Motor control apparatus for determining motor type and image forming apparatus

A motor control apparatus includes: an excitation unit configured to excite a plurality of excitation phases of a motor; a measurement unit configured to measure a physical amount that changes according to an inductance of at least one of a plurality of coils that make up the plurality of excitation phases, when each of the plurality of excitation phases is excited; and a determination unit configured to determine a type of the motor based on measurement values of the physical amount measured by the measurement unit when each of the plurality of excitation phases is excited.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to technology for controlling a motor, and in particular relates to technology for performing determination on a motor to be controlled.

Description of the Related Art

In image forming apparatuses, a DC brushless motor, a brushed DC motor, a stepping motor, or the like is used for a driving source of a rotating member. A sensorless motor that does not have a Hall element for detecting the rotation position of a rotor is also used as a DC brushless motor. EP2437391 discloses a configuration for estimating the rotation position of a rotor of a sensorless motor even when a power supply voltage is unstable.

In EP2437391, a condition for applying a pulse voltage is changed when a power supply voltage is unstable. However, in the configuration of EP2437391, when using a plurality of motors having coils with different inductances and rotors with different magnetic forces, the condition for applying a pulse voltage cannot be changed to a condition suitable for the motor to be controlled.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, a motor control apparatus includes: an excitation unit configured to excite a plurality of excitation phases of a motor; a measurement unit configured to measure a physical amount that changes according to an inductance of at least one of a plurality of coils that make up the plurality of excitation phases, when each of the plurality of excitation phases is excited; and a determination unit configured to determine a type of the motor based on measurement values of the physical amount measured by the measurement unit when each of the plurality of excitation phases is excited.

DESCRIPTION OF THE EMBODIMENTS

Embodiments will be described below in detail with reference to the attached drawings. Note that the following embodiments do not limit the invention according to the scope of the claims. A plurality of features are described in the embodiments, but all of these features are not necessarily essential to the invention, and a plurality of features may be suitably combined. Furthermore, in the attached drawings, the same reference numerals are assigned to the same or similar configurations, and an overlapping description is omitted.

First Embodiment

FIG. 1shows an image forming apparatus10according to this embodiment, which is a printer, a copier, a multi-function peripheral, a facsimile, or the like. The image forming apparatus10overlays toner images of four colors, namely yellow (Y), magenta (M), cyan (C), and black (K) to form a full-color image. InFIG. 1, Y, M, C and K at the ends of reference signs indicate that the colors of toner images with which members denoted by the reference signs are involved when the toner images were formed are respectively yellow, magenta, cyan, and black. Note that, in the following description, when it is not necessary to distinguish colors, reference signs without Y, M, C and K at their ends are used. A photosensitive member11is driven and rotated in the clockwise direction of the figure when forming an image. A charging unit12charges the surface of the photosensitive member11to a uniform potential. An exposure unit13exposes the surface of the photosensitive member11to light so as to form an electrostatic latent image on the photosensitive member11. A developing roller15of a developing unit develops the electrostatic latent image of the photosensitive member11using toner by outputting a developing bias, and visualizes it as a toner image. A primary transfer unit16transfers the toner image formed on the photosensitive member11, onto an intermediate transfer belt17by applying a primary transfer bias. Note that, as a result of toner images formed on the photosensitive members11being overlaid and transferred onto the intermediate transfer belt17, a full-color image is formed on the intermediate transfer belt17.

The intermediate transfer belt17is driven and rotated in the counter-clockwise direction of the figure by a drive roller20. Accordingly, the toner image transferred onto the intermediate transfer belt17is conveyed to an opposing position of a secondary transfer unit19. On the other hand, a recording member (sheet) P stored in a cassette21is conveyed along a conveyance path23, and is conveyed to the opposing position of the secondary transfer unit19. Rollers for conveying the recording member P are provided on the conveyance path23. The secondary transfer unit19transfers the toner image on the intermediate transfer belt17onto the recording member P by applying a secondary transfer bias. The recording member P is then conveyed to a fixing device24. The fixing device24applies heat and pressure to the recording member P, and fixes the toner image to the recording member P. After the toner image is fixed, the recording member P is discharged to the outside of the image forming apparatus.

In this embodiment, a motor151transmits its drive force to a photosensitive member11K, a charging unit12K, a developing roller15K, a primary transfer unit16K, and a drive roller20K via a gear mechanism (not illustrated). A motor152transmits its drive force to photosensitive members11Y,11M, and11C, charging units12Y,12M, and12C, developing rollers15Y,15M, and15C, and primary transfer units16Y,16M, and16C via gear mechanisms (not illustrated).

FIG. 2shows a control configuration of the image forming apparatus. A control unit40, upon receiving image data of an image to be formed from a host computer220via a communication controller210, starts image formation. When image formation is started, the control unit40controls a motor control unit41so as to drive and rotate motors150that include the motor151and the motor152, and perform rotation drive control of rotating members such as the photosensitive member11, conveyance control of the recording member P, and the like. The control unit40also controls the exposure unit13so as to form an electrostatic latent image on the photosensitive member11. Furthermore, the control unit40controls a high voltage power supply160so as to output a bias for image formation to the charging unit12, the developing roller15, the primary transfer unit16, and the secondary transfer unit19. Accordingly, a toner image is formed on the recording member P. In addition, the control unit40controls the fixing device24so as to fix a toner image to the recording member P. A low voltage power supply120outputs a DC voltage. The DC voltage output by the low voltage power supply120is used for driving and rotating the motor151and the motor152, for example. The control unit40displays the status of the image forming apparatus in a display unit200. Note that the control unit40includes a microcomputer (processor) and a memory. The memory stores various types of control programs and data, and the microcomputer controls the units of the image forming apparatus10based on the various types of control programs and data stored in the memory.

Next, a configuration of the motor control unit41that controls the motor151will be described with reference toFIG. 3. Note that the motor152has a configuration similar to that of the motor151, and also has a similar control configuration, and thus a description of the motor152is omitted. The motor control unit41includes a processing unit51realized by a microcomputer and the like. A communication port52performs serial data communication with the control unit40. A pulse width modulation (PWM) port58outputs PWM signals for driving switching elements of a three-phase inverter60. The switching elements of the three-phase inverter60are, for example, FETs, and are driven by the PWM signals. The three-phase inverter is supplied with a DC voltage from the low voltage power supply120. As a result of the switching elements of the three-phase inverter60being turned on/off using the PWM signals, excitation currents (coil currents) flow through a plurality of coils73(U phase),74(V phase), and75(W phase) of the motor151. In this manner, the three-phase inverter60operates as an excitation unit that excites the motor151. In addition, the excitation currents in the coils73,74, and75are converted into a voltage by a resistor63, and is input to an AD converter53of the processing unit51, as a value indicating the excitation currents. A nonvolatile memory55is a storage unit that stores data to be used for processing that is performed by the processing unit51, and the like.

Next, the structure of the motor151will be described with reference toFIG. 4. In this embodiment, the motor151includes a stator71having six slots and a rotor72having four poles. The stator71includes coils73,74, and75of three respective phases (U, V, and W). The rotor72is constituted by permanent magnets, and includes two sets of N and S poles. Here, in general, a coil such as the coil73,74, or75has a configuration in which a copper wire is wound around a core that is formed by stacking electrical steel sheets. Also, the magnetic permeability of an electrical steel sheet decreases when an external magnetic field is present. The inductance of a coil is proportional to the magnetic permeability of a core, and therefore when the magnetic permeability of the core decreases, the inductance of the coil also decreases. For example, because the U-phase coil73inFIG. 4opposes only an S pole of the rotor72, the degree of reduction in inductance of the U-phase coil73is larger than that of the W-phase coil75that opposes both an S pole and an N pole of the rotor72. Also, the amount of change in inductance differs depending on whether or not the direction of a magnetic field generated by an excitation current is the same as the direction of an external magnetic field. Specifically, in a state inFIG. 4, when an excitation current is caused to flow such that the direction of the magnetic field generated by the U-phase coil73is the same as the magnetic field generated by the opposing S pole of the rotor72, that is, the U phase is an N pole, the amount of reduction in inductance increases relative to a case where the excitation current is caused to flow in a direction such that the U phase is an S pole. As described above, the detected inductance differs depending on the stopping position of the rotor72and the excitation phase.

There are six excitation phases, namely U-V, U-W, V-U, V-W, W-U, and W-V phases for the motor151of this embodiment. Note that the excitation in the X-Y phase means that an excitation current is caused to flow from the X-phase coil to the Y-phase coil. As described above, while the rotor72is stopped, the inductance that is detected when a certain excitation phase is excited differs depending on a stopping position of the rotor72. The inductance also differs depending on an excitation phase that is excited. If the inductance differs, the rate of rise of a current also differs. Therefore, if the excitation phases are excited only for a predetermined period while the rotor72is stopped, excitation currents are measured, and the largest value is detected, the largest value that is detected differs depending on an excitation phase, for example, as shown inFIGS. 5A and 5B.

Here, when the inductances of the coils73to75of the motor151increase, the excitation currents decrease, and thus the largest value also decreases. Conversely, when the inductances of the coils73to75decrease, the excitation currents increase, and thus the largest value also increases. In addition, if the magnetic force of the rotor72is high, the influence of the magnetic force of the rotor72on the inductance is large, and thus the difference in the largest value of the excitation currents when the excitation phases are excited increases. Conversely, if the magnetic force of the rotor72is low, the influence of the magnetic force of the rotor72on the inductance is small, and thus the difference in the largest value of the excitation currents when the excitation phases are excited is small.

In this embodiment, as shown inFIGS. 5A and 5B, the processing unit51excites the excitation phases for a predetermined period, and determines a type of a motor to be controlled, based on the largest value of excitation currents measured while the excitation phases are excited. In the following description, the largest value of excitation currents of the excitation phases measured in this manner is referred to as a measurement value or measurement result of the excitation phases. There are two determination methods. A first method is a method for performing determination based on the magnitude of measurement values, and a second method is a method for performing determination based on the difference between measurement values of the excitation phases. For example, if a determination is made as to which motor is to be controlled from among a plurality of motors having the coils73to75with different inductances, the first method can be used. Also, if a determination is made as to which motor is to be controlled from among a plurality of motors having the rotors72with different magnetic forces, the second method can be used.

First, the first method will be described. Note that, in the following description, two types of motors having the coils73to75with different inductances are used for the image forming apparatus10, and a motor with a smaller inductance is referred to as a motor A, and a motor with a larger inductance is referred to as a motor B.FIGS. 5A and 5Bshow measurement results of the respective excitation phases of the motor A and the motor B. The processing unit51notifies the control unit40of whether or not the largest measurement result exceeds a predetermined threshold, and the control unit40determines whether or not the motor that is being used is the motor A or the motor B, according to whether or not the largest measurement result exceeds the predetermined threshold. InFIG. 5A, there are measurement results that exceed the threshold, but, inFIG. 5B, all of the measurement results are smaller than the threshold. In this case, if there is a measurement result that exceeds the threshold, the control unit40determines that the motor that is being used is the motor A, and if there is no measurement result that exceeds the threshold, determines that the motor that is being used is the motor B. The control unit40then selects and sets, based on the determined type of the motor151, parameters for controlling the motor151, such as a voltage of the low voltage power supply120, a control gain, a filter constant, a voltage application pattern, and a current amount during forced commutation.

Next, the second method will be described. Note that, in the following description, two types of motors having the rotors72with different materials, sizes, structures, and the like are used for the image forming apparatus10. If the materials, sizes, structures, and the like are different, the magnetic forces of the rotors72are also different. In the following description, a motor in which the magnetic force of the rotor72is smaller is referred to as a motor C and a motor in which the magnetic force of the rotor72is larger is referred to as a motor D.FIGS. 6A and 6Bshow measurement results of the excitation phases of the motor C and the motor D. The processing unit51notifies the control unit40of whether or not the difference between the largest measurement result and the second largest measurement result exceeds a threshold, and the control unit40determines whether the motor151that is being used is the motor C or the motor D, in accordance with whether or not the difference exceeds the threshold. The difference inFIG. 6Ais smaller than the difference inFIG. 6B. Note that, in this example, the difference inFIG. 6Adoes not exceed the threshold, but the difference inFIG. 6Bexceeds the threshold. In this case, if the difference does not exceed the threshold, the control unit40determines that the motor is the motor C, and if the difference exceeds the threshold, determines that the motor is the motor D. The control unit40then selects and sets, based on the determined type of the motor151, parameters for controlling the motor151, such as a voltage of the low voltage power supply120, a control gain, a filter constant, a voltage application pattern, and a current amount during forced commutation.

Note that, inFIGS. 6A and 6B, the difference between the largest measurement result and the second largest measurement result is compared with the threshold, but there are cases where the largest measurement result and the second largest measurement result are substantially the same regardless of the magnitude of the magnetic force of each of the rotors72, depending on the stopping position of the rotor72. In this case, if the difference between the largest measurement result and the second largest measurement result is used, an error arises in determination on the type of the motor. Therefore, a configuration can also be adopted in which the difference between the largest measurement result and the third largest measurement result or any measurement result smaller than the third largest measurement result is compared with the threshold.

Note that, in this embodiment, in each of the first method (FIGS. 5A and 5B) and the second method (FIGS. 6A and 6B), a determination is made between two types of motors using one threshold. However, a configuration can be adopted in which the magnitude of inductance or the magnitude of the magnetic force of the rotor72is evaluated in three or more stages using two or more thresholds, and a determination can be made between three or more types of motors. Furthermore, a determination can be made between types of motors with different inductances and different magnetic forces of the rotors72by using both the first method and the second method. For example, if one threshold is used in each of the first method and the second method, a determination can be made between, in total, four types of motors, namely a motor with a small inductance and a small magnetic force, a motor with a small inductance and a large magnetic force, a motor with a large inductance and a small magnetic force, and a motor with a large inductance and a large magnetic force.

Note that, in this embodiment, regarding the excitation phases, the largest value of excitation currents is measured and detected as a physical amount that changes according to the magnitude of the inductance. However, it is sufficient that the physical amount that changes according to the inductances of the coils73to75can be detected, and the present invention is not limited to a configuration for detecting the largest value of excitation currents. For example, it is also possible to adopt a configuration for detecting the speed of a change in the excitation current during excitation. For example, it is also possible to adopt a configuration for measuring a current value after a predetermined time has elapsed since excitation. It is also possible to use an average value, an effective value, a peak value, an average value excluding a peak value, an integrated value, and the like when the excitation phases are excited for a predetermined time, for example.

In addition, in this embodiment, the largest value of excitation currents is used as a physical amount that changes according to the magnitude of inductance. Here, the smaller the inductance is, the larger the largest value of excitation currents becomes. Therefore, when a physical amount that decreases as the inductance decreases is used as a physical amount that changes according to the magnitude of inductance, a determination criterion in the above description changes according to the physical amount. Note that a person skilled in the art can understand the way the determination criterion changes, and thus a detailed description thereof is omitted. Note that the first method shown inFIGS. 5A and 5Bcorresponds to a method of comparing a measurement result indicating that the impedance is the smallest with a threshold, and, if the measurement result indicating that the impedance is the smallest is below the threshold, determining that the motor is the motor A, and otherwise determining that the motor is the motor B. Also, the second method shown inFIGS. 6A and 6Bcorresponds to a method of obtaining the difference between a measurement result indicating that the impedance is the smallest and a measurement result indicating that the impedance is the second smallest, and, if the difference does not exceed a threshold, determining that the motor is the motor C, and otherwise determining that the motor is the motor D.

Second Embodiment

Next, a second embodiment will be described with a focus on differences from the first embodiment. In the first embodiment, a difference in the inductances of the coils73to75is determined based on the largest value of measurement result. However, when the property of the motor151such as the magnetic force of the rotor72is very strong, there are cases where the largest measurement result is very large compared to other measurement results. In such cases, if measurement results excluding the largest measurement result are used, the type of the motor151can be determined more accurately.

Note that, in the following description, two types of motors having the coils73to75with different inductances are used for the image forming apparatus10, and the motor with a smaller inductance is referred to as a motor E, and the motor with a larger inductance is referred to as a motor F.FIGS. 7A and 7Bshow measurement results of the excitation phases of the motor E and the motor F. The magnetic forces of the rotors72of the motor E and the motor F are very high, and thus the largest measurement result is very large compared with the other measurement results. In this embodiment, the processing unit51notifies the control unit40of whether or not a measurement result that exceeds a predetermined threshold is included in the second largest measurement result and measurement results smaller than the second largest measurement result. InFIG. 7A, there are measurement results that exceed the threshold, but, inFIG. 7B, the second largest measurement result and the measurement results smaller than the second largest measurement result are all smaller than the threshold. In this case, if there is a measurement result that exceeds the threshold, the control unit40determines that the motor is the motor E, and if there is no measurement result that exceeds the threshold, determines that the motor is the motor F. The control unit40then selects and sets, based on the determined type of the motor151, parameters for controlling the motor151, such as a voltage of the low voltage power supply120, a control gain, a filter constant, a voltage application pattern, and a current amount during forced commutation.

Note that a configuration can also be adopted in which the average value of the second largest measurement result and measurement results smaller than the second largest measurement result is compared with a threshold instead of comparing the second largest measurement result and measurement results smaller than the second largest measurement result with the threshold.FIGS. 7A and 7Balso show the average value of the second largest measurement result and measurement results smaller than the second largest measurement result. The control unit40determines that the motor is the motor E if the average value exceeds the threshold, and determines that the motor is the motor F if the average value does not exceed the threshold.

Note that, inFIGS. 7A and 7B, the second largest measurement result or a measurement result smaller than the second largest measurement result is compared with the threshold, but there are cases where, depending on the stopping position of the rotor72, the largest measurement result and the second largest measurement result are substantially the same. In this case, if the second largest measurement result or a measurement result smaller than the second largest measurement result is used, an error may occur in determination on a motor type. Therefore, a configuration can also be adopted in which any one of the third largest measurement result and measurement results smaller than the third largest measurement result is compared with a threshold.

Third Embodiment

Next, a third embodiment will be described with a focus on differences from the first and second embodiments. If the property of the motor151such as the magnetic force of the rotor72is very low, there are cases where, in a method of the second embodiment, accurate determination cannot be performed. In such cases, if the average value of all of the measurement results is used, the type of the motor151can be determined accurately.

In the following description, two types of motors having the coils73to75with different inductances are used for the image forming apparatus10, and a motor with a smaller inductance is referred to as a motor G, and a motor with a larger inductance is referred to as a motor H.FIGS. 8A and 8Bshow measurement results of the excitation phases of the motor G and the motor H. The magnetic forces of the rotors72of the motor G and the motor H are low, and thus the difference between the largest measurement result and the smallest measurement result is small. In this embodiment, the processing unit51notifies the control unit40of whether or not the average value of all of the measurement results exceeds a threshold. InFIG. 8A, the average value exceeds the threshold, but, inFIG. 8B, the average value is smaller than the threshold. If the average value exceeds the threshold, the control unit40determines that the motor is the motor G, and if the average value does not exceed the threshold, determines that the motor is the motor H. The control unit40then selects and sets, based on the determined type of the motor151, parameters for controlling the motor151, such as a voltage of the low voltage power supply120, a control gain, a filter constant, a voltage application pattern, and a current amount during forced commutation.

Other Embodiments

Note that, in the above embodiments, in order to determine a motor type, a physical amount that changes according to the magnitude of inductance is measured and detected. As described above, the physical amount that is measured and detected when the excitation phases are excited differs depending on the stopping position of the rotor72and an excitation phase that is excited, and thus the control unit40can determine a motor type, and can also determine the stopping position of the rotor72. Accordingly, the control unit40selects and sets, based on the determined type of the motor151, parameters for controlling the motor151, and start forced commutation control based on the determined stopping position of the rotor72.

Note that, in the above embodiments, the motor control unit41, which is a constituent element of the image forming apparatus10, is referred to as such, but the motor control unit41can also be an apparatus, and be referred to as a motor control apparatus. In addition, an apparatus that includes the control unit40and the motor control unit41can be a motor control apparatus. In addition, in the above embodiments, the motor151and the motor152cause a rotating member related to image formation of the image forming apparatus10such as the photosensitive member11to rotate, but the present invention can also be applied to a motor for conveying the recording member P. In addition, the configuration of the motor151and the motor152is not limited to the configuration shown inFIG. 4, and a motor with another pole number or another number of phases may also be adopted.

This application claims the benefit of Japanese Patent Application No. 2019-008598, filed on Jan. 22, 2019, and Japanese Patent Application No. 2019-202622, filed on Nov. 7, 2019, which are hereby incorporated by reference herein in their entirety.