阅读说明：本技术 一种离心风机、具有该离心风机的吸油烟机及其控制方法 (Centrifugal fan, range hood with centrifugal fan and control method of range hood ) 是由 马志豪 余旭锋 于 2019-08-08 设计创作，主要内容包括：本发明公开了一种离心风机,包括蜗壳、设置在蜗壳内的叶轮组件以及用于驱动叶轮组件的第一电机,所述蜗壳上形成有进风口,所述主电机具有第一输出轴,其特征在于：所述叶轮组件包括同轴间隔布置的第一叶轮和第二叶轮,所述第一叶轮靠近进风口,所述第二叶轮设置在第一叶轮远离进风口的一侧,所述离心风机还包括第二电机,所述次电机包括定子和设置在定子外周的转子、由此构成外转子电机,所述次电机的定子与主电机的第一输出轴连接,所述次电机的定子和转子分别连接第一叶轮和第二叶轮中的其中一个、从而能带动第一叶轮和第二叶轮转动。还公开了一种具有该离心风机的吸油烟机,以及该吸油烟机的控制方法。(The invention discloses a centrifugal fan, which comprises a volute, an impeller assembly arranged in the volute and a first motor used for driving the impeller assembly, wherein an air inlet is formed on the volute, the main motor is provided with a first output shaft, and the centrifugal fan is characterized in that: the centrifugal fan further comprises a second motor, the secondary motor comprises a stator and a rotor arranged on the periphery of the stator, the secondary motor forms an outer rotor motor, the stator of the secondary motor is connected with a first output shaft of the main motor, and the stator and the rotor of the secondary motor are respectively connected with one of the first impeller and the second impeller so as to drive the first impeller and the second impeller to rotate. Also discloses a range hood with the centrifugal fan and a control method of the range hood.)

1. A centrifugal fan comprises a volute (1), an impeller assembly (2) arranged in the volute (1) and a first motor (3) used for driving the impeller assembly (2), wherein an air inlet (11) is formed in the volute (1), the main motor (3) is provided with a first output shaft (31), and the centrifugal fan is characterized in that: the impeller assembly (2) comprises a first impeller (21) and a second impeller (22) which are coaxially arranged at intervals, the first impeller (21) is close to the air inlet (11), the second impeller (22) is arranged on one side, away from the air inlet (11), of the first impeller (21), the centrifugal fan further comprises a second motor (4), the secondary motor (4) comprises a stator (43) and a rotor (44) which is arranged on the periphery of the stator (43), an outer rotor motor is formed by the stator (43), the stator (43) of the secondary motor (4) is connected with the first output shaft (31) of the main motor (3), and the stator (43) and the rotor (44) of the secondary motor (4) are respectively connected with one of the first impeller (21) and the second impeller (22), so that the first impeller (21) and the second impeller (22) can be driven to rotate.

2. The centrifugal fan of claim 1, wherein: the secondary motor (4) is provided with a second output shaft (41) connected with the stator (43) and is a double-output-shaft motor, one second output shaft (41) of the secondary motor (4) is connected with the first output shaft (31), the other second output shaft (41) of the secondary motor (4) is connected with the first impeller (21), the rotor (44) is connected with the second impeller (22), and the main motor (3), the secondary motor (4) and the impeller assembly (2) are coaxially arranged.

3. The centrifugal fan of claim 2, wherein: first impeller (21) include first preceding dish (211), first back dish (212), set up first blade (213) between first preceding dish (211) and first back dish (212) and first supporting disk (214), first supporting disk (214) are connected with first back dish (212), second output shaft (41) and first supporting disk (214) of inferior motor (4) are connected.

4. The centrifugal fan of claim 3, wherein: the first support disc (214) is of an axial fan structure.

5. The centrifugal fan of claim 2, wherein: the second impeller (22) comprises a second front disc (221), a second rear disc (222), second blades (223) arranged between the second front disc (221) and the second rear disc (222), and a second supporting disc (224), the periphery of the second supporting disc (224) is connected with the second rear disc (222), and the second supporting disc is gradually sunken towards the first impeller (21) from the periphery to the middle, the rotor (44) of the secondary motor (4) penetrates through the end part, close to the first impeller (21), of the second supporting disc (224), and the rotor (44) of the secondary motor (4) is connected and fixed with the second supporting disc (224) in the circumferential direction.

6. The centrifugal fan of claim 1, wherein: the motor is characterized in that a supporting base (45) is arranged between the main motor (3) and the secondary motor (4), the secondary motor (4) is rotatably supported on the supporting base (45), a lead revolving groove (451) which is arranged around the periphery of the secondary motor (4) is formed in the supporting base (45), and the secondary motor (4) further comprises a rolling conductor (452) which is nested in the lead revolving groove (451).

7. The centrifugal fan of claim 6, wherein: the support base (45) is provided with a support (46), one end of the support (46) is fixedly connected with the support base (45), and the other end of the support is fixedly connected with the main motor (3).

8. A range hood with a centrifugal fan according to any one of claims 1 to 7, comprising a box body (5), characterized in that: the centrifugal fan is arranged in the box body (5).

9. The range hood of claim 8, wherein: an oil smoke sensor (6) is arranged in the box body (5) and at the upstream of the centrifugal fan.

10. A control method of a range hood as claimed in claim 9, comprising the steps of:

1) starting the range hood;

2) receiving a user instruction;

3) the user commands to enter a step 4) if the single impeller mode is required to be entered), and enter a step 5) if the double impeller mode is required to be entered;

4) if the mode is the single impeller mode, locking the secondary motor (4);

4.1) starting the main motor (3) to enable the first impeller (21) and the second impeller (22) to synchronously rotate;

4.2) judging whether the mode is the intelligent mode, if so, entering the step 4.3), and if not, returning to the step 2);

4.3) reading the current oil smoke concentration value detected by the oil smoke sensor (6);

4.4) judging whether the oil smoke concentration is greater than a preset threshold value, if so, adjusting the rotating speed of the main motor (3) to increase the rotating speed of the main motor (3), returning to the step 4.3), returning to the step 2 until the oil smoke concentration is lower than the preset threshold value, keeping the current rotating speed when the rotating speed of the main motor (3) reaches the rotating speed limit value of the main motor (3), or inputting a new instruction by a user to operate according to the new instruction; if not, returning to the step 2);

5) if the mode is the double-impeller mode, the secondary motor (4) is locked;

5.1) starting the main motor (3) to enable the first impeller (21) and the second impeller (22) to synchronously rotate until the rotating speed is increased to a preset specified rotating speed;

5.2) starting the secondary motor (4) to separate the rotating speeds of the first impeller (21) and the second impeller (22);

5.3) judging whether the mode is the intelligent mode, if so, entering a step 5.4), and if not, returning to the step 2);

5.4) reading the current oil smoke concentration value detected by the oil smoke sensor (6);

5.5) judging whether the oil smoke concentration is larger than a preset threshold value, if so, adjusting the rotating speed of the secondary motor (4), increasing the rotating speed of the secondary motor (4), and entering the step 5.6), otherwise, returning to the step 2);

5.6) reading the current oil smoke concentration value detected by the oil smoke sensor (6), judging whether the oil smoke concentration is still larger than a threshold value, and if so, entering the step 5.7); if not, clearing the number of times of adjusting the rotating speed of the motor (4), and returning to the step 2);

5.7) judging whether the upper limit of the number of times of rotating speed adjustment of the secondary motor (4) is reached, if so, adjusting the rotating speed of the main motor (3), increasing the rotating speed of the main motor (3), and returning to the step 5.4) until the oil smoke concentration is lower than a preset threshold, returning to the step 2), keeping the current rotating speed when the rotating speed of the main motor (3) reaches the rotating speed limit value of the main motor (3), or inputting a new instruction by a user to operate according to the new instruction; if not, go back to step 2).

Technical Field

The invention relates to a power device, in particular to a centrifugal fan, a range hood with the centrifugal fan and a control method of the range hood.

Background

The range hood has become an indispensable kitchen appliance for people since the entrance into China in the nineties of the last century. The main functions of the range hood are that oil smoke generated when a user cooks is sucked from the air inlet through the fan system impeller, the oil smoke is filtered by using the air inlet filter screen and the impeller, and the filtered oil smoke is discharged from the air outlet, so that the purification work of the kitchen environment is completed, the fan impeller is used as a core component of the range hood, the structure of the range hood is reasonably configured, the oil smoke suction effect is improved, the escape of the oil smoke is reduced, and the improvement of the air quality of the kitchen has important influence.

The range hood on the current market generally adopts a single air inlet and single air outlet structure, and can be divided into a single-fan range hood and a double-fan range hood according to the number of fans in the range hood. The single-fan range hood comprises an impeller assembly and a motor, wherein the motor and the impeller are placed in the volute in a direct connection mode, the impeller is integrally and rigidly connected, and all blades rotate synchronously; the double-fan range hood comprises two impeller assemblies and two motors, the connection mode of the motors and the impellers is the same as that of a single motor, and the two fan systems are arranged on the vertical plane of the air inlet in parallel.

Referring to fig. 10, the fan includes a volute 1 ', an impeller 2' and a main motor 3 'for driving the impeller 2', an air inlet 11 'is formed on the volute 1', the impeller 2 'and the main motor 3' are generally fixedly connected, that is, an output shaft of the main motor 3 'is directly connected with a shaft of the impeller 2', and the flow direction of air in the fan is shown by an arrow in fig. 10. The problems with this design are as follows: 1) For an impeller with a certain width, the flow rate at the air inlet 11 'is hardly restricted, and for the impeller far away from the air inlet 11', most of the air is sucked and flows by the upper (for convenience of description, "upper" refers to the upper direction in fig. 10, "lower" refers to the lower direction in fig. 10), so most of the air has the radial velocity, that is, the upper air does not move downwards when there is no pressure perpendicular to the radial direction, and the air supplement in the dashed line box is difficult; 2) air causes upper portion pressure reduction because the impeller rotation of upper portion in the dotted line frame, therefore has the trend of upward movement, can offset the partial centrifugal force that the impeller produced in the dotted line frame promptly for this partial impeller exhaust efficiency reduces, therefore the oil smoke suction and exhaust ability is relatively weak, and fan system performance receives the restriction, influences customer experience.

And along with the continuous promotion of quality of life, range hood manufacturer constantly pursues big amount of wind and big wind pressure to try to get better oil absorption cigarette effect, for obtaining better user experience, prior art generally increases, measures such as improvement motor performance are generally through the size to parts such as wind channel, impeller, motor obtain better oil absorption cigarette effect, so both increased the cost, also wasted the resource, and do not solve the fundamental problem, simultaneously, if the part size increases will influence the kitchen design.

Disclosure of Invention

The first technical problem to be solved by the present invention is to provide a centrifugal fan, which can reduce the influence of the impeller at the air inlet on the impeller far away from the air inlet, and improve the air exhaust efficiency of the impeller.

The second technical problem to be solved by the invention is to provide a range hood with the centrifugal fan.

The third technical problem to be solved by the invention is to provide a control method of the range hood.

The technical scheme adopted by the invention for solving the first technical problem is as follows: a centrifugal fan comprises a volute, an impeller assembly arranged in the volute and a first motor used for driving the impeller assembly, wherein an air inlet is formed in the volute, the main motor is provided with a first output shaft, and the centrifugal fan is characterized in that: the centrifugal fan further comprises a second motor, the secondary motor comprises a stator and a rotor arranged on the periphery of the stator, the secondary motor forms an outer rotor motor, the stator of the secondary motor is connected with a first output shaft of the main motor, and the stator and the rotor of the secondary motor are respectively connected with one of the first impeller and the second impeller so as to drive the first impeller and the second impeller to rotate.

In order to ensure that the centrifugal fan works stably and safely, the secondary motor is provided with a second output shaft connected with the stator and is a double-output-shaft motor, one second output shaft of the secondary motor is connected with the first output shaft, the other second output shaft of the secondary motor is connected with the first impeller, the rotor is connected with the second impeller, and the main motor, the secondary motor and the impeller assembly are coaxially arranged.

Preferably, in order to facilitate the connection between the first impeller and the secondary motor, the first impeller includes a first front disc, a first rear disc, a first blade disposed between the first front disc and the first rear disc, and a first support disc, the first support disc is connected to the first rear disc, and the second output shaft of the secondary motor is connected to the first support disc.

In order to further increase the air inlet volume of the second impeller, the first supporting disc is of an axial fan structure.

Preferably, in order to facilitate connection between the second impeller and the secondary motor, the second impeller includes a second front disc, a second rear disc, second blades disposed between the second front disc and the second rear disc, and a second support disc, a periphery of the second support disc is connected to the second rear disc, and is gradually recessed toward the first impeller from the periphery to the middle, a rotor of the secondary motor passes through an end portion of the second support disc close to the first impeller, and the rotor of the secondary motor is fixedly connected to the second support disc in the circumferential direction.

In order to supply power to the rotating secondary motor, a supporting base is arranged between the main motor and the secondary motor, the secondary motor is rotatably supported on the supporting base, a lead rotary groove surrounding the periphery of the secondary motor is formed in the supporting base, and the secondary motor further comprises a rolling conductor nested in the lead rotary groove.

In order to avoid the movement of the supporting seat, a support is arranged on the supporting base, one end of the support is fixedly connected with the supporting base, and the other end of the support is fixedly connected with the main motor.

The technical scheme adopted by the invention for solving the second technical problem is as follows: the utility model provides a range hood with centrifugal fan as above, includes the box, its characterized in that: the centrifugal fan is arranged in the box body.

In order to automatically control the operation of the centrifugal fan, an oil smoke sensor is arranged in the box body and at the upstream of the centrifugal fan.

The technical scheme adopted by the invention for solving the third technical problem is as follows: a control method of the range hood comprises the following steps:

1) starting the range hood;

2) receiving a user instruction;

3) the user commands to enter a step 4) if the single impeller mode is required to be entered), and enter a step 5) if the double impeller mode is required to be entered;

4) if the mode is the single impeller mode, locking the secondary motor;

4.1) starting the main motor to enable the first impeller and the second impeller to synchronously rotate;

4.2) judging whether the mode is the intelligent mode, if so, entering the step 4.3), and if not, returning to the step 2);

4.3) reading the current oil smoke concentration value detected by the oil smoke sensor;

4.4) judging whether the oil smoke concentration is greater than a preset threshold value, if so, adjusting the rotating speed of the main motor to increase the rotating speed of the main motor, returning to the step 4.3), returning to the step 2) until the oil smoke concentration is lower than the preset threshold value, keeping the current rotating speed when the rotating speed of the main motor reaches the rotating speed limit value of the main motor, or inputting a new command by a user to operate according to the new command; if not, returning to the step 2);

5) if the mode is a double-impeller mode, the secondary motor is locked;

5.1) starting the main motor to enable the first impeller and the second impeller to synchronously rotate until the rotating speed is increased to a preset specified rotating speed;

5.2) starting the secondary motor to separate the rotating speeds of the first impeller and the second impeller;

5.3) judging whether the mode is the intelligent mode, if so, entering a step 5.4), and if not, returning to the step 2);

5.4) reading the current oil smoke concentration value detected by the oil smoke sensor (6);

5.5) judging whether the oil smoke concentration is larger than a preset threshold value, if so, adjusting the rotating speed of the secondary motor, increasing the rotating speed of the secondary motor, and entering the step 5.6), otherwise, returning to the step 2);

5.6) reading the current oil smoke concentration value detected by the oil smoke sensor, judging whether the oil smoke concentration is still larger than a threshold value, and if so, entering the step 5.7); if not, clearing the number of times of motor speed adjustment, and returning to the step 2);

5.7) judging whether the upper limit of the times of the secondary motor rotating speed adjustment is reached, if so, adjusting the rotating speed of the main motor, increasing the rotating speed of the main motor, returning to the step 5.4), returning to the step 2) until the oil smoke concentration is lower than a preset threshold value, keeping the current rotating speed when the rotating speed of the main motor reaches the rotating speed limit value of the main motor, or inputting a new instruction by a user to operate according to the new instruction; if not, go back to step 2).

Compared with the prior art, the invention has the advantages that: the working states of the main motor and the secondary motor are combined through a double-fan cascade mode to achieve two working modes, the optimal oil smoke absorption effect is achieved through the minimum energy consumption while the oil smoke absorption effect is considered, the problem of excessive power in the working process is reduced, the current situation that the air exhaust efficiency of the existing impeller is low when the impeller is far away from an air inlet can be improved through rotating speed separation, the integral air exhaust volume of the centrifugal fan is increased under the same working condition, the integral performance of the centrifugal fan is improved, and the oil smoke absorption effect is improved; under the same air quantity requirement, the control is more accurate, the rotation speed adjustment in a wider range is realized, and the range of applicable oil smoke scenes is wider; and can be according to two impeller rotational speeds of oil smoke concentration automatically regulated under intelligent mode, convenient succinct.

Drawings

FIG. 1 is a schematic view of a centrifugal fan according to an embodiment of the present invention;

FIG. 2 is a cross-sectional view of a centrifugal fan in accordance with an embodiment of the present invention;

FIG. 3 is a schematic view of the centrifugal fan of FIG. 1 with a hidden volute;

FIG. 4 is an exploded schematic view of the centrifugal fan of FIG. 3;

FIG. 5 is an exploded schematic view of a drive mechanism of the centrifugal fan of FIG. 1;

FIG. 6 is a schematic view of an impeller exit velocity analysis;

fig. 7 is a schematic view of a centrifugal fan applied to a range hood according to an embodiment of the present invention;

fig. 8 is a sectional view of the centrifugal fan according to the embodiment of the present invention applied to a range hood;

fig. 9 is a control flowchart of the range hood according to the embodiment of the present invention;

fig. 10 is a schematic view of a prior art centrifugal fan.

Detailed Description

The invention is described in further detail below with reference to the accompanying examples.

Referring to fig. 1 to 5, a centrifugal fan 100 is mainly used for a range hood, and can also be used in other occasions requiring a centrifugal fan. The centrifugal fan 100 includes a scroll casing 1, an impeller assembly 2 disposed within the scroll casing 1, a primary motor 3 for driving the impeller assembly 2 to rotate, and a secondary motor 4.

The volute 1 has the same structure as the existing volute, and is provided with an air inlet 11 and an air outlet 12. The impeller assembly 2 includes a first impeller 21 and a second impeller 22 which are coaxially arranged at a distance, whereby the impeller assembly 2 is divided into two independent structures in the width direction (axial direction) and both are located in the same scroll casing 1. Wherein the first impeller 21 is disposed near the air inlet 11 of the scroll casing 1, and the second impeller 22 is disposed on a side of the first impeller 21 away from the air inlet 11.

The first impeller 21 includes a first front disk 211, a first rear disk 212, first blades 213 disposed between the first front disk 211 and the first rear disk 212, and a first support disk 214. The second impeller 22 includes a second front disk 221, a second rear disk 222, second blades 223 disposed between the second front disk 221 and the second rear disk 222, and a second support disk 224. The first blade 213 and the second blade 223 are plural and arranged at intervals in the circumferential direction, respectively. The first support plate 214 is connected to the first rear plate 212 of the first impeller 21, preferably in the form of an axial fan, and is connected to the first rear plate 212 via fan blades, thereby increasing the intake of the second impeller 22. The periphery of the second support disk 224 is connected to the second rear disk 222 of the second impeller 22, and gradually concaves toward the first impeller 21 from the periphery to the middle, and the end portion close to the first impeller 21 is flat, and the end portion far from the first impeller 21 is open.

The main motor 3 is partly located outside the second impeller 22 and partly extends into the second support disc 224 of the second impeller 22. The secondary motor 4 is partly located within the second impeller 22 and partly extends into the first impeller 21. The primary motor 3 has a first output shaft 31, the secondary motor 4 has a second output shaft 41, and the secondary motor 4 is a dual output shaft motor. One of the second output shafts 41 of the sub-motor 4 is connected to the first output shaft 31, and the other second output shaft 41 is directly connected to the first support plate 214 of the first impeller 21. The first output shaft 31 and the second output shaft 41 are coaxially arranged, and the first output shaft 31 and the second output shaft 41 are rigidly connected by a coupling 42. The secondary motor 4 further includes a stator 43 and a rotor 44 disposed on the outer periphery of the stator 43, thereby forming an outer rotor motor, and if a servo motor is used, the second output shaft 41 is connected to the stator 43 at the same rotational speed. The secondary motor 4 may be inserted through an end of the second support plate 224 near the first impeller 21, such that the rotor 44 of the secondary motor 4 is fixedly connected to the second support plate 224 in the circumferential direction.

The impeller assembly 2, the main motor 3 and the secondary motor 4 are coaxially arranged, so that the working is more stable and safer.

A supporting base 45 is arranged between the main motor 3 and the secondary motor 4, the secondary motor 4 can be rotatably supported on the supporting base 45 through a bearing, the coupling 42 can penetrate through the supporting base 45, and a lead wire revolving groove 451 which surrounds the periphery of the secondary motor 4 is arranged on the supporting base 45. Since the sub-motor 4 needs to rotate relative to the scroll casing 1 as a whole, the input and output currents of the sub-motor 4 need to be supplied through the lead rotary groove 451, that is, the current supply of the sub-motor 4 is not connected through a simple wire, but the input and output of the current are realized by the rolling conductor 452 nested in the lead rotary groove 451, the rolling conductor 452 performs the rotary motion relative to the first output shaft 31 of the main motor 3 in the lead rotary groove 451, and the input and output of the current are realized by the contact of the rolling conductor 452 and the wall surface of the lead rotary groove 451.

The support base 45 is provided with a bracket 46, in this embodiment, four support legs 461 are adopted, and one end of each support leg 461 is fixedly connected with the support base 45, and the other end is fixedly connected with the main motor 3. And the main motor 3 is also fixedly connected with the volute 1 (such as a rear cover plate), so that the positions of the support base 45, the main motor 3 and the volute 1 are relatively fixed.

Thereby, the rotation speed of the first impeller 21 is controlled by the main motor 3, and the rotation speed of the second impeller 22 is controlled by both the main motor 3 and the sub motor 4. The impeller assembly 2 of the present invention can operate in two modes of operation. The first output shaft 31 of the main motor 3 outputs a rotation speed of r1, the rotor 44 of the sub motor 4 outputs a rotation speed of r2, the stator 43 of the sub motor 4 (the rotation speed of the second output shaft 41) outputs a rotation speed of r3, the first impeller 21 rotates at r4, and the second impeller rotates at r 5.

In the single-impeller mode: at this time, the secondary motor 4 is in a locked state, where r2 is r3, where the locked state refers to that the rotor 44 of the secondary motor 4 is not moved relative to the stator 43 of the secondary motor 4, and since the second output shaft 41 of the secondary motor 4 is rigidly connected to the first output shaft 31 of the main motor 3 through the coupling 42, the rotor 44 and the stator 43 of the secondary motor 4 and the first output shaft 31 of the main motor 3 rotate at the same speed, r1 is r2 is r3, and the first impeller 21 is further rotated by the second output shaft 41 of the secondary motor 4, r4 is r3, the secondary motor 4 rotates the second impeller 22 through the rotor 44, r5 is r2, and therefore r4 is r5, that is, the first impeller 21 and the second impeller 22 operate at the same speed, which is the same as a single impeller in the prior art.

Dual impeller mode: at this time, the secondary motor 4 is powered on and is no longer in a locked state, r2 ≠ r3, namely, the rotor 44 of the secondary motor 4 rotates relative to the stator 43 of the secondary motor 4, since the second output shaft 41 of the secondary motor 4 is rigidly connected with the first output shaft 31 of the main motor 3, r3 ═ r1, the rotation speed of the first impeller 21 is consistent with the rotation speed of the stator 43 of the secondary motor 4, namely, r4 ═ r3, the rotation speed of the second impeller 22 is consistent with the rotor 44 of the secondary motor 4, namely, r5 ═ r2, and since r2 ≠ r3, r4 ≠ r5, namely, the rotation speeds of the first impeller 21 and the second impeller 22 are different.

Referring to fig. 2 and 6, where c is the absolute velocity of the air as it exits the impeller, α is the angle between the air as it exits and the tangential direction of the impeller, u is the tangential velocity of the impeller, w is the relative velocity of the air along the tangential direction of the blades, β is the angle between the tangential direction of the blades and the tangential direction of the impeller, and H is the radial velocity component. Under the general assumption that the air flows out of the impeller without affecting each other, the volume of the air discharged from the impeller is Q, the width (axial length) of the impeller assembly 2 is b, and the outer diameter is r, the volume of the air discharged from the conventional impeller is

Q＝2πrHb

When the conventional impeller is divided into two independent first impeller 21 and second impeller 22 as in the present embodiment, the width of the first impeller 21 is b1, the width of the second impeller 22 is b2, and b2 is mb1, the radial component of the air outlet speed of the first impeller 21 is u1, and the ratio of the rotation speed of the second impeller 22 to the rotation speed of the first impeller 21 is n, at this time, the volume of the air discharged by the impeller assembly 2 is equal to n

Q₁＝2πr(1+mn)u₁b₁

When the rotation speed of the first impeller 21 coincides with that of the integral impeller, the impeller assembly 2 of the present embodiment relatively increases the volume of the air discharged therefrom by an amount of

p＝(Q₁-Q)/Q

Taking parameters of an impeller of a range hood of a certain model on the current market as an example, calculating the relative increment of the volume of the discharged air after the impeller is separated, wherein the parameters of the impeller are as follows: b is 0.13m, m is 0.5, alpha is 15 deg., beta is 20 deg., n is 1.5, r is 0.125m, the rotation speed of motor is 1000 rpm, and the air quantity is 15m³And/min. Substituting the data into the above calculation yields p-0.0954, i.e. under the condition of keeping the rotation speed of the main motor 3 unchanged, the impeller assembly 2 is divided into two independent impellers, and the rotation speed of the second impeller 22 is increased, so that the relative increment of the volume of the air discharged by the impeller assembly 2 as a whole is 0.0954, which theoretically increases to 16.431m³/min。

Regarding the width ratio of the second impeller 22 to the impeller assembly 2 as a whole, the preferable value range of b2/b in the embodiment is 1/5-1/3, and if the width ratio is too small, the relative increase of the volume is hardly changed as can be seen from the above calculation; if the width ratio is too big, then it is as good as with the whole improvement rotational speed of former integral type impeller, and because second impeller 22 width increases, lead to second impeller 22 self to appear keeping away from the problem of the inefficiency of airing exhaust of air intake department.

Therefore, in the double-impeller mode, the two independent first impellers 21 and second impellers 22 are arranged, and the rotating speed of the second impeller 22 is increased to be greater than that of the first impeller 21, so that the negative pressure at the second impeller 22 is higher than that at the first impeller 21, the negative pressure at the first impeller 21 is higher than that at the air inlet 11, and an axial pressure gradient is formed by the air inlet 11, the first impeller 21 and the second impeller 22 together, thereby increasing the speed of the air in the direction away from the air inlet 11 in the axial direction. Therefore, the invention utilizes the rotating speed to make up the difficulty of air supplement and the reduction of centrifugal force caused by the rotation of the first impeller 21, improves the axial air flow rate, improves the air exhaust efficiency of the whole impeller and achieves better performance under the condition of the same size structure.

Referring to fig. 7 and 8, a range hood includes a fume collecting hood 8 and a box 5 disposed above the fume collecting hood 8, the centrifugal fan 100 is disposed in the box 5, and a fume sensor 6 is further disposed in the box 5 and at an upstream of the centrifugal fan 100. The range hood can be provided with a main controller 7, the oil smoke sensor 6, the main motor 3 and the secondary motor 4 are all electrically connected to the main controller 7, and the main controller 7 receives signals of the oil smoke sensor 6 so as to control the operation of the main motor 3 and the secondary motor 4. It is of course possible to provide a separate controller to receive the signal from the smoke sensor 6 to control the operation of the primary and secondary motors 3, 4.

Referring to fig. 9, the control method of the range hood includes the following steps:

1) starting the range hood;

2) receiving a user instruction, for example, a user may input an instruction to the main controller 7 by pressing a key;

3) the user commands to enter a step 4) if the single impeller mode is required to be entered), and enter a step 5) if the double impeller mode is required to be entered;

4) if the single-impeller mode is adopted, the main controller 7 sends a signal to lock the secondary motor 4, and the secondary motor 4 is switched on with locking current, namely the rotor 44 of the secondary motor 4, the stator 43 of the secondary motor 4 and the second output shaft 41 are kept synchronous;

4.1) the main controller 7 starts the main motor 3 and supplies working current to the main motor 3 to enable the first impeller 21 and the second impeller 22 to synchronously rotate;

4.2) judging whether the mode is an intelligent mode, and under the intelligent mode, automatically controlling the operation of the main motor 3 and the secondary motor 4 by the main controller 7 through receiving a detection signal of the oil smoke sensor 6; if yes, go to step 4.3), if not, go back to step 2);

4.3) the main controller 7 reads the current oil smoke concentration value detected by the oil smoke sensor 6, a plurality of oil smoke sensors 6 can be arranged, and then the detected values are averaged;

4.4) the main controller 7 judges whether the oil smoke concentration is greater than a preset threshold value, if so, the rotating speed of the main motor 3 is adjusted to increase the rotating speed of the main motor 3, and the step 4.3) is returned until the oil smoke concentration is lower than the preset threshold value, the step 2) is returned until the rotating speed of the main motor 3 reaches the rotating speed limit value of the main motor 3, the current rotating speed is kept, or a user inputs a new instruction to operate according to the new instruction; if not, returning to the step 2);

5) if the mode is the double-impeller mode, the main controller 7 sends a signal to lock the secondary motor 4, namely, the rotor 44 of the secondary motor 4 keeps synchronous with the stator 43 and the second output shaft 41 of the secondary motor 4;

5.1) starting the main motor 3 by the main controller 7, introducing working current into the main motor 3, and when the rotating speed of the two impellers is increased to a preset specified rotating speed;

5.2) starting the secondary motor 4 by the main controller 7, and introducing working current to the secondary motor 4 to separate the rotating speeds of the first impeller 21 and the second impeller 22;

5.3) judging whether the mode is an intelligent mode, and under the intelligent mode, automatically controlling the operation of the main motor 3 and the secondary motor 4 by the main controller 7 through receiving a detection signal of the oil smoke sensor 6; if yes, go to step 5.4), if not, go back to step 2);

5.4) the main controller 7 reads the current oil smoke concentration value detected by the oil smoke sensor 6, a plurality of oil smoke sensors 6 can be arranged, and then the detected values are averaged;

5.5) the main controller 7 judges whether the oil smoke concentration is larger than a preset threshold value, if so, the rotating speed of the secondary motor 4 is adjusted, the rotating speed of the secondary motor 4 is increased, and the step 5.6) is carried out, and if not, the step 2) is carried out;

5.6) the main controller 7 reads the current oil smoke concentration value detected by the oil smoke sensor 6, judges whether the oil smoke concentration is still larger than the threshold value, and if so, enters the step 5.7); if not, clearing the number of times of adjusting the rotating speed of the motor 4, and returning to the step 2);

5.7) the main controller 7 judges whether the upper limit of the number of times of the rotating speed adjustment of the secondary motor 4 is reached, if so, the rotating speed of the main motor 3 is adjusted, the rotating speed of the main motor 3 is increased, and the step 5.4) is returned until the oil smoke concentration is lower than the preset threshold value, the step 2) is returned until the rotating speed of the main motor 3 reaches the rotating speed limit value of the main motor 3, the current rotating speed is kept, or a user inputs a new instruction to operate according to the new instruction; if not, go back to step 2).

According to the invention, through a double-fan cascade mode, the working states of the main motor 3 and the secondary motor 4 are combined to achieve two working modes, and the rotating speeds of the two impellers can be automatically adjusted according to the oil smoke concentration in an intelligent mode, so that the device is convenient and simple, the oil smoke absorption effect is considered, the minimum energy consumption is realized to achieve the optimal oil smoke absorption effect, the problem of surplus power in the working process is reduced, the current situation that the air exhaust efficiency of the existing impeller is low when the existing impeller is far away from an air inlet can be improved through rotating speed separation (the rotating speed of the second impeller 22 is greater than that of the first impeller 21), under the same working condition, the integral air exhaust amount of the centrifugal fan is increased, the integral performance of the centrifugal fan is improved; under the same air quantity requirement, the control is more accurate, the rotating speed adjustment in a wider range is realized, and the range is more widely applicable to oil smoke scenes.