JP2010066447A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printer which makes deceleration start time of rotation of a transfer belt agree with that of rotation of a photoreceptor drum with high accuracy. <P>SOLUTION: The printer 100 includes a timing changing means 616 which makes a stepping motor control means 603 decelerate rotation of a stepping motor 402a after it makes a DC brushless motor control means 604 synchronize the rotation of a DC brushless motor 4041a with the rotation of the stepping motor 402a when a motor synchronism discrimination means 611 discriminates that rotational speed of the DC brushless motor 4041a is decreased together with 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 accurately matching a deceleration start point of rotation of a transfer belt with a deceleration start point of rotation of a photosensitive drum.

  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. There is sex. 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. In addition, 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 startup and at the time of startup.

  Specifically, when the rotation of the photosensitive drum is decelerated / stopped along with the rotation of the transfer belt, the response time is faster than when the speed is increased, and the transfer belt rotation deceleration start time (or stop time) And the deceleration start point (or stop point) of the rotation of the photosensitive drum is likely to deviate. Therefore, due to the deviation, sliding of the surface of the photosensitive drum and the surface of the transfer belt, wear, and three-color (four-color) toner images developed on the separate photosensitive drums are positioned on the transfer belt at appropriate positions. This causes a secondary problem that it is impossible to prevent color misregistration, which is a phenomenon that is not transferred to the surface.

  For example, the technique described in Patent Document 1 is not a technique that synchronizes the rotation of the photosensitive drum (supporting body) and the transfer belt (intermediate transfer body). There is a problem that it is difficult to decelerate and stop the rotation. Further, since the rotation of the motor for rotating the photosensitive drum is controlled by feedback control, and it is generally difficult to control the rotation at the time of falling by the feedback control, the transfer belt rotation deceleration start time (or stop time) It is further difficult to match the deceleration start point (or stop point) of the rotation of the photosensitive drum.

  As another technique, stepping motor control means for controlling the rotation of the stepping motor based on a control signal that is a pulse signal for controlling the rotation of the motor, and acceleration / deceleration of the rotation of the stepping motor based on the control signal of the stepping motor In response to this, image forming apparatuses having DC brushless motor control means for controlling acceleration / deceleration of rotation of the DC brushless motor have appeared. However, in the image forming apparatus, predetermined calculation processing or the like is applied to the control signal of the stepping motor. There is a problem that the calculation processing time, the control signal communication time, etc. are likely to occur, and the motor rotation control delay and communication delay are likely to occur.

  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 the transfer belt rotation decelerating start time and the photosensitive drum rotation decelerating start. An object of the present invention is to provide an image forming apparatus capable of matching the time point with high accuracy.

  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 provided with a carrier motor control unit is assumed.

  In the image forming apparatus, when a signal to accelerate or decelerate the rotation of the intermediate transfer body motor or the image carrier motor is received, it is determined whether or not the rotation speed of the image carrier motor is reduced together with the rotation speed of the intermediate transfer body motor. When the motor synchronization determination means for determining and the motor synchronization determination means determine that the rotation speed of the image carrier motor is reduced together with the rotation speed of the intermediate transfer body motor, the rotation of the intermediate transfer body motor is transmitted to the image carrier motor control means. After the rotation of the image carrier motor is synchronized, the intermediate transfer body motor control means includes a timing changing means for decelerating the rotation of the intermediate transfer body motor.

  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 a signal indicating acceleration / deceleration of the rotation of the intermediate transfer body motor or the image carrier motor is received, a method 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 is: For example, there is a method of detecting and discriminating a control signal input to the intermediate transfer body motor control means 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, frequency, HI signal, or LOW signal.

  As another method, for example, information indicating the driving state of the image forming apparatus and information indicating whether the rotation speed of the image carrier motor is accelerated or decelerated together with the rotation speed of the intermediate transfer body motor are stored in association with each other. A storage means is prepared. 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.

  The information indicating the driving state of the image forming apparatus includes, for example, a sleep state indicating a power saving state, a state where an image can be formed, a color printing state indicating a color printing state, a monochrome printing state indicating a monochrome printing state, and three colors Examples include a released state and a three-color drive state.

  In addition, the timing changing unit synchronizes the rotation of the image carrier motor with the rotation of the intermediate transfer member motor, and the timing changing time, which is the time required for the synchronization, has elapsed. After the detection, the intermediate transfer body motor control means can be configured to decelerate the rotation of the intermediate transfer body motor.

  According to the image forming apparatus of the present invention, when the motor synchronization determining means determines that the rotation speed of the image carrier motor is reduced together with the rotation speed of the intermediate transfer body motor, the rotation of the intermediate transfer body motor is transmitted to the image carrier motor control means. After the rotation of the image carrier motor is synchronized, the intermediate transfer body motor control means is provided with a timing changing means for decelerating the rotation of the intermediate transfer body motor.

  Thus, when the intermediate transfer member motor control means decelerates the rotation of the intermediate transfer member motor, the image carrier motor already synchronized with the rotation of the intermediate transfer member motor also simultaneously decelerates the rotation. Therefore, when switching the rotation of the image carrier motor to deceleration, generation of communication time (communication delay) required for exchange of control signals, generation of processing time required for predetermined arithmetic processing, control delay of rotation of the image carrier motor Therefore, it is possible to prevent the occurrence of a deviation between the synchronization start time of the image carrier motor, that is, the deceleration start time of the image carrier motor and the deceleration start time of the intermediate transfer body motor. Furthermore, it is possible to decelerate the image carrier motor together with the intermediate transfer body motor on the condition that the deceleration start time of the image carrier motor and the deceleration start time of the intermediate transfer body motor substantially coincide with each other. It becomes possible to stop the body at the same time. As a result, it is possible to appropriately prevent sliding, wear, and color misalignment between the surface of the intermediate transfer member and the surface of the image carrier caused by the misregistration.

  Further, after the timing changing means detects that the timing change time has elapsed since the image carrier motor control means synchronizes the rotation of the image carrier motor with the rotation of the intermediate transfer body motor, the intermediate transfer body The motor control means can be configured to decelerate the rotation of the intermediate transfer member motor.

  As a result, the image carrier motor control means synchronizes the rotation of the intermediate transfer body motor with the rotation of the intermediate transfer body motor, and then the intermediate transfer body motor control means immediately decelerates the rotation of the intermediate transfer body motor. Therefore, it is possible to smoothly reduce the rotational speed of the image carrier motor together with the rotational speed of the intermediate transfer body motor without causing unnecessary waiting time.

  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 4041a 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 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. Switching to a 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, with reference to FIG. 6 to FIG. 7, a description will be given of a procedure in which the image forming apparatus of the present invention matches the transfer belt rotation decelerating start time with the photosensitive drum rotation decelerating start time with high accuracy. 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. In the following, the procedure for the printer to enter the sleep state will be described, but the same applies to the procedure for the user to turn off the power and enter the stop state.

  First, rotation control of the stepping motor 402a and rotation control of the DC brushless motor 4041a when the printer 100 is in a state where image formation is possible will be described.

  The stepping motor control means 603 that controls the rotation of the stepping motor 402a receives a control signal (in FIG. 4) that corresponds to the rotational speed (constant speed A) at which the image forming means 602 can form an image. Therefore, the stepping motor control unit 603 maintains the rotational speed of the stepping motor 402a at the steady speed A. The frequency of the maintenance signal A is constant, and the maintenance signal A is input to the target speed calculation means 605 that constitutes the DC brushless motor control means 604 due to the configuration of the printer.

  On the other hand, the DC brushless motor control unit 604 maintains the rotation of the DC brushless motor 4041a based on the rotation speed (the steady speed B) that can be formed by the DC brushless motor 4041a transmitted by the image forming unit 602. ing.

  Specifically, when the steady speed B is input to the target speed calculation means 605 constituting the DC brushless motor control means 604, the target speed calculation means 605 calculates the target speed (based on the maintenance signal A ( The steady speed B is reset (switched) as a target value from the previously set target speed) and transmitted to the feedback control means 606.

  The feedback control means 606 that has received the steady speed B 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 and the steady speed B, which are calculated by feedback pulses (described later). Then, the control value is transmitted to the PWM means 609.

  The calculation of the control value will be briefly described below.

  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.

  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 4041a.

  Upon receiving the current rotational speed and the steady speed B, the feedback control means 606 calculates a speed difference between the steady speed B and the current rotational speed, and corresponds to the speed difference and the steady speed of the DC brushless motor 4041a. Based on the control parameters (“Kp”, “Kd”, “Ki”), a proportional control value, a differential control value, and an integral control value (hereinafter referred to as a control value) are calculated (FIG. 7: S106).

  The control parameter is determined based on PID control that controls the current rotational speed to converge to the steady speed B (which is also the target speed, that is, the target value) by combining proportional control, integral control, and differential control. Parameter.

  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 steady speed B and the current rotational speed, and 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. (Also referred to as a differential constant).

  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.

  Note that both the current rotational speed and the steady speed correspond to numerical values (data), and the feedback control means 606 calculates a control value based on the numerical values. Therefore, it should be noted that a phase comparator or the like used for rotation control of the DC brushless motor 4041a has not been conventionally used.

  When the control value is calculated, the Fordback control unit 606 transmits the control value to the PWM unit 609. The PWM means 609 generates a PWM signal based on the control value and inputs it to the drive pulse input means 610. The drive pulse input unit 610 inputs a drive pulse corresponding to the control value to the DC brushless motor 4041a based on the PWM signal. The rotation of the DC brushless motor 4041a is maintained.

  Next, the control procedure of the present invention will be described.

  For example, when a sleep time, which is a waiting time until the transition from the image formable state to the sleep state (stopped state) elapses, the image forming unit 602 transitions from the image formable state to the sleep state.

  When transitioning to the sleep state, the image forming unit 602 corresponds to a control signal indicating transition to the sleep state (a signal or instruction signal indicating acceleration / deceleration of the rotation of the stepping motor 402a or the DC brushless motor 4041a, and the sleep state Is transmitted to the motor synchronization determination means 611 (FIG. 7: S101).

  When receiving the sleep state transition instruction signal, the motor synchronization determination unit 611 refers to the motor synchronization table stored in the motor synchronization storage unit 615 and decelerates the rotation speed of the DC brushless motor 4041a together with the rotation speed of the stepping motor 402a. It is determined whether or not to perform (FIG. 7: S102).

  In the motor synchronization table 800, as shown in FIG. 8, a command item 801 (“color printable” is an item indicating the content of a control signal (command signal) transmitted from the image forming unit 602 to the motor synchronization determining unit 611. State "802," sleep state (stop state) "803," three-color release state "804," three-color drive state "805, etc.), and the rotational speed of the DC brushless motor 4041a along with the rotational speed of the stepping motor 402a Information 806 (“Accelerate together” 807, “Decelerate together” 808, “Accelerate DC brushless motor” 809, “Decelerate DC brushless motor” 810, etc.) indicating whether or not to perform is stored in association with each other. .

  For example, “Color printing is possible” indicating that the photosensitive drums corresponding to yellow, magenta, cyan, and black are all rotated from a stopped state (sleep state) to a state in which color printing can be performed (image forming state). “None state” 802 stores “accelerate together” 807 indicating that the rotational speed of the DC brushless motor 4041a is accelerated together with the rotational speed of the stepping motor 402a.

  Further, in the “sleep state (stop state)” 803 indicating the transition from the image formable state to the sleep state (stop state), the rotation speed of the DC brushless motor 4041a is decelerated together with the rotation speed of the stepping motor 402a. “Decelerate together” 808 is stored in association with each other.

  Further, from the state where image formation is possible, the photosensitive drums corresponding to yellow, magenta, and cyan are shifted to a stopped state, and the state is shifted to a state where only the photosensitive drum corresponding to black is rotated (a state where monochrome printing is possible). In the “three-color release state” 804 indicating this, “DC brushless motor deceleration” 809 indicating that only the rotational speed of the DC brushless motor 4041a is decelerated is stored in association.

  Further, in the “three-color drive state” 805 indicating that the photosensitive drums corresponding to yellow, magenta, and cyan are rotated from the three-color release state to shift to a state where color printing is possible, the rotation of the DC brushless motor 4041a is performed. “Acceleration of DC brushless motor” 810 indicating that only the speed is accelerated is stored in association.

  With the above configuration, the motor synchronization determination unit 611 is configured to rotate the DC brushless motor 4041a together with the rotation speed of the stepping motor 402a based on the control signal (command signal) input from the image forming unit 602 and the motor synchronization table 800. It is possible to determine whether or not to decelerate.

  The three-color release state corresponds to, for example, a shift from the color print mode to the monochrome print mode, and the three-color drive state corresponds to a shift from the monochrome print mode to the color print mode.

  Hereinafter, 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 4041a. The same applies to the rotation of. Note that the rotation of the photosensitive drum corresponding to black and the DC brushless motor 4041a needs to maintain the rotation in the “three-color release state” and the “three-color drive state”. Information indicating that the rotation speed is maintained (for example, “−”) is stored in association with the “color release state” 804 and the “three-color drive state” 805.

  The motor synchronization determination unit 611 reduces the rotation speed of the DC brushless motor 4041a together with the rotation speed of the stepping motor 402a based on the “sleep state (stop state)” 803 corresponding to the sleep state transition instruction signal and the motor synchronization table 800. If it is discriminated, the discrimination result is transmitted to the timing changing means 616 (FIG. 7: S103 YES).

  The timing changing unit 616 that has received the determination result causes the DC brushless motor control unit 604 to synchronize the rotation of the DC brushless motor 4041a with the rotation of the stepping motor 402a, and then causes the stepping motor control unit 603 to rotate the stepping motor 402a. Decelerate.

  Specifically, the timing changing unit 616 transmits a control signal (synchronization instruction signal) for synchronizing the rotation of the DC brushless motor 4041a to the rotation of the stepping motor 402a to the image forming unit 602 (FIG. 7: S104). .

  Upon receiving the synchronization instruction signal, the image forming unit 602 sends a signal (calculation signal B) (in FIG. 4, a calculation instruction) to the target speed calculation unit 605 constituting the DC brushless motor control unit 604 to calculate the target speed. Control signal B) is transmitted (FIG. 7: S105).

  Note that when the image forming unit 602 transmits the calculation signal B to the target speed calculation unit 605, the stepping motor control unit 603 controls the rotation while maintaining the rotation speed of the stepping motor 402a at the steady speed A. It becomes a state. In other words, since the image forming unit 602 inputs the control signal (maintenance signal A) corresponding to the steady speed A to the stepping motor control unit 603, the maintenance signal A is At the same time as the stepping motor control means 603, the target speed calculation means 605 is input.

  Therefore, 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 maintenance signal A and resets the target speed from the steady speed B set as the target value (switching). The rotation of the DC brushless motor 4041a is controlled.

  The procedure from calculating the target speed to controlling the rotation of the DC brushless motor 4041a is 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 sustain signal A input from the image forming unit 602, and the number of internal timer pulses existing per one pulse of the sustain signal A is counted. This counted number is defined as a stepping motor count number Na.

  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. Therefore, the value obtained by multiplying the count number Na by the speed coefficient is a value obtained by converting the rotation speed at which the image forming of the stepping motor 402a can be performed into the rotation speed at which the DC brushless motor 4041a can perform image formation, and is calculated based on the maintenance signal A. It is understood that the set target speed becomes a value (or approximate value) that matches the steady speed B of the DC brushless motor 4041a.

  The speed coefficient depends on, for example, the number of rotations (rpm) of the motor corresponding to the rotation speed of the motor and the frequency (Hz) of the control signal (corresponding to the above-mentioned maintenance signal and instruction clock signal) input to the motor control means. It is determined. 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.

  When the target speed calculation unit 605 calculates the target speed, the target speed is transmitted to the feedback control unit 606. Upon receiving the target speed, the feedback control means 606 calculates a speed difference between the target speed and the current rotational speed input from the current rotational speed calculation means 607, and responds to the target speed based on the speed difference. A control value corresponding to the control parameter (“Kp”) to be calculated is calculated.

  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 the control value so that the current rotational speed follows the target speed of the DC brushless motor 4041a as needed, and the PWM means 609, The DC brushless motor control means 604 inputs the drive pulse to the DC brushless motor 4041a via the drive pulse input means 610, and the rotational speed of the DC brushless motor 4041a is maintained.

  Therefore, as will be described later, even if the maintenance signal A input to the target speed calculation means 605 is switched to a signal (deceleration signal A) for decelerating the rotation speed of the stepping motor 402a, the DC brushless motor 4041a It is possible to prevent an undershoot phenomenon, which is a phenomenon in which the rotation speed is significantly larger than the target rotation speed.

  Here, it is possible to form an image of the DC brushless motor 4041a based on the maintenance signal A (“control signal used for rotation control of the stepping motor 402a during steady rotation”) input to the stepping motor control means 603. Since the drive pulse corresponding to the rotational speed (corresponding to the “encoder pulse generated from the encoder 507 of the DC brushless motor 4041a during steady rotation”) of the speed coefficient is input to the DC brushless motor 4041a, naturally the DC brushless Note that the motor 4041a maintains a steady speed B (rotation speed at which image formation is possible).

  In the above-described procedure, until the timing changing unit 616 transmits a signal (deceleration instruction signal) indicating that the rotation speed of the stepping motor 402a is reduced to the image forming unit 602, the target speed calculating unit 605, the feedback control unit 606, and the like. Will be repeated. That is, when the image forming unit 602 continues to input the maintenance signal A to the target speed calculating unit 605 together with the stepping motor control unit 603, the target speed calculating unit 605 can rotate the rotation speed (steady speed A) of the stepping motor 402a. The target speed of the DC brushless motor 4041a synchronized with () 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) corresponding to the rotational speed (steady speed B) at which the DC brushless motor 4041a can form an image. Command signal). As a result, the drive pulse input means 610 maintains the rotational speed of the DC brushless motor 4041a at a rotational speed at which image formation is possible.

  Thereby, before the rotational speed of the stepping motor 402a is decelerated, the surface linear speed of the photosensitive drum 10Y rotated by the DC brushless motor 4041a is synchronized with the surface linear speed of the transfer belt rotated by the stepping motor 402a. Thus, the rotational speed of the DC brushless motor 4041a can be maintained at a rotational speed at which an image can be formed.

  In the area A1 of FIG. 9A, the frequency of the control signal (maintenance signal A) input to the stepping motor control unit 603 when the image forming unit 602 transmits the calculation signal B to the target speed calculation unit 605, and DC The time-dependent change with the frequency of the encoder pulse of the brushless motor 4041a is shown. The time point when the image forming unit 602 transmits the calculation signal B corresponds to the time point when the target speed calculation unit 605 switches the target value from the steady speed B to the target speed, and this time point is indicated by a switching time point a.

  As can be seen from the area A1 in FIG. 9A, before and after the switching time point a, the frequency of the encoder pulse of the DC brushless motor 4041a is a speed coefficient (a = B / A) with respect to the frequency of the maintenance signal A of the stepping motor 402a. It is understood that it is maintained. This is because a target speed is calculated based on the maintenance signal A, and a drive pulse corresponding to the target speed is input to the DC brushless motor 4041a.

  Prior to the switching time point a, the feedback control means 606 employs control parameters (“Kp”, “Kd”, “Ki”) for making the current rotational speed coincide with the steady speed, and calculates a control value. On the other hand, after the switching time point a, the control value (“Kp”) for causing the current rotational speed to follow the target speed is adopted to calculate the control value. For this reason, the frequency of the encoder pulse of the DC brushless motor 4041a is substantially constant before the switching time point a, but has a slightly varied value (having fluctuations by a predetermined width) after the switching time point a. Note that it is maintained and slightly lacks stability.

  The timing change means 616 is a time preset by the user or the like, and the DC brushless motor control means 604 is a time required for the DC brushless motor 4041a to synchronize with the rotation of the stepping motor 402a. A timer circuit is provided for detecting the passage of time. Therefore, after the DC brushless motor control unit 604 detects that the timing change time has elapsed since the transmission of the synchronization instruction signal to the image forming unit 602, the image forming unit 602 reduces the rotational speed of the stepping motor 402a. A signal to this effect (deceleration instruction signal) is transmitted (FIG. 7: S106 → S107).

  In this way, the timing changing unit 616 transmits control signals (corresponding to the control signal A and the control signal B in FIG. 4) that the image forming unit 602 transmits to the stepping motor control unit 603 or the DC brushless motor control unit 604. Control is executed.

  The image forming unit 602 that has received the deceleration instruction signal receives a signal (deceleration signal A) indicating that the rotation speed of the stepping motor 402a is to be reduced from the maintenance signal A that has been transmitted so far (in FIG. 4, control of the deceleration instruction). The deceleration signal A is transmitted to the stepping motor control means 603.

  When receiving the deceleration signal A, the stepping motor control means 603 starts decelerating the rotation of the stepping motor 402a (FIG. 7: S108).

  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 continuously (stepwise) decreases the frequency of the deceleration signal A until the current rotational speed of the stepping motor 402a reaches the stop speed.

  As described above, since the control signal A output from the image forming unit 602 is input to the target speed calculating unit 605 simultaneously with the stepping motor control unit 603, the image forming unit 602 outputs the maintenance signal A to the deceleration signal A. At the same time, the deceleration signal A is input to the stepping motor control means 603 and the target speed calculation means 605.

  Since the target speed calculation means 605 has already calculated the control value based on the input maintenance signal A, the target speed calculation means 605 switches from the maintenance signal to the deceleration signal, and at the same time, based on the deceleration signal. The control value is calculated. Therefore, for example, the deceleration signal is input to the stepping motor control unit 603 at the same time as the communication speed of the calculation signal received by the target speed calculation unit 605 or the control delay caused by communication exchange does not occur. The calculating means 605 calculates the target speed corresponding to the deceleration signal.

  Further, the feedback control means 606 calculates a control value based on the speed difference between the target speed and the current rotation speed and the control parameter corresponding to the deceleration, and as a result, the PWM means 609, the drive pulse input means Via 610, a drive pulse for reducing the rotational speed of the DC brushless motor 404a is input to the DC brushless motor 404a.

  The DC brushless motor 404a reduces rotation based on the input drive pulse. It should be noted that the occurrence of undershoot phenomenon is suppressed by the control parameter corresponding to the deceleration.

  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 stop speed (stop state) of the stepping motor 402a. That is, when the image forming unit 602 continuously reduces the frequency of the deceleration signal A to the frequency of the control signal corresponding to the stop state (the control signal at the time of start-up set in the initial stage of the stepping motor 402a), the decrease is made. Corresponding to the minute, the target speed calculating means 605 calculates the target speed of the DC brushless motor 4041a synchronized with the rotation of the stepping motor 402a, and the feedback control means 606 is a speed between the target speed and the current rotational speed. A control value is calculated based on the difference and a predetermined control parameter. The PWM signal converted based on the calculated control value becomes a clock signal whose duty continuously decreases 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 stepping motor control means 603 finishes decelerating the rotation speed of the stepping motor 402a, that is, when the rotation speed of the stepping motor 402a reaches the stop speed, DC brushless motor control is performed corresponding to the arrival time (stop time). The means 604 finishes reducing the rotational speed of the DC brushless motor 404a. That is, the stop time of the stepping motor 402a substantially coincides with the stop time of the DC brushless motor 4041a, the transfer belt and the photosensitive drum stop simultaneously, and the printer 100 shifts to the sleep state (FIG. 5: S109). ).

  In a region A2 of FIG. 9A, a control signal (input to the stepping motor control unit 603 when the stepping motor control unit 603 receives the deceleration signal A and shifts to a sleep state (stopped state) (when stopped) ( The change with time of the frequency of the deceleration signal A) and the frequency of the encoder pulse of the DC brushless motor 4041a is shown. Note that the time when the stepping motor control unit 603 receives the deceleration signal is the time when the image forming unit 602 switches from the maintenance signal A to the deceleration signal (the image forming unit 602 calculates the deceleration signal with the stepping motor control unit 603 and the target speed calculation). Corresponding to the point of time of transmission to the means 605, and this point of time is indicated by the switching point of time b.

  As can be seen from the area A2 in FIG. 9A, when the frequency of the control signal input to the stepping motor control means 603 decreases at the switching time point b, simultaneously with the decrease, the frequency of the encoder pulse of the DC brushless motor 4041a decreases. Yes. Further, the frequency of the encoder pulse of the DC brushless motor 4041a is decelerated while maintaining the speed coefficient (a = B / A) with respect to the frequency of the deceleration signal A of the stepping motor 402a, in other words, the DC brushless motor 4041a. It is understood that the rotation of the DC brushless motor 4041A and the stepping motor 402a are stopped (zero) almost simultaneously, in synchronization with the rotation of the stepping motor 402a. Therefore, the rotational speeds of the stepping motor 402a and the DC brushless motor 4041a are decelerated in a state where the surface linear velocity of the transfer belt B1 and the surface linear velocity of the photosensitive drum 10Y coincide with each other, and further, the stepping motor 402a and the DC brushless motor 4041a is stopped simultaneously. There is no undershoot phenomenon.

  For reference, a conventional control procedure will be described.

  In FIG. 9B, when the sleep time has elapsed, the image forming unit 602 transmits the deceleration signal A to the stepping motor control unit 603 and the target speed calculation unit 605, and further, the calculation signal B is transmitted to the target speed calculation unit 605. 6 shows the change with time of the frequency of the control signal (deceleration signal A) input to the stepping motor control means 603 and the frequency of the encoder pulse of the DC brushless motor 4041a when transmitted to the stepping motor. In FIG. 9B, assuming that the image forming unit 602 transmits the deceleration signal and the calculation signal at the same time, the time point at which the image forming unit 602 transmits the signal simultaneously is indicated by a transmission time point c.

  As can be seen from FIG. 7B, the frequency of the control signal input to the stepping motor control means 603 starts to decrease immediately from the transmission time point c, but the frequency of the encoder pulse of the DC brushless motor 4041a is It is understood that the decrease starts after elapse of a predetermined time (for example, usually a time of tens of milliseconds, hereinafter referred to as a delay time) from c.

  This is because the stepping motor control means 603 controls the rotation of the stepping motor 402a by a control signal, whereas the DC brushless motor control means 604 controls the rotation of the DC brushless motor 4041a based on feedback control. It is due to that. That is, in the rotation control of the DC brushless motor 4041a, as described above, the procedure (process) in which the target speed calculation unit 605 calculates the target speed based on the deceleration signal, and the Fordback control unit 606 uses the target speed and the current rotation speed. It is necessary to perform a procedure (process) or the like for calculating a control value based on the above, and exchange of control signals corresponding to the procedure (process), the number of processes, and a calculation time occur. As a result, the DC brushless motor 4041a The frequency of the encoder pulse starts to decrease after the delay time has elapsed.

  When the delay time occurs, there is a difference between the deceleration start time of the DC brushless motor 4041a (photosensitive drum rotation start time) and the deceleration start time of the stepping motor 402a (transfer belt rotation start time). Therefore, the difference causes a difference between the stop time of the DC brushless motor 4041a (stop time of rotation of the photosensitive drum) and the stop time of the stepping motor 402a (stop time of rotation of the transfer belt). As a result, the stop position of the photosensitive drum or the stop position of the transfer belt does not stop at a preset position, causing a positional shift between the transfer belt and the photosensitive drum. Surface sliding, wear and color shift will occur.

  As shown in FIG. 9B, after the frequency of the control signal input to the stepping motor control means 603 becomes zero (after the stepping motor 402a is stopped), the DC brushless motor 4041a is delayed by almost a delay time. It is understood that the frequency of the encoder pulse is zero (the DC brushless motor 4041a is stopped).

  As described above, when the motor synchronization determining means determines that the rotation speed of the DC brushless motor is reduced together with the rotation speed of the stepping motor, the DC brushless motor control means causes the rotation of the DC brushless motor to be synchronized with the rotation of the stepping motor. The stepping motor control means includes a timing changing means for decelerating the rotation of the stepping motor.

  Thereby, when the stepping motor control means decelerates the rotation of the intermediate transfer body motor, the DC brushless motor already synchronized with the rotation of the stepping motor also decelerates the rotation at the same time. Therefore, when switching the rotation of the DC brushless motor to deceleration, the occurrence of communication time (communication delay) required for exchange of control signals, the generation of processing time required for predetermined calculation processing, and the control delay of rotation of the DC brushless motor are eliminated. Thus, it is possible to prevent the occurrence of deviation between the synchronization start time of the DC brushless motor, that is, the deceleration start time of the DC brushless motor and the deceleration start time of the stepping motor. Furthermore, it is possible to decelerate the DC brushless motor together with the stepping motor under the condition that the deceleration start time of the DC brushless motor and the deceleration start time of the stepping motor substantially coincide, and the transfer belt and the photosensitive drum are stopped simultaneously. Is possible. As a result, it is possible to appropriately prevent sliding, wear and color misalignment between the transfer belt surface and the photosensitive drum surface caused by the misregistration.

  Further, after the timing changing means detects that the timing change time has elapsed since the DC brushless motor control means synchronizes the rotation of the DC brushless motor with the rotation of the stepping motor, the stepping motor control means It can be configured to decelerate the rotation of the motor.

  As a result, the DC brushless motor control means synchronizes the rotation of the DC brushless motor with the rotation of the stepping motor, and the stepping motor control means immediately decelerates the rotation of the stepping motor. It is possible to smoothly reduce the rotational speed of the DC brushless motor together with the rotational speed of the stepping motor without generating time.

  In the above description, the control when the motor synchronization determination unit 611 reduces the rotation speed of the DC brushless motor 4041a together with the rotation speed of the stepping motor 402a, that is, when the sleep state transition instruction signal is received from the image forming unit 602. Although it becomes a procedure, about other procedures, it is controlled as follows, for example.

  In the sleep state (or stopped state), when the image forming unit 602 transmits a control signal (image formation shift instruction signal) for shifting to a color printable state (image formable state) to the motor synchronization determination unit 611. (FIG. 7: S101), the motor synchronization determination unit 611 determines the DC brushless motor together with the rotation speed of the stepping motor 402a based on the “color printable state” 803 corresponding to the image formation transition instruction signal and the motor synchronization table 800. It is determined that the rotational speed of 4041a is to be accelerated (FIG. 7: S102 → S103NO).

  When the motor synchronization determination unit 611 transmits the determination result to the timing change unit 616, the motor synchronization determination unit 611 accelerates the rotation of the stepping motor 402a, and causes the DC brushless motor control unit 604 to rotate the DC brushless motor 4041a to the rotation of the stepping motor 402a. Synchronize.

  Specifically, the timing changing unit 616 transmits a signal (acceleration instruction signal) for accelerating the rotation speed of the stepping motor 402a to the image forming unit 602, and then the DC brushless motor 4041a is rotated to rotate the stepping motor 402a. A signal (synchronization instruction signal) is transmitted to synchronize the rotation (FIG. 7: S110).

  Then, after the image forming unit 602 transmits a signal (acceleration signal A) for accelerating the rotation speed of the stepping motor 402a to the stepping motor control unit 603, the calculation signal B, the steady speed B, and the target speed calculation unit 605 are transmitted. After the rotation of the stepping motor 402a is accelerated, the DC brushless motor control means 604 can synchronize the rotation of the DC brushless motor 4041a with the rotation of the stepping motor 402a (FIG. 7: S111).

  Further, when the image forming unit 602 transmits a control signal (three-color release instruction signal) to shift to the monochrome printing enabled state to the motor synchronization determining unit 611 in the color printing enabled state, the motor synchronization determining unit 611 Based on the “three-color release state” 803 corresponding to the three-color release instruction signal and the motor synchronization table 800, only the rotational speed of the DC brushless motor 4041a corresponding to the three colors (yellow, magenta, cyan) is decelerated. Is determined.

  When the motor synchronization determination unit 611 transmits the determination result to the timing change unit 616 (FIG. 7: S101), the DC brushless motor control unit 604 corresponding to the three colors decelerates and stops the rotation speed of the DC brushless motor 4041a. (FIG. 7: S102 → S103NO).

  When transmitting the determination result to the timing changing unit 616, the motor synchronization determining unit 611 causes the DC brushless motor control unit 604 corresponding to the three colors to decelerate the rotation speed of the DC brushless motor 4041a.

  Specifically, the timing changing unit 616 transmits a signal (deceleration instruction signal) for decelerating the rotation speed of the DC brushless motor 4041a corresponding to the three colors to the image forming unit 602 (FIG. 7: S110). Then, the image forming unit 602 transmits a signal indicating that the rotational speed of the DC brushless motor 4041a is decelerated (deceleration signal B) or a stop speed of the DC brushless motor 4041a to the target speed calculating unit 605, and three colors (yellow, Only the rotational speed of the DC brushless motor 4041a corresponding to magenta and cyan) is decelerated and stopped, and the state is shifted to a three-color release state (a state capable of monochrome printing) (FIG. 7: S111). In this case, the image forming unit 602 transmits the maintenance signal A to the stepping motor control unit 603.

  In a state where monochrome printing is possible, when the image forming unit 602 transmits a control signal (three-color drive instruction signal) for shifting to the three-color drive state to the motor synchronization determination unit 611 (FIG. 7: S101), the motor The synchronization determination unit 611 rotates the DC brushless motor 4041a corresponding to the three colors (yellow, magenta, cyan) based on the “three-color drive state” 803 corresponding to the three-color drive instruction signal and the motor synchronization table 800. It is determined that only acceleration is performed (FIG. 7: S102 → S103NO).

  When the motor synchronization determination unit 611 transmits the determination result to the timing change unit 616, the DC brushless motor control unit 604 corresponding to the three colors accelerates the rotational speed of the DC brushless motor 4041a.

  Specifically, the timing changing unit 616 transmits a signal (acceleration instruction signal) for accelerating the rotation speed of the DC brushless motor 4041a corresponding to the three colors to the image forming unit 602 (FIG. 7: S110). Then, the image forming unit 602 transmits a signal indicating that the rotational speed of the DC brushless motor 4041a is accelerated (acceleration signal B) and the steady speed B to the target speed calculating unit 605, and three colors (yellow, magenta, cyan) are transmitted. Only the rotational speed of the DC brushless motor 4041a corresponding to () is accelerated (FIG. 7: S111). In this case as well, the image forming unit 602 transmits the maintenance signal A to the stepping motor control unit 603.

  In this way, before the image forming unit 602 transmits a control signal to the stepping motor control unit 603 or the DC brushless motor control unit 604, the motor synchronization determination unit 611 determines whether the intermediate transfer body motor or the image carrier motor is Based on the signal for accelerating and decelerating the rotation and the motor synchronization table 800, it is determined whether or not the rotation speed of the image carrier motor is to be reduced together with the rotation speed of the intermediate transfer body motor. Further, based on the determination result, the timing changing unit 616 controls the control signals (corresponding to the control signal A and the control signal B in FIG. 4) transmitted to the stepping motor control unit 603 or the DC brushless motor control unit. Execute.

  Note that the timing change time of the embodiment of the present invention is set as the time required for the DC brushless motor control means to synchronize the rotation of the DC brushless motor with the rotation of the stepping motor. The time may be longer than the above-described delay time, which is the time taken into consideration, and approximate to the delay time. When the time is set, the rotation of the stepping motor is decelerated as soon as the rotation of the DC brushless motor is synchronized with the rotation of the stepping motor, so that the printer can be efficiently stopped.

  Further, in the embodiment of the present invention, the motor synchronization determining means, together with the rotation speed of the stepping motor, is based on a signal (instruction signal) for accelerating / decelerating the rotation of the stepping motor or DC brushless motor transmitted from the image forming means. Although it is configured to determine whether or not to reduce the rotational speed of the DC brushless motor, other configurations may be used.

  For example, the image forming unit adopts a configuration that combines a motor synchronization determination unit and a timing change unit, and a stepping motor acceleration / deceleration control signal that indicates the acceleration / deceleration start time of the stepping motor by a pulse signal HI signal or LOW signal The DC brushless motor acceleration / deceleration control signal indicating the acceleration / deceleration start time of the DC brushless motor with a pulse signal HI signal or LOW signal is sent to the stepping motor control means and the DC brushless motor control means according to the timing change time. Can be configured to transmit to.

  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 when the rotation of the DC brushless motor is stopped. However, for example, the start characteristic of the DC brushless motor (for example, the equipped gear, etc.) The differential control parameter “calculates (outputs) the differential control value according to the differential value obtained by differentiating the speed difference between the target speed of the DC brushless motor and the current rotational speed according to the member, radius, circumference, specifications, etc. "Kd" may be further added and employed.

  In the embodiment of the present invention, the DC brushless motor control means uses a predetermined control parameter, and the rotational speed of the DC brushless motor corresponding to the differential speed between the current rotational speed and the target speed (steady speed B). For example, before generating the drive pulse, the feedback control means constituting the DC brushless motor control means is supplied with a proportional control value (hereinafter referred to as a proportional control value) calculated with a predetermined control parameter. A process for determining whether or not the control value belongs to a predetermined range may be provided. The range is determined by whether or not the duty of the drive pulse generated based on the control value belongs to a predetermined range (range from 0 to 100%). The duty (duty ratio) is the ratio of the width of one pulse of the HI signal to the period of one pulse. With the above configuration, it is possible to stably control the rotational drive.

  Further, in the embodiment of the present invention, the scene in which the state where the image can be formed is shifted to the sleep state has been described. For example, when the printer is turned off or the user issues a command signal corresponding to the stop of the image formation. When the means receives the same, the same applies to a printer having a high-speed printing mode and a normal printing mode and shifting from the high-speed printing mode to the normal printing mode.

  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, a stepping motor control circuit that controls the rotation of the stepping motor based on a control signal that is a pulse signal that controls the rotation of the motor, and a DC brushless according to the acceleration / deceleration of the rotation of the stepping motor based on the control signal of the stepping motor. In an image forming apparatus including a DC brushless motor control circuit for controlling acceleration / deceleration of motor rotation, when a signal to accelerate / decelerate the rotation of the stepping motor or the DC brushless motor is received, the DC brushless motor together with the rotation speed of the stepping motor is received. If the motor synchronization determination circuit for determining whether to reduce the rotation speed of the motor and the motor synchronization determination circuit decelerate the rotation speed of the DC brushless motor together with the rotation speed of the stepping motor, the DC brushless motor control circuit Steppi After synchronizing the rotation of the DC brushless motor to rotation of Gumota, the stepping motor control circuit may be configured and a timing changing circuit for decelerating the rotation of the stepping motor.

  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. This is effective as an image forming apparatus that can be highly matched.

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 acceleration or deceleration rotational speed curve 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.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Printer 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 rotational speed calculation means 609 PWM means 610 Drive pulse input means 611 Motor synchronization determination means 615 Motor synchronization storage means 616 Timing change 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.
When receiving a signal for accelerating / decelerating the rotation of the intermediate transfer body motor or the image carrier motor, motor synchronization determination means for determining whether to reduce the rotation speed of the image carrier motor together with the rotation speed of the intermediate transfer body motor When,
When the motor synchronization determining means determines that the rotation speed of the image carrier motor is 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. After synchronization, the intermediate transfer body motor control means has a timing changing means for decelerating the rotation of the intermediate transfer body motor,
An image forming apparatus comprising:   The timing changing means detects that the timing change time, which is the time required for the synchronization, has elapsed since the image carrier motor control means synchronizes the rotation of the image carrier motor with the rotation of the intermediate transfer body motor. 2. The image forming apparatus according to claim 1, wherein later, the intermediate transfer body motor control means decelerates the rotation of the intermediate transfer body motor.

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