JP2013183514A - Motor drive device, sheet conveyer, and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the service life of a gear from being shortened due to backlash and to quickly rotate a motor shaft, in a conveyance motor consisting of a DC brushless motor.SOLUTION: A motor control circuit for controlling drive of a conveyance motor consisting of a DC brushless motor performs, in a first acceleration period, first acceleration processing that accelerates motor rotation speed with predetermined first acceleration characteristics, performs, in a second acceleration period, second acceleration processing that accelerates the motor rotation speed with second acceleration characteristics superior in acceleration performance to the first acceleration characteristics, and performs, in a start-up period prior to the first acceleration period, drive start processing that causes a driver circuit having not output a voltage to output a voltage higher than the output voltage in the first acceleration processing to a motor coil, to start driving the conveyance motor.

Description

  The present invention relates to a motor driving device that controls driving of a DC brushless motor, and a sheet conveying device and an image forming apparatus using the motor driving device.

  Conventionally, for example, a DC brushless motor as described in Patent Document 1 is known as a motor. The DC brushless motor is a motor that sequentially switches coils to be excited by a driver circuit without using a mechanism for sliding the rectifying brush against a commutator (contact). The driver circuit grasps the rotation angle of the DC brushless motor based on a Hall signal from a Hall element as a rotation angle detection means mounted on the DC brushless motor. For example, in the case of a DC brushless motor with a three-phase coil, a process in which the rotation angle of the DC brushless motor changes by 120 [°], 240 [°], 0 (360) [°], and 120 [°]. Thus, the coils to be excited are sequentially switched to the first, second, and third phases. Maintenance performance can be improved as compared with a motor with a DC brush that requires cleaning work for the abrasion powder of the rectifying brush or that the rectifying brush needs to be replaced periodically.

  However, the DC brushless motor is liable to cause a phenomenon called backlash that is slightly reversed due to a reaction when stopped. When backlash occurs, the teeth of the motor gear fixed to the motor shaft are separated from the teeth of the driven gear receiving the driving force from the motor gear. In this state, no load is applied to the DC brushless motor by the gear or the driven body, so the DC brushless motor starts to rotate vigorously at the same time as driving. Further, since the teeth of the motor gear and the teeth of the driven gear are vigorously collided to promote wear and damage of the gear teeth, there is a problem that the life of the gear is shortened.

  Therefore, the present inventors are developing a new motor drive device that performs the following control. That is, after the first acceleration voltage for accelerating the rotation speed of the DC brushless motor with the predetermined first acceleration characteristic is output and the motor driving is started, the output voltage is set to a value that is larger than the first acceleration voltage. It is control which switches to the voltage for 2 accelerations. By gradually raising the rotational speed of the DC brushless motor by the output of the first acceleration voltage, the teeth of the motor gear can collide with the driven gear at a slower speed than in the past. In addition, by switching the output voltage from the first acceleration voltage to a larger second acceleration voltage, compared to the case where the first acceleration voltage is continuously output, the time from the start of driving until the rotational speed reaches the target value. “Acceleration required time” can be shortened.

  However, in the initial stage of driving, the rotation speed is increased more slowly than in the prior art by the output of the first acceleration voltage, so that the “required acceleration time” becomes longer than in the prior art. As a result of experiments conducted by the inventors, it has been found that, in particular, the time lag from when the output of the first acceleration voltage is started until the motor shaft is actually started to rotate is lengthened. In this time lag, a static frictional force acting between a motor shaft of a DC brushless motor and a bearing that rotatably receives the motor shaft is involved. With a voltage for rotating a DC brushless motor at a lower acceleration than before, a considerable amount of time is required to make the rotational driving force of the motor shaft larger than its static frictional force. As a result, the “acceleration required time” was significantly longer than before.

  The present invention has been made in view of the above background, and an object thereof is to provide the following motor driving device, sheet conveying device, and image forming apparatus. That is, for a DC brushless motor, it is a motor driving device or the like that can suppress a reduction in gear life due to backlash and can rotate a motor shaft quickly.

  In order to achieve the above object, the invention of claim 1 is directed to the DC brushless motor, the rotation angle detection means for detecting the rotation angle of the DC brushless motor, and the detection result by the rotation angle detection means. In a motor drive device having a driver circuit that switches a coil to be excited among a plurality of coils in a brushless motor, and a control unit that controls driving of the DC brushless motor via the driver circuit, the rotation of the DC brushless motor In order to accelerate the speed with a predetermined first acceleration characteristic, a first acceleration process in which a relatively low voltage is output from the driver circuit to the coil, and after the first acceleration process, the rotational speed is increased to the first acceleration. In order to accelerate with the second acceleration characteristic, which is superior to the characteristic, a relatively high voltage is applied. A value higher than the relatively low voltage in the first acceleration process from the second acceleration process that is output from the inverter circuit to the coil and the driver circuit that did not output the voltage prior to the first acceleration process. The control means is configured to execute a drive start process for outputting the voltage of the current to the coil and starting the drive of the DC brushless motor.

  In the present invention, in the first acceleration process, a relatively low voltage is supplied to the DC brushless motor to accelerate the motor rotation at a low acceleration, and the motor gear is separated from the driven gear by backlash. By making these teeth collide with the driven gear at a slower speed than before, it is possible to suppress a reduction in the life of the gear due to backlash.

  In the present invention, the second acceleration process is performed after the first acceleration process to accelerate the rotation of the DC brushless motor at a higher acceleration, compared with the case where the target value is reached with a low acceleration. Thus, the “acceleration required time” can be shortened.

  In the present invention, prior to the first acceleration process, a drive start process is performed, and a higher voltage than the first acceleration process is output to the DC brushless motor to start driving the motor. The time lag from the start of voltage output to the actual rotation of the motor shaft can be examined in advance by testing. By outputting a voltage higher than that in the first acceleration process, the time lag can be shortened and the motor shaft can be rapidly rotated as compared with the case where a voltage having the same value as that in the first acceleration process is output.

  In the drive start process, if the motor shaft starts to rotate while maintaining a high voltage, the tooth of the motor gear collides with the driven gear while rapidly accelerating the rotation of the motor shaft. By performing the first acceleration process immediately before the time lag described above, it is possible to ensure that the teeth of the motor gear collide with the driven gear at a slower speed than before.

1 is a schematic configuration diagram showing a copier according to an embodiment. FIG. 2 is a partial configuration diagram illustrating an enlarged part of an image forming unit in the copier. FIG. 3 is a partial enlarged view showing a part of a tandem part composed of four image forming units in the image forming part. FIG. 2 is a perspective view showing a scanner and an ADF of the copier. The expanded block diagram which shows the principal part structure of the same ADF with the upper part of a scanner. FIG. 3 is a plan configuration diagram illustrating a motor driving device for rotationally driving a first conveying roller of a pair of conveying rollers in the sheet feeding device of the copier. The expansion perspective view which shows the conveyance motor of the motor drive device from the front. The expansion perspective view which shows the conveyance motor from back. The perspective view which shows the 1st example of the code wheel mounted in the conveyance motor. The perspective view which shows the 2nd example of the same code wheel. The block diagram which shows the principal part of the electric circuit in the motor drive device. The graph which shows the relationship between the elapsed time from the drive start of the conveyance motor drive-controlled by the motor control circuit of the motor drive device, and the motor rotation speed. The graph which shows the relationship between the elapsed time after the drive start of the conveyance motor, and the output voltage with respect to the coil of a conveyance motor. FIG. 3 is a block diagram illustrating a main part of an electric circuit in the motor driving device of the copying machine according to the embodiment. The graph which shows a 1st acceleration characteristic. The graph which shows a 2nd acceleration characteristic. The block diagram which shows a part of internal structure in the position and speed tracking control circuit of a motor control circuit. FIG. 2 is a plan configuration diagram showing a motor driving device for rotationally driving a reading entrance roller of the ADF of the copier. FIG. 9 is a perspective view showing a transport motor used in a motor driving device for driving a pair of transport rollers of a copying machine according to a first modification from the front. The perspective view which shows the same conveyance motor from the back. The perspective view which shows the modification of the conveyance motor. FIG. 9 is a schematic configuration diagram illustrating an image forming unit 1 of a copying machine according to a second modification. FIG. 9 is a schematic configuration diagram showing a copying machine according to a third modification.

Hereinafter, an embodiment in which the present invention is applied to an electrophotographic copying machine (hereinafter simply referred to as a copying machine) will be described.
First, a basic configuration of the copying machine according to the embodiment will be described. FIG. 1 is a schematic configuration diagram illustrating a copying machine according to an embodiment. The copying machine includes an image forming unit 1 as an image forming apparatus, a sheet supply device 40, and an image reading unit 50. The image reading unit 50 as an image reading apparatus includes a scanner 150 fixed on the image forming unit 1 and an automatic document feeder (hereinafter referred to as ADF) 51 as a sheet conveying device supported by the scanner 150. ing.

  The sheet supply device 40 includes two paper feed cassettes 42 arranged in multiple stages in the paper bank 41, a feed roller 43 that feeds recording sheets from the paper feed cassette, and a separation roller that separates the sent recording sheets one by one. 45 etc. In addition, a plurality of conveyance roller pairs 46 that convey a recording sheet as a sheet member to the sheet feeding path 37 as a conveyance path of the image forming unit 1 are also provided.

  The paper feed cassette 42 is housed inside in a state of a sheet bundle in which a plurality of recording sheets are stacked. The sending roller 43 is pressed against the uppermost recording sheet. When the feed roller 43 rotates, the uppermost recording sheet of the sheet bundle is sent out from the paper feed cassette 42.

  In the vicinity of the paper feed cassette 42, the first conveyance roller of the conveyance roller pair 46 and the second conveyance roller disposed on the side (right side in the figure) contact each other to form a conveyance nip. Yes. Further, a separation roller 45 is disposed below the first conveyance roller, and a separation conveyance nip is formed by contacting the first conveyance roller from below.

  The recording sheet sent out from the paper feed cassette 42 by the rotational drive of the sending roller 43 is separated into a separation / conveying nip formed by contact between the first conveying roller of the pair of conveying rollers 46 and the separation roller 45 arranged below the first conveying roller. enter in. In the separation and conveyance nip, the conveyance force directed from the sheet feeding cassette 42 side to the feeding path 44 side with respect to the recording sheet while the first conveyance roller contacting the upper surface of the recording sheet is rotated counterclockwise in the drawing. Is granted. On the other hand, the separation roller 45 that contacts the lower surface of the recording sheet is rotationally driven in the counterclockwise direction in the figure, and applies a conveying force from the feeding path 44 side to the sheet feeding cassette 42 side to the recording sheet. Thus, the recording sheet is returned to the paper feed cassette 42.

  When only one recording sheet is sent out from the sheet feeding cassette 42, the first conveying roller and the separation roller 45 apply conveying forces in the opposite directions to the recording sheet at the separation and conveyance nip. Thus, a load exceeding a predetermined threshold is applied to the drive transmission system of the separation roller 45. Then, a torque limiter disposed in the drive transmission system is activated to cut off transmission of driving force from a DC brushless motor (not shown) to the separation roller 45. As a result, the separation roller 45 follows the recording sheet conveyed by the first conveyance roller, and the recording sheet is discharged from the separation conveyance nip toward the feeding path 44.

  On the other hand, when a plurality of recording sheets are fed out from the sheet feeding cassette 42, the first conveying roller at the separation / conveying nip feeds the feeding path 44 from the sheet feeding cassette 42 side to the uppermost recording sheet. The uppermost recording sheet is fed from the separation and conveyance nip toward the feeding path 44 side by applying a conveyance force toward the side. On the other hand, the lower recording sheet is fed from the separation / conveying nip by applying a conveying force from the feeding path 44 toward the sheet feeding cassette to the recording sheet on which the separation roller is positioned on the lower side. Return to the paper cassette 42 side. As a result, at the separation and conveyance nip, the uppermost recording sheet is separated from the other recording sheets and is sent out to the feeding path 44 in a single state.

  The recording sheet that has entered the feeding path 44 enters the conveyance nip of the conveyance roller pair 46 and is given a conveyance force from the lower side in the vertical direction toward the upper side. As a result, the recording sheet is conveyed toward the sheet feeding path 37 of the image forming unit 1 in the feeding path 44.

  The image forming unit 1 as an image forming unit includes an optical writing device 2 and four image forming units 3K, Y, and M that form black, yellow, magenta, and cyan (K, Y, M, and C) toner images. , C, transfer unit 24, paper transport unit 28, registration roller pair 33, fixing device 34, switchback device 36, paper feed path 37, and the like. Then, a light source such as a laser diode or LED (not shown) disposed in the optical writing device 2 is driven to irradiate the four drum-shaped photosensitive members 4K, Y, M, and C with the laser light L. . By this irradiation, electrostatic latent images are formed on the surfaces of the photoreceptors 4K, Y, M, and C, and the latent images are developed into toner images via a predetermined development process.

  FIG. 2 is an enlarged partial configuration diagram illustrating a part of the internal configuration of the image forming unit 1. FIG. 3 is a partially enlarged view showing a part of a tandem part composed of four image forming units 3K, Y, M, and C. The four image forming units 3K, Y, M, and C have substantially the same configuration except that the colors of the toners to be used are different from each other. Therefore, in FIG. The subscript C is omitted.

  Each of the image forming units 3K, Y, M, and C is a unit that supports the photosensitive member and various devices disposed around the photosensitive member as a single unit and supports the image forming unit 1 main body. Can be removed. Taking the black image forming unit 3K as an example, this has a charging device 23, a developing device 6, a drum cleaning device 15, a static elimination lamp 22 and the like around the photosensitive member 4. This copying machine has a so-called tandem type configuration in which four image forming units 3K, Y, M, and C are arranged so as to face an intermediate transfer belt 25, which will be described later, along the endless movement direction. ing.

  As the photoreceptor 4, a drum-shaped member is used in which a photosensitive layer is formed by applying a photosensitive organic photosensitive material to a base tube made of aluminum or the like. However, an endless belt may be used.

  The developing device 6 develops the latent image using a two-component developer containing a magnetic carrier and a nonmagnetic toner (not shown). In order to transfer the toner in the two-component developer carried on the developing sleeve 12 to the photosensitive member 4, the agitating unit 7 that conveys the two-component developer accommodated in the inside and supplies the developing sleeve 12 with stirring. Development section 11.

  The stirring unit 7 is provided at a position lower than the developing unit 11, and is provided on the bottom surface of the developing case 9, two conveying screws 8 arranged in parallel to each other, a partition plate provided between these screws. A toner density sensor 10 and the like are included.

  The developing unit 11 includes a developing sleeve 12 that faces the photosensitive member 4 through the opening of the developing case 9, a magnet roller 13 that is non-rotatably provided inside the developing sleeve 12, a doctor blade 14 that approaches the developing sleeve 12, and the like. ing. The developing sleeve 12 has a non-magnetic rotatable cylindrical shape. The magnet roller 12 has a plurality of magnetic poles that are sequentially arranged from the position facing the doctor blade 14 in the rotational direction of the sleeve. Each of these magnetic poles applies a magnetic force to the two-component developer on the sleeve at a predetermined position in the rotation direction. As a result, the two-component developer sent from the stirring unit 7 is attracted and carried on the surface of the developing sleeve 13 and a magnetic brush is formed along the magnetic field lines on the sleeve surface.

  The magnetic brush is regulated to an appropriate layer thickness when passing through the position facing the doctor blade 14 as the developing sleeve 12 rotates, and then conveyed to the developing region facing the photoconductor 4. Then, the toner is transferred onto the electrostatic latent image by the potential difference between the developing bias applied to the developing sleeve 12 and the electrostatic latent image on the photosensitive member 4, thereby contributing to development. Further, as the developing sleeve 12 rotates, the developing sleeve 12 is returned to the developing portion 11 again, and after being separated from the sleeve surface by the influence of the repulsive magnetic field formed between the magnetic poles of the magnet roller 13, the developing sleeve 12 is returned to the stirring portion 7. An appropriate amount of toner is supplied to the two-component developer in the stirring unit 7 based on the detection result of the toner density sensor 10. The developing device 6 may employ a one-component developer that does not include a magnetic carrier, instead of one that uses a two-component developer.

  As the drum cleaning device 15, a system in which the cleaning blade 16 made of an elastic body is pressed against the photoconductor 4 is used, but another system may be used. For the purpose of enhancing the cleaning property, this example employs a system having a contact conductive fur brush 17 whose outer peripheral surface is in contact with the photoreceptor 4 so as to be rotatable in the direction of the arrow in the figure. The fur brush 17 also serves to apply the lubricant to the surface of the photosensitive member 4 while scraping the lubricant from a solid lubricant (not shown) into a fine powder. A metal electric field roller 18 for applying a bias to the fur brush 17 is rotatably provided in the direction of the arrow in the figure, and the tip of the scraper 19 is pressed against it. The toner attached to the fur brush 17 is transferred to the electric field roller 18 to which a bias is applied while rotating in contact with the fur brush 17 in the counter direction. Then, after being scraped from the electric field roller 18 by the scraper 19, it falls onto the recovery screw 20. The collection screw 20 conveys the collected toner toward the end of the drum cleaning device 15 in the direction orthogonal to the drawing sheet surface, and transfers it to the external recycling conveyance device 21. The recycle conveyance device 21 sends the delivered toner to the developing device 15 for recycling.

  The neutralization lamp 22 neutralizes the photoreceptor 4 by light irradiation. The surface of the photoreceptor 4 that has been neutralized is uniformly charged by the charging device 23 and then subjected to optical writing processing by the optical writing device 2. As the charging device 23, a charging device that rotates a charging roller to which a charging bias is applied while contacting the photosensitive member 4 is used. A scorotron charger or the like that performs a non-contact charging process on the photoreceptor 4 may be used.

  In FIG. 2 described above, the K, Y, M, and C toner images are transferred to the photoreceptors 4K, Y, M, and C of the four image forming units 3K, Y, M, and C by the processes described above. It is formed.

  A transfer unit 24 is arranged below the four image forming units 3K, Y, M, and C. The transfer unit 24 as a belt driving device moves the intermediate transfer belt 25 stretched by a plurality of rollers endlessly in the clockwise direction in the drawing while contacting the photoreceptors 4K, Y, M, and C. As a result, primary transfer nips for K, Y, M, and C in which the photoreceptors 4K, Y, M, and C abut the intermediate transfer belt 25 that is an endless belt member are formed. In the vicinity of the primary transfer nips for K, Y, M, and C, the intermediate transfer belt 25 is moved to the photoreceptors 4K, Y, M, and C by primary transfer rollers 26K, Y, M, and C disposed inside the belt loop. Pressing toward C. A primary transfer bias is applied to the primary transfer rollers 26K, Y, M, and C by a power source (not shown). As a result, a primary transfer electric field for electrostatically moving the toner images on the photoreceptors 4K, Y, M, and C toward the intermediate transfer belt 25 is formed in the primary transfer nips for K, Y, M, and C. Has been. In the drawing, a toner image is formed on each of the primary transfer nips on the front surface of the intermediate transfer belt 25 that sequentially passes through the primary transfer nips for K, Y, M, and C with endless movement in the clockwise direction. Are sequentially superimposed and primarily transferred. By this primary transfer of superposition, a four-color superposed toner image (hereinafter referred to as a four-color toner image) is formed on the front surface of the intermediate transfer belt 25.

  Below the transfer unit 24 in the figure, a paper transport unit 28 is provided between the drive roller 30 and the secondary transfer roller 31 to endlessly move the endless paper transport belt 29. The intermediate transfer belt 25 and the paper transport belt 29 are sandwiched between the secondary transfer roller 31 and the lower stretching roller 27 of the transfer unit 24. As a result, a secondary transfer nip is formed in which the front surface of the intermediate transfer belt 25 and the front surface of the paper transport belt 29 come into contact with each other. A secondary transfer bias is applied to the secondary transfer roller 31 by a power source (not shown). On the other hand, the lower stretching roller 27 of the transfer unit 24 is grounded. Thereby, a secondary transfer electric field is formed in the secondary transfer nip.

  A registration roller pair 33 is disposed on the right side of the secondary transfer nip in the drawing. A registration roller sensor (not shown) is disposed near the entrance of the registration nip of the registration roller pair 33. The recording sheet conveyed from the sheet supply device (not shown) toward the registration roller pair 33 is temporarily stopped after a predetermined time when the leading edge is detected by the registration roller sensor, and the registration nip of the registration roller pair 33 is stopped. Butt the tip.

  When the prior application of the recording sheet hits the registration nip, the registration roller pair 33 resumes roller rotation driving at a timing at which the recording sheet can be synchronized with the four-color toner image on the intermediate transfer belt 25, and the recording sheet is moved to the secondary position. Send to transfer nip. In the secondary transfer nip, the four-color toner images on the intermediate transfer belt 25 are collectively transferred to the recording sheet by the action of the secondary transfer electric field and the nip pressure, and become a full color image combined with the white color of the recording sheet. The recording sheet that has passed through the secondary transfer nip is separated from the intermediate transfer belt 25 and is conveyed to the fixing device 34 along with its endless movement while being held on the front surface of the paper conveyance belt 29.

  Transfer residual toner that has not been transferred to the recording sheet at the secondary transfer nip is attached to the surface of the intermediate transfer belt 25 that has passed through the secondary transfer nip. This transfer residual toner is scraped off and removed by a belt cleaning device in contact with the intermediate transfer belt 25.

  The recording sheet conveyed to the fixing device 34 is fixed to a full color image by pressurization or heating in the fixing device 34, and then sent from the fixing device 34 to the paper discharge roller pair 35 and then to the outside of the apparatus. Discharged.

  In FIG. 1 described above, a switchback device 36 is disposed under the paper transport unit 22 and the fixing device 34. As a result, the recording sheet that has undergone the image fixing process on one side is switched by the switching claw to the recording sheet reversing device side, where it is reversed and enters the secondary transfer transfer nip again. Then, after the secondary transfer process and the fixing process of the image are performed on the other side, the sheet is discharged onto a discharge tray.

  The scanner 150 fixed on the image forming unit 1 and the ADF 51 fixed on the scanner 150 have a fixed reading unit and a moving reading unit 152. The moving reading unit 152 is disposed immediately below a second contact glass (not shown) fixed to the upper wall of the casing of the scanner 150 so as to come into contact with the document MS, and illustrates an optical system including a light source and a reflection mirror. It can be moved in the middle / left / right direction. Then, in the process of moving the optical system from the left side to the right side in the figure, the light emitted from the light source is reflected by a document (not shown) placed on the second contact glass and then passed through a plurality of reflecting mirrors. The light is received by the image reading sensor 153 fixed to the scanner body.

  On the other hand, the fixed reading unit includes a first surface fixed reading unit 151 disposed in the scanner 150 and a second surface fixed reading unit (not shown) disposed in the ADF 51. A first surface fixed reading unit 151 having a light source, a reflection mirror, an image reading sensor such as a CCD, etc. is arranged directly below a first contact glass (not shown) fixed to the upper wall of the casing of the scanner 150 so as to contact the document MS. It is installed. Then, when a document MS conveyed by the ADF 51 described later passes over the first contact glass, the light emitted from the light source is sequentially reflected on the document surface and received by the image reading sensor via a plurality of reflecting mirrors. To do. Thus, the first surface of the document MS is scanned without moving the optical system including the light source and the reflection mirror. The second surface fixed reading unit scans the second surface of the document MS after passing through the first surface fixed reading unit 151.

  An ADF 51 disposed on the scanner 150 includes a document placing table 53 for placing the document MS before reading on the main body cover 52, a transport unit 54 for transporting the document MS as a sheet member, and after reading. A document stacking table 55 for stacking the originals MS is held. As shown in FIG. 4, it is supported by a hinge 159 fixed to the scanner 150 so as to be swingable in the vertical direction. Then, by swinging, it moves like an open / close door, and the first contact glass 154 and the second contact glass 155 on the upper surface of the scanner 150 are exposed in the opened state. In the case of a single-sided original such as a book in which one corner of the original bundle is bound, the originals cannot be separated one by one and cannot be transported by ADF. Therefore, in the case of a single-sided original, the ADF 51 is opened as shown in FIG. 4, and then the single-sided original with the page to be read open is placed face down on the second contact glass 154, and then the ADF is close up. Then, the image of the page is read by the moving reading unit 152 shown in FIG.

  On the other hand, in the case of a document bundle in which a plurality of independent documents MS are simply stacked, the documents MS are automatically conveyed one by one by the ADF 51, while the first surface fixed reading unit 151 in the scanner 150 or the first document in the ADF 51. The two-surface fixed reading unit can sequentially read. In this case, after setting the document bundle on the document placing table 53, a copy start button (not shown) is pressed. Then, the ADF 51 sends the originals MS of the original bundle placed on the original placement table 53 into the conveyance unit 54 in order from the top, and conveys the original MS toward the original stack table 55 while inverting it. In the course of this conveyance, immediately after the document MS is reversed, the original MS is passed directly over the first surface fixed reading unit 151 of the scanner 150. At this time, the image on the first surface of the document MS is read by the first surface fixed reading unit 151 of the scanner 150.

  FIG. 5 is an enlarged configuration diagram showing the main configuration of the ADF 51 together with the upper portion of the scanner 150. The ADF 51 includes a document setting unit A, a separation feeding unit B, a registration unit C, a turn unit D, a first reading conveyance unit E, a second reading conveyance unit F, a paper discharge unit G, a stack unit H, and the like.

  The document setting unit A includes a document placement table 53 on which a bundle of documents MS is set. The separation feeding unit B separates and feeds the originals MS one by one from the set of originals MS set. The registration unit C temporarily abuts on the fed original MS and aligns the original MS to send it out. Further, the turn portion D has a curved conveyance portion that is curved in a C-shape, and the document MS is turned upside down in the curved conveyance portion so as to be turned upside down. The first reading / conveying unit E conveys the document MS on the first contact glass 155 and is disposed below the first contact glass 155 and inside the scanner (not shown). Is to read the first side of the document MS. The second reading / conveying unit F allows the second fixed reading unit 95 to read the second surface of the document MS while conveying the document MS under the second fixed reading unit 95. The paper discharge unit G discharges the original MS from which both-side images are read toward the stack unit H. The stack unit H stacks the original MS on the stack table 55.

  The original MS is placed on the movable original table 54 that can swing in the directions of arrows a and b in the drawing according to the thickness of the bundle of originals MS, and the rear end of the original is placed on the original table 53. It is set in the state of being put on. At this time, the position in the width direction is adjusted by abutting side guides (not shown) against both ends in the width direction (the direction orthogonal to the drawing surface) on the document placement table 53. The document MS set in this way pushes up the lever member 62 that is swingably disposed above the movable document table 54. Accordingly, the document set sensor 63 detects the setting of the document MS and transmits a detection signal to a controller (not shown). This detection signal is sent from the controller to the reading control unit of the scanner via the I / F.

  The document placing table 53 holds a first length sensor 57 and a second length sensor 58 which are made of a reflective photosensor or an actuator type sensor for detecting the length of the document MS in the conveyance direction. These length sensors detect the length of the document MS in the conveyance direction.

  Above the bundle of documents MS placed on the movable document table 54, a pickup roller 80 supported by a cam mechanism so as to be movable in the vertical direction (arrow c and d directions in the figure) is disposed. . This cam mechanism can be driven by a pickup motor 56 to move the pickup roller 80 up and down. When the pickup roller 80 moves upward, the movable document table 54 swings in the direction of arrow a in the drawing, and the pickup roller 80 contacts the uppermost document MS in the bundle of documents MS. When the movable document table 54 further rises, the table rise detection sensor 59 eventually detects the rise of the movable document table 54 to the upper limit. As a result, the pickup motor 56 stops and the movable document table 54 stops rising.

  For the main body operation unit consisting of a numeric keypad and a display provided in the main body of the copying machine, the operator performs key operations for setting the reading mode indicating the double-sided reading mode or the single-sided reading mode, and a copy start key. Is pressed. When the copy start key is pressed, a document feed signal is transmitted from a main body control unit (not shown) to the controller of the ADF 51. Then, the pickup roller 80 is rotationally driven by the normal rotation of the paper feed motor 76 to send out the original MS on the movable original table 54 from the movable original table 54.

  When setting the double-sided reading mode or the single-sided reading mode, it is possible to collectively set the double-sided or single-sided setting for all the originals MS placed on the movable original table 54. Also, the first and tenth originals MS are set to the double-sided reading mode, while the other originals MS are set to the single-sided reading mode. Can also be set.

  The document MS sent out by the pickup roller 80 serving as a sending member enters the separation conveyance unit B and is sent to a contact position with the paper feed belt 84. The paper feed belt 84 is stretched by a drive roller 82 and the like, and is endlessly moved in the clockwise direction in the drawing by the rotation of the drive roller 82 accompanying the forward rotation of the paper feed motor 76. A separation roller 85 that is driven to rotate clockwise in the drawing by the forward rotation of the paper feed motor 76 is in contact with the lower stretched surface of the paper feed belt 84. At the contact portion, the surface of the paper feed belt 84 moves in the paper feed direction. On the other hand, the separation roller 85 is in contact with the paper feed belt 84 at a predetermined pressure, and when the paper is in direct contact with the paper feed belt 84 or only one original MS is sandwiched between the contact portions. At that time, it is carried around to the belt or the document MS. However, when a plurality of documents MS are sandwiched between the contact portions, the accompanying force is lower than the torque of the torque limiter, so that the document is rotated clockwise in the figure opposite to the accompanying direction. As a result, a moving force in the direction opposite to the paper feed is applied to the original MS below the uppermost position by the separation roller 85, and only the uppermost original MS is separated from several originals.

  The original MS separated into one sheet by the action of the paper feed belt 84 and the separation roller 85 enters the registration portion C. Then, the tip is detected when passing just below the butting sensor 72. At this time, the pickup roller 80 receiving the driving force of the pickup motor 56 is still driven to rotate. However, the original MS is separated from the original MS by the lowering of the movable original table 54, so that the original MS has an endless moving force of the paper feed belt 84. Only conveyed by. Then, the endless movement of the paper feeding belt 84 continues for a predetermined time from the timing when the leading edge of the document MS is detected by the abutment sensor 72, and the leading edge of the document MS is driven to rotate while being in contact with the pull-out driving roller 86. It abuts against the contact portion with the pullout drive roller 87.

  The pull-out driven roller 87 plays a role of transporting the document MS to the intermediate roller pair 66 on the downstream side in the document transport direction, and is driven to rotate by reverse rotation of the paper feed motor 76. When the paper feed motor 76 rotates in the reverse direction, the pull-out driven roller 87 and one of the rollers in the intermediate roller pair 66 in contact with each other start to rotate, and the endless movement of the paper feed belt 84 stops. At this time, the rotation of the pickup roller 80 is also stopped.

  The document MS sent from the pull-out driven roller 87 passes directly below the document width sensor 73. The document width sensor 73 has a plurality of paper detection units including reflection type photosensors, and these paper detection units are arranged in the document width direction (direction orthogonal to the drawing sheet). Based on which paper detection unit detects the document MS, the size of the document MS in the width direction is detected. The length of the document MS in the conveyance direction is detected based on the timing from when the leading edge of the document MS is detected by the abutting sensor 72 until the trailing edge of the document MS is not detected by the abutting sensor 72. .

  The leading edge of the document MS whose size in the width direction is detected by the document width sensor 73 enters the turn portion D and is sandwiched between the abutting portions between the rollers of the intermediate roller pair 66. The conveyance speed of the original MS by the intermediate roller pair 66 is set to be higher than the conveyance speed of the original MS in the first reading conveyance section E described later. This shortens the time until the document MS is sent to the first reading conveyance unit E.

  The leading edge of the document MS conveyed in the turn part D passes through the position where the document leading edge faces the reading entrance sensor 67. As a result, when the leading edge of the document MS is detected by the reading inlet sensor 67, the leading edge of the original MS is conveyed to the position of the pair of reading inlet rollers (a pair of 89 and 90) on the downstream side in the conveying direction. The document conveyance speed by the roller pair 66 is reduced. Further, with the start of rotation of the reading motor (not shown), one roller in the reading inlet roller pair (89, 90), one roller in the reading outlet roller pair 92, and one roller in the second reading outlet roller pair 93. Starts rotating.

  In the turn section D, the upper and lower surfaces are reversed and the conveyance direction is folded while the document MS is conveyed on the curved conveyance path between the intermediate roller pair 66 and the reading entrance roller pair (89, 90). . Then, the leading edge of the document MS that has passed through the nip between the rollers of the reading entrance roller pair (89, 90) passes directly below the registration sensor 65. When the leading edge of the document MS is detected by the registration sensor 65 at this time, the document transport speed is reduced while applying a predetermined transport distance, and the transport of the document MS is temporarily stopped before the first reading transport unit E. . Further, a registration stop signal is transmitted to a reading control unit (not shown).

  When the reading control unit that has received the registration stop signal transmits a reading start signal, the rotation of the reading motor is resumed until the leading edge of the document MS reaches the first reading conveyance unit E under the control of the controller of the ADF 51. The conveyance speed of the document MS is increased to the conveyance speed of. Then, at the timing when the leading edge of the document MS calculated based on the pulse count of the reading motor reaches the reading position by the first fixed reading unit 151, the controller scans the first surface of the document MS with respect to the reading control unit. A gate signal indicating a direction effective image area is transmitted. This transmission is continued until the trailing edge of the document MS exits the reading position by the first fixed reading unit 151, and the first surface of the document MS is read by the first fixed reading unit 151.

  The document MS that has passed through the first reading conveyance unit E passes through a reading exit roller pair 92 described later, and then the leading end of the document MS is detected by the paper discharge sensor 61. When the single-sided reading mode is set, reading of the second side of the document MS by the second fixed reading unit 95 described later is not necessary. Accordingly, when the leading edge of the document MS is detected by the paper discharge sensor 61, the forward rotation drive of the paper discharge motor is started, and the lower paper discharge roller in the drawing roller pair 94 in the drawing in the clockwise direction in the drawing. Driven by rotation. Further, the timing at which the trailing edge of the document MS exits the nip of the discharge roller pair 94 is calculated based on the discharge motor pulse count after the leading edge of the document MS is detected by the discharge sensor 61. Based on this calculation result, the drive speed of the discharge motor is decelerated at the timing immediately before the trailing edge of the document MS comes out of the nip of the discharge roller pair 94, and the document MS jumps out of the stack base 55. Paper is discharged at such a speed.

  On the other hand, when the double-sided reading mode is set, the timing until the paper MS reaches the second fixed reading unit 95 after the leading edge of the document MS is detected based on the pulse count of the reading motor. Calculated. At that timing, a gate signal indicating an effective image area in the sub-scanning direction on the second surface of the document MS is transmitted from the controller to the reading control unit. This transmission is continued until the trailing edge of the document MS exits the reading position by the second fixed reading unit 95, and the second surface of the document MS is read by the second fixed reading unit 95.

  The second fixed reading unit 95 as a reading unit includes a contact image sensor (CIS), and for the purpose of preventing a reading vertical streak caused by a paste-like foreign material adhering to the document MS adhering to the reading surface. The reading surface is coated. A second reading roller 96 serving as a document supporting unit that supports the document MS from the non-reading surface side is disposed at a position facing the second fixed reading unit 95. The second reading roller 96 serves to prevent the document MS from floating at the reading position by the second fixed reading unit 95 and to function as a reference white portion for acquiring shading data in the second fixed reading unit 95. I'm in charge.

  As described above, in the feeding path 44 of the sheet feeding device 40 in FIG. 1, the recording sheet is applied with the conveying force directed upward at the conveyance nip of the conveyance roller pair 46, so that the recording sheet becomes the image forming unit 1. It is conveyed toward the paper feed path 37.

  FIG. 6 is a plan configuration diagram showing a motor driving device for rotationally driving the first conveying roller 46 a of the conveying roller pair 46. The motor drive device includes a motor control circuit 200, a transport motor 210 including an inner rotor type DC brushless motor, and a speed reducer 225.

  The motor control circuit 200 functions as a control unit that controls the rotational drive of the transport motor 210 based on a detection result by a motor encoder described later. When the motor shaft 214 of the transport motor 210 rotates by driving the transport motor 210, the rotational speed of the motor gear 213 fixed to the motor shaft 214 is decelerated by the speed reducer 225, and then the first transport roller 46a as a driven body. Is transmitted to.

  The speed reducer 225 rotates on the same rotational axis as the first speed reduction gear 221 that meshes with the motor gear 213, the second speed reduction gear 222 that meshes with this, the third speed reduction gear 223 that meshes with this, and the first transport roller 46a. As described above, the fourth reduction gear meshes with the third reduction gear 223 while being fixed to the shaft member of the first conveying roller 46a.

  Next, a characteristic configuration of the copier according to the embodiment will be described. FIG. 7 is an enlarged perspective view showing the transport motor 210 of the motor drive device from the front. FIG. 8 is an enlarged perspective view showing the transport motor 210 from the rear. As shown in these drawings, the motor shaft 213 of the transport motor 210 protrudes forward from the motor main body at the front portion of the motor main body while passing through the motor main body in the front-rear direction, and the rear portion of the motor main body. Projecting backward from the motor body.

  A driver board 216 is fixed to the rear side of the motor body, and a driver circuit for exciting the three-phase coils of the transport motor 210 in a predetermined order is mounted on the driver board 216. The motor shaft 213 also protrudes backward through the driver board 216.

  A code wheel 211a of a motor encoder 211 as a rotation amount detecting means is fixed at a position behind the driver board 216 in the motor shaft 213, and on the same rotational axis as the motor shaft 213 as the motor shaft 213 rotates. Rotate with. As shown in FIG. 9, the code wheel 211 a includes a plurality of slits SL arranged at a predetermined pitch in the rotation direction. An optical sensor 211b made of a transmissive photosensor is fixed to the driver board 216 of the transport motor 210 so as to sequentially detect the slits SL as the code wheel 211a rotates (see FIG. 8). Although not shown for convenience, a cover member that covers the driver board 216 and the motor encoder 211 is fitted into the rear end portion of the motor body of the transport motor 210.

  In order to ensure that the code wheel 211a is rotated in synchronization with the motor shaft 213 even if expansion and contraction occurs due to temperature change, the code wheel 211a is not only press-fitted into the motor shaft 213 but also attached to the motor shaft 213 by an adhesive. It is desirable to adhere.

  As the code wheel 211a, the one obtained by processing the wheel main body and the slit SL by punching a metal plate is used. Since the code wheel 211a is made of metal, it is possible to suppress the expansion and contraction due to the temperature change and reduce the variation of the slit pitch over time. However, it is easy to attach foreign matters such as dust to the burrs generated during the punching process. Therefore, instead of the code wheel 211a shown in FIG. 9, the code wheel 211a shown in FIG. 10 may be used. The code wheel 211a includes a plurality of dark portions DP that are arranged at a predetermined pitch in the rotation direction as marks. The dark part DP is formed by a half etching process using a photolithography method. A part having a mirror-finished layer coated on the surface is used as a substrate, and the part where the mirror-finished layer is removed by half etching to expose the dark part layer is the dark part DP. The dark portion DP can be processed with high accuracy. However, the cost is increased by half-etching. In addition, since it is weak against oils and fats, handling is required.

  When the code wheel 211a shown in FIG. 10 is used, the optical sensor 211b is made of a reflective photosensor instead of a transmissive photosensor. May be detected.

  As described above, in the copying machine according to the embodiment, the driver circuit and the motor encoder 211 serving as the rotation amount detection unit are mounted on the transport motor 210.

  FIG. 11 is a block diagram showing a main part of an electric circuit in the motor drive device. The motor control circuit 200 that controls the driving of the conveyance motor 210 formed of a DC brushless motor is formed as a separate body from the conveyance motor 210 and is fixed to the main body of the image forming unit (1 in FIG. 1).

  FIG. 12 is a graph showing the relationship between the elapsed time from the start of driving of the transport motor 210 controlled by the motor control circuit 200 and the motor rotation speed. The origin in this graph indicates the driving start time when the driving voltage starts to be output to the transport motor 210. The transport motor 210 does not start rotating during the start-up period until a certain time lag elapses from the drive start time. When the activation period has passed, the rotation is started, and the process proceeds to a first acceleration period in which the rotation speed is increased at a relatively low acceleration. Thereafter, a second acceleration period in which the rotation speed is increased at a higher acceleration than the first acceleration period, a constant speed rotation period in which the motor shaft is rotated at a constant speed, a deceleration period in which the rotation speed is decelerated and then the rotation is stopped. To move sequentially.

  FIG. 13 is a graph showing the relationship between the elapsed time from the start of driving of the transport motor 210 and the output voltage with respect to the coil of the transport motor 210. The motor control circuit 200 performs drive start processing during the startup period. In this drive start process, a “drive start voltage” is output to the motor coil from the driver circuit 212 that has not output a voltage until the drive start event. This “driving start voltage” has a larger value than the “first acceleration voltage” output during the first acceleration time. As shown in the figure, when the start period ends, the output of the “drive start voltage” ends. However, if the “drive voltage voltage” continues to be output even after the start period elapses, the transport motor 210 will eventually be output. The motor shaft begins to rotate vigorously. Then, when the transport motor 210 is backlashed and stopped, the teeth of the motor gear may collide with the driven gear vigorously. Therefore, the activation period is set to a time slightly shorter than the time lag from the start of output of the “drive start voltage” until the motor shaft starts to rotate. The time lag can be measured by a preliminary test.

  In addition, when the timing from the start of driving shifts from the startup period to the first acceleration period, the motor control circuit 200 performs the first acceleration process. In the first acceleration process, a relatively low “first acceleration voltage” is output from the driver circuit 212 to the motor coil in order to accelerate the rotation speed of the transport motor 210 with a predetermined first acceleration characteristic. Thereby, in the 1st acceleration period, the rotational speed of the conveyance motor 210 accelerates comparatively slowly (refer FIG. 12).

  Note that the start-up to the first acceleration period, which is the sum of the start-up period and the first acceleration period, is set to the same length as the “maximum backlash amount recovery period”. Specifically, the “maximum backlash recovery period” is measured as follows. That is, the first acceleration for outputting the “first acceleration voltage” after the start-up period for outputting the “driving start voltage” from the state where the transport motor 210 is intentionally stopped at the maximum backlash state. The process is carried out and the time taken for the motor shaft to rotate by the same amount as the maximum backlash amount is measured. That time is the “maximum backlash recovery period”.

  Next, when the timing from the start of driving shifts from the first acceleration period to the second acceleration period, the motor control circuit 200 performs the second acceleration process. In the second acceleration process, in order to accelerate the rotation speed of the transport motor 210 with the second acceleration characteristic that is superior to the first acceleration characteristic, a relatively high value of the “second acceleration voltage” is applied to the driver. Output from the circuit 212 to the motor coil. Thereby, the rotational speed of the conveyance motor 210 starts to rise more rapidly than the first acceleration period (see FIG. 12).

  It should be noted that the motor control circuit 200 determines the pulse signal frequency after the frequency of the pulse signal sent from the motor encoder 211 has reached a predetermined target frequency, that is, after the rotational speed of the motor has reached a predetermined target speed. The output voltage from the driver circuit 212 is controlled so that the frequency is stabilized at the target frequency. By such constant speed rotation processing, the transport motor 210 is stably rotated at the target speed during the constant speed rotation period.

  Further, when a predetermined timing at which the stop process of the transport motor 210 is to be started, the motor control circuit 200 performs a deceleration process for gradually decreasing the output voltage from the driver circuit 212 and eventually stopping the output. . Thereby, in the deceleration period, the rotation speed of the conveyance motor 210 is decelerated, and the rotation stops before long.

  In such a series of motor control, during the first acceleration period, while the rotation of the transport motor 210 is accelerated at a low acceleration, the teeth of the motor gear that are separated from the driven gear by backlash are moved with respect to the driven gear. By making the vehicle collide at a slower speed than in the past, it is possible to suppress a reduction in the life of the gear due to backlash. In addition, by accelerating the rotation of the transport motor 210 at a higher acceleration during the second acceleration period, the “acceleration required time” is compared with the case where the target value is reached while maintaining a low acceleration equivalent to the first acceleration period. Can be shortened. Also, in the start-up period, by outputting a “drive start voltage” having a value higher than the “first acceleration voltage” in the first acceleration period, compared to the case where driving is started at the “first acceleration voltage”. The motor shaft can be rotated quickly by shortening the time lag.

  In addition, although the example which employ | adopted the thing of the value equivalent to the "2nd acceleration voltage" was demonstrated as a "drive start voltage", the thing larger than a "2nd acceleration voltage" A value smaller than the “acceleration voltage” may be employed. However, the conditions “driving start voltage”> “first acceleration voltage” and “first acceleration voltage” <“second acceleration voltage” must be provided.

  In addition, although an example in which a “drive start voltage” having a constant value is output in the start-up period has been described, the value of the “drive start voltage” may be changed. In this case, the average value of the “drive start voltage” in the start-up period needs to be larger than the “first acceleration voltage”. Further, although an example of outputting a fixed value of “first acceleration voltage” has been described, the “first acceleration voltage” may be changed. In this case, the average value of the “first acceleration voltage” in the first acceleration period may be lower than the “drive start voltage” and the “second acceleration voltage”. Further, although an example of outputting the “second acceleration voltage” having a constant value has been described, the “second acceleration voltage” may be changed. In this case, the average value of the “second acceleration voltage” in the second acceleration period may be higher than the “first acceleration voltage”.

  Conventionally, in a drive system that requires a quantitative operation, such as a paper conveyance device mounted in an image forming apparatus, a stepping motor that is a kind of AC motor has been generally used. However, since the stepping motor rotates by an amount that exactly corresponds to the number of pulses emitted from the control device, it is a very suitable motor for quantitative driving. However, in order to prevent the occurrence of step-out, under conditions where there is a margin in torque so as not to disturb the rotation cycle even when a load of about 1.3 times the maximum load or about twice the average load is applied. There is a problem that wasteful power is consumed because of driving.

  On the other hand, the motor driving device described in Patent Document 1 adjusts the driving amount of a DC brushless motor, which is a driving source, based on the result of detecting the rotation amount of a roller, which is a driven body, by an encoder, thereby quantitatively determining the roller. Realizes rotational driving. In the DC brushless motor, a current corresponding to the load torque flows to the coil, so there is no current loss as in the stepping motor. For this reason, useless power consumption can be suppressed compared with the case where a stepping motor is used.

  However, in the motor drive device described in Patent Document 1, there is a risk of causing instability of the motor rotation by mixing noise into the Hall signal (rotation sensing signal) sent from the Hall element or the like to the driver circuit. Specifically, it is necessary to individually supply excitation voltages to the coils from the driver circuit to the DC brushless motor. Since the coils to be excited are switched in a very short time, the drive power supply that flows the excitation current according to the rotation of the motor in the plurality of drive power wires for individually guiding the excitation voltage to each coil. Electric wires are switched at high speed. Then, noise is mixed in the hall signal communicated by the signal wires that are wound around together with the plurality of drive power wires, and the rotation of the DC brushless motor becomes unstable.

  Therefore, in this copying machine, the driver circuit 212 is mounted on the transport motor 210 formed of a DC brushless motor. Thereby, compared with the motor drive device described in Patent Document 1, the distance between the driver circuit and the motor coil is made closer. Then, without providing a harness in which a plurality of drive power supply wires and signal wires are bundled between the driver circuit 212 and the motor body, an excitation voltage is supplied from the driver circuit 212 to the motor coil by the electrodes on the circuit board. The hall signal is transmitted from the hall element 217 to the driver circuit 212. As a result, by suppressing the generation of noise when switching the coil to be excited at high speed, or by suppressing the mixing of the generated noise into the Hall signal, the motor rotation caused by the mixing of noise into the Hall signal can be reduced. Instability can be suppressed.

Next, an example copier in which a more characteristic configuration is added to the copier according to the embodiment will be described. Unless otherwise specified, the configuration of the copying machine according to the embodiment is the same as that of the embodiment.
[Example]
FIG. 14 is a block diagram illustrating a main part of an electric circuit in the motor driving device of the copying machine according to the embodiment. In the figure, the motor control circuit 200 includes a target position / speed calculation circuit 201, a position / speed tracking control circuit 202, a motor rotation amount / speed calculation circuit 203, and the like.

  The target signal generation unit 250 is configured separately from the motor driving device, and according to the progress of the print job, the target rotation amount, the target rotation speed, and the target rotation stop of the first transport roller (46a). A target signal such as a position is generated. A main control unit that controls the overall control of various devices in the image forming unit (1) may function as the target signal generation unit 250.

  As the motor control circuit 200, a circuit composed of a one-chip microcomputer or a circuit composed of a control ASIC (Application Specific Integrated Circuit) is used.

  The target signal sent from the target signal generation means 250 to the motor control circuit 200 is input to the target position / speed calculation circuit 201 of the motor control circuit 200. Based on the input target signal, the target position / speed calculation circuit 201 calculates a target motor stop position for stopping the first transport roller (46a) in a target rotation posture, and uses the result as a target position signal. Output. Further, based on the target signal, a target motor rotation speed for rotating the first transport roller (46a) at the target rotation speed is calculated, and the result is output as a target speed signal.

  As an optical sensor of the motor encoder 211 mounted on the transport motor 210, a two-channel optical sensor having two light receiving portions that receive light after passing through the slit SL is used. The two light receiving units are arranged so as to satisfy the following conditions. In other words, when the slit SL of the code wheel 211a is opposed to the first light receiving portion, the second light receiving portion is opposed to the wheel non-slit portion existing on the side of the slit SL. Based on the change in the ratio between the amount of light received by the first light-receiving unit and the amount of light received by the second light-receiving unit, the moment when the slit SL of the code wheel 211 is opposed to each light-receiving unit without deviation is accurately grasped. Is done. The first light receiving unit outputs a voltage corresponding to the amount of received light as a pulse signal A. The second light receiving unit outputs a voltage corresponding to the amount of received light as a pulse signal B.

  The pulse signal A and pulse signal B output from the optical sensor 211 b are input to the motor rotation amount / speed calculation circuit 203 of the motor control circuit 200. The motor position / velocity calculation path 203 calculates the motor rotation amount based on the result of calculating the pulse rising number and the pulse frequency for the pulse signal A and the pulse signal B, respectively, and outputs the result as a motor rotation amount signal. Further, the motor rotation speed is calculated, and the result is output as a motor rotation speed signal.

  The position / speed tracking control circuit 202 constantly supplies GND (-power) to the driver circuit 212. Further, if necessary, excitation + power (+ 24V) and signal + power (+ 5V) are supplied to the driver circuit 212. Furthermore, the brake signal, the PWM signal, and the direction signal (CW, CCW) are individually output to the driver circuit 212 as necessary. As the direction signal, either a normal rotation signal for performing a normal rotation command or a reverse rotation signal for performing a reverse rotation command is output. The PWM signal is for instructing an excitation voltage value output from the driver circuit 212 to the coil of the transport motor 210.

  The transport motor 210 has a hall element 217. The Hall element as the rotation angle detection means has become 0 [°] (360 °) as a reference for the rotation angle posture of the motor shaft 213 of the transport motor 210, or 120 [°] and 240 [°]. The hall signal for indicating this is output to the driver circuit 212.

  The driver circuit 212 includes an output adjustment unit that adjusts the output of the excitation voltage for the coil of the transport motor 210 based on the PWM signal output from the position / speed tracking control circuit 202 of the motor control circuit 200, and the three-phase in the transport motor 210. The coil switching part which switches the coil which outputs an excitation voltage among these coils is comprised. The output adjusting unit adjusts the value of the excitation voltage per unit time flowing through the coil via the coil switching unit by turning on and off the output of the voltage of +24 [V] to the coil switching unit based on the PWM signal. The coil switching unit includes a pre-driver and a plurality of FETs (field effect transistors). As the plurality of FETs, at least the first FET for turning on / off the output of the U excitation voltage for exciting the first phase coil, and the on / off of the output of the V excitation voltage for exciting the second phase coil. And a third FET for turning on and off the output of the W excitation voltage for exciting the third phase coil. The FETs individually output gate voltages for controlling switching by the FETs from the pre-drivers. The pre-driver individually controls on / off of the gate voltage for the three FETs based on the Hall signal from the Hall element 217, thereby converting the excitation voltage output to the transport motor 210 into the U excitation voltage, the V excitation voltage, and the like. And switching with W excitation voltage. By this switching, a rotational force by switching the magnetic field is applied to the motor shaft 213 of the transport motor 210.

  The position / speed tracking control circuit 202 calculates a deviation amount of the motor rotation speed signal sent from the motor rotation amount / speed calculation circuit 203 from the target speed signal, and adjusts the PWM signal based on the deviation amount. Thus, the excitation voltage for the transport motor 210 is adjusted, and a speed adjustment process for controlling the rotational speed of the transport motor 210 to the target rotational speed is performed. By this speed adjustment processing, the rotational speed of the first transport roller 46a that is a driven body driven by the transport motor 210 can be freely adjusted. Such speed adjustment processing is performed by feedback control using PID control.

  The motor drive device detects the rotation speed of the first conveyance roller 46a that is rotationally driven by the conveyance motor 210, and the motor encoder 211 mounted on the conveyance motor 210 detects the rotation speed of the first conveyance roller 46a as shown in FIG. Rotation speed is detected directly. In such a configuration, the rotational speed of the transport motor 210 is higher than that of the motor driving device described in Patent Document 1 in which the change in the rotational speed of the transport motor is indirectly detected based on the rotational speed change of the first transport roller 46a. Quickly detect changes. Then, according to the detection result, the rotation speed of the transport motor 210 is quickly returned to the original speed, so that the rotational speed instability of the first transport roller 46a due to the load fluctuation can be suppressed.

  Further, in this motor drive device, the driver circuit 216 in which the driver circuit 212 is incorporated is mounted on the transport motor 210, so that the driver circuit 212 is disposed at a position away from the transport motor 210 compared to the conventional case. The distance between the driver circuit 210 and the coil of the transport motor 210 is reduced. As a result, an excitation voltage is applied from the driver circuit 212 to the motor coil by the electrodes on the driver board 216 without providing a harness in which a plurality of driving power supply wires and signal wires are bundled between the driver circuit 212 and the transport motor 210. It is possible to supply or transmit a hall signal as a sensing signal from the transport motor 210 to the driver circuit 212. As a result, by suppressing the generation of noise when switching the coil to be excited at high speed, or by suppressing the mixing of the generated noise into the Hall signal, the motor rotation caused by the mixing of noise into the Hall signal can be reduced. Instability can be suppressed.

  In addition, between the driver circuit 212 and the motor control circuit 200, excitation + power supply, GND, brake signal, PWM signal, direction signal, signal + power supply, pulse signal A, and pulse signal B are individually led. A harness made up of eight electric wires is wound around. In this harness, only one electric wire is provided for guiding the excitation + power source that is the source of the excitation voltage, and +24 V is stably supplied to this electric wire over a long period of time. Unlike between the driver circuit 212 and the transport motor 210, the high-speed switching of the + 24V conduction line that accompanies the switching of the coil to be excited is not performed, so that no noise is generated due to the high-speed switching. For this reason, even if the electric wire for leading the exciting power source, the electric wire for guiding the pulse signal A, and the electric wire for guiding the pulse signal B are wound together, the pulse signal A and the pulse signal B No noise mixing occurs.

  The position / speed tracking control circuit 202 grasps the total rotation amount of the transport motor 210 from the start-up based on the motor rotation amount signal sent from the motor rotation amount / speed calculation circuit 203. Then, based on the comparison between the grasping result and the target position signal, the carrier motor 210 grasps the braking timing that becomes the target rotation amount, and stops outputting the PWM signal to the driver circuit 212 at the braking timing, A brake signal is output, and a target stop process for stopping the transport motor 210 at a target rotation angle and posture is performed. Thereby, the 1st conveyance roller 46a driven by the conveyance motor 210 and the 2nd conveyance roller 46b which rotates with this can be stopped by a target rotation angle attitude | position. Such target stop processing is performed by feedback control using PID control.

  In a state where the transport motor 210 is stopped, the position / speed tracking control circuit 202 performs a hold process. In this hold process, the presence or absence of forward rotation or reverse rotation of the motor shaft 213 is monitored based on the motor rotation amount signal sent from the motor rotation amount / speed calculation circuit 203. When forward rotation is detected, the transport motor 210 is driven in reverse rotation by an amount corresponding to the forward rotation amount. When reverse rotation is detected, the transport motor 210 is driven forward by an amount according to the reverse rotation amount. To do. As a result, the first transport roller (46a) driven by the rotational driving force of the transport motor 210 is constrained to the target rotational posture. In such a configuration, the apparatus can be downsized and the apparatus configuration can be simplified by restraining the conveyance motor 210 to a desired rotation angle posture by hold control regardless of the attachment of the helical gear.

  As the optical sensor 211, one having a resolution of 45 [LPI] is used. Further, as the code wheel 211a, one having 100 slits SL per round is used. The reason for this is as follows. That is, conventionally, an HB type stepping motor has been generally used as a drive source for the transport roller pair. The basic resolution of the HB type stepping motor is 200 pulses (two-phase excitation). It is 400 pulses for 1-2 phase excitation and 800 pulses for W1-2 phase excitation. It is desirable to obtain the same capability as that of the resolution with the transport motor 210 including a DC brushless motor. Since DC brushless motors are generally used at a rotational speed more than twice that of stepping motors, considering the reduction ratio, the basic resolution is half of 100 pulses and the basic resolution of the stepping motor (two-phase It is possible to demonstrate the same ability as (excitation). Further, by using the pulse signals A and B respectively output from the two light receiving portions of the optical sensor 211b, it is possible to generate 200 pulses multiplied by 2 and 400 pulses multiplied by 4 for one rotation of the motor. Therefore, it is also possible to exhibit the same ability as the resolution at the time of 1-2 phase excitation or W1-2 phase excitation of the stepping motor. Therefore, the code wheel 211a provided with 100 slits SL per round is used.

  Further, by using an optical sensor 211b having a resolution of 45 [LPI], the central circle diameter φ of the code wheel 211a provided with 100 slits SL is kept at 17.97 [mm]. Thereby, the code wheel 211a is accommodated within the diameter of the transport motor 210, and the increase in the diameter of the transport motor 210 due to the mounting of the code wheel 211a can be avoided. When the code wheel pulse is doubled to 200 pulses, the central circle diameter φ of the code wheel 211a is increased to 35.93 [mm]. It is very difficult to accommodate this central circle φ within the diameter of the transport motor 210. In addition, even if the code wheel pulse is 1.5 times 150 pulses, since the response frequency does not exceed the use limit, the resolution is preferably 45 [LPI].

  In FIG. 8, a connector 215 is fixed to the driver board 216. The connector 215 is engaged with a harness connector provided at the end of the harness that is wound around from the motor control circuit 200. The number of pins of the connector 215 is as follows: excitation + power receiving pin, GND receiving pin, brake signal receiving pin, PWM signal receiving pin, direction signal receiving pin, signal + power receiving pin, pulse signal A output 8 pins for receiving a pulse signal and a pin for receiving a pulse signal. In FIG. 11, although not shown for convenience, a +5 [V] power supply wiring and a GND wiring extend from the driver circuit 212 to the optical sensor 211b.

  The arrangement pitch of pins in the connector 215 is 1.5 [mm]. Further, the arrangement order of the pins is as follows. That is, pin 1 = excitation + power supply reception pin, pin 2 = GND reception pin, pin 3 = brake signal reception pin, pin 4 = PWM signal reception pin, pin 5 = direction signal reception Pin 6, Pin = Signal + Power Supply Acceptance Pin, Pin 7 = Pulse Signal A Output Pin, Pin 8 = Pulse Signal Acceptance Pin. By moving the combination of the pulse signal A output pin (No. 7) and the pulse signal reception pin (No. 8) away from the 24 [V] excitation + power supply reception pin (No. 1), the pulse signal It is possible to efficiently suppress noise from being mixed in.

  In order for the transport motor 210 to exhibit the same controllability as the HB type stepping motor, it is necessary to read the slit SL and the dark portion DP with high accuracy. Therefore, it is necessary to keep the positional error in the rotational direction at the sensor reading position within one rotation of the code wheel 211a in the state assembled to the motor to 0.3 [%] or less. For such a position error, it is desirable to use components in which the dimensional accuracy of the code wheel 211a, the assembly accuracy of the code wheel 211a with respect to the motor shaft 213, the straightness of the motor shaft, and the like are strictly controlled.

  In FIG. 14, the position / speed tracking control circuit 202 performs the above-described drive start processing, first acceleration processing, second acceleration processing, constant speed rotation processing, and deceleration processing. A ROM (not shown) is provided. In this ROM, the above-mentioned “drive voltage” value, “first acceleration voltage” value, “second acceleration voltage” value, and first acceleration characteristics are stored. The first algorithm shown, the second algorithm showing the second acceleration characteristic, the deceleration voltage pattern data in the deceleration process, and the like are stored.

  In the drive start process (startup period) described above, the position / speed tracking control circuit 202 stores in advance in the ROM a PWM signal for causing the driver circuit 212 to output the “drive voltage” stored in the ROM. Output only the length of the startup period.

  FIG. 15 is a graph showing the first acceleration characteristic represented by the first algorithm. FIG. 16 is a graph showing the second acceleration characteristic represented by the second algorithm. These acceleration characteristics are represented by the inclination of the graph in two-dimensional coordinates of the vertical axis indicating the value of the pulse frequency [Hz] and the horizontal axis indicating the elapsed time [s] since the start of the motor. The pulse frequency is the frequency of the pulse signal A or pulse signal B output from the optical sensor 211b, and represents the rotational frequency of the motor. The greater the slope of the graph, the better the acceleration. As can be seen from FIGS. 15 and 16, the first acceleration characteristic is inferior to the second acceleration characteristic in terms of acceleration (the slope of the graph of FIG. 15 <the slope of the graph of FIG. 16).

  Note that the origin of the graph of FIG. 15 indicates the beginning of the first acceleration period. Further, the origin of the graph of FIG. 16 indicates the beginning of the second acceleration period. The second acceleration period starts from a state in which the rotational speed has already risen to some extent during the first acceleration period, so that the pulse frequency rises from a value larger than 0 at the origin of the graph as shown in FIG.

  When the first acceleration process described above is started, the position / speed tracking control circuit 202 first starts the timing process and outputs a PWM signal corresponding to the “first acceleration voltage”. The feedforward control is performed to determine the output voltage with a predetermined value or a predetermined pattern. However, not just feedforward control but simply feedback control is combined. Specifically, the following processing is periodically repeated. That is, the pulse frequency at the timing of the time measurement result is specified from the first algorithm (graph of FIG. 15) as the target frequency (target rotation speed). Then, feedback control is performed in which a voltage corresponding to the difference between the frequency of the pulse signal sent from the motor encoder 211 and the target frequency is superimposed on the “first acceleration voltage”. As a result, the acceleration of the motor follows the first acceleration characteristic.

  Further, the position / speed tracking control circuit 202 determines the timing for shifting from the first acceleration period to the second acceleration period based on the above-described difference. Specifically, when the frequency of the pulse signal transmitted from the motor encoder 211 is smaller than the target frequency and the difference between the two exceeds a threshold value, the first acceleration period shifts to the second acceleration period. This is for the reason explained below. That is, in a drive transmission system using a speed reducer, since the gear circumference and the number of teeth are determined with priority on the reduction ratio, a relatively large gap is generated between the motor gear and the driven gear meshing therewith. . Due to this large gap, the teeth of the motor gear are greatly separated from the teeth of the driven gear during backlash. Also in the motor drive device according to the embodiment, the teeth of the motor gear 213 and the teeth of the first reduction gear 221 as the driven gear are in a separated state. In the first acceleration period, the timing at which the teeth of the motor gear collide with the driven gear (hereinafter referred to as meshing timing) varies. However, at that timing, the motor rotation speed rapidly decreases as shown at time t1 in FIG. This is because the load torque with respect to the motor rapidly increases with the start of gear engagement. That is, in the first acceleration period, when the frequency of the pulse signal rapidly decreases and the above-described difference exceeds the threshold, the meshing timing is reached before the end of the first acceleration period is reached. . In this case, the “acceleration required time” can be further shortened by immediately shifting to the second acceleration period and increasing the acceleration without waiting for the end of the first acceleration period.

  In the second acceleration period, the position / speed tracking control circuit 202 accelerates the rotation speed of the transport motor 210 at once according to the second acceleration characteristic that is superior to the first acceleration characteristic. Specifically, the following processing is repeatedly performed at predetermined time intervals. That is, the motor rotation frequency actual measurement value is calculated based on the pulse signal, and the difference between the calculation result and the target frequency (vertical value of the second acceleration characteristic) is obtained. Then, the duty ratio of the PWM signal is adjusted according to this difference, and the excitation voltage is increased or decreased according to the difference. As a result, the acceleration of the motor follows the second acceleration characteristic. In the second acceleration period, similarly to the first acceleration period, the feedforward control and the feedback control are performed in combination.

  FIG. 17 is a block diagram showing a part of the internal configuration of the position / speed tracking control circuit 182 of the motor control circuit. The position / speed tracking control circuit 182 outputs a PWM signal using the illustrated internal circuit during the first acceleration period and the second acceleration period. This internal circuit includes a position feedforward control circuit 182a, a speed feedforward control circuit 182b, a position feedback control circuit 182c, a speed feedback control circuit 182d, a speed detection circuit 182e, a first addition / subtraction circuit 182f, a second addition / subtraction circuit 182g, and an addition circuit. 182h and the like. The conveyance motor (210) composed of a DC brushless motor is inevitably inferior in position follow-up and speed follow-up at start-up and stop as compared with a stepping motor. Therefore, the operating characteristics at the start and stop of the transport motor are investigated in advance, and the position tracking profile and speed to improve the position tracking and speed tracking at startup and stop based on the operating characteristics. A tracking profile is constructed and stored in the target position / velocity calculation circuit (181). The target position / speed calculation circuit generates a target position signal and a target speed signal based on these profiles.

  The target position signal received by the position / speed tracking control circuit 182 is input as an addition value to the first addition / subtraction circuit 182f. A position detection signal constructed based on the pulse signal from the motor encoder is input to the first addition / subtraction circuit 182f as a subtraction value. When the actual motor rotation position (position detection signal) and the target rotation position (target position signal) are the same, the total value becomes zero. On the other hand, when the actual motor rotation position is ahead of the target rotation position, the total value becomes negative. Further, when the actual motor rotation position is delayed from the target rotation position, the total value becomes positive. The total value is input to the position feedback control circuit 182c. The position feedback control circuit 182c converts the input total value from position to speed and outputs it as a first feedback signal.

  The target position signal received by the position / speed tracking control circuit 182 is also input to the position feedforward control circuit 182a. The position feedforward control circuit 182a converts the target position into a speed and outputs it as a first feedforward signal. The first feedback signal output from the position feedback control circuit 182c and the first feedforward signal output from the position feedforward control circuit 182a are respectively input as addition values to the second addition / subtraction circuit 182g.

  The position detection signal received by the position / speed tracking control circuit 182 is also input to the speed detection circuit 182e. The speed detection circuit 182e calculates the rotational speed of the motor based on the time change of the input position detection signal, and outputs the result as a speed detection signal. This speed detection signal is input as a subtraction value to the second addition / subtraction circuit 182g.

  The total value in the second addition / subtraction circuit 182g is input to the speed feedback circuit 182d. The speed feedback circuit 182d converts the total value of the input speeds into a voltage value for realizing an increase / decrease of the speed (increase in the case of a plus sign, decrease in the case of a minus sign), and an adder circuit 182h. Output to.

  On the other hand, the target speed signal received by the position / speed tracking control circuit 182 is input to the speed feedforward control circuit 182b. The speed feedforward control circuit 182b converts the input target speed into a voltage value for realizing it, and outputs the voltage value to the adder circuit 182b. Then, the voltage addition result in the adding circuit 182b is output to the driver circuit as a PWM signal.

  In such a configuration, a feedback control value based on the difference between the speed detection result and the target speed and a feedback control value based on the difference between the position detection result and the target position with respect to the feedforward control value based on the position tracking profile or the speed tracking profile. As a result, the DC brushless motor can exhibit position followability and speed followability comparable to a stepping motor.

  In the ADF 51 shown in FIG. 5, as described above, one roller in the reading inlet roller pair (89, 90), one roller in the reading outlet roller pair 92, and one roller in the second reading outlet roller pair 93. Each roller rotates using a reading motor as a driving source. The reading motor is a DC brushless motor having the same configuration as that of the transport motor 210. The motor driving device for driving the reading motor has the same configuration as the motor driving device for driving the transport motor 210. That is, the present invention is also applied to a motor driving device for driving the reading motor.

  FIG. 18 is a plan configuration diagram showing a motor driving device for rotationally driving the reading entrance roller 89 and the like. This motor drive device has a motor control circuit 300, a reading motor 310 composed of a DC brushless motor, and a speed reducer.

  The motor control circuit 300 functions as a control unit that controls the rotational drive of the reading motor 310 based on the detection result by the motor encoder 311. When the motor shaft 313 is rotated by driving the reading motor 310, the rotational speed of a motor gear (not shown) fixed to the motor shaft is decelerated by a speed reducer and then transmitted to a reading inlet roller 89 as a driven body. The reduction gear 225 includes a first reduction gear 321 meshing with the motor gear, a second reduction gear 322 meshing with the gear, a third reduction gear 323 meshing with the gear, a fourth reduction gear 324 meshing with the gear, and a reading inlet roller 89. And a fifth reduction gear 325 that rotates on the same rotation axis.

  The paper discharge roller pair 94 of the ADF 51 rotates using a paper discharge motor as a drive source. The paper discharge motor is a DC brushless motor having the same configuration as the transport motor 210. The motor driving device for driving the paper discharge motor has the same configuration as the motor driving device for driving the transport motor 210. That is, the present invention is also applied to a motor driving device for driving the paper discharge motor.

Next, a description will be given of a copying machine according to each modification in which a partial configuration of the copying machine according to the embodiment is improved. Unless otherwise specified, the configuration of the copying machine according to each modification is the same as that of the embodiment.
[First Modification]
FIG. 19 is a perspective view showing a transport motor 210 used in a motor driving device for driving the transport roller pair of the copying machine according to the first modification from the front. FIG. 20 is a perspective view showing the transport motor 210 from the back. In the first modified example, the conveyance motor 210 is an outer rotor type DC brushless motor. The motor encoder 211 includes a code rotor unit 211c integrally formed with the outer rotor 219 of the transport motor 210, and an optical sensor 211b including a reflective photosensor that detects a plurality of slits provided in the code rotor unit 211c. ing.

  The outer rotor type DC brushless motor is a motor that is suitable for use under conditions that require excellent constant speed, and the frequency of the FG signal emitted from the built-in FG signal generator is externally applied. Generally, a PLL circuit for adjusting to an input target frequency is provided. In the first modification, when the transport motor 210 is rotated at the target speed, the PLL circuit is used. For this reason, the position / speed tracking control circuit 202 outputs the FG signal target value to the transport motor 210 instead of performing the speed adjustment process described above.

  In addition to the one provided with a plurality of slits as shown in FIG. 19, as the code rotor portion 211c, it is also possible to adopt one provided with a plurality of dark portions as marks as shown in FIG.

[Second Modification]
FIG. 22 is a schematic configuration diagram showing the image forming unit 1 of the copying machine according to the second modification. The image forming unit 1 includes a paper feed cassette 42 and a conveyance roller pair 46. The motor driving device for driving the conveying roller pair 46 has the same configuration as the motor driving device for driving the conveying roller pair of the sheet supply device 40 of the copying machine according to the embodiment.

[Third Modification]
FIG. 23 is a schematic configuration diagram showing a copying machine according to a third modification. This copier has only one black image forming unit 3 as an image forming unit. Then, when the recording sheet is passed through the transfer nip formed by contact between the photosensitive member of the image forming unit 3 and the transfer roller, the toner image on the photosensitive member is transferred to the recording sheet. A sheet supply device 40 that supplies a recording sheet to the image forming unit 1 has the same configuration as that of the embodiment.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
[Aspect A]
DC brushless motor (for example, transport motor 210), a driver circuit (for example, driver circuit 212) for exciting the coil of the DC brushless motor, and the driver circuit to grasp the switching timing of the excitation coil of the DC brushless motor. A rotation angle detection means (for example, Hall element 217) for detecting the rotation angle of the DC brushless motor, and a control means (for example, motor control circuit 200) for controlling the driving of the DC brushless motor via the driver circuit. In the drive device,
In order to accelerate the rotational speed of the DC brushless motor with a predetermined first acceleration characteristic, a first acceleration process for outputting a relatively low voltage from the driver circuit to the coil, and the rotation after the first acceleration process. In order to accelerate the speed with the second acceleration characteristic that is superior to the first acceleration characteristic, the second acceleration process for outputting a relatively high voltage from the driver circuit to the coil, and the first acceleration process. Prior to starting the driving of the DC brushless motor, the driver circuit that has not output a voltage outputs a voltage having a value higher than the relatively low voltage in the first acceleration process to the coil. The control means is configured to perform the driving start process.

[Aspect B]
Aspect B is the aspect according to aspect A, in which the driver circuit and a rotation amount detection means (for example, motor encoder 211) for detecting the rotation amount of the DC brushless motor with higher accuracy than the rotation angle detection means are used in the DC brushless motor. The control means is mounted so as to carry out a process of determining an execution start timing of the second acceleration process based on a detection result by the rotation amount detection means when the first acceleration process is performed. It is characterized by comprising. In such a configuration, as described above, it is possible to suppress instability of the motor rotation caused by noise mixed in the rotation sensing signal (for example, Hall signal). In addition, when the timing of meshing is reached before the end of the first acceleration period, without waiting for the end of the first acceleration period, it is immediately shifted to the second acceleration period to increase the acceleration. “Acceleration time” can be further shortened.

[Aspect C]
Aspect C is a feedback means (for example, a position / frequency sensor) for feeding back the difference between the target rotational speed of the DC brushless motor and the detection result by the rotation amount detection means to control of the output voltage to the excitation coil. A speed follow-up control circuit 202) and a feedforward means (for example, a position / speed follow-up control circuit 202) for outputting a predetermined value of voltage to the exciting coil is provided in the control means, and the first acceleration processing In the second acceleration process, the control means is configured to perform a process of correcting the output voltage value determined by the feedforward means by feedback control by the feedback means, respectively. Is. In this configuration, as described above, the DC brushless motor can exhibit position followability and speed followability comparable to a stepping motor.

[Aspect D]
Aspect D is an aspect in which, in aspect C, as a driver circuit, an output adjustment unit that adjusts the output of excitation voltage to the coil based on the PWM signal output from the control means, and a coil that excites among a plurality of coils in the DC brushless motor Using a coil switching unit that switches between the two in a predetermined order. In such a configuration, it is possible to reduce the cost by adopting a commercially available driver circuit.

[Aspect E]
Aspect E is an optical detection of a code wheel fixed to the motor shaft and a plurality of marks (for example, slit SL and dark portion DP) provided on the code wheel as a rotation amount detecting means in aspect C or D. And a rotation amount detecting means covered with a cover member. In such a configuration, it is possible to suppress a decrease in detection accuracy due to the adhesion of the foreign matter by suppressing the adhesion of the foreign matter to the light receiving portion of the optical sensor by the cover member.

[Aspect F]
Aspect F is characterized in that, in aspects C to E, an inner rotor type DC brushless motor is used. In such a configuration, the acceleration of the driven body can be freely adjusted due to the favorable acceleration adjustability of the inner rotor type DC brushless motor.

[Aspect G]
Aspect G is characterized in that an outer rotor type DC brushless motor is used as a DC brushless motor in aspects C to E. In such a configuration, the speed adjustment process can be performed using a PLL circuit mounted on an outer rotor type DC brushless motor.

200: Motor control circuit (control means)
202: Position / speed tracking control circuit (feedback means, feedforward means)
210: Conveyance motor (DC brushless motor)
211: Motor encoder (rotation amount detection means)
212: Driver circuit 212
217: Hall element (rotation angle detection means)

JP 2010-133990 A

Claims (10)

Based on the detection result by the DC brushless motor, the rotation angle detection means for detecting the rotation angle of the DC brushless motor, and the detection result by the rotation angle detection means, among the plurality of coils in the DC brushless motor, a coil to be excited is selected. In a motor drive device having a driver circuit for switching, and a control means for controlling the drive of a DC brushless motor via the driver circuit,
A first acceleration process for outputting a relatively low voltage from the driver circuit to the coil in order to accelerate the rotational speed of the DC brushless motor with a predetermined first acceleration characteristic;
After the first acceleration process, in order to accelerate the rotation speed with a second acceleration characteristic that is superior to the first acceleration characteristic, a relatively high voltage is output from the driver circuit to the coil. Acceleration processing,
Prior to the first acceleration process, a voltage having a value higher than the relatively low voltage in the first acceleration process is output to the coil from the driver circuit that has not output a voltage, and the DC A motor driving apparatus characterized in that the control means is configured to perform a driving start process for starting driving of a brushless motor. The motor driving device according to claim 1,
The DC brushless motor is mounted with the driver circuit and a rotation amount detection means for detecting the rotation amount of the DC brushless motor with higher accuracy than the rotation angle detection means,
The control means is configured to perform a process of determining an execution start timing of the second acceleration process based on a detection result by the rotation amount detection means when the first acceleration process is being performed. A motor drive device characterized by. The motor driving device according to claim 2, wherein
Feedback means for feeding back the difference between the target rotational speed of the DC brushless motor and the detection result by the rotation amount detection means to control of the output voltage to the excitation coil, and a voltage having a predetermined value as the excitation coil Feedforward means for outputting to the control means,
In the first acceleration process, the second acceleration process, and the constant speed rotation process for rotating the DC brushless motor at a constant speed, the output voltage values determined by the feedforward means are respectively used as the feedback means. A motor drive device characterized in that the control means is configured to perform a process of correcting by feedback control according to the above. In the motor drive device of Claim 3,
As the driver circuit, an output adjustment unit that adjusts the output of the excitation voltage to the coil based on the PWM signal output from the control means, and among the plurality of coils in the DC brushless motor, the coils to be excited are in a predetermined order. A motor driving device comprising a coil switching unit that is switched in step 1). The motor driving device according to claim 3 or 4,
As the rotation amount detecting means, a code wheel fixed to the motor shaft and an optical sensor that optically detects a plurality of marks provided on the code wheel are used, and the rotation amount detecting means is used. A motor drive device characterized by being covered with a cover member. In the motor drive device in any one of Claims 3 thru | or 5,
An inner rotor type motor is used as the DC brushless motor. In the motor drive device in any one of Claims 3 thru | or 5,
An outer rotor type motor is used as the DC brushless motor. The motor driving device according to claim 7, wherein
As the DC brushless motor, a motor equipped with an FG signal generator as the rotation amount detecting means is used,
As the driver circuit, processing for adjusting the rotational speed of the DC brushless motor to a value corresponding to the reference signal based on the FG signal from the FG signal generator and the reference signal sent from the control means. A motor drive device characterized by using what is to be implemented. Sheet conveyance comprising: a sheet conveyance member that conveys a sheet member pressed against its endlessly moving surface along with the endless movement of the surface; and motor driving means that drives a motor that is a driving source of the sheet conveyance member In the device
9. A sheet conveying apparatus using the motor driving apparatus according to claim 1 as the motor driving means. In an image forming apparatus comprising: a sheet conveying device that conveys a recording sheet as a sheet member; and an image forming unit that forms an image on the recording sheet.
An image forming apparatus using the sheet conveying device according to claim 9 as the sheet conveying means.

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