JPH0341120Y2 - - Google Patents

Description

[Detailed explanation of the idea]

[Industrial Application Field] The present invention relates to a centrifugal blower used in automobile air conditioners, etc., and particularly to a centrifugal blower used with an inside/outside air switching box. [Description of Prior Art] In recent years, as the quality of vehicles has become higher, there has been an increasing demand for suppressing the noise inside the vehicle cabin as low as possible. One of the loudest types of noise is the noise generated by the interior unit of an automobile air conditioner. According to research conducted by the inventors of the present invention, it has been found that the noise radiated from the inlet of the centrifugal blower is the largest in the noise generated by the vehicle interior unit. When examined in more detail, in the conventional centrifugal blower, the centrifugal fan 101 causes the suction port 102a to
As shown in FIG. 1, when air flows into the scroll casing 102 from
It was found that a non-uniform wind speed distribution occurred in a, and this was the cause of the noise. That is, when the centrifugal fan 101 rotates at high speed (at a large air volume), the suction port 102
As shown in A of FIG. 1, the wind speed distribution at point a is biased toward the scroll casing connection port 102b, and when the centrifugal fan 101 rotates at low speed (low air volume).
In this case, as shown in FIG. 1B, the inlet 10
It turned out that it was concentrated in the center of 2a. That is, in an automotive air conditioner, the scroll casing of the centrifugal blower is arranged adjacent to the inside/outside air switching box, and the air introduced from the inside/outside air switching box is passed through the air passage in at least one of the cases of inside air introduction or outside air introduction. is bent toward the suction port 102a of the scroll casing 102. Therefore, with the bending of the air flow, the wind speed distribution becomes non-uniform, and this non-uniformity becomes particularly noticeable when the air volume is large, causing noise. [Problems to be solved by the invention] The present invention was devised based on the above experimental results, and even when the blower has a large air volume, it alleviates the unevenness of the wind speed distribution caused by the bending of the air flow. The purpose is to make air flow into the suction port of the scroll casing with the wind speed distribution as uniform as possible, thereby reducing noise. [Structure] In order to achieve the above object, the present invention disposes a noise reduction member between the inside/outside air switching box and the scroll casing. In particular, in the present invention, the noise reduction member is provided with a flat plate part forming the wall surface of the internal/external air switching box, and a cylindrical part having one end continuous with the flat plate part and the other end communicating with the suction port. Moreover, in the present invention, the inner diameter of the cylindrical portion is made substantially the same as the inner diameter of the suction port. It is assumed that one end of the cylindrical portion of the present invention does not face at least one of the inside air inlet and the outside air inlet. [Function] By employing the above configuration, the function of the cylindrical portion satisfactorily corrects the non-uniformity of the air velocity distribution when the air flow passes through the cylindrical portion. here,
For example, Japanese Utility Model Publication No. 45-13966 discloses an air passage with a tapered cross section to guide the air flow toward the blower, but such a tapered cross section does not increase the flow velocity. The contribution of making the connection velocity distribution uniform is small. For it,
In the present invention, by using a cylindrical portion, it is possible to satisfactorily achieve uniformity of the wind speed distribution as described above. Further, in the present invention, since one end of the cylindrical portion is continuous with the flat plate portion, the air flow toward the cylindrical portion is smoothly guided by the flat plate portion. Here, for example, JP-A-53-1309 shows a protruding cylindrical part, but when the cylindrical part is protruded in this way, the air flow is greatly bent at the end of the cylindrical part. This will end up causing turbulence in the airflow. Furthermore, in the present invention, the inner diameter of the cylindrical portion is the same as the inlet of the scroll casing, and
Since this suction port and the circumferential surface of the blade of the centrifugal fan are arranged almost opposite to each other, the air flow passing through the cylindrical part is directed toward the centrifugal fan without sudden expansion or contraction of the flow, Fan efficiency can be increased. Here, for example,
Publication No. 58000 shows a blower in which the circumferential surface of the centrifugal fan blades and the suction port do not face each other, but in this case, the air flow expands rapidly after passing through the suction port, resulting in a decrease in fan efficiency. will come. [Description of Examples] The present invention will be described below with reference to Examples shown in the drawings. This embodiment is applied to a centrifugal blower for an automobile air conditioner. As shown in FIG. 2, a resin internal/external air switching box 3 of an automobile air conditioner is provided with an internal air inlet 3a and an external air inlet 3b. Further, an inside/outside air switching damper 1 is rotatably mounted on a shaft 2 so as to open and close the inside air inlet 3a and the outside air inlet 3b. Further, on the downstream side of the inside/outside air switching box 3, as shown in FIG. 3, which is a view from arrow A in FIG. It is integrally molded with the box 3, and the peripheral portion of the circular hole 9a is formed into a smooth arc shape. This square flat plate part 9
On the downstream side of b, a cylindrical portion 9c having the same inner diameter _D1 as the circular hole 9a is integrally molded with the rectangular flat plate portion 9b. Here, the noise reduction member 9 is composed of the rectangular flat plate portion 9b and the cylindrical portion 9c. The inside/outside air switching box 3 configured as described above has a joint 3
It is attached to the resin scroll casing 4 by pressing f and 3g using well-known plate springs (not shown) or the like. scroll casing 4
is provided with an inlet 4a having the same inner diameter as the inner diameter of the cylindrical portion 9c.When attaching the inside/outside air switching box 3 to the scroll casing 4, the inlet 4a
In a, the tip of the cylindrical portion 9c of the noise reduction member 9 is
It is fixed with adhesive etc. without any gaps. Inlet port 4a
A centrifugal fan 5 made of resin is housed inside the scroll casing 4 at the lower end of the scroll casing 4 . As shown in FIG. 2, the centrifugal fan 5 is composed of a plurality of blades 5a and a truncated conical connecting portion 5b in an internal space integrally formed with the blades 5a. The connecting portion 5b of the centrifugal fan 5 connects to the output shaft 6 of the motor 6.
It is attached to a by a well-known fixing technique such as screwing. The motor 6 is connected via the flange 7 to
It is attached to the scroll casing 4 with screws 8 and the like. Further, a connection port 4b is provided on the side of the centrifugal fan 5 of the scroll casing 4 for blowing air inside the scroll casing 4 to a downstream part. This connection port 4b is connected to a ventilation duct provided with a heat exchanger (not shown). Next, the operation of the embodiment having the above configuration will be explained. In FIG. 2, when the inside/outside air switching damper 1 opens the inside air inlet 3a, the inside air inlet 3a
The more introduced internal air passes through the inside of the cylindrical portion 9c of the noise reduction member 9, is sucked into the scroll casing 4 from the suction port 4a, and is blown downstream from the connection port 4b by the centrifugal fan 5. Here, the wind speed distribution at the suction port 4a is such that the air is
When passing through c, it is homogenized. That is, when the centrifugal fan 5 rotates at high speed (at a large air volume), the wind speed distribution at the suction port 4a is as shown in C in FIG.
As compared with the conventional method shown in A of FIG. 1, a uniform product can be obtained so that the particles are concentrated at the center. In addition, when the centrifugal fan 5 is rotating at low speed (when the air volume is small),
A more uniform wind speed distribution as shown in D in FIG. 2 can be obtained compared to the conventional one shown in B in FIG. 1. As described above, as a result of the uniformity of the wind velocity distribution at the suction port 4a, the noise at the suction port 4a can be significantly reduced. In the above embodiment, the noise reduction member 9 is integrally molded with the internal/external air switching box 3, but it may be integrally molded with the inlet 4a of the scroll casing 4, or it may be manufactured as a separate part and It may be fixed to at least one of the air switching boxes 3 by adhesive or mechanical means. Further, the material of the noise reduction member 9 is not limited to resin, and metal may be used. Next, another embodiment of the present invention will be described. In the embodiment shown in FIG. 2, as shown in FIG. 5, a noise reduction member 10 made of coal tar-containing urethane foam having a cylindrical through hole 10a having the same inner diameter as the inlet 4a is attached to the scroll casing 4 inside the internal/external air switching box 3. It is characterized by being affixed to the top surface of the board with an adhesive. At this time, the side surface of the inside/outside air switching box 3 of the noise reduction member 10 functions as the flat plate part 9b in the embodiment shown in FIG. 2, and its cylindrical through hole 1
0a is 9c of the cylindrical portion in the embodiment shown in the second figure.
functions. Therefore, the inner diameter of the through hole 10a substantially matches the inner diameter of the suction port 4a. Note that the other configurations are the same as those of the first embodiment shown in FIG. 2, so explanations will be omitted. The coal tar-containing urethane foam forming the noise reduction member 10 of this embodiment has a sound absorbing effect. Therefore, when the intake air passes through the through hole 10a, the wind speed distribution is made uniform and part of the noise is absorbed, so that the air blower is even louder than the centrifugal blower of the first embodiment shown in FIG. A noise reduction effect can be obtained. Next, a comparative example of the present invention will be explained. In this comparative example, as shown in FIG.
It is characterized by being provided in a. In this case, the cylindrical portion 11 may be integrally molded with the resin scroll casing 4, or may be separate from the scroll casing 4 and fixed to the scroll casing 4 with an adhesive or the like. The rest of the configuration is the same as that of the first embodiment, so a description thereof will be omitted. In this comparative example as well, as in the first and second embodiments of the present invention, when the intake air passes inside the cylindrical portion 11, the wind speed distribution is made uniform, so noise can be reduced. . However, in this case, since there is no flat plate part 9b as shown in the first embodiment, a part of the air introduced into the inside/outside air switching box is transmitted between the cylindrical noise member 11 and the inner wall of the inside/outside air switching box 3. After going around the recess 12 formed in the cylindrical noise reduction member 11 , it is introduced into the cylindrical noise reduction member 11 . Therefore,
The noise reduction effect is inferior to that of the centrifugal blower according to the first embodiment of the present invention. Next, the experimental results of this example conducted by the present inventors will be explained. First, the experimental results of the first example will be explained. In FIG. 4, the horizontal axis represents the air volume, and the vertical axis represents the noise level reduction effect, with the noise level of the conventional centrifugal blower shown in FIG. 1 being zero. In addition, in the experiment, the inner diameter of the cylindrical part 9c of the noise reduction member was set to D ₁ = 120
mm, the height of the cylindrical portion 9c is H ₁ = 10 mm, and H ₁ = 20
Centrifugal fan 5 with external diameter 140 mm for each mm
I did it using . In addition, the broken line a in Figure 4 is H ₁
The solid line b shows the case where H 1 =10 mm, and the solid line b shows the case where H ₁ =20 mm. As a result of the above experiment, as shown in Table 1, it was confirmed that the noise could be reduced.

[Table] As can be seen from Table 1, it was found that noise can be reduced more when H ₁ = 20 mm than when H ₁ = 10 mm. That is, the higher the height of the cylindrical portion 9c, the greater the noise reduction effect. However, once the height reaches a certain level, for example around 30 mm, the noise reduction effect is saturated, so there is no need to increase the height any higher. Further, in the above experiment, when the voltage applied to the motor 6 was set to 12V and the air volume of the present example and the conventional blower were investigated, it was found that the same air volume was obtained. Therefore, according to this embodiment, noise reduction was possible without reducing the capacity (air volume) of the centrifugal blower. Next, experimental results of the second example and the comparative example will be explained. In the experiment, in the second embodiment, the inner diameter D ₂ of the cylindrical through hole 10a of the noise reduction member 10 was 120 mm, and the height H ₂ was 20 mm.
In the comparative example, the inner diameter of the cylindrical part of the noise reduction part 11 is
Assuming that D ₃ = 120 mm and the height of the cylindrical portion H ₃ = 20 mm, each example has an outer diameter of 140 mm as in the first example.
The test was carried out using a 5 mm centrifugal fan. In FIG. 7, the horizontal axis represents the air volume, and the vertical axis represents the noise level reduction effect, with the noise level of the conventional centrifugal blower shown in FIG. 1 being zero. Further, the solid line c in the figure shows the case of the second example, and the broken line d shows the case of the comparative example. The experimental results shown in FIG. 4 above are summarized in Table 2 as follows.

[Effect of idea]

As mentioned above, the centrifugal blower of the present invention has a noise reduction member that has a flat plate part forming the wall of the inside/outside air switching box and a cylindrical part continuous to this flat part, so it is smoother to the scroll casing than the inside/outside air switching box. can direct air flow. As a result, the noise reduction effect of the cylindrical portion of the present invention can be exhibited even more effectively, and even when used as an automobile air conditioner, the interior unit can be made quieter.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the structure of a conventional centrifugal blower, Fig. 2 is a sectional view showing the structure of a centrifugal blower according to the first embodiment of the present invention, and Fig. 3 is a sectional view showing the structure of a centrifugal blower according to the first embodiment of the present invention. 4 is a characteristic diagram showing the noise level reduction effect of the first embodiment of the present invention; FIG. 5 is a sectional view showing the structure of the second embodiment of the present invention; FIG. 6 is a sectional view showing the structure of a comparative example of the present invention, and FIG. 7 is a characteristic diagram showing the difference in noise level reduction effect between the second embodiment of the present invention and the comparative example. 4...Scroll casing, 4a...Intake port, 5...Centrifugal fan, 9, 10...Noise reduction member.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) An inside/outside air switching box having an inside air inlet and an outside air inlet, and a device housed within the inside/outside air switching box that selectively opens and closes the inside air inlet and the outside air inlet. an internal/external air switching damper; a scroll casing that is arranged adjacent to the internal/external air switching box and has a circular intake port for sucking air from the internal/external air switching box and a connection port for blowing air to a downstream part; A plurality of blades are arranged on a circumference, and the inner peripheral surfaces of the blades arranged on the circumference are arranged in the scroll casing in close proximity to the inner surface of the casing so that the inner peripheral surfaces of the blades arranged on the circumference substantially face the inlet. a centrifugal fan disposed between the inside and outside air switching box and the scroll casing, and a flat plate part forming a wall surface of the inside and outside air switching box, one end of which is continuous with the flat plate part, and the inside air inlet and the scroll casing. a noise reduction member; a cylindrical portion having an inner diameter substantially the same as that of the inlet, the other end of which opens in the outside air switching box so as not to face at least one of the outside air inlet ports and communicates with the inlet; A centrifugal blower characterized by: (2) The centrifugal blower according to claim 1, wherein the noise reduction member is made of a sound absorbing material.