Roller bearing assembly

#This invention relates to roller bearing assemblies, and more particularly to a roller bearing assembly suitable for use with speed change gearing, for example, having a plurality of large and small gears mounted on a single shaft so as to increase the rigidity of the gear and prevent vibration, noise, wear and damage which would otherwise be caused to occur by a reduction in the rigidity of the shaft.

#The bearing assembly of the type described is suitable for use with a shaft required to have high strength. In recent years, automotive vehicles for transporting passengers have to be equipped with a multistage transmission in order to minimize fuel consumption while maintaining motive power at a level high enough to travel in a wide range of travelling conditions including a travel on expressways, a travel on city roads where traffic is so heavy that the roads are congested, a travel on uphill roads in a mountainous region and a travel on a tortuous road. Such speed change gearing is limited by dimensions, cost, weight and other conditions and is required to be inexpensive, light in weight and compact in size.

#An object of this invention is to provide a roller bearing assembly suitable for use with speed change gearing which meets the aforesaid requirements.

#FIG. 1 is a sectional view of the essential portions of a manual transmission for automotive vehicles incorporating therein one embodiment of the present invention;

#FIG. 2 is a sectional view taken along the line II--II in FIG. 1; and

#FIG. 3 is an exploded perspective view of the countershaft center bearing shown in FIG. 2.

#A preferred embodiment of the present invention will now be described by referring to the accompanying drawings.

#The embodiment is shown as being incorporated in a manual transmission for automotive vehicles. In FIG. 1, an output shaft 1 and a countershaft 2 are located parallel to each other and rotatably supported by a transmission case 3a, an intermediate plate 3b and an extension housing 3c. Gears are formed integrally with the shafts or attached thereto by spline connection. A countershaft reverse gear 4 is selectively brought into meshing engagement with a reverse gear 5 on the output shaft 1 through a reverse idler gear, not shown. The countershaft 2 has at its right end portion a ball bearing 6, a countershaft 5-speed gear 7, the countershaft reverse gear 4 and a countershaft center bearing 8. The countershaft reverse gear 4 is formed integrally with the countershaft 2, and the countershaft 5-speed gear 7 is attached to the countershaft 2 by spline connection. In a countershaft of the prior art, the countershaft reverse gear has hitherto been attached to the countershaft by spline connection. This arrangement has been inevitable because of the fact that a difficulty is encountered in assembling the parts of the transmission since the volume of the outer diameter of an output shaft center bearing 12, the thickness of the intermediate plate 3b (transmission case) and the bulk of the bearing make the inner diameter of the inner race of the countershaft center bearing 8 smaller than the outer diameter of the countershaft reverse gear 4. When the countershaft reverse gear is attached to the countershaft by spline connection after the latter is inserted in the countershaft center bearing which is constructed as a unitary structure as aforesaid, some difficulty would be encountered. That is, since the countershaft reverse gear has an outer diameter which is too small as compared with the diameter which the countershaft is required to have, the spline would have too small a diameter if the root of tooth of the countershaft reverse gear had a sufficiently large thickness, thereby reducing the rigidity of the countershaft. The same goes for the spline for connecting the countershaft 5-speed gear to the countershaft. Thus the countershaft would be flexed and vibration and noise would be caused by changes in tooth bearing when the gears mesh with each other, thereby making fretting of the spline inevitable. Also, tilting of the countershaft would shorten the service life of the bearing.

#The countershaft center bearing 8 according to the present invention is not formed as a unitary structure and is constructed by assembling parts, so that it is possible to form the countershaft reverse gear 4 integrally with the countershaft 2.