JP6354344B2 - Image forming apparatus and motor control apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus having a plurality of motors and a motor control apparatus, and to a technique for controlling an inrush current of a motor.

  2. Description of the Related Art Conventionally, there are image forming apparatuses that include a plurality of motors as drive sources, and control inrush current generated when starting each of the plurality of motors within a range allowed by a power supply circuit, wiring, and the like ( Patent Document 1). In the image forming apparatus disclosed in Patent Document 1, inrush current generated in each motor such as a main motor and a polygon motor is measured in advance. Then, the image forming apparatus performs control to suppress the inrush current by sequentially starting while shifting the start timing of each motor.

JP 2004-138840 A

  However, although the above-described image forming apparatus can suppress the inrush current as compared with the case where a plurality of motors are started simultaneously, since the motors need to be started sequentially, the rotational speeds of all the motors are stabilized and desired. The time required until the print quality process can be ensured becomes longer. That is, in this image forming apparatus, even if the inrush current can be suppressed, there is a possibility that the start-up time becomes long.

  The technology disclosed in the present application has been proposed in view of the above problems. An object of the present invention is to provide an image forming apparatus and a motor control apparatus having a plurality of motors, which can suppress an inrush current at the start of the motor and shorten the start-up time.

  In order to solve the above problems, an image forming apparatus according to the present invention includes a first motor that is driven in accordance with a supplied current, a first on period in which current supply to the first motor is turned on, and a first motor. The first driving circuit for controlling the rotation speed of the first motor by changing the first on period for the first period including the first off period in which the current supply is turned off, and according to the supplied current A second on-period is defined for a second cycle including a second motor to be driven, a second on-period in which current supply to the second motor is turned on, and a second off period in which current supply to the second motor is turned off. By changing, the second drive circuit for controlling the rotation speed of the second motor, the image forming unit for forming an image on the sheet as the first and second motors are driven, and the first motor by the first drive circuit The current supply state to A transmission circuit for transmitting to the drive circuit, the second drive circuit to the second motor during the first off period of the first motor based on the supply state in response to the activation of the first and second motors The current supply is turned on.

  In order to solve the above-described problem, the motor control device of the present invention includes a first motor that is driven in accordance with a supplied current, a first on period in which current supply to the first motor is turned on, and a first A first driving circuit that controls the rotation speed of the first motor by changing the first on period for the first period that includes the first off period in which the current supply to the motor is turned off, and the supplied current In response to a second period consisting of a second motor driven in response, a second on period in which current supply to the second motor is turned on, and a second off period in which current supply to the second motor is turned off, A second drive circuit that controls the rotation speed of the second motor by changing the period; and a transmission circuit that transmits a current supply state to the first motor by the first drive circuit to the second drive circuit. A second drive circuit comprising: a first drive circuit; 2 in response to the activation of the motor, based on the supply state, and wherein turning on the current supply to the second motor during the first off-period of the first motor.

  In the image forming apparatus described in the present invention, the inrush current at the start of the motor can be suppressed and the start-up time can be shortened.

It is sectional drawing of the printer of 1st Example. FIG. 2 is a block diagram illustrating a part of the configuration of a printer. It is a circuit diagram which controls the 1st and 2nd motor. It is a wave form diagram which illustrated the phase of the PWM control signal which the 1st control part supplies to the switching element of the 1st inverter. It is a timing chart for comparing the PWM control signal of the 1st motor and the 2nd motor. It is a graph which shows the consumption current in the power supply circuit with a starting, and the rotational speed of a 1st and 2nd motor. It is a timing chart for comparing the PWM control signals of the main motor and the polygon motor in the second embodiment. It is a circuit diagram which controls the 1st and 2nd motor in 3rd Example. It is a timing chart for comparing the PWM control signals of the main motor and the polygon motor in the third embodiment.

(First embodiment)
An embodiment of the present application will be described below with reference to the drawings. A printer 10 that is a first embodiment of the image forming apparatus according to the present invention shown in FIG. 1 is a color laser printer that forms a color image on a sheet (paper, OHP sheet, etc.) by electrophotography. In FIG. 1, the right side of the sheet is defined as the front side of the apparatus, and the side that comes to the left hand (the front side of the sheet) when the apparatus is viewed from the front side is defined as the left side.

  First, a schematic configuration of the printer 10 will be described. As shown in FIG. 1, the printer 10 includes a substantially box-shaped housing 11 and a frame member (not shown) provided inside the housing 11. The frame member is assembled with a paper feeding unit 13, an image forming unit 15, a transport unit 17, a fixing device 19, and the like. In addition, a main motor 65 (see FIG. 2) is provided in the housing 11 on the left side with respect to the image forming unit 15, the transport unit 17, and the like. The main motor 65 transmits the driving force to the paper feed unit 13, the transport unit 17 and the like via a transmission gear (not shown). A paper feed cassette 25 is provided below the housing 11. The paper feed cassette 25 is a substantially box-like body that is open at the top and accommodates sheets therein. The paper feed cassette 25 is configured to be slidable rearward from the front side of the printer 10 and inserted into the housing 11, and can be pulled out from the housing 11 toward the front to be removed.

  A discharge tray 27 for discharging a sheet on which an image is formed is provided on the upper surface of the housing 11. In the housing 11, the printer 10 has a substantially “S” -shaped transport path R from the lower paper feed unit 13 to the upper discharge tray 27 via the transport unit 17, the image forming unit 15, the fixing device 19, and the like. To convey the sheet. A front cover 29 is provided on the front surface of the housing 11 so as to be openable and closable with a lower end portion as a swinging central axis.

  Next, details of each component of the printer 10 will be described. The sheet feeding unit 13 feeds the sheets stored in the sheet feeding cassette 25 to the transport path R one by one by the sheet feeding roller 31 and the separation pad 33. The conveyance roller 35 and the registration roller 39 are disposed at a portion of the conveyance path R that is turned backward in a substantially U shape, and a sheet fed from the sheet feeding cassette 25 to the conveyance path R is directed to the image forming unit 15. Transport. The transport unit 17 is disposed between the paper feed cassette 25 and the image forming unit 15 and includes a transport belt 17A, four transfer rollers 18, and the like. The conveying belt 17A is wound around a driving roller 17B positioned below the rear end side of the image forming unit 15 and a driven roller 17C positioned below the front end side. The conveying belt 17A circulates between the driving roller 17B and the driven roller 17C as the driving roller 17B rotates in synchronization with the paper feeding unit 13. The upper surface of the conveyance belt 17A extends substantially horizontally just below the image forming unit 15, and is a sheet conveyance surface 17D that contacts the back surface of the sheet and conveys the sheet.

  Each of the transfer rollers 18 is installed in a state of contacting the conveyance belt 17A from the back surface side of the sheet conveyance surface 17D. The conveyance belt 17A is made of, for example, conductive rubber, and is negatively charged when a transfer voltage is applied to each transfer roller 18, and the sheet is adsorbed to the sheet conveyance surface 17D by the electrostatic force, and along the conveyance path R. Transport.

  The image forming unit 15 includes a scanner unit 43 and four process cartridges 44. Each of the process cartridges 44 corresponds to four colors of black, yellow, magenta, and cyan. In the following description, if it is necessary to distinguish each color, the subscripts of K (black), C (cyan), M (magenta), and Y (yellow) are added to the reference numerals of the respective parts, and it is not necessary to distinguish them. In this case, the subscript is omitted. Each process cartridge 44 includes a photosensitive drum 47 that faces the transfer roller 18 with the sheet conveying surface 17 </ b> D interposed in the vertical direction, and a developing unit 49 that is positioned obliquely above the photosensitive drum 47.

  The scanner unit 43 is located at the top of the housing 11 and includes a laser light source, a polygon mirror, an fθ lens, a reflecting mirror, and the like. The polygon mirror has, for example, a plurality of mirror surfaces and is driven to rotate at high speed by a polygon motor 66 (see FIG. 2). The polygon mirror is rotated at a high speed to periodically deflect the laser light emitted from the laser light source, and sequentially form scanning lines on the photosensitive drum 47 via the fθ lens and the reflecting mirror. Each photosensitive drum 47 is irradiated with laser light on its surface, and an electrostatic latent image corresponding to four colors of black, yellow, magenta, and cyan is formed.

  Each of the process cartridges 44 is disposed along the front-rear direction between the scanner unit 43 and the sheet conveyance surface 17D in the vertical direction. In other words, the process cartridges 44 are arranged along the sheet conveyance direction. Accordingly, the printer 10 is a so-called direct tandem type image forming apparatus in which the process cartridges 44 are arranged along the conveyance direction within a predetermined range on the sheet conveyance path R.

  The photosensitive drums 47 of the respective colors are obtained by forming a positively chargeable photosensitive layer on the outermost layer of a resin cylindrical body. A charger 51 is disposed in the vicinity of each photosensitive drum 47 so as to face the photosensitive layer of the photosensitive drum 47. Each developing unit 49 is formed in a box shape having an opening on the lower rear side, and is provided in a toner storage chamber 45A provided in the upper part of the interior for storing toner, a supply roller 45B provided in the lower part of the toner storage chamber 45A, and a toner. A developing roller 45C that is exposed from the opening of the storage chamber 45A and faces the photosensitive drum 47 is provided. The toner in the toner storage chamber 45A is supplied to the developing roller 45C by the rotation of the supply roller 45B. The toner supplied to the developing roller 45C is carried on the surface of the developing roller 45C, adjusted to a predetermined thickness by the layer thickness regulating blade, and then supplied to the surface of the photosensitive drum 47.

  Further, the black process cartridge 44K operates with a driving source different from the process cartridges 44Y, 44M, and 44C of other colors (yellow, magenta, and cyan). In the process cartridge 44K, the photosensitive drum 47 and the like are rotationally driven by a first motor 77 (see FIG. 2). The process cartridges 44Y, 44M, and 44C are rotationally driven by a second motor 78 (see FIG. 2) shared by the photosensitive drum 47 and the like.

  In each process cartridge 44, each of the photosensitive drums 47 is held by a frame-shaped drawer 53 and each developing unit 49 is detachable from the drawer 53 in order to facilitate maintenance and replacement of consumables. Is held in. The drawer 53 is configured such that the front cover 29 is opened, the drawer 53 can be pulled out from the housing 11 in the forward direction, and can be inserted into the housing 11 in the rear direction. A detection unit 61 is provided below the drive roller 17B to detect image density and positional deviation by irradiating the patch marks formed on the surface of the conveyance belt 17A with infrared light. The detection unit 61 is configured such that light emitted from the detection unit 61 toward the conveyance belt 17 </ b> A passes or is blocked by the shutter member 63.

  The fixing device 19 is located downstream of the image forming unit 15 in the conveyance direction in the sheet conveyance path R, and includes a heating roller 19A and a pressure roller 19B. The heating roller 19A rotates in synchronization with the conveyance belt 17A and the like, and applies a conveyance force to the sheet while heating the toner transferred to the sheet. On the other hand, the pressure roller 19B is driven to rotate while pressing the sheet toward the heating roller 19A. As a result, the fixing device 19 heats and melts the toner transferred to the sheet to fix it on the sheet, and conveys the sheet to the downstream side of the conveyance path R. The conveyance path R is curved in a substantially U shape upward on the downstream side of the fixing device 19. The discharge roller 55 and the discharge tray 27 are located on the most downstream side in the conveyance direction of the conveyance path R.

  A control unit 71 shown in FIG. 2 is provided in the housing 11. FIG. 2 is a block diagram illustrating a part of the configuration of the printer 10. The controller 71 controls each of the above-described components (first motor 77, second motor 78, main motor 65, polygon motor 66, etc.) to perform an image forming operation. The control unit 71 drives the main motor 65 to operate the paper feeding unit 13, the transport unit 17, and the like. The control unit 71 controls the scanner unit 43 by driving the polygon motor 66 as the sheets in the sheet feeding cassette 25 are conveyed to the image forming unit 15, and controls the first and second motors 77 and 78. The photosensitive drum 47, the process cartridge 44, and the like are driven to control the operation described above. The surface of each of the photosensitive drums 47 is uniformly positively charged by the charger 51 while rotating, and then exposed to a laser beam emitted from the scanner unit 43, and the surface is subjected to static corresponding to the image forming data. An electrostatic latent image is formed.

  On the other hand, the positively charged toner carried on the developing roller 45C is formed on the surface of the photosensitive drum 47 as the developing roller 45C rotates while being in contact with the photosensitive drum 47. It is supplied to the electrostatic latent image. As a result, each of the photosensitive drums 47 makes the electrostatic latent image visible and carries a toner image by reversal development on the surface. The toner image carried on the surface of each photosensitive drum 47 is transferred to the sheet by a transfer voltage applied to each transfer roller 18. Then, when the sheet on which the toner images of a plurality of colors are sequentially transferred is conveyed to the fixing device 19, the toner image is fixed by being heated and pressed by the heating roller 19A and the pressure roller 19B. Finally, the sheet on which the image is formed is discharged to the discharge tray 27, and the image forming operation is completed.

  The control unit 71 controls the above-described image forming operation by a program that operates on the CPU, for example. Alternatively, the control unit 71 may be configured by dedicated hardware such as an ASIC, for example, to control the image forming operation. Further, the control unit 71 may be configured to control the image forming operation using, for example, software processing and hardware processing together.

  The control unit 71 controls the speed detection circuit 68, the display unit 73, the operation unit 75, and the power supply circuit 81 in addition to the first motor 77 described above. The speed detection circuit 68 detects the rotational speed of various motors (the first motor 77, the second motor 78, the main motor 65, the polygon motor 66, etc.), and outputs it to the controller 71. The speed detection circuit 68 can calculate the rotational speeds of various motors using pulse output signals from, for example, a resolver, an encoder, and a hall element. The display unit 73 includes various lamps, a liquid crystal panel, and the like, and the lighting of each lamp and the display content of the liquid crystal panel are changed by the control unit 71. The operation unit 75 includes an input panel, an input switch, and the like, and outputs an operation signal corresponding to a user operation on the input panel or the like to the control unit 71. FIG. 2 illustrates the portion of the printer 10 according to the present application. In addition to the configuration described above, the printer 10 is provided with, for example, a network interface (not shown) for connecting to an external device.

  Next, control of a plurality of motors by the control unit 71 of this embodiment will be described. In the first embodiment, a first motor 77 and a second motor 78 will be described as an example of a plurality of motors. FIG. 3 shows an example of a circuit diagram for controlling the first motor 77 and the second motor 78. The first motor 77 is, for example, a brushless motor that is driven and rotated by three-phase alternating current, and is provided with a stator around which windings L1 of U-phase, V-phase, and W-phase are wound, and a permanent magnet for field. And a rotor formed on the substrate. Similarly, the second motor 78 is, for example, a brushless motor that is driven and rotated by three-phase alternating current, and is driven to rotate independently of the first motor 77.

  The printer 10 includes a first inverter 83 for supplying power to the first motor 77 and a second inverter 85 for supplying power to the second motor 78. The power supply circuit 81 supplies power of the rated voltage VCC to the first inverter 83 and the second inverter 85, thereby supplying power to the first motor 77 and the second motor 78 via the first inverter 83 and the second inverter 85. Supply. In the following description, since the second inverter 85 has the same configuration as the first inverter 83, the first inverter 83 will be described as a representative, and a detailed description of the second inverter 85 will be omitted as appropriate.

  The first inverter 83 has six switching elements SW1. The switching element SW1 is, for example, a MOSFET. Note that the switching element SW1 may be another switching element such as a bipolar transistor or IGBT. Each of the switching elements SW1 includes a total of three pairs of switching elements SW1 connected between the positive side terminal and the negative side (ground GND side) terminal of the power supply circuit 81. The connection point of each pair of switching elements SW1 is connected to the winding L1 of each phase of the first motor 77. Accordingly, the first inverter 83 can change the aspect of the rotating magnetic field excited in the winding L1 of each phase by changing the ratio of the on period and the off period of the switching element SW1. The power supply circuit 81 supplies the rated voltage VCC to the first motor 77 as an intermittent pulse voltage corresponding to the ratio between the on period and the off period of the switching element SW1.

  The first control unit 87 of the control unit 71 is connected to the switching element SW1 of the first inverter 83, and the PWM control signal for the switching element SW1 of the first inverter 83 (signals UH, VH... WL in the figure). ) Is output. Note that the PWM control signal UH is a PWM control signal for turning on / off the switching element SW1 connected to the positive terminal among the pair of switching elements SW1 corresponding to the U phase. The PWM control signal UL is a PWM control signal for turning on / off the switching element SW1 connected to the negative terminal corresponding to the U phase. Further, in the following description, a symbol such as UH is attached to the PWM control signal when it is necessary to distinguish each phase, and the symbol is omitted when collectively referred to.

  FIG. 4 illustrates the phase of the PWM control signal that the first control unit 87 supplies to the switching element SW <b> 1 of the first inverter 83. As shown in FIG. 4, the PWM control signal corresponding to each phase is supplied to the switching element SW1 of each phase as a pulse signal whose phase is shifted by 120 degrees from each other. The first control unit 87 turns on and off the switching element SW1 a plurality of times within one energization period of the PWM control signal (a pulse signal indicated by “PW” in the drawing) (see the PWM control signal x1H in FIG. 5). ) And the on / off of energization supplied from the first inverter 83 to the winding L1 of the first motor 77 is controlled (PWM control). Thereby, the first control unit 87 can control the rotational speed S <b> 1 of the first motor 77 via the first inverter 83.

  Further, as shown in FIG. 3, the first inverter 83 is connected to a first comparator 91 for monitoring the peak value of the current flowing through each switching element SW1, the wiring connected to the switching element SW1, and the like. A voltage applied to both ends of a detection resistor R1 connected between the negative terminal side of the switching element SW1 and the ground GND is input to the non-inverting input terminal of the first comparator 91. The reference voltage Vref1 is input to the inverting input terminal of the first comparator 91. The first comparator 91 compares the voltage of the resistor R1 with the reference voltage Vref1, and outputs the comparison result as a detection signal SI1 to the first controller 87.

  The first comparator 91 inverts the signal level of the detection signal SI1 from the low level to the high level when the peak value of the current flowing through the switching element SW1 exceeds a predetermined value and the voltage of the resistor R1 becomes equal to or higher than the reference voltage Vref1. Therefore, the first controller 87 can monitor the peak value of the current flowing through each switching element SW1 of the first inverter 83 by determining the signal level of the detection signal SI1. When the peak current value of the switching element SW1 exceeds a predetermined value, the first control unit 87 stops supplying the PWM control signal to the first inverter 83 and turns off all the switching elements SW1. Thus, the first control unit 87 can protect the circuit by preventing the overcurrent from flowing through the switching element SW1 of the first inverter 83, the wiring connecting the switching element SW1, and the like.

  Similarly, the second control unit 89 of the control unit 71 is excited in the winding L2 of each phase of the second motor 78 by changing the ratio of the ON period and the OFF period of the switching element SW2 of the second inverter 85. The mode of the rotating magnetic field can be changed. The second control unit 89 turns on and off the switching element SW2 a plurality of times within the energization period PW (see FIG. 4) of the PWM control signal corresponding to each phase, and switches from the second inverter 85 to the winding L2 of the second motor 78. Controls on / off of the energization supplied. Thereby, the second control unit 89 can control the rotational speed S <b> 2 of the second motor 78 via the second inverter 85.

  The voltage applied to both ends of the detection resistor R2 connected between the negative terminal side of the switching element SW2 and the ground GND is applied to the non-inverting input terminal of the second comparator 93 provided in the second inverter 85. Entered. The reference voltage Vref <b> 2 is input to the inverting input terminal of the second comparator 93. The second comparator 93 compares the voltage of the resistor R2 with the reference voltage Vref2, and outputs the comparison result to the second control unit 89 as the detection signal SI2. The second controller 89 stops supplying the PWM control signal to the second inverter 85 when the peak value of the current flowing through the switching element SW2 exceeds a predetermined value based on the detection signal SI2 of the second comparator 93. To do. As described above, the control unit 71 controls the switching of the switching element SW2 of the second inverter 85 by the second control unit 89 independently of the switching element SW1 of the first inverter 83 controlled by the first control unit 87. Therefore, each of the motors 77 and 78 can be independently driven and controlled.

  Here, after the first and second motors 77 and 78 start to start, the control unit 71 temporarily supplies the PWM control signal to the first and second inverters 83 and 85 at the same time. Energization that occurs simultaneously in the starting state until the current sum Is of the current value I1 of the current supplied to 77 and the current value I2 of the current supplied to the second motor 78 does not exceed the rated current I3 of the power supply circuit 81 Control is performed so that the PWM control signal is supplied to only one of the first and second inverters 83 and 85 within the period PW. In the present embodiment, the controller 71 gives priority to the operation of the first inverter 83 (first motor 77). The “starting start” of the first and second motors 77 and 78 referred to here is a PWM control signal from the first and second control units 87 and 89 to the first and second inverters 83 and 85. Refers to the time when the supply of

  As shown in FIG. 3, the first control unit 87 includes a first transmission circuit 95 that transmits the permission signal EN <b> 1 to the second control unit 89. The permission signal EN1 is a signal indicating whether or not the second control unit 89 may supply a PWM control signal to the second inverter 85. For example, the second control unit 89 stops supplying the PWM control signal to the second inverter 85 when the low-level permission signal EN1 is input. In this state, when the first control unit 87 receives the high-level detection signal SI1 from the first comparator 91 after starting the first motor 77, the first control unit 87 supplies the PWM control signal to the first inverter 83. To stop. The first transmission circuit 95 changes the signal level of the enable signal EN1 from the low level to the high level in accordance with the stop of the supply of the PWM control signal to the first inverter 83. When the second control unit 89 detects that the signal level of the enable signal EN1 is inverted, the second control unit 89 starts to start the second motor 78, that is, starts supplying the PWM control signal to the second inverter 85. The first and second control units 87 and 89 perform such exclusive PWM control in the activated state, thereby shifting the generation time of the inrush current flowing through the first and second inverters 83 and 85 at the time of activation. It is possible to suppress the increase in superposition and to shorten the startup time. The process in which the control unit 71 determines the activation state will be described later.

  Next, the operation at the time of starting the first and second inverters 83 and 85 will be described. In the PWM control signal shown in FIG. 4, the duty ratios of the high level and low level of the PWM control signal, that is, the on period and the off period of the switching elements SW1 and SW2, are changed within one energization period PW. The first and second control units 87 and 89 change the on period and the off period in the energization period PW by pulse width modulation. The first and second control units 87 and 89 perform PWM control of the first and second inverters 83 and 85 within the energization period PW, and in other words, the duty ratio of the PWM control signal, in other words, the on period and the off period. The rotational speeds S1 and S2 of the motors 77 and 78 are brought close to the target speeds St1 and St2 (see FIG. 6).

  FIG. 5 shows the PWM control signal x1H (UH, VH, UH, VH, VH) of the switching element SW1 on the positive terminal side of the U, V, or W phase among the clock signal CLK1 of the first motor 77 and the three-phase PWM control signal. A timing chart corresponding to any one of WH), a switching signal on the positive terminal side of one of the phases U, V, and W among the clock signal CLK2 of the second motor 78 and the three-phase PWM control signal. The timing chart which matched PWM control signal x2H (any one of UH, VH, and WH) of SW2 is shown. Further, in the first and second motors 77 and 78 of the present embodiment, the clock signals CLK1 and CLK2 that are operation clocks of the PWM control have the same cycle. An example in which the cycles of the clock signals CLK1 and CLK2 are different will be described later. FIG. 5 schematically shows the PWM control signals x1H and x2H.

  In the present embodiment, each of the first and second inverters 83 and 85 is subjected to switching control independently of each other by the first and second control units 87 and 89. For this reason, the PWM control signals x1H and x2H supplied to the first and second inverters 83 and 85 are in phase with each other in the same cycle of the clock signals CLK1 and CLK2, or in a different phase (U, V, or W phase). This is the PWM control signal. For example, the PWM control signals x1H and x2H may be in phase with each other in the same period, and may be in phase with each other, or may be in phase with each other as the PWM control signal UH and PWM control signal VH.

  First, the first and second control units 87 and 89 start the first and second motors 77 and 78 in synchronization with the energization period PW (see FIG. 4) on the positive terminal side, The process of supplying x2H to the first and second inverters 83 and 85 is started. The first control unit 87 corresponding to the first motor 77 having a high priority supplies the PWM control signal x1H to the switching element SW1 in synchronization with the rising edge of the clock signal CLK1 at time T0. On the other hand, the second control unit 89 limits the supply of the PWM control signal x2H in synchronization with the rising edge of the clock signal CLK2 because the enable signal EN1 from the first transmission circuit 95 is at the low level at the time T0. .

  Here, a voltage is applied to the windings L1 and L2 of the first and second motors 77 and 78 upon startup. The windings L1 and L2 exhibit a low resistance value when a voltage is applied when the first and second motors 77 and 78 are stopped or when the rotational speeds S1 and S2 of the motors 77 and 78 are low. High inrush current occurs. In addition, the current flowing through the windings L1, L2 decreases as the rotational speeds S1, S2 of the first and second motors 77, 78 increase. For this reason, the first and second control units 87 and 89 are connected to the first and second inverters based on the detection signals SI1 and SI2 of the first and second comparators 91 and 93 for a certain period after starting. By stopping the supply of PWM control signals x1H and x2H to 83 and 85, the current values I1 and I2 of the current supplied to the first and second motors 77 and 78 exceed the rated current I3 of the power supply circuit 81, respectively. Limit to not.

  For example, when a predetermined voltage or higher is generated in the resistor R1 of the first inverter 83 at time T1, the first comparator 91 inverts the signal level of the detection signal SI1. The first control unit 87 stops the supply of the PWM control signal x1H to the first inverter 83 based on the detection signal SI1, and limits the current value I1 so as not to exceed the rated current I3 of the power supply circuit 81. In this case, a period from time T0 to time T1 in the PWM control signal x1H of the first inverter 83 is an on period ONT1 in which the switching element SW1 is turned on. Also, the supply of the PWM control signal x1H of the first inverter 83 is started in synchronization with the next rising edge of the clock signal CLK1 at time T4. Accordingly, the period from the time T1 to the time T4 in the PWM control signal x1H of the first inverter 83 is an off period OFT1 in which the switching element SW1 is turned off.

  For example, if there is no possibility that the current value I1 exceeds the rated current I3 due to the inrush current, the first controller 87 increases the rotational speed S1 of the first motor 77 to the target speed St1 in a shorter time. The PWM control signal x1H is supplied until time T3 (waveform indicated by a broken line in FIG. 5). For the period from time T0 to time T3, for example, the first control unit 87 determines a necessary time according to the rotational speed S1 and torque of the first motor 77. However, in actuality, the current value I1 may exceed the rated current I3 due to the inrush current. Therefore, the actual ON period ONT1 of the PWM control signal x1H is shortened in order to protect the circuit such as the first inverter 83. Therefore, in the printer 10 of the present embodiment, the time limited by the inrush current is used to shift the timing of supplying power to the first and second motors 77 and 78, thereby suppressing the inrush current and the start time. Shorten.

  That is, at time T1, the first transmission circuit 95 changes the enable signal EN1 from the low level to the high level. Then, the second control unit 89 detects a change in the signal level of the enabling signal EN1, and starts supplying the PWM control signal x2H to the second inverter 85. At the next time T2, similarly to the first control unit 87, the second control unit 89 stops supplying the PWM control signal x2H to the second inverter 85, and the current value I2 is the rated current of the power supply circuit 81. Limit not to exceed I3. In this case, a period from time T1 to time T2 in the PWM control signal x2H of the second inverter 85 is an on period ONT2 in which the switching element SW2 is turned on. Further, in one cycle from time T0 to time T4 in the PWM control signal x2H of the second inverter 85, a period excluding the on period ONT2 is an off period OFT2 in which the switching element SW2 is turned off.

  Then, the first and second control units 87 and 89 have the current sum Is of the current value I1 and the current value I2 when the PWM control signal is simultaneously supplied to the first and second inverters 83 and 85 as the power source. The exclusive PWM control described above is continued until time T21 when the startup state exceeding the rated current I3 of the circuit 81 ends. After time T21, the first and second control units 87 and 89 end the above-described exclusive PWM control. Soon, the rotational speeds S1 and S2 of the first and second motors 77 and 78 converge to the respective target speeds St1 and St2, and become stable. When the rotation speeds S1 and S2 of the first and second motors 77 and 78 are stabilized, the printer 10 can start a printing process that guarantees a desired print image quality. Here, “the rotational speeds S1 and S2 are stable” means, for example, a state in which the time during which the rotational speeds S1 and S2 are within a range of ± several% with respect to the target speeds St1 and St2 continues for a predetermined time. Say.

  The second control unit 89 starts supplying the PWM control signal x2H with a delay from the supply timing of the PWM control signal x1H of the first control unit 87, but even if no current limitation occurs. The supply of the PWM control signal x2H is stopped until the next clock signals CLK1 and CLK2 rise. In the second control unit 89 of the present embodiment, when no current limitation occurs, the PWM control signal x2H is supplied at the end of a desired ON period determined according to the rotational speed S2 and torque of the second motor 78. Stop. Specifically, at time T6 in FIG. 5, the second control unit 89 starts supplying the PWM control signal x2H to the second inverter 85 based on the permission signal EN1. On the other hand, the second control unit 89 stops supplying the PWM control signal x2H at time T7 when the desired on period ends, regardless of whether or not there is a current limit. Thus, when the first control unit 87 starts supplying the PWM control signal x1H, the second control unit 89 stops supplying the PWM control signal x2H.

Next, a description will be given of a process in which the control unit 71 determines the transition from the activated state of the first and second motors 77 and 78 to a state where the current sum Is does not exceed the rated current I3 of the power supply circuit 81.
As shown in FIG. 3, the control unit 71 includes a current value I1 of current supplied from the power supply circuit 81 to the first inverter 83 and the first motor 77, and a second inverter 85 and second motor 78 from the power supply circuit 81. The current value I2 of the current supplied to is input.

  FIG. 6 shows current values I1 and I2 and rotational speeds S1 and S2 that change as the first and second motors 77 and 78 are started. A waveform Wi1 in FIG. 6 shows a change with time of the current value I1 corresponding to the first motor 77. A waveform Wi2 indicates a change with time of the current value I2 corresponding to the second motor 78. A waveform Wis represents a waveform obtained by synthesizing the waveform Wi1 and the waveform Wi2, that is, a change with time of the current sum Is.

  A waveform Ws1 indicates a change with time in the rotational speed S1 of the first motor 77. A waveform Ws2 represents a change with time of the rotation speed S2 of the second motor 78. As shown in FIG. 6, in this embodiment, the target speed St1 targeted by the first control unit 87 that controls the first motor 77 is the target targeted by the second control unit 89 that controls the second motor 78. It is faster than the speed St2.

  First, the control unit 71 compares the current sum Is of current values I1 and I2 that increase and decrease when the first and second motors 77 and 78 are started up with the rated current I3 of the power supply circuit 81 to thereby determine the first and second motors. It is determined whether the startup states 77 and 78 have ended. Note that, in the first and second inverters 83 and 85 of the present embodiment, exclusive PWM control is performed. Therefore, when attention is paid to the timing at a certain time until the time T21, either one of the two inverters 83 and 85 is used. Current is supplied only to For this reason, the current sum Is here does not mean the sum of the current values I1 and I2 of the currents generated simultaneously, for example, the sum of the current values I1 and I2 supplied during the same period of the clock signals CLK1 and CLK2. Can be defined. Moreover, since the current is supplied at the same time after the time T21, the current sum Is is a value obtained by combining the current values I1 and I2.

  More specifically, an inrush current is generated in the windings L1 and L2 when the first and second motors 77 and 78 are started. The peak value of the inrush current decreases as the rotation speeds S1 and S2 (the waveforms Ws1 and Ws2 in the figure) of the first and second motors 77 and 78 increase. For this reason, as shown in FIG. 6, the waveforms Wi <b> 1 and Wi <b> 2 increase after a certain time from the startup and reach a maximum value, and then decrease.

  For example, the waveform Wis of the current sum Is increases from the time of startup, exceeds the rated current I3 once, and further increases to a maximum value. Further, the waveform Wis starts to decrease after reaching the maximum value, and becomes the rated current I3 again at time T21. In a state where the waveform Wis decreases from the maximum value to the rated current I3, the peak value of the inrush current in the first and second inverters 83 and 85 is small, and the current limitation based on the detection signals SI1 and SI2 is not executed. Or the number of times it is executed is low. As a result, even if the first and second inverters 83 and 85 are energized simultaneously after the lapse of time T21, the possibility that the sum of the current values I1 and I2 exceeds the rated current I3 of the power supply circuit 81 is extremely low. Yes. Therefore, the control unit 71 detects the timing at which the rated current I3 is reached again after the waveform Wis has reached the maximum value as the end of the startup state of the first and second motors 77 and 78. For example, the control unit 71 calculates the current sum Is based on the current values I1 and I2 input from the power supply circuit 81. When the control unit 71 detects that the current sum Is has decreased to the rated current I3 after taking the maximum value, the control unit 71 determines that the starting states of the first and second motors 77 and 78 have ended.

  When the control unit 71 detects that the current sum Is is less than the rated current I3 at time T21 shown in FIGS. 5 and 6, the control unit 71 is based on the permission signal EN1 from the first transmission circuit 95 of the first control unit 87. The exclusive PWM control by the second control unit 89 is terminated. Thereby, the second control unit 89, in other words, regardless of the signal level of the enable signal EN1 transmitted from the first transmission circuit 95 (the current supply state to the first motor 77 by the first control unit 87). Regardless of whether the first control unit 87 turns on the switching element SW1 of the first inverter 83, the PWM control based on the clock signal CLK2 is performed. The second control unit 89 supplies the PWM control signal x2H in synchronization without delaying the rising timing of the clock signal CLK2.

  In addition, the structure which determines whether the starting state of the 1st and 2nd motors 77 and 78 was complete | finished is not restricted to the structure which uses the above-mentioned current sum Is. The control unit 71 may determine whether or not the first and second motors 77 and 78 are activated based on the elapsed time since the activation of the first and second motors 77 and 78 is started. For example, the average time of the time T21 when the current sum Is becomes the rated current I3 is measured in advance by simulation or the like, and the average time is set in the control unit 71. As a result, the control unit 71 can determine the time point when the set average time has elapsed since the start of the start as the transition from the start state to the stable state.

  Alternatively, the control unit 71 may determine whether or not the first and second motors 77 and 78 are in the activated state based on the rotational speeds S1 and S2 of the first and second motors 77 and 78, respectively. For example, the rotational speed N1 (see FIG. 6) of the second motor 78 and the rotational speed N2 of the first motor 77 when the current sum Is is less than the rated current I3 are acquired in advance and set in the control unit 71. Thereby, for example, the control unit 71 sets the time when the rotation speeds S1 and S2 of the first and second motors 77 and 78 have reached the rotation speeds N1 and N2 as the end of the activation state after starting the activation. It becomes possible to judge. Alternatively, the control unit 71 sets the time when any one of the rotation speeds S1 and S2 of the first and second motors 77 and 78 has reached the rotation speeds N1 and N2 in the activated state. You may determine as completion | finish.

  The determination of the timing for ending the exclusive PWM control is not limited to the timing at which the current sum Is of the current values I1 and I2 decreases to the rated current I3. For example, the control unit 71 detects when the signal levels of the detection signals SI1 and SI2 of the first and second comparators 91 and 93 are not inverted for a predetermined time, in other words, the rush that flows into the switching elements SW1 and SW2. The timing at which the peak value of the current does not exceed the limit value for a predetermined time may be set as the timing at which the exclusive process ends.

  Incidentally, the 1st control part 87 and the 1st inverter 83 are examples of a 1st drive circuit. The first transmission circuit 95 is an example of a transmission circuit. The permission signal EN1 is an example of a supply state. The on period ONT1 is an example of a first on period. The off period OFT1 is an example of a first off period. The cycle of the clock signal CLK1 is an example of a first cycle. The second control unit 89 and the second inverter 85 are an example of a second drive circuit. The on period ONT2 is an example of a second on period. The off period OFT2 is an example of a second off period. The cycle of the clock signal CLK2 is an example of a second cycle. The control unit 71 in the case where the activation state is determined based on the current sum Is is an example of a current detection circuit. The power supply circuit 81 is an example of a current source. The control unit 71 when determining the activation state based on the elapsed time is an example of a timer circuit.

As described above, according to the first embodiment described above, the following effects are obtained.
<Effect 1> The first controller 87 turns the switching element SW1 of the first inverter 83 on and off, and changes the ON period ONT1 during which the power (current) supply to the first motor 77 is turned on, thereby changing the first motor 77. The rotational speed S1 is controlled. Similarly, the second control unit 89 turns on / off the switching element SW2 of the second inverter 85, and changes the ON period ONT2 during which the power supply to the second motor 78 is turned on, thereby rotating the rotation speed S2 of the second motor 78. To control. The first control unit 87 includes a first transmission circuit 95 for transmitting the permission signal EN <b> 1 indicating whether or not power is being supplied to the first motor 77 to the second control unit 89. Then, the second control unit 89 performs the first control during the OFF period OFT1 of the first motor 77 based on the permission signal EN1 transmitted from the first transmission circuit 95 when the first and second motors 77 and 78 are activated. 2 Power supply to the motor 78 is turned on. The first and second control units 87 and 89 perform such exclusive PWM control in the activated state, thereby generating an inrush current flowing in the windings L1 and L2 of the first and second motors 77 and 78. It is possible to suppress the increase in superimposed time by shifting the time. Thus, according to the printer 10, it is possible to prevent the occurrence of problems such as failure of the power supply circuit 81 and disconnection of the wiring connecting the power supply circuit 81 and the first and second inverters 83 and 85. .

  In addition, the first motor 77 of this embodiment has a higher priority than the second motor 78, and power is supplied prior to the second motor 78. Therefore, the first motor 77 can shorten the time until it stabilizes at the target speed St1. Here, if both the first and second motors 77 and 78 are not in a stable state, the image forming unit 15 cannot drive the process cartridges 44 of all colors and start a desired printing process. For this reason, in order to shorten the starting time of the entire image forming unit 15, the first and second motors 77 and 78 need to shorten the starting time of the motor having the longer starting time. For example, it is assumed that the first motor 77 according to the present embodiment has a longer start-up time until the first motor 77 is stabilized at the target speed St2 than the second motor 78. In this case, in the printer 10 of the present embodiment, the priority of the first motor 77 having a longer startup time is increased, so that the startup of the image forming unit 15 is started even if the startup time of the second motor 78 is slightly delayed. It is possible to reduce the time, and thus the time required until the printing process of the printer 10 can be started. As described above, according to the printer 10 of the present embodiment, it is possible to suppress the inrush current at the start-up and shorten the start-up time.

<Effect 2> The first controller 87 monitors the peak value of the current flowing through each switching element SW1 of the first inverter 83 by determining the signal level of the detection signal SI1 of the first comparator 91. When the peak current value of the switching element SW1 exceeds the upper limit value, the first control unit 87 stops supplying the PWM control signal to the first inverter 83 and turns off all the switching elements SW1. That is, the first control unit 87 shortens the ON period ONT1 according to the current limit. Thus, the first control unit 87 can protect the circuit by preventing the overcurrent from flowing through the switching element SW1 of the first inverter 83, the wiring connecting the switching element SW1, and the like. On the other hand, since the OFF period OFT1 of the first motor 77 becomes relatively long due to the current limitation, the second control unit 89 can easily supply power to the second motor 78.

<Effect 3> The first control unit 87 starts supplying power to the first motor 77 in synchronization with the next rising edge of the clock signal CLK1 after stopping the power supply to the first motor 77 due to current limitation. (See time T4 in FIG. 5). That is, the first controller 87 performs PWM control according to the clock signal CLK1 regardless of the supply state of the second motor 78. In such a configuration, the first control unit 87 does not need to monitor the supply state of the second control unit 89.

<Effect 4> The cycle of the clock signal CLK1 used for the PWM control by the first controller 87 is the same as the cycle of the clock signal CLK2 of the second controller 89. As a result, the first and second control units 87 and 89 can perform processing synchronously, and simplification of processing contents for performing exclusive PWM control can be achieved.

<Effect 5> The target speed St1 of the first motor 77 of this embodiment is faster than the target speed St2 of the second motor 78. In general, a motor having a high target speed St1, St2 has a long startup time. Therefore, in the printer 10 of the present embodiment, it is possible to shorten the time required until the printing process can be started by increasing the priority of the first motor 77 having a longer startup time.

<Effect 6> When the control unit 71 detects that the current sum Is becomes the rated current I3 at time T21 (see FIGS. 5 and 6), the control unit 71 determines the second control unit 89 based on the permission signal EN1. Exclusive PWM control is terminated. The second control unit 89 performs PWM control based on the clock signal CLK2 regardless of the signal level (supply state) of the enable signal EN1 transmitted from the first transmission circuit 95. In a state where the current sum Is decreases to the rated current I3, the first and second inverters 83 and 85 are less likely to be current limited, and exceed the rated current I3 of the power supply circuit 81 even when energized at the same time. The possibility is very low. Therefore, according to the printer 10, it is possible to appropriately determine and supply the timing for starting energization to the first and second inverters 83 and 85 at the same time, and to reduce the load on the power supply circuit 81.

<Effect 7> The control unit 71 calculates the current sum Is based on the current values I1 and I2 input from the power supply circuit 81, for example. When the controller 71 detects that the current sum Is has decreased to the rated current I3 after taking the maximum value, the controller 71 determines that the transition is from the startup state to the stable state. Thereby, the control unit 71 can appropriately determine the timing of starting energization to the first and second inverters 83 and 85 at the same time.

(Second embodiment)
Next, a second embodiment will be described with reference to FIG. In the first embodiment, the case where the clock signals CLK1 and CLK2 of the first and second motors 77 and 78 have the same period has been described as an example. However, in the second embodiment, the periods of the clock signals CLK1 and CLK2 are different from each other. The case will be described. As an example, in the second embodiment, a case will be described in which a main motor 65 is applied as a motor driven by a clock signal CLK1 having a long cycle and a polygon motor 66 is applied as a motor driven by a clock signal CLK2 having a short cycle. In the following description, description will be made using the timing chart of FIG. The circuits for driving the main motor 65 and the polygon motor 66 can be realized by a circuit similar to the circuit shown in FIG. 3 and will be described using the same reference numerals.

  As shown in FIG. 7, first, as the main motor 65 and the polygon motor 66 are activated, the first and second control units 87 and 89 (see FIG. 3) send the PWM control signals x1H and x2H to the first and first PWM signals. 2 The process of supplying to the inverters 83 and 85 is started. The high-priority main motor 65 is supplied with power in synchronization with the rise of the clock signal CLK1 at time T0 (see the ON period ONT1 in the figure). On the other hand, the polygon motor 66 is limited in power supply in accordance with the supply state of the main motor 65. The main motor 65 starts supplying power from time T1 behind the polygon motor 66.

  Further, since the cycle of the clock signal CLK2 of the polygon motor 66 is shorter than that of the clock signal CLK1 of the main motor 65, the rising of the clock signal CLK2 occurs again at time T3 during the off period OFT1 of the main motor 65. When the second control unit 89 that drives the polygon motor 66 detects that the first inverter 83 is not supplying power to the main motor 65 based on the permission signal EN <b> 1 of the first transmission circuit 95, the second inverter 85. Is operated to supply power to the polygon motor 66 (see the ON period ONT2 in the figure). The second control unit 89 supplies power to the polygon motor 66 in synchronization with the rising edge of the clock signal CLK2. That is, in this embodiment, a motor with a low priority is set to a motor with a short cycle of the clock signal CLK2 (polygon motor 66 in this embodiment), so that a motor with a high priority (main motor 65 in this embodiment) is set. ) During the off period OFT1 is increased.

  In this embodiment, priority is given to PWM control to the main motor 65. For this reason, as shown in FIG. 7, when the clock signal CLK1 of the first control unit 87 rises during the ON period ONT2 started from the time T5, the second control unit 89 changes to the enable signal EN1 of the first transmission circuit 95. Based on this, the power supply to the polygon motor 66 is stopped. For example, even if the second control unit 89 is scheduled to supply power from time T5 to time T7, the supply is stopped at time T6 when the clock signal CLK1 rises due to the limitation associated with the driving of the first control unit 87. It will be.

  Incidentally, the main motor 65 is an example of a first motor. The cycle of the clock signal CLK1 is an example of a first cycle. The polygon motor 66 is an example of a second motor. The cycle of the clock signal CLK2 is an example of a second cycle.

As described above, according to the second embodiment described above, the following effects are obtained.
<Effect 1> The clock signal CLK2 of the polygon motor 66 has a shorter period than the clock signal CLK1 of the main motor 65. In such a configuration, by giving priority to the main motor 65 having a long cycle, the opportunity to supply power to the polygon motor 66 having a short cycle is increased while considering the supply state to the main motor 65. The startup time can be shortened.

<Effect 2> When the second controller 89 detects that the first inverter 83 is not supplying power to the main motor 65 at the timing when the clock signal CLK2 rises, the polygon motor 66 synchronizes with the rise of the clock signal CLK2. To supply power. Thereby, the polygon motor 66 is immediately supplied with power when the clock signal CLK2 rises during the off period OFT1 of the main motor 65.

<Effect 3> According to the printer 10 of this embodiment, for example, the target speed of the polygon motor 66 (target speed St2 in the first embodiment) is changed to the target speed of the main motor 65 (target speed St1 in the first embodiment). In the case where it is faster than the above, it is possible to shorten the time required for starting the printing process by increasing the opportunity to supply power to the polygon motor 66 having a longer startup time.

<Effect 4> Generally, the clock signal CLK2 used for controlling the polygon motor 66 has a shorter period than the clock signal CKL1 of the main motor 65. Therefore, it is extremely effective to perform the exclusive PWM control corresponding to the above-described cycle for the main motor 65 and the polygon motor 66.

(Third embodiment)
Next, a third embodiment will be described with reference to FIGS. In the first embodiment, the case where only the first control unit 87 includes the first transmission circuit 95 has been described as an example. In the third embodiment, the case where the second control unit 89 also includes the second transmission circuit 97 will be described. . As an example, in the third embodiment, a case of a main motor 65 driven by a clock signal CLK1 having a long cycle and a polygon motor 66 driven by a clock signal CLK2 having a short cycle will be described. In the following description, the same components as those in the first and second embodiments are denoted by the same reference numerals, and the description thereof is omitted as appropriate.

  As shown in FIG. 8, the second transmission circuit 97 that drives the polygon motor 66 includes a second transmission circuit 97 that transmits the permission signal EN <b> 2 to the first control unit 87. The second transmission circuit 97 changes the signal level of the enable signal EN2 as the supply of the PWM control signal to the second inverter 85 stops due to current limitation. The first controller 87 starts supplying the PWM control signal to the first inverter 83 based on the permission signal EN2. That is, the first and second control units 87 and 89 of the third embodiment are configured to monitor the supply state of each other.

  For this reason, as shown in FIG. 9, the second control unit 89 is scheduled to supply power even if the clock signal CLK1 of the first control unit 87 rises during the ON period ONT2 started from the time T5. Until then, the power supply to the polygon motor 66 is continued. On the other hand, even if the clock signal CLK1 rises at time T6, the first controller 87 stops the power supply to the main motor 65 until time T7 based on the permission signal EN2 of the second transmission circuit 97. Therefore, in the first and second control units 87 and 89 of this embodiment, when one of the control units supplies the PWM control signal, the other control unit supplies one of the PWM control signals. Will wait until is finished.

  Incidentally, the second transmission circuit 97 is an example of a transmission circuit. The main motor 65 is an example of a first motor. The cycle of the clock signal CLK1 is an example of a first cycle. The polygon motor 66 is an example of a second motor. The cycle of the clock signal CLK2 is an example of a second cycle.

As described above, according to the third embodiment described above, the following effects are obtained.
<Effect 1> In addition to the first control unit 87, the control unit 71 includes a second transmission circuit 97 that transmits a supply state to the second transmission circuit 97 as well. The first controller 87 starts supplying the PWM control signal to the first inverter 83 based on the permission signal EN2 of the second transmission circuit 97. In such a configuration, the first and second control units 87 and 89 monitor each other's supply state, so that exclusive control can be more reliably performed.

In addition, this invention is not limited to said each Example, It is possible to implement in the various aspect which gave various change and improvement based on the knowledge of those skilled in the art.
For example, in each of the above embodiments, the printer 10 capable of color printing has been described as an example of the image forming apparatus of the present application, but the present invention is not limited to this. For example, the image forming apparatus may be a monochrome printer having a single color or a multifunction machine having a FAX function in addition to an image forming function.

  Alternatively, the technology disclosed in the present application can also be applied to a motor control device that controls a plurality of motors, for example, a motor control device of an image reading device. In this motor control device, for example, as a motor provided in the image reading device, a motor of an automatic document feeding (auto document feeder: ADF) device that takes in a sheet, or a moving reading (flatbed: FB) that moves a carriage for reading an image. It can be used to control the motor of the device. In this case, the motor control device does not need to include the image forming unit 15.

  In addition, the first and second control units 87 and 89 may perform current control in the startup state by a method different from the detection signals SI1 and SI2 of the first and second comparators 91 and 93. For example, the first and second control units 87 and 89 may limit the power supply time and limit the current at startup. In this case, the first and second inverters 83 and 85 can be changed to a circuit configuration in which the first and second comparators 91 and 93 are omitted.

The control unit 71 may perform exclusive PWM control for three or more motors.
In the first embodiment, for example, as shown at time T <b> 1 in FIG. 5, the second control unit 89 supplies power to the second motor 78 immediately after the power supply to the first motor 77 is stopped. Although it is set to start, it may be set to start supply after a certain time from time T1.
In the first embodiment, the second inverter 85 may not include the second comparator 93.

  In the above embodiment, the exclusive PWM control is stopped at time T21 when the state where the current sum Is of the current value I1 and the current value I2 exceeds the rated current I3 of the power supply circuit 81 ends. Exclusive PWM control may be performed continuously.

  DESCRIPTION OF SYMBOLS 10 Printer (image forming apparatus), 15 Image forming part, 47 Photosensitive drum (photosensitive body), 65 Main motor, 66 Polygon motor, 68 Speed detection circuit, 71 Control part (1st and 2nd drive circuit, timing circuit, Current detection circuit), 77 first motor, ONT1 ON period (first ON period), OFT1 OFF period (first OFF period), 78 second motor, ONT2 ON period (second ON period), OFT2 OFF period (first) 2 off period), 83 first inverter (first drive circuit), 85 second inverter (second drive circuit), 81 power supply circuit (current source), 87 first control unit (first drive circuit), 89 second Control unit (second drive circuit), 95, 97 First and second transmission circuits (transmission circuit).

Claims (15)

A first motor driven in accordance with a supplied current;
By changing the first on-period for a first period consisting of a first on-period for turning on the current supply to the first motor and a first off-period for turning off the current supply to the first motor. A first drive circuit for controlling the rotational speed of the first motor;
A second motor driven in accordance with the supplied current;
By changing the second on-period for a second period consisting of a second on-period in which the current supply to the second motor is turned on and a second off period in which the current supply to the second motor is turned off. A second drive circuit for controlling the rotational speed of the second motor;
An image forming unit that forms an image on a sheet in accordance with driving of the first and second motors;
A transmission circuit for transmitting a current supply state to the first motor by the first drive circuit to the second drive circuit;
With
The second drive circuit turns on current supply to the second motor during a first off period of the first motor based on the supply state in response to activation of the first and second motors. An image forming apparatus.   At least one of the first and second drive circuits has a current value exceeding the upper limit value when a current value of current supplied to at least one of the first and second motors exceeds an upper limit value. 2. The image forming apparatus according to claim 1, wherein at least one of the first and second on-periods is shortened as compared with a case where there is not.   The first drive circuit turns on the current supply to the first motor in accordance with a timing at which the next first cycle starts after the current supply to the first motor is turned off. The image forming apparatus according to claim 1. A second transmission circuit for transmitting the state of supply of current to the second motor according to prior Symbol second driving circuit to the first driving circuit,
The first drive circuit turns on current supply to the first motor during a second off period of the second motor based on a current supply state to the second motor by the second drive circuit. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The image forming apparatus according to claim 1, wherein the first period has the same length as the second period.   The target speed of the first motor at start-up controlled by the first drive circuit is faster than the target speed of the second motor at start-up controlled by the second drive circuit. Item 6. The image forming apparatus according to Item 5.   The image forming apparatus according to claim 1, wherein the second period is shorter than the first period.   The second drive circuit is configured to start the second cycle when the current supply to the first motor of the first drive circuit is turned off when the second cycle is started. The image forming apparatus according to claim 7, wherein the current supply to the second motor is also turned on.   The target speed of the second motor at start-up controlled by the second drive circuit is faster than the target speed of the first motor at start-up controlled by the first drive circuit. The image forming apparatus according to claim 7 or 8. The first motor is a main motor that rotationally drives a photoreceptor included in the image forming unit,
The image forming apparatus according to claim 7, wherein the second motor is a polygon motor that rotationally drives a polygon mirror that scans the photosensitive member with laser light.   The second drive circuit determines that the sum of currents supplied to each of the first and second motors does not exceed a rated current of a current source that supplies current to the first and second motors. 11. The image forming apparatus according to claim 1, wherein the current supply to the second motor is turned on regardless of the supply state transmitted from the transmission circuit. . A speed detection circuit for detecting a rotation speed of at least one of the first and second motors;
The image according to claim 11, wherein the second drive circuit determines whether the current sum exceeds a rated current of the current source based on a rotation speed detected by the speed detection circuit. Forming equipment. A timing circuit that counts an elapsed time since the start of at least one of the first and second motors;
12. The image forming according to claim 11, wherein the second drive circuit determines whether or not the current sum exceeds a rated current of the current source based on an elapsed time measured by the timing circuit. apparatus. A current detection circuit for detecting a current value of a current supplied to the first and second motors;
The image according to claim 11, wherein the second drive circuit determines whether or not the current sum exceeds a rated current of the current source based on a current value detected by the current detection circuit. Forming equipment. A first motor driven in accordance with a supplied current;
By changing the first on-period for a first period consisting of a first on-period for turning on the current supply to the first motor and a first off-period for turning off the current supply to the first motor. A first drive circuit for controlling the rotational speed of the first motor;
A second motor driven in accordance with the supplied current;
By changing the second on-period for a second period consisting of a second on-period in which the current supply to the second motor is turned on and a second off period in which the current supply to the second motor is turned off. A second drive circuit for controlling the rotational speed of the second motor;
A transmission circuit for transmitting a current supply state to the first motor by the first drive circuit to the second drive circuit;
With
The second drive circuit turns on current supply to the second motor during a first off period of the first motor based on the supply state in response to activation of the first and second motors. A motor control device.

Images