JP5003700B2 - pump - Google Patents

Description

  The present invention relates to a positive displacement pump that moves a fluid by changing a volume in a pump chamber by a piston or a diaphragm, and more particularly, to a highly reliable pump having a high flow rate.

As a conventional pump of this type, a structure in which a check valve is attached between an inlet channel and an outlet channel and a pump chamber whose volume can be changed is generally used. (For example, see Patent Document 1)
Also, as a pump configuration that generates a flow in one direction using the viscous resistance of the fluid, a valve is provided in the outlet channel, and the inlet channel has a larger fluid resistance than the outlet channel when the valve is opened. There is a thing of the structure made like this. (For example, see Patent Document 2)
In addition, as a pump configuration that improves the reliability of the pump without using moving parts in the valve part, a configuration including a compression component in which the pressure drop of the inlet flow channel and the outlet flow channel is different depending on the flow direction. There are things. (For example, see Patent Document 3 and Non-Patent Document 1)

JP-A-10-220357 Japanese Patent Application Laid-Open No. 08-312537 Japanese National Patent Publication No. 08-506874 Anders Olsson, An improved valve-less pump fabricating using deep reactive ion etching, 1996 IEEE 9th International 1 Workshop on MicroEm. 479-484

However, the configuration of Patent Document 1 requires a check valve for both the inlet channel and the outlet channel, and there is a problem that pressure loss is large when fluid passes through the two check valves. In addition, since the check valve repeatedly opens and closes, there is a risk of fatigue damage, and there is a problem that reliability increases as the number of check valves increases.
In the configuration of Patent Document 2, it is necessary to increase the fluid resistance of the inlet-side flow path in order to reduce the backflow generated in the inlet flow path during the pump discharge stroke. Then, since the fluid is introduced into the pump chamber against the fluid resistance in the pump suction stroke, the suction stroke becomes considerably longer than the discharge stroke. Therefore, the frequency of the pump discharge / intake cycle becomes considerably low.

  A pump that moves a piston or diaphragm up and down generally has a higher flow rate and higher output as the frequency of the piston or diaphragm moving up and down is higher. However, since the configuration of Patent Document 2 can be driven only at a low frequency as described above, there is a problem that a small and high output pump cannot be realized.

  The configuration of Patent Document 3 has a configuration in which a net flow rate is caused to flow in one direction due to a difference in pressure drop depending on a flow direction of a fluid passing through a compression component according to increase / decrease of a pump chamber volume. As the pressure increases, the reverse flow rate increases, and there is a problem that the pump does not operate at a high load pressure. According to Non-Patent Document 1, the maximum load pressure is about 0.760 atm.

  Therefore, the present invention reduces the number of mechanical on-off valves, reduces pressure loss and increases reliability, supports high load pressure, supports high frequency driving, increases pump discharge fluid volume, and further improves driving efficiency. The purpose is to provide a good pump.

In order to solve the above-described problems, a pump according to the present invention includes an actuator that displaces a movable wall such as a piston or a diaphragm, a drive unit that drives and controls the actuator, and a pump whose volume can be changed by the displacement of the movable wall. A pump having a chamber, an inlet channel for allowing working fluid to flow into the pump chamber, and an outlet channel for allowing working fluid to flow out of the pump chamber, the outlet channel communicating with the pump chamber during pump operation The combined inertance value of the inlet channel is smaller than the combined inertance value of the outlet channel, and the inlet channel is less than the fluid resistance when the working fluid flows into the pump chamber. A fluid resistance element that decreases, and the driving unit includes a cycle control unit that changes a motion cycle of the movable wall. When the pressure of the flop chamber becomes absolutely 0 atm, the pump chamber volume compression step of the movable wall driving the actuator to start.

In the pump of the present invention, the valve only needs to be arranged in the inlet flow path, and the fluid resistance element such as a valve only needs to be arranged in the inlet flow path. Can increase the sex.
Further, no displacement magnifying mechanism is arranged between the piston or diaphragm and the actuator that drives the piston or diaphragm, and viscous resistance is not used for the valve, so that high-frequency driving can be supported. Therefore, it is possible to realize a small, lightweight and high output pump that fully utilizes the performance of the actuator.

It is a figure which shows the longitudinal cross-section of the pump of 1st Embodiment which concerns on this invention. It is a graph which shows operation | movement of the pump of 1st Embodiment. It is a graph which shows the state from which a discharge fluid volume changes, when frequencies differ. It is a graph which shows the waveform mode of a predetermined frequency. It is a graph which shows the waveform mode of a frequency different from FIG. The block diagram of the period control means of 1st Embodiment which concerns on this invention is shown. It is a figure which shows the map memorize | stored by the period control means of 1st Embodiment. The block diagram of the period control means of 2nd Embodiment which concerns on this invention is shown. It is a flowchart which shows the procedure in which the period control means of 2nd Embodiment which concerns on this invention performs a process. It is a flowchart which shows the procedure which the pressure-cycle conversion circuit of 3rd Embodiment concerning this invention performs a process. The block diagram of the period control means of 4th Embodiment which concerns on this invention is shown. It is a figure which shows the map memorize | stored by the period control means of 4th Embodiment. The block diagram of the period control means of 5th Embodiment which concerns on this invention is shown. It is a flowchart which shows the procedure in which the displacement-period conversion circuit of 5th Embodiment concerning this invention performs a process. The block diagram of the period control means of 6th Embodiment which concerns on this invention is shown. It is a flowchart which shows the procedure which the flow-speed-period conversion circuit of 6th Embodiment concerning this invention performs a process. It is a flowchart which shows the procedure which the flow-speed-period conversion circuit of 7th Embodiment concerning this invention performs a process. It is a figure which shows the pump of 8th Embodiment which concerns on this invention.

Hereinafter, a plurality of embodiments according to the present invention will be described with reference to the drawings.
First, the structure of a pump according to each embodiment of the present invention will be described with reference to FIG. FIG. 1 shows a longitudinal section of the pump of the present invention. A circular diaphragm 5 is disposed at the bottom of the cylindrical case 7. The diaphragm 5 is elastically deformable with the outer periphery green being fixedly supported by the case 7. On the bottom surface of the diaphragm 5, a piezoelectric element 6 that expands and contracts in the vertical direction of the drawing is arranged as an actuator for moving the diaphragm 5.

  A narrow space between the diaphragm 5 and the upper wall of the case 7 is a pump chamber 3, and an inlet channel 1 provided with a check valve 4 as a fluid resistance element toward the pump chamber 3, and always during pump operation. An outlet channel 2 which is a pipe having a narrow hole communicated with the pump chamber is opened. A part of the outer periphery of the parts constituting the inlet channel 1 serves as an inlet connection pipe 8 for connecting an external element (not shown) to the pump. A part of the outer periphery of the parts constituting the outlet channel 2 is an outlet connecting pipe 9 for connecting an external element (not shown) to the pump. Further, both the inlet channel and the outlet channel have rounded portions 15a and 15b obtained by rounding the inlet side of the working fluid.

Here, the inertance value L is defined. When the cross-sectional area of the flow path is S, the length of the flow path is l, and the density of the working fluid is ρ, L = ρ × l / S. When the differential pressure of the flow path is ΔP and the flow rate flowing through the flow path is Q, the relation of ΔP = L × dQ / dt is derived by modifying the equation of motion of the fluid in the flow path using the inertance value L. It is.
That is, the inertance value L indicates the degree of influence that the unit pressure has on the temporal change in the flow rate. The larger the inertance value L, the smaller the temporal change in the flow rate, and the smaller the inertance value L, the larger the temporal change in the flow rate.

In addition, the combined inertance value for parallel connection of multiple flow paths and serial connection of flow paths of different shapes is combined with the inertance values of individual flow paths in the same way as the parallel connection and series connection of inductances in electrical circuits. To calculate.
In addition, the inlet channel referred to here refers to a channel up to the end surface of the inlet connecting pipe 8 on the fluid inflow side. However, when the pulsation absorbing means is connected in the middle of the pipeline, it refers to the flow path from the inside of the pump chamber 3 to the connecting portion with the pulsation absorbing means. Furthermore, when the inlet flow paths 1 of a plurality of pumps merge, it refers to the flow path from the pump chamber 3 to the merge section. The same applies to the outlet channel.

Based on FIG. 1, the symbol relationship of the flow path length and area of the inlet flow path 1 and the outlet flow path 2 is demonstrated. In the inlet channel 1, the length of the reduced diameter pipe section near the check valve 4 is L1, the area is S1, the length of the remaining expanded pipe section is L2, and the area is S2. In the outlet channel 2, the length of the conduit of the outlet channel 2 is L3 and the area is S3.
The inertance relationship between the inlet channel 1 and the outlet channel 2 will be described using the above symbols and the density ρ of the working fluid.

  The inertance of the inlet channel 1 is calculated as ρ × L1 / S1 + ρ × L2 / S2. On the other hand, the inertance of the outlet channel 2 is calculated as ρ × L3 / S3. These flow paths have a dimensional relationship that satisfies ρ × L1 / S1 + ρ × L2 / S2 <ρ × L3 / S3.

  In the above configuration, the shape of the diaphragm 5 is not limited to a circular shape. Further, for example, in order to protect the pump components from an excessive load pressure applied when the pump is stopped, even if a valve element is arranged in the outlet flow path 2, it is only necessary to communicate with the pump chamber at least during pump operation. . The check valve 4 is not limited to a valve that opens and closes due to a fluid pressure difference, but may be a type that can control opening and closing with a force other than the fluid pressure difference.

  Furthermore, any actuator 6 that moves the diaphragm 5 may be used as long as it expands and contracts. However, in the pump structure of the present invention, the actuator and the diaphragm 5 are connected without a displacement magnifying mechanism. Since it can be operated at a high frequency, by using the piezoelectric element 6 having a high response frequency as in this embodiment, the flow rate can be increased by high-frequency driving, and a small and high-output pump can be realized. Similarly, a giant magnetostrictive element having high frequency characteristics may be used.

Further, since the mechanical on-off valve has only to be arranged on the suction side, the flow rate decrease due to the valve is reduced and the reliability is also increased.
In all of the present embodiment to the eighth embodiment, the working fluid introduced into the pump uses water. However, other fluids such as alcohol-based, oil-based, and some additives may be used.

Next, the motion period of the diaphragm in the pump having the structure shown in FIG. 1 will be described with reference to FIGS. 2, 3, 4 and 5. FIG.
FIG. 2 shows the waveform W1 of the displacement of the diaphragm 5 when the pump is operated, the waveform W2 of the internal pressure of the pump chamber 3, the volume velocity of the fluid passing through the outlet channel 2 (the sectional area of the outlet pipe × the fluid The waveform W3 of the flow velocity, in this case the amount equal to the flow rate), and the waveform of the volume velocity W4 of the fluid passing through the check valve 4 are shown. Further, the load pressure Pfu shown in FIG. 2 is a fluid pressure at a position downstream of the outlet flow rate 2, and the suction side pressure Pky is a fluid pressure upstream of the inlet channel 1.

As shown in the waveform W1 of the displacement of the diaphragm 5, the region where the slope of the waveform is positive is a process in which the piezoelectric element 6 extends and the volume of the pump chamber 3 decreases. The region where the waveform slope is negative is a process in which the piezoelectric element 6 is contracted and the volume of the pump chamber 3 is increased.
A flat waveform section displaced by about 4.5 μm is the maximum displacement amount of the diaphragm 5, that is, the displacement position of the diaphragm 5 at which the volume of the pump chamber 3 is minimized.

  As shown in the waveform W2 of the change in the internal pressure of the pump chamber 3, when the process of decreasing the volume of the pump chamber 3 starts, the increase in the internal pressure of the pump chamber 3 starts. Then, before the process of reducing the volume of the pump chamber 3 ends, the maximum pressure in the pump chamber 3 reaches the maximum value and begins to decrease. The point at which the internal pressure is maximum is a point at which the volume velocity of the excluded fluid by the diaphragm 5 is equal to the volume velocity of the fluid in the outlet channel 2 indicated by the waveform W3.

This is because before this time,
Volumetric velocity of the excluded fluid—volumetric velocity of the fluid passing through the outlet channel 2> 0
Therefore, the fluid in the pump chamber 3 is compressed by that amount, and the pressure in the pump chamber 3 rises. After this time,
Volume velocity of excluded fluid-volume velocity of fluid passing through outlet channel 2 <0
This is because the compression amount of the fluid in the pump chamber 3 is reduced by that amount, and the pressure in the pump chamber 3 is lowered accordingly.

The pressure in the pump chamber 3 is expressed as ΔV, where the volume change of the fluid in the pump chamber 3 at each time is ΔV.
ΔV = Excluded fluid volume by diaphragm + Suction fluid volume-Varies according to the relationship between the discharge fluid volume and the compressibility of the fluid. Therefore, even in the process in which the volume of the pump chamber 3 is decreasing, the pressure in the pump chamber 3 may be lower than the load pressure Pfu.

  Further, in the case of FIG. 2, when the pressure in the pump chamber 3 is lower than the suction side pressure Pky and approaches zero absolute pressure, the components dissolved in the working fluid are gasified to form bubbles and aeration Yong occurs and is saturated near absolute zero atmosphere. However, if the entire flow path system including the pump is pressurized and the suction side pressure Pky is sufficiently high, aeration and cavitation may not occur.

Further, as shown in the waveform W3 of the volume velocity of the fluid in the outlet channel 2, in the outlet channel 2, the period in which the pressure in the pump chamber 3 is larger than the load pressure Pfu is almost the increase period of the volume velocity of the fluid. It has become. And when the pressure in the pump chamber 3 falls below the load pressure Pfu, the volume velocity of the fluid in the outlet channel 2 also starts to decrease.
If the pressure difference between the pressure in the pump chamber 3 and the load pressure Pfu is ΔPout, the fluid resistance in the outlet channel 2 is Rout, the inertance is Lout, and the volume velocity of the fluid is Qout, the fluid in the outlet channel 2 ,

Therefore, the rate of change in volume velocity of these fluids is equal to the difference between ΔPout and Rout × Qout divided by the inertance value Lout. Then, a value obtained by integrating the volume velocity of the fluid indicated by the waveform W3 for one cycle is the discharged fluid volume per cycle.

  Further, as shown in the waveform W4 of the change in volume velocity of the fluid passing through the check valve 4, when the pressure in the pump chamber 3 decreases below the suction side pressure Pky in the inlet flow path 1, the check valve causes the pressure difference. 4 opens and the volume velocity of the fluid begins to increase. Further, when the pressure in the pump chamber 3 increases and increases above the suction side pressure Pky, the volume velocity of the fluid starts to decrease. And the backflow is prevented by the check effect of the check valve 4.

  If the differential pressure between the pressure in the pump chamber 3 and the suction side pressure Pky is ΔPin, the fluid resistance in the outlet channel 2 is Rin, the inertance is Lin, and the volume velocity of the fluid is Qin, the fluid in the inlet channel 1 ,

Therefore, the rate of change of these fluid volume velocities is also equal to the difference between ΔPin and R in × Qin divided by the inertance value Lin of the inlet channel 1.
A value obtained by integrating the volume velocity of the fluid indicated by the waveform W4 for one cycle is the suction fluid volume per cycle. The suction fluid volume is equal to the discharge fluid volume calculated by the waveform W3.
Here, if the inertance definition is time integrated,

It becomes. Since the inertance value is constant, the amount of change in the fluid volume velocity Q of the fluid in the pipe during that period increases as the integral value of the differential pressure across the pipe increases. Considering the outlet channel 2, the larger the integrated value of the differential pressure between the internal pressure of the pump chamber 3 and the load pressure Pfu, the faster the fluid in the outlet channel 2 flows in the discharge direction (= has a large momentum). Flow) and the discharge fluid volume increases. Until the momentum decreases, a large amount of fluid can be introduced into the pump chamber 3 from the inlet channel 1 side, and at the same time, the time until the discharge fluid volume and the suction fluid volume become equal also increases. That is, in the outlet channel 2, the discharge flow rate (= intake flow rate) of the pump per cycle and the time until the discharge fluid volume and the intake fluid volume become equal depending on the value of the left side of the expression (3). Change. When the displacement speed of the diaphragm in the pump chamber volume reduction process is increased, the value on the left side of the equation (3) tends to increase.

Next, the timing at which the next drive voltage is applied after the previous drive voltage is applied to the piezoelectric element 6 will be described.
As described above, the pressure in the pump chamber 3 is expressed by ΔV indicating the volume change of the fluid in the pump chamber 3 at each time.
ΔV = Excluded fluid volume by diaphragm 5 + Suction fluid volume − Varies according to the relationship between the discharged fluid volume and the fluid compressibility. And since the outlet flow path 2 and the pump chamber 3 are communicating with the pump of this structure, when ΔV = 0, the pressure in the pump chamber 3 becomes equal to the load pressure Pfu. Therefore, in the range of ΔV <0, the pressure in the pump chamber 3 is lower than the load pressure Pfu. Therefore, when the next drive voltage is applied to the piezoelectric element 6 in the range of ΔV <0, the displacement volume until ΔV = 0 is set so that the pressure in the pump chamber 3 becomes equal to the load pressure Pfu. Used to compress the fluid and wasted.

  By preventing such a wasteful consumption of the excluded volume, it is possible to increase the discharge fluid volume of the pump. For this purpose, after the end of driving for one pumping (after the net amount of the excluded fluid volume by the diaphragm 5 becomes zero), after the time when the discharge fluid volume and the suction fluid volume become equal, the next piezoelectric element A driving voltage for 6 is preferably applied.

  However, the pressure wave of the fluid in the pump chamber 3 changes due to various factors. When the diaphragm 5 is moved in a SIN waveform, the discharge fluid volume changes as shown in FIG. 3 with respect to the driving cycle. FIG. 3 shows two discharge fluid volume peaks. FIG. 4 and FIG. 5 show the pressure in the pump chamber 3 and the diaphragm displacement in the driving cycle corresponding to each peak. FIG. 4 shows a driving state called a first harmonic mode in which the cycle of the diaphragm displacement and the cycle of the pump chamber pressure are equal. FIG. 5 shows that the cycle of the pump chamber pressure is doubled compared to the cycle of the diaphragm displacement. This is a driving state called the second harmonic mode. 4 and 5, the pressure waveform in the pump chamber is different, and the value on the left side of the equation (3) described above is also different. Specifically, the second harmonic mode in FIG. 5 has a larger pressure waveform peak than the first harmonic mode in FIG. 4, and the value on the left side of equation (3) is also larger. Therefore, as described above, the time at which the discharge fluid volume and the suction fluid volume become equal also changes. (FIG. 5 showing the second harmonic mode has a longer time until the discharge fluid volume and the suction fluid volume become equal compared to FIG. 4 showing the first harmonic mode). The discharge fluid volume peak shown in FIG. 3 exists at a driving frequency at which the time when the discharge fluid volume and the suction fluid volume become equal to the period during which the diaphragm moves in the direction of compression of the pump chamber volume. The reason why the pressure waveform of the pump chamber is different in these two modes is that the displacement amount of the diaphragm is the same, but the displacement speed of FIG. 5 is shorter than that of FIG. Because it is fast.

  In this way, the pressure in the pump chamber 3 is particularly large due to changes in displacement time, maximum displacement amount, displacement speed, and load pressure in the direction in which the piezoelectric element 6 is driven and the diaphragm 5 decreases the volume of the pump chamber 3. As a result, the time when the discharge fluid volume and the suction fluid volume become equal also changes, and after the previous drive voltage is applied to the piezoelectric element 6, the optimal timing for applying the next drive voltage also changes.

Description will be added again based on FIG.
In FIG. 3, the discharge fluid volume increases when the second harmonic is generated rather than the first harmonic. Further, when driven in the second harmonic mode, the number of check valve opening / closing operations is ½ of the drive frequency, and as can be seen from FIG. 3, the check valve opened / closed in the second harmonic mode is opened / closed in the first harmonic mode. This is less than the number of times the check valve is opened and closed when it is driven. In general, fatigue failure is related to the number of repeated loads. Therefore, the durability of the check valve is improved by driving in the second harmonic mode. Although FIG. 3 shows the case where the diaphragm drive waveform is a SIN waveform, the same applies to other cases where the diaphragm is driven with a waveform close to the SIN waveform or a drive waveform whose displacement speed is a function of the drive cycle. Arise.

Further, as described above, the discharge fluid volume peak frequency in FIG. 3 corresponds to the time when the discharge fluid volume and the suction fluid volume become equal (= time when the pump chamber pressure becomes equal to the load pressure) and the diaphragm compresses the pump chamber volume. The period of movement in the direction is the drive frequency that is well tuned each time. Here, this frequency is referred to as an in-pump fluid resonance frequency.
The resonance frequency of the mechanical parts constituting the pump chamber such as the actuator, the diaphragm, and other wall parts constituting the pump chamber (the volume change of the pump chamber 3 is maximum at this frequency), and the fluid resonance frequency in the pump Are made substantially equal to each other, so that the displacement amount of the actuator alone can be reduced without reducing the volume of fluid discharged from the pump. This has the effect of driving the pump efficiently because the internal loss of the actuator is reduced.

Next, FIGS. 6 and 7 show a first embodiment according to the present invention.
FIG. 6 is a block diagram of the driving unit 20 that controls the driving of the piezoelectric element 6 according to the present embodiment, and includes a cycle control circuit (cycle control unit) 22 and a voltage waveform generation circuit 24.
The voltage waveform generation circuit 24 generates a voltage waveform set once before receiving a trigger signal every time a trigger signal to be described later is received, and a piezoelectric circuit that amplifies the voltage waveform to a predetermined power required for driving. And an amplification amplifier circuit 24b that supplies the element 6.

  The cycle control circuit 22 is a combination of an input value and an I / O port 22a to which a signal of displacement (displacement time), maximum displacement, and load pressure is input in a direction in which the volume of the pump chamber 3 is decreased. The optimal motion cycle for the above is experimentally determined in advance, and the ROM 22b that records the map shown in FIG. 7 and the input value to the I / O port 22a are referred to the ROM 22b, and a trigger signal is generated at the corresponding cycle. CPU22c which performs.

According to the present embodiment, the cycle control circuit 22 selects the optimum cycle for the change in displacement time, maximum displacement, and load pressure, and controls the piezoelectric element 6 so that the discharge flow volume and the suction flow volume are equal. In addition, since the diaphragm 5 is displaced in a state where the suction flow volume is large, wasteful consumption of the excluded fluid volume can be prevented and the discharge fluid volume of the pump can be increased.
Moreover, in this embodiment, since it is not necessary to provide a sensor in the inside of the pump chamber 3, it is suitable when the pump chamber 3 is a narrow space.

Next, FIGS. 8 and 9 show a second embodiment according to the present invention.
The drive unit 20 of this embodiment shown in FIG. 8 includes a cycle control circuit (cycle control unit) 22 and a voltage waveform generation circuit 24.
The voltage waveform generation circuit 24 has the same configuration as that of the block diagram shown in FIG. 6 and generates a voltage waveform set before receiving a trigger signal once every time a trigger signal described later is received.
The cycle control circuit 22 includes a pressure-cycle conversion circuit 22d that generates a trigger signal based on a detection value of a pressure sensor (pump pressure detection means) 28 disposed in the pump.

FIG. 9 is a flowchart showing the processing procedure of the pressure-cycle conversion circuit 22d.
First, in step S4, a pressure threshold value Psh is set. The threshold value Psh is a value that is equal to or greater than the output value when the suction side pressure Pky is applied to the pressure sensor 28. In this way, there is no false detection due to a subtle pressure increase at low pressure.

Next, the process proceeds to step S <b> 6 and a trigger signal is output to the waveform generation circuit 24.
Next, the process proceeds to step S8, where the waveform generation circuit 24 checks whether or not the output of one voltage waveform has been completed, and if completed, the process proceeds to step S10.
In step S <b> 10, the pressure Pin <b> 1 of the first pump chamber 3 is measured by the pressure sensor 28.

Next, the process proceeds to step S12, and the pressure Pin2 in the second pump chamber 3 is measured by the pressure sensor 28.
Subsequently, the process proceeds to step S14, and whether the relationship between the threshold value Psh, the pressure Pin1 of the first pump chamber 3 and the pressure Pin2 of the second pump chamber 3 is a relationship of Pin1 <Psh <Pin2. To check. If the relation Pin1 <Psh <Pin2 is established, the process proceeds to step S16. If the relation Pin1 <Psh <Pin2 is not established, the process proceeds to step S18.

In step S18, the value of the pressure Pin2 of the second pump chamber 3 is set as the pressure Pin1 of the first pump chamber 3, and the process returns to step S12.
In step S16, it is confirmed whether the control of the piezoelectric element 6 is continued or stopped. When the control of the piezoelectric element 6 is stopped, the process is stopped, and when the control of the piezoelectric element 6 is continued. Return to step S6.

As described above, according to the present embodiment, the cycle control circuit 22 applies the drive voltage to the next piezoelectric element 6 when the pressure in the pump chamber 3 increases beyond the preset threshold value Psh with respect to the change in the load pressure. can do.
If a value equal to or higher than the output value when the load pressure Pfu is applied to the pressure sensor 28 is used, the diaphragm 5 starts to be displaced at a point where the discharge fluid volume is equal to the suction fluid volume or the suction fluid volume is larger. , Wasteful consumption of the excluded fluid volume is prevented, and the discharge fluid volume of the pump increases.

In addition to the pressure sensor 28, the pump pressure detecting means may calculate the pressure in the pump chamber 3 by measuring the strain amount of the diaphragm with a strain gauge or a displacement sensor. Alternatively, the pressure in the pump chamber 3 may be calculated by measuring the deformation of the pump housing with a strain gauge. Further, a passive valve is provided on the inlet flow path 1 side, and deformation due to the pressure of the pump chamber 3 when the valve is closed is measured by a strain gauge or a displacement sensor, and the pressure of the pump chamber 3 is calculated. Also good. Further, in order to measure the displacement of the piezoelectric element 6, a strain gauge is attached to the piezoelectric element 6, and a measured value (actual displacement) is measured by an applied voltage or applied charge (target displacement amount) to the piezoelectric element 6 and the strain gauge. The pressure in the pump chamber 3 may be calculated from the amount) and the Young's modulus of the piezoelectric element 6. Since these methods do not need to be provided inside the pump chamber 3, it is possible to promote downsizing of the pump. As the strain gauge, any type may be used, such as a strain gauge that detects the amount of strain by resistance change, capacitance change, or voltage change.
Further, the pressure sensor may be arranged in the pump including the pump chamber and the outlet flow. However, it is preferable to arrange the pressure sensor in the pump chamber because the pressure inside the pump can be accurately measured.

Next, FIG. 10 shows a third embodiment according to the present invention.
This figure is also a flowchart showing the processing procedure of the pressure-cycle conversion circuit 22d shown in FIG. 8, and since it has the same configuration as that shown in FIG. 8, the block diagram of the driving means 20 is omitted.

First, in step S30, a period T1 is selected from a plurality of periods Ti (i = 1, 2, 3,...) Of the diaphragm 5. From the next time onward, another cycle Ti is changed and selected.
Next, the process proceeds to step S32, where it is confirmed whether calculation of the calculation value Fi described later has been completed for all cycles Ti. If not completed, the process proceeds to step S38, and if completed, step S36 is performed. Migrate to
In step S38, the trigger signal Si is output.

Next, the process proceeds to step S44, and the pressure Pin of the pump chamber 3 is measured by the pressure sensor 28.
Subsequently, the process proceeds to step S46, and it is confirmed whether or not the relationship between the reference value (predetermined value) Pa and the pressure Pin of the pump chamber 3 is Pa ≦ Pin. Here, the reference value Pa is a pressure value of the pump chamber 3 before the piezoelectric element 6 is driven. If the relationship of Pa ≦ Pin is established in this step, the process proceeds to step S50. If the relationship of Pa ≦ Pin is not established, the process returns to step S44.

  Next, the process proceeds to step S50, and the pressure Pin of the pump chamber 3 is stored in the stored pressure value Pmj (j = 1, 2, 3,..., And the value of j is incremented each time this step is processed). The process proceeds to step S52, the time at the time of measurement is stored in the elapsed time TMmj (j = 1, 2, 3,...), And then the process proceeds to step S54.

  In step S54, the pressure in the pump chamber is measured, and it is confirmed whether or not the relationship between the measured value Pin and the reference value Pa satisfies the relationship Pa> Pin. If Pa> Pin, the process proceeds to step S56. If Pa> Pin, the process returns to step S50.

In step S56, the stored pressure value Pmj, the reference value Pa, and the elapsed time TMmj are used, and the difference between the stored pressure value Pmj and the reference value Pa is integrated over time to calculate the calculated value Fi, and then the process returns to step S30. .
Then, in step S36, which is the transition destination when the calculation of the calculation values Fi for all the periods Ti of the diaphragm 5 is completed in step S32, the maximum value among the calculation values F1, F2, F3. calculate.

Next, the process proceeds to step S58, and after selecting the cycle Ti of the diaphragm 5 corresponding to the predetermined calculated value Fi that has become the maximum value, the process ends.
Then, the driving unit 20 controls the driving of the piezoelectric element 6 so that the diaphragm 5 is displaced at the selected period Ti.

  As described above, when the processing of the pressure-cycle conversion circuit 22d shown in FIG. 10 is performed, it is possible to select the cycle in which the calculated value Fi corresponding to the left side of the equation (3) is maximum. On the other hand, when the diaphragm 5 is driven at an optimal cycle at which the discharge fluid volume and the suction fluid volume are equal or the suction fluid volume is larger, as described above, in the pump chamber volume compression process, the excluded fluid Since there is no wasteful volume consumption, the pump chamber pressure is further increased, the pump discharge fluid volume is further increased, and this corresponds to the left side of the equation (3) as compared with the case of driving with a non-optimal cycle. The value also increases. Therefore, if the motion cycle of the diaphragm is controlled as in the present embodiment, the diaphragm can be driven with an optimal motion cycle, wasteful consumption of the excluded fluid volume can be prevented, and the discharge fluid volume of the pump can be increased.

Although the piezoelectric element 6 can be controlled with high accuracy by integrating the difference between the pressure value Pmj and the reference value Pa over time, for example, the difference between the peak value of the pressure Pin of the pump chamber 3 and the reference value Pa, and the reference value Pa It is also possible to use a value obtained by integrating the time when the pressure Pin is set.
Incidentally, in the pump according to the present invention, the outlet pipe (downstream from the outlet channel 2) connected to the outlet channel 2 and the pump chamber 3 communicate with each other, so the pressure in the pump chamber 3 before being driven is It is equal to the load pressure Pfu. Therefore, the load pressure Pfu can be determined by measuring the pressure in the pump chamber 3 before driving.

Therefore, the pressure in the pump chamber before driving the piezoelectric element 6 is not set to the reference value Pa, and the load pressure Pfu can be obtained by another method and the processing of the third embodiment shown in FIG. 10 can be performed.
As another method, when the load pressure Pfu is known in advance, it is convenient and desirable to use the value. It is also desirable to provide a means for measuring the load pressure Pfu and use the measured value because it can cope with various load pressures Pfu that cannot be assumed in advance. Further, when driving for several waveforms is temporarily stopped at the time of driving the pump (for example, when driving at 2 kHz, if 2000 waveforms are driven, 10 waveforms are stopped and 2000 waveforms are driven). Since the pressure oscillation in the pump chamber 3 stops, the pressure in the pump chamber 3 at that time is equal to the load pressure Pfu. Therefore, using the load pressure Pfu as the value of the pressure sensor 28 serving as the pump pressure detecting means can cope with various load pressures Pfu, and does not require a new means for measuring the load pressure. This is preferable.

  Further, a calculation value Fi for a certain movement cycle and a correction amount to be added to the movement cycle in order to make it an ideal maximum calculation value Fmax are obtained in advance by experiments or the like, and these are calculated in the ROM of the displacement control means. If the calculation value Fi is calculated and stored, and a means for correcting the motion cycle of the diaphragm 5 is provided by referring to the map, the displacement speed is controlled at a higher speed while obtaining the same effect. be able to.

Next, FIGS. 11 and 12 show a fourth embodiment according to the present invention.
As shown in FIG. 11, the cycle control circuit 22 of this embodiment includes an I / O port 22a, a ROM 22b, and a CPU 22c. The I / O port 22a includes a pressure sensor (in the pump) The pressure information of the pump chamber 3 is input from the pump pressure detecting means 28. Further, in the ROM 22b, an internal pressure peak value of the pressure sensor 28 obtained during an experiment in advance and a correction amount for making the optimum period a load as shown in FIG. It is recorded as a map by pressure.

  When the waveform generation circuit 24 of the present embodiment outputs the first drive voltage, the cycle control circuit 22 generates a trigger signal in the reference motion cycle T0, and the waveform generation circuit 24 starts outputting the second drive voltage, After the measurement by the pressure sensor 28 is started and the peak value is calculated from the measured value, the corresponding correction amount is found with reference to the ROM 22b. From the next time, the trigger signal is generated at a cycle obtained by adding the correction amount to the reference motion cycle. It is designed to output. In addition, the method of calculating | requiring load pressure can use all the methods demonstrated in 3rd Embodiment similarly.

  Also in this embodiment, the diaphragm 5 is displaced in a state where the discharge flow volume and the suction flow volume are equal or the suction flow volume is large by selecting the optimum cycle and sending the drive voltage waveform to the piezoelectric element 6. , Wasteful consumption of the excluded fluid volume can be prevented, and the discharge fluid volume of the pump can be increased.

Next, FIGS. 13 and 14 show a fifth embodiment according to the present invention.
The drive unit 20 of this embodiment shown in FIG. 13 includes a cycle control circuit (cycle control unit) 22 and a voltage waveform generation circuit 24. The cycle control circuit 22 generates a trigger signal based on the detection value of the displacement sensor 30 that detects the open / close displacement state of the check valve 4 that opens and closes due to the pressure difference provided in the inlet flow path 1 in the pump. A conversion circuit 22e is provided.
FIG. 14 is a flowchart showing the processing procedure of the displacement-cycle conversion circuit 22e.
First, in step S60, a threshold value X0 corresponding to the amount of displacement when the check valve 1 that closes the inlet channel 1 is substantially closed is set.
Next, the process proceeds to step S62, and a trigger signal is output.
Next, the process proceeds to step S64, where it is confirmed whether or not the output of one voltage waveform has been completed. When the output is completed, the process proceeds to step S66.

In step S <b> 66, the displacement amount X of the check valve 1 is measured by the displacement sensor 30.
Next, the process proceeds to step S68, and whether or not the relationship between the displacement amount (threshold value) X0 of the check valve 1 that closes the inlet flow path 1 and the measured displacement amount X satisfies the relationship X ≦ X0. Check. When the relationship of X ≦ X0 is established, the process proceeds to step S70, and when the relationship of X ≦ X0 is not established, the process returns to step S66.

In step S70, it is confirmed whether the control of the piezoelectric element 6 is continued or stopped. When the control of the piezoelectric element 6 is stopped, the process is stopped, and when the control of the piezoelectric element 6 is continued, the step S62. Return to.
In the present embodiment, after the application of the drive voltage for one cycle is completed, the increase amount of the suction fluid volume gradually becomes larger than the increase amount of the discharge fluid volume, and the discharge fluid volume and the suction fluid volume become substantially equal. It is used that the intake valve is closed. Therefore, the displacement-cycle conversion circuit 22e performs processing so as to apply the next drive voltage to the piezoelectric element 6 when the check valve 1 is in a state of closing the inlet flow path 1, and thereby the discharge fluid volume and Since the diaphragm 5 starts to be displaced when the suction fluid volume is substantially equal to the suction fluid volume, wasteful consumption of the excluded fluid volume can be prevented, and the discharge fluid volume of the pump can be increased.

Further, in this embodiment, since the piezoelectric element 6 is driven after the check valve 1 is closed, it is possible to prevent the excluded fluid volume due to the diaphragm 5 from flowing backward from the inlet channel 1 and being lost.
Next, FIGS. 15 and 16 show a sixth embodiment according to the present invention.
The drive unit 20 of the present embodiment shown in FIG. 15 includes a cycle control circuit (cycle control unit) 22 and a voltage waveform generation circuit 24. The cycle control circuit 22 is arranged in the outlet flow path 2 in the pump. The flow rate-period conversion circuit 22f that generates a trigger signal based on the detected value of the flow rate sensor (flow rate measuring means) 30 is provided.

FIG. 16 is a flowchart showing the processing procedure of the flow velocity-cycle conversion circuit 22f.
First, in step S72, the period T1 is selected from the plurality of periods Ti (i = 1, 2, 3,...) Of the diaphragm 5. From the next time onward, another cycle Ti is changed and selected.
Next, the process proceeds to step S74, where it is confirmed whether calculation of a flow rate difference ΔVi, which will be described later, is completed for all cycles Ti. If not completed, the process proceeds to step S80, and if completed, step S78 is performed. Migrate to

In step S80, the trigger signal Si is output.
Next, the process proceeds to step S84, and the maximum flow velocity Vmax of the outlet channel 2 is calculated.
Next, the process proceeds to step S86, and the minimum flow velocity Vmin of the outlet channel 2 is calculated.
Next, the process proceeds to step S90, and a flow rate difference ΔV between the maximum flow rate Vmax and the minimum flow rate Vmin is calculated.

Next, the process proceeds to step S92, the flow rate difference ΔV is stored in the stored flow rate value ΔVi (i = 1, 2, 3,...), And the process returns to step S72.
When the calculation of the flow velocity difference ΔVi for all the cycles Ti is completed, the process proceeds to step S78, and the maximum value among the velocity differences ΔV1, ΔV2, ΔV3,.

Next, the process proceeds to step S94, and after selecting the cycle Ti corresponding to the predetermined speed difference ΔVi having the maximum value, the process is terminated.
Then, the driving unit 20 controls the driving of the piezoelectric element 6 so that the diaphragm 5 is displaced at the selected period Ti.

  As described above, in this embodiment, as shown by the equation (3), the time integral value of the difference between the fluid volume velocity in the integration period and the pressure difference between the pressure in the pump chamber 3 and the load pressure corresponds to 1: 1. In addition, it is used that the time integration value increases as the diaphragm is driven with a good motion cycle. Therefore, when the processing of the flow rate-cycle conversion circuit 22f shown in FIG. 16 is performed, the diaphragm can be driven at an optimal motion cycle, wasteful consumption of the excluded fluid volume can be prevented, and the discharge fluid volume of the pump can be increased. In addition, a pump with high driving efficiency can be provided.

Next, FIG. 17 is a flowchart showing a processing procedure of the flow velocity-cycle conversion circuit 22f as the seventh embodiment.
First, in step S100, a threshold value Vsh of the flow velocity of the outlet channel 2 is set.
Next, the process proceeds to step S102, and a trigger signal is output.
Next, the process proceeds to step S104, where it is confirmed whether or not the output of one voltage waveform has been completed. If the output has been completed, the process proceeds to step S106.

In step S106, the flow velocity sensor 32 measures the first flow velocity Vin1 of the outlet flow path 2.
Next, the process proceeds to step S108, and the flow velocity Vin2 of the second outlet channel 2 is measured by the flow velocity sensor 32.
Next, the process proceeds to step S110, and the relationship between the threshold value Vsh, the flow velocity Vin1 of the first outlet flow channel 2 and the flow velocity Vin2 of the second outlet flow channel 2 is a relationship of Vin1 <Vsh <Vin2. Check if it exists. When the relation Vin1 <Vsh <Vin2 is established, the process proceeds to step S112. When the relation Vin1 <Vsh <Vin2 is not established, the process proceeds to step S114.

In step S114, the value of the flow velocity Vin2 of the second outlet flow channel 2 is set as the flow velocity Vin1 of the first outlet flow channel 2 and the process returns to step S108.
In step S112, it is confirmed whether the control of the piezoelectric element 6 is to be continued or stopped. When the control of the piezoelectric element 6 is stopped, the process is stopped, and when the control of the piezoelectric element 6 is continued. The process returns to step S102.

  As described above, in the present embodiment, as shown in FIG. 2, the fluid in the outlet channel 2 has a flow rate during the period in which the pump internal pressure is lower than the load pressure after the application of the drive voltage for one time is finished. However, if the discharge fluid volume is equal to the suction fluid volume or the suction fluid volume is increased, the pump internal pressure becomes higher than the load pressure, and the flow velocity in the outlet channel 2 starts to increase. Yes. Therefore, if the control for applying the driving voltage to the next piezoelectric element 6 is performed at the time when the flow velocity of the outlet flow path 2 increases as in the flow velocity-cycle conversion circuit 22f of the present embodiment, the discharge fluid volume and the suction fluid Since the diaphragm 5 starts to be displaced at a point where the volume is equal or the suction fluid volume is larger, useless consumption of the excluded fluid volume is prevented, and the discharge fluid volume of the pump increases.

  Although not shown, the flow velocity peak value when the diaphragm is moved in a certain reference period T0, and the correction amount to be added to the reference period when it is set to the maximum flow velocity peak value are classified according to the displacement speed of the diaphragm, and There is also a method in which a map is recorded in a ROM or the like constituting the cycle control circuit 22 in advance by experiment for each load pressure. In that case, when the diaphragm is moved at a certain reference period T0 under the known diaphragm displacement speed and load pressure conditions, measurement by the flow velocity sensor 32 is started, and the peak value is calculated from the measured value. After that, the corresponding correction amount is found with reference to the ROM map, and from the next time, the trigger signal is output in a cycle obtained by adding the correction amount to the reference cycle T0. Even if it does in this way, there can exist an effect similar to embodiment mentioned above.

  As the flow rate sensor 32, an ultrasonic type, a method of measuring by converting the flow rate into pressure, a hot wire type flow rate sensor, or the like can be used. Moreover, the position where the flow velocity sensor 32 is installed may be on the downstream side including the outlet channel.

Further, FIG. 18 shows an eighth embodiment according to the present invention.
In the present embodiment, a chamber 40 capable of storing a fluid is connected to the outlet flow path 2 of the pump. The chamber 40 and a liquid level sensor 42 provided in the chamber 40 constitute a moving fluid volume measuring means, and liquid level height detection information is input from the liquid level sensor 42 to the driving means 20. ing.

  The chamber 40 is initially emptied. When the fluid is discharged from the outlet channel 2 of the pump, the driving unit 20 measures the discharge time and the liquid level, and calculates the discharge volume per unit time of the diaphragm 5. Then, the motion cycle of the diaphragm 5 is appropriately set so that the discharge volume becomes maximum. As a result, the diaphragm can be moved with an optimal movement cycle that maximizes the volume of the discharged fluid per unit time, and a pump with high driving efficiency can be provided.

  Further, the chamber 40 and the liquid level sensor 42 provided in the chamber 40 are not moving fluid volume measuring means, but a pulsation absorbing buffer is provided in the inlet channel 1 or the outlet channel 2 (not shown). There may be provided a moving fluid volume measuring means for measuring the displacement amount of the buffer film and outputting it to the driving means 20, and the movement period of the diaphragm 5 may be set so that the displacement amount of the buffer film is maximized. . This is because the buffer film vibrates with a larger amplitude as the discharge fluid volume (= suction fluid volume) per pumping cycle increases, so when the displacement amount of the buffer film is maximum, the buffer film per pumping cycle. This is because the discharge fluid volume (= suction fluid volume) is also maximized.

  1: inlet channel, 2: outlet channel, 3: pump chamber, 4: check valve, 5: diaphragm (movable wall), 6: piezoelectric element (actuator), 20: driving means, 22: cycle control circuit ( Cycle control means), 22d: pressure-cycle conversion circuit, 22e: displacement-cycle conversion circuit, 24: waveform generation circuit, 28: pressure sensor (pump pressure detection means), 30: displacement sensor, 32: flow velocity sensor (flow velocity measurement) Means), 40: chamber (moving fluid volume measuring means), 42: liquid level sensor (moving fluid volume measuring means)

Claims (1)

An actuator for displacing a movable wall such as a piston or a diaphragm, a driving means for driving and controlling the actuator, a pump chamber whose volume can be changed by the displacement of the movable wall, and an inlet flow channel for flowing a working fluid into the pump chamber And a pump provided with an outlet channel for allowing the working fluid to flow out of the pump chamber,
The outlet channel communicates with the pump chamber during pump operation, the combined inertance value of the inlet channel is smaller than the combined inertance value of the outlet channel, and working fluid flows into the pump chamber in the inlet channel A fluid resistance element that is smaller than the fluid resistance when the fluid resistance flows out,
The drive means includes a cycle control means for changing a motion cycle of the movable wall,
The period control means drives the actuator so that the pump chamber volume compression process of the movable wall starts when the pressure in the pump chamber reaches absolute 0 atmosphere .

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