JP2005351223A - Thermoacoustic engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermal acoustic engine capable of quickly stopping in response to a request. <P>SOLUTION: This thermal acoustic engine 20 has an air columnar pipe 21 sealed with a hydraulic fluid, a resonance part 23 and a heat accumulator 25 arranged in the air columnar pipe 21, and generates thermal acoustic self-exciting vibration of the hydraulic fluid by forming a temperature gradient between both end parts of the heat accumulator 25. A variable throttle valve 28 is arranged in a loop part 22 of the air columnar pipe 21. A progressive wave for progressing to a high temperature heat exchanger 26 from a low temperature heat exchanger 27 is mainly cut off by closing the variable throttle valve 28, to thereby, surely and quickly damp and vanish the thermal acoustic self-exciting vibration in the air columnar pipe 21, and operation of the thermal acoustic engine 20 is stopped. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thermoacoustic engine that forms a temperature gradient between both ends of a heat storage means arranged in an air column tube and generates thermoacoustic self-excited vibration of a working fluid in the air column tube.

  Conventionally, a refrigerator utilizing a thermoacoustic phenomenon has been proposed (see, for example, Patent Document 1). This refrigerator includes a pipe filled with gas, a stack disposed inside the pipe and sandwiched between a high temperature side heat exchanger and a low temperature side heat exchanger, and a high temperature side at a position asymmetric with the stack. And a regenerator arranged together with the heat exchanger and the low temperature side heat exchanger. This refrigerator generates a self-excited vibration of gas in the stack by forming a temperature gradient between both ends of the stack, and stores it in the regenerator by propagation of standing waves and traveling waves obtained thereby. It is.

  Conventionally, an apparatus for recovering exhaust heat of an internal combustion engine using a thermoacoustic phenomenon has been proposed (see, for example, Patent Document 2). This device includes a resonance pipe connected to an exhaust gas purification catalytic converter of an internal combustion engine, a stack provided at one end of the resonance pipe, and a transducer provided at the other end of the resonance pipe. In this apparatus, one end of the stack is heated by heat generated from the catalytic converter, and a temperature gradient is applied between both ends of the stack. Thereby, sound waves are generated in the stack, and the energy of the sound waves is converted into electric energy by the transducer.

  Furthermore, conventionally, a thermoacoustic generator that generates a pressure gradient in the gas in the loop pipe by forming a temperature gradient between both ends of the heat storage section in the loop pipe and generates electric power in accordance with a traveling wave generated by the pressure vibration. Has also been proposed (see, for example, Patent Document 3). This thermoacoustic generator has a starter / generator including a linear motor and a piston cylinder. The starter / generator functions as a starter motor when the thermoacoustic generator is activated, and reciprocally moves the piston cylinder to apply pressure vibration to the gas at an arbitrary frequency to generate self-oscillation of the gas in the loop tube. When pressure vibration due to self-excited oscillation occurs in the loop tube, the starter / generator functions as a generator that generates power in accordance with traveling waves generated by the pressure vibration.

Japanese Patent No. 3015786 JP 2002-122020 A Japanese Patent Laid-Open No. 2003-324932

  As described above, exhaust heat (waste heat) of the internal combustion engine can be recovered by utilizing the thermoacoustic phenomenon. On the other hand, in an apparatus that applies a temperature gradient between both ends of the stack using the heat of the catalytic converter (direct heating of the stack by the catalytic converter), the catalytic converter is not sufficiently warmed up. However, the heat of the catalytic converter is applied to the stack, and the catalytic converter may not be warmed up quickly. In such a case, originally, the use of the thermoacoustic phenomenon should be forcibly stopped in accordance with the demand on the cold energy use side or the internal combustion engine side, but the catalytic converter and the stack are substantially connected. And it is difficult to stop the application of the temperature gradient between the both ends of the stack. Further, even if the heating of the stack can be stopped, in this case, the temperature gradient is not instantaneously reduced, so that it takes time to completely stop the use of the thermoacoustic phenomenon.

  Then, this invention aims at provision of the thermoacoustic engine which can be stopped rapidly according to a request | requirement.

  A thermoacoustic engine according to the present invention has an air column tube in which a working fluid is sealed, and heat storage means arranged inside the air column tube, and forms a temperature gradient between both ends of the heat storage unit. In a thermoacoustic engine that generates thermoacoustic self-excited vibration of a working fluid, the thermoacoustic engine includes vibration stopping means that stops thermoacoustic self-excited vibration regardless of a temperature gradient formed between both ends of the heat storage means. .

  In this thermoacoustic engine, when there is a request to stop its operation, the thermoacoustic self-excited vibration in the air column tube is forced by the vibration stopping means regardless of the temperature gradient formed between both ends of the heat storage means. Be stopped. Thereby, it becomes possible to stop a thermoacoustic engine early compared with the case where the provision of the temperature gradient with respect to a thermal storage means is stopped. Even if the application of the temperature gradient to the heat storage means cannot be stopped, if the thermoacoustic self-excited vibration itself is stopped, the heat storage means does not convert heat energy into vibration energy. Therefore, when this thermoacoustic engine is stopped (after forcibly stopping the thermoacoustic self-excited vibration), the heat energy of the heat source for heating the heat storage means is hardly lost. It becomes possible to divert the heat energy that has not been used for the conversion from the heat energy to the vibration energy for other purposes.

  In the thermoacoustic engine of the present invention, the vibration stopping means preferably includes a member for blocking propagation of vibration in the air column tube. Further, the vibration stopping means may include means for absorbing vibration in the air column tube. Furthermore, the vibration stopping means may reduce the pressure of the working fluid in the air column tube. Moreover, it is preferable that the thermoacoustic engine according to the present invention further includes a resonator. In this case, the vibration stopping means may change a resonance frequency in the resonator. By adopting any of these configurations, it becomes possible to stop thermoacoustic self-excited vibration in the air column tube reliably and promptly.

  The thermoacoustic engine according to the present invention preferably further includes a high-temperature heat exchanger disposed on one end side of the heat storage means, and this high-temperature heat exchanger is preferably provided with the exhaust gas of the internal combustion engine as a heat source.

  Even under such a configuration, it is possible to stop the thermoacoustic engine at an early stage as required. Then, the energy of the exhaust gas that has not been used for conversion from thermal energy to vibration energy in the heat storage means can be effectively diverted to other uses such as catalyst warm-up.

  The internal combustion engine further includes an exhaust purification catalyst for purifying the exhaust gas, and it is preferable to operate the vibration stopping means when the exhaust purification catalyst needs to be warmed up. Further, the thermoacoustic engine according to the present invention includes an abnormality detecting means for detecting an abnormality of at least one of the internal combustion engine and the thermoacoustic engine, and means for operating the vibration stopping means when an abnormality is detected by the abnormality detecting means. Are preferably included.

  According to the present invention, it is possible to realize a thermoacoustic engine that can be quickly stopped as required.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

[First Embodiment]
FIG. 1 is a schematic configuration diagram showing a first embodiment of a thermoacoustic engine according to the present invention. As shown in the figure, the thermoacoustic engine 20 is applied to, for example, an internal combustion engine 1 used as a travel drive source of a vehicle. First, the internal combustion engine 1 to which the thermoacoustic engine 20 is applied will be briefly described. The internal combustion engine 1 burns a mixture of fuel and air in a combustion chamber 3 formed in the cylinder block 2 and burns it. The piston 4 is reciprocated in the chamber 3 to generate power.

  The intake port of the combustion chamber 3 is connected to the intake manifold 5, and the exhaust port of the combustion chamber 3 is connected to the exhaust manifold 6. In addition, an intake valve Vi that opens and closes an intake port, an exhaust valve Ve that opens and closes an exhaust port, a spark plug 7, and an injector 8 are disposed for each combustion chamber 3 in the cylinder head of the internal combustion engine 1. The intake manifold 5 is connected to a surge tank 9, and an air supply pipe L <b> 1 is connected to the surge tank 9. The air supply pipe L1 is connected to an air intake port (not shown) via the air cleaner 10. Further, a throttle valve 11 is incorporated in the middle of the supply pipe L1 (between the surge tank 9 and the air cleaner 10). On the other hand, the exhaust manifold 6 is connected to an exhaust pipe L2, and a front-stage catalyst device 12a and a rear-stage catalyst device 12b each including an exhaust purification catalyst are incorporated in the exhaust pipe L2.

  The thermoacoustic engine 20 of the present invention is used to recover the exhaust heat of the internal combustion engine 1 as described above. The thermoacoustic engine 20 has an air column tube 21 formed of stainless steel or the like so as to have a circular cross section, and inside the air column tube 21 is an operation such as nitrogen, helium, argon, a mixed gas of helium and argon. A fluid (inert gas) is enclosed. As shown in FIG. 1, the air column tube 21 includes a loop portion 22 formed in a substantially rectangular loop shape, and a resonance portion 23 connected to one corner portion of the loop portion 22. The resonance part 23 includes a tube part 23a having a circular cross section approximately the same diameter as the loop part 22, and a closed end part 23b connected to the tip of the tube part 23a, and functions as a resonator. The diameter of the closed end portion 23b is gradually increased from the distal end of the tube portion 23a toward the closed end, and a transducer (converting sound wave energy (acoustic energy) into electrical energy is provided at the closed end of the closed end portion 23b. (Sound / electrical conversion means) 24 is arranged.

  A heat accumulator (heat storage means) 25 is disposed inside the loop portion 22 of the air column tube 21. The heat accumulator 25 has a plurality of narrow flow paths extending in parallel with the axial direction of the air column tube 21 at the arrangement location. As the heat accumulator 25, a honeycomb structure made of ceramic or the like, a thin mesh made of stainless steel or copper or the like arranged at a minute interval, a nonwoven fabric in which metal fibers such as stainless steel are gathered, or the like can be used. A high temperature heat exchanger 26 is disposed adjacent to one end side of the heat accumulator 25, and a low temperature heat exchanger 27 is disposed adjacent to the other end side of the heat accumulator 25. That is, the heat accumulator 25 is arranged in a state of being sandwiched between the high temperature heat exchanger 26 and the low temperature heat exchanger 27.

  The high temperature heat exchanger 26 uses the exhaust gas of the internal combustion engine 1 as a heat source, and the heat transfer pipe of the high temperature heat exchanger 26 is incorporated in the exhaust pipe L <b> 2 of the internal combustion engine 1. In the present embodiment, the high-temperature heat exchanger (its heat transfer pipe) 26 is incorporated in the exhaust pipe L2 between the front-stage catalyst apparatus 12a and the rear-stage catalyst apparatus 12b, but is incorporated upstream of the front-stage catalyst apparatus 12a. May be. The heat transfer tubes constituting the low-temperature heat exchanger 27 are incorporated in the cooling system L3 of the internal combustion engine 1, and the low-temperature heat exchanger 27 uses the cooling water flowing through the cooling system L3 as a heat source (cold heat source). . The cooling system L3 includes an on-off valve 14. By closing the on-off valve 14, the supply of cooling water to the low temperature heat exchanger (its heat transfer tube) 27 can be stopped.

  A movable throttle valve 28 as vibration stopping means is disposed inside the air column tube 21. In the present embodiment, the movable throttle valve 28 is disposed in a region of the loop portion 22 where the high temperature heat exchanger 26 and the low temperature heat exchanger 27 are communicated without passing through the heat accumulator 25. The movable throttle valve 28 includes a valve body 28a capable of almost completely closing the air column tube 21 (loop portion 22), and an actuator (not shown) that moves the valve body 28a. The valve body 28a does not need to be able to completely close the air column tube 21 (loop portion 22), and may be any valve body that can block the fluid flow (vibration) to some extent.

  The thermoacoustic engine 20 includes an electronic control unit (hereinafter referred to as “ECU”) 40 that functions as control means. The ECU 40 includes a CPU, a ROM, a RAM, an input / output port, a storage device, etc., all not shown. The on-off valve 14 and the movable throttle valve 28 (actuator) of the cooling system L3 are connected to the input / output ports of the ECU 40, respectively, and these are controlled by the ECU 40. Further, a pressure sensor 29 is installed in the air column tube 21 of the thermoacoustic engine 20 in the vicinity of a connection portion between the loop portion 22 and the resonance portion 23. The pressure sensor 29 is connected to the input / output port of the ECU 40, detects the pressure of the working fluid in the air column tube 21, and gives a signal indicating the detected value to the ECU 40. Furthermore, a temperature sensor Tc for detecting the catalyst temperature (catalyst bed temperature) is installed in the pre-stage catalyst device 12a of the internal combustion engine 1. The temperature sensor Tc is connected to an input / output port of the ECU 40, and the temperature sensor Tc gives a signal indicating the detected value to the ECU 40.

  In the thermoacoustic engine 20 configured as described above, for example, the internal combustion engine 1 is operated in a state in which the on-off valve 14 is opened, and after the exhaust gas from the combustion chamber 3 passes through the pre-catalyst device 12a, high-temperature heat exchange is performed. When it passes through the vessel 26, the operation starts. In this case, since the temperature of the exhaust gas that has passed through the pre-stage catalyst device 12a reaches about 900 ° C. at the maximum, one end of the heat accumulator 25 is heated by the exhaust gas flowing through the high-temperature heat exchanger 26. Raise the temperature. On the other hand, the low-temperature heat exchanger 27 of the thermoacoustic engine 20 has cooling water at a relatively low temperature (generally atmospheric temperature immediately after the cold start of the internal combustion engine 1 and approximately 80 to 90 ° C. after completion of warm-up). Therefore, the other end of the heat accumulator 25 is cooled by cooling water flowing through the low-temperature heat exchanger 27. As a result, a large temperature gradient is formed between both ends of the heat accumulator 25, and as a result, thermoacoustic self-excited vibration (sound wave) of the working fluid is generated.

  When the frequency of the self-excited vibration (sound wave) of the working fluid generated in this way matches the resonance frequency in the resonance part 23, a standing wave is formed in the resonance part 23. Further, a traveling wave traveling from the low temperature heat exchanger 27 to the high temperature heat exchanger 26 is formed in the loop portion 22. And the vibration part of the transducer 24 arrange | positioned at the closed end part 23b is vibrated by the standing wave formed in the resonance part 23. FIG. The transducer 24 converts standing wave energy (acoustic energy) in the resonance unit 23 into electric energy, and the obtained electric energy is supplied to a predetermined electric load via a controller (not shown). Thereby, according to the thermoacoustic engine 20 of this invention, the exhaust heat of the internal combustion engine 1 can be collect | recovered efficiently, and the electric power for predetermined | prescribed electric loads can be obtained. Instead of arranging the transducer 24 in the resonance unit 23, a unit of a heat accumulator, a high temperature heat exchanger, and a low temperature heat exchanger is arranged in the loop unit 22, and the exhaust heat energy recovered by the thermoacoustic engine 20 is used. Then, the unit may be operated as a refrigerator.

  Here, in the above-described thermoacoustic engine 20, since the high-temperature heat exchanger 26 is incorporated in the exhaust pipe L2, basically, a part of the heat of the exhaust gas is taken away by the high-temperature heat exchanger 26. Become. Therefore, when the internal combustion engine 1 is started, the temperature of the exhaust gas is lowered on the downstream side of the high-temperature heat exchanger 26, so that the warming-up of the rear catalyst device 12b may not be promoted. In such a case, it is preferable to forcibly stop the use of the thermoacoustic phenomenon in response to a request from the internal combustion engine 1 side. In addition, for some reason, the internal pressure of the air column tube 21 may increase excessively, or the transducer 24 may break down. It becomes necessary to be able to stop. However, in the thermoacoustic engine 20, since the high-temperature heat exchanger 26 is incorporated in the exhaust pipe L <b> 2, it is difficult to stop applying the temperature gradient between the both ends of the heat accumulator 25 once the internal combustion engine 1 is activated. It is.

  In view of such a point, in the thermoacoustic engine 20, the ECU 40 repeatedly executes a stop control routine shown in FIG. 2 at predetermined intervals. As shown in FIG. 2, when the execution timing of this routine is reached, the ECU 40 first obtains the catalyst temperature in the pre-catalyst device 12a based on the signal from the temperature sensor Tc, and the obtained catalyst temperature is a predetermined threshold value. It is determined whether or not the following is true (S10). The threshold value is determined in advance as a lower limit value for sufficiently warming up the front catalyst device 12a and the rear catalyst device 12b, and is stored in the storage device of the ECU 40.

  When it is determined in S10 that the catalyst temperature in the pre-catalyst device 12a is equal to or lower than the threshold value, the ECU 40 further determines whether or not the thermoacoustic engine 20 is operating based on a signal from the pressure sensor 29, for example (automatically). It is determined whether or not excitation vibration has occurred (S12). When it is determined that the thermoacoustic engine 20 is in operation, the ECU 20 uses the thermoacoustic phenomenon, that is, the operation of the thermoacoustic engine 20 regardless of the temperature gradient formed between both ends of the heat accumulator 25. An immediate stop process for forcibly and promptly stopping is executed (S14).

  That is, in this embodiment, the ECU 40 controls the movable throttle valve 28 so that the loop portion of the air column tube 21 is almost completely blocked by the valve body 28a (S14). Thereby, the traveling wave propagating from the low temperature heat exchanger 27 to the high temperature heat exchanger 26 is mainly blocked by the valve body 28a of the movable throttle valve 28, so that the thermoacoustic self-excited vibration in the air column tube 21 is generated. The operation of the thermoacoustic engine 20 is stopped regardless of the temperature gradient between both ends of the heat accumulator 25, which is surely and quickly attenuated / disappeared. And by stopping the thermoacoustic self-excited vibration itself in this way, even if the exhaust gas from the internal combustion engine 1 flows through the heat transfer tube of the high-temperature heat exchanger 26, the heat accumulator 25 converts the heat energy into vibration energy. No conversion is performed.

  Accordingly, when the thermoacoustic engine 20 is stopped (after the thermoacoustic self-excited vibration is forcibly stopped), the temperature of the high-temperature heat exchanger 26 (its heat transfer tube) is about the same as the inflowing exhaust gas. Therefore, the heat energy of the exhaust gas passing through the high-temperature heat exchanger 26 is hardly lost. Therefore, the heat energy of the exhaust gas that has not been used for the conversion from the heat energy to the vibration energy is warmed up by the catalyst ( In particular, it can be used for warming up the post-catalyst device 12b. In addition, as described above, the thermoacoustic self-excited vibration itself is directly cut off and attenuated / disappeared by the movable throttle valve 28, thereby making it extremely early compared to the case where the application of the temperature gradient to the heat accumulator 25 is stopped. The thermoacoustic engine 20 can be stopped.

  On the other hand, if it is determined in S10 that the catalyst temperature in the pre-catalyst device 12a exceeds the threshold value, the ECU 40 has not issued a signal indicating abnormality from the internal combustion engine 1, the transducer 24, the pressure sensor 29, or the like. It is determined whether or not (S16). If it is determined in S16 that a signal indicating some abnormality is issued, the ECU 40 determines whether or not the thermoacoustic engine 20 is in operation in S12 and determines that the thermoacoustic engine 20 is in operation. If so, the immediate stop process of S14 is executed. As a result, when any abnormality occurs in at least one of the internal combustion engine 1 and the thermoacoustic engine 20, the thermoacoustic engine 20 is quickly stopped. If it is determined in S12 that the thermoacoustic engine 20 is not operating, or if it is determined in S16 that an abnormal signal has not been issued, the above-described immediate stop process is not executed, and again The processes after S10 are repeatedly executed.

[Second Embodiment]
The thermoacoustic engine according to the second embodiment of the present invention will be described below with reference to FIG. Note that the same reference numerals are given to the same elements as those described in relation to the first embodiment described above, and redundant descriptions are omitted.

  The thermoacoustic engine 20A shown in FIG. 3 also has basically the same configuration as the thermoacoustic engine 20 of the first embodiment, and the fuel and air are mixed inside the combustion chamber 3 formed in the cylinder block 2. The present invention is applied to the internal combustion engine 1 that burns air and reciprocates the piston 4 in the combustion chamber 3 to generate power. And the thermoacoustic engine 20A of this embodiment contains the means to absorb the vibration in the air column tube 21 as a vibration stop means instead of the above-mentioned movable throttle valve.

  That is, the sound absorbing tank 30 is connected to the air column tube 21 (in this embodiment, the tube portion 23a) via the short communication tube L4. The sound absorbing tank 30 defines a closed space, and a sound absorbing material 31 such as foamed urethane is preferably attached to the inner surface thereof. In addition, an on-off valve 32 is disposed inside the communication pipe L4. The on-off valve 32 includes a valve body 32a that can close the communication pipe L4 almost completely and an actuator (not shown) that is controlled by the ECU 40 to move the valve body 32a. The on-off valve 32 is normally set in a state in which the communication pipe L4 is almost completely closed.

  Also in the thermoacoustic engine 20A configured in this way, a stop control routine substantially similar to that shown in FIG. 2 is executed. That is, also in this embodiment, it is determined that the catalyst temperature in the pre-catalyst device 12a is equal to or lower than a predetermined threshold value, or it is determined that a signal indicating some abnormality is generated, and further, the thermoacoustic engine 20A is When it is operating, an immediate stop process of the thermoacoustic engine 20A is executed. In the present embodiment, during the immediate stop process, the ECU 40 fully closes the on-off valve 32 of the communication pipe L4.

  As a result, the flow of the working fluid in the air column tube 21 is dispersed in the closed end portion 23b and the sound absorbing tank 30, so that the thermoacoustic self-excited vibration in the air column tube 21 is reliably and quickly damped. The operation of the thermoacoustic engine 20A is stopped regardless of the temperature gradient between both ends of the heat accumulator 25. In this case as well, after the thermoacoustic engine 20A is stopped, the heat energy of the exhaust gas is hardly lost in the high-temperature heat exchanger 26. Therefore, the exhaust gas that has not been used for conversion from heat energy to vibration energy is used. It becomes possible to use the heat energy of the gas for catalyst warm-up (particularly for warm-up of the post-catalyst device 12b). Further, as described above, it is possible to stop the thermoacoustic engine 20A earlier by attenuating and eliminating the thermoacoustic self-excited vibration itself as compared with the case where the application of the temperature gradient to the heat accumulator 25 is stopped. Become.

  Furthermore, the sound absorbing tank 30 as vibration stopping means is branched from the resonance portion 23 of the air column tube 21 via the communication pipe L4. Since the communication pipe L4 is provided with the on-off valve 32, the on-off valve 32 is provided. Is closed, the sound absorbing tank 30 is almost completely separated from the air column tube 21 (resonance portion 23). Therefore, during the normal operation of the thermoacoustic engine 20A (while the on-off valve 32 is closed), the sound absorption tank 30 does not affect the thermoacoustic self-excited vibration in the air column tube 21. That is, the vibration stopping means that can absorb the vibration in the air column tube can be arranged so as not to disturb the normal operation of the thermoacoustic engine.

[Third Embodiment]
Hereinafter, a thermoacoustic engine according to a third embodiment of the present invention will be described with reference to FIG. The same elements as those described in relation to the first embodiment described above are denoted by the same reference numerals, and redundant description is omitted.

  The thermoacoustic engine 20B shown in FIG. 4 also has basically the same configuration as the thermoacoustic engine 20 of the first embodiment, and the fuel and air are mixed inside the combustion chamber 3 formed in the cylinder block 2. The present invention is applied to the internal combustion engine 1 that burns air and reciprocates the piston 4 in the combustion chamber 3 to generate power. And the thermoacoustic engine 20B of this embodiment has a means to change the pressure (average pressure) of the working fluid in the air column tube 21 as a vibration stop means.

  In other words, a working fluid storage tank (working fluid storage means) 36 is connected to the air column tube 21 (the pipe portion 23a in the present embodiment) of the thermoacoustic engine 20B via a working fluid pipe L5 having a pump 35 in the middle. Has been. The pump 35 can suck the working fluid in the air column tube 21 and pump it into the working fluid storage tank 36. One end of a working fluid pipe L6 having an on-off valve (normally closed) 37 is connected to the working fluid storage tank 36, and the other end of the working fluid pipe L6 is connected to the air column pipe 21 (this embodiment). Then, it is connected to the pipe part 23a). Furthermore, the working fluid storage tank 36 is provided with a pressure sensor 38 for detecting the pressure of the working fluid therein. The pressure sensor 38 is connected to an input / output port of the ECU 40, detects the pressure of the working fluid in the working fluid storage tank 36, and gives a signal indicating the detected value to the ECU 40.

  Since the working fluid in the air column tube 21 is introduced into the working fluid storage tank 36 by operating the pump 35 with the on-off valve 37 of the working fluid tube L6 closed, the working fluid in the air column tube 21 is introduced. The average pressure will decrease. Further, by opening the on-off valve 37 in a state where the working fluid pressurized by the pump 35 and having a relatively high pressure is stored in the working fluid storage tank 36, the high pressure working fluid is supplied via the working fluid pipe L6. Is introduced (returned) into the air column tube 21, thereby increasing the average pressure of the working fluid in the air column tube 21. That is, the working fluid pipes L5 and L6, the pump 35, the working fluid storage tank 36, the on-off valve 37, and the like function as an average pressure setting unit that changes the average pressure of the working fluid in the air column pipe 21.

  Also in the thermoacoustic engine 20B configured in this way, a stop control routine substantially similar to that shown in FIG. 2 is executed. That is, also in this embodiment, it is determined that the catalyst temperature in the pre-catalyst device 12a is equal to or lower than a predetermined threshold value, or it is determined that a signal indicating some abnormality is generated, and further, the thermoacoustic engine 20B is When it is in operation, an immediate stop process of the thermoacoustic engine 20B is executed. In the present embodiment, in the immediate stop process, the ECU 40 until the pressure of the working fluid in the air column tube 21 detected by the pressure sensor 29 falls below a predetermined threshold (until no pressure amplitude is substantially recognized). The pump 35 is operated with the on-off valve 37 of the working fluid pipe L6 closed.

  As a result, the working fluid in the air column tube 21 is transferred into the working fluid storage tank 36, so that the thermoacoustic self-excited vibration in the air column tube 21 is forcibly and quickly attenuated / disappeared to store heat. Regardless of the temperature gradient between both ends of the vessel 25, the operation of the thermoacoustic engine 20B is stopped. In this case as well, after the thermoacoustic engine 20B is stopped, the heat energy of the exhaust gas is hardly lost in the high-temperature heat exchanger 26. Therefore, the exhaust gas that has not been used for conversion from heat energy to vibration energy is used. It becomes possible to use the heat energy of the gas for catalyst warm-up (particularly for warm-up of the post-catalyst device 12b). Further, as described above, it is possible to stop the thermoacoustic engine 20B at an early stage by attenuating and eliminating the thermoacoustic self-excited vibration itself as compared with the case where the application of the temperature gradient to the heat accumulator 25 is stopped. It becomes.

  Further, by stopping the pump 35 and closing the on-off valve 37, the working fluid storage tank 36 is almost completely separated from the air column tube 21 (resonance unit 23), so that during normal operation of the thermoacoustic engine 20B. The working fluid storage tank 36 does not affect the thermoacoustic self-excited vibration in the air column tube 21. That is, the vibration stopping means for changing the pressure of the working fluid in the air column tube can also be arranged so as not to disturb the normal operation of the thermoacoustic engine.

  When the thermoacoustic engine 20B is stopped as described above, the on-off valve 37 is opened at an appropriate timing before restarting, and the working fluid in the working fluid storage tank 36 is put into the air column pipe 21. It is preferable to return and set the pressure (average pressure) of the working fluid in the air column tube 21 to a predetermined value. In addition, since the average pressure of the working fluid in the air column tube 21 and the thermal efficiency when generating the thermoacoustic self-excited vibration and the output (acoustic output) of the thermoacoustic engine have a predetermined correlation, the pump It is also possible to obtain desired thermal efficiency and acoustic output in the thermoacoustic engine 20B by controlling the average pressure of the working fluid in the air column pipe 21 by controlling the 35 and the on-off valve 37.

[Fourth Embodiment]
Hereinafter, a thermoacoustic engine according to a fourth embodiment of the present invention will be described with reference to FIG. The same elements as those described in relation to the first embodiment described above are denoted by the same reference numerals, and redundant description is omitted.

  The thermoacoustic engine 20C shown in FIG. 4 has basically the same configuration as the thermoacoustic engine 20 of the first embodiment, and the fuel and air are mixed inside the combustion chamber 3 formed in the cylinder block 2. The present invention is applied to the internal combustion engine 1 that burns air and reciprocates the piston 4 in the combustion chamber 3 to generate power. And the thermoacoustic engine 20C of this embodiment has a means to change the resonance frequency (resonance frequency of the working fluid in the air column tube 21) in the resonance part 23 as a vibration stop means.

  That is, in the thermoacoustic engine 20C of the present embodiment, the movable tube 51 having an outer diameter smaller than the inner diameter of the tube portion 23a is slidably disposed inside the tip of the tube portion 23a of the resonance portion 23. An actuator (fluid pressure cylinder) 52 for moving the moving tube 51 in parallel with the tube portion 23a is disposed inside the closed end portion 23b. The actuator 52 is connected to a fluid source (not shown) via the opening / closing valve 53, and the pipe length of the resonance unit 23 can be changed by operating the opening / closing valve 53 to activate the actuator 52. That is, the movable tube 51 and the actuator 52 function as frequency setting means that can change the resonance frequency in the resonance unit 23.

  Also in the thermoacoustic engine 20C configured as described above, a stop control routine substantially similar to that shown in FIG. 2 is executed. Also in this embodiment, it is determined that the catalyst temperature in the pre-catalyst device 12a is equal to or lower than a predetermined threshold value, or it is determined that a signal indicating some abnormality is issued, and the thermoacoustic engine 20C is operating. In this case, an immediate stop process of the thermoacoustic engine 20C is executed. In the present embodiment, during the immediate stop process, the ECU 40 controls the actuator 52 (open / close valve 53) so that the self-excited vibration frequency of the working fluid does not match the resonance frequency in the resonance unit 23. That is, in the immediate stop process, the ECU 40 moves the moving tube 51 so as to rapidly increase or decrease the pipe length of the resonance unit 23 according to a predetermined procedure, or move the moving tube 51. The resonance frequency in the resonance part 23 is rapidly changed by reciprocating the.

  Thereby, the thermoacoustic self-excited vibration in the air column tube 21 is surely and quickly attenuated / disappeared, and the operation of the thermoacoustic engine 20C is stopped regardless of the temperature gradient between both ends of the heat accumulator 25. Become. In this case as well, after the thermoacoustic engine 20C is stopped, the heat energy of the exhaust gas is hardly lost in the high-temperature heat exchanger 26. Therefore, the exhaust gas that has not been used for conversion from heat energy to vibration energy is used. It becomes possible to use the heat energy of the gas for catalyst warm-up (particularly for warm-up of the post-catalyst device 12b). Further, as described above, the thermoacoustic engine 20C can be stopped earlier than when the application of the temperature gradient to the heat accumulator 25 is stopped by attenuating and eliminating the thermoacoustic self-excited vibration itself. It becomes possible.

  The resonance frequency of the working fluid in the air column tube 21 and the thermal efficiency when generating the thermoacoustic self-excited vibration and the output (acoustic output) of the thermoacoustic engine have a predetermined correlation. By controlling the frequency setting means including the tube 51 and the actuator 52 to bring the resonance frequency close to the target value, it is possible to obtain desired thermal efficiency and acoustic output in the thermoacoustic engine 20C.

[Fifth Embodiment]
Hereinafter, a thermoacoustic engine according to a fifth embodiment of the present invention will be described with reference to FIG. The same elements as those described in relation to the first embodiment described above are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 6 is a schematic configuration diagram showing a main part of a thermoacoustic engine 20D according to the fifth embodiment of the present invention. The thermoacoustic engine 20D of this embodiment also has basically the same configuration as the thermoacoustic engine 20 of the first embodiment, and burns a fuel / air mixture inside a combustion chamber formed in the cylinder block. And is applied to an internal combustion engine that generates power by reciprocating a piston in a combustion chamber. As shown in FIG. 6, the thermoacoustic engine 20 </ b> D includes a high-temperature heat exchanger 260 connected to the front-stage catalyst device (catalytic converter) 12 a.

  The high-temperature heat exchanger 260 includes a heat transfer member 261 made of metal or the like for transferring heat generated from the pre-catalyst device 12 a to the heat accumulator 25. A space 262 is defined in the heat transfer member 261 so as to be positioned between the upstream catalyst device 12a and the air column tube 21, and this space 262 is usually filled with a liquid metal LM such as sodium or mercury. Has been. Further, a cylinder 265 having a piston 264 is connected to the space 262 through a pipe 263. When the piston 264 is moved to the right in FIG. 6, the liquid metal LM in the space 262 of the heat transfer member 261 is transferred (drawn) into the cylinder 265 as shown in FIG. Further, when the piston 264 is moved to the left in the drawing, the liquid metal LM in the cylinder 265 can be pushed out toward the space 262 of the heat transfer member 261 and the space 262 can be filled with the liquid metal LM. A vent pipe 266 is connected to the space 262 of the heat transfer member 261 as shown in FIG.

  Also in the thermoacoustic engine 20D configured as described above, a stop control routine substantially similar to that shown in FIG. 2 is executed. Also in this embodiment, it is determined that the catalyst temperature in the pre-catalyst device 12a is equal to or lower than a predetermined threshold value, or it is determined that a signal indicating some abnormality is generated, and the thermoacoustic engine 20D is further operated. When it is in operation, an immediate stop process of the thermoacoustic engine 20D is executed. In the present embodiment, during the immediate stop process, the piston 264 is moved rightward in FIG. 6, and the entire amount of the liquid metal LM is discharged from the space 262 of the heat transfer member 261.

  Thereby, the space 262 of the heat transfer member 261 is filled with air, and an air insulation layer is formed between the pre-catalyst device 12 a and the heat accumulator 25. That is, since the provision of the temperature gradient between the both ends of the heat accumulator 25 is stopped, the thermoacoustic self-excited vibration in the air column tube 21 disappears, regardless of the temperature gradient between the both ends of the heat accumulator 25. The operation of the thermoacoustic engine 20D is stopped. Then, after the entire amount of the liquid metal LM is discharged from the space 262 of the heat transfer member 261, the region on the upstream side catalyst device 12a side of the space 262 of the heat transfer member 261 is the exhaust gas flowing into the upstream side catalyst device 12a. Therefore, the heat energy of the exhaust gas is hardly lost in the high-temperature heat exchanger 260. As a result, it becomes possible to use the heat energy of the exhaust gas that has not been used for the conversion from the heat energy to the vibration energy to warm up the front catalyst device 12a or the rear catalyst device 12b (not shown).

1 is a schematic configuration diagram showing a first embodiment of a thermoacoustic engine according to the present invention. It is a flowchart for demonstrating the procedure which stops the thermoacoustic engine of FIG. It is a schematic block diagram which shows 2nd Embodiment of the thermoacoustic engine by this invention. It is a schematic block diagram which shows 3rd Embodiment of the thermoacoustic engine by this invention. It is a schematic block diagram which shows 4th Embodiment of the thermoacoustic engine by this invention. It is a schematic block diagram for demonstrating 5th Embodiment of the thermoacoustic engine by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 12a The front | former stage catalyst apparatus 12b The back | latter stage catalyst apparatus 20,20A, 20B, 20C, 20D Thermoacoustic engine 21 Air column tube 22 Loop part 23 Resonance part 24 Transducer 25 Heat accumulator 26,260 High temperature heat exchanger 27 Low temperature heat exchanger 28 Movable throttle valve 30 Sound absorbing tank 35 Pump 36 Working fluid storage tank 51 Moving pipe 52 Actuator 261 Heat transfer member 262 Space 264 Piston 265 Cylinder L2 Exhaust pipe LM Liquid metal Tc Temperature sensor

Claims (8)

An air column tube in which the working fluid is sealed, and heat storage means disposed inside the air column tube, and a temperature gradient is formed between both end portions of the heat storage unit so that the thermoacoustic self-excitation of the working fluid is performed. In a thermoacoustic engine that generates vibration,
A thermoacoustic engine comprising vibration stopping means for stopping the thermoacoustic self-excited vibration irrespective of a temperature gradient formed between both ends of the heat storage means.   The thermoacoustic engine according to claim 1, wherein the vibration stopping unit includes a member for blocking propagation of vibration in the air column tube.   The thermoacoustic engine according to claim 1, wherein the vibration stopping means includes means for absorbing vibration in the air column tube.   The thermoacoustic engine according to claim 1, wherein the vibration stopping unit reduces the pressure of the working fluid in the air column tube.   The thermoacoustic engine according to claim 1, further comprising a resonator, wherein the vibration stopping unit changes a resonance frequency of the resonator.   The high-temperature heat exchanger disposed on one end side of the heat storage means is further provided, and the high-temperature heat exchanger uses exhaust gas from the internal combustion engine as a heat source. Thermoacoustic engine.   The internal combustion engine further includes an exhaust purification catalyst for purifying exhaust gas, and further includes means for operating the vibration stopping means when the exhaust purification catalyst needs to be warmed up. Item 7. The thermoacoustic engine according to item 6. An abnormality detection means for detecting an abnormality of at least one of the internal combustion engine and the thermoacoustic engine, and means for operating the vibration stopping means when an abnormality is detected by the abnormality detection means, The thermoacoustic engine according to claim 6 or 7.

Images