Patent Application
20120129043
The present invention relates to an assembled battery having at least two cells, and a lead plate for electrically connecting these cells.
Conventionally, for example, an assembled battery as described in the Patent Document 1 is known. The assembled battery as described in the Patent Document 1 has a plurality of batteries (cells) and a lead plate for electrically connecting these batteries. The lead plate and the batteries are spot welded to each other.
When this kind of assembled battery is produced, one lead plate is caused to contact against a surface of the cell, and a pair of electrodes is caused to contact at adjacent positions on this single lead plate. With this state, electric current is applied from one electrode to the other electrode through the surface of the cell to generate Joule heat corresponding to the resistance value of the lead plate, thereby to melt the surface of the lead plate facing to the cell.
However, in the method, the electrodes are caused to contact at the adjacent positions on the single lead plate. Thus, the electric current flows between the electrodes through the lead plate itself that is located between the electrodes. As a result, there is a problem that the Joule heat cannot be generated in an effective manner at the target welding position (the surface of the lead plate facing on the cell).
As a structure to solve this problem, for example, an assembled battery 100 having lead plates as shown in
The assembled battery 100 comprises four cells 101A to 101D, and a single lead plate 102 for electrically connecting the cells 101A to 101D. This lead plate 102 integrally has a first connecting unit 102a for connecting the cell 101A and the cell 101B, a second connecting unit 102b for connecting the cell 101B and the cell 101C, a third connecting unit 102c for connecting the cell 101C and the cell 101D, and an external connecting unit 102d connected to the cell 101A and an external instrument (e.g., a safety device). The joints between these connecting units 102a to 102d are electric resistance welded to the cells 101A to 101D, respectively.
In addition, a slit 103a is formed between a welding position A11 and a welding position A12 of the cell 101A, a slit 103b is formed between a welding position B11 and a welding position B12 of the cell 101B, a slit 103c is formed between a welding position C11 and a welding position C12 of the cell 101C, and a slit 103d is formed between a welding position D11 and a welding position D12 of the cell 101D, in the lead plate 102.
For example, electrodes E1 and E2 (see
However, in the conventional assembled battery 100 as shown in
In addition, in the assembled battery 100 shown in
An object of the present invention is to provide an assembled battery with which reactive current can be reduced and flexibility in cell layout can be increased, and a method for producing such an assembled battery.
In order solve the aforementioned problems, the present invention provides a method for producing an assembled battery having a first cell, a second cell electrically connected to the first cell, and at least one connected member electrically connected to the first cell and the second cell, comprising: a preparation step of preparing a first lead plate that is adapted to electrically connect the first cell and the second cell, and a second lead plate that is adapted to electrically connect the second cell and the connected member; an contacting step of causing one end of the first lead plate and one end of the second lead plate to contact against the second cell, in such a manner that the one end of the first lead plate and the one end of the second lead plate are spaced apart from each other with a predetermined first gap therebetween; a first welding step of electric resistance welding the first lead plate and the second lead plate to the second cell by means of causing electrodes to contact, from the side opposite to the second cell, against the one end of the first lead plate and the one end of the second lead plate, respectively, which have contacted against the second cell, and applying electric current between the electrodes; a second welding step of welding the other end of the first lead plate and the first cell; and a connection step of electrically connecting the other end of the second lead plate and the at least one connected member.
In addition, the present invention provides an assembled battery having a first cell, a second cell electrically connected to the first cell, and a connected member electrically connected to the first cell and the second cell, comprising: a first lead plate that is provided so as to span between the first cell and the second cell, the first lead plate being adapted to electrically connect the first cell and the second cell; and a second lead plate that is provided so as to span between the second cell and the connected member, the second lead plate being adapted to electrically connect the second cell and the connected member, wherein the first lead plate and the second lead plate are electric resistance welded to the second cell in such a manner that an end of the first lead plate and an end of the second lead plate are spaced apart from each other with a predetermined plate gap therebetween, and only an electric resistance welded portion that is formed by one of a pair of positive and negative electrodes for electric resistance welding is formed between the end of the first lead plate and the second cell, and only an electric resistance welded portion that is formed by the other of the pair of positive and negative electrodes for the electric resistance welding is formed between the end of the second lead plate and the second cell.
According to the present invention, it is possible to provide a method for producing an assembled battery with which electric resistance welding can be performed more efficiently and flexibility in cell layout can be increased.
Now, referring to the drawings, an embodiment of the present invention is described. The following embodiment is an example in which the present invention is implemented, and is not intended to limit a technical scope of the present invention.
Referring to
The assembled battery 3A comprises four cells 4A to 4D, lead plates 5A to 5C that electrically connect these cells 4A to 4D, a lead plate 6 that electrically connects the cell 4A and the safety device 8, and a fixed plate 7 fixed to the cell 4D.
The cells 4A to 4D are arranged in series with their centers located on a generally same arc in the side view shown in
The lead plate 5A is secured so as to span between the cell 4A and the cell 4B located adjacent to the cell 4A. More specifically, the lead plate 5A is a strip-shaped metal plate and has one end that is electric resistance welded to the cell 4A at one welding position A2 and the other end that is electric resistance welded to the cell 4B at one welding position B1.
The lead plate 5B is secured so as to span between the cell 4B and the cell 4C located adjacent to the cell 4B. More specifically, the lead plate 5B is a strip-shaped metal plate and has one end that is electric resistance welded to the cell 4B at one welding position B2 and the other end that is electric resistance welded to the cell 4C at one welding position C1.
The lead plate 5C is secured so as to span between the cell 4C and the cell 4D located adjacent to the cell 4C. More specifically, the lead plate 5C is a strip-shaped metal plate and has one end that is electric resistance welded to the cell 4C at one welding position C2 and the other end that is electric resistance welded to the cell 4D at one welding position D1.
The lead plate 6 is secured so as to span between the cell 4A and the safety device 8 located adjacent to the cell 4A on the opposite side of the cell 4B. More specifically, the lead plate 6 is a strip-shaped metal plate and has one end that is electric resistance welded to the cell 4A at one welding position A1 and the other end that is electrically connected to the safety device 8 at a connection point which is not shown.
The fixed plate 7 is a circular metal plate and is electric resistance welded to an end surface of the cell 4D at one welding position D2.
Now, a method for manufacturing the battery pack 1 is described with reference to
First, the lead plates 5A to 5C, 6, and the fixed plate 7 that are made of nickel-plated iron are prepared (preparation step). More specifically, in the preparation step, for example, the lead plates 5A to 5C, 6, and the fixed plate 7 are prepared that are formed by punching a metal plate. In addition, in the preparation step, the lead plates 5A to 5C, 6, and the fixed plate 7 may be formed by cutting a metal tape (lead plate component member) extending in a predetermined direction, along the longitudinal direction thereof.
Next, as shown in
Next, with the lead plates 5A to 5C, 6, and the fixed plate 7 positioned so that they will have a predetermined weld-on positional relationship (positional relationship after completion shown in
More specifically, in this holding step, a holder 10 as shown in
After the lead plates 5A to 5C, 6, and the fixed plate 7 are held on the holder 10, as shown in an arrow Y1 in
Next, as shown in
Next, as shown in
Next, the lead plate 6 and the safety device 8 are electrically connected to each other (connection step) to produce the assembled battery 3A. Then, this assembled battery 3A is contained in the container 2 to complete the battery pack 1.
It should be noted that the order of connecting (welding) the cells 4A to 4D and the safety device 8 to the lead plates 5A to 5C, 6, and the fixed plate 7 is not limited to the aforementioned order. However it is necessary that the welding at the welding positions A1 and A2 is made simultaneously, welding at the welding positions B1 and B2 is made simultaneously, welding at the welding positions C1 and C2 is made simultaneously, and welding at the welding positions D1 and D2 is made simultaneously. In addition, welding at the welding positions A1 to D2 can be made simultaneously by using four pairs (eight) electrodes.
As described above, according to the embodiment, the electric current flows between the lead plate 5A and the lead plate 6 that are spaced apart from each other and caused to contact against the cell 4A. Thus, the electric current flows between the lead plate 5A and the lead plate 6 through the cell 4A. In this way, according to the embodiment, the electric current is prevented from flowing between the pair of electrodes E1 and E2 through the lead plate itself. This reduces reactive current that does not contribute electric resistance welding. The same applies between the welding position B1 and the welding position B2, between the welding position C1 and the welding position C2, and between the welding position D1 and the welding position D2.
Furthermore, in the embodiment, four lead plates 5A to 5C and 6 are used as the lead plates connecting the cells 4A to 4D and the safety device 8. Unlike the conventional assembled batteries where a single lead plate is used to connect a plurality of cells (see, for example,
In the embodiment, the lead plates 5A to 5C are caused to contact against the cells 4A to 4D with the lead plates 5A to 5C held by the holder 10 in a predetermined positional relationship. Unlike a case where the lead plates 5A to 5C are caused to contact against the cells 4A to 4D while positioning them, the positioning of the lead plates 5A to 5C is completed in the holding step and then the lead plates 5A to 5C are caused to contact against the cells 4A to 4D. Thus, the lead plates 5A to 5C can easily be caused to contact against the cells 4A to 4D.
In the embodiment, the fixed plate 7 is welded to the cell 4D. Even when the cell 4D is connected only with the cell 4C, the reactive current can be reduced by using the fixed plate 7. More specifically, in the embodiment, the fixed plate 7 and the lead plate 5C are spaced apart from each other and are caused to contact against the cell 4D to flow the electric current between the fixed plate 7 and the lead plate 5C. Accordingly, the electric current flows between the fixed plate 7 and the lead plate 5C through the cell. Thus, according to the embodiment, the electric current is prevented from flowing between the pair of electrodes E1 and E2 through the lead plate itself. This reduces reactive current that does not contribute electric resistance welding.
While the embodiment has been described in conjunction with the welding in which the fixed plate 7 is used, the fixed plate 7 may be omitted. More specifically, with the lead plate 5C put on the cell 4D, one electrode (the electrode E1, by way of example) is caused to contact against the lead plate 5C, and the other electrode (the electrode E2, by way of example) is caused to directly contact against the cell 4D. In this state, it is possible to apply a voltage across the electrodes E1 and E2 to weld the cell 4D and the lead plate 5C. When this welding procedure is employed, it is preferable that the heat capacity of the electrode E2 is larger than the heat capacity of the electrode E1 in order to facilitate separation between the cell 4D and the electrode E2 after welding. More specifically, for example, the diameter of the electrode E2 may be determined to be larger than that of the electrode E1. Alternatively, the electrode E2 may be made of a material having a larger heat capacity than that of the electrode E1. This makes it possible to suppress melting of a part of the cell 4D that is caused to contact against the electrode E2.
While the embodiment employs the lead plates 5A to 5C and 6 made of nickel-plated iron, the lead plates 5A to 5C and 6 made of copper may be employed. Because the lead plates 5A to 5C and 6 made of copper that is a material having a smaller resistance value than the nickel-plated iron is used, it is possible to produce assembled batteries having less internal resistance (losses). The smaller resistance value is disadvantageous in efficiency of generating Joule heat during the electric resistance welding, but in the production method, as described above, the electric current is prevented from flowing through the lead plate itself. This reduces reactive current that does not contribute electric resistance welding. Thus, even when the lead plates 5A to 5C and 6 made of copper are used, the electric resistance welding can be made with a relatively low electric current value.
In addition, in the preparation step, the lead plates 5A to 5C, 6, and the fixed plate 7 can be prepared by cutting the metal tape (lead plate component member) extending in a predetermined direction, along the longitudinal direction thereof. This reduces the kinds of components and parts to be prepared and also reduces costs, as compared with a case where the lead plates 5A to 5C, 6, and the fixed plate 7 are individually prepared by using, for example, press working.
It should be noted, in the embodiment, the positional relationship between the welding positions A1 and A2, the positional relationship between the welding positions B1 and B2, the positional relationship between the welding positions C1 and C2, and the positional relationship between the welding positions D1 and D2 are different positional relationships from each other. Now, as shown in
Referring to
First, the electrodes E1 and E2 are supported in such a manner that the gap between the electrodes E1 and E2 for the electric resistance welding is identical to the pitches PA to PD, and that the line segment connecting between the centers of the electrodes E1 and E2 is in parallel to the imaginary lines CA to CD (supporting step).
Next, in the contacting step, the lead plates 5A to 5C, 6, and the fixed plate 7 are caused to contact against the cells 4A to 4D while positioning, considering the relative positional relationship and the gap between the electrodes E1 and E2 supported in the supporting step. In other words, the lead plates 5A to 5C, 6, and the fixed plate 7 are caused to contact against the cells 4A to 4D in such a manner that the corresponding lead plates 5A to 5C and 6 or the fixed plate 7 are positioned on the welding positions A1 to D2.
Next, positioning on the welding positions A1 and A2 is made by displacing the electrodes E1 and E2 supported in the supporting step on the X-Y plane without rotating the electrodes E1 and E2 around the Z-axis relative to the lead plates 5A to 5C, 6, and the fixed plate 7, and the electrodes E1 and E2 are displaced in the direction of the Z-axis to cause them to contact against the lead plates 5A and 6. In this state, the electric resistance welding can be made at the welding positions A1 and A2.
Next, the electrodes E1 and E2 are displaced in the direction of the Z-axis to separate them from the lead plates 5A and 6. The electrodes E1 and E2 are then displaced on the X-Y plane. In this way, the electrodes E1 and E2 are positioned at the welding positions B1 and B2, respectively, and the electrodes E1 and E2 are displaced in the direction of the Z-axis to cause them to contact against the lead plates 5A and 5B, respectively. With this state, the resistance welding at the welding positions B1 and B2 can be made.
Likewise, the electrodes E1 and E2 can be displaced for the welding positions C1 and C2 and then for the welding positions D1 and D2.
In this embodiment, the electric resistance welding can be made while the electrodes E1 and E2 are supported at the same positions for the plurality of welding positions A1 to D2, by using these two electrodes E1 and E2. Thus, the electric resistance welding can be made efficiently in comparison with a case where the positional relationship and the space of the electrodes E1 and E2 are changed according to the welding position.
It should be noted that, the embodiment describes the way to displace the electrodes E1 and E2 relative to the lead plates 5A to 5C, 6, and the fixed plate 7 (the cells 4A to 4C and the safety device 8). However, it is not limited thereto. For example, the lead plates 5A to 5C, 6, and the fixed plate 7 may be displaced relative to the electrodes E1 and E2.
In addition, the embodiment describes the way to weld the pair of positive and negative electrodes E1 and E2 each at one position. However, the tip of each of the electrodes E1 and E2 may be divided and the welding may be made at two or more positions for each electrode. This makes it possible to weld between the lead plates 5A to 5C, 6, and the fixed plate 7 and the cells 4A to 4D at several positions, restricting rotation of the lead plates 5A to 5C, 6, and the fixed plate 7 and the cells 4A to 4D.
Now, detailed description is made about a predetermined gap between the lead plates formed in the contacting step. It should be noted that, in the embodiment, the gaps between the lead plate 6 and the lead plate 5A, between the lead plate 5A and the lead plate 5B, between the lead plate 5B and the lead plate 5C, and between the lead plate 5C and the fixed plate 7 have a same target value. Thus, the description is made for the gap formed between the lead plate 6 and the lead plate 5A, as an example.
First, the lower limit value of the predetermined gap is described. The lower limit value of the predetermined gap is defined as the gap to prevent any discharge between the lead plate 6 and the lead plate 5A. More specifically, in the embodiment, the lower limit value of the predetermined gap falls within a range not smaller than 0.01 but not larger than 0.15 mm. How to determine this is described below.
Whether or not arc occurs between the parallel electrodes (lead plates) can be defined as the following Equation 1, according to the Paschen's Law.
V=f(pd) [Equation 1]
More specifically, voltage V applied across the electrodes is described as a function of a product of gas pressure p (Torr) and a gap distance d (m) between the electrodes. In the embodiment, the gas pressure p is constant under the atmospheric conditions, so that the Equation 1 can be expressed as the following Equation 2.
V=Cd≈1.0×d [Equation 2]
More specifically, the voltage V can be given by a product of a proportionality constant C and the gap distance d between the electrodes. The proportionality constant C is equal to 3 kV/mm under dry air conditions. This means that, under dry air conditions, the discharge can be prevented in a range lower than a straight line Ch1 shown in
When a lead plate used is punched out of a metal plate, raised burr may be created at a side edge surface of the lead plate. An allowable value of the burr height (tolerance) is about ⅓ of the thickness of the lead plate. For example, when the thickness of the lead plate is 0.15 mm, the allowable value of the burr height is 0.05 mm. Thus, when the lead plates forming the pair are opposed to each other, there is a possibility that a burr of 0.1 mm exists on the inner side of each lead plate. Taking the aforementioned tolerance into consideration, it is more preferable that the gap between the lead plates (the gap distance d between the electrodes) is equal to or larger than 0.15 mm.
Next, the upper limit value of the predetermined gap is described. The upper limit value of the predetermined gap is defined as a gap to achieve, in the welding step, a heat amount Q with which the bottom of an iron battery case 4A1 (see
As shown in
In addition, as shown in
As shown in
Referring to
Wherein Δt is a time interval (ms) during which the voltage V is continuously applied. As described above, the total resistance value (R1+R2+R3) can be approximated by the resistance value R2 of the bottom of the battery case 4A1. Thus, the Equation 3 can be replaced by the following Equation 4.
Using this Equation 4, the heat amount required to form a nugget of 1 mm in diameter and 0.1 mm in depth in the bottom of the battery case 4A1 can be given by the following Equation 5.
By substituting the following three different voltage values (8V, 10V, and 12V) into the aforementioned Equation 4, the following Equations 6 to 8 can be obtained. In the Equations 5 to 7, the Δt has a constant value of 2.25 ms.
As apparent from these Equations 6 to 8, the heat amount Q is defined as a function of L2. More specifically, in
Now, referring to
The lower limit value of the gap L2 has the smallest value of 0.01 (mm) that is obtained when no tolerance is considered. On the other hand, the upper limit value of the gap L2 has the largest value of 7 (mm) when the voltage applied across the electrodes E1 and E2 is equal to 12 (V). This indicates that 0.01≦L2≦7 can be used under conditions where a voltage equal to or higher than 12 (V) is applied without considering the tolerance. When the gap L2 is determined within this range, the electric resistance welding can be certainly achieved by using a lead plate in which no tolerance due to, for example, burr should be considered and by applying a higher voltage.
In addition, the lower limit value of the gap L2 is equal to 0.15 (mm) when the tolerance is taken into consideration. On the other hand, the upper limit value of the gap L2 is equal to 5 (mm) when the voltage of 8 (V) is applied across the electrodes E1 and E2. Accordingly, 0.15≦L2≦5 can be used under conditions where a voltage equal to or higher than 8 (V) is applied while considering the tolerance. The gap L2 defined within this range allows to certainly achieve the electric resistance welding at a lower voltage, even when a lead plate punched out of a metal plate is used.
It should be noted that the aforementioned specific embodiment mainly includes the invention having the following configuration.
In order solve the aforementioned problems, the present invention provides a method for producing an assembled battery having a first cell, a second cell electrically connected to the first cell, and at least one connected member electrically connected to the first cell and the second cell, comprising: a preparation step of preparing a first lead plate that is adapted to electrically connect the first cell and the second cell, and a second lead plate that is adapted to electrically connect the second cell and the connected member; an contacting step of causing one end of the first lead plate and one end of the second lead plate to contact against the second cell, in such a manner that the one end of the first lead plate and the one end of the second lead plate are spaced apart from each other with a predetermined first gap therebetween; a first welding step of electric resistance welding the first lead plate and the second lead plate to the second cell by means of causing electrodes to contact, from the side opposite to the second cell, against the one end of the first lead plate and the one end of the second lead plate, respectively, which have contacted against the second cell, and applying electric current between the electrodes; a second welding step of welding the other end of the first lead plate and the first cell; and a connection step of electrically connecting the other end of the second lead plate and the at least one connected member.
In the present invention, the electric current is applied between the first lead plate and the second lead plate that are separated from each other and caused to contact against the second cell. Therefore, the electric current flows between the first lead plate and the second lead plate through the cell. Thus, according to the present invention, the electric current is prevented from flowing through the lead plate itself between the pair of electrodes. This reduces reactive current that does not contribute electric resistance welding.
Furthermore, in the present invention, two lead plates (the first lead plate and the second lead plate) are employed as the lead plates for connecting the first cell, the second cell, and the connected member. In comparison to the conventional assembled batteries where a single lead plate is used to connect a plurality of cells, the layout of the cells and the connected member can be varied freely within a range where the lead plates can reach, without changing the shape of the lead plates.
It should be noted that, the “connected member” as used in the present invention is not limited to the components other than the cells, such as the safety device, and a cell is also included when such a cell is provided in addition to the first cell and the second cell.
In the production method, it is preferable that the method further comprises a positioning step of positioning the first cell, the second cell, and the at least one connected member, in a predetermined positional relationship as a weld-on positional relationship of the first lead plate and the second lead plate; and a holding step of holding the first lead plate and the second lead plate with the first lead plate and the second lead plate being positioned in the predetermined positional relationship as the weld-on positional relationship relative to the first cell, the second cell, and the at least one connected member, and wherein, in the contacting step, the first lead plate and the second lead plate are caused to contact against the second cell while keeping the positional relationship held in the holding step.
According to this production method, unlike a case where the first lead plate and the second lead plate are caused to contact against the second cell while positioning these lead plates, the positioning of the first lead plate and the second lead plate is completed in the holding step and then these lead plates are caused to contact against the second cell. Thus, the lead plates can easily be caused to contact against the second cell.
In the production method, it is preferable that, in the contacting step, the first gap is determined as a gap to achieve, in the first welding step, a heat amount with which a second cell welded portion can be molten, the second cell welded portion being provided on the second cell to weld the first lead plate and the second lead plate.
In this production method, the first gap is determined as a gap to achieve the heat amount with which the second cell welded portion can be molten. The total heat amount obtained in the first welding step depends on the total resistance value of the first lead plate, the second cell welded portion, and the second lead plate through which the electric current flows. The total resistance value is proportional to the length of the path through which the electric current flows, that is, the sum of the thickness of the first lead plate, the size of the first gap, and the thickness of the second lead plate. The thickness of each lead plate is very small. Thus, the size of the first gap is relatively larger than the thickness of each lead plate. This means that the size of the first gap significantly affects the total resistance value. Accordingly, by adjusting the first gap as in the case of the production method, the heat amount obtained in the first welding step can be determined efficiently.
In the production method, it is preferable that, in the contacting step, the first gap is determined as a gap that is not larger than a size within a range between 5 mm and 7 mm.
According to this production method, the upper limit value of the first gap can be determined within a range from the gap (7 mm) to achieve the necessary heat amount with the voltage value of 8 V to the gap (5 mm) to achieve the necessary heat amount with the voltage value of 12 V, under normal welding conditions (e.g., the voltage is applied across the electrodes for about 2 ms).
In the production method, it is preferable that, in the contacting step, the first gap is determined as a gap to prevent discharge between one end of the first lead plate and one end of the second lead plate.
According to this production method, the first gap is determined as a minimum gap to prevent discharge between the lead plates, allowing production of a compact assembled battery.
In the production method, it is preferable that, in the contacting step, the first gap is determined as a gap that is equal to or larger than a size within a range between 0.01 mm and 0.15 mm.
According to this production method, the lower limit value of the first gap can be determined within a range from the gap (0.01 mm) to prevent the discharge when each lead plate has the dimensions exactly as designed under normal welding conditions (atmospheric conditions) to the gap (0.15 mm) to prevent the discharge when the tolerance (e.g., 0.05 mm for each lead plate) during the production of the lead plates is considered.
In the production method, it is preferable that, in the preparation step, a fixed plate that is fixed to the first cell is further prepared; in the contacting step, the fixed plate and the other end of the first lead plate are caused to contact against the first cell in such a manner that the fixed plate and the other end of the first lead plate are spaced apart from each other with a predetermined second gap therebetween; and in the second welding step, the electrodes are caused to contact, from the side opposite to the first cell, against the fixed plate and the other end of the first lead plate, respectively, which have contacted against the first cell, and the electric current is applied to the electrodes to thereby electric resistance weld the fixed plate and first lead plate to the first cell.
According to this production method, when nothing other than the second cell is to be connected to the first cell, i.e., when there is no corresponding lead plate to be matched with the first lead plate, the reactive current can be reduced as in the case of the welding step by means of preparing the fixed plate. More specifically, in the production method, the fixed plate and the first lead plate are caused to contact against the first cell with a gap therebetween, and the electric current is applied between the fixed plate and the first lead plate. As a result, the electric current flows between the fixed plate and the first lead plate through the cell. Thus, according to the production method, the electric current is prevented from flowing through the lead plate itself between the pair of electrodes. This reduces reactive current that does not contribute electric resistance welding.
In the production method, it is preferable that, in the contacting step, the second gap is determined as a gap to achieve, in the second welding step, a heat amount with which a first cell welded portion can be molten, the first cell welded portion being provided on the first cell to weld the fixed plate and the first lead plate.
In this production method, the second gap is determined as a gap to achieve the heat amount with which the first cell welded portion can be molten. The total heat amount obtained in the second welding step depends on the total resistance value of the fixed plate, the first cell welded portion, and the first lead plate through which the electric current flows. The total resistance value is proportional to the length of the path through which the electric current flows, that is, the sum of the thickness of the fixed plate, the size of the second gap, and the thickness of the first lead plate. The thickness of each of the fixed plate and the first lead plate is very small. Thus, the size of the second gap is relatively larger than the thickness of each of the fixed plate and the first lead plate. This means that the size of the second gap significantly affects the total resistance value. Accordingly, by adjusting the second gap as in the case of the production method, the heat amount obtained in the second welding step can be determined efficiently.
In the production method, it is preferable that, in the contacting step, the second gap is determined as a gap that is not larger than a size within a range between 5 mm and 7 mm.
According to this production method, the upper limit value of the second gap can be determined within a range from the gap (7 mm) to achieve the necessary heat amount with the voltage value of 8 V to the gap (5 mm) to achieve the necessary heat amount with the voltage value of 12 V, under normal welding conditions (e.g., the voltage is applied across the electrodes for about 2 ms).
In the production method, it is preferable that, in the contacting step, the second gap is determined as a gap to prevent discharge between the fixed plate and the other end of the first lead plate.
According to this production method, the second gap is determined as a minimum gap to prevent discharge between the fixed plate and the first lead plate, allowing production of a compact assembled battery.
In the production method, it is preferable that, in the contacting step, the second gap is determined as a gap that is equal to or larger than a size within a range between 0.01 mm and 0.15 mm.
According to this production method, the lower limit value of the second gap can be determined within a range from the gap (0.01 mm) to prevent the discharge when each of the fixed plate and the first lead plate has the dimensions exactly as designed under normal welding conditions (atmospheric conditions) to the gap (0.15 mm) to prevent the discharge when the tolerance (e.g., 0.05 mm for each of the fixed plate and the first lead plate) during the production of the fixed plate and the first lead plate is considered.
In the production method, it is preferable that, the connected member includes a third cell and a fourth cell; in the preparation step, a third lead plate for electrically connecting the third cell and the fourth cell is prepared; in the contacting step, the other end of the second lead plate and one end of the third lead plate are caused to contact against the third cell in such a manner that the other end of the second lead plate and the one end of the third lead plate are spaced apart from each other with a predetermined third gap therebetween; and in the connection step, the electrodes are caused to contact, from the side opposite to the third cell, against the other end of the second lead plate and the one end of the third lead plate which have contacted the third cell, and the electric current is applied to the electrodes to thereby electric resistance weld the second lead plate and the third lead plate to the third cell; the method further comprising a third welding step of welding the other end of the third lead plate and the fourth cell.
According to this method, when the first to fourth cells are connected by using the first to third lead plates, the reactive current can be reduced at a welding position for the second cell as well as at a welding position for the third cell.
In the production method, the method further comprises a supporting step of supporting a pair of rod-shaped electrodes in such a manner that the electrodes are spaced apart from each other with a gap corresponding to the first gap and the third gap therebetween; in the contacting step, one end of the first lead plate and one end of the second lead plate are caused to contact against the second cell and the other end of the second lead plate and one end of the third lead plate are caused to contact against the third cell, according to the positional relationship and the gap between the rod-shaped electrodes supported in the supporting step; and the first welding step and the third welding step are successively performed by displacing, on a plane perpendicular to the longitudinal direction of the rod-shaped electrodes, the relative position between the rod-shaped electrodes supported in the supporting step and the first lead plate, the second lead plate, and the third lead plate without displacing the relative position around an axis that is parallel to the longitudinal direction of the rod-shaped electrodes, and by causing separation and contact between the rod-shaped electrodes and the first lead plate, the second lead plate, and the third lead plate in the longitudinal direction of the rod-shaped electrodes.
According to this method, for example, in the contacting step, the lead plates on the X-Y plane (the plane perpendicular to the longitudinal direction of the rod-shaped electrode) and the rod-shaped electrodes supported in the supporting step are displaced in the X-Y direction to position the rod-shaped electrodes at the welding positions of the respective lead plates, and then the rod-shaped electrodes and the lead plates are contacted and separated to and from in the direction of the Z-axis (the longitudinal direction of the rod-shaped electrode). Thus, the first welding step and the third welding step can be performed successively.
In the method, the expression “according to the positional relationship and the gap between the rod-shaped electrodes” means that the lead plates are positioned according to the positional relationship and the gap between the rod-shaped electrodes in such a manner that the rod-shaped electrodes can be positioned on the one end of the first lead plate and one end of the second lead plate, respectively, and the rod-shaped electrodes can be positioned on the other end of the second lead plate and one end of the third lead plate, respectively, by displacing the relative position between the rod-shaped electrodes and the lead plates on a plane perpendicular to the longitudinal direction of the rod-shaped electrodes without displacing them around an axis that is parallel to the longitudinal direction of the rod-shaped electrodes.
In the production method, it is preferable that, in the contacting step, the third gap is determined as a gap to achieve, in the connection step, a heat amount with which a third cell welded portion can be molten, the third cell welded portion being provided on the third cell to weld the second lead plate and the third lead plate.
In this production method, the third gap is determined as a gap to achieve the heat amount with which the third cell welded portion can be molten. The total heat amount obtained in the connection step depends on the total resistance value of the second lead plate, the third cell welded portion, and the third lead plate through which the electric current flows. The total resistance value is proportional to the length of the path through which the electric current flows, that is, the sum of the thickness of the second lead plate, the size of the third gap, and the thickness of the third lead plate. The thickness of each lead plate is very small. Thus, the size of the third gap is relatively larger than the thickness of each lead plate. This means that the size of the third gap significantly affects the total resistance value. Accordingly, by adjusting the third gap as in the case of the production method, the heat amount obtained in the connection step can be determined efficiently.
In the production method, it is preferable that, in the contacting step, the third gap is determined as a gap that is not larger than a size within a range between 5 mm and 7 mm.
According to this production method, the upper limit value of the third gap can be determined within a range from the gap (7 mm) to achieve the necessary heat amount with the voltage value of 8 V to the gap (5 mm) to achieve the necessary heat amount with the voltage value of 12 V, under normal welding conditions (e.g., the voltage is applied across the electrodes for about 2 ms).
In the production method, it is preferable that, in the contacting step, the third gap is determined as a gap to prevent discharge between the other end of the second lead plate and one end of the third lead plate.
According to this production method, the third gap is determined as a minimum gap to prevent discharge between the lead plates, allowing production of a compact assembled battery.
In the production method, it is preferable that, in the contacting step, the third gap is determined as a gap that is equal to or larger than a size within a range between 0.01 mm and 0.15 mm.
According to this production method, the lower limit value of the third gap can be determined within a range from the gap (0.01 mm) to prevent the discharge when each lead plate has the dimensions exactly as designed under normal welding conditions (atmospheric conditions) to the gap (0.15 mm) to prevent the discharge when the tolerance (e.g., 0.05 mm for each lead plate) during the production of the lead plates is considered.
In the production method, it is preferable that, in the preparation step, the first lead plate and the second lead plate are prepared, both of which are made of copper.
In this production method, for example, lead plates made of copper that is a material having a smaller resistance value than the nickel-plated iron is used. Thus, it is possible to produce assembled batteries having less internal resistance (losses). The smaller resistance value is disadvantageous in efficiency of generating Joule heat during the electric resistance welding. However, in the production method, the electric current is prevented from flowing through the lead plate itself. This reduces reactive current that does not contribute electric resistance welding. Thus, even when the lead plates made of copper are used, the electric resistance welding can be made with a relatively low electric current value.
In the production method, it is preferable that, in the preparation step, the first lead plate and the second lead plate are prepared by cutting a lead plate component member extending in a predetermined direction, along the longitudinal direction thereof.
In this production method, two lead plates (the first lead plate and the second lead plate) can be prepared by using the lead plate component member. This reduces the kinds of components and parts to be prepared and also reduces costs, as compared with a case where the lead plates are individually prepared by using, for example, press working. Furthermore, as in the production method, when the lead plates are prepared by cutting the lead plate component member, it is possible to quickly respond to a design change in length of the lead plate(s).
In addition, the present invention provides an assembled battery produced by using the production method.
Moreover, the present invention provides an assembled battery having a first cell, a second cell electrically connected to the first cell, and a connected member electrically connected to the first cell and the second cell, comprising: a first lead plate that is provided so as to span between the first cell and the second cell, the first lead plate being adapted to electrically connect the first cell and the second cell; and a second lead plate that is provided so as to span between the second cell and the connected member, the second lead plate being adapted to electrically connect the second cell and the connected member, wherein the first lead plate and the second lead plate are electric resistance welded to the second cell in such a manner that an end of the first lead plate and an end of the second lead plate are spaced apart from each other with a predetermined plate gap therebetween, and only an electric resistance welded portion that is formed by one of a pair of positive and negative electrodes for electric resistance welding is formed between the end of the first lead plate and the second cell, and only an electric resistance welded portion that is formed by the other of the pair of positive and negative electrodes for the electric resistance welding is formed between the end of the second lead plate and the second cell.
In the assembled battery according to the present invention, it is possible to provide an assembled battery with which reactive current can be reduced and flexibility in cell layout can be increased.
More specifically, in the assembled battery according to the present invention, the lead plates are electric resistance welded to the second cell in such a manner that the end of the first lead plate and the end of the second lead plate are spaced apart from each other with a predetermined gap therebetween. Furthermore, an electric resistance welded portion is formed by one of a pair of positive and negative electrodes between the end of the first lead plate and the second cell, and an electric resistance welded portion is formed by the other of the pair of positive and negative electrodes between the end of the second lead plate and the second cell. Thus, upon the production of the assembled battery according to the present invention, the electric resistance welding can be made by applying electric current between the first lead plate and the second lead plate which are spaced apart from each other and are caused to contact against the second cell. In this electric resistance welding, the electric current flows between the first lead plate and the second lead plate through the second cell. Therefore, the assembled battery according to the present invention is made by using the production method in which the electric current is prevented from flowing between the pair of electrodes through the lead plate itself. This reduces reactive current that does not contribute electric resistance welding in the production procedure.
Furthermore, in the assembled battery according to the present invention, two lead plates (the first lead plate and the second lead plate) are employed as the lead plates for connecting the first cell, the second cell, and the connected member. In comparison to the conventional assembled batteries where a single lead plate is used to connect a plurality of cells, the layout of the cells and the connected member can be varied freely within a range where the lead plates can reach, without changing the shape of the lead plates.
It should be noted that, the “connected member” as used in the present invention is not limited to the components other than the cells, such as the safety device, and a cell is also included when such a cell is provided in addition to the first cell and the second cell.
According to the present invention, it is possible to provide a method for producing an assembled battery with which electric resistance welding can be performed more efficiently and flexibility in cell layout can be increased.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2010-160429 | Jul 2010 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2011/003957 | 7/11/2011 | WO | 00 | 1/27/2012 |
