JP5000453B2 - Piezoelectric pump with built-in driver - Google Patents

Description

  The present invention relates to a piezoelectric pump having a piezoelectric pump and its control board built in the same housing.

A piezoelectric pump forms a variable volume chamber (liquid pump chamber) between a plate-like piezoelectric vibrator and a housing, and vibrates the piezoelectric vibrator to change the volume of the variable volume chamber to obtain a pump action. Yes. More specifically, a pair of flow valves connected to the variable volume chamber have a pair of check valves having different flow directions (a check valve that allows fluid flow to the variable volume chamber and a reverse valve that allows fluid flow from the variable volume chamber). When the volume of the variable volume chamber is changed by the vibration of the piezoelectric vibrator, the operation of closing one of the pair of check valves and opening the other is repeated accordingly, so that a pump action is obtained. Such a piezoelectric pump is used, for example, as a cooling water circulation pump of a water-cooled notebook personal computer. A piezoelectric vibrator and a control board (driver) that supplies a drive signal to the piezoelectric vibrator are housed in the same housing. Miniaturization and thinning are attempted (Patent Documents 1 to 4).
JP-A-5-329442 JP-A-6-188729 JP 2001-251874 A JP 2005-86184 A

  The control board of the piezoelectric pump includes a drive control component for the piezoelectric vibrator, such as a waveform generation circuit that generates a sine wave signal for drive control, a boost circuit that boosts a low input voltage from the power supply, and a voltage signal after boosting In general, a high voltage control circuit that provides a piezoelectric vibrator with a high voltage drive signal obtained by synthesizing a sine wave signal is mounted. In such a drive control system for generating a high voltage, the amount of current flowing through the output line of the high voltage drive signal (the amount of input current to the piezoelectric vibrator) is monitored, and when an abnormal current is detected, the high voltage drive signal A protection circuit that forcibly cuts off the output is provided.

  However, when external noise is applied to the output line of the high voltage drive signal, the external noise is erroneously detected as an abnormal current by the protection circuit, and the output of the high voltage drive signal is frequently interrupted. Yes. Patent Documents 1 to 4 disclose that a bypass capacitor is used as a countermeasure for removing noise generated from the inside of the power supply. However, a method for removing external noise so as to avoid erroneous detection of abnormal current by the protection circuit is disclosed. Not. In order to remove external noise, it is common to attach a relatively large external attachment component such as a coil to the output section. To obtain a sufficient noise countermeasure effect, the piezoelectric pump control board is enlarged. Invite. In addition, noise removal using beads is performed, but no complete countermeasure has been achieved.

  The present invention is based on the above awareness of the problem. The piezoelectric pump with a built-in driver that can eliminate the noise component of the high-voltage drive signal to avoid erroneous detection of the protection circuit and realize a stable pump operation can be realized with a small electronic device such as a notebook PC. The purpose is to obtain a UL standard that is easy to obtain and small in size so that it can be easily installed in equipment.

  In the present invention, if a bypass capacitor is arranged between the output line of the high-voltage drive signal and the ground, external noise on the high-voltage drive signal can be removed (absorbed), and erroneous detection by the protection circuit can be avoided. It was completed paying attention to.

  That is, the present invention accommodates in a single housing a piezoelectric vibrator that forms a liquid pump chamber on at least one surface of the front and back, and a control board on which a drive control component for the piezoelectric vibrator is mounted. A high-voltage control circuit that outputs a high-voltage drive signal to the piezoelectric vibrator on the control board. And a protection circuit that monitors the amount of current flowing through the output line of the high voltage drive signal and forcibly terminates the output of the high voltage drive signal when an abnormal current is detected. A bypass capacitor is provided between the output line and ground.

The capacitance of the bypass capacitor is preferably 10% or less of the element capacity of the piezoelectric vibrator. According to this aspect, an increase in current consumption due to the provision of the bypass capacitor can be suppressed.
Preferably, the bypass capacitor is connected to the output line at a position closer to the piezoelectric vibrator than a connection point between the output line and the protection circuit.

  Specifically, the control board has a digital waveform generation circuit that generates a sine wave digital signal for drive control, an active filter that extracts only low frequency components from the sine wave digital signal generated by the digital waveform generation circuit, and an input And a high voltage control circuit that synthesizes the boosted DC voltage signal and the sine wave digital signal that has passed through the active filter to generate a high voltage drive signal. It is practical.

  According to the present invention, since the bypass capacitor is provided between the output line of the high voltage drive signal and the ground, the noise component from the outside in the high voltage drive signal is removed, so that erroneous detection of the protection circuit can be avoided and stable. Thus, a piezoelectric pump with a built-in driver that can realize the pump operation is obtained.

  1 to 6 show the overall configuration of a piezoelectric pump 100 according to an embodiment of the present invention. The piezoelectric pump 100 includes a piezoelectric vibrator 10, a housing 20, and a drive substrate 50. The housing 20 includes an upper lid (upper housing) 20A, a main housing 20B, and a lower lid (lower housing) 20C. The main housing 20B is opened to the upper lid 20A side and has a circular recess 41 (see FIGS. 3 and 5). ) Is formed, and the substrate housing recess 51 (see FIGS. 4 and 5) is formed by opening the lower lid 20C. On the periphery of the circular recess 41, an O-ring housing annular groove 41a is formed concentrically.

  As shown in FIGS. 3 and 5, the piezoelectric vibrator 10 includes a circular metal shim 11 and a circular piezoelectric body 12 formed on one of the front and back surfaces of the shim 11. In this embodiment, the shim 11 faces the liquid pump chamber P side, and the piezoelectric body 12 faces the atmosphere chamber A side.

The shim 11 is a conductive metal thin plate made of stainless steel having a thickness of about 30 to 300 μm or 42 alloy, and the piezoelectric body 12 is made of PZT (Pb (Zr, Ti) O ₃ ) having a thickness of about 50 to 300 μm, for example. It is comprised from the piezoelectric material of this, and the polarization process is given to the front and back direction. Such a piezoelectric vibrator is well known. When an alternating electric field (high voltage drive signal) is applied to the front and back of the piezoelectric body 12, a cycle in which one of the front and back of the piezoelectric body 12 extends and the other contracts is repeated, and the shim 11 (piezoelectric vibrator 10) vibrates.

  As shown in FIG. 5, a first power supply line (lead member) 14 is conductively connected to the piezoelectric vibrator 10 through a conductive rubber 18 at the surface periphery of the piezoelectric body 12. The conductive rubber 18 is made of conductive rubber that maintains its rubber property and has a small volume resistivity value. In addition, the second power supply line 15 is connected to the wiring connection protrusion 11 c that is integrally formed by protruding from the shim 11 in the radial direction.

  An O-ring 27 is inserted into the O-ring housing annular groove 41a of the main housing 20B, and the piezoelectric vibrator 10 is inserted into the circular recess 41. The piezoelectric vibrator 10 is tightly supported in a liquid-tight manner by placing the upper cover 20A on the main housing 20B with the annular guide 28 interposed on the periphery of the piezoelectric vibrator 10. A liquid pump chamber P is formed between the piezoelectric vibrator 10 and the circular recess 41, and an air chamber (atmosphere pump chamber) A is formed between the piezoelectric vibrator 10 and the upper lid 20A.

  In the main housing 20B, a suction-side liquid reservoir chamber 42 and a discharge-side liquid reservoir chamber 43 are formed in the circular concave portion 41 so as to be positioned at an eccentric symmetry position with respect to the plane center of the piezoelectric vibrator 10 (circular concave portion 41). Yes. Between the suction-side liquid reservoir chamber 42 and the liquid pump chamber P, and between the discharge-side liquid reservoir chamber 43 and the liquid pump chamber P, a suction-side check valve 32 and a discharge-side check valve 33 are provided, respectively. The main housing 20B is formed with a suction port 24 and a discharge port 25 communicating with the suction-side liquid storage chamber 42 and the discharge-side liquid storage chamber 43.

  The suction-side check valve 32 is a suction-side check valve that allows a fluid flow from the suction port 24 to the liquid pump chamber P and does not allow the reverse fluid flow. The discharge-side check valve 33 is a liquid pump chamber. This is a discharge-side check valve that allows fluid flow from P to the discharge port 25 but does not allow the reverse fluid flow.

  The check valves 32 and 33 have the same configuration, and are provided with umbrellas 32b and 33b made of an elastic material on perforated substrates 32a and 33a that are bonded and fixed to the flow path.

  In the main housing 20B, feed line storage grooves 45 and 46 are formed in the cylindrical portion 44 around the circular recess 41 so as to have different circumferential positions (FIGS. 4 and 5). The power supply line storage grooves 45 and 46 pass the first power supply line 14 and the second power supply line 15, and have a large cross-sectional area so that a sufficient air circulation space can be ensured even in the passed state.

  The main housing 20B is formed with an important lack (atmosphere chamber passage, through hole) 52 that allows the atmosphere chamber A and the substrate housing recess 51 to communicate with each other via the power supply line housing grooves 45 and 46 (FIGS. 4 and 4). 5). As shown in FIG. 4, the upper surface of the important piece 52 is closed by the upper lid 20A that covers the main housing 20B.

  The main housing 20B also has an external communication path (hole) 54 that allows the substrate storage recess 51 to communicate with the outside. Accordingly, the substrate housing recess 51 communicates with the atmosphere chamber A via the important part 52 and the power supply line housing grooves 45 and 46 and communicates with the outside via the external communication path 54. For this reason, the atmosphere chamber A communicates with the outside even when the drive substrate 50 is fitted in the substrate housing recess 51 of the main housing 20B and covered with the lower lid 20C. That is, when the piezoelectric vibrator 10 vibrates and the volume of the atmospheric chamber A is reduced, an outward air flow is generated through the power supply line storage grooves 45 and 46, the important part 52, the substrate storage recess 51 and the external communication path 54. On the contrary, when the volume of the atmospheric chamber A increases, an inward air flow is generated through the external communication path 54, the substrate housing recess 51, the important part 52, and the power supply line housing grooves 45 and 46.

  On the drive substrate 50, an electronic circuit component 53 (FIGS. 4 and 5) that performs drive control on the piezoelectric vibrator 10 and a printed wiring (not shown) that connects the electronic circuit components 53 are formed. . The first power supply line 14 and the second power supply line 15 guided to the outside of the atmospheric chamber A (circular recess 41) through the power supply line storage grooves 45 and 46 are connected to the drive substrate 50. Heat generated by the electronic circuit component 53 on the drive substrate 50 is generated by the outward air flow through the power supply line storage grooves 45 and 46, the important part 52, the substrate storage recess 51 and the external communication path 54, or the external communication path 54 and the substrate. The air is released to the outside by the inward air flow passing through the storage recess 51, the important notch 52 and the power supply line storage grooves 45, 46. In addition, since the drive board 50 is housed in the main housing, a circuit board that generates a high voltage enters the inside from the outside of the piezoelectric pump 100, which is advantageous for obtaining the UL standard and the like. Therefore, the degree of freedom of arrangement in a small electronic device such as a notebook PC increases.

Next, drive control of the piezoelectric vibrator 10 will be described with reference to FIGS.
FIG. 6 is a block diagram showing a drive control system (electronic circuit component 53) of the piezoelectric vibrator 10. As shown in FIG. This drive control system includes a power supply 500, a booster circuit 501, a digital waveform generation circuit 502, a secondary active filter 503, a high voltage control circuit 504, an output line 505, and an output current feedback control line (protection circuit). 506 and a bypass capacitor 507. The power supply 500, the booster circuit 501, the digital waveform generation circuit 502, and the secondary active filter 503 constitute a low voltage unit that processes a low voltage signal (DC voltage signal DC1), and includes a high voltage control circuit 504, an output current feedback control line. (Protection circuit) 506 and bypass capacitor 507 constitute a high voltage unit for processing a high voltage signal (DC voltage signal DC2).

  The booster circuit 501 boosts the DC voltage signal (low voltage signal) DC1 input from the power supply 500 and outputs a DC voltage signal (high voltage signal) DC2 higher than the DC voltage signal DC1 to the high voltage control circuit 504. In this embodiment, for example, a DC voltage signal DC1 of 5V is boosted to a DC voltage signal DC2 of 200V. The booster circuit 501 may be provided in the high voltage control circuit 504.

  The digital waveform generation circuit 502 receives the DC voltage signal DC1 from the power supply 500 and generates a sine wave digital signal S1 for driving control for the piezoelectric vibrator 10. The frequency and amplitude of the sine wave digital signal S <b> 1 can be appropriately set according to the driving mode of the piezoelectric vibrator 10. Since the sine wave digital signal S1 represents a sine wave waveform by a non-continuous digital value (voltage value), a stepwise voltage change, that is, a locally steep voltage change occurs along the time axis. The sine wave digital signal S1 can be brought close to an ideal continuous sine wave waveform by increasing the resolution of the time axis and the voltage axis, but there is a limit in the configuration of the digital waveform generation circuit 502. In the sine wave digital signal S1 of the present embodiment, the maximum amplitude (amplitude from the positive peak to the negative peak) Vpp is set to 3V.

  The secondary active filter 503 receives the sine wave digital signal S1 generated by the digital waveform generation circuit 502, blocks a frequency component higher than a predetermined cut-off frequency fc in the sine wave digital signal S1, and Only low frequency components below the cut-off frequency fc are extracted. Since the high frequency component is removed by the secondary active filter 503, the sine wave digital signal S2 has a smooth signal waveform with no stepwise steep voltage change, and approaches an ideal sine wave waveform. The maximum amplitude Vpp of the sine wave digital signal S2 is 3V, as in the sine wave digital signal S1 before passing through the secondary active filter 503. FIG. 7 shows a specific circuit configuration example of a secondary active filter 503 including an operational amplifier OP, resistors R1 and R2, and capacitors C1 and C2.

  The high voltage control circuit 504 can drive the piezoelectric vibrator 10 by synthesizing the DC voltage signal DC2 that has been boosted by the boosting circuit 501 and the smooth sine wave digital signal S2 that has passed through the secondary active filter 503. A high voltage drive signal S3 of a level is generated. The high voltage drive signal S3 has a smooth signal waveform (sinusoidal waveform) with no steep voltage change like the sine wave digital signal S2. The high voltage control circuit 504 of the present embodiment generates a high voltage drive signal S3 having an amplitude (amplitude from 0V to one of the positive and negative peaks) Vop of 170V.

  The output line 505 is a signal line that connects between the high voltage control circuit 504 and the piezoelectric vibrator 10, and provides the piezoelectric vibrator 10 with the high voltage drive signal S 3 generated by the high voltage control circuit 504.

The output current feedback control line (protection circuit) 506 is connected to the output line 505 and the wiring part in the high voltage control circuit 504, and the amount of current flowing through the output line 505 (the amount of input current to the piezoelectric vibrator 10) is determined. Monitor and forcibly cut off the output of the high voltage drive signal S3 (output from the high voltage control circuit 504) when an abnormal current is detected. In the present embodiment, when the amount of current flowing through the output line 505 exceeds the first specified value, it is assumed that the piezoelectric vibrator 10 is short-circuited, and the amount of current is equal to the second specified value. If it falls below, it is assumed that the piezoelectric vibrator 10 is in an open state (no load), so that the output of the high voltage drive signal S3 is cut off.

  The bypass capacitor 507 is located between the output line 505 and the output current feedback control line (protection circuit) 506 on the piezoelectric vibrator 10 side, and is connected between the output line 505 and the ground G. Is absorbed in the high voltage drive signal S3 passing through the output line 505.

  Since the bypass capacitor 507 functions as a load of the power source 500 together with the piezoelectric vibrator 10, an increase in current consumption can be suppressed as the electrostatic capacitance is smaller. Actually, the electrostatic capacitance Cb of the bypass capacitor 507 is set within 10% of the element capacitance C of the piezoelectric vibrator 10 (Cb / C ≧ 0.1). In this embodiment, the element capacity of the piezoelectric vibrator 10 is 0.05 μF, and the electrostatic capacity of the bypass capacitor 507 is 0.005 μF.

  When the high voltage drive signal S3 is given, the piezoelectric vibrator 10 vibrates (elastically deforms) forward and backward based on the high voltage drive signal S3. In the process of expanding the volume of the liquid pump chamber P by the vibration of the piezoelectric vibrator 10, the piezoelectric pump 100 opens the suction side check valve 32 and closes the discharge side check valve 33. In the process of reducing the volume of the liquid pump chamber P while the liquid flows into the chamber P, the discharge side check valve 33 is opened and the suction side check valve 32 is closed. Liquid flows out. Thereby, a pump action is obtained. During this pumping action, the bypass capacitor 507 absorbs noise on the output line 505 (high voltage drive signal S3), so that no noise is superimposed on the output current feedback control line (protection circuit) 506, and noise is superimposed. An abnormal current due to will not occur. As a result, output interruption of the high voltage drive signal S3 due to erroneous detection of the protection circuit (output current feedback control line 506) can be avoided, and stable pump operation can be realized.

  The drive substrate 50 mounted with the above drive control system could be formed very small, 20 mm × 31 mm and 4.5 mm thick. As a result, the piezoelectric pump 100 can be downsized to 34 mm × 50 mm and a thickness of 8 mm after housing the drive substrate 50 in the housing 20. Although it is conceivable that the noise removing means is provided with a coil instead of the bypass capacitor 507, when the coil is used, the drive substrate 50 becomes large and difficult to be housed in the housing 20.

In this piezoelectric pump 100, the frequency of malfunction (noise stop probability) of the protection circuit (output current feedback control line 506) is made by changing the capacitance Cb of the bypass capacitor 507 while keeping the element capacitance C of the piezoelectric vibrator 10 constant. The measurement results obtained by measuring are shown in Table 1 and FIG. FIG. 8 shows the ratio (capacity ratio Cb / C) of the electrostatic capacitance Cb of the bypass capacitor 507 and the element capacitance C of the piezoelectric vibrator 10 and the frequency of occurrence of malfunction [%] in the protection circuit (output current feedback control line 506). And a graph showing the relationship between the current consumption [mA] of the entire drive control system.

From Table 1, it can be seen that when the capacity ratio Cb / C is 100% or less and 0.1% or more, the noise stop probability is 0%, and the effect is obtained.
In Table 1 and FIG. 8, the capacity ratio Cb / C = 0.0% is a comparative example in which the bypass capacitor 507 is not provided, the malfunction occurrence frequency of the protection circuit is 40%, and the current consumption is 210 mA. It was.

On the other hand, when the capacitance ratio Cb / C> 0, the bypass capacitor 507 is provided. By providing the bypass capacitor 507, the malfunction occurrence frequency of the protection circuit becomes 0%, and no abnormal current due to external noise is generated in the output current feedback control line (protection circuit) 506, that is, the output line 505 It is clear that external noise has been removed. Further, it is clear that the amount of current consumption increases as the bypass capacitor 507 increases in capacitance. If the capacitance ratio Cb / C ≧ 0.1%, it is equivalent to the case where the bypass capacitor 507 is not provided with a current consumption 209 mA, and if the capacitance ratio Cb / C ≦ 10%, the bypass capacitor 507 is not provided with a current consumption 215 mA. It can be determined that the increase in current consumption is suppressed in some cases. In response to this result, in the present embodiment, the electrostatic capacitance Cb of the bypass capacitor 507 is set within 10% of the element capacitance C of the piezoelectric vibrator 10.

It is a top view which shows the piezoelectric pump by one Embodiment of this invention. It is the same rear view. It is sectional drawing which follows the III-III line | wire of FIG. 1, FIG. It is sectional drawing which follows the IV-IV line of FIG. 1, FIG. It is a disassembled perspective view of the same piezoelectric pump. It is a block diagram explaining the drive control system of the same piezoelectric pump. 7 is a specific circuit configuration example of the secondary active filter in FIG. 6. It is a graph which shows the relationship between the capacity | capacitance ratio of a bypass capacitor and a piezoelectric vibrator, the malfunction occurrence frequency of a protection circuit, and the consumption current amount.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Piezoelectric pump 10 Piezoelectric vibrator 20 Housing 50 Drive board 500 Power supply 501 Booster circuit 502 Digital waveform generation circuit 503 Secondary active filter 504 High voltage control circuit 505 Output line 506 Output current feedback control line (protection circuit)
507 Bypass capacitor

Claims (4)

A piezoelectric vibrator forming a liquid pump chamber on at least one side of the front and back in a single housing;
A piezoelectric pump with a built-in driver that houses a control board on which a drive control component for the piezoelectric vibrator is mounted, and vibrates the piezoelectric vibrator to supply and discharge liquid into the liquid pump chamber to perform a pumping action. ,
The control board monitors a high voltage control circuit that outputs a high voltage drive signal to the piezoelectric vibrator, and an amount of current flowing through the output line of the high voltage drive signal, and detects the abnormal voltage when the high voltage is detected. And a protection circuit for forcibly terminating the output of the drive signal,
And a driver built-in piezoelectric pump, wherein a bypass capacitor is provided between the output line of the high-voltage drive signal and the ground.   2. The piezoelectric pump with a built-in driver according to claim 1, wherein the ratio of the electrostatic capacity of the bypass capacitor to the element capacity of the piezoelectric vibrator is within 10%.   3. The driver built-in piezoelectric pump according to claim 1, wherein the bypass capacitor is connected to the output line at a position closer to the piezoelectric vibrator than a connection point between the output line and the protection circuit. .   4. The driver built-in piezoelectric pump according to claim 1, wherein the control board includes a digital waveform generation circuit that generates a sine wave digital signal for drive control, and a sine generated by the digital waveform generation circuit. An active filter that extracts only a low frequency component from the wave digital signal and a booster circuit that boosts the input DC voltage signal are provided, and the high voltage control circuit passes through the boosted DC voltage signal and the active filter. A piezoelectric pump with a built-in driver that synthesizes a sine wave digital signal to generate the high voltage drive signal.

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