Abstract:
An external combustion engine provided with a pipe-shaped main container with a heating portion and a cooling portion, an output part converting displacement of the liquid part of said working fluid generated due to the change in volume of said working fluid accompanying generation and condensation of said steam to mechanical energy for output, a venturi provided at a communicating part of the main container and an auxiliary container, a communicating member forming a communicating passage bypassing the venturi and communicating the main container and the auxiliary container, and a shutting means for closing the communicating passage at the time of normal operation and opening the communicating passage at the time of startup, wherein at the time of startup, the pressure loss at the communicating passage becomes smaller than a saturated steam pressure at the temperature of the heating portion.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to an external combustion engine generating and liquefying steam of a working fluid, using the accompanying change in volume of the working fluid to displace a liquid part of the working fluid, and converting this to mechanical energy for output. 
         [0003]    2. Description of the Related Art 
         [0004]    In the past, this type of external combustion engine has also been called a “liquid piston steam engine”. A working fluid is sealed in a pipe-shaped main container flowably in a liquid state. Part of the liquid state working fluid is heated to evaporate at a heating portion formed at one end of the main container, while the steam of the working fluid is cooled to condense at a cooling portion formed at the intermediate part of the main container. By alternately repeatedly evaporating and condensing this working fluid, the liquid phase part of the working fluid is made to cyclically displace (so-called “self vibration”) and the self vibration of the liquid phase part of this working fluid is taken out at the output part as mechanical energy (for example, see Japanese Patent Publication (Kokai) No. 2007-255259). 
         [0005]    This art aims at controlling the average value of the internal pressure of the main container so as to approach the target value. Therefore, it can improve the output and efficiency of the external combustion engine. More specifically, by sealing the working fluid in an auxiliary container separate from the main container in the liquid state and connecting the main container and the auxiliary container through a venturi, the internal pressure of the auxiliary container is stabilized at a pressure substantially equal to the average value of the internal pressure of the main container. 
         [0006]    Further, the target value of the average value of the internal pressure of the main container is calculated based on the temperature of the heater etc. and the working fluid in the auxiliary container is compressed or expanded by the piston mechanism so as to control the internal pressure of the auxiliary container to approach the target value. By doing this, the average value of the internal pressure of the main container is made to change to track the internal pressure of the auxiliary container and approach the target value. 
       SUMMARY OF THE INVENTION 
       [0007]    In this art, if the external combustion engine is stopped and the heating of the working fluid by the heater is stopped, the temperature of the heater gradually falls to the ambient temperature. When the external-combustion engine stops, if steam of the working fluid has built up in the main container, the saturated steam pressure of the working fluid also falls along with the drop in temperature of the heater and the steam of the working fluid condenses and liquefies. For this reason, the internal pressure of the main container falls. 
         [0008]    When the internal pressure of the main container falls more than the internal pressure of the auxiliary container, the working fluid in the auxiliary container passes through the venturi and gradually flows into the main container whereby the amount of working fluid in the main container becomes excessive. This phenomenon particularly occurs in the winter when the ambient temperature is low. 
         [0009]    In this way, in the state where the amount of the working fluid in the main container becomes excessive, if the external combustion engine is restarted and the heater is used to heat the working fluid: part of the working fluid will vaporize and the internal pressure of the main container will rise. If the internal pressure of the main container rises more than the internal pressure of the auxiliary container, the excess part of the working fluid in the main container passes through the venturi and is returned to the auxiliary container. When the excess part of the working fluid in the main container all returns to the auxiliary container and the amount of the working fluid in the main container becomes a suitable amount, a predetermined output is generated. 
         [0010]    However, with a venturi, the working fluid can only flow a very little at a time, so time ends up being taken for the excess part of the working fluid in the main container to all return to the auxiliary container. For this reason, there is the problem that the startup time from restart to the time when a predetermined output is obtained, ends up becoming longer. 
         [0011]    To avoid this problem at the time of restart, it is necessary to make the external combustion engine stop at a timing where steam of the working fluid has not built up in the main container. The operation for stopping the external combustion engine ends up being extremely troublesome. 
         [0012]    Therefore, the assignee previously filed Japanese Patent Application No. 2007-27848 (below, called the “related art”) in Japan claiming an external combustion engine able to quickly generate a predetermined output after start of startup. In this related art, not only are the main container and the auxiliary container communicated through a venturi, but also the main container and the auxiliary container are communicated by a communicating passage bypassing the venturi. Furthermore, a valve for shutting the communicating passage is provided. At the time of normal operation, the valve is closed, while at the time of startup, the valve is opened. 
         [0013]    Due to this, at the time of normal operation, the main container and the auxiliary container are communicated only through the venturi, while at the time of startup, the main container and the auxiliary container are communicated not only through the venturi, but also through the communicating passage. Further, at the time of startup, the generator forming the output part is supplied with electric power from the outside to drive the generator so that the piston passes bottom dead center at least one time. 
         [0014]    In this case, at the time of startup, the piston moves from top dead center toward bottom dead center, whereby the working fluid in the main container is compressed, so the excess part of the working fluid in the main container passes through the communicating passage and is quickly returned to the auxiliary container. For this reason, it is possible to shorten the startup time from restart to the time when a predetermined output is obtained. 
         [0015]    However, according to detailed studies of the inventors, it is learned that in this related art, there is the problem that if the liquid part of the working fluid flows into the heating portion at the time of startup, heat loss ends up occurring. That is, at the time of startup when output cannot be taken out, if the liquid part of the working fluid flows into the heating portion and heat exchange is performed between the heating portion and the liquid part of the working fluid, that amount of heat cannot be taken out as output and ends up becoming heat loss. 
         [0016]    The inventors studied preventing air from flowing from the output part side into the main container by sealing a working fluid inside the output part. In this study as well, after the external combustion engine was stopped, the working fluid in the output part gradually flowed into the main container and the amount of working fluid in the main container became excessive. In this study as well, a similar problem occurred in this related art. That is, it is desirable that after the start of startup, the excess part of the working fluid in the main container quickly be returned to the output part and the predetermined output be quickly produced. 
         [0017]    The present invention, in consideration of this problem, has as its object keeping the liquid part of the working fluid from flowing into the heating portion at the time of startup. 
         [0018]    To achieve the object, in the aspect of the invention as set forth in claim  1 , there is provided an external combustion engine provided with: 
         [0019]    a pipe-shaped main container in which a working fluid is sealed flowable in a liquid state, 
         [0020]    a heating portion formed at a location at one end of the main container and heating the part of the working fluid in the main container to generate steam of the working fluid, 
         [0021]    a cooling portion formed at a location of said main container on the other end side thereof from the heating portion and cooling the steam to condense, 
         [0022]    an output part communicating with the other end of the main container and converting displacement of the liquid part of the working fluid generated due to the change in volume of the working fluid accompanying generation and condensation of the steam to mechanical energy for output, 
         [0023]    an auxiliary container communicating with the main container and having the working fluid sealed inside it, 
         [0024]    a venturi provided at a communicating part between the main container and the auxiliary container, 
         [0025]    a communicating member forming a communicating passage bypassing the venturi and communicating the main container and the auxiliary container, and 
         [0026]    a shutting means closing the communicating passage at the time of normal operation and opening the communicating passage at the time of startup, 
         [0027]    the output part having a piston displacing upon receiving pressure from the liquid part of the working fluid and a cylinder slidably holding the piston, 
         [0028]    the output part being driven as a startup means at the time of the startup, 
         [0029]    a displacement speed of the piston becoming the displacement speed of the piston at the time of normal operation or more when the output part is driven as the startup means, 
         [0030]    the communicating passage being formed so that when the output part is driven as the startup means and the displacement speed of the piston becomes the displacement speed of the piston at the time of normal operation or more, the pressure loss at the communicating passage becomes smaller than a saturated steam pressure at the temperature of the heating portion. 
         [0031]    According to this, at the time of startup, the pressure loss at the communicating passage becomes smaller than the saturated steam pressure at the temperature of the heating portion, so the excess part of the working fluid in the main container can more easily flow to the communicating passage side than the heating portion side and as a result the liquid part of the working fluid can be kept from flowing into the heating portion. 
         [0032]    In the aspect of the invention as set forth in claim  2 , there is provided the external combustion engine as set forth in claim  1  wherein 
         [0033]    the output part has a casing communicating with the main container through the cylinder and having the working fluid sealed in it, 
         [0034]    the auxiliary container is formed by the casing, 
         [0035]    the venturi is formed by a very small clearance between the piston and the cylinder, and 
         [0036]    the communicating passage bypasses the cylinder and communicates the casing and the main container. 
         [0037]    According to this, the flow length of the communicating passage can easily be made shorter, so the pressure loss at the communicating passage can easily be made smaller than the saturated steam pressure at the temperature of the heating portion. 
         [0038]    In the aspect of the invention as set forth in claim  3 , there is provided an external combustion engine provided with 
         [0039]    a pipe-shaped main container in which a working fluid is sealed flowable in a liquid state, 
         [0040]    a heating portion formed at a location at one end of the main container and heating the part of the working fluid in the main container to generate steam of the working fluid, 
         [0041]    a cooling portion formed at a location of said main container on the other end side thereof from the heating portion and cooling the steam to condense, 
         [0042]    an output part communicating with the other end of the main container and converting displacement of the liquid part of the working fluid generated due to the change in volume of the working fluid accompanying generation and condensation of the steam to mechanical energy for output, 
         [0043]    an auxiliary container communicating with the main container and having the working fluid sealed inside it, 
         [0044]    a venturi provided at a communicating part between the main container and the auxiliary container, 
         [0045]    a communicating passage bypassing the venturi and communicating the main container and the auxiliary container, and 
         [0046]    a shutting means closing the communicating passage at the time of normal operation and opening the communicating passage at the time of startup, 
         [0047]    the output part having a piston displacing upon receiving pressure from the liquid part of the working fluid and a cylinder slidably holding the piston, 
         [0048]    the output part being driven as a startup means at the time of the startup, 
         [0049]    when the output part is driven as the startup means, a displacement speed of the piston becoming slower than a displacement speed of the piston at the time of normal operation. 
         [0050]    According to this, at the time of startup, it is possible to lower the flow rate of the working fluid flowing through the communicating passage and possible to reduce the pressure loss at the communicating passage compared with the time of normal operation. For this reason, at the time of startup, it is possible to make the excess part of the working fluid in the main container easily flow to the communicating passage side and as a result suppress the flow of the liquid part of the working fluid to the heating portion. 
         [0051]    In the aspect of the invention as set forth in claim  4 , there is provided the external combustion engine as set forth in claim  3  wherein when the output part is driven as the startup means, the displacement speed of the piston is a speed whereby the pressure loss at the communicating passage becomes smaller than the saturated steam pressure at the temperature of the heating portion. 
         [0052]    Due to this, at the time of startup, the excess part of the working fluid in the main container more easily flows to the communicating passage side rather than the heating portion side, so it is possible to suppress the liquid part of the working fluid flowing into the heating portion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0053]    These and other objects and features of the present invention will become clearer from the following description of the preferred embodiments given with reference to the attached drawings, wherein: 
           [0054]      FIG. 1  is a view showing an outline of an external combustion engine in a first embodiment of the present invention; 
           [0055]      FIG. 2  is a timing chart showing the operation at the time of startup in the first embodiment; 
           [0056]      FIG. 3  is a timing chart showing the operation at the time of startup in a second embodiment; and 
           [0057]      FIG. 4  is a view showing an outline of an external combustion engine of a third embodiment. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
       [0058]    Below, a first embodiment of the present invention will be explained. The present embodiment applies the external combustion engine according to the present invention to a power generating system.  FIG. 1  is a view showing an outline of the power generating system according to this embodiment. The basic configuration of this power generating system is similar to that of the engine disclosed in Japanese Patent Publication (Kokai) No. 2007-255259, so first the part of the configuration common with this will be explained. 
         [0059]    An external combustion engine  10  makes a movable body  2  in which a permanent magnet is buried displace by vibration to drive a generator  1  generating an electromotive force. This is provided with a main container  11  in which a working fluid  12  is sealed flowable in a liquid state, a heater  13  heating the working fluid  12  in the main container  11  to vaporize it, and a cooler  14  cooling the steam of the working fluid  12  vaporized by heating by the heater  13 . In the present embodiment, water is used as the working fluid  12 , but a refrigerant etc. may also be used. 
         [0060]    In the present embodiment, the heater  13  is designed to exchange heat with a high temperature gas (for example, automobile exhaust gas). The heater  13  may also be configured by an electric heater. Further, in the present embodiment, the cooler  14  has cooling water circulating in it. While not illustrated, in the circulating circuit of the cooling water is arranged a radiator radiating the heat which the cooling water robs from the steam of the working fluid  12 . 
         [0061]    In the main container  11 , a portion contacting the heater  13 , that is, a heating portion  11   a , and a portion contacting the cooler  14 , that is, a cooling portion  11   b , are preferably made of materials superior in heat conductivity. In the present embodiment, the heating portion  11   a  and cooling portion  11   b  are made of copper or aluminum. The heating portion  11   a  may have the heater  13  formed integrally with it, while the cooling portion  11   b  may have the cooler  14  formed integrally with it. 
         [0062]    On the other hand, in the main container  11 , an intermediate part  11   c  between the heating portion  11   a  and the cooling portion  11   b  is preferably made of a material superior in heat insulation. In the present embodiment, the working fluid  12  is made water, so this is made stainless steel. The part of the main container  11  at the generator  1  side from the cooling portion  11   b  is also made of stainless steel superior in heat insulation. 
         [0063]    The main container  11  is a pipe-shaped pressure container formed into a generally U-shape with a bent part  11   d  positioned at its bottommost part and first and second straight parts  11   e  and  11   f  extending in the vertical direction. At the first straight part  11   e  of the main container  11  at one end across the bent part  11   d  (right side of  FIG. 1 ) are arranged the heater  13  and cooler  14 . The heater  13  is positioned at a higher side than the cooler  14 . 
         [0064]    While not shown, to secure space for vaporization of the working fluid  12 , at the top end part of the first straight part  11   e , a predetermined volume of gas (for example, air) is sealed. 
         [0065]    On the other hand, at the top end of the second straight part  11   f  at the other side of the main container  11  across the bent part  11   d  (left side of  FIG. 1 ), the generator  1  is arranged. Inside the casing  1   a  of the generator  1 , an output takeout piston  15  displacing by receiving pressure from the liquid part of the working fluid  12  is arranged slidably in a cylinder  15   a . The generator  1  corresponds to the output part in the present invention. 
         [0066]    The piston  15  is coupled with a shaft  2   a  of the movable body  2  in the casing  1   a  of the generator  1 . At the opposite side of the piston  15  across the movable body  2 , a spring  3  forming an elastic means for generating an elastic force pushing the movable body  2  to the piston  15  side is provided. 
         [0067]    As the details will be explained later, the generator  1  can be driven by electric power supplied from the outside. At the time of startup of the external combustion engine  10 , the generator  1  functions as a startup means (starter motor) for making the piston  15  displace to make the external combustion engine  10  start up. When generator  1  is driven as a startup means, the displacement speed of the piston  15  is set at the displacement speed of the piston  15  at the time of normal operation or more. 
         [0068]    In the main container  11 , above the bent part  11   d , an auxiliary container  16  is arranged for adjusting the internal pressure of the main container  11  (below, referred to as the “main container pressure”). The bent part  11   d  and a bottom of the auxiliary container  16  are communicated through a venturi  17 . The inner volume of this auxiliary container  16  is designed to be smaller than the inner volume of the main container  11 . 
         [0069]    The venturi  17  acts to stabilize the internal pressure Pt of the auxiliary container  16  (below, referred to as the “auxiliary, container pressure”) at a pressure substantially equal to an average value of the main container pressure (below, referred to as the “main container average pressure”). In the present embodiment, as the venturi  17 , a fixed venturi with a reduced flow diameter is used. 
         [0070]    The bottom part in the auxiliary container  16  is filled with the working fluid  12  in a liquid state. The top part in the auxiliary container  16  is filled with a gas  18 . As the gas  18 , a gas insoluble in the working fluid  12  is preferably used. In the present embodiment, as the gas  18 , helium, which is insoluble in water, is used. The auxiliary container  16  may also be filled inside it with only the liquid state working fluid  12 . 
         [0071]    The auxiliary container  16  and venturi  17  are preferably made of materials superior in heat insulation. In the present embodiment, the auxiliary container  16  and venturi  17  are made of stainless steel. 
         [0072]    A piston mechanism  19  serving as a pressure adjustment mechanism for adjusting the auxiliary container pressure Pt is comprised of a pressure adjustment piston  19   a  and an electric actuator  19   b . The pressure adjustment piston  19   a  is arranged at the top end in the auxiliary container  16  and is designed to be driven back and forth in the vertical direction by the external electric actuator  19   b  of the auxiliary container  16 . 
         [0073]    Next, an outline of an electronic control unit in the present embodiment will be explained. A control system  21  is comprised by a known microcomputer having a CPU, ROM, RAM, etc. and its peripheral circuits. 
         [0074]    The control system  21  receives as input detection signals for control of the piston mechanism  19  from a heating portion temperature sensor  22  for detecting a temperature T 1  of the heating portion  11   a  (below, called the “heating portion temperature”), a cooling portion temperature sensor  23  for detecting a temperature T 2  of the cooling portion  11   b  (below, referred to as the “cooling portion temperature”), and a pressure sensor  24  for detecting an auxiliary container pressure Pt. The control system  21  is designed to control the drive of the electric actuator  19   b  based on the detection signals from the sensors  22  to  24 . 
         [0075]    In the present embodiment, to obtain a predetermined output quickly after the beginning of startup, the following point is changed from the engine disclosed in Japanese Patent Publication (Kokai) No. 2007-255259. That is, in the present embodiment, a communicating part adjusting means for adjusting the flow area etc. of the communicating part between the main container  11  and the auxiliary container  16  is provided. 
         [0076]    This communicating part adjusting means is comprised of a communicating member  25  forming a communicating passage  25   a  bypassing the venturi  17  and communicating the main container  11  and the auxiliary container  16 , a check valve  26  arranged in the communicating passage  25   a , and a valve  30  comprising a shutting means shutting the communicating passage  25   a.    
         [0077]    More specifically, the communicating passage  25   a  communicates the bent part  11   d  of the main container  11  and the bottom part of the auxiliary container  16  where the working fluid  12  is present. The flow area of the communicating passage  25   a  is larger than the flow area of the venturi  17 . 
         [0078]    The flow area and flow length of the communicating passage  25   a  are set so that the flow loss (pressure loss) of the communicating passage  25   a  becomes smaller than the saturated steam pressure at the heating portion temperature T 1  when the generator  1  is driven as a startup means and the displacement speed of the piston  15  is the displacement speed of the piston  15  at the time of normal operation or more. In the present embodiment, the communicating passage  25   a  is made of stainless steel. 
         [0079]    The check valve  26  allows the flow of the working fluid  12  in the communicating passage  25   a  from the main container  11  to the auxiliary container  16  and prevents the backflow of the working fluid  12  from the auxiliary container  16  to the main container  11 . In the present embodiment, as the check valve  26 , a spring type check valve having a spring part  26   a  is used. This is designed to open when the main container pressure is larger than the auxiliary container pressure Pt. 
         [0080]    The valve  30  is controlled to open and close by the control system  21  so that it closes at the time of normal operation and opens only at the time of startup of the external combustion engine  10 . 
         [0081]    Next, the operation in the above configuration will be explained. 
         [0082]    The basic operation is similar to that of the engine disclosed in Japanese Patent Publication (Kokai) No. 2007-255259, so only an outline will be simply explained. 
         [0083]    If operating the heater  13  and the cooler  14 , the working fluid (water)  12  in the heating portion  11   a  is heated to vaporize by the heater  13 . When the high temperature, high pressure steam of the working fluid  12  builds up in the heating portion  11   a , and the level of the working fluid  12  in the first straight part  11   e  of the main container  11  is pushed down. 
         [0084]    This being the case, in the main container  11 , the liquid part of the working fluid  12  displaces from the first straight part  11   e  side to the second straight part  11   f  side and pushes up the piston  15  at the generator  1  side. At this time, the piston  15  pushes against the spring  3  to make it elastically deform. 
         [0085]    Further, when the level of the working fluid  12  in the first straight part  11   e  falls down to the cooling portion  11   b  and the steam of the working fluid  12  enters in the cooling portion  11   b , this steam is cooled by the cooler  14  to become liquefied, so the force pushing down the level of the working fluid  12  in the first straight part  11   e  is canceled out. 
         [0086]    As a result, the piston  15  at the generator  1  side pushed up once by the expansion of the steam of the working fluid  12  descends due to the elastic recovery force of the spring  3 , the liquid part of the working fluid  12  displaces from the second straight part  11   f  side to the first straight part  11   e  side in the main container  11 , and the level at the first straight part  11   e  side rises. 
         [0087]    This operation is repeated until the operations of the heater  13  and cooler  14  are stopped. The liquid part of the working fluid  12  in the main container  11  displaces cyclically (so-called self vibration) and makes the movable body  2  of the generator  1  move up and down. 
         [0088]    The control system  21  performs control to adjust the main container pressure. An outline of this control will be explained below. The control system  21  uses the heating portion temperature T 1  and the steam pressure curve of the working fluid  12  stored in advance in the control system  21  to calculate the saturated steam pressure of the working fluid  12  at the heating portion temperature T 1 . Further, it uses the cooling portion temperature T 2  and the steam pressure curve of the working fluid  12  to calculate the saturated steam pressure of the working fluid  12  at the cooling portion temperature T 2 . 
         [0089]    Next, the target value of the main container average pressure will be calculated. In the present embodiment, the average value of the saturated steam pressure of the working fluid  12  at the heating portion temperature T 1  and the saturated steam pressure of the working fluid  12  at the cooling portion temperature T 2  is calculated and this average value is made the target value of the main container average pressure. 
         [0090]    The saturated steam pressure of the working fluid  12  at the cooling portion temperature T 2  becomes substantially equal to the atmospheric pressure (0.1 MPa), so the average value of the saturated steam pressure of the working fluid  12  at the heating portion temperature T 1  and the atmospheric pressure (0.1 MPa) may also be made the target value. The value suitably corrected on the basis of these average values, may also be made the target value. 
         [0091]    When the auxiliary container pressure Pt is lower than the target value, the electric actuator  19   b  pushes out the pressure adjustment piston  19   a  and reduces the volume of the auxiliary container  16 . Due to this, the working fluid  12  in the auxiliary container  16  is compressed and the auxiliary container pressure Pt rises. 
         [0092]    On the other hand, when the auxiliary container pressure Pt is higher than the target value, it pulls in the pressure adjustment piston  19   a  and reduces the volume of the auxiliary container  16 . Due to this, the working fluid  12  in the auxiliary container  16  expands and auxiliary container pressure Pt falls. 
         [0093]    In this way, the main container average pressure changes tracking the auxiliary container pressure and approaches the target value. Therefore, even if the heating portion temperature T 1  fluctuates, the main container average pressure can be maintained at substantially the target value, so a drop in the performance due to fluctuations in the heating portion temperature T 1  (output and efficiency) can be prevented. 
         [0094]    Next, the characterizing operation of this configuration will be explained. 
         [0095]    In the above configuration, if the external combustion engine  10  stops when the piston  15  is positioned at other than bottom dead center, the steam of the working fluid  12  is present in the first straight part  11   e  of the main container  11 . In that state, the heating of the working fluid  12  by the heater  13  stops. As a result, the heating portion temperature T 1  gradually falls down to the ambient temperature. Further, as the heating portion temperature T 1  falls and the saturated steam pressure declines, the steam of the working fluid  12  is condensed and liquefies and the main container pressure falls. 
         [0096]    If the main container pressure ends up falling below the auxiliary container pressure Pt, the working fluid  12  in the auxiliary container  16  passes through the venturi  17  and flows into the main container  11  whereupon the amount of the working fluid  12  in the main container  11  (below, called “the amount of liquid in the main container”) becomes excessive. This phenomenon easily occurs particularly in the winter when the ambient temperature is low. 
         [0097]    In this way, when the amount of liquid in the main container becomes excessive, a predetermined output cannot be obtained. However, in the present embodiment, as explained below, at the time of restart of the external combustion engine  10 , the excess part of the amount of liquid in the main container (surplus liquid for operation) can be quickly drained to the auxiliary container  16 , so it is possible to obtain the predetermined output quickly after the start of restart. 
         [0098]      FIG. 2  is a timing chart showing the operation at the time of startup of the external combustion engine  10 . At the time of startup of the external combustion engine  10 , the generator  1  is driven as the startup means. Specifically, the generator  1  is driven by electric power supplied from the outside and makes the output takeout piston  15  displace by at least one cycle. 
         [0099]    At this time, the displacement speed of the piston  15  becomes the same as or larger than the displacement speed of the piston  15  at the time of normal operation. In the case of  FIG. 2 , the displacement speed of the piston  15  at this time becomes the same as the displacement speed of the piston  15  at the time of normal operation. 
         [0100]    While the generator  1  is driven as a startup means and the piston  15  is made to displace by 1 cycle or more, the piston  15  passes bottom dead center at least one time. When the piston  15  moves from top dead center toward bottom dead center, the working fluid  12  in the main container  11  is compressed and the main container pressure rises to the maximum operating pressure Pcmax or more. 
         [0101]    In the present embodiment, when the external combustion engine  10  is stopped, the pressure adjustment piston  19   a  is operated to the top end most position of  FIG. 1  and the auxiliary container pressure Pt becomes the smallest pressure. For this reason, the main container pressure becomes larger than the auxiliary container pressure Pt. 
         [0102]    When not providing the communicating passage  25   a , if the main container pressure becomes larger than the auxiliary container pressure Pt, the working fluid  12  in the main container  11  passes through only the venturi  17  and flows a very little at a time to the auxiliary container  16 . For this reason, it ends up taking time for the excess part of the amount of liquid in the main container to drain to the auxiliary container  16 . 
         [0103]    In the present embodiment, if the main container pressure becomes larger than the auxiliary container pressure Pt, the check valve  26  arranged at the communicating passage  25   a  opens and the working fluid  12  in the main container  11  passes through the check valve  26  and flows to the auxiliary container  16  side. At the time of startup of the external combustion engine  10 , the valve  30  is opened for exactly a predetermined time, so the working fluid  12  in the main container  11  passes through the communicating passage  25   a  and flows into the auxiliary container  16 . 
         [0104]    In short, in the present embodiment, at the time of normal operation, the main container  11  and the auxiliary container  16  are communicated through only the small communicating area venturi  17 , while at the time of startup, the main container  11  and the auxiliary container  16  are communicated not only through the venturi  17 , but also through the communicating passage  25   a  with a larger communicating area than the venturi  17 . For this reason, the excess part of the amount of liquid in the main container can be quickly drained to the auxiliary container  16 , so it is possible to shorten the startup time from restart to when a predetermined output is obtained. 
         [0105]    Furthermore, in the present embodiment, the communicating passage  25   a  is formed so that when the generator  1  is driven as a startup means and the displacement speed of the piston  15  becomes the displacement speed of the piston  15  at the time of normal operation or more, the pressure loss at the communicating passage  25   a  becomes smaller than the saturated steam pressure at the heating portion temperature T 1 . Therefore, at the time of startup, the excess part of the amount of liquid in the main container more easily flows to the communicating passage  25   a  side than the heating portion  11   a  side and as a result it is possible to suppress the inflow of the liquid part of the working fluid  12  to the heating portion  11   a.    
         [0106]    As a result, at the time of startup when output cannot be taken out, it is possible to suppress heat exchange between the heating portion and the liquid part of the working fluid, so it is possible to reduce the heat loss at the time of startup. 
         [0107]    In the case of  FIG. 2 , while the valve  30  is opened, the working fluid  12  in the main container  11  ends up flowing out somewhat to the auxiliary container  16 . Even if the amount of liquid in the main container sometimes ends up being somewhat insufficient, after that the working fluid  12  in the auxiliary container  16  will pass through the venturi  17  and gradually flow into the main container  11  whereby the amount of liquid in the main container will be secured in a suitable level. 
         [0108]    The valve  30  is closed at the time of normal operation, so even if the check valve  26  is opened at the time of normal operation of the external combustion engine  10 , the valve  30  prevents the working fluid  12  from passing through the communicating passage  25   a  and flowing into the auxiliary container  16 . Therefore, at the time of normal operation, the working fluid  12  will not pass through the communicating passage  25   a  and flow into the auxiliary container  16 , so that a reduction in the amount of liquid in the main container may not be caused. As a result, the drop in performance of the external combustion engine  10  is prevented. 
       Second Embodiment 
       [0109]    In the first embodiment, the flow area and flow length of the communicating passage  25   a  are used to set the pressure loss of the communicating passage  25   a . In the second embodiment, the displacement speed of the piston  15  at the time of startup of the external combustion engine  10  is set to reduce the pressure loss of the communicating passage  25   a.    
         [0110]      FIG. 3  is a timing chart showing the operation at the time of startup in the present embodiment. In the present embodiment as well, in the same way as the first embodiment, at the time of startup of the external combustion engine  10 , power is supplied to the generator  1  from the outside to drive the generator  1  and make the piston  15  displace by one cycle or more. In the present embodiment, at this time, the generator  1  is driven by a low frequency. Specifically, for example, the external load of the generator  1  is made larger to reduce the drive frequency of the generator  1 . 
         [0111]    Due to this, the displacement speed of the piston  15  at the time of startup of the external combustion engine  10  becomes smaller and the flow rate of the working fluid  12  flowing through the communicating passage  25   a  falls, so the pressure loss of the communicating passage  25   a  can be reduced. 
         [0112]    In the present embodiment, the displacement speed of the piston  15  at the time of startup of the external combustion engine  10  is made slower than at the time of normal operation so as to make the pressure loss of the communicating passage  25   a  smaller than the saturated steam pressure at the heating portion temperature T 1 . For this reason, it is possible to obtain effects similar to the first embodiment. 
       Third Embodiment 
       [0113]    The third embodiment prevents the air in the generator  1  from passing through the very small clearance between the piston  15  and the cylinder  15   a  and flowing into the main container  11  by sealing the working fluid  12  inside the casing  1   a  of the generator  1 .  FIG. 4  is a view showing an outline of the external combustion engine  10  in the present embodiment. 
         [0114]    The main container  11  and the casing  1   a  are communicated through a communicating passage  40   a  formed in the communicating member  40 . In the present embodiment, as the shutoff valve  41  forming the shutting means for shutting the communicating passage  40   a , a one-way valve is used. This one-way valve opens when the main container pressure becomes higher than the pressure in the casing  1   a.    
         [0115]    The pressure loss of the communicating passage  40   a  is set smaller than the saturated steam pressure at the heating portion temperature T 1 . In the present embodiment, the operating pressure of the shutoff valve  41  is also set smaller than the saturated steam pressure at the heating portion temperature T 1 . 
         [0116]    In the present embodiment, after the external combustion engine  10  stops, the working fluid  12  in the casing  1   a  passes through the very small clearance between the piston  15  and the cylinder  15   a  and gradually flows into the main container  11  whereby the amount of liquid in the main container becomes excessive. However, at the time of restart of the external combustion engine  10 , the shutoff valve  41  opens and the working fluid  12  in the main container  11  passes through the communicating member  40  and flows into the casing  1   a  corresponding to the auxiliary container. For this reason, the excess part of the amount of liquid in the main container (surplus amount of liquid for operation) can be quickly drained from the auxiliary container. 
         [0117]    Furthermore, the pressure loss of the communicating passage  40   a  becomes smaller than the saturated steam pressure at the heating portion temperature T 1 , so at the time of startup, the excess part of the amount of liquid in the main container flows easier to the communicating passage  40   a  side than the heating portion  11   a  side. As a result, the flow of the liquid part of the working fluid  12  to the heating portion  11   a  can be suppressed. Therefore, the heat loss at the time of startup can be reduced. 
         [0118]    As will be understood from  FIG. 4 , the present embodiment is configured to enable the flow length of the communicating passage  40   a  to be made shorter, so it is easy to make the pressure loss of the communicating passage  40   a  smaller than the saturated steam pressure at the heating portion temperature T 1 . 
         [0119]    In the present embodiment, the piston mechanism  19  in the first embodiment etc. are not provided, so it is not possible to adjust the main container pressure. As a modification of the embodiment, the generator  1  may be provided with a piston mechanism  19  to adjust the main container pressure in the same way as the first embodiment. In this modification, the very small clearance between the piston  15  and the cylinder  15   a  exhibits the function as the venturi  17  in the first embodiment. 
       Other Embodiments 
       [0120]    In the above embodiments, the example is shown of the main container  11  being formed in a single tubular shape as a whole, but the invention is not limited to this. In the main container  11 , the portion at the heating portion  11   a  side may be formed by a plurality of branched pipes and the remaining part may be formed by a single merged pipe. 
         [0121]    In the above embodiments, the example is shown of the present invention being applied to an external combustion engine  10  provided with a single main container  11 , but the present invention may also be applied to an external combustion engine provided with a plurality of main containers  11  and coupling the plurality of main containers  11  by a single output part. 
         [0122]    In the above embodiments, the case of application of the present invention to the drive source of a power generating system was explained, but the external combustion engine of the present invention may also be utilized as a drive source for something other than a power generating system. 
         [0123]    While the invention has been described with reference to specific embodiments chosen for purpose of illustration, it should be apparent that numerous modifications could be made thereto by those skilled in the art without departing from the basic concept and scope of the invention.