JP2010019182A - Piezoelectric pump driving circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piezoelectric pump driving circuit for achieving pumping operation superior in quietness by removing the noise components of alternating voltage applied to a piezoelectric vibrator. <P>SOLUTION: The piezoelectric pump driving circuit is stored in a housing together with the piezoelectric vibrator having a pump chamber formed on at least one of the surface and the reverse, for driving the piezoelectric vibrator with alternating voltage. It comprises a high voltage control part for applying alternating voltage to the piezoelectric vibrator, and a parallel capacitor provided between the high voltage control part and the piezoelectric vibrator and connected in parallel to the piezoelectric vibrator. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a drive circuit for a piezoelectric pump that is housed in the same housing as a piezoelectric vibrator that acts as a pump and drives the piezoelectric vibrator with an alternating voltage.

A piezoelectric pump forms a variable volume chamber (pump chamber) between a plate-shaped piezoelectric vibrator and a housing, and vibrates the piezoelectric vibrator, thereby changing the volume of the variable volume chamber to obtain a pump action. . 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. In recent years, such a piezoelectric pump has been used as a cooling water circulation pump of a water-cooled notebook personal computer. The piezoelectric vibrator and a drive circuit for driving the piezoelectric vibrator with an alternating voltage are housed in the same housing and are small. To make it thinner and thinner.
JP-A-2-253890 JP-A-6-14563 Japanese Patent Laid-Open No. 6-310772 JP-A-8-237960 JP 2002-339872 A JP 2003-244964 A

  The drive circuit of a piezoelectric pump generally has a high voltage control unit that generates an AC voltage, and drives the piezoelectric vibrator with this AC voltage. However, when a rectangular wave voltage is used as an AC voltage applied to the piezoelectric vibrator, the volume time change of the piezoelectric vibrator is increased and the pump performance is improved as compared with the case of using a sine wave voltage. An instantaneous inrush current generated by the above acts as noise. Not only the rectangular wave voltage but all edge portions included in the voltage waveform of the AC voltage applied to the piezoelectric vibrator become noise sources. Noise is a major problem in liquid-cooled piezoelectric pumps that require quietness. For this reason, conventionally, the piezoelectric vibrator had to be driven by a sine wave voltage or a pseudo sine wave voltage based on a sine wave. If sine wave voltage or pseudo sine wave voltage is used, circuit efficiency will be low, so measures to improve efficiency will be required, circuit scale cannot be reduced, and general-purpose ICs cannot be used. It was.

  An object of the present invention is to obtain a piezoelectric pump drive circuit capable of removing a noise component of an AC voltage applied to a piezoelectric vibrator and realizing a pump operation excellent in silence based on the above problem awareness.

  In the present invention, if a capacitor connected in parallel with the piezoelectric vibrator is arranged on the output side of the high voltage control unit, even if the piezoelectric vibrator is driven with an AC voltage other than a sine wave voltage, the noise component of the AC voltage is a capacitor. It was completed by paying attention to the fact that noise can be reduced by removing the noise and that the degree of freedom in circuit design is increased by using an AC voltage other than a sine wave voltage.

  That is, the present invention is a piezoelectric pump drive circuit that is housed in a housing together with a piezoelectric vibrator that forms a pump chamber on at least one side of the front and back, and drives the piezoelectric vibrator with an alternating voltage. A high voltage control unit for applying a voltage is provided, and a parallel capacitor connected in parallel to the piezoelectric vibrator is provided between the high voltage control unit and the piezoelectric vibrator.

  The parallel capacitor is preferably disposed between an electric resistor connected in series to the high voltage control unit and an electric resistor connected in series to the piezoelectric vibrator. According to this aspect, the noise filter is configured by the electric resistor and the parallel capacitor, and the noise of the AC voltage can be further reduced.

  The parallel capacitor is preferably composed of a pair of capacitors connected in series, and is connected to the ground between the pair of capacitors. According to this aspect, since the electric charge accumulated in the pair of capacitors flows to the ground, the electric charge held in the capacitors can be suppressed, and there is no possibility that the parallel capacitor becomes a noise source with respect to the piezoelectric vibrator. Further, since the withstand voltage required for each capacitor constituting the parallel capacitor is suppressed, the degree of freedom in design is increased.

  The capacitance of the parallel capacitor is preferably at least 1/2 of the element capacity of the piezoelectric vibrator. By doing in this way, it can prevent that the electric current which arises by spike noise flows into a piezoelectric vibrator.

  It is practical that the high voltage control unit applies a rectangular wave voltage to the piezoelectric vibrator. If the piezoelectric vibrator is driven with a rectangular wave voltage, the circuit efficiency is better than when the piezoelectric vibrator is driven with a sine wave voltage, and the circuit configuration can be simplified by using a general-purpose IC. It is advantageous to make.

  According to the present invention, a capacitor provided to be connected in parallel with the piezoelectric vibrator on the output side of the high voltage control unit, the noise component (inrush) of the AC voltage applied from the high voltage control unit to the piezoelectric vibrator. Therefore, it is possible to obtain a piezoelectric pump drive circuit capable of reducing noise and realizing pump operation with excellent quietness.

  1 to 5 show the overall configuration of a piezoelectric pump 100 having a drive circuit according to the present invention. The piezoelectric pump 100 is a driver built-in type piezoelectric pump in which the piezoelectric vibrator 10 and the drive circuit 50 are housed in a single housing 20.

  The housing 20 includes an upper lid (upper housing) 20A, a main housing 20B, and a lower lid (lower housing) 20C. In the main housing 20B, a circular recess 41 (FIGS. 3 and 5) is formed to open to the upper lid 20A side, and a substrate storage recess 51 (FIGS. 4 and 5) is formed to open to the lower lid 20C side. Yes. 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 thin metal plate made of stainless steel or 42 alloy having a thickness of about 30 to 300 μm, and the piezoelectric body 12 is a piezoelectric material such as PZT (Pb (Zr, Ti) O ₃ ) having a thickness of about 50 to 600 μm. It is composed of materials and is polarized in the front and back direction. Such a piezoelectric vibrator is well known. When an AC voltage 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. The piezoelectric vibrator 10 has a unimorph structure, but may have a bimorph or multimorph structure.

  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 located 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 not vice versa. 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 circuit 50 is fitted in the substrate housing recess 51 of the main housing 20B and covered with the lower lid 20C.

  The drive circuit 50 includes an electronic circuit component 53 (FIGS. 4 and 5) that performs drive control on the piezoelectric vibrator 10 and printed wiring (not shown) that connects the electronic circuit components 53 on the substrate. Yes. 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 circuit 50.

  Next, drive control of the piezoelectric vibrator 10 by the drive circuit 50 of the present invention will be described with reference to FIG.

  FIG. 6 is a block diagram showing a drive control system of the piezoelectric vibrator 10. The drive circuit 50 includes a power supply 500, a booster circuit 501, and a waveform generation circuit 502 in a low voltage part that processes a low voltage (DC voltage DC1), and a high voltage control in a high voltage part that processes a high voltage (DC voltage DC2). A circuit 503 is provided.

  The booster circuit 501 boosts the DC voltage DC1 input from the power supply 500 and outputs a DC voltage DC2 higher than the DC voltage DC1 to the high voltage control circuit 503. In this embodiment, for example, a DC voltage DC1 of 5V is boosted to a DC voltage DC2 of 200V.

  The waveform generation circuit 502 receives the DC voltage DC1 from the power supply 500 and generates a rectangular wave signal S1 for driving control for the piezoelectric vibrator 10. The frequency and amplitude of the rectangular wave signal S1 can be set as appropriate within the range of the input voltage according to the driving mode of the piezoelectric vibrator 10.

  The high voltage control circuit 503 synthesizes the DC voltage DC2 boosted by the booster circuit 501 and the rectangular wave signal S2 generated by the waveform generation circuit 502 to generate an AC voltage S3 at a level capable of driving the piezoelectric vibrator 10. The AC voltage S3 is generated and applied to the piezoelectric vibrator 10. The signal waveform of the AC voltage S3 is a rectangular wave corresponding to the rectangular wave signal S2. The high voltage control circuit 503 of the present embodiment generates an AC voltage S3 having an amplitude (amplitude from the peak to the peak of the voltage applied between the front and back electrodes of the piezoelectric vibrator) Vop of 175V.

  The high voltage control circuit 503 can be configured by a general-purpose IC by using the rectangular wave AC voltage S3. As a result, the circuit efficiency can be improved, the circuit scale can be simplified and the size can be reduced.

  The pair of output lines 504 of the high voltage control circuit 503 is connected to the first power supply line 14 and the second power supply line 15 which are a pair of input lines of the piezoelectric vibrator 10 via the first to fourth electric resistors R1 to R4. Connected to the ground via the fifth electric resistor R5.

  The driving circuit 50 includes a parallel connection between the high voltage control circuit 503 and the piezoelectric vibrator 10, that is, between the pair of output lines 504 of the high voltage control circuit 503. A capacitor C is provided. The parallel capacitor C is located between the first and second electric resistors R1 and R2 on the high voltage control circuit 503 side and the third and fourth electric resistors R3 and R4 on the piezoelectric vibrator 10 side. A noise filter is comprised with the bodies R1-R5. As described above, the AC voltage S3 is a rectangular wave voltage, and overshoot and undershoot that are likely to occur in the AC voltage S3 are reduced by the electric resistors R1 to R5, and the inrush current generated when the AC voltage S3 is turned on / off is a parallel capacitor. Since it is absorbed by C, the noise component (spike noise) of the current waveform applied to the piezoelectric vibrator 10 can be reduced.

  The parallel capacitor C includes a pair of capacitors C1 and C2 connected in series, and is connected to the ground at an intermediate position between the pair of capacitors C1 and C2. Since the noise component absorbed by the capacitors C1 and C2 flows to the ground, the accumulated charge of the capacitors C1 and C2 can be suppressed to a small value. That is, there is no possibility that the capacitors C1 and C2 act as noise sources of the piezoelectric vibrator 10. Further, since the drive waveform applied to the piezoelectric vibrator 10 becomes large at the zero cross point at which the waveform is switched, spike noise can be reduced more effectively by providing a ground between the pair of capacitors C1 and C2. The pair of capacitors C1 and C2 are the same capacitor. The parallel capacitor C can of course be composed of a single capacitor, but if it is composed of a plurality of capacitors as in this embodiment, the withstand voltage required for each capacitor can be suppressed, and the degree of design freedom is increased. Expand.

  If the capacitance of the parallel capacitor C is small, a current caused by spike noise flows to the piezoelectric vibrator 10 side, and therefore, it is preferable that the capacitance of the parallel capacitor C is equal to or larger than the element capacity of the piezoelectric vibrator 10. In this embodiment, the element capacity of the piezoelectric vibrator 10 is 62 μF, and the electrostatic capacity of the bypass capacitor 507 is 39 μF.

  When the AC voltage S3 is applied, the piezoelectric vibrator 10 vibrates forward and backward based on the AC voltage S3. In the process of expanding the volume of the liquid pump chamber P due to 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 AC voltage S3 applied to the piezoelectric vibrator 10 is a rectangular high voltage, but noise is applied before the piezoelectric vibrator 10 is applied due to the filter effect of the parallel capacitor C and the electric resistors R1 to R5. Since the component is removed, noise can be reduced. Thereby, a quiet pump operation | movement is realizable.

  In the above embodiment, noise is reduced by the parallel capacitor C connected in parallel with the piezoelectric vibrator 10, and the piezoelectric vibrator 10 is driven by the rectangular wave AC voltage S3, thereby improving the circuit efficiency and the high voltage control circuit. In 503, the circuit scale using a general-purpose IC is simplified and reduced in size. Specifically, the drive circuit 50 can be formed very small with a size of 20 mm × 31 mm and a thickness of 4.5 mm. As a result, the piezoelectric pump 100 can be downsized to 34 mm × 50 mm and a thickness of 8 mm after the drive circuit 50 is accommodated in the housing 20.

  As a noise removing means, it is conceivable to provide a coil instead of the parallel capacitor C or in addition to the parallel capacitor C. However, if a coil is used, spike noise cannot be removed, and the drive circuit 50 has a large size. It is difficult to make it housed in the housing 20.

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.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Piezoelectric pump 10 Piezoelectric vibrator 20 Housing 50 Drive board 500 Power supply 501 Booster circuit 502 Waveform generation circuit 503 High voltage control circuit 504 Output line C Parallel capacitor C1, C2 Capacitor R1-R5 Electric resistor

Claims (5)

A piezoelectric pump drive circuit that is housed in a housing together with a piezoelectric vibrator that forms a pump chamber on at least one side of the front and back, and drives the piezoelectric vibrator with an alternating voltage,
A high voltage control unit for applying an AC voltage to the piezoelectric vibrator, and a parallel capacitor connected in parallel to the piezoelectric vibrator is provided between the high voltage control unit and the piezoelectric vibrator. A drive circuit for a piezoelectric pump. 2. The piezoelectric pump drive circuit according to claim 1, wherein the parallel capacitor is disposed between an electric resistor connected in series to the high-voltage control unit and an electric resistor connected in series to the piezoelectric vibrator. 3. Piezoelectric pump drive circuit. 3. The piezoelectric pump drive circuit according to claim 1, wherein the parallel capacitor includes a pair of capacitors connected in series and is connected to the ground between the pair of capacitors. 4. The piezoelectric pump drive circuit according to claim 1, wherein the parallel capacitor has a capacitance of ½ or more of an element capacity of the piezoelectric vibrator. 5. 5. The piezoelectric pump drive circuit according to claim 1, wherein the high-voltage control unit applies a rectangular wave voltage to the piezoelectric vibrator. 6.

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