JP7803079B2 - Battery unit gas exhaust structure - Google Patents

Description

The present invention relates to a gas exhaust structure for a battery unit having multiple battery cells arranged side by side.

Battery cells are equipped with a gas exhaust valve that opens when abnormal heat generation causes gas to be generated inside, resulting in high internal pressure. Battery units are equipped with an exhaust gas duct that directs exhaust gases emitted from the battery cells to the outside to prevent the exhaust gases from damaging surrounding battery cells. If the temperature of the exhaust gases emitted from this exhaust gas duct is high, there is a concern that the exhaust gases may damage equipment around the battery unit. Therefore, it is desirable to reduce the temperature of the exhaust gases as they pass through the exhaust gas duct.

Patent Document 1 describes the installation of multiple flat plate sections within an exhaust gas duct, which changes the flow direction of exhaust gas multiple times in a zigzag pattern. By lengthening the path traveled by the exhaust gas, the method promotes heat exchange between the exhaust gas and the exhaust gas duct, thereby lowering the exhaust gas temperature.

International Publication No. WO2016/136193

The above method of lengthening the exhaust gas flow path requires the installation of multiple flat plate sections within the exhaust gas duct in order to lower the exhaust gas temperature. This makes the duct structure more complex and increases the product cost.

The present invention aims to reduce the temperature of exhaust gases emitted from battery cells without complicating the exhaust gas duct structure.

To solve the above problems, the present invention actively utilizes turbulent heat transfer to lower exhaust gas temperatures.

The gas exhaust structure for a battery unit disclosed herein comprises a battery module having a plurality of battery cells arranged in parallel, and an exhaust gas duct provided therein through which exhaust gas emitted from the battery cells flows and is exhausted to the outside,
The exhaust gas duct comprises an exhaust gas inlet, a tapered passage through which the exhaust gas flowing in from the inlet passes, the passage width of which narrows as it goes further forward, and a shielding wall that blocks the forward movement of the exhaust gas that has passed through the tapered passage and deflects the exhaust gas sideways, thereby causing a vortex in the exhaust gas at an adjacent location separated by the passage wall of the tapered passage, an exhaust port that discharges the exhaust gas to the outside opens so as to face the location where the vortex is caused in the exhaust gas, the exhaust gas duct has the inlet and the exhaust port for each battery cell, and for each battery cell, a pair of tapered passages that extend in the same direction along a line connecting the inlet and the exhaust port of the exhaust gas duct are arranged symmetrically with respect to the line on both sides of the line, and the shielding wall widens in front of the pair of tapered passages so as to block the forward movement of the exhaust gas that has passed through each tapered passage .

According to this design, the flow velocity of the exhaust gas increases as it passes through the tapered passage. Then, when it collides with the barrier wall, its flow direction deviates laterally, generating a strong exhaust gas vortex. This increases the temperature gradient of the exhaust gas near the barrier wall where the exhaust gas collides. Furthermore, new exhaust gas is drawn into the vortex generated in the area adjacent to the tapered passage, increasing the temperature gradient of the exhaust gas near the passage wall. This increases the heat transfer coefficient from the exhaust gas to the barrier wall and the passage wall. Furthermore, the formation of the vortex increases the time the exhaust gas flows inside the exhaust gas duct. This increases the heat transfer coefficient from the exhaust gas to the barrier wall and the passage wall, and the longer the flow time of the exhaust gas, resulting in a significant temperature drop of the exhaust gas before reaching the exhaust outlet of the exhaust gas duct. Furthermore, the exhaust gases that pass through the tapered passages on both sides of the line connecting the inlet and the outlet are blocked by the barrier wall and collide with each other as they flow along the barrier wall. As a result, two strong vortices are generated symmetrically on both sides of the line between the two tapered passages, which facilitates heat transfer from the exhaust gas to both tapered passages, resulting in a significant decrease in the exhaust gas temperature.

In one embodiment, each of the plurality of battery cells has a rectangular shape in a plan view, is arranged side by side in a short side direction of the rectangle, and is provided with a gas release valve at the center of a long side direction on an upper surface of each battery cell, for releasing gas generated inside the battery cell;
the inlet of the exhaust gas duct opens to correspond to the gas exhaust valve at the center of the long side of the battery cell, and the outlet of the exhaust gas duct opens to correspond to an end side of the long side of the battery cell;
The tapered passages on both sides of the line connecting the inlet and the outlet are each inclined so that the passage wall on the side closer to the line gets farther away from the line as it goes forward, and the passage width in the direction in which the battery cells are arranged is tapered.

This allows gas released from each battery cell to be cooled and discharged through the exhaust gas duct from the inlet corresponding to each gas exhaust valve. In this embodiment, the tapered passages on both sides of the line connecting the inlet and outlet have inclined passage walls on the side closest to the line, tapering the passage width in the direction in which the battery cells are arranged side by side. Therefore, the inclined passage walls act as a guide, promoting the flow of exhaust gas into the tapered passage, and the inclined passage walls contribute to the formation of a vortex flow of exhaust gas that reverses direction due to being blocked by the shielding wall. This results in a significant drop in the temperature of the exhaust gas before it reaches the exhaust port of the exhaust gas duct.

In one embodiment, the tapered passage provided for one of the adjacent battery cells and located closer to the other battery cell, and the tapered passage provided for the other battery cell and located closer to the one battery cell, are spaced apart in the direction in which the battery cells are arranged side by side, and a gap is provided between the tip of the passage wall on the side farthest from the line of each of the tapered passages and the shielding wall.

The fact that the tapered passages on one side of adjacent battery cells and the tapered passages on the other side are spaced apart in the direction in which the battery cells are arranged means that the two tapered passages do not share the passage wall on the side farther from the line, but each have their own separate passage wall on that side. This increases the amount of heat transferred from the exhaust gas to the passage wall. Furthermore, because a gap is formed between the tip of the passage wall on the side farther from the line and the shielding wall, exhaust gas flowing between the two tapered passages also passes through the gap and merges with the exhaust gas passing through the tapered passage. Therefore, exhaust gas flowing between the two tapered passages is also caught in a vortex and loses heat to the shielding wall and passage wall, which helps to lower the temperature of the exhaust gas leaving the exhaust port.

In one embodiment, a tip of a passage wall of the tapered passage farther from the line protrudes forward than a tip of the passage wall closer to the line, so that more of the exhaust gas passing through the tapered passage flows to an adjacent portion of the tapered passage on the line side, which is advantageous for strengthening the formation of vortex flows in the adjacent portion.

According to the present invention, exhaust gas is passed through a tapered passage, and the forward movement of the exhaust gas passing through the passage is interrupted by a shielding wall, which deflects the exhaust gas to the side, thereby generating a vortex in the exhaust gas at an adjacent location separated by the passage wall of the tapered passage. This increases the heat transfer coefficient from the exhaust gas to the shielding wall and passage wall, and therefore significantly reduces the temperature of the exhaust gas from when it enters the exhaust gas duct to when it reaches the exhaust outlet.

FIG. FIG. FIG. 4 is a plan view showing the internal structure of the exhaust gas duct. Streamline diagram of exhaust gas in the exhaust gas duct (streamline diagram along line B-B in Figure 6). Detailed streamline diagram of exhaust gases in a section of an exhaust gas duct. Streamline diagram along line A-A in Figure 4. FIG. 4 is a plan view showing the internal structure of an exhaust gas duct of a comparative example. FIG. 10 is a graph showing the results of unsteady calculation of the outlet gas temperature of each of the example, the comparative example, and the case without ribs. FIG. 10 is a graph showing the results of unsteady calculation of the heat transfer coefficient from exhaust gas to the rib for each of the example and the comparative example. FIG. 10 is a graph showing the results of unsteady calculation of the amount of heat transfer from exhaust gas to the rib for each of the example and the comparative example. 4 is a plan view similar to FIG. 3 according to another embodiment;

The following describes a preferred embodiment of the present invention with reference to the accompanying drawings. The following description of the preferred embodiment is merely exemplary in nature and is not intended to limit the present invention, its applications, or its uses.

<Battery unit>
The battery unit 1 shown in FIG. 1 is for use in a vehicle and includes a battery module 3 made up of a plurality of chargeable and dischargeable battery cells 2 arranged side by side, and an exhaust gas duct 4 is provided above the battery module 3 .

As shown in Figure 2, the battery cell 2 has a rectangular parallelepiped shape with opposing sides wider than the other sides, top, and bottom. A gas exhaust valve 5 is provided in the center of the top surface of the battery cell 2, which is rectangular in plan view, to release gas generated inside the battery cell 2, and positive and negative electrode terminals 6, 7 are provided on both ends of the top surface.

As shown in Figure 1, multiple battery cells 2 are arranged side by side so that they overlap in the direction of the short sides of their upper surfaces, i.e., so that their wide sides face each other. Although not shown, refrigerant passage members are interposed between adjacent battery cells 3.

<Exhaust gas duct structure>
The exhaust gas duct 4 is a rectangular duct that passes through and discharges exhaust gas ejected from the gas exhaust valves 5 of the battery cells 2 to the outside. The exhaust gas duct 4 extends above the battery module 3 in the direction in which the battery cells 2 are arranged side by side (hereinafter referred to as the "cell arrangement direction"). Multiple exhaust ports 8 are open at intervals in the cell arrangement direction on both side edges of the top surface of the exhaust gas duct 4.

As shown in Figure 3, an exhaust gas inlet 9 opens at the bottom surface of one end of the exhaust gas duct 4, in the center of the duct width direction. Inside the exhaust gas duct 4, a tapered passage 14 and a vortex generating section 16 are formed by multiple horizontal ribs 11 extending in the duct width direction and multiple inclined ribs 12, 13 inclined relative to the duct width direction. The horizontal ribs 11 and inclined ribs 12, 13 form the passage walls of the tapered passage 14. A detailed explanation is provided below.

The exhaust gas inlet 9 opens at a position corresponding to the gas exhaust valve 5 of the battery cell 2 at the end of the module, which could become a trigger cell for thermal runaway in the battery module 3 in the event of a vehicle collision, etc. The exhaust gas outlet 8 opens at a position corresponding to each end of the long side of the top surface of the battery cells 2 other than the trigger cell.

The horizontal ribs 11 and the inclined ribs 12 and 13 are flat ribs that rise from the bottom surface of the exhaust gas duct 4. The inclined ribs 12 and 13 are inclined in opposite directions. Inside the exhaust gas duct 4, four horizontal ribs 11, two inclined ribs 12, and two inclined ribs 13 are provided, one for each of the other battery cells 2.

Specifically, two horizontal ribs 11 and two inclined ribs 12, 13 are arranged inside the exhaust gas duct 4 in a position corresponding to one end of the top surface of each battery cell 2 (toward one end in the duct width direction). The two horizontal ribs 11 are arranged facing each other in the direction of the short side of the top surface of the battery cell 2 (the direction in which the cells are arranged side by side), with the exhaust outlet 8 between them. Between the two horizontal ribs 11, an inclined rib 12 is arranged, inclined so that it approaches one of the horizontal ribs 11 closer to the inlet 9 as it approaches the end in the duct width direction, and an inclined rib 13 is arranged, inclined so that it approaches the other horizontal rib 11 farther from the inlet 9 as it approaches the end in the duct width direction.

In addition, two horizontal ribs 11 and two inclined ribs 12, 13 are arranged inside the exhaust gas duct 4 in a position corresponding to the other end of the top surface of each battery cell 2 (towards the other end in the duct width direction). As with the positions near one end described above, the two horizontal ribs 11 are arranged facing each other in the direction of the short side of the top surface of the battery cell 2 (the direction in which the cells are arranged side by side), with the exhaust outlet 8 between them. Between the two horizontal ribs 11, an inclined rib 13 is arranged, inclined so that it approaches one of the horizontal ribs 11 closer to the inlet 9 as it approaches the end in the duct width direction, and an inclined rib 12 is arranged, inclined so that it approaches the other horizontal rib 11 farther from the inlet 9 as it approaches the end in the duct width direction.

The inclined rib 12 is inclined so that it approaches one of the horizontal ribs 11 as it approaches the end of the duct width, and this horizontal rib 11 and inclined rib 12 form a tapered passage 14 whose passage width in the cell arrangement direction gradually narrows as it approaches the end of the duct width. Similarly, the inclined rib 13 is inclined so that it approaches the other horizontal rib 11 as it approaches the end of the duct width, and this horizontal rib 11 and inclined rib 13 form a tapered passage 14 whose passage width in the cell arrangement direction gradually narrows as it approaches the end of the duct width.

The side walls of the exhaust gas duct 4 stand in front of one tapered passage 14 closer to the inlet 9 and the other tapered passage 14 further from the inlet 9. These side walls form a wide shielding wall 15 that blocks the forward movement of exhaust gas that has passed through each tapered passage 14. The exhaust gas that has passed through the tapered passage 14 is blocked by the shielding wall 15 and is deflected to the side. Thus, the inclined ribs 12, 13 of the tapered passage 14 and the shielding wall 15 form a vortex generating section 16, which will be described in detail later.

In this example, the tapered passage 14 provided for one of the adjacent battery cells 2 and located closer to the other battery cell 2, and the tapered passage 14 provided for the other battery cell 2 and located closer to the one battery cell 2, are spaced apart in the cell arrangement direction. In other words, the two tapered passages 14 do not share the same horizontal rib 11, but are formed using separate horizontal ribs 11. In addition, there is a gap between the end of the inclined rib 12 closest to the center of the duct width direction and the end of the inclined rib 13 closest to the center of the duct width direction.

When viewed from the perspective of a line L connecting two opposing exhaust ports 8 in the duct width direction, the one tapered passage 14 and the other tapered passage 14 are arranged symmetrically with respect to the reference line L and extend in the same direction along the line L. Furthermore, the pair of tapered passages 14 provided on both sides of the reference line L have inclined ribs 12, 13, which form the passage walls closer to the reference line L, inclined away from the line L as they move forward, so that the passage width in the direction of cell arrangement is tapered.

Furthermore, when viewed from the perspective of a center line extending in the longitudinal direction of the exhaust gas duct 4, the tapered passages 14 on one side of the duct width and the tapered passages 14 on the opposite side are arranged symmetrically with respect to that line.

The outlet 8 opens at a position facing the vortex generating section 16, offset laterally from the forward position of the tapered passage 14.

The horizontal ribs 11 and inclined ribs 12 or 13 that form each tapered passage 14 have the tip of the horizontal rib 11 that forms the passage wall farther from the reference line L and faces the shielding wall 15 protruding further forward than the tip of the inclined rib 12 or 13 that forms the passage wall closer to the reference line L. Furthermore, a gap 17 is provided between the tip of each horizontal rib 11 and the shielding wall 15, allowing exhaust gas to pass through.

<Flow of exhaust gas in exhaust gas duct>
Next, the flow of exhaust gas in the exhaust gas duct 4 will be described with reference to the results of streamline analysis of exhaust gas in the exhaust gas duct 4 shown in FIGS.

As shown in Figure 4, a vortex flow of exhaust gas is generated between the wall 10 at one end of the exhaust gas duct 4 in the longitudinal direction of the duct, where the inlet 9 is located, and the two end-side horizontal ribs 11 closest to the inlet 9, as follows: The gas flows in from the inlet 9, is blocked by the wall 10 at one end of the duct, and flows toward both side walls of the duct (shielding walls 15), generating a gas flow from each side wall toward the center of the duct width along the end-side horizontal ribs 11. This gas flow then collides with a gas flow that travels directly from the inlet 9 between the two end-side horizontal ribs 11, generating a vortex flow 18 between the inlet 9 and each of the two end-side horizontal ribs 12.

As shown in Figure 5, exhaust gas that escapes between the two end-side horizontal ribs 12 enters the two tapered passages 14 above the battery cell. The two streams of exhaust gas, whose flow velocity increases after passing through each of these two tapered passages 14, are blocked by the shielding wall 15 and collide into each other as opposing flows, generating a vortex 19 between the two tapered passages 14, i.e., in the vortex generating section 16.

As described above, a vortex is generated in the exhaust gas in the vortex generating section 16, and as shown in Figure 6, the exhaust gas is discharged from this vortex generating section 16 to the outside through the exhaust port 8.

As described above, exhaust gas flowing in through the inlet 9 generates vortices 18 between the inlet 9 and the horizontal ribs 11 near the end, and then generates vortices 19 in the vortex generating section 16 after passing through the tapered passage 14. This lengthens the time the exhaust gas flows inside the exhaust gas duct 4, promoting heat transfer from the exhaust gas to the duct wall and ribs 11-13 that make up the exhaust gas duct 4, lowering the temperature of the exhaust gas.

Furthermore, creating vortices in the exhaust gas means that the exhaust gas flow becomes more turbulent. This increases the temperature gradient of the exhaust gas near the main wall of the exhaust gas duct 4 and near the wall surfaces of the ribs 11-13. In other words, the heat transfer coefficient from the exhaust gas to the duct main wall and ribs 11-13 increases, efficiently lowering the temperature of the exhaust gas.

In the vortex generating section 16, the tapered passages 14 increase the flow velocity of the exhaust gas, which then hits the shielding wall 15 and deflects the exhaust gas sideways, creating a strong vortex. Furthermore, because the tips of the horizontal ribs 11 farther from the reference line L are closer to the shielding wall 15 than the inclined ribs 12 and 13 closer to the reference line L, exhaust gas that passes through the tapered passages 14 tends to flow toward the reference line L, i.e., toward the vortex generating section 16. This is advantageous for strengthening the vortex flow of the exhaust gas in the vortex generating section 16. Furthermore, because gaps 17 are provided between the tips of the horizontal ribs 11 and the shielding wall 16, exhaust gas flowing toward the shielding wall 15 from between the horizontal ribs 11 facing each other in the cell arrangement direction also passes through the gaps 17 and merges with the exhaust gas that has passed through the tapered passages 14. This also works to strengthen the vortex flow of the exhaust gas in the vortex generating section 16.

<Exhaust gas duct performance evaluation>
An exhaust gas duct 4 with ribs (hereinafter referred to as "Comparative Example") and an exhaust gas duct without ribs (hereinafter referred to as "Without Ribs") were manufactured as shown in Fig. 7. The performance of this Comparative Example, the duct without ribs, and the exhaust gas duct 4 according to the above embodiment (hereinafter referred to as "Example") was investigated.

As shown in Figure 7, the comparative example is an exhaust gas duct in which a plurality of vertical ribs 21 extending in the longitudinal direction of the duct are arranged at intervals in the width and longitudinal directions of the duct on a duct body similar to that of the example. The rib-less duct is formed only with a duct body similar to that of the example, and does not have ribs. The shape and size of the duct body, as well as the size and arrangement of the exhaust gas inlet 9 and outlet 8, are the same for the example, comparative example, and rib-less duct. The number of ribs and the total surface area of the ribs are the same for the example and comparative example.

For the above example, comparative example, and no ribs, the outlet gas temperature, i.e., the temperature of the exhaust gas discharged from the outlet 8 closest to the inlet 9, was determined using unsteady state analysis. The results are shown in Figure 8.

The comparative example with vertical ribs had a lower outlet gas temperature than the example without ribs, but the peak outlet gas temperature still temporarily exceeded 300°C, the ignition point of the electrolyte contained in the gas released from the battery cell. In contrast, the peak temperature in the example was approximately 150°C lower than the comparative example, and safety is expected to be significantly improved.

Figures 9 and 10 show the results of calculating the heat transfer coefficient α and heat transfer amount Q from the exhaust gas to the rib for the above example and comparative example. In the example, the heat transfer coefficient α is larger and the heat transfer amount Q is larger than in the comparative example. This is the effect of creating a strong vortex flow of exhaust gas within the duct, as described above.

<Another embodiment>
In the previous embodiment, the inlet 9 of the exhaust gas duct 4 was provided only at a location corresponding to the trigger cell. As shown in Figure 11, the exhaust gas duct 4 of this embodiment has an inlet 9 provided for each battery cell 2 of the battery module.

That is, an inlet 9 opens on the bottom surface of the exhaust gas duct 4 in the center of the duct width direction, corresponding to the gas exhaust valve 5 of each battery cell 2. An outlet 8 is also provided for each battery cell 2. The arrangement of the horizontal ribs 11 and inclined ribs 12, 13 is basically the same as the arrangement of the horizontal ribs 11 and inclined ribs 12, 13 provided for each battery cell 2 other than the trigger cell in the previous embodiment.

However, in the section of the exhaust gas duct 4 corresponding to the battery cell 2 at the very end of the battery module, the wall 10 at one end of the duct is replaced with a horizontal rib 11. That is, a tapered passage 14 is formed by the wall 10 at one end of the duct and each of the inclined ribs 12, 13. In addition, in the sections corresponding to the second and third battery cells 2 from the end of the battery module, the horizontal rib 11 is replaced with a V-rib 24 formed by combining flat ribs 22, 23 rising from the bottom surface of the exhaust gas duct 4 in a V-shape.

The flat ribs 22, 23 that make up the V-rib 24 are joined at their base ends, located near the center of the duct width, to prevent exhaust gas from passing through, and are inclined so that the gap between them widens toward the ends of the duct width. The tips of the flat ribs 22, 23 abut against the duct side wall, i.e., the shielding wall 15, to prevent exhaust gas from entering the inside of the V-rib 24.

In the area of the exhaust gas duct 4 where the V-rib 24 is provided, the flat rib 22 and inclined rib 12 that make up the V-rib 24 form a tapered passage 14, and the flat rib 23 and inclined rib 13 form a tapered passage 14.

Accordingly, in this embodiment, a pair of tapered passages 14 are provided symmetrically with respect to a reference line L connecting the inlet 9 and outlet 8 provided for each electrical installation cell 2. The space between the inclined ribs 12, 13 of each of the pair of tapered passages 14 forms a vortex generating portion 16.

In this embodiment, when gas is released from the gas exhaust valve 5 of each battery cell 2, the exhaust gas flows into the exhaust gas duct 4 from the inlet 9 directly above the gas exhaust valve 5. Much of the gas passes through the tapered passages 14 located on both sides of the reference line L, and is blocked from moving forward by the shielding walls 15, causing it to deviate toward the reference line L, generating a gas vortex in the vortex generating section 16. Therefore, as with the previous embodiment, the temperature of the gas drops significantly before it is discharged from the exhaust port 8.

Where the V-ribs 24 are provided in the exhaust gas duct 4, exhaust gas cannot penetrate inside the V-ribs 24, so a large amount of exhaust gas flows into the tapered passage 14, where the V-ribs 24 form the passage wall. This is advantageous for strengthening the vortex flow in the vortex flow generating section 16. Furthermore, because the flat ribs 22, 23 that make up the V-rib 24 abut against the shielding wall 15, all of the exhaust gas that passes through the tapered passage 14 heads toward the vortex flow generating section 16. This allows for the generation of a strong vortex flow in the vortex flow generating section 16.

In addition, V-shaped ribs 24 may be used instead of the other transverse ribs 11, and transverse ribs 11 may be used instead of V-shaped ribs 24.

REFERENCE SIGNS LIST 1 Battery unit 2 Battery cell 3 Battery module 4 Exhaust gas duct 5 Gas exhaust valve 6 Electrode terminal 7 Electrode terminal 8 Exhaust port 9 Inlet 11 Horizontal rib 12 Inclined rib 13 Inclined rib 14 Tapered passage 15 Shielding wall 16 Vortex generating portion 17 Gap 19 Vortex

Claims (4)

A gas exhaust structure for a battery unit, in which a battery module formed by arranging a plurality of battery cells in parallel is provided with an exhaust gas duct through which exhaust gas emitted from the battery cells flows and is exhausted to the outside,
The exhaust gas duct includes an inlet for the exhaust gas, a tapered passage through which the exhaust gas flowing in from the inlet passes, the passage width of which narrows as it goes further, and a shielding wall that interrupts the forward movement of the exhaust gas that has passed through the tapered passage and deflects the exhaust gas laterally, thereby generating a vortex in the exhaust gas at an adjacent location separated by the passage wall of the tapered passage, and an exhaust port that discharges the exhaust gas to the outside opens so as to face the location where the vortex in the exhaust gas is generated ,
the exhaust gas duct has the inlet and the outlet for each battery cell;
a pair of the tapered passages extending in the same direction along a line connecting the inlet and the outlet of the exhaust gas duct are arranged symmetrically with respect to the line for each battery cell, and the pair of tapered passages are arranged on both sides of the line connecting the inlet and the outlet of the exhaust gas duct, and the pair of tapered passages are arranged symmetrically with respect to the line;
The gas exhaust structure for a battery unit , wherein the shielding wall expands in front of the pair of tapered passages so as to block the forward movement of the exhaust gas that has passed through each of the tapered passages . In claim 1 ,
each of the plurality of battery cells has a rectangular shape in a plan view, is arranged in a row in a direction of a short side of the rectangle, and is provided with a gas release valve at the center of a long side of an upper surface of each battery cell, for releasing gas generated inside;
the inlet of the exhaust gas duct opens to correspond to the gas exhaust valve at the center of the long side of the battery cell, and the outlet of the exhaust gas duct opens to correspond to an end side of the long side of the battery cell;
a gas exhaust structure for a battery unit, wherein the tapered passages on both sides of a line connecting the inlet and the outlet are inclined so that the passage wall on the side closer to the line becomes farther away from the line as it goes forward, and the passage width in the direction in which the battery cells are arranged is tapered. In claim 2 ,
a tapered passage provided for one of the adjacent battery cells and positioned closer to the other battery cell, and a tapered passage provided for the other battery cell and positioned closer to the one battery cell, the tapered passage being spaced apart in the juxtaposition direction of the battery cells, and a gap being provided between the shielding wall and the tip of the passage wall on the side farther from the line of each of the tapered passages. In claim 3 ,
A gas discharge structure for a battery unit, wherein a tip of a passage wall on a side of the tapered passage farther from the line protrudes further forward than a tip of the passage wall on a side closer to the line.