Range hood, grease detection method and cleaning control method

Abstract

The invention discloses a range hood, a grease detection method and a cleaning control method.The range hood comprises a centrifugal fan, the centrifugal fan comprises a volute and an impeller arranged in the volute, and the impeller comprises blades made of metal; the detection module is provided with at least two transmitting antennas and at least two receiving antennas, the transmitting antennas can transmit microwaves to the blades at the corresponding positions, the receiving antennas receive the microwaves reflected by the blades, the transmitting antennas are arranged in the circumferential direction of the volute at intervals, and the number of the transmitting antennas is matched with that of the receiving antennas; the processing assembly is electrically connected with the antennas and can control the transmitting frequency of the transmitting antenna, so that the thickness of the grease accumulated on the blade can be judged according to the microwaves received by the receiving antenna; or the thickness, the grease type and the oxidation degree of the grease accumulated on the leaf can be judged according to the microwaves received by the receiving antenna.

Description

Technical Field

[0001] This invention relates to an oil fume purification device, and more particularly to a range hood, a method for detecting grease in the range hood, and a cleaning control method for the range hood based on the grease detection results. Background Technology

[0002] Range hoods have become an indispensable kitchen appliance in modern homes. They operate on the principles of fluid dynamics, using a centrifugal fan inside to draw in and exhaust cooking fumes, and a filter to remove some of the grease particles.

[0003] After prolonged use, a large amount of oil and dust accumulates inside the casing of a range hood, especially in centrifugal fans where oil and dust buildup is severe. For example, a range hood disclosed in Chinese patent application number 202310919004.9 has a vertically arranged fan. When the impeller stops rotating, one side is at its lowest point. Accumulated grease gathers along the blade structure and drips down to this lowest position, resulting in more grease accumulation at this point than in other areas. This also means that the impeller's dynamic balance is disrupted, causing the entire unit to vibrate and requiring cleaning and maintenance (similar problems exist with other fan arrangements).

[0004] Most range hoods currently use accumulated impeller running time to remind users to maintain their appliances. However, firstly, different users have different cooking habits, resulting in significant differences in grease buildup on the impeller blades. In areas like Sichuan and Chongqing, grease may have accumulated heavily before the maintenance reminder time is due, while in areas with lighter diets, no obvious contamination may be visible even after several cycles. Therefore, relying solely on accumulated time for reminders is prone to misjudgment. If users find no obvious dirt after in-home cleaning or automatic cleaning, they may feel that the reminders are unpredictable, leading to a poor user experience.

[0005] Secondly, the position of the impeller during operation and after it stops results in different areas having varying levels of oil contact and accumulation. Some areas have thicker oil, while others have thinner oil. Time-based reminders cannot account for the actual oil accumulation in different areas. In some areas, the coating has peeled off, while in others, it is not cleaned properly.

[0006] Furthermore, relying solely on time-based reminders is prone to misjudgment. This can easily lead to situations where users find no obvious dirt after on-site or automatic cleaning, resulting in feelings that the manufacturer's judgment is uncontrollable, unintelligent, overcharged, and provides a poor user experience.

[0007] Finally, ordinary sensors are usually installed on the volute and mainly detect the outer surface and end face of the impeller. They cannot detect deposits on the inner side of the impeller pressure surface or in narrow flow channels. However, in reality, the inner pressure surface is more prone to grease accumulation because it faces inward, which has become an industry problem for impeller contamination detection. Summary of the Invention

[0008] The first technical problem to be solved by the present invention is to provide a range hood that improves the accuracy of pollution detection, in order to address the shortcomings of the prior art.

[0009] The second technical problem to be solved by the present invention is to provide a method for detecting grease in range hoods, which addresses the shortcomings of the prior art and improves the accuracy of contamination detection, and also enables multi-dimensional detection.

[0010] The third technical problem to be solved by the present invention is to provide a cleaning control method for range hoods that addresses the shortcomings of the prior art and improves cleaning efficiency and effectiveness.

[0011] The technical solution adopted by the present invention to solve the first technical problem mentioned above is as follows: a range hood, comprising a centrifugal fan, wherein the centrifugal fan includes a volute and an impeller disposed within the volute, and the impeller comprises blades made of metal; characterized in that:

[0012] The range hood also includes:

[0013] The detection module includes a transmitting antenna capable of emitting microwaves to a blade at a corresponding location and a receiving antenna capable of receiving microwaves reflected from the blade. At least two transmitting antennas are arranged at circumferential intervals along the volute, and the number of transmitting and receiving antennas is matched.

[0014] The processing component, electrically connected to each antenna, is capable of controlling the transmission frequency of the transmitting antenna, thereby enabling the determination of the thickness of grease accumulated on the blade based on the microwaves received by the receiving antenna; or enabling the determination of the thickness, type, and degree of oxidation of the grease accumulated on the blade based on the microwaves received by the receiving antenna.

[0015] By arranging a microwave antenna array on the volute and using the metal ring volute as a microwave resonant cavity, the microwave antennas arranged at different angles form multi-angle incident radiation, which resonates with the resonant cavity to form multi-angle edge diffraction. The microwave diffracted oil fumes directly reach the back of the blade (the detection blind zone of traditional optical and capacitive sensing schemes). This solves the technical problem that traditional contact sensors cannot detect deposits on the back of the impeller and in narrow flow channels, and realizes non-contact quantitative detection of three-dimensional dirt distribution. It can obtain relatively accurate grease thickness, and since the measurement is non-contact, it can avoid the various defects caused by mechanical and other contact measurements.

[0016] The first technical solution adopted by the present invention to solve the second technical problem mentioned above is: a method for detecting grease in a range hood, using the range hood described above, characterized in that: the grease detection method includes the following steps:

[0017] 1) Signal transmission and reception: The processing component controls the transmitting antenna to transmit microwave signals to the impeller, the receiving antenna receives the reflected signals, and the processing component extracts phase information from the signals received by the receiving antenna;

[0018] 2) Phase difference calculation: The processing component calculates the difference between the phase of the currently received signal and the reference phase.

[0019] 3) Calculation of grease thickness d: Where λ is the emitted microwave wavelength; ε r The dielectric constant of the grease is set.

[0020] Preferably, in step 2), the reference phase is the phase calibrated when the impeller has no grease accumulation.

[0021] The second technical solution adopted by the present invention to solve the second technical problem mentioned above is: a method for detecting grease in a range hood, using the range hood described above, characterized in that: the grease detection method includes the following steps:

[0022] 1) Signal transmission and reception: The processing component controls the transmitting antenna to transmit microwave signals to the impeller, the receiving antenna receives the reflected signals, and the processing component extracts phase information from the signals received by the receiving antenna;

[0023] 2) Phase difference calculation: The processing component calculates the difference between the phase of the currently received signal and the reference phase.

[0024] 3) Calculation of grease thickness d: Where λ is the emitted microwave wavelength; ε r The dielectric constant of the grease is set.

[0025] 4) Perform signal transmission and reception again, and calculate the phase difference again. The frequency of the microwave signal transmitted by the transmitting antenna in this step is different from that in step 1). Based on the newly obtained phase difference and the d obtained in step 3), the current grease dielectric constant is deduced. Based on the current grease dielectric constant, the grease type and oxidation degree are obtained by looking up the table. The table of correspondence between microwave frequency, grease dielectric constant, grease type and oxidation degree is pre-stored in the storage module electrically connected to the processing component.

[0026] Preferably, in step 2), the reference phase is the phase calibrated when the impeller has no grease accumulation.

[0027] The first technical solution adopted by the present invention to solve the third technical problem mentioned above is: a cleaning control method for a range hood, wherein the range hood includes a cleaning device for cleaning a centrifugal fan, characterized in that:

[0028] The cleaning control method includes the following steps:

[0029] 1) Turn on the range hood;

[0030] 2) Perform grease thickness detection: Start periodic self-check, obtain grease thickness d according to the grease detection method described above, sort the grease thickness d corresponding to each blade, and determine whether the thickest grease thickness exceeds the preset threshold d0. When the thickest grease thickness exceeds the threshold d0, proceed to step 3).

[0031] 3) Matching cleaning strategy:

[0032] 3.1) Trigger the cleaning device to perform self-cleaning or control the centrifugal fan to remove oil;

[0033] 3.2) Perform a second test using the method in step 2) and compare it with the threshold d0 to determine whether it meets the standard. If it does, return to step 2); otherwise, upgrade the cleaning intensity.

[0034] The second technical solution adopted by the present invention to solve the third technical problem mentioned above is: a cleaning control method for a range hood, wherein the range hood includes a cleaning device for cleaning a centrifugal fan, characterized in that:

[0035] The cleaning control method includes the following steps:

[0036] 1) The range hood starts up and the detection module initializes;

[0037] 2) Enter single-frequency detection mode, obtain the grease thickness d according to the grease detection method described above. If the grease thickness d does not exceed the threshold d0, then normal ventilation is performed. If the grease thickness d exceeds the threshold d0, then proceed to step 3).

[0038] 3) Trigger graded cleaning: First, control the centrifugal fan to remove oil, then detect the current grease thickness. If the grease thickness has not decreased, use the cleaning device to perform self-cleaning. After completion, proceed to step 4).

[0039] 4) Activate multi-frequency detection mode: Obtain the grease type and oxidation degree according to the grease detection method described above, and perform different cleaning according to the oxidation degree: if not oxidized, an alkaline cleaning agent is recommended; if partially oxidized, a neutral cleaning agent is recommended; if completely oxidized, an acidic cleaning agent is recommended. After adding the recommended cleaning agent to the cleaning device, perform cleaning. After cleaning, check the grease thickness again according to the single-frequency detection mode and make a judgment. If it still exceeds the threshold d0, it is not up to standard and a manual maintenance reminder is sent. If it does not exceed the threshold d0, it means it is within the normal range and cleaning is complete.

[0040] Furthermore, in step 4), after obtaining the type of oil, the number of days of consuming the same type of oil is counted based on the oil type. If the number of consecutive days exceeds a certain number, a reminder is given to switch foods to achieve healthy cooking reminders.

[0041] Compared with the prior art, the advantages of this invention are as follows: by arranging a microwave antenna group on the volute, using a metal annular volute as a microwave resonant cavity, and using microwave antennas arranged at different angles to form multi-angle incident radiation and resonating with the resonant cavity to form multi-angle edge diffraction, the microwave diffracted oil fumes directly reach the back of the blade (the detection blind zone of traditional optical and capacitive sensing schemes), which solves the technical problem that traditional contact sensors cannot detect deposits on the back of the impeller and in narrow flow channels, and realizes non-contact quantitative detection of three-dimensional dirt distribution. It can obtain a relatively accurate grease thickness, and since the measurement is non-contact, it can avoid the various defects caused by mechanical and other contact measurements. Attached Figure Description

[0042] Figure 1 This is a side view of the range hood according to the first embodiment of the present invention.

[0043] Figure 2 This is a cross-sectional view (left-right cross-section) of the range hood according to the first embodiment of the present invention;

[0044] Figure 3 This is a cross-sectional view (front and back section) of the range hood according to the first embodiment of the present invention;

[0045] Figure 4 This is a schematic diagram of the centrifugal fan and its cleaning device of the range hood according to the first embodiment of the present invention;

[0046] Figure 5 This is a schematic diagram of the centrifugal fan and its cleaning device of the range hood according to the first embodiment of the present invention (and...). Figure 4 (Different perspectives);

[0047] Figure 6 This is a schematic diagram of part of the electrical box and cleaning device of the range hood according to the first embodiment of the present invention;

[0048] Figure 7 This is a cross-sectional view of the centrifugal fan of the range hood according to the first embodiment of the present invention;

[0049] Figure 8 This is a graph showing the relationship between grease thickness and contamination level in the impeller according to the first embodiment of the present invention.

[0050] Figure 9 This is a control principle diagram of the range hood according to the first embodiment of the present invention;

[0051] Figure 10 This is a control flowchart of the range hood according to the first embodiment of the present invention;

[0052] Figure 11 This is a control flowchart of the range hood according to the second embodiment of the present invention. Detailed Implementation

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

[0054] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential," etc., indicating orientation or positional relationships, are based on the orientation or positional relationships shown in the accompanying drawings and are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Since the embodiments disclosed in this invention can be arranged in different directions, these terms indicating direction are only for illustration and should not be regarded as limitations. For example, "upper" and "lower" are not necessarily limited to directions opposite to or consistent with the direction of gravity. In addition, features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0055] Example 1

[0056] See Figures 1 to 7 A range hood includes a centrifugal fan 1, which comprises a volute 11, an impeller 12 disposed within the volute 11, and a motor 13 for driving the impeller 12 to rotate. The centrifugal fan 1 can be housed within a fan frame 2. In this embodiment, the range hood is a top-mounted type, and also includes a smoke collection hood 3 located below the fan frame 2. Alternatively, it can be a side-mounted, low-mounted, or other existing types of range hoods. The centrifugal fan 1 includes a volute 11, an impeller 12 disposed within the volute 11, and a motor 13 for driving the impeller 12 to rotate.

[0057] After prolonged use, grease will accumulate on the blades 121 of the impeller 12. The pressure surface (concave) of the blades 121 is more prone to accumulating thicker grease, which can clog the passage, affect the smoke extraction aerodynamic effect, and increase noise.

[0058] Therefore, the range hood also includes a detection module, which is set on the annular wall 112 of the volute 11. This detection module is a terahertz transceiver module. The detection module is set on the outer side of the annular wall, and the annular wall of the volute 11 can have openings at the positions corresponding to the detection module so that the detection module can emit laser to the impeller 12 and receive the laser reflected by the impeller 12.

[0059] The detection module is located 5-15 mm from the edge of the impeller 12. The detection module is a microwave antenna, consisting of a transmitting antenna and a receiving antenna. At least two transmitting antennas are arranged at circumferential intervals along the volute 11, and the number of transmitting and receiving antennas is matched. In this embodiment, eight antennas, numbered A to H, are arranged at circumferential intervals along the annular wall 112 of the volute 11, forming a microwave antenna array. The initial detection module is denoted as antenna A (reference numeral 41). Figure 7 The diagram shows antennas arranged in a clockwise rotation of 60° (reference numeral 42), then 45° (reference numeral 43), then 45° (reference numeral 44), then 45° (reference numeral 45), then 45° (reference numeral 46), then 60° (reference numeral 47), and finally 60° (reference numeral 48). Antennas C, D, and E are spaced relatively close together because this area is near the bottom of the volute 11, where grease accumulates; denser placement improves detection capability in this area. Other numbers of detection modules can also be selected.

[0060] When in use, the antennas can be divided into receiving and transmitting groups. Based on the polarization direction of the antennas, horizontally polarized H (primarily targeting planar areas) and vertically polarized V (enhancing curved surface detection capabilities) are arranged respectively. When in use, the H / V polarized antennas are integrated to optimize the reflection characteristics of the 12 curved surface of the metal blade. The specific grouping is as follows: Receiving group: Antenna B(H), Antenna D(H), Antenna F(H) and Antenna H(H); Transmitting group: Antenna A(V), Antenna C(V), Antenna E(V) and Antenna G(V).

[0061] In use, multiple signal groups, such as four antenna groups, transmit orthogonally coded signals (e.g., Gold code sequences) simultaneously to prevent mutual interference. The receiving group of four antenna groups receives the signals in real time and separates the received signals through code division multiplexing (CDMA).

[0062] The range hood also includes a cleaning device for cleaning the centrifugal fan 1, see also Figures 2-6 The cleaning device includes a water tank 51 for storing cleaning media, which can be water or cleaning agent. The water tank 51 can be connected to tap water or other containers. The cleaning device also includes a heating or steam generating module 52, a water pump or water valve 53, a three-way valve 54, a first conduit 551, a second conduit 552, a third conduit 553, a spray arm 56, and a drive mechanism 57.

[0063] The first conduit 551 connects the heating or steam generating module 52 and the spray arm 56 to enable fluid communication between them. The spray arm 56 extends within the volute 11 of the centrifugal fan 1, located between the wall of the volute 11 and the impeller 12, and preferably extends in a direction parallel to the axial direction of the centrifugal fan 1. The spray arm 56 is provided with nozzles 561, which can be used to spray heated or steam-state cleaning media onto the blades 121 of the impeller 12 (or partially onto the volute 11). The spray arm 56 may also be provided with brush heads 562, which can be used to remove grease from the blades 121. A drive mechanism 57 is located outside the volute 11 and is used to drive the spray arm 56 to rotate about its own axis (in a direction parallel to the axial direction of the centrifugal fan 1). It can be any existing rotary drive module, such as a motor. This allows the direction of the nozzle 561 and / or brush head 562 to be changed by driving the spray arm 56 to achieve thorough cleaning, or to rotate the nozzle 561 and / or brush head 562 toward the wall of the volute 11 when cleaning is not required, reducing the risk of grease blockage and grease accumulation.

[0064] The range hood also includes an electrical box 6, which includes a power board 61 and a radiator 62 for heat dissipation of the power board 61. The radiator 62 can be in the form of heat dissipation fins. The three-way valve 54 is a valve body with one inlet and two outlets. The water tank 51 is connected to one inlet of the three-way valve 54 via a water pump or water valve 53 through a second conduit 552 (the water pump or water valve 53 is located at the connection between the water tank 51 and the second conduit 552 to control whether cleaning medium is supplied). One outlet of the three-way valve 54 is connected to the heating or steam generation module 52, and the other outlet is connected to the water tank 51 via a third conduit 553. The second conduit 552 can bend through the heat dissipation fins of the radiator 62, through which the cleaning medium in the water tank 51 enters the second conduit 552 via a water pump or water valve 53. The cleaning medium in the second conduit 552 exchanges heat with the radiator 62. After being preheated, the cleaning medium enters the three-way valve 54 and then enters the heating or steam generation module 52 to be heated or vaporized, thereby spraying and cleaning through the nozzles 561 on the spray arm 56. Unused cleaning medium can enter the third conduit 553 through the three-way valve 54 and then return to the water tank 51.

[0065] See Figure 9 The range hood of this embodiment further includes a processing component 7, which has a processor. The motor 13 (and its drive module) of the centrifugal fan 1, the heating or steam generating module 52 of the cleaning device, the water pump or water valve 53, the drive mechanism 57, and the detection module are all electrically connected to the processing component 7. Furthermore, the processing component 7 may also be electrically connected to a switch module 71, a storage module 72, and a lamp module 73, which are identical to those in the prior art. The processing component 7 can control the transmission frequency of the transmitting antenna.

[0066] After receiving the microwave signal, the detection module performs calculations by the processing component 7. Specifically, the physical principle of grease detection in this embodiment is as follows: Although the blade 121 and the volute 11 are made of metal (galvanized steel plate with a thickness of 0.4-0.8mm), the microwave does not penetrate the metal body, but achieves grease detection on the concave surface through the following collaborative mechanism:

[0067] 1. Skin effect limits penetration:

[0068] Formula for skin depth of microwaves in metals:

[0069] in:

[0070] ω = 2πf (at 2.4GHz, ω ≈ 1.5 × 10⁻⁶) 10 (rad / s), where σ is the conductivity of galvanized steel, typically 1.04 × 10⁻⁶. 7 S / m, μ is the permeability, typically 90 × 10⁻⁶. -7 H / m. Substituting the calculation results: δ≈1.2μm (much smaller than the thickness of the metal plate), this indicates that microwaves cannot penetrate the metal body, but can detect grease through surface effects.

[0071] 2. The resonant cavity and edge diffraction allow microwaves to enter the concave surface of blade 121.

[0072] The metal volute 11, generally ring-shaped (usually spiral), encloses the impeller 12. Therefore, electromagnetic waves emitted by antennas at different angles continuously oscillate within the volute 11, forming a resonant cavity that achieves a higher signal quality factor. In other words, the volute 11 contains a metal cavity designed to allow a high-frequency electromagnetic field to oscillate continuously. Through energy localization, multi-mode resonance excitation, and dynamic frequency tuning, the microwave resonant cavity enhances the intensity of weak diffraction signals from the back of the impeller 12 and the narrow flow channel to a detectable range (sensitivity increased by 5–10 times).

[0073] Furthermore, the wavelength of the commonly used 2.4GHz microwave in civilian applications is approximately 125mm, which is much larger than the radius of curvature of blade 121, such as 8–20mm. Therefore, significant diffraction waves are generated at the edge of blade 121 (the resonant cavity can enhance the diffraction capability), and the diffraction waves can enter the concave surface region of blade 121 for detection. The microwave path is as follows: transmitting antenna → grease on the convex surface and outer edge of blade 121 → diffraction at the metal edge → grease on the concave surface of blade 121 → receiving antenna.

[0074] The mechanism for detecting grease using the above principle is (the dielectric properties of the grease layer change the reflected wave):

[0075] A specific frequency microwave signal is emitted to an impeller 12 containing grease. The microwaves are reflected from both the grease layer and the metal surface, causing interference between the two reflected waves. The thicker the grease, the greater the phase difference between the two reflected waves. By measuring the phase change of the microwave reflected signal, the grease thickness can be deduced by detecting the phase difference change. While conventional microwave or optical methods rely on the intensity of the reflected wave (which is easily affected by oil fumes), this invention improves accuracy by 10 times through phase difference detection, enabling the detection of thickness changes on the order of 0.1 mm.

[0076] Typical testing steps are as follows:

[0077] 1) Signal transmission and reception: Processing component 7 controls the detection module to transmit microwave signals (2.4GHz) to the impeller using an antenna array, the receiving antenna receives the reflected signals, and processing component 7 extracts phase information;

[0078] 2) Phase difference calculation: In the laboratory or when newly installed and not in use, first calibrate the reference phase when there is no grease (direct reflection from the metal surface). When using, measure the phase when there is grease and calculate the difference between the two.

[0079] 3) Calculation of grease thickness d: Where λ is the incident microwave wavelength (approximately 125 mm at 2.4 GHz); ε r This is the dielectric constant of grease (calibrated value; for general household mixed use, it can be calculated as 3).

[0080] Example: If measured Therefore, the grease thickness d≈0.45mm can be calculated using the above formula.

[0081] The judgment and calculation in the control method of this invention are completed by processing component 7. See also Figure 10 The control method for the range hood in this embodiment includes the following steps:

[0082] 1) When the range hood is turned on for the first time, a microwave environment scan can be performed to determine whether the benchmark calibration is complete. If yes, proceed to step 2); otherwise, perform no-load calibration.

[0083] 2) Perform grease thickness detection: Start periodic self-check, transmit microwaves with the transmitting antenna and receive microwaves with the receiving antenna, obtain the grease thickness d in the above manner, sort the grease thickness d of each blade 121, obtain the blade 121 with the thickest grease, and determine whether it exceeds the threshold d0. The value range of d0 can be 0.4mm to 2mm. If yes, proceed to step 3); if no, update the health status.

[0084] 3) Matching cleaning strategy:

[0085] 3.1) Query the stored grease thickness and contamination relationship (which can be determined experimentally) to trigger the self-cleaning or oil-slinging mode of the cleaning device. The oil-slinging mode refers to the impeller 12 (motor 13) being raised to, for example, 3000 rpm and then stopped abruptly, followed by reverse power to make the impeller rotate at 500 rpm for 30 seconds. This mainly utilizes centrifugal force F=mω 2 r, the critical peeling force of oil stains F_c=η·σ (η is the adhesion coefficient, σ is the cohesive force of the oil film), when ω≥√(F_c / mr) it will automatically detach (the experimentally measured ω_min=40rad / s); during self-cleaning, nozzle 561 can rotate and spray, water pressure requirement: ≥0.2MPa (micro water pump flow rate ≥200ml / min);

[0086] 3.2) Perform a second check using the method in step 2) to determine whether the standard is met (similarly compared with the threshold d0). If yes, record the maintenance log and return to step 2). If no, upgrade the cleaning intensity, such as increasing water pressure or increasing the oil-slinging speed.

[0087] Example 2

[0088] In this embodiment, the difference from Embodiment 1 is that the transmitting antenna emits multi-band microwaves, which can identify the type and degree of oxidation of grease, thereby automatically recommending a suitable cleaning agent and improving intelligence and cleaning ability.

[0089] The principle behind this embodiment for identifying oil type and oxidation level is: the differences in molecular structure among different oils lead to their dielectric properties (dielectric constant ε). r The dielectric response of materials at different frequencies varies with frequency. Typical data are shown in Table 1 below (different test methods may have slight deviations, but the trend is the same):

[0090] frequency <![CDATA[Animal oil (ε r )]]> <![CDATA[Vegetable oil (ε r )]]> <![CDATA[Oxidized oil (ε r )]]> 1GHz 2.7 3.3 4.2 2.4GHz 2.5 3.1 3.8 5.8GHz 2.3 3 3.4

[0091] Table 1: Reference Table of Dielectric Constants of Greases at Different Frequency Bands

[0092] During lipid oxidation, the main components change from triglycerides (>98%) to diglycerides (partially oxidized) + free fatty acids (20-40%). Complete oxidation results in polymers + rancid products (>50%). The overall change in these components during oxidation leads to variations in the dielectric constant ε. r Increase: The number of polar groups (carbonyl, hydroxyl) increases. This is based on the chemical composition or the reaction of functional groups with detergents. When oils are oxidized (e.g., 5.8g corresponds to ε),... r ≤3) Alkaline detergents are recommended for initial oxidation (e.g., 5.8g corresponds to 3 < ε). r ≤3.3) Neutral enzymatic hydrolysants are recommended for cleaning, as they offer more targeted cleaning capabilities.

[0093] The table showing the correspondence between microwave frequency, oil type, and degree of oxidation can be pre-stored in a storage module 72 that is electrically connected to the processing component 7.

[0094] Therefore, no chemical reagents or contact sampling are required. After initially calculating the grease thickness d based on the method in Example 1, other frequency bands such as 5.8 GHz or 1 GHz are used, based on the current phase difference combined with... Inverse calculation of permittivity ε r Table 1 provides a continuous monitoring reference for healthy cooking by analyzing the type of oil and whether it is oxidized (the fatty acid composition of different oils is complementary, avoiding nutritional imbalance caused by a single type of oil; if a certain type of oil, such as animal oil, exceeds a certain number of days, such as 4 days, it is recommended to switch to another type, such as vegetable oil, for 3 days, to achieve a healthy rotation every week or every two weeks) and reminds you to use targeted cleaning agents, which can improve cleaning efficiency by 40% and reduce water consumption by 30%.

[0095] Compared to the single-frequency detection scheme in Embodiment 1, the multi-frequency band detection scheme in this embodiment has the following advantages, as shown in Table 2:

[0096]

[0097]

[0098] Table 2: Comparison of different detection methods

[0099] The detection of oil type and oxidation level in the embodiment includes the following steps:

[0100] 1) Transmit microwave signals (switch to frequencies such as 5.8 or 1 GHz);

[0101] 2) Receive reflected signals;

[0102] 3) Calculate the phase difference

[0103] 4) Calculate the dielectric constant using the grease thickness d estimated by single frequency, and determine the grease type and degree of oxidation by referring to the table.

[0104] See Figure 11 The grease detection and cleaning control method for the range hood in this embodiment includes the following steps:

[0105] 1) The range hood starts up and the detection module initializes;

[0106] 2) Enter single-frequency detection mode. If the grease thickness d calculated according to Example 1 does not exceed the threshold d0, then normal ventilation is performed. If it exceeds the threshold d0, proceed to step 3).

[0107] 3) Trigger graded cleaning: First, control the centrifugal fan 1 to throw oil (impeller 12 rotates forward and backward to throw oil), then detect the current grease thickness. If the grease thickness has not decreased, use the cleaning device to perform self-cleaning. After completion, proceed to step 4).

[0108] 4) Activate multi-frequency detection mode: The transmitting antenna transmits microwaves of different frequency bands, and the receiving antenna receives the reflected microwaves of different frequency bands. According to the above method, the dielectric spectrum features are extracted using the grease thickness and phase difference (the dielectric constant is extracted). The processing component 7 identifies the grease type according to the dielectric constant based on the pre-stored correspondence table. Then, proceed to steps 5) and 7) respectively.

[0109] 5) Determination of oxidation degree: The processing component 7 determines the degree of oxidation based on the dielectric constant according to the pre-stored corresponding table. If there is no oxidation, an alkaline cleaning agent is recommended; if there is partial oxidation, a neutral cleaning agent is recommended; if there is complete oxidation, an acidic cleaning agent is recommended. After adding the recommended cleaning agent (to water tank 51), cleaning is carried out. After completion, proceed to step 6).

[0110] 6) After cleaning, check the grease thickness again. If it still exceeds the threshold d0, it is not up to standard and a manual maintenance reminder is sent. If it does not exceed the threshold d0, it means it is within the normal range, cleaning is complete, and it can be used normally.

[0111] 7) Count the number of days that the same type of oil is consumed based on the type of oil, and remind you to switch foods if the number of consecutive days exceeds a certain number.

[0112] The term "fluid connectivity" as used in this invention refers to the spatial relationship between two components or parts (hereinafter referred to as the first part and the second part, respectively), that is, a fluid (gas, liquid, or a mixture of both) can flow from the first part along a flow path and / or be transported to the second part. This can be a direct connection between the first part and the second part, or an indirect connection between the first part and the second part through at least one third party. This third party can be a fluid channel such as a pipe, channel, conduit, guide, hole, or groove, or a chamber or combination thereof that allows fluid to flow through.

Claims

1. A range hood, comprising a centrifugal fan (1), the centrifugal fan (1) comprising a volute (11) and an impeller (12) disposed within the volute (11), the impeller (12) comprising metal blades (121); characterized in that: The range hood also includes: The detection module has a transmitting antenna capable of emitting microwaves to a blade (121) at a corresponding position and a receiving antenna capable of receiving microwaves reflected by the blade (121). The transmitting antennas are at least two in number and arranged at circumferential intervals along the volute (11), and the number of transmitting and receiving antennas is matched. The processing component (7) is electrically connected to each antenna and can control the transmission frequency of the transmitting antenna, thereby being able to determine the thickness of grease accumulated on the blade (121) based on the microwave received by the receiving antenna; or being able to determine the thickness, type and degree of oxidation of grease accumulated on the blade (121) based on the microwave received by the receiving antenna.

2. A method for detecting grease in a range hood, using the range hood according to claim 1, characterized in that: The oil detection method includes the following steps: 1) Signal transmission and reception: The processing component (7) controls the transmitting antenna to transmit microwave signals to the impeller (12), the receiving antenna receives the reflected signals, and the processing component (7) extracts phase information from the signals received by the receiving antenna; 2) Phase difference calculation: The processing component (7) calculates the difference between the phase of the currently received signal and the reference phase. 3) Calculation of grease thickness d: Where λ is the emitted microwave wavelength; ε r The dielectric constant of the grease is set.

3. The grease detection method for a range hood according to claim 2, characterized in that: In step 2), the reference phase is the phase calibrated when the impeller (12) has no grease accumulation.

4. A method for detecting grease in a range hood, using the range hood according to claim 1, characterized in that: The oil detection method includes the following steps: 1) Signal transmission and reception: The processing component (7) controls the transmitting antenna to transmit microwave signals to the impeller (12), the receiving antenna receives the reflected signals, and the processing component (7) extracts phase information from the signals received by the receiving antenna; 2) Phase difference calculation: The processing component (7) calculates the difference Δφ between the phase of the currently received signal and the reference phase; 3) Calculation of grease thickness d: Where λ is the emitted microwave wavelength; ε r The dielectric constant of the grease is set; 4) The signal is transmitted and received again, and the phase difference is calculated again. The frequency of the microwave signal transmitted by the transmitting antenna in this step is different from that in step 1). Based on the newly obtained phase difference and combined with d obtained in step 3), the current grease dielectric constant is deduced. The grease type and oxidation degree are obtained by looking up the table based on the current grease dielectric constant. The table of correspondence between microwave frequency, grease dielectric constant, grease type and oxidation degree is stored in advance in the storage module (72) electrically connected to the processing component (7).

5. The grease detection method for a range hood according to claim 4, characterized in that: In step 2), the reference phase is the phase calibrated when the impeller (12) has no grease accumulation.

6. A cleaning control method for a range hood, the range hood comprising a cleaning device for cleaning a centrifugal fan (1), characterized in that: The cleaning control method includes the following steps: 1) Turn on the range hood; 2) Perform grease thickness detection: Start periodic self-check, obtain grease thickness d according to the grease detection method according to claim 2 or 3, sort the grease thickness d corresponding to each blade (121), and determine whether the thickest grease thickness exceeds the preset threshold d0. When the thickest grease thickness exceeds the threshold d0, proceed to step 3). 3) Matching cleaning strategy: 3.1) Trigger the cleaning device to perform self-cleaning or control the centrifugal fan (1) to perform oil removal; 3.2) Perform a second test using the method in step 2) and compare it with the threshold d0 to determine whether it meets the standard. If it does, return to step 2); otherwise, upgrade the cleaning intensity.

7. A cleaning control method for a range hood, the range hood comprising a cleaning device for cleaning a centrifugal fan (1), characterized in that: The cleaning control method includes the following steps: 1) The range hood starts up and the detection module initializes; 2) Enter single-frequency detection mode, obtain the grease thickness d according to the grease detection method according to claim 2 or 3. If the grease thickness d does not exceed the threshold d0, then normal ventilation is performed. If the grease thickness d exceeds the threshold d0, then proceed to step 3). 3) Trigger graded cleaning: First, control the centrifugal fan (1) to remove oil, then detect the current grease thickness. If the grease thickness has not decreased, use the cleaning device to perform self-cleaning. After completion, proceed to step 4). 4) Activate multi-frequency detection mode: According to the grease detection method of claim 4 or 5, the grease type and oxidation degree are obtained, and different cleaning methods are used according to the oxidation degree: if it is not oxidized, an alkaline cleaning agent is recommended; if it is partially oxidized, a neutral cleaning agent is recommended; if it is completely oxidized, an acidic cleaning agent is recommended. After adding the recommended cleaning agent to the cleaning device, cleaning is performed. After cleaning, the grease thickness is detected again according to the single-frequency detection mode for judgment. If it still exceeds the threshold d0, it is not up to standard, and a manual maintenance reminder is sent. If it does not exceed the threshold d0, it means it is within the normal range, and cleaning is completed.

8. The cleaning control method for a range hood according to claim 7, characterized in that: In step 4), after obtaining the type of oil, the number of days of consuming the same type of oil is counted based on the type of oil, and a reminder is given to switch foods if the number of consecutive days exceeds a certain number.

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