JP5811680B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus.

  Conventionally, electrophotographic image forming apparatuses are known as printers, copiers, and the like. In this image forming apparatus, when a deviation occurs in the conveyed paper, that is, when the paper is deviated from a specified conveyance reference position in a direction (paper width direction) orthogonal to the paper conveyance direction, There is a possibility that an image to be formed is displaced from the original proper position, leading to a decrease in print quality. For this reason, the image forming apparatus includes a transport position moving unit configured to be swingable along the paper width direction, and adjusts the paper transport position by swinging the transport position moving unit (swing mode). . For example, the transport position moving unit is driven by an electric motor.

  For example, Patent Document 1 discloses an image including a skew roller that moves the paper toward the reference guide side, and a transport position moving unit (transport roller) that is provided downstream of the skew roller and is movable in the paper width direction. A forming apparatus is disclosed. In this image forming apparatus, a skewed roller abuts a sheet against a reference guide to correct the skew, and thereafter the sheet is nipped by a conveying roller, and the conveying roller is moved in the sheet width direction.

  Further, for example, in Patent Document 2, a gate unit that can be positioned by abutting the leading end of a sheet, and a transport position moving unit (a pair of resist rollers that can be contacted and separated) are provided upstream of the gate unit in the sheet transport direction. An image forming apparatus is disclosed. The image forming apparatus performs positioning by the gate unit in a state in which the registration roller pair is separated, and after the positioning, the registration roller pair is brought into contact to open the gate unit, and the registration roller pair makes a sheet of paper at a predetermined timing. Transport downstream. Then, the image forming apparatus moves the registration roller pair in the paper width direction according to the deviation amount of the paper. In this case, the image forming apparatus switches the driving method and the rotational speed of the motor that drives the movement of the registration roller pair according to the deviation amount of the sheet.

JP-A-11-189355 JP 2008-24507 A

By the way, according to the above-described method, when the printing quality requested by the user is at a level that does not require the rocking process, the rocking mode is set so that the rocking process is stopped due to a power saving viewpoint or a malfunction. It is not considered until it is not executed. In addition, when image formation is performed in the non-oscillation mode that does not execute the oscillation mode, the conveyance position movement unit unexpectedly moves when the sheet passes through the conveyance position movement unit, and the conveyance position movement unit There is a problem that the paper will be displaced as the paper passes. Here, the movement of the transport position moving unit includes factors such as mechanical vibration, impact when the paper enters the transport position moving unit, and passage when the paper has a large inclination.

  The present invention has been made in view of such circumstances, and an object of the present invention is to suppress misalignment of the sheet that occurs when the sheet passes through the transport position moving unit in a stationary state.

In order to solve such a problem, the first invention is an electric motor that operates when a winding is excited by energization, and is swingable along a paper width direction that is a direction perpendicular to the paper transport direction. An image forming apparatus comprising: a conveyance position moving unit configured to move a conveyed sheet along the sheet width direction by being driven by an electric motor; and a control unit that controls an excitation current for the electric motor. I will provide a. In this case, the control unit has, as the switchable operation mode, a swing mode that adjusts the paper transport position by swinging the transport position moving unit and a non-swing mode that does not execute the swing mode. When the operation mode is the swing mode, the swinging process is performed in which the excitation current is turned on and the drive pulse corresponding to the swing amount of the transport position moving unit is output to the electric motor. In some cases, non-oscillation processing for turning on the excitation current is performed. In addition, when the operation mode is the non-oscillation mode, the control unit performs non-oscillation processing corresponding to the passage period in which the sheet passes through the transport position moving unit, and turns off the excitation current in the period excluding the passage period. To do.

  In the present invention, it is preferable that the control unit variably controls the voltage level applied to the swing motor when the excitation current is turned on according to the type of paper.

In addition, the second invention is configured to be swingable along an electric motor that operates when the winding is excited by energization, and a paper width direction that is a direction perpendicular to the paper conveyance direction. Provided is an image forming apparatus having a conveyance position moving unit that moves a conveyed sheet along a sheet width direction by a motor and a control unit that controls an excitation current for an electric motor. In this case, the control unit has, as the switchable operation mode, a swing mode that adjusts the paper transport position by swinging the transport position moving unit and a non-swing mode that does not execute the swing mode. When the operation mode is the swing mode, the swinging process is performed in which the excitation current is turned on and the drive pulse corresponding to the swing amount of the transport position moving unit is output to the electric motor. In some cases, non-oscillation processing for turning on the excitation current is performed. In addition, when the operation mode is the swing mode, the control unit performs a swing process corresponding to a passing period in which the sheet passes through the transport position moving unit, and turns off the excitation current in a period other than the passing period.

In the first or second aspect of the invention, the control unit moves the transport position moving unit to a predetermined initial position before moving the transport position moving unit according to the amount of deviation of the paper. It is preferable to move it.

In the first invention or the second invention, the transport position moving unit is preferably a pair of registration rollers arranged on the upstream side of the image forming position for forming an image on the paper in the paper transport path. .

  According to the present invention, in the non-oscillation mode, a static torque is generated in the electric motor by turning on the excitation current. The movement of the transfer position moving unit is regulated by this static torque. As a result, it is possible to suppress a situation in which the transport position moving unit moves unexpectedly when the paper passes through the transport position moving unit, and the paper is displaced due to the passage of the transport position moving unit. it can.

1 is a configuration diagram schematically showing an image forming apparatus according to a first embodiment. Explanatory drawing showing the main parts of the transport path centering on the registration rollers Explanatory drawing showing the swinging state of the registration roller Block diagram schematically showing a control system of an image forming apparatus Flow chart showing control procedure of swing motor Explanatory drawing which shows typically the structure of the conveyance roller in the image forming apparatus concerning 2nd Embodiment.

(First embodiment)
FIG. 1 is a configuration diagram schematically illustrating an image forming apparatus according to the first embodiment. This image forming apparatus is an electrophotographic image forming apparatus such as a copying machine, and forms a full-color image by arranging a plurality of photoconductors facing one intermediate transfer belt in a vertical direction. A tandem type color image forming apparatus.

  The image forming apparatus mainly includes a document reading device SC, four sets of image forming units 10Y, 10M, 10C, and 10K, and a fixing device 50, which are housed in one casing.

  The document reader SC scans and exposes an image of the document with the optical system of the scanning exposure device, reads the reflected light with a line image sensor, and obtains an image signal. This image signal is subjected to processing such as A / D conversion, shading correction, and compression, and then input to the control unit 11 as image data. Note that the image data input to the control unit 11 is not limited to data read by the document reading device SC, but is, for example, data received from a personal computer connected to the image forming device or another image forming device. Also good.

  The four image forming units 10Y, 10M, 10C, and 10K include an image forming unit 10Y that forms a yellow (Y) image, an image forming unit 10M that forms a magenta (M) image, and a cyan (C) image. An image forming unit 10 </ b> C to be formed and an image forming unit 10 </ b> K that forms a black (K) image.

  The image forming unit 10Y includes a photosensitive drum 1Y and a charging unit 2Y, an optical writing unit 3Y, a developing device 4Y, and a drum cleaner 5Y arranged around the photosensitive drum 1Y. Similarly, the image forming units 10M, 10C, and 10K include photoconductor drums 1M, 1C, and 1K and charging units 2M, 2C, and 2K, optical writing units 3M, 3C, and 3K, and developing devices 4M, 4C, 4K and drum cleaners 5M, 5C, 5K.

  The surfaces of the photosensitive drums 1Y to 1K are uniformly charged by the charging units 2Y to 2K, and latent images are formed on the photosensitive drums 1Y to 1K by scanning exposure by the optical writing unit 3Y. . Further, the developing devices 4Y to 4K develop latent images on the photosensitive drums 1Y to 1K by developing with toner. As a result, toner images corresponding to yellow, magenta, cyan, and black are formed on the respective photosensitive drums 1Y to 1K. The toner images formed on the photosensitive drums 1Y to 1K are sequentially transferred to predetermined positions on the rotating intermediate transfer belt 6 by primary transfer rollers 7Y, 7M, 7C, and 7K.

  The color toner images transferred onto the intermediate transfer belt 6 are transferred onto the paper P by the transfer roller 9 when the paper P is conveyed at a predetermined timing.

  The paper transport unit 20 transports the paper P. The paper P is accommodated in the paper feed tray 21, and the first sheet of the paper P accommodated in the paper feed tray 21 is taken in by the first paper feed unit 22 and sent out to the main transport path. In this main transport path, an image forming position for forming an image on the paper P, in this embodiment, a transfer position for transferring a toner image onto the paper P (that is, a nip portion between the intermediate transfer belt 6 and the secondary transfer roller 9). On the upstream side, intermediate transport rollers 23 to 25, a loop roller 26, and a registration roller 27 are arranged. The paper P delivered from the first paper supply unit 22 is transported to a transfer position by being transported by a plurality of transport members including intermediate transport rollers 23 to 25, a loop roller 26 and a registration roller 27. Each conveyance member is comprised by the conveyance roller pair, for example.

  FIG. 2 is an explanatory diagram showing the main part of the transport path of the paper P around the registration roller 27. Specifically, the paper P fed from the paper feed tray 21 is conveyed by the loop roller 26 and abuts against the registration roller 27 in a rotation stopped state. Then, as the loop roller 26 continues to rotate for a predetermined time, a loop is formed on the paper P, thereby correcting the bending of the paper P (skew correction). Thereafter, when the registration roller 27 starts to rotate at a predetermined timing and resumes the conveyance of the paper P, the registration roller 27 performs a swing process or a non-oscillation process to be described later while transporting the paper P to the fixing device 50. Transport P.

  FIG. 3 is an explanatory view showing a swinging state of the registration roller 27. The registration roller 27 is configured to be swingable along a paper width direction CD (a direction perpendicular to the paper transport direction FD on the paper surface of the paper P). The registration roller 27 is connected to an output shaft of a swing motor 28 through a power transmission mechanism (not shown). The registration roller 27 can be moved along the paper width direction CD by being driven by the swing motor 28. For this reason, the registration roller 27 moves the conveyed paper P along the paper width direction CD by moving along the paper width direction CD in accordance with the passage period when the paper P passes through the registration roller 27. (Transfer position moving part). Thereby, the registration roller 27 can adjust the transport position of the paper P.

  The swing motor 28 is an electric motor that operates when a winding is excited by energization, for example, a stepping motor. When the excitation current is turned on, a steady voltage is applied to the oscillating motor 28 (specifically, its windings), thereby preventing the rotation of the output shaft by static torque. . In addition, when a drive pulse is input as an excitation current, a pulse voltage is applied to the swing motor 28 (specifically, its windings), thereby depending on the number of drive pulses. The output shaft of the oscillating motor 28 rotates at the rotation angle and the rotation speed corresponding to the pulse period.

  As shown in FIG. 1 again, the fixing device 50 is a device that fixes an unfixed toner image onto the paper P. For example, the fixing device 50 includes a pair of fixing members (for example, a fixing roller) that form a fixing nip portion, The heater is configured to heat one or both of the fixing members. In the fixing device 50, the sheet P passes through the fixing nip portion in the conveyance process of the sheet P, so that the toner image is applied to the sheet through the action of the pressure by the pair of fixing members and the heat of the fixing member. Fixing is performed.

  The paper P subjected to the fixing process by the fixing device 50 is discharged by a paper discharge roller to a paper discharge tray 29 attached to the outer side surface of the housing. When image formation is performed also on the back surface of the paper P, the paper P on which image formation on the front surface of the paper has been completed is conveyed by the guide member 30 to the reverse roller 31 below. The reversing roller 31 pinches the rear end of the conveyed paper P, reverses the paper P by reverse feeding, and sends it out to the refeed conveyance path. The sheet P sent out to the refeed conveyance path is conveyed by a plurality of conveyance members including intermediate conveyance rollers 32 and 33 and a pre-registration roller 34, and thereby the main conveyance path on the upstream side of the loop roller 26. Return the paper P to the top. Each conveyance member is composed of a conveyance roller pair.

  FIG. 4 is a block diagram schematically showing a control system of the image forming apparatus according to the present embodiment. The control unit 11 has a function of controlling the image forming apparatus in an integrated manner, and includes a CPU 11a, a memory 11b such as a ROM and a RAM, an HDD (Hard Disk Drive) 11c as an auxiliary storage device, a communication I / F unit 11d, and the like. These elements are connected to each other via a bus.

The control unit 11 controls each unit of the image forming apparatus (for example, the image forming units 10Y to 10K, the paper transport unit 20, the fixing device 50, and the like), thereby executing the following processes, and the toner image on the paper P. Form.
(1) Charge the photosensitive drums 1Y to 1K (2) Form the electrostatic latent images on the photosensitive drums 1Y to 1K by the optical writing units 3Y to 3K (3) Toner on the formed electrostatic latent images (4) The toner images on the photosensitive drums 1Y to 1K are primarily transferred to the intermediate transfer belt 6. (5) The sheet P is conveyed by the sheet conveying unit 20. (6) The toner image on the intermediate transfer belt 6 is transferred. Secondary transfer onto the paper P (7) The toner image transferred onto the paper P by the fixing device 50 is subjected to a fixing process.

  Further, in relation to the present embodiment, the control unit 11 controls the operating state of the swing motor 54 by controlling the excitation current for the swing motor 54. Here, the control unit 11 has a swing mode and a non-swing mode as switchable operation modes, and switches the control mode of the swing motor 54 according to the operation mode.

  Hereinafter, the control concept of the rocking mode will be described. In general, the paper P transported along the transport path is such that the reference position Cpp of the paper P in the paper width direction CD coincides with the reference position (hereinafter referred to as “transport reference position”) Cst on the transport path in the paper width direction CD. (Refer to FIG. 3). For example, the reference position of the paper P is set at the center of the paper P, and the transport reference position Cst is set at the center of the transport path in the paper width direction CD. In this case, both the image forming positions by the image forming units 10Y to 10K and the conveyance reference position Cst are set in advance according to a predetermined relationship, so that the paper P and the toner image are properly aligned with each other. A toner image is formed on P.

  However, when the image forming apparatus is actually operated, as shown in FIG. 3, a deviation occurs in the conveyance position of the sheet P in the sheet width direction CD, and the reference position Cpp of the sheet P is shifted from the conveyance reference position Cst. The reality that it ends up may occur. The deviation of the sheet P is caused by the sheet P being conveyed over a relatively long distance, for example, the sheet P is conveyed to the transfer position via the reverse roller 31 and the refeed conveyance path. This may be caused by the influence of a mechanical error of the conveying member. In addition, the initial storage state of the paper P stored in the paper feed tray 21 can be a factor of the deviation of the paper P.

  Therefore, the control unit 11 has a swing mode as an operation mode, and adjusts the transport position of the paper P by swinging the registration roller 27. In addition, the control unit 11 can select not only the swing mode as the operation mode but also the non-oscillation mode that does not execute the swing mode as the operation mode.

  In this embodiment, the selection of the operation mode is determined by the user. In other words, the swing mode is not necessarily executed when power saving is desired or the image quality is not particular. Therefore, from the viewpoint of user friendliness, the operation mode can be set by the user, and the control unit 11 selects the operation mode set by the user.

  In order to perform such control, signals from the tip detection sensor 35, the offset sensor 36, the registration sensor 37, the intermediate conveyance sensor 38, the pre-registration sensor 39, and the operation unit 60 are input to the control unit 11. .

  The leading edge detection sensor 35 is disposed between the transfer position in the main transport path and the registration roller 27, and detects the arrival of the paper P at the detection position of the sensor (a position just before the transfer position by a predetermined distance). The tip detection sensor 35 is, for example, a reflective optical sensor having a light emitting element and a light receiving element. The detection result of the leading edge detection sensor 35 is used to control the timing of transporting the paper P to the transfer position.

  The deviation sensor 36 detects the amount of deviation of the paper P. As the displacement sensor 36, for example, a linear image sensor (for example, a CCD line sensor) in which a plurality of light receiving elements are arranged linearly along the paper width direction CD can be used. Specifically, the deviation sensor 36 detects the amount of deviation as well as the deviation direction of the paper P by detecting the distance from the conveyance reference position Cst to the edge of the paper P. The detection result of the deviation sensor 36 is used to determine the amount of movement of the registration roller 27 in the swing process.

  The registration sensor 37 is disposed between the registration roller 27 and the loop roller 26 in the main transport path, and the arrival of the leading edge of the paper P to the detection position of the sensor (a position in front of the registration roller 27 by a predetermined distance). To detect. The detection result of the registration sensor 37 is used to control the rotation timing of the registration roller 27.

  The intermediate conveyance sensor 38 is disposed between the loop roller 26 and the intermediate conveyance roller 25 in the main conveyance path, and the leading edge of the paper P to the detection position of the sensor (a position in front of the loop roller 26 by a predetermined distance). Detect arrival. On the other hand, the pre-registration sensor 39 is disposed between the pre-registration roller 34 and the intermediate conveyance roller 33 in the re-feed conveyance path, and moves to a sensor detection position (a position that is a predetermined distance before the pre-registration roller 34). The arrival of the leading edge of the paper P is detected. The detection result of the intermediate conveyance sensor 38 or the pre-registration sensor 39 is used for controlling the rotation timing of the loop roller 26.

  The operation unit 60 outputs various information set by the user to the control unit 11. As the operation unit 60, for example, a touch panel capable of performing an input operation according to information displayed on the display can be used. Through the operation unit 60, the user can set printing conditions, for example, selection of the rocking mode or the non-rocking mode, the type of paper P (for example, the amount and size), the image density, and the like. Further, the control unit 11 can display various messages to the user via the operation unit 60 by controlling the operation unit 60.

  FIG. 5 is a flowchart showing a control procedure of the swing motor according to the present embodiment. The processing shown in this flowchart is executed by the control unit 11 in response to a job start command.

  First, in step 1 (S1), the control unit 11 reads the printing conditions set through the operation unit 60. The control unit 11 can recognize information about whether the swing mode is selected as the operation mode or the non-swing mode and the type of the paper P from the read printing conditions.

  In step 2 (S2), the control unit 11 determines whether or not the operation mode is the swing mode. If an affirmative determination is made in step 2, that is, if the operation mode is the swing mode, the process proceeds to step 3 (S3). On the other hand, if a negative determination is made in step 2, that is, if the operation mode is the non-oscillation mode, the process proceeds to step 10 (S10) described later.

  In step 3, the control unit 11 determines whether or not the paper P is conveyed toward the registration roller 27. For example, the control unit 11 can make the determination based on the detection status of the registration sensor 37, the intermediate conveyance sensor, or the pre-registration sensor 39. However, since it is sufficient for this determination to be able to determine the situation where the paper P reaches the registration roller 27 before that, for example, paper detection for detecting the paper P sent from the paper feed tray 21 to the main transport path. The detection result of a sensor (not shown) can also be used. If an affirmative determination is made in step 3, that is, if the paper P is conveyed, the process proceeds to step 4 (S4). On the other hand, if a negative determination is made in step 3, that is, if the paper P is not being conveyed, the process of step 3 is performed again.

  In step 4, the control unit 11 turns on the excitation current for the swing motor 28. That is, the control unit 11 switches the excitation current from off to on. As the excitation current is turned on, a certain level of reference voltage is applied to the swing motor 28.

  In step 5 (S5), the control unit 11 outputs a drive pulse including a predetermined number of pulses to the swing motor 28. When a pulse voltage is applied to the swing motor 28 by the output of the drive pulse, the output shaft of the swing motor 28 is rotated by a predetermined number, so that the registration roller 27 is moved to the home position.

  After the registration roller 27 moves to the home position, when the conveyed paper P hits the registration roller 27, the control unit 11 continues to rotate the loop roller 26 for a predetermined time to form a loop on the paper P. . Then, the control unit 11 restarts the conveyance of the paper P by starting the rotation of the registration roller 27 at a predetermined timing.

  In step 6 (S 6), when the paper P reaches the deviation sensor 36, the control unit 11 detects the deviation amount through the deviation sensor 36.

  In step 7 (S7), the control unit 11 outputs a drive pulse including a predetermined number of pulses to the swing motor 28 based on the detected deviation amount. When a pulse voltage is applied to the oscillating motor 28 by this drive pulse, the output shaft of the oscillating motor 28 rotates by a predetermined number, and the registration roller 27 moves according to the amount of deviation of the paper P. Is done. Specifically, the control unit 11 moves the registration roller 27 by an amount corresponding to the deviation amount in a direction opposite to the deviation direction. At this time, since the paper P passing through the registration roller 27 is sandwiched by the registration roller 27, the transport position of the paper P that is not moved by the registration roller 27 is also moved.

  As a premise for executing Step 7, the control unit 11 switches the state of the roller pair from the press contact state to the separated state for each transport member positioned upstream of the registration roller 27. It is sufficient that such switching is executed at least during a period in which the registration roller 27 is driven by the swing motor 28.

  In addition, when the processing of step 7 is executed, the registration roller 27 may be moved after the conveyance of the paper P is once stopped. However, in this embodiment, in order to suppress a decrease in productivity, the registration roller 27 is moved in the paper width direction CD in parallel with the paper feed of the paper P by the registration roller 27.

  In step 8 (S8), the control unit 11 determines whether the trailing edge of the paper P has passed the registration roller 27 or not. For example, the control unit 11 performs the above-described determination based on the elapsed time after the trailing edge of the paper P passes the registration sensor 37 based on the conveyance speed of the paper P and the detection result of the registration sensor 37. Can do. Alternatively, the control unit 11 performs the above-described determination based on the elapsed time after the leading edge of the paper P passes through the registration sensor 37 based on the size and conveyance speed of the paper P and the detection result of the registration sensor 37. be able to. If the determination in step 8 is affirmative, that is, if the trailing edge of the paper P has passed the registration roller 27, the process proceeds to step 9 (S9). On the other hand, if a negative determination is made in step 8, that is, if the trailing edge of the paper P has not passed the registration roller 27, the determination in step 8 is performed again.

  In step 9 (S9), the control unit 11 turns off the excitation current for the swing motor 28, and ends this process.

  On the other hand, in step 10 following the negative determination in step 2 described above, the control unit 11 determines whether or not the paper P has been transported toward the registration roller 27 as in the processing in step 3. If an affirmative determination is made in step 10, that is, if the paper P is conveyed, the process proceeds to step 11 (S11). On the other hand, if a negative determination is made in step 10, that is, if the paper P is not being conveyed, the process of step 10 is performed again.

  In step 11, the control unit 11 sets the voltage level applied to the swing motor 28 when the excitation current is turned on, based on the type of paper P, specifically, the amount or size of paper. The greater the amount of paper P or the larger the size of the paper P, the greater the force that the paper P gives to the registration roller 27 when passing through the registration roller 27. Therefore, according to the magnitude of the force, It is preferable to set a static torque by the swing motor 28. Therefore, the control unit 11 sets the static torque of the swing motor 28, that is, the voltage level applied to the swing motor 28 according to the type of the paper P. Specifically, the control unit 11 sets the voltage level so that the voltage level applied to the swing motor 28 increases as the amount of the paper P increases or the size of the paper P increases. .

  In step 12 (S12), the control unit 11 turns on the excitation current for the swing motor 28. As the exciting current is turned on, the voltage of the level set in step 11 is applied to the swing motor 28.

  Then, after step 12, the control unit 12 proceeds to the process of step 8 described above, and turns off the excitation current for the swing motor 28 on condition that the trailing edge of the paper P has determined that the registration roller 27 has passed. Then, this process ends.

  When printing on a plurality of sheets P as a job command, a predetermined process may be repeatedly executed according to the operation mode. That is, when the operation mode is the swing mode, the processes from step 6 to step 8 are repeated until the final sheet is reached. On the other hand, when the operation mode is the swing mode, the trailing edge of the final sheet is It is sufficient to perform the processing up to step 8 until it passes.

  As described above, in this embodiment, when the operation mode is the swing mode, the control unit 11 turns on the excitation current and outputs a drive pulse corresponding to the swing amount of the registration roller 27 to the electric motor. Processing is performed (steps 4 and 7). On the other hand, when the operation mode is the non-oscillation mode, the control unit 11 performs non-oscillation processing for turning on the excitation current (step 12).

  According to such a configuration, in the non-oscillation mode, a static torque is generated in the oscillation motor 28 by turning on the excitation current. The movement of the registration roller 27 is regulated by this static torque. As a result, it is possible to suppress a situation in which the registration roller 27 moves unexpectedly when the paper P passes the registration roller 27 and the paper P is displaced due to the passage of the registration roller 27. it can.

  Further, in the swing mode, by turning on the excitation current and outputting the drive pulse, the output shaft of the swing motor 28 rotates by a predetermined number of rotations, and the registration roller 53 moves along the sheet width direction CD. It is moved by an amount corresponding to the offset amount. As a result, the transport position of the paper P is corrected in accordance with the transport reference position Cst. Therefore, the transport reference position Cst and the center position Cpp of the paper P are appropriately aligned, and a toner image can be formed at an appropriate position on the paper P.

  In the present embodiment, when the operation mode is the non-oscillation mode, the control unit 11 performs the non-oscillation process corresponding to the passage period during which the paper P passes the registration roller 27, and excludes the passage period. Then, the excitation current is turned off. According to such a configuration, since the excitation current is turned off during periods other than the passage period in which the deviation can occur, it is possible to suppress a situation in which power consumption increases.

  Further, the control unit 11 variably controls the voltage level applied to the swing motor when the excitation current is turned on according to the type of the paper P (step 11). According to such a configuration, since the static torque can be set according to the force applied from the paper P to the registration roller 27, the deviation of the paper P accompanying the passage of the registration roller 27 can be appropriately suppressed, Further, unnecessary power consumption can be suppressed.

  In the present embodiment, when the operation mode is the swing mode, the control unit 11 performs the swing process corresponding to the passage period in which the paper P passes the registration roller 27, and the excitation is performed in the period other than the passage period. The current is off. According to such a configuration, since the excitation current is turned off during periods other than the passage period in which the deviation can occur, it is possible to suppress a situation in which power consumption increases.

  Further, in the present embodiment, the control unit 11 moves the registration roller 27 in accordance with the amount of deviation of the paper P (step 7), and moves the registration roller to a predetermined home position (initial position). 27 is moved (step 5). For example, when the registration roller 27 is moved according to the deviation of the paper P, the registration roller 27 is moved to the home position, and then the registration roller 27 is moved according to the deviation of the paper P. In this case, there is a case where there is no time for executing a series of procedures unless the conveyance of the paper P is temporarily stopped. However, a decrease in productivity can be suppressed by moving to the home position in advance.

(Second Embodiment)
The image forming apparatus according to the second embodiment will be described below. The image forming apparatus according to the second embodiment is different from that of the first embodiment in that the control unit 11 autonomously selects an operation mode. Note that the description of the same configuration as that of the first embodiment will be omitted, and hereinafter, the description will focus on the differences.

  As shown in the first embodiment, when the registration roller 27 is moved in accordance with the deviation amount of the paper P, the state of the transport roller upstream of the registration roller 27 is switched from the pressure contact state to the separation state. ing. This switching is because if the registration roller 27 is moved while the upstream conveying roller is in a pressure contact state, the paper P may be twisted, which may lead to a decrease in print quality.

  In this case, there is no problem if all of the upstream conveying rollers can be switched between the pressure contact state and the separated body, but switching to the separated body without providing a drive mechanism due to space or cost problems. There may be upstream transport rollers that cannot.

  FIG. 6 is an explanatory diagram schematically illustrating the configuration of the transport roller in the image forming apparatus according to the second embodiment. For example, as shown in FIG. 6, a transport roller 40 arranged on a transport path for transporting the paper P from the manual paper feed tray, or a transport roller upstream of the intermediate transport roller 24 (intermediate transport roller 23 or the like) The configuration is such that only the pressure contact state cannot be switched to the separated state. In addition, a large-capacity paper feeding device may be disposed in front of the image forming apparatus, and the paper P may be fed from the large-capacity paper feeding device to the image forming apparatus. The same applies to the transport roller.

  Therefore, in the present embodiment, the control unit 11 determines whether to select the swing mode or the non-swing mode as the operation mode based on the printing conditions. Specifically, when the size of the paper P to be transported is specified in the printing conditions, the control unit 11 compares the specified size with the upper limit size stored in the memory 11b and the like. When the specified size is larger than the upper limit size, the control unit 11 selects the non-oscillation mode as the operation mode. On the other hand, the control unit 11 determines that the specified size is smaller than the upper limit size. In this case, the swing mode is selected as the operation mode. In this case, the upper limit size is a transport roller that cannot switch between the pressed state and the separated body when the registration roller 27 is moved according to the amount of deviation of the paper P in consideration of the transport configuration in the machine. It is set as the minimum value of the paper size that remains interfered. In other words, the non-oscillation mode is an operation mode that is selected based on the relationship between the arrangement configuration in the conveyance path of the paper P with respect to the conveyance member that can be switched between the pressure contact state and the separation state, and the paper size.

  As described above, according to the present embodiment, it is possible to appropriately determine a scene in which the swing mode cannot be executed due to mechanical restrictions. Thus, it is possible to suppress the occurrence of a situation in which the paper P is twisted by forcing the swing mode.

  The image forming apparatus according to the embodiment of the present invention has been described above, but the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the invention. .

SC image reading apparatus 10Y to 10K image forming unit 10M image forming unit 11 control unit 20 paper transport unit 21 paper feed tray 22 first paper feed unit 23 to 25 intermediate transport roller 26 loop roller 27 registration roller 28 swing motor 29 paper discharge Tray 30 Guide member 31 Reverse roller 32, 33 Intermediate transport roller 34 Pre-registration roller 50 Fixing device 60 Operation unit

Claims (5)

An electric motor that operates when the winding is excited by energization,
A transport position configured to be swingable along a paper width direction which is a direction orthogonal to the paper transport direction, and is driven by the electric motor to move the transported paper along the paper width direction. A moving part;
A control unit for controlling the excitation current for the electric motor,
The controller is
As a switchable operation mode, there are a swing mode in which the transport position of the paper is adjusted by swinging the transport position moving unit, and a non-swing mode in which the swing mode is not executed.
When the operation mode is the swing mode, a swing process of turning on the excitation current and outputting a drive pulse corresponding to the swing amount of the transfer position moving unit to the electric motor is performed.
When the operation mode is the non-oscillation mode, a non-oscillation process for turning on the excitation current is performed ,
When the operation mode is the non-oscillation mode, the non-oscillation process is performed corresponding to the passage period during which the sheet passes through the transport position moving unit, and the excitation current is turned off in the period excluding the passage period. An image forming apparatus. The image forming apparatus according to claim 1 , wherein the control unit variably controls a voltage level applied to the swing motor when the excitation current is turned on according to a type of paper. apparatus.   An electric motor that operates when the winding is excited by energization,
  A transport position configured to be swingable along a paper width direction which is a direction orthogonal to the paper transport direction, and is driven by the electric motor to move the transported paper along the paper width direction. A moving part;
  A control unit for controlling the excitation current for the electric motor,
  The controller is
  As a switchable operation mode, there are a swing mode in which the transport position of the paper is adjusted by swinging the transport position moving unit, and a non-swing mode in which the swing mode is not executed.
  When the operation mode is the swing mode, a swing process of turning on the excitation current and outputting a drive pulse corresponding to the swing amount of the transfer position moving unit to the electric motor is performed.
  When the operation mode is the non-oscillation mode, a non-oscillation process for turning on the excitation current is performed,
  When the operation mode is the swing mode, the swing process is performed in correspondence with a passing period in which the sheet passes through the transport position moving unit, and the excitation current is turned off in a period other than the passing period. An image forming apparatus.   The control unit moves the transport position moving unit to a predetermined initial position prior to moving the transport position moving unit according to a deviation amount of the sheet. Item 4. The image forming apparatus according to any one of Items 1 to 3.   The said conveyance position moving part is a pair of registration roller arrange | positioned upstream from the image formation position which forms an image on a sheet | seat in the conveyance path | route of a sheet | seat. Image forming apparatus.

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