Rotary shafts – gudgeons – housings – and flexible couplings for ro – Coupling facilitates relative axial motion between coupled...
Reexamination Certificate
2001-07-25
2004-02-17
Binda, Greg (Department: 3679)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Coupling facilitates relative axial motion between coupled...
C464S181000, C403S359600
Reexamination Certificate
active
06692365
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a propeller shaft and a method for producing the same and, more particularly to a propeller shaft characterized by a joint construction between a propeller shaft main body and a yoke and a method for producing the same.
2. Description of the Related Art
A propeller shaft is a constituent component of the power transmission system of a front-engine and rear-wheel drive automotive vehicle which functions to transmit power generated by the engine to the rear wheels. The propeller shaft is, for example, disposed between the transmission and the differential of the automotive vehicle to function to transmit the rotating torque of the engine to the rear wheels.
In general, the propeller shaft comprises a tubular shaft main body, a yoke joined to one end of the shaft main body for connection to the transmission and a yoke joined to the other end of the shaft main body for connection to the differential. In recent years, to meet a demand for light-weight propeller shafts, propeller shafts have tended to be used in which the shaft main body is formed of fiber reinforced plastic (hereinafter, referred to as “FRP”). In the propeller shafts having the shaft main body of FRP, the metallic yoke is joined to the shaft main body with a part thereof being fittingly inserted into the shaft main body. In order to transmit high rotating torque generated by the engine to the rear wheels without any loss therebetween, it is crucial to prevent the occurrence of slippage between an inner circumferential surface of the shaft main body and an outer circumferential surface of the part of the yoke which is fittingly inserted into the shaft main body at the joint portion of the shaft main body and the yoke so as to assure the proper transmission of the torque therebetween. To make this happen, in many propeller shafts, serrations having axially extending teeth are formed in the outer circumferential surface of the relevant part of the yoke, so that this serrated portion is fittingly inserted into the shaft main body to be joined thereto for transmission of sufficient torque (in this specification, the term “axially” means an axial direction of the propeller shaft, and hereinafter, unless otherwise stated, the term “axially” means the axial direction of the propeller shaft).
On the other hand, there has been a tendency for a crushable construction to be adopted on the body of the automotive vehicle so as to absorb impact energy generated at the time of collision of the vehicle with another vehicle by the body to alleviate the impact that would otherwise be imparted to the passengers with a view to securing the safety of the passengers at the time of such a collision. In the event that the automotive vehicle having the crushable construction encounters in an accident involving a frontal or rear-ended collision, that is to say, that a compression load is applied to the propeller shaft in an axial direction, it is considered that the propeller shaft acts just like an impact returning rod or a prop and interferes with the absorption of the impact energy by the body. To cope with this, with a view to eliminating the interference with the absorption of impact by the body, there have been developed propeller shafts which are designed based on a concept in which the yoke sinks into the shaft main body at the time of collision. In this type of propeller shafts, it is desirable that a force required when the yoke sinks into the shaft main body or the sinking force is as small as possible.
In the propeller shaft having the aforesaid construction, however, the serrations are formed in the outer circumferential surface of the yoke to assure the proper transmission of torque, and in the event that an axial compression load is applied to the propeller shaft, the yoke has to sink into the shaft main body while the teeth of the serrations cut in the inner circumferential surface of the shaft main body, this extremely increasing the sinking force.
To cope with this, studies were made to develop technologies for reducing the sinking force of the propeller shaft with the yoke having serrations formed in the outer circumferential surface thereof, and as an example of the technologies so developed, Japanese Unexamined patent Publication 7-208445 (JP-A-7-208445) discloses a propeller shaft in which a shaft main body comprises a main layer extending over the whole of the shaft body in an axial direction thereof and a partial layer provided inside the main layer and including reinforcing fibers, wherein a yoke has a wedge having a leading end which confronts an inter-layer portion between the main layer and the partial layer, whereby when an axial compression load is applied to the yoke, the wedge separates the main layer and the partial layer from each other and sinks into the shaft main body while tearing open the shaft main body.
In this propeller shaft, the yoke having serrations formed in the outer circumferential surface thereof is press fitted into the shaft main body so as to be joined to the inner circumferential surface of the partial layer, and the transmission of rotating torque is secured between the partial layer and the yoke. On the other hand, when an axial compression load is applied to the yoke, the partial layer and the main layer of the shaft main body are separated from each other, and the yoke sinks into the shaft main body together with the partial layer to thereby reduce the sinking force. Namely, according to the construction of this propeller shaft, the aforesaid problem is solved by a construction in which the propeller shaft is divided into a portion for securing high rotating torque transmission properties and a portion for securing a small sinking force.
However, while the propeller shaft disclosed in JP-7-208445 is said to provide a smaller sinking force when compared to a conventional propeller shaft in which a yoke having serrations formed in an outer circumferential surface thereof is simply fittingly inserted into a shaft main body (hereinafter, referred to as a “conventional propeller shaft”), the sinking force provided thereby still does not meet the satisfactory level as a certain force is still required to separate the integrally formed main and partial layers from each other. In addition, in this propeller shaft, even when there is applied no axial compression load to the yoke or during a normal operation, depending upon the condition where the main and partial layers are integrally formed, it may be considered that the two layers separate from each other. Furthermore, since the main and partial layers have to be provided on the shaft main body and the wedge has to be provided on the yoke, the production process becomes complicated, this increasing the production cost. Thus, the propeller shaft disclosed in JP-7-208445 is still suffering from the aforesaid problems at this point in time.
SUMMARY OF THE INVENTION
The present invention was made to solve the aforesaid problem of compatibility of sufficient torque transmission with a smaller sinking force, which propeller shafts are facing, which each have a mechanism in which a yoke sinks into a shaft main body thereof, and an object thereof is to provide a propeller shaft that can provide a smaller sinking force while securing good rotating torque transmission properties, and which is simple in construction and low in production cost, by forming in advance grooves in an inner circumferential surface of a shaft main body for serration teeth to travel therealong when a yoke sinks into the shaft main body. The other object of the invention is to provide a method for producing the same propeller shaft through a simple work.
With a view to attaining the objects, according to a first aspect of the invention, there is provided a propeller shaft comprising a tubular shaft main body made of FRP and a metallic yoke having an inserting portion which has serrations having axially extending teeth formed in an outer circumferential surface thereof and mounted in at least
Kondo Toshiro
Miyashita Yasuki
Suzuki Koya
Yasui Yoshiharu
Binda Greg
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Morgan & Finnegan , LLP
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