Patent Description:
The present invention relates to a battery pack case including an over-fusion prevention structure. More particularly, the present invention relates to a battery pack case including an over-fusion prevention structure capable of preventing external defects from occurring on a coupling portion of the battery pack case due to over-fusion when ultrasonic welding is performed for coupling of the battery pack case.

A battery pack constituted by secondary batteries connected to each other in series or in parallel is used as an energy source for medium- or large-sized devices, which require high output and high capacity. The battery pack may include a plurality of battery cells, a structure configured to perform electrical connection between the battery cells, a structure configured to control the operation of the battery cells, and a structure configured to adjusting heat generation/heat dissipation of the battery cells in a battery pack case, and coupling of the battery pack case is performed in the state in which the structures are received therein to manufacture the battery pack.

As a coupling method of a battery pack case manufactured using a polymer resin, there is used a method of pressurizing the polymer resin in a molten state using frictional heat by ultrasonic vibration in order to achieve fusion. If a joint of the battery pack case is over-fused or pressing force is inaccurately controlled, the molten resin flows outwards, whereby burrs are generated.

<FIG> is a vertical sectional view of a coupling portion of a conventional battery pack case, and <FIG> is a front view of the coupling portion of the battery pack case of <FIG>.

Referring to <FIG>, the battery pack case is constituted by a first case <NUM> located above and a second case <NUM> located below. A projecting portion <NUM> is formed on a coupling portion of the first case <NUM> at a middle part of the first case in a thickness direction D thereof so as to project downwards therefrom, and a grooved portion <NUM> is formed in a coupling portion of the second case <NUM> at a middle part of the second case in a thickness direction D thereof so as to be concave. The projecting portion <NUM> of the first case <NUM> is inserted into and fixed to the grooved portion <NUM> of the second case <NUM>, whereby the battery pack case is assembled.

The projecting portion <NUM> includes an energy director <NUM> formed at the end thereof such that the width of the energy director in the thickness direction D thereof is gradually decreased. When vibration is applied to the first case <NUM> and the second case <NUM>, the energy director <NUM> is melted in the grooved portion <NUM> of the second case <NUM> while being vibrated, whereby the grooved portion <NUM> is filled with the projecting portion <NUM>.

At this time, if the first case is excessively pressed toward the second case in the state in which the energy director <NUM> is melted, the energy director may be over-fused, whereby some of the melted energy director may flow out of the case. As a result, burrs <NUM> may be generated, as shown in <FIG>.

<FIG> shows the state in which the burrs <NUM> are generated at the coupling portions of the first case <NUM> and the second case <NUM> due to over-fusion. In order to prevent generation of defects, such as burrs, it is important to maintain a uniform distance between the first case and the second case in a height direction thereof at the coupling portions of the first case and the second case.

In connection therewith, <CIT> discloses a battery pack configured such that a battery pack case includes a front case and a rear case, a plurality of fusion protrusions made of a resin is formed along the edge of the rear case, i.e. the part of the rear case that contacts the front case, and outflow prevention recesses configured to prevent outflow of the fusion protrusions are formed along the edge of the front case at the region of the front case that contacts the fusion protrusions of the rear case.

However, the outflow prevention recesses of <CIT> have difficulty completely preventing the fusion protrusions from flowing out of the outflow prevention recesses when the fusion protrusions are melted. That is, time and force control is necessary when the front case and the rear case are coupled to each other, and, if the fusion protrusions flow out of the outflow prevention recesses in the state in which the fusion protrusions are melted, it is difficult to prevent external defects, such as the burrs of <FIG>, from occurring between the battery cases.

<CIT> discloses a vibration fusion structure between a resin case and a resin cover capable of preventing burrs generated when the resin case and the resin cover are fused to each other using vibration from leaking out into an inner space surrounded by the resin case and the resin cover, wherein projection portions projecting from the resin case and the resin cover are fused to each other by vibration to form a joint at fused portions of the resin case and the resin cover and wherein an inner burr concealment wall, an outer burr concealment wall, and a middle burr concealment wall are formed in order to prevent melting and flowing of the projecting portions.

In <CIT>, when the fused portions are melted, it is possible to prevent the melted portions from flowing out of coupling portions of the resin case and the resin cover to a certain extent, since the plurality of concealment walls is formed. However, it is not possible to completely prevent burrs from flowing out of the coupling portions of the resin case and the resin cover, like <CIT>.

Therefore, there is a need for a battery pack case having a structure capable of fundamentally preventing generation of external defects as the result of an energy director of a battery case melted by vibration heat flowing out of the battery case.

Further prior art is desribed in <CIT>, <CIT> and <CIT>.

The present invention has been made in view of the above problems, and it is an object of the present invention to provide a battery pack case including an over-fusion prevention structure capable of preventing generation of burrs on a coupling portion of the battery pack case due to over-fusion of the battery pack case, thereby reducing external defects.

In order to accomplish the above object, the present invention provides a battery pack case configured to receive a plurality of battery cells, the battery pack case including a first case and a second case coupled to each other through an engagement between the first case and the second case, wherein a projecting portion is formed on a coupling portion of the first case at a middle part of the first case in a thickness direction thereof so as to project therefrom, wherein a grooved portion is formed in a coupling portion of the second case at a middle part of the second case in a thickness direction thereof such that the projecting portion is inserted into the grooved portion, and wherein a uniform gap is formed along the entire outer peripheries of the first case and the second case between the outside of the projecting portion of the first case and the outside of the grooved portion of the second case, wherein a support structure configured to form the gap is formed in the grooved portion of the second case, wherein a stopper rib is formed in the grooved portion of the second case as the support structure,.

wherein a stopper recess is formed at the position of the projecting portion of the first case corresponding to the stopper rib, and wherein the sum of the height of the stopper rib and the height of the projecting portion at the part thereof at which the stopper recess is formed is greater than the depth of the grooved portion of the second case.

The depth of the stopper recess may be less than the height of the projecting portion.

The projecting portion may include an energy director configured to be melted by thermal fusion and a support portion excluding the energy director.

The support structure may be formed on at least one side of each of outer peripheries of the first case and the second case at which the first case and the second case are coupled to each other.

The support structure may be formed on the entireties of outer peripheries of the first case and the second case at which the first case and the second case are coupled to each other.

As is apparent from the above description, in a battery pack case according to the present invention, a support structure is formed at coupling portions of a first case and a second case, whereby it is possible to maintain a uniform coupling distance between the first case and the second case even when coupling force is excessively applied to the first case and the second case in the state in which a projecting portion of the first case is melted.

Since the coupling distance between the first case and the second case is maintained uniform, as described above, it is possible to prevent generation of burrs due to over-fusion at the coupling portions of the first case and the second case, whereby it is possible to reduce an external defect rate.

An embodiment of the present invention will be described in detail with reference to the accompanying drawings.

A battery pack case according to the present invention includes a first case and a second case, which are separated from each other. The first case and the second case have a structure in which the first case and the second case are coupled to each other through engagement therebetween.

Specifically, a projecting portion is formed on a coupling portion of the first case at a middle part of the first case in a thickness direction thereof so as to project therefrom, and a grooved portion is formed in a coupling portion of the second case at a middle part of the second case in a thickness direction thereof such that the projecting portion is inserted into the grooved portion. Consequently, the projecting portion may be inserted into the grooved portion, whereby engagement therebetween may be achieved.

In connection therewith, <FIG> is a vertical sectional view of coupling portions of a first case and a second case according to the present invention.

Referring to <FIG> shows the state in which ultrasonic welding is being performed in the state in which the first case <NUM> and the second case <NUM> are coupled to each other, and <FIG> shows the state in which ultrasonic welding has been completed.

The battery pack case includes the first case <NUM> and the second case <NUM>. A projecting portion <NUM> is formed on a coupling portion of the first case <NUM> at a middle part of the first case <NUM> in a thickness direction D thereof so as to project downwards therefrom, and a grooved portion <NUM> is formed in a coupling portion of the second case <NUM> at a middle part of the second case <NUM> in a thickness direction D thereof such that the projecting portion <NUM> is inserted into the grooved portion. The projecting portion <NUM> is inserted into the grooved portion <NUM>, whereby the first case and the second case are primarily coupled to each other.

When ultrasonic vibration is applied to the first case <NUM> and the second case <NUM> in this state, frictional heat is generated at the interface between the projecting portion <NUM> of the first case <NUM> and the grooved portion <NUM> of the second case <NUM>, whereby the end of the projecting portion <NUM> is melted. That is, the projecting portion <NUM> includes an energy director <NUM> configured to be melted by heat and a support portion <NUM> excluding the energy director <NUM>.

A separation space is present between the projecting portion <NUM> and the inner surface of the grooved portion <NUM> before the first case <NUM> and the second case <NUM> are thermally fused to each other. <FIG> shows the state in which ultrasonic welding is being performed, wherein half or more of the energy director <NUM> is melted. When the first case <NUM> and the second case <NUM> are pressed so as to be closer to each other while the energy director <NUM> is melted, the separation space between the projecting portion <NUM> and the inner surface of the grooved portion <NUM> is fully filled with the melted energy director.

The grooved portion <NUM> of the second case <NUM> is configured to have a structure in which opposite sides of a concave groove project. When ultrasonic welding is performed in the state in which the projecting portion <NUM> is inserted into the grooved portion <NUM>, therefore, it is possible to prevent bending of the projecting portion and to maintain the projecting shape of the projecting portion in the grooved portion <NUM>.

Also, even in the state in which the energy director <NUM> is melted by ultrasonic welding, a uniform gap H is formed between the outside <NUM> of the projecting portion <NUM> of the first case and the outside <NUM> of the grooved portion <NUM> of the second case, since a support structure is formed at the first case <NUM> and the second case <NUM> according to the present invention, as shown in <FIG> and <FIG>.

As described above, the gap H is formed between the outside <NUM> of the projecting portion of the first case and the outside <NUM> of the grooved portion of the second case, as the coupling portions of the first case and the second case, along the entire outer peripheries thereof, whereby it is possible to solve a conventional problem in that burrs are generated on the coupling portions due to over-fusion of the battery case. Consequently, it is possible to remarkably reduce external defects.

<FIG> is a perspective view of the first case according to the present invention, and <FIG> is a perspective view of the second case according to the present invention.

Referring to <FIG> and <FIG>, a support structure is formed at the outer periphery of one open surface of the first case <NUM> and the outer periphery of one open surface of the second case <NUM> in order to form the gap H of <FIG>.

Specifically, the projecting portion <NUM> of the first case <NUM> includes an energy director <NUM> and a support portion <NUM>, and a stopper recess <NUM> is formed in the projecting portion <NUM>.

A stopper rib <NUM>, which is a support structure configured to maintain the gap H between the first case <NUM> and the second case <NUM>, is formed in the grooved portion <NUM> of the second case <NUM>. The stopper rib <NUM> is formed in the grooved portion <NUM> so as to project upwards, and performs a function of preventing the projecting portion of the first case <NUM> from being deeply coupled to the grooved portion even when the projecting portion is excessively melted.

In consideration of the fact that ultrasonic welding must be performed in the state in which the projecting portion <NUM> is deeply inserted into the grooved portion <NUM> to a certain extent in order to achieve stable fusion, however, it is preferable for the stopper recess <NUM> to be formed at the position of the projecting portion <NUM> corresponding to the stopper rib <NUM> such that the stopper rib <NUM> is mounted in the stopper recess <NUM>.

Also, in consideration of the fact that the energy director <NUM> is melted and the grooved portion <NUM> is filled with the melted energy director <NUM> in the state in which the stopper rib <NUM> is mounted in the stopper recess <NUM> in order to achieve sealing of the battery pack, the support portion <NUM> must be provided at the part at which the stopper recess <NUM> is formed in order to completely seal the battery pack. Consequently, it is preferable for the depth a1 of the stopper recess to be less than the height a2 of the projecting portion.

Meanwhile, the energy director is melted such that the height of the energy director is reduced or removed in the state in which the stopper rib <NUM>, which is formed so as to project, is disposed in the stopper recess <NUM>. At this time, the stopper rib must be deeply inserted into the innermost side of the stopper recess in order to stably fix the first case and the second case to each other. Consequently, the depth of the stopper recess <NUM> may be greater than the height of the stopper rib <NUM> based on the state before the energy director is melted.

<FIG> is a vertical sectional view showing the state in which the first case and the second case are fused to each other.

Referring to <FIG>, the sum b1 of the height of the stopper rib <NUM> and the height of the projecting portion <NUM> at the part thereof at which the stopper recess is formed is greater than the depth b2 of the grooved portion of the second case <NUM> in the state in which the first case <NUM> and the second case <NUM> are coupled and thermally fused to each other. That is, in the state in which the first case and the second case are coupled and thermally fused to each other, the lower end of the support portion is coupled to the stopper rib in contact therewith, and the sum of the height of the support portion and the height of the stopper rib is greater than the depth b2 of the grooved portion of the second case.

The reason for this is that the support structure is formed at the first case and the second case such that a uniform gap H is formed between the outside <NUM> of the projecting portion of the first case and the outside <NUM> of the grooved portion of the second case in the state in which the first case and the second case are coupled and thermally fused to each other.

In a concrete example, the support structure may be constituted by a pair of a stopper recess and a stopper rib, and the support structure may be formed on at least one side of each of the outer peripheries of the first case and the second case at which the first case and the second case are coupled to each other. That is, one or more pairs of stopper recesses and stopper ribs may be formed on the one side of each of the outer peripheries.

Alternatively, the support structure may be formed on the entire outer peripheries of the first case and the second case at which the first case and the second case are coupled to each other. That is, one or more support structures, each of which is constituted by a pair of a stopper recess and a stopper rib, may be formed on one side of each of the outer peripheries, and a plurality of support structures may be disposed at the entire outer peripheries. The support structures may be disposed so as to be spaced apart from each other by a predetermined distance, or may be disposed only on the straight outer periphery portions excluding corners of the outer peripheries.

As described above, the battery pack case according to the present invention includes a support structure configured to prevent over-fusion between the first case and the second case as the result of excessively close coupling therebetween when the first case and the second case are thermally fused to each other in a state of being coupled to each other. The stopper recess of the first case is caught by the stopper rib of the second case by the provision of the support structure, whereby the first case is prevented from being further inserted into the grooved portion of the second case. Consequently, it is possible to prevent a melted battery case resin from flowing out over the side walls of the grooved portion, and therefore it is possible to prevent external defects at the coupling portion of the battery pack case.

Additionally, the battery pack case according to the present invention may be a case for battery packs that are used as energy sources for various kinds of devices, wherein a through-hole, through which electrode terminals of battery cells received in the battery pack case are withdrawn outwards, may be formed in the battery pack case.

Claim 1:
A battery pack case configured to receive a plurality of battery cells, the battery pack case comprising:
a first case (<NUM>) and a second case (<NUM>) coupled to each other through an engagement between the first case (<NUM>) and the second case (<NUM>),
wherein a projecting portion (<NUM>) is formed on a coupling portion of the first case (<NUM>) at a middle part of the first case (<NUM>) in a thickness direction (D) thereof so as to project therefrom,
wherein a grooved portion (<NUM>) is formed in a coupling portion of the second case (<NUM>) at a middle part of the second case (<NUM>) in a thickness direction (D) thereof such that the projecting portion (<NUM>) is inserted into the grooved portion (<NUM>), and
wherein a uniform gap (H) is formed along the entire outer peripheries of the first case (<NUM>) and the second case (<NUM>) between an outside (<NUM>) of the projecting portion (<NUM>) of the first case (<NUM>) and an outside (<NUM>) of the grooved portion (<NUM>) of the second case (<NUM>),
wherein a support structure configured to form the gap (H) is formed in the grooved portion (<NUM>) of the second case (<NUM>),
characterized in that a stopper rib (<NUM>) is formed in the grooved portion (<NUM>) of the second case (<NUM>) as the support structure,
wherein a stopper recess (<NUM>) is formed at a position of the projecting portion (<NUM>) of the first case (<NUM>) corresponding to the stopper rib (<NUM>),
wherein a sum (b1) of a height of the stopper rib (<NUM>) and a height (a2) of the projecting portion (<NUM>) at a part thereof at which the stopper recess (<NUM>) is formed is greater than a depth (b2) of the grooved portion (<NUM>) of the second case (<NUM>).