Motor control device and image forming apparatus

Abstract

To solve a problem in which a measured value measured for determining the type of a motor is affected by a change according to the situation of the measurement in addition to a change due to the difference in the type of the motor, which may reduce the accuracy of control according to the type of the motor.SOLUTION: A motor controller has current detection means that detects coil current; control means that controls voltage application means to cause the coil current to flow in a plurality of coils in a plurality of patterns, and controls the current detection means to detect the coil current according to each of the patterns; a first power supply that outputs first voltage to the plurality of coils; a second power supply that outputs second voltage to the control means; and voltage detection means that detects the first voltage and the second voltage. The control means corrects the coil current detected by the current detection means based on a detection result from the voltage detection means, and determines the type of the motor based on the corrected coil current.SELECTED DRAWING: Figure 14

Description

Technical Field

[0001] The present invention relates to motor control technology.

Background Art

[0002] A motor is used as a drive source for each member of an image forming apparatus. Such a motor may be designed to selectively use a plurality of motors of different types. Since the characteristics of a motor can vary depending on its type, the image forming apparatus needs to change control parameters according to the type of the motor to be driven. Therefore, the image forming apparatus needs to determine the type of the motor to be driven. Patent Document 1 discloses a method of measuring the time required for acceleration and deceleration of a motor and determining the motor type from the measured time.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The measured value measured to determine the type of a motor is affected by changes according to the measured situation in addition to changes due to differences in the types of motors. As a result, there is a risk that the accuracy of control according to the type of the motor may be reduced.

[0005] The invention according to the present application has been made in view of the above situation, and an object thereof is to suppress a reduction in the accuracy of control according to the type of a motor.

Means for Solving the Problems

[0006] To achieve the above objective, a motor control device is provided, comprising: a voltage application means for applying a first voltage to a motor having a plurality of coils to cause a coil current to flow through the plurality of coils; a current detection means for detecting the coil current; a control means for causing the voltage application means to cause the plurality of coils to flow the coil current in a plurality of patterns, and the current detection means to detect the coil current corresponding to each pattern; a first power supply for outputting the first voltage to the plurality of coils; a second power supply for outputting a second voltage to the control means; and a voltage detection means for detecting the first voltage and the second voltage, wherein the control means corrects the coil current detected by the current detection means based on the detection result of the voltage detection means, and determines the type of motor based on the corrected coil current. [Effects of the Invention]

[0007] According to the present invention, it is possible to suppress the decrease in control accuracy depending on the type of motor. [Brief explanation of the drawing]

[0008] [Figure 1] Schematic diagram of an image forming apparatus [Figure 2] Control configuration diagram of an image forming apparatus [Figure 3] Motor control unit configuration diagram [Figure 4] Motor configuration diagram [Figure 5] This diagram shows the voltage applied to the coil and the time variation of the coil current during the rotor stop position detection process. [Figure 6] This diagram shows the maximum coil current for each coil current pattern, for each different rotor stopping position. [Figure 7] This diagram shows the maximum coil current for each coil current pattern, for each different rotor stopping position. [Figure 8] A diagram showing the template. [Figure 9] Diagram illustrating how to calculate the difference for a single template. [Figure 10]Diagram illustrating the relationship between measured coil current and the drive power supply voltage / control power supply voltage. [Figure 11] Diagram illustrating the relationship between measured value V and drive power supply voltage / control power supply voltage. [Figure 12] Diagram illustrating the relationship between measured coil current and measured value V. [Figure 13] A graph showing the variation in measured coil current. [Figure 14] A flowchart showing how to determine the motor type. [Figure 15] Diagram illustrating the relationship between measured values ​​V1 / V2 and the drive power supply voltage / control power supply voltage. [Modes for carrying out the invention]

[0009] The embodiments will be described in detail below with reference to the attached drawings. Note that the following embodiments do not limit the invention as defined in the claims. While the embodiments describe multiple features, not all of these features are essential to the invention, and the features may be combined in any way. Furthermore, in the attached drawings, identical or similar configurations are given the same reference numerals, and redundant descriptions are omitted.

[0010] <First Embodiment> Figure 1 is a configuration diagram of the image forming apparatus 10 according to this embodiment. The image forming apparatus 10 is, for example, a printer, copier, multifunction device, or facsimile. Sheets stored in the cassette 25 are fed into the sheet transport path by the feed roller 26. The transport roller 27 transports the fed sheets downstream. The image forming unit 1 forms a toner image on an internal image carrier based on image data and transfers the formed toner image to the sheet. The sheet with the transferred toner image is transported to the fuser unit 24. The fuser unit 24 heats and pressurizes the sheet to fix the toner image to the sheet. After the toner image is fixed, the sheet is discharged to the outside of the image forming apparatus 10. The motor 15F is a drive source that drives the rollers of the fuser unit 24. The image forming apparatus 10 may also have motors other than the motor 15F that drive other components (not shown).

[0011] Figure 2 shows the control configuration of the image forming apparatus 10. The printer control unit 11 controls the entire image forming apparatus 10 including the aforementioned image forming unit 1 and fixing unit 24. The printer control unit 11 has a processor (not shown) and a memory that stores programs and various control data. The processor of the printer control unit 11 performs various processes for controlling the image forming apparatus 10 by executing the programs stored in the memory of the printer control unit 11. At that time, the printer control unit 11 uses the control data stored in the memory. The communication controller 21 communicates with the host computer 22 and receives image data of the image formed by the image forming apparatus 10 from the host computer 22. The motor control unit 14 controls the motor 15F under the control of the printer control unit 11.

[0012] Figure 3 shows the details of the control configuration of the motor 15F. The motor control unit 14 has a microcomputer (hereinafter referred to as a microcontroller) 51. The microcontroller 51 communicates with the printer control unit 11 via the communication port 52. Also, the reference clock generation unit 56 of the microcontroller 51 is connected to the crystal oscillator 50 and generates a reference clock based on the output of the crystal oscillator 50. The counter 54 performs a counting operation based on the reference clock. The microcontroller 51 outputs a pulse width modulation signal (PWM signal) from the PWM port 58. In the present embodiment, the microcontroller 51 outputs a total of six PWM signals, namely, the high-side PWM signals (U-H, V-H, W-H) and the low-side PWM signals (U-L, V-L, W-L) for each of the three phases (U, V, W) of the motor 15F. Therefore, the PWM port 58 has six terminals U-H, V-H, W-H, U-L, V-L, W-L.

[0013] Each terminal of the PWM port 58 is connected to the gate driver 61, and the gate driver 61 performs ON / OFF control of each switching element of the three-phase inverter 60 based on the PWM signal. Note that the inverter 60 has a total of six switching elements, three on the high side and three on the low side for each phase, and the gate driver 61 controls each switching element based on the corresponding PWM signal. As the switching element, for example, a transistor or FET can be used. In this embodiment, it is assumed that when the PWM signal is high, the corresponding switching element turns on, and when it is low, the corresponding switching device turns off. The output 62 of the inverter 60 is connected to the coils 73 (U phase), 74 (V phase), and 75 (W phase) of the motor 15F. By performing ON / OFF control of each switching element of the inverter 60, the motor current (excitation current) of each coil 73, 74, 75 can be controlled. Thus, the gate driver 61 and the inverter 60 function as a voltage application unit that applies a voltage to the plurality of coils 73, 74, and 75 to cause a coil current to flow through the plurality of coils 73, 74, and 75. The motor current flowing through each of the coils 73, 74, 75 is converted by the resistor 63 into a voltage having a voltage value corresponding to the current value. The voltage value of the resistor 63 is input to the AD converter 53 of the microcomputer 51. The AD converter 53 converts the voltage value (analog value) of the resistor 63 into a digital value (also referred to as AD conversion). The microcomputer 51 detects the current value of the coil current based on the digital value output by the AD converter 53. Thus, the resistor 63 and the AD converter 53 constitute a measurement unit that measures the current value of the coil current. Further, the microcomputer 51 has a non-volatile memory 55 and a memory 57 that hold and store various data and the like used for controlling the motor 15F.

[0014] Figure 4 is a configuration diagram of the motor 15F. The motor 15F has a six-slot stator 71 and a four-pole rotor 72. The stator 71 has coils 73, 74, 75 for each phase. The rotor 72 is composed of permanent magnets and has two sets of N poles and S poles.

[0015] Generally, a coil consists of a core made of laminated electromagnetic steel sheets around which copper wire is wound. The permeability of electromagnetic steel sheets decreases in the presence of an external magnetic field. Since the inductance of a coil is proportional to the permeability of the core, a decrease in the permeability of the core results in a decrease in the inductance of the coil. For example, in Figure 4, the U-phase coil 73 faces only the south pole of the rotor 72, so the rate of decrease in inductance is greater than that of the W-phase coil 75, which faces both the south and north poles of the rotor 72.

[0016] Furthermore, the amount of change in inductance differs depending on whether the direction of the magnetic field generated by the coil current and the direction of the magnetic field generated by the rotor 72's magnetic poles are the same or opposite. Specifically, in the state shown in Figure 4, if the coil current is passed through the U-phase coil 73 in the same direction as the magnetic field generated by the S pole of the opposing rotor 72, that is, so that the U-phase becomes the N pole, the decrease in inductance will be greater than when the coil current is passed so that the U-phase becomes the S pole. In addition, because the iron loss of the coil changes as the inductance changes, the resistance component of the coil also changes.

[0017] As described above, the inductance and resistance of the coil, i.e., the impedance, changes depending on the stopping position (rotational phase at stopping) of the rotor 72 and the coil current pattern. In this embodiment, the coil current pattern refers to a pattern specified by the two phases that are excited by the flow of coil current (hereinafter referred to as the excitation phases) and the direction in which the coil current flows. Specifically, in this embodiment, since the motor 15F is 3-phase, there are six patterns: "UV", "UW", "VW", "VU", "WU", and "WV". Here, "XY" means that the X phase and Y phase are the excitation phases, and that current flows from the X phase coil to the Y phase coil. In this embodiment, when the coil current pattern is "XY", the X phase is the N pole and the Y phase is the S pole.

[0018] The motor control unit 14 needs to detect the rotor's stopping position (rotation phase) before starting the motor 15F, that is, when the motor 15F starts rotating. In this embodiment, the motor control unit 14 sequentially flows the coil currents of the six patterns described above and detects the rotor's stopping position by comparing the maximum values ​​of the coil currents in each pattern. First, the PWM signals for flowing the coil currents of each pattern will be explained.

[0019] Figure 5 shows the time variation of the duty cycle of the PWM signal applied to the UH and VH terminals, and the time variation of the coil current, when the coil current of pattern "UV" (one of the six patterns described above) is applied. In section A of Figure 5, the duty cycle of the PWM signal applied to the UH terminal is varied sinusoidally. Section A corresponds to the half-wave period of the sine wave, and at the beginning and end of section A, the duty cycle of the PWM signal applied to the UH terminal is set to 0%. Although not shown in the figure, in section A, the duty cycle of the PWM signal applied to the VL terminal is always set to 100%, i.e., high level. Furthermore, in section A, the duty cycle of the PWM signals applied to the other terminals is always set to 0%, i.e., low level. As a result, current flows from the U-phase coil 73 to the V-phase coil 74. In the following section B, the duty cycle of the PWM signal applied to the VH terminal is varied sinusoidally, similar to the PWM signal applied to the UH terminal in section A. Although not shown in the diagram, in section B, the duty cycle of the PWM signal applied to the UL terminal is always set to a high level. Furthermore, in section B, the duty cycle of the PWM signals applied to the other terminals is always set to a low level. This allows the current from the U-phase coil 73 to the V-phase coil 74 to be attenuated so that it approaches zero at the end of section B. As shown in Figure 5, applying a PWM signal makes the coil current sinusoidal. Making the coil current sinusoidal suppresses the noise generated by coil vibration. The same applies to the PWM signals applied to each terminal to drive the coil currents of the other patterns.

[0020] Figures 6 and 7 show the maximum coil current when the above six patterns of coil current are applied. Note that the stopping position of the rotor 72 is different in Figures 6(A) to 6(C) and Figures 7(A) to 7(C). Specifically, in Figure 6(A), the rotor 72 is stopped with its south pole facing the U-phase coil 73 and its north pole facing the V-phase coil 74, as shown in Figure 4. In Figure 6(B), the rotor 72 is stopped with its south pole facing the U-phase coil 73 and its north pole facing the W-phase coil 75. In Figure 6(C), the rotor 72 is stopped with its south pole facing the V-phase coil 74 and its north pole facing the W-phase coil 75. In Figure 7(A), the rotor 72 is stopped with its south pole facing the V-phase coil 74 and its north pole facing the U-phase coil 73. In Figure 7(B), the rotor 72 is stopped with its south pole facing the W-phase coil 75 and its north pole facing the U-phase coil 73. In Figure 7(C), the rotor 72 is stopped with its south pole facing the W-phase coil 75 and its north pole facing the V-phase coil 74.

[0021] For example, in Figure 6(A), the maximum coil current of pattern "UV" is greater than the maximum coil current of the other patterns. This is because, in the state shown in Figure 4, when the coil current of pattern "UV" is applied, the combined impedance of the U-phase coil 73 and the V-phase coil 74 becomes the smallest. Therefore, when the result shown in Figure 6(A) is obtained, the motor control unit 14 can determine that the rotor 72 is stopped in the state shown in Figure 4, that is, with its S pole facing the U-phase coil 73 and its N pole facing the V-phase coil 74. Then, according to the determined stopping position of the rotor 72, the motor control unit 14 controls the coil current to start the motor 15F.

[0022] Next, we will explain why the motor control unit 14 determines the motor type. Generally, the motor control unit 14 controls the rotational speed and coil current of the motor 15F using PI control. During PI control, the motor control unit 14 determines the optimal gain for the motor type as a control parameter, based on the characteristics of the motor 15F. If the determined control parameter is not appropriate, unevenness may occur in the rotational speed of the motor 15F. Unevenness in the rotational speed of the motor 15F can cause image defects in the images formed by the image forming apparatus 10. For this reason, the motor control unit 14 needs to determine the motor type and set control parameters appropriate for the determined motor type.

[0023] The following describes a method for determining the motor type, using as an example a case where two motor types, A and B, may be used as the motor 15F of the image forming apparatus 10. Motor types A and B have different motor characteristic values ​​such as inductance and resistance. Furthermore, the present invention is also applicable when three or more types of motors may be used.

[0024] First, as shown in Figures 6 and 7, the maximum value of each coil current pattern differs depending on the stopping position of the rotor 72. However, the result of sorting the six maximum coil current values ​​obtained at a given stopping position of the rotor 72 in descending or ascending order is approximately the same regardless of the stopping position of the rotor 72. Therefore, in this embodiment, for various types of motors that can be used in the image forming apparatus 10, the maximum values ​​of the six coil current patterns sorted in descending order are used as templates for each type. Figure 8 shows examples of templates for type A and type B. The template for type A is reference information for determining whether or not a motor is of type A. Similarly, the template for type B is reference information for determining whether or not a motor is of type B. Each template has six reference values ​​sorted in descending order.

[0025] A template for type A can be generated, for example, as follows: First, the rotor 72 of a type A motor is stopped at one of the six stopping positions, and the maximum coil current for each pattern is measured. Then, the maximum values ​​for each pattern are sorted in descending order. This process is performed for multiple type A motors at each of the six stopping positions. By calculating the average of the measurements of the same rank, a template for type A can be generated. Alternatively, a template for type A can be generated by calculation based on the characteristics of a type A motor. The same applies to type B.

[0026] As described above, before starting the motor 15F, the motor control unit 14 applies six patterns of coil current to determine the stopping position of the rotor 72, and measures the maximum value of these currents as the measured value (hereinafter also referred to as the measured value of the coil current). In other words, the motor control unit 14 measures six measured values. The motor control unit 14 sorts the six measured values ​​in the same descending order as the template to obtain measurement information. The motor control unit 14 calculates the difference between the measurement information and the template. In this embodiment, the difference between the measurement information and the template is defined as the product of the squares of the differences between the template's reference value and the measured value of the coil current that has the same rank as the reference value among the six measured values ​​of the coil current in the measurement information. Figure 9 is an explanatory diagram of the calculation method for the difference of measurement information for type A template shown in Figure 8.

[0027] As shown in Figure 9, the motor control unit 14 calculates the difference between the k-th reference value of the template (where k is an integer from 1 to 6) and the k-th measured value of the measurement information as ΔEk. Then, the motor control unit 14 calculates the difference ΔE of the measurement information for template type A as ΔE = Σ(Ek 2) is calculated as follows. Note that Σ represents the sum of k=1 to 6. The motor control unit 14 calculates the difference ΔE with each template and determines that the motor 15F is of the type corresponding to the template with the smallest difference ΔE. As described above, by using the squared error for ΔE, the difference is calculated to be large, making it easy to compare the ΔE of each template. However, ΔE can also be defined as the sum of the absolute values ​​of the differences between the measured value of the measurement information and the reference value of the corresponding rank of the template. In other words, ΔE can also be defined as ΔE=Σ|Ek|. Note that other values ​​that can evaluate the degree of deviation between the measurement information and the reference information can also be used as values ​​related to the difference.

[0028] Furthermore, the non-volatile memory 55 stores threshold values ​​in advance for determining coil current abnormalities. For example, external noise superimposed on the coil of the motor 15F may cause currents exceeding expectations to flow. Also, excessive coil current may flow due to a circuit failure. The threshold values ​​are set to detect such coil current abnormalities.

[0029] The motor control unit 14 compares the minimum value of ΔE with a threshold value to determine whether ΔE is greater than the threshold value. If the minimum value of ΔE is less than the threshold value, the motor control unit 14 determines the type of motor. If the minimum value of ΔE is greater than the threshold value, the motor control unit 14 determines that the coil current is abnormal. Since an abnormal coil current may prevent the motor control unit 14 from correctly determining the type of motor, it reacquires the coil current. If the minimum value of ΔE remains greater than the threshold value even after repeating the determination a predetermined number of times, the motor control unit 14 determines that a steady-state abnormality, not a transient abnormality, has occurred in the motor 15F. The motor control unit 14 then terminates the motor type determination process and notifies that an abnormality has occurred in the motor 15F.

[0030] Figure 10 shows the configuration for detecting the measured value of the coil current and the relationship between the measured value of the coil current and the power supply. As shown in Figure 10, the motor drive circuit 100, including the inverter 60, is supplied with a power supply voltage for motor drive, for example, 24V (also referred to as the drive power supply voltage). The AD converter 53 is supplied with a power supply voltage for control, for example, 3.3V (also referred to as the control power supply voltage). The coil current from the motor 15F is detected by the AD converter 53 as a current detection means. The measured value of the coil current, which has been converted to voltage by the resistor 63, has a positive correlation with the drive power supply voltage. Therefore, when the drive power supply voltage is high, the measured value of the coil current is high, and when the drive power supply voltage is low, the measured value of the coil current is low. Also, the measured value of the coil current has a negative correlation with the control power supply voltage. Therefore, when the control power supply voltage is high, the measured value of the coil current is low, and when the control power supply voltage is low, the measured value of the coil current is high.

[0031] Consequently, if the motor 15F is installed in an image forming apparatus with different drive power supply voltages or control power supply voltages, the measured coil current will be affected by variations in the drive power supply voltage or control power supply voltage. In other words, even with the same motor 15F, the measured coil current may change. Therefore, voltage variation correction is performed according to the drive power supply voltage or control power supply voltage, as described later.

[0032] Figure 11 shows the configuration for detecting the measured value V, the relationship between the drive power supply voltage and the measured value V, and the relationship between the control power supply voltage and the measured value V. As shown in Figure 11, the measured value V is measured by converting the drive power supply voltage using an AD converter 53 as a voltage detection means. The AD converter 53 is driven by the control power supply voltage. The measured value V, as a result of detection by the voltage detection means, has a positive correlation with the drive power supply voltage. Therefore, when the drive power supply voltage is high, the measured value V is high, and when the drive power supply voltage is low, the measured value V is low. Also, the measured value V has a negative correlation with the control power supply voltage. Therefore, when the drive power supply voltage is high, the measured value V is low, and when the drive power supply voltage is low, the measured value V is high.

[0033] Figure 12 shows the relationship between the measured coil current described in Figure 10 and the measured value V described in Figure 11. From Figures 10 and 11, both the measured coil current and the measured value V have a positive correlation with the drive power supply voltage and a negative correlation with the control power supply voltage. In other words, there is a positive correlation between the measured coil current and the measured value V; when the measured coil current is large, the measured value V is also large, and when the measured coil current is small, the measured value V is also small.

[0034] Next, we will explain the method for correcting measured coil current values ​​using Figure 13. Figure 13 shows the maximum measured coil current values ​​(marked with circles) when six different coil current patterns are applied to a motor of type A, as shown in Figure 6. Similarly, the maximum measured coil current values ​​for a motor of type B are shown with crosses (marked with crosses). The measured coil current values ​​for each motor serve as the reference values ​​for determining the type of motor.

[0035] On the other hand, the value indicated by the triangle symbol is the measured coil current of the motor, used to determine the type of motor. The value indicated by the triangle symbol is the value when there is no variation in the drive power supply voltage and control power supply voltage. However, if the drive power supply voltage and control power supply voltage vary in the direction of decreasing voltage, the measured coil current will be measured as a value smaller than the value indicated by the triangle symbol, resulting in the value indicated by the square symbol. In other words, if the value indicated by the triangle symbol, which represents no variation, is measured, it can be determined that it is a motor of type A. However, if the value indicated by the square symbol is measured due to the influence of variation, a motor of type A will be mistakenly identified as a motor of type B.

[0036] To suppress such misclassification, the measured value of the coil current is corrected. The specific method for correcting the measured value of the coil current is described below. The correction coefficient X is the ratio between the measured value V (Vs), which is a pre-prepared reference voltage, and the measured value V (Vm), which is measured to determine the type of motor. Since the correction coefficient X is the ratio of the reference measured value Vs to the measured measured value Vm, it is a correction value that represents how much the drive power supply voltage or control power supply voltage is fluctuating relative to the reference value.

[0037] Furthermore, as shown in Figure 12, there is a positive correlation between the measured coil current and the measured value V. Therefore, multiplying the measured coil current by the correction coefficient X is equivalent to multiplying the measured coil current by the rate of fluctuation of the drive power supply voltage or control power supply voltage relative to the reference. In other words, a correction is performed to obtain a measured coil current that suppresses the effects of variations in the drive power supply voltage or control power supply voltage.

[0038] The corrected coil current is calculated by multiplying the correction coefficient X by the measured coil current. Then, the difference ΔE between the corrected coil current and the reference coil current is calculated using the corrected coil current. As a result, even if the drive power supply voltage or control power supply voltage fluctuates, the effect of the fluctuations on the corrected coil current can be suppressed. Therefore, the decrease in the accuracy of motor type determination can also be suppressed.

[0039] Figure 14 is a flowchart showing the method for determining the motor type. The motor control unit 14 performs motor type determination before starting the motor 15F. In S10, the motor control unit 14 applies coil current for each pattern, measures the maximum value as the measured value, and acquires the measurement information in order to determine the stopping position of the rotor 72. In S11, the motor control unit 14 calculates a correction coefficient X from a reference measured value Vs and a measured measured value Vm. Then, it multiplies the measured value of the coil current by the correction coefficient X and performs correction. This suppresses the influence of variations in the drive power supply voltage or the control power supply voltage. The motor control unit 14 determines the stopping position of the rotor 72 based on the corrected measured value of the coil current for each pattern.

[0040] In S12, the motor control unit 14 sorts the corrected coil current measurements in descending order. In S13, the motor control unit 14 calculates the difference ΔE between each template and the corrected measurement. In S14, the motor control unit 14 determines whether the minimum value of the difference ΔE exceeds a threshold. If the minimum value of the difference ΔE is greater than the threshold, the process returns to S10. If the minimum value of the difference ΔE is less than the threshold, the process proceeds to S14.

[0041] If the minimum value of the difference ΔE is greater than the threshold, the motor control unit 14 determines that the measured value of the coil current is abnormal. If the measured value of the coil current is abnormal, the type of motor 15F cannot be correctly determined, so the process is repeated from S10 to recalculate the measurement value. If, even after repeating the process a predetermined number of times, the minimum value of the difference ΔE in S14 is still greater than the threshold, the motor control unit 14 determines that a steady-state abnormality has occurred, rather than a transient abnormality, and terminates the process shown in Figure 14. In this case, the motor control unit 14 notifies that an abnormality has occurred in the motor 15F. If S14 is Yes, it may be determined immediately that an abnormality has occurred in the motor 15F.

[0042] In S14, the motor control unit 14 determines the type of motor 15F by comparing the difference ΔE for each of the different templates. More specifically, the motor control unit 14 determines that the type of motor 15F is the type of the template with the smallest difference ΔE. In S16, the motor control unit 14 sets control parameters appropriate to the type determined in S15. The relationship between the type and the control parameters is stored in the non-volatile memory 55 beforehand. After that, the motor control unit 14 starts rotation control of the motor 15F.

[0043] In this embodiment, the motor type can be determined before starting the motor 15F. The motor type is determined using the measured values ​​that the motor control unit 14 has measured to determine the stopping position of the rotor 72. In this way, no additional measurements are required for determining the motor type, so the time until the motor starts up is not prolonged. Furthermore, the information that is pre-set in the non-volatile memory 55 for each motor type is one template and a threshold, so the amount of data required for determining the motor type is small. Moreover, since the motor type can be determined by a simple comparison process between the template and the measurement information, the size of the program executed by the microcontroller 51 is kept small, and the execution time is also short. Therefore, the time until the motor starts up can be kept from becoming long.

[0044] In the above embodiments, the motor type was determined, but the motor control unit 14 actually sets control parameters suitable for the motor being controlled. In other words, the motor control unit 14 may set control parameters corresponding to the template with the smallest difference ΔE without recognizing the motor type. In this case, the "type template" in the above embodiments becomes the "control parameter template". Also, the reference values ​​of the templates were sorted in descending order, and therefore the multiple measured values ​​of the measurement information were sorted in descending order, but a configuration in ascending order is also possible.

[0045] Furthermore, in the above embodiment, correction was performed using the measured value of the coil current and the correction coefficient X. However, in determining the type of motor, it is sufficient to suppress the influence of fluctuations in the drive power supply voltage or the control power supply voltage, and a configuration in which the template is corrected using the template and the correction coefficient X is also acceptable.

[0046] Furthermore, although the motor control unit 14 is referred to as such in each of the above embodiments because it is a component of the image forming apparatus 10, the motor control unit 14 can also be treated as a single device and called a motor control device. Alternatively, a device including the printer control unit 11 and the motor control unit 14 can also be called a motor control device. In addition, in the above embodiments, the motor 15F was a motor for driving the fixing unit 24. However, the present invention can also be applied to any motor for driving rotating members of the image forming apparatus 10, such as a motor for driving rollers that transport sheets or a motor for driving members of the image forming unit 1. Moreover, the configuration of the motor 15F is not limited to the configuration shown in Figure 4, and may be a motor with a different number of poles or phases.

[0047] In this way, even if fluctuations occur in the drive power supply voltage or the control power supply voltage, the effect of these fluctuations on the measured values ​​can be suppressed. In other words, it is possible to suppress a decrease in the control accuracy according to the type of motor.

[0048] <Second Embodiment> The second embodiment will be described focusing on the differences from the first embodiment. In the first embodiment described above, the measured value of the coil current was corrected using a correction coefficient X as the ratio between the measured value Vm and a reference measured value Vs. In this embodiment, the measured value of the coil current is corrected using measured values ​​V1 and V2 detected by an AD converter that drives the drive power supply voltage and the control power supply voltage, respectively, with different power supply voltages A (for example, 5V). In other words, the measured value of the coil current is corrected using the rate of fluctuation of either the drive power supply voltage or the control power supply voltage relative to a reference, or the rate of fluctuation of both. Note that a detailed explanation of the image forming apparatus and other components similar to those in the first embodiment will be omitted here.

[0049] Figure 15 shows the relationship between the measured values ​​of the drive power supply voltage, control power supply voltage, and coil current, and the measured values ​​V1 and V2. Measured value V1 is detected by the AD converter 153, which drives the drive power supply voltage with the control power supply voltage A. Measured value V2 is detected by the AD converter 253, which drives the control power supply voltage with the control power supply voltage A.

[0050] In this case, the drive power supply voltage and control power supply voltage are positively correlated with the measured values ​​V1 and V2, respectively, and the measured value of the coil current is also positively correlated with the measured values ​​V1 and V2. Therefore, when the measured values ​​of the drive power supply voltage, control power supply voltage and coil current are large, the measured values ​​V1 and V2 will be large. Conversely, when the measured values ​​of the drive power supply voltage, control power supply voltage and coil current are small, the measured values ​​V1 and V2 will be small. For this reason, the measured value of the coil current is positively correlated with the drive power supply voltage and control power supply voltage.

[0051] Furthermore, by calculating the ratio of the measured drive power supply voltage and control power supply voltage to pre-prepared reference voltages for each, the rate of fluctuation of the drive power supply voltage and control power supply voltage relative to the reference can be determined. By multiplying one or both of these fluctuation rates by the measured coil current, the measured coil current can be corrected to suppress the effects of fluctuations in the drive power supply voltage and control power supply voltage.

[0052] As described above, according to this embodiment, by correcting the measured value of the coil current using either the drive power supply voltage, the control power supply voltage, or both, the influence of fluctuations on the measured value can be suppressed. In other words, it is possible to suppress a decrease in the accuracy of control according to the type of motor.

[0053] In each of the above embodiments, the maximum value of the coil current when a coil current that increases and decreases sinusoidally over a predetermined period was passed was used as the measured value of the coil current, and the stopping position of the rotor 72 and the motor type were determined by this value. This is because the maximum value of the coil current differs depending on the impedance of the coil. However, the present invention is not limited to measuring the maximum value of the coil current, and can be configured to measure any other physical quantity that can determine the inductance or impedance of the motor. For example, the rate at which the coil current rises varies depending on the impedance. Therefore, the value of the coil current after a predetermined period from the start of flowing the coil current can be used as the measured value. Alternatively, the integral value of the coil current over a predetermined period of time can be used as the measured value.

[0054] [Other embodiments] The present invention can also be realized by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or storage medium, and by having one or more processors in the computer of that system or device read and execute the program. It can also be realized by a circuit (e.g., an ASIC) that implements one or more functions. [Explanation of Symbols]

[0055] 14 Motor Control Unit 15F Motor

Claims

1. A voltage application means that applies a first voltage to a motor having multiple coils to cause coil current to flow through the multiple coils, A current detection means for detecting the coil current, The voltage application means causes the coil current to flow through the plurality of coils in a plurality of patterns, and the current detection means causes the coil current corresponding to each pattern to be detected. A first power supply that outputs the first voltage to the plurality of coils, A second power supply that outputs a second voltage to the control means, A motor control device having voltage detection means for detecting the first voltage and the second voltage, The motor control device is characterized in that the control means corrects the coil current detected by the current detection means based on the detection result of the voltage detection means, and determines the type of motor based on the corrected coil current.

2. The system includes a holding means for holding the reference voltages of the first voltage and the second voltage, The motor control device according to claim 1, characterized in that the control means corrects the coil current detected by the current detection means based on the detection result of the voltage detection means and the reference voltage.

3. The motor control device according to claim 2, characterized in that the control means determines a correction coefficient as the ratio of the reference measurement to the measured value based on the measured value obtained as a result of detection by the voltage detection means and a reference measured value corresponding to the reference voltage, and determines a correction value for correcting the coil current based on the correction coefficient.

4. The holding means holds reference information indicating a reference value corresponding to the type of motor, The motor control device according to claim 3, characterized in that the control means determines the type of motor based on the corrected coil current and the reference information.

5. The motor control device according to claim 4, characterized in that the control means determines the difference between a plurality of corrected coil currents and the corresponding reference value, and determines the type of motor based on the difference.

6. The motor control device according to claim 5, characterized in that the control means determines the magnitude order for each of the plurality of corrected coil currents, determines the magnitude order for each of the plurality of reference values, and determines that the reference value having the same magnitude order as the coil current is the reference value corresponding to the coil current.

7. The motor control device according to claim 6, characterized in that the control means uses the sum of the squares of the differences obtained for each of the coil currents as the difference.

8. The motor control device according to claim 6, characterized in that the control means takes the sum of the absolute values ​​of the differences obtained for each of the coil currents as the difference.

9. The motor control device according to claim 5, characterized in that the control means reacquires the coil current if the minimum difference obtained for each of the coil currents is greater than a threshold.

10. The motor control device according to claim 1, characterized in that the control means further determines the stopping position of the rotor of the motor based on a plurality of coil currents.

11. The motor control device according to claim 1, characterized in that the control means determines the control parameters of the motor based on the type of motor.

12. A rotating member for transporting sheets along a transport path, Image forming means for forming an image on the sheet being transported along the transport path, The motor that drives the rotating member or the image forming means A motor control device according to any one of claims 1 to 11, An image forming apparatus characterized by comprising:

13. Image forming means for forming an image on a sheet, A voltage application means that applies a first voltage to a motor having multiple coils to cause coil current to flow through the multiple coils, A current detection means for detecting the coil current, The voltage application means causes the coil current to flow through the plurality of coils in a plurality of patterns, and the current detection means causes the coil current corresponding to each pattern to be detected. A first power supply that outputs the first voltage to the plurality of coils, A second power supply that outputs a second voltage to the control means, An image forming apparatus having voltage detection means for detecting the first voltage and the second voltage, The image forming apparatus is characterized in that the control means corrects the coil current detected by the current detection means based on the detection result of the voltage detection means, and determines the control parameters of the image forming means based on the corrected coil current.

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