JP5243088B2 - Electric compressor - Google Patents

Description

  The present invention relates to an electric compressor having a built-in compression mechanism section that compresses refrigerant and an electric motor that drives the compression mechanism section.

  This type of conventional electric compressor includes a compression mechanism section that compresses refrigerant, an electric motor that drives the compression mechanism section, and a motor control circuit section that drives and controls the electric motor. Since the electric motor is built in at least the sealed space of the housing together with the compression mechanism, the electric motor itself, the wiring for the electric motor, the connector, and the like are arranged in an environment filled with the refrigerant.

  When the electric compressor is stopped, the refrigerant flowing from not only the housing but also from an evaporator or the like changes to a liquid phase, and a so-called liquid stagnation state occurs in which the refrigerant changed to the liquid phase accumulates in the housing. And it may be restarted in such a liquid sleeping state.

  Here, the electric motor is PWM controlled, and a voltage of several hundred volts is applied as the maximum voltage. Further, since the volume resistivity of the refrigerant is lower in the liquid phase than in the gas phase, as shown in FIG. 5, the insulation space distance is about several millimeters when the refrigerant is in the liquid phase. Therefore, since a high voltage is applied to the electric motor, wiring, and connector in a state where the liquid phase refrigerant is filled, if there is a place where the insulation state is not perfect due to a covering defect or the like, there is a possibility of causing a leakage or a short circuit. is there.

Here, Patent Document 1 proposes an electric compressor provided with a liquid stagnation prevention means. In Patent Document 1, when it is determined that liquid stagnation has occurred in the housing, the electric motor is rotated at a low speed so that the compression mechanism functions as a liquid refrigerant discharge pump to discharge the liquid refrigerant from the housing. This prevents liquid refrigerant compression.
Patent Publication No. 2952839

  However, although the conventional electric compressor can prevent liquid compression, the voltage level itself applied to the voltage motor is a high voltage from the start of driving. That is, since a high voltage is applied to an electric motor or the like in a state where a liquid-phase refrigerant is filled, if there is a portion where the insulation state is not perfect due to a covering defect or the like, there is a possibility of causing a leakage or a short circuit.

  Then, an object of this invention is to provide the electric compressor which can prevent malfunctions, such as electric leakage resulting from the stagnation of a liquid refrigerant, and a short circuit as much as possible.

The invention according to claim 1, which achieves the above object, is an electric compressor in which a compression mechanism portion for compressing a refrigerant and an electric motor for driving the compression mechanism portion are built in a housing, and when there is a drive command, the electric motor was driven at a low voltage, thereafter, switches the electric motor to the normal high-voltage, current output said PWM controlled to the electric motor at a low voltage (6) is a PWM controlled the high voltage This is the same as the current output to the electric motor (6) .

  The invention according to claim 2 is the electric compressor according to claim 1, wherein the switching from the low voltage to the high voltage drive is performed when it is determined that the liquid phase refrigerant is not actually accumulated in the housing. Features.

  A third aspect of the invention is the electric compressor according to the first or second aspect, wherein the start of driving at a low voltage is performed when it is determined that liquid-phase refrigerant is actually accumulated in the housing. It is characterized by.

  A fourth aspect of the invention is the electric compressor according to the first or second aspect, wherein the start of driving at a low voltage is determined when there is a possibility that liquid-phase refrigerant is accumulated in the housing. It is characterized by performing.

  The invention according to claim 5 is the electric compressor according to claim 4, wherein the possibility of whether or not the liquid-phase refrigerant is accumulated in the housing depends on at least the time from the previous drive stop and the outside air temperature. Judgment is made on the basis of either one.

  According to the first aspect of the present invention, since a low voltage is applied to the electric motor when the electric compressor is started, liquid refrigerant stagnations in the housing, and the electric motor or the like is filled with the liquid phase refrigerant. Even in the situation, the insulation space distance is long, and after the liquid-phase refrigerant in the housing is discharged by the low voltage drive, it is switched to the normal high voltage drive. Accordingly, it is possible to prevent as much as possible problems such as electric leakage and short circuit due to the stagnation of the liquid refrigerant.

  According to the invention of claim 2, in addition to the effect of the invention of claim 1, since high voltage driving is performed after it is determined that there is no liquid refrigerant stagnation in the housing, leakage due to liquid refrigerant stagnation, Problems such as short-circuits can be reliably prevented.

  According to the invention of claim 3, in addition to the effect of the invention of claim 1 or claim 2, when the liquid refrigerant does not actually stagnate at the start-up, normal high voltage driving can be performed from the beginning.

  According to the invention of claim 4, in addition to the effect of the invention of claim 1 or claim 2, when it is determined that there is no possibility of liquid refrigerant stagnation at startup, normal high voltage driving is performed from the beginning. be able to.

  According to the invention of claim 5, the same effect as that of the invention of claim 4 can be obtained.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  1 to 4 show an embodiment of the present invention, FIG. 1 is a sectional view of an electric compressor, FIG. 2 is a drive circuit block diagram of the electric motor, FIG. 3 is a control flowchart of the electric motor, and FIG. FIG. 4B is a current waveform diagram for the electric motor, FIG. 4B is a voltage waveform diagram for the electric motor during high voltage driving, and FIG. 4C is a voltage waveform diagram for the electric motor during low voltage driving.

  As shown in FIG. 1, the electric compressor 1 has a housing 2. The housing 2 includes a substantially cylindrical compressor housing member 3, a front housing member 4 disposed on one opening side surface of the compressor housing member 3, and a motor housing disposed on the other opening side surface of the compressor housing member 3. It is comprised from the member 5. The compressor housing member 3, the front housing member 4 and the motor housing member 5 are all made of an aluminum alloy.

  The compression mechanism unit 10 is accommodated in the compressor housing member 3. The compression mechanism unit 10 includes a cylinder block 11 and a front side block 12 and a rear side block 13 that are respectively disposed on both side surfaces of the cylinder block 11. The blocks 11, 12 and 13 are fixed by bolts (not shown), and a cylinder chamber 14 is formed in the blocks 11, 12 and 13. The cylinder block 11 and the side blocks 12 and 13 on both sides are made of an aluminum alloy like the housing members 3, 4 and 5.

  A rotor 15 is accommodated in the cylinder chamber 14. A rotation shaft 16 passes through the center of the rotor 15, and the rotor 15 and the rotation shaft 16 are fixed. The rotating shaft 16 is rotatably supported by the front side block 12 and the rear side block 13. The rear side of the rotating shaft 16 protrudes outside from the rear side block 13.

  Vane grooves 17 that open to the outer peripheral surface are formed at equally spaced positions on the outer peripheral side of the rotor 15. A vane 18 is disposed in each vane groove 17 so as to protrude freely. A high-pressure refrigerant supply path (not shown) is opened at the bottom of the vane groove 17. Each vane 18 is configured to be biased in the protruding direction by the back pressure of the high-pressure refrigerant. Each vane 18 moves while contacting the inner wall of the cylinder chamber 14 by the biasing force in the protruding direction as described above when the rotary shaft 16 rotates. A plurality of compression chambers are formed in the cylinder chamber 14 between the adjacent vanes 18. Each compression chamber expands its volume in accordance with the rotation of the rotor 15 and repeats a suction stroke for sucking refrigerant, a compression stroke for reducing the volume, compressing the sucked refrigerant, and discharging the refrigerant.

  The refrigerant suction path 20 communicates a suction port (not shown) and a cylinder suction port (not shown) that opens to the cylinder chamber 14. The refrigerant is supplied to the cylinder chamber 14 through the refrigerant suction path 20.

  The refrigerant discharge path 21 communicates a cylinder discharge port (not shown) that opens to the cylinder chamber 14 and a discharge port 21a. The compressed refrigerant in the cylinder chamber 14 is discharged through the refrigerant discharge path 21. The refrigerant discharge path 21 passes through a motor housing chamber 5a of the electric motor 6 described below.

  The electric motor 6 is housed in the motor housing chamber 5 a of the motor housing member 5. The electric motor 6 includes a motor rotor 23 fixed to the rotary shaft 22 and a stator 24 fixed to the inner peripheral surface of the motor housing member 5. Both end portions of the rotating shaft 22 are rotatably supported by the motor housing member 5 and the rear side block 13 via ball bearing members 25a and 25b, respectively. One end side of the rotation shaft 22 is connected to the rotation shaft 16 of the compression mechanism unit 10. On the outer periphery of the motor rotor 23, S poles and N poles are alternately magnetized in the circumferential direction. The stator 24 includes a core (not shown) and a coil (not shown) wound around the core. This coil is electrically connected to the connector 30 via an electric wire (not shown). A hermetic terminal 31 is attached to the connector 30. The hermetic terminal 31 is connected to a motor control circuit 33 (shown in FIG. 2) housed in a motor control chamber 32.

  As shown in FIG. 2, the motor control circuit 33 includes an inverter circuit 34, a transformer circuit 35, a voltage control unit 36, and an inverter control unit 38. The transformer circuit 35 is interposed between the battery 37 and the inverter circuit 34, and varies the transformed power of the transformer circuit 35 based on a control command from the voltage controller 36. Specifically, the transformer circuit 35 outputs the voltage from the battery 37 as a normal high voltage (for example, 300 V) without transforming, or changes the voltage to a lower voltage (for example, 100 V) lower than this and outputs it.

  The inverter control unit 38 controls the inverter circuit 34 to operate the electric motor 6 based on a compressor on / off command, a rotation speed command, and the like from the air conditioner amplifier 39 that performs temperature setting and the like.

  The inverter circuit 34 is interposed between the transformer circuit 35 and the electric motor 6 and converts the direct current from the transformer circuit 35 into three-phase alternating current (U, V, W) based on the control command of the inverter control unit 38. Specifically, when a low voltage (for example, 100 V) is supplied from the transformer circuit 35, the electric motor is converted into the current shown in FIG. 4A by the PWM-controlled low voltage shown in FIG. 4C. 6 is output. Further, when a high voltage (for example, 300 V) is supplied from the transformer circuit 35, the voltage is converted to the current shown in FIG. 4A by the PWM-controlled high voltage shown in FIG. .

  The detection output of the float sensor 40 is supplied to the voltage control unit 36, and the voltage control unit 36 executes the flowchart of FIG. The contents of this flowchart will be described in the operation section.

  The float sensor 40 is disposed in the motor storage chamber 5 a that constitutes the refrigerant discharge path 21. The motor housing chamber 5a is a space where liquid phase refrigerant accumulates, and the float sensor 40 detects the liquid level of the liquid refrigerant.

  Next, the operation of the electric compressor 1 will be described. As shown in FIG. 3, when there is a command to start driving the electric compressor 1 (step S1), the detection output of the float sensor 40 is read to determine whether liquid refrigerant is accumulated in the housing 2 (step S2). . If there is a stagnation of the liquid refrigerant, a low voltage transformation command is issued to the transformer circuit 35. As a result, the electric motor 6 is supplied with the current shown in FIG. 4A at the low voltage shown in FIG. 4C, and the electric motor 6 is driven at a low voltage (step S3). When the electric motor 6 is driven at a low voltage, the rotation shaft 16 of the compression mechanism unit 10 rotates together with the rotation of the rotation shaft 22, thereby starting the compression of the refrigerant. In this low voltage driving process, the detection output of the float sensor 40 is constantly checked. If the stagnation of the liquid refrigerant is eliminated, that is, if the liquid-phase refrigerant is discharged from the housing 2 (step S4), a high voltage transformation command is issued to the transformer circuit 35. As a result, the electric motor 6 is supplied with the current shown in FIG. 4A at the high voltage shown in FIG. 4B, and the electric motor 6 is switched to high voltage driving (step S5).

  Further, when it is determined that the liquid refrigerant is not accumulated in the housing 2 from the detection output of the float sensor 40 at the time of starting the driving of the electric compressor 1, the electric compressor 1 is driven from the beginning with high voltage driving (step S5).

  When there is a drive stop command for the electric compressor 1 (step S6), the drive of the electric compressor 1 is stopped (step S7).

  As described above, in this embodiment, the electric motor 6 is driven at a low voltage when a drive command is issued, and then the electric motor 6 is switched to a normal high voltage drive. Accordingly, since a low voltage is applied to the electric motor 6 at the time of startup, liquid refrigerant stagnations in the housing 2, and the insulation space is maintained even when the electric motor 6 and the like are filled with liquid phase refrigerant. The distance can be increased (see FIG. 5), and the liquid-phase refrigerant in the housing 2 is discharged by low-voltage driving, and then switched to normal high-voltage driving. Accordingly, it is possible to prevent as much as possible problems such as electric leakage and short circuit due to the stagnation of the liquid refrigerant. In addition, a lubricant having a low volume resistivity can be used as a lubricant or refrigerant.

  In this embodiment, the switching from the low voltage to the high voltage drive is performed when it is determined that the liquid phase refrigerant is not actually accumulated in the housing 2. Therefore, since it is determined that the liquid refrigerant does not stagnate in the housing 2 and high voltage driving is performed, problems such as electric leakage and short circuit due to the liquid refrigerant stagnation can be reliably prevented.

  In this embodiment, driving at a low voltage when the electric compressor 1 is started is performed when it is determined that the liquid-phase refrigerant is actually accumulated in the housing 2. Therefore, when the liquid refrigerant does not actually stagnate at the start-up as in this embodiment, normal high voltage driving can be performed from the beginning.

(Modification)
In the above embodiment, when the electric compressor 1 is started, it is checked whether or not liquid refrigerant stagnation actually occurs. However, whether or not there is a possibility of liquid refrigerant stagnation is determined. Voltage driving may be performed, and high voltage driving may be performed if there is no possibility. This has the advantage that the float sensor 40 is not necessary.

  The presence or absence of the possibility of stagnation of the liquid refrigerant is determined based on at least one of the time from the previous driving stop time and the outside air temperature. For example, if 24 hours or more have elapsed since the previous driving stop point, it is determined that liquid refrigerant has accumulated, and if it is less than 24 hours, it is determined that liquid refrigerant has not accumulated. If the outside air temperature is equal to or lower than the predetermined temperature, it is determined that the liquid refrigerant is accumulated, and if it exceeds the predetermined temperature, it is determined that the liquid refrigerant is not accumulated. It may be determined whether or not the liquid refrigerant is accumulated from both the stop time and the outside air temperature.

  In the embodiment, the switching from the low voltage driving to the high voltage driving is performed based on the detection output of the float sensor 40, but the liquid refrigerant stagnation determination is determined from the output value of the inverter circuit 34. Also good.

  In the above embodiment, the input voltage of the inverter circuit 34 is transformed, but the voltage applied to the electric motor 6 may be adjusted by transforming the output voltage of the inverter circuit 34. For example, a voltage control unit is provided between the inverter circuit and the electric motor so as to interpose the transformer circuit and control the transformer circuit. Then, the AC output of the inverter circuit is transformed by the transformer circuit, and the level of the transformed voltage is controlled by the voltage control unit.

1 is a cross-sectional view of an electric compressor according to an embodiment of the present invention. FIG. 1 is a block diagram of an electric motor drive circuit according to an embodiment of the present invention. 1 is a flowchart illustrating control of an electric motor according to an embodiment of the present invention. 1 shows an embodiment of the present invention, where (a) is a current waveform diagram for an electric motor, (b) is a voltage waveform diagram for an electric motor during high-voltage driving, and (c) is for an electric motor during low-voltage driving. FIG. It is a characteristic diagram of a voltage and insulation space distance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric compressor 2 Housing 6 Electric motor 10 Compression mechanism part

Claims (5)

An electric compressor (1) in which a compression mechanism section (10) for compressing refrigerant and an electric motor (6) for driving the compression mechanism section (10) are built in a housing (2),
When there is a drive command, the electric motor (6) is driven at a low voltage, and then the electric motor (6) is switched to a normal high voltage drive ,
The electric current output to the electric motor (6) at the low voltage under PWM control is the same as the electric current output to the electric motor (6) at the high voltage under PWM control. Compressor (1). An electric compressor (1) according to claim 1,
The electric compressor (1) is characterized in that the switching from the low voltage to the high voltage drive is performed when it is determined that liquid phase refrigerant is not actually accumulated in the housing (2). The electric compressor (1) according to claim 1 or 2,
The electric compressor (1) is characterized in that the drive start at the low voltage is performed when it is determined that liquid-phase refrigerant is actually accumulated in the housing (2). The electric compressor (1) according to claim 1 or 2,
The electric compressor (1) is characterized in that the driving at the low voltage is started when it is determined that there is a possibility that liquid-phase refrigerant is accumulated in the housing (2). An electric compressor (1) according to claim 4,
The possibility that liquid phase refrigerant is accumulated in the housing (2) is determined based on at least one of the time from the previous drive stop time and the outside air temperature. Compressor (1).

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