A VEHICLE CHASSIS TRANSVERSE STRUCTURAL MEMBER

Abstract: A vehicle transverse structural member (1), particularly for heavy vehicles. The structural member incorporates an axle and wheel assembly having independently sprung hub units(4). The structural member 1 provides both extra strength and stiffness for a chassis in addition to providing for improved wheel control.

Description: The invention relates to a vehicle chassis, and more particularly to a chassis transverse structural member for a heavy vehicle. At present, such transverse structural members are generally welded or bolted to longitudinal chassis members to form a chassis which is a separate entity from axle and wheel assemblies which are resiliently secured to the chassis (see for example DE-B-1 045 253). This arrangement unfortunately results in the chassis providing extensive twisting movement in response to force input at the wheels. In this way, the chassis generally supplements vertical wheel movement allowed by shock absorbers. Such chassis movement is, however, unpredictable and results in a partially uncontrolled movement of the wheels. This is especially true at high vehicle speeds. Further, the large unsprung weight and the rigid coupling between wheels on opposite sides of the vehicle inherent in this arrangement adversely affect vehicle performance and contribute to road damage. Additionally, as a result of the extensive twisting of the chassis, special mounting arrangements for the vehicle payload, engine and cab are required. Other disadvantages are that there is little versatility in location of axle and wheel assemblies on the chassis and construction of the chassis and mounting of such assemblies is time-consuming. In the field of axle and wheel assemblies, US 2,163,981 (Lawrence) discloses a motor vehicle rear axle and wheel assembly which has an axle housing, and hub units connected by upper and lower support members. The assembly may be rigidly secured to a motor vehicle frame. This rigid connection is stated as being to avoid the necessity of having universal joints to accommodate mutual movement between the differential and a motor vehicle frame. Thus, the assembly was clearly not designed to act as a transverse structural member for a chassis. It appears that the assembly was not intended for use with heavy vehicles because the motor vehicle is mentioned as having a floor, which indicates a motor car. Accordingly, it appears that this document is not relevant to the field of chassis' for heavy vehicles. United Kingdom Patent Specifications GB-A-1,128,251 and GB-A-1,028,316 describe suspension arrangements each having an axle housing and hub units supported by support members and spring units. The axle housing is secured to a vehicle frame. Resilient bushings, however, are used for some of the connections and, further, the wheel hub is also directly connected to the vehicle frame in GB-A-1,128,251. These suspension arrangements do not prevent chassis twist or significantly improve wheel stability as the suspension arrangement does not contribute to chassis stiffness. A further problem with these suspension arrangements is that they are relatively complex due to the number of connections to a vehicle chassis, resulting in difficulties in manufacture and installation. For example, it would be extremely difficult to connect the suspension arrangements of these inventions at various longitudinal positions on a heavy vehicle. The present invention is directed towards providing a vehicle chassis transverse structural member which leads to simpler heavy vehicle manufacture, to a chassis which has little twisting movement, and to improved heavy vehicle control. According to the invention, there is provided a modular chassis transverse structural member for a heavy vehicle having a pair of longitudinal chassis members, comprising:- an axle housing having a differential gear assembly, the housing being of high strength construction sufficient to resist stresses arising in heavy vehicle chassis transverse structural members; a pair of transverse load transfer members on the axle housing for rigid connection with the pair of longitudinal chassis members to form an integral chassis structure, each load transfer member being mounted for engagement in the transverse direction with the associated longitudinal chassis member; and a pair of independently sprung hub units, each having an associated hub drive shaft extending from the axle housing, a spring unit, and upper and lower support members for said hub unit connected by means of upper and lower steering articulation joints so that the hub unit is steerable. By incorporating a drive axle and wheel assembly in a transverse structural member, manufacture and installation of such an assembly is relatively simple and inexpensive. Securing the members to longitudinal chassis members leads to immediate manufacture of the vehicle chassis and wheel assemblies. A further advantage of the invention is that chassis weight for heavy vehicles is substantially reduced as there is no need for separate transverse structural members in addition to those of the invention. As the hub units are independently sprung and there is no movement of the axle housing relative to the vehicle body, an extremely steady foundation for active control of wheel movement is provided. This overcomes the problem of force input at wheels providing extensive twisting movement of a conventional chassis. Because the support members have steering articulation joints, the option of connecting the hub units for steering is provided, thus improving modularity of the transverse structural member. In one embodiment, each load transfer member has a connection surface in a plane extending substantially longitudinally and vertically. This is a particularly suitable arrangement for load transfer in a transverse direction and for connection with a longitudinal chassis member. In one embodiment, the axle housing is of high strength cast iron construction. This is a simple and inexpensive construction of housing which has the necessary strength to accommodate the torsional and bending loads required of the chassis. Preferably, each steering articulation joint is a spherical ball joint. Such a joint allows steering movement and movement in other directions to accommodate shock and force input at wheels. Further, the spherical ball joints have a relatively large surface area for accommodation of stress. In this latter embodiment, each spherical ball joint has an upper portion formed by the support member and a lower portion formed by the hub unit, so that in use force input at the hub unit does not tend to disconnect the ball joint. This leads to reliability of the ball joint. Ideally, the support member is of high strength cast iron construction. Again, this is a simple and inexpensive construction of member which may accommodate the stresses involved in a heavy vehicle suspension. In another embodiment, there are two spring units associated with each hub unit. In this latter embodiment, the two spring units may be connected to the lower support member. In this latter embodiment, the lower support member may be in the form of a wishbone member and the upper support member may be an elongate arm. The invention will be more clearly understood from the following description of some preferred embodiments thereof, given by example only with reference to the accompanying drawings in which:- Fig. 1 is a perspective view from above of one side of a vehicle chassis transverse structural member according to the invention; Fig. 2 is a diagrammatic cross-sectional side view of four of the structural members mounted on a heavy vehicle; and Fig. 3 is a part cross sectional diagrammatic end view of an alternative construction of transverse structural member, in use. Referring to the drawings, and initially to Fig. 1 there is illustrated a vehicle chassis transverse structural member indicated generally by the reference numeral 1. The structural member 1 comprises an axle housing of a differential gear assembly (not shown) formed by a support casting 2 of cast-iron construction, having a pair of transverse struts 3 for rigid connection with a vehicle. The structural member 1 further comprises a pair of independently sprung hub units 4, each driven by a transverse hub drive shaft 5 pivotally connected at its inner and outer ends by universal joints (not shown) to the support casting 2 and the associated hub unit 4, respectively. The structural member 1 further incorporates two support members for each hub unit 4, namely, a lower support member 6 and an upper support member 7. In this case, the lower support member 6 is in the form of a wishbone member pivotally connected at pins 8 to the support casting 2 and to a stub axle 14 of the hub unit 4 at a spherical ball joint 9. The hub unit upper support member 7 is in the form of an arm connected to the stub axle 14 at a spherical ball joint 10 at its outer end and at its inner end it is pivotly connected at pins 12 to a spring bracket 13. Each hub unit 4 has two associated spring units, in this case springs 15. Each spring 15 is connected to a lower spring bracket 16 which is pivotly connected to the hub unit lower support member 6. At their upper ends, the springs 15 are connected to the springs bracket 13. In this case, the upper and lower hub unit support members 7 and 6 and the stub axle 14 are of high strength cast iron construction. Referring now to Fig. 2, four of the structural members 1 are illustrated in use. Parts similar to those described with reference to Fig. 1 are identified by the same reference numerals. In this embodiment, the structural members 1 form part of a chassis of a heavy vehicle and are bolted between two longitudinal box sections 31. Mounted between the longitudinal box sections 31 there is an engine 32 driving a gearbox 33, which in turn feeds a transverse drop box 34. Vehicle drive shafts 35 with universal joint connections transfer drive from the transfer drop box 34 to the differental gear assemblies of each of the structural members 1. The support casting 2 of each structural member 1 is bolted to the longitudinal box sections 31 at the struts 3 and the spring brackets 15 are also bolted to the longitudinal box sections 31. It will be appreciated that the only connections required for the structural member 1 are bolt connections at the struts 3 and the spring brackets 13. The structural member 1 may, therefore, be easily mounted at any desired position on a vehicle, or indeed, a trailer. As the structural member 1 forms part of the chassis and the hub units are independently sprung, an extremely steady foundation for active control of wheel movement is provided. This overcomes the problem of force input at wheels providing extensive twisting movement of a conventional chassis. A further advantage of the invention is that chassis weight for vehicles, and especially heavy vehicles is substantially reduced as there is no need for separate transverse structural members. Further, as there is no movement of the axle housing relative to the chassis and the vehicle body work connected to it, it is envisaged that the body work may be mounted low on the chassis and indeed it may be connected directly to the structural member 1. As the hub units 4 are connected to the hub drive shafts 5 by universal joints and to the upper and lower support members 7 and 6 by spherical ball joints, they may be easily connected to a steering mechanism for steering. If it is not desired to use the wheels for steering, the hub units 4 may be relatively easily rigidly secured to the support casting 2 by tracking levers or other support members to prevent turning. It will further be appreciated that as the structural member 1 may be relatively easily connected to other chassis members, installation time and costs are significantly reduced. Further, the invention allows drive to be relatively easily transferred to heavy trailers. Another advantage is that road damage is greatly reduced as wheels on opposite sides of the vehicle are each independently sprung. It will also be appreciated that as the support casting, the brackets, the stub axles and the support members for the hub units are all of high strength cast iron construction, the structural member 1 is relatively cheap to manufacture, in addition to being extremely durable and suitable for use with heavy vehicles on unsuitable road conditions. Referring now to Fig. 3 there is illustrated an alternative construction of structural member according to the invention indicated generally by the reference numeral 40. The structural number 40 incorporates an axle housing for a differential gear assembly 43 formed by a support casting 41 of rectangular box construction having two transverse reaction members 42 projecting upwardly and outwardly therefrom. The structural member 40 incorporates a pair of independently sprung hub units 44 supported by a lower wishbone member 45 and an upper wishbone member 46. Each of the wishbone members 45 and 46 is pivotally mounted on the support casting 41 at its inner end by pins 48 and is connected to the hub unit 44 by spherical ball joints 49. Each hub unit 44 also has a hub drive shaft 50 connected at its inner end to the differential gear assembly 43 by a universal joint 51 and at its other end to the hub unit 44 by a universal joint 52. In this case, each hub unit 44 has one associated spring unit, namely a spring and damper assembly 55 connected intermediate the upper wishbone member 46 and the associated transverse reaction member 42. Wheels 56 are mounted on each hub unit 44. The support casting 41 is illustrated in this case welded to longitudinal box sections 57 of a heavy vehicle 58. No other connections are required. The major difference between the structural members 1 and 40 of the invention are that in the latter the shock absorbers and the upper support members for the hub units are connected directly to the support casting of the structural member. A separate bracket is not provided in the latter case. The hub unit 44 includes outboard disc brakes 59. Needless to say, the invention is not limited to the particular arrangements illustrated. For example, any type of spring unit may be used, for example, springs, or spring and damper assemblies. Hydro-pneumatic, pneumatic torsion bar or leaf configuration springs may be used. Further, the dampers will be direct acting strut, level rotary or any other suitable configuration. It is also envisaged that the support members for the hub unit may be of any construction other than those illustrated. The hub unit of the invention may incorporate a speed reduction gear assembly. Although the structural member of the invention has been illustrated in one embodiment with outboard disc brakes, it is envisaged that inboard disc brakes may alternatively be used.

Claims: A modular chassis transverse structural member (1) for a heavy vehicle having a pair of longitudinal chassis members (31), comprising:- an axle housing (2) having a differential gear assembly, the housing (2) being of high strength construction sufficient to resist stresses arising in heavy vehicle chassis transverse structural members; a pair of transverse load transfer members (3) on the axle housing (2) for rigid connection with the pair of longitudinal chassis members (31) to form an integral chassis structure, each load transfer member (3) being mounted for engagement in the transverse direction with the associated longitudinal chassis member (31); and a pair of independently sprung hub units (4), each having an associated hub drive shaft (5) extending from the axle housing (2), a spring unit (15), and upper and lower support members (6, 7) for said hub unit connected by means of upper and lower steering articulation joints (9, 10) so that the hub unit (4) is steerable. A transverse structural member (1) as claimed in claim 1, wherein each load transfer member has a connection surface in a plane extending substantially longitudinally and vertically. A transverse structural member (1) as claimed in claims 1 or 2, wherein the axle housing (2) is of high strength cast iron construction. A transverse structural member (1) as claimed in any of claims 1 to 3, wherein each steering articulation joint is a spherical ball joint (9, 10). A transverse structural member (1) as claimed in claim 4, wherein each spherical ball joint (9, 10) has an upper portion formed by the support member (6, 7) and a lower portion formed by the hub unit (4) so that, in use, force input at the hub unit does not tend to disconnect the ball joint (9, 10). A transverse structural member (1) as claimed in any preceding claim, wherein each support member (6, 7) is of high strength cast iron construction. A transverse structural member (1) as claimed in any preceding claim, wherein there are two spring units (15) associated with each hub unit (4). A transverse structural member as claimed in claim 7, wherein the two spring units (15) are connected to the lower support member (6). A transverse structural member (1) as claimed in claim 8, wherein the lower support member is in the form of a wishbone member and the upper support member (7) is an elongate arm.

Inventors: TIMONEY, EANNA PRONSIAS, TIMONEY, SEAMUS GEAROID
Applicants: TECHNOLOGY INVESTMENTS LIMITED
Application year: 1988
Main classification: B60G3
IPC codes: B60G11, B60K17, B60G3, B60G99