JPS6258786B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a liquid atomization device that atomizes liquid fuel such as kerosene or light oil, water, medicinal solution, recording liquid, etc. using an electric vibrator. .

Configurations of Conventional Examples and Their Problems Various types of liquid atomization devices have been proposed in the past, and many of them use electric vibrators such as piezoelectric elements.

For example, (1) a piezoelectric element is bolted or glued to a horn-shaped vibrator, the mechanical vibration amplitude of the piezoelectric element is amplified by the horn-shaped vibrator, and a liquid is supplied and dripped onto the amplitude amplifying surface at the tip of the horn. (2) A device that injects an array of ultrasonic atomized particles, which has been put into practical use in inkjet recording devices in recent years, and has a piezoelectric vibrator installed at one end of the liquid chamber. , with an orifice installed at the other end, the pressure increase in the liquid chamber due to the vibration of the piezoelectric vibrator is transmitted to the orifice via the liquid, and as a result, atomized particles can be sprayed from the orifice at a considerable scattering speed. There are atomization devices that can do this.

However, the conventional ultrasonic atomization device described above had various drawbacks.

The atomization device (1) requires high machining precision for the horn-shaped vibrator and a pump to supply the liquid, so it is expensive, and the method of supplying the liquid to the atomization surface is complicated. It was hot. Further, in order to obtain an atomization amount of 20 c.c./min, a considerably large power consumption of 5 to 10 watts is required, and the atomization ability is not sufficient.

The atomizing device (2) had the advantage of being simple in structure and stable in operation, as is clear from the fact that it is used in inkjet. Since the configuration transmits the information to the orifice via the liquid, when a typical liquid containing a large amount of dissolved air is used, cavitation bubbles will occur in the liquid chamber, and these bubbles will prevent stable atomization operation. It had the disadvantage of being unsustainable. Therefore, in order to atomize ordinary liquids, dissolved air must be degassed, which is extremely lacking in versatility.

By the way, the vibrating part as mentioned above is usually used at the resonance point as a piezoelectric element unit.
In an unloaded state where no liquid is supplied, the impedance of the piezoelectric element becomes very small. In the case of utilizing such resonance, protection of the drive stage has become a major issue, and depending on the configuration, loss in the drive element portion may become excessive, leading to destruction. Therefore, the structure has become complicated, such as by detecting the temperature rise of the drive section output stage element and stopping the drive when the temperature is abnormally high to prevent the element from being destroyed.

Purpose of the Invention The present invention eliminates the drawbacks of the conventional atomizing device, has a simple configuration, is compact, has low power consumption, and provides a misting device that prevents damage to the drive unit and vibrator under no-load conditions. The purpose is to provide a

Structure of the Invention The atomization device of the present invention includes a pressurizing chamber filled with a liquid for ejection, a supply section supplying the liquid to the pressurizing chamber, a discharge section discharging gas from the pressurizing chamber, and a pressurizing chamber filled with a liquid for ejection. a nozzle section provided to face a pressurizing chamber; an electric vibrator that energizes the nozzle section to vibrate the nozzle; a drive impedance detection section for the electric vibrator; and a drive impedance detection section. The electric vibrator includes a comparison section that compares a signal from the section with a predetermined value, and a drive section that controls a signal that drives the electric vibrator.

As described later, a predetermined power is applied to the electric vibrator to detect and compare the drive impedance,
Since the drive signal for ejecting droplets is applied after the pressurized chamber is reliably filled with liquid, there is no risk of damage to the output stage elements due to the application of large power under no-load conditions, resulting in a simple configuration. Safety measures will also be taken.

DESCRIPTION OF EMBODIMENTS Next, an embodiment of the present invention will be described based on FIG.

This figure is a sectional view showing the configuration of an oil hot air fan to which the atomization device of the present invention is applied.

A driving operation section 2 is provided on the top surface of a case 1 of the warm air fan, and operation signals are sent to a control section 3 that performs sequence control, electric vibrator drive control, and the like. The blower motor 4 is activated by the control unit 3 that receives the operation start signal. A blower fan 5 that supplies combustion air and a suction fan 6 that generates negative pressure, which will be described later, are coaxially connected to the blower motor 4.

Combustion air enters from the suction port 7 through the rotation of the blower fan 5, passes through the orifice portion 8, and enters the atomization chamber 9 and the secondary air chamber 10 as shown by the arrows.
is sent to the combustion chamber 11, exhaust pipe 12,
released as exhaust gas.

On the other hand, the kerosene fuel stored in tank 13 is
The liquid is sent to a leveler 14 that controls the liquid level to a substantially constant height A. When the operation is stopped, the liquid level in the fuel supply pipe 16 to the atomizing section 15 is also controlled to be the same height B as A in the figure. However, when the operation started, the blower motor 4
starts to rotate, negative pressure (for example,
−P ₁ =−10 mmAq) is generated, and a negative pressure difference (for example, −P ₂ =−30 mmAq) is generated between the high pressure side 18 and the negative pressure side 19 due to the rotation of the suction fan. Since this high pressure side 18 is connected to the downstream side of the orifice 8, the negative pressure side 19 is the sum of the above-mentioned negative pressures (-
P ₃ = -P ₁ + (-P ₂ ) = -40mmAq). The low pressure side 19 is a pipe 20 connected to the atomizing section 15, so that the liquid level B in the fuel supply pipe 16 is raised by the negative pressure _-P3 mentioned above, and kerosene is poured into the atomizing section 15. While filling, the liquid level is further raised and balanced at the height C in the pipe 20.

The above operation is performed during the pre-purge period of the blower fan 5, and the atomization section 15 completes preparation for the atomization operation during this period. In other words, it is filled with liquid fuel.

Next, the control section 3 activates the igniter 21 and energizes the atomization section 15 to eject atomized particles 22 into the atomization chamber 9 . The atomized particles are instantly ignited and combusted by the ignition power, and are mixed with secondary air to form a flame-holding flame 2 at the tip of the combustion tube 23.
4 and sustains combustion. Reference numeral 25 denotes a flame rod, which is a flame detection element, and monitors ignition, misfire, and combustion status. 26 is a convection fan for sending out hot air.

Next, the atomizing section 15, which is an embodiment of the present invention, will be explained in more detail with reference to the cross-sectional view of FIG.
Items with the same numbers as in FIG. 1 are equivalents having the same functions. The body 27 is fixed to the wall surface 28 of the atomization chamber with screws 29. A cylindrical pressurized chamber 30 is formed in the body 27 and communicates with the aforementioned fuel supply pipe 16 and gas discharge pipe 20. Reference numeral 31 denotes a nozzle portion facing one side of the pressurizing chamber 30, and its outer periphery is joined to the body 27. A spherical protrusion 32 having a fine hole for ejecting droplets is formed at the center of the nozzle portion 31 .

Furthermore, an annular electric vibrator, here a piezoelectric element 33, is bonded to the nozzle portion 31. This piezoelectric element 33 is made of piezoelectric ceramic that has been polarized in the thickness direction, and has an electrode surface on the joint surface with the nozzle portion 31 and on the opposite surface. A lead wire 34 transmits a drive signal to the piezoelectric element 33, one of which is soldered to one side of the piezoelectric element 33, and the other connected to the body 27 with a screw 35. When the mechanical vibration of the piezoelectric element 33 is excited by the drive signal, the nozzle part 31 is also energized and vibrates, and as a result, the liquid in the pressurizing chamber 30 is ejected as atomized particles.

By the way, in the above-mentioned case, the atomizing section 15 is filled with liquid fuel during the pre-purge period by the blower fan, and then the atomizing section is driven. In this embodiment, the filling of the liquid fuel into the atomization section 15 is described as follows.
This is performed using drive impedance detection, which will be described below.

FIG. 3 shows the characteristics of the current flowing through the piezoelectric element 33 constituting the atomizing section with respect to the driving frequency. The horizontal axis is the frequency, and the vertical axis is the current value. It can be seen that in the method of exciting the nozzle section 31 using the resonance of the piezoelectric element 33, the frequency r is the resonance point. At this time, even if the same voltage is applied to the piezoelectric element 33, the current value is as high as i r1 as shown by the solid line when there is no load and no liquid is filled in the pressurizing chamber 30, which means that the piezoelectric element ₃₃ cannot be driven as a vibrator unit. When the impedance is low and the pressurizing chamber 30 is loaded with liquid, the current value is as low as i _r2 as shown by the broken line. In other words, it can be seen that there is a large difference in the drive impedance of the vibrator unit depending on the presence or absence of a load. It is also understood that the current flowing to the piezoelectric element 33 can be converted into the drive impedance.

Next, FIG. 4 is a block diagram showing drive impedance detection and its signal processing.
The signal is transmitted to the piezoelectric element 33 via the output driver 37. Reference numeral 38 denotes a drive impedance detection section that detects the current flowing through the piezoelectric element 33 and detects the magnitude of the drive impedance as described above. This detection signal is sent to 39 comparison units, and 4
It is compared with the signal of the predetermined value setting section of 0, and the piezoelectric element 3
It is determined whether or not the drive impedance of No. 3 is equal to or greater than a predetermined value, and the determination signal is transmitted to the drive unit 41 including the oscillator 36 and the output driver 37 described above. In other words,
As shown in FIG. 3, the current value of the piezoelectric element 33 varies greatly depending on the presence or absence of liquid in the pressurizing chamber 30, so by detecting this, it can be determined whether or not the liquid is filled. It can be done. In particular, in the oil hot air blower shown in the example, the above determination can be made by applying a predetermined low voltage to the piezoelectric element 33 during the pre-purge period and detecting and comparing the current values according to the combustion sequence. Become.

In Figure 5, the timing chart for the oil hot air fan clarifies its operation. The horizontal axis of A to D represents the elapsed time, and the vertical axis represents the signal level. As shown in A, the blower motor drive signal is applied at t=t ₀ , and as shown in B, a predetermined low drive signal is applied to the piezoelectric element 33 at t=t ₁ . Here t
= The reason why we have timer elements from t ₀ to t ₁ is as follows.
This is because a margin time was expected until the liquid supply pipe and the pressurizing chamber 30 are sufficiently filled with liquid, but depending on the applied power, a configuration in which t ₀ =t ₁ is also possible. D is the drive impedance detection section 38
It represents a signal change from t=t ₁ to higher than the predetermined value setting part signal, and at t=t ₂ it becomes lower than the predetermined signal. This means that at t=t ₀ , the blower fan 5
It is shown that the specified drive impedance state is reached at t=t ₂ after the motor starts rotating. This t=
At _t2 , a determination signal is output from the comparator 39 as shown in C, and the signal processing route shown in FIG. , atomization is started.
This situation is shown in B and D.

In the example of FIG. 5B, the drive signal to the piezoelectric element 33 is switched to a predetermined value at t=t ₂ , but it is also possible to gradually increase the drive signal to a predetermined drive level. Further, a time limit element is provided from t= _t1 , and if the drive impedance does not exceed a predetermined value by the time the time limit exceeds the time limit, it is regarded as abnormal. Alternatively, it is also possible to consider countermeasures such as detecting that once the impedance exceeds a predetermined value and atomization has started, but an abnormality occurs midway through and the impedance suddenly drops, resulting in a blank firing state, and then stopping the drive of the piezoelectric element 33. It will be done.

Effects of the Invention According to the atomization device of the present invention, the following effects can be obtained.

In other words, a predetermined drive signal is applied after detecting that the pressurized chamber is filled with the liquid to be sprayed, for example, by the drive impedance converted from the current flowing to the vibrator, so that the pressurization chamber is filled with the liquid to be sprayed. It is possible to apply large power and protect the output drive unit and the element itself from destruction.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the configuration of an embodiment of the present invention applied to an oil hot air blower, Fig. 2 is a sectional view showing the configuration of the atomizing section, and Fig. 3 is the current and frequency of the electric vibrator. Figure 4 is a block configuration diagram showing the drive impedance detection and processing, Figure 5 is a diagram showing the characteristics of the same.
Figure A shows the temporal characteristics of the blower motor drive signal, Figure B shows the piezoelectric element drive signal, Figure C shows the comparison unit output signal, and Figure D shows the temporal characteristics of the drive impedance detection unit signal, respectively. 16... Supply section for supplying liquid, 20... Gas discharge section, 30... Pressurization chamber, 31... Nozzle section, 3
3...Piezoelectric element (electric vibrator), 38...Drive impedance detection section, 39...Comparison section, 41...
…Drive part.

Claims (1)

[Scope of Claims] 1. A pressurizing chamber filled with liquid, a supply section for supplying liquid to the pressurizing chamber, a discharge section for discharging gas from the pressurizing chamber, and the pressurizing chamber. a nozzle section provided so as to face the nozzle section, an electric vibrator that energizes and excites the nozzle section, a drive impedance detection section for the electric vibrator, and a signal from the drive impedance detection section that is set to a predetermined value. An atomizing device comprising: a comparison section for comparing the electric vibrator; and a drive section for controlling a drive signal to the electric vibrator. 2. The atomization device according to claim 1, wherein the atomization device is configured so that the current flowing to the electric vibrator is detected by a drive impedance detection section.