JP2010239701A - Fuel cell system and piezoelectric pumping device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact and inexpensive fuel cell system capable of obtaining stable liquid sending operations of piezoelectric pumps, and to provide a piezoelectric pumping device. <P>SOLUTION: The piezoelectric pump 104 supplies fuel to a fuel cell power generation section (cell) 101 for generating electric power by performing pumping operation for repeating suction and discharge operations of fuel by bend operation of a piezoelectric element. The piezoelectric element 1045 of the piezoelectric pump 104 is driven by a drive circuit 5 for generating a drive voltage of a square-wave drive waveform. A resistor element 8 is connected between the drive circuit 5 and the piezoelectric element 1045 to compose an RC integrating circuit along with capacitance inherent in the piezoelectric element. The drive waveform is deformed to a waveform having a gentle rise for supply to the piezoelectric element 1045. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fuel cell system and a piezoelectric pump device applied to the fuel cell system.

  There have been remarkable miniaturizations of electronic devices such as mobile phones and portable information terminals, and along with the miniaturization of these electronic devices, attempts have been made to use fuel cells as a power source. A fuel cell has the advantage that it can generate electricity only by supplying fuel and air, and can generate electricity continuously by replacing only the fuel. Therefore, if it can be downsized, it can be used as a power source for small electronic devices. It is valid.

  Therefore, a direct methanol fuel cell (hereinafter, referred to as DMFC; Direct Methanol Fuel Cell) has attracted attention as a fuel cell. Such DMFCs are classified according to the liquid fuel supply system, such as an active system such as a gas supply type and a liquid supply type, and an internal vaporization type that vaporizes the liquid fuel in the fuel storage section inside the battery and supplies it to the fuel electrode. Among these, the passive type is particularly advantageous for reducing the size of the DMFC.

  Conventionally, as such a passive DMFC, as disclosed in Patent Document 1, for example, a membrane electrode assembly (fuel cell) having a fuel electrode, an electrolyte membrane, and an air electrode is removed from a resin box-like container. The thing of the structure arrange | positioned on the fuel accommodating part which becomes is considered.

Patent Documents 2 to 4 also disclose a configuration in which a DMFC fuel cell and a fuel storage unit are connected via a flow path. In these Patent Documents 2 to 3, the supply amount of the liquid fuel can be adjusted based on the shape and diameter of the flow path by supplying the liquid fuel supplied from the fuel storage portion to the fuel cell via the flow path. In particular, in Patent Document 3, liquid fuel is supplied from the fuel storage portion to the flow path by a pump. In this case, as a pump for supplying liquid fuel, for example, a piezoelectric pump using a piezoelectric element (diaphragm) as disclosed in Patent Document 4 is known.
International Publication No. 2005/112172 Pamphlet JP 2005-518646 A JP 2006-089552 A JP 2001-271757 A

  Incidentally, high-concentration methanol is used as a fuel in a conventional fuel cell using a DMFC as a main power generation unit. In order to perform a highly efficient power generation operation using such methanol as a fuel, for example, it is desirable to operate at a high temperature of about 50 ° C.

  However, if the temperature of the main power generation unit is operated at around 50 ° C., in a small fuel cell used for portable electronic devices, the heat of the power generation unit is transferred to the entire housing of the device. The fuel tank and other parts around the pump for sending the fuel may become hot, and the liquid is usually sent at a temperature very close to 64.7 ° C., which is known as the boiling point of methanol at a steady pressure. An action may be performed.

  On the other hand, a piezoelectric pump used for supplying liquid fuel is a drive circuit that is configured by a simple switching circuit or the like and generates a substantially rectangular wave drive voltage.

  However, if such a drive waveform is supplied to a piezoelectric pump that performs a liquid feeding operation in a high-temperature atmosphere, the piezoelectric element (diaphragm) is suddenly deformed due to a sudden rise in the drive waveform, so that the pump chamber The pressure may decrease rapidly. For this reason, so-called cavitation, in which bubbles are generated in the liquid fuel in the pump chamber, is likely to occur, and this causes the discharge pressure of the pump to drop and the liquid feeding operation to become unstable, making stable liquid feeding difficult. Cause problems.

  Therefore, conventionally, it has been considered to use a sine waveform or a sawtooth waveform with a gradual rise as the drive voltage waveform to avoid a sudden drop in the pressure in the pump chamber during fuel suction to prevent cavitation. It has been. However, a drive circuit for generating a sine waveform, a sawtooth waveform, or the like as a drive voltage requires the use of various active elements for waveform shaping, which complicates the circuit configuration and reduces the size of the fuel cell system. In addition to hindering the transition, there was a problem of increasing prices.

  In addition, an overcurrent may flow to the piezoelectric pump due to a short circuit accident of the switching circuit constituting the drive circuit. In such a case, since the piezoelectric element is directly connected to the drive circuit, the piezoelectric element of the piezoelectric pump However, there was a risk of damage due to overcurrent.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fuel cell system and a piezoelectric pump device that can obtain a stable liquid feeding operation for a piezoelectric pump and are small and inexpensive. .

  The invention according to claim 1 has a fuel cell main body that generates electric power by supplying fuel and a piezoelectric element, and repeatedly supplies and discharges fuel to the fuel cell main body by a deformation operation of the piezoelectric element. A piezoelectric pump, a driving means for generating a driving voltage having a rectangular waveform, and driving the piezoelectric element of the piezoelectric pump by the driving voltage; connected between the driving means and the piezoelectric element; and the piezoelectric element It comprises an RC integration circuit together with a specific capacitance, and a resistance element that transforms the drive waveform into a gradually rising waveform.

  According to a second aspect of the present invention, in the first aspect of the present invention, the drive waveform generated by the drive means includes a positive half wave and a negative half wave, and the piezoelectric pump is connected to the positive side of the drive waveform. The fuel suction operation is performed by a half wave, and the fuel discharge operation is performed by a negative half wave.

  The invention according to claim 3 is the invention according to claim 1 or 2, further comprising a diode connected in parallel to the resistance element, wherein the positive half-wave or the negative half-wave of the drive waveform has a steep rise. It is characterized by maintaining it.

  The invention according to claim 4 includes a piezoelectric pump having a piezoelectric element, and repeatedly supplying and discharging fuel to the fuel cell body by a deformation operation of the piezoelectric element, and a drive waveform having a rectangular wave shape. A drive means that generates a drive voltage and drives the piezoelectric element of the piezoelectric pump by the drive voltage, and is connected between the drive means and the piezoelectric element, and constitutes an RC integration circuit together with the capacitance inherent to the piezoelectric element. And a resistance element that deforms the drive waveform into a gradually rising waveform.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to obtain the stable liquid feeding operation | movement to a piezoelectric pump, it can provide the fuel cell system and piezoelectric pump apparatus which are small and cheap also in price.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 shows a schematic configuration of a fuel cell system according to a first embodiment of the present invention.

  In FIG. 1, reference numeral 1 denotes a fuel cell main body (DMFC). The fuel cell main body 1 includes a fuel cell power generation unit (cell) 101 that constitutes an electromotive unit, a fuel storage unit 102 that stores liquid fuel, and a fuel storage unit 102. And a flow path 103 connecting the fuel cell power generation unit (cell) 101 and a piezoelectric pump 104 as fuel supply control means for transferring liquid fuel from the fuel storage unit 102 to the fuel cell power generation unit (cell) 101. Yes. The piezoelectric pump 104 will be described later.

  FIG. 2 is a cross-sectional view for explaining the fuel cell main body 1 in more detail.

  In this case, the fuel cell power generation unit 101 includes an anode (fuel electrode) 13 having an anode catalyst layer 11 and an anode gas diffusion layer 12, and a cathode (air electrode / oxidation) having a cathode catalyst layer 14 and a cathode gas diffusion layer 15. The electrode assembly 16 has a membrane electrode assembly (MEA) composed of a proton (hydrogen ion) conductive electrolyte membrane 17 sandwiched between the anode catalyst layer 11 and the cathode catalyst layer 14. ing.

  Here, examples of the catalyst contained in the anode catalyst layer 11 and the cathode catalyst layer 14 include a simple substance of a platinum group element such as Pt, Ru, Rh, Ir, Os, and Pd, an alloy containing the platinum group element, and the like. It is done. For the anode catalyst layer 11, it is preferable to use Pt—Ru, Pt—Mo, or the like having strong resistance to methanol, carbon monoxide, or the like. Pt, Pt—Ni or the like is preferably used for the cathode catalyst layer 14. However, the catalyst is not limited to these, and various substances having catalytic activity can be used. The catalyst may be either a supported catalyst using a conductive support such as a carbon material or an unsupported catalyst.

  Examples of the proton conductive material constituting the electrolyte membrane 17 include a fluorine resin (Nafion (registered trademark) (trade name, manufactured by DuPont)) such as a perfluorosulfonic acid polymer having a sulfonic acid group, and Flemion (registered trademark). (Trade name, manufactured by Asahi Glass Co., Ltd.)), organic materials such as hydrocarbon resins having a sulfonic acid group, or inorganic materials such as tungstic acid and phosphotungstic acid. However, the proton conductive electrolyte membrane 17 is not limited to these.

  The anode gas diffusion layer 12 laminated on the anode catalyst layer 11 serves to uniformly supply fuel to the anode catalyst layer 11 and also serves as a current collector for the anode catalyst layer 11. The cathode gas diffusion layer 15 laminated on the cathode catalyst layer 14 serves to uniformly supply the oxidant to the cathode catalyst layer 14 and also serves as a current collector for the cathode catalyst layer 14. The anode gas diffusion layer 12 and the cathode gas diffusion layer 15 are made of a porous substrate.

  A conductive layer is laminated on the anode gas diffusion layer 12 and the cathode gas diffusion layer 15 as necessary. As these conductive layers, for example, a porous layer (for example, mesh) made of a conductive metal material such as Au or Ni, a porous film, a foil body, a conductive metal material such as stainless steel (SUS), gold or the like. A composite material coated with a highly conductive metal is used. Rubber O-rings 19 are interposed between the electrolyte membrane 17 and a fuel distribution mechanism 105 and a cover plate 18, which will be described later, thereby preventing fuel leakage and oxidant leakage from the fuel cell power generation unit 101. is doing.

  The cover plate 18 has an opening (not shown) for taking in air as an oxidant. A moisture retaining layer and a surface layer are disposed between the cover plate 18 and the cathode 16 as necessary. The moisturizing layer is impregnated with a part of the water generated in the cathode catalyst layer 14 to suppress the transpiration of water and promote uniform diffusion of air to the cathode catalyst layer 14. The surface layer adjusts the amount of air taken in, and has a plurality of air inlets whose number, size, etc. are adjusted according to the amount of air taken in.

  A fuel distribution mechanism 105 is disposed on the anode (fuel electrode) 13 side of the fuel cell power generation unit 101. A fuel storage unit 102 is connected to the fuel distribution mechanism 105 via a liquid fuel flow path 103 such as a pipe.

  Liquid fuel corresponding to the fuel cell power generation unit 101 is stored in the fuel storage unit 102. Examples of the liquid fuel include methanol fuels such as aqueous methanol solutions of various concentrations and pure methanol. The liquid fuel is not necessarily limited to methanol fuel. The liquid fuel may be, for example, an ethanol fuel such as an ethanol aqueous solution or pure ethanol, a propanol fuel such as a propanol aqueous solution or pure propanol, a glycol fuel such as a glycol aqueous solution or pure glycol, dimethyl ether, formic acid, or other liquid fuel. In any case, liquid fuel corresponding to the fuel cell power generation unit 101 is stored in the fuel storage unit 102.

  Fuel is introduced into the fuel distribution mechanism 105 from the fuel storage portion 102 via the flow path 103. The flow path 103 is not limited to piping independent of the fuel distribution mechanism 105 and the fuel storage unit 102. For example, when the fuel distribution mechanism 105 and the fuel storage unit 102 are stacked and integrated, a fuel flow path connecting them may be used. The fuel distribution mechanism 105 only needs to be connected to the fuel storage unit 102 via the flow path 103.

  Here, as shown in FIG. 3, the fuel distribution mechanism 105 includes at least one fuel inlet 21 through which fuel flows through the flow path 103 and a plurality of fuel outlets 22 through which fuel and its vaporized components are discharged. The fuel distribution plate 23 having As shown in FIG. 2, a gap 24 serving as a fuel passage led from the fuel inlet 21 is provided inside the fuel distribution plate 23. The plurality of fuel discharge ports 22 are directly connected to gaps 24 that function as fuel passages.

  The fuel introduced into the fuel distribution mechanism 105 from the fuel inlet 21 enters the gap portion 24 and is guided to the plurality of fuel discharge ports 22 through the gap portion 24 functioning as the fuel passage. For example, a gas-liquid separator (not shown) that transmits only the vaporized component of the fuel and does not transmit the liquid component may be disposed in the plurality of fuel discharge ports 22. As a result, the fuel vaporization component is supplied to the anode (fuel electrode) 13 of the fuel cell power generation unit 101. The gas-liquid separator may be installed as a gas-liquid separation membrane or the like between the fuel distribution mechanism 105 and the anode 13. The vaporized component of the fuel is discharged from a plurality of fuel discharge ports 22 toward a plurality of locations on the anode 13.

A plurality of fuel discharge ports 22 are provided on the surface of the fuel distribution plate 23 in contact with the anode 13 so that fuel can be supplied to the entire fuel cell power generation unit 101. The number of the fuel discharge ports 22 may be two or more. However, in order to equalize the fuel supply amount in the plane of the fuel cell power generation unit 101, the fuel discharge ports 22 of 0.1 to 10 / cm ² are provided. It is preferable to form it so that it exists.

  A piezoelectric pump 104 serving as a fuel transfer control unit is inserted into a flow path 103 that connects between the fuel distribution mechanism 105 and the fuel storage unit 102. The piezoelectric pump 104 has a pump body 1041 having a hollow portion as shown in FIG. The pump main body 1041 is divided into a first space portion 1043 and a second space portion 1044 by a partition wall 1042 having flexibility inside. The partition wall 1042 is provided with a piezoelectric element 1045 on a surface on the second space portion 1044 side. The piezoelectric element 1045 is of a bimorph type. The piezoelectric element 1045 is deformed by a driving voltage generated by the driving circuit 5 described later. Here, a driving waveform having a rectangular waveform described later is used as the driving voltage, and the positive half of the driving waveform is used. The wave is bent into the illustrated broken line a state and the negative half wave is bent into the illustrated broken line b state. The first space 1043 has a fuel supply port 1046 connected to the fuel storage unit 102 described above on the side surface and a fuel discharge port connected to the fuel distribution mechanism 105 on the fuel cell power generation unit 101 side described above on the front surface. 1047 is provided, and the pressure in the first space portion 1043 is lowered by the bending operation of the piezoelectric element 1045 in the state of the broken line a in the figure, so that the fuel in the fuel storage portion 102 passes through the fuel supply port 1046 to the first space portion 1043. The pressure in the first space portion 1043 is increased by the suction operation of the piezoelectric element 1045 in the state indicated by the broken line b in the figure, and the fuel in the first space portion 1043 is transferred to the fuel cell power generation unit 101 through the fuel discharge port 1047. Forced to discharge. In this case, the fuel supply port 1046 and the fuel discharge port 1047 are provided with check valves (not shown) for preventing the back flow of fuel.

  The piezoelectric pump 104 is not a circulation pump through which fuel is circulated, but is a fuel supply pump that transfers fuel from the fuel storage unit 102 to the fuel distribution mechanism 105 to the last. By supplying the fuel when necessary with such a piezoelectric pump 104, the controllability of the fuel supply amount is improved.

  In such a configuration, the fuel stored in the fuel storage unit 102 is transferred through the flow path 103 by the piezoelectric pump 104 and supplied to the fuel distribution mechanism 105. The fuel released from the fuel distribution mechanism 105 is supplied to the anode (fuel electrode) 13 of the fuel cell power generation unit 101. In the fuel cell power generation unit 101, the fuel diffuses through the anode gas diffusion layer 12 and is supplied to the anode catalyst layer 11. When methanol fuel is used as the fuel, an internal reforming reaction of methanol shown in the following formula (1) occurs in the anode catalyst layer 11. When pure methanol is used as the methanol fuel, the water generated in the cathode catalyst layer 14 or the water in the electrolyte membrane 17 is reacted with methanol to cause the internal reforming reaction of the formula (1). Alternatively, the internal reforming reaction is caused by another reaction mechanism that does not require water.

CH ₃ OH + H ₂ O → CO ₂ + 6H ⁺ + 6e ⁻ (1)
Electrons (e ⁻ ) generated by this reaction are guided to the outside via a current collector, supplied to the load side as so-called output, and then guided to the cathode (air electrode) 16. Further, protons (H ⁺ ) generated by the internal reforming reaction of the formula (1) are guided to the cathode 16 through the electrolyte membrane 17. Air is supplied to the cathode 16 as an oxidant. Electrons (e ⁻ ) and protons (H ⁺ ) that have reached the cathode 16 react with oxygen in the air according to the following equation (2) in the cathode catalyst layer 14, and water is generated with this reaction.

6e ⁻ + 6H ⁺ + (3/2) O ₂ → 3H ₂ O (2)
Returning to FIG. 1, the fuel cell main body 1 configured as described above includes a fuel cell power generation unit (cell) 101 connected to an output detection unit 6 and a DC-DC converter (voltage adjustment circuit) 2 as output adjustment means. Yes. The output detection unit 6 detects the output of the fuel cell power generation unit (cell) 101, for example, an output current, and outputs a detection signal corresponding to the output current to the control unit 7.

  The DC-DC converter 2 includes a switching element and an energy storage element (not shown). The DC-DC converter 2 stores / releases electric energy generated by the fuel cell body 1 by the switching element and the energy storage element, An output generated by boosting a relatively low output voltage to a sufficient voltage is generated. The output of the DC-DC converter 2 is supplied to the auxiliary power supply 4. Although the standard boost type DC-DC converter 2 is shown here, other circuit systems can be used as long as the boost operation is possible.

  An auxiliary power supply 4 is connected to the output end of the DC-DC converter 2 to constitute a so-called hybrid fuel cell. The auxiliary power supply 4 can be charged by the output of the DC-DC converter 2 and supplies a current to an instantaneous load fluctuation of the electronic device main body 3, and the fuel cell is in a fuel-depleted state. When the main body 1 is incapable of generating power, it is used as a driving power source for the electronic device main body 3. As the auxiliary power source 4, a chargeable / dischargeable secondary battery (for example, a lithium ion rechargeable battery (LIB)) or an electric double layer capacitor) is used.

  A drive circuit 5 is connected to the auxiliary power supply 4. The drive circuit 5 is connected to the piezoelectric element 1045 of the piezoelectric pump 104 via the resistance element 8. That is, the resistance element 8 is connected in series to the piezoelectric element 1045. The driving circuit 5 generates a driving voltage for driving the piezoelectric pump 104 using the auxiliary power source 4 as a power source. A switching element (not shown) is turned on / off by a control signal of the control unit 7 and is shown in FIG. A drive waveform having a rectangular wave shape is output. Since the piezoelectric element 1045 has a specific capacitance, the resistance element 8 forms an RC integration circuit together with the capacitance of the piezoelectric element 1045, and the drive waveform is shown in FIG. As shown in b), the waveform is deformed into a slowly rising waveform.

  A controller 7 is connected to the drive circuit 5. The control unit 7 controls the entire system, and includes an output setting unit 701 and a pump control unit 702. The output setting unit 701 sets the output (power generation amount) of the fuel cell main body 1 based on the comparison result between the detection signal of the output detection unit 6 and a preset target value. The pump control unit 702 determines the operation period of the drive circuit 5, that is, the operation period of the piezoelectric pump 104, along with the ON / OFF of the switching element (not shown) of the drive circuit 5 based on the output (power generation amount) set by the output setting unit 701. The control signal to be determined is output.

  Next, the operation of the embodiment configured as described above will be described.

  Now, when the fuel cell system is set to the startup mode, fuel is supplied to the fuel cell power generation unit 101 via the piezoelectric pump 104. The output generated by the fuel cell power generation unit 101 is boosted to a sufficient voltage by the DC-DC converter 2 and supplied to the electronic device main body 3 and charged to the auxiliary power supply 4.

  In this state, the output setting unit 701 of the control unit 7 sets the output (power generation amount) of the fuel cell body 1 based on the comparison result between the detection signal of the output detection unit 6 and a preset target value, and pump control A control signal based on the output (power generation amount) set by the output setting unit 701 is output from the unit 702. As a result, the switching element (not shown) of the drive circuit 5 is turned on and off, and the operation period of the drive circuit 5, that is, the operation period of the piezoelectric pump 104 is controlled, and the output (power generation amount) of the fuel cell power generation unit 101 depends on the target value. Controlled.

  In this case, the drive circuit 5 turns on and off a switching element (not shown) by a control signal of the pump control unit 702, and outputs a drive waveform having a rectangular waveform as shown in FIG. This drive waveform is transformed into a slowly rising waveform as shown in FIG. 5B by the time constant of the RC integration circuit composed of the piezoelectric element 1045 having a specific capacitance and the resistance element 8, It is supplied to the pump 104. In this state, as shown in FIG. 4, the piezoelectric pump 104 causes the piezoelectric element 1045 to bend in the state indicated by the broken line a in the positive half wave p (see FIG. 5B) of the drive waveform, and the negative side of the drive waveform. The bending operation is performed in the state indicated by the broken line b in the half wave n (see FIG. 5B). In this case, the pressure in the first space portion 1043 decreases due to the bending operation of the piezoelectric element 1045 in the state indicated by the broken line a in the figure, so that the fuel in the fuel storage portion 102 is sucked into the first space portion 1043 from the fuel supply port 1046. In addition, the pressure in the first space portion 1043 is increased by the bending operation of the piezoelectric element 1045 in the illustrated broken line b state, so that the fuel in the first space portion 1043 flows from the fuel discharge port 1047 to the fuel cell power generation unit 101. The liquid is forcibly discharged, and the liquid feeding operation is performed by repeating these operations. In this case, the piezoelectric pump 104 applies a drive voltage at a timing at which fuel is sucked from the fuel supply port 1046 and a drive waveform with a gradual rise is applied as shown in FIG. It is possible to prevent the occurrence of so-called cavitation, in which bubbles are generated in the fuel in the first space portion 1043 without a sudden drop in the internal pressure.

  Therefore, in this case, the piezoelectric pump 104 that repeatedly performs the pumping operation of the fuel suction and discharge operations by the bending operation of the piezoelectric element is used for the fuel supply of the fuel cell power generation unit 101 that generates electric power. The piezoelectric element 1045 is driven by a drive circuit 5 that generates a drive voltage having a rectangular waveform, and a resistance element 8 is connected in series with the piezoelectric element 1045 to form an RC integration circuit together with the capacitance inherent to the piezoelectric element. The drive waveform is deformed and supplied to the piezoelectric element 1045 with a gentle rise. As a result, during the suction operation of the piezoelectric pump 104, a slowly rising drive waveform is applied to the piezoelectric element 104, and the pressure in the piezoelectric pump 104 is prevented from rapidly decreasing during the suction operation. Therefore, it is possible to surely prevent so-called cavitation, in which bubbles are generated in the fuel in the piezoelectric pump 104, to obtain a sufficiently large discharge pressure in the piezoelectric pump 104, and to obtain a stable liquid feeding operation. be able to.

  In addition, a drive waveform with a gentle rise is obtained by simply connecting the resistance element 8 between the drive circuit 5 and the piezoelectric element 1045, so that a drive that generates a conventional sine waveform, sawtooth waveform, or the like is provided. Compared to a circuit using various active elements for waveform shaping, the circuit configuration can be simplified, and a small and inexpensive fuel cell system can be realized.

  Furthermore, when a short circuit accident or the like occurs in a switching element (not shown) constituting the drive circuit 5, an overcurrent may flow from the drive circuit 5 to the piezoelectric pump 104. In such a case, the drive circuit 5 and the piezoelectric pump 104 Since the resistance element 8 is connected in series between the two, the inflow of overvoltage to the piezoelectric pump 104 can be prevented by the current limiting action of the resistance element 8, and the piezoelectric element is damaged by the overcurrent. Can also be prevented.

(Modification)
In the first embodiment, a resistance element 8 is connected in series between the drive circuit 5 and the piezoelectric pump 104, and an RC integration circuit constituted by the piezoelectric element 1045 and the resistance element 8 having a specific capacitance is provided. As shown in FIG. 5B, a drive waveform with a gradual rise is generated and supplied to the piezoelectric element 1045 based on the time constant. In this case, the piezoelectric element 1045 is moved by the negative half wave of the drive waveform. In the case of a curved operation in the state of the broken line b shown in the figure, the driving is performed with a gradually rising drive waveform, so that the pressure in the first space portion 1043 at the time of fuel discharge decreases, and the fuel supply amount may decrease. Therefore, in this modification, as shown in FIG. 1, the diode 9 having the polarity shown by the broken line is connected to the resistance element 8 in parallel. Others are the same as FIG.

  In this manner, when a rectangular driving waveform as shown in FIG. 6A is output from the driving circuit 5 as a driving voltage, the positive half wave p of this driving waveform has a specific capacitance. As shown in FIG. 6 (b), it is transformed into a slowly rising waveform as shown in FIG. 6 (b) by the time constant of the RC integration circuit constituted by a series circuit of the piezoelectric element 1045 and the resistance element 8, and is supplied to the piezoelectric pump 104. Further, in the negative half wave n of the drive waveform, since the resistance element 8 is short-circuited by the diode 9 having the illustrated polarity and the RC integration circuit does not operate, a waveform having a steep rising as shown in FIG. The piezoelectric pump 104 is supplied as it is. As a result, the piezoelectric pump 104 is supplied with a driving voltage having a driving waveform with a positive rising half wave p that gradually rises when the fuel is sucked, but when the fuel is discharged, the negative pumping side with a steep rising edge is supplied. Since the driving voltage of the wave n is supplied, the pressure in the first space portion 1043 at the time of fuel discharge can be sufficiently increased, and the fuel supply amount can be prevented from being lowered by reducing the fuel supply amount. Sufficient fuel supply to 101 can be ensured.

  Here, an example of connection of the diode 9 in the case where the positive half wave of the drive voltage is applied when the piezoelectric pump 104 sucks the fuel and the negative half wave of the drive voltage is applied when the fuel is discharged is shown. Needless to say, when using a piezoelectric pump configured to apply the negative half-wave and the positive half-wave of the drive voltage during fuel discharge, it is necessary to reversely connect the polarity of the diode 9 to the resistance element 8. Yes.

  Even if it does in this way, the effect similar to 1st Embodiment can be acquired.

  By the way, according to the result of the experiment, in the conventional driving of the piezoelectric element with the driving waveform having a rectangular wave shape, the discharge temperature of the piezoelectric pump 104 is 100% at a normal temperature of 25 ° C. When the heat generation temperature of the fuel cell body 1 rose to 55 ° C., the discharge pressure of the piezoelectric pump 104 was reduced to 40%. However, the resistance element 8 was connected in series with the piezoelectric element 1045 of the present invention, and the piezoelectric element 1045 had its own characteristic. In the case where the RC integration circuit is configured together with the capacitance, when the time constant of the RC integration circuit at this time is about 0.01 or more, even if the heat generation temperature of the fuel cell body 1 rises to 55 ° C., the piezoelectric pump It was confirmed that the discharge pressure of 104 recovered to 70% or more, and a stable liquid feeding operation could be obtained for the piezoelectric pump 104. Further, when a diode 9 is further connected in parallel with the resistance element 8 described in the above-described modification, the heating temperature of the fuel cell body 1 is 55 when the time constant of the RC integration circuit is set to about 0.01 or more. It was confirmed that the discharge pressure of the piezoelectric pump 104 recovered to about 85% even when the temperature was raised to 0 ° C., and a more stable liquid feeding operation could be obtained for the piezoelectric pump 104.

  In addition, this invention is not limited to the said embodiment, In the implementation stage, it can change variously in the range which does not change the summary.

  Furthermore, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements. For example, even if some constituent requirements are deleted from all the constituent requirements shown in the embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and is described in the column of the effect of the invention. If the above effect is obtained, a configuration from which this configuration requirement is deleted can be extracted as an invention.

  Further, the vaporized component of the liquid fuel supplied to the fuel cell power generation unit may be all supplied as the vaporized component of the liquid fuel, but the present invention is applied even when a part is supplied in the liquid state. be able to.

1 is a diagram showing a schematic configuration of a fuel cell system according to a first embodiment of the present invention. Sectional drawing for demonstrating in detail the fuel cell main body of 1st Embodiment. The perspective view of the fuel distribution mechanism used for the fuel cell main body of 1st Embodiment. The figure which shows schematic structure of the piezoelectric pump used for 1st Embodiment. The figure for demonstrating the waveform of the drive voltage used for 1st Embodiment. The figure for demonstrating the waveform of the drive voltage used for the modification of 1st Embodiment.

DESCRIPTION OF SYMBOLS 1 ... Fuel cell main body, 101 ... Fuel cell power generation part 102 ... Fuel accommodating part, 103 ... Flow path 104 ... Piezoelectric pump, 1041 ... Pump main body 1041
1042 ... Partition, 1043 ... First space portion, 1044 ... Second space portion 1045 ... Piezoelectric element, 1046 ... Fuel supply port, 1047 ... Fuel discharge port 105 ... Fuel distribution mechanism, 106 ... Temperature sensor, 2 ... DC / DC converter,
DESCRIPTION OF SYMBOLS 3 ... Electronic equipment main body, 4 ... Auxiliary power supply, 5 ... Drive circuit 6 ... Output detection part, 7 ... Control part, 701 ... Output setting part, 702 ... Pump control part,
DESCRIPTION OF SYMBOLS 8 ... Resistance element, 9 ... Diode, 11 ... Anode catalyst layer, 12 ... Anode gas diffusion layer 13 ... Anode, 14 ... Cathode catalyst layer 15 ... Cathode gas diffusion layer, 16 ... Cathode 17 ... Electrolyte membrane, 18 ... Cover plate 19 ... O-ring, 21 ... fuel inlet 22 ... fuel outlet, 23 ... fuel distribution plate 24 ... gap

Claims (4)

A fuel cell main body that generates electric power by supplying fuel; and
A piezoelectric pump having a piezoelectric element and supplying fuel to the fuel cell main body by repeatedly sucking and discharging the fuel by a deformation operation of the piezoelectric element;
Driving means for generating a driving voltage having a rectangular waveform and driving the piezoelectric element of the piezoelectric pump by the driving voltage;
A resistance element connected between the driving means and the piezoelectric element, and forming an RC integration circuit together with a capacitance specific to the piezoelectric element, and transforming the driving waveform into a gradually rising waveform;
A fuel cell system comprising: The driving waveform generated by the driving means consists of a positive half wave and a negative half wave,
2. The fuel cell system according to claim 1, wherein the piezoelectric pump performs a fuel suction operation by a positive half-wave of the drive waveform and a fuel discharge operation by a negative half-wave. 3. The fuel cell system according to claim 1, further comprising a diode connected in parallel to the resistance element, wherein the sharp rising of the positive half-wave or the negative half-wave of the driving waveform is maintained. A piezoelectric pump having a piezoelectric element and supplying fuel to the fuel cell main body by repeatedly sucking and discharging the fuel by a deformation operation of the piezoelectric element;
A driving means for generating a driving voltage having a rectangular driving waveform and driving the piezoelectric element of the piezoelectric pump by the driving voltage;
A resistance element connected between the driving means and the piezoelectric element, forming an RC integration circuit together with a capacitance inherent to the piezoelectric element, and transforming the driving waveform into a gradually rising waveform;
A piezoelectric pump device comprising:

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