KR20230061718A - Leak test system for electric vehicle battery - Google Patents

Abstract

The present invention is to provide a leak test system for an electric vehicle battery, in which, by using helium gas as a trace gas, an accurate leak test compared to an air leak test method is possible, through a cooling line forming a flow channel between batteries, a battery cell is maintained in top condition, and it is possible to solve the problem of the contamination of a chamber due to oil leakage from a general bearing during vacuum work using a dry vacuum pump with a dry bearing. For this, the present invention comprises: a chamber for storing a table plate storing at least one battery cell; a dry vacuum pump for converting the chamber into a vacuum state; a helium injection pump for injecting helium gas into a battery cell when the inside of the chamber is in the vacuum state by the dry vacuum pump; and a leak detector for determining, when there is helium gas leaking from the battery cell, whether a leak occurred in the battery cell by detecting the helium gas leaked into the chamber.

Description

Leak test system for electric vehicle battery {Leak test system for electric vehicle battery}

The present invention relates to a leak test system for an electric vehicle battery, and more particularly, to a leak test system for an electric vehicle battery using helium as a tracer gas and using a dry vacuum pump.

An electric vehicle driven by a battery uses a lithium iron phosphate battery that has a high energy density or a lithium iron phosphate battery that has a low energy density rather than a lithium ion battery, but has a high number of reuses. A lithium ion battery or a lithium iron phosphate battery is commonly referred to as a lithium battery, and since lithium constituting a lithium battery has a high energy density, it may explode at any time if handled incorrectly even at room temperature.

Cylindrical, prismatic, and pouch-type lithium batteries used in electric vehicles are used, but the pouch-type is declining due to the recent electric vehicle fire issue, and cylindrical and prismatic batteries are becoming mainstream.

A lithium battery pack mounted on an electric vehicle is composed of a series-parallel combination of hundreds to thousands of unit cells. Cells are connected in series according to the rated voltage of the motor mounted on the electric vehicle to form a module, and the entire battery pack is composed by connecting the modules in parallel according to the required current of the motor. Unit cells constituting a lithium battery pack are usually protected by metal cans to resist vibration, shock, high temperature, low temperature, and moisture penetration that occur during driving of an electric vehicle.

However, if the metal can protecting the cell is cracked due to a manufacturing problem and cannot properly protect the inside of the cell, or if there is a concern that the contents of the cell may leak to the outside, the battery pack made of the cell may not perform properly. Otherwise, there is a risk that the battery pack may explode.

In this regard, battery manufacturers operate test systems that test whether manufactured unit cells are sealed. Such a test system is called a leak test system, and an air leak test method is mainly used.

The air leak test method arranges battery cells in a chamber, seals the chamber, injects air into the chamber, and then determines whether the cell is defective or not by using a pressure damping method. If there is a cell in which airtightness is not maintained among the cells located in the chamber, the air injected into the chamber is introduced into the cell and the air pressure in the chamber is reduced.

However, the air leak test method has a disadvantage in that the air pressure that can be applied to the chamber is as low as e ^-2 mbar.l/s, so that it may not be detected well depending on the leak state of the cell, and thus the reliability is not high.

For these drawbacks, the industry proposes a helium leak test method as an alternative.

The helium leak test method is a method of performing a leak test on a cell by putting helium gas inside a cell using helium as a tracer gas or putting helium gas outside (inside a chamber) of a finished cell.

Helium is an inert gas with little chemical reactivity, so there is no risk of explosion by reacting with lithium, and it is in the spotlight as a safe leak test method because it is not reactive with chemicals inside the cell.

In addition, since it can detect up to e ^-09 mbar.l/s, it has the advantage of being able to detect leaks more precisely than the existing air leak test method.

Currently, the helium leak test method is used in machinery or ships, and the present applicant intends to apply the helium leak test method to a leak test for battery cells.

- Republic of Korea Patent Publication No. 10-2017-0074454 (Title of Invention: Apparatus and method for detecting error leakage of electric vehicle battery cover and outputting the detection result) - Republic of Korea Patent Registration No. 10-2027308 (Title of Invention: Leak Test Device for Electric Vehicle Battery Cover)

An object of the present invention is to provide a leak test system for an electric vehicle battery that can perform a more precise leak test than conventional air leak test methods using helium gas as a tracer gas.

An object of the present invention is to provide a leak test system for an electric vehicle battery that does not damage the characteristics of the battery cell by lowering the temperature of the battery cell when performing a leak test on the battery cell.

An object of the present invention is to provide a leak test system for an electric vehicle battery that minimizes chamber contamination caused by oil leaking from an existing vacuum pump by converting a chamber accommodating battery cells into a vacuum state using a dry vacuum pump.

According to the present invention, the above object is a battery cell when the inside of the chamber is in a vacuum state by a chamber for accommodating a table plate for accommodating at least one battery cell, a dry vacuum pump for converting the chamber to a vacuum state, and a dry vacuum pump. It is achieved by a helium injection pump for injecting helium gas and a leak detector that detects helium gas leaking into the chamber when there is helium gas leaking from the battery cell and determines whether a leak occurs in the battery cell.

According to the embodiments of the present invention, by using helium gas as a tracer gas, it is possible to perform a more precise leak test compared to the air leak test method, and to maintain the state of the battery cells in the best way through the cooling line forming a flow path between the battery cells. can

In addition, according to embodiments of the present invention, during vacuum work using a dry vacuum pump to which a dry bearing is applied, it is possible to solve the problem of oil leaking from a general bearing and contaminating the chamber.

1 shows a block conceptual diagram of a leak test system for an electric vehicle battery according to an embodiment of the present invention.
2 shows a reference drawing for explaining a helium detection method of a leak detector.
3 shows a perspective view of a dry bearing applied to the dry vacuum pump of the present invention.
4 shows a cross-sectional view of a dry vacuum pump according to an embodiment of the present invention.

Hereinafter, a leak test system for an electric vehicle battery according to the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, only these embodiments will complete the disclosure of the present invention, and will fully cover the scope of the invention to those skilled in the art. It is provided to inform you.

In addition, throughout the specification, when a certain component is said to "include", it means that it may further include other components, not excluding other components unless otherwise stated. In addition, throughout the specification, "on" means to be located above or below the target part, and does not necessarily mean to be located on the upper side with respect to the direction of gravity.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. At this time, it should be noted that in the accompanying drawings, the same components are indicated by the same reference numerals as much as possible. In addition, detailed descriptions of well-known functions and configurations that may obscure the gist of the present invention will be omitted. For the same reason, in the accompanying drawings, some components are exaggerated, omitted, or schematically illustrated.

A battery cell referred to in the present invention may refer to one of a cylindrical cell, a prismatic cell, and a prismatic battery module.

The cylindrical cell refers to a type of battery cell that has the same external appearance as a battery and is protected by a metal can. The cylindrical cell is a standard mainly used by Tesla, and the model name of the battery cell is defined by diameter-length. For example, a Tesla 21700 battery cell refers to a diameter of 21 mm and a length of 70 mm.

The square is a name given to the shape of an aluminum can when it is square, and the basic battery electrode structure is the same as that of a conventional lithium battery. It has low energy density compared to the cylindrical shape, but it is strong against external impact and has good durability, so it corresponds to the type of battery cell recently ordered by Volkswagen from CATL in China.

Meanwhile, among prismatic battery cells, there is a modular prismatic battery in which an output current is increased by stacking a plurality of battery cells in parallel in one rectangular case.

The module-type prismatic battery is similar in appearance to a general prismatic battery, but has a difference in that its output current increases according to the number of battery cells stacked in parallel. In the present invention, a modular prismatic battery is also treated as a prismatic battery cell.

The battery cell referred to in the present invention refers to a lithium battery cell, and the lithium battery cell may mean any one of a lithium ion type and a lithium iron phosphate type. In the present invention, whether a prismatic battery cell or a cylindrical battery cell, a single name "battery cell" will be given and described.

Hereinafter, the present invention will be described in detail with reference to the drawings.

1 shows a block conceptual diagram of a leak test system for an electric vehicle battery according to an embodiment of the present invention.

Referring to FIG. 1, the leak test system for an electric vehicle battery according to an embodiment includes a chamber 110, a leak detector 120, a vacuum sensor 130, a dry vacuum pump 140, a helium injection pump 150, and a cooling system. It is configured to include a pump 160.

The chamber 110 accommodates the battery cells 10a to 10f and includes a table plate 111 therein to align and fix the battery cells 10a to 10f.

The table plate 111 can regularly accommodate and fix one, two or more battery cells 10a to 10f at regular intervals.

Preferably, the table plate 111 may include a fixing device capable of fixing the battery cells 10a to 10f on a plate-shaped frame, and the inside of the chamber 110 is in a vacuum state or helium gas is supplied to the battery. When injected into the cells 10a to 10f, the battery cells 10a to 10f do not float and remain fixed in the plate-shaped frame. The table plate 111 may have various shapes according to the shapes of the battery cells 10a to 10f. For example, when the battery cells 10a to 10f are cylindrical, the table plate 111 is provided with a cylindrical storage portion capable of accommodating the cylindrical battery cells 10a to 10f, but the battery cells 10a to 10f have a prismatic shape. In the case of a cell, a fixing jig suitable for the outer diameter of the prismatic battery may be provided on the plate-shaped frame.

When the helium gas is detected inside the chamber 110 after the helium gas is injected into the battery cells 10a to 10f, the leak detector 120 determines whether the battery cells 10a to 10f are leaked. judge

When there is damage or cracks in the battery cells 10a to 10f accommodated in the table plate 111, the helium gas sealed inside the battery cells 10a to 10f leaks from the battery cells 10a to 10f and the chamber 110 ) leaked into the interior. At this time, since the inside of the chamber 110 is in a vacuum state, the concentration of the helium gas leaked from the chamber 110 increases.

The leak detector 120 detects helium gas leaked into the chamber 110 .

A method of using bellows with a magnetic field applied to the leak detector 120 to detect the helium gas may be used, which will be described with reference to FIG. 2 .

2 shows a reference drawing for explaining a helium detection method of a leak detector.

Referring to FIG. 2 together, the leak detector 120 has a bellows having a curved section, and helium gas containing impurities is introduced to one side (source) of a bellows having a curved section. At this time, a strong magnetic field is applied to the bellows.

Among the helium gas discharged from the chamber 110, impurities having a large mass are destroyed by being caught in a magnetic field. Helium is a Group 2 element, the smallest and lightest element after hydrogen. Helium is applied to the leak detector 120 along the bent bellows without being destroyed by a magnetic field applied to the bellows. That is, helium gas having a minimum mass due to a mass difference between helium and impurities may be applied to the leak detector 120 and detected.

When helium gas is detected inside the chamber 110, the leak detector 120 determines that defects (such as cracks, tears, flares, and holes) have occurred in the battery cells 10a to 10f. When the leak detector 120 determines that a defect has occurred in the battery cells 10a to 10f, the leak test system for an electric vehicle battery according to the embodiment stops the leak test and releases the vacuum state of the chamber 110. Thereafter, after opening the chamber 110 and exposing the battery cells 10a to 10f to the air, a sniffer may be used to track the detailed location of the defect.

The vacuum sensor 130 detects the vacuum state inside the chamber 110 and feeds it back to the dry vacuum pump 140 . The dry vacuum pump 140 converts the inside of the chamber 110 into a vacuum state at a pressure of 0.1 Torr (10 ⁻¹ mbar) or less, and may be driven to a user-set target vacuum level and then stopped.

The dry vacuum pump 140 does not require application of lubricating oil, unlike oil rotary type vacuum pumps commonly used in vacuum devices.

In general, a vacuum pump compresses or circulates gas while performing a rotational motion of a motor or a linear reciprocating motion of a screw. Friction occurs between parts that rotate or reciprocate and parts that support them, and when the friction is severe, heat generation increases, and sludge from the parts may flow into the chamber 110 due to the friction. Therefore, the vacuum pump uses a lubricant for reducing friction between parts and smooth motor rotation.

However, when the vacuum pump is operated and converted to a vacuum state, as the pressure difference between the gas flowing into the vacuum pump and the gas discharged increases, the liquid lubricant flows into the chamber 110, and the liquid lubricant flows into the chamber 110. The lubricant may flow inside the chamber 110 and may adhere to the battery cells 10a to 10f or mechanical parts inside the chamber 110 .

Accordingly, the present applicant intends to propose a dry vacuum pump 140 that does not use a lubricant. The dry vacuum pump 140 according to the present invention is characterized in that a dry bearing is applied to a driving shaft to prevent liquid lubricant from flowing into the chamber 110 . The dry bearing will be described with reference to FIG. 3 .

3 shows a perspective view according to an example of a dry bearing applied to a dry vacuum pump.

Referring to FIG. 3 , the dry bearing 141 according to the embodiment has a ring shape and is composed of an outer layer 141a and an inner layer 141b to form a multi-layer structure.

The outer layer 141a is made of a metal material such as stainless to support a ring-shaped structure. The inner layer 141b is a non-metal material and may be any one of a Teflon composite material and a carbon compound.

Teflon, a compound of fluorine and carbon, has high chemical heat resistance and low friction coefficient. In addition, when the Teflon compound is used in the inner layer 141b, since there is no liquid lubricant in the inner layer 141b, when the dry vacuum pump 140 converts the inside of the chamber 110 into a vacuum, the inside of the chamber 110 Liquid lubricant does not flow in.

The helium injection pump 150 injects helium gas into the battery cells 10a to 10f. It is preferable that the inside of the chamber 110 is in a vacuum state before the helium injection pump 150 injects the helium gas into the battery cells 10a to 10f.

The cooling pump 160 supplies cooling water into the chamber 110 . The cooling pump 160 is connected to a cooling line installed inside the chamber 110, and the cooling line consists of a flow path passing between the battery cells 10a to 10f mounted on the table plate 111.

The cooling pump 160 may supply cooling water to flow paths formed between the battery cells 10a to 10f and circulate the cooling water. Preferably, a radiator for cooling the heated cooling water may be disposed outside the chamber 110 .

On the other hand, the cooling line may be formed of a heat pipe instead of a pipe through which cooling water flows. The heat pipe may have a shape of a metal tube in which a refrigerant such as alcohol flows through a metal having a spongy structure and achieves thermal equilibrium. When the cooling line is configured as a heat pipe, a cooling line having a long and thin radial structure may be arranged inside the chamber 110 to dissipate heat from the inside of the chamber 110 . At this time, the end of the heat pipe located outside the chamber 110 must be connected to a separate radiator to discharge the absorbed heat.

4 shows a cross-sectional view of a dry vacuum pump according to an embodiment of the present invention.

Referring to the figure, in the dry vacuum pump 140 according to the embodiment, a pair of roots rotors 142a and 142b are built into the front end of the pump, and a drive motor 148 is mounted on the proximal end, and a pair of The screw rotors 145a and 145b of are embedded coaxially with the roots rotors 142a and 142b.

The ends of the screw rotors 145a and 145b penetrate the partition wall 144, respectively, and the portions penetrating the partition wall 144 are rotatably supported by dry bearings 143a and 143b, respectively.

On the other hand, the proximal shafts 149a and 149b of the screw rotors 145a and 145b are rotatably supported by dry bearings 147a and 147b disposed on the end wall 146 .

Accordingly, the dry vacuum pump 140 includes a pair of screw rotors 145a and 145b and a pair of Roots rotors 142a and 142b coaxially mounted at the tips thereof, and is compact in configuration, A desired degree of vacuum and required power characteristics can be obtained by using the roots rotors 142a and 142b and the screw rotors 145a and 145b.

The dry vacuum pump 140 described above has dry bearings supporting the roots rotors 142a and 142b and the screw rotors 145a and 145b on the intake port (i) side where vacuum and atmospheric pressure can be repeated during pump operation. Since the (143a, 143b) are located, even if a pressure difference due to vacuum is applied to the dry bearings (143a, 143b), something such as lubricant does not flow into the chamber 110 from the dry bearings (143a, 143b), and the driving motor (148) Do not apply excessive load or foreign substances to

110: chamber 111: table plate
120: leak detector 130: vacuum sensor
140: dry vacuum pump 150: helium injection pump
160: cooling pump

Claims (6)

a chamber accommodating a table plate accommodating at least one battery cell;
a dry vacuum pump for converting the chamber into a vacuum state;
a helium injection pump for injecting helium gas into the battery cell when the inside of the chamber is in a vacuum state by the dry vacuum pump; and
When there is helium gas leaking from the battery cell, a leak detector detects the helium gas leaking into the chamber and determines whether a leak occurs in the battery cell; Leak test system. According to claim 1,
The leak test system for an electric vehicle battery, characterized in that it further comprises; a cooling line in which a flow path is formed along between the battery cells and one side is located outside the chamber and the other side is located inside the chamber. According to claim 2,
The cooling line is
The leak test system for an electric vehicle battery, characterized in that it has a flow path for moving the cooling water to the outside of the chamber after the coolant flowing from the outside of the chamber absorbs heat between the cells. According to claim 2,
The cooling line is
It consists of a heat pipe,
A leak test system for an electric vehicle battery, characterized in that a refrigerant is injected into the heat pipe and the refrigerant moves inside and outside the chamber to perform heat exchange. According to claim 1,
The dry vacuum pump,
A dry bearing on the driving shaft of the motor; leak test system of an electric vehicle battery, characterized in that it is fastened to block oil leakage in a vacuum state. According to claim 5,
The dry bearing,
The inner layer and the outer layer are composed of different materials and have a ring shape,
The outer layer is composed of any one of a metal and a metal composite,
The inner layer is composed of any one of a Teflon compound and a carbon compound, and the leak test system of an electric vehicle battery, characterized in that different materials form a multi-layer.

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