JP2007313725A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable to convey a medium to be recorded with a high accuracy by controlling to drive a driving motor in accordance with a difference in the actual amount of conveyance against the target amount of conveyance when a paper is conveyed through a conveying path with a winding angle on a conveying roller not smaller than a definite value during conveying the paper, the paper is conveyed through a conveying path approximately in the horizontal direction, or the paper with a different thickness is conveyed. <P>SOLUTION: In accordance with an inputting amount of a motor obtained from a motor inputting amount detecting circuit 107 for detecting electric voltage or electric current given to a sub-scanning motor 31 for conveying the paper 12, the conveying speed of the paper 12 and the kind of the medium to be recorded, a corrected value of the amount of driving of the motor stored on every conveying path and every kind of the medium to be recorded in a data storing part 108 is read out, and a corrected value of the amount of driving of the sub-scanning motor 31 is operated, and the target amount of conveyance obtained from a position/speed profile is corrected to control driving of the sub-scanning motor 31. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus that conveys a recording medium via a conveyance roller.

  As an image forming apparatus such as a printer, a facsimile machine, a copying machine, and a multifunction machine of these, for example, a liquid ejection apparatus including a recording head composed of a liquid ejection head that ejects liquid droplets of a recording liquid (liquid) is used. While conveying a medium (hereinafter also referred to as “paper”, the material is not limited, and the medium, recording medium, transfer material, recording paper, etc. are also used synonymously), a recording liquid (hereinafter referred to as a liquid) Some of them perform image formation (recording, printing, printing, and printing are also used synonymously) by attaching the ink to the paper.

  The image forming apparatus means an apparatus for forming an image by discharging a liquid onto a medium such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, ceramics, etc. The term “not only” means not only giving an image having a meaning such as a character or a figure to a medium but also giving an image having no meaning such as a pattern to the medium. Further, the liquid is not limited to the recording liquid and ink, and is not particularly limited as long as it is a liquid capable of forming an image. Further, the liquid ejecting apparatus means an apparatus that ejects liquid from the liquid ejecting head, and is not limited to an apparatus that performs image formation.

  By the way, in the image forming apparatus, when a plurality of types of paper can be used, the amount of slip and the amount of feed (too much) differ depending on the type of paper. As described above, if the slipping amount and the feeding amount are different at the time of conveyance, the actual conveyance amount differs even if the conveyance amount is the same, and the image quality may deteriorate depending on the paper.

Therefore, conventionally, in Patent Document 1, by inputting information on the manufacturer, model number, and amount of paper information from the operation unit of the image forming apparatus, the control unit obtains control data in the control unit based on the obtained information. Refer to each control condition to change, monitor the paper feed motor current during paper feeding, estimate the paper thickness of the transfer paper from the current value change amount of the paper feed motor, and correct the change amount by that value It is described to do.
JP 2003-084507 A

Japanese Patent Application Laid-Open No. 2004-228688 discloses an image forming unit that forms an image on a sheet, a conveyance unit that conveys the sheet, and a sheet discharge so that stable image recording can be performed regardless of the thickness of the sheet. A plurality of feeding units that feed the sheet to the image forming unit, and the plurality of feeding units have independent thickness tolerances of the sheets to be fed, and each feeding unit. Japanese Patent Application Laid-Open No. 2003-259561 describes that a sheet thickness detecting means for detecting the thickness of the sheet is provided on the upstream side of the sheet conveying path.
JP 2001-026342 A

In addition, Patent Document 3 discloses a cutting position control device in a recording apparatus in which a conveying roller is used when a cutting position reaches a cutter blade from a recording head without causing a slip between a recording material and the conveying roller. The data storage means has a first drive amount and a paper feed correction value set according to the type of recording material, and the first drive amount when the cut position advances from the recording head to the cutter blade. It is described that the constitution is such that the positional relationship between the cutting position and the cutter blade is corrected by adding a paper feed correction value to the above.
JP 2003-260833 A

In Patent Document 4, in order to obtain a normal image even if slippage of the document due to paper type or deterioration with time occurs in the document processing apparatus, the document speed during document scanning is rotated following the document movement. Detected by an encoder attached to the driven roller and holds the detected document speed in association with the position on the document, and after a predetermined reading, the corresponding position according to the document speed at each position on the held document It is described that an interpolation process for interpolating and adding a new line between these lines or a thinning process for removing a line at a corresponding position is performed.
JP 2002-232656 A

In Patent Document 4, as a conveyance correction method of a recording / reading device, there is an error in a paper feeding amount due to a thickness of a recording medium, a stiffness, a surface friction coefficient, or the like, or wear of a paper feeding roller due to paper passing. In order to correct the sheet conveyance error due to the change, it is described that the conveyance pattern at the time of recording by the recording means is different from the conveyance pattern at the time of reading.
JP 2001-315389 A

  By the way, as the image forming apparatus, the first transport path for forming an image while transporting the paper in the horizontal direction by changing the direction of the paper fed from the lower side of the apparatus main body by about 90 degrees via the transport roller. And a second transport path (generally performed as manual feed) that feeds the paper in a substantially horizontal direction and forms an image while transporting the paper in the horizontal direction as it is. is there.

In such an image forming apparatus, since the paper is stretched on the front surface of the paper by the winding of the paper on the transport roller in the first transport path and the paper is contracted on the back surface, the transport diameter of the transport roller that determines the transport amount of the paper is the transport roller. The conveyance control is performed assuming that approximately half the thickness of the sheet is added to the diameter of the sheet. Also, slippage may occur in the first transport path depending on the thickness of the paper.
In contrast, since the paper is transported in the substantially horizontal direction in the second transport path, the transport diameter of the transport roller that determines the transport amount of the paper is transported assuming that the diameter of the transport roller is approximately half the thickness of the paper. Take control.

  Therefore, even if the target transport amount is the same, the actual transport amount may differ depending on the transport path, and the actual transport amount may vary depending on the thickness (paper thickness) of the paper. Here, if the thickness of the paper is manually input or detected by a detection means such as an optical sensor, there is a problem that an erroneous input occurs or the configuration becomes complicated.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus that can perform high-precision conveyance with a simple configuration.

  In order to solve the above problems, an image forming apparatus according to the present invention includes an image forming unit that forms an image on a recording medium, a conveying roller that constitutes a conveying unit that conveys the recording medium, and drives the conveying roller. Drive motor, motor input amount detection means for detecting a voltage or current input to the drive motor, the drive amount of the drive motor is corrected based on the detection result of the motor input amount detection means and the conveyance speed of the recording medium. And means.

  Here, it is preferable to have two or more types of conveyance paths having different winding angles around the conveyance roller when conveying the recording medium, and to correct the drive amount of the drive motor in accordance with each conveyance path. In this case, the storage unit stores the correction value of the driving amount of the drive motor corresponding to the type of recording medium and each conveyance path, and the correction value stored in the storage unit according to the type of recording medium and the conveyance path. It is preferable to correct the drive amount of the drive motor based on the above. In this case, when the correction value of one type of recording medium among the correction values corresponding to the type of recording medium is changed, the correction value of another type of recording medium can also be changed. Furthermore, the correction value of the drive motor is determined depending on whether the rear end portion of the recording medium is opposed to the conveyance roller and when the rear end portion of the recording medium is shifted from the state facing the conveyance roller to the non-opposing state. It can be configured to change.

  An image forming apparatus according to the present invention includes an image forming unit that forms an image on a recording medium, a conveying roller that constitutes a conveying unit that conveys the recording medium, a driving motor that drives the conveying roller, and the driving motor. A motor input amount detection means for detecting a voltage or current input to the recording medium, and a means for changing the drive pattern of the drive motor based on the detection result of the motor input amount detection means and the conveyance speed of the recording medium. did.

  Here, it is possible to have two or more types of conveyance paths having different winding angles around the conveyance roller when conveying the recording medium, and to change the drive motor drive pattern according to each conveyance path. In this case, a storage unit storing a drive motor drive pattern or a drive pattern correction value corresponding to the type of recording medium and each conveyance path is provided, and stored in the storage unit according to the type of recording medium and the conveyance path. It is preferable to correct the driving pattern of the driving motor based on the driving pattern or the correction value of the driving pattern. In this case, when the drive pattern of the drive motor or the correction value of the drive pattern among the drive motor drive pattern or the correction value of the drive pattern corresponding to the type of the recording medium is changed, The drive pattern of the recording medium or the correction value of the drive pattern can also be changed. Further, the drive motor drive pattern or when the rear end portion of the recording medium faces the transport roller and when the rear end portion of the recording medium shifts from the state facing the transport roller to the state facing the transport roller. The drive pattern correction value can be changed.

  According to the image forming apparatus of the present invention, an image forming unit that forms an image on a recording medium, a conveying roller that constitutes a conveying unit that conveys the recording medium, a drive motor that drives the conveying roller, Motor input amount detection means for detecting voltage or current input to the drive motor, means for correcting the drive amount of the drive motor based on the detection result of the motor input amount detection means and the conveyance speed of the conveyance roller, or a drive pattern Therefore, without adopting a complicated configuration, the drive motor is driven and controlled according to the difference in the transport amount according to the thickness of the recording medium and the transport path, so that the target is covered with high accuracy. A recording medium can be conveyed.

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, an example of an image forming apparatus according to the present invention will be described with reference to FIGS. FIG. 1 is an explanatory side view for explaining the overall structure of the mechanism section of the image forming apparatus, and FIG. 2 is a plan view for explaining the mechanism section.
In this image forming apparatus, a carriage 3 is slidably held in a main scanning direction by a guide rod 1 and a guide rail 2, which are guide members horizontally mounted on left and right side plates (not shown), and a driving pulley 6A is driven by a main scanning motor 4. 2 is moved and scanned in the direction indicated by the arrow (main scanning direction) in FIG. 2 via a timing belt 5 stretched between the roller and the driven pulley 6B.

  The carriage 3 includes, for example, four recording heads 7y serving as image forming units including liquid ejection heads that eject ink droplets of yellow (Y), cyan (C), magenta (M), and black (K), respectively. , 7c, 7m, and 7k (referred to as “recording head 7” when the colors are not distinguished) are arranged in a direction crossing the main scanning direction and the ink droplet ejection direction is directed downward. ing.

  The liquid discharge head constituting the recording head 7 includes a piezoelectric actuator such as a piezoelectric element, a thermal actuator that uses a phase change caused by liquid film boiling using an electrothermal transducer such as a heating resistor, and a metal phase change caused by a temperature change. A shape memory alloy actuator using an electrostatic force, an electrostatic actuator using an electrostatic force, and the like provided as pressure generating means for generating a pressure for discharging a droplet can be used. In addition, the configuration is not limited to an independent head for each color, and may be configured with one or a plurality of liquid ejection heads having a nozzle row composed of a plurality of nozzles that eject droplets of a plurality of colors.

  The carriage 3 is also equipped with sub-tanks 8 for each color for supplying ink of each color to the recording head 7. Ink is supplied to the sub tank 8 from a main tank (ink cartridge) (not shown) via an ink supply tube 9.

  On the other hand, as a paper feeding unit for feeding paper 12 stacked on a paper stacking unit (pressure plate) 11 such as a paper feeding cassette 10, a half-moon roller (for separating and feeding the paper 12 one by one from the paper stacking unit 11) A separation pad 14 made of a material having a large friction coefficient is provided facing the sheet feeding roller 13 and the sheet feeding roller 13, and the separation pad 14 is urged toward the sheet feeding roller 13 side.

  In order to convey the sheet 12 fed from the sheet feeding unit below the recording head 7, a conveyance belt 21 for electrostatically attracting and conveying the sheet 12 and a guide 15 from the sheet feeding unit. A counter roller 22 for transporting the sheet 12 fed between the conveyor belt 21 and the conveyor belt 21, and for shifting the sheet 12 fed substantially vertically upward by approximately 90 ° to follow the conveyor belt 21. A conveyance guide 23 and a first pressure roller 25 </ b> A and a second pressure roller 25 </ b> B urged toward the conveyance belt 21 by a pressing member 24 are provided. In addition, a charging roller 26 as a charging unit for charging the surface of the transport belt 21 is provided.

  Here, the conveyor belt 21 is an endless belt, and is stretched between the conveyor roller 27 and the tension roller 28, and the conveyor roller 27 rotates from the sub-scanning motor 31 via the timing belt 32 and the timing roller 33. By doing so, it is configured to circulate in the belt conveyance direction (sub-scanning direction) of FIG. A guide member 29 is disposed on the back side of the conveying belt 21 corresponding to the image forming area by the recording head 7. The charging roller 26 is disposed so as to come into contact with the surface layer of the transport belt 21 and rotate following the rotation of the transport belt 21.

  As shown in FIG. 2, an encoder wheel 34 is attached to the shaft of the transport roller 27, and an encoder sensor 35 for detecting a slit of the encoder wheel 34 is provided. An encoder 36 is configured.

  Further, as shown in FIG. 1, an encoder sheet 42 having slits is provided along the moving direction of the carriage 3, and the carriage 3 is provided with an encoder sensor 43 for detecting the slits of the encoder sheet 42. The encoder wheel 42 and the encoder sensor 43 constitute a linear encoder 44.

  Further, as a paper discharge unit for discharging the paper 12 recorded by the recording head 7, a separation claw 51 for separating the paper 12 from the transport belt 21, a paper discharge roller 52 and a paper discharge roller 53, and a discharge And a paper discharge tray 54 for stocking the paper 12 to be printed.

  A double-sided paper feeding unit 55 is detachably mounted on the back. The double-sided paper feeding unit 55 takes in the paper 12 returned by the reverse rotation of the transport belt 21, reverses it, and feeds it again between the counter roller 22 and the transport belt 21.

  In addition, a manual sheet feeding unit 60 that manually feeds the sheet 12 is provided on the upper surface of the duplex feeding unit 55.

  Further, as shown in FIG. 2, a maintenance / recovery mechanism 56 for maintaining and recovering the nozzle state of the recording head 7 is disposed in the non-printing area on one side of the carriage 3 in the scanning direction.

  The maintenance / recovery machine 56 is provided with caps 57 for capping each nozzle surface of the recording head 7, a wiper blade 58 as a blade member for wiping the nozzle surface, and for discharging the thickened recording liquid. An empty discharge receiver 59 for receiving droplets when performing empty discharge for discharging droplets that do not contribute to recording is provided.

  In the image forming apparatus configured as described above, the sheets 12 set in the sheet feeding tray 10 below the apparatus are separated and fed one by one, and the sheet 12 fed substantially vertically upward is guided by the guide 15. It is sandwiched between the conveyor belt 21 and the counter roller 22 and conveyed. Further, the leading end is guided by the conveyance guide 23 and pressed against the conveyor belt 21 by the first pressure roller 25A, and follows the outer peripheral surface of the conveyance roller 27. The conveyance direction is changed by about 90 ° (conveyance path A in FIG. 3). Further, the sheet is fed from the manual sheet feeding unit 60 in a substantially horizontal direction and sent between the first pressure roller 25A facing the conveyance roller 27 and the conveyance belt 21 (conveyance path B in FIG. 3).

  Here, an AC voltage supply unit applies an alternating voltage that alternately repeats positive and negative to the charging roller 26 by a control unit (not shown), and a charging voltage pattern that alternates the conveying belt 21, that is, a sub-scanning direction that is a circumferential direction. In addition, charging is performed with a pattern in which plus and minus are alternately repeated with a predetermined width. When the paper 12 is fed onto the charged transport belt 21, the paper 12 is attracted to the transport belt 21 by electrostatic force, and the paper 12 is transported in the sub-scanning direction by the circular movement of the transport belt 21.

  Therefore, by driving the recording head 7 according to the image signal while moving the carriage 3 in the forward and backward directions, ink droplets are ejected onto the stopped paper 12 to record one line. After transporting a predetermined amount, the next line is recorded. Upon receiving a recording end signal or a signal that the trailing edge of the paper 12 has reached the recording area, the recording operation is finished and the paper 12 is discharged onto the paper discharge tray 54.

  In the case of double-sided printing, when recording on the front surface (surface to be printed first) is completed, the recording belt 12 is fed into the double-sided paper feeding unit 61 by rotating the conveyor belt 21 in the reverse direction. The paper 12 is reversed (with the back surface being the printing surface), fed again between the counter roller 22 and the transport belt 21, controlled in timing, and transported onto the transport bell 21 as described above. After recording on the back side, the sheet is discharged onto the discharge tray 54.

  During printing (recording) standby, the carriage 3 is moved to the maintenance / recovery mechanism 55 side, and the nozzle surface of the recording head 7 is capped by the cap 57, and the nozzles are kept in a wet state. To prevent. In addition, the recording liquid is sucked from the nozzle in a state where the recording head 7 is capped by the cap 57, and a recovery operation is performed to discharge the thickened recording liquid and bubbles, and the ink adhered to the nozzle surface of the recording head 7 by this recovery operation. Wiping is performed with a wiper blade 58 in order to remove the cleaning. In addition, an idle ejection operation for ejecting ink not related to recording is performed before the start of recording or during recording. Thereby, the stable ejection performance of the recording head 7 is maintained.

Next, an outline of the control unit of the image forming apparatus will be described with reference to FIG. This figure is an overall block diagram of the control unit.
The control unit controls the entire image forming apparatus. The main control unit 101 includes a microcomputer that also serves as means for correcting the drive amount of the drive motor according to the present invention (or means for changing the drive pattern). And a print control unit 102 composed of a microcomputer for controlling printing.

  Then, the main control unit 101 sets the main scanning motor 4 and the sub scanning motor 31 to the main scanning motor driving circuit 103 and the sub scanning motor 31 in order to form an image on the paper 12 based on the print processing information input from the communication circuit 100. Drive control is performed via the scanning motor 104, and control such as sending print data to the print control unit 102 is performed.

  A detection signal from a carriage position detection circuit 105 that detects the position of the carriage 3 is input to the main control unit 101, and the main control unit 101 controls the movement position and movement speed of the carriage 3 based on this detection signal. To do. The carriage position detection circuit 105 reads the number of slits of the encoder sheet 42 arranged in the scanning direction of the carriage 3 with a photo sensor (encoder sensor) 43 mounted on the carriage 3 and counts the position of the carriage 3. To detect. The main scanning motor driving circuit 103 rotates the main scanning motor 4 according to the carriage movement amount input from the main control unit 101 to move the carriage 3 to a predetermined position at a predetermined speed.

  Further, a detection signal from a conveyance amount detection circuit 106 that detects the movement amount of the conveyance belt 21 is input to the main control unit 101, and the main control unit 101 detects the movement amount and movement speed of the conveyance belt 21 based on this detection signal. To control. The carry amount detection circuit 106 detects the carry amount by reading and counting the number of slits of the rotary encoder sheet 34 attached to the rotation shaft of the carry roller 27 with a photo sensor (encoder sensor) 35. The sub-scanning motor driving circuit 104 rotates the sub-scanning motor 31 in accordance with the conveyance amount input from the main control unit 101, rotationally drives the conveyance roller 22, and moves the conveyance belt 21 to a predetermined position at a predetermined speed. Move.

  Here, the main control unit 101 receives a detection signal from a motor input amount detection circuit 107 that detects an input amount (voltage or current) to the sub-scanning motor 31. The data storage means configured by the EEPROM 108 stores (stores) correction values relating to the driving amount of the sub-scanning motor 31 for the recording medium and correction values relating to the driving amount of the sub-scanning motor 31 for the conveyance paths A and B. Yes. The main control unit 101 also performs control for correcting the drive amount when the sub-scanning motor 31 is rotationally driven based on the motor input amount detection signal, information on the conveyance path, and the correction value stored in the EEPROM 108.

  Further, the main control unit 101 performs control for charging the transport belt 21 by applying an AC bias to the charging roller 26 via the AC bias supply unit 111. Further, the main control unit 101 rotates the sheet feeding roller 13 once by giving a sheet feeding roller driving command to the sheet feeding roller driving circuit 112. The main control unit 101 rotationally drives a motor (not shown) of the maintenance / recovery mechanism 56 via the maintenance / recovery mechanism drive motor drive circuit 113, thereby raising and lowering the cap 57, raising and lowering the wiper blade 58, and driving a suction pump (not shown). And so on.

  The print control unit 102 generates pressure for ejecting droplets of the recording head 8 based on the signal from the main control unit 101 and the carriage position and conveyance amount from the carriage position detection circuit 105 and the conveyance amount detection circuit 106. Data for driving the means is generated, and the above-described image data is transferred to the head drive circuit 110 as serial data, and the transfer clock, latch signal, and droplet control necessary for transferring the image data and confirming the transfer, etc. In addition to outputting a signal (mask signal) etc. to the head drive circuit 110, it is composed of a D / A converter, a voltage amplifier, a current amplifier, etc. for D / A converting the pattern data of the drive signal stored in the ROM. Drive waveform generator and drive waveform selection means to be given to the head driver, one drive pulse (drive signal) or a plurality of drive pulses And it generates and outputs a composed drive waveform (drive signal) to the head drive circuit 110.

  The head drive circuit 110 selectively selects a drive signal constituting a drive waveform supplied from the print control unit 102 based on image data corresponding to one row of the print head 8 that is input serially. The recording head 7 is driven by applying it to a driving element (for example, a piezoelectric element as described above) that generates energy for discharging the ink. At this time, by selecting a driving pulse constituting the driving waveform, for example, dots having different sizes such as large droplets (large dots), medium droplets (medium dots), and small droplets (small dots) can be distinguished. it can.

The drive control of the sub-scanning motor in this image forming apparatus will be described with reference to FIG. FIG. 5 is a block diagram for functionally explaining portions related to sub-scan driving control and correction processing in the control unit.
First, an output signal (output pulse) of a rotary encoder 36 composed of an encoder wheel 34 and an encoder sensor 35 provided on the shaft of the conveying roller 27 is given to an encoder signal processing unit 201, and the encoder signal processing unit 201 And converted into position information. The obtained speed and position information is synthesized by a signal processing synthesis unit 202 that can be configured by an ASIC or the like, and then given to the comparison calculation unit 203. The transport amount detection circuit 106 described above includes the rotary encoder 26, the encoder signal processing unit 201, and the signal processing synthesis unit 202.

  On the other hand, information of the speed / position profile (driving pattern of the sub-scanning motor 31) stored in the speed / position profile storage unit 204 is given to the comparison calculation unit 203, and the comparison calculation unit 203 receives these signals. The velocity and position information (combined information) given from the processing synthesis unit 202 and the value of the velocity / position profile stored in the velocity / position profile storage unit 204 correspond to the correction value given from the correction amount calculation unit 206 described later. The deviation between the target position and the current position is calculated by comparing with the corrected value.

  Then, based on the deviation obtained by the comparison calculation unit 203, the PID control calculation unit 205 performs PID calculation to generate a PWM signal. That is, the PID control calculation unit 205 calculates the control value by performing PID (proportional, integral, differentiation) control on the deviation from the comparison calculation unit 203. Here, assuming that the sub-scanning motor 31 is driven by PWM (Pulse Width Modulation) control, the PID control calculation unit 205 performs PID control on the deviation to obtain the PWM duty ratio. By giving the duty ratio to the motor driver (sub-scanning motor driving circuit) 104 and driving the sub-scanning motor 31 by the driving amount by PWM control, the conveying belt 31 is moved by the target moving amount at the target speed. Drive to the target position.

  On the other hand, the motor input amount detection circuit 107 detects a drive voltage or drive current applied from the motor driver 104 to the sub-scanning motor 31 and outputs it to the correction amount calculation unit 206. The data storage unit 108 also includes a correction value for the driving amount of the sub-scanning motor 21 corresponding to the type of paper, a correction value for the driving amount of the sub-scanning motor 21 for each of the conveyance paths A and B for each of the conveyance paths A and B. Each value is stored and held.

  The correction amount calculation unit 206 converts the detection result from the motor input amount detection circuit 107, the conveyance speed from the position / velocity profile 204, the conveyance path information indicating the conveyance path, and the sheet type information indicating the sheet type. Based on this, the correction value stored in the data storage unit 108 is read out, the correction value of the driving amount of the sub-scanning motor 31 is calculated, and is supplied to the comparison calculation unit 203 described above.

  Thereby, the comparison calculation unit 203 calculates the deviation between the value obtained by correcting the value related to the target position / speed given from the speed / position profile 204 and the detected speed / position value given from the signal processing synthesis unit 202. The sub-scanning motor 31 is driven and controlled by a drive amount corresponding to the motor input amount, the conveyance speed, the conveyance path, and the paper type.

  This point will be further described. As described above, in this image forming apparatus, the fed paper 12 is conveyed from the lower side in a substantially vertical upward direction and is attracted to the conveyance belt 21 and is substantially conveyed to the conveyance roller 27. Winding at 90 °, turning the direction, transporting in a substantially horizontal direction, and substantially horizontal with respect to the recording head 7 serving as an image forming unit that is fed from the manual paper feeding unit 60 and records on the paper 12. And a conveyance path B for conveying the paper 12.

  Here, in the conveyance path A, as shown in FIG. 6 (illustrated without the conveyance belt 21), the sheet 12 is formed on the surface of the sheet 12 due to the thickness of the sheet and the winding of the sheet around the conveyance roller 27 by approximately 90 °. Stretches and shrinks on the back. Therefore, the conveyance diameter that determines the conveyance amount of the paper 12 is a value obtained by adding almost half of the thickness Dy of the paper 12 to the conveyance roller diameter Dh (here, including the thickness of the conveyance belt 21). The feed radius Ro is set to Ro = Dh + Dy / 2.

  On the other hand, the actual feed radius Ro by the transport roller 27 in the transport path B for guiding and transporting the paper in the substantially horizontal direction with respect to the image forming unit is Ro = Dh.

  In the transport path A, the transport load is proportional to the thickness of the paper, and it can be predicted that the paper slips depending on the transport force.

  Therefore, first, a correction value for the driving amount of the sub-scanning motor 31 is calculated by the correction amount calculation unit 206 from the conveyance speed of the paper 12, the motor input amount to the sub-scanning motor 31 and the conveyance path, and the target of the sub-scanning motor 31 is calculated. By correcting the drive amount to be driven and driving the sub-scanning motor 31, the paper can be transported with an accurate transport amount in both the transport paths A and B.

  Here, the timing at which the motor input amount detection circuit 107 detects the motor input amount value 31 is the position where the conveyance load is the largest, and in the configuration of this image forming apparatus, the leading edge of the sheet is the first pressure roller 25A in FIG. It is preferable to measure at a position in contact with.

  In this way, by obtaining the paper transport load from at least the change in the transport speed (constant) and the motor input amount, the paper thickness can be predicted from the paper transport load, and the paper transport is based on this. By correcting the drive amount of the sub-scan motor corresponding to the amount, the paper can be transported with the correct transport amount regardless of the transport path, paper thickness difference, paper slip, etc. Can be reduced. Furthermore, by changing the correction value of the driving amount according to the difference in the conveyance path, the conveyance force of the sheet, the conveyance load, the thickness, etc., it is possible to reduce image disturbance due to the difference in the conveyance path and the thickness of the sheet.

  In particular, in an image forming apparatus that transports a plurality of types of paper and has a curvature of a paper transport path of 60 ° or more, as described above, the winding angle of the transport roller when the paper is fed is more than a certain value (almost 60). In a transport path where the paper feed amount is determined by the transport roller diameter, the transport diameter that determines the paper transport amount by winding the paper adds approximately half the paper thickness to the transport roller diameter. Also, if the paper transport load is large, slip may occur between the transport roller and the paper, so the motor drive amount is corrected (or changed) according to the transport path and transport load. This makes it possible to transport the paper with an accurate transport amount, reduce image distortion, and improve image quality.

  Further, as described above, the calculation of the correction value is performed based on the paper conveyance speed, the motor input amount, the selection of the conveyance path, and the correction value data stored in the data storage unit 108. As a result, the calculation unit 33 calculates a correction value for the conveyance amount, and outputs the result to the motor drive unit 34 to convey the paper. As described above, the correction value of the drive amount of the drive motor corresponding to the type of recording medium and each transport path is stored in the data storage means (unit) in advance, and the storage means is stored according to the type of recording medium and the transport path. The correction calculation is simplified by correcting the drive amount of the drive motor based on the correction value stored in.

Next, correction value change control stored in the data storage unit will be described with reference to FIG.
If an error occurs between the actual transport amount and the correction value data stored in the data storage unit 108 due to wear of the transport roller 27, the correct transport amount cannot be obtained.

  Therefore, using the correction value data stored in the data storage unit 108, a specific pattern for adjustment is printed out on a specific sheet, and the result of the user's determination that the image is not disturbed most is the result. Numerical value, pattern No. Enter in In response to this, the correction value of the specific sheet stored in the data storage unit 108 is changed. Further, according to the change of the correction value of the specific paper, the correction value of other paper stored in the data storage unit 108 is also changed by reflecting the change result.

  As described above, when the correction value of the motor driving amount is changed for one sheet, an error occurs in the correction value data stored in the data storage unit by changing the correction value for the other sheet. In some cases, it is possible to maintain accurate conveyance amount control by changing the correction value so as to correct the error, and to greatly reduce the trouble of correcting the error of the correction value data stored in the data storage means. it can.

Next, another example of motor drive amount correction control in paper conveyance will be described with reference to FIG.
In the correction control described above, when a sheet is conveyed on the conveyance path A in which the winding angle to the conveyance roller 27 is equal to or larger than a certain value (approximately 60 ° or more) when the sheet is fed, the trailing edge of the sheet is the conveyance roller. The motor drive amount is corrected with the same correction amount (correction value) even after leaving 27 winding.

  However, the amount of conveyance after the trailing edge of the paper leaves the winding of the conveying roller 27 is determined only by the diameter of the conveying roller 27, and it is not necessary to take into account almost half of the thickness of the paper 12. If the correction is performed, the transport amount is deviated. Also, since the conveyance load and the conveyance force are greatly different before and after the trailing edge of the sheet leaves the conveyance roller 27, the amount of sliding of the sheet is also different. For this reason, an accurate conveyance amount cannot be obtained, which may be a cause of image distortion.

  Therefore, in the correction control of this example, after feeding, it is determined whether or not the trailing edge of the sheet is in front of the first pressure roller 25A (meaning upstream in the sheet conveying direction). When it is in front of the first pressure roller 25A, the motor drive amount is corrected using the first correction value data stored in the data storage unit 108, and the rear end of the sheet is not in front of the first pressure roller 25A. That is, after the trailing edge of the sheet passes through the first pressure roller 25A, the motor drive amount is corrected using the second correction value data stored in the data storage unit 108.

  In the control using the second correction value data, the transport diameter Ro is changed from the corrected feed diameter to which the half of the sheet thickness Dy is added, to the transport roller diameter Dh. Whether or not the trailing edge of the sheet has passed through the first pressure roller 25A is predicted from, for example, the timing at which the trailing edge of the sheet has passed the registration sensor that detects the sheet on the downstream side or the upstream side of the registration roller 22. Can be done.

  As described above, when a sheet is conveyed on a conveyance path having a wrapping angle around the conveyance roller at a certain level (approximately 60 ° or more) during conveyance of the sheet, the rear end portion of the recording medium is opposed to the conveyance roller. By changing the correction value of the drive amount of the drive motor when the rear end portion of the recording medium has shifted from the state facing the transport roller to the state facing the transport roller, the sheet is transported with a more accurate transport amount. be able to.

  In the above-described embodiment, an example in which the drive amount of the drive motor is corrected is described. However, a plurality of drive patterns (for each type of recording medium) in advance for each conveyance path or in addition to this. (Position / speed profile) is created, and the drive pattern is switched according to the motor input amount, the selected conveyance path, and the type of recording medium. Can be driven, and the same effect as the above-described embodiment can be obtained. In other words, the correction of the driving amount obtains the target transport amount by changing the amount of feeding the driving roller itself by predicting paper slipping, etc., but switching the driving pattern does not change the driving amount itself. Etc. are changed to suppress the slip itself, thereby obtaining a desired transport amount.

  In this case, either a configuration in which the drive pattern is changed by switching the drive pattern itself or a configuration in which the drive pattern is changed as a result by correcting a value obtained from the drive pattern can be employed.

  In the above-described embodiment, the example in which the present invention is applied to an image forming apparatus having a printer configuration has been described. However, the present invention can be similarly applied to an image forming apparatus having a combined printer / fax / copier function. In the above-described embodiment, an example is described in which the present invention is applied to an image forming apparatus including a conveying unit using a conveying belt. However, an image forming apparatus including a conveying unit that uses only a conveying roller without using a belt is also described. The same can be applied.

1 is a schematic side view illustrating an example of an image forming apparatus according to the present invention. It is principal part plane explanatory drawing of the apparatus. It is typical explanatory drawing with which it uses for description of the conveyance path of the apparatus. It is block explanatory drawing which shows the outline | summary of the control part of the apparatus. It is a block explanatory view functionally explaining a part related to the conveyance amount control of the control unit. It is explanatory drawing with which it uses for description of the conveyance diameter by a conveyance roller. It is a flowchart with which it uses for description of adjustment (change) of the correction value data memorize | stored in the data storage part. It is a flowchart with which it uses for description of the other example of conveyance control.

Explanation of symbols

3 ... carriage 7 ... recording head (liquid ejection head)
10 ... paper feed tray 12 ... paper (recording medium)
21 ... Conveying belt 27 ... Conveying roller 31 ... Sub-scanning motor (drive motor)
Reference Signs List 60: manual paper feed unit 104 ... sub-scanning motor drive circuit 107 ... motor input amount detection circuit 108 ... data storage unit (correction value storage means)
203 ... Comparison calculation unit 204 ... Position / speed profile storage unit 206 ... Correction value calculation unit

Claims (10)

Image forming means for forming an image on a recording medium;
A transport roller constituting transport means for transporting the recording medium;
A drive motor for driving the transport roller;
Motor input amount detection means for detecting the voltage or current input to the drive motor;
An image forming apparatus comprising: a means for correcting a drive amount of the drive motor based on a detection result of the motor input amount detection means and a conveyance speed of the recording medium.   The image forming apparatus according to claim 1, wherein when the recording medium is conveyed, the image forming apparatus has two or more types of conveyance paths having different winding angles around the conveyance roller, and the drive motor is driven according to each conveyance path. An image forming apparatus that corrects the amount.   The image forming apparatus according to claim 2, further comprising a storage unit that stores a correction value of a driving amount of the driving motor corresponding to the type of the recording medium and each transport path, and the type of the recording medium and the transport path. The image forming apparatus, wherein the drive amount of the drive motor is corrected based on the correction value stored in the storage unit.   4. The image forming apparatus according to claim 3, wherein, among the correction values according to the type of the recording medium, when the correction value of one type of recording medium is changed, the correction value of another type of recording medium is changed. The image forming apparatus is also changed.   5. The image forming apparatus according to claim 2, wherein a portion up to a rear end portion of the recording medium is opposed to the conveyance roller, and a rear end portion of the recording medium is opposed to the conveyance roller. An image forming apparatus, wherein the correction value of the drive motor is changed when the state shifts from a state to a state where they do not face each other. Image forming means for forming an image on a recording medium;
A transport roller constituting transport means for transporting the recording medium;
A drive motor for driving the transport roller;
Motor input amount detection means for detecting the voltage or current input to the drive motor;
An image forming apparatus comprising: a means for changing a drive pattern of the drive motor based on a detection result of the motor input amount detection means and a conveyance speed of the recording medium.   The image forming apparatus according to claim 6, wherein when the recording medium is conveyed, the image forming apparatus has two or more types of conveyance paths having different winding angles around the conveyance roller, and the drive motor is driven according to each conveyance path. An image forming apparatus characterized by changing a pattern.   The image forming apparatus according to claim 7, further comprising a storage unit that stores a drive pattern of the drive motor or a correction value of the drive pattern according to the type of the recording medium and each conveyance path, and the type of the recording medium. And an image forming apparatus that corrects the drive pattern of the drive motor based on a drive pattern stored in the storage unit or a correction value of the drive pattern according to a transport path.   9. The image forming apparatus according to claim 8, wherein the driving pattern of the driving motor or the correction value of the driving pattern according to the type of the recording medium is corrected for the driving pattern or driving pattern of one type of recording medium. An image forming apparatus, wherein when a value is changed, a drive pattern of another type of recording medium or a correction value of the drive pattern is also changed. 10. The image forming apparatus according to claim 6, wherein a portion up to a rear end portion of the recording medium faces the transport roller and a rear end portion of the recording medium faces the transport roller. An image forming apparatus, wherein the driving pattern of the driving motor or the correction value of the driving pattern is changed when the state shifts from a state to a state where it does not face.

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