JP2013168293A - Explosion-proof valve for battery pack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To give an explosion-proof valve 21 of a battery pack a function as a vent hole to eliminate a need for separately providing an air vent having a ventilation film.SOLUTION: An explosion-proof valve 21 comprises: an explosion-proof valve case 22 formed of a synthetic resin, and forming an annular ring shape; an O-ring 23 sealing between this explosion-proof valve case 22 and a pack case; a circular sheet-like ventilation film 24 attached to the case 22 so as to close a central opening 22a of the explosion-proof valve case 22; and a circular plate-like protector 25 formed of a synthetic resin, and overlapped and arranged outside this ventilation film 24. Notches 61 as vent holes are provided around the protector 25, and a small amount of air can go in and out via the ventilation film 24. When an internal pressure rapidly rises at battery abnormality, the protector 25 is folded, and locking by locking projections 52 is released to drop the protector 25, and therefore, a large passage cross sectional area is secured instantaneously to release the internal pressure.

Description

  The present invention relates to an explosion-proof valve for a battery pack in which a plurality of single cells (hereinafter referred to as cells) are accommodated in a pack case, and more particularly to an explosion-proof valve for a relatively large battery pack that serves as a power source for an electric vehicle.

  For example, a battery pack used in an electric vehicle is basically configured in a state in which a pack case is sealed in order to prevent rainwater, car wash water, and the like from entering the interior. In this case, in order to avoid pressure changes in the pack case due to charging / discharging and temperature changes between daytime and nighttime, the inside and outside of the pack case communicate with each other, in other words, allow relatively small amounts of air to enter and exit. A vent (which is often called a breathing hole) needs to be provided. As this ventilation hole, in order to avoid the intrusion of rainwater or the like through the ventilation hole, as disclosed in Patent Document 1 and the like, a ventilation film that selectively allows only gas to pass without passing liquid, It is common to combine.

  On the other hand, a battery pack provided with an explosion-proof valve capable of quickly releasing the internal pressure when a large amount of gas is suddenly generated inside the battery pack is known. One example of the explosion-proof valve is disclosed in Patent Document 2. In general, the explosion-proof valve is normally closed, and when the internal pressure is greatly increased, for example, the explosion-proof valve opens with the destruction of some parts.

  In Patent Document 1, it is described that the air hole provided with the air permeable membrane is for releasing the gas generated in the cell.

Japanese Utility Model Publication No. 60-163264 JP 2000-58016 A

  The vents are intended to ensure a small amount of air in and out when the battery is functioning, so that a large passage area is not necessary, but rather a minimum size to prevent foreign objects from entering. It is desirable to do so.

  On the other hand, the explosion-proof valve requires a considerably large passage area. In particular, it is desirable to provide a sufficiently large explosion-proof valve in a high-voltage battery pack accommodating a large number of cells.

  Therefore, for example, a configuration in which a ventilation film is simply stacked on one hole as in Patent Document 1 cannot serve both of the ventilation hole and the explosion-proof valve. In the configuration of Patent Document 1, the size of the explosion-proof valve is insufficient, and a sudden increase in internal pressure cannot be dealt with at all. Further, if the size of the hole is made large enough for the explosion-proof valve with the configuration of Patent Document 1, there is a problem that the air-permeable film exposed to the outside is easily deformed by collision with foreign matter. .

  An object of the present invention is to provide the explosion-proof valve with a function as a vent for allowing a small amount of air to enter and exit.

The explosion-proof valve according to the present invention is a battery pack in which a plurality of cells are accommodated in a sealed pack case.
A gas permeable membrane that is arranged so as to close an opening provided in a part of the pack case and selectively allows gas to pass without passing liquid, and breaks or deforms as the battery pack internal pressure increases,
A plate-like protector that is placed on the outer side of the gas permeable membrane and is held at the peripheral edge so as to fall off due to bending deformation due to a predetermined pressure difference;
A vent hole that opens outward and allows a small amount of air to flow through the vent membrane;
It is configured with.

  In such a configuration, a small amount of air enters and exits through the vent hole between the inside and outside of the pack case. The air entering and exiting in this way passes through the gas permeable membrane disposed so as to close the opening. Since this gas-permeable membrane allows only gas to pass through selectively without passing liquid such as rainwater, rainwater does not enter the pack case. Further, since the vent hole that opens to the outside can be made sufficiently small, there is little risk of collision and entry of foreign matter.

  On the other hand, when the gas is suddenly generated and the internal pressure rapidly rises, the gas permeable membrane is easily broken or deformed, and the plate-like protector is pressed outward by the internal pressure. Therefore, the plate-like protector bends and deforms so as to bulge outward, and along with this, the peripheral edge is unlocked and falls off instantaneously. In other words, the gas permeable membrane is broken and the protector is blown outward, and a large passage cross-sectional area is instantaneously secured as an explosion-proof valve. A slit that facilitates deformation of the protector may be formed on the outer surface of the protector.

  In one desirable mode, the above-mentioned vent hole is arranged along the peripheral part of the above-mentioned protector, for example, can be formed as a notch which notched the peripheral part of the protector.

  In one embodiment, the notch is positioned on the outer peripheral side of the outer shape of the gas permeable membrane so as not to overlap the gas permeable membrane, and guide grooves for guiding the air flowing from the notch to the gas permeable membrane side Is provided on the outer peripheral side of the gas permeable membrane.

  In this way, since minute foreign matter contained in the air flowing in from the vent hole along the direction orthogonal to the vent film collides with the bottom surface of the guide groove, it does not collide directly with the vent film. Therefore, partial breakage of the gas permeable membrane is prevented.

  In the present invention, the vent hole may be formed as a through hole in the central portion of the protector, for example.

  The explosion-proof valve can be attached to the pack case as it is. However, in one aspect, the explosion-proof valve case further includes an annular explosion-proof valve case that holds the vent film and the protector as one unit. A case is attached to the opening of the pack case by a plurality of locking claws.

  According to the present invention, the explosion-proof valve includes a function as a vent hole, and a small amount of air is allowed to enter and exit through the vent hole and the vent film that are relatively small, and at the same time the internal pressure suddenly rises. Can open the inside of the pack case with a sufficiently large passage cross-sectional area as an explosion-proof valve. Therefore, the configuration can be simplified as compared with the case where the vent hole and the explosion-proof valve are provided separately.

The side view of the electric vehicle provided with the battery pack. The bottom view of this electric vehicle. The perspective view of a battery pack. The perspective view of the explosion-proof valve part of a lower case. The exploded perspective view of an explosion-proof valve. The perspective view which looked at the explosion-proof valve from the back. Sectional drawing of the explosion-proof valve along the surface which passes a vent hole. The expanded perspective view of the principal part which shows the latching protrusion of a protector. The perspective view which shows the state which the protector deform | transformed and dropped out.

  Hereinafter, an embodiment in which the explosion-proof valve of the present invention is applied to a battery pack for an electric vehicle will be described in detail with reference to the drawings.

  1 and 2 schematically show an electric vehicle 2 in which a battery pack 1 having an explosion-proof valve according to the present invention is used. The electric vehicle 2 has a configuration in which a drive motor unit 4 is mounted on a front portion of a vehicle body 3 and drives front wheels 5. The battery pack 1 serving as an energy source for the drive motor unit 4 has a substantially rectangular box shape as a whole, and is attached to the lower surface of the vehicle body floor 3a from the lower side at a position in front of the rear wheel 6. Therefore, the lower surface of the battery pack 1 is exposed on the lower surface side of the vehicle, and the battery pack 1 protrudes downward as compared with the surrounding vehicle body floor 3a.

  FIG. 3 is a perspective view of the battery pack 1 as viewed from an obliquely rear side of the vehicle. The battery pack 1 has a large number of cells accommodated in a sealed pack case 10 including a lower case 11 constituting a lower portion and an upper case 12 constituting an upper portion. Although the arrangement of the cells is not shown, for example, a flat lithium ion cell sealed with a laminate film is used, and a plurality of (for example, four) cells are stacked in a flat rectangular box-shaped metal case. A battery module is configured as the housed one. The battery modules are further configured as a stack which is stacked and fixed to each other. Finally, the plurality of stacks are accommodated in the pack case 10. For example, a total of several tens of battery modules are housed in the pack case 10 and are connected in series to obtain a voltage of several hundred volts necessary for driving the vehicle. The lithium ion cell may be provided with an explosion-proof seal valve that peels off the seal portion and releases the internal pressure when the internal pressure rises.

  The lower case 11 and the upper case 12 are both made of an aluminum alloy die-cast, and are connected to each other by a plurality of bolts at the peripheral edge. A liquid gasket is previously applied as a sealing material to the joint surfaces of the two at the time of joining, thereby forming a sealed space in the pack case 10. Therefore, inflow of moisture or the like from the outside is prevented, and corrosion of the connection portion of the battery module is suppressed.

  Thus, in order to allow a relatively small amount of air to enter and exit between the inside and outside of the pack case 10 that is basically sealed, the lower case 11 heads toward the rear of the vehicle in order to release the sudden increase in internal pressure. As shown in FIG. 4, explosion-proof valves 21 are arranged on the rear wall 11 a at two locations on the left and right.

  The explosion-proof valve 21 has a flat disk shape as a whole. As shown in FIG. 5, the explosion-proof valve case 22 made of a synthetic resin having an annular shape, and the explosion-proof valve case 22 and the lower case 11 An O-ring 23 that seals the gap, a circular sheet-like gas permeable membrane 24 that is attached to the case 22 so as to close the central opening 22 a of the explosion-proof valve case 22, and an outer layer of the gas permeable membrane 24. And a synthetic resin protector 25 having a circular plate shape.

  As shown in FIGS. 6 and 7, the explosion-proof valve case 22 is formed so that the inner peripheral cylindrical wall 31 constituting the central opening 22 a slightly protrudes toward the back surface side. Locking claws 32 extend further in the axial direction from four locations. These locking claws 32 can be elastically deformed in the radial direction by the elasticity of the synthetic resin material, and each has a locking portion 32a swelled in the outer radial direction at the tip. As shown in FIG. 7, a circular opening 27 corresponding to the diameter of the cylindrical wall 31 is formed in the rear wall 11a of the lower case 11 to which the explosion-proof valve 21 is attached. The cylindrical wall 31 is fitted into the opening 27 and is retained by four locking claws 32. The O-ring 23 is mounted on the outer periphery of the cylindrical wall 31 and is sandwiched between the rear wall 11a of the lower case 11 and the bottom surface of the annular groove 33 of the explosion-proof valve case 22, as shown in FIG.

  As shown in FIG. 6, a drain hole 35 is formed in the lowermost part on the back side of the explosion-proof valve case 22 so that water droplets do not collect inside the explosion-proof valve 21 or in the annular groove 33 of the lower case 11. Yes. A locating pin 36 is formed on the outer peripheral surface of the explosion-proof valve case 22 at a position 180 degrees different from the position of the drain hole 35. The locating pin 36 is located on the back side of the outer peripheral edge of the explosion-proof valve case 22 serving as a mounting reference surface. Protruding to Corresponding to this locating pin 36, a locating recess (not shown) is formed in the rear wall 11a of the lower case 11, and when the explosion proof valve 21 is attached, they are fitted together so that the explosion proof valve case 22 is in a correct posture (ie, water It is attached in a state where the punching hole 35 is vertically downward.

  On the other hand, on the surface side of the explosion-proof valve case 22, the first support surface 39 has a cylindrical surface 38 a on the inner periphery of the annular rim portion 38 on the outer peripheral edge and is retracted by a predetermined amount from the front end surface 38 b of the rim portion 38. Is formed in an annular shape (details will be a partially missing annular shape as will be described later), and the second support surface 40 is formed in an annular shape at a position further retracted from the first support surface 39 by a predetermined amount. Has been. In other words, the diameter of the rim portion 38 gradually decreases from the front end surface 38b of the rim portion 38 to the first support surface 39 and the second support surface 40, and the second support surface 40 is adjacent to the central opening 22a. ing. The rim portion 38 front end surface 38b, the first support surface 39, and the second support surface 40 all form a plane orthogonal to a central axis (not shown) passing through the center of the explosion-proof valve case 22.

  The gas permeable membrane 24 is a sheet-like membrane made of a known material that can selectively pass only gas without allowing liquid to pass through. For example, a porous membrane of polytetrafluoroethylene having water repellency is used. . In the present invention, the material of the gas permeable membrane 24 is not limited at all, and any material may be used. The air-permeable membrane 24 having a circular shape has a diameter corresponding to the second support surface 40 described above, and an outer peripheral edge is supported on the second support surface 40 and is bonded and fixed by an appropriate adhesive. Yes. The gas permeable membrane 24 is a thin membrane, and the step between the second support surface 40 and the first support surface 39 is larger than the thickness of the gas permeable membrane 24. Are separated from each other in the axial direction of the central axis.

  As shown in FIGS. 5 and 7, a protector 25 having a circular plate shape is attached to the first support surface 39. The protector 25 has a plate thickness corresponding to a step from the front end surface 38 b of the rim portion 38 of the explosion-proof valve case 22 to the first support surface 39, and the outer peripheral cylindrical surface 25 a is a cylindrical surface 38 a of the inner periphery of the rim portion 38. The diameter is set so as to fit relatively tightly.

  Further, in this embodiment, a groove or slit 51 extending in the diametrical direction is formed on the surface side of the protector 25, and is locked at two positions on the circumference that are 90 degrees different from the slit 51. Each of the protrusions 52 is provided. FIG. 8 shows details of the locking projection 52, and as shown in the figure, the cylindrical surface 25a of the protector 25 is formed so as to project into a substantially rectangular parallelepiped shape. And the end surface which goes to the surface side of the protector 25 has stood | emitted perpendicularly | vertically from the cylindrical surface 25a as the latching surface 52a, while the end surface which goes to the back surface side of the protector 25 has comprised the curved circular arc surface as the guide surface 52b. .

  Corresponding to the locking protrusions 52, rectangular locking recesses 54 with which the locking protrusions 52 can be respectively engaged are formed at two locations on the cylindrical surface 38a of the explosion-proof valve case 22. In the illustrated example, the locking projections 52 and the corresponding locking recesses 54 are provided at angular positions that are the uppermost and lowermost portions of the explosion-proof valve 21, respectively. The water drain hole 35 and the locate pin 36 are overlapped with each other, and as shown in FIG. 6, the water drain hole 35 and the locate pin 36 are formed so as to communicate with the concave portions of the drain hole 35 and the locate pin 36.

  Since the locking projection 52 has the curved guide surface 52b as described above, if the protector 25 is simply pushed into the inside of the rim portion 38, the locking projection 52 is easily accompanied by slight deformation of the resin material. It enters into the locking recess 54. And once both are fitted, they are securely fixed and held by the vertical locking surface 52a. At this time, the back surface of the outer peripheral portion of the protector 25 is in a state of being appropriately pressed against the first support surface 39 of the explosion-proof valve case 22.

  Here, in the protector 25, substantially U-shaped cutout portions 61 serving as vent holes are cut out at four locations on the peripheral edge. In the illustrated example, four notches 61 are arranged every 90 degrees. The notch 61 extends in the radial direction from the cylindrical surface 25a on the outer periphery of the protector 25 to the inner peripheral side. However, as is apparent from FIG. 7, it is in a range that does not overlap with the gas permeable membrane 24. A notch 61 is provided on the outer peripheral side of the outer circle of the gas permeable membrane 24.

  As described above, the protector 25 is supported on the first support surface 39 of the explosion-proof valve case 22, and the first support surface 39 is provided on the notch 61 as shown in FIGS. 5 and 7. Guide grooves 63 having a width slightly larger than the projected shape of the notch 61 are provided in the radial direction at corresponding positions (that is, at four positions every 90 degrees). The guide groove 63 extends from the cylindrical surface 38a inside the rim portion 38 to the stepped surface inside the first support surface 39. In the illustrated example, the groove bottom surface is the same plane as the second support surface 40. It is formed to become. The guide groove 63 may be shallower than the illustrated example, and the groove bottom surface may be located at an intermediate position between the second support surface 40 and the first support surface 39.

  In the explosion-proof valve 21 configured as described above, the inside of the pack case 10 and the external environment are always in communication with each other via the notch 61 serving as a ventilation hole. A relatively small amount of air can enter and exit as the temperature changes. That is, a function as a so-called breathing hole or ventilation hole can be obtained. The air entering and exiting in this way always passes through the gas permeable membrane 24, so that even if rain water or car wash water enters the cutout portion 61, for example, the air does not enter the pack case 10. In particular, the opening area of each notch 61 is very small compared to the overall size of the explosion-proof valve 21, and the protector 25 protects the ventilation film 24 against relatively large foreign objects such as stepping stones. Therefore, the low-strength gas permeable membrane 24 is not broken. Moreover, the air flow through the notch 61 basically flows in parallel with the central axis of the explosion-proof valve 21, and thus changes direction toward the inner peripheral side after colliding with the groove bottom surface of the guide groove 63 and the outer peripheral part of the ventilation film 24. And flow in a direction substantially parallel to the gas permeable membrane 24. Therefore, partial damage to the gas permeable membrane 24 is less likely to occur compared to a configuration in which a small foreign object that passes through the notch 61 directly collides with the gas permeable membrane 24.

  On the other hand, when the gas is suddenly generated and the internal pressure in the pack case 10 rapidly rises, the fragile air-permeable membrane 24 is easily deformed or broken (or the adhesive part is peeled off), and the internal pressure is directly applied to the protector 25. Works. When receiving pressure in this manner, the plate-like protector 25 is bent and deformed so as to be bent along the slit 51 having low rigidity, as shown in FIG. With such deformation, the two locking projections 52 located in the direction perpendicular to the slit 51 move inward from each other, and come out of the locking recess 54 of the explosion-proof valve case 22. Therefore, the protector 25 is instantaneously dropped due to the pressure difference, and the entire central opening 22a of the explosion-proof valve case 22 is opened. That is, the protector 25 is blown off while being deformed as shown in FIG. 9, and a large opening area is instantaneously secured. If only one of the two locking projections 52 comes off, the protector 25 will drop off immediately.

  Therefore, the internal pressure can be reliably released in the event of an explosion-proof valve 21. It should be noted that by adjusting the depth, width, etc. of the slit 51, it is possible to easily change how much the protector 25 falls off with a pressure difference. Further, if the material of the protector 25 is appropriately selected, the same function can be achieved without providing the slit 51.

  As mentioned above, although one Example of this invention was described, this invention is not limited to the said Example, A various deformation | transformation is possible.

  For example, in the above-described embodiment, the notch 61 is provided on the protector 25 side as a vent hole. However, a notch portion serving as a vent hole can be formed on the rim part 38 side of the explosion-proof valve case 22, not a notch. Vent holes can also be provided in the form of through holes. Further, depending on the size of the vent hole and the strength of the vent film, a configuration in which the vent hole is formed in the central region of the protector 25 that overlaps with the vent film 24 is also possible.

  Moreover, although the said Example demonstrated the example applied to the battery pack 1 for electric vehicles, of course, it can apply similarly to the battery pack of other uses.

DESCRIPTION OF SYMBOLS 1 ... Battery pack 10 ... Pack case 21 ... Explosion-proof valve 22 ... Explosion-proof valve case 24 ... Ventilation film 25 ... Protector 51 ... Slit 52 ... Locking protrusion 61 ... Notch part 63 ... Guide groove

Claims (6)

In a battery pack in which a plurality of cells are housed in a sealed pack case,
A gas permeable membrane that is arranged so as to close an opening provided in a part of the pack case and selectively allows gas to pass without passing liquid, and breaks or deforms as the battery pack internal pressure increases,
A plate-like protector that is placed on the outer side of the gas permeable membrane and is held at the peripheral edge so as to fall off due to bending deformation due to a predetermined pressure difference;
A vent hole that opens outward and allows a small amount of air to flow through the vent membrane;
A battery pack explosion-proof valve.   The explosion-proof valve for a battery pack according to claim 1, wherein the vent hole is disposed along a peripheral edge portion of the protector.   The explosion-proof valve for a battery pack according to claim 2, wherein the vent hole includes a cutout portion formed by cutting out a peripheral edge of the protector.   The notch is located on the outer peripheral side of the outer shape of the gas permeable membrane so as not to overlap the gas permeable membrane, and a guide groove for guiding the air flowing from the notch to the gas permeable membrane is provided on the outer side of the gas permeable membrane The explosion-proof valve for the battery pack according to claim 3, wherein the explosion-proof valve is provided on the battery pack.   An annular explosion-proof valve case that holds the gas permeable membrane and the protector as a unit is further provided, and the explosion-proof valve case is attached to the opening of the pack case by a plurality of locking claws. The explosion-proof valve for the battery pack according to any one of claims 1 to 4.   The explosion-proof valve for a battery pack according to any one of claims 1 to 5, wherein a slit that facilitates deformation of the protector is formed on an outer surface of the protector.

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