JP6287765B2 - Electric compressor - Google Patents

Description

  The present invention relates to an electric compressor.

  Conventionally, a housing into which a refrigerant is sucked, a compression unit that is accommodated in the housing and compresses the refrigerant, an electric motor that is accommodated in the housing and drives the compression unit, and a drive circuit that drives the electric motor, An electric compressor provided is known (see, for example, Patent Document 1). Patent Document 1 describes that a drive circuit is attached to the outer surface of the housing, and the drive circuit is cooled by heat exchange between the refrigerant and the drive circuit via the housing. Has been. Furthermore, for example, in Patent Document 2, there are a three-phase modulation mode and a two-phase modulation mode as drive modes of a drive circuit for driving an electric motor mounted on an electric vehicle, and the number of rotations of the electric motor, etc. Thus, the point of switching the drive mode of the drive circuit is described.

JP 2003-324900 A JP 2007-110780 A

  Here, when the electric compressor is operated under a condition where the ambient temperature around the electric compressor or the intake refrigerant temperature that is the refrigerant sucked into the housing is low, the temperature of the drive circuit becomes excessively low. There is. In this case, for example, the temperature of the drive circuit may become lower than the lower limit value of the operation guarantee range of the drive circuit, and an abnormality may occur in the drive circuit.

  In particular, when the drive circuit is operating to drive the drive motor, heat related to power loss is generated in the drive circuit. However, when the operation of the drive circuit stops, heat related to power loss does not occur in the drive circuit. For this reason, when the operation of the drive circuit stops, the drive circuit may be cooled by the refrigerant sucked just before the stop, and the temperature of the drive circuit may become excessively low.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to provide an electric compressor that can suppress the temperature of a drive circuit from becoming excessively low.

  An electric compressor that achieves the above object includes a housing into which a refrigerant is sucked, a compression part that is accommodated in the housing and compresses and discharges the refrigerant, and is accommodated in the housing and drives the compression part. An electric motor, a drive circuit that is thermally coupled to the housing and drives the electric motor, a temperature measuring unit that measures the temperature of the drive circuit, and the drive circuit to control the electric motor And a driving mode for driving the driving circuit includes a two-phase modulation mode and a three-phase modulation mode. The control unit is configured so that the temperature of the driving circuit is within an operation guarantee range of the driving circuit. The temperature of the drive circuit measured by the temperature measurement unit in a situation where the drive mode of the drive circuit is the two-phase modulation mode so as not to become lower than the lower limit value. When a switching trigger temperature below defined, the driving mode of the driving circuit, characterized in that it comprises a low temperature driving mode control unit for switching from the two-phase modulation mode in the three-phase modulation mode.

  According to such a configuration, there are a two-phase modulation mode and a three-phase modulation mode as drive modes of the drive circuit. The three-phase modulation mode is a drive mode of the drive circuit in which the heat generation amount of the drive circuit is likely to be larger than the two-phase modulation mode. For this reason, the temperature of the drive circuit is lower than the switching trigger temperature in a situation where the drive mode of the drive circuit is the two-phase modulation mode so that the temperature of the drive circuit does not become lower than the lower limit value of the operation guarantee range of the drive circuit. The driving mode of the driving circuit is switched from the two-phase modulation mode to the three-phase modulation mode. As a result, the amount of heat generated in the drive circuit can be increased, so that the temperature of the drive circuit can be prevented from becoming excessively low. In addition, since the temperature of the drive circuit can be kept high to some extent, even when the heat generation of the drive circuit stops with the stop of the electric motor, the temperature of the drive circuit becomes excessively low. Can be suppressed.

  With respect to the electric compressor, the low temperature driving mode control unit is configured so that the low temperature driving mode control unit switches the driving mode of the driving circuit from the two-phase modulation mode to the three-phase modulation mode. When the temperature of the driving circuit measured by the above becomes a switching release temperature that is higher than the switching trigger temperature, the driving mode of the driving circuit is switched from the three-phase modulation mode to the two-phase modulation mode. Good. According to such a configuration, when the driving mode of the driving circuit is switched from the two-phase modulation mode to the three-phase modulation mode by the low temperature driving mode control unit, The drive mode is switched from the three-phase modulation mode to the two-phase modulation mode. Thereby, the power loss in the drive circuit can be reduced while maintaining the temperature of the drive circuit to a certain level.

  In the electric compressor, the control unit sets a driving mode of the driving circuit to the two-phase modulation mode or the three-phase modulation mode based on a modulation parameter including the rotation speed of the electric motor. A control unit, and when the driving mode of the driving circuit is switched from the two-phase modulation mode to the three-phase modulation mode by the low temperature driving mode control unit, the normal driving mode control unit Therefore, it is preferable that the drive mode of the drive circuit is not changed from the three-phase modulation mode to the two-phase modulation mode. According to such a configuration, by including the normal time drive mode control unit that sets the drive mode of the drive circuit to the two-phase modulation mode or the three-phase modulation mode based on the modulation parameter including the rotation speed of the electric motor, The electric motor can be stably rotated while reducing power loss.

  In such a configuration, when the driving mode is switched from the two-phase modulation mode to the three-phase modulation mode by the low-temperature driving mode control unit, the three-phase modulation mode to the two-phase modulation mode by the normal driving mode control unit is performed. The drive mode of the drive circuit is not changed. Thereby, after the drive mode of the drive circuit is switched from the two-phase modulation mode to the three-phase modulation mode by the low temperature drive mode control unit, the drive mode of the drive circuit is returned to the two-phase modulation mode by the normal drive mode control unit. Such inconveniences can be avoided.

  In the electric compressor, the control unit increases the carrier frequency of the drive circuit when the drive mode of the drive circuit is switched from the two-phase modulation mode to the three-phase modulation mode by the low-temperature drive mode control unit. It is preferable to provide a carrier frequency variable section. According to such a configuration, when the driving mode is switched from the two-phase modulation mode to the three-phase modulation mode by the low-temperature driving mode control unit, the power loss of the driving circuit is increased by increasing the carrier frequency of the driving circuit. Can be further increased. Thereby, the calorific value of the drive circuit can be further increased, and it is possible to more suitably suppress the temperature of the drive circuit from becoming excessively low.

  With respect to the electric compressor, the drive circuit has a switching element that operates normally when the temperature is equal to or higher than the lower limit value of the operation guarantee range, and the electric circuit is turned on and off periodically. The motor is driven, and the switching trigger temperature may be set higher than a lower limit value of the operation guarantee range. According to this configuration, when the drive mode of the drive circuit is the two-phase modulation mode, the drive circuit drive is performed by the low temperature drive mode control unit before the temperature of the drive circuit reaches the lower limit of the guaranteed operation range. The mode is switched from the two-phase modulation mode to the three-phase modulation mode in which the heat generation amount is larger than that of the two-phase modulation mode. Thereby, it can suppress that the temperature of a drive circuit approaches the lower limit of an operation guarantee range. Therefore, it can suppress that the temperature of a switching element becomes lower than the lower limit of an operation guarantee range.

  According to this invention, it can suppress that the temperature of a drive circuit becomes low too much.

The schematic diagram which shows the outline | summary of a heat pump. The circuit diagram of an inverter. The flowchart which shows the process at the time of low temperature. (A) is a graph which shows the time change of inverter temperature, (b) is a time chart which shows the drive mode of an inverter, (c) is a time chart which shows the ON / OFF aspect of normal time drive mode control.

  Hereinafter, an embodiment of the electric compressor will be described. The electric compressor of this embodiment is used for a heat pump, for example. Moreover, the heat pump of this embodiment is mounted, for example in the vehicle, and is used as a car air conditioner.

  As shown in FIG. 1, the heat pump 100 includes an electric compressor 10 and an external refrigerant circuit 101 that supplies refrigerant to the electric compressor 10. The external refrigerant circuit 101 has, for example, a heat exchanger and an expansion valve. The heat pump 100 heats and cools the interior of the vehicle by compressing the refrigerant by the electric compressor 10 and performing heat exchange and expansion of the refrigerant by the external refrigerant circuit 101.

  The heat pump 100 includes an air conditioning ECU 102 that controls the entire heat pump 100. The air conditioning ECU 102 is configured so as to be able to grasp the in-vehicle temperature, the set temperature of the car air conditioner, and the like, and based on these parameters, an ON / OFF command to the electric compressor 10, a command to instruct the rotation speed r, etc. Send various commands.

  The electric compressor 10 includes a housing 11 in which a suction port 11 a into which a refrigerant is sucked from an external refrigerant circuit 101 is formed, and a compression unit 12 and an electric motor 13 housed in the housing 11.

  The housing 11 has a substantially cylindrical shape as a whole, and is formed of a material having heat conductivity (for example, a metal such as aluminum). The housing 11 has a discharge port 11b through which a refrigerant is discharged.

  The compression unit 12 compresses the refrigerant sucked into the housing 11 from the suction port 11a and discharges the compressed refrigerant from the discharge port 11b. In addition, the specific structure of the compression part 12 is arbitrary, such as a scroll type, a piston type, and a vane type.

  The electric motor 13 drives the compression unit 12. The electric motor 13 includes, for example, a columnar rotation shaft 21 that is rotatably supported with respect to the housing 11, a cylindrical rotor 22 that is fixed to the rotation shaft 21, and a stator 23 that is fixed to the housing 11. And have. The axial direction of the rotating shaft 21 and the axial direction of the cylindrical housing 11 coincide with each other. The stator 23 includes a cylindrical stator core 24 and a coil 25 wound around teeth formed on the stator core 24. The rotor 22 and the stator 23 face each other in the radial direction of the rotating shaft 21.

  As shown in FIG. 1, the electric compressor 10 includes an inverter unit 30 having an inverter 31 as a drive circuit for driving the electric motor 13 and a case 32 in which the inverter 31 is accommodated. The coil 25 of the electric motor 13 and the inverter 31 are connected by a connector or the like (not shown).

  The case 32 is formed of a material having heat conductivity (for example, a metal such as aluminum), and includes a plate-like base member 41 and a bottomed cylindrical cover member 42 assembled to the base member 41. Have. The base member 41 is in contact with the housing 11, specifically, with respect to the wall portion 11 c opposite to the discharge port 11 b of both wall portions in the axial direction of the housing 11. ) To the housing 11. Thereby, the case 32 in which the inverter 31 is accommodated is attached to the housing 11. That is, the inverter 31 is integrated with the electric compressor 10 of the present embodiment.

  The inverter 31 includes, for example, a circuit board 51 fixed to the base member 41 and a power module 52 electrically connected to the circuit board 51. Various electronic components and wiring patterns are mounted on the circuit board 51. For example, a temperature sensor 53 is mounted as a temperature measuring unit that measures the ambient temperature in the case 32. A connector 54 is provided on the outer surface of the cover member 42 in the case 32, and the circuit board 51 and the connector 54 are electrically connected. Power is supplied to the inverter 31 from a DC power source E as an external power source via the connector 54, and the air conditioning ECU 102 and the inverter 31 are electrically connected.

  Here, the inverter 31 is disposed at a position where it is thermally coupled to the housing 11. Specifically, the power module 52 of the inverter 31 is in contact with the base member 41. As already described, the base member 41 is in contact with the wall portion 11 c of the housing 11. For this reason, the inverter 31 (specifically, the power module 52) and the housing 11 are thermally coupled via the base member 41.

  As shown in FIG. 2, the coil 25 of the electric motor 13 has a three-phase structure including, for example, a u-phase coil 25u, a v-phase coil 25v, and a w-phase coil 25w. That is, the electric motor 13 is a three-phase motor. Each coil 25u-25w is Y-connected, for example.

  The power module 52 includes u-phase power switching elements Qu1 and Qu2 corresponding to the u-phase coil 25u, v-phase power switching elements Qv1 and Qv2 corresponding to the v-phase coil 25v, and w-phase power switching corresponding to the w-phase coil 25w. Elements Qw1 and Qw2 are provided. That is, the inverter 31 is a so-called three-phase inverter.

  Each power switching element Qu1, Qu2, Qv1, Qv2, Qw1, Qw2 (hereinafter simply referred to as each power switching element Qu1-Qw2) is configured by, for example, an IGBT. Each power switching element Qu1-Qw2 operates normally when the temperature of each power switching element Qu1-Qw2 is equal to or higher than a predetermined operation lower limit temperature Tmin and equal to or lower than a predetermined operation upper limit temperature. That is, the operation lower limit temperature Tmin is the lower limit value of the operation guarantee range of each power switching element Qu1 to Qw2, in other words, the lower limit value of the operation guarantee range of the inverter 31 (power module 52). That is, the inverter 31 (power module 52) operates normally when the temperature is not less than the operation lower limit temperature Tmin and not more than the operation upper limit temperature.

  The u-phase power switching elements Qu1 and Qu2 are connected to each other in series via a connection line, and the connection line is connected to the u-phase coil 25u. And direct-current power from DC power supply E is input into the serial connection body of each u phase power switching element Qu1, Qu2. The other power switching elements Qv1, Qv2, Qw1, and Qw2 are connected in the same manner as the u-phase power switching elements Qu1 and Qu2, except that the corresponding coils are different. . The inverter 31 has a smoothing capacitor C1 connected in parallel to the DC power source E.

  The power module 52 includes a control unit 55 that controls the inverter 31 (specifically, switching operations of the power switching elements Qu1 to Qw2). The control unit 55 drives, that is, rotates the electric motor 13 by periodically turning on / off each of the power switching elements Qu1 to Qw2.

  The control unit 55 performs PWM control of the inverter 31. Specifically, the control unit 55 generates a control signal using the carrier signal (carrier wave signal) and the command voltage value signal (comparison target signal). And the control part 55 can control the rotation speed r of the electric motor 13 by carrying out the variable control of the ON / OFF duty ratio of each power switching element Qu1-Qw2 using the produced | generated control signal. When the control unit 55 is electrically connected to the air conditioning ECU 102 and receives a command value or the like of the rotational speed r from the air conditioning ECU 102, the control unit 55 rotates the electric motor 13 at the rotational speed r corresponding to the command value.

  Note that the carrier frequency of the inverter 31 is the frequency of the carrier signal. In the present embodiment, the carrier frequency that is normally used is the initial frequency. The initial frequency is 20 kHz, for example. The specific waveform of the carrier signal is arbitrary, for example, a triangular wave or a sawtooth wave.

  As shown in FIG. 2, the inverter 31 includes a current value measurement unit 61 that measures a current value I flowing through the electric motor 13 and transmits the measurement result to the control unit 55. The electric compressor 10 includes a rotation speed detector 62 that detects the rotation speed r of the electric motor 13 and transmits the detection result to the control unit 55. Thereby, the control part 55 can grasp | ascertain the electric current value I and the rotation speed r. The current value measuring unit 61 is mounted on, for example, the circuit board 51 (see FIG. 1).

  Here, the drive mode of the inverter 31 includes a three-phase modulation mode and a two-phase modulation mode. The three-phase modulation mode is a driving mode in which periodic ON / OFF (switching operation) of all-phase power switching elements Qu1 to Qw2 is always performed. In the present embodiment, the two-phase modulation mode means that the periodic ON / OFF of the power switching element of any phase among the power switching elements Qu1 to Qw2 of all phases is sequentially stopped every predetermined period (phase angle). Drive mode. That is, in the two-phase modulation mode, the periodic ON / OFF of any one of the three phases of power switching elements stops in turn, while the other two-phase power switching elements are periodically turned on / off. This is a drive mode in which the OFF is performed. The state where the periodic ON / OFF of the power switching element is stopped is a state where the power switching element is fixed in the ON state or the OFF state.

  The two-phase modulation mode is a drive mode in which the power switching elements Qu1 to Qw2 are turned on / off less frequently than the three-phase modulation mode. For this reason, the power loss and the heat generation amount of the inverter 31 are likely to be larger in the three-phase modulation mode than in the two-phase modulation mode.

  On the other hand, the three-phase modulation mode is a drive mode in which the voltage waveform flowing through each of the coils 25u to 25w can be accurately controlled and the current ripple is likely to be smaller than in the two-phase modulation mode. For this reason, the three-phase modulation mode is preferably used, for example, when the load applied to the electric motor 13 is relatively large.

  As shown in FIG. 2, the control unit 55 sets the drive mode of the inverter 31 to the two-phase modulation mode or the three-phase modulation mode based on the modulation parameter including the rotation speed r of the electric motor 13. A normal driving mode control unit 71 is provided. The normal drive mode control is performed when the rotational speed r of the electric motor 13 changes periodically or during the operation of the electric motor 13 except in a special situation where it is prohibited by the low temperature control unit 72 described later. It is done as an opportunity. Specifically, the normal driving mode control unit 71 grasps the rotational speed r and current value I of the electric motor 13, and the grasped rotational speed r of the electric motor 13 corresponds to the current value I of the electric motor 13. It is then determined whether or not it is equal to or higher than the threshold rotation speed rth set. When the rotational speed r of the electric motor 13 is equal to or greater than the threshold rotational speed rth, the normal driving mode control unit 71 sets the drive mode of the inverter 31 to the two-phase modulation mode while rotating the electric motor 13. When the number r is less than the threshold rotation number rth, the drive mode of the inverter 31 is set to the three-phase modulation mode. That is, in the present embodiment, the current value I and the rotation speed r of the electric motor 13 are adopted as the modulation parameters.

The temperature sensor 53 transmits the measurement result to the control unit 55. The control unit 55 grasps the inverter temperature T that is the temperature of the inverter 31 based on the measurement result of the temperature sensor 53.
Here, the inverter temperature T is, for example, the temperature of the power module 52. In this case, the control unit 55 stores data related to the correlation between the measured temperature of the temperature sensor 53 and the temperature of the power module 52 in advance, and corresponds to the measurement result of the temperature sensor 53 by referring to the data. The temperature of the power module 52 is derived, and the derived temperature is set as the inverter temperature T. That is, the temperature sensor 53 is used to measure the inverter temperature T.

  The inverter temperature T is not limited to the above, and may be any temperature as long as the temperature is related to the inverter 31. For example, the measured value measured by the temperature sensor 53, that is, the ambient temperature in the case 32 may be used.

  Here, when the heat pump 100 operates under a low temperature condition (for example, the ambient temperature is −30 ° C. or lower and the suction refrigerant temperature is −45 ° C. or lower), the housing 11 and the base member 41 are excessively cooled by the refrigerant. As a result, the inverter temperature T may be excessively lowered. For example, when the intake refrigerant temperature is lower than the operation lower limit temperature Tmin, the inverter temperature T may approach the operation lower limit temperature Tmin or become lower than the operation lower limit temperature Tmin during the rotation of the electric motor 13. Then, an abnormality may occur in the power module 52.

  In particular, the inverter temperature T may become excessively low based on the rotation of the electric motor 13 being stopped. More specifically, since the power switching elements Qu1 to Qw2 are periodically turned ON / OFF while the electric motor 13 is rotating, heat related to the switching loss is generated in the power switching elements Qu1 to Qw2. . On the other hand, when the rotation of the electric motor 13 is stopped, the periodic ON / OFF of the power switching elements Qu1 to Qw2 is stopped, so that heat related to the switching loss is not generated in the power switching elements Qu1 to Qw2. For this reason, when the electric motor 13 in rotation stops, each power switching element Qu1-Qw2 may be excessively cooled by the refrigerant | coolant suck | inhaled just before the stop. Therefore, for example, when the intake refrigerant temperature is lower than the operation lower limit temperature Tmin, the inverter temperature T may be lower than the operation lower limit temperature Tmin due to the stop of the electric motor 13.

  On the other hand, as shown in FIG. 2, the control unit 55 of the present embodiment includes a low temperature control unit 72 that performs a low temperature response process for suppressing the inverter temperature T from becoming excessively low. . The low temperature response process will be described with reference to FIG. Note that the low temperature response process is periodically performed while the electric motor 13 is rotating. In the following description, it is assumed that the heat pump 100 is in a heating operation.

  As shown in FIG. 3, the low temperature control unit 72 first obtains the inverter temperature T in step S101. In subsequent step S102, the low temperature control unit 72 determines whether or not the inverter temperature T grasped in step S101 is equal to or lower than a predetermined low temperature stop temperature Tstop. The low temperature stop temperature Tstop is a temperature higher than the operation lower limit temperature Tmin.

  When the inverter temperature T is equal to or lower than the low temperature stop temperature Tstop, the low temperature control unit 72 proceeds to step S103, stops the electric motor 13, and ends the low temperature response process. When the electric motor 13 is stopped, the control unit 55 transmits a notification to that effect to the air conditioning ECU 102. When the air conditioning ECU 102 receives the notification, the control unit 55 receives a predetermined notification unit (such as an indicator lamp). ) May be used to make a notification (alarm) to that effect.

  On the other hand, when the inverter temperature T is higher than the low temperature stop temperature Tstop, the low temperature control unit 72 controls the drive mode of the inverter 31 at low temperatures in steps S104 to S114. In the present embodiment, the “low temperature driving mode control unit” is included in the control unit 55 (specifically, the low temperature control unit 72), and the control unit 55 executes the processes of steps S104 to S114. The function corresponds to the function of the “low temperature drive mode control unit”.

  Specifically, the low temperature control unit 72 first determines in step S104 whether or not the current drive mode of the inverter 31 is the two-phase modulation mode. When the current drive mode of the inverter 31 is the two-phase modulation mode, the low temperature control unit 72 proceeds to step S105 and determines whether or not the inverter temperature T is equal to or lower than a predetermined switching trigger temperature Tth1. To do. The switching trigger temperature Tth1 is a temperature higher than the operation lower limit temperature Tmin and the low temperature stop temperature Tstop, for example, −20 ° C.

  When the inverter temperature T is higher than the switching trigger temperature Tth1, the low temperature control unit 72 ends the low temperature response process without switching the drive mode of the inverter 31. On the other hand, when the inverter temperature T is equal to or lower than the switching trigger temperature Tth1, the low temperature control unit 72 proceeds to step S106 and switches the drive mode of the inverter 31 from the two-phase modulation mode to the three-phase modulation mode.

  In order to distinguish from the drive mode switching control of the inverter 31 (normal drive mode control) by the normal drive mode control unit 71, in the following description, the drive mode switch control of the inverter 31 by the low temperature control unit 72 will be described. This is called low temperature drive mode control.

  Thereafter, the low temperature control unit 72 prohibits the normal driving mode control in step S107. Specifically, the low temperature control unit 72 prevents the normal driving mode control unit 71 from changing the drive mode of the inverter 31 from the three-phase modulation mode to the two-phase modulation mode.

  In subsequent step S108, the low temperature control unit 72 makes the carrier frequency of the inverter 31 higher than the initial frequency. Specifically, the low temperature control unit 72 changes the carrier frequency of the inverter 31 from the initial frequency to a low temperature frequency that is higher than the initial frequency. In this embodiment, the “carrier frequency variable unit” is included in the control unit 55 (specifically, the low temperature control unit 72), and the function of the control unit 55 executing the process of step S108 is “carrier frequency”. It corresponds to the function of “variable part”.

  Thereafter, in step S109, the low temperature control unit 72 switches the drive mode in step S106. Specifically, the low temperature drive mode control changes the drive mode of the inverter 31 from the two-phase modulation mode to the three-phase modulation. A low temperature switching flag for specifying that the mode has been switched is set in a predetermined storage area provided in the low temperature control unit 72. And the low temperature control part 72 complete | finishes this low temperature response process.

  On the other hand, if the drive mode of the inverter 31 is not the two-phase modulation mode in step S104, it means that the drive mode of the inverter 31 is the three-phase modulation mode. In this case, the low temperature control unit 72 makes a negative determination in step S104 and proceeds to step S110.

  In step S110, the low temperature control unit 72 switches the inverter 31 from the two-phase modulation mode to the three-phase modulation mode by the low temperature drive mode control, and then the inverter temperature T is higher than the switching trigger temperature Tth1. It is determined whether or not a certain switching release temperature Tth2 has been reached. Specifically, the low temperature control unit 72 determines whether or not there is a low temperature switching flag and the inverter temperature T is equal to or higher than the switching release temperature Tth2.

  As already described, the low temperature switching flag is set when the drive mode is switched in step S106. For this reason, the presence of the low temperature switching flag means that the three-phase modulation mode is set by the low temperature driving mode control, not the three-phase modulation mode by the normal driving mode control. . For this reason, the low-temperature control unit 72 determines whether or not the low-temperature switching flag is present, so that the three-phase modulation mode is set according to the rotational speed r of the electric motor 13 or the three-phase modulation mode is controlled by the low-temperature driving mode control. It is possible to distinguish whether the mode is the modulation mode.

  When there is no low temperature switching flag or when there is a low temperature switching flag but the inverter temperature T is lower than the switching release temperature Tth2, the low temperature control unit 72 does not change the drive mode of the inverter 31 and End the low temperature response process. In this case, the drive mode of the inverter 31 is maintained in the three-phase modulation mode.

  On the other hand, when there is a low temperature switching flag and the inverter temperature T is equal to or higher than the switching release temperature Tth2, the low temperature control unit 72 proceeds to step S111 and changes the drive mode of the inverter 31 from the three-phase modulation mode to the two-phase modulation mode. Switch to modulation mode.

  Further, in step S112, the low temperature control unit 72 cancels the prohibition of the normal driving mode control. Specifically, the low temperature control unit 72 permits the normal drive mode control unit 71 to change the drive mode of the inverter 31. In subsequent step S113, the low temperature control unit 72 changes the carrier frequency of the inverter 31 from the low temperature frequency to the initial frequency. And the low temperature control part 72 erase | eliminates the low temperature switching flag in step S114, and complete | finishes this low temperature response process.

  Next, the effect | action of this embodiment is demonstrated using FIG. FIG. 4A shows an example of the time change of the inverter temperature T under the condition that the rotation speed r of the electric motor 13 is not less than the threshold rotation speed rth and the suction refrigerant temperature is lower than the operation lower limit temperature Tmin. Show. FIG. 4B shows the drive mode of the inverter 31, and FIG. 4C shows the ON / OFF mode of the normal drive mode control. In FIG. 4C, the state where the normal driving mode control is prohibited is set to OFF, and the state where the normal driving mode control is not prohibited is set to ON. In FIG. 4A, the time change of the inverter temperature T when the drive mode is not switched is indicated by a two-dot chain line.

  As shown in FIGS. 4A and 4B, in a situation where the drive mode of the inverter 31 is the two-phase modulation mode, when the inverter temperature T becomes the switching trigger temperature Tth1 at the timing t1, The drive mode of the inverter 31 is switched from the two-phase modulation mode to the three-phase modulation mode by the drive mode control. Thereby, since the emitted-heat amount of the inverter 31 becomes large, the inverter temperature T rises.

  Further, as shown in FIG. 4C, the normal drive mode control is prohibited (ON → OFF) at the timing t1. That is, change of the drive mode of the inverter 31 from the three-phase modulation mode to the two-phase modulation mode by the normal drive mode control unit 71 is prohibited. Thereby, even if the rotation speed r is equal to or greater than the threshold rotation speed rth, the drive mode of the inverter 31 does not become the two-phase modulation mode.

  After that, as shown in FIG. 4A, when the inverter temperature T reaches the switching release temperature Tth2 at the timing t2, the drive mode of the inverter 31 is switched by the low temperature driving mode control. Specifically, as shown in FIG. 4B, the drive mode of the inverter 31 is switched from the three-phase modulation mode to the two-phase modulation mode. Thereby, since the power loss of the inverter 31 becomes small, the efficiency of the inverter 31 becomes high. On the other hand, since the heat generation amount of the inverter 31 is reduced, the inverter temperature T is lowered. Further, as shown in FIG. 4C, the prohibition of the normal driving mode control is canceled at the timing t2.

  After that, when the inverter temperature T becomes the switching trigger temperature Tth1 again at the timing t3, the drive mode of the inverter 31 is switched from the two-phase modulation mode to the three-phase modulation mode by the low temperature drive mode control, and the normal drive mode control is performed. It is forbidden. When the inverter temperature T reaches the switching release temperature Tth2 at the timing t4, the drive mode of the inverter 31 is switched from the three-phase modulation mode to the two-phase modulation mode, and the prohibition of the normal drive mode control is released.

  From the above, the electric compressor 10 continues operation in a state where the inverter temperature T is within a predetermined range (specifically, a range slightly wider than the range from the switching trigger temperature Tth1 to the switching release temperature Tth2). . For this reason, compared with the case where the drive mode is not switched (see the two-dot chain line in FIG. 4A), the operation of the electric compressor 10 is easily continued.

  When the electric motor 13 is stopped at the timing t5, the inverter 31 is cooled by the refrigerant sucked immediately before the stop, and the inverter temperature T is rapidly decreased. However, since the inverter temperature T immediately before the stop of the electric motor 13 is within the range of the switching trigger temperature Tth1 set higher than the operation lower limit temperature Tmin and the low temperature stop temperature Tstop, The inverter temperature T is unlikely to be lower than the operation lower limit temperature Tmin.

According to the embodiment described above in detail, the following effects are obtained.
(1) The electric compressor 10 including the housing 11 in which the compression unit 12 and the electric motor 13 are accommodated and the refrigerant is sucked, and the inverter 31 disposed at a position where the refrigerant is thermally coupled to the housing 11 A temperature sensor 53 used for measuring the inverter temperature T and a control unit 55 for controlling the electric motor 13 by controlling the inverter 31 are provided. The drive modes for driving the inverter 31 include a two-phase modulation mode and a three-phase modulation mode. The low temperature control unit 72 of the control unit 55 is in a situation where the drive mode of the inverter 31 is the two-phase modulation mode so that the inverter temperature T does not become lower than the operation lower limit temperature Tmin that is the lower limit value of the operation guarantee range of the inverter 31. , The inverter 31 has a function of performing low-temperature drive mode control for switching the drive mode of the inverter 31 from the two-phase modulation mode to the three-phase modulation mode based on the fact that the inverter temperature T becomes equal to or lower than the switching trigger temperature Tth1. Thus, the amount of heat generated in the inverter 31 can be increased by switching the drive mode of the inverter 31 from the two-phase modulation mode to the three-phase modulation mode. Therefore, a decrease in inverter temperature T can be suppressed.

  In particular, when the electric motor 13 stops, no heat is generated in the inverter 31. Then, for example, the inverter temperature T can be lower than the operation lower limit temperature Tmin. On the other hand, in this embodiment, the inverter temperature T may be maintained at a somewhat high temperature (for example, the switching trigger temperature Tth1 or higher) by the low temperature driving mode control. Thereby, even if it is a case where the electric motor 13 stops, the situation where the inverter temperature T becomes lower than the operation | movement minimum temperature Tmin can be suppressed, for example. Therefore, it is possible to suitably cope with a decrease in the inverter temperature T accompanying the stop of the electric motor 13.

  (2) The low temperature control unit 72 of the control unit 55 causes the inverter temperature T to be higher than the switching trigger temperature Tth1 after the drive mode of the inverter 31 is switched from the two-phase modulation mode to the three-phase modulation mode by the low temperature drive mode control. When the switching cancellation temperature Tth2 is reached, which is a high temperature, the drive mode of the inverter 31 is switched from the three-phase modulation mode to the two-phase modulation mode. Thereby, the power loss of the inverter 31 can be reduced while maintaining the inverter temperature T high to some extent.

  (3) The control unit 55 includes a normal-time drive mode control unit 71 that sets the drive mode of the inverter 31 to the two-phase modulation mode or the three-phase modulation mode based on the modulation parameter including the rotation speed r of the electric motor 13. ing. Thereby, for example, when the rotational speed r is relatively low, the operation mode of the electric motor 13 can be realized by setting the drive mode of the inverter 31 to the three-phase modulation mode, while the rotational speed r is relatively high. If it is high, the power loss of the inverter 31 can be reduced by setting the drive mode of the inverter 31 to the two-phase modulation mode.

  In such a configuration, the low-temperature control unit 72 prohibits the normal-time drive mode control when the drive mode is switched from the two-phase modulation mode to the three-phase modulation mode by the low-temperature drive mode control. Specifically, the low temperature control unit 72 prevents the normal driving mode control unit 71 from changing the drive mode of the inverter 31 from the three-phase modulation mode to the two-phase modulation mode. Thereby, after the drive mode of the inverter 31 is switched from the two-phase modulation mode to the three-phase modulation mode by the low temperature drive mode control, before the inverter temperature T becomes the switching release temperature Tth2, the normal drive mode control unit 71 The inconvenience that the drive mode of the inverter 31 is returned to the two-phase modulation mode can be avoided.

  (4) When the driving mode of the inverter 31 is switched from the two-phase modulation mode to the three-phase modulation mode by the low temperature driving mode control, the low temperature control unit 72 increases the carrier frequency of the inverter 31 (step S108). Thereby, since the further improvement of the emitted-heat amount of the inverter 31 can be aimed at, the fall of the inverter temperature T can be suppressed more suitably.

  (5) The inverter 31 includes power switching elements Qu1 to Qw2 that operate normally when the temperature is equal to or higher than a predetermined operating lower limit temperature Tmin, and the power switching elements Qu1 to Qw2 are periodically turned on / off. By doing so, the electric motor 13 is driven. The switching trigger temperature Tth1 is set higher than the operation lower limit temperature Tmin. As a result, the inverter temperature T becomes the switching trigger temperature Tth1 before the inverter temperature T reaches the operation lower limit temperature Tmin, and the drive mode of the inverter 31 is switched from the two-phase modulation mode to the three-phase modulation mode by the low-temperature drive mode control. Therefore, it can suppress that the temperature of each power switching element Qu1-Qw2 becomes lower than the operation | movement minimum temperature Tmin.

  (6) The electric motor 13 is configured to stop based on the inverter temperature T being equal to or lower than the low temperature stop temperature Tstop, which is a temperature higher than the operation lower limit temperature Tmin. As a result, the electric motor 13 can be stopped before the inverter temperature T reaches an excessively low temperature such as the operation lower limit temperature Tmin. On the other hand, when the electric motor 13 stops, for example, comfort in the vehicle interior decreases.

  On the other hand, in this embodiment, the switching trigger temperature Tth1 is set higher than the low temperature stop temperature Tstop. Accordingly, the drive mode of the inverter 31 is switched from the two-phase modulation mode to the three-phase modulation mode by the low-temperature drive mode control before the inverter temperature T becomes the low temperature stop temperature Tstop. Thereby, it is possible to avoid the inverter temperature T from becoming the low temperature stop temperature Tstop, or to increase the time until the inverter temperature T reaches the low temperature stop temperature Tstop. Thus, for example, comfort can be improved.

  (7) The electric compressor 10 includes a base member 41 as a heat transfer member that is thermally coupled to both the housing 11 and the inverter 31 (specifically, the power module 52). Thereby, since heat exchange is performed between the refrigerant and the inverter 31 via the housing 11 and the base member 41, the temperature of the inverter 31 using the refrigerant can be adjusted.

  In particular, the base member 41 constitutes a case 32 in which the inverter 31 is accommodated, and is used to attach the case 32 to the housing 11. In other words, since the temperature of the inverter 31 can be adjusted using the base member 41 used to attach the inverter 31 to the housing 11, the base member 41 can be multifunctional.

In addition, you may change the said embodiment as follows.
The power module 52 of the inverter 31 and the base member 41 may not be in contact with each other and may be arranged apart from each other. Even in this case, since the ambient temperature in the case 32 is adjusted by the refrigerant, the temperature of the power module 52 is adjusted accordingly.

  The base member 41 may be omitted and the cover member 42 may be fixed to the wall portion 11c of the housing 11. In this case, the inverter 31 is accommodated in a space defined by the cover member 42 and the wall portion 11 c of the housing 11. Even in such a configuration, the inverter 31 and the housing 11 are thermally coupled. In short, the inverter 31 may be disposed at a position where it is thermally coupled to the housing 11. In this case, the inverter 31 may be separated from or in contact with the base member 41 or the wall portion 11 c of the housing 11.

  The specific numerical values such as the switching trigger temperature Tth1 and the switching release temperature Tth2 are arbitrary as long as the inverter temperature T can be suppressed from falling below the operation lower limit temperature Tmin when the electric motor 13 is stopped.

  ○ Switching conditions for switching the drive mode of the inverter 31 from the three-phase modulation mode to the two-phase modulation mode by the low-temperature drive mode control are arbitrary, for example, from the two-phase modulation mode to the three-phase modulation mode by the low-temperature drive mode control. It may be that a predetermined period has elapsed since the drive mode was switched.

The threshold rotation speed rth may be a fixed value that does not vary regardless of the current value I.
In the embodiment, the carrier frequency is a variable value that is set high when the drive mode of the inverter 31 is switched from the two-phase modulation mode to the three-phase modulation mode by the low-temperature drive mode control, but is not limited thereto. It may be a fixed value (initial frequency).

  In the embodiment, the current value I and the rotation speed r of the electric motor 13 are employed as the modulation parameters, but are not limited thereto. For example, instead of or in addition to the current value I, the pressure in the compression unit 12 or the like may be employed. Further, the modulation parameter may be only the rotation speed r of the electric motor 13.

  In the embodiment, the presence / absence of the low temperature switching flag is adopted as a judgment material for judging whether the three-phase modulation mode is based on the normal driving mode control or the low temperature driving mode control. Is not limited to this and is arbitrary. For example, it may be determined whether or not the normal driving mode control is prohibited.

  ○ In the two-phase modulation mode, the periodic ON / OFF of one fixed phase power switching element, which is predetermined among the three phases, is always stopped, while the other two-phase power switching elements are periodically turned ON / OFF. It may be a drive mode in which OFF is always performed.

  In the embodiment, the low temperature control unit 72 has the low temperature switching flag, and when the inverter temperature T is equal to or higher than the switching release temperature Tth2, the inverter 31 of the inverter 31 is controlled regardless of the rotation speed r of the electric motor 13. Although the process of switching the drive mode from the three-phase modulation mode to the two-phase modulation mode has been executed, the present invention is not limited to this. For example, when the low temperature control unit 72 makes an affirmative determination in step S110, the current rotational speed r and current value I of the electric motor 13 are grasped, and the grasped rotational speed r is obtained as the grasped current value I. It may be determined whether or not it is equal to or higher than the corresponding threshold rotation number rth. When the rotational speed r is equal to or greater than the threshold rotational speed rth, the low temperature control unit 72 switches the drive mode of the inverter 31 from the three-phase modulation mode to the two-phase modulation mode, while the rotational speed r is the threshold rotational speed. If it is less than rth, the drive mode of the inverter 31 may be maintained in the three-phase modulation mode. Thereby, it is possible to avoid unnecessary switching of the drive mode of the inverter 31.

(Circle) heat pump 100 is not restricted to a vehicle, You may mount in another apparatus. The electric compressor 10 may be used for applications other than the heat pump 100.
The attachment position of the inverter unit 30 with respect to the housing 11 is arbitrary, and may be, for example, the outer surface of a portion of the housing 11 that faces the outer peripheral surface of the stator 23.

  The temperature sensor 53 may measure the temperature of the base member 41. In this case, the control unit 55 may estimate the temperature of the power module 52 from the temperature of the base member 41, and use the estimated temperature as the inverter temperature T.

Next, a preferable example that can be grasped from the embodiment and another example will be described below.
(B) The electric motor is a three-phase motor, and the drive circuit is a three-phase inverter, The electric compressor according to any one of claims 1 to 5.

  DESCRIPTION OF SYMBOLS 10 ... Electric compressor, 11 ... Housing, 12 ... Compression part, 13 ... Electric motor, 31 ... Inverter (drive circuit), 41 ... Base member (heat transfer member), 52 ... Power module, 55 ... Control part, 71 ... Normal drive mode control unit, 72 ... Low temperature control unit, 100 ... Heat pump, r ... Electric motor speed, T ... Inverter temperature, Tth1 ... Switching trigger temperature, Tth2 ... Switching release temperature, Tmin ... Operation lower limit temperature.

Claims (4)

A housing into which refrigerant is sucked;
A compressing unit housed in the housing and compressing and discharging the refrigerant;
An electric motor housed in the housing and driving the compression section;
A drive circuit that is thermally coupled to the housing and drives the electric motor;
A temperature measuring unit for measuring the temperature of the drive circuit;
A control unit for controlling the electric motor by controlling the drive circuit;
With
The drive mode for driving the drive circuit includes a two-phase modulation mode and a three-phase modulation mode,
The control unit is measured by the temperature measurement unit in a situation where the drive mode of the drive circuit is the two-phase modulation mode so that the temperature of the drive circuit does not become lower than the lower limit value of the operation guarantee range of the drive circuit. A low-temperature driving mode control unit that switches the driving mode of the driving circuit from the two-phase modulation mode to the three-phase modulation mode when the temperature of the driving circuit that has been set becomes equal to or lower than a predetermined switching trigger temperature. ,
The drive circuit includes a switching element that operates normally when the temperature is equal to or higher than a lower limit value of the guaranteed operating range, and drives the electric motor by periodically turning the switching element ON / OFF. Yes,
The electric compressor characterized in that the switching trigger temperature is set higher than a lower limit value of the operation guarantee range .   The low temperature driving mode control unit is configured to measure the driving measured by the temperature measuring unit after the driving mode of the driving circuit is switched from the two-phase modulation mode to the three-phase modulation mode by the low temperature driving mode control unit. 2. The drive mode of the drive circuit is switched from the three-phase modulation mode to the two-phase modulation mode when a circuit temperature becomes equal to or higher than a switching release temperature that is higher than the switching trigger temperature. Electric compressor. The control unit includes a normal-time drive mode control unit that sets the drive mode of the drive circuit to the two-phase modulation mode or the three-phase modulation mode based on a modulation parameter including the rotation speed of the electric motor,
When the driving mode of the driving circuit is switched from the two-phase modulation mode to the three-phase modulation mode by the low temperature driving mode control unit, the control unit controls the driving circuit of the driving circuit by the normal driving mode control unit. The electric compressor according to claim 1 or 2, wherein a drive mode is not changed from the three-phase modulation mode to the two-phase modulation mode.   The control unit includes a carrier frequency variable unit configured to increase a carrier frequency of the drive circuit when the drive mode of the drive circuit is switched from the two-phase modulation mode to the three-phase modulation mode by the low temperature drive mode control unit. The electric compressor as described in any one of Claims 1-3 provided.