Machine element or mechanism – Elements – Cams
Reexamination Certificate
2000-01-27
2001-10-02
Bucci, David A. (Department: 3682)
Machine element or mechanism
Elements
Cams
C123S090600, C029S888100, C251S251000
Reexamination Certificate
active
06295893
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a hollow cam shaft (camshaft) having a structure in which an end piece is pressure-welded to a hollow shaft particularly capable of enclosing burr or flush generated at a time when the end piece is pressure-welded to the hollow shaft. Further, in the above meaning, the hollow cam shaft of the present invention may be referred to as end piece pressure welded type hollow cam shaft or hollow cam shaft having an end piece pressure-welded structure.
A cam shaft constituting one element of an engine of an automobile, for example, is usually manufactured by assembling and fixing a hollow shaft and various pieces such as cam piece, journal piece, end piece and the like. In the prior art, the Japanese Patent Laid-open Publication No. SHO 54-86456 discloses a method of fixing an end piece to a hollow shaft by means of brazing and soldering, and on the other hand, the Japanese Patent Laid-open Publication No. HEI 7-167152 discloses a method of fixing an end piece to a hollow shaft by fitting, under pressure, i.e. press-fitting, the end piece into the hollow shaft. Furthermore, a fixing method utilizing a welding process is also known.
However, the method by means of brazing or welding requires consumable goods or materials such as filler material (metal), flux, sealed gas or other, and furthermore, in the press-fitting method, it is necessary to preliminarily carry out a machine working to the end piece and the hollow shaft with high performance. Accordingly, in these conventional methods, there are provided problems of simplifying processes or steps, reducing cost and so on.
Taking the above matters into consideration, the inventors of the subject application attempted to fix both the end piece and the hollow shaft by means of friction welding, which has been well known in the prior art. The friction welding method is a method of abutting materials to be joined, applying a pressure thereto, performing a mechanical relative movement at their mating surfaces and then joining these materials by a friction heat generated through the relative movement thereof. The joining method by means of such friction welding does not require a consumable goods or products such as filler material used in the blazing and soldering method mentioned above. Furthermore, this joining method does not preliminarily require a precise mechanical (machine) working of the end piece and the hollow shaft. Accordingly, this joining method has advantages in comparison with the other methods mentioned above.
FIG. 6
is a sectional view showing one example of an end piece pressure-welding type hollow cam shaft
61
which was manufactured by the inventors through the frictional welding.
With reference to
FIG. 6
, an end piece
63
is fixed to a hollow shaft
62
by means of the friction welding, burrs
65
and
66
are formed to both inner and outer peripheral surface sides of a pressure-welding (welded) portion
64
. Although the outer burr
66
formed to the outer peripheral surface side can be easily removed through a simple mechanical working, it is very difficult to remove the inner burr
65
formed to the inner peripheral surface side. When the hollow cam shaft
61
with the inner burr
65
being not removed, particularly, in a case where an inner hollow portion inside the cam shaft is utilized as an oil passage, there is a fear of the falling of the burr
65
and the invading of foreign materials into an inside of an engine, which may give a significant damage to a valve moving mechanism and, hence, to the whole structure of the engine.
SUMMARY OF THE INVENTION
An object of the present invention is to substantially eliminate defects or drawbacks encountered in the prior art mentioned above and to provide a hollow cam shaft capable of enclosing a burr formed at a time of joining an end piece and a hollow shaft through a friction welding.
This and other objects can be achieved according to the present invention by providing a hollow cam shaft which comprises a hollow shaft having an inner hollow portion and an end piece which is pressure-welded to at least one end of the hollow shaft,
the end piece comprising an end member which is pressure-welded to the one end of the hollow shaft and an enclosure member extending from the end member in an axial direction thereof so as to be inserted into the inner hollow portion of the hollow shaft at a time of pressure welding to define an enclosure space in the inner hollow portion of the hollow shaft, and
the enclosure member being composed of a sealing portion having an outer shape which is substantially the same as an inner shape of the hollow shaft and a connection portion connecting an end surface of the end member of the end piece and the sealing portion so as to define the enclosure space between the enclosure member and the hollow shaft into which a burr generated at the pressure welding time is enclosed.
In a preferred embodiment of the above aspect of the present invention, the end piece is formed with an escape groove for escaping the burr formed at the pressure welding time. The escape groove is formed to an inner peripheral side of the pressure welding portion of the end member of the end piece. The escape groove may be formed to an outer peripheral portion of the connection portion on the side of the end member.
The end member and the enclosure member of the end piece are integrally formed from one solid member or independently formed and then joined together.
The pressure welding is preferably a friction welding performed by means of friction heat generated by rotating either one of the end piece and the hollow shaft with respect to the other one thereof.
According to the hollow cam shaft having an end piece pressure welded structure mentioned above, since the burr generated inside the hollow shaft in the pressure-welding process can be enclosed in the enclosure space defined by the enclosure member composed of the sealing portion and the connection portion, it is not necessary to specifically carry out the burr removing process. Particularly, in the case of the hollow cam shaft utilizing its outer periphery as an oil passage, it is possible to prevent the fallen burr from invading into the engine, so that it is possible to prevent the valve moving mechanism of an engine or, moreover, the entire structure of the engine itself from being damaged by the burr. Furthermore, the sealing portion has the outer shape substantially equal to the inner shape of the hollow shaft, so that when the enclosure member is inserted into the hollow shaft, this sealing portion will serve as guide portion thereby to easily guide the hollow shaft to the predetermined pressure welding portion of the end member. Still furthermore, it is possible to properly form the enclosure space having a size and/or shape in conformity with the generation amount and generation mode of the inner burr generated at the friction welding time by suitably adjusting the outer diameter and axial length of the connection portion, thus the inner burr being completely enclosed in the enclosure space. Therefore, according to the present invention, the hollow cam shaft can be easily manufactured by the joining method utilizing the pressure welding process, and hence, the manufacturing processes can be made simple and easy and the manufacturing cost can be also reduced.
According to the preferred embodiment of the present invention, in the structure that the burr escape groove is formed to the end piece, the burr generated inside the hollow shaft at the friction welding time can be smoothly discharged by forming the escape groove. As a result, the clean surface of the pressure welded portion suitable for generating the heat in the friction welding process and joining the surfaces to be welded can be ensured. Furthermore, the smooth discharging of the burr can achieve such effects as that a force for restricting the burr generation is not applied to another portion, that the generation of any deformation or distortion can be also restricted and that the fal
Ogawa Eiji
Takeguchi Shunsuke
Bucci David A.
Kim Chong H.
Nippon Piston Ring Co. Ltd.
Parkhurst & Wendel L.L.P.
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