Dirt detection method and dirt detection device for range hood and range hood

Abstract

The invention relates to a smudginess detection method and a smudginess detection device for a range hood and the range hood, and the smudginess detection method realizes accurate detection of the smudginess degree of an impeller by adopting a scheme of fusing current monitoring and pressure difference monitoring and dynamically compensating pollution accumulation along with time. The problems that a pure air pressure difference detection mode is easily interfered by state changes of a filter screen and a public flue and a pure current detection mode is easily interfered by temperature rise of a power grid and a motor are solved, and due to the fact that the smudginess detection mode is a non-contact mode, various defects caused by contact measurement such as a mechanical mode can be avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of range hoods, and in particular to a dirt detection method and a dirt detection device for a range hood, and a range hood. Background Art

[0002] Range hoods have become an indispensable kitchen appliance in modern homes. They operate using the principles of fluid dynamics, using a centrifugal fan mounted inside the hood to draw in and exhaust oil fumes, while a filter removes some grease particles. A centrifugal fan consists of a volute, an impeller mounted within the volute, and a motor that drives the impeller. As the impeller rotates, negative pressure is generated at the fan's center, drawing oil fumes from beneath the hood into the fan. After acceleration, the impeller collects them in the volute and directs them outside. The impeller in the fan system is a key component susceptible to oil contamination, affecting its performance. Currently, most range hoods use a maintenance reminder system that accumulates impeller operating time. However, this method has several drawbacks: First, cooking habits vary greatly among users, leading to significant variations in the accumulation of oil on the impeller blades. In regions like Sichuan and Chongqing, oil accumulation may be severe before the maintenance reminder arrives, while in regions like Zhejiang and Jiangsu, no significant contamination may be observed after several reminder cycles. This can lead users to mistrust the accuracy of cleaning reminders. Secondly, the position of the impeller during operation and after operation causes differences in the amount of oil contacted and accumulated in different areas. Some areas are thick, while others are thin. Time-based reminders cannot take into account the actual accumulation of oil in different areas. The coatings in some areas have fallen off, while some areas are not cleaned. Furthermore, reminder methods that rely solely on time accumulation have a high rate of misjudgment, which can easily lead to users finding that there is no obvious dirt after door-to-door cleaning or automatic cleaning, and feeling that the manufacturer's judgment is uncontrollable, unintelligent, and charges randomly, resulting in a poor experience. In addition, there are also current detection or simple pressure difference detection to determine whether the impeller is contaminated and whether the fan is working properly, such as a method for detecting the weight of oil on fan blades and a range hood with application number CN202311452271.6, and a range hood and cleaning reminder method thereof with CN202310535199.7.

[0003] However, the above-mentioned range hood dirtiness detection methods all adopt a single-factor detection method. Among them, the current monitoring method alone is susceptible to attenuation interference caused by grid voltage fluctuations, motor efficiency and motor heating, and the pressure difference monitoring method alone cannot distinguish between impeller dirtiness and front-end filter blockage or rear-end flue blockage.

[0004] Therefore, the existing dirt detection method of the range hood needs to be further improved. Summary of the Invention

[0005] The first technical problem to be solved by the present invention is to provide a range hood dirt detection method that can more accurately detect the accumulation of dirt on the impeller surface in response to the current status of the existing technology.

[0006] The second technical problem to be solved by the present invention is to provide a dirt detection device that applies the above-mentioned dirt detection method in response to the current status of the existing technology.

[0007] The third technical problem to be solved by the present invention is to provide a range hood using the above-mentioned dirt detection device in view of the current status of the existing technology.

[0008] The technical solution adopted by the present invention to solve the first technical problem is: a method for detecting dirtiness of a range hood, characterized by comprising the following steps:

[0009] S1. Install a pressure difference detection module near the air inlet and outlet of the range hood fan system, and use the pressure difference detection module and the current detection module in the motor drive system to obtain operating data in real time;

[0010] S2. Pre-establishing reference current values ​​I0 and reference pressure difference values ​​ΔP0 corresponding to different rotation speeds of the range hood in the cleaning state, and then fitting to form corresponding reference curves;

[0011] S3, collecting the actual current value I and the actual pressure difference value ΔP at the current speed of the range hood in real time, and then calculating the current residual δI = |I-I0| / I0 and the pressure difference residual δΔP = |ΔP-ΔP0| / ΔP0 respectively;

[0012] S4. Based on the above current residual δI and voltage difference residual δΔP, dynamically calculate the corresponding current credibility factor γ I and pressure difference credibility factor γ ΔP :

[0013] γ I =e -λ·δI ;

[0014] γ ΔP =e -λ·δΔP ;

[0015] Among them, λ is the preset sensitivity coefficient;

[0016] S5. Normalize the above current credibility factor and voltage difference credibility factor to obtain corresponding dynamic weights:

[0017] The dynamic weight of the current credibility factor is: A = γI / (γI+γΔP);

[0018] The dynamic weight of the pressure difference credibility factor is: B = γΔP / (γI+γΔP);

[0019] The above dynamic weights meet the conditions: A+B=1;

[0020] S6. Fusion calculates the dirtiness index D = A·δI + B·δΔP, and then determines the dirtiness level based on the numerical range of the dirtiness index D.

[0021] The above-mentioned "clean state" generally refers to the standard operating condition of the range hood without oil accumulation, such as the performance of a new machine when it is used for the first time or after professional cleaning as the judgment benchmark.

[0022] The aforementioned "differential pressure detection module" generally refers to a sensor combination that measures the gas pressure difference between two points in a flow path, such as a differential pressure transmitter, a dual pressure sensor + a microprocessor, etc.

[0023] In order to improve the accuracy of the fitted reference curve, in the above step S2, the establishment of the reference parameters includes the following steps: collecting I0(ωi) and ΔP0(ωi) at multiple motor speed points ωi, and generating the reference curve of I0=f1(ω) and ΔP0=f2(ω) by piecewise linear fitting or polynomial fitting:

[0024] The reference curve corresponding to the current is I0=k1ω+c1;

[0025] The reference curve corresponding to the pressure difference is: ΔP0=k2ω 2 +c2;

[0026] And store the coefficients (k1, c1, k2, c2) corresponding to the reference curve.

[0027] Considering that a too small λ may make the credibility factor insensitive to residuals, while a too large λ may amplify the impact of noise and reduce stability, the sensitivity coefficient λ in step S4 is set to a value range of 8-12. Limiting the sensitivity coefficient to this range: λ = 8-12 can effectively balance sensitivity and noise immunity. When λ < 8, the credibility factor decreases too slowly, making it impossible to effectively distinguish between normal and abnormal states. When λ > 12, even slight fluctuations can cause a sharp drop in credibility, easily triggering the fault mechanism.

[0028] Considering the failure of a single sensor (such as reading drift), if dynamic weighting is continued to be used, the dirt index may be seriously distorted. Therefore, in step S5, when one of the pressure difference detection module or the current detection module fails, the weight adjustment mechanism is automatically triggered:

[0029] If δI ≥ 0.5, then force A = 0, B = 1;

[0030] If δΔP≥0.5, then A=1 and B=0 are forced to be set.

[0031] The above-mentioned automatic trigger weight adjustment mechanism can achieve fault isolation and failure protection. That is, when the residual of a parameter is ≥0.5 (that is, the deviation is ≥50%), its weight is forced to 0, completely eliminating the influence of fault data; ensuring that the system can still output reliable judgments based on valid parameters in the event of local faults.

[0032] As an improvement, in step S6, after determining the dirt level, a cleaning reminder action corresponding to the level is executed:

[0033] When D < 0.1, it is judged to be in normal state;

[0034] When 0.1≤D<0.3, it is judged as light pollution and a corresponding warning signal is issued;

[0035] When 0.3≤D<0.5, it is judged as moderate pollution and a corresponding warning signal is issued;

[0036] When D≥0.5, it is judged as severe pollution and a corresponding warning signal is issued.

[0037] The Dirt Index (D) is divided into four levels (Normal / Light / Medium / Heavy) to more accurately match cleaning needs. The aforementioned reminder signal can be at least one of an audio and visual reminder, a display message reminder, and a cloud push notification, thereby preventing performance degradation or safety hazards caused by oil accumulation.

[0038] Considering that different pollution levels require differentiated treatment, manual operation is inefficient and difficult to perform, step S6 further includes the following steps:

[0039] When 0.1≤D<0.3, light pollution treatment is triggered: the corresponding indicator light is turned on and the impeller is started to rotate, and the range hood is in oil-stripping mode;

[0040] When 0.3≤D<0.5, moderate pollution treatment is triggered: the corresponding indicator light is lit and the automatic cleaning program is started;

[0041] When D≥0.5, a severe pollution alarm is triggered: the corresponding indicator light is lit and a door-to-door cleaning service request is pushed.

[0042] The above-mentioned "oil-stripping mode" refers to the operation of stripping liquid oil from the impeller surface using centrifugal force.

[0043] As an improvement, the oil-swing mode is to control the fan speed to increase to 110%-150% of the current gear and maintain it for a preset time.

[0044] The technical solution adopted by the present invention to solve the second technical problem is: a dirt detection device for a range hood, comprising a housing and a fan system disposed within the housing, the fan system comprising a volute, an impeller disposed within the volute, and a drive motor for driving the impeller to rotate, the volute having an air inlet and an air outlet, and a pressure difference detection module being disposed near the air inlet and the air outlet of the volute;

[0045] It also includes a current detection module and a controller for obtaining the current signal of the driving motor. The controller is electrically connected to the above-mentioned current detection module and pressure difference detection module, and determines the contamination level of the impeller according to the above-mentioned range hood contamination detection method.

[0046] The technical solution adopted by the present invention to solve the third technical problem is: a range hood, characterized in that it includes the above-mentioned dirt detection device of the range hood and a self-cleaning device for cleaning the impeller. When the dirt detection device detects that the dirt level of the impeller reaches a set level, the automatic cleaning program is started and the impeller is cleaned by the self-cleaning device.

[0047] As an improvement, the self-cleaning device includes a heating device or a steam generator for heating the cleaning liquid, a liquid supply pump for supplying the cleaning liquid to the heating device or the steam generator, and a nozzle member arranged adjacent to the impeller.

[0048] Compared with the existing technology, the advantages of the present invention are as follows: the dirt detection method of the range hood of the present invention realizes accurate detection of the dirtiness of the impeller by adopting a dynamic compensation scheme that combines current monitoring and pressure difference monitoring with pollution accumulation over time, avoiding the problem that the simple air pressure difference detection method is easily interfered by changes in the state of the filter and the public flue and the simple current detection method is easily interfered by the power grid and the temperature rise of the motor. Moreover, because this dirt detection method is non-contact, it can also avoid various defects caused by mechanical and other contact measurements. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 This is a schematic diagram of the installation of a range hood according to an embodiment of the present invention;

[0050] Figure 2 This is a schematic diagram of the three-dimensional structure of the range hood according to an embodiment of the present invention with part of the cover plate of the casing omitted;

[0051] Figure 3 A schematic diagram of the structure of the blade passages between adjacent blades being blocked during the process of gradually increasing impeller contamination level;

[0052] Figure 4 Flowchart of a range hood dirt detection method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0053] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0054] In the present specification and claims, directional terms such as "front," "back," "up," "down," "left," "right," "side," "top," and "bottom" are used to describe various exemplary structural parts and components of the present invention. However, these terms are used herein for convenience of description only and are based on the exemplary orientations shown in the accompanying drawings. Because the embodiments disclosed herein can be arranged in various orientations, these directional terms are intended for illustrative purposes only and should not be construed as limiting. For example, "up" and "down" are not necessarily limited to directions opposite to or consistent with the direction of gravity.

[0055] Figures 1-4 A preferred embodiment of the range hood dirt detection method, dirt detection device and range hood of the present invention is shown.

[0056] A method for detecting dirtiness of a range hood comprises the following steps:

[0057] S1. A pressure differential detection module 21 is installed near the air inlet 111 and air outlet 112 of the range hood's fan system. This pressure differential detection module 21 and a current detection module (not shown) in the motor drive system are used to acquire real-time operating data. The "pressure differential detection module" in this embodiment generally refers to a sensor combination that measures the gas pressure difference between two points in a flow path. Examples include a differential pressure transmitter, a dual pressure sensor, and a microprocessor.

[0058] The principle behind using the current detection module is as follows: When the impeller is contaminated, grease adheres to the pressure surface of the blades, resulting in uneven mass distribution. Meanwhile, blocked passages increase windage, leading to increased motor load torque. According to the law of conservation of energy, motor power P = T × ω (torque × angular velocity). When the load torque T increases, if the speed ω remains constant (for variable frequency motors), the current or power will increase.

[0059] The principle of air duct resistance monitoring using differential pressure sensor is as follows: Dirty impeller leads to a decrease in the effective cross-sectional area of ​​the channel between the blades, such as Figure 3 As shown, according to the Bernoulli equation in fluid mechanics, the duct resistance ΔP is proportional to the square of the flow rate Q (ΔP∝Q 2 By monitoring the pressure difference between the air inlet and outlet of the fan system, the degree of impeller blockage can be indirectly reflected.

[0060] S2. Pre-establish reference current values ​​I0 and reference pressure difference values ​​ΔP0 corresponding to different speeds of the range hood in a clean state, and then fit them to form corresponding reference curves; the aforementioned "clean state" generally refers to a standard operating condition of the range hood without oil accumulation, such as the performance of a new range hood when it is used for the first time or after professional cleaning, as a judgment benchmark.

[0061] More specifically, in order to improve the accuracy of the fitted reference curve, in the above-mentioned step S2, the establishment of the reference parameters includes the following steps: collecting I0(ωi) and ΔP0(ωi) at multiple motor speed points ωi, and generating a reference curve of I0=f1(ω) and ΔP0=f2(ω) by piecewise linear fitting or polynomial fitting:

[0062] The reference curve corresponding to the current is I0=k1ω+c1; (This reference curve is the motor linear load model)

[0063] The reference curve corresponding to the pressure difference is: ΔP0=k2ω 2 +c2; (This reference curve is obtained by simplifying the Bernoulli equation)

[0064] And store the coefficients (k1, c1, k2, c2) corresponding to the reference curve, that is, the reference parameters.

[0065] S3. After the range hood is turned on, the benchmark parameters are loaded. After the user selects the corresponding air volume level, the actual current value I and the actual pressure difference value ΔP at the current speed of the range hood are collected in real time. After filtering and denoising (such as using Kalman filtering denoising), the current residual δI = |I-I0| / I0 and the pressure difference residual δΔP = |ΔP-ΔP0| / ΔP0 are calculated respectively.

[0066] In the dual-sensor (i.e., current detection module and pressure difference detection module) fusion detection, it is necessary to dynamically adjust the weights of the two to achieve the following goals: one is the residual sensitivity balance: when the residual (the degree of deviation from the reference value) of a certain sensor increases, reduce its influence weight on the final dirtiness index D to avoid misjudgment due to single sensor failure or noise interference. The other is adaptive robustness: there is no need to pre-calibrate the statistical characteristics of sensor noise, and automatically adjust the weight through real-time residual feedback. In addition, it is also necessary to ensure that the sum of the weights is equal to 1, so that the dirtiness index D is always a normalized indicator. In a physical sense, when the residual δ increases, the credibility γ decreases exponentially, such as δ = 0 (no deviation), γ = 1 (completely credible), δ = 0.3 (moderate deviation), γ = e -10×0.3 ≈0.05 (very low credibility). Based on this, the steps for dynamically calculating the credibility factor based on the residual are as follows:

[0067] S4. Based on the above current residual δI and voltage difference residual δΔP, dynamically calculate the corresponding current credibility factor γ Iand pressure difference credibility factor γ ΔP :

[0068] γ I =e -λ·δI ;

[0069] γ ΔP =e -λ·δΔP ;

[0070] Among them, λ is a preset sensitivity coefficient, and λ is introduced to control the sensitivity of credibility to residuals. Considering that λ is too small, the credibility factor may be insensitive to residuals, and λ is too large, which may amplify the influence of noise and reduce stability. A slight residual can cause the weight to drop significantly. For this reason, in the above-mentioned S4 step, the value range of the sensitivity coefficient λ is 8-12. Limiting the sensitivity coefficient to this range: λ = 8 ~ 12 can better balance sensitivity and noise resistance. When λ < 8, the credibility drops too slowly and cannot effectively distinguish between normal and abnormal states; when λ > 12, slight fluctuations will cause a sudden drop in credibility, which can easily trigger the fault mechanism by mistake. Through experimental debugging, λ = 10 can achieve a balance between noise suppression and sensitivity, so this embodiment can set λ = 10.

[0071] S5. Normalize the above current credibility factor and voltage difference credibility factor to obtain corresponding dynamic weights:

[0072] The dynamic weight of the current credibility factor is: A = γI / (γI+γΔP);

[0073] The dynamic weight of the pressure difference credibility factor is: B = γΔP / (γI+γΔP);

[0074] The above dynamic weights meet the conditions: A+B=1;

[0075] If the two sensor residuals are the same, the weights are equal to 0.5

[0076] If a single sensor fails (e.g. δI = 1), then Weight A also approaches 0, and weight B approaches 1. At this point, the system relies on the pressure difference detection data to avoid misjudgments due to single sensor failure or large data fluctuations, and vice versa. In other words, if a single sensor failure (such as reading drift) is considered, continuing to use dynamic weights may seriously distort the dirt index. Therefore, in step S5, when one of the pressure difference detection module or the current detection module fails, the weight adjustment mechanism is automatically triggered:

[0077] If δI ≥ 0.5, then force A = 0, B = 1;

[0078] If δΔP≥0.5, then A=1 and B=0 are forced to be set.

[0079] The above-mentioned automatic trigger weight adjustment mechanism can achieve fault isolation and failure protection. That is, when the residual of a parameter is ≥0.5 (that is, the deviation is ≥50%), its weight is forced to 0, completely eliminating the influence of fault data; ensuring that the system can still output reliable judgments based on valid parameters in the event of local faults.

[0080] S6. Fusion calculates the dirt index D = A·δI + B·δΔP, and then determines the dirt level based on the numerical range of the dirt index D. In step S6, after determining the dirt level, perform a cleaning reminder action corresponding to the level:

[0081] When D < 0.1, it is judged to be in normal state;

[0082] When 0.1≤D<0.3, it is judged as light pollution and a corresponding warning signal is issued;

[0083] When 0.3≤D<0.5, it is judged as moderate pollution and a corresponding warning signal is issued;

[0084] When D≥0.5, it is judged as severe pollution and a corresponding warning signal is issued.

[0085] The Dirt Index (D) is divided into four levels (Normal / Light / Medium / Heavy) to more accurately match cleaning needs. The aforementioned reminder signal can be at least one of an audio and visual reminder, a display message reminder, and a cloud push notification, thereby preventing performance degradation or safety hazards caused by oil accumulation.

[0086] Taking into account that different pollution levels require differentiated treatment, manual operation is inefficient and difficult to implement, therefore, in step S6, the following steps are also included: when 0.1≤D<0.3, light pollution treatment is triggered: the corresponding indicator light is turned on and the impeller is started to rotate, and the oil-stripping mode of the range hood is executed; the above-mentioned "oil-stripping mode" refers to the operation of using centrifugal force to peel off the liquid oil on the surface of the impeller. Specifically, the oil-stripping mode is: controlling the fan speed to increase to 110%-150% of the current gear, and maintaining it for a preset time. When 0.3≤D<0.5, moderate pollution treatment is triggered: the corresponding indicator light is turned on and the automatic cleaning program is started. After the automatic cleaning program is completed, the above-mentioned dirt index D is continued to be retested; when D≥0.5, a heavy pollution alarm is triggered: the corresponding indicator light is turned on and a door-to-door cleaning service request is pushed.

[0087] The reference table for dirt level judgment and action response is as follows

[0088]

[0089] This embodiment also relates to a range hood contamination detection device, comprising a housing and a fan system disposed within the housing. The fan system includes a volute 11, an impeller 12 disposed within the volute 11, and a drive motor 13 for rotating the impeller 12. The volute 11 has an air inlet 111 and an air outlet 112. A pressure differential detection module 21 is disposed near the air inlet 111 and the air outlet 112 of the volute. The contamination detection device also includes a current detection module for acquiring a current signal from the drive motor and a controller. The controller is electrically connected to the current detection module and the pressure differential detection module and determines the contamination level of the impeller according to the range hood contamination detection method described above.

[0090] This embodiment also relates to a range hood, comprising the aforementioned dirt detection device and a self-cleaning device for cleaning the impeller. When the dirt detection device detects that the impeller has reached a set level of dirt, an automatic cleaning process is initiated, and the self-cleaning device cleans the impeller 12. The self-cleaning device includes a heating device or steam generator 31 for heating cleaning fluid, a liquid supply pump 32 for supplying cleaning fluid to the heating device or steam generator 31, and a nozzle member 33 positioned adjacent to the impeller. Specifically, the liquid supply pump 32 or water box 34 and steam generator 31 are provided on the top plate of the range hood casing 1. To facilitate cleaning in conjunction with the aforementioned dirt detection scheme, the liquid supply pump or water box is used to introduce clean water, with the option of adding detergent. Furthermore, considering that high temperature or steam can aid cleaning, a heating module or steam generation module is added. (The water can also be preheated by using the water flow through the radiator of the power board 14 to improve energy efficiency and reduce the temperature rise of the power board.) The nozzle part can be a stainless steel fan-shaped nozzle, installed on the inner wall of the volute, and the spray angle covers the axial area of ​​the impeller. When the dirt level is ≥ moderate (D ≥ 0.3): the controller starts the self-cleaning program: the liquid supply pump works for 2 minutes, and the impeller is rotated at a low speed synchronously to make the steam evenly cover the blades. When D ≥ 0.5, the door-to-door cleaning service appointment link is pushed to the user's mobile phone through the Wi-Fi module. The above-mentioned nozzle part can change the spray direction or be hidden by the motor. The installation structure and working process of the various components of the above-mentioned self-cleaning device are all existing technologies and will not be repeated here.

[0091] The dirt detection method for the range hood of this embodiment achieves accurate detection of the dirtiness of the impeller by integrating current monitoring and pressure difference monitoring with a dynamic compensation scheme for pollution accumulation over time, thereby avoiding the problem that a simple air pressure difference detection method is easily interfered with by changes in the state of the filter and the public flue, and a simple current detection method is easily interfered with by the power grid and the temperature rise of the motor. Moreover, because this dirt detection method is non-contact, it can also avoid various defects caused by contact measurements such as mechanical ones.

Claims

1. A method for detecting dirtiness of a range hood, characterized in that The following steps are involved: S1. Install a pressure difference detection module near the air inlet and outlet of the range hood fan system, and use the pressure difference detection module and the current detection module in the motor drive system to obtain operating data in real time; S2. Pre-establishing reference current values ​​I0 and reference pressure difference values ​​ΔP0 corresponding to different rotation speeds of the range hood in the cleaning state, and then fitting to form corresponding reference curves; S3, collecting the actual current value I and the actual pressure difference value ΔP at the current speed of the range hood in real time, and then calculating the current residual δI = |I-I0| / I0 and the pressure difference residual δΔP = |ΔP-ΔP0| / ΔP0 respectively; S4. Based on the above current residual δI and voltage difference residual δΔP, dynamically calculate the corresponding current credibility factor γ I and pressure difference credibility factor γ Δ P : c I =e -λ·δI ; c Δ P =e -λ·δΔP ; Among them, λ is the preset sensitivity coefficient; S5. Normalize the above current credibility factor and voltage difference credibility factor to obtain corresponding dynamic weights: The dynamic weight of the current credibility factor is: A = γI / (γI+γΔP); The dynamic weight of the pressure difference credibility factor is: B = γΔP / (γI+γΔP); The above dynamic weights meet the conditions: A+B=1; S6. Fusion calculates the dirtiness index D = A·δI + B·δΔP, and then determines the dirtiness level based on the numerical range of the dirtiness index D.

2. The range hood dirt detection method according to claim 1, characterized in that: In the above step S2, the establishment of the reference parameters includes the following steps: collecting I0(ωi) and ΔP0(ωi) at multiple motor speed points ωi, and generating the reference curves of I0=f1(ω) and ΔP0=f2(ω) by piecewise linear fitting or polynomial fitting: The reference curve corresponding to the current is I0=k1ω+c1; The reference curve corresponding to the pressure difference is: ΔP0=k2ω 2 +c2; And store the coefficients (k1, c1, k2, c2) corresponding to the reference curve.

3. The range hood dirt detection method according to claim 2, characterized in that: In the above step S4, the value range of the sensitivity coefficient λ is 8-12.

4. The range hood dirt detection method according to claim 1, characterized in that: In step S5, when one of the voltage difference detection module and the current detection module fails, the weight adjustment mechanism is automatically triggered: If δI ≥ 0.5, then force A = 0, B = 1; If δΔP≥0.5, then A=1 and B=0 are forced to be set.

5. The method for detecting dirtiness of a range hood according to any one of claims 1 to 4, characterized in that: In step S6, after determining the dirt level, a cleaning reminder action corresponding to the level is executed: When D < 0.1, it is judged to be in normal state; When 0.1≤D<0.3, it is judged as light pollution and a corresponding warning signal is issued; When 0.3≤D<0.5, it is judged as moderate pollution and a corresponding warning signal is issued; When D≥0.5, it is judged as severe pollution and a corresponding warning signal is issued.

6. The range hood dirt detection method according to claim 5, characterized in that: In step S6, the following steps are also included: When 0.1≤D<0.3, light pollution treatment is triggered: the corresponding indicator light is turned on and the impeller is started to rotate, and the range hood is in oil-stripping mode; When 0.3≤D<0.5, moderate pollution treatment is triggered: the corresponding indicator light is lit and the automatic cleaning program is started; When D≥0.5, a severe pollution alarm is triggered: the corresponding indicator light is lit and a door-to-door cleaning service request is pushed.

7. The range hood dirt detection method according to claim 6, characterized in that: The oil-swing mode is to control the fan speed to increase to 110%-150% of the current gear and maintain it for a preset time.

8. A dirt detection device for a range hood, characterized by: The fan comprises a casing and a fan system disposed in the casing, the fan system comprising a volute, an impeller disposed in the volute, and a drive motor for driving the impeller to rotate, the volute having an air inlet and an air outlet, and a pressure difference detection module being provided near the air inlet and the air outlet of the volute; The range hood device further comprises a current detection module and a controller for obtaining a current signal of the driving motor. The controller is electrically connected to the current detection module and the pressure difference detection module, and determines the contamination level of the impeller according to the contamination detection method for the range hood according to any one of claims 1 to 7.

9. A range hood, characterized in that: It includes the dirt detection device of the range hood as claimed in claim 8 and a self-cleaning device for cleaning the impeller. When the dirt detection device detects that the dirt level of the impeller reaches a set level, the automatic cleaning program is started and the impeller is cleaned by the self-cleaning device.

10. The range hood according to claim 9, characterized in that: The self-cleaning device includes a heating device or a steam generator for heating cleaning liquid, a liquid supply pump for supplying cleaning liquid to the heating device or the steam generator, and a nozzle member arranged adjacent to the impeller.

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