Patent Publication Number: US-2021180511-A1

Title: Turbocharger

Description:
TECHNICAL FIELD 
     The present disclosure relates to a turbocharger that is suitably employed in a diesel engine or the like provided in a ship, for example. 
     BACKGROUND ART 
     In the related art, turbochargers configured to compress air and supply the air as combustion air for internal combustion engines into combustion chambers are known. The turbochargers have widely been used in two-stroke low-speed engines such as diesel engines for ships and diesel engines for power generation, for example. Such a turbocharger is adapted such that a compressor configured to compress the combustion air and a turbine that serves as a drive source for the compressor are coupled to each other via a rotor shaft, are accommodated in a casing, and integrally rotate. The turbine is driven using exhaust gas discharged from an internal combustion engine as a drive source, for example. 
     As a type of turbocharger, a hybrid turbocharger in which an electric-powered generator is connected to a rotor shaft via a coupling is known (see Patent Literature 1, for example). The hybrid turbocharger can compress air and supply the air as combustion air into a combustion chamber of an internal combustion engine similarly to an ordinary turbocharger and can also generate power using excessive exhaust gas discharged from the internal combustion engine. 
     In addition, as a type of turbocharger, a power-assisted turbocharger in which an electric motor is connected to a rotor shaft is known (see Patent Literature 2, for example). The power-assisted turbocharger has a motor downsized by omitting a power generating function of an electric-powered generator used in a hybrid turbocharger and narrowing its function to an electric motor function (assisting function). 
     CITATION LIST 
     Patent Literature 
     [PTL 1] 
     the Publication of Japanese Patent No. 4648347 
     [PTL 2] 
     Japanese Unexamined Patent Application, Publication No. 2015-158161 
     SUMMARY OF INVENTION 
     Technical Problem 
     In a case of a turbocharger with an overhang structure in which no bearing is provided at a motor rotor itself, the motor rotor is connected to an extended portion of a rotor shaft of the turbocharger, and the motor rotor is supported by the rotor shaft of the turbocharger as in Patent Literature 2, a motor and an impeller inlet are inevitably located close to each other, and it is thus possible to use air flowing into the impeller for cooling the motor. However, in a case of a turbocharger with a coupling structure in which a motor is connected to a drive shaft, which is connected to a turbine, via an intermediate shaft and a coupling, the motor and an impeller inlet are separated from each other, it is thus difficult to use air flowing into the impeller for cooling the motor, and it is necessary to additionally provide a cooling mechanism such as a cooling water circulation mechanism as in Patent Literature 1 in order to sufficiently cool the motor. 
     The present disclosure has been made in view of such circumstances, and an object of the present disclosure is to provide a turbocharger capable of efficiently guiding a fluid to an impeller and improving cooling performance of the motor or the generator even in a turbocharger with a coupling structure. 
     Solution to Problem 
     In order to solve the aforementioned problems, the turbocharger employs the following means. 
     In other words, a turbocharger according to an aspect of the present disclosure includes: a suction part configured to suction a fluid; an impeller configured to compress the fluid supplied from the suction part; a drive shaft having one end to which the impeller is attached; an intermediate shaft provided at the one end of the drive shaft such that the drive shaft extends in an axial direction from a downstream side to an upstream side of the impeller; a motor or a generator having a rotor attached to a distal end of the intermediate shaft via a coupling, a stator provided so as to correspond to the rotor, and a body portion configured to hold the stator; and a cover formed into a tubular shape to surround the intermediate shaft and the coupling. 
     The turbocharger according to the aspect has a coupling structure in which the rotor is attached to the distal end of the intermediate shaft via the coupling. Also, the cover with a tubular shape to surround the intermediate shaft and the coupling is provided. With this configuration, the cover can separate a flow flowing into the impeller to the outside and the inside of the cover and can curb interference between the mutual flows. Also, it is possible to uniformly reduce the flow passage area around the cover along a flowing direction of the fluid. In this manner, it is possible to reduce a pressure loss of the fluid flowing into the impeller, to rectify the fluid, and thereby to prevent a decrease in speed of the fluid. Also, it is possible to sufficiently secure the flow amount of the fluid flowing into the impeller. In other words, it is possible to efficiently guide the fluid to the impeller. At the same time, it is possible to reliably guide the fluid into the motor or into the generator (between the rotor and the stator), and cooling performance of the motor or the generator using the fluid is thus improved. 
     Note that it is not necessary for the cover with the tubular shape to surround the entire intermediate shaft in the longitudinal direction, and it is only necessary for the cover to surround a part of the intermediate shaft in the longitudinal direction. 
     Also, in the turbocharger according to an aspect of the present disclosure, the suction part is provided on an upstream side of the motor or the generator, and an inner diameter of the cover is greater than an outer diameter of the rotor. 
     In the turbocharger according to the aspect, the suction part is located downstream relative to the motor or the generator, and the inner diameter of the cover is greater than the outer diameter of the rotor. In this manner, it is possible to reliably guide the fluid into the motor or into the generator as well, and cooling performance of the motor or the generator using the fluid is thus improved. Therefore, it is possible to raise output power without changing a physical size of the motor or the generator. Also, it is not necessary to additionally provide a cooling mechanism for cooling the motor or the generator, which can lead to cost reduction. 
     Also, in the turbocharger according to an aspect of the present disclosure, an outer diameter of the cover is equivalent to an outer diameter of an end of a hub of the impeller on a side of the cover. 
     In the turbocharger according to the aspect, the outer diameter of the cover is equivalent to the outer diameter of the end of the hub on the side of the cover. In this manner, it is possible to secure a flow passage area of the fluid flowing into the impeller and to smooth the flow of the fluid. 
     Also, in the turbocharger according to an aspect of the present disclosure, the cover is splittable along a longitudinal direction. 
     In the turbocharger according to the aspect, the cover is splittable along the longitudinal direction. Since the motor (or the generator), the intermediate shaft, the coupling, and the like are concentrated in a location to which the cover is attached, a working space is limited. The splittable cover improves assembling properties. 
     Also, in the turbocharger according to an aspect of the present disclosure, the cover is provided with a rib along a longitudinal direction. 
     In the turbocharger according to the aspect, the cover is provided with the rib along the longitudinal direction. In this manner, it is possible to secure strength even in a case in which the cover is formed into a thin structure. In other words, it is possible to achieve weight reduction and to secure the strength of the cover. 
     Also, in the turbocharger according to an aspect of the present disclosure, the cover is attached on a side of the motor or on a side of the generator. 
     In the turbocharger according to the aspect, the cover is attached on the side of the motor or on the side of the generator. In this manner, it is not necessary to additionally provide a support structure for placing the cover, and it is possible to achieve cost reduction. 
     Advantageous Effects of Invention 
     According to the turbocharger of the present disclosure, it is possible to efficiently guide the fluid to the impeller and to improve cooling performance of the motor or the generator even in a turbocharger with a coupling structure. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a vertical sectional view illustrating a turbocharger according to an embodiment of the present disclosure. 
         FIG. 2  is a sectional view of a motor illustrated in  FIG. 1  taken along the cut line A-A. 
         FIG. 3  is a right side view of an upper cover illustrated in  FIG. 1 . 
         FIG. 4  is a bottom view of the upper cover illustrated in  FIG. 3 . 
         FIG. 5  is a right side view of a lower cover illustrated in  FIG. 1 . 
         FIG. 6  is a plan view of the lower cover illustrated in  FIG. 5 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, a turbocharger according to an embodiment of the present disclosure will be described with reference to drawings. 
     First, a configuration of a turbocharger  10  according to the embodiment will be described. 
     The turbocharger  10  is a turbocharger such as a hybrid turbocharger or a power-assisted turbocharger used for enhancing combustion efficiency of a diesel engine (internal combustion engine) used for a ship, for example, by raising a pressure of air (gas) to be supplied to the diesel engine to be equal to or greater than a specific pressure (atmospheric pressure, for example). 
     As illustrated in  FIG. 1 , the turbocharger  10  includes a drive shaft  18 , a compression unit  10   a , an intermediate shaft  16 , a motor  14 , a suction part  10   b , and a cover  30 . 
     The compression unit  10   a  is provided with an impeller  12 . The impeller  12  includes a hub  12   d  and a plurality of blades  12   c  provided at the hub  12   d . The impeller  12  is attached to the drive shaft  18 , which is supported by a bearing (not illustrated) so as to be able to rotate about an axial line X, on a side of one end. Also, a turbine (not illustrated) that is driven and rotated by exhaust gas discharged from the diesel engine is provided at the drive shaft  18  on a side of the other end. In other words, the impeller  12  provided at the compression unit  10   a  is coupled to the turbine (not illustrated) via the drive shaft  18 . 
     On the side of the one end of the drive shaft  18  to which the impeller  12  is attached, the intermediate shaft  16  that is on a coaxial line of the drive shaft  18  is provided in a direction in which the drive shaft  18  extends along the axial line X from the impeller  12  toward the upstream side of an air flow (from the right side toward the left side in  FIG. 1 ). The drive shaft  18  and the intermediate shaft  16  are coupled to each other via a second coupling  20   b . Note that the drive shaft  18  may extend in the axial direction and the extended portion of the drive shaft  18  may be caused to serve as a shaft corresponding to the intermediate shaft  16  without providing the second coupling  20   b.    
     On the other hand, the motor  14  is mounted on the intermediate shaft  16  on a side of an end (the left side in  FIG. 1 ) to which the drive shaft  18  is not coupled. The motor  14  includes a rotor  14   a , a stator  14   c  provided with a clearance in a radial direction of the rotor  14   a , and a body portion  14   b  configured to hold the stator  14   c . The body portion  14   b  includes a plurality of supports  14   d  extending in the radial direction. The stator  14   c  is supported relative to a casing  10   c  of the turbocharger  10  by the body portion  14   b  provided with these supports  14   d.    
     Both ends of the rotor  14   a  are supported by a bearing  14   e  provided at the body portion  14   b  so as to be able to rotate about the axial line X. Also, an end of the rotor  14   a  on the side of the intermediate shaft  16  (the right side in  FIG. 1 ) and the intermediate shaft  16  are coupled to each other via a first coupling  20   a.    
     The turbocharger  10  according to the embodiment employs a so-called coupling structure in which the rotor  14   a  is attached to the end of the intermediate shaft  16  via the first coupling  20   a  as described above. 
     The suction part  10   b  of the turbocharger  10  is provided at the motor  14  on the side to which the intermediate shaft  16  is not coupled, and an external fluid is suctioned from the suction part  10   b . A silencer, for example, is provided on the upstream side of the suction part  10   b.    
     Also, the turbocharger  10  according to the embodiment includes a cover  30  formed into a tubular shape to surround the intermediate shaft  16  and the first coupling  20   a . The cover  30  has a substantially cylindrical shape and has a structure in which the cover  30  can be split into halves along a longitudinal direction. In other words, the cover  30  is configured of an upper cover  30   a  as illustrated in  FIGS. 3 and 4  and a lower cover  30   b  as illustrated in  FIGS. 5 and 6 . Also, a plurality of ribs  30   c  standing along the longitudinal direction are provided at each of the upper cover  30   a  and the lower cover  30   b  on a side of an outer periphery of a cylindrical surface formed of a thin plate. At this time, the inner diameter of the cover  30  is greater than the outer diameter of the rotor  14   a  and is set to be similar to or greater than the inner diameter of the stator  14   c  as illustrated in  FIG. 1 . Also, the outer diameter of the cover  30  is set to be equivalent to the hub diameter of the impeller  12 . The hub diameter is an outer diameter of the end of the hub  12   d  on the side of the cover  30 . One end of the cover  30  is secured to the supports  14   d  disposed at the intermediate shaft  16  on the side of the motor  14 . Note that the support may be provided from an air inlet guide  10   d  to secure the cover  30 . Also, the cover  30  with a tubular shape does not necessarily surround the entire intermediate shaft  16  in the longitudinal direction, and it is only necessary for the cover  30  to surround a part of the intermediate shaft  16  in the longitudinal direction. In addition, the shape of the cover  30  with a tubular shape is not limited to a cylindrical shape and may be a polygonal tubular shape. 
     Next, the turbocharger  10  according to the embodiment will be described in further detail. 
     As illustrated in  FIG. 1 , the impeller  12  included in the compression unit  10   a  is attached to the drive shaft  18 , which extends along the axial line X, on the side of one end and rotates about the axial line X with rotation of the drive shaft  18  about the axial line X. The turbine (not illustrated) is attached to the drive shaft  18  on the side of the other end to which the impeller  12  is not attached. The drive shaft  18  rotates about the axial line X with rotation of the turbine about the axial line X. In other words, the impeller  12 , the drive shaft  18 , and the turbine integrally rotate about the axial line X. 
     In the turbocharger  10 , exhaust gas discharged from the diesel engine causes the turbine to rotate about the axial line X. With the rotation of the turbine, the impeller  12  rotates about the axial line X via the drive shaft  18 . By the impeller  12  rotating about the axial line X, the fluid flowing from a suction port  12   a  is compressed and is then discharged from a discharge port  12   b . Once the impeller  12  starts to rotate about the axial line X (once the compression starts), a negative pressure is generated in the vicinity of the suction port  12   a . External fluid is suctioned from the suction part  10   b  using the negative pressure. In other words, a flow of the fluid from the suction part  10   b  toward the compression unit  10   a  is formed. 
     The flow of the fluid from the suction part  10   b  to the compression unit  10   a  is roughly classified into a cooling air flow Fb that is distributed to the inside of a clearance between the rotor  14   a  and the stator  14   c  and a suctioned air flow Fa other than the cooling air flow Fb. Note that these names of the flows of the fluid are names for distinguishing the flows and do not mean that only the cooling air flow Fb acts for cooling the motor  14 , for example. 
     The suctioned air flow Fa passes through portions between the supports  14   d  (see  FIG. 2 ) from the suction part  10   b  and is guided to the suction port  12   a  of the impeller  12 . 
     On the other hand, the cooling air flow Fb passes through the inside of the clearance between the rotor  14   a  and the stator  14   c . The cooling air flow Fb passing through the inside of the clearance takes away a heat of the motor  14 , which has generated a heat, and as a result, the cooling air flow Fb acts for cooling the motor  14 . Note that the suctioned air flow Fa acts for cooling the motor  14  from the outside of the body portion  14   b.    
     The cooling air flow Fb that has flowed out from the clearance between the rotor  14   a  and the stator  14   c  is guided into the cover  30  that surrounds the first coupling  20   a  and the intermediate shaft  16 . Note that the suctioned air flow Fa and the cooling air flow Fb do not interfere with each other in the cover  30 . Also, the flow passage area around the cover  30  is uniformly reduced along the flowing direction of the fluid due to the cover  30 . 
     The cooling air flow Fb that has been guided into the cover  30  flows out from a cover opening  30   d  near the suction port  12   a  where the negative pressure has been generated. The cooling air flow Fb that has flowed out meets the suctioned air flow Fa and is guided to the suction port  12   a.    
     Note that the aforementioned motor  14  may be a motor  14  configured to cause the impeller  12  to rotate using electric power and assist a supercharging ability in a case in which the diesel engine is operated with low output power and discharged exhaust gas cannot give a sufficient supercharging ability to the turbocharger  10 , or may be a generator that causes the rotor  14   a  to rotate via the drive shaft  18  coupled to the turbine, the coupling, and the intermediate shaft  16  and generates power in a case in which excessive exhaust gas is discharged from the diesel engine. In regard to the generator, the motor  14  may be caused to function as a generator. 
     According to the turbocharger  10  of the embodiment, the following advantages are achieved. 
     The cover  30  can curb an interference between mutual flows, namely the suctioned air flows Fa and the cooling air flow Fb outside and inside the cover  30 . Also, it is possible to uniformly reduce the flow passage area around the cover  30  along the flowing direction of the fluid. In this manner, it is possible to prevent a decrease in speed of the suctioned air flow Fa by reducing a pressure loss of the suctioned air flow Fa guided to the suction port  12   a  of the impeller  12  or rectifying the suctioned air flow Fa. Also, it is possible to sufficiently secure the flow amount of the suctioned air flow Fa to be guided to the suction port  12   a  of the impeller  12 . In other words, it is possible to efficiently guide the suctioned air flow Fa to the impeller  12 . 
     At the same time, the cooling air flow Fb can reliably be guided into the motor  14  as well (the clearance between the rotor  14   a  and the stator  14   c ). This is because the cooling air flow Fb that has flowed out from the clearance between the rotor  14   a  and the stator  14   c  is not affected by an interference from the suctioned air flow Fa and the flow of the cooling air flow Fb can thus be maintained. Also, since the inner diameter of the cover  30  is greater than the outer diameter of the rotor  14   a  and is set to be similar to or greater than the inner diameter of the stator  14   c , the cooling air flow Fb that has flowed out from the clearance between the rotor  14   a  and the stator  14   c  is unlikely to be affected by an interference from the cover  30 . Further, the cooling air flow Fb that has flowed out from the clearance is guided into the cover  30 , flows out from the cover opening  30   d  in the vicinity of the suction port  12   a  where the negative pressure has been generated, and then meets the suctioned air flow Fa. At this time, the outer diameter of the cover  30  is set to be equivalent to the hub diameter of the impeller  12 . In a case in which the outer diameter of the cover  30  is greater than the hub diameter, an interference occurs between the cover  30  and the suctioned air flow Fa. Also, in a case in which the outer diameter of the cover  30  is smaller than the hub diameter, the cover opening  30   d  is excessively reduced in size, and it is not possible to efficiently guide the cooling air flow Fb to the vicinity of the suction port  12   a . If the outer diameter of the cover  30  is equivalent to the hub diameter of the impeller  12 , such phenomena can be avoided. It is possible to maintain the flow rate of the cooling air flow Fb in the cover  30  by causing the cover opening  30   d  to approach the suction port  12   a  where the negative pressure has been generated and efficiently guiding the cooling air flow Fb to the vicinity of the suction port  12   a  in this manner. As a result, it is possible to maintain the flow rate of the cooling air flow Fb distributed through the clearance between the rotor  14   a  and the stator  14   c . These advantages improve cooling performance of the motor  14  using the cooling air flow Fb. In this manner, it is possible to raise output power without changing a physical size of the motor  14 . Also, it is not necessary to additionally provide a cooling mechanism for cooling the motor  14 , and cost reduction can thus be achieved. 
     In a case in which no cover  30  is provided in a coupling structure in which the motor  14  and the inlet of the impeller  12  are separated from each other, the suctioned air flow Fa and the cooling air flow Fb interfere with each other, the flows are disturbed, and this may lead to a probability that the suctioned air flow Fa cannot efficiently be guided to the impeller  12  and the performance of the turbocharger  10  is degraded or that the flow of the cooling air flow Fb cannot be maintained and the cooling performance of the motor  14  is degraded. Also, since the cooling air flow Fb meets the suctioned air flow Fa at a location separated from the vicinity of the suction port  12   a  where the negative pressure has been generated, a pressure difference from the vicinity of the suction port  12   a  is reduced, and this may lead to a probability that the cooling air flow Fb is not appropriately formed. Further, since the flow passage area around the cover  30  is steeply enlarged along the flowing direction of the fluid, there is a probability that the performance of the turbocharger  10  is degraded due to a pressure loss. 
     Also, it is possible to improve assembling properties of the cover  30  by configuring the cover  30  to be splittable along the longitudinal direction. The space in which the cover  30  is placed has to be accessed from a portion between the supports  14   d  on the upper side, and components such as the motor  14  and the intermediate shaft  16  are concentrated in the space. However, in a case in which the cover  30  is split into the upper cover  30   a  and the lower cover  30   b , it is possible to reduce the size of the cover  30  that is caused to pass between the supports  14   d  into a half, which facilitates the access. Also, a state in which the lower cover  30   b  is assembled with the supports  14   d  on the lower side is achieved in advance, and components configuring the motor  14  and components such as the intermediate shaft  16  are then placed thereafter, for example. Then, the upper cover  30   a  is finally attached to the lower cover  30   b  secured in advance, and it is thus possible to improve assembling properties of the cover  30 . 
     In addition, it is possible to secure the strength of the cover  30  using the ribs  30   c  even if the cover  30  is formed to have a thin structure by providing the ribs  30   c  along the longitudinal direction of the cover  30  and thereby to achieve weight reduction based on the thin structure of the cover  30 . 
     REFERENCE SIGNS LIST 
     
         
           10  Turbocharger 
           10   a  Compression unit 
           10   b  Suction part 
           10   c  Casing 
           10   d  Air inlet guide 
           12  Impeller 
           12   a  Suction port 
           12   b  Discharge port 
           12   c  Blade 
           12   d  Hub 
           14  Motor 
           14   a  Rotor 
           14   b  Body portion 
           14   c  Stator 
           14   d  Support 
           14   e  Bearing 
           16  Intermediate shaft 
           18  Drive shaft 
           20   a  First coupling (coupling) 
           20   b  Second coupling (coupling) 
           30  Cover 
           30   a  Upper cover 
           30   b  Lower cover 
           30   c  Rib 
           30   d  Cover opening 
         Fa Suctioned air flow 
         Fb Cooling air flow