JP4123559B2 - Centrifugal blower - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a centrifugal blower used for an air conditioner for automobiles, and particularly relates to a technical field for reducing vibration noise of a centrifugal impeller.
[0002]
[Prior art]
Conventionally, as this type of centrifugal blower, for example, as disclosed in Japanese Patent Application Laid-Open No. 9-126193, a device that prevents backflow of air in the gap between the scroll casing and the centrifugal impeller is known. It has been. In this case, the bell mouth provided at the periphery of the air inlet at the top of the scroll casing in the region where the backflow phenomenon is likely to occur in the rotational direction of the centrifugal impeller from −60 ° to + 60 ° starting from the nose portion of the scroll casing. The inner diameter of the nose portion is reduced without reducing the blowing performance of the entire blower by covering the entire blade upper surface of the centrifugal impeller only in the above-described region where the backflow phenomenon is likely to occur. The blowing noise caused by the collision between the suction air flow and the reverse flow in the vicinity is reduced.
[0003]
Further, as a modification of the above-mentioned conventional one, a plurality of fixed wings are provided on the back surface of the bell mouth, and a small and stable vortex is forcibly generated in that portion to increase the pressure, thereby preventing backflow of air. There is also something like that.
[0004]
[Problems to be solved by the invention]
However, the conventional centrifugal blower has a problem that the angle of attack of each blade with respect to the air flow sucked into the centrifugal impeller becomes extremely large, and vibration noise in the centrifugal impeller tends to be generated.
[0005]
That is, as shown in FIG. 5, the velocity vector of the air flow sucked into the centrifugal impeller 1 is shown as a vector v0 in the fixed coordinate system, but the centrifugal impeller 1 is rotating at high speed. The velocity vectors of the blades 1b, 1b,... Are shown as a vector vb in the same figure in a fixed coordinate system. In the motion coordinate system based on each blade 1b, the relative velocity vector of the air flow is This is shown as a vector vr in FIG. In other words, the air flow enters the blades 1b obliquely from the front, and a large number of continuous vortices are generated behind the blades 1b, so that a considerable amount of energy given from the blades 1b. The part turns into vibration and noise.
[0006]
In addition, the centrifugal impeller must be operated at a higher speed in response to such a decrease in the air blowing efficiency, and as a result, there is a risk of a vicious circle in which vibration noise becomes excessively large.
[0007]
Furthermore, in the above conventional centrifugal blower, the shape of the bell mouth of the casing is not symmetrical with respect to the rotational axis of the impeller, so if the dimensions and shape are not designed and processed very precisely, the noise increases depending on the use conditions. There is a risk of inviting.
[0008]
The present invention has been made in view of such various points. The object of the present invention is to focus on the air flow sucked into the centrifugal impeller from the bell mouth and correct the flow to correct the centrifugal impeller. The purpose of this is to improve the ventilation efficiency and reduce the noise.
[0009]
[Means for Solving the Problems]
In order to achieve the above object, according to the solution of the present invention, a pre-swirl flow is given to the air flow sucked into the centrifugal impeller from the bell mouth, and the angle of attack of each blade of the centrifugal impeller with respect to the air flow is set. I tried to make it smaller than before.
[0010]
Specifically, in the invention described in claim 1, a large number of blades are arranged side by side in the circumferential direction, and a centrifugal impeller that blows out the sucked air radially outward, and the centrifugal impeller is housed inside. And a casing in which an air suction port is formed by a bell mouth on one end side in the axial direction of the rotating shaft of the centrifugal impeller and a spiral air discharge passage is formed around the centrifugal impeller. Assuming a centrifugal blower equipped. And a plurality of fixed blades for providing a pre-swirl flow in a direction in which the angle of attack of each blade is reduced with respect to the air flow sucked into the centrifugal impeller from the air suction port on the casing on the inner peripheral side of the centrifugal impeller Each of the plurality of fixed blades adjacent to the inner peripheral side of the blades so that the air flow flows radially outward along the fixed blades and flows between the blades of the centrifugal impeller. It is set as the structure arrange | positioned .
[0011]
According to this configuration, the air sucked into the casing via the bell mouth provided on one end side in the axial direction of the rotating shaft of the centrifugal impeller flows radially outward along the plurality of fixed blades. Since the centrifugal impeller is sucked after being given the pre-swirl flow, the angle of attack of the blades of the centrifugal impeller rotating at high speed with respect to the air flow is smaller than that in the prior art. As a result, the separation of the air flow behind each blade can be suppressed, and the generation of vortices can be reduced as compared with the prior art. Therefore, the vibration noise in the centrifugal impeller can be reduced.
[0012]
In addition, since the generation of vortices behind the blades is reduced, the air blowing efficiency is improved, so that the centrifugal impeller can be operated at a lower rotational speed than the conventional one. In addition to further reduction, energy saving is also achieved.
[0013]
In addition, the plurality of fixed blades only need to be able to give a pre-swirl flow to the air sucked into the centrifugal impeller, and do not rotate at a high speed like the centrifugal impeller. It does not have to be precise.
[0014]
According to a second aspect of the present invention, the plurality of fixed wings according to the first aspect of the present invention are provided on the bell mouth of the casing so as to extend in the rotation axis direction of the impeller. This makes it possible to dispose the plurality of fixed blades on the radially inner side of the centrifugal impeller with a simple structure without separately providing a new member for fixing the plurality of fixed blades to the casing side. .
[0015]
In a third aspect of the invention, the plurality of fixed wings in the second aspect of the invention are formed integrally with the bell mouth. As a result, the structure can be further simplified, and an increase in the number of parts and assembly man-hours can be prevented, thereby reducing the size and cost of the apparatus. This is a particularly effective merit when the present invention is applied to, for example, an automotive air conditioner.
[0016]
According to a fourth aspect of the present invention , on the same premise as the first aspect of the present invention , a reinforcing ring member for connecting a plurality of fixed wings provided on the bell mouth of the casing to each other at the end opposite to the bell mouth is provided. And Thus, the plurality of fixed wings can be reliably held at predetermined intervals by the reinforcing ring member. Further, since the reinforcing ring member is provided at the ends of the plurality of fixed wings, the influence on the air flow can be minimized.
[0017]
In the invention described in claim 5, the reinforcing ring member in the invention described in claim 4 is formed integrally with the plurality of fixed wings. This is, as possible out to prevent the increase in the number of components and assembly steps by the reinforcing ring member.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0019]
1 and 2 show a centrifugal blower A according to an embodiment in which the present invention is applied to a blower of an automotive air conditioner. This blower A is integrated with an upstream side of a blower duct of a vehicle air conditioner (not shown). Provided with an internal / external air switching mechanism.
[0020]
In both the drawings, reference numeral 1 denotes a sirocco-type centrifugal impeller, which has a large number of blades 1b, 1b extending in the vertical direction (hereinafter referred to as the vertical direction) in FIG. Are arranged at a constant pitch in the circumferential direction, and the upper ends of the blades 1b, 1b,... Are connected to each other by the reinforcing ring member 1c on the outer peripheral side and are held at equal intervals. The main plate 1a, the blades 1b, 1b,... And the reinforcing ring member 1c are integrally formed of a resin such as polypropylene. Reference numeral 2 denotes a scroll casing for accommodating the centrifugal impeller 1, which has a bell mouth 3 that forms an air suction port 2 a on the upper surface thereof, and in the casing 2 around the centrifugal impeller 1, A spiral air discharge passage 4 having an opening cross-sectional area that gradually increases from the nose portion 2b is formed so as to surround the centrifugal impeller 1.
[0021]
The scroll casing 2 is divided into upper and lower parts, and a perfect air inlet 2a is opened at a substantially central part in a plan view of the upper casing member 6, and the opening edge is tapered over the entire circumference. The bell mouth 3 is formed. On the back surface (lower surface) of the bell mouth 3, a large number of fixed wings 5a, 5a,... Extending in the vertical direction are arranged over the entire circumference at a constant pitch in the circumferential direction. The lower end portions of the blades 5a, 5a,... Are connected to each other by the reinforcing ring member 5b on the inner peripheral side and are held at equal intervals, so that a sirocco-type fixed impeller 5 is configured. Since the reinforcing ring member 5b is disposed at the lower ends of the fixed wings 5a, 5a,..., The air flow turbulence due to the reinforcing ring member 5b can be minimized. The fixed impeller 5 is integrally formed with a resin such as polypropylene together with the bell mouth 3 and the casing member 6.
[0022]
On the other hand, an electric motor 8 is fixed to the lower surface of the lower casing member 7, and an output shaft 8 a of the electric motor 8 is inserted into a through hole 7 a provided in the casing member 7 and protrudes upward. It is fastened to the main plate 1a of the impeller 1 in a rotating manner. Then, the centrifugal impeller 1 is rotationally driven in the clockwise direction in FIG. 1 by the electric motor 8, so that air sucked from above the scroll casing 2 through the bell mouth 3 is preliminarily moved by the fixed impeller 5. A swirl flow is given and sucked into the centrifugal impeller 1, kinetic energy is given by the centrifugal impeller 1, and the air is blown outward in the radial direction. The water head is converted into a pressure water head and sent out toward a blower duct (not shown).
[0023]
Here, as a characteristic part of the present invention, the flow of air given by the fixed impeller 5 and sucked into the centrifugal impeller 1 will be described with reference to FIG. Since the air flows radially outward along the fixed wings 5a, 5a,... Of the fixed impeller 5, its velocity vector changes along each fixed wing 5a as shown as a vector vp in the figure. When sucked into the centrifugal impeller 1, in the fixed coordinate system, the blades 1b, 1b,... Of the centrifugal impeller 1 are pushed from behind as indicated by a vector v0 in FIG.
[0024]
However, in reality, the centrifugal impeller 1 is rotating at a high speed, and the velocity vector of each blade 1b is shown as a vector vb in the fixed coordinate system in FIG. The relative velocity vector of the air flow in the motion coordinate system is along each blade 1b as shown by the vector vr in the figure, and this causes separation of the air flow behind each blade 1b. Is suppressed, and the generation of vortices is less than in the prior art.
[0025]
Further, as shown by a dotted line in FIG. 4 near the nose portion 2b of the scroll casing 2, even if the air flowing through the air discharge passage 4 tries to flow backward through the gap between the centrifugal impeller 1 and the back of the bell mouth 3, The air is pushed back on the outer peripheral surfaces of the fixed wings 5a, 5a,... To prevent backflow.
[0026]
Therefore, in this embodiment, a pre-swirl flow is given to the air sucked into the centrifugal impeller 1 by the plurality of fixed blades 5a, 5a, ... of the fixed impeller 5, and the blades 1b of the centrifugal impeller 1 against the air flow, By making the angle of attack of 1b,... Extremely small, generation of vortices behind each blade 1b can be suppressed, and vibration noise in the centrifugal impeller 1 can be reduced. Further, since the generation of vortices behind the blades 1b, 1b,... Is reduced, the air blowing efficiency is improved, so that the centrifugal impeller 1 can be operated at a lower rotational speed than in the prior art. In addition to further reducing vibration noise, energy saving is also achieved.
[0027]
Further, as in the past, the simple principle of blocking air that attempts to flow backward through the gap with the scroll casing 2 above the centrifugal impeller 1 by the fixed blades 5a, 5a,. The backflow of air can be prevented under a wide range of use conditions without much influence on the change of the airflow, that is, without requiring a very precise design, and this can also reduce vibration noise.
[0028]
In addition, since the fixed blades 5a, 5a,... Of the fixed impeller 5 are merely guide plates that give a pre-swirl flow to the air, a high dynamic balance like the centrifugal impeller 1 that rotates at high speed is not required, Dimensional tolerances and shot conditions during molding are not so strict. For this reason, it can be integrally formed with the upper casing member 6 together with the bell mouth 3, and accordingly, an increase in the size and cost of the apparatus due to an increase in the number of parts and the number of assembly steps can be prevented. This is a particularly great advantage when used as a blower for an automotive air conditioner in which a casing is generally integrally formed of resin.
[0029]
In addition, this invention is not limited to the said embodiment, Other various embodiment is included. For example, in the above embodiment, the fixed impeller 5 is constituted by a plurality of fixed wings provided on the bell mouth 3, 5a, 5a,... And the reinforcing ring member 5b, but the reinforcing ring member 5b is not necessarily provided. Good. Moreover, in the said embodiment, although the fixed impeller 5 is integrally molded with the casing member 6 with the bell mouth 3, it is not restricted to this, You may make it each shape | mold and assemble separately. Furthermore, it is also possible to apply the centrifugal blower A of the present invention to a device other than an automobile air conditioner.
[0030]
【The invention's effect】
As described above, according to the centrifugal blower of the invention of the first aspect, the pre-swirl flow is given to the air sucked into the centrifugal impeller by the plurality of fixed blades, and the blades of the centrifugal impeller with respect to the air flow are provided. Since the angle of attack was made smaller than before, the design and manufacture of the dimensions and shapes were not made very precise, and the generation of vortices behind the blades was reduced to reduce the vibration noise in the centrifugal impeller. be able to. Along with this, the centrifugal impeller is operated at a lower rotation, so that vibration noise can be further reduced and energy can be saved.
[0031]
According to invention of Claim 2, it can be set as a simple structure, without providing a new member separately by providing a some fixed wing | blade in the bellmouth of a casing.
[0032]
According to the third aspect of the present invention, the plurality of fixed wings are integrally formed with the bell mouth, thereby reducing the size and cost of the device. For example, it is particularly effective when applied to an automobile air conditioner. Benefits are gained.
[0033]
According to the fourth aspect of the invention, the plurality of fixed wings can be reliably held by the reinforcing ring member while minimizing the influence on the air flow.
[0034]
According to the invention of claim 5, wherein, as possible out to prevent the increase in the number of components and assembly steps by the reinforcing ring member.
[Brief description of the drawings]
FIG. 1 is a plan view showing a centrifugal blower A according to an embodiment of the present invention.
2 is a cross-sectional view taken along the line II-II in FIG.
FIG. 3 is an explanatory view showing the flow of air sucked into a centrifugal impeller through between fixed blades in a plan view.
FIG. 4 is a cross-sectional view showing a state in which the reverse flow of the air flow is blocked by the fixed wing.
FIG. 5 is a view corresponding to FIG. 3 showing an air flow in a conventional centrifugal blower.
[Explanation of symbols]
A Centrifugal blower X Rotational axis 1 of centrifugal impeller 1 Centrifugal impeller 1a Blade 2 Scroll casing 2a Air suction port 3 Bell mouth 4 Air discharge passage 5a Multiple fixed blades 5b of fixed impeller Reinforcing ring member

Claims (5)

Many blades are arranged side by side in the circumferential direction, and a centrifugal impeller that blows out the sucked air radially outward;
The centrifugal impeller is accommodated therein, and an air suction port is formed by a bell mouth on one end side in the axial direction of the rotation shaft of the centrifugal impeller, and spiral air is formed around the centrifugal impeller. In a centrifugal blower provided with a casing in which a discharge passage is formed,
The casing on the inner peripheral side of the centrifugal impeller is provided with a plurality of fixed blades that give a pre-swirl flow in a direction in which the angle of attack of each blade is reduced with respect to the air flow sucked into the centrifugal impeller from the air suction port. And
Each of the plurality of fixed blades is adjacent to the inner peripheral side of the blade so that the air flow flows radially outward along the fixed blade and flows between the blades of the centrifugal impeller. centrifugal blower, characterized in that it is arranged Te. In claim 1,
The centrifugal blower characterized in that the plurality of fixed blades are provided on a bell mouth of the casing so as to extend in the rotation axis direction of the impeller. In claim 2,
A centrifugal blower characterized in that a plurality of fixed wings are formed integrally with a bell mouth. Many blades are arranged side by side in the circumferential direction, and a centrifugal impeller that blows out the sucked air radially outward;
The centrifugal impeller is accommodated therein, and an air suction port is formed by a bell mouth on one end side in the axial direction of the rotation shaft of the centrifugal impeller, and spiral air is formed around the centrifugal impeller. In a centrifugal blower provided with a casing in which a discharge passage is formed,
The casing on the inner peripheral side of the centrifugal impeller is provided with a plurality of fixed blades that give a pre-swirl flow in a direction in which the angle of attack of each blade is reduced with respect to the air flow sucked into the centrifugal impeller from the air suction port. And
The plurality of fixed blades, with are provided in the casing of the bellmouth so as to extend in the direction of the rotation axis of the impeller, the reinforcing ring member thereof fixed wing linked together by the end opposite the said bell mouth A centrifugal blower characterized by being provided. In claim 4,
The reinforcing ring member is formed integrally with a plurality of fixed wings.

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