JP2005291149A - Fluid drive device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To dissolve a problem that although there is a technique of arranging fin pitch angles unequally and offsetting positions of fins on a front and a back surface by a half pitch as a technique for reducing fan noise, an overall value of the noise in an audible frequency range to human beings is not reduced. <P>SOLUTION: When a number of fins 21a is represented as N and a rotation speed of an electric motor 1 is represented as S (revolution number/sec), a value calculated by N×S is set higher than the audible frequency range of human beings. This causes a primary peak of the fan noise to be generated in a high range outside the audio frequency range and the fan noise audible to human beings can be reduced. All the fin pitch angles are set equally and the primary peak of the fan noise does not change. The number of the fins 21a is set to be a prime number and the primary and secondary peaks and the like are not generated in the audible frequency range. A slope portion is formed at a terminal end of a swirl chamber 28 for gradually decreasing a volume space and the fan noise when the primary peak of the fan noise passes through the audible frequency range can be reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a fluid drive device that drives a fluid by rotating a plurality of fins with an electric motor, and more particularly to a technique for reducing fan noise.

Techniques to reduce fan noise in electric air pumps (an example of a fluid drive device): (1) Distributing the fin pitch angles of the impeller unevenly, and (2) modulating the rotational position of the fins on the front and back surfaces of the impeller A technique of shifting by half a pitch at the position of point 0 is known.
According to the above (1) and (2), this technology reduces fan energy by causing sounds generated on the front and back surfaces of an impeller to interfere with each other to cancel out sound energy (see, for example, Patent Document 1). ).

However, by adjusting the fin pitch angle to be non-uniform and shifting the fin positions on the front and back surfaces, a high-level noise peak does not occur in the noise frequency during normal rotation, but the level is not increased due to the non-uniform fin pitch angle. A large number of low noise peaks occur in a dispersed manner. As a result, there is a drawback that the overall value of noise within the human audible frequency band is not reduced.
Japanese Patent Laid-Open No. 9-209997

  The present invention has been made in view of the above-described problems, and the object thereof is to shift noise peak frequency to a high frequency outside the human audible frequency band, so that noise audible to humans can be kept low. It is in the provision of a fluid drive.

[Means of claim 1]
The fluid drive device adopting the means of claim 1 is obtained by N × S (× is multiplication), where N is the number of fins and S is the number of rotations per second when the electric motor is normally rotated. The value obtained is higher than the human audible frequency band.
By providing in this way, the frequency (N × S) of the primary peak of fan noise is generated on the high frequency side outside the human audible frequency band, and the fan noise audible to humans is kept low. Can do.

[Means of claim 2]
In the fluid drive device employing the means of claim 2, the fin pitch angles of the fins are uniformly provided.
By providing in this way, the peak frequency of the fan noise can be concentrated at one point of the primary peak and there is no frequency fluctuation of the primary peak. For this reason, the frequency of the primary peak of fan noise can be completely shifted to a high frequency outside the human audible frequency band.

[Means of claim 3]
In the fluid driving device employing the means of claim 3, the number of fins is provided as a prime number. By providing in this way, it can prevent that the noise peak by a fan generate | occur | produces besides a primary peak. As a result, it is possible to prevent the 0.5th order peak of fan noise from occurring in the human audible frequency band. That is, it is possible to prevent the noise peak from being dispersed and to prevent the noise peak from occurring in the human audible frequency band.

[Means of claim 4]
The fluid drive device adopting the means of claim 4 is a vortex-type blower device, and an inclined portion that gradually reduces the volume space at the end of the vortex chamber toward the rotation direction of the fin at the end of the discharge port side in the vortex chamber Is provided.
By providing an inclined part that gradually reduces the volume space of the vortex chamber at the end of the vortex chamber, the pressure change when the fin enters the end of the vortex chamber becomes gentle, and when the fin enters the end Noise energy generated can be reduced. As a result, the noise level of the fan noise when the primary peak of the fan noise passes through the audible frequency band at the start of rotation and when the rotation is stopped can be kept low.

  The fluid drive device of the best mode is to rotate and drive a plurality of fins by an electric motor, where N is the number of fins, and S is the number of rotations per second when the electric motor is normally rotated. The value obtained by N × S is set higher than the human audible frequency band.

A first embodiment in which the present invention is applied to an electric air pump will be described with reference to FIGS.
The electric air pump compresses and discharges air, and is used, for example, in a secondary air supply system that supplies pressurized secondary air upstream of an exhaust gas purifying catalyst mounted on an automobile. It is.
In the first embodiment, an example in which a double-blade eddy current type blower device is used as an electric air pump will be described.

As shown in FIG. 1, the electric air pump according to this embodiment includes an electric motor 1, a vortex type blower 2, and an air duct 4 incorporating a filter 3.
(Description of electric motor 1)
The electric motor 1 shown in the first embodiment is a direct current motor (DC motor), and a field 7 (stator) configured by arranging a plurality of magnets 6 on the inner periphery of a cylindrical yoke 5. An armature 8 (rotor) disposed on the inner periphery of the magnet 7 and a brush assembly 12 disposed in the motor housing 11 include a plurality of brushes 10 that abut on a commutator 9 provided in the armature 8.

The armature 8 includes a rotary shaft 13 rotatably supported in the electric motor 1, an armature core 14 fixed to the outer periphery of the rotary shaft 13, a plurality of armature coils wound around the armature core 14, and the armature coils. And a plurality of commutators 9 connected to the.
The brush assembly 12 includes a brush 10 that is pressed against the commutator 9, a brush holding member 15 that holds the brush 10 slidably toward the commutator 9, a spring 16 that biases the brush 10 toward the commutator 9, and a brush holding member. 15 includes a spacer 17 that supports the motor housing 11 in the motor housing 11.

(Explanation of blower 2)
The blower 2 shown in the first embodiment is a two-blade type vortex type and includes an impeller 21 and a blower housing 22.
The impeller 21 has a substantially disk shape and is provided with a large number of fins 21a on both sides of the outer periphery thereof. The center of the disk portion is connected to the end of the rotating shaft 13 of the electric motor 1 via a coupling means 23. It is combined and rotates integrally with the rotating shaft 13.
The blower housing 22 includes a first case 25 coupled to the motor housing 11 by screws 24 and a second case 27 coupled to the first case 25 by clips 26. A vortex chamber 28 is formed inside the blower housing 22 to compress air by the movement of a large number of fins 21 a caused by the rotation of the impeller 21.

The vortex chamber 28 has a substantially C-shape (circular shape with a part cut off) along the outer periphery of the impeller 21, and forms a space through which air flows around a portion where a large number of fins 21a are provided.
As shown in FIG. 2, a suction port 31 for introducing external air into the vortex chamber 28 is provided at the start end 28 a of the vortex chamber 28 (the portion where the fin 21 a starts to enter the vortex chamber 28). As shown in FIG. 1, the suction port 31 is connected to the downstream end of the air duct 4. A discharge port 32 for discharging the air compressed in the vortex chamber 28 to the outside is provided at the end 28b of the vortex chamber 28 (the portion where the fin 21a exits from the vortex chamber 28).

(Electric air pump operation)
In the electric air pump having the above configuration, when the electric motor 1 is energized (for example, connected to a battery mounted on the vehicle via a relay or the like), the impeller 21 rotates together with the rotating shaft 13.
When the impeller 21 rotates, the air in the vortex chamber 28 is compressed from the start end 28a side to the end end 28b side by the movement of the numerous fins 21a. Since negative pressure is generated at the suction port 31, air filtered by the filter 3 is guided to the suction port 31, and high pressure is generated at the discharge port 32, so that air pressurized inside the vortex chamber 28 is discharged. It is discharged from the outlet 32.
Here, the rotation speed at which the electric motor 1 is normally used is referred to as a normal rotation speed. The electric motor 1 according to the first embodiment shows an example in which only switching between energization (on) and non-energization (off) is performed. The electric motor 1 is energized to stabilize the rotating shaft 13 and the impeller 21. Thus, the rotating speed corresponds to the normal rotating speed.

(Characteristics of Example 1)
The electric air pump according to the first embodiment is provided with a technology for reducing noise audible to humans by shifting the peak frequency of fan noise to a high frequency outside the human audible frequency band. Will be described.

Since the electric air pump has a structure in which a large number of fins 21a rotate in one direction and each fin 21a gives a flow velocity to the air, (1) each time air compressed by each fin 21a is guided to the discharge port 32 The pressure fluctuates and pulsation noise is generated, and (2) fins are formed in the partition 33 (see FIG. 2) that blocks communication between the vortex chamber 28 between the end 28b and the start end 28a of the vortex chamber 28 in the blower housing 22. Wind noise is generated each time 21a enters.
The pulsating sound of (1) above is a sound generated when the pressure of the air driven by each fin 21a fluctuates due to communication with the discharge port 32. Therefore, the frequency of the pulsating sound is mainly the same as that of the fin 21a. It depends on the cycle at which the discharge port 32 intersects.
Similarly, since the wind noise in (2) is a sound generated when each fin 21a enters the partition portion 33, the frequency of the wind noise mainly depends on the cycle at which the fin 21a and the partition portion 33 intersect. To do.

Thus, since both the pulsating sound and the wind noise are sounds depending on the cycle in which the fixing member (discharge port 32, partition portion 33) and the fin 21a intersect, fan noise (pulsation sound and wind noise). The primary peak of occurs in a cycle in which the fixing member and the fin 21a intersect.
That is, when the number of fins 21a is N (sheets) and the number of rotations per second of the electric motor 1 is S (rotations / sec), a value F (Hz) obtained by N × S (× is multiplication). The primary peak of fan noise occurs.

(A) In the electric air pump of the first embodiment, the fixing member and the fin 21a intersect each other in the normal rotation speed range of the electric motor 1 (the speed range where the electric motor 1 is energized and the electric motor 1 rotates stably). The cycle (frequency) to be performed is set to a value higher than the human audible frequency band.
That is, when the number of fins 21a is N (sheets) and the number of rotations per second when the electric motor 1 rotates regularly is S (rotations / sec), the value F obtained by N × S Is set higher than the audible frequency band Fh (Hz) (N × S = F ≧ Fh).
Here, the “human audible frequency band” of the present invention is within a frequency range that can be heard by a normal person, and the “frequency higher than the human audible frequency band” means a frequency that is higher than a frequency that can be heard by a normal person. It is. As a specific example, it is 20 kHz or more.

As described above, fan noise is generated in a cycle in which the fixing member and the fins 21a intersect. Therefore, when the fins 21a are provided on the front and back surfaces of the impeller 21 as in the first embodiment, the fan noise is generated. Fan noise due to the front-side fins 21a and fan noise due to the back-side fins 21a are generated.
Therefore, the number of front-side fins 21a and the number of back-side fins 21a are provided so as to satisfy the above condition (N × S = F ≧ Fh). In Example 1, the number of fins 21a on the front and back sides is the same, and each is 79 as will be described later.

(B) In Example 1, the fin pitch angles of the fins 21a provided on the front and back sides of the impeller 21 are all provided uniformly as shown in FIG.
In addition, in this Example 1, although the position of the rotation direction of the fin 21a of the front and back of the impeller 21 shows an example which corresponds in front and back as shown in FIG.3 (b), the rotation direction of the fin 21a of the front and back is shown. May be shifted by a half pitch at the position of the modulation point 0.

(C) In the first embodiment, the number of fins 21 a provided on the front and back sides of the impeller 21 is a prime number.
Specifically, 79 fins 21 a are respectively formed on the front and back of the impeller 21. Note that the value F (Hz) obtained by 79 × S is set to 20.5 kHz, where S (rotation / sec) is the number of rotations per second during normal rotation of the electric motor 1. That is, the fan noise primary peak is set to 20.5 kHz, and the fan noise primary peak is set to satisfy the condition that the frequency is higher than the human audible frequency band (20 kHz or more).

(D) In the first embodiment, the end portion 28b of the vortex chamber 28 is provided with an inclined portion 34 that gradually decreases the volume space of the end portion 28b of the vortex chamber 28 in the rotational direction of the fin 21a. The inclined portion 34 is provided at a portion where the fin 21a of the partition portion 33 partitioning the vortex chamber 28 enters, and in the first embodiment, as shown in FIG. 2, the inclined portion 34 gradually increases in the rotation direction of the fin 21a. It is formed by a V-shaped inclined groove (notch groove) that becomes shallower.
In the first embodiment, since the fins 21a are provided on the front and back of the impeller 21, the front fin 21a enters the partition portion 33 and the back fin 21a enters the partition portion 33. Each is provided with an inclined portion 34 by an inclined groove.
Here, the number of the inclined grooves may be a number other than the two shown in FIG. 2 (one or three or more). Moreover, you may provide the inclination part 34 by providing a slope in the site | part where the fin 21a penetrate | invades the partition part 33 instead of an inclination groove | channel. Further, the inclined portion 34 may be provided at a site where the outer peripheral edge of the fin 21 a enters the partition portion 33.

(Effect of Example 1)
In the electric air pump according to the first embodiment, as shown in the above (A), the number of fins 21a is N (sheets), and the number of rotations per second when the electric motor 1 is normally rotated is S (rotations / sec). In this case, the value F obtained by N × S is set higher than the human audible frequency band Fh (Hz) (N × S = F ≧ Fh).
As a result, the frequency F (Hz) of the primary peak of the fan noise is generated in a high frequency outside the human audible frequency band, and the fan noise that can be heard by humans can be kept low.

In the electric air pump of the first embodiment, as shown in (B) above, the fin pitch angles of the fins 21a provided on the front and back of the impeller 21 are all provided uniformly.
As a result, the peak frequency of the fan noise can be concentrated at one point of the primary peak, and the frequency of the primary peak does not fluctuate. For this reason, the frequency of the primary peak of fan noise can be completely shifted to a high frequency outside the human audible frequency band.

In the electric air pump according to the first embodiment, as shown in the above (C), the number of fins 21a provided on the front and back of the impeller 21 is provided as a prime number (79).
As a result, it is possible to prevent occurrence of fan noise half-order peaks, quarter-order peaks, and the like within a human audible frequency band. That is, it is possible to prevent the noise peak from being dispersed and to prevent the noise peak from occurring in the human audible frequency band.

  In the electric air pump according to the first embodiment, as shown in the above (D), the inclined portion that gradually reduces the volume space of the end 28b of the vortex chamber 28 toward the end 28b of the vortex chamber 28 toward the rotation direction of the fin 21a. 34 is provided. By providing the end portion 28b of the vortex chamber 28 with the inclined portion 34 that gradually reduces the volume space of the vortex chamber 28, the change in pressure generated when the fin 21a intersects the partition portion 33 becomes gentle, and the fin 21a The wind noise when crossing the partition 33 can be reduced. This can reduce fan noise when the primary peak of fan noise passes through the audible frequency band when rotation of the electric air pump is started and when rotation is stopped.

(Modification)
In the above embodiment, the present invention is applied to an electric air pump that pressurizes and discharges air. However, the present invention is applied to a fluid drive device that pressurizes and discharges a gas (such as gas) other than air. May be. Further, the present invention may be applied to a fluid drive device that pressurizes and discharges a gas-liquid mixed fluid in which a gas and a liquid (for example, a mist-like liquid) are mixed.
In the above embodiment, the fluid drive device using the two-blade type impeller 21 (electric air pump in the embodiment) is shown as an example. However, the impeller of the single blade type (that is, the type using fins with no distinction between the front and back) is used. The present invention may be applied to the fluid drive device used.
In the above embodiment, the vortex type fluid drive device (electric air pump in the embodiment) is shown as an example. However, the present invention may be applied to other centrifugal fluid drive devices, or an axial flow type fluid drive device. You may apply this invention to a drive device.

It is sectional drawing of an electric air pump. It is explanatory drawing of the inclination part provided in the partition part. It is explanatory drawing of the fin provided in the impeller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electric motor 2 Blower 21 Impeller 21a Fin 22 Blower housing 28 Swirl chamber 28b End of vortex chamber 31 Suction port 32 Ejection port 34 Inclined part

Claims (4)

In a fluid drive device that rotationally drives a plurality of fins by an electric motor,
The number of fins is N,
When the number of rotations per second when the electric motor rotates regularly is S,
A fluid driving apparatus characterized in that a value obtained by N × S is set higher than a human audible frequency band. The fluid drive device according to claim 1,
A fluid driving device characterized in that the fin pitch angle of each fin is uniform. In the fluid drive device according to claim 1 or 2,
The fluid driving apparatus according to claim 1, wherein the number of fins is a prime number. In the fluid drive unit according to any one of claims 1 to 3,
This fluid drive is
An impeller having the plurality of fins;
A blower housing that covers the impeller and forms a swirl chamber along the plurality of fins from a fluid suction port toward a fluid discharge port, and a vortex flow blower device,
The fluid drive device according to claim 1, wherein an inclined portion that gradually decreases a volume space at the end of the vortex chamber toward the rotation direction of the fin is provided at the end of the vortex chamber on the discharge port side.

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