JPH02188700A - Blower - Google Patents

Abstract

PURPOSE:To obtain a blower with a large wind quantity, a large wind pressure, and without reduction of wind quantity by dividing a path formed by a casing into two paths, locating a heater at least in one of the parallel paths, and raising the temperature in the path by the heater. CONSTITUTION:A cylindrical ring 8 is provided between moving vanes and a suction opening to divide the noise propagation path into the inside and outside of the ring 8. Film-shaped heaters 9 are provided on outside of the ring 8 and on inside of a housing 1. When the temperature in the outside path is raised, the phases of sound wave propagated in the outside path and sound wave propagated in the inside path are changed so that respective sound waves can be negated each other at the suction opening 6. With the generated heat quantity of the heaters 9, good results can be obtained in general operating conditions when the heat quantity can be changed by using a control device. Noise emitted from the suction opening 6 can thus, greatly be reduced.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a low-noise system that suppresses the propagation of noise generated inside the casing, such as fan wind noise, motor rotation noise, and casing internal resonance noise, to the outside. This relates to a blower.

[Conventional technology]

BACKGROUND ART In recent years, with the progress and miniaturization of office automation equipment and home appliances, small size and large air volume blowers such as fans and dryers for cooling electronic devices have become necessary.

Generally, as shown in FIG. 4, a dryer includes a motor 2 as a driving source, moving blades 3 rotatably driven by the motor 2, guide blades 4, and a heater 5 as a heat source in a hollow casing 1.
The air introduced into the casing 1 by the rotation of the rotor blades 3 from the suction port 6 provided at one location of the casing 1 is heated by the heater 5, and then the air is provided at another location of the casing l. Hot air is blown out from the lower part.

The basic performance of a dryer is to be small, lightweight, and secure a specified air volume.In order to meet these requirements, it has been considered to increase the rotational speed of the rotor blades 3 to increase the air volume. It will be done. However, a problem arises in that the noise increases as the rotational speed of the rotor blades 3 increases.

In order to avoid such problems, efforts are being made to ensure a specified air volume at low rotational speeds by improving the characteristics of the motor 2 and the shape of the rotor blades 3, but it is difficult to obtain satisfactory results. Not yet reached.

In the above explanation, a dryer is used as an example of a blower, but the blower is not limited to this, and noise can be a problem even if the blower is used in other devices such as pumps and air conditioners. There is.

[Problem to be solved by the invention]

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide a blower that does not cause a decrease in air volume, has a large air volume, large wind pressure, and has low noise.

[Means to solve the problem]

The air blower according to the present invention divides a flow path formed by a casing, arranges a heater in at least one of the parallel flow paths, and uses the heater to increase the temperature in the flow path, thereby increasing the sound waves passing through. The phase of the sound waves passing through other channels is controlled to be in opposite phase at the end of the casing,
This is to suppress the propagation of noise Q generated from the rotor blades or motor to the outside due to the interference of sound waves.

〔Basic principle〕

First, the basic principle of the present invention will be explained. Consider a flow path 10 as shown in FIG. Assume that noise is generated from a sound source 11 in the flow path 10, propagates from left to right in the flow path 10, and is radiated to the outside from the end 12 of the flow path 10. This wave path is divided into upper and lower halves as shown in FIG. 3, a film-shaped heater 13 is disposed in the upper passage, and by passing an electric current through the heater 13, the temperature of the air in the upper passage is increased.

Let the temperature of the air in the upper passage be T'C1 and the temperature in the lower passage be t"c (T> t). At this time, the sound speed of the sound wave propagating in the lower passage is C1. Letting the sound speed of a sound wave be C'', c and c'' are expressed by the following equation (1).

Therefore, the wavelengths λ and λ° of each path are respectively calculated by the following equation (2), where f is the frequency of the noise source.

λ = When the length of the passage where the heater is installed is L, the number of waves included in the length L (m) of the upper passage is N, and the number of waves included in the length of the lower passage is N. Each wave is calculated by the following equation (3), where N is the number of waves to be generated.

λ C ...−・−−−−・ (3) Difference in the number of waves in Nio's path When the number after the decimal point of n=N' -N is in the range of 0.25 to 0.75, 2 The waves that have passed through the two passages interfere at the outlet 12, cancel each other out, and reduce the noise radiated from the outlet. When the decimal point of n is 0.5, the waves passing through the two paths have a phase shift of 180"C at the exit, and the amount of noise reduction is maximized.

By applying the above basic principles to the blower,
According to the present invention, the noise radiated from inside the blower to the outside can be reduced without increasing the resistance of the flow path (that is, without reducing the air volume or wind pressure).

〔Example〕

This dryer, an embodiment of which is shown in FIG. 1, has the same structure as the conventional example shown in FIG. 4 above, except for the parts described below. By disposing a cylindrical ring 8 in the passage between the rotor blade 3 and the suction port 6, the noise propagation path is
Divide into two parts: inside and outside. By providing a film-shaped heater 9 on the outside of the ring 8 and the inside of the housing 1, the temperature of the outside passage is increased, thereby changing the phase of the sound wave propagating in the outside passage and the sound wave propagating inside, thereby increasing the suction. At mouth 6, they cancel each other out. The calorific value of the heater 9 may be set to heat the blown air to a temperature calculated based on the above basic principle, but if the calorific value can be changed using a control device, the The effect can be increased depending on the state of use. This greatly reduces the noise radiated from the suction port 6.

〔Effect of the invention〕

As described above, according to the blower of the present invention, unlike when using a device that diffracts sound waves, the flow path resistance does not increase, that is, the air volume hardly decreases, and
Noise leaking to the outside from the air inlet, the air outlet, or both can be reduced.

[Brief explanation of the drawing]

1 to 3 are cross-sectional views showing one embodiment of the present invention,
FIG. 4 is a sectional view showing a conventional example. 1... Casing, 2... Air outlet, 3... Moving blade,
4... Guide vane, 5... Heater, 6... Inlet, 7
...Air outlet, 8...Ring, 9...Heater. 1st 2nd WJ

Claims (1)

[Claims] (1) In a blower consisting of a motor, a rotor blade driven by the motor, and a casing that encases and fixes the motor and rotor blade, the flow path in front or behind the rotor blade is divided and arranged in parallel. at least one of the flow paths;
Alternatively, a blower that reduces the noise generated by the fan and motor and radiated to the outside of the casing by installing a heater on the wall of the flow path and controlling the temperature of the air within the flow path.