JPS581280B2 - centrifugal blower - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a centrifugal blower that has increased air blowing capacity, improved air blowing performance, and reduced noise caused by air blowing.

As shown in FIG. 1, a conventional centrifugal blower is composed of a fan 2 having a large number of blades 1, and a casing 6' that surrounds the fan 2 and is formed from a top plate 3', a back plate 4, and a side plate 5. ing.

Then, the casing 6' is provided with a rounded part having a small local pressure loss coefficient on its top plate 3' in order to maintain the pressure difference between the inside and outside of the casing 6', equalize the flow, and suppress local pressure loss. A nozzle-shaped suction opening 7' equal to the inner diameter of the blades of the fan 2 and a delivery outlet 8 are provided, and a pressure branch point tongue 9 is provided near the outlet 8 to prevent the delivered air from rolling back. It is formed.

The air is sucked in through the opening 7', enters the casing 6' as the fan 2 rotates, moves inside the casing 6' in the rotational direction of the fan 1, and is sent out through the discharge port 8.

However, when the air is delivered using this centrifugal blower,
The air inside the casing 6' is not all sent out to the outlet 8 according to one rotation of the fan 2, and in fact only 30% of the total air is sent out to the outlet 8.
A certain amount of air remains inside the casing 6'.

This is because the effect of the pressure branch point tongue 9 is not perfect and the air that is about to be sent out is entangled.

That is, as shown in Fig. 2A, the inside of the casing 6' is divided into eight quadrants (I), (■)..., (■),
If we observe the dynamic pressure (Pk) and static pressure (Ps) inside the casing 6' when air is blown by the centrifugal blower, we can see that immediately after the pressure branch point tongue 9 of the casing 6', as shown in the opening of Figure 2, The static pressure (Ps) becomes negative, and as a result, the air that is about to be sent out is rewound into the negative pressure region of the (■), (■), and (■) quadrants.

For this reason, the blowing performance of the centrifugal blower is reduced and large noise is generated.

Also, as in Japanese Utility Model Application Publication No. 50-27406, the center of the suction opening and the center of the fan are made eccentric, and one of the opening edges is positioned outward from the outer diameter line of the fan, thereby increasing the wind pressure. It was proposed to do so.

However, with this blower shape, the other edge of the opening is located inward from the inner diameter of the fan, so the air sucked in by the rotation of the fan is not guided smoothly through the opening, resulting in an additional drawback that noise increases. It was revealed that

The present invention has been made in view of these points, and one embodiment thereof will be described with reference to the drawings.

1. First, in the embodiment shown in FIGS. 3 and 4, the same symbols as in FIG.

That is, the diameter of the suction opening 7 is approximately equal to the outer diameter (Do) of the fan 2 in the negative pressure region ((I), (■), (■) quadrants) immediately after the pressure branch point tongue 9 of the casing 6. Then, the edge part 10 of this opening 7 is made to coincide with the outer diameter line 11 of the fan 2, and the other area is made substantially equal to the inner diameter (DI) of the fan 2, and the other edge part 12 of this opening 7 is made to match the outer diameter line 11 of the fan 2. Inner diameter wire 13
The suction opening 7 is shaped like an egg by bulging (5) in the negative pressure region so as to match the shape of the suction opening 7.

In FIG. 4 showing the dimensional relationship with the fan 2, this suction opening 7 is: ■0.9×D1/2<RL<1.1×DI/2■0.8
It is desirable to satisfy the following relationship: ×D0/2<M<1.5×D0/2■RS<RL (where RS is the radius of curvature of the bulging portion A of the opening 7).

Therefore, due to the suction opening 7 encompassing the negative pressure area immediately behind the tongue portion 9, no negative pressure area is generated inside the casing 7, and air is smoothly sent out from the discharge port 8.

Therefore, there is an advantage that the air blowing capacity becomes large, and the average suction wind velocity of the air becomes low, so that the noise is also reduced.

The effect will be shown below using one experimental example.

In a blower having a fan with D1=160 (mm) and Dc=188 (mm), RL=1. OXDI/2, M
If the suction opening 7 is formed so that = 1.0 x Do/2, the noise will be approximately 3 dB in the flow rate range of 200 to 400 m/H compared to the conventional one in which the suction opening 7' has a diameter of 160 mm. The flow rate decreases to about 0.25 to 0.0 in the rotational speed range of 500 to 1400 R, P, and M. Increased by 45 m3/H.

As described above, according to the centrifugal blower of the present invention, a casing that surrounds the fan is constructed from a top plate having a suction opening, a back plate, and a side plate, and a pressure branch point tongue is formed in this casing. A part of the edge of the suction opening is aligned with an outer diameter line of the fan in a negative pressure region immediately after the dot tongue;
In addition, since the other edge of the opening is made to coincide with the inner diameter line of the fan in other areas, the pressure in the negative pressure area increases, which increases the air blowing capacity and improves the air blowing performance. be effective.

[Brief explanation of the drawing]

Figure 1 shows a conventional centrifugal blower, where A is a front view, the opening in the figure is a cross-sectional view taken along I-■' in Figure A, and Figure 2 A is a front view showing the division of the casing in Figure 1 A. 3 is a front view showing an embodiment of the present invention, and FIG. 1... Blade, 2... Fan, 3... Top plate, 4... Back plate, 5... Side plate, 6... Casing, 7... Suction opening, 9... Tongue.

Claims (1)

[Claims] 1 Construct a casing that surrounds the fan from a top plate, a back plate, and a side surface that have a suction opening, and form a pressure branch point tongue in this casing, and in a negative pressure area immediately after this pressure branch point tongue. A centrifugal blower characterized in that a part of the edge of the suction opening is aligned with an outer diameter line of the fan, and another edge of the opening is aligned with an inner diameter line of the fan.