JP2009127476A - Stirling engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the starting torque of a Stirling engine. <P>SOLUTION: This Stirling engine 100 has a heat exchanger 108, a high temperature side cylinder 101, a low temperature side cylinder 102, a high temperature side piston 103 reciprocating in the high temperature side cylinder 101, a low temperature side piston 104 reciprocating in the low temperature side cylinder 102, a working fluid discharge passage 31 making the low temperature side cylinder 102 communicated with an external part of a casing 100C, and a working fluid passage opening/closing valve 30 arranged in the working fluid discharge passage 31. When starting the Stirling engine 100, the working fluid passage opening/closing valve 30 is opened, and discharges a working fluid in a low temperature side operation space MSL to the outside of the Stirling engine 100. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a Stirling engine that can reduce torque at startup.

  There has been proposed a technique for recovering exhaust heat from an internal combustion engine mounted on a vehicle such as a passenger car, a bus, or a truck by using the heat engine as an exhaust heat recovery engine. An external combustion engine is suitable for such an application. For example, a Stirling engine having excellent theoretical thermal efficiency is used as the exhaust heat recovery engine. For example, Patent Document 1 discloses a technique for starting a Stirling engine using an electric motor.

Japanese Patent Laid-Open No. 5-38956

  The Stirling engine does not start unless a starting torque larger than the torque generated during operation of the Stirling engine is input. For this reason, it is necessary to prepare starting means capable of generating a large starting torque, which is wasteful. The present invention has been made in view of the above, and an object thereof is to reduce the starting torque of a Stirling engine.

  In order to achieve the above-described object, a Stirling engine according to the present invention includes a heater that heats a working fluid, a regenerator that is connected to the heater and through which the working fluid passes, and is connected to the regenerator. A Stirling having a heat exchanger that includes a cooler that cools the working fluid, a cylinder into which the working fluid that has passed through the heat exchanger flows in and out, and a piston that reciprocates within the cylinder. When starting the Stirling engine, the engine includes a working fluid pressure adjusting means for discharging the working fluid from a space where the working fluid exists to the outside of the Stirling engine.

  As a preferred aspect of the present invention, in the Stirling engine, the cylinder is composed of a first cylinder connected to the heater and a second cylinder connected to the cooler, and the working fluid pressure adjusting means includes The working fluid is preferably discharged from at least one of the inside of the regenerator, the inside of the cooler, and the inside of the second cylinder.

  As a preferred aspect of the present invention, in the Stirling engine, the cylinder is composed of a first cylinder connected to the heater and a second cylinder connected to the cooler, and the working fluid pressure adjusting means includes It is desirable to discharge the working fluid from at least one of the inside of the second cylinder and the inside of the cooler.

  As a preferred aspect of the present invention, in the Stirling engine, it is desirable that the piston reciprocates after the working fluid is discharged from the space where the working fluid exists to the outside of the Stirling engine.

  According to the present invention, the starting torque of the Stirling engine can be reduced.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited by the best mode for carrying out the invention (hereinafter referred to as an embodiment). In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those in a so-called equivalent range. In the following, a case where a Stirling engine is used and thermal energy is recovered from exhaust gas of an internal combustion engine will be described as an example.

  In this embodiment, when the Stirling engine is started, the working fluid in the space where the working fluid exists is discharged out of the space, and the pressure of the working fluid existing in the space is discharged (for example, the Stirling engine). (During normal operation), the feature is that it is reduced. First, the configuration of the Stirling engine according to the present embodiment will be described.

  FIG. 1 is a cross-sectional view showing a Stirling engine according to the present embodiment. FIG. 2 is a cross-sectional view illustrating a configuration example of a gas bearing provided in the Stirling engine according to the present embodiment and a configuration example of an approximate linear mechanism used for supporting a piston. The Stirling engine 100 according to the present embodiment is a so-called external combustion engine, which converts thermal energy such as exhaust gas into kinetic energy and extracts it as rotational motion of the crankshaft 110. That is, the crankshaft 110 is an output shaft of the Stirling engine 100. The crankshaft 110 rotates about the rotation axis Zr.

  The Stirling engine 100 is an α-type in-line two-cylinder Stirling engine. And the high temperature side piston 103 which is the 1st piston stored in the inside of the high temperature side cylinder 101 which is the 1st cylinder, and the low temperature side which is the 2nd piston stored in the inside of the low temperature side cylinder 102 which is the 2nd cylinder The piston 104 is arranged in series.

  The high temperature side cylinder 101 and the low temperature side cylinder 102 are supported and fixed directly or indirectly to a substrate 111 which is a reference body. In the Stirling engine 100 according to the present embodiment, the substrate 111 serves as a position reference for each component of the Stirling engine 100. By comprising in this way, the relative positional accuracy of each said component can be ensured.

  As will be described later, in the Stirling engine 100 according to the present embodiment, the gas bearing GB is interposed between the high temperature side cylinder 101 and the high temperature side piston 103 and between the low temperature side cylinder 102 and the low temperature side piston 104. By directly or indirectly attaching the high temperature side cylinder 101 and the low temperature side cylinder 102 to the reference substrate 111, the clearance between the piston and the cylinder can be maintained with high accuracy, so that the function of the gas bearing GB can be sufficiently exhibited. Can be made. Further, the Stirling engine 100 can be easily assembled.

  Between the high temperature side cylinder 101 and the low temperature side cylinder 102, a heat exchanger 108 including a substantially U-shaped heater (heater) 105, a regenerator 106, and a cooler 107 is disposed. Thus, by making the heater 105 substantially U-shaped, the heater 105 can be easily arranged in a relatively narrow space such as in the exhaust gas passage of the internal combustion engine. Further, by arranging the high temperature side cylinder 101 and the low temperature side cylinder 102 in series as in the Stirling engine 100, the heater 105 can be relatively easily placed in a cylindrical space such as the exhaust gas passage 5 of the internal combustion engine. Can be arranged.

  One end of the heater 105 is disposed on the high temperature side cylinder 101 side, and the other end is disposed on the regenerator 106 side. The regenerator 106 has one end disposed on the heater 105 side and the other end disposed on the cooler 107 side. One end of the cooler 107 is disposed on the regenerator 106 side, and the other end is disposed on the low temperature side cylinder 102 side.

  A working fluid (air in this embodiment) is sealed in the high temperature side cylinder 101, the low temperature side cylinder 102, and the heat exchanger 108, and a Stirling cycle is caused by heat supplied from the heater 105 and heat discharged from the cooler 107. Composed. As a result, the Stirling engine 100 generates an output. The output generated by the Stirling engine 100 is taken out from the crankshaft 110. Here, the space inside the high temperature side cylinder 101 where the working fluid exists is called a high temperature side working space MSH, and the space inside the low temperature side cylinder 102 where the working fluid exists is called a low temperature side working space MSL. When they are not distinguished from each other, they are simply referred to as a working space MS. The working space MS is a space in which the working fluid inside is expanded or compressed.

  Here, for example, the heater 105 and the cooler 107 can be configured by bundling a plurality of tubes made of a material having high thermal conductivity and excellent heat resistance. Moreover, the regenerator 106 can be comprised with a porous heat storage body. The configurations of the heater 105, the cooler 107, and the regenerator 106 are not limited to this example, and a suitable configuration can be selected according to the heat conditions of the heat source, the specifications of the Stirling engine 100, and the like.

  The high temperature side piston 103 and the low temperature side piston 104 are supported in the high temperature side cylinder 101 and the low temperature side cylinder 102 via a gas bearing GB. That is, the piston is reciprocated in the cylinder without using lubricating oil. Thereby, the friction between the piston and the cylinder can be reduced, and the thermal efficiency of the Stirling engine 100 can be improved. Further, by reducing the friction between the piston and the cylinder, for example, the Stirling engine 100 can be recovered by recovering thermal energy even under low heat source and low temperature difference operating conditions such as exhaust heat recovery of an internal combustion engine. .

  In order to constitute the gas bearing GB, the clearance tc between the high temperature side piston 103 and the high temperature side cylinder 101 shown in FIG. 2 is set to several tens of μm over the entire circumference of the high temperature side piston 103 and the high temperature side cylinder 101. The low temperature side piston 104 and the low temperature side cylinder 102 have the same configuration. The high temperature side cylinder 101, the high temperature side piston 103, the low temperature side cylinder 102, and the low temperature side piston 104 can be configured using, for example, a metal material that is easy to process.

  In the present embodiment, gas (in the present embodiment, the same air as the working fluid) a is blown out from an air supply port HE provided on the side walls of the high temperature side piston 103 and the low temperature side piston 104 to form the gas bearing GB. As shown in FIGS. 1 and 2, a high temperature side piston internal space 103IR and a low temperature side piston internal space 104IR are formed inside the high temperature side piston 103 and the low temperature side piston 104, respectively.

  The high temperature side piston 103 is provided with a gas inlet HI for supplying the gas a to the high temperature side piston internal space 103IR, and the low temperature side piston 104 is supplied with the gas a to the low temperature side piston internal space 104IR. A gas inlet HI is provided. A gas supply pipe 118 is connected to each gas inlet HI. One end of the gas supply pipe 118 is connected to the gas bearing pump 117 and guides the gas a discharged from the gas bearing pump 117 to the high temperature side piston inner space 103IR and the low temperature side piston inner space 104IR.

  The gas a introduced into the high temperature side piston internal space 103IR and the low temperature side piston internal space 104IR flows out from the air supply port HE provided on the side walls of the high temperature side piston 103 and the low temperature side piston 104 to form the gas bearing GB. . This gas bearing GB is a static pressure gas bearing. Further, gas intake holes are provided at the tops of the high temperature side piston 103 and the low temperature side piston 104, and the gas a, which is a working fluid, is supplied from the gas intake hole to the high temperature side piston inner space 103IR and the low temperature side piston inner space 104IR. The gas bearing GB may be configured by flowing out from the air inlet HE. In addition, although the gas bearing GB of this embodiment is a static pressure gas bearing, you may use a dynamic pressure gas bearing.

  The reciprocating motion of the high temperature side piston 103 and the low temperature side piston 104 is transmitted to the crankshaft 110 which is the output shaft by the connecting rod 109, where it is converted into rotational motion. Note that the connecting rod 109 may be supported by an approximate linear mechanism (eg, a grasshopper mechanism) 119 shown in FIG. In this way, the high temperature side piston 103 and the low temperature side piston 104 can be reciprocated substantially linearly.

  In this way, if the connecting rod 109 is supported by the approximate linear mechanism 119, the side force FS (force in the radial direction of the piston) of the high temperature side piston 103 becomes almost zero, so even with the gas bearing GB having a small load capacity. The high temperature side piston 103 and the low temperature side piston 104 can be sufficiently supported. In this embodiment, most of the side force FS is supported by the approximate linear mechanism 119, and the side force FS that is generated when the reciprocating motion of the low temperature side piston 104 deviates from the approximate linear motion is supported by the gas bearing GB. .

  As shown in FIG. 1, the constituent elements such as the high temperature side cylinder 101, the high temperature side piston 103, the connecting rod 109, and the crankshaft 110 that constitute the Stirling engine 100 are stored in a casing 100C. Here, the housing 100C of the Stirling engine 100 includes a crankcase 114A and a cylinder block 114B. The inside of the casing 100C is pressurized by a pressurizing pump 115 that is a pressurizing means in the casing.

  In the present embodiment, the switching valve 116 is provided between the pressurizing pump 115 and the housing 100C. When pressurizing the inside of the housing 100C, the switching valve 116 is operated so that the pressurizing pump 115 and the housing 100C communicate with each other, and then the inside of the housing 100C is pressurized with the pressurizing pump 115. When the inside of the housing 100C is pressurized to a specified pressure, the switching valve 116 is operated so as to cut off the communication between the pressurizing pump 115 and the inside of the housing 100C. In addition, when the pressure in the casing 100C is not sufficiently low when the Stirling engine 100 is started, the switching valve 116 is operated so that the inside of the casing 100C communicates with the atmosphere, and the inside of the casing 100C is Reduce pressure.

  When the working fluid takes in heat energy by pressurizing the inside of the housing 100C with the pressurizing pump 115 and pressurizing the working fluid in the high temperature side working space MSH, the low temperature side working space MSL, and the heat exchanger 108. Increase the capacity of the working fluid. As a result, more output can be extracted from the crankshaft 110, which is the output shaft of the Stirling engine 100.

  When the Stirling engine 100 generates a specified output, the inside of the housing 100C is pressurized to a specified pressure (for example, about 1 MPa), for example. For this reason, it is necessary to keep the airtightness between the crankshaft 110 and the housing 100C, and to extract the rotational motion of the crankshaft 110 to the outside of the housing 100C. For this reason, in this embodiment, as shown in FIG. 1, the output of the crankshaft 110 is transmitted via the magnetic coupling 10 that transmits the rotation of the crankshaft 110 to the driven shaft (magnetic coupling driven shaft) 2 without contact. Is taken out of the housing 100C. That is, the output of the Stirling engine 100 is extracted from the magnetic coupling driven shaft 2 provided in the magnetic coupling 10.

  As shown in FIG. 1, a speed increasing device 20 is provided as conversion means for changing and outputting the torque of the crankshaft 110, and the rotational speed of the crankshaft 110 is increased before being input to the magnetic coupling 10. May be. As a result, the torque of the crankshaft 110 can be reduced, so that the torque transmission capacity of the magnetic coupling 10 can be suppressed. When starting the Stirling engine 100, the output of the starting means such as an electric motor is input to the magnetic coupling driven shaft 2 to rotate the crankshaft 110. In this case, the speed increasing device 20 is used as the speed reducing device. Function as. As a result, the input torque (that is, the starting torque) to the magnetic coupling driven shaft 2 can be reduced, so that the torque transmission capacity of the magnetic coupling 10 can be suppressed.

  FIG. 3 is a conceptual diagram showing changes in the starting torque of the Stirling engine. When starting the Stirling engine 100 shown in FIG. 1, the crankshaft 110 is driven from the outside. Since the pressure of the working fluid existing in the working space MS changes periodically, the starting torque Ts applied to the crankshaft 110 also changes periodically as shown by the dotted line in FIG. The starting torque Ts applied to the crankshaft 110 when starting the Stirling engine 100 needs to be large enough to overcome the maximum pressure of the working fluid existing in the working space MS and drive the high temperature side piston 103 and the low temperature side piston 104. is there. In the example shown in FIG. 3, a starting torque of Ts_m is required at the maximum.

  Further, when the inside of the casing 100C of the Stirling engine 100 is pressurized, a larger starting torque Ts is required to drive the crankshaft 110 from the outside. In this embodiment, since the output of the Stirling engine 100 is taken out of the housing 100C via the magnetic coupling 10, when the Stirling engine 100 is started in a pressurized state, the torque that can be transmitted by the magnetic coupling 10 Capacity increases. Further, when the Stirling engine 100 is started by an electric motor (electric motor / generator), it is necessary to use an electric motor / generator having a large torque.

  On the other hand, when the output is taken out by pressurizing the inside of the casing 100C of the Stirling engine 100, a large torque is required when the Stirling engine 100 is started, but the output torque Te of the Stirling engine 100 once the Stirling engine 100 is started is Is smaller than the starting torque Ts. For this reason, it is wasteful to prepare the magnetic coupling 10 having a large torque transmission capacity or to prepare the motor / generator having a large torque only for starting the Stirling engine 100.

  Therefore, in the present embodiment, when starting the Stirling engine 100, for example, the working fluid pressure in the working space MS is reduced by discharging the working fluid from the working space MS to the outside of the Stirling engine 100. Thereby, as shown by the solid line in FIG. 3, the starting torque Ts is reduced from Ts_m to Ts_d as compared with the case where the pressure of the working fluid in the working space MS is not lowered. As a result, there is no need to prepare the magnetic coupling 10 having a large torque transmission capacity or a motor / generator having a large torque.

  The working fluid is discharged to the outside of the Stirling engine 100 from any one of the high temperature side working space MSH, the low temperature side working space MSL, and the cooler 107 of the heat exchanger 108. In the Stirling engine 100 shown in FIG. 1, a working fluid discharge passage 31 that communicates the low temperature side working space MSL and the outside of the casing 100C of the Stirling engine 100 is provided in the low temperature side cylinder 102, and the working fluid is supplied from the low temperature side working space MSL. Discharge outside Stirling engine 100. The working fluid discharge passage 31 is provided with a working fluid passage opening / closing valve 30 that opens and closes the working fluid discharge passage 31.

  The working fluid passage opening / closing valve 30 is a working fluid pressure adjusting means. By opening the working fluid passage opening / closing valve 30, the low temperature side working space MSL communicates with the outside of the casing 100C, and the working fluid passage opening / closing valve 30 is opened from the low temperature side working space MSL. The working fluid is discharged to the outside of the Stirling engine 100. Accordingly, the pressure of the working fluid filled in the high temperature side working space MSH, the low temperature side working space MSL, and the heat exchanger 108 is lower than before the working fluid passage opening / closing valve 30 is opened. As a result, the starting torque Ts of the Stirling engine 100 can be reduced more than before the working fluid passage opening / closing valve 30 is opened.

  In the present embodiment, since the pressure of the working fluid in the working space MS may be reduced, the operation is performed from at least one of the high temperature side working space MSH, the heater 105, the regenerator 106, the cooler 107, and the low temperature side working space MSL. The fluid may be discharged to the outside of the Stirling engine 100. However, since the working fluid in the high temperature side working space MSH and the heater 105 is heated by the exhaust gas Ex of the internal combustion engine, if the high temperature working fluid is discharged, there is a risk of affecting peripheral equipment. In addition, the working fluid heated by the exhaust gas Ex is discharged, resulting in a reduction in exhaust heat recovery efficiency.

  Therefore, in this embodiment, it is preferable to discharge the working fluid to the outside of the Stirling engine 100 at least from a location where the temperature of the working fluid is lower than that of the regenerator 106. That is, it is preferable to discharge the working fluid from at least one of the regenerator 106, the cooler 107, and the low temperature side working space MSL to the outside of the Stirling engine 100. More preferably, the working fluid is preferably discharged from at least one of the cooler 107 and the low temperature side working space MSL where the temperature of the working fluid becomes lower than that of the regenerator 106, and further, the working fluid is operated from the low temperature side working space MSL. It is preferred to drain the fluid. Accordingly, since the relatively low temperature working fluid is discharged to the outside of the Stirling engine 100, it is possible to reduce the influence on peripheral devices and to suppress a reduction in the recovery efficiency of exhaust heat.

  In the present embodiment, the working fluid is discharged to the outside of the Stirling engine 100 from at least one of the inside of the cooler 107 and the low temperature side working space MSL (that is, inside the low temperature side cylinder 102). It is more preferable to discharge the working fluid. In this way, the opening for taking out the working fluid from the working space MS and the heat exchanger 108 can be reduced, so that the risk of leakage of the working fluid due to the opening is reduced, and the Stirling engine 100 reliability is improved.

  When discharging the working fluid from the cooler 107, the working fluid discharge passage 31 a communicating with the outside of the Stirling engine 100 is connected to the working fluid passage provided in the cooler 107. The working fluid passage opening / closing valve 30 is provided in the working fluid discharge passage 31a. When the Stirling engine 100 is started, the working fluid passage opening / closing valve 30 is opened, and the working fluid in the cooler 107 is discharged to the outside of the Stirling engine 100.

  When the working fluid is discharged from the low temperature side working space MSL, the working fluid discharge passage 31 is connected to an opening provided in a side portion of the low temperature side cylinder 102. At this time, it is preferable to provide the opening at the side of the low temperature side cylinder 102 between the top surface of the low temperature side piston 104 and the cooler 107 at the top dead center and connect the working fluid discharge passage 31. In this way, regardless of the position of the low temperature side piston 104, the working fluid in the low temperature side working space MSL can be discharged to the outside of the Stirling engine 100, and the pressure of the working fluid can be reliably reduced.

  As shown in FIG. 1, the pressure of the working fluid that has passed through the working fluid passage opening / closing valve 30 on the outlet 30e side (downstream in the flow direction of the working fluid) of the working fluid passage opening / closing valve 30 is larger than a preset pressure. Otherwise, the pressure holding valve 32 may be provided as pressure holding means that cannot be opened. For example, the valve opening pressure of the pressure holding valve 32 is P1. Here, P1 is a value lower than the pressure during normal operation of the Stirling engine 100 described later, for example, when the crankshaft 110 is rotated with a torque smaller than the maximum torque that can be transmitted by the magnetic coupling 10. The pressure is set such that the high temperature side piston 103 and the low temperature side piston 104 can reciprocate.

  When the valve opening pressure of the pressure holding valve 32 is P1, and the pressure of the working fluid that has passed through the working fluid passage opening / closing valve 30 is greater than P1, the working fluid in the low temperature side working space MSL is reduced in the Stirling engine 100. It is discharged outside. Accordingly, when the pressure of the working fluid at the time of starting the Stirling engine 100 is larger than P1, the working fluid that has passed through the working fluid passage opening / closing valve 30 is discharged to the outside of the Stirling engine 100. As a result, for example, the Stirling engine 100 can be started in a torque range that can be transmitted by the magnetic coupling 10.

  On the other hand, when the pressure of the working fluid that has passed through the working fluid passage opening / closing valve 30 is P1 or less, the working fluid in the low temperature side working space MSL is not discharged to the outside of the Stirling engine 100. For this reason, since the maximum pressure of the working fluid does not fall below P1, the pressure of the working fluid can be prevented from excessively decreasing, and a reduction in exhaust heat recovery efficiency of the Stirling engine 100 can be suppressed. Further, even when the working fluid is repressurized, the amount of pressurization can be suppressed, so that the time and energy required for pressurization can be suppressed. Thus, by providing the pressure holding means that does not open unless the pressure exceeds a preset pressure, it is possible to reduce the starting torque by reducing the pressure of the working fluid to the pressure required when starting the Stirling engine 100, and to reduce the working fluid. It can suppress that the pressure of falls too much.

  4, 5, and 6 are schematic diagrams illustrating a configuration example of an exhaust heat recovery system using the Stirling engine according to the present embodiment. In these exhaust heat recovery systems 80, 81, 82, the Stirling engine 100 recovers thermal energy from the exhaust gas Ex of the internal combustion engine 1 that is a power generation source of the vehicle and generates an output. That is, the Stirling engine 100 functions as an exhaust heat recovery device that recovers exhaust heat from the internal combustion engine 1 and converts it into output.

  In the exhaust heat recovery system 80 shown in FIG. 4, the output of the Stirling engine 100 is combined with the output of the internal combustion engine 1 and taken out from the output shaft (heat engine output shaft) 1se of the internal combustion engine 1. The heat engine output shaft 1se is connected to the differential gear device 9 of the vehicle, and the outputs of the Stirling engine 100 and the internal combustion engine 1 are transmitted to the drive wheels 7 of the vehicle via the heat engine output shaft 1se and the differential gear device 9. Drive this.

  The Stirling engine 100 is disposed in the vicinity of the internal combustion engine 1 which is a heat engine for exhaust heat recovery. At this time, the Stirling engine 100 and the internal combustion engine 100 are arranged so that the magnetic coupling driven shaft 2 (corresponding to the output shaft of the Stirling engine 100) of the magnetic coupling 10 provided in the Stirling engine 100 and the heat engine output shaft 1se are substantially parallel to each other. An engine 1 is arranged. Thereby, the output generated by the Stirling engine 100 can be transmitted to the heat engine output shaft 1se using a belt, a chain, a gear train, or the like. Further, the Stirling engine 100 can be used for exhaust heat recovery of the internal combustion engine 1 without making a major design change to the existing internal combustion engine 1.

  The heater 105 of the Stirling engine 100 is disposed in the exhaust gas passage 5 of the internal combustion engine 1. The Stirling engine 100 collects thermal energy of the exhaust gas Ex discharged from the internal combustion engine 1 from the heater 105 and generates an output. This output is extracted from the magnetic coupling driven shaft 2 of the magnetic coupling 10 provided in the Stirling engine 100.

  A Stirling engine pulley 3S is attached to the magnetic coupling driven shaft 2. A pulley 3E for an internal combustion engine is attached to the heat engine output shaft 1se. An endless belt 4 serving as power transmission means is hung on the pulley 3S for Stirling engine and the pulley 3E for internal combustion engine. With such a configuration, the output generated by the Stirling engine 100 is transmitted to the heat engine output shaft 1se. The output generated by the Stirling engine 100 is taken out from the heat engine output shaft 1se together with the output generated by the internal combustion engine 1. The mechanism for transmitting the output of the Stirling engine 100 to the heat engine output shaft 1se is not limited to such a mechanism. For example, an endless chain and a sprocket can be used, or a gear train can be used.

  The internal combustion engine 1 and the Stirling engine 100 are mounted on a vehicle such as a passenger car or a truck, for example, and serve as a power generation source for the vehicle. The internal combustion engine 1 always generates an output as a main power generation source while the vehicle is running. On the other hand, Stirling engine 100 cannot generate the minimum necessary output unless the temperature of exhaust gas Ex reaches a certain level. Accordingly, when the temperature of the exhaust gas Ex exceeds a predetermined temperature, the Stirling engine 100 generates an output by the thermal energy recovered from the exhaust gas Ex of the internal combustion engine 1 and drives the vehicle together with the internal combustion engine 1. Thus, the Stirling engine 100 becomes a power generation source that the vehicle follows.

  Between the internal combustion engine 1 that is a heat engine and the Stirling engine 100 that is an exhaust heat recovery engine, a clutch 6 that is a power interrupting means is provided. In the present embodiment, the clutch 6 is attached to the heat engine output shaft 1se. When the clutch 6 is engaged, the crankshaft 110 of the Stirling engine 100 and the heat engine output shaft 1se are mechanically connected. As a result, the output generated by the Stirling engine 100 is transmitted to the heat engine output shaft 1se via the clutch 6. When the clutch 6 is released, the connection between the internal combustion engine 1 and the Stirling engine 100 is released, so that the output of the Stirling engine 100 is not transmitted from the internal combustion engine pulley 3E to the heat engine output shaft 1se. The operation of the clutch 6 is controlled by the activation control device 50.

  An activation control device 50 that performs activation control of the Stirling engine according to the present embodiment includes an activation control unit 51 that activates the Stirling engine 100, and an in-casing pressurization control unit 52 that pressurizes the casing 100C of the Stirling engine 100. Is provided. The activation control device 50 is configured by combining memories such as a microcomputer, a RAM (Random Access Memory), and a ROM (Read Only Memory), for example. The functions of the activation control unit 51 and the in-casing pressure control unit 52 are realized by, for example, a computer program of a microcomputer that constitutes the activation control device 50. Thereby, start control of the Stirling engine according to the present embodiment is realized. Note that the activation control device 50 may implement the functions of the activation control unit 51 and the in-casing pressure control unit 52 using dedicated hardware instead of the computer program.

  Sensors for acquiring information when executing the start control of the Stirling engine according to the present embodiment are connected to the start control device 50. These sensors are an exhaust gas temperature sensor 60 which is an exhaust gas temperature detection means for detecting the temperature (exhaust gas temperature) of the exhaust gas Ex discharged from the internal combustion engine 1, and an internal pressure detection for detecting the pressure in the housing 100C of the Stirling engine 100. These are a pressure sensor 61 inside the casing, which is a means, and a Stirling engine rotational speed sensor 62 that detects the rotational speed of the Stirling engine 100. The Stirling engine rotational speed sensor 62 detects the rotational speed per unit time of the Stirling engine 100, and specifically detects the rotational speed of the magnetic coupling driven shaft 2.

  In addition, the activation control device 50 is connected to a control target when performing activation control of the Stirling engine according to the present embodiment. This control target is the working fluid passage opening / closing valve 30 for opening and closing the working fluid discharge passage 31 connected to the clutch 6, for example, the low temperature side working space MSL of the Stirling engine 100, and the pressurizing pump 115. With such a configuration, the start-up control device 50 enables the clutch 6 and the pressurizing pump based on the temperature of the exhaust gas Ex (exhaust gas temperature) acquired from the exhaust gas temperature sensor 60 and the pressure sensor 61 in the housing and the pressure in the housing 100C. The operation of 115 is controlled.

  When starting the Stirling engine 100, the start control unit 51 of the start control device 50 engages the clutch 6 during the operation of the internal combustion engine 1. As a result, the output of the internal combustion engine 1 is transmitted to the Stirling engine 100 through the internal combustion engine pulley 3E, the belt 4, the Stirling engine pulley 3S, the magnetic coupling driven shaft 2, and the magnetic coupling 10. Then, the Stirling engine 100 is started by a part of the output generated by the internal combustion engine 1. As described above, in the exhaust heat recovery system 80 shown in FIG. 4, the internal combustion engine 1 functions as a starter of the Stirling engine 100.

  The exhaust heat recovery system 81 shown in FIG. 5 has substantially the same configuration as the exhaust heat recovery system 80 shown in FIG. 4, but the auxiliary machine 11 is driven by the output of the Stirling engine 100 or the output of the Stirling engine 100 is changed to the internal combustion engine. It differs in that it can be selected whether to take out from the heat engine output shaft 1se together with the output generated by the engine 1. In the exhaust heat recovery system 81, the magnetic coupling driven shaft 2 of the magnetic coupling 10 provided in the Stirling engine 100 is connected to the auxiliary clutch 6s via the Stirling engine pulley 3S. The auxiliary machine clutch 6s is also connected to the auxiliary machine 11.

  The auxiliary machine 11 is, for example, a vehicle generator or a compressor of a vehicle air conditioner. After the Stirling engine 100 is started, when a predetermined output can be generated, the accessory clutch 6s is engaged, and the accessory 11 is driven by the output generated by the Stirling engine 100. When starting the Stirling engine 100, the start control unit 51 of the start control device 50 engages the clutch 6 during the operation of the internal combustion engine 1. As a result, similarly to the above-described exhaust heat recovery system 80, the internal combustion engine 1 functions as an activation means of the Stirling engine 100 and activates the Stirling engine 100.

  When the Stirling engine 100 is started to generate an output by the heat energy recovered from the exhaust gas Ex of the internal combustion engine 1, the clutch 6 is released and the accessory clutch 6s is engaged. As a result, the auxiliary machine 11 is driven by the output of the Stirling engine 100. When there is no request for driving the auxiliary machine 11, the clutch 6 is engaged and the auxiliary machine clutch 6s is released. As a result, the output of the Stirling engine 100 is combined with the output of the internal combustion engine 1, taken out from the output shaft (heat engine output shaft) 1 s of the internal combustion engine 1, and driven through the differential gear device 9 to drive wheels 7 of the vehicle. Is transmitted to. The other configuration of the exhaust heat recovery system 81 shown in FIG. 5 is the same as that of the exhaust heat recovery system 80 shown in FIG.

  In the exhaust heat recovery system 82 shown in FIG. 6, the magnetic coupling driven shaft 2 of the magnetic coupling 10 included in the Stirling engine 100 is connected to the electric motor / generator 8. Then, the motor / generator 8 is driven by the output generated by the Stirling engine 100. As a result, the output generated by the Stirling engine 100 is converted into electricity and taken out.

  When starting the Stirling engine 100, the electric motor / generator 8 is used as the electric motor. In this case, the Stirling engine 100 is driven by the output generated by the electric motor / generator 8. As described above, in the exhaust heat recovery system shown in FIG. 6, the electric motor / generator 8 functions as a starter of the Stirling engine 100. When the Stirling engine 100 is started and generates an output by the thermal energy recovered from the exhaust gas Ex of the internal combustion engine 1, the electric motor / generator 8 is used as a generator. As a result, the output generated by the Stirling engine 100 is converted into electricity.

  The motor / generator 8 is connected to the start control device 50, and the operation of the motor / generator 8 is controlled by the start control device 50. The other configuration of the exhaust heat recovery system 82 shown in FIG. 6 is the same as that of the exhaust heat recovery system 80 shown in FIG. Next, the start-up control procedure for the Stirling engine according to this embodiment will be described.

  FIG. 7 is a timing chart when the Stirling engine according to this embodiment is started. FIG. 8 is a flowchart showing a procedure for starting control of the Stirling engine according to the present embodiment. In starting the Stirling engine 100 shown in FIG. 1 and FIGS. 4 to 6, the internal combustion engine 1 shown in FIGS. 4 to 6 is started and exhaust gas Ex having a predetermined temperature is supplied to the heater 105 of the Stirling engine 100. It is necessary to Therefore, when executing the start control of the Stirling engine according to the present embodiment, it is assumed that the internal combustion engine 1 is started.

  In the example shown in FIG. 7, the internal combustion engine 1 is started at time t = 0, and the engine speed Ne, which is the speed per unit time of the internal combustion engine, increases with time. And exhaust gas temperature (theta) e rises with progress of time t. The exhaust gas temperature θe when the Stirling engine 100 can operate independently is defined as the exhaust gas temperature θes at the start of the Stirling engine. The fact that the Stirling engine 100 can be operated independently means that the Stirling engine 100 exhibits a minimum operation function. Demonstrating the minimum driving function means that the Stirling engine 100 overcomes internal friction and the inertial mass of the drive system and generates output.

  When the exhaust gas temperature θe reaches the exhaust gas temperature θes at the start of the Stirling engine, the Stirling engine 100 can be operated independently, so that the Stirling engine 100 can be started. The period until the exhaust gas temperature θe reaches the exhaust gas temperature θes at the start of the Stirling engine, that is, the period until t = tss is the warm-up period of the Stirling engine 100. To determine whether or not the Stirling engine 100 has been warmed up is to determine whether or not the Stirling engine 100 can be operated independently. That is, it is determined whether or not the Stirling engine 100 can be started depending on whether or not the Stirling engine 100 has been warmed up.

  Note that it may be determined whether or not the Stirling engine 100 can be started based on the temperature of the heater 105 of the Stirling engine 100 shown in FIGS. In this case, when the actual temperature of the heater 105 exceeds the temperature of the heater 105 when the Stirling engine 100 can operate independently, it is determined that the Stirling engine 100 can be started. Note that the temperature of the heater 105 when the Stirling engine 100 can operate independently is obtained in advance by analysis or experiment.

  In executing the start control of the Stirling engine according to the present embodiment, in step S101, the start control unit 51 of the start control device 50 shown in FIGS. 4 to 6 determines whether or not the Stirling engine 100 has been warmed up. judge. This is determined, for example, based on whether or not the exhaust gas temperature θe detected by the exhaust gas temperature sensor 60 shown in FIGS. 4 to 6 exceeds the exhaust gas temperature θes at the start of the Stirling engine. When it is determined No in step S101, that is, when the startup control unit 51 determines that the warming-up of the Stirling engine 100 has not ended (when θe ≦ θes), the Stirling engine 100 is not capable of autonomous operation. Since it is possible and cannot be started, the start control of the Stirling engine is ended.

  When it is determined Yes in step S101, that is, when the activation control unit 51 determines that the warming-up of the Stirling engine 100 has been completed (when θe> θes), the Stirling engine 100 can be operated independently. Can be started. In this case, the Stirling engine 100 can be started after the Stirling engine 100 is warmed up, that is, after t = tss in FIG.

  When it determines with Yes by step S101, it progresses to step S102 and the starting control part 51 determines whether the output of the Stirling engine 100 is required. Even if the Stirling engine 100 can be started, the output of the Stirling engine 100 is used when it is not necessary to drive the auxiliary machine 11 shown in FIG. 5 or when the electric power generation by the electric motor / generator 8 shown in FIG. 6 is unnecessary. Is determined to be unnecessary. When it determines with No by step S102, ie, when the starting control part 51 determines with the output of the Stirling engine 100 being unnecessary, the starting control of a Stirling engine is complete | finished.

  When it determines with Yes in step S102, ie, when the starting control part 51 determines with the output of the Stirling engine 100 being required, the Stirling engine 100 is started. When starting the Stirling engine 100, the start control unit 51 reduces the pressure of the working fluid of the Stirling engine 100 in step S <b> 103, that is, lowers the pressure of the working fluid than during the normal operation of the Stirling engine 100. Specifically, the working fluid passage opening / closing valve 30 shown in FIGS. 4 to 6 is opened, and the working fluid is discharged from the inside of the low temperature side working space MSL or the inside of the cooler 107 shown in FIG.

  When the pressure of the working fluid of the Stirling engine 100 is decreased, the activation control unit 51 activates the Stirling engine 100 in step S104. In starting the Stirling engine 100, for example, in the exhaust heat recovery systems 80 and 81 shown in FIGS. 4 and 5, the start control unit 51 engages the clutch 6 and uses a part of the output of the internal combustion engine 1. The crankshaft 110 of the Stirling engine 100 is rotated. As a result, the high temperature side piston 103 and the low temperature side piston 104 are reciprocated to start the Stirling engine 100. In the exhaust heat recovery system 82 shown in FIG. 6, the start control unit 51 drives the electric motor / generator 8 as an electric motor to rotate the crankshaft 110 of the Stirling engine 100. As a result, the high temperature side piston 103 and the low temperature side piston 104 are reciprocated to start the Stirling engine 100.

  Thus, in this embodiment, when starting the Stirling engine 100, the high temperature side piston 103 and the low temperature side piston 104 are reciprocated in a state where the pressure of the working fluid of the Stirling engine 100 is lower than that during normal operation. Exercise. Thereby, the starting torque of the Stirling engine 100 can be reduced. The pressure of the working fluid during normal operation of the Stirling engine 100 is, for example, the pressure of the working fluid (rated pressure) when the Stirling engine 100 is operated at the rated output. Here, the rated output is a use limit guaranteed for the Stirling engine 100, and is an output that the Stirling engine 100 can generate continuously for a certain time (for example, one hour). The rated pressure is a pressure required when the Stirling engine 100 is operating at the rated output.

  The pressure of the working fluid during normal operation of the Stirling engine 100 is, for example, the Stirling engine at the exhaust gas temperature when the internal combustion engine 1 is operated under certain operating conditions (for example, when running at a constant speed of 60 km / h). 100 may be a pressure (for example, 10 MPa) necessary for generating an output having a certain size (for example, 2 kW).

  In the present embodiment, the startup torque Ts of the Stirling engine 100 can be reduced by the above-described control. Therefore, in the exhaust heat recovery systems 80 and 81 shown in FIGS. 4 and 5, the internal combustion engine 1 when the clutch 6 is engaged is used. Torque fluctuation is reduced. As a result, there is an advantage that a decrease in drivability of a vehicle on which the internal combustion engine 1 and the Stirling engine 100 are mounted can be suppressed. Further, in the exhaust heat recovery system 82 shown in FIG. 6, the motor / generator 8 can be downsized. Furthermore, in the exhaust heat recovery systems 80 to 82 shown in FIGS. 4 to 6, since the torque that can be transmitted by the magnetic coupling 10 can be reduced, the magnetic coupling 10 can be reduced in size.

  When the Stirling engine 100 is activated, the Stirling engine speed Nse increases with time. When the Stirling engine 100 is started, the process proceeds to step S105, and the start control unit 51 compares the current Stirling engine speed Nse with a preset decompression end speed Nsef. The decompression end rotational speed Nsef is a parameter for determining whether or not the Stirling engine 100 has started the independent operation, and is set to, for example, the minimum rotational speed when the Stirling engine 100 operates autonomously.

  When it determines with No by step S105, ie, when the starting control part 51 determines with it being Nse <= Nsef, it progresses to step S106 and the starting of the Stirling engine 100 is continued. Specifically, the crankshaft 110 of the Stirling engine 100 is rotated while the pressure of the working fluid of the Stirling engine 100 is lower than that during normal operation, and the high temperature side piston 103 and the low temperature side piston 104 are reciprocated.

  When it is determined Yes in step S105, that is, when the activation control unit 51 determines that Nse> Nsef, it can be determined that the Stirling engine 100 is activated and is operating independently. In this case, the process proceeds to step S <b> 107 and the activation control unit 51 closes the working fluid passage opening / closing valve 30 shown in FIGS. 4 to 6 and stops discharging the working fluid to the outside of the Stirling engine 100. Thereby, the activation control unit 51 stops the pressure reduction of the working fluid (time t = tdf).

  When the Stirling engine 100 is activated and operates independently, the Stirling engine rotation speed Nse increases and reaches the rotation speed (rated rotation speed) Nsec at the rated output at time t = tc. In this state, the Stirling engine 100 collects exhaust heat from the exhaust gas of the internal combustion engine 1 to drive the drive wheels 7 and the auxiliary machines 11 of the vehicle, or generate electric power using the electric motor / generator 8 as a generator. Or

  Since the decompression end rotational speed Nsef is lower than the rated rotational speed Nsec, it is possible to avoid an unnecessary decrease in the pressure of the working fluid by determining the self-sustained operation of the Stirling engine 100 based on the decompression end rotational speed Nsef. As a result, the Stirling engine 100 can be started with the pressure drop of the working fluid kept to the minimum necessary, so that the reduction of exhaust heat efficiency due to the excessive pressure drop of the working fluid can be suppressed. Further, as will be described later, even when pressurizing the inside of the housing 100C to pressurize the working fluid in the working space MS and the heat exchanger 108, the minimum pressurization is sufficient. Thereby, energy consumption for pressurizing the inside of the housing 100C can be suppressed.

  In this embodiment, since the working fluid of the Stirling engine 100 is discharged to the outside in step S103 to reduce the pressure of the working fluid, the operations in the high temperature side working space MSH, the low temperature side working space MSL, and the heat exchanger 108 are performed. The fluid pressure is lower than during normal operation. As a result, there is a possibility that the planned output cannot be obtained from the Stirling engine 100. For this reason, when the Stirling engine 100 collects exhaust heat, the exhausted working fluid is supplemented, and the working fluid in the high temperature side working space MSH, the low temperature side working space MSL, and the heat exchanger 108 is supplied during normal operation. It is preferable to apply pressure up to

  In this case, when the exhaust heat is recovered by the Stirling engine 100, the in-casing pressurization control unit 52 of the start control device 50 shown in FIGS. 4 to 6 starts the pressurization pump 115 and the pressurization pump 115. The casing 100C is pressurized by operating the switching valve 116 so as to communicate with the inside of the casing 100C. And it pressurizes until the pressure of the working fluid in the high temperature side working space MSH, the low temperature side working space MSL, and the heat exchanger 108 becomes the pressure of the working fluid during normal operation (for example, the rated pressure described above). Thereby, the planned output can be reliably obtained from the Stirling engine 100.

  Whether the pressure of the working fluid in the high temperature side working space MSH, the low temperature side working space MSL, and the heat exchanger 108 becomes the pressure of the working fluid during normal operation or not is shown in FIGS. 4 to 6. This can be determined based on the pressure in the casing 100 </ b> C acquired from 61. Further, the in-casing pressurization control unit 52 may perform feedback control of the pressurizing pump 115 so that the deviation between the pressure in the casing 100C and the preset pressure in the casing 100C becomes zero.

  As described above, in this embodiment, the Stirling engine is started in a state where the pressure of the working fluid of the Stirling engine is lower than that during normal operation. Thereby, the torque required when starting the Stirling engine can be reduced.

  As described above, the exhaust heat recovery engine and the start control device according to the present invention are useful for starting the exhaust heat recovery engine, and are particularly suitable for suppressing the start torque.

It is sectional drawing which shows the Stirling engine which concerns on this embodiment. It is sectional drawing which shows the structural example of the gas bearing with which the Stirling engine which concerns on this embodiment is provided, and the structural example of the approximate linear mechanism used for support of a piston. It is a conceptual diagram which shows the change of the starting torque of a Stirling engine. It is a mimetic diagram showing an example of composition of an exhaust heat recovery system using a Stirling engine concerning this embodiment. It is a mimetic diagram showing an example of composition of an exhaust heat recovery system using a Stirling engine concerning this embodiment. It is a mimetic diagram showing the example of composition of the exhaust heat recovery system using the Stirling engine concerning this embodiment. It is a timing chart at the time of starting of the Stirling engine concerning this embodiment. It is a flowchart which shows the procedure of starting control of the Stirling engine which concerns on this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 5 Exhaust gas path 6 Clutch 6s Auxiliary clutch 8 Electric motor / generator 10 Magnetic coupling 11 Auxiliary machine 30 Working fluid passage opening / closing valve 30e Outlet 31, 31a Working fluid discharge passage 32 Pressure holding valve 50 Start control device 51 Start Control unit 52 Pressure control unit in casing 60 Exhaust gas temperature sensor 61 Pressure sensor in casing 62 Stirling engine speed sensor 80, 81, 82 Waste heat recovery system 100 Stirling engine 100C casing 101 High temperature side cylinder 102 Low temperature side cylinder 103 High temperature side Piston 104 Low temperature side piston 105 Heater 106 Regenerator 107 Cooler 108 Heat exchanger 115 Pressurizing pump 117 Gas bearing pump 119 Approximate linear mechanism MSH High temperature side working space MSL Low temperature side working space

Claims (4)

A heat exchanger comprising: a heater that heats the working fluid; a regenerator that is connected to the heater and through which the working fluid passes; and a cooler that is connected to the regenerator and cools the working fluid. When,
A cylinder into which the working fluid that has passed through the heat exchanger flows in and out;
A Stirling engine having a piston that reciprocates in the cylinder,
When starting the Stirling engine, the Stirling engine is provided with a working fluid pressure adjusting means for discharging the working fluid from the space where the working fluid exists to the outside of the Stirling engine. The cylinder includes a first cylinder connected to the heater and a second cylinder connected to the cooler,
The Stirling according to claim 1, wherein the working fluid pressure adjusting means discharges the working fluid from at least one of the inside of the regenerator, the inside of the cooler, and the inside of the second cylinder. engine. The cylinder includes a first cylinder connected to the heater and a second cylinder connected to the cooler,
The Stirling engine according to claim 1, wherein the working fluid pressure adjusting means discharges the working fluid from at least one of the inside of the second cylinder and the inside of the cooler.   The Stirling engine according to any one of claims 1 to 3, wherein the piston reciprocates after the working fluid is discharged from the space where the working fluid exists to the outside of the Stirling engine.

Images