Patent Application
20150171389
1. Field of the Invention
The present invention relates to a battery pack.
2. Description of Related Art
A battery pack including plural secondary battery cells can be used repeatedly as a power source by supplying electric energy from the outside of the battery, that is, by storing electric energy inside the battery by recharging the battery when the residual capacity of the battery is reduced.
As a method of recharging the battery pack, there exists a dedicated charging station in a case of an electric car, and recently, there is a method of recharging the battery from an outlet at home. Other various power supply methods are known in addition to the above at the time of recharging the battery. Especially, in a case of a hybrid car, a generator is actuated by utilizing the power of an engine during running, and generated electricity is stored.
In recent years, a type of a car which can recharge the battery from an outlet at home when the car is stopped has appeared in the hybrid car. There is also a method of recharging the battery by regenerating heat generated at the time of applying a brake in the case of the car.
A related-art battery pack in which battery cells are housed in a metal case and both ends of the cells are connected to current collecting plates is known (for example, refer to Japanese Patent No. 4923314 (Patent Document 1)).
In the drawing, battery cells 2 are housed in a metal block 11 in a state where directions of positive electrodes are aligned.
A positive-electrode current collecting plate 4 is welded to the positive electrode side of the battery cells 2, and a negative-electrode current collecting plate 5 is welded to the negative electrode side. A resin holder 10 is interposed between the current collecting plate and the battery cells 2, thereby performing insulation between positive electrodes and negative electrodes and preventing short circuit. The positive-electrode current collecting plate 4 and the negative-electrode current collecting plate 5 are fixed to the resin holder 10 by screws 12.
As typified by the battery pack described in Patent Document 1, a battery pack using lithium-ion rechargeable batteries normally constructs a system by combining plural battery cells. In this case, the positive electrodes/the negative electrodes of respective battery cells are connected to one current collecting plate respectively, and a widely used method for the connection is welding.
The battery back including plural battery cells is difficult to be used as the battery pack when any one cell indicating an abnormal state exists due to some factors. For example, the above state corresponds to cases where electrical characteristics are not satisfied due to the mixture of a battery cell which does not satisfy required characteristics or a welding failure between the positive electrodes/the negative electrodes of the battery cells and the current collection plate in manufacturing processes.
When excessive electric current flows into a particular cell due to short circuit caused by a foreign object inside the cell or a welding defect with respect to the current collecting plate during the use of the battery pack, one cell can be remarkably deteriorated or the function as the battery can be lost.
In this case, the battery pack can be used again if only the battery cell indicating the abnormal state can be changed, or normal battery cells are collected from plural battery packs and newly combined. However, it is difficult to separate normal battery cells from the current collecting plate without impairing the shape or electrical characteristics when the battery cells and the current collection plates are welded as described in Patent Document 1.
Accordingly, the present invention has been made for solving the above related-art problems, and an object thereof is to provide a battery pack which operates as the battery pack without problems, capable of taking out battery cells by disassembling the battery pack easily and safely as compared with the related-art battery pack and capable of using the taken battery cells again without impairment in positive electrodes and negative electrodes.
In order to achieve the above object, a battery pack according to the present invention is provided with compressed springs between a case and a current collecting plate of the battery pack as well as provided with claws in the case in consideration of safety at the time of assembling and disassembling the battery as described later.
According to the structure, the device can function as the battery as the battery cells constantly contact the current collecting plates by a force of returning the springs to an original length in the above structure, and the battery can be disassembled easily and safely even when the function as the battery pack is impaired due to some defects, therefore, the change of the battery cells as well as reuse of normal battery cells can be easily performed.
As described above, assembly and disassembly can be easily performed by using the battery pack according to the present invention.
When a failure occurs due to abnormality of a battery cell, only the failed battery cell can be easily changed even after the assembly of the battery pack has been completed. Even in a case of a battery which has been used for a long period of time as an in-vehicle battery and has come to the end of the life of the battery due to capacity deterioration, the battery pack can be easily disassembled and battery cells can be used again when they are useful in other applications.
Hereinafter, embodiments of the present invention will be explained with reference to the drawings.
In
The number of battery cells 2 included in the battery pack 1 is determined based on the performance required for the battery such as the necessary capacity and voltage, therefore, it is not particularly limited. The battery cells 2 are arranged so that directions of all positive electrodes and negative electrodes are aligned.
The number of cell holders 3 provided in one battery pack 1 is one or two. The cell holder 3 serves a function of holding the battery cells 2. The connection between the cell holder 3 and the current collection plate must not be broken when some external load is generated during the operation as the battery or when the battery cells 2 are inclined at the time of assembling the battery pack 1.
In order to prevent the above, when one cell holder is provided, the height of the cell holder 3 for holding the battery cells 2 is desirably set to 20% or more of the height of the cells, and when two cell holders are provided, each height of the cell holders 3 is set to 10% or more of the height of the cells.
A material of the cell holder 3 is not particularly limited, and may be selected according to characteristics of the battery. It is suitable to use, for example, a resin material with low thermal conductivity or the like as heat propagation to adjacent battery cells can be suppressed. In this case, the height of the cell holder 3 is desirably as small as possible in the above-described range.
When focusing on the suppression of temperature increase of the cells during the normal use, a metal material with high thermal conductivity such as aluminum is preferably used. In this case, it is desirable to set the height of the cell holder 3 to be higher as the thermal conductivity is increased.
The positive-electrode current collecting plate 4 is connected to the battery cells 2 in the positive electrode side and the negative-electrode current collecting plate 5 is connected thereto in the negative electrode side, respectively. As it is necessary that the current collecting plate is connected to the current collection plate of another battery pack 1, a terminal is extended to the outside of the case 7.
It is possible to apply a method in which both terminals are arranged in the positive electrode side or the negative electrode side as shown in
The battery cells 2, the cell holder 3, the positive-electrode current collecting plate 4 and the negative-electrode current collecting plate 5 are housed inside the case 7.
At least one spring 6 is arranged between the positive-electrode current collecting plate 4/the negative-electrode current collecting plate 5 and the case 7. The battery pack 1 is formed in a state where the springs 6 are compressed.
At this time, a distance L between a top surface (positive side) and a floor surface (negative side) of the case 7 is equal to a sum of lengths obtained when the springs 6 in the positive electrode side and the negative electrode side are compressed (la and lb respectively), a thickness D of the positive-electrode current collecting plate 4 and a thickness “d” of the negative-electrode current collecting plate 5 and a height “h” of the battery cells 2. That is, the following expression holds.
L=h+D+d+1a+1b
The battery cells 2 are allowed to contact the two current collecting plates by utilizing a force of returning the compressed springs 6 to the natural length, thereby performing electrical connection.
According to the above structure, even when any of positions of the battery cells 2, the positive-electrode current collecting plate 4 and the negative-electrode current collecting plate 5 is displaced due to reception of some load from the outside, the displacement can be absorbed by the compressed springs 6, therefore, the contact state between the battery cells and the current collecting plates can be constantly kept and electric current is not disrupted.
Although the number of the springs 6 is not particularly limited, it is desirable that the springs 6 are arranged at least five places in total, which are the center and four corners of the current collecting plate as shown in
When vibration load is frequently applied and large load is assumed by the mounting on an electric car or a hybrid car, it is desirable to arrange the springs 6 at least just above the battery cells and just below the battery cells so as to correspond to the number of battery cells.
An object of the battery pack 1 according to the present invention is to allow the battery cells 2 to be used again as described later. Accordingly, a structure in which the battery cells 2 are not bonded to the current collecting plates is applied, however, the springs 6 may be bonded to the positive-electrode collecting plate 4 and the negative-electrode collecting plate 5 by means of welding and the like.
The case 7 has a structure which is vertically separated into two and is easily opened and closed by a fastener 8. The case 7 may also has a structure in which the battery cells 2 housed inside are completely enclosed.
In the case where cooling of the battery cells 2 is necessary as shown in
It is desirable that a material of the case 7 has high insulating performance such as a resin material, however, it is not particularly limited as long as insulation in the outside of the battery pack 1 is secured as well as the case 7 is electrically insulated from the positive-electrode current collecting plate 4, the negative-electrode current collecting plate 5 and the springs 6 by methods such as applying an insulating material or adhering an insulating thin film on the surface of the case.
The battery pack 1 according to the present invention has a structure in which the battery cells 2 are fixed by the cell holder 3 and are sandwiched by the positive-electrode current collecting plate 4 and the negative-electrode current collecting plate 5 from both electrodes, and further, they are surrounded by the case from upper and lower sides in a state where the springs are disposed above and below the two current collecting plates, and upper and lower portions of the case are fixed by the fastener 8.
In order to close the upper and lower portions of the case after the all components inside the case 7 are arranged at the time of assembling the battery pack 1, it is necessary to fix the fastener 8 in a state where the case is pressed by a large force from upper and lower sides for compressing the springs. It is dangerous to perform the above work by human hands. There is also a danger that the case 7 is suddenly ejected when the fastener 8 is released at the time of disassembling the battery pack 1 as a large force of returning the compressed springs 6 to the natural length is acted.
In order to solve the above problems and perform assembly and disassembly safely, the case 7 of the battery pack 1 according to the present invention is provided with claws 9 in an upper part of a side surface of the upper case and a lower part of a side surface of the lower case as shown in
After the current collecting plate is completely pushed to the position of the claws 9, the current collecting plate does not move beyond the position of the claws 9 even when the force of returning the compressed springs 6 to the natural length is acted.
It is necessary to arrange at least one or more claws 9 at each surface in both sides of the case 7 in the long side. When the claws 9 are arranged only in the long side, it is preferable that one claw 9 having a width slightly shorter than the length of the side surface is provided, or that two or more claws 9 to be arranged at least in two places near both ends of the current collecting plate are provided. The claws 9 can be provided also in the short side if structurally possible.
In the above state, the battery cells 2 fixed to the cell holder 3 are interposed between the cases as shown in
In order to further increase the safety during the work, a jig for supporting the case or the current collecting plate may be used at the time of attaching the current collecting plate to the case or at the time of connecting or opening upper and lower portions of the case. Especially at the time of disassembly, the battery pack can be disassembled extremely safely by fixing the battery pack 1 to the jig first, opening the fastener 8 in that state, and gradually moving the jig.
It is necessary that flat surfaces of the claws 9 which receive the current collecting plate are positioned closer to the center of the cells with respect to top surfaces or bottom surfaces of the cells in the state of the battery pack 1 for allowing the claws 9 of the case 7 to serve the above function. When the flat surfaces receiving the current collecting plate are positioned farther from the center of the cells with respect to the top surfaces or the bottom surfaces of the cells, a gap is generated between the cells and the current collecting plate when the assembly is completed as the battery pack, which interrupts electrical connection.
When both claws 9 are positioned in the same level, the contact between the cells and the current collecting plate is held in the state where assembly is completed. For example, if the case is deformed due to the effect of vibration generated at that time of running of the car when used as an in-vehicle battery, there is a possibility that electrical connection is broken as the cells are separated from the current collecting plate.
Accordingly, a distance between the flat surface receiving the current collecting plate and the top surface or the bottom surface of the case is larger than the distance between the top surfaces or the bottom surfaces of the cells and the top surface or the bottom surface of the case, however, in the case where the distance is too large, it is difficult to achieve the object of the safe assembly or disassembly.
The flat surface receiving the current collecting plate is preferably positioned approximately 0.5 mm to 2 mm closer to the center of the cells with respect to the position of the top surfaces or the bottom surfaces of the battery cells when assembly is completed as the battery pack. The reason why approximately 0.5 mm to 2 mm is preferable is based on knowledge in which it is necessary to secure at least 0.5 mm or more as the lower limit when considering the tolerance of the parts as 0.2 mm, and it becomes difficult to perform disassembly safely when the distance is longer than 2 mm as the upper limit though the springs are extended to a position where the current collecting plate is caught by claws when the device is disassembled.
The shape of the claws 9 is a pentagonal prism in
The area of the flat surface as the contact surface with respect to the current collecting plate is not particularly limited, however, when the area is increased, the volume of the battery pack 1 is increased and energy density is reduced, therefore, it is preferable that the area is smaller. When the positive-electrode current collecting plate 4 or the negative-electrode current collecting plate 5 and the springs 6 are attached to the case 7, the claws 9 are pushed by the force of the springs. As a stress generated in the claws 9 at this time must not exceed a yield stress of the material used for the case 7, the smallest area is determined according to the material.
In the battery pack 1 having the above structure, it is easy to assemble or disassemble the battery as well as the battery cells 2 are not welded to the current collecting plate, therefore, the battery cells are taken out without damage at the time of disassembly, which enables recycling.
Even when a failure is discovered in the battery cell at the time of manufacturing, only the corresponding cell can be easily changed, therefore, a yield of the battery pack can be improved.
The case where all the positive electrodes/the negative electrodes of the battery cells 2 are aligned in the same direction has been explained in Embodiment 1. The present invention can be applied to a case where the positive electrodes and the negative electrodes are alternately aligned in adjacent cells.
In this case, it is difficult to use a piece of positive-electrode current collecting plate 4 or negative-electrode current collecting plate 5 shown in Embodiment 1. However, a current collecting plate is formed by adhering terminals connecting between positive electrodes and negative electrodes of adjacent cells to a piece of plate having insulation performance, thereby fabricating the battery pack 1 similar to Embodiment 1.
The battery cells 2 having a cylindrical shape are used in Embodiment 1, however, battery cells having a square shape can be used. The square-shape cell has the positive electrode and the negative electrode in the same surface, which differs from the cylindrical cell. Accordingly, it is sufficient that the claws 9 of the resin case 7 shown in Embodiment 1 are provided only in one side of the case.
As it is difficult to use a piece of current collecting plate as shown in Embodiment 1 in the square-shape battery, the plate in which terminals are adhered to the plate having insulation performance is preferably used in the same manner as Embodiment 2.
The present invention can be applied to transportation equipment such as the electric car and the hybrid car as well as applications of a storage battery at home, a stock power supply used in case of emergency.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2013-257824 | Dec 2013 | JP | national |
