Patent Application
20230275310
This nonprovisional application is based on Japanese Patent Application No. 2022-028192 filed on Feb. 25, 2022 with the Japan Patent Office, the entire contents of which are hereby incorporated by reference.
The present technology relates to a battery pack.
There has been known a battery pack having a case in which a plurality of battery cells are accommodated. It has been also a conventional practice that when an internal pressure of the case is increased, a safety valve is opened to adjust the internal pressure. Examples of a structure of such a safety valve are illustrated in, for example, Japanese Patent Laying-Open No. 2020-021897, Japanese Patent Laying-Open No. 2008-117756, Japanese Patent Laying-Open No. 60-245883, and Japanese National Patent Publication No. 2020-522105.
When opening the safety valve, it is required not to excessively increase the internal pressure of the case and is required to appropriately adjust a flow velocity of gas ejected from inside of the case. The conventional structure of the safety valve cannot necessarily address such requirements sufficiently.
It is an object of the present technology to provide a battery pack in which highly reliable pressure adjustment and ejection velocity adjustment can be performed when an internal pressure is increased.
A battery pack according to the present technology includes: a battery cell; a pack case that accommodates the battery cell and that is provided with an opening; and a valve structure provided to open and close the opening. The valve structure includes a valve member having a valve body portion fitted to an inner peripheral surface of the opening, and a biasing member provided inside the pack case. When an internal pressure of the pack case is increased, the valve member is moved to an outer side of the pack case so as to form a clearance between an outer peripheral surface of the valve body portion and the inner peripheral surface of the opening, and the biasing member biases the valve member toward an inner side of the pack case.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.
Hereinafter, embodiments of the present technology will be described. It should be noted that the same or corresponding portions are denoted by the same reference characters, and may not be described repeatedly.
It should be noted that in the embodiments described below, when reference is made to number, amount, and the like, the scope of the present technology is not necessarily limited to the number, amount, and the like unless otherwise stated particularly. Further, in the embodiments described below, each component is not necessarily essential to the present technology unless otherwise stated particularly. Further, the present technology is not limited to one that necessarily exhibits all the functions and effects stated in the present embodiment.
It should be noted that in the present specification, the terms “comprise”, “include”, and “have” are open-end terms. That is, when a certain configuration is included, a configuration other than the foregoing configuration may or may not be included.
Also, in the present specification, when geometric terms and terms representing positional/directional relations are used, for example, when terms such as “parallel”, “orthogonal”, “obliquely at 45°”, “coaxial”, and “along” are used, these terms permit manufacturing errors or slight fluctuations. In the present specification, when terms representing relative positional relations such as “upper side” and “lower side” are used, each of these terms is used to indicate a relative positional relation in one state, and the relative positional relation may be reversed or turned at any angle in accordance with an installation direction of each mechanism (for example, the entire mechanism is reversed upside down).
In the present specification, the term “battery” is not limited to a lithium ion battery, and may include another battery such as a nickel-metal hydride battery.
Electrode terminals 110 are formed on housing 120. Electrode terminals 110 have a positive electrode terminal 111 and a negative electrode terminal 112 arranged side by side along an X axis direction (second direction) orthogonal to a Y axis direction (first direction). Positive electrode terminal 111 and negative electrode terminal 112 are provided to be separated from each other in the X axis direction.
Housing 120 has a rectangular parallelepiped shape, and forms an external appearance of battery cell 100. Housing 120 includes: a case body 120A that accommodates an electrode assembly (not shown) and an electrolyte solution (not shown); and a sealing plate 120B that seals an opening of case body 120A. Sealing plate 120B is joined to case body 120A by welding.
Housing 120 has an upper surface 121, a lower surface 122, a first side surface 123, a second side surface 124, and two third side surfaces 125.
Upper surface 121 is a flat surface orthogonal to a Z axis direction (third direction) orthogonal to the Y axis direction and the X axis direction. Electrode terminals 110 are disposed on upper surface 121. Lower surface 122 faces upper surface 121 along the Z axis direction.
Each of first side surface 123 and second side surface 124 is constituted of a flat surface orthogonal to the Y axis direction. Each of first side surface 123 and second side surface 124 has the largest area among the areas of the plurality of side surfaces of housing 120. Each of first side surface 123 and second side surface 124 has a rectangular shape when viewed in the Y axis direction. Each of first side surface 123 and second side surface 124 has a rectangular shape in which the X axis direction corresponds to the long-side direction and the Z axis direction corresponds to the short-side direction when viewed in the Y axis direction.
A plurality of battery cells 100 are stacked such that first side surfaces 123 of battery cells 100, 100 adjacent to each other in the Y direction face each other and second side surfaces 124 of battery cells 100, 100 adjacent to each other in the Y axis direction face each other. Thus, positive electrode terminals 111 and negative electrode terminals 112 are alternately arranged in the Y axis direction in which the plurality of battery cells 100 are stacked.
Gas-discharge valve 130 is provided in upper surface 121. When the temperature of battery cell 100 is increased in an abnormal manner (thermal runaway) and internal pressure of housing 120 becomes more than or equal to a predetermined value due to gas generated inside housing 120, gas-discharge valve 130 discharges the gas to outside of housing 120.
A safety valve 300 is provided in a side surface of main body 220. Safety valve 300 is normally in a valve-closed state, and is brought into a valve-opened state when the internal pressure is increased by gas discharged from battery cell 100.
Each of
As shown in
Safety valve 300 includes a valve member 310, an adjustment screw 320, a biasing member 330, and a stopper 340.
Valve member 310 includes a valve body portion 311, a stem portion 312, and an outer surface 313. Valve body portion 311 is fitted to the inner peripheral surface of opening 221. Valve body portion 311 is provided such that outer surface 313 does not protrude on an outer side with respect to outer surface 222 of case 200 when safety valve 300 is closed (state shown in
Adjustment screw 320 is screwed to a tip of stem portion 312. In the example of
Biasing member 330 is provided between adjustment screw 320 and stopper 340. An amount of change in shape (length) of biasing member 330 can be adjusted by adjusting an amount of screwing of adjustment screw 320.
When the internal pressure of case 200 is increased, valve member 310 is moved to the outer side of case 200 so as to form a clearance (flow path) between the outer peripheral surface of valve body portion 311 and the inner peripheral surface of opening 221 as shown in
On this occasion, as shown in
Each of
In the modification shown in
Also in the modification shown in
In the case where the biasing force of biasing member 330 is “strong”, when the flow rate of the generated gas is increased to increase the pressure, the internal pressure of case 200 may become more than a breakdown pressure (“BATTERY PACK BREAKDOWN PRESSURE” in
In the case where the biasing force of biasing member 330 is “weak”, when the flow rate of the generated gas is increased to discharge a large amount of gas from case 200, the flow velocity of the ejected gas may become less than a predetermined velocity (“IGNITION VELOCITY” in
In battery pack 1 according to the present embodiment, by adjusting the amount of screwing of adjustment screw 320 in advance, it is possible to adjust the biasing force by which biasing member 330 biases valve member 310 toward the inner side of case 200. Therefore, by such a simple operation, the biasing force of biasing member 330 can be precisely adjusted to the “moderate” state shown in
In the case where the biasing force of biasing member 330 is “moderate”, even when the flow rate of the generated gas is increased to increase the pressure, the internal pressure of case 200 does not become more than the breakdown pressure (“BATTERY PACK BREAKDOWN PRESSURE” in
Thus, according to battery pack 1 of the present embodiment, it is possible to perform highly reliable pressure adjustment and ejection velocity adjustment when the internal pressure of case 200 is increased.
Further, in each of the structures shown in
The structure of safety valve 300 according to the present embodiment is particularly effective when a battery cell 100 having high output and high capacity is used; however, characteristics of battery cell 100 are not limited in the present technology.
The gas discharged from battery cell 100 includes an ejected object of a material in the battery. As an example, a filter that can capture the ejected object from case 200 may be provided over opening 221. According to the structure of safety valve 300 of the present embodiment, clogging of the filter is suppressed, thus decreasing the internal pressure efficiently.
As an example, the cross sectional area of the flow path when safety valve 300 is opened is about 75 mm2 or more and 7500 mm2 or less. As an example, the diameter of opening 221 (the narrowest portion of the tapered shape) is about 20 mm or more and 100 mm or less. As an example, the spring constant of biasing member 330 is about 0.05 N/mm or more and 100 N/mm or less.
Although the embodiments of the present invention have been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the scope of the present invention being interpreted by the terms of the appended claims. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-028192 | Feb 2022 | JP | national |
