Steering wheel

Abstract: A steering wheel comprises a ring section (R), a boss section (B) arranged at the center of the ring section (R), at least two spoke sections (S) extending radially outward from the boss section (B) and connected to the ring section (R), a ring core arranged in the ring section, a boss arranged in the boss section, and a unitary integral connecting plate (12) connecting the ring core member and the boss, which connecting plate comprises a base part (22) adjacent to the boss and a spoke part (23) extending radially outward from the base part and connected to the ring core member, the connecting plate undergoing plastic deformation when subjected to a deforming force of impact, the deformation causing the ring section to become substantially perpendicular to the direction of the force of impact.

Description: BACKGROUND OF THE INVENTION Field of the Invention This invention relates to a steering wheel provided with a self-aligning mechanism according to the preamble of claim 1. Description of the Prior Art Fig. 1 shows a conventional steering wheel provided with a self-aligning mechanism (see Japanese Utility Model Laid-Open No. 60-9764: US Patent No. 4,709,944, US Patent No. 3,948,118). In this steering wheel W0 as illustrated, a steering wheel core member C0 comprises a core element 4 of a ring section R, core elements 3 of spoke sections S, a boss 1 of a boss section B which is connected to a steering shaft not shown, and a boss plate 2 for connecting the boss 1 and the spoke section core elements 3 together. Each core element of each section is made of steel and connected to other elements by welding. The boss plate 2 of the steering wheel W0 has a plurality of through holes 2a formed around the boss 1, thereby constituting the self-aligning mechanism. That is, the boss plate 2 has deformable portions 2b defined by low-rigidity narrow portions between the through holes 2a, so that when a force of impact acts on the ring section R of the steering wheel W0 attached to a steering shaft, the deformable portions 2b undergo plastic deformation; as a result, the plane of the ring section R becomes substantially perpendicular to the direction of the force of impact. 2c designates reinforcing ribs which project upward from the periphery of the boss plate 2 to reliably deform the deformable portions 2b when the force of impact acts on the ring section R. 2d and 2e designate puller holes and mounting holes used in mounting functional components, such as a horn switch mechanism, these holes 2d, 2e are also served like the through holes 2a for defining the deformable portions 2b. However, since the steering wheel core member C0 of the conventional steering wheel W0 is manufactured by connecting all the core elements of the individual sections together by welding, the number of manufacturing steps and the manufacturing cost of the steering wheel W0 increase. Further, some overlap width of welding must be included in each core element of each section to weld them with a given strength of welding, leading to a corresponding increase in size of the core member C0; thus, the weight of the steering wheel core member C0 and the weight of the steering wheel W0 increases. In the preamble of the claim 1, however, it is proceeded from a steering wheel as is shown in the printed publication DE-OS 25 30 594. This known steering wheel comprises a ring section having a core member and a coating layer, a boss section and a spoke section consisting of two spoke parts which extend radially outward from the boss section in opposite directions and which are connected to the ring section. The spoke section as well as the boss section are framed at their side edges by ribs which abut with their outer ends on the ring section. It is an object of the present invention to provide a steering wheel of this kind which can be manufactured in a reduced number of manufacturing steps and, therefore, at reduced manufacturing costs. According to the invention this problem is solved by the features in the characterizing part of claim 1. Therefore, the gist of the invention consists in the construction of the ribs which do not extend to the area of the spoke portion where the coating layer is molded. In other words, the coating layer is molded where the ribs for the spoke portions do not exist. For this reason, while forming the coating layer in a given metal mold the appearance of mold flashes which make for example the later installation of a horn more difficult can almost be prevented in an easy way so that a lengthy and expensive trimming work after the molding process is no longer necessary. While manufacturing the steering wheel according to the DE-OS 25 30 594 the coating layer is also formed by a molding process. On this occasion, as previously described, the coating layer must be prevented from advancing into areas of the spoke section and the boss section in which afterwards the installation of, for example, a horn is intended. However, with a rib construction according to the DE-OS 25 30 594 it is difficult to prevent resin material from flowing to unnecessary portions so that costly trimming works are necessary. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a plan view showing a conventional steering wheel; Fig. 2 is a plan view showing a steering wheel with a horn pad removed according to an embodiment of the present invention; Fig. 3 is a plan view showing a steering wheel core member used in the embodiment; Fig. 4 is a fragmentary sectional view taken along line IV-IV in fig. 2; Fig. 5 is a fragmentary sectional view taken along line V-V in fig. 2; Fig. 6 is a fragmentary sectional view taken along line VI-VI in Fig. 2; Fig. 7 is an explanatory diagram showing a self-aligning mechanism in the embodiment; and Fig. 8 is a plan view showing a further steering wheel core member used in a further embodiment. DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will now be described with reference to the drawings. In Fig. 2, a steering wheel W1 according to an embodiment comprises a ring section R, a boss section B arranged at the center of the ring section R, and two spoke sections S extending radially outward from the boss section B. As shown in Fig. 3, a steering wheel core member C1 of the steering wheel W1 comprises a core member 14 made of a ring-shaped steel pipe and arranged in the ring section R, a steel boss 11 arranged in the boss section B which is connected to a steering shaft 5 ( see Fig. 7 ) and a unitary integral connecting plate 12 made of steel sheet which connects the boss 11 and the ring core member 14 together. The connecting plate 12 comprises a base part 22 connected to the boss 11 and two spoke part 23 extending obliquely upward from the base part 22 and connected to the ring core member 14. The base part 22 constitutes a self-aligning mechanism which, when a force of impact acts on the ring section R after attachment to the steering shaft 5, makes the plane of the ring section R substantially perpendicular to the direction of the force of impact. The base part 22 has a plurality of vertical through holes 12a formed around the boss 11 such that low-rigidity deformable portions 12b are left between the through holes 12a which undergo plastic deformation when the force of impact acts thereon. 12c designates ribs projecting upward from the margin of the base part 22 and from a portion of the margin of each spoke part 23. The ribs 12c are provided to reliably deform the deformable portions 12b when the force of impact acts on the ring section R. 12d designates puller holes, 12e designates a mounting hole used in mounting a stationary contact plate 25 of a horn switch mechanism 19 hereinafter described, and 12f designates an opening through which a tongue piece 30a of a slip ring 30 hereinafter described passes, these holes or openings also serving like the through holes 12a for defining the deformable portions 12b ( see Figs. 2, 3 and 6 ). The spoke part 23 extends obliquely upward from the base part 22, and has a mounting position 23a formed in an intermediate portion thereof which in turn has a mounting hole 23b used in fixing the stationary contact plate 25 by a screw 21 ( see Figs. 3 and 4 ). The connecting plate 12 with the through holes 12a and the like is shaped by subjecting a steel sheet of given shape to stamping or the like. As shown in Figs. 2, and 4 through 6, the horn switch mechanism 19 comprises the stationary contact plate 25 made of sheet metal which is substantially quadrangular when viewed from above, and a movable contact plate 26 made of a metal leaf spring which is fixed to the stationary contact plate 25 by a rivet 28 with interposition of electrical insulating spacers 27A and 27B. The stationary contact plate 25 is fixed to the steering wheel core member C1 by fixing both mounting end portions 51 and 51 of the stationary contact plate 25 to the mounting positions 23a of the spoke part 23 by screws 21 and fixing a lower portion of a tongue piece 52 extending downward from the front margin of the stationary contact plate 25 to the base part 22 by a screw 20. It should be noted that when the stationary contact plate 25 is fixed to the steering wheel core member C1 by the screws 20 and 21, a lower cover 18 made of synthetic resin and used to cover a lower portion of the steering wheel W1 is also attached to the steering wheel core member C1 at the same time. After fixed to the steering wheel core member C1, the stationary contact plate 25 can be electrically connected to the negative side of a horn circuit via the core member C1, whereas the movable contact plate 26 is electrically connected, via a lead wire 29 connected to the rivet 28, to the tongue piece 30a of the slip ring 30 which is fixed in a lower portion of the lower cover 18 and capable of electrical connection to the positive side of the horn circuit. In the steering wheel W1 of the embodiment, a horn pad 16 made of synthetic resin is provided so as to cover the boss section B and the spoke sections S ( see Figs. 2, and 4 through 6 ). The horn pad 16 comprises a pad body 16a arranged on the upper side and an auxiliary plate 16b fixed to the under side of the pad body 16a by screws not shown. The auxiliary plate 16b has four lock legs 16c projecting downward at given positions and two guide protrusions 16d. The horn pad 16 is fixed to the stationary contact plate 25 by inserting the guide protrusions 16d of the auxiliary plate 16b connected to the pad body 16a in openings 54 formed in the stationary contact plate 25 and locking the lock legs 16c of the auxiliary plate 16b in lock holes 53 formed in the stationary contact plate 25. In Figs. 2 and 4, 15 designates a coating layer of synthetic resin provided to cover the core element 14 of the ring section R and partially each spoke part 23 of the connecting plate 12 which serves as the core member of each spoke section S. The manufacturing process of the steering wheel W1 of the embodiment will be described. First, the steering wheel core member C1 is manufactured by welding the connecting plate 12 (shaped to a given shape by stamping and boring ) to the boss 11 and the ring section core element 14. Here, the number of welding position is three ( that are between the connecting plate 12 and the boss 11 and between the connecting plate 12 and the ring core member 14 ), this being smaller than the number of welding position of the conventional steering wheel core member C0 ( equal to five ); thus, the welding process can be achieved readily, the overlap width of welding can be reduced, the number of manufacturing steps, manufacturing cost and weight of the steering wheel core member C1 can be decreased, and the steering wheel core member C1 can be made compact. After the steering wheel core member C1 is manufactured, the steering wheel core member C1 is set in a given metal mold, and the coating layer 15 is formed by injection molding or the like. Then, the stationary contact plate 25 with the movable contact plate 26 arranged thereto, together with the lower cover 18 with the slip ring 30 arranged thereto, is fixed to the steering wheel core member C1 by the screws 20 and 21. At this time, the lead wire 29 is of course connected to the slip ring 30. Then, by inserting and locking the guide protrusions 16d and lock legs 16c in the openings 54 and lock holes 53, the horn pad 16 made up integrally of the pad body 16a and the auxiliary plate 16b is fixed to the stationary contact plate 25, whereby the manufacture of the steering wheel W1 is complete. In the steering wheel core member C1 of the steering wheel W1 of the embodiment, the spoke parts and the base part (which are independent of each other in the prior art ) are formed integrally by the unitary integral connecting plate 12. Therefore, the work of welding the spoke part and the base part together ( required in the prior art ) is not necessary; thus, the number of manufactuirng steps and the manufacturing cost of the steering wheel core member C1 can be reduced, hence, the steering wheel W1 can be manufactured readily. Further, because of no need to weld the spoke part and the base part together in contrast with the prior art, any overlap width of welding hitherto considered to weld them is not required; thus, the steering wheel core member C1 can be made compact and light in weight, hence, the steering wheel W1 can be made compact and light in weight. Further, since the spoke parts 23 and the base part 22 make the unitary integral connecting plate 12, the characteristic frequency of the steering wheel W1 can be increased, whereby its resonance with the characteristic frequency of the vehicle body during idling or the like can be prevented. The foregoing embodiment has been described such that the steering wheel W1 has the two spoke section S. In this connection, if three or more spoke sections S are desired for the steering wheel, as illustrated by the two-dot chain line in Fig. 3, a desired steering wheel core member having an additional spoke section may be manufactured by welding a separate spoke core member 13 made of steel sheet to the base part 22 of the connecting plate 12 and to the ring core member 14. Further, the foregoing embodiment has been described such that the steering wheel core member C1 includes the connecting plate 12 made of steel sheet which corresponds to an integral combination of the conventional boss plate and spoke section core elements. In this connection, in order to constitute the self-aligning mechanism, it is sufficient that the base part 22 of the connecting plate 12 have the given through holes 12a and deformable portions 12b formed therein, and the connecting plate 12 may be made of a different material capable of plastic deformation. Further, where a connecting plate 220 as shown in Fig. 8 is to be made of a die casting metal capable of plastic deformation, such as light alloy aluminum, a ring section core element 240 may also be made of a die casting metal integrally at the same time.

Claims: A steering wheel for a vehicle, comprising a connecting plate (12), the middle portion of which is formed as a plastic deformable plate-shaped element (22) which is provided with a boss (11) from which some integral spoke parts (23) extend radially outwards said spoke parts (23) being connected with a ring section (R) having a ring core member (14) which is covered with a coating layer (15) together with an end portion of said spoke parts (23), wherein said plastic deformable plate-shaped element (22) which undergoes plastic deformation when subjected to a deforming force of impact, said deformation causing said ring section (R) to become substantially perpendicular to the direction of said force of impact, is integrally framed by a rib (12c) which is disposed in angles to a surface of said plate-shaped element (22) and extends along said spoke parts (23) characterized in that said rib (12c) terminates at a spoke portion before reaching said coating layer (15). A steering wheel according to claim 1, characterized in that said plate-shaped element (22) has a plurality of through holes (12a) arranged around said boss (11) such that low-rigidity deformable portions (12b) are formed between said through holes (12a). A steering wheel according to one of claims 1 or 2, characterized in that said connecting plate (12) is formed integrally by said plate-shaped element (22) and said spoke parts (23) which are fixed at their outer ends to said ring core member (14) by welding. A steering wheel according to one of claims 1 or 2, characterized in that said connecting plate (12) and said ring core member (14) are formed integrally and are made of a die casting metal such as light alloy aluminum. A steering wheel according to claim 1, characterized in that said boss (11), said connecting plate (12) and said ring core member (14) are made of steel. A steering wheel according to claim 1, characterized by a separate spoke core member (13) made of steel which is connected with said connecting plate (12) and said ring core member (14).

Inventors: FUJITA YOSHIYUKI, FUJITA, YOSHIYUKI
Applicants: TOYODA GOSEI KK, TOYODA GOSEI CO., LTD.
Application year: 1990
Main classification: B62D1
IPC codes: B62D1, B60Q5