WO2016050393A1

WO2016050393A1 - On-demand cooling of a power converter of a motor vehicle

Info

Publication number: WO2016050393A1
Application number: PCT/EP2015/068035
Authority: WO
Inventors: Sebastian Jansen; Tobias Trzebiatowski
Original assignee: Robert Bosch Gmbh
Priority date: 2014-10-02
Filing date: 2015-08-05
Publication date: 2016-04-07
Also published as: DE102014220103A1

Abstract

The invention relates to a method for cooling a power converter (25) of a motor vehicle, wherein a cooling of the power converter (25) is enabled by means of a liquid coolant of a cooling circuit (11) of an internal combustion engine (10) of the motor vehicle when a temperature (T_Inv) of the power converter (25) reaches or exceeds an upper temperature threshold value.

Description

description

title

The present invention relates to a method for cooling a power converter of a motor vehicle and a power converter cooling device.

PRIOR ART Electric motors which can be used for vehicle propulsion are known from the field of hybrid vehicles. The aim here is to support the combustion engine at low speeds at which it does not yet deliver its full torque (boost mode, turbo lag compensation). In addition, by active electric braking (regenerative operation), the kinetic energy of the vehicle can be fed back into the electrical system (recuperation). The electric motor is connected via a power converter (so-called inverter) to the electrical system.

For motor operation, the converter is operated as an inverter, which converts the vehicle electrical system DC voltage into an AC voltage. In regenerative mode, the power converter operates as a rectifier. Due to the large converted power an active cooling of the converter is appropriate. It is possible to cool the power converter with a liquid cooling medium, in particular with the cooling medium of the internal combustion engine cooling circuit. For this purpose, the heat sink of the power converter is provided with lines through which the coolant flows and the thermal power loss generated by the electronics dissipates. This ensures that the power converter can implement high electrical power without overheating.

A disadvantage of this arrangement is a negative impact on the life of the converter, since in addition to the maximum component temperature and the size and number of temperature strokes is relevant to damage. Since the internal combustion engine heats up quickly after starting, the power converter is heated to the final cooling water temperature almost without any further measures during almost every drive. The associated thermal cycle load of the power converter leads to excessive aging of the converter and can thus have a premature failure of the entire electric drive result.

One approach is to use a low-temperature cooling circuit to cool the converter. However, this approach leads to an undesirable additional effort in the vehicle and is to avoid because of the associated costs.

It is therefore desirable to provide a way in which power converters can be adequately cooled without, however, being exposed to unnecessary temperature swings.

Disclosure of the invention

According to the invention, a method for cooling a power converter of a motor vehicle and a power converter cooling device with the features of the independent claims are proposed. Advantageous embodiments are the subject of the dependent claims and the following description.

Against this background, the invention proposes to cool the power converter with the liquid coolant of the internal combustion engine cooling circuit, but to release or suppress the liquid coolant flow to the power converter taking into account the converter's temperature. First, the power converter is therefore not cooled by the liquid coolant of the engine cooling circuit, but by the ambient air, in particular by using appropriate Heatsink and / or fan. Preferably, the power converter or a heat sink of the power converter are arranged in an air flow, which is generated by a fan of the electric machine or by a fan of a heat exchanger of the engine cooling circuit.

This air cooling is sufficient in many driving cycles to protect the converter from impermissibly high maximum temperatures. The heating of the converter is delayed in this way and the converter temperature remains significantly below the temperature of the liquid coolant of the internal combustion engine, especially in short driving cycles. Only when the power converter has reached a certain temperature level (e.g., the final temperature of the engine coolant) will the fluid flow be activated and the temperature level maintained at a permissible level even at high electrical powers.

Such need-based power converter cooling can preferably be achieved by a switchable valve in the coolant flow to the power converter and / or a deactivatable coolant pump.

The invention increases the life of a water-cooled power converter even with connection to cooling circuits with high coolant end temperatures. By appropriate activation of the liquid coolant flow, a high maximum power can be achieved even in the long-term / long-term operation. The implementation effort is low, it can be used, for example, a simple electrically operated two-point valve without high demands on tightness and switching behavior. An integration of the valve in the converter radiator or a direct attachment to the converter are possible. This results in no additional integration effort for the vehicle manufacturer, since the valve is part of the electric drive. When integrated into / in the power converter, a passively opening valve can also be used, which closes when a specific converter temperature is reached. The valve then does not have to be controlled electrically and the additional expense for the electronic signal processing is eliminated. Since thus less heat is removed from the liquid coolant of the internal combustion engine, this reaches its final temperature faster, which has a positive effect on the pollutant emissions. A power converter cooling device according to the invention of a motor vehicle is set up to carry out a method according to the invention. For this purpose, it can have an arithmetic unit which has been set up in particular for this purpose, programmatically.

The implementation of the method in the form of software is also advantageous, since this causes particularly low costs, in particular if an executing control device is still used for further tasks and therefore exists anyway. Suitable data carriers for providing the computer program are, in particular, floppy disks, hard disks, flash memories, EEPROMs, CD-ROMs, DVDs and the like. It is also possible to download a program via computer networks (Internet, intranet, etc.).

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

The invention is illustrated schematically by means of exemplary embodiments in the drawing and will be described in detail below with reference to the drawing.

Brief description of the drawings

FIG. 1 shows a block diagram of a preferred embodiment of a converter cooling device according to the invention and its integration into the cooling circuit of a motor vehicle.

Figure 2 shows in a block diagram an alternative embodiment of a

Power converter for use in a power converter cooling device. Figure 3 shows in a block diagram another alternative embodiment of a power converter for use in a power converter cooling device.

Embodiment (s) of the invention

In the figures, identical or equivalent elements are provided with the same reference numerals. It should be emphasized that the embodiments of power converters, converter heatsinks, valves, pumps, triggering conditions and coolant guides described below and / or illustrated in FIGS. 1 to 3 can be combined as desired within the scope of the invention.

1 shows schematically in a block diagram a preferred embodiment of a power converter cooling device 100 according to the invention and its integration into the cooling circuit of a motor vehicle.

The motor vehicle has a hybrid drive and is driven by an internal combustion engine 10 and an electric machine 20. The internal combustion engine 10 has a liquid coolant circuit 1 1, in which liquid coolant is circulated by means of a pump 12. A thermostatic valve 13 controls the amount of the coolant through a heat exchanger 14.

The electric machine 20 is controlled by a power converter 25 which has an electronic part 30 and a heat sink 35, over which power components, in particular power transistors (e.g.

MOSFETs), the electronic part 30 to be cooled. The heat sink 35 of the power converter 25 has coolant lines that carry the liquid coolant.

The liquid coolant for the power converter 25 is diverted from the engine cooling circuit 1 1. In order to obtain a defined coolant flow through the heat sink 35, optionally a power converter coolant pump 40 shown here can be used. To block or release the coolant flow through the heat sink 35, a switchable shut-off valve 45 is part of the power converter cooling device 100, which prevents the flow of coolant to the power converter, as long as a power converter temperature T | _nv does not exceed an upper temperature threshold. The converter temperature Tinv is detected in the example shown in the electronic part 30, but can also be detected in the heat sink 35. For controlling the power converter cooling device 100, a computing unit 50 can be provided, which is set up programmatically for carrying out a method according to the invention. Expediently, the arithmetic unit 50 is integrated in the electronic part 30 of the power converter 25 as shown in FIG.

In the variant illustrated in FIG. 1, the shut-off valve 45 is actuated by the arithmetic unit 50 via a drive signal S _v . Likewise, the optional coolant pump 40 is actuated by the arithmetic unit 50 via a drive signal S _P. As input variables for the program processing, the arithmetic unit 50 is supplied with the converter temperature Tinv and optionally with a liquid coolant temperature T _K M. In dependence on these input variables, the arithmetic unit 50 determines the required switching state of the valve and controls the valve 45 and possibly the pump 40.

A preferred way to determine the required valve switching state is explained below. After the start of the vehicle, the valve 45 remains closed until the current richtertem temperature T | _{nv reaches} the predetermined upper temperature threshold. This threshold value can correspond, for example, to the final value (set value) of the liquid coolant of the internal combustion engine. In addition to the shut-off valve 45, the optional converter converter coolant pump 40 is also activated in such a way that a coolant volume flow to the converter 25 is conveyed only when the shut-off valve 45 is open. After parking the vehicle, the valve 45 is closed again.

Due to the delayed activation of the liquid cooling, the power converter 25 in many driving scenarios (in particular during short journeys) is not limited to the ma- ximale temperature level of the liquid coolant heated, which extends the life.

In order to additionally optimize the heating behavior, as shown in FIG. 1, the liquid coolant temperature T _K M can optionally be supplied to the program processing. In this case, it can be provided that the valve 45 is always opened (and preferably only so long) when the converter temperature Tinv is greater than that of the liquid coolant temperature T _K M. An advantage of this concept is that even in the driving situations in which the converter heats up faster than the coolant, a delayed heating of the

Electronics can be achieved. In addition, by closing the valve 45 at short-term excess temperature of the liquid coolant temperature peaks are kept away from the converter. In order to prevent too frequent opening and closing of the valve 45, switching hystereses are expediently provided, accordingly the valve 45 opens when the converter temperature T | _{nv reaches} the predetermined upper temperature threshold, and closes when the converter temperature Tinv reaches a predetermined lower temperature threshold, the lower temperature threshold being less than the upper temperature threshold.

An alternative to the use of a valve 45 is to use a pump 40, which reliably prevents the coolant volume flow to the power converter 25 in the off state. The control of the pump 40 is then carried out analogously to the described control of the valve 45.

A particularly advantageous variant of the invention with regard to the integration effort at the vehicle manufacturer is to integrate the switchable shut-off valve 45 into the electronic part 30, as shown in FIG. 2, or the heat sink 35 of the power converter 25, or to grow it directly on it. The unit consisting of converter and valve can then be delivered as a complete module and installed in the vehicle without additional components.

Another particularly simple realization option is shown in FIG. 3 and consists in the use of a passively controlled valve 45 '(eg Thermostatic valve based on bimetal or expansion element), which reacts to the converter temperature Tinv and opens when the predetermined upper threshold value is reached. Such a valve is particularly suitable for integration into the converter heat sink 35 and does not require any additional electronic signal processing.

In addition to the use of liquid cooling, it is advantageous to equip the heat sink 35 of the power converter 25 in addition to the lines for the liquid coolant with cooling ribs 36, which allow an improved heat transfer to the ambient air. In this way, in the phases with the valve closed, ie in the phases with pure air cooling, an additional delay of the heating can be achieved. Preferably, the cooling fins 36 are arranged in an air flow of a fan, as in FIG. 3 of a fan 21 of the electric machine 20.

Claims

claims

1 . A method for cooling a power converter (25) of a motor vehicle, wherein a cooling of the power converter (25) by means of a liquid coolant of a cooling circuit (1 1) of an internal combustion engine (10) of the motor vehicle is released when a temperature (T | _nv ) of the power converter (25 ) reaches or exceeds an upper temperature threshold.

2. The method of claim 1, wherein the cooling of the power converter (25) by means of the liquid coolant of the cooling circuit (1 1) of the internal combustion engine (10) of the motor vehicle is locked when the temperature (T | _nv ) of the power converter (25) has a lower temperature threshold reached or fallen below.

3. The method of claim 2, wherein the lower temperature threshold is less than the upper temperature threshold.

4. The method according to any one of the preceding claims, wherein the upper temperature threshold value is a temperature of the liquid coolant of the cooling circuit (1 1) of the internal combustion engine (10).

5. The method of claim 4, wherein the upper temperature threshold is a final temperature of the liquid coolant of the cooling circuit (1 1) of the internal combustion engine (10).

6. The method of claim 4, wherein the upper temperature threshold is a current temperature (T _K M) of the liquid coolant of the cooling circuit (1 1) of the internal combustion engine (10).

7. The method according to any one of the preceding claims, wherein the converter temperature (Tinv) in an electronic part (30) or in a heat sink (35) of the power converter (25) is detected.

8. The method according to any one of the preceding claims, wherein the power converter (25) of an electric drive of the motor vehicle is cooled.

A power converter cooling apparatus (100) arranged to perform a method according to any one of the preceding claims.

10. power converter cooling device (100) according to claim 9, a switchable shut-off valve (45, 45 ') and / or a controllable pump (40) for releasing the liquid coolant of the cooling circuit (1 1) of the internal combustion engine (10) for the power converter (25). having.

1 1. A power converter cooling apparatus (100) according to claim 9 or 10, comprising a cooling body (35) with coolant conduits carrying the liquid coolant.

12. The power converter cooling device (100) according to any one of claims 9 to 1 1, which has a computing unit (50) which is adapted to carry out a method according to one of claims 1 to 8.

13. converter cooling device (100) according to one of claims 9 to 12, which is structurally integrated into the power converter (25).

14. Motor vehicle with a hybrid drive from an internal combustion engine (10) and an electric machine (20), which is controlled by a power converter (25), and with a power converter cooling device (100) according to any one of claims 9 to 13.

15. Motor vehicle according to claim 14, at least in reference to claim 1 1, wherein the heat sink (35) arranged in an air flow of a fan (21) of the electric machine (20) or of a fan of a Heat exchanger (14) of the cooling circuit (1 1) of the internal combustion engine (10) of the motor vehicle is generated.