Vehicle suspensions

Abstract: A vehicle suspension has a hub carrier (12) to which a wheel (38) of a vehicle may be rotatably mounted, the hub carrier (12) is connected to a chassis or sub-frame (14) of the vehicle, by means of a pair of vertically separated upper and lower suspension arms (16, 18) being pivotally connected at one end to the vehicle chassis or sub-frame (14) and at the other end to the hub carrier (12). The hub carrier (12) has an arm (40) which extends upwardly from the point of connection (20) of the hub carrier (12) to the upper suspension arm (16), to an upper end (42) which is aligned substantially vertically above the load application point between the wheel (38) and the ground, the upper end (42) of said arm (40) being connected to a spring means (60).

Description: The present invention relates to vehicle suspensions and in particular to vehicle suspensions in which a hub carrier for a wheel of the vehicle is articulated by means of a pair of wishbones. In double wishbone suspensions used hitherto, suspension loads are transmitted through the wishbones and via spring and damper units, to the vehicle chassis. Such suspensions use ball joints which are required to transmit the wheel load through the articulating system to the spring/damper unit. Commercially available ball joints used in suspension systems require an internal pre-load to make the ball joints durable. This pre-load generates a frictional force as a result of the prevailing coefficient of friction which exits between the internal components of the ball joint. As a result, double wishbone suspensions produced hitherto, exhibit significant friction levels which lead to a reduction in the ride refinement of road vehicles. This effect is particularly serious in luxury and sports cars since the ride and handling performance is compromised to an unacceptable degree. EP0412322 discloses a suspension system with upper and lower suspension arms, loads on the suspension being reacted substantially vertically of a hub carrier. The suspension arms are however connected to the hub carrier by means of ball joints. The present invention provides a vehicle suspension in which suspension loads are substantially isolated from the wishbones so that the ball joints may be replaced by rolling element bearings which reduce the friction levels significantly with a consequent improvement in ride refinement and handling performance. In accordance with the present invention, a vehicle suspension comprises a hub carrier to which a wheel of the vehicle may be rotatably mounted, the hub carrier being connected to a chassis or sub-frame of a vehicle by means of a pair of vertically separated upper and lower suspension arms, each suspension arm being pivotally connected at one end to the vehicle chassis or sub-frame and at the other end to the hub carrier, the hub carrier having an arm which extends upwardly from the point of connection of the upper suspension arm, to an upper end which is aligned substantially vertically above the load application point between a wheel mounted on the hub carrier and the ground, the upper end of said arm being connected to a spring means characterised in that the suspension arms are pivotally connected to the hub carrier by rolling element bearings. Preferably the suspension arms are also connected to the vehicle chassis or sub-frame by rolling element bearings. With the suspension system disclosed above, substantially all the suspension loads are transmitted vertically to the spring means. As a result, only small lateral loads are applied through the suspension arms. The use of rolling element bearings, such as roller, ball, taper or needle bearings, in place of ball joints significantly reduces the friction with a consequent improvement in ride and performance of the suspension. The redirecting of the suspension loads will also allow the use of smaller and lighter suspension arms, with a resulting saving in cost and weight. The suspension according to the present invention is particularly suitable for use on the front, steered wheels of the vehicle. In order to permit steering of the wheels, a steering knuckle which defines a stub axle is preferably attached to the hub carrier by means of rolling element bearings, which permit rotation of the steering knuckle about an appropriate king pin angle. Various embodiments of the invention are now described, by way of example only, with reference to the accompanying drawings, in which:- Figure 1 is a diagrammatic side elevation of a vehicle suspension in accordance with the present invention; Figure 2 is a view similar to Figure 1, of an alternative embodiment of the invention; and Figure 3 is a view similar to Figure 1 of a further alternative embodiment of the invention. As illustrated in Figure 1, a suspension for the front wheel of a vehicle comprises a hub carrier 12 which is mounted with respect to a sub-frame 14 of the vehicle, by means of an upper and lower suspension arms 16 and 18. The upper and lower suspension arms 16 and 18 are each connected at one end to the hub carrier 12, by means of a roller bearing 20 and at the other end to the sub-frame 14, by means of a roller bearing 22. A steering knuckle 30 is mounted on the hub carrier 12 by means of rolling element bearings 32, 34, for rotation about an axis which is inclined at a king pin angle α. A steering knuckle 30 defines a stub axle 36 upon which a wheel 38 may be rotatably mounted in conventional manner. The steering knuckle 30 also has an arm (not shown) by which it may be connected to a steering rack, in conventional manner. The hub carrier 12 has an arcuate arm 40 which extends upwardly from the portion of the hub carrier 12 to which the upper suspension arm 16 is connected, the upper end 42 of the arm 40 being substantially aligned vertically with the point of contact 44 between the wheel 38 and the ground. The upper end 42 of the arm 40 is connected by a roller bearing 50 to a link 52, the other end of link 52 being pivotally connected by a roller bearing 54 to a horizontally disposed rocker arm 56. The arm 56 is pivoted intermediate of its ends to the vehicle chassis or sub-frame 14 by means of roller bearing 58. A helical spring/damper unit 60 of conventional construction is connected between the end of arm 56 remote from link 52 and the vehicle sub-frame 14 by means of roller bearings 64 and 66. With the suspension assembly described above, the suspension loads are transmitted vertically by the hub carrier 12 and link 52, to the rocker arm 56 and via the rocker arm 56 to the spring/damper unit 60. As a consequence, lateral loading of the suspension arms 16 and 18 is significantly reduced. The use of low friction roller bearing/bearings throughout the suspension, will significantly improve the ride and handling performance of the suspension. If required, rolling bearing elements which will permit a small amount of conical articulation, may be used. In the embodiment illustrated in Figure 2, the upper end 42 of arm 40 is connected directly to the lower end of a vertically disposed spring/damper unit 60, by means of roller bearings 70, the upper end of spring/damper unit 60 being connected to the vehicle chassis or sub-frame 14 by roller bearing 72. In the alternative embodiment illustrated in Figure 3, a link 52 connects the upper end 42 of arm 40 to a horizontally disposed leaf spring 76. While the above embodiments relate to front wheel suspensions in which the wheel is steerable, the present invention is equally applicable to rear suspensions of the vehicle, the stub axle for rotatably supporting the vehicle wheel being secured directly to the hub carrier.

Claims: A vehicle suspension comprising a hub carrier (12) to which a wheel (38) of the vehicle may be rotatably mounted, the hub carrier (12) being connected to a chassis or sub-frame (14) of a vehicle by means of a pair of vertically separated upper and lower suspension arms (16, 18), each suspension arm (16, 18) being pivotally connected at one end to the vehicle chassis or sub-frame (14) and at the other end to the hub carrier (12), the hub carrier (12) having an arm (40) which extends upwardly from the point of connection (20) of the hub carrier (12) to the upper suspension arm (16), to an upper end (42) which is aligned substantially vertically above the load application point between the wheel (38) mounted on the hub carrier (12) and the ground, the upper end (42) of said arm (40) being connected to a spring means (60; 76); characterised in that the suspension arms (16, 18) are pivotally connected to the hub carrier (12) by rolling element bearings (20). A vehicle suspension according to Claim 1 characterised in that the suspension arms (16, 18) are pivotally connected to the vehicle chassis or sub-frame (14) and to the hub carrier (12) for pivotal movement about axes substantially parallel to the longitudinal axis of the vehicle. A vehicle suspension according to Claim 1 or 2 characterised in that the upper end (42) of the hub carrier arm (40) is connected to the spring means (60; 76) by one or more rolling element bearings (50, 54, 58; 70). A vehicle suspension according to any one of Claims 2 to 3 characterised in that the rolling element bearings (50, 54, 58; 70) are roller bearings. A vehicle suspension according to any one of the preceding claims characterised in that the rolling element bearings (50, 54, 58; 70) permit a small degree of conical articulation. A vehicle suspension according to any one of the preceding claims characterised in that the upper end (42) of the hub carrier arm (40) is connected directly to a vertically disposed spring/damper unit (60). A vehicle suspension according to any one of Claims 1 to 5 characterised in that the upper end (42) of the hub carrier arm (40) is connected to a spring/damper unit (60) via a horizontally disposed rocker arm (56). A vehicle suspension according to any one of Claims 1 to 5 characterised in that the upper end (42) of the hub carrier arm (40) is connected to a horizontally disposed leaf spring (76). A vehicle suspension according to any one of the preceding claims characterised in that a steering knuckle (30) is mounted on the hub carrier (12) for rotation with respect thereto. A vehicle suspension according to Claim 9 characterised in that the steering knuckle (30) is mounted to the hub carrier (12) by means of rolling element bearings (32, 34).

Inventors: HEAP KENNETH JOHN DOUGLAS, HEAP, KENNETH JOHN DOUGLAS
Applicants: JAGUAR CARS, JAGUAR CARS LIMITED
Application year: 1996
Main classification: B60G3
IPC codes: B60G3, B60G11