JP2007033525A - Image forming apparatus and phase adjustment method for the apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To adjust phase relation between image carriers with high accuracy, in an image forming apparatus designed such that at least one or more image carriers are connected to each of a plurality of drive motors, and the plurality of drive motors are driven at a predetermined regular speed, thereby toner images formed on the corresponding image carriers are superposed to form a color image while rotating the image carriers. <P>SOLUTION: A rise time difference (tA-tB) is obtained taking the rise time of each drive motor into account. The timing of switching each drive motor from a phase detection speed Vi to a regular speed Vdef is controlled based on an output time difference Δts and the rise time difference (tA-tB), and thereby a phase difference between the photoreceptor drums is adjusted to a set phase angle. Accordingly, even if the rise time characteristic of each drive motor varies, the phase relations between the photoreceptor drums can appropriately be adjusted with high accuracy. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention connects at least one or more image carriers to each of a plurality of drive motors, and drives a plurality of image carriers while rotating the plurality of image carriers by driving the plurality of drive motors at a predetermined normal speed. The present invention relates to an image forming apparatus that forms a color image by superimposing toner images formed on each of the carriers, and particularly relates to a technique for adjusting the phase relationship among a plurality of image carriers.

  As an apparatus for forming a color image, a so-called tandem color image forming apparatus is known. In this image forming apparatus, a plurality of image forming stations that form toner images of different colors are arranged along the moving direction of a transfer medium such as an intermediate transfer belt. In each image forming station, an image carrier such as a photosensitive drum is rotated at a predetermined rotational speed, and a charging unit, an image writing unit, and a developing unit are disposed around the image carrier. Then, while rotating all the image carriers, the toner images formed on the respective image carriers are superimposed on the transfer medium to form a color image.

  In order to rotationally drive a plurality of image carriers in this way, it is roughly divided from the conventional ones. (1) A single drive motor is used and the rotational driving force of the drive motor is transmitted to each image carrier by a train wheel. And (2) a method using a plurality of drive motors. In particular, as the latter method, in the apparatus described in Patent Document 1, for example, three colors of yellow, magenta, and cyan are already phase-adjusted at the assembly stage and rotated by a common drive motor, while the black color is used. Is driven to rotate by a separate and independent drive motor.

  By the way, in such a tandem apparatus using a plurality of drive motors, periodic color misregistration may occur due to factors such as shaft runout of each image carrier and eccentricity of a gear directly connected to each image carrier. . Therefore, in order to correct this periodic color shift, a plurality of drive motors are individually controlled. That is, by controlling each drive motor individually, the phase relationship between the image carriers of the respective colors is adjusted by controlling the phases of the image carriers of the four colors. As a result, periodic color misregistration is suppressed and image quality is improved.

JP 2003-66676 A ([0029] to [0036])

  In the conventional apparatus, the phase adjustment is performed on the assumption that each drive motor is always driven with a constant rising characteristic. However, the load applied to the drive motor varies depending on various factors. For example, the image carrier has individual differences, and the rising characteristics may differ depending on the image carrier to be driven. Further, when operating not only the image carrier but also the developing unit corresponding to the image carrier using the driving force of the drive motor, the load on the drive motor according to the residual toner amount stored in the developing unit Fluctuates. Therefore, in order to perform the phase adjustment with high accuracy, it is necessary to consider the rising characteristics of the drive motor.

  The present invention has been made in view of the above-described problems, and connects a plurality of image carriers by connecting at least one image carrier to each of a plurality of drive motors and driving the plurality of drive motors at a predetermined normal speed. In an image forming apparatus for forming a color image by superimposing toner images formed on each of a plurality of image carriers while rotating the body, the object is to adjust the phase relationship between the image carriers with high accuracy And

  The present invention connects at least one or more image carriers to each of a plurality of drive motors, and drives a plurality of image carriers while rotating the plurality of image carriers by driving the plurality of drive motors at a predetermined normal speed. An image forming apparatus that forms a color image by superimposing toner images formed on each of the carriers, and is provided corresponding to each of the plurality of image carriers to achieve the above object. A plurality of phase detection means for detecting the reference position of the image carrier to be output and outputting a detection signal, and obtaining rise information related to the rise characteristics of each drive motor, and detecting a plurality of drive motors at a phase slower than the normal speed The output time difference of the detection signals from the plurality of phase detection means is calculated while driving at the speed, and the acceleration is performed from the phase detection speed to the normal speed based on the calculation result and the rise information. The timing is controlled for each drive motor is characterized in that a phase control means for performing a phase adjustment process for adjusting the phase relationship between a plurality of image bearing members.

  Further, the present invention connects at least one or more image carriers to each of the plurality of drive motors, and drives the plurality of drive motors at a predetermined normal speed while rotating the plurality of image carriers. A phase adjustment method for adjusting a phase relationship between a plurality of image carriers in an image forming apparatus for forming a color image by superimposing toner images formed on each of the image carriers, and achieving the above object Therefore, for each of the plurality of image carriers, the step of obtaining the rise information related to the rise characteristics of each drive motor and driving the plurality of drive motors at a phase detection speed slower than the normal speed Detecting a reference position and outputting a detection signal, obtaining a detection signal output time difference between a plurality of image carriers, and detecting a phase based on the output time difference and rise information The timing of accelerating the normal speed by controlling each drive motor is characterized by comprising the step of adjusting the phase relationship between a plurality of image bearing members from time.

  In the invention thus configured (image forming apparatus and phase adjustment method in the apparatus), the drive motor is driven at a phase detection speed slower than the normal speed before being driven to the normal speed. A plurality of image carriers are rotated by this motor drive, and phase detection means provided corresponding to each image carrier detects a reference position and outputs a detection signal. Therefore, the difference in detection signal output time between the image carriers corresponds to the phase difference between the image carriers. Therefore, when accelerating each drive motor from the phase detection speed to the normal speed, the phase relationship between the image carriers can be adjusted by controlling the acceleration timing according to the output time difference. However, the rising characteristics of each drive motor may differ individually. In view of this point, in the present invention, the rising information related to the rising characteristics of each drive motor is obtained before accelerating to the normal speed, and the timing for accelerating from the phase detection speed to the normal speed is determined based on the output time difference and the rising information. The phase relationship among a plurality of image carriers is adjusted by being controlled for each drive motor. Therefore, even if the loads applied to the drive motors are different from each other and the rising characteristics of the drive motors are different, the phase relationship between the image carriers can be adjusted appropriately and with high accuracy.

  Here, the “rise information related to the rise characteristics” includes the acceleration of each drive motor, the time required for each drive motor to reach a predetermined speed, and the relative difference between the drive motors for the time, etc. It is. For example, in a device that outputs a ready signal when each of a plurality of drive motors reaches a preset speed or a predetermined range including the set speed, rising information can be obtained using the ready signal. That is, for each of the plurality of drive motors, by setting the phase detection speed as the set speed, the drive motor is accelerated from the stopped state to the phase detection speed, and until the ready signal is output from the drive motor. Based on the acceleration time, “rise information” can be obtained. Also, the rise time difference between multiple drive motors that occurs when accelerating from the phase detection speed to the normal speed according to the difference in detection acceleration time between multiple drive motors is obtained as “rise information”. Also good. Then, the phase relationship between the plurality of image carriers may be adjusted by controlling the acceleration timing between the plurality of drive motors based on the output time difference and the rise information.

  Further, the rising information may be stored in advance in the storage means, and the timing of acceleration from the phase detection speed to the normal speed may be controlled for each drive motor based on the rising information and the output time difference. In the apparatus that stores the rising information in the storage unit as described above, the rising information stored in the storage unit may be corrected by obtaining the rising information at the same time when accelerating from the phase detection speed to the normal speed. For example, for each of a plurality of drive motors, the normal speed is set as the set speed to accelerate the drive motor from the phase detection speed to the normal speed, and obtain the rise time until the ready signal is output from the drive motor. The rising information stored in the storage means can be corrected based on the rising time. By correcting the rising information in this way, the quality of the rising information can be improved, and the accuracy of phase adjustment can be further improved.

  Further, the phase adjustment process is not limited to one type, and has the following first phase adjustment process and the following second phase adjustment process as the phase adjustment process in advance, and selectively executes one of them. You may comprise as follows. That is, in the first phase adjustment process, for each of the plurality of drive motors, the drive motor is accelerated from the stopped state to the phase detection speed by setting the phase detection speed as the set speed, and a ready signal is output from the drive motor. After obtaining the rise information based on the acceleration time for detection until output, calculate the output time difference of the detection signals from the plurality of phase detection means while driving at the phase detection speed, and based on the calculated result and the rise information This is a process of adjusting the phase relationship between a plurality of image carriers by controlling the timing of acceleration from the detection speed to the normal speed for each drive motor. The second phase adjustment process reads the rising information from the storage means. The output time difference of the detection signals from the plurality of phase detection means is calculated while driving at the phase detection speed, and the calculation result and the rise time are calculated. The timing to accelerate the normal rate from the phase detection rate based on the information is a process of adjusting the phase relationship between the plurality of image carriers by controlling each drive motor. In this way, by controlling the switching of the phase adjustment process, an appropriate phase adjustment process can be performed according to the operating status of the apparatus. For example, a predetermined initialization operation is often performed immediately after power-on of the apparatus, and the first phase adjustment process can be performed in parallel with this initialization operation.

  FIG. 1 is a diagram showing an embodiment of an image forming apparatus according to the present invention. The apparatus 1 includes color printing processing for forming a full-color image by superposing four color toners (developers) of black (K), cyan (C), magenta (M), and yellow (Y), and black (K ) To selectively execute a monochrome printing process for forming a monochrome image using only toner. In this image forming apparatus 1, when an image forming command (printing command) is given to a main controller (not shown) from an external device such as a host computer, an engine controller (not shown) is operated in accordance with the command from the main controller. Each part EG is controlled to execute a predetermined image forming operation, and an image corresponding to the image forming command is formed on a sheet (recording material) S such as a copy sheet, a transfer sheet, a sheet, and an OHP transparent sheet.

  1, an image forming apparatus 1 according to the present embodiment includes a housing body 2, a first opening / closing member 3 that is detachably mounted on the front surface of the housing body 2 (the right-hand side surface in FIG. 1), and the housing body 2. And a second opening / closing member 4 (also serving as a paper discharge tray) mounted on the upper surface so as to be freely opened and closed.

  In the housing main body 2, an electrical component box 5 containing a power circuit board, a main controller, and an engine controller is provided. An image forming unit 6, a transfer belt unit 9, and a paper feed unit 10 are also disposed in the housing body 2. On the other hand, a fixing unit 12 is disposed on the first opening / closing member 3 side. In this embodiment, the consumables in the image forming unit 6 and the paper feeding unit 10 are configured to be detachable from the housing body 2. The consumables and the transfer belt unit 9 can be removed and repaired or exchanged.

  The transfer belt unit 9 is disposed below the housing body 2 and is driven to rotate by a black drive motor described later, and a driven roller 15 disposed obliquely above the drive roller 14. An intermediate transfer belt 16 that is stretched between the rollers 14 and 15 and driven to circulate in the direction of the arrow D16 in the figure, and a belt cleaner 17 that abuts against the surface of the intermediate transfer belt 16. The driven roller 15 is disposed obliquely above the drive roller 14 (upward on the left hand in FIG. 1). For this reason, the intermediate transfer belt 16 rotates and moves in the direction D16 while being inclined. Further, the belt surface 16a in which the belt conveyance direction D16 when the intermediate transfer belt 16 is driven is downward (right downward in FIG. 1) is positioned below. In the present embodiment, the belt surface 16a is a belt tension surface (surface pulled by the drive roller 14) when the belt is driven, and the peripheral speed is lower than the peripheral speed of the photosensitive drum (image carrier) 20 of each color. have. In this way, by setting the peripheral speed of the intermediate transfer belt 16 to be slower than the peripheral speed of each photosensitive drum 20, the photosensitive drum 20 is pulled by the intermediate transfer belt 16 in a direction that suppresses rotation. Driving.

  The drive roller 14 also serves as a backup roller for the secondary transfer roller 19. A rubber layer having a thickness of about 3 mm and a volume resistivity of 100 kΩ · cm or less is formed on the peripheral surface of the drive roller 14, and secondary transfer is omitted by grounding through a metal shaft. A conductive path of the secondary transfer bias supplied from the bias generation unit via the secondary transfer roller 19 is used. Thus, by providing the driving roller 14 with a rubber layer having high friction and shock absorption, it is difficult for the impact when the sheet S enters the secondary transfer portion to be transmitted to the intermediate transfer belt 16, and deterioration of image quality is prevented. can do.

  In the present embodiment, the diameter of the driving roller 14 is smaller than the diameter of the driven roller 15. Thereby, the sheet S after the secondary transfer can be easily peeled by the elastic force of the sheet S itself. The driven roller 15 is also used as a backup roller for the belt cleaner 17. The belt cleaner 17 is provided on the side of the belt surface 16a facing downward in the transport direction, and includes a cleaning blade 17a that removes residual toner and a toner transport member that transports the removed toner, as shown in FIG. Yes. The cleaning blade 17a contacts the intermediate transfer belt 16 at a portion where the intermediate transfer belt 16 is wound around the driven roller 15, and cleans and removes toner remaining on the surface of the intermediate transfer belt 16 after the secondary transfer.

  The driving roller 14 and the driven roller 15 are rotatably supported by a support frame (not shown) of the transfer belt unit 9. Further, a primary transfer roller 21 is provided on the back surface of the belt surface 16a facing downward in the transport direction of the intermediate transfer belt 16 so as to face the photosensitive drum 20 of each image forming station Y, M, C, K described later. . These four primary transfer rollers 21 are rotatably supported with respect to the support frame, and are electrically connected to a primary transfer bias generator (not shown), and generate the primary transfer bias at an appropriate timing. A primary transfer bias is applied from the portion.

  The support frame is rotatable with respect to the housing main body 2 in the arrow direction D21 with the drive roller 14 as a rotation center. Then, by actuating an actuator (not shown), the support frame is rotated to face the photosensitive drums 20 of the yellow (Y), magenta (M), and cyan (C) image forming stations Y, M, and C. The primary transfer roller 21 arranged in this manner approaches the photosensitive drum 20 and moves away from the photosensitive drum 20. For this reason, when the primary transfer rollers 21 for yellow, magenta, and cyan are moved closer to the photosensitive drum 20, they are brought into contact with the photosensitive drum 20 with the intermediate transfer belt 16 interposed therebetween (solid line in FIG. 1). This contact position is the primary transfer position, and the toner image is transferred to the intermediate transfer belt 16 at the primary transfer position. Conversely, when the primary transfer rollers 21 for yellow, magenta, and cyan move away from the photosensitive drum 20, the photosensitive drum 20 and the intermediate transfer belt 16 of the image forming stations Y, M, and C are separated from each other (FIG. Dashed line in 1). On the other hand, the primary transfer roller 21 disposed facing the photosensitive drum 20 of the black (K) image forming station K rotates while being in contact with the photosensitive drum 20 with the intermediate transfer belt 16 interposed therebetween. Is configured to do. Therefore, as shown by the solid line in FIG. 1, the color printing process can be executed by positioning all the primary transfer rollers 21 on the photosensitive drum 20 side. On the other hand, as shown by a broken line in FIG. 5, the intermediate transfer belt is executed while only the monochrome printing process is performed by leaving the primary transfer roller 21 for black and separating the other primary transfer roller 21 from the photosensitive drum 20. 16 is separated from the image forming stations Y, M, and C, and yellow, magenta, and cyan colors can be set to a non-printing state. Note that the primary transfer roller 21 for black may also be configured to move away from the photosensitive drum 20 as necessary.

  A test pattern sensor 18 is installed on the support frame of the transfer belt unit 9 in the vicinity of the drive roller 14. This test pattern sensor 18 is a sensor for positioning each color toner image on the intermediate transfer belt 16, detecting the density of each color toner image, and correcting the color shift and image density of each color image.

  The image forming unit 6 includes image forming stations Y (for yellow), M (for magenta), C (for cyan), and K (for black) that form a plurality (four in this embodiment) of different color images. I have. Each of the image forming stations Y, M, C, and K is provided with a photosensitive drum 20 corresponding to the “image carrier” of the present invention. A charging unit 22, an image writing unit 23, a developing unit 24, and a photoconductor cleaner 25 are disposed around each photoconductor drum 20. Then, a charging operation, a latent image forming operation, and a toner developing operation are executed by these functional units. In FIG. 1, since the image forming stations of the image forming unit 6 have the same configuration, for convenience of illustration, only some of the image forming stations are denoted by reference numerals, and the other image forming stations are omitted. . Further, the arrangement order of the image forming stations Y, M, C, and K is arbitrary.

  The photosensitive drums 20 of the image forming stations Y, M, C, and K are disposed so as to be in contact with the belt surface 16a facing downward in the transport direction of the intermediate transfer belt 16 at the primary transfer position TR1. As a result, the image forming stations Y, M, C, and K are also arranged in a direction inclined to the left in the drawing with respect to the driving roller 14. Each of these photosensitive drums 20 is connected to a dedicated drive motor and is driven to rotate at a predetermined peripheral speed in the conveyance direction of the intermediate transfer belt 16 as indicated by an arrow D20 in the figure. The drive mechanism and drive control of the photosensitive drum 20 will be described in detail later.

  The charging unit 22 includes a charging roller whose surface is made of elastic rubber. The charging roller is configured to be driven to rotate in contact with the surface of the photosensitive drum 20 at a charging position, and at a peripheral speed in the driven direction with respect to the photosensitive drum 20 as the photosensitive drum 20 rotates. Followed rotation. The charging roller is connected to a charging bias generator (not shown), and receives the charging bias from the charging bias generator to charge the surface of the photosensitive drum 20 at the charging position.

  The image writing unit 23 is an array writing in which elements such as a liquid crystal shutter including a light emitting diode and a backlight are arranged in a line in the axial direction of the photosensitive drum 20 (direction perpendicular to the paper surface of FIG. 1). The head is used and is spaced from the photosensitive drum 20. The array-like writing head has a shorter optical path length and is more compact than the laser scanning optical system. Therefore, it can be disposed close to the photosensitive drum 20 and has the advantage that the entire apparatus can be downsized.

  Next, details of the developing unit 24 will be described on behalf of the image forming station K. The developing unit 24 includes a toner storage container 26 for storing toner, two toner agitation supply members 28 and 29 disposed in the toner storage container 26, and a partition member disposed in proximity to the toner agitation supply member 29. 30, a toner supply roller 31 disposed above the partition member 30, a developing roller 33 that contacts the toner supply roller 31 and the photosensitive drum 20 and rotates in a direction indicated by an arrow at a predetermined peripheral speed, and a developing roller And a regulating blade 34 abutting on the bearing 33.

  In each developing unit 24, the toner stirred and carried by the toner stirring supply member 29 is supplied to the toner supply roller 31 along the upper surface of the partition member 30. The toner thus supplied is supplied to the surface of the developing roller 33 via the supply roller 31. The toner supplied to the developing roller 33 is regulated to a predetermined layer thickness by the regulating blade 34 and is conveyed to the photosensitive drum 20. The charged toner is developed at a developing position where the developing roller 33 and the photosensitive drum 20 come into contact with each other by a developing bias applied to the developing roller 33 from a developing bias generator (not shown) electrically connected to the developing roller 33. Moves from the developing roller 33 to the photosensitive drum 20, and the electrostatic latent image formed by the image writing unit 23 is visualized.

  In this embodiment, a photoreceptor cleaner 25 is provided in contact with the surface of the photoreceptor drum 20 on the downstream side of the primary transfer position TR1 in the rotation direction D20 of the photoreceptor drum 20. The photoconductor cleaner 25 is in contact with the surface of the photoconductor drum 20 to remove the toner remaining on the surface of the photoconductor drum 20 after the primary transfer.

  The sheet feeding unit 10 includes a sheet feeding unit including a sheet feeding cassette 35 in which sheets S are stacked and held, and a pickup roller 36 that feeds the sheets S from the sheet feeding cassette 35 one by one. In the first opening / closing member 3, a registration roller pair 37 that defines the timing of feeding the sheet S to the secondary transfer region TR 2, and a secondary transfer unit that is pressed against the drive roller 14 and the intermediate transfer belt 16. A secondary transfer roller 19, a fixing unit 12, a paper discharge roller pair 39, and a duplex printing conveyance path 40 are provided.

  The secondary transfer roller 19 is provided so as to be able to come into contact with and separate from the intermediate transfer belt 16 and is driven to come into contact with and separate from a secondary transfer roller drive mechanism (not shown). The fixing unit 12 includes a heating roller 45 that includes a heating element such as a halogen heater and is rotatable, and a pressure roller 46 that presses and biases the heating roller 45. The image secondarily transferred to the sheet S is fixed to the sheet S at a predetermined temperature at a nip formed by the heating roller 45 and the pressure roller 46. In the present embodiment, the fixing unit 12 can be disposed in a space formed obliquely above the intermediate transfer belt 16, in other words, in a space opposite to the image forming unit 6 with respect to the intermediate transfer belt 16. Thus, heat transfer to the electrical component box 5, the image forming unit 6, and the intermediate transfer belt 16 can be reduced, and the frequency of performing the color misregistration correction operation for each color can be reduced.

  Further, the sheet S thus subjected to the fixing process is conveyed to a second opening / closing member (discharge tray) 4 provided on the upper surface portion of the housing body 2 via the discharge roller pair 39. Further, when images are formed on both sides of the sheet S, when the rear end portion of the sheet S on which the image is formed on one side as described above is conveyed to the reverse position behind the pair of discharge rollers 39. The rotation direction of the discharge roller pair 39 is reversed, whereby the sheet S is conveyed along the duplex printing conveyance path 40. Then, it is put on the conveyance path again before the registration roller pair 37. At this time, the surface of the sheet S to which the image is transferred by contacting the intermediate transfer belt 16 in the secondary transfer region TR2 is transferred first. It is the opposite side of the surface that was made. In this way, images can be formed on both sides of the sheet S.

  FIG. 2 is a schematic diagram showing the positional relationship between the intermediate transfer belt and the photosensitive drums of the respective colors, FIG. 3 is a diagram showing a driving mechanism for rotating the photosensitive drum, and FIG. 4 is a phase diagram of the photosensitive drum. It is a block diagram which shows the electric constitution which controls a relationship. Hereinafter, a drive mechanism and drive control for driving the photosensitive drum 20 will be described in detail with reference to these drawings.

  In the image forming apparatus 1 according to this embodiment, four color photosensitive drums 20 are provided. In order to rotationally drive these photosensitive drums 20, four drive motors 50 (50Y, 50M, 50C,. 50K). By controlling each drive motor 50, it is possible to independently rotate the photosensitive drums (image carriers) 20 of the respective colors. Although not shown in FIG. 2, the drive motors 50Y, 50M, 50C, and 50K are mechanically connected to the corresponding developing units 24, and the rotational driving force is applied to the developing roller 33 of the developing unit 24. In addition, the toner is supplied to the toner agitation supply members 28 and 29. Therefore, the load applied to the drive motor 50 varies depending on the amount of toner remaining in the developing unit 24. Since the drive mechanisms for rotating the photosensitive drum 20 have the same configuration, only the yellow drive mechanism will be described here, and the other toner colors will be described with the same or corresponding reference numerals. Omitted.

  In this embodiment, a DC brushless motor is employed as the yellow drive motor 50Y. A motor pinion 51 is attached to the rotating shaft of the drive motor 50Y, and an idle gear 52 is meshed with the motor pinion 51. An idle gear 53 is attached coaxially to the idle gear 52. When the rotational driving force of the drive motor 50Y is transmitted to the idle gear 52 via the motor pinion 51, the idle gears 52, 53 are integrated with each other. Rotate. On the other hand, the idle gear 53 is meshed with the photoconductor gear 54 that is mounted coaxially with the rotation shaft of the photoconductor drum 20, and the idle gear 53 is driven to rotate as described above, whereby the photoconductor drum 20Y. Is driven to rotate. In this embodiment, in order to form an image while rotating the photosensitive drum 20 at a target rotation speed of 132 rpm (one round time Tdef = 454.5 ms), for example, the normal speed Vdef of the drive motor 50Y is set to 1584 rpm. The reduction ratio of the driving force transmission mechanism having the gear configuration of the motor pinion 51 and the gears 52 to 54 can be set to 1/12.

  Further, in this embodiment, the photoconductor gear 54 directly connected to the rotating shaft of the photoconductor drum 20 has a larger diameter than the diameter (30 mm) of the photoconductor drum 20, and a recess 55 is formed at one place on the outer peripheral portion thereof. Is formed as the “reference position” of the present invention. A reflective optical sensor 56 is arranged as a phase detection sensor on the rotation locus of the recess 55. For this reason, every time the reference position (concave portion 55) of the photosensitive drum 20 passes through the phase detection sensor 56, a detection signal is output from the phase detection sensor 56 to the phase control unit 57 provided in the engine controller. That is, in this embodiment, the phase detection sensor 56 corresponds to the “phase detection means” of the present invention, and it is determined whether the photosensitive drum 20 has passed the reference position based on the output signal from the phase detection sensor 56. While being able to detect correctly, the rotation phase of the photosensitive drum 20 can be detected.

  Further, the drive motor 50Y is provided with a frequency generator 59Y, which generates a frequency signal (hereinafter referred to as “FG signal”) according to the rotational speed of the drive motor 50Y, and supplies it to the drive motor 50 and the phase control unit 57. Output. The configuration of the frequency generator 59Y is not particularly limited, but in this embodiment, a pulse signal obtained by dividing one rotation of the drive motor 50Y by 60 is output as an FG signal. Therefore, the FG signal output from the frequency generator 59Y reflects the rotational drive state of the drive motor 50Y that changes from moment to moment, and the drive motor 50Y reaches the drive speed set by the phase control unit 57 and is in a steady state. Of course, while it is in an unsteady state, for example, even while the rotational speed is being accelerated, the rotational drive state of the drive motor 50Y can be determined by referring to the FG signal. Accurately grasp.

  Each drive motor 50 and the drive mechanism are configured as described above. While the apparatus 1 is waiting for an image formation command (print command) from an external device such as a host computer, all the drive motors 50 stop rotating. ing. When a print command is given, the main controller converts the job data into a format suitable for the operation instruction of the engine unit EG and sends it to the engine controller. In response to this, the engine controller gives a drive command to the phase control unit 57 to rotate the photosensitive drum 20 at a desired target rotational speed (132 rpm). More specifically, after the phase control unit 57 adjusts the phase relationship between the photosensitive drums 20 by executing the processing described below, each of the photosensitive drums 20 is kept steady at a desired rotation speed (132 rpm). Rotate. Note that reference numeral 58 in FIG. 4 denotes a memory, which stores arithmetic expressions, control tables, and the like for phase adjustment described below. Reference numeral 61 denotes a temperature sensor for detecting the temperature inside the apparatus (in-machine temperature).

  FIG. 5 is a flowchart showing an operation for adjusting the rotational phase between the photosensitive drums. FIG. 6 is a timing chart showing the phase difference derivation and phase adjustment operations. Hereinafter, the phase difference detection operation and the rotation phase adjustment operation between the photosensitive drums will be described in detail with reference to these drawings. This phase adjustment process is also a “first phase adjustment process” in an embodiment described later.

In this apparatus, when a drive command is given from the engine controller to the phase control unit 57 in response to a print command from an external device, the drive speeds of the drive motors 50Y, 50M, 50C, and 50K are accelerated in two stages to a normal speed Vdef. Adjust to. As the first stage, the drive of all the drive motors 50Y, 50M, 50C, 50K is started simultaneously (step S101). In this embodiment, the drive speed of the drive motor 50 at this time is half the normal speed Vdef, that is, the phase detection speed Vi.
Vi = Vdef / 2 = 15884 rpm / 2 = 792 rpm
The phase control unit 57 gives control signals (pulse signals) to the motor rotation control units 60Y, 60M, 60C, and 60K so as to drive the drive motors 50 at the phase detection speed Vi. As a result, the motor rotation control units 60Y, 60M, 60C, and 60K operate the drive motors 50Y, 50M, 50C, and 50K, respectively, to start driving the photosensitive drum 20. Further, the phase control unit 57 waits for the ready (READY) signal to be output from the drive motor 50 for each color. The ready signal is a signal output from the drive motor 50 when the rotational speed of the drive motor 50 reaches a set speed or a set speed range (set speed ± several percent). In particular, in the first stage, the phase detection speed Vi is the set speed. Then, by detecting a ready signal from all the drive motors 50, the first stage speed adjustment is completed, and it is confirmed that the drive motor 50 and the photosensitive drum 20 are driven in a steady state. Can do. When the drive motor 50 is driven at the phase detection speed Vi, the rotational speed of the photosensitive drum 20 is 66 rpm, which is half the rotational speed (132 rpm) at the time of image formation, and the one-round time Ti of the photosensitive drum 20 is 909. Double to 1 ms.

  In this embodiment, for each toner color, the set speed is set to the phase detection speed Vi as described above, and the drive motor 50 is accelerated from the stopped state to the phase detection speed Vi. The time to output is calculated. Here, one of the four color photosensitive drums 20 is set as the reference side, and as shown in FIG. 6, the time tAs required from the start of the reference side drive motor 50 to the output of the ready signal is detected. On the other hand, the rest is set as the control side, and the time tBs required from the start of the control side drive motor 50 to the output of the ready signal is detected (step S102). In this embodiment, the times tAs and tBs correspond to the “detection acceleration time” of the present invention. Then, acquisition of rise information, detection of phase difference, and phase adjustment are performed in both. Here, only one of the remaining control side photosensitive drums 20 will be described as an example, but the same applies to the other control side photosensitive drums 20.

  In the next step S103, the difference between the acceleration times for detection tAs and tBs obtained in step S102 is obtained. Then, the rise time difference (tA-tB) corresponding to the time difference (tAs-tBs) thus obtained is read from the control table (FIG. 7) stored in the memory 58 (step S104). This rise time difference (tA−tB) is a value indicating the difference in rise time that occurs between the drive motors 50 when accelerating from the phase detection speed Vi to the normal speed Vdef, as will be described later. This corresponds to “rise information related to characteristics”. The units of detection acceleration times tAs, tBs, their time difference (tAs-tBs), and rise time difference (tA-tB) are (ms). Further, the method of deriving the rise time difference (tA−tB) is not limited to the above-described control table method, and may be configured to be obtained by an arithmetic expression, for example.

  Then, while driving all the drive motors 50 at the phase detection speed Vi, the phase difference between the photosensitive drums 20 is detected (steps S105 to S108). That is, when the photosensitive drum 20 is rotationally driven by the drive motor 50 and the reference position of the photosensitive drum 20 passes through the phase detection sensor 56, a detection signal is output from the phase detection sensor 56 to the phase control unit 57. This detection signal functions as a signal for detecting the rotational phase of the photosensitive drum 20, that is, a phase detection signal. By referring to the phase detection signal of each color, the position of the photosensitive drum 20 of the other color with respect to the reference color is detected. The phase difference can be obtained. That is, the phase difference (phase angle) between the reference side photosensitive drum 20 and the control side photosensitive drum 20 is the output time difference Δts of the detection signal output from the phase detection sensor 56 provided corresponding to each photosensitive drum 20. It corresponds to. Then, by measuring the output time difference Δts of the detection signal, the phase difference between them can be obtained, and it can be derived how much the actually measured phase difference is deviated from the preset phase difference (set phase angle α). Therefore, in this embodiment, when the reference position of the control photosensitive drum 20 is detected (step S105), the phase control unit 57 that has received this detection signal starts counting the output time difference Δts (step S106). In this embodiment, the count clock CLK is set to 1 kHz, and data processing is performed using the output time difference Δts as the count value.

Next, the counting of the output time difference Δts is continued until the reference position of the reference side photosensitive drum 20 is detected (steps S107 and S108). Thereby, an output time difference Δts indicating a phase difference between the reference side and the control side photosensitive drum 20 is obtained.
Further, the phase control unit 57 has the following formula: Δtm = ((Vi / (Vdef−Vi)) * Δts) + ((Tdef * Ti) / (Ti−Tdef) * (α / 360)) + (tA−tB)
Based on the above, the control time Δtm corresponding to the output time difference (phase difference) Δts and the rise time difference (tA−tB) is calculated (step S109). This control time Δtm corresponds to a timing difference in which the drive speed of the drive motor 50 is changed to the normal speed Vdef between the reference side and the control side as will be described below. Can be made to substantially coincide with the set phase angle α. For example, when the set phase angle α is “0”,
Δtm = ((Vi / (Vdef−Vi)) * Δts) + (tA−tB)
The phase angle between the reference side and the control side can be adjusted to zero by setting the control time Δtm determined by.

  When the reference side reference position (concave portion 55) is detected, the phase control unit 57 gives a control signal to the reference side motor rotation control unit 60 so as to drive the reference side drive motor 50 at the normal speed Vdef. Thus, the reference side drive motor 50 is driven at the normal speed Vdef while maintaining the drive speed of the control side drive motor 50 at the phase detection speed Vi (step S110). Thus, by providing a speed difference (= Vdef−Vi) between the drive motors, the phase angle of the reference-side and control-side photosensitive drum 20 can be changed over time. Therefore, in this embodiment, the phase angle is adjusted while maintaining the speed difference for the control time Δtm calculated as described above (steps S111 to S113). That is, counting is started simultaneously with the speed change of the reference side drive motor 50 (step S111). When the count value reaches the count value corresponding to the control time Δtm and the passage of the control time Δtm is confirmed (YES in step S112), the drive speed of the control side drive motor 50 is also phased. The detected speed Vi is changed to the normal speed Vdef (step S113). That is, the phase control unit 57 gives a control signal to the control-side motor rotation control unit 60 so as to drive the control-side drive motor 50 at the normal speed Vdef. Thus, by providing the speed difference for the control time Δtm, the phase difference between the reference side and the control side photosensitive drum 20 becomes the set phase angle α, and the phase relationship adjustment is completed, and the image can be formed as it is. it can.

  As described above, according to this embodiment, before driving the drive motor 50 at the normal speed Vdef, the detection output from the phase detection sensor 56 while driving at the phase detection speed Vi slower than the normal speed Vdef. Based on the signal, the phase difference between the photosensitive drums 20 is obtained as an output time difference Δts. Further, the rise time difference (tA-tB) is obtained in consideration of the rise characteristics of each drive motor 50. The timing difference between the photosensitive drums 20 is set by controlling the timing of accelerating each drive motor 50 from the phase detection speed Vi to the normal speed Vdef based on the output time difference Δts and the rise time difference (tA−tB). It is adjusted to α. Therefore, even if the rising characteristics of the drive motors 50 are individually different, the phase relationship between the photosensitive drums 20 can be adjusted appropriately and with high accuracy.

  Further, as a method of adjusting the drive speed of the drive motor 50 to the normal speed Vdef by changing it in two steps, for example, the phase detection speed Vi is set faster than the normal speed Vdef, and the speed is reduced after the phase difference is detected (output time difference Δts). Then, it can be considered to change to the normal speed Vdef. However, in the above embodiment, since a DC motor is used as the drive motor 50, it is difficult to accurately perform such deceleration control, and the deceleration pattern may vary depending on the load state on each drive motor 50. Therefore, setting the phase detection speed Vi slower than the normal speed Vdef is effective in preventing the occurrence of the above problem, and is particularly beneficial in an apparatus using a DC motor as the drive motor 50. It can be said.

  The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. For example, in the above embodiment, the control time Δtm corresponding to the output time difference Δts and the rise time difference (tA−tB) is calculated based on an arithmetic expression. However, for example, a control table as shown in FIG. 8 may be used. This control table associates the output time difference (count value) Δts and the control time Δtm for each rise time difference (tA−tB), and can be stored in the memory 58 in advance. In FIG. 8, only the control table when the rise time difference (tA-tB) is 22 (ms) is shown. Then, the control time Δtm corresponding to the actually measured output time difference Δts may be read out from the corresponding rise time difference (tA−tB) control table and determined. By using the control table in this way, the above-described arithmetic processing becomes unnecessary and phase adjustment control can be further simplified.

  As apparent from the control table of FIG. 8, when the set phase angle α is relatively large, the control time Δtm is longer than the one-round time Ti of the photosensitive drum 20. Therefore, for example, a time obtained by subtracting one round time Ti may be set as the control time Δtm. Thereby, an extra low speed rotation operation can be omitted and the time required for the phase adjustment can be shortened. This is the same in the embodiment in which the control time Δtm is obtained by an arithmetic expression.

  Further, the load state applied to the drive motor 50 may vary depending on the temperature inside the apparatus, so-called in-machine temperature. In order to cope with this, a plurality of types, for example, a high temperature control table, a normal temperature control table, and a low temperature control table can be stored in the memory 58 in advance. The phase control unit 57 can be configured to perform phase adjustment using a control table corresponding to the in-machine temperature detected by the temperature sensor 61. In this case, even if the in-machine temperature fluctuates, the phase adjustment corresponding to the fluctuation can be performed, and the phase relationship between the photosensitive drums 20 can be adjusted more accurately. This is the same in the embodiment in which the control time Δtm is obtained by an arithmetic expression.

  In the above embodiment, when the drive motor 50 is accelerated from the stopped state to the phase detection speed Vi, the detection acceleration times tAs and tBs are detected, and the rise time difference (tA−tBs) is based on the time difference (tAs−tBs). However, the method for obtaining the rise time difference (tA-tB) is not limited to this. For example, the time difference (tA−tB) may be stored in the memory 58 corresponding to the “storage means” of the present invention, and the time difference (tA−tB) may be read from the memory 58 as necessary. Further, the time difference (tA-tB) may be obtained while the drive speed of each drive motor 50 is accelerated from the phase detection speed Vi to the normal speed Vdef, and the time difference thus obtained (tA-tB). ) May correct the rise time difference (tA−tB) in the memory 58. Hereinafter, another embodiment of the present invention will be described in detail with reference to FIG.

  FIG. 9 is a flowchart showing another embodiment of the image forming apparatus according to the present invention. The main difference between this embodiment and the previous embodiment (FIG. 5) is the method of deriving the rise time difference (tA−tB), and the other configurations are basically the same as those of the previous embodiment. Hereinafter, the phase adjustment processing in this embodiment will be described focusing on the differences. This phase adjustment process is also a “second phase adjustment process” in the embodiment described below.

  In this embodiment, the memory 58 stores a predetermined value of the rise time difference (tA-tB). As this default value, for example, it may be set at the factory shipment stage of the apparatus, or it may be stored the rise time difference (tA-tB) at the previous power-off time. When a drive command is given from the engine controller to the phase control unit 57 in response to a print command from an external device, the phase control unit 57 reads the rise time difference (tA−tB) from the memory 58 (step S201) and drives. The drive speeds of the motors 50Y, 50M, 50C, and 50K are accelerated in two stages and adjusted to the normal speed Vdef. As the first stage, the drive of all the drive motors 50Y, 50M, 50C, 50K is started simultaneously (step S202).

Then, the reference position of the control-side photosensitive drum 20 is detected while the first stage speed adjustment is completed and the drive motor 50 and the photosensitive drum 20 are driven in a steady state (step S203). Receiving this detection signal, the phase control unit 57 starts counting the output time difference Δts (step S204). This counting operation is performed until the reference position of the reference side photoconductor drum 20 is detected (steps S205 and S206), whereby an output time difference Δts indicating the phase difference between the reference side and control side photoconductor drum 20 is obtained.
Further, the phase control unit 57 has the following formula: Δtm = ((Vi / (Vdef−Vi)) * Δts) + ((Tdef * Ti) / (Ti−Tdef) * (α / 360)) + (tA−tB)
Based on the above, a control time Δtm corresponding to the output time difference (phase difference) Δts and the rise time difference (tA−tB) is calculated (step S207). When the reference side reference position (concave portion 55) is detected, the phase control unit 57 gives a control signal to the reference side motor rotation control unit 60 so as to drive the reference side drive motor 50 at the normal speed Vdef. Thus, the reference side drive motor 50 is driven at the normal speed Vdef while maintaining the drive speed of the control side drive motor 50 at the phase detection speed Vi (step S208). Simultaneously with this speed change, acquisition of time tA is started (step S209) and counting is started (step S210). That is, when the drive speed of the drive motor 50 reaches the normal speed Vdef due to this speed change, a ready signal is output from the drive motor 50. Based on this signal, the reference side drive motor 50 is normally output from the phase detection speed Vi. The phase control unit 57 obtains the time tA required to rise to the speed Vdef. When the count value reaches the count value corresponding to the control time Δtm and it is confirmed that the control time Δtm has elapsed (determined as YES in step S211), the phase of the drive speed is also detected for the drive motor 50 on the control side. The speed Vi is changed to the normal speed Vdef (step S212). That is, the phase control unit 57 gives a control signal to the control-side motor rotation control unit 60 so as to drive the control-side drive motor 50 at the normal speed Vdef. Thus, by providing the speed difference for the control time Δtm, the phase difference between the reference side and the control side photosensitive drum 20 becomes the set phase angle α, and the phase relationship adjustment is completed, and the image can be formed as it is. it can.

Further, the time tB is acquired simultaneously with the speed change of the control side drive motor 50 (step S213). That is, the time from the speed change to the output of the ready signal is measured, and this is acquired as the rise time tB of the control side drive motor 50. Then, the rise time difference (tA−tB) is calculated (step S214), and the rise time difference (tA−tB) stored in the memory 58 is corrected based on the value (step S215). As the correction content, a plurality of rise time differences (tA-tB) already obtained as described above may be simply averaged or corrected while performing weighting processing. For example, the value (tA−tB) [0] calculated this time including the last 10 times ((tA−tB) [0], (tA−tB) [1]... (TA−tB) [9]) is stored in the memory 58. Remember the following formula
(tA−tB) = {(tA−tB) [9] + (tA−tB) [8] +... (tA−tB) [0]} / 10
Accordingly, the rise time difference (tA-tB) may be corrected.

  As described above, according to this embodiment, the rise time difference (tA−tB) is obtained from the memory 58 and the output time difference Δts and the rise time difference (tA−tB) are calculated based on the output time difference Δts and the rise time difference (tA−tB). Since the timing at which the drive motor 50 is accelerated from the phase detection speed Vi to the normal speed Vdef is controlled, the phase relationship between the photosensitive drums 20 can be adjusted appropriately and with high accuracy. Further, the rise times tA and tB when the drive motor 50 is accelerated from the phase detection speed Vi to the normal speed Vdef are measured, and the rise time difference (tA−tB) in the memory 58 is corrected based on these. Therefore, even if the load on the drive motor 50 changes according to the operation status of the apparatus, the rise time difference (tA-tB) is corrected to a value corresponding to the change. As a result, the phase relationship of the photosensitive drum 20 can be adjusted with higher accuracy.

  FIG. 10 is a flowchart showing another embodiment of the image forming apparatus according to the present invention. In this embodiment, there are two types of phase adjustment processing, that is, “first phase adjustment processing” and “second phase adjustment processing”, and the phase adjustment processing is selectively executed according to the operating status of the apparatus. . The “first phase adjustment process” is the adjustment process shown in FIG. 5, and the “second phase adjustment process” is the adjustment process shown in FIG. The former is suitable for phase adjustment at power-on or immediately after replacement of the image forming station because phase adjustment is performed without using the storage contents of the memory 58, that is, without considering the previous operating state at all. On the other hand, in the latter case, the contents stored in the memory 58 are used, that is, the phase adjustment is performed with reference to the immediately preceding phase adjustment situation, so that the apparatus operates continuously or intermittently without changing the apparatus configuration. Suitable for phase adjustment in situations where Therefore, in this embodiment, the phase adjustment process is selected and executed in accordance with the operation status of the apparatus as follows.

  In this embodiment, when the apparatus is turned on (step S1), each part of the apparatus is caused to execute an initialization operation. In parallel with the initialization operation, a first phase adjustment process is executed (step S1). S100). Since the first phase adjustment process is executed during the initialization operation as described above, it is not necessary to provide a dedicated time for adjusting the phase relationship between the photosensitive drums 20, which is efficient. Processing becomes possible. When the first phase adjustment process is completed, the rise time difference (tA−tB) obtained during the phase adjustment process is stored in the memory 58 (step S2). Then, a print command is awaited (step S3).

  When a print command is given, it is determined whether or not the image forming stations Y, M, C, and K for each color have been replaced immediately before, and the first phase adjustment process (step S100) or the second phase is performed according to the determination result. The adjustment process (step S200) is selectively executed. As described above, the reason for selecting the phase adjustment processing according to the station replacement is that the rise time difference (tA−tB) stored in the memory 58 immediately after the station replacement is a value corresponding to the image forming station after the replacement. This is because it cannot be referred to as it is. Therefore, when “YES” is determined in step S4, the first phase adjustment processing is executed (step S100), and the rise time difference (tA−tB) obtained during the phase adjustment is compared with that in the memory 58. On the other hand, when it is determined to be “NO”, the second phase adjustment process is executed (step S200). Thus, when the phase adjustment is completed, the printing process is executed (step S6), and the process returns to step S3 to wait for the next printing command.

  As described above, according to the present embodiment, it is possible to perform phase adjustment processing appropriate to the operation status by switching control of the phase adjustment processing according to the operation status of the apparatus, and to improve the accuracy of phase adjustment. Can do.

  In the above embodiment, the phase detection speed Vi is set to half of the normal speed Vdef. However, the phase detection speed Vi is not limited to this, and can be set slower than the normal speed Vdef. In the above embodiment, the rise time difference (tA−tB) is used as the rise information, but it is arbitrary as long as the information reflects the rise characteristic of the drive motor. Therefore, for example, the acceleration time for detection and the acceleration of the drive motor 50 can be used as “rise information” of the present invention.

  In the above-described embodiment, the reference position of the photosensitive drum 20 is detected by detecting the concave portion 55 provided in the photosensitive gear 54 that is directly connected to the rotation shaft of the photosensitive drum 20, and the phase detection sensor 56 detects the phase. Although the signal is output, the phase detection method is not limited to this, and any phase detection method can be used as long as it can detect the reference position of the photosensitive drum 20. For example, a characteristic portion that rotates with the rotation of the drum may be provided in a part of the photosensitive drum 20, and a sensor may be disposed on the rotation locus of the characteristic portion.

  In the above-described embodiment, the photosensitive drums 20Y, 20M, 20C, and 20K are connected to the drive motors 50Y, 50M, 50C, and 50K, respectively, and the respective photosensitive drums 20 are rotationally driven. At least one or more photosensitive drums may be connected to each other to rotate the four color photosensitive drums. For example, the black photosensitive drum 20K may be driven by a black driving motor, while the yellow, magenta, and cyan photosensitive drums may be driven by a color driving motor.

  Further, in each of the above embodiments, the present invention is applied to an apparatus that forms a color image using toners of four colors of yellow, magenta, cyan, and black. The types and number of toner colors are described above. Without being limited thereto, each of the plurality of image carriers is connected to each of the plurality of drive motors while at least one image carrier such as a photosensitive drum is connected to rotate the plurality of image carriers. The present invention can be applied to all image forming apparatuses that form a color image by superimposing toner images formed on the surface.

1 is a diagram showing an embodiment of an image forming apparatus according to the present invention. FIG. 3 is a schematic diagram illustrating an arrangement relationship between an intermediate transfer belt and photosensitive drums of respective colors. FIG. 3 is a diagram illustrating a driving mechanism that rotationally drives a photosensitive drum. FIG. 3 is a block diagram showing an electrical configuration for adjusting the phase relationship between the photosensitive drums. 6 is a flowchart illustrating an operation for adjusting the phase relationship between the photosensitive drums. The timing chart which shows derivation | leading-out of a phase difference, and phase adjustment operation | movement. The figure which shows the control table which linked | related the acceleration time difference and the rise time difference. The figure which shows the control table which linked | related output time difference and control time. FIG. 6 is a diagram showing another embodiment of the image forming apparatus according to the present invention. FIG. 5 is a diagram showing another embodiment of the image forming apparatus according to the present invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus 20, 20Y, 20M, 20C, 20K ... Photosensitive drum (image carrier), 50, 50Y, 50M, 50C, 50K ... Drive motor, 56, 56Y, 56M, 56C, 56K ... Phase detection Sensor (phase detection means) 57: Phase control unit 58 ... Memory (storage means)

Claims (10)

At least one image carrier is connected to each of the plurality of drive motors, and the plurality of image carriers are rotated while driving the plurality of drive motors at a predetermined normal speed. In an image forming apparatus that forms a color image by superimposing toner images formed on each body,
A plurality of phase detection means provided corresponding to each of the plurality of image carriers, each detecting a reference position of the corresponding image carrier and outputting a detection signal;
Obtain rise information related to the rise characteristics of each drive motor, and calculate the output time difference of detection signals from the plurality of phase detection means while driving the plurality of drive motors at a phase detection speed slower than the normal speed. Then, based on the calculation result and the rise information, a timing for accelerating from the phase detection speed to the normal speed is controlled for each drive motor, and a phase adjustment process for adjusting a phase relationship among the plurality of image carriers is executed. An image forming apparatus comprising: a phase control unit that performs the same. The image forming apparatus according to claim 1, wherein each of the plurality of drive motors outputs a ready signal when reaching a predetermined speed or a predetermined range including the set speed.
The phase control means accelerates the drive motor from the stopped state to the phase detection speed by setting the phase detection speed as the set speed for each of the plurality of drive motors, and outputs a ready signal from the drive motor. An image forming apparatus that obtains the rising information based on the acceleration time for detection until is output.   The phase control means is configured to determine a rise time between the plurality of drive motors generated when accelerating from the phase detection speed to the normal speed according to a difference in the detection acceleration time between the plurality of drive motors. The image forming apparatus according to claim 2, wherein a difference is obtained as the rising information, and acceleration timing is controlled among the plurality of drive motors based on the output time difference and the rising information.   The image forming apparatus according to claim 2, wherein the phase control unit calculates the output time difference after the ready signal is output from all drive motors. Further comprising storage means for storing the rising information,
The phase control means reads the rising information from the storage means and controls the timing for accelerating from the phase detection speed to the normal speed for each drive motor based on the rising information and the output time difference. Image forming apparatus. The image forming apparatus according to claim 5, wherein each of the plurality of drive motors outputs a ready signal when reaching a predetermined speed or a predetermined range including the set speed.
The phase control means accelerates the drive motor from the phase detection speed to the normal speed by setting the normal speed as the set speed for each of the plurality of drive motors, and a ready signal from the drive motor. An image forming apparatus that obtains a rising time until the image is output and corrects the rising information stored in the storage unit based on the rising time. The image forming apparatus according to claim 1, wherein each of the plurality of drive motors outputs a ready signal when reaching a predetermined speed or a predetermined range including the set speed.
Further comprising storage means for storing the rising information,
The phase control unit includes an image forming apparatus that selectively executes either one of the following first phase adjustment process and the following second phase adjustment process as the phase adjustment process.
In the first phase adjustment process, the drive motor is accelerated from a stopped state to the phase detection speed by setting the phase detection speed as the set speed for each of the plurality of drive motors, and from the drive motor After obtaining the rising information based on the acceleration time for detection until the ready signal is output, calculating the output time difference of the detection signals from the plurality of phase detection means while driving at the phase detection speed, the calculation result And a process of controlling the timing of acceleration from the phase detection speed to the normal speed based on the rising information for each drive motor to adjust the phase relationship between the plurality of image carriers,
The second phase adjustment process reads the rising information from the storage unit, calculates an output time difference of detection signals from the plurality of phase detection units while driving at the phase detection speed, and calculates the calculation result and the This is processing for adjusting the phase relationship between the plurality of image carriers by controlling the timing of acceleration from the phase detection speed to the normal speed for each drive motor based on the rise information. The image forming apparatus according to claim 7, wherein a predetermined initialization operation is performed immediately after power is turned on to the apparatus.
The phase control unit is an image forming apparatus that executes the first phase adjustment process in parallel with the initialization operation.   The phase control unit accelerates the drive motor from the phase detection speed to the normal speed by setting the normal speed as the set speed during the first phase adjustment process, and a ready signal is output from the drive motor. The image forming apparatus according to claim 8, wherein a rising time until output is obtained, and the rising information stored in the storage unit is rewritten based on the rising time. At least one image carrier is connected to each of the plurality of drive motors, and the plurality of image carriers are rotated while driving the plurality of drive motors at a predetermined normal speed. In an image forming apparatus for forming a color image by superimposing toner images formed on each of the bodies, a phase adjustment method for adjusting a phase relationship between the plurality of image carriers,
Obtaining rise information related to the rise characteristics of each drive motor;
A step of detecting a reference position of the image carrier and outputting a detection signal for each of the plurality of image carriers while driving the plurality of drive motors at a phase detection speed slower than the normal speed;
Obtaining an output time difference of detection signals between the plurality of image carriers;
Adjusting the phase relationship between the plurality of image carriers by controlling the timing of acceleration from the phase detection speed to the normal speed for each drive motor based on the output time difference and the rising information. A phase adjustment method in an image forming apparatus.

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