Patent Description:
The present invention relates to an HV busbar made of dissimilar metals and a method of manufacturing the same, and more particularly to an HV busbar that is capable of securely interrupting the flow of current while having high resistance to external impact and that is capable of easily adjusting current cutoff temperature in a battery pack and a method of manufacturing the same.

With technological development of mobile devices, such as mobile phones, laptop computers, camcorders, and digital cameras, and an increase in demand therefor, research on secondary batteries, which are capable of being charged and discharged, has been actively conducted. In addition, secondary batteries, which are energy sources substituting for fossil fuels causing air pollution, have been applied to an electric vehicle (EV), a hybrid electric vehicle (HEV), and a plug-in hybrid electric vehicle (P-HEV), and therefore there is an increasing necessity for development of secondary batteries. <CIT> discloses a battery pack and connecting bar applied to the same.

There are a nickel-cadmium battery, a nickel-hydride battery, a nickel-zinc battery, and a lithium secondary battery as currently commercialized secondary batteries. Thereamong, the lithium secondary battery is in the spotlight, since the lithium secondary battery has little memory effect, whereby the lithium secondary battery is capable of being freely charged and discharged, has a very low self-discharge rate, and has high energy density, compared to the nickel-based secondary batteries.

Meanwhile, a secondary battery used for small devices includes several battery cells. For vehicles, however, a plurality of battery modules is electrically connected to each other using a high voltage busbar (HV busbar) in order to increase capacity and output thereof. The HV busbar may be classified as a rigid busbar or a flexible busbar. The flexible busbar is frequently used to connect various electronic devices to each other, in addition to connection between battery modules in series or in parallel. In particular, the flexible busbar is applied to a complicated path having a narrow or bent space.

<FIG> is a conceptual view of a conventional battery pack, and <FIG> is an external perspective view of a conventional HV busbar.

As shown in <FIG>, in a battery pack including a total of six battery modules <NUM>, terminals <NUM> of the battery modules <NUM> that are horizontally arranged are located on the same plane, whereby a general rigid flat HV busbar <NUM> shown (a) of <FIG> is used. When terminals <NUM> of the battery modules <NUM> that are vertically arranged are connected to each other, a flexible HV busbar <NUM> shown in (b) of <FIG> is adopted. In the case in which a path for electrical connection between the battery modules <NUM> is further complicated, an HV busbar <NUM> having a shape shown in (c) of <FIG> may be adopted.

In general, the HV busbar <NUM> includes a metal plate <NUM> having a predetermined thickness and width and an insulative resin coating layer <NUM> provided so as to wrap the outer surface of the metal plate <NUM>.

Meanwhile, in the case in which high current flows in a battery pack due to exposure to high temperature, overcharging, external short circuit, needle penetration, or local damage, heat may be generated in a battery, whereby the battery may explode. For this reason, manual service disconnect (MSD), which is called a safety plug, and a fuse are generally mounted, whereby part expenses and volume of the battery pack are increased.

In connection therewith, Patent Document (<CIT>) discloses a part for secondary batteries installed on a path of current flowing in a secondary battery, wherein the part includes a metal plate having a slit formed in a lateral direction and a metal bridge having a lower melting point than the metal plate, the metal bridge being joined to the metal plate in a state of filling the slit.

The above patent document has an advantage in that, in the case in which overcurrent flows in the secondary battery, the part installed on the path of current flowing in the secondary battery is rapidly ruptured, whereby overcurrent is interrupted, and therefore safety in use of the secondary battery is secured, but has problems in that it is not easy to join the metal plate and the metal bridge to each other, since the metal plate and the metal bridge are dissimilar metals, and therefore the metal bridge must be joined to the metal plate so as to wrap the regions of the upper surface and the lower surface of the metal plate that are adjacent to the slit, whereby the part is structurally unstable, has low resistance to external impact, and is not easy to manufacture.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide an HV busbar capable of securely interrupting the flow of current even in the case in which the temperature of a battery pack is abnormally increased and a method of manufacturing the same.

It is another object of the present invention to provide an HV busbar that has high resistance to external impact and that is easy to manufacture and a method of manufacturing the same.

In order to accomplish the above objects, an HV busbar (<NUM>) configured to connect a plurality of battery modules to each other according to the present invention includes a conductor including a first metal plate (<NUM>) and a second metal plate (<NUM>) and an insulative resin coating layer on the outer circumferential surface of the conductor, wherein a first metal (<NUM>) constituting the first metal plate (<NUM>) and second metals (<NUM>) having a lower melting temperature than the first metal (<NUM>) are mixed in the second metal plate (<NUM>) in the state in which the second metals are dispersed.

Also, in the HV busbar according to the present invention, the upper surface and the lower surface of each of the second metals (<NUM>) may be exposed out of the second metal plate (<NUM>), and the side surface of each of the second metals may be in contact with the first metal (<NUM>).

Also, in the HV busbar according to the present invention, the second metals (<NUM>) may have different outer surface areas.

Also, in the HV busbar according to the present invention, when heated to a predetermined temperature or higher, the second metals (<NUM>) may be melted, whereby the sectional area of the second metal plate (<NUM>) may be reduced.

Also, in the HV busbar according to the present invention, when heated to a predetermined temperature or higher, a rupture portion (<NUM>) may be formed in the second metal plate (<NUM>).

Also, in the HV busbar according to the present invention, the first metal (<NUM>) may be copper or aluminum, and the second metals (<NUM>) may include at least one of indium (In) and tin (Sn).

Also, in the HV busbar according to the present invention, the first metal plate (<NUM>) may be provided in two, the second metal plate (<NUM>) may be provided in one, and the second metal plate (<NUM>) may be located between the first metal plates (<NUM>).

Also, in the HV busbar according to the present invention, the first metal plate (<NUM>) and the second metal plate (<NUM>) may be alternately located in a longitudinal direction, and the first metal plates (<NUM>) may be located at opposite edges in the longitudinal direction.

In addition, an HV busbar manufacturing method according to the present invention includes a first step of applying a predetermined temperature and pressure to first metal powder (<NUM>) while continuously supplying the first metal powder to form the first metal plate (<NUM>), a second step of applying a predetermined temperature and pressure to a metal powder mixture of first metal powder (<NUM>) and second metal powder (<NUM>) while continuously supplying the metal powder mixture for a predetermined time to form the second metal plate (<NUM>), and a third step of applying a predetermined temperature and pressure to the first metal powder (<NUM>) while continuously supplying the first metal powder to form the first metal plate (<NUM>), thereby preparing a conductor.

Also, in the HV busbar manufacturing method according to the present invention, the first metal powder (<NUM>) may be copper or aluminum, and the second metal powder (<NUM>) may be an alloy of indium (In) and tin (Sn).

Also, in the HV busbar manufacturing method according to the present invention, the particle size of the second metal powder (<NUM>) may be greater than the particle size of the first metal powder (<NUM>).

Also, the HV busbar manufacturing method according to the present invention may further include a fourth step of cutting the conductor to a predetermined length and a fifth step of coating the remaining surfaces of the conductor excluding opposite edges thereof with an insulative resin.

In addition, the present invention provides a battery pack including the HV busbar.

In an HV busbar according to the present invention and a method of manufacturing the same, a second metal plate, which is made of a mixture of a first metal and a second metal having a lower melting temperature than the first metal, is located between first metal plates, each of which is made of a first metal, whereby the first metal plate and the second metal plate are strongly coupled to each other, and therefore the HV busbar has high resistance to external impact.

Also, in the HV busbar according to the present invention and the method of manufacturing the same, when the temperature of a battery pack is increased to a melting temperature of the second metal, a predetermined region of the second metal plate is ruptured, whereby the flow of current is interrupted. Consequently, it is possible to easily adjust current cutoff temperature by changing the kind of the second metal.

Furthermore, in the HV busbar according to the present invention and the method of manufacturing the same, the HV busbar also serves as a fuse, whereby it is possible to omit a separate fuse and manual service disconnect (MSD) in the battery pack, and therefore it is possible to reduce manufacturing costs together with improvement in energy density.

Meanwhile, an HV busbar according to the present invention is defined as a busbar configured to electrically connect battery modules to each other, to electrically connect a battery module and a vehicle connector to each other, or to electrically connect battery packs to each other.

Hereinafter, an HV busbar made of dissimilar metals according to the present invention and a method of manufacturing the same will be described. As described with reference to <FIG> and <FIG>, the HV busbar according to the present invention, which is an HV busbar configured to connect a plurality of battery modules to each other, may be rigid or flexible and may be formed so as to have various shapes, and the outer surface of a metal plate constituting a conductor may be coated with an insulative resin.

<FIG> is a conceptual view of an HV busbar according to a first preferred embodiment of the present invention, and <FIG> is a conceptual view illustrating rupture of the HV busbar according to the present invention.

The HV busbar <NUM>, which electrically connects terminals of battery modules to each other, is configured in a flat shape having a predetermined thickness (Y-axis direction), a predetermined width (X-axis direction), and a predetermined length (Z-axis direction), and includes a first metal plate <NUM> corresponding to a non-cutting region and a second metal plate <NUM> corresponding to a cutting region.

In addition to a metal constituting the first metal plate <NUM>, the second metal plate <NUM> further includes a second metal having a different melting temperature from the metal constituting the first metal plate. That is, second metals <NUM> having the same outer surface area or different outer surface areas are present in the second metal plate <NUM> in a dispersed state.

Here, that the second metals <NUM> are dispersed in the second metal plate <NUM> means that the second metals <NUM> having predetermined sizes and surface areas are completely inserted or impregnated in a thickness direction of the second metal plate <NUM> (Y-axis direction) regularly or irregularly. That is, the second metals <NUM> are exposed outwards from the upper surface and the lower surface of the second metal plate <NUM>, whereas the side surface of each of the second metals is in completely tight contact with the metal constituting the first metal plate <NUM>.

Of course, the portions of the second metals <NUM> exposed from the upper and lower surfaces of the second metal plate <NUM> are present in a flat state, although the second metals may maintain the original shape at the time of manufacture thereof, such as a spherical shape or a needle shape.

In the case in which the first metal plate <NUM> constituting the HV busbar <NUM> is coupled to a positive electrode lead, it is preferable for the first metal plate to be made of an aluminum (Al) material generally used for the positive electrode lead. The reason for this is that it is possible to improve weldability and to minimize contact resistance at a coupling portion. In the same manner, it is preferable that, in the case in which the first metal plate <NUM> is coupled to a negative electrode lead, the first metal plate be made of copper (Cu) or a copper material coated with nickel (Ni) generally used for the negative electrode lead. However, the material is not particularly restricted as long as the material exhibits bondability and conductivity.

The second metal plate <NUM> may be made of a metal having a lower melting temperature than aluminum (Al) or copper (Cu) constituting the first metal plate <NUM>, such as indium (In), tin (Sn), or an alloy thereof. The reason for this is that, in the case in which the battery module is overheated due to short circuit or overcharging, it is necessary to rapidly rupture the HV busbar <NUM> in order to release electrical connection of the battery module. The second metals may be freely changed depending on a desired current cutoff temperature.

That is, as shown in <FIG>, when the battery module is normally operated, current flows via the flat HV busbar <NUM> ((a) of <FIG>). When the battery module is overheated to a melting temperature or higher of the second metals <NUM> due to short circuit in the battery module, however, the second metals <NUM>, each of which has a relatively low melting temperature, are melted first, whereby pores <NUM> are formed in the portions at which the second metals <NUM> have been present (see (b) of <FIG>). As a result, a rupture portion <NUM> is formed in a predetermined region, i.e. a region at which the second metals <NUM> are located adjacent to each other, whereby the HV busbar <NUM> is ruptured (see (c) of <FIG>).

Here, the technical principle by which rupture occurs based on the pores <NUM>, in which the second metals <NUM> have been present, will be described in brief. When the second metals <NUM> are melted and thus the pores <NUM> are formed, the surface area in which current is movable is reduced in the vicinity of the pores <NUM>, whereby resistance is increased. Consequently, heat is abruptly generated based on the region in which the pores <NUM> are formed, whereby the temperature of a first metal <NUM> is increased to the melting temperature thereof. As a result, the first metal connecting the pores <NUM> to each other is also melted, whereby the rupture portion <NUM> is formed in the second metal plate <NUM> and thus the second metal plate is cut.

Meanwhile, it is preferable for the second metals <NUM> to be present so as to have a surface area equivalent to <NUM> to <NUM>% of the surface area of the HV busbar <NUM> in the region thereof in the lateral direction (X-axis direction), the longitudinal direction (Z-axis direction), and the thickness direction (Y-axis direction) of the HV busbar. In the case in which the surface area of the second metals is less than <NUM>% of the surface area of the HV busbar, time taken until the HV busbar is ruptured is too long. In the case in which the surface area of the second metals is greater than <NUM>% of the surface area of the HV busbar, the HV busbar <NUM> may be ruptured by temporary overheating. Consequently, the above range is desirable.

Here, the second metals <NUM> may be located within a range of <NUM> to <NUM> in the longitudinal direction (Z-axis direction) of the HV busbar <NUM>.

Next, a second preferred embodiment of the present invention will be described. <FIG> is a conceptual view of an HV busbar according to a second preferred embodiment of the present invention.

The second embodiment is identical in construction to the first embodiment except that two second metal plates <NUM> are provided at the HV busbar <NUM> so as to be spaced apart from each other by a predetermined distance. Hereinafter, therefore, only different constructions will be described.

In the case in which two second metal plates <NUM>, each of which includes second metals <NUM>, are provided so as to be spaced apart from each other by a predetermined distance, it is possible to further increase a safety factor. That is, in the case in which one second metal plate <NUM> is provided, relatively long time is incurred until the HV busbar is ruptured or the occurrence of short circuit may be inhibited. In the case in which two second metal plates <NUM> are present at the HV busbar <NUM>, however, it is possible to more securely induce rupture of the HV busbar. Although two second metal plates <NUM> are shown in <FIG>, which is merely an illustration, it is obvious that three or more second metal plates may be provided.

Next, a method and apparatus for manufacturing the HV busbar according to the first embodiment of the present invention described above will be described.

<FIG> is a flowchart illustrating a method of manufacturing the HV busbar according to the first preferred embodiment of the present invention, and <FIG> is a schematic view of an apparatus for manufacturing the HV busbar according to the first preferred embodiment of the present invention.

The method of manufacturing the HV busbar according to the first embodiment of the present invention includes a first step of applying a predetermined temperature and pressure to first metal powder <NUM> while continuously supplying the first metal powder to form a first metal plate <NUM>, a second step of applying a predetermined temperature and pressure to a metal powder mixture of first metal powder <NUM> and second metal powder <NUM> while continuously supplying the metal powder mixture for a predetermined time to form a second metal plate <NUM>, a third step of applying a predetermined temperature and pressure to first metal powder <NUM> while continuously supplying the first metal powder to form a first metal plate <NUM>, thereby preparing a conductor, a fourth step of cutting the prepared conductor to a predetermined length, and a fifth step of coating the remaining surfaces of the conductor excluding opposite edges thereof with an insulative resin.

The busbar manufacturing apparatus according to the present invention may include a conveyor belt <NUM>, a tray <NUM>, a metal particle supply tank <NUM>, a roller <NUM>, and a heating means (not shown).

Specifically, in the first step, first metal powder <NUM> in a first supply tank <NUM> is continuously supplied to the tray <NUM>, which is located on the conveyor belt <NUM>, and at the same time the first metal powder is heated to a predetermined temperature while the first metal powder is pressed using the roller <NUM> to form a first metal plate <NUM> corresponding to a flat non-cutting region.

In the second step, supply of the first metal powder <NUM> from the first supply tank <NUM> is temporarily interrupted, and a metal powder mixture of first metal powder <NUM> and second metal powder <NUM> in a second supply tank <NUM> is heated and pressed using the roller <NUM> while the metal powder mixture is continuously supplied to the tray <NUM> to form a second metal plate <NUM> corresponding to a flat cutting region.

Here, the particle size of the second metal powder <NUM> may be changed depending on the target rupture current amount of an HV busbar <NUM>. As an example, the particle size of each of the first metal powder <NUM> and the second metal powder <NUM> may range from several nm to several mm. It is preferable that the particle size of the second metal powder <NUM> be greater than the particle size of the first metal powder <NUM>. The particle size of the second metal powder <NUM> may be <NUM> to <NUM> times the particle size of the first metal powder <NUM>. That is, the particle size of the first metal powder <NUM>, which has a relatively high melting point, is reduced in order to adjust sintering temperatures of the first metal powder <NUM> and the second metal powder <NUM> so as to be similar to each other. In the case in which the sintering temperatures of the first metal powder <NUM> and the second metal powder <NUM> are similar to each other, the particle size ratio therebetween is not limited to the above-defined particle size ratio.

In addition, the heating temperature in the first step and the second step is not particularly restricted. Any temperature capable of sintering the first metal powder <NUM> and the second metal powder <NUM> depending on the particle sizes of the first metal powder and the second metal powder is allowed.

In the third step, the supply of the metal powder mixture from the second supply tank is temporarily interrupted, and first metal powder <NUM> in the first supply tank <NUM> is pressed and heated while the first metal powder is continuously supplied to the tray <NUM> to form a first metal plate <NUM> corresponding to a non-cutting region.

After the first to third steps are performed, there is formed a conductor configured such that the second metal plate <NUM>, which is made of the mixture of the first metal powder <NUM> and the second metal powder <NUM> and which corresponds to the cutting region, is provided in the middle and such that a pair of first metal plates <NUM>, each of which is made of only the first metal powder <NUM> and each of which corresponds to the non-cutting region, are provided at opposite sides of the second metal plate <NUM>.

The fourth step is a step of cutting the prepared conductor to an appropriate length in consideration of the distance between battery modules to be connected to each other.

The fifth step is a step of uniformly forming a coating layer on the outer surface of the conductor using a thermosetting resin that exhibits high insulation, such as an epoxy resin or a polyester resin. Here, it is preferable to form the coating layer using a spray coating method. The reason for this is that, when the spray coating method is used, it is possible to easily adjust the thickness of the coating layer and to reduce coating time. The coating layer forming process corresponds to known technology, and therefore a detailed description thereof will be omitted.

Meanwhile, a step of bending the HV busbar <NUM> to a predetermined shape may be further included. Specifically, the bending step may be performed after cutting in the fourth step or after the coating layer is formed. However, it is preferable for the bending step to be performed before the coating layer is formed. The reason for this is that, in the case in which the HV busbar is bent after the coating layer is formed, a portion of the coating layer may be loosened and the surface of the coating layer at the bent portion is not smooth.

Next, a method of manufacturing the HV busbar according to the second embodiment of the present invention described above will be described.

<FIG> is a flowchart illustrating a method of manufacturing the HV busbar according to the second preferred embodiment of the present invention, and <FIG> is a schematic view of an apparatus for manufacturing the HV busbar according to the second preferred embodiment of the present invention.

As shown in <FIG> and <FIG>, the method of manufacturing the HV busbar according to the second embodiment of the present invention includes a first step of applying a predetermined temperature and pressure to first metal powder <NUM> while continuously supplying the first metal powder to form a first metal plate <NUM>, a second step of applying a predetermined temperature and pressure to a metal powder mixture of first metal powder <NUM> and second metal powder <NUM> while continuously supplying the metal powder mixture for a predetermined time to form a second metal plate <NUM>, a third step of applying a predetermined temperature and pressure to first metal powder <NUM> while continuously supplying the first metal powder to form a first metal plate <NUM>, a fourth step of applying a predetermined temperature and pressure to a metal powder mixture of first metal powder <NUM> and second metal powder <NUM> while continuously supplying the metal powder mixture for a predetermined time to form a second metal plate <NUM>, a fifth step of applying a predetermined temperature and pressure to first metal powder <NUM> while continuously supplying the first metal powder to form a first metal plate <NUM>, thereby preparing a conductor, a sixth step of cutting the prepared conductor to a predetermined length, and a seventh step of coating the remaining surfaces of the conductor excluding opposite edges thereof with an insulative resin.

The manufacturing method according to the second embodiment is identical to the manufacturing method according to the first embodiment described above except that two second metal plates <NUM> are provided and a first metal plate <NUM> is further provided between the second metal plates <NUM>. That is, the fourth step and the fifth step are repetitions of the second step and the third step, and another second metal plate <NUM> is formed through the fourth step and the fifth step.

Claim 1:
An HV busbar (<NUM>) configured to connect a plurality of battery modules to each other, the HV busbar (<NUM>) comprising:
a conductor comprising a first metal plate (<NUM>) and a second metal plate (<NUM>); wherein
a first metal (<NUM>) constitutes the first metal plate (<NUM>);
characterized in that
second metals (<NUM>) having a lower melting temperature than the first metal (<NUM>) are mixed in the second metal plate (<NUM>) in a state in which the second metals (<NUM>) are dispersed;
and in that the HV busbar comprises an insulative resin coating layer on an outer circumferential surface of the conductor.