JPH03168373A - Piezoelectric pump control device - Google Patents

Abstract

PURPOSE:To always stably and accurately control the quantity of discharge by directly detecting the mechanical vibration of the moving part of a piezoelectric pump by means of a displacement sensor, and converting this into a d.c. voltage for comparing this with a reference voltage, and on the basis of the result of comparison, by controlling the intensity of the a.c. signal for driving a movable part. CONSTITUTION:The a.c. signal from an oscillator 18 passes through an electronic volume 34, and is amplified by an amplifier 19, and then this is converted into mechanical vibration by a piezoelectric actuator 12, and the displacement of the mechanical vibration is enlarged by an enlarging mechanism 16. The mechanism 16 vibrates a diaphragm 9 to forcibly feed the fluid from a piezoelectric pump 1. When the reactive pressure of a forcibly feeding device changes with the lapse of time, the vibration of the diaphragm 9 also changes. A change sensor 27 senses the vibration of a steel plate 28 being vibrated together with the diaphragm 9, and outputs an electric signal. This signal is detected by the detection part of a sensor driving part 30, and is compared with a reference voltage by means of a comparator 32. On the basis of the comparison result, the electronic volume 34 controls the intensity of the a.c. signal, thus, the amplitude of the mechanism 16, or the diaphragm 9 can be controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] Industrial Application Field The present invention relates to a control device for a pressurized pump that pumps liquid, gas, etc.

2. Description of the Related Art Conventionally, as shown in FIG.
- Separate check valves 6 are provided at each discharge port 5.

The pump 1 further includes a housing 7 as a fixed part and a diaphragm 9 as a movable part.

The drive unit 2 includes a drive circuit 11, a piezoelectric actuator l2 that converts an electric signal into a mechanical displacement, and a leaf spring 15 that connects a stiff rod-shaped lever l3, a spring l4, and a diaphragm 9. It is made up of.

The drive circuit 11 consists of an oscillator 18 and an amplifier 19, and an AC signal of a predetermined frequency generated by the oscillator 18 is sent to the amplifier 1.
9, the amplitude is amplified.

The discharge port 5 is provided with a flow rate sensor 20 and a pressure sensor 21, and their detection signals are provided to a control circuit 23. The control circuit 23 controls the oscillator 1 based on a predetermined calculation.
8 and the amplification factor of amplifier 19.

Problems to be Solved by the Invention In the conventional piezoelectric pump shown in FIG. 9, a predetermined frequency f. The oscillator 18 generates a signal, and the amplifier 19 amplifies this signal.

And the frequency f. An AC signal with a tH width V0 is applied to the enlarging mechanism 16 to drive the pump section 1 and pump the liquid.

Regarding the target flow rate Q0, the output signal 9 of the drive circuit 1l (
f,,V,), the oscillation frequency rllf. Amplitude voltage V. The vibrations (fl, Vl) converted into mechanical vibrations by the enlarging mechanism 16 cause the flow 1iQyu to be discharged at the time of startup.

Therefore, the flow rate Q. is constantly monitored by the flow rate sensor 20 and pressure sensor 21 and transmitted to the control circuit 23.

As time passes, the load on the discharge side increases, which weakens the frequency of the diaphragm 9 and reduces the flow rate to Q. →Q. It changes as 10△Ql.

The control circuit performs an operation to reduce this amount of change ΔQl, and controls the oscillator 18 and amplifier 19. As a result, the output signal is modified to (f., V.) −+ (flVl), and this signal H (fL Vl) becomes the target flow 1t
Q. It works to give.

However, since the oscillator l8 and amplifier 19 are conventionally controlled based on fluctuations in flow rate and fluid pressure, a delay (time lag) occurs until the correction signal of the diaphragm 9 is changed to (fLV1).

Therefore? When the amount of change in iflQ is ΔQ1, the output signal (f
l, Vl), but before the result appears, the ejection {!
! There are many cases where the amount of change becomes ΔQ2 due to changes in the ++ environment.

The output signal (fl, V
l) operates when the amount of change due to the delay is ΔQ2, making it impossible to accurately adjust the flow rate.

Particularly in the case of small-sized, high-performance piezoelectric pumps, there are cases where the flow rate becomes insufficient or, conversely, the flow rate becomes excessive, resulting in tg ffi becoming unstable.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a piezoelectric pump that can always stably and accurately control the amount of feed by immediately responding to disturbances caused by changes in the viscosity of the handled liquid or the conditions of the pumping destination. It is an object.

[Structure of the Invention] Means for Solving the Problems In the present invention, as shown in FIG.
A displacement sensor 27 of a detection section for detecting mechanical vibration is provided opposite to the iron plate 28.

A sensor drive unit 30 that applies a high frequency to the detection unit Z displacement sensor 27, and a sensor drive unit 30 as shown in FIG.
A detection circuit 36 was provided.

Also, a comparator 32 for comparing the reference voltage determined by the output setter 33 of the detection circuit 36, an electronic volume control 34 for controlling the intensity of the AC signal output from the oscillator l8 based on the comparison result signal, and It includes a piezoelectric actuator 12 that mechanically vibrates in response to an output signal from a volumetric volume 34, an enlarging mechanism 16 that amplifies the amplitude of the mechanical vibration, and the diaphragm 9 that is connected to the enlarging mechanism and vibrates.

action The operation will be explained according to FIGS. 1 and 2.

The alternating current signal output from the oscillator 18 passes through the volume 34, is amplified by the amplifier 19, and is transmitted to the piezoelectric actuator l2.
The vibration is converted into mechanical vibration, and the displacement of the mechanical vibration is expanded by the expansion mechanism 16.

The expansion mechanism 16 vibrates the diaphragm 9 to increase the pump 1.
Fluid is pumped from When the counter pressure at the pumping destination changes over time, the vibration of the diaphragm 9 also changes. The displacement sensor 27 senses the vibration of the iron plate 28 that vibrates together with the diaphragm 9, and outputs an electric signal. This electrical signal is detected by the detection section of the sensor drive section 30 and input to the comparator 32 .

A comparator compares this detected signal with a reference voltage predetermined by the setting device 33.

This detection signal is a DC signal proportional to the amplitude of the diaphragm 9. On the other hand, since the electronic volume control unit 34 controls the intensity of the AC signal passing therethrough, it passes based on the comparison result. Reduce, maintain, and increase alternating current signals. The amplitude of the enlarging mechanism 16 is controlled by this uncontrolled alternating current signal, and the amplitude of the diaphragm 9 is also controlled.

If the amplitude of the diaphragm 9 is about to decrease due to a load change, the AC signal is increased; if the amplitude is the same, it is maintained; if the amplitude is about to increase, the AC signal is decreased.

Since the amplitude of the diaphragm 9 determines the amount of pumping by the pump 1, by keeping the amplitude of the diaphragm 9 constant regardless of changes in the load, the amount of pumping can be stably maintained.

Example The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is a drawing showing a first embodiment of an analog system, and the piezoelectric pump of the present invention is composed of a pump l and a driving section 22. In FIG.

The pump 1 is provided with a check valve 4 at the suction port 3 and another check valve 6 at the discharge port 5, and furthermore, the pump part l includes a housing 7 as a fixed part and a diaphragm 9 as a movable part. There is.

The drive section 22 includes a drive circuit 24, an enlargement mechanism l6, and a control circuit 25.

The expansion mechanism 16 includes a piezoelectric actuator 12 that converts an electric signal into mechanical displacement, a lever 13 that expands this displacement, and a coiled spring 14 that is fixed to the tip of the lever 13.
and a plate spring 15 whose one end is connected to the diaphragm 9 and the other end is connected to the tip of the lever 13.

The control circuit 25 includes an iron plate 28 fixed to the diaphragm 9.
, a displacement sensor 27 that detects the movement of this iron plate 28,
It is composed of a sensor drive circuit 30, a rectifier circuit 3l, a comparator 32, and a setting device 33.

The iron plate 28 is attached to the outer surface of the diaphragm 9.
It has a small area and is thin enough not to affect the vibration of the iron plate 28, and the distance to the displacement sensor 27 is close enough to the extent that it does not interfere with the vibration of the iron plate 28.

The drive circuit 24 includes an oscillator 18 that generates an alternating current signal, an electronic volume 34 that is controlled by the output signal of the comparator 32, and an electronic volume 34 that is controlled by the output signal of the comparator 32.
and an amplifier l9 that amplifies the signal output from the piezoelectric actuator 12 and supplies the amplified signal to the piezoelectric actuator 12.

FIG. 2 shows the drive circuit 24 and control circuit 25 of FIG. 1 in detail.

The oscillator 18 of the drive circuit 24 generates AC 100 of the power line.
A transformer circuit that supplies V50/60Hz is used. The electronic volume 34 is composed of base control transistors Q1 and Q2, and adjusts the strength of the AC signal passing through the second transistor Q2 depending on the magnitude of the control voltage applied to the base of the first transistor Q1. In this embodiment, the amplifier 19 is not used because the signal source ACIOOO■ has sufficient strength.

The sensor drive circuit 30 includes a modulation circuit 35 and a detection circuit 36.
, and an amplifier 37, from the modulation circuit 35 to the sensor 2.
Send a high frequency signal to 7.

The sensor 27 thereby generates a high frequency magnetic field, and the iron plate 28 on the diaphragm 9 influences this high frequency magnetic field ζ. Therefore, when the iron plate 28 is displaced, the high frequency signal of the modulation circuit 35 undergoes amplitude modulation.

When this modulated signal passes through the detection circuit 36, only this modulated component is extracted and becomes a signal proportional to the displacement of the diaphragm 9.

This detected signal passes through an amplifier 37 and a rectifier 31 to be made into a complete DC voltage.

The comparator 32 compares the DC voltage proportional to the amplitude of the diaphragm 9 with a reference voltage preset by the setter 33, and amplifies the difference between them to provide a current volume 340 control signal.

If 1. DC voltage proportional to amplitude>reference voltage, the amplitude of the diaphragm 9 becomes large and the flow rate increases, so the electronic volume 34 is throttled down to reduce the strength of the driving AC signal.

2. If the DC voltage is proportional to the amplitude (reference voltage), the amplitude of the diaphragm 9 will be small and the flow rate will be reduced, so the electronic volume 34 will be opened to increase the strength of the AC signal.

3. If DC constant pressure proportional to amplitude = reference voltage, the control signal becomes zero, the electronic volume 34 is not changed, and the AC signal is not changed.

Since the amount of change in the amplitude of the diaphragm 9 is directly detected by the sensor 27, no waveform deformation or phase shift occurs in the control signal, and real-time flow control without delay is performed.

Note that the target flow rate can be set arbitrarily by changing the reference voltage.

A second embodiment of the digital system will be explained with reference to FIGS. 3 and 4.

In this embodiment, the control circuit 25 includes a peak hold 39,
It includes a three-circuit analog/digital converter (A/D) 40, a microcomputer 41, and a digital setting device 42.

Figure 4 shows Figure 3 in detail and shows the peak hold 3
9 is provided with two circuits, a first peak hold 43 for holding the positive side peak and negative side peak of the detection signal waveform, respectively;
It consists of a second peak hold 44.

Each of the peak holds 43 and 44 has a reset end, and as shown in FIG. 5, the held peak value with the reset force is erased and a new peak value of the signal is held.

After being inverted by the inverter 45ζ, the negative side peak value is sent to the first person's power of the A/D 40, the positive side peak value is directly sent to the second person's power of the second A/D40, and the set reference pressure is sent to the third person's power.
They are sent to each person individually.

The output of the A/D 40 is input manually to a microcomputer 41, where it is compared with a reference voltage and other calculations are performed.

The AC oscillator 18 is of a type in which the frequency is set by a feedback signal from an operational amplifier, and the electronic volume 34 is controlled by the calculation result of a microcomputer 41.

The microcomputer 41 operates according to the flowchart shown in FIG. In step St, both peak holds 43 and 44 are reset, and in step S2, for a predetermined time,
Wait for at least one period of vibration of the diaphragm 9. In step S3, the values of the peak holes 43 and 44 are input to the A/D 40, and the reference voltage set in step S4 is input manually.

The amplitude voltage input in step S5 is compared with a reference voltage.

If amplitude value>reference voltage, the process proceeds to step S6, where the electronic volume controller 34 is throttled down to weaken the strength of the AC signal input to the amplification period 19.

Next, if the amplitude value=the reference voltage, the process proceeds to step S7, and the state of the electronic volume 34 is maintained.

If the reference voltage is oscillating, the process proceeds to step S8, where the electronic volume control 34 is opened and the strength of the alternating current signal supplied to the amplification period 19 is increased.

These steps St-S6, S7, and S8 are performed many times in order, for example, 10 times per second.

Next, experimental results for demonstrating the effects of each example will be described below.

In FIG. 7, water in tank A is backflowed into pipe B using the control device of the present invention, and the water is pumped up to a height of 100 cm. In order to clarify the effect, the drive device of the present invention and the conventional drive device will be switched by using the switch SW.

When water is discharged, the water column becomes higher and higher in pipe B, increasing the load on the piezoelectric pump. When the water is pushed up 100 cm, the head pressure = 100 / roar. In response to this increased load, the vibration of the diaphragm 9 tends to decrease, but the amount of water conveyed also decreases accordingly.

As shown in FIG. 8, in the present invention, since this amplitude reduction amount is corrected, the water supply amount remains stable at approximately 0.61±2 cc/sec until the water head reaches 0 to 100 cm.

In conventional equipment, the water head Ocm is 1. OOrc/Se
The water supply amount of e gradually decreases as the load increases, and reaches 0. 75cc/see, 0.3 at water head 100cm
5cc/sec and 1. 00cc-0.
35cc”0.65cc is also fluctuating.

The piezoelectric pump may be of a type in which the expansion mechanism 16 is omitted and the diaphragm is directly vibrated by a laminated piezoelectric actuator, or a type in which the bimorph diaphragm itself is vibrated by electricity.

Furthermore, the displacement sensor is not limited to a frequency vortex constant flow type, but may be a differential transformer type or a type in which a strain gauge (strain sensor) is attached to a soft buckling spring.

Note that the reference voltage may be manually set as a digital value directly within the microcomputer.

〔Effect of the invention〕

As explained above, according to the present invention, the mechanical vibration of the movable part of the piezoelectric pump is directly detected by the displacement sensor,
This detection signal is detected and converted into a DC voltage proportional to the amplitude, and this DC voltage is compared with a preset reference constant pressure, and based on this comparison result, the intensity of the AC signal that drives the movable part is controlled. This stabilizes the amplitude of the diaphragm in the moving part.

This also stabilizes the flow rate of the piezoelectric pump. By selecting the reference voltage, the target flow rate can be set, so an accurate pumping amount can be ensured.

The amplitude of the diaphragm uniquely determines the amount of pumping by the compression bomb, so if the amplitude of the diaphragm is accurately stabilized, the amount of pumping can be accurately stabilized.

Even if the load on the piezoelectric pump varies, the piezoelectric pump operates in accordance with the load, that is, in a manner that prevents changes in the amplitude of the diaphragm, making it possible to stabilize the flow rate.

Furthermore, the displacement signal detected by the displacement sensor accurately retains the vibration information of the diaphragm, and there is no waveform distortion change, phase shift, etc., and no control delay occurs at all.

Furthermore, since the sampling of the presence or absence of a change in the amplitude of the diaphragm is performed more than IO times per second, changes in the amplitude of the diaphragm due to load fluctuations can be quickly detected, that is, corrected.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of a piezoelectric pump control device of the present invention, FIG. 2 is a circuit diagram showing details of FIG. 1,
FIG. 3 is a block diagram showing a second embodiment of the present invention, FIG. 4 is a circuit diagram showing details of FIG. 3, FIG. 5 is a diagram showing the principle of peak hold, and FIG. 6 is a diagram showing the second embodiment. FIG. 7 is a diagram showing an experimental method for implementing the effects of the present invention, FIG. 8 is a graph diagram showing experimental results of the present invention, and FIG. 9 is a conventional block diagram.

Claims (1)

[Claims] 1. An oscillator that generates an alternating current signal, a movable part that converts the alternating current signal into mechanical vibration, and a piezoelectric pump that pumps fluid by using the vibration, the piezoelectric pump being provided near the movable part. The device includes a detection unit that senses the vibration and outputs a displacement signal, a comparison unit that compares the displacement signal with a predetermined reference signal, and a control unit that controls the intensity of the alternating current signal based on the comparison result. A piezoelectric pump control device characterized by: 2. If the displacement signal is larger than the reference signal, the control unit weakens the AC signal intensity, if they are equal, maintains the current intensity, and if smaller, increases the intensity. The piezoelectric pump control device 3 according to claim 1. The piezoelectric pump control device according to claim 1, wherein the movable part is a diaphragm that vibrates. 4. The piezoelectric pump control device according to claim 1, wherein the movable part is a piezoelectric element that vibrates in response to an electric signal. 5. The piezoelectric pump control device according to claim 1, wherein the movable part includes the piezoelectric element and a diaphragm driven by the piezoelectric element. 6. The piezoelectric pump control device according to claim 1, wherein the movable part is a bimorph piezoelectric actuator that vibrates with an electric signal. 7. The piezoelectric pump control device according to claim 1, wherein the detection section is a differential transformer. 8. The piezoelectric pump control device according to claim 1, wherein the detection section is a strain sensor. 9. The piezoelectric pump control according to claim 1, wherein the detection section comprises an iron plate fixed to the movable section, a high frequency modulation circuit modulated by vibrations of the iron plate, and a detection section that detects a modulated wave. Device.