JPS5941785B2 - Ultrasonic atomizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for atomizing liquid by the action of ultrasonic waves, and more specifically, to an apparatus for improving the start-up characteristics of the apparatus and for stabilizing the atomizing operation.

Fig. 1 is a cross-sectional view showing the configuration of a conventional ultrasonic atomizer, in which 1 is an atomization chamber, 2 is a liquid tank, 3 is a constant level gauge, 4 is a liquid, 5 is a liquid level, and 6 is a nozzle. 6a is a through hole, T is an electrostrictive ultrasonic transducer, 8 is a driving power source for driving the ultrasonic transducer □, 9 is a liquid ejected from the guide member 6,
10 is a fog, 11 is a blower fan, 12 is a conveying air, and 13 is a conveying pipe.

In FIG.
is supplied, the liquid level 5 is set using the constant liquid level gauge 3 so that the upper end of the guide member 6 protrudes from the liquid level 5, and high frequency power is supplied from the drive power source 8 to the ultrasonic transducer T. Child T
Ultrasonic waves are emitted from the air, liquid 9 is formed by the action of the ultrasonic waves, and mist 10 is generated. The mist 10 is transported to the outside from the transport pipe 13 by the transport air 12 sent from the blower fan 11 . FIG. 2 is a block diagram showing the configuration of a conventional ultrasonic drive power source 8. The power source 8 includes a rectifier circuit 15 that rectifies the input from the AC power source 14, a constant voltage circuit 16, and a self-oscillation type transistor oscillation circuit meter T. The high frequency output of the drive power supply 8 increases or decreases according to the input current to the oscillation circuit meter T.

Figure 3a shows the temperature T of the output transistor of the oscillation circuit meter T.
FIG. 2B is a characteristic diagram showing the relationship between the input current I and the input current I, and FIG.

Now, if the power switch is turned on at time O, the temperature T of the output transistor of the oscillation circuit meter T at that time.

An input current 10 determined by is input. After the power switch is turned on, the temperature T of the output transistor gradually increases due to self-heating of the output transistor and approaches the steady state Ti, but since the input current 10 at the time of startup is small, the amount of heat generated by the output transistor is also small, so the output transistor does not operate. The time required for the temperature T to reach the steady value Ti becomes longer. As the operating temperature T of the output transistor increases, the constants of the transistor change and the operating point changes, so the input current I has an operating concentration T of T. As it approaches the steady value Ti, it increases from 10 to the steady value T. Since the amount of atomization Q is proportional to the input to the ultrasonic transducer T, there is a drawback that the time required for the amount of atomization Q to reach the steady value Q is also longer. In addition, when the operating temperature of an output transistor increases, the collector current generally increases, and with constant voltage drive, the internal power consumption increases, so the operating temperature further rises, and if the junction temperature of the output transistor exceeds a certain temperature, thermal damage will occur. leading to. For this reason, temperature compensation is generally performed using a nonlinear element, but it is difficult to compensate completely. Now, if some disturbance causes the operating temperature T to rise from T1 to T2 at time 1, the output current 1 will increase from 1 to 2, and the operating temperature of the transistor will also rise, so it will continue to rise until it returns to the original steady state. This takes time, and during this time the output current becomes unstable.

Accordingly, the atomization amount Q also changes from Q1 to Q2 and becomes unstable. As described above, the conventional ultrasonic atomizer has (a) a long rise time until it reaches a steady state;

(b) The amount of atomization tends to fluctuate depending on the ambient temperature and is unstable. (c) There is a risk that the output transistor in the drive power supply will be thermally destroyed.

There were drawbacks such as:

This invention was made to eliminate the drawbacks of the conventional device described above, and by configuring the oscillation circuit that supplies high-frequency drive power to the ultrasonic transducer to be driven with a constant current, the drawbacks of the conventional device described above are eliminated. This is what we are trying to achieve.

FIG. 4 is a block diagram of an embodiment of the drive power supply for the ultrasonic transducer according to the present invention, in which 18 is a constant current circuit, 19 (limits the voltage applied to the output transistor to below the rated voltage of the output transistor), and 18 is a constant current circuit; A voltage limiting circuit drives the oscillation circuit 17 at a constant current below the rated voltage of the output transistor.

Figure 5 1 is a special diagram of the ultrasonic atomization device according to the present invention, and Figure a is a special diagram showing the relationship between the operating temperature T of the output transistor of the oscillation circuit and the output voltage V of the oscillation circuit. , same figure b
5 is a special chart showing changes in the atomization amount Q corresponding to the changes shown in FIG. 5a.

In FIG. 3, if the power switch is turned on at time 0, the input current 1 is changed to 1 by the constant current circuit 18.
Therefore, the operating temperature of the output transistor T
until reaching the steady state T1, the input voltage V increases from the steady state V to the higher V.

It gradually changes to approach V. Input voltage V at this time. The value of is limited by the function of the voltage limiting circuit 19 to a value that does not damage the output transistor and the ultrasonic transducer 7. In this way, at the time of startup, the power input to the output transistor increases, so the time until the steady temperature T1 is reached is shortened, and therefore the time until the atomization amount Q settles to the steady value Q1 is shortened. . Now, due to some disturbance, the operating temperature T of the output transistor becomes T,
Assuming that the input current 1 increases from T2 to
, to V2, and the input power to the output transistor decreases.

Therefore, the operating temperature T of the output transistor quickly returns from T2 to the original T1. When the operating temperature of the output transistor decreases from T1, the operation is reversed, and in this case as well, it quickly returns to T1. In this case, the amount of atomization Q also changes as the input voltage V changes, but the amount of change is smaller than in the case of a conventional constant voltage drive power supply, and the time required to return to the original state is also shorter. Become. Furthermore, since the driving power source 1 operates at a constant current, thermal runaway of the output transistors is suppressed and thermal damage is prevented.

In the embodiment described above, the constant current drive power supply is driven by the constant current 1 drive circuit 18, the voltage control circuit 19, and the constant current output through these circuits, and the oscillation circuit 17 outputs high frequency power. Although a configuration including the above is shown, the present invention is not limited to this example, and is characterized by a configuration in which the output transistor of the high-frequency power source that drives one ultrasonic transducer is driven by a constant current circuit. The circuit can be constructed as appropriate using known techniques.

The atomization device according to the present invention can be widely applied to devices that atomize liquid by the action of ultrasonic waves, and can be used, for example, in kerosene atomization devices in oil burners, humidifiers in air conditioners, etc. .

In this invention, the output transistor that outputs the driving high-frequency power of the ultrasonic transducer is driven by a constant current output power source, so that the amount of atomization rises quickly until it reaches a steady value, and the amount of atomization is reduced. The ultrasonic atomization device can be made stable, and the atomization device can have great practical advantages, such as not causing thermal damage to the output transistor.

[Brief explanation of drawings]

Figure 1 is a sectional view showing the configuration of a conventional ultrasonic atomizer, Figure 2 is a block diagram showing the configuration of a conventional single drive power source, and Figure 3 is a block diagram showing the configuration of a conventional ultrasonic atomizer.
Figure a is a special case diagram showing the relationship between the temperature and output current of the output transistor of one drive power supply, Figure 3 b is a special discharge diagram of the change in atomization amount corresponding to Figure 3 a, and Figure 4 is a special diagram of the present invention. FIG. 5a is a block diagram of an embodiment of the drive power supply according to the invention, and FIG.
(This is a special chart of changes in the amount of atomization corresponding to FIG. 5a.

Claims (1)

[Claims] 1 In a device configured to input high frequency power to an electrostrictive ultrasonic transducer and emit ultrasonic waves emitted by the ultrasonic transducer into the liquid to atomize the liquid. An ultrasonic atomization device characterized in that the transistor that outputs the high-frequency power is driven by a constant current power source whose output voltage is limited so as not to exceed a predetermined value.