Patent Publication Number: US-2023143278-A1

Title: Vehicle rear-side structure

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority from Japanese Patent Application No. 2021-181113 filed on Nov. 5, 2021, the entire contents of which are hereby incorporated by reference. 
     BACKGROUND 
     The disclosure relates to a vehicle rear-side structure. 
     To drive a motor for supplying driving force to a vehicle, a large-capacity vehicle battery, which supplies electric power to a motor, is loaded in an electric automobile or a hybrid electric automobile. This vehicle battery is heavy and large to secure a sufficient continuous driving distance, so that it is disposed under a seat or under a rear floor, for example. 
     Japanese Unexamined Patent Application Publication (JP-A) No. 2013-89448 discloses a battery module that can be protected from the impact of a vehicle accident, such as a collision. The battery module includes a lower frame body for fixing the battery module. The lower frame body includes a front frame, a rear frame, and side frames. The front frame and the side frames each have a fastening flange, and the fastening flanges are partially superimposed on each other and can be fixed together to the vehicle. This structure can enhance the effect of protecting the battery module. 
     JP-A No. 2008-183959 discloses an air-conditioning structure using a crossmember as an air channel. In this structure, the crossmember is disposed between roof side rails of a roof frame forming a body, and an air-conditioning warm air channel and an air-conditioning cool air channel are formed in the crossmember. 
     SUMMARY 
     An aspect of the disclosure provides a vehicle rear-side structure configured to ease an impact applied onto a battery pack of a vehicle upon an occurrence of a collision. The vehicle rear-side structure includes side frames and a rear-end-collision impact reducer. The side frames extend in a front-rear direction of the vehicle and are disposed at positions at which the side frames sandwich the battery pack therebetween in a widthwise direction of the vehicle. The rear-end-collision impact reducer is disposed between and above the side frames at a rear side of the battery pack. The rear-end-collision impact reducer is configured to allow air, which is to be sent to a battery stack included in the battery pack, to flow through the rear-end-collision impact reducer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification. The drawings illustrate an example embodiment and, together with the specification, serve to describe the principles of the disclosure. 
         FIG.  1    is a perspective view of a vehicle including a vehicle rear-side structure according to an embodiment of the disclosure; 
         FIG.  2    is a side sectional view of the vehicle including the vehicle rear-side structure according to the embodiment; 
         FIG.  3 A  is a perspective view of the vehicle rear-side structure according to the embodiment; 
         FIG.  3 B  is a rear view of the vehicle rear-side structure according to the embodiment; 
         FIG.  4    is a cutaway perspective view of the vehicle rear-side structure according to the embodiment; 
         FIG.  5 A  is a side sectional view of the vehicle rear-side structure according to the embodiment; 
         FIG.  5 B  is an enlarged side sectional view of a rear-end-collision impact reducer of the vehicle rear-side structure according to the embodiment; 
         FIG.  6 A  is a perspective view illustrating the configuration of a communicating duct in the vehicle rear-side structure according to the embodiment; 
         FIG.  6 B  is a top view illustrating the configuration of the communicating duct in the vehicle rear-side structure according to the embodiment; and 
         FIGS.  7 A,  7 B,  8 A, and  8 B  are side sectional views illustrating a sequential change of the shape of the vehicle rear-side structure according to the embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The technologies disclosed in the above-described publications still have room for improvement to effectively protect a battery module from the impact of a collision. 
     In the technology disclosed in JP-A No. 2013-89448, although the battery module is protected by the frames provided in the vehicle, using many frames enlarges the structure for protecting the battery module. This may increase the weight of the vehicle body and the complexity of the body structure and also raise the cost. 
     JP-A No. 2008-183959 describes that a member of a vehicle, such as a crossmember, is used to support the vehicle and is also used as an air channel, but it does not discuss the use of the crossmember to protect a battery module. 
     It is thus desirable to provide a vehicle rear-side structure including a member that can protect a battery stack loaded in a vehicle and can also be used as an air channel. 
     A vehicle  11  including a vehicle rear-side structure  20  according to an embodiment of the disclosure will now be described below in detail with reference to the accompanying drawings. Note that the following description is directed to an illustrative example of the disclosure and not to be construed as limiting to the disclosure. Factors including, without limitation, numerical values, shapes, materials, components, positions of the components, and how the components are coupled to each other are illustrative only and not to be construed as limiting to the disclosure. Further, elements in the following example embodiment which are not recited in a most-generic independent claim of the disclosure are optional and may be provided on an as-needed basis. The drawings are schematic and are not intended to be drawn to scale. Throughout the present specification and the drawings, elements having substantially the same function and configuration are denoted with the same numerals to avoid any redundant description. In the following description, front, rear, top, bottom, left, and right directions are used. Left and right are those when the vehicle  11  is seen from the rear side. 
       FIG.  1    is a perspective view of the vehicle  11  including the vehicle rear-side structure  20 . 
     The vehicle  11  is an automobile or a train, for example. A battery pack  10  having a high storage capacity is loaded in the vehicle  11  to supply electric power to a motor and various other electrical components mounted in a body  12 . Examples of the vehicle  11  are an electric vehicle (EV), a hybrid electric vehicle (HEV), and a plug-in hybrid electric vehicle (PHEV). 
     The battery pack  10  is disposed in a storage space  13  formed under a rear floor  15 . 
     The vehicle rear-side structure  20  is used to ease the impact of a collision on the battery pack  10  and is disposed to substantially surround the battery pack  10 . The structure and other features of the vehicle rear-side structure  20  will be discussed later by mainly referring to  FIGS.  3 A and  3 B . 
       FIG.  2    is a side sectional view of the vehicle  11  including the vehicle rear-side structure  20 . 
     The body  12  of the vehicle  11  includes a frame  18 . The frame  18  is disposed near the bottom of the body  12  and continuously extends from the front side to the rear side of the body  12 . The frame  18  is provided on each of the left and right sides of the body  12 . The rear side of the frame  18  serves as a side frame  21 . A rear frame  16  is disposed near the rear end of each side frame  21  and extends in the widthwise direction of the vehicle  11 . The upper end (surface) of the battery pack  10  is located at a higher position than the upper end (surface) of the side frames  21 . This will be discussed later. 
     The vehicle rear-side structure  20  includes the side frames  21  and a rear-end-collision impact reducer  28 . 
     The rear-end-collision impact reducer  28  is disposed at the rear side of the battery pack  10 . The rear-end-collision impact reducer  28  has a function of easing the impact of a rear-end collision. Details of the rear-end-collision impact reducer  28  will be discussed later by mainly referring to  FIGS.  5 A and  5 B . 
     A rear-end collision is an accident where a vehicle, such as a large vehicle  29  illustrated in  FIG.  2   , hits the vehicle  11  from behind. If the bottom end of the body of the large vehicle  29  is located at a higher position than the top surface of the side frame  21 , an override collision may occur. Upon the occurrence of an override collision, the battery pack  10  of the vehicle  11  may be seriously influenced by the impact of the collision. In the embodiment, the rear-end-collision impact reducer  28  is provided in the vehicle  11  to protect the battery pack  10  from an override collision. This will be discussed later. 
       FIG.  3 A  is a perspective view of the vehicle rear-side structure  20 .  FIG.  3 B  is a rear view of the vehicle rear-side structure  20 . 
     As illustrated in  FIG.  3 A , the rear-end-collision impact reducer  28  is disposed at the rear side of the battery pack  10 . The rear-end-collision impact reducer  28  is a substantially hollow member extending in the left-right direction and is an extrusion-molded aluminum member. Air, which is to be sent to a battery stack included in the battery pack  10 , flows through the rear-end-collision impact reducer  28 . This structure will be discussed later. 
     The battery pack  10  is a module having a built-in battery stack  23 , which will be explained later. The configuration of the battery pack  10  will be discussed later by mainly referring to  FIG.  5 A . 
     A blower  31  and an inlet duct  32  are coupled to the left end of the rear-end-collision impact reducer  28 . 
     The blower  31  contains a motor and a fan to send air. The blower  31  is coupled to the left end of the inlet duct  32 . 
     The left end of the inlet duct  32  is coupled to the blower  31 , while the right end thereof is coupled to the rear-end-collision impact reducer  28 . The right end of the rear-end-collision impact reducer  28  may be closed to enhance the airtightness. 
     Air from a compartment  14  of the vehicle  11  is sent to the battery stack  23  contained in the battery pack  10  via the blower  31 , the inlet duct  32 , and the rear-end-collision impact reducer  28 . With this structure, the battery stack  23  is cooled to be at a preset temperature range. An air channel formed from the rear-end-collision impact reducer  28  to the battery pack  10  will be explained later by mainly referring to  FIG.  6 A . 
     As illustrated in  FIG.  3 B , the side frame  21  is provided at each of the left and right sides of the body  12 . The rear-end-collision impact reducer  28  is provided between the side frames  21  next to the battery pack  10  and is disposed at the rear side of the battery pack  10 . The rear-end-collision impact reducer  28  is also located above the side frames  21 . The left and right sides of the rear-end-collision impact reducer  28  are bonded to the top surfaces of the side frames  21  by welding or fastening. 
     The top surface of the battery pack  10  is located at a higher position than the top surfaces of the side frames  21 . In one example, a length L 10  (see  FIG.  3 B ) between the top surface of the battery pack  10  and that of the side frame  21  is about 6 cm. With this configuration, in the case of the occurrence of the above-described override collision, the vehicle rear-side structure  20  may be seriously influenced by the impact of the collision. In the embodiment, however, the rear-end-collision impact reducer  28  is disposed at the rear side of the battery pack  10  and is located above the side frames  21 . This structure can protect the battery pack  10  from a rear-end collision, which will be discussed later. 
       FIG.  4    is a cutaway perspective view of the vehicle rear-side structure  20 . 
     In the vehicle rear-side structure  20 , the battery pack  10  is disposed in a region covered by the rear floor  15  and a vehicle floor  17 . 
     In one example, multiple battery stacks  23  are contained in the battery pack  10 . 
     Each battery stack  23  is constituted by multiple battery cells coupled to each other. The battery cells are secondary cells, such as nickel-metal hydride batteries or lithium-ion batteries. The battery cells each have a rectangular flat shape, for example, and are arranged along the longitudinal direction, that is, the left-right direction, of the battery stack  23 . The battery cells are arranged at substantially equal intervals with a gap therebetween. 
     The battery pack  10  includes a battery case  33  and a battery cover  34 . The battery case  33  is a container-like member with a top surface opened. The battery cover  34  is a plate-like member which closes the opened top surface of the battery case  33  from above. Components such as the battery stacks  23  are stored in a space substantially sealed by the battery case  33  and the battery cover  34 . 
       FIG.  5 A  is a side sectional view of the vehicle rear-side structure  20 .  FIG.  5 B  is an enlarged side sectional view of the rear-end-collision impact reducer  28 . 
     As illustrated in  FIG.  5 A , the rear-end-collision impact reducer  28  is disposed at the rear side of the battery pack  10 . The upper end (surface) of the rear-end-collision impact reducer  28  is located at a higher position than that of the battery pack  10 . Additionally, the upper end (surface) of the rear-end-collision impact reducer  28  is located at a higher position than that of the battery stack  23 . With this configuration, in the case of the occurrence of the above-described override collision, the battery pack  10  and the battery stack  23  can be protected from the override collision. This will be discussed later. 
     A tilt surface  24  is formed on the rear-end-collision impact reducer  28 . The top end of the tilt surface  24  is located at a position equivalent to or higher than the rear end of the top surface of the battery cover  34  of the battery  10 . With this configuration, in the case of the occurrence of an override collision with another vehicle, such as the large vehicle  29  illustrated in  FIG.  2   , the rear-end-collision impact reducer  28  can divert the large vehicle  29  toward the upward direction, thereby effectively protecting the battery stack  23  from the override collision. Additionally, as stated above, the rear-end-collision impact reducer  28  is not a member formed by bend-molding a steel strip, but is an extrusion-molded aluminum member. Hence, the rear-end-collision impact reducer  28  has a high mechanical strength. This can also effectively protect the battery stack  23  from the override collision. The upper end (surface) of the rear-end-collision impact reducer  28  is located at a higher position than the upper end (surface) of the side frames  21 . This can shift the impact of a rear-end collision toward the upward direction, thereby effectively protecting the battery stack  23  from the override collision. 
     As illustrated in  FIG.  5 B , the tilt surface  24  is formed at the upper rear side of the rear-end-collision impact reducer  28 . The tilt surface  24  is tilted upward toward the front side. With this configuration, upon the occurrence of an override collision with the large vehicle  29 , it is possible to shift the large vehicle  29  along the top surface of the battery cover  34 , thereby effectively protecting the battery stack  23  from the override collision. 
     The angle θ of the tilt surface  24  with respect to the horizontal surface is preferably 45 degrees or smaller, and more preferably, 30 degrees or smaller. Setting the angle θ to this range can enhance the effect of the rear-end-collision impact reducer  28  protecting the battery stack  23  from an override collision. 
       FIG.  6 A  is a perspective view illustrating the configuration of a communicating duct  25  in the vehicle rear-side structure  20 .  FIG.  6 B  is a top view illustrating the configuration of the communicating duct  25  seen from a different angle. 
     As illustrated in  FIGS.  6 A and  6 B , the communicating duct  25  is coupled to the intermediate portion of the rear-end-collision impact reducer  28 . The communicating duct  25  causes the rear-end-collision impact reducer  28  and the battery stack  23  (see  FIG.  4   ) to communicate with each other. 
     The communicating duct  25  includes a first communicating duct  26  and a second communicating duct  27 . The rear end of the first communicating duct  26  communicates with the left side of the rear-end-collision impact reducer  28 . The front end of the first communicating duct  26  communicates with a battery stack  23  (see  FIG.  4   ) located on the front side. The rear end of the second communicating duct  27  communicates with the right side of the rear-end-collision impact reducer  28 . The front end of the second communicating duct  27  communicates with a battery stack  23  (see  FIG.  4   ) located on the rear side. 
     A first air channel  35  is an air channel formed inside of the inlet duct  32 , the rear-end-collision impact reducer  28 , and the first communicating duct  26 . A second air channel  36  is an air channel formed inside of the inlet duct  32 , the rear-end-collision impact reducer  28 , and the second communicating duct  27 . 
     The second air channel  36  is longer than the first air channel  35 . In the embodiment, the cross-sectional area of the second communicating duct  27  is made larger than that of the first communicating duct  26 . This makes a pressure drop of the second communicating duct  27  having a longer air channel smaller, so that the pressure drop of the first communicating duct  26  and that of the second communicating duct  27  become substantially equal to each other. It is thus possible to reduce the temperature difference between a front-side battery stack  23  cooled by air passing through the first air channel  35  and a rear-side battery stack  23  cooled by air passing through the second air channel  36 . 
     The inside of the rear-end-collision impact reducer  28  is formed substantially straight from the left end to the right end without any locally decreased sectional area. This can reduce the pressure drop inside the rear-end-collision impact reducer  28  and make it less likely for a stress to concentrate on a specific portion of the rear-end-collision impact reducer  28 . 
       FIGS.  7 A,  7 B,  8 A, and  8 B  are side sectional views illustrating a sequential change of the shape of the vehicle rear-side structure  20  due to the occurrence of an override collision with the large vehicle  29 . 
     As illustrated in  FIG.  7 A , upon the occurrence of an override collision where the large vehicle  29  hits the vehicle  11  from behind, the body of the large vehicle  29  enters the inside of the vehicle  11  from above the rear frame  16 . 
     As illustrated in  FIG.  7 B , when the body of the large vehicle  29  further advances toward the front side, the front bottom end of the large vehicle  29  abuts against the tilt surface  24  of the rear-end-collision impact reducer  28 . Then, the impact of the collision is transmitted to the side frames  21  from the rear-end-collision impact reducer  28  and is thus eased. 
     As illustrated in  FIG.  8 A , the large vehicle  29  further advances to enter the vehicle  11 . At this time, the front bottom end of the large vehicle  29  is guided toward the upward direction by the tilt surface  24  of the rear-end-collision impact reducer  28 . As a result, the entire bottom side of the vehicle  11  is moved downward and the rear side of the battery pack  10  is also moved downward. It is thus less likely that the impact is directly applied to the battery pack  10 . 
     As illustrated in  FIG.  8 B , the front end of the large vehicle  29  stops over the battery pack  10 . Because of the function of the rear-end-collision impact reducer  28 , the battery pack  10  is not seriously influenced by the impact of the collision with the large vehicle  29 . It is thus less likely that the battery stacks  23  loaded in the battery pack  10  are damaged. 
     According to the above-described embodiment, the following advantages are achieved. 
     As illustrated in  FIG.  3 A , the rear-end-collision impact reducer  28 , which is a member for easing the impact of a collision on the battery pack  10 , also serves as a member for allowing air for cooling the battery stacks  23  to flow therethrough. This can save the provision of part of a duct for allowing cooling air to flow and thus reduce the number of components around the battery pack  10 , thereby simplifying the configuration and reducing the cost. 
     As illustrated in  FIGS.  7 A through  8 B , in the case of the occurrence of a rear-end collision, the front part of a vehicle having hit the vehicle  11  from behind, such as the large vehicle  29 , runs onto the tilt surface  24  of the rear-end-collision impact reducer  28 . This can ease the impact of the collision and accordingly protect the battery pack  10  from the impact. 
     As illustrated in  FIG.  3 B , both sides of the rear-end-collision impact reducer  28  are bonded to the side frames  21 . This can shift the impact of a collision applied to the rear-end-collision impact reducer  28  to the side frames  21 . 
     As illustrated in  FIG.  5 A , the upper end (surface) of the rear-end-collision impact reducer  28  is located at a higher position than the upper end (surface) of the battery stack  23 . In the case of the occurrence of a rear-side collision, the front part of a vehicle having hit the vehicle  11  from behind, such as the large vehicle  29 , runs onto the rear-end-collision impact reducer  28 . The impact of the collision on the battery stack  23  can thus be eased. 
     As illustrated in  FIG.  6 A , as a result of decreasing the pressure drop of the second communicating duct  27  having a longer air channel, air can be supplied to the plural battery stacks  23  substantially equally. 
     The disclosure has been described above through illustration of the above-described embodiment. However, the disclosure is not limited to this embodiment. Various modifications can be made without departing from the spirit and scope of the disclosure. The above-described aspects may be combined in a suitable manner.