JPS60247099A - Centrifugal fan - Google Patents

Abstract

PURPOSE:To smooth the air-flow flowing into the casing thus to reduce the noise near the suction port by projecting only such portion as having high flow- in speed of air of a bellmouth suction port by predetermined length toward the outside of scroll casing. CONSTITUTION:When fixed to an upper member 4a, the suction member 10 is projecting by predetermined length into an inner/outer air changeover box 3. In the region A' having the highest flow-in speed of air to be sucked into the scroll casing 4, the projecting distance L1 at the portion M1 is the longest while L2 at the portion M2 is the shortest. The uper end of the suction port 10a of the suction member 10 is formed smoothly from the longest distance L1 to the shortest distance L2 along a circular locus to be discribed by the tip of an inner/outer air changeover damper 9. Consequently, the air-flow in the scroll casing 4 will be smooth resulting in reduction of noise in the vicinity of the suction port 10a.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a centrifugal blower used in automobile air conditioners and the like.

[Prior art]

2. Description of the Related Art In recent years, as the quality of automobiles has improved, there has been an increasing demand for keeping the noise inside the vehicle cabin as low as possible.

One of the major sources of noise is the noise generated by the in-vehicle unit of an automatic military air conditioner.

According to research conducted by the present inventor, 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.

A more detailed examination shows that in conventional centrifugal blowers, when air flows into the scroll case 2 from the suction port 2a by the centrifugal fan l, the length of the bell mouth part is short, as shown in Figures 4 and 5. As a result, the direction of the incoming airflow changes rapidly, creating turbulence in the airflow, which has been found to be the cause of noise. Especially the fourth
The inventor of the present invention has confirmed that in the area A shown in the figures and FIG. 5, the amount of intake air is large, that is, the inflow velocity is high, and therefore the noise in this area A is large.

[Problem that the invention seeks to solve]

Therefore, in view of the above-mentioned prior art, the present invention has been made in order to reduce the noise at the air intake port of the scroll casing by smoothing the flow of air at the air intake port of the scroll casing. be.

[Means to solve the problem]

In order to solve the above problems, the centrifugal blower of the present invention is a blower in which a centrifugal multi-blade fan is provided in a scroll casing for sucking air through a bellmouth-shaped inlet. A portion having a high inflow velocity is configured to protrude outward from the scroll casing by a predetermined length, and this protrusion and other portions of the suction port are connected by a smooth curve. shall be.

〔Example〕

The present invention will be explained in detail below with reference to embodiments shown in the drawings.

This embodiment is applied to a centrifugal blower for an automobile air conditioner. As shown in FIGS. 1 and 2, the resin-made interior/exterior switching box 3 of the automobile air conditioner is provided with an inside air inlet 3a and an outside air inlet 3b, and an inside air inlet 3a and an outside air inlet An internal/external air switching damper 9 is rotatably mounted on a shaft 8 so as to open and close the internal/external air switching damper 3b. This internal/external air switching box 3 is integrally molded with a resin scroll casing 4 in which a centrifugal fan 5 is housed.

As shown in FIG. 1, the scroll casing 4 is divided into an upper member 4a and a lower member 4b in the vertical direction in the plane of the drawing at a dividing portion 40.
The interior and exterior air switching box 3 is divided into two parts.
is integrally molded with the upper member 4a. Further, an iron air suction member 10 is attached to the upper member 4a with a hissing member 11. This suction member 10 is opened with a circular bellmouth-shaped suction port 10a, and the air sucked into the inside/outside air switching box 3 is passed through the bellmouth-shaped suction port 10a.
It is designed to be sucked into the scroll casing 4 through 0a.

When the suction member 10 is attached to the upper member 4a, it protrudes into the inside/outside air switching box 3 by a predetermined distance. In this case, the part of the air sucked into the scroll casing 4 that has the highest inflow velocity is indicated by A' in FIG.
The portion is the longest, and the M2 portion located opposite the M1 portion is the shortest. In FIG. 1, the protrusion distance of the M1 portion is indicated by Ll, and the protrusion distance of the M2 portion is indicated by L2. Further, the upper end of the suction port 10a of the suction member 1o is smoothly shaped from the longest protruding distance to the shortest distance L2 along the arcuate locus drawn by the tip of the internal/external air switching damper 9.

A centrifugal fan 5 is installed in the lower member 4b of the scroll casing 4, which is formed as described above and located below the upper member 4a. As shown in FIG. 1, the centrifugal fan 5 is composed of a plurality of blades 5a and a hollow truncated conical connecting portion 5b integrally formed with the blades 5a. The connecting portion 5b of the centrifugal fan 5 is attached to the output shaft 6a of the motor 6 by a known fixing technique such as screwing. The motor 5 is attached to the scroll casing 4 via a flange 7. Further, on the side of the centrifugal fan 5 of the scroll casing 4, there is a connection port 4 for blowing the air inside the scroll casing 4 to the downstream part.
c is provided.

This connection port 4c is connected to a ventilation duct provided with a heat exchanger (not shown).

The lower member 4b to which the centrifugal fan 5 is attached as described above and the upper member 4a to which the inside/outside air switching box 3 is installed are the second
As shown in the figure, the four locations of the divided portion 4o are pressed and fixed by the elastic force of the plate springs 50.

Next, the operation of the embodiment having the above configuration will be explained.

In FIG. 1, the outside air switching damper 9 is connected to the outside air inlet 3.
b is open, outside air introduced from the air inlet 3b passes through the bellmouth-shaped suction port 10a, is sucked into the scroll casing 4, and is blown downstream through the connection port 4b by the centrifugal fan 5. be done. Here, inlet 1
The wind speed distribution at 0a is made uniform as the air passes through loa. That is, in this embodiment, of the air flowing inside the scroll casing 4, the region A where the flow velocity is the highest is
' Since the suction port 10a in the part ' is protruded by a maximum of L1, the air flow changes rapidly as shown in Fig. 5, but now it is smoother as shown by the arrow S in Fig. 3. 1, the noise near this suction port 10a is reduced.

FIG. 6 is a frequency analysis diagram showing the results of noise measurements conducted by the present inventors, in which the horizontal axis shows the protrusion distance L1, and the vertical axis shows the reduced sound pressure level of the noise. The measurement is JIS-B8330r.
Using a test device compliant with the ``Blower Testing and Inspection Method'', the outer diameter of the fan 4 was D1-140 mm, and the air flow rate was 312 i/h.
The test was carried out under conditions of a blower total pressure of 28°, 2 mm, and 1 lq. As described above, the longer the protrusion distance L1 is, the more the noise is reduced, and when L2=10cm and L+=30wm, a noise reduction effect of about 2.3 dB can be obtained compared to a case where the protrusion length is 10m all around.

As described above, according to this embodiment, by increasing the protrusion distance only in the region A' where the air flow velocity is highest, almost the same noise reduction effect as when increasing the protrusion distance around the entire circumference of the inlet can be obtained. As a result, it is possible to reduce noise without increasing the size of the inside/outside air switching box, and this is extremely effective for devices such as automotive air conditioners that are subject to limited installation space.

Note that the present invention is not limited to the above-mentioned embodiments, and can be modified in various ways. For example, the protruding shape of the suction member can be changed to the tip of the internal/external air switching damper 9, as shown in FIG. The protrusion distance L2 at the center may be minimized and the protrusion distance L1 at both ends may be maximized along the arcuate trajectory drawn by
Depending on the installation state of the inside/outside air switching damper 9, it is also possible to set the entire area A' in FIG. 2 to the protruding distance L+.

Furthermore, although the suction member 10 is made of iron, it may also be made of resin, and in that case, it is desirable that it be integrally molded with the upper member 4a.

〔Effect of the invention〕

As described above, according to the present invention, only the portion of the hellmouth-shaped inlet that sucks air into the scroll casing, where the air flow velocity is high, protrudes outward from the scroll casing by a predetermined length. This has the effect that the length of the air flowing into the scroll casing becomes smooth, and noise near the above-mentioned suction port can be reduced.

Therefore, compared to the case where the hellmouth-shaped inlet C protrudes over the entire circumference, the space in the air upstream side of the scroll casing can be effectively utilized.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an embodiment applied to the inside and outside air introduction part of an automobile air conditioner according to the present invention, a cross-sectional view taken along line I-1 in FIG. The figure is an enlarged sectional view of the main part of Fig. 1, Fig. 4 is a plan perspective view of a conventional scroll casing, Fig. 5 is a sectional view taken along line 13-B in Fig. 4, and Fig. 6 shows the protrusion distance L1 of the suction port. FIG. 7 is a characteristic diagram showing the change in the noise level when the noise level is changed, and FIG. 7 is a sectional view showing another embodiment of the suction member of the present invention. 4...Scroll casing, 5...Centrifugal fan,
6...Motor, 10...Suction member, 10a...Hellmouth-shaped intake port, Ll...Maximum protrusion distance, L2...
・Minimum protrusion distance. Representative Patent Attorney Takashi Okabe Figure 1 Figure 2 C Figure 4 Figure 5 Figure 6 L4 (mm) Figure 7

Claims (1)

[Claims] In a blower provided with a centrifugal multi-blade fan that sucks air through a bellmouth-shaped suction port in a scroll casing, at least a portion of the bellmouth-shaped suction port with a high air inflow velocity is directed outward from the scroll casing. A centrifugal blower characterized in that the protruding portion is protruded by a predetermined length, and the protruding portion and other portions of the suction port are connected by a smooth curve.