JPH02305399A - Fan device - Google Patents

Abstract

PURPOSE:To prevent resonance of an axial impeller with a motor for driving it by having characteristic frequency of the axial impeller in a fan device moved further to a high frequency area, therefore to decrease the torque fluctuation and vibration of the motor. CONSTITUTION:For an oil fan heater 1 with a fan device 3, an axial impeller 7 is arranged on the upstream side of an air duct 2, and a burning cylinder 5 for covering a burning room 4 and a blow-out port 6 are arranged on the downstream side. In this case, the fan device 3 is made up with the axial impeller 7, a motor 8 for driving it, a circuit 10 which controls the number of voltage waveform at a power supply 9 for the motor 8 to control input power to the motor 8. The axial impeller 7 has a blade 11 provided with recessed and protruded grooves 12 in a concentric manner to the outer periphery of the axial impeller 7. It is thus possible to move the characteristic frequency of the axial impeller 7 further to a high-frequency area, restrain the vibration of the motor 8 and prevent the resonance thereof with the axial impeller 7.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to the prevention of abnormal noise in a blower device that controls the number of revolutions.

BACKGROUND OF THE INVENTION An example in which a conventional blower device is used in an oil hot air fan will be described. As shown in FIG. 6, the oil hot air fan 21 includes a blower device 23 on the upstream side of a blower duct 22, and a combustion section 2 on the downstream side.
It consisted of a combustion tube 25 covering the combustion chamber 4 and an air outlet 26. Here, 13 is a multi-blade blower that sends primary air for combustion, 34 is a secondary air blowing passage, and 37 is a flame. The blower device consisted of an axial flow impeller 27, a motor 28, and a phase control circuit 20 for controlling the rotation speed of the motor.

The phase control circuit is a method of controlling input power to the motor by cutting off part of the voltage waveform of the motor drive power source 9 for a predetermined period of time. FIG. 7 shows the voltage waveform.

Problems to be Solved by the Invention In such a configuration, the phase control of the conventional air blower results in a frequency spectrum as shown in FIG. 8, which contains a very large number of high-order components of the fundamental frequency. The motor is subject to torque fluctuations due to this high-order component, and large vibrations are generated even at a high-order component, that is, a frequency of several hundred Hz.

On the other hand, the natural frequency of an impeller usually occurs in a band of 100 to several hundred sevens, and a typical vibration mode has a mode shape as shown in FIG. Figure 9 is a diagram of vibration holography, where the white part 38 extending from the center to the wing is the part with zero displacement.
Black and white stripes 39 on both sides represent vibrational displacement.

That is, it can be seen that this axial flow impeller is in a mode in which the blade surface is divided into four parts and vibrates. The frequency of this mode can be determined from the resonance peak shown in FIG. 10 through other experiments.

When the natural vibration of the impeller matches the high-order component vibration of the motor due to phase control, a resonance phenomenon occurs in which the blades vibrate greatly, resulting in the generation of extremely loud noise. Furthermore, in the oil hot air fan, the air blown from the axial impeller is also used as secondary air for combustion, so the sound generated by resonance is further amplified when it hits the flame, and it also reverberates inside the fan duct 22. In addition to the louder noise, combustion characteristics deteriorated due to the turbulence of the flame, resulting in an increase in CO and NOx in the exhaust gas, making the user uncomfortable.

The present invention solves these conventional problems by providing uneven grooves on the blades to increase the rigidity of the impeller, moving the natural frequency to a higher frequency band, and changing the motor drive method to the wavenumber of the power frequency. By using wave number control to control high-order torque vibrations, motor vibrations are reduced, preventing the generation of resonance noise in the blower, and preventing secondary problems such as deterioration of combustion characteristics. It is intended to.

Means for Solving the Problems In order to solve the above problems, the present invention includes an axial flow impeller, its motor, and a wave number of a voltage waveform of a power source that drives the motor to control input power to the motor. The blade of the impeller is provided with a plurality of uneven grooves concentrically with the outer periphery of the impeller.

Effect The present invention has the above configuration, which allows the natural frequency of the impeller to move to a higher frequency range, reduces motor torque fluctuation, suppresses motor vibration, and reduces the force that causes the impeller to vibrate. , it is possible to prevent resonance from occurring with the natural vibration of the impeller that has moved to a high frequency range.

EXAMPLE Hereinafter, an example of the air blower of the present invention will be described using an oil hot air fan.

As shown in FIG. 1, an oil hot air fan 1 using a blower device 3 of the present invention is provided with an axial impeller 7 on the upstream side of a blower duct 2, and a combustion tube that covers a combustion section 4 on the downstream side of the duct. 5 and an air outlet 6. As shown in FIG. 2, the blower device includes an axial impeller 7, a motor 8, and a wave number control circuit 10 that controls the wave number of a voltage waveform of a power source 9 that drives the motor to control the input power to the motor. The blades 11 of the axial impeller are provided with a plurality of grooves 12 concentrically with the outer periphery of the axial impeller. Figure 3 shows a wave number control circuit diagram. Here, 13 is a multi-blade blower that blows primary air for combustion, 14 is a secondary air blowing passage, 17 is a flame, 15 is a rotation speed sensor, and 16 is a voltage ON 10 F
It is a semiconductor element that performs F.

In such a configuration, by controlling the motor in wave numbers, the input voltage waveform to the motor becomes as shown in FIG. 4, and its frequency components become as shown in FIG. 5. As can be seen from FIG. 5, the wave number controlled voltage waveform has the advantage of containing almost no higher-order components of the fundamental frequency. The waveform in Figure 4 is slightly distorted, but if it is cut correctly at the zero-crossing point, the high frequency components will be further reduced. Due to this feature, the motor only oscillates at 2f at the fundamental frequency f, and higher-order high-frequency vibrations are significantly reduced.

On the other hand, the multi-blade of an axial flow impeller has multiple concave and convex grooves concentric with the outer circumference of the axial flow impeller, which greatly increases the rigidity of the blade and significantly shifts the natural frequency to a high frequency range. Become. The uneven groove 12 has smooth unevenness and does not need to be deep. A slight waviness is sufficient, but the greater the number of grooves, the stronger the rigidity. Furthermore, it is well known that if a damping steel plate is used as the impeller material, vibrations can be suppressed without the need for uneven grooves.

Therefore, vibration is also reduced by wave number control, and the natural frequency of the axial flow impeller is also shifted to a high frequency range, making it possible to completely prevent the resonance phenomenon that occurs when the vibration of the motor and the natural frequency of the blades match. Furthermore, since resonance noise is no longer generated, the flame is stably combusted by the air blown from the axial flow impeller, which reduces the amplification of peculiar sounds and the reduction of CO and NOx in exhaust gas.
It also prevents the concentration from increasing, making it comfortable and safe to use as a heater.

Moreover, the uneven grooves of the impeller are arranged in the circumferential direction and have the effect of smoothly guiding the flow of wind guided by the blades along the blades, thereby improving the blowing performance of the blower.

Effects of the Invention As described above, the blower of the present invention can move the natural frequency of the axial impeller to a higher frequency range, reduce motor torque fluctuations, suppress remoter vibration, and improve the axial flow impeller's natural frequency to a higher frequency range. Since the force that causes the impeller to vibrate is reduced, it is possible to prevent resonance from occurring with the natural vibration of the axial flow impeller that has moved to a high frequency range. In addition, the uneven grooves provided on the axial impeller can guide the wind flow along the blades, improving the air blowing performance. It is also possible to prevent future problems.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view of an oil hot air fan using an air blower according to an embodiment of the present invention, Fig. 2 is a side sectional view of the air blower, and Fig. 3 is a control circuit block diagram of the air blower. Figure 4 is a wave number control drive voltage waveform diagram of the same blower, Figure 5 is a frequency spectrum diagram of the drive voltage waveform of the same blower, Figure 6 is a side sectional view of an oil hot air fan using a conventional blower, FIG. 7 is a phase angle control drive voltage waveform diagram, FIG. 8 is a frequency spectrum diagram, FIG. 9 is a resonance mode holography diagram of a conventional impeller, and FIG. 10 is a resonance characteristic diagram of the same impeller. 7... Axial flow impeller, 8-... Motor, 9...
...Power supply, 10...Wave number control circuit, 11.
...Wing, 12...Irregular groove. Name of agent: Patent attorney Shigetaka Awano (1 person) N @7 Figure 0
40 (Wl-5 Goko) # Closed Fig. 8 Fig. 9 Fig. 10 Fig. 1 Supplement M liquid mark

Claims (1)

[Claims] An axial flow impeller and its motor are provided, and a wave number control circuit that controls the wave number of a voltage waveform of a power source that drives the motor to control the input power to the motor, and the blades of the impeller are A blower device with multiple grooves concentrically arranged around the outer circumference.