JP5513473B2 - Recording paper transport device, document feeding device, and image forming apparatus including them - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus, and more particularly to a recording paper conveying apparatus, a document feeding apparatus, and an image forming apparatus including the recording paper conveying apparatus that can prevent wasteful recording paper bending in front of a registration roller and thereby make the product compact. Relates to the device.

  In an image forming apparatus such as a copying machine, a recording sheet is pulled out from a paper feed tray and conveyed to an image forming unit, and an image is formed (printed) on the surface of the recording sheet. For example, when an electrophotographic system is used, a toner image carried on a photosensitive drum or a transfer body is transferred onto a conveyed recording sheet to obtain an image. The recording paper is pulled out from the paper feed tray by a roller, is sandwiched between opposing rollers arranged along the recording paper transport path, and is transported by the rotation of the roller. When the recording paper is pulled out from the paper supply tray, the leading edge of the recording paper may not be pulled out in a state orthogonal to the pulling-out direction and may be pulled out in a slightly rotated state. Even during the conveyance of the recording paper, the leading edge of the recording paper may not be conveyed in a state orthogonal to the conveyance direction. When the recording paper is conveyed to the transfer unit in a skewed state as described above, an image inclined with respect to the vertical or horizontal side of the recording paper is formed on the recording paper.

  A similar problem may occur when an original is transported to a scan position using an automatic document feeder (ADF) in the image forming apparatus. When the document is conveyed obliquely, the document is scanned obliquely.

  For this reason, conventionally, the skew of the recording sheet is corrected immediately before the registration roller for supplying the recording sheet to the transfer unit (upstream in the recording sheet conveyance direction). Specifically, the recording paper is conveyed to a registration roller that has stopped rotating by a conveyance roller (hereinafter also referred to as a pre-registration roller) disposed immediately before the registration roller, and the leading edge of the recording paper is brought into contact with the registration roller. After forming the deflection on the recording paper, the registration paper is rotated to convey the recording paper. For example, as shown in FIG. 1, the speeds of the registration roller and the pre-registration roller are controlled. The upper graph shows the time change of the speed Vr of the registration roller, and the lower graph shows the time change of the speed Vp of the pre-registration roller. The recording paper is conveyed by the pre-registration roller to just before the registration roller, and the pre-registration roller is temporarily stopped (time t0). The registration roller stops rotating until the leading edge of the recording paper reaches a predetermined position (immediately before the registration roller) and the pre-registration roller stops rotating. At time t1, the pre-registration roller starts to rotate (the registration roller is stopped). Immediately thereafter, the leading edge of the recording paper comes into contact with the registration roller, and a predetermined deflection is formed on the recording paper by time t3. Thereafter, the registration roller is rotated to convey the recording paper. As a result, even if the recording paper is conveyed in a skewed state up to the front of the registration roller, the recording paper in which the skew feeding is corrected is supplied to the transfer unit. However, in the period from time t3 to t6, the pre-registration roller rotates at a constant speed Vc, whereas the registration roller speed Vr is smaller than the pre-registration roller speed Vc, so that the recording paper is more bent. growing. The length corresponding to the area of the region S0 in which the diagonal line is drawn in FIG.

  In order to solve this problem, as shown in FIG. 2, the following Patent Document 1 discloses that a predetermined deflection is formed on a sheet (recording paper) by rotation of a pre-registration roller (pre-registration roller), and then a registration roller and A technique for preventing an increase in bending by accelerating the pre-registration roller at the same acceleration at a constant speed at the same time is disclosed.

JP 2010-111472 A

  However, in Patent Document 1, the rotation speed of the pre-registration roller for forming the predetermined deflection is a low speed (100 mm / mm) corresponding to the self-starting frequency at which the stepping motor that drives the pre-registration roller can start rotating. s), and since the pre-registration roller is once stopped, it takes time to form an image on the recording paper, and the performance of the image forming apparatus cannot be improved. This is especially a problem for high-speed machines.

  Therefore, the present invention can prevent wasteful bending of the recording paper or document immediately before the registration roller without degrading the performance, and a space for bending and holding the recording paper or document in an appropriate shape. An object of the present invention is to provide a compact recording paper conveyance device, a document feeding device, and an image forming apparatus including them.

  The above object can be achieved by the following.

  That is, the recording paper transport device according to the present invention includes a registration roller and a transport roller disposed adjacent to the registration roller and upstream of the recording paper transport direction, and transports the recording paper by rotating the transport roller. A recording paper transport device that forms a predetermined deflection on the recording paper by bringing the leading end of the recording paper into contact with the stopped registration roller, and forms the deflection on the recording paper by rotating the transport roller at a constant speed. In a state where the deflection is formed and the rotation speed of the conveyance roller is maintained at a constant speed, the registration roller is rotated to start conveyance of the recording paper by the registration roller, and the rotation speed of the registration roller becomes a predetermined speed. Sometimes, the rotation of the transport roller is further accelerated from a constant speed.

  Preferably, the recording paper transport device temporarily stops the transport roller at the time when the recording paper is transported until the front end of the recording paper is positioned in the vicinity of the stopped registration roller by rotating the transport roller, The conveyance roller is rotated at an accelerated speed to form a deflection on the recording paper.

  More preferably, the recording paper conveyance device accelerates the rotation of the registration roller after rotating the registration roller to start conveyance of the recording paper by the registration roller.

  More preferably, the recording paper transport device rotates the transport roller that is stopped at a constant acceleration and then rotates the transport roller at a constant speed, and further accelerates the rotation of the transport roller from the constant speed, and The acceleration for accelerating the rotation of the registration roller is equal to a constant acceleration.

  Preferably, the timing for further accelerating the rotation of the conveying roller from a constant speed is when the rotational speed of the registration roller becomes equal to the constant speed.

  More preferably, the recording paper transport device further includes a first drive device that rotates the registration roller and a second drive device that rotates the transport roller and is different from the first drive device.

  More preferably, the first driving device and the second driving device are stepping motors, and a pulse signal of a predetermined sequence for controlling the stepping motor is supplied to each of the first driving device and the second driving device. The driver further supplies a first sequence of pulse signals for rotating the transport roller at a constant speed to the first driving device to form a deflection on the recording paper, and the first sequence of pulse signals is supplied to the first sequence. In this state, the second sequence of pulse signals for rotating the registration rollers is supplied to the second driving device, and when the rotation speed of the registration rollers reaches a predetermined speed, the conveyance rollers are rotated. A pulse signal of a third sequence that further accelerates from a constant speed is supplied to the first driving device.

  Preferably, the recording paper transport device further includes a drive device, a first clutch that connects the registration roller to the drive device, and a second clutch that connects the transport roller to the drive device. The registration roller is rotated through the second clutch, and the conveying roller is rotated through the second clutch.

  The document feeder according to the present invention includes a registration roller and a conveyance roller disposed adjacent to the registration roller on the upstream side in the document conveyance direction, and conveys the document by rotating the conveyance roller and is stopped. Is a document feeding device that forms a predetermined deflection on the document by causing the leading edge of the document to abut against the registration roller of the document, and forms the deflection on the document by rotating the conveying roller at a constant speed, and the deflection is formed and conveyed. With the rotation speed of the roller maintained at a constant speed, the registration roller is rotated to start conveyance of the document by the registration roller. When the rotation speed of the registration roller reaches a predetermined speed, the conveyance roller is rotated. Accelerate further from a certain speed.

  An image forming apparatus according to the present invention includes at least one of the recording paper transport device and the document feeder.

  According to the present invention, the recording paper is not bent unnecessarily beyond the amount of bending necessary for correcting the skew of the recording paper or the document immediately before the registration roller without degrading the performance, and the appropriate bending is maintained. can do. Therefore, it is possible to reduce a space for holding the recording paper or the document appropriately bent so as not to be buckled between the registration roller and the pre-registration roller.

  Further, by setting the constant speed of the transport roller to a speed close to the image forming process speed or a speed not significantly lower than the process speed, a high-speed recording paper transport apparatus and an image forming apparatus using the same Can be made more compact.

  In addition, by setting the constant speed of the conveying roller to a speed close to the document scanning process speed or a speed not significantly lower than the process speed, a high-speed document feeder and an image forming apparatus using the same can be made more efficient. It can be made compact.

It is a timing chart which shows the control waveform of the conventional registration roller and the roller before registration. It is a timing chart which shows the control waveform of the conventional registration roller and the roller before registration. 1 is a cross-sectional view illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 4 is a schematic diagram illustrating a structure in the vicinity of a registration roller and a pre-registration roller of the image forming apparatus illustrated in FIG. 3. FIG. 5 is a block diagram showing a mechanism for controlling driving of the registration roller and the pre-registration roller shown in FIG. 4. 6 is a flowchart illustrating a control structure of a program that executes skew correction of the image forming apparatus according to the embodiment of the present invention. 4 is a timing chart showing an example of control waveforms of a registration roller and a pre-registration roller in the image forming apparatus according to the embodiment of the present invention. FIG. 5 is a diagram illustrating a conveyance state of recording paper by a registration roller and a pre-registration roller. It is a figure which shows the difference between the timing chart of FIG. 7, and the timing chart of FIG. It is a figure which shows the state which buckling of the recording paper produced. FIG. 4 is a cross-sectional view showing an automatic document feeder and an image reading device of the image forming apparatus shown in FIG. 3.

  In the following embodiments, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.

  Referring to FIG. 3, image forming apparatus 100 according to the embodiment of the present invention forms a multicolor or single color image on a predetermined recording sheet in accordance with image data generated by reading a document. The image forming apparatus 100 includes a main body device 110 and an automatic document feeder 120. The main body device 110 includes an optical scanning device 1, a developing device 2, a photosensitive drum 3, a cleaner unit 4, a charger 5, an intermediate transfer belt unit 6, a fixing unit 7, a paper feed cassette 81, and a paper discharge tray 91. It is configured. In addition to these, the image forming apparatus 100 also includes components necessary to function as an image forming apparatus.

  An image reading device 90 provided with a document placing table 92 made of transparent glass on which a document is placed is disposed on the main body device 110, and an automatic document feeder 120 is attached on the document placing table 92. ing. The automatic document feeder 120 automatically conveys the document on the document table 92. The automatic document feeder 120 is configured to be rotatable in the direction of arrow M, and the document can be placed by hand by opening the document table 92.

  The image data handled in the image forming apparatus 100 is decomposed into color image data using each color of black (K), cyan (C), magenta (M), and yellow (Y), that is, these four color components. Image data. Accordingly, four each of the developing device 2, the photosensitive drum 3, the charger 5, and the cleaner unit 4 are provided so as to form four types of latent images corresponding to the respective colors. Four image stations are configured to process magenta and yellow.

  The charger 5 is a device for uniformly charging the surface of the photosensitive drum 3 to a predetermined potential. In addition to the charger type as shown in FIG. 3, a contact type roller type or brush type charger is used. Sometimes.

  The optical scanning device 1 is a laser scanning unit (LSU) provided with a laser emitting unit, a reflection mirror, and the like. The optical scanning device 1 includes a polygon mirror that scans a laser beam and optical elements such as a lens and a mirror for guiding the laser light reflected by the polygon mirror to the photosensitive drum 3. As the optical scanning device 1, in addition to such a configuration, for example, an EL or LED writing head in which light emitting elements are arranged in an array can be employed.

  The optical scanning device 1 exposes the charged photosensitive drum 3 according to input image data, thereby forming an electrostatic latent image according to the image data on the surface thereof. The developing device 2 visualizes the electrostatic latent images formed on the respective photosensitive drums 3 with toner of four colors (YMCK). The cleaner unit 4 removes and collects toner remaining on the surface of the photosensitive drum 3 after development and image transfer.

  The intermediate transfer belt unit 6 disposed above the photosensitive drum 3 includes an intermediate transfer belt 61, an intermediate transfer belt driving roller 62, an intermediate transfer belt driven roller 63, an intermediate transfer roller 64, and an intermediate transfer belt cleaning unit 65. I have. Four intermediate transfer rollers 64 are provided corresponding to each color of YMCK.

  The intermediate transfer belt driving roller 62, the intermediate transfer belt driven roller 63, and the intermediate transfer roller 64 are driven to rotate while the intermediate transfer belt 61 is stretched. Each intermediate transfer roller 64 supplies a transfer bias described later in order to transfer the toner image on the corresponding photosensitive drum 3 onto the intermediate transfer belt 61.

  The intermediate transfer belt 61 is provided in contact with each photosensitive drum 3. A color toner image (multicolor toner image) is formed on the intermediate transfer belt 61 by sequentially superimposing and transferring the respective color toner images formed on the photosensitive drum 3 onto the intermediate transfer belt 61. The intermediate transfer belt 61 is formed in an endless shape using, for example, a film having a thickness of about 100 μm to 150 μm.

  The toner image is transferred from the photosensitive drum 3 to the intermediate transfer belt 61 by an intermediate transfer roller 64 that is in contact with the back side of the intermediate transfer belt 61. A high-voltage transfer bias (a high voltage having a polarity (+) opposite to the toner charging polarity (−)) is applied to the intermediate transfer roller 64 in order to transfer the toner image. The intermediate transfer roller 64 is a roller whose base is a metal (for example, stainless steel) shaft having a diameter of 8 to 10 mm and whose surface is covered with a conductive elastic material (for example, EPDM, urethane foam, or the like). With this conductive elastic material, a high voltage can be uniformly applied to the intermediate transfer belt 61. In this embodiment, a roller shape is used as the transfer electrode, but a brush or the like can also be used.

  As described above, the electrostatic images visualized according to the hues on the photosensitive drums 3 are stacked on the intermediate transfer belt 61. The image information (toner density distribution) thus laminated is transferred onto the recording paper by the transfer roller 10 disposed at the contact position between the recording paper and the intermediate transfer belt 61 as the intermediate transfer belt 61 rotates. .

  At this time, the intermediate transfer belt 61 and the transfer roller 10 are pressed against each other at a predetermined nip, and a voltage for transferring the toner onto the recording paper is applied to the transfer roller 10 (what is the toner charging polarity (−))? Reverse polarity (+) high voltage). Further, in order to obtain the nip constantly, either one of the transfer roller 10 and the intermediate transfer belt drive roller 62 is made of a hard material (metal or the like), and the other is made of a soft material such as an elastic roller (elastic rubber roller). , Foaming resin rollers, etc.) are used.

  Further, as described above, the toner attached to the intermediate transfer belt 61 by contacting the photosensitive drum 3 or the toner remaining on the intermediate transfer belt 61 without being transferred onto the recording paper by the transfer roller 10 is as follows. In order to cause toner color mixing in the process, the toner is removed and collected by the intermediate transfer belt cleaning unit 65. In the intermediate transfer belt cleaning unit 65, for example, a cleaning blade that contacts the intermediate transfer belt 61 is disposed as a cleaning member. The intermediate transfer belt 61 that contacts the cleaning blade is supported by the intermediate transfer belt driven roller 63 from the back side. Has been.

  The paper feed cassette 81 is a tray for storing recording paper used for image formation, and is provided below the optical scanning device 1 of the main body device 110. In addition, recording paper used for image formation can also be placed in the manual paper feed cassette 82. A paper discharge tray 91 provided in the main unit 110 is a tray for collecting printed recording sheets face down, that is, with the printing surface facing down.

  In the main body apparatus 110, the recording paper conveyance path S is set in a substantially vertical direction in order to send the recording paper of the paper feeding cassette 81 and the manual paper feeding cassette 82 to the paper discharge tray 91 via the transfer roller 10 and the fixing unit 7. Is formed. In the vicinity of the recording paper transport path S from the paper feed cassette 81 or the manual paper feed cassette 82 to the paper discharge tray 91, pickup rollers 11a and 11b, a plurality of transport rollers 12a to 12e, a registration roller 13, a transfer roller 10, and A fixing unit 7 and the like are arranged.

  The transport rollers 12 a to 12 e are small rollers for promoting and assisting the transport of the recording paper, and a plurality of transport rollers 12 a to 12 e are provided along the recording paper transport path S. The pickup roller 11 a is arranged near the end of the paper feed cassette 81, picks up recording paper from the paper feed cassette 81 one by one, and supplies it to the recording paper transport path S. Similarly, the pickup roller 11 b is disposed near the end of the manual paper feed cassette 82, picks up recording paper one by one from the manual paper feed cassette 82, and supplies it to the recording paper transport path S.

  The registration roller 13 temporarily holds the recording paper conveyed through the recording paper conveyance path S. Then, the recording paper is conveyed to the transfer roller 10 at the timing when the leading edge of the toner image on the photosensitive drum 3 and the leading edge of the recording paper coincide.

  The fixing unit 7 includes a heat roller 71 and a pressure roller 72. The heat roller 71 and the pressure roller 72 rotate with the recording paper interposed therebetween. Further, the heat roller 71 is set to a predetermined fixing temperature by the control unit based on a signal from a temperature detector (not shown), and by thermocompression bonding the toner to the recording paper together with the pressure roller 72. The multi-color toner image transferred to the recording paper is melted, mixed, and pressed to be thermally fixed to the recording paper. An external heating belt 73 for heating the heat roller 71 from the outside is provided.

  The recording paper conveyance path will be specifically described. As described above, the image forming apparatus 100 is provided with the paper feed cassette 81 that stores recording paper and the manual paper feed cassette 82 in advance. In order to feed the recording paper from these paper feeding cassettes 81 and 82, pickup rollers 11a and 11b are respectively arranged so as to guide the recording paper one by one to the recording paper transport path S.

  The recording paper unloaded from the paper feeding cassettes 81 and 82 is conveyed to the registration roller 13 by the conveying rollers 12a and 12e in the recording paper conveying path S, and the leading edge of the recording paper and the leading edge of the image information on the intermediate transfer belt 61 are connected. At the matching timing, the sheet is loaded into the transfer roller 10 and image information is written on the recording paper. Thereafter, the recording paper passes through the fixing unit 7, whereby the unfixed toner on the recording paper is melted and fixed by heat, and passes through the conveyance roller 12 b disposed at the end of the recording paper conveyance path S to the discharge tray 91. Discharged.

  The above-mentioned transport path is for a single-sided printing request for recording paper. When double-sided printing is requested, the conveyance roller 12b rotates reversely when the trailing edge of the recording paper that has finished single-sided printing and has passed through the fixing unit 7 as described above is gripped by the final conveyance roller 12b in the conveyance path. By doing so, the recording paper is guided to the transport rollers 12c and 12d. Thereafter, the recording paper is conveyed to the registration roller 13, printed on the back surface of the recording paper in the same manner as described above, and then discharged to the paper discharge tray 91.

  Hereinafter, the skew correction of the recording paper in the image forming apparatus 100, that is, the process of forming the deflection on the recording paper immediately before the registration roller 13 will be described.

  With reference to FIG. 4, the registration roller 13 includes a first drive roller 130 and a first driven roller 132. The first driving roller 130 and the first driven roller 132 are pressed against each other at a predetermined nip, and can be transported with a recording sheet interposed therebetween. The first driven roller 132 is passively driven by the first driving roller being driven by a motor described later. The transport roller 12e (pre-registration roller) includes a second drive roller 140 and a second driven roller 142. The second driving roller 140 and the second driven roller 142 are pressed against each other at a predetermined nip, and can be transported with a recording sheet interposed therebetween. The second driven roller 142 is passively driven by the second driving roller 140 being driven by a motor.

  A first conveyance guide 150 and a second conveyance guide 152 are disposed between the registration roller 13 and the pre-registration roller 12e. The 1st conveyance guide 150 and the 2nd conveyance guide 152 are arrange | positioned at predetermined intervals. The first transport guide 150 is provided with a recess so that the distance from the second transport guide 152 is increased. This prevents the recording paper from being bent finely and buckling, so that the recording paper can be gently bent in one direction.

  Near the pre-registration roller 12e (upstream of the recording paper transport path S), the leading edge of the recording paper transported along the recording paper transport path S is detected from the paper feed cassette 81 or the manual paper feed cassette 82. A sensor 160 is arranged. The sensor 160 may be any sensor that can detect the leading edge of the recording paper to be conveyed. The sensor 160 is a photo sensor including an actuator, for example. Further, the sensor 160 may be configured by arranging the light emitting element and the light receiving element to face each other across the recording paper conveyance path S.

  Referring to FIG. 5, a mechanism for driving registration roller 13 and conveyance roller 12e includes a control unit (hereinafter referred to as CPU) 200, a ROM (Read Only Memory) 202 for storing a program, and the like. RAM (Random Access Memory) 204, which is a volatile storage device, HDD (Hard Disk Drive) 206, which is a non-volatile storage device that retains data even when power is cut off, a timer 208, a motor driver 210, A registration roller drive motor 212 and a transport roller drive motor 214 are provided. The registration roller drive motor 212 is a motor for driving the first drive roller 130. The conveyance roller drive motor 214 is a motor for driving the second drive roller 140.

  The registration roller driving motor 212 and the conveyance roller driving motor 214 are stepping motors. The rotation speed of the stepping motor is determined by the frequency of the input pulse. The stepping motor receives a predetermined sequence of pulse signals from the motor driver 210 and changes the driving state (rotation state) accordingly. A predetermined control signal (a signal indicating the timing of starting and stopping the registration roller driving motor 212 and the conveyance roller driving motor 214) is transmitted from the CPU 200 to the motor driver 210. In response to this, the motor driver 210 reads out a pulse signal of a sequence corresponding to the control signal (command) from the CPU 200 from the ROM 202 and outputs it to the registration roller driving motor 212 and the conveying roller driving motor 214. The motor driver 210 can be realized, for example, as a general-purpose or dedicated electronic circuit and a program for operating it. The motor driver 210 can also be realized as a dedicated electronic circuit including a semiconductor device such as an ASIC.

  A program for executing skew correction in the image forming apparatus 100 will be described with reference to FIG. In the initial state, the registration roller 13 and the pre-registration roller 12e are stopped. The ROM 202 or the HDD 206 stores times Ta to Tf described later.

  In step 300, the CPU 200 determines whether or not the sensor 160 has detected a recording sheet. Specifically, the CPU 200 determines whether or not the signal from the sensor 160 is at a level that is output when the recording paper is detected. For example, the output signal from the sensor 160 is at a low level when no recording paper is detected, and is at a high level when a recording paper is detected. If it is determined that the recording paper has been detected, the control proceeds to step 302. Otherwise, step 300 is repeated.

  In step 302, the CPU 200 transmits a control signal for rotating the pre-registration roller (conveyance roller) 12 e to the motor driver 210. Upon receiving this control signal, the motor driver 210 outputs a predetermined sequence of pulse signals to the conveying roller drive motor 214 as described above. The conveyance roller driving motor 214 receives this pulse signal and rotates, whereby the pre-registration roller 12e rotates. Further, the CPU 200 acquires the current time from the timer 208 and stores it in a predetermined area of the RAM 204 as the start time.

  In step 304, the CPU 200 determines whether or not a predetermined time Ta has elapsed since the pre-registration roller 12e started rotating. Specifically, the CPU 200 acquires the current time from the timer 208, obtains the elapsed time from the start time stored in the RAM 204 in step 302, and determines whether or not the obtained value is greater than the time Ta. If it is determined that time Ta has elapsed, control proceeds to step 306. Otherwise, step 304 is repeated.

  In step 306, the CPU 200 transmits a control signal for stopping the pre-registration roller 12 e to the motor driver 210. Upon receiving this control signal, the motor driver 210 stops outputting the pulse signal to the transport roller drive motor 214, the transport roller drive motor 214 stops, and the rotation of the pre-registration roller 12e stops. At this time, when the rotation speed is controlled and stopped, for example, the number of pulses per short time is linearly reduced to zero. Further, the CPU 200 acquires the current time from the timer 208 and temporarily stores it in a predetermined area of the RAM 204 as a start time.

  Steps 300 to 306 are executed in the period up to time t0 in FIG. The upper graph in FIG. 7 shows the time change of the speed Vr of the registration roller 13, and the lower graph shows the time change of the speed Vp of the pre-registration roller 12e. FIG. 7 does not show the timing at which the pre-registration roller 12e starts to rotate in step 302. The pre-registration roller 12e rotates with the recording paper interposed therebetween, whereby the recording paper is introduced between the first conveyance guide 150 and the second conveyance guide 152. Thereafter, at time t0, the pre-registration roller 12e stops. Accordingly, by appropriately setting the time Ta, the leading edge of the recording paper can be stopped at a position away from the registration roller 13 by a predetermined distance (for example, immediately before the registration roller 13). Referring to FIG. 8, (A) shows a state where the sensor 160 detects the recording paper 180, and (B) shows a state where the leading edge of the recording paper 180 has stopped just before the registration roller 13.

  In step 308, the CPU 200 determines whether or not a predetermined time Tb has elapsed since the pre-registration roller 12e was stopped at time t0. Specifically, the CPU 200 acquires the current time from the timer 208, obtains the elapsed time from the start time stored in the RAM 204 in step 306, and determines whether or not the obtained value is greater than the time Tb. If it is determined that time Tb has elapsed, control proceeds to step 310. Otherwise, step 308 is repeated.

  In step 310, the CPU 200 transmits a control signal for rotating the pre-registration roller 12 e to the motor driver 210. Upon receiving this control signal, the motor driver 210 outputs a predetermined sequence of pulse signals (for example, a sequence in which the number of pulses per short time increases linearly) to the conveyance roller drive motor 214. The conveyance roller drive motor 214 receives this pulse signal and starts rotating. As a result, the pre-registration roller 12e starts to rotate and accelerates the rotation at a constant acceleration. Further, the CPU 200 acquires the current time from the timer 208 and stores it in a predetermined area of the RAM 204 as the start time. Step 310 is executed at time t1 in FIG.

  In step 312, the CPU 200 determines whether or not a predetermined time Tc has elapsed since the rotation of the pre-registration roller 12e was started at time t1. Specifically, the CPU 200 acquires the current time from the timer 208, obtains the elapsed time from the start time stored in the RAM 204 in step 310, and determines whether or not the obtained value is greater than the time Tc. If it is determined that the time Tc has elapsed, the control proceeds to step 314. Otherwise, step 312 is repeated.

  The period of steps 310 to 312 is a period of time t1 to t2 in FIG. Before the pre-registration roller 12e starts to rotate in step 310, the leading edge of the recording paper is immediately before the registration roller 13. Therefore, the recording paper is transferred to the registration roller 13 in a short time after the pre-registration roller 12e starts to rotate. Abut. Therefore, it is possible to suppress the impact sound (collision sound) generated when the leading edge of the recording paper comes into contact with the registration roller 13. Even if the leading edge of the recording paper comes into contact with the registration roller 13, the registration roller 13 is stopped, so that the recording paper bends along the first conveyance guide 150.

  In step 314, the CPU 200 transmits a control signal (control signal for stopping acceleration) for rotating the pre-registration roller 12 e whose rotation is being accelerated at a constant speed to the motor driver 210. Upon receiving this control signal, the motor driver 210 outputs a predetermined sequence of pulse signals (for example, equally spaced pulse signals) to the transport roller drive motor 214. The transport roller drive motor 214 receives this pulse signal, stops acceleration, and rotates at a constant speed. As a result, the pre-registration roller 12e rotates at a constant speed V1. Further, the CPU 200 acquires the current time from the timer 208 and stores it in a predetermined area of the RAM 204 as the start time. Step 314 is executed at time t2 in FIG.

  In step 316, the CPU 200 determines whether or not a predetermined time Td has elapsed since the pre-registration roller 12e was rotated at the constant speed V1 at time t2. Specifically, the CPU 200 acquires the current time from the timer 208, obtains the elapsed time from the start time stored in the RAM 204 in step 314, and determines whether or not the obtained value is greater than the time Td. If it is determined that the time Td has elapsed, control proceeds to step 318. Otherwise, step 316 is repeated.

  In step 318, the CPU 200 transmits a control signal for rotating the registration roller 13 to the motor driver 210. Upon receiving this control signal, the motor driver 210 outputs a predetermined sequence of pulse signals (for example, a sequence in which the number of pulses per short time increases linearly) to the registration roller drive motor 212. The registration roller drive motor 212 receives this pulse signal and starts rotating. As a result, the registration roller 13 starts rotating, and the rotation is accelerated at a constant acceleration equal to the acceleration of the pre-registration roller 12e. Further, the CPU 200 acquires the current time from the timer 208 and stores it in a predetermined area of the RAM 204 as the start time. Step 318 is executed at time t4 in FIG. FIG. 8C shows a state where the recording paper 180 is bent along the first conveyance guide 150 at time t4 (a state where the recording paper 180 is appropriately bent by an amount sufficient for skew correction).

  In step 320, the CPU 200 determines whether or not a predetermined time Te has elapsed since the rotation of the registration roller 13 was started at time t4. Specifically, the CPU 200 acquires the current time from the timer 208, obtains the elapsed time from the start time stored in the RAM 204 in step 318, and determines whether or not the obtained value is greater than the time Te. If it is determined that time Te has elapsed, control proceeds to step 322. Otherwise, step 320 is repeated.

  In step 322, the CPU 200 transmits a control signal for accelerating the rotation of the pre-registration roller 12 e to the motor driver 210. Upon receiving this control signal, the motor driver 210 outputs a predetermined sequence of pulse signals (for example, a sequence in which the number of pulses per short time increases linearly) to the conveyance roller drive motor 214. The conveyance roller drive motor 214 receives this pulse signal and accelerates the rotation. As a result, the pre-registration roller 12e accelerates rotation at a constant acceleration that is the same as the period from time t1 to time t2. Further, the CPU 200 acquires the current time from the timer 208 and stores it in a predetermined area of the RAM 204 as the start time. Step 322 is executed at time t5 in FIG. This time t5 is, for example, when the rotational speed of the registration roller 13 becomes equal to the rotational speed V1 of the pre-registration roller 12e that rotates at a constant speed.

The pre-registration roller 12e rotates at a constant speed V1 until the pre-registration roller 12e starts rotating at step 322 after the registration roller 13 starts rotating at step 318. 13 is not a not reach the speed V1. Accordingly, since the speed at which the pre-registration roller 12e introduces the recording paper between the first transport guide 150 and the second transport guide 152 is faster than the speed at which the recording paper is sent out from the registration roller 13, the recording paper is further bent. . This state is shown in FIG. FIG. 8D shows a state in which the recording paper 180 is bent along the first conveyance guide 150 at time t5. In FIG. 8D, the broken line represents the recording paper 180 in the state of (C). In this state, the recording paper 180 is bent more than in the state (C).

  In step 324, the CPU 200 determines whether or not a predetermined time Tf has elapsed since the rotation of the pre-registration roller 12e was accelerated at time t5. Specifically, the CPU 200 acquires the current time from the timer 208, obtains the elapsed time from the start time stored in the RAM 204 in step 322, and determines whether or not the obtained value is greater than the time Tf. If it is determined that time Tf has elapsed, control proceeds to step 326. Otherwise, step 324 is repeated.

  In step 326, the CPU 200 transmits a control signal (control signal for stopping acceleration) for rotating the registration roller 13 and the pre-registration roller 12 e to the motor driver 210. Upon receiving this control signal, the motor driver 210 outputs a predetermined sequence of pulse signals (for example, equally spaced pulse signals) to the registration roller drive motor 212 and the transport roller drive motor 214. The registration roller drive motor 212 and the transport roller drive motor 214 that have received this pulse signal rotate at a constant process speed (recording paper transport speed during image formation) Vc. Step 326 is executed at time t6 in FIG.

  Since the pre-registration roller 12e starts accelerating at time t5, the registration roller 13 and the pre-registration roller 12e rotate at the same speed, so the speed at which the recording paper is fed from the registration roller 13 and the pre-registration roller 12e However, the speed at which the recording paper is introduced between the first conveyance guide 150 and the second conveyance guide 152 is equal. Therefore, the amount of deflection of the recording paper is kept constant. This state is shown in FIG. The recording paper 180 is conveyed while the bending state between the first conveyance guide 150 and the second conveyance guide 152 is maintained in the same state as the bending state indicated by the solid line in (D).

  In step 328, the CPU 200 determines whether or not the registration roller 13 has completed transporting the recording paper. For example, if a sensor for detecting the trailing edge of the recording paper is disposed on the downstream side of the registration roller 13, the CPU 200 determines the signal level of the sensor. Further, it may be determined whether or not a predetermined time has elapsed since the rotation of the pre-registration roller 12e was started in step 314. If it is determined that the conveyance of the recording paper has been completed, the control proceeds to step 330. Otherwise, step 328 is repeated.

  In step 330, the CPU 200 transmits a control signal for stopping the registration roller 13 and the pre-registration roller 12 e to the motor driver 210. Upon receiving this control signal, the motor driver 210 stops outputting pulse signals to the registration roller driving motor 212 and the conveyance roller driving motor 214. As a result, the registration roller driving motor 212 and the conveyance roller driving motor 214 are stopped. At this time, when the rotation speed is controlled and stopped, for example, the number of pulses per short time is linearly reduced to zero.

  In step 332, the CPU 200 determines whether an end instruction has been received. The termination instruction is, for example, that the image forming apparatus 100 is turned off. If it is determined that an end instruction has been received, the program ends. Otherwise, control returns to step 300. Thus, when the image forming apparatus 100 is operated by the user and a predetermined number of copies are instructed, the above process is repeated until the predetermined number of copies are completed.

  As described above, in the image forming apparatus 100, when the recording paper is conveyed to the pre-registration roller 12e, the rotation of the pre-registration roller 12e is started, and the leading edge of the recording paper is just before the stopped registration roller 13. After being moved, it is temporarily stopped (time t0). Thereafter, the pre-registration roller is rotated (time t1) to bring the leading edge of the recording paper into contact with the registration roller 13, and the pre-registration roller 12e is rotated thereafter, whereby the first conveyance guide 150 and the second conveyance guide 152 are rotated. The recording paper can be bent appropriately between the times (time t4). When the recording paper is appropriately bent (time t4), the rotation of the registration roller 13 is started, and when the predetermined time (Te) has elapsed (time t5), the pre-registration roller 12e is accelerated again. Thereafter, since the registration roller 13 and the pre-registration roller 12e rotate at the same speed, as shown in FIG. It is conveyed by a pre-registration roller. Therefore, it is possible to suppress the recording paper from being bent and buckled (see FIG. 10) more than necessary for correcting skew feeding.

  When a predetermined time (Tf) has elapsed since the re-acceleration of the pre-registration roller 12e is started (time t6), the registration roller 13 and the pre-registration roller 12e are rotated at a constant speed Vc. As a result, the skew-corrected recording paper is supplied to the transfer roller 10. When the recording paper is separated from the pre-registration roller 12e, the deflection of the recording paper is not maintained, but the skew correction of the recording paper is maintained by the registration roller 13.

  Note that the times Ta to Tf take into consideration the required specifications of the image forming apparatus (number of processed sheets per unit time, etc.), characteristics of the stepping motor that drives the registration roller 13 and the pre-registration roller 12e, the amount of deflection of the recording paper, and the like. May be set as appropriate.

  Further, the constant speed V1 for rotating the pre-registration roller 12e at the times t2 to t5 can be set as appropriate. If the speed V1 is small, the time Tc + Td (time t1 to t4) from when the rotation of the pre-registration roller 12e is started until an appropriate deflection is formed becomes longer, but the excess deflection amount becomes smaller than that in the conventional case. Conversely, if the speed V1 is large, the time Tc + Td between the times t1 and t4 is shortened, but the excessive deflection becomes large. This will be described with reference to FIG.

  FIG. 9 shows the waveform of FIG. 1 (shown by a thick dotted line) and time t3 superimposed on FIG. Conventionally (FIG. 1), an appropriate deflection for skew correction is formed at time t3. On the other hand, in the above-described embodiment, after the pre-registration roller 12e is accelerated from the stop state, the constant speed V1 is smaller than the final process speed Vc. It takes time. As shown in the lower part of FIG. 9, since the bending due to the region S1, which has occurred in the past, does not occur, the pre-registration roller 12e is kept at a constant speed V1 until time t4 so that a region S2 having the same area as the region S1 is generated. Need to be maintained. The rotation of the registration roller 13 is started at time t4. In this state, the pre-registration roller 12e is at a constant speed V1, and therefore depends on the area of the region S3 between times t4 and t5 as shown in the upper part of FIG. Further unnecessary deflection occurs. Time t5 is the time when the registration roller 13 reaches the same speed as the pre-registration roller 12e. The area of the region S1 is smaller than the conventional area S0 (FIG. 1). That is, according to the present embodiment, the amount of unnecessary deflection can be made smaller than in the conventional case.

  From FIG. 9, as the speed V1 decreases, the area of the region S1 increases, so it is necessary to maintain the pre-registration roller 12e at the constant speed V1 for a longer time so that the area of the region S2 increases accordingly. However, since the time until the registration roller 13 reaches the speed V1 is shortened, the area of the region S1 is reduced, and unnecessary deflection is also reduced. On the other hand, if the speed V1 is increased, the area of the region S1 is decreased. Therefore, the pre-registration roller 12e may be maintained at the constant speed V1 for a shorter time so that the area of the region S2 is decreased accordingly. Since the time until the registration roller 13 reaches the speed V1 becomes longer, the area of the region S1 becomes larger and unnecessary deflection also becomes larger. In that case, there is a high possibility that the recording paper 180 will buckle as shown in FIG. Accordingly, the constant speed V1 of the pre-registration roller 12e depends on the required specifications of the image forming apparatus (number of processed sheets per unit time, etc.), characteristics of the registration roller 13 and the stepping motor that drives the pre-registration roller 12e, and the amount of deflection of the recording paper These may be set as appropriate in consideration of the above. The constant speed V1 is set to a speed close to the final process speed Vc (for example, 580 mm / s) or a speed not significantly lower than the process speed Vc, for example, about 1/2 times or more than the process speed Vc and less than 1 time. By doing so, it is possible to suppress the occurrence of unnecessary bending without degrading the performance of the image forming apparatus, and to realize a compact image forming apparatus.

  As described above, the acceleration of the pre-registration roller 12e and the registration roller 13 are equal, and the timing at which the pre-registration roller 12e is accelerated again from the constant speed V1 (time t5) is such that the speed of the registration roller 13 is the constant speed V1 of the pre-registration roller. It is preferable that However, as long as the skew correction is properly performed and buckling does not occur, the time t5 may slightly vary from when the speed of the registration roller 13 becomes equal to the constant speed V1 of the pre-registration roller.

  In the above description, the acceleration of the registration roller 13 and the pre-registration roller 12e is equal and constant. However, the present invention is not limited to this. Moreover, although the case where the acceleration of the pre-registration roller 12e is equal in the time t1-t2 and the time t5-t6 was demonstrated, it is not limited to this. Even if there is a slight difference in acceleration, adjustment of the time t4, t5, t6, etc. allows the skew correction of the recording paper to be executed appropriately and prevents buckling.

  In the above description, the recording paper is transported. However, the present invention is not limited to this. For example, the present invention can be applied to an automatic document feeder 120 that transports a document to a scan position. This will be specifically described below.

  Referring to FIG. 11, automatic document feeder 120 is pivotally supported on the back side of image reading device 90 by a hinge (not shown) and opened and closed by moving the front portion up and down. When the automatic document feeder 120 is opened, the platen glass 44 of the image reading device 90 is opened, and a document is placed on the platen glass 44.

  The image reading device 90 includes a platen glass 44, a first scanning unit 45, a second scanning unit 46, an imaging lens 47, a CCD (Charge Coupled Device) 48, and the like. When reading a document placed on the platen glass 44, the first scanning unit 45 and the second scanning unit 46 are used.

  The first scanning unit 45 includes an illumination device 51 and a first reflection mirror 52. The illumination device 51 includes an LED array 77 and a light guide member 78. The first scanning unit 45 exposes the document on the platen glass 44 by the illumination device 51 while moving at a constant speed V in the sub-scanning direction Y by a distance corresponding to the document size, and reflects the reflected light to the first reflection mirror. The light is reflected by 52 and guided to the second scanning unit 46. As a result, the image on the surface of the document (including color or black and white characters, figures, photographs, etc.) is scanned in the sub-scanning direction Y. The second scanning unit 46 includes a second reflection mirror 53 and a third reflection mirror 54. The second scanning unit 46 follows the first scanning unit 45 and moves at a speed V / 2, while reflecting the reflected light from the document by the second and third reflecting mirrors 53 and 54 to the imaging lens 47. Lead. The imaging lens 47 condenses the reflected light from the document on the CCD 48 and forms an image on the surface of the document on the CCD 48. The CCD 48 repeatedly scans the image of the document in the main scanning direction (direction perpendicular to the paper surface of FIG. 11), and outputs an analog image signal of one main scanning line each time scanning is performed. As a result, the document is scanned and image data is generated.

  The image reading device 90 can read not only a stationary document on the platen glass 44 but also an image on the surface of the document conveyed by the automatic document feeder 120. In this case, as shown in FIG. 11, the first scanning unit 45 is moved to the reading area below the document reading glass 84, and the second scanning unit 46 is arranged according to the position of the first scanning unit 45. In this state, the automatic document feeder 120 starts conveying the document.

  In the automatic document feeder 120, the pickup roller 55 is rotated in a state of being pressed against the document on the document tray 56, and a single document is drawn and conveyed. After aligning the leading ends, the document is passed between the document reading glass 84 and the reading guide plate 86, and the document is discharged from the discharge roller 58 to the discharge tray 49.

  When the document is transported, the illumination device 51 of the first scanning unit 45 illuminates the surface of the document through the document reading glass 84, and the reflected light from the surface of the document is reflected on each reflection mirror of the first and second scanning units 45 and 46 Then, the light is guided to the imaging lens 47, and the reflected light from the document surface is condensed on the CCD 48 by the imaging lens 47 to form an image on the document surface on the CCD 48. As a result, the image on the surface of the original is read.

  When reading the back side of the document, the intermediate tray 67 is rotated around its axis 69 as shown by a one-dot chain line, and the document is discharged from the discharge roller 58 to the discharge tray 49. The paper discharge roller 58 is stopped and the original is received on the intermediate tray 67. In this state, the paper discharge roller 58 is rotated in the reverse direction, and the document is guided to the registration roller 85 via the reverse conveyance path 68 to reverse the front and back of the document. Similarly to reading the image on the front side of the document, the image on the back side of the document is read, the intermediate tray 67 is returned to the original position indicated by the solid line, and the document is discharged from the discharge roller 58 to the discharge tray 49.

  If the original conveyed by the registration roller 85 is skewed and passes between the original reading glass 84 and the reading guide plate 86, the original is scanned in an oblique direction, and preferable image data can be obtained. Can not. Therefore, it is preferable to correct the skew of the original as in the case of image formation.

  When reading the surface of the document, the registration roller 85 is used as the registration roller 13 for transporting the recording paper, and the pickup roller 55 is used as the pre-registration roller 12e. That's fine. When reading the back side of the document, the registration roller 85 is the registration roller 13 for transporting the recording paper, and the paper discharge roller 58 to be rotated in reverse is the pre-registration roller 12e. A similar process may be executed. As a result, when reading either the front side or the back side of the document, the document can be skewed and passed between the document reading glass 84 and the reading guide plate 86. At this time, it is preferable that the constant speed of the pre-registration roller (the pickup roller 55 or the reversely rotated paper discharge roller 58) is a speed close to the document scanning process speed or a speed not significantly lower than the process speed. .

Instead of using the pickup roller 55 as the pre-registration roller 12e, along the document conveyance path between the pickup roller 55 and the registration roller 85 (for example, closer to the registration roller 85 than the pickup roller 55), A new conveyance roller may be installed, and the same processing as in steps 300 to 332 described above may be executed using the pre-registration roller 12e. In this case, when reading the back side of the document, the same processing as in steps 300 to 332 described above may be executed using the new conveyance roller as the pre-registration roller 12e.

  In the above description, the CPU 200 adjusts the amount of bending of the recording paper according to the passage of time. However, the present invention is not limited to this. For example, the CPU 200 may adjust the amount of deflection of the recording paper by determining whether a predetermined number of pulses have been transmitted to the registration roller driving motor 212 or the conveyance roller driving motor 214. The CPU 200 can obtain the number of pulses transmitted to the registration roller driving motor 212 and the conveyance roller driving motor 214 from the motor driver 210, for example.

  Further, as shown in FIG. 7, when controlling the rotation of the registration roller 13 and the pre-registration roller 12e, the recording paper is appropriately used for skew correction according to the characteristics of the recording paper transport mechanism of the image forming apparatus 100. A sequence of pulse signals for deflecting to a certain value can be specified. That is, t1 to t3 according to the process speed Vc of the registration roller 13 and the pre-registration roller 12e, the constant speed V1 (V1 <Vc) of the pre-registration roller 12e, and the control characteristics of the registration roller driving motor 212 and the conveyance roller driving motor 214. , T3 to t4, t4 to t5, t5 to t6, and the like can be appropriately determined. When the determined pulse sequence is used, it is not necessary to determine the passage of time or the number of pulses transmitted to the motor. For example, the front end of the recording paper reaches the pre-registration roller 12e by the sensor 160. When it is detected that this has occurred, it is only necessary to transmit a predetermined signal from the CPU 200 to the motor driver 210. Thereafter, the motor driver 210 reads a predetermined sequence of pulse signals (a pulse sequence for generating the entire velocity waveform as shown in FIG. 7) from the ROM 202, and sends it to the registration roller drive motor 212 and the transport roller drive motor 214. Just output.

When the CPU 200 determines the passage of time or the number of pulses transmitted to the motor to control the motor driver 210, the CPU 200 can control the timing to transmit the control signal, so the CPU 200 outputs the control signal. The speed waveform of the roller is determined at times t1, t3, t4, t5, and t6 (see FIG. 7) transmitted to the motor driver 210. However, when the pulse sequence of the entire waveform as shown in FIG. 7 is determined in advance, only the first time t1 is controlled, and all subsequent pulse sequences are determined.

  In addition, since the timing at which the conveyance of the recording paper is completed is substantially constant, the pulse sequence including the timing at which the registration roller 13 and the pre-registration roller 12e are stopped can be determined. If such a pulse sequence is used, it is not necessary to arrange a sensor for detecting the end of the recording paper on the downstream side of the registration roller 13.

  Moreover, although the case where the motor which drives each of the registration roller 13 and the pre-registration roller 12e was provided was demonstrated above, it is not limited to this. For example, the registration roller 13 and the pre-registration roller 12e may be driven by a single motor using an electromagnetic clutch. That is, a first electromagnetic clutch that transmits the rotation of the motor to the registration roller 13 and a second electromagnetic clutch that transmits the rotation of the motor to the pre-registration roller 12e are provided. A control signal is supplied to connect or release the first and second electromagnetic clutches. As a result, as shown in FIG. 7, the rotation of the registration roller 13 and the pre-registration roller 12e can be controlled.

  In the above, in step 300, when the recording paper is detected by the sensor 160, the pre-registration roller 12e starts rotating, and when the leading edge of the recording paper reaches the vicinity of the registration roller 13, the pre-registration roller 12e is temporarily stopped. However, the present invention is not limited to this. Even if the leading edge of the recording paper reaches the vicinity of the registration roller 13, the leading edge of the recording paper may be brought into contact with the registration roller 13 without stopping the rotation of the pre-registration roller 12e. In this case, a hitting sound (collision sound) is generated when the leading edge of the recording paper comes into contact with the registration roller 13, but the recording paper can be conveyed at a higher speed, and continuous image formation can be performed at a higher speed. Can be done.

  The present invention has been described above by describing the embodiment. However, the above-described embodiment is an exemplification, and the present invention is not limited to the above-described embodiment, and is implemented with various modifications. be able to.

12e Conveyance roller (roller before registration)
13 Registration roller 100 Image forming apparatus 130 First drive roller 132 First driven roller 140 Second drive roller 142 Second driven roller 150 First transport guide 152 Second transport guide 160 Sensor 200 Controller (CPU)
202 ROM
204 RAM
206 HDD
208 Timer 210 Motor driver 212 Registration roller driving motor 214 Conveying roller driving motor

Claims (12)

A registration roller, and a conveyance roller disposed adjacent to the registration roller and upstream in the conveyance direction of the recording paper. The conveyance roller is rotated to convey the recording paper, and the recording roller is stopped. A recording paper transport device that abuts the leading end of the paper and forms a predetermined deflection on the recording paper,
Rotating the transport roller at a constant speed to form the deflection on the recording paper,
In a state where the deflection is formed and the rotation speed of the conveyance roller is maintained at the constant speed, the registration roller is rotated to start conveyance of the recording paper by the registration roller,
When the rotation speed of the registration roller reaches a predetermined speed, the rotation of the transport roller is further accelerated from the constant speed ,
The conveyance of the recording paper, wherein the conveyance roller is rotated at the constant speed from the start of conveyance of the recording paper by the registration roller until the rotation of the conveyance roller is further accelerated from the constant speed. apparatus.   The conveyance roller is rotated, and when the recording paper is conveyed until the leading edge of the recording paper is positioned in the vicinity of the stopped registration roller, the conveyance roller is temporarily stopped, and then the conveyance roller is The recording paper transport device according to claim 1, wherein the bending is formed in the recording paper by being accelerated and rotated.   3. The recording paper conveyance device according to claim 1, wherein after the registration roller is rotated and conveyance of the recording paper by the registration roller is started, rotation of the registration roller is accelerated. After accelerating and rotating the stopped transport roller at a constant acceleration, the transport roller is rotated at the constant speed,
4. The recording paper conveying apparatus according to claim 3, wherein an acceleration for further accelerating the rotation of the conveying roller from the constant speed and an acceleration for accelerating the rotation of the registration roller are equal to the constant acceleration.   5. The recording paper transport according to claim 3, wherein the timing of further accelerating the rotation of the transport roller from the constant speed is when the rotational speed of the registration roller becomes equal to the constant speed. apparatus. First driving means for rotating the registration roller;
6. The recording paper transport apparatus according to claim 1, further comprising: a second drive unit that is different from the first drive unit that rotates the transport roller. 7. The first driving means and the second driving means are stepping motors;
A driver for supplying a pulse signal of a predetermined sequence for controlling the stepping motor to each of the first driving means and the second driving means;
The driver is
Supplying a pulse signal of a first sequence for rotating the transport roller at the constant speed to the second driving means to form the deflection on the recording paper;
In a state where the pulse signal of the first sequence is supplied to the second driving unit, a pulse signal of the second sequence for rotating the registration roller is supplied to the first driving unit,
When the rotation speed of the registration roller reaches a predetermined speed, a pulse signal of a third sequence for further accelerating the rotation of the transport roller from the constant speed is supplied to the second driving means. The recording paper transport device according to claim 6. Driving means;
A first clutch connecting the registration roller to the driving means;
A second clutch for connecting the transport roller to the drive means;
6. The driving device according to claim 1, wherein the driving unit rotates the registration roller through the first clutch and rotates the transport roller through the second clutch. The recording paper conveying apparatus according to the description.   2. The constant speed when the conveyance roller is rotated at a constant speed to form the deflection on the recording paper is at least 1/2 times and less than 1 time of an image forming process speed. 9. A recording paper transport device according to any one of items 1 to 8. A registration roller, and a conveyance roller disposed on the upstream side in the document conveyance direction adjacent to the registration roller. The conveyance roller is rotated to convey the document, and the leading edge of the document is moved to the stopped registration roller. A document feeding device that contacts a portion and forms a predetermined deflection on the document,
Rotating the conveying roller at a constant speed to form the deflection on the document,
In a state where the deflection is formed and the rotation speed of the conveyance roller is maintained at the constant speed, the registration roller is rotated to start conveyance of the document by the registration roller,
When the rotation speed of the registration roller reaches a predetermined speed, the rotation of the transport roller is further accelerated from the constant speed ,
A document feeding device that rotates the conveyance roller at the constant speed from the start of conveyance of the document by the registration roller to when the rotation of the conveyance roller is further accelerated from the constant speed .   11. The constant speed when the deflection is formed on the original by rotating the transport roller at a constant speed, and the constant speed is not less than 1/2 times and less than 1 time of a document scanning process speed. The document feeder described. An image forming apparatus comprising at least one of the recording paper conveyance device according to any one of claims 1 to 9 and the document feeding device according to claim 10 or 11 .

Images