Motor control device and electric pump device

Abstract

A motor control device and an electric pump device are provided. The motor control device controls a three-phase motor, and has a drive circuit that converts a direct-current power supply voltage into a three-phase alternating-current voltage and supplies the three-phase motor, a current detection section that detects a power supply current flowing in the drive circuit, a voltage detection section that detects terminal voltages of the three phases of the three-phase motor, and a control section that detects points at which induced voltages respectively appearing in the terminal voltages of the three phases cross a prescribed zero-crossing determination level as zero-crossing points, controls the drive circuit in accordance with a detection result of the zero-crossing points, and changes a value of the zero-crossing determination level in accordance with a power supply current value detected by the current detection section.

Description

Technical Field

[0001] This invention relates to motor control devices and electric pump devices. Background Technology

[0002] As a control method for sensorless motors, the following sensorless control is known: 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-crossing point, and the motor's energization is controlled based on the detection result of the zero-crossing point. Patent Document 1 discloses a technique for stably driving a sensorless motor in the low-speed range.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2010-273502

[0004] In low-temperature environments, when a sensorless motor is controlled at a speed close to the minimum required to generate an induced voltage capable of detecting zero crossings, the waveform of the induced voltage becomes distorted due to its dependence on the power supply current. This causes the timing of zero-crossing detection to deviate from the ideal timing, making stable sensorless control of the motor potentially difficult. The technology described in Patent Document 1 fails to address this technical challenge. Summary of the Invention

[0005] One aspect of the present invention is a motor control device that controls a three-phase motor, wherein the motor control device comprises: a drive circuit that converts a DC power supply voltage into a three-phase AC voltage and provides it to the three-phase motor; a current detection unit that detects the power supply current flowing in the drive circuit; a 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 where the induced voltage appearing in the three-phase terminal voltages 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 changes the value of the zero-crossing determination level based on the power supply current value detected by the current detection unit.

[0006] One aspect of the present invention is 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 of the above-described manner for controlling the three-phase motor.

[0007] According to the above-described manner of the present invention, a motor control device and an electric pump device are provided that can stably perform sensorless control of the motor even when the motor is rotated at a speed close to the minimum limit speed in a low-temperature environment. Attached Figure Description

[0008] Figure 1This is a block diagram schematically showing an electric pump device 100 having the motor control device 10 of this embodiment.

[0009] Figure 2 This is a diagram illustrating an example of the power-on mode and phase mode used in the sensorless 120° power-on method according to this embodiment.

[0010] Figure 3 This is a timing diagram illustrating the basic principle of the sensorless 120° energization method in this embodiment.

[0011] Figure 4 It is shown schematically in Figure 3 The first figure shows the waveform of the induced voltage exposed at the U-phase terminal 22u in P3 during the energization period.

[0012] Figure 5 It is shown schematically in Figure 3 The second figure shows the waveform of the induced voltage exposed at the U-phase terminal 22u in P3 during the energization period.

[0013] Figure 6 This is a flowchart showing the processes included in the extremely low-speed rotation control of the three-phase motor 20 executed by the control unit 14 in a low-temperature environment.

[0014] Label Explanation

[0015] 10: Motor control unit; 11: Drive circuit; 12: Shunt resistor (current detection unit); 13: Voltage detection circuit (voltage detection unit); 14: Control unit; 15: Storage unit; 20: Three-phase motor; 30: Pump; 40: Electric pump; 100: Electric pump unit; 200: DC power supply; F: Cooling oil. Detailed Implementation

[0016] Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0017] Figure 1 This is a block diagram schematically showing an electric pump device 100 having the motor control device 10 of this embodiment. Figure 1 As shown, the electric pump unit 100 includes a motor control unit 10 and an electric pump 40. The electric pump 40 includes a three-phase motor 20 and a pump 30. The electric pump unit 100 is, for example, a device that supplies cooling oil F to the drive motor of a hybrid vehicle.

[0018] The motor control device 10 is a device that controls the three-phase motor 20 of the electric pump 40 without the need for position sensors such as Hall sensors. Specifically, the motor control device 10 detects the point where the induced voltage appearing in the three-phase terminal voltages of the three-phase motor 20 intersects with a predetermined zero-crossing threshold 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 regarding the motor control device 10 will be explained later.

[0019] The three-phase motor 20 is, for example, an internal rotor type three-phase brushless DC motor, and is a sensorless motor without position sensors such as Hall sensors. 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.

[0020] In addition, although Figure 1 The diagram is omitted, but the three-phase motor 20 has a motor housing and a rotor and stator housed within the motor housing. The rotor is a rotating body supported by bearing components inside the motor housing. The stator is fixed inside the motor housing in a manner that surrounds the outer circumference of the rotor, generating the electromagnetic force required to rotate the rotor.

[0021] Shaft 21 is a shaft-like body coaxially engaged with the rotor while extending radially inward along the rotor. The U-phase terminal 22u, V-phase terminal 22v, and W-phase terminal 22w are exposed metal terminals on the surface of the motor housing. These terminals are electrically connected to the drive circuit 11 of the motor control device 10, as detailed later. The U-phase coil 23u, V-phase coil 23v, and W-phase coil 23w are excitation coils installed on the stator. They are connected in a star configuration inside the three-phase motor 20.

[0022] 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 energizing states of the U-phase coil 23u, V-phase coil 23v, and W-phase coil 23w are controlled by the motor control device 10, thereby generating the electromagnetic force required to rotate the rotor. As the rotor rotates, the shaft 21 also rotates synchronously with the rotor.

[0023] Pump 30 is located on one axial side of shaft 21 of three-phase motor 20 and is driven by three-phase motor 20 via shaft 21. Pump 30 is driven by three-phase motor 20, thereby discharging cooling oil F. Pump 30 has oil inlet 31 and oil outlet 32. After being drawn into the interior of pump 30 through oil inlet 31, cooling oil F is discharged to the outside of pump 30 through oil outlet 32. Thus, by connecting pump 30 and three-phase motor 20 axially adjacent to each other on shaft 21, an electric pump 40 is constituted.

[0024] The motor control unit 10 is a device that controls the three-phase motor 20 without a position sensor based on a speed command signal CS output from a host control unit (not shown). As an example, the host control unit is an onboard ECU (Electronic Control Unit) in a hybrid vehicle. The motor control unit 10 includes a drive circuit 11, a shunt resistor 12 (current detection unit), a voltage detection circuit 13 (voltage detection unit), a control unit 14, and a storage unit 15.

[0025] The drive circuit 11 converts the DC power supply voltage V M The circuit converts the DC voltage to three-phase AC voltage and supplies it to the three-phase motor 20. The drive circuit 11 draws the DC power supply voltage V from the DC power supply 200. M It is converted to three-phase AC voltage and output to the three-phase motor 20. As an example, the DC power supply 200 is one of several batteries installed in a hybrid vehicle, for instance, providing a 12V DC power supply voltage V to a 12V-based vehicle system. M .

[0026] The drive circuit 11 has a U-phase upper arm switch Q UH V-phase upper arm switch Q VH W-phase upper arm switch Q WH U-phase lower side arm switch Q UL V-phase lower arm switch Q VL and the W-phase lower side arm switch Q WL In this embodiment, each arm switch is, for example, an N-channel MOS-FET.

[0027] U-phase upper arm switch Q UH The drain terminal, the upper arm switch of phase V, Q VH The drain terminal and the upper arm switch of phase W Q WH The drain terminals are electrically connected to the positive terminal of the DC power supply 200. The U-phase lower arm switch Q... UL The source extreme element, V-phase lower side arm switch Q VL The source extreme element and the lower side arm switch Q of the W phase WLThe source terminals are electrically connected to the negative terminal of the DC power supply 200 via shunt resistor 12. Additionally, the negative terminal of the DC power supply 200 is electrically connected to the vehicle's grounding terminal.

[0028] U-phase upper arm switch Q UH The source terminal is connected to the U-phase terminal 22u of the three-phase motor 20 and the U-phase lower arm switch Q. UL The drain terminals are electrically connected respectively. The upper arm switch Q of phase V is connected. VH The source terminal is connected to the V-phase terminal 22V of the three-phase motor 20 and the V-phase lower arm switch Q. VL The drain terminals are electrically connected respectively. The upper arm switch Q of phase W is connected. WH The source terminal is connected to the W-phase terminal 22w of the three-phase motor 20 and the W-phase lower arm switch Q. WL The drain terminals are electrically connected respectively.

[0029] U-phase upper arm switch Q UH The gate terminal, the upper arm switch Q of the V phase VH The gate terminal and the upper arm switch Q of phase W WH The gate terminals are electrically connected to the control unit 14. Additionally, the lower arm switch Q of phase U is... UL The gate terminal, the lower arm switch of the V phase Q VL The gate terminal and the lower arm switch Q of phase W WL The gate terminals are also electrically connected to the control unit 14.

[0030] As described above, the drive circuit 11 is composed of a three-phase full-bridge circuit with three upper arm switches and three lower arm switches. The drive circuit 11, configured in this way, controls the switching of each arm switch via the control unit 14, and drives the DC power supply voltage V supplied by the DC power supply 200. M It is converted into three-phase AC voltage and output to the three-phase motor 20.

[0031] In this embodiment, a sensorless 120° energization method is illustrated as the energization method for the three-phase motor 20. For ease of explanation, the shunt resistor 12, voltage detection circuit 13, control unit 14, and storage unit 15 will be described below after explaining the basic principle of the sensorless 120° energization method. Furthermore, the basic principle of the sensorless 120° energization method described below is merely an example, and the present invention is not limited thereto.

[0032] When using a sensorless 120° power-on method, according to Figure 2 The power-on mode shown controls the switching of each arm switch. For example... Figure 2 As shown, the 120° energizing method includes six energizing modes: PA1, PA2, PA3, PA4, PA5, and PA6. In Figure 2 In the middle, from "Q" UH "to Q" WL In the column of “1” and “0”, “1” means that the corresponding arm switch is controlled to be turned on, and “0” means that the corresponding arm switch is controlled to be turned off.

[0033] exist Figure 3 In the diagram, the energizing period P1 from time t10 to time t11 represents the period during which each arm switch is controlled by the switch according to the energizing mode PA1. During this energizing period P1, the upper arm switch Q of phase U... UH and W-phase lower side arm switch Q WL The circuit is on, and the other arm switches are off. During the energizing period P1, only the upper arm switch Q of phase U is on. UH The switch is controlled by a specified duty cycle. During the energizing period P1, the drive current (power supply current) flows from the U-phase terminal 22u to the W-phase terminal 22w, and then to the U-phase coil 23u and the W-phase coil 23w. That is, the energized phases in P1 during the energizing period are the U-phase and the W-phase.

[0034] exist Figure 3 In the diagram, the energizing period P2 from time t11 to time t12 represents the period during which each arm switch is controlled by the switch according to the energizing mode PA2. During this energizing period P2, the upper arm switch Q of phase U... UH and V-phase lower side arm switch Q VL The circuit is on, and the other arm switches are off. During the energizing period, only the upper arm switch Q of phase U is active in P2. UH The switch is controlled by a specified duty cycle. During the energizing period P2, the drive current flows from the U-phase terminal 22u to the V-phase terminal 22v, and then to the U-phase coil 23u and the V-phase coil 23v. That is, the energized phases in P2 during the energizing period are the U-phase and the V-phase.

[0035] exist Figure 3 In the diagram, the energizing period P3 from time t12 to time t13 represents the period during which each arm switch is controlled by the switch according to the energizing mode PA3. During this energizing period P3, the upper arm switch Q of phase W... WH and V-phase lower side arm switch Q VL The circuit is on, and the other arm switches are off. During the energizing period, only the upper arm switch Q of phase W is on. WH The switch is controlled by a specified duty cycle. During the energizing period P3, the drive current flows from the W-phase terminal 22w to the V-phase terminal 22v, passing through the W-phase coil 23w and the V-phase coil 23v. That is, the energized phases in P3 during the energizing period are the W-phase and the V-phase.

[0036] exist Figure 3In the diagram, the energizing period P4 from time t13 to time t14 represents the period during which each arm switch is controlled by the switch according to the energizing mode PA4. During this energizing period P4, the upper arm switch Q of phase W... WH and U-phase lower side arm switch Q UL The circuit is on, and the other arm switches are off. During the energizing period, only the upper arm switch Q of phase W is active in phase P4. WH The switch is controlled by a specified duty cycle. During the energizing period P4, the drive current flows from the W-phase terminal 22w towards the U-phase terminal 22u to the W-phase coil 23w and the U-phase coil 23u. That is, the energizing phases in P4 during the energizing period are the W-phase and the U-phase.

[0037] exist Figure 3 In the diagram, the energizing period P5 from time t14 to time t15 represents the period during which each arm switch is controlled by the switch according to the energizing mode PA5. During this energizing period P5, the upper arm switch Q of phase V... VH and U-phase lower side arm switch Q UL The circuit is on, and the other arm switches are off. During the energizing period, only the upper arm switch Q of phase V is on. VH The switch is controlled by a specified duty cycle. During the energizing period P5, the power supply current flows from the V-phase terminal 22V to the U-phase terminal 22U, and then to the V-phase coil 23V and the U-phase coil 23U. That is, the energized phases in P5 during the energizing period are the V-phase and the U-phase.

[0038] exist Figure 3 In the diagram, the energizing period P6 from time t15 to time t16 represents the period during which each arm switch is controlled by the switch according to the energizing mode PA6. During this energizing period P6, the upper arm switch Q of phase V... VH and W-phase lower side arm switch Q WL The circuit is on, and the other arm switches are off. During the energizing period, only the upper arm switch Q of phase V is on. VH The switch is controlled by a specified duty cycle. During the energizing period P6, the power supply current flows from the V-phase terminal 22V to the W-phase terminal 22W, and then to the V-phase coil 23V and the W-phase coil 23W. That is, the energized phases in P6 during the energizing period are the V-phase and the W-phase.

[0039] By controlling the switching of each arm switch according to the six energizing modes described above, a rotating magnetic field is generated, causing the shaft 21 of the three-phase motor 20 to rotate 360° in a certain 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 certain direction. In other words, during each period from energizing period P1 to energizing period P6, the shaft 21 of the three-phase motor 20 rotates 60° in a certain direction.

[0040] The speed at which the power-on mode switches, i.e., the speed at which the power-on phase switches, is called the commutation frequency Fs. The unit of commutation frequency Fs is "Hz". When the period for switching control in one power-on mode is set as P (seconds), the commutation frequency Fs is expressed as "Fs = 1 / P".

[0041] Figure 3 The waveforms of the voltages appearing at the U-phase terminal 22u, V-phase terminal 22v, and W-phase terminal 22w of the three-phase motor 20 are shown. Figure 3 In this context, "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. Furthermore, the actual waveforms of the U-phase terminal voltage Vu, V-phase terminal voltage Vv, and W-phase terminal voltage Vw are waveforms with the same duty cycle as the switch, but... Figure 3 For convenience, only the envelope of the voltage waveform is shown.

[0042] The U-phase terminal voltage Vu becomes an effective voltage value determined by the switch duty cycle during energization in P1 and P2, and a ground level value (0V) during energization in P4 and P5. The V-phase terminal voltage Vv becomes an effective voltage value determined by the switch duty cycle during energization in P5 and P6, and a 0V during energization in P2 and P3. The W-phase terminal voltage Vw becomes an effective voltage value determined by the switch duty cycle during energization in P3 and P4, and a 0V during energization in P1 and P6. Thus, in the sensorless 120° energization mode, the phases for which the drive voltage required to drive the three-phase motor 20 is applied switch every 120°.

[0043] During the energization period P3, no drive current flows through the U-phase coil 23u, but the energy stored in the U-phase coil 23u is transmitted through the lower arm switch Q of the U-phase. UL The body diode carries a return current for a certain period of time in the U-phase coil 23u. As a result, a ringing phenomenon occurs, where the U-phase terminal voltage Vu becomes 0V for a certain period starting from the beginning of period P3. Afterwards, the U-phase terminal voltage Vu matches the induced voltage generated in the U-phase coil 23u. During energization period P3, the induced voltage at the midpoint of energization period P3, i.e., the moment after the three-phase motor 20 has rotated 30° from the beginning of energization period P3, is relative to the voltage at the neutral point N, i.e., the neutral point voltage V. N Crossing from the high-pressure side towards the low-pressure side.

[0044] Similarly, during the energization period P6, no drive current flows through the U-phase coil 23u, but the energy stored in the U-phase coil 23u is transmitted via the upper arm switch Q of the U-phase. UHThe body diode carries a return current for a certain period of time in the U-phase coil 23u. As a result, the U-phase terminal voltage Vu becomes the DC power supply voltage V for a certain period of time, starting from the beginning of the energizing period P6. M The ringing phenomenon occurs. Afterwards, the U-phase terminal voltage Vu matches the induced voltage generated in the U-phase coil 23u. During energization period P6, the induced voltage is at the midpoint of energization period P6, i.e., the moment after the three-phase motor 20 has rotated 30° from the start of energization period P6, relative to the neutral point voltage Vu. N Crossing from the low-pressure side towards the high-pressure side.

[0045] As described above, during the 360° rotation of the three-phase motor 20, induced voltage is only exposed at the U-phase terminal 22u during the energizing period (P3 and P6). Following the same principle, during the 360° rotation of the three-phase motor 20, induced voltage is only exposed at the V-phase terminal 22v during the energizing period (P1 and P4), and induced voltage is only exposed at the W-phase terminal 22w during the energizing period (P2 and P5). In the sensorless 120° energizing mode, to detect the phase of the three-phase motor 20, it is necessary to detect the neutral point voltage V. N The zero-crossing point of the point where the voltage intersects with the induced voltage.

[0046] exist Figure 3 In this context, "Zu" refers to the induced voltage exposed in the U-phase terminal 22u, which is the neutral point voltage V. N The following conditions trigger a low-level condition: the induced voltage exposed in the U-phase terminal 22u is higher than the neutral point voltage V. N The high timing becomes a high-level U-phase zero-crossing detection signal. "Zv" is the induced voltage exposed in the 22V V-phase terminal, which is the neutral point voltage V. N The following condition occurs when the voltage level becomes low, and the induced voltage exposed at the 22V terminal of phase V is higher than the neutral point voltage V. N The high timing becomes a high-level V-phase zero-crossing detection signal. "Zw" is the induced voltage exposed in the W-phase terminal 22w, which is the neutral point voltage V. N The following condition occurs when the voltage level becomes low, and the induced voltage exposed in phase W terminal 22w is higher than the neutral point voltage V. N The high timing becomes the high-level W-phase zero-crossing detection signal.

[0047] exist Figure 3 In this context, "Hu" is the U-phase phase detection signal with a 30° phase delay relative to the U-phase zero-crossing detection signal Zu. "Hv" is the V-phase phase detection signal with a 30° phase delay relative to the V-phase zero-crossing detection signal Zv. "Hw" is the W-phase phase detection signal with a 30° phase delay relative to the W-phase zero-crossing detection signal Zw.

[0048] Furthermore, the three-phase motor 20 rotates 60° during the time interval 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 detection signal Zu by half the measurement time, a U-phase phase detection signal Hu with a 30° phase delay relative to the U-phase zero-crossing detection signal Zu can be generated. The V-phase phase detection signal Hv and the W-phase phase detection signal Hw can also be generated using the same method.

[0049] like Figure 3 As shown, 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 vary regularly depending on six power-on modes. Hereinafter, the mode 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 vary depending on the power-on mode will be referred to as the phase mode. Figure 2 As shown, the sensorless 120° power-on phase mode includes six phase modes: PB1, PB2, PB3, PB4, PB5, and PB6. In Figure 2 In the columns “Hu”, “Hv”, and “Hw”, the “1” indicates that the corresponding phase detection signal is at a high level, and the “0” indicates that the corresponding phase detection signal is at a low level.

[0050] In the sensorless 120° power-on mode, the phase pattern is identified for each power-on period based on three phase detection signals Hu, Hv, and Hw. The power-on mode to be used in the next power-on period is determined based on the identification result of the phase pattern. Then, the power-on mode is switched to the next power-on mode when the phase pattern changes.

[0051] like Figure 3 As shown, for example, during the energizing period P1, the phase mode of energizing period P1 is identified as phase mode PB1 based on the phase detection signals Hu, Hv, and Hw. Since the phase mode of energizing period P1 is phase mode PB1, the energizing mode PA2 is determined to be the energizing mode used in the next energizing period P2. Then, at the moment when phase mode PB1 changes, i.e., when the V-phase phase detection signal Hv generates a falling edge, the energizing mode switches from energizing mode PA1 to energizing mode PA2.

[0052] In the sensorless 120° power-on mode, the switching of the power-on mode as described above is synchronized with the phase detection signals Hu, Hv, and Hw generated using the induced voltage generated in the three-phase motor 20 at 60° intervals. This allows for rotational control of the three-phase motor 20 without the need for position sensors such as Hall sensors. Hereinafter, the power-on control of the three-phase motor 20 synchronized 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".

[0053] The above describes the basic principle of the sensorless 120° energization method. In this method, to generate phase detection signals Hu, Hv, and Hw, it is necessary to detect the neutral point voltage V of the three-phase motor 20. N The zero-crossing point is the point where the induced voltage intersects with the zero-crossing point. However, if the speed of the three-phase motor 20 is not above the specified speed, no induced voltage capable of detecting the zero-crossing point will be generated. In the following description, the minimum speed required to generate an induced voltage capable of detecting the zero-crossing point will be referred to as the minimum limiting speed.

[0054] For example, when the electric pump unit 100 is used in a low-temperature environment, the load on the three-phase motor 20 increases due to the increased viscosity of the cooling oil F, thus requiring the three-phase motor 20 to rotate at a relatively low speed. In such a low-temperature environment, there are situations where the three-phase motor 20 is rotated at a speed close to its minimum limit. In this case, if the neutral point voltage V... N (=V M / 2) If the zero-crossing determination level is set and the point where the zero-crossing determination level intersects with the induced voltage is detected as the zero-crossing point, then due to the reasons explained below, it may be difficult to stably perform sensorless synchronous control of the three-phase motor 20, but this can be determined through the research of the inventors of this application.

[0055] Figure 4 It is shown schematically in Figure 3 The diagram shows the waveform of the induced voltage exposed at the U-phase terminal 22u during the energization period, that is, the induced voltage appearing in the U-phase terminal voltage Vu.

[0056] exist Figure 4 In the above, waveform W0 is the waveform of the induced voltage appearing in the U-phase terminal voltage Vu when the three-phase motor 20 is rotated at a speed sufficient to generate an induced voltage sufficient to detect the zero-crossing point. Hereinafter, waveform W0 will be referred to as the ideal induced voltage waveform.

[0057] exist Figure 4 In this context, LV0 is set as the neutral point voltage V. N (=V M / 2) Zero-crossing determination level. Hereinafter, LV0 will be referred to as the ideal zero-crossing determination level.

[0058] exist Figure 4 In this context, Pz0 is the zero-crossing point where the ideal zero-crossing determination level LV0 intersects with the ideal induced voltage waveform W0. Hereinafter, Pz0 will be referred to as the ideal zero-crossing point.

[0059] exist Figure 4 In this context, tz0 is the timing for detecting the ideal zero-crossing point Pz0. Hereinafter, tz0 will be referred to as the ideal zero-crossing detection timing.

[0060] The results of the inventors’ research show that when performing extremely low-speed rotation control that causes the three-phase motor 20 to rotate at a speed close to the minimum limit speed in a low-temperature environment, the waveform of the induced voltage is distorted according to the magnitude of the power supply current flowing in the drive circuit 11 (the drive current flowing in the three-phase motor 20).

[0061] exist Figure 4 In the diagram, waveform W1 is the waveform of the induced voltage appearing in the U-phase terminal voltage Vu when the power supply current of 30 (A) flows under the condition of extremely low speed rotation control of the three-phase motor 20. Hereinafter, waveform W1 will be referred to as the first induced voltage waveform.

[0062] exist Figure 4 In the diagram, waveform W2 is the waveform of the induced voltage appearing in the U-phase terminal voltage Vu when the power supply current of the three-phase motor 20 flows under extremely low speed rotation control. Hereinafter, waveform W2 will be referred to as the second induced voltage waveform.

[0063] exist Figure 4 In the diagram, waveform W3 is the waveform of the induced voltage appearing in the U-phase terminal voltage Vu when the power supply current of 10 (A) flows under the condition of extremely low speed rotation control of the three-phase motor 20. Hereinafter, waveform W3 will be referred to as the third induced voltage waveform.

[0064] like Figure 4 As shown, under the condition of extremely low speed rotation control of the three-phase motor 20, the smaller the power supply current flowing in the drive circuit 11, the more the waveform of the induced voltage appearing in the U-phase terminal voltage Vu is distorted compared with the ideal induced voltage waveform W0.

[0065] exist Figure 4 In this context, Pz1 is the zero-crossing point where the ideal zero-crossing determination level LV0 intersects with the first induced voltage waveform W1. Hereinafter, Pz1 will be referred to as the first zero-crossing point.

[0066] exist Figure 4 In this context, tz1 is the timing for detecting the first zero-crossing point Pz1. Hereinafter, tz1 will be referred to as the first zero-crossing detection timing.

[0067] like Figure 4 As shown, the first induced voltage waveform W1 is distorted compared with the ideal induced voltage waveform W0, and the first zero-crossing point Pz1 shifts to the left of the ideal zero-crossing point Pz0. As a result, the first zero-crossing detection timing tz1 shifts to the left of the ideal zero-crossing detection timing tz0.

[0068] exist Figure 4 In this context, Pz2 is the zero-crossing point where the ideal zero-crossing determination level LV0 intersects with the second induced voltage waveform W2. Hereinafter, Pz2 will be referred to as the second zero-crossing point. Figure 4 In this context, tz2 is the timing for detecting the second zero-crossing point Pz2. Hereinafter, tz2 will be referred to as the second zero-crossing detection timing.

[0069] like Figure 4 As shown, because the second induced voltage waveform W2 is significantly distorted compared to the first induced voltage waveform W1, the second zero-crossing point Pz2 shifts to the left of the first zero-crossing point Pz1, and thus the second zero-crossing detection timing tz2 shifts to the left of the first zero-crossing detection timing tz1.

[0070] exist Figure 4 In this context, Pz3 is the zero-crossing point where the ideal zero-crossing determination level LV0 intersects with the third induced voltage waveform W3. Hereinafter, Pz3 will be referred to as the third zero-crossing point.

[0071] exist Figure 4 In this context, tz3 is the timing for detecting the third zero-crossing point Pz3. Hereinafter, tz3 will be referred to as the third zero-crossing detection timing.

[0072] like Figure 4 As shown, because the third induced voltage waveform W3 is significantly distorted compared to the second induced voltage waveform W2, the third zero-crossing point Pz3 shifts to the left of the second zero-crossing point Pz2, and thus the third zero-crossing detection timing tz3 shifts to the left of the second zero-crossing detection timing tz2.

[0073] As described above, under extremely low-speed rotation control, the waveform of the induced voltage appearing in the U-phase terminal voltage Vu becomes significantly distorted due to the smaller the power supply current flowing in the drive circuit 11, causing the zero-crossing detection timing to shift to the left of the ideal zero-crossing detection timing tz0. Similarly, the zero-crossing detection timing based on the induced voltage appearing in the V-phase terminal voltage Vv and the zero-crossing detection timing based on the induced voltage appearing in the W-phase terminal voltage Vw also shift depending on the power supply current. As a result, the rising and falling edges of the phase detection signals Hu, Hv, and Hw deviate from the ideal timing, making it impossible to accurately switch the energizing mode at 60° intervals. This is because, under extremely low-speed rotation control of the three-phase motor 20, if the detection setting is the neutral point voltage V... N (=VM If the zero-crossing judgment level of / 2) is used as the point where the induced voltage crosses, it will be difficult to stably perform sensorless synchronous control of the three-phase motor 20.

[0074] To solve the aforementioned technical problem, in this embodiment, the value of the zero-crossing determination level is changed according to the power supply current flowing in the drive circuit 11. Hereinafter, refer to... Figure 5 The reason why sensorless synchronous control of the three-phase motor 20 can be stably performed by changing the value of the zero-crossing judgment level according to the power supply current is explained.

[0075] For example, in Figure 5 In this context, LV1 is a zero-crossing determination level with a value lower than the ideal zero-crossing determination level LV0. Hereinafter, LV1 will be referred to as the first zero-crossing determination level. Pz1' is the zero-crossing point where the first zero-crossing determination level LV1 intersects with the first induced voltage waveform W1. Hereinafter, Pz1' will be referred to as the first offset zero-crossing point. Figure 5 As shown, the timing of detecting the first offset zero-crossing point Pz1' is consistent with the ideal zero-crossing detection timing tz0.

[0076] exist Figure 5 In this context, LV2 is a zero-crossing determination level with a lower value than the first zero-crossing determination level LV1. Hereinafter, LV2 will be referred to as the second zero-crossing determination level. Pz2' is the zero-crossing point where the second zero-crossing determination level LV2 intersects with the second induced voltage waveform W2. Hereinafter, Pz2' will be referred to as the second offset zero-crossing point. Figure 5 As shown, the timing of detecting the second offset zero-crossing point Pz2' is consistent with the ideal zero-crossing detection timing tz0.

[0077] exist Figure 5 In this context, LV3 is a zero-crossing determination level with a lower value than the second zero-crossing determination level LV2. Hereinafter, LV3 will be referred to as the third zero-crossing determination level. Pz3' is the zero-crossing point where the third zero-crossing determination level LV3 intersects with the third induced voltage waveform W3. Hereinafter, Pz3' will be referred to as the third offset zero-crossing point. Figure 5 As shown, the timing of detecting the third offset zero-crossing point Pz3' is consistent with the ideal zero-crossing detection timing tz0.

[0078] like Figure 5 As shown, for example, when the power supply current is 30 (A), by shifting (changing) the value of the zero-crossing determination level from LV0 to LV1, the detection timing of the zero-crossing point where the induced voltage corresponding to the power supply current value of 30 (A) intersects with the zero-crossing determination level can be made consistent with the ideal zero-crossing detection timing tz0.

[0079] In addition, for example, when the power supply current is 20 (A), by shifting (changing) the value of the zero-crossing determination level from LV0 to LV2, it is possible to make the detection timing of the zero-crossing point where the induced voltage corresponding to the power supply current value of 20 (A) intersects with the zero-crossing determination level consistent with the ideal zero-crossing detection timing tz0.

[0080] In addition, for example, when the power supply current is 10 (A), by shifting (changing) the value of the zero-crossing determination level from LV0 to LV3, it is possible to make the detection timing of the zero-crossing point where the induced voltage corresponding to the power supply current value of 10 (A) intersects with the zero-crossing determination level consistent with the ideal zero-crossing detection timing tz0.

[0081] As described above, by changing the zero-crossing detection level according to the power supply current flowing in the drive circuit 11, even when the waveforms of the induced voltages appearing in the terminal voltages of the three phases are distorted due to the power supply current during ultra-low speed rotation control of the three-phase motor 20, the zero-crossing detection timing can be made approximately consistent with the ideal zero-crossing detection timing tz0. As a result, the rising and falling edges of the phase detection signals Hu, Hv, and Hw can be generated at approximately the ideal timing, thereby enabling high-precision switching of the energizing mode at 60° intervals. Therefore, sensorless synchronous control of the three-phase motor 20 can be stably performed during ultra-low speed rotation control.

[0082] Hereinafter, based on the explanation of the basic principle of the sensorless 120° power-on method described above and the explanation of the technical effects obtained by changing the value of the zero-crossing determination level according to the power supply current, the shunt resistor 12, voltage detection circuit 13, control unit 14 and storage unit 15 of the motor control device 10 of this embodiment will be explained.

[0083] Shunt resistor 12 detects the power supply current flowing in drive circuit 11. One end of shunt resistor 12 is connected to the lower arm switch Q of phase U. UL V-phase lower arm switch Q VL and the W-phase lower side arm switch Q WL The source terminals of the shunt resistor 12 are electrically connected. The other end of the shunt resistor 12 is electrically connected to the negative terminal of the DC power supply 200. Furthermore, one end of the shunt resistor 12 is electrically connected to the control unit 14. The power supply current flowing in the drive circuit 11 flows into the vehicle ground terminal via the shunt resistor 12. Therefore, a voltage proportional to the power supply current appears between the terminals of the shunt resistor 12. This voltage between the terminals of the shunt resistor 12 is provided to the control unit 14 as a power supply current value representing the detection result of the power supply current. Alternatively, a resistor voltage divider circuit may be provided between one end of the shunt resistor 12 and the control unit 14 as needed.

[0084] Voltage detection circuit 13 is a circuit that detects the terminal voltages of the three phases of the three-phase motor 20. Voltage detection circuit 13 is electrically connected to the U-phase terminal 22u, V-phase terminal 22v, and W-phase terminal 22w of the three-phase motor 20, respectively. Voltage detection circuit 13 detects the voltage at U-phase terminal 22u, i.e., the U-phase terminal voltage Vu, and provides this detected value to control unit 14. Voltage detection circuit 13 detects the voltage at V-phase terminal 22v, i.e., the V-phase terminal voltage Vv, and provides this detected value to control unit 14. Voltage detection circuit 13 detects the voltage at W-phase terminal 22w, i.e., the W-phase terminal voltage Vw, and provides this detected value to control unit 14. As an example, voltage detection circuit 13 is constructed using a resistor divider circuit.

[0085] The control unit 14 is, for example, a microprocessor such as an MCU (Microcontroller Unit). The control unit 14 is input with a speed command signal CS output from a host control device (not shown). The speed command signal CS is a signal indicating the target speed of the three-phase motor 20. The control unit 14 is connected to the storage unit 15 in a communicative manner via a communication bus (not shown). The control unit 14 executes a process according to a program pre-stored in the storage unit 15, causing the three-phase motor 20 to rotate at the target speed indicated by the speed command signal CS, details of which will be described later.

[0086] The control unit 14 performs A / D conversion on the voltage between the terminals of the shunt resistor 12 to obtain the power supply current value as digital data. The control unit 14 also performs A / D conversion on the output voltage of the voltage detection circuit 13 to obtain the U-phase terminal voltage Vu, V-phase terminal voltage Vv, and W-phase terminal voltage Vw as digital data. The control unit 14 detects the points where the induced voltages appearing in the three-phase terminal voltages intersect with a predetermined zero-crossing judgment level as zero-crossing points, and controls the drive circuit 11 based on the zero-crossing point detection results.

[0087] Specifically, the control unit 14 generates a U-phase zero-crossing detection signal Zu based on the detection result of the zero-crossing point where the induced voltage in the U-phase terminal voltage Vu intersects with the zero-crossing determination level, and generates a U-phase phase detection signal Hu with a phase delay of 30° relative to the U-phase zero-crossing detection signal Zu.

[0088] In addition, the control unit 14 generates a V-phase zero-crossing detection signal Zv based on the detection result of the zero-crossing point where the induced voltage in the V-phase terminal voltage Vv intersects with the zero-crossing determination level, and generates a V-phase phase detection signal Hv with a phase delay of 30° relative to the V-phase zero-crossing detection signal Zv.

[0089] In addition, the control unit 14 generates a W-phase zero-crossing detection signal Zw based on the detection result of the zero-crossing point where the induced voltage in the W-phase terminal voltage Vw intersects with the zero-crossing determination level, and generates a W-phase phase detection signal Hw with a phase delay of 30° relative to the W-phase zero-crossing detection signal Zw.

[0090] The control unit 14 switches the power-on mode based on the phase detection signals Hu, Hv, and Hw, and determines the switching duty cycle required to make the actual speed of the three-phase motor 20 match the target speed. It then controls the switching of each arm switch according to the determined duty cycle. As a result, a three-phase AC voltage that makes the actual speed of the motor 20 match the target speed is supplied from the drive circuit 11 to the three-phase motor 20.

[0091] The control unit 14 changes the zero-crossing determination level based on the power supply current value detected by the shunt resistor 12. Specifically, the control unit 14 calculates an offset value based on the power supply current value detected by the shunt resistor 12, and changes the zero-crossing determination level to a value obtained by offsetting the reference zero-crossing determination value with the offset value. The reference zero-crossing determination value is a reference value for the zero-crossing determination level. As an example, in this embodiment, the reference zero-crossing determination value is the DC power supply voltage V. M The value is half of the ideal zero-crossing level LV0. That is, in this embodiment, the reference zero-crossing determination value is set to the same value as the ideal zero-crossing determination level LV0.

[0092] Reference Figure 5 For example, when the power supply current is 30 (A), the control unit 14 calculates the offset value required to change the value of the zero-crossing determination level from the reference zero-crossing determination value (LV0) to LV1.

[0093] Additionally, for example, when the power supply current is 20 (A), the control unit 14 calculates the offset value required to change the value of the zero-crossing determination level from the reference zero-crossing determination value (LV0) to LV2.

[0094] Additionally, for example, when the power supply current is 10 (A), the control unit 14 calculates the offset value required to change the value of the zero-crossing determination level from the reference zero-crossing determination value (LV0) to LV3.

[0095] The formula used to calculate the offset value is prepared in advance through experiments or simulations, and is stored in the storage unit 15. Hereinafter, the formula used to calculate the offset value will be referred to as the offset formula.

[0096] The storage unit 15 includes: non-volatile memory storing programs and various setting data required for the control unit 14 to perform various processes; and volatile memory serving as a temporary data storage destination when the control unit 14 performs various processes. Non-volatile memory may be, for example, EEPROM (Electrically Erasable Programmable Read-Only Memory) or flash memory. Volatile memory may be, for example, RAM (Random Access Memory).

[0097] The storage unit 15 stores various data required to control the three-phase motor 20 via a sensorless 120° energization method. For example, the storage unit 15 pre-stores... Figure 2 The power-on mode and phase mode are shown. Additionally, the storage unit 15 pre-stores a reference zero-crossing determination value as the reference value for the zero-crossing determination level and an offset calculation formula for calculating the offset value. (Example...) Figure 1 As shown, the storage unit 15 can be disposed outside the control unit 14, or it can be built into the control unit 14.

[0098] Next, refer to Figure 6 The extremely low-speed rotation control of the three-phase motor 20, which is executed by the control unit 14 in a low-temperature environment, is explained in detail. Figure 6 This is a flowchart illustrating the various processes included in the ultra-low speed rotation control. When the target speed indicated by the speed command signal CS is close to the minimum speed limit, the control unit 14 starts the ultra-low speed rotation control of the three-phase motor 20. As an example, the speed close to the minimum speed limit is 300 rpm to 600 rpm. In addition, the three-phase motor 20 is in a stopped state when the ultra-low speed rotation control starts.

[0099] like Figure 6 As shown, when the control unit 14 starts the extremely low speed rotation control, it first aligns the rotor of the three-phase motor 20 (step S1), and after the rotor alignment is completed, it starts the forced commutation control of the three-phase motor 20 (step S2).

[0100] When the three-phase motor 20 is started using a sensorless 120° energization method, phase detection signals Hu, Hv, and Hw cannot be generated until the motor 20 reaches its minimum speed sufficient to generate the induced voltage capable of detecting zero crossing. Therefore, sensorless synchronous control of the three-phase motor 20 is impossible. Thus, when starting the three-phase motor 20 using a sensorless 120° energization method, the motor 20 must be energized according to a predetermined starting sequence until its minimum speed is reached.

[0101] As an example of a starting sequence, a starting sequence is generally known as follows: after aligning the rotor to a specific position (corresponding to one of the motor control states) by DC excitation of the three-phase motor 20 for a specified time, forced commutation control is performed to forcibly switch the energized phases (energizing mode) at a specified forced commutation frequency while applying a specified drive voltage to the energized phases. The processing of steps S1 and S2 is included in the known starting sequence described above, and therefore detailed explanations are omitted.

[0102] When forced commutation control begins, the rotational speed of the three-phase motor 20 gradually increases towards the speed corresponding to the forced commutation frequency. When forced commutation control begins, the control unit 14 acquires the power supply current value (step S3) and changes the zero-crossing determination level based on the acquired power supply current value (step S4). Specifically, in step S4, the control unit 14 reads the offset formula from the storage unit 15 and calculates the offset value by substituting the acquired power supply current value into the offset formula. Then, in step S4, the control unit 14 reads the reference zero-crossing determination value from the storage unit 15 and changes the zero-crossing determination level to a value obtained by offsetting the reference zero-crossing determination value with the offset value.

[0103] Reference Figure 5 For example, when the power supply current is 30 (A), the control unit 14 calculates the offset value required to change the value of the zero-crossing determination level from the reference zero-crossing determination value (LV0) to LV1. Then, the control unit 14 changes the value of the zero-crossing determination level to the value (LV1) obtained by offsetting the reference zero-crossing determination value (LV0) with the offset value.

[0104] After changing the value of the zero-crossing determination level as described above, the control unit 14 begins to detect the point where the induced voltage in the terminal voltages Vu, Vv, and Vw of each phase intersects with the zero-crossing determination level as a zero-crossing point, and determines whether a zero-crossing point has been detected n times consecutively (step S5). n is an integer of 2 or more.

[0105] In addition, the control unit 14 begins to process the generation of zero-crossing detection signals Zu, Zv and Zw for each phase based on the zero-crossing detection results of each phase, and to process the generation of phase detection signals Hu, Hv and Hw for each phase based on the zero-crossing detection signals Zu, Zv and Zw of each phase.

[0106] After forced commutation control begins, when the speed of the three-phase motor 20 reaches the minimum limit speed, a large induced voltage begins to appear in the terminal voltages Vu, Vv, and Vw of each phase, thereby initiating the detection of zero crossing. If it is determined in step S5 that zero crossing has been detected n times consecutively, it is inferred that the three-phase motor 20 has started to rotate stably at a speed above the minimum limit speed.

[0107] If the result in step S5 is "No," meaning the number of consecutive zero-crossing detections is less than n, it is inferred that the three-phase motor 20 has not yet stably started rotating at a speed above the minimum limit speed. In this case, the control unit 14 returns to the processing in step S3.

[0108] On the other hand, if the condition in step S5 is "yes," that is, if the number of consecutive zero-crossing detections reaches n, it is inferred that the three-phase motor 20 has stably started rotating at a speed above the minimum limit speed. In this case, the control unit 14 identifies the phase pattern of the current energizing period based on the phase detection signals Hu, Hv, and Hw, and determines the energizing mode to be used in the next energizing period based on the phase pattern identification result (step S6).

[0109] For example, such as Figure 3 As shown, assuming that during energization, when a zero-crossing point is detected in P1 where the induced voltage in the V-phase terminal voltage Vv intersects with the zero-crossing determination level, the number of consecutive zero-crossing point detections reaches n. Furthermore, in Figure 3 In this case, the zero-crossing detection level is set to the neutral point potential V. N (=V M / 2), but through the processing of steps S3 and S4, the value of the zero-crossing determination level is changed to a value based on the power supply current value.

[0110] Thus, when the number of consecutive zero-crossing detections in P1 during the power-on period reaches n, the control unit 14 identifies the phase pattern of P1 during the current power-on period based on the phase detection signals Hu, Hv, and Hw. During the power-on period of 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 refers to the phase pattern stored in the storage unit 15 (reference...) Figure 2 The phase mode of P1 during the current power-on period is identified as PB1.

[0111] Then, the control unit 14 determines the power-on mode to be used in the next power-on period based on the phase mode identification result. For example, as described above, if the control unit 14 identifies the phase mode of the current power-on period P1 as PB1, it refers to the power-on mode stored in the storage unit 15 (reference... Figure 2 The power-on mode PA2 is determined as the power-on mode that should be used in the next power-on period.

[0112] After determining the power-on mode to be used in the next power-on period, the control unit 14 switches the power-on mode to the power-on mode determined in step S6 (step S7) at the moment when the level of any one of the phase detection signals Hu, Hv, and Hw changes. For example, if the number of consecutive zero-crossing detections in power-on period P1 reaches n times as described above, when the three-phase motor 20 rotates 30° from the zero-crossing detection moment based on the induced voltage appearing in the V-phase terminal voltage Vv, the level of the phase detection signal Hv changes from a high level to a low level (see reference). Figure 3 (at time t11). Therefore, in this case, the control unit 14 switches the power-on mode to the power-on mode PA2 determined in step S6 at the moment when the phase detection signal Hv generates a falling edge (at time t11).

[0113] Furthermore, while switching the power-on mode, the control unit 14 determines the required switching duty cycle to ensure that the actual speed of the three-phase motor 20 matches the target speed, and controls the switching of each arm switch according to the determined switching duty cycle. For example, when switching the power-on mode to power-on mode PA2 as described above, the control unit 14 switches the upper arm switch Q of phase U. UH and V-phase lower side arm switch Q VL Set the control to ON, and set the remaining arm switches to OFF (see reference). Figure 2 In power-on mode PA2, control unit 14 only controls the upper arm switch Q of phase U. UH Switching control is performed based on the determined switch duty cycle (see reference). Figure 3 As a result, a three-phase AC voltage is supplied from the drive circuit 11 to the three-phase motor 20 so that the actual speed of the three-phase motor 20 matches the target speed.

[0114] Subsequently, the control unit 14 switches the power-on mode and controls the switching of each arm switch in 60° intervals, synchronized with the phase detection signals Hu, Hv, and Hw, to make the three-phase motor 20 rotate at the target speed. Thus, in step S6 and after step S6, the control unit 14 begins to control the three-phase motor 20 in a sensorless synchronous manner in sync with the phase detection signals Hu, Hv, and Hw.

[0115] As explained above, the motor control device 10 in this embodiment has a control unit 14. The control unit 14 detects the point where the induced voltage appearing in the three-phase terminal voltages intersects 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 changes the value of the zero-crossing determination level based on the power supply current value detected by the shunt resistor 12.

[0116] According to this embodiment, when the three-phase motor 20 is rotated at a speed close to its minimum limit in a low-temperature environment, even if the waveforms of the induced voltages appearing in the terminal voltages of the three phases are distorted due to the power supply current, the zero-crossing detection timing can be made approximately consistent with the ideal zero-crossing detection timing tz0. As a result, the rising and falling edges of the phase detection signals Hu, Hv, and Hw can be generated at approximately the ideal timing, thereby enabling high-precision switching of the power-on mode at 60° intervals. Therefore, even when the three-phase motor 20 is rotated at a speed close to its minimum limit in a low-temperature environment, stable sensorless synchronous control of the three-phase motor 20 can be achieved.

[0117] In addition, the motor control device 10 in this embodiment also has a storage unit 15 that stores a reference zero-crossing determination value as a reference value for zero-crossing determination level. The control unit 14 calculates an offset value based on the power supply current value detected by the shunt resistor 12 and changes the value of the zero-crossing determination level to a value obtained by offsetting the reference zero-crossing determination value with the offset value.

[0118] Therefore, the zero-crossing determination level can be changed through simple calculations, thus reducing the processing load on the control unit 14. Furthermore, since the zero-crossing determination level can be changed based on the power supply current, even if the waveforms of the induced voltages appearing in the three-phase terminal voltages are distorted due to the power supply current, the zero-crossing detection timing can be made approximately consistent with the ideal zero-crossing detection timing tz0. As a result, the power-on mode can be switched with high precision, and sensorless synchronous control of the three-phase motor 20 can be stably performed even when the three-phase motor 20 is rotated at a speed close to its minimum limit in low-temperature environments.

[0119] Furthermore, in this embodiment, the reference zero-crossing determination value is the DC power supply voltage V. M The value of 1 / 2.

[0120] Therefore, even if the waveforms of the induced voltages appearing in the three-phase terminal voltages are distorted due to the power supply current, the zero-crossing detection timing can be made to be approximately consistent with the zero-crossing detection timing at the intersection of the neutral point potential and the induced voltage (ideal zero-crossing detection timing tz0), thereby enabling higher precision switching of the power-on mode at 60° intervals.

[0121] (Modified Example)

[0122] The present invention is not limited to the above-described embodiments, and the various structures described in this specification can be appropriately combined within a range that does not contradict each other.

[0123] In the above embodiment, the control unit 14 calculates the offset value based on the power supply current value and changes the value of the zero-crossing determination level to a value obtained by offsetting the reference zero-crossing determination value with the offset value, but the method of changing the value of the zero-crossing determination level is not limited to this.

[0124] For example, the storage unit 15 may pre-store the correspondence between candidate values ​​of the zero-crossing determination level and the power supply current value. The control unit 14 reads the candidate value corresponding to the power supply current value detected by the shunt resistor 12 from the storage unit 15 and changes the value of the zero-crossing determination level to the read candidate value. The storage unit 15 may store the correspondence between the candidate values ​​of the zero-crossing determination level and the power supply current value in the form of tabular data or in the form of a mathematical formula. The correspondence between the candidate values ​​of the zero-crossing determination level and the power supply current value is prepared in advance through experiments or simulations and stored in the storage unit 15. As a result, the value of the zero-crossing determination level can be changed through simple processing, thus reducing the processing load of the control unit 14.

[0125] Reference Figure 5 For example, when the correspondence between the candidate values ​​of the zero-crossing determination level and the power supply current value is in the form of tabular data, LV1 is associated as a candidate value of the zero-crossing determination level relative to a power supply current value of 30 (A), LV2 is associated as a candidate value of the zero-crossing determination level relative to a power supply current value of 20 (A), and LV3 is associated as a candidate value of the zero-crossing determination level relative to a power supply current value of 10 (A).

[0126] In the above embodiments, an electric pump device 100 that supplies cooling oil F to a drive motor mounted in a hybrid vehicle is 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 for example, the present invention can also be applied to an electric pump device that supplies oil to a transmission. In addition, the fluid discharged from the electric pump is not limited to oil such as cooling oil.

Claims

1. A motor control device for controlling a three-phase motor, wherein, The motor control device has the following features: A drive circuit that converts DC power supply voltage into three-phase AC voltage and supplies it to the three-phase motor; A current detection unit detects the power supply current flowing in the drive circuit. The voltage detection unit detects the terminal voltages of the three phases of the three-phase motor; as well as The control unit detects the points where the induced voltages appearing at the terminals of the three phases intersect with a predetermined zero-crossing threshold, and uses these points as zero-crossing points to control the drive circuit. The control unit changes the value of the zero-crossing determination level based on the power supply current value detected by the current detection unit, in a manner that the detection timing of the zero-crossing point where the induced voltage and the zero-crossing determination level intersect in the terminal voltages of the three phases is consistent with the ideal zero-crossing detection timing. The ideal zero-crossing detection timing is the timing at which the induced voltage appearing in the terminal voltages of the three phases crosses with the ideal zero-crossing judgment level having a value of 1 / 2 of the DC power supply voltage, while the three-phase motor is rotated at the minimum speed required to generate the induced voltage that can detect the zero-crossing point.

2. The motor control device according to claim 1, wherein, The motor control device also has a storage unit that stores a reference zero-crossing determination value, which is half of the DC power supply voltage. The control unit calculates an offset value based on the power supply current value detected by the current detection unit, and changes the value of the zero-crossing determination level to a value obtained by offsetting the reference zero-crossing determination value with the offset value.

3. The motor control device according to claim 1, wherein, The motor control device also has a storage unit that stores the correspondence between candidate values ​​of the zero-crossing determination level and the power supply current value. The control unit reads the candidate value corresponding to the power supply current value detected by the current detection unit from the storage unit, and changes the value of the zero-crossing determination level to the read candidate value.

4. An electric pump device, comprising: A three-phase motor, which has a shaft; A pump, located on one axial side of the shaft, is driven by the three-phase motor via the shaft; and The motor control device according to any one of claims 1 to 3 controls the three-phase motor.

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