Patent Publication Number: US-9416788-B2

Title: Turbo compressor and refrigerator

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a turbo compressor and a refrigerator. More specifically, the present invention relates to a turbo compressor capable of compressing a fluid by a plurality of impellers and a refrigerator including the turbo compressor. 
     Priority is claimed on Japanese Patent Application No. 2009-170193, filed Jul. 21, 2009, the content of which is incorporated herein by reference. 
     2. Description of Related Art 
     There is known a turbo refrigerator or the like including a turbo compressor which compresses and discharges the refrigerant by means of a compressing means equipped with an impeller or the like as a refrigerator for cooling or refrigerating a material to be cooled such as water. 
     In the compressor, if the compression ratio increases, the discharging temperature of the compressor rises and the volumetric efficiency declines. Thus, in the turbo compressor included in the turbo refrigerator or the like as described above, the compression of the refrigerant is often performed so as to be divided into a plurality of stages. 
     In such a turbo compressor, the lubricant oil is supplied to sliding parts such as a bearing from an oil tank. Furthermore, in order to release the refrigerant gas, which is generated in the oil tank when the compressor starts, to the inlet side of the compressor, a pressure equalization pipe for making the oil tank and the compressor communicate with each other is disposed (for example, see Japanese Patent No. 3489631). 
     The turbo compressor essentially continues to operate over a long time at a constant rotation speed. However, for the purpose of energy saving, the operation ON/OFF is frequently performed. At this time, in the case where only the pressure equalization pipe is disposed, when the compressor is stopped, the refrigerant flows backward from a condenser into the compressor inlet, so that the pressure of the compressor inlet increases, whereby the refrigerant flows backward from the pressure equalization pipe into the oil tank side. There is a problem that the refrigerant flows backward to the oil tank and leaks from a labyrinth seal into a compressor flow path or a motor, and, at this time, the lubricant oil, which is being refueled to the bearing near the labyrinth, is also taken out as oil leakage, whereby the amount of oil in the oil tank is reduced. 
     SUMMARY OF THE INVENTION 
     The present invention provides a turbo compressor and a refrigerator which can suitably suppress the back flow of the refrigerant through the pressure equalization pipe to the oil tank side by means of a simple configuration. 
     According to a first aspect of the present invention, a turbo compressor relating to the present invention includes a case, a plurality of compression stages which are disposed in a rotatable manner with respect to the case via a sliding part, an oil tank in which lubricant oil to be supplied to the sliding parts is stored, a pressure equalization pipe which connects the oil tank with the vicinity of the inlet of the compression stages, and a check valve which allows only the movement of the fluid from the oil tank side to the compression stage side in the pressure equalization pipe. 
     The turbo compressor has the check valve. For this reason, when the pressure of the compressor inlet side becomes higher than that of the oil tank side during operation stop, the check valve can be closed to block the pressure equalization pipe. 
     According to a second aspect of the present invention, the turbo compressor relating to the present invention includes a suction capacity adjusting portion disposed in the inlet of the compression stage, and an end of the pressure equalization pipe is opened to and is disposed in a relay space provided on the case so as to communicate with the rear surface of the suction capacity adjusting portion. 
     In the turbo compressor, the relay space, which communicates with the rear surface of the suction capacity adjusting portion reaching the lowest pressure during operation, also reaches the low pressure. For this reason, the inside of the oil tank can also be made to have low pressure through the pressure equalization pipe, whereby the lubricant oil can be suitably collected by the oil tank. 
     According to a third aspect of the present invention, the turbo compressor relating to the present invention has the check valve built into the case. 
     In the turbo compressor, since the check valve does not protrude outside the case, it is possible to secure the air-tightness of the overall case and promote the space saving of the overall compressor. 
     According to a fourth aspect of the present invention, a refrigerator relating to the present invention includes a condenser that cools and liquefies the compressed refrigerant, an evaporator which cools a material to be cooled by evaporating the liquefied refrigerant to take the vaporization heat from the material to be cooled, and a turbo compressor which compresses the refrigerant evaporated by the evaporator to supply the same to the condenser, wherein the above-mentioned turbo compressor is used as the turbo compressor. 
     The refrigerator exhibits the same working effects as the turbo compressor. 
     According to the present invention, it is possible to suitably suppress the back flow of the refrigerant through the pressure equalization pipe to the oil tank side by means of a simple configuration. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a block diagram showing a schematic configuration of a turbo refrigerator relating to an embodiment of the present invention. 
         FIG. 2  is a vertical sectional view of a turbo compressor included in the turbo refrigerator relating to an embodiment of the present invention. 
         FIG. 3  is a vertical sectional view of a turbo compressor included in the turbo refrigerator relating to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     An embodiment of a turbo compressor and a refrigerator relating to the present invention will be described with reference to  FIGS. 1 and 2 . 
     A turbo refrigerator (a refrigerator)  1  relating to the present embodiment is, for example, installed on a building or a factory so as to create the cooling water for air conditioning. As shown in  FIG. 1 , the turbo refrigerator  1  includes a condenser  2 , an economizer  3 , an evaporator  5  and a turbo compressor  6 . 
     The condenser  2  is supplied with a compressed refrigerant gas X 1 , which is a refrigerant (a fluid) compressed in a gas state, and makes the compressed refrigerant gas X 1  a refrigerant liquid X 2  by cooling and liquefying the compressed refrigerant gas X 1 . As shown in  FIG. 1 , the condenser  2  is connected to the turbo compressor  6  via a flow path R 1  through which the compressed refrigerant gas X 1  flows and is connected to the economizer  3  via a flow path R 2  through which the refrigerant liquid X 2  flows. An expansion valve  7  for decompressing the refrigerant liquid X 2  is installed in the flow path R 2 . 
     The economizer  3  temporarily stores the refrigerant liquid X 2  which has been decompressed in the expansion valve  7 . The economizer  3  is connected to the evaporator  5  via a flow path R 3  through which the refrigerant liquid X 2  flows. Furthermore, the economizer  3  is connected to the turbo compressor  6  via a flow path R 4  through which gaseous components X 3  of the refrigerant generated in the economizer  3  flow. An expansion valve  8  for further decompressing the refrigerant liquid X 2  is installed in the flow path R 3 . The flow path R 4  is connected to the turbo compressor  6  so as to supply the gaseous components X 3  to a second compression stage  26  described below which is included in the turbo compressor  6 . 
     The evaporator  5  cools the material to be cooled by evaporating the refrigerant liquid X 2  to take the vaporization heat from the material to be cooled such as water. The evaporator  5  is connected to the turbo compressor  6  via a flow path R 5  through which a refrigerant gas X 4  generated by the evaporation of the refrigerant liquid X 2  flows. The flow path R 5  is connected to a first compression stage  25  described below which is included in the turbo compressor  6 . 
     The turbo compressor  6  compresses the refrigerant gas X 4  to produce the compressed refrigerant gas X 1 . As described above, the turbo compressor  6  is connected to the condenser  2  via the flow path R 1  through which the compressed refrigerant gas X 1  flows. Furthermore, the turbo compressor  6  is connected to the evaporator  5  via the flow path R 5  through which the refrigerant gas X 4  flows. 
     As shown in  FIG. 2 , the turbo compressor  6  includes a case  10 , a plurality of compression stages  12  which are disposed rotatably with respect to the case  10  via a sliding part  11 , an oil tank  13  in which the lubricant oil to be supplied to the sliding part  11  is stored, a pressure equalization pipe  15  which connects the oil tank  13  with the vicinity of the inlet of the compression stages  12 , and a check valve  16  which allows only the movement of the fluid from the oil tank  13  side to the compression stages  12  side in the pressure equalization pipe  15 . 
     The case  10  is divided into a motor housing  17 , a compressor housing  18  and a gear housing  20 , and those parts are connected to each other in a separable manner. In the motor housing  17 , an output shaft  21  which rotates around an axis O′, and a motor  22 , which is connected to the output shaft  21  and drives the compression stages  12 , are disposed. The output shaft  21  is rotatably supported by a first bearing  23  fixed to the motor housing  17 . Herein, the sliding part  11  includes not only the first bearing  23  but a second bearing  28 , a third bearing  30 , a gear unit  31  or the like described below. 
     The compression stages  12  include a first compression stage  25  which sucks and compresses the refrigerant gas X 4  (see  FIG. 1 ), and a second compression stage  26  which further compresses the refrigerant gas X 4  compressed in the first compression stage  25  to discharge the refrigerant gas X 4  as the compressed refrigerant gas X 1  (see  FIG. 1 ). The first compression stage  25  is disposed on the compressor housing  18  and the second compression stage  26  is disposed on the gear housing  20 . 
     The first compression stage  25  has a plurality of first impellers  25   a , a first diffuser  25   b , a first scroll chamber  25   c  and a suction port  25   d . The plurality of first impellers  25   a  is fixed to a rotational shaft  27 , which is driven for rotation around the axis O by means of the motor  22 , and imparts speed energy to the refrigerant gas X 4  which is supplied from a thrust direction to discharge the refrigerant gas X 4  in a radial direction. The first diffuser  25   b  compresses the refrigerant gas X 4  by converting the speed energy imparted to the refrigerant gas X 4  by the first impeller  25   a  into pressure energy. The first scroll chamber  25   c  leads the refrigerant gas X 4  compressed by the first diffuser  25   b  to the outside of the first compression stage  25 . The suction port  25   d  sucks the refrigerant gas X 4  to supply the same to the first impeller  25   a . The first diffuser  25   b , the first scroll chamber  25   c  and a part of the suction port  25   d  is formed by a first housing  25   e  surrounding the first impeller  25   a . 
     A plurality of inlet guide vanes (suction capacity adjusting portions)  25   g  for adjusting the suction capacity of the first compression stage  25  is installed in the suction port  25   d  of the first compression stage  25 . The respective inlet guide vanes  25   g  can rotate so that apparent areas from the flow direction of the refrigerant gas X 4  can be altered by means of a driving mechanism  25   i.    
     A relay space  25   h , which forms a ring shape centered on the axis O, is dividedly formed in the first housing  25   e , which is the outer peripheral portion of the first impeller  25   a  in the first compression stage  25 , and the suction port  25   d  at the upstream side of the first impeller  25   a . An end  15   a  of the pressure equalization pipe  15  is connected to the relay space  25   h , and the driving mechanism  25   i  for driving the inlet guide vanes  25   g  is housed inside the relay space  25   h.    
     The relay space  25   h  communicates with the rear surface side of the inlet guide vanes  25   g  in the suction port  25   d  via a slight gap  25   k . As a result, it is configured such that the pressure of the relay space  25   h  is always equal to that of the suction port  25   d . The relay space  25   h  is connected to an accommodation space S 1  described below by means of the pressure equalization pipe  15 . 
     The second compression stage  26  includes a second impeller  26   a , a second diffuser  26   b , a second scroll chamber  26   c  and an inlet scroll chamber  26   d . The second impeller  26   a  imparts speed energy to the refrigerant gas X 4 , which is compressed in the first compression stage  25  and is supplied from the thrust direction, to discharge the refrigerant gas X 4  in the radial direction. The second diffuser  26   b  compresses the refrigerant gas X 4  by converting the speed energy imparted to the refrigerant gas X 4  by the second impeller  26   a  to the pressure energy to discharge the refrigerant gas X 4  as the compressed refrigerant gas X 1 . The second scroll chamber  26   c  leads the compressed refrigerant gas X 1  discharged from the second diffuser  26   b  to the outside of the second compression stage  26 . The inlet scroll chamber  26   d  guides the refrigerant gas X 4  compressed in the first compression stage  25  to the second impeller  26   a . The second diffuser  26   b , the second scroll chamber  26   c  and a part of the inlet scroll chamber  26   d  are formed by a second housing  26   e  surrounding the second impeller  26   a . 
     The second impeller  26   a  is fixed to the rotational shaft  27  such that the rear surface thereof is mated with that of the first impeller  25   a , and the rotational movement force from the output shaft  21  of the motor  22  is transmitted to the rotational shaft  27 , so that the rotational shaft  27  rotates around the axis O, whereby the second impeller  26   a  is driven for rotation. The second diffuser  26   b  is annularly disposed around the second impeller  26   a.    
     The second scroll chamber  26   c  is connected to the flow path R 1  for supplying the condenser  2  with the compressed refrigerant gas X 1  to supply the flow path R 1  with the compressed refrigerant gas X 1  led from the second compression stage  26 . 
     In addition, the first scroll chamber  25   c  of the first compression stage  25  and the inlet scroll chamber  26   d  of the second compression stage  26  are connected with each other via an outside piping (not shown) which is provided separately from the first compression stage  25  and the second compression stage  26 , whereby the refrigerant gas X 4  compressed in the first compression stage  25  is supplied to the second compression stage  26  via the outside piping. The above-mentioned flow path R 4  (see  FIG. 1 ) is connected to the outside piping, whereby the gaseous components X 3  of the refrigerant generated in the economizer  3  is supplied to the second compression stage  26  via the outside piping. 
     The rotational shaft  27  is rotatably supported by the second bearing  28  fixed to the gear housing  20  and by the third bearing  30  fixed to the compressor housing  18 . 
     In the gear housing  20 , an accommodation space S 1  is formed which accommodates a gear unit  31  for transmitting the driving force of the output shaft  21  to the rotational shaft  27  and a demister  32  for preventing the mixing of the oil mist. The oil tank  13  is disposed under the accommodation space S 1 . The oil tank  13  also communicates with a space S 2  formed inside the compressor housing  18 . The check valve  16  is disposed in the demister  32  and is connected to the other end  15   b  of the pressure equalization pipe  15 . In addition, the check valve  16  does not necessarily need to be disposed in the demister  32  and may be connected to the pressure equalization pipe  15 . 
     The gear unit  31  includes a low speed gear  33  fixed to the output shaft  21  of the motor  22  and a high speed gear  35  which is fixed to the rotational shaft  27  and is engaged with the low speed gear  33 . In addition, the rotational movement force of the output shaft  21  of the motor  22  is transmitted to the rotational shaft  27  such that the rotational speed of the rotational shaft  27  is greater than the rotational speed of the output shaft  21 . 
     Next, the operation of the turbo refrigerator  1  and the turbo compressor  6  relating to the present embodiment will be described. 
     First of all, along with the operation start of the turbo refrigerator  1  and the turbo compressor  6 , the lubricant oil is supplied from the oil tank  13  to the sliding part  11  by means of an oil pump (not shown). Then, the motor  22  is driven, so that the rotational movement force of the output shaft  21  of the motor  22  is transmitted to the rotation shaft  27  via the gear unit  31 , whereby the first compression stage  25  and the second compression stage  26  are driven for rotation. 
     When the first compression stage  25  is driven for rotation, the suction port  25   d  of the first compression stage  25  enters a negative pressure state, whereby the refrigerant gas X 4  from the flow path R 5  flows in the first compression stage  25  via the suction port  25   d . At this time, the suction capacity is suitably adjusted by means of the inlet guide vanes  25   g . 
     The refrigerant gas X 4  that flowed into the first compression stage  25  flows in the first impeller  25   a  from the thrust direction, is imparted with the speed energy by the first impeller  25   a  and is discharged in the radial direction. 
     When the first impeller  25   a  is driven for rotation and the suction port  25   d  enters the negative pressure state, the inside of the relay space  25   h  communicating with the gap  25   k  also enters the negative pressure state. For this reason, since the pressure of the accommodation space S 1  side becomes higher than that of the relay space  25   h  side, the check valve  16  enters an open state, whereby the suction port  25   d  situated at the upstream side of the first impeller  25   a  enters a state of communicating with the oil tank  13  via the gap  25   k , the relay space  25   h , the pressure equalization pipe  15 , the check valve  16 , and the accommodation space S 1 . In addition, the pressure of the suction port  25   d  becomes substantially the same as that of the inside of the oil tank  13 , and the inside of the oil tank  13  also enters the negative pressure state. For this reason, the lubricant oil, which has flowed down from the sliding parts  11  which are supplied with the lubricant oil such as the first bearing  23 , the second bearing  28 , the third bearing  30 , and the gear unit  31 , moves toward the oil tank  13  which has entered the negative pressure state and is collected. 
     The refrigerant gas X 4  discharged from the first impeller  25   a  is compressed by converting the speed energy to the pressure energy by means of the first diffuser  25   b . The refrigerant gas X 4  discharged from the first diffuser  25   b  is led to the outside of the first compression stage  25  via the first scroll chamber  25   c.    
     In addition, the refrigerant gas X 4  led to the outside of the first compression stage  25  is supplied to the second compression stage  26  via the outside piping. 
     The refrigerant gas X 4  supplied to the second compression stage  26  flows into the second impeller  26   a  from the thrust direction via the inlet scroll chamber  26   d  and is discharged in the radial direction imparted with the speed energy by the second impeller  26   a.    
     The speed energy of the refrigerant gas X 4  discharged from the second impeller  26   a  is converted to the pressure energy by the second diffuser  26   b , whereby the refrigerant gas X 4  is further compressed and becomes the compressed refrigerant gas X 1 . 
     The compressed refrigerant gas X 1  discharged from the second diffuser  26   b  is led to the outside of the second compression stage  26  via the second scroll chamber  26   c.    
     In addition, the compressed refrigerant gas X 1  led to the outside of the second compression stage  26  is supplied to the condenser  2  via the flow path R 1 . 
     On the other hand, when the turbo refrigerator  1  is stopped due to energy saving measures or the like, the refrigerant flows backward from the condenser  2  to the inlet of the turbo compressor  6 , whereby the pressure of the suction port  25   d  increases. At this time, since the pressure in the relay space  25   h  becomes higher than that of the accommodation space S 1 , the back flow of the refrigerant is generated to the pressure equalization pipe  15  side, but the check valve  16  is closed. In this way, even when the pressure of the relay space  25   h  side increases, the pressure in the oil tank  13  (the accommodation space S 1 ) is maintained, since the back flow of the refrigerant to the oil tank  13  side is blocked. 
     In the turbo refrigerator  1  and the turbo compressor  6 , since the check valve  16  is disposed in the turbo compressor  6 , when the pressure of the inlet side of the turbo compressor  6  becomes higher than that of the oil tank  13  (the accommodation space S 1 ) side during operation stop, the check valve  16  can be closed to block the pressure equalization pipe  15 . Thus, it is possible to suitably suppress the back flow of the refrigerant to the oil tank  13  (the accommodation space S 1 ) side through the pressure equalization pipe  15  even with a simple configuration, which can suitably suppress the leakage of the lubricant oil due to the leakage of the refrigerant from the oil tank  13  (the accommodation space S 1 ) to the motor  22  or the like. 
     In particular, the one end  15   a  of the pressure equalization pipe  15  opens to the relay space  25   h  provided so as to communicate with the rear surface of the inlet guide vane  25   g . Thus, during operation, it is possible to make the pressure in the oil tank  13  (the accommodation space S 1 ) the same as in the relay space  25   h  with negative pressure to allow the oil tank  13  to suitably collect the lubricant oil. 
     In addition, since the check valve  16  is built in the case  10 , it is possible to promote the space saving of the overall turbo compressor  6  while securing the air-tightness without the check valve  16  being protruded outside the case  10 . 
     Furthermore, the technical scope of the present invention is not limited to the above-mentioned embodiment, and various modifications can be added without departing from the gist of the present invention. 
     For example, in the above-mentioned embodiments, although it has been described that the check valve  16  is built into the case  10 , the present invention is not limited thereto, and, as shown in  FIG. 3 , the present invention may be a turbo compressor  42  and a turbo refrigerator  1  in which a pressure equalization pipe  15  is disposed at the outside of the case  10 , the oil tank  13  (the accommodation space S 1 ) communicates with the relay space  25   h , and the check valve  16  is disposed in the middle of the pressure equalization pipe  15 . 
     Furthermore, in the above-mentioned embodiments, although the configuration including the two compression stages (the first compression stage  25  and the second compression stage  26 ) has been described, the present invention is not limited thereto, but a configuration including one or three or more compression stages may be adopted. 
     In addition, although, a case  10 , of the turbo compressor, in which the motor housing  17 , the compressor housing  18 , and the gear housing  20  are each dividedly formed, has been described, the present invention is not limited thereto, and, for example, a configuration, in which the motor is disposed between the first compression stage and the second compression stage, may be adopted. 
     While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the appended claims.