Battery unit

A vehicle body includes an accommodating portion that accommodates a battery pack. A communication hole, which connects the outside and the inside the accommodating portion, is formed in one of the side walls of the vehicle body. The battery pack includes battery cells and a sealed case that accommodates the battery cells. The sealed case includes a case main body having an opening and a lid member fixed to the case main body. The lid member has a first releasing portion and a second releasing portion. A connecting portion for connecting a charging plug to the battery pack is inserted in the communication hole. The connecting portion is connected to the battery cells via wires. The first releasing portion and the second releasing portion are arranged to face a wall of an accommodating body.

TECHNICAL FIELD

The present invention relates to a battery unit that includes an accommodating body that accommodates a battery pack.

BACKGROUND ART

Battery packs have been known that accommodate battery cells in a sealed case. In a battery pack, the internal pressure of the sealed case must be lowered when the internal pressure is high.

Patent Document 1 discloses a battery module that accommodates rechargeable batteries in a housing. A gas discharging member, which is opened at a preset pressure, is attached to each rechargeable battery. The housing has a gas discharging hole and a valve member, which closes the gas discharging hole. In the battery module, the valve member is opened when the internal pressure of the housing reaches a preset pressure.

Typically, a cable is attached to the battery pack to connect the battery pack to an external device. In the configuration of Patent Document 1, opening the valve member may cause gas to be discharged from the housing toward the cable. This may damage the cable and thus hamper charging/discharging of the battery pack.

PRIOR ART DOCUMENT

Patent Document

SUMMARY OF THE INVENTION

Problems that the Invention is to Solve

Accordingly, it is an objective of the present invention to provide a battery unit that is configured to restrain damage to a cable.

Means for Solving the Problems

To achieve the foregoing objective and in accordance with one aspect of the present invention, a battery unit including a battery pack and an accommodating body is provided. The accommodating body includes an accommodating portion, which accommodates the battery pack. The battery pack includes a battery module, which is configured by a plurality of battery cells, a sealed case, which accommodates the battery module, and a connector, which is provided in the sealed case and to which a cable for supplying power to the battery module is connected. The accommodating body includes a communication hole, which connects an inside and an outside of the accommodating portion to each other. The sealed case includes a releasing portion, which releases a pressure in the sealed case. The releasing portion is arranged to face a wall of the accommodating body.

With this configuration, when the releasing portion is opened, the gas in the sealed case is discharged toward the wall of the accommodating body. The cable is connected to the connector and extends to the communication hole from the connector. With this configuration, since the releasing portion is not arranged to face the communication hole, the cable is not directly exposed to the gas discharged from the sealed case. This restrains damage to the cable by the gas discharged from the sealed case.

The releasing portion is preferably arranged such that an imaginary line connecting the releasing portion and the wall of the accommodating body does not overlap with the communication hole.

The releasing portion is preferably arranged to face a wall of the accommodating body that is different from the wall that has the communication hole.

The releasing portion is preferably arranged to face a wall of the accommodating body that is on a opposite side from the wall that has the communication hole.

With this configuration, when the releasing portion is opened, the gas in the sealed case is discharged in a direction opposite from the cable. This further effectively restrains damage to the cable.

MODES FOR CARRYING OUT THE INVENTION

A battery unit according to one embodiment of the present invention will now be described with reference toFIGS. 1 to 5. The battery unit is mounted in a forklift. In the following description, the forward, backward, leftward, rightward, upward, and downward directions are defined with reference to the state in which the operator of the forklift is facing forward.

As shown inFIGS. 1 and 2, a forklift10, which is an industrial vehicle, includes drive wheels12at a front lower part of a vehicle body11. The forklift10also includes steerable wheels13at a rear lower part of the vehicle body11. The forklift10further includes a cargo handling device at the front part of the vehicle body11. The cargo handling device includes a mast14, which is attached to the front part of the vehicle body11and extends upward. A pair of left and right forks16is attached to the mast14via a lift bracket15. Lift cylinders17and tilt cylinders18are coupled to the mast14to operate the forks16. The forks16are lifted and lowered together with the lift bracket15by the lift cylinders17. The forks16are tilted together with the mast14by the tilt cylinders18. A cargo19is mounted on the forks16. The vehicle body11includes a vehicle driving motor M1, which functions as the driving source for the drive wheels12, and a cargo handling motor M2, which functions as the driving source for the forks16.

A cab20is arranged at the center of the vehicle body11. An operator seat21, on which the operator is seated, is provided in the cab20. A steering wheel22is arranged in front of the operator seat21. A battery pack30is mounted in the vehicle body11below the cab20. The forklift10is a battery forklift having the vehicle driving motor M1and the cargo handling motor M2. The vehicle driving motor M1and the cargo handling motor M2are driven by the battery pack30, which serves as a power source. The vehicle body11includes a connecting portion23, via which a charging plug P is connected to the battery pack30. The battery pack30is connected to a charging station S, which is an external device, via a cable C, which has the charging plug P.

As shown inFIG. 3, the vehicle body11, which serves as an accommodating body, includes an accommodating portion31, which accommodates the battery pack30. The vehicle body11and the battery pack30configure a battery unit U. The accommodating portion31is a rectangular space surrounded by six walls. A bottom wall32, on which the battery pack30is placed, an upper wall33, which is located on the opposite side from the bottom wall32, and four side walls34configure the walls of the accommodating body. One of the side walls34has a communication hole35, which connects the outside and the inside of the accommodating portion31to each other. The connecting portion23is inserted in the communication hole35.

As shown inFIGS. 3 and 4, a battery pack30includes a sealed case41. The sealed case41accommodates a battery module M, which includes battery cells61. The sealed case41includes a case main body42having an opening and a lid member43fixed to the case main body42. The case main body42is shaped as a rectangular tube with a closed end. The lid member43is shaped like a rectangular flat plate. The case main body42has an opening edge44surrounding the opening. The opening edge44has threaded holes45, into which bolts B are threaded. Each bolt B extends through the lid member43and is threaded to one of the threaded holes45. Among the four ends51to54of the lid member43, ends on opposite sides are defined as a first end51and a second end52. The other ends, which are different from the first and second ends51,52and on opposite sides from each other, are defined as a third end53and a fourth end54.

The bolts B extend through through-holes provided in the first end51and the second end52. The bolts B extend through the through-holes formed in a part of the first end51and the through-holes formed in a part of the second end52. The bolts B are not provided in the vicinity of each corner of the lid member43. That is, no bolt B is provided in a part of the first end51that is close to the third end53, a part of the first end51that is close to the fourth end54, a part of the second end52that is close to the third end53, or a part of the second end52that is close to the fourth end54. In other words, no bolts B are provided in the third end53or the fourth end54. In each of the first and second ends51,52, the bolts B are aligned between the third end53and the fourth end54.

A first imaginary line L1connects one of the bolts B at the first end51that is closest to the third end53to one of the bolts B at the second end52that is closest to the third end53. Specifically, the first imaginary line L1connects the part of the bolt B at the first end51that is closest to the third end53to the part of the bolt B at the second end52that is closest to the third end53. The area between the first imaginary line L1and the third end53is a first releasing portion55.

A second imaginary line L2connects one of the bolts B at the first end51that is closest to the fourth end54to one of the bolts B at the second end52that is closest to the fourth end54. Specifically, the second imaginary line L2connects the part of the bolt B at the first end51that is closest to the fourth end54to the part of the bolt B at the second end52that is closest to the fourth end54. The area between the second imaginary line L2and the fourth end54is a second releasing portion56.

When the internal pressure of the sealed case41increases, the first releasing portion55and the second releasing portion56start being deformed away from the opening edge44. This creates a clearance between the first releasing portion55and the opening edge44and a clearance between the second releasing portion56and the opening edge44. The gas in the sealed case41is discharged through these clearances. That is, parts of the lid member43are designed to function as valves for reducing the pressure in the sealed case41.

A connector47is attached to the exterior of the sealed case41. The connector47is electrically connected to the battery cells61accommodated in the sealed case41. Wires48are connected to the connector47. Each of the wires48are connected to one of the battery cells61via the connector47. The wires48extend from the connector47to the communication hole35. Specifically, the wires48are inserted in the communication hole35and connected to the connecting portion23. With this configuration, when the charging plug P shown inFIGS. 1 and 2is connected to the connecting portion23, the battery cells61and the charging station S are electrically connected via the connecting portion23, the wires48, and the connector47. In this case, the cable that supplies power to the battery module M is configured by the wires48, which connect the connecting portion23and the connector47to each other.

As shown inFIG. 5, the battery cell61includes a battery case62, an electrode assembly63accommodated in the battery case62, and electrolytic solution64. The battery cell61is, for example, a lithium-ion rechargeable battery or a nickel-metal hydride battery. The battery case62includes a main body65and a lid66. The main body65accommodates the electrode assembly63and the lid66closes the opening of the main body65. The main body65is shaped as a rectangular box. The lid66is shaped as a rectangular plate. The lid66has a pressure relief valve67. The pressure relief valve67is opened when the internal pressure of the battery case62exceeds a specified pressure. The specified pressure is set such that, when the internal pressure of the battery case62increases, the pressure relief valve67is broken before the battery case62is damaged.

As shown inFIG. 3, the battery pack30is accommodated in the accommodating portion31with the lid member43facing away from the side wall34having the communication hole35. Accordingly, the first releasing portion55and the second releasing portion56are arranged to face the upper wall33, the bottom wall32, and the side wall34on the opposite side from the side wall34having the communication hole35. That is, among the walls that configure the accommodating body, the first releasing portion55and the second releasing portion56are arranged to face walls different from the side wall34having the communication hole35. A releasing portion facing a wall portion of the accommodating body refers to a state in which, when the releasing portion is opened and gas is discharged, the wall exists in the discharging direction of the gas. That is, the wires48, which are connected to the connector47, are not arranged on the imaginary line that connects the inner surface of the wall of the accommodating body and an opening end of the opening edge44that is exposed when a releasing portion is opened. With the above described configuration, when the lid member43is deformed to create clearances between the opening edge44and the lid member43, the gas in the sealed case41is discharged through the clearances. That is, it only needs to arrange a wall that is a part of the walls configuring the accommodating body in the direction in which the clearance is opened. In the present embodiment, the upper wall33and a side wall34are arranged in the opening direction of the first releasing portion55, and the bottom wall32and a side wall34are arranged in the opening direction of the second releasing portion56.

Operation of the battery unit U as described above will now be described wither reference toFIGS. 3 to 5.

As shown inFIGS. 3 and 5, when there is an abnormality in any of the battery cells61, gas is generated in the battery case62and the internal pressure of the battery case62increases. When the internal pressure of the battery case62exceeds the specified pressure, the pressure relief valve67of the battery case62is broken. When the pressure relief valve67is broken, the gas in the battery case62is discharged to the interior of the sealed case41.

When gas is discharged from the battery cell61to the interior of the sealed case41as shown inFIGS. 3 and 4, the internal pressure of the sealed case41increases. This opens the first releasing portion55and the second releasing portion56of the lid member43. Then, the gas is discharged toward the upper wall33and the side wall34from the first releasing portion55. Also, the gas is discharged toward the bottom wall32and the side wall34from the second releasing portion56.

Accordingly, the above described embodiment provides the following advantages.(1) The first releasing portion55is arranged to face the upper wall33and one of the side walls34. Also, the second releasing portion56is arranged to face the bottom wall32and the side wall34. Thus, when the internal pressure of the sealed case41increases and the first releasing portion55and the second releasing portion56are opened, the gas in the sealed case41is discharged toward the bottom wall32, the upper wall33, and the side wall34. The wires48are therefore not directly exposed to the gas discharged from the sealed case41. This restrains damage to the wires48.(2) The first releasing portion55and the second releasing portion56are arranged to face the side wall34on the opposite side from the side wall34having the communication hole35. In this case, the gas reaches the wires48after a relatively long time from when the gas is discharged from the sealed case41. Thus, when reaching the wires48, the temperature of the gas has sufficiently dropped from the temperature immediately after being discharged from the sealed case41. This further effectively restrains damage to the wires48. Through the communication hole35, the gas, the temperature of which has sufficiently dropped from the temperature immediately after being discharged from the sealed case41, is discharged to the exterior of the vehicle body11. This restrains damage to the charging station S by high-temperature gas.

The present embodiment may be modified as follows.

As shown inFIG. 6, the releasing portion may be a valve71, which is attached by a hole72in the sealed case41. In this case, when the internal pressure of the sealed case41increases, the valve71is broken and opened. The gas in the sealed case41is discharged in the axial direction of the hole72. That is, it only needs to arrange the communication hole35and the wires48at positions displaced from an imaginary line connecting the periphery of the hole72and the inner surface of the wall of the accommodating body. Also, the releasing portion that is opened when the valve71is broken may face the side wall34having the communication hole35as long as the releasing portion does not face the wires48. The sealed case41may have a thin portion that is thinner than the remaining portion. In this case, the releasing portion corresponds to a part where the thin portion is broken and opened.

As shown inFIG. 7, the connecting portion23in the communication hole35may be omitted. In this case, the charging plug P is inserted in the accommodating portion31via the communication hole35and is directly connected to the connector47. In this case, the cable that supplies power to the battery module M is a cable C, which connects the charging station S and the charging plug P to each other. The cable C is connected to the connector47via the charging plug P and extends toward the communication hole35from the connector47. This configuration also restrains damage to the charging plug P and the cable C.

The accommodating portion31may have any shape. For example, the accommodating portion31may be cylindrical or polygonal.

The accommodating body does not necessarily need to be the vehicle body11, but may be a case that accommodates the battery pack30. That is, the battery pack30may be mounted in an apparatus other than the forklift10.

The external device may be a load connected to the battery pack30. Specifically, the external device may be one of the vehicle driving motor M1and the cargo handling motor M2, which are driven by the battery pack30as the power source. In this case, the accommodating body may have a communication hole35in which wires48connecting the load to the battery pack30are inserted.

The number of releasing portions may be one or greater than two.