Machine element or mechanism – Control lever and linkage systems – Elements
Reexamination Certificate
1999-11-23
2001-04-17
Luong, Vinh T. (Department: 3682)
Machine element or mechanism
Control lever and linkage systems
Elements
C074S558000, C074S558500, C428S317100, C428S327000, C156S293000, C264S494000
Reexamination Certificate
active
06216556
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a steering wheel to be used when a vehicle is steered, and a process for manufacturing the steering wheel.
2. Description of Related Art
In a steering wheel of the prior art, a smooth decorative layer is formed on the surface of a ring portion to be gripped at steering time (as disclosed in Unexamined Published Japanese Patent Application No. 8-310407).
Moreover, this steering wheel having the decorative layer is molded by the following process. First, a steering wheel core is set in a mold. Also, a skin for the decorative layer is set while leaving a clearance around the steering wheel core. A coating layer is then poured into the clearance between the core and the skin to mold the steering wheel.
In short, the portion including the skin for the decorative layer is integrally prepared.
The ring portion is a three-dimensional portion having a curved face. In order to match the curved face of the outer circumference of the ring portion, the decorative layer has had to be prepared accordingly. This has caused considerable inconvenience for steering wheel manufacturers.
Here, in order to eliminate this inconvenience in the manufacture of the steering wheel, it is conceivable to attach the decorative layer by means of an adhesive to the surface of the molding coating layer. It is, however, necessary to so adhere the decorative layer such that no level difference occurs on the outer circumference of the coating layer that has a section in the axial direction of the steering wheel. This necessity stems from the need to prevent degradation in the touch and feeling of the decorative layer.
When the decorative layer can be adhered without causing a level difference, however, the working of the terminals of the decorative layer is troublesome.
SUMMARY OF THE INVENTION
With a view to solving the above-specified problems, an object of the invention is to provide a steering wheel for which a smooth decorative layer can be formed easily on the surface of a ring portion, and a process for manufacturing the steering wheel.
In order to achieve this object, according to the invention, there is provided a steering wheel comprising a ring portion to be gripped at steering time. The ring portion includes: a core, a core coating layer (also referred to herein as a coating layer) for coating the core and a decorative layer to be arranged on the surface of the coating layer. The decorative layer has a printed layer and a protective coating layer. The printed layer is formed by hydraulic transfer, and is arranged to cover the surface of the coating layer. The protective coating layer is transparent, and is arranged to cover the surface of the printed layer so as to protect the printed layer.
The printed layer formed by the hydraulic transfer is formed such that, even if its printed surface is curved, it has a small and uniform thickness. This makes it possible to form a smooth decorative layer easily on the surface of the ring portion. The printed layer is naturally covered with the protective coating layer to promote durability. As a result, the printed layer does not peel off, even when the ring portion is gripped and steered. This also prevents the appearance of the ring portion from being degraded.
In the steering wheel according to the invention, therefore, a smooth and durable decorative layer can be easily formed on the surface of the ring portion.
Moreover, the decorative layer is desirably arranged at a portion of the ring portion apart from the spoke portions.
In this case, the printed layer need not be formed during hydraulic transfer in the vicinity of the spoke portions, which are largely curved three-dimensionally on the coating layer surface of the ring portion. This makes it possible to prevent runs in the pattern of the printed layer. As a result, the decorative layer can have a printed layer with a beautiful pattern.
The coating layer may be made of a synthetic resin having a hardness (JIS A) of 40 to 90, or no less than 95.
A steering wheel having a coating layer made of a synthetic resin having a hardness (JIS A) of 40 to 90 can provide a soft feeling when the ring portion is gripped.
On the other hand, a steering wheel having a coating layer made of a synthetic resin having a hardness (JIS A) no less than 95 can provide a firm grip feeling. In the steering wheel thus constructed, the ring portion can be gripped without any sense of strangeness, even when the printed layer is colored with a grain pattern or a metallic tone.
The decorative layer is arranged at a portion of the surface of the coating layer, and a skin is arranged at the remainder of the surface of the coating layer. A level difference portion for folding therein the end portions of the skin is arranged at the remainder of the surface of the coating layer. In this steering wheel, its design effects are improved by a skin. In the present steering wheel, moreover, the end portions of the skin can be easily folded within the level difference portion after the molding step.
And, in this steering wheel, slits extending in the circumferential direction of the ring portion section are desirably arranged at the portion where the coating layer is covered with the skin.
In this steering wheel, a molding shrinkage occurs at the time of molding the coating layer. Then, an internal stress is established to shrink the coating layer in the circumferential direction of the plane of the ring portion. In this steering wheel, however, the slits extending in the circumferential direction of the section of the ring portion are arranged at the portion where the coating layer is covered with the skin.
As a result, the portion of the slits extending along the circumferential direction of the section of the coating layer is deformed in order to extend the slits. In other words, the stress is not concentrated only at the portion where there is a level difference. This makes it possible to suppress cracking or deformation of the level difference portion, which might otherwise cause defective products.
Any cracks or deformations at the portion of the slits are covered with the skin. The result is that the ring portion has a deteriorated appearance.
Thus, the steering wheel having such slits as described above results in improving yield ratio, while also suppressing the occurrence of defects at the time of molding the coating layer.
Moreover, the steering wheel having the slits extending in the circumferential direction of the section of the ring portion can achieve the following actions and effects. Even if the ring portion core is coated therearound with the coating layer made of the hard synthetic resin, more specifically, the rigidity of the ring portion can be lowered. Therefore, when the ring portion, is impacted, the ring portion can be smoothly deformed. As a result, the steering wheel can effectively absorb the energy of the impact.
The coating layer is desirably arranged such that the sectional area of the coating layer at the portion where the slits are arranged is smaller than that of the coating layer at the level difference portion.
In this steering wheel, concentrated stress at the time of molding shrinkage acts without fail on the slits portion. As a result, this steering wheel enables a suppression of cracking or deformation at the level difference portion, which might otherwise cause defects.
Moreover, in this steering wheel, the coating layer at the portion arranged a decorative layer is made of a hard synthetic resin substantially. Also, the coating layer at the portion arranged a skin is made of a soft synthetic resin substantially.
In this steering wheel, the portion of the decorative layer and the portion of the skin have a different feeling when touched. As a result, the steering wheel enables an improved grip feeling when gripped.
Still moreover, the portion made of a hard synthetic resin is arranged at a portion apart from the spoke portions. Also, the portion made of a soft synthetic resin is arranged at a portion of the spoke portio
Hayashi Mikine
Koyama Tooru
Nagata Atsushi
Yamamoto Tadashi
Luong Vinh T.
Toyoda Gosei Co,., Ltd.
Winthrop LLP Pillsbury
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