Use of a cooling pipe for electrically powered vehicles

Abstract

The invention relates to the use of a pipe (1) as a line section in a cooling circuit for a coolant, wherein: the cooling circuit is a component of a battery-cooling system of an electric car; the pipe (1) is a multi-layered pipe; the pipe (1) comprises an innermost layer (2) which comes into contact with the coolant; and the innermost layer (2) comprises a conductivity additive for increasing the electrical conductivity.

Description

[0001] Use of a cooling pipe for electrically powered vehicles

[0002] Description:

[0003] The invention relates to the use of a pipe as a line section in a cooling circuit of a coolant, wherein the cooling circuit is part of a battery cooling system of an electric car, wherein the pipe is a multi-layer pipe, wherein the pipe has an innermost layer which comes into contact with the coolant.

[0004] US 2013 / 0037154 A1 discloses the use of a multilayer pipe for conveying cooling oil for cooling components within motor vehicles with internal combustion engines. However, this device is only partially suitable for cooling drive batteries for electrically powered motor vehicles ("electric cars"), which is primarily due to the limited cooling capability of the disclosed pipe.

[0005] The invention is therefore based on the object of specifying a pipe which is better suited for electric cars and in particular for cooling electric cars - in particular batteries or drive batteries of electric cars - or enables greater cooling capacities.

[0006] This object is achieved by using a pipe as a line section in a cooling circuit of a coolant, wherein the cooling circuit is part of a battery cooling system of an electric car, wherein the pipe is a multi-layer pipe, wherein the pipe has an innermost layer that comes into contact with the coolant, characterized in that the innermost layer has a conductivity additive for increasing the electrical conductivity. The invention is based, first of all, on the finding that conventional fluid lines - as disclosed, for example, in US 2013 / 0037154 A1 - do not provide the required cooling capacity. Batteries or drive batteries of electric cars weigh several hundred kilograms and become very hot, especially during rapid charging, so that a very considerable cooling capacity must be provided.This is especially true due to the fact that the vehicle is stationary during charging and the airflow cannot therefore be used to assist cooling.

[0007] The invention is further based on the finding that a high volume flow of the coolant is essential for achieving high cooling performance. A high volume flow can be achieved by a higher pumping capacity with a constant inner pipe diameter, or by a larger inner pipe diameter with a constant pumping capacity—or a combination of these two variants. The invention is based, in particular, on the finding that the variant with the larger inner pipe diameter is more economically advantageous, provided the entire vehicle is considered and not just the fluid lines.

[0008] It was found that the high volume flow and the large internal diameter, and the associated relatively large friction surface between the coolant and the innermost layer, cause a relatively high electrostatic charge. This charge is particularly critical when cooling batteries or traction batteries, so that the battery cooling system is exposed to a relatively high risk of ignition or fire. In the case of electric cars, this is compounded by the fact that they are already difficult to extinguish. The electrostatic charge that continuously occurs during the flow of the fluid or coolant is counteracted by a continuous electrostatic discharge using the conductivity additive in the innermost layer. This makes sudden discharges or electric shocks significantly less likely or even completely avoids them.This effect is particularly advantageous in conjunction with immersion cooling, as the discharges are continuously and precisely carried on by the coolant and thus by the batteries. This significantly reduces the risk of fire in electric vehicles with large-diameter cooling tubes.

[0009] The invention is also based on the finding that the added conductivity additive according to the invention does not dissolve in the inner layer, but rather forms a phase in the form of small particles within the innermost layer. These particles, or the interfaces between these particles, are ultimately sites with an increased probability of crack formation, which weakens the innermost layer somewhat.

[0010] However, it was found that the increased cracking probability of the innermost layer is preferable at the expense of the innermost layer's increased electrical conductivity. Thus, layers further outward in the tube can compensate for the weakness of the innermost layer and also act as a barrier to the coolant. The result is a cooling tube that increases cooling performance without simultaneously increasing the fire risk, thus solving the problem mentioned above.

[0011] The term “electric car” preferably refers to purely electrically or partially electrically powered vehicles that use at least one electric motor for propulsion. The electric car is particularly preferably a battery-electric car that draws the energy for the electric drive motor partially or exclusively from a battery or drive battery. The term “battery” particularly preferably refers to drive batteries for or in electric cars. A drive battery of an electric car preferably comprises a housing. The drive battery advantageously has a plurality of electrically interconnected individual cells. The plurality of individual cells is expediently enclosed by the housing. The plurality of individual cells can be divided into several cell blocks, wherein each cell block can have a plurality of individual cells.The individual cells may be grouped into cell blocks in electrical and / or mechanical terms (positioning, arrangement).

[0012] The battery cooling system expediently comprises the cooling circuit and / or electrical components and / or electronic components and / or software components. The cooling circuit is preferably a component of a refrigeration machine. The cooling circuit preferably comprises fluid-carrying components (e.g., heat exchanger, compressor, throttle) and / or fluid lines of the refrigeration machine. The refrigeration machine is, in particular, a compression refrigeration machine. The cooling circuit of the compression refrigeration machine expediently comprises a plurality of fluid-carrying components and, in particular, a compressor or condenser and / or a heat source-side heat exchanger or evaporator and / or a heat sink-side heat exchanger or condenser or condenser and / or a throttle. It is expedient for the heat source-side heat exchanger or evaporator to exchange heat with the battery or drive battery.The heat exchanger / condenser / compressor on the heat sink side is advantageously cooled by air cooling. The air cooling can, for example, comprise a fan and a metallic heat-conducting element. The tube preferably forms a conduit section between two or more fluid-carrying components of the cooling circuit. The tube expediently has a central or longitudinal axis. The central or longitudinal axis expediently defines an axial, a radial, and a circumferential direction. The tube is preferably rotationally symmetrical with respect to the central or longitudinal axis over at least one axial section.

[0013] It is preferred that the conductivity additive comprises carbon and, for example, graphite or a conductive carbon black. Advantageously, the innermost layer comprises a plastic into which the conductivity additive is mixed to increase electrical conductivity. It is highly preferred that the conductivity additive is mixed with a plastic of the innermost layer. The conductivity additive is preferably not a plastic. It is highly preferred that the material of the innermost layer has a specific resistance of at most 100, 50, 20, 10, or 5 ohms. This ensures a sufficiently strong discharge tendency, so that the innermost layer can be designed relatively thin.

[0014] It is particularly preferred that the battery cooling system is an immersion cooling system. The term “immersion cooling system” preferably refers to a cooling system in which the individual cells and / or individual cell blocks of a drive battery are in direct contact with the coolant and are flushed by the coolant. It is preferred that the drive battery comprise an inlet for the coolant into the interior of the housing of the drive battery. Expediently, the housing comprises an outlet for the coolant. Immersion cooling is to be distinguished in particular from battery cooling systems in which plate-like heat exchangers are attached to the walls of the drive battery on the inside or outside of the housing, because here the individual cells or cell blocks do not come into direct contact with the coolant.Preferably, electrical components and / or the interior of the housing of a traction battery with immersion cooling are designed to come into contact with the coolant. The immersion cooling system enables very rapid heat dissipation, particularly the heat generated during charging, compared to conventional battery cooling systems that, for example, use cooling plates as heat exchange elements on the traction battery. However, due to the much larger surface area, a significantly larger volume flow and thus a larger inner diameter of the pipes within the cooling circuit are required.

[0015] It is preferred that the coolant be electrically insulating or dielectric. Preferably, the coolant comprises at least one oil, wherein the proportion of the at least one oil(s) constitutes more than 50, 70, 90, or 95 wt.% of the coolant.

[0016] It is highly preferred that the pipe comprises at least one plastic. Advantageously, the pipe comprises at least 30, 50, 70, 90, or 95 wt.% plastic. This allows for cost-effective production of the pipe by extrusion.

[0017] According to a particularly preferred embodiment, the pipe comprises at least one carrier layer, wherein the at least one carrier layer preferably comprises a plastic. The plastic of the at least one carrier layer is preferably a polyamide - in particular PA6 - and / or a fluoropolymer, in particular ethylene tetrafluoroethylene (ETFE). Good barrier effects against the coolant or the cooling oil are achieved with both PA6 and ETFE. This is relevant in view of the increased probability of cracking in the innermost layer. ETFE is preferred over other fluoropolymers due to its properties as a thermoplastic. Polyamides are preferred over fluoropolymers in the carrier layer because they are more mechanically robust. The carrier layer preferably encloses the innermost layer. The carrier layer advantageously lies against the innermost layer.The carrier layer(s) advantageously has / have a layer thickness or a combined layer thickness of at least 0.4, 0.6, or 0.7 mm, respectively. It is highly preferred that the carrier layer comprises the same plastic as the innermost layer. If the carrier layer comprises the same plastic as the innermost layer, the carrier layer adheres excellently to the innermost layer. The at least one carrier layer(s) advantageously has / have a layer thickness or a combined layer thickness of at most 2.0, 1.7, or 1.5 mm, respectively. The carrier layer(s) is / are preferably free of an additive for increasing electrical conductivity.

[0018] It is particularly advantageous if the innermost layer of the pipe is made of a polyamide or a fluoropolymer. This ensures that the conductivity additive in the innermost layer is well integrated into both polyamides and fluoropolymers. Consequently, the likelihood of leaching and cracking are minimized. In the case of polyamides, the amide groups create dipoles that form hydrogen bonds with the conductivity additive, thus firmly integrating the additive particles into the polyamide matrix. Fluoropolymers are very durable materials, so they inherently protect the conductivity additive from leaching. The polyamide of the innermost layer is preferably PA6 or PA9T. The fluoropolymer of the innermost layer is preferably ETFE. The pipe advantageously comprises an outer layer.This ensures very good mechanical protection from the outside and also good chemical protection against weather influences and other influences within the motor vehicle. In particular, the outer layer ensures that the carrier layer does not also have to assume the function of shielding from the outside, so that the carrier layer can be limited to the functions of mechanical support and the barrier effect. The outer layer can be the outermost layer of the pipe. According to one embodiment, the outer layer can be enclosed by another layer. According to a preferred embodiment, the outer layer comprises a polyamide and preferably PA12 and / or PA6.12. It is advantageous that the layer thickness of the outer layer is at least 0.10, 0.15, or 0.20 mm. The layer thickness of the outer layer is expediently at most 0.9, 0.7, 0.5, or 0.4 mm.

[0019] It is preferred that the tube has an adhesive layer. The adhesive layer advantageously encloses the carrier layer and preferably rests against the carrier layer. The outer layer expediently encloses the adhesive layer. It is preferred that the outer layer rests against the adhesive layer. The adhesive layer may have a layer thickness of at most 0.3, 0.25, 0.20, or 0.15 mm. The adhesive layer preferably comprises a plastic. The plastic of the adhesive layer may be a blend. The blend may comprise the plastic of the carrier layer and the plastic of the outer layer. The adhesive layer may comprise an adhesion modifier to improve the adhesion of the plastic of the adhesive layer, for example maleic anhydride.

[0020] According to a preferred embodiment, the innermost layer has a

[0021] The layer thickness is a maximum of 0.5, 0.4, or 0.3 mm. This ensures that only the smallest possible portion of the pipe wall is loaded or weakened by additive particles, so that the pipe achieves relatively high stability overall. The layer thickness of the innermost layer is advantageously at least 0.05, 0.06, 0.07, or 0.08 mm. This allows for sufficient, continuous wetting of the inside of the pipe with the innermost layer, taking into account the additive particles.

[0022] Advantageously, the pipe wall thickness is at least 0.5, 0.7, or 0.9 mm. This ensures sufficient stability of the pipe or pipe wall, even in the event of an accident, despite the relatively large inner diameter of this pipe due to the high volume flow. This compensates for the stability disadvantage of large pipes or pipes with a large inner diameter. The pipe wall thickness is preferably at most 3.0, 2.5, or 2.0 mm.

[0023] The pipe advantageously has an inner diameter of at least 10, 12, 13, or 14 mm. This ensures sufficient flow without requiring larger pumps or compressors. The inner diameter of the pipe, or the clear inner diameter, is preferably no more than 50, 40, 35, or 30 mm. The term "inner diameter" preferably refers to the clear inner diameter. In the case of corrugated pipes, this refers to the inner diameter formed by a corrugation trough over half a circumference (= clear inner diameter).

[0024] According to one embodiment, the pipe comprises—expediently in the axial direction—at least one corrugated pipe section. This makes the pipe more flexible overall and thus significantly more resilient—particularly in the event of an accident. Providing a corrugated pipe section thus counteracts the greater instability or risk of breakage and cracking that accompanies the provision of a relatively large inner diameter. The term 'corrugated pipe section' preferably refers to varying inner diameters and / or outer diameters or a varying inner contour and / or outer contour of the pipe wall along at least one axial section of the pipe, viewed in longitudinal section, wherein this variation of the inner and / or outer diameter or the inner and / or outer contour preferably forms a repeating pattern or repeating patterns. The contour of the repeating pattern is expediently sawtooth-shaped, square-wave-shaped, and / or wave-shaped.It is particularly preferred that an inner and / or outer contour of the wave troughs be curved. It is possible that an inner and / or outer contour of the wave crests be parallel to the longitudinal axis of the tube.

[0025] The repeat pattern preferably has an axial length (wavelength) of at most 50, 20 or 10 mm, as viewed in longitudinal section. The wavelength of the repeat pattern is advantageously at least 1.0, 1.5 or 2.0 mm. It is preferred that the corrugated pipe section comprises a plurality of periods of the repeat pattern. The corrugated pipe section may have a length of at least 50, 75 or 100 mm. According to a very preferred embodiment, the corrugated pipe section corresponds to at least 30%, 50%, 70%, 90%, 95% or 97% of the axial length of the pipe. An amplitude of the repeat pattern is preferably at least 0.5, 0.7 or 0.8 mm. An amplitude of the repeat pattern is preferably at most 3.0, 2.0 or 1.5 mm. According to one embodiment, the repeat pattern forms a closed ring in one revolution.According to one embodiment, the repeat pattern is generated by a spiral course, so that the repeat pattern does not form a closed ring in a complete circuit.

[0026] According to one embodiment, the pipe is a smooth pipe along its entire length, or the pipe has no corrugated pipe sections along its entire length. The term "smooth pipe" preferably means a constant inner diameter and / or constant outer diameter along the entire length of the pipe.

[0027] Advantageously, the pipe is part of a fluid line, wherein the fluid line has at least one line connector, wherein the line connector is preferably designed as a coupling socket. This shifts the complexity of the fluid technology away from a fluid-carrying component to be connected to the fluid line itself. As a result, suppliers can provide simpler connections to the units, thereby ensuring better division of labor and overall cost-effectiveness.

[0028] An embodiment of the invention is explained in more detail below with reference to two schematic figures.

[0029] Fig. 1 shows a cross section through a pipe according to the invention and

[0030] Fig. 2 shows a longitudinal section through the pipe from Fig. 1 .

[0031] Fig. 1 discloses an embodiment of a pipe 1 according to the invention. According to the invention, the pipe 1 is used as a line section in a cooling circuit of a cooling system of an electric car. The cooling system preferably cools a drive battery of the electric car. The cooling system or battery cooling system is preferably designed as an immersion cooling system. The cooling circuit of this embodiment expediently comprises several fluid-carrying components. A dielectric coolant, and particularly preferably a cooling oil, is preferably used as the coolant for the immersion cooling system.

[0032] The fluid-carrying components preferably comprise a compressor, an evaporator, a condenser, and / or a throttle. It is expedient for the evaporator to exchange heat with the battery or drive battery. The condenser is advantageously cooled by air cooling. The air cooling can, for example, comprise a fan and a metallic heat-conducting element. The pipe is preferably a conduit section that is fluidically arranged between at least two fluid-carrying components. Due to T-connectors, the pipe 1 can also be fluidically arranged between three or more fluid-carrying components.

[0033] The battery cooling system or immersion cooling system is preferably a component of an electric vehicle's rapid charging system. The charging curve of the rapid charging system is preferably designed so that the charging power at a 25% charge level is no less than 10 kW, 15 kW, 20 kW, 30 kW, or 40 kW. The term "charging curve" preferably refers to the maximum possible charging power plotted against the charge level under ideal charging conditions (temperature, electrical infrastructure, etc.).

[0034] The pipe 1 of this embodiment comprises a total of four layers 2, 3,

[0035] 4, 5, see Fig. 1. The innermost layer 2 preferably comprises PA6 as the main component (relative maximum weight fraction) and may have a layer thickness of 0.15 mm. The innermost layer 2 particularly preferably comprises a conductivity additive to increase electrical conductivity. The conductivity additive preferably comprises a conductive carbon black. The material of the innermost layer 2 advantageously has a specific resistance of 1 μm.

[0036] According to a preferred aspect of the invention, the pipe 1 has a carrier layer 3. The carrier layer 3 advantageously comprises the same plastic as the innermost layer 2, so that the carrier layer 3 of this exemplary embodiment preferably comprises PA6 as its main component. Preferably, the carrier layer 3 contains no additive to increase electrical conductivity. This ensures that the carrier layer 3 adheres well to the innermost layer 2, while at the same time, the absence of conductive carbon black and preferably of any particles in the carrier layer 3 ensures particularly high fracture strength. The layer thickness of the carrier layer 3 in this exemplary embodiment is 0.95 mm.

[0037] The pipe 1 of this exemplary embodiment advantageously has an outer layer 5. The outer layer 5 preferably comprises a plastic, more preferably a polyamide, and particularly preferably PA12 or PA6.12. The layer thickness of the outer layer 5 can be, for example, 0.3 mm. Preferably, the pipe 1 comprises an adhesive layer 4 between the carrier layer 3 and the outer layer 5. The adhesive layer 4 may have a layer thickness of 0.1 mm. The adhesive layer 4 of this exemplary embodiment preferably comprises a PA6 / 12 copolymer and therefore adheres very well to both the PA6 carrier layer 3 and the outer layer 5. In this exemplary embodiment, the carrier layer 3 encloses the innermost layer 2, with the carrier layer 3 preferably adjoining the innermost layer 2. The adhesive layer 4 advantageously encloses the carrier layer 3, with the adhesive layer 4 preferably adjoining the carrier layer 3.It is preferred that the outer layer 5 encloses the adhesive layer 4, wherein the outer layer 5 preferably rests against the adhesive layer 4.

[0038] The dot-dash line in Fig. 2 represents an axis (central or longitudinal axis) of the pipe 1. The four layers 2, 3, 4, 5 from Fig. 1 are not shown in Fig. 2 for the sake of simplicity. The pipe 1 preferably comprises a corrugated pipe section, wherein the corrugated pipe section in this embodiment accounts for 90% of the axial length of the pipe 1. The corrugated pipe section preferably has a plurality of corrugation troughs 6 and corrugation crests 7.

[0039] The wave troughs 6 define a (clear) inner diameter ID. An outer side of the wave crests 7 determines an outer diameter AD. The distance between two wave crests 7 or two wave troughs 6 in the axial direction expediently defines a wavelength WL. A wave trough 6 and a wave crest 7 together preferably form a repeating pattern with the wavelength WL. According to Fig. 2, an amplitude A preferably corresponds to half the radial distance between a wave crest 7 and a wave trough 6 on the outside of the tube 1.

[0040] In this exemplary embodiment, the inner diameter ID of the pipe 1 may be around 16 mm. It is preferred that the thickness of the pipe wall amounts to 1.5 mm - preferably measured in a corrugation trough 6. The amplitude A of the corrugations in the pipe wall is 1 mm in this exemplary embodiment. Consequently, the outer diameter AD of this exemplary embodiment amounts to 23 mm. The wavelength WL of the repeat pattern may be 4 mm. The pipe 1 of the present exemplary embodiment combines high flexibility with a relatively thick and therefore correspondingly robust pipe wall, so that the pipe 1 ensures particularly high safety in the event of an accident. The use of polyamide 6 in the innermost layer 2 and also in the carrier layer 3 ensures good chemical resistance to coolants, in particular to cooling oils.By adding conductive carbon black, static charges are reliably discharged in a controlled manner via the innermost layer 2, so that the drive battery in particular is protected from spontaneous electrical discharges.

[0041] While the outer layer 5 ensures good protection against external influences—especially in the event of an accident—the adhesive layer 4 provides a strong bond between the outer layer 5 and the carrier layer 3. The carrier layer 3, in turn, is very well bonded to the innermost layer 2 due to the same main component, PA6, creating a very robust and resilient layered composite. This very robust layered composite, combined with high flexibility, allows for correspondingly large inner diameters (ID), thus enabling high cooling performance.

[0042] List of reference symbols:

Claims

Claims:

1. Use of a pipe (1) as a line section in a cooling circuit of a coolant, wherein the cooling circuit is part of a battery cooling system of an electric car, wherein the pipe (1) is a multi-layer pipe, wherein the pipe (1) has an innermost layer (2) which comes into contact with the coolant, characterized in that the innermost layer (2) has a conductivity additive for increasing the electrical conductivity.

2. Use according to claim 1, wherein the battery cooling system is an immersion cooling system.

3. Use according to one of claims 1 or 2, wherein the tube (1) comprises at least one carrier layer (3), wherein the at least one carrier layer (3) preferably comprises a polyamide and / or a fluoropolymer.

4. Use according to one of claims 1 to 3, wherein the innermost layer (2) of the tube (1) comprises a polyamide and / or a fluoropolymer.

5. Use according to one of claims 1 to 4, wherein the pipe (1) comprises an outer layer (5), wherein the outer layer (5) preferably comprises a polyamide.

6. Use according to one of claims 1 to 5, wherein a layer thickness of the innermost layer (2) is at most 0.5 or 0.4 or 0.3 mm.

7. Use according to one of claims 1 to 6, wherein a pipe wall thickness of the pipe (1) is at least 0.5 or 0.7 or 0.9 mm.

8. Use according to one of claims 1 to 7, wherein the tube (1) has an inner diameter (ID) of at least 12 or 13 or 14 mm.

9. Use according to one of claims 1 to 8, wherein the pipe (1) comprises at least one corrugated pipe section.

10. Use according to one of claims 1 to 9, wherein the pipe is part of a fluid line, wherein the fluid line has at least one line connector, wherein the line connector is preferably designed as a coupling socket.

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