Indirect cooling system capable of uniformly cooling battery modules and battery pack including the same

Disclosed herein are a cooling system and a battery pack including the same. The cooling system includes a refrigerant introduction port, through which liquid refrigerant is introduced, a refrigerant discharge port, through which the liquid refrigerant is discharged, a plurality of refrigerant pipes configured to communicate with the refrigerant introduction port or the refrigerant discharge port, one or more pipe connection members configured to interconnect two or more of the refrigerant pipes such that the refrigerant pipes communicate with each other, the pipe connection members being configured to divide the liquid refrigerant or to change the flow direction of the liquid refrigerant between the connected refrigerant pipes, and a plurality of cooling plates, each of which has a hollow flow channel communicating with at least one of the refrigerant pipes and each of which has one surface on which a corresponding one of the battery modules is mounted, the liquid refrigerant being circulated along the hollow flow channel.

TECHNICAL FIELD

This application claims the benefit of Korean Patent Application No. 10-2015-0172265 filed on Dec. 4, 2015 with the Korean Intellectual Property Office, the disclosure of which is herein incorporated by reference in its entirety.

The present invention relates to an indirect cooling system capable of uniformly cooling battery modules and a battery pack including the same.

BACKGROUND

In recent years, a secondary battery, which can be charged and discharged, has been widely used as an energy source for wireless mobile devices. In addition, the secondary battery has attracted considerable attention as a power source for electric vehicles (EV), hybrid electric vehicles (HEV), and plug-in hybrid electric vehicles (Plug-in HEV), which have been developed to solve problems, such as air pollution, caused by existing gasoline and diesel vehicles that use fossil fuels.

Small-sized mobile devices use one or a few battery cells for each device. On the other hand, middle or large-sized devices, such as vehicles, use a battery module including a plurality of modularized battery cells or a battery pack including a plurality of battery modules electrically connected to each other, because high output and large capacity are necessary for such middle or large-sized devices.

Preferably, a middle or large-sized battery module or a middle or large-sized battery pack is manufactured so as to have as small a size and weight as possible. For this reason, a prismatic battery or a pouch-shaped battery, which can be stacked with high integration and has a small weight to capacity ratio, is usually used as a battery cell (i.e. a unit cell) of the middle or large-sized battery module or the middle or large-sized battery pack. In particular, much interest is currently focused on the pouch-shaped battery, which uses an aluminum laminate sheet as a sheathing member, because the pouch-shaped battery is lightweight, the manufacturing cost of the pouch-shaped battery is low, and it is easy to modify the shape of the pouch-shaped battery.

Battery cells constituting the middle or large-sized battery module or the middle or large-sized battery pack are secondary batteries that can be charged and discharged. Consequently, a large amount of heat is generated from the high-output, large-capacity secondary batteries during the charge and discharge of the secondary batteries. In particular, the laminate sheet of a pouch-shaped battery cell has a polymer material exhibiting low thermal conductivity coated on the surface thereof, with the result that it is difficult to effectively lower the overall temperature of the battery cell.

If heat, generated from the battery cells during the charge and discharge of the battery cells, is not effectively removed from the battery cells, the heat accumulates in the battery cells, with the result that deterioration of the battery cells is accelerated. According to circumstances, the battery cells may even catch fire or explode. For this reason, a high-output, large-capacity battery module or a high-output, large-capacity battery pack needs a cooling system for cooling battery cells mounted in the battery module or the battery pack.

Meanwhile, at least one battery module mounted in a middle or large-sized battery pack is generally manufactured by stacking a plurality of battery cells with high integration. In this case, the battery cells are stacked in the state in which the battery cells are arranged at predetermined intervals such that heat, generated from the battery cells during the charge and discharge of the battery cells, is removed. For example, the battery cells may be sequentially stacked in the state in which the battery cells are arranged at predetermined intervals without using an additional member. Alternatively, in the case in which the battery cells have low mechanical strength, one or more battery cells may be mounted in a cartridge, and a plurality of cartridges may be stacked to constitute a battery module. In the above structure, refrigerant flow channels may be defined between the stacked battery cells or between the stacked battery modules such that heat accumulating between the stacked battery cells or between the stacked battery modules is effectively removed.

In the battery pack cooling structure described above, however, a plurality of refrigerant flow channels must be provided so as to correspond to a plurality of battery cells or battery modules, with the result that the overall size of the battery pack is increased.

In addition, if the battery pack includes a larger number of battery cells, a larger number of parts are added to the cooling structure, with the result that the volume of the battery pack is increased, the manufacturing process is complicated, and cost incurred to design the cooling structure is greatly increased.

Furthermore, a plurality of parts is used to constitute a structure in which heat from the battery modules or the battery cells is transferred to the refrigerant flow channels, by which the heat is removed, with the result that thermal conductivity is lowered and thus cooling efficiency is reduced.

Therefore, there is a high necessity for a cooling system that can be designed so as to have a compact structure while exhibiting high cooling efficiency.

Technical Problem

The present invention has been made to solve the above problems and other technical problems that have yet to be resolved.

Specifically, it is an object of the present invention to provide a cooling system having a compact structure that is capable of uniformly removing heat generated from battery modules without using a large number of members.

It is another object of the present invention to provide a battery pack configured to be installed in a device, such as a vehicle, without positional limitations.

Technical Solution

In accordance with one aspect of the present invention, the above and other objects can be accomplished by the provision of a cooling system for cooling a plurality of battery modules, the cooling system including a refrigerant introduction port, through which liquid refrigerant is introduced, a refrigerant discharge port, through which the liquid refrigerant is discharged, a plurality of refrigerant pipes configured to communicate with the refrigerant introduction port or the refrigerant discharge port, one or more pipe connection members configured to interconnect two or more of the refrigerant pipes such that the refrigerant pipes communicate with each other, the pipe connection members being configured to divide the liquid refrigerant or to change the flow direction of the liquid refrigerant between the connected refrigerant pipes, and a plurality of cooling plates, each of which has a hollow flow channel communicating with at least one of the refrigerant pipes and each of which has one surface on which a corresponding one of the battery modules is mounted, the liquid refrigerant being circulated along the hollow flow channel, wherein the liquid refrigerant is divided by the pipe connection members, the divided streams of liquid refrigerant are supplied to the respective cooling plates, and the divided streams of liquid refrigerant are combined after being discharged from the respective cooling plates, whereby the battery modules are cooled by the respective cooling plates as the result of thermal conduction of the divided streams of liquid refrigerant.

That is, in the cooling system according to the present invention, the coolant flow channels are defined in the cooling plates, on which the battery modules are mounted. Compared to the structure in which the coolant flow channels are defined between the battery modules or between the battery cells, therefore, the cooling system according to the present invention has a compact structure. In addition, the divided streams of liquid refrigerant are introduced into the respective cooling plates to independently cool the battery modules mounted on the respective cooling plates, thereby achieving high uniformity of cooling of the battery modules.

Particularly, in the cooling system according to the present invention, the liquid refrigerant is supplied to the respective cooling plates in the state in which the temperature of the liquid refrigerant is almost uniform as the result of systematic coupling among the refrigerant pipes. Hereinafter, the structure of the cooling system according to the present invention will be described in detail through the following non-limiting examples.

In a concrete example, the refrigerant pipes may include a first refrigerant pipe connected to the refrigerant introduction port, a second refrigerant pipe connected to the refrigerant discharge port, a plurality of third refrigerant pipes disposed between the first refrigerant pipe and the second refrigerant pipe in the state of being connected to the respective pipe connection members such that the third refrigerant pipes communicate with the first refrigerant pipe and the second refrigerant pipe, and a plurality of fourth refrigerant pipes connected to the third refrigerant pipes via the pipe connection members, the fourth refrigerant pipes also being connected to the flow channels of the respective cooling plates.

More specifically, in the present invention, the third refrigerant pipes may be connected to the pipe connection members in order to guide the overall circulation of the liquid refrigerant. In addition, some of the third refrigerant pipes may be connected to the first refrigerant pipe and the second refrigerant pipe, with the result that the refrigerant introduction port and the refrigerant discharge port may communicate with the third refrigerant pipes.

Consequently, the liquid refrigerant may flow from the refrigerant introduction port to the first refrigerant pipe, and may then be circulated along the third refrigerant pipes. Subsequently, the liquid refrigerant may be discharged through the refrigerant discharge port via the second refrigerant pipe.

The fourth refrigerant pipes are pipes disposed between the third refrigerant pipes, along which the liquid refrigerant is circulated, and the cooling plates for interconnecting the third refrigerant pipes and the cooling plates. The fourth refrigerant pipes may guide the liquid refrigerant from the third refrigerant pipes to the cooling plates, or may guide the liquid refrigerant from the cooling plates to the third refrigerant pipes.

The first refrigerant pipe and the second refrigerant pipe may each have an inner diameter greater than the inner diameter of each of the other refrigerant pipes such that a large amount of liquid refrigerant can be introduced into the first refrigerant pipe and a large amount of liquid refrigerant can be discharged from the second refrigerant pipe and such that the liquid refrigerant can be pressurized and accelerated when the liquid refrigerant flows from a refrigerant pipe having a larger inner diameter to a refrigerant pipe having a smaller inner diameter. Specifically, the first refrigerant pipe and the second refrigerant pipe may each have an inner diameter equivalent to 101% to 200% of the inner diameter of each of the third refrigerant pipes.

If the first refrigerant pipe and the second refrigerant pipe each have an inner diameter less than 101% of the inner diameter of each of the third refrigerant pipes, the amount of liquid refrigerant that is introduced and discharged is too small to be smoothly circulated in the cooling system, and the liquid refrigerant is not sufficiently pressurized or accelerated, which is not desirable.

If the first refrigerant pipe and the second refrigerant pipe each have an inner diameter greater than 200% of the inner diameter of each of the third refrigerant pipes, on the other hand, the overall size of the cooling system is increased, and the mobility of the liquid refrigerant in the pipe connection members connected to the third refrigerant pipes is reduced due to excessive fluid pressure, which is also not desirable.

Meanwhile, at least one of the pipe connection members may be connected to at least one of the third refrigerant pipes and at least one of the fourth refrigerant pipes such that the liquid refrigerant is divided and distributed into the at least one of the third refrigerant pipes and the at least one of the fourth refrigerant pipes, thereby adjusting the flow direction of the liquid refrigerant.

That is, some of the liquid refrigerant may flow into a fourth refrigerant pipe through a pipe connection member, and the remainder of the liquid refrigerant may flow along a third refrigerant pipe.

Subsequently, the remainder of the liquid refrigerant may be divided and distributed into another fourth refrigerant pipe and another third refrigerant pipe through another pipe connection member.

Alternatively, at least one of the pipe connection members may be connected to at least one of the third refrigerant pipes and at least one of the fourth refrigerant pipes such that liquid refrigerant divided and distributed into the at least one of the third refrigerant pipes and the at least one of the fourth refrigerant pipes is combined into a single body of liquid refrigerant, thereby adjusting the flow rate of the liquid refrigerant.

Specifically, the liquid refrigerant is circulated along the flow channels defined in the cooling plates, flows into the fourth refrigerant pipes, and reaches the pipe connection members. Since the third refrigerant pipes are connected to the pipe connection members, the liquid refrigerant flowing in the fourth refrigerant pipes is combined with the liquid refrigerant flowing in the third refrigerant pipes in the pipe connection members.

Each of the pipe connection members may include a plurality of connection conduits connected to the refrigerant pipes in order to adjust the flow direction of the liquid refrigerant and to combine the divided streams of liquid refrigerant.

Specifically, each of the pipe connection members may include n (n=2) connection conduits for interconnecting the refrigerant pipes in the state in which ends of the connection conduits are inserted into the refrigerant pipes. When n is equal to or greater than 3, at least one of the connection conduits may have an inner diameter equivalent to 5% to 99% of the inner diameter of each of the other connection conduits.

Consequently, the liquid refrigerant may be divided and distributed into the respective connection conduits such that the liquid refrigerant can be guided to different refrigerant pipes.

In addition, the liquid refrigerant may be divided and distributed into the connection conduits at different flow speeds and flow rates due to different inner diameters of the connection conduits.

In general, cooling speed is greatly affected by the circulation of the liquid refrigerant. For this reason, the flow speed of the liquid refrigerant is critical. As a result, it is advantageous to supply the liquid refrigerant to the cooling plates, in which cooling is actually performed, at a high flow speed. Consequently, the connection conduits through which the liquid refrigerant is distributed into the cooling plates may have a relatively small inner diameter. The fourth refrigerant pipes, which communicate with the respective cooling plates, may be connected to the connection conduits through which the liquid refrigerant is distributed into the cooling plates.

Meanwhile, it is advantageous for a large amount of liquid refrigerant not having undergone heat exchange, i.e. a large amount of liquid refrigerant having a temperature substantially equal to the temperature of the liquid refrigerant when the liquid refrigerant is introduced through the refrigerant introduction port, to flow along the third refrigerant pipes, which guide the overall circulation of the liquid refrigerant, and to be divided and distributed through the respective pipe connection members, before the liquid refrigerant is supplied to the cooling plates. For this reason, the connection conduits connected to the third refrigerant pipes may have a relatively large inner diameter.

That is, in the cooling system according to the present invention, the connection conduits connected to the respective refrigerant pipes may have different inner diameters such that the liquid refrigerant can be distributed into the respective refrigerant pipes at different flow speeds and different flow rates. As described above, the difference in inner diameter between the connection conduits may be 5% to 99%.

If the difference in inner diameter between the connection conduits is less than 1%, the liquid refrigerant is little pressurized and accelerated when the liquid refrigerant is divided, with the result that rapid circulation in the cooling plates is not achieved, which is not desirable. If the difference in inner diameter between the connection conduits is greater than 99%, on the other hand, the flow pressure of the liquid refrigerant is increased, whereas the flow speed of the liquid refrigerant is decreased, which is also not desirable.

In consideration of the above description, the difference in inner diameter between the connection conduits may be specifically 10% to 90%, and more specifically 30% to 80%.

As described above, the flow speed and flow rate of the liquid refrigerant affect the cooling uniformity and efficiency of the cooling system. In the present invention, therefore, the inner diameters of the refrigerant pipes may also be designed in consideration of the flow speed and flow rate of the liquid refrigerant. Consequently, the flow speed and flow rate of the liquid refrigerant flowing in the refrigerant pipes may be set based on the inner diameters of the connection conduits and the inner diameters of the refrigerant pipes connected to the connection conduits.

In the cooling system according to the present invention, however, in the case in which the third refrigerant pipes, which guide the overall circulation of the liquid refrigerant, and the fourth refrigerant pipes, which guide only a portion of the liquid refrigerant, are considerably different from each other in terms of the flow speed and flow rate of the liquid refrigerant, the overall mobility of the liquid refrigerant may be reduced or the liquid refrigerant may stagnate at specific points in the cooling system (for example, the pipe connection members through which the liquid refrigerant is combined), with the result that the cooling efficiency of the cooling system may be greatly reduced. For this reason, the ratio of the inner diameter of the fourth refrigerant pipes to that of the third refrigerant pipes may have a specific value.

In a concrete example, each of the fourth refrigerant pipes may have an inner diameter equivalent to 5% to 99% of the inner diameter of each of the third refrigerant pipes.

The inner diameter of each of the fourth refrigerant pipes may be set to accelerate the liquid refrigerant toward the cooling plates in the same manner as in the pipe connection members. If the difference in inner diameter between the fourth refrigerant pipes and the third refrigerant pipes is less than 1%, the liquid refrigerant is little accelerated, with the result that rapid circulation in the cooling plates is not achieved, which is not desirable. If the difference in inner diameter between the fourth refrigerant pipes and the third refrigerant pipes is greater than 99%, on the other hand, the flow pressure of the liquid refrigerant is increased and fluid resistance is increased, with the result that the flow speed of the liquid refrigerant is greatly decreased, which is also not desirable.

In the present invention, as previously described, the fourth refrigerant pipes may be classified into fourth refrigerant pipes for guiding the liquid refrigerant to the cooling plates and fourth refrigerant pipes for guiding the liquid refrigerant from the cooling plates to the pipe connection members. The fourth refrigerant pipes for guiding the liquid refrigerant to the cooling plates and the fourth refrigerant pipes for guiding the liquid refrigerant from the cooling plates to the pipe connection members may be different from each other in terms of size.

Specifically, the fourth refrigerant pipes for guiding the liquid refrigerant from the cooling plates to the pipe connection members may have a relatively large inner diameter, which is advantageous in discharging a large amount of liquid refrigerant from the cooling plates to the pipe connection members.

However, it is not desirable for the inner diameter of the fourth refrigerant pipes to be equal to the inner diameter of the third refrigerant pipes, since it is advantageous for the flow speed of the liquid refrigerant to be high even in the above structure. In this case, therefore, each of the fourth refrigerant pipes may have an inner diameter equivalent to 30% to 99%, and specifically 60% to 99%, of the inner diameter of each of the third refrigerant pipes.

On the other hand, the fourth refrigerant pipes for guiding the liquid refrigerant to the cooling plates may have a relatively small inner diameter in order to accelerate the liquid refrigerant. For example, each of the fourth refrigerant pipes may have an inner diameter equivalent to 30% to 99%, specifically 10% to 90%, and more specifically 50% to 80%, of the inner diameter of each of the third refrigerant pipes.

Each of the connection conduits is inserted into a corresponding one of the refrigerant pipes in an interference fitting fashion such that the refrigerant pipes are connected to the connection conduits. For such interference fitting, each of the refrigerant pipes may have an inner diameter smaller than the diameter of a corresponding one of the connection conduits. Specifically, each of the refrigerant pipes may have an inner diameter equivalent to 70% to 100% of the diameter of a corresponding one of the connection conduits. In addition, in this structure, the liquid refrigerant may be accelerated when the liquid refrigerant flows into the refrigerant pipes through the connection conduits.

If each of the refrigerant pipes has an inner diameter less than 70% of the diameter of a corresponding one of the connection conduits, the liquid refrigerant does not smoothly flow to the refrigerant pipes since the inner diameter of each of the refrigerant pipes is too small. Furthermore, interference fitting is substantially impossible, which is not desirable. If each of the refrigerant pipes has an inner diameter greater than 100% of the diameter of a corresponding one of the connection conduits, each of the refrigerant pipes and a corresponding one of the connection conduits cannot be securely coupled to each other, which is also not desirable.

The refrigerant pipes may be configured to have at least one selected from between a straight structure and a curved structure.

For example, each of the fourth refrigerant pipes, which are connected to the cooling plates, may have a curved structure such that the fourth refrigerant pipes can be flexibly connected to the cooling plates regardless of the positions of the cooling plates. The third refrigerant pipes, which guide the overall circulation of the liquid refrigerant in the cooling system, may have a straight structure such that the length of the third refrigerant pipes is minimized.

Each of the straight refrigerant pipes may be made of a rigid plastic material. For example, the rigid plastic material may be high-strength nylon or polyvinyl chloride, which exhibits high mechanical strength and high insulation for the liquid refrigerant. However, the present invention is not limited thereto.

In addition, each of the straight refrigerant pipes may be coupled to a corresponding one of the pipe connection members as the result of the end of each of the straight refrigerant pipes wrapping the corresponding one of the pipe connection members by thermal shrinkage. According to circumstances, each of the straight refrigerant pipes and a corresponding one of the pipe connection members may be more securely coupled to each other using a binding member, such as a clamping member.

Each of the curved refrigerant pipes may be made of a flexible rubber material that is capable of being partially stretched or curved such that the curved refrigerant pipes can be flexibly connected to the cooling plates. Specifically, each of the curved refrigerant pipes may be made of ethylene propylene diene monomer (EPDM), which exhibits high elasticity and mechanical strength.

In addition to the fourth refrigerant pipes, the first refrigerant pipe and the second refrigerant pipe may be curved so as to flexibly correspond to the positions of the refrigerant introduction port and the refrigerant discharge port.

In addition, each of the curved refrigerant pipes may be securely coupled to a corresponding one of the pipe connection members as the result of a clamping member wrapping the end of the curved refrigerant pipe in the state in which the curved refrigerant pipe is inserted into a corresponding one of the connection conduits of the pipe connection member.

Meanwhile, in a concrete example, each of the cooling plates may be configured to have a structure in which a first conduit and a second conduit, which communicate with the hollow flow channel in the cooling plate, protrude outward from the cooling plate, the first conduit of each of the cooling plates may be connected to a corresponding one of the fourth refrigerant pipes into which the liquid refrigerant is introduced, and the second conduit of each of the cooling plates may be connected to a corresponding one of the fourth refrigerant pipes from which the liquid refrigerant is discharged.

Each of the cooling plates may include a base plate having a plurality of protrusions formed thereon and a cover plate coupled to the base plate in the state of being in tight contact with the protrusions for defining a flow channel in the remaining space of the base plate excluding the protrusions.

Consequently, each of the cooling plates may be configured to have a structure in which the flow channel, along which the liquid refrigerant flows, is defined in the space in the base plate defined by the protrusions. The base plate and the cover plate may be fastened to each other using mechanical fastening members, such as bolts and nuts. In addition, a water-tight member, made of rubber or silicon, may be provided between the base plate and the cover plate in order to prevent the leakage of liquid refrigerant from between the base plate and the cover plate.

The protrusions may include first protrusions discontinuously protruding from one end of the base plate toward the other end of the base plate and a second protrusion disposed between the first protrusions, the second protrusion continuously protruding from one end of the base plate toward the other end of the base plate.

A vortex may be generated in the liquid refrigerant between the discontinuously protruding first protrusions, whereby the flow speed of the liquid refrigerant may be increased.

In general, cooling speed is proportional to the flow speed of liquid refrigerant before heat exchange and to the speed at which the liquid refrigerant is distributed over the area to be cooled. Therefore, it is advantageous for the liquid refrigerant to rapidly flow and be distributed in the flow channel defined in each of the cooling plates, in which cooling is performed through actual heat exchange.

In the present invention, as described above, a vortex may be generated in the liquid refrigerant between the discontinuously protruding first protrusions, by which the liquid refrigerant is irregularly divided, with the result that the liquid refrigerant may flow while being more rapidly distributed, thereby increasing the cooling speed of each of the cooling plates and thus improving the cooling efficiency of each of the cooling plates.

Each of the first protrusions may be generally configured to have a streamlined structure in order to reduce fluid resistance to the liquid refrigerant. In addition, the first protrusions may have different sizes and shapes. Alternatively, the first protrusions may have the same size and shape. In addition, the distributed liquid refrigerant is circulated along the hollow flow channel while being guided by the continuously protruding second protrusions.

The base plate may be provided on the surface thereof opposite the surface on which the protrusions are formed with an insulating material, such as plastic foam or heat-resistant ceramic, in order to prevent the introduction of heat into the flow channel from the outside, excluding a corresponding one of the battery modules.

The cover plate may be provided on the surface thereof that is disposed in tight contact with a corresponding one of the battery modules, specifically on the surface thereof opposite the surface that faces the base plate, with a thermal interface material (TIM) pad for accelerating thermal conduction in order to achieve more efficient thermal conduction between the cover plate and the battery module. The thermal interface material pad reduces thermal conduction resistance in the state of being in contact with the battery module.

The thermal interface material pad may be made of thermally conductive grease, thermally conductive epoxy-based bond, thermally conductive silicone, thermally conductive adhesive tape, or a graphite sheet. However, the present invention is not limited thereto. Any one of the above-mentioned materials may be used, or two or more of the above-mentioned materials may be combined.

As described above, each of the cooling plates is configured to have a structure in which heat generated from a corresponding one of the battery modules is removed by the liquid refrigerant flowing in the cooling plate. Specifically, each of the cooling plates may be configured such that a corresponding one of the battery modules is mounted on the cover plate and such that each of the cooling plates receives heat from a corresponding one of the battery modules and transfers the heat to the liquid refrigerant flowing in the hollow flow channel, thereby cooling the battery module. Consequently, it is possible for the cooling plates to cool the battery modules through the above-described process.

In addition, at least one of the cooling plates may have an area equivalent to 100% to 300% of the area of each of the other cooling plates, and the at least one of the cooling plates may be different in size and shape of the protrusions from the other cooling plates.

The area of each of the cooling plates may correspond to the size of a corresponding one of the battery modules, which is mounted on the cooling plate. In the cooling system according to the present invention, a plurality of battery modules having different sizes and shapes may be mounted on cooling plates having different areas such that the battery modules can be cooled by the respective cooling plates.

In a middle or large-sized battery pack including a plurality of battery modules, however, the overall performance of the battery pack is reduced if the performance of some of the battery modules is reduced. One of the main factors that cause such performance nonuniformity is nonuniformity of cooling between the battery modules. For this reason, it is necessary for the cooling system to have a structure that is capable of minimizing the temperature difference between the battery modules.

In the cooling system according to the present invention, therefore, the flow speed and flow rate of the liquid refrigerant may be set based on the inner diameters of the connection conduits and the inner diameters of the refrigerant pipes connected to the connection conduits, as described above. Consequently, the flow speed and flow rate of the liquid refrigerant may be changed in the cooling plates, which have different cooling areas, whereby the cooling speed in the cooling plates may be maintained uniform.

In addition, the flow speed and flow rate of the liquid refrigerant in each of the cooling plates may be changed by varying the size and the shape of the protrusions.

For example, a cooling plate having a relatively small cooling area may be configured such that a small number of protrusions are provided and the shape of the protrusions is relatively small. As a result, the liquid refrigerant may be circulated along the hollow flow channel defined in the cooling plate at a relatively low flow speed and a relatively low flow rate. On the other hand, a cooling plate having a relatively large cooling area may be configured such that a large number of protrusions are provided and the shape of the protrusions is relatively large. As a result, the liquid refrigerant may be circulated along the hollow flow channel defined in the cooling plate at a relatively high flow speed and a relatively high flow rate.

The cover plate and the base plate of each of the cooling plates may be made of a material that exhibits high thermal conductivity. Specifically, the cover plate and the base plate of each of the cooling plates may be made of at least one selected from among copper, aluminum, tin, nickel, stainless steel, and thermally conductive polymer. However, the present invention is not limited thereto.

In brief, the cooling structure of the cooling system according to the present invention is configured such that the liquid refrigerant is circulated along the third refrigerant pipes, some of the liquid refrigerant in the third refrigerant pipes is introduced into the cooling plates through the pipe connection members, cooling is performed in the cooling plates as described above, and the liquid refrigerant is gathered in the third refrigerant pipes.

More specifically, the liquid refrigerant introduced into the first refrigerant pipe through the refrigerant introduction port may be divided into first liquid streams, which flow in the third refrigerant pipes via the pipe connection members, and second liquid streams, which flow in the fourth refrigerant pipes via the pipe connection members.

The second liquid streams may be introduced into the hollow flow channels in the cooling plates via the fourth refrigerant pipes and the first conduits connected to the fourth refrigerant pipes, may flow along the hollow flow channels, and may be discharged from the cooling plates via the second conduits and the fourth refrigerant pipes connected to the second conduits.

Subsequently, the discharged second liquid streams may be guided to the pipe connection members via the fourth refrigerant pipes connected to the second conduits and may be combined with the first liquid streams flowing in the third refrigerant pipes connected to pipe connection members, and the combined liquid refrigerant may be discharged through the refrigerant discharge port via the second refrigerant pipe.

In a concrete example, the cooling system may be configured such that N−1 (N≥3) cooling plates are arranged side by side in the lateral direction to constitute a cooling plate array, a first cooling plate is disposed in front of the cooling plates so as to correspond to the middle part of the cooling plate array, and the refrigerant introduction port and the refrigerant discharge port are arranged side by side in front of the first cooling plate in the state in which the refrigerant introduction port and the refrigerant discharge port are connected to the first refrigerant pipe and the second refrigerant pipe, respectively.

In this case, the first cooling plate and the N−1 (N≥3) cooling plates may be arranged to have an overall T-shaped structure when viewed from above.

The refrigerant introduction port and/or the refrigerant discharge port may be provided therein with a temperature sensor for measuring the temperature of the liquid refrigerant that passes through the refrigerant introduction port and/or the refrigerant discharge port.

Some of the third refrigerant pipes may be arranged along opposite sides of the first cooling plate in the state of being connected to the first refrigerant pipe and the second refrigerant pipe via corresponding ones of the pipe connection members, and the other third refrigerant pipes may be connected to the third refrigerant pipes that are arranged along the opposite sides of the first cooling plate via corresponding ones of the pipe connection members disposed between the first cooling plate and the cooling plate array.

The fourth refrigerant pipes may be further connected to the pipe connection members, and the cooling plates may communicate with the refrigerant introduction port or the refrigerant discharge port in the state of being connected to the fourth refrigerant pipes.

In accordance with another aspect of the present invention, there is provided a battery pack including the cooling system with the above-stated construction, the battery pack including a plurality of battery modules, each of which includes a plurality of battery cells and which are mounted on the cooling plates of the cooling system in the state of being in tight contact with the cooling plates, a bottom housing, on which the battery modules and the cooling system are mounted, and a top housing coupled to an outer edge of the bottom housing for isolating the battery modules and the cooling system from the outside, wherein at least one of the battery modules is different from the other battery modules in terms of the direction in which the batteries are arranged.

The battery pack according to the present invention includes battery modules configured to have different battery cell arrangement structures, whereby it is possible to configure the battery pack such that the battery pack has various sizes, shapes, and structures. Consequently, it is possible to overcome limitations in installation of the battery pack in a device, such as a vehicle, and to minimize the ratio of the volume to the capacity of the battery pack, whereby it is possible to maximize the utilization of the space in the device. In addition, it is possible to more easily repair or inspect the battery pack in the limited space.

In a concrete example, the battery modules may be classified into a first battery module assembly and a second battery module assembly, and the direction in which the battery cells belonging to the first battery module assembly are arranged may be different from the direction in which the battery cells belonging to the second battery module assembly are arranged.

In other words, the battery modules constituting the battery pack according to the present invention may be classified into a first battery module assembly and a second battery module assembly depending on the direction in which the battery cells constituting the battery modules are arranged.

The first battery module assembly may be mounted on the first cooling plate and/or the cooling plate located at the middle part of the cooling plate array, and the second battery module assembly may be mounted on the other cooling plates of the cooling plate array.

The battery pack is configured to have a structure in which the battery module assemblies are generally arranged in a T shape. Consequently, in the case in which the battery pack is installed in the central region of a device, such as a vehicle, when viewed from above, weight may be equally applied to the left and right sides of the device, whereby it is possible to dynamically design the device in consideration of the weight applied to the device by the battery pack with greater ease.

In the battery pack according to the present invention, the kind of each of the battery cells is not particularly restricted. In a concrete example, the battery cell may be a lithium secondary battery, such as a lithium ion battery or a lithium ion polymer battery, which exhibits high energy density, discharge voltage, and output stability.

In general, a lithium secondary battery includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolytic solution containing lithium salt.

The positive electrode may be manufactured, for example, by applying a mixture of a positive electrode active material, a conductive agent, and a binder to a positive electrode current collector and drying the mixture. A filler may be further added to the mixture as needed.

The positive electrode active material may be, but is not limited to, a layered compound, such as a lithium cobalt oxide (LiCoO2) or a lithium nickel oxide (LiNiO2), or a compound replaced by one or more transition metals; a lithium manganese oxide represented by a chemical formula Li1+xMn2-xO4(where x=0 to 0.33) or a lithium manganese oxide, such as LiMnO3, LiMn2O3, or LiMnO2; a lithium copper oxide (Li2CuO2); a vanadium oxide, such as LiV3O3, LiFe3O4, V2O5, or Cu2V2O7; an Ni-sited lithium nickel oxide represented by a chemical formula LiNi1-xMxO2(where M═Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x=0.01 to 0.3); a lithium manganese composite oxide represented by a chemical formula LiMn2-xMxO2(where M═Co, Ni, Fe, Cr, Zn, or Ta, and x=0.01 to 0.1) or a chemical formula Li2Mn3MO8(where M=Fe, Co, Ni, Cu, or Zn); LiMn2O4having Li of a chemical formula partially replaced by alkaline earth metal ions; a disulfide compound; or Fe2(MoO4)3.

The conductive agent is generally added so that the conductive agent has 1 to 30 weight % based on the total weight of the compound including the positive electrode active material. The conductive agent is not particularly restricted so long as the conductive agent exhibits high conductivity while the conductive agent does not induce any chemical change in a battery to which the conductive agent is applied. For example, graphite, such as natural graphite or artificial graphite; carbon black, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or summer black; conductive fiber, such as carbon fiber or metallic fiber; metallic powder, such as carbon fluoride powder, aluminum powder, or nickel powder; conductive whisker, such as a zinc oxide or potassium titanate; a conductive metal oxide, such as a titanium oxide; or conductive materials, such as polyphenylene derivatives, may be used as the conductive agent.

The binder is a component assisting in binding between the active material and conductive agent and in binding with the current collector. The binder is generally added in an amount of 1 to 30 weight % based on the total weight of the compound including the positive electrode active material. As examples of the binder, there may be used polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinyl pyrollidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluoro rubber, and various copolymers.

The filler is an optional component used to inhibit expansion of the positive electrode. There is no particular limit to the filler so long as it does not cause chemical changes in a battery to which the filler is applied, and is made of a fibrous material. As examples of the filler, there may be used olefin polymers, such as polyethylene and polypropylene; and fibrous materials, such as glass fiber and carbon fiber.

The negative electrode may be manufactured by applying and drying a negative electrode active material to a negative electrode current collector. The above-described components may be selectively added to the negative electrode active material as needed.

The separator is interposed between the positive electrode and the negative electrode. As the separator, for example, an insulative thin film exhibiting high ion permeability and high mechanical strength may be used. The separator generally has a pore diameter of 0.01 to 10 μm and a thickness of 5 to 300 μm. As the material for the separator, for example, a sheet or non-woven fabric made of olefin polymer, such as polypropylene, which exhibits chemical resistance and hydrophobicity, glass fiber, or polyethylene is used. In a case in which a solid electrolyte, such as a polymer, is used as an electrolyte, the solid electrolyte may also function as the separator.

In addition, in a concrete example, the separator may be an organic/inorganic composite porous safety reinforcing separator (SRS) for improving the safety of a battery.

The SRS separator may be manufactured by applying inorganic particles and a binder polymer, as active layer components, to a polyolefin separator base. In addition to a porous structure included in the separator base, a uniform porous structure may be formed due to interstitial volumes among the inorganic particles, as the active layer component.

In the case in which the organic/inorganic composite porous separator is used, it is possible to restrain the increase in thickness of the battery due to swelling at the time of formation as compared with the case in which a normal separator is used. In addition, in the case in which a polymer that can gel at the time of impregnating a liquid electrolytic solution is used as the binder polymer, the polymer may also be used as an electrolytic.

In addition, the organic/inorganic composite porous separator may exhibit excellent adhesive characteristics by adjusting the contents of the inorganic particles and the binder polymer, which are active layer components in the separator. Consequently, a battery assembly process may be easily carried out.

The inorganic particles are not particularly restricted so long as the inorganic particles are electrochemically stable. That is, the inorganic particles that can be used in the present invention are not particularly restricted so long as the inorganic particles are not oxidized and/or reduced within an operating voltage range (e.g. 0 to 5 V based on Li/Li+) of a battery to which the inorganic particles are applied. In particular, in the case in which inorganic particles having ion conductivity are used, it is possible to improve ion conductivity in an electrochemical element, thereby improving the performance of the battery. Consequently, it is preferable that ion conductivity of the inorganic particles be as high as possible. In addition, in the case in which the inorganic particles have high density, it may be difficult to disperse the inorganic particles at the time of coating, and the weight of the battery may increase. For these reasons, it is preferable that density of the inorganic particles be as low as possible. Additionally, in the case in which the inorganic particles have high permittivity, a degree of dissociation of electrolyte salt, such as lithium salt, in a liquid electrolyte may increase, thereby improving ion conductivity of the electrolytic solution.

The non-aqueous electrolytic solution containing lithium salt is composed of a polar organic electrolytic solution and lithium salt. As the electrolytic solution, a non-aqueous liquid electrolytic solution, an organic solid electrolyte, or an inorganic solid electrolyte may be used.

As examples of the organic solid electrolyte, mention may be made of polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphoric acid ester polymers, poly agitation lysine, polyester sulfide, polyvinyl alcohols, polyvinylidene fluoride, and polymers containing ionic dissociation groups.

In addition, in order to improve charge and discharge characteristics and flame retardancy, for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphoric triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salts, pyrrole, 2-methoxy ethanol, aluminum trichloride, or the like may be added to the non-aqueous electrolytic solution. According to circumstances, in order to impart incombustibility, the non-aqueous electrolytic solution may further include halogen-containing solvents, such as carbon tetrachloride and ethylene trifluoride. Furthermore, in order to improve high-temperature retention characteristics, the non-aqueous electrolytic solution may further include carbon dioxide gas.

In accordance with a further aspect of the present invention, there is provided a device including the battery pack. The device may be any one selected from the group consisting of an electric vehicle, a hybrid electric vehicle, and a plug-in hybrid electric vehicle.

DETAILED DESCRIPTION OF THE EMBODIMENTS

FIGS. 1 and 2are perspective views showing a cooling system according to an embodiment of the present invention, andFIG. 3is an enlarged view showing a refrigerant introduction port.

Referring to these figures, the cooling system, denoted by reference numeral100, includes a refrigerant introduction port102, through which liquid refrigerant is introduced, a refrigerant discharge port104, through which the liquid refrigerant is discharged, a plurality of refrigerant pipes131,132,140a,140b,142a,142b,150a,150b,152a,152b,154a,154b,156a, and156bconfigured to communicate with the refrigerant introduction port102and the refrigerant discharge port104, pipe connection members160,162,164, and166configured to interconnect two or more of the refrigerant pipes such that the refrigerant pipes communicate with each other, and a plurality of cooling plates110,122,124, and126, each of which has one surface on which a corresponding battery module is mounted.

In the refrigerant introduction port102is mounted a temperature sensor170for measuring the temperature of the liquid refrigerant that passes through the refrigerant introduction port102. In the present invention, for example, water, R-11, R-12, R-22, R-134A, R-407C, or R-410A may be used as the liquid refrigerant.

The cooling plates110,122,124, and126include a cooling plate array120, in which the cooling plates122,124, and126are arranged side by side in the lateral direction, and a first cooling plate110disposed in front of the cooling plates122,124, and126so as to correspond to the middle part of the cooling plate array120.

Consequently, the cooling plates110,122,124, and126are arranged to have an overall T-shaped structure.

The refrigerant pipes131,132,140a,140b,142a,142b,150a,150b,152a,152b,154a,154b,156a, and156binclude a first refrigerant pipe131connected to the refrigerant introduction port102, a second refrigerant pipe132connected to the refrigerant discharge port104, a plurality of third refrigerant pipes140a,140b,142a, and142bconnected to the pipe connection members160,162,164, and166, respectively, for guiding the liquid refrigerant such that the liquid refrigerant flows from the refrigerant introduction port102to the refrigerant discharge port104, and a plurality of fourth refrigerant pipes150a,150b,152a,152b,154a,154b,156a, and156bconnected to the third refrigerant pipes140a,140b,142a, and142bvia the pipe connection members160,162,164, and166, the fourth refrigerant pipes150a,150b,152a,152b,154a,154b,156a, and156balso being connected to the cooling plates110,122,124, and126.

The refrigerant introduction port102and the refrigerant discharge port104are arranged side by side in front of the first cooling plate110in the state in which the refrigerant introduction port102and the refrigerant discharge port104are connected to the first refrigerant pipe131and the second refrigerant pipe132, respectively.

The third refrigerant pipe140ais connected to the first refrigerant pipe131via the pipe connection member160. The third refrigerant pipe140bis connected to the second refrigerant pipe132via the pipe connection member162.

The third refrigerant pipes140aand140B are arranged along the opposite sides of the first cooling plate110.

The third refrigerant pipes140aand140B, arranged along the opposite sides of the first cooling plate110, are connected respectively to the third refrigerant pipes142aand142B via the pipe connection members164and166, which are disposed between the first cooling plate110and the cooling plate array120.

That is, in the present invention, the third refrigerant pipes140a,140b,142a, and142bare connected to the pipe connection members160,162,164, and166in order to guide the overall circulation of the liquid refrigerant.

In addition, some of the third refrigerant pipes, i.e. the third refrigerant pipes140aand140B, are connected to the first refrigerant pipe131and the second refrigerant pipe132, respectively, with the result that the refrigerant introduction port102and the refrigerant discharge port104communicate with the third refrigerant pipes140a,140b,142a, and142b.

The fourth refrigerant pipes150a,150b,152a,152b,154a,154b,156a, and156bare pipes for interconnecting the third refrigerant pipes140a,140b,142a, and142b, along which the liquid refrigerant is circulated, and the cooling plates110,122,124, and126between the third refrigerant pipes140a,140b,142a, and142band the cooling plates110,122,124, and126. A pair of fourth refrigerant pipes is connected to each of the cooling plates, and a pair of fourth refrigerant pipes is connected to different third refrigerant pipes.

The liquid refrigerant is introduced into the first cooling plate110and is discharged from the first cooling plate110as follows. One selected from between a pair of fourth refrigerant pipes150aand150b, i.e. the fourth refrigerant pipe150a, guides the liquid refrigerant from the third refrigerant pipe140ato the first cooling plate110, and the other selected from between the fourth refrigerant pipes150aand150b, i.e. the fourth refrigerant pipe150b, guides the liquid refrigerant from the first cooling plate110to the third refrigerant pipe140b. The flow of the liquid refrigerant to the other cooling plates122,124, and126is the same as the flow of the liquid refrigerant to first cooling plate110.

Consequently, the fourth refrigerant pipes150aand150bcommunicate with the third refrigerant pipes140a,140b,142a, and142b, with the result that the fourth refrigerant pipes150aand150bcommunicate with the refrigerant introduction port102and the refrigerant discharge port104, respectively.

The first refrigerant pipe131has a larger inner diameter than the third refrigerant pipe140asuch that a large amount of liquid refrigerant is introduced into the first refrigerant pipe131and such that the liquid refrigerant is accelerated in the third refrigerant pipe140a. The same equally applies to the second refrigerant pipe132.

In addition, the third refrigerant pipes140a,140b,142a, and142bhave a larger inner diameter than the fourth refrigerant pipes150a,150b,152a,152b,154a,154b,156a, and156b.

FIGS. 4 and 5show the structure of the pipe connection members. For the sake of convenience, the structure in which the pipe connection members are connected to the first refrigerant pipe131and the second refrigerant pipe132will be described by way of example.

Referring first toFIG. 4, the pipe connection member160includes a first connection conduit180, a second connection conduit182and a third connection conduit184, ends of which are inserted into the refrigerant pipes in order to interconnect the refrigerant pipes.

The first connection conduit180is inserted into one end of the first refrigerant pipe131in an interference fitting fashion.

In addition, the first refrigerant pipe131may be securely coupled to the pipe connection member160by a clamping member192, which is disposed so as to wrap the end of the first refrigerant pipe131, in the state in which the first connection conduit180of the pipe connection member160is inserted into the end of the first refrigerant pipe131.

The second connection conduit182is inserted into one end of the third refrigerant pipe140ain an interference fitting fashion. In this state, the third refrigerant pipe140athermally shrinks such that the end of the third refrigerant pipe140awraps the second connection conduit182. Although not shown in the figure, the third refrigerant pipe140amay be more securely coupled to the pipe connection member160by a binding member, such as a clamping member.

The third connection conduit184is inserted into one end of the fourth refrigerant pipe150ain an interference fitting fashion.

In addition, the fourth refrigerant pipe150amay be securely coupled to the pipe connection member160by a clamping member193, which is disposed so as to wrap the end of the fourth refrigerant pipe150a, in the state in which the third connection conduit184of the pipe connection member160is inserted into the end of the fourth refrigerant pipe150a.

When the liquid refrigerant reaches the pipe connection member160through the first connection conduit180via the first refrigerant pipe131, the liquid refrigerant is divided and distributed into the second connection conduit182and the third connection conduit184. Specifically, the liquid refrigerant is divided into a first liquid stream191, which flows in the third refrigerant pipe140a, and a second liquid stream192, which flows in the fourth refrigerant pipe150a.

In addition, the connection conduits180,182, and184have different inner diameters. Specifically, the inner diameter of the first connection conduit180is greater than the inner diameter of the second connection conduit182, and the inner diameter of the second connection conduit182is greater than the inner diameter of the third connection conduit184.

As a result, the first liquid stream191, which flows from the first connection conduit180to the second connection conduit182, is accelerated, and the second liquid stream192, which flows from the first connection conduit180to the third connection conduit184, is accelerated.

The pipe connection member162(seeFIG. 5), which is connected to the second refrigerant pipe132, has a structure identical to the structure of the pipe connection member160.

However, the liquid refrigerant flows in the pipe connection member162, which is connected to the second refrigerant pipe132, toward the refrigerant discharge port104. As a result, a first liquid stream191a, which flows in the third refrigerant pipe140b, and a second liquid stream192a, which flows in the fourth refrigerant pipe150bare combined in the pipe connection member162. The combined liquid refrigerant is discharged through the refrigerant discharge port104via the second refrigerant pipe132.

The structure of the pipe connection members164and166is substantially identical to the structure of the pipe connection members160and162except that each of the pipe connection members164and166has a different number of connection conduits from the number of the connection conduits of each of the pipe connection members160and162so as to correspond to the number of refrigerant pipes connected to each of the pipe connection members164and166.

In addition, all of the pipe connection members160,162,164, and166have the same structure in which the liquid refrigerant is divided and distributed into the third refrigerant pipe and the fourth refrigerant pipe and the same structure in which the liquid refrigerant flowing in the third refrigerant pipe and the liquid refrigerant flowing in the fourth refrigerant pipe are combined.

Referring toFIGS. 6 and 7, the cooling plate124includes a base plate220having a plurality of protrusions222,224, and226formed thereon and a cover plate210coupled to the base plate220in the state of being in tight contact with the protrusions222,224, and226for defining a flow channel230in the remaining space of the base plate220excluding the protrusions222,224, and226.

That is, the cooling plate124is configured to have a structure in which the flow channel230, along which the liquid refrigerant flows, is defined in the space in the base plate220defined by the protrusions222,224, and226.

The cover plate210is provided on the surface thereof that is disposed in tight contact with a corresponding battery module with a thermal interface material pad212for accelerating thermal conduction in order to achieve more efficient thermal conduction between the cover plate210and the battery module.

The base plate220is provided on the surface thereof opposite the surface on which the protrusions are formed with an insulating material228for preventing the introduction of heat into the flow channel230from the outside, excluding the battery module.

In addition, the base plate220and the cover plate210are fastened to each other using bolts and nuts.

Meanwhile, the protrusions222,224, and226include first protrusions222and224, which protrude from one end of the base plate220toward the other end of the base plate220, and a second protrusion226, which is disposed between the first protrusions222and224and which protrudes from one end of the base plate220toward the other end of the base plate220.

Each of the first protrusions222and224has a length smaller than the length of the second protrusion226. In the present invention, the shape of each of the first protrusions222and224, which separately protrude from the base plate220, is defined as a discontinuous shape. On the other hand, the shape of the second protrusion226, which extends from one end of the base plate220, is defined as a continuous shape.

In the above structure, the liquid refrigerant is irregularly divided by the first protrusions222and224, with the result that the liquid refrigerant is distributed more rapidly and, at the same time, a vortex is generated in the region in which the liquid refrigerant is divided, whereby the flow speed of the liquid refrigerant is increased.

Each of the first protrusions222and224is generally configured to have a streamlined structure in order to reduce fluid resistance to the liquid refrigerant.

The divided and distributed liquid refrigerant flows along the second protrusion226, which is longer than each of the first protrusions222and224. The flow direction of the liquid refrigerant is changed by about 180 degrees at the end of the second protrusion226.

The above structure has an advantage in that the flow distance of the liquid refrigerant that flows along the hollow flow channel230defined in the cooling plate124is increased, thereby improving cooling efficiency.

The cooling plate124is configured to have a structure in which a first conduit201and a second conduit202, which communicate with the hollow flow channel230, protrude outward from the cooling plate124.

The fourth refrigerant pipe154a, into which the liquid refrigerant is introduced, is connected to the first conduit201, and the fourth refrigerant pipe154b, from which the liquid refrigerant is discharged, is connected to the second conduit202.

Consequently, the second liquid stream of the liquid refrigerant is introduced into the hollow flow channel230of the cooling plate124through the first conduit201via the fourth refrigerant pipe154a, and performs cooling while flowing along the hollow flow channel230.

Subsequently, the second liquid stream is discharged from the cooling plate124via the second conduit202and the fourth refrigerant pipe154b, which is connected to the second conduit202.

The discharged second liquid stream is guided to the pipe connection member164(seeFIG. 2) via the fourth refrigerant pipe154b, which is connected to the second conduit202, and is combined with the first liquid stream in the third refrigerant pipe142b(seeFIG. 1), which is connected to the pipe connection member164. The combined liquid refrigerant may be discharged through the refrigerant discharge port104via the second refrigerant pipe132.

The cooling and flow processes of the liquid refrigerant in each of the cooling plates110,122, and126are identical to those of the liquid refrigerant in the cooling plate124.

FIGS. 8 and 9show a cooling plate having a larger cooling area than the cooling plate shown inFIGS. 6 and 7.

Referring toFIGS. 8 and 9, the cooling plate122has a cooling area equivalent to about 200% of the cooling area of the cooling plate124shown inFIGS. 6 and 7.

That is, the cooling plate122is similar in basic structure to the cooling plate124shown inFIGS. 6 and 7. However, the size of the cooling plate122is different from the size of the cooling plate124. In addition, as shown inFIG. 9, the size and shape of protrusions251and252formed on a base plate250are different from the size and shape of the protrusions formed on the base plate of the cooling plate124shown inFIGS. 6 and 7.

Specifically, the protrusions251and252of the cooling plate122include first protrusions251, which discontinuously protrude from one end of the base plate250toward the other end of the base plate250, and second protrusions252, which are disposed between the first protrusions251and which continuously protrude from one end of the base plate250toward the other end of the base plate250.

In the above structure, the liquid refrigerant is divided by the discontinuously protruding first protrusions251, and a vortex is generated due to the irregular flow of the liquid refrigerant, thereby increasing the flow speed of the liquid refrigerant while improving the distribution of the liquid refrigerant.

In the cooling system100according to the present invention described above, the coolant flow channels are defined in the cooling plates, on which the battery modules are mounted. Compared to the structure in which the coolant flow channels are defined between the battery modules or between the battery cells, therefore, the cooling system according to the present invention has a compact structure. In addition, the divided liquid refrigerant is introduced into the respective cooling plates to independently cool the battery modules mounted on the respective cooling plates, thereby achieving high cooling uniformity with respect to the battery modules.

Meanwhile,FIG. 10is a partial perspective view showing a battery pack according to an embodiment of the present invention including the cooling system shown inFIGS. 1 to 9, andFIG. 11is an overall perspective view of the battery pack according to the embodiment of the present invention.

Referring toFIGS. 10 and 11, the battery pack, denoted by reference numeral300, includes a cooling system100, a plurality of battery modules321,322,323, and324, each of which includes a plurality of battery cells and which are mounted on cooling plates110,122,124, and126of the cooling system100in the state of being in tight contact with the cooling plates110,122,124, and126, a bottom housing310, on which the battery modules321,322,323, and324and the cooling system100are mounted, and a top housing390coupled to the outer edge of the bottom housing310for isolating the battery modules321,322,323, and324and the cooling system100from the outside.

The bottom housing310includes a first bottom housing311, which is configured to have a rectangular structure when viewed from above, and a second bottom housing312, which is configured to have a rectangular structure when viewed from above. The second bottom housing312is connected to the middle region of a longer side of the outer edge of the first bottom housing311.

A plurality of first fastening holes313, through which the bottom housing310is coupled to the top housing390using coupling members, and a plurality of second fastening holes314, through which the battery pack300is mounted and fixed to a device, are formed in the outer edge of the bottom housing310.

The battery modules321,322,323, and324are classified into a first battery module assembly321and322and a second battery module assembly323and324. The direction in which battery cells belonging to the first battery module assembly321and322are arranged is different from the direction in which battery cells belonging to the second battery module assembly323and324are arranged. In addition, the size of each battery module of the first battery module assembly321and322is different from the size of each battery module of the second battery module assembly323and324.

Each battery module of the first battery module assembly321and322includes a single unit module constituted by a plurality of battery cells. One battery module of the second battery module assembly323and324includes three unit modules323a,323b, and323c, which are arranged adjacent to each other, and the other battery module of the second battery module assembly323and324includes three unit modules324a,324b, and324c, which are arranged adjacent to each other.

Referring toFIG. 11, the top housing390is coupled to the outer edge of the bottom housing310using a plurality of fastening members315in the state in which the battery modules321,322,323, and324are mounted in the top housing390.

The top housing390is provided on the outer edge thereof with a plurality of beads391for improving rigidity of the top housing390.

In various device operating conditions, therefore, it is possible to more effectively and safely protect the battery modules321,322,323, and324in the battery pack300against external physical impact or stress.

The top housing390is provided at one side surface thereof with a vent unit393for discharging gas from the top housing390.

The vent unit393is configured to have a structure in which each through hole393aformed in one surface of the top housing390is covered by a micro-porous gas transmission film393b.

The top housing390is provided in a region thereof corresponding to a manual service device341and a fuse box with an opening392. The manual service device341is exposed outward through the opening392of the top housing390.

At the time of repairing or inspecting the battery pack300, therefore, it is possible for a worker to break the electrical connection of the battery pack300using the manual service device341and the fuse box, which are exposed through the opening392of the top housing390, without removing the top housing390from the battery pack300. Consequently, it is possible to effectively prevent the occurrence of an electrical accident, which may occur when the top housing390is removed from the battery pack300.

INDUSTRIAL APPLICABILITY

As is apparent from the above description, in the cooling system according to the present invention, the coolant flow channels are defined in the cooling plates, on which the battery modules are mounted. Compared to the structure in which the coolant flow channels are defined between the battery modules or between the battery cells, therefore, the cooling system according to the present invention has a compact structure. In addition, the divided liquid refrigerant is introduced into the respective cooling plates to independently cool the battery modules mounted on the respective cooling plates, thereby achieving high cooling uniformity with respect to the battery modules.

In addition, the battery pack according to the present invention includes battery modules configured to have different battery cell arrangement structures, whereby it is possible to configure the battery pack such that the battery pack has various sizes, shapes, and structures. Consequently, it is possible to overcome limitations in installation of the battery pack in a device, such as a vehicle, and to minimize the ratio of the volume to the capacity of the battery pack, whereby it is possible to maximize the utilization of space in the device. In addition, it is possible to more easily repair or inspect the battery pack in the limited space.