Image forming device

Abstract

To solve a problem in which: without omission of operations to estimate an initial position in a motor that drives a pick-up roller, the FPOT of a print job 2 in an image forming apparatus cannot be reduced; constantly holding a rotor in a period from the completion of a print job 1 until the start of the print job 2 increases power consumption.SOLUTION: Excitation of winding of a motor 402 that drives a pick-up roller 19 is maintained for a period from the completion of a print job 1 until the lapse of a predetermined time. As a result, the FPOT in a print job 2 is reduced. Compared with a case in which a rotor is constantly held in a period from when the print job 1 is completed until the start of the print job 2 is instructed, power consumption can be reduced.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] The present invention relates to the control of a motor in an image forming apparatus. [Background technology]

[0002] Conventionally, there is known a technique for estimating the stop position (initial position) of the rotor of a brushless DC motor by utilizing the fact that inductance changes depending on the rotor position when starting the brushless DC motor. Patent Document 1 describes a configuration in which the initial position is estimated based on the responsiveness of the current when a voltage is applied to the windings of the brushless DC motor, and driving of the brushless DC motor is started based on the estimated initial position.

[0003] In an image forming apparatus, when a brushless DC motor that drives a transport roller that transports a recording medium is stopped and the excitation of the windings is cut off, and then the brushless DC motor is started again, the following may occur. Specifically, the rotor position when the brushless DC motor starts to drive may be different from the position when the motor stopped due to vibrations of the image forming apparatus or the like. Therefore, when the brushless DC motor is started to drive after the excitation of the windings of the brushless DC motor is cut off, it is necessary to estimate the initial position as described above. The operation of estimating the initial position takes a certain amount of time.

[0004] Patent Document 2 describes an image forming apparatus in which the rotor of a brushless DC motor that drives a registration roller that corrects skew of a recording medium is held after print job 1 is completed. Patent Document 2 also describes that with this configuration, it is possible to omit the operation of estimating the initial position of the rotor of the brushless DC motor that drives the registration roller when an instruction to start print job 2 is given after print job 1 is completed. Patent Document 2 further describes that the above configuration makes it possible to shorten the first print output time (FPOT), which is the time from when a user issues a print instruction in print job 2 until the first sheet of recording medium is output. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-104263 [Patent Document 2] Japanese Patent Application Publication No. 2019-195232 Summary of the Invention [Problem to be solved by the invention]

[0006] Even if the operation of estimating the initial position of the motor that drives the registration roller is omitted, the FPOT of print job 2 in the image forming apparatus cannot be reduced unless the operation of estimating the initial position of the motor that drives the pickup roller that feeds recording media loaded on the stacking tray is omitted. However, while Patent Document 2 describes control of the brushless DC motor that drives the registration roller, it does not describe control of the motor that drives the pickup roller. In other words, the configuration in Patent Document 2 does not allow the FPOT of print job 2 in the image forming apparatus to be reduced.

[0007] Furthermore, in the configuration of Patent Document 2, because the operation of estimating the initial position is omitted, there is a possibility that the rotor will always be held during the period from when print job 1 ends until an instruction to start print job 2 is issued. For example, if the period from when print job 1 ends until when print job 2 starts is several tens of minutes or more, the power consumption during that period in Patent Document 2 will be greater than the power consumption when the rotor is not held during that period.

[0008] In view of the above-mentioned problems, an object of the present invention is to provide an image forming apparatus that can reduce FPOT while suppressing power consumption in the image forming apparatus. [Means for solving the problem]

[0009] In order to solve the above problems, an image forming apparatus according to the present invention comprises: a loading section on which recording media are loaded; a pickup roller that feeds the recording medium loaded in the loading section; a first motor that drives the pickup roller; a conveying roller that is provided downstream of the pickup roller in a conveying direction in which the recording medium is conveyed and that conveys the recording medium fed by the pickup roller; a second motor that drives the conveying roller; an image forming means for forming an image on the recording medium fed by the pickup roller; a receiving unit that receives an instruction to start an image forming job for forming an image on the recording medium; When the receiving unit receives an instruction to start a first job as the image forming job, a current is supplied to a winding of the first motor in a first stop state in which a rotor of the first motor is stopped, and the First motor A control means for executing a first initial operation for determining a phase of the rotor, the control means performing the first initial operation for determining a phase of the rotor in the first stopped state based on the phase determined by the first initial operation. First motor Controlling the current supplied to the windings so that the rotor rotates a second initial operation is performed in which a current is supplied to a winding of the second motor in a second stop state in which the rotor of the second motor is stopped, and a phase of the rotor of the second motor in the second stop state is determined based on the current flowing through the winding of the second motor; and the current supplied to the winding of the second motor is controlled so that the rotor of the second motor in the second stop state rotates based on the phase determined by the second initial operation. a control means for controlling the and When the first job is completed, the control means First motor The rotor is held in the first phase. First motor Controlling the current supplied to the windings; The control means First motor When the receiving unit receives an instruction to start a second job as the image forming job during a first period from when the rotor is held at the first phase until a first predetermined time has elapsed, the first initial operation is not performed and the held First motor As the rotor rotates, First motor Controlling the current supplied to the windings; If the receiving unit does not receive an instruction to start the second job during the first period, the control unit First motor Stops supplying current to the winding death, the control means stops supplying current to the windings of the second motor when the rotation of the rotor of the second motor is stopped; When the control means receives an instruction to start the second job, the control means executes the second initial operation, and then controls the current supplied to the windings of the second motor so that the rotor of the second motor in the second stop state rotates based on the phase determined by the second initial operation. It is characterized by: In order to solve the above problems, the image forming apparatus according to the present invention comprises: a loading section on which recording media are loaded; a pickup roller that feeds the recording medium loaded in the loading section; a first motor that drives the pickup roller; a conveying roller that is provided downstream of the pickup roller in a conveying direction in which the recording medium is conveyed and that conveys the recording medium fed by the pickup roller; a second motor that drives the conveying roller; an image forming means for forming an image on the recording medium fed by the pickup roller; a receiving unit that receives an instruction to start an image forming job for forming an image on the recording medium; a control means for executing a first initializing operation, when the receiving unit receives an instruction to start a first job as the image formation job, of supplying a current to a winding of the first motor in a first stop state in which a rotor of the first motor is stopped, and determining a phase of the rotor of the first motor in the first stop state based on the current flowing through the winding, and controlling the current supplied to the winding so that the rotor of the first motor in the first stop state rotates based on the phase determined by the first initializing operation; and a control means for executing a second initializing operation, when the receiving unit receives an instruction to start a first job as the image formation job, of supplying a current to a winding of the first motor in a first stop state in which a rotor of the first motor is stopped, and determining a phase of the rotor of the second motor in the second stop state based on the current flowing through the winding of the second motor, and controlling the current supplied to the winding of the second motor so that the rotor of the second motor rotates in the second stop state based on the phase determined by the second initializing operation; and the control means controls the current supplied to the windings of the first motor so that the rotor of the first motor is maintained at a first phase when the first job is completed; when the receiving unit receives an instruction to start a second job as the image formation job during a first period from when the rotor of the first motor is held at the first phase until a first predetermined time has elapsed, the control means controls the current supplied to the windings of the first motor so that the held rotor of the first motor rotates without performing the first initial operation; the control means stops supplying current to a winding of the first motor when the receiving unit does not receive an instruction to start the second job during the first period; when the control means stops rotation of the rotor of the second motor, the control means controls the current supplied to the windings of the second motor so that the rotor of the second motor is maintained in a second phase; The control means is characterized in that it stops supplying current to the windings of the second motor when a time shorter than the first predetermined time has elapsed since the rotor of the second motor was held in the second phase. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an image forming apparatus that can reduce FPOT while suppressing power consumption in the image forming apparatus. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a cross-sectional view illustrating an image forming apparatus. [Figure 2] FIG. 2 is a block diagram showing a control configuration of the image forming apparatus according to the first embodiment. [Figure 3] FIG. 2 is a block diagram showing the configuration of a motor control device. [Figure 4] FIG. 2 is a diagram illustrating the structure of a motor. [Figure 5] FIG. 4 is a diagram showing the relationship between the rotor stop position and the excitation phase. [Figure 6] 1 is a diagram showing the relationship between the U-phase, V-phase, and W-phase and a rotating coordinate system represented by the d-axis and q-axis. FIG. [Figure 7] FIG. 2 is a block diagram illustrating a configuration of a vector control unit. [Figure 8] FIG. 4 is a diagram showing a drive sequence of a motor. [Figure 9] 4 is a flowchart illustrating motor control by a CPU in the first embodiment. [Figure 10] FIG. 10 is a block diagram showing an example of a control configuration of an image forming apparatus 100 according to a third embodiment. [Figure 11] FIG. 2 is a diagram illustrating a detection area of ​​a human body detection sensor. [Figure 12] FIG. 4 is a diagram showing a drive sequence of a motor. [Figure 13] 10 is a flowchart illustrating motor control by a CPU in the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Preferred embodiments of the present invention will be described below with reference to the drawings. However, the shapes of the components and their relative positions described in the embodiments may be changed as appropriate depending on the configuration of the device to which the present invention is applied and various conditions, and the scope of the present invention is not intended to be limited to the following embodiments.

[0013] [First embodiment] [Image forming device] 1 is a cross-sectional view showing the configuration of a color electrophotographic copying machine (hereinafter referred to as an image forming apparatus) 100 used in this embodiment. Note that the image forming apparatus is not limited to a copying machine, and may be, for example, a facsimile machine, a printing machine, a printer, etc. Furthermore, the recording method is not limited to an electrophotographic method, and may be, for example, an inkjet method. Furthermore, the type of the image forming apparatus may be either a monochrome type or a color type.

[0014] The configuration and functions of the image forming apparatus 100 will be described below with reference to Fig. 1. As shown in Fig. 1, the image forming apparatus 100 has an original reading device 200 including an original feeding device 201 and a reading device 202, and an image printing device 301.

[0015] <Document reader> The documents P loaded on the document stacking section 2 of the document feeder 201 are fed one by one by a pickup roller 3, and then transported further downstream by a feed roller 4. A separation roller 5 is provided opposite the feed roller 4 and presses against the feed roller 4. The separation roller 5 is configured to rotate when a load torque equal to or greater than a predetermined torque is applied to the separation roller 5, and has the function of separating documents that are fed in a stack of two.

[0016] The pickup roller 3 and the feed roller 4 are connected by a swing arm 12. The swing arm 12 is supported on the rotation shaft of the feed roller 4 so as to be rotatable around the rotation shaft of the feed roller 4.

[0017] The document P is conveyed by the feed roller 4 and the like, and is discharged onto the discharge tray 10 by the discharge roller 11.

[0018] The reading device 202 is provided with a document reading section 16 that reads an image on the first side of a document being conveyed. Image information read by the document reading section 16 is output to an image printing device 301.

[0019] The document feeder 201 is also provided with a document reading unit 17 that reads the image on the second side of the document being conveyed. The image information read by the document reading unit 17 is output to the image printing device 301 in the same manner as described for the document reading unit 16.

[0020] As described above, the document is read.

[0021] Furthermore, there are a first reading mode and a second reading mode as document reading modes. The first reading mode is a mode in which an image of a document transported by the method described above is read. The second reading mode is a mode in which an image of a document placed on the document glass 214 of the reading device 202 is read by the document reading unit 16, which moves at a constant speed. Normally, an image of a sheet-like document is read in the first reading mode, and an image of a bound document such as a book or pamphlet is read in the second reading mode.

[0022] <Image printing device> A sheet storage tray 18 for storing recording media is provided inside the image printing device 301. Note that a recording medium is a medium on which an image is formed by an image forming device, and includes, for example, paper, resin sheets, cloth, OHP sheets, labels, etc.

[0023] The recording medium stored in the sheet storage tray 18 is sent out by a pickup roller 19 and sent to the registration rollers 20 by conveyance rollers 39, 40, 41, 42, etc.

[0024] The image printing device 301 is also provided with a manual feed tray 44 for loading recording media. The recording media loaded on the manual feed tray 44 are sent out by a pickup roller 43 and then sent to the registration rollers 20 by conveyance rollers 44, 42, etc.

[0025] The leading edge of the recording medium conveyed by the pre-registration roller 37 hits the registration roller 20. As a result, a loop is formed in the recording medium between the registration roller 20 and the pre-registration roller 37, and the skew of the recording medium is corrected (reduced).

[0026] The image signals output from the document reading device 200 are input for each color component to optical scanning devices 21Y, 21M, 21C, and 21K, each of which includes a semiconductor laser and a polygon mirror. Specifically, the image signal for yellow output from the document reading device 200 is input to optical scanning device 3Y, and the image signal for magenta output from the document reading device 200 is input to optical scanning device 3M. Furthermore, the image signal for cyan output from the document reading device 200 is input to optical scanning device 3C, and the image signal for black output from the document reading device 200 is input to optical scanning device 3K. Note that, although the following description will be given of a configuration for forming a yellow image, similar configurations apply to magenta, cyan, and black.

[0027] The outer peripheral surface of the photosensitive drum 22Y is charged by the charger 23Y. After the outer peripheral surface of the photosensitive drum 22Y is charged, a laser beam corresponding to an image signal input from the document reading device 200 to the optical scanning device 21Y is irradiated onto the outer peripheral surface of the photosensitive drum 22Y from the optical scanning device 21Y via an optical system including a polygon mirror and other mirrors. As a result, an electrostatic latent image is formed on the outer peripheral surface of the photosensitive drum 22Y.

[0028] Subsequently, the electrostatic latent image is developed with toner in a developing unit 24Y as a developing section, and a toner image is formed on the outer peripheral surface of the photosensitive drum 22Y. The toner image formed on the photosensitive drum 22Y is transferred to a transfer belt 27 as an intermediate transfer body by a transfer roller 25Y provided at a position facing the photosensitive drum 22Y. Note that toner remaining on the outer peripheral surface of the photosensitive drum 22Y after the toner image has been transferred to the transfer belt 27 is collected by a cleaning unit 26Y.

[0029] The yellow, magenta, cyan, and black toner images transferred onto the transfer belt 27 are then transferred onto the recording medium by a pair of transfer rollers 28. A high voltage is applied to the pair of transfer rollers 28, and the toner images are transferred onto the recording medium due to this high voltage. In synchronization with this transfer timing, the registration rollers 20 feed the recording medium into the pair of transfer rollers 28.

[0030] As described above, the recording medium onto which the toner image has been transferred is sent to the fixing device 29, which serves as a fixing unit, and the toner image is fixed to the recording medium by heating and pressurizing the recording medium by the fixing device 29. In this way, an image is formed on the recording medium by the image forming apparatus 100.

[0031] When an image is formed on a recording medium in single-sided printing mode, the recording medium that has passed through the fixing unit 29 is discharged to a discharge tray 31 by a discharge roller 30. When an image is formed on a recording medium in double-sided printing mode, the fixing unit 29 performs a fixing process on the first side of the recording medium, and the recording medium is then conveyed to a reversing path 32 by a reversing roller 38. The recording medium conveyed to the reversing path 32 has its first and second sides reversed by the reversing roller 38 and is conveyed to a conveyance guide provided with conveyance rollers 33, 34, 35, and 36. The recording medium is conveyed again to the registration rollers 20 by the conveyance rollers 33, 34, 35, 36, etc., and an image is formed on the second side of the recording medium in the manner described above. The recording medium is then discharged to a discharge tray 31 by a discharge roller 30.

[0032] The above is a description of the configuration and functions of image forming apparatus 100.

[0033] <Control configuration of image forming apparatus> Fig. 2 is a block diagram showing an example of the control configuration of the image forming apparatus 100. As shown in Fig. 2, the system controller 151 includes a CPU 151a, a ROM 151b, and a RAM 151c. The system controller 151 is also connected to the image processing unit 112, an operation unit 152, an analog-to-digital (A / D) converter 153, a high-voltage control unit 155, motor control devices 157 and 158, sensors 159, and an AC driver 160. The system controller 151 is capable of transmitting and receiving data and commands to and from each of the connected units.

[0034] The CPU 151a reads and executes various programs stored in the ROM 151b to execute various sequences related to a predetermined image formation sequence.

[0035] RAM 151c is a storage device that stores various data such as set values ​​for high voltage control unit 155, command values ​​for motor control devices 157 and 158, and information received from operation unit 152.

[0036] System controller 151 transmits setting value data of various devices provided inside image forming apparatus 100, which are necessary for image processing in image processing unit 112, to image processing unit 112. Furthermore, system controller 151 receives signals from sensors 159, and sets setting values ​​for high voltage control unit 155 based on the received signals.

[0037] High voltage control unit 155 supplies the necessary voltage to high voltage unit 156 (chargers 23Y, 23M, 23C, 23K, developers 24Y, 24M, 24C, 24K, transfer roller pair 28, etc.) according to the set value set by system controller 151.

[0038] Motor control device 157 controls the brushless DC motor in response to a command output from CPU 151a. Motor control device 158 controls brushless DC motor 403 in response to a command output from CPU 151a. Although only two motor control devices are shown in FIG. 2, three or more motor control devices may be provided in the image forming apparatus. Although only two motors are shown in FIG. 2, three or more motors are actually provided in the image forming apparatus. Furthermore, one motor control device may control multiple motors.

[0039] The A / D converter 153 receives a detection signal detected by a thermistor 154 for detecting the temperature of the fixing heater 161, converts the detection signal from an analog signal to a digital signal, and sends the digital signal to the system controller 151. The system controller 151 controls the AC driver 160 based on the digital signal received from the A / D converter 153. The AC driver 160 controls the fixing heater 161 so that the temperature of the fixing heater 161 reaches a temperature required for performing the fixing process. The fixing heater 161 is a heater used for the fixing process, and is included in the fixing unit 29.

[0040] The system controller 151 controls the operation unit 152 to display an operation screen on a display unit provided on the operation unit 152, which allows the user to set image forming conditions such as the type of recording medium to be used (hereinafter referred to as paper type). The system controller 151 receives information set by the user from the operation unit 152 and controls the operation sequence of the image forming apparatus 100 based on the information set by the user. The system controller 151 also transmits information indicating the status of the image forming apparatus to the operation unit 152. Note that information indicating the status of the image forming apparatus includes, for example, the number of images formed, the progress of the image forming operation, and information regarding sheet jams and double feeds in the document reading device 201 and the image printing device 301. The operation unit 152 displays the information received from the system controller 151 on the display unit. Note that, in this embodiment, while the operation unit 152 is being operated, the setting data and the like set on the operation unit 152 are transmitted from the operation unit 152 to the CPU 151a at predetermined time intervals.

[0041] As described above, the system controller 151 controls the operation sequence of the image forming apparatus 100 .

[0042] {Power Mode} In this embodiment, operation unit 152 is provided with a switch that is operated by a user to switch the power mode of image forming apparatus 100. Image forming apparatus 100 has a normal power mode and a power saving mode (sleep mode) as power modes.

[0043] The normal power mode is a state in which printing (image formation) on a recording medium can be performed by the image printing device 301. In the normal power mode, power is supplied to, for example, the system controller 151, the high voltage control unit 155, the motor control devices 157 and 158, the AC driver 160, and the like.

[0044] Furthermore, when the power mode is the power saving mode, power consumption is lower than in the normal power mode and printing (image formation) on a recording medium is not performed by the image printing device 301. In the power saving mode, for example, power is supplied to the system controller 151, but power is not supplied to the high voltage control unit 155, the motor control devices 157 and 158, the AC driver 160, etc.

[0045] [Motor control device] Next, motor control device 157 will be described. Motor control device 158 has the same configuration as motor control device 157, and therefore description thereof will be omitted. Brushless DC motor 402 (hereinafter referred to as motor 402) and brushless DC motor 403 (hereinafter referred to as motor 403) described below are not provided with sensors such as hall elements for detecting the rotation phase of the rotors of the motors.

[0046] 3 is a block diagram showing an example of the configuration of the motor control device 157. The motor control device 157 is configured with at least one ASIC, and executes the functions described below.

[0047] The motor control device 157 includes a processing unit 500. The processing unit 500 includes a reference clock generating unit 501, a counter 503, an AD converter 504, a non-volatile memory 506, and a vector control unit 507.

[0048] Reference clock generating section 501 generates a reference clock based on a signal from crystal oscillator 502. Counter 503 counts the pulse signal output from CPU 151a and determines the period of the pulse signal based on the count value and the reference clock.

[0049] A pulse width modulation (PWM) port 505 outputs a PWM signal for driving each switching element of the three-phase inverter 600. The switching elements of the three-phase inverter 600 are, for example, field effect transistors (FETs), and when the FETs are driven by the PWM signal, current is supplied to a plurality of windings 701 (U phase), 702 (V phase), and 703 (W phase) of the motor 402.

[0050] The current supplied to each of the windings 701, 702, and 703 is detected by the resistor 601 and the AD converter 504. Specifically, the voltage across the resistor 601 is converted from an analog value to a digital value by the AD converter 504, and the current supplied to each of the windings 701, 702, and 703 is detected.

[0051] In this embodiment, the current flowing in the winding of each phase is detected by resistor 601 provided at the point where the U-phase, V-phase, and W-phase wiring are connected, but this is not limiting. For example, the current flowing in the W-phase winding may be calculated based on the current detected by resistors provided in the U-phase wiring and V-phase wiring, or the current flowing in each phase winding may be detected by resistors provided in the U-phase, V-phase, and W-phase, respectively. In other words, it is sufficient to detect the current flowing in each phase using known technology.

[0052] <Motor structure> 4 is a diagram illustrating the structure of the motor 402 (motor 403). In this embodiment, the motor 402 is provided with three-phase (U, V, W) windings 701, 702, 703 wound around a stator.

[0053] Rotor 705 is made of a permanent magnet and has an N pole and an S pole. The stopping position of rotor 705 (rotation phase when stopped) is determined by the combination of excited windings 701, 702, and 703, i.e., the excitation phase. In the following explanation, exciting the X and Y phases means exciting the X phase to become an N pole and the Y phase to become an S pole.

[0054] <Detecting stopping position> Next, a description will be given of detection of the phase (stop position) of rotor 705 when rotor 705 is stopped. In this embodiment, the stop position of rotor 705 is detected by utilizing the fact that the inductance of each of windings 701, 702, and 703 changes depending on the stop position of rotor 705.

[0055] Generally, windings are made of copper wire wound around a core made of laminated electromagnetic steel sheets. The magnetic permeability of electromagnetic steel sheets decreases in the presence of an external magnetic field. In other words, when an external magnetic field is present, the inductance of the winding, which is proportional to the magnetic permeability of the core, also decreases.

[0056] For example, as shown in Figure 4, when rotor 705 is stopped so that the center of the south pole region of rotor 705 is located at the position opposite V-phase winding 702, the influence of the external magnetic field caused by rotor 705 is large, and the rate of decrease in inductance of winding 702 is large.

[0057] The rate of decrease in inductance also varies depending on the direction of the current flowing through the V-phase winding 702. Specifically, when the direction of the magnetic field caused by the current flowing through the winding 702 is the same as the direction of the external magnetic field from the rotor 705, the rate of decrease in inductance is greater than when the direction of the magnetic field caused by the current flowing through the winding 702 is opposite to the direction of the external magnetic field from the rotor 705. That is, in the case of Figure 4, the rate of decrease in inductance is greater when the V-phase (winding 702) is excited to the north pole than when the V-phase (winding 702) is excited to the south pole.

[0058] 4, the W phase (winding 703) faces both the south pole and the north pole of rotor 705. Therefore, the influence of the external magnetic field from rotor 705 is small, and the rate of decrease in inductance of winding 703 is small.

[0059] In this way, the inductance of each of the windings 701, 702, 703 depends on the stopping position of the rotor 705.

[0060] 5A shows the relationship between the stop position of rotor 705 and the combined inductance of the UV phase, which is one of the excitation phases. In the following description, the stop position of rotor 705 will be referred to by its excitation phase. The combined inductance of the UV phase refers to the combined inductance of windings 701 and 702 measured by passing a current so that the U phase is the north pole and the V phase is the south pole.

[0061] In this embodiment, the inductance is detected by detecting a physical quantity that changes in response to a change in inductance. For example, since the rise speed of the current (voltage) flowing through the winding varies depending on the inductance value, the rise speed is measured.

[0062] Specifically, as shown in FIG. 5B, the processing unit 500 turns on the PWM signal for a predetermined period Tson. Then, the processing unit 500 measures the rise speed by detecting the voltage generated across the resistor 601 using the AD converter 504 a predetermined time (time Tsns) after the PWM signal is turned on. Note that the predetermined period Tson is a period during which the rotor 705 does not move due to the generated torque. The relationship between the stopping position of the rotor 705, the excitation phase through which current flows, and the voltage generated across the resistor 601 is stored in advance in the nonvolatile memory 507.

[0063] 5(C) shows the relationship between the stop position of the rotor 705 and the voltage generated across the resistor 601 when a current flows through the UV phase. As shown in FIG. 5(C), the voltage generated across the resistor 601 when a current flows through the UV phase is maximum when the rotor 705 is stopped at the UV phase position. In this way, the voltage generated across the resistor 601 varies depending on the stop position of the rotor 705, so the processing unit 500 can determine the stop position of the rotor 705 from the voltage across the resistor 601. Specifically, for example, the processing unit 500 can measure the voltage across the resistor 601 (i.e., the current flowing through the winding) after a predetermined time when a current flows through one or more excitation phases, and determine the stop position of the rotor 705 from the information stored in the nonvolatile memory 507.

[0064] The above-described method for detecting the stop position is merely an example in this embodiment, and is not limited to this. That is, any known technique for detecting the stop position of the rotor based on the current flowing through the windings may be used, without using a Hall element or rotary encoder to detect the stop position of the rotor.

[0065] <Motor control> {Synchronization control} After detecting the stop position of the rotor 705, the motor control device 157 determines the excitation phase for fixing the rotor 705 at the stop position, and controls the three-phase inverter 600 so that current is supplied to the determined excitation phase.

[0066] The CPU 151a outputs pulse signals to the motor control device 157 based on the operation sequence of the motor 402. The number of pulse signals corresponds to the target phase of the rotor 705, and the frequency of the pulse signals corresponds to the target speed of the rotor 705.

[0067] The motor control device 157 switches the excitation phase each time a pulse signal is input from the CPU 151a. For example, when a pulse signal is input after exciting the UV phase, the motor control device 157 controls the three-phase inverter 600 to excite the UW phase. When another pulse signal is input, the motor control device 157 controls the three-phase inverter 600 to excite the VW phase. In this embodiment, the motor control device 157 detects the stop position of the rotor 705 and then performs synchronous control to drive the motor 402 in accordance with the pulse signal output from the CPU 151a as described above. Note that in the synchronous control, the drive current flowing through the windings 701, 702, and 703 is controlled so that a current of a predetermined magnitude flows through the windings 701, 702, and 703. Specifically, to prevent the motor from losing synchronization even when a fluctuation in the load torque applied to the rotor occurs, a drive current having a magnitude (amplitude) corresponding to a torque estimated to be required for rotor rotation plus a predetermined margin is supplied to the windings. This is because synchronous control does not use a configuration in which the magnitude of the drive current is controlled based on determined (estimated) rotation phase or rotation speed (feedback control is not performed), so the drive current cannot be adjusted according to the load torque applied to the rotor. Note that the larger the current magnitude, the greater the torque applied to the rotor. Also, the amplitude corresponds to the magnitude of the current vector.

[0068] {Vector control} In this embodiment, when the frequency of pulses output from the CPU 151a (i.e., a value corresponding to the target speed of the rotor 705) becomes equal to or greater than a predetermined value while the motor control device 157 is performing synchronous control, the motor control device 157 performs vector control using the vector control unit 507. Note that when the frequency of pulses output from the CPU 151a becomes smaller than a predetermined value while the motor control device 157 is performing vector control while the motor control device 157 is performing vector control, the motor control device 157 may be configured to perform vector control using the vector control unit 507 when a rotational speed ω, which will be described later, becomes equal to or greater than a predetermined value while the motor control device 157 is performing synchronous control. That is, it is only necessary that when the value corresponding to the rotational speed of the rotor becomes equal to or greater than a predetermined value while the motor control device 157 is performing synchronous control, the motor control device 157 performs vector control using the vector control unit 507.

[0069] FIG. 6 illustrates the relationship between the U-phase, V-phase, and W-phase and a rotating coordinate system represented by the d-axis and q-axis. In FIG. 6, the α-axis, which corresponds to the U-phase winding, and the β-axis, which is perpendicular to the α-axis, are defined in the stationary coordinate system. Also in FIG. 6, the d-axis is defined along the direction of the magnetic flux generated by the magnetic poles of the permanent magnets used in the rotor 705, and the q-axis is defined along the direction 90 degrees counterclockwise from the d-axis (the direction perpendicular to the d-axis). The angle between the α-axis and the d-axis is defined as θ, and the rotational phase of the rotor 705 is represented by the angle θ. Vector control uses a rotating coordinate system based on the rotational phase θ. Specifically, vector control uses the q-axis component (torque current component) that generates torque in the rotor and the d-axis component (excitation current component) that affects the strength of the magnetic flux penetrating the winding, which are current components in the rotating coordinate system of the current vector corresponding to the drive current flowing through the winding. In FIG. 6, the counterclockwise rotation direction of the rotor 705 is depicted as the positive direction.

[0070] Vector control is a control method for controlling a motor by performing speed feedback control, which controls the values ​​of torque current components and excitation current components so as to reduce the deviation between a command speed representing a target rotor speed and the actual rotation speed. There is also a method for controlling a motor by performing phase feedback control, which controls the values ​​of torque current components and excitation current components so as to reduce the deviation between a command phase representing a target rotor phase and the actual rotation phase.

[0071] 7 is a block diagram showing an example of the configuration of the vector control unit 507. The vector control unit 507 is configured with at least one ASIC, and executes the functions described below.

[0072] The vector control unit 507 includes circuits for performing vector control, such as a speed controller 801, a current controller 802, coordinate inverse converters 803 and 804, and coordinate converters 805 and 806. The coordinate converter 805 converts current vectors corresponding to the drive currents flowing through the U-, V-, and W-phase windings of the motor 402 into a stationary coordinate system represented by the α- and β-axes using Clarke transformation. The coordinate converter 806 then converts the current values ​​converted into the stationary coordinate system represented by the α- and β-axes by the coordinate converter 804 into a rotating coordinate system represented by the q- and d-axes. As a result, the drive currents flowing through the windings are represented by the q-axis component (q-axis current) and the d-axis component (d-axis current), which are current values ​​in the rotating coordinate system. The q-axis current corresponds to a torque current that generates torque in the rotor 705 of the motor 402. The d-axis current corresponds to an excitation current that affects the strength of the magnetic flux penetrating the windings of the motor 402. Vector control unit 507 can control the q-axis current and the d-axis current independently. As a result, vector control unit 507 can efficiently generate the torque required to rotate rotor 705 by controlling the q-axis current in accordance with the load torque applied to rotor 705. That is, in vector control, the magnitude of the current vector shown in FIG. 6 changes in accordance with the load torque applied to rotor 705.

[0073] The vector control unit 507 determines the rotation phase θ and rotation speed ω of the rotor 705 of the motor 402 by a method to be described later, and performs vector control based on the determined results.

[0074] As described above, the counter 503 calculates the frequency of the pulse signal output from the CPU 151a. A value corresponding to the frequency of the pulse signal calculated by the counter 503, i.e., a command speed ω_ref representing the target speed of the rotor 705, is input to the vector control unit 507.

[0075] The subtractor 101 calculates and outputs the deviation Δω between the rotation speed ω of the rotor 705 of the motor 402 and the command speed ω_ref.

[0076] The speed controller 801 acquires the deviation Δω at a period T (for example, 200 μs). The speed controller 801 generates and outputs a q-axis current command value iq_ref (target value) and a d-axis current command value id_ref based on proportional control (P), integral control (I), and differential control (D) so that the deviation output from the subtractor 101 becomes small. Specifically, the speed controller 801 generates and outputs a q-axis current command value iq_ref and a d-axis current command value id_ref based on P control, I control, and D control so that the deviation output from the subtractor 101 becomes zero. Note that P control is a control method in which the value of a controlled object is controlled based on a value proportional to the deviation between a command value and an estimated value. Furthermore, I control is a control method in which the value of a controlled object is controlled based on a value proportional to the time integral of the deviation between a command value and an estimated value. Furthermore, D control is a control method in which the value of a controlled object is controlled based on a value proportional to the time change of the deviation between a command value and an estimated value. In this embodiment, the speed controller 801 generates the q-axis current command value iq_ref and the d-axis current command value id_ref based on PID control, but the present invention is not limited to this. For example, the speed controller 801 may generate the q-axis current command value iq_ref and the d-axis current command value id_ref based on PI control. When a permanent magnet is used for the rotor, the d-axis current command value id_ref, which affects the strength of the magnetic flux passing through the winding, is usually set to 0, but the present invention is not limited to this.

[0077] The drive currents flowing through the U-, V-, and W-phase windings of the motor 402 are converted from analog values ​​to digital values ​​by the AD converter 504. The cycle at which the AD converter 504 samples the current is, for example, equal to or shorter than the cycle T at which the speed controller 801 acquires the deviation Δω (for example, 25 μs).

[0078] The current values ​​iu, iv, and iw of the driving current converted from analog values ​​to digital values ​​by the AD converter 504 are input to the coordinate converter 805 .

[0079] The coordinate converter 805 converts the input current values ​​iu, iv, and iw into current values ​​iα and iβ in the stationary coordinate system using the following equations.

[0080]

number

[0081] The current values ​​iα and iβ in the stationary coordinate system are expressed by the magnitude I of the current vector corresponding to the drive current flowing through the U-phase, V-phase, and W-phase windings and the phase θe of the current vector, as shown in the following equation: The phase θe of the current vector is defined as the angle between the α-axis and the current vector. iα=I*cos(θe) (4) iβ=I*sin(θe) (5) These current values ​​iα and iβ are input to a coordinate converter 806 and an induced voltage determiner 807 .

[0082] The coordinate converter 806 converts the current values ​​iα and iβ in the stationary coordinate system into the current value iq of the q-axis current and the current value id of the d-axis current in the rotating coordinate system using the following equations. id=iα*cosθ+iβ*cosθ (6) iq=-iα*sinθ+iβ*cosθ (7) The subtractor 102 receives the q-axis current command value iq_ref output from the speed controller 801 and the current value iq output from the coordinate converter 806. The subtractor 102 calculates the deviation between the q-axis current command value iq_ref and the current value iq, and outputs the deviation to the current controller 802.

[0083] The subtractor 103 also receives the d-axis current command value id_ref output from the speed controller 801 and the current value id output from the coordinate converter 806. The subtractor 103 calculates the deviation between the d-axis current command value id_ref and the current value id, and outputs the deviation to the current controller 802.

[0084] The current controller 802 generates the drive voltage Vq based on PID control so as to reduce the deviation output from the subtractor 102. Specifically, the current controller 802 generates the drive voltage Vq so as to reduce the deviation output from the subtractor 102 to zero, and outputs the drive voltage Vq to the coordinate inverse converter 505.

[0085] Furthermore, the current controller 802 generates a drive voltage Vd based on PID control so as to reduce the deviation output from the subtractor 103. Specifically, the current controller 802 generates a drive voltage Vd so as to reduce the deviation output from the subtractor 103 to zero, and outputs the drive voltage Vd to the coordinate inverse converter 803.

[0086] In this embodiment, the current controller 802 generates the drive voltages Vq and Vd based on PID control, but this is not limiting. For example, the current controller 802 may generate the drive voltages Vq and Vd based on PI control.

[0087] The coordinate inverse converter 803 inversely converts the drive voltages Vq and Vd in the rotating coordinate system output from the current controller 802 into drive voltages Vα and Vβ in the stationary coordinate system using the following equations. Vα=Vd*cosθ-Vq*sinθ (8) Vβ=Vd*sinθ+Vq*cosθ (9) The coordinate inverse converter 803 outputs the inversely converted drive voltages Vα and Vβ to the induced voltage determiner 512 and the coordinate inverse converter 804 .

[0088] The coordinate inverse converter 804 converts the input drive voltages Vα and Vβ into a U-phase drive voltage Vu, a V-phase drive voltage Vv, and a W-phase drive voltage Vw using the following equations.

[0089]

number

[0090] The coordinate inverse converter 804 outputs the converted drive voltages Vu, Vv, and Vw to the three-phase inverter 600 .

[0091] The three-phase inverter 600 is driven by a PWM signal based on the drive voltages Vu, Vv, and Vw input from the coordinate inverse converter 804. As a result, the three-phase inverter 600 generates drive currents iu, iv, and iw according to the drive voltages Vu, Vv, and Vw, and supplies the drive currents iu, iv, and iw to the windings of each phase of the motor 402, thereby driving the motor 402.

[0092] Next, a configuration for determining the rotational phase θ will be described. The rotational phase θ of the rotor 705 is determined using values ​​Eα and Eβ corresponding to the induced voltages induced in the U-phase, V-phase, and W-phase windings of the motor 402 by the rotation of the rotor 705. Eα and Eβ are the induced voltage values ​​corresponding to the α-axis and β-axis, respectively. The induced voltage values ​​are determined (calculated) by an induced voltage determiner 807. Specifically, the induced voltages Eα and Eβ are determined by the following equations from the current values ​​iα and iβ output from the coordinate converter 805 and the drive voltages Vα and Vβ output from the coordinate inverse converter 803.

[0093]

number

[0094] Here, R is the winding resistance and L is the winding inductance. The values ​​of winding resistance R and winding inductance L are specific to the motor 402 being used, and are stored in advance in ROM 151b or a memory (not shown) provided in the motor control device 157.

[0095] The induced voltages Eα and Eβ determined by the induced voltage determiner 807 are output to a phase determiner 808 .

[0096] The phase determiner 808 determines the rotational phase θ of the rotor 705 of the motor 402 based on the ratio between the induced voltages Eα and Eβ output from the induced voltage determiner 807, using the following equation:

[0097]

number

[0098] In this embodiment, the phase determiner 808 determines the rotation phase θ by performing a calculation based on equation (15), but this is not limiting. For example, the phase determiner 808 may determine the rotation phase θ by referring to a table showing the relationship between the induced voltages Eα and Eβ and the rotation phase θ corresponding to the induced voltages Eα and Eβ.

[0099] The rotation phase θ obtained as described above is input to a speed determiner 809 , a coordinate inverse converter 803 , and a coordinate converter 805 .

[0100] Speed ​​determiner 809 determines rotation speed ω based on the change over time in rotation phase θ output from phase determiner 808. The following equation (16) is used to determine the speed.

[0101]

number

[0102] The rotation phase ω obtained as described above is input to the subtractor 101 .

[0103] When vector control is performed, the vector control unit 507 repeatedly performs the above-described control.

[0104] As described above, the vector control unit 507 in this embodiment performs vector control using speed feedback control that controls the current value in the rotating coordinate system so as to reduce the deviation between the command speed ω_ref and the rotational speed ω. By performing vector control, it is possible to prevent the motor from going out of step, and to prevent an increase in motor noise and power consumption due to excess torque.

[0105] In this embodiment, the rotation phase θ and the rotation speed ω are determined based on the equations (13) to (16), but this is not limitative. That is, the rotation phase θ and the rotation speed ω may be determined by any known method.

[0106] [Motor drive sequence] Next, the drive sequence of motor 402 in this embodiment will be described. In this embodiment, the following configuration is applied, thereby reducing power consumption in the image forming apparatus and shortening FPOT. In the following description, motor 402 drives pickup roller 19.

[0107] 8 is a diagram showing the drive sequence of the motor 402. The drive sequence of the motor 402 will be described below with reference to the diagram.

[0108] 8, when the CPU 151a is instructed to start print job 1 from, for example, an external device such as a PC or the operation unit 152 (time T1), the CPU 151a controls the motor control device 157 to start driving the motor 402. As a result, the motor control device 157 starts an operation (initialization operation) to detect the stop position of the rotor of the motor 402.

[0109] When detection of the stop position of the rotor of motor 402 is completed (time T2), motor control device 157 drives motor 402 by synchronous control, and then executes vector control. Specifically, motor control device 157 drives motor 402 by synchronous control so that the rotor rotates in a direction corresponding to the rotation direction of pickup roller 19 when pickup roller 19 feeds the recording medium, and then executes vector control. Then, motor 402 is driven at a predetermined rotation speed.

[0110] Thereafter, when the driving of the motor 402 ends based on the image formation sequence (time T3), the motor control device 157 holds the rotor of the motor 402 at the stopped position for a predetermined time Ta (post-excitation). Specifically, the motor control device 157 maintains excitation of the winding of the phase corresponding to the position where the rotor of the motor 402 is stopped. Note that the predetermined time Ta is the time from time T3 to time T4 in FIG. 8, and is set in advance to a time longer than the time required for the vibration of the rotor 705 of the motor 402 to subside. The post-excitation causes the vibration of the rotor 705 of the motor 402 to subside.

[0111] In this embodiment, the motor control device 157 maintains excitation of the windings of the motor 402 for a period from time T4 until a predetermined time Td has elapsed, thereby maintaining the rotor of the motor 402 at a desired phase. Note that the excitation phase when the rotor is maintained is the same as the excitation phase during the post-excitation period, for example.

[0112] If a command to start a new print job is not received even after a predetermined time Td has elapsed since time T4, the motor control device 157 turns off excitation to the windings of the motor 402. On the other hand, if the CPU 151a notifies the motor control device 157 that a command to start print job 2 has been received during the period from time T4 until the predetermined time Td has elapsed (time T2'), the motor control device 157 starts driving the motor 402 without detecting the stop position of the rotor of the motor 402. That is, the motor 402 is driven by synchronous control, and then vector control is performed. The motor 402 is then driven at a predetermined rotation speed. In this embodiment, if a state in which a command to start a new print job is not received continues for a predetermined time Te from time T4, the power mode of the image forming apparatus is switched from the normal power mode to the sleep mode. The predetermined time Te is a time that is equal to or shorter than the predetermined time Td (a second predetermined time).

[0113] Thereafter, when driving of the motor 402 ends based on the image formation sequence (time T3'), the motor control device 157 performs post-excitation. When a state in which no instruction to start a new print job has been issued continues for a predetermined time Td from time T4' (time T5'), the motor control device 157 turns off excitation to the windings of the motor 402. The period from time T3' to time T4' corresponds to the predetermined time Ta.

[0114] 9 is a flowchart illustrating the control of the motors 402 and 403 by the CPU 151a. The CPU 151a as a receiving unit starts the processing of the flowchart when an instruction to start a print job is received from an external device such as the operation unit 152 or a PC.

[0115] In S101, the CPU 151a controls the motor control device 157 to detect the stop position of the stopped motor 402. As a result, the motor control device 157 detects the stop position of the rotor of the motor 402 (initial operation).

[0116] Thereafter, in S102, the CPU 151a controls the motor control device 157 to start driving the motor 402. As a result, the motor control device 157 starts driving the motor 402.

[0117] Next, when the print operation is completed in S103, in S104 the CPU 151a controls the motor control device 157 to stop driving the motor 402. As a result, the rotation of the motor 402 is stopped.

[0118] Next, in S105, the CPU 151a controls the motor control device 157 to maintain the excitation of the motor 402. As a result, the rotor of the motor 402 is held at a desired position.

[0119] After the print job is completed in S106, if the predetermined time Td has not elapsed since the print job was completed in S107, the process proceeds to S108.

[0120] If an instruction to start a new print job has not been received in S108, the process returns to S107.

[0121] On the other hand, if an instruction to start a new job is received in S108, the process returns to S102.

[0122] Furthermore, in S107, if a predetermined time Td has elapsed since the end of the print job, in S109, the CPU 151a controls the motor control device 157 to stop excitation of the motor 402. As a result, excitation of the windings of the motor 402 is stopped.

[0123] As described above, in this embodiment, the motor control device 157, which controls the motor 402 that drives the pickup roller 19, maintains excitation of the windings of the motor 402 for a period of time from the end of print job 1 until the predetermined time Td has elapsed since post-excitation. As a result, the rotor of the motor 402 is maintained at the desired phase. Furthermore, if the start of a new print job is not instructed even after the predetermined time Td has elapsed since post-excitation, the motor control device 157 turns off excitation of the windings of the motor 402. As described above, in this embodiment, excitation of the windings of the motor 402 that drives the pickup roller 19, which is the most upstream transport roller among the transport rollers that transport the recording medium in print job 2, is maintained for a period of time from the end of print job 1 until the predetermined time has elapsed. As a result, when the start of print job 2 is instructed, driving of the motor 402 can be started without performing an operation to detect the stop position of the rotor of the motor 402. In other words, the FPOT for print job 2 is reduced. Furthermore, power consumption can be reduced compared to when the rotor is held constantly during the period from the end of print job 1 until an instruction to start print job 2 is issued. In other words, the configuration of this embodiment makes it possible to provide an image forming apparatus that can reduce power consumption in the image forming apparatus while shortening FPOT.

[0124] If an instruction to execute print job 2 is input while print job 1 is being executed, CPU 151a controls motor control device 157 to maintain excitation of the windings of motor 402 after print job 1 is completed and excitation is performed. As a result, print job 2 can be started immediately after print job 1 is completed without performing an operation to detect the stop position of the rotor of motor 402. In other words, FPOT can be shortened.

[0125] In this embodiment, the timing at which the printing operation ends corresponds to the timing at which the pickup roller 19 finishes feeding the final recording medium in a print job (image forming job), but this is not limited to this. For example, the timing at which the printing operation ends may correspond to the timing at which the image fixing to the final recording medium in a print job ends, or the timing at which the image transfer to the final recording medium in a print job ends may correspond to the timing at which the printing operation ends. Furthermore, for example, the timing at which the discharge of the final recording medium in a print job to the outside of the machine by the discharge rollers may correspond to the timing at which the printing operation ends. The timing at which the image fixing to the final recording medium ends may be determined based on a sensor provided downstream of the fuser 29. Furthermore, the timing at which the image transfer to the final recording medium ends may be determined based on a sensor provided downstream of the transfer unit 28. Furthermore, the timing at which the discharge of the final recording medium to the outside of the machine by the discharge rollers ends may be determined based on a sensor provided downstream of the discharge rollers 30.

[0126] Second Embodiment The description of the configuration of the image forming apparatus 100 that is the same as that of the first embodiment will be omitted.

[0127] [Motor drive sequence] Next, the drive sequence of motor 402 in this embodiment will be described. In this embodiment, the following configuration is applied to provide an image forming apparatus that can reduce power consumption and shorten FPOT in the image forming apparatus. In the following description, motor 402 drives pickup roller 19.

[0128] In this embodiment, while the operation unit 152 is being operated, setting data and the like in the operation unit 152 are transmitted from the operation unit 152 to the CPU 151a at predetermined time intervals.

[0129] In this embodiment, the motor control device 157 maintains the excitation of the windings of the motor 402 for a period from time T4 until a predetermined time Td has elapsed, thereby keeping the rotor of the motor 402 at a desired phase. Furthermore, if the motor control device 157 is notified by the operation unit 152 that the operation unit 152 is being operated while the excitation of the windings of the motor 402 is being maintained, the motor control device 157 maintains the excitation of the windings of the motor 402 for a period from the notification until a predetermined time Td has elapsed. That is, in this embodiment, if the motor control device 157 is notified by the operation unit 152 that the operation unit 152 is being operated while the excitation of the windings of the motor 402 is being maintained, the motor control device 157 maintains the excitation of the windings of the motor 402 for a period longer than the predetermined time Td. Thus, in this embodiment, the motor control device 157 extends the period during which the excitation of the windings of the motor 402 is maintained when there is a possibility that the start of print job 2 will be instructed. As a result, when an instruction to start print job 2 is given, driving of motor 402 can be started without performing an operation to detect the stop position of the rotor of motor 402. That is, FPOT for print job 2 is shortened. Also, power consumption can be reduced compared to when the rotor is always held during the period from the end of print job 1 until the instruction to start print job 2 is given. That is, the configuration of this embodiment makes it possible to provide an image forming apparatus that can reduce FPOT while suppressing power consumption in the image forming apparatus.

[0130] Third Embodiment Description of portions of the image forming apparatus 100 that are the same as those in the first embodiment will be omitted. Fig. 10 is a block diagram showing an example of the control configuration of the image forming apparatus 100 in this embodiment. The image forming apparatus 100 in this embodiment is provided with a human body detection sensor 162. The human body detection sensor 162 is a sensor in which infrared sensors that receive infrared rays are arranged in a matrix, and detects people by receiving infrared rays emitted from the people. The human body detection sensor (human presence sensor) 162 transmits the detection result to the CPU 151a.

[0131] 11 is a diagram illustrating the detection area of ​​the human body detection sensor 162. The human body detection sensor 162 detects whether or not a person is present within a detection area 300.

[0132] [Motor drive sequence] Next, the drive sequence of motor 402 in this embodiment will be described. In this embodiment, the following configuration is applied to provide an image forming apparatus that can reduce power consumption and shorten FPOT in the image forming apparatus. In the following description, motor 402 drives pickup roller 19.

[0133] In this embodiment, the motor control device 157 maintains excitation of the windings of the motor 402 for a period from time T4 until a predetermined time Td has elapsed, thereby keeping the rotor of the motor 402 at a desired phase. Furthermore, if the human body detection sensor 162 detects a person as an object while maintaining excitation of the windings of the motor 402, the motor control device 157 maintains excitation of the windings of the motor 402 for a period from the detection until a predetermined time Td has elapsed. That is, in this embodiment, if the human body detection sensor 162 detects a person as an object while maintaining excitation of the windings of the motor 402, the motor control device 157 maintains excitation of the windings of the motor 402 for a period longer than the predetermined time Td. Thus, in this embodiment, the motor control device 157 maintains excitation of the windings of the motor 402 when there is a possibility that the start of print job 2 will be instructed. As a result, when the start of print job 2 is instructed, driving of the motor 402 can be started without performing an operation to detect the stop position of the rotor of the motor 402. That is, the FPOT for print job 2 is shortened. Also, power consumption can be reduced compared to when the rotor is always held during the period from when print job 1 ends until an instruction to start print job 2 is issued. That is, the configuration of this embodiment makes it possible to provide an image forming apparatus that can shorten the FPOT while suppressing power consumption in the image forming apparatus.

[0134] In the first to third embodiments, the case where motor 402 drives pickup roller 19 has been described, but this is not limitative. For example, the configuration of this embodiment may be applied to a motor that drives a transport roller other than pickup roller 19.

[0135] Furthermore, in the first to third embodiments, motor 402 is configured to drive pickup roller 19, but, for example, motor 402 may be configured to drive pickup roller 19 and conveyance roller 39. In other words, motor 402 may be configured to drive a plurality of conveyance rollers including pickup roller 19.

[0136] Furthermore, in the first to third embodiments, the motor 402 is configured to drive the pickup roller 19, but the motor 402 may be configured to drive the pickup roller 43, for example.

[0137] [Fourth embodiment] The description of the configuration of the image forming apparatus 100 that is the same as that of the first embodiment will be omitted.

[0138] [Motor drive sequence] The drive sequence of motors 402 and 403 in this embodiment will be described below. In this embodiment, the following configuration is applied to provide an image forming apparatus that can reduce FPOT while suppressing power consumption in the image forming apparatus. In the following description, motor 402 drives pickup roller 19, and motor 403 drives paper discharge roller 30, which is provided downstream of pickup roller 19 in the transport direction in which the recording medium is transported.

[0139] 12 is a diagram showing the drive sequence of the motors 402 and 403. The drive sequence of the motors 402 and 403 will be described below with reference to the diagram.

[0140] As shown in FIG. 12, when the start of print job 1 is instructed, for example, from an external device such as the operation unit 152 or a PC (time T1), excitation of the windings in the motor 402 begins, and an operation (initialization) is performed to detect the stopping position of the rotor of the motor 402.

[0141] When detection of the stop position of the rotor of motor 402 is completed (time T2), motor 402 is driven by synchronous control, and then vector control is performed. Specifically, motor control device 157 drives motor 402 by synchronous control so that the rotor rotates in a direction corresponding to the rotation direction of pickup roller 19 when pickup roller 19 feeds the recording medium, and then executes vector control. Then, motor 402 is driven at a predetermined rotation speed.

[0142] Thereafter, when the driving of the motor 402 ends based on the image formation sequence (time T5), the motor control device 157 holds the rotor of the motor 402 at the stopped position. Specifically, the motor control device 157 maintains the excitation of the winding of the phase corresponding to the position where the rotor of the motor 402 is stopped.

[0143] As shown in FIG. 12, when a predetermined time Ts has elapsed from time T1 (time T3), excitation of the windings of motor 403 begins, and an operation (initialization) of detecting the stop position of the rotor of motor 403 is performed.

[0144] When detection of the stop position of the rotor of motor 403 is completed (time T4), motor 403 is driven by synchronous control, and then vector control is performed. Specifically, motor control device 158 drives motor 403 by synchronous control so that the rotor rotates in a direction corresponding to the rotation direction of paper discharge roller 30 when paper discharge roller 30 discharges the recording medium, and then executes vector control. Then, motor 403 is driven at a predetermined rotation speed.

[0145] Thereafter, when the driving of the motor 403 ends based on the image formation sequence (time T6), the motor control device 158 turns off the excitation of the windings of the motor 403. As a result, the supply of current to the windings of the motor 403 is stopped.

[0146] 12, in this embodiment, when print job 1 ends (time T7), excitation to the windings of motor 403 is turned off, but excitation to the windings of motor 402 is turned on. In this embodiment, motor control device 157 maintains excitation to the windings of motor 402 for a period of time until a predetermined time Td has elapsed since print job 1 ended, thereby keeping the rotor of motor 402 at the desired phase. If a command to start a new print job is not issued even after the predetermined time Td has elapsed since print job 1 ended, motor control device 157 turns off excitation to the windings of motor 402.

[0147] When an instruction to start print job 2 is given from, for example, an external device such as the operation unit 152 or a PC during the period from the end of print job 1 until a predetermined time Td has elapsed (time T2'), the motor control device 157 starts driving the motor 402 without performing an operation to detect the stop position of the rotor of the motor 402. That is, the motor 402 is driven by synchronous control, and then vector control is performed. Then, the motor 402 is driven at a predetermined rotation speed.

[0148] Thereafter, when the driving of the motor 402 ends based on the image formation sequence (time T5'), the motor control device 157 holds the rotor of the motor 402 in the stopped position. Specifically, the motor control device 157 maintains excitation of the winding of the phase corresponding to the position where the rotor of the motor 402 is stopped. When a state in which no instruction to start a new print job has been given continues for a predetermined time Td after the end of print job 2 (time T8'), the motor control device 157 turns off the excitation to the winding of the motor 402.

[0149] As shown in FIG. 12, at time T3', excitation of the windings of motor 403 is started, and an operation (initialization) for detecting the stop position of the rotor of motor 403 is performed.

[0150] When the detection of the stop position of the rotor of the motor 403 is completed (time T4'), the motor 403 is driven by synchronous control, and then vector control is performed, and the motor 403 is driven at a predetermined rotation speed.

[0151] Thereafter, when the driving of the motor 403 ends based on the image formation sequence (time T6'), the motor control device 158 turns off the excitation of the windings of the motor 403. As a result, the supply of current to the windings of the motor 403 is stopped.

[0152] 13 is a flowchart illustrating how the CPU 151a controls the motors 402 and 403. When an instruction to start a print job is received from an external device such as the operation unit 152 or a PC, the CPU 151a starts the processing of the flowchart.

[0153] In S101, the CPU 151a controls the motor control device 157 to detect the stop position of the motor 402. As a result, the motor control device 157 detects the stop position of the rotor of the motor 402.

[0154] Thereafter, in S102, the CPU 151a controls the motor control device 157 to start driving the motor 402. As a result, the motor control device 157 starts driving the motor 402.

[0155] Next, in S103, the CPU 151a controls the motor control device 158 to detect the stop position of the motor 403. As a result, the motor control device 158 detects the stop position of the rotor of the motor 403.

[0156] Thereafter, in S104, the CPU 151a controls the motor control device 158 to start driving the motor 403. As a result, the motor control device 158 starts driving the motor 403.

[0157] When the print operation is completed in S105, in S106 the CPU 151a controls the motor control device 157 to stop driving the motor 402. As a result, the rotation of the motor 402 is stopped.

[0158] Next, in S107, the CPU 151a controls the motor control device 157 to maintain the excitation of the motor 402. As a result, the rotor of the motor 402 is held at a desired position.

[0159] In S108, the CPU 151a controls the motor control device 158 to stop driving the motor 403. As a result, the rotation of the motor 403 is stopped.

[0160] Next, in S109, the CPU 151a controls the motor control device 158 to stop the excitation of the motor 403. As a result, the excitation of the windings of the motor 403 is stopped.

[0161] After the print job is completed in S110, if the predetermined time Td has not elapsed since the print job was completed in S111, the process proceeds to S112.

[0162] If an instruction to start a new print job has not been received in S112, the process returns to S111.

[0163] On the other hand, if an instruction to start a new job is received in S112, the process returns to S102.

[0164] Furthermore, in S111, if a predetermined time Td has elapsed since the end of the print job, in S113 the CPU 151a controls the motor control device 157 to stop excitation of the motor 402. As a result, excitation of the windings of the motor 402 is stopped.

[0165] As described above, in this embodiment, the motor control device 157, which controls the motor 402 that drives the pickup roller 19, maintains excitation of the windings of the motor 402 for a period of time Td after print job 1 ends. As a result, the rotor of the motor 402 is maintained at the desired phase. Furthermore, if the start of a new print job is not instructed even after the predetermined time Td has elapsed since print job 1 ended, the motor control device 157 turns off excitation of the windings of the motor 402. As described above, in this embodiment, excitation of the windings of the motor 402 that drives the pickup roller 19, which is the most upstream transport roller among the transport rollers that transport the recording medium in print job 2, is maintained for a period of time after print job 1 ends until a predetermined time has elapsed. As a result, when an instruction to start print job 2 is issued, driving of the motor 402 can be started without performing an operation to detect the stop position of the rotor of the motor 402. In other words, the FPOT for print job 2 is reduced.

[0166] Furthermore, the motor control device 158, which controls the motor 403 that drives the paper discharge roller 30, stops excitation of the windings of the motor 403 when print job 1 ends. This is because even if an operation to detect the rotor stop position of the motor 403 is performed after an instruction to start print job 2 is issued, the motor 403 can be accelerated to a predetermined rotational speed before the conveyed recording medium reaches the paper discharge roller 30, and this does not affect the decrease in FPOT. This configuration reduces power consumption compared to when excitation of the windings of all motors in the image forming apparatus is maintained after the print job ends. Note that in this embodiment, the time required from time T2' in FIG. 8 to the operation to detect the rotor stop position of the motor 403 and accelerate the motor 403 to a predetermined rotational speed is shorter than the time from time T2' until the recording medium reaches the paper discharge roller 30.

[0167] With the above configuration, it is possible to provide an image forming apparatus that can reduce FPOT while suppressing power consumption in the image forming apparatus.

[0168] In the present embodiment, the motor 402 drives the pickup roller 19, and the motor 403 drives the discharge roller 30. However, the present embodiment is not limited to this. For example, the motor 402 may drive at least one of the transport rollers upstream of the pair of transfer rollers 28, and the motor 403 may drive at least one of the transport rollers downstream of the pair of transfer rollers 28. That is, at least one of the motors driving the transport rollers upstream of the pair of transfer rollers 28 may be configured to maintain excitation of its windings for a predetermined time Td after print job 1 ends. Also, at least one of the motors driving the transport rollers downstream of the pair of transfer rollers 28 may be configured to stop excitation of its windings when print job 1 ends. That is, the image forming apparatus 100 may have a motor that maintains excitation of its windings for a predetermined time Td after print job 1 ends, and a motor that stops excitation of its windings when print job 1 ends. This configuration reduces power consumption compared to when the excitation of the windings of all motors in the image forming apparatus is maintained for a uniform period of time after the end of a print job.

[0169] Furthermore, in this embodiment, when the driving of the motor 403 is completed, the motor control device 158 turns off the excitation of the windings of the motor 403 (stops the supply of current to the windings of the motor 403), but this is not limited to this. For example, when the driving of the motor 403 is completed, the motor control device 158 may maintain the excitation of the windings of the motor 403 for a time shorter than the predetermined time Td. With this configuration, power consumption is reduced compared to when the excitation of the windings of all motors in the image forming apparatus is maintained for a uniform time after the end of a print job.

[0170] In addition, in this embodiment, excitation of the windings of the motor 403 is started when a predetermined time Ts has elapsed since an instruction to start a print job was issued, but this is not limited to this. For example, excitation of the windings of the motor 403 may be started when an instruction to start a print job is issued.

[0171] In addition, in this embodiment, motor 402 is configured to drive pickup roller 19, but, for example, motor 402 may be configured to drive pickup roller 19 and conveyance roller 39. In other words, motor 402 may be configured to drive multiple conveyance rollers including pickup roller 19.

[0172] Furthermore, in this embodiment, the motor 402 is configured to drive the pickup roller 19, but the motor 402 may be configured to drive the pickup roller 43, for example.

[0173] In this embodiment, the case where motor 402 drives pickup roller 19 has been described, but application of this embodiment is not limited to this. For example, motor 402 may be configured to drive at least one of the transport rollers provided inside image forming apparatus 100. With such a configuration, power consumption is reduced compared to when excitation of the windings of all motors in the image forming apparatus is maintained for a uniform period of time after the end of a print job.

[0174] In the first to fourth embodiments, the timing at which the printing operation ends corresponds to the timing at which the pickup roller 19 ends feeding of the final recording medium in a print job (image forming job). The timing at which the pickup roller 19 ends feeding of the final recording medium in a print job may be determined based on a sensor provided in the image forming apparatus that detects the recording medium being conveyed. Specifically, for example, the timing at which the sensor provided between the pickup roller 19 and the feed roller 39 detects that the leading edge of the final recording medium in the print job has passed may correspond to the timing at which the printing operation ends.

[0175] The timing at which the printing operation ends is not limited to the timing at which the pickup roller 19 finishes feeding the final recording medium in a print job (image forming job). For example, the timing at which the printing operation ends may correspond to the timing at which the image fixing to the final recording medium in a print job ends, or the timing at which the image transfer to the final recording medium in a print job ends may correspond to the timing at which the printing operation ends. Furthermore, for example, the timing at which the discharge of the final recording medium in a print job outside the machine by the discharge rollers may correspond to the timing at which the printing operation ends. The timing at which the image fixing to the final recording medium ends may be determined based on a sensor provided downstream of the fuser 29. Furthermore, the timing at which the image transfer to the final recording medium ends may be determined based on a sensor provided downstream of the transfer unit 28. Furthermore, the timing at which the discharge of the final recording medium outside the machine by the discharge rollers ends may be determined based on a sensor provided downstream of the discharge rollers 30.

[0176] In the vector control in the first to fourth embodiments, the motors 402 and 403 are controlled by performing speed feedback control, but the present invention is not limited to this. For example, the motors 402 and 403 may be controlled by feeding back the rotation phase θ of the rotors of the motors 402 and 403.

[0177] Furthermore, in the first to fourth embodiments, a brushless DC motor is used as the motor that drives the load, but other motors such as a stepping motor, a DC motor, etc. Also, the number of phases of the windings of the motor is not limited to three (U phase, V phase, and W phase) and may be any number other than three.

[0178] In the first to fourth embodiments, the function of the motor control device 157 may be included in the CPU 151a.

[0179] In the first to fourth embodiments, the initialization operation involves detecting the stop position of the motor, but this is not limiting. For example, the initialization operation may involve exciting a predetermined phase of the motor to attract the rotor to that predetermined phase.

[0180] The phase in which the motor 402 is held may be the same as the phase in which the motor 403 is held, or may be a different phase.

[0181] The photosensitive drum, the charger, the developing device, the transfer roller, the transfer belt, etc. are included in the image forming unit. [Explanation of symbols]

[0182] 18-seat storage tray 19, 43 Pickup roller 44 Manual feed tray 151a CPU 157, 158 Motor control device 301 Image printing device 402, 403 Brushless DC Motor

Claims

1. a loading section on which recording media are loaded; a pickup roller that feeds the recording medium loaded in the loading section; a first motor that drives the pickup roller; a conveying roller that is provided downstream of the pickup roller in a conveying direction in which the recording medium is conveyed and that conveys the recording medium fed by the pickup roller; a second motor that drives the conveying roller; an image forming means for forming an image on the recording medium fed by the pickup roller; a receiving unit that receives an instruction to start an image forming job for forming an image on the recording medium; a control means for executing a first initializing operation, when the receiving unit receives an instruction to start a first job as the image forming job, of supplying a current to a winding of the first motor in a first stop state in which a rotor of the first motor is stopped, and determining a phase of the rotor of the first motor in the first stop state based on the current flowing through the winding, and controlling the current supplied to the winding so that the rotor of the first motor in the first stop state rotates based on the phase determined by the first initializing operation; and a control means for executing a second initializing operation, when the receiving unit receives an instruction to start a first job as the image forming job, of supplying a current to a winding of the first motor in a first stop state in which a rotor of the first motor is stopped, and determining a phase of the rotor of the second motor in the second stop state based on the current flowing through the winding of the second motor, and controlling the current supplied to the winding of the second motor so that the rotor of the second motor rotates in the second stop state based on the phase determined by the second initializing operation; and the control means controls the current supplied to the windings of the first motor so that the rotor of the first motor is maintained at a first phase when the first job is completed; when the receiving unit receives an instruction to start a second job as the image forming job during a first period from when the rotor of the first motor is held at the first phase until a first predetermined time has elapsed, the control means controls the current supplied to the windings of the first motor so that the held rotor of the first motor rotates without performing the first initial operation; the control means stops supplying current to a winding of the first motor when the receiving unit does not receive an instruction to start the second job during the first period; the control means stops supplying current to the windings of the second motor when the rotation of the rotor of the second motor is stopped; an image forming apparatus characterized in that, when the control means receives an instruction to start the second job, it performs the second initial operation and then controls the current supplied to the windings of the second motor so that the rotor of the second motor in the second stop state rotates based on the phase determined by the second initial operation.

2. a loading section on which recording media are loaded; a pickup roller that feeds the recording medium loaded in the loading section; a first motor that drives the pickup roller; a conveying roller that is provided downstream of the pickup roller in a conveying direction in which the recording medium is conveyed and that conveys the recording medium fed by the pickup roller; a second motor that drives the conveying roller; an image forming means for forming an image on the recording medium fed by the pickup roller; a receiving unit that receives an instruction to start an image forming job for forming an image on the recording medium; a control means for executing a first initializing operation, when the receiving unit receives an instruction to start a first job as the image forming job, of supplying a current to a winding of the first motor in a first stop state in which a rotor of the first motor is stopped, and determining a phase of the rotor of the first motor in the first stop state based on the current flowing through the winding, and controlling the current supplied to the winding so that the rotor of the first motor in the first stop state rotates based on the phase determined by the first initializing operation; and a control means for executing a second initializing operation, when the receiving unit receives an instruction to start a first job as the image forming job, of supplying a current to a winding of the first motor in a first stop state in which a rotor of the first motor is stopped, and determining a phase of the rotor of the second motor in the second stop state based on the current flowing through the winding of the second motor, and controlling the current supplied to the winding of the second motor so that the rotor of the second motor rotates in the second stop state based on the phase determined by the second initializing operation; and the control means controls the current supplied to the windings of the first motor so that the rotor of the first motor is maintained at a first phase when the first job is completed; when the receiving unit receives an instruction to start a second job as the image forming job during a first period from when the rotor of the first motor is held at the first phase until a first predetermined time has elapsed, the control means controls the current supplied to the windings of the first motor so that the held rotor of the first motor rotates without performing the first initial operation; the control means stops supplying current to a winding of the first motor when the receiving unit does not receive an instruction to start the second job during the first period; the control means controls the current supplied to the windings of the second motor so that the rotor of the second motor is maintained in a second phase when the rotation of the rotor of the second motor is stopped; an image forming apparatus characterized in that the control means stops supplying current to the windings of the second motor when a time shorter than the first predetermined time has elapsed since the rotor of the second motor was held in the second phase;

3. 3. The image forming apparatus according to claim 1, wherein the transport roller is a paper discharge roller that discharges the recording medium to the outside of the image forming apparatus.

4. 4. The image forming apparatus according to claim 1, wherein the second motor is a brushless DC motor.

5. the image forming apparatus has an operation unit that is operated by a user and that sets image forming conditions for the image forming unit, 5. The image forming apparatus according to claim 1, wherein, when the operation unit is operated during the first period, the control unit controls the current supplied to the winding so that the rotor is maintained at the first phase for a period longer than the first predetermined time.

6. The image forming apparatus according to any one of claims 1 to 5, characterized in that when the pickup roller completes feeding of the final recording medium in the first job as the end of the first job, the control means controls the current supplied to the winding so that the rotor is maintained in the first phase.

7. The image forming apparatus according to any one of claims 1 to 5, characterized in that when image formation by the image forming means on the final recording medium in the first job is completed as the end of the first job, the control means controls the current supplied to the winding so that the rotor is maintained in the first phase.

8. The image forming apparatus according to any one of claims 1 to 5, characterized in that when the final recording medium in the first job is discharged outside the image forming apparatus as the end of the first job, the control means controls the current supplied to the winding so that the rotor is maintained in the first phase.

9. the image forming apparatus has a first power mode in which image formation by the image forming unit can be performed, and a second power mode in which power consumption is lower than that in the first power mode and image formation by the image forming unit is not performed, the control means maintains the first power mode for a second period from the end of the image forming job until a second predetermined time has elapsed; the control means switches the power mode from the first power mode to the second power mode after a second predetermined time has elapsed since the image forming job was completed if an instruction to start the second job is not received during the second period; 9. The image forming apparatus according to claim 1, wherein the first predetermined time is equal to or shorter than the second predetermined time.

10. 10. The image forming apparatus according to claim 1, wherein the first motor is a brushless DC motor.

11. the image forming apparatus includes a detection unit that detects a current flowing through a winding of the first motor, and a phase determination unit that determines a rotation phase of the rotor based on the current detected by the detection unit; the control means starts rotation of the rotor in the first stopped state by supplying a current of a predetermined magnitude to the winding based on the phase determined by the first initial operation; When a value corresponding to the rotation speed of the rotor becomes greater than a predetermined value after the rotor starts to rotate, the control of the first motor is started by vector control; 11. The image forming apparatus according to claim 1, wherein in the vector control, the control means controls the current flowing through the windings based on a torque current component, which is a current component in a rotating coordinate system based on the rotation phase determined by the phase determination means and which generates torque in the rotor, and an excitation current component, which is a current component in the rotating coordinate system and which affects the strength of the magnetic flux passing through the windings.

12. the control means sets a target value of the torque current component in the vector control so that a deviation between the rotation phase determined by the phase determination means and a command phase representing a target phase of the rotor becomes small; 12. The image forming apparatus according to claim 11, wherein the control means controls the current flowing through the winding in the vector control so that a deviation between the detected value of the torque current component and a target value of the torque current component becomes small.

13. the control means determines the rotational speed of the rotor; the control means sets a target value of the torque current component in the vector control so that a deviation between the determined rotation speed and a command speed representing a target speed of the rotor becomes small; 12. The image forming apparatus according to claim 11, wherein the control means controls the current flowing through the winding in the vector control so that a deviation between the detected value of the torque current component and a target value of the torque current component becomes small.

14. 14. The image forming apparatus according to claim 11, wherein the value corresponding to the rotation speed of the rotor corresponds to a target speed of the rotor.

Images