JP2833472B2 - Underfloor structure of vehicle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of an underfloor of a vehicle, and more particularly, to a device such as a differential gear or a fuel tank which can be efficiently cooled.

[0002]

2. Description of the Related Art A conventional underfloor structure of a vehicle is disclosed in Japanese Patent Application Laid-Open No. Hei 5-330457, which was previously proposed by the present applicant. In this conventional technique, the lower side of a high-pressure part such as an engine room usually formed at the front of a vehicle is closed with a floor member, and the floor member is communicated with the high-pressure part substantially at a target position with respect to the vehicle center line. It forms a pair of hot air discharge portions that direct the air in the high-pressure portion to the rear wheel and flows out, and between the pair of hot air discharge portions, reduces the flow of air flowing from the front of the vehicle along the lower side of the floor member. And a throttle portion for directing and flowing out to a heat generating portion such as a transmission or a differential gear on the lower side of the floor behind the floor member.

With such a configuration, a high-pressure airflow having a sufficiently low flow velocity flows out toward the rear wheels from the hot air discharge portion communicating with the engine room, but the airflow proceeds to the rear of the vehicle. Gradually spreads to the left and right of the vehicle as
Since almost the entire rear wheel is covered, the effect of reducing the air force applied to the rear wheel and reducing the air resistance acting on the vehicle is obtained. On the other hand, since the air flow, which has a relatively high speed due to the contraction, is supplied toward the transmission and the differential gear from the throttle portion, an effective cooling action can be obtained, and the high-speed air flow can be reduced. The effect that the lift is reduced by the effect is also obtained.

[0004]

Although the above-mentioned conventional underfloor structure of the vehicle can provide the above-mentioned remarkable functions and effects, there are still points to be improved. I understood. That is, in the above-described conventional technique, as shown in FIG. 20, which is a side view conceptually showing the configuration of the lower portion of the floor of the vehicle, the center under cover 20
Differential gear by making fast airflow u ₁ relatively to flow to the floor back side, that, a transmission 2 which is disposed behind the engine 1, the driving force from the transmission 2 through the propeller shaft 3 is transmitted by Heat is taken from the lower surface of the heat generating portion such as 4 to obtain a cooling effect. However, in a vehicle in which the engine 1 is mounted in the front part of the vehicle body, hot air in the engine room flows into a groove-shaped floor tunnel 21 formed on the back side of the floor to accommodate the propeller shaft 3 and the like. It creates a very slow airflow u ₅ of the flow is from being made stagnation s consisting of hot air here covers the upper surface of the differential gear 4 flowing floor tunnel 21 to the rear.

That is, the high-temperature and low-speed air flow u ₅ existing in the floor tunnel 21 reduces the heat radiation effect on the upper surfaces of the transmission 2 and the differential gear 4. There is an unsolved problem that it cannot be dealt with simply by cooling the lower surface side of the gear 4.

The present invention has been made in view of such unresolved problems of the conventional technology. In particular, the influence of hot air flowing from an engine room into a floor tunnel is determined by using an expensive member or the like. It is an object of the present invention to provide a vehicle underfloor structure that can be effectively solved without any problem.

[0007]

To achieve the above object, according to the first aspect of the present invention , an engine is mounted on a front portion of a vehicle body.
And an underfloor structure of a vehicle having a groove-shaped floor tunnel extending in the vehicle front-rear direction on the back side of the floor, wherein a lower side of an engine room is closed with an engine undercover.
Close and behind the engine undercover
In addition, a center under cover having an introduction duct for guiding the air flowing rearward from the front of the vehicle to the rear on the floor rear side is provided on the floor rear side in front of the rear end of the floor tunnel .

[0008] On the other hand, in order to achieve the above object, an invention according to claim 2 is an underfloor for a vehicle having an engine mounted on a front portion of a vehicle body and having a groove-shaped floor tunnel extending in the vehicle front-rear direction on the back side of the floor. A lower portion of the engine room is closed with an engine undercover, and the air in the engine room is directed to the rear wheels at a substantially target position across the vehicle center line of the engine undercover. Along with forming the hot air discharging portion, a narrowed portion is formed between the pair of hot air discharging portions to reduce the air flowing backward from the front of the vehicle to the rear on the floor rear side and flow out to the rear,
A center under cover having an introduction duct for guiding air flowing rearward from the front of the vehicle to the rear of the vehicle on the floor rear side is provided behind the throttle portion.

According to a third aspect of the present invention, in the vehicle underfloor structure according to the second aspect,
The width of the inlet duct is smaller than the width of the outlet portion on the outflow side. According to a fourth aspect of the present invention, in the vehicle underfloor structure according to the first to third aspects of the present invention, the height of the vehicle front end of the center undercover is arranged at the rear portion of the engine. It is the same as or higher than the height of the lower surface of the transmission to be installed.

Further, according to a fifth aspect of the present invention, in the vehicle underfloor structure according to the first to fourth aspects of the present invention, a lower surface of a transmission disposed at a rear portion of the engine and a lower surface of the center undercover are provided. The lower surface was continuous. Further, the invention according to claim 6 is the invention according to claim 1.
In the vehicle underfloor structure according to the invention according to claim 5, the shape of the introduction duct is such that the width dimension thereof is equal to
The shape gradually increased from both front sides toward the rear side of the vehicle .

According to a seventh aspect of the present invention, in the vehicle underfloor structure according to the first to sixth aspects, the floor tunnel is a tunnel for accommodating a rotating shaft of a driving force transmission system. An air guide is provided to surround a portion of the rotating shaft which is guided by the air guided by the center under cover. Further, according to an eighth aspect of the present invention, in the vehicle underfloor structure according to the first to seventh aspects of the invention, a communication pipe is provided for communicating the inside of the engine room with the space near the side surface of the transmission.

According to a ninth aspect of the present invention, in the vehicle underfloor structure according to the first to eighth aspects of the present invention, the introduction duct is provided at a vehicle rear end.
An air guide for controlling the direction of air flow was provided.

[0013]

According to the first aspect of the present invention, for example, the air flow on the lower surface of the floor generated during traveling of the vehicle is guided upward by the introduction duct of the center under cover. Then
It flows rearward of the vehicle along the floor tunnel, the back surface of the floor, etc., and reaches a space near a heat generating portion such as a differential gear near the rear end of the floor tunnel . And
Since the airflow on the lower surface side of the floor is a traveling wind, the temperature of the airflow is sufficiently lower than that of hot air generated in an engine room or the like. Therefore, the airflow cools a heat generating portion such as a differential gear.

Next, according to the second aspect of the present invention, a high-pressure air flow having a sufficiently low flow velocity flows toward the rear wheels from the hot air discharge portion formed in the engine under cover. The airflow gradually spreads in the left-right direction of the vehicle as it travels rearward of the vehicle, and covers substantially the entire rear wheel. On the other hand, from the constricted portion, the airflow that is relatively high speed due to the contraction flows out backward,
The high-speed airflow is guided upward by the introduction duct of the center undercover, reaches the heat generating portion such as a differential gear located behind, and generates heat such as the differential gear in the same manner as the invention according to the first aspect. Is cooled. In other words, according to the second aspect of the present invention, a high-speed airflow is positively generated on the lower surface side of the floor by the engine undercover, and the high-speed airflow is guided upward by the center undercover. Cooling is performed more efficiently than the invention according to item 1.

In the invention according to claim 3, the entire width of the introduction duct of the center undercover is present in the airflow flowing out of the throttle portion of the engine undercover. Therefore, all of the air flow guided upward by the introduction duct is the air flow flowing out of the throttle portion, so that the effect of the invention according to claim 2 is more reliably exhibited. In the invention according to claim 4, since the vehicle front end of the center undercover is located at the same level or higher than the lower surface of the transmission, the vehicle front end of the center under cover is It does not disturb the airflow flowing from the front to the back of the vehicle along the back of the floor.

Further, in the invention according to claim 5,
Since the lower surface of the transmission and the lower surface of the center undercover are continuous with each other, the vehicle front end of the center under cover can be further securely moved from the vehicle front along the floor back surface as compared with the invention according to the fourth aspect. It does not disturb the airflow that flows through. Further, in the invention according to claim 6, airflow through the full lower back side to the rear from the front of the vehicle is guided efficiently upward.

Here, usually, on the rear side of the vehicle, there is a rotating shaft constituting a driving force transmission system such as a propeller shaft in a state accommodated in the floor tunnel, and is guided upward by the center under cover. Since the air hits a rotating shaft such as a propeller shaft, the rotation of the rotating shaft disturbs the air flow and may not reach a heat generating portion such as a differential gear.

Therefore, according to the invention of claim 7, since the air guide is provided in a portion where the air guided by the center under cover hits, the air flow guided upward can be prevented from being disturbed. There is a high possibility that the airflow reaches a heat generating portion such as a differential gear.
On the other hand, according to the invention of claim 8, since the communication pipe communicating the inside of the engine room and the space near the side surface of the transmission is provided, a part of the hot air in the engine room is close to the side of the transmission side through the communication pipe. Therefore, the amount of hot air reaching the differential gear and the like via the floor tunnel and the like is reduced.

According to the ninth aspect of the invention, the direction of the air flow guided upward from the center undercover is finely adjusted by the air guide provided on the air outflow side of the introduction duct. For example, when it is desired to efficiently cool the differential gear, adjusting the air guide makes the air flow contact the upper surface or both side surfaces of the differential gear.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 to 4 are views showing the configuration of the first embodiment of the present invention. FIG. 1 is a bottom view conceptually showing the configuration on the rear side of the vehicle floor, and FIG. FIG.

First, the structure will be described.
10FL, 10FR are front wheels as steered wheels, 10RL, 10RR
Is a rear wheel as a drive wheel, and the rear wheels 10FL and 10FR are composed of an engine 1 mounted on a front part of the vehicle, a transmission 2, a propeller shaft 3, a differential gear 4, drive shafts 5, 5, and the like. The driving force is transmitted via a driving force transmission system. That is, the vehicle shown in FIG. 1 is a so-called FR (front engine-rear drive) vehicle. Reference numeral 6 denotes an exhaust pipe connecting between the exhaust side of the engine 1 and the muffler 7.

On the lower surface side of the engine 1, the engine 1
An engine under cover 20 is disposed so as to close an engine room accommodating the engine. The engine under cover 20 is made of, for example, a resin material or a steel plate material, has a substantially flat plate shape as shown in FIG. 3 which is a perspective view thereof, and is fixed substantially horizontally to the vehicle body. The engine under cover 20 is formed with a pair of hot air discharge portions 20A and one throttle portion 20B.

Of these, a pair of hot air discharging portions 20A
Is a substantially groove formed by folding a part of both sides of the engine under cover 20 across the vehicle center line so that the rear side of the vehicle is lowered, and a side part 20b that guides both sides of the bottom part 20a. The upper surface of the duct is open in the engine room, and the opening at the rear end is slightly outward in the vehicle width direction so as to point to the rear wheels 10FL and 10FR on the same side of the vehicle center line. Leaning on.

The throttle section 20B is provided with both hot air discharge sections 20B.
A is a groove-shaped duct formed at a portion sandwiched between the side portions 20b on the inner side in the vehicle width direction of A, and is open on the front and rear surfaces and the lower surface side, and is oriented substantially coaxially with the vehicle center line in the vehicle front and rear direction.
However, the width dimension is equal to the width dimension of the transmission 2. In this embodiment, the opening 20c is formed at the rear end of the throttle 20B so that the lower surface of the engine 1 is exposed. The reason why the opening 20c is formed is that oil can be changed through the oil pan 1a of the engine 1 without removing the engine under cover 20.

On the other hand, immediately after the transmission 2,
The center of the floor tunnel 21 (see FIG. 2) is formed so as to cover a part of the lower surface opening side of a floor tunnel 21 (see FIG. 2) formed of a groove extending in the vehicle front-rear direction formed on the back surface of the floor so as to accommodate a driving force transmission system such as the propeller shaft 3. An under cover 25 is provided. The center under cover 25 is also made of, for example, a resin material or a steel plate material, has a substantially flat plate shape as shown in FIG. 4 which is a perspective view thereof, and is fixed horizontally to the vehicle body. Then, at the center of the center under cover 25 in the vehicle width direction, an introduction duct 25A oriented in a direction along the vehicle center line in a horizontal plane is formed by pressing and bending a part of the plate-shaped body upward, for example. Is formed.

That is, the introduction duct 25A has an upper portion 25a bent so that the rear end of the vehicle is raised, and a pair of substantially triangular side portions 25 that guide both sides of the upper portion 25a.
b, and the lower surface side of the duct is open. Further, in this embodiment, the width dimension of the inlet duct 25A, gradually large comb toward the vehicle rear side of the outlet side from the vehicle front side of the inflow side.

As shown in FIG. 2, the center under cover 25 is disposed at the same level as or higher than a straight line L indicating the same height as the lower surface of the transmission 2 disposed immediately before the center under cover 25. together are, as shown in FIG. 1, the maximum width W ₁ of the introduction duct 25A is constricted portion 20B
It is smaller than the width W _2. Next, the operation of the present embodiment will be described.

That is, as shown in FIG. 5 in which the flow of air generated during traveling by the engine under cover 20 is indicated by an arrow, while the vehicle is traveling, the hot air in the engine room flows from the hot air discharging portions 20A on both sides to the bottom of the floor. Is discharged to the side,
As heated air exhaust unit 20A airflow u ₂ slow and relatively flowing at high temperatures as a base point is created. Then, the air flow u ₂ is thus directed toward the vehicle rear, the hot air discharge unit 20A is the rear wheels 10RL, it is directed to a 10RR, and the throttle portion 20B formed between them heated air exhaust unit 20A since the width is substantially identical to the transmission 2, which air stream u _2, as shown in FIG. 6, through the trajectory as to extend in the vehicle width direction while passing through the slightly away from the side of the transmission 2 The vehicle reaches the rear wheels 10RL and 10RR, and covers the rear wheels 10RL and 10RR.

As a result, the aerodynamic force applied to the rear wheels 10RL, 10RR is reduced, and the air resistance acting on the vehicle is reduced, so that the fuel efficiency is improved. On the other hand, while the vehicle is traveling, an airflow is generated on the back side of the floor from the front to the rear of the vehicle. The airflow is, as shown in FIG. , the fast airflow u ₁ relatively velocity is flowed contracted by the slow airflow u ₂ that is made in both sides in the vehicle width direction. Then, the air flow u _1, the outer portion is relatively low because the flow of air, yet the transmission 2 and differential gear flows backward along the substantially vehicle centerline floor back surface side as shown in FIG. 6 4 so as to touch the lower surface side thereof, so that heat can be effectively removed from the lower surfaces of the transmission 2 and the differential gear 4. That is, by creating the air flow u ₁ by the engine under cover 20, the cooling effect on the lower surface side of the transmission 2 and the differential gear 4 as the heat generating portion can be improved.

The interaction between the air flows u ₁ and u ₂ also has the effect of significantly reducing the rear wheel lift.
The reason why the lift is lowered, while the air flow u ₁ flows toward the rear from the front to the rear substantially straight near the vehicle center line, the rear wheels 10RL airflow u _2, directed to 10RR As a result, it is considered that the vicinity of the drive shaft 5 becomes a depletion region and a negative pressure is generated here.

Further, the air flow u ₁ also passes through the lower surface of the center under cover 25 disposed immediately after the transmission 2, but the air flowing around the object flows along the surface of the object. And the width dimension of the introduction duct 25A is set as described above.
Because more of this retraction action of the air have a pronounced shape, as shown in part of the air flow u ₁ is pulled up to the vehicle body by the introduction duct 25A 7 passing through the lower surface side of the center bottom cover 25 A simple air flow u ₃ is created.

Then, since the rear end portion on the discharge side of the introduction duct 25A faces obliquely upward, as shown in FIG. 8, the airflow u ₃ guided upward flows into the floor tunnel 21 and the air flow u ₃ flows upward. After flowing backward in the floor tunnel 21 and reaching the upper surface of the differential gear 4, the flow velocity thereof is as fast as the air flow u ₁ , so that the air flows over the differential gear 4 without forming a stagnation in the space above the differential gear 4. And is discharged outside the floor tunnel 21. At this time, the stagnation of the hot air which has conventionally reached the upper surface of the differential gear 4 from the engine room via the floor tunnel 21 is also eliminated.

That is, the air flow u ₃ created by the introduction duct 25A flows so as to touch the upper surface of the differential gear 4 as the heat generating portion, and the temperature of the air flow u ₃ is relatively low similarly to the air flow u _1. Therefore, heat can be effectively removed from the upper surface side of the differential gear 4, and the cooling effect on the upper surface side of the differential gear 4 can be improved.

As described above, according to the structure of the present embodiment, the cooling effect can be improved particularly on both the upper surface side and the lower surface side of the differential gear 4, so that the ambient temperature of the differential gear 4 decreases, The oil temperature of the differential gear 4 is greatly reduced.
FIGS. 9 to 11 show the oil temperature of the differential gear 4 (FIG. 9) and the ambient temperature of the differential gear 4 (FIG. 10) in the present embodiment and the conventional example (the structure in which the center under cover 25 is removed from the structure of the present embodiment). ) And the wind speed around the differential gear 4 (FIG. 11) are shown in comparison with the results confirmed in an actual running experiment. As is apparent from FIG. Compared with the conventional case, the differential oil temperature is particularly 100 km /
In a high-speed region of h or more, a reduction effect of about 5 to 10 ° C. can be obtained. The reason is shown in FIGS.
As can be seen from FIG. 5, the ambient temperature of the differential gear 4 decreases and the ambient wind speed increases. In other words, as a result of providing the center under cover 25 and positively generating the airflow u ₃ in the floor tunnel 21, the cooling effect of the differential gear 4 can be significantly improved.

In this embodiment, since the width W ₁ of the introduction duct 25A is smaller than the width W ₂ of the throttle 20B, the entirety of the introduction duct 25A can be placed in the air flow u ₁ . it can. Accordingly, since it is possible to make the air flow u ₃ ensures, it is possible to reliably obtain the cooling effect of the differential gear 4 upper surface side as described above. Furthermore, in the present embodiment, as shown in FIG. 2 in particular, the height direction position of the lower surface of the center under cover 25 disposed horizontally is positioned lower than the lower surface (straight line L) of the transmission 2 disposed immediately before. Also, the upper end of the center under cover 25 does not project below the lower surface of the transmission 2. Therefore, by providing the center under cover 25, the air flow u ₁
Is not disturbed, so that the cooling effect described above does not deteriorate. In this embodiment, the height of the lower surface of the center under cover 25 is higher than the straight line L, but may be the same height as the straight line L.

[0036] Then, in the present embodiment, the hot air in the engine room, consists of a hot air discharge portion 20A formed in the engine under cover 20 configured to discharge the air flow u ₂ obliquely rear side, for example, traffic jam such as when a an air flow u ₂ be the substantially rear wheels 10RL, go flows toward the 10RR, there is no necessity to stay just below the engine under cover 1, so that once discharged hot air to heat the radiator (not shown) Can be avoided.

Further, since the center under cover 25 is not a particularly expensive member, it does not cause a significant increase in cost despite the above-described excellent effects.
FIGS. 12 and 13 are views showing a second embodiment of the present invention, and are both side views conceptually showing the configuration on the back side of the vehicle floor, similarly to FIG. 2 of the first embodiment. In addition,
The same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will not be repeated. The other configurations not shown are the same as those of the first embodiment.

That is, the present embodiment is characterized in that the front end of the center under cover 25 on the vehicle is arranged at the same height as the lower surface of the transmission 2 and is continuous between them. With such a configuration, for example, as shown in FIG. 12 or FIG. 13, the center under cover 25 is mistakenly attached diagonally, Center under cover 2
5, the air flow on the back side of the floor is not disturbed, the air flow u ₃ can be reliably introduced into the floor tunnel 21, and the cooling effect described in the first embodiment can be reliably obtained. You can do it.

Other functions and effects are the same as those of the first embodiment. FIGS. 14 and 15 are views showing a third embodiment of the present invention. FIG. 14 is a side view conceptually showing a configuration on the back side of the vehicle floor, similar to FIG. 2 of the first embodiment. Fifteen
FIG. 2 is a perspective view of a main part of the present embodiment. The other components not shown are the same as in the first embodiment.

That is, when a rotary shaft such as the propeller shaft 3 of the driving force transmission system exists in the floor tunnel 21, the air flow u ₃ guided into the floor tunnel 21 by the center under cover 25 causes the rotation of the propeller shaft 3. It is conceivable that the cooling effect of the differential gear 4 decreases due to the disturbance. Therefore, in the present embodiment, a gutter-shaped air guide 30 having an open upper surface so as to surround a portion of the propeller shaft 3 where the air flow u ₃ hits.
Was provided.

With this configuration, as shown in FIG. 15, the air flow u ₃ can surely enter the floor tunnel 21 without being disturbed by the rotation of the propeller shaft 3. The cooling effect of the differential gear 4 described in the embodiment can be more reliably obtained. Other functions and effects are the same as those of the first embodiment.

FIGS. 16 and 17 are views showing a fourth embodiment of the present invention. FIG. 16 is a side view conceptually showing the configuration of the back side of the vehicle floor, similar to FIG. 2 of the first embodiment. FIG. 17 is a plan view showing a main part of the present embodiment. The other components not shown are the same as in the first embodiment.
That is, in the present embodiment, the communication pipe 36 is provided for communicating the space on the rear side of the engine 1 with the space on the lower side on both sides of the transmission 2, and the communication pipe 36 extends across the transmission 2 as a whole. An inlet 36A having a width slightly larger than that of the transmission 2 is formed at the upper end facing the engine room at a lower end located at the lower side of both sides of the transmission 2. Is formed with a discharge port 36B facing obliquely outward.

[0043] With such a structure, heat of the engine 1 upward, to be exhausted to the transmission 2 side downwards through the communicating pipe 36, reduce or eliminate the hot air stream u ₅ as shown in FIG. 20 be able to. As a result, the effect of cooling the differential gear 4 can be performed more efficiently, and the effect of heating the upper surface of the transmission 2 by the hot air discharged from the engine room can be suppressed.

Moreover, since the discharge port 36B of the communication pipe 36 is positioned slightly diagonally outward below both side surfaces of the transmission 2, the hot air exhausted from the discharge port 36B can be removed by the center under cover 25. Introduction duct 2
There is no such thing as being sucked up by 5A and being introduced into the floor tunnel 21. Other functions and effects are described in the first
This is the same as the embodiment.

FIGS. 18 and 19 are views showing a fifth embodiment of the present invention. FIG. 18 is a perspective view of the center under cover 25, and FIG. 19 is a bottom view of the center under cover 25. The other components not shown are the same as in the first embodiment. That is, the center under cover 2 of the present embodiment
5 is basically the same as the first embodiment, plate-shaped introduction duct 25A in the central portion of the body is formed.
An air duct 37 that controls the direction of the airflow blown out from the introduction duct 25A is provided at the vehicle rear mold end (blowing side) of the introduction duct 25A.

The air duct 37 is connected to the introduction duct 25A.
A pair of flat plates 37 continuous with the upper side and lower side of the blowing side of
A, 37B, and four standing plates 37a to 37d vertically interposed between the flat plates 37A, 37B. The flat plates 37A and 37B have a trapezoidal shape with the vehicle front side being the upper bottom, and standing plates 37a and 37d are interposed between both oblique sides.
Standing plates 37b and 37c are arranged inside the standing plates 37a and 37d in parallel with them. However, the standing plate 37
The distance between a and 37b and the distance between the uprights 37c and 37d are about 1/5 to 1/6 of the width of the flat plates 37A and 37B. Further, at least for the upper flat plate 37A, so as not to interfere with the rise of the air flow u _3, the rear is fixed to lift slightly.

Therefore, in the air guide 37, a duct 38A having a vehicle rear opening extending on both sides in the vehicle width direction is formed at a relatively wide central portion, and a duct 38A is formed on both sides of the passage 38A. This means that the duct 38B facing outward in the vehicle width direction is formed. With such a structure, as shown in FIG. 19, when the air flow u ₃ introduction duct 25A is made to reach the air duct 37, the flow of the central portion, almost out of the vehicle center line through the duct 38A the air flow u ₃₁ entering the floor tunnel without, but on both sides flow to pass duct 38B, the airflow u ₃₂ inclined outward in the vehicle width direction.
Therefore, the airflow that enters the floor tunnel from the introduction duct 25A becomes the airflows u ₃₁ and u ₃₂ that spread radially.

[0048] Then, because so touched airflow u ₃₂ is also on both sides of the differential gear 4, becomes the top surface of the differential gear 4, all of the cooling air of the lower surface and both side surfaces are provided, the cooling effect It becomes extremely efficient and the cooling effect is further improved. Other functions and effects are the same as those of the first embodiment.

In each of the above embodiments, a structure particularly suitable for cooling the differential gear 4 as a heat generating portion has been described. However, efficient cooling by the present invention is not limited to the differential gear 4. .
For example, by appropriately adjusting the opening direction of the opening direction or the air duct 37 of the inlet duct 25A, toward the main cooling portion such as a fuel tank airflow u ₃ may be oriented.

In each of the above embodiments, the case where the engine under cover 20 is provided in addition to the center under cover 25 has been described.
0 does not have to be provided. In this case, the airflow that naturally flows on the back side of the floor while the vehicle is running is guided upward by the introduction duct of the center undercover 25. Therefore, the airflow slightly decreases as compared with the case where the engine undercover 20 is provided. The same cooling effect as in each embodiment can be obtained.

Further, in each of the above embodiments, the case where one center under cover 25 is provided has been described. However, the number of the center under cover 25 is not limited to one. For example, a plurality of center under covers 25 are arranged in the vehicle longitudinal direction or the vehicle width direction or both directions. It may be provided.

[0052]

As described above, according to the first aspect of the present invention, since the center undercover having the introduction duct for guiding the air flowing from the front to the rear of the vehicle upward on the back surface of the floor is provided, the inside of the floor tunnel is provided. since it is possible to introduce the cooling air, it can be cooled efficiently heat generating portion such as a differential gear, nor lead to particularly significant cost, there is an effect that.

According to the second aspect of the present invention, since the engine under cover having the hot air discharge portion and the throttle portion and the center under cover having the introduction duct are provided,
Since the high-speed airflow created by the throttle section of the engine undercover is introduced upward by the introduction duct,
A more effective cooling action can be obtained. And
With the invention according to claim 3, since all of the airflow guided upward by the introduction duct is the airflow flowing out of the throttle portion,
The effect of the invention according to claim 2 can be more reliably obtained.

Further, according to the fourth and fifth aspects of the present invention, since the air flow flowing on the back side of the floor is not disturbed, the cooling effect of the first to third aspects of the present invention is reduced. There is no such thing as. Further, according to the invention of claim 6, there is an effect that the airflow on the back surface side of the floor can be efficiently introduced upward.

According to the seventh aspect of the present invention, since the air flow introduced upward can be prevented from being disturbed by the rotation of the rotating shaft, the air flow can reach a heat generating portion such as a differential gear. And the cooling effect can be more reliably obtained. Further, according to the invention of claim 8, since a part of the hot air in the engine room flows out into the space near the side surface of the transmission through the communication pipe, the hot air reaching the differential gear and the like via the floor tunnel and the like is reduced. The cooling effect can be further improved.

According to the ninth aspect of the present invention, the direction of the air flow guided upward from the center under cover can be adjusted more finely. For example, when it is desired to efficiently cool the differential gear, the air guide is used. By adjusting the air flow, the air flow can also be brought into contact with the upper surface or both side surfaces of the differential gear, and there is an effect that extremely efficient cooling can be performed.

[Brief description of the drawings]

FIG. 1 is a bottom view of a vehicle according to a first embodiment of the present invention.

FIG. 2 is a side view conceptually showing the configuration on the floor back side in the first embodiment.

FIG. 3 is a perspective view of an engine under cover.

FIG. 4 is a perspective view of a center under cover.

FIG. 5 is an explanatory diagram of an air flow created by an engine under cover.

FIG. 6 is a bottom view for explaining the air flow on the back surface side of the floor.

FIG. 7 is an explanatory diagram of an air flow created by a center undercover.

FIG. 8 is a side view for explaining the air flow on the back surface side of the floor.

FIG. 9 is a graph for explaining the effect of the first embodiment.

FIG. 10 is a graph for explaining the effect of the first embodiment.

FIG. 11 is a graph for explaining the effect of the first embodiment.

FIG. 12 is a side view conceptually showing the configuration on the floor back side in the second embodiment.

FIG. 13 is a side view conceptually showing the configuration on the floor back side in the second embodiment.

FIG. 14 is a side view conceptually showing the configuration on the floor back side in the third embodiment.

FIG. 15 is a perspective view conceptually showing the configuration on the floor back side in the third embodiment.

FIG. 16 is a side view conceptually showing the configuration on the floor back side in the fourth embodiment.

FIG. 17 is a plan view conceptually showing the configuration on the floor back side in the fourth embodiment.

FIG. 18 is a perspective view of a center undercover in the fifth embodiment.

FIG. 19 is a bottom view of the center undercover illustrating the operation of the fifth embodiment.

FIG. 20 is a side view conceptually showing the configuration of the conventional floor back side.

[Description of Signs] 1 Engine 2 Transmission 3 Propeller shaft (rotating shaft) 4 Differential gear 10FL, 10FR Front wheel 10RL, 10RR Rear wheel 20 Engine under cover 20A Hot air exhaust portion 20B Restrictor 21 Floor tunnel 25 Center under cover 25A Introductory duct 30 Air guide 36 Communication pipe 37 Air guide

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-330457 (JP, A) JP-A-1-80581 (JP, U) JP-A-3-103882 (JP, U) JP-A-3-103 44086 (JP, U) JP 4-95575 (JP, U) JP 2-69583 (JP, U) JP 1-73471 (JP, U) (58) Field surveyed (Int. Cl. ⁶ , DB name) B62D 25/20

Claims (9)

(57) [Claims] 1. A under-floor structure of a vehicle having a floor tunnel of the channel extending in the longitudinal direction of the vehicle in the vehicle body front engine is mounted and flow <br/> A back side, the engine Le
With the engine under cover
At the rear of the engine under cover and
An underfloor for a vehicle, wherein a center undercover having an introduction duct for guiding air flowing from the front to the rear of the vehicle upward on the backside of the floor is disposed on the backside of the floor in front of the rear end of the lower tunnel. Construction. 2. An underfloor structure of a vehicle having an engine mounted on a front portion of a vehicle body and having a groove-shaped floor tunnel extending in a vehicle front-rear direction on a rear surface of the floor, wherein a lower portion of an engine room is closed by an engine undercover. Then, at the approximate target position across the vehicle center line of the engine under cover,
The air in the engine room is formed as a pair of hot air discharge portions that flow out toward the rear wheels, and between the pair of hot air discharge portions, air that flows rearward from the front of the vehicle to the rear on the floor rear surface side is contracted. A center under cover having an introduction duct which guides air flowing rearward from the front of the vehicle to the rear of the floor on the back side of the floor is formed behind the narrowed portion. Under floor structure. 3. The underfloor structure of a vehicle according to claim 2, wherein a width of the introduction duct is smaller than a width of the throttle portion on an outflow side. 4. The vehicle according to claim 1, wherein a height of a front end of the center undercover on the vehicle is equal to or higher than a height of a lower surface of a transmission disposed at a rear portion of the engine. An underfloor structure for a vehicle described in Crab. 5. The underfloor structure for a vehicle according to claim 1, wherein a lower surface of a transmission disposed at a rear portion of the engine and a lower surface of the center undercover are continuous with each other. 6. The shape of the introduction duct is measured in the width direction.
Law gradually increases from the vehicle front side to the vehicle rear side.
The underfloor structure of a vehicle according to any one of claims 1 to 5, wherein the underfloor structure has a shape. 7. The floor tunnel is a tunnel for accommodating a rotating shaft of a driving force transmission system, and is provided with an air guide that surrounds a portion of the rotating shaft that is guided by air guided by the center under cover. An underfloor structure for a vehicle according to claim 6. 8. A communication pipe for communicating between the engine room and a space near the side surface of the transmission.
An underfloor structure for a vehicle according to claim 7. 9. An air guide for controlling the direction of air flow is provided at an end of the introduction duct on the vehicle rear side.
An underfloor structure for a vehicle according to any one of claims 8 to 8.