Motor-driven compressor

Abstract

Motor-driven compressor (10) with: a housing (11) into which a fluid is drawn; a compression part (12) which is housed in the casing (11), wherein the compression part (12) compresses and discharges the fluid; an electric motor (13) housed in the casing (11), wherein the electric motor (13) drives the compression part (12); and a control circuit (31) that controls the electric motor (13), characterized by: a modulation procedure control unit (61) which sets a modulation procedure of the control circuit (31) to three-phase modulation or two-phase modulation; a temperature measuring section (53) that measures the temperature of the control circuit (31); a high-temperature (HT) shutdown control unit that shuts down the electric motor (13) when the temperature measured by the temperature measuring section (53) is higher than or equal to a predetermined high-temperature (HT) shutdown temperature; and a high-temperature (HT) shutdown temperature setting section, wherein, if the modulation method is three-phase modulation, the HT shutdown temperature setting section sets the HT shutdown temperature to a three-phase high-temperature (HT) shutdown temperature, and, if the modulation method is two-phase modulation, the HT shutdown temperature setting section sets the HT shutdown temperature to a two-phase high-temperature (HT) shutdown temperature that is higher than the three-phase HT shutdown temperature, wherein the control circuit (31) and the housing (11) are thermally coupled to each other, in a situation where the modulation method is three-phase modulation, the modulation method control unit (61) switches the modulation method from three-phase modulation to two-phase modulation when a predetermined two-phase modulation condition is met, and The two-phase modulation condition includes that a speed of the electric motor (13) is greater than or equal to a predetermined threshold speed.

Description

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a motor-driven compressor.

[0002] Traditionally, a motor-driven compressor was known to consist of a housing into which a refrigerant is drawn, a compression element housed within the housing that compresses a fluid, an electric motor housed within the housing that drives the compression element, and a control circuit that controls the electric motor. Reference is made, for example, to publication JP 2003-324900A. This publication also describes that the control circuit is mounted on the outer surface of the housing and that heat exchange occurs between the fluid and the control circuit via the housing to cool the control circuit.

[0003] Depending on the ambient temperature around the motor-driven compressor or the intake fluid temperature (the temperature of the fluid drawn into the housing), the temperature of the control circuit can exceed the upper limit of its guaranteed operating range or fall below the lower limit. In such cases, the control circuit may fail to function or function poorly. Conversely, it is desirable for the motor-driven compressor to operate continuously for as long as possible in certain situations.

[0004] Publication US 2007 / 0273239A1, which represents the closest prior art, discloses a generic motor-driven compressor according to the preamble of the independent claims.

[0005] Further state of the art is known from publication US 2010 / 0 315 024 A1, publication JP 2002 - 262 580 A and the subsequently published publication DE 10 2016 102 789 A1. SUMMARY OF THE INVENTION

[0006] Accordingly, one object of the present invention is to provide a motor-driven compressor that is configured to operate continuously while preventing the temperature of the control circuit from being excessively high or excessively low.

[0007] To achieve the aforementioned objective, a motor-driven compressor is provided according to the invention, as described in the independent claims, with advantageous embodiments or further developments of this being described in the corresponding dependent claims.

[0008] Further aspects and advantages of the present invention will become apparent from the following description when considered in conjunction with the accompanying drawings, which illustrate the principles of the invention by way of example. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The invention, along with its tasks and advantages, can best be understood by referring to the following description of the currently preferred embodiments together with the accompanying drawings, whereby the following applies: Fig. Figure 1 is a schematic representation of a motor-driven compressor and a vehicle air conditioning unit or vehicle air conditioning system; Fig. Figure 2 is a circuit diagram showing the electrical configuration of the motor-driven compressor; Fig. Figure 3 is a flowchart of a high-temperature (HT) shutdown control process; Fig. Figure 4 is a flowchart of a low-temperature (LT) shutdown control process; Fig. Figure 5 is a graph showing changes in the inverter's temperature over time in a high-temperature state; and Fig. Figure 6 is a graph showing changes in the inverter's temperature over time in a low-temperature state. DETAILED DESCRIPTION OF PREFERRED EXECUTION EXAMPLES

[0010] A motor-driven compressor 10 according to an exemplary embodiment is now described. The motor-driven compressor 10 of the present exemplary embodiment is installed on a vehicle and used in the vehicle air conditioning unit 100. This means that, in the present invention, the fluid to be compressed by the motor-driven compressor 10 is a refrigerant.

[0011] As it is in Fig. As shown in Figure 1, the vehicle air conditioning unit 100 comprises the engine-driven compressor 10 and an external coolant circuit 101 that supplies the fluid to the engine-driven compressor 10. The external coolant circuit 101 includes, for example, a heat exchanger and an expansion valve. The engine-driven compressor 10 compresses the coolant, and the external coolant circuit 101 performs a heat exchange of the coolant and expands the coolant. This enables the vehicle air conditioning unit 100 to cool or heat the passenger compartment.

[0012] The vehicle air conditioning unit 100 includes an air conditioning ECU 102, which controls the entire vehicle air conditioning unit 100. The air conditioning ECU 102 is configured to receive parameters such as the passenger compartment temperature and a target temperature. Based on these parameters, the air conditioning ECU 102 issues various commands, such as an ON / OFF command, to the motor-driven compressor 10.

[0013] The motor-driven compressor 10 comprises a housing 11, a compression element 12, and an electric motor 13. The housing 11 has an inlet opening 11a into which the coolant is drawn from the external coolant circuit 101. The compression element 12 and the electric motor 13 are housed within the housing 11.

[0014] The housing 11 is essentially cylindrical as a whole and is made of a thermally conductive material (a metal such as aluminum). The housing 11 has an outlet opening through which the coolant is discharged.

[0015] The compression element 12 compresses the coolant that has been drawn into the housing 11 via the inlet opening 11a and discharges the compressed coolant via the outlet opening 11b. The compression element 12 can have any design, such as a screw design, a piston design, or a paddle wheel design.

[0016] The electric motor 13 drives the compression unit 12. The electric motor 13 comprises a rotating shaft 21, which is rotatably mounted, for example, by the housing 11, a cylindrical rotor 22, which is attached to the rotating shaft 21, and a stator 23, which is attached to the housing 11. The axis of the rotating shaft 21 coincides with the axis of the cylindrical housing 11. The stator 23 comprises a cylindrical stator core 24 and coils 25 wound around the teeth of the stator core 24. The rotor 22 and the stator 23 are oriented opposite each other along the axis of the rotating shaft 21.

[0017] As it is in Fig. As shown in Figure 1, the motor-driven compressor 10 comprises an inverter unit 30, which includes an inverter 31 and a compartment or enclosure 32. The inverter 31 serves as a control circuit that drives the electric motor 13, and the compartment or enclosure 32 houses the inverter 31. The coils 25 of the electric motor 13 and the inverter 31 are connected to each other by connecting parts (not shown).

[0018] The compartment or enclosure 32 consists of a material with heat transfer properties (for example, a metal such as aluminum) and comprises a plate-like base element 41 and a cylindrical cover or casing element 42, which has one closed side and is mounted on the base element 41. The base element 41 is in contact with the housing 11. Specifically, the base element 41 contacts a wall area 11c, which is one of the wall areas on the opposite sides in the axial direction of the housing and is located on the side opposite the outlet opening 11b. In this state, the base element 41 is attached to the housing with bolts or screws 43, which act as fasteners. Accordingly, the compartment or enclosure 32, which houses the inverter 31, is attached to the housing 11.This means that the inverter 31 is integrated with the motor-driven compressor 10 of the present embodiment.

[0019] The inverter 31 comprises, for example, a printed circuit board 51 and a power module 52, which is electrically connected to the printed circuit board 51. The printed circuit board 51 has various electronic components and a wiring structure. A temperature sensor 53 is installed on the printed circuit board 51. The temperature sensor 53 serves as a temperature measuring section that, for example, measures the temperature of the inverter 31. The temperature sensor 53 measures the temperature of the inverter 31 directly or indirectly. For example, the temperature sensor 53 detects the ambient temperature inside the compartment or enclosure 32 as a temperature that indirectly represents the temperature of the inverter 31. A connector 54 is provided on the outer surface of the compartment or enclosure 32. The printed circuit board 51 and the connector 54 are electrically connected to each other.The inverter 31 receives power or energy from a DC source E, which serves as an external energy source, via the connection or terminal part 54. The air conditioning ECU 102 and the inverter 31 are electrically connected.

[0020] The inverter 31 is positioned thermally coupled to the housing 11. Specifically, the power module 52 of the inverter 31 is in contact with the base element 41. As described above, the base element 41 contacts the wall area 11c of the housing 11. Thus, the inverter 31 (specifically the power module 52) and the housing 11 are thermally coupled to each other via the base element 41.

[0021] As it is in Fig. As shown in Figure 2, the coils 25 of the electric motor 13, for example, have a three-phase configuration, with a u-phase coil 25u, a v-phase coil 25v, and a w-phase coil 25w. This means that the electric motor 13 is a three-phase motor. The coils 25u to 25w are connected in a star configuration.

[0022] The power module 52 comprises u-phase power switching elements Qu1, Qu2, corresponding to the u-phase coil 25u, v-phase power switching elements Qv1, Qv2, corresponding to the v-phase coil 25v, and w-phase power switching elements Qw1, Qw2, corresponding to the w-phase coil 25w. This means that the inverter 31 is a three-phase inverter.

[0023] The switching elements Qu1, Qu2, Qv1, Qv2, Qw1 and Qw2 (hereinafter referred to simply as the switching elements Qu1 to Qw2) are each formed, for example, by an insulated-gate bipolar transistor (IGBT). Each of the switching elements Qu1 to Qw2 operates normally when its temperature is higher than or equal to a predetermined lower operating temperature limit Tmin and lower than or equal to a predetermined upper operating temperature limit Tmax.

[0024] The upper operating temperature limit Tmax is the upper limit of the guaranteed operating range of the power switching elements Qu1 to Qw2. In other words, the upper operating temperature limit Tmax is the upper limit of the guaranteed operating range of the inverter 31. The lower operating temperature limit Tmin is the lower limit of the guaranteed operating range of the power switching elements Qu1 to Qw2. In other words, the lower operating temperature limit Tmin is the lower limit of the guaranteed operating range of the inverter 31.

[0025] The u-phase power switching elements Qu1 and Qu2 are connected in series via a connecting wire that is linked to the u-phase coil 25u. The circuit body or structure of the u-phase power switching elements Qu1 and Qu2 receives the DC power from the DC source E. With the exception of the connected coil, the other switching elements Qv1, Qv2, Qw1, and Qw2 have the same connection structure as the u-phase power switching elements Qu1 and Qu2, and their descriptions are omitted. The DC source E is, for example, an electrical storage device such as a battery or an electrical double-layer capacitor.

[0026] The inverter 31 includes a smoothing capacitor C1, which is connected in parallel to the DC power source E. The power module 52 includes freewheeling diodes Du1 to Dw2, which are connected in parallel to the power switching elements Qu1 to Qw2.

[0027] The motor-driven compressor 10 includes a control unit 55, which controls the inverter 31 (specifically, switching the power switching elements Qu1 to Qw2). The control unit 55 is connected to the gate terminals of the power switching elements Qu1 to Qw2. The control unit 55 periodically switches the power switching elements Qu1 to Qw2 ON and OFF to control, drive, or rotate the electric motor 13.

[0028] The control unit 55 performs pulse-width modulation (PWM) control of the inverter 31. Specifically, the control unit 55 uses a carrier signal and a command voltage value signal (reference signal) to generate a control signal. The control unit 55 performs ON / OFF control of the power switching elements Qu1 to Qw2 using the generated control signal, thereby converting DC power into AC power. The AC power obtained through this conversion is supplied to the electric motor 13 to drive it.

[0029] Furthermore, the control unit 55 controls the control signal to vary the duty cycle or the relative on-time of the ON / OFF control of the power switching elements Qu1 to Qw2. By varying the duty cycle or the relative on-time, the control unit 55 controls the rotational speed (number of revolutions per unit of time) of the electric motor 13. The control unit 55 is electrically connected to the air conditioning ECU 102. When it receives information from the air conditioning ECU 102 regarding a target rotational speed, the control unit 55 causes the electric motor 13 to rotate at the target speed. Hereinafter, the rotational speed of the electric motor 13 is simply referred to as the rotational speed.

[0030] Furthermore, the control unit 55 controls the control signal to adjust a modulation factor that represents the ratio of the amplitude of the AC voltage output by the inverter 31 to the voltage of the DC source E (hereinafter referred to simply as the power source voltage). The control unit 55 receives the power source voltage and a required voltage, corresponding to a voltage necessary to drive the electric motor 13, and adjusts the modulation factor M according to the power source voltage so that the output voltage of the inverter 31 becomes the required voltage.

[0031] As it is in Fig. As shown in Figure 2, the control unit 55 comprises a modulation method control unit 61, which controls the modulation method of the inverter 31 (hereinafter referred to simply as the modulation method). The modulation method will now be described.

[0032] In the present embodiment, the modulation method of the inverter 31 comprises three-phase modulation and two-phase modulation. Three-phase modulation is a modulation method in which the power switching elements Qu1 to Qw2 are subjected to periodic ON-OFF operation (switching operation) by all phases. In the present embodiment, two-phase modulation is a modulation method in which the periodic ON-OFF operation of one of the power switching elements Qu1 to Qw2, namely the periodic ON-OFF operation of the power switching element by one of the three phases, is sequentially stopped at each predetermined period (phase angle).This means that two-phase modulation is a modulation method in which the periodic ON-OFF operation of the power switching element of one of the three phases is sequentially stopped, while periodic ON-OFF operations of the power switching elements of the other two phases are carried out. The state in which the periodic ON-OFF operation of a power switching element is stopped refers to a state in which the power switching element remains switched ON or OFF.

[0033] Compared to three-phase modulation, the power switching elements Qu1 to Qw2 are switched ON or OFF less frequently. Therefore, the power loss and heat generation of the inverter 31 are more likely to increase with three-phase modulation than with two-phase modulation.

[0034] Compared to two-phase modulation, three-phase modulation is configured to precisely control the voltage waveform flowing through coils 25u to 25w, and it is likely to reduce current ripple. Therefore, three-phase modulation is preferably used, for example, in a case where the load applied to electric motor 13 is relatively large.

[0035] In the two-phase modulation of the present embodiment, for example, both the power switching elements Qu1, Qv1, Qw1 on the upper arm and the power switching elements Qu2, Qv2, Qw2 on the lower arm are used. In other words, the power switching elements Qu1 to Qw2 are each subjected to a stopping process.

[0036] In a situation where the modulation method is three-phase modulation, the modulation method control unit 61 switches the modulation method from three-phase modulation to two-phase modulation when a predetermined two-phase modulation condition is met. The two-phase modulation condition is defined, for example, by a rotational speed and / or a modulation factor. Specifically, the two-phase modulation condition can be met when the rotational speed is greater than or equal to a predetermined threshold speed and the modulation factor is greater than or equal to a predetermined threshold modulation factor.

[0037] In a situation where the modulation method is two-phase modulation, the modulation method control unit 61 switches the modulation method from two-phase modulation to three-phase modulation when the two-phase modulation condition is no longer met.

[0038] This means that two-phase modulation is used when the rotational speed is relatively high. The flow rate or velocity of the coolant drawn into housing 11 increases as the rotational speed increases. Therefore, if the modulation method is two-phase modulation, the flow rate or velocity of the coolant drawn into housing 11 tends to be higher compared to a case where the modulation method is three-phase modulation.

[0039] As it is in Fig. As shown in Figure 2, the control unit 55 comprises a field weakening control unit 62, which performs field weakening control with respect to the electric motor 13 when a predetermined field weakening condition is met. The field weakening condition refers, for example, to a state in which the back electromotive force generated in the motor 13 is equal to the energy source voltage.

[0040] When the speed of electric motor 13 is increased while the energy source voltage is low, the magnetic flux generated by the rotation of the electric motor produces a counter-electromotive force. When this counter-electromotive force equals the energy source voltage applied to electric motor 13, the speed of electric motor 13 can no longer be increased.

[0041] In contrast, the field weakening control suppresses the back electromotive force generated by the rotation of the electric motor 13. Specifically, the field weakening control suppresses the back electromotive force by causing the inverter 31 to output a current to the electric motor 13 that weakens the magnetic flux generated by its rotation. Therefore, even in a case where the power source voltage is relatively low, the motor-driven compressor 10 is allowed to operate at a high speed while maintaining a high, constant torque.

[0042] Field weakening control is implemented, for example, when the modulation method is two-phase modulation and overmodulation control is used. In overmodulation control, a power switching element, representing an object to be operated, is held in an ON state for a predetermined period longer than the carrier period. Field weakening control is implemented under a relatively low power source voltage environment. Therefore, the power loss and heat generation of inverter 31 are more likely to be reduced with field weakening control than with normal control. The power switching element representing an object to be operated is different from the power switching elements in a stopped state.

[0043] The temperature sensor 53 transmits the measurement result to the control unit 55. This allows the control unit 55 to receive a measured temperature Tm, which is measured by the temperature sensor 53. The control unit 55 periodically executes a high-temperature (HT) shutdown control process and a low-temperature (LT) shutdown control process to control the shutdown of the motor-driven compressor 10 (specifically the electric motor 13), so that the temperature of the inverter 31 remains within the guaranteed operating range during operation of the motor-driven compressor 10 (i.e., during rotation of the electric motor 13).

[0044] The high-temperature (HT) shutdown control process is configured to stop operation of the motor-driven compressor 10 when the measured temperature Tm is higher than or equal to a predetermined high-temperature (HT) shutdown temperature Th. The HT shutdown temperature Th is set to be lower than the maximum operating temperature Tmax. The control unit 55 varies the HT shutdown temperature Th according to the control mode of the inverter 31. The details of the HT shutdown control process are now described in conjunction with the control for varying the HT shutdown temperature Th.

[0045] As it is in Fig. As shown in Figure 3, the control unit 55 receives the measured temperature Tm from the measurement result of the temperature sensor 53 in step S101. Then, in step S102, the control unit 55 determines whether the current modulation method is three-phase modulation. If the current modulation method is three-phase modulation, the control unit 55 makes a positive determination in step S102 and proceeds to step S103. In step S103, the control unit 55 determines whether the measured temperature Tm obtained in step S101 is higher than or equal to a predetermined three-phase high-temperature (HT) cutoff temperature Th1. The three-phase HT cutoff temperature Th1 is a value of the HT cutoff temperature Th, which is set when the modulation method is three-phase modulation.

[0046] If the measured temperature Tm is lower than the three-phase high-temperature (HT) shutdown temperature Th1, the control unit 55 terminates the HT shutdown control process without further processing. Conversely, if the measured temperature Tm is higher than or equal to the three-phase HT shutdown temperature Th1, the control unit 55 executes a shutdown process to switch off the electric motor 13 in step S104 and terminates the HT shutdown control process. During the shutdown process, the control unit 55 stops the periodic ON-OFF operation of the power switching elements Qu1 to Qw2.

[0047] If the current modulation method is not three-phase modulation, that is, if the current modulation is two-phase modulation, the control unit 55 makes a negative determination in step S102 and proceeds to step S105, as described in Fig. Figure 3 is shown. In step S105, the control unit 55 determines whether field weakening control is executed. If field weakening control is not executed, that is, if the field weakening control unit 62 does not execute field weakening control, the control unit 55 proceeds to step S106. In step S106, the control unit 55 determines whether the measured temperature Tm is higher than or equal to a predetermined primary two-phase high-temperature (HT) shutdown temperature Th2. The primary two-phase HT shutdown temperature Th2 is a value of the HT shutdown temperature Th that is set when the modulation method is two-phase modulation and field weakening control is not executed, that is, when normal control is executed. The primary two-phase HT shutdown temperature Th2 is set to be higher than the three-phase HT shutdown temperature Th1.

[0048] If the measured temperature Tm is lower than the primary two-phase HT shutdown temperature Th2, the control unit 55 terminates the HT shutdown control process without further processing. In contrast, if the measured temperature Tm is higher than or equal to the primary two-phase HT shutdown temperature Th2, the control unit 55 executes the shutdown process to switch off the electric motor 13 in step S104 and terminates the HT shutdown control process.

[0049] When field weakening control is executed, the control unit 55 makes a positive determination in step S105 and proceeds to step S107. In step S107, the control unit 55 determines whether the measured temperature Tm is higher than or equal to a predetermined secondary two-phase high-temperature (HT) shutdown temperature Th3. The secondary two-phase HT shutdown temperature Th3 is a value of the HT shutdown temperature Th that is set when the modulation method is two-phase modulation and field weakening control is executed. The secondary two-phase HT shutdown temperature Th3 is set to be higher than the three-phase HT shutdown temperature Th1 and higher than the primary two-phase HT shutdown temperature Th2. That is, the following expression is satisfied: Three-phase HT shutdown temperature Th1 < Primary two-phase HT shutdown temperature Th2 < Secondary two-phase HT shutdown temperature Th3 < Operating temperature limit Tmax.

[0050] If the measured temperature Tm is lower than the secondary two-phase HT shutdown temperature Th3, the control unit 55 terminates the HT shutdown control process without further processing. In contrast, if the measured temperature Tm is higher than or equal to the secondary two-phase HT shutdown temperature Th3, the control unit 55 executes the shutdown process to switch off the electric motor 13 in step S104 and terminates the HT shutdown control process. In the present embodiment, the control unit 55 corresponds to a high-temperature (HT) shutdown control unit and a high-temperature (HT) shutdown temperature setting section.

[0051] The LT shutdown control process will now be described. The LT shutdown control process is configured to stop operation of the motor-driven compressor 10 when the measured temperature Tm falls to or below a predetermined LT shutdown temperature Ti. The LT shutdown temperature Ti is set to be higher than the operating temperature lower limit Tmin. The control unit 55 varies the LT shutdown temperature Ti according to the control mode of the inverter 31. The details of the LT shutdown control process are now described in conjunction with the control for varying the LT shutdown temperature Ti.

[0052] As it is in Fig. As shown in Figure 4, the control unit 55 receives the measured temperature Tm from the measurement result of the temperature sensor 53 in step S201. Then, in step S202, the control unit 55 determines whether the current modulation method is three-phase modulation. If the current modulation method is three-phase modulation, the control unit 55 makes a positive determination in step S202 and proceeds to step S203. In step S203, the control unit 55 determines whether the measured temperature Tm obtained in step S201 is less than or equal to a predetermined three-phase low-temperature (LT) cutoff temperature Ti1. The three-phase LT cutoff temperature Ti1 is a value of the LT cutoff temperature Ti that is set when the modulation method is three-phase modulation.

[0053] If the measured temperature Tm is higher than the three-phase LT shutdown temperature Ti1, the control unit 55 terminates the HT shutdown control process without further processing. In contrast, if the measured temperature Tm is lower than or equal to the three-phase LT shutdown temperature Ti1, the control unit 55 executes the shutdown process to switch off the electric motor 13 in step S204 and terminates the LT shutdown control process.

[0054] If the current modulation method is not three-phase modulation, that is, if the current modulation is two-phase modulation, the control unit 55 makes a negative determination in step S202 and proceeds to step S205, as described in Fig. Figure 4 shows that in step S205, the control unit 55 determines whether field weakening control is executed. If field weakening control is not executed, the control unit 55 proceeds to step S206 and determines whether the measured temperature Tm is less than or equal to a predetermined primary two-phase low-temperature (LT) shutdown temperature Ti2. The primary two-phase LT shutdown temperature Ti2 is a value of the LT shutdown temperature Ti that is set when the modulation method is two-phase modulation and field weakening control is not executed (that is, when normal control is executed). The primary two-phase LT shutdown temperature Ti2 is set to be higher than the three-phase LT shutdown temperature Ti1.

[0055] If the measured temperature Tm is higher than the primary two-phase LT shutdown temperature Ti2, the control unit 55 terminates the LT shutdown control process without further processing. In contrast, if the measured temperature Tm is lower than or equal to the primary two-phase LT shutdown temperature Ti2, the control unit 55 executes the shutdown process to switch off the electric motor 13 in step S204 and terminates the LT shutdown control process.

[0056] When field weakening control is executed, the control unit 55 makes a positive determination in step S205 and proceeds to step S207. In step S207, the control unit 55 determines whether the measured temperature Tm is less than or equal to a predetermined secondary two-phase low-temperature (LT) shutdown temperature Ti3. The secondary two-phase LT shutdown temperature Ti3 is a value of the LT shutdown temperature Ti that is set when the modulation method is two-phase modulation and field weakening control is executed. The secondary two-phase LT shutdown temperature Ti3 is set to be higher than the three-phase LT shutdown temperature Ti1 and higher than the primary two-phase LT shutdown temperature Ti2.This means that the following expression is satisfied: secondary two-phase LT shutdown temperature Ti3 > primary two-phase LT shutdown temperature Ti2 > three-phase LT shutdown temperature Ti1 > lower operating temperature limit Tmin.

[0057] If the measured temperature Tm is higher than the secondary two-phase LT shutdown temperature Ti3, the control unit 55 terminates the LT shutdown control process without further processing. In contrast, if the measured temperature Tm is lower than or equal to the secondary two-phase LT shutdown temperature Ti3, the control unit 55 executes the shutdown process to switch off the electric motor 13 in step S204 and terminates the LT shutdown control process. In the present embodiment, the control unit 55 corresponds to a low-temperature (LT) shutdown control unit and a low-temperature (LT) shutdown temperature setting section.

[0058] An operation of the present embodiment will now be described with reference to Fig. 5 and Fig. 6 described. Fig. Figure 5 is a graph showing examples of changes in the temperature of inverter 31 over time in a high-temperature state, and Fig. Figure 6 is a graph showing examples of changes in the temperature of inverter 31 over time in a low-temperature state.

[0059] In Fig. Line 5 represents an example of a temperature change in a case where the modulation method is three-phase modulation, and line fh2 represents an example of a temperature change in a case where the modulation method is two-phase modulation and field weakening control is not performed.

[0060] Similarly, in Fig. 6 a line fi1 represents an example of a temperature change in a case where the modulation method is three-phase modulation, and a line fi2 represents an example of a temperature change in a case where the modulation method is two-phase modulation and field weakening control is not performed.

[0061] For illustrative purposes, shows Fig. Figure 5 schematically shows the three-phase high-temperature (HT) shutdown temperature Th1 and the primary two-phase HT shutdown temperature Th2, together with the operating temperature limit Tmax. In reality, the measured temperature Tm may differ from the temperature of the inverter 31. Therefore, the motor-driven compressor 10 does not necessarily stop operation every time the temperature of the inverter 31 is higher than or equal to the three-phase HT shutdown temperature Th1 or the primary two-phase HT shutdown temperature Th2. Strictly speaking, the temperature used to determine whether to stop operation is the measured temperature Tm. The same applies to Fig. 6.

[0062] First, a high-temperature case is described. As described above, the heat generation quantity of inverter 31 is more likely to be increased when the modulation method is three-phase modulation than when the modulation method is two-phase modulation. As described in Fig. As shown in Figure 5, it is therefore more likely that the rate or speed of temperature increase is higher with three-phase modulation compared to two-phase modulation. Specifically, the slope of line fh1, which corresponds to three-phase modulation, is greater than the slope of line fh2, which corresponds to two-phase modulation.

[0063] Due to certain factors, the temperature of the inverter 31 cannot be reduced immediately after the electric motor 13 is switched off. These factors include, for example, an electrical discharge of the smoothing capacitor C1 and the generation of a counter-electromotive force, which is accompanied by a cessation of the periodic ON-OFF operation of the power switching elements Qu1 to Qw2.

[0064] A time delay can occur between the time the measured temperature Tm reaches the HT shutdown temperature Th and the time the electric motor 13 actually shuts down. The temperature rise during this delay is likely to be large in three-phase modulation, where the rate or speed of temperature rise is high. Furthermore, the magnitude of the difference between the measured temperature Tm and the temperature of the inverter 31 is likely to be higher in three-phase modulation, where the amount of heat generated is relatively large, than in two-phase modulation, where the amount of heat generated is relatively small.

[0065] In a case where the modulation method in such a situation is three-phase modulation, the temperature of the inverter 31 can exceed the operating temperature limit Tmax, as indicated by a dashed line fha in Fig. 5 indicates that the operation of the motor-driven compressor 10 is stopped when the measured temperature Tm is higher than or equal to the primary two-phase HT shutdown temperature Th2, not the three-phase HT shutdown temperature Th1.

[0066] In contrast, in the present embodiment, if the modulation method is three-phase modulation, the operation of the motor-driven compressor 10 is stopped based on the fact that the measured temperature Tm is higher than or equal to the three-phase high-temperature (HT) shutdown temperature Th1, which is lower than the primary two-phase HT shutdown temperature Th2. Accordingly, it is unlikely that the temperature of the inverter 31 will exceed the operating temperature limit Tmax.

[0067] If the modulation method is two-phase modulation, the rate or speed of temperature increase is lower than with three-phase modulation. Therefore, in a case where the modulation method is two-phase modulation, the operation of the motor-driven compressor 10 will be stopped in a state where, for example, the difference between the temperature of the inverter 31 and the operating temperature limit Tmax is excessively large, as indicated by a dashed line fhb ​​in Fig. As indicated in section 5, the operation of the motor-driven compressor 10 is stopped when the measured temperature Tm is higher than or equal to the three-phase HT cutoff temperature Th1. In this case, the operation of the motor-driven compressor 10 is stopped, although normal operation is permitted to continue. This may cause the driver some discomfort.

[0068] In contrast, in the present embodiment, if the modulation method is two-phase modulation, the operation of the motor-driven compressor 10 is stopped when the measured temperature Tm is higher than or equal to the two-phase high-temperature (HT) cutoff temperature Th2, which is higher than the three-phase HT cutoff temperature Th1. This makes it unlikely that the motor-driven compressor 10 will be switched off, although normal operation is permitted to continue.

[0069] Next, a low-temperature case is described. In this case, the amount of heat generated is more likely to be reduced if the modulation method is two-phase modulation than if the modulation method is three-phase modulation. As described in Fig. As shown in Figure 6, it is therefore more likely that the rate or speed of temperature decrease is higher for two-phase modulation compared to three-phase modulation. Specifically, the slope of line fi2, which corresponds to two-phase modulation, is greater than the slope of line fi1, which corresponds to three-phase modulation.

[0070] Even after the electric motor 13 is switched off, the temperature of the inverter 31 can be reduced due to the cooling effect of the coolant that was drawn into the housing immediately before the electric motor 13 is switched off.

[0071] A time delay can occur between the time the electric motor 13 actually switches off and the time the measured temperature Tm reaches the HT switch-off temperature Th. The temperature decrease during this time delay is likely to be large in the case of two-phase modulation, where the rate or speed of temperature decrease is high.

[0072] In a case where the modulation method in such a situation is two-phase modulation, the temperature of the inverter 31 can be reduced to or below the lower operating temperature limit Tmin, as indicated by a dashed line fib in Fig. 6 indicates that the operation of the motor-driven compressor 10 is stopped when the measured temperature Tmin is lower than or equal to the three-phase LT shutdown temperature Ti1, not the primary two-phase LT shutdown temperature Ti2.

[0073] In contrast, in the present embodiment, the operation of the motor-driven compressor 10 is stopped when the measured temperature Tmin is lower than or equal to the primary two-phase LT shutdown temperature Ti2, which is higher than the three-phase LT shutdown temperature Ti1 when the modulation method is two-phase modulation. Accordingly, it is unlikely that the temperature of the inverter 31 will drop below the lower operating temperature limit Tmin.

[0074] If the modulation method is three-phase modulation, the rate or speed of temperature decrease is lower than with two-phase modulation. Therefore, in a case where the modulation method is three-phase modulation, the operation of the motor-driven compressor 10 will be stopped in a state where, for example, the difference between the temperature of the inverter 31 and the lower operating temperature limit Tmin is excessively large, as indicated by a dashed line fia in Fig. As indicated in section 6, the operation of the motor-driven compressor 10 is stopped when the measured temperature Tmin is lower than or equal to the two-phase HT cutoff temperature Ti2. In this case, the operation of the motor-driven compressor 10 is stopped, although normal operation is permitted to continue. This may cause the driver some discomfort.

[0075] In contrast, in the present embodiment, if the modulation method is three-phase modulation, the operation of the motor-driven compressor 10 is stopped when the measured temperature Tm is lower than or equal to the three-phase LT shutdown temperature Ti1, which is lower than the primary two-phase LT shutdown temperature Ti2. This makes it unlikely that the motor-driven compressor 10 will be stopped, although normal operation is permitted to continue.

[0076] The present embodiment described above has the following advantages. (1) The motor-driven compressor 10 comprises the compression unit 12, which compresses the coolant serving as the fluid; the electric motor 13, which drives the compression unit 12; the inverter 31, which is a control circuit configured to drive the electric motor 13; the temperature sensor 53, which measures the temperature of the inverter 31; and the control unit 55, which controls the inverter 31. When the temperature Tm measured by the temperature sensor 53 is higher than or equal to the predetermined high-temperature (HT) shutdown temperature Th, the control unit 55 executes the HT shutdown control process to switch off the electric motor 13. In the HT shutdown control process, the control unit 55 sets the HT shutdown temperature Th to the three-phase HT shutdown temperature Th1 if the modulation method is three-phase modulation.If the modulation method is two-phase modulation, the control unit 55 sets the HT shutdown temperature Th to one of the two-phase HT shutdown temperatures Th2, Th3, which are higher than the three-phase HT shutdown temperature Th1.

[0077] With this configuration, the high-temperature (HT) shutdown temperature Th is set to the relatively low three-phase HT shutdown temperature Th1 when the modulation method is three-phase modulation, where the heat generation of the inverter 31 is relatively large, so the temperature is likely to rise. This prevents the temperature of the inverter 31 (specifically the power module 52) from rising excessively. In contrast, the HT shutdown temperature Th is set to one of the relatively low two-phase HT shutdown temperatures Th2 or Th3 when the modulation method is two-phase modulation. This ensures that the operation of the motor-driven compressor 10 continues smoothly and safely. Since the heat generation is small during two-phase modulation and the temperature is not easily affected, the HT shutdown temperature Th is set to one of the relatively low two-phase HT shutdown temperatures Th2 or Th3.Since the temperature is only slightly increased, it is unlikely that the temperature of the inverter 31 will rise excessively, even if the HT shutdown temperature Th is set to a relatively high temperature, as described above. This allows the motor-driven compressor 10 to continue operating while preventing the temperature of the inverter 31 from rising excessively.

[0078] (2) The inverter 31 includes the power switching elements Qu1 to Qw2, which operate normally when the temperature is lower than or equal to the predetermined maximum operating temperature Tmax. The inverter 31 performs periodic ON-OFF operation with respect to the power switching elements Qu1 to Qw2 to control or drive the electric motor 13. The HT shutdown temperature Th is set to be lower than the maximum operating temperature Tmax. Accordingly, the electric motor 13 is switched off by the HT shutdown control process before the measured temperature Tm reaches the maximum operating temperature Tmax. This prevents the temperature of the inverter 31 from exceeding the maximum operating temperature Tmax.

[0079] (3) The inverter 31 and the housing 11 are thermally coupled. Thus, the inverter 31 is cooled by the coolant that is drawn into the housing 11. The flow rate or velocity of the coolant drawn into the housing 11 depends on the rotational speed of the electric motor 13.

[0080] In a situation where the modulation method is three-phase modulation, the modulation method control unit 61 switches the modulation method from three-phase modulation to two-phase modulation when the predetermined two-phase modulation condition is met. The two-phase modulation condition includes the requirement that the speed of the electric motor 13 is greater than or equal to the threshold speed.

[0081] In this configuration, the flow rate or velocity of the coolant drawn into the housing 11 is more likely to be increased in the case of two-phase modulation than in the case of three-phase modulation, since the rotational speed is higher when the modulation method is two-phase modulation than when the modulation method is three-phase modulation. Accordingly, the inverter 31 is cooled more effectively by the coolant when the modulation method is two-phase modulation. Therefore, even if the high-temperature (HT) shutdown temperature Th is set to one of the two-phase HT shutdown temperatures Th2 or Th3, which is higher than the three-phase HT shutdown temperature Th1, when the modulation method is two-phase modulation, it is unlikely that the temperature of the inverter 31 will exceed the operating temperature limit Tmax.Therefore, the motor-driven compressor 10 is enabled to continue its operation if the modulation method is two-phase modulation.

[0082] (4) The control unit 55 includes the field weakening control unit 62, which performs field weakening control with respect to the electric motor 13 when the predetermined field weakening condition is met. Thus, even in a case where the energy source voltage is low, the motor-driven compressor 10 is enabled to operate at a high speed while maintaining a high constant torque.

[0083] The heat generation of the inverter 31 is more likely to be reduced during field weakening control than during normal control. Since the temperature of the inverter 31 is not easily or significantly increased during field weakening control, it is therefore unlikely that the temperature of the inverter 31 will exceed the operating temperature limit Tmax, even if the high-temperature (HT) shutdown temperature Th is increased during field weakening control. Accordingly, the control unit 55 of the present embodiment sets the HT shutdown temperature Th to the primary two-phase HT shutdown temperature Th2 when the modulation method is two-phase modulation and field weakening control is not being executed.The control unit 55 also sets the high-temperature (HT) shutdown temperature Th to the secondary two-phase HT shutdown temperature Th3, which is higher than the primary two-phase HT shutdown temperature Th2, when the modulation method is two-phase modulation and field weakening control is in operation. Therefore, when the modulation method during field weakening control is two-phase modulation, the motor-driven compressor 10 is allowed to continue operating while the inverter 31 temperature is prevented from exceeding the operating temperature limit Tmax.

[0084] (5) When the measured temperature Tm, as measured by the temperature sensor 53, falls to or below the predetermined LT shutdown temperature Ti, the control unit 55 executes the LT shutdown control process to switch off the electric motor 13. During the LT shutdown control process, the control unit 55 sets the LT shutdown temperature Ti to the three-phase LT shutdown temperature Ti1 if the modulation method is three-phase modulation. If the modulation method is two-phase modulation, the control unit 55 sets the LT shutdown temperature Ti to one of the two-phase LT shutdown temperatures Ti2 or Ti3 that is higher than the three-phase LT shutdown temperature Ti1.

[0085] With this configuration, the LT shutdown temperature Ti is set to one of the relatively high two-phase LT shutdown temperatures Ti2 and Ti3 when the modulation method is two-phase modulation, where the heat generation of the inverter 31 is relatively small, so the temperature is likely to decrease. This prevents the temperature of the inverter 31 (specifically the power module 52) from dropping excessively. In contrast, the LT shutdown temperature Ti is set to the relatively low three-phase LT shutdown temperature Ti1 when the modulation method is three-phase modulation. This ensures that the operation of the motor-driven compressor 10 continues simply and safely.Since the amount of heat generated during three-phase modulation is large and the temperature does not simply decrease, it is unlikely that the temperature of the inverter 31 will drop excessively, even if the LT shutdown temperature Ti is set to a relatively low temperature, as described above. This allows the motor-driven compressor 10 to continue operating while preventing the temperature of the inverter 31 from dropping excessively.

[0086] (6) The power switching elements Qu1 to Qw2 operate normally when the temperature is higher than or equal to the predetermined lower operating temperature limit Tmin. The LT shutdown temperature Ti is set to be higher than the lower operating temperature limit Tmin. Accordingly, the electric motor 13 is switched off by the LT shutdown control process before the measured temperature Tm reaches the lower operating temperature limit Tmin. This prevents the temperature of the inverter 31 from dropping below the lower operating temperature limit Tmin.

[0087] (7) As in the case of point (3) of the advantages, where the two-phase modulation condition is specified, it is less likely that the inverter 31 will be cooled by the coolant when the modulation method is three-phase modulation than when the modulation method is two-phase modulation. Therefore, even if the LT shutdown temperature Ti is set to the three-phase LT shutdown temperature Ti1, which is lower than the primary two-phase LT shutdown temperature Ti2 when the modulation method is three-phase modulation, it is unlikely that the temperature of the inverter 31 will be reduced below the operating temperature lower limit Tmin. Therefore, it is possible for the motor-driven compressor 10 to continue operating when the modulation method is three-phase modulation.

[0088] (8) Since the heat generation of the inverter 31 is more likely to decrease during field weakening control than during normal control, the temperature of the inverter 31 is lowered more easily during field weakening control than during normal control. Accordingly, the control unit 55 sets the low-temperature (LT) shutdown temperature Ti to the primary two-phase LT shutdown temperature Ti2 when the modulation method is two-phase modulation and field weakening control is not executed. The control unit 55 also sets the high-temperature (HT) shutdown temperature Ti to the secondary two-phase LT shutdown temperature Ti3, which is higher than the primary two-phase LT shutdown temperature Ti2, when the modulation method is two-phase modulation and field weakening control is executed.If the modulation method during field weakening control is two-phase modulation, it is therefore possible for the motor-driven compressor 10 to continue its operation, while preventing the temperature of the inverter 31 from dropping below the operating temperature lower limit Tmin.

[0089] The exemplary embodiment presented above can be modified as follows.

[0090] The temperature sensor 53 can detect the temperature of the circuit board 51, which indirectly indicates the temperature of the inverter 31. This means that the temperature sensor 53 can be modified as long as it detects the temperature of the inverter 31 directly or indirectly. As long as the temperature sensor 53 is located in or on the inverter 31, it can be positioned anywhere.

[0091] The specific configuration of each of the power switching elements Qu1 to Qw2 is not limited to an insulated gate bipolar transistor (IGBT), but can be any switching element such as a power MOSFET.

[0092] In the illustrated embodiment, the two-phase modulation condition is defined by both the rotational speed and the modulation factor, but it can only be defined by one of these.

[0093] The field weakening control unit 62 can be omitted. This means that the field weakening control does not need to be implemented. In this case, the secondary two-phase high-temperature shutdown temperature Th3 and the secondary two-phase low-temperature shutdown temperature Ti3 can also be omitted.

[0094] In the illustrated embodiment, the control unit 55 is configured to execute both the HT shutdown control process and the LT shutdown control process, but it can be configured to execute only one of them.

[0095] The compartment or the cover / enclosure 32 can be attached to the housing 11 at any position.

[0096] The power module 52 and the base element 41 of the inverter 31 do not necessarily have to be in contact with each other, but can be separated. Even in this case, the ambient temperature in the compartment or the casing / enclosure 32 is regulated by the coolant, and the temperature of the power module 52 is regulated accordingly.

[0097] The base element 41 can be omitted, and the cover or casing element 42 can be attached to the wall area 11c of the housing 11. In this case, the inverter 31 is housed in the space defined by the cover or casing element 42 and the wall area 11c of the housing 11. Even in this configuration, the inverter 31 and the housing 11 are thermally coupled. This means that any configuration that thermally couples the inverter 31 and the housing 11 can be used.

[0098] Two-phase modulation is not limited to methods that use both the upper and lower arms; it can also be a method that uses only the lower arm. In other words, two-phase modulation can stop the operation of only the power switching elements Qu2, Qv2, and Qw2 of the lower arm.

[0099] The motor-driven compressor or compressor 10 can be installed on any structure or construction that distinguishes it from a vehicle.

[0100] In the illustrated embodiment, the motor-driven compressor 10 is used in the vehicle air conditioning unit 100, but it can be used in any other device. For example, if the vehicle is a fuel cell vehicle (FCV) that has a fuel cell, the motor-driven compressor 10 can be used in a supply device that provides air to the fuel cell. This means that the fluid to be compressed can be any fluid, such as a refrigerant or air.

[0101] Therefore, the present examples and embodiments are to be regarded as illustrative and not as limiting, and the invention is not limited to the details given herein, but can be modified within the scope and equivalence of the attached claims.

[0102] A motor-driven compressor comprises an electric motor, a drive circuit, a modulation method control unit, a temperature sensing section, a high-temperature (HT) shutdown control unit, and a high-temperature (HT) shutdown temperature setting section. The high-temperature (HT) shutdown control unit shuts off the electric motor when the temperature measured by the temperature sensing section is higher than or equal to a predetermined high-temperature (HT) shutdown temperature. If the modulation method is three-phase modulation, the HT shutdown temperature setting section sets the HT shutdown temperature to a three-phase high-temperature (HT) shutdown temperature. If the modulation method is two-phase modulation, the HT shutdown temperature setting section sets the HT shutdown temperature to a two-phase high-temperature (HT) shutdown temperature that is higher than the three-phase HT shutdown temperature.

Claims

Motor-driven compressor (10) comprising: a housing (11) into which a fluid is drawn; a compression element (12) housed in the housing (11), wherein the compression element (12) compresses and discharges the fluid; an electric motor (13) housed in the housing (11), wherein the electric motor (13) drives the compression element (12); and a control circuit (31) that controls the electric motor (13), characterized by: a modulation method control unit (61) that sets a modulation method of the control circuit (31) to three-phase modulation or two-phase modulation; a temperature measuring section (53) that measures a temperature of the control circuit (31); a high-temperature (HT) shutdown control unit that shuts off the electric motor (13).when the temperature measured by the temperature measuring section (53) is higher than or equal to a predetermined high-temperature (HT) shutdown temperature; and a high-temperature (HT) shutdown temperature setting section, wherein, if the modulation method is three-phase modulation, the HT shutdown temperature setting section sets the HT shutdown temperature to a three-phase high-temperature (HT) shutdown temperature, and, if the modulation method is two-phase modulation, the HT shutdown temperature setting section sets the HT shutdown temperature to a two-phase high-temperature (HT) shutdown temperature that is higher than the three-phase HT shutdown temperature, wherein the control circuit (31) and the housing (11) are thermally coupled, in a situation where the modulation method is three-phase modulation, the modulation method control unit (61) switches the modulation method from three-phase modulation to two-phase modulation,when a predetermined two-phase modulation condition is met, and the two-phase modulation condition includes that a speed of the electric motor (13) is greater than or equal to a predetermined threshold speed. Motor-driven compressor (10), comprising: a housing (11) into which a fluid is drawn; a compression element (12) housed in the housing (11), wherein the compression element (12) compresses and discharges the fluid; an electric motor (13) housed in the housing (11), wherein the electric motor (13) drives the compression element (12); and a control circuit (31) that controls the electric motor (13), characterized by: a modulation method control unit (61) that sets a modulation method of the control circuit (31) to three-phase modulation or two-phase modulation; a temperature measuring section (53) that measures a temperature of the control circuit (31); a high-temperature (HT) shutdown control unit that shuts down the electric motor (13) when the temperature measured by the temperature measuring section (53) is higher than or equal to a predetermined high-temperature (HT) shutdown temperature;a high-temperature (HT) shutdown temperature setting section, wherein, if the modulation method is three-phase modulation, the HT shutdown temperature setting section sets the HT shutdown temperature to a three-phase high-temperature (HT) shutdown temperature, and, if the modulation method is two-phase modulation, the HT shutdown temperature setting section sets the HT shutdown temperature to a two-phase high-temperature (HT) shutdown temperature that is higher than the three-phase HT shutdown temperature;and a field weakening control unit (62) which performs field weakening control with respect to the electric motor (13) when a predetermined field weakening condition is met, wherein, if the modulation method is two-phase modulation and the field weakening control is not performed, the HT shutdown temperature setting section sets the HT shutdown temperature to a primary two-phase HT shutdown temperature which is higher than the three-phase HT shutdown temperature, and if the modulation method is two-phase modulation and the field weakening control is performed, the HT shutdown temperature setting section sets the HT shutdown temperature to a secondary two-phase HT shutdown temperature which is higher than the primary two-phase HT shutdown temperature. Motor-driven compressor (10) according to claim 1 or 2, wherein the control circuit (31) comprises switching elements (Qu1, Qu2, Qv1, Qv2, Qw1, Qw2) that operate normally when a temperature of the control circuit (31) is lower than or equal to an operating temperature limit, the control circuit (31) periodically switches the switching elements (Qu1, Qu2, Qv1, Qv2, Qw1, Qw2) ON and OFF to control the electric motor (13), and the HT cut-off temperature is set to be lower than the operating temperature limit. Motor-driven compressor (10) comprising: a housing (11) into which a fluid is drawn; a compression element (12) housed in the housing (11), wherein the compression element (12) compresses and discharges the fluid; an electric motor (13) housed in the housing (11), wherein the electric motor (13) drives the compression element (12); and a control circuit (31) that controls the electric motor (13), characterized by: a modulation method control unit (61) that sets a modulation method of the control circuit (31) to three-phase modulation or two-phase modulation; a temperature measuring section (53) that measures a temperature of the control circuit (31); a low-temperature (LT) shutdown control unit that shuts down the electric motor (13) when the temperature measured by the temperature measuring section (53) is lower than or equal to a predetermined low-temperature (LT) shutdown temperature;and a low-temperature (LT) shutdown temperature setting section, wherein, if the modulation method is three-phase modulation, the LT shutdown temperature setting section sets the LT shutdown temperature to a three-phase low-temperature (LT) shutdown temperature, and, if the modulation method is two-phase modulation, the LT shutdown temperature setting section sets the LT shutdown temperature to a two-phase low-temperature (LT) shutdown temperature that is higher than the three-phase LT shutdown temperature. Motor-driven compressor (10) according to claim 4, wherein the control circuit (31) and the housing (11) are thermally coupled, in a situation where the modulation method is three-phase modulation, the modulation method control unit (61) switches the modulation method from three-phase modulation to two-phase modulation when a predetermined two-phase modulation condition is met, and the two-phase modulation condition includes that a speed of the electric motor (13) is greater than or equal to a predetermined threshold speed. Motor-driven compressor (10) according to claim 4 or 5, further comprising a field weakening control unit (62) which performs field weakening control with respect to the electric motor (13) when a predetermined field weakening condition is met, wherein, if the modulation method is two-phase modulation and the field weakening control is not performed, the LT shutdown temperature setting section sets the LT shutdown temperature to a primary two-phase LT shutdown temperature which is higher than the three-phase LT shutdown temperature, and if the modulation method is two-phase modulation and the field weakening control is performed, the LT shutdown temperature setting section sets the LT shutdown temperature to a secondary two-phase LT shutdown temperature which is higher than the primary two-phase LT shutdown temperature. Motor-driven compressor (10) according to one of claims 4 to 6, wherein the control circuit (31) comprises switching elements (Qu1, Qu2, Qv1, Qv2, Qw1, Qw2) that operate normally when a temperature of the control circuit (31) is higher than or equal to a lower operating temperature limit, the control circuit (31) periodically switches the switching elements (Qu1, Qu2, Qv1, Qv2, Qw1, Qw2) ON and OFF to control the electric motor (13), and the LT cut-off temperature is set to be higher than the lower operating temperature limit.

Images