparatus according to 5.

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