Vehicle running differential pressure type front combination lamp active demisting method based on Bernoulli principle

Abstract

The invention discloses a Bernoulli principle-based active demisting method for a vehicle running differential pressure type front combination lamp, and relates to the technical field of vehicle illumination and fluid control. An air inlet flow guide assembly is arranged to be connected with the air flow stagnation area of the active air inlet grille and the air inlet connector; an exhaust ventilation assembly is arranged and integrated in an airflow acceleration area below the fender, and an exhaust connector is sealed; when the vehicle is in a running state, the fluid static pressure difference generated by the two areas is used for driving external air to enter the lamp cavity through the air inlet assembly and be exhausted through the exhaust assembly. According to the self-adaptive defogging device, an active airflow circulation loop without electric drive is established, forced convection is driven by differential pressure potential energy generated by vehicle running kinetic energy, self-adaptive defogging with the ventilation rate linearly increased along with the vehicle speed is achieved, the problems that traditional passive breathing is low in efficiency and an electronic defogging device is high in cost are solved, and the condensation risk of the lens is effectively eliminated.

Description

Technical Field

[0001] This application relates to the field of vehicle lighting and fluid control technology, and in particular to an active defogging method for vehicle driving pressure differential type front combination lamps based on Bernoulli's principle. Background Technology

[0002] With the development of automotive lighting technology, light-emitting diodes (LEDs) have gradually replaced halogen and xenon lamps as the mainstream light source for front combination lights due to their advantages such as high luminous efficiency, low energy consumption, and high design flexibility. However, the thermal radiation characteristics of LED light sources differ from traditional light sources; they radiate less heat towards the lens, resulting in a relatively low temperature on the inner surface of the lens. When the hot, humid air inside the combination light comes into contact with the lens, which is cooled by the external environment, it easily condenses and forms fog on the inner surface of the lens. This not only affects the vehicle's appearance but also alters the light distribution, reduces illumination brightness, and thus impacts nighttime driving safety.

[0003] Currently, the mainstream solution to the problem of fogging in front combination lights typically employs a passive breathing structure. This involves placing a waterproof and breathable membrane or cover on the lamp housing, utilizing the Brownian motion of air molecules or the slight pressure difference generated by thermal expansion and contraction within the lamp to facilitate gas exchange between the inside and outside. However, this passive method, relying on natural diffusion and convection, has a very limited gas exchange rate and struggles to cope with complex and changing driving environments. Especially when the vehicle is traveling at high speeds or encountering rain or car washes, the strong wind-cooling effect of external airflow on the lens surface causes a sharp increase in the internal condensation rate. In these situations, the dehumidification capacity of the passive breathing structure often lags behind the condensation rate, making it difficult for the fog to dissipate.

[0004] To improve defogging efficiency, existing technologies employ active intervention methods such as introducing electric fans, electrically heated coatings, or placing desiccants. While these methods improve defogging performance to some extent, they also introduce new technical bottlenecks. For example, built-in fans and electric heating devices consume additional electrical energy, increase the complexity of wiring harness layout and electromagnetic compatibility risks, and the introduction of mechanical moving parts reduces the overall reliability and durability of the vehicle lighting system. Desiccant solutions suffer from moisture saturation failure and difficulties in replacement and maintenance, and after saturation, they can become a secondary moisture source inside the lamp. Therefore, developing an active defogging technology that can adaptively adjust ventilation efficiency according to vehicle driving conditions, while possessing a simple and reliable structure, without increasing power consumption or electronic components, has become a key technical challenge in the field of vehicle lighting. Summary of the Invention

[0005] The purpose of this invention is to provide an active defogging method for vehicle driving pressure differential front combination lamps based on Bernoulli's principle, which at least solves the technical problems of existing passive breathing structures for front combination lamps having low gas exchange rates and difficulty in dealing with fogging caused by wind cooling effects when vehicles are driving at high speeds, as well as traditional active defogging devices relying on electric drive, having complex structures, and being costly.

[0006] This invention provides the following solution:

[0007] This invention provides an active defogging method for front combination lamps based on Bernoulli's principle and pressure differential. The method involves configuring an air intake port and an exhaust port on the lamp housing of the front combination lamp. The air intake port connects to the interior of the lamp housing, and the exhaust port also connects to the interior of the lamp housing. An air intake guide assembly is configured, with one end physically connected to the airflow collection point in the active air intake grille area of ​​the vehicle, and the other end airtightly connected to the air intake port. An exhaust venting assembly is configured, integrated into the housing area of ​​the front combination lamp extending to below the vehicle fender and covering and sealing the exhaust port. When the vehicle is in motion, the hydrostatic pressure difference generated between the active air intake grille area and the vehicle fender area drives external air to enter the lamp housing through the air intake guide assembly and exit through the exhaust venting assembly.

[0008] In some embodiments of the present invention, the formation mechanism of the hydrostatic pressure difference is based on the aerodynamic characteristics of the vehicle body surface: the active air intake grille area is located on the windward side, where the airflow velocity is stagnant relative to the vehicle body surface, forming a high static pressure zone; the vehicle fender area is located on the streamlined side, where the airflow velocity is greater than or equal to the vehicle speed, forming a low static pressure zone. The driving pressure difference between the intake and exhaust ports increases with the increase of vehicle speed, thereby establishing a pressure gradient at both ends of the lamp housing.

[0009] In some embodiments of the present invention, the step of configuring the air intake guide assembly includes: setting an air intake collection head with a flared structure at the starting end of the air intake guide assembly, and mechanically anchoring the air intake collection head to the frame of the active air intake grille or the inner support structure of the front bumper using a fixing bracket. A guide hose is selected to connect the air intake collection head and the air intake interface, and a U-shaped or S-shaped settling section is set along the arrangement path of the guide hose from the air intake collection head to the air intake interface, with the lowest point of the settling section being lower than the height of the air intake interface. Furthermore, a grille or coarse filter can be set at the inlet of the air intake collection head.

[0010] In some embodiments of the present invention, the method further includes the step of optimizing the internal flow field: an internal airflow duct is connected inside the lamp cavity, one end of the internal airflow duct is connected to an air inlet, and the other end extends to the inner surface of the lens of the front combination lamp. The air outlet of the internal airflow duct is constructed as a flat nozzle, and the air outlet is oriented towards the lower edge or corner area of ​​the lens to guide dry airflow to flush the fogging area.

[0011] In some embodiments of the present invention, the step of configuring the exhaust and ventilating assembly includes: injection molding an exhaust seat on the housing wall of the lamp cavity, opening a vent window in the center of the exhaust seat, and setting a support rib inside the vent window. A waterproof and breathable membrane made of expanded polytetrafluoroethylene microporous material is selected, and the waterproof and breathable membrane is sealed and fixed to the end face of the exhaust seat by ultrasonic welding or insert injection molding process.

[0012] Furthermore, the method also includes protection and airflow guiding steps: an external airflow guiding shield is fastened and installed on the exhaust seat, and the external airflow guiding shield is configured to cover a waterproof and breathable membrane. An exhaust buffer chamber is defined between the inner wall of the external airflow guiding shield and the outer surface of the waterproof and breathable membrane. Several airflow guiding exhaust holes are opened on the side wall or bottom wall of the external airflow guiding shield, and the opening plane of the airflow guiding exhaust holes is set to face away from the windward side when the vehicle is traveling, using the external airflow to generate a suction effect.

[0013] In some embodiments of the present invention, the method includes switching between a passive breathing step and an active defogging step: when the vehicle is stationary and the hydrostatic pressure difference is zero, or when the vehicle is traveling at low speed and the hydrostatic pressure difference is insufficient to overcome the system flow resistance, a waterproof and breathable membrane is used to facilitate molecular diffusion gas exchange between the lamp cavity and the external environment. The active circulation step, which drives external air into the lamp cavity, is triggered when the vehicle speed reaches the critical starting flow rate, which is set to a range of 15 km / h to 25 km / h.

[0014] In some embodiments of the present invention, in order to adapt to different vehicle layouts, the location of the airflow collection point can be selected from the lower air intake of the front bumper of the vehicle, the front edge of the hood, or the positive pressure area at the front of the vehicle chassis; the location of the exhaust ventilation component can be selected from the inside of the front wheel arch, the negative pressure area in the middle of the chassis, or the guide groove area on the side of the front bumper.

[0015] The above solution achieves the following beneficial technical effects:

[0016] This application connects the air intake guide assembly to the air stagnation zone of the active air intake grille and places the exhaust vent assembly in the airflow acceleration zone of the fender. It utilizes the hydrostatic pressure difference generated by vehicle movement to establish an air circulation loop that runs through the lamp cavity. This mechanism can achieve active defogging without electric drive, and the air exchange rate through the lamp cavity automatically increases with the increase of vehicle speed. This adaptive characteristic makes the defogging capability just right to match the lamp condensation risk that is aggravated by the enhanced wind cooling effect when the vehicle is driving at high speed.

[0017] This application utilizes an internal airflow channel within the lamp cavity that points towards the inner surface of the lens to direct the introduced high-speed dry airflow to areas prone to fogging. This structure transforms disordered cavity ventilation into forced convection sweeping of the lens surface, increasing the local convective heat transfer coefficient of the lens's inner surface and disrupting the saturated humidity environment of the boundary layer. This allows for faster evaporation of the condensed water film and a reduction in dew point temperature compared to simple natural diffusion.

[0018] This application solves the waterproof and dustproof problems while ensuring high airflow through the design of the settling section on the air intake path and the protective structure at the exhaust end. The U-shaped or S-shaped settling section on the guide hose uses the principle of gravity to prevent rainwater from directly entering the lamp. The external guide shield not only prevents the direct impact of high-pressure car wash water jets and splashing sand on the waterproof and breathable membrane through the back opening, but also uses the suction effect generated when the external airflow flows over the surface of the shield to further reduce the exhaust end pressure and enhance the overall driving pressure difference of the system. Attached Figure Description

[0019] Figure 1 This is a flowchart illustrating the operation of the active defogging system of the present invention. Detailed Implementation

[0020] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. 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.

[0021] See attached document Figure 1 This invention provides an active defogging system for vehicle driving pressure differential type front combination lamps based on Bernoulli's principle, which is applied to the front lighting device of a vehicle.

[0022] The system includes a front combination lamp, an air intake guide assembly, and an exhaust vent assembly. The front combination lamp has a lamp housing to accommodate the light source and optical components. The lamp housing is a relatively enclosed space, and its housing is equipped with air intake and exhaust ports.

[0023] The air intake interface is located on the side of the front combination light near the vehicle's active air intake grille. The active air intake grille is located in the frontal wind-impact area of ​​the vehicle's front bumper. The exhaust interface is located on the side of the front combination light near the vehicle's fender. The fender is located on the side of the vehicle, in the airflow streamline area when the vehicle is in motion. The active air intake grille mentioned in this embodiment is only a preferred implementation location for a high-pressure source. In other embodiments, the air intake point of the air intake guide assembly can also be located at the lower air intake of the vehicle's front bumper, the hood's leading edge stagnation area, or the positive pressure area at the front of the vehicle's chassis. Similarly, the fender is only a preferred implementation location for a low-pressure source. The exhaust point of the exhaust ventilation assembly can also be located inside the front wheel arch, in the negative pressure area in the middle of the chassis, or in the guide groove area on the side of the front bumper. As long as a hydrostatic pressure difference satisfying formula (2) can be formed between the two points when the vehicle is in motion. All of these fall within the protection scope of this invention.

[0024] The air intake guide assembly includes a guide hose. One end of the guide hose is physically connected to the airflow collection point in the active air intake grille area, and the other end is airtightly connected to the air intake interface of the lamp housing. The guide hose is configured to introduce high-pressure air from the active air intake grille area into the lamp housing.

[0025] The exhaust venting assembly includes a waterproof and breathable membrane. This membrane covers and seals the exhaust inlet. The exhaust inlet is located in the pointed area below the fender of the front combination lamp housing. This area corresponds to a low-pressure zone in the external airflow field of the vehicle. The waterproof and breathable membrane is configured to allow gas molecules to pass through while blocking liquid water and particulate matter from entering.

[0026] The defogging mechanism of this system is based on the aerodynamic pressure difference generated during vehicle operation. When the vehicle is in motion, there is a hydrostatic pressure difference between the active air intake grille area and the fender area. According to Bernoulli's principle in fluid mechanics, assuming air is incompressible and ignoring the gravitational potential energy effect caused by the height difference, the energy conservation relationship between the two points is expressed by formula (1):

[0027] ;

[0028] in: This indicates the static air pressure at the inlet of the air intake assembly (i.e., the active air intake grille area); This indicates the static air pressure at the outlet of the exhaust vent assembly (i.e., the fender area); Indicates air density; This indicates the external airflow velocity at the inlet of the air intake guide assembly; This indicates the external airflow velocity at the outlet of the exhaust venting component.

[0029] When the vehicle is in motion, the active grille is positioned on the windward side, where the airflow velocity... Compared to the near-stationary state of the car body surface, kinetic energy is converted into pressure energy, forming a high static pressure zone. The fender is located on a streamlined side, where the airflow velocity... The airflow velocity is positively correlated with vehicle speed, resulting in a high-velocity area and a low-static-pressure zone. This creates a driving pressure difference between the intake and exhaust ports of the lamp housing. .

[0030] Drive pressure difference The calculation is expressed by formula (2):

[0031] ;

[0032] To quantify the impact of vehicle speed on the system, the vehicle speed is set to... In the idealized model, we set... and At this point, the maximum theoretical pressure difference This can be expressed by formula (3):

[0033] ;

[0034] In the driving pressure difference Under the influence of the air intake assembly, dry external air enters the lamp cavity through the intake guide assembly and is discharged through the exhaust vent assembly, forming a continuous air circulation. The flow rate of this air circulation, i.e., the air exchange rate, is... It can be expressed by formula (4):

[0035] ;

[0036] in: This indicates the volumetric flow rate through the lamp cavity; Indicates the effective cross-sectional area of ​​the flow guiding hose; This represents the flow coefficient, which is determined by the length of the flow guide hose, the roughness of its inner wall, and the air permeability resistance of the waterproof and breathable membrane. Indicates the vehicle's speed.

[0037] The above structure and connection relationship ensure that when the combination lamp is in working condition and the vehicle is moving, the gas flow direction inside the lamp cavity is always from the air intake port to the exhaust port, and active defogging is achieved by using the pressure difference generated by the kinetic energy of the vehicle.

[0038] The air intake guide assembly mainly consists of a guide hose, an air intake collection head, and a fixed bracket.

[0039] The flow guiding hose is made of ethylene propylene rubber or thermoplastic elastomer, featuring high temperature resistance, aging resistance, and flexibility. The inner diameter of the flow guiding hose is set as follows: Its numerical range depends on the required air exchange rate. The space allocated to the front of the vehicle is typically set between 8mm and 15mm. The guide hose has a reinforced rib structure in its wall to prevent collapse under high-temperature conditions in the engine compartment or under negative pressure intake. Specifically, the guide hose is made of a material with a temperature resistance rating of -40℃ to 125℃ to withstand the extreme thermal cycling environment in the engine compartment. Furthermore, the connection method between the guide hose and the intake interface is not limited to clamps. In embodiments with high automation requirements, quick-connect couplings with O-ring seals or rotary locking mechanisms can also be used to ensure an airtight leakage rate of less than 5ml / min@5kPa.

[0040] The air intake sensor is located at the beginning of the guide hose and within the frame area of ​​the vehicle's active air intake grille. The air intake sensor has a flared structure with an opening cross-sectional area larger than that of the guide hose, configured to reduce pressure loss at the airflow inlet and increase air intake volume. The opening of the air intake sensor is parallel to the vehicle's longitudinal axis of travel and directly faces the oncoming airflow during vehicle movement to capture maximum dynamic pressure.

[0041] The mounting bracket, made of rigid plastic or metal, mechanically anchors the air intake sensor to the stationary frame of the active air intake grille or the inner support structure of the front bumper. The mounting bracket is positioned to avoid the movement trajectory of the active air intake grille blades, ensuring that the air intake sensor remains in a constant high-pressure stagnation zone and does not change position with the opening and closing of the grille blades.

[0042] On the front combination lamp side, the air intake interface is a cylindrical boss structure integrally formed on the back of the lamp housing. The axis of the air intake interface is perpendicular to or tangential to the wall of the lamp cavity. The end of the air guide hose is fitted onto the outer wall of the air intake interface and is circumferentially tightened by fastening clamps to achieve an airtight connection.

[0043] To further optimize the defogging effect inside the lamp housing, an internal airflow duct is connected to the air intake interface within the lamp housing. This internal airflow duct is a tubular or grooved structure extending to the inner surface of the front combination lamp's lens. The internal airflow duct can be assembled as a separate injection-molded part onto the lamp's decorative frame, or it can be integrally injection-molded from the main body of the decorative frame to form the airflow channel. Its outlet geometry can be designed as a flat nozzle to increase the airflow coverage width, causing the airflow blowing towards the lens to be distributed in a fan shape, thereby expanding the effective defogging area. The outlet of the internal airflow duct faces the fog-prone area of ​​the lens (usually the lower edge or corner of the lens). The internal airflow duct is configured to directly guide the high-speed dry airflow introduced from the flexible guide tube to the inner surface of the lens, forming a wall-attached airflow on the inner surface of the lens. This accelerates the evaporation and dissipation of condensate by enhancing the local convective heat transfer coefficient.

[0044] In addition, a grid or coarse filter is installed at the inlet of the air intake end to intercept external debris such as sand, insects, and dead leaves with a diameter larger than a preset threshold, preventing them from entering the guide hose or the lamp housing. The guide hose, along its path from the air intake end to the air intake interface, includes a U-shaped or S-shaped settling section. The lowest point of this settling section is lower than the height of the air intake interface, designed to prevent rainwater from flowing directly into the lamp housing due to gravity along the pipe.

[0045] The exhaust ventilation component is integrated into the rear structure of the front combination lamp housing, specifically located in the pointed corner area of ​​the housing extending below the vehicle fender. This pointed corner area corresponds to the airflow acceleration zone on the side of the vehicle in terms of aerodynamic shape. As airflow passes the front corner and flows rearward along the fender surface, the increased streamline curvature leads to increased flow velocity, thereby creating a stable low static pressure field on the surface of this area.

[0046] The exhaust and ventilation assembly mainly consists of an exhaust seat, a waterproof and breathable membrane, and an external flow guide and protective cover.

[0047] The vent base is a raised structure integrally injection molded onto the wall of the lamp housing. A vent window is located in the center of the vent base. The vent window contains cross-shaped or honeycomb-shaped support ribs. These support ribs are configured to increase the structural strength of the vent window and provide physical support for the waterproof and breathable membrane covering it, preventing excessive deformation or rupture of the membrane under severe pressure fluctuations or external mechanical impacts.

[0048] The waterproof and breathable membrane is made of expanded polytetrafluoroethylene (ePTFE) microporous material. This material has a multi-directional stretched node and fibrous structure, with micropore sizes controlled between 0.2 and 3.0 micrometers. This pore size physically allows water vapor molecules with a diameter of approximately 0.0004 micrometers to pass through freely, while utilizing the material's low surface energy to create a hydrophobic barrier, blocking droplets, rainwater, and car wash water jets with diameters typically greater than 100 micrometers from entering. In terms of specific implementation parameters, the selected waterproof and breathable membrane has an inlet water pressure greater than 10 kPa, ensuring no water permeability failure during high-pressure car washes (the impact pressure reaching the headlight surface after nozzle pressure decay is typically about 5-8 kPa). Simultaneously, the typical air permeability of this membrane is selected between 4000 ml / min / cm²@70 mbar and 8000 ml / min / cm²@70 mbar to balance air permeability efficiency and protection level. The waterproof and breathable membrane is sealed and fixed to the end face of the exhaust seat by ultrasonic welding or insert injection molding process, ensuring that only gas can be exchanged through the membrane and there is no bypass leakage.

[0049] The external airflow guide cover is fastened onto the exhaust seat, completely enclosing the waterproof and breathable membrane. A preset distance is maintained between the inner wall of the external airflow guide cover and the outer surface of the waterproof and breathable membrane, forming an exhaust buffer chamber. The external airflow guide cover is not a completely enclosed structure; its side walls or bottom walls have several airflow guide and exhaust holes.

[0050] The opening plane of the exhaust vent is parallel to or forms an acute angle with the mainstream airflow direction outside the vehicle, and the opening faces away from the windward side when the vehicle is moving. This geometric configuration prevents external sand, gravel, and high-pressure water from directly impacting the waterproof and breathable membrane. Simultaneously, when the high-speed airflow in the fender area sweeps across the outer surface of the external airflow shield, a suction effect is generated at the exhaust vent, reducing the air pressure within the exhaust buffer chamber. This suction effect, combined with the already low static pressure environment in the fender area, further reduces the pressure value at the exhaust end. This increases the overall driving pressure difference of the system. .

[0051] This structure enables the exhaust ventilation component to have dual functions: when the vehicle is stationary or moving at low speed, it relies on the Brownian motion of molecules to balance the air pressure and humidity inside and outside the lamp through a waterproof and breathable membrane; when the vehicle is moving at medium to high speed, it acts as a high-efficiency low-pressure air extraction unit, working with the intake air guide component to achieve directional active airflow circulation.

[0052] The vehicle is traveling at a speed During forward movement, the airflow field around the vehicle body exhibits a specific pressure distribution gradient. This gradient is determined by the geometry and aerodynamic characteristics of the vehicle body's outer surface.

[0053] The active grille area is located at the very front of the vehicle and is considered a stagnation zone in aerodynamics. When relative airflow impacts this vertical or near-vertical surface, the airflow is obstructed and stagnant, affecting the relative velocity of air particles. It decreases sharply and approaches zero. According to Bernoulli's principle of energy conservation, the kinetic energy lost by the airflow is converted into the static pressure energy of the fluid, causing the static pressure in that region to decrease. Higher than far-field atmospheric pressure This creates a positive pressure zone.

[0054] Conversely, the fender area is located on the side of the vehicle and is typically designed with a certain radius of curvature to guide airflow. When airflow bypasses the corner of the front of the car and enters this area, it is forced to accelerate to maintain continuity, resulting in a localized flow velocity at that location. The elevation is increased, and usually exceeds the vehicle's speed. The increase in flow velocity causes static pressure energy to be converted into kinetic energy, thus increasing the static pressure in that region. Below far-field atmospheric pressure This can even create a negative pressure zone.

[0055] This embodiment utilizes a physical connection channel to couple the two regions with pressure differences. The internal cavity of the front combination lamp is connected in series between the intake air guide assembly and the exhaust vent assembly, forming an airflow bypass that spans the positive and negative pressure zones. Due to A pressure gradient with a constant direction is established at both ends of the lamp cavity. This pressure gradient does not depend on active devices such as electric fans or heaters, but is directly generated by the relative motion between the vehicle and the air. In essence, it converts the mechanical energy of the vehicle's movement into pressure potential energy that drives the flow of the defogging airflow through a fluid medium.

[0056] This embodiment quantifies the physical mechanism of the airflow circulation inside the drive headlight combination lamp. The model is based on Bernoulli's equation for incompressible fluids and analyzes the fluid state between the inlet of the intake guide assembly (defined as point 1) and the outlet of the exhaust vent assembly (defined as point 2).

[0057] For points 1 and 2 on the same streamline, the energy conservation equation is given by formula (5):

[0058] ;

[0059] in: Represents hydrostatic pressure; This represents air density, which is approximately 1.225 kg / m³ under standard atmospheric pressure and at 25 degrees Celsius. Represents fluid velocity; Represents gravitational acceleration; This represents the height relative to the reference plane.

[0060] In practical applications of vehicle engineering, the height difference between the intake manifold and the exhaust manifold is typically less than 0.5 meters. This height difference is significant relative to the aerodynamic pressure difference generated by the vehicle's high-speed operation. The resulting gravitational potential energy term It is extremely small and is negligible in engineering calculations. Therefore, the equation simplifies to formula (6):

[0061] ;

[0062] To solve for the driving pressure difference across the system This embodiment introduces vehicle speed. As the independent variable, the following boundary conditions are set:

[0063] Intake boundary conditions: Point 1 is located on the windward side of the active air intake grille. In this area, relative airflow is obstructed and stagnant, forming a stagnation point. The relative airflow velocity at this point is [value missing] in a coordinate system with the vehicle as the reference frame. It is approximated to 0. At this point, the pressure at the intake port is... Approximately the total pressure of the airflow.

[0064] Exhaust-end boundary conditions: Point 2 is located in the side flow field of the fender. Airflow through this region does not separate and remains attached. The relative air velocity at this point is [value missing] in a coordinate system with the vehicle as the reference frame. Equal to or slightly greater than the vehicle's speed To construct a conservative engineering calculation model, we set... At this time, the pressure at the exhaust port... Static pressure close to that of free flow.

[0065] Substituting the above boundary conditions into formula (6), we obtain the final quantification formula (7) for the pressure difference driving model:

[0066] ;

[0067] Formula (7) shows the pressure difference of the airflow circulation inside the driving lamp. With vehicle speed It is proportional to the square of.

[0068] When the vehicle is stationary ( )hour, The system has no active driving force. As the vehicle starts and accelerates, It exhibits parabolic growth. For example, when the vehicle speed doubles, the driving pressure difference increases to four times. This nonlinear gain characteristic allows the system to obtain significantly enhanced pressure potential energy under high-speed driving conditions (when the front combination lights typically face a more severe challenge in air cooling and are prone to condensation), thereby providing stronger airflow driving force to counteract the risk of condensation.

[0069] This embodiment further establishes the air exchange rate. Mathematical correlation with system geometric parameters and vehicle driving conditions is used to quantitatively evaluate the system's defogging efficiency. Air exchange rate. Defined as the volume of air flowing through the internal cavity of the front combination lamp per unit time, it directly determines the efficiency of replacing the hot and humid air inside the cavity with the dry and cold air outside.

[0070] Based on the orifice outflow and pipeline flow theories of fluid mechanics, a pressure difference exists between the intake and exhaust ports. Under these conditions, the flow rate through this ventilation duct Described by formula (8):

[0071] ;

[0072] Formula (7) in the aforementioned differential pressure driven model Substitute into equation (8) to eliminate the fluid density And the constant term, we obtain the direct relationship between flow rate and vehicle speed (9):

[0073] ;

[0074] Formula (9) reveals the core operating characteristic of this system: air exchange rate. With vehicle speed They exhibit a linear proportional relationship. The physical definitions and technological impacts of each parameter are as follows:

[0075] (Effective flow cross-sectional area): This parameter is mainly determined by the inner diameter cross-sectional area of ​​the flow guiding hose. In the embodiment, by selecting a flow guiding hose with a larger inner diameter (e.g., increasing the inner diameter from 8mm to 12mm), the effective flow area can be directly increased. This value, thus multiplying the air exchange rate at the same vehicle speed. This parameter is a primary variable in the system design for adjusting the defogging capability.

[0076] (System flow coefficient): This is a dimensionless comprehensive physical quantity that characterizes the flow efficiency of airflow throughout the entire circulation path. The value range is usually less than 1, and its magnitude is jointly constrained by the following flow resistance factors:

[0077] Frictional resistance along the flow path: The longer the flow guide hose and the greater the roughness of its inner wall, the greater the frictional resistance along the flow path. Decrease.

[0078] Local resistance: The number of bends in the pipeline, the shape factor of the intake sampling end, and the expansion and contraction structure of the exhaust port all contribute to local pressure loss.

[0079] Flow resistance of the breathable component: The waterproof and breathable membrane in the exhaust ventilator is the component with the highest flow resistance in the entire circuit. Its air permeability (usually measured in ml / min / cm²@70mbar) directly determines the flow resistance of the ventilator. The upper limit. In this embodiment, expanded polytetrafluoroethylene (ePTFE) material with high air permeability is selected to reduce air permeability resistance, thereby maximizing... value.

[0080] Defogging efficiency correlation: Formula (9) shows that as the vehicle speed increases... The increase in the flow rate of dry air entering the lamp cavity Linear increase. This high-speed airflow produces two physical effects:

[0081] Humidity displacement effect: It quickly expels the high humidity air accumulated in the cavity and introduces the outside air with lower relative humidity, reducing the water vapor partial pressure in the cavity and disrupting the dew point conditions.

[0082] Convection evaporation effect: Increases the convective heat transfer coefficient of the inner surface of the lens, accelerates the phase change evaporation process of the condensed liquid water film, and the evaporated water vapor is then carried out by the airflow.

[0083] Therefore, by optimizing the diameter of the flow guiding hose And optimize pipeline routing and select breathable membranes to improve flow coefficient. This ensures that the system can generate an air exchange rate sufficient to eliminate fogging inside the front combination lights within the commonly used low-to-medium speed to high-speed driving range. .

[0084] When the vehicle is stationary or crawling at very low speed (e.g.) At this time, the external airflow field has not yet formed a significant dynamic pressure. At this point, the pressure difference between the inlet of the intake guide assembly and the outlet of the exhaust vent assembly is significant. Approaching zero. Under this condition, the system switches to a passive working mode, mainly relying on the waterproof and breathable membrane in the exhaust and venting components to maintain the microenvironmental balance of the lamp cavity.

[0085] In passive operating mode, the system's physical mechanism shifts from being dominated by macroscopic convection to being dominated by microscopic molecular diffusion. When the current combination lamp is lit, the heat generated by the light source causes the temperature of the gas inside the lamp cavity to rise. According to the ideal gas law (Charles' Law), within a cavity of relatively constant volume, the temperature increase will lead to a decrease in internal gas pressure. Rise. When Greater than the external atmospheric pressure At this time, the waterproof and breathable membrane allows expanding air molecules to permeate and escape from the inside out, preventing the lamp housing from deforming or failing to seal due to overpressure.

[0086] Conversely, when the light fixture is turned off and cools down, or when the external ambient temperature drops suddenly, the air pressure inside the light fixture cavity decreases, creating a negative pressure. At this time, external air molecules permeate from the outside to the inside through the waterproof and breathable membrane to replenish the pressure difference and balance the pressure difference between the inside and outside.

[0087] In this process, although the air intake guide assembly physically connects the lamp cavity to the external environment, the relatively long length (usually greater than 500mm) and relatively small diameter of the guide hose result in flow resistance along the path due to its aspect ratio, making its efficiency as a breathing channel far lower than that of a waterproof and breathable membrane. Therefore, under static and low-speed operating conditions, most of the gas exchange is completed through the exhaust breathable assembly.

[0088] Furthermore, the microporous structure (pore size 0.2-3.0 micrometers) of the waterproof and breathable membrane plays a crucial barrier role at this stage. Utilizing the material's hydrophobic properties, it allows gas molecules to freely enter and exit while effectively preventing condensation droplets accumulated on the inside of the fenders during stationary conditions, water flow during car washes, and environmental dust particles from entering the lamp housing. This ensures the cleanliness and dryness of the lamp's interior, laying the foundation for active defogging during subsequent driving.

[0089] When the vehicle accelerates to a medium-to-high speed driving state (e.g.) When the flow rate reaches a critical threshold, the system enters active defogging mode. At this point, there is a critical flow rate required for activation. This critical value depends on the overall friction loss of the system. It only applies when the vehicle's speed... When the generated dynamic head is greater than the total pressure loss of the pipeline system, the effective active circulation flow rate is... It has only just begun to form. Based on fluid simulation and actual measurements, the effective critical flow velocity for startup in this embodiment was determined. The setting is within the range of 15km / h to 25km / h, ensuring that the active defogging function can be triggered when the vehicle is driving on regular urban roads. As the vehicle speed increases, based on the aforementioned fluid dynamics principles, a significant positive pressure is established at the air intake collection end of the air intake guide assembly. A negative pressure is formed outside the exhaust vent assembly located in the fender area. The resulting driving pressure difference It overcomes the flow resistance of the flow guide hose and waterproof breathable membrane, and stimulates and maintains a continuous unidirectional airflow circulation.

[0090] The specific path and physical process of this active airflow circulation are as follows:

[0091] First, a stream of relatively cool and dry fresh air from the external environment is captured by the air intake sensor. Due to the ramming effect generated by the vehicle's movement, this airflow is forced into the guide hose.

[0092] Subsequently, the high-pressure airflow is delivered along the guide hose to the air intake of the front combination lamp and enters the lamp housing. To maximize defogging efficiency, the airflow does not diffuse randomly within the housing but is guided directionally by the internal guide duct. The internal guide duct propels the high-speed airflow onto the inner surface of the lens.

[0093] When the dry airflow passes over the inner surface of the lens, a vigorous exchange of mass and heat occurs. The airflow absorbs heat from the lens surface through convection and absorbs condensed water droplets or water vapor about to condense through mass transfer. The high-speed airflow continuously washes away the stagnant air layer accumulated in the dead corners of the lens, effectively reducing the boundary layer thickness and relative humidity in that area.

[0094] Finally, the exhaust gas, carrying moisture and heat, flows towards the exhaust port under the pressure within the lamp housing. At the exhaust venting assembly, due to the Venturi suction effect generated by the external airflow shield and the low-pressure environment in the fender area itself, the exhaust gas is accelerated and drawn in, then discharged through the waterproof and breathable membrane into the free flow field outside the vehicle body.

[0095] This process is a dynamic equilibrium continuous cycle. As the vehicle's speed increases... Further increase in circulating air volume As the speed increases linearly, the defogging capability also increases. This adaptive adjustment characteristic with vehicle speed perfectly addresses the increased risk of headlight fogging due to enhanced air cooling at high speeds, thus achieving intelligent, on-demand defogging without sensor control or electric drive.

[0096] The defogging method provided by this invention utilizes fluid dynamics principles to reconstruct the heat and moisture exchange balance of the front combination lamps. Through the synergistic effect of the aforementioned structure and process, the system achieves triple defogging intervention in the physical environment:

[0097] First, the dew point environment is disrupted. Fog formation is essentially caused by condensation when the hot, humid air inside the lamp housing comes into contact with the lens, which is cooled by external cold air, resulting in a local temperature below the dew point. This system introduces dry external air through an air intake guide assembly, continuously diluting the water vapor concentration inside the lamp housing and reducing absolute humidity. This directly lowers the dew point temperature of the internal air, making it difficult for saturation condensation conditions to be reached on the lens surface.

[0098] Second, forced convection acceleration. Traditional car lights mainly rely on natural convection for heat and moisture transfer, which is inefficient and prone to creating dead zones in corners. This system utilizes the pressure difference generated by the vehicle's kinetic energy. Driven by forced convection, the high-speed airflow increases the convective heat transfer coefficient on the inner surface of the lens, accelerates the evaporation phase change rate of liquid condensate, and shifts the static evaporation-condensation equilibrium towards rapid evaporation.

[0099] Third, thermal load management. The continuously flowing cool air carries away moisture and excess heat generated by the LED light source and driver circuit. This air-cooling effect reduces the thermal stress on the internal components of the lamp, and indirectly mitigates the moisture absorption caused by the rapid cooling effect after the engine is turned off when the lamp is parked by reducing the temperature difference between the inside and outside.

[0100] In summary, this invention constructs a passive fluid loop of high-pressure intake-cavity scavenging-low-pressure exhaust, converting the aerodynamic energy dissipated on the surface during vehicle operation into the driving potential energy required for defogging. This mechanism eliminates the need for additional electric heating films, desiccants, or electric fans, avoiding power consumption and electromagnetic interference issues. Furthermore, with no moving mechanical parts, it boasts extremely high reliability and durability, completely resolving the technical contradiction between the insufficient defogging efficiency of traditional passive breathing structures for vehicle lights and the high cost of active defogging devices.

[0101] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A vehicle driving pressure differential type active defogging method for front combination lamps based on Bernoulli's principle, characterized in that, Includes the following steps: An air inlet and an exhaust outlet are provided on the lamp housing of the front combination lamp. The air inlet is connected to the inside of the lamp housing, and the exhaust outlet is connected to the inside of the lamp housing. Configure an air intake guide assembly, physically connecting one end of the air intake guide assembly to the airflow collection point in the active air intake grille area of ​​the vehicle, and airtightly connecting the other end to the air intake interface; An exhaust ventilation component is configured, which is integrated into the housing area extending from the front combination light to below the vehicle fender and covers and seals the exhaust port. When the vehicle is in motion, the hydrostatic pressure difference generated between the active air intake grille area and the vehicle fender area drives external air to enter the lamp cavity through the air intake guide assembly and exit through the exhaust vent assembly.

2. The active defogging method for vehicle driving pressure differential type front combination lamps based on Bernoulli's principle according to claim 1, characterized in that, The steps for configuring the air intake guide assembly include: An air intake sampling head with a flared structure is provided at the starting end of the air intake guide assembly, and the air intake sampling head is mechanically anchored to the frame of the active air intake grille or the inner support structure of the front bumper by a fixed bracket. A flexible guide hose is selected to connect the air intake sampling end and the air intake interface. A U-shaped or S-shaped settling section is set on the arrangement path of the flexible guide hose from the air intake sampling end to the air intake interface. The lowest point of the settling section is lower than the height of the air intake interface.

3. The active defogging method for vehicle driving pressure differential type front combination lamps based on Bernoulli's principle according to claim 2, characterized in that, The method further includes: An internal air duct is connected inside the lamp cavity. One end of the internal air duct is connected to the air inlet, and the other end extends to the inner surface of the lens of the front combination lamp. The air outlet of the internal air duct is constructed as a flat nozzle, and the air outlet is oriented toward the lower edge or corner area of ​​the lens.

4. The active defogging method for vehicle driving pressure differential type front combination lamps based on Bernoulli's principle according to claim 1, characterized in that, The steps for configuring the exhaust and ventilation components include: An exhaust seat is injection molded on the housing wall of the lamp cavity, a ventilation window is opened in the center of the exhaust seat, and a support rib is provided inside the ventilation window; A waterproof and breathable membrane made of expanded polytetrafluoroethylene microporous material is used, and the waterproof and breathable membrane is sealed and fixed to the end face of the exhaust seat by ultrasonic welding or insert injection molding process.

5. The active defogging method for vehicle driving pressure differential type front combination lamps based on Bernoulli's principle according to claim 4, characterized in that, The method further includes: An external flow guide shield is fastened and installed on the exhaust seat, and the external flow guide shield is configured to cover the waterproof and breathable membrane. An exhaust buffer cavity is defined between the inner wall of the external flow guide shield and the outer surface of the waterproof and breathable membrane. A number of airflow guiding and exhaust holes are opened on the side wall or bottom wall of the external airflow guiding and protective cover, and the opening plane of the airflow guiding and exhaust holes is set to face away from the windward side when the vehicle is traveling.

6. The active defogging method for vehicle driving pressure differential type front combination lamps based on Bernoulli's principle according to claim 1, characterized in that, The active air intake grille area corresponds to the airflow stagnation area on the vehicle body surface; the vehicle fender area corresponds to the airflow acceleration area on the side of the vehicle body.

7. The active defogging method for vehicle driving pressure differential type front combination lamps based on Bernoulli's principle according to claim 1, characterized in that, The method further includes a passive breathing step: when the vehicle is stationary and the hydrostatic pressure difference is zero, or when the vehicle is traveling at low speed and the hydrostatic pressure difference is insufficient to overcome the system flow resistance, a waterproof and breathable membrane is used to facilitate molecular diffusion gas exchange between the lamp cavity and the external environment.

8. The active defogging method for vehicle driving pressure differential type front combination lamps based on Bernoulli's principle according to claim 1, characterized in that, The step of driving external air into the lamp cavity is triggered when the vehicle speed reaches the critical starting flow rate, and the numerical range of the critical starting flow rate is set to 15km / h to 25km / h.

9. The active defogging method for vehicle driving pressure differential type front combination lamps based on Bernoulli's principle according to claim 2, characterized in that, The method further includes: setting a grid or coarse filter at the inlet of the air intake collection head.

10. The active defogging method for vehicle driving pressure differential type front combination lamps based on Bernoulli's principle according to claim 1, characterized in that, The location of the airflow collection point is selected from the lower air intake of the front bumper of the vehicle, the front edge of the hood, or the positive pressure area at the front of the vehicle chassis; the location of the exhaust ventilation component is selected from the inside of the front wheel arch, the negative pressure area in the middle of the chassis, or the guide groove area on the side of the front bumper.

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