JP5220523B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus, and more particularly to an image forming apparatus capable of preventing scratches and the like that occur between a photosensitive drum and a transfer belt at the time of starting or stopping.

  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 methods, 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 that rotationally drives the image carrier, and a drive motor that rotationally drives the intermediate transfer member, and transfers the toner image transferred to the intermediate transfer member to a recording medium. In the image forming apparatus for obtaining a recorded 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, and when the clock control motor is started up And an image forming apparatus characterized by controlling the rotational speed of the clock control motor in accordance with a predetermined speed curve at least at one time of falling. There has been disclosed.

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.

  Therefore, 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 is generated between the photosensitive drum and the transfer belt at the time of starting or stopping. An object of the present invention is to provide an image forming apparatus capable of preventing scratches and the like.

  In order to solve the above-described problems and achieve the object, an image forming apparatus according to the present invention includes an image carrier motor that transmits rotation to an image carrier on which a toner image is formed based on Fordback control, and a motor. An image forming apparatus including an intermediate transfer member motor that transmits rotation to an intermediate transfer member to which a toner image formed on the image carrier is transferred based on a control signal that is a pulse signal for controlling the rotation of the toner image. .

The image forming apparatus, when accelerating or decelerating the rotational speed of the image carrier motor with the rotational speed of the intermediate transfer member motor, a control signal input to the intermediate transfer member motor, a first time capture circuit Is compared with an internal timer pulse having a stable pulse cycle, and the number of internal timer pulses present per one pulse of the control signal is counted, and the counted number is multiplied by a predetermined speed coefficient. , and the target speed calculating means for calculating the multiplication value as a target speed, and the current rotational speed is the current rotational speed of the image carrier motor calculated by Ford back pulses fed back from the rotation of the image carrier motor the speed difference between the target speed above target speed calculating means is calculated, based on the predetermined control parameter, the image carrier And a feedback control means for controlling the rotation of the over data.

  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.

  If the image carrier motor is a motor that transmits (rotates) rotation based on 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. For example, a motor employing a pulse width modulation (hereinafter referred to as PWM) control method is applicable. 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 body motor may be any motor as long as it transmits (rotates) rotation based on the control signal. For example, when a control signal having a predetermined frequency is input, the intermediate transfer body motor is rotated at predetermined angles. Stepping motors that are rotatable motors are applicable.

  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.

  Examples of a method for calculating the target speed, which is the rotational speed of the image carrier motor synchronized with the rotational speed of the intermediate transfer body motor, based on the control signal include the following methods. 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 into a control signal for the carrier motor and inputting the rotation signal to the image carrier motor based on the control signal.

  For example, a feedback control method such as PID control can be adopted as a method of calculating a control signal synchronized with the control signal of the intermediate transfer body motor based on the current rotation speed and the target speed.

Further, the target speed calculating means, the number of the above counts, by multiplying the speed coefficient which is a ratio of the rotational speed of the image carrier motor for the rotational speed of the intermediate transfer member motor in steady rotation, and the multiplied value It may be configured to calculate a target speed.

  The internal timer pulse (internal timer clock, internal timer clock signal) is obtained by, for example, using a time capture circuit (time capture means) that generates an internal timer pulse with a stable pulse period, Based on the internal timer pulse and the control signal for controlling the rotation of the intermediate transfer body motor, the count number of the control signal can be calculated.

  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.

Further, when the rotational speed of the image carrier motor accelerates to or decelerates the rotation speed of the intermediate transfer member motor, said feedback control means, the control for the control parameters, to match the current rotational speed to the target speed from the parameter is switched on the control parameters for follow current rotational speed to the target speed can be configured to control the rotation of the image carrier motor.

  The control parameter corresponds to a method for feedback control of the motor. For example, when PID control is employed for the rotation of the motor, the control parameter corresponds to a proportional constant, a differential constant, an integral constant, or the like. Control parameters for causing the current rotational speed to follow the target speed can be realized by a combination of the proportionality constants and the like.

  When the feedback control means switches the control parameter, it is necessary to determine the control parameter, and the following method can be adopted as the determination method. For example, a storage unit that associates a target item (target speed, steady speed) and a control parameter corresponding to the target item is provided in advance, and the feedback control unit is based on the target item and the storage unit. What is necessary is just to comprise so that the control parameter corresponding to the time of acceleration (deceleration) of an image carrier motor may be discriminated (acquired). The control parameter corresponding to the acceleration (deceleration) of the image carrier motor is employed as a control parameter for causing the current rotational speed to follow the target speed. On the other hand, a control parameter for making the current rotational speed coincide with the steady speed (target speed) may be adopted as the steady speed.

  According to the image forming apparatus of the present invention, when the rotational speed of the image carrier motor is accelerated or decelerated together with the rotational speed of the intermediate transfer body motor, it is synchronized with the rotational speed of the intermediate transfer body motor based on the control signal. A target speed calculation unit that calculates a target speed, which is a rotation speed of the image carrier motor, and a feedback control unit that controls the rotation of the image carrier motor based on the current rotation speed and the target speed are provided. .

  Thus, when the rotational speed of the image carrier motor is accelerated or decelerated together with the rotational speed of the intermediate transfer body motor, the rotational speed of the image carrier motor can be controlled to be synchronized with the rotational speed of the intermediate transfer body motor. It becomes possible. Therefore, the rotation of the image carrier motor is performed by synchronizing (or following) the surface linear velocity of the image carrier rotated by the image carrier motor with the surface linear velocity of the intermediate transfer member rotated by the intermediate transfer member motor. The speed and the rotational speed of the intermediate transfer body motor can be accelerated or decelerated. As a result, the difference in speed generated between the surface linear velocity of the image carrier and the surface linear velocity of the intermediate transfer member is minimized, and the scratch between the image carrier and the intermediate transfer member caused by the speed difference, It is possible to prevent slip marks and the like. Further, it is possible to prevent positional deviation between the image carrier and the intermediate transfer body, and it is also possible to prevent occurrence of trouble such as color deviation that occurs during color printing.

The target speed calculation means is the ratio of the rotation speed of the image carrier motor to the rotation speed of the intermediate transfer body motor at the time of steady rotation in the count number calculated based on the internal timer pulse and the control signal. The target speed can be calculated by multiplying the speed coefficient.

  As a result, when the rotational speed of the image carrier motor is accelerated or decelerated together with the rotational speed of the intermediate transfer body motor, the relationship between the rotational speed of the intermediate transfer body motor and the rotational speed of the image carrier motor during steady rotation is obtained. While maintaining, the rotational speed of the image carrier motor is accelerated or decelerated. Therefore, the rotational speed of the image carrier motor is accelerated or decelerated under the condition that the surface linear velocity of the intermediate transfer member rotated by the intermediate transfer member motor matches the surface linear velocity of the image carrier rotated by the image carrier motor. It becomes possible to do. As a result, it is possible to prevent scratches, slip marks, and the like generated between the intermediate transfer member and the image carrier, and it is possible to prevent troubles such as color misregistration.

  Further, when the rotational speed of the image carrier motor is accelerated or decelerated together with the rotational speed of the intermediate transfer body motor, the feedback control means determines the current rotational speed from the control parameter for matching the current rotational speed with the target speed. By switching to a control parameter for following the target speed, the rotation of the image carrier motor can be controlled.

  Accordingly, when the rotational speed of the image carrier motor is accelerated or decelerated together with the rotational speed of the intermediate transfer body motor, the control parameter for causing the current rotational speed to follow the target speed, that is, when the image carrier motor is accelerated or It is possible to control the rotation of the image carrier motor so as to synchronize with the intermediate transfer body motor using the control parameter corresponding to the deceleration. For this reason, the rotation speed of the image carrier motor and the rotation speed of the intermediate transfer body motor are appropriately accelerated or decelerated while suppressing the overshoot phenomenon or the undershoot phenomenon that occurs when the image carrier motor is accelerated or decelerated. Is possible.

  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. That is, the image forming apparatus of the present invention only needs to include an image forming unit, such as a copying machine or a multifunction machine having a function as a facsimile machine (MFP: Multi Function Peripheral) or a copying machine having only a copying function. 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 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, with reference to FIGS. 6 to 7, a detailed description will be given of a procedure in which the printer 100 according to the present invention prevents scratches or the like generated between the photosensitive drum and the transfer belt at the time of starting or stopping. . 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.

  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. The DC brushless motor and the stepping motor are connected to each other. Each is rotating at a predetermined rotational speed (rotational speed) (hereinafter referred to as a rotational speed at which an image can be formed or a steady speed). 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, 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.

  In the sleep state, since the rotation of both the stepping motor 402a and the DC brushless motor 4041a is stopped (a state in which the rotation speed is zero), the image forming unit 602 causes the stepping motor control unit 603 to rotate the stepping motor 402a. 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 rotation speed (rotational speed) of the stepping motor 402a, the image forming unit 601 increases the frequency of the acceleration signal A as the stepping motor 402a accelerates. To the stepping motor control means 602. 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 601 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, the image forming unit 601 inputs the acceleration signal A described above to the stepping motor control unit 602 and also to the target speed calculation unit 605 constituting the DC brushless motor control unit 604.

  Further, separately from the acceleration signal A, the image forming unit 602 sends a signal (calculation signal B) (calculation instruction control signal B in FIG. 4) to the target speed calculation unit 605 to calculate the target speed. The steady speed (referred to as steady speed B) of the DC brushless motor 4041a is transmitted (FIG. 7: S102). The target speed is the rotational speed of the DC brushless motor 4041a synchronized with the rotational speed of the stepping motor 402a.

  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 acceleration signal A input to the stepping motor control unit 602 (FIG. 7: S104).

  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.

  When calculating the stepping motor count number Na, as shown in FIG. 8A, the rising point of one pulse of the acceleration signal A (starting point of one pulse of HI signal) is set as the starting point 801, and the rising point of the next one pulse ( The start point of the subsequent HI signal of one pulse) is set as the end point 802, and the number Na of internal timer pulses existing between the start point 801 and the end point 802 is counted.

  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. In the above description, the target speed calculation unit 605 counts based on the rising point of one pulse, but may count based on the falling 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.

  Even if the rotation speed of the stepping motor 402a is fixed, the surface linear velocity of the transfer belt B1 is, for example, the degree of tension of the transfer belt, its thickness, material, circumference, driving roller radius, circumference, stepping motor gear. It varies depending on parameters such as ratio. Further, the surface linear velocity of the photosensitive drum 10Y is not limited to parameters such as the radius, peripheral length, surface properties, material, and gear ratio of the DC brushless motor, even if the rotational speed of the DC brushless motor 4041a is fixed. Fluctuates depending on Accordingly, the respective surface linear velocities are adjusted to appropriate surface linear velocities by appropriately changing the design of the parameters described above in advance.

  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.

  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.

  A speed reducer having a predetermined reduction ratio is inserted between the DC brushless motor 4041a and the photosensitive drum 10Y so that the rotational speed of the DC brushless motor 4041a and the rotational speed of the photosensitive drum 10Y are appropriately adjusted. You may comprise.

  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 calculating the DC brushless motor count number Nb, the method is the same as the method of calculating the stepping motor count number Na. However, as shown in FIG. 8B, the rising point of one pulse of the feedback pulse (starting point of the HI signal of one pulse) ) As the start time point 803, and the rising time point of the next one pulse (the start time point of the subsequent one pulse HI signal) as the end time point 804, the internal timer pulse existing between the start time point 803 and the end time point 804 The number of pulses Nb is counted. Note that 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.

  As shown in FIG. 8, at the initial start-up, the rotational speed of the DC brushless motor is close to zero. Therefore, the DC brushless motor count number Nb may be significantly larger than the stepping motor count number Na. Understood.

  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 unit 606 receives the current rotation speed and the target speed, the feedback control unit 606 refers to the feedback control table stored in the feedback control storage unit 608 to determine (determine) the control parameter corresponding to the acceleration of the DC brushless motor 4041a. (FIG. 7: S105). The determination procedure corresponds to a control parameter switching procedure by the feedback control means 606.

  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).

  Further, as shown in FIG. 9, the feedback control table 900 stores a target item 901 corresponding to the target value of the rotational speed of the DC brushless motor and a control parameter 902 corresponding to the target item in association with each other.

  In the column of the target item 901, for example, when the target speed calculated by the target speed calculation unit 605 is set as a target value, the “target speed” is the steady speed B transmitted to the target speed calculation unit 605 by the image forming unit 602. Is set as a target value, “steady speed” is stored in association with each other.

  In the control parameter 702 column, control parameters combining “Kp”, “Ki”, and “Kd” are stored in association with each other according to a predetermined target item.

  For example, when the feedback control means 606 receives “target speed”, it is necessary to calculate a control value that follows the current rotational speed to the target speed, and therefore “Kp” is stored in association with it. That is, the “Kp” is a control parameter for following the current rotational speed to the target speed, and is a control parameter corresponding to the acceleration or deceleration of the DC brushless motor 4041a. The “target speed” is set to “Kd” along with “Kd” in accordance with the starting characteristics or stopping characteristics (for example, a member such as a gear, a radius, a circumferential diameter, specifications, etc.) of the DC brushless motor 4041a. You may comprise so that it may relate.

  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 that the current rotational speed follows the target speed of the DC brushless motor 4041a as needed. 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 rotational speed is larger than the target rotational speed.

  On the other hand, when the feedback control means 606 receives the steady speed B, it calculates a control value that makes the current rotational speed equal to the steady speed B (matches the steady speed B of the DC brushless motor 4041a with the current rotational speed). Therefore, “Kp”, “Kd”, and “Ki” are all stored in association with each other.

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

  When the feedback control means 604 determines the control parameter “Kp” corresponding to the “target speed” from the feedback control table 900, the speed difference between the target speed and the current rotational speed is calculated, and based on the speed difference, “ A proportional control value (hereinafter referred to as a control value) corresponding to “Kp” is calculated (FIG. 7: S106). In other words, the feedback control means 606 controls the current rotational speed to follow the target speed from the control parameters (“Kp”, “Kd”, “Ki”) for matching the current rotational speed to the target speed. Switching to the parameter (“Kp”) controls the rotation of the DC brushless motor 4041a.

  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. The duty (duty ratio) is the ratio of the width of one pulse of the HI signal to the period of one pulse.

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: S107).

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.
Accordingly, the rotational speed of the DC brushless motor 4041a is synchronized with (follows) the surface linear speed of the photosensitive drum 10Y rotated by the DC brushless motor 4041a with the surface linear speed of the transfer belt rotated by the stepping motor 402a. And the rotation speed of the stepping motor 402a can be accelerated.

  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: S108).

  In the area 10A of FIG. 10, the frequency of the control signal (acceleration signal A) input to the stepping motor control means 603 and the DC brushless when the printer 100 transitions from the sleep state to the image formable state (at the time of startup). The time-dependent change with the frequency of the encoder pulse of the motor 4041a was shown. As can be seen from the region 10A in FIG. 10, 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.

  Furthermore, in the region 10A of FIG. 10, it is understood that the feedback control unit 606 calculates a proportional control value corresponding to the control parameter “Kp” based on the speed difference between the target speed and the current rotational speed.

  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 refers to the feedback control table 900 to determine a control parameter corresponding to the steady speed.

  In the feedback control table 900, since the control parameters “Kp”, “Kd”, and “Ki” are stored in association with “steady speed”, the feedback control unit 606 includes the control parameters “Kp”, “Kd”, “Ki” is determined, and based on the speed difference between the steady speed B and the current rotational speed, the proportional control value, differential control value, and integral control value corresponding to “Kp”, “Kd”, and “Ki” are determined. calculate.

  In other words, the determination procedure and the control value calculation procedure are for the feedback control means 606 to match the current rotation speed to the target speed from the control parameter (“Kp”) for causing the current rotation speed to follow the target speed. The control parameters (“Kp”, “Kd”, “Ki”) are switched to 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.

In the area 10B of FIG. 10, the change with time of the frequency of the control signal input to the stepping motor control means 603 and the frequency of the encoder pulse of the DC brushless motor 4041a when the printer 100 can form an image (in a steady state) is shown. Indicated. As can be seen from the region 10B of FIG. 10, the frequency of the encoder pulse of the DC brushless motor 4041a maintains the speed coefficient (a = B / A) with respect to the frequency of the control signal of the stepping motor 402a. In (color printing), it is understood that the surface linear velocity of the transfer belt B1 and the surface linear velocity of the photosensitive drum 10Y are kept in agreement.

  Further, in the region 10B of FIG. 10, the feedback control means 606 controls the control values corresponding to the control parameters “Kp”, “Kd”, “Ki” based on the speed difference between the steady speed B and the current rotational speed. Is understood to be calculated.

  Next, a procedure for stopping the driving of the photosensitive drum and the transfer belt will be described.

  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, until the image forming state is shifted to the sleep state (stopped state). When the sleep time, which is the waiting time, elapses, the image forming unit 602 shifts from an image formable state to a sleep state.

  Specifically, the image forming unit 602 sends a signal to the stepping motor control unit 603 to reduce the rotational speed of the stepping motor 402a (deceleration signal A) (corresponding to the control signal A for instructing deceleration in FIG. 4). Is transmitted (FIG. 7: S101). The deceleration signal A is an instruction clock signal (clock signal, clock) having a predetermined frequency and pulse width.

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

  Further, the image forming unit 602 inputs the above-described deceleration signal A 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 (calculation signal B) (in FIG. 4, a control signal B for calculation instruction) to the target speed calculation unit 605 to calculate the target speed. Transmit (FIG. 7: S103).

  When the target speed calculation means 605 receives the calculation signal B, based on the deceleration signal A input to the stepping motor control means 603, as described above, the target speed calculation means 605 is a DC brushless that has a rotation speed synchronized with the rotation speed of the stepping motor 402a. The target speed of the motor 4041a is calculated (FIG. 7: S104). When the target speed calculation unit 605 calculates the target speed, the target speed is transmitted to the Fordback control unit 606.

  When receiving the target speed, the feedback control unit 606 refers to the feedback control table 900 and determines a control parameter corresponding to the target speed (FIG. 7: S105).

  In the feedback control table 900, since the control parameter “Kp” is stored in association with “target speed”, the feedback control means 606 discriminates the control parameter “Kp”, and receives the received target speed and the current rotational speed. The proportional control value corresponding to “Kp” is calculated based on the speed difference between the two (FIG. 7: S106).

  In other words, the determination procedure and the control value calculation procedure are based on the current rotation from the control parameters (“Kp”, “Kd”, “Ki”) for the feedback control means 606 to match the current rotation speed with the target speed. The rotation of the DC brushless motor 4041a is controlled by switching to a control parameter (“Kp”) for causing the speed to follow the target speed.

  When the calculation of the control value is completed, the feedback control unit 606 determines whether the calculated control value is within a predetermined range, and transmits the determined 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 means 610 inputs a drive pulse for reducing the rotational speed of the DC brushless motor 4041a to the DC brushless motor 4041a based on the PWM signal. The rotational speed of the DC brushless motor 4041a is reduced in synchronization with the rotational speed of the stepping motor 402a (FIG. 7: S107).
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 decreases the frequency of the deceleration signal A to the frequency of the control signal corresponding to the stop state (the control signal at the start of the stepping motor), the decrease amount In response, the target speed calculation 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 calculates the speed difference between the target speed and the current rotation speed. And a control value is calculated based on 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.

  Accordingly, the rotational speed of the DC brushless motor 4041a is synchronized with (follows) the surface linear speed of the photosensitive drum 10Y rotated by the DC brushless motor 4041a with the surface linear speed of the transfer belt rotated by the stepping motor 402a. And the rotation speed of the stepping motor 402a can be reduced.

  When the rotation speed of the stepping motor 402a reaches the stop speed, the rotation speed of the DC brushless motor 4041a becomes the stop speed 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: S108).

  In the area 10C of FIG. 10, a control signal (deceleration signal A) input to the stepping motor control means 603 when the printer 100 shifts from a state where image formation is possible to a sleep state (stop state) (when stopped). The change with time of the frequency and the frequency of the encoder pulse of the DC brushless motor 4041a is shown. As can be seen from the region 10C in FIG. 10, 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 control signal of the stepping motor 402a. In other words, it is understood that the rotation of the DC brushless motor 4041a is decelerated in synchronization with the rotation of the stepping motor 402a, and the DC brushless motor 4041a and the stepping motor 402a stop almost simultaneously. 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.

Furthermore, in region 10C of FIG. 10, it is understood that the feedback control means 606 calculates a proportional control value corresponding to the control parameter “Kp” based on the speed difference between the target speed and the current rotational speed.

  When the printer 100 shifts to the sleep state, the image forming unit 602 stops the input of the deceleration signal A to the stepping motor control unit, so that the rotation of the stepping motor 402a is stopped. Further, since the input of the deceleration signal A to the target speed calculation unit 605 is also stopped, the DC brushless motor control unit 604 stops the rotation of the DC brushless motor.

  Thus, when accelerating or decelerating the rotational speed of the DC brushless motor together with the rotational speed of the stepping motor, the target speed that is the rotational speed of the DC brushless motor synchronized with the rotational speed of the stepping motor is set based on the control signal. A target speed calculation means for calculating, and a feedback control means for controlling the rotation of the DC brushless motor based on the current rotation speed and the target speed are provided.

  Thereby, when the rotational speed of the DC brushless motor is accelerated or decelerated together with the rotational speed of the stepping motor, the rotational speed of the DC brushless motor can be controlled to be synchronized with the rotational speed of the stepping motor. For this reason, the rotational speed of the DC brushless motor and the stepping motor are set such that the surface linear speed of the photosensitive drum rotated by the DC brushless motor is synchronized with (or follows) the surface linear speed of the transfer belt rotated by the stepping motor. It becomes possible to accelerate or decelerate the rotational speed. As a result, the speed difference generated between the surface linear velocity of the photosensitive drum and the surface linear velocity of the transfer belt is minimized, and scratches and slip marks between the photosensitive drum and the transfer belt due to the speed difference are generated. Etc. can be prevented. Further, it is possible to prevent positional deviation between the photosensitive drum and the transfer belt, and it is also possible to prevent troubles such as color deviation that occurs during color printing.

  The target speed calculation means calculates a speed coefficient, which is a ratio of the rotational speed of the DC brushless motor to the rotational speed of the stepping motor at the time of steady rotation, to the count number calculated based on the internal timer pulse and the control signal. The target speed can be calculated by multiplication.

  Thus, when the rotational speed of the DC brushless motor is accelerated or decelerated together with the rotational speed of the stepping motor, the relationship between the rotational speed of the stepping motor and the rotational speed of the DC brushless motor during steady rotation is maintained, and the DC brushless motor is maintained. The rotational speed of the motor is accelerated or decelerated. Therefore, the rotational speed of the DC brushless motor can be accelerated or decelerated under the condition that the surface linear velocity of the transfer belt rotated by the stepping motor and the surface linear velocity of the photosensitive drum rotated by the DC brushless motor match. Become. As a result, it is possible to prevent scratches, slip marks, and the like generated between the transfer belt and the photosensitive drum, and it is possible to prevent troubles such as color misregistration.

  Further, when the rotational speed of the DC brushless motor is accelerated or decelerated together with the rotational speed of the stepping motor, the feedback control means sets the current rotational speed to the target speed based on a control parameter for making the current rotational speed coincide with the target speed. It can be configured to control the rotation of the DC brushless motor by switching to a control parameter for tracking.

Accordingly, when the rotational speed of the DC brushless motor is accelerated or decelerated together with the rotational speed of the stepping motor, the control parameter for causing the current rotational speed to follow the target speed, that is, when the DC brushless motor is accelerated or decelerated corresponds. Using the control parameter, the rotation of the DC brushless motor can be controlled to synchronize with the stepping motor. Therefore, it is possible to appropriately accelerate or decelerate the rotational speed of the DC brushless motor and the rotational speed of the stepping motor while suppressing the overshoot phenomenon or the undershoot phenomenon that occurs when the DC brushless motor is accelerated or decelerated. .

  Further, in the embodiment of the present invention, when the sleep time elapses, the image forming unit shifts from the image formable state to the sleep state, transmits the deceleration signal A to the stepping motor control unit, and the DC brushless motor control unit However, for example, when the printer is turned off or when the image forming unit receives a command signal corresponding to the stop of driving by the user, the stepping motor control unit and the DC You may comprise so that the said deceleration signal and a calculation signal may be transmitted to a brushless motor control means.

  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 image carrier motor that transmits rotation to an image carrier on which a toner image is formed based on Fordback control, and a control signal that is a pulse signal that controls rotation of the motor is formed on the image carrier. In an image forming apparatus including an intermediate transfer member motor that transmits rotation to an intermediate transfer member to which a toner image is transferred, when the rotation speed of the image carrier motor is accelerated or decelerated together with the rotation speed of the intermediate transfer member motor, Based on the control signal, a target speed calculation circuit that calculates a target speed that is the rotation speed of the image carrier motor synchronized with the rotation speed of the intermediate transfer body motor, and a Ford back pulse fed back from the rotation of the image carrier motor On the basis of the current rotation speed, which is the current rotation speed of the image carrier motor, and the target speed calculated by the target speed calculation means. It may be configured to and a feedback control circuit for controlling the rotation of the image carrier motor. The feedback control circuit corresponds to, for example, a control arithmetic circuit.

  In the embodiment of the present invention, the image forming unit is configured to transmit the control signal to the stepping motor control unit and to the DC brushless motor control unit (target speed calculation unit), but other configurations are employed. It doesn't matter. For example, when the DC brushless motor control means accelerates (decelerates) the rotation of the DC brushless motor, the control signal input to the stepping motor control means is referred to, and the rotation of the intermediate transfer body motor is based on the control signal. A target speed that is the rotational speed of the image carrier motor synchronized with the speed may be calculated.

  Further, as a determination when accelerating or decelerating the rotation speed of the DC brushless motor together with the rotation speed of the stepping motor, other determination methods may be adopted. For example, the control signal (acceleration signal, deceleration signal) input to the stepping motor control means and the control signal (acceleration signal, deceleration signal) input to the DC brushless motor control means are converted into the stepping motor control means and the DC brushless motor. Before the operation of the control means, it is obtained from both, and is configured to include motor synchronization determination means for determining whether to accelerate (decelerate) the rotational speed of the DC brushless motor together with the rotational speed of the stepping motor, It does not matter if it is determined.

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 has scratches or the like generated between the photosensitive drum and the transfer belt at the time of starting or stopping. This is effective as an image forming apparatus that can be prevented.

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 the embodiment of the present invention. It is a figure which shows an example of the control signal, feedback pulse, and internal timer pulse which concern on embodiment of this invention. It is a figure which shows an example of the DC brushless motor control 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.

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 rotational speed calculation means 608 Feedback control storage means 609 PWM means 610 Drive pulse input means

Claims (3)

An image carrier motor that transmits rotation to an image carrier on which a toner image is formed based on Fordback control, and a toner that is formed on the image carrier based on a control signal that is a pulse signal that controls rotation of the motor In an image forming apparatus comprising an intermediate transfer body motor that transmits rotation to an intermediate transfer body to which an image is transferred,
When accelerating to or decelerating the rotational speed of the image carrier motor with the rotational speed of the intermediate transfer member motor, a control signal input to the intermediate transfer member motor, the period of the pulse generated from the first time capture circuit Is compared with a stable internal timer pulse, counts the number of internal timer pulses per one pulse of the control signal, multiplies the counted number by a predetermined speed coefficient, and calculates the multiplied value. Target speed calculation means for calculating the target speed;
The speed difference between the current rotational speed and the target speed target speed calculating means has calculated is the current rotational speed of the image carrier motor calculated by Ford back pulses fed back from the rotation of the image carrier motor , based on the predetermined control parameters, and feedback control means for controlling the rotation of the image carrier motor,
An image forming apparatus comprising: The target speed calculation means multiplies the counted number by a speed coefficient that is a ratio of the rotation speed of the image carrier motor to the rotation speed of the intermediate transfer body motor at the time of steady rotation , and calculates the multiplied value as a target. the image forming apparatus according to claim 1, characterized in that calculated as velocity. When accelerating to or decelerating the rotational speed of the image carrier motor with the rotational speed of the intermediate transfer member motor, said feedback control means, the control parameter, the control parameter for matching the current rotational speed to the target speed , by switching the control parameter for follow current rotational speed to the target speed, the image forming apparatus according to claim 1 or 2, characterized in that for controlling the rotation of the image carrier motor.

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