JPH07167095A - Electric fan - Google Patents

Abstract

PURPOSE:To reduce the generation of noise and to provide a sufficient blast amount by a method wherein the specified number of blades are arranged separately from each other in a peripheral direction on the periphery of a boss part rotated through the drive force of an electric motor and each blade is formed such a manner that a portion ranging from a blade root to a blade tip forms an advance blade having a specified angle of advance. CONSTITUTION:A fan used as a forced fan arranged on a position situated upper stream from a capacitor comprises a cylindrical boss part 200: and blades 300 arranged at equal intervals around the boss part 200. The number of blades 300 is set to 9-13 blades and each blade 300 forms an advance blade and has an angle of advance phi fronting on a portion ranging from a blade root 301 to a blade tip 302 and being set to 35-45 deg.. An angle (an inclination angle) thetabetween the tangential line of the front edge in a rotation direction of the blade 300 and a radial line from the center of the boss part 200 is set to 20-10 deg. at the blade root part 301 and 50-70 deg. at the blade tip part 302 and the shape of the blade 300 is formed such a manner that a warp ratio obtained by dividing a warp height by the length of a chord is set to 7-15% at the blade root 301.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric fan, and is particularly effective when used as a push-in type electric fan for sending cooling air to a radiator of an automobile or a condenser of an air conditioner for an automobile. 2. Description of the Related Art Conventionally, as shown in FIG. 2, a push-type electric fan for an automobile is arranged in front of a condenser 100 arranged in an engine room of the automobile,
A push-in electric fan 101 that sends cooling air to the condenser 100 and a suction-type electric fan 103 that is disposed behind the radiator 102 and sucks cooling air from the condenser 100 and the radiator 102 are known.
In FIG. 2, 104 is an engine for driving a car,
Reference numeral 105 is a front grill that draws in vehicle speed air into the engine room.

Of these, particularly the push-type electric fan 10
No. 1 is arranged near the front grill 105, and as a result, its noise has been a problem. However, conventionally, the noise of the push-type electric fan 101 was evaluated only by the overall value.

[0003]

SUMMARY OF THE INVENTION According to the present invention, the noise of the electric fan used in the push-in type is subjected to a sensory evaluation not only as an overall value but also as to whether a person feels uncomfortable as noise. The task is to reduce noise. A further object of the present invention is to make it possible to obtain a sufficient amount of air flow in a fan that can substantially reduce noise as described above.

[0004]

As a result of various experiments conducted by the present inventors based on the above problems, the present invention provides a fan with 9 to 13 blades circumferentially spaced around the boss portion. The shape was set. Further, the shape of the fan is a forward blade having an advancing angle φ of 35 to 45 degrees when the blade tip faces the blade tip. Further, the inclination angle θ formed by the tangential direction on the front side in the rotation direction of the blade and the radiation from the center of the boss portion is −20 to 10 degrees at the blade root of the blade and 5 at the blade tip.
The shape is from 0 degree to 70 degrees, and the shape is such that it gradually and continuously increases from the blade root toward the blade tip.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of the present invention will be described below with reference to the drawings.
The electric fan of the present invention is used as a push-in type fan arranged on the upstream side of the condenser in FIG. This fan is composed of a cylindrical boss portion 200 as shown in FIG. 1 and blades 300 arranged around the boss portion at equal intervals.

In a preferred example of the present invention, 11 blades 300 are arranged in the circumferential direction as shown in FIG.
Regarding the desirable number of blades, the experimental study conducted by the present inventors will be described first. FIG. 3 is an explanatory diagram showing the relationship between the sound pressure level of the fan and the frequency. The sound pressure level shown in FIG. 3 represents a typical example of various fans.

In FIG. 3, the overall value of the overall sound pressure level is 60 to 80 dB in the conventional typical fan. Or, it is the protrusion amount of the peak sound of the fan rotation primary component from the ground noise, and is the frequency of the rotation primary component. This frequency is [rotation speed] ×
[Number of blades] / 60 (Hz) In the case of a conventional typical five-blade fan, the amount of protrusion was 20 to 30 db and the frequency was 167 Hz at a rotation speed of 2000 rpm.

Conventionally, this fan noise was evaluated only by the overall value, but it was not possible to accurately determine whether or not a person feels uncomfortable as noise only by this overall value. This is because not only the overall value but also the peak sound greatly affects discomfort as noise due to human hearing characteristics. That is, the more prominent the peak sound is, the more annoying it is, and the frequency of the peak sound is also related to the timbre.

As described above, when considering the fan noise, not only the overall value which has been conventionally examined, but also the peak sound protrusion amount and the frequency have a significant influence. Therefore, the inventors further conducted an experimental study on the peak sound protrusion amount. The primary component is presumed to occur due to the periodic pressure fluctuation due to the rotation of the blades. Therefore, by varying the periodic pressure fluctuation, the peak sound protrusion amount and the peak sound frequency can be controlled. it is conceivable that.

In order to change the periodic pressure fluctuation, it is sufficient to change the rotation speed of the motor for driving the fan.
In a motor used in a push-type electric fan for an automobile as shown in (4), it is not common to variably control the rotation speed of the motor. The motor of the push-type electric fan used for automobiles has a constant rotation speed of about 2000 rpm. Therefore, the present inventors set the number of blades of the fan to an optimum value to optimize the sensory evaluation for noise.

FIG. 4 shows the result of an experiment conducted by the present inventors. As shown in FIG. 4, the number of blades of the fan is 5, 7, 9,
11 and 13, and the diameter of each fan is 300
Then, the peak sound frequency, the peak sound projection amount, and the overall value were measured. As is clear from FIG. 4, the overall value tends to increase as the number of fan blades increases, but the peak sound protrusion amount decreases as the number of fan blades increases. Further, the frequency at which the peak sound is generated also changes to a higher frequency as the number of blades of the fan increases. It is expected that the sensory evaluation of the peak sound protrusion amount will be improved by increasing the number of blades, but the overall value is the opposite, and both tend to be in conflict. Therefore, it is predicted that there is an optimum value for sensory evaluation depending on the number of blades.

Therefore, the present inventors conducted a comprehensive sensory evaluation on the number of blades of the fan based on the peak sound protrusion amount, the peak sound frequency and the overall value. This is to evaluate whether the noise of each fan is good or bad by actually listening to the sound by a dozen or more listeners in five grades, and evaluate the average score as a sensory point. As a result, the tendency as shown in FIG. 5 was obtained. That is, as shown in FIG. 5, the fan sets the number of blades to 11
The number of blades is the best evaluation, and the number of blades is 9 or more and 15 or less, and the discomfort of noise can be suppressed. Based on such experimental results, the number of blades 300 was set to 11 in the embodiment of the present invention, as shown in FIG.

However, in the example of the present invention, the number of the blades 300 of the fan is set to 11 to alleviate the problem of noise. However, as shown in FIG. The overall value tends to gradually increase as it is increased. Therefore, the present inventors next focused on reducing the overall value as a new subject.

Therefore, the present inventors have made the fan blades 300
When the actual air flow in the section was examined by visualization,
A tendency as shown in FIG. 6 (b) was observed. As shown in FIG. 6 (a), the angle between the tangent line 400 of the fan rotation direction and the actual air flow direction 401, that is, the mixed flow angle δ was examined. While there are
As the blade 300 moves toward the tip 302 side, this mixed flow angle δ
Was confirmed to have grown. This is because an axial fan normally has a mixed flow angle δ of 0, and a large mixed flow angle δ is considered to cause an abnormality in the flow of wind. The inventors of the present invention consider that the overall value of noise is increased in the fan as a whole by increasing the mixed flow angle δ, and in order to reduce the mixed flow angle δ,
Adopted forward wing as shown in.

As shown in FIG. 7, the advancing angle φ of the advancing blade is determined by the radiation 2 from the center of the boss portion 200 at the blade base 301 portion (shown by A in the drawing) on the leading edge side 303 in the rotational direction of the blade 300.
01 and wing base 301 (A) and wing tip 302 (B)
It is defined by the angle with the imaginary line L connecting with. The blade tip 302 side (indicated by B in the drawing) on the front edge 303 side in the rotation direction of the advancing blade is a virtual point on the outer diameter point 304 of the fan. This is because, as is clear from FIG. 7, since the actual blade 300 has a rounded shape on the leading edge side 303 of the tip 302, the leading edge 303 is rounded.
This is because the tip 302 on the side is slightly retracted from the virtual tip B.

FIG. 8 shows that the number of blades of the fan is 11, and the advance angle φ defined by the above definition is appropriately changed.
The mixed flow angle δ at the tip and the overall value of fan noise are measured. In the experimental result of FIG. 8, the forward angle φ
The larger the value of, the smaller the mixed flow angle δ at the tip portion 302 of the blade 300 becomes. When the advancing angle φ is about 40 degrees, the mixed flow angle δ becomes 0, and when the advancing angle φ is increased to 60 degrees, the mixed flow angle δ becomes negative.

Therefore, the overall angle of fan noise is reduced most when the advancing angle φ in the vicinity of the mixed flow angle δ at the tip portion 302 is 0 is about 40 degrees. Compared with the fans having the advancing angles φ of 20 ° and 60 °, in order to lower the overall value, the advancing angle φ may be set to 30 to 50 °, and it is recognized that the advancing angle φ is particularly preferably about 35 to 45 °.

In the fan of the embodiment of the present invention shown in FIG. 1, the advancing angle φ of the fan is set to 40 based on the result of this experiment.
It is a forward wing. Next, in the advancing blade with the advancing angle φ of 40 degrees, the inventors of the present invention set the shape of the leading edge 303 in the rotating direction of the blade 300 so that the mixed flow angle δ defined in FIG. We proceeded with the study to make the shape 0 degrees at all positions.

From the experimental results shown in FIG. 6B, attention is paid to the fact that the mixed flow angle δ gradually increases from the blade tip 301 of the blade 300 toward the blade tip 302. The shape is gradually increased toward the blade tip 302. The inclination angle θ is, as shown in FIG. 7, the front edge portion 30 of the blade 300.
3 is the angle between the tangent line m at 3 and the radiation P from the center O of the boss 200.

When the shape of the fan blades 300 was set as described above and the flow generated by the fan was visualized, the experimental results were as shown in FIG. 9 (b). That is, by setting the inclination angle θ as described above, the mixed flow angle δ could be suppressed to 0 at almost all positions from the blade root to the tip. In addition, in FIG. 9, the forward angle φ
Angle of flow in a fan with 11 blades, where
Is shown as a comparative example.

As described above, in an advancing blade having an advancing angle φ of 40 degrees, it is necessary to make the inclination angle θ at the leading edge 303 of the blade 300 smaller at the blade base 301 and larger at the blade tip 302. It is also effective in reducing the overall noise value by making the flow angle δ close to 0 degree. further,
The present inventors next proceeded with a study on how it is desirable to set the inclination angle θ at the intermediate portion of the blade 300. As a result, it was confirmed that it is desirable to set the inclination angle θ as shown in FIG. That is, the inclination angle θ at the blade base 301 is 0 degree and the inclination angle θ _B of the blade tip 302 is 6 degrees.
It is desirable to set it to about 0 degree and to increase continuously during that time. The inclination angle θ that determines the shape of the front edge 303 of the blade of the advancing blade in the rotational direction makes the mixed flow angle δ as shown in FIG. I was confirmed that I could do it.

In this way, the advancing angle φ of the blade 300 is 40
The number of blades is 11, and the overall value of noise is improved while improving the sensory evaluation of fan noise by making the forward blade of about 10 degrees and making the inclination angle θ small at the blade base 301 portion and large at the blade tip 302 portion. Could be reduced. However, according to the study by the present inventor, although the noise can be sufficiently reduced as described above, it is recognized that the blowing performance tends to be reduced by increasing the number of blades of the fan (see FIG. 11).

In the experiment of FIG. 11, the warp ratio h / l obtained by dividing the warp height h of the blade 300 by the chord length l (see FIG. 12), the blade mounting angle β of the blade 300 (see FIG. 12), And the solidity 1 / t obtained by dividing the chord length 1 by the blade pitch t (see FIG. 7).
(Refer to FIG. 4) has the same shape as a conventional fan and has a plurality of fans that are the advancing blades of the present invention described above, and shows the relationship between the number of blades and the blowing performance. As shown in FIG. 11, if the shape of the blades 300 is the same as that of the conventional one, as the number of blades is increased, the blowing performance is deteriorated.

Therefore, the inventors of the present invention next conducted an experimental study aiming at improving the blowing performance of the fan. The method disclosed in Japanese Patent Application No. 3-338667 was used for this examination. The present inventors set the warpage ratio h / l to 2.5% at the blade tip 302, and set the blade base warpage ratio (h / l) b to 4%.
The fans having the warp ratio distributions shown in FIG. 13 as A, B, C, D, E, and F, which are 8%, 10%, 12%, 14%, and 16%, respectively, are created, and their blowing performances are created. Were compared.

The comparison result is shown in FIG. From FIG. 14, the air blowing performance is improved by changing the warpage ratio (h / l) b, and particularly the air blowing performance is improved by setting the warpage ratio (h / l) b of the blade root 301 portion to 7 to 15%. It was confirmed to do. Above all, the warpage ratio (h / l) b of the blade base 301 is 1
It was confirmed that the ventilation performance becomes maximum at around 2%.
However, as shown in FIG. 14 in comparison with the conventional 5-blade level, even if the blade sled ratio (h / l) b is devised, it is possible to obtain the same blowing performance as the conventional one with 11 blades. It was not achieved at that time.

It is considered that this is because when the solidity 1 / t is the same, the chord length 1 becomes smaller as the number of blades is increased. Therefore, the present inventors have paid attention to the relationship between the fact that the blowing performance decreases as the number of blades increases and the chord length l decreases. The fan produces a pressure difference between the front and the back of the fan as well as the action of generating wind. In particular, in a push-in type fan as shown in FIG. 2, in order to blow air into the condenser 100 and the radiator 102, a pressure difference corresponding to the ventilation resistance of the condenser 100 and the radiator 102 must be generated before and after the fan 101.

Here, a fan having a small chord length l but a large number of blades 300 and a fan 30 having a large chord length l but having a large chord length l
We will compare it with a fan with a small number of zero. When the fan diameter is the same and the same air volume is sent to the heat exchanger, the pressure difference before and after the fan is considered to be the same. Therefore, assuming that both fans have the same pressure difference across them,
In order to send the same amount of air, a fan having a small chord length l and a large number of blades has a large pressure gradient before and after the fan.

The large pressure gradient means that the blade 30
This means that the flow on the 0th surface is easily separated. The flow separation leads to a reduction in the blowing performance, and this is considered to be related to the reduction in the blowing performance of a fan having a small chord length l. Therefore, the present inventors have focused on increasing the chord length l as a means for further improving the blowing performance. That is, an attempt was made to improve the blowing performance by increasing the solidity 1 / t, which is the ratio of the chord length 1 to the blade pitch t. The solidity 1 / t of a conventional general fan is less than 0.6 at the blade tip.

As shown in FIG. 15, the present inventors set the value of solidity 1 / t of the blade tip 302 portion to 0.58,
Fan G with 0.7, 0.8, 0.9, and 1.0
The fan performances of the H, I, J, and K fans were compared. As a result, the blowing performance characteristics as shown in FIG. 16 were recognized, and the solidity (l / t) t at the blade tip 302 was set to 0.
It was confirmed that if the range is from 7 to 0.95, the blowing performance obtained with the conventional five blades can be obtained.

As described above, according to the study by the present inventors,
The distribution of the sled ratio h / l is set so as to rapidly increase from the blade central portion to the blade root 301, and the sled ratio h / l is set to 7 to 15% at the blade root 301 portion, and the solidity l / t If the distribution is constantly or smoothly reduced from the blade tip 301 to the blade tip 302 and the blade tip solidity (l / t) t is 0.7 to 0.95, the number of blades is 11 as described above. As a result, it was confirmed that even a fan with reduced noise can exhibit sufficient blowing performance at the same time. It should be noted that the distribution of the warpage ratio does not have to be a curve having a single decrease from the blade root 301 to the blade center as shown in FIG. 13, and for example, a portion where the warpage ratio h / l is almost constant in the blade root 301 portion. There may be. The warp ratio h / l may be slightly increased from the blade center to the blade tip 302. According to the study by the present inventors, even if the warp ratio is slightly changed from the blade root to the blade tip as described above, almost the same blowing performance is recognized.

[0031]

As described above, according to the present invention, the number of blades of the pushing fan is 9 to 13, and the advance angle φ is
Since the angle is 35 to 45 degrees, the fan noise can be reduced. Further, the inclination angle θ of the leading edge of the blade in the rotation direction is −20 to +10 degrees at the blade tip portion, is 50 to 70 degrees at the blade tip portion, and gradually increases from the blade tip to the blade tip. Because of the shape, the above noise reduction effect could be further improved.

Further, the warpage ratio of the fan blades is 7 to
By setting it to 15%, it was possible to maintain the blowing performance as well as the above noise reduction effect. Furthermore, by setting the solidity at the blade tip to be 0.7 to 0.95, it was possible to further improve both the effect of reducing noise and the effect of air blowing performance.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of a fan of the present invention.

FIG. 2 is an explanatory diagram showing an installation example of a pushing fan.

FIG. 3 is an explanatory diagram showing the sound pressure level of the pushing fan.

FIG. 4 is an explanatory diagram showing the relationship between the number of fans and fan noise.

FIG. 5 is an explanatory diagram showing the relationship between the number of fans and the sensory evaluation of noise.

FIG. 6 is an explanatory view showing an air flow of a conventional fan.

FIG. 7 is a front view showing a main part of the fan of the present invention.

FIG. 8 is an explanatory diagram showing the relationship between the advancing angle of the blade and noise.

FIG. 9 is an explanatory view showing the air flow of the fan of the present invention.

FIG. 10 is an explanatory view showing an inclination angle θ related to the fan of the present invention.

FIG. 11 is an explanatory diagram showing the relationship between the number of blades and the blowing performance.

FIG. 12 is a sectional view taken along line XX of FIG.

FIG. 13 is an explanatory diagram showing the relationship between the blade cross-section position and the warpage ratio.

FIG. 14 is an explanatory diagram showing the relationship between the blade sled ratio and the blowing performance.

FIG. 15 is an explanatory diagram showing a relationship between a blade cross-section position and solidity.

FIG. 16 is an explanatory diagram showing the relationship between blade tip solidity and air blowing performance.

[Explanation of symbols]

 200 Boss 300 Blade 301 Blade Base 302 Blade Tip

Claims (4)

[Claims] 1. An electric fan rotatably driven by an electric motor, comprising: a boss portion that receives a driving force of the electric motor to rotate; and 9 to 13 boss portions that are circumferentially separated from each other around the boss portion. An electric fan, comprising: a blade, the blade being a forward blade having a forward angle φ of 35 to 45 degrees with the blade tip facing the blade tip. 2. The electric fan according to claim 1, wherein an inclination angle θ formed by a tangent line on the leading edge side in the rotation direction of the blade and radiation from the center of the boss portion is −20 to 10 degrees at the blade root portion, An electric fan having a tip portion of 50 to 70 degrees and a gradual increase from the blade root to the blade tip. 3. The electric fan according to claim 1, wherein a warpage ratio h / l obtained by dividing a blade warpage height h by a chord length l is:
An electric fan characterized in that the warp ratio h / l of the blade root portion is set to 7 to 15% by rapidly increasing from the blade center to the blade root. 4. The electric fan according to any one of claims 1 to 3, wherein the blade length chord length l is divided by a blade pitch t to determine solidity 1 /
An electric fan characterized in that the distribution of t is reduced uniformly or smoothly from the blade root to the blade tip, and the blade solidity 1 / t is set to 0.7 to 0.95.