JPS6235923B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a blower for an air conditioner for an automobile, and more particularly to a soundproofing mechanism for noise propagating from a bellmouth portion to a passenger compartment.

As shown in Japanese Utility Model Application No. 53-82164, this type of blower has a problem in that noise propagates from the bell mouth of the blower into the passenger compartment. The same publication describes a system in which a sound insulating board is installed near the inside air intake port, and the sound insulating board reflects and collects noise toward the inside of the instrument panel, preventing the noise from directly propagating toward the occupants. There is. Although conventional technology can reduce the noise that propagates directly to the occupants, the noise that is reflected by the sound insulation board or instrument panel eventually reaches the occupants' ears. Furthermore, depending on the frequency of the noise, there is a problem in that the sound insulating plate or the instrument panel itself is vibrated by the noise radiated from the blower and resonates, producing a beat.

An object of the present invention is to suppress the noise emission itself from inside the blower in order to prevent the above-mentioned problem from occurring.

A feature of the present invention is that a sound absorbing material is attached to the inner wall of the internal/external air switching chamber of the blower to absorb and attenuate the noise radiated from the bell mouth in the internal/external air switching chamber, thereby reducing the noise radiated to the outside of the blower.

An embodiment of the present invention will be described below with reference to FIGS. 1 to 3. 1 is an impeller driven by a motor 2. The impeller 1 is housed in a spiral scroll composed of a motor-side scroll 3 and a fan-side scroll 4, which are separated during manufacture.The impeller 1 is rotated at a predetermined rotation speed. Therefore, the air sucked in from the bell mouth portion 5 located at the spiral center of the fan side scroll 4 is converted into the required wind performance. On the opposite side of the bell mouth 5 from the fan, that is, on the upstream side, there is an inside/outside air switching chamber 6 for separating outside air introduction and inside air introduction. Depending on the position of the inside air/outside air switching door 7, it is possible to select whether air is taken in through the inside air inlet 8 or through the inlet 9. A sound absorbing material 10 is bonded with an adhesive between the inner wall surface 11 of the inside/outside air switching chamber 6 on the bell mouth 5 side and a virtual surface formed by a trajectory drawn by the side surface of the inside/outside air switching door 7. has been done.

Furthermore, soft elastic materials 7a and 7b, such as sponges, are pasted on the front and back sides of the inside/outside air switching door 7.
Three wall surfaces of the inside/outside air switching chamber 6 located at the entrance of the bell mouth 5 are formed by the elastic material and the sound absorbing materials 10, 10.

Thus, when the switching door 7 is set to introduce inside air, the wind noise generated at the bell mouth is absorbed by the sound absorbing materials 10, 10 and the elastic material 7a, and propagates from the inside air inlet 8 into the passenger compartment. is prevented.

On the other hand, when the switching door 7 is set to introduce outside air, the sound from outside the vehicle that enters from the outside air inlet 9 is absorbed by the sound absorbing materials 10, 10 and the elastic body 7a before reaching the bell mouth 5. It is possible to suppress noise from outside the vehicle and propagation into the vehicle interior due to the wind blown into the vehicle interior from the blower.

Note that even without the elastic bodies 7a and 7b of the switching door 7, a considerable noise reduction effect can be achieved.

Furthermore, when cotton was used as the sound absorbing material, a better sound reduction effect was obtained than with foamed polystyrene or the like.

According to the present invention, there are the following effects on low noise. That is, for example, when the impeller 1 rotates when introducing inside air, the air taken in from the inside air introduction port 8 passes through the inside/outside air switching chamber 6, reaches the bell mouth 5, and passes from the inside of the impeller 1 through the blade section to the impeller. It exits from the outer periphery of 1, spirals inside the scroll, and is discharged. During this period, noise is generated due to air separation and turbulence, especially in the blades of the impeller 1, near the bell mouth 5, and inside the scroll. It radiates into the cabin, giving passengers an unpleasant feeling. However, this sound wave passes through the inside air/outside air switching chamber 6 as a conduit using air as a medium, but the sound absorbing material 10
The sound energy is attenuated by the viscosity of the air when passing through the sound absorbing material 10, and the area inside the sound absorbing material 10 is small with the inner wall surface 11 of the sound absorbing material 10 as a boundary, and the other passages are wide. When the emitted sound waves collide with the inner wall surface of the inside/outside air switching chamber 6, which serves as a reflector, and return, they interfere with newly incoming sound waves and have the effect of attenuating the sound energy, resulting in noise dissipated into the passenger compartment. becomes lower.

Figure 4 shows the frequency-noise level characteristics measured at a position 50 cm away from the inside air inlet toward the passenger compartment.The broken line shows the characteristics of a conventional system in which no sound-absorbing material is installed on the inside/outside air switching interior wall, and the solid line shows the main line. The characteristics of the device according to the invention are shown. As shown in Fig. 4, this effect has a significant damping effect in the range of 800 to 4000 Hz compared to when there is no sound absorbing material 10, and the damping effect is particularly large in the vicinity of 1000 to 3000 Hz, which is audible to humans. It can be seen that there is a 3 dB effect on the level (73 dB for the conventional device and 70 dB for the device of the present invention), which is very advantageous in reducing noise.

According to the present invention described above, the inside air/outside air switching chamber 6
By providing the sound absorbing material 10 on the inner wall surface 11 of
Noise reduction around 800-4000Hz was achieved.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an embodiment of the present invention;
Fig. 2 is a front view showing an embodiment of the present invention, Fig. 3 is a sectional view of an inside/outside air switching room showing an embodiment of the present invention, and Fig. 4 shows the noise frequency characteristics of the present invention and a conventional example. This is a drawing for comparison. 1... Impeller, 2... Motor, 3... Motor side scroll, 4... Fan side scroll, 5...
Bell mouth part, 6... Inside/outside air switching room, 7... Inside/outside air switching door, 8... Inside air inlet, 9... Outside air inlet, 10... Sound absorbing material, 11... Inner wall surface.

Claims (1)

[Scope of Claims] 1. An inside air inlet and an outside air inlet provided on the upstream side of the bell mouth, and provided inside the outside air switching door,
In a device having an inside/outside air switching door that opens and closes using a single point as a fulcrum and selectively switches, a sound absorbing material is attached to an area of the inner wall surface of the inside/outside air switching chamber that faces the side surface of the door. Features of a blower for automotive air conditioners. 2. The blower for an air conditioner for an automobile as set forth in claim 1, wherein the sound absorbing material is made of cotton. 3. A blower for an air conditioner for an automobile as set forth in claim 1, characterized in that an elastic body having a sound-absorbing effect is attached to at least one surface of the inside/outside air switching door.