Automatic water drainage device for fuel filter and control method of automatic water drainage device

Abstract

The invention is suitable for the technical field of fuel filters, and particularly relates to an automatic water drainage device for a fuel filter and a control method thereof.The automatic water drainage device comprises a filter body, a filter base is arranged at one end of the filter body, an electric pump is installed on the surface of the filter base, and the outer side of the filter body is sleeved with a lower shell; an air inlet electromagnetic valve is installed on the surface of the filter seat, an air inlet is formed in the surface of the air inlet electromagnetic valve, a water drainage electromagnetic valve is installed on the surface of the lower shell, and a water drainage opening is formed in the surface of the water drainage electromagnetic valve. The problem that the speed is low in an existing automatic water drainage technology is effectively solved. Different from a traditional design that a water draining valve and an air inlet valve are both located at the bottom of a filter and pressure is balanced by means of synchronous air inlet, the efficient design is adopted, the water draining process is not obviously affected by negative pressure of an inner cavity any more, and therefore the water draining speed is greatly increased.

Description

Technical Field

[0001] The invention relates to the technical field of fuel filters, in particular to an automatic water draining device for a fuel filter and a control method thereof. Background Art

[0002] In the existing fuel filter drainage technology, the water in the fuel is easily deposited at the bottom of the filter because its density is greater than that of the fuel. The drainage of the accumulated water needs to be handled by an automatic drain device. However, the existing automatic drain technology usually adopts a design in which the drain valve and the intake valve are located at the bottom of the filter at the same time. During the draining process, the inner cavity of the filter is often in a negative pressure state due to the gravity of the fuel. The drainage of water requires the introduction of external air by the intake valve to balance the internal and external pressures. When the negative pressure in the inner cavity is significant, the intake process is relatively slow, which leads to a slower draining rate. Therefore, in the existing technology, the drainage efficiency is low, and it is difficult to meet the demand for efficient and fast drainage.

[0003] Since this drainage method requires simultaneous intake and water drainage operations in actual applications, the system is often affected by changes in internal and external pressures during operation, resulting in a lengthy drainage process and the possibility of poor drainage under low temperatures or complex working conditions. The long drainage process not only affects the normal operation of the vehicle's fuel system, but may also have an adverse effect on precision components such as fuel injectors and fuel pumps due to water retention in the filter, thereby affecting the overall performance and operating stability of the engine. Therefore, the existing automatic water drainage technology has great limitations in dealing with internal cavity negative pressure and intake balance. Summary of the invention

[0004] The purpose of the embodiments of the present invention is to provide an automatic water draining device for a fuel filter and a control method thereof, aiming to solve the technical problems mentioned in the background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] An automatic water drain device for a fuel filter comprises a filter body, wherein one end of the filter body is provided with a filter seat, an electric pump is installed on the surface of the filter seat, a lower housing is sleeved on the outer side of the filter body, an air intake solenoid valve is installed on the surface of the filter seat, an air intake port is provided on the surface of the air intake solenoid valve, a water drain solenoid valve is installed on the surface of the lower housing, and a water drain port is provided on the surface of the water drain solenoid valve;

[0007] The inner bottom of the lower shell is provided with a third water detection electrode, a second water detection electrode and a first water detection electrode, and the height of the third water detection electrode is greater than that of the second water detection electrode, and the height of the second water detection electrode is greater than that of the first water detection electrode.

[0008] Furthermore, the air intake solenoid valve is connected to the interior of the filter seat, and the water discharge solenoid valve is connected to the interior of the lower shell.

[0009] Furthermore, a controller is installed on the surface of the lower shell.

[0010] Furthermore, a third connecting harness is arranged on the surface of the controller, a first connecting harness is arranged on the surface of the controller and the air intake solenoid valve, a second connecting harness is arranged on the surface of the controller and the electric pump, and a fourth connecting harness is arranged between the controller and the water drain solenoid valve.

[0011] Furthermore, a protective cover is provided on the surface of the lower shell, and the controller is arranged inside the protective cover.

[0012] A control method for an automatic water drain device for a fuel filter comprises the following steps:

[0013] Step S1, analyzing whether the time for which the water level inside the fuel filter is below the third water detection electrode exceeds a first preset time;

[0014] Step S2, if it is determined that the time for which the water level inside the fuel filter is below the third water detection electrode exceeds a first preset time, obtaining a vehicle instrument panel control instruction, and analyzing whether to allow the fuel filter to drain water according to the vehicle instrument panel control instruction;

[0015] Step S3, if it is determined that the fuel filter is allowed to drain water, obtain the engine speed data and the fuel temperature data;

[0016] Step S4, judging whether the engine is running and whether the fuel temperature is greater than 0 degrees Celsius according to the engine speed data and the fuel temperature data;

[0017] Step S5, if it is determined that the engine is in a stopped state and the fuel temperature is greater than 0 degrees Celsius, the air intake solenoid valve and the water drain solenoid valve are controlled to open to drain the fuel filter;

[0018] Step S6, during the water draining process, analyzing whether the water level inside the fuel filter is lower than the second water detection electrode, if it is determined that the water level inside the lower housing is lower than the second water detection electrode, controlling the air intake solenoid valve and the water draining solenoid valve to close, and stopping the water draining operation;

[0019] Step S7, controlling the electric pump to operate for a second preset time period, and then turning off the electric pump.

[0020] Furthermore, in step S1, the preset duration is 10 seconds.

[0021] The present invention provides an automatic water draining device for a fuel filter and a control method thereof, which has the following beneficial effects:

[0022] The problem of slow speed in existing automatic water draining technology is effectively solved. Unlike the traditional design in which the drain valve and the air intake valve are both located at the bottom of the filter and rely on synchronous air intake to balance the pressure, the present invention adopts a more efficient design so that the draining process is no longer significantly affected by the negative pressure of the inner cavity, thereby greatly improving the drainage speed. The device can not only quickly drain the accumulated water, but also ensure the normal operation of the fuel system, does not affect the start-up and working efficiency of the engine, and has good practicality and adaptability. It better meets the needs of vehicles in actual use, improves the maintenance efficiency of the fuel system, and extends the service life of engine components. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a structural schematic diagram of an automatic water draining device for a fuel filter.

[0024] Figure 2 The present invention is a front plan view of an automatic water drain device for a fuel filter.

[0025] Figure 3 The figure is a schematic diagram of the surface structure of an automatic water drain device for a fuel filter.

[0026] Figure 4 The present invention is a schematic diagram of the upward structure of an automatic water drain device for a fuel filter.

[0027] Figure 5 The present invention is a schematic diagram of the internal structure of a lower shell in an automatic water drain device for a fuel filter.

[0028] Figure 6 The present invention is a control logic schematic diagram of a control method for an automatic water draining device of a fuel filter.

[0029] Figure 7 The present invention is a CAN communication control logic schematic diagram of a control method for an automatic water drain device of a fuel filter.

[0030] In the figure: 1. filter seat; 2. filter body; 3. lower shell; 4. first connecting harness; 5. air intake solenoid valve; 6. electric pump; 7. second connecting harness; 8. water discharge solenoid valve; 9. water discharge port; 10. third connecting harness; 11. air intake port; 12. fourth connecting harness; 13. first water detection electrode; 14. second water detection electrode; 15. third water detection electrode; 16. controller. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0032] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0033] like Figure 1-Figure 5 As shown, an automatic water drain device for a fuel filter provided by an embodiment of the present invention comprises a filter body 2, and a filter seat 1 is provided at one end of the filter body 2, an electric pump 6 is installed on the surface of the filter seat 1, a lower housing 3 is sleeved on the outer side of the filter body 2, an air intake solenoid valve 5 is installed on the surface of the filter seat 1, and an air intake port 11 is provided on the surface of the air intake solenoid valve 5, and a water drain solenoid valve 8 is installed on the surface of the lower housing 3, and a water drain port 9 is provided on the surface of the water drain solenoid valve 8. The air intake solenoid valve 5 is connected to the interior of the filter seat 1, and the water drain solenoid valve 8 is connected to the interior of the lower housing 3.

[0034] The inner bottom of the lower shell 3 is provided with a third water detecting electrode 15 , a second water detecting electrode 14 and a first water detecting electrode 13 . The height of the third water detecting electrode 15 is greater than that of the second water detecting electrode 14 , and the height of the second water detecting electrode 14 is greater than that of the first water detecting electrode 13 .

[0035] The surface of the lower housing 3 is provided with a controller 16. The surface of the controller 16 is provided with a third connection harness 10, the surfaces of the controller 16 and the air intake solenoid valve 5 are provided with a first connection harness 4, the surfaces of the controller 16 and the electric pump 6 are provided with a second connection harness 7, and the fourth connection harness 12 is provided between the controller 16 and the water discharge solenoid valve 8.

[0036] In one embodiment of the present invention, the automatic water draining device includes a variety of key components that work together in the system. The filter body 2 is used to filter the fuel and trap water and impurities. Since water has a greater specific gravity than fuel, it will be deposited at the bottom of the filter. One end of the filter is equipped with a filter seat 1, which is tightly connected to the filter body 2 and supports components such as the electric pump 6 and the intake solenoid valve 5. After the water draining process is completed, the electric pump can compress the air in the inner cavity of the filter to ensure that the fuel system returns to a normal pressure state after the drainage is completed, so as to ensure the smooth start of the engine.

[0037] The air intake solenoid valve 5 is used together with the air intake port 11 and is installed on the filter seat 1. By controlling the opening and closing of the air intake solenoid valve 5, air enters the inner cavity of the filter. This balances the internal and external pressures during the water discharge process, so that water can be discharged smoothly from the water discharge port 9. The lower shell 3 is sleeved on the outside of the filter body 2, and three water detection electrodes (the first water detection electrode 13, the second water detection electrode 14, and the third water detection electrode 15) are installed at the bottom. They detect water levels at different heights respectively to ensure accurate monitoring of water accumulation.

[0038] The first water-detecting electrode 13 is located at the lowest position and usually serves as a negative electrode. When the water level rises and contacts the electrode, a circuit is formed through the conductivity of the water, providing a preliminary water level signal to the controller, indicating that there is a small amount of water in the filter. The second water-detecting electrode 14 is located at an intermediate height and serves as a positive electrode. When the water level rises to this point, the conduction of water will transmit a signal to the controller, but will not trigger any operation and is only used to monitor further changes in the water level. When the third water-detecting electrode 15 (the highest position, serving as a positive electrode) detects that the water level has reached its height, the controller 16 triggers an alarm and opens the air intake solenoid valve 5 and the water discharge solenoid valve 8 under appropriate conditions (such as the engine speed is 0, the ambient temperature is greater than 0°C, etc.) to discharge the accumulated water. During the water discharge process, the water level gradually decreases. When the water level drops below the second water-detecting electrode 14, it means that the water discharge operation is completed. The controller 16 immediately closes the air intake and water discharge solenoid valves and starts the electric pump 6 to compress the air in the filter to ensure that the system pressure is restored, thereby facilitating the restart of the engine. When the water level drops to the first water detection electrode 13, the controller 16 continues to monitor the water level change to ensure that the system responds to the water accumulation situation at any time.

[0039] In this way, the device effectively solves the problem of slow speed in existing automatic water draining technology. Unlike the traditional design in which the drain valve and the air intake valve are both located at the bottom of the filter and rely on synchronous air intake to balance the pressure, the present invention adopts a more efficient design so that the draining process is no longer significantly affected by the negative pressure of the inner cavity, thereby greatly improving the drainage speed. The device can not only quickly drain the accumulated water, but also ensure the normal operation of the fuel system without affecting the start-up and working efficiency of the engine, and has good practicality and adaptability. It better meets the needs of the vehicle in actual use, improves the maintenance efficiency of the fuel system, and extends the service life of engine components.

[0040] In this embodiment, a protective cover is provided on the surface of the lower housing 3, and the controller 16 is arranged inside the protective cover. The design of the protective cover has multiple advantages. First, it can effectively protect the controller 16 from the external environment such as dust, moisture and impact, and enhance the durability and reliability of the system. Secondly, the protective cover can prevent vibration from interfering with the controller and ensure the stability of the device during vehicle driving. In addition, the design of the protective cover also helps to simplify the maintenance of the equipment, making it more convenient to replace or check the controller, thereby improving the long-term performance and safety of the entire automatic water discharge device.

[0041] like Figure 6 As shown, in one embodiment of the present invention, a control method for an automatic water drain device for a fuel filter comprises the following steps:

[0042] Step S1, analyzing whether the time for which the water level inside the fuel filter is below the third water detection electrode 15 exceeds a first preset time;

[0043] Step S2, if it is determined that the time for which the water level inside the fuel filter is below the third water detection electrode 15 exceeds a first preset time, obtain a vehicle dashboard control instruction, and analyze whether to allow the fuel filter to drain water according to the vehicle dashboard control instruction;

[0044] Step S3, if it is determined that the fuel filter is allowed to drain water, obtain the engine speed data and the fuel temperature data;

[0045] Step S4, judging whether the engine is running and whether the fuel temperature is greater than 0 degrees Celsius according to the engine speed data and the fuel temperature data;

[0046] Step S5, if it is determined that the engine is in a stopped state and the fuel temperature is greater than 0 degrees Celsius, the air intake solenoid valve 5 and the water drain solenoid valve 8 are controlled to open to drain the fuel filter;

[0047] Step S6, during the water draining process, analyzing whether the water level inside the fuel filter is lower than the second water detection electrode 14, if it is determined that the water level inside the lower housing 3 is lower than the second water detection electrode 14, controlling the air intake solenoid valve 5 and the water draining solenoid valve 8 to close, and stopping the water draining operation;

[0048] Step S7, controlling the electric pump 6 to operate for a second preset time period, and then turning off the electric pump 6.

[0049] In this embodiment, the control method includes multiple steps to ensure that the water in the fuel filter can be automatically discharged under appropriate conditions and maintain the normal operation and safety of the entire system. First, the device detects whether the water level inside the fuel filter exceeds the third water detection electrode 15, and determines whether the time the water level is at this position exceeds the first preset time. The basis for this judgment is that when the water level remains high for a long time, it means that the amount of water accumulated in the filter has reached the warning level and needs further treatment.

[0050] If the time that the water level is at the third water-detecting electrode 15 does exceed the first preset time, the system will obtain a control instruction from the vehicle dashboard and determine whether to allow the water release operation based on the instruction. The implementation basis of this step is to ensure that the water release operation is consistent with the driver's intention and the operating status of the vehicle, so as to avoid water release in inappropriate circumstances, thereby increasing the safety and flexibility of the system.

[0051] After confirming that draining is allowed, the system further obtains the engine speed data and fuel temperature data. This step is crucial because the fuel filter draining operation can only be performed under specific conditions. Specifically, the system will analyze whether the engine is stopped and whether the fuel temperature is higher than 0 degrees Celsius. These judgment conditions are set to ensure that draining is performed when the engine is not running to avoid affecting the fuel supply system, while ensuring that the fuel temperature is suitable for operation to prevent freezing and other conditions from affecting the draining process.

[0052] When the system determines that the engine has stopped running and the fuel temperature is greater than 0 degrees Celsius, the controller 16 will issue a command to open the air intake solenoid valve 5 and the water discharge solenoid valve 8, thereby starting the water discharge operation of the fuel filter. At this time, the external air enters the filter cavity through the air intake solenoid valve 5 to balance the internal pressure, so that the accumulated water can be smoothly discharged from the water discharge port of the lower shell 3. During the water discharge process, the system monitors the water level changes in the lower shell 3 in real time. When it is detected that the water level drops below the second water detection electrode 14, it means that the accumulated water has been basically drained.

[0053] When the water level is lower than the second water detection electrode 14, the controller 16 will close the air intake solenoid valve 5 and the water drain solenoid valve 8, and stop the water draining operation to prevent too much air from entering the system and affecting the normal function of the fuel filter. Next, the system controls the electric pump 6 to start and keep running for a second preset period of time. The electric pump 6 is started to compress the air in the filter to ensure that the appropriate pressure is re-established in the filter cavity after draining the water, so that the fuel system can quickly return to normal working condition when the engine is started next time. After the electric pump 6 has been running for the second preset time, the controller 16 will automatically turn off the electric pump, and the entire water draining operation process will end.

[0054] In summary, the design of this control method fully considers multiple key factors such as water level, engine status, temperature, etc., to ensure that the fuel filter can automatically complete the water draining operation under safe and effective conditions. When the system detects the water level, it uses the precise monitoring of the water detection electrode to ensure that the water draining process is only started when the water level reaches the warning line, avoiding the burden on the system caused by frequent operations. At the same time, by analyzing the operating status of the engine and the fuel temperature, the system can ensure that the water draining operation is carried out under appropriate conditions, avoid draining water when the engine is running, prevent adverse effects on the fuel supply, and ensure the stable operation of the engine and fuel system.

[0055] In addition, during the automatic water discharge process, the coordinated work of the air intake solenoid valve and the water discharge solenoid valve allows the internal and external pressures to be quickly balanced during water discharge, thereby speeding up the water discharge. Compared with the traditional method of manually adjusting the pressure, this automated design greatly shortens the drainage time and improves the operating efficiency. Even in a low temperature environment, the system will first check the fuel temperature to ensure that the water is discharged within the appropriate temperature range to prevent the problem of water freezing caused by low temperature, thereby further ensuring the stability and durability of the device.

[0056] Each step in the control method has clear triggering and shut-off conditions, such as stopping the water discharge when the water level is lower than the second water detection electrode, or automatically shutting down the electric pump after reaching the preset operation time, which provides a guarantee for the precise operation of the device. The final operation stage of the electric pump not only effectively restores the appropriate pressure in the filter, but also ensures that the system can quickly enter normal working state when it is started next time.

[0057] This design makes the automatic water draining process of the fuel filter not only more intelligent, but also adaptable to a variety of actual use environments, reducing the necessity of human intervention and the difficulty of maintenance. Overall, this control method significantly improves the reliability and durability of the fuel system, allowing the vehicle to maintain a good operating state under complex working conditions, reducing the potential damage to the engine and fuel system caused by water problems, and greatly improving the convenience and safety of vehicle use.

[0058] In this embodiment, in step S1, the preset duration is 10 seconds. First, the 10-second time setting can effectively distinguish between instantaneous water level fluctuations and continuous water accumulation. If the water level only touches the third water detection electrode 15 for a short time, this may be a short-term water level fluctuation caused by bumps or fuel sloshing during vehicle driving, rather than an actual water accumulation problem. By setting a duration of 10 seconds, the system can avoid erroneously triggering the water release operation due to short-term fluctuations, thereby improving the operating stability of the device.

[0059] Secondly, the 10-second delay setting helps protect system components and avoid frequent switching actions. The automatic water discharge process involves the opening and closing operations of the air intake solenoid valve and the water discharge solenoid valve. Without proper delay, the system may increase the wear of the solenoid valve due to unnecessary startup and shorten its service life. Setting a 10-second delay can ensure that the water discharge operation is only started in the case of real and continuous water accumulation, extending the overall service life of the system.

[0060] In addition, 10 seconds is a relatively reasonable time interval, which is short enough to respond in time after water accumulation occurs, avoiding damage to the engine and fuel system caused by water being retained in the fuel filter for a long time. This setting balances the needs of response speed and preventing misoperation, making the entire water release process both agile and ensuring the accuracy of operation, thereby better protecting the normal operation of the fuel system.

[0061] In this embodiment, in step S6, the second preset time length is 30 seconds. The basis for this setting is to ensure that the electric pump 6 can fully operate for a period of time to compress the air in the filter and restore the normal pressure of the system cavity.

[0062] The 30-second time setting has been carefully balanced so that the electric pump can effectively inject air into the filter cavity during the emptying process, thereby ensuring that there is no excessive negative pressure left in the filter after the water is drained and maintaining proper pressure balance. This is crucial for restarting the engine, because after the pressure in the filter cavity returns to normal levels, the fuel can flow more smoothly into the engine, ensuring that the vehicle can start smoothly.

[0063] At the same time, this time setting is long enough to allow the electric pump to complete its work task, but not too long to avoid unnecessary energy consumption and excessive operation of the electric pump, thereby improving the energy efficiency of the system and the service life of the electric pump. Therefore, the second preset time of 30 seconds strikes a balance between time and efficiency, ensuring the normal function of the system while extending the life of the electric pump and other related components.

[0064] like Figure 7 As shown, in the above steps, the transmission of part of the information and the execution of the instructions are completed through CAN (Controller Area Network) communication. Specifically, when the system obtains the control instructions of the car dashboard and the engine speed data, it uses CAN communication to transmit the data in real time. Through CAN communication, the controller 16 can receive the instruction of whether to allow water discharge from the dashboard, and at the same time obtain the status information of the engine, such as whether the speed is zero, and whether the fuel temperature is greater than 0°C. The application of CAN communication ensures the reliability and real-time nature of these data transmissions, so that the controller can make timely judgments based on the latest vehicle status, thereby accurately controlling the opening and closing of the intake solenoid valve 5 and the water discharge solenoid valve 8, and ensuring the efficiency and safety of the automatic water discharge process.

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An automatic water drain device for a fuel filter, comprising a filter body (2), wherein one end of the filter body (2) is provided with a filter seat (1), an electric pump (6) is mounted on the surface of the filter seat (1), and a lower housing (3) is sleeved on the outer side of the filter body (2), characterized in that: An air intake solenoid valve (5) is installed on the surface of the filter seat (1), and an air intake port (11) is provided on the surface of the air intake solenoid valve (5); a water discharge solenoid valve (8) is installed on the surface of the lower housing (3), and a water discharge port (9) is provided on the surface of the water discharge solenoid valve (8); The inner bottom of the lower shell (3) is provided with a third water detection electrode (15), a second water detection electrode (14) and a first water detection electrode (13), and the height of the third water detection electrode (15) is greater than the height of the second water detection electrode (14), and the height of the second water detection electrode (14) is greater than the height of the first water detection electrode (13).

2. The automatic water draining device for a fuel filter according to claim 1, characterized in that: The air intake solenoid valve (5) is connected to the interior of the filter seat (1), and the water discharge solenoid valve (8) is connected to the interior of the lower shell (3).

3. The automatic water draining device for a fuel filter according to claim 1, characterized in that: A controller (16) is mounted on the surface of the lower housing (3).

4. The automatic water draining device for a fuel filter according to claim 3, characterized in that: A third connecting harness (10) is arranged on the surface of the controller (16), a first connecting harness (4) is arranged on the surface of the controller (16) and the air intake solenoid valve (5), a second connecting harness (7) is arranged on the surface of the controller (16) and the electric pump (6), and a fourth connecting harness (12) is arranged between the controller (16) and the water discharge solenoid valve (8).

5. The automatic water draining device for a fuel filter according to claim 3, characterized in that: The surface of the lower housing (3) is provided with a protective cover, and the controller (16) is arranged inside the protective cover.

6. A control method for an automatic water drain device for a fuel filter, characterized in that: The following steps are involved: Step S1, analyzing whether the time for which the water level inside the fuel filter submerges the third water detection electrode (15) exceeds a first preset time; Step S2, if it is determined that the time for which the water level inside the fuel filter submerges the third water detection electrode (15) exceeds a first preset time, obtaining a vehicle instrument panel control instruction, and analyzing whether to allow the fuel filter to drain water according to the vehicle instrument panel control instruction; Step S3, if it is determined that the fuel filter is allowed to drain water, obtain the engine speed data and the fuel temperature data; Step S4, judging whether the engine is running and whether the fuel temperature is greater than 0 degrees Celsius according to the engine speed data and the fuel temperature data; Step S5, if it is determined that the engine is in a stopped state and the fuel temperature is greater than 0 degrees Celsius, the air intake solenoid valve (5) and the water drain solenoid valve (8) are controlled to open to drain the fuel filter; Step S6, during the water draining process, analyzing whether the water level inside the fuel filter is lower than the second water detection electrode (14); if it is determined that the water level inside the lower housing (3) is lower than the second water detection electrode (14), controlling the air intake solenoid valve (5) and the water draining solenoid valve (8) to close, and stopping the water draining operation; Step S7, controlling the electric pump (6) to operate for a second preset time period, and then shutting down the electric pump (6).

7. A control method for an automatic water drain device for a fuel filter according to claim 6, characterized in that: In step S1, the preset time length is 10 seconds.

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