Motor vehicle and method for operating a cooling device
A separate coolant circuit with a lower maximum temperature for power electronics addresses the limitations of existing cooling systems, enhancing current and torque capacity in inverters and electric machines by optimizing thermal management.
Patent Information
- Application Number
- CN202111297005.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Priority Date
- 2020-11-02
- Filing Date
- 2021-11-01
- Publication Date
- 2024-12-10
- Estimated Expiration
- 2041-11-01
AI Technical Summary
Existing cooling systems for power electronics and electric machines in hybrid and electric vehicles are limited by coolant temperature, restricting the maximum current and torque in the pulse-controlled inverters, particularly IGBTs, due to thermal mass differences and inefficient cooling strategies.
Implementing a separate second coolant circuit with a lower maximum temperature for power electronics, such as IGBTs, to enhance cooling efficiency and allow higher current flow, while maintaining a higher temperature in the first circuit for the electric machine.
Enables higher torque and drive power by allowing increased current through the pulse-controlled inverter, reducing thermal stress and energy consumption, and avoiding additional cooling circuit modifications.
Smart Images
Figure CN114448174B_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a motor vehicle having a drive train with an electric machine, to which a power battery and power electronics including at least one pulse-controlled inverter are assigned, and a cooling device for cooling the electric machine, the power electronics and the power battery, wherein the electric machine is cooled in a first cooling circuit by means of a coolant having a first maximum temperature in a supply line. The invention also relates to a method for operating a cooling device in such a motor vehicle. Background Art
[0002] Hybrid vehicles and electric vehicles use electric motors (electric motors) as drive devices in the powertrain. Here, the electric motor can be fed by a power battery equipped for it. Here, high voltages, for example, in the range of 60V to 1.5kV, are usually used. Accordingly, the power battery can also be called a high-voltage battery. In the case of electric vehicles and so-called plug-in hybrid vehicles, which have an internal combustion engine in the powertrain in addition to the electric motor, the power battery can be charged from the outside by a charging device, for example, at a charging post or similar facilities.
[0003] In order to be able to operate the electric machine with traction energy, power electronics are required, which usually have at least one pulse-controlled inverter (PWR). The pulse-controlled inverter in turn usually has a plurality of semiconductor switches, in particular insulated gate bipolar transistors (IGBTs), which, like the electric machine and the power battery, need to be cooled during operation, so that a certain current can be allowed in the pulse-controlled inverter, in particular in the IGBTs. The greater the current flowing through the pulse-controlled inverter, the greater the torque in the electric machine. Since the thermal mass / heat-related mass in the pulse-controlled inverter, i.e., in particular the IGBTs, is small compared to the electric machine, for example less than one kilogram, it is known in the prior art that the power electronics are first cooled in a cooling section in a cooling circuit system, after which the return line from the power electronics is conveyed to another cooling section of the electric machine, so that the return line from the power electronics forms a supply line to the electric machine. The coolant of the cooling device circulating in the cooling circuit system is then conveyed by the electric machine to the cooling section again, where the heat is dissipated as is known in principle. For plug-in hybrid vehicles, it is known in the prior art, for example, to supply the power electronics, i.e. in the coolant supply line, with a coolant, for example water, which is set to a maximum temperature of 75° C. The slightly heated coolant is then fed to the electric machine. With such a coolant supply temperature of 75° C., the maximum current that can be maintained for 10 seconds for the components of the pulse-controlled inverter, in particular the IGBTs, is limited to 480 A. For electric vehicles, in another example, the maximum temperature in the coolant supply line for the power electronics is 65° C., which allows a maximum current of 530 A that can be maintained for 10 seconds in the pulse-controlled inverter. In this case, the electric machine should generally not be operated at a lower coolant temperature, for example in order to achieve the lowest possible friction.
[0004] Document DE 10 2016 100 861 A1 relates to the control of power reduction of a rectifier / inverter module (PIM). In this case, a system comprises a DC battery pack, a converter coolant circulation system, a first temperature sensor and a second temperature sensor, a multiphase motor, and a PIM connected to the battery pack and to the motor. A controller can be operated to selectively reduce the power of the PIM and thereby reduce the command torque on the motor. To this end, the controller estimates the junction temperature of the semiconductor switches of the PIM using the temperature of the coolant, the temperature of the PIM and a set of electrical values. When the temperature of the PIM exceeds a calibrated maximum temperature, the power is reduced.
[0005] Document CN 108705956 A discloses a motor controller temperature control system for an electric vehicle and a corresponding method. When the temperature of the IGBT exceeds a first temperature threshold, an air cooling device is controlled to cool the motor controller. When the temperature of the IGBT is lower than a second temperature threshold, a liquid cooling device is used to cool the motor controller, wherein the second temperature threshold is higher than the first temperature threshold. Summary of the invention
[0006] The object of the present invention is to specify an improved embodiment of the cooling device compared to this, in particular one that permits a higher power.
[0007] To achieve this object, the invention provides in a motor vehicle of the type mentioned at the outset that the power electronics are cooled in a second coolant circuit separate from the first coolant circuit by means of a coolant in the feed line having a second maximum temperature lower than the first maximum temperature.
[0008] According to the invention, it has been recognized that a lower coolant temperature allows a higher current in the pulse-controlled inverter, in particular in the IGBTs or other semiconductor switches of the pulse-controlled inverter, which in turn enables a higher torque in the electric machine and thus a higher drive power. Therefore, in order to ensure that low temperatures can be achieved at the pulse-controlled inverter, according to the invention, the power electronics are removed from the first cooling circuit, which uses a higher first maximum temperature for the electric motor, i.e. the electric machine, as the drive motor, and are cooled in a second coolant circulation system, in which the coolant with a lower maximum temperature can cool the pulse-controlled inverter, in particular its semiconductor switches. Therefore, for the second cooling circuit, the second maximum temperature in the supply line to the power electronics is lower than for the first cooling circuit, the first maximum temperature in the supply line to the electric machine.
[0009] If, for example, a plug-in hybrid vehicle (PHEV) known from the prior art is compared with an electric vehicle (BEV) known from the prior art, there is already a difference in the coolant supply temperature for the electric machine, namely a coolant supply temperature of 75° C. in the case of a PHEV and a coolant supply temperature of 65° C. in the case of a BEV, which results in a difference of, for example, 50 A in the maximum current flowing through the semiconductor switches, in particular the IGBTs, if the power electronics connected upstream of the electric machine are cooled. If, for example, a first maximum temperature of 75° C. is now reduced to a second maximum temperature of 65° C. or lower for a PHEV, a correspondingly higher maximum current in the pulse-controlled inverter is permitted. Since, in a plug-in hybrid vehicle, higher temperatures are usually present in the cooling circuit for the electric machine anyway, a higher, achievable positive effect results, so that the motor vehicle can preferably be a plug-in hybrid vehicle. In a specific example, the first maximum temperature may be 65° C. (or higher) for an electric vehicle or 75° C. (or higher) for a plug-in hybrid vehicle, while the second maximum temperature may be, for example, in the range of 50° C.-55° C. Generally speaking, it is advantageous to operate at least one pulse-controlled inverter and / or at least one semiconductor switch, in particular an IGBT, of the pulse-controlled inverter taking into account a maximum current limit that can be maintained / flowed for 10 seconds, wherein the current limit is selected to be greater than the current limit possible when cooled at the first maximum temperature and / or greater than or equal to 500 A, in particular greater than or equal to 530 A. For an exemplary embodiment, starting from a first temperature of 75° C. and decreasing to a second temperature of 65° C., the current limit can be increased from 480 A to 530 A, wherein a further decrease may, for example, lead to a current limit of up to 580 A or more possible, which is possible without the risk of damage.
[0010] In a particularly advantageous improvement of the present invention, it can be provided that the second cooling circuit is also used to cool the power battery. In other words, the already existing second cooling circuit of the power battery can also be used to add a cooling section for the power electronics. Here, the power battery is usually cooled at a lower temperature in the supply line, so it has been proven to be particularly advantageous to use the battery coolant circulation system as a second cooling circuit for cooling the power electronics. In this way, the provision of an additional cooling circuit is avoided. Here, as is also generally provided in known motor vehicles, it can also be provided that the power battery and the power electronics are installed adjacently in the motor vehicle, in particular even in a common component, so that only a short, additional coolant path is required.
[0011] In a particularly preferred design of the present invention, the cooling section of the second cooling circulation system for cooling the power electronics can be arranged in the return line of the cooling section for the power battery. In this way, since there is no cooling activity upstream of the power battery, the supply temperature for the power battery does not need to be changed. On the other hand, it has been shown that the coolant flowing out of the cooling section for the power battery is mostly only very slightly heated, so that the second maximum temperature in the supply line to the power electronics is always significantly lower than the first maximum temperature in the supply line to the motor, thereby obtaining the advantages of the present invention without having to adjust or manipulate the second cooling circuit of the power battery in a different way. In other words, the return line of the power battery is used as the supply line for the power electronics. If, for example, a maximum coolant temperature of 50°C is set in the supply line to the power battery, then a second maximum temperature in the return line of the power battery and therefore in the supply line to the power electronics can be, for example, 55°C or lower, which results in a clear gain, in particular compared to a situation where, for example, the first maximum temperature in the supply line to the electric machine is 65°C or 75°C.
[0012] In this case, it can also be provided that the coolant flow rate of the cooling section of the power electronics is lower than the coolant flow rate of the cooling section of the power battery, wherein a volume compensation section is provided in parallel with the cooling section of the power electronics in a second cooling circuit in order to discharge excess coolant. In this way, volume compensation can be achieved, because the power battery can usually have a relatively large thermal mass, for example in the range of 100 kg to 150 kg, whereas the thermal mass of the semiconductor switches, in particular the IGBTs, in the pulse-controlled inverter is significantly smaller, for example less than 1 kg.
[0013] As already mentioned, the first maximum temperature can be in the range of 60° C. to 80° C., for example, wherein the removal of the power electronics from the cooling circuit for the electric machine can also be achieved particularly advantageously, and a higher maximum temperature can be used in the supply line to the electric machine. Therefore, an advantageous embodiment of the invention can provide that a temperature greater than 75° C., in particular greater than 85° C., is selected as the first maximum temperature in the supply line to the electric machine. This is because it has been shown that at higher operating temperatures of the electric machine, the electric machine can be operated with low friction, which can lead to a reduction in the current consumption.
[0014] In general, it can be said that the cooling device can also have at least one control device for controlling the operation of the cooling device in addition to the cooling circuit, which control device can, in particular, adjust to a first maximum temperature and a second maximum temperature and / or temporarily to a lower temperature control value based on the temperature measurement value of at least one temperature sensor in each cooling circuit. Here, the temperature at the element to be cooled / to be cooled itself can also be measured. In principle, it is also conceivable to adjust the current control value of the first cooling circuit and the second cooling circuit by the control device, but within the scope of the invention, the supply temperature for the power electronics in the second cooling circuit can in principle remain lower than the supply temperature in the first cooling circuit.
[0015] As already mentioned, the invention can be used particularly advantageously in plug-in hybrid vehicles which additionally also have an internal combustion engine in the drive train. The at least one pulse-controlled inverter can include, for example, at least one IGBT as the element (and semiconductor switch) to be cooled.
[0016] In addition to a motor vehicle, the invention also relates to a method for operating such a cooling device in a motor vehicle according to the invention, wherein the electric machine is cooled in a first cooling circuit by means of cooling water at a first maximum temperature in a supply line to the electric machine, wherein the first maximum temperature is lower than a second maximum temperature in a supply line to a power electronics system, which is cooled in a second cooling circuit separate from the first cooling circuit. All the embodiments concerning the motor vehicle according to the invention can be transferred analogously to the method according to the invention, so that the advantages already mentioned can also be achieved with this method. BRIEF DESCRIPTION OF THE DRAWINGS
[0017] Further advantages and details of the invention emerge from the exemplary embodiments described below and with reference to the drawings.
[0018] The figure shows:
[0019] Figure 1 A schematic diagram of a motor vehicle according to the invention is shown, and
[0020] Figure 2 The embodiment of an exemplary embodiment of a cooling device of a motor vehicle is shown. DETAILED DESCRIPTION
[0021] Figure 1 The schematic diagram of a motor vehicle 1 according to the invention is shown, which is designed as a plug-in hybrid vehicle by way of example. The motor vehicle 1 comprises an electric machine 3 and an internal combustion engine 4 in a drive train 2. The invention can also be applied to purely electric vehicles; in this case, the internal combustion engine 4 is omitted.
[0022] The electric machine 3 designed as a conventional electric motor is connected to a power battery 8 (high voltage battery) via a power electronics 5, which includes a pulse inverter 6 (PWR) with six IGBTs 7. In order to cool the electric machine 3, the power electronics 5 and the power battery 8, the motor vehicle 1 also has a cooling device 9, which can also include at least one temperature sensor and / or a control device for controlling the operation of the cooling device. The cooling device 9 uses cooling water guided in a cooling circuit as a coolant.
[0023] Figure 2 The use of the cooling circuit system in the cooling device 9 is shown in more detail. Accordingly, the cooling device 9 comprises a first cooling circuit system 10, which is used to cool the motor 3, wherein Figure 2 For the sake of simplicity, only the components to be cooled are shown, but the usual components of a cooling circuit system including a cooling unit etc. are not shown, which are only generally shown as a block 11 .
[0024] The first cooling circuit 10 uses a coolant at a first maximum temperature in the supply line 12 to the electric machine 3. This first temperature can be, for example, in the range of 65° C. to 95° C., but is preferably selected to be a temperature greater than 75° C., particularly preferably greater than 85° C. In this way, the electric machine 3 can be operated with low friction due to the higher temperature, which leads to a saving of electrical energy.
[0025] The second cooling circulation system 13 is used to cool the power battery 8 and the power electronic device 5, wherein the cooling section 14 for cooling the power electronic device 5 is connected downstream of the cooling section 15 for cooling the power battery 8. In other words, the return line 16 of the power battery 8 also forms the supply line 17 for the power electronic device 5 at the same time. Since the thermal mass of the power electronic device 5 is significantly smaller than the thermal mass of the power battery 8, less coolant flow and therefore less coolant volume are required at the power electronic device, and thus a volume compensation section 18 is provided.
[0026] The second cooling circuit 13 uses the maximum supply temperature in the supply line 19 to the power battery 8, currently a maximum supply temperature of 50°C, and thus provides an only slightly increased maximum supply temperature, for example a maximum supply temperature in the range of 51°C to 55°C, as the second maximum temperature in the supply line 17 to the power electronics 5.
[0027] In this way, the pulse-controlled inverter 6 or, more specifically, its IGBT 7 as a component to be cooled can be kept at a temperature, for example, 20° C. or lower, lower than the motor 3, which enables a higher current to be passed through the pulse-controlled inverter or its IGBT. For example, the maximum current limit value that can flow through the IGBT 7 over a period of 10 seconds can be approximately 100 A higher than in the case of cooling the power electronics 5 in the supply line 12 to the motor 3. In a specific design, for example, a 10-second maximum current of 580 A can be defined, which is different from 480 A at 75° C.
Claims
1. A motor vehicle (1) having a drive train (2) with an electric motor (3) equipped with a power battery (8) and a power electronics system (5) including at least one pulse-controlled inverter (6), the motor vehicle also having a cooling device (9) for cooling the electric motor (3), the power electronics system (5) and the power battery (8), wherein: The electric machine (3) is cooled in a first cooling circuit (10) by means of a coolant having a first maximum temperature in a supply line (12), It is characterized in that The power electronic device (5) is cooled in a second cooling circuit (13) separate from the first cooling circuit (10) by means of a coolant in a supply line (17) having a second maximum temperature, which is lower than the first maximum temperature. The second cooling circulation system (13) is also used to cool the power battery (8). A cooling section (14) of a second cooling circuit system (13) for cooling a power electronic device (5) is arranged in a return line (16) of a cooling section (15) for a power battery (8).
2. The motor vehicle (1) according to claim 1, It is characterized in that The at least one pulse-controlled inverter (6) is operated taking into account a maximum current limit value which can be maintained for 10 seconds, wherein the current limit value is selected to be greater than a current limit value which is possible when cooling at the first temperature.
3. The motor vehicle (1) according to claim 2, characterized in that At least one semiconductor switch of a pulse-controlled inverter (6) is operated taking into account a maximum current limit which can be maintained for 10 seconds.
4. The motor vehicle (1) according to claim 2, characterized in that The current limit is selected to be greater than or equal to 500A.
5. The motor vehicle (1) according to claim 1, It is characterized in that The coolant flow rate of the cooling section (14) of the power electronic device (5) is lower than the coolant flow rate of the cooling section (15) of the power battery (8), wherein, in order to discharge excess coolant, a volume compensation section (18) is provided in parallel with the cooling section (14) of the power electronic device (5).
6. Motor vehicle (1) according to claim 1, It is characterized in that A power battery (8) and a power electronic device (5) are installed adjacent to each other in a motor vehicle (1).
7. Motor vehicle (1) according to claim 1 or 2, It is characterized by: A temperature greater than 75° C. is selected as the first temperature.
8. Motor vehicle (1) according to claim 1 or 2, It is characterized in that The motor vehicle is designed as a plug-in hybrid vehicle which also has an internal combustion engine (4) in the drive train (2).
9. Motor vehicle (1) according to claim 1 or 2, It is characterized in that The at least one pulse-controlled inverter (6) comprises at least one IGBT (7) as a component to be cooled.
10. The motor vehicle (1) according to claim 3, characterized in that The semiconductor switch is an IGBT (7).
11. The motor vehicle (1) according to claim 2, characterized in that The current limit is selected to be greater than or equal to 530A.
12. The motor vehicle (1) according to claim 6, characterized in that The power battery (8) and the power electronics (5) are installed in a common assembly.
13. The motor vehicle (1) according to claim 7, characterized in that A temperature greater than 85° C. is selected as the first temperature.
14. A method for operating a cooling device (9) in a motor vehicle (1) according to any one of claims 1 to 13.