A leak detection device and method for a vehicle evaporative fuel system

Abstract

This invention discloses a leak detection device and method for an automotive fuel evaporation system. The device includes: a charcoal canister solenoid valve, a low-pressure pipeline sealing valve, a charcoal canister, a fuel tank, a fuel tank pressure sensor, and a control device. The low-pressure pipeline sealing valve, the charcoal canister solenoid valve, the charcoal canister, and the fuel tank are connected in sequence. The fuel tank pressure sensor is installed on the fuel tank. The control device is used to control the opening of the low-pressure pipeline sealing valve and the charcoal canister solenoid valve, and to obtain the pressure drop amplitude. If the pressure drop amplitude is not greater than a first threshold, it is determined that there is a large leakage fault in the fuel evaporation system. If the pressure drop amplitude is greater than the first threshold, it is controlled to close the low-pressure pipeline sealing valve and the charcoal canister solenoid valve. The current vacuum attenuation gradient is calculated. If the current vacuum attenuation gradient is not greater than a second threshold, it is determined that there is a small leakage fault in the fuel evaporation system. If the current vacuum attenuation gradient is greater than the second threshold, it is determined that there is no leakage in the fuel evaporation system.

Description

Technical Field

[0001] This invention relates to the field of automotive fuel evaporation system technology, and in particular to a leak detection device and method for automotive fuel evaporation systems. Background Technology

[0002] The core component of the existing China VI fuel evaporation system, the charcoal canister solenoid valve, retains the structure and function of components from the China V fuel evaporation system, using a single charcoal canister solenoid valve as the sealing element. However, due to the stricter emission limits for evaporative pollutants under the China VI emission regulations and the increased requirements for pollutant emissions during refueling, the demand for desorption of fuel vapor within the charcoal canister of the fuel evaporation system is significantly greater than in the China V system. This has led to a much higher frequency of use for the charcoal canister solenoid valve, causing wear and tear from prolonged high-frequency operation, resulting in decreased sealing performance and durability. Consequently, this leads to inaccurate leak detection in the fuel evaporation system. Summary of the Invention

[0003] This invention provides a leak detection device and method for an automotive fuel evaporation system. By using a charcoal canister solenoid valve and a low-pressure pipeline sealing valve as sealing elements during leak detection, the sealing performance is not solely dependent on the charcoal canister solenoid valve, but is shared by both the charcoal canister solenoid valve and the low-pressure pipeline sealing valve, thereby improving the durability of the charcoal canister solenoid valve.

[0004] An embodiment of the present invention provides a leak detection device for an automotive fuel evaporation system, comprising:

[0005] charcoal canister solenoid valve, low-pressure pipeline sealing valve, charcoal canister, fuel tank, fuel tank pressure sensor and control equipment;

[0006] The low-pressure pipeline sealing valve, the charcoal canister solenoid valve, the charcoal canister, and the fuel tank are connected in sequence.

[0007] The fuel tank pressure sensor is mounted on the fuel tank;

[0008] The control device is used to control the opening of the low-pressure pipeline sealing valve and the charcoal canister solenoid valve, and to obtain the pressure drop amplitude; if the pressure drop amplitude is not greater than a first threshold, it is determined that there is a large leakage fault in the fuel evaporation system; if the pressure drop amplitude is greater than the first threshold, it controls the low-pressure pipeline sealing valve and the charcoal canister solenoid valve to close; it calculates the current vacuum degree decay gradient; if the current vacuum degree decay gradient is not greater than a second threshold, it is determined that there is a small leakage fault in the fuel evaporation system; if the current vacuum degree decay gradient is greater than the second threshold, it is determined that there is no leakage in the fuel evaporation system.

[0009] Furthermore, the control of the low-pressure pipeline sealing valve and the charcoal canister solenoid valve to open includes:

[0010] Perform fault detection on the charcoal canister solenoid valve and the low-pressure pipeline sealing valve respectively. If there is no fault in either the charcoal canister solenoid valve or the low-pressure pipeline sealing valve, control the low-pressure pipeline sealing valve and the charcoal canister solenoid valve to open.

[0011] Furthermore, fault detection of the charcoal canister solenoid valve includes:

[0012] The solenoid valve of the charcoal canister and the sealing valve of the low-pressure pipeline are closed to obtain the first pressure from the oil tank pressure sensor.

[0013] If the first pressure is less than the third threshold, it is determined that the carbon canister solenoid valve has a stuck, normally open fault.

[0014] If the first pressure is not less than the third threshold, then control the opening of the carbon canister solenoid valve and the low-pressure pipeline sealing valve to obtain the second pressure of the oil tank pressure sensor within the first preset time range.

[0015] If the second pressure is less than the fourth threshold, the charcoal canister solenoid valve is determined to be fault-free.

[0016] If the second pressure is not less than the fourth threshold, then it is determined that the charcoal canister solenoid valve has a low flow fault.

[0017] Furthermore, it also includes: charcoal canister ventilation valve;

[0018] The charcoal canister ventilation valve is connected to the charcoal canister;

[0019] Before performing fault detection on the charcoal canister solenoid valve and the low-pressure pipeline sealing valve, the following steps are also included:

[0020] Control the charcoal canister solenoid valve and the low-pressure pipeline sealing valve to close, and control the charcoal canister ventilation valve to open;

[0021] Obtain the third pressure from the tank pressure sensor within the second preset time range;

[0022] If the third pressure is not equal to the fifth threshold, then it is determined that the charcoal canister ventilation valve is stuck.

[0023] If the third pressure is equal to the fifth threshold, then the charcoal canister ventilation valve is determined to be fault-free and is closed.

[0024] Furthermore, it also includes: the intake manifold;

[0025] The intake manifold is connected to the low-pressure pipeline sealing valve;

[0026] The control device is also used for:

[0027] When the engine is detected to be running and the fuel vaporization system reaches the desorption condition, the low-pressure pipeline sealing valve and the charcoal canister solenoid valve are opened to create a negative pressure in the intake manifold and desorb the fuel vapor in the charcoal canister.

[0028] The fuel vapor in the charcoal canister is generated from fuel in the fuel tank and then transferred to the charcoal canister.

[0029] Furthermore, it also includes: a refueling vent valve;

[0030] One end of the refueling vent valve is connected to the fuel tank, and the other end of the refueling vent valve is connected to the charcoal canister.

[0031] The fuel vapor in the charcoal canister is generated from fuel in the fuel tank and then transferred to the charcoal canister, including:

[0032] After fuel vapor is generated in the fuel tank, it enters the charcoal canister through the refueling vent valve.

[0033] Furthermore, the control device is also used for:

[0034] When the vehicle engine stops, the low-pressure line sealing valve and the charcoal canister solenoid valve are closed so that the charcoal canister solenoid valve can absorb and filter fuel vapors.

[0035] Based on the above-described apparatus embodiments, the present invention provides corresponding method embodiments;

[0036] One embodiment of the present invention provides a method for detecting leaks in an automotive fuel evaporation system, which is applicable to a device for detecting leaks in an automotive fuel evaporation system.

[0037] The method for detecting leaks in the automotive fuel evaporation system includes:

[0038] Control the opening of the low-pressure pipeline sealing valve and the carbon canister solenoid valve, and obtain the pressure drop rate;

[0039] If the pressure drop is not greater than the first threshold, it is determined that there is a large leakage fault in the fuel evaporation system.

[0040] If the pressure drop exceeds the first threshold, the low-pressure pipeline sealing valve and the carbon canister solenoid valve will be closed.

[0041] Calculate the current vacuum decay gradient. If the current vacuum decay gradient is not greater than the second threshold, it is determined that there is a minor leak in the fuel evaporation system.

[0042] If the current vacuum decay gradient is greater than the second threshold, it is determined that there is no leak in the fuel evaporation system.

[0043] The following benefits can be obtained by implementing the present invention:

[0044] This invention provides a leak detection device and method for an automotive fuel evaporation system. The device includes: a charcoal canister solenoid valve, a low-pressure line sealing valve, a charcoal canister, a fuel tank, a fuel tank pressure sensor, and a control device. By sequentially connecting the low-pressure line sealing valve, the charcoal canister solenoid valve, the charcoal canister, and the fuel tank, and simultaneously controlling the opening or closing of the charcoal canister solenoid valve and the low-pressure line sealing valve via the control device during leak detection, the airtightness of the fuel evaporation system can be detected based on the formed sealed space. By using the charcoal canister solenoid valve and the low-pressure line sealing valve as a common sealing element during detection, based on the principle that a greater spring force in the sealing element results in better sealing, the charcoal canister solenoid valve and the low-pressure line sealing valve share the sealing force required for sealing. This avoids the sealing performance depending solely on the charcoal canister solenoid valve, reduces the sealing force requirements of the charcoal canister solenoid valve, improves the durability of the charcoal canister solenoid valve, and enhances its responsiveness. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the structure of a leak detection device for an automotive fuel evaporation system provided in an embodiment of the present invention.

[0046] Figure 2 This is a flowchart of a leak detection method provided in an embodiment of the present invention.

[0047] Figure 3 This is a flowchart of a process for fault detection of each seal in the current system before leak detection, provided by an embodiment of the present invention.

[0048] Figure 4 This is a structural diagram of a low-pressure pipeline sealing valve provided in an embodiment of the present invention.

[0049] Figure 5 This is a flowchart of a fuel vapor desorption process provided in an embodiment of the present invention.

[0050] Figure 6 This is a flowchart of fuel vapor filtration under parking conditions provided by an embodiment of the present invention.

[0051] Figure 7 This is a schematic flowchart of a method for detecting leaks in an automotive fuel evaporation system according to an embodiment of the present invention. Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] To facilitate understanding of the technical process of the embodiments of this application, the functions of some components involved in the embodiments of this application are explained below:

[0054] Fuel tank (1): Used to store gasoline and gasoline vapors that evaporate during vehicle use.

[0055] Fueling vent valve (2): Used to discharge fuel vapor generated in the fuel tank during the refueling process, and to close the valve after the fuel tank is filled to the set volume to increase the fuel tank pressure, so that the fuel nozzle stops refueling and avoids excessive refueling.

[0056] Fuel tank pressure sensor (3): monitors the vapor pressure in the fuel evaporation system to determine whether there is a leak in the fuel evaporation system and to help determine whether the charcoal canister vent valve, charcoal canister solenoid valve and low-pressure pipeline sealing valve are working properly.

[0057] Charcoal canister (4): Used to adsorb fuel vapor generated in the fuel tank during refueling and vehicle use. At the same time, when the engine is running, the fuel vapor is carried into the engine for combustion through engine desorption, so as to reduce the evaporation of fuel vapor into the atmosphere.

[0058] Charcoal canister vent valve (5): By controlling the opening and closing of the valve, the fuel evaporation system is made into a closed system, thereby determining whether there is a leak in the fuel evaporation system and assisting in determining whether the low-pressure pipeline sealing valve is working properly.

[0059] Vent filter (6): During charcoal desorption, it keeps clean, fresh air passing through the charcoal canister to carry fuel vapor to the engine.

[0060] Carbon canister solenoid valve (7): By controlling the opening frequency of the carbon canister solenoid valve, the air flow through the carbon canister is controlled, thereby realizing the desorption and flushing of the carbon canister under different working conditions.

[0061] Fuel filler cap (8): Seal the fuel system during fuel evaporation system sealing test.

[0062] Low-pressure pipeline sealing valve (10): By controlling the opening and closing of the valve, the fuel evaporation system is made into a closed system, thereby determining whether there is a leak in the fuel evaporation system.

[0063] like Figure 1 The image shows a leakage detection device for an automotive fuel evaporation system provided in an embodiment of the present invention, comprising: a charcoal canister solenoid valve, a low-pressure pipeline sealing valve, a charcoal canister, a fuel tank, a fuel tank pressure sensor, and a control device.

[0064] The low-pressure pipeline sealing valve, the charcoal canister solenoid valve, the charcoal canister, and the fuel tank are connected in sequence.

[0065] The fuel tank pressure sensor is mounted on the fuel tank;

[0066] The control device is used to control the opening of the low-pressure pipeline sealing valve and the charcoal canister solenoid valve, and to obtain the pressure drop amplitude; if the pressure drop amplitude is not greater than a first threshold, it is determined that there is a large leakage fault in the fuel evaporation system; if the pressure drop amplitude is greater than the first threshold, it controls the low-pressure pipeline sealing valve and the charcoal canister solenoid valve to close; it calculates the current vacuum degree decay gradient; if the current vacuum degree decay gradient is not greater than a second threshold, it is determined that there is a small leakage fault in the fuel evaporation system; if the current vacuum degree decay gradient is greater than the second threshold, it is determined that there is no leakage in the fuel evaporation system.

[0067] Specifically, when performing leak detection on the automotive fuel evaporation system, the required components include at least: a charcoal canister solenoid valve (7), a low-pressure line sealing valve (10), a charcoal canister (4), a fuel tank (1), a fuel tank pressure sensor (3), and control equipment (not shown in the figure).

[0068] The low-pressure pipeline sealing valve (10), the charcoal canister solenoid valve (7), the charcoal canister (4), and the fuel tank (1) are as follows: Figure 1 The connection is made in the manner shown, and a sealed space is formed when the low-pressure pipeline sealing valve (10) and the charcoal canister solenoid valve (7) are closed. Preferably, fuel needs to be added to the fuel tank (1) regularly, so the device may also include a filler cap (8) and a filler pipe (9), so that fuel can be added through the filler cap (8) and the fuel can enter the fuel tank (1) through the filler pipe (9). It should be noted that the filler cap (8) is usually closed when not refueling or when leak detection is being performed to ensure that the fuel vapor generated in the fuel tank (1) does not leak into the atmosphere and cause pollution.

[0069] In the enclosed space constructed by the current low-pressure pipeline sealing valve (10), charcoal canister solenoid valve (7), charcoal canister (4), and fuel tank (1), the pressure of the enclosed space is detected based on the fuel tank pressure sensor (3) installed on the fuel tank (1). Optionally, the fuel tank pressure sensor (3) can be installed on any pipeline in the formed enclosed space. In this embodiment and Figure 1 The provided configuration is only one preferred setting.

[0070] In a preferred embodiment, controlling the opening of the low-pressure pipeline sealing valve and the charcoal canister solenoid valve includes: performing fault detection on the charcoal canister solenoid valve and the low-pressure pipeline sealing valve respectively, and controlling the opening of the low-pressure pipeline sealing valve and the charcoal canister solenoid valve when there is no fault in either the charcoal canister solenoid valve or the low-pressure pipeline sealing valve.

[0071] Specifically, such as Figure 2The diagram shown is a flowchart of the leak detection process provided by this invention. When performing a leak check, the first step is to check the sealing performance of the charcoal canister solenoid valve (7) and the low-pressure pipeline sealing valve (10). If no fault is detected, the control device opens the low-pressure pipeline sealing valve (10) and the charcoal canister solenoid valve (7). If a charcoal canister vent valve (5) is present, it must also be closed. The pressure drop after opening the charcoal canister solenoid valve (7) and the low-pressure pipeline sealing valve (10) is calculated by comparing the pressure measured by the fuel tank pressure sensor (3) before and after opening the charcoal canister solenoid valve (7) and the low-pressure pipeline sealing valve (10). If the calculated pressure drop is not greater than the set value of the pressure change amplitude (i.e., the aforementioned first threshold), it is determined that there is a large number of leaks in the fuel evaporation system, and a corresponding fault alarm is issued. If the calculated pressure drop is greater than the set value of the pressure change range (i.e., the first threshold mentioned above), then there is no major leakage fault in the fuel evaporation system. The charcoal canister solenoid valve (7) and the low-pressure pipeline sealing valve (10) are closed to form a sealed space. At the same time, the current vacuum attenuation gradient is calculated based on the sealed space formed. If the current vacuum attenuation gradient is not greater than the set value of the vacuum attenuation gradient (i.e., the second threshold mentioned above), then it is determined that there is a minor leakage fault in the fuel evaporation system, and a corresponding fault alarm is issued. If the current vacuum attenuation gradient is greater than the set value of the vacuum attenuation gradient (i.e., the second threshold mentioned above), then it is determined that there is no leakage in the fuel evaporation system. That is, after detecting both large and small leaks, it is determined that there is no leakage, i.e., there is no leakage fault in the current system.

[0072] In a preferred embodiment, fault detection of the charcoal canister solenoid valve includes: controlling the charcoal canister solenoid valve and the low-pressure pipeline sealing valve to close, and acquiring a first pressure from the fuel tank pressure sensor; if the first pressure is less than a third threshold, then determining that the charcoal canister solenoid valve has a stuck normally open fault; if the first pressure is not less than the third threshold, then controlling the charcoal canister solenoid valve and the low-pressure pipeline sealing valve to open, and acquiring a second pressure from the fuel tank pressure sensor within a first preset time range; if the second pressure is less than a fourth threshold, then determining that the charcoal canister solenoid valve is fault-free; if the second pressure is not less than the fourth threshold, then determining that the charcoal canister solenoid valve has a low flow fault.

[0073] In another preferred embodiment, the system further includes: a charcoal canister ventilation valve; the charcoal canister ventilation valve is connected to the charcoal canister; before performing fault detection on the charcoal canister solenoid valve and the low-pressure pipeline sealing valve respectively, the system further includes: controlling the charcoal canister solenoid valve and the low-pressure pipeline sealing valve to close, and controlling the charcoal canister ventilation valve to open; taking a third pressure from the tank pressure sensor within a second preset time range; if the third pressure is not equal to a fifth threshold, then determining that the charcoal canister ventilation valve has a jamming fault; if the third pressure is equal to the fifth threshold, then determining that the charcoal canister ventilation valve is fault-free, and closing the charcoal canister ventilation valve.

[0074] Specifically, such as Figure 3 The diagram shown is a flowchart of the fault detection process for each seal in the current system before leak detection, provided in this embodiment. First, the low-pressure pipeline sealing valve (10) and the charcoal canister solenoid valve (7) are opened to determine whether the diagnostic conditions of the evaporation system are met. Only when the diagnostic conditions are met will the next step be executed. The diagnostic conditions are fixed settings, namely, the engine coolant temperature is 60°C, the intake air temperature is 25°C, the vehicle is idling, and there are no other engine system faults. If there are other engine system faults, there is no need to perform fault detection on each seal, and a corresponding alarm indicating the presence of an engine system fault is issued. If there are no faults, the diagnosis of each seal in the current fuel evaporation system is performed.

[0075] First, close the low-pressure pipeline sealing valve (10) and the charcoal canister solenoid valve (7), and open the charcoal canister vent valve (5); obtain the pressure of the fuel tank pressure sensor (i.e., the third pressure) within the set time (i.e., the second preset time range mentioned above), and determine whether the third pressure is equal to the corresponding set value (i.e., the fifth threshold mentioned above); if it is not equal, it is determined that the charcoal canister vent valve (5) has a stuck fault; if it is equal, the charcoal canister vent valve (5) is not faulty, and the charcoal canister vent valve (5) is closed. Calculate whether the current fuel vapor evaporation pressure rise gradient value is greater than the corresponding set value. If it is, it is determined that the system has a fault, and the detection ends; if not, proceed to the next step. Obtain the current fuel system pressure (i.e., the first pressure mentioned above), and determine whether it is less than the corresponding set value (i.e., the third threshold mentioned above). If it is, it is determined that the charcoal canister solenoid valve (7) has a stuck normally open fault; if not, it is considered that the charcoal canister solenoid valve (7) does not have a stuck normally open fault, and control the charcoal canister solenoid valve (7) and the low-pressure pipeline sealing valve (10) to open. The oil tank pressure (i.e., the second pressure) within a set time period (i.e., the first preset time range mentioned above) is obtained. It is determined whether the second pressure is less than the corresponding set value 1 (i.e., the fourth threshold mentioned above). If it is, it is determined that the charcoal canister solenoid valve (7) is fault-free. If not, it is determined that the charcoal canister solenoid valve (7) has a low flow fault and a corresponding alarm is issued.

[0076] It should be noted that when opening the charcoal canister solenoid valve (7) and the low-pressure pipeline sealing valve (10), due to the presence of the low-pressure pipeline sealing valve (10), the spring in the charcoal canister solenoid valve (7) can be appropriately reduced in sealing force, making the opening process more sensitive, thereby ensuring opening performance at low flow rates. Furthermore, when selecting the low-pressure pipeline sealing valve (10), its spring force can be increased to ensure sealing performance. The spring force of the low-pressure pipeline sealing valve (10) is increased by raising the spring base, thereby increasing the spring compression force on the sealing surface and ensuring reliable sealing. The condition for adjusting the spring force is that the durability can reach 10. 6 The leakage was zero. The spring force of the charcoal canister solenoid valve (7) is reduced by lowering the height of the bottom step base of the spring to decrease the spring compression, thus enabling sensitive overcoming of the spring force when the magnetic core is energized, thereby opening the charcoal canister solenoid valve. The spring force adjustment condition is a durability operation of 10... 8 The initial traffic deviation was less than 3%.

[0077] like Figure 4 The diagram shown is a structural diagram of a low-pressure pipeline sealing valve (10) provided in this embodiment, which includes: a fixed iron core, a moving iron core, a guide sleeve, an upper housing, a sealing gasket, a spring, a coil, a guide post, a lower housing, and a pin. For better sealing, a larger spring force results in better sealing; for better responsiveness, a smaller spring force results in a more sensitive response. This invention adds a low-pressure pipeline sealing valve (10) and increases the spring force in the low-pressure pipeline sealing valve (10) to achieve higher sealing performance, while reducing the spring force in the charcoal canister solenoid valve (7) to make it more sensitive. This reduces wear on the charcoal canister solenoid valve (7) while ensuring good sealing performance throughout the system.

[0078] In a preferred embodiment, the system further includes: an intake manifold; the intake manifold is connected to the low-pressure line sealing valve; the control device is further configured to: when the vehicle engine is detected to be running and the fuel evaporation system reaches the desorption condition, control the low-pressure line sealing valve and the charcoal canister solenoid valve to open, so as to create a negative pressure in the intake manifold to desorb the fuel vapor in the charcoal canister; wherein the fuel vapor in the charcoal canister is generated from fuel in the fuel tank and then transferred to the charcoal canister.

[0079] Specifically, such as Figure 5The diagram shown is a flowchart of a fuel vapor desorption process provided in this embodiment. When desorbing fuel vapor from the automotive fuel evaporation system, i.e., when the engine is detected to be running and the fuel evaporation system reaches the desorption conditions, the low-pressure pipeline sealing valve (10) and the charcoal canister solenoid valve (7) are opened. When opening the charcoal canister solenoid valve (7), its PWM (Pulse Width Modulation) is controlled, and its duty cycle is kept within the range of 10% to 50%. This creates a negative pressure in the intake manifold, thereby desorbing the fuel vapor in the charcoal canister (4).

[0080] In another preferred embodiment, it further includes: a refueling vent valve; one end of the refueling vent valve is connected to the fuel tank, and the other end of the refueling vent valve is connected to the charcoal canister; the fuel vapor in the charcoal canister is generated from the fuel in the fuel tank and then transferred to the charcoal canister, including: after the fuel vapor is generated from the fuel in the fuel tank, it enters the charcoal canister through the refueling vent valve.

[0081] Specifically, a fuel tank (1) and a charcoal canister (4) are connected by a fuel vent valve (2), so that the fuel vapor generated in the fuel tank can enter the charcoal canister (4) through the fuel vent valve (2), thereby completing the corresponding fuel vapor desorption.

[0082] In a preferred embodiment, the control device is further configured to: control the low-pressure pipeline sealing valve and the charcoal canister solenoid valve to close when the vehicle engine is detected to have stopped, so that the charcoal canister solenoid valve absorbs and filters fuel vapor.

[0083] Specifically, such as Figure 6 The diagram shown is a flowchart of a fuel vapor filtration process under parking conditions provided in this embodiment. When the vehicle engine is detected to be off, the low-pressure pipeline sealing valve (10) and the charcoal canister solenoid valve (7) are closed, allowing the charcoal canister (4) to absorb and filter the fuel vapor before releasing it into the atmosphere, thereby reducing air pollution.

[0084] It should be added that the single charcoal canister solenoid valve used in the current fuel evaporation system, in order to meet the sealing requirements, results in about 10% of the charcoal canister solenoid valve parts failing to meet the opening sensitivity requirements. Furthermore, this structure, combined with the current control method, leads to wear and tear on the sealing surface of the charcoal canister solenoid valve. After about 3 years of use, approximately 5% of the charcoal canister solenoid valves will experience leakage and report a stuck, normally open fault. By using the solution of this invention, only an additional low-pressure pipeline sealing valve is needed (increasing the cost by about 50 yuan), and a matching control method is set. The sealing performance is guaranteed by the sealing valve, while the flexible adjustment of the desorption flow is guaranteed by the charcoal canister solenoid valve. This solves the contradiction between sensitivity and durable sealing that exists with the current single charcoal canister solenoid valve, avoiding low desorption flow faults and leakage faults due to poor sealing caused by durability, and reducing after-sales maintenance costs (repair and replacement costs are at least about 150 yuan per time). In other words, implementing this invention can also reduce operating costs in the long term.

[0085] Based on the above-described method embodiments, the present invention provides corresponding method embodiments.

[0086] like Figure 7 As shown, an embodiment of the present invention provides a method for detecting leaks in an automotive fuel evaporation system, applicable to the aforementioned leak detection device for automotive fuel evaporation systems, comprising:

[0087] Step S1: Control the low-pressure pipeline sealing valve and the charcoal canister solenoid valve to open, and obtain the pressure drop amplitude; if the pressure drop amplitude is not greater than the first threshold, it is determined that there is a large leakage fault in the fuel evaporation system; if the pressure drop amplitude is greater than the first threshold, control the low-pressure pipeline sealing valve and the charcoal canister solenoid valve to close.

[0088] Step S2: Calculate the current vacuum decay gradient. If the current vacuum decay gradient is not greater than the second threshold, it is determined that there is a small leak in the fuel evaporation system; if the current vacuum decay gradient is greater than the second threshold, it is determined that there is no leak in the fuel evaporation system.

[0089] It should be noted that the device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Furthermore, in the accompanying drawings of the device embodiments provided by this invention, the connection relationships between modules indicate that they have communication connections, which can be specifically implemented as one or more communication buses or signal lines. Those skilled in the art can understand and implement this without any creative effort.

[0090] Those skilled in the art will clearly understand that, for convenience and brevity, the specific working process of the device described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0091] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A leak detection device for an automotive fuel evaporation system, characterized in that, include: charcoal canister solenoid valve, low-pressure pipeline sealing valve, charcoal canister, fuel tank, fuel tank pressure sensor and control equipment; The low-pressure pipeline sealing valve, the charcoal canister solenoid valve, the charcoal canister, and the fuel tank are connected in sequence. The fuel tank pressure sensor is mounted on the fuel tank; The control device is used to control the opening of the low-pressure pipeline sealing valve and the charcoal canister solenoid valve, and to obtain the pressure drop amplitude; if the pressure drop amplitude is not greater than a first threshold, it is determined that there is a large leakage fault in the fuel evaporation system; if the pressure drop amplitude is greater than the first threshold, it controls the low-pressure pipeline sealing valve and the charcoal canister solenoid valve to close; it calculates the current vacuum degree decay gradient; if the current vacuum degree decay gradient is not greater than a second threshold, it is determined that there is a small leakage fault in the fuel evaporation system; if the current vacuum degree decay gradient is greater than the second threshold, it is determined that there is no leakage in the fuel evaporation system. The control of the low-pressure pipeline sealing valve and the carbon canister solenoid valve to open includes: Perform fault detection on the charcoal canister solenoid valve and the low-pressure pipeline sealing valve respectively. When there is no fault in either the charcoal canister solenoid valve or the low-pressure pipeline sealing valve, control the low-pressure pipeline sealing valve and the charcoal canister solenoid valve to open. Fault detection of the charcoal canister solenoid valve includes: The solenoid valve of the charcoal canister and the sealing valve of the low-pressure pipeline are closed to obtain the first pressure from the oil tank pressure sensor. If the first pressure is less than the third threshold, it is determined that the carbon canister solenoid valve has a stuck, normally open fault. If the first pressure is not less than the third threshold, then control the opening of the carbon canister solenoid valve and the low-pressure pipeline sealing valve to obtain the second pressure of the oil tank pressure sensor within the first preset time range. If the second pressure is less than the fourth threshold, the charcoal canister solenoid valve is determined to be fault-free. If the second pressure is not less than the fourth threshold, then it is determined that the charcoal canister solenoid valve has a low flow fault.

2. The leakage detection device for an automotive fuel evaporation system as described in claim 1, characterized in that, Also includes: Charcoal canister ventilation valve; The charcoal canister ventilation valve is connected to the charcoal canister; Before performing fault detection on the charcoal canister solenoid valve and the low-pressure pipeline sealing valve, the following steps are also included: Control the charcoal canister solenoid valve and the low-pressure pipeline sealing valve to close, and control the charcoal canister ventilation valve to open; Obtain the third pressure from the tank pressure sensor within the second preset time range; If the third pressure is not equal to the fifth threshold, then it is determined that the charcoal canister ventilation valve is stuck. If the third pressure is equal to the fifth threshold, then the charcoal canister ventilation valve is determined to be fault-free and is closed.

3. The leakage detection device for an automotive fuel evaporation system as described in claim 2, characterized in that, Also includes: Intake manifold; The intake manifold is connected to the low-pressure pipeline sealing valve; The control device is also used for: When the engine is detected to be running and the fuel vaporization system reaches the desorption condition, the low-pressure pipeline sealing valve and the charcoal canister solenoid valve are opened to create a negative pressure in the intake manifold and desorb the fuel vapor in the charcoal canister. The fuel vapor in the charcoal canister is generated from fuel in the fuel tank and then transferred to the charcoal canister.

4. The leakage detection device for an automotive fuel evaporation system as described in claim 3, characterized in that, Also includes: Fuel vent valve; One end of the refueling vent valve is connected to the fuel tank, and the other end of the refueling vent valve is connected to the charcoal canister. The fuel vapor in the charcoal canister is generated from fuel in the fuel tank and then transferred to the charcoal canister, including: After fuel vapor is generated in the fuel tank, it enters the charcoal canister through the refueling vent valve.

5. A leak detection device for an automotive fuel evaporation system as described in claim 4, characterized in that, The control device is also used for: When the vehicle engine stops, the low-pressure line sealing valve and the charcoal canister solenoid valve are closed so that the charcoal canister solenoid valve can absorb and filter fuel vapors.

6. A method for detecting leaks in an automotive fuel evaporation system, characterized in that, Applicable to a leak detection device for an automotive fuel evaporation system as described in any one of claims 1-5; The method for detecting leaks in the automotive fuel evaporation system includes: Control the opening of the low-pressure pipeline sealing valve and the carbon canister solenoid valve, and obtain the pressure drop rate; If the pressure drop is not greater than the first threshold, it is determined that there is a large leakage fault in the fuel evaporation system. If the pressure drop exceeds the first threshold, the low-pressure pipeline sealing valve and the carbon canister solenoid valve will be closed. Calculate the current vacuum decay gradient. If the current vacuum decay gradient is not greater than the second threshold, it is determined that there is a minor leak in the fuel evaporation system. If the current vacuum decay gradient is greater than the second threshold, it is determined that there is no leak in the fuel evaporation system; The control of the low-pressure pipeline sealing valve and the carbon canister solenoid valve to open includes: Perform fault detection on the charcoal canister solenoid valve and the low-pressure pipeline sealing valve respectively. When there is no fault in either the charcoal canister solenoid valve or the low-pressure pipeline sealing valve, control the low-pressure pipeline sealing valve and the charcoal canister solenoid valve to open. Fault detection of the charcoal canister solenoid valve includes: The solenoid valve of the charcoal canister and the sealing valve of the low-pressure pipeline are closed to obtain the first pressure from the oil tank pressure sensor. If the first pressure is less than the third threshold, it is determined that the carbon canister solenoid valve has a stuck, normally open fault. If the first pressure is not less than the third threshold, then control the opening of the carbon canister solenoid valve and the low-pressure pipeline sealing valve to obtain the second pressure of the oil tank pressure sensor within the first preset time range. If the second pressure is less than the fourth threshold, the charcoal canister solenoid valve is determined to be fault-free. If the second pressure is not less than the fourth threshold, then it is determined that the charcoal canister solenoid valve has a low flow fault.

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