Patent Publication Number: US-2021189950-A1

Title: Supercharging device

Description:
TECHNICAL FIELD 
     The present invention relates to a supercharging device that improves a motor-driven supercharger to increase versatility. 
     BACKGROUND ART 
     A turbocharger is a well-known supercharging device that increases engine power by using exhaust energy from the engine to rotate a compressor impeller and performs supercharging. In the turbocharger, a time lag (turbo lag) may occur before supercharging begins during acceleration. To compensate for the time lag until supercharging begins during acceleration, a motor-driven supercharger that includes an electrically powered impeller may be used together with the turbocharger. 
     Generally, the motor-driven supercharger is used effectively only under situations that are easily affected by the turbo lag described above such as during rapid acceleration. Thus, it is desirable that the motor-driven supercharger be used effectively in more various situations. Accordingly, patent document 1 discloses an example of a supercharging device that improves the motor-driven supercharger and makes the motor-driven supercharger versatile. The supercharging device includes a planetary gear mechanism that incorporates a sun gear, a ring gear, and a planetary gear. An impeller is coupled to one of the sun gear, the ring gear, and the planetary gear, and power from the engine is input to one of the two remaining gears. The last gear is rotated by a motor-generator (electric device). 
     When the motor-generator is actuated as a motor in a state in which a brake acts to restrict rotation of the impeller, the power output from the motor is transferred to the engine, not the impeller. In this way, the supercharging device assists the engine to realize mild hybrid. 
     Alternatively, the motor-generator can be actuated as a generator to generate electric power from engine power. This allows for effective use of the supercharging device by actuating the supercharging device for mild hybrid or as an electric generator even when the motor does not rotate the impeller, that is, when the supercharging device is not used as a motor-driven compressor. 
     PRIOR ART LITERATURE 
     Patent Literature 
     
         
         Patent Document 1: Japanese National Phase Laid-Open Patent Publication No. 2009-520915. 
       
    
     SUMMARY OF THE INVENTION 
     Problem to be Solved by the Invention 
     However, the supercharging device described in patent document 1 has a tendency to be enlarged. As shown in  FIG. 1  of patent document 1, when the motor-generator is arranged outward from the planetary gear mechanism in an axial direction, that is, when the motor-generator and the planetary gear mechanism are arranged next to each other in the axial direction, the dimension of the supercharging device increases in the axial direction. Further, as shown in FIG. 2 of patent document 1, when the motor-generator is arranged outward from the ring gear in a radial direction, the dimension of the supercharging device increases in the radial direction. This adversely affects the mountability of the supercharging device on a vehicle. 
     One object of the present invention is to limit enlargement of a supercharging device that improves the motor-driven supercharger and makes the motor-driven supercharger versatile. 
     Means for Solving the Problem 
     A supercharging device that solves the above problem includes an impeller, a motor-generator, a planetary gear mechanism, and a restriction mechanism. The impeller includes a shaft. The motor-generator is configured to perform supercharging by rotating the impeller when functioning as a motor. The planetary gear mechanism includes a sun gear, a ring gear, a plurality of planetary gears, and a carrier. The shaft is coupled to the sun gear. The ring gear is configured to be rotated by power from the engine. The planetary gears are arranged between the sun gear and the ring gear. The carrier is coupled to the planetary gears. The restriction mechanism is configured to restrict rotation of the impeller. The carrier includes a cylindrical portion, through which the shaft extends. The motor-generator includes a rotor and a stator. The rotor is integrated with the outer circumferential surface of the cylindrical portion. The stator is arranged outward from the rotor in a radial direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross-sectional side view of a supercharging device in accordance with the first embodiment. 
         FIG. 2A  is a schematic diagram showing the action of a planetary gear mechanism when the supercharging device of  FIG. 1  is actuated as a motor-driven compressor,  FIG. 2B  is a schematic diagram showing the action of a planetary gear mechanism when the supercharging device of  FIG. 1  is actuated for mild hybrid, and  FIG. 2C  is a schematic diagram showing the action of a planetary gear mechanism when the supercharging device of  FIG. 1  is actuated as a generator. 
         FIG. 3  is a cross-sectional side view of a supercharging device in accordance with the second embodiment. 
         FIG. 4A  is a schematic diagram showing the action of a planetary gear mechanism when the supercharging device of  FIG. 3  is actuated as a motor-driven compressor,  FIG. 4B  is a schematic diagram showing the action of a planetary gear mechanism when the supercharging device in  FIG. 3  is actuated for mild hybrid, and  FIG. 4C  is a schematic diagram showing the action of a planetary gear mechanism when the supercharging device of  FIG. 3  is actuated as a generator. 
     
    
    
     EMBODIMENTS OF THE INVENTION 
     First Embodiment 
     A supercharging device in accordance with a first embodiment will now be described with reference to the drawings. In the description hereafter, the supercharging device is used together with a turbocharger. However, the turbocharger may be omitted. 
     As shown in  FIG. 1 , the supercharging device  1  includes a housing  40  that accommodates an impeller  10 , a planetary gear mechanism  20 , and a motor-generator  30 . The impeller  10  is rotated to pressurize intake gas, which is supplied to the engine, and perform supercharging. The housing  40  includes a first housing portion  41  that mainly accommodates the planetary gear mechanism  20 , a second housing portion  42  that mainly accommodates the motor-generator  30 , and a third housing portion  43  that mainly accommodates the impeller  10 . 
     The planetary gear mechanism  20  includes a sun gear  21  that is an external gear, a ring gear  22  that is an internal gear having a larger diameter than the sun gear  21 , a plurality of planetary gears  23  that are external gears, and a carrier  24  that is coupled to the planetary gears  23 . The ring gear  22  is arranged around the sun gear  21 , and the planetary gears  23  are arranged between the sun gear  21  and the ring gear  22 . The carrier  24  rotates at a rotation speed that is the same as the rotation speed of planetary gears  23  rotating (orbiting) around the sun gear  21 . 
     The sun gear  21  is coupled to one end (left end as viewed in  FIG. 1 ) of a shaft  11 . Further, the impeller  10  is coupled to the other end (right end as viewed in  FIG. 1 ) of the shaft  11 . Thus, the impeller  10 , the shaft  11 , and the sun gear  21  rotate integrally with one another. 
     A rotation shaft  22   a  of the ring gear  22  is partially projected from the first housing portion  41 , and a pulley  51  is coupled to the projected portion. A belt  52  runs around the pulley  51  to transfer power from the engine (rotation of crankshaft) so that the power from the engine is input via the belt  52  and the pulley  51  to the rotation shaft  22   a . As described below, when the supercharging device  1  is actuated for mild hybrid, the motor-generator  30  functions as a motor and the output of the motor-generator  30  is transferred via the rotation shaft  22   a , the pulley  51 , and the belt  52  to the engine. A first clutch  53  is arranged between the pulley  51  and the rotation shaft  22   a . The first clutch  53  is selectively switchable between a connected state that connects the pulley  51  and the rotation shaft  22   a  and a disconnected state that disconnects the pulley  51  and the rotation shaft  22   a.    
     The carrier  24 , which is coupled to the planetary gears  23 , includes a cylindrical portion  24   a , and the shaft  11  extends through the cylindrical portion  24   a . The shaft  11  is coaxial with the cylindrical portion  24   a . A second clutch  12  is arranged between the shaft  11  and the cylindrical portion  24   a . The second clutch  12  is selectively switchable between a connected state that connects the shaft  11  and the cylindrical portion  24   a  (carrier  24 ) and a disconnected state that disconnects the shaft  11  and the cylindrical portion  24   a  (carrier  24 ). When the second clutch  12  is switched to the connected state, the shaft  11  and the carrier  24  are rotatable integrally with each other. When the second clutch  12  is switched to the disconnected state, the shaft  11  and the carrier  24  are rotatable relative to each other. 
     Further, the first clutch  53  and the second clutch  12  are, for example, configured by electromagnetic clutches. The first clutch  53  and the second clutch  12  are switchable between the connected state and the disconnected state by a command from a controller  60 . 
     The motor-generator  30  includes a rotor  31  and a stator  32 . The rotor  31  is integrated with the outer circumferential surface of the cylindrical portion  24   a  of the carrier  24 , and the stator  32  is arranged outward from the rotor  31  in the radial direction. Accordingly, the impeller  10 , the shaft  11 , the planetary gear mechanism  20 , and the motor-generator  30  are coaxial. The rotor  31  includes, for example, magnets. The stator  32  includes, for example, coils that are energized and controlled by the controller  60 . Nonetheless, the rotor  31  and the stator  32  are not specifically limited to the above configurations. Further, the phrase “the rotor  31  is integrated with the outer circumferential surface of the cylindrical portion  24   a ” means that the rotor  31  is mounted on or fixed to the outer circumferential surface of the cylindrical portion  24   a  so that the rotor  31  and the cylindrical portion  24   a  rotate integrally with each other. 
     A switching circuit  61  electrically connects the stator  32 , which includes the coils, to the controller  60  and a battery  62 . The switching circuit  61  includes a motor circuit that has the motor-generator  30  function as a motor and a generator circuit that has the motor-generator  30  function as a generator. The motor circuit and the generator circuit are switchable in accordance with a command from the controller  60 . 
     When actuating the motor-generator  30  as a motor, the controller  60  switches the switching circuit  61  to the motor circuit to supply power from the battery  62  via the switching circuit  61  to the stator  32 , and rotates the rotor  31  integrally with the carrier  24 . When actuating the motor-generator  30  as a generator, the controller  60  switches the switching circuit  61  to the generator circuit so that the rotor  31  receives power from the engine and rotates integrally with the carrier  24 . Thus, the battery  62  is charged by the stator  32  via the switching circuit  61 . 
     The operation of the supercharging device  1  will now be described with reference to  FIG. 2 . The controller  60  determines whether to actuate the supercharging device  1  as a motor-driven compressor, a mild hybrid, or a generator based on, for example, the operation amount of the accelerator or the rotation speed of the engine. 
     For example, when the operation amount of the accelerator is rapidly increased while the rotation speed of the engine is in a low range, a turbo lag has a tendency to occur in the turbocharger. Thus, to assist supercharging when a turbo lag occurs, the supercharging device  1  is actuated as a motor-driven compressor. Specifically, the controller  60  connects the first clutch  53 , disconnects the second clutch  12 , and switches the switching circuit  61  to the motor circuit. In this case, as shown in  FIG. 2A , the rotor  31  rotates so that the planetary gears  23  rotate (orbit) in a direction opposite to the rotation direction of the ring gear  22 . This rotates the sun gear  21  at a rotation speed obtained by multiplying a relative rotation speed difference of the ring gear  22  and the planetary gears  23  by a speed-up ratio. As a result, the rotation speed of the impeller  10  is increased. However, the first clutch  53  may be disconnected since engine power does not necessarily have to be used for supercharging. 
     Instead of using the power from the motor (motor-generator  30 ) for supercharging, the use of the power to directly assist the rotation of the engine may, in some cases, be preferable. In such a case, the controller  60  connects both the first clutch  53  and the second clutch  12  and switches the switching circuit  61  to the motor circuit so that the supercharging device  1  is actuated for mild hybrid. In this case, as shown in  FIG. 2B , the rotor  31  rotates so that the planetary gears  23  rotate (orbit) in the same direction as the rotation direction of the ring gear  22 . Thus, the ring gear  22  is rotated by the planetary gears  23  and some of the power from the motor (motor-generator  30 ) is transferred via the pulley  51  and the belt  52  to the engine. This assists the rotation of the engine. 
     Finally, for example, during deceleration or the like, the supercharging device  1  is actuated as a generator to charge the battery  62  with engine power. In this case, the controller  60  connects both the first clutch  53  and the second clutch  12  and switches the switching circuit  61  to the generator circuit. Consequently, as shown in  FIG. 2C , as the power from the engine rotates the ring gear  22 , the planetary gears  23  rotate (orbit). This integrally rotates the rotor  31  with the carrier  24  and generates power with the stator  32 . The power charges the battery  62  via the switching circuit  61 . In this state, the sun gear  21  rotates integrally with the planetary gears  23 . Thus, the impeller  10  is rotated and supercharging is slightly performed. The second clutch  12  may be disconnected during power generation. In this case, the rotation of the impeller  10  will not be restricted by the second clutch  12  and a large amount of engine power will be used to rotate the impeller  10 . Thus, this may decrease the power generation efficiency. 
     Second Embodiment 
     A supercharging device in accordance with a second embodiment will now be described with reference to  FIG. 3 . In the first embodiment, the second clutch  12  is arranged between the cylindrical portion  24   a  of the carrier  24  and the shaft  11  and functions as a restriction mechanism that restricts rotation of the impeller  10 . The second embodiment differs from the first embodiment in that, instead of the second clutch  12 , a third clutch  13  is arranged between the impeller  10  and the housing  40 . Otherwise, the structure is the same as the first embodiment. Thus, same reference numerals are given to those components that are the same as the corresponding components of the first embodiment. Such components will not be described. 
     In the supercharging device  2  in accordance with the second embodiment, as described above, the third clutch  13  is arranged between the impeller  10  and the housing  40 . More specifically, the third clutch  13  is arranged between a back surface of the impeller  10  and a side surface of the second housing portion  42  that opposes the back surface of the impeller  10 . The third clutch  13  is, for example, configured by an electromagnetic clutch. Further, the third clutch  13  is selectively switchable between a connected state that connects the impeller  10  and the second housing portion  42  and a disconnected state that disconnects the impeller  10  and the second housing portion  42 . When a command from the controller  60  connects the third clutch  13 , the impeller  10  is connected to the stationary second housing portion  42 . This stops the rotation of the impeller  10 . When the third clutch  13  is disconnected, the impeller  10  is rotatable. 
     The operation of the supercharging device  2  is basically the same as that of the supercharging device  1  in accordance with the first embodiment. That is, when actuating the supercharging device  2  as a motor-driven compressor, the controller  60  connects the first clutch  53 , disconnects the third clutch  13 , and switches the switching circuit  61  to the motor circuit. This increases the rotation speed of the impeller  10  (refer to  FIG. 4A ). 
     When actuating the supercharging device  2  for mild hybrid, the controller  60  connects both the first clutch  53  and the third clutch  13  and switches the switching circuit  61  to the motor circuit. This transfers the power from the motor (motor-generator  30 ) via the pulley  51  and the belt  52  to the engine and assists rotation of the engine (refer to  FIG. 4B ). 
     When actuating the supercharging device  2  as a generator, the controller  60  connects both the first clutch  53  and the third clutch  13  and switches the switching circuit  61  to the generator circuit. This rotates the rotor  31  with the power from the engine. As a result, the power generated with the stator  32  charges the battery  62  via the switching circuit  61  (refer to  FIG. 4C ). 
     When the supercharging device  2  in accordance with the second embodiment is actuated as a mild hybrid or a generator, as shown in  FIGS. 4B and 4C , the third clutch  13  is connected to completely stop the rotation of the sun gear  21 . That is, the second embodiment differs from the first embodiment in that the rotation of the impeller  10  is completely stopped. 
     Advantages 
     In both the supercharging device  1  in accordance with the first embodiment and the supercharging device  2  in accordance with the second embodiment, the carrier  24  of the planetary gear mechanism  20  includes the cylindrical portion  24   a , through which the shaft  11  of the impeller  10  extends. Further, the motor-generator  30  includes the rotor  31 , which is integrated with the outer circumferential surface of the cylindrical portion  24   a , and the stator  32 , which is arranged outward from the rotor  31  in the radial direction. The arrangement of the motor-generator  30  outward in the radial direction from the cylindrical portion  24   a , through which the shaft  11  extends, eliminates the need for arranging the motor-generator  30  outward from the planetary gear mechanism  20  in the axial direction. This avoids enlargement of the supercharging devices  1  and  2  in the axial direction. Further, the diameter of the cylindrical portion  24   a  is decreased and a space is obtained in the radial direction between the cylindrical portion  24   a  and the outer circumference of the ring gear  22 . The space is sufficient for accommodating the motor-generator  30  and enlargement of the supercharging devices  1  and  2  can be avoided in the radial direction. Hence, enlargement of the supercharging devices  1  and  2  is limited in both the axial and radial directions. 
     In the supercharging device  1  in accordance with the first embodiment, the restriction mechanism that restricts rotation of the impeller  10  is configured as the second clutch  12 , which is selectively switchable between the connected state that connects the cylindrical portion  24   a  and the shaft  11  and the disconnected state that disconnects the cylindrical portion  24   a  and the shaft  11 . When the second clutch  12  is connected, the carrier  24  and the shaft  11  become integrally rotatable and rotate the impeller  10 . 
     When actuating the supercharging device  1  as a generator, in a state in which the sun gear  21  is completely stopped (refer to  FIG. 4C ) in the supercharging device  2  in accordance with the second embodiment, the planetary gears  23  are reduced in speed when rotating (orbiting) as the power from the engine rotates the ring gear  22 . As a result, the rotation speed of the rotor  31  is decreased. In the supercharging device  1  in accordance with the first embodiment, as shown in  FIG. 2C , the planetary gears  23  integrally rotate with the sun gear  21  as the power from the engine rotates the ring gear  22 . In this case, the planetary gears  23  are not reduced in speed, and the rotor  31  rotates at a higher rotation speed than that in the second embodiment. That is, in the supercharging device  1  in accordance with the first embodiment, the power generation efficiency is improved when the supercharging device  1  is actuated as a generator. 
     In the supercharging device  2  in accordance with the second embodiment, the restriction mechanism that restricts rotation of the impeller  10  is configured as the third clutch  13 , which is selectively switchable between the connected state that connects the impeller  10  and the housing  40  and the disconnected state that disconnects the impeller  10  and the housing  40 . In the supercharging device  2  in accordance with the second embodiment, when the third clutch  13  is connected, rotation of the impeller  10  is completely stopped. 
     When actuating the supercharging device  2  for mild hybrid, compared to when the planetary gears  23  are rotated integrally with the sun gear  21  in the supercharging device  1  in accordance with the first embodiment (refer to  FIG. 2B ), as shown in  FIG. 4B , the rotation speed (orbit speed) of the planetary gears  23  can be higher when the sun gear  21  is stopped. This allows the power from the motor (motor-generator  30 ) to assist the engine even when the engine is running at higher rotation speeds. 
     OTHER EMBODIMENTS 
     The present invention is not limited to the above embodiments, and the elements in the embodiments may be combined or changed within the scope of the claims. 
     For example, in the second embodiment, the third clutch  13  is arranged between the impeller  10  and the housing  40  and connection of the third clutch  13  stops rotation of the impeller  10 . Nonetheless, the location of the clutch may be changed as long as rotation of the impeller  10  can be stopped. 
     Further, a supercharging device may include both the second clutch  12  and the third clutch  13 . As described above, the arrangement of the second clutch  12  improves the power generation efficiency of the supercharging when actuated as a generator. Further, the arrangement of the third clutch  13  allows for assistance of the engine even in a high speed rotation range. Thus, the arrangement of both the second clutch  12  and the third clutch  13  in a supercharging device allows for suitable switching and improves the supercharging device that functions as a generator and functions to realize mild hybrid.