TWI542788B - Centrifugal blower with asymmetric blade spacing - Google Patents

Description

Centrifugal blower with asymmetric blade spacing

This invention relates to portable electronic products and, more particularly, to blowers or fans that are particularly suitable for use in air cooling systems for portable electronic products.

Axial flow and centrifugal fans or blowers are typically implemented in a cooling system of an electronic device to assist in cooling the electronic device when the electronic device becomes too hot. A typical fan design includes an impeller having blades that are spaced at equal angles relative to one another. Uniformly spaced fan blades allow the impeller to be balanced. When the fan blades are not evenly spaced, the impeller can have acoustic artifacts, imbalance problems, and thermal penalties. Unbalance can result in increased vibration stress, wear on the bearing and motor structure of the fan, and quality issues.

Typically, the noise source for the fan is air flow and from the motor. One of the flow-induced noise sources is the blade passage frequency (BPF) tone. The BPF and related harmonics are related to the pressure disturbances that occur when each fan blade passes a fixed reference point. The tip of the blade produces periodic pressure waves that generate tones.

The main motor noise source is the pole passage frequency (PPF) tone. The PPF is the vibration generated by the magnetic poles in the motor of the fan and the resulting pressure wave. The BPF will typically be perceived as a tone and can be amplified when it coincides with the PPF. BPF tones and PPF tones are emitted from blowers or fans and can be disturbed when they are heard. User of the product. Another source of noise comes from the interaction with the struts on the fan or any other type of obstacle. Therefore, there is a need for a sufficiently balanced fan with reduced noise.

In summary, the embodiments disclosed herein describe implementations of non-uniform blade spacing and centrifugal blowers to portable electronic products with acceptable balance in centrifugal blowers.

The present invention describes a centrifugal blower. The centrifugal blower includes at least: a motor having a plurality of pole passes, wherein the number of magnetic pole passages is an even number; and thirty one blades each of which has a nominal blade angle value One of the nominal blade angles is associated with an angular displacement between adjacent impeller blades. The thirty-one impeller blades are each asymmetrically spaced about a central hub such that each impeller blade is positioned about the central hub such that one of the nominal blade angle values is equal to 360° and one of the centrifugal blowers The operational characteristic values are considered to be within a predetermined operational characteristic value range. In the depicted embodiment, a first nominal blade angle value is 10.1034°; a second nominal blade angle value is 10.0229°; a third nominal blade angle value is 13.1577°; a fourth nominal blade angle The value is 13.22929°; a fifth nominal blade angle value is 13.6692°; a sixth nominal blade angle value is 13.0442°; a seventh nominal blade angle value is 13.5653°; an eighth nominal blade angle value is 11.9834°; a ninth nominal blade angle value of 11.6129°; a tenth nominal blade angle value of 10.1071°; an eleventh nominal blade angle value of 11.2424°; a twelfth nominal blade angle value 10.1532°; a tenth The three nominal blade angle values are 10.1816°; the fourteenth nominal blade angle value is 9.7922°; the fifteenth nominal blade angle value is 13.4336°; and the sixteenth nominal blade angle value is 13.6681°; The seventeenth nominal blade angle value is 12.6663°; the eighteenth nominal blade angle value is 9.5578°; the nineteenth nominal blade angle value is 10.0681°; and the twentieth nominal blade angle value is 10.7533°. a twenty-first nominal blade angle value of 11.1850 °; a twenty-second nominal blade angle value of 13.5670 °; a twenty-third nominal blade angle value of 12.7242 °; a twenty-fourth nominal The blade angle value is 13.1224°; a twenty-fifth nominal blade angle value is 13.0726°; a twenty-sixth nominal blade angle value is 13.1187°; and a twenty-seventh nominal blade angle value is 12.0408°; The twenty-eighth nominal blade angle value is 10.6195°; a twenty-nineth nominal blade angle value is 9.5566°; a thirtieth nominal blade angle value is 9.6588°; and a thirty-first nominal blade angle The value is 9.6605°.

In one aspect of the described embodiment, the blade angles each have a tolerance of +/- 5%.

Other aspects and advantages will be apparent from the following detailed description taken in the claims.

The described embodiments are to be understood in a

The described embodiments are directed to a centrifugal fan or blower that can be implemented in a cooling system of a portable electronic device, such as a laptop. It should be understood that the described embodiments can also be used with other non-portable electronic devices, such as desktop computers. The centrifugal fan or blower in the described embodiment provides air cooling for the portable electronic device compared to conventional fans, while the perceived sound from the fan is reduced.

Embodiments are discussed below with reference to Figures 1-12. However, those skilled in the art should readily appreciate that the detailed description of the figures herein is for the purpose of explanation, as the invention extends beyond these limited embodiments.

As discussed above, a typical fan design includes an impeller having a uniform blade spacing. That is, as shown in FIG. 1, the blades 110 of the impeller 100 are spaced apart from each other by equal angles A, B, and C. As illustrated in Fig. 1, the angles A, B, and C between the blades 110 are equal to each other. The uniform spacing of the blades 110 provides a balance because the mass of the impeller 100 is evenly distributed, and also provides a constant pitch frequency over time as the fan rotates. Typically, the impeller 100 has a plurality of blades to avoid lining up or combining the harmonics of the blades with the harmonics of the poles in the motor. Since the magnetic pole channels are usually even, a prime number is usually chosen for the number of blades. It should be understood that if the harmonics of the blade are combined with the harmonics of the magnetic pole, the noise from the fan will increase. Therefore, the industry standard provides evenly spaced blades when the impeller has a number of blades.

One method of minimizing noise from the fan is to control the spectral distribution of the pure tones produced by the fan. The energy of the scattered tones across several discrete frequencies can make the tone appear less noisy to the listener by reducing the perception of the tone BPF. The uneven spacing of the fan blades while maintaining the balance of the impeller is a method of controlling the pure tone effect. 2 illustrates an impeller 200 of a centrifugal blower having unevenly spaced blades 210. As shown, the angles D, E, and F are not equal to each other. To determine the spacing of the non-uniform blade spacing configurations, the position of the evenly spaced fan blades 110 can be modified in a sinusoidal amplitude pattern. The equation that can be used for the modified angular interval according to sinusoidal modulation is: θ _i '= θ _i + Δ θ sin( mθ _i ) where θ _i is the original spacing angle of the ith blade in a uniformly spaced configuration, θ _i ' after the modification of the i-th new nominal angle of the blade spacing angles, △ θ change (amplitude modulation) the percentage of the maximum spacing angle, the number and pattern of use is to be sinusoidal m (modulation cycle in a single rotation of the fan The number of times that are repeated). It should be understood that the equations set forth above can be applied to larger fans, such as axial fans, which can be balanced by increasing the weight of critical locations on the impeller.

The noise caused by this sinusoidal modulation is represented by the following equation: f(t) = A ₀ sin(2π F ₀ t + △φ sin2πυ t ), where A ₀ is the amplitude of the basic blade passing tone, F ₀ = I f _s ( I is the number of blades and f _s is the rotational frequency of the shaft), the modulation frequency υ = mf _s , and the phase modulation amplitude Δφ = I Δ θ .

The eardrum in the human ear has the function of dispersing the frequency of incoming sound waves. The dispersion of the frequency of the sound waves causes the sound of a certain frequency to cause some parts of the eardrum to vibrate more than others. 3 is a graph comparing the sound frequency distribution of an impeller 100 having a uniform blade spacing with an impeller 200 having a non-uniform blade spacing along the eardrum. As shown in Figure 3, the noise from the two impellers 100, 200 causes a similar amount of neurons to be stimulated throughout the same period of time. However, the impeller 200 with non-uniform blade spacing causes a large acoustic wave frequency. The spread intensity, the greater the spread intensity will reduce the BPF tone. It should be understood that the measurement reduction of the BPF tone may not fully reflect the reduction of the perceived BPF tone.

In conventional fans, the impeller blades are evenly spaced to achieve equilibrium. The uniform spacing also provides a constant BPF tone frequency over time as the fan rotates. When the blades are not evenly spaced, an imbalance may occur, and as the fan rotates, the BPF tone frequency is not constant over time. For large fans, weight can be added to critical points on some fan blades for balancing. However, weight cannot be used in small fans in an efficient manner, such as for small fans in portable devices. In order to achieve an acceptable balance in such small fans with non-uniformly spaced blades, the balance must be inherent to the design of the fan itself. The embodiments described herein are designed such that even if the blades are not evenly spaced around the central hub or shaft of the impeller, the fans are balanced and the BPF tone frequency remains constant over time, thereby reducing the noise emitted from the fan. In some embodiments, the blower has a diameter of 150 cm or less.

According to an embodiment, the centrifugal blower has at least 15 impeller blades 210 that are non-uniformly spaced about the center hub or impeller shaft member 220 and that extend from the center hub or impeller shaft member 220. That is, the blades 210 are not evenly spaced from each other. To reduce fan noise, the number of impeller blades 210 is selected to be different than the number of magnetic pole channels in motor 230 to avoid combining the harmonics of blade 210 with the harmonics of the magnetic poles. If the harmonics of the magnetic pole merge with the harmonics of the blade 210, the BPF tone and the PPF tone increase, causing an increase in noise from the fan. Therefore, if the harmonics of the magnetic pole are not combined with the harmonics of the blade, then The perceived noise from the fan will be reduced. It should be understood that if there are multiple sources of noise in the fan, the sources of noise should not be combined to minimize noise.

Although the blades 210 are not uniformly spaced, the impeller 200 is capable of maintaining an acceptable balance while rotating. The angles D, E, and F of each of the spaces between the non-uniformly spaced impeller blades are determined by the position of the blades 210. As shown in FIG. 2, the angles D, E, and F between the blades 210 are not equal to each other. Although the position of the impeller blades 210 is evenly distributed along at least two repeated sinusoidal patterns, the impeller blades 210 are unevenly or non-uniformly spaced around the central hub 220. The angles D, E, and F of each of the spaces between the blades 210 are determined by the position of the blades. The position of each of the impeller blades 210 corresponds to a unique point on the repeated sinusoidal pattern and can be expressed by the following equation: θ _i '= θ _i + θ _i ^* α ^* cos( m x) where θ _i is uniform The original separation angle of the spacer blades (the number of blades / 360 °), θ _i ' is the new interval angle of the i-th nominal blade angle after modification in the non-uniform spacing configuration, the α system and the interval angle change (modulation amplitude △ θ ) is the maximum percentage, m is the number of sinusoidal patterns to be used (the number of times the modulation cycle is repeated in a single revolution of the fan), and 0 x 2π.

4 illustrates noise reduction provided by a fan having non-uniformly spaced impeller blades, in accordance with an embodiment. 4 is a graphical comparison of sound produced by a fan having uniformly spaced impeller blades and a fan having non-uniform spaced impeller blades. In this embodiment, as shown in Figure 4, the main tone (at about 2300 Hz) is reduced in a non-uniform spaced fan and the sidebands are introduced (at about 1900 Hz and 2700 Hz). The sideband represents the dispersion of the frequency of the sound waves, causing a reduction in noise. It should be understood that the perceived noise reduction can be greater than The noise reduction is measured.

As discussed above, the fan has at least 15 impeller blades. According to an embodiment, there are 17 impeller blades that are non-uniformly spaced around the central hub. In another embodiment, there are 23 non-uniform spaced impeller blades. In some embodiments, the impeller has 29 blades or less. As shown in FIG. 5, if there are too few blades, non-desired modulation artifacts can be introduced, thereby increasing the noise emitted from the fan. As shown in Figure 5, a fan with 13 non-uniformly spaced impeller blades produces a higher main tone (at approximately 1300 Hz) than a fan with uniform spaced impeller blades, and produces a high sideband (at approximately 1100 Hz and 1500 Hz).

As discussed above, each of the impeller blades 210 surrounding the central hub 220 corresponds to a unique point on at least two repeated sinusoidal patterns. At least two repeated sinusoidal patterns are used to maintain balance. According to an embodiment, an even number of repeated sinusoidal patterns are used. That is, the blades 210 are spaced according to an even number of sinusoidal patterns. In an embodiment with a single fan, two repeated sinusoidal patterns are used. In some embodiments, four repeated sinusoidal patterns are used. Those skilled in the art will appreciate that in some embodiments, more than one fan is implemented in the device and two or four repeated sinusoidal patterns are used. Preferably, no more than four repeating sinusoidal patterns are used. So it’s at 2 m 4 hours is especially effective. Those skilled in the art should understand that the chord can be used to replace the cosine in the equation, using the following equation: θ _i '= θ _i + θ _i ^* α ^* sin( m x).

In one embodiment, the variable a associated with the maximum percentage change in the angular separation is particularly effective when maintained in the range of from about 0.01 to about 0.07. According to another embodiment, the alpha system is in the range of from about 0.01 to about 0.05. If α is too large, low frequency modulation can be perceived. If α is too small, there may be no perceived pitch reduction. Similarly, the percentage change in spacing from a uniform spaced configuration is particularly effective in the range of from about 1% to about 7%. That is, each of the blade positions is modified from about 1% to about 7% compared to a uniformly spaced impeller blade having the same number of impeller blades. When a single fan is used in a system, the number m of sinusoidal patterns to be used should be equal to two.

According to another embodiment, the centrifugal blower has a plurality of impeller blades spaced apart in a non-uniform manner about the central hub. As discussed above, the prime number of blades prevent the harmonics of the blades from combining or combining with the harmonics of the magnetic poles. Since the magnetic pole channels are usually even, selecting the number of impeller blades equal to the prime number prevents the BPF tones from combining with the PPF tones.

The number of blades required and the frequency range with the largest BPF tone determine the percent variability of the spacing between the blades. The higher the frequency of interest, the more effective it is to reduce the perceived pitch without introducing other artifacts. The blade pass frequency (BPF) frequency is modulated and perceived as being less disturbing to the user or less powerful to the user. The average energy reduction at small frequency steps, but the modulation must be small enough not to perceive low frequency artifacts.

6 is a flow chart of a method of making a fan in accordance with one described embodiment. In step 600, a motor 230 is provided in the fan. Motor 230 has an even number of pole passages. At least 15 impeller blades 210 are provided in step 610. The number of impeller blades 210 is different from the number of magnetic pole channels in motor 230. In step 620, the impeller blades 210 are then positioned non-uniformly around the central hub 220 such that each blade 210 corresponds to at least two repeated sinusoids A unique point on the pattern.

7 is a flow chart of a method of making a fan in accordance with another embodiment. In step 700, a plurality of vanes 210 of at least 17 are selected for the impeller. In step 710, the impeller blades are non-uniformly spaced around the central hub by positioning each of the impeller blades 210 such that they correspond to unique points on an even number of repeated sinusoidal patterns.

It should be noted that thin profiles have been found to be aesthetically pleasing to a large number of users and are therefore an ideal industrial design consideration in the manufacture of portable electronic devices such as laptops. The centrifugal blower in the described embodiment can be manufactured in a smaller size than conventional fans. Therefore, the smaller blower implemented in the portable device allows the portable device to have a thin profile. Those skilled in the art will appreciate that the embodiments described herein are also applicable to axial flow fans that can have larger sizes.

Asymmetric blade spacing embodiment

8 through 12 illustrate features of an asymmetric blade spacing embodiment in which a centrifugal blower can be formed such that the impeller blades are each associated with a nominal blade angle value and (i) are asymmetrically spaced from each other and (ii) The sum of the nominal blade angle values of the asymmetrically spaced impeller blades is equal to 360°. In an embodiment, the tolerance factor can be attributed to the blade angle, which means that the blade angle values can each vary within a range of values depending on the tolerance factor (plus or minus) without seriously affecting the centrifugal blower. The required performance characteristics (it should be noted that even in the case of possible variations in blade angle values, the sum of the blade angle values of the impeller blades must still equal 360°). For example, the blade angle value may have a tolerance factor of +/- 5%. Therefore, for each group of asymmetrically spaced blades State, can calculate the operational characteristics of a group corresponding to the centrifugal blower. These operational characteristics can be analyzed for use in a portable computing device. In one embodiment, the operational characteristics can be compared to the desired operational characteristics of a group of centrifugal blowers. In another embodiment, the operational characteristics can be compared to another set of operational characteristics associated with another configuration of the asymmetrically spaced blades. In this case, a more optimal configuration of the asymmetrically selected blades can be selected for the final design or for further improvement.

In an embodiment, the centrifugal blower may include thirty-one (31) blades having the blade angle values of Table 1 according to FIG. 8 and embodied as the blade assembly 900 of FIG. 9 and FIG. The blade assembly is 1000. In another embodiment, the centrifugal blower may include sixty-one (61) vanes having vane angle values as described in Table 2 of FIG. 11 and embodied as the vane assembly 1200 shown in FIG.

The advantages of the invention are numerous. Different aspects, embodiments, or implementations may yield one or more of the following advantages. One advantage of the present invention is that the fan in the device is much quieter and less disturbing to the user. The thermal performance of a fan utilizing the fan described herein is equivalent to a fan prior to use of the technology. Another advantage of these fans is that the fan wheel is still balanced because the center of mass is still on the shaft of the impeller. Again, the design in the embodiments described herein allows for a smaller fan, which in turn allows the portable device to be smaller.

The many features and advantages of the present invention are apparent from the written description, and therefore, In addition, many modifications and variations will be apparent to those skilled in the <RTIgt; operating. All suitable modifications and equivalents belonging to the scope of the invention may be employed.

100‧‧‧ impeller

110‧‧‧ blades

200‧‧‧ impeller

210‧‧‧ leaves

220‧‧‧Center hub/impeller shaft

230‧‧‧ motor

900‧‧‧ blade assembly

1000‧‧‧ blade assembly

1200‧‧‧ blade assembly

1 is a top plan view of an impeller having blades that are evenly spaced about a central hub.

2 is a top plan view of an embodiment of an impeller having blades that are not uniformly spaced around a central hub.

Figure 3 is a graph comparing the sound frequency distribution of an impeller having a uniform blade spacing with an impeller having a non-uniform blade spacing along the eardrum.

4 is a graphical comparison of sound produced by a fan having uniformly spaced impeller blades and a fan having non-uniform spaced impeller blades.

Figure 5 is a graphical comparison of the sound produced by a fan having uniformly spaced impeller blades and a fan having 13 non-uniform spaced impeller blades.

6 is a flow chart of a method of making a fan in accordance with one described embodiment.

7 is a flow chart of a method of making a fan in accordance with another embodiment.

8 through 12 show additional embodiments of a fan assembly having an asymmetric blade profile in accordance with the described embodiments.

Claims (2)

A centrifugal blower comprising: a motor having a plurality of magnetic pole passages, wherein the number of magnetic pole passages is an even number; and thirty one impeller blades, wherein each of the thirty one impeller blades is Having a nominal blade angle associated with one of the nominal blade angle values, the nominal blade angle being an angular displacement between adjacent impeller blades, wherein the thirty-one impeller blades are each asymmetrically spaced about a central hub such that Positioning each impeller blade around the central hub such that one of the nominal blade angle values is equal to 360° and one of the centrifugal blower operating characteristic values is within a predetermined operational characteristic value range, wherein a first nominal The blade angle value is 10.1034°; a second nominal blade angle value is 10.0229°; a third nominal blade angle value is 13.1577°; a fourth nominal blade angle value is 13.22929°; a fifth nominal blade angle The value is 13.6692°; a sixth nominal blade angle value is 13.0442°; a seventh nominal blade angle value is 13.5653°; an eighth nominal blade angle value is 11.9834°; a ninth nominal The slice angle value is 11.6129°; a tenth nominal blade angle value is 10.1071°; an eleventh nominal blade angle value is 11.2424°; a twelfth nominal blade angle value is 10.1532°; a thirteenth standard The blade angle value is 10.11816°; the 14th nominal blade angle value is 9.7922°; the fifteenth nominal blade angle value is 13.4336°; the 16th nominal blade angle value is 13.6681°; The seven nominal blade angle value is 12.6663°; the eighteenth nominal blade angle value is 9.5578°; the nineteenth nominal blade angle value is 10.0681°; A twentieth nominal blade angle value is 10.7533°; a twenty-first nominal blade angle value is 11.1550°; a twenty-second nominal blade angle value is 13.5670°; a twenty-third nominal blade angle The value is 12.7242°; a twenty-fourth nominal blade angle value is 13.1224°; a twenty-fifth nominal blade angle value is 13.0726°; a twenty-sixth nominal blade angle value is 13.1187°; a second The seventeenth nominal blade angle value is 12.0408°; the twenty-eighth nominal blade angle value is 10.6195°; the twenty-nineth nominal blade angle value is 9.5566°; and the thirtieth nominal blade angle value is 9.6588 °; and a thirty-first nominal blade angle value of 9.6605 °. The centrifugal blower of claim 1, wherein each of the nominal blade angle values has a tolerance range of +/- 5%.