JP6750549B2 - Electric compressor - Google Patents

Description

The present invention relates to an electric compressor, and more particularly to an electric compressor configured to be connected to a vehicle-mounted main power source.

Japanese Patent Laying-Open No. 2005-326054 (Patent Document 1) discloses an electric compressor configured to be connected to a vehicle-mounted battery. This electric compressor includes a step-up/down converter, an inverter, and an AC motor. When starting the electric compressor at low temperature, the buck-boost converter steps down the output voltage to less than the voltage of the battery. The inverter outputs the DC current input from the buck-boost converter as it is to the AC motor without converting the DC power supplied from the buck-boost converter into AC power. The electric motor does not rotate even when a direct current flows through the coil of the AC motor, but the coil of the AC motor generates heat. Therefore, according to this electric compressor, the AC motor can be heated at a low temperature without generating noise due to the rotation of the AC motor (see Patent Document 1).

JP, 2005-326054, A

For example, in order to increase the cruising distance of a vehicle, a high-voltage power storage device may be adopted as a vehicle-mounted main power source (for example, a battery for traveling). When the voltage of the main power source becomes high, it is necessary to improve the dielectric strength of the parts to which the high voltage is applied. As a result, for example, the inverter of the electric compressor or the electric motor connected to the main power supply may become large. The problem of increasing the size of such an electric compressor and the means for solving the problem are not particularly examined in Patent Document 1 described above.

The present invention has been made to solve such a problem, and an object thereof is to suppress the increase in size of an electric compressor configured to be connected to a main power supply mounted on a vehicle. ..

The electric compressor according to the present invention is configured to be connected to a main power supply mounted on a vehicle. The electric compressor includes a compression unit, an electric motor, an inverter, a step-down converter, a control device, a housing, and a cover. The compression unit is configured to compress the refrigerant. The electric motor is configured to drive the compression unit. The inverter is configured to convert DC power supplied from the main power supply into AC power and supply AC power to the electric motor. The step-down converter is connected to the input terminal of the inverter and is configured to step down the input voltage of the inverter below the voltage of the main power supply. The control device is configured to perform PWM (Pulse Width Modulation) control of the inverter and the step-down converter. The housing houses the compression unit and the electric motor. The cover is attached to the housing to form a circuit chamber that houses the inverter, the step-down converter, and the control device. A suction port for sucking the refrigerant is provided in the housing. The control device is configured to make the carrier frequency in the PWM control of the step-down converter higher than the carrier frequency in the PWM control of the inverter.

According to this electric compressor, the carrier frequency in the PWM control of the step-down converter is set high, and the energy stored in the coil of the step-down converter is reduced by one switching, so the coil of the step-down converter can be downsized. .. Furthermore, the circuit room accommodating the step-down converter and the cover forming the circuit room can be downsized.

Preferably, the step-down converter is located closer to the intake port than the inverter in the circuit room.

According to this electric compressor, since the step-down converter is located closer to the intake port than the inverter, the heat generation of the step-down converter is suppressed even if the step-down converter carrier frequency is higher than the inverter carrier frequency. can do. As a result, for example, it is possible to prevent an increase in the number of parts and an increase in the number of parts for preventing overheating of the step-down converter, and thus it is possible to suppress an increase in the size of the electric compressor.

More preferably, the electric compressor further includes a communication circuit. The communication circuit is configured to communicate with a vehicle system external to the electric compressor. The communication circuit is housed in the circuit room and is configured to be connected to a vehicle-mounted auxiliary power source. The voltage of the sub power supply is lower than the voltage of the main power supply. The low-voltage part in the circuit room to which the voltage of the sub power source is applied includes the communication circuit and is arranged along the wall surface of the circuit room.

Since the voltage difference between the component and the wall surface is reduced due to the low voltage part being adjacent to the wall surface, for example, compared with the case where the step-down converter and the wall surface are arranged adjacent to each other, the insulation distance (gap between the wall surface) Can be shortened. As a result, according to this electric compressor, it is possible to prevent the electric compressor from increasing in size.

More preferably, the inverter is arranged between the step-down converter and the low voltage section including the communication circuit.

In this electric compressor, since the voltage difference between adjacent components is small, it is possible to shorten the insulation distance between components as compared with, for example, a case where the step-down converter and the communication circuit are arranged adjacent to each other. it can. As a result, according to this electric compressor, it is possible to prevent the electric compressor from increasing in size.

More preferably, the compression unit, the electric motor, and the circuit chamber are arranged in the rotation axis direction of the electric motor in the order of the compression unit, the electric motor, and the circuit chamber. The suction port is provided in the housing at a position closer to the circuit chamber than the electric motor.

In this electric compressor, since the suction port is closer to the circuit chamber than the electric motor, the inside of the circuit chamber (step-down converter and inverter) is cooled by the suction gas before being warmed by the electric motor. Therefore, according to this electric compressor, as compared with the case where the suction port is closer to the electric motor than the circuit room, it is possible to suppress an increase in the number of parts and an increase in the number of parts for preventing overheating of the step-down converter and the inverter. Therefore, it is possible to prevent the electric compressor from increasing in size.

More preferably, the electric compressor further includes a filter circuit. The filter circuit is connected to the input terminal of the step-down converter and is housed in the circuit chamber.

According to this electric compressor, the carrier frequency in the PWM control of the step-down converter is set high, the energy stored in the coil of the step-down converter is suppressed to a small value by one switching, and the ripple current flowing in the filter circuit becomes small. The parts of the filter circuit connected to the input side of the step-down converter can be downsized.

According to the present invention, it is possible to suppress the increase in size of an electric compressor configured to be connected to a main power supply mounted on a vehicle.

It is a figure which shows the structure of a vehicle air conditioner. It is a circuit diagram which shows an inverter unit and other circuits connected to an inverter unit. It is a figure for demonstrating the carrier frequency of a step-down converter and an inverter. It is a figure for demonstrating the applied voltage of an inverter unit and another circuit connected to an inverter unit. FIG. 4 is a cross-sectional view taken along the line IV-IV of FIG. 1 and is a diagram for explaining the arrangement location of each component in the circuit chamber. FIG. 9 is a diagram for explaining a carrier frequency of a step-down converter in Modification 1. FIG. 11 is a diagram for explaining the locations of arrangement of the ultra-high voltage part, the high voltage part, and the low voltage part in the circuit chamber in Modification 2; FIG. 10 is a diagram for explaining the arrangement locations of the ultra-high voltage part, the high voltage part, and the low voltage part in the circuit chamber in Modification 3;

Hereinafter, embodiments will be described in detail with reference to the drawings. It should be noted that the same or corresponding parts in the drawings are designated by the same reference numerals and the description thereof will not be repeated.

[Vehicle air conditioner configuration]
FIG. 1 is a diagram showing a configuration of a vehicle air conditioner 100 to which an electric compressor 10 according to the present embodiment is applied. Referring to FIG. 1, a vehicle air conditioner 100 is mounted on a vehicle and is configured to cool and heat the vehicle interior. Vehicle air conditioner 100 includes an electric compressor 10, an external cooling circuit 101, and an air conditioning ECU 102.

The external cooling circuit 101 is configured to supply the refrigerant to the electric compressor 10. The external cooling circuit 101 includes, for example, a heat exchanger and an expansion valve. The electric compressor 10 is configured to compress the refrigerant supplied from the external cooling circuit 101. That is, in the vehicle air conditioner 100, the electric compressor 10 compresses the refrigerant, and the external cooling circuit 101 performs heat exchange and expansion of the refrigerant. As a result, the vehicle interior is cooled and heated.

The air conditioning ECU 102 has a CPU (Central Processing Unit) and a memory (not shown) built therein, and controls each device of the vehicle air conditioning device 100 based on information stored in the memory and information from each sensor (not shown). The air conditioning ECU 102 can recognize, for example, the temperature set by the user for air conditioning in the vehicle interior and the current temperature in the vehicle interior. The air conditioning ECU 102 transmits various commands such as an on/off command to the electric compressor 10 based on these parameters, for example.

The electric compressor 10 includes a housing 11, a compression unit 12, an electric motor 13, and an inverter unit 30. The electric compressor 10 can be connected to the vehicle-side system 200 via a cable 150 and is configured to receive a direct current from the vehicle-side system 200. The relationship between the electric compressor 10 and the vehicle-side system 200 will be described later in detail.

The housing 11 has a substantially cylindrical shape and houses the compression unit 12 and the electric motor 13 therein. The housing 11 is formed with a suction port 11a through which the refrigerant is sucked from the external cooling circuit 101 and a discharge port 11b through which the refrigerant is discharged.

The compression unit 12 is configured to compress the refrigerant sucked from the suction port 11a and discharge the compressed refrigerant from the discharge port 11b. The compression unit 12 may be any type of scroll type, piston type, vane type, and the like.

The electric motor 13 is configured to drive the compression unit 12. The electric motor 13 includes, for example, a rotating shaft 21, a rotor 22, and a stator 23. The rotary shaft 21 has a cylindrical shape and is rotatably supported by the housing 11. The rotor 22 has a cylindrical shape and is fixed to the rotating shaft 21. The stator 23 is fixed to the housing 11. The rotor 22 and the stator 23 face each other in the radial direction of the rotary shaft 21. The stator 23 includes a cylindrical stator core 24 and a coil 25. The coil 25 is formed by winding around the teeth of the stator core 24.

The inverter unit 30 includes an inverter 31, a step-down converter 70, a cover 32, and various circuits (for example, a communication circuit 80, a filter circuit 63, drive circuits 53 and 72, a power supply circuit 55, an insulation circuit 60, and a control device 61. ) And. The various circuits are arranged in a circuit chamber 33 formed inside the cover 32. Various circuits will be described later in detail.

The inverter 31 is a drive circuit that drives the electric motor 13. The inverter 31 is connected to the coil 25 of the electric motor 13 via a connector or the like (not shown). The inverter 31 is configured to convert DC power supplied from the vehicle-side system 200 (main power supply B1 (described later)) into AC power and supply the converted AC power to the electric motor 13.

The inverter 31 is electrically connected to the circuit board 51. The wiring pattern is mounted on the circuit board 51, and in addition to the inverter 31, the step-down converter 70 and various circuits (for example, the communication circuit 80, the filter circuit 63, the drive circuits 53 and 72, the power supply circuit 55, the insulating circuit). 60 and a control device 61) are mounted. Since these circuits are mounted on the same substrate, the inverter unit 30 can be downsized as compared with the case where these circuits are mounted on different substrates.

The step-down converter 70 is configured to step down the input voltage of the inverter 31 below the voltage of the main power source B1. The voltage after being stepped down by the step-down converter 70 is applied to the inverter 31. Therefore, even if the main power source B1 has a high voltage, the high voltage is not directly applied to the inverter 31, so that the dielectric strength required for each component forming the inverter 31 can be suppressed low. As a result, upsizing of the inverter 31 is suppressed.

The cover 32 is fixed to the housing 11 with bolts 43. By attaching the cover 32 to the housing 11, the circuit chamber 33 that houses the inverter 31, the step-down converter 70, the control device 61, and the like is formed. A connector 54 is provided on the outer surface of the cover 32, and the circuit board 51 and the connector 54 are electrically connected.

In the electric compressor 10, the compression unit 12, the electric motor 13, and the circuit chamber 33 (cover 32) are arranged such that the compression unit 12, the electric motor 13, the circuit chamber 33 (cover) from the discharge port 11b side in the direction of the rotating shaft 21. 32). The suction port 11a is provided in the housing 11 at a position closer to the circuit chamber 33 (cover 32) than the electric motor 13. Therefore, in the electric compressor 10, the inside of the circuit chamber 33 (cover 32) is cooled by the suction gas (refrigerant) that has not been warmed by the electric motor 13. As a result, according to the electric compressor 10, as compared with the case where the suction port 11a is closer to the electric motor 13 than the circuit chamber 33 (cover 32), the inside of the circuit chamber 33 (cover 32) (the step-down converter 70 and the inverter). Since it is possible to suppress the increase in the number of parts and the increase in the number of parts for preventing overheating in 31), it is possible to suppress the increase in size of the electric compressor 10.

The connector 54 is configured to be connected with the cable 150. DC power is supplied from the vehicle-side system 200 (main power supply B1) to the inverter 31 via the connector 54 and the cable 150.

[Circuit configuration of electric compressor]
FIG. 2 is a circuit diagram showing the inverter unit 30 and other circuits connected to the inverter unit 30. Referring to FIG. 2, electric compressor 10 can be connected to vehicle-side system 200 via cable 150 (FIG. 1). The vehicle-side system 200 includes a main power supply B1.

The main power source B1 is a power storage element configured to be chargeable and dischargeable. The main power source B1 is configured to include, for example, a secondary battery such as a lithium-ion battery, a nickel hydrogen battery or a lead storage battery, or a storage element such as an electric double layer capacitor. The main power source B1 is configured to supply DC power to the electric compressor 10 in a state where the vehicle system 200 is connected to the electric compressor 10.

The electric compressor 10 includes an electric motor 13 and an inverter unit 30. The electric motor 13 is a so-called three-phase motor. The electric motor 13 is driven by using the AC power supplied from the inverter unit 30 (inverter 31).

The inverter unit 30 includes a filter circuit 63, a step-down converter 70, an inverter 31, drive circuits 53 and 72, a power supply circuit 55, a communication circuit 80, an insulating circuit 60, and a control device 61.

The filter circuit 63 includes a common mode filter F1, a coil L1, and capacitors C1 and C2. The common mode filter F1 is connected to the positive electrode line PL1 and the negative electrode line NL1. The coil L1 is connected to the positive electrode line PL1. The capacitors C1 and C2 are connected in series between the positive electrode line PL1 and the negative electrode line NL1.

The step-down converter 70 is configured to step down the input voltage of the inverter 31 below the voltage of the main power source B1. The step-down converter 70 is connected between the filter circuit 63 and the inverter 31. That is, the step-down converter 70 is connected to the output terminal of the filter circuit 63 and the input terminal of the inverter 31.

Step-down converter 70 includes a switching element T1, a diode D1, a coil L2, and a capacitor C3. The switching element T1 and the diode D1 are connected in series between the positive electrode line PL1 and the negative electrode line NL1. The coil L2 is connected between the node N5 and the node N4 between the switching element T1 and the diode D1. A capacitor C3 is connected between the node N5 and the negative electrode line NL2. The capacitor C3 also functions as a smoothing capacitor of the inverter 31.

In step-down converter 70, energy is stored in coil L2 when drive circuit 72 connected to the gate terminal of switching element T1 outputs an ON signal. When the output of the ON signal of the drive circuit 72 is stopped, the coil L2 tries to maintain the current, generates an electromotive force, and causes the current to flow through the diode D1. In step-down converter 70, the voltage after step-down is adjusted by adjusting the duty cycle of switching element T1.

The inverter 31 is a so-called three-phase inverter. Inverter 31 includes switching elements TU1 and TU2 connected in series between positive electrode line PL2 and negative electrode line NL2 (hereinafter, also referred to as “between power line pairs”), and switching element TV1 connected in series between power line pairs. It includes TV2 and switching elements TW1 and TW2 connected in series between the pair of power lines. Each of the switching elements TU1, TU2, TV1, TV2, TW1, TW2 (hereinafter, also referred to as “switching element TU1-TW2”) is configured by, for example, an IGBT (Insulated Gate Bipolar Transistor). Diodes DU1, DU2, DV1, DV2, DW1 and DW2 are respectively connected in antiparallel to the switching elements TU1-TW2.

A node N1 between the switching element TU1 and the switching element TU2 is connected to a U-phase coil (not shown) of the electric motor 13. A node N2 between the switching element TV1 and the switching element TV2 is connected to a V-phase coil (not shown) of the electric motor 13. A node N3 between the switching element TW1 and the switching element TW2 is connected to a W-phase coil (not shown) of the electric motor 13.

The drive circuit 72 is configured to drive the switching element T1 of the step-down converter 70. The drive circuit 72 switches ON/OFF of the switching element T1 according to the control signal output from the control device 61.

The drive circuit 53 is configured to drive the switching elements TU1-TW2 of the inverter 31. The drive circuit 53 switches ON/OFF of each switching element according to a control signal output from the control device 61.

The power supply circuit 55 is configured to receive power from the sub power supply B2 of the vehicle side system 200. The sub power source B2 is a power storage element configured to be chargeable/dischargeable, and is, for example, an auxiliary battery. The voltage of the sub power supply B2 is lower than the voltage of the main power supply B1. The sub power source B2 is configured to include, for example, a secondary battery such as a lithium ion battery, a nickel hydrogen battery or a lead storage battery, or a power storage element such as an electric double layer capacitor. The power supply circuit 55 is configured to convert the power supplied from the sub power supply B2 into a desired power. The converted electric power is supplied to the control device 61, for example.

The communication circuit 80 is an interface for communication between the vehicle side system 200 (for example, the air conditioning ECU 102) and the control device 61. The communication circuit 80 receives, for example, a command indicating the target rotation speed of the electric motor 13 from the air conditioning ECU 102 (FIG. 1) and outputs the received command to the control device 61. The communication circuit 80 is supplied with power from the sub power supply B2, for example. The communication circuit 80 is connected to the control device 61 via the insulating circuit 60. The insulating circuit 60 is composed of, for example, a photo coupler.

The control device 61 has a CPU and a memory (not shown) built therein, and controls the drive circuits 72 and 53 based on the information stored in the memory and the information from each sensor. The control device 61 drives the step-down converter 70 by driving the drive circuit 72, for example. Further, the control device 61 drives the drive circuit 53 to drive the inverter 31.

[Carrier frequency of inverter and converter]
For example, suppose that electric compressor 10 is not provided with step-down converter 70 and main power supply B1 has a high voltage. In this case, since a high voltage is applied to the inverter 31 and the electric motor 13, the dielectric strength required for each component of the inverter 31 and the electric motor 13 becomes high. As a result, for example, the inverter 31 and the electric motor 13 may be upsized. In electric compressor 10 according to the present embodiment, since step-down converter 70 is provided, high voltage of main power supply B1 is not directly applied to inverter 31 or electric motor 13. Therefore, according to the electric compressor 10, it is possible to suppress the dielectric strength required for each component of the inverter 31 and the electric motor 13, and it is possible to prevent the inverter 31 and the electric motor 13 from increasing in size.

The electric compressor 10 is further devised to reduce the size of the main body (suppress the increase in size). Specifically, the control device 61 is configured to control the drive circuits 72 and 53 so that the carrier frequency in the PWM control of the step-down converter 70 is higher than the carrier frequency in the PWM control of the inverter 31.

FIG. 3 is a diagram for explaining carrier frequencies of step-down converter 70 and inverter 31. Referring to FIG. 3, the horizontal axis represents frequency and the vertical axis represents output voltages of drive circuits 72 and 53.

The carrier frequency in the PWM control of the inverter 31 is, for example, the frequency f1. On the other hand, the carrier frequency in the PWM control of step-down converter 70 is frequency f2, for example. The frequency f2 is higher than the frequency f1. That is, the carrier frequency of step-down converter 70 is higher than the carrier frequency of inverter 31.

In the electric compressor 10, since the carrier frequency in the PWM control of the step-down converter 70 is set high, the energy stored in the coil L2 becomes small by one switching of the switching element T1. As a result, according to the electric compressor 10, the coil L2 can be downsized.

Further, in the electric compressor 10, since the carrier frequency in the PWM control of the step-down converter 70 is set to be high, the energy stored in the coil L2 by one switching of the switching element T1 is suppressed to a small value and flows into the filter circuit 63. The ripple current becomes small. As a result, according to the electric compressor 10, the components of the filter circuit 63 connected to the input side of the step-down converter 70 can be downsized.

Further, according to the electric compressor 10, the carrier frequency in the PWM control of the inverter 31 is set low, so that the leakage current from the stator 23 of the electric motor 13 can be suppressed, and the heat generation of the switching elements TU1-TW2 can be suppressed. Can be suppressed.

It should be noted that increasing the carrier frequencies of both the step-down converter 70 and the inverter 31 is not preferable because both of them become hot. Further, in order to increase the drive frequency of the inverter 31, it is necessary to increase all the drive frequencies of the switching elements TU1-TW2 (six). Therefore, the drive frequency of the switching element T1 (one) of the step-down converter 70 is increased. Cost more than raising.

[Parts layout for effective cooling]
As described above, in the electric compressor 10, the carrier frequency of the step-down converter 70 is set higher than the carrier frequency of the inverter 31, so that the step-down converter 70 is likely to have a higher temperature than the inverter 31. Therefore, in the electric compressor 10, a configuration capable of effectively cooling the step-down converter 70 is adopted. In order to effectively cool the step-down converter 70, the arrangement of each component in the circuit chamber 33 (cover 32 (FIG. 1)) is devised. First, before describing the arrangement of each component in the circuit room 33, the premise will be described.

FIG. 4 is a diagram for explaining applied voltages of the inverter unit 30 and other circuits connected to the inverter unit 30. Referring to FIG. 4, when the inverter unit 30 and other circuits connected to the inverter unit 30 are classified by applied voltage, they are classified into an ultra-high voltage section 71, a high-voltage section 35, and a low-voltage section 81. can do. The ultra high voltage section 71, the high voltage section 35, and the low voltage section 81 can be recognized as wiring patterns to which different voltages are applied.

In the ultra high voltage section 71, the voltage of the main power source B1 before the step-down by the step-down converter 70 is applied. The ultrahigh voltage section 71 includes, for example, a filter circuit 63 and a step-down converter 70. In the high voltage section 35, the voltage after being stepped down by the step-down converter 70 is applied. The high voltage unit 35 includes, for example, an inverter 31. In the low voltage section 81, the voltage of the sub power source B2 is applied. The low-voltage unit 81 includes, for example, the power supply circuit 55 and the communication circuit 80.

FIG. 5 is a cross-sectional view taken along the line IV-IV in FIG. 1 and is a diagram for explaining the arrangement location of each component in the circuit chamber 33 (cover 32). Referring to FIG. 5, the refrigerant is sucked from the suction port 11a and flows through the back surface side (inside the housing 11) of the cover 32. In the circuit chamber 33 (cover 32), the ultra high voltage part 71 including the step-down converter 70 is arranged at the position closest to the suction port 11a. The high voltage section 35 including the inverter 31 is arranged next to the suction port 11a next to the ultra high voltage section 71. The low voltage section 81 including the communication circuit 80 is arranged at the farthest position from the suction port 11a. More specifically, the switching element of the step-down converter 70 is arranged closer to the intake port than the switching element of the inverter 31.

That is, in the electric compressor 10, the step-down converter 70 is arranged closer to the suction port 11 a than the inverter 31. Therefore, according to the electric compressor 10, even if the carrier frequency of the step-down converter 70 is higher than the carrier frequency of the inverter 31, the step-down converter 70 can be cooled by the cooler refrigerant, so that the step-down converter 70 is cooled. Can be done effectively.

Further, in the electric compressor 10, the low voltage portion 81 including the communication circuit 80 is arranged along the wall surface of the circuit chamber 33 (inner surface of the cover 32). Since the low-voltage portion is adjacent to the wall surface, the voltage difference between the component and the wall surface is small. Therefore, for example, the insulation distance of the space is shortened as compared with the case where the step-down converter 70 and the wall surface are adjacently arranged. be able to. As a result, according to the electric compressor 10, it is possible to prevent the electric compressor 10 from increasing in size.

Further, in the electric compressor 10, the inverter 31 (high voltage portion 35) is arranged so as to separate (between) the step-down converter 70 (ultra high voltage portion 71) and the communication circuit 80 (low voltage portion 81). Has been done. Specifically, the wiring pattern including the inverter to which the high voltage is applied separates the wiring pattern including the step-down converter to which the ultra high voltage is applied and the wiring pattern including the communication circuit to which the low voltage is applied. Therefore, the voltage difference between the adjacent components is reduced, so that the insulation distance between the components can be shortened as compared with, for example, the case where the step-down converter 70 and the communication circuit 80 are arranged adjacent to each other. As a result, according to the electric compressor 10, it is possible to prevent the electric compressor 10 from increasing in size. Further, since the communication circuit 80 is arranged at a position far from the high frequency part such as the step-down converter 70, the communication by the communication circuit 80 is hardly affected by the radiation noise. Therefore, it is possible to reduce the number of components for radiation noise, and it is possible to prevent the electric compressor 10 from increasing in size.

As described above, in electric compressor 10 according to the present embodiment, control device 61 is configured to make the carrier frequency in the PWM control of step-down converter 70 higher than the carrier frequency in the PWM control of inverter 31. .. According to the electric compressor 10, it is possible to prevent the electric compressor 10 from increasing in size.

[Modification 1]
In the above-described embodiment, the carrier frequency of step-down converter 70 is constant. However, the carrier frequency of step-down converter 70 does not necessarily have to be constant. For example, the carrier frequency of step-down converter 70 may be changed periodically.

FIG. 6 is a diagram for explaining the carrier frequency of step-down converter 70 in the first modification. Referring to FIG. 6, the horizontal axis represents frequency and the vertical axis represents output voltages of drive circuits 72 and 53.

The carrier frequency in the PWM control of the inverter 31 is, for example, the frequency f11. On the other hand, the carrier frequency in the PWM control of step-down converter 70 is periodically changed, for example, between frequencies f12 and f13. The lowest frequency f12 of the carrier frequencies of the step-down converter 70 is higher than the carrier frequency f11 of the inverter 31.

In electric compressor 10 according to the first modification, the carrier frequency of step-down converter 70 is periodically changed, so that the radio noise of a specific frequency is suppressed from becoming significantly large. Therefore, according to the electric compressor 10, the number of parts for reducing the radio noise can be reduced, so that the electric compressor 10 can be prevented from being upsized (downsized).

[Modification 2]
In the above-described embodiment, the ultra high voltage section 71, the high voltage section 35, and the low voltage section 81 are arranged at the positions shown in FIG. However, the arrangement of the ultra high voltage section 71, the high voltage section 35, and the low voltage section 81 is not necessarily limited to such an example.

FIG. 7 is a diagram for explaining the location of the ultra-high voltage section 71, the high-voltage section 35, and the low-voltage section 81 in the circuit room 33 in the second modification. With reference to FIG. 7, the ultra-high voltage portion 71 is arranged at the position closest to the suction port 11a. Thereby, step-down converter 70 can be cooled effectively. Further, the low voltage portion 81 opposes the wall surface of the circuit room 33 in a wide range. Since the distance between the low voltage portion 81 and the cover 32 can be shortened as described above, the range in which the low voltage portion 81 faces the wall surface of the circuit chamber 33 becomes wider, so that the circuit chamber 33 can be downsized. You can

[Modification 3]
In the above-described embodiment, the ultra high voltage section 71, the high voltage section 35, and the low voltage section 81 are arranged at the positions shown in FIG. However, the arrangement of the ultra high voltage section 71, the high voltage section 35, and the low voltage section 81 is not necessarily limited to such an example.

FIG. 8 is a diagram for explaining the arrangement locations of the ultra-high voltage section 71, the high voltage section 35, and the low voltage section 81 in the circuit room 33 in the third modification. Referring to FIG. 8, ultra-high voltage portion 71 is arranged at a position closest to suction port 11 a, and high-voltage portion 35 is arranged at a position next to suction port 11 a next to ultra-high voltage portion 71. ing. The low voltage portion 81 is arranged at a position farthest from the suction port 11a. Also in the electric compressor 10 according to the third modification, the ultra-high voltage portion 71 is arranged at the position closest to the suction port 11a, so that the step-down converter 70 can be effectively cooled.

The embodiments disclosed this time are to be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and is intended to include meanings equivalent to the claims and all modifications within the scope. For example, in the above-described embodiment, the shape of the cover 32 is a bottomed cylindrical shape, and the inner peripheral surface of the cover 32 constitutes the wall surface of the circuit chamber 33, but the shape of the cover 32 is not limited to this. A cylindrical wall surface may be provided upright from the end surface of the housing, and a plate-shaped cover may be fastened to the wall surface to form the wall surface of the circuit chamber.

10 Electric Compressor, 11 Housing, 11a Suction Port, 11b Discharge Port, 11c Wall, 12 Compressor, 13 Electric Motor, 21 Rotating Shaft, 22 Rotor, 23 Stator, 24 Stator Core, 25 Coil, 30 Inverter Unit, 31 Inverter , 32 cover, 33 circuit room, 35 high voltage part, 43 volt, 51 circuit board, 53, 72 drive circuit, 54 connector, 55 power supply circuit, 60 insulation circuit, 61 control device, 63 filter circuit, 70 step-down converter, 71 Ultra high voltage section, 80 communication circuit, 81 low voltage section, 100 vehicle air conditioner, 101 external cooling circuit, 102 air conditioning ECU, 150 cable, 200 vehicle side system, PL1, PL2 positive line, NL1, NL2 negative line, T1, TU1, TU2, TV1, TV2, TW1, TW2 switching element, D1, DU1, DU2, DV1, DV2, DW1, DW2 diode, C1, C2, C3 capacitor, F1 common mode filter, L1, L2 coil, N1, N2. N3, N4, N5 nodes, B1 main power supply, B2 sub power supply.

Claims (4)

An electric compressor configured to be connected to an on-vehicle main power source,
A compressor configured to compress the refrigerant,
An electric motor configured to drive the compression unit,
An inverter configured to convert DC power supplied from the main power supply to AC power and supply AC power to the electric motor,
A step-down converter connected to the input terminal of the inverter and configured to step down the input voltage of the inverter to less than the voltage of the main power supply;
A controller configured to perform PWM (Pulse Width Modulation) control of the inverter and the step-down converter;
A housing that houses the compression unit and the electric motor;
A cover that forms a circuit chamber that accommodates the inverter, the step-down converter, and the control device by being attached to the housing,
The housing is provided with a suction port for sucking the refrigerant,
Wherein the control device, the carrier frequency in the PWM control of the buck converter, is configured to be higher than the carrier frequency in the PWM control of the inverter,
Further comprising a communication circuit configured to communicate with a vehicle system external to the electric compressor,
The communication circuit is housed in the circuit room, and is configured to be connected to a vehicle-mounted auxiliary power source.
The voltage of the sub power supply is lower than the voltage of the main power supply,
The low voltage portion in the circuit chamber to which the voltage of the sub power supply is applied includes the communication circuit, and is arranged along the wall surface of the circuit chamber,
In the circuit chamber, the inverter is disposed between the step-down converter and the low voltage section,
The electric compressor including the inverter includes a wiring pattern including the step-down converter and a wiring pattern including the communication circuit . The electric compressor according to claim 1, wherein the step-down converter is located closer to the suction port than the inverter in the circuit chamber. The compression unit, the electric motor, and the circuit chamber are arranged in the order of the compression unit, the electric motor, and the circuit chamber in the rotation axis direction of the electric motor.
The electric compressor according to claim 1 or 2 , wherein the suction port is provided in the housing at a position closer to the circuit chamber than the electric motor. The electric compressor according to any one of claims 1 to 3 , further comprising a filter circuit connected to an input terminal of the step-down converter and housed in the circuit chamber.

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