A lithium battery helium detection equipment vacuum device and lithium battery helium detection method

Abstract

The application discloses a kind of lithium battery helium detection equipment vacuum devices and lithium battery helium detection method, it is characterized by: including rack, vacuum pump on mounting rack, vacuum buffer tank, connecting pipe and valve, the air inlet and air outlet are equipped on the vacuum pump, the air inlet is connected with air inlet pipe, the air inlet pipe is used to connect air inlet with the vacuum cavity to be pumped;The main gas port and the secondary gas port are equipped on the vacuum buffer tank, and the secondary gas port is used to be connected with molecular pump;The connecting pipe is used to connect the main gas port with the air inlet pipe;The valve is two, including first valve and second valve respectively, the second valve is set on the connecting pipe, for opening or closing the main gas port;The first valve is set on the air inlet pipe, and is set between the vacuum cavity to be pumped and connecting pipe, for connecting the air inlet with the vacuum cavity to be pumped or closed.The application reduces cost, improves helium detection safety.

Description

Technical Field

[0001] This invention relates to the field of lithium battery production and processing, and more particularly to a vacuum device for lithium battery helium testing equipment and a lithium battery helium testing method. Background Technology

[0002] In the helium detection process of lithium battery manufacturing, the helium detection equipment needs to be equipped with two vacuum pumps, each performing a different function: The first is a cell / vacuum chamber roughing vacuum pump, whose core responsibility is to periodically and rapidly pump the cell cavity and detection vacuum chamber from atmospheric pressure to the target low vacuum of 20-30 Pa under the production line cycle requirements. This is a high-frequency start-stop and periodic pressure change condition. The second is a backing pump for the helium detector molecular pump, whose core function is to provide the pre-vacuum environment required for the molecular pump to start and to continuously maintain the back pressure at the exhaust end of the molecular pump at 5-10 Pa, ensuring that the molecular pump and mass spectrometer chamber are in a stable high vacuum working state for a long time.

[0003] Currently, these two vacuum pumps are centrally located on the lower rack or cabinet at the bottom of the equipment, primarily employing either oil-driven rotary vane vacuum pumps or dry vacuum pumps. While oil-driven rotary vane vacuum pumps offer advantages such as extremely low initial purchase cost and high ultimate vacuum per pump at the same pumping speed, they suffer from persistent problems like oil vapor backflow and pump oil emulsification, leading to a sharp decline in lifespan and performance under high-frequency operating conditions. More importantly, lithium-ion battery cells have zero tolerance for oil contamination; oil vapor can cause increased internal resistance, a drastic drop in cycle life, and even thermal runaway safety incidents. Furthermore, oil vapor can contaminate the ion source and detector of the helium mass spectrometer, causing a surge in helium background, zero-point drift, and a significant increase in the minimum detectable leak rate, potentially even rendering core components unusable. Additionally, the workshop contains flammable electrolyte vapors (such as NMP and carbonates) after lithium-ion battery filling, and the flammable pump oil from the oil-driven rotary vane pumps poses a risk of combustion and explosion, failing to meet the compliance requirements for explosion-proof workshops.

[0004] Dry vacuum pumps eliminate oil backflow and emulsification risks, withstand frequent start-stop cycles, maintain stable long-term performance, and are easy to maintain. However, their initial purchase cost is higher at the same pumping speed, approximately 4 to 5 times that of oil-lubricated rotary vane vacuum pumps. As lithium battery helium testing requirements become increasingly stringent, oil-lubricated rotary vane vacuum pumps will gradually be completely replaced by dry vacuum pumps. However, directly using two dry vacuum pumps would significantly increase equipment procurement costs, thereby increasing enterprise production costs.

[0005] In current mass-produced lithium battery helium testing equipment, the two vacuum pumps have pumping capacities of 60 m³ / h and 15 m³ / h, respectively, and are arranged close together below the machine. Since a single vacuum pump's inlet can only achieve one pressure condition, it cannot simultaneously meet the dual requirements of periodic pressure fluctuations (from atmospheric pressure to 30 Pa) and stable back pressure at the molecular pump's exhaust end (5-10 Pa). Therefore, all current mass-produced helium testing equipment uses two vacuum pumps. Some companies, in an effort to reduce costs, are still using high-risk oil-driven rotary vane vacuum pumps, failing to balance cost and safety. Summary of the Invention

[0006] The purpose of this invention is to provide a vacuum device for lithium battery helium testing equipment and a lithium battery helium testing method. By using this structure and method, the cost is effectively reduced and the safety of lithium battery helium testing is improved.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is: a vacuum device for lithium battery helium detection equipment, comprising: frame; A vacuum pump is mounted on the frame. The vacuum pump has an air inlet and an air outlet. An air inlet pipe is connected to the air inlet and the air inlet pipe is used to connect the air inlet to the vacuum chamber to be evacuated. A vacuum buffer tank, wherein the vacuum buffer tank is provided with a main gas port and a secondary gas port, the secondary gas port being used to connect to a molecular pump; A connecting pipe, which connects the main air inlet to the air inlet pipe; The valves are two in number, including a first valve and a second valve. The second valve is disposed on the connecting pipe and is used to open or close the main air port. The first valve is disposed on the air inlet pipe and between the vacuum chamber to be evacuated and the connecting pipe, and is used to connect or close the air inlet to the vacuum chamber to be evacuated.

[0008] In the above technical solution, the valve is a baffle valve; And / or, the baffle valve is a pneumatic baffle valve.

[0009] In the above technical solution, the two valves are arranged at intervals, and the connecting pipe includes a U-shaped pipe and a side pipe. The U-shaped pipe is located beside the two valves. One end of the U-shaped pipe is connected to the air inlet pipe, one end of the side pipe is connected to the other end of the U-shaped pipe, and the other end of the side pipe is connected to the main air port. The second valve is located at the connection between the U-shaped pipe and the side pipe.

[0010] In the above technical solution, the air inlet and the auxiliary air inlet are arranged facing upwards, and the main air inlet is arranged facing the vacuum pump.

[0011] In the above technical solution, the bottom of the frame is provided with multiple support casters equipped with brakes.

[0012] In the above technical solution, the first end of the connecting pipe is connected to the air inlet pipe, and the second end of the connecting pipe is connected to the main air port; The first valve is located between the first end of the connecting pipe and the vacuum chamber to be evacuated.

[0013] In the above technical solution, a branch pipe is provided on the side wall of the air intake pipe. One end of the branch pipe is connected to the air intake pipe, and the other end of the branch pipe is connected to the outside. The branch pipe is located between the first valve and the air intake port. A third valve is provided on the branch pipe and is located on the connecting pipe. The third valve is used to open and close the branch pipe.

[0014] In the above technical solution, the vacuum pump is a dry vacuum pump; And / or, the dry vacuum pump is a dry screw vacuum pump or a dry scroll vacuum pump.

[0015] This invention also provides a lithium battery helium detection method, which uses the vacuum device for lithium battery helium detection equipment described above, and the steps are as follows: S1. The controller controls the first valve to close and the second valve to open, starts the vacuum pump, and the vacuum pump evacuates the vacuum buffer tank. When the pressure inside the vacuum buffer tank drops to 5Pa, the molecular pump of the helium detector is started and the molecular pump enters the working state. S2. The helium detection host puts multiple battery cells into the vacuum chamber to be evacuated and seals it. The controller controls the first valve to open and the second valve to close. At this time, the vacuum pump evacuates the vacuum chamber until the pressure inside the vacuum chamber drops to 25Pa~30Pa and is maintained for a period of time to complete the helium leak detection. S3. After the helium leak detection is completed, the vacuum chamber to be emptied is emptied. The controller controls the first valve to close and the second valve to open. The vacuum pump evacuates the vacuum buffer tank and reduces the pressure inside the vacuum buffer tank to 4.5Pa-5Pa. At the same time, the helium detection main unit replaces the battery cell in the vacuum chamber to be emptied and continues to repeat step S2.

[0016] In the above technical solution, in step S1, the vacuum pump pumps the vacuum buffer tank for 25s to 40s, and the vacuum buffer tank stabilizes the pressure of the molecular pump at 5Pa to 9Pa. And / or, in step S2, the vacuum pump evacuates the vacuum chamber to be evacuated for 4s to 6s, and after the pressure in the vacuum chamber drops to 25Pa to 30Pa, it is maintained for 3s to 5s. And / or, in step S3, the time for the helium detector main unit to replace the battery cell in the vacuum chamber to be evacuated is 7s to 10s; the time for the vacuum pump to evacuate the vacuum buffer tank is 2s to 4s.

[0017] Due to the application of the above technical solution, the present invention has the following advantages compared with the prior art: 1. The present invention uses a combination of a vacuum pump, a vacuum buffer tank, and two valves to achieve helium detection of lithium batteries, which is more cost-effective compared with the previous structure that used two vacuum pumps; 2. In this invention, the vacuum pump evacuates the cavity to be evacuated, and the vacuum buffer tank maintains the pressure of the molecular pump. Compared with the structure using two vacuum pumps, when the vacuum pump switches to the cell evacuation stage, the vacuum buffer tank can provide a temporary stable pressure environment for the helium detector molecular pump. During the cell replacement process, the vacuum pump is used to evacuate the vacuum buffer tank through the cooperation of two valves to maintain the pressure of the vacuum buffer tank, thereby ensuring the stable pressure environment of the molecular pump and effectively improving the utilization rate of the vacuum pump. 3. The vacuum pump used in this invention is a dry vacuum pump, and only one dry vacuum pump is needed. Compared with the previous use of two low-cost oil rotary vane vacuum pumps, the cost is controlled and the safety is also stronger. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure in Embodiment 1 of the present invention; Figure 2 This is a three-dimensional structural diagram of Embodiment 1 of the present invention.

[0019] The components include: 1. Frame; 2. Vacuum pump; 3. Vacuum buffer tank; 4. Connecting pipe; 5. Inlet pipe; 6. Auxiliary air port; 7. First valve; 8. Second valve; 9. Electrical control cabinet; 10. U-shaped pipe; 11. Side pipe; 12. Support casters. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and embodiments: Example 1: See Figure 1 , 2 As shown, a vacuum device for lithium battery helium detection equipment includes a frame 1, a vacuum pump 2 mounted on the frame 1, a vacuum buffer tank 3, a connecting pipe 4, and valves. The vacuum pump 2 is provided with an air inlet and an air outlet. An air inlet pipe 5 is connected to the air inlet, and the air inlet pipe 5 is used to connect the air inlet to the vacuum chamber to be evacuated. In this embodiment, the vacuum pump is a dry vacuum pump. In a preferred embodiment, the dry vacuum pump is a dry screw vacuum pump; In another preferred embodiment, the dry vacuum pump is a dry scroll vacuum pump.

[0021] The vacuum buffer tank 3 is provided with a main gas port and a secondary gas port 6, and the secondary gas port is used to connect to the molecular pump. The connecting pipe 4 is used to connect the main air port and the air inlet pipe 5; The system comprises two valves, a first valve 7 and a second valve 8. The second valve 8 is mounted on the connecting pipe 4 and is used to open or close the main air port. The first valve 7 is mounted on the air inlet pipe 5 and positioned between the vacuum chamber to be evacuated and the connecting pipe 4, and is used to connect or close the air inlet to the vacuum chamber. Preferably, both valves are high-speed response self-locking valves, and the two valves can be interlocked, meaning they cannot be opened or closed simultaneously.

[0022] This invention also provides a lithium battery helium detection method, which uses the vacuum device for lithium battery helium detection equipment described above, and the steps are as follows: S1. Equipment Initialization: The controller closes the first valve and opens the second valve, starting the vacuum pump. The vacuum pump evacuates the vacuum buffer tank. When the pressure inside the vacuum buffer tank drops to 5Pa, the molecular pump of the helium detector is started, and the molecular pump enters the working state. An electrical control cabinet 9 is installed on the frame, with the controller located inside. The control cabinet can be equipped with a connector for quick connection to the helium detector main unit. This facilitates rapid replacement of the vacuum device (e.g., if the vacuum device is damaged, it can be removed and replaced with a spare; the connector enables quick electrical connection between the controller and the helium detector main unit, allowing for rapid connection of the inlet pipe and auxiliary port to the helium detector main unit), minimizing disruption to the operation of the helium detector equipment.

[0023] S2. The helium detection host puts multiple sets of battery cells (e.g., 10 sets) into the vacuum chamber to be evacuated and seals it. The controller controls the first valve to open and the second valve to close. At this time, the vacuum pump evacuates the vacuum chamber until the pressure inside the vacuum chamber drops to 25Pa~30Pa and is maintained for a period of time to complete one helium leak detection. S3. After the helium leak detection is completed, the vacuum chamber to be emptied is emptied, the controller controls the first valve to close and the second valve to open, the vacuum pump evacuates the vacuum buffer tank and reduces the pressure inside the vacuum buffer tank to 4.5Pa-5Pa (preferably 4.5Pa), and then the vacuum pump enters standby mode. S4. When evacuating the vacuum buffer tank, the helium detector main unit replaces the battery cell in the vacuum chamber to be evacuated. After the replacement is completed, the vacuum chamber to be evacuated is sealed, the first valve is opened, the second valve is closed, the vacuum pump is activated, and the vacuum chamber to be evacuated is evacuated until the pressure in the vacuum chamber drops to 25Pa~30Pa and is maintained for a period of time to complete one helium leak detection. Repeat steps S3 and S4 to test the battery cell.

[0024] In this invention, the vacuum pump is a dry vacuum pump with a maximum ultimate vacuum of ≤0.1 Pa, preferably ≤0.05 Pa, ensuring that the initial pressure of the vacuum buffer tank is reduced to a lower level, thereby improving the buffering stability of the vacuum buffer tank; the pumping capacity is ≥150 m³ / h (preferably 150 m³ / h-200 m³ / h), which can pump the vacuum chamber to be pumped (used to house the battery cells) / the battery cells inside it from atmospheric pressure to below 30 Pa within 5-6 seconds, and can reduce the pressure inside the vacuum buffer tank from 10 Pa to below 5 Pa within 2-3 seconds, meeting the requirements for rapid pumping and switching. The vacuum buffer tank has a volume of ≥100 L and good sealing performance, used to provide a temporary pressure-stabilized environment for the molecular pump of the helium detector. Based on leakage calculations, the initial pressure of the vacuum buffer tank during molecular pump operation is set to 5 Pa. With a standard air leakage rate of 15 mL / min, the pressure rise rate is 0.25 Pa / s, which can meet the pressure buffering requirement for at least 20 seconds. This ensures that when the vacuum pump switches to the cell coarse evacuation stage (in step S2, the vacuum pump evacuates the vacuum chamber to be evacuated, which not only reduces the pressure in the vacuum chamber but also evacuates the cell placed inside), the pre-vacuum of the molecular pump can still be kept stable within the safe range of 5 Pa-10 Pa. The volume of the vacuum buffer tank can be adjusted according to the helium detection cycle and leakage rate (100 L-200 L). The larger the volume, the longer the pressure buffering time and the higher the operational safety.

[0025] The controller is used to connect to the vacuum pump, two valves, and the helium detection host. It can set the interlock switching time of the two valves and receive valve opening and closing signals from the helium detection host (such as the completion of sealing of the vacuum chamber to be evacuated, the completion of battery cell replacement, etc.) to ensure that the entire system works in an orderly manner according to the helium detection cycle.

[0026] In step S1, the vacuum pump evacuates the vacuum buffer tank for 25s to 40s, preferably 33s, which takes a relatively long time to evacuate the vacuum buffer tank from atmospheric pressure. The vacuum buffer tank maintains a stable pressure of 5Pa to 9Pa for the molecular pump, not exceeding 10Pa, which ensures the normal operation of the molecular pump.

[0027] In step S2, the vacuum pump evacuates the vacuum chamber for 4s to 6s, and after the pressure in the vacuum chamber drops to 25Pa to 30Pa, it is maintained for 3s to 5s. In step S3, the time for the helium detector to replace the battery cell in the vacuum chamber to be evacuated is 7s to 10s, generally around 10s; the time for the vacuum pump to evacuate the vacuum buffer tank is 2s to 4s.

[0028] In this invention, the entire helium detection cycle is approximately 20 seconds (or within 20 seconds). Except for step S1, where the vacuum buffer tank is evacuated from atmospheric pressure to a low-pressure state, the vacuum buffer tank is maintained at a low pressure (within 10 Pa) thereafter. The low pressure in the vacuum buffer tank is maintained by a vacuum pump, eliminating the need for prolonged depressurization; only a short time is required to reduce the pressure. During the entire helium detection cycle (approximately 20 seconds), the time spent evacuating the vacuum chamber and the battery cell is approximately 10 seconds (evacuation time is approximately 5-6 seconds, and after the pressure drops to 25-30 Pa, it is maintained for 4-5 seconds). The evacuation time of the vacuum buffer tank is approximately 4 seconds, preferably 2-3 seconds (during the operation of the molecular pump, the pressure inside the vacuum buffer tank will rise, but will not exceed 10 Pa; therefore, the time spent by the vacuum pump to reduce the pressure in the vacuum buffer tank from below 10 Pa to 4.5-5 Pa is approximately 4 seconds). The vacuum pump remains in standby mode for the remaining time. If a defective battery cell with a large leak is detected in step S2, it will cause the pressure inside the vacuum buffer tank to rise rapidly. The controller can control the vacuum pump to shorten the evacuation time of the vacuum chamber to be evacuated and cut off the evacuation of the vacuum buffer tank in advance to ensure that the pressure inside the vacuum buffer tank does not exceed 10Pa, so as to ensure the normal operation of the molecular pump.

[0029] Compared to the previous structure that used two vacuum pumps, this invention only requires one vacuum pump, one vacuum buffer tank, and two valves, significantly reducing costs. Furthermore, the use of a dry vacuum pump completely eliminates the need for oil-lubricated rotary vane vacuum pumps, preventing oil vapor backflow and pump oil emulsification. This avoids the performance degradation and thermal runaway risks caused by oil contamination, prevents oil vapor contamination of the helium mass spectrometer's core components, extends equipment lifespan, and eliminates the risk of flammable pump oil explosion, meeting explosion-proof workshop compliance requirements. Simultaneously, through the interlocking switching of two high-speed valves and the pressure stabilizing effect of the vacuum buffer tank, a single vacuum pump can simultaneously meet the dual requirements of rough evacuation of the cell / vacuum chamber (periodic pressure fluctuations) and maintenance of the pre-vacuum of the molecular pump (pressure stability), adapting to the production line cycle of existing lithium battery helium testing without affecting detection efficiency and accuracy. Moreover, dry vacuum pumps are resistant to frequent start-stop cycles, have stable long-term performance, and are easy to maintain. The volume of the vacuum buffer tank can be flexibly adjusted (according to actual needs), ensuring the reliable operation of the entire helium detection system. They have a high fault tolerance rate and are suitable for long-term use in mass-produced lithium battery helium detection equipment.

[0030] In this embodiment, the valve is a baffle valve; preferably, the baffle valve is a pneumatic baffle valve with a response time ≤0.2s, good sealing performance, and a switching life ≥5 million cycles. Furthermore, the two valves are interlocked to prevent pressure disturbances caused by simultaneous operation of two paths (one connecting the vacuum pump to the vacuum buffer tank, and the other connecting the vacuum pump to the vacuum chamber to be evacuated). Of course, the valve can also be of other structures (especially fast-response valves), as long as it can achieve the cutting off and opening of the corresponding pipeline.

[0031] See Figure 1 , 2 As shown, the two valves are arranged at intervals. The connecting pipe 4 includes a U-shaped pipe 10 and a side pipe 11. The U-shaped pipe 10 is located beside the two valves. One end of the U-shaped pipe 10 is connected to the air inlet pipe 5, and one end of the side pipe 11 is connected to the other end of the U-shaped pipe 10. The other end of the side pipe 11 is connected to the main air port. The second valve 8 is located at the connection point between the U-shaped pipe 10 and the side pipe 11. Of course, the connecting pipe can also have other structures or forms, depending on the actual situation.

[0032] In this embodiment, the air inlet and auxiliary air inlet are arranged upwards, and the main air inlet is arranged towards the vacuum pump. The connecting pipe is arranged vertically, with its bottom connected to the air inlet of the vacuum pump and its top used to connect to the vacuum chamber to be evacuated on the helium detection main unit, for auxiliary... Figure 1 For example, the vacuum buffer tank is located behind the vacuum pump. The U-shaped opening of the U-tube faces right, and the right side of the front end of the U-tube connects to the middle of the connecting pipe. The rear end of the side pipe connects to the main air port at the front end of the vacuum buffer tank, and the front end of the side pipe connects to the right side of the rear end of the U-tube. The first valve is located on the connecting pipe, between the U-tube and the vacuum chamber to be evacuated. The second valve is located at the connection between the U-tube and the side pipe. This design makes full use of space, reduces space occupation, and minimizes the occupation of the top space of the equipment. When the first valve is open, the second valve is closed. At this time, when the vacuum pump is working, the air inlet of the vacuum pump generates negative pressure, which can only act on the vacuum chamber to be evacuated, performing negative pressure detection on the battery cell. When the first valve is closed and the second valve is open, the vacuum pump inlet generates negative pressure, which can only act on the vacuum buffer tank through the connecting pipe to reduce the pressure in the vacuum buffer tank. One of the two valves is open and the other is closed; both valves cannot be open simultaneously (in another embodiment, both valves can be closed simultaneously). The interlocking of the two valves is controlled by a controller to achieve the alternating switching of the two pumping paths (one pumping path is connected to the vacuum buffer tank, and the other pumping path is connected to the vacuum chamber to be pumped).

[0033] The first end of the connecting pipe is connected to the air inlet pipe, and the second end of the connecting pipe is connected to the main air port; the first valve is located between the first end of the connecting pipe and the vacuum chamber to be evacuated. (See attached image) Figure 1 Taking the direction as an example, the first end of the connecting pipe is the right side of the front end of the U-shaped pipe, and the second end of the connecting pipe is the rear end of the side pipe.

[0034] In one embodiment of this invention, a dry screw vacuum pump is used, with an ultimate vacuum of 1 Pa (the lower the ultimate vacuum, the higher the cost; therefore, the ultimate vacuum of this vacuum pump is 1 Pa. Of course, a vacuum pump with an even lower ultimate vacuum can be selected according to actual needs, but the cost will be higher. Therefore, in this embodiment, a dry screw vacuum pump with an ultimate vacuum of 1 Pa is selected based on cost and actual needs). The pumping capacity is 180 m³ / h, capable of pumping the battery cell / vacuum chamber from atmospheric pressure to 28 Pa within 5 seconds, and reducing the pressure in the vacuum buffer tank from 10 Pa to 4.5 Pa within 2.5 seconds. The valve is a baffle valve with a response time of 0.15 s. The vacuum buffer tank has a volume of 150 L, is made of stainless steel, has good sealing performance, and is initially set at 5 Pa. With a standard air leakage rate of 15 mL / min, the pressure rise rate is 0.17 Pa / s, which can meet the pressure buffering requirement for 30 seconds. The controller uses a PCL controller, which can set the switching time of the two valves, receive signals from the helium detector host, control valve switching and dry vacuum pump operation through a preset algorithm, and monitor the pressure in the buffer tank in real time to achieve automatic adjustment when the pressure is abnormal.

[0035] In another embodiment, the vacuum pump is a dry vortex vacuum pump with an ultimate vacuum of 0.5 Pa and a pumping capacity of 100 m³ / h; the vacuum buffer tank has a volume of 100 L, an initial pressure of 5 Pa, and a pressure rise rate of 0.25 Pa / s when the standard air leakage rate is 15 mL / min, which can meet the pressure buffering requirement for 20 seconds; the high-speed response self-locking valve has a response time of 0.2 seconds.

[0036] See Figure 2 As shown, the bottom of the frame 1 is equipped with multiple braked support casters 12. The presence of braked support casters facilitates movement to any position, thus making maintenance and storage easy.

[0037] In another embodiment, a branch pipe is provided on the side wall of the air intake pipe, one end of the branch pipe is connected to the air intake pipe, and the other end of the branch pipe is connected to the outside. The branch pipe is located between the first valve and the air intake port. A third valve is provided on the branch pipe and is located on the connecting pipe. The third valve is used to open and close the branch pipe.

[0038] In this invention, the entire helium detection system takes approximately 20 seconds to complete one test, while the vacuum pump operates for about 14 seconds, leaving a 6-second standby time. During standby, the vacuum pump either does not run or runs at a very low speed, mostly remaining stationary. For example, if it doesn't run during standby, the vacuum pump needs to start and stop three times per minute. If it runs at a very low speed during standby, the vacuum pump needs to undergo three accelerations and decelerations per minute. Frequent start-stops will inevitably shorten the lifespan of the vacuum pump and increase the maintenance rate. Frequent accelerations and decelerations also consume more energy than running at a stable speed for a long time, and the vacuum pump motor is more prone to damage. Therefore, in this embodiment, a branch pipe is provided, with a third valve on the branch pipe. The first and second valves can be closed simultaneously, but not opened simultaneously. After the battery cell replacement and vacuum buffer tank evacuation are completed, the first and second valves are closed, and the third valve is opened. At this time, the vacuum pump's inlet is directly connected to the outside through the branch pipe, allowing the vacuum pump to maintain normal operation without needing to decelerate or stop. After the battery cell replacement is complete, when vacuuming the battery cells is required, the third valve closes, the second valve closes, and the first valve opens. Once the vacuuming is complete, the first valve closes, the second valve opens, and the third valve remains closed while evacuating the vacuum buffer tank. After evacuating the vacuum buffer tank, the second valve closes again, the first valve remains closed, the third valve opens, and the first valve remains closed. This cycle repeats. During this process, the vacuum pump does not need to be frequently started and stopped, nor does it need frequent acceleration and deceleration, resulting in lower energy consumption (the vacuum pump consumes a lot of energy during startup, and the motor's starting power is also at its maximum; the motor's energy consumption is also high during acceleration). It can operate at a uniform speed, which minimizes energy consumption. Furthermore, without frequent starts and stops, or frequent acceleration and deceleration, its service life is longer.

[0039] More preferably, one end of the branch pipe is not connected to the outside, but to nitrogen or other cryogenic gases. This can cool the vacuum pump, prevent it from working in a high-temperature environment for a long time, extend its service life, and reduce the maintenance rate.

[0040] In the description of this invention, it should be understood that the terms "upper," "lower," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0041] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. For instance, the two components can be mechanically connected by contact or abutting; they can also be directly hooked or connected by an intermediate medium; or they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

Claims

1. A vacuum device for lithium battery helium detection equipment, characterized in that: include: frame; A vacuum pump is mounted on the frame. The vacuum pump has an air inlet and an air outlet. An air inlet pipe is connected to the air inlet and the air inlet pipe is used to connect the air inlet to the vacuum chamber to be evacuated. A vacuum buffer tank, wherein the vacuum buffer tank is provided with a main gas port and a secondary gas port, the secondary gas port being used to connect to a molecular pump; A connecting pipe, which connects the main air inlet to the air inlet pipe; The valves are two in number, including a first valve and a second valve. The second valve is disposed on the connecting pipe and is used to open or close the main air port. The first valve is disposed on the air inlet pipe and between the vacuum chamber to be evacuated and the connecting pipe, and is used to connect or close the air inlet to the vacuum chamber to be evacuated.

2. The vacuum device for lithium battery helium detection equipment according to claim 1, characterized in that: The valve is a baffle valve; And / or, the baffle valve is a pneumatic baffle valve.

3. The vacuum device for lithium battery helium detection equipment according to claim 1, characterized in that: The two valves are arranged at intervals. The connecting pipe includes a U-shaped pipe and a side pipe. The U-shaped pipe is located beside the two valves. One end of the U-shaped pipe is connected to the air inlet pipe. One end of the side pipe is connected to the other end of the U-shaped pipe. The other end of the side pipe is connected to the main air port. The second valve is located at the connection between the U-shaped pipe and the side pipe.

4. The vacuum device for lithium battery helium detection equipment according to claim 1, characterized in that: The air inlet and auxiliary air inlet are positioned upwards, and the main air inlet is positioned towards the vacuum pump.

5. The vacuum device for lithium battery helium detection equipment according to claim 1, characterized in that: The bottom of the frame is equipped with multiple support casters with brakes.

6. The vacuum device for lithium battery helium detection equipment according to claim 1, characterized in that: The first end of the connecting pipe is connected to the air inlet pipe, and the second end of the connecting pipe is connected to the main air port; The first valve is located between the first end of the connecting pipe and the vacuum chamber to be evacuated.

7. The vacuum device for lithium battery helium detection equipment according to claim 6, characterized in that: A branch pipe is provided on the side wall of the air intake pipe. One end of the branch pipe is connected to the air intake pipe, and the other end of the branch pipe is connected to the outside. The branch pipe is located between the first valve and the air intake port. A third valve is provided on the branch pipe and is located on the connecting pipe. The third valve is used to open and close the branch pipe.

8. The vacuum device for lithium battery helium detection equipment according to claim 1, characterized in that: The vacuum pump is a dry vacuum pump; And / or, the dry vacuum pump is a dry screw vacuum pump or a dry scroll vacuum pump.

9. A method for helium detection in lithium batteries, characterized in that: The steps of using the vacuum device for lithium battery helium detection equipment as described in any one of claims 1-8 are as follows: S1. The controller controls the first valve to close and the second valve to open, starts the vacuum pump, and the vacuum pump evacuates the vacuum buffer tank. When the pressure inside the vacuum buffer tank drops to 5Pa, the molecular pump of the helium detector is started and the molecular pump enters the working state. S2. The helium detection host puts multiple battery cells into the vacuum chamber to be evacuated and seals it. The controller controls the first valve to open and the second valve to close. At this time, the vacuum pump evacuates the vacuum chamber until the pressure inside the vacuum chamber drops to 25Pa~30Pa and is maintained for a period of time to complete the helium leak detection. S3. After the helium leak detection is completed, the vacuum chamber to be emptied is emptied. The controller controls the first valve to close and the second valve to open. The vacuum pump evacuates the vacuum buffer tank and reduces the pressure inside the vacuum buffer tank to 4.5Pa-5Pa. At the same time, the helium detection main unit replaces the battery cell in the vacuum chamber to be emptied and continues to repeat step S2.

10. The lithium battery helium detection method according to claim 9, characterized in that: In step S1, the vacuum pump pumps the vacuum buffer tank for 25s to 40s, and the vacuum buffer tank stabilizes the molecular pump pressure at 5Pa to 9Pa. And / or, in step S2, the vacuum pump evacuates the vacuum chamber to be evacuated for 4s to 6s, and after the pressure in the vacuum chamber drops to 25Pa to 30Pa, it is maintained for 3s to 5s. And / or, in step S3, the time for the helium detector main unit to replace the battery cell in the vacuum chamber to be evacuated is 7s to 10s; the time for the vacuum pump to evacuate the vacuum buffer tank is 2s to 4s.

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