WO2015080659A1

WO2015080659A1 - Cooling system

Info

Publication number: WO2015080659A1
Application number: PCT/SE2014/051414
Authority: WO
Inventors: Artion LAMADRID
Original assignee: Scania CV AB
Current assignee: Scania CV AB
Priority date: 2013-11-29
Filing date: 2014-11-27
Publication date: 2015-06-04
Anticipated expiration: 2016-05-29
Also published as: DE112014005146T5

Abstract

A cooling system for cooling of at least two components (3, 5, 6) generating heat during operation, and having different cooling requirements, comprising at least two cooling circuits (2, 4) with one pump (10, 11) each, for pumping of coolant past said component of the circuit and a heat exchanger (12, 13) for delivery to another medium of heat emitted by the component and absorbed by the coolant. The cooling system also comprises a connecting conduit (15), which connects all said cooling circuits (2, 4) with each other at their inlets to the respective pumps (10, 11), and an expansion tank (16) common to the cooling circuits connected to said connecting conduit.

Description

Cooling system FI ELD OF TH E I NVENTION

The present invention relates to a cool ing system for cool ing of at least two components, generating heat when in operation and having different cooli ng requirements, the system comprising at least two cool ing circuits, each of which has :

• a pu mp for pumpi ng coolant past said component in the circuit and

• a heat exchanger for delivery to another medi u m, such as the surrounding air, of heat absorbed from the component by the coolant.

I n general , the invention relates to cool ing systems with at least two cooling circuits for cooling of components with different cooling requirements, e.g . because there is a wish to maintai n them within dif- ferent temperature areas, althoug h the cooli ng requirements may differ in other ways, e. g . the components may withstand temperature fluctuations to different extents, and different cooling circuits are therefore preferable. It is also conceivable that the desired temperature of the different components generating heat during operation only differs by a few degrees, but that the heat amount required to cool one component is significantly greater than what is required for cooling of the second component, and it may therefore be reasonable to have a circuit with a larger heat exchanger and a larger pu mp than is the case in another circuit. More specifically, the invention relates to cooling systems for arrangement where the avai lability of space is li mited, such as in motor vehicles, and for this reason the invention will mainly be described for this application , for purposes of elucidating , but not li miting the invention .

For motor veh icles with hybrid drive systems, i .e. a drive system which comprises both a combustion engine and an electric machine, the electric energy storage, such as the battery pack, and the power electronics, used to control the energy exchange between the energy storage and the electric machi ne, will be heated during use due to the inner resistance of these. I n heavy goods vehicles, such as trucks and buses, the batteries i n a said battery pack may be considerably strained and develop a lot of heat, since it is desirable to recycle as much kinetic energy as possible when braking the vehicle. The temperature of the batteries is entirely decisive for how quickly they age, which means it is i mportant to observe the associated temperature setpoints of the batteries. These temperature setpoints, however, are significantly lower than the temperatures the power electronics, such as i nverters and DC/DC converters, are able to withstand. This means that if a cooling system is provided with the batteries as wel l as the power electronics in one and the same cooling ci rcuit, then either the batteries will age too quickly, or the power electronics will be cooled unnecessari ly vigorously, with a waste of energy as a result. For this reason , there is a desire to divide the cooling of these components, with different temperature setpoi nts. If there is a lack of space, it is preferable to have one cooling system with two cool ing circuits, as descri bed above, rather than two separate cooli ng systems. BACKGROUND TECHNOLOGY

US 2012/0186290 describes a system of the type described above; this, however, basically requires as much space and is as heavy as two separate cooling systems.

SUMMARY OF THE INVENTION

The objective of the present invention is to provide a cooling system of the type defined above, which is improved in at least some respect in relation to prior art cooling systems of this type.

According to the invention, this objective is achieved by providing such a cooling system with the features listed in the characterising portion of claim 1.

Since the cooling circuits of this cooling system share the coolant thanks to the connecting conduit between them and have a joint expansion tank, both space and weight required for the cooling system may be saved, which also leads to a cost saving. Still, it is possible to cool the components belonging to the different circuits in accordance with their cooling requirements, e.g. within different temperature areas, since the pumps may be operated entirely independently of each other, i.e. with different speeds, if required. As a result, energy is saved, since the different components do not need to be cooled down to the same level, as would be the case if they were arranged in one single cooling system.

According to one embodiment of the invention, the cooling system comprises, for each one of the said cooling circuits, a deaeration conduit leading from the highest point of the respective circuit to the expansion tank, with a check valve arranged in the deaeration conduit, to prevent a flow of coolant from the expansion tank to said point in the circuit. By arranging such check valves in the deaeration conduits, there is no risk of forced back flows from the expansion tank to said point in these, or any risk of the pu mps worki ng against each other in some modes. The "hig hest point" as used herei n means the hig hest local point or another suitable point where air may be expected to accu mulate.

According to another embodi ment of the invention , at least one of the cool ing circuits comprises a bypass conduit leading past the circuit's heat exchanger, and a control device adapted to control the flow of coolant in the cooling circuit so that it passes whol ly or partly throug h the heat exchanger and/or wholly or partly throug h the bypass conduit. Throug h the existence of such a bypass conduit another possibil- ity of controll ing the cooli ng ability of the cooling circuit in question is obtai ned. I n another embodi ment of the i nvention this possi bility is further expanded by arranging a device in said bypass conduit, the device being adapted to supply heat energy, in a controllable manner, to the coolant passing throug h the bypass conduit. Thus, even the temperature of the coolant coming from the component in question may be increased before it reaches the component again . This entails that the component wil l not be cooled, but instead heated. This may be desirable in case the component in question has a temperature that is below the component's range of temperature setpoints. I n case said component is e.g . a battery i n a motor vehicle, the temperature range in question could extend between +1 0°C and +40°C, and when starting the vehicle i n the winter, the batteries could have a temperature that is outside this range, in which case it is advantageous to be able to heat the batteries quickly, so that they end up within said tem- perature range. According to another embodi ment of the invention , each said cooling circuit is adapted to cool at least one component having temperature setpoints within a range, which does not overlap the range for the temperature setpoints of the component or the components that the other said cooling circuit(s) are adapted to cool .

According to another embodi ment of the invention , the cooli ng system comprises a device adapted to i mpact the heat exchange i n said heat exchanger, and to bring one and the same coolant, separate from the coolant in said cooling circuits, to pass first throug h the heat exchanger belongi ng to the cooli ng circuit for the component with the lowest temperature setpoints, and then , sequentially, throug h the heat exchangers for components with increasi ngly hig h temperature set- poi nts. Such an internal arrangement of the heat exchangers contrib- utes to the cooli ng system 's compactness, while it ensures that the coolant that is broug ht to pass throug h the heat exchangers is at its coldest, when it passes throug h the heat exchanger belonging to the cooling circuit with the component supposed to be kept within the lowest temperature area.

According to another embodi ment of the invention , constituti ng a further development of said embodi ment, said heat exchangers are arranged in a row after each other, and said device comprises a fan adapted to generate a flow of air i n the di rection of said row, and past said heat exchangers. Such a placement and cooling of the heat exchangers results in a compact air duct.

According to another embodi ment of the invention , the cool ing circuits are adapted for cooli ng of components with temperature setpoints within ranges that differ by at least 2°C, at least 1 0°C or at least 20°C from each other, i .e. the hig hest temperature setpoint of one of the components belonging to one of the cooli ng circuits is at least 2°C, at least 1 0°C or at least 20°C lower than the lowest temperature setpoint of another component belonging to another cooling circuit.

According to another embodi ment of the i nvention , one of said cooling circuits is adapted to cool a component which has a poorer resistance to temperature variations than a component or components, adapted to be cooled by said other cooli ng circuit(s) . The present invention hereby provides for a possibility to efficiently satisfy different cooli ng requirements, where e.g . the temperature of one of the cool ing cir- cuits must fluctuate fairly much , and where the components in another of the cooling circuits are sensitive to temperature fluctuations, which subjects them to mechanical fatigue.

According to another embodi ment of the invention , each said cooling circuit is adapted to cool at least one component, whose cooling requirement varies differently during operation of the component, than does the cooli ng requirement of a component or components adapted to be cooled by the other said cool ing ci rcuit(s) . Thus, e.g . different cooling requirements of the components belonging to different circuits may be met, i n case these cooling requirements differ because they have different requirements in different operating modes, e.g . i n the form of a component in the form of an inverter with a requirement for strong cooling when starting a hybrid vehicle, and subsequently a smaller cool ing requirement.

According to another embodi ment of the invention , the cooli ng system is adapted to be arranged in a motor vehicle with a hybrid drive system and to cool , with one of said cool ing circuits, an electrical energy storage, such as a battery pack connected to an electric machine of the vehicle, and to, with the other cooli ng circuit, cool at least one power electronics component, such as an inverter, arranged to control the exchange of electric power between said energy storage and said electric machine. This constitutes a particularly advantageous application of the innovative cooling system, since the availability of space is limited in motor vehicles, especially such motor vehicles, and weight is a significant parameter. In particular, this applies to heavy goods vehicles, such as trucks and buses. The energy storage could be of a different type, such as super capacitors (so-called supercaps).

The invention also relates to the use of a cooling system according to claim 13 and a motor vehicle with the features listed in claim 14.

Other advantages and advantageous features of the invention are set out in the description below.

BRIEF DESCRIPTION OF THE DRAWING

Below are descriptions of an example embodiment of the invention with reference to the enclosed drawing, in which:

Fig 1 is a very schematic view illustrating the structure of a cooling system according to the present invention.

DETAILED DESCRIPTION OF AN EMBODIMENT ACCORDING TO THE INVENTION A cooling system for cooling of a battery pack and power electronics arranged between this battery pack and an electric machine in a vehicle 1, with a hybrid drive system, is very schematically shown in Fig 1. The cooling system comprises two cooling circuits, namely a first 2 for cooling of a said battery pack 3 and a second 4 for cooling of power electronics in the form of a DC/DC converter 5 and an inverter 6, arranged for energy exchange between the battery pack 3 and an electric machine 7 in the vehicle. The path for such energy exchange is schematically illustrated by a dashed line, and the energy flow is according to the arrow 8 when the vehicle is braked, when the electric machine functions as a generator, and according to the arrow 9, when the electric machine functions as an engine.

Both circuits have one pump 10, 11 each for pumping of coolant, e.g. water, in the direction of the circuit's arrows past the battery pack 3 and the inverter 6 and the DC/DC converter 5, for cooling thereof. Meanwhile, the battery pack 3 may have a setpoint area for its tem- perature within the range of +10°C to +40°C, while both the components 5 and 6 in the other cooling circuit could have a corresponding temperature area between +60°C and +80°C (even though they are able to withstand -40°C). It would also be possible for more components than those displayed to be cooled by the respective cooling cir- cuits, and e.g. a passenger area in the vehicle could be cooled by the first cooling circuit 2, and the electric machine 7 and an electric compressor, which are able to withstand higher temperatures, could be cooled by the other cooling circuit. In both cooling circuits there is a heat exchanger 12, 13 for delivery to another medium of heat absorbed from the cooling circuit's components by the coolant flowing in the respective cooling circuit, i.e., in the displayed case, air that is brought to forcedly flow past the heat exchangers via a fan 14. In this case both the heat exchangers 12 and 13 are arranged in a row, also in order to let the heat exchanger 12, belonging to the first cooling circuit 2, be passed first by the air, so that this heat exchanger obtains air which is as cold as possible.

A connecting conduit 15 connects the cooling circuits 2 and 4 with each other, at their inlet to the respective pumps 10, 11. An expansion tank 16, common to the cooling circuits, is connected to the connecting conduit 15. In order for as little heat as possible to "spill over" to the first cooling circuit 2 from the cooling circuit 4, the connecting point between these is the coldest point in the respective circuit.

For each one of the cooling circuits, a deaeration conduit 1 7, 1 8 is arranged, leading from the hig hest point 1 9, 20 of the respective circuit to the expansion tank 1 6. The position of the points 1 9, 20 may be entirely different in the respective ci rcuit than as drawn i n the figure, and depends entirely on the three di mensional structure of the circuits. I n the deaeration conduits a check valve 21 , 22 is arranged, to prevent the flow of coolant from the expansion tank 1 6 to said poi nts 1 9, 20 in the circuit. Accordingly, no back-flow can be forced from the expansion tank to the respective circuit and the pu mps cannot work against each other, which they would otherwise risk doi ng in certain modes.

I n the first cooli ng circuit 2, a bypass conduit 23 is arranged past this cooling circuit's heat exchanger 1 2, and in this bypass conduit a device 24 is arranged, which is adapted to controllably supply heat energy to coolant passi ng throug h the bypass conduit. A three-way valve 25 is arranged for distribution of the flow of coolant between the heat exchanger 1 2 and the bypass conduit 23.

It is further ill ustrated that a temperature sensor 26 is arranged in the first cool ing circuit, which sensor may naturally also be arranged in the second cooling ci rcuit if needed. A control device 27 is arranged to control the three-way valve 25, the fan 1 4 and the pu mps 1 0, 1 1 in order to thus control the cooling action of the respective cooli ng circuit. Accordingly, the two cooling circuits may be controlled independently of each other.

The function of the cool ing system according to the invention is as fol lows. When the vehicle has been at a standstil l in cold weather and is started, e.g . only the first pu mp 1 0 of the first circuit 2 may be operated to circulate coolant i n the first circuit 2 throug h the heater 24, i .e. without passing the heat exchanger 1 2, i n order to heat the battery to a temperature within the temperature setpoint range of the bat- tery pack. At continued operation of the vehicle, the battery pack 3 and the power electronics components 5, 6 may then be cooled down to stay within said temperature range, throug h suitable control of the output of the fan 1 4 and the pu mps 1 0, 1 1 . However, the second cooling circuit could be started at the same ti me as the first, in order to cool load losses but also the power electronics, if these generate the electric power operating the heater. If the vehicle is e. g. braked forcefully, there is a great need to cool down the components, and the ai r flow is forced past the heat exchangers 1 2, 1 3, and the pu mps 1 0, 1 1 are operated with a hig h output, while the output may be reduced considerably in case the vehicle is operated at cruising speed with the use of only the combustion engine for its propulsion .

The i nvention is obviously not l i mited i n any way to the embodi ment descri bed above, but nu merous possible modifications thereof should be obvious to a person skilled in the area, without such person departing from the spi rit of the invention as defined by the appended clai ms.

For example, the cool ing circuits could be equipped with a said by- pass conduit, which also does not need to have any heater.

The cooling system may have more than two said cool ing circuits, which have a joint expansion tank. I n such case, the connecting conduit that connects the cooling circuits has several branches. The ex- pansion tank wil l then also have several inlets from the deaeration conduits.

Claims

1. Cooling system for cooling of at least two components (3, 5, 6) that generate heat when in operation, and having different cool- ing requirements, comprising at least two cooling circuits (2, 4), each of which has:

• a pump (10, 11) for pumping coolant past said component in the circuit and

• a heat exchanger (12, 13) for delivery to another medium, such as the surrounding air, of heat absorbed from the component by the coolant,

characterised in that the cooling system also comprises a connecting conduit (15) that connects all said cooling circuits (2, 4) with each other at their inlets to the respective pumps (10, 11), and an expansion tank (16) common to the cooling circuits connected to said connecting conduit.

2. Cooling system according to claim 1, characterised in that it comprises, for each one of said cooling circuits (2, 4), a deaera- tion conduit (17, 18) which in the respective circuit leads from the highest point (19, 20), defined as a local high point or another point where air may accumulate, to the expansion tank (16), and in that a check valve (21, 22) is arranged in the deaeration conduit, to prevent the flow of coolant from the expansion tank (16) to said point in the circuit.

3. Cooling system according to claim 1 or 2, characterised in that at least one (2) of the cooling circuits comprises a bypass conduit (23), leading past the heat exchanger (12) of this circuit, and a control device (27) adapted to control the flow of coolant in the cooling circuit, so that it passes wholly or partly through the heat exchanger (12) and/or wholly or partly through the bypass conduit (23).

Cooling system according to claim 3, characterised in that a device (24) is arranged in said bypass conduit (23) adapted to con- trollably supply heat energy to coolant passing through the bypass conduit.

Cooling system according to any one of the previous claims, characterised in that each said cooling circuit (2, 4) is adapted to cool at least one component (3) with temperature setpoints within a range that does not overlap with the range of temperature setpoints of the component (5, 6) or the components, which said other cooling circuit(s) are adapted to cool.

Cooling system according to claim 5, characterised in that it comprises a device (14) adapted to impact the heat exchange in said heat exchangers (12, 13) and to bring one and the same coolant, separate from the coolant in said cooling circuits (2, 4), to first pass through the heat exchanger (12) belonging to the cooling circuit (2) for the component (3) with the lowest temperature setpoints and then, sequentially, through the heat exchangers (13) for components (5, 6) with increasingly high temperature setpoints.

Cooling system according to claim 6, characterised in that said heat exchangers (12, 13) are arranged in a row after each other, and that said device (14) comprises a fan adapted to generate a flow of air in the direction of said row, past said heat exchangers (12, 13). Cooling system accordi ng to clai m 5, depending on clai m 3 or 4, characterised in that the cooli ng circuit (2) for the component with the lowest temperature setpoints comprises a said bypass conduit (23) .

Cooling system according to any one of clai ms 5-8, characterised in that the cool ing circuits (2, 4) are adapted for cool ing of components (3, 5, 6) with temperature setpoints within ranges that differ by at least 2°C, at least 1 0°C or at least 20°C from each other, i .e. the highest temperature setpoint of one (3) of the components belonging to one (2) of the cooling circuits is at least 2°C, at least 1 0°C or at least 20°C lower than the lowest temperature setpoint of another component (5, 6) belonging to another cooling circuit (4).

Cooling system according to any one of clai ms 1 -4, characterised in that one of said cool ing ci rcuits is adapted to cool a component, which has a poorer resistance to temperature variations than a component or components adapted to be cooled by said other cooling circuit(s) .

Cooling system according to any one of clai ms 1 -4, characterised in that each said cooli ng circuit is adapted to cool at least one component, whose cooli ng requirement varies differently during operation of the component, than does the cool ing requirement of a component or components adapted to be cooled by the other said cooling circuit(s) . Cooling system according to any one of the previous claims characterised in that it is adapted to be arranged in a motor vehicle (1) with a hybrid drive system and to cool, with one (2) of said cooling circuits, an electric power storage (3) connected to an electric machine (7) in the vehicle, and with another cooling circuit (4) to cool at least one power electronics component (5, 6) arranged to control the exchange of electric energy between said energy storage (3) and said electric machine (7).

Use of a cooling system according to any one of claims 1-12 in a motor vehicle (1), for cooling of at least two components generating heat during operation and having different cooling requirements.

Motor vehicle, characterised in that it comprises a cooling system according to any one of claims 1-12 for cooling of at least two components generating heat during operation and having different cooling requirements.