Method for predictably controlling a coolant pump of a drive system of a vehicle

Abstract

The invention relates to a method for predictably controlling a coolant pump of a drive system of a vehicle, wherein a coolant pump (14) is operated via an electric drive (15) to circulate a coolant, which is controlled by means of a power electronics unit (16). In the method, the coolant volume flow delivered by the coolant pump (14) is controlled by the service life-dependent temperature of the power electronics unit (16).

Description

Technical Field

[0001] The invention relates to a method for predictably controlling a coolant pump of a drive system of a vehicle, wherein the coolant pump is operated via an electric drive for circulating the coolant, the electric drive being controlled by means of power electronics. Background Art

[0002] The drive system in vehicles with medium power (>50 kW) to high power (300 kW) is cooled by liquid coolant. The required coolant flow and pressure are generated by an electrically driven pump. The pump power is usually specified by the vehicle manufacturer in the form of a pump characteristic curve. Furthermore, the pump power is dependent on the coolant temperature or its temperature-dependent viscosity. Since the coolant pump is controlled based on temperature or pressure, the load on the coolant pump is significantly higher than required. Summary of the Invention

[0003] The object of the present invention is to provide a method for predictable control of a coolant pump, in which the thermal load of an inverter of a power electronics device is varied.

[0004] According to the present invention, this object is achieved by controlling the coolant volume flow delivered by the coolant pump using the service life-dependent temperature of the power electronics. This has the advantage that the coolant pump can be controlled independently of its performance parameters, such as volume flow and pressure. Although the control causes the coolant pump to age more rapidly than the power electronics, its service life is predictively determined. However, because the coolant pump is more cost-effective than the power electronics, premature replacement of the coolant pump reduces maintenance costs compared to replacing the power electronics.

[0005] Advantageously, the remaining service life of the power electronics is determined based on the current vehicle driving characteristics, wherein the temperature difference between the current detected temperature of the power electronics and the temperature of the power electronics under standard driving characteristics is determined, and the coolant volume flow that needs to be reset by the coolant pump is derived from this temperature difference. By studying the current vehicle driving characteristics, their influence on the service life of the power electronics can be predicted particularly accurately.

[0006] In one embodiment, the temperature of the power electronics detected in real time is calculated from the power loss of the power electronics. Since this power loss can be easily determined from a characteristic curve of the power electronics or by online calculation, the temperature can be determined cost-effectively.

[0007] In one variant, the current vehicle driving behavior is determined as the vehicle load characteristics over a predetermined driving period, wherein the predetermined driving period is selected so as to yield a sufficient amount of driving information to determine the remaining service life of the power electronics. The load characteristics are considered to be the driving behavior of the driver currently driving the vehicle. Because driving behavior can vary greatly from driver to driver, the control of the coolant pump can be determined with high precision based on the current driving style.

[0008] In one embodiment, the standard driving characteristic corresponds to the partial load driving characteristic of the vehicle. Advantageously, a driving characteristic predefined by the vehicle manufacturer can be used as the standard driving characteristic.

[0009] Advantageously, the power loss calculation of the power electronics and / or the temperature calculation of the power electronics and / or the determination of the temperature difference are performed continuously during the real-time vehicle driving behavior, thereby always providing real-time parameters for determining the foreseeable service life of the power electronics.

[0010] In another embodiment, the number of temperature differences is determined using a statistical algorithm, preferably a rainflow algorithm. Thus, a simple, known algorithm is used.

[0011] In one development, new driving characteristics are set as a function of the determined remaining service life of the power electronics and the volume flow of the coolant pump is reduced. This allows the coolant pump to be controlled predictively without requiring parameters such as the temperature and pressure of the coolant pump. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The present invention has various embodiments, one of which will be described in detail with reference to the accompanying drawings.

[0013] It shows:

[0014] Figure 1 A schematic diagram of a vehicle drive train with an electric motor is shown.

[0015] Figure 2 An embodiment of the method according to the invention is shown,

[0016] Figure 3 A schematic diagram showing the service life characteristic curve of power electronic equipment,

[0017] Figure 4 An exemplary schematic diagram is shown of a plurality of different driving characteristics of a vehicle. DETAILED DESCRIPTION

[0018] exist Figure 1shows a schematic diagram of an exemplary drive train for a hybrid vehicle. Drive train 1 includes an internal combustion engine 2 and an electric motor 3. A hybrid disconnect clutch 4 is located between internal combustion engine 2 and electric motor 3, immediately downstream of internal combustion engine 2. Internal combustion engine 2 and hybrid disconnect clutch 4 are connected to each other via a crankshaft 5. Electric motor 3 has a rotatable rotor 6 and a stationary stator 7. The output shaft 8 of hybrid disconnect clutch 4 is connected to a transmission 9, which includes a coupling element (not shown in detail), such as a second clutch or a torque converter, which is located between electric motor 3 and transmission 9. Transmission 9 transmits the torque generated by internal combustion engine 2 and / or electric motor 3 to drive wheels 10 of the hybrid vehicle. Electric motor 3 and internal combustion engine 2 are controlled by a drive engine controller 11.

[0019] The hybrid disconnect clutch 4, which is arranged between the internal combustion engine 2 and the electric motor 3, is engaged to start the internal combustion engine 2 during hybrid vehicle driving using the torque generated by the electric motor 3 or to drive the vehicle during boost operation using the driven internal combustion engine 2 and the electric motor 3. However, pure electric driving using only the electric motor 3 is also possible by disengaging the hybrid disconnect clutch 4. In this drive system 1, the electric motor 3 is controlled by the power amplifier 12.

[0020] The electric motor 3 is cooled by a coolant circuit 13 in which a coolant circulates via a coolant pump 14 driven by a further electric motor 15. Power electronics 16 are provided for controlling the further electric motor 15 and include a microprocessor 17.

[0021] The microprocessor 17 includes algorithms for predictively controlling the coolant pump 14, as in Figure 2 In a first block 100, the real-time vehicle driving characteristics are determined via the driving cycle. In a block 200, the phase currents are measured from the real-time vehicle driving characteristics when the further electric motor 15 controls the cooling pump 14. In a block 300, the losses of the power electronics 16 are calculated from the phase currents. In a block 400, the temperature of the power electronics 16 is determined from this loss calculation. In a block 500, the real-time temperature measured at the power electronics 16 and a standard temperature T corresponding to the partial load state of the vehicle are determined using a rain flow algorithm. krit The calculations in blocks 300 to 500 are performed continuously online. In block 600, the remaining service life of the power electronics 16 is calculated from the temperature difference ΔT. This calculation is performed by averaging over a predetermined driving period or a predetermined vehicle distance. In block 700, the future driving characteristics are set based on the service life determined in block 600, for example using a simple comparator, and the volume flow is set for controlling the coolant pump 14.

[0022] exist Figure 3shows the number of permissible temperature change cycles of the power electronics 16 as a function of the temperature difference ΔT. Region A shows low temperature differences ΔT, which lead to a reduction in the volume flow of the coolant pump 14. Region B shows moderate temperature differences ΔT, at which the volume flow remains constant. In contrast, region C shows high temperature differences ΔT, which lead to an increase in the volume flow of the coolant pump.

[0023] exist Figure 4 Schematic diagrams of several different driving characteristics of a vehicle are shown, illustrating the junction temperature T of the semiconductor components of the power electronics unit 16 over time t. Curve D shows the trend during low-load operation, while curve E shows the temperature of the power electronics unit 16 during partial-load operation, and curve F shows the temperature during full-load operation. Arrow G points to the low-load characteristic, which corresponds to a small temperature difference ΔT between the partial-load and full-load characteristics. This means that a slightly lower flow rate of the coolant pump 14 is set here. Arrow H also points to the low-load characteristic, but this corresponds to an intermediate temperature difference between the partial-load and full-load characteristics. Here, a low flow rate can be set at the cooling water pump 14. In the region of arrow K, the low-load characteristic corresponds to a high temperature difference ΔT between the partial-load and full-load characteristics, with a significantly lower flow rate being set.

[0024] During full-load driving, the components of the power electronics 16 are subjected to severe thermal stress. Here, the coolant pump 14 is quickly adjusted to a higher volume flow or may have to deliver a continuously higher volume flow. This ensures that the power electronics meet the vehicle manufacturer's service life requirements despite the high thermal stress.

[0025] During partial-load or low-load driving, the components of the power electronics 16 are subject to less thermal load, causing the coolant pump 14 to be adjusted to a higher volume flow much more slowly or to be continuously adjusted to a low volume flow. Because the thermal load on the power electronics 16 is significantly lower, the service life of the power electronics is significantly longer than required, and the coolant pump 14 can also remain adjusted to a low volume flow for significantly longer. This method allows the service life of the coolant pump 14 to be shortened in a targeted manner, shortening the service life of the power electronics 16 or, in accordance with the vehicle manufacturer's service life requirements, reducing the service life of the coolant pump and the service life of the power electronics.

[0026] Reference Signs List

[0027] 1 Drivetrain

[0028] 2 Internal combustion engine

[0029] 3. Electric Motor

[0030] 4 Hybrid disconnect clutch

[0031] 5 Crankshaft

[0032] 6 rotors

[0033] 7 stator

[0034] 8 driven shaft

[0035] 9 Transmission

[0036] 10 drive wheels

[0037] 11. Drive controller

[0038] 12 Power Amplifier

[0039] 13 Coolant circuit

[0040] 14 Coolant pump

[0041] 15 Another motor

[0042] 16 Power Electronics Devices

[0043] 17 Microprocessor

Claims

1. A method for predictably controlling a coolant pump of a drive system of a vehicle, wherein: The coolant pump (14) is operated via an electric drive (15) to circulate the coolant, which is controlled by means of a power electronic device (16), characterized in that the coolant volume flow delivered by the coolant pump (14) is controlled by the temperature of the power electronic device (16) in relation to the remaining service life, i.e., the coolant pump (14) is controlled independently of the power parameter of the coolant pump (14); wherein the remaining service life of the power electronic device (16) is determined based on the current vehicle driving characteristics, wherein the temperature of the power electronic device (16) detected in real time and the temperature of the standard driving characteristics (T krit ), the remaining service life of the power electronics device (16) is calculated from the temperature difference (ΔT), and the coolant volume flow that needs to be reset by the coolant pump (14) is derived from the temperature difference (ΔT).

2. The method according to claim 1, characterized in that The temperature of the power electronic device (16) detected in real time is calculated from the power loss of the power electronic device (16).

3. The method according to claim 2, characterized in that The real-time vehicle driving behavior is determined as a vehicle load behavior over a predetermined driving time period, wherein the predetermined driving time period is selected such that a sufficient amount of information about the real-time vehicle driving behavior is obtained to determine the remaining service life of the power electronic device (16).

4. The method according to at least one of the preceding claims, characterized in that The standard driving behavior corresponds to the partial load driving behavior of the vehicle.

5. The method according to any one of the preceding claims 1 to 3, characterized in that The power loss of the power electronics (16) and / or the temperature of the power electronics (16) and / or the temperature difference (ΔT) are calculated continuously during the current vehicle driving behavior.

6. The method according to claim 5, characterized in that The temperature difference (ΔT) is determined using a statistical algorithm.

7. The method according to claim 5, characterized in that New driving characteristics are set as a function of the determined remaining service life of the power electronics (16) and the coolant volume flow of the coolant pump (14) is reduced.

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