Centrifugal fan and electronic equipment

Abstract

The embodiment of the invention relates to the field of fans, and provides a centrifugal fan and electronic equipment. An impeller of the centrifugal fan is of a structure comprising M groups of blades, each group of blades comprises a plurality of blades with different lengths, the inner diameters of the plurality of blades in each group of blades are the same, and when the impeller comprises a plurality of groups of blades (namely M is greater than 1), the arrangement modes of the groups of blades are the same. Therefore, the BPF of the impeller can be reduced, the weighting value corresponding to the BPF can be adjusted to be a fractional weighting value, the sound pressure level of the reduced BPF is also reduced, and the total noise of the centrifugal fan is also reduced.

Description

Technical Field

[0001] The present application relates to the field of fans, and more specifically, to a centrifugal fan and an electronic device. Background Art

[0002] The cooling system of electronic equipment is usually equipped with a fan. Centrifugal fans are widely used in laptops, desktop computers, mobile air conditioners and other electrical appliances due to their advantages such as large suction and compact structure. The centrifugal fan includes a volute and an impeller. The impeller is arranged in the volute. After the gas is sucked in by the impeller, it is thrown out from the circumference of the impeller and discharged from the air outlet of the volute to realize the air supply of the electronic equipment.

[0003] As the heat generation power of electronic components increases, the required air volume of centrifugal fans is also increasing. To increase the air volume of centrifugal fans of the same size, it is generally achieved by increasing the speed of the centrifugal fans. However, increasing the speed will increase the noise, affecting the silent experience of the product.

[0004] Therefore, there is an urgent need to provide a centrifugal fan and solve the noise problem of the fan without affecting the air volume of the centrifugal fan. Summary of the invention

[0005] The embodiments of the present application provide a centrifugal fan and an electronic device, which can effectively reduce the noise of the centrifugal fan.

[0006] In a first aspect, a centrifugal fan is provided, comprising:

[0007] A volute, wherein a receiving cavity is formed in the volute, one end of the volute is formed as an air outlet, and a volute tongue is provided in the volute adjacent to the air outlet;

[0008] An impeller is accommodated in the accommodating cavity, the impeller includes a hub and fan blades fixedly connected to the hub, the fan blades include M groups of blades, wherein each group of blades includes a plurality of blades of different lengths, the inner diameters of the plurality of blades in each group of blades are the same, and when M is greater than 1, the blades of each group of the M groups of blades are circumferentially distributed around the hub in the same arrangement manner, and M is an integer greater than or equal to 1.

[0009] The centrifugal fan provided in the embodiment of the present application has an impeller structure including M groups of blades, each group of blades includes multiple blades of different lengths, and the inner diameters of the multiple blades in each group of blades are the same, which means that the outer diameters of the multiple blades in each group of blades are not completely the same. In this way, for blades of different lengths in each group of blades, the gap between the blades of different lengths and the volute tongue changes, thereby adjusting the noise of the centrifugal fan. In the case where the length of each group of blades is not exactly the same, when the impeller includes multiple groups of blades (i.e., M is greater than 1), the arrangement of each group of blades is the same. In this way, a group of blades can be regarded as a whole, and the event of a group of blades passing through the volute tongue when the impeller rotates can be regarded as one event. When the impeller rotates one circle and passes through M groups of blades, the event of M groups of blades passing through the volute tongue can be regarded as M identical events. In this way, the number M of M groups of blades can be regarded as the order. According to the formula of blade passing frequency BPF=n*K / 60, when the total number of blades of the impeller remains unchanged, the order K of the centrifugal fan with blades of the same length in the prior art is the total number of blades, while the order K of the centrifugal fan of the present application is the number M of all blades of the impeller. The order K becomes smaller, so that the BPF also becomes smaller, so that the weighted value corresponding to the BPF can be adjusted to a small weighted value, and the sound pressure level of the reduced BPF also becomes smaller, thereby reducing the total noise of the centrifugal fan.

[0010] In addition, the larger the gap between the shorter blades in each set of blades and the volute, the less interaction between the airflow between the shorter blades and the volute will be, thereby also having the effect of reducing noise.

[0011] Optionally, the groups of blades are distributed at equal intervals along the circumference of the hub.

[0012] In the centrifugal fan provided in the embodiment of the present application, each group of blades is distributed at equal intervals along the circumference of the hub, which can better achieve the dynamic balance of the impeller.

[0013] Optionally, the circumferential spacing between any two adjacent groups of blades in the M groups of blades is the same as the circumferential spacing between any two adjacent blades in each group of blades.

[0014] In the centrifugal fan provided in the embodiment of the present application, the circumferential spacing between any two adjacent groups of blades in the M groups of blades is the same as the circumferential spacing between any two adjacent blades in each group of blades, which means that the circumferential spacing between any two blades in the M groups of blades is the same. In this way, the dynamic balance of the impeller can be better achieved and the installation design process is simplified.

[0015] Optionally, the multiple blades of each group of blades with different lengths correspond to multiple lengths, one length corresponds to at least one blade, and the ratio of the difference between the longest length and the shortest length among the multiple lengths to the longest length is less than or equal to a length difference threshold.

[0016] The centrifugal fan provided in the embodiment of the present application limits the difference between the longest length and the shortest length of the blades 122 so that the length difference of the blades in each group of blades is not too large, thereby minimizing the impact on the working area and mechanical balance of the blades, thereby reducing the impact on the working capacity of the impeller.

[0017] Optionally, the length difference threshold is less than or equal to 30%.

[0018] Optionally, the multiple blades with different lengths in each group of blades are arranged in a manner of increasing length, decreasing length, increasing first and then decreasing, or decreasing first and then increasing.

[0019] Optionally, each blade in each group of blades includes an inner section close to the hub and an outer section away from the hub, the inner section is a first curved surface, and the outer section is a second curved surface.

[0020] The centrifugal fan provided in the embodiment of the present application can meet the working principle of the impeller by designing the inner and outer sections of the blades as curved surfaces, which not only makes the working capacity of the impeller better, but also makes the noise of the centrifugal fan smaller.

[0021] Optionally, a curvature of the second curved surface is greater than a curvature of the first curved surface.

[0022] In the centrifugal fan provided in the embodiment of the present application, since the outer section of the blade is the area mainly used for doing work, by making the curvature of the second curved surface greater than the curvature of the first curved surface, the outer section with a large curvature can enable the blade to have better work-doing capacity.

[0023] Optionally, the inner sections of the blades in each group of blades are the same in length.

[0024] In the centrifugal fan provided by the embodiment of the present application, when the lengths of the inner sections of the blades in each group of blades are the same, the outer sections of the blades with different lengths are different, so that it is convenient to process and design blades of different lengths. Specifically, in implementation, all blades with the same length can be processed and designed first, and then the outer sections of specific blades can be cut, and the outer sections of the blades can be cut according to the designed dimensions, and finally blades with different lengths are formed. It can be seen that the inner sections of the blades with different lengths obtained in this way are the same and the outer sections 1222, and the processing and design process is relatively convenient and efficient.

[0025] Optionally, the centrifugal fan further includes a reinforcement ring, which is fixedly connected to the ends of the M groups of blades away from the hub.

[0026] The centrifugal fan provided in the embodiment of the present application has the problem of shaking or even deformation because the end of the blade away from the hub is easily affected by air resistance. Therefore, a reinforcement ring is connected to the end of the blade away from the hub to provide a certain support for the blade, increase the blade's resistance to fracture, and provide the blade with a better ventilation effect.

[0027] Optionally, the end of the shortest blade in each group of blades away from the hub does not exceed the outer end of the reinforcement ring.

[0028] In the centrifugal fan provided in the embodiment of the present application, for blades of different lengths, the end of the longer blade away from the hub may extend beyond the reinforcement ring. The area extending beyond the reinforcement ring serves as a free end and is still susceptible to shaking due to air resistance. Therefore, by ensuring that the end of the shortest blade away from the hub does not extend beyond the outer side of the reinforcement ring, the area where the end of the longer blade away from the hub extends beyond the reinforcement ring can be reduced, thereby further enhancing the strength of the blade.

[0029] Optionally, the end of the shortest blade in each group of blades away from the hub is flush with the outer end of the reinforcement ring.

[0030] The centrifugal fan provided in the embodiment of the present application makes the end of the shortest blade in each group of blades away from the hub flush with the outer end of the reinforcement ring, while minimizing the area where the end of the longer blade away from the hub exceeds the reinforcement ring to better enhance the strength of the longer blade, and can also maximize the area where the shortest blade is connected and in contact with the reinforcement ring, thereby ensuring the strength of the shortest blade as much as possible. Therefore, the strength of the long blade and the short blade is comprehensively considered, and the strength of the entire impeller is improved as a whole.

[0031] In a second aspect, an electronic device is provided, comprising a housing and a centrifugal fan as described in any one of the embodiments of the first aspect, wherein the centrifugal fan is installed in the housing.

[0032] Optionally, the electronic device is a laptop computer. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic structural diagram of the centrifugal fan provided in an embodiment of the present application applied to a laptop computer.

[0034] Figure 2 It is a schematic structural diagram of the laptop computer provided in an embodiment of the present application from another perspective.

[0035] Figure 3 It is a schematic structural diagram of a local area of ​​a laptop computer with the back cover removed provided in an embodiment of the present application.

[0036] Figure 4 It is a schematic structural diagram of another partial area of ​​a laptop computer with the back cover removed provided by an embodiment of the present application.

[0037] Figure 5 It is a schematic structural diagram of the centrifugal fan provided in an embodiment of the present application.

[0038] Figure 6 yes Figure 5 Exploded view of a centrifugal fan.

[0039] Figure 7 It is a schematic structural diagram of the impeller provided in the embodiment of the present application.

[0040] Figure 8 It is a schematic structural diagram of the impeller provided in an embodiment of the present application from another perspective.

[0041] Fig. 9 It is a schematic structural diagram of the structure of the centrifugal fan provided in an embodiment of the present application without the cover plate.

[0042] Fig.10 Provided is a frequency spectrum diagram of the noise of a centrifugal fan with impellers having blades of the same length in the prior art.

[0043] Fig.11 It is a spectrum diagram of the noise of the centrifugal fan of the embodiment of the present application provided when the total number of blades of the impeller remains unchanged.

[0044] Fig.12 yes Figure 8 Schematic diagram of the local area of ​​the impeller at A.

[0045] Fig.13 This is another schematic structural diagram of the impeller provided in an embodiment of the present application.

[0046] Fig.14 The embodiment of the present application provides Fig.13 Spectrum diagram of the noise of the centrifugal fan obtained from the impeller.

[0047] Fig.15 This is another schematic structural diagram of the impeller provided in an embodiment of the present application.

[0048] Fig.16 The embodiment of the present application provides Fig.15 Spectrum diagram of the noise of the centrifugal fan obtained from the impeller.

[0049] Reference numerals

[0050] 1. Main unit assembly; 2. Rotating shaft assembly; 3. Screen assembly; 20. Back cover; Opening 30a, outlet 30b; 40. Heat exchange device; 10. Centrifugal fan; 11. Volute; 111. Air inlet; 112. Air outlet; 113. Accommodating chamber; 114. Volute tongue; 11a. Cover plate; 11b. Volute body; 12. Impeller; 121. Hub; 1211. Shaft hole; 1212. Putty groove; 122. Blade; 1221. Inner section of blade 122; 1222. Outer section of blade 122; 123. Reinforcement ring; 123a. Outer end of reinforcement ring 123; 13. Main shaft; 14. Motor. DETAILED DESCRIPTION

[0051] The technical solution in this application will be described below in conjunction with the accompanying drawings.

[0052] A centrifugal fan is a mechanical increasing device that achieves pressurization by accelerating the gas. That is, based on the principle of converting kinetic energy into potential energy, the gas is accelerated by a high-speed rotating impeller, and then decelerated and the flow direction is changed to convert kinetic energy into potential energy (or pressure). Since centrifugal fans can efficiently increase the pressure of gas, the fan has a large suction force and is widely used in many fields.

[0053] The centrifugal fan of the embodiment of the present application can be applied to various electronic devices that require heat dissipation. For example, the electronic device can be a desktop computer, a laptop computer, a mobile air conditioner, a range hood, or the like.

[0054] Figure 1 It is a schematic structural diagram of the centrifugal fan provided in an embodiment of the present application applied to a laptop computer. Figure 2 It is a schematic structural diagram of the laptop computer provided in an embodiment of the present application from another perspective. Figure 3 It is a schematic structural diagram of a local area of ​​a laptop computer with the back cover removed provided in an embodiment of the present application.

[0055] refer to Figure 1 and Figure 2 The laptop computer includes a host assembly 1, a hinge assembly 2, and a screen assembly 3. The screen assembly 3 and the host assembly 1 are rotationally connected via the hinge assembly 2. Specifically, one end of the hinge assembly 2 is fixedly connected to the screen assembly 3, and the other end is fixedly connected to the host assembly 1. When the laptop computer is opened, the screen assembly 3 rotates clockwise relative to the host assembly 1, and the torsion provided by the hinge assembly 2 enables the laptop computer to maintain a stable open state. When the laptop computer is closed, the screen assembly 3 rotates counterclockwise relative to the host assembly 1, and the torsion provided by the hinge assembly 2 enables the screen assembly 3 to fall freely. Exemplarily, two hinge assemblies 2 are provided in the laptop computer. For example, along the axis direction of the hinge assembly 2, the two hinge assemblies 2 are symmetrically arranged.

[0056] refer to Figure 2 and Figure 3 The host assembly 1 includes a host housing (not shown in the figure), and the host housing contains various components, for example, the main body housing contains circuit boards, chips, centrifugal fans 10, heat exchange devices, batteries, speakers, wireless devices, sensors and other components. The host housing includes a rear cover 20 (such as Figure 2 As shown in FIG. 1 , the rear cover 20 is detachably connected to the main body of the host housing. The rear cover 20 includes an opening 30a, and air enters from the opening 30a to be sucked in by the centrifugal fan 10 to achieve ventilation of the notebook computer.

[0057] For example, two centrifugal fans 10 may be installed in the laptop computer, and the two centrifugal fans 10 are symmetrically arranged. Correspondingly, the back cover 20 may include two inlets 30a, and one inlet 30a corresponds to one centrifugal fan 10. In this way, not only the ventilation efficiency of the laptop computer can be improved, but also the balance of ventilation can be achieved. For example, in order to protect the electrical components in the host assembly 1 as much as possible while achieving air intake, the inlet 30a may be a grid-type opening to prevent large particles or impurities from entering the host assembly 1 through the inlet 30a, thereby affecting the life of the internal electrical components.

[0058] Figure 4 It is a schematic structural diagram of another partial area of ​​a laptop computer with the back cover removed provided by an embodiment of the present application.

[0059] refer to Figure 4 The centrifugal fan 10 is installed in the main body housing, and the centrifugal fan 10 includes a volute 11 and an impeller 12, and the impeller 12 is installed in the volute 11. After the gas is sucked in by the impeller 12 through the inlet 30a, it is thrown out from the circumference of the impeller 12 and discharged from the air outlet (not shown in the figure) of the volute 11. The gas passes through the heat exchange device 40 and is finally discharged from the outlet 30b of the main body housing, thereby exhausting the gas from the laptop computer.

[0060] As described in the prior art, increasing the air volume of a centrifugal fan by increasing the rotation speed will increase the noise, affecting the silent experience of the product. Therefore, the embodiment of the present application provides a centrifugal fan, in which the impeller blades are arranged as multiple groups of blades and each group of blades includes multiple blades of incomplete length, which can effectively solve the noise problem without substantially affecting the air volume of the fan.

[0061] The embodiments of the present application relate to the noise reduction problem of a centrifugal fan. For ease of description, relevant concepts regarding noise are first introduced.

[0062] 1. Sound pressure and sound pressure level (SPL)

[0063] Sound pressure refers to the disturbance of the atmospheric pressure at a certain point in space by the sound waves generated by the noise source. It is the change in atmospheric pressure caused by the disturbance of the sound waves, that is, the residual pressure of the atmospheric pressure. It is equivalent to the pressure change caused by a sound wave disturbance superimposed on the atmospheric pressure. The unit of sound pressure is Pascal (pa).

[0064] The sound pressure level is represented by the symbol SPL, which is defined as the ratio of the measured sound pressure effective value p(e) to the reference sound pressure p(ref) taken by the common logarithm and then multiplied by 20, that is: SPL = 20lg[p(e) / p(ref)]. The unit of sound pressure level is decibel. In air, the reference sound pressure p(ref) is generally taken as 2*10e -5 Pa.

[0065] 2. Weighting principle

[0066] Weighted is also called weighting or auditory compensation. It has two meanings: one is the artificial correction added to the measured value in consideration of the different conditions of the equipment during normal use and measurement, which is called weighting. Or it can be understood as: a correction coefficient added during measurement to correctly reflect the object being measured. For example, when measuring noise, since the human ear is most sensitive to 1-5kHz and is insensitive to low-frequency components, when evaluating the noise level from the auditory point of view, it is necessary to weight each part of the audio spectrum, that is, when measuring noise, it is necessary to pass it through a filter equivalent to the auditory frequency characteristics to reflect the sharp sensitivity of the human ear near 3000Hz and the poor sensitivity at 60Hz. This is weighting.

[0067] The sensitivity of the human ear to sound varies with the frequency of the sound. In order to simulate the different sensitivities of the human ear at different frequencies, IEC 61672-1 defines frequency weightings A, C and Z. Through frequency weighting, the electrical signal is corrected to a signal that is similar to the hearing. The sound pressure level measured by frequency weighting is no longer the sound pressure level of an objective physical quantity (called linear sound pressure level), but a sound pressure level corrected by the sense of hearing, called weighted sound level or noise level.

[0068] A-weighting simulates the human ear's response to sound and the frequency characteristics of the human ear to low-intensity noise below 55 decibels, so that the mid- and low-frequency bands of the electrical signal have a greater attenuation. The A-weighted filter covers a frequency range of 20Hz to 20KHz. Measurements using A-weighting are usually marked with dB(A), such as LAeq, LAFmax, LAE, etc. A indicates that A-weighting is used. A-weighted sound level is the most widely used type of noise measurement in the world because its characteristic curve is close to the hearing characteristics of the human ear.

[0069] C-weighting simulates the frequency characteristics of the human ear to high-intensity noise, that is, the response of the human ear at relatively high sound levels. C-weighting is mainly used to evaluate the peak of high sound pressure levels. It can also be used to measure entertainment noise, but the transmission of bass noise may be problematic. Measurements using C-weighting are usually marked For example, LCeq, LCPeak, LCE, etc., C means that C weighting is used.

[0070] Z-weighting is the horizontal response in the frequency range 20Hz to 20KHz, ±1.5dB, excluding the microphone response. Measurements using Z-weighting are usually marked with dB(Z), such as LZeq, LZFmax, LZE, etc. C indicates that C-weighting is used.

[0071] Table 1 shows the weighting values ​​of different frequencies in different ways. It can be seen that different frequencies correspond to different weighting values. The result of adding the original sound pressure level of a certain frequency to the corresponding weighting value is the sound pressure level of the frequency after weighting. Taking the frequency of 10Hz and A weighting as an example, the A weighting value corresponding to the frequency of 10Hz is -70.4dB. Assuming that the original sound pressure level is 100dB, the result after weighting is 100-70.4=29.6dB.

[0072] Table 1

[0073]

[0074]

[0075] 3. Blade passing frequency (BPF)

[0076] The main noise of centrifugal fans is caused by the interference between the rotation of the impeller and the dynamic and static of the volute tongue. The airflow flowing out of the flow channel of the impeller will periodically impact the volute tongue, generating a large pulsating pressure on the impeller and the volute tongue, forming a noise with obvious frequency characteristics that is positively correlated with the speed. Therefore, BPF is the noise frequency caused by the blades of the centrifugal fan passing through the volute tongue, also known as the fundamental frequency, or the fundamental frequency of the noise peak. The frequencies of other noise peaks are multiples of BPF.

[0077] The sound pressure level of the centrifugal fan in the BPF can be referred to as the sound pressure level of the BPF. The sound pressure level of the BPF is the peak sound pressure level, which affects the total noise. Under normal circumstances, the greater the sound pressure level of the BPF, the greater the total noise, and the smaller the sound pressure level of the BPF, the smaller the total noise. It should be understood that the sound pressure level of the BPF described here and below is the sound pressure level after the original sound pressure level is weighted, that is, the sound pressure level of the BPF is the sound pressure level obtained by adding the original sound pressure level of the BPF to the weighted value.

[0078] For the convenience of description, in the following text, unless otherwise specified, the sound pressure level of a certain frequency refers to the weighted sound pressure level of the frequency, that is, the sound pressure level after the original sound pressure level of the frequency is weighted. The original sound pressure level of a certain frequency is the unweighted sound pressure level.

[0079] Below, the design principle of the present application is first briefly described, and then, based on this, the centrifugal fan proposed in the present application is introduced in combination with the structure.

[0080] As mentioned above, the sound pressure level of the centrifugal fan in the BPF affects the total noise. The greater the sound pressure level of the BPF, the greater the total noise, and the smaller the sound pressure level of the BPF, the smaller the total noise. Based on this, it can be understood that reducing the sound pressure level of the BPF can reduce the total noise.

[0081] In Table 1, it can be seen that different frequencies correspond to different weighting values. In general, when the various parameters of the centrifugal fan remain unchanged, the original sound pressure level of the centrifugal fan at different frequencies is basically the same (for example, the original sound pressure level is basically the same in the range of 20Hz to 20kHz), and the weighted sound pressure level of different frequencies is the sum of the original sound pressure level and the weighting value. Therefore, the main factor affecting the weighted sound pressure level of different frequencies is the weighting value. Based on this, for the sound pressure level of the BPF, the BPF can be adjusted to a frequency range with a low weighting value by adjusting the BPF. In this way, due to the adjustment of the BPF, the weighting value corresponding to the adjusted BPF becomes smaller, thereby reducing the sound pressure level of the adjusted BPF, thereby reducing the total noise.

[0082] Assuming that the BPF of a centrifugal fan is approximately 4000Hz, then, in order to reduce noise, the BPF can be adjusted to a frequency such as 1600Hz, 1250Hz, 1000Hz, 800Hz, etc., whose weighted value is less than the weighted value corresponding to 4000Hz. In this way, the sound pressure level of the adjusted BPF becomes smaller, thereby reducing the total noise.

[0083] The following is an analysis of how to adjust the BPF to a frequency range corresponding to a low weighting value.

[0084] The impeller of a centrifugal fan is a rotating structure. The essence of the BPF of a rotating structure is to describe the order. The order is essentially related to the number of times a certain event (collision, meshing, impact) occurs when the rotating part rotates one circle. It is a multiple of the speed or frequency. The unit of speed is r / min, which means the number of revolutions per minute. The unit of frequency is Hz, which means the number of revolutions per second. For example, 1 order is 1 times the frequency, K order is K times the frequency, and K is the order.

[0085] It can be understood that as a rotating structure, it will produce a response (vibration and / or noise) of a certain amplitude, and this response will change as the speed changes. The order is the response of the rotating structure to vibration and / or noise caused by rotation. There is a corresponding relationship between this order response and the speed or frequency. To be precise, the order is a multiple of the speed or frequency. The vibration and noise response of the rotating structure usually appears at multiples of the speed or frequency, that is, at these orders.

[0086] For a rotating shaft, the order of the rotating shaft is 1 times the rotation frequency. For example, if the speed of the rotating shaft is 600r / min, the rotation frequency is 600 / 60=10Hz, and the order of the rotating shaft is 1, and the order of the rotating shaft is 1 times the rotation frequency, that is, 10Hz.

[0087] For the impeller of a centrifugal fan, the structures of multiple blades of the impeller are the same. When the impeller rotates one circle, multiple identical blades will pass through. Therefore, the order of the impeller is the number of blades with the same structure that pass through one circle. The product of the order and the rotation frequency is the order. For example, if the impeller includes 6 blades with the same structure and the speed is 1500r / min, the rotation frequency is 1500 / 60=25Hz, then the order of the impeller is 25Hz*6=150Hz, and the order of the impeller is 6, that is, when the impeller rotates one circle, 6 blades with the same structure will pass through.

[0088] For the centrifugal fan, in order to facilitate the overall description, the order of the centrifugal fan is replaced by the BPF of the centrifugal fan for description below.

[0089] Regarding the BPF of the centrifugal fan, for impellers with the same blade structure, the number of the same events that occur in one rotation of the impeller can be understood as the number of times blades with the same structure pass through the volute tongue. Therefore, the formula for the BPF of the centrifugal fan can be described as: BPF = n*K / 60, where n represents the speed of the impeller of the centrifugal fan, the unit is r / min, K represents the order, and for impellers with the same blade structure, K is the total number of blades in the impeller.

[0090] Therefore, in order to adjust the BPF to the frequency range of low weighting value, K needs to be adjusted. Then, without changing the number of blades, it is necessary to reduce the BPF by reducing K. Based on this, the applicant proposes to design the blades of the impeller of the centrifugal fan into multiple groups of blades. The lengths of the multiple blades in each group of blades are not exactly the same. The number of blades in each group of blades, the arrangement of blades of different lengths, and the shape are the same. In other words, each group of blades is exactly the same. In this way, a group of blades can be regarded as a whole. When the impeller rotates, the event of a group of blades passing through the volute tongue can be regarded as one event. When the impeller rotates one circle and passes through multiple groups of blades, the event of multiple groups of blades passing through the volute tongue can be regarded as multiple identical events. In this way, the number of groups of blades is the order. For the same number of blades, compared with the prior art, the order of the centrifugal fan of the present application becomes smaller. In this way, the BPF also becomes smaller, and the BPF can be adjusted to the frequency range of low weighting value.

[0091] It should be understood that the lengths of the multiple blades in each group of blades are not exactly the same, which refers to all cases except "the lengths of the multiple blades are exactly the same", including: the case where the lengths of the multiple blades are not exactly the same, and the case where some of the multiple blades have the same length and some have different lengths. Alternatively, the lengths of the multiple blades in each group of blades are not exactly the same, which can be understood as the multiple blades in each group of blades correspond to multiple lengths, and one length corresponds to at least one blade. For example, the total number of blades of the impeller of a centrifugal fan is 12, including 4 groups of blades, each group of blades includes 3 blades, the 3 blades correspond to 3 lengths, and one blade corresponds to one length, that is, the lengths of the 3 blades are not the same, or the 3 blades correspond to 2 lengths, 2 of which correspond to one length, and the other blade corresponds to another length, that is, the 3 blades correspond to 2 lengths.

[0092] During design, a small weighting value can be determined based on actual conditions. The frequency corresponding to the weighting value can be used as the BPF of the centrifugal fan. When n is known, K can be determined according to the formula BPF=n*K / 60. The number of blades in each group can be obtained based on the ratio between the total number of known blades and K. Further design can be done for blades in each group that are not exactly the same length.

[0093] The following, combined Figures 5 to 16 , the structure of the centrifugal fan proposed in this application is explained.

[0094] Figure 5 It is a schematic structural diagram of the centrifugal fan provided in an embodiment of the present application. Figure 6 yes Figure 5 Exploded view of a centrifugal fan.

[0095] refer to Figure 5 and Figure 6The centrifugal fan 10 includes a volute 11 , an impeller 12 , a motor 14 and a main shaft 13 , and the impeller 12 , the motor 14 and the main shaft 13 are all installed in the volute 11 .

[0096] refer to Figure 6 An accommodating chamber 113 is formed in the volute 11 , and the accommodating chamber 113 is used to accommodate the impeller 12 .

[0097] refer to Figure 5 and Figure 6 An air inlet 111 is formed at one end of the volute 11, and a blade channel formed between the blades 122 of the impeller 12 is leaked out of the air inlet 111. The air inlet 111 is connected to the accommodating chamber 113, and the opening direction of the air inlet 111 is the same as the axial direction of the impeller 12. In this way, the gas passes through the air inlet 111 axially (such as Figure 5 The air flows into the impeller 12 in the direction of the arrow marked at the air inlet 111. The other end of the volute 11 is formed with an air outlet 112, the opening direction of the air outlet 112 is perpendicular to the axial direction of the impeller 12, or in other words, the air outlet 112 is arranged on one side relative to the radial direction of the impeller 12, and the gas passes through the work of the impeller 12 and is finally discharged from the air outlet 112 (as shown in FIG. Figure 5 The direction of the arrow marked at the middle air outlet 112).

[0098] Exemplarily, the volute 11 includes a cover plate 11a and a volute body 11b, and the cover plate 11a is fixedly connected to the volute body 11b. In one example, the cover plate 11a and the volute body 11b are fixedly connected by fasteners or welding. In another example, the cover plate 11a and the volute body 11b can be integrally formed. An air inlet 111 is provided on the cover plate 11a, and an accommodating cavity 113 for accommodating the impeller 12 is formed between the cover plate 11a and the volute body 11b, and an air outlet 112 is formed between the cover plate 11a and the volute body 11b.

[0099] refer to Figure 6 A volute tongue 114 is provided near the air outlet 112 of the volute 11 . The volute tongue 114 is a tongue-shaped structure. The volute tongue 114 as a whole extends toward the impeller 12 (or the accommodating chamber 113 ), which can prevent the gas from circulating in the volute 11 .

[0100] It should be understood that the structure of the volute 11 shown above is only for illustrative purposes and should not be construed as limiting the embodiments of the present application. The shape of the volute 11 can be arbitrary, as long as the air outlet 112 is perpendicular to the axial direction of the impeller.

[0101] refer to Figure 6The impeller 12 includes a hub 121 and blades, and the blades include a plurality of blades 122, and the plurality of blades 122 are fixedly connected to the hub 121. The hub 121 is provided with an axial hole 1211, and the main shaft 13 is sleeved and fixedly connected in the axial hole 1211. A mounting groove (not shown in the figure) is provided on one side of the hub 121 away from the cover plate 11a of the volute 11, and the motor 14 is installed in the mounting groove. When the motor 14 runs, it drives the main shaft 13 to rotate, and the main shaft 13 drives the impeller 12 to rotate, and the impeller 12 does work.

[0102] When the impeller 12 rotates, the air in the blade channel (the flow channel formed between the blades) of the impeller 12 moves outward under the action of centrifugal force, and a vacuum is generated in the middle of the impeller 12. The gas is axially sucked in through the air inlet 111. The sucked gas is turned 90° at the entrance of the impeller 12 and then enters the blade channel. Under the action of the blades, it acquires kinetic energy and pressure energy. The airflow thrown out from the blade channel enters the volute 11 and is finally discharged from the air outlet 112 of the volute 11 to realize the air supply of the centrifugal fan.

[0103] Figure 7 It is a schematic structural diagram of the impeller provided in the embodiment of the present application. Figure 8 It is a schematic structural diagram of the impeller provided in an embodiment of the present application from another perspective.

[0104] refer to Figure 7 and Figure 8 The fan blades include a plurality of blades 122 , and the plurality of blades 122 are formed into M groups of blades. Each blade 122 of each group of blades is fixedly connected to the hub 121 , and M is an integer greater than or equal to 1.

[0105] For each set of blades, each set of blades includes a plurality of blades 122 of different lengths, and the inner diameters of the plurality of blades 122 of each set of blades are the same. In other words, the outer diameters of the plurality of blades 122 of each set of blades are different. As mentioned above, the lengths of the plurality of blades 122 of each set of blades are different, which can be specifically understood as the plurality of blades 122 of each set of blades corresponding to a plurality of lengths, one length corresponding to at least one blade 122, that is, one length corresponding to one blade 122 or a plurality of blades 122.

[0106] In one example, the plurality of blades 122 of each set of blades correspond to a plurality of lengths, and one blade 122 corresponds to one length. Figure 7 and Figure 8Taking the impeller 12 shown as an example, the fan blades include 63 blades 122, forming 21 groups of blades (i.e., M=21), each group of blades includes 3 blades 122, and the lengths of the three blades 122 are all different, and one blade 122 corresponds to one length. For ease of description, the three blades 122 can be respectively recorded as blade 122a, blade 122b, and blade 122c, blade 122a is the shortest, blade 122c is the longest, and blade 122b is in the middle. Figure 7 and Figure 8 In the example of , one length corresponds to one blade 122. In other examples below, one length may also correspond to multiple blades 122, which may be referred to in the following description and will not be repeated here.

[0107] In another example, the multiple blades 122 of each blade group correspond to multiple lengths, a portion of the multiple lengths corresponds to multiple blades 122, and another portion of the length corresponds to one blade 122, wherein the number of blades 122 corresponding to each length in the portion of lengths may be the same or different. For example, the impeller 12 includes 63 blades 122, and the 63 blades 122 are formed into 7 groups of blades, each group of blades includes 9 blades 122, and the 9 blades 122 correspond to 4 lengths, which are recorded as length 1, length 2, length 3, and length 4, wherein length 1, length 2, and length 3 correspond to 2 blades 122, respectively, and length 4 corresponds to 1 blade 122.

[0108] In another example, the plurality of blades 122 of each set of blades correspond to a plurality of lengths, and each length corresponds to a plurality of blades 122. For example, the impeller 12 includes 12 blades 122, and the 12 blades include 3 sets of blades, each set of blades includes 4 blades, and the 4 blades correspond to 2 lengths, and one length corresponds to 2 blades 122.

[0109] When the number M of blade groups 122 is greater than 1, the blades in each of the M blade groups are circumferentially distributed around the hub 121 in the same arrangement. In other words, the blades 122 of different lengths in each blade group are arranged in the same manner.

[0110] It can be understood that since the lengths of the multiple blades 122 of each blade group are not completely the same, the arrangement of the blades 122 of different lengths in each group will affect the BPF of the impeller 12. Therefore, we define that the arrangement of the blades in each group is the same. The arrangement of the blades can be based on the length of the blades and the principle of arrangement and combination, and the specific arrangement is not limited.

[0111] For example, the multiple blades 122 of each group of blades with different lengths may be arranged in a manner that their lengths increase in sequence, decrease in sequence, increase first and then decrease, or decrease first and then increase. In other words, the blades are arranged in a manner that their lengths increase in sequence, decrease in sequence, increase first and then decrease, or decrease first and then increase. In other examples, the multiple blades 122 of each group of blades with different lengths may also be arranged in other ways, for example, the multiple blades 122 of each group of blades with different lengths may be arranged in a manner that their lengths increase first and then decrease, and then increase.

[0112] It should be noted that when describing the arrangement of the blades 122, the rotation direction of the impeller 12 is used as a reference direction for description. Figure 7 In the figure, the impeller 12 rotates in the counterclockwise direction as indicated by the arrow, and thus the arrangement of the blades 122 is described in the counterclockwise direction.

[0113] Continue with Figure 7 Taking the 21 groups of blades as an example, the lengths of the three blades 122 in each group of blades are different, the length of blade 122a is the shortest, and the length of blade 122c is the longest. According to the principle of permutation and combination, Figure 7 The rotation direction shown is the reference direction. The three blades 122 can be arranged in 6 ways. For example, the three blades 122 in each group are arranged in a way that the length increases first and then decreases. There are two ways of arrangement. One way is to arrange the blades 122 in the same way. Figure 7 The arrangement method 1 in the figure is used, that is, each group of blades is arranged in the order of blade 122a, blade 122c and blade 122b. Another method is to arrange them in the order of blade 122b, blade 122c and blade 122a (not shown in the figure). For another example, the three blades 122 in each group are arranged in descending length, such as Figure 7 For example, the three blades 122 in each group are arranged in the order of blade 122c, blade 122b and blade 122a. For another example, the three blades 122 in each group are arranged in the order of increasing length (not shown in the figure), that is, the three blades 122 in each group are arranged in the order of blade 122a, blade 122b and blade 122c. For another example, the three blades 122 in each group are arranged in the order of decreasing length first and increasing length later. There are two possible arrangements. One is to arrange the blades 122 in the order of decreasing length first and increasing length later. Figure 7 The arrangement is performed in arrangement method 3, that is, each group of blades is arranged in the order of blade 122b, blade 122a and blade 122c. Another arrangement is to arrange in the order of blade 122c, blade 122a and blade 122b (not shown in the figure).

[0114] It should be understood that, taking a group of blades as a whole, the blades in each group are completely identical, not only in the same arrangement, but also in the same shape and other aspects. In layman's terms, a group of blades can be regarded as a periodic combination, and multiple groups of blades can be regarded as multiple identical periodic combinations.

[0115] Since the lengths of the blades in each blade group are not exactly the same, when the centrifugal fan 10 is working, when the blades 122 of each blade group rotate to the same position relative to the volute tongue, the gaps between the blades 122 of different lengths in each blade group and the volute tongue 114 are different.

[0116] Fig. 9 Schematic diagram of the structure of the centrifugal fan provided by the embodiment of the present application without the cover plate. Fig. 9 , taking the position S of the black dot in the figure as the reference point of the volute tongue 114, when the three blades of different lengths in a group of blades rotate to the same position relative to the position S, the gap between the blade 122c and the position S is the smallest, and the gap between the blade 122a and the position S is the largest. Since the main noise of the centrifugal fan is caused by the dynamic and static interference between the rotation of the impeller 12 and the volute tongue 114, the gap between the volute tongue 114 and the blade 122 affects the noise. In the embodiment of the present application, the gap between the volute tongue 114 and the blade 122 is adjusted by adjusting the length of the blade 122, thereby reducing the BPF of the centrifugal fan 10 and ultimately achieving the effect of reducing noise.

[0117] The centrifugal fan provided in the embodiment of the present application has an impeller structure including M groups of blades, each group of blades includes multiple blades of different lengths, and the inner diameters of the multiple blades in each group of blades are the same, which means that the outer diameters of the multiple blades in each group of blades are not completely the same. In this way, for blades of different lengths in each group of blades, the gap between the blades of different lengths and the volute tongue changes, thereby adjusting the noise of the centrifugal fan. In the case where the length of each group of blades is not exactly the same, when the impeller includes multiple groups of blades (i.e., M is greater than 1), the arrangement of each group of blades is the same. In this way, a group of blades can be regarded as a whole, and the event of a group of blades passing through the volute tongue when the impeller rotates can be regarded as one event. When the impeller rotates one circle and passes through M groups of blades, the event of M groups of blades passing through the volute tongue can be regarded as M identical events. In this way, the number M of M groups of blades can be regarded as the order. According to the formula of blade passing frequency BPF=n*K / 60, when the total number of blades of the impeller remains unchanged, the order K of the centrifugal fan with blades of the same length in the prior art is the total number of blades, while the order K of the centrifugal fan of the present application is the number M of all blades of the impeller. The order K becomes smaller, so that the BPF also becomes smaller, so that the weighted value corresponding to the BPF can be adjusted to a small weighted value, and the sound pressure level of the reduced BPF also becomes smaller, thereby reducing the total noise of the centrifugal fan. In addition, the larger the gap between the shorter blades in each set of blades and the volute, the less interaction between the airflow between the shorter blades and the volute will be, thereby also having the effect of reducing noise.

[0118] Fig.10 Provided is a frequency spectrum diagram of the noise of a centrifugal fan with impellers having blades of the same length in the prior art. Fig.11 It is a spectrum diagram of the noise of the centrifugal fan of the embodiment of the present application provided when the total number of blades of the impeller remains unchanged.

[0119] exist Fig.10 and Fig.11 In the figure, the horizontal axis represents the noise frequency, and the vertical axis represents the weighted sound pressure level, which is expressed in SPL. The weighting method used is A weighting. Fig.10 and Fig.11 In the figure, except for the difference in blade length, other parameters of the centrifugal fan remain unchanged. It is assumed that the total number of blades of the impeller of the centrifugal fan is 63 and the rotation speed is 4000RPM (ie, 4000r / min).

[0120] In the prior art, in the structure of the centrifugal fan with blades of the same length, the order K is 63, and the BPF of the centrifugal fan is calculated by the formula = 4000*63 / 60 = 4200Hz, and the A weighted value corresponding to 4200Hz is about 0.9dB; Fig.10It can be seen that the BPF of the centrifugal fan obtained through the test is actually distributed around 4200Hz, which is basically consistent with the result obtained by the formula calculation. The final total noise value is 40.5dB.

[0121] It should be understood that the results obtained from theoretical design calculations may not be completely consistent with the results obtained from actual product testing. A certain range of errors is allowed between the two. The explanation of the effect of the spectrum diagram below is the same here.

[0122] In the centrifugal fan provided in the embodiment of the present application, it is assumed that 63 blades are divided into 21 groups of blades, each group of blades includes 3 blades, and the lengths of the 3 blades in each group are different, and the designs of the blades in each group are the same. In this way, the order of the centrifugal fan of this structure is 21. The BPF of the centrifugal fan is calculated by the formula: 4000*21 / 60=1400Hz, which is less than 4200Hz in the prior art. The A weighted value corresponding to 1400Hz is also less than the 0.9dB weighted value corresponding to 4200Hz, which is about 0.77dB. Fig.11 It can be seen that the BPF of the centrifugal fan obtained through the test is actually distributed around 1400Hz, which is basically consistent with the result obtained by the formula calculation. The final total noise value is 39.43dB, which is less than the 40.5dB noise value of the prior art.

[0123] It should be noted that for the sound pressure level of BPF, compared with Fig.10 , based on theoretical design, due to Fig.11 The weighting value of 1400Hz is small, so the sound pressure level at 1400Hz should also be smaller than Fig.10 However, since the weighted value of 1400Hz (0.77dB) is not much different from the weighted value of 4200Hz (0.9dB), plus the test error of the actual product, the final result is Fig.11 The sound pressure level at 1400 Hz may be slightly higher, which is within a reasonable error range and should not be considered that the embodiment of the present application cannot achieve the effect of noise reduction. In fact, although the sound pressure level at 1400 Hz may be slightly higher, overall, Fig.11 The total noise is reduced (by Fig.10 It can be understood that, although the sound pressure level at 1400 Hz may be slightly higher due to various factors such as errors, the impeller structure of the embodiment of the present application disperses the energy of the entire centrifugal fan and the energy is no longer concentrated, so that the sound pressure level of the frequency near the BPF is reduced overall, thereby achieving the effect of reducing noise.

[0124] It can be seen that the centrifugal fan provided in the embodiment of the present application, which has an impeller with M groups of blades and each group of blades including multiple blades of different lengths, can reduce the order of the centrifugal fan from the total number of blades to the number of blade groups M, thereby reducing the BPF of the centrifugal fan, so as to reduce the weighting value corresponding to the BPF, thereby reducing the sound pressure level of the BPF, so as to achieve the effect of reducing the total noise of the centrifugal fan.

[0125] As mentioned above, the multiple blades 122 of each group of blades have different lengths and correspond to multiple lengths, and one length corresponds to at least one blade 122. If the length of the blade 122 is too long or too short, it may affect the working area and mechanical balance of the blade 122, thereby affecting the working capacity of the impeller 12.

[0126] Therefore, the present application proposes that, in some embodiments, the ratio of the difference between the longest length and the shortest length of the multiple lengths of the blade 122 to the longest blade is less than or less than the length difference threshold.

[0127] In this way, by limiting the difference between the longest length and the shortest length of the blade 122, the length difference of the blades 122 in each group of blades should not be too large, so as to minimize the impact on the working area and mechanical balance of the blade 122, thereby reducing the impact on the working capacity of the impeller 12.

[0128] In implementation, the length difference threshold can be designed reasonably, and the embodiment of the present application does not impose any limitation on this. Exemplarily, the length difference threshold is less than or equal to 30%, for example, the length difference threshold can be 30%, 25%, 20%, 15%, 10%, 8%, etc.

[0129] In the embodiment of the present application, the shape of the blade 122 can be any form, for example, the shape of the blade 122 can be flat, can be curved, or can be a combination of flat and curved. Figure 8 Each blade 122 in each set of blades includes an inner section 1221 close to the hub 121 and an outer section 1222 away from the hub 121 , the inner section 1221 is a first curved surface, and the outer section 1222 is a second curved surface.

[0130] It should be understood that the directions of the curved surfaces of the blades 122 are the same.

[0131] It should also be understood that the first curved surface and the second curved surface may be curved surfaces of any form. For example, the curve shape of the cross section of the first curved surface and the second curved surface forms a Bezier curve.

[0132] By designing the inner section 1221 and the outer section 1222 of the blade 122 as curved surfaces, the working principle of the impeller can be satisfied, which not only improves the working capacity of the impeller but also reduces the noise of the centrifugal fan.

[0133] In one example, the curvature of the second curved surface is greater than the curvature of the first curved surface.

[0134] The inner section 1221 of the blade 122 is mainly used to support the entire blade, and the outer section 1222 of the blade 122 is mainly used to do work. Therefore, by making the curvature of the second curved surface greater than the curvature of the first curved surface, the outer section 1222 with a large curvature can make the blade 122 have better work-doing capacity.

[0135] For each blade 122 in each set of blades, in one example, the lengths of the inner sections 1221 of each blade 122 in each set of blades are the same.

[0136] It should be understood that when the lengths of the inner segments 1221 of each blade 122 in each group of blades are the same, the outer segments 1222 of blades 122 with different lengths are different, so that it is convenient to process and design blades of different lengths. Specifically, in implementation, all blades 122 with the same length can be processed and designed first, and then the outer segments 1222 of specific blades 122 are cut, and the outer segments 1222 of the blades are cut according to the designed size, and finally blades 122 with different lengths are formed. It can be seen that the inner segments 1221 of the blades 122 with different lengths obtained in this way are the same and the outer segments 1222 are different, and the processing and design process is relatively convenient and efficient.

[0137] It should also be understood that for the blades designed and processed based on the above method, regardless of whether the lengths of the blades are the same, the curvature of the first curved surface of the inner section 1221 of each blade 122 in each group of blades is the same, and the curvature of the second curved surface of the outer section 1222 of each blade 122 in each group of blades is also the same.

[0138] by Figure 8 Taking the impeller 122 shown as an example, each set of blades includes three blades 122, and the lengths of the three blades 122 are different, one blade 122 corresponds to one length, and the inner sections 1221 of blades 122a, blades 122b, and blades 122c are the same in length, and the lengths of the outer sections 1222 are different, the length of the outer section 1222 of blade 122a is the shortest, the length of the outer section 1222 of blade 122c is the longest, and the length of the outer section 1222 of blade 122b is moderate. In addition, the inner sections 1221 of blades 122a, blades 122b, and blades 122c have the same radius of curvature, and the outer sections 1222 of blades 122a, blades 122b, and blades 122c have the same radius of curvature.

[0139] It should be understood that the shape of the blade 122 described above is only for illustrative purposes and should not be construed as limiting the embodiments of the present application. For example, in other embodiments, the inner section 1221 of the blade 122 is a plane, and the outer section 1222 of the blade 122 is a curved surface.

[0140] refer to Figure 7 and Figure 8 In some embodiments, the centrifugal fan 10 further includes a reinforcement ring 123 , which is connected to the ends of the M groups of blades away from the hub 121 .

[0141] The reinforcing ring 123 is an annular structure, and the hollow portion of the annular structure allows most of the blades 122 to leak out, so that the gas can enter the blade channels between the blades 122 .

[0142] Since the end of the blade 122 away from the hub 121 is easily affected by air resistance and may cause shaking or even deformation, the reinforcement ring 123 is connected to the end of the blade 122 away from the hub 121 to provide certain support for the blade 122, increase the strength of the blade 122, and provide a better ventilation effect for the blade 122.

[0143] In one example, reference Figure 8 The end of the shortest blade 122 in each group of blades away from the hub 121 does not exceed the outer end 123a of the reinforcement ring 123.

[0144] It should be understood that the outer end 123 a of the reinforcement ring 123 refers to the outer end 123 a of the reinforcement ring 123 in the circumferential direction.

[0145] It should also be understood that the end of the shortest length blade 122 away from the hub 121 does not exceed the outer end 123a of the reinforcement ring 123, which means that the end of the shortest length blade 122 away from the hub 121 is located on the inner side of the outer end 123a of the reinforcement ring 123, or is flush with the outer end 123a of the reinforcement ring 123.

[0146] For blades 122 of different lengths, the end of the longer blade 122 away from the hub 121 may extend beyond the reinforcing ring 123, for example. Figure 8 The ends of blades 122b and 122c away from the hub 121 extend beyond the reinforcement ring 123. The areas extending beyond the reinforcement ring 123 serve as free ends and are still susceptible to shaking due to air resistance. Therefore, by ensuring that the end of the shortest blade 122 away from the hub 121 does not extend beyond the outer side of the reinforcement ring 123, the area where the end of the longer blade 122 away from the hub 121 extends beyond the reinforcement ring 123 can be reduced, thereby further enhancing the strength of the blade 122.

[0147] Exemplarily, the end of the shortest blade 122 in each set of blades, which is away from the hub 121 , is flush with the outer end 123 a of the reinforcement ring 123 .

[0148] Continue with Figure 8Taking the impeller 12 shown as an example, the blade 122 with the shortest length is the blade 122 a , and the end of the blade 122 a away from the hub 121 is flush with the outer end 123 a of the reinforcement ring 123 .

[0149] In the above embodiment, by making the end of the shortest blade 122 in each group of blades away from the hub 121 flush with the outer end 123a of the reinforcing ring 123, while minimizing the area where the end of the longer blade 122 away from the hub 121 exceeds the reinforcing ring 123 to better enhance the strength of the longer blade 122, the area where the shortest blade 122 is connected and in contact with the reinforcing ring 123 can be maximized, thereby ensuring the strength of the shortest blade 122 as much as possible. Therefore, the strength of the long blade 122 and the short blade 122 is comprehensively considered, and the strength of the entire impeller 12 is improved as a whole.

[0150] In embodiments where the impeller 12 includes multiple sets of blades, in some embodiments, reference Figure 7 and Figure 8 , each group of blades of the M groups of blades are equally spaced along the circumference of the hub 121. In this way, the dynamic balance of the impeller 122 can be better achieved.

[0151] Each group of blades is equally spaced along the circumference of the hub 121, which can be understood as the circumferential spacing between any two adjacent groups of blades being the same. The circumferential spacing between any two adjacent groups of blades being the same means that, along the same direction (e.g., the rotation direction of the impeller 122), the circumferential spacing between the last blade in the previous group of blades and the first blade in the next group of blades is the same.

[0152] In the above-mentioned embodiment in which each group of blades is distributed at equal intervals along the circumference of the hub 121, the circumferential spacing between two adjacent groups of blades can be arbitrary and is not limited here.

[0153] In some embodiments, reference Figure 7 and Figure 8 , the circumferential spacing between any two adjacent groups of blades is the same as the circumferential spacing between any two adjacent blades in each group of blades.

[0154] The circumferential spacing between any two adjacent groups of blades actually represents the circumferential spacing between the two blades closest to each other in the two groups of blades. The circumferential spacing between the two blades closest to each other in the two groups of blades is the same as the circumferential spacing between any two adjacent blades in each group of blades, which actually means that the circumferential spacing between any two adjacent blades in all blades of the M group of blades is the same. In this way, by making the circumferential spacing between any two blades 122 the same, the dynamic balance of the impeller 12 can be better achieved, and the installation design process is simplified.

[0155] It should be understood that the circumferential spacing between the blades 122 in the embodiment of the present application is the same, which means that the circumferential spacing between the blades 122 on any circumference is the same.

[0156] For example, in implementation, the circumferential spacing between the blades 122 can be determined based on the circumference of a circle of the impeller 12 and the total number of blades, and the circumferential spacing between the blades 122 finally determined is the circumferential spacing on the circle. For example, taking the circumference of the circle where the inner diameter of the blade 122 is located as the reference length, the ratio between the circumference of the circle and the total number of blades of the impeller 122 can be used as the circumferential spacing between the blades 122, which is the circumferential spacing of the blades 122 on the circle where the inner diameter of the blade 122 is located, and is also the circumferential spacing of the blades 122 at one end close to the hub 121.

[0157] In other embodiments, the blades of each group may not need to be equally spaced, that is, the circumferential spacing between any two adjacent groups of blades may not be the same. In this case, in order to solve the dynamic balance problem, dynamic balance can be achieved by adding a mass block to the hub 121.

[0158] Fig.12 yes Figure 8 Schematic diagram of the local area of ​​the impeller at A. Fig.12 The wheel hub 121 is provided with a filling groove 1212 along the circumference of the wheel hub 121 . The filling groove 1212 is located outside the mounting groove for mounting the motor 14 . A mass block (not shown in the figure) can be filled in the filling groove 1212 to achieve dynamic balance.

[0159] It should be noted that due to Figure 8 The M groups of blades are distributed at equal intervals. Therefore, there is basically no problem of dynamic balance, and there is no need to open a filler groove 1212. The filler groove 1212 is illustrated here only to illustrate that the dynamic balance problem is solved by other means, and does not mean that the filler groove 1212 is opened in the actual product.

[0160] Based on the above noise reduction principle analysis, it can be known that the number of groups M of blades 122 in the impeller 12 of the present application is equivalent to the order in the formula BPF=n*K / 60. When the total number of blades of the impeller 12 remains unchanged, in theory, the smaller M is (that is, the more blades in each group), the smaller the BPF of the centrifugal fan will be, and the final total noise will be smaller.

[0161] Fig.13 is another schematic structural diagram of an impeller provided in an embodiment of the present application. Figure 7 and Figure 8 In contrast, the impeller 12 still includes 63 impellers, but the difference is that the impeller 12 includes 7 groups of blades 122, which is less than Figure 7 and Figure 8The 21 groups of blades shown, each group of blades includes 9 blades 122, denoted as blade 122a, blade 122b, blade 122c, blade 122d, blade 122e, blade 122f, blade 122g, blade 122h and blade 122i. The lengths of the 9 blades 122 are all different, that is, one blade 122 corresponds to one length, and the 9 blades 122 are arranged in an increasing length manner, that is, the lengths of the 9 blades 122 increase sequentially.

[0162] Fig.14 The embodiment of the present application provides Fig.13 Spectrum diagram of the noise of the centrifugal fan obtained from the impeller.

[0163] For comparison, only the length of the blades 122 in the impeller 12 is changed, and other parameters of the centrifugal fan remain unchanged. As above, the total number of blades of the impeller of the centrifugal fan is 63, and the rotation speed is 4000 RPM (ie, 4000 r / min).

[0164] Since the 63 blades of the impeller 12 are divided into 7 groups of blades, each group of blades includes 9 blades, and the lengths of the 9 blades in each group are different, and the design of each group of blades is the same, the order of the centrifugal fan of this structure is 7. The BPF of the centrifugal fan is calculated by the formula = 4000*7 / 60 = 466.67Hz, which is less than Fig.10 The A-weighted values ​​corresponding to 4200 Hz and 466.67 Hz of the prior art shown are also smaller than the 0.9 dB weighted value corresponding to 4200 Hz, which is about -3.76 dB. The sound pressure level at 466.67 Hz is 17.49 dB, which is also smaller than Fig.10 The sound pressure level at 4200Hz; Fig.14 It can be seen that the BPF of the centrifugal fan obtained through the test is 467.3Hz, which is basically consistent with the result obtained by the formula calculation. The final total noise value is 38.34dB, which is lower than the 40.5dB noise value of the prior art, greatly reducing the noise.

[0165] In contrast Fig.13 The impeller and Figure 7 or Figure 8 The impeller is based on Figure 7 or Figure 8 The BPF of the centrifugal fan with an impeller is about 1400Hz, the weighted value corresponding to the BPF is 0.77dB, and the final total noise value is 39.43dB. Fig.13The BPF of the centrifugal fan with an impeller of 467.3 Hz is obtained, the weighted value is -3.76 dB, and the final total noise value is 38.34 dB. It can be seen that the actual measurement results are basically consistent with the theoretical design, that is, when the total number of blades of the impeller 12 remains unchanged, the smaller M is (that is, the more blades in each group), the smaller the BPF of the centrifugal fan is, and the final total noise will be smaller.

[0166] Fig.15 is another schematic structural diagram of an impeller provided in an embodiment of the present application. Fig.13 The difference is that the arrangement and length of the nine blades 122 in a set of blades are different.

[0167] exist Fig.15 , 63 blades 122 include 7 groups of blades 122, the number of groups is less than Figure 7 and Figure 8 The 21 groups of blades shown, each group of blades includes 9 blades 122, denoted as blade 122a, blade 122b, blade 122c, blade 122d, blade 122e, blade 122f, blade 122g, blade 122h and blade 122i. The 9 blades 122 correspond to 5 lengths, which are length 1, length 2, length 3, length 4 and length 5 in order from small to large, with length 1 being the shortest and length 5 being the longest. The 9 blades are arranged in a manner of increasing length first and then decreasing length, wherein length 1 corresponds to blade 122a and blade 122i, length 2 corresponds to blade 122b and blade 122h, length 3 corresponds to blade 122c and blade 122g, length 4 corresponds to blade 122d and blade 122f, and length 5 corresponds to blade 122e.

[0168] Fig.16 The embodiment of the present application provides Fig.15 Similarly, only the length of the blades 122 in the impeller 12 is changed, and other parameters of the centrifugal fan remain unchanged.

[0169] based on Fig.15 The impeller of the impeller 12 has 63 blades divided into 7 groups of blades. Thus, the order of the centrifugal fan of this structure is 7. The BPF of the centrifugal fan is calculated by the formula = 4000*7 / 60 = 466.67Hz, which is less than Fig.10 The A-weighted values ​​corresponding to 4200 Hz and 466.67 Hz of the prior art shown are also smaller than the 0.9 dB weighted value corresponding to 4200 Hz, which is about -3.76 dB. The sound pressure level at 466.67 Hz is 17.49 dB, which is also smaller than Fig.10 The sound pressure level at 4200Hz; Fig.16It can be seen that the BPF of the centrifugal fan obtained through the test is 455.4Hz, and the sound pressure level at 455.4Hz is 18.3dB, which is basically consistent with the result calculated by the formula. The final total noise value is 38.2dB, which is less than the noise value of 40.5dB in the prior art, greatly reducing the noise.

[0170] In the related art, the impeller of the axial flow fan also has a structure with blades of different lengths, but this impeller with blades of different lengths does not solve the problem of noise reduction, but is to solve the problem that the turbulence generated near the hub of the axial flow fan interferes with the airflow discharge and affects the heat dissipation efficiency. The reasons are analyzed below. The formula for centrifugal force is Among them, a is the centripetal acceleration, m is the effective mass of the object, v is the tangential velocity of the centrifugal rotor, w is the angular velocity of the centrifugal rotor (i.e., impeller) rotation, and r is the centrifugal radius, i.e., the length of the impeller blades.

[0171] It can be seen that when w remains unchanged, r has a greater impact on the centrifugal force; since v = w*r, v also has a greater impact on the centrifugal force. And v is proportional to noise, so the change of v has a great impact on the noise. The larger v is, the greater the noise is.

[0172] For axial flow fans, the gas flow direction of the axial flow fan is parallel to the axial direction of the impeller, that is, the gas enters along the axial direction of the impeller and is finally discharged along the axial direction of the impeller. When the impeller rotates, the gas enters the impeller axially from the air inlet, and is pushed by the blades on the impeller to increase the energy of the gas, and then flows into the guide vanes. The guide vanes deflect the airflow into axial flow, and finally discharge axially from the air outlet. Based on this working principle of the axial flow fan, the centrifugal force of the axial flow fan itself is much smaller than that of the centrifugal fan. The centrifugal force is small and v is small. Therefore, even if the change of r can affect v and the centrifugal force, the change of r has little effect on the noise and can even be ignored because the centrifugal force and r are both small. Therefore, in axial flow fans, the change of r cannot achieve the noise reduction effect, and technicians have no motivation to achieve the purpose of noise reduction by changing r.

[0173] For centrifugal fans, the centrifugal force is very large, v is large, and the change of r affects v and centrifugal force, resulting in a greater impact of the change of r on noise. Therefore, in centrifugal fans, changing the length of the blades can effectively affect the noise, and by reasonably designing the length of the blades, it can effectively play a role in noise reduction. Moreover, based on the explanation of the design principle above and the verification of the frequency response curve of the structure, it can be effectively proved that changing the length of the blades through reasonable design can achieve the purpose of noise reduction.

[0174] It should be understood that in the embodiments of the present application, unless otherwise clearly specified and limited, the terms "connection", "fixed connection", "contact" and the like should be understood in a broad sense. For ordinary technicians in this field, the specific meanings of the above-mentioned various terms in the embodiments of the present application can be understood according to specific circumstances.

[0175] Exemplarily, for "connection", it can be various connection methods such as fixed connection, rotating connection, flexible connection, sliding connection, one-piece molding, electrical connection, contact connection, etc.; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the internal connection between two elements or the interaction relationship between two elements.

[0176] Exemplarily, for "fixed connection", one element can be directly or indirectly fixedly connected to another element; the fixed connection can include mechanical connection, welding, bonding or one-piece molding, among which the mechanical connection can include riveting, bolting, threaded connection, key connection, snap connection, lock connection, plug-in and other methods, and the bonding can include adhesive bonding and solvent bonding and other methods.

[0177] Exemplarily, the interpretation of "contact" can be direct or indirect contact between one element and another element; in addition, the contact between the two elements described in the embodiments of the present application can be understood as contact within the allowable range of installation error, and there may be a very small gap caused by the installation error.

[0178] It should also be understood that the “parallel” or “perpendicular” described in the embodiments of the present application may be understood as “approximately parallel” or “approximately perpendicular”.

[0179] It should also be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly indicate the number of technical features indicated. Features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0180] In the embodiments of the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may mean that the first feature is in direct contact with the second feature, or the first feature and the second feature are in indirect contact through an intermediate medium. Moreover, a first feature being “above”, “above”, and “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below”, and “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0181] It should also be understood that the terms "inside", "outside", "top", "bottom", "front", "back", etc., indicating the orientation or positional relationship (if any) are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0182] In the embodiments of the present application, "at least one" means one or more, and "more than one" means two or more. "At least part of an element" means part or all of an element. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may mean: A exists alone, A and B exist at the same time, and B exists alone, where A and B may be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship.

[0183] It should be noted that, in the embodiments of the present application, the same figure mark is used to represent the same component or the same part. For the same parts in the embodiments of the present application, the figure may only mark one of the parts or components as an example. It should be understood that the figure mark also applies to other identical parts or components.

[0184] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims. In short, the above is only a preferred embodiment of the technical solution of the present application, and is not used to limit the protection scope of the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A centrifugal fan, characterized in that: include: A volute, wherein a receiving cavity is formed in the volute, one end of the volute is formed as an air outlet, and a volute tongue is provided in the volute adjacent to the air outlet; An impeller is accommodated in the accommodating cavity, the impeller includes a hub and fan blades fixedly connected to the hub, the fan blades include M groups of blades, wherein each group of blades includes a plurality of blades of different lengths, the inner diameters of the plurality of blades in each group of blades are the same, and when M is greater than 1, the blades of each group of the M groups of blades are circumferentially distributed around the hub in the same arrangement manner, and M is an integer greater than or equal to 1.

2. The centrifugal fan according to claim 1, characterized in that: The groups of blades are distributed at equal intervals along the circumference of the hub.

3. The centrifugal fan according to claim 2, characterized in that: The circumferential spacing between any two adjacent groups of blades in the M groups of blades is the same as the circumferential spacing between any two adjacent blades in each group of blades.

4. The centrifugal fan according to any one of claims 1 to 3, characterized in that: The multiple blades of each group of blades that are not completely the same length correspond to multiple lengths, one length corresponds to at least one blade, and the ratio of the difference between the longest length and the shortest length of the multiple lengths to the longest length is less than or equal to a length difference threshold.

5. The centrifugal fan according to claim 4, characterized in that: The length difference threshold is less than or equal to 30%.

6. The centrifugal fan according to any one of claims 1 to 5, characterized in that: The multiple blades with different lengths in each group of blades are arranged in a manner that their lengths increase in sequence, decrease in sequence, increase first and then decrease, or decrease first and then increase.

7. The centrifugal fan according to any one of claims 1 to 6, characterized in that: Each blade in each group of blades includes an inner section close to the hub and an outer section away from the hub, the inner section is a first curved surface, and the outer section is a second curved surface.

8. The centrifugal fan according to claim 7, characterized in that: The curvature of the second curved surface is greater than the curvature of the first curved surface.

9. The centrifugal fan according to claim 7 or 8, characterized in that: The inner sections of the blades in each group of blades have the same length.

10. The centrifugal fan according to any one of claims 1 to 9, characterized in that: The centrifugal fan further comprises a reinforcement ring, which is fixedly connected to the ends of the M groups of blades away from the hub.

11. The centrifugal fan according to claim 10, characterized in that: The end of the shortest blade in each group of blades away from the hub does not exceed the outer end of the reinforcement ring.

12. The centrifugal fan according to claim 11, characterized in that: The end of the shortest blade in each group of blades away from the hub is flush with the outer end of the reinforcement ring.

13. An electronic device, characterized in that: The electronic device comprises a housing and a centrifugal fan according to any one of claims 1 to 12, wherein the centrifugal fan is installed in the housing.

14. The electronic device according to claim 13, characterized in that: The electronic device is a notebook computer.

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