JPS647833B2 - - 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 a piezoelectric 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 electrical vibrators such as piezoelectric vibrators.

For example, a device that injects an ultrasonic atomized particle array, which has been put into practical use in injection recording devices in recent years, has a configuration in which a piezoelectric vibrator is installed at one end of the liquid chamber and an orifice at the other end, and the piezoelectric vibrator vibrates. There is an atomizer that transmits the pressure change in the liquid chamber due to the liquid to an orifice through the liquid, and as a result, the atomized particles can be ejected from the orifice at a considerable scattering speed.

However, this atomizer is configured to transmit the pressure change in the liquid chamber due to the vibration of the vibrator to the orifice via the liquid, so when using a general liquid containing a large amount of dissolved air, the Cavitation bubbles are generated in the room, and a stable atomization operation cannot be maintained due to the bubbles. Therefore, in order to atomize ordinary liquids, dissolved air must be degassed, and when filling ink into a liquid chamber, an exhaust port is provided, pressurized ink is injected, and air in the liquid chamber is exhausted. This required a very elaborate filling operation in which the exhaust port was closed when the ink overflowed. Moreover, whether or not the liquid chamber is reliably filled with liquid is checked at the time when the ink is actually ejected and printed on the recording paper.

Another conventional example is shown in FIG. 1 is an atomizer using a piezoelectric element, 2 is a tank for storing liquid, 3 is a liquid supply pipe, 4 is a gas exhaust pipe,
5 is a fan that guides liquid through the exhaust pipe 4 in order to fill the atomizer with liquid, and 6 is a liquid detector provided in the middle of the exhaust pipe. The operation of this conventional example is to drive the atomizer 1 after the liquid detector 6 detects that the exhaust pipe is reliably filled with the liquid to be sprayed. Although this device can detect that the exhaust pipe is filled with liquid to a predetermined position, it cannot detect whether the liquid chamber of the atomizer is completely filled with liquid. In other words, large air bubbles or the like may be trapped inside the liquid chamber.

Purpose of the invention The present invention solves such conventional problems,
An object of the present invention is to provide an atomization device that continues an injection operation while a liquid to be ejected is reliably supplied into a pressurized chamber.

Structure of the Invention In order to achieve this object, the present invention includes a body including a pressurizing chamber filled with liquid, a supply section for supplying liquid to the pressurizing chamber, and a supply section facing the pressurizing chamber. an atomizer configured with a nozzle part having a nozzle provided therein, an electric vibrator that energizes the nozzle part and vibrates the nozzle; a drive part that drives the atomizer; and a drive part that drives the atomizer. Detects the oscillation frequency of
It is comprised of a frequency determination section that makes a determination, and a drive control section that controls the operation of the drive section of the atomizer based on the signal from the frequency determination section.

With this configuration, the drive signal frequency of the piezoelectric vibrator is detected, and the determining section determines whether the frequency is a predetermined frequency or not. As a result, it has the effect of stopping the operation of the atomizer drive section when the frequency is not a predetermined frequency.

DESCRIPTION OF EMBODIMENTS The configuration of an atomizer according to an embodiment of the present invention will be explained below with reference to FIG. Pressurized chamber 7 filled with liquid
The body 8 equipped with this is fixed to a mounting plate 10 with screws 9. The liquid enters the pressurizing chamber 7 through the supply pipe 11, and during the atomization operation, the gas discharge pipe 12 is filled halfway. Reference numeral 13 denotes a nozzle portion facing one side of the pressurizing chamber 7, and its outer periphery is joined to the body 8. A spherical protrusion 14 having a fine hole for ejecting droplets is formed at the center of the nozzle portion 13 . Furthermore, a ring-shaped piezoelectric element 15 is attached to the nozzle portion 13 . This piezoelectric element 15 is a piezoelectric ceramic polarized in the thickness direction, and has electrodes on the surface to be joined to the nozzle and on the opposite surface. 16 is a lead wire that transmits a drive signal to the piezoelectric element 15;
is soldered to one electrode surface of the electrode, and the other is connected to the body 8 with a screw 17. When the mechanical vibration of the piezoelectric element 15 is excited by the drive signal, the nozzle part 13 is also urged and vibrates, so that the liquid in the pressurizing chamber 7 is discharged as atomized particles 18 as a result.

Incidentally, the liquid to be supplied to the pressurizing chamber 7 may be filled halfway into the gas exhaust pipe 12 depending on the installation configuration of the atomizer, but as another method, usually the liquid is supplied to the pressurizing chamber 7 and the The inside of the pipe 12 is empty, and before entering the droplet ejection sequence, for example, the exhaust pipe 1
Negative pressure may be applied through 2 to fill the pressurized chamber 7 with liquid and at the same time draw the liquid to the middle of the exhaust pipe 12.

FIG. 3 is an electrical equivalent circuit that approximates the piezoelectric element 15, with 19 equivalent parallel capacitances C ₁ and 2
Series inductance of 0, 21, 22
It consists of Lo, capacitance Co, and resistance Ro.

FIG. 4 shows a current change a and a spray amount change b when a driving signal (for example, a sine wave) is applied to the piezoelectric element 15 of the atomizer with a varying frequency. I _F in a is the characteristic under load when the pressurized chamber 7 is filled with liquid, and I _E is the characteristic under no load when the pressurized chamber 7 is filled with liquid. ing. In the characteristics of I _F and I _E , respectively, the third
The series resonance of Lo20 and Co21 shown in the figure _{is 2,1}
appears as a current peak value at each frequency.
Electrical resonance point ₂ during liquid-filled loads
is at a frequency lower than electrical resonance point ₁ under no load. This is because liquid, which has a larger mass than gas, is applied as a vibration load to the piezoelectric element. That is, from the spray characteristics shown in FIG. 2B, a peak of the spray amount appears near the electrical resonance point ₂ , and the electrical resonance point is clearly different from that under no load.
Therefore, by detecting the frequency at which the electrical resonance point occurs, it is possible to determine whether or not the pressurizing chamber of the atomizer is filled with liquid as a load.

FIG. 5 shows an embodiment of the atomization device of the present invention. 15 is a piezoelectric element, and 23 is a drive section. This drive section includes an amplifier section 24 and a feedback section 25, and is of a self-excited oscillation type that utilizes the electrical characteristics of a piezoelectric element as part of the oscillation system. For example, there is a modified Colpitts type that is used in a region where the piezoelectric element exhibits inductance with respect to the driving frequency. 26 in the same figure
is a frequency determination unit that detects the oscillation frequency of the self-excited oscillation system and determines whether the frequency is a predetermined frequency or not. When this frequency determination section determines that the pressurized chamber of the atomizer is filled with liquid as a load, that is, when the oscillation frequency is ₂ as explained in FIG. Part 2
7 continues driving the piezoelectric element. However, when it is determined that there is no load in the pressurizing chamber, that is, when the oscillation frequency is ₁ instead of ₂ , the drive control section 27 stops the operation of the drive section. Through this operation, the drive unit operates and sprays when the pressurized chamber is reliably filled with liquid.

FIG. 6 shows another embodiment of the invention. Components with the same numbers as in FIG. 5 are components having the same functions. Reference numeral 28 denotes an oscillation section, which is driven by a separately excited oscillation method in this figure. In the case of this method, the drive frequency is not determined by the electrical characteristics of the piezoelectric element as in the self-excited type, so for example, the frequency of the transmitter is scanned to find the electrical resonance point, that is, the current peak point, and then The driving frequency is detected by the frequency detection section 26.
The frequency determination section 26 determines whether the detected frequency is a predetermined frequency or not. the result,
Whether or not to control the drive section is the same as the operation shown in FIG. 5.

By the way, the same applies to the systems shown in Figures 5 and 6, but if a large drive power is applied with no load in the pressurized chamber, the vibration amplitude of the piezoelectric element will become excessive and the atomizer structure will be damaged. Therefore, a value smaller than the driving power applied during normal operation is applied until it is determined by frequency determination whether the pressurizing chamber is filled with liquid or not. This results in
The presence or absence of a load can be determined without damaging the element.

Effects of the Invention As described above, the atomization device of the present invention provides the following effects.

Even if the driving means of the piezoelectric vibrator is self-excited,
Even if it is a separately excited type, it has a frequency determination section that detects the drive frequency and determines whether it is a predetermined frequency or not and controls the operation of the drive section. It is possible to reliably determine whether the fuel is filled or not, and the atomizer can be driven in an appropriate atomizing state.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional atomizer, Fig. 2 is a block diagram of an atomizer according to an embodiment of the present invention, and Fig. 3 is an electrical equivalent circuit diagram of an atomizer using a piezoelectric vibrator. , 4th
Figure a is a characteristic diagram of drive current versus frequency, b is a characteristic diagram of spray amount versus frequency, Figure 5 is a block diagram of the atomizer, and Figure 6 is a block diagram showing another embodiment of the atomizer. be. 7... Pressure chamber, 8... Body, 11... Supply section, 13... Nozzle section, 15... Piezoelectric vibrator, 2
3... Drive unit, 26... Frequency determination unit, 27...
Drive control section.

Claims (1)

[Claims] 1. A body equipped with a pressurized chamber filled with liquid;
A supply unit for supplying liquid to the pressurizing chamber, a nozzle unit having a nozzle facing the pressurizing chamber, and a piezoelectric vibrator that biases the nozzle unit to vibrate the nozzle. a drive unit that drives the atomizer; a frequency determination unit that detects and determines the oscillation frequency of the drive unit; and a drive control that controls the operation of the drive unit based on a signal from the frequency determination unit. Atomization device consisting of parts. 2. The drive control unit controls the atomizer driving power from the drive unit to a value smaller than that during steady atomization until the oscillation frequency is detected and determined by the frequency determination unit. Atomization device according to scope 1.