JP5464268B2 - Lower body structure - Google Patents

Description

  The present invention relates to a vehicle body lower structure that stabilizes an air flow under a vehicle body floor.

  Conventionally, a floor under cover has been provided at the lower part of the vehicle body in order to rectify air under the vehicle body floor and improve aerodynamic characteristics. On the other hand, there is a desire to lower the floor as much as possible in order to secure the interior space of the vehicle body. In order to meet this demand, it is necessary to lower the floor under cover disposed below the floor as much as possible.

  In Patent Document 1, it is proposed to provide a wing-shaped rectifying fin on a diffuser at the rear of the vehicle body or a floor under cover of the vehicle body. When the rectifying fin is provided under the floor of the vehicle body, downforce is generated in the vehicle body. As a result, the grip force of the tire is improved, so that the steering performance such as turning performance and straight running stability is improved.

  However, when the rectifying fins are provided on the front floor under cover, there is a problem that the rectification under the floor is disturbed. In addition, if the rectifying fins protrude downward from the front floor undercover, the appearance deteriorates, the stepping stones easily hit the rectifying fins, the road surface easily interferes with the rectifying fins, and the height of the vehicle body from the ground is reduced. .

  Among the above problems, the problem of chipping that makes it easy for stepping stones to hit the rectifying fins, the problem of interference between the rectifying fins and the road surface, and the problem that the height of the vehicle body from the ground is lowered are, for example, the upper part of the front floor under cover. It can be solved by placing it on However, if the front floor under cover is installed on the upper side, it will not be possible to meet the desire to secure the indoor space by lowering the floor as much as possible.

JP 2009-90681 A

  The object of the present invention is to provide operability, aerodynamic characteristics, interference between the front floor undercover and the road surface, and chipping resistance against stepping stones despite the provision of the wing fins on the front floor undercover. Another object of the present invention is to provide a vehicle body lower structure that can secure a sufficient space in the vehicle interior.

  In order to solve the above-described problem, according to a first aspect of the present invention, a vehicle body lower structure having a front floor under cover under the floor of the vehicle body is provided. The vehicle body lower structure is formed by recessing the front floor under cover upward, and having a rectangular opening edge, and disposed in the recess so as not to protrude downward from the general surface of the front floor under cover. In addition, a wing fin having a blade thickness in the left-right direction of the vehicle body is provided. The chord length of the airfoil fin is in the range of 70 to 280 mm.

  According to this configuration, the operability, aerodynamic characteristics, interference between the front floor undercover and the road surface, and chipping resistance against stepping stones can be obtained even though the wing fins are provided on the front floor undercover. A sufficient space in the passenger compartment can be secured.

  In the above vehicle body lower structure, the recess has an inner top wall including an inclined surface, and a portion corresponding to the inner top wall of the recess is formed so as to become deeper toward the rear from the front part of the opening edge. The top wall is preferably provided with airfoil fins.

  According to this configuration, air flows into the recess along the slope of the inner top wall while the vehicle is running. And when air passes along an airfoil fin, since the flow velocity of air is raised, a down force is obtained and maneuverability improves.

  In the vehicle body lower structure, the recess further includes a rear side wall including an inclined surface, and the rear side wall is connected to the front surface connected to the rear end of the inner top wall and the rear surface connected to the general surface of the front floor undercover. The portion corresponding to the rear side wall of the recess is preferably formed so as to become shallower from the front side to the rear side of the rear side wall.

  According to this configuration, the air flowing along the rear side wall moves to the general surface of the front floor undercover while the vehicle is running. At that time, the distance between the front floor under cover and the road surface is abruptly narrowed at the connection portion between the rear side wall and the general surface of the front floor under cover, so that the air flow rate is increased. As a result, downforce is obtained, and the operability is improved. In addition to the flat surface, the slope includes a concave surface and a convex surface that are curved surfaces.

  In the vehicle body lower structure described above, it is preferable that at least a pair of recesses and at least a pair of wing fins disposed in each recess are arranged symmetrically with respect to a center line extending in the front-rear direction of the vehicle body. .

  According to this configuration, the pair of recesses and the pair of wing fins disposed in each recess are disposed symmetrically with respect to the center line extending in the front-rear direction of the vehicle body. As a result, the above-mentioned down force is generated symmetrically with respect to the center line, so that the operability is improved. Also, the roll rigidity of the vehicle body is improved.

  In the vehicle body lower structure described above, it is preferable that the pair of recesses and the pair of wing fins disposed in the recesses are respectively disposed at positions sandwiching the center of gravity of the vehicle body in a state where the vehicle body is viewed in plan view. .

  According to this configuration, the pair of recesses and the pair of airfoil fins disposed in each recess are respectively disposed at positions sandwiching the center of gravity of the vehicle body in a state where the vehicle body is viewed in plan view. As a result, the downforce caused by each wing fin is generated in a well-balanced manner with respect to the center of gravity of the vehicle body, thereby improving the maneuverability.

The side view of the vehicle body of one Embodiment of this invention. The bottom view which shows the under floor of a vehicle body. The perspective view of a front floor undercover. The characteristic view which shows the relationship between downforce and aerodynamic characteristic (cd), and the chord length of an airfoil fin. (A) is a top view of an airfoil fin. (B) is a longitudinal sectional view, and (c) is a transverse sectional view.

  Hereinafter, an embodiment in which the lower body structure of the present invention is embodied will be described with reference to FIGS. As shown in FIG. 2, the vehicle has a pair of wheels 12 a to 12 d before and after the vehicle. A plurality of under covers 20 to 50 are provided under the floor of the vehicle body 10.

  The engine under cover 20 is disposed below the engine room between the front wheels 12 a and 12 b at the front of the vehicle body 10, and the pair of front floor under covers 30 and 40 are disposed at both sides of the vehicle body 10 at the center in the front-rear direction of the vehicle body 10. The rear floor under cover 50 is disposed at the rear part of the vehicle body 10. The under cover controls the air flow that flows from the front to the rear of the vehicle body 10 when the vehicle is traveling.

  The positions of the pair of front floor undercovers 30 and 40 are symmetrical with respect to a center line O extending in the front-rear direction of the vehicle body 10, as shown in FIG. As shown in FIG. 3, the front floor undercovers 30, 40 are provided with a recess 60 and airfoil fins 70 disposed in the recess 60. The pair of airfoil fins 70 of the front floor undercovers 30 and 40 are respectively disposed at positions sandwiching the center of gravity P of the vehicle body 10 in a state where the vehicle body 10 is viewed in plan. FIG. 2 is a view of the vehicle body 10 as viewed from the bottom. As in a plan view, the pair of wing fins 70 of the front floor undercovers 30 and 40 are respectively positioned at positions where the center of gravity P of the vehicle body 10 is sandwiched. Has been placed.

  The recesses 60 and the wing fins 70 respectively provided in the front floor undercovers 30 and 40 have the same configuration. Therefore, only the recess 60 and the wing fin 70 provided in the front floor under cover 30 will be described. The portions constituting the recess 60 and the wing fin 70 of the front floor under cover 40 are respectively given the same reference numerals as the portions constituting the recess 60 and the wing fin 70 of the front floor under cover 30, and the description thereof is omitted. To do.

  As shown in FIG. 3, the recess 60 is formed by denting the general surface 32 of the front floor undercover 30 upward, and includes a rectangular opening edge 60 a. The general surface means a portion excluding a portion where the shape changes rapidly, and a portion where the shape does not change or a portion where the shape change is smooth and continuous.

  The recess 60 has an inverted V shape when cut along the longitudinal direction of the vehicle body. The recess 60 has an inner top wall 61 and a rear side wall 62 including a front part connected to the rear end of the inner top wall 61 and a rear part connected to the general surface 32. A portion corresponding to the inner top wall 61 of the recess 60 is formed so as to become deeper from the front portion of the opening edge 60a toward the rear. The rear side wall 62 is an inclined surface 62 a, and a portion corresponding to the rear side wall 62 of the recess 60 is formed so as to become shallower from the rear end of the inner top wall 61 toward the rear.

  The angle θ1 of the inner top wall 61 with respect to the road surface G is in the range of 4 ° to 6 °, and is preferably an angle upward from the road surface G, but is not limited to this range and direction. As the angle θ1 increases, the change in the distance between the inner top wall 61 and the road surface G that becomes larger toward the rear becomes more remarkable. The angle θ1 is a value that takes into consideration the vehicle speed of a general passenger car, the flow velocity of air under the vehicle body floor during travel of the passenger vehicle, the vertical fluctuation of the vehicle body, and the like. In the present embodiment, the angle θ1 of the inner top wall 61 with respect to the road surface G (horizontal plane) is 4.5 °.

  When the plane perpendicular to the center line of the vehicle body 10 and the road surface G is a vertical plane, the inclination angle θ2 of the rear side wall 62 with respect to the vertical plane is in the range of 45 ° to 60 °, but is limited to this range. Not.

  The angle θ2 is a value that takes into consideration the vehicle speed of a general passenger car, the flow velocity of air under the vehicle body floor during travel of the passenger vehicle, the vertical fluctuation of the vehicle body, and the like. With the rear side wall 62 formed in this way, the air that has entered the recess 60 flows again to the general surface 32 located behind the front floor undercover 30, and between the rear end of the rear side wall 62 and the road surface G. Downforce can be generated efficiently. In the present embodiment, the inclination angle θ2 of the rear side wall 62 with respect to the vertical plane is 45 °.

  In the present embodiment, the slope of the inner top wall 61 and the slope of the rear side wall 62 are connected in an inverted V shape. Instead, when the length of the opening edge 60a in the front-rear direction is sufficiently long, the slope of the inner top wall 61 and the slope of the rear side wall 62 are set so that the deepest part of the recess 60 forms a horizontal surface or a curved surface. You may connect.

  The recess 60 includes left and right side walls 63 and 64 that face each other. As shown in FIGS. 2 and 3, airfoil fins 70 are provided on the inner top wall 61. The airfoil fin 70 does not protrude below the general surface 32 of the front floor undercover 30. The airfoil fin 70 is arranged such that its center line extending in the front-rear direction coincides with the center line extending in the front-rear direction of the recess 60.

The lower end surface of the airfoil fin 70 may be disposed above the general surface 32, but is preferably disposed so as to be flush with the general surface 32.
The planar shape of the airfoil fin 70 has a cross-sectional shape of the wing. That is, the front end of the airfoil fin 70 has a gently curved surface, and the rear end of the airfoil fin 70 is sharply pointed. The width in the left-right direction of the airfoil fin 70 is the blade thickness.

  As shown in FIG. 5A, the chord length a from the front end to the rear end of the airfoil fin 70 is preferably in the range of 70 to 280 mm. When the chord length a is less than 70 mm, as shown in FIG. 4, the downforce becomes small and the maneuverability cannot be obtained. Therefore, the chord length a of the airfoil fin 70 is preferably 70 mm or more. On the other hand, when the chord length a exceeds 280 mm, the drag coefficient cd representing the aerodynamic characteristic is deteriorated, and the fuel efficiency is deteriorated.

  The ratio (b / a) of the maximum blade thickness b of the airfoil fin 70 to the chord length a is preferably in the range of 8 to 17%. As the ratio (b / a) of the maximum blade thickness b of the airfoil fin 70 to the chord length a decreases, the shape of the airfoil fin 70 becomes thinner.

  When the length from the front end of the airfoil fin 70 to the maximum blade thickness position on the center line extending in the front-rear direction of the airfoil fin 70 is c, the ratio of the maximum blade thickness position to the chord length a (c / a ) Is preferably in the range of 30 to 35%. As the ratio (c / a) of the maximum blade thickness position to the chord length a decreases, the maximum blade thickness position approaches the front end of the airfoil fin 70, and the rear end of the airfoil fin 70 has a sharper shape.

  The ratio (b / a) of the maximum blade thickness b of the airfoil fin 70 to the chord length a is 8 to 17%, and the ratio (c / a) to the chord length a at the maximum blade thickness position is 30 to 35%. Then, air can be smoothly flowed in consideration of a general wing shape.

In this embodiment, the ratio (b / a) of the maximum blade thickness b to the chord length a is 14%, and the ratio (c / a) of the maximum blade thickness position to the chord length a is 32%.
According to the vehicle body lower structure described above, the air that has entered the floor from the front end of the vehicle body 10 flows smoothly through the engine under cover 20, the front floor under covers 30, 40, and the rear floor under cover 50 while the vehicle is running. This increases the air flow rate. In particular, in the front floor undercovers 30 and 40, air flows into the recess 60 along the inner top wall 61 as indicated by an arrow in FIG. The air flow rate is increased between the airfoil fin 70 and the left and right side walls 63 and 64. Further, the air that has passed through the inner top wall 61 flows between the rear side wall 62 and the road surface G as shown by the arrow in FIG.

As a result, the pair of left and right wing fins 70 stabilizes the air flow under the floor of the vehicle body 10. For this reason, at the time of high-speed driving, the maneuverability is improved and the air resistance is reduced.
According to this embodiment, the following effects can be obtained.

  (1) The vehicle body lower structure of the present embodiment includes a recess 60 formed by recessing the front floor undercovers 30, 40 upward and having a square opening edge 60a. An airfoil fin 70 having a blade thickness in the left-right direction of the vehicle body 10 is provided in the recess 60. The airfoil fin 70 does not protrude below the general surface 32 of the front floor undercover 30. The chord length a of the airfoil fin 70 is in the range of 70 to 280 mm. As a result, in spite of the provision of the airfoil fins 70 on the front floor under cover 30, it is possible to ensure the maneuverability and aerodynamic characteristics. Further, since the airfoil fin 70 does not protrude downward from the general surface 32 of the front floor undercovers 30 and 40, interference between the airfoil fin 70 and the road surface G can be avoided, and the chipping resistance of the airfoil fin 70 to the stepping stones can be avoided. Will improve. Therefore, the maneuverability and aerodynamic characteristics can be ensured, the interference between the airfoil fin 70 and the road surface G can be avoided, and the chipping resistance of the airfoil fin 70 against the flying stone is improved. Further, since the airfoil fins 70 do not protrude downward from the general surface 32 of the front floor undercovers 30 and 40, only the distance between the front floor undercover 30 and the road surface G needs to be considered. Therefore, a sufficient space in the vehicle compartment can be secured.

  (2) In the vehicle body lower structure of the present embodiment, the portion corresponding to the inner top wall 61 of the recess 60 is formed to become deeper from the front portion of the opening edge 60a toward the rear. The inner top wall 61 is provided with airfoil fins 70. As a result, air flows into the recess 60 along the slope of the inner top wall 61 while the vehicle is traveling. And since the flow velocity of air is raised when air passes along the wing | blade type | mold fin 70, a down force is obtained and maneuverability improves.

  (3) In the vehicle body lower structure of the present embodiment, the recess 60 further includes a rear side wall 62, and the rear side wall 62 is connected to the rear end of the inner top wall 61 and the front floor undercover 30, It includes a rear portion connected to 40 general surfaces 32. The rear side wall 62 includes a slope 62 a, and a portion corresponding to the rear side wall 62 of the recess 60 is formed so as to become shallower from the front part of the rear side wall 62 toward the rear part. As a result, the air flowing along the rear side wall 62 moves to the general surface 32 of the front floor undercovers 30 and 40 while the vehicle is traveling. At that time, since the distance between the front floor undercovers 30 and 40 and the road surface G is abruptly narrowed at the connection portion between the rear side wall 62 and the general surface 32 of the front floor undercovers 30 and 40, the flow velocity of air is increased. . As a result, downforce is obtained, and the operability is improved.

  (4) In the vehicle body lower structure of the present embodiment, the pair of recesses 60 and the pair of wing fins 70 disposed in each recess 60 are symmetrical with respect to the center line extending in the front-rear direction of the vehicle body 10. Has been placed. As a result, the above-described down force is generated symmetrically with respect to the center line O, so that the operability is improved. Also, the roll rigidity of the vehicle body is improved.

  (5) In the vehicle body lower structure of the present embodiment, the pair of recesses 60 and the pair of wing fins 70 disposed in each recess 60 have the center of gravity P of the vehicle body 10 in a state in which the vehicle body 10 is viewed in plan view. It is arrange | positioned in the position which pinches | interposes, respectively. As a result, the downforce caused by each airfoil fin 70 is generated in a well-balanced manner with respect to the center of gravity of the vehicle body 10, so that the operability is improved.

In addition, you may change embodiment of this invention as follows.
In the embodiment, the front floor undercovers 30 and 40 may be integrally formed.

  In the above-described embodiment, a single front floor under cover may be provided at the center of the vehicle body 10 in the front-rear direction, and only one wing fin may be provided on the single front floor under cover.

  In the embodiment, two or more pairs of recesses 60 and two or more pairs of airfoil fins 70 disposed in each recess 60 are bilaterally symmetrical with respect to the center line O extending in the front-rear direction of the vehicle body 10. You may arrange.

-The vehicle body lower part structure of this invention may be applied to a sports car other than a passenger car.
In the above embodiment, the ratio (b / a) of the maximum blade thickness b of the airfoil fin 70 to the chord length a may be outside the range of 8 to 17%, and the chord at the maximum blade thickness position The ratio (c / a) to the length a may be outside the range of 30 to 35%.

Claims (5)

In the vehicle body lower structure having a front floor under cover under the floor of the vehicle body,
A recess formed by recessing the front floor undercover upward and having a square opening edge;
The wing-shaped fin having a blade thickness in the left-right direction of the vehicle body, and disposed in the recess so as not to protrude downward from the general surface of the front floor undercover,
A vehicle body lower structure characterized in that a chord length of the wing fin is in a range of 70 to 280 mm.   The concave portion has an inner top wall including an inclined surface, and a portion corresponding to the inner top wall of the concave portion is formed to be deeper from the front portion of the opening edge toward the rear, and the inner top wall The vehicle body lower part structure according to claim 1, wherein the airfoil fin is provided.   The recess further includes a rear side wall including an inclined surface, and the rear side wall has a front part connected to a rear end of the inner top wall and a rear part connected to a general surface of the front floor undercover. The vehicle body lower part structure according to claim 2, wherein a portion of the recess corresponding to the rear side wall is formed so as to become shallower from the front part to the rear part of the rear side wall.   2. The at least one pair of recesses and at least a pair of airfoil fins disposed in each of the recesses are disposed symmetrically with respect to a center line extending in the front-rear direction of the vehicle body. The vehicle body lower part structure according to any one of claims 3 to 4.   The pair of recesses and the pair of airfoil fins disposed in each of the recesses are respectively disposed at positions sandwiching the center of gravity of the vehicle body when the vehicle body is viewed in plan view. The vehicle body lower part structure according to any one of claims 1 to 3.

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