Leak diagnostor for evaporative emission system

Abstract

The utility model provides a leakage diagnosis device for an evaporative emission system. The leakage diagnosis device comprises a shell, a pressurization assembly, a one-way valve assembly and a pipeline switching assembly. The shell comprises an air inlet, an air outlet, a first chamber and a second chamber, the first chamber and the second chamber are respectively communicated with the air inlet, the air outlet is communicated with the second chamber, and the first chamber is communicated with the second chamber and the air outlet through a first pipeline; the pressurizing assembly and the one-way valve assembly are arranged in the first cavity, the pipeline switching assembly is located in the second cavity, and the pipeline switching assembly is used for controlling communication between the first pipeline and the second cavity; the first chamber, the second chamber and the first pipeline are arranged in the shell, and the pipeline switching assembly is arranged in the second chamber, so that switching of different gas guide passages of the first chamber, the atmosphere outlet and the carbon tank is realized, pressure is favorably established for the evaporation system, the pressure is detected, and the running state of the system is quickly and accurately judged; and judging whether leakage exists in the system.

Description

Technical Field

[0001] This utility model relates to the field of vehicle testing technology, and more specifically, to a leak diagnostic tool for evaporative emission systems. Background Technology

[0002] During vehicle use, it is essential to detect leaks in the evaporative emission system, which consists of the fuel tank and the entire evaporative piping. This is where fuel tank leak diagnostic modules come in.

[0003] The existing method for leak diagnosis in fuel evaporative emission systems involves installing a DMTL module within the system. This module integrates a motor-driven rotary vane pump and a solenoid valve. The module's internal flow channels include a main chamber open to the atmosphere and a high-pressure chamber. The high-pressure chamber has a reference port for calibration. The DMTL leak diagnosis module operates in two modes: reference mode and diagnostic mode, switched using a solenoid valve. By energizing the solenoid coil within the valve, the electromagnetic force drives the iron core and valve together, opening and closing the valve. Switching between these modes allows the rotary vane pump to either pump air into the reference port or pump air into the entire evaporative emission system. The motor current of the rotary vane pump is compared between these two modes to determine if a leak larger than 0.5 mm is present. However, due to the relatively low diagnostic current of the rotary vane pump (20-50mA), the diagnostic results are greatly affected by the environment, especially factors such as air humidity, the friction of the rotary vane pump, wear, and foreign object jamming. Based on actual market feedback, the probability of misdiagnosis is relatively high. In addition, the reference hole between the solenoid valve and the rotary vane pump makes the pipeline complex and the accuracy of the test results low.

[0004] Therefore, existing technologies suffer from technical problems such as being highly susceptible to environmental influences, having a high misdiagnosis rate, and low accuracy of test results. Utility Model Content

[0005] The main objective of this invention is to provide a leak diagnostic device for evaporative emission systems, in order to solve the technical problems of existing diagnostic methods being greatly affected by the environment, having a high misdiagnosis rate, and low accuracy of test results.

[0006] To achieve the above objectives, according to one aspect of the present invention, a leak diagnostic device for an evaporative emission system is provided, the leak diagnostic device comprising:

[0007] The housing includes an air inlet, an air outlet, a first chamber, and a second chamber. The first chamber and the second chamber are respectively connected to the air inlet, and the air outlet is connected to the second chamber. The first chamber is connected to the second chamber and the air outlet through a first pipeline.

[0008] A pressurizing assembly, which is fixedly connected to the housing, is disposed in the first chamber on the side away from the first pipeline;

[0009] A one-way valve assembly, which is connected to the pressurizing assembly, is disposed in the first chamber and located between the pressurizing assembly and the first pipeline;

[0010] A pipeline switching assembly is located in the second chamber. The pipeline switching assembly includes a solenoid valve, a sealing valve, and a return spring. The pipeline switching assembly is used to control the fluid communication between the first pipeline and the second chamber. So when the first pipeline is connected to the second chamber, the gas pressurized by the pressurization assembly can pass through the one-way valve, the first pipeline, and the second chamber in sequence, and finally leave the housing from the gas outlet.

[0011] Furthermore, a first valve seat is provided on the side of the second chamber near the first pipeline. The first valve seat has a cylindrical structure with one end open. The bottom surface and / or side surface of the valve seat are connected to the air outlet. At least a portion of the pressurizing component can abut against the first valve seat to close or open the ventilation path between the second chamber and the air outlet. A first vent hole is provided at the bottom of the first valve seat, and the first vent hole is connected to the first pipeline.

[0012] Furthermore, the solenoid valve includes a fixed iron core and an armature. The fixed iron core has a through hole at its center. At least a portion of the sealing valve passes through the through hole at the center of the fixed iron core. Driven by electromagnetic force and the action of a return spring, the sealing valve reciprocates in the second chamber.

[0013] Furthermore, the sealing valve includes a valve stem, a sealing valve frame, and an elastic sealing part. One end of the valve stem passes through the central through hole of the fixed iron core, and the other end of the valve stem is detachably connected to the sealing valve frame. The elastic sealing part is connected to the sealing valve frame and can abut against the first valve seat under the action of the solenoid valve.

[0014] Furthermore, one end of the return spring abuts against the elastic sealing part, and the other end of the return spring abuts against the first valve seat.

[0015] Furthermore, the pipeline switching assembly also includes a bracket, the bracket having a connecting hole in the middle, the sealing valve passing through the connecting hole and connected to the solenoid valve, and the bracket having ribs for limiting the movement path of the sealing valve.

[0016] Furthermore, the one-way valve assembly includes: a second valve seat, at least a portion of which is sealed and fixedly connected to the housing, the second valve seat having a mounting hole located at the center of the second valve seat and at least one vent hole located around the mounting hole; and an umbrella valve, which is fixedly connected to the second valve seat through the mounting hole, at least a portion of which is made of an elastic material, the elastic material covering the vent hole.

[0017] Furthermore, the second valve seat includes a body and a connecting portion. The connecting portion is a cylindrical shape with one end open, extending from the body toward the first pipeline. The outer wall of the connecting portion abuts and is fixed to the inner wall of the first pipeline.

[0018] Furthermore, an elastic sealing ring is provided between the outer wall of the connecting part and the inner wall of the first pipeline; the umbrella valve includes a valve stem and an umbrella-shaped sealing part, the valve stem is connected to the mounting hole, and a positioning part is provided on the valve stem, the positioning part being able to abut against the side of the second valve seat away from the first pipeline.

[0019] Furthermore, the housing also has a third chamber, which is connected to the first pipeline, and the first chamber, the second chamber, and the third chamber are arranged in parallel.

[0020] The leak diagnostic device for evaporative emission systems provided by this utility model forms multiple gas guide paths between the first chamber and the carbon canister by setting a first chamber, a second chamber, and a first pipeline in the housing, and setting a pipeline switching component in the second chamber. This realizes different gas guide paths between the first chamber and the atmospheric outlet and the carbon canister, which is conducive to establishing pressure in the evaporation system. By detecting the pressure, the operating status of the system can be quickly and accurately determined, and whether there is a leak in the system can be determined. The structure is simple and easy to assemble. Attached Figure Description

[0021] The accompanying drawings, which form part of this application, are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an undue limitation of the present invention. In the drawings:

[0022] Figure 1 A schematic diagram of a leak diagnostic device for an evaporative emission system according to the present invention is shown.

[0023] Figure 2 A schematic diagram of the structure of the housing according to the present invention is shown;

[0024] Figure 3 A schematic diagram of the one-way valve according to the present invention is shown;

[0025] Figure 4A schematic diagram of the valve cover according to the present invention is shown.

[0026] Figure 5 A schematic diagram of the valve seat according to the present invention is shown.

[0027] Figure 6 A schematic diagram of the support structure according to the present invention is shown.

[0028] The above figures include the following reference numerals:

[0029] 10. Housing; 11. Air inlet; 12. Air outlet; 13. First chamber; 14. Second chamber; 141. First valve seat; 142. First vent hole; 15. First pipeline; 16. Upper housing; 17. Lower housing; 20. Pressurization assembly; 30. One-way valve assembly; 31. Second valve seat; 311. Body; 312. Connecting part; 32. Umbrella valve; 321. Connecting rod; 322. Umbrella-shaped sealing part; 40. Pipeline switching assembly; 41. Solenoid valve; 411. Fixed iron core; 412. Armature; 42. Sealing valve; 421. Valve stem; 422. Sealing valve frame; 423. Elastic sealing part; 43. Return spring; 44. Bracket; 441. Rib; 442. Limiting ring. Detailed Implementation

[0030] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present utility model or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the scope of protection of the present utility model.

[0031] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this application. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0032] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps described in these embodiments do not limit the scope of this invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0033] During vehicle use, to prevent volatile substances in the fuel tank from being directly released into the air, a carbon canister is usually installed between the fuel tank and the atmosphere to absorb the evaporative emissions from the fuel tank. To ensure the absorption effect, it is necessary to check for leaks in the evaporative emission system, which consists of the fuel tank and the entire evaporative piping.

[0034] However, as mentioned earlier, the existing detection method using DMTL modules has a relatively high probability of misdiagnosis. In addition, the reference hole between the solenoid valve and the rotary vane pump results in complex piping and low accuracy of the detection results.

[0035] To address the technical problems of complex piping and cumbersome installation in existing technologies, this invention provides a leak diagnostic device for evaporative emission systems.

[0036] like Figures 1 to 6 As shown, this utility model provides a leak diagnostic device for an evaporative emission system. The leak diagnostic device includes a housing 10, a pressurization assembly 20, a one-way valve assembly 30, and a pipeline switching assembly 40. The housing 10 includes an air inlet 11, an air outlet 12, a first chamber 13, and a second chamber 14. The air inlet 11 is connected to the outside air to provide fresh air to the system. The air outlet 12 is connected to a carbon canister, allowing high-pressure air or fresh air to be selectively introduced into the fuel tank through the carbon canister. The first chamber 13 and the second chamber 14 are respectively connected to the air inlet 11, and the air outlet 12 is connected to the second chamber 14. The first chamber 13 is connected to the second chamber 14 and the air outlet 12 through a first pipeline 15, thus giving the first chamber 13 two air passages that can achieve fluid communication with the outside atmosphere and the air outlet 12, respectively.

[0037] The air inlet 11 is located in the middle of the housing 10, between the first chamber 13 and the second chamber 14. This arrangement is beneficial for the pipeline arrangement between the first chamber 13, the second chamber 14 and the air inlet 11.

[0038] The housing 10 includes an upper housing 16 and a lower housing 17, which are sealed together. An air inlet 11, an air outlet 12, and a first pipeline 15 are all located on the lower housing 17. An electrical connector for electrical connection with the vehicle is provided on the upper housing 16. The first chamber 13 and the second chamber 14 are jointly enclosed by the upper housing 16 and the lower housing 17.

[0039] Optionally, the upper housing 16 and the lower housing 17 are snap-fitted together or laser-welded; both the upper housing 16 and the lower housing 17 are integrally formed, which can reduce costs and further improve the airtightness of the housing.

[0040] The pressurizing assembly 20 is fixedly connected to the housing 10. The pressurizing assembly 20 is located on the side of the first chamber 13 away from the first pipeline 15. The pressurizing assembly 20 can pressurize the air entering the first chamber 13 and transmit the pressurized high-pressure air to the one-way valve assembly 30. The one-way valve assembly 30 is connected to the pressurizing assembly 20 and is located within the first chamber 13, between the pressurizing assembly 20 and the first pipeline 15. Thus, the high-pressure gas transmitted from the pressurizing assembly 20 can enter the first pipeline 15 through the one-way valve assembly 30. By arranging the one-way valve assembly 30, a one-way transmission path from the first chamber 13 to the second chamber 14 can be defined, allowing high-pressure gas to be transmitted to the carbon canister and oil tank through the second chamber 14.

[0041] The pipeline switching assembly 40 is located in the second chamber 14. The pipeline switching assembly 40 includes a solenoid valve 41, a sealing valve 42 and a return spring 43. Under the control of the solenoid valve 41, the sealing valve 42 controls the fluid communication between the first pipeline 15 and the second chamber 14. Thus, when the first pipeline 15 is connected to the second chamber 14, the gas pressurized by the pressurizing assembly 20 can pass through the one-way valve, the first pipeline 15 and the second chamber 14 in sequence, and finally leave the housing from the outlet 12 and enter the oil tank through the carbon canister.

[0042] The leak diagnostic device provided by this utility model, by setting a first chamber 13, a second chamber 14 and a first pipeline 15 in the housing, and setting a pipeline switching component 40 in the second chamber 14, forms multiple gas guiding paths between the first chamber 13 and the carbon canister. This realizes different gas guiding paths between the first chamber 13 and the atmospheric outlet and the carbon canister, which is conducive to establishing pressure in the evaporation system. By monitoring the pressure, the operating status of the system can be quickly and accurately determined, and whether there is a leak in the system can be determined. The structure is simple and the assembly is convenient.

[0043] Furthermore, a first valve seat 141 is provided on the side of the second chamber 14 near the first pipeline 15. The first valve seat 141 has a cylindrical structure with one end open. The bottom surface and / or side surface of the valve seat are connected to the air outlet 12. The sealing valve 42 can abut against the first valve seat 141 under the drive of the solenoid valve 41 to close or open the ventilation path between the second chamber 14 and the air outlet 12. A first vent hole 142 is provided at the bottom of the first valve seat 141. The first vent hole 142 is connected to the first pipeline 15. Thus, when the sealing valve 42 abuts against the first valve seat 141, the sealing valve 42 simultaneously cuts off the communication path between the second chamber 14 and the first chamber 13, as well as between the second chamber 14 and the outside. At this time, the first chamber 13 is directly connected to the carbon canister only through the first pipeline 15.

[0044] Preferably, a spring abutment portion is formed inside the first valve seat 141, and a first vent hole 142 is formed at the center of the spring abutment portion. The outer diameter of the spring abutment portion matches the inner diameter of the return spring 43 to achieve quick assembly and positioning of the return spring 43.

[0045] Furthermore, the housing may also be provided with a third chamber, which is connected to the first pipeline 15. The first chamber 13, the second chamber 14 and the third chamber are arranged in parallel. The third chamber is connected to a pressure sensor, so that the pressure in the system can be collected through the pressure sensor.

[0046] As shown in the figure, the pressurization assembly 20 includes an air pump located in the first chamber 13. The air inlet 11 of the housing is connected to the chamber at the air pump end. Gas enters the chamber of the air pump section through the inlet. The air pump inlet is connected to the interior of the chamber. The air pump outlet is connected to the one-way valve assembly 30. After passing through the air pump, the gas passes through the one-way valve, the second chamber 14, the air outlet 12, and enters the carbon canister in sequence, thereby establishing pressure for the evaporation system.

[0047] The solenoid valve 41 includes a fixed iron core 411 and an armature 412. At least a part of the sealing valve 42 passes through the central through hole of the fixed iron core 411 and is axially positioned. Driven by electromagnetic force and under the action of the return spring 43, the sealing valve 42 reciprocates in the second chamber 14.

[0048] Specifically, the sealing valve 42 includes a valve stem 421, a sealing valve frame 422, and an elastic sealing part 423. One end of the valve stem 421 passes through the central through hole of the fixed iron core 411, and the other end of the valve stem 421 is detachably connected to the sealing valve frame 422. The elastic sealing part 423 is connected to the sealing valve frame and can abut against the first valve seat 141 under the action of the solenoid valve 41, thereby achieving a seal on the first valve seat 141.

[0049] Preferably, the elastic sealing part 423 is made of rubber and can be fixed to the sealing valve skeleton by vulcanization; the valve stem 421 is provided with a first positioning ring and a second positioning ring, the sealing valve skeleton is provided with an installation part and a clearance opening, the valve stem 421 is fixedly connected to the installation part through the clearance opening, and the installation positioning of the installation part is achieved by the first positioning ring and the second positioning ring.

[0050] To ensure smooth opening of the passage, one end of the return spring 43 abuts against the elastic sealing part 423, and the other end of the return spring 43 abuts against the spring abutment part in the first valve seat 141. After the solenoid valve 41 is de-energized, the return spring 43 pushes the sealing valve 42 upward to open the air passage between the second chamber 14 and the first pipeline 15 and the air outlet 12. At the same time, under the force of the return spring 43, the sealing valve frame 422 abuts against the step of the first positioning ring of the valve stem 421, thereby improving the stability of the connection between the valve stem 421 and the sealing valve frame.

[0051] Furthermore, the pipeline switching assembly 40 also includes a bracket 44, with a connecting hole in the middle of the bracket 44. The sealing valve 42 passes through the connecting hole and is connected to the solenoid valve 41. The bracket 44 is provided with a rib plate 441 for limiting the movement path of the sealing valve 42. The sealing valve skeleton 422 and the rib plate 441 are in clearance fit in the circumferential direction, thereby ensuring circumferential positioning.

[0052] Among them, three ribs 441 can be provided, and the three ribs 441 are evenly distributed around the sealing valve skeleton. A limiting ring 442 can also be provided at the front end of the rib 441. The limiting ring 442 can further ensure the centering of the sealing valve skeleton during the movement.

[0053] In another embodiment of this application, the one-way valve assembly 30 includes a second valve seat 31 and an umbrella valve 32. At least a portion of the second valve seat 31 is sealed and fixedly connected to the housing. The second valve seat 31 has a mounting hole located at the center of the second valve seat 31 and at least one vent hole located around the mounting hole. When there are two or more vent holes, the vent holes are evenly distributed around the mounting hole. The umbrella valve 32 is fixedly connected to the second valve seat 31 through the mounting hole. At least a portion of the umbrella valve 32 is made of elastic material, and the elastic material covers the vent holes, thereby achieving a seal on the vent holes. When the pressure in the first pipeline 15 is large, the pressure in the first pipeline 15 acts on the surface of the umbrella valve 32, causing the umbrella valve 32 to abut against the vent holes, thereby achieving a seal on the vent holes.

[0054] Furthermore, the second valve seat 31 includes a body 311 and a connecting part 312. The connecting part 312 is a cylindrical shape with one end open and extends from the body 311 toward the first pipeline 15. The outer wall of the connecting part 312 abuts and is fixed to the inner wall of the first pipeline 15.

[0055] To improve the airtightness of the system, an elastic sealing ring is provided between the outer wall of the connecting part 312 and the inner wall of the first pipeline 15, and an installation groove for installing the elastic sealing ring is provided on the outer periphery of the second valve seat 31; the installation groove facilitates the installation and positioning of the elastic sealing ring; preferably, the elastic sealing ring can be, for example, an O-ring.

[0056] The umbrella valve 32 includes a connecting rod 321 and an umbrella-shaped sealing part 322. The valve stem 421 and the umbrella-shaped sealing part 322 are integrally formed. The connecting rod 321 is connected to the mounting hole. The outer diameter of the valve stem 421 gradually decreases from the end connected to the umbrella-shaped sealing part 322 to the end away from the umbrella-shaped sealing part 322. A positioning part is provided on the connecting rod 321. The positioning part can abut against the side of the second valve seat 31 away from the first pipeline 15. This arrangement is beneficial to the assembly and fixation between the valve stem 421 and the second valve seat 31.

[0057] The umbrella-shaped sealing part 322 is made of rubber and can cover the vent hole, thereby achieving a one-way seal on the vent hole.

[0058] During use, the solenoid valve 41 is a normally open solenoid valve. When the solenoid valve 41 is de-energized, it opens, and the air inlet 11 and air outlet 12 of the housing are directly connected in the second chamber 14, ensuring low air flow resistance during carbon canister desorption. When the solenoid valve 41 is energized, it closes, shutting off the channel connecting the air inlet 11 and air outlet 12 inside the housing. Gas must be pumped from the air inlet 11 of the housing to the one-way valve assembly 30 inside the housing via the air pump, and then enter the carbon canister through the first pipeline 15, forming a stable pressure for monitoring whether there is a leak in the system.

[0059] Specifically, various pressure testing methods can be used to determine whether a leak exists, for example:

[0060] By pressurizing the oil tank to build up the internal pressure to 5 kPa (set value), the measured pressure build-up time is compared with the pressure build-up time when a standard leak hole is present in the oil tank. A longer depressurization time compared to the time required to build up pressure with a standard leak hole indicates a failure. If the depressurization time is too long, it may indicate a system leak, or a malfunction in the diaphragm pump itself, preventing rapid pressure build-up. Alternatively...

[0061] Once the system pressure reaches 5 kPa, the leakage situation in the oil tank and evaporator exhaust system is determined by comparing the time it takes for the evaporator system pressure to decrease from 4 kPa to 3 kPa. If the time taken to reduce pressure is shorter than the system's set time, or if the calculated pressure reduction rate is faster than the set rate, then a leak exists; or...

[0062] Once the system pressure is built up to 5 kPa, the integral of the pressure in the evaporator system decreasing from 4 kPa to 3 kPa over time is used to determine the leakage status of the oil tank and evaporator exhaust system; if the calculated integral value is smaller than the set value, then a leak exists.

[0063] The leak diagnostic device provided by this utility model, by setting a first chamber 13, a second chamber 14 and a first pipeline 15 in the housing, and setting a pipeline switching component 40 in the second chamber 14, forms multiple gas guiding paths between the first chamber 13 and the carbon canister. This realizes different gas guiding paths between the first chamber 13 and the atmospheric outlet and the carbon canister, which is conducive to establishing pressure in the evaporation system. By monitoring the pressure, the operating status of the system can be quickly and accurately determined, and whether there is a leak in the system can be determined. The structure is simple and the assembly is convenient.

[0064] In the description of this utility model, it should be understood that the directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this utility model. The directional terms "inner" and "outer" refer to the inner and outer contours of each component itself.

[0065] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0066] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be construed as limiting the scope of protection of this utility model.

[0067] The above are merely preferred embodiments of this utility model and are not intended to limit the scope of this utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A leak diagnostic device for an evaporative emission system, characterized in that, The leak diagnostic tool includes: The housing includes an air inlet and an air outlet. A first chamber and a second chamber are formed inside the housing. The first chamber and the second chamber are respectively connected to the air inlet. The air outlet is connected to the second chamber. The first chamber is connected to the second chamber and the air outlet through a first pipeline. A pressurizing assembly, which is fixedly connected to the housing, is disposed on the side of the first chamber away from the first pipeline; A one-way valve assembly, which is connected to the pressurizing assembly, is disposed in the first chamber and located between the pressurizing assembly and the first pipeline; A pipeline switching assembly is located in the second chamber. The pipeline switching assembly includes a solenoid valve, a sealing valve, and a return spring. The pipeline switching assembly is used to control the fluid communication between the first pipeline and the second chamber. So when the first pipeline is connected to the second chamber, the gas pressurized by the pressurization assembly can pass through the one-way valve, the first pipeline, and the second chamber in sequence, and finally leave the housing from the gas outlet.

2. The leak diagnostic device for an evaporative emission system according to claim 1, characterized in that, A first valve seat is provided on the side of the second chamber near the first pipeline. The first valve seat has a cylindrical structure with one end open. The bottom surface and / or side surface of the first valve seat are connected to the air outlet. At least a portion of the pressurizing component can abut against the first valve seat to close or open the ventilation path between the second chamber and the air outlet. A first vent hole is provided at the bottom of the first valve seat, and the first vent hole is connected to the first pipeline.

3. The leak diagnostic device for an evaporative emission system according to claim 2, characterized in that, The solenoid valve includes a fixed iron core and an armature. The fixed iron core has a through hole at its center. At least a portion of the sealing valve passes through the through hole at the center of the fixed iron core. Driven by electromagnetic force and the action of a return spring, the sealing valve reciprocates in the second chamber.

4. The leak diagnostic device for an evaporative emission system according to claim 3, characterized in that, The sealing valve includes a valve stem, a sealing valve frame, and an elastic sealing part. One end of the valve stem passes through a through hole in the center of the fixed iron core, and the other end of the valve stem is detachably connected to the sealing valve frame. The elastic sealing part is connected to the sealing valve frame and can abut against the first valve seat under the action of the solenoid valve.

5. The leak diagnostic device for an evaporative emission system according to claim 4, characterized in that, One end of the return spring abuts against the elastic sealing part, and the other end of the return spring abuts against the first valve seat.

6. The leak diagnostic device for an evaporative emission system according to claim 3, characterized in that, The pipeline switching assembly also includes a bracket with a connecting hole in the middle. The sealing valve passes through the connecting hole and is connected to the solenoid valve. The bracket is provided with ribs for limiting the movement path of the sealing valve.

7. The leak diagnostic device for an evaporative emission system according to claim 1, characterized in that, The one-way valve assembly includes: A second valve seat, at least a portion of which is sealed and fixedly connected to the housing, the second valve seat having a mounting hole located at the center of the second valve seat and at least one vent hole located around the mounting hole; An umbrella-shaped valve is fixedly connected to the second valve seat through the mounting hole. At least a portion of the umbrella-shaped valve is made of an elastic material, which covers the vent hole.

8. The leak diagnostic device for an evaporative emission system according to claim 7, characterized in that, The second valve seat includes a body and a connecting part. The connecting part is a cylindrical shape with one end open and extends from the body toward the first pipeline. The outer wall of the connecting part abuts and is fixed to the inner wall of the first pipeline.

9. The leak diagnostic device for an evaporative emission system according to claim 8, characterized in that, An elastic sealing ring is provided between the outer wall of the connecting part and the inner wall of the first pipeline; the umbrella valve includes a valve stem and an umbrella-shaped sealing part, the valve stem is connected to the mounting hole, and a positioning part is provided on the valve stem, the positioning part being able to abut against the side of the second valve seat away from the first pipeline.

10. The leak diagnostic device for an evaporative emission system according to claim 1, characterized in that, The housing includes an upper housing and a lower housing. The lower part of the upper housing is sealed to the upper part of the lower housing. The upper housing and the lower housing are integrally formed and enclose the first chamber, the second chamber, and the first pipeline.

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