Motor-driven compressor

Abstract

A motor-driven compressor (20) comprising: an electric motor (23); a housing (21) which accommodates the electric motor (23) and contains a suction opening (21a) into which a refrigerant is sucked; a compression section (22) configured to be driven by the electric motor (23) and configured to suck in and compress the refrigerant in the housing (21); and an inverter device (31) configured to drive the electric motor (23), wherein the inverter device (31) comprises an inverter circuit (40) having switching elements (Q1-Q6) included in upper arms and lower arms of the u, v, w phases, wherein the inverter circuit (40) is configured to convert DC voltage into AC voltage when a switching operation is performed for the switching elements (Q1-Q6) and supplies the AC voltage to the electric motor (23), a current sensor (41, 42) configured to detect a value of the current supplied to the electric motor (23), a coordinate converter (65) configured to calculate a d-axis current value and a q-axis current value using a detected value of the current sensor (41, 42), a speed controller (61) configured to generate a d-axis current command and a q-axis current command using a difference between a speed command and a speed estimate for the electric motor (23), a current controller (64) configured to calculate a d-axis voltage command value using a difference between the d-axis current command value and the d-axis current value and to calculate a q-axis voltage command value using a difference between the q-axis current command value and the q-axis current value, a pulse width modulation controller (71) configured to control the switching elements (Q1-Q6) using the d-axis voltage command value and the q-axis voltage command value, and a speed estimator (69) configured to calculate the speed estimate using the d-axis current value, the q-axis current value, the d-axis voltage command value, and the q-axis voltage command value, the speed controller (61) generates the d-axis current setpoint and the q-axis current setpoint in such a way that the required torque for driving the electric motor (23) is generated, the inverter device (31) has a heat-generating current command section (70) configured to increase a temperature of the electric motor (23) by changing the d-axis current command value and the q-axis current command value, and the heat-generating current command value section (70) is configured to change the d-axis current command value and the q-axis current command value such that the d-axis current command value and the q-axis current command value are shifted in a direction in which the d-axis current value increases along a constant torque curve in a dq coordinate system, and a stress limit ellipse and the constant torque curve intersect at a pair of intersection points on an enhanced field side and a weakened field side, the heat-generating current command section (70) is configured to generate the d-axis current command and the q-axis current command at the intersection point of the voltage limit ellipse and the constant torque curve on the boosted side in a dq coordinate system, wherein the voltage limit ellipse depends on an input voltage and a rotational speed, wherein the heat-generating current command section (70) is configured to define, in the dq coordinate system, an upper current limit circle in a range not greater than a limit current value for a temperature of a component of the inverter circuit (40), and changes the d-axis current command value and the q-axis current command value such that the d-axis current command value and the q-axis current command value are shifted to an intersection point of the upper current limit circle and the constant torque curve, and a current limit circuit and the constant torque curve intersect at a pair of intersection points on a strengthened field side and a weakened field side, the intersection point on the strengthened field side is in a range where the d-axis current value and the q-axis current value are positive, and the intersection point on the strengthened field side is set as the heat generation control operating point.

Description

BACKGROUND1. Area

[0001] The present disclosure relates to a motor-driven compressor. 2. Description of the related art

[0002] Vehicles, such as electric vehicles, are equipped with an air conditioning system. A motor-driven compressor can be used in the refrigeration cycle of the air conditioning system. The motor-driven compressor includes a compression section driven by an electric motor. Vector control can be implemented to control the electric motor with an inverter. See, for example, Japanese Patent Application Publication No. 2017-184594.

[0003] In one known method, a cooling device, such as a heat pump or a hot gas heater, is operated as a heating device by switching on part of a refrigerant channel in the cooling device. In such a heating device, it is desirable for the heater to start operating in a shorter period of time. To achieve this, it is effective to quickly increase the temperature of a refrigerant using the motor-driven compressor.

[0004] A vector control system, a control method and device, an air conditioning system, and a storage medium are previously known from CN 1 097 68748 A. The vector control system comprises a control module and a variable frequency drive module, wherein the control module comprises a weak magnetic current, a maximum torque current ratio control unit, and an adjustment module.

[0005] The dissertation by KHAN, Waqar Ahmed; Aalto University: “Torque maximizing and flux weakening N control of synchronous machines”, 2016, pp. 1-55, also deals with this technology. SUMMARY

[0006] This summary is intended to present a selection of concepts in simplified form, which are described in more detail below in the detailed description. This summary is not intended to identify key features or essential features of the subject matter, nor is it intended to serve as an aid in determining the scope of the claimed subject matter.

[0007] It is an object of the present disclosure to provide a motor-driven compressor capable of rapidly heating a refrigerant.

[0008] This object is at least partially achieved with a motor-driven compressor according to claim 1.

[0009] A motor-driven compressor that achieves the above-described object comprises an electric motor, a housing that houses the electric motor and has a suction port into which a refrigerant is sucked, a compression section configured to be driven by the electric motor and configured to suck in and compress the refrigerant in the housing, and an inverter device configured to drive the electric motor. The inverter device includes an inverter circuit with switching elements included in upper arms and lower arms of u-, v-, and w-phases, the inverter circuit being configured to convert DC voltage to AC voltage when a switching operation is performed for the switching elements and supply the AC voltage to the electric motor, a current sensor configured to detect a value of the current supplied to the electric motor,a coordinate converter configured to calculate a d-axis current value and a q-axis current value using a detected value of the current sensor, a speed controller configured to generate a d-axis current command value and a q-axis current command value using a difference between a speed command value and a speed estimate for the electric motor, a current controller configured to calculate a d-axis voltage command value using a difference between the d-axis current command value and the d-axis current value and to calculate a q-axis voltage command value using a difference between the q-axis current command value and the q-axis current value, a pulse width modulation controller configured to control the switching elements using the d-axis voltage command value and the q-axis voltage command value controls, and a speed estimator configured tothat it calculates the speed estimate using the d-axis current value, the q-axis current value, the d-axis voltage command value, and the q-axis voltage command value. The speed controller generates the d-axis current command value and the q-axis current command value to generate the necessary torque to drive the electric motor. The inverter device includes a heat-generating current command value section configured to increase a temperature of the electric motor by changing the d-axis current command value and the q-axis current command value. The heat-generating current command section is configured to change the d-axis current command and the q-axis current command such that the d-axis current command and the q-axis current command are shifted in a direction in which the d-axis current value increases along a constant torque curve in a dq coordinate system,and a voltage limit ellipse and the constant torque curve intersect each other at a pair of intersection points on an enhanced field side and a reduced field side, wherein the heat-generating current command section is configured to generate the d-axis current command value and the q-axis current command value at the intersection point of the voltage limit ellipse and the constant torque curve on the enhanced side in a dq coordinate system, wherein the voltage limit ellipse depends on an input voltage and a rotational speed, and wherein the heat-generating current command section is configured to define, in the dq coordinate system, an upper current limit circle in a range not greater than a limit current value for a temperature of a component of the inverter circuit, and to change the d-axis current command value and the q-axis current command value,that the d-axis current setpoint and the q-axis current setpoint are shifted to an intersection point of the upper current limit circle and the constant torque curve, and a current limit circle and the constant torque curve intersect at a pair of intersection points on a strengthened field side and a weakened field side, the intersection point on the strengthened field side is in a range where the d-axis current value and the q-axis current value are positive, and the intersection point on the strengthened field side is set as the heat generation control operating point.

[0010] Further features and aspects will become apparent from the following detailed description, drawings and claims. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a partial sectional view schematically showing an in-vehicle engine-driven compressor according to an embodiment. Fig. 2 is a block diagram showing the configuration of the inverter device. Fig. 3 is a flowchart illustrating the operation of the present embodiment. Fig. Figure 4A is a diagram illustrating the control current vector. Fig. Figure 4B is a diagram of the current waveform. Fig. Figure 5 is a control current vector diagram illustrating shifts in the heat-generating current rise. Fig. Figure 6A is a diagram illustrating the control current vector. Fig. Figure 6B is a diagram of the current waveform. Fig. Figure 7 is a diagram showing a bra curve. Fig. Figure 8 is a diagram illustrating the control current vector. Fig. Figure 9 is a control current vector diagram illustrating shifts in the heat-generating current rise. Fig. 10 is a flowchart illustrating the operation of the present embodiment. Fig. Figure 11 is a diagram illustrating the control current vector. Fig. Figure 12 is a graph showing a loss distribution on the constant torque curve. Fig. 13 is a flowchart illustrating the operation of another embodiment. Fig. Figure 14 is a diagram showing a map for determining the limit current value. Fig. Figure 15 is a graph showing a loss distribution on the constant torque curve. Fig. Figure 16 is a diagram illustrating the control current vector.

[0011] In the drawings and the detailed description, the same reference numbers refer to the same elements. The drawings may not be to scale, and the relative size, proportions, and representation of the elements in the drawings may be exaggerated for clarity, illustration, and ease of reading. DETAILED DESCRIPTION

[0012] This description provides a comprehensive understanding of the described methods, devices, and / or systems. Modifications and equivalents of the described methods, devices, and / or systems will be apparent to one skilled in the art. The sequence of operations is exemplary and may be changed by one skilled in the art, except for operations that necessarily occur in a particular order. Descriptions of functions and structures well known to those skilled in the art have been omitted.

[0013] Exemplary embodiments may take various forms and are not limited to the described examples. However, the described examples are thorough and complete, and will fully convey the scope of the disclosure to one skilled in the art.

[0014] An in-vehicle engine-driven compressor 20 according to an embodiment of the present disclosure will now be described.

[0015] The on-vehicle motor-driven compressor 20 of the present embodiment is used in a vehicle air conditioner 10. A heat pump mode is used in the on-vehicle motor-driven compressor 20. The heat pump mode includes a refrigeration cycle in which a refrigerant circulates. This cycle uses an evaporator, the on-vehicle motor-driven compressor 20, a condenser, and an expansion valve. The evaporator causes the refrigerant to be heated by outside air and evaporated. The evaporated refrigerant is compressed by the on-vehicle motor-driven compressor 20. Subsequently, the condenser liquefies the refrigerant and heats the air. In the expansion valve, the pressure of the refrigerant then decreases, and the temperature of the refrigerant drops. In the refrigeration cycle, the evaporator absorbs heat from the outside air, thereby increasing the temperature of the refrigerant.This allows the refrigerant to heat the interior by exchanging heat with the indoor air via the condenser.

[0016] As in Fig. As shown in Figure 1, the vehicle air conditioning system 10 includes the in-vehicle motor-driven compressor 20 and an external refrigerant circuit 100 that supplies refrigerant to the in-vehicle motor-driven compressor 20. The external refrigerant circuit 100 includes devices such as the evaporator, the condenser, and the expansion valve. The in-vehicle motor-driven compressor 20 compresses the refrigerant, and the external refrigerant circuit 100 performs heat exchange of the refrigerant and expands the refrigerant. This allows the passenger compartment to be cooled and heated.

[0017] The vehicle air conditioning system 10 includes an air conditioning ECU 101 that controls the entire vehicle air conditioning system 10. The air conditioning ECU 101 is capable of receiving parameters such as the passenger compartment temperature and a target temperature. Based on these parameters, the air conditioning ECU 101 issues various commands, such as an ON / OFF command, to the in-vehicle motor-driven compressor 20.

[0018] The in-vehicle engine-driven compressor 20 includes a housing 21, a compression section 22, and an electric motor 23. The housing 21 includes a suction port 21a into which a refrigerant is sucked from the external refrigerant circuit 100. The compression section 22 and the electric motor 23 are housed in the housing 21.

[0019] The entire housing 21 is essentially cylindrical. The housing 21 contains an outlet opening 21b from which a refrigerant is discharged.

[0020] The compression section 22 draws in and compresses the refrigerant in the housing 21, and discharges the compressed refrigerant from the outlet port 21b. The compression section 22 can be of any type, such as a scroll type, a piston type, and an impeller type. The specific structure of the compression section 22 can be changed depending on the type.

[0021] The electric motor 23 is a three-phase motor and is configured to drive the compression section 22. The electric motor 23 includes a columnar rotary shaft 26 rotatably supported by the housing 21, a cylindrical rotor 24 fixed to the rotary shaft 26, and a stator 25 fixed to the housing 21. The rotor 24 includes a cylindrical rotor core 24b in which magnets 24a are embedded. The magnets 24a are permanent magnets. The axis of the rotary shaft 26 coincides with the axis of the cylindrical housing 21. The stator 25 includes a cylindrical stator core 25a and coils 25b wound around the teeth of the stator core 25a. The rotor 24 and the stator 25 face each other in the radial direction of the rotary shaft 26.

[0022] The in-vehicle motor-driven compressor 20 includes an inverter unit 30. The inverter unit 30 includes an inverter device 31 configured to drive the electric motor 23, and a housing 32 that houses the inverter device 31. The coils 25b of the electric motor 23 are electrically connected to the inverter device 31. The housing 32 is fixed to the housing 21 with bolts 33 serving as fastening means. That is, the in-vehicle motor-driven compressor 20 of the present embodiment is integrated with the inverter device 31.

[0023] The inverter device 31 includes a circuit board 34 and a power module 35 electrically connected to the circuit board 34. Various types of electronic components are mounted on the circuit board 34. The outer surface of the housing 32 is provided with a connector 36. The circuit board 34 and the connector 36 are electrically connected to each other. The inverter device 31 is supplied with power via the connector 36. Furthermore, the air conditioning ECU 101 and the inverter device 31 are electrically connected to each other.

[0024] In the in-vehicle motor-driven compressor 20, the housing 21 thus accommodates the compression section 22 and the electric motor 23 that drives the compression section 22. The in-vehicle motor-driven compressor 20 incorporates an inverter device 31 that supplies power to the motor 23. When the electric motor 23 drives the compression section 22, refrigerant is sucked into the housing 21 from the suction port 21a. The refrigerant then flows in the axial direction of the rotating shaft 26 and is then sucked into the compression section 22 by the electric motor 23. After being compressed by the compression section 22, the refrigerant is discharged from the outlet port 21b. As the refrigerant flows through the housing 21, heat can be exchanged between the electric motor 23 and the refrigerant.

[0025] As in Fig. 2, the inverter device 31 includes an inverter circuit 40 and an inverter control device 50. The inverter control device 50 includes a drive circuit 55 and a controller 60.

[0026] The inverter circuit 40 includes six switching elements Q1 to Q6 and six diodes D1 to D6. Insulated gate bipolar transistors (IGBTs) are used as the switching elements Q1 to Q6. The switching element Q1, contained in a U-shaped upper arm, and the switching element Q2, contained in a U-shaped lower arm, are connected in series between a positive electrode busbar Lp and a negative electrode busbar Ln. The switching element Q3, contained in a V-phase upper arm, and the switching element Q4, contained in a V-phase lower arm, are connected in series between the positive electrode busbar Lp and the negative electrode busbar Ln. The switching element Q5, contained in a W-phase upper arm, and the switching element Q6, contained in a W-phase lower arm, are connected in series between the positive electrode busbar Lp and the negative electrode busbar Ln.Diodes D1 to D6 are each connected in antiparallel to switching elements Q1 to Q6. Battery B, which serves as the DC power supply, is connected to the positive electrode busbar Lp and the negative electrode busbar Ln.

[0027] A portion where the switching element Q1 and the switching element Q2 are connected is connected to the u-phase terminal of the electric motor 23. A portion where the switching element Q3 and the switching element Q4 are connected is connected to the v-phase terminal of the electric motor 23. A portion where the switching element Q5 and the switching element Q6 are connected is connected to the w-phase terminal of the electric motor 23. The inverter circuit 40 including the switching elements Q1 to Q6 included in the upper arms and lower arms is configured to convert DC voltage (the voltage across the battery B) into AC voltage when the switching operation of the switching elements Q1 to Q6 is performed, and supply the AC voltage to the electric motor 23.

[0028] Each of the switching elements Q1 to Q6 includes a gate terminal to which the control circuit 55 is connected. The control circuit 55 performs a switching operation for the switching elements Q1 to Q6 of the inverter circuit 40 using control signals.

[0029] A current sensor 41 is provided between the section connecting the two u-phase switching elements Q1, Q2 and the u-phase terminal of the electric motor 23. A current sensor 42 is provided between the section connecting the two v-phase switching elements Q3, Q4 and the v-phase terminal of the electric motor 23. Thus, the inverter device 31 includes the current sensors 41, 42, which detect the value of the current supplied to the electric motor 23.

[0030] In the present embodiment, no rotational position sensor is used. That is, the use of a position sensor is omitted in the present embodiment. An estimated rotation angle θ (rotational position) of the electric motor 23 is calculated by a rotation angle estimator 69 (described later) from a d-axis current value Id and a q-axis current value Iq, and from a d-axis voltage command value Vd* and a q-axis voltage command value Vq*. The d-axis current and the q-axis current flow through the electric motor 23. The d-axis includes the current direction in which the magnetic flux is generated in the same direction as the magnetic flux generated by the permanent magnets in the electric motor 23. The q-axis includes a direction in which the q-axis is shifted by π / 2 from the d-axis.

[0031] The controller 60 includes a speed controller 61, subtractors 62, 63, 68, a current controller 64, a coordinate converter 65 (three-phase to two-phase converter), a coordinate converter 66 (two-phase to three-phase converter), a pulse width modulation (PWM) generator 67, the rotation angle estimator 69 serving as a rotation speed estimator that calculates a rotation speed estimate, and a heat-generating current command section 70. The coordinate converter 66 (two-phase to three-phase converter) and the PWM generator 67 constitute a PWM controller 71 that controls the switching elements Q1 to Q6 with the d-axis voltage command value Vd* and the q-axis voltage command value Vq*.

[0032] The coordinate converter 65 detects a u-phase current Iu and a v-phase current Iv flowing through the electric motor 23, and a w-phase current Iw flowing through the electric motor 23, from the current detection values ​​obtained by the current sensors 41, 42. Furthermore, the coordinate converter 65 uses the u-phase current Iu, the v-phase current Iv, the w-phase current Iw, and an estimated rotation angle θ (rotational position) of the electric motor 23 calculated by the rotation angle estimator 69 to convert the u-phase current Iu, the v-phase current Iv, and the w-phase current Iw into a d-axis current value Id (excitation component current) and a q-axis current value Iq (torque component current). That is, the coordinate converter 65 calculates the d-axis current value Id and the q-axis current value Iq from the detected values ​​of the current sensors 41, 42.The d-axis current value Id (excitation component current) is a current vector component that generates a field in the current flowing through the electric motor 23. The q-axis current value Iq (torque component current) is a current vector component that generates a torque in the current flowing through the electric motor 23.

[0033] The subtractor 68 calculates a difference Δω between a speed command value ω* for the electric motor 23, received from the air conditioning ECU 101 (upper ECU), and an estimated speed ω serving as a speed estimation value. The estimated speed ω is obtained using an estimated speed calculated by the rotation angle estimator 69.

[0034] The speed controller 61 calculates the d-axis current command value Id* and the q-axis current command value Iq* such that the difference Δω between the speed command value ω* received from an external device and the estimated speed ω becomes 0. That is, the speed controller 61 uses the difference Δω between the speed command value ω* for the electric motor 23 and the estimated speed ω, which serves as a speed estimate, to generate the d-axis current command value Id* and the q-axis current command value Iq*.

[0035] The heat-generating current setpoint section 70 processes the d-axis current setpoint Id* and outputs it as the d-axis current setpoint Id**. Furthermore, the heat-generating current setpoint section 70 processes the q-axis current setpoint Iq* and outputs it as the q-axis current setpoint Iq**. The details will be described later.

[0036] The subtractor 62 calculates a difference ΔId between the d-axis current command value Id** and the d-axis current value Id. The subtractor 63 calculates a difference ΔIq between the q-axis current command value Iq** and the q-axis current value Iq. The current controller 64 calculates the d-axis voltage command value Vd* and the q-axis voltage command value Vq* from the difference ΔId and the difference ΔIq. That is, the current controller 64 uses the difference ΔId between the d-axis current command value Id** and the d-axis current value Id to calculate the d-axis voltage command value Vd* and the difference ΔIq between the q-axis current command value Iq** and the q-axis current value Iq to calculate the q-axis voltage command value Vq*.The coordinate converter 66 uses the rotation angle θ (rotational position) of the electric motor 23 calculated by the rotation angle estimator 69 to convert the d-axis voltage command value Vd* and the q-axis voltage command value Vq* into voltage command values ​​Vu, Vv, Vw, which are voltages applied to the electric motor 23.

[0037] The PWM generator 67 normalizes the voltage setpoints Vu, Vv, and Vw with the value of the inverter's supply voltage. Based on the result of the triangular wave comparison, the PWM generator 67 outputs PWM control signals to turn the switching elements Q1 to Q6 of the inverter circuit 40 on or off.

[0038] That is, the controller 60 uses the currents iu, iv, iw of the u, w, and v phases flowing through the electric motor 23 to control the switching elements Q1 to Q6 arranged on the current path of the electric motor 23 so that the speed of the electric motor 23 assumes a setpoint. The signals from the PWM generator 67 are sent to the control circuit 55.

[0039] The rotation angle estimator 69 uses the d-axis current value Id, the q-axis current value Iq, the d-axis voltage command value Vd*, and the q-axis voltage command value Vq* to calculate (ie, estimate) the estimated rotation angle θ and the estimated rotational speed ω (estimated angular velocity) of the electric motor 23.

[0040] With reference to Fig. 4A, the speed controller 61 described above generates the d-axis current command value Id* and the q-axis current command value Iq* so that a necessary torque for driving the electric motor 23 occurs. That is, the speed controller 61 generates the d-axis current command value Id* and the q-axis current command value Iq* at a control operating point corresponding to the load torque on a maximum torque curve (minimal copper loss).

[0041] When the outside air temperature is low, the heat pump is difficult to absorb heat from the outside air. Therefore, the heat-generating current setpoint section 70, located downstream of the speed controller 61, performs the Fig. 3 to accelerate heating of the passenger compartment. Specifically, the current setpoint section 70 releases heat with the electric motor 23 and heats a refrigerant to accelerate heating of the passenger compartment. Even when a hot gas heater is used, the current setpoint section 70 performs the same processes as when the heat pump is used, causing the electric motor 23 to release heat and heat a refrigerant to accelerate heating of the passenger compartment.

[0042] The heat-generating current command value section 70 in the inverter device 31 increases the temperature of the electric motor 23 by changing the d-axis current command value Id* and the q-axis current command value Iq*. The heat-generating current command value section 70 changes the d-axis current command value Id* and the q-axis current command value Iq* so that they are shifted in a direction in which the d-axis current value Id along the constant torque curve in the Fig. 5 shown dq coordinate system increases.

[0043] In Fig. 3, the heat-generating current setpoint section 70 determines in step S100 whether a heat-generating control command has been issued from the air conditioning ECU 101 (upper ECU), that is, whether a refrigerant heating command serving as a refrigerant temperature increase command has been issued from an external device. If the heat-generating control command (the refrigerant heating command) has been issued, the current setpoint section 70 changes the d-axis current setpoint and the q-axis current setpoint as described below. As shown in Fig. 5, the current command section 70 generates the d-axis current command and the q-axis current command from the control operating point at the intersection of the constant torque curve and an upper limit circle on a boosted field side.

[0044] First, the heat generating current set value section 70 goes from step S100 to step S101 in Fig. 3 to calculate a resultant current setpoint. Then, if the resultant current setpoint is separated from the upper current limit, the heat-generating current setpoint section 70 determines whether the resultant current setpoint is greater than an upper current limit in step S102. If the resultant current setpoint is not greater than the upper limit, the current setpoint section 70 adds an operation amount to the d-axis current value in step S104. If the resultant current setpoint is greater than the upper limit, the heat-generating current setpoint section 70 subtracts the operation amount from the d-axis current value in step S103.

[0045] Referring to Fig. 5, the current command section 70 increases the heat-generating current and shifts the control operating point to a heat-generating control operating point, so that the electrical energy resulting from copper loss and core loss is converted into thermal energy. Thus, the heat-generating current command section 70 generates the d-axis current command and the q-axis current command from the control operating point at the intersection of the constant torque curve and the upper limit circle on the boosted field side.

[0046] More specifically, the heat generating current set value section 70 calculates in step S101 of Fig. 3 a resulting current setpoint Ic* from the d-axis current setpoint Id* and the q-axis current setpoint Iq*.

[0047] In step S103 of Fig. 3, the heat-generating current setpoint section 70, based on the d-axis current setpoint Id*, updates the d-axis current setpoint Id* by an amount corresponding to the d-axis current setpoint Id1* in Fig. 5 corresponds.

[0048] Where Id * ba is the current setpoint of the d-axis before the update and Id * fr is the current setpoint of the d-axis after the update.

[0049] In step S104 of Fig. 3, the heat-generating current setpoint section 70 updates the d-axis current setpoint Id* based on the d-axis current setpoint Id* by an amount corresponding to the d-axis current setpoint Id1* in Fig. 5 corresponds.

[0050] Where Id * ba is the d-axis current setpoint before the update, and Id * fr is the d-axis current setpoint after the update.

[0051] When the heat generating current set value section 70 completes step S100, step S101, step S102 and step S104 of Fig. 3 is repeated in this order, the operating point shifts from the control operating point to the heat-generating control operating point on the maximum torque curve in Fig. 5. After the operating point has changed from the control operating point to the heat-generating control operating point on the maximum torque curve in Fig. 5, the heat-generating current setpoint section 70 repeats step S100, step S101, step S102 and step S103 of Fig. 3 in this order and repeats step S100, step S101, step S102 and step S104 of Fig. 3 in that order.

[0052] At this time, speed control is performed with a q-axis current command calculated by a conventional speed controller, and the current is supplied in the d-axis so that the difference between the upper limit current value and the q-axis current command becomes zero.

[0053] The electric motor 23, which is used for an engine-driven compressor, is cooled by a refrigerant. When control is performed to increase the loss in the electric motor 23, the refrigerant is heated more quickly. As a result, the passenger compartment is heated in a shorter time. That is, the heating of the passenger compartment is accelerated when the vehicle air conditioner 10 is started at a low temperature.

[0054] Maximum torque control is used as the control mode for the vehicle's internal motor-driven compressor 20. As shown in the Fig. 4A and Fig. As shown in Figure 4B, with maximum torque control, the control is performed in a phase with a minimum motor current for the torque required for motor operation. This minimizes the copper loss generated. This prevents waste heat from being recovered to heat a refrigerant.

[0055] Motor losses include copper losses and core losses. Copper losses are caused by the coil resistance and the motor current. Core loss is determined by hysteresis loss and eddy current loss. Hysteresis losses occur due to changes in the magnetic resistance and magnetic flux in the core. Eddy current losses occur due to the electrical resistance of the core and the eddy currents generated in the core.

[0056] In the present embodiment, as shown in Fig. 2, the heat-generating current setpoint section 70 (efficiency deterioration current setpoint section) is provided downstream of the speed controller 61.

[0057] As in Fig. As shown in Figure 6A, the intersection point of the constant torque curve and the upper current limit (field amplification direction) is used as the control operating point. This increases the motor current, as shown by the solid line in Fig. 6B, when the motor current at minimal copper loss, as shown by the dashed line in Fig. 6B. This worsens the copper loss. That is, as shown in the Fig. 6A and Fig. As shown in Figure 6B, increasing the motor current worsens the copper loss.

[0058] When the intersection point of the constant torque curve and the upper current limit circle (current upper limit circle) on the boosted field side is used as the control operating point, the core loss (hysteresis loss) deteriorates with the increase of the area of ​​the BH curve due to an increase in the magnetic flux density, as shown by the solid line in Fig. shown, compared to the dashed line in Fig. Maximum torque control shown. This allows waste heat to be recovered.

[0059] That is, as in Fig. As shown, when current is supplied to the enhanced field side to increase the magnetic flux density of the core, the BH curve area increases. This worsens the core loss (hysteresis loss).

[0060] The embodiment described above offers the following advantage. (1) The in-vehicle motor-driven compressor 20, which serves as a motor-driven compressor, includes the electric motor 23, the housing 21, the compression section 22, and the inverter device 31. The housing 21 houses the electric motor 23 and includes the suction port 21a into which a refrigerant is sucked. The compression section 22 is configured to be driven by the electric motor 23 and to suck and compress the refrigerant in the housing 21. The inverter device 31 is configured to drive the electric motor 23. The inverter device 31 includes the inverter circuit 40, the current sensors 41, 42, the coordinate converter 65, the speed controller 61, the current controller 64, the PWM controller 71, and the rotation angle estimator 69. The inverter circuit 40 includes the switching elements Q1 to Q6 included in the upper arms and the lower arms of the u, v, w phases.The inverter circuit 40 is configured to convert DC voltage into AC voltage when a switching operation is performed for the switching elements Q1 to Q6 and supply the AC voltage to the electric motor 23. The current sensors 41, 42 are configured to detect the value of the current supplied to the electric motor 23. The coordinate converter 65 is configured to calculate the d-axis current value Id and the q-axis current value Iq using the detected values ​​of the current sensors 41, 42. The speed controller 61 is configured to generate the d-axis current command value Id* and the q-axis current command value Iq* using the difference Δω between the speed command value ω* for the electric motor 23 and the estimated speed ω, which serves as the speed estimate value.The current controller 64 is configured to calculate the d-axis voltage command value Vd* using the difference ΔId between the d-axis current command value Id* and the d-axis current value Id, and to calculate the q-axis voltage command value Vq* using the difference ΔIq between the q-axis current command value Iq* and the q-axis current value Iq. The PWM controller 71 is configured to control the switching elements Q1 to Q6 using the d-axis voltage command value Vd* and the q-axis voltage command value Vq*. The rotation angle estimator 69 serving as a speed estimator is configured to calculate the estimated speed ω serving as a speed estimation value using the d-axis current value Id, the q-axis current value Iq, the d-axis voltage command value Vd*, and the q-axis voltage command value Vq*.The speed controller 61 is configured to generate the d-axis current command value Id* and the q-axis current command value Iq* to generate the required torque to drive the electric motor 23. The inverter device 31 includes the heat-generating current command value section 70, which is configured to increase the temperature of the electric motor 23 by changing the d-axis current command value Id* and the q-axis current command value Iq*. The heat-generating current command value section 70 is configured to change the d-axis current command value Id* and the q-axis current command value Iq* to shift them in the direction in which the d-axis current value Id increases along the constant torque curve in the dq coordinate system.

[0061] Therefore, when the current command section 70 receives the refrigerant temperature increase command from an external device, the switching elements Q1 to Q6 are controlled by the d-axis current command value Id** and the q-axis current command value Iq** to shift in the direction in which the d-axis current value Id increases along the constant torque curve in the dq coordinate system. Thus, control is performed to increase the loss of the electric motor 23 to heat a refrigerant with the heat generated in the electric motor 23. Specifically, the loss in the core of the electric motor 23 can be increased by increasing the d-axis current value Id. At this time, the torque generated in the electric motor 23 by the d-axis current and the q-axis current is constant, and thus the rotational speed of the electric motor 23 is stable. This prevents the generation of unnecessary noise. Thus, the refrigerant can be heated quickly.Specifically, while in a case where a car air conditioner is operated as a heat pump or hot gas heater, heating control is required to heat all of the refrigerant, in the present embodiment, by rapidly heating the refrigerant, the passenger compartment can be heated in a shorter period of time.

[0062] The present disclosure is not limited to the above-described embodiment, but may be modified, for example, as follows.

[0063] As in Fig. As shown in Figure 8, the operating point must be within the current upper limit circle and within a voltage limit ellipse. The current upper limit circle depends on the rated current of the inverter (motor), while the voltage limit ellipse depends on the input voltage and the speed. To operate according to a command speed, the selected current vector must be within these two limit circles. Therefore, if a decrease in the input voltage and / or an increase in the command speed reduces the voltage limit ellipse in a case where the operating point is outside the voltage limit ellipse, the speed will decrease due to the lack of output voltage. Thus, the speed cannot be maintained at the heat-generating control operating point.

[0064] To get this problem under control, as in Fig. As shown, the heat-generating control operating point switches from the boosted field side to a weakened field side when the difference between the target speed and the estimated speed (estimated speed) is greater than a threshold due to the lack of input voltage. Even on the weakened field side, the current at the heat-generating control operating point remains unchanged, and thus also the copper loss. This enables the utilization of the waste heat.

[0065] More precisely, the current setpoint section 70 carries out the Fig. 10 shown processes. In Fig. 10, step S200, step S201, step S202 and step S203 become Fig. 3 added.

[0066] In step S200 of Fig. 10, if the speed difference Δω is greater than or equal to a predetermined value, it is determined that the speed difference has increased due to the lack of input voltage. In order to shift the heat-generating control operating point (regulation operating point) to the weaker field side, the process proceeds to step S201. In step S201, it is determined whether the resulting current command value is greater than the upper current limit. If the resulting current command value is not greater than the upper current limit, the operation amount is subtracted from the d-axis current value in step S203. If the resulting current command value is greater than the upper current limit, the operation amount is added to the d-axis current value in step S202.

[0067] Thus, the heat-generating current command section 70 changes the d-axis current command Id* and the q-axis current command Iq* to shift in a direction in which the d-axis current value Id decreases along the constant torque curve when the difference Δω between the speed command ω* and the estimated speed ω (speed estimate) is greater than the threshold. Accordingly, even when the voltage limit ellipse shrinks due to a decrease in the input voltage or an increase in the command speed, the difference between the speed command and the estimated speed (speed estimate) becomes greater than the threshold when the shift to the control operating point on the weak field side occurs.In addition, when a limit in the magnitude of the current vector occurs in the dq coordinate system, the difference between the speed command value and the estimated speed (speed estimate value) can be reduced by changing the d-axis current command value and the q-axis current command value to shift them in the direction in which the d-axis current value decreases along the constant torque curve, and the refrigerant can be heated using the heat generated in the electric motor by a control that increases the loss of the electric motor.

[0068] If at this point, as in Fig. 11, the heat-generating control operating point (regulation operating point) is shifted to the weakened field side as described above, the loss achieved in the core loss is reduced. To address this problem, as shown in Fig. shown, in the case of a motor where the core loss accounts for a larger proportion of the total loss than the copper loss, the condition that the total loss is the maximum (the most amplified side in the selection range of the current vector in Fig. ), is defined as the heat-generating control operating point. This means, as in Fig. As shown in Figure 11, the heat-generating control operating point is defined as the intersection point of the voltage limit ellipse and the constant torque curve.

[0069] Furthermore, the embodiment described above can be modified as follows.

[0070] The heat-generating current setpoint section 70 carries out the Fig. 13 to prevent overheating of the switching elements Q1 to Q6, which are components of the inverter circuit 40. In Fig. 13, step S300 is to Fig. 3 added.

[0071] In step S300 of Fig. 13 is made with reference to a Fig. 14, when the temperatures of the switching elements Q1 to Q6 (the components of the inverter circuit 40) become higher, the limit current value is set smaller and limited.

[0072] As in Fig. As shown in Figure 15, the size of the current limit circuit is varied depending on the temperatures of the inverter components (i.e., the temperatures of the switching elements Q1 to Q6). Specifically, as the temperatures of the switching elements Q1 to Q6 (the components of the inverter circuit 40) increase, the size of the current limit circuit is reduced to reduce the current flowing through the electric motor.

[0073] Since, as in Fig. 15, the temperatures of the switching elements Q1 to Q6 (the components of the inverter circuit 40) may exceed their thermal resistance temperatures as the motor current increases, the heat-generating control can be continued by limiting the current according to the component temperatures.

[0074] Thus, the current command section 70 is configured to define the current upper limit circle in the dq coordinate system within a range not larger than the current limit for the temperature of the components of the inverter circuit 40 (e.g., the temperatures of the switching elements Q1 to Q6), and to change the d-axis current command Id* and the q-axis current command Iq* to shift them to the intersection point of the current upper limit circle and the constant torque curve. This prevents overheating of the components of the inverter circuit 40. This allows control to continue with the generation of the d-axis current command Id* and the q-axis current command Iq* at the intersection point of the constant torque curve and the current upper limit circle in the heat-generating current command section 70.

[0075] Furthermore, the embodiment described above can be modified as follows.

[0076] In the example described above, the current limit circuit is reduced depending on the temperatures of the switching elements Q1 to Q6, which are the components of the inverter circuit 40. Instead, as shown in Fig. 16, a limitation is carried out when there is no intersection point of the constant torque curve and the required torque due to a reduction of the current limit circuit (a normal control operating point in Fig. 16), so that the speed decreases and the load torque decreases. Alternatively, a limitation is carried out to keep the speed so that the current limit circuit does not have an operating point that is less than or equal to the normal control operating point in Fig. is.

[0077] Instead of a heat pump or hot gas heater, an air conditioner can also be used to quickly heat a refrigerant. For example, it is effective to quickly evaporate a liquefied refrigerant in a container in the refrigeration cycle by heating the refrigerant in the container.

[0078] Another option is to use a system that switches between heating and cooling by allowing a refrigerant to flow in the opposite direction within the refrigeration circuit. This also allows the refrigerant to be heated quickly.

[0079] Various changes in form and details may be made to the above examples without departing from the spirit and scope of the claims and their equivalents. The examples are for the purpose of description only and not of limitation. Descriptions of features in each example are to be considered applicable to similar features or aspects in other examples. Suitable results may be obtained by performing operations in a different order and / or by combining components in a described system, architecture, device, or circuit differently and / or by substituting or supplementing other components or their equivalents for them. The scope of the disclosure is defined by the claims and their equivalents, not the detailed description. All variations within the scope of the claims and their equivalents are intended to be included within the disclosure.

Claims

[1] A motor-driven compressor (20) comprising: an electric motor (23); a housing (21) which accommodates the electric motor (23) and contains a suction opening (21a) into which a refrigerant is sucked; a compression section (22) configured to be driven by the electric motor (23) and configured to suck in and compress the refrigerant in the housing (21); and an inverter device (31) configured to drive the electric motor (23), wherein the inverter device (31) comprises an inverter circuit (40) having switching elements (Q1-Q6) included in upper arms and lower arms of the u, v, w phases, wherein the inverter circuit (40) is configured to convert DC voltage into AC voltage when a switching operation is performed for the switching elements (Q1-Q6) and supplies the AC voltage to the electric motor (23), a current sensor (41, 42) configured to detect a value of the current supplied to the electric motor (23), a coordinate converter (65) configured to calculate a d-axis current value and a q-axis current value using a detected value of the current sensor (41, 42), a speed controller (61) configured to generate a d-axis current command and a q-axis current command using a difference between a speed command and a speed estimate for the electric motor (23), a current controller (64) configured to calculate a d-axis voltage command value using a difference between the d-axis current command value and the d-axis current value and to calculate a q-axis voltage command value using a difference between the q-axis current command value and the q-axis current value, a pulse width modulation controller (71) configured to control the switching elements (Q1-Q6) using the d-axis voltage command value and the q-axis voltage command value, and a speed estimator (69) configured to calculate the speed estimate using the d-axis current value, the q-axis current value, the d-axis voltage command value, and the q-axis voltage command value, the speed controller (61) generates the d-axis current setpoint and the q-axis current setpoint in such a way that the required torque for driving the electric motor (23) is generated, the inverter device (31) has a heat-generating current command section (70) configured to increase a temperature of the electric motor (23) by changing the d-axis current command value and the q-axis current command value, and the heat-generating current command value section (70) is configured to change the d-axis current command value and the q-axis current command value such that the d-axis current command value and the q-axis current command value are shifted in a direction in which the d-axis current value increases along a constant torque curve in a dq coordinate system, and a stress limit ellipse and the constant torque curve intersect at a pair of intersection points on an enhanced field side and a weakened field side, the heat-generating current command section (70) is configured to generate the d-axis current command and the q-axis current command at the intersection point of the voltage limit ellipse and the constant torque curve on the boosted side in a dq coordinate system, wherein the voltage limit ellipse depends on an input voltage and a rotational speed, wherein the heat-generating current command section (70) is configured to define, in the dq coordinate system, an upper current limit circle in a range not greater than a limit current value for a temperature of a component of the inverter circuit (40), and changes the d-axis current command value and the q-axis current command value such that the d-axis current command value and the q-axis current command value are shifted to an intersection point of the upper current limit circle and the constant torque curve, and a current limit circuit and the constant torque curve intersect at a pair of intersection points on a strengthened field side and a weakened field side, the intersection point on the strengthened field side is in a range where the d-axis current value and the q-axis current value are positive, and the intersection point on the strengthened field side is set as the heat generation control operating point. [2] The motor-driven compressor (20) according to claim 1, wherein the heat-generating current command section (70) is configured to change the d-axis current command value and the q-axis current command value such that the d-axis current command value and the q-axis current command value are shifted in a direction in which the d-axis current value decreases along the constant torque curve when a difference between the speed command value and the speed estimate value is greater than a threshold value.

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