Motor vehicle wheel set

Abstract

The invention relates to a motor vehicle wheel assembly comprising: a cradle (12) having two opposite cradle ends; two wheel supports respectively connected to said two cradle ends (46) and each adapted to receive a wheel; two struts respectively surmounting said two wheel supports; a torsion bar (42) having a rectilinear middle part (44) and two opposite bar ends (46) bent, said middle part (44) being installed so as to be able to rotate along said cradle (12). Said cradle (12) further comprises an elastic return member (74) located between said two cradle ends; and said middle part (44) comprises a lug (70) adapted to cooperate with said elastic return member (74) to dampen the simultaneous movement of said wheel supports relative to said cradle (12). Figure to be published with the abstract: Fig. 3

Description

Title of the invention: Motor vehicle wheel assembly

[0001] The present invention relates to a front or rear motor vehicle wheel set.

[0002] One area of application envisaged is, in particular, that of four-wheel drive motor vehicle trains. This type of vehicle is not only suitable for driving on roads, but also off-road, on more or less uneven terrain.

[0003] Also, vehicles of this type include a powered front wheel set and a powered rear wheel set.

[0004] The wheel assemblies each comprise a cradle having two opposite ends and two wheel supports respectively connected to the two ends of the cradle by suspension arms. The two wheel supports are respectively surmounted by two struts, on which the body shell of the motor vehicle rests. The struts are axially compressible and they comprise a return spring and a damping system. In addition, the wheel assembly also comprises a torsion bar which connects the opposite suspension arms or the two struts. It aims in particular to limit the rolling of the vehicle when it is in motion. It is commonly called an "anti-roll bar".

[0005] Also, the struts include a "shock stop", which comprises an elastically deformable member, which absorbs the energy at the end of the compression stroke of the strut. Thus, the "shock stop" makes it possible to limit the stroke of the strut during impacts, for example on a damaged road, where the wheel of the vehicle comes directly into a hole, or conversely when the vehicle crosses a speed bump.

[0006] Therefore, the "shock absorbers" limit the amplitude of wheel travel, and thus, they allow the suspension elements to be preserved. But in return, the vehicles' bridge crossing capabilities are limited, which hinders the vehicle's ability to move over rough terrain.

[0007] Also, a problem which arises and which the present invention aims to solve is to provide wheel sets whose suspension elements are preserved, but also whose bridge crossing capacities are sufficient so that the vehicle can move on difficult and uneven terrain.

[0008] In order to solve this problem, and according to a first object, there is proposed a motor vehicle wheel assembly comprising: a cradle having two opposite cradle ends; two wheel supports respectively connected to said two cradle ends and each adapted to receive a wheel; two struts respectively surmounting said two wheel supports and adapted to be compressed when said wheel supports are driven in movement relative to said cradle; a torsion bar having a rectilinear middle part and two opposite bar ends bent and symmetrical to each other, said middle part being installed movable in rotation along said cradle, while said two opposite bar ends are respectively connected to said struts.

[0009] Said cradle further comprises an elastic return member located between said two cradle ends; and said middle part of said torsion bar comprises a tab adapted to cooperate with said elastic return member to dampen the simultaneous movement of said wheel supports relative to said cradle.

[0010] Thus, a characteristic of the invention lies in the implementation of an elastic return member on the cradle and a lug secured to the torsion bar, which lug cooperates with the elastic return member. In this way, the elastic return member plays the role of the "shock stops" by limiting the rotation of the torsion bar. Consequently, it is possible to do without the "shock stops" on the struts and thus obtain greater wheel travel, and therefore greater axle crossing capabilities.

[0011] It will be observed that when the vehicle is moving over rough terrain, and in particular in bridge crossing situations, one of the ends of the torsion bar is driven upwards, while the other is driven downwards, and consequently, the area of the middle part receiving the lug remains stationary.

[0012] On the other hand, when the vehicle is moving on a road and encounters, for example, a speed bump, the two ends of the torsion bar are stressed in the same direction and consequently, the lug comes to bear against the elastic return member. And the latter then plays the role of the vertical travel limitations of the conventional “shock stops” type.

[0013] Advantageously, and according to the invention, the struts are respectively additionally equipped with shortened “shock stops”. These shorter “shock stops” make it possible to limit the extreme wheel travel during an asymmetrical impact only partially stressing the elastic return member, without however impairing the maximum amplitude of wheel travel.

[0014] According to a preferred embodiment of the invention, said elastic return member is located substantially equidistant from said two beam ends. And in addition, the lug of the torsion bar is located substantially equidistant from its two ends and it then comes to bear on the elastic return member.

[0015] Advantageously, and according to the invention, said cradle is equipped with two bearings spaced from each other to receive said middle part of said torsion bar. Thus, the two bearings are installed coaxially on the cradle and the two ends of the middle part of the torsion bar, which middle part is straight, are rotatably mounted in the two bearings respectively.

[0016] According to a particularly advantageous embodiment of the invention, said cradle is hollow to receive said elastic return member, and furthermore has an opening in line with said elastic return member to allow the passage of said lug. In this way, the elastic return member is installed in a dead volume of the cradle, and consequently, its installation does not cause any modification of the position of the elements of the usual wheel train.

[0017] Also, according to the invention, each of said two opposite bar ends has a first portion bent relative to said middle portion and a second portion bent relative to said first portion forming a crank. Therefore, the second bent portion is connected to the corresponding strut by means of a connecting rod. Consequently, the movement of the strut is adapted to cause the movement of the second bent portion which then imparts a rotational torque to the middle portion of the torsion bar.

[0018] Furthermore, according to the invention, each of the first portions is curved in a plane substantially perpendicular to said middle part. In this way, the ends of the torsion bar are substantially longer and thus offer more flexibility. In other words, their buckling capacity is increased.

[0019] Furthermore, in accordance with the invention, said two wheel supports are respectively connected to said two cradle ends by suspension arms. The suspension arms are pivotally mounted both on the cradle ends and also on the wheel supports. In this way, the wheels can oscillate relative to the cradle while remaining vertical.

[0020] According to another object of the invention, there is provided a motor vehicle having a front part and a rear part, and each of said front and rear parts is equipped with a wheel set as described above.

[0021] Other features and advantages of the invention will emerge from reading the description given below of a particular embodiment of the invention, given for informational purposes but not as a limitation, with reference to the appended drawings in which:

[0022] [Fig.l] is a schematic front view of a wheel train at rest in accordance with the invention;

[0023] [Fig.2] is a schematic top view of a wheel train according to the invention;

[0024] [Fig.3] is a schematic three-quarter rear perspective view of the wheel set cut along the median plane III - III illustrated in [Fig.l]; and,

[0025] [Fig.4] is a schematic front view of the wheel set shown in [Fig.l] in a working position.

[0026] [Fig.l] shows from the front, a front wheel set 10 of a motor vehicle. However, the invention is also suitable for a vehicle rear wheel assembly.

[0027] The front wheel set 10 is inscribed in an orthogonal reference frame X, Y, Z, in which the X axis extends in a front-rear longitudinal direction of the motor vehicle, oriented towards the rear; the Y axis extends in a transverse direction of the vehicle, oriented from left to right when in a rolling situation; and the Z axis extends in a vertical direction, oriented away from the ground.

[0028] The front wheel assembly 10 firstly comprises a cradle 12 extending transversely in the direction Y. The cradle 12 is hollow and has a right end 14 opposite a left end 16. It also has an upper wall 15 opposite a lower wall 17.

[0029] Also, the wheel train 10 comprises a right lower arm 18 mounted articulated on the right end 14, and a left lower arm 20 mounted articulated on the left end 16 of the cradle 12.

[0030] The end of the right lower arm 18 is mounted articulated on a right wheel support 21, and on the opposite side, the end of the left lower arm 20 is mounted articulated on a left wheel support 23.

[0031] Also, a right wheel 24 installed on the right wheel support 21 and a left wheel 26 installed on the left wheel support 23 are shown in broken lines.

[0032] The wheel supports 21, 23 are then surmounted respectively by a right strut 28 and a left strut 30.

[0033] The different elements of the struts 28, 30 have the same references because they are identical and they have exactly the same functions.

[0034] Each of the struts comprises a cylinder 32 directly secured to the wheel supports 21, 23 in which at least one piston connected to a rod slides, which are not shown. The rod and the inlet of the cylinder 32 are protected by a blow-off 34. The rod bears against an upper cup 36. According to one embodiment of the invention, thin elastomer parts are interposed between the upper cup 36 and the end of the rod to form “shock stops” that are shorter than those used in the struts according to the prior art.

[0035] Also, each cylinder 32 is provided with a lower cup 38 and a helical spring 40 engages between the lower cup 38 and the upper cup 36.

[0036] Thus, the body shell of the motor vehicle, not shown, rests on the upper cups 36. Therefore, when the vehicle is rolling, the two struts 28, 30 are adapted to compress axially, and to release, according to the vertical component Z, and to oscillate around their equilibrium position. The piston and the rod moving inside the cylinder 32 are adapted precisely to dampen these oscillations.

[0037] Furthermore, the wheel train 10 comprises a torsion bar 42 extending transversely along the cradle 12. It is made of steel. Also, it has a substantially circular section of between 4 cm in diameter and 6 cm in diameter, for example.

[0038] In [Fig.2] we find the front wheel assembly 10 without its struts. We also find the cradle 12 there. It has a front wall 43 opposite a rear wall 45. Also, we see in more detail the torsion bar 42, which has a rectilinear middle part 44 and a right bar end 46 symmetrical with a left bar end 48 with respect to the median plane III - III.

[0039] The middle part is rotatably mounted in two bearings 50, 52 spaced from each other and mounted on the upper wall 15 of the cradle 12, so that the middle part 44 extends transversely in the direction Y.

[0040] Furthermore, the straight bar end 46 has a first straight portion 54 bent towards the front of the vehicle in the direction -X, and substantially at a right angle to the middle portion 44, and a second straight portion 56 extending the first portion 54 and bent back at a right angle to the first portion 54. The second portion 56 thus extends in a direction substantially parallel to the middle portion 44, forming a crank.

[0041] In the same way, on the other hand, the left bar end 48 has a first left portion 58 bent towards the front of the vehicle substantially parallel to the first portion 54, and substantially at a right angle to the middle part 44, and a second left portion 60 extending the first portion 58 and bent back at a right angle to the first portion 58. The second portion 60 extends in a direction substantially parallel to the middle part 44, also forming a crank.

[0042] Also, the second right portion 56 of the right bar end 46 ends in a right free end 62, while on the other hand, the second left portion 60 of the left bar end 48 ends in a left free end 64.

[0043] In [Fig. 1], it will be observed that the first right portion 54 of the right bar end 46 and the first left portion 58 of the left bar end 48 substantially form an arc of a circle. This arc of a circle defines a plane substantially perpendicular to the middle portion 44 of the torsion bar 42. Also, the concave portion of this arc of a circle is oriented towards the cradle 12.

[0044] We also find in [Fig.l], the two free ends, right 62, and left 64 of the second right 56 and left 60 portions of the respective ends 46, 48 of the torsion bar 42.

[0045] Also, the right free end 62 is connected to the cylinder 32 of the right strut 28 by means of a right connecting rod 66, while the left free end 64 is connected to the cylinder 32 of the left strut 30 by means of a left connecting rod 68. These two connecting rods 66, 68 extend along a vertical component Z.

[0046] Furthermore, in [Fig. 1] there appears, in accordance with the invention, a tab 70 secured to the middle part 44 of the torsion bar 42. The tab 70 is situated substantially equidistant from the two ends 46, 48 of the torsion bar 42 and it penetrates through the upper wall 15 inside the cradle 12 as will be explained below with reference to [Fig. 3].

[0047] Thus, in section in [Fig.3], we find the cradle 12 and the middle part 44 of the torsion bar 42, which middle part 44 is extended by the first straight portion 54 of the end of the straight bar 46.

[0048] We then find the tab 70 secured to the middle part 44 and which extends along a vertical component through a light 72 made in the upper wall 15 of the cradle 12. Thus, the tab 70 extends between the front wall 43 and the rear wall 45 of the cradle 12, and closer to the rear wall 45.

[0049] Furthermore, inside the cradle 12, there is installed an elastic return member 74 interposed between the front wall 43 and the tab 70. The elastic return member 74 is, according to one embodiment, a helical spring. According to another embodiment, the elastic return member 74 is made of an elastomeric polymer material, for example polyurethane. Also, a combination of a polymer material and a helical spring is envisaged.

[0050] It is thus understood, taking into account the elements described above with regard to [Fig. 3], that the rotational movement of the torsion bar 42 in the clockwise direction H causes the pivoting of the tab 70 inside the cradle 12 towards the front wall 43. And consequently, this rotational movement of the torsion bar 42 causes the compression of the elastic return member 74. The latter thus tends to oppose this rotation as will be explained below with reference to [Fig. 1].

[0051] Thus, when the right 24 and left 26 wheels of the wheel set 10 simultaneously or almost simultaneously approach a speed bump for example, taking into account the inertia of the vehicle in rectilinear motion parallel to the surface of the road on which it is traveling, these right 24 and left 26 wheels are driven more or less abruptly according to a vertical component +Z, while the two corresponding struts 28, 30 are compressed axially.

[0052] Consequently, the two right 66 and left 68 connecting rods exert two upward forces respectively on the two free ends, right 62, and left 64 of the second right 56 and left 60 portions of the respective ends 46, 48 of the torsion bar 42.

[0053] Therefore, the middle part 44 of the torsion bar 42 is driven in rotation following the clockwise direction H as illustrated in [Fig.3] to which reference will be made again. Thus, the lug 70 is driven in pivoting towards the front wall 43 of the cradle 12 and thereby compresses the elastic return member 74. The latter, by compressing itself, opposes the pivoting movement of the lug 70. Therefore, it absorbs the shock caused by the two wheels 24, 26 coming alongside the aforementioned speed bump.

[0054] Thus, it is possible to do without the “shock stops” usually used in conventional wheel sets.

[0055] On the other hand, in situations such as illustrated in [Fig.4], where the wheel set 10 of the vehicle is stressed in a crossed slope, the absence of usual “shock stops” allows a greater amplitude of wheel travel.

[0056] We thus find the wheel train 10, as described with regard to [Fig. 1] in a situation where the right wheel 24 is driven vertically according to the upward vertical component +Z, while conversely, the left wheel 26 is driven vertically according to the downward component -Z. Such a situation occurs when, conversely, the rear wheel train, not shown, is inclined in the opposite direction, in other words, when the right rear wheel is lowered, while the left rear wheel is raised. In other words, the two wheel trains are inclined in opposite directions, this situation is called: "bridge crossing".

[0057] Consequently, the right strut 28 not shown in [Fig.4] is compressed to the maximum, without being prevented by a “shock stop”, and therefore, it drives, according to a maximum amplitude, the right free end 62 of the second right portion 56 of the right bar end 46 via the right connecting rod 66 according to the upward vertical component +Z.

[0058] Conversely, the left wheel 26 is driven vertically according to the downward vertical component -Z. Consequently, the left strut 30 not shown in [Fig.4] is in maximum extension, and it drives, according to a maximum amplitude, the left free end 64 of the second left portion 60 of the left bar end 48 via the left connecting rod 68 according to the downward vertical component -Z.

[0059] Consequently, the torsion bar 42 is precisely driven in torsion, and plays its role of elastic return. On the other hand, the portion of the middle part 44 to which the tab 70 is integral, which portion is located substantially equidistant from the two right 46 and left 48 ends of the torsion bar 42, is neutral. Therefore, it remains in a fixed position and the tab 70 is not driven in pivoting.

[0060] In this way, the amplitude of movement of the two wheels 24, 26 is greater than it is when the struts are equipped with conventional “shock stops”.

Claims

Claims

1. Wheel assembly (10) of a motor vehicle comprising: - a cradle (12) having two opposite cradle ends (14, 16); - two wheel supports (21, 23) respectively connected to said two cradle ends (46, 48) and adapted to each receive a wheel (24, 26); - two struts (28, 30) respectively surmounting said two wheel supports (21, 23) and adapted to be compressed when said wheel supports are driven in movement relative to said cradle (12); - a torsion bar (42) having a rectilinear middle part (44) and two opposite bar ends (46, 48) bent and symmetrical to each other, said middle part (44) being installed movable in rotation along said cradle (12), while said two opposite bar ends (46, 48) are respectively connected to said struts (28, 30);characterized in that said cradle (12) further comprises an elastic return member (74) located between said two cradle ends (14, 16); and in that said middle portion (44) of said torsion bar (42) comprises a lug (70) adapted to cooperate with said elastic return member (74) to dampen the simultaneous movement of said wheel supports (21, 23) relative to said cradle (12).;

2. Wheel train according to claim 1, characterized in that said elastic return member (74) is located substantially equidistant from said two cradle ends (14, 16).

3. Wheel train according to claim 1 or 2, characterized in that said cradle (12) is equipped with two bearings (50, 52) spaced from each other to receive said middle part (44) of said torsion bar (42).

4. Wheel train according to any one of claims 1 to 3, characterized in that said cradle (12) is hollow to receive said elastic return member (74), and in that it further has an opening (72) at right angles to said elastic return member (74) to allow the passage of said lug (70).

5. Wheel train according to any one of claims 1 to 4, characterized in that each of said two opposite bar ends

6.

7.

8. (46, 48) has a first portion (54, 58) bent relative to said middle part (44) and a second portion (56, 60) bent relative to said first portion (54, 58) forming a crank. Wheel train according to claim 5, characterized in that each of the first portions (54, 58) is curved in a plane substantially perpendicular to said middle part (44). Wheel train according to any one of claims 1 to 6, characterized in that said two wheel supports (21, 23) are respectively connected to said two cradle ends (14, 16) by suspension arms (18, 20). Motor vehicle having a front part and a rear part, characterized in that each of said front and rear parts is equipped with a wheel set (10) according to any one of claims 1 to 7.

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