Motor control device and electric pump device

Abstract

To provide a motor control device and an electric pump device with which it is possible to stably exercise sensorless control of a motor, even when the motor is rotated at a low duty ratio.SOLUTION: One embodiment in a motor control device according to the present invention controls a three-phase motor. The motor control device comprises a drive circuit that converts a DC power supply voltage to a three-phase AC voltage and supplies it to the three-phase motor, a first voltage detection unit that detects the three-phase terminal voltages of the three-phase motor, and a control unit that detects a point at which a first voltage value that is a detected terminal voltage value crosses a prescribed zero-cross determination level, as a zero-cross point, and controls the drive circuit on the basis of the result of the zero-cross point detection. When the output duty ratio to the three-phase motor is smaller than or equal to a prescribed threshold, the control unit multiplies the first voltage value by a first coefficient that is inversely proportional to the output duty ratio so as to correct the first voltage value.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a motor control device and an electric pump device.

Background Art

[0002] As a control method for a sensorless motor, sensorless control is known in which the point where the induced voltage appearing in each of the three-phase terminal voltages of the motor intersects with the neutral point potential is detected as a zero-cross point, and energization control of the motor is performed based on the detection result of the zero-cross point. Patent Document 1 below discloses a technique for stably driving a sensorless motor in a low rotation range.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When controlling a sensorless motor at a low duty ratio, the detected value of the induced voltage may deviate from the theoretical voltage value due to response delay of hardware in the motor control device or the like. In this case, the detection timing of the zero-cross point may deviate from the ideal timing, and as a result, it may be difficult to stably perform sensorless control of the motor. The technique of Patent Document 1 above cannot solve such technical problems.

Means for Solving the Problems

[0005] One aspect of the motor control device of the present invention is a motor control device for controlling a three-phase motor, comprising: a drive circuit that converts a DC power supply voltage into a three-phase AC voltage and supplies it to the three-phase motor; a first voltage detection unit that detects the terminal voltages of the three phases of the three-phase motor; and a control unit that detects the point at which the first voltage value, which is the detected value of the terminal voltage, intersects with a predetermined zero-crossing determination level as a zero-crossing point, and controls the drive circuit based on the detection result of the zero-crossing point, wherein the control unit corrects the first voltage value by multiplying the first voltage value by a first coefficient inversely proportional to the output duty cycle when the output duty cycle for the three-phase motor is less than or equal to a predetermined threshold.

[0006] One embodiment of the electric pump device of the present invention comprises a three-phase motor having a shaft, a pump located on one axial side of the shaft and driven by the three-phase motor via the shaft, and a motor control device of the above embodiment for controlling the three-phase motor. [Effects of the Invention]

[0007] According to the above-described aspect of the present invention, a motor control device and an electric pump device are provided that can stably perform sensorless control of a motor even when the motor is rotated at a low duty cycle. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic block diagram showing an electric pump device 100 equipped with a motor control device 10 in this embodiment. [Figure 2] Figure 2 shows an example of the energizing pattern and phase pattern used in the sensorless 120° energizing method in this embodiment. [Figure 3] Figure 3 is a timing chart illustrating the basic principle of the sensorless 120° energization method in this embodiment. [Figure 4]Figure 4 shows the waveforms of the induced voltages appearing at the three-phase terminal voltages Vu, Vv, and Vw when sensorless synchronous control of the three-phase motor 20 is performed with a high duty cycle. [Figure 5] Figure 5 shows the waveforms of the induced voltages appearing at the three-phase terminal voltages Vu, Vv, and Vw when sensorless synchronous control of the three-phase motor 20 is performed with a low duty cycle. [Figure 6] Figure 6 is a flowchart showing each process included in the motor control performed by the control unit 14. [Modes for carrying out the invention]

[0009] One embodiment of the present invention will be described in detail below with reference to the drawings. Figure 1 is a schematic block diagram showing an electric pump device 100 equipped with a motor control device 10 in this embodiment. As shown in Figure 1, the electric pump device 100 comprises a motor control device 10 and an electric pump 40. The electric pump 40 comprises a three-phase motor 20 and a pump 30. The electric pump device 100 is a device that supplies cooling oil F to a drive motor mounted on, for example, a hybrid vehicle.

[0010] The motor control device 10 is a device that controls the three-phase motor 20 of the electric oil pump 40 without the use of position sensors such as Hall sensors. Specifically, the motor control device 10 detects the point where the induced voltage appearing at each of the three-phase terminal voltages of the three-phase motor 20 intersects a predetermined zero-crossing judgment level as the zero-crossing point, and controls the energization of the three-phase motor 20 based on the detection result of the zero-crossing point. Details of the motor control device 10 will be described later.

[0011] The three-phase motor 20 is, for example, an inner rotor type three-phase brushless DC motor and is a sensorless motor that does not have a position sensor such as a Hall sensor. The three-phase motor 20 has a shaft 21, a U-phase terminal 22u, a V-phase terminal 22v, a W-phase terminal 22w, a U-phase coil 23u, a V-phase coil 23v, and a W-phase coil 23w.

[0012] Although not shown in Figure 1, the three-phase motor 20 includes a motor housing and a rotor and stator housed within the motor housing. The rotor is a rotating body rotatably supported by bearing components inside the motor housing. The stator is fixed inside the motor housing, surrounding the outer surface of the rotor, and generates the electromagnetic force necessary to rotate the rotor.

[0013] The shaft 21 is a shaft-like body that is coaxially joined to the rotor, passing through the radially inner side of the rotor in an axial direction. The U-phase terminal 22u, V-phase terminal 22v, and W-phase terminal 22w are metal terminals exposed from the surface of the motor housing. As will be described in detail later, the U-phase terminal 22u, V-phase terminal 22v, and W-phase terminal 22w are each electrically connected to the drive circuit 11 of the motor control device 10. The U-phase coil 23u, V-phase coil 23v, and W-phase coil 23w are excitation coils provided on the stator. For example, the U-phase coil 23u, V-phase coil 23v, and W-phase coil 23w are star-connected inside the three-phase motor 20.

[0014] The U-phase coil 23u is electrically connected between the U-phase terminal 22u and the neutral point N. The V-phase coil 23v is electrically connected between the V-phase terminal 22v and the neutral point N. The W-phase coil 23w is electrically connected between the W-phase terminal 22w and the neutral point N. The energization state of the U-phase coil 23u, V-phase coil 23v, and W-phase coil 23w is controlled by the motor control device 10, generating the electromagnetic force necessary to rotate the rotor. As the rotor rotates, the shaft 21 also rotates in sync with the rotor.

[0015] The pump 30 is located on one axial side of the shaft 21 of the three-phase motor 20 and is driven by the three-phase motor 20 via the shaft 21. When the pump 30 is driven by the three-phase motor 20, the pump 30 discharges the cooling oil F. The pump 30 has an oil suction port 31 and an oil discharge port 32. The cooling oil F is sucked into the pump 30 from the oil suction port 31 and then discharged to the outside of the pump 30 from the oil discharge port 32. Thus, the electric pump 40 is constituted by connecting the pump 30 and the three-phase motor 20 adjacent to each other in the axial direction of the shaft 21.

[0016] The motor control device 10 is a device that controls the three-phase motor 20 without a position sensor based on a rotation speed command signal CS output from a higher-level control device (not shown). As an example, the higher-level control device is an in-vehicle ECU (Electronic Control Unit) mounted on a hybrid vehicle. The motor control device 10 includes a drive circuit 11, a first voltage detection circuit 12 (first voltage detection unit), a second voltage detection circuit (second voltage detection unit) 13, a control unit 14, and a storage unit 15.

[0017] The drive circuit 11 is a circuit that converts the DC power supply voltage V M into a three-phase AC voltage and supplies it to the three-phase motor 20. The drive circuit 11 converts the DC power supply voltage V M supplied from the DC power supply 200 into a three-phase AC voltage and outputs it to the three-phase motor 20. As an example, the DC power supply 200 is one of a plurality of batteries mounted on a hybrid vehicle, and supplies a 12V DC power supply voltage V M to, for example, a 12V in-vehicle system.

[0018] The drive circuit 11 includes an upper-arm switch Q UH for the U phase, an upper-arm switch Q VH for the V phase, an upper-arm switch Q WH for the W phase, a lower-arm switch Q UL for the U phase, a lower-arm switch Q VL for the V phase, and a lower-arm switch Q WLIn this embodiment, each arm switch is, for example, an N-channel MOS-FET.

[0019] U-phase upper arm switch Q UH Drain terminal, V-phase upper arm switch Q VH The drain terminal and the W-phase upper arm switch Q WH The drain terminals are electrically connected to the positive terminals of the DC power supply 200. U-phase lower arm switch Q UL Source terminal, V-phase lower arm switch Q VL The source terminal and the W-phase lower arm switch Q WL The source terminals are electrically connected to the negative terminal of the DC power supply 200 via the shunt resistor 12. The negative terminal of the DC power supply 200 is electrically connected to the vehicle's ground.

[0020] U-phase upper arm switch Q UH The source terminals are the U-phase terminal 22u of the three-phase motor 20 and the U-phase lower arm switch Q. UL It is electrically connected to the drain terminals of each. V-phase upper arm switch Q VH The source terminals are the V-phase terminal 22V of the three-phase motor 20 and the V-phase lower arm switch Q. VL It is electrically connected to the drain terminals of each. W-phase upper arm switch Q WH The source terminals are the W-phase terminal 22w of the three-phase motor 20 and the W-phase lower arm switch Q. WL It is electrically connected to the drain terminals of each.

[0021] U-phase upper arm switch Q UH The gate terminal, V-phase upper arm switch Q VH The gate terminal and the W-phase upper arm switch Q WH The gate terminals are electrically connected to the control unit 14. Also, the U-phase lower arm switch Q UL The gate terminal, V-phase lower arm switch Q VL The gate terminal and the W-phase lower arm switch Q WLThe gate terminals are also electrically connected to the control unit 14.

[0022] As described above, the drive circuit 11 is composed of a three-phase full-bridge circuit having three upper arm switches and three lower arm switches. With the drive circuit 11 configured in this way, each arm switch is switched by the control unit 14, thereby controlling the DC power supply voltage V supplied from the DC power supply 200. M This is converted to a three-phase AC voltage and output to the three-phase motor 20.

[0023] In this embodiment, we illustrate the case where a sensorless 120° energizing method is used as the energizing method for the three-phase motor 20. For the sake of explanation, the basic principle of the sensorless 120° energizing method will be explained below, followed by a description of the first voltage detection circuit 12, the second voltage detection circuit 13, the control unit 14, and the memory unit 15. Note that the basic principle of the sensorless 120° energizing method described below is merely an example, and the present invention is not limited thereto.

[0024] When using the sensorless 120° energization method, each arm switch is switched based on the energization pattern shown in Figure 2. As shown in Figure 2, the energization pattern of the 120° energization method includes six energization patterns PA1, PA2, PA3, PA4, PA5 and PA6. In Figure 2, "Q UH " to "Q WL In the column up to ", the numbers "1" and "0" indicate that the corresponding arm switch is controlled to the ON position, and "0" indicates that the corresponding arm switch is controlled to the OFF position.

[0025] In Figure 3, the energizing period P1 from time t10 to time t11 represents the period during which each arm switch is switched based on the energizing pattern PA1. During this energizing period P1, the U-phase upper arm switch Q UH And W-phase lower arm switch Q WL The and turn on, and the remaining arm switches turn off. During the energized period P1, the U-phase upper arm switch Q UHOnly the switching is controlled with a predetermined switching duty cycle. During the energizing period P1, drive current (power supply current) flows from the U-phase terminal 22u to the W-phase terminal 22w through the U-phase coil 23u and the W-phase coil 23w. In other words, the energized phases during the energizing period P1 are the U-phase and the W-phase.

[0026] In Figure 3, the energizing period P2 from time t11 to time t12 represents the period during which each arm switch is switched based on the energizing pattern PA2. During this energizing period P2, the U-phase upper arm switch Q UH and V-phase lower arm switch Q VL The switch turns ON, and the remaining arm switches turn OFF. Even during the power-on period P2, the U-phase upper arm switch Q UH Only the switching is controlled with a predetermined switching duty cycle. During the energizing period P2, drive current flows from the U-phase terminal 22u to the V-phase terminal 22v through the U-phase coil 23u and the V-phase coil 23v. In other words, the energized phases during the energizing period P2 are the U-phase and the V-phase.

[0027] In Figure 3, the energizing period P3 from time t12 to time t13 represents the period during which each arm switch is switched based on the energizing pattern PA3. During this energizing period P3, the W-phase upper arm switch Q WH and V-phase lower arm switch Q VL The switch turns ON, and the remaining arm switches turn OFF. During the energized period P3, the upper arm switch Q of the W phase is turned ON. WH Only the switching is controlled with a predetermined switching duty cycle. During the energizing period P3, drive current flows from the W-phase terminal 22w to the V-phase terminal 22v through the W-phase coil 23w and the V-phase coil 23v. In other words, the energized phases during the energizing period P3 are the W-phase and the V-phase.

[0028] In Figure 3, the energizing period P4 from time t13 to time t14 represents the period during which each arm switch is switched based on the energizing pattern PA4. During this energizing period P4, the W-phase upper arm switch Q WH and U-phase lower arm switch Q ULThe switch turns ON, and the remaining arm switches turn OFF. Even during the power-on period P4, the upper arm switch Q of the W phase remains ON. WH Only the switching is controlled with a predetermined switching duty cycle. During the energizing period P4, drive current flows from the W-phase terminal 22w to the U-phase terminal 22u through the W-phase coil 23w and the U-phase coil 23u. In other words, the energized phases during the energizing period P4 are the W-phase and the U-phase.

[0029] In Figure 3, the energizing period P5 from time t14 to time t15 represents the period during which each arm switch is switched based on the energizing pattern PA5. During this energizing period P5, the V-phase upper arm switch Q VH and U-phase lower arm switch Q UL The switch turns ON, and the remaining arm switches turn OFF. During the power-on period P5, the V-phase upper arm switch Q VH Only the switching is controlled with a predetermined switching duty cycle. During the energizing period P5, power supply current flows from the V-phase terminal 22v to the U-phase terminal 22u through the V-phase coil 23v and the U-phase coil 23u. In other words, the energized phases during the energizing period P5 are the V-phase and the U-phase.

[0030] In Figure 3, the energizing period P6 from time t15 to time t16 represents the period during which each arm switch is switched based on the energizing pattern PA6. During this energizing period P6, the V-phase upper arm switch Q VH And W-phase lower arm switch Q WL The switch turns ON, and the remaining arm switches turn OFF. Even during the power-on period P6, the V-phase upper arm switch Q VH Only the switching is controlled with a predetermined switching duty cycle. During the energizing period P6, power supply current flows from the V-phase terminal 22v to the W-phase terminal 22w through the V-phase coil 23v and the W-phase coil 23w. In other words, the energized phases during the energizing period P6 are the V-phase and the W-phase.

[0031] According to the six energization patterns described above, each arm switch is switched and controlled, generating a rotating magnetic field that rotates the shaft 21 of the three-phase motor 20 360° in a constant direction. As a result, during the period from time t10 to time t16, the shaft 21 of the three-phase motor 20 rotates 360° in a constant direction. In other words, during each of the energization periods P1 to P6, the shaft 21 of the three-phase motor 20 rotates 60° in a constant direction.

[0032] The speed at which the energization pattern switches, that is, the speed at which the energized phase switches, is called the commutation frequency Fs. The unit of commutation frequency Fs is "Hz". When the period during which switching control is performed in one energization pattern is P (seconds), the commutation frequency Fs is expressed as "Fs = 1 / P".

[0033] Figure 3 shows the voltage waveforms appearing at the U-phase terminal 22u, V-phase terminal 22v, and W-phase terminal 22w of the three-phase motor 20. In Figure 3, "Vu" is the U-phase terminal voltage appearing at the U-phase terminal 22u. "Vv" is the V-phase terminal voltage appearing at the V-phase terminal 22v. "Vw" is the W-phase terminal voltage appearing at the W-phase terminal 22w. Note that the actual waveforms of the U-phase terminal voltage Vu, V-phase terminal voltage Vv, and W-phase terminal voltage Vw have the same duty cycle as the switching duty cycle, but for convenience, only the envelopes of the voltage waveforms are shown in Figure 3.

[0034] The U-phase terminal voltage Vu is the effective voltage value determined by the switching duty cycle during energization periods P1 and P2, and becomes the ground level value, i.e., 0V, during energization periods P4 and P5. The V-phase terminal voltage Vv is the effective voltage value determined by the switching duty cycle during energization periods P5 and P6, and becomes 0V during energization periods P2 and P3. The W-phase terminal voltage Vw is the effective voltage value determined by the switching duty cycle during energization periods P3 and P4, and becomes 0V during energization periods P1 and P6. In this way, in the sensorless 120° energization method, the phase to which the drive voltage required to drive the three-phase motor 20 is applied switches every 120°.

[0035] During the energizing period P3, no drive current flows through the U-phase coil 23u, but the energy stored in the U-phase coil 23u drives the U-phase lower arm switch Q. UL A return current flows through the body diode to the U-phase coil 23u for a certain period of time. As a result, a ringing phenomenon occurs where the U-phase terminal voltage Vu becomes 0V for a certain period of time from the start of period P3. After that, the U-phase terminal voltage Vu matches the induced voltage generated in the U-phase coil 23u. During the energizing period P3, the induced voltage is the voltage at the neutral point N, which is the neutral point voltage V, at the midpoint of the energizing period P3, that is, when the three-phase motor 20 has rotated 30° from the start of the energizing period P3. N It intersects from the high-pressure side to the low-pressure side.

[0036] Similarly, during the energizing period P6, no drive current flows through the U-phase coil 23u, but the energy stored in the U-phase coil 23u drives the U-phase upper arm switch Q. UH A return current flows through the body diode to the U-phase coil 23u for a certain period of time. As a result, the U-phase terminal voltage Vu is the DC power supply voltage V for a certain period of time from the start of the energizing period P6. M A ringing phenomenon occurs. Subsequently, the U-phase terminal voltage Vu matches the induced voltage generated in the U-phase coil 23u. During the energizing period P6, the induced voltage is equal to the neutral point voltage V at the midpoint of the energizing period P6, that is, when the three-phase motor 20 has rotated 30° from the start of the energizing period P6. N It intersects from the low-pressure side to the high-pressure side.

[0037] As described above, while the three-phase motor 20 rotates 360°, an induced voltage is exposed at the U-phase terminal 22u only during energized periods P3 and P6. Similarly, while the three-phase motor 20 rotates 360°, an induced voltage is exposed at the V-phase terminal 22v only during energized periods P1 and P4, and an induced voltage is exposed at the W-phase terminal 22w only during energized periods P2 and P5. In the sensorless 120° energized system, the neutral point voltage V is used to detect the phase of the three-phase motor 20. N It is necessary to detect the zero-crossing point, which is the point where the voltage and the induced voltage intersect.

[0038] In Figure 3, "Zu" is the induced voltage exposed at the U-phase terminal 22u, which is the neutral point voltage V. N The voltage becomes low at the following timing, and the induced voltage exposed at the U-phase terminal 22u is the neutral point voltage V. N This is a U-phase zero-crossing point detection signal that becomes high level at the timing when the voltage increases further. "Zv" is the induced voltage exposed at the V-phase terminal 22V, which corresponds to the neutral point voltage V N The voltage becomes low at the following timing, and the induced voltage exposed at the V-phase terminal 22V is the neutral point voltage V. N This is a V-phase zero-crossing point detection signal that becomes high level at the timing when the voltage increases further. "Zw" is the induced voltage exposed at the W-phase terminal 22w that corresponds to the neutral point voltage V. N The voltage becomes low at the following timing, and the induced voltage exposed at the W-phase terminal 22w is the neutral point voltage V. N This is a W-phase zero-crossing point detection signal that becomes high level at the timing when the signal becomes even higher.

[0039] In Figure 3, "Hu" is the U-phase phase detection signal, which has a 30° phase delay over the U-phase zero-crossing point detection signal Zu. "Hv" is the V-phase phase detection signal, which has a 30° phase delay over the V-phase zero-crossing point detection signal Zv. "Hw" is the W-phase phase detection signal, which has a 30° phase delay over the W-phase zero-crossing point detection signal Zw.

[0040] Furthermore, the three-phase motor 20 rotates 60° in the time between two adjacent zero-crossing points on the time axis. Therefore, by measuring the time between two adjacent zero-crossing points on the time axis and delaying the U-phase zero-crossing point detection signal Zu by half the time of that measurement, a U-phase phase detection signal Hu with a 30° phase delay relative to the U-phase zero-crossing point detection signal Zu can be generated. The V-phase phase detection signal Hv and the W-phase phase detection signal Hw can be generated in the same manner.

[0041] As shown in Figure 3, the levels of the U-phase phase detection signal Hu, the V-phase phase detection signal Hv, and the W-phase phase detection signal Hw change regularly depending on the six energization patterns. Hereafter, the patterns in which the levels of the U-phase phase detection signal Hu, the V-phase phase detection signal Hv, and the W-phase phase detection signal Hw change depending on the energization pattern will be referred to as phase patterns. As shown in Figure 2, the phase patterns of the sensorless 120° energization method include six phase patterns PB1, PB2, PB3, PB4, PB5, and PB6. In Figure 2, "H U "H V " and "H W In the column, "1" and "0" indicate that the corresponding phase detection signal is at a high level, and "0" indicates that the corresponding phase detection signal is at a low level.

[0042] In the sensorless 120° energization method, the phase pattern is recognized for each energization period based on three phase detection signals Hu, Hv, and Hw. Based on the recognition result of the phase pattern, the energization pattern to be used for the next energization period is determined. Then, the energization pattern is switched to the next energization pattern at the timing when the phase pattern changes.

[0043] As shown in Figure 3, for example, during the energizing period P1, the phase pattern for the energizing period P1 is recognized as phase pattern PB1 from the phase detection signals Hu, Hv, and Hw. Since the phase pattern for the energizing period P1 is phase pattern PB1, energizing pattern PA2 is determined to be the energizing pattern used in the next energizing period P2. Then, at the timing when phase pattern PB1 changes, that is, when a falling edge occurs in the V-phase phase detection signal Hv, the energizing pattern is switched from energizing pattern PA1 to energizing pattern PA2.

[0044] In the sensorless 120° energization method, the switching of the energization patterns described above is performed at 60° intervals in synchronization with the phase detection signals Hu, Hv, and Hw generated using the induced voltage generated in the three-phase motor 20, thereby enabling rotational control of the three-phase motor 20 without the need for position sensors such as Hall sensors. Hereinafter, the process of controlling the energization of the three-phase motor 20 in synchronization with the phase detection signals Hu, Hv, and Hw generated using the induced voltage generated in the three-phase motor 20 will be referred to as "sensorless synchronous control".

[0045] The above is the basic principle of the sensorless 120° energization method. As can be understood from the above explanation, in order to generate the phase detection signals Hu, Hv, and Hw in the sensorless 120° energization method, the neutral point voltage V of the three-phase motor 20 is used. N It is necessary to detect the zero-crossing point, which is the point where the voltage and the induced voltage intersect.

[0046] Figure 4 shows the waveforms of the induced voltages appearing at the three-phase terminal voltages Vu, Vv, and Vw when sensorless synchronous control of the three-phase motor 20 is performed with a high duty cycle. In Figure 3, only the envelope of the voltage waveform is shown for convenience, but as shown in Figure 4, the waveform of the induced voltage actually observed has the same duty cycle as the output duty cycle (switching duty cycle) for the three-phase motor 20.

[0047] In Figure 4, waveform W0 is the waveform of the induced voltage obtained by theoretical calculation. That is, waveform W0 is a waveform that shows the time change of the theoretical voltage value of the induced voltage. Hereafter, waveform W0 will be referred to as the "theoretical waveform W0 of the induced voltage". As shown in Figure 4, the theoretical waveform W0 of the induced voltage is a rectangular waveform.

[0048] Furthermore, in Figure 4, waveform W1 is the waveform of the induced voltage detected by the motor control device 10. The three-phase terminal voltages Vu, Vv, and Vw input to the motor control device 10 are converted into digital data via an A / D converter. In this specification, the digital data obtained from hardware such as the A / D converter built into the motor control device 10 is referred to as the "detected value." That is, waveform W1 is a waveform that shows the temporal change of the detected value of the induced voltage. Hereafter, waveform W1 will be referred to as the "detected waveform W1 of the induced voltage."

[0049] As shown in Figure 4, when sensorless synchronous control of the three-phase motor 20 is performed with a high duty cycle, the detected waveform W1 of the induced voltage closely matches the theoretical waveform W0. In this case, the neutral point voltage V of the three-phase motor 20 N Since the detection timing of the zero-crossing point where the induced voltage intersects closely matches the ideal timing, sensorless control of the three-phase motor 20 can be performed stably.

[0050] Figure 5 shows the waveforms of the induced voltages appearing at the three-phase terminal voltages Vu, Vv, and Vw when sensorless synchronous control of the three-phase motor 20 is performed with a low duty cycle. As shown in Figure 5, when sensorless synchronous control of the three-phase motor 20 is performed with a low duty cycle, the detected waveform W1 of the induced voltage becomes a waveform with significant distortion compared to the theoretical waveform W0 due to the response delay of the hardware in the motor control device 10.

[0051] In other words, if sensorless synchronous control of the three-phase motor 20 is performed with a low duty cycle, the detected values ​​of the induced voltages appearing at each of the three-phase terminal voltages Vu, Vv, and Vw may be lower than the theoretical voltage value by the amount of the offset voltage Vost. In this case, the neutral point voltage of the three-phase motor 20 V N The detection timing of the zero-crossing point where the induced voltage intersects may deviate from the ideal timing, potentially making it difficult to stably control the three-phase motor 20 without sensors.

[0052] The motor control device 10 of this embodiment has a configuration that solves the above technical problems. The following describes the first voltage detection circuit 12, the second voltage detection circuit 13, the control unit 14, and the memory unit 15 of the motor control device 10 of this embodiment, based on the basic principles and technical challenges of the sensorless 120° energization method described above.

[0053] The first voltage detection circuit 12 is a circuit that detects the terminal voltages of the three phases of the three-phase motor 20. The first voltage detection circuit 12 is electrically connected to the U-phase terminal 22u, V-phase terminal 22v, and W-phase terminal 22w of the three-phase motor 20. As an example, the first voltage detection circuit 12 is configured as a resistive voltage divider circuit. The first voltage detection circuit 12 outputs the voltage at the U-phase terminal 22u to the control unit 14 as the U-phase terminal voltage Vu. The first voltage detection circuit 12 outputs the voltage at the V-phase terminal 22v to the control unit 14 as the V-phase terminal voltage Vv. The first voltage detection circuit 12 outputs the voltage at the W-phase terminal 22w to the control unit 14 as the W-phase terminal voltage Vw.

[0054] The second voltage detection circuit 13 detects the DC power supply voltage V input to the drive circuit 11. M This is a circuit for detecting the voltage. As an example, the second voltage detection circuit 13 is a resistive voltage divider circuit including a first resistive element 13a and a second resistive element 13b. One end of the first resistive element 13a is electrically connected to the positive terminal of the DC power supply 200. The other end of the first resistive element 13a is electrically connected to one end of the second resistive element 13b and to the control unit 14. The other end of the second resistive element 13b is electrically connected to the negative terminal of the DC power supply 200. The second voltage detection circuit 13 detects the voltage Vin across the terminals of the second resistive element 13b as the DC power supply voltage V M This is output to the control unit 14.

[0055] The control unit 14 is a microprocessor, such as an MCU (Microcontroller Unit). The control unit 14 receives a rotation speed command signal CS output from a higher-level control unit (not shown). The rotation speed command signal CS is a signal that instructs the target rotation speed of the three-phase motor 20. The control unit 14 is connected to the storage unit 15 via a communication bus (not shown) so as to be able to communicate. As will be described in detail later, the control unit 14 executes a process to rotate the three-phase motor 20 at the target rotation speed instructed by the rotation speed command signal CS, according to a program pre-stored in the storage unit 15.

[0056] The control unit 14 incorporates multiple A / D converters. The three-phase terminal voltages Vu, Vv, and Vw input to the control unit 14 from the first voltage detection circuit 12, and the DC power supply voltage V input to the control unit 14 from the second voltage detection circuit 13, are used. M These are each converted into digital data via an A / D converter. The control unit 14 acquires the digital data obtained from the A / D converter as detected values ​​of the three-phase terminal voltages Vu, Vv, and Vw, and also the DC power supply voltage V M This will be obtained as the detected value.

[0057] The control unit 14 detects the point where the first voltage value Vobs, which is the detected value of each of the three-phase terminal voltages Vu, Vv, and Vw, intersects a predetermined zero-crossing determination level as a zero-crossing point, and controls the drive circuit 11 based on the detection result of the zero-crossing point. The zero-crossing determination level is the neutral point voltage V of the three-phase motor 20. N (=V M ( / 2)

[0058] In this embodiment, in order to solve the above technical problems, the control unit 14 corrects the first voltage value Vobs by multiplying it by a first coefficient K1 that is inversely proportional to the output duty cycle Dout when the output duty cycle Dout for the three-phase motor 20 is below a predetermined threshold. For example, when the output duty cycle Dout is below a first threshold Dth1, the control unit 14 calculates the first coefficient K1 by multiplying the value obtained by subtracting the output duty cycle Dout from the first threshold Dth1 by a first correction value G1. The first coefficient K1 is expressed by the following equation (1). As an example, the first threshold Dth1 is 20%. K1 = (Dth1 - Dout) × G1 …(1)

[0059] Furthermore, in this embodiment, the control unit 14 controls the DC power supply voltage V M The first voltage value Vobs is corrected by multiplying the first voltage value Vobs by a second coefficient K2, which is proportional to the detected second voltage value Vin, and the first coefficient K1 described above. For example, the control unit 14 calculates the second coefficient K2 by multiplying the second voltage value Vin by a third correction value G3. The second coefficient K2 is expressed by the following equation (2). K2 = Vin × G3 …(2)

[0060] In other words, in this embodiment, the control unit 14 corrects the first voltage value Vobs based on the following equation (3) when the output duty cycle Dout is less than or equal to the first threshold Dth1. In the following equation (3), Vcal is the corrected first voltage value Vobs. Vcal = Vobs × K² × K¹ ​​…(3)

[0061] As explained using Figures 4 and 5, when the output duty cycle Dout for the three-phase motor 20 is below a predetermined threshold, the first voltage values ​​Vobs, which are the detected values ​​of the three-phase terminal voltages Vu, Vv, and Vw, respectively, become lower than the ideal voltage value by the offset voltage Vost due to the response delay of the hardware in the motor control device 10. In this case, by multiplying the first voltage value Vobs by a first coefficient K1 that is inversely proportional to the output duty cycle Dout, the first voltage value Vobs can be increased as the output duty cycle Dout decreases, bringing it closer to the ideal voltage value.

[0062] Furthermore, the ideal voltage value of the first voltage value Vobs is the DC power supply voltage V M It increases proportionally to the DC power supply voltage V. Therefore, in addition to the first coefficient K1, the DC power supply voltage V is also a factor. M By multiplying the first voltage value Vobs by a second coefficient K2, which is proportional to the detected second voltage value Vin, the first voltage value Vobs can be brought more accurately closer to the ideal voltage value. As a result, the detection timing of the zero-crossing point, where the first voltage values ​​Vobs(Vcal), which are the detected values ​​of the three-phase terminal voltages Vu, Vv, and Vw respectively, intersect with the zero-crossing judgment level, can be made to almost match the ideal timing, enabling accurate switching of the energization pattern at 60° intervals.

[0063] The first correction value G1 and the third correction value G3 are values ​​determined in advance through experiments or simulations. The first correction value G1 and the third correction value G3 are stored in the memory unit 15 beforehand. For example, the first correction value G1 is a value of 1 or greater, and the third correction value G3 is a value of 0 or greater but less than 1.

[0064] The control unit 14 generates a U-phase zero-crossing point detection signal Zu based on the detection result of the zero-crossing point where the first voltage value Vobs of the U-phase terminal voltage Vu intersects with the zero-crossing determination level, and generates a U-phase phase detection signal Hu which has a phase delay of 30° with respect to the U-phase zero-crossing point detection signal Zu. Furthermore, the control unit 14 generates a V-phase zero-crossing point detection signal Zv based on the detection result of the zero-crossing point where the first voltage value Vobs of the V-phase terminal voltage Vv intersects with the zero-crossing determination level, and generates a V-phase phase detection signal Hv which has a phase delay of 30° with respect to the V-phase zero-crossing point detection signal Zv. Furthermore, the control unit 14 generates a W-phase zero-crossing point detection signal Zw based on the detection result of the zero-crossing point where the first voltage value Vobs of the W-phase terminal voltage Vw intersects with the zero-crossing determination level, and generates a W-phase phase detection signal Hw which has a phase delay of 30° with respect to the W-phase zero-crossing point detection signal Zw.

[0065] The control unit 14 switches the energization pattern based on the phase detection signals Hu, Hv, and Hw, and determines the output duty cycle (switching duty cycle) Dout necessary to match the actual rotational speed of the three-phase motor 20 to the target rotational speed. The control unit 14 then controls the switching of each arm switch with the determined output duty cycle Dout. As a result, a three-phase AC voltage that matches the actual rotational speed of the motor 20 to the target rotational speed is supplied from the drive circuit 11 to the three-phase motor 20.

[0066] The memory unit 15 includes a non-volatile memory that stores programs and various setting data necessary for the control unit 14 to execute various processes, and a volatile memory that is used as a temporary storage location for data when the control unit 14 executes various processes. The non-volatile memory is, for example, EEPROM (Electrically Erasable Programmable Read-Only Memory) or flash memory. The volatile memory is, for example, RAM (Random Access Memory).

[0067] The memory unit 15 stores various data necessary for controlling the three-phase motor 20 using a sensorless 120° energizing method. For example, the memory unit 15 pre-stores the energizing pattern and phase pattern shown in Figure 2. The memory unit 15 also pre-stores the first correction value G1 and the third correction value G3.

[0068] Next, the operation of the motor control device 10 configured as described above will be explained. Figure 6 is a flowchart showing each process included in motor control performed by the control unit 14. After power-on, when the control unit 14 is instructed to reach a target rotational speed by a rotational speed command signal CS input from a higher-level control device, it starts the motor control process shown in Figure 6.

[0069] As shown in Figure 6, when the control unit 14 starts motor control while the three-phase motor 20 is stopped, it first aligns the rotor of the three-phase motor 20 (step S1), and after the rotor alignment is completed, it starts forced commutation control of the three-phase motor 20 (step S2).

[0070] When starting a three-phase motor 20 using a sensorless 120° energization method, the control unit 14 cannot generate phase detection signals Hu, Hv, and Hw until the rotational speed of the three-phase motor 20 reaches the minimum limit rotational speed at which an induced voltage capable of detecting the zero-crossing point is generated. Therefore, sensorless synchronous control cannot be performed. For this reason, when starting a three-phase motor 20 using a sensorless 120° energization method, it is necessary to control the energization of the three-phase motor 20 according to a predetermined starting sequence until the rotational speed of the three-phase motor 20 reaches the minimum limit rotational speed.

[0071] As an example of a startup sequence, a commonly known startup sequence involves aligning the rotor of a three-phase motor 20 to a specific position (a position corresponding to one of the motor control states) by applying DC excitation for a predetermined time, and then performing forced commutation control by forcibly switching the energized phase (energy flow pattern) at a predetermined forced commutation frequency while applying a predetermined drive voltage to the energized phase. Since the processes of steps S1 and S2 are included in the known startup sequence as described above, a detailed explanation will be omitted.

[0072] When forced commutation control is initiated, the rotational speed of the three-phase motor 20 gradually increases toward the rotational speed corresponding to the forced commutation frequency. When forced commutation control is initiated, the control unit 14 detects the terminal voltage of the phase in which an induced voltage appears during the current energization period, which is the first voltage value Vobs, and the DC power supply voltage V M The second voltage value Vin, which is the detected value, is obtained (step S3).

[0073] Then, the control unit 14 determines whether the output duty cycle Dout during the current energization period is less than or equal to the first threshold Dth1 (step S4). If the output duty cycle Dout during the current energization period is less than or equal to the first threshold Dth1 (step S4: Yes), the control unit 14 corrects the first voltage value Vobs obtained in step S3 based on equations (1), (2), and (3) above (step S5).

[0074] Specifically, in step S5, the control unit 14 calculates the first coefficient K1 by substituting the output duty cycle Dout during the current energization period, the first threshold Dth1, and the first correction value G1 stored in the storage unit 15 into equation (1). The control unit 14 also calculates the second coefficient K2 by substituting the second voltage value Vin obtained in step S3 and the third correction value G3 stored in the storage unit 15 into equation (2). Then, the control unit 14 calculates the corrected first voltage value Vobs(Vcal) by substituting the first voltage value Vobs obtained in step S3, the first coefficient K1, and the second coefficient K2 into equation (3).

[0075] After executing the process in step S5, the control unit 14 proceeds to step S6. On the other hand, if the output duty cycle Dout during the current energization period is greater than the first threshold Dth1 (step S4: No), the control unit 14 skips step S5 and proceeds to step S6.

[0076] The control unit 14 starts a process to detect zero-crossing points where the first voltage value Vobs, which is the detected terminal voltage of the phase in which an induced voltage appears during the current energization period, intersects with the zero-crossing determination level, and determines whether or not zero-crossing points have been detected n times consecutively (step S6). n is an integer of 2 or more. The control unit 14 then starts the process of generating zero-crossing point detection signals Zu, Zv, and Zw for each phase based on the detection results of the zero-crossing points of each phase, and the process of generating phase detection signals Hu, Hv, and Hw for each phase based on the zero-crossing point detection signals Zu, Zv, and Zw for each phase.

[0077] After the forced commutation control is initiated, when the rotational speed of the three-phase motor 20 reaches the minimum limit rotational speed, relatively large induced voltages begin to appear in the terminal voltages Vu, Vv, and Vw of each phase, and zero-crossing points begin to be detected. If it is determined in step S6 that zero-crossing points have been detected n times consecutively, it is estimated that the three-phase motor 20 has started to rotate stably at a rotational speed above the minimum limit rotational speed.

[0078] If the answer in step S6 is "No," that is, if the number of consecutive zero-crossing point detections is less than n, it is presumed that the three-phase motor 20 has not yet started rotating stably at a rotational speed equal to or greater than the minimum limit rotational speed. In this case, the control unit 14 returns to the process in step S3.

[0079] On the other hand, if the answer in step S6 is "Yes," that is, if the number of consecutive zero-crossing point detections reaches n, it is estimated that the three-phase motor 20 has started to rotate stably at a rotational speed above the minimum limit rotational speed. In this case, the control unit 14 recognizes the phase pattern of the current energization period based on the phase detection signals Hu, Hv, and Hw, and determines the energization pattern to be used in the next energization period based on the recognition result of the phase pattern (step S7).

[0080] For example, as shown in Figure 3, let's assume that the number of consecutive zero-crossing detections has reached n times when a zero-crossing point is detected where the first voltage value Vobs, which is the detected value of the V-phase terminal voltage Vv where the induced voltage appears during the energizing period P1, intersects with the zero-crossing judgment level.

[0081] When the number of consecutive zero-crossing point detections during the energizing period P1 reaches n, the control unit 14 recognizes the phase pattern of the current energizing period P1 based on the phase detection signals Hu, Hv, and Hw. During the energizing period P1, the phase detection signals Hu and Hv are at a high level ("1"), and the phase detection signal Hw is at a low level ("0"). In this case, the control unit 14 recognizes that the phase pattern of the current energizing period P1 is PB1 by referring to the phase pattern stored in the memory unit 15 (see Figure 2).

[0082] The control unit 14 then determines the energizing pattern to be used in the next energizing period based on the recognition result of the phase pattern. For example, as described above, if the control unit 14 recognizes that the phase pattern of the current energizing period P1 is PB1, it refers to the energizing patterns stored in the storage unit 15 (see Figure 2) and determines that the energizing pattern PA2 should be used in the next energizing period.

[0083] After determining the energizing pattern to be used for the next energizing period, the control unit 14 switches the energizing pattern to the one determined in step S7 (step S8) when the level of any of the phase detection signals Hu, Hv, and Hw changes. For example, if the number of consecutive zero-crossing detections in the energizing period P1 reaches n times as described above, the level of the phase detection signal Hv changes from a high level to a low level when the three-phase motor 20 rotates 30° from the zero-crossing detection timing based on the induced voltage appearing in the V-phase terminal voltage Vv (see time t11 in Figure 3). Therefore, in this case, the control unit 14 switches the energizing pattern to the energizing pattern PA2 determined in step S7 at the timing when a falling edge occurs in the phase detection signal Hv (time t11).

[0084] Furthermore, along with switching the energization pattern, the control unit 14 determines the output duty cycle Dout necessary to match the actual rotational speed of the three-phase motor 20 to the target rotational speed, and controls the switching of each arm switch with the determined output duty cycle Dout. For example, when the energization pattern is switched to energization pattern PA2 as described above, the control unit 14 controls the U-phase upper arm switch Q UH and V-phase lower arm switch Q VL It controls the U-phase upper arm switch Q to turn on, and controls the remaining arm switches to turn off (see Figure 2). In the energization pattern PA2, the control unit 14 controls the U-phase upper arm switch Q UH Switching control is performed using only the determined output duty cycle Dout (see Figure 3). As a result, a three-phase AC voltage is supplied from the drive circuit 11 to the three-phase motor 20 that matches the actual rotational speed of the three-phase motor 20 to the target rotational speed.

[0085] Subsequently, the control unit 14 rotates the three-phase motor 20 at the target rotational speed by switching the energization pattern and controlling the switching of each arm switch at 60° intervals in synchronization with the phase detection signals Hu, Hv, and Hw. In this way, from step S7 onward, the control unit 14 starts sensorless synchronous control to control the three-phase motor 20 in synchronization with the phase detection signals Hu, Hv, and Hw.

[0086] When sensorless synchronous control is initiated, the rotational speed of the three-phase motor 20 gradually increases toward the target rotational speed. When sensorless synchronous control is initiated, the control unit 14 detects the terminal voltage of the phase in which an induced voltage appears during the current energization period, which is the first voltage value Vobs, and the DC power supply voltage V M The second voltage value Vin, which is the detected value, is obtained (step S9).

[0087] Then, the control unit 14 determines whether the output duty cycle Dout during the current energization period is less than or equal to the first threshold Dth1 (step S10). If the output duty cycle Dout during the current energization period is less than or equal to the first threshold Dth1 (step S10: Yes), the control unit 14 corrects the first voltage value Vobs obtained in step S9 based on equations (1), (2), and (3) above (step S11).

[0088] Specifically, in step S11, the control unit 14 calculates the first coefficient K1 by substituting the output duty cycle Dout during the current energization period, the first threshold Dth1, and the first correction value G1 stored in the storage unit 15 into equation (1). The control unit 14 also calculates the second coefficient K2 by substituting the second voltage value Vin obtained in step S9 and the third correction value G3 stored in the storage unit 15 into equation (2). Then, the control unit 14 calculates the corrected first voltage value Vobs(Vcal) by substituting the first voltage value Vobs obtained in step S9, the first coefficient K1, and the second coefficient K2 into equation (3).

[0089] After executing the process in step S11, the control unit 14 proceeds to step S12. On the other hand, if the output duty cycle Dout during the current energization period is greater than the first threshold Dth1 (step S10: No), the control unit 14 skips step S11 and proceeds to step S12.

[0090] The control unit 14 determines whether a zero-crossing point has been detected where the first voltage value Vobs, which is the detected terminal voltage of the phase in which an induced voltage appears during the current energization period, intersects with the zero-crossing determination level (step S12). If no zero-crossing point is detected (step S12: No), the control unit 14 returns to step S9. On the other hand, if a zero-crossing point is detected (step S12: Yes), the control unit 14 returns to step S7.

[0091] As described above, after sensorless synchronous control is initiated, the control unit 14 repeats the processes from step S7 to step S12, thereby supplying a three-phase AC voltage from the drive circuit 11 to the three-phase motor 20 that matches the actual rotational speed of the three-phase motor 20 to the target rotational speed. As a result, the rotational speed of the three-phase motor 20 reaches the target rotational speed.

[0092] As described above, the motor control device 10 in this embodiment uses a DC power supply voltage V M The system includes a drive circuit 11 that converts the current into a three-phase AC voltage and supplies it to a three-phase motor 20, a first voltage detection circuit 12 that detects the three-phase terminal voltages Vu, Vv, and Vw of the three-phase motor 20, and a control unit 14 that detects the point where the first voltage values ​​Vobs of the three-phase terminal voltages Vu, Vv, and Vw intersect with a predetermined zero-crossing determination level as a zero-crossing point, and controls the drive circuit 11 based on the detection result of the zero-crossing point. The control unit 14 corrects the first voltage value Vobs by multiplying the first voltage value Vobs by a first coefficient K1 that is inversely proportional to the output duty cycle Dout of the three-phase motor 20 when the output duty cycle Dout is below a predetermined threshold. When the output duty cycle Dout for the three-phase motor 20 is below a predetermined threshold, the first voltage values ​​Vobs, which are the detected values ​​of the three-phase terminal voltages Vu, Vv, and Vw, respectively, become lower than the ideal voltage value by an offset voltage Vost due to the response delay of the hardware in the motor control device 10. In this case, by multiplying the first voltage value Vobs by a first coefficient K1 that is inversely proportional to the output duty cycle Dout, the first voltage value Vobs can be increased as the output duty cycle Dout decreases, bringing it closer to the ideal voltage value. As a result, the zero-cross detection timing can be made to almost coincide with the ideal timing, and the energization pattern can be switched accurately at 60° intervals. Therefore, according to this embodiment, sensorless control of the three-phase motor 20 can be stably performed even when the three-phase motor 20 is rotated at a low duty cycle.

[0093] Furthermore, in this embodiment, the control unit 14 calculates a first coefficient K1 by multiplying the value obtained by subtracting the output duty cycle Dout from the first threshold Dth1 by a first correction value G1 when the output duty cycle Dout is less than or equal to the first threshold Dth1. By using the first coefficient K1 calculated in this way, the first voltage value Vobs can be brought closer to the ideal voltage value, thereby allowing the zero-cross detection timing to be matched more precisely to the ideal timing.

[0094] Furthermore, the motor control device 10 of this embodiment receives the DC power supply voltage V input to the drive circuit 11. M The control unit 14 further includes a second voltage detection circuit 13 for detecting the DC power supply voltage V M The first voltage value Vobs is corrected by multiplying the first voltage value Vobs by a second coefficient K2, which is proportional to the detected second voltage value Vin, and the first coefficient K1 mentioned above. The ideal voltage value of the first voltage value Vobs is the DC power supply voltage V M It increases proportionally to the DC power supply voltage V. Therefore, in addition to the first coefficient K1, the DC power supply voltage V is also a factor. M By multiplying the first voltage value Vobs by a second coefficient K2, which is proportional to the detected second voltage value Vin, the first voltage value Vobs can be brought closer to the ideal voltage value. As a result, the zero-cross detection timing can be matched more precisely to the ideal timing.

[0095] Furthermore, in this embodiment, the control unit 14 calculates the second coefficient K2 by multiplying the second voltage value Vin by the third correction value G3. By using the second coefficient K2 calculated in this way, the first voltage value Vobs can be brought closer to the ideal voltage value, thereby allowing the zero-cross detection timing to be matched more precisely to the ideal timing.

[0096] [Variation] The present invention is not limited to the embodiments described above, and the configurations described herein can be combined as appropriate, within the bounds of non-inconsistency.

[0097] In the above embodiment, a configuration was described in which the control unit 14 calculates the first coefficient K1 by multiplying the value obtained by subtracting the output duty cycle Dout from the first threshold Dth1 by a first correction value G1 when the output duty cycle Dout is less than or equal to the first threshold Dth1, but the present invention is not limited thereto.

[0098] For example, the control unit 14 may calculate the first coefficient K1 by multiplying the value obtained by subtracting the output duty cycle Dout from the first threshold Dth1 by the first correction value G1 when the output duty cycle Dout is less than or equal to the first threshold Dth1 and greater than the second threshold Dth2. Alternatively, the control unit 14 may calculate the first coefficient K1 by multiplying the value obtained by subtracting the output duty cycle Dout from the second threshold Dth2 by the second correction value G2 when the output duty cycle Dout is less than or equal to the second threshold Dth2.

[0099] The second threshold Dth2 is smaller than the first threshold Dth1. For example, the first threshold Dth1 is 20% and the second threshold Dth2 is 15%. The second correction value G2 is a value determined in advance by experiment or simulation. The second correction value G2 is stored in the memory unit 15 along with the first correction value G1 and the third correction value G3. For example, the second correction value G2 is a value of 1 or greater.

[0100] As described above, by calculating an appropriate first coefficient K1 corresponding to the output duty cycle Dout in both cases—when the output duty cycle Dout is less than or equal to the first threshold Dth1 and greater than the second threshold Dth2, and when the output duty cycle Dout is less than or equal to the second threshold Dth2—the first voltage value Vobs can be brought closer to the ideal voltage value in both cases, thereby allowing the zero-cross detection timing to be matched more precisely to the ideal timing.

[0101] In the above embodiment, an electric pump device 100 that supplies cooling oil F to a drive motor mounted on a hybrid vehicle was exemplified as an electric pump device of the present invention. However, the electric pump device of the present invention is not limited to this, and can be applied to, for example, an electric pump device that supplies oil to a transmission. Furthermore, the fluid discharged from the electric pump is not limited to oil such as cooling oil. In addition, the motor control device of the present invention may be used as a control device for controlling a three-phase motor mounted on a device other than an electric pump device.

[0102] Furthermore, this technology can be configured as follows: (1) A motor control device for controlling a three-phase motor, comprising: a drive circuit that converts a DC power supply voltage into a three-phase AC voltage and supplies it to the three-phase motor; a first voltage detection unit that detects the terminal voltages of the three phases of the three-phase motor; and a control unit that detects a point where the first voltage value, which is the detected value of the terminal voltage, intersects with a predetermined zero-crossing determination level as a zero-crossing point, and controls the drive circuit based on the detection result of the zero-crossing point, wherein the control unit corrects the first voltage value by multiplying the first voltage value by a first coefficient inversely proportional to the output duty cycle when the output duty cycle for the three-phase motor is less than or equal to a predetermined threshold. (2) The motor control device according to (1), wherein the control unit calculates the first coefficient by multiplying the value obtained by subtracting the output duty cycle from the first threshold by a first correction value when the output duty cycle is less than or equal to a first threshold. (3) The motor control device according to (1), wherein the control unit calculates the first coefficient by multiplying the value obtained by subtracting the output duty cycle from the first threshold by a first correction value when the output duty cycle is less than or equal to a first threshold and greater than a second threshold, and calculates the first coefficient by multiplying the value obtained by subtracting the output duty cycle from the second threshold by a second correction value when the output duty cycle is less than or equal to a second threshold. (4) A motor control device according to any one of (1) to (3), further comprising a second voltage detection unit for detecting the DC power supply voltage input to the drive circuit, wherein the control unit corrects the first voltage value by multiplying the first voltage value by a second coefficient proportional to the second voltage value which is the detected value of the DC power supply voltage and the first coefficient. (5) The motor control device according to (4), wherein the control unit calculates the second coefficient by multiplying the second voltage value by a third correction value. (6) An electric pump device comprising a three-phase motor having a shaft, a pump located on one axial side of the shaft and driven by the three-phase motor via the shaft, and a motor control device according to any one of (1) to (5) for controlling the three-phase motor.

[0103] The configurations described herein can be combined as appropriate, provided they are not contradictory. [Explanation of symbols]

[0104] 10...Motor control device, 11...Drive circuit, 12...First voltage detection circuit (first voltage detection unit), 13...Second voltage detection circuit (second voltage detection unit), 14...Control unit, 15...Storage unit, 20...Three-phase motor, 30...Pump, 40...Electric pump, 100...Electric pump device, 200...DC power supply, F...Cooling oil

Claims

1. A motor control device for controlling a three-phase motor, A drive circuit that converts a DC power supply voltage into a three-phase AC voltage and supplies it to the three-phase motor, A first voltage detection unit for detecting the terminal voltages of the three phases of the three-phase motor, A control unit detects the point at which the first voltage value, which is the detected value of the terminal voltage, intersects with a predetermined zero-crossing determination level, and controls the drive circuit based on the detection result of the zero-crossing point. Equipped with, The control unit corrects the first voltage value by multiplying it by a first coefficient inversely proportional to the output duty cycle when the output duty cycle for the three-phase motor is below a predetermined threshold. The control unit calculates the first coefficient by multiplying the value obtained by subtracting the output duty cycle from the first threshold by a first correction value when the output duty cycle is less than or equal to a first threshold. Motor control device.

2. A motor control device for controlling a three-phase motor, A drive circuit that converts a DC power supply voltage into a three-phase AC voltage and supplies it to the three-phase motor, A first voltage detection unit for detecting the terminal voltages of the three phases of the three-phase motor, A control unit detects the point at which the first voltage value, which is the detected value of the terminal voltage, intersects with a predetermined zero-crossing determination level, and controls the drive circuit based on the detection result of the zero-crossing point. Equipped with, The control unit corrects the first voltage value by multiplying it by a first coefficient inversely proportional to the output duty cycle when the output duty cycle for the three-phase motor is below a predetermined threshold. The control unit, If the output duty cycle is less than or equal to a first threshold and greater than a second threshold, the first coefficient is calculated by multiplying the value obtained by subtracting the output duty cycle from the first threshold by a first correction value. When the output duty cycle is less than or equal to the second threshold, the first coefficient is calculated by multiplying the value obtained by subtracting the output duty cycle from the second threshold by the second correction value. Motor control device.

3. The drive circuit further comprises a second voltage detection unit for detecting the DC power supply voltage input to the drive circuit, The control unit corrects the first voltage value by multiplying the first voltage value by a second coefficient, which is proportional to the detected value of the DC power supply voltage, and the first coefficient. The motor control device according to claim 1 or 2.

4. The motor control device according to claim 3, wherein the control unit calculates the second coefficient by multiplying the second voltage value by a third correction value.

5. A three-phase motor having a shaft, A pump located on one axial side of the shaft and driven via the shaft by the three-phase motor, A motor control device according to claim 1 or 2 for controlling the three-phase motor, An electric pump device equipped with the following features.

Images