Abstract:
An oil pump driving device drives an oil pump using at least one of rotation generated by an electric motor and rotation generated by an engine. The oil pump driving device includes: a first transmission unit to which the rotation generated by the electric motor is transmitted; a second transmission unit to which the rotation generated by the engine is transmitted; a third transmission unit configured to transmit rotation to the oil pump; and an engaging unit configured to cause the third transmission unit to engage with the first transmission unit, with the second transmission unit, or with the first and second transmission units.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an oil pump driving device. 
       BACKGROUND ART 
       [0002]    JP 2001-289315A discloses a conventional technique to drive one oil pump by transmitting, to the oil pump, rotation generated by an engine and an electric motor using a planetary gear mechanism. 
       SUMMARY OF INVENTION 
       [0003]    However, with the foregoing technique, the oil pump is always connected to the engine and the electric motor. Even when the oil pump can be driven using only the electric motor, the engine and the oil pump are not disconnected from each other, and rotation generated by the engine is always transmitted to the oil pump. Therefore, the engine drives the oil pump even when the engine does not need to drive the oil pump. This leaves room for improvement in the fuel economy of the engine. 
         [0004]    The present invention has been conceived to solve the foregoing problem. It is an object of the present invention to improve the fuel economy of an engine by disconnecting the engine and an oil pump from each other when the oil pump is driven by an electric motor. 
         [0005]    An oil pump driving device according to an aspect of the present invention is an oil pump driving device for driving an oil pump using at least one of rotation generated by an electric motor and rotation generated by an engine, the oil pump driving device comprising: a first transmission unit, the rotation generated by the electric motor being transmitted to the first transmission unit; a second transmission unit, the rotation generated by the engine being transmitted to the second transmission unit; a third transmission unit configured to transmit rotation to the oil pump; and engaging means configured to cause the third transmission unit to engage with the first transmission unit, with the second transmission unit, or with the first and second transmission units. 
         [0006]    According to this aspect, the third transmission unit transmitting rotation to the oil pump and the second transmission unit to which rotation generated by the engine is transmitted can be disengaged, and the first transmission unit to which rotation generated by the motor is transmitted can be engaged to only the third transmission unit. Thereby, the fuel economy of the engine can be improved. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0007]      FIG. 1  is a schematic cross-sectional view of an oil pump driving device according to an embodiment of the present invention. 
           [0008]      FIG. 2  is an enlarged schematic view of a part of the oil pump driving device. 
           [0009]      FIG. 3  shows a case in which an oil pump is driven using only an electric motor. 
           [0010]      FIG. 4A  is an explanatory diagram showing a method of engagement between a second synchronization gear and a hub. 
           [0011]      FIG. 4B  is an explanatory diagram showing the method of engagement between the second synchronization gear and the hub. 
           [0012]      FIG. 4C  is an explanatory diagram showing the method of engagement between the second synchronization gear and the hub. 
           [0013]      FIG. 5  shows a case in which the oil pump is driven using only an engine. 
           [0014]      FIG. 6  shows a case in which the oil pump is driven using the electric motor and the engine. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0015]    The following describes an embodiment of the present invention with reference to the attached drawings. 
         [0016]    A description is now given of an oil pump driving device according to an embodiment of the present invention with reference to  FIG. 1 .  FIG. 1  is a schematic cross-sectional view of the oil pump driving device. In the following description, the oil pump driving device according to the present embodiment is mounted on a vehicle. 
         [0017]    An oil pump driving device  1  includes a rotation output unit  2 , an engine rotation input unit  3 , a second synchronization gear  4 , a first synchronization gear  5 , a synchromesh mechanism  6 , a motor rotation input unit  7 , a shift fork  8 , and an actuator  9 . 
         [0018]    The rotation output unit  2  includes a first input sprocket  21 , a first chain  22 , and a first output sprocket  23 . 
         [0019]    The first input sprocket  21  is arranged so as to share the same rotation axis O with an electric motor  12 , and includes a shaft part  21   a  extending along the rotation axis O. The shaft part  21   a  is rotatably supported by a case  13  at one end portion thereof, and by the motor rotation input unit  7  at the other end portion thereof. Splines are formed on an outer circumferential wall of the shaft part  21   a  on the electric motor  12  side such that they mate with splines formed on a hub  61  of the synchromesh mechanism  6 . Accordingly, the first input sprocket  21  and the hub  61  rotate integrally. 
         [0020]    The first output sprocket  23  is joined to a driving shaft of an oil pump  11  via a joining member, and transmits, to the oil pump  11 , rotation transmitted via the first input sprocket  21  and the first chain  22 . 
         [0021]    The engine rotation input unit  3  includes a second input sprocket  31 , a second chain  32 , and a second output sprocket  33 . 
         [0022]    Rotation generated by an engine  14  is transmitted to the second input sprocket  31 . The second input sprocket  31  transmits the rotation generated by the engine  14  to the second output sprocket  33  via the second chain  32 . 
         [0023]    The second output sprocket  33  shares the rotation axis O. The shaft part  21   a  of the first input sprocket  21  penetrates through the second output sprocket  33 , and the second output sprocket  33  is rotatably supported by the shaft part  21   a  of the first input sprocket  21 . The second output sprocket  33  has a second output sprocket hollow cylinder  33   a  extending from a radially inner sidewall toward the electric motor  12  along the rotation axis O. Splines are formed on an outer circumferential wall of the second output sprocket hollow cylinder  33   a  such that they mate with splines formed on an inner circumferential wall of the second synchronization gear  4 . Accordingly, the second output sprocket  33  and the second synchronization gear  4  rotate integrally. 
         [0024]    The second synchronization gear  4  shares the rotation axis O. Splines are formed on the inner circumferential wall of the second synchronization gear  4  such that they mate with the splines formed on the second output sprocket hollow cylinder  33   a.  Also, splines are formed on an outer circumferential wall of the second synchronization gear  4  such that they can mate with splines formed on a sleeve  62  of the synchromesh mechanism  6 . 
         [0025]    The motor rotation input unit  7  shares the rotation axis O. A main shaft of the electric motor  12  mates with the motor rotation input unit  7 , and the motor rotation input unit  7  is rotatably supported by the case  13 . The motor rotation input unit  7  has a hollow cylinder  7   a  extending toward the first input sprocket  21  along the rotation axis O. The shaft part  21   a  of the first input sprocket  21  is inserted into and rotatably supported by the hollow cylinder  7   a.  Splines are formed on an outer circumferential wall of the hollow cylinder  7   a  such that they mate with splines formed on an inner circumferential wall of the first synchronization gear  5 . Accordingly, the motor rotation input unit  7  and the first synchronization gear  5  rotate integrally. 
         [0026]    Splines are formed on the inner circumferential wall of the first synchronization gear  5  such that they mate with the splines formed on the hollow cylinder  7   a  of the motor rotation input unit  7 . Also, splines are formed on an outer circumferential wall of the first synchronization gear  5  such that they can mate with the splines formed on the sleeve  62  of the synchromesh mechanism  6 . 
         [0027]    The synchromesh mechanism  6  will now be described with reference to  FIGS. 1 and 2 .  FIG. 2  is a schematic view of a part of the synchromesh mechanism  6 . 
         [0028]    The synchromesh mechanism  6  is interposed between the second synchronization gear  4  and the first synchronization gear  5 , and shares the rotation axis O. The synchromesh mechanism  6  includes the hub  61 , the sleeve  62 , synchronization keys  63 , a second synchronizer ring  64 , and a first synchronizer ring  65 . The synchromesh mechanism  6  causes the first input sprocket  21  to engage with at least one of the second synchronization gear  4  and the first synchronization gear  5 , and transmits at least one of rotation generated by the engine  14  and rotation generated by the electric motor  12  to the oil pump  11 . 
         [0029]    The shaft part  21   a  of the first input sprocket  21  penetrates through the hub  61 . Splines are formed on an inner circumferential wall of the hub  61  such that they mate with the splines formed on the shaft part  21   a  of the first input sprocket  21 . Also, splines are formed on an outer circumferential wall of the hub  61  such that they mate with the splines on the sleeve  62 . Accordingly, the hub  61  and the sleeve  62  rotate integrally. A plurality of cutouts  61   a  extending in an axial direction are formed on an outer circumferential side of the hub  61 . Each cutout  61   a  is provided with a synchronization key  63 . 
         [0030]    Each synchronization key  63  is joined to the hub  61  via a spring  66 , and is in contact with an inner circumferential wall of the sleeve  62  as it is pushed radially outward by the spring  66 . When the sleeve  62  moves in the direction of the rotation axis O via the shift fork  8 , the synchronization keys  63  move in the direction of the rotation axis O, together with the sleeve  62 , due to a friction force generated between the synchronization keys  63  and the sleeve  62 . When the sleeve  62  causes the hub  61  (first input sprocket  21 ) to engage with the second synchronization gear  4  or the first synchronization gear  5  by moving in the direction of the rotation axis O, the synchronization keys  63  come into contact with the second synchronizer ring  64  or the first synchronizer ring  65 , thereby reducing a rotational speed difference between the hub  61  and the second synchronization gear  4  or the first synchronization gear  5 . 
         [0031]    The sleeve  62  has a shape of a hollow cylinder. Splines are formed on the inner circumferential wall of the sleeve  62 , and a groove  62   a  is formed on an outer circumferential wall of the sleeve  62  along a circumferential direction. The shift fork  8  engages with the groove  62   a  such that the sleeve  62  is rotatable on the shift fork  8 . When the shift fork  8  moves in the direction of the rotation axis O, the sleeve  62  moves in the direction of the rotation axis O in harmony with the movement of the shift fork  8 . The splines formed on the inner circumferential wall of the sleeve  62  always mate with the splines formed on the outer circumferential wall of the hub  61 , and also mate with the splines formed on the outer circumferential wall of the second synchronization gear  4  and/or the splines formed on the outer circumferential wall of the first synchronization gear  5  in accordance with the movement of the shift fork  8 . That is to say, the sleeve  62  causes the hub  61  to engage with at least one of the second synchronization gear  4  and the first synchronization gear  5 , and also causes the hub  61  (first input sprocket  21 ) to rotate in synchronization with at least one of the second synchronization gear  4  and the first synchronization gear  5 . 
         [0032]    The second synchronizer ring  64  is interposed between the hub  61  and the second synchronization gear  4 . A radially inner side of the second synchronizer ring  64  comes into contact with the second synchronization gear  4 . The second synchronizer ring  64  has a plurality of chamfers  64   a.  When the sleeve  62  causes the hub  61  to engage with the second synchronization gear  4 , the second synchronizer ring  64 , together with the synchronization keys  63 , reduces the rotational speed difference between the hub  61  and the second synchronization gear  4 , thereby facilitating mating of the splines formed on the sleeve  62  with the splines formed on the outer circumferential wall of the second synchronization gear  4 . 
         [0033]    The first synchronizer ring  65  is interposed between the hub  61  and the first synchronization gear  5 . A radially inner side of the first synchronizer ring  65  comes into contact with the first synchronization gear  5 . The first synchronizer ring  65  has a plurality of chamfers  65   a.  When the sleeve  62  causes the hub  61  to engage with the first synchronization gear  5 , the first synchronizer ring  65  facilitates mating of the splines formed on the sleeve  62  with the splines formed on the outer circumferential wall of the first synchronization gear  5 , similarly to the second synchronizer ring  64 . 
         [0034]    The actuator  9  causes the sleeve  62  to move in the axial direction via the shift fork  8 . The actuator  9  is, for example, a solenoid. 
         [0035]    The operations according to the present embodiment will now be described. 
         [0036]    When driving the oil pump  11  using only the electric motor  12 , the shift fork  8  is moved toward the electric motor  12  using the actuator  9 , and the sleeve  62  causes the first synchronization gear  5  and the hub  61  to engage with each other, as shown in  FIG. 3 . Consequently, the first synchronization gear  5  and the hub  61  (first input sprocket  21 ) rotate in synchronization with each other. Rotation generated by the electric motor  12  is transmitted to the motor rotation input unit  7 , the first synchronization gear  5 , the sleeve  62 , the hub  61 , the first input sprocket  21 , the first chain  22 , and the first output sprocket  23  in the stated order, and then transmitted to the oil pump  11 . The oil pump  11  is driven using only the electric motor  12 , for example, during idling stop control for automatically stopping the engine  14 , and when the vehicle is running at a high speed or a constant speed. 
         [0037]    When driving the oil pump  11  using only the electric motor  12  in the above-described manner, the sleeve  62  leaves the second synchronization gear  4  and the hub  61  disengaged from each other. Therefore, when the engine  14  is driven, rotation generated by the engine  14  is not transmitted to the hub  61 . 
         [0038]    A method of engagement between the first synchronization gear  5  and the hub  61  will now be described in detail with reference to  FIGS. 4A to 4C . For the sake of explanation, the second synchronization gear  4  is omitted in  FIGS. 4A to 4C . 
         [0039]    When the shift fork  8  moves toward the first synchronization gear  5  (electric motor  12 ) in a state where the first synchronization gear  5  and the hub  61  are disengaged from each other, the sleeve  62  and the synchronization keys  63  move toward the first synchronization gear  5  together with the shift fork  8 , and the synchronization keys  63  come into contact with the first synchronizer ring  65  ( FIG. 4A ). Consequently, a friction force is generated between the synchronization keys  63  that rotate together with the sleeve  62  and the first synchronizer ring  65 , and also between the first synchronizer ring  65  and the first synchronization gear  5 . Accordingly, the first synchronization gear  5  rotates, and the rotational speed difference between the hub  61  and the first synchronization gear  5  is reduced. It should be noted that splines  62   b  formed on the sleeve  62  are not in contact with the first synchronizer ring  65 , and the friction force between the first synchronizer ring  65  and the first synchronization gear  5  is relatively small. 
         [0040]    When the sleeve  62  moves further toward the first synchronization gear  5  together with the shift fork  8 , a tip part  62   c  of the splines  62   b  formed on the inner circumferential wall of the sleeve  62  comes into contact with the chamfers  65   a  provided on an outer circumferential wall of the first synchronizer ring  65  ( FIG. 4B ). As the sleeve  62  comes into direct contact with the first synchronizer ring  65 , the friction force between the first synchronizer ring  65  and the first synchronization gear  5  increases, the rotational speed difference between the hub  61  and the first synchronization gear  5  is further reduced, and the hub  61  and the first synchronization gear  5  eventually rotate in synchronization with each other. When the hub  61  and the first synchronization gear  5  rotate in synchronization with each other, the splines  62   b  push away the chamfers  65   a  in the circumferential direction, thereby enabling the sleeve  62  to move further toward the first synchronization gear  5 . 
         [0041]    When the sleeve  62  moves further toward the first synchronization gear  5  together with the shift fork  8 , the splines  62   b  formed on the inner circumferential wall of the sleeve  62  mate with the splines formed on the outer circumferential wall of the first synchronization gear  5  ( FIG. 4C ). As the hub (sleeve  62 ) and the first synchronization gear  5  are rotating in synchronization with each other, the splines  62   b  formed on the inner circumferential wall of the sleeve  62  easily mate with the splines formed on the outer circumferential wall of the first synchronization gear  5 . In the above-described manner, the use of the synchromesh mechanism  6  facilitates engagement between the hub  61  and the first synchronization gear  5 . 
         [0042]    When driving the oil pump  11  using only the engine  14 , the shift fork  8  is moved toward the first input sprocket  21  using the actuator  9 , and the sleeve  62  causes the second synchronization gear  4  and the hub  61  to engage with each other, as shown in  FIG. 5 . 
         [0043]    Rotation generated by the engine  14  is transmitted to the second input sprocket  31 , the second chain  32 , the second output sprocket  33 , the second synchronization gear  4 , the sleeve  62 , the hub  61 , the first input sprocket  21 , the first chain  22 , and the first output sprocket  23  in the stated order, and then transmitted to the oil pump  11 . The oil pump  11  is driven using only the engine  14 , for example, when driving in an urban area. It should be noted that the sleeve  62  leaves the first synchronization gear  5  and the hub  61  disengaged from each other. 
         [0044]    When the sleeve  62  causes the second synchronization gear  4  and the hub  61  to engage with each other, the second synchronization gear  4  and the hub  61  can easily engage with each other in a manner similar to the engagement between the first synchronization gear  5  and the hub  61 . 
         [0045]    In order to drive the oil pump  11  using the electric motor  12  and the engine  14 , the sleeve  62  causes the hub  61  to engage with the second synchronization gear  4  and the first synchronization gear  5  as shown in  FIG. 6 . The oil pump  11  is driven using the electric motor  12  and the engine  14 , for example, when driving on a climbing road and when accelerating the vehicle. 
         [0046]    Rotation generated by the engine  14  is transmitted to the second input sprocket  31 , the second chain  32 , the second output sprocket  33 , the second synchronization gear  4 , and the hub  61 . Rotation generated by the electric motor  12  is transmitted to the motor rotation input unit  7 , the first synchronization gear  5 , and the hub  61 . Thereafter, rotation is transmitted to the first input sprocket  21 , the first chain  22 , and the first output sprocket  23  in the stated order, and then transmitted to the oil pump  11 . 
         [0047]    The advantageous effects of the embodiment of the present invention will now be described. 
         [0048]    When driving the oil pump  11  using only the electric motor  12 , the second synchronization gear  4  and the hub  61  are disengaged from each other, and hence the oil pump  11  and the engine  14  are disconnected from each other. In this way, the load on the engine  14  can be reduced, and the fuel economy of the engine  14  can be improved. 
         [0049]    When driving the oil pump  11  using only the engine  14 , the first synchronization gear  5  and the hub  61  are disengaged from each other. When the first synchronization gear  5  and the hub  61  are in engagement with each other without the electric motor  12  being driven, the engine  14  needs to rotate a driving shaft (rotor) of the electric motor  12  in addition to the oil pump  11 . This increases the load on the engine  14  and lowers the fuel economy. In such a case, the present embodiment makes it possible to prevent lowering of the fuel economy of the engine  14  because the first synchronization gear  5  and the hub  61  are disengaged from each other. 
         [0050]    The sleeve  62  can also cause the hub  61  to engage with the second synchronization gear  4  and the first synchronization gear  5  so as to drive the oil pump  11  using rotation generated by the engine  14  and rotation generated by the electric motor  12 . Consequently, for example, when driving on a climbing road and when accelerating the vehicle, rotation generated by the electric motor  12  is transmitted to the oil pump  11 . In this way, the electric motor  12  assists driving of the oil pump  11 , and rotation generated by the engine  14  can be used for driving of the vehicle. Accordingly, the driving performance of the vehicle can be improved. 
         [0051]    When driving the oil pump  11  using the electric motor  12 , the sleeve  62  causes the hub  61 , which mates with the first input sprocket  21  that transmits rotation to the oil pump  11 , to engage with the first synchronization gear  5  to which rotation generated by the electric motor  12  is transmitted. Accordingly, the first synchronization gear  5  and the hub  61  (first input sprocket  21 ) rotate in synchronization with each other. This makes it possible to suppress rotation generated by the electric motor  12  from being transmitted to the oil pump  11  in a decelerated state. Therefore, when driving the oil pump  11  using the electric motor  12 , an increase in the rotational speed of the electric motor  12  can be suppressed, and hydraulic pressure can be generated by the oil pump  11  without using the high-performance electric motor  12 . 
         [0052]    Furthermore, when driving the oil pump  11  using the engine  14 , the sleeve  62  causes the hub  61 , which mates with the first input sprocket  21  that transmits rotation to the oil pump  11 , to engage with the second synchronization gear  4  to which rotation generated by the engine  14  is transmitted. Accordingly, the second synchronization gear  4  and the hub  61  (first input sprocket  21 ) rotate in synchronization with each other. This makes it possible to suppress rotation generated by the engine  14  from being transmitted to the oil pump  11  in a decelerated state. When the rotational speed of the engine  14  is low, if the rotation of the engine  14  is transmitted to the oil pump  11  in a decelerated state, there is a possibility that the engine  14  alone cannot cause the oil pump  11  to generate the necessary hydraulic pressure. In this case, driving the electric motor  12  enables the oil pump  11  to generate the necessary hydraulic pressure, but requires consumption of electric power by the electric motor  12 . On the other hand, in the present embodiment, the rotation generated by the engine  14  can be suppressed from being transmitted to the oil pump  11  in a decelerated state, and hence the occurrence of the foregoing situation and consumption of electric power can be suppressed. 
         [0053]    The synchromesh mechanism  6  is used to cause the hub  61  (first input sprocket  21 ) to engage with the second synchronization gear  4  to which the rotation generated by the engine  14  is transmitted, or with the first synchronization gear  5  to which the rotation generated by the electric motor  12  is transmitted. Accordingly, smooth engagement can be achieved. 
         [0054]    This concludes the description of the embodiment of the present invention. It should be noted that the above-described embodiment merely illustrates a part of application examples of the present invention, and is not intended to limit a technical scope of the present invention to specific configurations of the above-described embodiment. 
         [0055]    The present application claims for priority based on Japanese Patent Application No. 2013-62498 filed with Japan Patent Office on Mar. 25, 2013, and the entire contents of this application are incorporated in this Description by reference.