Image forming apparatus

Abstract

To provide a technique capable of applying a motor driving voltage at a higher duty while stabilizing an image forming operation.SOLUTION: The image forming apparatus includes a motor that generates a driving force for driving an image forming unit and includes a plurality of coils, an inverter that applies a voltage to the plurality of coils, a current detection unit that detects a current flowing through the plurality of coils, and a control unit that controls the inverter based on a detection result of the current detection unit. The current detection unit is capable of executing, in the current detection period, a first current detection operation of starting current detection after a predetermined settling time has elapsed, and a second current detection operation of starting detection at a timing earlier than the elapse of the predetermined settling time.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus that forms an image on a recording material by electrophotography. [Background technology]

[0002] Electrophotographic image forming apparatuses often use motors such as stepping motors, brushed motors, and brushless motors as drive sources for transporting recording materials such as paper. For example, Patent Document 1 proposes a motor control device and an image forming apparatus using a sensorless DC brushless motor that does not have a Hall element for detecting the rotor's rotational position. In this sensorless DC brushless motor, instead of detecting the rotor's position using a Hall element, the rotor's position is detected by the current values ​​flowing through multiple coils of the motor. Specifically, analog information of the current values ​​obtained through a shunt resistor is quantized into digital information using an AD converter or the like, and the rotor's rotational position is then estimated by the motor control device. Based on the estimated rotational position, the amount of current to be applied to each coil is determined by PWM voltage control using an inverter.

[0003] One method of arranging the aforementioned shunt resistors is to place them between the low-side switching element in the inverter and ground (low-side shunt resistor method). The low-side shunt resistor method is cost-effective because it allows the use of an AD converter with a low withstand voltage. Furthermore, this method, in which a shunt resistor is installed in each of the motor's multiple coils, makes it possible to simultaneously detect the current in the coils of each phase of the motor and accurately detect the rotor position, thereby stabilizing the rotation speed and suppressing uneven rotation of the motor. For example, when installing shunt resistors in a three-phase DC brushless motor, three shunt resistors (three shunt resistors) are required.

[0004] In image forming apparatuses, large rotational irregularities in the motor used as the drive source for conveying recording materials can cause image defects. Therefore, it is necessary to suppress motor rotational irregularities. Therefore, when an image forming apparatus uses a sensorless-controlled three-phase DC brushless motor as the drive source, a low-side three-shunt resistor system is often adopted. [Prior art documents] [Patent documents]

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

[0006] In an AD converter, which quantizes the current value obtained through a shunt resistor, the analog information is charged into a sampling capacitor and then quantized. AD converter circuits used in image forming devices generally have a multiplexer configuration with multiple inputs. Therefore, when switching the multiplexer on the controller side to the circuit containing the analog information to be acquired, switching is required, and periods of instability in the analog information read by the AD converter occur due to switching noise, etc.

[0007] When using sensorless DC brushless motor control in an image forming apparatus such as that described in Patent Document 1, there is a concern that reading the current with an AD converter before this unstable period subsides could result in large current detection errors. As a result, there is a possibility that the motor's rotational fluctuations could become large. For this reason, a settling time is provided after the aforementioned switching, and reading with the AD converter is performed only after waiting for the switching noise to subside.

[0008] The low-side triple shunt resistor method described above requires simultaneous detection of the coil currents of all three phases. Therefore, all low-side switching elements must be on during the time it takes for the AD converter to read the signals for each phase—that is, while waiting for the switching noise of each phase to subside—while the low-side switching elements are turned off to prevent through-current, preventing current from flowing through the coils. This places restrictions on the on-duty when PWM-controlling the motor voltage. For example, if the PWM period is 50 μs and the AD converter takes 2 μs to read the signals, then 2 μs x 3 phases = 6 μs, resulting in a maximum duty cycle of 88%. This means that a high-duty voltage approaching 100% cannot be applied, and sufficient voltage may not be applied during high loads such as startup. To handle temporary high loads during startup, a motor with specifications exceeding the steady-state load must be selected, which is cost-intensive.

[0009] An object of the present invention is to provide a technique that enables application of a motor drive voltage at a higher duty while stabilizing the image forming operation. [Means for solving the problem]

[0010] In order to solve the above-mentioned problems, an image forming apparatus according to the present invention comprises: an image forming section for forming an image on a recording material; a motor having a plurality of coils that generates a driving force for driving the image forming unit; an inverter that applies a voltage to the plurality of coils; a current detection unit that detects currents flowing through the plurality of coils; a control unit that controls the inverter based on a detection result of the current detection unit; In an image forming apparatus comprising: the control unit controls the inverter to stop applying the voltage during a current detection period for the current detection unit to detect the current; The current detection unit is capable of executing, during the current detection period, a first current detection operation that starts detecting the current after a predetermined settling time has elapsed, and a second current detection operation that starts the detection at a timing earlier than the predetermined settling time has elapsed. It is characterized by: [Effects of the Invention]

[0011] According to the present invention, it is possible to apply a motor drive voltage at a higher duty while stabilizing the image forming operation. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating a hardware configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] FIG. 1 is a diagram showing a control configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 3] FIG. 1 is a diagram showing a control configuration of a motor in an embodiment of the present invention. [Figure 4] 1 is a diagram showing the configuration of a motor according to an embodiment of the present invention; [Figure 5] FIG. 1 is a diagram showing a configuration of a current detection unit in an embodiment of the present invention; [Figure 6] FIG. 1 shows a PWM voltage control configuration according to an embodiment of the present invention. [Figure 7] Diagram showing noise that can occur in analog information during switching [Figure 8] FIG. 10 is a diagram showing a settling time switching operation in an embodiment of the present invention. [Figure 9] A diagram showing the settling time switching operation during contact and separation DETAILED DESCRIPTION OF THE INVENTION

[0013] The following detailed description of the embodiments of the present invention will be given with reference to the accompanying drawings. However, the dimensions, materials, shapes, and relative positions of the components described in the embodiments may be changed as appropriate depending on the configuration of the device to which the invention is applied and various conditions. In other words, the scope of the present invention is not intended to be limited to the following embodiments. Furthermore, although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0014] Example 1 An image forming apparatus according to a first embodiment of the present invention will be described with reference to FIGS.

[0015] FIG. 1 is a schematic cross-sectional view showing an example of the hardware configuration included in an image forming apparatus according to an embodiment of the present invention. Here, the present invention is described as being applied to an image forming apparatus that forms an image on a recording material using an electrophotographic method. However, the present invention is not limited to image forming apparatuses and can also be applied to any motor control device that performs sensorless control. Image forming apparatus 10 is a full-color machine that prints using four colors of toner: yellow (Y), magenta (M), cyan (C), and black (K). The suffixes Y, M, C, and K in the figures indicate which of the four color toner images the component is responsible for forming. In the following description, the suffixes Y, M, C, and K will be omitted wherever necessary to distinguish between colors.

[0016] The image forming unit of the image forming apparatus 10 includes a photosensitive drum 11 as an electrophotographic photosensitive member, a charging roller 12 as a charging unit, an exposure unit 13, and a developing roller 14 as a developing unit, for forming four toner images of Y, M, C, and K, respectively. The photosensitive drum 11 is charged by the charging roller 12 to which a charging bias is applied from a high-voltage power supply (not shown), and then an electrostatic latent image is formed by scanning light from the exposure unit 13. The electrostatic latent image formed on the photosensitive drum 11 as an image carrier is developed by toner carried by the developing roller 14 as a developer carrier, thereby becoming a visible toner image (developer image). The toner image formed on the photosensitive drum 11 is transferred to an intermediate transfer belt 16 by a primary transfer roller 15. A sheet 20 is transported from a cassette 20 through a transport path 21, and the toner image is transferred from the intermediate transfer belt 16 to the sheet 20 by a secondary transfer roller 18. Thereafter, the sheet 20 is heated and pressed in a fixing section 23, whereby the toner image is fixed. The sheet 20 on which the toner image has been fixed is discharged by a pair of discharge rollers 24 to the outside of the image forming apparatus.

[0017] The motor 150 generates a driving force for driving image forming units such as the photosensitive drum 11, charging roller 12, exposure unit 13, and developing roller 14 via a gear mechanism (not shown). The driving force of the motor 150 is also used as a driving source for driving a conveying roller for conveying the sheet 20 via a gear mechanism. In this embodiment, the motor 150 is configured by a DC brushless motor.

[0018] The control configuration of the image forming apparatus 10 is shown in Figure 2. The image forming apparatus 10 includes a printer control unit 30, an exposure unit 13, a fixing unit 23, a motor control unit 31, and a communication controller 200. The printer control unit 30 includes a processor (not shown) and memory for storing programs and various control data. The communication controller 200 communicates with a host computer 210 to receive data for image formation from the host computer 210. Based on the received data, the processor in the printer control unit 30 executes a program stored in the memory of the printer control unit 30 to perform the image formation process. The printer control unit 30 sends a signal to the motor control unit 31 to drive the motor 150 to rotate, thereby driving rotating members such as the photosensitive drum 11 and controlling the transport of the sheet 20.

[0019] 3 shows the control configuration of the motor 150. The motor control unit 31 receives commands from the printer control unit 30 and controls the motor 150 under the control of the printer control unit 30. Motor Control The unit 31 has a processing unit 310, a gate driver 315, and an inverter 316. The processing unit 310 has a pulse width modulation (PWM) port 311, an arithmetic unit 312, a memory 313, and an AD (analog-digital) converter 314, and performs serial data communication with the printer control unit 30. The memory 313 stores data and programs for controlling the motor 150. The processing unit 310 controls the drive of the inverter 316 by sending a PWM signal to the gate driver 315 via the PWM port 311.

[0020] The inverter 316 is connected to the motor 150 and includes high-side switching elements IS1, IS3, and IS5 and low-side switching elements IS2, IS4, and IS6 for each phase of the coil of the motor 150. Therefore, if the motor 150 is a three-phase motor (U-phase, V-phase, and W-phase) as shown in FIG. 3, the inverter 316 is a three-phase inverter including six switching elements IS1 to IS6. The switching elements IS1 to IS6 of the inverter 316 are configured by transistors or FETs. Terminals (G1 to G6) for on / off control of the switching elements IS1 to IS6 of the inverter 316 are connected to the gate driver 315, and the on / off of the switching elements IS1 to IS6 is controlled in accordance with the PWM signal from the PWM port 311. For example, the gate driver 315 controls the G1 terminal of the inverter 316 by changing the voltage applied to the G1 terminal of the gate driver 315 based on the PWM output output from the UH terminal of the PWM port 311, thereby switching the switching element IS1 on and off.

[0021] The inverter 316 controls the on / off of internal switching elements IS1 to IS6 to control the coil currents flowing through the coils 151 (U phase), 152 (V phase), and 153 (W phase) of the motor 150. Shunt resistors 317, 318, and 319 are arranged between the low-side switching elements IS2, IS4, and IS6 in the inverter 316 and the ground. The currents flowing through the coils 151 to 153 are converted into voltages by the shunt resistors 317, 318, and 319, which are connected in series to the ground terminal of the inverter 316 corresponding to the coils 151 to 153, and then converted into digital values ​​by the AD converter 314. The calculation unit 312 measures the coil currents of the respective phases based on the digital values ​​converted by the AD converter 314. The memory 313 has a function of storing the acquired coil current data.

[0022] Here, in order for the shunt resistors 317, 318, and 319 to convert the coil currents into voltages, the low-side switching elements IS2, IS4, and IS6 must be turned on to establish electrical continuity between the shunt resistors 317, 318, and 319 and the coils of each phase. Therefore, to prevent through current, the high-side switching elements IS1, IS3, and IS5 must be turned off. For example, when simultaneously detecting the currents in the coils 151 (U phase), 152 (V phase), and 153 (W phase), the high-side switching elements IS1, IS3, and IS5 are all turned off, and the low-side switching elements IS2, IS4, and IS6 are all turned on.

[0023] FIG. 4 shows a configuration diagram of the motor 150. The motor 150 has a six-slot stator 154 and a four-pole rotor 155. The stator 154 has coils 151 (U phase), 152 (V phase), and 153 (W phase), and each of the coils 151 to 153 is star-connected and electrically connected. Therefore, there are six excitation phases in total: UV, UW, VU, VW, WU, and WV. For example, when current flows from coil 151 (U phase) to coil 152 (V phase), the UV phase is excited, and coil 151 (U phase) is excited to the north pole, and coil 152 (V phase) is excited to the south pole. The rotor 155 is made up of a permanent magnet and has two pairs of south and north poles. The rotational phase of the rotor 155 can be defined based on when the rotor 155 is in a predetermined position. For example, in this embodiment, when the state in FIG. 4 is set to an electrical angle of 0, if the rotor rotates counterclockwise from the state in FIG. 4 by a mechanical angle of π, the electrical angle becomes 2π.

[0024] The configuration of the current detection unit is shown in Figure 5. The AD converter 314 is connected to shunt resistors 317, 318, and 319 of each phase via a multiplexer 32. The multiplexer 32 can be connected to each coil 151 (U phase), 152 (V phase), and 153 (W phase) of the motor 150 and to circuits having analog information other than the motor control unit 31 (not shown). The motor control unit 31 controls the inverter 316 based on the current measured by the calculation unit 312 as the detection result of the current detection unit.

[0025] Based on instructions from printer control unit 30, multiplexer 32 controls the on / off of switching elements MS inside multiplexer 32 so that circuits having analog information to be read are connected to AD converter 314. Switching elements MS include switching elements MSu, MSv, MSw, and MS1 to MSx corresponding to the multiple circuits selectively connected to AD converter 314. After the voltage of a circuit in multiplexer 32 whose switching element MS is turned on is charged to sampling capacitor 320, AD converter 314 reads the analog information of that circuit.

[0026] Here, switching noise occurs when the switching element MS inside the multiplexer 32 is switched on and off. Therefore, when the AD converter 314 converts analog information into digital information, a predetermined waiting time (settling time) is provided after the switching of the switching element MS inside the multiplexer 32, and then reading is performed by the AD converter 314. For example, when the currents of the coils 151 (U phase), 152 (V phase), and 153 (W phase) are detected simultaneously, a current detection time of about 2 μs × 3 phases = 6 μs can be provided assuming a settling time of 2 μs per phase.

[0027] FIG. 6 shows an example of a PWM voltage waveform. The PWM port 311 controls the gate driver 315, which turns on and off the switching elements IS1 to IS6 of the inverter 316. This inputs a PWM voltage, as shown in FIG. 6, to each of the coils 151 to 153. As a result, a sinusoidal current, as shown in FIG. 6, flows through each of the coils 151 to 153. As described above, when simultaneously detecting currents, the high-side switching elements IS1, IS3, and IS5 must be turned off. Therefore, the PWM voltage is turned off for the current detection time, including the settling time. Therefore, in situations requiring a high on-duty, the PWM voltage cannot be turned on for the current detection time, preventing the desired current from flowing to the motor 150. For example, if the PWM voltage control period is 50 μs and the current detection time is set to 6 μs, the on-duty is limited to a maximum of 88%.

[0028] 7 shows an example of noise that may occur in the analog information read by the AD converter 314 during switching. When the switching element MS of the multiplexer 32 is switched to the circuit having the analog information to be read by the AD converter 314 in the multiplexer 32, noise occurs in the analog information, resulting in a period of unstable voltage.

[0029] 7(a) shows an example of typical control in which the settling time is set to the noise convergence period (first settling time). As shown in FIG. 7(a), by reading AD at the timing when the unstable voltage state subsides and the detected value of the controller becomes equivalent to the true value, it is possible to reduce errors in current detection and suppress uneven rotation of the motor 150.

[0030] Figure 7(b) shows an example in which the settling time is set to the period during which AD reading is performed before noise convergence (second settling time). As shown in Figure 7(b), by setting a settling time that is shorter than the original AD reading timing shown in Figure 7(a), the current detection time can be shortened and the on-duty of the PWM voltage can be increased.

[0031] Here, when AD reading is performed before noise convergence as shown in FIG. 7(b), there is a possibility that rotational irregularities of the motor 150 will increase due to a large error in the detected current value. Here, a state in which the error in the detected current value is large can be understood as, for example, a state in which a detected current exceeds or falls below a predetermined range that can be said to be a current detected when the voltage is stable, i.e., a state in which the detected current magnitude varies widely. Furthermore, rotational irregularities of the motor 150 can be understood as meaning periodic fluctuations in the rotational speed of the motor 150. A state in which rotational irregularities are large can be understood as a state in which the periodic fluctuations in the rotational speed of the motor 150 are large.

[0032] In the case of a motor used in an image forming apparatus, such as motor 150, if rotational irregularities become large during image formation, this can adversely affect the image transferred to sheet 20. Therefore, a settling time is provided that is long enough to allow post-switching noise to converge, as shown in FIG. 7(a), i.e., long enough for the fluctuations in the voltage read by AD converter 314 from shunt resistors 317-319 to converge within a predetermined range. For example, if the PWM period is 50 μs and the reading time required by the AD converter is 2 μs, then 2 μs × 3 phases = 6 μs is required, resulting in a maximum duty cycle of 88%. On the other hand, even if rotational irregularities of motor 150 become large during timing when image formation is not being performed, the adverse effect on the image forming apparatus can be said to be minor. Therefore, when image formation is not performed, such as during startup, a settling time is provided to perform AD reading without waiting for noise convergence as shown in FIG. 7B, i.e., at an early timing that does not require whether the fluctuations in the voltages read by the AD converter 314 from the shunt resistors 317-319 have converged within a predetermined range. This allows the on-duty of the PWM voltage control of the motor 150 to be increased to nearly 100%, enabling the use of a smaller motor. Specifically, if the reading time required by the AD converter 314 is shortened from 2 μs to 0.5 μs when the PWM period is 50 μs, the maximum duty can be increased from 88% to 97%, which is close to 100%.

[0033] Figure 8 shows an example of the settling time switching operation. As mentioned above, the first settling time is used during the image formation period, and the second settling time is used during the non-image formation period, thereby providing the advantages of each. Therefore, as shown in Figure 8, the period from when the motor starts to when image formation begins is used as the second settling time, and the on-duty limit is increased. On the other hand, the settling time is switched to the first settling time when image formation begins or after a predetermined time has elapsed since the target speed was reached.

[0034] During the current detection period, the current detection unit detects the current flowing through each of the coils 151-153. This current detection begins after a predetermined settling time has elapsed since the inverter 316 stopped applying voltage to each of the coils 151-153 of the motor 150. For example, in the current detection operation during the image formation period (first current detection operation), the settling time is set so that current detection begins after a predetermined time has elapsed after the rotational speed of the motor 150 reaches a predetermined target speed from the start of acceleration (first settling time). On the other hand, in the current detection operation during the non-image formation period (second current detection operation), the settling time is set so that current detection begins after the rotational speed of the motor 150 reaches a predetermined target speed from the start of acceleration but before the predetermined time has elapsed (second settling time). In other words, the second settling time is shorter than the first settling time, and the second current detection operation begins current detection earlier than the first settling time in the first current detection operation. Therefore, the current detection period when the second current detection operation is performed is shorter than the current detection period when the first current detection operation is performed, and the shorter period allows the inverter 316 to apply voltage to each coil 151 to 153 of the motor 150 for a longer period of time.

[0035] The first settling time may be set so that the first current detection operation can be performed after, for example, fluctuations in the rotation speed of the motor 150 relative to a predetermined target speed have converged to a predetermined range. The second settling time may be set so that the second current detection operation can be performed before fluctuations in the rotational speed of the motor 150 relative to a predetermined target speed converge within a predetermined range. Alternatively, the second current detection operation may be configured to be performed when an operation of the image forming unit that places a greater load on the motor 150 than the operation for which the first current detection operation is performed is being performed. For example, the settling time may be switched to the first settling time after a predetermined time has elapsed since the motor speed reached the target value and became a light load under steady rotation. In other words, the first current detection operation may be performed during steady rotation of the motor 150, and the second current detection operation may be performed, for example, when the motor 150 is started up or accelerating.

[0036] As described above, in the first current detection operation, the settling time is set to a length that allows the periodic fluctuation in the rotation speed of the motor 150 (rotation unevenness) to be kept below a predetermined level. This makes it possible to reduce rotation unevenness of the motor 150 during image formation. Furthermore, in the second current detection operation, the settling time is set to the shortest possible length, regardless of whether or not the rotation unevenness occurs. This shortens the time required to apply voltage to the motor 150 (enabling voltage application to the motor 150 to be performed at an earlier timing), and increases the on-duty limit. Therefore, it becomes possible to apply a motor drive voltage at a higher duty while stabilizing the image formation operation.

[0037] Example 2 In the first embodiment, an example of controlling the current detection time by switching between the first settling time and the second settling time at startup was described. In the second embodiment, an example of controlling the current detection time by switching between the first settling time and the second settling time at the time of load fluctuation such as contact / separation will be described with reference to Figures 1, 7, and 9. In the following, a description of parts common to the first embodiment will be omitted.

[0038] Generally, an image forming apparatus such as that shown in FIG. 1 has a mechanism for contacting and separating the photosensitive drum 11 and the developing roller 14 in consideration of the lifespan of the photosensitive drum 11. That is, the photosensitive drum 11 and the developing roller 14 are configured to be able to be in a contact state in which they are in contact with each other, and a separated state (non-contact state) in which they are separated from each other. Specifically, there are three states: a state in which the photosensitive drums 11Y, M, C, and K and the developing rollers 14Y, M, C, and K are all in contact with each other (full-color contact); a state in which only the photosensitive drum K and the developing roller 14K are in contact with each other (mono-color contact); and a state in which all are separated from each other (full separation). When switching between these contact and separation states, an actuator such as an SL (not shown) is used as a trigger to switch the state using the power of a motor 150.

[0039] Figure 9 shows an example of the settling time switching operation when the load fluctuates in this embodiment. Here, time t1 is the timing when the contact-separation state is switched from the full-separation state to the full-color contact state. Time t2 is the timing when the non-image formation period transitions to the image formation period. Time t3 is the timing when the image formation period transitions to the non-image formation period. Time t4 is the timing when the contact-separation state is switched from the full-color contact state to the full-separation state. Time t5 is the timing when the non-image formation period transitions to the image formation period.

[0040] During the contact / separation operation, a mechanism for contacting and separating the developing roller 14 needs to be operated, which places a load on the motor 150, which is the drive source. For example, if the contact / separation state is switched from the full-separation state to the full-color contact state while the motor 150 is rotating steadily at time t1 in Figure 9, a period X1 occurs in which the motor load required of the motor 150 temporarily increases due to a load fluctuation in the image forming unit. Similarly, if the contact / separation state is switched at time t4, a period X2 occurs in which the motor load temporarily increases.

[0041] As described in the first embodiment, if AD reading is performed before noise convergence as shown in FIG. 7(b), it may adversely affect the image transferred to the sheet 20. Therefore, a settling time is provided during the image formation period to allow sufficient time for noise convergence as shown in FIG. 7(a). On the other hand, during non-image formation periods, even if the rotational irregularity of the motor 150 increases, the adverse effect on the image forming apparatus is considered to be minor, so AD reading can be performed without waiting for noise convergence as shown in FIG. 7(b). Therefore, a second settling time can be set during non-image formation periods such as from time t0 to t2 and from time t3 to t5. As a result, the on-duty of the PWM voltage control of the motor 150 can be increased to nearly 100% during periods such as X1 and X2, when the motor load is temporarily heavy, allowing the use of a smaller motor.

[0042] The above embodiments can be combined with each other.

[0043] The disclosure of the embodiments of the present invention includes the following configurations. (Configuration 1) an image forming section for forming an image on a recording material; a motor having a plurality of coils that generates a driving force for driving the image forming unit; an inverter that applies a voltage to the plurality of coils; a current detection unit that detects currents flowing through the plurality of coils; a control unit that controls the inverter based on a detection result of the current detection unit; In an image forming apparatus comprising: the control unit controls the inverter to stop applying the voltage during a current detection period for the current detection unit to detect the current; The current detection unit is capable of executing, during the current detection period, a first current detection operation that starts detecting the current after a predetermined settling time has elapsed, and a second current detection operation that starts the detection at a timing earlier than the predetermined settling time has elapsed. An image forming apparatus characterized by: (Configuration 2) When the settling time is a first settling time, the second current sensing operation is a current sensing operation that starts the sensing after a second settling time that is shorter than the first settling time has elapsed. 2. The image forming apparatus according to claim 1. (Configuration 3) the current detection period when the second current detection operation is performed is shorter than the current detection period when the first current detection operation is performed; 3. The image forming apparatus according to claim 1 or 2. (Configuration 4) the first current detection operation is performed during an image formation period in which the image forming unit performs an image forming operation to form an image on a recording material, the second current detection operation is performed during a non-image formation period in which the image forming unit does not perform the image formation operation. The image forming apparatus according to any one of the first to third configurations. (Configuration 5) the second current detection operation is executed when an operation of the image forming unit that applies a larger load to the motor than an operation for which the first current detection operation is executed is performed. The image forming apparatus according to any one of the first to fourth configurations. (Configuration 6) the first current detection operation is performed during steady rotation of the motor; the second current sensing operation is performed at start-up of the motor; The image forming apparatus according to any one of the first to fifth aspects. (Configuration 7) the second current sensing operation is performed when the motor is accelerating. The image forming apparatus according to any one of the first to sixth configurations. (Configuration 8) The first current detection operation is executed after a predetermined time has elapsed after the rotation speed of the motor has reached a predetermined target speed from the start of acceleration. the second current detection operation is executed after the rotation speed of the motor reaches a predetermined target speed from the start of acceleration and before a predetermined time has elapsed. The image forming apparatus according to any one of the first to seventh configurations. (Configuration 9) the first current detection operation is performed after fluctuations in the rotational speed of the motor relative to a predetermined target speed have converged to a predetermined range; the second current detection operation is performed before fluctuations in the rotational speed of the motor relative to a predetermined target speed converge to a predetermined range. The image forming apparatus according to any one of the first to eighth configurations. (Configuration 10) the control unit controls the switching elements of the inverter with a PWM signal; A voltage corresponding to the duty of the PWM signal is applied to the plurality of coils. The image forming apparatus according to any one of the first to ninth configurations. (Configuration 11) the current detection unit detects the current using a plurality of shunt resistors connected in series to a ground terminal of the inverter corresponding to the plurality of coils; The image forming apparatus according to any one of the first to tenth embodiments. (Configuration 12) the current detection unit has an AD converter for converting voltages corresponding to the currents flowing through the plurality of coils, which are acquired using the plurality of shunt resistors, into digital values; the AD converter is connected to the plurality of shunt resistors via a multiplexer having a plurality of switching elements corresponding to the plurality of shunt resistors; the settling time is a time from when the switching elements of the multiplexer are switched to when the AD converter starts reading the voltage from the shunt resistor. 12. The image forming apparatus according to claim 11. (Configuration 13) the first current detection operation is performed after a fluctuation in the voltage read from the shunt resistor by the AD converter after the switching has converged to a predetermined range; the second current detection operation is performed before fluctuations in the voltage read from the shunt resistor by the AD converter after the switching converge to a predetermined range. 13. The image forming apparatus according to claim 12. (Configuration 14) the settling time is set to a length that can suppress the amount of periodic fluctuation in the rotation speed of the motor to a predetermined value or less. 14. The image forming apparatus according to any one of the first to thirteenth aspects. (Configuration 15) the image forming unit includes an image carrier and a developer carrier, the image carrier and the developer carrier are configured to be capable of being in a contact state in which they are in contact with each other and in a spaced state in which they are spaced apart from each other, the second current detection operation is performed when the image carrier and the developer carrier are moved in contact with or away from each other. The image forming apparatus according to any one of the first to fourteenth configurations. [Explanation of symbols]

[0044] 10... Image forming apparatus, 30... Printer control unit, 150... Motor, 151, 152, 153... Coil, 314... AD converter, 316... Inverter, 317, 318, 319... Shunt resistor

Claims

1. an image forming section for forming an image on a recording material; a motor having a plurality of coils that generates a driving force for driving the image forming unit; an inverter that applies a voltage to the plurality of coils; a current detection unit that detects currents flowing through the plurality of coils; a control unit that controls the inverter based on a detection result of the current detection unit; In an image forming apparatus comprising: the control unit controls the inverter to stop applying the voltage during a current detection period for the current detection unit to detect the current; The current detection unit is capable of executing, during the current detection period, a first current detection operation that starts detecting the current after a predetermined settling time has elapsed, and a second current detection operation that starts the detection at a timing earlier than the predetermined settling time has elapsed. An image forming apparatus characterized by:

2. When the settling time is a first settling time, the second current sensing operation is a current sensing operation that starts the sensing after a second settling time that is shorter than the first settling time has elapsed. The image forming apparatus according to claim 1 .

3. the current detection period when the second current detection operation is performed is shorter than the current detection period when the first current detection operation is performed; The image forming apparatus according to claim 1 .

4. the first current detection operation is performed during an image formation period in which the image forming unit performs an image forming operation to form an image on a recording material, the second current detection operation is performed during a non-image formation period in which the image forming unit does not perform the image formation operation. The image forming apparatus according to claim 1 .

5. the second current detection operation is executed when an operation of the image forming unit that applies a larger load to the motor than an operation for which the first current detection operation is executed is performed. The image forming apparatus according to claim 1 .

6. the first current detection operation is performed during steady rotation of the motor; the second current sensing operation is performed at start-up of the motor; The image forming apparatus according to claim 1 .

7. the second current sensing operation is performed when the motor is accelerating. The image forming apparatus according to claim 1 .

8. The first current detection operation is executed after a predetermined time has elapsed after the rotation speed of the motor has reached a predetermined target speed from the start of acceleration. the second current detection operation is executed after the rotation speed of the motor reaches a predetermined target speed from the start of acceleration and before a predetermined time has elapsed. The image forming apparatus according to claim 1 .

9. the first current detection operation is performed after fluctuations in the rotational speed of the motor relative to a predetermined target speed have converged to a predetermined range; The second current sensing operation detects a variation in the rotational speed of the motor relative to a predetermined target speed. Before converging to a certain range, The image forming apparatus according to claim 8 .

10. the control unit controls a switching element of the inverter by a PWM signal; A voltage corresponding to the duty of the PWM signal is applied to the plurality of coils. The image forming apparatus according to claim 1 .

11. the current detection unit detects the current using a plurality of shunt resistors connected in series to a ground terminal of the inverter corresponding to the plurality of coils; The image forming apparatus according to claim 1 .

12. the current detection unit has an AD converter for converting voltages corresponding to the currents flowing through the plurality of coils, which are acquired using the plurality of shunt resistors, into digital values; the AD converter is connected to the plurality of shunt resistors via a multiplexer having a plurality of switching elements corresponding to the plurality of shunt resistors; the settling time is a time from when the switching elements of the multiplexer are switched to when the AD converter starts reading the voltage from the shunt resistor; The image forming apparatus according to claim 11.

13. the first current detection operation is performed after a fluctuation in the voltage read from the shunt resistor by the AD converter after the switching has converged to a predetermined range; the second current detection operation is performed before fluctuations in the voltage read from the shunt resistor by the AD converter after the switching converge to a predetermined range. The image forming apparatus according to claim 12.

14. the settling time is set to a length that can suppress the amount of periodic fluctuation in the rotation speed of the motor to a predetermined value or less. The image forming apparatus according to claim 1 .

15. the image forming unit includes an image carrier and a developer carrier, the image carrier and the developer carrier are configured to be capable of being in a contact state in which they are in contact with each other and in a spaced state in which they are spaced apart from each other, the second current detection operation is performed when the image carrier and the developer carrier are moved in contact with or away from each other. The image forming apparatus according to claim 1 .

Images