Motor control unit, motor, and pump device

Abstract

The invention provides a motor control unit capable of suppressing noise generated from a motor. The motor control unit (10) has: a drive voltage line (13) that supplies a drive voltage to the inverter (12); a first capacitor (21) electrically connected between a portion of the drive voltage line (13) between the inverter (12) and the inductor (18) and a ground line (100); a second capacitor (22) electrically connected between a portion of the drive voltage line (13) closer to the input side than the first capacitor (21) and a ground line (100); a third capacitor 23 electrically connected between the second capacitor 22 and the ground 100; a common line 14 electrically connected to a neutral point 65 and an intermediate point M of the three-phase coil 6; and a resistor 20 electrically connected in series with the second capacitor 23 or the third capacitor 23.

Description

Technical Field

[0001] The present invention relates to a motor used in a pump device, etc. In addition, the present invention relates to a motor control unit for controlling the motor. Background Art

[0002] Patent document 1 discloses a pump device. The pump of the document has an electric motor, an impeller fixed to the rotor of the electric motor, and a housing that accommodates the impeller and divides a pump chamber. The electric motor has a rotor that can rotate around a central axis and a stator core with a three-phase coil.

[0003] As the motor of the pump device, a motor with noise countermeasures is sometimes used (for example, Patent Document 2). The motor of Patent Document 2 has a control device, which includes a capacitor arranged in parallel between the neutral point of the three-phase coil and a predetermined reference potential. Since the control device includes the capacitor, the voltage at the neutral point is smoothed. As a result, the noise generated by the motor is suppressed.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2020-159336

[0007] Patent Document 2: Japanese Patent Application Publication No. 2001-352792 Summary of the invention

[0008] Technical problem to be solved by the invention

[0009] Here, the pump device is often used together with other precision equipment. When used in a vehicle-mounted pump or the like, it is required to further suppress the noise generated by the motor of the pump device. In this case, when only the motor of Patent Document 2 is used for the pump device, there is a problem that it is not sufficient as a noise countermeasure.

[0010] Therefore, an object of the present invention is to provide a motor control unit capable of suppressing noise generated from a motor, a motor having the motor control unit, and a pump device having the motor.

[0011] Technical solutions adopted to solve technical problems

[0012] In order to solve the above-mentioned problem, the motor control unit of the present invention controls a motor having a three-phase coil wound on a stator core, and is characterized in that it has: a motor control unit, which controls the rotation of the motor according to a control signal; an inverter, which applies a driving voltage supplied from a driving power supply to the three-phase coil based on an output signal from the motor control unit; a driving voltage line, which supplies the driving voltage to the inverter; an inductor, which is electrically connected in series with the driving voltage line; a first capacitor, which is electrically connected between a portion of the driving voltage line between the inverter and the inductor and a ground line; a second capacitor, which is electrically connected between a portion of the driving voltage line closer to the input side than the first capacitor and the ground line; a third capacitor, which is electrically connected between the second capacitor and the ground line; a common line, which is electrically connected to a neutral point of the three-phase coil and an intermediate point between the second capacitor and the third capacitor; and a resistor, which is electrically connected in series with the second capacitor or the third capacitor.

[0013] In the present invention, there is an inductor electrically connected in series with a driving voltage line, and a first capacitor electrically connected between a portion of the driving voltage line between an inverter and the inductor and a ground line. If so configured, the driving voltage flowing through the driving voltage line can be smoothed, and thus noise generated in the driving voltage line can be suppressed.

[0014] In addition, in the present invention, there are: a second capacitor electrically connected between a portion of the driving voltage line closer to the input side than the first capacitor and the ground line; a third capacitor electrically connected between the second capacitor and the ground line; and a common line electrically connected to the neutral point of the three-phase coil and the middle point between the second capacitor and the third capacitor. If configured in this way, the neutral point electrically connected to the common line is clamped by the second capacitor and the third capacitor, so that even if a voltage with a large amplitude is generated at the neutral point, the voltage can be smoothed. As a result, the noise generated in the motor can be suppressed.

[0015] In addition, in the present invention, a resistor is provided, and the resistor is electrically connected in series with the second capacitor or the third capacitor. If configured in this way, even when a voltage with a large amplitude is generated at the neutral point, the voltage can be smoothed. Thus, the noise generated in the motor can be suppressed.

[0016] In the present invention, the resistor may include a first resistor and a second resistor, the first resistor being electrically connected between the input side portion of the drive voltage line and the second capacitor, and the second resistor being electrically connected between the third capacitor and the ground line. In addition, in the present invention, the resistor may include a first resistor and a second resistor, the first resistor being electrically connected between the second capacitor and the midpoint, and the second resistor being electrically connected between the midpoint and the third capacitor. Accordingly, the noise generated in the motor can be suppressed.

[0017] In the present invention, preferably, when the resistance values ​​of the first resistor and the second resistor are set to Ra, the following conditional formula is satisfied:

[0018] 100Ω≤Ra.

[0019] This greatly reduces the noise generated in the motor.

[0020] In the present invention, the resistor can be connected in series to the common line. In this case, preferably, when the resistance value of the resistor is set to Ra, the following conditional formula is satisfied:

[0021] 100Ω≤Ra.

[0022] This greatly reduces the noise generated in the motor.

[0023] In the present invention, preferably, when the electrostatic capacitance of each of the second capacitor and the third capacitor is set to C1, the following conditional expression is satisfied:

[0024] 1.0μF ≤ C1 ≤ 4.7μF.

[0025] Here, when the electrostatic capacitance C1 of each of the second capacitor and the third capacitor is smaller than 1.0μF, the voltage at the neutral point cannot be sufficiently smoothed, and the noise reduction effect generated in the motor is low. In addition, when each electrostatic capacitance C1 is greater than 4.7μF, the voltage at the neutral point is excessively smoothed, so the rotation characteristics of the motor are low. As a result, it is difficult to exert the performance of the motor. Therefore, if the electrostatic capacitance C1 of each of the second capacitor and the third capacitor satisfies 1.0μF≤C1≤4.7μF, the noise generated in the motor can be suppressed without reducing the rotation characteristics of the motor.

[0026] In the present invention, it is preferred that the second capacitor is electrically connected between a portion of the drive voltage line closer to the input side than the inductor and the ground line. If so configured, the effect of suppressing noise generated in the motor is greater than when the second capacitor is electrically connected between a portion of the drive voltage line closer to the output side than the inductor and the ground line.

[0027] In the present invention, preferably, when the electrostatic capacitance of the first capacitor is set to C2, the following conditional expression is satisfied:

[0028] 100μF≤C2.

[0029] Here, when the electrostatic capacitance C2 of the first capacitor is less than 100 μF, the current ripple tends to become larger, and the driving voltage flowing through the driving voltage line cannot be fully smoothed. Therefore, it is difficult to effectively suppress the noise generated in the driving voltage line. Therefore, if the electrostatic capacitance C2 of the first capacitor satisfies 100 μF ≤ C2, the noise generated in the voltage line can be suppressed. In addition, since the current ripple is suppressed, the first capacitor will not be overheated. Therefore, the characteristics and reliability of the first capacitor can be ensured.

[0030] In the present invention, it is preferred to include: a control signal line for inputting the control signal to the motor control unit; and a fourth capacitor electrically connected between the control signal line and a ground line. With such a configuration, the control signal transmitted in the control signal line can be smoothed, thereby removing noise generated in the control signal line.

[0031] In the present invention, it is preferable to include: a ferrite bead electrically connected in series with the control signal line at a portion closer to the input side of the control signal line than the fourth capacitor; and a sixth capacitor electrically connected between a portion closer to the input side of the control signal line than the ferrite bead and a ground line. If configured in this way, noise generated in the control signal line can be further removed.

[0032] In the present invention, it is preferred to include: an FG output line for transmitting a rotation speed signal corresponding to the rotation speed of the motor to an external device; and a fifth capacitor electrically connected between the FG output line and a ground line. If so configured, the rotation speed signal transmitted in the FG output line can be smoothed, and thus noise generated in the FG output line can be removed.

[0033] In the present invention, preferably, when the electrostatic capacitance of the fifth capacitor is set to C3, the following conditional expression is satisfied:

[0034] C3≤0.1μF.

[0035] Here, when the electrostatic capacitance C3 of the fifth capacitor is greater than 0.1 μF, the noise generated in the FG output line can be removed, but the output waveform of the speed signal is more likely to become flat. Therefore, since the external device cannot detect the speed signal of the motor with high accuracy, it is difficult to control the motor to a desired speed. Therefore, if the electrostatic capacitance C3 of the fifth capacitor satisfies C3 ≤ 0.1 μF, the noise generated in the FG output line can be removed, and the motor can be controlled to a desired speed.

[0036] The present invention provides an electric motor, characterized by comprising: a rotor capable of rotating about a central axis; a stator core having a three-phase coil; and the above-mentioned electric motor control unit. If so configured, noise generated in the electric motor can be suppressed.

[0037] The present invention provides a pump device, characterized by comprising: the above-mentioned motor; an impeller, the impeller being fixed to the rotor; and a housing, the housing accommodating the impeller and dividing a pump chamber. If so configured, the noise generated by the pump device is suppressed, so that the precision equipment used around the pump device is not easily affected by the noise.

[0038] Effects of the Invention

[0039] According to the present invention, the driving voltage flowing through the driving voltage line can be smoothed by the inductor and the first capacitor, so the noise generated in the driving voltage line can be suppressed. In addition, the neutral point electrically connected to the common line is clamped by the second capacitor and the third capacitor, and the resistor is electrically connected in series with the second capacitor or the third capacitor, so even if a voltage with a large amplitude is generated at the neutral point, the voltage can be smoothed. As a result, the motor control unit can suppress the noise generated in the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] [ Figure 1 ] is an explanatory diagram schematically showing a cross-section of a pump device according to an embodiment of the present invention.

[0041] [ Figure 2 ] is a schematic circuit diagram of the motor control unit of implementation mode 1.

[0042] [ Figure 3 ] is a schematic circuit diagram of a motor control unit of a comparative example.

[0043] [ Figure 4 ] is a diagram illustrating the noise reduction effect.

[0044] [ Figure 5 ] is a graph showing the noise peak when the resistance value Ra and the electrostatic capacitance C1 are changed.

[0045] [ Figure 6 ] is a diagram comparing the electrostatic capacitance of capacitors.

[0046] [ Figure 7 ] is a schematic circuit diagram of the motor control unit of embodiment 2.

[0047] [ Figure 8 ] is a schematic circuit diagram of a motor control unit of other embodiments. DETAILED DESCRIPTION

[0048] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Figure 1 1 is an explanatory diagram schematically showing a cross section of a pump device according to an embodiment of the present invention. Figure 1 As shown, the pump device 1 includes: a motor 2 having a rotor 5 that can rotate around a central axis L; an impeller 3 that is fixed to one side L1 of the central axis L relative to the rotor 5; and a housing 4 that accommodates the impeller 3 and divides a pump chamber 4A. The housing 4 is attached to the motor 2 from one side L1 of the motor 2. The pump device 1 moves the fluid in the pump chamber 4A by rotating the impeller 3 and the rotor 5 integrally around the central axis L.

[0049] The motor 2 includes a rotor 5 that can rotate around a central axis L, a stator 7 that includes a three-phase coil 6, a resin sealing member 8 that covers the stator 7, and a circuit board 9 that is connected to the three-phase coil 6. The motor 2 is a three-phase motor, and the three-phase coil 6 includes a U-phase coil, a V-phase coil, and a W-phase coil. The three-phase coil 6 is wound around a stator core 70 of the stator 7 via an insulator 71. A magnet is provided on the outer peripheral surface of the rotor 5.

[0050] The circuit board 9 is located on the other side L2 of the stator 7. A motor control unit 10 for controlling the motor 2 is formed on the circuit board 9. The motor control unit 10 controls the rotation of the motor 2 by controlling the power supply to the three-phase coil 6.

[0051] Figure 2 is a schematic circuit diagram of the motor control unit 10. Figure 2 As shown, the motor 2 controlled by the motor control unit 10 includes a U-phase coil 61, a V-phase coil 62, and a W-phase coil 63. The three-phase coils 6 are connected in a star shape.

[0052] The motor control unit 10 includes: a motor control unit 11 that controls the rotation of the motor 2 according to a PWM signal; an inverter 12 that applies a driving voltage supplied from a driving power source to the three-phase coil 6 based on an output signal from the motor control unit 11; a driving voltage line 13 that supplies a driving voltage to the inverter 12; and a common line 14 that is connected to a neutral point 65 of the three-phase coil 6. The motor control unit 10 includes: a control signal line 15 that inputs a PWM signal from an external device to the motor control unit 11; and an FG output line 16 that transmits a speed signal corresponding to the speed of the motor 2 to the external device.

[0053] The motor control unit 10 includes an inductor 18 , a first capacitor 21 , a second capacitor 22 , a third capacitor 23 , a fourth capacitor 24 , a fifth capacitor 25 , a sixth capacitor 26 , a ferrite bead 19 , and a resistor 20 .

[0054] The motor control unit 11 is composed of an IC chip or the like disposed on the circuit board 9. The motor control unit 11 outputs an output signal for controlling the inverter 12 based on a PWM signal input from an external device. In addition, the motor control unit 11 outputs a speed signal corresponding to the speed of the rotor 5 to the external device. In order to make the motor 2 a desired speed, the external device outputs a PWM signal to the motor control unit 11 based on the speed signal.

[0055] Inverter 12 includes switching elements Q1 and Q2 constituting upper and lower arms for U phase, switching elements Q3 and Q4 constituting upper and lower arms for V phase, and switching elements Q5 and Q6 constituting upper and lower arms for W phase. MOS FETs are used as each of switching elements Q1 to Q6, for example.

[0056] The drain of the switching element Q1, the drain of the switching element Q3, and the drain of the switching element Q5 are connected to the driving voltage line 13. The source of the switching element Q2, the source of the switching element Q4, and the source of the switching element Q6 are connected to the ground line 100 via the shunt resistor Rs. Both ends of the shunt resistor Rs are connected to the motor control unit 11 from the output line 121 and the output line 122 via the resistors R33 and R34.

[0057] The source of the switching element Q1 and the drain of the switching element Q2 are connected to the U-phase coil 61 of the three-phase coil 6. The source of the switching element Q3 and the drain of the switching element Q4 are connected to the V-phase coil 62 of the three-phase coil 6. The source of the switching element Q5 and the drain of the switching element Q6 are connected to the W-phase coil 63 of the three-phase coil 6.

[0058] A capacitor 51 is connected to the source of the switching element Q1 and the drain of the switching element Q2 on the side opposite to the side connected to the U-phase coil 61 of the three-phase coil 6. A capacitor 52 is connected to the source of the switching element Q3 and the drain of the switching element Q4 on the side opposite to the side connected to the V-phase coil 62 of the three-phase coil 6. A capacitor 53 is connected to the source of the switching element Q5 and the drain of the switching element Q6 on the side opposite to the side connected to the W-phase coil 63 of the three-phase coil 6. The capacitors 51 to 53 are charging and discharging capacitors of the bootstrap circuit.

[0059] Bootstrapping diodes D31 to D33 are connected between the capacitors 51 to 53 and the motor control unit 11 , respectively. The diodes D31 to D33 are connected to the motor control unit 11 via a resistor R31 .

[0060] Resistors R11 to R16 are connected between the gate and source of each switching element Q1 to Q6. Resistors R21 to R26 are connected between the gate of each switching element Q1 to Q6 and the motor control unit 11. Filters 41 to 46 are connected between the drain and source of each switching element Q1 to Q6. Filters 41 to 46 are composed of resistors and capacitors connected in series.

[0061] The inverter 12 is a circuit that converts the driving voltage supplied from the driving voltage line 13 into a three-phase alternating current by switching the switching elements Q1 to Q6, and rotates the rotor 5 of the motor 2 by passing the three-phase alternating current driving voltage to the motor 2. The inverter 12 drives the motor 2 based on the output signal output by the motor control unit 11.

[0062] The driving voltage line 13 supplies power to the motor control unit 11 and the inverter 12. In this embodiment, a rated voltage of 12V is applied to the driving voltage line 13. An inductor 18 and a first capacitor 21 are connected to the driving voltage line 13. The inductor 18 is electrically connected in series with the driving voltage line 13. The first capacitor 21 is electrically connected between a portion of the driving voltage line 13 between the inverter 12 and the inductor 18 and a ground line. In this embodiment, the electrostatic capacitance C2 of the first capacitor 21 is 150μF.

[0063] The driving voltage line 13 is connected to a capacitor 27 and a diode 31. The capacitor 27 is electrically connected between a portion of the driving voltage line 13 closer to the output side than the first capacitor 21 and the ground line 100. The diode 31 is electrically connected between a portion of the driving voltage line 13 between the inductor 18 and the first capacitor 21 and the ground line 100.

[0064] A first line 131 and a second line 132 are connected to the driving voltage line 13. The first line 131 and the second line 132 are electrically connected to the motor control unit 11, and supply power to the motor control unit 11. The first line 131 is branched on the output side of the capacitor 27 and is electrically connected to the motor control unit 11. The capacitor 28 electrically connected to the ground line 100 is connected to the first line 131. The second line 132 is electrically connected to the motor control unit 11 via the resistor R32.

[0065] A second capacitor 22 is connected to the driving voltage line 13. The second capacitor 22 is electrically connected between a portion of the driving voltage line 13 that is closer to the input side than the first capacitor 21 and the ground line. More specifically, the second capacitor 22 is electrically connected between a portion of the driving voltage line 13 that is closer to the input side than the inductor 18 and the ground line. The third capacitor 23 is electrically connected between the second capacitor 22 and the ground line 100. That is, the second capacitor 22 and the third capacitor 23 are connected in series between the driving voltage line 13 and the ground line 100 on the input side that is closer to the inductor 18. In this embodiment, the second capacitor 22 and the third capacitor 23 are composed of the same capacitor. That is, the electrostatic capacitance C1 of the second capacitor 22 and the electrostatic capacitance C1 of the third capacitor 23 are the same. In addition, the electrostatic capacitance C1 of each of the second capacitor 22 and the third capacitor 23 is preferably 1.0μF≤C1≤4.7μF.

[0066] Here, the common line 14 is electrically connected to the middle point M between the second capacitor 22 and the third capacitor 23. That is, the neutral point 65 electrically connected to the common line 14 is sandwiched between the second capacitor 22 and the third capacitor 23. In addition, the ground line 17 is connected between the third capacitor 23 and the ground line 100.

[0067] The resistor 20 is electrically connected in series with the second capacitor 22 or the third capacitor 23. In this embodiment, the resistor 20 includes a first resistor 201 and a second resistor 202, wherein the first resistor 201 is electrically connected in series between the input side of the driving voltage line 13 and the second capacitor 22, and the second resistor 202 is electrically connected in series between the third capacitor 23 and the ground line 100. In this embodiment, the first resistor 201 and the second resistor 202 are composed of the same resistor. That is, the resistance value Ra of the first resistor 201 and the second resistor 202 is the same. In addition, the resistance value Ra of the first resistor 201 and the second resistor 202 is preferably 100Ω≤Ra.

[0068] The control signal line 15 transmits a PWM signal from an external device to the motor control unit 11. A ferrite bead 19, a fourth capacitor 24, a sixth capacitor 26, and a resistor R3 are connected to the control signal line 15. The fourth capacitor 24 is electrically connected between the control signal line 15 and the ground line 100. The ferrite bead 19 is electrically connected in series with the control signal line 15 at a portion closer to the output side of the control signal line 15 than the fourth capacitor 24. The sixth capacitor 26 is electrically connected between a portion closer to the output side of the control signal line 15 than the ferrite bead 19 and the ground line 100. The resistor R3 is electrically connected in series with the control signal line 15 at a portion closer to the output side of the control signal line 15 than the sixth capacitor 26.

[0069] The third line 151 connected to the first line 131 is connected to the control signal line 15. The third line 151 is electrically connected to the control signal line 15 between the ferrite bead 19 and the resistor R3. The third line 151 is electrically connected in series with the resistor R2.

[0070] The FG output line 16 transmits the speed signal of the motor 2 output from the motor control unit 11 to the external device. The fifth capacitor 25, the resistor R1, and the NOT gate Q7 are connected to the FG output line 16. The fifth capacitor 25 is electrically connected between the FG output line 16 and the ground line 100. The resistor R1 is electrically connected in series with the FG output line 16 at a portion closer to the input side of the FG output line 16 than the fifth capacitor 25. The NOT gate Q7 is electrically connected in series with the FG output line 16 at a portion closer to the input side of the FG output line 16 than the resistor R1. In this embodiment, the electrostatic capacitance C3 of the fifth capacitor 25 is 0.047μF.

[0071] (Effect)

[0072] The motor control unit 10 of this embodiment includes an inductor 18 and a first capacitor 21, wherein the inductor 18 is electrically connected in series with the drive voltage line 13, and the first capacitor 21 is electrically connected between a portion of the drive voltage line 13 between the inverter 12 and the inductor 18 and the ground line 100. With this configuration, the drive voltage flowing through the drive voltage line 13 can be smoothed, and thus the noise generated in the drive voltage line 13 can be suppressed.

[0073] In addition, the motor control unit 10 of this embodiment includes: a second capacitor 22 and a third capacitor 23, wherein the second capacitor 22 is electrically connected between the portion of the driving voltage line 13 closer to the input side than the first capacitor 21 and the ground line 100, and the third capacitor 23 is electrically connected between the second capacitor 22 and the ground line 100. The common line 14 is electrically connected to the neutral point 65 of the three-phase coil 6 and the middle point M between the second capacitor 22 and the third capacitor 23. Therefore, since the neutral point 65 electrically connected to the common line 14 is sandwiched by the second capacitor 22 and the third capacitor 23, even when a voltage with a large amplitude is generated at the neutral point 65, the voltage can be smoothed. Thus, the noise generated in the motor 2 can be suppressed. In addition, since the second capacitor 22 is electrically connected between the portion of the driving voltage line 13 closer to the input side than the inductor 18 and the ground line 100, the effect of suppressing the noise generated in the motor 2 is greater than the case where the second capacitor 22 is electrically connected between the portion of the driving voltage line 13 closer to the output side than the inductor 18 and the ground line 100.

[0074] In addition, the motor control unit 10 of this embodiment includes a resistor 20, which is electrically connected in series with the second capacitor 22 or the third capacitor 23. The resistor 20 includes a first resistor 201 and a second resistor 202, wherein the first resistor 201 is electrically connected in series between the input side portion of the drive voltage line 13 and the second capacitor 22, and the second resistor 202 is electrically connected in series between the third capacitor 23 and the ground line 100. In this embodiment, the first resistor 201 and the second resistor 202 are composed of the same resistor. Therefore, the noise generated in the motor 2 can be further suppressed.

[0075] Here, noise in a motor including the motor control unit 10 of the present embodiment and a motor including the motor control unit 10B of a comparative example will be described. Figure 3 This is a schematic circuit diagram of a motor control unit 10B of a comparative example. Except that the resistor 20 is not provided and the electrostatic capacitance C1 of the second capacitor 22 and the third capacitor 23 are different, Figure 3 The motor control unit 10B of the comparative example shown has the same structure as the motor control unit 10 of the present embodiment. Figure 3 The motor control unit 11, the inverter 12, the control signal line 15, the FG output line 16, etc. are omitted. Figure 3 The second capacitor 22 and the third capacitor 23 of the illustrated motor control unit 10B each have an electrostatic capacitance C1 of 0.1 μF.

[0076] Figure 4 is a diagram illustrating the noise reduction effect. Figure 4The results of measuring the noise levels generated from a motor including the motor control unit 10 of the present embodiment and a motor including the motor control unit 10B of the comparative example by a magnetic field antenna method test are shown. Figure 4 The resistance value Ra of the first resistor 201 and the second resistor 202 of the motor control unit 10B of the present embodiment shown is 1 kΩ, and the electrostatic capacitance C1 of each of the second capacitor 22 and the third capacitor 23 is 1.0 μF. Figure 4 As shown, in the AM frequency band (0.51 to 1.71 MHz), the motor of this embodiment can suppress the generation of noise more than the motor of the comparative example.

[0077] Next, the resistance value Ra and the electrostatic capacitance C1 are described. Figure 5 Graph showing the noise peak value when the resistance value Ra and the electrostatic capacitance C1 are changed. Figure 5 As shown, if the resistance value Ra of the first resistor 201 and the second resistor 202 is set to 100Ω≤Ra, the motor of this embodiment can suppress the noise peak in the AM band more than the motor of the comparative example. In addition, if the resistance value Ra of the first resistor 201 and the second resistor 202 is set to 1kΩ≤Ra, the motor of this embodiment can suppress the noise peak in the AM band by about 3dB compared with the motor of the comparative example, so the effect of further suppressing the noise peak in the AM band is large. In addition, when the respective resistance values ​​Ra are less than 100Ω, the noise reduction effect generated in the motor 2 cannot be fully obtained.

[0078] In addition, if Figure 5 As shown, if the electrostatic capacitance C1 of the second capacitor 22 and the third capacitor 23 is set to 1.0μF≤C1≤4.7μF, the motor of this embodiment can suppress the noise peak in the AM band more than the comparative motor. In addition, if the electrostatic capacitance C1 of the second capacitor 22 and the third capacitor 23 is set to 2.0μF≤C1≤4.7μF, the motor of this embodiment can further suppress the noise peak in the AM band compared with the comparative motor. In addition, when each electrostatic capacitance C1 is less than 1.0μF, the voltage at the neutral point cannot be fully smoothed, and the noise reduction effect generated in the motor cannot be fully obtained. In addition, when the electrostatic capacitance C1 is greater than 4.7μF, the rotation characteristics of the motor are low because the voltage at the neutral point is excessively smoothed.

[0079] The motor control unit 10 of this embodiment includes: a control signal line 15 for inputting a PWM signal from an external device to the motor control unit 11; and a fourth capacitor 24 electrically connected between the control signal line 15 and the ground line 100. Therefore, since the PWM signal transmitted in the control signal line 15 can be smoothed, the noise generated in the control signal line 15 can be removed. In addition, the motor control unit 10 of this embodiment includes: a ferrite bead 19 electrically connected in series with the control signal line 15 at a portion closer to the output side of the control signal line 15 than the fourth capacitor 24; and a sixth capacitor 26 electrically connected between a portion closer to the output side of the control signal line 15 than the ferrite bead 19 and the ground line 100. If it is configured in this way, the noise generated in the control signal line 15 can be further removed.

[0080] The motor control unit 10 of this embodiment includes: an FG output line 16 that transmits a rotation speed signal corresponding to the rotation speed of the motor 2 to an external device; and a fifth capacitor 25 that is electrically connected between the FG output line 16 and the ground line 100. Therefore, since the rotation speed signal transmitted in the FG output line 16 can be smoothed, noise generated in the FG output line 16 can be removed.

[0081] Here, the electrostatic capacitance of the first capacitor 21 and the fifth capacitor 25 will be described. Figure 6 This is a diagram comparing the electrostatic capacitance of capacitors.

[0082] like Figure 6 As shown in (A), when the electrostatic capacitance C2 of the first capacitor 21 is less than 100μF, the current ripple tends to become larger, and the driving voltage flowing through the driving voltage line 13 cannot be sufficiently smoothed. Therefore, it is difficult to effectively suppress the noise generated in the driving voltage line 13. Therefore, in this embodiment, the electrostatic capacitance C2 of the first capacitor 21 is 150μF, which satisfies 100μF≤C2, so the noise generated in the driving voltage line 13 can be suppressed. In addition, since the current ripple is suppressed, the first capacitor 21 will not be overheated. Therefore, the characteristics and reliability of the first capacitor 21 can be ensured.

[0083] like Figure 6As shown in (B), when the electrostatic capacitance C3 of the fifth capacitor 25 is greater than 0.1μF, the noise generated in the FG output line 16 can be removed, but the output waveform of the speed signal is easy to become flat. Therefore, since the external device cannot detect the speed signal of the motor 2 with high accuracy, it is difficult to control the motor 2 to the desired speed. Therefore, in this mode, the electrostatic capacitance C3 of the fifth capacitor 25 is 0.047μF, which satisfies C3≤0.1μF, so the noise generated in the FG output line 16 can be removed, and the motor 2 can be controlled to the desired speed.

[0084] Since the motor 2 of this embodiment is provided with the motor control unit 10, the noise generated by the motor 2 is suppressed. Therefore, when the motor 2 of this embodiment is used for the pump device 1, since the noise generated from the pump device 1 is suppressed, the precision equipment used around the pump device 1 is not easily affected by the noise. In addition, in the above embodiment, the case where the motor 2 is used for the pump device 1 is described, but the motor 2 can be used for various purposes.

[0085] (Implementation method 2)

[0086] Next, the motor control unit 10A of the second embodiment is described. The motor control unit 10A of the second embodiment is different from the motor control unit 10 of the first embodiment in that the positions of the first resistor 201 and the second resistor 202 are different. Therefore, in the second embodiment, the same reference numerals are sometimes given to the same structures as those in the first embodiment, and the description thereof is omitted. Figure 7 1 is a schematic circuit diagram of a motor control unit 10A according to Embodiment 2. Figure 7 In the figure, the motor control unit 11, the inverter 12, the control signal line 15, the FG output line 16, etc. are omitted.

[0087] like Figure 7 As shown, in the motor control unit 10A of this embodiment, the resistor 20 includes a first resistor 201 and a second resistor 202, which are electrically connected in series between the second capacitor 22 and the middle point M, and are electrically connected in series between the middle point M and the third capacitor 23. In this embodiment, the first resistor 201 and the second resistor 202 are composed of the same resistor. In this embodiment, the resistance value Ra of the first resistor 201 and the second resistor 202 is 1 kΩ, and the electrostatic capacitance C1 of the second capacitor 22 and the third capacitor 23 is 1.0 μF. Figure 4 As shown in FIG. 1 , in the AM frequency band (0.51 to 1.71 MHz), the motor equipped with the motor control unit 10A of the present embodiment can suppress the generation of noise more than the motor equipped with the motor control unit 10B of the comparative example. Figure 5As shown, the motor including the motor control unit 10A of this embodiment can suppress the noise peak in the AM band by about 4 dB compared with the comparative example motor. Therefore, the motor including the motor control unit 10A of this embodiment can obtain the same effects as those of the first embodiment.

[0088] (Other Implementations)

[0089] Next, other embodiments will be described. Figure 8 FIG. 1 is a schematic circuit diagram of a motor control unit 10C according to another embodiment. Figure 8 As shown, one resistor 20 may be connected in series to the common line 14. Thus, the resistor 20 is electrically connected in series to the third capacitor 23. In this case, as in the above embodiment, the resistance value Ra of the resistor 20 is preferably 100Ω≤Ra. Accordingly, in this embodiment, the same effect as in the above embodiment can be obtained.

[0090] Furthermore, the present technology can adopt the following structures. (1)

[0092] A motor control unit controls a motor having a three-phase coil wound on a stator core, characterized by comprising:

[0093] a motor control unit configured to control the rotation of the motor according to a control signal;

[0094] an inverter for applying a driving voltage supplied from a driving power supply to the three-phase coil based on an output signal from the motor control unit;

[0095] a driving voltage line, the driving voltage line supplying the driving voltage to the inverter;

[0096] an inductor electrically connected in series with the driving voltage line;

[0097] a first capacitor electrically connected between a portion of the driving voltage line between the inverter and the inductor and a ground line;

[0098] a second capacitor electrically connected between a portion of the driving voltage line closer to the input side than the first capacitor and a ground line;

[0099] a third capacitor, the third capacitor being electrically connected between the second capacitor and a ground line;

[0100] a common line electrically connected to a neutral point of the three-phase coil and a midpoint between the second capacitor and the third capacitor; and

[0101] A resistor is electrically connected in series with the second capacitor or the third capacitor. (2)

[0103] The motor control unit according to (1) is characterized in that:

[0104] The resistor includes a first resistor and a second resistor. The first resistor is electrically connected between the input side portion of the driving voltage line and the second capacitor. The second resistor is electrically connected between the third capacitor and a ground line. (3)

[0106] The motor control unit according to (1) is characterized in that:

[0107] The resistor includes a first resistor and a second resistor, the first resistor being electrically connected between the second capacitor and the intermediate point, and the second resistor being electrically connected between the intermediate point and the third capacitor. (4)

[0109] The motor control unit according to (1) is characterized in that:

[0110] The resistors are connected in series to the common line. (5)

[0112] The motor control unit according to (2) or (3), characterized in that:

[0113] When the resistance values ​​of the first resistor and the second resistor are each set to Ra, the following conditional expression is satisfied:

[0114] 100Ω≤Ra. (6)

[0116] The motor control unit according to (4) is characterized in that:

[0117] When the resistance value of the resistor is set to Ra, the following conditional formula is satisfied:

[0118] 100Ω≤Ra. (7)

[0120] The motor control unit according to any one of (1) to (6), characterized in that:

[0121] When the electrostatic capacitance of each of the second capacitor and the third capacitor is set to C1, the following conditional expression is satisfied:

[0122] 1.0μF ≤ C1 ≤ 4.7μF. (8)

[0124] The motor control unit according to any one of (1) to (7), characterized in that:

[0125] The second capacitor is electrically connected between a portion of the driving voltage line that is closer to an input side than the inductor and a ground line. (9)

[0127] The motor control unit according to any one of (1) to (8), characterized in that:

[0128] When the electrostatic capacitance of the first capacitor is set to C2, the following conditional expression is satisfied:

[0129] 100μF≤C2. (10)

[0131] The motor control unit according to any one of (1) to (9), characterized by comprising:

[0132] a control signal line that inputs the control signal to the motor control unit; and

[0133] A fourth capacitor is electrically connected between the control signal line and a ground line. (11)

[0135] The motor control unit according to (10) is characterized by comprising:

[0136] a ferrite bead electrically connected in series with the control signal line at a portion closer to the input side of the control signal line than the fourth capacitor; and

[0137] A sixth capacitor is electrically connected between a portion of the control signal line that is closer to the input side than the ferrite bead and a ground line. (12)

[0139] The motor control unit according to any one of (1) to (11), characterized by comprising:

[0140] an FG output line, the FG output line transmitting a speed signal corresponding to the speed of the motor to an external device; and

[0141] A fifth capacitor is electrically connected between the FG output line and a ground line. (13)

[0143] The motor control unit according to (12) is characterized in that:

[0144] When the electrostatic capacitance of the fifth capacitor is set to C3, the following conditional expression is satisfied:

[0145] C3≤0.1μF. (14)

[0147] An electric motor having:

[0148] A rotor, wherein the rotor is rotatable about a central axis;

[0149] a stator having a three-phase coil; and

[0150] The motor control unit according to any one of (1) to (13). (15)

[0152] A pump device comprising:

[0153] (14) The electric motor described;

[0154] an impeller fixed to the rotor; and

[0155] A casing accommodates the impeller and defines a pump chamber.

[0156] Description of Reference Numerals

[0157] 1: Pump device; 2: Motor; 3: Impeller; 4: Housing; 4A: Pump chamber; 5: Rotor; 6: Three-phase coil; 7: Stator; 8: Resin sealing component; 9: Circuit board; 10, 10A, 10B, 10C: Motor control unit; 11: Motor control unit; 12: Inverter; 13: Drive voltage line; 14: Common line; 15: Control signal line; 16: FG output line; 17: Ground line; 18: Inductor; 19: Ferrite bead; 20: Resistor; 21: First capacitor; 22: Second capacitor; 23: Third capacitor; 24: Fourth capacitor; 25: Fifth capacitor; 26: Sixth capacitor; 61: U-phase coil; 62: V-phase coil; 63: W-phase coil; 65: Neutral point; 70: Stator core; 71: Insulator; 100: Ground line; 201: First resistor; 202: Second resistor; M: Midpoint.

Claims

1. A motor control unit for controlling a motor having a three-phase coil wound around a stator core, characterized in that: have: a motor control unit configured to control the rotation of the motor according to a control signal; an inverter for applying a driving voltage supplied from a driving power supply to the three-phase coil based on an output signal from the motor control unit; a driving voltage line, the driving voltage line supplying the driving voltage to the inverter; an inductor electrically connected in series with the driving voltage line; a first capacitor electrically connected between a portion of the driving voltage line between the inverter and the inductor and a ground line; a second capacitor electrically connected between a portion of the driving voltage line closer to the input side than the first capacitor and a ground line; a third capacitor, the third capacitor being electrically connected between the second capacitor and a ground line; a common line electrically connected to a neutral point of the three-phase coil and a midpoint between the second capacitor and the third capacitor; as well as A resistor is electrically connected in series with the second capacitor or the third capacitor.

2. The motor control unit according to claim 1, characterized in that: The resistor includes a first resistor and a second resistor. The first resistor is electrically connected between the input-side portion of the driving voltage line and the second capacitor. The second resistor is electrically connected between the third capacitor and a ground line.

3. The motor control unit according to claim 1, characterized in that: The resistor includes a first resistor and a second resistor, the first resistor being electrically connected between the second capacitor and the intermediate point, and the second resistor being electrically connected between the intermediate point and the third capacitor.

4. The motor control unit according to claim 1, characterized in that: The resistors are connected in series to the common line.

5. The motor control unit according to claim 2 or 3, characterized in that: When the resistance values ​​of the first resistor and the second resistor are each set to Ra, the following conditional expression is satisfied: 100Ω≤Ra.

6. The motor control unit according to claim 4, characterized in that: When the resistance value of the resistor is set to Ra, the following conditional formula is satisfied: 100Ω≤Ra.

7. The motor control unit according to claim 1, characterized in that: When the electrostatic capacitance of each of the second capacitor and the third capacitor is set to C1, the following conditional expression is satisfied: 1.0μF ≤ C1 ≤ 4.7μF.

8. The motor control unit according to claim 1, characterized in that: The second capacitor is electrically connected between a portion of the driving voltage line that is closer to an input side than the inductor and a ground line.

9. The motor control unit according to claim 1, characterized in that: When the electrostatic capacitance of the first capacitor is set to C2, the following conditional expression is satisfied: 100μF≤C2.

10. The motor control unit according to claim 1, characterized in that: have: a control signal line for inputting the control signal to the motor control unit; and A fourth capacitor is electrically connected between the control signal line and a ground line.

11. The motor control unit according to claim 10, characterized in that: have: a ferrite bead electrically connected in series with the control signal line at a portion closer to the input side of the control signal line than the fourth capacitor; and A sixth capacitor is electrically connected between a portion of the control signal line that is closer to the input side than the ferrite bead and a ground line.

12. The motor control unit according to claim 1, characterized in that: have: an FG output line, the FG output line being used to transmit a speed signal corresponding to the speed of the motor to an external device; and A fifth capacitor is electrically connected between the FG output line and a ground line.

13. The motor control unit according to claim 12, characterized in that: When the electrostatic capacitance of the fifth capacitor is set to C3, the following conditional expression is satisfied: C3≤0.1μF.

14. An electric motor, comprising: A rotor, wherein the rotor is rotatable about a central axis; a stator having a three-phase coil; and The motor control unit as claimed in claim 1.

15. A pump device comprising: The electric motor according to claim 14; an impeller fixed to the rotor; and A casing accommodates the impeller and defines a pump chamber.

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