BUSBAR FOR INCREASING ALLOWANCE CURRENT AND REDUCING HEATING VALUE, AND PRODUCTION METHOD THEREOF

A busbar and a busbar manufacturing method in which at least one current groove in the body of the busbar is included or at least two current sticks are attached to one side of the base busbar to be spaced apart, such that an allowable current of busbar is increased by more than 1% and a generated heat amount is reduced by more than 2% at the same time.

TECHNICAL FIELD

The present invention relates to a current busbar, and more particularly, provides a busbar in which an allowable current is increased and a generated heat amount is reduced at the same time.

BACKGROUND ART

A busbar is a generic term for a rod-shaped conductive product that transmits electrical energy that can be used instead of a cable. Because a busbar can deliver more electrical energy in the same volume compared to conventional cables, in configuring the battery pack, the busbar is used for the connection between battery cells, modules or external terminals of the battery pack in the field of electric field that requires various capacities of energy or high current such as light electric vehicle (LEV), uninterruptible power supply (UPS), unmanned vehicle (AGV), electric vehicle (EV), and the like.

In such a busbar, the maximum current that can safely flow is determined according to the size and material including the length and cross-sectional area, and this is called the allowable current. When a current flows in the busbar, joule heat is generated, and when the current flows beyond the allowable current, there is a problem of causing strength or carbonization of insulation due to temperature rise.

In fields that require high capacity energy or current, a busbar with high allowable current is required, and for this, an increase in size is inevitable, but the space inside the battery pack is limited, and therefore, the conventional busbar does not satisfy the required allowable current or solve the problem of heat generation due to temperature rise.

Therefore, if it is impossible to increase the size of the busbar due to the limitation of the internal design space of the battery pack, there is a need for a busbar that can reduce the amount of generated heat and increase the allowable current while maintaining the space of the busbar occupying the battery pack.

The technology underlying the present invention is disclosed in the following patent documents.

DISCLOSURE OF THE INVENTION

Technical Problem

An object of the present invention is to provide a busbar having the effect of increasing the allowable current while reducing the amount of generated heat for cases where it is not possible to increase the size of the busbar due to the limitation of the internal space of the battery pack.

Technical Solution

The present invention provides a busbar capable of increasing an allowable current while reducing the amount of generated heat by including a current groove in the busbar.

More specifically, in a busbar according to an embodiment of the present invention, the busbar includes a conductive busbar body and at least one current groove on at least one surface of the conductive busbar body, wherein each current groove includes sidewall parts, and a bottom part forming a bottom surface of the current groove, wherein a number of the current grooves, a depth of the sidewall part, and a width of the bottom part are set to increase a surface area of the entire busbar.

In a busbar according to the embodiment of the present invention, the busbar includes: a base busbar made of a conductive body; and at least two or more current sticks attached to at least one surface of the base busbar and spaced apart from one another by a predetermined interval, wherein at least one current groove is formed between adjacent current sticks among the two or more current sticks, wherein each current groove includes a sidewall part defining a thickness of the current stick; and a bottom part defining the predetermined interval, wherein a number of the current grooves, a depth of the sidewall part, and a width of the bottom part are set to increase a surface area of the entire busbar.

A width and thickness of the busbar are formed of 25 mm and 4 mm, respectively.

The number of the current grooves is three, and the depth of the sidewall part and the width of the bottom part of the current groove are 2 mm and 2 mm, respectively, and it is characterized in that the allowable current of the busbar is increased by 1% or more and the generated heat amount is reduced by 2% or more compared to a busbar not having a current groove.

The number of the current grooves is 5, and the depth of the sidewall part and the width of the bottom part of the current groove are 2 mm and 1 mm, respectively, and it is characterized in that the allowable current of the busbar is increased by 5% or more and the generated heat amount is reduced by 10% or more compared to a busbar not having a current groove.

The number of the current grooves is 6, and the depth of the sidewall part and the width of the bottom part of the current groove are 2 mm and 1 mm, respectively, and it is characterized in that it is set so that the allowable current of the busbar is increased by 10% or more and the generated heat amount is reduced by 15% or more compared to a busbar not having a current groove.

The temperature change of the busbar is determined by Equation 1 below, and the allowable current of the busbar is determined by Equation 2 below.

wherein in Equation 1 or 2, (θ−θn) is a temperature change value (° C.), S is a cross-sectional area of the busbar, and P is a circumference of the surface of the busbar cross-section.

Advantageous Effects

According to an embodiment of the present invention, the busbar can reduce the generated heat amount compared to the same current by increasing the surface area by configuring the current groove, and also has the effect of increasing the allowable current based on the same generated heat amount.

MODE FOR CARRYING OUT THE INVENTION

Hereinafter, with reference to the accompanying drawings, an embodiment of the present invention will be described in detail. However, the present invention is not limited to the embodiments disclosed below, and will be implemented in various different forms. Only the embodiments of the present invention are provided to complete the disclosure of the present invention, and to completely inform those of ordinary skill in the art the scope of the invention. In order to explain the embodiment of the present invention, the drawings may be exaggerated, parts irrelevant to the description may be omitted from the drawings, and the same reference numerals in the drawings refer to the same elements.

1. Allowable Current of Prior Art Busbar

Referring toFIG.1, the conventional busbar is made of a metal material and is formed in a conductive plate shape, and a coupling groove capable of coupling to terminals of a battery cell, a module, and a pack may be configured together.

The maximum allowable current capacity of the busbar is determined by the size or material including the length and cross-sectional area. Therefore, the width and thickness of the cross-section may be set to have a predetermined cross-sectional area in order to flow a large current to the busbar, but may be limited according to the space inside the battery pack.

Similarly, as the cross-sectional area of the busbar increases, the resistance decreases and the generated heat amount is reduced, but the size of the cross-sectional area is limited according to the space inside the battery pack.

Based on the width and thickness of the busbar being 25 mm and 4 mm, respectively, the allowable current of the busbar is calculated based on the Melson & Both equation of Equation 1 below.

where k is a conditions coefficient, θ is the maximum operating temperature of the conductor, I is the current capacity, S is the cross-sectional area of the conductor, P is the circumference of the conductor, θnis the ambient temperature (θn≤40° C.). (θ−θn) is the allowable temperature rise or change value (° C.), a is the temperature coefficient of resistance when the ambient temperature is exceeded, and ρ20is the resistivity of the conductor at ambient temperature.

Table 1 below shows the temperature change and allowable current calculation values of the prior art busbar that does not include a current groove.

TABLE 1Temperature change and allowable current of prior art busbarCross-TemperatureCurrentsectionalSectionTemperaturechangeAllowablechangeWidthThicknessareacircumferencechangeratiocurrentratioClassification(mm)(mm)(mm2)(mm)calculation(%)calculation(%)Prior254100585840.001711—49—art

2. Configuration of Busbar of Present Invention

The present invention is an invention in which a plurality of current grooves200are configured in a conductive busbar body100, and in order to simply calculate the temperature change rate and current change, which is different from the busbar of the prior art in which the current groove is not formed, by omitting the coefficient of Equation 1, the temperature change and allowable current can be calculated by the following Equations 2 and 3, which are expressed only by the cross-sectional area (S) and the circumferential length (P) of the cross-section.

wherein in Equation 2 or 3 above, (θ−θn) is a temperature change value (° C.), S is a cross-sectional area of the busbar, and P is a circumference of the surface of the busbar cross-section. In the busbar10of the present invention, the size of the busbar10may be limited due to the lack of space that the busbar10can occupy in the battery pack of the prior art busbar10, and therefore, the allowable current of the busbar10is limited or the problem that the generated heat amount cannot be reduced is solved.

A first aspect of the present invention will be described with reference toFIG.2.

Referring toFIG.2, the busbar10of the present invention constitutes at least one current groove200on one surface of the conductive busbar body100. When two or more current grooves200are formed, each current groove200may be separately disposed on the upper surface, lower surface or side surface of the conductive body. In addition, when two or more current grooves200are formed, they may all be formed on one surface of the conductive body, and in this case, each current groove200is configured to be spaced apart from each other by a predetermined distance.

The current groove200is formed on at least one surface of the conductive busbar body100, and the shape of the formed current groove200may be formed in various shapes, such as a square, a triangle, or a semicircle, and in an embodiment of the present invention, as a current groove200formed in a square shape, it will be described as a current groove200composed of side wall portions210on both sides and a bottom portion220on the lower surface.

FIG.2shows a sidewall part210having a predetermined depth a and a bottom part220having a predetermined width b.

The sidewall part210and the bottom part220of the current groove200in Table 2 below show the number of current grooves200according to the embodiment of the present invention, the cross-sectional area of the busbar, the surface perimeter of the cross-section, a temperature change, a temperature change rate, an allowable current, and a current change rate according to the depth a of the sidewall part210and the width (b) of the bottom part220.

In the table, the first column of the calculated temperature change column is the value calculated by Equation 2, and the second column is the inverse.

The values of the temperature change ratio (%) column are the ratio of the temperature change value compared to the prior art in each embodiment when the temperature change value of the busbar10of the prior art is 100.

The values of the current change ratio (%) column are ratios of allowable current change values compared to the prior art in each embodiment when the allowable current value of the busbar10of the prior art is 100.

A second aspect of the present invention will be described with reference toFIG.3.

Referring toFIG.3, the busbar10of the present invention is composed of a base busbar400made of one conductive material, and a current stick500made of at least one conductive material attached to one surface of the base busbar400, and when two or more current sticks500are attached, the busbars10are attached at a predetermined interval.

The base busbar400may be formed in various shapes, and as in the first aspect of the present invention, the base busbar400is configured to have a predetermined length and cross-sectional area, but the width and thickness of the section are set according to the change in heating temperature and allowable current required by the user.

The current stick500may also be formed in various shapes, such as a polygon or a semicircle including a square, a triangle, and the like, and in an embodiment of the present invention, as a current stick500having a rectangular cross-section, the horizontal and vertical lengths and the predetermined intervals spaced apart of each current stick500are set according to the change in heating temperature and allowable current required by the user.

Embodiments 1 to 6 below describe the first aspect of the present invention, and embodiments 7 to 12 describe the second aspect.

When three current grooves200having a depth a of the sidewall part210and a width b of the bottom part220of 2 mm×2 mm, respectively, are formed on one or both sides of the busbar10, the temperature change and allowable current can be calculated through Equations 2 and 3 above. By configuring the current groove200in the busbar10, the cross-sectional area is reduced, but the cross-sectional circumference is increased such that the temperature change rate is reduced to 98% compared to the prior art, and the allowable current is increased to 101%.

When five current grooves200having a depth a of the sidewall part210and a width b of the bottom part220of 2 mm×2 mm, respectively, are formed on one side or both sides of the busbar10, the temperature change rate is reduced to 99%, and the allowable current is 100%, so it can be confirmed that the effect of forming the current groove200is less than that of Embodiment 1.

When three current grooves200having a depth a of the sidewall part210and a width b of the bottom part220of 2 mm×1 mm, respectively, are formed on one or both sides of the busbar10, the temperature change rate is reduced to 93%, and the allowable current is increased to 104%. When compared with Embodiment 1 having the same number of current grooves200, in Embodiment 3, since the size of the bottom part220of the current groove200is formed smaller, the size of the lost cross-sectional area is smaller, so it can be confirmed that the formation effect of the current groove200is greater. Therefore, it is advantageous to form the current groove200with a smaller size of the bottom part220than the sidewall part210.

Based on the results of Embodiment 3, five current grooves200having a depth a of the sidewall part210and a width b of the bottom part220of 2 mm×1 mm, respectively, are formed on one or both sides of the busbar10. The temperature change rate decreases to 90%, and the allowable current increases to 106%. Compared to Embodiment 3, the cross-sectional area is reduced by forming a lot of current grooves200, but it can be seen that the effect of forming the current groove200is greatly increased by increasing the length of the perimeter of the surface of the cross section.

Based on the results of Embodiments 3 to 4, six current grooves200having a depth a of the sidewall part210and a width b of the bottom part220of 2 mm×1 mm, respectively, are formed on one or both sides of the busbar10. The temperature change rate decreases to 85%, and the allowable current increases to 110%. As can be seen from the results of Embodiments 3 to 4, the cross-sectional area is greatly reduced by forming a lot of current grooves200, but it can be seen that the effect of forming the current groove200is greatly increased by increasing the length of the perimeter of the surface of the cross section.

When ten current grooves200having a depth a of the sidewall part210and a width b of the bottom part220of 2 mm×1 mm, respectively, are formed on one or both sides of the busbar10, the temperature change rate is reduced to 86%, and the allowable current is increased to 110%. In the case of Embodiments 3 to 5, as the surface perimeter of the cross-section increases as the cross-sectional area decreases, the temperature change can be greatly reduced and the current change rate can also increase, but depending on the size and number of the current grooves200, the reduction of the cross-sectional area has a greater effect than the increase of the surface circumference of the cross-section of the busbar10so that it can be seen that the effect of forming the current groove200is reduced.

Embodiment 7 to 12 are examples specifically applied to the thickness of the base busbar400and the width and thickness of the current stick500in the second aspect of the present invention. Embodiments 7 to 12 are embodiments according to the second aspect of the present invention using the current stick500shown inFIG.3and the related description, and the width and thickness of the base busbar400, the width and thickness of the current stick500, and the interval at which the current stick500is spaced apart are set so as to correspond to Embodiments 1 to 6 according to the first aspect of the present invention. Therefore, the width and thickness of the busbar of the second aspect are the width and thickness of the busbar10including the base busbar and the current stick500.

As in Embodiment 1, in order to configure Embodiment 7 so that the current groove200having a depth a of the sidewall part210and a width b of the bottom part220of 2 mm×2 mm, respectively, has the same effect as the three formed on the upper surface of the busbar body100, for example, first, the width and thickness of the base busbar400are formed to be 25 mm and 2 mm, respectively. In addition, the thickness of the current stick500is set to 2 mm so that the sum of the thickness of the base busbar400is 4 mm. A total of four current sticks500are attached to the upper surface of the base busbar400, and two of them must be arranged in line with both end lines of the base busbar400. The sum of the widths of each current stick500should be set to be 19 (=25−6) mm, and for example, in order to have the four current sticks500have the same width, the width of each current stick500may be set to 4.75 mm.

As in Embodiment 2, in order to configure Embodiment 8 so that the current grooves200having a depth a of the sidewall part210and a width b of the bottom part220of 2 mm×2 mm, respectively, have the same effect as the five formed on the upper surface of the busbar body100, for example, first, the width and thickness of the base busbar400are formed to be 25 mm and 2 mm, respectively. In addition, the thickness of the current stick500is set to 2 mm so that the sum with the thickness of the base busbar400is 4 mm, and a total of six current sticks500are attached to the upper surface of the base busbar400, and two of them must be arranged in line with both end lines of the base busbar400. The sum of the widths of each current stick500should be set to be 15 (=25−10) mm, and for example, in order to have the six current sticks500have the same width, the width of each current stick500may be set to 2.5 mm.

As in Embodiment 3, in order to configure Embodiment 9 so that the current groove200having a depth a of the sidewall part210and a width b of the bottom part220of 2 mm×1 mm, respectively, has the same effect as the three formed on the upper surface of the busbar body100, for example, first, the width and thickness of the base busbar400are formed to be 25 mm and 2 mm, respectively. In addition, the thickness of the current stick500is set to 2 mm so that the sum with the thickness of the base busbar400is 4 mm, and a total of four current sticks500are attached to the upper surface of the base busbar400, and two of them must be arranged in line with both end lines of the base busbar400. The sum of the widths of each current stick500should be set to be 22 (=25-3) mm, and for example, in order to have the four current sticks500have the same width, the width of each current stick500may be set to 5.5 mm.

As in Embodiment 4, in order to configure Embodiment 10 so that the current grooves200having a depth a of the sidewall part210and a width b of the bottom part220of 2 mm 1 mm, respectively, have the same effect as the five formed on the upper surface of the busbar body100, for example, first, the width and thickness of the base busbar400are formed to be 25 mm and 2 mm, respectively. In addition, the thickness of the current stick500is set to 2 mm so that the sum with the thickness of the base busbar400is 4 mm, and a total of six current sticks500are attached to the upper surface of the base busbar400, and two of them must be arranged in line with both end lines of the base busbar400. The sum of the widths of each current stick500should be set to be 20 (=25−5) mm, and for example, in order for the six current sticks500to have the same width, the width of each current stick500may be set to about 3.3 mm, but in this case, the width of each of two current sticks500is formed to be 3 mm, and the width of each of four current sticks500is formed to be 3.5 mm, and each of them can be replaced by arranging each spaced apart 2 mm apart.

As in Embodiment 5, in order to configure Embodiment 11 so that the current grooves200having a depth a of the sidewall part210and a width b of the bottom part220of 2 mm×1 mm, respectively, have the same effect as the six formed on the upper surface of the busbar body100, for example, first, the width and thickness of the base busbar400are formed to be 25 mm and 2 mm, respectively. In addition, the thickness of the current stick500is set to 2 mm so that the sum with the thickness of the base busbar400is 4 mm, and a total of seven current sticks500are attached to the upper surface of the base busbar400, and two of them must be arranged in line with both end lines of the base busbar400. The sum of the widths of each current stick500should be set to be 19 (=25−6) mm, and for example, in order for the seven current sticks500to have the same width, the width of each current stick500may be set to about 2.6 mm, but in this case, the width of each of two current sticks500is formed to be 2.5 mm, and the width of each of five current sticks500is formed to be 2.8 mm, and each of them can be replaced by arranging each spaced apart 1 mm apart.

As in Embodiment 6, in order to configure Embodiment 12 so that the current grooves200having a depth a of the sidewall part210and a width b of the bottom part220of 2 mm×1 mm, respectively, have the same effect as the ten formed on the upper surface of the busbar body100, for example, first, the width and thickness of the base busbar400are formed to be 25 mm and 2 mm, respectively. In addition, the thickness of the current stick500is set to 2 mm so that the sum with the base busbar400is 4 mm, and a total of eleven current sticks500are attached to the upper surface of the base busbar400, and two of them must be arranged in line with both end lines of the base busbar400. The sum of the widths of each current stick500should be set to be 15 (=25−10) mm, and for example, in order for the eleven current sticks500to have the same width, the width of each current stick500may be set to about 1.5 mm, but in this case, the width of each of ten current sticks500is formed to be 1.4 mm, and the width of one current stick500is formed to be 1 mm, or the width of each of ten current sticks500is formed to be 1.3 mm, and the width of one current stick500is formed to be 2 mm, and each of them can be replaced by arranging each spaced apart 1 mm apart.

The configuration of the busbar according to the first aspect of the present invention describes the effect of forming the current groove200when the cross-sectional area is reduced by configuring the current groove200in the busbar body100but the length of the perimeter of the surface of the cross-section is increased. In this way, in a case where a plurality of formed current grooves200are respectively formed on the upper and lower surfaces of the busbar body100, when the sum of the depth a of the sidewall part210of each current groove200is formed smaller than the total thickness of the busbar body100, for example, the thickness of the busbar body100is 4 mm and the sum of the depth a of each current groove200sidewall part210located on the upper and lower surfaces is less than 4 mm, the upper and lower current grooves200face each other and may be positioned side by side or alternately positioned. On the other hand, when the sum of the lengths of the sidewall parts210of each current groove200located on the upper and lower surfaces is formed over the entire thickness of the busbar body100, for example, the thickness of the busbar body100is 4 mm and the sum of the depth a of the sidewall part210of the current groove200located on the upper and lower surfaces is 4 mm or more, the upper and lower current grooves200are alternately positioned.

In addition, the configuration of the busbar according to the second aspect of the present invention may replace the current groove200of the busbar according to the first aspect at a predetermined interval formed by each current stick500by attaching the current stick500having a predetermined thickness and width to the base busbar400. In the above embodiments 7 to 12, the structure in which the current stick500is attached only to the upper surface of the base busbar400has been described, but by adjusting the thickness of the current stick500and the thickness of the base busbar400according to the temperature change and allowable current that the user wants to use, the current stick500may be attached to each of the upper and lower surfaces of the base busbar400.

2. Manufacturing Method of Present Invention Busbar

A. Method for Manufacturing Busbar According to First Aspect of Present Invention

(1) In the method of manufacturing a busbar according to the first aspect of the present invention, a conductive busbar body100is provided based on a prior art busbar, and a current groove200is formed in the busbar body100. As a method of forming the current groove200, there are a physical method of applying a laser or pressure to the position of the current groove200to be formed of the busbar body100, a chemical method using etching, or a method using a mold or a mold or a mold casting, a method is only selectively used according to the size and material of the busbar body100or the size of the current groove200, and the specific method is not limited.

B. Method for Manufacturing Busbar According to Second Aspect of Present Invention

(1) In the method of manufacturing a busbar according to the second aspect of the present invention, a current stick500of a conductive material having a predetermined width, thickness and length is bonded to the base busbar400having a smaller thickness than that of the prior art busbar at predetermined intervals. As the bonding method, there may be methods such as compression, attachment, and growth, but only selectively used according to the size and material of the base busbar400and the current stick500, and the specific method is not limited.

A predetermined interval for bonding the current stick500forms the current groove200described above, and constitutes the width b of the bottom part220of the current groove200.

In this way, the base busbar400and the current stick500connected thereto together constitute the busbar10.

The above embodiments of the present invention are intended to illustrate the present invention, not to limit the present invention. It should be noted that the configurations and methods disclosed in the above embodiments of the present invention may be combined and modified in various forms by combining or intersecting with each other, and modifications thereof may also be considered within the scope of the present invention. That is, the present invention will be implemented in a variety of different forms within the scope of the claims and equivalent technical spirit, and those skilled in the art to which the present invention pertains will understand that various embodiments are possible within the scope of the technical spirit of the present invention.