Abstract:
A driving force transmission device of a vehicle includes: a main body; a carrying up gear; a drive shaft; and a blocking member. A gear that transmits a driving force to the vehicle is housed in the main body. The carrying up gear carries up a lubricating oil stored in the main body. The drive shaft has, in the shaft, a lubricating oil storage space into which the carried up lubricating oil is introduced and a lubricating oil discharge hole through which the lubricating oil in the lubricating oil storage space is supplied to a bearing unit. The blocking member blocks the lubricating oil discharge hole in accordance with a rotational speed of the drive shaft.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority from Japanese Patent Application No. 2016-107354 filed on May 30, 2016, the entire contents of which are hereby incorporated by reference. 
       BACKGROUND 
     1. Technical Field 
       [0002]    The present invention relates to a driving force transmission device of a vehicle. 
       2. Related Art 
       [0003]    In the related art, for instance, in Japanese Unexamined Patent Application Publication (JP-A) No. 2007-057093, a configuration in which, in a decelerator that uses an electric motor as a driving source and includes a differential gear and a parallel shaft, a bearing is lubricated in an oil passage through a drive shaft including a gear from a catch tank provided above the gear is disclosed. 
         [0004]    In addition, in JP-A No. 2012-017764, a configuration in which, in a lubrication structure of a planetary gear mechanism that is used for a drive unit configured to distribute a driving force of a motor and an engine in a hybrid vehicle, oil trapped around the planetary gear lubricates a bearing through an opening guide (a liquid reservoir) of a shaft for the planetary gear is disclosed. 
         [0005]    In a unit including a rotating member such as a gear mechanism, if there is insufficient lubricating oil for lubricating the rotating member, there is a possibility of defects such as burning of a gear. In particular, in a method in which a lubricating oil is dispersed by being carried up by a gear and the lubricating oil is supplied, since an amount of lubricating oil dispersed depends on a rotational speed, an amount of lubricating oil dispersed particularly during low speed running decreases and a bearing and the like on a motor shaft at a distance from an oil surface are likely to be insufficiently lubricated. Accordingly, it is desirable to appropriately supply a lubricating oil in accordance with running conditions. 
         [0006]    However, in the technology described in JP-A No. 2007-057093, supply of a lubricating oil in accordance with running conditions is not considered at all. In addition, in the technology described in JP-A No. 2012-017764, a lubricating oil is supplied by an oil pump and when lubricating oil is dispersed by carrying up, optimal supply of the lubricating oil in accordance with running conditions is not considered at all. 
       SUMMARY OF THE INVENTION 
       [0007]    It is desirable to provide a novel and improved driving force transmission device of a vehicle that makes it possible to optimally perform lubrication in accordance with running conditions of the vehicle. 
         [0008]    An aspect of the present invention provides a driving force transmission device of a vehicle, the driving force transmission device including: a main body in which a gear configured to transmit a driving force to the vehicle is housed; a carrying up gear configured to carry up a lubricating oil stored in the main body; a drive shaft that has, in the shaft, a lubricating oil storage space into which the carried up lubricating oil is introduced and a lubricating oil discharge hole through which the lubricating oil in the lubricating oil storage space is supplied to a bearing unit; and a blocking member configured to block the lubricating oil discharge hole in accordance with a rotational speed of the drive shaft. 
         [0009]    The blocking member may open the lubricating oil discharge hole when the drive shaft rotates at a low speed and supply the lubricating oil in the lubricating oil storage space to the bearing unit, and block the lubricating oil discharge hole when the drive shaft rotates at a high speed and accumulate the lubricating oil in the lubricating oil storage space. 
         [0010]    The blocking member may be disposed inside the lubricating oil storage space to block the lubricating oil discharge hole with a centrifugal force generated by a rotation of the drive shaft. The driving force transmission device may include an elastic member configured to perform biasing in a direction in which the blocking member is separated from the lubricating oil discharge hole. 
         [0011]    The elastic member may include a conical spring. 
         [0012]    The lubricating oil storage space may have an end that is open in an axial direction of the drive shaft. The driving force transmission device may include a rib on a wall surface of the main body, the rib guiding the carried up lubricating oil to the end. 
         [0013]    The bearing unit may include a bearing. The driving force transmission device may include an annular bearing holder that protrudes from the wall surface of the main body and holds the bearing. The carried up lubricating oil may be introduced into a space inside the bearing holder from an opening provided in the bearing holder and be introduced into the lubricating oil storage space from the end. 
         [0014]    The driving force transmission device of a vehicle may include: a guide member configured to guide the lubricating oil introduced into the space inside the bearing holder from the opening to an inside of the lubricating oil storage space. 
         [0015]    The gear may include a helical gear. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a schematic cross-sectional view illustrating a configuration of a gear box of a vehicle according to an example of the present invention and the vicinity thereof; 
           [0017]      FIG. 2  is a schematic cross-sectional view illustrating a configuration of a gear box of a vehicle according to the example of the present invention and the vicinity thereof; 
           [0018]      FIG. 3  is a schematic cross-sectional view illustrating an enlarged vicinity of a gear and a drive shaft of  FIG. 2 ; 
           [0019]      FIG. 4  is a schematic cross-sectional view illustrating a cross section along a dashed line C-C′ in  FIG. 3 ; 
           [0020]      FIG. 5  is a schematic cross-sectional view illustrating a cross section along a dashed line B-B′ in  FIG. 3  and is a schematic diagram during high speed running; 
           [0021]      FIG. 6  is a schematic diagram illustrating a state in which a gear box is viewed in directions of rotation axes of gears similarly to  FIG. 1  and is a schematic diagram during low speed running; and 
           [0022]      FIG. 7  is a schematic cross-sectional view illustrating a cross section along a dashed line B-B′ in  FIG. 3  similarly to  FIG. 5  and is a schematic diagram during low speed running. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    Hereinafter, preferred examples of the present invention will be described in detail with reference to the appended drawings. Note that, in this specification and the appended drawings, structural elements that have substantially the same function and structure are denoted with the same reference numerals, and repeated description of these structural elements is omitted. 
         [0024]      FIG. 1  and  FIG. 2  are schematic cross-sectional views illustrating a configuration of a gear box  100  of a vehicle according to an example of the present invention and the vicinity thereof. In one example, the gear box  100  may serve as a “driving force transmission device.” As an instance, the gear box  100  is a parallel shaft using a helical gear and is a decelerator of an EV vehicle which performs lubrication with an oil bath splash scheme. 
         [0025]      FIG. 1  illustrates a state in which the gear box  100  is viewed in a direction of rotation axes of gears. In addition,  FIG. 2  schematically illustrates a state in which the inside of the gear box  100  is viewed from the upper side in  FIG. 1  in a direction orthogonal to rotation axes of gears. As illustrated in  FIG. 1  and  FIG. 2 , the gear box  100  includes a gear  10 , a reduction gear  20 , and a gear  30 . The reduction gear  20  includes a large diameter gear  22  and a small diameter gear  24 . The gears are supported by a main body  110  of the gear box  100  through a bearing  40 . While the gears include helical gears in the configuration instance illustrated in  FIG. 1  and  FIG. 2 , the gears may include spur gears. 
         [0026]    As illustrated in  FIG. 1  and  FIG. 2 , the gear  10  is engaged with the large diameter gear  22 , and the small diameter gear  24  is engaged with the gear  30 . In addition, as illustrated in  FIG. 2 , the gear  10  is integrally formed with a drive shaft  202  of a prime mover (motor)  200  and the gear  30  is integrally formed with a drive shaft  42  of a wheel  300 . In such a configuration, when the drive shaft  202  and the gear  10  rotate in a direction of an arrow A 1  in  FIG. 1  due to the driving of the prime mover  200 , the reduction gear  20  rotates as the gear  10  rotates, the gear  30  also rotates in a direction of an arrow A 2 , and the wheel  300  is driven. 
         [0027]      FIG. 1  illustrates a state during high speed running. As illustrated in  FIG. 1 , lubricating oil accumulates in a bottom of the gear box  100  and a part of the gear  30  is immersed in the lubricating oil. When the gear  30  rotates in a direction of the arrow A 2 , lubricating oil is carried up by the gear  30  and is supplied to the gear  10 , the gear  20 , the gear  30  and the bearing  40 . Therefore, it is possible to lubricate the gears and the bearing  40 . In this manner, the gear  30  functions as a carrying up gear configured to carry up lubricating oil. 
         [0028]    In a gear of an oil bath splash scheme illustrated in  FIG. 1  and  FIG. 2 , a direction in which lubricating oil is dispersed by carrying up is originally a circumferential tangential direction in a rotation direction of the gear  30 , but the helical gear has a twist angle. Therefore, lubricating oil is dispersed in a resultant force direction (a direction of an arrow A 12  illustrated in  FIG. 2 ) from an axial direction and a circumferential tangential direction of a gear along a twist angle. In addition, since an amount of lubricating oil dispersed is proportional to a peripheral speed of a gear, the dispersing amount increases as a vehicle speed increases. Therefore, an amount of lubricating oil dispersed increases during high speed running, and the gear  10 , the gear  20 , the gear  30  and the bearing  40  can be sufficiently lubricated with the dispersed lubricating oil. 
         [0029]      FIG. 3  is a schematic cross-sectional view illustrating an enlarged vicinity of the gear  10  and the drive shaft  202  in  FIG. 2 . In addition,  FIG. 4  is a schematic cross-sectional view illustrating a cross section along a dashed line C-C′ in  FIG. 3 . In addition,  FIG. 5  is a schematic cross-sectional view illustrating a cross section along a dashed line B-B′ in  FIG. 3  and illustrates a state during high speed running. As illustrated in  FIG. 3  and  FIG. 4 , in the vicinity of the bearing  40  disposed on an end of the gear  10  of the drive shaft  202 , a bearing holder  112  into which the bearing  40  is inserted is provided. The bearing holder  112  is integrally formed with the main body  110 . A notch is provided in the upper part of the bearing holder  112  and an opening  112   a  is formed by the notch. The opening  112   a  communicates with a space  114  formed by the bearing holder  112 , the main body  110  and the bearing  40 . 
         [0030]    As illustrated in  FIG. 4 , a rib  115  extends vertically upward from the upper part of the bearing holder  112 . The rib  115  is disposed adjacent to the opening  112   a.  In addition, a guide  116  is provided at a position corresponding to the center of the drive shaft  202  inside the bearing holder  112 . The guide  116  has a gutter-like shape, is integrally formed with the main body  110 , and is provided below the opening  112   a.    
         [0031]    As illustrated in  FIG. 3 , the drive shaft  202  has a hollow structure and a lubricating oil storage space  202   a.  The guide  116  is inserted into the lubricating oil storage space  202   a  inside the drive shaft  202  from the main body  110 . 
         [0032]    Lubricating oil dispersed in a direction of the arrow A 12  in  FIG. 2  during high speed running is introduced into the space  114  through the rib  115  and the opening  112   a  in a direction of an arrow A 14  as illustrated in  FIG. 3 . The lubricating oil introduced into the space  114  is introduced into the drive shaft  202  from an end of the drive shaft  202  along the guide  116  disposed below the opening  112   a  and is supplied to the lubricating oil storage space  202   a  in the shaft. 
         [0033]    As illustrated in  FIG. 5 , a lubricating oil discharge hole  202   b  is provided in the drive shaft  202 . The lubricating oil storage space  202   a  inside the drive shaft  202  and an external area communicate through the lubricating oil discharge hole  202   b.    
         [0034]    A conical spring  301  and a weight  302  are provided in each lubricating oil discharge hole  202   b.  In one example, the conical spring  301  may serve as an “elastic member.” In one example, the weight  302  may serve as a “blocking member.” The conical spring  301  includes a compression spring which has one end fixed to an inner circumferential surface of the drive shaft  202  and the other end fixed to the weight  302 . Also, the conical spring  301  is an instance of an elastic member and may include another spring. 
         [0035]    During high speed running as illustrated in  FIG. 5 , a rotational speed of the drive shaft  202  is high and a centrifugal force applied to the weight  302  increases. When the centrifugal force applied to the weight  302  exceeds an elastic force (spring force) with which the conical spring  301  is compressed, the conical spring  301  is compressed and the weight  302  and the conical spring  301  block the lubricating oil discharge hole  202   b.  More specifically, when the centrifugal force applied to the weight  302  is greater than an elastic force with which the conical spring  301  is compressed, since a force with which the weight  302  is brought into close contact with an inner surface of the drive shaft  202  is applied and adjacent wires constituting the conical spring  301  come in close contact with each other, the lubricating oil discharge hole  202   b  is blocked. Accordingly, the lubricating oil introduced into the lubricating oil storage space  202   a  remains in the drive shaft  202 . 
         [0036]      FIG. 6  is a schematic diagram illustrating a state in which the gear box  100  is viewed in a direction of rotation axes of gears similarly to  FIG. 1  and illustrates a state during low speed running. In addition,  FIG. 7  is a schematic cross-sectional view illustrating a cross section along a dashed line B-B′ in  FIG. 3  similarly to  FIG. 5  and illustrates a state during low speed running. During low speed running, since the gear  30  rotates slowly, an amount of lubricating oil dispersed by being carried up by the gear  30  is small and it is difficult to lubricate a part away from an oil surface of the lubricating oil. That is, the lubricating oil is not able to be dispersed to the rib  115  positioned above the drive shaft  202  and the opening  112   a  of the bearing holder  112 . 
         [0037]    On the other hand, during high speed running, a centrifugal force applied to the weight  302  is greater than an elastic force of the conical spring  301  and the weight  302  and the conical spring  301  block the lubricating oil discharge hole  202   b.  However, during low speed running, a centrifugal force applied to the weight  302  decreases and the weight moves to the center of the drive shaft  202  as illustrated in  FIG. 7 . Therefore, a state in which the weight  302  and the conical spring  301  block the lubricating oil discharge hole  202   b  is released, and the lubricating oil discharge hole  202   b  is opened. As a result, during high speed running, the lubricating oil accumulated in the lubricating oil storage space  202   a  is discharged from the lubricating oil discharge hole  202   b  and is supplied to the bearings  40  at both ends of the drive shaft  202 . 
         [0038]    As described above, in the present example, the lubricating oil storage space  202   a  for in-shaft lubrication is provided in the drive shaft  202  which is relatively distant from an oil surface of the lubricating oil, and the lubricating oil discharge hole  202   b  is opened to the bearing  40  supporting the drive shaft  202  from the lubricating oil storage space  202   a.  During low speed running, when the lubricating oil discharge hole  202   b  is opened, the lubricating oil is discharged from the lubricating oil storage space  202   a  and is supplied to the bearing  40 . In addition, during high speed running, the lubricating oil dispersed by being carried up by the gear  30  is directly supplied to the bearing  40  and is supplied to the lubricating oil storage space  202   a.  In addition, during high speed running, when the lubricating oil discharge hole  202   b  is blocked, discharge of the lubricating oil from the lubricating oil storage space  202   a  stops and the lubricating oil accumulates in the lubricating oil storage space  202   a.    
         [0039]    In addition, the conical spring  301  and the weight  302  are attached to the inner side of the lubricating oil discharge hole  202   b.  During low speed running, since a centrifugal force applied to the weight  302  is equal to or less than a spring force of the conical spring  301 , the weight is positioned at the center of the drive shaft  202  and the lubricating oil discharge hole  202   b  is opened. In addition, during high speed running, a centrifugal force applied to the weight  302  is greater than a spring force of the conical spring  301  and it is possible to block the lubricating oil discharge hole  202   b  by the weight  302  and the conical spring  301 . 
         [0040]    In addition, during high speed running, the dispersed lubricating oil flows into the space  114  on a rear surface of the bearing  40  through the rib  115  and is supplied to the lubricating oil storage space  202   a  inside the drive shaft  202  through the guide  116 . 
         [0041]    During low speed running, a proportion of lubricating oil dispersed is small. Particularly, it is difficult to supply lubricating oil to a place which is relatively distant from an oil surface of a lubricating oil through dispersing. In addition, during low speed running, since an amount of heat generated by the bearing  40  is also low, an amount of lubricating oil supplied is smaller than that during high speed running. Therefore, during low speed running, when the lubricating oil discharge hole  202   b  is opened, the bearing  40  is lubricated with the lubricating oil accumulated in the lubricating oil storage space  202   a.  On the other hand, during high speed running, a proportion of lubricating oil dispersed is large, and the bearing  40  can be lubricated with the dispersed lubricating oil. Therefore, the lubricating oil discharge hole  202   b  is blocked and the lubricating oil accumulates in the lubricating oil storage space  202   a.  The amount of lubricating oil which decreases in the lubricating oil storage space  202   a  during low speed running is restored to its original state during high speed running, and a concern of there being insufficient lubricating oil during low speed running can be eliminated. 
         [0042]    As described above, according to the present example, when lubricating oil accumulates in the lubricating oil storage space  202   a  during high speed running and is discharged during low speed running, a structure in which insufficient lubrication does not occur in all speed ranges such as during low speed running and during high speed running can be obtained and lubrication of the bearing  40  can be preserved. Therefore, it is not necessary to forcibly perform lubrication using an oil pump or the like and it is possible to ensure necessary lubrication with a simple structure. 
         [0043]    Although the preferred examples of the present invention have been described in detail with reference to the appended drawings, the present invention is not limited thereto. It is obvious to those skilled in the art that various modifications or variations are possible insofar as they are within the technical scope of the appended claims or the equivalents thereof. It should be understood that such modifications or variations are also within the technical scope of the present invention. 
         [0044]    As described above, according to the present invention, it is possible to provide a driving force transmission device of a vehicle that makes it possible to optimally perform lubrication in accordance with running conditions of the vehicle.