JP2010066448A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printer which can appropriately switch control of rotation of a photoreceptor drum synchronizing with rotation of a transfer belt. <P>SOLUTION: An image forming apparatus includes a synchronism switching means 612 which makes a DC brushless motor control means 604 synchronize the rotation of a DC brushless motor 4041a with rotation of the stepping motor 402a when a motor synchronism discrimination means 611 discriminates that rotational speed of the DC brushless motor 4041a is increased or decreased together with rotational speed of the stepping motor 402a, and which makes the DC brushless motor control means 604 control the rotation of the DC brushless motor 4041a on the basis of a control signal fit to the characteristics of a rotational speed curve when the motor synchronism discrimination means 611 discriminates that the rotational speed of the DC brushless motor 4041a is not increased or decreased together with the rotational speed of the stepping motor 402a. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus capable of appropriately switching control of rotation of a photosensitive drum synchronized with rotation of a transfer belt.

  In recent years, image forming apparatuses are provided with a plurality of functions that can be provided, and are becoming multifunctional. The functions include a facsimile transmission / reception function, a scan function, a print function, a post-processing function represented by a staple function and a punch function, a power saving function, and the like in addition to a copy function, and various types. Further, along with the diversification of the above functions, an automatic document feeder (ADF) capable of automatically and sequentially feeding documents to be provided with functions has been installed.

  Such an image forming apparatus is commercially available as, for example, a copying machine, a printer, a facsimile machine, or a multifunction machine. Among the image forming systems, for example, a toner image on an image carrier (photosensitive drum) is intermediately transferred. A system (intermediate transfer image forming apparatus) that transfers to a recording medium (sheet) through a body is employed.

  In the intermediate transfer type image forming apparatus, the image carrier is rotated by a carrier motor, and the intermediate transfer member and the record carrier are rotated by a drive motor. Since the image carrier and the intermediate transfer member rotate while being in contact with each other, if the surface linear velocity (surface linear velocity) of the image carrier and the intermediate transfer member is different, the surface of the image carrier and the surface of the intermediate transfer member Rub against each other and wear, and the wear is promoted. Therefore, conventionally, a stepping motor is used as a carrier motor for rotating the image carrier and a drive motor for rotating the intermediate transfer member, respectively, and the number of input pulses is controlled to control the surface of the image carrier and the intermediate transfer member. The linear velocity of the surface of the was matched.

  However, the stepping motor consumes a large amount of power and generates a large operating noise. Therefore, a carrier motor that rotates the image carrier and a drive motor that rotates the intermediate transfer member or the recording medium carrier are controlled by a drive pulse (command clock signal) that is a pulse that rotates the motor and a feedback signal. If a clock control motor (hereinafter referred to as an image carrier motor), for example, a DC brushless motor, is used, occurrence of the above-described problems can be suppressed. Therefore, DC brushless motors have begun to be adopted.

  However, with a DC brushless motor, it is difficult to correctly control the rotation speed of the motor at the time of startup and shutdown. Therefore, when a DC brushless motor is used as the carrier motor and the drive motor, the DC brushless motor is started and started up. At the time of lowering, there is a large difference in the linear velocity of the surface between the image carrier and the intermediate transfer member, or between the image carrier and the recording medium carrier, and this causes significant friction and wear between them, shortening the service life. It is done.

  Furthermore, if there is a large difference between the surface linear velocities of the image carrier and the intermediate transfer member, the image carrier and the intermediate transfer member are rubbed, causing blurring and horizontal streaks in the image, and the image quality is deteriorated. . The same applies to the case where a DC brushless motor is used for the drive motor that drives the recording medium carrier and the carrier motor that drives the image carrier. For these reasons, conventionally, a stepping motor is usually used as the carrier motor and the drive motor. However, this has unavoidably suffered from the disadvantage that the power consumption and the operating noise increase.

  In order to solve the above problem, Japanese Patent Application Laid-Open No. 2005-189794 (Patent Document 1) transfers at least one image carrier on which a toner image is formed and a toner image formed on the image carrier. An intermediate transfer member, a carrier motor for rotating the image carrier, and a drive motor for rotating the intermediate transfer member. The toner image transferred to the intermediate transfer member is transferred to a recording medium for recording. In the image forming apparatus for obtaining an image, at least one of the carrier motor and the drive motor is composed of a clock control motor controlled by a command clock signal and a feedback signal. Disclosed is an image forming apparatus characterized by controlling the rotation speed of the clock control motor in accordance with a predetermined speed curve at least at one time of lowering It has been.

With the above configuration, since the clock control motor controlled by the command clock signal and the feedback signal is used as at least one of the carrier motor and the drive motor, the power consumption can be reduced, and the operation noise can be generated. It can be suppressed.
JP 2005-189794 A

  However, in the technique described in Patent Document 1, the startup time, which is the time from the start of acceleration (deceleration) to the stabilization of the rotation speed, is extended to stabilize the operation, and the startup time may be increased. In addition, there is a possibility that sufficient constant speed characteristics cannot be obtained for providing a stepped speed clock (a driving pulse having a stepped frequency) for reducing the amount of memory used. Further, depending on the use conditions, it is considered that the drum speed overshoot (undershoot) is greatly generated at the steady speed, and there is a problem that the rotation control of the motor is not stable at the time of starting and falling.

  Further, in the case of an image forming apparatus having a plurality of tandem image forming units capable of color printing, for example, when the mode is switched from color printing to monochrome printing, the drive motor is rotated (intermediate transfer member is rotated). While maintaining, it is necessary to stop the rotation of the carrier motor of the image forming unit corresponding to color printing (rotation of the photosensitive drum corresponding to color printing). In that case, there is a desire to appropriately execute the rotation control of the clock control motor without causing the surface of the image carrier and the surface of the intermediate transfer member to rub and wear each other. The above-mentioned demand is, for example, an image forming apparatus that employs a three-color release mechanism that stops rotation of a photosensitive drum such as yellow corresponding to color printing while maintaining the rotation of a black photosensitive drum necessary for monochrome printing. Is especially important.

  Accordingly, the present invention has been made to solve the above-described problem, and has improved the above-mentioned problem by changing the fundamental configuration, and appropriately controls the rotation of the photosensitive drum synchronized with the rotation of the transfer belt. An object is to provide a switchable image forming apparatus.

  In order to solve the above-described problems and achieve the object, an image forming apparatus according to the present invention includes an intermediate transfer member that controls rotation of an intermediate transfer member motor based on a control signal that is a pulse signal that controls rotation of the motor. An image for controlling the acceleration / deceleration of the rotation of the image carrier motor in accordance with the acceleration / deceleration of the rotation of the intermediate transfer motor based on the motor control means and the control signal of the image carrier motor synchronized with the control signal of the intermediate transfer motor. An image forming apparatus including a carrier motor control unit is assumed.

  The image forming apparatus, when accelerating / decelerating the rotation speed of the image carrier motor, motor synchronization determination means for determining whether the rotation speed of the image carrier motor and the rotation speed of the intermediate transfer body motor are increased or decreased; When the motor synchronization determining means determines that the rotation speed of the image carrier motor is accelerated and decelerated together with the rotation speed of the intermediate transfer body motor, the image carrier motor control means sends the rotation of the image carrier motor to the rotation of the intermediate transfer body motor. Synchronization switching means for synchronizing.

  The control signal that is a pulse signal is a signal for controlling the rotation of the motor, and the shape of the pulse does not have to be strictly a square wave (rectangular wave), and if the object of the present invention is achieved, It may be a sawtooth wave, a triangular wave, or a pulse having a shape related thereto. The control signal is completely different from the drive pulse described later.

  Any image carrier can be used as long as it can form a toner image. For example, a photosensitive drum having a cylindrical shape or a drum having a related shape is applicable.

  The image carrier motor may be a motor that transmits (rotates) rotation based on, for example, a control signal for controlling rotation of the motor based on feedback control and a pulse fed back from rotation of the image carrier motor. Any motor may be used. The motor corresponds to, for example, a motor that employs a pulse width modulation (hereinafter referred to as PWM) control method. For example, a DC brushless motor corresponds to the motor that rotates by PWM control, but other motors that employ a control method related to the PWM control method may be used.

  The pulse fed back from the rotation of the image carrier motor is a feedback signal (encoder pulse signal, feedback pulse) generated by the rotation of the motor, and is a periodic signal corresponding to the rotational speed of the motor. This feedback pulse is output by, for example, a speed detection sensor including a rotary encoder (encoder). The rotary encoder has a function to convert the number of rotations of the motor (analog signal) into the number of pulses (digital signal). There are photoelectric conversion methods such as photoelectric, brush, and magnetic types. But it can be adopted. The feedback pulse may be, for example, a function generator signal (Frequency Generator signal, FG signal, Frequency) that is a signal oscillated by a function generator connected to a DC brushless motor.

  The intermediate transfer member may be any member as long as the formed toner image is transferred to the image carrier, and may be, for example, an endless transfer belt or a belt having a related shape.

  The intermediate transfer member motor may be any motor as long as it is a motor that transmits (rotates) rotation based on a control signal. The motor corresponds to, for example, a stepping motor that is a motor that can rotate at a predetermined angle when a control signal having a predetermined frequency is input.

  Accelerating the rotation speed of the motor corresponds to starting up (starting up) the motor, and reducing the rotation speed of the motor corresponds to lowering (stopping) the motor.

  A method for controlling the acceleration / deceleration of the rotation of the image carrier motor according to the acceleration / deceleration of the rotation of the intermediate transfer body motor based on the control signal of the image carrier motor synchronized with the control signal of the intermediate transfer body motor is, for example, This method can be adopted.

  For example, the number of pulses, frequency, speed, acceleration, phase, etc. of the control signal for controlling the rotation of the intermediate transfer body motor are calculated, and the calculation result is converted into a control signal for the image carrier motor, and the conversion is performed. There is a method of rotating the image carrier motor based on the control signal. For example, the control signal for controlling the rotation of the intermediate transfer body motor is compared with the internal timer pulse to calculate the count number of the control signal, the count number is multiplied by a predetermined speed coefficient, and the result of further multiplication is imaged. There is a method of converting the control signal for the carrier motor and controlling the rotation of the image carrier motor based on the control signal.

  As the internal timer pulse (internal timer clock, internal timer clock signal), for example, a time capture circuit (time capture means) that generates an internal timer pulse with a stable pulse period can be used. The image carrier motor control means can calculate the count number of the control signal based on the internal timer pulse and the control signal for controlling the rotation of the intermediate transfer body motor.

  Since the speed coefficient only needs to indicate the ratio of the rotational speed of the image carrier motor to the rotational speed of the intermediate transfer body motor at the time of steady rotation, for example, the reference rotational speed when calculating the speed coefficient, You may change into parameters, such as a frequency of a drive pulse, and surface linear velocity.

  When accelerating / decelerating the rotational speed of the image carrier motor, a method for determining whether to accelerate / decelerate the rotational speed of the image carrier motor together with the rotational speed of the intermediate transfer body motor is, for example, to the intermediate transfer body motor control means. There is a method of detecting and discriminating an input control signal and a control signal input to the image carrier motor control means. It is possible to determine whether the control signal is an acceleration signal or a deceleration signal according to the pulse width and frequency.

  Further, as other methods, for example, a print mode indicating the driving state of the image forming apparatus, information indicating whether the rotational speed of the image carrier motor is accelerated or decelerated, input by the user or the image forming apparatus, Storage means is provided for storing information indicating whether to accelerate or decelerate the rotation speed of the transfer body motor. Based on the storage means, it is possible to determine whether or not to accelerate and decelerate the rotational speed of the image carrier motor together with the rotational speed of the intermediate transfer body motor.

  Examples of the print mode include a sleep state indicating a power saving state, a color print state indicating a color print state, a monochrome print state indicating a monochrome print state, and the like.

  The information indicating whether the rotational speed of the image carrier motor (intermediate transfer body motor) is accelerated or decelerated may be any information such as characters, figures, symbols, etc. For example, when accelerating, “acceleration” And “decelerate” can be stored when decelerating.

  When the motor synchronization determination means determines that the rotation speed of the image carrier motor is accelerated and decelerated together with the rotation speed of the intermediate transfer body motor, the synchronization switching means causes the image carrier motor control means to rotate the image of the intermediate transfer body motor. Any method may be used to synchronize the rotation of the carrier motor, but the following method can be employed.

  For example, information indicating that the rotation speed of the image carrier motor is accelerated and decelerated together with the rotation speed of the intermediate transfer body motor is associated with information indicating that the rotation of the image carrier motor is synchronized with the rotation of the intermediate transfer body motor. Prepare a storage means for storing. When the rotational speed of the image carrier motor is accelerated and decelerated along with the rotational speed of the intermediate transfer body motor based on the storage means, the synchronization switching means sends an image to the image carrier motor control means to rotate the intermediate transfer body motor. It is possible to synchronize the rotation of the carrier motor.

  Furthermore, a rotation speed curve storage means for storing a rotation speed curve indicating a change over time in the characteristic of the control signal when accelerating / decelerating the image carrier motor alone is provided, and the motor synchronization determining means is configured to rotate the image carrier motor. If it is determined that the speed is not accelerated / decelerated together with the rotational speed of the intermediate transfer body motor, the synchronization switching means sends the image carrier motor control means to the image carrier motor based on a control signal that matches the characteristics of the rotational speed curve. It can be configured to control the rotation.

  When accelerating / decelerating the image carrier motor alone, for example, when switching from color printing to monochrome printing, the rotation of the image carrier motor for color printing is stopped (three-color release mechanism), or from monochrome printing to color printing. This corresponds to the case where the rotation of the image carrier motor for color printing is stopped when switching to printing (three-color drive mechanism).

  The characteristics of the control signal correspond to the characteristics of the pulse signal, such as frequency, speed, acceleration, phase, and the like. The characteristics of these pulse signals correspond to the rotation speed of the image carrier motor. The rotational speed curve may be a curve that shows the change over time in the characteristics of the control signal. For example, it may be a curve corresponding to a result measured in advance by the user, a curve corresponding to an experimental result, or a predetermined approximate expression. .

  The control signal in accordance with the characteristics of the rotational speed curve has the characteristics (frequency, speed, acceleration, phase, etc.) of the pulse signal corresponding to the shape of the rotational speed curve (inclination, first derivative, second derivative, etc.). It means a control signal. For example, the frequency of the control signal is adopted as a reference.

  When the motor synchronization determining means determines that the rotation speed of the image carrier motor is not accelerated / decelerated together with the rotation speed of the intermediate transfer body motor, the synchronization switching means sends the image carrier motor control means the characteristics of the rotation speed curve. Any method may be used as a method for controlling the rotation of the image carrier motor based on the control signal matched to the above, but the following method can be adopted.

  For example, storage means is provided for storing information indicating that the rotation speed of the image carrier motor is not accelerated / decelerated together with the rotation speed of the intermediate transfer body motor and information indicating that the rotation speed curve is referred to. Based on the storage means, when the rotational speed of the image carrier motor is not accelerated / decelerated together with the rotational speed of the intermediate transfer body motor, the synchronous switching means causes the image carrier motor control means to change the characteristic of the rotational speed curve. Based on the combined control signal, the rotation of the image carrier motor can be controlled.

  According to the image forming apparatus of the present invention, when accelerating / decelerating the rotation speed of the image carrier motor, the motor synchronization for determining whether the rotation speed of the image carrier motor is accelerated or decelerated together with the rotation speed of the intermediate transfer body motor. When the determining means and the motor synchronization determining means determine that the rotational speed of the image carrier motor is accelerated / decelerated together with the rotational speed of the intermediate transfer body motor, the image carrier motor control means is instructed to rotate the intermediate transfer body motor. And a synchronous switching means for synchronizing the rotation of the body motor.

  As a result, the rotational speed of the image carrier motor is accelerated together with the rotational speed of the intermediate transfer body motor, where a speed difference between the surface linear speed of the intermediate transfer body and the surface linear speed of the image carrier is likely to occur. Alternatively, when decelerating, the rotational speed of the image carrier motor is accelerated or decelerated in synchronization with the rotational speed of the intermediate transfer body motor. A difference in speed is unlikely to occur, and scratches and the like that occur between the intermediate transfer member and the image carrier can be prevented.

  Further, when the motor synchronization determination means determines that the rotation speed of the image carrier motor is not accelerated / decelerated together with the rotation speed of the intermediate transfer body motor, the synchronization switching means sends the rotation speed curve to the image carrier motor control means. The rotation of the image carrier motor can be controlled based on a control signal that matches the above characteristics.

  Thereby, when accelerating or decelerating the rotation speed of the image carrier motor independently of the intermediate transfer member motor, the condition that the surface of the image carrier for color printing and the surface of the intermediate transfer member do not rub or wear each other, that is, The rotational speed of the image carrier motor can be independently accelerated or decelerated in accordance with the acceleration fluctuation or deceleration fluctuation of the control signal characteristic (rotational speed) measured in advance. Therefore, for example, from color printing to monochrome printing, from monochrome printing to color printing, while appropriately suppressing the speed difference generated between the surface linear velocity of the image carrier for color printing and the surface linear velocity of the intermediate transfer member. Mode switching can be performed smoothly. As a result, if necessary, the rotation control of the image carrier motor is flexibly changed, and the rotation of the image carrier motor can be performed without causing the intermediate transfer member surface and the image carrier surface to rub and wear each other. Appropriate control, that is, stable start / stop characteristics of the image carrier motor can be obtained.

  Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments thereof.

<Image forming apparatus>
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. For convenience of explanation, the position and size of the members are drawn with emphasis as appropriate in the drawings. In the following embodiments, a printer will be described as an example of the image forming apparatus of the present invention, but the present invention is not limited to this. In other words, the image forming apparatus of the present invention only needs to have an image forming unit, such as a copying machine or a so-called multi function peripheral (MFP) having a function as a facsimile machine, a copying machine having only a copying function, or the like. There may be.

  FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present embodiment.

  FIG. 1 shows an example of an image forming apparatus to which the present invention is applied, using a printer 100 as an example, and includes tandem image forming units FY, FM, FC, and FK for forming a color image. Yes. The image forming units FY, FM, FC, and FK are in contact with the transfer belt B1, the cleaning unit B2 for cleaning the surface of the transfer belt B1, and the transfer belt B1 along the moving direction of the transfer belt B1. The yellow, cyan, magenta, and black photosensitive drums 10Y, 10M, 10C, and 10K are provided.

  The yellow photosensitive drum 10Y includes a developing device HY for developing the electrostatic latent image formed on the peripheral surface of the photosensitive drum 10Y with toner, and a peripheral surface for charging the peripheral surface of the photosensitive drum 10Y. A charger 11Y is provided next to the charger 11Y. Similarly, chargers 11M and 11C for charging the peripheral surfaces of the developing devices HM, HC, and HK and the photosensitive drums 10M to 10K with respect to the photosensitive drums 10M, 10C, and 10K for magenta, cyan, and black. , 11K are provided. Further, in order to transfer the toner images carried on the peripheral surfaces of the photosensitive drums 10Y to 10K to the transfer belt B1, the transfer rollers B1 are provided on the peripheral surfaces of the photosensitive drums 10Y to 10K with the transfer belt B1 therebetween. 20Y, 20M, 20C, and 20K are arranged.

  The rotation of the motor that transmits the rotation to each photosensitive drum is controlled by feedback control based on a control signal (clock signal) for controlling the rotation of the motor and a feedback pulse generated by the rotation of the motor. For example, a DC brushless motor (DC brushless motor) is employed as the image carrier motor.

  The transfer belt B <b> 1 is stretched between the driving roller 21 and the driven roller 22, and is given a predetermined tension by the tension roller 23. The transfer belt B1 moves in the direction of the arrow. Therefore, the four photosensitive drums 10Y to 10K rotate counterclockwise in FIG.

  The motor that transmits the rotation to the transfer belt B1 includes an intermediate transfer body motor whose rotation is controlled based on a control signal for controlling the rotation of the motor, and the intermediate transfer body motor has a predetermined frequency, for example. When the control signal is input, a stepping motor that is a motor that can rotate at a predetermined angle is employed. Note that the stepping motor changes the rotation angle by adjusting the frequency of the control signal, and as a result, the rotation speed (rotation speed) is changed.

  As shown in FIG. 2, the peripheral surfaces of the photosensitive drums 10Y to 10K are charged to predetermined potentials by chargers 11Y, 11M, 11C, and 11K, respectively, and originals are exposed by exposure devices 12Y, 12M, 12C, and 12K. An image corresponding to the image is written, thereby forming an electrostatic latent image. The electrostatic latent images are developed into different color toner images by the developing devices HY, HM, HC, and HK, respectively. The toner images of the respective colors are transferred onto the transfer belt B1 by the transfer rollers 20Y to 20K, and the toner images are superimposed on the transfer belt B1.

  The toner remaining on the surface of the photosensitive drums 10Y to 10K after the transfer is performed as described above is wiped off by the blade 35, and is output to a predetermined container by the discharge roller 31, and then the photosensitive drums 10Y to 10K. The surface is neutralized by the static eliminator 13.

  On the other hand, the paper P is separated from the cassette 2 capable of storing a plurality of paper P by the transport unit 6 with a predetermined interval between the paper P toward the image forming units FY, FM, FC, and FK. Be transported. The toner image transferred to the transfer belt B1 is transferred by the secondary transfer unit 3 to the paper P conveyed to the image forming units FY, FM, FC, and FK.

  The control unit 30 includes image forming units FY and FM including the photosensitive drums 10Y to 10K, the developing devices HY, HM, HC, and HK, the chargers 11Y, 11M, 11C, and 11K, and the transfer rollers 20Y to 20K. , Controls the operation control of each image forming member in FC and FK. Also, the operation control of the transport mechanism including the transport roller B1 is performed.

  Next, the configuration of the developing device HY will be described. The configurations of the developing devices HY, HM, HC, and HB for the respective colors are the same.

  The developing device HY includes a developing container 40 and a developing roller 40a, and the developing container 40 stores therein a powdery developer composed of yellow toner particles and a carrier.

  The developing roller 40a is in contact with the photosensitive drum 10, and a toner corresponding to an image instructed to be formed from the upper apparatus by the potential difference between the electrostatic latent image on the surface of the photosensitive drum 10 and the developing bias applied to the developing roller 40a. An image is formed on the surface of the photosensitive drum 10 (development operation).

  Under such a configuration, the image forming apparatus 1 that has received an instruction for image formation from a host device such as a personal computer (PC) or the like forms toner images of each color corresponding to the received image data in the image forming units FY, FM. , FC, and FB. The toner image formed in each image forming unit is transferred to the intermediate transfer belt B1, and is superimposed on the intermediate transfer belt B1 to form a color toner image.

  In synchronism with the formation of the color toner image, the paper stored in the paper storage unit 2 is taken out from the paper storage unit 2 one by one by a paper feeding device (not shown) and transported on the paper transport unit 6. Then, the sheet is fed to the secondary transfer unit 3 in synchronization with the primary transfer to the intermediate transfer belt B1, and the color toner image on the intermediate transfer belt B1 is secondarily transferred to the sheet by the secondary transfer unit 3. The sheet on which the color toner image has been transferred is further conveyed to the fixing unit 4 where the color toner image is fixed on the sheet by heat and pressure. Further, the paper is discharged by a paper discharge device 5 to a paper discharge tray section 7 provided on the outer periphery of the image forming apparatus 1. The toner remaining on the intermediate transfer belt B1 after the secondary transfer is removed from the intermediate transfer belt B1 by the cleaning unit B2 of the intermediate transfer belt.

  FIG. 3 is a schematic configuration diagram relating to control of the printer 100 according to the present embodiment.

  The printer 100 includes a CPU (CENTRAL Processing Unit) 301, a RAM (Random Access Memory) 302, a ROM (Read Only Memory) 303, an HDD (Hard Disk Drive) 304, and a driver 305 corresponding to each driving unit in the above printing. 306 is connected. The CPU 301 uses, for example, the RAM 202 as a work area, executes a program stored in the ROM 303, the HDD 304, or the like, and exchanges data and commands with the driver 305 based on the execution result, as shown in FIG. The operation of each driving unit is controlled.

  The above is a description of the printer 100 in general.

  Here, the printer 100 according to the embodiment of the present invention does not employ a conventionally known mechanical configuration of a DC brushless motor, a control circuit, a configuration equivalent to a CPU, and the like.

  Conventionally known DC brushless motor control circuits include, for example, a phase comparator, a filter control processing circuit, a PWM circuit, and a DC brushless motor driver. The phase comparator compares a command clock signal (control signal) input from the printer engine with a feedback signal input from the encoder of the DC brushless motor to calculate a phase difference or the like. The filter control processing circuit performs a filtering process, a predetermined calculation process, and the like on the phase difference input from the phase comparator, and inputs a predetermined control value to the PWM circuit. The PWM circuit generates a PWM signal that is a speed command signal based on the input control value, and inputs the PWM signal to the DC brushless motor driver. Then, the DC brushless motor driver inputs a drive pulse (drive signal) corresponding to the PWM signal to the DC brushless motor, and controls the rotation of the DC brushless motor. Conventionally, the rotation of the DC brushless motor is feedback-controlled with the above-described configuration and procedure.

  The machine configuration, control configuration, control procedure, and the like in the printer 100 according to the embodiment of the present invention will be described in detail below.

<Embodiment of the present invention>
<< Machine configuration of printer >>
FIG. 4 shows a mechanical configuration of the printer 100 according to the embodiment of the present invention.

  The printer 100 includes an engine 401, a stepping motor driver 402, a stepping motor 402a, a DC brushless motor CPU 403 that controls the rotation of each DC brushless motor, and the color of each photosensitive drum (yellow, cyan, magenta, black). DC brushless motor drivers 4041, 4042, 4043, and 4044 (also referred to as power drivers) and DC brushless motors 4041a, 4042a, 4043a, and 4044a corresponding to the respective colors.

  The engine 401 controls the printer 100 such as driving, stopping, and image formation, and inputs a control signal A (command signal, instruction clock signal) related to the rotation of the stepping motor 402 a to the stepping motor driver 402. The control signal A corresponds to, for example, an instruction clock signal that is a pulse signal for controlling the rotation of the stepping motor 402a. Further, the engine 401 is configured to input the control signal A to the stepping motor driver 402 and simultaneously to the DC brushless motor CPU 403 (described later).

  The engine 401 is a control signal different from the control signal A, and inputs a control signal B relating to the rotation start and rotation stop of each DC brushless motor 4041a, 4042a, 4043a, 4044a to the DC brushless motor CPU 403.

  The stepping motor driver 402 inputs a drive pulse to the stepping motor 402a based on the control signal A input from the engine 401. The stepping motor 402a transmits rotation to the driving roller 21 (not shown).

  In addition to the control signal B from the engine 401, the DC brushless motor CPU 403 receives a control signal A input from the engine 402 to the stepping motor driver 402. Based on the control signal B and the control signal A, the DC brushless motor CPU 403 inputs a predetermined speed command signal to the DC brushless motor drivers 4041, 4042, 4043, and 4044 (described later).

  The DC brushless motor drivers 4041, 4042, 4043, and 4044 input drive pulses to the DC brushless motors 4041a, 4042a, 4043a, and 4044a based on a speed command signal input from the CPU 403 for DC brushless motor. Each DC brushless motor 4041a, 4042a, 4043a, 4044a transmits rotation to the respective photosensitive drums 10Y, 10C, 10Y, 10K (not shown) (described later).

<< Printer control configuration >>
Next, the DC brushless motor CPU 403 which is a control configuration (control circuit) of the DC brushless motor will be described in detail.

  FIG. 5 shows the configuration of the CPU 403 for DC brushless motor according to the embodiment of the present invention. As shown in FIG. 5, in the printer 100 according to the embodiment of the present invention, a mechanism that automatically operates based on a CPU or the like so as to follow a target value using a feedback pulse or the like generated from an encoder (described later) as a control amount. The servo control mechanism is adopted.

  The DC brushless motor CPU 403, which will be described later, is described as controlling the photosensitive drum 10Y corresponding to yellow and the DC brushless motor 4041a that transmits the rotation to the photosensitive drum 10Y, but magenta, cyan, black The same applies to the photosensitive drums 10C, 10Y, and 10K and the DC brushless motors 4042a, 4043a, and 4044a corresponding to the above.

  The DC brushless motor CPU 403 mainly includes a first time capture circuit 501, a speed coefficient circuit 502, a target speed setting circuit 503, a second time capture circuit 504, a control arithmetic circuit 505, and a PWM circuit 506. It consists of.

  The first time capture circuit 501 is configured such that a control signal equivalent to the control signal A input from the engine 401 to the stepping motor driver 402 is input simultaneously. The first time capture circuit 501 compares the control signal A input from the engine 401 with the internal timer pulse signal, and counts the number of internal timer pulse signals included in one pulse width of the control signal A ( Will be described later). The counted number is input to the speed coefficient circuit 502.

  The speed coefficient circuit 502 multiplies the input count number by a speed coefficient stored in advance in the memory unit of the speed coefficient circuit 502 to calculate a target speed that is a target value. By the multiplication, the count number is converted from a value corresponding to the stepping motor 402a to a value corresponding to the DC brushless motor 4041a. The target speed is calculated and updated every time the count number is input to the speed coefficient circuit 502 (every time the count number is counted). The speed coefficient circuit 502 inputs the calculated target speed to the target speed setting circuit 503.

  The target speed setting circuit 503 inputs the target speed input from the speed coefficient circuit 502 to the control arithmetic circuit 505, or sets the target speed to a steady speed input from the engine 401 in advance when the printer 100 is started or stopped. Switch to stop speed (described later).

  The second time capture circuit 504 is configured to receive an encoder pulse signal (motor rotation speed signal, feedback signal) generated from an encoder 507 provided in the DC brushless motor 4041a. The second time capture circuit 504 compares the encoder pulse signal input from the encoder 507 with the internal timer pulse signal, and counts the number of internal timer pulse signals included in one pulse width of the encoder pulse signal (described later). To do). The counted number is calculated as a value (current rotation speed) corresponding to the current rotation speed of the DC brushless motor 4041a.

  As the target speed and the current rotational speed, a speed difference obtained by dividing the current rotational speed from the target speed is calculated, and the speed difference is input to the control arithmetic circuit 505.

  The control arithmetic circuit 505 employs PID control, which is one of feedback control methods, and calculates a control value from the input speed difference based on a control parameter used for PID control. The control arithmetic circuit 505 inputs the calculated control value to the PWM circuit 506.

  The PWM circuit 506 generates a PWM signal based on the input control value, and inputs the PWM signal to the DC brushless motor driver 4041 as a speed command signal.

  The rotation of the DC brushless motor 4041a is controlled by executing a program or the like stored in a predetermined memory. The above circuits, drivers and the like operate as respective means described later.

<< Printer control procedure >>
Next, a procedure in which the image forming apparatus of the present invention switches the rotation control of the photosensitive drum according to the print mode will be described with reference to FIGS. FIG. 6 is a functional block diagram of the printer according to the present invention. FIG. 7 is a flowchart for illustrating the execution procedure of the present invention. Details of each part not directly related to the present invention are omitted.

<< About startup procedure >>
When the printer 100 is in a sleep state in which power consumption during standby is suppressed, the user uses a terminal connected to the printer 100 to issue an instruction (color printed matter) to the printer 100 regarding color printing. When the output instruction is input, the communication unit 601 of the printer 100 receives the command via the network connected to the terminal.

  The communication unit 601 transmits the command to the image forming unit 602, and the image forming unit 602 cancels the sleep state of the printer 100 and shifts to a state where image formation is possible. The state in which image formation is possible is a state in which the surface linear velocity of each photosensitive drum and the surface linear velocity of the transfer belt coincide with each other and are rotated with each other, and the DC brushless motor 4041a and the stepping motor 402a. Are rotated at a predetermined rotation speed (rotation speed) (hereinafter referred to as a rotation speed at which image formation is possible). The surface linear velocity (surface linear velocity) means a rotational velocity in a tangential direction with respect to a point on the surface of the rotating body in the rotating body.

  Hereinafter, the rotation of the photosensitive drum 10Y corresponding to yellow and the DC brushless motor 4041a that transmits the rotation to the photosensitive drum 10Y will be described. However, the photosensitive drum corresponding to magenta, cyan, and black, and the DC brushless motor The same applies to rotation.

  In the sleep state, since the rotation of both the stepping motor 402a and the DC brushless motor 4041a is stopped (a state where the rotation speed is zero), the image forming unit 602 sends the rotation of the stepping motor 402a to the stepping motor control unit 603. A signal for accelerating the speed (acceleration signal A) (corresponding to the acceleration instruction control signal A in FIG. 4) is transmitted (FIG. 7: S101). The acceleration signal A is an instruction clock signal (clock signal, clock) having a predetermined frequency and pulse width.

  When receiving the acceleration signal A, the stepping motor control means 603 starts the rotation of the stepping motor 402a (FIG. 7: S102).

  Specifically, the stepping motor control unit 603 inputs a drive pulse for accelerating the rotation speed of the stepping motor 402a to the stepping motor 402a based on the acceleration signal A input from the image forming unit 602. When the rotation of the stepping motor 402a is started, the rotation of the driving roller 21 connected to the rotation shaft of the motor is started, and the rotation is transmitted to the transfer belt B1 wound around the driving roller 21, and the rotation of the transfer belt B1 is started. Is started.

  Since the frequency of the drive pulse input to the stepping motor 402a corresponds to the number of rotations (rotational speed) of the stepping motor 402a, the image forming unit 602 increases the frequency of the acceleration signal A with the acceleration of the stepping motor 402a. To the stepping motor control means 603. The frequency of the acceleration signal A corresponds to the frequency of the drive pulse, and the rotation speed of the stepping motor 402a increases as the frequency of the drive pulse increases.

  The image forming unit 602 continuously (stepwise) increases the frequency of the acceleration signal A until the current rotational speed of the stepping motor 402a reaches a steady speed (constant speed A) of the stepping motor 402a. I will let you.

  Further, for the reason of the configuration of the printer 100, the image forming unit 602 inputs the acceleration signal A described above to the stepping motor control unit 603 and also to the target speed calculation unit 605 constituting the DC brushless motor control unit 604. To do.

  Further, separately from the acceleration signal A, the image forming unit 602 sends a signal (acceleration signal B) for accelerating the rotational speed of the DC brushless motor 4041a to the target speed calculating unit 605 (in FIG. The control signal B) and the steady speed (referred to as steady speed B) of the DC brushless motor 4041a are transmitted (FIG. 7: S103).

  When the image forming unit 602 transmits the acceleration signal B to the target speed calculating unit 605, the motor synchronization determining unit 611 that monitors the image forming unit 602 in advance detects that the rotational speed of the DC brushless motor 4041a is accelerated.

  The motor synchronization determination unit 611 that has detected that the rotational speed of the DC brushless motor 4041a is accelerated detects the acceleration signal A transmitted from the image forming unit 602 to the stepping motor control unit 603 from the image forming unit 602, and the stepping motor. It is determined whether or not to accelerate / decelerate the rotational speed of the DC brushless motor together with the rotational speed. In the above description, since the acceleration signal A and the acceleration signal B, the motor synchronization determination unit 611 determines that the rotation speed of the DC brushless motor is accelerated together with the rotation speed of the stepping motor.

  When the motor synchronization determination unit 611 makes the determination, the determination result is transmitted to the synchronization switching unit 612. When receiving the determination result, the synchronization switching unit 612 refers to the synchronization switching table 800 stored in the synchronization switching storage unit 613 and determines whether to calculate the target speed (FIG. 7: S104). The target speed is the rotational speed of the DC brushless motor 4041a synchronized with the rotational speed of the stepping motor 402a.

  As shown in FIG. 8A, the synchronization switching table 800 includes a determination result 801 indicating a result determined by the motor synchronization determining unit 611 and information 802 indicating whether or not the target speed calculating unit 605 calculates a target speed. It is stored in association.

  Among the determination results, information indicating that the rotational speed of the DC brushless motor is accelerated and decelerated together with the rotational speed of the stepping motor (for example, “accelerate together” 803 and “decelerate together” 804) includes target speed calculation means 605. Is stored in association with information indicating that the target speed is calculated (for example, “target speed calculation” 805, 806).

  On the other hand, information indicating that the DC brushless motor rotational speed is not accelerated / decelerated together with the rotational speed of the stepping motor (for example, “Non-accelerate” 807, “Non-decelerate” 808) in the determination result includes a rotational speed curve. Is stored in association with information indicating that the target speed calculation unit 605 sets the rotation speed stored in the target value as a target value (for example, “Rotation speed curve reference” 809, 810).

  With the above configuration, the synchronization switching unit 612 can determine whether or not to calculate the target speed based on the synchronization switching table 800. In other words, the synchronization switching unit 612 causes the DC brushless motor control unit 604 to synchronize the rotation of the DC brushless motor with the rotation of the stepping motor or based on a control signal in accordance with the characteristics of the rotation speed curve, depending on conditions. Thus, it is possible to determine whether to control the rotation of the DC brushless motor.

  When the synchronization switching means 612 determines that the target speed is calculated based on the synchronization switching table 800, the target speed calculation means 605 sends a signal (calculation signal B) to calculate the target speed (in FIG. 4, control of the calculation instruction). Signal B) is transmitted (FIG. 7: S105 YES).

  Upon receiving the calculation signal B, the target speed calculation unit 605 calculates the target speed based on the acceleration signal A (acceleration signal A input to the stepping motor control unit 603) input from the image forming unit 602. (FIG. 7: S106).

  The target speed is calculated as follows.

  The target speed calculation means 605 is provided with a first time capture circuit that generates an internal timer pulse (also referred to as an internal timer clock signal) with a stable pulse period. The timer pulse is compared with the acceleration signal A input from the image forming unit 602, and the number of internal timer pulses existing per one pulse of the acceleration signal A is counted. This counted number is defined as a stepping motor count number Na.

  Note that the count is performed for each period preset by the user or for each pulse of the acceleration signal. Further, since the frequency of the acceleration signal A increases with time, as a result, the stepping motor count number Na decreases as the frequency of the acceleration signal A increases. The pulse width of the internal timer pulse is preferably sufficiently narrow compared with the pulse width of the acceleration signal A. The target speed calculation unit 605 counts, for example, based on the rising time point of one pulse, but may count based on the falling time point of one pulse. Further, the target speed calculation means 605 may measure the pulse width of the acceleration signal A.

  When the target speed calculation unit 605 calculates the stepping motor count number Na in one pulse, the target number calculation unit 605 multiplies the count number Na by a predetermined correction coefficient (hereinafter referred to as a speed coefficient). That is, the target speed is calculated.

  The speed coefficient indicates the ratio of the rotational speed of the DC brushless motor 4041a to the rotational speed of the stepping motor 402a during steady rotation (when image formation is possible). This ratio corresponds to a ratio of conditions in which the surface linear velocity of the transfer belt B1 rotated by the stepping motor 402a and the surface linear velocity of the photosensitive drum 10Y rotated by the DC brushless motor 4041a coincide.

  Note that an image forming apparatus including a plurality of photosensitive drums, such as the printer 100 according to the embodiment of the present invention, is usually configured so that all the photosensitive drums have the same radius. If the speed coefficient for the photosensitive drum is employed, the surface linear velocity of all the photosensitive drums can be matched with the surface linear velocity of the transfer belt.

  The speed coefficient is, for example, the number of revolutions (rpm) of the motor corresponding to the rotational speed of the motor or the frequency of the control signal (corresponding to the acceleration signal, deceleration signal, or instruction clock signal described above) input to the motor control means ( Hz). Using the frequency as a reference, the frequency of a control signal used for rotation control of the stepping motor 402a during steady rotation is A (Hz), and the frequency of the encoder pulse generated from the encoder 507 of the DC brushless motor 4041a during steady rotation is B (Hz). ), The speed coefficient a (−) is B / A.

  In addition, since the motor rotation speed (rpm) corresponds to the surface linear velocity of the transfer belt or the photosensitive drum, if the surface linear velocity of the transfer belt or the photosensitive drum during steady rotation can be measured, the speed coefficient Is calculated as follows.

  Since the calculated target speed is calculated based on the control signal of the stepping motor 402a as described above, the target speed is synchronized with the rotation of the stepping motor 402a by adopting the target speed for subsequent feedback control. It is possible to realize the rotation of the DC brushless motor 4041a.

  When the target speed calculation unit 605 calculates the target speed, the target speed is transmitted to the feedback control unit 606. The feedback control unit 606 executes feedback control based on PID control. The feedback control unit 606 calculates a predetermined control value based on the current rotation speed corresponding to the current rotation speed of the DC brushless motor 4041a calculated by a feedback pulse (described later) and the target speed, The control value is transmitted to the PWM means 609.

  The calculation of the control value is executed as follows.

  The DC brushless motor 4041a has a predetermined number corresponding to the rotation of the connecting shaft that connects the rotating shaft of the DC brushless motor 4041a and the rotating shaft of the photosensitive drum 10Y by a predetermined rotation angle. Encoder 507 that outputs encoder pulses (encoder pulses, hereinafter referred to as feedback pulses) is provided, and the encoder 507 outputs the feedback pulses to the current rotational speed calculation means 607 constituting the DC brushless motor control means 604. It is input from time to time.

  In addition to the first time capture circuit, the current rotation speed calculation means 607 is provided with a second time capture circuit that generates an internal timer pulse with a stable pulse period. Compares the internal timer pulse with the feedback pulse input from the encoder 507, and counts the number of internal timer pulses present per one pulse of the feedback pulse. This counted number is defined as a DC brushless motor count number Nb.

  The count is performed for each period preset by the user or for each pulse of the acceleration signal. Furthermore, the frequency of the feedback pulse increases as the rotational speed of the DC brushless motor 4041a increases. As a result, the DC brushless motor count number Nb decreases as the frequency of the feedback pulse increases.

  When the current rotation speed calculation unit 607 calculates the DC brushless motor count number Nb in one pulse, the count number Nb is transmitted to the feedback control unit 606 as the current rotation speed of the DC brushless motor.

  When the feedback control means 606 receives the current rotational speed and the target speed, it determines a control parameter (“Kp”) corresponding to the acceleration of the DC brushless motor 4041a, and a speed difference between the target speed and the current rotational speed. And a proportional control value (hereinafter referred to as a control value) corresponding to the control parameter “Kp” is calculated based on the speed difference (FIG. 7: S107).

  The control parameter is a parameter determined based on PID control for controlling the current rotational speed to converge to a target speed by combining proportional control, integral control, and differential control.

  For example, the control parameter includes a proportional control parameter “Kp” (also referred to as a proportional constant) that calculates (outputs) a proportional control value corresponding to the speed difference between the target speed and the current rotational speed, and integrates the speed difference. An integral control parameter “Ki” (also referred to as an integral constant) for calculating an integral control value corresponding to the integrated value, and a differential control parameter “Kd” for calculating a differential control value corresponding to a differential value obtained by differentiating the speed difference ( This is also referred to as a differential constant).

  When the DC brushless motor 4041a is accelerated or decelerated, the proportional control parameter “Kp” is employed.

  With the above configuration, when accelerating the rotational speed of the DC brushless motor 4041a, the feedback control means 606 calculates a control value so as to follow the current rotational speed as needed at the target speed of the DC brushless motor 4041a. The DC brushless motor control means 604 inputs the drive pulse to the DC brushless motor 4041a via the PWM means 609 and the drive pulse input means 610, and the rotational speed of the DC brushless motor 4041a is sequentially accelerated. Therefore, it is possible to prevent an overshoot phenomenon, which is a phenomenon in which the rotational speed of the DC brushless motor 4041a greatly exceeds the target rotational speed. Even when the DC brushless motor control means 604 sequentially reduces the rotational speed of the DC brushless motor 4041a, the rotational speed of the DC brushless motor 4041a is adopted by adopting the control parameter “Kp” corresponding to the deceleration of the DC brushless motor 4041a. However, it is possible to prevent the undershoot phenomenon, which is a phenomenon in which the rotation speed is larger than the target rotational speed.

  Both the current rotation speed and the target speed correspond to a numerical value (data) called a count number, and the feedback control means 606 calculates a control value based on the numerical value. Therefore, it should be noted that a phase comparator or the like that is conventionally used for rotation control of a DC brushless motor has not been adopted.

  When the calculation of the control value is completed, the feedback control unit 606 determines whether or not the calculated control value belongs within a predetermined range. The range is determined based on, for example, whether or not the duty of the PWM signal (speed command signal) generated based on the control value by the PWM means 609 belongs to an allowable range (range from 0 to 100%). The predetermined range is calculated in advance so as to correspond to the allowable range.

  If the control value is included in the predetermined range as a result of the determination, the feedback control unit 606 transmits the control value to the PWM unit 609 as it is. On the other hand, when the control value is not included in the predetermined range, the feedback control unit 606 is configured to transmit a predetermined control value set in advance by the user to the PWM unit 609. When the control value is less than 0, the feedback control unit 606 is configured to transmit the control value to the PWM unit 609 as 0.

  When the PWM means 609 receives the control value, it generates a PWM signal based on the control value and inputs it to the drive pulse input means 610. Based on the PWM signal, the drive pulse input means 610 inputs a drive pulse for accelerating the rotation speed of the DC brushless motor 4041a to the DC brushless motor 4041a. The DC brushless motor 4041a starts rotating based on the input drive pulse (FIG. 7: S108).

  The above-described procedure is repeated by the target speed calculation means 605 and the feedback control means 606 until the stepping motor control means 603 reaches the steady speed A of the rotation speed of the stepping motor 402a. That is, when the image forming unit 602 continuously increases the frequency of the acceleration signal A to the frequency of the control signal corresponding to the steady speed A, the target speed calculating unit 605 corresponds to the increase, and the target speed calculating unit 605 The target speed of the DC brushless motor 4041a synchronized with the rotation of the motor is calculated, and the feedback control means 606 calculates a control value based on the speed difference between the target speed and the current rotational speed and a predetermined control parameter. . The calculated control value is converted into a PWM signal via the PWM means 609. The PWM signal is a clock signal (speed command signal) whose duty is continuously increased while maintaining a predetermined frequency. Become. As a result, the drive pulse input means 610 inputs a drive pulse for increasing the rotational speed of the DC brushless motor to the DC brushless motor 4041a.

  When the rotation speed of the stepping motor 402a reaches the steady speed A, the rotation speed of the DC brushless motor 4041a reaches the steady speed B corresponding to the arrival. As a result, the printer 100 shifts to a state where image formation is possible (FIG. 7: S109).

  In a region 9A of FIG. 9, a control signal (acceleration) input to the stepping motor control means 603 when the rotation of the photosensitive drum 10Y corresponding to color printing is shifted from the sleep state to a state where image formation is possible (at the time of startup). The change with time of the frequency of the signal A) and the frequency of the encoder pulse of the DC brushless motor 4041a is shown.

  As can be seen from the region 9A of FIG. 9, the frequency of the encoder pulse of the DC brushless motor 4041a is increased while maintaining the speed coefficient (a = B / A) with respect to the frequency of the control signal of the stepping motor 402a. In other words, it is understood that the rotation of the DC brushless motor 4041a is increased in synchronization with the rotation of the stepping motor 402a. Accordingly, the rotational speeds of the stepping motor 402a and the DC brushless motor 4041a are accelerated while the surface linear velocity of the transfer belt B1 and the surface linear velocity of the photosensitive drum 10Y are matched.

  When the printer 100 shifts to a state in which image formation is possible, the image forming unit 602 inputs a control signal corresponding to the steady speed A to the stepping motor control unit 603, so that the stepping motor control unit 603 rotates the rotation speed of the stepping motor 402a. Is maintained at a steady speed A. The control signal corresponding to the steady speed A is input to the target speed calculation unit 605. Since the frequency of the control signal is constant, the target speed calculated by the target speed calculation unit 605 is constant. Become.

  When the target speed calculation means 605 detects that the target speed calculated by the target speed calculation means 605 itself is constant, the target speed to be transmitted to the feedback control means 606 is the steady speed B first received from the image forming means 602. Switch to.

  In the case of switching to the steady speed B, the target speed calculation unit 605 detects that the target speed calculated by the target speed calculation unit 605 itself is constant or detects that the target speed has converged to a predetermined value. It is judged by doing.

  When the target speed calculation means 605 transmits the steady speed B to the feedback control means 606, the feedback control means 606 discriminates control parameters (“Kp”, “Kd”, “Ki”) corresponding to the steady speed, and the steady speed. A speed difference between B and the current rotational speed is calculated, and control values corresponding to the control parameters “Kp”, “Kd”, and “Ki” are calculated based on the speed difference.

  At the time of steady rotation of the DC brushless motor 4041a, the proportional control parameters “Kp”, “Kd”, and “Ki” are employed.

  With the above configuration, the DC brushless motor control means 604 can stably control the rotation of the DC brushless motor 4041a.

  The feedback control means 606 inputs drive pulses corresponding to these control values to the DC brushless motor 4041a via the PWM means 609 and the drive pulse input means 610. The rotation of the DC brushless motor 4041a is executed stably.

  Note that the photosensitive drums 10M, 10C, and 10K other than the photosensitive drum 10Y corresponding to yellow rotate in the same manner, and their rotations are controlled by the respective DC brushless motors.

  When the rotation speed of the stepping motor 402a and the rotation speed of the DC brushless motor 4041a are stabilized, the image forming unit 602 forms a toner image on each of the photosensitive drums 10Y based on a command for image formation for color printing. The toner image is transferred to the transfer belt B1 and the printed matter is output. Thereby, one job is completed.

<< About the operation procedure of the three-color release mechanism >>
Next, a description will be given of a procedure in which a three-color release mechanism that receives a command relating to monochrome image formation and stops the photosensitive drum corresponding to color printing operates.

  For example, when the communication unit 601 receives an instruction related to image formation for monochrome printing when color printing is completed, the image forming unit 602 includes a photosensitive drum (yellow) corresponding to color printing among a plurality of photosensitive drums. , A signal (deceleration signal B) for decelerating the rotational speed of the photosensitive drums 10Y, 10M, and 10K corresponding to magenta and cyan is transmitted to the DC brushless motor control unit 604 of the photosensitive drum corresponding to color printing. .

  Here, the DC brushless motor control means 604 for the photosensitive drum corresponding to yellow will be described, but the same applies to other DC brushless motor control means corresponding to color printing.

  The image forming unit 602 transmits the deceleration signal B (deceleration instruction control signal B in FIG. 4) to the target speed calculation unit 605 constituting the DC brushless motor control unit 604 (FIG. 7: S103).

  On the other hand, since it is necessary to maintain the rotation of the stepping motor, the image forming unit 602 inputs a control signal corresponding to the steady speed A to the stepping motor control unit 603. Therefore, the stepping motor control means 603 maintains the rotation speed of the stepping motor 402a at the steady speed A. For reasons of the configuration of the printer 100, a control signal (maintenance signal A) corresponding to the steady speed A is input to the target speed calculation means 605 separately from the deceleration signal B. For the above reasons, S101 and S102 are omitted.

  When the image forming unit 602 transmits the deceleration signal B to the target speed calculating unit 605, the motor synchronization determining unit 611 that monitors the image forming unit 602 detects that the rotational speed of the DC brushless motor 4041a is decreased.

  The motor synchronization determination unit 611 that has detected that the rotational speed of the DC brushless motor 4041a has been reduced detects the maintenance signal A transmitted from the image forming unit 602 to the stepping motor control unit 603 from the image forming unit 602, and the stepping motor It is determined whether or not to accelerate / decelerate the rotational speed of the DC brushless motor together with the rotational speed. In the above description, since the maintenance signal A and the deceleration signal B, the motor synchronization determination unit 611 determines that the rotation speed of the DC brushless motor is not decelerated together with the rotation speed of the stepping motor.

  When the motor synchronization determination unit 611 makes the determination, the determination result is transmitted to the synchronization switching unit 612. When receiving the determination result, the synchronization switching means 612 refers to the synchronization switching table 800 and determines whether or not to calculate the target speed (FIG. 7: S104).

  This case corresponds to the “refer to rotational speed curve” corresponding to the determination result “both do not decelerate”. That is, the target speed calculation means 605 sets the rotation speed stored in the rotation speed curve as the target value.

  When it is determined that the synchronization switching means 612 refers to the rotation speed curve based on the synchronization switching table 800, a signal (reference signal B) for referring to the rotation speed curve is sent to the target speed calculation means 605 (reference instruction in FIG. 4). Control signal B) is transmitted (FIG. 7: S105 NO).

  The target speed calculation means 605 that has received the reference signal B refers to the deceleration rotational speed curve corresponding to the time of deceleration of the DC brushless motor 4041a stored in the rotational speed curve storage means 614, and the rotational speed of the deceleration rotational speed curve. Is set as a target value (FIG. 7: S110). This setting is updated and set according to the deceleration rotational speed curve as time passes.

  As shown in FIG. 10, the deceleration rotational speed curve 10A is a curve (also referred to as a slow-down table) showing the change over time in the rotational speed when the DC brushless motor 4041a alone is decelerated. The initial rotational speed (time Zero) is set to the steady speed B of the DC brushless motor 4041a, the rotational speed gradually decreases with time, and when the predetermined time 10B elapses, the rotational speed decreases rapidly and stops (zero). ).

  The fluctuation of the rotational speed of the deceleration rotational speed curve is appropriately changed according to parameters such as the radius, circumference, surface properties, material, the gear ratio of the DC brushless motor 4041a, the properties of the transfer belt, etc. However, with the above configuration, when the rotational speed of the DC brushless motor 4041a is reduced independently of the stepping motor 402a, the surface of the photosensitive drum for color printing and the surface of the transfer belt are not rubbed or worn with each other. It is possible to reduce the rotational speed of the DC brushless motor 4041a in accordance with the deceleration fluctuation of the rotational speed measured in advance. Therefore, mode switching from color printing to monochrome printing is smoothly executed while appropriately suppressing the occurrence of a speed difference between the surface linear velocity of the photosensitive drum used for color printing and the surface linear velocity of the transfer belt. In addition, since the rotation of the photosensitive drum for color printing is stopped, it is possible to reduce wasteful power consumption.

  The unit of the rotational speed of the deceleration rotational speed curve is equivalent to the target speed.

  When the target speed calculation means 605 sets the rotational speed referred from the deceleration rotational speed curve, the target speed is transmitted to the feedback control means 606 as the target speed described above. Since the current rotation speed is input from the current rotation speed calculation means 607 to the feedback control means 606, the feedback control means 606 uses the control parameter ("Kp") corresponding to the deceleration of the DC brushless motor 4041a, A speed difference between the rotational speed of the deceleration rotational speed curve and the current rotational speed is calculated, and a proportional control value corresponding to the control parameter “Kp” is calculated based on the speed difference (FIG. 7: S107).

  The feedback control unit 606 inputs a drive pulse corresponding to the proportional control value to the DC brushless motor 4041a via the PWM unit 609 and the drive pulse input unit 610. The rotation of the DC brushless motor 4041a is decelerated.

  In a region 9B of FIG. 9, a control signal (to be input to the stepping motor control means 603 when the rotation of the photosensitive drum 10Y corresponding to color printing is shifted from an image formable state to a stopped state (during deceleration)). The time-dependent change of the frequency of the maintenance signal A) and the frequency of the encoder pulse of the DC brushless motor 4041a is shown.

  As can be seen from the region 9B of FIG. 9, the frequency of the control signal input to the stepping motor 402a is constant while maintaining a predetermined frequency, whereas the frequency of the encoder pulse of the DC brushless motor 4041a is constant. It is understood that the motor 402a decreases independently of the frequency of the control signal and further enters a stop state while exhibiting a deceleration fluctuation that matches the deceleration rotational speed curve.

  When the DC brushless motor control unit 604 decelerates the rotation of the DC brushless motor 4041a based on the deceleration rotational speed curve and stops the photosensitive drum 10Y for color printing, the image forming unit 602 performs an image corresponding to monochrome printing. Based on the formation command, a toner image is formed on the photosensitive drum corresponding to black, the toner image is transferred to the transfer belt, and the printed matter is output (FIG. 7: S108 → S109). Thereby, one job is completed.

  Thus, when accelerating / decelerating the rotational speed of the DC brushless motor, the motor synchronization determining means for determining whether to accelerate / decelerate the rotational speed of the DC brushless motor together with the rotational speed of the stepping motor, and the motor synchronization determining means include: When it is determined that the rotational speed of the DC brushless motor is accelerated / decelerated together with the rotational speed of the stepping motor, the DC brushless motor control means 604 is provided with a synchronous switching means for synchronizing the rotation of the DC brushless motor with the rotation of the stepping motor. ing.

  As a result, when the rotational speed of the DC brushless motor is accelerated or decelerated together with the rotational speed of the stepping motor, a speed difference between the surface linear speed of the transfer belt and the surface linear speed of the photosensitive drum is likely to occur. Since the rotational speed of the DC brushless motor is accelerated or decelerated in synchronization with the rotational speed of the stepping motor, the speed difference between the surface linear speed of the transfer belt and the surface linear speed of the photosensitive drum is unlikely to occur. It is possible to prevent scratches and the like generated between the belt and the photosensitive drum.

  Further, when the motor synchronization determining means determines that the rotation speed of the DC brushless motor is not accelerated / decelerated together with the rotation speed of the stepping motor, the synchronization switching means causes the DC brushless motor control means 604 to change the characteristic of the rotation speed curve. Based on the combined control signal, the rotation of the DC brushless motor can be controlled.

  As a result, when the rotational speed of the DC brushless motor is accelerated or decelerated independently of the stepping motor, the surface of the photosensitive drum for color printing and the surface of the transfer belt are not rubbed or worn with each other, that is, measured in advance. The rotational speed of the DC brushless motor can be independently accelerated or decelerated in accordance with the acceleration fluctuation or deceleration fluctuation of the control signal characteristics (rotational speed). For this reason, for example, a mode from color printing to monochrome printing, or from monochrome printing to color printing, while appropriately suppressing the speed difference between the surface linear velocity of the photosensitive drum for color printing and the surface linear velocity of the transfer belt. Switching can be performed smoothly. As a result, if necessary, the rotation control of the DC brushless motor is flexibly changed, and the rotation of the DC brushless motor is appropriately controlled without causing the transfer belt surface and the photosensitive drum surface to rub and wear each other. In other words, it is possible to obtain a stable start / stop characteristic of the DC brushless motor.

  In the following, a procedure for releasing the three-color release mechanism and a procedure for shifting the printer to the stop state or the sleep state will be described for reference.

<< Regarding the release operation procedure of the three-color release mechanism >>
For example, when monochrome printing is completed, when the communication unit 601 receives a command relating to image formation for color printing again, the image forming unit 602 causes the photosensitive drum (yellow, magenta, A signal (acceleration signal B) for accelerating the rotation speed of the photosensitive drums 10Y, 10M, and 10C corresponding to cyan and a steady speed (referred to as steady speed B) of the DC brushless motor are photosensitive colors corresponding to color printing. This is transmitted to the DC brushless motor control means 604 of the body drum.

  Similarly to the above, the DC brushless motor control means 604 for the photosensitive drum corresponding to yellow will be described, but the same applies to other DC brushless motor control means corresponding to color printing.

  The image forming unit 602 transmits the acceleration signal B (acceleration instruction control signal B in FIG. 4) and the steady speed B to the target speed calculation unit 605 constituting the DC brushless motor control unit 604 (FIG. 7: S103).

  On the other hand, since the image forming unit 602 inputs a control signal (maintenance signal A) corresponding to the steady speed A to the stepping motor control unit 603, the stepping motor control unit 603 changes the rotation speed of the stepping motor 402a to the steady speed A. Is maintained. The maintenance signal A is input to the target speed calculation means 605 separately from the deceleration signal B for reasons of the configuration of the printer 100. As described above, S101 and S102 are omitted.

  When the image forming unit 602 transmits the acceleration signal B to the target speed calculating unit 605, the motor synchronization determining unit 611 monitoring the image forming unit 602 detects that the rotational speed of the DC brushless motor 4041a is accelerated.

  Further, the motor synchronization determination unit 611 detects the maintenance signal A transmitted from the image forming unit 602 to the stepping motor control unit 603 and adds the rotation speed of the DC brushless motor together with the rotation speed of the stepping motor. Determine whether to decelerate. In the above description, since the maintenance signal A and the acceleration signal B, the motor synchronization determination unit 611 determines that the rotation speed of the DC brushless motor is not decelerated together with the rotation speed of the stepping motor.

  When the motor synchronization determination unit 611 makes the determination, the determination result is transmitted to the synchronization switching unit 612. When receiving the determination result, the synchronization switching means 612 refers to the synchronization switching table 800 and determines whether or not to calculate the target speed (FIG. 7: S104).

  This case corresponds to the “refer to the rotational speed curve” corresponding to the determination result “not accelerated together”. Therefore, when the synchronization switching unit 612 determines that the rotation speed curve is referred to based on the synchronization switching table 800, a signal (reference signal B) (refer to FIG. 4) indicating that the rotation speed curve is referred to the target speed calculation unit 605. Reference control signal B) is transmitted (FIG. 7: S105 NO).

  The target speed calculation means 605 that has received the reference signal B refers to the acceleration rotational speed curve corresponding to the acceleration of the DC brushless motor 4041a stored in the rotational speed curve storage means, and determines the rotational speed of the acceleration rotational speed curve. The target value is set (FIG. 7: S110). This setting is updated and set according to the acceleration rotational speed curve as time passes.

  As shown in FIG. 10, the acceleration rotation speed curve 10C is a curve (also referred to as a slow-up table) showing a change in rotation speed over time when the DC brushless motor 4041a alone is accelerated, and the initial rotation speed is The rotation speed is set to correspond to the time when the DC brushless motor is started up, and when the predetermined time 10D elapses, the rotation speed rapidly increases. After the time elapses, the rotation speed gradually increases to the steady speed B ( It is a curve that increases up to a rotation speed at which image formation is possible.

  The variation in the rotational speed of the acceleration rotational speed curve is appropriately changed in design according to parameters such as the radius, circumference, surface properties, material of the photosensitive drum 10Y, the gear ratio of the DC brushless motor 4041a, and the properties of the transfer belt. However, with the above configuration, when the rotational speed of the DC brushless motor 4041a is accelerated independently of the stepping motor 402a, the surface of the photosensitive drum for color printing and the surface of the transfer belt are not rubbed and worn with each other. The rotational speed of the DC brushless motor 4041a can be accelerated in accordance with the acceleration fluctuation of the rotational speed measured in advance. Therefore, mode switching from monochrome printing to color printing is smoothly executed while appropriately suppressing the occurrence of a speed difference between the surface linear velocity of the photosensitive drum used for color printing and the surface linear velocity of the transfer belt. It becomes possible.

  Note that the unit of the rotational speed of the acceleration rotational speed curve is equal to the target speed.

  When the target speed calculation means 605 sets the rotational speed referred from the acceleration rotational speed curve, the target speed is transmitted to the feedback control means 606 as the target speed described above. Since the current rotation speed is input from the current rotation speed calculation means 607 to the feedback control means 606, the feedback control means 606 uses the control parameter ("Kp") corresponding to the deceleration of the DC brushless motor 4041a, A speed difference between the rotational speed of the deceleration rotational speed curve and the current rotational speed is calculated, and a proportional control value corresponding to the control parameter “Kp” is calculated based on the speed difference (FIG. 7: S107).

  The feedback control unit 606 inputs a drive pulse corresponding to the proportional control value to the DC brushless motor 4041a via the PWM unit 609 and the drive pulse input unit 610. The rotation of the DC brushless motor 4041a is accelerated.

  In a region 9C of FIG. 9, a control signal (to be input to the stepping motor control means 603 when the rotation of the photosensitive drum 10Y corresponding to color printing is shifted from a stopped state to a state where image formation is possible (during acceleration)). The time-dependent change of the frequency of the maintenance signal A) and the frequency of the encoder pulse of the DC brushless motor 4041a is shown.

  As can be seen from the region 9C in FIG. 9, the frequency of the control signal input to the stepping motor control means 603 is constant while maintaining a predetermined frequency, whereas the drive pulse input to the DC brushless motor 4041a. Is increased independently of the frequency of the control signal of the stepping motor 402a, and it is understood that an image forming state is reached while showing acceleration fluctuations that match the acceleration rotation speed curve.

  When the DC brushless motor control means 604 accelerates the rotational speed of the DC brushless motor 4041a based on the acceleration rotational speed curve and rotates the photosensitive drum for color printing to a rotational speed at which image formation is possible, the image forming means 602. However, based on an image forming command corresponding to color printing, a toner image is formed on each photosensitive drum, the toner image is transferred to a transfer belt, and output of a printed matter is executed (FIG. 7: S108 → S109). Thereby, one job is completed.

  When the image forming state is entered, the rotational speed of the acceleration rotational speed curve becomes constant. Therefore, the target speed calculation unit 605 detects this and first transmits the rotational speed to be transmitted to the feedback control unit 606. Switching to the steady speed B received from the image forming means 602.

  When the target speed calculation means 605 transmits the steady speed B to the feedback control means 606, the feedback control means 606 calculates the speed difference between the steady speed B and the current rotational speed, and based on the speed difference, the steady speed The control value corresponding to the control parameter (“Kp”, “Kd”, “Ki”) corresponding to is calculated.

  The feedback control means 606 inputs drive pulses corresponding to these control values to the DC brushless motor 4041a via the PWM means 609 and the drive pulse input means 610. The rotation of the DC brushless motor 4041a is executed stably.

<< Procedure for stopping >>
Next, the procedure for shifting the printer to the sleep state will be described, but the same applies to the procedure for the user to turn off the power and shift to the stop state.

  Further, for example, when the stepping motor control unit 603 and the DC brushless motor control unit 604 maintain the rotation speeds of the respective motors at a steady speed, the process from the state where image formation is possible to the transition to the sleep state is performed. When the sleep time, which is a waiting time, has elapsed, the image forming unit 602 shifts from an image formable state to a sleep state.

  Specifically, the image forming unit 602 transmits a signal (deceleration signal A) for decelerating the rotation speed of the stepping motor 402a to the stepping motor control unit 603 (FIG. 7: S101).

  When receiving the deceleration signal A, the stepping motor control means 603 starts decelerating the rotation of the stepping motor 402a (FIG. 7: S102).

  Specifically, the stepping motor control means 603 inputs a driving pulse for reducing the rotational speed of the stepping motor 402a to the stepping motor 402a based on the deceleration signal A input from the image forming means 602. When the rotation of the stepping motor 402a is decelerated, the rotation of the transfer belt B1 is decelerated.

  The image forming unit 602 sets the frequency of the deceleration signal A until the current rotational speed of the stepping motor 402a (close to the steady speed A) reaches a stop speed (for example, a rotational speed corresponding to the startup of the stepping motor 402a). Decrease continuously (stepwise).

  On the other hand, the image forming unit 602 inputs the deceleration signal A described above to the stepping motor control unit 603 and also to the target speed calculation unit 605 constituting the DC brushless motor control unit 604. In addition to the deceleration signal A, the image forming unit 602 sends a signal (deceleration signal B) indicating that the rotational speed of the DC brushless motor 4041a is reduced to the target speed calculation unit 605 (in FIG. A control signal B) is transmitted (FIG. 7: S103).

  When the image forming unit 602 transmits the deceleration signal B to the target speed calculating unit 605, the motor synchronization determining unit 611 that monitors the image forming unit 602 in advance detects that the rotational speed of the DC brushless motor 4041a is reduced.

  The motor synchronization determination unit 611 that has detected that the rotational speed of the DC brushless motor 4041a is decelerated detects the deceleration signal A transmitted from the image forming unit 602 to the stepping motor control unit 603 from the image forming unit 602, and detects the stepping motor. It is determined whether or not the rotational speed of the DC brushless motor is accelerated and decelerated together with the rotational speed. In the above description, since the deceleration signal A and the deceleration signal B, the motor synchronization determination unit 611 determines that the rotational speed of the DC brushless motor is reduced together with the rotational speed of the stepping motor.

  When the motor synchronization determination unit 611 makes the determination, the determination result is transmitted to the synchronization switching unit 612. When receiving the determination result, the synchronization switching unit 612 refers to the synchronization switching table 800 stored in the synchronization switching storage unit 613 and determines whether to calculate the target speed (FIG. 7: S104).

  This case corresponds to “target speed calculation” corresponding to the determination result “decelerate together”. That is, the target speed calculation unit 605 calculates the target speed based on the deceleration signal A, and the target speed calculation unit 605 sets the target speed as a target value.

  When the synchronization switching means 612 determines that the target speed is calculated based on the synchronization switching table 800, the target speed calculation means 605 sends a signal (calculation signal B) to calculate the target speed (in FIG. 4, control of the calculation instruction). Signal B) is transmitted (FIG. 7: S105 YES).

  When the target speed calculation unit 605 receives the calculation signal B, the target speed calculation unit 605 calculates the target speed based on the deceleration signal A input from the image forming unit 602 (FIG. 7: S106).

  The procedure for calculating the target speed is the same as that described above. In brief, the target speed calculation unit 605 compares the internal timer pulse with the deceleration signal A input from the image forming unit 602, and determines the deceleration signal A. The number Na of internal timer pulses existing per one pulse is counted.

  When the target speed calculation means 605 calculates the stepping motor count number Na in one pulse of the deceleration signal A, the target speed calculation means 605 multiplies the count number Na by a speed coefficient, and calculates the multiplied value as a target value, that is, a target speed. .

  When the target speed calculation unit 605 calculates the target speed, the target speed is transmitted to the feedback control unit 606. Since the current rotation speed is input from the current rotation speed calculation means 607 to the feedback control means 606, the feedback control means 606 uses the control parameter ("Kp") corresponding to the deceleration of the DC brushless motor 4041a, A speed difference between the target speed and the current rotation speed is calculated, and a proportional control value corresponding to the control parameter “Kp” is calculated based on the speed difference (FIG. 7: S107).

  The feedback control unit 606 inputs a drive pulse corresponding to the proportional control value to the DC brushless motor 4041a via the PWM unit 609 and the drive pulse input unit 610. The rotation of the DC brushless motor 4041a is decelerated (FIG. 7: S108).

  The above-described procedure is repeated by the target speed calculation means 605 and the feedback control means 606 until the stepping motor control means 603 reaches the rotation speed of the stepping motor 402a to the stop speed. That is, when the image forming unit 602 continuously decreases the frequency of the deceleration signal A to the frequency corresponding to the stop speed, the target speed calculation unit 605 is synchronized with the rotation of the stepping motor 402a corresponding to the decrease. The target speed of the DC brushless motor 4041a is calculated, and the feedback control unit 606 calculates a control value based on the speed difference between the target speed and the current rotation speed and a predetermined control parameter. The calculated control value is converted into a PWM signal via the PWM means 609. The PWM signal becomes a clock signal whose duty is continuously reduced while maintaining a predetermined frequency. As a result, the drive pulse input means 610 inputs a drive pulse for reducing the rotational speed of the DC brushless motor to the DC brushless motor 4041a.

  When the rotation speed of the stepping motor 402a reaches the stop speed, the DC brushless motor control means 604 ends the reduction of the rotation speed of the DC brushless motor 4041a in response to the arrival. As a result, the transfer belt and the photosensitive drum are simultaneously stopped, and the printer 100 shifts to the sleep state (FIG. 7: S109).

  In an area 9D of FIG. 9, the rotation is input to the stepping motor control means 603 when the rotation of the photosensitive drum 10Y corresponding to color printing is shifted from the image formable state to the sleep state (stopped state) (when stopped). The change with time of the frequency of the control signal (deceleration signal A) and the frequency of the encoder pulse of the DC brushless motor 4041a is shown.

  As can be seen from the region 9D in FIG. 9, the frequency of the encoder pulse of the DC brushless motor 4041a decreases with respect to the frequency of the control signal of the stepping motor 402a while maintaining the speed coefficient (a = B / A), that is, It is understood that the frequency is decreased in synchronization with the frequency of the control signal of the stepping motor 402a, reaches a predetermined frequency, and is stopped. Accordingly, the rotational speeds of the stepping motor 402a and the DC brushless motor 4041a are decelerated while the surface linear velocity of the transfer belt B1 and the surface linear velocity of the photosensitive drum 10Y are matched.

  In the embodiment of the present invention, the embodiment for switching the mode from color printing to monochrome printing and from monochrome printing to color printing has been described. However, the number of mode switching increases or decreases, for example. A scene (for example, a scene in which commands corresponding to monochrome printing and color printing are transmitted a plurality of times), a scene in which the order of each mode is interchanged (for example, color printing, monochrome printing, monochrome printing, monochrome printing) Sent scene). Even in a scene where only a predetermined mode is executed (for example, a scene where only a command corresponding to monochrome printing is transmitted a plurality of times), the effect of the present invention is exhibited.

  Further, in the acceleration (deceleration) rotation speed curve of the embodiment of the present invention, the target speed calculation means corresponds to the target speed calculated based on the control signal input to the stepping motor control means as the characteristic of the control signal. Although configured to store the rotational speed, other modes may be used. For example, the control signal input to the stepping motor control means may be a control signal in a rotation speed curve, and a change with time such as the frequency of the control signal may be stored as a curve. With the above configuration, the target speed calculation means compares the control signal of the rotational speed curve with the internal timer pulse, counts the number of internal timer pulses existing per one pulse of the control signal, and calculates the speed coefficient. To calculate the target speed.

  In the embodiment of the present invention, the motor synchronization determination means includes control signals (acceleration signal A, deceleration signal A, maintenance signal A) input to the stepping motor control means, and control signals input to the target speed calculation means. By monitoring and referring to the image forming means (acceleration signal B, deceleration signal B), it is determined whether to accelerate or decelerate the rotational speed of the DC brushless motor together with the rotational speed of the stepping motor. Further, the synchronization switching means is configured to determine whether to calculate the target speed or to refer to the rotation speed curve based on the determination result of the synchronization switching table and the motor synchronization determination means. Other configurations may be adopted in addition to the configuration.

  For example, in addition to the above-described control signal, the image forming unit may be a stepping motor acceleration / deceleration control signal indicating the stepping motor acceleration / deceleration start time as a pulse signal HI signal or LOW signal, and DC brushless motor acceleration / deceleration start. A DC brushless motor acceleration / deceleration control signal whose time point is indicated by a pulse signal HI signal or LOW signal is input to the synchronous switching means.

  Further, as shown in FIG. 8B, the synchronous switching storage means includes information indicating whether the acceleration / deceleration control signal of the stepping motor is a HI signal or a LOW signal (“High”, “Low”), and DC brushless. Information indicating whether the acceleration / deceleration control signal of the motor is a HI signal or a LOW signal (“High”, “Low”, “−” indicating that there is no rise or fall), and target speed calculation means 605 Information indicating whether or not to calculate the target speed ("target speed calculation", "refer to the rotational speed curve") is associated and stored as a table.

  When accelerating / decelerating the rotational speed of the DC brushless motor together with the rotational speed of the stepping motor, that is, “High” corresponds to the acceleration / deceleration control signal of the stepping motor and “High” corresponds to the acceleration / deceleration control signal of the DC brushless motor; When “Low” corresponds to the acceleration / deceleration control signal of the stepping motor and “Low” corresponds to the acceleration / deceleration control signal of the DC brushless motor, “target speed calculation” is stored in association with the table.

  When the rotation speed of the DC brushless motor is not accelerated / decelerated together with the rotation speed of the stepping motor, that is, “High” (“−”) is displayed in the acceleration / deceleration control signal of the stepping motor and “Low” is displayed in the acceleration / deceleration control signal of the DC brushless motor. In the table above, “Low” (“−”) corresponds to the acceleration / deceleration control signal of the stepping motor and “High” corresponds to the acceleration / deceleration control signal of the DC brushless motor. "Is stored in association with each other.

  With the above configuration, the image forming means inputs the predetermined stepping motor acceleration / deceleration control signal and the DC brushless motor acceleration / deceleration control signal to the synchronous switching means, whereby the synchronous switching means is stored in the synchronous switching storage means. Based on the above table, it is possible to simultaneously determine whether to accelerate / decelerate the rotational speed of the DC brushless motor together with the rotational speed of the stepping motor and whether to calculate the target speed or refer to the rotational speed curve.

  For example, when the image forming unit inputs the acceleration / deceleration control signal of the stepping motor of the HI signal and the acceleration / deceleration control signal of the DC brushless motor of the HI signal to the synchronous switching unit at the start-up, as shown in FIG. At the start time 901, it is determined that the synchronization switching means calculates the target speed based on the table, the acceleration / deceleration control signal of the stepping motor, and the acceleration / deceleration control signal of the DC brushless motor.

  On the other hand, when the three-color release mechanism operates, the image forming means inputs the acceleration / deceleration control signal of the stepping motor that is neither the HI signal nor the LOW signal and the acceleration / deceleration control signal of the DC brushless motor of the LOW signal to the synchronous switching means. As shown in FIG. 9, at the start of deceleration 901 of the DC brushless motor for color printing, the synchronous switching means rotates based on the table, the acceleration / deceleration control signal of the stepping motor, and the acceleration / deceleration control signal of the DC brushless motor. It becomes possible to discriminate by referring to the velocity curve. The same applies to the release operation of the three-color release mechanism and the stop state.

  In the embodiment of the present invention, the DC brushless motor and the photosensitive drum are directly connected (coupled). For example, a predetermined reduction ratio is set between the DC brushless motor and the photosensitive drum. It is also possible to provide a speed reducer that adjusts the rotational speed of the DC brushless motor and the rotational speed of the photosensitive drum as appropriate.

  In the embodiment of the present invention, the proportional control parameter “Kp” is adopted as the control parameter corresponding to the acceleration (deceleration) of the DC brushless motor. The differential control value corresponding to the differential value obtained by differentiating the speed difference between the target speed of the DC brushless motor and the current rotational speed is calculated (output) in accordance with the member such as the gear, the radius, the circumference, the specifications, etc. A differential control parameter “Kd” (also referred to as a differential constant) may be further added and employed.

  Further, the procedure at the time of stopping according to the present embodiment is applicable even when, for example, the printer is turned off or the image forming unit receives a command signal corresponding to the stop of driving by the user other than the sleep time. Is possible.

  In addition, all or a part of each means constituting the embodiment of the present invention may include predetermined circuit elements (for example, diodes, operational amplifiers, resistors, transistors, switching elements, etc.) and hardware resources (for example, CPU that is an arithmetic element) Etc.) may be realized as a circuit.

  For example, an intermediate transfer member motor control circuit that controls the rotation of the intermediate transfer member motor based on a control signal that is a pulse signal that controls the rotation of the motor, and an image carrier motor control that is synchronized with the control signal of the intermediate transfer member motor In an image forming apparatus comprising an image carrier motor control circuit for controlling the acceleration / deceleration of the rotation of the image carrier motor in accordance with the acceleration / deceleration of the rotation of the intermediate transfer motor based on the signal, the rotational speed of the image carrier motor is controlled. In the case of acceleration / deceleration, a motor synchronization determination circuit for determining whether to accelerate / decelerate the rotation speed of the image carrier motor together with the rotation speed of the intermediate transfer body motor, and the motor synchronization determination circuit include the rotation speed of the image carrier motor. Is determined to accelerate / decelerate along with the rotational speed of the intermediate transfer body motor, the image carrier motor control circuit synchronizes the rotation of the image carrier motor with the rotation of the intermediate transfer body motor. It may be configured to and a period switching circuit.

  And a rotation speed curve storage circuit for storing a rotation speed curve indicating a change over time in the characteristics of the control signal when accelerating and decelerating the image carrier motor alone. When it is determined that the speed is not accelerated / decelerated together with the rotation speed of the intermediate transfer body motor, the synchronization switching circuit sends the image carrier motor control circuit to the image carrier motor control circuit based on a control signal that matches the characteristics of the rotation speed curve. The rotation may be controlled.

  In the embodiment of the present invention, the printer is configured to include each unit. However, a program that realizes each unit may be stored in a storage medium, and the storage medium may be provided. In the above configuration, the program is read by the printer, and the printer implements the above-described units. In that case, the program itself read from the recording medium exhibits the effects of the present invention. Furthermore, it is also possible to provide a storage method for storing the steps executed by each means in a hard disk.

  As described above, the image forming apparatus according to the present invention is useful not only for a printer, but also for a copying machine, a multi-function machine, and the like, and is capable of appropriately switching the rotation control of the photosensitive drum synchronized with the rotation of the transfer belt. It is effective as a forming apparatus.

1 is a conceptual diagram illustrating an overall configuration inside a printer according to an embodiment of the present invention. FIG. 2 is a diagram illustrating details of an image forming unit according to an embodiment of the present invention. It is a figure which shows the structure of the control system hardware of the invention which concerns on embodiment of this invention. 1 is a diagram illustrating a mechanical configuration of a printer according to an embodiment of the present invention. It is a figure which shows the control structure of the DC brushless motor which concerns on embodiment of this invention. FIG. 2 is a functional block diagram of a printer in an embodiment of the present invention. It is a flowchart for showing the execution procedure of embodiment of this invention. It is a figure which shows an example of the synchronous switching table which concerns on embodiment of this invention. It is a figure which shows an example of a time-dependent change of the frequency of the control signal of the stepping motor which concerns on embodiment of this invention, and the frequency of the encoder pulse of DC brushless motor. It is a figure which shows an example of the acceleration or deceleration rotational speed curve which concerns on embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Printer 601 Communication means 602 Image formation means 603 Stepping motor control means 604 DC brushless motor control means 605 Target speed calculation means 606 Feedback control means 607 Current rotation speed calculation means 609 PWM means 610 Drive pulse input means 611 Motor synchronization discrimination means 612 Synchronization Switching means 613 Synchronous switching storage means 614 Rotational speed curve storage means

Claims (2)

An intermediate transfer body motor control means for controlling the rotation of the intermediate transfer body motor based on a control signal which is a pulse signal for controlling the rotation of the motor, and an image carrier motor control signal synchronized with the control signal of the intermediate transfer body motor. And an image carrier motor control means for controlling the acceleration / deceleration of the rotation of the image carrier motor according to the acceleration / deceleration of the rotation of the intermediate transfer motor.
A motor synchronization determining means for determining whether to accelerate or decelerate the rotational speed of the image carrier motor together with the rotational speed of the intermediate transfer body motor when accelerating or decelerating the rotational speed of the image carrier motor;
When the motor synchronization determining means determines that the rotation speed of the image carrier motor is accelerated and decelerated together with the rotation speed of the intermediate transfer body motor, the image carrier motor control means sends the rotation of the image carrier motor to the rotation of the intermediate transfer body motor. Synchronization switching means for synchronizing
An image forming apparatus comprising: Furthermore, a rotation speed curve storage means for storing a rotation speed curve indicating a change over time in the characteristics of the control signal when accelerating / decelerating the image carrier motor alone is provided,
When the motor synchronization determining means determines that the rotation speed of the image carrier motor is not accelerated / decelerated together with the rotation speed of the intermediate transfer body motor, the synchronization switching means sends the image carrier motor control means the characteristics of the rotation speed curve. The image forming apparatus according to claim 1, wherein the rotation of the image carrier motor is controlled on the basis of a control signal matched with the image forming apparatus.

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