A fuel evaporation control system

Abstract

The present invention discloses a fuel evaporation control system. It includes an engine control unit, a fuel tank assembly, a carbon canister assembly, and an on-vehicle leak diagnosis device. The on-vehicle leak diagnosis device includes an upper end cover, a booster pump assembly, a valve body, a lower end cover, a sliding float, a micro spring, a rubber diaphragm assembly, and a micro switch. When the booster pump assembly is not powered on, the first pipe joint communicates with the second pipe joint through the lateral hole of the conduit to allow air flow through; when the booster pump assembly is powered on, a part of the air flow flows into the passage of the second pipe joint through the lateral hole of the conduit, and another part of the air flow enters the detection chamber through the detection hole of the conduit to push the rubber diaphragm assembly to deform and cause the micro switch to act. The engine control unit determines whether the system leaks according to the action condition of the micro switch. The present invention can diagnose the leakage of the system pipeline without adding a pressure sensor, with lower cost, and the modular function of the device has a higher integration degree, which is convenient for later maintenance.

Description

Technical Field

[0001] The invention belongs to the technical field of vehicle fuel vapor leakage diagnosis, and in particular relates to a fuel evaporation control system. Background Art

[0002] The fuel evaporation control system is usually composed of a fuel tank assembly, a carbon canister assembly, an ash filter, a carbon canister desorption control valve and its connecting pipes. If any part in the fuel evaporation control system leaks, the system will fail and eventually pollute the environment. Therefore, the newly issued emission regulations have clearly required the installation of an on-board diagnostic system (OBD) to identify possible leaks and send signals, and then provide the corresponding data to the on-board memory for the factory to perform offline diagnosis.

[0003] The German patent discloses a device for detecting the tightness of a motor vehicle fuel system. The device is composed of a vane pump, an electromagnetic reversing valve, a reference orifice plate, and the calibration logic is to judge whether the fuel system is leaking by comparing the voltage and current characteristics of the vane pump passing through the fuel system and the reference orifice plate. Due to the complex structure and high cost of the device, its application range is small.

[0004] Application number: 202010889204.0 Chinese patent discloses a patent for an on-board leak diagnostic device and a fuel evaporation control system. The device is equipped with an upper end cover, a boost pump assembly, a valve body, a lower end cover, a sliding float, a micro spring and other components. However, when the device is used in a fuel evaporation control system, a pressure sensor needs to be added to the system, which is costly. Summary of the invention

[0005] The purpose of the present invention is to solve the deficiencies of the above-mentioned background technology and provide a fuel evaporation control system.

[0006] The technical solution adopted by the present invention is: a fuel evaporation control system, comprising an engine control unit, a fuel tank assembly, a carbon canister assembly and an on-board leakage diagnosis device, wherein the atmospheric pipe port of the carbon canister assembly is connected to the on-board leakage diagnosis device, and the rear of the on-board leakage diagnosis device is connected to an ash filter; the carbon canister desorption port of the carbon canister assembly is connected to a desorption control valve, and the engine control unit is respectively connected to the on-board leakage diagnosis device and the desorption control valve through a wiring harness;

[0007] The on-vehicle leakage diagnostic device comprises an upper end cover, a boost pump assembly, a valve body, a lower end cover, a sliding float, a micro spring, a rubber diaphragm assembly and a micro switch, wherein the upper end cover is fixedly arranged at the top end of the valve body, and the lower end cover is fixedly arranged at the bottom end of the valve body; the upper end cover is provided with a first pipe joint connected to the ash filter, and the valve body is provided with a second pipe joint connected to the atmospheric pipe port of the carbon canister; a boost pump chamber and a conduit are provided in the valve body, a detection chamber is provided on one side of the valve body, the boost pump assembly is installed in the boost pump chamber, and the sliding float and the micro spring are installed in the conduit; the micro switch is sealed and fixed to the opening side of the detection chamber, the micro switch is electrically connected to the engine control unit, and the rubber diaphragm is provided between the detection chamber and the micro switch to divide the detection chamber into two closed spaces;

[0008] When the boost pump assembly is not powered, the first pipe joint and the second pipe joint are connected through the lateral hole of the conduit to enable airflow to pass through; when the boost pump assembly is powered, the airflow from the ash filter enters the boost pump assembly from the first pipe joint, is compressed by the boost pump assembly, and the airflow pressure overcomes the force of the micro spring to push the sliding float upward, and a part of the airflow flows into the passage of the second pipe joint through the lateral hole of the conduit, and the other part of the airflow enters the detection chamber through the detection hole of the conduit to push the rubber diaphragm assembly to deform and activate the microswitch. The engine control unit determines whether the system is leaking based on the action of the microswitch.

[0009] Furthermore, the rubber diaphragm assembly includes a floating plate, a rubber ring and a sealing ring, the floating plate is fixed to one end of the rubber ring, the sealing ring is fixed to the other end of the rubber ring, the side of the sealing ring close to the floating plate is gap-matched with the flange inner ring of the detection chamber, the side of the sealing ring away from the floating plate is sealingly matched with the edge of the side end cover of the micro switch, and a boss is provided in the middle of a side surface of the floating plate close to the rubber ring, the boss is in contact with the spring sheet of the micro switch, and when the airflow enters the detection chamber, the floating plate is pushed to move, thereby causing the spring sheet in contact with the boss to deform and cause the micro switch to operate.

[0010] Furthermore, a plurality of supporting frustums are provided on a side of the floating plate away from the rubber ring.

[0011] Furthermore, the micro switch includes a side end cover, a spring and two switch PIN pins, the inner edge of the side end cover is sealed with the rubber diaphragm assembly and the detection chamber, the two switch PIN pins are fixed inside the side end cover, one end of the two switch PIN pins is used to be electrically connected to the engine control unit, the other end of one switch PIN pin is fixedly connected to one end of the spring, the other end of the other switch PIN pin is spaced a certain distance from the other end of the spring, and the other end of the spring is in contact with the rubber diaphragm assembly.

[0012] Furthermore, the spring sheet includes a plug-in slot, a connecting plate and a movable spring plate, one end of the plug-in slot is vertically fixed to one end of the connecting plate, the other end of the plug-in slot is arranged inside the side end cover and connected to the other end of a switch PIN foot, the other end of the connecting plate is connected to one end of the movable spring plate, and the other end of the movable spring plate is spaced a certain distance from the other end of the other switch PIN foot.

[0013] Furthermore, the movable spring plate and the connecting plate are located in the same plane, the width of the movable spring plate is greater than the width of the connecting plate, the connecting portion of the movable spring plate and the connecting plate has a smooth transition, and a protrusion is provided on the side of the movable spring plate away from the connecting plate.

[0014] Furthermore, the inner edge of the side end cover is provided with a side cover groove and a side cover welding rib, the side cover groove is sealingly matched with the sealing strip on the rubber diaphragm assembly, and the side cover welding rib is sealingly matched with the flange surface on the detection chamber.

[0015] Furthermore, a breathing hole is provided on the side end cover.

[0016] Furthermore, two detection holes are arranged on the catheter at intervals, and two air guide holes are arranged on the inner wall of the detection chamber at intervals. The two detection holes are coaxially arranged with the two air guide holes respectively, the diameter of the air guide hole is larger than the diameter of the detection hole, and the hole spacing between the two detection holes is smaller than the height of the sliding float.

[0017] Furthermore, the center lines of the lateral holes, the detection holes, and the catheter are perpendicular to each other.

[0018] The beneficial effects of the present invention are:

[0019] 1. The on-vehicle leakage diagnosis device provided in the fuel evaporation control system of the present invention is provided with a detection chamber on the valve body, and cooperates with a rubber diaphragm assembly and a micro switch, so that system pipeline leakage diagnosis can be performed without adding a pressure sensor, which is lower in cost, and the modular function integration of the device is higher, which is convenient for later maintenance.

[0020] 2. The on-board leakage diagnosis device provided in the fuel evaporation control system of the present invention, when not powered, the micro spring pushes the float downward, at which time the upper port (connected to the ash filter) and the middle pipe port (connected to the carbon canister) are interconnected, so that the carbon canister is directly connected to the ash filter, and the ventilation pressure drop of the fuel evaporation control system is small.

[0021] 3. The on-board leakage diagnosis device provided in the fuel evaporation control system of the present invention starts working when the boost pump is powered on. A part of the airflow coming in from the first pipe joint enters the system after being compressed by the boost pump, and the other part enters the detection chamber to squeeze the rubber diaphragm assembly to deform the micro switch. Since the output flow of the boost pump is a constant value, a reference time can be calibrated. When the vehicle is leak checked, after the ECU issues a leak check command (i.e., the boost pump starts working when powered on), it waits until the reference time is reached to determine whether the micro switch is in a passage state: if it is in a passage state, it can be determined that the fuel evaporation control system is not leaking, otherwise it can be determined that the system is leaking. This judgment logic is simpler and more reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a connection diagram of the fuel evaporation control system of the present invention in a PHEV vehicle.

[0023] Figure 2 The figure is a connection diagram of the fuel evaporation control system of the present invention in a common vehicle model.

[0024] Figure 3 The diagram is a gas flow diagram of the vehicle-mounted leakage diagnostic device of the present invention in normal state.

[0025] Figure 4 The diagram is a schematic diagram of the gas flow direction of the vehicle-mounted leakage diagnosis device of the present invention during leakage inspection.

[0026] Figure 5 It is a cross-sectional view (vertical) of the vehicle-mounted leakage diagnostic device of the present invention.

[0027] Figure 6 It is an exploded view of the vehicle-mounted leakage diagnostic device of the present invention.

[0028] Figure 7 It is a cross-sectional view (vertical) of the upper end cover of the present invention.

[0029] Figure 8 It is a schematic diagram of the structure of the booster pump assembly of the present invention.

[0030] Fig. 9 It is a schematic diagram of the three-dimensional structure of the valve body of the present invention.

[0031] Fig.10 It is a top view of the valve body of the present invention.

[0032] Fig.11 for Fig.10 AA section view in.

[0033] Fig.12 It is a schematic diagram of the lower end cover structure of the present invention.

[0034] Fig.13 This is a cross-sectional view (vertical) of the sliding float of the present invention.

[0035] Fig.14 It is a schematic diagram of a rubber diaphragm assembly from one perspective of the present invention.

[0036] Fig.15 FIG. 4 is a schematic diagram of the rubber diaphragm assembly of the present invention from another perspective.

[0037] Fig.16 It is a schematic plan view of the rubber diaphragm assembly of the present invention.

[0038] Fig.17 It is a cross-sectional view of the rubber diaphragm assembly of the present invention.

[0039] Fig.18 Schematic diagram of the micro switch of the present invention.

[0040] Fig.19 for Fig.18 BB section view in.

[0041] Fig. 20 It is a schematic diagram of the spring on the micro switch of the present invention.

[0042] In the figure: 00, on-board leakage diagnosis device; 10, upper end cover; 11, first pipe joint; 12, harness joint; 12a, positive PIN pin; 12b, negative PIN pin; 13, upper end cover welding rib; 20, boost pump assembly; 21, motor; 21a, motor positive wire; 21b, motor negative wire; 22, gas compression mechanism; 22a, air inlet; 22b, air outlet; 2 2c, O-ring; 30, valve body; 31, second pipe joint; 32, spring guide rib plate; 33, booster pump chamber; 34, mounting structure; 35, positive pressure vent; 36, conduit; 36a, lateral hole; 36b, detection hole; 37, detection chamber; 37a, air guide hole; 37b, flange; 40, lower end cover; 41, raised cavity; 42, lower end cover welding rib; 43, recessed rib plate; 50, Sliding float; 51, outer wall of float; 52, spring groove; 53, weight-reducing inner cavity; 60, micro spring; 70, rubber diaphragm assembly; 71, floating plate; 71a, anti-slip column; 71b, boss; 71c, supporting round table; 72, rubber ring; 72a, vulcanized rib; 73, sealing ring; 73a, sealing strip; 80, micro switch; 81, side end cover; 81a, side cover groove; 81b, side cover welding Connecting ribs; 81c, positioning ribs; 81d, breathing holes; 82, switch PIN pins; 83, spring pieces; 83a, plug-in slots; 83b, connecting plates; 83c, movable spring plates; 100, ash filter; 200, charcoal canister assembly; 200a, charcoal canister adsorption port; 200b, charcoal canister desorption port; 200c, charcoal canister atmospheric port; 300, desorption control valve; 400, fuel tank isolation valve; 500, fuel tank assembly. DETAILED DESCRIPTION

[0043] The specific embodiments of the present invention are further described below in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0044] like Figure 1 , Figure 3 , Figure 4 The figure shows the connection diagram and working principle of the fuel evaporation control system of the present invention in the PHEV model, which includes an engine control unit ECU, a fuel tank assembly 500, a carbon canister assembly 200 and an on-board leakage diagnostic device 00. A normally closed fuel tank isolation valve 400 is connected between the fuel tank assembly 500 and the carbon canister assembly 200; an ash filter 100 is connected to the rear of the on-board leakage diagnostic device 00, and a carbon canister desorption port 200b of the carbon canister assembly 200 is connected to a desorption control valve 300. The engine ECU is connected to the fuel tank isolation valve 500, the desorption control valve 300 and the on-board leakage diagnostic device 00 through a wiring harness connector.

[0045] The reference time needs to be obtained by measuring the average value during vehicle calibration. The specific calibration method is recommended as follows: connect the vehicle-mounted leakage diagnosis device 00 of the present invention to a fuel evaporation control system (no leakage) in parallel with a standard leakage hole (φ0.5mm or φ1mm) to simulate its leakage point; under the extreme conditions of the system (the fuel tank is empty and the presence of fuel will cause the reference time to decrease), measure the time when the vehicle-mounted leakage diagnosis device 00 of the present invention is fed back as a passage in this state, and the average value of the multiple measured times is the reference time.

[0046] When the car is refueling, the ECU receives a signal that the fuel tank cover is opened and sends a power-on signal to the fuel tank isolation valve 400. After the fuel tank isolation valve 400 is opened, the fuel vapor enters the carbon canister assembly 200 through the pipeline and is adsorbed by the activated carbon. When the clean air displaced from the carbon canister assembly 200 reaches the vehicle-mounted leakage diagnosis device 00 of the present invention, Figure 3 As shown, the airflow flows directly to the first pipe joint 11 through the second pipe joint 31 and is finally released into the atmosphere through the ash filter 100, thereby reducing the emission of fuel vapor.

[0047] When checking for automobile leakage, the ECU first energizes the fuel tank isolation valve 400 according to a pre-set program to open it and release the gas pressure stored in the fuel tank assembly 500. Then, it sends a power-on signal to the device 00 of the present invention, and the desorption control valve 300 is not energized and is in a normally closed state. Figure 4As shown, the vehicle-mounted leakage diagnosis device 00 of the present invention absorbs air from the ash filter 100, and the air enters the boost pump assembly 20 through the first pipe joint 11. The pressure generated after compression will overcome the force of the micro spring 60, pushing the sliding float 50 to move upward. When it moves to the set position, the gas compressed by the boost pump assembly 20 flows into the fuel evaporation control system through the second pipe joint 31. At the same time, the rubber diaphragm assembly 70 is subjected to pressure, causing it to move. If the fuel evaporation control system does not leak, the rubber diaphragm assembly 70 will deform greatly, and the active spring plate 83c that pushes the spring sheet 83 will be deformed to connect its two switch PIN pins 82. At this time, the circuit fed back to the ECU is in the on-state; otherwise, the circuit fed back to the ECU is in the off-state. The ECU can determine whether the fuel system is leaking by obtaining the on-off information of the feedback circuit within the reference time. The on-state means no leakage, and the off-state means leakage.

[0048] like Figure 2 , Figure 3 , Figure 4 The figure shows the connection diagram and working principle of the fuel evaporation control system of the present invention in a common vehicle, which includes an engine control unit ECU, a fuel tank assembly 500, a carbon canister assembly 200 and an on-board leakage diagnostic device 00. The rear of the on-board leakage diagnostic device 00 is connected to an ash filter 100, and the carbon canister desorption port 200b of the carbon canister assembly 200 is connected to a desorption control valve 300. The engine ECU is connected to the desorption control valve 300 and the on-board leakage diagnostic device 00 through a wiring harness connector.

[0049] When the car is refueling, the fuel vapor formed in the fuel tank assembly 500 enters the carbon canister assembly 200 through the pipeline and is adsorbed by the activated carbon. When the clean air displaced from the carbon canister assembly 200 reaches the vehicle-mounted leakage diagnosis device 00 of the present invention, Figure 3 As shown, the airflow flows directly to the first pipe joint 11 through the second pipe joint 31 and is finally released into the atmosphere through the ash filter 100, thereby reducing the emission of fuel vapor.

[0050] When checking for automobile leakage, the ECU sends a power-on signal to the vehicle-mounted leakage diagnosis device 00 according to a pre-set program, and the desorption control valve 300 is not powered and is in a normally closed state. Figure 4As shown, the vehicle-mounted leakage diagnosis device 00 of the present invention absorbs air from the ash filter 100, and the air enters the boost pump assembly 20 through the first pipe joint 11. The pressure generated after compression will overcome the force of the micro spring 60, pushing the sliding float 50 to move upward. When it moves to the set position, the gas compressed by the boost pump assembly 20 flows into the fuel evaporation control system through the second pipe joint 31. At the same time, the rubber diaphragm assembly 70 is subjected to pressure, causing it to move. If the fuel evaporation control system does not leak, the rubber diaphragm assembly 70 will deform greatly, and will push the spring 83 to deform so that its two switch PIN pins 82 are connected. At this time, the circuit fed back to the ECU is in the on-state; otherwise, the circuit fed back to the ECU is in the off-state. The ECU can determine whether the fuel system is leaking by obtaining the on-off information of the feedback circuit within the reference time. The on-state means no leakage, and the off-state means leakage.

[0051] like Figure 5 , Figure 6 As shown, the vehicle-mounted leakage diagnostic device includes an upper end cover 10, a booster pump assembly 20, a valve body 30, a lower end cover 40, a sliding float 50, a micro spring 60, a rubber diaphragm assembly 70 and a micro switch 80. The upper end cover 10 is provided with a first pipe joint 11, and the valve body 30 is provided with a second pipe joint 31; in a fuel evaporation control system (such as Fig.13 and Fig.14 ) The first pipe joint 11 of the device is connected to the ash filter 100, and the second pipe joint 31 is connected to the atmospheric pipe port 200c of the carbon canister. A boost pump chamber 33 and a conduit 36 ​​are provided in the valve body 30, and a detection chamber 37 is provided on one side of the valve body 30. The boost pump assembly 20 is installed in the boost pump chamber 33, and the sliding float 50 and the micro spring 60 are installed in the conduit 36; the micro switch 80 is sealed and fixed on the opening side of the detection chamber 37, and the micro switch 80 is connected to the engine control unit through an electrical signal. The rubber diaphragm assembly 70 is arranged between the detection chamber 37 and the micro switch 80 to divide the detection chamber into two closed spaces.

[0052] In the present invention, when the boost pump assembly 20 is not powered, the first pipe joint 11 and the second pipe joint 21 are connected through the lateral hole 36a of the conduit 36 ​​to achieve airflow; when the boost pump assembly 20 is powered, the airflow enters the boost pump assembly 20 from the first pipe joint 11, is compressed by the boost pump assembly 20, and the airflow pressure overcomes the action of the micro spring 60, pushing the sliding float 50 to move upward, a part of the airflow flows into the passage of the second pipe joint 31 through the lateral hole 36a of the conduit, and another part of the airflow enters the detection chamber through the detection hole 36b of the conduit to push the rubber diaphragm assembly 70 to deform and actuate the micro switch 80, and the engine control unit determines whether the system is leaking according to the action of the micro switch.

[0053] like Figure 7As shown, the upper end cover 10 is provided with not only a first pipe joint 11, but also a wiring harness joint 12 connected to a power source. The wiring harness joint 12 is provided with a positive PIN pin 12a and a negative PIN pin 12b, the positive PIN pin 12a is connected to the positive lead 21a of the motor, and the negative PIN pin 12b is connected to the negative lead 21b of the motor. The upper end cover 10 is provided with an upper end cover welding rib 13 welded to the valve body 30, and after the upper end cover 10 is welded to the valve body 30, the first pipe joint 11 and the air inlet 22a of the booster pump assembly 20 can be connected.

[0054] like Figure 8 As shown, the booster pump assembly 20 includes a motor 21 and a gas compression mechanism 22, wherein the motor 21 is provided with a motor positive wire 21a and a motor negative wire 21b, and the gas compression mechanism 22 is provided with an air inlet pipe 22a and an air outlet pipe 22b, wherein the air outlet pipe 22b is equipped with an O-ring 22c, and the air outlet pipe 22b and the positive pressure vent 35 are assembled to form a seal to prevent the positive pressure gas generated by the gas compression mechanism 22 from communicating with the air inlet pipe 22a.

[0055] like Figure 9-11 As shown, the valve body 30 is provided with a mounting structure 34 connected to the vehicle frame on the outside, and the mounting structure 34 is designed as a self-tapping screw fixing structure. The valve body 30 is also provided with a second pipe joint 31 connected to the carbon canister atmospheric port 200c; the valve body 30 is provided with a booster pump chamber 33 and a conduit 36 ​​(using an injection molded metal conduit), and the inner wall of the conduit 36 ​​and the outer wall 51 of the float are matched with each other, and the matching clearance is set to be between 0.08 and 0.05 mm for the best. There is an angle between the center line of the conduit lateral hole 36a and the detection hole 36b and the center line of the conduit 36 ​​in three-dimensional space, and the angle is set to be vertical for the best. There is an angle between the detection hole 36b and the lateral hole 36a in three-dimensional space, and the angle is set to be vertical for the best. The lateral hole 36a is provided with a guide rib 36c passing through the center of the circle, and the guide rib can reduce the friction of the sliding float on the upper edge of the lateral hole when it moves upward. The aperture of the detection hole 36b is set to be between 0.5 and 0.7 mm for the best. The hole spacing L of the two detection holes 36b is slightly smaller than the radial height h of the sliding float 50, so that when the sliding float 50 moves upward, the detection hole 36b at the lower end is connected to the air outlet 22b, and the sliding float 50 can automatically close the detection hole 36b at the upper end. The upper end of the conduit 36 ​​is designed with a spring guide rib plate 32 for fixing the micro spring 60, which can not only play the function of fixing the spring, but also does not affect the passage of airflow. The inner cavity of the detection chamber 37 can accommodate the rubber diaphragm assembly 70; the two detection holes 36b are coaxially arranged with the two air guide holes 37a, and the inner diameter of the air guide hole 37a is slightly larger than the inner diameter of the detection hole 36b. The inner ring plane of the detection chamber flange 37b can be interference-fitted with the sealing strip 72a to form an independent cavity space. The outer ring plane of the detection chamber flange 37b can be fused with the side cover welding rib 81b to form a weld.

[0056] like Fig.12 As shown, the lower end cover 40 is provided with a lower end cover welding rib 42 welded to the valve body 30. After the lower end cover 40 is welded to the valve body 30, the outlet pipe 22b of the booster pump assembly 20 and the conduit 36 ​​can be connected. The lower end cover 40 is provided with a raised cavity 41 to achieve a smooth transition of the air flow and avoid excessive ventilation pressure drop. The lower end cover 40 is provided with a recessed rib plate 43 to limit the stroke of the sliding float 50.

[0057] like Fig.13 As shown, in order to maintain the characteristics of wear resistance and self-lubrication, the sliding float 50 is preferably made of metal material or self-lubricating plastic material. The sliding float 50 is provided with a spring groove 52 for assembling the micro spring 60. The float outer wall 51 of the sliding float 50 is clearance-matched with the inner diameter of the metal conduit 36. In order to reduce the weight of the sliding float 50, a float weight reduction cavity 53 is designed. The outer diameter of the micro spring 60 is clearance-matched with the spring groove 52. The assembly working elastic force of the spring 60 can be determined according to the assembly direction of the fuel evaporation system vehicle leakage diagnosis device 00 on the whole vehicle; the limit working elastic force of the micro spring 60 can be calculated according to the preset opening pressure.

[0058] like Figure 14-17 As shown, the rubber diaphragm assembly 70 is composed of a floating plate 71, a rubber ring 72 and a sealing ring 73, wherein the floating plate 71 is made of plastic, the rubber ring 72 and the sealing ring 73 are both made of rubber, the rubber ring 72 and the sealing ring 73 are integrally formed, and the floating plate 71 and the rubber ring 72 are vulcanized and compounded together (the floating plate 71 is first realized by injection molding, and then placed in a rubber mold and vulcanized with rubber materials). The boss 71b is located at the center of one side of the floating plate 71, and the upper end surface is in a spherical state. When the rubber diaphragm assembly 70 is deformed by air pressure (mainly the compression deformation of the rubber ring 72), the boss 71b will push the movable spring plate 83c in the spring sheet 83 to deform it. Three supporting round platforms 71c are provided on the other side of the floating plate, on the one hand to ensure the durability of the floating plate 71, and on the other hand to ensure that there is enough distance between the floating plate and the inner wall of the detection chamber to avoid the floating plate from sticking to the inner wall of the detection chamber during the deformation process, resulting in insufficient airflow thrust. The edge of the sealing ring 73 cooperates with the side cover groove 81a as a sealing strip 73a. When the micro switch 80 is welded to the valve body 30, the sealing strip 73a divides the space between the detection chamber 37 and the micro switch 80 into two closed spaces. The vulcanized ribs 72a and the anti-slip column 71a are provided to ensure that the floating plate 71 and the rubber ring 72 form a better fusion.

[0059] like Figure 18-20As shown, the micro switch 80 includes three parts: a side cover 81, two switch PIN pins 82 and a spring 83. The side cover 81 is made of engineering plastic (PA6, POM, etc.), and is provided with a side cover groove 81a for assembling the sealing strip 73a; the side cover welding rib 81b is a feature designed for welding with the detection chamber flange 37b, and the positioning rib 81c is for positioning the direction during welding. When the rubber diaphragm assembly 70 changes shape, it can breathe through the breathing hole 81d provided on the side cover 81, maintaining the pressure balance in the cavity of the micro switch 80. The spring piece 83 includes a plug-in slot 83a, a connecting plate 83b and a movable spring plate 83c. The movable spring plate 83c and the connecting plate 83b are located in the same plane. The width of the movable spring plate 83c is greater than the width of the connecting plate 83b. The connecting portion 83d of the movable spring plate 83c and the connecting plate 83b is smoothly transitioned. The movable spring plate 83c is provided with a protrusion 83e on the side away from the connecting plate. The design of the width, smooth transition and protrusion is to ensure that the movable spring plate is within the contactable range of the boss 71b. The design of the smooth transition is to reduce the deformation stress of the movable spring plate. There are two switch PIN pins 82 with a certain spacing, which are embedded in the mold when the side end cover 81 is injection molded. After the injection molding is completed, the plug-in slot 83a of the spring piece 83 is inserted into one of the switch PIN pins 82. When the assembly is completed, it is necessary to ensure that a distance is maintained between the movable spring plate 83c and the end of the other switch PIN pin 82. The preferred distance is set between 1.5 and 3 mm. The material of the spring 83 should be a thin sheet with certain elasticity and being a conductor, and the preferred material is a copper alloy or a stainless steel sheet.

[0060] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in the field.

Claims

1. A fuel evaporation control system, characterized in that: it includes an engine control unit, a fuel tank assembly, a carbon canister assembly and an on-vehicle leak diagnosis device. The atmosphere pipe orifice of the carbon canister assembly is connected to the on-vehicle leak diagnosis device, and a gray filter is connected to the rear of the on-vehicle leak diagnosis device; the carbon canister desorption orifice of the carbon canister assembly is connected to a desorption control valve, and the engine control unit is respectively connected to the on-vehicle leak diagnosis device and the desorption control valve through a wire harness; the on-vehicle leak diagnosis device includes an upper end cover, a booster pump assembly, a valve body, a lower end cover, a sliding float, a micro spring, a rubber diaphragm assembly and a micro switch. The upper end cover is fixedly arranged at the top of the valve body, and the lower end cover is fixedly arranged at the bottom of the valve body; a first pipe joint connected to the gray filter is arranged on the upper end cover, and a second pipe joint connected to the carbon canister atmosphere pipe orifice is arranged on the valve body; a booster pump chamber and a conduit are arranged in the valve body, a detection chamber is arranged on one side of the valve body, the booster pump assembly is installed in the booster pump chamber, and the sliding float and the micro spring are installed in the conduit; the micro switch is hermetically fixed on the opening side of the detection chamber, the micro switch is electrically connected to the engine control unit, and the rubber diaphragm is arranged between the detection chamber and the micro switch to divide the detection chamber into two closed spaces; when the booster pump assembly is not powered on, the first pipe joint and the second pipe joint are communicated through the lateral hole of the conduit to realize the passage of air flow; when the booster pump assembly is powered on, the air flow from the gray filter enters the booster pump assembly from the first pipe joint, is compressed by the booster pump assembly, the air flow pressure overcomes the acting force of the micro spring, and pushes the sliding float to move upward. Part of the air flow flows into the passage of the second pipe joint through the lateral hole of the conduit, and another part of the air flow enters the detection chamber through the detection hole of the conduit to push the rubber diaphragm assembly to deform and make the micro switch act. The engine control unit judges whether the system leaks according to the action condition of the micro switch.

2. The fuel evaporation control system according to claim 1, characterized in that: the rubber diaphragm assembly includes a floating plate, a rubber ring and a sealing ring. The floating plate is fixed at one end of the rubber ring, the sealing ring is fixed at the other end of the rubber ring. The side of the sealing ring close to the floating plate is in clearance fit with the inner ring of the flange of the detection chamber, and the side of the sealing ring away from the floating plate is in sealed fit with the edge of the side end cover of the micro switch. A boss is arranged in the middle of the side of the floating plate close to the rubber ring, and the boss contacts the elastic piece of the micro switch. When the air flow enters the detection chamber, it pushes the floating plate to move, thereby driving the elastic piece in contact with the boss to deform and making the micro switch act.

3. The fuel evaporation control system according to claim 2, characterized in that: a plurality of support round platforms are arranged on the side of the floating plate away from the rubber ring.

4. The fuel evaporation control system according to claim 1, characterized in that: The microswitch includes a side end cover, a shrapnel, and two switch PIN feet. The inner edge of the side end cover is sealingly fitted with a rubber diaphragm assembly and a detection chamber. The two switch PIN feet are fixed inside the side end cover. One end of the two switch PIN feet is used for electrical connection with an engine control unit. One end of one switch PIN foot is fixedly connected to one end of the shrapnel, and the other end of the other switch PIN foot is spaced a certain distance from the other end of the shrapnel. The other end of the shrapnel contacts the rubber diaphragm assembly.

5. The fuel evaporation control system according to claim 4, characterized in that: The shrapnel includes a plugging groove, a connecting plate, and a movable elastic plate. One end of the plugging groove is vertically fixed to one end of the connecting plate. The other end of the plugging groove is arranged inside the side end cover and connected to the other end of one switch PIN foot. The other end of the connecting plate is connected to one end of the movable elastic plate. The other end of the movable elastic plate is spaced a certain distance from the other end of the other switch PIN foot.

6. The fuel evaporation control system according to claim 5, characterized in that: The movable elastic plate and the connecting plate are in the same plane. The width of the movable elastic plate is greater than the width of the connecting plate. The connecting part of the movable elastic plate and the connecting plate has a smooth transition. A protruding part is provided on the side of the movable elastic plate away from the connecting plate.

7. The fuel evaporation control system according to claim 4, characterized in that: The inner edge of the side end cover is provided with a side cover groove and a side cover welding rib. The side cover groove is sealingly fitted with a sealing strip on the rubber diaphragm assembly. The side cover welding rib is sealingly fitted with a flange surface on the detection chamber.

8. The fuel evaporation control system according to claim 4, characterized in that: The side end cover is provided with a breathing hole.

9. The fuel evaporation control system according to claim 1, characterized in that: Two detection holes are provided at intervals on the conduit. Two air guide holes are provided at intervals on the inner side wall of the detection chamber. The two detection holes are coaxially arranged with the two air guide holes respectively. The diameter of the air guide hole is greater than the diameter of the detection hole. The hole distance between the two detection holes is less than the height of the sliding float.

10. The fuel evaporation control system according to claim 1, characterized in that: The center lines of the lateral holes, the detection holes, and the conduit are perpendicular to each other in pairs.

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