Patent Description:
In recent years, the demand for portable electronic products such as notebooks, video cameras, mobile phones, or the like is rapidly increasing, and the development of electric vehicles, energy storage batteries, robots, satellites, or the like is in earnest. For this reason, high-performance secondary batteries enabling repeated charging and discharging are being actively researched.

Secondary batteries commercialized at the present include nickel cadmium batteries, nickel hydrogen batteries, nickel zinc batteries, and lithium secondary batteries. Among them, lithium secondary batteries are in the spotlight due to advantages such as free charging and discharging by little memory effect compared to nickel-based secondary batteries, and very low self-discharge rate and high energy density.

The lithium secondary battery mainly uses a lithium-based oxide and a carbon material as a positive electrode active material and a negative electrode active material, respectively. Also, the lithium secondary battery includes an electrode assembly in which a positive electrode plate and a negative electrode plate respectively coated with the positive electrode active material and the negative electrode active material are disposed with a separator being interposed therebetween, and an exterior, namely a battery case, for hermetically storing the electrode assembly together with an electrolyte.

In addition, the lithium secondary battery may be classified depending on the exterior shape into a can-type secondary battery in which an electrode assembly is included in a metal can and a pouch-type secondary battery in which an electrode assembly is included in a pouch made of an aluminum laminate sheet.

In particular, the demand for large-capacity battery modules applied to electric vehicles or the like is increasing recently. Such a large-capacity battery module includes a plurality of battery cells. Thus, when a fire or explosion occurs in a part of the plurality of battery cells, high-temperature fragments of the electrode assembly, flames, and high-temperature gas are discharged to adjacent other battery cells to increase the temperature thereof. Accordingly, thermal runaway, fire, or the like may be propagated to adjacent other battery cells to cause a secondary explosion, thereby increasing the damage.

The prior art relevant for the present invention are given by <CIT> and <CIT>.

The present disclosure is designed to solve the problems of the related art, and therefore the present disclosure is directed to providing a battery module with improved stability against fire or explosion, a battery pack and a vehicle including the same.

Also, it will be easily understood that the objects and advantages of the present disclosure may be realized by the means shown in the appended claims.

The present invention is as defined in the annexed independent claims. Particular embodiments are given by the additional features of the dependent claims.

In one aspect of the present disclosure, there is provided a battery module, comprising:.

Also, two or more ventilation holes may be provided in a region of the screen member that faces the exposure hole.

In addition, the ventilation hole may be configured to have a diameter gradually decreasing in an outward direction.

Also, the ventilation hole may be shaped so that the screen member is perforated in a zigzag form.

Moreover, the battery module further comprises a connection plate interposed between the screen member and the module case and having electric conductivity, the connection plate including a body portion having a plate shape extending in a horizontal direction, a connection portion extending from the body portion to contact the electrode terminal, and a connection hole formed by opening a part of the body portion so that the connection portion is located in the opening thereof.

In addition, the connection plate includes an extension portion configured to protrusively extend in a horizontal direction from an outer circumference of the connection hole to hide a part of the connection hole.

Further, the module case includes a plurality of cover portions configured to protrude toward the connection plate from an outer circumference of the plurality of exposure holes, respectively, the cover portion having a hollow and being shaped to have an open top end.

Also, the cover portion may include a bending part bent at the open top end to extend in a horizontal direction to hide a part of the connection hole of the connection plate.

In addition, in another aspect of the present disclosure, there is also provided a battery pack, comprising at least one battery module as above.

Moreover, in another aspect of the present disclosure, there is also provided a vehicle, comprising at least one battery module as above.

According to an embodiment of the present disclosure, the battery module according to the present disclosure includes the screen member. This structure may physically block the movement of a high-temperature active material discharged from the exploded battery cell to adjacent battery cells while maintaining the function of ejecting the gas and flame generated when the battery cell is ignited. By doing so, when any one of the plurality of battery cells behaves abnormally (electric short, thermal runaway), if the battery cell explodes to eject the internal material to the outside, gas and flame are ejected through the exposure hole, but the movement of the high-temperature active material is suppressed by the screen member. Therefore, it is possible to prevent the ejected internal material from moving to other adjacent battery cells through other adjacent exposure holes. That is, by forming the ventilation hole to be smaller than the exposure hole, the screen member may allow the high-temperature gas ejected through the exposure hole to pass through the ventilation hole, but prevents the ejected fragments of the electrode assembly from passing through the ventilation hole. Accordingly, in the present disclosure, it is possible to prevent chain ignition, such as propagating of thermal runaway, fire or explosion to other battery cells, thereby greatly improving the safety.

<FIG> is a perspective view schematically showing a battery module according to an embodiment of the present disclosure. <FIG> is an exploded perspective view schematically showing the battery module according to an embodiment of the present disclosure. Also, <FIG> is a sectional view schematically showing a battery cell of the battery module according to an embodiment of the present disclosure.

Referring to <FIG>, a battery module <NUM> according to an embodiment of the present disclosure includes a plurality of battery cells <NUM>, a module case <NUM>, and a screen member <NUM>.

Specifically, the battery cell <NUM> may include an electrode assembly <NUM>, a battery can <NUM>, and a cap assembly <NUM>. For example, the battery cell <NUM> may be a cylindrical battery cell. In addition, the battery cell <NUM> electrode terminals <NUM> respectively located at an upper portion and a lower portion thereof. The plurality of battery cells <NUM> may be electrically connected by a connection plate <NUM> having a metal material. The plurality of battery cells <NUM> may be electrically connected in series, in parallel, or in series and in parallel, through the connection plate <NUM>.

The electrode assembly <NUM> may have a wound structure with a separator being interposed between a positive electrode plate and a negative electrode plate. A positive electrode tab <NUM> may be attached to the positive electrode plate and connected to the cap assembly <NUM>, a negative electrode tab <NUM> may be attached to the negative electrode plate and connected to a lower end of the battery can <NUM>.

The battery can <NUM> may have an empty space so that the electrode assembly <NUM> may be accommodated therein. In particular, the battery can <NUM> may be configured in a cylindrical shape with an open top end. In addition, the battery can <NUM> may be made of a metal material such as steel or aluminum to secure rigidity. In addition, the negative electrode tab may attached to the bottom of the battery can <NUM>, such that not only the lower portion of the battery can <NUM> but also the battery can <NUM> itself may function as a negative electrode terminal.

The cap assembly <NUM> may be coupled to the open top end of the battery can <NUM> to seal the open top end of the battery can <NUM>. The cap assembly <NUM> may have a circular or rectangular shape depending on the shape of the battery can <NUM>, and may include sub-components such as a top cap C1, a vent unit C2, and a gasket C3.

Here, the top cap C1 may be located at an uppermost portion of the cap assembly <NUM> and configured to protrude upward. In particular, the top cap C1 may function as a positive electrode terminal in the battery cell <NUM>. Accordingly, the top cap C1 may be electrically connected to an external device, for example another battery cell <NUM> or a charging device, through the connection plate <NUM> or the like. The top cap C1 may be made of, for example, a metal material such as stainless steel or aluminum. If a severe explosion or fire occurs at the battery cell <NUM>, at least a part of the top cap C1 may be torn or detached from the battery can <NUM>, thereby opening the battery can <NUM>.

In addition, the vent unit C2 may be configured to be deformed (ruptured) when the internal pressure of the battery cell <NUM>, namely the internal pressure of the battery can <NUM>, increases over a predetermined level, so that the gas inside the battery can <NUM> may be discharged to the outside through an opening D of the top cap C1. Here, the predetermined level of the internal pressure may be <NUM> to <NUM> atmospheres. At this time, when the battery cell <NUM> explodes due to an abnormal behavior, the cap assembly <NUM> may be detached from the battery can <NUM>. In addition, when gas explodes in the battery cell <NUM>, the gas generated therein and fragments of the electrode assembly <NUM> or the like may be ejected to the outside.

Moreover, the gasket C3 may be made of a material with electrical insulation so that edge portions of the top cap C1 and the vent unit C2 may be insulated from the battery can <NUM>.

Meanwhile, the cap assembly <NUM> may further include a current interrupt device C4. The current interrupt device C4 is also called CID. When the internal pressure of the battery increases due to gas generation so that the shape of the vent unit C2 is reversed, the contact between the vent unit C2 and the current interrupt device C4 may be broken, or the current interrupt device C4 may be damaged, thereby blocking the electrical connection between the vent unit C2 and the electrode assembly <NUM>.

The above configuration of the battery cell <NUM> is widely known to those skilled in the art at the time of filing of this application, and thus will not be described in more detail. In addition, although an example of the cylindrical battery cell <NUM> is illustrated in <FIG>, the battery module <NUM> according to the present disclosure is not limited to the configuration of the battery cell <NUM> having a specific shape. That is, various types of battery cells known at the time of filing of this application may be employed in the battery module <NUM> according to the present disclosure.

In addition, the module case <NUM> is configured to accommodate the plurality of battery cells <NUM> therein. The module case <NUM> may include an upper frame <NUM> and a lower frame <NUM>. Each of the upper frame <NUM> and the lower frame <NUM> may include a plurality of hollows <NUM> configured so that the plurality of battery cells <NUM> are partially inserted therein.

Moreover, the module case <NUM> has a plurality of exposure holes <NUM>. Each of the plurality of exposure holes <NUM> may be formed by perforating a part of the module case <NUM> so that the upper portion and the lower portion of each of the plurality of battery cells <NUM> may be exposed to the outside. For example, as shown in <FIG>, a plurality of exposure holes <NUM> may be provided in each of the upper surface of the upper frame <NUM> and the lower surface of the lower frame <NUM> so that the electrode terminals <NUM> respectively provided to the upper portion and the lower portion of the plurality of battery cells <NUM> are exposed to the outside. The exposure hole <NUM> may be formed at a position corresponding to the vent unit C2 of the battery cell <NUM>. For example, in the battery cell <NUM> of <FIG>, the vent unit C2 is located at a top end of the battery cell <NUM>, and thus the exposure hole <NUM> is provided at the top end of the battery cell <NUM>. More specifically, the exposure hole <NUM> may be provided at a position adjacent to the opening D of the top cap C1 through which the gas discharged from the vent unit C2 is discharged to the outside of the battery can <NUM>.

Preferably, the exposure hole <NUM> may be formed in a size that may cover the entire opening D of the battery can <NUM>. For example, referring to <FIG> as an example, the top cap C1 of the battery can <NUM> may have a ring-shaped opening D. At this time, the exposure hole <NUM> may be configured to have a diameter greater than or equal to the diameter of the ring-shaped opening D.

In addition, the screen member <NUM> is located in any one or more of the upper portion and the lower portion of the module case <NUM>. For example, as shown in <FIG>, each of the two screen members <NUM> may be located at the upper portion and the lower portion of the module case <NUM>. The screen member <NUM> may be made of a material having high thermal conductivity while being electrically insulating. For example, the screen member <NUM> may include a silicone resin.

The screen member <NUM> may have a plate shape as a whole. For example, the screen member <NUM> may have a plate shape extending in a horizontal direction to cover a portion of the module case <NUM> where the plurality of exposure holes <NUM> are formed. Each screen member <NUM> may have a ventilation hole <NUM> having a smaller size than the exposure hole <NUM>. The ventilation hole <NUM> may have a size of <NUM>% to <NUM>% based on the size of the exposure hole <NUM>, for example. In addition, when the battery cell <NUM> is configured to open a specific part by an explosion, the ventilation hole <NUM> may be configured to have a smaller size than the opening size of the opened portion.

Therefore, according to this configuration of the present disclosure, the battery module <NUM> according to the present disclosure includes the screen member <NUM>. This structure may physically block the movement of a high-temperature active material discharged from the exploded battery cell to adjacent battery cells while maintaining the function of ejecting, namely venting, the gas and flame generated when the battery cell is ignited. By doing so, when any one of the plurality of battery cells <NUM> behaves abnormally, if the battery cell <NUM> explodes to eject the internal material to the outside, gas and flame are ejected through the exposure hole <NUM>, but the movement of the high-temperature active material is suppressed by the screen member <NUM>. Therefore, it is possible to prevent the ejected internal material from moving to other adjacent battery cells <NUM> through other adjacent exposure holes <NUM>. That is, by forming the ventilation hole <NUM> to be smaller than the exposure hole <NUM>, the screen member <NUM> may allow the high-temperature gas ejected through the exposure hole <NUM> to pass through the ventilation hole <NUM>, but prevents the ejected fragments of the electrode assembly from passing through the ventilation hole <NUM>. Accordingly, in the present disclosure, it is possible to prevent chain ignition, such as propagating of thermal runaway, fire or explosion to other battery cells <NUM>, thereby greatly improving the safety.

<FIG> is a plan view schematically showing a screen member of a battery module according to another embodiment of the present disclosure.

Referring to <FIG> along with <FIG>, in a battery module <NUM> according to another embodiment of the present disclosure, two or more screen members <NUM> may be provided in a region A where the ventilation hole <NUM> faces the exposure hole <NUM>. For example, as shown in <FIG>, the screen member <NUM> may have six regions A facing six exposure holes <NUM>. At this time, approximately six ventilation holes <NUM> may be located in six regions A of the screen member <NUM> respectively facing the six exposure holes <NUM>.

Therefore, according to this configuration of the present disclosure, since the screen member <NUM> of the present disclosure has two or more ventilation holes <NUM> at positions corresponding to the exposure holes <NUM>, when the battery cell <NUM> explodes, the ejected gas is effectively discharged, and fragments of the electrode assembly may be screened not to pass through the ventilation hole <NUM>. That is, a part of the plurality of ventilation holes <NUM> may be formed at positions spaced apart not to face the opening of the battery cell <NUM> that is generated in the battery cell <NUM> when the battery cell <NUM> explodes, thereby preventing the scattered solid materials from passing through the ventilation hole <NUM>.

<FIG> is a partial sectional view schematically showing a screen member of a battery module according to still another embodiment of the present disclosure.

Referring to <FIG> along with <FIG>, in the screen member <NUM> of the battery module <NUM> according to still another embodiment of the present disclosure, the ventilation hole <NUM> may be configured to have a diameter gradually decreasing in an outward direction (a direction away from the battery cell <NUM>, an upper direction in this embodiment). That is, a tapered structure K may be provided on the inner surface of the ventilation hole <NUM>. For example, as shown in <FIG>, an inlet of the ventilation hole <NUM> at an inner side close to the battery cell <NUM> may be larger than an outlet at an outer side. Moreover, the ventilation hole <NUM> may have an inclined inner surface that is inclined toward the diameter center of the opening from the inlet at an inner side to the outlet at an outer side.

Therefore, according to this configuration of the present disclosure, in the present disclosure, since the ventilation hole <NUM> is configured to have a diameter gradually decreasing in an outward direction, when the battery cell <NUM> explodes, it is possible to effectively discharge the ejected gas G but prevent the accompanying fragments of the electrode assembly from passing by being blocked by the inclined inner surface of the ventilation hole <NUM>. That is, if the ventilation hole <NUM> has an inner surface of the tapered structure K so that its diameter gradually decreases in an outward direction, the area capable of screening the fragments of the electrode assembly may be further increased, thereby more effectively preventing the scattered solid materials from passing through the ventilation hole <NUM>.

Referring to <FIG> along with <FIG>, in the screen member <NUM> of the battery module <NUM> according to still another embodiment of the present disclosure, the ventilation hole <NUM> may be shaped so that the screen member <NUM> is perforated in a zigzag form along the thickness direction of the screen member <NUM>. For example, the ventilation hole <NUM> may be shaped so that the ventilation hole <NUM> is perforated to be inclined in one direction from an inlet formed close to the battery cell <NUM>, and the penetrating direction is changed to be inclined in the other direction at the other side.

Therefore, according to this configuration of the present disclosure, since the screen member <NUM> of the present disclosure has the ventilation hole <NUM> of a zigzag form, when the battery cell <NUM> explodes, the ejected gas may pass through the ventilation hole <NUM>, but accompanying fragments of the electrode assembly may be blocked by the inclined inner surface of the ventilation hole <NUM> not to pass. Accordingly, in the present disclosure, the high-temperature fragments of the electrode assembly do not move to other adjacent battery cells <NUM> due to the explosion of the battery cell <NUM>, thereby preventing thermal runaway or fire from occurring due to the moved fragments of the electrode assembly.

Meanwhile, referring to <FIG> again, the battery module <NUM> of the present disclosure further includes a connection plate <NUM>. The connection plate <NUM> is interposed between the screen member <NUM> and the module case <NUM>. The connection plate <NUM> has electrical conductivity. For example, the connection plate <NUM> may include a metal such as aluminum, copper, or nickel.

In addition, the connection plate <NUM> includes a body portion <NUM>, a connection portion <NUM>, and a connection hole <NUM>. The body portion <NUM> may have a plate shape extending in a horizontal direction. The body portion <NUM> may be mounted to the upper portion or the lower portion of the module case <NUM>. For example, as shown in <FIG>, the two connection plates <NUM> may be mounted to the upper portion and the lower portion of the module case <NUM>, respectively.

Moreover, the connection portion <NUM> is formed to extend from the body portion <NUM> to contact the electrode terminal <NUM>. For example, as shown in <FIG>, the connection portion <NUM> may have a bifurcated structure protrusively extending from the body portion <NUM>. The connection portion <NUM> may be welded to the electrode terminal <NUM>. At this time, as a welding method, resistance welding may be used, for example.

In addition, the connection hole <NUM> may be configured such that a part of the body portion <NUM> is opened and the connection portion <NUM> is located inside the opening. The connection hole <NUM> may have an approximately circular shape. The connection hole <NUM> may be configured to face the exposure hole <NUM> of the module case <NUM>.

<FIG> is a partial perspective view schematically showing a connection plate of the battery module according to still another embodiment of the present disclosure.

Referring to <FIG>, the connection plate <NUM> may include an extension portion <NUM> configured to cover a part of the connection hole <NUM>. The extension portion <NUM> may have a shape protrusively extending from an edge of the connection hole <NUM> in a horizontal direction. The extension portion <NUM> may be a portion protruding toward the connection portion <NUM> from the edge of the connection hole <NUM>. For example, as shown in <FIG>, the connection plate <NUM> may be configured such that five extension portions <NUM> protrude from the edge of the connection hole <NUM> toward the connection portion <NUM>.

<FIG> is a partial sectional view schematically showing a part of the battery module, taken along the line C-C' of <FIG>.

Referring to <FIG> along with <FIG> and <FIG>, in the battery module <NUM> according to an embodiment of the present disclosure, a plurality of cover portions <NUM> may be provided to the upper surface or the lower surface of the module case <NUM>. The plurality of cover portions <NUM> may have a rib shape protruding toward the connection plate <NUM> from an outer circumference of each of the plurality of exposure holes <NUM>. The cover portion <NUM> may be formed with a hollow penetrating in a vertical direction. The cover portion <NUM> formed on the upper surface of the module case <NUM> may have an open top end. For example, as shown in <FIG>, the module case <NUM> may include six cover portions <NUM> protruding from the upper surface of the module case <NUM> toward the connection plate to cover the six exposure holes <NUM>.

In addition, the connection plate <NUM> may be mounted on the top end of the cover portion <NUM>. That is, the top surface of the cover portion <NUM> may be in contact with the lower surface of the connection plate <NUM>. In addition, the screen member <NUM> may be mounted to the upper surface of the connection plate <NUM>. The exposure hole <NUM>, the connection hole <NUM> and the ventilation hole <NUM> may be configured to communicate with each other. Therefore, ultimately, the vent unit C2 of the battery cell <NUM>, the opening D of the top cap C1, the exposure hole <NUM>, and the ventilation hole <NUM> may all be positioned on the same line. Accordingly, the path for discharging gas is minimized, so that the gas may be smoothly discharged to the outside of the battery cell <NUM>. The space between the upper surface of the upper frame <NUM> and the connection plate <NUM> may serve as a venting space in front of the battery cell <NUM>.

Moreover, when an abnormal behavior of the battery cell <NUM> occurs so that the internal material is ejected to the outside, the cover portion <NUM> may be configured to prevent the internal material from moving to other adjacent battery cells <NUM> through other adjacent exposure holes <NUM>. The cover portion <NUM> may have a cylindrical shape to surround the exposure hole <NUM>.

Therefore, according to this configuration of the present disclosure, the module case <NUM> included in the battery module <NUM> according to the present disclosure includes the cover portion <NUM> protruding from the outer circumference of the exposure hole <NUM> toward the connection plate <NUM>. This structure may physically block the movement of a high-temperature active material discharged from the exploded battery cell to adjacent battery cells while maintaining the function of ejecting, namely venting, the gas and flame generated when the battery cell is ignited. By doing so, when the battery cell <NUM> behaves abnormally to explode so that the internal material is ejected, gas and flame are ejected through the exposure hole <NUM>, but the movement of the high-temperature active material is suppressed by the cover portion <NUM>. Therefore, it is possible to prevent the internal material from moving to other adjacent battery cells <NUM> through other exposure holes <NUM>, thereby preventing chain ignition, such as propagating of thermal runaway, fire or explosion to other battery cells <NUM>. Accordingly, the present disclosure may greatly improve the safety.

In the present disclosure, since the top surface of the cover portion <NUM> is in contact with the lower surface of the connection plate <NUM>, even if an explosion occurs in some of the plurality of battery cells <NUM>, it is possible to prevent the high-temperature active material, gas and flame from moving to adjacent battery cells <NUM> through the empty space between the connection plate <NUM> and the module case <NUM>. The space between the upper surface of the upper frame <NUM> and the connection plate <NUM> serves as a venting space in front of the battery cell <NUM>, and the cover portion <NUM> maintains the venting space in an upward direction of the battery cell <NUM>, while making the venting space maintaining the venting space to be independent for each battery cell <NUM> in a lateral direction of the battery cell <NUM>. Accordingly, the cover portion <NUM> may suppress that the high-temperature active material is discharged to move to adjacent battery cells <NUM>, while maintaining the function of ejecting the gas and flame generated during ignition. The cover portion <NUM> constitutes an isolated mechanism structure for each battery cell <NUM> so as to suppress the scattering of an active material mass. In this way, chain ignition may be suppressed, thereby greatly improving the safety of the battery module <NUM> of the present disclosure.

<FIG> is a vertical sectional view schematically showing a part of the battery module according to still another embodiment of the present disclosure.

Referring to <FIG>, in the battery module <NUM> according to still another embodiment of the present disclosure, when compared with the cover portion of <FIG>, the cover portion <NUM> may further include a bending part 132a. The bending part 132a may be configured to hide a part of the exposure hole <NUM> of the module case <NUM>. The bending part 132a may be a portion bent to extend in a horizontal direction from an end of the cover portion <NUM> protruding upward. The bending part 132a may be configured to hide a part of the open end formed by the hollow of the cover portion <NUM>. For example, the bending part 132a may be configured to be bent toward the central from the open end of the upper portion of the cover portion <NUM> so that the opening of the open end is more narrowed.

Therefore, according to this configuration of the present disclosure, in the present disclosure, even if an explosion occurs in some of the plurality of battery cells <NUM> to eject an internal material (e.g., an active material), the amount of material discharged to the outside of the module case <NUM> may be effectively reduced by the bending part 132a. Accordingly, it is possible to effectively reduce the movement of the internal material ejected from the exploded battery cell <NUM> to other adjacent battery cells <NUM>. Ultimately, in the present disclosure, it is possible to provide the battery module <NUM> with greatly improved safety.

Meanwhile, a battery pack according to an embodiment of the present disclosure includes at least one battery module <NUM> as described above and a battery management system (BMS) electrically connected to the battery module <NUM>. The BMS may include various circuits or elements to control charging and discharging of the plurality of battery cells.

Meanwhile, a vehicle (not shown) according to an embodiment of the present disclosure includes at least one battery module <NUM> as described above and a vehicle body having an accommodation space for accommodating the battery module <NUM>. For example, the vehicle may be an electric vehicle, an electric scooter, an electric wheelchair, or an electric bike.

Claim 1:
A battery module (<NUM>), comprising:
a plurality of battery cells (<NUM>), each having electrode terminals (<NUM>) respectively formed at an upper portion and a lower portion thereof;
a module case (<NUM>) configured to accommodate the plurality of battery cells (<NUM>) and having a plurality of exposure holes (<NUM>) configured to expose the upper portion or the lower portion of the battery cell (<NUM>);
a screen member (<NUM>) located at any one or more of an upper portion and a lower portion of the module case (<NUM>) and having a plate shape, the screen member (<NUM>) being configured to have a ventilation hole (<NUM>) with a smaller size than the exposure hole (<NUM>); and
a connection plate (<NUM>) interposed between the screen member (<NUM>) and the module case (<NUM>) and having electric conductivity, the connection plate (<NUM>) including a body portion (<NUM>) having a plate shape extending in a horizontal direction, a connection portion (<NUM>) extending from the body portion (<NUM>) to contact the electrode terminal (<NUM>), and a connection hole (<NUM>) formed by opening a part of the body portion (<NUM>) so that the connection portion (<NUM>) is located in the opening thereof,
wherein the module case (<NUM>) includes a plurality of cover portions (<NUM>) configured to protrude toward the connection plate (<NUM>) from an outer circumference of the plurality of exposure holes (<NUM>), respectively, the cover portion (<NUM>) having a hollow and being shaped to have an open top end.