TW201408887A - Centrifugal blower with asymmetric blade spacing - Google Patents

Abstract

A centrifugal blower in a cooling system of an electronic device having asymmetrical blade spacing with acceptable balance. The asymmetrical blade spacing is determined according to a set of desired acoustic artifacts that are favorable and balance that is similar to that found with equal fan blade spacing. In one embodiment, the fan impeller can include thirty one fan blades.

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 the cooling system of the electronic device to assist in cooling the electronic device as it becomes overheated. A typical fan design includes an impeller having blades that are equally angularly spaced relative to one another. Evenly 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 cause increased vibration stress, bearing load on the fan and wear on the motor structure, and quality issues.

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

The main motor noise source is the pole passage frequency (PPF) tone. The PPF is a vibration generated by a magnetic pole in a motor of a fan and a resultant pressure wave. The BPF will typically be perceived as a tone and can be amplified if it coincides with the PPF. BPF and PPF tones are emitted from a blower or fan and are audible for the production of a blower or fan The user of the product can be annoying. Another source of noise comes from the interaction with the struts on the fan or any other kind of obstacle. Therefore, there is a need for a fan that has a sufficient balance of reduced noise.

Broadly speaking, the embodiments disclosed herein describe a non-uniform blade spacing with an acceptable balance in a centrifugal blower and the implementation of the centrifugal blower in a portable electronic product.

Describe a centrifugal blower. The centrifugal blower includes: at least one motor having a plurality of pole passes, wherein the number of magnetic pole passages is an even number; and thirty one blades, each of the blades having a nominal A nominal blade angle of blade angle values is associated, the nominal blade angle value being 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 the centrifugal blower An operational characteristic value is considered to be within a predetermined range of one of the operational characteristic values. In the depicted embodiment, a first nominal blade angle value is 10.7772°, a second nominal blade angle value is 11.5672°; a third nominal blade angle value is 12.7214°; a fourth nominal blade angle It is 12.6427°; a fifth nominal blade angle value is 11.7955°; a sixth nominal blade angle value is 10.7489°; a seventh nominal blade angle value is 10.2102°; an eighth nominal blade angle value is 10.5044 °; a ninth nominal blade angle value of 11.4303 °; a tenth nominal blade angle value of 11.2102 °; an eleventh nominal blade angle value of 11.6129 °; a twelfth nominal blade angle value of 13.0226 °; tenth The three nominal blade angle values are 11.2263°; a fourteenth nominal blade angle value is 10.8982°; a fifteenth nominal blade angle value is 9.924°; and a sixteenth nominal blade angle value is 12.0156°; The seventeenth nominal blade angle value is 13.4934°; the eighteenth nominal blade angle value is 13.0156°; the nineteenth nominal blade angle value is 12.3276°; and the twentieth nominal blade angle value is 12.4769°. a twenty-first nominal blade angle value of 11.9925°; a twenty-second nominal blade angle value of 11.6586°; a twenty-third nominal blade angle value of 10.5831°; a twenty-fourth nominal The blade angle value is 9.7324°; a twenty-fifth nominal blade angle value is 9.8737°; a twenty-sixth nominal blade angle value is 10.1688°; and a twenty-seventh nominal blade angle value is 12.4466°; The twenty-eighth nominal blade angle value is 10.2032°; a twenty-nineth nominal blade angle value is 13.0570°; a thirtieth nominal blade angle value is 13.3501°; and a thirty-first nominal blade angle The value is 13.2334°. 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 of the invention.

The same reference numerals are used to refer to the same structural elements in the accompanying drawings.

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

Embodiments are discussed below with reference to Figures 1-12. However, it will be readily apparent to those skilled in the art that the detailed description of the figures herein is for the purpose of explanation, and the present invention is beyond the scope of the invention.

As discussed above, a typical fan design includes an impeller having a uniform blade spacing. That is, the blades 110 of the impeller 100 are spaced at equal angles A, B, C relative to each other, as shown in FIG. As illustrated in Figure 1, the angles A, B, C between the blades 110 are equal to each other. The uniform spacing of the blades 110 provides a balance due to the uniform distribution of the mass of the impeller 100, 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 merging the harmonics of the blades with the harmonics of the poles in the motor. For the number of blades, the prime number is usually chosen because the magnetic pole channels are usually even. 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 is to provide evenly spaced blades when the impeller has a number of blades.

One way to minimize noise from the fan is to control the spectral distribution of the pure tones produced by the fan. Dispersing the energy of the tones over several discrete frequencies can make the tones less confusing to the listener by reducing the perception of the pitch BPF. One method of controlling the pure pitch effect by unevenly spacing the fan blades while maintaining the impeller balance. 2 illustrates an impeller 200 of a centrifugal blower having non-uniformly 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 ' is the new interval angle of the i- th nominal blade angle after modification, Δ θ is the maximum percentage of the interval angle change (modulation amplitude), and m is the number of sine patterns to be used (the modulation cycle is The number of repetitions of a fan in a single turn). It should be understood that the equations set forth above may be applicable to larger fans such as axial fans that may be balanced by the addition of weights at critical locations on the impeller.

The noise resulting from 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 fundamental harmonic blade passing through the tone, F ₀ = I f _s ( I is the number of blades, and f _s is the rotation frequency of the shaft), the modulation frequency υ = mf _s , and the phase modulation amplitude Δφ = I Δ θ .

The base film in the human ear has the function of dispersing the frequency of the incoming sound waves. The dispersion of the frequency of the sound waves causes the sound of a certain frequency to cause some positions of the base film to vibrate more than other positions. 3 is a graph comparing the sound frequency distribution along the base film of the impeller 100 having a uniform blade spacing and the sound frequency distribution along the base film of the impeller 200 having a non-uniform blade spacing. As shown in Figure 3, the noise from the two impellers 100, 200 causes a similar amount of neurons to be excited within the same time period. However, the impeller 200 with non-uniform blade spacing causes a greater spread intensity of the acoustic wave frequency, which reduces the BPF tones. should It is understood that the reduction in the measurement of BPF tones may not fully reflect the perceived decrease in BPF tones.

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. Unbalance can occur when the blades are not evenly spaced, and the BPF tone frequency is not constant over time as the fan rotates. For large fans, heavy objects can be attached to critical locations on certain fan blades for balance. However, for small fans, such as those used in portable devices, heavy objects cannot be used in an efficient manner. 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 to balance the fan even if the blades are unevenly spaced around the center hub or shaft of the impeller, and the BPF tone frequency remains constant over time, thereby reducing the self-fan emission The noise. 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 around the central hub or impeller shaft 220 and extend from the central hub or impeller shaft 220. That is, the blades 210 are not evenly spaced apart from one another. 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 poles merge with the harmonics of the blades 210, the BPF and PPF tones increase, resulting in increased noise from the fan. Therefore, if the harmonics of the magnetic pole are not combined with the harmonics of the blade, the perceived noise from the fan will decrease. It should be understood that if stored in a fan In multiple sources of noise, the noise sources should not be combined to minimize noise.

Although the blades 210 are not evenly spaced, the impeller 200 is still capable of maintaining an acceptable balance while rotating. The angles D, E, 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 Figure 2, the angles D, E, 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, F of each of the spaces between the blades 210 are determined by the blade position. 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 The original separation angle of the evenly spaced blades (the number of blades / 360°), θ _i ' is the new interval angle of the i- th nominal blade angle after modification, α and the interval angle change (modulation amplitude Δ θ ) The maximum percentage is related, 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 the noise reduction provided by a fan having non-uniformly spaced impeller blades in accordance with an embodiment. Figure 4 is a graphical comparison of the sound produced by a fan having uniformly spaced impeller blades with the sound produced by a fan having non-uniformly spaced impeller blades. In this embodiment, as shown in Figure 4, the main tone (at about 2300 Hz) is reduced in a non-uniformly spaced fan and the sidebands are introduced (at about 1900 Hz and 2700 Hz). The sidebands indicate the dispersion of the frequency of the sound waves, resulting in a reduction in noise. Should understand, feel It is known that the noise reduction can be even greater than the measured noise reduction.

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-uniformly spaced impeller blades. In some embodiments, the impeller has 29 blades or fewer blades. If too few blades are present, unwanted modulation artifacts can be introduced, thereby enhancing the noise emitted from the fan, as shown in FIG. As shown in Figure 5, a fan with 13 non-uniformly spaced impeller blades produces not only the main tones (at about 1300 Hz) of the fan above the uniformly spaced impeller blades, but also produces high sidebands (at About 1100 Hz and 1500 Hz).

As discussed above, the position of each of the impeller blades 210 around 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, up to four repeated sinusoidal patterns are used. So at 2 m 4 hours is especially effective. Those skilled in the art will appreciate that the cosine in the equation can be replaced by a sine, using the following equation: θ _i ' = θ _i + θ _i * α * sin( m x) In one embodiment, the angle of change is the largest The percentage related variable a is particularly effective when maintained in the range of from about 0.01 to about 0.07. According to another embodiment, a 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 from the evenly spaced configuration is particularly effective in the range of about one percent to about seven percent. That is, each of the blade positions is modified by about one percent to about seven percent compared to uniformly spaced impeller blades having the same number of impeller blades. When a single fan is used in the 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 blade from combining or combining with the harmonics of the magnetic poles. Since the magnetic pole channels are usually even, the number of impeller blades is chosen to be equal to the prime number to prevent 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 percentage of variability in the spacing between the blades. The higher the frequency of interest, the more effective the variation is in reducing the perceived pitch without introducing other artifacts. The blade pass frequency (BPF) frequency is modulated and perceived to be less annoying or less aggressive to the user. The average energy of the small frequency steps is reduced, but the modulation must be small enough to not allow low frequency artifacts to be perceived.

6 is a flow chart of a method of making a fan in accordance with the described embodiments. 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. leaf The number of wheel blades 210 is different from the number of magnetic pole channels in the 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 a unique point on at least two repeated sinusoidal patterns.

7 is a flow chart of a method of making a fan in accordance with another embodiment. In step 700, at least 17 prime impeller blades 210 are selected for the impeller. In step 710, the impeller blades 210 are non-uniformly spaced around the center hub by positioning each of the impeller blades 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 for a large number of users and are therefore a desirable 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 may cause impeller blades to be associated with nominal blade angle values and (i) asymmetrically spaced apart from each other and (ii) asymmetrically spaced. The sum of the nominal blade angle values of the 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 based on the tolerance factor (plus or minus) without seriously affecting the desired performance characteristics of the centrifugal blower. (note that even in In the case of a possible change in the blade angle value, the sum of the blade angle values of the impeller blades must still be equal to 360°). For example, the tolerance factor for the blade angle value can be +/- 5%. Thus, for each configuration of the asymmetrically spaced blades, one of the operational characteristics of the corresponding centrifugal blower can be calculated. Operating characteristics can be analyzed for use in a portable computing device. In one embodiment, the operational characteristics can be compared to the desired operating characteristics of one of the centrifugal blowers. In another embodiment, the operational characteristics may be compared to another set of operational characteristics associated with another configuration of the asymmetrically spaced blades. In this environment, a better 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) having a blade angle value according to Table 1 depicted in FIG. 8 and embodied as the blade assembly 900 of FIG. 9 and the blade assembly 1000 of FIG. ) a blade. In another embodiment, the centrifugal blower can include sixty-one (61) blades having blade angle values as described in Table 2 of FIG. 11 and embodied as the blade assembly 1200 shown in FIG.

The advantages of the invention are numerous. Different aspects, embodiments, or implementations can produce 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 annoying to the user. The thermal performance of a fan utilizing the fans described herein is equivalent to a fan prior to use of the technology. Another advantage of these fans is that the fan wheel can still be balanced because the center of mass is still on the shaft of the impeller. Again, the design in the embodiments described herein allows the fan to be smaller, which in turn allows the portable device to be smaller.

Many of the features and advantages of the present invention are apparent from the written description, and All such features and advantages of the invention are intended to be covered by the appended claims. In addition, many modifications and variations are obvious to those skilled in the art, and the invention is not limited to the exact construction and operation as illustrated and described. Accordingly, all suitable modifications and equivalents may be employed within the scope of the invention.

100‧‧‧ impeller

110‧‧‧ blades

200‧‧‧ impeller

210‧‧‧ Impeller blades

220‧‧‧Center hub

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 non-uniformly spaced around a central hub.

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

Figure 4 is a graphical comparison of the sound produced by a fan having uniformly spaced impeller blades with the sound produced by a fan having non-uniformly spaced impeller blades.

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

6 is a flow chart of a method of making a fan in accordance with the described embodiments.

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 asymmetrical distribution of blades 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 a plurality of impeller blades, wherein each of the plurality of impeller blades is associated with a nominal blade angle Correspondingly, the nominal blade angle is an angular displacement between adjacent impeller blades, wherein the plurality of 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 angles is summed to a total of 360°, and one of the centrifugal blower operating characteristic values is considered to be within a predetermined range of operating characteristic values, wherein a first nominal blade angle value is 10.7892 °, a second nominal blade angle value of 11.5672 °; a third nominal blade angle value of 12.7214 °; a fourth nominal blade angle of 12.62627 °; a fifth nominal blade angle value of 11.7955 °; The sixth nominal blade angle value is 10.7489°; a seventh nominal blade angle value is 10.2102°; an eighth nominal blade angle value is 10.5044°; and a ninth nominal blade angle value is 11 .4303°; a tenth nominal blade angle value of 11.2102°; an eleventh nominal blade angle value of 11.6129°; a twelfth nominal blade angle value of 13.0226°; a thirteenth nominal blade angle The value is 11.2263°; a fourteenth nominal blade angle value is 10.8982°; a fifteenth nominal blade angle value is 9.924°; a sixteenth nominal blade angle value is 12.0156°; a seventeenth nominal The blade angle value is 13.49430°; an 18th nominal blade angle value is 13.0156°; a 19th nominal blade angle value is 12.3276°; Twenty nominal blade angle values are 12.4769°; a twenty-first nominal blade angle value is 11.9955°; a twenty-second nominal blade angle value is 11.6586°; a twenty-third nominal blade angle value is 10.5831°; a twenty-fourth nominal blade angle value of 9.7324°; a twenty-fifth nominal blade angle value of 9.8737°; a twenty-sixth nominal blade angle value of 10.1688°; a twenty-seventh The nominal blade angle value is 12.4466°; a twenty-eighth nominal blade angle value is 10.2032°; a twenty-nineth nominal blade angle value is 13.0570°; and a thirtieth nominal blade angle value is 13.3501°; And a thirty-first nominal blade angle value of 13.2334 °. The centrifugal blower of claim 1, wherein each of the nominal blade angle values has a tolerance range of +/- 5%.