CN118353336A - Motor control device - Google Patents

Abstract

The present invention relates to a motor control device capable of suppressing a decline in abnormality determination accuracy of a current sensor. The motor control device (14) is provided with a1 st current sensor (29) provided on a negative bus bar (L2) and a2 nd current sensor (30) provided on a u-phase power transmission line (25 u). The 2 nd current sensor (30) is a Hall element type. The acquisition unit (36) acquires the detection value of the 1 st current sensor (29) and the detection value of the 2 nd current sensor (30) when the control unit (34) performs on/off control on the 3-phase upper arm switching elements (Qu 1, qv1, qw 1) and the 3-phase lower arm switching elements (Qu 2, qv2, qw 2), respectively. A determination unit (35) determines an abnormality of each of the current sensors (29, 30) based on the detection value of the 1 st current sensor (29) and the detection value of the 2 nd current sensor (30) when a current flows through the u-phase power transmission line (25 u) and the w-phase power transmission line (25 w).

Description

Motor control device

Technical Field

The present invention relates to a motor control device.

Background

For example, patent document 1 discloses a current sensor abnormality detection device that uses a plurality of current sensors for determining abnormality of a current sensor used in a motor generator. In addition, when a plurality of current sensors are used for determining abnormality of the current sensor, a hall element type current sensor may be used as the current sensor. The hall element type current sensor can detect a current by converting a magnetic field generated around an electric wire into a voltage using the hall effect of the hall element.

Prior art literature

Patent literature

Patent document 1: japanese patent laid-open publication No. 2011-223733

Disclosure of Invention

Problems to be solved by the invention

However, the detection accuracy of the hall element type current sensor is affected by the magnetic field and is degraded. Therefore, when the hall element type current sensor is used to determine an abnormality of the current sensor, the determination accuracy may be lowered.

Means for solving the problems

The motor control device for solving the above problems is provided with: an upper arm switching element of 3 phases and a lower arm switching element of 3 phases are electrically connected between the positive bus and the negative bus; a control unit that controls on/off of the 3-phase upper arm switching element and the 3-phase lower arm switching element, respectively; a1 st current sensor provided on the bus of the negative electrode and detecting a current flowing through the 3-phase lower arm switching element; a 2 nd current sensor provided on one 1 st power transmission line among 3 rd power transmission lines electrically connecting the 3 rd phase motor between the 3 rd phase upper arm switching element and the 3 rd phase lower arm switching element, and detecting a current flowing in the 3 rd phase motor; an acquisition unit that acquires a detection value of the 1 st current sensor and a detection value of the 2 nd current sensor; and a determination unit that determines abnormality of each current sensor by comparing the 2 detected values obtained from the obtaining unit, wherein the 2 nd current sensor is a hall element, and the determination unit determines abnormality of each current sensor based on the detected value of the 1 st current sensor and the detected value of the 2 nd current sensor when the control unit performs on/off control of the 3 rd upper arm switching element and the 3 rd lower arm switching element, respectively, when the 3 st power transmission line is a 3 rd power transmission line and the other power transmission line is a 2 nd power transmission line, which are the power transmission lines other than the 1 st power transmission line and closest to the 2 nd current sensor, among the 3 rd power transmission lines.

Thus, the abnormality of each current sensor is determined by the determination unit using the detection values when the 1 st power transmission line and the 2 nd power transmission line are supplied with current. Therefore, with the 2 nd current sensor, it is difficult to be influenced by the magnetic field generated at the 2 nd power transmission line, and it is not influenced by the magnetic field from the 3 rd power transmission line. Accordingly, the deterioration of the detection accuracy of the 2 nd current sensor due to the influence of the magnetic field generated in the 2 nd power transmission line can be suppressed, and the deterioration of the determination accuracy of the abnormality of the current sensor can be suppressed.

In the motor control device, the 1 st current sensor may include a shunt resistor.

In the motor control device, the determination unit may determine that the current sensor is abnormal when an absolute value of a difference between the detection value of the 1 st current sensor and the detection value of the 2 nd current sensor is equal to or greater than a threshold value.

Thus, abnormality of each current sensor can be determined based on the actual detection values of the 1 st current sensor and the 2 nd current sensor.

In the motor control device, the determination unit may determine that the current sensor is abnormal when a ratio of one of the detection value of the 1 st current sensor and the detection value of the 2 nd current sensor to the other detection value of the one detection value serving as a reference is out of a range of a threshold value.

In this way, the abnormality of each current sensor can be determined.

In the motor control device, the 3-phase motor and the motor control device may be mounted on an electric compressor. Thus, the abnormality of the electric motor caused by the abnormality of the 1 st current sensor and the 2 nd current sensor can be quickly detected.

With respect to the motor control device, the 2 nd current sensor may be surrounded by a shielding member that shields the magnetic field.

Thus, the shielding member can further hardly affect the magnetic field of the hall element of the 2 nd current sensor, and therefore, the decline of the detection accuracy of the 2 nd current sensor can be further suppressed. As a result, the decline of the accuracy of determining the abnormality of the current sensor can be further suppressed.

Effects of the invention

According to the present invention, it is possible to suppress a decrease in the accuracy of determining an abnormality of a current sensor.

Drawings

Fig. 1 is a block diagram showing an air conditioner for a vehicle.

Fig. 2 is a diagram showing an example of the configuration of the inverter circuit and the motor control device.

Fig. 3 is a diagram illustrating the flow of current.

Fig. 4 is a diagram illustrating the flow of current in another example.

Fig. 5 is a diagram showing an example of the configuration of an inverter circuit and a motor control device according to still another example.

Description of the reference numerals

The positive bus of L1 …, the negative bus of L2 …, qu1, qv1, qw1 … as u-phase switching element, v-phase switching element, w-phase switching element of upper arm switching element of 3 phases, qu2, qv2, qw2 … as u-phase switching element, v-phase switching element, w-phase switching element of lower arm switching element of 3 phases, 10 … electric compressor, 11 … as electric motor of 3 phases motor, 14 … motor control device, 24u … u-phase coil, 24v … v-phase coil, 24w … w-phase coil, 25u … as u-phase power transmission line of 1 st power transmission line, 25v … as v-phase power transmission line of 3 rd power transmission line, 25w … as w-phase power transmission line of 2 nd power transmission line, 29 … 1 st current sensor, 30 … nd current sensor, 31 … shielding member, 34 … control part, 35 … judgment part, 36 … acquisition part.

Detailed Description

An embodiment of the motor control device will be described below with reference to fig. 1 to 3.

< Motor control device >

As shown in fig. 1 and 2, a motor control device 14 and an electric motor 11 are mounted on an electric compressor 10. The motor control device 14 controls the electric motor 11 of the electric compressor 10. The motor-driven compressor 10 is used for an in-vehicle air conditioner 101.

< Vehicle-mounted air conditioner >

The vehicle-mounted air conditioner 101 is mounted on the vehicle 100. The vehicle air conditioner 101 includes an electric compressor 10, an external refrigerant circuit 102, an air conditioner ECU (Electronic Control Unit: electronic control unit) 103, and an electric storage device 104 as an external power source.

The external refrigerant circuit 102 supplies the refrigerant as a fluid to the motor-driven compressor 10. The external refrigerant circuit 102 includes, for example, a heat exchanger, an expansion valve, and the like. The in-vehicle air conditioner 101 performs cooling and heating of the vehicle interior. The cooling and heating of the vehicle interior are performed by compressing the refrigerant by the motor-driven compressor 10 and performing heat exchange and expansion of the refrigerant by the external refrigerant circuit 102.

The air conditioning ECU103 controls the entire vehicle air conditioning apparatus 101. The air conditioning ECU103 grasps the in-vehicle temperature, the set temperature of the in-vehicle air conditioning apparatus 101, and the like. The air conditioning ECU103 transmits various commands such as a command rotational speed to the electric compressor 10 based on parameters such as the temperature in the vehicle and the set temperature of the in-vehicle air conditioner 101.

The power storage device 104 may be any device as long as it can charge and discharge dc power. For example, secondary batteries, electric double layer capacitors, and the like. The power storage device 104 is used as a dc power supply for the electric compressor 10. A positive electrode bus L1 of inverter circuit 13 is connected to the positive electrode of power storage device 104. A negative electrode bus L2 of inverter circuit 13 is connected to a negative electrode of power storage device 104. In the inverter circuit 13, a dc voltage is applied between the positive electrode bus L1 and the negative electrode bus L2.

< Electric compressor >

The electric compressor 10 includes an electric motor 11, a compression unit 12, and a motor control device 14. The compression section 12 is driven by an electric motor 11.

The electric motor 11 includes a rotary shaft 21, a rotor 22 fixed to the rotary shaft 21, a stator 23 facing the rotor 22, and u-phase coils 24u, v-phase coils 24v, and w-phase coils 24w wound around the stator 23. The electric motor 11 is a 3-phase motor. In the following description, when u-phase coil 24u, v-phase coil 24v, and w-phase coil 24w are not distinguished from each other, these coils are referred to as "3-phase coils 24u, 24v, 24w".

The rotor 22 includes permanent magnets 22a. The permanent magnet 22a is embedded in the rotor 22. The 3-phase coils 24u, 24v, 24w are, for example, Y-wired. The connection method of the 3-phase coils 24u, 24v, and 24w is not limited to the Y-connection, and may be arbitrary, for example, a triangle connection. The 3-phase coils 24u, 24v, and 24w are energized in a predetermined pattern, and the rotor 22 and the rotary shaft 21 rotate.

The compression unit 12 is driven by the electric motor 11 to compress the refrigerant. The compression unit 12 compresses the refrigerant supplied from the external refrigerant circuit 102 by rotation of the rotary shaft 21. The compression portion 12 discharges the compressed refrigerant to the external refrigerant circuit 102. The compression unit 12 is configured by a scroll type, a piston type, a vane type, or the like.

< Motor control device >

The motor control device 14 includes an inverter circuit 13, a control unit 34, a determination unit 35, an acquisition unit 36, a1 st current sensor 29, and a2 nd current sensor 30.

< Inverter Circuit >

Inverter circuit 13 converts the dc power output from power storage device 104 into ac power. The electric motor 11 is driven by ac power output from the inverter circuit 13.

As shown in fig. 2, the inverter circuit 13 includes switching elements of 3 phases. The inverter circuit 13 includes u-phase switching elements Qu1 and Qu2 corresponding to the u-phase coil 24u, v-phase switching elements Qv1 and Qv2 corresponding to the v-phase coil 24v, and w-phase switching elements Qw1 and Qw2 corresponding to the w-phase coil 24 w. In the following description, when u-phase switching elements Qu1, qu2, v-phase switching elements Qv1, qv2, and w-phase switching elements Qw1, qw2 are not distinguished from each other, they are described as "3-phase switching elements Qu1 to Qw2".

The 3-phase switching elements Qu1 to Qw2 are realized by power switching elements such as IGBTs (Insulated Gate Bipolar Transistor: insulated gate bipolar transistors). The u-phase switching element Qu1 has a reflux diode Du1, and the u-phase switching element Qu2 has a reflux diode Du2. The v-phase switching element Qv1 has a reflux diode Dv1, and the v-phase switching element Qv2 has a reflux diode Dv2. The w-phase switching element Qw1 has a reflux diode Dw1, and the w-phase switching element Qw2 has a reflux diode Dw2. In the following description, the description will be made as "reflux diodes Du1 to Dw2" when the reflux diodes Du1, du2, dv1, dv2, dw1, dw2 are not distinguished from each other. The cathodes of the reflux diodes Du1 to Dw2 are connected to the collectors of the corresponding 3-phase switching elements Qu1 to Qw 2. The anodes of the reflux diodes Du1 to Dw2 are connected to the emitters of the corresponding 3-phase switching elements Qu1 to Qw 2.

A u-phase switching element Qu1 as an upper arm switching element and a u-phase switching element Qu2 as a lower arm switching element are connected in series between the positive electrode bus bar L1 and the negative electrode bus bar L2. Further, between the positive electrode bus bar L1 and the negative electrode bus bar L2, a v-phase switching element Qv1 as an upper arm switching element and a v-phase switching element Qv2 as a lower arm switching element are connected in series. Further, a w-phase switching element Qw1 as an upper arm switching element and a w-phase switching element Qw2 as a lower arm switching element are connected in series between the positive electrode bus bar L1 and the negative electrode bus bar L2. Accordingly, the motor control device 14 includes 3-phase upper arm switching elements Qu1, qv1, qw1 and 3-phase lower arm switching elements Qu2, qv2, qw2 electrically connected between the positive electrode bus bar L1 and the negative electrode bus bar L2, which are positive and negative electrode bus bars. In the following description, when u-phase switching element Qu1, v-phase switching element Qv1, and w-phase switching element Qw1 are not distinguished from each other, the upper arm switching elements Qu1 to Qw1 of "3 phases" are described. In the following description, when u-phase switching element Qu2, v-phase switching element Qv2, and w-phase switching element Qw2 are not distinguished from each other, these are described as "3-phase lower arm switching elements Qu2 to Qw2". In the inverter circuit 13, the upper arm switching elements Qu1 to Qw1 of 3 phases and the lower arm switching elements Qu2 to Qw2 of 3 phases are arranged in the order of u-phase, v-phase, and w-phase.

The intermediate point of the series circuit based on the u-phase switching elements Qu1, qu2 is connected to the u-phase coil 24u via the u-phase power transmission line 25 u. The intermediate point of the series circuit based on the v-phase switching elements Qv1, qv2 is connected to the v-phase coil 24v via the v-phase power transmission line 25 v. The intermediate point of the series circuit based on the w-phase switching elements Qw1, qw2 is connected to the w-phase coil 24w via the w-phase power transmission line 25 w.

The inverter circuit 13 includes 3-phase power transmission lines connecting the 3-phase switching elements Qu1 to Qw2 to the 3-phase coils 24u, 24v, and 24 w. Accordingly, the motor control device 14 includes a 3-phase power transmission line electrically connecting the 3-phase motor between the 3-phase upper arm switching elements Qu1 to Qw1 and the 3-phase lower arm switching elements Qu2 to Qw 2.

Specifically, the inverter circuit 13 includes a u-phase power transmission line 25u, a v-phase power transmission line 25v, and a w-phase power transmission line 25w. In the inverter circuit 13, u-phase power transmission lines 25u, v-phase power transmission lines 25v, and w-phase power transmission lines 25w are provided as patterns on a substrate, not shown. The u-phase power transmission lines 25u, v-phase power transmission lines 25v, and w-phase power transmission lines 25w are arranged such that at least a part thereof is arranged in 3 rows on the mounting surface. That is, the u-phase power transmission lines 25u, v-phase power transmission lines 25v, and w-phase power transmission lines 25w each have 3 rows of portions arranged.

Specifically, the u-phase power transmission lines 25u, v-phase power transmission lines 25v, and w-phase power transmission lines 25w are arranged in the order of arrangement of the u-phase power transmission lines 25u, v-phase power transmission lines 25v, and w-phase power transmission lines 25w along one direction. Therefore, the power transmission lines arranged in 3 columns are the arrangement order of the u-phase power transmission line 25u, the v-phase power transmission line 25v, and the w-phase power transmission line 25 w.

The u-phase power transmission line 25u, the v-phase power transmission line 25v, and the w-phase power transmission line 25w are adjacent to each other with a predetermined interval. That is, the u-phase power transmission line 25u is adjacent to the v-phase power transmission line 25v, and the v-phase power transmission line 25v is adjacent to the w-phase power transmission line 25 w. Therefore, the v-phase power transmission line 25v is sandwiched by the u-phase power transmission line 25u and the w-phase power transmission line 25 w. That is, the v-phase power transmission line 25v is a power transmission line in the middle among the power transmission lines arranged in 3 columns. The u-phase power transmission line 25u is one of 2 power transmission lines other than the v-phase power transmission line 25v in the middle, and the w-phase power transmission line 25w is the other.

< 1 St Current sensor >

The 1 st current sensor 29 is provided on the negative electrode bus bar L2. The 1 st current sensor 29 detects currents flowing through the 3-phase lower arm switching elements Qu2 to Qw 2. The 1 st current sensor 29 is a current sensor having a shunt resistor. When a current flows through the 1 st current sensor 29, a potential difference is generated across the shunt resistor. The 1 st current sensor 29 detects the value of the current flowing in the electric motor 11 based on the voltage across the shunt resistor. Accordingly, the 1 st current sensor 29 detects the current output from the inverter circuit 13. The 1 st current sensor 29 outputs the detection value to the motor control device 14.

< 2 Nd Current sensor >

The 2 nd current sensor 30 is provided on the u-phase power transmission line 25u, which is one of the 3-phase power transmission lines. Therefore, the u-phase power transmission line 25u is one of the 3-phase power transmission lines, i.e., the 1 st power transmission line. Here, among the 3-phase power transmission lines, the power transmission line closest to the 2 nd current sensor 30 as the power transmission line other than the u-phase power transmission line 25u is the v-phase power transmission line 25v, and the other power transmission line is the w-phase power transmission line 25w. Thus, the v-phase power transmission line 25v is the 3 rd power transmission line, and the w-phase power transmission line 25w is the 2 nd power transmission line. The w-phase power transmission line 25w is the power transmission line farthest from the 2 nd current sensor 30.

The 2 nd current sensor 30 detects a current flowing in the electric motor 11. The 2 nd current sensor 30 is a hall element type current sensor. The hall element is an element that converts a magnetic field generated around an electric wire into a voltage by using the hall effect. The 2 nd current sensor 30 detects a current value based on the voltage converted by the hall element. The 2 nd current sensor 30 is a so-called unprotected current sensor that does not include a shielding member. The shielding member is a member that shields the magnetic field around the shielding member, but the 2 nd current sensor 30 does not include the shielding member. In the present embodiment, since the 2 nd current sensor 30 is not provided with a shielding member, the influence of the magnetic field generated in the v-phase power transmission line 25v easily affects the 2 nd current sensor 30. On the other hand, the influence of the magnetic field generated in the w-phase power transmission line 25w farthest from the u-phase power transmission line 25u hardly affects the 2 nd current sensor 30. The 2 nd current sensor 30 detects a current flowing through the u-phase power transmission line 25 u. The 2 nd current sensor 30 outputs the detection value to the motor control device 14.

< Control part >

The control unit 34 is implemented by executing a program (software) by a hardware processor such as a CPU (Central Processing Unit: central processing unit). Some or all of these components may be realized by hardware (Circuit part; including Circuit (s)) such as LSI (LARGE SCALE Integration: large-scale integrated Circuit), ASIC (Application SPECIFIC INTEGRATED Circuit: application specific integrated Circuit), FPGA (Field-Programmable gate array) GATE ARRAY, GPU (Graphics Processing Unit) or the like, or may be realized by cooperation of software and hardware. The program may be stored in advance in a storage device (not shown) including a non-transitory storage medium such as an HDD (HARD DISK DRIVE: hard disk drive) and a flash memory included in the motor control device 14. The storage device is realized by, for example, the various storage devices described above, an EEPROM (ELECTRICALLY ERASABLE PROGRAMMABLE READ ONLY MEMORY: electrically erasable programmable Read Only Memory), a ROM (Read Only Memory), a RAM (Random Access Memory: random access Memory), or the like.

The control unit 34 controls the on/off of the 3-phase switching elements Qu1 to Qw2 by using the detection value of the 1 st current sensor 29 and the detection value of a voltage sensor, not shown, and controls the driving of the electric motor 11. The control unit 34 controls the drive voltage of the electric motor 11 by pulse width modulation. Specifically, the control unit 34 generates a PWM signal using a high-frequency triangular wave signal called a carrier signal and a voltage command signal for instructing a voltage. Then, the control unit 34 uses the generated PWM signal to perform on/off control of the upper arm switching elements Qu1 to Qw1 of the 3 phases and the lower arm switching elements Qu2 to Qw2 of the 3 phases. Thereby, the direct current from power storage device 104 is converted into alternating current. Then, the converted ac current is outputted to the electric motor 11 as a current of each phase, thereby controlling the driving of the electric motor 11.

Here, the energization pattern controlled by the control unit 34 will be described.

< Energization pattern 1>

The control unit 34 turns on the u-phase switching element Qu1 and the v-phase switching element Qv2 to flow a current to the u-phase coil 24u and the v-phase coil 24v of the electric motor 11. At this time, the current flowing in the v-phase switching element Qv2 is detected by the 1 st current sensor 29.

< Energization pattern 2>

The control unit 34 turns on the v-phase switching element Qv1 and the w-phase switching element Qw2 to flow a current to the v-phase coil 24v and the w-phase coil 24w of the electric motor 11. At this time, the current flowing in the w-phase switching element Qw2 is detected by the 1 st current sensor 29.

< Energization pattern 3>

The control unit 34 turns on the w-phase switching element Qw1 and the u-phase switching element Qu2 to flow current to the w-phase coil 24w and the u-phase coil 24u of the electric motor 11. At this time, the current flowing in the u-phase switching element Qu2 is detected by the 1 st current sensor 29.

< Energization pattern 4>

The control unit 34 causes the u-phase switching element Qu1 and the w-phase switching element Qw2 to flow current to the u-phase coil 24u and the w-phase coil 24w of the electric motor 11. At this time, the current flowing in the w-phase switching element Qw2 is detected by the 1 st current sensor 29.

< Energization pattern 5>

The control unit 34 turns on the v-phase switching element Qv1 and the u-phase switching element Qu2 to flow a current to the v-phase coil 24v and the u-phase coil 24u of the electric motor 11. At this time, the current flowing in the u-phase switching element Qu2 is detected by the 1 st current sensor 29.

< Energization pattern 6>

The control unit 34 turns on the w-phase switching element Qw1 and the v-phase switching element Qv2 to flow a current to the w-phase coil 24w and the v-phase coil 24v of the electric motor 11. At this time, the current flowing in the v-phase switching element Qv2 is detected by the 1 st current sensor 29.

In the energization modes 1 to 6, the switching elements other than the on switching element are turned off. Therefore, the control unit 34 performs on/off control of the 3-phase upper arm switching elements Qu1 to Qw1 and the 3-phase lower arm switching elements Qu2 to Qw 2.

< Acquisition part >

The acquisition unit 36 is connected to the determination unit 35. The acquisition unit 36 acquires the detection value of the 1 st current sensor 29 and the detection value of the 2 nd current sensor 30. Specifically, the obtaining unit 36 obtains the detection value of the 1 st current sensor 29 and the detection value of the 2 nd current sensor 30 when the control unit 34 performs on/off control on the 3-phase upper arm switching elements Qu1 to Qw1 and the 3-phase lower arm switching elements Qu2 to Qw2, respectively.

< Determination section >

The determination unit 35 determines abnormality of each of the current sensors 29 and 30. The determination unit 35 is activated when the control unit 34 controls the inverter circuit 13 in the energization mode 4. The determination unit 35 obtains the detection value of the 1 st current sensor 29 and the detection value of the 2 nd current sensor 30 from the obtaining unit 36. The determination unit 35 compares the obtained 2 detection values to determine abnormality of each of the current sensors 29 and 30.

The detection value of the 1 st current sensor 29 is a current value after the electric motor 11 flows. The detection value of the 2 nd current sensor 30 is a current value before the electric motor 11 flows. Therefore, the detection value of the 1 st current sensor 29 and the detection value of the 2 nd current sensor 30 are theoretically the same value if the detection accuracy of the sensors and the like are not considered. That is, the detection values of the 1 st current sensor 29 and the 2 nd current sensor 30 should be the same when they are normal.

Here, when any one of the 1 st current sensor 29 and the 2 nd current sensor 30 has an abnormality such as a fault, the detection value of the current sensor having the abnormality is a value greatly deviated from the normal value, which is the current value when both the current sensors 29 and 30 are normal. At this time, if no abnormality occurs in any other of the 1 st current sensor 29 and the 2 nd current sensor 30, the 2 detection values are greatly different. With the above, the determination unit 35 determines abnormality of each of the current sensors 29 and 30.

The determination unit 35 obtains the detection value of the 2 nd current sensor 30 and the detection value of the 1 st current sensor 29 from the obtaining unit 36, and compares the absolute value of the difference between the two detection values with a threshold value. The threshold value is set as follows. First, detection values obtained when abnormality occurs in each of the 1 st current sensor 29 and the 2 nd current sensor 30 are obtained in advance by experiments or the like. Then, the threshold value is set with the minimum value of the absolute value of the difference between the detection values obtained when one of the current sensors 29 and 30 is abnormal and the other is normal as a reference.

When the absolute value of the difference between the detected values is equal to or greater than the threshold value, the determination unit 35 determines that either one of the 1 st current sensor 29 and the 2 nd current sensor 30 is abnormal.

On the substrate, the u-phase power transmission line 25u is adjacent to the v-phase power transmission line 25 v. Thus, v-phase power transmission line 25v is closest to current sensor 2. Therefore, when a current flows through the v-phase power transmission line 25v, the influence of the magnetic field generated around the v-phase power transmission line 25v greatly affects the 2 nd current sensor 30. In the present embodiment, the 2 nd current sensor 30 is a hall element without a shielding member. Therefore, the influence of the magnetic field is greater in the ground wave and reaches the 2 nd current sensor 30. The closer the current sensor 30 is to the magnetic field, the greater the influence of the magnetic field is on the ground wave and the current sensor 30. The greater the influence of the magnetic field, the lower the detection accuracy of the 2 nd current sensor 30. For example, although the 2 nd current sensor 30 is normal, the detection value of the 2 nd current sensor 30 may be an abnormal value greatly deviated from the normal value. Thus, the absolute value of the difference between the detected values becomes equal to or greater than the threshold value. As a result, although the 1 st current sensor 29 and the 2 nd current sensor 30 are normal, the determination unit 35 determines that either the 1 st current sensor 29 or the 2 nd current sensor 30 is abnormal. As a result, the determination accuracy of the determination unit 35 is lowered.

Therefore, when determining the abnormality of each of the current sensors 29 and 30, that is, when determining the abnormality of each of the current sensors 29 and 30 by the determining unit 35, the determining unit 35 determines the abnormality of each of the current sensors 29 and 30 based on the detection value of the 1 st current sensor 29 and the detection value of the 2 nd current sensor 30 when the current flows through the u-phase power transmission line 25u and the w-phase power transmission line 25 w. That is, the determination unit 35 uses the detection value obtained by suppressing the influence of the magnetic field generated by the w-phase power transmission line 25w as the detection value of the 2 nd current sensor 30.

< Determination of abnormality by determination section >

Next, the determination of abnormality of each of the current sensors 29 and 30 by the determination unit 35 will be described together with the operation of the motor control device 14.

The abnormality of each of the current sensors 29 and 30 is determined when the inverter circuit 13 is controlled in the energization mode 4 by the control unit 34.

As shown in fig. 3, the control unit 34 turns on the u-phase switching element Qu1 and the w-phase switching element Qw2 to flow current to the u-phase coil 24u and the w-phase coil 24w of the electric motor 11. As shown by the one-dot chain line in fig. 3, current flows from u-phase switching element Qu1 to u-phase power transmission line 25u, u-phase coil 24u, w-phase coil 24w, w-phase power transmission line 25w, w-phase switching element Qw2, and negative bus bar L2. Thus, the current flows to the 1 st current sensor 29 after flowing through the 2 nd current sensor 30. The acquisition unit 36 acquires the detection value of the 1 st current sensor 29 and the detection value of the 2 nd current sensor 30 when the inverter circuit 13 is controlled in the energization mode 4. When the control unit 34 performs on/off control of the upper arm switching elements Qu1 to Qw1 of the 3 phases and the lower arm switching elements Qu2 to Qw2 of the 3 phases in order to be in the power-on mode 4, no magnetic field is generated around the v-phase power transmission line 25 v. In addition, although a magnetic field is generated around the w-phase power transmission line 25w, the w-phase power transmission line 25w is farthest from the 2 nd current sensor 30. Thus, with the 2 nd current sensor 30, there is no influence of the magnetic field from the v-phase power transmission line 25v, and it is difficult to be influenced by the magnetic field generated around the w-phase power transmission line 25 w. Therefore, if the 2 nd current sensor 30 is normal, the detection accuracy of the 2 nd current sensor 30 does not decrease to a normal value.

The determination unit 35 obtains the detection value of the 2 nd current sensor 30 and the detection value of the 1 st current sensor 29 from the obtaining unit 36, and compares the absolute value of the difference between the two detection values with a threshold value. When the absolute value of the difference between the detected values is equal to or greater than the threshold value, the determination unit 35 determines that either the 1 st current sensor 29 or the 2 nd current sensor 30 is abnormal.

As the case where the absolute value of the difference between the detected values is equal to or greater than the threshold value, a case where the 1 st current sensor 29 is abnormal and the 2 nd current sensor 30 is normal, a case where the 1 st current sensor 29 is normal and the 2 nd current sensor 30 is abnormal, and a case where each of the 1 st current sensor 29 and the 2 nd current sensor 30 is abnormal are assumed.

According to the above embodiment, the following effects can be obtained.

(1) The abnormality determination of each of the current sensors 29 and 30 by the determination unit 35 is performed using the detection value when the current flows through the u-phase power transmission line 25u and the w-phase power transmission line 25w in the energization pattern 4. Therefore, with the 2 nd current sensor 30, it is difficult to be influenced by the magnetic field generated at the w-phase power transmission line 25w, and there is no influence of the magnetic field from the v-phase power transmission line 25 v. Accordingly, the decrease in the detection accuracy of the 2 nd current sensor 30 due to the influence of the magnetic field generated in the w-phase power transmission line 25w can be suppressed, and therefore, the decrease in the determination accuracy of the abnormality of each of the current sensors 29 and 30 can be suppressed. As a result, as the 2 nd current sensor 30, a hall element type current sensor without a shielding member can be used. Thus, the cost of the 2 nd current sensor 30 can be suppressed as compared with the case of using a hall element type current sensor having a shielding member.

(2) In general, in the motor control device 14, since the electronic components are disposed in the vicinity of the positive electrode bus bar L1 and the negative electrode bus bar L2, the influence of the magnetic field generated by the electronic components easily affects the vicinity of the positive electrode bus bar L1 and the negative electrode bus bar L2. On the other hand, in the motor control device 14, since no electronic component is disposed in a portion near the electric motor 11 among the 3-phase power transmission lines 25u, 25v, and 25w, the influence of the magnetic field generated by the electronic component hardly affects the respective power transmission lines 25u, 25v, and 25w. The 2 nd current sensor 30 is provided on the u-phase power transmission line 25 u. Therefore, not only the influence of the magnetic field generated in the w-phase power transmission line 25w but also the influence of the magnetic field generated in the electronic component hardly reaches the 2 nd current sensor 30. Therefore, the 2 nd current sensor 30 is preferably provided on the u-phase power transmission line 25u than on the positive electrode bus line L1 and the negative electrode bus line L2.

(3) The 2 nd current sensor 30 is provided on the u-phase power transmission line 25 u. Therefore, the 2 nd current sensor 30 detects the value of the current flowing in the electric motor 11. Therefore, even when a failure or the like of the 1 st current sensor 29 occurs, the driving of the electric motor 11 can be controlled using the detection value of the 2 nd current sensor 30.

(4) The 1 st current sensor 29 is a current sensor having a shunt resistor. Therefore, the 1 st current sensor 29 can be made inexpensive.

(5) The determination unit 35 determines that the current sensors 29 and 30 are abnormal when the absolute value of the difference between the detection value of the 1 st current sensor 29 and the detection value of the 2 nd current sensor 30 is equal to or greater than a threshold value. Therefore, the determination unit 35 can determine the abnormality of each of the current sensors 29, 30 based on the actual detection values of the 1 st current sensor 29 and the 2 nd current sensor 30.

(6) The motor control device 14 controls the electric motor 11 of the electric compressor 10. The motor control device 14 controls the driving of the electric motor 11 using the detection value of the 1 st current sensor 29. The determination unit 35 of the motor control device 14 determines abnormality of each of the current sensors 29 and 30 with high accuracy. Therefore, the abnormality of the electric motor 11 caused by the abnormality of the 1 st current sensor 29 can be quickly found.

The embodiment can be modified as follows. The embodiments and the following modifications can be combined with each other within a range that is not technically contradictory.

The determination unit 35 may always be activated when the electric motor 11 is driven. When the control unit 34 controls the inverter circuit 13 in the power-on mode 4, the determination unit 35 determines an abnormality of each of the current sensors 29 and 30 based on the detection value of the 1 st current sensor 29 and the detection value of the 2 nd current sensor 30.

The 1 st current sensor 29 and the 2 nd current sensor 30 may be hall element type current sensors each having no shielding member. With such a configuration, the cost of the motor control device 14 can be further suppressed.

In this case, the detection values of the 1 st current sensor 29 and the 2 nd current sensor 30 are the same detection values of the hall element type current sensors. The determination unit 35 calculates a ratio of the detection value of the 1 st current sensor 29 to the detection value of the 2 nd current sensor 30 with respect to the detection value of the other of the detection values as a reference. When the calculated ratio is out of the threshold range, the determination unit 35 determines that each of the current sensors 29 and 30 is abnormal. The threshold value of the ratio is obtained in advance by an experiment or the like, and the detection value obtained when abnormality occurs in each of the 1 st current sensor 29 and the 2 nd current sensor 30. The threshold value is set with the minimum value of the ratio of the detection values obtained when one of the current sensors 29 and 30 is abnormal and the other is normal as a reference.

The 1 st current sensor 29 and the 2 nd current sensor 30 may be hall element type current sensors surrounded by a shielding member.

The 2 nd current sensor 30 may be provided in the w-phase power transmission line 25w. In this case, the abnormality of each of the current sensors 29 and 30 is determined by the determination unit 35 using the detection value when the current flows through the u-phase power transmission line 25u and the w-phase power transmission line 25w in the energization mode 3. As shown by the one-dot chain line in fig. 4, current flows from w-phase switching element Qw1 through w-phase power transmission line 25w, w-phase coil 24w, u-phase coil 24u, u-phase power transmission line 25u, u-phase switching element Qu2, and negative electrode bus bar L2 to current sensor 29 of 1 st phase. In this case, the 1 st power transmission line is a w-phase power transmission line 25w, and the 2 nd power transmission line is a u-phase power transmission line 25u. The 3 rd power transmission line is a v-phase power transmission line 25v.

As shown in fig. 5, the 2 nd current sensor 30 may be surrounded by a shielding member 31. The shielding member 31 is a member that shields a magnetic field around the shielding member 31. The 2 nd current sensor 30 is surrounded by the shielding member 31, and therefore the influence of the magnetic field generated in the v-phase power transmission line 25v and the w-phase power transmission line 25w is more difficult to reach the 2 nd current sensor 30. As a result, the decline in the detection accuracy of the 2 nd current sensor 30 can be further suppressed.

The order of arrangement of the u-phase power transmission lines 25u, v-phase power transmission lines 25v, and w-phase power transmission lines 25w may be changed as appropriate. For example, the 3-phase power transmission lines may be arranged in the order of the v-phase power transmission line 25v, the u-phase power transmission line 25u, and the w-phase power transmission line 25w in one direction. In this case, the v-phase power transmission line 25v is the 1 st power transmission line, and the w-phase power transmission line 25w is the 2 nd power transmission line. In addition, the u-phase power transmission line 25u is referred to as a3 rd power transmission line.

In the arrangement of the u-phase power transmission line 25u, the v-phase power transmission line 25v, and the w-phase power transmission line 25w, the 2 nd current sensor 30 may be provided on the v-phase power transmission line 25v, and the v-phase power transmission line 25v may be the 1 st power transmission line. In this case, one of the u-phase power transmission line 25u and the w-phase power transmission line 25w is the 3 rd power transmission line closest to the 2 nd current sensor 30, and the other of the u-phase power transmission line 25u and the w-phase power transmission line 25w is the 2 nd power transmission line.

Claims (6)

1. A motor control device is characterized by comprising:

An upper arm switching element of 3 phases and a lower arm switching element of 3 phases are electrically connected between the positive bus and the negative bus;

A control unit that controls on/off of the 3-phase upper arm switching element and the 3-phase lower arm switching element, respectively;

a1 st current sensor provided on the bus of the negative electrode and detecting a current flowing through the 3-phase lower arm switching element;

A2 nd current sensor provided on one 1 st power transmission line among 3 rd power transmission lines electrically connecting the 3 rd phase motor between the 3 rd phase upper arm switching element and the 3 rd phase lower arm switching element, and detecting a current flowing in the 3 rd phase motor;

an acquisition unit that acquires a detection value of the 1 st current sensor and a detection value of the 2 nd current sensor; and

A determination unit that compares the 2 detection values obtained by the obtaining unit to determine abnormality of each current sensor,

The 2 nd current sensor is a Hall element type,

When the power transmission line closest to the 2 nd current sensor as the power transmission line other than the 1 st power transmission line among the 3-phase power transmission lines is the 3 rd power transmission line and the other power transmission lines are the 2 nd power transmission line,

The acquisition unit acquires the detection value of the 1 st current sensor and the detection value of the 2 nd current sensor when the control unit performs on/off control of the 3-phase upper arm switching element and the 3-phase lower arm switching element, respectively,

The determination unit determines an abnormality of each of the current sensors based on the detection value of the 1 st current sensor and the detection value of the 2 nd current sensor when the current flows through the 1 st power transmission line and the 2 nd power transmission line.

2. The motor control device according to claim 1, wherein,

The 1 st current sensor includes a shunt resistor.

3. The motor control device according to claim 1 or 2, wherein,

The determination unit determines that the current sensor is abnormal when the absolute value of the difference between the detection value of the 1 st current sensor and the detection value of the 2 nd current sensor is equal to or greater than a threshold value.

4. The motor control device according to claim 1 or 2, wherein,

The determination unit determines abnormality in each of the current sensors when a ratio of one of the detection values of the 1 st current sensor and the 2 nd current sensor to the other detection value of the one detection value serving as a reference is out of a range of a threshold value.

5. The motor control device according to any one of claims 1 to 4, wherein,

The 3-phase motor and the motor control device are mounted on an electric compressor.

6. The motor control device according to any one of claims 1 to 5, wherein,

The 2 nd current sensor is surrounded by a shielding member that shields the magnetic field.