JP3773882B2 - battery pack - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a battery pack in which unit cells are housed in a case, and more particularly to a battery pack in which unit cells are housed with the lateral width of the case as small as possible.
[0002]
[Prior art]
The case for storing the unit cell needs to have a firm and strong structure. This battery pack is manufactured by molding a case separated into a main body case and a lid case with plastic or the like, putting a unit cell in the main body case, and closing the opening of the main body case with the lid case. The main body case is formed into a box shape having side walls and end walls so that the unit cells can be accommodated. A unit cell is put inside the side wall and the end wall, and the opening between the side wall and the end wall is closed with a lid case. At this time, it is important to firmly connect the side wall and the end wall of the main body case to the lid case. The main body case and the lid case are connected by ultrasonic welding. The battery packs connected with this structure need to have a predetermined thickness on the side wall and the end wall in order to firmly ultrasonically weld the main body case and the lid case. Further, the side walls connected by ultrasonic welding are provided with a connecting groove on one side and a ridge fitted into the connecting groove on the other side so that the welding positions are not shifted from each other. The side wall to be ultrasonically welded with this structure needs to be thicker than 0.65 to 0.8 mm, for example.
[0003]
[Problems to be solved by the invention]
Although the thickness of the side wall of the main body case can be increased to improve the connection strength between the main body case and the lid case, this increases the outer shape of the case. The present invention has been developed for the purpose of solving this drawback. An important object of the present invention is to provide a battery pack capable of firmly connecting a main body case and a lid case without increasing the outer shape of the case.
[0004]
[Means for Solving the Problems]
In the battery pack of the present invention, a unit cell 2 having corner curved surfaces 2A on both side surfaces is housed in a case 1. The case 1 is ultrasonically welded to a main body case 1A having a pair of side walls 4 and an end wall 5 that house the unit cell 2 inside, and an opening between the side wall 4 and the end wall 5 of the main body case 1A. Lid case 1B. The side wall 4 of the main body case 1A has an edge portion that is ultrasonically welded to the lid case 1B and protrudes from the inside of the case 1 toward the corner curved surface 2A of the unit cell 2 to form a thick welded portion 6. The inner width of the thick weld portion 6 provided on the side wall 4 is narrower than the width of the unit cell 2. In the main body case 1 </ b> A, the side wall 4 is elastically deformed so that the unit cell 2 is inserted between the pair of side walls 4. The lid case 1B has a vertical wall 15 that is ultrasonically welded to the end wall 5 of the main body case 1A. The end wall 5 of the main body case 1A is connected to the side wall 4 at both ends and is provided with a recess 9 in the middle. The vertical wall 15 of the lid case 1B has a protrusion 16 that is fitted into the recess 9 of the main body case 1A. The case 1 is formed by ultrasonically welding the vertical wall 15 of the lid case 1B to the end wall 5 of the main body case 1A, and ultrasonically welding the lid case 1B to the thick weld portion 6 of the side wall 4 of the main body case 1A. The unit cell 2 is housed.
[0005]
The main body case 1 </ b> A can bend a boundary portion between the bottom surface and the side wall 4 along the corner curved surface 2 </ b> A of the unit cell 2 with a larger radius of curvature than the corner curved surface 2 </ b> A. The lid case 1 </ b> B can open the electrode window 13 in the protruding portion 16 of the vertical wall 15.
[0006]
Furthermore, the main body case 1 </ b> A can be provided with a recess 9 in the end wall 5 connected to one end of the side wall 4. The main body case 1 </ b> A can be provided with an inner surface groove 10 at the other end portion of the side wall 4, and the inner surface groove 10 can make the side wall 4 thinner to facilitate elastic deformation.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. However, the embodiment described below exemplifies a battery pack for embodying the technical idea of the present invention, and the present invention does not specify the battery pack as follows.
[0008]
Further, in this specification, in order to facilitate understanding of the scope of claims, the numbers corresponding to the members shown in the examples are referred to as “the scope of claims” and “the means for solving the problems”. It is added to the member shown by. However, the members shown in the claims are not limited to the members in the embodiments.
[0009]
The battery pack shown in FIGS. 1 to 6 includes a unit cell 2 that is a secondary battery and a case 1 that houses the unit cell 2. The unit cell 2 which is a secondary battery is a lithium ion secondary battery. However, the unit cell 2 can be any rechargeable battery such as a nickel-hydrogen battery or a nickel-cadmium battery. The unit cell 2 shown in the figure is a prismatic battery having corner curved surfaces 2A on both side surfaces. A thin battery or a cylindrical battery can also be used for the unit cell 2.
[0010]
In the battery pack of FIG. 5, in addition to the unit cell 2, a circuit board 3 is disposed at a fixed position of the case 1. The circuit board 3 fixes an electronic component that realizes a protection circuit for the unit cell 2 and an output terminal 17. The circuit board 3 is connected to the unit cell 2 via a lead plate (not shown) and is disposed at a fixed position in the case 1.
[0011]
The case 1 includes a main body case 1A and a lid case 1B which are separately molded with thermoplastic plastic. The lid case 1B is connected by ultrasonic welding to the opening of the main body case 1A in which the unit cell 2 and the circuit board 3 are arranged at fixed positions.
[0012]
The main body case 1 </ b> A is formed in a box shape having a pair of side walls 4 and end walls 5 so as to accommodate the unit cells 2 inside. As shown in the sectional view of FIG. 6, the side wall 4 is provided with a thick weld portion 6 at a portion where the lid case 1 </ b> B is ultrasonically welded. The thick weld 6 does not protrude outside the case 1 but protrudes inside the case 1. Further, the thick welded portion 6 is an edge portion that is ultrasonically welded to the lid case 1B in order to effectively use the gap formed in the corner curved surface 2A of the unit cell 2, and the corner curved portion of the unit cell 2 is curved. It is provided so as to protrude toward the surface 2A. As shown in FIG. 6, when the unit cell 2 is housed in the main body case 1A, the corner curved surface 2A of the unit cell 2 is positioned on the bottom surface side and the opening side of the main body case 1A. The thick weld portion 6 is provided so as to protrude toward the corner curved surface 2A on the opening side. This is because the unit cell 2 is placed inside the side wall 4. Further, the main body case 1A is a boundary portion between the bottom surface and the side wall 4, and a portion facing the corner curved surface 2A on the bottom surface side of the unit cell 2 is curved along the corner curved surface 2A of the unit cell 2. The corner bending portion 12 is used. The corner bending portion 12 can be curved with a larger radius of curvature than the corner curved surface 2A of the unit cell 2, and the side wall 4 can be easily elastically deformed. In the main body case 1 </ b> A, the side wall 4 is easily elastically deformed, and the unit cell 2 can be easily inserted between the pair of side walls 4.
[0013]
The thick weld portion 6 protrudes inward and is formed thick. For example, the thickness of the thick weld portion 6 is set to 1 mm, and the thickness of the side wall 4 that is not the thick weld portion 6 is formed to 0.4 mm. However, the thickness of the thick welded portion 6 and the side wall 4 needs to be changed depending on the weight and size of the unit cell 2, the strength of the plastic used for the case 1, and the like. The battery pack for storing the heavy and large unit cell 2 is formed by thickly forming the thick welded portion 6 and the side wall 4. Therefore, the thickness of the thick weld portion 6 is, for example, 0.8 to 1.5 mm, and the thickness of the side wall 4 is 0.3 to 0.8 mm.
[0014]
The main body case 1 </ b> A shown in the figure has a connection groove 8 on the welding surface of the thick weld portion 6. The projection 7 of the lid case 1B is inserted into the coupling groove 8, and the side wall 4 and the lid case 1B are coupled so as not to be displaced. Although not shown, it is also possible to provide a ridge on the welding surface of the thick welded portion, and to provide a connecting groove for receiving this ridge in the lid case. The thick welded portion 6 is formed so as to gradually become thicker toward the welded surface, that is, gradually thicker along the corner curved surface 2A of the unit cell 2. The thick welded portion 6 having this structure smoothly guides the unit cell 2 to the inside of the side wall 4 and abuts the corner curved surface 2A of the unit cell 2 over a wide area. For this reason, the thick weld part 6 does not contact the unit cell 2 locally to be damaged.
[0015]
The pair of side walls 4 that are thickened by providing the thick welded portion 6 make the inner width of the thick welded portion 6 narrower than the width of the unit cell 2. This is to reduce the lateral width of the case 1 as much as possible. In the main body case 1A having this structure, the side wall 4 is elastically deformed and the unit cell 2 is inserted. The side walls 4 which are thinned to make the lateral width of the case 1 as small as possible have both ends connected to the end walls 5 and the end walls 5 serve as reinforcing ribs to improve the bending strength. The end wall 5 reinforces the side wall 4 and makes it difficult for the side wall 4 to deform when the unit cell 2 is inserted. The end wall 5 reinforces the side wall 4, but both ends thereof are connected to the side wall 4 so that the side wall 4 can be deformed, and a recess 9 is provided in the middle. The recess 9 provided in the end wall 5 makes it easy to extend the upper end edge of the end wall 5, that is, the welded portion to the vertical wall 15. This is because the recess 9 separates the upper edge on both sides. When the unit cell 2 is inserted, the side wall 4 needs to be deformed in a direction in which the inner width of the thick welded portion 6 increases. In order for the side wall 4 to deform in this direction, it is necessary to extend the upper edge of the end wall 5. The end wall 5 without the recess 9 is extremely difficult to extend, and both ends are connected to the side wall 4 to prevent the side wall 4 from being deformed. An end wall 5 provided with a recess 9 in the middle and separating both end portions connected to the side wall 4 is easy to extend at the upper end edge and to easily deform the side wall 4. The end wall 5 of this structure brings a part line, which is a boundary connected by ultrasonic welding to the vertical wall 15 of the lid case 1B, close to the bottom surface side of the main body case 1A, and lowers the end wall 5 in the middle. is doing. As the recess 9 of the end wall 5 is made wider and deeper, the side wall 4 can be easily deformed. The end wall 5 is provided with a recess 9 to deform the side wall 4 to the extent that the unit cell 2 can be inserted, but also functions to reinforce the side wall 4. Therefore, the width and depth of the recess 9 are specified so that the side wall 4 can be deformed so that the unit cell 2 can be inserted. For example, the width of the recess 9 is specified to be 15 to 80%, preferably 15 to 50%, more preferably 15 to 30% of the total length of the end wall 5. The depth of the recess 9 is specified to be, for example, 20 to 100%, preferably 30 to 80%, more preferably about 30 to 60% of the height of the end wall 5.
[0016]
The body case 1A shown in the figure is provided with a recess 9 only in one end of the side wall 4, the end wall 5 connected to the lower left end in FIG. 5, and the other end of the side wall 4, upper right in the figure. An inner surface groove 10 is provided at the end of the inner wall, and the side wall 4 is thinned by the inner surface groove 10 to facilitate elastic deformation. Since the inner surface groove 10 makes the side wall 4 easily deformable, the thick weld portion 6 is not provided on the weld surface. However, in order to connect the lid case 1B to a fixed position, the lid case 1B is molded into a fitting shape for positioning the ridges 7 of the lid case 1B. Since the side wall 4 provided with the inner surface groove 10 is easily deformed by the inner surface groove 10, the end wall 5 connected to the end portion on this side has a shape without a recess. Furthermore, the inner surface groove 10 has a predetermined width so that the side wall 4 can be easily deformed. For example, the inner groove 10 has a width of about 2 to 3 mm.
[0017]
The main body case 1A shown in FIG. 5 is provided with a step 11 at a portion where the inner surface groove 10 of the side wall 4 is provided, and the circuit board 3 is disposed here. Since the step 11 is formed by the end wall 5, the end wall 5 is formed in a shape having the step 11. The end wall 5 with the step 11 is connected to the side wall 4. The end wall 5 has an electrode window 13 that exposes the output terminal 17 fixed to the circuit board 3 to the outside, and opens to a surface projecting to the outside.
[0018]
In the above battery pack, the electrode window 13 is opened in the end wall 5 where the recess 9 is not provided, and the output terminal 17 is disposed inside the electrode window 13. However, as shown in FIG. 7, the battery pack of the present invention can also have a structure in which the electrode window 13 is opened in the protruding portion 16 of the vertical wall 15 disposed on the end wall 5 provided with the recess 9. . In this battery pack, an output terminal 17 is disposed inside the electrode window 13. The output terminal 17 is fixed to a circuit board (not shown), and is fixed inside the vertical wall 15 provided with the electrode window 13. As described above, the structure in which the electrode window 13 is opened in the vertical wall 15 of the lid case 1B is such that when the unit cell 2 is housed in the main body case 1A, that is, when the side wall 4 is elastically deformed, the electrode window 13 and its peripheral portion. Is not affected by the side wall 4 that is elastically deformed. For this reason, when the side wall 4 is elastically deformed, it is possible to effectively prevent the portion from being damaged or deformed due to stress acting on the electrode window 13 and its peripheral portion. Furthermore, since the vertical wall 15 that opens the electrode window 13 is not restricted to elastically deform the side wall 4, there is a feature that the strength of the peripheral portion of the electrode window 13 can be increased to a sufficient thickness. In particular, the structure in which the electrode window 13 is provided in the protruding portion 16 of the vertical wall 15 has a feature that the opening area of the electrode window 13 can be increased.
[0019]
In the above battery pack, the recess 9 is provided in the end wall 5 connected to one end of the side wall 4. However, in the battery pack of the present invention, the side walls can be easily deformed by providing recesses in both end walls provided at both ends of the side walls. As described above, the structure in which the concave portions are provided in both the end walls can easily deform the side walls without providing the inner surface grooves in the end portions of the side walls.
[0020]
The end wall 5 is connected to the vertical wall 15 of the lid case 1B by ultrasonic welding. Therefore, the end wall 5 is provided with a connecting groove on the welding surface, and the vertical wall 15 of the lid case 1B is provided with a protrusion that can be inserted into the connecting groove. However, it goes without saying that protrusions can be provided on the end walls and connection grooves can be provided on the vertical walls.
[0021]
The lid case 1B is integrally formed with a vertical wall 15 that is ultrasonically welded to the end wall 5 of the main body case 1A. The vertical wall 15 has a protrusion 16 that is fitted into the recess 9 of the main body case 1A. The vertical wall 15 of the lid case 1B is ultrasonically welded to the end wall 5 of the main body case 1A. The lid case 1B is also ultrasonically welded to the thick welded portion 6 provided on the side wall 4 of the main body case 1A. The lid case 1B is provided with connecting walls 14 on both sides for ultrasonic welding to the side wall 4 of the main body case 1A. That is, the lid case 1B is formed in a shape that allows the connecting wall 14 and the vertical wall 15 to be connected to the side wall 4 and the opening of the end wall 5 of the main body case 1A. The lid case 1B shown in the figure is provided with a connecting wall 14 and is ultrasonically welded to the side wall 4. However, the connecting wall is not necessarily welded to the side wall. This is because although not shown, both sides of the lid case can be ultrasonically welded to the side wall.
[0022]
The above battery pack is assembled as follows.
(1) The unit cell 2 connecting the circuit board 3 is placed in the main body case 1A from which the lid case 1B is separated. At this time, since the width of the unit cell 2 is narrower than the inner width of the thick weld portion 6, the side wall 4 is elastically deformed and the unit cell 2 is inserted between the side walls 4. In this state, the unit cell 2 and the circuit board 3 are disposed at fixed positions of the main body case 1A.
(2) Place the lid case 1B on the opening of the main body case 1A.
(3) Place the main body case 1A on the base, press the upper surface of the lid case 1B with an ultrasonic horn, and ultrasonically vibrate the lid case 1B with the ultrasonic horn. Sonic welding. The ultrasonic welded lid case 1B and main body case 1A weld the connecting wall 14 of the lid case 1B to the side wall 4 of the main body case 1A and the vertical wall 15 of the lid case 1B to the end wall 5.
[0023]
Since the battery pack manufactured as described above is ultrasonically welded to the main body case 1A on the entire circumference of the lid case 1B, it can be made to have an extremely strong structure. However, the battery pack of the present invention does not necessarily require ultrasonic welding of the entire circumference of the lid case 1B to the opening of the main body case 1A, and can be connected without welding a part thereof.
[0024]
【The invention's effect】
The battery pack of the present invention has the feature that the main body case and the lid case can be firmly connected while the case is made the minimum size. That is, the battery pack of the present invention is provided with a thick welded portion projecting inside the case on the side wall of the main body case, the inner width of the side wall opening is narrower than the unit cell, and the side wall is elastically deformed, This is because the unit cell is inserted between the side walls. In particular, the battery pack of the present invention is provided with a recess in the middle of the main body case end wall to facilitate deformation of the side wall. For this reason, a unit cell can be smoothly inserted between narrow side walls.
[0025]
Further, in the battery pack of the present invention, since the end wall is connected to the end portion of the side wall, the end wall acts as a reinforcing rib that prevents the side wall from being bent. For this reason, an end part wall reinforces a side wall and improves the intensity | strength of a side wall, especially bending strength. However, the structure in which the end wall reinforces the side wall cannot be smoothly inserted when the unit cell is inserted by deforming the side wall. Therefore, a concave portion is provided in the middle of the end wall to bend the unit cell. While facilitating, the side walls are reinforced with end walls. Further, since the protrusion provided on the vertical wall of the lid case is inserted into this concave portion and ultrasonic welding is performed, the side wall is reinforced by the end wall and the vertical wall in the assembled state, and is firmly strong. It becomes a structure.
[0026]
Furthermore, in the battery pack according to claim 2 of the present invention, since the boundary portion between the bottom surface and the side wall of the main body case is curved along the corner curved surface of the unit cell, when the unit cell is put into the main body case, While easily deforming the side wall, it can be firmly and tough.
[Brief description of the drawings]
1 is a bottom view of a battery pack according to an embodiment of the present invention. FIG. 2 is a front view of the battery pack shown in FIG. 1. FIG. 3 is a rear view of the battery pack shown in FIG. FIG. 5 is a partially enlarged perspective view showing a state in which a unit cell is inserted into the main body case. FIG. 6 is a cross-sectional view of the battery pack shown in FIG. 1. FIG. Rear view of an example battery pack [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Case 1A ... Main body case 1B ... Lid case 2 ... Cell 2A ... Corner curved surface 3 ... Circuit board 4 ... Side wall 5 ... End wall 6 ... Thick welding part 7 ... Projection 8 ... Connection groove 9 ... Concave 10 ... Inner groove 11 ... Step 12 ... Corner bend 13 ... Electrode window 14 ... Connecting wall 15 ... Vertical wall 16 ... Protrusion 17 ... Output terminal

Claims (5)

A battery pack in which a unit cell (2) having corner curved surfaces (2A) on both sides is stored in a case (1), and the case (1) is a pair of units storing a unit cell (2) inside. A body case (1A) having a side wall (4) and an end wall (5), and a lid that is ultrasonically welded to the opening of the side wall (4) and the end wall (5) of the body case (1A) With a case (1B)
The side wall (4) of the main body case (1A) is an edge portion that is ultrasonically welded to the lid case (1B), and is directed to the corner curved surface (2A) of the unit cell (2), inside the case (1). The inner width of the thickness welded portion (6) provided on the pair of side walls (4) is made narrower than the width of the unit cell (2), and the side wall ( 4) is elastically deformed so that the unit cell (2) is inserted between the pair of side walls (4),
The lid case (1B) has a vertical wall (15) ultrasonically welded to the end wall (5) of the main body case (1A), and the end wall (5) of the main body case (1A) 4) is provided with a recess (9) in the middle, and the vertical wall (15) of the lid case (1B) has a protrusion (16) that fits into the recess (9) of the body case (1A). Then, the vertical wall (15) of the lid case (1B) is ultrasonically welded to the end wall (5) of the main body case (1A), and the lid case (1B) is attached to the side wall (4) of the main body case (1A). A battery pack in which the unit cell (2) is accommodated by ultrasonic welding to the thick weld (6). The boundary between the bottom surface of the main body case (1A) and the side wall (4) is curved along the corner curved surface (2A) of the unit cell (2) with a larger radius of curvature than the corner curved surface (2A). The battery pack according to claim 1. The battery pack according to claim 1, wherein an electrode window (13) is opened in the protrusion (16) of the vertical wall (15) of the lid case (1B). The battery pack according to claim 1, wherein a recess (9) is provided in an end wall (5) connected to one end of the side wall (4). The end wall (5) connected to one end of the side wall (4) is provided with a recess (9), the other end of the side wall (4) is provided with an inner surface groove (10), and an inner surface groove ( The battery pack according to claim 4, wherein the side wall (4) is thinned by 10) to facilitate elastic deformation.

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