Range hood and control method thereof

Abstract

The invention relates to an extractor hood and a control method thereof.The extractor hood comprises a machine shell and a draught fan arranged in the machine shell, an oil fume parameter detector is arranged in the machine shell and comprises an optical signal sensor, and the oil fume parameter detector further comprises a Venturi tube and a vortex generator enabling fluid to generate vortex motion; the swirl generator is arranged in the Venturi tube and is adjacent to the inlet end of the Venturi tube; and the optical signal sensor is positioned at the downstream of the airflow direction of the swirl generator. According to the range hood, oil smoke concentration and airflow speed detection can be achieved at the same time without an additional flow sensor, separation of oil smoke and air is increased through the spiral flow generator, the detectability of oil smoke changes is further improved through Venturi acceleration, spiral precession of the vortex core around the axis also strengthens rotary separation of air and oil smoke, and the detection efficiency is improved. The action intensity of oil smoke on light is enhanced, so that the detection of small smoke is expanded more conveniently, and the purposes of wide measuring range, high linearity and more reliable detection are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of oil fume purification, and in particular to a range hood and a control method thereof. Background Art

[0002] As an essential kitchen appliance in every household, the range hood draws in oil fume from the air inlet through the high-speed rotating impeller in the volute, filters the oil fume using the impeller, and discharges the filtered oil fume from the air outlet to purify the kitchen air.

[0003] The fan of a traditional range hood runs at a fixed gear or speed, and cannot automatically adjust the gear of the fan according to the amount of oil smoke in different cooking scenes. In order to realize oil smoke detection, the existing technology often simply uses the principle that oil smoke affects the refractive index of light in the air to realize the judgment of the size of oil smoke, but it is not related to the current air flow speed, and the response speed is slow. It even needs to be equipped with an additional flow sensor to judge whether the current oil smoke matches the air flow speed. However, this method is costly, has a low degree of intelligence, and is not convenient for users to operate in practice. In addition, there is the principle of light reflection, but it often does not respond in time when detecting weak oil smoke, and it is inaccurate in judging the user's initial cooking or small smoke state, which is slow to respond and not intelligent. In addition, some of the light scattering methods use light scattering to respond to small smoke in time, but large smoke is easy to exceed the range, and the response to large smoke is non-linear. Therefore, it is necessary to further improve the existing technology. Summary of the invention

[0004] The first technical problem to be solved by the present invention is to provide a range hood that can simultaneously detect oil fume concentration and airflow velocity without the need for an additional flow sensor in view of the above-mentioned prior art.

[0005] The second technical problem to be solved by the present invention is to provide a control method for the range hood as mentioned above, which can accurately adjust the fan speed so that the air flow speed and the oil fume concentration are more matched.

[0006] The technical solution adopted by the present invention to solve the above-mentioned first technical problem is: a range hood, comprising a casing and a fan arranged in the casing, an oil fume parameter detector is arranged in the casing, and the oil fume parameter detector includes an optical signal sensor, characterized in that: the oil fume parameter detector also includes a venturi tube and a swirler that causes the fluid to produce a vortex motion, the swirler is arranged in the venturi tube and adjacent to the inlet end of the venturi tube, and the optical signal sensor is located downstream in the airflow direction of the swirler.

[0007] In order to facilitate the detection of oil smoke signals, the optical signal sensor includes a light emitter and a light receiver, which are respectively arranged on two opposite inner wall surfaces of the venturi tube, and the light receiver faces the light emitter in a direction perpendicular to the airflow direction.

[0008] Preferably, the vortex generator comprises a plurality of cyclone blades extending along the airflow direction, each cyclone blade extends radially outward from the middle and is arranged radially, each cyclone blade is arc-shaped, and all the cyclone blades rotate clockwise or counterclockwise as a whole.

[0009] In order to ensure the consistency of the flow direction of the oil smoke before it passes through the vortexer, and thereby obtain more accurate oil smoke signals and airflow velocity, the oil smoke parameter detector also includes a rectifying module for rectifying the flow direction of the oil smoke, and the rectifying module is arranged upstream of the airflow direction of the Venturi tube.

[0010] Preferably, the rectifier module comprises a base body, in which a plurality of channels extending along the airflow direction are provided, and outlets of the channels face the inlet end of the venturi tube.

[0011] In order to eliminate the influence of backflow on oil smoke, the oil smoke parameter detector also includes a backflow eliminator, which is located in the venturi tube and is arranged adjacent to the outlet end of the venturi tube. The backflow eliminator is located downstream of the optical signal sensor.

[0012] Preferably, the backflow eliminator comprises a plurality of grid plates extending along the airflow direction, each grid plate extending radially outward from the middle and arranged in a radial shape, and a backflow elimination channel is formed between two adjacent grid plates.

[0013] In order to improve the installation stability of the grille plate, the backflow eliminator also includes a connecting plate extending along the airflow direction, each connecting plate is correspondingly arranged between two adjacent grille plates, and each connecting plate is arc-shaped, and the overall cross-section formed by all the connecting plates is circular.

[0014] Preferably, the Venturi tube includes a straight tube structure located in the middle and a trumpet-shaped structure formed by gradually expanding the diameter outward from both ends of the straight tube structure, and the ends of the two trumpet-shaped structures away from the straight tube structure correspond to the inlet end and the outlet end of the Venturi tube respectively, and the optical signal sensor is arranged on the straight tube structure.

[0015] In order to improve the control accuracy of the range hood, a pressure sensor for detecting the pressure in the Venturi tube is also installed on the Venturi tube, and the detection position of the pressure sensor is located on the plane where the light emitted by the light emitter is located.

[0016] The technical solution adopted by the present invention to solve the second technical problem is: a control method of the range hood as described above, characterized by comprising:

[0017] Step 1: acquiring the oil smoke signal value detected by the optical signal sensor according to the first sampling period, and averaging the oil smoke signal values ​​collected within the first set time to obtain the oil smoke average value △P1;

[0018] Step 2, judging whether △P1 is greater than the oil smoke reference threshold value Pa, if so, controlling the fan in the range hood to start to a preset gear or keep the fan started, and turning to step 3; if not, judging that there is no obvious oil smoke or water vapor, and turning off or keeping the fan turned off after waiting for a second set time, and turning to step 1;

[0019] Step 3, determine the oil fume scene that the current range hood is in according to ΔP1, and find the maximum speed Vb and the minimum speed Va that do not cause smoke to escape in the corresponding oil fume scene according to the oil fume scene that the current range hood is in;

[0020] Step 4: Perform Fourier transform processing on the oil smoke signal value collected within the set time, and then obtain the main frequency f of the oil smoke passing through the vortex center flow, and calculate the air flow velocity V according to K=f / V, where K is the basic parameter calibrated before the range hood leaves the factory;

[0021] Step 5: Compare the calculated air flow velocity V with the maximum velocity Vb and the minimum velocity Va, and adjust the fan speed according to the comparison result.

[0022] Preferably, the specific process of determining the oil fume scene in which the current range hood is located in step 3 is as follows:

[0023] Compare △P1 with the first oil smoke setting value Pb and the second oil smoke setting value Pc respectively, Pb<Pc;

[0024] If △P1<Pb, it means that the current oil fume scene of the range hood is a small oil fume scene;

[0025] If Pb≤△P1≤Pc, it means that the current oil fume scene of the range hood is the medium oil fume scene;

[0026] If △P1>Pc, it means that the oil fume scene of the current range hood is a heavy oil fume scene.

[0027] Preferably, the specific comparison process in step 5 is:

[0028] If V<Va, increase the current fan speed;

[0029] If Va≤V≤Vb, maintain the current fan speed;

[0030] If V>Vb, the current fan speed is reduced.

[0031] Preferably, in step 3, before searching for the maximum speed Vb and the minimum speed Va without smoke leakage in the corresponding oil fume scene according to the oil fume scene in which the current range hood is located, the following steps are also included:

[0032] Acquire the pressure value detected by the pressure sensor according to the second sampling period, and average the pressure values ​​collected within the second set time to obtain the pressure average value △F1;

[0033] It is determined whether ΔF1 is greater than a first pressure reference threshold Fa. If so, it is determined that the fan is running; if not, it is determined that the fan is not running, and the fan in the range hood is controlled to start to a preset gear.

[0034] Preferably, if it is determined in step 2 that there is no obvious oil smoke or water vapor, the following steps are further included:

[0035] Step a, read the current fan operation information, determine whether the current fan is running, if yes, adjust the current fan to the lowest gear, and proceed to step b; if no, proceed to step 1;

[0036] Step b, obtaining the pressure value detected by the pressure sensor according to the second sampling period, and averaging the pressure values ​​collected within the second set time to obtain the pressure average value △F1;

[0037] Determine whether △F1 is greater than the second pressure reference threshold Fb. If so, keep the fan running at the current gear and go to step 1; if not, turn off the fan and go to step 1.

[0038] Compared with the prior art, the advantages of the present invention are: by arranging a swirler and a venturi tube, the swirler forces the fluid medium to produce regular and violent vortex flow motion. When this medium with regular vortex motion enters the contraction section of the venturi tube, its flow velocity will be enhanced. Finally, the fluid will flow through the diffusion section of the venturi tube, the fluid flow velocity will be reduced, and backflow will be generated under the action of pressure, forming a phenomenon similar to the vortex shedding of a blunt body vortex street, and under the action of the backflow, the "vortex core" of the vortex flow will spirally precess around the axis. Therefore, the vortex generator increases the separation of oil smoke and air, and the Venturi acceleration further improves the detectability of oil smoke changes. The spiral precession of the "vortex core" around the axis also strengthens the rotational separation of air and oil smoke, making the oil smoke parameter detector have a triple amplification effect, enhancing the intensity of the effect of oil smoke on light, making it easier to expand the detection of small smoke, and achieve a wide range, high linearity, and more reliable detection purposes; in addition, the frequency of the spiral precession of the "vortex core" around the axis is proportional to the speed of the fluid. Therefore, the airflow velocity is calculated by measuring the precession frequency of the spiral vortex, and then the oil smoke concentration and airflow velocity detection can be realized simultaneously without an additional flow detection module. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic diagram of the structure of a range hood in Embodiment 1 of the present invention;

[0040] Figure 2 for Figure 1 The structural diagram of the oil smoke parameter detector;

[0041] Figure 3 for Figure 2 A cross-sectional view of

[0042] Figure 4 for Figure 2 Exploded diagram of

[0043] Figure 5 This is a state diagram of oil smoke passing through the oil smoke parameter detector in the first embodiment of the present invention;

[0044] Figure 6 is a flow chart of a range hood control method in Embodiment 1 of the present invention;

[0045] Figure 7 This is a schematic diagram of the structure of the oil smoke parameter detector in the second embodiment of the present invention;

[0046] Figure 8 This is a flow chart of a range hood control method in Embodiment 2 of the present invention. DETAILED DESCRIPTION

[0047] The present invention is further described in detail below with reference to the accompanying drawings.

[0048] Embodiment 1:

[0049] like Figures 1 to 5 As shown, the range hood in this embodiment includes a housing 1 and a fan 2 disposed in the housing 1. A fume parameter detector 3 is disposed in the housing 1, and the fume parameter detector 3 can be used to detect fume concentration and airflow velocity. The fume parameter detector 3 in this embodiment is disposed on the inner wall of the housing 1 facing the lower part of the air inlet of the fan 2. The fume sucked by the range hood must pass through this position, so arranging the fume parameter detector 3 at this position can achieve more accurate data detection.

[0050] The oil fume parameter detector 3 includes an optical signal sensor 31, a venturi tube 32, a swirler 33, a rectifier module 34 and a backflow eliminator 35, wherein the swirler 33 causes the fluid to generate a vortex motion, the rectifier module 34 is used to rectify the flow direction of the oil fume, the swirler 33 is arranged in the venturi tube 32 and is arranged adjacent to the inlet end of the venturi tube 32, the optical signal sensor 31 is located downstream of the swirler 33 in the airflow direction, and the rectifier module 34 is arranged upstream of the venturi tube 32 in the airflow direction; the backflow eliminator 35 is located in the venturi tube 32 and is arranged adjacent to the outlet end of the venturi tube 32, and the backflow eliminator 35 is located downstream of the optical signal sensor 31.

[0051] like Figure 3 As shown, the optical signal sensor 31 in this embodiment includes a light emitter 311 and a light receiver 312, and the light emitter 311 and the light receiver 312 are respectively arranged on two opposite inner wall surfaces of the venturi tube 32, and the light receiver 312 faces the light emitter 311 in a direction perpendicular to the airflow direction. In addition, the rectifier module 34 includes a base body, and a plurality of channels 341 extending along the airflow direction are provided in the base body, and the outlets of the channels 341 face the inlet end of the venturi tube 32.

[0052] like Figure 4 As shown, the vortex generator 33 includes a plurality of cyclone blades 331 extending in the direction of the airflow, each cyclone blade 331 extends radially outward from the middle and is arranged radially, each cyclone blade 331 is arc-shaped, and all cyclone blades 331 are clockwise or counterclockwise in rotation as a whole. In addition, the backflow eliminator 35 includes a plurality of grille plates 351 extending in the direction of the airflow and connecting plates 353 extending in the direction of the airflow, each grille plate 351 extends radially outward from the middle and is arranged radially, and a backflow elimination channel 352 is formed between two adjacent grille plates 351; each connecting plate 353 is correspondingly arranged between two adjacent grille plates 351, and each connecting plate 353 is arc-shaped, and the overall cross-section formed by all connecting plates 353 is circular.

[0053] In this embodiment, the venturi tube 32 includes a straight tube structure 321 located in the middle and a trumpet-shaped structure 322 that gradually expands outward from both ends of the straight tube structure 321. The ends of the two trumpet-shaped structures 322 away from the straight tube structure 321 correspond to the inlet end and the outlet end of the venturi tube 32, respectively. The optical signal sensor 31 is arranged on the straight tube structure 321.

[0054] like Figure 5 As shown, when the range hood is working, the chaotic airflow entering from the air inlet of the range hood is first rectified into a standard airflow by the rectifier module 34 and then enters the venturi tube 32. It first passes through the vortex generator 33 to force the fluid medium to produce a regular and violent vortex flow motion. When this regular vortex motion medium enters the horn-shaped structure 322 (i.e., the contraction section) at the most upstream of the venturi tube 32, its flow rate will be enhanced; finally, the fluid will flow through the straight tube structure 321 and the horn-shaped structure 322 (i.e., the diffusion section) at the most downstream. In the fluid flow section), the fluid velocity decreases, and a backflow is generated under the action of pressure, forming a phenomenon similar to the vortex shedding of a blunt body vortex street. Under the action of the backflow, the "vortex core" of the vortex flow makes a spiral precession around the axis, and the frequency of the precession is proportional to the velocity of the fluid. Therefore, the fluid flow rate can be known by measuring the precession frequency of the vortex, and there is good linearity within the flow measurement range. The pressure or vortex precession frequency f in the flow field has the following relationship with the inlet flow velocity v: K = f / v, K is obtained by test calibration or simulation at the factory.

[0055] Because the fluid passing through the swirler itself enhances the separation of oil smoke and air, and the Venturi tube acceleration further improves the detectability of oil smoke changes, the spiral precession of the "vortex core" around the axis also strengthens the rotational separation of air and oil smoke, so that the oil smoke parameter detector 3 has the triple effects of vortex, Venturi acceleration and central flow periodic rotation propulsion, which enhances the intensity of the effect of oil smoke on light, making it easier to expand the detection of small smoke, and achieve a wide range, high linearity, and more reliable detection purpose.

[0056] The central flow precesses in a spiral around the axis, and for a fixed detection position, it will show periodicity, and the base frequency signal obtained by Fourier transformation of the optical receiving signal can be separated to obtain the pressure in the flow field or the vortex precession frequency f. According to the pre-calibrated K, the airflow velocity v can be obtained through K=f / V, and then the actual flow rate of the current range hood can be obtained by looking up the table based on this, or the flow rate Q can be obtained directly by looking up the table based on the comparison table of f and flow rate Q. Therefore, there is no need to set up an additional flow detection module. Its flow rate and oil smoke detection are at the same position, which is more reference for judgment than a separate flow rate sensor.

[0057] like Figure 6 As shown, the control method of the range hood in this embodiment includes:

[0058] Step 1: acquiring the oil smoke signal value detected by the optical signal sensor according to the first sampling period, and averaging the oil smoke signal values ​​collected within the first set time to obtain the oil smoke average value △P1;

[0059] The first sampling period mentioned above is a set value, and its value can be determined based on experiments or experience;

[0060] In this embodiment, before step 1, the method further includes controlling whether the range hood is in manual operation or intelligent mode. If the intelligent mode is turned on, the intelligent monitoring mode is started and the process goes to step 1.

[0061] Step 2, judging whether △P1 is greater than the oil smoke reference threshold value Pa, if so, controlling the fan in the range hood to start to a preset gear or keep the fan started, and turning to step 3; if not, judging that there is no obvious oil smoke or water vapor, and turning off or keeping the fan turned off after waiting for a second set time, and turning to step 1;

[0062] The above-mentioned oil smoke reference threshold Pa is a set value, and its value can be determined based on experiments or experience;

[0063] Step 3, determine the oil fume scene that the current range hood is in according to ΔP1, and find the maximum speed Vb and the minimum speed Va that do not cause smoke to escape in the corresponding oil fume scene according to the oil fume scene that the current range hood is in;

[0064] The specific process of determining the oil fume scene that the current range hood is in is as follows:

[0065] Compare △P1 with the first oil smoke setting value Pb and the second oil smoke setting value Pc respectively, Pb<Pc;

[0066] If △P1<Pb, it means that the current oil fume scene of the range hood is a small oil fume scene;

[0067] If Pb≤△P1≤Pc, it means that the current oil fume scene of the range hood is the medium oil fume scene;

[0068] If △P1>Pc, it means that the current oil smoke scene of the range hood is a heavy oil smoke scene;

[0069] The above-mentioned small oil smoke scene, medium oil smoke scene and large oil smoke scene are determined according to the amount of oil smoke, wherein the values ​​of Pb and Pc can be adaptively changed according to the actual application scene;

[0070] In this embodiment, a memory is set in the range hood, and a table is pre-set in the memory, which is used to store the maximum speed Vb and the minimum speed Va without smoke leakage in the corresponding oil fume scene of the range hood. The oil fume scene of the current range hood can be obtained by looking up the table to find the maximum speed Vb and the minimum speed Va without smoke leakage in the corresponding oil fume scene;

[0071] Step 4: Perform Fourier transform processing on the oil smoke signal value collected within the set time, and then obtain the main frequency f of the oil smoke passing through the vortex center flow, and calculate the air flow velocity V according to K=f / V, where K is the basic parameter calibrated before the range hood leaves the factory;

[0072] Step 5: Compare the calculated air flow velocity V with the maximum velocity Vb and the minimum velocity Va, and adjust the fan speed according to the comparison result;

[0073] The specific comparison process is: if V<Va, then increase the speed of the current fan; if Va≤V≤Vb, then maintain the current speed of the fan; if V>Vb, then reduce the current speed of the fan.

[0074] Embodiment 2:

[0075] like Figure 7 As shown, different from the first embodiment, the venturi tube 32 in this embodiment is further provided with a pressure sensor 4 for detecting the pressure inside the venturi tube 32 , and the detection position of the pressure sensor 4 is located on the plane where the light emitted by the light emitter 311 is located.

[0076] like Figure 8 As shown, different from the first embodiment, the control method of the range hood in this embodiment further includes:

[0077] In step 3, before searching for the maximum speed Vb and the minimum speed Va without smoke leakage in the corresponding oil fume scene according to the oil fume scene in which the current range hood is located, the following steps are also included:

[0078] Acquire the pressure value detected by the pressure sensor according to the second sampling period, and average the pressure values ​​collected within the second set time to obtain the pressure average value △F1;

[0079] It is determined whether ΔF1 is greater than a first pressure reference threshold Fa. If so, it is determined that the fan is running; if not, it is determined that the fan is not running, and the fan in the range hood is controlled to start to a preset gear.

[0080] In addition, if it is determined in step 2 that there is no obvious oil smoke or water vapor, the following steps are also included:

[0081] Step a, read the current fan operation information, determine whether the current fan is running, if yes, adjust the current fan to the lowest gear, and proceed to step b; if no, proceed to step 1;

[0082] Step b, obtaining the pressure value detected by the pressure sensor according to the second sampling period, and averaging the pressure values ​​collected within the second set time to obtain the pressure average value △F1;

[0083] Determine whether △F1 is greater than the second pressure reference threshold Fb. If so, keep the fan running at the current gear and go to step 1; if not, turn off the fan and go to step 1.

[0084] The above-mentioned second sampling period, first pressure reference threshold Fa and second pressure reference threshold Fb are set values, and their values ​​can be determined based on experiments or experience.

[0085] In this embodiment, by detecting the pressure value, a smarter experience of sucking out the grease and shutting down the machine after cooking can be achieved. In the above-mentioned embodiment 1, a delayed shutdown is adopted to absorb the heat; and in this embodiment, when there is residual heat in the cooking area below, the temperature of the inhaled air is slightly higher than the room temperature, the density is slightly lower, and the pressure value is less than the calibration value, and the reference value is compared to distinguish whether the temperature has dropped to a safe value, thereby improving the intelligent experience.

[0086] In the specification and claims of the present invention, terms indicating directions, such as "front", "rear", "up", "down", "left", "right", "side", "top", "bottom", etc., are used to describe various exemplary structural parts and elements of the present invention, but these terms are used here only for the purpose of convenience of description and are determined based on the exemplary orientations shown in the accompanying drawings. Since the embodiments disclosed in the present invention can be arranged in different directions, these terms indicating directions are only used as explanations and should not be regarded as limitations. For example, "up" and "down" are not necessarily limited to directions opposite to or consistent with the direction of gravity.

Claims

1. A range hood, comprising a housing (1) and a fan (2) arranged in the housing (1), wherein a fume parameter detector (3) is arranged in the housing (1), and the fume parameter detector (3) comprises an optical signal sensor (31), characterized in that: The oil smoke parameter detector (3) further comprises a venturi tube (32) and a swirler (33) for causing the fluid to generate a vortex motion. The swirler (33) is arranged inside the venturi tube (32) and adjacent to the inlet end of the venturi tube (32). The optical signal sensor (31) is located downstream of the swirler (33) in the airflow direction.

2. The range hood according to claim 1, characterized in that: The optical signal sensor (31) comprises a light emitter (311) and a light receiver (312), wherein the light emitter (311) and the light receiver (312) are respectively arranged on two opposite inner wall surfaces of the venturi tube (32), and the light receiver (312) faces the light emitter (311) in a direction perpendicular to the airflow direction.

3. The range hood according to claim 1, characterized in that: The vortex generator (33) comprises a plurality of cyclone blades (331) extending along the airflow direction, each cyclone blade (331) extending radially outward from the middle and arranged in a radial shape, each cyclone blade (331) is arc-shaped, and all the cyclone blades (331) rotate in a clockwise or counterclockwise direction as a whole.

4. The range hood according to any one of claims 1 to 3, characterized in that: The oil fume parameter detector (3) further comprises a rectifying module (34) for rectifying the flow direction of the oil fume, wherein the rectifying module (34) is arranged upstream in the airflow direction of the venturi tube (32).

5. The range hood according to claim 4, characterized in that: The rectifier module (34) comprises a base body, in which a plurality of channels (341) extending along the airflow direction are provided, and outlets of the channels (341) face the inlet end of the venturi tube (32).

6. The range hood according to claim 4, characterized in that: The oil smoke parameter detector (3) further comprises a backflow eliminator (35), wherein the backflow eliminator (35) is located inside the venturi tube (32) and is arranged adjacent to the outlet end of the venturi tube (32), and the backflow eliminator (35) is located downstream of the optical signal sensor (31).

7. The range hood according to claim 6, characterized in that: The backflow eliminator (35) comprises a plurality of grid plates (351) extending along the airflow direction, each grid plate (351) extending radially outward from the middle and arranged in a radial shape, and a backflow elimination channel (352) is formed between two adjacent grid plates (351).

8. The range hood according to claim 7, characterized in that: The backflow eliminator (35) further comprises a connecting plate (353) extending along the airflow direction, each connecting plate (353) being arranged between two adjacent grid plates (351), and each connecting plate (353) being arc-shaped, and the overall cross-section formed by all the connecting plates (353) being circular.

9. The range hood according to claim 6, characterized in that: The venturi tube (32) comprises a straight tube structure (321) located in the middle and trumpet-shaped structures (322) formed by gradually expanding in diameter from both ends of the straight tube structure (321) outwards, the ends of the two trumpet-shaped structures (322) away from the straight tube structure (321) respectively corresponding to the inlet end and the outlet end of the venturi tube (32), and the optical signal sensor (31) is arranged on the straight tube structure (321).

10. The range hood according to claim 2, characterized in that: A pressure sensor (4) for detecting the pressure inside the Venturi tube (32) is also mounted on the Venturi tube (32), and the detection position of the pressure sensor (4) is located on the plane where the light emitted by the light emitter (311) is located.

11. A control method for a range hood according to any one of claims 1 to 10, characterized in that include: Step 1: acquiring the oil smoke signal value detected by the optical signal sensor according to the first sampling period, and averaging the oil smoke signal values ​​collected within the first set time to obtain the oil smoke average value △P1; Step 2, judging whether △P1 is greater than the oil smoke reference threshold value Pa, if so, controlling the fan in the range hood to start to a preset gear or keep the fan started, and turning to step 3; if not, judging that there is no obvious oil smoke or water vapor, and turning off or keeping the fan turned off after waiting for a second set time, and turning to step 1; Step 3, determine the oil fume scene that the current range hood is in according to ΔP1, and find the maximum speed Vb and the minimum speed Va that do not cause smoke to escape in the corresponding oil fume scene according to the oil fume scene that the current range hood is in; Step 4: Perform Fourier transform processing on the oil smoke signal value collected within the set time, and then obtain the main frequency f of the oil smoke passing through the vortex center flow, and calculate the air flow velocity V according to K=f / V, where K is the basic parameter calibrated before the range hood leaves the factory; Step 5: Compare the calculated air flow velocity V with the maximum velocity Vb and the minimum velocity Va, and adjust the fan speed according to the comparison result.

12. The control method according to claim 11, characterized in that: The specific process of determining the oil fume scene of the current range hood in step 3 is as follows: Compare △P1 with the first oil smoke setting value Pb and the second oil smoke setting value Pc respectively, Pb<Pc; If △P1<Pb, it means that the current oil fume scene of the range hood is a small oil fume scene; If Pb≤△P1≤Pc, it means that the current oil fume scene of the range hood is the medium oil fume scene; If △P1>Pc, it means that the oil fume scene of the current range hood is a heavy oil fume scene.

13. The control method according to claim 11, characterized in that: The specific comparison process in step 5 is as follows: If V<Va, increase the current fan speed; If Va≤V≤Vb, maintain the current fan speed; If V>Vb, the current fan speed is reduced.

14. The control method according to any one of claims 11 to 13, characterized in that: In step 3, before searching for the maximum speed Vb and the minimum speed Va without smoke leakage in the corresponding oil fume scene according to the oil fume scene where the current range hood is located, the following steps are also included: Acquire the pressure value detected by the pressure sensor according to the second sampling period, and average the pressure values ​​collected within the second set time to obtain the pressure average value △F1; It is determined whether ΔF1 is greater than a first pressure reference threshold Fa. If so, it is determined that the fan is running; if not, it is determined that the fan is not running, and the fan in the range hood is controlled to start to a preset gear.

15. The control method according to claim 14, characterized in that: If it is determined in step 2 that there is no obvious oil smoke or water vapor, the following steps are also included: Step a, read the current fan operation information, determine whether the current fan is running, if yes, adjust the current fan to the lowest gear, and proceed to step b; if no, proceed to step 1; Step b, obtaining the pressure value detected by the pressure sensor according to the second sampling period, and averaging the pressure values ​​collected within the second set time to obtain the pressure average value △F1; Determine whether △F1 is greater than the second pressure reference threshold Fb. If so, keep the fan running at the current gear and go to step 1; if not, turn off the fan and go to step 1.

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