1. Field
Exemplary embodiments relate to a wheel support device for a vehicle, and in particular to a wheel support device including a bearing that rotatably supports a wheel.
2. Description of Related Art
When a vehicle, such as an automobile, runs, static electricity is generated in the vehicle since the air flows while being in friction contact with the vehicle. Also, static electricity is generated, due to repeated contact and separation of each portion of tires with and from a road surface as wheels of the vehicle rotate, and also due to relative movements of constituent components of an engine and a brake system, for example.
The vehicle is substantially electrically insulated from the ground due to the presence of the tires having low electric conductivity. Therefore, if static electricity is generated in the vehicle, the vehicle body, etc. are electrostatically charged (generally with positive charges). Since radio noise is likely to be generated if the vehicle body, etc. are charged, structures for reducing electric charges carried by the vehicle have been studied, and various structures have been proposed.
For example, a bearing device having an inner race member, an outer race member, and a plurality of rolling elements interposed between the race members is described in Japanese Patent Application Publication No. 2006-234093 (JP 2006-234093 A). The bearing device has seal devices each including an elastic member that contacts one of the race members, and the interior of the bearing device is filled with conductive grease.
In the bearing device as described in JP 2006-234093 A, electric charges can be moved from the grease to the race members since the grease has electric conductivity. However, in a situation where the vehicle body, etc. are electrically charged, members surrounding the bearing device are also electrically charged, and therefore, charges cannot be moved from the race members to the surrounding members. Therefore, the grease cannot be effectively prevented from being electrically charged. In order to transfer charges from the race members to the surrounding members, it is necessary to remove or eliminate charges carried by the surrounding members of the bearing device by earthing, by means of a special device, such as an electrostatic eliminator, as described in Japanese Patent Application Publication No. 2008-181694 (JP 2008-181694 A), for example.