Patent Publication Number: US-2015064039-A1

Title: Fluid machine and rankine cycle

Description:
TECHNICAL FIELD 
     The present invention relates to a fluid machine and a Rankine cycle. 
     BACKGROUND ART 
     There is known a scroll fluid machine having a shared structure between an expander of a Rankine cycle and a compressor of an air-conditioner (refer to JP 2005-273452A). In this fluid machine, a planetary gear mechanism and a motor/generator are provided between a pulley and the scroll fluid machine, and the fluid machine switches between an expander operation and a compressor operation by switching a rotational speed of the motor/generator. 
     SUMMARY OF INVENTION 
     However, in the technique of JP 2005-273452A, the motor/generator is necessary to switch between the expander operation and the compressor operation, so that the configuration becomes complicated. 
     It is therefore an object of this disclosure to provide a fluid machine capable of switching between an expander operation and a compressor operation with a simple configuration. 
     According to an aspect of this disclosure, there is provided a fluid machine including: a first shaft that rotates in synchronization with an engine crankshaft; a compressor/expander fluid machine that operates as an expander rotating by converting energy of a refrigerant into mechanical energy in rotation of one direction, and operates as a compressor by compressing and discharging the refrigerant in rotation of the other direction; a planetary gear mechanism having a sun gear connected to the second shaft rotating in synchronization with the compressor/expander fluid machine, a ring gear connected to the first shaft, a plurality of planetary gears that mesh with the ring gear and the sun gear and rotate around the sun gear, and a planetary carrier that supports a rotation shaft of the planetary gear; a first clutch that locks or releases the planetary carrier and one of the ring gear and the sun gear; a second clutch that locks or releases the planetary carrier and a housing; and a clutch control unit that controls locking/releasing of the first and second clutches depending on whether the compressor/expander fluid machine operates as an expander or a compressor. 
     The foregoing and additional features and characteristics of this disclosure will become more apparent from the following detailed description considered with the reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a skeleton diagram illustrating fluid machine according to a first embodiment; 
         FIG. 2A  is a skeleton diagram illustrating a fluid machine according to the first embodiment when a scroll fluid machine operates as an expander; 
         FIG. 2B  is a skeleton diagram illustrating a fluid machine according to the first embodiment when a scroll fluid machine operates as a compressor; 
         FIG. 3  is a schematic diagram illustrating operation of the scroll fluid machine; 
         FIG. 4  is a schematic diagram illustrating a rotational speed of the scroll fluid machine in combination with a locking/releasing state of a pair of clutches and their operation mode; 
         FIG. 5A  is a velocity diagram illustrating operation of a planetary gear mechanism when a first clutch is released, and a second clutch is locked; 
         FIG. 5B  is a velocity diagram illustrating operation of a planetary gear mechanism when the first clutch is locked, and the second clutch is released; 
         FIG. 5C  is a velocity diagram illustrating operation of the planetary gear mechanism when both the clutches are released; 
         FIG. 6A  is a diagram illustrating motions of each element of an actual planetary gear mechanism in connection with  FIG. 5A ; 
         FIG. 6B  is a diagram illustrating motions of each element of the actual planetary gear mechanism in connection with  FIG. 5B ; 
         FIG. 6C  is a diagram illustrating motions of each element of the actual planetary gear mechanism in connection with  FIG. 5C ; 
         FIG. 7  is a schematic block diagram illustrating the entire system of a Rankine cycle having the fluid machine according to the first embodiment; 
         FIG. 8A  is a schematic block diagram illustrating the entire system of a Rankine cycle when the scroll fluid machine operates as an expander; 
         FIG. 8B  is a schematic block diagram illustrating the entire system of a Rankine cycle when the scroll fluid machine operates as a compressor; 
         FIG. 9  is a skeleton diagram illustrating a fluid machine according to a second embodiment; 
         FIG. 10  is a schematic block diagram illustrating the entire system of a Rankine cycle having the fluid machine according to the second embodiment; 
         FIG. 11  is a skeleton diagram illustrating a fluid machine according to a third embodiment; 
         FIG. 12  is a schematic plan diagram illustrating the planetary gear mechanism according to the third embodiment; 
         FIG. 13  is a skeleton diagram illustrating a fluid machine according to a fourth embodiment; 
         FIG. 14A  is a skeleton diagram illustrating the fluid machine according to the fourth embodiment when the scroll fluid machine operates as an expander; and 
         FIG. 14B  is a skeleton diagram illustrating the fluid machine according to the fourth embodiment when the scroll fluid machine operates as a compressor. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
       FIG. 1  is a skeleton diagram illustrating a fluid machine  1  according to a first embodiment.  FIG. 2A  is a skeleton diagram when a scroll fluid machine  11  operates as an expander, and  FIG. 2B  is a skeleton diagram when the scroll fluid machine  11  operates as a compressor. 
     The fluid machine  1  according to the first embodiment includes a scroll fluid machine  11 , a planetary gear  31 , a pair of clutches  41  and  42 , and a pulley  51  (first shaft). 
     First, an overview of the scroll fluid machine  11  will be described with reference to  FIG. 3 .  FIG. 3  is a schematic diagram illustrating operation of the scroll fluid machine. Referring to  FIG. 3 , the scroll fluid machine  11  includes a cylindrical casing  12 , a fixed scroll  13 , and a movable scroll  14 . 
     The fixed scroll  13  has a plate-like board portion (not illustrated) and a tooth portion  13   a  protruding to the movable scroll  14  side from the board portion. The movable scroll  14  also has a plate-like board portion (not illustrated) and a tooth portion  14   a  protruding to the fixed scroll  13  side from the board portion. The tooth portions  13   a  and  14   a  of the scrolls  13  and  14 , respectively, is formed in a spiral shape rotating counterclockwise such that a radius of curvature increases slowly from one end, and a pair of tooth portions  13   a  and  14   a  are combined to have the same spiral winding direction. In this case, the tooth portions  13   a  and  14   a  make line contact in a plurality of places to form an enclosed space (working chamber) between a pair of the neighboring line contacts. 
     The fixed scroll  13  is fixed to the cylindrical casing  12 . The movable scroll  14  is revolved with respect to an axis decentered from the rotation shaft  21  (second shaft, refer to  FIG. 1 ) located on the center of the cylindrical casing  12 . If the movable scroll  14  is revolved in one direction (either of clockwise or counterclockwise in  FIG. 3 ), the line contact position of a pair of the tooth portions  13   a  and  14   a  moves slowly in the same direction while a fluid is enclosed in the enclosed space (working chamber) formed between a pair of the neighboring line contacts. For this reason, for example, when the movable scroll  14  is revolved counterclockwise (forward rotation) in  FIG. 3 , a volume of the enclosed space formed between a pair of the neighboring line contacts increases slowly. In comparison, when the movable scroll  14  is revolved clockwise (reverse rotation) in  FIG. 3 , the enclosed space formed between a pair of the neighboring line contacts is reduced slowly. 
     In the leftmost diagram of  FIG. 3 , out of states of the enclosed space formed between a pair of the neighboring line contacts, a smallest state of the pair of enclosed spaces  15  is formed in the center. Focusing on this pair of enclosed spaces  15 , as the movable scroll  14  is revolved forward, the pair of the enclosed spaces are enlarged slowly as a pair of the enclosed spaces  16  and  17  as illustrated in the second and third diagrams from the left side of  FIG. 3 , and positions thereof are deviated toward the outer circumference. In the rightmost diagram of  FIG. 3 , the pair of enclosed spaces  18  having the largest state are formed in the outermost circumference side. In practice, there are other pairs of enclosed spaces formed between a pair of the neighboring line contacts as well, and a similar change is generated in other enclosed spaces. 
     Meanwhile, in a different way, a pair of the largest enclosed spaces  18  out of the enclosed spaces formed between a pair of the neighboring line contacts are formed in the outermost circumference as illustrated in the rightmost side of  FIG. 3 . Focusing on this pair of enclosed spaces  18 , as the movable scroll  14  is reversely revolved, the pair of enclosed spaces are reduced slowly as a pair of enclosed spaces  17  and  16 , and their positions are deviated into the inner circumference as illustrated in the second and third diagrams from the right side of  FIG. 3 . In addition, in the leftmost diagram of  FIG. 3 , a pair of the smallest enclosed spaces  15  are formed in the center. In practice, there are other pairs of enclosed spaces formed between a pair of the neighboring line contacts as well, and a similar change is generated in other enclosed spaces. 
     Using such a characteristic caused by the revolution of the movable scroll  14 , the scroll fluid machine  11  can operate as an expander in the case of the forward rotation and can be operated as a compressor in the case of the reverse rotation. The movable scroll  14  has a rotation shaft  21 . 
     In order to allow a fluid (refrigerant) for actuating the scroll fluid machine  11  to access the scroll fluid machine  11 , the casing  12  is provided with a first access port  22  (refer to  FIG. 1 ) that allows the fluid to access the pair of the smallest enclosed spaces  15  illustrated in the leftmost side of  FIG. 3 . In addition, the casing  12  is provided with a second access port  23  (refer to  FIG. 1 ) for allowing the fluid to access the pair of largest enclosed spaces  18  illustrated in the rightmost side of  FIG. 3 . 
     When the scroll fluid machine  11  operates as an expander, a high-pressure/high-temperature refrigerant gas (fluid) is introduced from the first access port  22  as illustrated in  FIG. 2A . The high-pressure/high-temperature refrigerant gas introduced from the first access port  22  to the enclosed space  15  drives the movable scroll  14  with an inflating pressure (the rotation shaft  21  rotates forwardly). As the enclosed space is enlarged, the refrigerant inside the enclosed space  15  weakens a force of driving the movable scroll  14  (refer to a state change indicated by the right direction of  FIG. 3 ). As the movable scroll  14  finally arrives at the outer circumference, the refrigerant gas is discharged to the outside of the second access hole  23  as illustrated in  FIG. 2A . The movable scroll  14  is continuously driven by consecutively introducing the high-temperature/high-pressure refrigerant gas from the first access hole  22  (the rotation shaft  21  continuously rotates forwardly). As a result, the heat energy of the high-temperature/high-pressure refrigerant gas (fluid) can be converted into rotational energy (mechanical energy). 
     Meanwhile, when the scroll fluid machine  11  operates as a compressor, the rotation shaft  21  of the scroll fluid machine  11  rotates (reversely) by virtue of external power, and the refrigerant gas is introduced from the second access hole  23  as illustrated in  FIG. 2B . The refrigerant gas introduced into the enclosed space  18  from the second access hole  23  is compressed as the enclosed space is reduced (refer to a state change of the left direction illustrated in  FIG. 3 ). As the movable scroll  14  arrives at the center, the refrigerant gas having a higher temperature and a higher pressure than those of the atmosphere is discharged into the outside from the first access hole  22  as illustrated in  FIG. 2B . By continuously performing the reverse rotation of the rotation shaft  21  of the scroll fluid machine  11  to continuously introduce the refrigerant gas from the second access hole  23 , the refrigerant gas having a higher temperature and a higher pressure than those of the atmosphere may be continuously discharged from the first access hole  22 . 
     Here, a fluid machine capable of operating as an expander by converting energy of the fluid into mechanical energy in the case of rotation in one direction and operating as a compressor by compressing and discharging the fluid in the case of rotation in the other direction is defined as a “compressor/expander fluid machine.” Although the scroll fluid machine  11  is exemplified as the compressor/expander fluid machine in the first embodiment, the invention is not limited thereto. Without limiting to the scroll type, any positive displacement type fluid machine, such as a piston type or a vane type, may be used as the compressor/expander fluid machine if the enclosed space is enlarged in the case of rotation of one direction and is reduced in the case of reverse rotation of the other direction. Therefore, other types of the fluid machines may be used instead of the scroll fluid machine  11 . 
     Alternatively, a fluid machine that operates as a motor that rotates by converting energy of a fluid into mechanical energy in the case of rotation in one direction and operates as a pump that compresses and discharges a fluid in the case of rotation of the other direction may be defined as a “pump/motor fluid machine.” In this definition, the aforementioned scroll fluid machine  11  is a pump/motor fluid machine. That is, the pump/motor fluid machine may be used instead of the compressor/expander fluid machine. 
     Returning to  FIG. 1 , when the scroll fluid machine  11  operates as an expander, it is necessary to rotate the shaft  21  forwardly. When the scroll fluid machine  11  operates as a compressor, it is necessary to rotate the rotation shaft  21  reversely. For this reason, a technique of the related art has been discussed, in which the scroll fluid machine switches between the expander operation and the compressor operation of the scroll fluid machine by switching the rotational speed of the motor/generator. 
     However, in the technique of the related art, a motor/generator is necessary to switch between the expander operation and the compressor operation, and the configuration thereof is complicated accordingly. 
     In the technique of the related art, the motor/generator operates as a generator when the scroll fluid machine operates as an expander. In this case, since the rotation of the scroll fluid machine is transmitted to the motor/generator in an accelerated manner, the motor/generator (generator) rotates fast (for example, 10,000 rpm). As the motor/generator rotates fast, friction increases. Therefore, recovery efficiency is degraded, and a fuel efficiency improvement range is reduced. 
     In the technique of the related art, most of the mechanical energy (kinetic power) obtained by operating the scroll fluid machine as an expander is recovered as electric power and is stored in a battery. For this reason, if rotation of an engine is assisted using kinetic power, the kinetic power obtained by the scroll fluid machine is converted into electric power using the motor/generator, and the converted electric power is re-converted into kinetic power. That is, since a loss caused by the conversion is significant, the fuel efficiency improvement range using kinetic power assist is reduced. Furthermore, when the motor/generator is used, electric circuitry such as an inverter is necessary, which increases cost, and a large-capacity battery is necessary to store the recovered electric power. As a result, the technique of the related art is only applicable to a hybrid vehicle in reality and has limited compatibility. 
     In this regard, the inventors of this disclosure studied whether or not the operation of the scroll fluid machine can switch between a compressor operation and an expander operation without using a motor/generator. That is, using a planetary gear mechanism  31  and a pair of clutches  41  and  42  as a control element, the operation of the scroll fluid machine switches between the expander operation and the compressor operation. 
     According to this disclosure, the engine rotation is assisted by directly transmitting, to the engine, mechanical energy (kinetic power) obtained by operating the scroll fluid machine  11  as an expander. Specifically, a belt drive unit is configured such that a belt  55  is looped and driven between a pulley  51  and a crank pulley  54  of the engine  53  to rotate the pulley  51  and the engine crankshaft in synchronization. It is noted that this disclosure is not limited to a pulley/belt transmission unit, but may be applicable to a chain transmission unit or a gear transmission unit as well. 
     The planetary gear mechanism  31  includes a sun gear  32 , a ring gear  33 , a plurality of planetary gears  34  that mesh with both the sun gear  32  and the ring gear  33  and surrounds the sun gear  32 , and a planetary carrier  35  for fixing the shafts of the planetary gears  34 . 
     The rotation shaft  52  of the pulley  51  is connected to the ring gear  33 , and the rotation shaft  21  of the scroll fluid machine  11  is connected to the shaft of the sun gear  32 . A first clutch  41  is provided between the planetary carrier  35  and the ring gear  33  to engage/release the planetary carrier  35  and the ring gear  33 . A second clutch  42  is provided between the planetary carrier  35  and the housing  36  to engage/release the planetary carrier  35  and the housing  36 . The arrangement of the first clutch  41  is not limited thereto. Alternatively, a first clutch  41 ′ may be provided between the planetary carrier  35  and the sun gear  32  (refer to the dotted line in  FIG. 1 ). 
       FIG. 4  is a table showing a rotational speed of the scroll fluid machine  11  in combination with the locking/releasing states of a pair of clutches  41  and  42  and their operation mode when a rotational speed of the pulley  52  is set to 1000 rpm.  FIGS. 5A to 5C  are velocity diagrams illustrating the operation of the planetary gear mechanism  31 .  FIGS. 6A to 6C  are diagrams illustrating motions of each element of an actual planetary gear mechanism  31  to match  FIGS. 5A to 5C , respectively. 
     It is noted that a gear ratio between the ring gear  33  and the sun gear  32  is set to 2:1 in  FIGS. 4 ,  5 A to  5 C, and  6 A to  6 C. Such a gear ratio between the ring gear  33  and the sun gear  32  is set based on the following reasons. Specifically, a value of the refrigerant volume flow rate necessary to operate the scroll fluid machine  11  as an expander and a value of the refrigerant volume flow rate necessary to operate the scroll fluid machine  11  as a compressor were examined. A ratio between both the values was 1:2. For this reason, it is necessary to increase a rotational speed twice in the compressor operation, compared to the expander operation. Typically, it is known that the necessary value of the refrigerant volume flow rate in the compressor operation is higher than that of the expander operation. 
       FIG. 5A  is a velocity diagram when the first clutch  41  is released, and the second clutch  42  is locked. In this state, the pulley  51  is driven by virtue of the power of the engine  53 . Since the planetary carrier  35  is connected to the housing  36  as the second clutch  42  is locked (refer to  FIG. 2A ), a rotational speed of the planetary carrier  35  becomes zero rpm. For convenient description purposes, it is assumed that the pulley  51  rotates at a rotational speed of 1000 rpm in synchronization with the engine rotation. In this case, the rotational speed of the sun gear  32  is accelerated to −2000 rpm due to a reduction gear ratio. The sign in front of “2000 rpm” means that the sun gear  33  rotates reversely to the rotational direction of the pulley  51 . 
       FIG. 5B  is a velocity diagram when the first clutch  41  is locked, and the second clutch  42  is released. It is noted that the rotational speed of the pulley  51  is assumed to 1000 rpm for comparison with  FIG. 5A . Since the planetary carrier  35  is connected to the ring gear  33  as the first clutch  41  is locked (refer to  FIG. 2B ), the ring gear  33  and the planetary carrier  35  have the same rotational speed of 1000 rpm. For this reason, the sun gear  32  also has the same rotational speed of 1000 rpm. In other words, the pulley  51  and the rotation shaft  21  of the scroll fluid machine  11  are coupled in a direct linkage state. 
       FIG. 5C  is a velocity diagram when both the clutches  41  and  42  are released. It is noted that the rotational speed of the pulley  51  is assumed to 1000 rpm for comparison with  FIGS. 5A and 5B . In this state, it is possible to remove torque transmission between the pulley  51  and the rotation shaft  21  of the scroll fluid machine  11 . It is noted that, since the rotational speed of the sun gear  33  becomes zero rpm, the planetary carrier  35  rotates at a rotational speed corresponding to a point where a line between the zero rpm point of the sun gear  33  and the 1000 rpm point of the pulley  51  intersects with a vertical line of the planetary carrier  35 . 
     While the pulley  51  is a drive side in  FIG. 5A , the scroll fluid machine  11  is a drive side in  FIG. 5B . That is, it is recognized that, if the scroll fluid machine  11  operates as an expander in the state of  FIG. 5B , and the rotation shaft  21  rotates forward at a rotational speed of 1,000 rpm, it is possible to rotate the pulley  51  at the same rotational speed of 1,000 rpm. In this manner, the fluid energy is converted into the rotational energy using the scroll fluid machine  11 , and the converted rotational energy is used to assist rotation of the engine  53 . Meanwhile, it is recognized that, if the pulley  51  rotates forward at a rotational speed of 1000 rpm by driving the engine from the state of  FIG. 5A , it is possible to rotate the rotation shaft  21  reversely at a rotational speed of 2,000 rpm and use the scroll fluid machine  11  as a compressor. 
     As described above, according to this embodiment, a gear ratio between the ring gear  33  and the sun gear  32  is set to twice. However, the invention is not limited thereto. Instead, the gear tooth ratio between the ring gear  33  and the sun gear  32  may be set to 1.5 to 4. This will be described below. 
     Comparison will be made between vehicles having large and small sizes (or engine displacement). An air-conditioning capability does not change significantly if the number of persons in a vehicle is the same. Therefore, a require value of the refrigerant flow rate of the compressor does not change significantly between vehicles having large and small sizes, but the waste heat amount increases for a vehicle having the larger size. Therefore, in order to increase a waste heat recovery amount, a required value of the refrigerant flow rate of the expander increases in a vehicle having a large size, compared to vehicle having a small size. If (a rating of) the compressor/expander fluid machine is upgraded as the size of the vehicle increases, the gear ratio is reduced relatively because it is not necessary to increase a rotational speed of the compressor in the vehicle having a large size accordingly. Meanwhile, it is necessary to relatively increase a rotational speed of the compressor in the vehicle having a small size, and the gear ratio is set to be relatively higher. Through a study for a gear ratio range in consideration of a size of a vehicle, that is, a practical engine displacement and a rating of the compressor/expander fluid machine in a practical case, it was recognized that a suitable gear ratio range is 1.5 to 4. 
       FIG. 7  is a schematic block diagram illustrating the entire system of a Rankine cycle  61  having the fluid machine  1  according to this embodiment.  FIG. 8A  is a schematic block diagram illustrating the entire system of the Rankine cycle  61  when the scroll fluid machine  11  operates as an expander.  FIG. 8B  is a schematic block diagram illustrating the entire system of the Rankine cycle  61  when the scroll fluid machine operates as a compressor. The Rankine cycle  61  has a refrigerant pump  62 , a vaporizer  63 , a scroll fluid machine  11  as an expander, and a condenser  64 . Each element is connected to each other by the refrigerant path  71  to  74  where the refrigerant such as R134a is circulated. 
     A shaft of the refrigerant pump  62  is integrated with the rotation shaft  52  of the pulley  51  (refer to  FIG. 1 ). Therefore, the refrigerant pump  62  is driven by the output power (kinetic power) generated from the scroll fluid machine  11 , and the generated kinetic power is transmitted to the engine  53  through the belt drive unit  51 ,  55 , and  54  to assist rotation of the engine  53 . 
     The refrigerant from the refrigerant pump  62  is supplied to the vaporizer  63  through the refrigerant path  71 . The vaporizer  63  is a heat exchanger that performs heat exchange between a high temperature medium and the refrigerant from the refrigerant pump  62  to evaporate and heat the refrigerant. The high temperature medium may include an engine coolant. 
     The refrigerant from the vaporizer  63  is supplied to the scroll fluid machine  11  as an expander through the refrigerant path  72 . The scroll fluid machine  11  as an expander converts heat into rotational energy by inflating the evaporated and heated refrigerant. The kinetic power recovered to the scroll fluid machine  11  as an expander drives the refrigerant pump  62  and is transmitted to the engine  53  through the belt drive unit to assist rotation of the engine  53 . 
     The refrigerant from the scroll fluid machine  11  as an expander is supplied to the condenser  64  through the refrigerant path  73 . The condenser  64  is a heat exchanger that performs heat exchange between the external air and the refrigerant to cool and liquefy the refrigerant. For this reason, the condenser  64  is cooled using a fan  65 . 
     The refrigerant liquefied by the condenser  64  is returned to the refrigerant pump  62  through the refrigerant path  74 . The refrigerant returned to the refrigerant pump  62  is sent to the vaporizer  63  again using the refrigerant pump  62  and circulates around each element of the Rankine cycle  61 . 
     In this manner, it is possible to operate the scroll fluid machine  11  as an expander. 
     Next, a description will be made for a refrigeration cycle  80 . The refrigeration cycle  80  is combined with the Rankine cycle  61  in order to share the refrigerant circulating through the Rankine cycle  61 . The refrigeration cycle  80  has a scroll fluid machine  11  as a compressor, a condenser  64 , and an evaporator  82 . 
     A first bypass path  81  that branches from the refrigerant path  74  and merges to the refrigerant path  73  is inserted into the evaporator  82 . In addition, a second bypass path  87  that branches from the refrigerant path  72  and merges to the refrigerant path  73  in the downstream side from the merging portion  85  of the first bypass path  81  is provided. 
     The scroll fluid machine  11  as a compressor is driven by the engine to compress the refrigerant to make a high-temperature/high-pressure refrigerant gas. That is, a driving force of the engine is transmitted to the rotation shaft  21  through the belt drive unit  54 ,  55 , and  51  to drive the scroll fluid machine  11 . 
     The refrigerant from the scroll fluid machine  11  serving as a compressor merges into the refrigerant path  73  through the second bypass path  87  and is supplied to the condenser  64 . The condenser  64  is a heat exchanger that performs heat exchanger with the external air to condense and liquefy the refrigerant. 
     The liquid refrigerant from the condenser  64  is supplied to the evaporator  82  through the first bypass path  81  branching from the refrigerant path  74 . The evaporator  82  is disposed inside the casing of the air-conditioner unit along with a heater core (not illustrated). The evaporator  82  is a heat exchanger that evaporates the liquid refrigerant from the condenser  64  and cools the conditioning air from a blower fan using latent heat of this evaporation. 
     The refrigerant evaporated by the evaporator  82  is returned to the scroll fluid machine  11  serving as a compressor through the refrigerant path  73 . It is noted that a mixing ratio between the conditioning air cooled by the evaporator  82  and the conditioning air heated by the heater core is changed depending on an opening level of an air mixing door, so that a temperature is adjusted to a value set by a user. 
     The merging portion of the second bypass path  87  is provided with a three-way valve  88  having three ports A, B, and C. The three-way valve  88  is a valve for switching the fluid path. For example, in a valve close state of the three-way valve  88 , the ports A and B are connected, and the ports A and C are disconnected. Meanwhile, in a valve open state, the ports A and B are disconnected, and the ports A and C are connected. 
     When the scroll fluid machine  11  operates as an expander, it is necessary to circulate the refrigerant as indicated by the arrow of  FIG. 8A . For this reason, a check valve  89  for preventing a reverse flow of the refrigerant in the refrigerant path  73  from the merging portion  85  to the first bypass path  81  is provided in the first bypass path  81 . 
     Meanwhile, when the scroll fluid machine  11  operates as a compressor, it is necessary to circulate the refrigerant as indicated by the arrow of  FIG. 8B . For this reason, a switch valve  90  for opening or closing the refrigerant path  74  is provided in the refrigerant path  74 . When the scroll fluid machine  11  operates as a compressor, the switch valve  90  is fully closed, so that a liquid refrigerant from the condenser  64  is guided to the evaporator  82 . When the scroll fluid machine  11  operates as an expander, the switch valve  90  is fully opened, so that the liquid refrigerant from the condenser  64  is guided to the refrigerant pump  62 . 
     When the scroll fluid machine  11  operates as a compressor, a check valve  91  for preventing a backflow of the refrigerant from the scroll fluid machine  11  to the vaporizer  63  is provided in the refrigerant path  72 . 
     The engine controller  95  (clutch control unit) controls the three-way valve  88 , the switch valve  90 , a pair of the clutches  41  and  42 , and the three-way valve  88 . Since a driving range for driving the Rankine cycle  61  is determined in advance, the engine controller  95  determines whether or not a driving condition is within the Rankine cycle driving range. If the driving condition is within the Rankine cycle driving range, it is determined that the scroll fluid machine  11  operates as an expander. In this case, an instruction is made such that the switch valve  90  has a full open state, the first clutch  41  is released, and the second clutch  42  is locked. The three-way valve  88  is not turned on. 
     The engine controller  95  monitors whether or not there is an air-conditioning request. If there is an air-conditioning request, and the refrigerant from the evaporator  82  has a temperature exceeding an upper limitation temperature, it is determined that the scroll fluid machine  11  operates as a compressor. In this case, an instruction is made such that the switch valve  90  has a full closed state, the first clutch  41  is locked, and the second clutch  42  is released. The three-way valve  88  is turned on. 
     Here, the functional effects of this embodiment will be described. 
     A fluid machine according to this embodiment includes: a pulley  51  (first shaft) that rotates in synchronization with the crankshaft of the engine  53 ; a scroll fluid machine  11  (compressor/expander fluid machine) that operates as an expander by converting energy of the refrigerant (fluid) into mechanical energy when it rotates in one direction or operates as a compressor by compressing the refrigerant (fluid) when it rotates in the other direction; a planetary gear mechanism  31  having a sun gear  32  connected to the shaft  21  of the scroll fluid machine  11  (second shaft rotating in synchronization with the compressor/expander fluid machine), a ring gear  33  connected to the pulley  51 , a plurality of planetary gears  34  rotating around the sun gear  32  by meshing with the ring gear  33  and the sun gear  32 , and a planetary carrier  35  that supports the rotation shaft of the planetary gear  34 ; a first clutch  41  that locks or releases the planetary carrier  35  and the ring gear  33 ; and a second clutch  42  that locks or releases the planetary carrier  35  and the housing  36 . According to this embodiment, unlike the technique of the related art, it is possible to switch between the expander operation and the compressor operation with a simple structure without a motor/generator. 
     In the related art, most of the mechanical energy (kinetic power) obtained in the expander operation is recovered as electric power. However, according to this embodiment, the mechanical energy is directly transmitted to the engine through the belt drive unit  51 ,  55 , and  54  without conversion to the electric power to assist engine rotation. According to this embodiment, unlike the apparatus of the related art, a loss is not generated in conversion from electric power to kinetic power, and the kinetic power can be transmitted in a mechanical energy state, so that it is possible to obtain excellent efficiency. Unlike the technique of the related art, it is possible to obtain excellent fuel efficiency even at the same expander output. Since the mechanical energy is not recovered as electric power, a high capacity battery is not necessary. This embodiment may also be applicable to various types of devices without limiting to a hybrid vehicle. 
     According to this embodiment, when the scroll fluid machine  11  (compressor/expander fluid machine) operates as an expander, the engine controller  95  (clutch control unit) performs control such that the first clutch  41  is locked, and the second clutch  42  is released. Therefore, as the planetary carrier  35  and the ring gear  33  rotate in synchronization, it is possible to rotate the pulley  51  and the scroll fluid machine  11  in the same direction. That is, in the technique of the related, the motor/generator (generator) rotates at a high speed when the scroll fluid machine  11  operates as an expander. However, according to this embodiment, since the second clutch  42  is locked, the ring gear  33  is integrated with the planetary carrier  35 . Therefore, in the configuration of this embodiment, since there is no portion that rotates at a high speed carelessly, it is possible to prevent degradation of efficiency caused by the high speed rotation. 
     According to this embodiment, when the scroll fluid machine  11  (compressor/expander fluid machine) operates as a compressor, the engine controller  95  (clutch control unit) performs control such that the first clutch  41  is released, and the second clutch  42  is locked. Therefore, since rotation of the planetary carrier  35  stops, it is possible to rotate the pulley  51  and the scroll fluid machine  11  reversely to each other. 
     According to this embodiment, the gear ratio between the ring gear  33  and the sun gear  32  is set to 1.5 to 4. Therefore, it is possible to set the gear ratio to match a practical engine displacement. 
     According to this embodiment, a gear ratio between the ring gear  33  and the sun gear  32  (number of ring gear teeth/number of sun gear teeth) is set to match a ratio between the refrigerant volume flow rate necessary in the expander when the scroll fluid machine  11  (compressor/expander fluid machine) operates as an expander and a refrigerant volume flow rate necessary in the compressor when the scroll fluid machine  11  operates as a compressor. As a result, it is possible to satisfy both the refrigerant volume flow rate necessary in the expander and the refrigerant volume flow rate necessary in the compressor. 
     Second Embodiment 
       FIG. 9  is a skeleton diagram illustrating a fluid machine  1  according to a second embodiment, and  FIG. 10  is a schematic block diagram illustrating the entire system of a Rankine cycle  61  having the fluid machine  1  according to the second embodiment, in which like reference numerals denote like elements as in  FIGS. 1 and 7  of the first embodiment. 
     According to the first embodiment, the shaft of the refrigerant pump  62  is integrated with the rotation shaft  52  of the pulley  51  (refer to  FIG. 1 ). For this reason, the refrigerant pump  62  is driven when the scroll fluid machine  11  operates as both the expander and the compressor. However, as recognized from  FIG. 8B , when the scroll fluid machine  11  operates as a compressor, it is not necessary to operate the refrigerant pump  62  in practice. If the refrigerant pump  62  is driven unnecessarily when the scroll fluid machine  11  is driven using the engine power, the engine power is consumed uselessly. 
     In this regard, according to the second embodiment, the refrigerant pump  62  is driven when the scroll fluid machine  11  operates as an expander, and the refrigerant pump  62  stops when the scroll fluid machine  11  operates as a compressor. For this reason, according to the second embodiment, a gear  101  is provided in the rotation shaft  35   a  of the planetary carrier  35 . The gear  101  operates in synchronization with the planetary carrier  35 . In addition, in order to drive the refrigerant pump  62 , the gear  101  meshes with a gear  102  for driving the refrigerant pump  62 . The refrigerant pump  62  may include, for example, a gear type pump. 
     As a result, when the scroll fluid machine  11  operates as an expander, the first clutch  41  is locked. Therefore, the planetary carrier  35  rotates along with the pulley  51  at a rotation speed ratio of 1:1 (refer to  FIG. 5B ). As the planetary carrier  35  rotates, the refrigerant pump  62  is driven by the gear  101  driven in synchronization with the planetary carrier  35  and the gear  102  meshing with the gear  101 . That is, when the scroll fluid machine  11  operates as an expander, the refrigerant pump  62  is driven. 
     Meanwhile, when the scroll fluid machine  11  operates as a compressor, the second clutch  42  is locked. Therefore, the planetary carrier  35  does not rotate (refer to  FIG. 5A ). If the planetary carrier  35  does not rotate, the gears  101  and  102  do not rotate, and the refrigerant pump  62  is not driven. That is, when the scroll fluid machine  11  operates as a compressor, the refrigerant pump  62  is not driven. 
     In this manner, the Rankine cycle according to the second embodiment includes, in addition to the fluid machine  1  according to the first embodiment, a refrigerant pump  62  that supplies a liquid refrigerant; an vaporizer  63  that heats and vaporizes the liquid refrigerant supplied from the refrigerant pump  62 ; an expander that rotates by converting energy of the refrigerant vaporized in the vaporizer  63  into mechanical energy; and a condenser  64  that condenses the refrigerant discharged from the expander to recover it to a liquid refrigerant. In this Rankine cycle, the refrigerant pump  62  is driven by the rotation shaft of the planetary carrier  35  of the fluid machine  1 , and the expander is a compressor/expander fluid machine  11  of the fluid machine  1 . As a result, the refrigerant pump  62  is driven only when the Rankine cycle  61  operates. Therefore, it is possible to suppress useless consumption of the engine power caused by driving the refrigerant pump  62  even when the Rankine cycle  61  is not operated. 
     Third Embodiment 
       FIG. 11  is a skeleton diagram illustrating a fluid machine  1  according to a third embodiment, and  FIG. 12  is a schematic plan diagram illustrating a planetary gear mechanism  31  according to the third embodiment, in which like reference numerals denote like elements as in  FIG. 9  of the second embodiment. 
     The third embodiment is based on the configuration of the second embodiment. Specifically, according to the third embodiment, the refrigerant pump  62  is driven when the scroll fluid machine  11  operates as an expander, and the refrigerant pump  62  stops when the scroll fluid machine  11  operates as a compressor. In addition, according to the third embodiment, a freewheel clutch  113  is provided in all of the planetary gears  34  in the planetary gear mechanism  31 , and the first clutch  41  is removed. 
     Typically, the freewheel clutch  113  is provided in all of three planetary gears  34 . However, in some cases, the freewheel clutch  113  may be omitted partially and may be provided in one of the planetary gears. In this case, as illustrated in  FIG. 12 , one of the planetary gears  34  (upper gear in  FIG. 12 ) includes a rotation shaft  111  and an external teeth gear  112  rotatable independently from the rotation shaft  111  and concentrically with the rotation shaft  111 . In addition, the freewheel clutch  113  is interposed between the inner circumference of the external teeth gear  112  and the outer circumference of the rotation shaft  111 . It is noted that, although the freewheel clutch  113  is provided in the upper planetary gear  34  in  FIG. 12 , the invention is not limited thereto. That is, the freewheel clutch  113  may be provided in the lower left or lower right planetary gear  34 . 
     The freewheel clutch  113  includes a housing  114 , a ball  115 , a spring  116 , and a spring retainer  117 . The housing  114  is formed in an arc shape having a thickness in a radial direction. The outer circumference  114   a  of the housing  114  is fixed to the inner circumference of the external teeth gear  112 , and the inner circumference  114   b  of the housing  114  is slidable along the outer circumference  111   a  of the rotation shaft  11 . The housing  114  has a pair of hollows in the inner circumferential side. Each of the hollows houses a ball  115 , a spring  116  that biases the ball  115  in one circumferential direction (counterclockwise in  FIG. 12 ), and a spring retainer  114  that retains the spring  116 . 
     In  FIG. 12 , when the sun gear  32  rotates counterclockwise, the external teeth gear  112  meshing with the sun gear  32  rotates clockwise along with the freewheel clutch  113 . In this case, the ball  115  is inserted between the housing  114  and the rotation shaft  111  to engage (or lock) both the housing  114  and the rotation shaft  111 . As the freewheel clutch  113  is locked, the external teeth gear  112  and the rotation shaft  111  moves in synchronization. For this reason, the planetary carrier  35  rotates counterclockwise, and the ring gear  33  also rotates counterclockwise. That is, as illustrated in  FIG. 5B , the sun gear  32 , the planetary carrier  35 , and the ring gear  33  rotate in synchronization. When the freewheel clutch  113  is locked, the same function is generated as in the case where the first clutch  41  is locked in the second embodiment. That is, the scroll fluid machine  11  operates as an expander. 
     Meanwhile, when the sun gear  32  rotates clockwise, the ball  115  of the freewheel clutch  113  compresses the spring  116  resisting to a biasing force of the spring  116 . In this case, the ball  115  does not engage (lock) the housing  114  and the rotation shaft  111 . For this reason, rotation of the external teeth gear  112  is not transmitted to the rotation shaft  111 , and the planetary carrier  35  does not rotate. That is, as illustrated in  FIG. 5A , the planetary carrier  35  does not rotate even when the sun gear  32  rotates. When the freewheel clutch  113  is not locked, the same function is generated as in the case where the first clutch  41  of the second embodiment is released. That is, the scroll fluid machine  11  operates as a compressor. 
     In this manner, since the freewheel clutch  113  serves as the first clutch  41  of the second embodiment, the first clutch is replaced with the freewheel clutch  113  as illustrated in  FIG. 11  according to the third embodiment. 
     According to the third embodiment, the first clutch  41  of the first embodiment is replaced with the freewheel clutch  113  that fixes the planetary carrier  35  and one of the ring gear  33  and the sun gear  32  when the compressor/expander fluid machine  11  operates as an expander. As a result, it is possible to suppress a useless power consumption caused by driving the refrigerant pump  62  even when the Rankine cycle  61  is not operated. In addition, it is possible to provide a simple structure. 
     Fourth Embodiment 
       FIG. 13  is a skeleton diagram illustrating a fluid machine  1  according to a fourth embodiment, in which like reference numerals denote like elements as in  FIG. 1  of the first embodiment. In the first to third embodiments, the planetary gear mechanism  31  is used to switch between the expander operation and the compressor operation. Meanwhile, according to the fourth embodiment, a transmission mechanism  121  is used instead of the planetary gear mechanism  31  in order to switch between the expander operation and the compressor operation. 
     As illustrated in  FIG. 13 , a transmission mechanism  121  includes a gear train of first, second, and third gears  123 ,  124 , and  125  meshing with each other and a gear train of fourth and fifth gears  127  and  128  meshing with each other. Both the gear trains are arranged to face each other. The shafts of the second, third, and fifth gears  124 ,  125 , and  128  are fixed to the housing  36 . In this case, the first to third gears  123 ,  124 , and  125  have the same number of teeth, and the fourth gear  127  has a larger number of teeth than that of the fifth gear  128 . 
     The shaft of the first gear  123  and the shaft of the fourth gear  127  are positioned side by side and are connected to each other through the second clutch  42 . In addition, the shaft of the third gear  125  and the shaft of the fifth gear  128  are positioned side by side and are connected to each other through first clutch  41 . 
     When the scroll fluid machine  11  operates as an expander, the second clutch  42  is locked, and the first clutch  41  is released as illustrated in  FIG. 14A . In this case, the rotation shaft  21  and the pulley  51  are connected in a direct linkage manner. That is, the pulley  51  is driven by kinetic power obtained by the scroll fluid machine  11  serving as an expander. 
     When the scroll fluid machine  11  operates as a compressor, the second clutch  42  is released, and the first clutch  41  is locked as illustrated in  FIG. 14B . In this case, the rotation shaft  21  reversely rotates by the pulley  51 . That is, by driving the scroll fluid machine  11  as a compressor using the engine power, it is possible to provide a refrigerant gas having a higher temperature and a higher pressure than those of the atmosphere by compressing the refrigerant gas. Since the rotational direction of the rotation shaft  21  is reverse to that of the pulley  51 , and the fourth gear  127  has a larger number of teeth than that of the fifth gear  128 , the rotation of the pulley  51  can be transmitted to the rotation shaft  21  in an accelerated manner. Therefore, it is possible to rotate the compressor (scroll fluid machine  11 ) in an accelerated manner. 
     The invention is not limited to those described above. 
     The application claims a priority of Japanese Patent Application No. 2012-090907 filed with the Japan Patent Office on Apr. 12, 2012, the entire content of which is incorporated herein by reference.