WO2014098675A1

WO2014098675A1 - A thermal management system for cooling a vehicle battery unit and a method for cooling a vehicle battery unit

Info

Publication number: WO2014098675A1
Application number: PCT/SE2012/051453
Authority: WO
Inventors: Erik Hjerpe; Yngve Håland; David Sturk; Mats Johanson
Original assignee: Autoliv Development Ab
Priority date: 2012-12-20
Filing date: 2012-12-20
Publication date: 2014-06-26
Also published as: WO2014098706A1

Abstract

The present invention relates to a vehicle thermal management system (5, 5', 5'', 5''', 5'''') which comprises a pipe arrangement (6) and is arranged to cool a vehicle battery unit (2) by means of a coolant that is arranged to run in the pipe arrangement (6) through a part of, or adjacent to, the vehicle battery unit (2). The thermal management system (5, 5', 5'', ''', 5'''') further comprises at least one pyrotechnical charge (12; 29a-29h; 35) which is positioned in an auxiliary coolant unit (13, 13', 13'', 13''', 13'''') which is arranged to provide an enhanced flow (20, 31, 37, 38) of at least one type of coolant when the pyrotechnical charge (12; 29a-29h; 35) is detonated (18, 36). The present invention also relates to a corresponding method.

Description

TITLE

A thermal management system for cooling a vehicle battery unit and a method for cooling a vehicle battery unit DESCRIPTION OF THE INVENTION

The present invention relates to a vehicle thermal management system which comprises a pipe arrangement and is arranged to cool a vehicle battery unit by means of a coolant that is arranged to run in the pipe arrangement through a part of, or adjacent to, the vehicle battery unit.

The present invention also relates to a method for providing auxiliary cooling to a vehicle battery unit that uses a vehicle thermal management system for cooling.

In view of increasing concerns over the environmental impact of motor vehicles powered by internal combustion engines, there is now increased interest and importance in providing motor vehicles which produce less pollution, mainly in the form of exhaust fumes which are deemed harmful to the environment .

It is therefore becoming more and more common to provide motor vehicles which are powered electrically, at least during periods of their operation. For example, vehicles which solely are driven by a large electrical motor drawing its power from a rechargeable battery or so-called "hybrid" motor vehicles which typically combine an efficient internal combustion engine with an electric motor drawing its power from a rechargeable battery. Hybrid vehicles are driven by the electric motor whenever possible or convenient, but are driven by the internal combustion engine when the propulsive power offered by the motor is insufficient to meet the instant performance demand. Instead of batteries, capacitors are also conceivable as electrical energy storage units and energy sources. Combinations of these are also conceivable. The term "battery" and "battery unit" as used in this text is therefore intended to refer to any suitable electrical energy storage device including, but not limited to, an electrochemical battery and/or a capacitor.

Battery units used in vehicles of the above types are relatively large in order to provide sufficient electrical power for the electrical propulsive motor. Such battery units are typically configured for a voltage of approximately 300V and to store an amount of electrical energy that typically lies about 15-20 kWh. Such voltages and energy content represent a significant electrical hazard, particularly in the event of the vehicle being involved in a crash, or an internal short-circuit occurring within the battery. In the event of a short-circuit occurring either internally, or externally as a result of a crash, battery units of the type described above can become extremely hot and hence represent a risk of fire or explosion .

Due to the large currents drawn from the battery unit during normal conditions, different types of battery unit cooling arrangement are used. These are normally constituted by some type of a thermal management system using fluid thermal medium where for example water based liquids are used. The system further comprises a heat exchanging unit. Such a heat exchanging unit may for example exchange heat with passenger compartment air, air outside the vehicle. The efficiency of such a system is dependent on the circulation properties and the liquid's ability to transport heat. Should the circulation fail due to a collision and similar, the thermal management system will also fail. Furthermore, at such an occasion, undesired heat generation as described above might be of such a magnitude that the capacity of the thermal management system is insufficient anyway. There is therefore a need for restoring and prolonging the functionality of the thermal management system in those cases, otherwise thermal runaway may be initiated in the battery unit, which is highly undesirable .

The document EP2216849 discloses a safety arrangement configured to cool a battery unit at an accident situation or battery malfunction. The safety arrangement comprises a source of compressed inert gas and a flow-release actuator arranged to release a flow of the gas from the source onto the battery unit at such a situation, so as to cool the battery unit.

There is however a need for a battery unit cooling arrangement which provides an improvement to the previously known technology in this field of technology, and it is an object of the present invention to provide an improved battery unit cooling arrangement for motor vehicles.

Said object is achieved by means of a vehicle thermal management system which comprises a pipe arrangement and is arranged to cool a vehicle battery unit by means of a coolant that is arranged to run in the pipe arrangement through a part of, or adjacent to, the vehicle battery unit. The thermal management system further comprises at least one pyrotechnical charge which is positioned in an auxiliary coolant unit, the auxiliary coolant unit being arranged to provide an enhanced flow of at least one type of coolant when the pyrotechnical charge is detonated. Said object is also achieved by means of a method for providing auxiliary cooling to a vehicle battery unit that uses a vehicle thermal management system for cooling. The method comprises the steps of detonating a pyrotechnical charge; and using the forces from said detonation to provide an enhanced flow of at least one type of coolant.

According to an example, the auxiliary coolant unit comprises a connecting pipe that is arranged to guide expanding gasses into the pipe arrangement when said pyrotechnical charge is detonated .

According to another example, the auxiliary coolant unit comprises a turbine housing which in turn comprises a turbine with a plurality of turbine flanges which are attached to a center shaft and are in contact with a normal flow of coolant in the pipe arrangement. At least one flange is provided with at least one pyrotechnical charge. Each pyrotechnical charge is arranged to be detonated such that the turbine moves in such a way that an enhanced flow of said coolant is provided.

Alternatively, when detonated, a pyrotechnical charge may instead be arranged to exert a pulling force at a wire that is attached to, and wound around, the center shaft. In this way, the center shaft is revolved and the turbine moves in such a way that an enhanced flow of said coolant is provided.

According to another example, the auxiliary coolant unit comprises a sealing membrane or wall and a pyrotechnical charge 35. The pyrotechnical charge is arranged to at least partly open the sealing membrane or wall when detonated, such that a coolant is allowed to flow through the sealing membrane or wall when opened. According to another example, the coolant that is allowed to flow through the sealing membrane or wall when opened is directed either to flow over the battery unit or into the pipe arrangement via a connecting pipe, providing an enhanced flow.

Other examples are disclosed in the dependent claims.

A number of advantages are obtained by means of the present invention. Mainly, an enhanced flow of coolant is quickly provided to a vehicle battery unit, when the cooling of an existing cooling arrangement is determined to be insufficient.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be described more in detail with reference to the appended drawings, where:

Figure 1 shows a schematical side view of a vehicle equipped with a battery unit; Figure 2 shows a schematical view of a thermal management system;

Figure 3 shows a schematical view of an auxiliary coolant unit according to a first example in a first state;

Figure 4 shows a schematical view of an auxiliary coolant unit according to a first example in a second state;

Figure 5 shows a schematical view of an auxiliary coolant unit according to a second example in a first state;

Figure 6 shows a schematical view of an auxiliary coolant unit according to a second example in a second state; Figure 7 shows a schematical view of an auxiliary coolant unit according to an alternative to the second example in a first state; Figure 8 shows a schematical view of an auxiliary coolant unit according to an alternative to the second example in a second state;

Figure 9 shows a schematical view of a thermal management system according to a third example in a first state;

Figure 10 shows a schematical view of a thermal management system according to a third example in a second state ;

Figure 11 shows a schematical view of a thermal management system according to a fourth example;

Figure 12 shows a schematical view of a thermal management system according to a fifth example; and

Figure 13 shows a flowchart of a method according to the

present invention. DETAILED DESCRIPTION

With reference to Figure 1, showing a side view of an electrically powered vehicle 1, a battery unit 2 is mounted to the outer side of a floor 3 of the vehicle 1. The battery unit 2 is positioned between the wheels 4a, 4b of the vehicle 1, such that the battery unit 2 contributes with an even load and low mass center. The vehicle 1 has a longitudinal extension L along its main driving direction. With reference also to Figure 2, the vehicle 1 comprises a thermal management system 5 which is connected to the battery unit 2 via a pipe arrangement 6 and is arranged to cool the battery unit 2 by means of a coolant, that may be liquid and/or gas, that runs in the pipe arrangement 6 during normal running conditions, the pipe arrangement 6 running through a part of, or being adjacent to, the battery unit 2.

The thermal management system 5 further comprises a heat exchanging unit 7, which in itself is of a well-known kind and may comprise a compressor 8. The heat exchanging unit 7 may for example be arranged to exchange heat with passenger compartment air or air outside the vehicle 1. The heat exchanging unit 7 also comprises a pump 9 that is arranged for creating a flow of the coolant in the pipe arrangement 6 in a direction indicated with a first coolant flow arrow 10 and a second coolant flow arrow 11.

According to the present invention, the thermal management system 5 further comprises at least one pyrotechnical charge 12 which is positioned in an auxiliary coolant unit 13, the pyrotechnical charge 12 being arranged to be detonated in a situation when the flow of coolant is determined to be insufficient or has stopped. The auxiliary coolant unit 13 is arranged to provide an enhanced flow of coolant when the pyrotechnical charge 12 is detonated. Such a situation may have been caused by a malfunction that in turn may have been caused by a collision. The flow may be enhanced by means of the pyrotechnical charge 12 in several ways; a number of examples will be discussed in the following. According to a first example, as shown in Figure 2, the auxiliary coolant unit 13 is positioned adjacent the heat exchanging unit 7 and is connected to the pipe arrangement 6. During normal running, the pump 9 provides a sufficient flow of coolant in the pipe arrangement 6. As shown in Figure 3, showing a detailed cut-open view of the auxiliary coolant unit 13, there is normally a flow 21 of coolant through a pipe part 6a, being comprised in the pipe arrangement 6, passing through the auxiliary coolant unit 13, where a pyrotechnical unit 14 comprised in the auxiliary coolant unit 13 in turn comprises a housing 15, a pyrotechnical charge 12 and a connecting pipe 16.

The connecting pipe 16 has a first end 16a that is facing the pyrotechnical charge 12 in the housing 15, and a second end 16b that has exited the housing 15 and connects the housing with the pipe part 6a passing through the auxiliary coolant unit 13. The pipe part 6a has a uni-directional valve aperture 17 in which the connecting pipe 16 enters, the uni-directional valve aperture preventing the coolant from escaping through the aperture 17 and into the connecting pipe 16, not allowing flow from the pipe part 6a into the connecting pipe 16.

As shown in Figure 4, when the flow of coolant has been determined to be insufficient, the pyrotechnical charge is detonated 18, and expanding gasses 19 that result from the detonation travel towards the pipe part 6a, via the connecting pipe 16 through the uni-directional valve aperture 17, such that it protrudes into the pipe part 6a and provides an enhanced flow 20. As shown in Figure 4, a gas supplying valve 22 is arranged to inject ambient air 23, that is swept into the pipe arrangement by means of the motion of the gasses, said injected air 23 also contributing to an enhanced flow 20. The uni-directional valve aperture 17 could instead be an openable sealing in the form a foil aperture, where a thin foil, membrane or similar prevents flow from the pipe part 6a to enter the connecting pipe 16. When the pyrotechnical charge is detonated 18, the foil is destroyed, such that the gasses may enter the pipe part 6a.

It is also conceivable that the expanding gasses instead, or also, are arranged to open a coolant container (not shown) such that more coolant is provided from the container, which previously has been sealed from the pipe arrangement 6, into the pipe arrangement 6.

In the above cases, the pressure of the coolant is increased, which in turn increases the boiling temperature of the coolant. This is desirable, since an increased boiling temperature results in that more heat may be absorbed by the coolant. For example, for water the boiling temperature is increased to about 120°C when the pressure is increased to 2 bar, which means that about additional 20°C of heat capacity may be stored in the coolant and dissipated from the heat source. However, in order to avoid breakage and further damage to the battery unit 2, a pressure release valve 24 is arranged to open and release gas, vapor and/or liquid as indicated with a pressure valve arrow 25 when a certain pressure limit is reached in order to allow additional pressure rise, for example when the coolant has been used to its limit and its vapor expands in the thermal management system 5. According to a second example of a thermal management system 5' with reference to Figure 2 and Figure 5, Figure 5 showing a detailed cut-open view of an auxiliary coolant unit 13' according to the second example, there is normally a flow of coolant through a pipe part 6a' , being comprised in the pipe arrangement 6, via a turbine housing 26 in the auxiliary coolant unit 13' . The turbine housing 26 is shown cut-open and comprises a turbine 27 with a plurality of turbine flanges 27a-27h, where the flanges are attached to a center shaft 43 and are in contact with a normal flow 28 of coolant. Each flange 27a-27h is provided with a pyrotechnical charge 29a- 29h.

As shown in Figure 6, when the flow of coolant has been determined to be insufficient, a first pyrotechnical charge 29a has been detonated, such that the turbine has started moving, indicated by a turbine arrow 30, in such a way that an enhanced flow 31 of the coolant is provided. After a certain time, an adjacent second pyrotechnical charge 29b is detonated 36, as shown in Figure 6, such that the turbine's movement is maintained to a sufficient degree. The remaining pyrotechnical charges 29c-29h are then detonated one after the other in the same way such that the turbine's movement is maintained to a sufficient degree. It is even conceivable that each pyrotechnical charge 29a-29h comprises a number of sub-charges (not explicitly shown) , where only a sub-charge is detonated each time, allowing the detonations to pass several turns on the turbine's flanges 27a-27h. The timing between the detonations is preferably set to a sufficient value, or may alternatively be adaptively set. The number of flanges 27a-27h and the number of pyrotechnical charges/sub-charges 29a-29h may of course vary. At least one flange 27a-27h should be provided with at least one pyrotechnical charge 29a-29h.

Alternatively, as shown in Figure 7, showing a similar arrangement of an auxiliary coolant unit 13' a as the one shown in Figure 5 and Figure 6, there are no pyrotechnical charges 29a-29h at the flanges 27a-27h. Instead, a wire 44 is attached to, and wound around, the center shaft 43 as schematically indicated in Figure 7. The wire 44 is furthermore guided outside the turbine housing 26 and into a wire propulsion housing 45. As shown in Figure 7, the wire 44 is wound onto a wire shaft 46 in the wire propulsion housing 45. The wire propulsion housing 45 further comprises a pyrotechnical charge 47.

With reference to Figure 8, when the flow 28 of coolant has been determined to be insufficient, the pyrotechnical charge 47 is detonated 48. When the pyrotechnical charge 47 is detonated 48, it is arranged to transfer its forces to revolving the wire shaft 47. In this way, when the pyrotechnical charge 46 is detonated 48, the wire 44 is wound onto the wire shaft 47 and rewound from the center shaft 43. Due to friction forces, when unwinding, the wire 44 revolves the center shaft 43, indicated by a turbine arrow 30, in such a way that an enhanced flow 31 of the coolant is provided.

It is not described in detail how the pyrotechnical charge 47 is arranged to transfer its forces to revolving the wire shaft 47 when detonated 48, since many previously known arrangements are conceivable for the skilled person, for example in the field of seat-belt pre-tension devices. It is conceivable that the turbine 27' in this example comprises a symmetrical weight 49 as indicated with a dashed line in Figure 7 and Figure 8, for example in the form of a disc or a rim, which is concentrically arranged with respect to the center shaft 43. By means of the symmetrical weight 49, a moment of inertia is added such that when the pyrotechnical charge 46 is detonated 48 and transfers its forces to revolving the wire shaft 47 and thus the center shaft 43 and the turbine 27' by means of the wire 44, a certain amount of energy from the detonation forces are stored in the revolving symmetrical weight 49. In this way, the revolving motion is maintained for a longer time then without the symmetrical weight 49, the detonation forces thus being more efficiently used .

The above is one example of how a wire or similar may be used, many other alternatives for creating a pulling force at a wire by means of a pyrotechnical charge are of course conceivable. Generally, when a pyrotechnical charge 46 is detonated 48, it is arranged to exert a pulling force at a wire 44 that is attached to, and wound around, the center shaft 43, such that the center shaft 43 is revolved and the turbine 27 moves in such a way that an enhanced flow 31 of the coolant is provided.

As a further alternative, a pyrotechnical charge may be arranged to act on the center shaft 43 directly when detonated instead of using the wire shaft and the wire.

According to a third example with reference to Figure 9, the thermal management system 5' ' comprises a connecting pipe 32 that runs between the pipe arrangement 6 of the thermal management system 5' ' and an existing vehicular cooling system 33, comprised in the vehicle 1. The auxiliary coolant unit 13' ' according to the third example is positioned at the connecting pipe 32, comprising an openable sealing between the thermal management system 5' ' and the vehicular cooling system 33. For this purpose, the auxiliary coolant unit 13'' comprises a sealing membrane or wall 34, and a pyrotechnical charge 35. When detonated, the pyrotechnical charge 35 is arranged to open the sealing membrane or wall 34, for example by means of the expanding gases themselves, or by means of an object (not shown) that is driven through the membrane or wall 34 by means of the expanding gases. As shown in Figure 9, there is a normal flow of coolant, indicated with a first coolant flow arrow 10 and a second coolant flow arrow 11. As shown in Figure 9, the flow of coolant has been determined to be insufficient and the pyrotechnical charge 35 has been detonated, such that the pipe arrangement 6 of the thermal management system 5' ' and the vehicular cooling system 33 now are connected, the vehicular cooling system 33 providing an enhanced coolant flow 37, 38 and increased pressure, which provides those advantages discussed previously.

The vehicular cooling system 33 may be in the form of an air- conditioning system arranged for passenger comfort. The vehicular cooling system 33 may alternatively be constituted by the engine cooling system. In the latter case, the pipe arrangement 6 of the thermal management system 5' ' and the vehicular cooling system 33 should not be connected until the thermal management system 5' ' absorbed such an amount of heat that it is warmer than the vehicular cooling system 33.

Furthermore, in the latter case, the connecting pipe 32 may instead, in an alternative thermal management system 5' ' ' according to a fourth example, not be connected to the pipe arrangement 6, but is instead arranged to lead the released engine coolant 39 to flow freely over the battery unit 2, after the detonation of a pyrotechnical charge opening up a sealing membrane or wall in an auxiliary coolant unit 13' ' ' in the same way as in the previous example, such that a direct cooling effect is provided as shown in Figure 11.

Furthermore, in all cases, with reference to Figure 12 the coolant of the thermal management system 5' ' ' ' according to a fifth example, possibly mixed with a coolant from a vehicular cooling system, may also be allowed to flow freely 40 over the battery unit 2 after a controlled opening of the pipe arrangement 6 at a suitable position as shown in Figure 10; suitably after the detonation of a pyrotechnical charge opening up a sealing membrane or wall in an auxiliary coolant unit 13'''' in the same way as in the previous example. Such an opening is made by means of a detonation of a pyrotechnical charge .

The use of a vehicular cooling system according to the above is preferably a later action that is preceded by any one of the examples discussed above with reference to Figure 3 - Figure 8. Several auxiliary coolant units 13, 13', 13'', 13' ' ' , 13' ' ' ' may thus be installed in a vehicle, with parallel functionality, where the auxiliary coolant units 13, 13' , 13' ' , 13' ' ' , 13' ' ' ' may be used one after the other or at the same time.

With reference to Figure 13, the present invention also relates to a method for providing auxiliary cooling to a vehicle battery unit 2 that uses a vehicle thermal management system 5 for cooling. The method comprises the steps of:

41: detonating a pyrotechnical charge 12; 29a-29h; 35; and 42: using the forces from said detonation to provide an enhanced flow of at least one type of coolant.

The present invention is not limited to the examples described above, but may vary freely within the scope of the appended claims. For example, the sealing membrane or wall 34 is at least partially opened when a corresponding pyrotechnical charge is detonated.

Claims

1. A vehicle thermal management system (5, 5', 5", 5''', 5'''') which comprises a pipe arrangement (6), the thermal management system (5, 5', 5", 5''', 5'''') being arranged to cool a vehicle battery unit (2) by means of a coolant that is arranged to run in the pipe arrangement (6) through a part of, or adjacent to, the vehicle battery unit (2), characterized in that the thermal management system (5, 5', 5", 5''', 5'''') further comprises at least one pyrotechnical charge (12; 29a-29h; 35) which is positioned in at least one auxiliary coolant unit (13, 13' , 13' ' , 13' ' ' , 13""), said auxiliary coolant unit (13, 13', 13", 13"', 13"") being arranged to provide an enhanced flow (20, 31, 37, 38) of at least one type of coolant when the pyrotechnical charge (12; 29a-29h; 35) is detonated (18, 36) .

2. A vehicle thermal management system according to claim 1, characterized in that the thermal management system

(5) comprises a pressure release valve (24) that is arranged to open and release gas, vapor and/or liquid (25) when a certain pressure limit is reached.

3. A vehicle thermal management system according to any one of the claims 1 or 2, characterized in that the enhanced flow (20, 31, 37, 38) is provided to the pipe arrangement (6) .

4. A vehicle thermal management system according to any one of the previous claim, characterized in that an auxiliary coolant unit (13) comprises a connecting pipe (16) that is arranged to guide expanding gasses into the pipe arrangement

(6) when said pyrotechnical charge (12) is detonated.

5. A vehicle thermal management system according to claim 4, characterized in that the thermal management system

(5) comprises a gas supplying valve (22) that is arranged to inject ambient air (23).

6. A vehicle thermal management system according to any one of the claims 1-3, characterized in that an auxiliary coolant unit (13') comprises a turbine housing (26) which in turn comprises a turbine (27) with a plurality of turbine flanges (27a-27h) , where the flanges (27a-27h) are in contact with a normal flow (28) of coolant in the pipe arrangement

(6) , at least one flange (27a-27h) being provided with at least one pyrotechnical charge (29a-29h) , each pyrotechnical charge (29a-29h) being arranged to be detonated such that the turbine (27) moves in such a way that an enhanced flow (31) of said coolant is provided.

7. A vehicle thermal management system according to any one of the claims 1-3, characterized in that an auxiliary coolant unit (13' a) comprises a turbine housing (26) which in turn comprises a turbine (27') with a plurality of turbine flanges (27a-27h) attached to a center shaft (43), where the flanges (27a-27h) are in contact with a normal flow (28) of coolant in the pipe arrangement (6), where the auxiliary coolant unit (13' a) comprises a pyrotechnical charge (47) that, when detonated, is arranged to exert a pulling force at a wire (44) that is attached to, and wound around, the center shaft (43) , such that the center shaft (43) is revolved and the turbine (27) moves in such a way that an enhanced flow (31) of said coolant is provided.

8. A vehicle thermal management system according to any one of the claims 1 or 2, characterized in that an auxiliary coolant unit (13'', 13''', 13'''') comprises a sealing membrane or wall (34), and a pyrotechnical charge (35), the pyrotechnical charge (35) being arranged to at least partly open the sealing membrane or wall (34) when detonated, such that a coolant is allowed to flow through the sealing membrane or wall (34) when opened.

9. A vehicle thermal management system according to claim 5, characterized in that the coolant that is allowed to flow through the sealing membrane or wall (34) when opened is directed to flow (40) over the battery unit (2).

10. A vehicle thermal management system according to claim 8, characterized in that the coolant that is allowed to flow through the sealing membrane or wall (34) when opened is directed into the pipe arrangement (6) via a connecting pipe (32), providing an enhanced flow (37, 38).

11. A vehicle thermal management system according to any one of the claims 8-10, characterized in that the coolant that is allowed to flow through the sealing membrane or wall (34) when opened originates from a vehicular cooling system (33) which is separated from the thermal management system (5''') before the sealing membrane or wall (34) is opened.

12. A method for providing auxiliary cooling to a vehicle battery unit (2) that uses a vehicle thermal management system (5, 5', 5", 5"', 5"") for cooling, characterized in that the method comprises the steps of:

(41) detonating (18, 36) a pyrotechnical charge (12; 29a-29h; 35); and

(42) using the forces from said detonation to provide an enhanced flow of at least one type of coolant.

13. A method according to claim 12, characterized in that the forces from said detonation (18, 36) are used to provide an enhanced flow of at least one type of coolant in the vehicle thermal management system (5, 5', 5'').

14. A method according to claim 13, characterized in that the enhanced flow of at least one type of coolant in the vehicle thermal management system is accomplished either by supplying coolant to the thermal management system or by increasing the pressure of the existing coolant in the thermal management system (5, 5', 5'').

15. A method according to claim 12, characterized in that the forces from said detonation are used to provide an enhanced flow of at least one type of coolant over the vehicle battery unit (2), outside the vehicle thermal management system (5' " , 5" " ) .