Rotary shafts – gudgeons – housings – and flexible couplings for ro – Shafting – Nonmetalic shaft or component
Reexamination Certificate
1999-06-16
2002-10-15
Browne, Lynne H. (Department: 3629)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Shafting
Nonmetalic shaft or component
C464S183000, C138S141000, C138S143000, C428S036910
Reexamination Certificate
active
06464591
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a rotary shaft for transmitting power and more particularly it relates to a power transmission shaft represented by a propeller shaft or drive shaft used as a power transmission shaft for automobiles.
2. Prior Art
The propeller shaft used as the power transmission shaft of an automobile is a propeller shaft for transmitting power from the variable speed gear device to the speed reduction gear device and is connected to them through constant velocity joints installed on the opposite ends thereof, the construction being such as to be capable of accommodating changes in length and angle caused by changes in the relative position between the variable speed gear device and the speed reduction gear device.
As the joints and the intermediate shaft disposed between the joints, which constitute the propeller shaft, it has been common practice to use steel articles. Further, from the viewpoint of bending rigidity, a longer shaft is constructed such that it is split into three or four portions and the intermediate region is supported by a center bearing support. Therefore, it has been required to improve such construction from the viewpoint of weight, cost, etc.
Thus, recently, as exemplified in
FIG. 10
, it has been proposed to use a hollow shaft made of fiber reinforced plastic (hereinafter referred to as FRP) of high bending rigidity (see Japanese Patent Kokai Hei 3-249429). This change of material from steel to FRP makes it possible not only to achieve weight reduction but to use a longer shaft while making splitting unnecessary and dispensing with the intermediate support bearing, in which respect it becomes possible to reduce weight and cost.
In this connection, in order to secure the strength of the joined portions to realize torque transmission when joining an intermediate shaft of FRP to metal parts at the shaft ends, it has been common practice to make the cross-sectional shape of the shaft ends polygonal, to roughen the contact surfaces as by knurling in the portion where the hollow shaft ends overlap, to crimp the hollow shaft of FRP, or to force a metal part into the core of the hollow shaft, thereby achieving the joining. Further, there are various other means contrived, including applying an adhesive for joining to the contact interface between the FRP hollow shaft end and a metal part, and making use of processing, such as surface roughening, crimping, or press-fitting, combined with an adhesive, so as to retain the joining strength.
With these methods, however, cause problems in an aspect of formation; the processing of the shaft ends becomes difficult, the outer diameter has to be increased in order to secure the strength of the joined portion or axial slip-off preventive measures have to be additionally taken in order to secure reliability. Further, the methods which involve crimping an FRP hollow shaft or press-fitting a metal part into the core of the hollow shaft, entail a decrease in binding force during press fitting due to creep or stress relaxation in the FRP; thus, circumferential slip or axial slip-off sometimes occur, having serious shortcomings including a lack of long-term reliability in the product functions.
When attention is paid to the joined portion, it is seen that it is only through the area of contact between the FRP and the metal part that torque transmission either using the friction force utilizing as the drag the binding force exerted during press-fitting or using the chemical or physical adhesive force of an adhesive applied to the contact interface is effected. In this case, trying to cope with an excessive torque which is impulsively produced, one increases the amount of press fit so as to maximize the area of the contact interface or increases the amount of elastic deformation of the FRP caused by press fitting. During manufacture and processing, however, cracks are produced in the FRP or creep or stress relaxation during use cannot be avoided, thus producing problems in joining.
On the other hand, in the case where a hollow shaft made of FRP is used as an intermediate shaft in a propeller shaft which is a power transmission shaft in order to provide for lightening, low fuel consumption, cost reduction, antivibration, and noise reduction, there is a problem which has to be solved that the outer diameter of the hollow shaft has to be decreased in consideration of the limited space in an automobile.
SUMMARY OF THE INVENTION
The present invention relates to providing a power transmission shaft constructed in such a manner as to ensure realization of appropriate torque transmission under normal load conditions while securing sufficient joining strength against the impulsively exerted excessive torque, and to retain the reliability in the joined portions during long-term use. The present invention provides for a power transmission shaft constructed by the winding of a membrane, film, foil or thin sheet in layers. The power transmission shaft comprises a longitudinal middle portion composed of FRP layers, end portions composed of metal layers, and a transitional portion disposed between the middle portion and each end portion and composed of a composite layer of FRP layers and metal layers. The joining, as by welding, pinning, press-fitting, or friction welding, of metal ports such as joint elements, is effected at the ends or the ends and transitional portions. The ends or the ends and transitional portion secure the strength necessary for joining to joints or the like and enable the joining which can be retained for a long time.
An object of the invention is to provide a power transmission shaft intended to meet the above requirement for improvements, constructed in such a manner as to enable the joining of metal parts to the ends of an FRP hollow shaft to be effected by welding, pinning, press fitting or the like, to ensure realization of appropriate torque transmission under normal load conditions while securing a sufficient joining strength against impulsively exerted excessive torque, and to retain the reliability in the joined portions during long-term use.
As technical means for achieving the object, the present invention provides a power transmission shaft, wherein the longitudinal middle portion is constituted by an FRP laminated structure made of FRP wound into a pipe form, the shaft ends are constituted by a metal laminated structure made of a winding of metal membrane (film), foil or thin sheet, and the transitional portion between the middle portion and the shaft end is constituted by a composite laminated structure in the form of a combination of the FRP laminated structure and metal laminated structure. The shaft ends or the shaft ends and transitional portion secure the strength necessary for joining to joints or the like and enable the joining which can be retained for a long time to be made.
In other words, in the portions adjacent the shaft ends, the shaft comprises, successively from the middle portion toward the shaft ends, a laminated structure of FRP alone, a laminated structure having a combination of FRP and a metal film, and a laminated structure of metal film alone. In the transitional portion having a combination of FRP and metal films, the metal film is bonded to the FRP films as it is sandwiched therebetween and such laminated structures are united in layers, whereby the area of joining is remarkably enlarged. In respect of any of the circumferential and axial components of a force applied to the power transmission shaft, the force can be transmitted with a sufficient enduring strength even if a high shear stress is produced.
Further, since the part associated with the joining at the shaft ends is not a single FRP body, it is possible to effect such a reliable perfect joining method as welding or friction pressure welding for joining a metal laminate and a metal part. For example, in spite of the fact that the FRP uses a plastic material as a matrix even in the transitional portion having a combination of FRP and metal films, its
Arent Fox Kintner Plotkin & Kahn
Binda Grey
Browne Lynne H.
NTN Corporation
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