FR2846290A1 - Automobile emergency braking device comprises profiled bottom under bodywork at first height able to rapidly occupy lower height in response to release signal - Google Patents

Abstract

The emergency braking device comprises a profiled bottom (10,20) located under the bodywork (1) having a shape which causes a vertical support by means of a Venturi effect. The profiled bottom is located at a first height and able to rapidly occupy a second height lower than the first height in response to a release signal. The bodywork is lowered by release means (7) which control the suspension height.

Description

Emergency braking device and method for a motor vehicle

  The invention relates to a braking device and method.

  emergency for a motor vehicle.

  There are situations where extreme emergency braking 10 is necessary to avoid an accident. Current vehicles, with conventional braking devices, have limited deceleration capacities of the order of 1 G. This technical limit of conventional braking systems, imposed by the connection between the tire and the road, results in

  considerable braking distances.

  There are known emergency braking systems consisting of

  apply a brake shoe or an additional brake plate to the ground, the descent of which is triggered in the event of an accident.

  These plates can be simple friction plates, as known from document US 4,325,465, or include vacuum means as known from documents US 3,116,897, US 3,167,154, US 4,317,507, US 4,896 749, WO 00/44599. All these devices require special means to create this depression, generally a vacuum pump, and most also require special devices to apply the depression and guarantee the sealing of the application by means of flexible lips 25 or the like. These devices have many drawbacks. They are

  often bulky and pose a storage problem under the vehicle. It is often difficult to seal the suction cavity. The power consumption of the vacuum pump is excessive, but above all the start-up of the vacuum pump requires far too long to be able to be used effectively in the context of emergency braking.

  In a different context, it has also already been proposed to use the vacuum in a skirt disposed under a vehicle to create a vertical support on the vehicle and improve its grip on the road, as for example according to documents US 1 698 482, US 3,209,849, US 3,232,633, 35 US 3,628,625. This skirt may be partly retractable, for example by means of inflation, as shown in document US 3

894,609.

  It has also been proposed to improve the grip of vehicles, in particular race cars, by using the aerodynamic effect of Venturi making it possible to create a depression under the vehicle. For example, document US 3,776,587 shows a plate fixed below the body at the front of the car, making it possible to create a venturi helping to keep the car on the ground, especially when cornering. GB 2,269,142 shows the combination of the Venturi effect and various fins to improve ground stability. Document US 4,386,801 discloses a profiled bottom disposed under the body of the vehicle and the shape of which is designed to cause a permanent vertical support by Venturi effect. Side skirts complete the air confinement under the body. The bottom is

  fixed height attached to the vehicle axles.

  Other means of emergency braking are known, such as anchoring to the ground (for example by document CN 1075683) or backfire braking, but these systems have drawbacks, such as that of degrading the road for the first and not to be ecological for the second. The object of the invention is to remedy the drawbacks of traditional emergency braking systems and to propose a new emergency braking system which makes it possible to very quickly generate a

  efficient vehicle deceleration without harming the environment.

  The invention achieves its object by proposing an emergency braking device 25 for a vehicle of the type comprising a profiled bottom disposed under the body of the vehicle and whose shape is such as to cause vertical support by Venturi effect, characterized in that that the bottom is disposed at a first height and capable of coming quickly, in response to a trigger signal, to occupy a second height less than the first, said second height and the shape of the profiled bottom when it is at this second height being likely to cause a Venturi effect support

  additional vertical suddenly acting on the vehicle.

  Thus, unlike the prior art represented by document US Pat. No. 4,386,801 which uses the Venturi effect permanently (and moreover 35 in the context essentially of motor racing), the invention aims to use the effect Venturi only during an emergency braking situation. In a first embodiment, the profiled bottom is permanently in place under the vehicle body, at a fixed distance therefrom or even coincident with the body bottom, and triggering means

  acting in response to the trigger signal, play on the suspension to cause the vehicle body to drop quickly from the ground. These means acting on the suspension can be either means acting on a suspension control or else destructive means instantly reducing the suspension height.

  In a second embodiment, the profiled bottom under the body is movable relative to the body and held by mounting means which make it possible to move said bottom from the body when the emergency braking is triggered. The retracted bottom may retain its profiled shape or be in a modified shape during retraction, the shape of the bottom then being different in the high position (the shape there preferably being flat to facilitate retraction) and in the low position. The bottom is advantageously constituted by sections of articulated plates

  likely to take, in the deployed position, a convergent shape.

  The immediate increase in the vertical support of the vehicle when triggering according to the invention results in better grip of

  tires on the ground and therefore better braking.

  We can further increase this braking by providing pads

  braking linked to the vehicle body or the profiled bottom and coming into contact with the ground when emergency braking is triggered.

  In all the embodiments, it is advantageous to provide

  side skirts for confining the flow, and preferably retractable skirts when the bottom is in the high position. These skirts associated with the profiled bottom can receive the brake pads also associated with the bottom.

  The invention also relates to an emergency braking method for a vehicle of the type comprising a profiled bottom disposed under the body of the vehicle and whose shape is such as to cause a vertical support by Venturi effect, characterized in that quickly passing, in response to a trigger signal, the bottom of a first height to a second height less than the first, said second height and the shape of the profiled bottom when it is at this second height being of a nature to cause by Venturi effect an additional vertical support suddenly acting on

the vehicle.

  Other characteristics and advantages of the invention will become apparent from

  reading the description which follows, with reference to the accompanying drawings

  in which: FIG. 1 is a diagrammatic side view of the body of a vehicle equipped with a fixed profiled underbody, in accordance with a first embodiment of the invention, FIG. 2 is a diagrammatic view of side of the body of a vehicle equipped with a movable profiled underbody, in accordance with a second embodiment of the invention,

  FIG. 3 is a perspective view of a variant of the movable profiled base according to the second embodiment.

  Figure 1 shows the body 1 of a vehicle resting in normal position on the front 2 and rear 3 suspensions of the wheels 4 and 5. The body 1 has a flat bottom 10 or is doubled by such a flat bottom 10 constituting the profiled bottom of the invention, and comprising in particular a converging inclined part 20 at the front, here corresponding to the front axle passage. In

  this position, the bottom 10 is at a significant distance from the ground 6 and the Venturi effect is at a first level, generally relatively weak and negligible, even zero. The flat bottom 10 nevertheless makes it possible to reduce aerodynamic friction in the underbody and therefore goes in the direction of a reduction in fuel consumption.

  When the emergency braking conditions are detected, by the driver or by a detection device incorporated in the vehicle, means 7 allow the suspensions 2 and 3 to be lowered instantaneously, so that the body 1 finds itself in the low position marked 1 ', in which the profiled bottom 10, in position 10', is very close to the ground 6. In this position, the Venturi effect is at the second level, clearly superior to the

  first, and therefore becomes very sensitive and effective.

  The means 7 for lowering the suspension can be produced in several forms: -with piloted suspensions, the actuation being effected by hydraulic or electric jacks, -with a sudden rupture of an element of the suspension, such as a spring , spring cup, etc. -with a pyrotechnic cartridge which propels the vehicle on

the stops.

  Simultaneously with the lowering of the suspension, vertical side skirts 8 were deployed; these side skirts were in the high position of the body kept folded horizontally under the bottom 10. These side skirts 8 are intended to laterally close the underside of

  body and form with the ground 6 and said bottom 10 'a conduit with a flattened rectangular section in which the Venturi effect will be applied, by virtue of the inlet convergent 11 in position 11'. The skirts 8, rubbing against the road 6, are made of a wear-resistant material. They seal the flow 15.

  The whole system allows a very significant reduction in the braking distance. For example, for a normal distance of 75 meters when the vehicle is traveling at 130 km / h on a dry road, the braking distance with the invention can increase to 35 m with a deceleration of the order of 4 G. 20 The figures 2 and 3 illustrate another embodiment of the invention. The system essentially consists of a movable profiled plate 20 under the body 1 between a retracted position where it is stored under the body 1 (position not shown) and a deployed position

  shown in Figures 2 and 3 o it descends near the ground 6.

  The plate 20 is supported at the body 1 by slide links 21 shown schematically in Figure 2, which allow the plate to descend vertically and, once in contact with the ground, the plate 20 can remain substantially parallel to the ground independently pitch

  vehicle (pitch in particular related to sudden braking).

  As shown in Figure 2, the plate 20 has a major

  almost horizontal part 24, slightly convergent. This part 24 is preceded by a strongly convergent part 22, 23. On the other hand, the plate 20 is bordered laterally by vertical skirts 25 which may be of different nature depending on the sections 22, 23, 24 of the plate. These skirts 25 35 are retracted when the plate is in the raised position.

  On the other hand, there are provided braking pads 26 constituted for example by the underside of the skirts 25, made, over their entire length or only over a part thereof, made of a material with a high coefficient of friction. The plate 20 and its skirts 25 form a rapidly decreasing cross-sectional duct and causing, by Venturi effect, the creation of a vertical support which is transformed, thanks to the sliding links 21 into a component

  horizontal brake drag 27.

  Figure 3 details an alternative embodiment of the plate 20, 10 consisting of a main section 24 bordered by rubber pads 28 constituting for this section both the confinement skirt and the brake pads. These pads 28 can optionally be fitted with metallic and grooved inserts or provided with various reliefs intended to improve their adhesion and their transverse barrier effect for flow. At the front of the section 24 are articulated two converging sections 22 and 23, forming the inlet of the flow confinement conduit. These two sections are bordered by parallel resistant strands 29 organized like a broom and constituting the confinement skirt for these sections. These strands can moreover extend even in front of the input plate 23, as shown. Tie rods 30 and telescopic tie rods 31 are provided to articulate the plate 20 to the body. Wheels 32 can be provided to help the plate to correctly position itself on the road when it is deployed during emergency braking. In one embodiment, the height of the skirts 28 at the outlet from the flow confinement duct is 20 mm while the height of the skirts 29 at the inlet is 170 mm. The flow section, about 0.17 m2 at inlet 33 is only 0.016 m2 at outlet 34, which creates a strong vertical support by Venturi effect and therefore a

  heavy braking on the plate 20.

  A hatch 35 can be provided in section 24 of the plate 20.

  It is possible to make another connection of the plate and the body than the slide connections 21. One can use tensioned cables, the plate being permanently on the ground, or arms provided with ball joints in both.

  tips to control the descent of the plate.

  The plate can be made up of articulated sections as shown intended to take their relative positions after deployment * thanks to an ad hoc tie system or the like. Alternatively, the plate can be made of a shape memory material which can be stored flattened under the body but regains its profiled shape when the plate is

  lowered in the event of emergency braking.

Claims (10)

  1. Emergency braking device for a vehicle of the type comprising a profiled bottom (10, 20) disposed under the body (1) of the vehicle and whose shape is such as to cause vertical support by Venturi effect, characterized in that the profiled bottom (10, 20) is disposed under the vehicle body at a first height and capable of coming quickly, in response to a trigger signal, to occupy a second height less than the first, said second height and the shape from the profiled bottom 10 (10, 20) when it is at this second height being such as to cause by Venturi effect an additional vertical support acting suddenly on the vehicle.   2. Device according to claim 1, characterized in that the profiled bottom 15 (10) is permanently in place under the vehicle body, at a fixed distance from the latter and trigger means (7) acting in response to the signal trigger trigger lowering   fast of the vehicle body (1) with respect to the ground.   3. Device according to claim 2, characterized in that the means (7) for lowering the body (1) of the vehicle are chosen from suspension height control means and destruction means   reducing the suspension height.   4. Device according to claim 1, characterized in that the profiled bottom (20) is movable relative to the body (1) and maintained by mounting means (21,30) which allow to move said bottom (20) from the cash register   when emergency braking is triggered.   5. Device according to claim 4, characterized in that the bottom (20) takes a different shape in its high position and in its low position. 6. Device according to claim 5, characterized in that the bottom (20) is constituted by sections (24, 22, 23) of articulated plate and taking   a convergent shape in the deployed position.   7. Device according to any one of claims 1 to 6, characterized   in that side skirts (8, 29) are associated with the profiled bottom (10,).   8. Device according to claim 7, characterized in that the side skirts (8, 10 29) are retractable when the bottom is in the high position.   9. Device according to any one of claims 1 to 8, characterized   in that braking pads (28) are associated with the profiled bottom.   10. Emergency braking method for a vehicle of the type comprising a profiled bottom (10, 20) disposed under the body (1) of the vehicle and whose shape is such as to cause a vertical support by Venturi effect, characterized in that that the bottom (10, 20) is rapidly passed, in response to a trigger signal, from a first height to a second height 20 lower than the first, said second height and the shape of the profiled bottom when it is at this second height being of such a nature as to cause by Venturi effect an additional vertical support acting suddenly on the vehicle.