In-vehicle motor-driven compressor and method for controlling an in-vehicle motor-driven compressor

Abstract

In-vehicle motor-driven compressor with: a compressor unit configured to compress fluid; an electric motor configured to drive the compressor unit; an inverter configured to drive the electric motor, wherein The inverter has a switching element configured to switch and convert a DC voltage from a battery into an AC voltage to drive the electric motor, and has a diode connected in parallel to the switching element. The vehicle's internal motor-driven compressor also has the following features: a temperature rise estimator configured to estimate a temperature rise of the diode based on a calculated reverse current, an input voltage of the diode, and a thermal resistance of the diode, where the reverse current is a current flowing from the electric motor through the diode to the battery when the electric motor is stopped and a counter-electromotive force of the electric motor exceeds an input voltage of the battery, and A speed control configured to set a speed limit of the electric motor based on the estimated temperature rise of the diode, such that the junction temperature of the diode does not exceed a maximum junction temperature of the diode when the electric motor is stopped and the reverse current flows through the diode, and the speed of the electric motor is limited to less than or equal to the speed limit.

Description

background

[0001] The following description relates to an in-vehicle / vehicle-side engine-driven compressor and a method for controlling the in-vehicle / vehicle-side engine-driven compressor.

[0002] An in-vehicle, engine-driven compressor has a compressor unit that compresses a fluid and an electric motor that drives the compressor unit.

[0003] JP 2017-180 211 A, for example, describes an in-vehicle, motor-driven compressor with an inverter that drives the electric motor. The inverter has switching elements that perform switching to drive the electric motor and diodes connected in parallel to the switching elements. The switching elements perform the switching such that the inverter converts the DC voltage from a vehicle battery into an AC voltage. The resulting AC voltage is applied to the electric motor as an operating voltage to drive and control the electric motor.

[0004] The vehicle's internal motor-driven compressor is powered by the vehicle battery and is therefore affected by the battery's input voltage. The battery voltage changes depending on the vehicle's operating conditions. This can lower the input voltage from the battery to the internal motor-driven compressor. If the battery input voltage to the internal motor-driven compressor is low, and the electric motor is stopped while operating at high speed, the opposing voltage of the electric motor's motive force (opposing motive force) exceeds the battery's input voltage. This causes a reverse current to flow from the electric motor, through an inverter, to the vehicle battery. Specifically, when the electric motor stops, the switching elements do not complete the switching operation.This causes a reverse current to flow from the electric motor, through the diodes, to the battery. If the reverse electromotive voltage of the electric motor is high, an excessive reverse current flows through the diodes. The diodes fail when their junction temperature exceeds a maximum junction temperature.

[0005] In this context, for example, the maximum speed of the electric motor can be limited according to the battery's input voltage. However, even in situations where more energy can be supplied from the vehicle battery to the vehicle's internal motor-driven compressor, the maximum speed is still limited by the battery's input voltage. This reduces the operating range of the vehicle's internal motor-driven compressor.

[0006] Furthermore, JP 2016 - 31 021 A reveals that the rotational speed of an electric motor is maintained at or below a threshold rotational speed when the electric motor is not stopped.

[0007] KR 10 2012 0 064 455 A discloses that a motor speed can be limited to avoid damage to high-voltage components.

[0008] US 7 488 921 B2 refers to the fact that the rotational speed of an electric drive is reduced when a junction temperature reaches a limit.

[0009] CN 1 01 064 426 A discloses that overheating of inverter power devices can be prevented by reducing the electric motor output torque when the electric motor is stopped. Summary

[0010] This summary is intended to introduce, in simplified form, a selection of concepts that are described in more detail below. This summary is neither intended to identify principal features or essential characteristics of the claimed subject matter, nor is it intended to serve as an aid in determining the scope of the claimed subject matter.

[0011] The purpose of the following description is to provide a vehicle-internal motor-driven compressor and a method for controlling a vehicle-internal motor-driven compressor that extends the operating / working range of the vehicle-internal motor-driven compressor and avoids diode breakage / defection when the input voltage of a battery is low and an electric motor is stopped while operating at high speed.

[0012] In general terms, an in-vehicle, engine-driven compressor has a compressor unit, an electric motor, and an inverter. The compressor unit is configured to compress a fluid. The electric motor is configured to drive the compressor unit. The inverter is configured to drive the electric motor. The inverter has a switching element and a diode. The switching element is configured to switch and convert a DC voltage from a battery into an AC voltage to drive the electric motor. The diode is connected in parallel to the switching element. The in-vehicle, engine-driven compressor also has a temperature rise estimator and a speed controller. The temperature rise estimator is configured to estimate the temperature rise of the diode based on a calculated / expected reverse current, the diode's turn-on voltage, and the diode's thermal resistance.The reverse current is a current that flows from the electric motor through the diode to the battery when the electric motor is stopped and the motor's reverse voltage exceeds the battery's input voltage. The speed control is configured to set a speed limit for the electric motor based on the estimated temperature rise of the diode. This ensures that the diode's junction temperature does not exceed a maximum junction temperature when the electric motor is stopped and the reverse current flows through the diode, thus limiting the electric motor's speed to less than or equal to the speed limit.

[0013] According to another general aspect, a method for controlling an in-vehicle, engine-driven compressor is provided. The in-vehicle, engine-driven compressor has a compressor unit, an electric motor, and an inverter. The compressor unit is configured to compress fluid. The electric motor is configured to drive the compressor unit. The inverter is configured to drive the electric motor. The inverter has a switching element and a diode. The switching element is configured to switch and convert a DC voltage from a battery into an AC voltage to drive the electric motor. The diode is connected in parallel with the switching element. The method involves estimating the temperature rise of the diode based on a calculated / expected reverse current, a turn-on voltage of the diode, and a thermal resistance of the diode.The reverse current is a current that flows from the electric motor through the diode to the battery when the electric motor is stopped and the reverse electromotive voltage of the electric motor exceeds the input voltage of the battery. The control method further involves setting a speed limit for the electric motor based on the estimated temperature rise of the diode, such that the diode's junction temperature does not exceed a maximum junction temperature when the electric motor is stopped and the reverse current flows through the diode, and limiting the electric motor's speed to less than or equal to this speed limit.

[0014] According to another general aspect, an in-vehicle, engine-driven compressor has a compressor unit, an electric motor, and an inverter. The compressor unit is configured to compress fluid. The electric motor is configured to drive the compressor unit. The inverter is configured to drive the electric motor. The inverter has a switching element and a diode. The switching element is configured to switch and convert a DC voltage from a battery into an AC voltage to drive the electric motor. The diode is connected in parallel to the switching element. The in-vehicle, engine-driven compressor has a circuit configured to estimate the temperature rise of the diode based on a calculated / expected reversing current, the diode's turn-on voltage, and the diode's thermal resistance.The reverse current is a current that flows from the electric motor through the diode to the battery when the electric motor is stopped and the motor's reverse voltage exceeds the battery's input voltage. The circuit is configured to set a speed limit for the electric motor based on the estimated temperature rise of the diode. This ensures that the diode's junction temperature does not exceed a maximum junction temperature when the electric motor is stopped and the reverse current flows through the diode, thus limiting the electric motor's speed to less than or equal to the speed limit.

[0015] Other features and aspects emerge from the following detailed description, the figures, and the requirements. Brief description of the characters Fig. Figure 1 is a cross-sectional view of an in-vehicle, motor-driven compressor according to one embodiment. Fig. Figure 2 is a schematic diagram showing the electrical configuration of the vehicle's internal engine-driven compressor as shown in Fig. 1 shown. Fig. Figure 3 is a characteristic curve that shows changes in the temperature of diodes when a reverse current flows through the diodes. Fig. Figure 4 is a characteristic curve that shows changes in a current flowing through an electric motor. Fig. Figure 5 is a schematic diagram showing the electrical configuration of an in-vehicle engine-driven compressor according to another embodiment.

[0016] In the drawings and the detailed description, the same reference symbols refer to the same elements. The drawings may not be to scale, and the relative size, proportions, and representation of elements in the drawings may be exaggerated for clarity, illustration, and convenience. Detailed description

[0017] The following detailed description is intended to help the reader gain a comprehensive understanding of the methods, devices, and / or systems described herein. However, various changes, modifications, and equivalents of the methods, devices, and / or systems described herein will be apparent for any of the usual skills found in the prior art. The work / operational procedures described herein are merely examples and are not limited to those presented here, but may be modified as is the case for any of the usual skills found in the prior art, with the exception of operations that necessarily follow a specific sequence. Descriptions of functions and designs known for any of the usual skills found in the prior art may also be omitted for the sake of clarity and conciseness.

[0018] The features described herein can be implemented in various forms and are not to be understood as limited to the examples described herein. Rather, the examples described herein have been provided in such a way as to make this disclosure thorough and complete and to convey the full scope of the disclosure to one of the usual skills in the prior art.

[0019] A vehicle-integrated, motor-driven compressor according to one embodiment is now described with reference to the Fig. 2 to 4 described. The vehicle-integrated motor-driven compressor in the present embodiment, that is, a motor-driven compressor configured to be installed / mounted in a vehicle, is used, for example, with a vehicle air conditioning system.

[0020] As in Fig. As shown in Figure 1, a vehicle-integrated, motor-driven compressor 10 has a housing 11. The housing 11 accommodates a compressor unit 12, which compresses a coolant / refrigerant, which is a fluid, and an electric motor 13, which drives the compressor unit 12. For example, the compressor unit 12 is a screw / spiral compressor unit with a fixed screw / spiral (not shown) mounted in the housing 11 and a movable screw / spiral (not shown) positioned opposite the fixed screw / spiral. The compressor unit 12 need not be a screw / spiral compressor unit and could, for example, be a piston compressor unit or a vane compressor unit.

[0021] The housing 11 has an inlet 11a and an outlet 11b. Furthermore, the housing 11 accommodates a rotating shaft / axis 14. The rotating shaft 14 is rotatably mounted within the housing 11. The electric motor 14 has a rotor 13a and a stator 13b. The rotor 13a is attached to the rotating shaft 14 and rotates integrally with it. The stator 13b has teeth and is attached to an inner circumferential surface of the housing 11 that surrounds the rotor 13a. Coils 15 are wound around the teeth of the stator 13b. Energy is supplied to the coils 15 to rotate the rotor 13a and the rotating shaft 14.

[0022] Inlet 11a is connected to one end of an external coolant circuit 17. Outlet 11b is connected to the other end of the external coolant circuit 17. The coolant is drawn / suctioned from the external coolant circuit 17 through inlet 11a into the housing 11. The compressor unit 12 compresses the coolant drawn into the housing 11. The coolant compressed by the compressor unit 12 is discharged from outlet 11b into the external coolant circuit 17 and returned to the housing 11 via a heat exchanger or an expansion valve of the external coolant circuit 17. The vehicle's internal engine-driven compressor 10 and the external coolant circuit 17 form a vehicle air conditioning system 18.

[0023] The housing 11 has an end wall 11c to which an inverter cover 19 is coupled. An inverter 20, which drives the electric motor 13, is housed in a space defined by the inverter cover 19 and the end wall 11c of the housing 11. The compressor unit 12, the electric motor 13, and the inverter 20 are arranged sequentially in an axial direction along the rotating shaft.

[0024] As in Fig. As shown in Figure 2, the coils 15 of the electric motor 13 form a three-phase construction with a u-phase coil 15u, a v-phase coil 15v and a w-phase coil 15w. In the present embodiment, the u-phase coil 15u, the v-phase coil 15v and the w-phase coil 15w are connected in a Y-connection.

[0025] Inverter 20 has switching elements Qu1, Qu2, Qv1, Qv2, Qw1, and Qw2. These switching elements perform the switching to drive the electric motor 13. For example, the switching elements Qu1, Qu2, Qv1, Qv2, Qw1, and Qw2 are insulated-gate bipolar transistors (IGBTs are used as power switching elements). Each switching element Qu1, Qu2, Qv1, Qv2, Qw1, and Qw2 is connected to diodes Du1, Du2, Dv1, Dv2, Dw1, and Dw2. Diodes Du1, Du2, Dv1, Dv2, Dw1, and Dw2 are connected in parallel to each switching element Qu1, Qu2, Qv1, Qv2, Qw1, and Qw2. In the following description, “the diodes Du1, Du2, Dv1, Dv2, Dw1 and Dw2” can be referred to as diodes “Du1 to Dw2”.

[0026] The two switching elements Qu1 and Qu2 are connected in series, the switching elements Qv1 and Qv2 are connected in series, and the switching elements Qw1 and Qw2 are connected in series. Each switching element Qu1, Qu2, Qv1, Qv2, Qw1, and Qw2 has a gate that is electrically connected to a controller 40. Each switching element Qu1, Qu2, Qv1, Qv2, Qw1, and Qw2 has a collector that is connected to the positive terminal of a vehicle battery 30. Each switching element Qu2, Qv2, and Qw2 has an emitter that is electrically connected to the negative terminal of the vehicle battery 30. The emitter of switching element Qu1 and the collector of switching element Qu2 are electrically connected to the u-phase coil 15u via a midpoint between the two switching elements Qu1 and Qu2.The emitter of switching element Qv1 and the collector of switching element Qv2 are electrically connected to the v-phase coil 15v via a midpoint between the two switching elements Qv1 and Qv2. The emitter of switching element Qw1 and Qw2 is electrically connected to the w-phase coil via a midpoint between the two switching elements Qw1 and Qw2.

[0027] Furthermore, the inverter 20 has a capacitor 31 connected in parallel to the battery 30. For example, the capacitor 31 is a film capacitor or an electrolytic capacitor.

[0028] The controller 40 controls the drive voltage of the electric motor 13 using pulse-width modulation (PWM). Specifically, the controller 40 generates a pulse-width modulation (PWM) signal with a high-frequency triangular waveform, referred to as the carrier signal, and a voltage command signal, which commands a voltage. The controller 40 uses the generated PWM signals to control the switching between on and off of the switching elements Qu1, Qu2, Qv1, Qv2, Qw1, and Qw2. This converts the DC voltage of the battery 30 into an AC voltage. Accordingly, the switching elements Qu1, Qu2, Qv1, Qv2, Qw1, and Qw2 perform the switching to convert the DC voltage of the battery 30 into an AC voltage. The AC voltage is then applied to the electric motor 13 as the drive voltage / operating voltage to power and control the electric motor 13.

[0029] Furthermore, the controller 40 controls the PWM signals to variably control the duty cycle of the switching elements Qu1, Qu2, Qv1, Qv2, Qw1, and Qw2. This controls the speed of the electric motor 13. The controller 40 is electrically connected to an air conditioning ECU 41. When information regarding a target speed of the electric motor 13 is received from the air conditioning ECU 41, the controller 40 rotates the electric motor 13 to the target speed.

[0030] The vehicle's internal motor-driven compressor 10 has an input voltage detector 32 that detects the input voltage of the battery 30. The input voltage detector 32 is electrically connected to the control unit 40 to transmit the detection result to the control unit 40.

[0031] Furthermore, the vehicle's internal motor-driven compressor 10 has a speed detector 33 that detects the rotational speed of the electric motor 13. The speed detector 33 is electrically connected to the control unit 40 in order to transmit the detection result to the control unit.

[0032] When the electric motor 13 is stopped and the voltage of the reverse electromotive force (reverse electromotive voltage) of the electric motor 13 exceeds the input voltage of the battery 30, the current flowing from the electric motor 13 through the diodes Du1 to Dw2 to the battery 30 is called a reverse current. The controller 40 stores a characteristic curve that shows the relationship between the reverse current and the speed of the electric motor 13. Furthermore, the controller 40 is configured, based on the speed of the electric motor 13 detected by the speed detector 33, to calculate the reverse current that should flow from the electric motor 13 through the diodes Du1 to Dw2 to the battery 30.

[0033] The controller 40 stores a calculation program that calculates a temperature increase of the diodes Du1 to Dw2 based on the counter-current that is to flow from the electric motor 13 via the diodes Du1 to Dw2 to the battery 30, a switch-on voltage of the diodes Du1 to Dw2 and a thermal resistance of the diodes Du1 to Dw2.

[0034] The turn-on voltage and thermal resistance of diodes Du1 to Dw2 are fixed values ​​determined in advance by their characteristic curves. The turn-on voltage is the voltage between an anode and a cathode of diodes Du1 to Dw2. More precisely, it is the voltage between the anode and cathode of diodes Du1 to Dw2 when a forward voltage is applied and current begins to flow. Controller 40 stores the turn-on voltage and thermal resistance of diodes Du1 to Dw2 in advance.

[0035] When the electric motor 13 is stopped and the reverse electromotive voltage of the electric motor 13 exceeds the input voltage of the battery 30, the current flowing from the electric motor 13 through the diodes Du1 to Dw2 to the battery 30 is a reverse current. The controller 40 is configured to estimate the temperature rise of the diodes Du1 to Dw2 based on the expected reverse current, the turn-on voltage of the diodes Du1 to Dw2, and the thermal resistance of the diodes Du1 to Dw2. Accordingly, the controller 40 corresponds to a temperature rise estimator.

[0036] The controller 40 stores a characteristic curve that shows the relationship between the calculated temperature rise of diodes Du1 to Dw2 and a speed limit of the electric motor 13. Furthermore, the controller 40 stores a (maximum) junction temperature of diodes Du1 to Dw2. The controller 40 limits the speed of the electric motor 13 so that its speed does not exceed a set speed limit. That is, the controller 40 limits the speed of the electric motor 13 to less than or equal to the set speed limit. Accordingly, the controller 40 sets the speed limit of the electric motor based on the calculated temperature rise of diodes Du1 to Dw2 and limits the speed of the electric motor 13 so that its speed does not exceed the set speed limit. Thus, the controller 40 corresponds to a speed controller.

[0037] The functionality of the present embodiment will now be described.

[0038] The controller 40 calculates the temperature rise of the diodes Du1 to Dw2 based on the reverse current that is to flow from the electric motor 13 via the diodes Du1 to Dw2 to the battery 30, the switch-on voltage of the diodes Du1 to Dw2 and the thermal resistance of the diodes Du1 to Dw2.

[0039] The controller 40 then sets the speed limit of the electric motor 13 based on the calculated temperature rise of diodes Du1 to Dw2 such that the (junction) temperature of diodes Du1 to Dw2 does not exceed the (maximum) junction temperature of diodes Du1 to Dw2, even when the electric motor is stopped and the reverse current flows through diodes Du1 to Dw2. Furthermore, the controller 40 limits the speed of the electric motor 13 so that the speed of the electric motor 13 does not exceed the set speed limit.

[0040] Energy is supplied by the vehicle's battery 30. Thus, the vehicle's internal motor-driven compressor 10 is influenced by the input voltage of battery 30. The voltage of battery 30 changes according to the vehicle's condition. The input voltage supplied by battery 30 to the vehicle's internal motor-driven compressor 10 can be reduced. If the input voltage of battery 30 is low and the electric motor 13 is stopped while operating at high speed, the voltage of the reverse electromotive force (reverse electromotive voltage) of the electric motor 13 will not exceed the input voltage of battery 30. This generates a reverse current to flow from the electric motor 13, via the inverter 20, to battery 30. Specifically, when the electric motor 13 is stopped, the switching elements Qu1, Qu2, Qv1, Qv2, Qw1, and Qw2 do not switch.Thus, the reverse current flows from the electric motor 13 via the diodes Du1 to Dw2 to the battery 30.

[0041] Fig. Figure 3 shows changes in the (junction) temperature of diodes Du1 to Dw2 resulting from the reverse current flowing through diodes Du1 to Dw2.

[0042] The controller 40 sets the speed limit of the electric motor 13 based on the calculated temperature rise of diodes Du1 to Dw2 such that the (junction) temperature of diodes Du1 to Dw2 does not exceed the (maximum) junction temperature of the diodes, even when the electric motor 13 is stopped and the reverse current flows through diodes Du1 to Dw2. Furthermore, the controller 40 limits the speed of the electric motor 13 so that the speed of the electric motor 13 does not exceed the speed limit. Thus, the (junction) temperature of diodes Du1 to Dw2, as shown in Fig. Figure 3 shows that the (maximum) junction temperature does not increase, even when the counter-current flowing through diodes Du1 to Dw2 greatly increases the (junction) temperature of diodes Du1 to Dw2.

[0043] As in Fig. As shown in Figure 4, the reverse current flowing through diodes Du1 to Dw2 decreases gradually after the electric motor is stopped. Accordingly, the (junction) temperature of diodes Du1 to Dw2 decreases, as shown in Figure 4. Fig. As shown in Figure 2, this can also be done step by step. This avoids damage / breakage of diodes Du1 to Dw2.

[0044] The above embodiment has the advantages described below.

[0045] (1) The controller 40 sets the speed limit of the electric motor 13 based on the calculated temperature rise of diodes Du2 to Dw2 to prevent damage to the diodes Du2 to Dw2. Furthermore, the controller 40 limits the speed of the electric motor 13 so that the speed of the electric motor 13 does not exceed the speed limit. For example, to prevent damage to diodes Du1 to Dw2, the maximum speed limit of the electric motor 13 can be set according to the battery. In contrast, the above embodiment does not set the maximum speed limit of the electric motor 13 according to the input voltage of the battery 30 if more energy / power can be supplied to the vehicle's internal engine-driven compressor 10.Thus, the above embodiment extends the operating range of the vehicle's internal motor-driven compressor 10 and prevents the diodes Du1 to Dw2 from breaking down when the input voltage of the battery 30 is low and the electric motor 13 is stopped while operating at high speed.

[0046] It should be clear to those skilled in the art that the present invention can be implemented in many other specific forms without departing from the teaching or scope of the invention. In particular, it should be understood that the present invention can be implemented in the following forms. The foregoing embodiment can be modified as described below.

[0047] As in Fig. As shown in Figure 5, the vehicle's internal motor-driven compressor 10 can have a temperature detector 24 that detects the (junction) temperature of diodes Du1 to Dw2. The temperature detector 34 is electrically connected to the controller 40 to transmit the detection result to the controller 40. Thus, the temperature detector 34 corresponds to a temperature estimator that estimates the (junction) temperature of diodes Du1 to Dw2.

[0048] If the junction temperature of diodes Du1 to Dw2 detected by temperature detector 34 is lower than a predetermined junction temperature that is lower than the (maximum) junction temperature of diodes Du1 to Dw2, the controller 40 increases the speed limit of the electric motor 13. Furthermore, if the junction temperature of diodes Du1 to Dw2 detected by temperature detector 35 is higher than the predetermined junction temperature, the controller 40 decreases the speed limit of the electric motor 13.

[0049] Accordingly, the speed limit of the electric motor 13 can be changed based on the junction temperature of diodes Du1 to Dw2 detected by the temperature detector 34. For example, if the junction temperature of diodes Du1 to Dw2 is lower than the predetermined junction temperature, the margin / range between the junction temperature of diodes Du1 to Dw2 and the (maximum) junction temperature of diodes Du1 to Dw2 is relatively large. Consequently, the controller 40 can further increase the speed limit of the electric motor 13. This further extends the operating range of the vehicle's internal motor-driven compressor 10.Furthermore, if the junction temperature of diodes Du1 to Dw2 is higher than the predetermined junction temperature, the margin / range between the junction temperature of diodes Du1 to Dw2 and the (maximum) junction temperature of diodes Du1 to Dw2 is relatively small. Accordingly, the controller 40 reduces the speed limit of the electric motor 13 to adequately prevent diodes Du1 to Dw2 from failing.

[0050] In the Fig. In the embodiment shown in Figure 5, the temperature detector 24 can detect the (junction) temperature near diodes Du1 to Dw2. Based on the (junction) temperature detected by the temperature detector 35, the controller 40 can estimate the temperature of diodes Du1 to Dw2. In this case, the controller 40 and the temperature detector 34 correspond to a temperature estimator that estimates the (junction) temperature of diodes Du1 to Dw2.

[0051] In this embodiment, the vehicle-integrated, motor-driven compressor 10 can be configured such that the inverter 20 is oriented radially outwards along the axis of rotation / rotational shaft 14 relative to the housing 11. This means that the compressor unit 12, the electric motor 13, and the inverter 20 do not need to be arranged in the axial direction of the rotational shaft 14.

[0052] In this embodiment, the vehicle's internal motor-driven compressor 10 forms the vehicle air conditioning system 18. Alternatively, for example, the vehicle's internal motor-driven compressor 10 can be installed in a fuel cell vehicle, wherein the compressor unit 12 compresses compressed air, which serves as a fluid for the fuel cell.

[0053] In this embodiment, the vehicle's internal motor-driven compressor 10 has a speed detector 33, which detects the rotational speed of the electric motor 13 and transmits the detection result to the controller 40. However, the vehicle's internal motor-driven compressor 10 does not necessarily have to have the speed detector 33. Instead of detecting the rotational speed of the electric motor 13, the vehicle's internal motor-driven compressor 10 can estimate the rotational speed of the electric motor 13. For example, the vehicle's internal motor-driven compressor 10 can perform position sensorless control to estimate the position of the electric motor 13. Then, the vehicle's internal motor-driven compressor 10 can estimate the rotational speed of the electric motor 13 between its current position and its position during a driving cycle. The estimated rotational speed can be transmitted to the controller 40.

[0054] The controller 40 (more precisely, the temperature rise estimator, the speed controller, and the temperature estimator) can be a circuit that 1) has at least one processor running a computer program (software), 2) has at least one dedicated hardware circuit, such as an application-specific integrated circuit (AISC), to execute at least part of a process, or 3) a combination of the above. A processor has a CPU and memory such as RAM or ROM. The memory stores program code or instructions configured for the CPU to execute processes. The memory, which is a computer-readable medium, can be any available medium accessible to a general-purpose or dedicated computer.

[0055] The present examples and embodiments are to be regarded as illustrative and not limiting, and the invention is not to be limited to the information contained herein, but may be modified within the scope and equivalence of the attached claims.

Claims

[1] In-vehicle motor-driven compressor with: a compressor unit configured to compress fluid; an electric motor configured to drive the compressor unit; an inverter configured to drive the electric motor, whereby The inverter has a switching element configured to switch and convert a DC voltage from a battery into an AC voltage to drive the electric motor, and has a diode connected in parallel to the switching element. The vehicle's internal motor-driven compressor also has the following features: a temperature rise estimator configured to estimate a temperature rise of the diode based on a calculated reverse current, an input voltage of the diode, and a thermal resistance of the diode, where the reverse current is a current flowing from the electric motor through the diode to the battery when the electric motor is stopped and a counter-electromotive force of the electric motor exceeds an input voltage of the battery, and A speed control configured to set a speed limit of the electric motor based on the estimated temperature rise of the diode, such that the junction temperature of the diode does not exceed a maximum junction temperature of the diode when the electric motor is stopped and the reverse current flows through the diode, and the speed of the electric motor is limited to less than or equal to the speed limit. [2] Vehicle-internal motor-driven compressor according to claim 1, further comprises: a temperature estimator configured to estimate the temperature of the diode, where the speed control is configured to to increase the speed limit if the diode temperature estimated by the temperature estimator is lower than a predetermined temperature that is lower than the junction temperature, and in order to to reduce the speed limit if the temperature estimated by the temperature estimator is higher than the predetermined temperature. [3] Method for controlling an in-vehicle engine-driven compressor, wherein the in-vehicle engine-driven compressor has a compressor unit configured to compress fluid, an electric motor configured to drive the compressor unit, and an inverter configured to drive the electric motor, the inverter having a switching element configured to switch and convert a DC voltage from the battery into an AC voltage to drive the electric motor, and a diode connected in parallel to the switching element, the method comprising the following steps: Estimating a temperature rise of the diode based on a calculated reverse current, an input voltage of the diode and a thermal resistance of the diode, where the reverse current is a current flowing from the electric motor through the diode to the battery when the electric motor is stopped and a counter-electromotive force of the electric motor exceeds an input voltage of the battery; Setting a speed limit for the electric motor based on the estimated temperature rise of the diode such that the diode's junction temperature does not exceed a maximum junction temperature when the electric motor is stopped and the reverse current flows through the diode; and Limiting the speed of the electric motor to less than or equal to the speed limit.

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