Note: Descriptions are shown in the official language in which they were submitted.
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METHOD FOR FIXING ON INLAY ELEMENT
ONTO A SHAFT AND A SHAFT ASSEMBLY
OBTAINED BY SUCH METHOD
BACKGROUND OF THE INVENTION
The present invention relates to a method for fixing
an annular element onto a shaft and a shaft assembly
obtained by such method The shaft may be, for example, a
camshaft and the annular element may be for example, a cam
piece or a journal piece used in an automobile.
In automobiles, many camshafts axe produced by means
of sistering, in which, at first, a preliminarily sistered
cam piece or journal piece is fixed onto a shaft tempo-
rarity before being permanently fixed as a result of the completion of sistering. In such an operation, it is
necessary that the temporarily fixed cam piece be anchored
to the shaft so that it is not displaced relative to the
shaft either in the axial direction or in the rotating
direction. For thus purpose, conventional assembling of a
camshaft assembly of the above-described type has been
carried out according to the following method comprising
the steps of. forming an axially extending groove on an
outer wall or the shaft and forming an axially extending
projection on an inner surface of a through hole of the
piece, the groove and projection having respective cross
sections which enable them to fit tightly together,
inserting the shaft into the through hole of the piece
while engaging the projection tightly with the groove,
thereby securing the piece to the shaft temporarily before
permanently fixing it onto the shaft as a result of
completion of sistering.
However, the above method is disadvantageous in that
there is an unavoidable dimensional variance between the
groove and the projection. If the variance is large, the
projection is loosely fitted to the groove, resulting in a
reduction of holding capacity between the two elements; on
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the other hand, if the projection is fitted -too tightly to
the groove, breakage of the projection and groove results.
SUMMARY OF THE INVENTION
It is an object of the present invention Jo provide a
method for fixing an annular element onto a shaft and
thereby solve the above mentioned problems by easier
operation.
Another object of the present invention is -to provide
a shaft assembly obtained by such method, which assembly is
conveniently utilized especially in thy case where it is
necessary to fix an annular element onto a shaft tempo-
rarity before permanently fixing said annular element onto
the shaft by sistering or brazing.
One object is attained by a method for fixing an
annular element onto a shaft, said element having a through
hole into which said shaft is loosely inserted, according
to the present invention, said method comprising the steps
of: forming an axially extending groove on an outer wall
of said shaft and forming an axially extending projection
on an inner surface of said hole of said element over the
whole length thereof, said groove and said projection
having respective cross sections which enable them to fit
loosely together; inserting said shaft into said hole while
engaging said projection with said groove so as to prevent
a relative rotating motion; and after determining the axial
position of said element relative to said shaft, deforming
said outer wall of said sheaf L adjacent to said groove at
two positions near the terminating ends of said projection
so that said outer wall protrudes into said groove, thereby
fixing said element onto said shaft.
Another object of the present invention is attained by
a shaft assembly comprising a shaft an an annular element
fixed onto said shaft, said element having a through hole --
into which said shaft is inserted, wherein said shaft has
an axially extending groove on an outer wall ox said shaft
and said element has on axially extending projection on an
inner surface of said hole of said element over -the whole
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length thereof, said groove and said projection having
respective cross sections enabling them to be loosely
fitted to each other, and the outer wall of said shaft
adjacent to said groove is deformed at two positions near
the terminating ends of said projection so that said outer
wall protrudes into said groove with said shaft being
inserted into said hole of said element.
The present invention will now be described in greater
detail with reference to the accompanying drawings which
illustrate the preferred embodiments of the invention, in
which:
Fig. 1 shows a top view of a preferred embodiment
of a camshaft assembly, according to the present invention;
Fig. shows a section taken along the line A-A
in Fig. l;
Fig. 3 shows an enlarged partial section taken
along the line B-B in Fig. l;
Figs. pa and 4b show schematically how a tool is
pressed to cause an outer wall surrounding a groove of a
shaft to be deform at different angles;
Fig. 5 shows a schematic top view in which a tool
having a beveled edge is used to deform the outer wall of
the shaft adjacent to the groove; and
Fig. 6 shows a schematic view in which a tool
having a V-shaped edge is used to deform the outer wall of
the shaft adjacent to the groove.
DESCRIPTION OF A PROOFREAD EMBODIMENT
Referring to Figs. 1 and 2, a shaft assembly 1 is
shown which can be applied to a camshaft assembly in an
internal combustion engine though it is no. limited to a
camshaft. In the camshaft assembly production process, a
shaft 2 is made of a hollow pipe, onto which an annular
element 3, for example, a cam piece or a journal piece, is
fixed. Such annular piece 3 is made by sistering. At
first, it is compacted in the mold and preliminarily
sistered; then it is assembled onto the shaft 2 before
completion of sistering and the above assembly is finally
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sistered so that the piece 3 is fixed onto the shaft 2
permanently.
On the cylindrical outer wall 4 of the shaft 2 there
is formed a groove 5 with a triangular cross section which
extends axially parallel to the axis of the shaft 2. The
annular element 3 has a hole 6 through which the shaft 2 is
inserted. Between the outer wall 4 of the shaft 2 and the
inner surface of the hole 6 of the annular element 3 there
is a certain clearance for loose fitting ox the two elements
2 and 3. Further, on the inner surface of the hole 6 of
the annular element 3 there is formed an axially extending
projection 7 integral with the element 3 over the whole
length thereof, a cross section of which projection sub-
staunchly corresponds to that of the groove 5. The
groove 5 and projection 7 are formed with such a tolerance
that they can fit loosely when the shaft 2 is inserted into
the hole 6 of the annular element 3 since it is not nieces-
spry that they fit tightly as in the conventional case.
The shaft 2 is inserted into the hole 6 of the annular
element 3 while engaging the projection 7 with the groove 5,
thereby preventing a relative rotating motion between the
annular element 3 and the shaft 2. After determining the
axial position of the annular element 3 with respect to the
shaft 2, the two elements 2 and 3 are held by a suitable
holding tool (not shown). In this state, the outer wall 4
adjacent to the groove S is deformed at two positions
represented by the numeral 8 in Fig. 1, these two positions
8 being located near the terminating ends of the axially
extending projection 7.
Figure 3 shows a camshaft assembly 1 in which the
above-described deformation is caused by a tool 9 which
presses the outer wall 4 of the shaft 2 in a direction
perpendic1l1ar.~to--.the axially-extending groove Asian by
the arrow. The initial shape (shown by the broken line) of
the outer wall 4 surrounding the groove 5 is deformed so
that said outer wall protrudes into the groove 4, as shown
by the numeral 4', and protrudes toward the end of the
axially extending projection 7 at both sides of the annular
element 3 so that the relative axial movement of the element
3 and the shaft 2 is obstructed, that is, the element 3 is
fixed onto the shaft 2. Then the elements of the camshaft
assembly l are permanently joined to each other by means of
a suitable process such as final sistering, brazing, or any
other operation.
On effecting such deformation of the outer jowl of
the shaft 2, the tool 9 presses the outer wall 4 at an
angle with respect the normal line at the groove center.
If the angle is large, as shown in Fig. pa, the force F
may be small, but a part of the wall may be removed by
shearing. If the angle is small, as shown in Fig. 4b, a
great force F is needed to deform the outer wall, and the
tool life is decreased. The present invention proposes a
tool which is used in the above-described operation. One
example of the tool 9 is shown in Fig. 5, in which the
tool I has a beveled edge 10. with the aid of this
tool 9', as shown in Fig. 5, deformation is effected by
applying a small force F without shearing of the wall.
In Fig. 6, the tool 9" has a V-shaped edge, by which
the outer wall 4 is deformed to protrude into the groove 5
on both sides of the groove 5.
In the illustrated embodiments, cross sections of thy
groove 5 and the projection 7 are triangular cross sections
corresponding to each other. However, they can be cross
sections of various shapes which enable the projection and
the groove to engage with each other so as to prevent a
relative rotating motion.
