Safe intermittent spray type fire extinguishing apparatus and method

Abstract

Provided are a safe intermittent spray type fire extinguishing apparatus and method. The fire extinguishing apparatus comprises a housing (1) and a gas-producing fire extinguishing agent (2) arranged in the housing (1). A front cover (3) is arranged on the front side of the housing (1). Nozzles (4) are formed on the surface of the front cover (3). The end face of the gas-producing fire extinguishing agent (2) is connected to one end of an activation part (5). A piston (7) in sliding fit with the housing (1) is arranged in the housing (1). The piston (7) is connected to the bottom of the front cover (3) by means of a screw (6.1) of a ball screw mechanism (6). The top of the screw (6.1) is fixedly connected to the center of a rotating cover (8). A liquid fire extinguishing agent (12) is arranged between the piston (7) and the front cover (3). Spray holes (9) are formed in the surface of the rotating cover (8). When the rotating cover (8) rotates, the spray holes (9) and the nozzles (4) periodically overlap and intersect. The piston (7) comprises a thrust piston (7.1) located outside, and a pressure relief piston (7.2) located inside. The screw (6.1) is arranged inside of the pressure relief piston (7.2) in a penetrating manner. A limiting cylinder (15) matched with the pressure relief piston (7.2) is arranged at the center of the bottom of the front cover (3). The fire extinguishing apparatus can continuously carry out the intermittent spray process, and the risk of re-combustion is prevented. In addition, when the fire extinguishing stage is completed, high-pressure gas is released in time, so that the safety of the fire extinguishing apparatus can be ensured.

Description

A safe intermittent spraying fire extinguishing device and method Technical Field

[0001] The present invention relates to the technical field of new energy battery fire extinguishing, and in particular to a safe intermittent spraying fire extinguishing device and method. Background Art

[0002] When new energy batteries experience thermal runaway, they often continue to produce flammable gases. Traditional aerosol fire extinguishing devices are difficult to extinguish the flames instantly. Pulse fire extinguishing devices can extinguish the flames instantly but cannot achieve the effect of continuous suppression. When the pulse fire extinguishing device is used in combination with the traditional aerosol fire extinguishing device, the pulse fire extinguishing device can extinguish the flames instantly generated by the thermal runaway of the battery, and the traditional aerosol fire extinguishing device can suppress the flames to a certain extent after the pulse fire extinguishing device is sprayed. Theoretically, the combination of the two overcomes each other's shortcomings and can extinguish the flames instantly and achieve the effect of continuous suppression; however, the following problems still exist. Taking the battery compartment where the battery is located as an example, when the battery experiences thermal runaway, a large amount of flammable gas escapes from the battery and enters the battery box. At this time, after the fire extinguishing device is activated, due to the large gas production of the traditional aerosol fire extinguishing device, the aerosol fire extinguishing agent will quickly fill the entire battery box (that is, the battery In the battery compartment), only part of the flammable gas is pushed out of the battery compartment during this process, and more flammable gas is often pressed inside the battery and cannot be completely discharged due to the excessive positive pressure in the battery compartment when the aerosol fire extinguishing device is sprayed. Therefore, when the aerosol fire extinguishing device is completed, the pressure in the battery compartment drops, and a large amount of flammable gas escapes from the inside of the battery again, and there is still a risk of re-ignition; in addition, when the fire extinguishing device currently used is completed at the fire extinguishing stage, there is still a certain amount of high-pressure gas in its gas production compartment, which will pose a safety hazard, that is, there is a risk of explosion. Therefore, it is necessary to discharge the high-pressure gas in time when the fire extinguishing stage is completed to ensure the safety of the fire extinguishing device; therefore, it is necessary to improve the traditional aerosol fire extinguishing device and design a fire extinguishing device that can spray continuously and intermittently, so that the pressure of the battery box increases and decreases periodically, and has a pressure relief function, thereby solving the above problems. Summary of the Invention

[0003] The purpose of the present invention is to overcome the above-mentioned shortcomings and provide a safe intermittent spraying fire extinguishing device and method, which can continuously perform the intermittent spraying process, so that the pressure of the battery box increases and decreases periodically, which is conducive to the complete discharge of the combustible gas inside the battery in the battery box, preventing the risk of re-ignition, and discharging the high-pressure gas in time when the fire extinguishing stage is completed to ensure the safety of the fire extinguishing device.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solution: a safe intermittent spraying fire extinguishing device, comprising a shell and a gas-generating fire extinguishing agent arranged in the shell, a front cover is provided on the front side of the shell, a nozzle is provided on the surface of the front cover, the end face of the gas-generating fire extinguishing agent is connected to one end of the starting component, a piston is provided in the shell and slidingly matched with the piston, the piston is connected to the bottom of the front cover through a screw of a ball screw mechanism, the top of the screw is fixedly connected to the center of the rotating cover, liquid fire extinguishing agent is provided between the piston and the front cover, a spray hole is provided on the surface of the rotating cover, and when the rotating cover rotates, the spray hole and the nozzle periodically overlap and intersect; the piston comprises a thrust piston located on the outside and a pressure relief piston located on the inside, a screw is passed through the inside of the pressure relief piston, and a limiting cylinder cooperating with the pressure relief piston is provided at the center of the bottom of the front cover.

[0005] Preferably, the ball screw mechanism includes a nut fixed inside the pressure relief piston, the spiral groove area where the nut contacts the screw is filled with balls, and the top side of the screw is rotatably connected to the center of the front cover through a bearing.

[0006] Preferably, the rotating cover is located on the upper side of the front cover, the height of the limiting cylinder is greater than the thickness of the piston, a limiting rod cooperating with the thrust piston is provided at the side of the bottom of the front cover, the height of the limiting rod is less than the height of the limiting cylinder, the top of the limiting cylinder is fixedly connected to the bottom of the front cover, and the top of the screw is passed through the limiting cylinder.

[0007] Preferably, the central area of ​​the thrust piston is interference fit with the outer side of the pressure relief piston.

[0008] Preferably, the gas-generating fire extinguishing agent is a columnar structure formed by pressing aerosol generating agent powder, and the liquid fire extinguishing agent is perfluorohexanone fire extinguishing agent.

[0009] Preferably, the starting component is an electric ignition head or a thermal wire structure.

[0010] Preferably, the outer edge of the front cover is threadedly connected to the top of the shell, and the bottom of the shell is threadedly connected to the outer edge of the rear cover.

[0011] Preferably, the gas-generating fire extinguishing agent is located in the area where the back cover is located, and a silica gel layer is provided between the outer surface of the gas-generating fire extinguishing agent and the inner surface of the back cover.

[0012] Preferably, a guide rail is vertically provided on the inner side of the shell, and a guide groove is provided on the outer side of the thrust piston, and the guide groove is slidably matched with the guide rail.

[0013] In addition, the present invention also discloses a fire extinguishing method of the above-mentioned safe intermittent spraying fire extinguishing device, which comprises the following steps:

[0014] S1: When thermal runaway occurs in the battery box, the starting component ignites the gas-generating fire extinguishing agent, which generates gas;

[0015] S2: The airflow thrust piston moves toward the position of the front cover, and the ball screw mechanism causes the screw to rotate.

[0016] S3: When the screw rotates, the rotating cover is driven to rotate, so that the spray holes on the surface of the rotating cover and the spray holes on the surface of the front cover periodically overlap and intersect;

[0017] S4: When the nozzle hole and the nozzle outlet coincide, the liquid fire extinguishing agent is ejected from the nozzle. Under the action of the high temperature inside the battery box, it is converted into gas to extinguish the fire inside the battery box. When the nozzle hole and the nozzle outlet intersect, the shell is sealed and the pressure is held back. Finally, the above process is repeated periodically to realize the intermittent spraying process, so that the pressure inside the battery box increases and decreases periodically.

[0018] S5: When the pressure inside the battery box increases, the combustible gas diluted by the fire extinguishing material is pressed out from the gaps in the battery box. When the pressure inside the battery box decreases, the combustible gas inside the battery escapes and enters the battery box, and the above process is repeated in a cycle.

[0019] S6: When the piston moves to the point where the pressure relief piston collides with the limit cylinder, the pressure relief piston is blocked by the limit cylinder and stops moving, while the external thrust piston continues to move upward due to the thrust of the gas on the lower side. At this time, the thrust piston separates upward from the pressure relief piston, and the through hole in the center area of ​​the thrust piston is exposed. The thrust piston stops when it moves to contact the limit rod, leaving a gap between the thrust piston and the front cover. Finally, the high-pressure gas generated by the gas-generating fire extinguishing agent is discharged upward from the through hole in the center area of ​​the thrust piston, and finally discharged from the nozzle and nozzle.

[0020] Beneficial effects of the present invention:

[0021] In the present invention, the airflow thrust piston moves toward the position of the front cover, and the ball screw mechanism causes the screw to rotate; when the screw rotates, it drives the rotating cover to rotate, so that the spray holes on the surface of the rotating cover and the nozzles on the surface of the front cover periodically overlap and intersect, so that the liquid fire extinguishing agent can be continuously sprayed intermittently, so that the pressure of the battery box increases and decreases periodically, which is conducive to the complete discharge of combustible gases inside the batteries in the battery box and prevents the risk of re-ignition; in addition, the present invention can discharge high-pressure gas in time when the fire extinguishing stage is completed through the cooperation process between the thrust piston, the pressure relief piston and the limit cylinder, thereby ensuring the safety of the fire extinguishing device. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG1 is a schematic diagram of the internal structure of a safe intermittent spraying fire extinguishing device;

[0023] FIG2 is a schematic diagram of the three-dimensional structure of FIG1 ;

[0024] FIG3 is a schematic diagram of the top structure of the front cover in FIG1 ;

[0025] FIG4 is a schematic diagram of the cross-sectional structure of the piston in FIG1 cooperating with the inner wall of the housing. Implementation Method

[0026] The present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

[0027] As shown in Figures 1 to 4, a safe intermittent spraying fire extinguishing device includes a shell 1 and a gas-generating fire extinguishing agent 2 arranged in the shell 1. A front cover 3 is provided on the front side of the shell 1, and a nozzle 4 is opened on the surface of the front cover 3. The end face of the gas-generating fire extinguishing agent 2 is connected to one end of the starting component 5. A piston 7 is provided in the shell 1 and is slidably matched with the piston 7. The piston 7 is connected to the bottom of the front cover 3 through a screw 6.1 of a ball screw mechanism 6. The top of the screw 6.1 is fixedly connected to the center of a rotating cover 8. Liquid fire extinguishing agent 12 is provided between the piston 7 and the front cover 3. A nozzle 9 is opened on the surface of the rotating cover 8. When the rotating cover 8 rotates, the nozzle 9 and the nozzle 4 periodically overlap and intersect; the piston 7 includes a thrust piston 7.1 located on the outside and a pressure relief piston 7.2 located on the inside. The screw 6.1 is passed through the inside of the pressure relief piston 7.2. A limiting cylinder 15 is provided at the center of the bottom of the front cover 3 to cooperate with the pressure relief piston 7.2.

[0028] Preferably, the ball screw mechanism 6 includes a nut 6.2 fixedly mounted within the pressure relief piston 7.2. The spiral groove area where the nut 6.2 contacts the screw 6.1 is filled with balls. The top side of the screw 6.1 is rotatably connected to the center of the front cover 3 via a bearing. The ball screw mechanism 6 is a commonly used component in the mechanical field and includes a nut 6.2, a screw 6.1, a ball return pipe, balls, a dust cover, a deflector, and other components. Since the balls roll along the spiral groove area formed by the screw and nut during operation, the movement resistance is extremely small. Therefore, when the pressure relief piston 7.2 is pressurized and moves upward, it drives the nut 6.2 upward, and the screw 6.1 rotates, thereby driving the rotating cover 8 to rotate. In addition, in the present invention, the bearing can effectively limit the screw 6.1, making its rotation process stable and reliable, while preventing the screw 6.1 from axial movement.

[0029] Preferably, the rotating cover 8 is located on the upper side of the front cover 3. The height of the retaining cylinder 15 is greater than the thickness of the piston 7. A retaining rod 16 is provided on the side of the bottom of the front cover 3 to engage with the thrust piston 7.1. The retaining rod 16 is less than the height of the retaining cylinder 15. The top of the retaining cylinder 15 is fixedly connected to the bottom of the front cover 3, and the top of the screw 6.1 is inserted into the retaining cylinder 15. When the height of the retaining cylinder 15 is greater than the thickness of the piston 7, the thrust piston 7.1 can only move upward and completely disengage from the pressure relief piston 7.2 when the pressure relief piston 7.2 moves upward and contacts the retaining cylinder 15, thereby exposing the through hole for gas to pass through. In this embodiment, the surface of the front cover 3 may also be covered with a protective film to prevent moisture in the air from entering the housing 1 through the spray holes 9 and the nozzle 4, and to prevent the liquid fire extinguishing agent within the housing 1 from leaking out. Because the protective film itself is relatively thin, it is only used during the storage and transportation of the fire extinguishing device. In the event of a fire, the fire extinguishing agent can easily break through the protective film without affecting the normal spraying process.

[0030] Preferably, the central area of ​​the thrust piston 7.1 is interference-fitted with the outer side of the pressure relief piston 7.2. In this embodiment, the thrust piston 7.1 and the pressure relief piston 7.2 are both made of rubber. A through-hole is provided in the central area of ​​the thrust piston 7.1, into which the outer side of the pressure relief piston 7.2 is squeezed to complete the interference fit process. The interior of the pressure relief piston 7.2 is fixedly connected to the nut 6.2. Since the compression ratio of gas is greater than that of liquid, during the normal spraying phase, i.e., the process in which the entire piston 7 moves upward to push the liquid fire extinguishing agent 12 out of the nozzle 4, relative slippage between the thrust piston 7.1 and the pressure relief piston 7.2 is not likely to occur. Moreover, static friction exists between the two, making it unlikely for slippage to occur. Therefore, the thrust piston 7.1 and the pressure relief piston 7.2 will move as a whole. In addition, a slot and boss connection method can be further adopted between the interior of the pressure relief piston 7.2 and the nut 6.2. This connection method is not likely to cause relative slippage.

[0031] Preferably, the gas-generating fire extinguishing agent 2 is a columnar structure formed by pressing aerosol generating agent powder, and the liquid fire extinguishing agent 12 is perfluorohexanone fire extinguishing agent. When the aerosol generating agent burns, it produces a large amount of gas, which in turn propels the piston 7. Perfluorohexanone fire extinguishing agent, selected as liquid fire extinguishing agent 12, has a boiling point of 49°C and readily vaporizes under the high temperature during a fire, thereby changing the air pressure in the release area. Furthermore, this aerosol generating agent pressed into a columnar structure burns more slowly than powdered aerosol generating agents, ensuring the continuous release of the fire extinguishing agent.

[0032] The aerosol generator is a prior art, for example, the invention patent disclosed in Chinese Patent Publication No. CN101745195B is "An aging-resistant aerosol generator and its preparation process", which discloses that the aerosol generator is composed of an oxidant, a reducing agent, and a binder. The oxidant is potassium nitrate, the binder is phenolic resin, and the reducing agent is melamine. The mass percentages thereof are: potassium nitrate 74% to 80%, phenolic resin 8% to 15%, and the balance is melamine.

[0033] Its preparation method is:

[0034] Step 1: dissolving phenolic resin in ethanol to prepare a phenolic resin solution with a mass concentration of 40% to 55%;

[0035] Step 2: Grind the oxidizing agent and reducing agent to a fineness of 80-200 standard mesh, mix them according to the required proportion, and sieve them through 80-200 mesh three times to make them evenly mixed;

[0036] Step 3: Then add the phenolic resin solution to the mixed powder, stir for 10 minutes, and then use a 40-mesh screen to force granulate. Then dry the agent in an environment with a temperature of 40°C and a relative humidity of less than 20% until the volatile components are less than 1%;

[0037] Step 4: The dried medicine is pressed under a pressure of 10 MPa to form an aerosol generating agent column structure.

[0038] Preferably, the starting component 5 is an electric ignition head or a thermal wire structure. When the starting component 5 is an electric ignition head structure, it can be connected to a fire detection device, which is a temperature sensor and / or a smoke sensor. When a fire, overheating, or the like occurs, the fire detection device detects the high temperature environment generated in the battery compartment due to the fire and sends a signal to the microprocessor, which controls the starting component 5 to ignite the gas-generating fire extinguishing agent 2. When the starting component 5 is a thermal wire structure, the thermal wire structure can be directly ignited when a fire occurs, and then the thermal wire directly ignites the gas-generating fire extinguishing agent 2, without the need for additional fire detection devices and other external equipment, which is simpler and less costly.

[0039] Preferably, the outer edge of the front cover 3 is threadedly connected to the top of the housing 1, and the bottom of the housing 1 is threadedly connected to the outer edge of the rear cover 10. Through this threaded connection method, the convenience of installation of the entire fire extinguishing device can be improved and the production process is convenient.

[0040] Preferably, the gas-generating fire extinguishing agent 2 is located in the area where the back cover 10 is located, and a silicone layer 11 is provided between the outer surface of the gas-generating fire extinguishing agent 2 and the inner surface of the back cover 10. The silicone layer 11 can effectively isolate the heat generated by the combustion of the gas-generating fire extinguishing agent 2, preventing the surface temperature of the back cover 10 and the housing 1 from being too high.

[0041] Preferably, a guide rail 13 is vertically provided on the inner side of the housing 1, and a guide groove 14 is provided on the outer side of the thrust piston 7.1, and the guide groove 14 slides with the guide rail 13. The sliding cooperation between the guide groove 14 and the guide rail 13 can ensure the stability of the movement of the piston 7 and prevent the piston 7 from rotating radially.

[0042] Furthermore, in order to ensure that the contact area between the piston 7 and the screw 6.1 does not cause the perfluorohexanone liquid fire extinguishing agent to leak from the gap during the storage and transportation stage, a sealing ring can be added to the contact area between the lower end of the piston 7 and the screw 6.1 to effectively prevent the above-mentioned leakage.

[0043] In addition, the present invention also discloses a fire extinguishing method of the above-mentioned safe intermittent spraying fire extinguishing device, which comprises the following steps:

[0044] S1: When a battery in the battery box experiences thermal runaway, the starting component 5 ignites the gas-generating fire extinguishing agent 2, and the gas-generating fire extinguishing agent 2 generates gas;

[0045] S2: The airflow thrust piston 7 moves toward the position of the front cover 3, and the ball screw mechanism 6 causes the screw 6.1 to rotate.

[0046] S3: When the screw 6.1 rotates, it drives the rotating cover 8 to rotate, so that the spray holes 9 on the surface of the rotating cover 8 and the nozzles 4 on the surface of the front cover 3 periodically overlap and intersect;

[0047] S4: When the spray hole 9 and the nozzle 4 coincide with each other, the liquid fire extinguishing agent 12 is sprayed out from the nozzle 4, and is converted into gaseous state by the high temperature in the battery box to extinguish the fire in the battery box. When the spray hole 9 and the nozzle 4 are staggered, the shell 1 is sealed and a pressure-holding process is performed. Finally, the above process is repeated periodically to realize an intermittent spraying process, so that the pressure in the battery box increases and decreases periodically. In this step, when the fire extinguishing material is sprayed from the nozzle to extinguish the fire in the battery box, the gas inside the battery box increases, causing the pressure to increase. When the shell is sealed and a pressure-holding process is performed, the internal pressure of the battery box is released from the gap of the battery box itself, and the pressure decreases. Therefore, the pressure in the battery box increases and decreases periodically.

[0048] S5: When the pressure inside the battery box increases, the flammable gas diluted by the fire extinguishing substance is pressed out from the gaps in the battery box. When the pressure inside the battery box decreases, the flammable gas inside the battery escapes and enters the battery box, and the above process is repeated. Through this low-pressure and high-pressure reciprocating cycle, the flammable gas generated in the battery can eventually be diluted by the fire extinguishing substance and continuously discharged from the battery compartment, completing the entire fire extinguishing process and effectively preventing the risk of re-ignition.

[0049] S6: When the piston 7 moves to the point where the pressure relief piston 7.2 collides with the limiting cylinder 15, the pressure relief piston 7.2 is blocked by the limiting cylinder 15 and stops moving, while the external thrust piston 7.1 continues to move upward due to the thrust of the gas below. At this time, the thrust piston 7.1 moves upward and separates from the pressure relief piston 7.2, exposing the through hole in the center area of ​​the thrust piston 7.1. The thrust piston 7.1 stops when it contacts the limiting rod 16, leaving a gap between the thrust piston 7.1 and the front cover 3. Finally, the high-pressure gas generated by the gas-generating fire extinguishing agent 2 is discharged upward from the through hole in the center area of ​​the thrust piston 7.1, and finally discharged from the nozzle 4 and the nozzle hole 9. This step allows the high-pressure gas to be discharged in a timely manner when the fire extinguishing stage is completed, thereby ensuring the safety of the fire extinguishing device. In addition, in this embodiment, a certain gap can be reserved between the front cover 3 and the rotating cover 8. In this way, if the spray hole 9 is misaligned with the nozzle 4 in the final stage, the high-pressure gas can still pass through the through hole in the central area of ​​the thrust piston 7.1 and be discharged from the nozzle 4, the gap between the front cover 3 and the rotating cover 8, and the spray hole 9.

[0050] The above embodiments are merely preferred technical solutions of the present invention and should not be construed as limiting the present invention. The embodiments and features in the embodiments of this application may be arbitrarily combined with each other unless they conflict. The scope of protection of the present invention shall be the technical solutions described in the claims, including equivalent alternatives to the technical features of the technical solutions described in the claims. Equivalent alternatives and improvements within this scope are also within the scope of protection of the present invention.

Claims

1. A safe intermittent spraying fire extinguishing device, comprising a housing (1) and a gas-generating fire extinguishing agent (2) disposed in the housing (1), a front cover (3) being disposed on the front side of the housing (1), a nozzle (4) being disposed on the surface of the front cover (3), an end surface of the gas-generating fire extinguishing agent (2) being connected to one end of a starting component (5), characterized in that: The housing (1) is provided with a piston (7) in sliding engagement with the housing (1); the piston (7) is connected to the bottom of the front cover (3) via a screw (6.1) of a ball screw mechanism (6); the top of the screw (6.1) is fixedly connected to the center of a rotating cover (8); a liquid fire extinguishing agent (12) is provided between the piston (7) and the front cover (3); a spray hole (9) is provided on the surface of the rotating cover (8); when the rotating cover (8) rotates, the spray hole (9) and the nozzle (4) overlap and intersect periodically; the piston (7) comprises a thrust piston (7.1) located outside and a pressure relief piston (7.2) located inside; the screw (6.1) is passed through the interior of the pressure relief piston (7.2); and a limiting cylinder (15) in cooperation with the pressure relief piston (7.2) is provided at the center of the bottom of the front cover (3).

2. A safe intermittent spraying fire extinguishing device according to claim 1, characterized in that: The ball screw mechanism (6) comprises a nut (6.2) fixed inside a pressure relief piston (7.2), a spiral groove area where the nut (6.2) contacts the screw rod (6.1) is filled with balls, and the top side of the screw rod (6.1) is rotatably connected to the center of the front cover (3) via a bearing.

3. A safe intermittent spraying fire extinguishing device according to claim 1, characterized in that: The rotating cover (8) is located on the upper side of the front cover (3); the height of the limiting cylinder (15) is greater than the thickness of the piston (7); a limiting rod (16) cooperating with the thrust piston (7.1) is provided at the side of the bottom of the front cover (3); the height of the limiting rod (16) is less than the height of the limiting cylinder (15); the top of the limiting cylinder (15) is fixedly connected to the bottom of the front cover (3); and the top of the screw rod (6.1) is inserted into the limiting cylinder (15).

4. A safe intermittent spraying fire extinguishing device according to claim 1, characterized in that: The central area of ​​the thrust piston (7.1) is interference-fitted with the outer side of the pressure relief piston (7.2).

5. A safe intermittent spraying fire extinguishing device according to claim 1, characterized in that: The gas-generating fire extinguishing agent (2) is a columnar structure formed by pressing aerosol generating agent powder, and the liquid fire extinguishing agent (12) is a perfluorohexanone fire extinguishing agent.

6. A safe intermittent spraying fire extinguishing device according to claim 1, characterized in that: The starting component (5) is an electric ignition head or a thermal wire structure.

7. A safe intermittent spraying fire extinguishing device according to claim 1, characterized in that: The outer edge of the front cover (3) is threadedly connected to the top of the shell (1), and the bottom of the shell (1) is threadedly connected to the outer edge of the rear cover (10).

8. A safe intermittent spraying fire extinguishing device according to claim 7, characterized in that: The gas-generating fire extinguishing agent (2) is located in the area where the rear cover (10) is located, and a silica gel layer (11) is provided between the outer surface of the gas-generating fire extinguishing agent (2) and the inner surface of the rear cover (10).

9. A safe intermittent spraying fire extinguishing device according to claim 1, characterized in that: A guide rail (13) is also vertically provided on the inner side of the housing (1), and a guide groove (14) is provided on the outer side of the thrust piston (7.1), wherein the guide groove (14) is in sliding cooperation with the guide rail (13).

10. A fire extinguishing method using the safe intermittent spraying type fire extinguishing device according to any one of claims 1 to 9, characterized in that: It includes the following steps: S1: When a battery in the battery box experiences thermal runaway, the starting component (5) ignites the gas-generating fire extinguishing agent (2), and the gas-generating fire extinguishing agent (2) generates gas; S2: The airflow thrust piston (7) moves toward the position of the front cover (3), and the ball screw mechanism (6) causes the screw (6.1) to rotate. S3: When the screw (6.1) rotates, the rotating cover (8) is driven to rotate, so that the spray holes (9) on the surface of the rotating cover (8) and the spray ports (4) on the surface of the front cover (3) are periodically overlapped and staggered; S4: When the spray hole (9) and the nozzle (4) overlap, the liquid fire extinguishing agent (12) is sprayed out from the nozzle (4) and, under the action of the high temperature in the battery box, is converted into a gaseous state to extinguish the fire in the battery box. When the spray hole (9) and the nozzle (4) intersect, the housing (1) is sealed and a pressure holding process is performed. Finally, the above process is repeated periodically to achieve an intermittent spraying process, so that the pressure in the battery box increases and decreases periodically. S5: When the pressure in the battery box increases, the combustible gas diluted by the fire extinguishing material is pressed out from the gap of the battery box. When the pressure in the battery box decreases, the combustible gas inside the battery escapes and enters the battery box, and the above process is repeated in a cycle. S6: When the piston (7) moves to the point where the pressure relief piston (7.2) collides with the stop cylinder (15), the pressure relief piston (7.2) is blocked by the stop cylinder (15) and stops moving, while the external thrust piston (7.1) continues to move upward due to the thrust of the gas below. At this time, the thrust piston (7.1) separates upward from the pressure relief piston (7.2), and the through hole in the center area of ​​the thrust piston (7.1) is exposed. The thrust piston (7.1) stops moving when it contacts the stop rod (16), so that a gap remains between the thrust piston (7.1) and the front cover (3). Finally, the high-pressure gas generated by the gas-generating fire extinguishing agent (2) is discharged upward from the through hole in the center area of ​​the thrust piston (7.1), and finally discharged from the nozzle (4) and the nozzle hole (9).

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