GB2068314A - Energy absorbing steering wheel - Google Patents

Abstract

A steering wheel, moulded of a high grade nylon, comprises an integral rim, spokes and a thin wall energy absorbing sleeve 13. The rim is disposed in coaxial relationship to and axially spaced from the hub. The sleeve 13 in plan view has a substantially rectangular configuration of decreasing size from its upper end downwardly toward the hub. The walls of the sleeve are convoluted. <IMAGE>

Description

SPECIFICATION Energy absorbing steering wheel The present invention relates to steering wheels for motor vehicles, and more particularly, to impact energy absorbing steering wheels.

U.S. Patent 3,016,764 issued January 16, 1962 to R. H. Fredericks et al for a "Safety Steering Wheel" discloses a two-stage collapsible steering wheel comprising a flexible rim steering wheel having a steel armature that provides the necessary torsional stiffness for steering the vehicle while permitting axial displacement of the rim under relatively low impact load conditions. The armature is supported on a central energy absorbing structure constructed and arranged to progressively collapse under load to absorb any impact energy over and above that causing axial displacement of the rim.

Since the development of the Fredericks et al steering wheel assembly, attempts have been made to substitute plastic materials for the all steel construction. The primary advantage of the use of plastic materials is the weight saving that may be achieved, a factor that is becoming more critical as the demand grows in the marketplace for more fuel efficient vehicles. Prior art patents documenting the evolution of the all metal steering wheel assembly toward an all plastic steering wheel include U.S. Patent 3,167,974 issued February 2, 1 965 to. K. Wilfert for a "Steering Wheel", 3,802,291 issued April 9, 1974 to F. E. Young, Jr. et al for a "Soft Steering Wheel Rim", 3,938,404 issued February 17, 1976 to G.Murase et al for an "Energy Absorbing Steering Assembly" and 4,010,658 issued on March 8, 1977 to G.

H. Muller et al for a "Steering Wheel Having a Flexible Rim" All of these prior art patents disclose composite structures, i.e. steering wheel assemblies utilizing steel and plastic materials. The present invention provides a steering wheel assembly in which the only major metal component is the metal hub for mounting the steering wheel on the vehicle-steering shaft.

According to the invention there is provided an energy absorbing steering wheel mounted on a hub, the steering wheel being molded of a high impact grade nylon and comprising an integral rim spokes and a thin wall energy absorbing sleeve, the rim being disposed in a coaxial and axially spaced relation to the hub, and the energy absorbing sleeve when observed in the plan view having a substantially rectangular configuration of decreasing size from its upper end downwardly toward the hub, the walls of the sleeve having a convoluted configuration arranged to provide a high degree of energy absorbing at relatively constant load in the event of impact directed substantially axially of the hub.

The present invention will now be described with reference to the accompanying drawings, wherein: Figure 1 is a plan view of a steering wheel assembly incorporating the principles of the present invention; Figure 2 is an enlarged sectional view taken substantially on the line 2-2 of Fig. 1; Figure 3 is an enlarged sectional view taken substantially on the line3-3 of Fig. 1; Figure 4 is a fragmentary bottom view of the steering wheel assembly; Figure 5 is a view looking in the direction of the arrow 5 of Fig. 4; and Figure 6 is a section view taken substantially on the line 6-6 of Fig. 1 looking in the direction of the arrows.

Referring now to the drawings, there is shown a steering wheel, generally designated 10, embodying the present invention. The steering wheel comprises basically a rim 11, spokes 12, and an energy absorbing sleeve 13, all of which are supported on a hub 14.

The rim 11, the spokes 1 2 and the energy absorbing sleeve 1 3 are integrally molded of a high impact grade nylon. There is no metal involved other than in the hub 14.

As in a conventional steering wheel the rim 11 is disposed in a coaxial relationship to the hub 14 and the plane of the rim is axially displaced from the hub.

The rim 11 has small cored-out pockets 1 5 on its underside 16, see Fig. 4. The cored-out pockets 1 5 have a dual function. First, they reduce the weight of the rim and, therefore, that of the steering wheel. Second, the coredout pockets control the rigidity of the rim. In an energy absorbing steering wheel it is highly desirable for the rim structure to have a substantial amount of flexibility under high chest impact loads during frontal vehicle crashes to provide full chest contact. Yet the rim structure must have sufficient rigidity for the steering function and to act as a grab bar.

As seen in Figs. 4 and 6, the spokes 12 also are cored-out. The cored-out pockets 1 7 extend longitudinally of the spokes and function to reduce the weight of the steering wheel and to control the rigidity of the spoke and rim structure.

The energy absorbing sleeve 13, when viewed in the plan view, as in Fig. 1, has a substantially rectangular configuration. The sleeve 1 3 is of a diminishing size from top to bottom. That is, if a plurality of planes were axially spaced in parallel relationship from top to bottom of the sleeve, the area of the rectangle in each plane would be smaller than the area of the plane above it. The sleeve 1 3 is of a thin wall construction with four convoluted walls formed by wall portions of an ogival configuration. At its upper end, the sleeve 1 3 is outwardly reinforced by a thickened rectangular annulus 1 8 of substantially square cross section to which the spokes 1 2 are integrally cantilevered.The annulus 18 also is provided with a plurality of cored-out weight reduction pockets 1 9 extending inwardly from the upper face 21 thereof.

The sleeve 1 3 sidewalls terminate in an inwardly turned flat base portion 22 that is centrally apertured at 23 to receive the hub 14. The hub 14 has an impact extruded cylindrical body 24 having a radially extending annular flange 25. The flange 25 has a circle of integral aluminum semi-tubular rivets 26. The rivets 26 project through a matching set of holes in the shell base 22 and a steel plate or stamping 27 and are spun over to clamp the plastic material between the flange 25 and the plate 27. The steel plate 27 serves to increase the contact area to reduce stress concentration particularly of the rivets 26 with the plastic of the sleeve base 22.

The upper half of hub 14 is internally splined at 28 to be received on the splined upper end of a vehicle steering shaft (not shown).

The steering wheel 10 preferably has four spokes 1 2 which, in the normal centered position of the steering wheel as shown in Fig. 1, have a configuration in which the upper two spokes 1 2a extend outwardly to the rim 11 in alignment with each other from the upper corner portons 29 of the short sides of the rectangular annulus 1 8 of the sleeve 1 3. The lower two spokes 1 2b extend from the lower corner portions 31 of the annulus 18 in an angular downwardly direction. The particular arrangement of spokes on each side of the steering wheel is conventional and provides substantial increase in rim stiffness while allowing the use of spokes that permit low deflection rates in bending out of the plane of the unstressed steering wheel.A low deflection rate of the spokes is desirable to protect the vehicle operator in the event of a frontal collision involving the vehicle. That is, when the anterior surface of the driver's abdominal region strikes the steering wheel rim, the spokes allow the rim to deflect without excessive reaction force until the thoracic region contacts the large surface area of a hub cover 32. The force applied to the hub cover 32, if sufficiently great, will be transmitted to and cause collapse of the energy absorbing sleeve 13.

The hub cover 32 is molded in a substantially rectangular configuration from a suitable color impregnable plastic. The cover 32 is hollow having suitable cross ribs 33 to provide the necessary rigidity while minimizing the weight.

The cover 32 is held in place by suitable self-tapping screws 34 around its perimeter.

A high impact grade of nylon was chosen for the substantially all plastic steering wheel because it possesses physical properties that make it unnecessary to cover or coat the nylon. In the manufacture of plastic steering wheels from polycarbonate materials, a second molding operation is required since the polycarbonate preferably must be coated by a polyvinylchloride plastic (PVC). Additional advantages derived from the nylon construction compared to a composite polycarbonate/PVC is substantial weight reduction as a result of (1) lower specific gravity of nylon, and (2) elimination of the plastic filling the cored-out pockets of the rim and spokes which become PVC filled in a second molding operation.

Since the nylon is not covered with a nonstructural material cspecially PVC which adds no rigidity to the structure, the nylon can be distributed in the rim and spoke sections to obtain increased section modulus. This beneficial effect tends to offset the lower flexural modulus of nylon compared to a material such as polycarbonate.

Claims (7)

1. An energy absorbing steering wheel mounted on a hub, the steering wheel being molded of a high impact grade nylon comprising an integral rim, spokes and a thin wall energy absorbing sleeve, the rim being disposed in a coaxial and axially spaced relation to the hub, and the energy absorbing sleeve when observed in the plan view having a substantially rectangular configuration of decreasing size from its upper end downwardly toward the hub, the walls of the sleeve having a convoluted configuration arranged to provide a high degree of energy absorbing at relatively constant load in the event of impact directed substantially axially of the hub.

2. A steering wheel according to Claim 1, in which: the rim has small cored-out pockets on its underside and the spokes have coredout pockets on their lower face, the cored-out pockets providing weight reduction and the desired flexibility in the rim and spokes.

3. An energy absorbing steering wheel according to Claim 1 or Claim 2, wherein the energy absorbing sleeve having at its upper end a thickened annulus to which the spokes are cantilevered and at its lower end an apertured base plate which receives and is secured to the hub, the wall of the sleeve comprising wall sections depending from a rectangle side of the thickened annulus and terminating at the sleeve base.

4. A steering wheel according to Claim 3, in which: the spokes are integrated with the sleeve annulus at each short rectangle side of the latter.

5. A steering wheel according to Claim 3 or Claim 4, in which: the thickened annulus at the top of the sleeve is provided with a plurality of cored-out weight reduction pockets extending inwardly from the upper face thereof.

6. A steering wheel according to any one of the preceding claims, in which the energy absorbing sleeve side wall convolutions are formed by portions of substantially ogival shape.

7. A steering wheel substantially as hereinbefore described with reference to and as shown in the accompanying drawings.