JP7718151B2 - Vehicle undercarriage - Google Patents

Description

This invention relates to a vehicle undercarriage structure that cools a heat-generating element located below the floor panel of a vehicle using wind from a fan or wind generated when the vehicle is running under the floor.

Conventionally, a vehicle undercarriage has been known in which a heating element such as a DC-DC converter (direct current voltage converter) is located below the floor panel of the vehicle, an undercover fixed to the vehicle body is located below the heating element, and a fan (see radiator fan) is provided in front of the heating element to cool a heat source component such as a radiator and generate airflow toward the rear of the vehicle in the space between the undercover and the floor panel.

When the vehicle is stopped, such as when idling, the air from the fan can adequately cool the heat-generating element. However, for example, when towing a leisure boat or similar vehicle to the rear of the vehicle via a trailer hitch, the load increases while the vehicle is moving, and the air generated by the fan becomes hot, making it difficult to cool the heat-generating element with this hot air.

As disclosed in Patent Document 1, a structure has already been invented in which a hole is formed in the undercover and the airflow from under the floor that flows through the hole is used to cool the heat-generating element.

However, in the conventional structure disclosed in Patent Document 1, the hot air generated by the fan and flowing toward the rear of the vehicle blocks (i.e., blocks) the underfloor airflow flowing in through the holes, making it impossible to guide the underfloor airflow up to the top of the heat-generating element, and therefore preventing sufficient cooling of the heat-generating element.

JP 2018-58383 A

The object of this invention is to provide a vehicle undercarriage structure that prevents hot air from the fan from being directed toward the top of the heat-generating element when the vehicle is running normally, allowing the heat-generating element to be cooled down to its upper surface using the airflow from under the floor when the vehicle is stopped, while allowing the air from the fan to be directed toward the heat-generating element to cool it even when there is no airflow from under the floor when the vehicle is stopped.

This invention is a vehicle undercarriage comprising: a heating element provided below a floor panel of the vehicle; an undercover fixed to the vehicle body and provided below the heating element; and a fan in front of the heating element that cools a heat source member and generates airflow in a rearward direction in the space between the undercover and the floor panel, wherein the undercover has a hole portion that introduces airflow from under the undercover from a position forward of the heating element when the vehicle is moving, and a slope portion that slopes upward from the front end of the hole toward the rear, and a wall member that is provided in the vehicle fore-and-aft region where the slope portion is provided, overlapping with an upper part of the heating element in a front view of the vehicle, and a space portion that allows air to flow in from the fan between the upper end of the slope portion and the lower end of the wall member, wherein the upper end of the slope portion overlaps with the vehicle's vertical center part in a front view of the vehicle, and the slope portion is located on an extension of the wall member in a side view of the vehicle.

The heating element may be, for example, an electric control part such as a DC-DC converter (direct current to direct current converter) or a drive system part such as a differential.
Furthermore, the heat source member may be, for example, an air-cooling element of an internal combustion engine such as a radiator, or in the case of an electric vehicle, an air-cooling element of a motor.

With this invention, when the vehicle is running normally, the wall member prevents the wind (hot air) from the fan from being directed toward the top of the heating element, and the underfloor airflow is guided from the hole along the underside of the slope to the top of the heating element, thereby cooling not only the bottom surface of the heating element but also the top surface of the heating element.

On the other hand, when the vehicle is stopped, the air from the fan that flows in from the space hits the heat generating element, so the heat generating element can be cooled even without wind from running.
The sloped portion allows the outside air to be drawn in without disturbing the flow of wind generated when the vehicle is traveling under the floor, due to the viscosity of the air flowing along the underside of the sloped portion.

As an aspect of the present invention, an opening suppression portion may be provided extending upward from a rear end portion of the hole portion.
According to this invention, the opening prevention portion prevents water kicked up from the road surface by the wheels and moisture contained in muddy water from entering through the hole, thereby preventing the heating element from becoming wet.

As an aspect of the present invention, the rear end of the slope portion and the front end of the opening suppression portion may be disposed at substantially the same position in the vehicle front-rear direction.
According to this invention, the opening area of the hole can be minimized while preventing the water from getting in.

As an aspect of the present invention, a connecting wall portion that connects the slope portion and the opening suppression portion may be provided on both sides of the hole in the vehicle width direction.
With this invention, the connecting wall portion can block water or muddy water from entering from both sides of the hole in the vehicle width direction, and the connecting wall portion also guides the wind from under the floor, allowing for even better cooling of the heat-generating element.

As an aspect of the present invention, the opening suppression portion may be inclined upward toward the front of the vehicle.
According to this invention, the opening prevention portion having the above-mentioned inclined structure can block the intrusion path of water and muddy water.

As an aspect of the present invention, the slope portion may be formed in a shape that widens toward the rear of the vehicle in a plan view.
According to this invention, the area where the hole is provided can be minimized, and a structure that does not impede the under-cover function can be achieved, while still ensuring an air guide shape that more effectively cools the heat generating element.

In one aspect of the present invention, wall portions may be provided on the sides of the hole and on both sides of the heating element in the vehicle width direction, and the wall portions may be provided in the longitudinal region where the slope portion is provided.
With this invention, when the vehicle is running normally, the wall portion prevents the wind (hot air) from the fan from being directed toward the heat generating element, and the underfloor running wind (cooling air) guided from the hole along the underside of the slope portion can be concentrated toward the heat generating element.

This invention prevents hot air from the fan from being directed toward the top of the heat-generating element when the vehicle is running normally, allowing the heat-generating element to be cooled down to its upper surface by the airflow from under the floor. On the other hand, when the vehicle is stopped, the fan's air can be directed toward the heat-generating element to cool it even when there is no airflow from under the floor.

FIG. 2 is a cross-sectional view taken along line AA in FIG. 1; 2 is a cross-sectional view of the main part taken along line BB in FIG. 1; 2 is a cross-sectional view of the main part taken along line CC in FIG. 1; 2 is a cross-sectional view of the left side of the vehicle taken along line DD in FIG. 1; FIG. 2 is a bottom view of the main part of the vehicle undercarriage with the undercover removed. FIG. 4 is a top perspective view showing the undercover structure in the vicinity of the heat generating element. 5 is an explanatory diagram illustrating the flow of underfloor running air and hot air relative to the heating element; FIG.

The vehicle undercarriage structure includes a heating element provided below a floor panel of the vehicle, an undercover fixed to the vehicle body and provided below the heating element, and a fan that cools a heat source member and generates a rearward-flowing airflow in a space between the undercover and the floor panel in front of the heating element, the undercover preventing hot air from the fan from being guided to the top of the heating element during normal vehicle driving, and allowing the heating element to be cooled up to its upper surface by underfloor airflow while the vehicle is stopped, even when there is no underfloor airflow, by directing air from the fan to the heating element. The under-cover has a hole that introduces the airflow from under the under-cover from a position forward of the heating element when the vehicle is traveling, and a slope that slopes upward from the front end of the hole toward the rear. In the longitudinal region of the vehicle where the slope is provided, a wall member is provided that overlaps with the upper part of the heating element when viewed from the front of the vehicle, and a space is provided between the upper end of the slope portion and the lower end of the wall member that allows the inflow of air from the fan. The upper end of the slope portion overlaps with the central part of the heating element in the vertical direction when viewed from the front of the vehicle, and the slope portion is located on an extension of the wall member when viewed from the side of the vehicle .

An embodiment of the present invention will be described in detail below with reference to the drawings.
The drawings show the undercarriage of a vehicle, with Figure 1 being a bottom view showing the undercarriage of the vehicle, Figure 2 being a cross-sectional view taken along line A-A in Figure 1, Figure 3 being a cross-sectional view of a key part taken along line B-B in Figure 1, Figure 4 being a cross-sectional view of a key part taken along line C-C in Figure 1, and Figure 5 being a cross-sectional view of the left side of the vehicle taken along line D-D in Figure 1.

6 is a bottom view of the main part of the vehicle lower structure with the undercover removed, and FIG. 7 is a top perspective view of the undercover structure in the vicinity of the heating element.
Although the present invention can also be applied to electric vehicles, the following embodiment will be described with reference to a structure adopted in a vehicle with a system in which the rear wheels are driven by an engine mounted in the front of the vehicle, i.e., a front engine rear wheel drive (FR) system.

As shown in Figure 2, a dash lower panel 3 (dash panel) is provided to separate an engine compartment 1 from a passenger compartment 2 in the longitudinal direction of the vehicle. A dash cross member 4 is joined and fixed to the lower front part of the dash lower panel 3, and a cowl reinforcement 5 is joined and fixed to the upper front part of the dash lower panel 3.
A dash cross closed section 6 extending in the vehicle width direction is formed between the front surface of the dash lower panel 3 and the dash cross member 4 .

The dash lower panel 3 described above is mounted horizontally between a pair of left and right hinge pillars 7, 7 extending in the vertical direction of the vehicle, and a pair of left and right front side frames 8, 8 extend from the dash lower panel 3 toward the front of the vehicle. A pair of left and right apron reinforcements 9, which serve as vehicle body strength members, are provided above and on the outside of each front side frame 8 in the vehicle width direction.

A suspension housing 10 is provided between the upper apron reinforcement 9 and the lower front side frame 8. The front end of the apron reinforcement 9 and the front end of the front side frame 8 are connected in the vertical direction by a connecting member 11.
A heat exchanger unit 12 for cooling the engine air is disposed at the front end of the engine compartment 1.

This heat exchanger unit 12 includes a radiator 13 as a heat source, a radiator fan 14 as a fan, and a radiator cowling 15. The radiator 13 is a heat exchanger that uses the wind generated by the vehicle's running and the wind from the radiator fan 14 to air-cool the engine coolant. The radiator fan 14 is located rearward of the radiator 13 and is a fan that cools the radiator 13, a heat source, in front of the DC-DC converter 42, a heat-generating element described below, and generates rearward airflow in the space 53 (see Figure 2) between the undercovers 49-52 and the front floor panel 16.

On the other hand, a front floor panel 16 is provided at the lower rear end of the dash lower panel 3. This front floor panel 16 extends rearward from the lower rear end of the dash lower panel 3, and forms the floor surface of the passenger compartment 2. A tunnel section 17 is integrally or integrally formed at the center of the vehicle width direction of this front floor panel 16, protruding toward the passenger compartment 2 and extending in the fore-and-aft direction of the vehicle, as shown in Figures 1 and 5.

As shown in Figures 2 and 5, a tunnel side frame 18 extending in the fore-and-aft direction of the vehicle is provided at the corner between the lower end of the tunnel section 17 and the inner end of the front floor panel 16 in the vehicle width direction, and a tunnel side closed cross section 19 extending in the fore-and-aft direction of the vehicle is formed between the corner and the tunnel side frame 18.

As shown in Figures 3 and 4, an upwardly rising bent portion 16a is integrally formed at the rear end of the front floor panel 16, and a kick-up member 20 is attached to this bent portion 16a. This kick-up member 20 has a kick-up portion 20a that extends in the vertical direction and a rearward extending portion 20b that extends rearward from the upper end of the kick-up portion 20a.

A cross member 21 (the so-called No. 3 cross member) is joined and fixed between the lower end of the kick-up portion 20a and the rearward extending portion 20b of the kick-up member 20, and a cross member closed cross section 22 extending in the vehicle width direction is formed between the kick-up member 20 and the cross member 21.

As shown in FIG. 2, seat mounting brackets 23, 24 are provided at a distance in the longitudinal direction of the vehicle in the middle of the front floor panel 16. A cross member 25 (known as a No. 2.5 cross member) extending in the vehicle width direction is joined and fixed to the upper part of the front floor panel 16 in the middle of the longitudinal direction of the vehicle between the rear seat mounting bracket 24 of the vehicle and the kick-up portion 20a of the kick-up member 20.

As shown in Figures 3, 4, and 5, a cross-member closed cross section 26 extending in the vehicle width direction is formed between the above-mentioned cross member 25 and the front floor panel 16, and is configured to improve the rigidity of the lower vehicle body.

As shown in Figures 1 to 5, side sills 27 are provided at both left and right ends of the front floor panel 16 in the vehicle width direction as vehicle body rigidity members extending in the vehicle longitudinal direction. These side sills 27 are formed by joining a side sill outer 28 shown in Figure 1 with a side sill inner 29 shown in Figures 2 to 5, and have a closed cross section that extends in the vehicle longitudinal direction.

As shown in FIG. 5, the side sill inner panel 29 includes an inner wall 29a located on the inside in the vehicle width direction, an upper wall 29b and a lower wall 29c extending outward in the vehicle width direction from the upper and lower ends of the inner wall 29a, an upper joining flange portion 29d extending upward from the outer end of the upper wall 29b in the vehicle width direction, and a lower joining flange portion 29e extending downward from the outer end of the lower wall 29c in the vehicle width direction. For ease of explanation, in FIGS. 3 and 4, the area E29 of the side sill inner panel 29 in the vertical direction of the vehicle is indicated by an arrow. Also, as shown in FIG. 5, a joint member 30 is provided in the middle of the side sill inner panel 29 in the longitudinal direction of the vehicle.

As shown in Figure 5, a seat mounting bracket 31 is provided straddling the upper inner side of the cross member 25 in the vehicle width direction and the skirt portion of the tunnel section 17, and a seat mounting bracket 32 is provided straddling the upper outer side of the cross member 25 in the vehicle width direction and the upper wall 29b of the side sill inner 29.

As shown in Figures 3 and 5, a floor frame 33 is provided that extends in the fore-and-aft direction of the vehicle, spanning the outer underside of the front floor panel 16 in the vehicle width direction and the inner wall 29a of the side sill inner 29. A floor frame closed cross section 34 that extends in the fore-and-aft direction of the vehicle is formed between the floor frame 33 and the front floor panel 16.

The above-mentioned floor frame 33 has a bottom wall 33a, an inner wall 33b and an outer wall 33c that rise upward from both inner and outer ends of the bottom wall 33a in the vehicle width direction, and a joining flange portion 33d that extends inward in the vehicle width direction from the upper end of the inner wall 33b, and is formed with an approximately U-shaped cross section.
As shown in FIG. 5, the joining flange portion 33d of the floor frame 33 is joined and fixed to the underside of the front floor panel 16, and the outer wall 33c of the floor frame 33 is joined and fixed to the inner wall 29a of the side sill inner 29.

As shown in Figure 1, a pair of left and right front wheels 35, 35 are suspended from the vehicle body via front suspension arms. A front mudguard 36 and a rear mudguard 37 are provided on the front wheel-facing surface of the wheelhouse that surrounds and separates the upper half of the front wheels 35.

As shown in FIG. 1, a front side under cover 38 having a generally triangular shape in bottom view is provided on the front side of the lower end of the front mudguard 36 and protruding forward of the vehicle.
In the drawing, reference numeral 39 denotes a rear floor panel, and 40 denotes a rear wheel.

As shown in Figure 5, a DC-DC converter (direct current voltage converter) 42 serving as a heating element is provided below the vehicle's front floor panel 16 via a heating element support bracket 41.

As shown in Figures 5 and 6, the heating element support bracket 41 has a length in the vehicle width direction that extends between the bracket mounting portion 18a of the tunnel side frame 18, which is located on the inner side in the vehicle width direction, and the bottom wall 33a of the floor frame 33, which is located on the outer side in the vehicle width direction. The heating element support bracket 41 also has mounting portions 41a and 41b for mounting to the vehicle body at both inner and outer ends in the vehicle width direction.

As shown in Figures 5 and 6, the mounting portion 41a on the inner side of the heating element support bracket 41 in the vehicle width direction is fixed to the bracket mounting portion 18a of the tunnel side frame 18 using fastening members such as bolts 43 and nuts. The mounting portion 41b on the outer side of the heating element support bracket 41 in the vehicle width direction is fixed to the bottom wall 33a of the floor frame 33 using fastening members such as bolts 44 and nuts 45.

As shown in FIGS. 2, 3 and 4, the heating element support bracket 41 is provided below the front floor panel 16 so as to be positioned between the cross member 25 and the kick-up member 20.
A DC-DC converter 42 serving as a heating element is attached to the bracket body 41c of the heating element support bracket 41 using a plurality of sets of fastening members 46 such as bolts and nuts.

As shown in FIGS. 1 and 2, a plurality of under covers 47 to 52 are provided under the vehicle body.
The under cover 47 covers the area from directly below the heat exchanger unit 12 to below the middle part of the engine room 1 in the fore-and-aft direction of the vehicle, and in the width direction of the vehicle, the front part of the cover covers the space between the front side under covers 38, 38, and the rear part of the cover is a front under cover that covers the space between the front side frames 8, 8.

The undercover 48 is an intermediate undercover that covers the area from the lower middle of the engine compartment 1 to the lower part of the dash lower panel 3 in the longitudinal direction of the vehicle, and in the width direction of the vehicle, the front part of the cover covers the area between the front side frames 8, 8, and the rear part of the cover covers the area between the rear mudguards 37, 37.

The undercover 49 is a first undercover that covers from the lower portion of the dash lower panel 3 to the lower middle portion of the front floor panel 16 in the vehicle longitudinal direction, and from the lower middle portion of the tunnel portion 17 in the vehicle width direction to the lower portion of the side sill inner panel 29 on the left side of the vehicle in the vehicle width direction.

The undercover 50 is a second undercover that covers the area from below the middle portion of the front floor panel 16 in the longitudinal direction of the vehicle to below the rear portion of the rear floor panel 39, and in the width direction of the vehicle, from below the tunnel side frame 18 to below the side sill inner 29 on the left side of the vehicle.

The undercover 51 is a third undercover that covers from the lower portion of the dash lower panel 3 to the lower middle portion of the front floor panel 16 in the vehicle longitudinal direction, and from the lower middle portion of the tunnel portion 17 in the vehicle width direction to the lower portion of the side sill inner panel 29 on the right side of the vehicle in the vehicle width direction.

The undercover 52 is a fourth undercover that covers the area from below the middle portion of the front floor panel 16 in the longitudinal direction of the vehicle to below the rear portion of the rear floor panel 39, and in the width direction of the vehicle, from below the tunnel side frame 18 to below the side sill inner 29 on the right side of the vehicle.

As shown in FIGS. 1 and 2, the undersides of the undercovers 47 to 52 are formed to be substantially flat, and the undercovers 47 to 52 are fixed to the vehicle body.
2, the second undercover 50 of the undercovers 47 to 52 is provided below the DC-DC converter 42, which is a heating element. Furthermore, a space 53 is formed between each of the first to fourth undercovers 49 to 52 and the front floor panel 16, for allowing the radiator fan 14 and wind generated by the vehicle traveling to flow rearward.

That is, in this embodiment, a radiator fan 14 is provided in front of the DC-DC converter 42 of the vehicle as a fan that cools the radiator 13 and generates rearward airflow in the space 53 between the undercovers 49 to 52 and the front floor panel 16.
Of the first to fourth under-covers 49 to 52, the second under-cover 50 is configured as shown in FIGS.

In other words, the second undercover 50 comprises an undercover main body 50a whose undersurface is formed in a generally flat shape, a vertical wall portion 50b that rises upward from the outer end of the undercover main body 50a in the vehicle width direction and extends in the fore-and-aft direction of the vehicle, and an upper wall portion 50c that extends outward in the vehicle width direction from the upper end of the vertical wall portion 50b. For ease of explanation, in Figures 3 and 4, the area E50 of the second undercover 50 in the vehicle up-down direction is indicated by an arrow.

In addition, the undercover main body 50a of the second undercover 50 described above is integrally formed with a plurality of ribs 50d that rise upward from the undercover main body 50a and extend in any direction, thereby improving the rigidity of the second undercover 50.
Furthermore, as shown in FIGS. 1 and 7, an opening 50e is formed in the front portion of the under-cover body 50a of the second under-cover 50 and at a position close to the tunnel portion 17.

As shown in Figure 4, the second under-cover 50 has a hole 54 formed therein that introduces the airflow from under the second under-cover 50, i.e., the underfloor airflow e1 (see Figure 8), from a position forward of the DC-DC converter 42, which is a heat-generating element, while the vehicle is in motion. For ease of explanation, the area E54 of the hole 54 in the fore-and-aft direction of the vehicle is indicated by an arrow in Figure 4.

The second undercover 50 also has a sloped portion 55 that slopes upward toward the rear from the front end 54a of the hole 54. In this embodiment, the sloped portion 55 has an inclination angle of 25 degrees, but the inclination angle is not limited to this value.

Furthermore, in the region of the vehicle in the longitudinal direction where the slope section 55 is provided (i.e., within the longitudinal range of the slope section 55), a wall member 56 is provided that overlaps the upper part of the DC-DC converter 42 when viewed from the front of the vehicle.

In this embodiment, the wall member 56 is formed in an inclined shape, tilting downward from the front end of the bracket body 41c of the heating element support bracket 41 toward the front. In other words, the wall member 56 is formed integrally with the heating element support bracket 41.

Here, the wall member 56 is formed with a low front and high rear shape at an inclination angle of approximately 60 degrees relative to the bracket body 41c of the heating element support bracket 41, but is not limited to this numerical value of the inclination angle.
As shown in FIG. 5, the wall member 56 is provided so as to overlap substantially the entire upper portion of the DC-DC converter 42 in the vehicle width direction when viewed from the front of the vehicle.

Furthermore, as shown in Figure 4, a space 57 is provided between the upper inclined end of the slope portion 55 and the lower inclined end of the wall member 56, allowing air from the radiator fan 14 to flow in.

In short, the second undercover 50 described above has a hole 54 that introduces wind generated when the vehicle is traveling underneath the second undercover 50 from a position forward of the DC-DC converter 42, and a slope 55 that slopes upward toward the rear from the front end 54a of the hole 54. In the region of the vehicle in the fore-and-aft direction where the slope 55 is provided, a wall member 56 is provided that overlaps the upper part of the DC-DC converter 42 in a front view of the vehicle, and a space 57 is provided between the upper end of the slope 55 and the lower end of the wall member 56 to allow wind from the radiator fan 14 to flow in.

As a result, as shown in Figure 8, when the vehicle is running normally, the wall member 56 prevents the wind (hot air) e2 from the radiator fan 14 from being directed toward the top of the DC-DC converter 42, and the underfloor running wind e1 is guided from the hole 54 in the second under-cover 50 along the underside of the sloped portion 55 to the top of the DC-DC converter 42, thereby cooling not only the bottom surface of the DC-DC converter 42 but also the top surface of the DC-DC converter 42.

On the other hand, when the vehicle is stopped (in this embodiment, when the engine is idling and running without load), the wind from the radiator fan 14 flowing in from the space 57 hits the DC-DC converter 42, allowing the DC-DC converter 42 to be cooled even without underfloor running wind e1.

As shown in Figure 4, a water shielding plate 58 is provided as an opening suppression portion that extends upward from the rear end 54b of the hole 54. In this embodiment, the water shielding plate 58 is formed so that it slopes upward toward the front of the vehicle.

More specifically, the water shielding plate portion 58 is inclined at an angle of approximately 25 degrees relative to the under-cover body 50a of the second under-cover 50, with a front-high, rear-low slope. The front end of the water shielding plate portion 58 is positioned lower than the rear end of the slope portion 55, and an underfloor running air introduction hole 59 is formed between the rear end of the slope portion 55 and the front end of the water shielding plate portion 58. The inclination angle of the water shielding plate portion 58 is not limited to the 25 degrees shown in the example.

In this way, by providing a water shielding plate 58 as an opening prevention portion extending upward from the rear end 54b of the hole 54, the water shielding plate 58 prevents water kicked up from the road surface by the front wheels 35 shown in Figure 1 and moisture e3 contained in muddy water (see Figure 8) from entering the DC-DC converter 42 through the hole 54, thereby preventing the DC-DC converter 42 from becoming wet.

Furthermore, the water shielding plate portion 58 is configured to be inclined upward toward the front of the vehicle, thereby blocking the intrusion path of water and muddy water.
4, the inclined rear end of the slope portion 55 and the inclined front end of the water shielding plate portion 58 are disposed at approximately the same position in the vehicle longitudinal direction, thereby minimizing the opening area of the hole portion 54 and suppressing water from reaching the DC-DC converter 42.

Furthermore, as shown in Figures 3 and 7, connecting walls 60, 61 are provided on both the left and right sides of the hole 54 in the vehicle width direction, connecting the slope portion 55 and the water shielding plate portion 58.

The connecting wall 60 on the slope section 55 side is formed in the shape of a right triangle when viewed from the side of the vehicle, with its base connected to the undercover main body 50a at the front edge of the hole 54, its hypotenuse connected to the end of the slope section 55 in the vehicle width direction, and its opposite side connected to the opposite side of the connecting wall 61 on the water shielding plate section 58 side.

The connecting wall 61 on the water shielding plate 58 side is formed in the shape of a right triangle when viewed from the side of the vehicle, with its base connected to the under-cover main body 50a at the rear edge of the hole 54, its oblique side connected to the end of the water shielding plate 58 in the vehicle width direction, and its opposite side connected to the opposite side of the connecting wall 60 on the slope section 55 side.

As a result, the connecting walls 60, 61 block water and muddy water from entering from both sides of the hole 54 in the vehicle width direction, and the left and right connecting walls 60, 61 guide the underfloor traveling wind e1, thereby further improving cooling of the DC-DC converter 42.

In addition, as shown in Figures 5 and 7, the slope portion 55 is formed in a shape that widens toward the rear of the vehicle when viewed from above. In other words, the slope portion 55 is formed so that its widthwise dimension at the front end is relatively small and its widthwise dimension becomes relatively larger toward the rear end.

This minimizes the area required for the hole 54, ensuring a structure that does not impede the under-cover function, while still providing an airflow guide shape that more effectively cools the DC-DC converter 42, which acts as a heat source.

5 to 7, vertical walls 62 are provided as wall portions on both sides of the hole 54 in the vehicle width direction in front of the DC-DC converter 42. In this embodiment, as shown in Fig. 7, a pair of left and right vertical walls 62, 62 are provided on both left and right sides of the underfloor running air introduction hole 59 in the vehicle width direction, extending inward and outward in the vehicle width direction from the boundary between the front connecting wall portion 60 and the rear connecting wall portion 61.
The vertical wall 62 is provided in the front-rear direction region where the slope portion 55 is provided.

As a result, during normal vehicle operation, the vertical wall 62 prevents the wind (hot air) from the radiator fan 14 from being guided toward the DC-DC converter 42, and the underfloor traveling wind (cooling air) e1 (see Figure 8) guided from the hole 54 along the underside of the slope 55 is concentrated toward the DC-DC converter 42.

FIG. 8 is an explanatory diagram showing the flow of underfloor traveling air e1 and air (hot air) e2 from the radiator fan 14 relative to the DC-DC converter 42 as a heat generating element.
The operation of the vehicle undercarriage structure constructed as above will be described below with reference to FIG.

When the vehicle is running normally, air (hot air) e2 from the radiator fan 14 flows from the front to the rear of the vehicle through the space 53, and this air (hot air) e2 is prevented from being guided above the DC-DC converter 42 by the wall member 56 integrated with the heating element support bracket 41.

Therefore, the air (hot air) e2 from the radiator fan 14 flows upward and rearward along the wall member 56, and then flows above the heating element support bracket 41 toward the rear of the vehicle.
In particular, when a boat or the like is towed to the rear of the vehicle via a trailer hitch, the engine load during driving becomes even greater and the wind generated by the radiator fan 14 becomes hot air. Therefore, by using the wall member 56 to divert the hot air e2 above the heating element support bracket 41, the thermal impact on the DC-DC converter 42 can be reduced.

When the vehicle is traveling normally as described above, underfloor traveling wind e1 is generated. This underfloor traveling wind e1 is introduced from the hole 54 in the second under-cover 50, through the underside of the sloped portion 55, and via the underfloor traveling wind inlet hole 59 into the space where the DC-DC converter 42 is located.

The underfloor traveling airflow e1 introduced from the underfloor traveling airflow inlet 59 into the space where the DC-DC converter 42 is located is divided into airflow flowing above the DC-DC converter 42 and airflow flowing below the DC-DC converter 42, as shown by the arrows in Figure 8, thereby cooling the DC-DC converter 42 from its bottom to its top.

On the other hand, when the vehicle is stopped, underfloor running airflow e1 is not generated. When the vehicle is stopped, air from the radiator fan 14 hits the DC-DC converter 42 through the space 53 between the undercovers 49-52 and the front floor panel 16, and the space 57 between the upper end of the slope section 55 and the lower end of the wall member 56, thereby cooling the DC-DC converter 42.

When the vehicle is traveling as described above, if the front wheels 35 kick up water e3 contained in muddy or water from the road surface, this water e3 flows rearward along the underside of the second under-cover 50 along with the underfloor traveling wind e1. However, water e3 flowing rearward and upward from the area where the hole 54 is formed first hits the water shielding plate 58, as shown by the arrow in Figure 8, and then bounces off this water shielding plate 58 downward. This prevents the DC-DC converter 42 from becoming wet.

In the diagram, arrow F indicates the front of the vehicle, arrow R indicates the rear of the vehicle, arrow IN indicates the inward direction in the vehicle width direction, arrow OUT indicates the outward direction in the vehicle width direction, and arrow UP indicates the top of the vehicle.

As described above, the vehicle undercarriage according to the above embodiment is a vehicle undercarriage comprising: a heating element (DC-DC converter 42) provided below the vehicle floor panel (front floor panel 16); an undercover (second undercover 50) fixed to the vehicle body and provided below the heating element (DC-DC converter 42); and a fan (radiator fan 14) located in front of the heating element (DC-DC converter 42) to cool a heat source member (radiator 13) and generate rearward airflow in the space 53 between the undercover (second undercover 50) and the floor panel (front floor panel 16). The second undercover (50) has a hole 54 that introduces airflow from under the undercover (second undercover 50) from a position forward of the heating element (DC-DC converter 42) while the vehicle is moving, and a slope 55 that slopes upward and rearward from the front end 54a of the hole 54. In the region of the vehicle in the fore-and-aft direction where the slope 55 is provided, a wall member 56 is provided that overlaps the upper part of the heating element (DC-DC converter 42) in a front view of the vehicle, and a space 57 is provided between the upper end of the slope 55 and the lower end of the wall member 56 to allow air from the fan (radiator fan 14) to flow in (see Figures 2, 4, and 8).

With this vehicle undercarriage structure, when the vehicle is running normally, the wall member 56 prevents the wind (hot air) e2 from the fan (radiator fan 14) from being directed toward the top of the heat-generating element (DC-DC converter 42), and the underfloor running wind e1 is guided from the hole 54 along the underside of the sloped portion 55 to the top of the heat-generating element (DC-DC converter 42), thereby cooling not only the underside of the heat-generating element (DC-DC converter 42) but also the top surface of the heat-generating element (DC-DC converter 42).

On the other hand, when the vehicle is stopped, the wind from the fan (radiator fan 14) flowing in from the space 57 hits the heat generating element (DC-DC converter 42), so that the heat generating element (DC-DC converter 42) can be cooled even without wind from running.
The slope portion 55 allows the outside air to be drawn in without disturbing the flow of underfloor traveling wind e1 due to the viscosity of the air flowing along the underside of the slope portion 55.

The vehicle undercarriage also includes an opening suppression portion (water shielding plate portion 58) extending upward from the rear end portion 54b of the hole portion 54 (see FIG. 4).
With such a vehicle undercarriage structure, the opening suppression portion (water barrier portion 58) prevents water kicked up from the road surface by the wheels (front wheels 35) and moisture contained in muddy water from entering through the hole portion 54, thereby preventing the heating element (DC-DC converter 42) from becoming wet.

Furthermore, in this vehicle undercarriage structure, the rear end of the slope portion 55 and the front end of the opening suppression portion (water shield plate portion 58) are disposed at approximately the same position in the vehicle fore-and-aft direction (see FIG. 4).
According to such a vehicle undercarriage structure, the opening area of the hole 54 can be minimized while preventing the heat generating element (DC-DC converter 42) from being exposed to water.

Furthermore, in the undercarriage structure of such a vehicle, connecting wall portions 60, 61 are provided on both sides of the hole portion 54 in the vehicle width direction, connecting the slope portion 55 and the opening suppression portion (water barrier portion 58) (see Figures 3 and 7).
With this type of vehicle undercarriage structure, the connecting walls 60, 61 can block water and muddy water from entering from both sides of the hole 54 in the vehicle width direction, and the connecting walls 60, 61 guide the underfloor running wind e1, thereby allowing the heat-generating element (DC-DC converter 42) to be cooled even more effectively.

Additionally, in such a vehicle undercarriage structure, the opening suppressing portion (water shielding plate portion 58) is inclined upward toward the front of the vehicle (see FIG. 4).
According to such a vehicle undercarriage structure, the opening suppressing portion (water blocking plate portion 58) having the above-mentioned inclined structure can block the intrusion path of water and muddy water.

In addition, in such a vehicle undercarriage structure, the slope portion 55 is formed in a shape that widens toward the rear of the vehicle in a plan view (see FIGS. 5 and 7).
According to such a vehicle undercarriage structure, the area in which the hole 54 is provided can be minimized, and the structure does not impede the function of the undercover 50, while ensuring an air guide shape for more effectively cooling the heat-generating element (DC-DC converter 42).

Furthermore, in this vehicle undercarriage, walls (vertical walls 62) are provided on the sides of the hole 54 and on both sides of the heating element (DC-DC converter 42) in the vehicle width direction, and these walls are provided in the longitudinal region where the slope portion 55 is provided (see Figure 7).

With this vehicle undercarriage structure, during normal vehicle operation, the wall (vertical wall 62) prevents the wind (hot air) e2 from the fan (radiator fan 14) from being directed toward the heat-generating element (DC-DC converter 42), and the underfloor traveling wind (cooling air) e1 guided from the hole 54 along the underside of the slope 55 can be concentrated toward the heat-generating element (DC-DC converter 42).

In the configuration of this invention and the correspondence with the above-mentioned embodiment,
The heat source member of the present invention corresponds to the radiator 13 of the embodiment.
Similarly,
The fan corresponds to the radiator fan 14,
The floor panel corresponds to the front floor panel 16,
The heating element corresponds to the DC-DC converter 42,
The undercover corresponds to the second undercover 50,
The opening suppression portion corresponds to the water shielding plate portion 58,
The wall portion corresponds to the vertical wall 62,
The present invention is not limited to the configurations of the above-described embodiments.

For example, in the above embodiment, the DC-DC converter 42, which is an electrical control component, was used as the heating element, but the heating element may also be a differential, which is a drivetrain component.

Furthermore, in the above embodiment, the radiator 13, which is an air-cooling element of an internal combustion engine, was used as an example of the heat source member, but when the present invention is applied to an electric vehicle, the heat source member may also be a motor.

As described above, the present invention is useful for a vehicle undercarriage that includes a heating element provided below a floor panel of the vehicle, an undercover that is fixed to the vehicle body and provided below the heating element, and a fan that is located in front of the heating element and that cools a heat source member and generates a rearward-flowing wind in the space between the undercover and the floor panel.

13... Radiator (heat source member)
14...Radiator fan (fan)
16...Front floor panel (floor panel)
42...DC-DC converter (heating element)
50...Second undercover (undercover)
53... Space 54... Hole portion 55... Slope portion 56... Wall member 57... Space portion 58... Water shield plate portion (opening suppression portion)
60, 61...connecting wall portion 62...vertical wall (wall portion)

Claims (7)

a heating element provided below a floor panel of the vehicle;
an undercover fixed to the vehicle body and provided below the heating element;
a fan in front of the heat generating element that cools a heat source member and generates a rearward airflow in a space between the undercover and the floor panel,
The above under cover is
a hole portion that introduces airflow from under the undercover from a position forward of the heating element when the vehicle is traveling;
a slope portion extending upward from the front end of the hole toward the rear,
a wall member provided in a vehicle front-rear direction region where the slope portion is provided, the wall member being provided so as to overlap an upper portion of the heating element in a front view of the vehicle;
a space portion that allows airflow from the fan to flow in is provided between an upper end of the slope portion and a lower end of the wall member ,
an upper end of the slope portion and a central portion of the heating element in the vehicle vertical direction overlap each other in a front view of the vehicle;
A vehicle undercarriage structure characterized in that the slope portion is located on an extension line of the wall member in a side view of the vehicle . 2. The vehicle undercarriage structure according to claim 1, further comprising an opening suppression portion extending upward from a rear end of the hole portion. 3. The vehicle undercarriage structure according to claim 2, wherein the rear end of the slope portion and the front end of the opening suppression portion are disposed at substantially the same position in the vehicle longitudinal direction. 4. The vehicle undercarriage structure according to claim 2, further comprising connecting walls that connect the slope portion and the opening suppression portion on both sides of the hole in the vehicle width direction. 5. The vehicle undercarriage structure according to claim 2, wherein the opening suppression portion is inclined upward toward the front of the vehicle. 6. The vehicle undercarriage structure according to claim 1, wherein the slope portion is formed in a shape that widens toward the rear of the vehicle in a plan view. A vehicle undercarriage structure as described in any one of claims 1 to 6, wherein wall portions are provided on the sides of the hole and on both sides of the heating element in the vehicle width direction, and the wall portions are provided in the fore-and-aft region where the slope portion is provided.