Background of the Invention In a steering wheel of the initially named kind, polyurethane is frequently used as the plastic material at which the jacketing is secured because of its good workability and its comparatively high strength. The jacketing can for example be formed of a real wood veneer or another precious material in order to give the steering wheel an appealing appearance and to offer a surface which is pleasant for the user to grip.

Summary of the Invention The object of the invention is to further develop a steering wheel of the initially named kind in such a manner that it has a lower total weight compared with conventional steering wheels while having the same strength.

The invention satisfies the object by a steering wheel with the features in accordance with claim 1 and in particular in that the plastic material which is arranged between the base body and the jacketing forms a grid structure which is formed on at the base body and which supports the jacketing at the base body.

In the invention it is achieved through the grid structure which is formed of a plastic material that, in spite of the lesser material expenditure

for the plastic material as a result of the grid structure, a steering wheel with high strength and high inherent stability can be manufactured which is comparable in its properties with conventional steering wheels. Thus the steering wheel in accordance with the invention exhibits the same behavior in impact tests as a steering wheel in which the base body, which is formed of metal, is provided with polyurethane as plastic material. Furthermore, the steering wheel in accordance with the invention has the advantage that it has a lower weight compared with conventional steering wheels as a result of its grid structure. Through intentional reinforcement of the grid structure it is furthermore possible to impart additional strength to the steering wheel in particularly highly stressed sections in which the driver for example usually braces himself during a braking of the motor vehicle.

Further advantageous further developments result from the following description, the drawings and the subordinate claims.

Thus in a preferred embodiment it is proposed to form the grid structure of a large number of ribs which project outwardly from the base body 14 and at which the jacketing is supported with it inner side which faces the base body. Through the ribs of the grid structure, the forces which are exerted on the jacketing and which are applied by the user to the steering wheel during the travel of the motor vehicle are transmitted in predetermined, definite directions to the base body at which the jacketing is uniformly supported by the grid structure in such a manner that the steering wheel in accordance with the invention has a sufficient inherent stability even when large forces are acting on it.

The grid structure is preferably formed of a large number of transverse ribs which are preferably uniformly spaced with respect to one another and which project outwardly from the base body approximately transversely to the peripheral direction of the latter. The transverse ribs are in turn connected to one another by longitudinal ribs which likewise project outwardly in the peripheral direction of the base body. Through the thereby forming a honeycombed grid structure it is achieved that forces which are

exerted on a transverse or longitudinal rib are deviated through the ribs, which are firmly connected to one another, and that the rib which is maximally stressed is supported both in its longitudinal and in its transverse direction by the ribs which are adjacent to it.

In this embodiment it is advantageous in particular when in a steering wheel with a ring-shaped base body the longitudinal ribs, which align with one another in the peripheral direction of the base body, in each case form a closed ring, through which the arising forces are deviated in the peripheral direction of the base body and thus the maximum stress at the point of the steering wheel at which the force is exerted is reduced.

Polypropylene, which is on the one hand simple to process and on the other hand is substantially more economical in its manufacture and processing in comparison with polyurethane in particular, is in particular suitable as the plastic material for the grid structure, so that the steering wheel in accordance with the invention can be manufactured with a lower expenditure than steering wheels in the manufacture of which polyurethane is used as the plastic material.

The base body is preferably formed as a cast part, in particular as an injection molded part, and manufactured of aluminum or an aluminum alloy, so that the total weight of the steering wheel is further reduced.

In order to impart an appealing appearance to the steering wheel, it is further proposed to manufacture the jacketing for example of a real wood veneer or another precious material. Alternatively, it is also possible to form the jacketing of carbon fibers in order to impart additional strength to the steering wheel.

In a preferred embodiment the jacketing is formed of at least two jacketing shells which are preferably releasably connected to one another, which are placed onto the grid structure and which are connected to the latter.

In this way the steering wheel can be adapted without a great cost and complexity to the individual customer's wishes during its manufacture through the assembly of differently designed jacketing shells, with it always being

possible to use the same base body with grid structure in its manufacture in spite of differing optical designs of the steering wheel. The jacketing shells are preferably firmly connected to the grid structure through latch connections.

Brief Description of the Drawings The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:- Figure 1 is a steering wheel in accordance with the invention in perspective illustration, Figure 2 is a sectional view of the steering wheel along the section line A-A in Fig. 1, Figure 3 is an enlarged perspective illustration of a section of the steering wheel in accordance with Fig. 1 with the omission of a jacketing, and Figure 4 is a sectioned view of the steering wheel in accordance with the invention along the section line B-B in Fig. 2.

Description of the Preferred Embodiment Fig. 1 shows a steering wheel 10 for a motor vehicle in perspective illustration. The approximately circular steering wheel 10 has three spokes 12 which extend radially inwardly, which run together in a steering wheel hub (not illustrated), and with which the steering wheel 10 can be secured at a non-illustrated steering column of the motor vehicle in a known manner.

As the cross-section of the steering wheel 10 illustrated in Fig.

2 shows, the steering wheel 10 has a base body 14 which is approximately ring-shaped (cf. Fig. 1) and which has an approximately U-shaped cross- sectional shape, with the two limbs 16 and 18 of the base body 14 extending in the direction of the lower side which faces away from the visible side of the steering wheel 10. The base body 14 and the spokes 12 which are formed on it are cast of an aluminum alloy.

As Fig. 3 shows, approximately circular transverse ribs 20 of a grid structure 22 project outwardly from the base body 14 transversely to the peripheral direction of the latter and are arranged at the base body 14 approximately concentrically to the latter. The transverse ribs 20 of the grid structure 22, which is formed of polypropylene, are distributed with approximately the same distance over the entire periphery of the base body 14, with each transverse rib 20 being arranged in a plane which extends normally to the peripheral direction of the base body 14 and which extends in the direction of the steering wheel hub of the steering wheel 10.

Between mutually adjacent transverse ribs 20 three longitudinal rib pairs 24,26,28 are in each case provided, which are formed integrally with the transverse ribs 20 and are moulded on at the base body 14. Each longitudinal rib pair 24,26 and 28, respectively, has a longitudinal rib which projects downwardly from the base body 14 in the direction of the limbs 16 and 18 and a longitudinal rib which aligns with the former and projects from the base body 14 in the opposite direction. As Figs. 3 and 4 show, the longitudinal rib pairs 24,26 and 28, which are arranged in each case between two adjacent transverse ribs 20, align with the adjoining longitudinal rib pairs, so that the grid structure 22 has a total of three rings 30,32 and 34 which are formed from the longitudinal rib pairs 24,26 and 28 and which extend in the peripheral direction of the base body 14. The free end sides of the longitudinal rib pairs 24,26 and 28 end at about the same height with the circumferential edges of the transverse ribs 20, so that the grid structure 22 forms a honeycombed structure which completely surrounds the base body 14 and of which the support surfaces for a jacketing 30 (cf. Fig. 2) which are formed by the circumferential edges of the transverse ribs 20 and the end sides of the longitudinal rib pairs 24,26 and 28 have approximately the same radial distance from the areal center of gravity of the base body 14.

The jacketing 36, which is formed of a precious wood, carbon fibers or the like and which imparts to the steering wheel 10 an appealing appearance and a surface which is pleasant for the user to grip, has a first

jacketing shell 38 and a second jacketing shell 40. The two jacketing shells 38 and 40 are designed in such a manner that they are uniformly supported with their respective inner sides at the support surfaces being formed by the grid structure 22, wherein the two jacketing shells 38 and 40, which are illustrated to be U-shaped in cross-section in Fig. 2, are firmly connected at their circumferential edges to the grid structure 22.

For this purpose a radially inwardly projecting latching nose 42 and 44, respectively, as well as 46 and 48, respectively, is formed at each circumferential edge of each jacketing shell 38 and 40 respectively. The latching noses 42 and 44 as well as 46 and 48 of the circumferential edges of the two jacketing shells 38 and 40, which lie in mutual contact, are in each case latched in a common cut-out 50 and 52 which is formed at each transverse rib 20 in such a manner that the two jacketing shells 38 and 40, respectively, are firmly connected to the grid structure 22 and thereby indirectly to the base body 14.

Through the grid structure 22 it is achieved that forces which are exerted at the steering wheel 10 are uniformly further transmitted to the base body 14 of the steering wheel 10, so that possibly arising force peaks are reduced and an overstressing of individual periphery sections of the steering wheel 10 are avoided. Moreover, a lower total weight compared with conventional steering wheels is achieved through the honeycombed grid structure 22, with an extremely economical manufacture of the steering wheel 10 becoming possible through the use of polypropylene as the plastic material for the grid structure 22 in comparison with the use of polyurethane.