JP2022002433A - Motor controller, starting method of motor and image forming device - Google Patents

Abstract

To suppress step-out of a motor when a brushless DC motor in a sensorless system is started.SOLUTION: A motor controller 10 includes: a driving circuit 40 for applying voltage to a stator winding 31 of a motor 30; and a control unit 20 for controlling the driving circuit 40 by a vector control system. The control unit 20 estimates a value of a motor parameter including a resistance value of the stator winding 31 on the basis of a driving history of the motor 30 when the motor 30 is started, and starts the motor 30 on the basis of the estimated motor parameter.SELECTED DRAWING: Figure 1

Description

The present disclosure relates to a motor control device, a method of starting a motor, and an image forming device, and particularly to control of a sensorless brushless DC motor (also referred to as a permanent magnet synchronous motor).

In the control of a sensorless brushless DC motor, the voltage applied to the motor is adjusted by estimating the magnetic pole position using motor constants such as winding resistance value and interlinkage magnetic flux value. At this time, since the winding temperature and magnet temperature change due to changes in the ambient temperature and heat generated by driving the motor, the values of the motor constants such as the winding resistance value and the interlinkage magnetic flux value required for calculating the magnetic pole position also change. do. Therefore, if the magnetic pole position is estimated without changing the value of the motor constant as the initial value, the motor efficiency may decrease or step-out may occur because the value deviates from the actual motor constant value.

Japanese Unexamined Patent Publication No. 2018-11403 (Patent Document 1) discloses an example of a parameter correction process for correcting a parameter value indicating an interlinkage magnetic flux based on a measured value of winding resistance. Specifically, first, the resistance value of the winding resistance is obtained based on the detected U-phase current and V-phase current values and the voltage command value corresponding to the current. Next, the winding temperature is estimated based on the resistance value of the winding resistance, and the magnet temperature is estimated based on the winding temperature. Then, the value of the interlinkage magnetic flux is estimated based on the magnet temperature (see paragraphs [0062] to [0067]).

Further, according to the above document, the motor control device executes the parameter correction process when the start command is given by the host control device. After the parameter values (interlinkage magnetic flux φh, winding resistance value Rh) are corrected in the parameter correction process, the motor control device starts sensorless control (see paragraphs [805] and [0086]).

Japanese Unexamined Patent Publication No. 2018-11403

If a current is passed through the stator windings of the motor to correct the motor constant before the motor is started, the torque generated by the current may drive the rotor to rotate. In particular, in the case of an inner rotor type brushless DC motor having a small inertia, the rotor is likely to be rotationally driven. In this case, the following problems occur.

First, when the initial position of the magnetic pole of the rotor is estimated at the time of starting the motor and then a current is passed through the stator winding for measuring the winding resistance, an error occurs in the initial magnetic pole position due to the rotation of the rotor. Further, if the initial speed of the rotor is not 0 when the motor is started, a speed deviation occurs immediately after the start. In order to correct this speed deviation, the motor control device tries to drive the rotor in the reverse rotation direction, so that the motor may fall into an oscillating state. Due to the above causes, the motor often goes out of step.

This disclosure has been made in consideration of the above problems. One of the objects of this disclosure is to provide a motor control device capable of suppressing step-out of a motor when a sensorless brushless DC motor is started.

The motor control device of one embodiment is a motor control device that controls a sensorless type motor. The motor control device includes a drive circuit that applies a voltage to the stator windings of the motor, and a control unit that controls the drive circuit by a vector control method. When the motor is started, the control unit estimates the value of the motor parameter including the resistance value of the stator winding based on the drive history of the motor, and starts the motor based on the estimated motor parameter.

According to the above embodiment, when the motor is started, the value of the motor parameter including the resistance value of the stator winding is estimated based on the drive history of the motor, and the motor is started based on the estimated motor parameter. It is possible to suppress the step-out of the motor.

It is a block diagram which shows the whole structure of a motor control device. It is a figure for demonstrating the coordinate axis for displaying an alternating current and a magnetic pole position in sensorless vector control. It is a functional block diagram which shows an example of the structure and operation of a sensorless vector control circuit. It is a figure which shows the relationship between the U-phase voltage command value, the V-phase voltage command value, and the W-phase voltage command value, and an electric angle. It is a flowchart which shows the control procedure of a brushless DC motor in a certain job. It is a flowchart which shows the procedure of estimating the interlinkage magnetic flux value during motor operation. It is a functional block diagram which shows the estimation procedure of the housing surface temperature by a parameter correction part. It is a timing diagram for demonstrating the procedure of estimating the parameter such as a winding resistance at the time of starting a motor when the start and stop of a motor are repeated. It is a flowchart which shows the procedure of estimating the parameter such as a winding resistance at the time of starting a motor. It is a flowchart which shows the modification of the parameter estimation procedure of FIG. It is a timing diagram conceptually showing the time change of the U-phase current and the rotor rotation speed at the time of starting a motor. It is a timing diagram which shows the comparative example of FIG. It is a figure for demonstrating the rotation of a rotor which occurs by applying a voltage to a stator winding at the time of resistance measurement. It is a flowchart which shows the procedure of estimating the motor parameter such as a winding resistance at the time of starting a motor in the motor control device of Embodiment 2. It is a flowchart which shows the procedure of step S330 of FIG. 14 in detail. It is a flowchart which shows the 1st modification of the parameter estimation procedure of FIG. It is a flowchart which shows the 2nd modification of the parameter estimation procedure of FIG. It is a timing diagram conceptually showing the time change of the U-phase current and the rotor rotation speed at the time of motor start in the case of Embodiment 2. FIG. It is sectional drawing which shows an example of the structure of an image forming apparatus.

Hereinafter, each embodiment will be described in detail with reference to the drawings. In the following description, the same or corresponding parts may be designated by the same reference numerals and the description may not be repeated. Further, in the following description, the multiplication symbol is represented by "・" or "×".

<Embodiment 1>
[Overall configuration of motor control device]
FIG. 1 is a block diagram showing an overall configuration of a motor control device. The motor control device 10 drives and controls a sensorless three-phase brushless DC motor (BLDCM: Brushless DC Motor) 30. As shown in FIG. 1, the motor control device 10 includes a drive circuit 40, a sensorless vector control circuit 50, and a host control circuit 70. Since it is a sensorless system, it is not provided with a Hall element or encoder for detecting the rotational position of the rotor.

The drive circuit 40 is a PWM (Pulse Width Modulation) control type inverter circuit, and converts a direct current drive voltage DV into a three-phase AC voltage and outputs it. Specifically, the drive circuit 40 causes the brushless DC motor 30 to have a U-phase voltage based on the inverter drive signals U +, U−, V +, V−, W +, and W−, which are PWM signals received from the sensorless vector control circuit 50. U _M, V-phase voltage _V M, and supplies the W-phase voltage _{W M.} The drive circuit 40 includes an inverter circuit 41, a U-phase current detection circuit 43U, a V-phase current detection circuit 43V, and a predrive circuit 44.

The inverter circuit 41 includes a U-phase arm circuit 42U, a V-phase arm circuit 42V, and a W-phase arm circuit 42W. These arm circuits 42U, 42V, 42W are connected in parallel to each other between the node to which the DC drive voltage DV is given and the node to which the ground voltage GND is given. Hereinafter, for the sake of brevity, the node to which the DC drive voltage DV is given may be referred to as a drive voltage node DV, and the node to which the ground voltage GND is given may be referred to as a ground node GND.

The U-phase arm circuit 42U includes a high-potential side U-phase transistor FU + and a low-potential side U-phase transistor FU- connected in series with each other. The connection node Nu of the U-phase transistors FU + and FU- is connected to one end of the U-phase winding 31U of the brushless DC motor 30. The other end of the U-phase winding 31U is connected to the neutral point 32.

As shown in FIG. 1, the connection of the U-phase winding 31U, the V-phase winding 31V, and the W-phase winding 31W of the brushless DC motor 30 is a star connection. In this specification, the U-phase winding 31U, the V-phase winding 31V, and the W-phase winding 31W are collectively referred to as a stator winding 31.

Similarly, the V-phase arm circuit 42V includes a high-potential side V-phase transistor FV + and a low-potential side V-phase transistor FV- connected in series with each other. The connection node Nv of the V-phase transistors FV + and FV- is connected to one end of the V-phase winding 31V of the brushless DC motor 30. The other end of the V-phase winding 31V is connected to the neutral point 32.

Similarly, the W-phase arm circuit 42W includes a high-potential side W-phase transistor FW + and a low-potential side W-phase transistor FW- connected in series with each other. The connection node Nw of the W-phase transistors FW + and FW- is connected to one end of the W-phase winding 31W of the brushless DC motor 30. The other end of the W-phase winding 31W is connected to the neutral point 32.

The U-phase current detection circuit 43U and the V-phase current detection circuit 43V are circuits for detecting the motor current by a two-shunt method. Specifically, the U-phase current detection circuit 43U is connected between the U-phase transistor FU- on the low potential side and the ground node GND. The V-phase current detection circuit 43V is connected between the V-phase transistor FV- on the low potential side and the grounded node GND.

The U-phase current detection circuit 43U and the V-phase current detection circuit 43V include a shunt resistor. The resistance value of the shunt resistor is a small value on the order of 1/10Ω. Therefore, the signal representing the U-phase current Iu detected by the U-phase current detection circuit 43U and the signal representing the V-phase current Iv detected by the V-phase current detection circuit 43V are amplified by an amplifier (not shown). After that, the signal representing the U-phase current Iu and the signal representing the V-phase current Iv are AD-converted by an AD (Analog-to-Digital) converter (not shown) and then incorporated into the sensorless vector control circuit 50.

The W-phase current Iw can be obtained from Kirchhoff's current law, that is, Iw = -Iu-Iv, from the U-phase current Iu and the V-phase current Iv, and therefore does not need to be detected. More generally, the current of any two of the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw may be detected, and the current value of the other one phase is the detected two-phase current. It can be calculated from the value.

The predrive circuit 44 amplifies the inverter drive signals U +, U−, V +, V−, W +, W−, which are PWM signals received from the sensorless vector control circuit 50, and amplifies the transistors FU +, FU−, FV +, FV−. , FW +, and FW- are output to the gates, respectively.

The types of transistors FU +, FU−, FV +, FV−, FW +, and FW− are not particularly limited. For example, it may be a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), a bipolar transistor, or an IGBT (Insulated Gate Bipolar Transistor).

The sensorless vector control circuit 50 is a circuit for vector-controlling the brushless DC motor 30, and generates inverter drive signals U +, U−, V +, V−, W +, and W− and supplies them to the drive circuit 40. Further, when the brushless DC motor 30 is started, the sensorless vector control circuit 50 estimates the initial position of the magnetic pole of the rotor in a stationary state by an inductive sense method.

The sensorless vector control circuit 50 may be configured as a dedicated circuit such as an ASIC (Application Specific Integrated Circuit), or may realize its function by using an FPGA (Field Programmable Gate Array) and / or a microcomputer or the like. It may be configured in.

The upper control circuit 70 is configured based on a computer equipped with a CPU (Central Processing Unit), a memory, and the like. The upper control circuit 70 outputs a start command, a stop command, a speed command value, and the like to the sensorless vector control circuit 50.

Unlike the above, the sensorless vector control circuit 50 and the upper control circuit 70 may be configured by an ASIC, FPGA, or the like as one control circuit. In this disclosure, the main body that controls the drive circuit 40 is collectively referred to as a control unit 20. The control unit 20 may be considered to correspond to the sensorless vector control circuit 50, or may be considered as a combination of the sensorless vector control circuit 50 and the upper control circuit 70. Further, the control unit 20 may be configured by a dedicated circuit such as an ASIC, may be configured by an FPGA or a microcomputer, or may be configured by combining some of them. ..

[About the axis of the sensorless vector control method]
FIG. 2 is a diagram for explaining a coordinate axis for displaying an alternating current and a magnetic pole position in sensorless vector control. The angle is expressed by an electric angle which is a phase of the output voltage and the output current of the drive circuit 40.

With reference to FIG. 2, in vector control, the three-phase alternating current (U-phase, V-phase, W-phase) flowing through the stator winding 31 of the three-phase brushless DC motor 30 rotates in synchronization with the permanent magnet of the rotor. Variable conversion to phase components. Specifically, the direction of the magnetic poles of the rotor 35 is defined as the d-axis, and the direction in which the phase is advanced by 90 ° in electrical angle from the d-axis is defined as the q-axis. Further, the angle (electrical angle) of the d-axis from the U-phase coordinate axis is defined as θ.

Here, in the case of the sensorless vector control method, which is a control method that does not have a position sensor for detecting the rotation angle of the rotor, it is necessary to estimate the position information representing the rotation angle of the rotor by some method. The estimated magnetic pole direction is defined as the γ axis, and the direction in which the phase advances by 90 ° in electrical angle from the γ axis is defined as the δ axis. _{Let θ M} be the angle (electrical angle) of the γ axis from the U phase coordinate axis. _{The delay of θ M} with respect to θ is defined as Δθ.

The coordinate axes of FIG. 2 are also used when estimating the initial position of the magnetic poles of the rotor in a stationary state by the inductive sense method when starting the motor. In this case, the true position of the magnetic poles of the rotor is represented by the electrical angle θ. In order to estimate the initial position of the magnetic pole, the electric angle (also referred to as energization angle or voltage application angle) of the current flowing through the stator winding 31 is represented _{by θ M.}

Here, the inductance method is effective when a voltage at a level at which the rotor does not rotate is applied to the stator windings at a plurality of electric angles, depending on the positional relationship between the magnetic pole position of the rotor and the current magnetic field due to the stator windings. It utilizes the property that the small inductance changes slightly. Specifically, when the stator current is passed in the d-axis direction corresponding to the direction of the magnetic poles of the rotor, the magnetic flux due to the permanent magnet of the rotor and the magnetic flux due to the current are added. As a result, the inductance decreases due to the occurrence of magnetic saturation, and the decrease in inductance can be detected by the change in the stator current. Further, in the case of a permanent magnet embedded type (IPM: Interior Permanent Magnet) motor, a salient polarity is generated in which the inductance in the q-axis direction is larger than the inductance in the d-axis direction. Therefore, in this case, even if magnetic saturation does not occur, the effective inductance decreases in the case of d-axis current.

[Configuration of sensorless vector control circuit]
FIG. 3 is a functional block diagram showing an example of the configuration and operation of the sensorless vector control circuit. With reference to FIG. 3, the sensorless vector control circuit 50 includes a coordinate conversion unit 55, a rotation speed control unit 51, a current control unit 52, a coordinate conversion unit 53, a PWM conversion unit 54, and a magnetic pole position estimation unit 56. It includes an initial position estimation unit 57, connection changeover switches 58 and 59, a parameter correction unit 60, and a storage unit 61 composed of a non-volatile memory.

With reference to FIG. 3, when the motor is in operation, the connection changeover switch 58 is switched to the T1 side, so that the current control unit 52 and the coordinate conversion unit 53 are connected. Further, by switching the connection changeover switch 59 to the T3 side, the coordinate conversion unit 55 and the magnetic pole position estimation unit 56 are connected. On the other hand, when estimating the initial magnetic pole position of the rotor while the motor is stopped, the connection changeover switch 58 is switched to the T2 side, so that the initial position estimation unit 57 and the coordinate conversion unit 53 are connected. Further, by switching the connection changeover switch 59 to the T4 side, the coordinate conversion unit 55 and the initial position estimation unit 57 are connected.

The connection changeover switches 58 and 59 are shown as functional configurations, and the specific configuration is not limited. For example, the switching function of the connection changeover switches 58 and 59 may be realized by hardware such as a semiconductor switch or by software.

Hereinafter, the operation of the sensorless vector control circuit 50 during the motor operation will be described first. Next, the initial position estimation of the magnetic poles of the rotor in the stationary state will be described. Next, correction of the winding resistance value Rh and the interlinkage magnetic flux value φh, which are parameters used in the sensorless vector control, will be described.

[Sensorless vector control during motor operation]
During the motor operation, the coordinate conversion unit 55 outputs a signal representing the U-phase current Iu detected by the U-phase current detection circuit 43U of the drive circuit 40 and the V-phase current Iv detected by the V-phase current detection circuit 43V. receive. The coordinate conversion unit 55 calculates the W phase current Iw from the U phase current Iu and the V phase current Iv. Then, the coordinate conversion unit 55 generates a γ-axis current Iγ and a δ-axis current Iδ by performing coordinate conversion of the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw.

Specifically, first, the coordinate conversion unit 55 converts the three-phase currents of the U-phase, V-phase, and W-phase into the two-phase currents of the α-axis current Iα and the β-axis current Iβ according to the Clarke conversion. Next, the coordinate conversion unit 55 converts the α-axis current Iα and the β-axis current Iβ into the γ-axis current Iγ and the δ-axis current Iδ, which are rotating coordinate systems, according to the Park conversion. _{In the Park conversion, the electric angle θ M} in the magnetic pole direction estimated by the magnetic pole position estimation unit 56, that is, the angle of the γ axis from the U-phase coordinate axis is used. The coordinate conversion unit 55 receives information on the _{estimated magnetic pole position θ M} from the magnetic pole position estimation unit 56 via the connection changeover switch 59.

The rotation speed control unit 51 receives a start command, a stop command, and a target rotation speed Nf * from the host control circuit 70. The target electrical angular velocity ω * can be calculated by 2π × Np × Nf * using the pole logarithm Np. The rotation speed control unit 51 uses, for example, PI control (proportional / integral control) or PID control (proportional / integral control) from _{the target electric angular velocity ω * and the electric angular velocity ω M} of the rotor 35 estimated by the magnetic pole position estimation unit 56. The γ-axis current command value Iγ * and the δ-axis current command value Iδ * for the brushless DC motor 30 are determined by (differential control) or the like.

The current control unit 52 has the γ-axis current command value Iγ * and the δ-axis current command value Iδ * given by the rotation speed control unit 51, and the current γ-axis current Iγ and δ-axis current given by the coordinate conversion unit 55. From Iδ, the γ-axis voltage command value Vγ * and the δ-axis voltage command value Vδ * are determined, for example, by PI control or PID control.

The coordinate conversion unit 53 receives the γ-axis voltage command value Vγ * and the δ-axis voltage command value Vδ * from the current control unit 52. The coordinate conversion unit 53 and the current control unit 52 are connected via the connection changeover switch 58. The coordinate conversion unit 53 converts the γ-axis voltage command value Vγ * and the δ-axis voltage command value Vδ * into coordinates, so that the U-phase voltage command value Vu *, the V-phase voltage command value Vv *, and the W-phase voltage command value Generate Vw *.

Specifically, first, the coordinate conversion unit 53 converts the γ-axis voltage command value Vγ * and the δ-axis voltage command value Vδ * into the α-axis voltage command value Vα * and the β-axis voltage command value Vβ * according to the inverse Park conversion. Convert. _{In the inverse Park conversion, the electric angle θ M} in the magnetic pole direction estimated by the magnetic pole position estimation unit 56, that is, the angle of the γ axis from the U-phase coordinate axis is used. Next, the coordinate conversion unit 53 converts the α-axis voltage command value Vα * and the β-axis voltage command value Vβ * into three-phase U-phase voltage command values Vu *, V-phase voltage command values Vv *, according to the inverse Clarke conversion. And convert to W phase voltage command value Vw *. For the conversion from the two phases of α and β to the three phases of U, V, and W, a space vector transformation can be used instead of the inverse Clarke transformation.

The PWM conversion unit 54 of the transistors FU +, FU-, FV +, FV-, FW +, FW- based on the U-phase voltage command value Vu *, the V-phase voltage command value Vv *, and the W-phase voltage command value Vw *. Inverter drive signals U +, U−, V +, V−, W +, and W−, which are PWM signals for driving the gates, are generated.

_{The magnetic pole position estimation unit 56 represents the current electric angular velocity ω M} of the rotor 35 and the magnetic pole position from the γ-axis current Iγ and the δ-axis current Iδ and the γ-axis voltage command value Vγ * and the δ-axis voltage command value Vδ *. The electric angle θ _M is estimated. _{Specifically, the magnetic pole position estimation unit 56 calculates an electric angular velocity ω M} such that the γ-axis induced voltage is set to 0, and estimates an _{electric angle θ M} representing the magnetic pole position from the electric angular velocity ω _M. The magnetic pole position estimation unit 56 _{outputs the estimated electric angular velocity ω M} to the upper control circuit 70 and outputs it to the rotation speed control unit 51. Further, the magnetic pole position estimation unit 56 _{outputs information of the electric angle θ M} representing the estimated magnetic pole position to the coordinate conversion units 53 and 55.

[Estimation of the initial position of the magnetic poles of the rotor in the stationary state]
Since the magnetic pole position estimation unit 56 described above utilizes the induced voltage generated in the stator winding 31, it cannot be used when the rotor is stationary. Therefore, instead of the magnetic pole position estimation unit 56, the initial position estimation unit 57 that estimates the initial position of the magnetic pole of the rotor 35 by the inductive sense method is used.

Here, in the inductive sense method, a constant voltage is continuously or intermittently applied to the stator winding 31 while sequentially changing a plurality of energization angles, and the change in the current flowing through the stator winding 31 changes for each energization angle. Detected. Here, the energization time to the stator winding 31 and the magnitude of the applied voltage are set to a level at which the rotor 35 does not rotate. However, if the energization time is too short or the magnitude of the applied voltage is too small, the initial position of the magnetic pole cannot be detected, so care must be taken.

Specifically, the method often used to detect the direction of the magnetic poles of the rotor is to keep the energization time for each energization angle and the command value of the applied voltage (specifically, the command value of the γ-axis voltage) constant, and energize time. The peak value of the γ-axis current is detected, and it is determined that the energization angle at which the maximum peak value is obtained (that is, the energization angle at which the effective inductance is minimized) is the direction of the magnetic pole.

When estimating the initial magnetic pole position of the rotor 35 with reference to FIG. 3, the connection changeover switch 58 is switched to the T2 side, so that the initial position estimation unit 57 and the coordinate conversion unit 53 are connected. Further, by switching the connection changeover switch 59 to the T4 side, the coordinate conversion unit 55 and the initial position estimation unit 57 are connected. In this case, among the components of the sensorless vector control circuit 50, the initial position estimation unit 57, the coordinate conversion unit 53, the PWM conversion unit 54, and the coordinate conversion unit 55 are used.

The initial position estimation unit 57 sets the magnitude of the γ-axis voltage command value Vγ *, the electric angle θ _M (also referred to as the energization angle θ _M ) of each phase voltage applied to the stator winding 31, and the energization time. The initial position estimation unit 57 sets the δ-axis voltage command value Vδ * to 0.

The magnitude of the γ-axis voltage command value Vγ * and the energization time are set to such a magnitude that a γ-axis current Iγ having a sufficient SN ratio can be obtained within a range in which the rotor 35 is not rotated. The electric angle θ _M is set to a plurality of angles in the range of 0 degrees to 360 degrees. For example, the initial position estimation unit 57 _{changes the electric angle θ M} from 0 degrees to 330 degrees in increments of 30 degrees.

The coordinate conversion unit 53 converts the γ-axis voltage command value Vγ * and the δ-axis voltage command value Vδ * (= 0) into coordinates, so that the U-phase voltage command value Vu *, the V-phase voltage command value Vv *, and W Generates the phase voltage command value Vw *. For this coordinate transformation, for example, the above-mentioned inverse Park transformation and inverse Clarke transformation are used.

FIG. 4 is a diagram showing the relationship between the U-phase voltage command value, the V-phase voltage command value, and the W-phase voltage command value and the electric angle. In FIG. 4, the amplitude of the voltage command value is standardized to 1. As shown in FIG. 4, the U-phase voltage command value Vu *, the V-phase voltage command value Vv *, and the W-phase voltage command value Vw * can be set for _{any θ M.} For example, when θ _M = 0 °, Vu * = 1 and Vv * = Vw * = −0.5. When θ _M = 30 °, Vu * = (√3) / 2, Vv * = 0, Vw * = − (√3) / 2.

With reference to FIG. 3 again, the PWM conversion unit 54 determines the transistors FU +, FU−, FV +, based on the U-phase voltage command value Vu *, the V-phase voltage command value Vv *, and the W-phase voltage command value Vw *. Inverter drive signals U +, U−, V +, V−, W +, and W−, which are PWM signals for driving the gates of FV−, FW +, and FW−, respectively, are generated.

According to the generated inverter drive signals U +, U−, V +, V−, W +, W−, the drive circuit 40 is a U-phase winding 31U, a V-phase winding 31V, and a W-phase winding 31W of the brushless DC motor 30. supplying U-phase voltage _U M, V-phase voltage _V M, the W-phase voltage _{W M} to. The total number of pulses of the inverter drive signal corresponds to the set energization time. The U-phase current detection circuit 43U and the V-phase current detection circuit 43V provided in the drive circuit 40 detect the U-phase current Iu and the V-phase current Iv, respectively. The signals representing the detected U-phase current Iu and V-phase current Iv are input to the coordinate conversion unit 55.

The coordinate conversion unit 55 calculates the W phase current Iw from the U phase current Iu and the V phase current Iv. Then, the coordinate conversion unit 55 generates a γ-axis current Iγ and a δ-axis current Iδ by performing coordinate conversion of the U-phase current Iu, the V-phase current Iv, and the W-phase current Iw. The above-mentioned Clarke transformation and Park transformation are used for this coordinate transformation. Here, the γ-axis current Iγ corresponds to a current component having the same electric angle as the energization angle, and the δ-axis current Iδ corresponds to a current component having an electric angle different from the energization angle by 90 degrees.

The initial position estimation unit 57 estimates the initial magnetic pole position θ (electrical angle) based on the change in the magnitude of the γ-axis current Iγ according to the position of the permanent magnet of the rotor. For example, the initial position estimation unit 57 sets the electric angle θ _M when the γ-axis current Iγ has a peak value as the initial magnetic pole position.

[Operation of parameter correction unit 60]
Next, the correction of the winding resistance value Rh and the interlinkage magnetic flux value φh will be described. These motor parameters (also referred to as motor constants) are used when performing sensorless vector control on the brushless DC motor 30. The motor constant is corrected for each calculation cycle of the rotor position and rotation speed during motor operation, and is corrected immediately before the motor is started. For the correction calculation of the motor constant, correction information such as the drive history of the brushless DC motor 30 and the parameters required for the calculation is used. These drive histories and correction information are stored in, for example, a storage unit 61 as a non-volatile memory.

As shown in FIG. 3, during operation of the motor, the parameter correction unit 60 has voltage command values Vγ * and Vδ *, and γ-axis currents Iγ and δ-axis currents Iδ (U-phase current Iu) corresponding to the voltage command values. And based on the detected value of the V-phase current Iv), the winding resistance value Rh is calculated. The parameter correction unit 60 estimates the correction value of the interlinkage magnetic flux value φh based on the calculated winding resistance value Rh. The details of the estimation method will be described later with reference to FIG.

On the other hand, when the motor is started, the parameter correction unit 60 estimates the winding resistance value Rh and the interlinkage magnetic flux value φh based on the drive history of the brushless DC motor 30. Details of the estimation method will be described later with reference to FIGS. 7 and 8. As described above, when the motor is started, unnecessary rotation of the rotor can be prevented by preventing a current from flowing through the stator winding 31 for measuring the winding resistance.

[Control procedure for brushless DC motor 30]
Hereinafter, the control procedure of the brushless DC motor 30 by the sensorless vector control circuit 50 will be briefly described.

FIG. 5 is a flowchart showing a control procedure of a brushless DC motor in a certain job. The job shown in FIG. 5 is executed according to a command from the host control circuit 70 shown in FIGS. 1 and 3.

In step S10, the initial position estimation unit 57 of the sensorless vector control circuit 50 estimates the initial magnetic pole position when the motor start command from the upper control circuit 70 is received. For the estimation of the initial magnetic pole position, for example, the above-mentioned inductive sense method is used.

In the next step S20, the parameter correction unit 60 of the sensorless vector control circuit 50 executes correction processing for the winding resistance value Rh and the interlinkage magnetic flux value φh. The specific procedure will be described later with reference to FIGS. 7 and 8.

In the next step S30, the sensorless vector control circuit 50 starts the brushless DC motor 30 using the corrected winding resistance value Rh and the interlinkage magnetic flux value φh. After that, the upper control circuit 70 controls _{the brushless DC motor 30 so that the electric angular velocity ω M} of the rotor 35 becomes the target electric angular velocity ω * given by the upper control circuit 70.

While the brushless DC motor 30 is in operation, the parameter correction unit 60 executes correction processing for the winding resistance value Rh and the interlinkage magnetic flux value φh for each calculation cycle of the rotor position (step S40). The specific procedure will be described later with reference to FIG. The sensorless vector control circuit 50 controls the brushless DC motor 30 by using the corrected winding resistance value Rh and the interlinkage magnetic flux value φh.

In step S50, the sensorless vector control circuit 50 stops the rotation of the rotor 35 when it receives a stop command from the host control circuit 70.

After that, if the job continues (NO in step S60), the process returns to step S10. In this case, when the sensorless vector control circuit 50 receives the motor start command from the upper control circuit 70, the initial magnetic pole position is estimated (step S10), and the winding resistance value Rh and the interlinkage magnetic flux value φh are corrected. Execute (step S20). Then, the above steps S30 to S50 are executed.

[Parameter correction during motor operation]
Hereinafter, the procedure for correcting the winding resistance value Rh and the interlinkage magnetic flux value φh during motor operation as shown in step S40 of FIG. 5 will be described in detail. The following relational expressions (1) to (3) are used to correct the winding resistance value Rh and the interlinkage magnetic flux value φh.

First, when the winding resistance value at the reference temperature Ts is Rs and the temperature coefficient is α1, the winding resistance value Rh at the winding temperature T1 is
(Rh-Rs) / Rs = α1 · (T1-Ts) ... (1)
Given in. In the case of a metal material such as copper wire, the temperature coefficient α1 is a positive value, and the winding resistance value Rh increases as the winding temperature T1 increases.

Next, when the interlinkage magnetic flux value at the reference temperature Ts is φs and the temperature coefficient is α2, the interlinkage magnetic flux value φh at the magnet temperature T2 is
(Φh−φs) / φs = α2 ・ (T2-Ts)… (2)
Given in. In rare earth magnets such as neodymium magnets, the temperature coefficient α2 is generally a negative value, and the interlinkage magnetic flux value φh decreases as the magnet temperature T2 increases.

Further, as a result of conducting an experiment with the ambient temperature as the reference temperature Ts, a ratio β was used between the winding temperature T1 and the magnet temperature T2.
T2-Ts = β ・ (T1-Ts)… (3)
There is a relationship represented by. That is, the magnet temperature T2 changes substantially following the winding temperature T1. However, in the case of T1 ≦ Ts or T2 ≦ Ts, T1 = T2. In the case of the inner rotor type brushless DC motor, the value of the ratio β is close to 1, for example, 0.95. In the case of an outer rotor type brushless DC motor, the value of the ratio β is about 0.5.

FIG. 6 is a flowchart showing a procedure for estimating the interlinkage magnetic flux value during motor operation. Hereinafter, the flowchart of FIG. 6 will be described with reference to the functional block diagram of FIG.

First, in step S100, the parameter correction unit 60 sets the winding resistance value based on the voltage command values Vγ * and Vδ * and the γ-axis currents Iγ and δ-axis currents Iδ calculated from the detected current values Iu and Iv. Calculate Rh.

Specifically, according to the voltage equation of the brushless DC motor,
Vγ * = (Rh + p ・ Lγ) ・ Iγ-ω _M・ Lδ ・ Iδ… (4A)
Vδ * = ω _M・ Lγ ・ Iγ + (Rh + p ・ Lδ) ・ Iδ + ω _M・ φh… (4B)
Is true. In the above equations (4A) and (4B), the time derivative operator is represented by p, the γ-axis inductance value is represented by Lγ, the δ-axis inductance value is represented by Lδ, and the electric angular velocity is represented _{by ω M.} When the time derivative operator p is approximated by 0, from the above equation (4A),
Rh = (Vγ * + ω _M・ Lδ ・ Iδ) / Iγ… (5)
Can calculate the winding resistance value Rh. The winding resistance value Rh may be calculated using the above equation (4B). The values of the inductances Lγ and Lδ, which are parameters necessary for the above calculation, are stored in the storage unit 61 as correction information.

In the next step S200, the parameter correction unit 60 calculates the interlinkage magnetic flux value φh from the winding resistance value Rh based on the above equations (1) to (3). For example, the parameter correction unit 60 calculates the winding temperature T1 from the winding resistance value Rh based on the above equation (1), and calculates the magnet temperature T2 from the winding temperature T1 based on the above equation (3). The interlinkage magnetic flux value φh is calculated from the magnet temperature T2 based on the above equation (2).

In the above calculation, various parameters necessary for the calculation using the above equations (1) to (3), that is, the temperature coefficients α1 and α2, the ratio β, the reference temperature Ts, and the winding resistance value Rs and the chain at the reference temperature Ts. The cross flux value φs is stored in the storage unit 61 as correction information. The parameter correction unit 60 executes the calculations of the above equations (1) to (3) by referring to these correction information.

As a modification of the above, a table showing the relationship between the winding resistance value Rh and the interlinkage magnetic flux value φh may be prepared in advance based on the above equations (1) to (3). In this case, the parameter correction unit 60 determines the interlinkage magnetic flux value φh corresponding to the winding resistance value Rh by referring to the table.

[Parameter correction method when starting the motor]
Next, a method for correcting the winding resistance value Rh and the interlinkage magnetic flux value φh at the time of starting the motor as shown in step S20 of FIG. 5 will be described in detail.

Normally, while the motor is stopped, the winding resistance value Rh can be measured by passing a current through the stator winding 31 of the brushless DC motor 30. However, in the motor control device of the first embodiment, such actual measurement of the winding resistance value Rh is not performed immediately before starting the motor. The reason for this is to avoid the risk of the rotor rotating due to the application of a voltage to the stator winding 31.

Therefore, the motor control device of the first embodiment estimates the temperature of the stator winding 31 at the time of starting the motor based on the drive history of the brushless DC motor 30 and the elapsed time after the motor is stopped.

Specifically, the power loss Plus [W] of the brushless DC motor 30, the surface area A [m ² ] of the motor housing, the heat transfer coefficient h [W / m ² K] from the surface of the motor housing to the outside, and the housing. Using the body surface temperature T3, the heat capacity C [J / K] of the motor housing, the ambient temperature Ts, and the time t, an equation relating to the energy balance of the brushless DC motor 30, that is,
Plus-h ・ A (T3-Ts) = C ・ dT3 / dt… (6)
Is true.

The power loss Plus in the first term on the left side of the above equation (6) represents the energy per unit time consumed in each part of the motor as heat or other loss (that is, the amount of heat generated inside the motor per unit time). The power loss Plus can be obtained by subtracting the output power Pout [W] (that is, the work to the outside per unit time) from the input power Pin [W] to the brushless DC motor 30. That is,
Plus = Pin-Pout… (7)
Is true.

The input power Pin is obtained by using the γ-axis current Iγ, the δ-axis current Iδ, the γ-axis voltage command value Vγ *, and the δ-axis voltage command value Vδ *.
Pin = Iγ ・ Vγ * ＋ Iδ ・ Vγ *… (8)
Can be calculated according to. Alternatively, the input power Pin uses the U-phase current Iu, the V-phase current Iv, the W-phase current Iw, the U-phase voltage command value Vu *, the V-phase voltage command value Vv *, and the W-phase voltage command value Vw *. ,
Pin = Iu ・ Vu * ＋ Iv ・ Vv * ＋ Iw ・ Vw *… (9)
It may be calculated according to.

The output power Pout is obtained by using the rotation speed Nf [1 / sec] of the motor and the torque Tf [Nm] of the motor.
Pout = 2π ・ Nf ・ Tf… (10)
Can be calculated according to. Further, the motor torque Tf uses the δ-axis current Iδ, the interlinkage magnetic flux value φh, and the pole logarithm Np.
Tf = Np ・ Iδ ・ φh… (11)
Can be calculated according to. The current interlinkage magnetic flux value φh can be calculated by the method described with reference to FIG. The pole logarithm Np is stored in the storage unit 61 as correction information.

The second term on the left side of the above equation (6) represents the amount of heat [J / s] that flows out from the surface of the housing that houses the motor per unit time. When the heat is forcibly released by using a fan or the like, the heat transfer coefficient h is changed to a larger value.

The right side of the above equation (6) represents the time change (that is, dE / dt) of the total thermal energy E stored inside the housing of the motor. Assuming that the housing surface temperature changes from T3 (n-1) to T3 (n) during the calculation period Δt (where n is an integer), the right-hand side of the above equation (6) is
[T3 (n) -T3 (n-1)] · C / Δt ... (12)
Can be approximated as. By using the above equations (6) to (12), the housing surface temperature T3 can be calculated numerically for each calculation period Δt.

Further, as a result of conducting an experiment using the ambient temperature Ts as a reference temperature, a ratio η was used between the winding temperature T1 and the housing surface temperature T3.
T3-Ts = η ・ (T1-Ts)… (13)
There is a relationship represented by. That is, the housing surface temperature T3 changes substantially following the winding temperature T1. However, in the case of T1 ≦ Ts or T3 ≦ Ts, T1 = T3. By using this equation (13), the winding temperature T1 can be calculated from the housing surface temperature T3.

FIG. 7 is a functional block diagram showing a procedure for estimating the housing surface temperature by the parameter correction unit. The explanations so far about the calculation method of the time change of the housing surface temperature T3 are summarized.

With reference to FIG. 7, the parameter correction unit 60 functionally has an output power calculation unit 80, an input power calculation unit 81, a constant multiplier 84,85, and a subtractor 82,83,88. It includes an adder 86, a housing temperature storage unit 87, and a winding temperature estimation unit 89.

The output power calculation unit 80 uses the γ-axis current Iγ calculated by the coordinate conversion unit 55, the electric angular velocity ω _M estimated by the magnetic pole position estimation unit 56, and the interlinkage magnetic flux value φh stored in the storage unit 61. Based on this, the output power Pout is calculated according to the above equations (10) and (11).

The input power calculation unit 81 includes the γ-axis voltage command value Vγ * and the δ-axis voltage command value Vδ * output from the current control unit 52, and the γ-axis current Iγ and the δ-axis current Iδ calculated by the coordinate conversion unit 55. Is used to calculate the input power Pin according to the above equation (8). The subtractor 82 calculates the power loss Plus by subtracting the output power Pout from the input power Pin.

On the other hand, the subtractor 88 subtracts the ambient temperature Ts from the housing surface temperature T3 (n-1) calculated one calculation cycle before. The constant multiplier 85 multiplies the subtraction result of the subtractor 88, that is, T3 (n-1) -Ts, by the heat transfer coefficient h and the surface area A of the housing of the motor.

The subtractor 83 subtracts the calculation result of the constant multiplier 85, that is, h × A × [T3 (n-1) −Ts] from the power loss Plus. As a result, the amount of change in the total thermal energy E per unit time is calculated.

The constant multiplier 84 multiplies the subtraction result of the subtractor 83 by the calculation period with the elapsed time Δt, and further divides the multiplication result by the heat capacity C of the housing. As a result, the amount of change in the housing surface temperature T3 during the elapsed time Δt is calculated. The adder 86 calculates the current housing surface temperature T3 (n) by adding the housing surface temperature T3 (n-1) one calculation cycle before to the amount of change in the housing surface temperature T3. ..

The housing temperature storage unit 87 stores the calculated current housing surface temperature T3 (n). Further, as described above, the subtractor 88 subtracts Ts from the calculated current housing surface temperature T3 (n). Hereinafter, the same procedure is repeated.

The above is a method of estimating the housing surface temperature T3 when the motor is being driven. When the brushless DC motor 30 is stopped, the input power Pin, the output power Pout, and the power loss Plus are all zero. In this case, the subsequent change in the housing surface temperature T3 can be calculated based on the housing surface temperature T3 (n) calculated immediately before the motor is stopped. If the ambient temperature Ts does not change with time, the ambient temperature Ts after a predetermined time has elapsed from the time when the motor is stopped is analyzed by integrating the equation (6) when the power loss Plus is 0. Can be calculated.

The winding temperature T1 is calculated by the winding temperature estimation unit 89. Specifically, the winding temperature estimation unit 89 calculates the winding temperature T1 from the current housing surface temperature T3 according to the above equation (13). Since the winding temperature T1 during motor drive can also be calculated by the method described with reference to FIG. 6, by comparing this calculation result with the calculation result of the winding temperature T1 based on the equation (13). , The ratio η of equation (13) can be calibrated.

[Parameter correction procedure when starting the motor]
Hereinafter, the parameter correction procedure at the time of starting the motor will be described with reference to the timing diagram of FIG. 8 and the flowchart of FIG.

FIG. 8 is a timing diagram for explaining a procedure for estimating parameters such as winding resistance at the time of starting the motor when the motor is repeatedly started and stopped. In the timing diagram of FIG. 8, the time change of the housing surface temperature T3 is shown by a broken line, and the time change of the motor rotation speed Nf is shown by a solid line. These values are shown with emphasis on features and are not proportional to actual values.

FIG. 9 is a flowchart showing a procedure for estimating parameters such as winding resistance when the motor is started.

The motor is stopped until the time t11 in FIG. Since this stopped state continues for a considerable period of time, it is assumed that the winding temperature T1, the magnet temperature T2, and the housing surface temperature T3 are all equal to the ambient temperature Ts. The parameter correction unit 60 acquires the ambient temperature Ts at this time as the initial temperature T3 (0) of the housing surface and stores it in the housing temperature storage unit 87 of FIG. 7 (step S200 of FIG. 9).

When the motor is started at time t11, the parameter correction unit 60 calculates the input power Pin and the output power Pout. Using the calculated input power Pin and output power Pout and the ambient temperature Ts, the parameter correction unit 60 uses the housing surface temperature T3 after one calculation cycle Δt from the initial temperature T3 (0) of the housing surface temperature. Calculate (1). Similarly, the parameter correction unit 60 calculates the housing surface temperatures T3 (2), T3 (3), ... For each calculation cycle (step S210).

When the motor is stopped at time t12, the calculation results of the input power Pin and the output power Pout become 0. In this case, the parameter correction unit 60 calculates the housing surface temperature T3 (x + 1) in the next calculation cycle based on the housing surface temperature T3 (x) calculated immediately before the motor is stopped. Similarly, the parameter correction unit 60 calculates the housing surface temperature T3 (x + 2), T3 (x + 3), ... For each calculation cycle (step S220). When the ambient temperature Ts is constant, the housing surface temperature after a predetermined time has elapsed analytically from the housing surface temperature T3 (x) calculated immediately before the motor is stopped (for example, immediately before the next motor start). T3 can be calculated (step S220).

The motor is started at time t13. The parameter correction unit 60 estimates the winding temperature T1, the winding resistance value Rh, and the interlinkage magnetic flux value φh using the housing surface temperature T3 calculated immediately before the time t13.

Specifically, the parameter correction unit 60 estimates the winding temperature T1 from the housing surface temperature T3 according to the above equation (13) (step S230). Next, the parameter correction unit 60 estimates the winding resistance value Rh from the winding temperature T1 according to the above equation (1) (step S240). Further, the parameter correction unit 60 estimates the interlinkage magnetic flux value φh from the winding temperature T1 according to the above equations (2) and (3) (step S250). The sensorless vector control circuit 50 controls the brushless DC motor 30 at startup using these estimated parameters.

Similarly, the brushless DC motor 30 is in the operating state between the time t13 and the time t14, between the time t15 and the time t16, between the time t17 and the time t18, and between the time t19 and the time t20. Be controlled. The parameter correction unit 60 estimates the winding temperature T1, the winding resistance value Rh, and the interlinkage magnetic flux value φh at the timings t15, t17, and t19 for starting the brushless DC motor 30. When estimating various parameters at time t15, the parameter correction unit 60 uses the estimated value of the housing surface temperature T3 at time t13 as the initial temperature (step S200 in FIG. 9).

[Modification example of correction procedure when starting the motor]
In the estimation procedure of FIG. 9, the housing surface temperature T3 was estimated based on the input power Pin, the output power Pout, and the ambient temperature Ts even while the motor was being driven. On the other hand, as described with reference to FIG. 6, while the motor is being driven, the voltage command values Vγ * and Vδ * and the γ-axis currents Iγ and the δ-axis currents Iδ calculated from the detected current values Iu and Iv are used. Based on this, the winding resistance value Rh can be calculated. Therefore, instead of the estimation procedure of FIG. 9, the winding temperature T1 and the housing surface temperature T3 can be estimated from the calculated winding resistance value Rh. Hereinafter, description will be given with reference to the drawings.

FIG. 10 is a flowchart showing a modified example of the parameter estimation procedure of FIG. In the estimation procedure of FIG. 10, steps S205 and S215 are executed instead of steps S200 and S210 of FIG. Subsequent steps S220 to S250 are the same as in the case of FIG. 9, and thus the description will not be repeated.

In step S205 of FIG. 10, the parameter correction unit 60 is based on the voltage command values Vγ * and Vδ * immediately before the motor is stopped and the γ-axis currents Iγ and δ-axis currents Iδ calculated from the detected current values Iu and Iv. , The winding resistance value Rh is calculated according to the above equation (4A).

In the next step S215, the parameter correction unit 60 calculates the winding temperature T1 according to the above equation (1) based on the calculated winding resistance value Rh. Further, the parameter correction unit 60 estimates the housing surface temperature T3 according to the above equation (13) based on the calculated winding temperature T1.

[Effect of Embodiment 1]
As described above, according to the motor control device of the first embodiment, when the motor parameter such as the winding resistance value Rh is corrected at the time of driving the motor, the winding resistance value Rh is set by passing a current through the stator winding 31. Not actually measured. Instead, the motor control device estimates the winding temperature T1 at the time of starting the motor based on the drive history of the motor, and determines the winding resistance value Rh and the interlinkage magnetic flux value φh based on the estimated winding temperature T1. presume. As a result, it is possible to prevent the motor from rotating due to the actual measurement of the winding resistance value Rh, so that it is possible to prevent the motor from stepping out immediately after starting. Hereinafter, the effect of the first embodiment will be further described with reference to the drawings.

FIG. 11 is a timing diagram conceptually showing the time change of the U-phase current and the rotor rotation speed at the time of starting the motor. In FIG. 11 and subsequent FIGS. 12 and 18, the U-phase current Iu and the rotor speed Nf are shown with emphasis on features and are not proportional to actual values.

With reference to FIG. 11, the initial position estimation unit 57 of the sensorless vector control circuit 50 estimates the initial position of the magnetic pole of the rotor from the time t1 to the time t2 by using the inductive sense method. As shown in FIG. 11, in the inductive sense method, a short-time pulsed current having a relatively small magnitude is repeatedly applied to the stator winding 31. Therefore, the rotor does not rotate during this period, and the rotor rotation speed Nf remains 0.

Immediately before time t2, the parameter correction unit 60 estimates the winding temperature T1 and corrects the winding resistance value Rh and the interlinkage magnetic flux value φh based on the estimated winding temperature T1. The sensorless vector control circuit 50 activates the brushless DC motor 30 by vector control based on these estimated motor parameters at time t2. The brushless DC motor 30 is normally started, the rotor rotation speed Nf gradually increases, and after a slight overshoot, it settles at a steady value.

FIG. 12 is a timing diagram showing a comparative example of FIG. With reference to FIG. 12, between time t1 and time t2, the initial position estimation unit 57 estimates the initial position of the magnetic pole of the rotor by using the inductive sense method as in the case of FIG.

Between the next time t2 and time t3, the sensorless vector control circuit 50 passes a current through the stator winding 31 in order to measure the winding resistance value Rh of the stator winding 31. The parameter correction unit 60 calculates the winding resistance value Rh based on the voltage command values Vu *, Vv *, Vw * and the detected values of the U-phase current Iu and the V-phase current Iv. Further, the parameter correction unit 60 corrects the interlinkage magnetic flux value φh based on the winding resistance value Rh.

The sensorless vector control circuit 50 activates the brushless DC motor 30 by vector control based on these estimated motor parameters at time t3. However, in the case of FIG. 12, the rotor is rotated by the stator winding 31 at the time of resistance measurement. That is, the initial speed of the rotor is not 0 at time t3. In this case, since a speed deviation occurs immediately after the start-up, the sensorless vector control circuit 50 applies torque in the reverse rotation direction to the rotor in order to correct this speed deviation. As a result, the rotor rotation speed Nf vibrates and the motor steps out.

FIG. 13 is a diagram for explaining the rotation of the rotor caused by applying a voltage to the stator winding during resistance measurement. With reference to FIG. 13, the sensorless vector control circuit 50 causes a current to flow from the V-phase winding and the W-phase winding to the U-phase winding when measuring the resistance value Rh of the stator winding 31. In this case, a magnetic flux in the direction shown by the broken line in FIG. 13 is generated.

On the other hand, the direction of the magnetic poles of the rotor when the motor is stopped is shown by a solid line. As shown in FIG. 13, when the direction of the current magnetic field and the direction of the magnetic pole are different, torque is generated. As a result, in the case of FIG. 13, the rotor rotates in the clockwise direction.

In the motor control device of the first embodiment, the winding resistance value Rh is estimated based on the drive history of the motor, and no current is passed through the stator winding 31, so that the rotation of the rotor due to the above-mentioned cause can be prevented.

<Embodiment 2>
The motor control device of the second embodiment estimates the winding resistance value Rh from the drive history according to the starting condition at the time of starting the motor, and applies a current to the stator winding 31 to obtain the winding resistance value Rh. It is configured so that it can be switched between the case of actual measurement and the case of actual measurement.

The hardware configuration of the motor control device 10 shown in FIG. 1 and the functional configuration of the control unit 20 shown in FIGS. 3 and 7 are basically the same in the case of the second embodiment. Therefore, these explanations will not be repeated. Further, the control procedure of the brushless DC motor 30 shown in FIG. 5 is the same as in the case of the second embodiment except for a part of step S20. Therefore, the detailed explanation will not be repeated.

[Parameter correction procedure when starting the motor]
FIG. 14 is a flowchart showing a procedure for estimating motor parameters such as winding resistance at the time of starting the motor in the motor control device of the second embodiment. As shown in FIG. 8, it is assumed that the start and stop of the motor are repeated in one job.

With reference to FIG. 14, in step S300, the parameter correction unit 60 determines whether or not the start condition that the start of the motor this time is the first start of the motor in the job being executed is satisfied. If it is not the first motor start (NO in step S300), the parameter correction unit 60 advances the process to step S310.

In step S310, the parameter correction unit 60 estimates the winding temperature T1 at the time of starting based on the starting history of the motor. Specifically, the method described in steps S200 to S230 of FIG. 9 may be used, or the method described in steps S205 to S230 of FIG. 10 may be used.

In the next step S320, the parameter correction unit 60 estimates the winding resistance value Rh from the winding temperature T1 according to the above equation (1). In the next step S340, the parameter correction unit 60 estimates the interlinkage magnetic flux value φh from the winding temperature T1 according to the above equations (2) and (3).

On the other hand, in step S300, if the parameter correction unit 60 determines that the motor is started for the first time in the job (YES in step S300), the process proceeds to step S330.

In step S330, the sensorless vector control circuit 50 measures the winding resistance value Rh by passing a current through the stator winding 31. The specific procedure will be described later with reference to FIG.

In the next step S340, the parameter correction unit 60 estimates the interlinkage magnetic flux value φh from the winding temperature T1 according to the above equations (2) and (3).

FIG. 15 is a flowchart showing the procedure of step S330 of FIG. 14 in detail. In step S10 of FIG. 5, it is assumed that the estimated value of the _{initial magnetic pole position θ M has already been obtained by the inductive sense method.}

With reference to FIG. 15, in step S400, the sensorless vector control circuit 50 applies voltages Vu *, Vv *, Vw * to the stator winding 31 at _{an electrical angle θ M representing the estimated initial magnetic pole position.} Specifically, if the γ-axis voltage command value Vγ * is set to a predetermined value and the δ-axis voltage command value Vδ * is set to 0, the voltage command value of each phase is set using the voltage amplitude Vo.
Vu * ＝ Vo ・ cosθ _M … (14A)
Vv * = Vo · cos (θ _M −120 °)… (14B)
Vw * = Vo · cos (θ _M −240 °)… (14C)
It is expressed as.

By applying the voltages Vu *, Vv *, and Vw * to the stator winding 31 at the _{electric angle θ M} representing the initial magnetic pole position estimated in this way, no torque is applied to the rotor 35. Therefore, the rotation of the rotor 35 can be prevented.

In the next step S410, the parameter correction unit 60 calculates the γ-axis current Iγ from the detected U-phase current Iu and V-phase current Iv. Then, the parameter correction unit 60 calculates the winding resistance value Rh by dividing the γ-axis voltage command value Vγ * by the γ-axis current Iγ based on the equation (5).

[Modified Example of Embodiment 2]
The selection of whether to estimate the winding resistance value Rh from the drive history at the start of the motor or to actually measure the winding resistance value Rh by applying a current to the stator winding 31 may be based on other conditions.

FIG. 16 is a flowchart showing a first modification of the parameter estimation procedure of FIG. The parameter estimation procedure of FIG. 16 is different from the case of FIG. 14 in that step S300A is executed instead of step S300. It is assumed that the brushless DC motor 30 and the motor control device are mounted on an electric device.

In step S300A of FIG. 16, the parameter correction unit 60 determines whether or not the start of the motor this time satisfies the start condition that the start of the motor is the first start after the power of the electric device is turned on. The parameter correction unit 60 advances the process to step S310 if it is not the first activation (NO in step S300A) and proceeds to step S330 if it is the first activation (YEs in step S300A). Since the other steps in FIG. 16 are the same as in the case of FIG. 14, the same or corresponding steps are designated by the same reference numerals and the description is not repeated.

FIG. 17 is a flowchart showing a second modification of the parameter estimation procedure of FIG. The parameter estimation procedure of FIG. 17 differs from that of FIG. 14 in that step S300B is executed instead of step S300.

In step S300B of FIG. 17, the parameter correction unit 60 satisfies the start condition that the pause time interval from the stop of the motor to the start of the current motor is equal to or longer than the predetermined time interval Tr. To judge. The parameter correction unit 60 advances the process to step S310 when the pause time interval is less than the defined time interval Tr (NO in step S300B), and advances the process to step S310, and when the pause time interval is greater than or equal to the defined time interval Tr (step S300B). YES) Proceed to step S330. Since the other steps in FIG. 17 are the same as in the case of FIG. 14, the same or corresponding steps are designated by the same reference numerals and the description is not repeated.

[Effect of Embodiment 2]
As described above, according to the motor control device of the second embodiment, when the starting condition determined at the time of starting the motor is satisfied, a current is actually applied to the stator winding 31 to set the winding resistance value Rh. Measure. As a result, the motor parameters can be corrected more accurately than in the case of estimating the motor parameters such as the winding resistance value Rh and the interlinkage magnetic flux value φh based on the drive history.

Further, when a current is applied to the stator winding 31, voltages Vu *, Vv *, Vw * are applied to the stator winding 31 at _{an electric angle θ M} representing the initial magnetic pole position estimated by the inductive sense method. .. As a result, no torque is applied to the rotor 35, so that the rotation of the rotor 35 can be prevented.

The initial magnetic flux position estimated by the inductive sense method may include an error. Therefore, it is desirable to reduce the current value flowing through the stator winding 31 within a range in which sufficient measurement accuracy of the winding resistance value Rh can be obtained. Hereinafter, the effect of the second embodiment will be further described with reference to the drawings.

FIG. 18 is a timing diagram conceptually showing the time change of the U-phase current and the rotor rotation speed at the time of starting the motor in the case of the second embodiment.

With reference to FIG. 18, the initial position estimation unit 57 of the sensorless vector control circuit 50 estimates the initial position of the magnetic pole of the rotor from the time t1 to the time t2 by using the inductive sense method. Similar to the case of FIG. 11, in the inductive sense method, a short-time pulsed current having a relatively small magnitude is repeatedly applied to the stator winding 31.

Between the next time t2 and time t3, the sensorless vector control circuit 50 passes a current through the stator winding 31 in order to measure the winding resistance value Rh of the stator winding 31. When measuring the winding resistance value Rh, it is necessary to apply a voltage until the current flowing through the stator winding 31 is saturated, so that the voltage application time is relatively long. However, in the case of the second embodiment, since the voltages Vu *, Vv *, Vw * are applied to the stator winding 31 at the _{electric angle θ M} representing the initial magnetic pole position estimated by the inductive sense method, the rotor is It does not rotate, and the rotor rotation speed Nf is maintained at 0.

The parameter correction unit 60 calculates the winding resistance value Rh based on the voltage command values Vu *, Vv *, Vw * and the detected values of the U-phase current Iu and the V-phase current Iv. Further, the parameter correction unit 60 corrects the interlinkage magnetic flux value φh based on the winding resistance value Rh.

The sensorless vector control circuit 50 activates the brushless DC motor 30 by vector control based on these estimated motor parameters at time t3. The brushless DC motor 30 is normally started, the rotor rotation speed Nf gradually increases, and after a slight overshoot, it settles at a steady value.

<Embodiment 3>
In the third embodiment, the motor control device described in the first and second embodiments is used to control a brushless DC motor for driving a paper feed roller, a timing roller, a transfer roller, and the like of the image forming apparatus. explain.

[Configuration example of image forming apparatus]
FIG. 19 is a cross-sectional view showing an example of the configuration of the image forming apparatus. It should be noted that the cross-sectional view of FIG. 19 is schematic, and a part of the cross-sectional view is enlarged or the aspect ratio is changed to facilitate the illustration.

With reference to FIG. 19, the image forming apparatus 180 includes an image forming unit 181 configured as a tandem color printer, a paper feeding mechanism 182, a temperature sensor 190, and a document reading device 160 as a scanner. The image forming apparatus 180 may be configured as a multifunction peripheral device (MFP: Multifunction Peripheral) connected to a network and having functions such as a printer, a scanner, a copier, and a facsimile.

The image forming unit 181 as a printer includes four photoconductor cartridges 191, 192, 193, 194, a primary transfer roller 131, a transfer belt 132, a toner bottle 123, a secondary transfer roller 133, and a fixing device. It is equipped with 105.

The photoconductor cartridges 191, 192, 193, and 194 form toner images of four colors of yellow (Y), magenta (M), cyan (C), and black (K), respectively. Each of the photoconductor cartridges 191, 192, 193, and 194 includes a cylindrical photoconductor 110, a charger 111, an image exposure device 112 including a light source, and a developing device 102 including a developing roller 121.

The charger 111 uniformly charges the surface of the photoconductor 110 to a predetermined potential. The image exposure apparatus 112 exposes an image corresponding to the original image to the charged region of the photoconductor 110. As a result, an electrostatic latent image is formed on the photoconductor 110. The developing apparatus 102 forms a visible toner image by adhering toner to the electrostatic latent image by using the developing roller 121 to which the developing bias is applied.

It should be noted that four toner bottles 123 are provided corresponding to the photoconductor cartridges 191, 192, 193, and 194, respectively. Toner is supplied from the toner bottle 123 to the corresponding photoconductor cartridge. Inside the toner bottle 123, a stirring blade 124 for stirring the toner is provided.

Four primary transfer rollers 131 are provided facing each of the four photoconductors 110. The transfer belt 132 is pressure-welded with each photoconductor 110 and the corresponding primary transfer roller 131. Further, a bias that attracts toner is applied to the primary transfer roller 131. As a result, the visible toner image on the surface of the photoconductor 110 after development is transferred to the transfer belt 132.

The visible toner image transferred onto the transfer belt 132 is conveyed to the position of the secondary transfer roller 133. A transfer voltage is applied to the secondary transfer roller 133 as well as the primary transfer roller. As a result, the visible toner image conveyed by the transfer belt 132 is transferred to the paper, which is the recording medium 183, at the nip portion between the secondary transfer roller 133 and the transfer belt 132.

The visible toner image transferred to the recording medium 183 is conveyed to the fixing device 105. The fixing device 105 has a fixing roller 150, and the visible toner image is fixed on the recording medium 183 by heating and pressurizing the recording medium 183 by the fixing roller 150. The recording medium 183 after fixing is discharged to the paper ejection tray 152 by the paper ejection roller 151.

The paper feed mechanism 182 takes in the paper as the recording medium 183 from the paper feed cassettes 140 and 142 and conveys it to the secondary transfer roller 133. The paper feed mechanism 182 includes paper feed cassettes 140 and 142, paper feed rollers 141 and 143, a transfer roller 144, and a timing roller 145.

The recording media 183 housed in the first-stage paper cassette 140 are taken out one by one by the paper feed roller 141 and conveyed to the timing roller 145. The recording media 183 housed in the second-stage paper cassette 142 are taken out one by one by the paper feed roller 143, and are conveyed to the timing roller 145 via the transfer roller 144.

The timing roller 145 temporarily stops the supplied recording medium 183. As a result, the timing at which the visible toner image transferred on the transfer belt 132 is conveyed to the secondary transfer roller 133 and the timing at which the recording medium 183 is supplied to the secondary transfer roller 133 are adjusted.

The temperature sensor 190 detects the ambient temperature Ts of the brushless DC motor for driving various rollers.

The document reading device 160 generates image data by reading the document image on the document paper 161. In the example shown in FIG. 17, the document reading device 160 is provided on the upper part of the image forming unit 181. The document reading device 160 includes a document table 162, a paper feed roller 170, a document transfer roller 163, 171, a document ejection roller 172, a paper ejection tray 173, a light source 164, a mirror 165, a lens 166, and a CCD. It is equipped with an image sensor 167 such as (Charged-Coupled Devices).

The manuscript paper 161 placed on the manuscript table 162 is taken in one by one by the paper feed roller 170. The manuscript paper 161 reaches the document reading position by being transported by the document transport rollers 163 and 171.

At the document reading position, the document image on the document paper 161 is irradiated with light from the light source 164. The light reflected on the surface of the manuscript paper 161 is reflected by the mirror 165, then condensed by the lens 166, and incident on the image sensor 167. As a result, the original image on the original paper 161 is formed on the sensor surface of the image sensor 167, and the image data of the original image is generated by the image sensor 167.

The document paper 161 that has passed the document reading position is ejected to the output tray 173 by the document ejection roller 172.

[Effect of Embodiment 3]
In the image forming apparatus 180, the brushless DC motor for driving the timing roller 145 or the like used for transporting paper frequently starts and stops. In this case, if the rotor moves before the motor starts, the paper will be fed out accordingly, causing jam. By applying the motor control device described in the first and second embodiments, it is possible to prevent the rotor from moving as much as possible before the motor is started, so that the occurrence of jam can be suppressed.

The embodiments disclosed this time should be considered to be exemplary and not restrictive in all respects. The scope of this application is indicated by the scope of claims rather than the above description, and is intended to include all modifications within the meaning and scope of the claims.

10 motor control device, 20 control unit, 30 brushless DC motor, 31 stator winding, 35 rotor, 40 drive circuit, 50 sensorless vector control circuit, 56 magnetic pole position estimation unit, 57 initial position estimation unit, 60 parameter correction unit, 61 Storage unit, 70 upper control circuit, 80 output power calculation unit, 81 input power calculation unit, 141,143,170 paper feed roller, 144 transport roller, 145 timing roller, 180 image forming device, 181 image drawing unit, 182 paper feed Mechanism, 190 temperature sensor.

Claims (11)

A motor control device that controls a sensorless motor.
A drive circuit that applies a voltage to the stator windings of the motor,
A control unit that controls the drive circuit by a vector control method is provided.
When the motor is started, the control unit estimates the value of the motor parameter including the resistance value of the stator winding based on the drive history of the motor, and starts the motor based on the estimated motor parameter. Motor control device. When the motor is started, the control unit estimates the value of the motor parameter including the resistance value of the stator winding based on the drive history of the motor when the first start condition is not satisfied. The motor according to claim 1, wherein the resistance value of the stator winding is measured when the first start condition is satisfied, and other motor parameters are estimated based on the measured resistance value of the stator winding. Control device. The motor control device according to claim 2, wherein the control unit estimates the initial position of the magnetic pole of the rotor of the motor at the time of starting the motor, before estimating the motor parameters. When the first start-up condition is satisfied, the control unit applies a voltage to the stator winding at an electric angle representing the estimated initial position of the magnetic pole to obtain a resistance value of the stator winding. The motor control device according to claim 3, which is actually measured. The control unit executes a job of repeatedly starting and stopping the motor, and the control unit executes the job.
The motor control device according to any one of claims 2 to 4, wherein the first start condition is the first start of the motor of the job. The first start condition is any one of claims 2 to 4, which includes the first start of the motor after turning on the power of the motor and the electric device including the motor control device. The motor control device described. The motor control device according to any one of claims 2 to 4, wherein the first start condition includes that the elapsed time from the last stop of the motor is at least a predetermined time interval. The drive history includes information on input power input to the motor, information on output power output from the motor, and information on the elapsed time since the motor was last stopped, according to claims 1 to 1. 7. The motor control device according to any one of 7. The drive history includes information on the resistance value of the stator winding based on the voltage command value and the current detection value immediately before the motor was stopped last time, and information on the elapsed time since the motor was stopped last time. The motor control device according to any one of claims 1 to 7. It is a method of starting a sensorless motor,
The motor is driven and controlled by a vector control method.
The above-mentioned activation method is
The step of estimating the value of the motor parameter including the resistance value of the stator winding based on the drive history of the motor, and
A method of starting a motor, comprising a step of starting the motor based on the estimated motor parameters. A transport mechanism that transports paper from a paper cassette using multiple rollers,
A printer that forms an image on the conveyed paper,
An image forming apparatus comprising the motor control device according to any one of claims 1 to 9, which controls a motor for driving at least one of the plurality of rollers.

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