FR3052719A1 - "MOTOR VEHICLE ROLLING TRAIN EQUIPPED WITH A HOMOCINETIC JOINT PROTECTIVE SHIELD" - Google Patents

Abstract

The invention relates to a train (10) rolling of a motor vehicle comprising: - at least one wheel (12) rotatably mounted on a structure of the motor vehicle; a wheel shaft (26); a homokinetic joint (30) coupling the wheel shaft (26) with the driving wheel (12) and comprising a bellows (42) for protecting an elastomer material; a device for protecting the bellows (42); characterized in that the protective device is formed by a shield (46) which is fixedly mounted with respect to a structural element of the motor vehicle and which is arranged radially away from the constant velocity joint (30).

Description

"Motor vehicle rolling stock equipped with a protective shield for a constant velocity joint"

TECHNICAL FIELD OF THE INVENTION The invention relates to a motor vehicle running gear comprising a constant velocity joint equipped with a protective bellows of elastomeric material. The invention more particularly relates to a running gear of a motor vehicle comprising: - at least one driving wheel rotatably mounted on a structure of the motor vehicle; - a wheel shaft; - A constant velocity joint coupling the wheel shaft with the driving wheel and having a protective bellows elastomeric material; a device for protecting the bellows.

BACKGROUND ART OF THE INVENTION

The motor vehicle trains carrying the drive wheels are equipped with wheel shafts that allow transmission of engine torque to the drive wheels. A first inner end of each wheel shaft is coupled to a transmission torque shaft of the gearbox. The assembly formed by the engine and the gearbox is mounted on a suspended structure element of the vehicle, for example a chassis, while a second outer end of each wheel shaft is coupled with a rocket of the associated drive wheel free mounting in rotation on an unsprung structural element of the vehicle, for example a stub axle.

As is known, said suspended structural element is articulated with the unsprung structural element via at least one suspension arm, such as a wishbone. Thus, the suspended structural element is likely to move in a movement at least vertical relative to the unsprung structural element.

In addition, when the wheels of said motor vehicle train are steered, the unsprung structural element is pivotally mounted about a substantially vertical axis relative to the suspended structural element of the motor vehicle to allow to steer the steering wheels in both ways.

In order for the wheel shaft to be able to follow the movements of the suspension and the steering of the wheels, it is known to articulate each end of the wheel shaft via homokinetic joints, in particular constant velocity ball joints. Such constant velocity joints allow the wheels to be driven without causing irregular rotation of the shafts.

The first inner end of the wheel shaft is thus coupled with the transmission shaft via a homokinetic joint allowing axial sliding of the shaft and a ball joint. Such a constant velocity joint is for example a seal called "tripod joint".

The second outer end of the wheel shaft is coupled with the wheel spindle via a constant velocity joint allowing only a ball joint connection. This is for example a ball joint. The invention relates more specifically to the constant velocity joint coupling the second outer end of the wheel shaft with the wheel spindle. This constant velocity joint comprises rolling elements, in particular balls, which are lubricated for example by means of a reserve of grease.

To ensure that the rolling elements operate without jamming and noise, the constant velocity joint is equipped with a bellows that surrounds these rolling elements to retain the grease while preventing particles from coming into contact with the rolling elements. Such a bellows is made of a thick elastomeric material that does not hinder the movements of the constant velocity joint.

The bellows of the constant velocity joint coupled with the wheel rocket is exposed directly to splashes of blunt bodies, such as gravel, pieces of wood, etc. When the bellows is pierced, the lubricating grease escapes and particles are likely to come into contact with the rolling elements. The homokinetic joint then becomes noisy or even deteriorates.

To solve this problem, it has already been proposed to equip the constant velocity joint with a rigid protective sleeve which completely surrounds the bellows to screen the bodies projected. This protective sleeve is carried by a member integral in rotation with the wheel spindle. A narrow radial space is reserved between the bellows and the sleeve to prevent the bellows from rubbing against the sleeve when the constant velocity joint is bent. This sleeve is made of thin sheet.

However, it was found that this sleeve was likely to deform permanently during a particularly violent percussion with a blunt body. Due to the proximity of the sleeve to the bellows, the sleeve thus deformed comes into permanent contact with the bellows. When the seal is flexed, the sleeve rubs against the bellows. Repeated friction eventually causes premature wear of the bellows resulting in leakage of lubricating grease, or even deterioration of the constant velocity joint.

BRIEF SUMMARY OF THE INVENTION The invention proposes a motor vehicle train of the type described above, characterized in that the protection device is formed by a shield which is fixedly mounted relative to a structural element of the motor vehicle and which is arranged radially away from the constant velocity joint.

According to other characteristics of the invention: the structure of the vehicle comprises at least one unsprung structural element which carries the rotating drive wheel, and at least one suspended structure element which is articulated with the non-structural element suspended via at least one suspension arm; - the shield is attached to a non-suspended structural element; - The shield is attached to a brake caliper which is itself attached to said unsprung structural element; the shield comprises at least one axial front section which masks the constant-velocity joint forwardly in the direction of normal movement of the vehicle; the shield comprises at least one lower axial section which masks the homokinetic joint towards the ground; the shield partially envelops the constant velocity joint; the shield has a plurality of holes; the shield is made of a heat-conducting metallic material such as aluminum; - The shield is made of a rigid plastic material.

BRIEF DESCRIPTION OF THE FIGURES Other features and advantages of the invention will emerge during the reading of the detailed description which will follow for the understanding of which reference will be made to the appended drawings in which: FIG. 1 is a sectional view transverse along the sectional plane 1-1 of Figure 3 which shows a motor vehicle undercarriage having a constant velocity joint connecting a wheel axle with a wheel shaft; - Figure 2 is a front view which shows the undercarriage of Figure 1 which is equipped with a shield made according to a first embodiment of the invention; - Figure 3 is a longitudinal sectional view along the sectional plane 3-3 of Figure 2 which shows the constant velocity joint protected by the shield attached to a brake caliper; - Figure 4 is a cross-sectional view on a larger scale which shows the homokinetic joint of the undercarriage of Figures 1 to 3; FIG. 5 is a detail view showing the constant velocity joint flexed so that the wheel spindle forms an angle with the wheel shaft; - Figure 6 is a front view which shows the protective shield of the constant velocity joint of Figure 3; - Figure 7 is a sectional view along the section plane 7-7 of Figure 6 which shows the shape of the shield; FIG. 8 is an end view of the shield of FIG. 6; - Figure 9 is a view similar to that of Figure 8 which shows a second embodiment of the invention wherein the shield is more enveloping.

DETAILED DESCRIPTION OF THE FIGURES

In the remainder of the description, the following will be adopted without limitation: longitudinal orientation directed from rear to front according to the direction of normal movement of the motor vehicle; vertical directed from the bottom up orthogonally to the road; - transverse orthogonal to the longitudinal and vertical directions.

It will also adopt an axial orientation directed coaxially with the axis "A" of rotation of the drive wheel of the vehicle and radial directions directed from the axis of rotation of the wheel to the outside.

The terms "exterior" and "interior" will be used in relation to the transverse proximity of an element to a median longitudinal vertical plane of the vehicle. An interior element will thus be close to the median plane.

In the remainder of the description, elements having an identical structure or similar functions will be designated by the same reference.

FIG. 1 partially shows a motor vehicle rolling gear. This is a front train of a motor vehicle. The rolling gear 10 comprises at least one driving wheel 12 rotatably mounted on a structure of the motor vehicle. Such a rolling train here comprises two driving wheels 12 of which only one is shown.

The driving wheel 12 is rotated about a generally transverse axis "A" by an element 14 of unsprung structure via a rocket wheel 16. The rocket wheel 16 is mounted to rotate with the wheel 12. The unsprung structure element 14 is formed by a knuckle bearing a rolling bearing housing the knuckle carrier 14. The wheel 12 has been shown in FIG. broken lines for reasons of clarity.

The knuckle 14 is hinged with an element 18 of suspended structure of the vehicle via at least one arm 20 suspension. The element 18 of suspended structure is for example formed by a chassis of the vehicle. The suspension arm 20 forms a connecting rod, each end of which is pivotally mounted about a substantially longitudinal axis on the knuckle carrier 14, on the one hand, and on the frame 18, on the other hand.

The front train also includes a suspension strut and a shock absorber that are not shown. In the case of a forward train here, the driving wheel 12 is also steering. For this purpose, the knuckle 14 is pivotally mounted about a vertical axis (not shown) relative to the chassis 18 of the motor vehicle.

As illustrated in FIG. 2, the wheel spindle 16 here carries a brake disk 21 which rotates solidly with the wheel 12. A brake caliper 23 overlapping the brake disk 21 is here fixed to the rocket carrier 14. The brake caliper 23 is more particularly fixed longitudinally in front of the axis "A" of rotation of the wheel 12 as can be seen in FIG.

The chassis 18 of the vehicle comprises a rotary transmission shaft 22 which is linked to the output of a gearbox 22 carried by the chassis 18. The torque of the transmission shaft 22 is intended to be transmitted to the driving wheel 12 via a wheel shaft 26 of generally transverse axis.

An inner end of the wheel shaft 26 is coupled with the transmission shaft 22 by a first homokinetic joint 28 forming a ball joint connection and further allowing a transverse sliding clearance of the wheel shaft 26 with respect to the transmission shaft 22. The first homokinetic joint 28 is for example a tripod joint.

An outer end of the wheel shaft 26 is coupled with the wheel spindle 16 via a second homokinetic joint 30 making a ball joint connection. The second homokinetic joint is for example a ball joint.

In the following, we will focus more particularly on the second homokinetic joint coupling the wheel shaft 26 with the rocket 1 6.

The second homokinetic joint is shown in greater detail in FIG. 4. It has a nut 32 which is attached to the outer end of the wheel shaft 26. The nut 32 comprises a section-shaped track of sphere on which balls 34, for example six balls 34, are held in rolling contact by a cage 36. The nut 32 thus equipped with its balls 34 is inserted into a complementary bowl 38 axially open at the inner end of the wheel rocket 16. The concave face of the bowl 38 is provided with grooves 40 extending axially in an arc centered on the track of the nut 32. Each groove 40 receives a ball 34 associated guide.

This arrangement allows the coupling of the rocket 16 with the wheel shaft 26 by circumferential contact between the balls 34 and the grooves 40 while allowing a ball joint connection by rolling the balls 34 in the grooves 40.

Thus, as shown in FIG. 5, the homokinetic joint is capable of being bent so that the wheel shaft 26 forms an angle of deviation with respect to the axis of the rocket 16 while retaining its coupling function.

Since the driving wheel 12 is also directing, such a homokinetic joint enables the driving wheel 12 to pivot by an angle sufficient to allow the steering of the vehicle, for example at an angle α of 50 ° in both directions with respect to its neutral direction.

Alternatively, the arrangement of the bowl and the nut are likely to be reversed, the bowl being then carried by the wheel shaft and the nut being carried by the wheel axle.

To protect the balls 34, the bowl 38 is closed by a bellows 42 of protection made of a flexible material, in particular elastomeric material. The bellows 42 is for example made by molding an elastomeric material.

The bellows 42 forms a conical sleeve which extends from the periphery of the bowl 38 to a fastening section of the wheel shaft 26. The bellows 42 is for example fixed at both ends by clamps 44 clamping. The invention proposes a device for protecting the bellows 42 which makes it possible to prevent the bellows 42 from being directly hit by projections of a blunt body and which will not rub against the bellows 42 even in the event of deformation.

As illustrated in FIGS. 2 and 3, the protection device comprises a rigid shield 46 which is fixedly mounted relative to a structural element of the motor vehicle and which is arranged radially at a distance "D" from the constant velocity joint, for example to several centimeters, to avoid any friction whatever the angle of deviation of which is bent the constant velocity joint. As shown in FIGS. 6 to 8, the shield 46 is formed by a plate that extends axially.

The shield 46 has a thickness "e" sufficient to deflect the bodies without being deformed, as shown in Figure 7. The shield 46 thus forms a deflection screen on which the projected bodies bounce before reaching the bellows 42 .

The shield 46 is made of a metallic material such as aluminum. Its thickness "e" is for example about 3 mm.

Alternatively, the shield is made of a rigid plastic material.

The shield 46 is here attached to a non-suspended structural element. In the examples shown in the figures, it is attached to an inner face of the brake caliper 23.

In a variant not shown of the invention, the shield is attached to the suspension arm.

To allow its fixing, an inner axial end edge of the shield 46 is equipped with a fastening flange 48, as shown in FIG. 8. The flange 48 is for example intended to be fixed by means of screws at the brake caliper 23. In this respect, the flange 48 has fixing holes which are here two in number.

Advantageously, the shield 46 is fixed to the brake caliper 23 by the screws which fix the brake caliper 23 to the stub axle.

The shield 46 thus fixed on the brake caliper 23 forms a tongue which protrudes axially towards the inside of the vehicle from the brake caliper 23.

Thus positioned, the shield 46 also makes it possible to simultaneously protect the ducts which allow the hydraulic control of the brake.

In addition, when the shield 46 is made of a good heat conducting metal material, such as aluminum, it participates in the cooling of the brake caliper 23 forming a radiator which conducts the heat produced during braking.

The shield 46 has a curved shape about a transverse axis so as to partially enclose the homokinetic joint. Thus, it protects the homokinetic joint only under privileged angles, especially forward.

In a first embodiment shown in FIG. 3, the shield 46 has a front panel 46A which masks the homokinetic joint longitudinally forwardly in the direction of normal movement of the vehicle. It has indeed been found that in a motor vehicle, the majority of foreign bodies are projected longitudinally backwards against a front face of the bellows 42.

Some vehicles, such as construction machinery or off-road vehicles, are also exposed to shocks with foreign bodies coming from the ground. Thus, according to a second embodiment of the invention shown in FIG. 9, the shield 46 comprises at least one substantially horizontal lower section 46B which forms a screen between the homokinetic joint 30 and the ground 48. In the example shown in FIG. 9, the shield 46 simultaneously comprises a lower section 46B and a front section 46A for enveloping the homokinetic joint more than in the embodiment of FIG. 3.

In addition, the shield 46 has a plurality of holes 50. These holes 50 are nevertheless sufficiently narrow to allow the bodies large enough to be stopped to damage the bellows 42.

These holes 50 are for example made at least in the lower pan 46B to allow the evacuation of liquids or particles likely to accumulate in the shield 46.

In a variant that can be combined with any one of the embodiments of the invention, the holes 50 are made in the entire shield 46 to lighten it. The shield 46 forms for example a grid. The arrangement made according to the teachings of the invention thus makes it possible to effectively protect the bellows 42 of the homokinetic joint 30 without any risk of premature wear in the event of slight deformation of the shield 46.

In addition, when it is made of a heat conducting material, the shield 46 attached to the brake caliper 23 advantageously allows to participate in the evacuation of the heat caused by braking by forming a radiator. Such an arrangement makes it possible simultaneously to perform a protection function of the homokinetic joint and a heat removal function in a compact and inexpensive manner.

In addition, the attachment of the shield 46 and the brake caliper 23 with common fastening screws allows a quick and economical mounting of the shield 46 on the vehicle.

Claims (10)

Motor vehicle rolling train (10) comprising: at least one driving wheel (12) rotatably mounted on a structure of the motor vehicle; a wheel shaft (26); a homokinetic joint (30) coupling the wheel shaft (26) with the driving wheel (12) and comprising a bellows (42) for protecting an elastomer material; a device for protecting the bellows (42); characterized in that the protective device is formed by a shield (46) which is fixedly mounted with respect to a structural element of the motor vehicle and which is arranged radially away from the constant velocity joint (30). 2. Train (10) rolling according to the preceding claim, characterized in that the vehicle structure comprises: - at least one element (16) of unsprung structure which carries the wheel (12) rotation; - At least one element (18) of suspended structure which is articulated with the element (16) of non-suspended structure via at least one arm (20) of suspension. 3. Train (10) rolling according to the preceding claim, characterized in that the shield (46) is attached to a member (16) of unsprung structure. 4. Train (10) rolling according to the preceding claim, characterized in that the shield (46) is attached to a brake caliper (23) which is itself attached to said element (16) of unsprung structure. 5. Train (10) rolling according to any one of the preceding claims, characterized in that the shield (46) comprises at least one front axial section (46A) which masks the constant-velocity joint (30) forwardly in the direction normal movement of the vehicle. 6. Train (10) rolling according to any one of the preceding claims, characterized in that the shield (46) comprises at least one lower axial section (46B) which masks the constant-velocity joint (30) towards the ground (48). 7. Train (10) rolling according to any one of claims 5 or 6, characterized in that the shield (46) partially envelops the joint (30) homokinetic. 8. Train (10) rolling according to any one of the preceding claims, characterized in that the shield (46) has a plurality of holes (50). 9. Train (10) rolling according to any one of the preceding claims, characterized in that the shield (46) is made of a heat-conducting metal material such as aluminum. 10. Train (10) rolling according to any one of claims 1 to 8, characterized in that the shield (46) is made of a rigid plastic material.