Arrangement for joining outer ring and shaft of homokinetic joint

There is provided an arrangement for mechanically and reliably joining a shell-type outer ring of a homokinetic joint and its shaft. A circular hole (4) is formed in a press formed end wall of an outer ring (1). A polygonal surface or serrated grooves are formed on the inner periphery of the hole (4). A protrusion (7) provided at one end of a shaft (5) is press-fitted in the hole (4) to join the outer ring and the shaft so that they will not rotate relative to each other. A caulking tool is used to deform protrusion (7) to form caulked portion (14) so that the outer ring (1) is prevented from moving axially relative to shaft (5).

TECHNICAL FIELD 
This invention relates to an arrangement for joining an outer ring of a 
homokinetic joint to its shaft. 
BACKGROUND ART 
Shell type outer ring, which can be formed by pressing, have been gaining 
attention because they are lightweight and can be manufactured 
inexsensively. 
But since a shell-type outer ring is formed from a thin steel plate, it is 
difficult to rigidly join with a shaft. A weak joint between the outer 
ring and the shaft could markedly lower the performance of the homokinetic 
joint. 
Unexamined Japanese Patent Publication 58-8831 proposes to join a 
shell-type outer ring to a shaft by means of bolts or by welding. 
But bolting or welding reqiures a step in addition to forming an outer ring 
by pressing. Since such a completely different manufacturing step must to 
be carried out in a single manufacturing line, workability tends to be 
low. 
Moreover, in the welding method, the strength of the outer ring tends to 
drop at its joint due to the influence of welding heat. Also, in 
situations where welding is not uniform; a high loading torque may break 
the joint portion between the outer ring and the shaft. 
An object of this invention is to provide an arrangement for joining the 
outer ring of a homokinetic joint to its shaft with high reliability, not 
by welding, but by a simple mechanical means. 
According to this invention, there is provided an arrangement for joining 
an outer ring to a shaft of a homokinetic joint. The arrangement is 
comprised of a hole formed in the outer ring to receive the shaft, the 
hole being formed by pressing. The hole, in turn, has a plurality of flat 
surfaces or grooves. One end of the shaft is then press-fitted into the 
hole to join the outer ring to the shaft. 
Preferably, the inner surface of the hole is harder than the engaging 
portion at one end of the shaft. 
Since the outer ring and the shaft are prevented from turning relative to 
each other by the flat surfaces or serrated grooves formed on the inner 
periphery of the hole of the outer ring in which the shaft is 
press-fitted, the outer ring and the shaft can be coupled together with 
high reliability. 
Since the surface of the hole formed in the outer ring is harder than the 
portion of the shaft inserted into the hole, the shaft can be held stably 
in position once it is press-fitted in the hole, with the portion of the 
shaft fitted in the hole deformed so as to conform to the shape of the 
hole.

DETAILED DESCRIPTION OF THE INVENTION 
The embodiments of this invention will now be described with reference to 
the drawings. 
As shown in FIGS. 1 and 2, an outer ring 1 is a cup-shaped member formed by 
pressing a thin-walled steel pipe or a cylindrical material having a 
closed bottom. A plurality of track grooves 2 are formed in the inner 
periphery of the outer ring 1 so that the outer ring has a petal-shaped 
cross-section. A homokinetic joint is assembled by mounting a torque 
transmission member 3 comprising balls, a cage and an inner ring in the 
outer ring 1. The outer ring 1 has a hole 4 formed in the center of its 
end wall la by punching. 
The hole 4 has a polygonal surface 8 as shown in FIG. 2A or a serrated 
surface 10 as shown in FIG. 3A. The surface 8 or 10 is hardened by 
carburizing or induction hardening. 
A shaft 5 has a large-diameter portion 11 at one end and a protrusion 7 
formed at the end of the large-diameter portion 11 and with the 
protression 7 being inserted into the hole 4 of the outer ring 1. Threads 
6 are formed on the outer periphery of the shaft 5 at the other end 
thereof. 
The surface of the protrusion 7 is not hardened. Its diameter is slightly 
larger than that of the hole 4. A seal 12 is fitted in a groove 13 formed 
in a shoulder between the protrusion 7 and the large-diameter portion 11. 
The shaft 5 is joined to the outer ring 1 by press-fitting the protrusion 7 
of the shaft 5 into the hole 4 of the outer ring 1 as shown in FIG. 1A, 
and striking the end of the protrusion 7 protruding into the outer ring 1 
in the axial direction with a caulking tool 9 to form a caulked portion 14 
at the end of the shaft 5, as shown in FIG. 1B. 
By press-fitting and caulking, the polygonal shape of the surface 8 and the 
serration of the surface 10 are transferred to the projection 7, so that 
the outer ring 1 is prevented from rotating. By caulking, the shaft 5 is 
joined to the outer ring 1 without any axial play therebetween. The outer 
ring 1 will rotate together with the shaft 5. Caulking the end of the 
projection 7 has an additional effect of correcting any deformation of the 
end wall la of the outer ring 1 that may occur upon press-fitting the 
shaft 5 into the hole 4. 
FIGS. 4A and 4B show the second embodiment, in which a shaft 5, including a 
threaded portion 6 at one end thereof, is slightly smaller in diameter 
than the hole 4 of the outer ring 1, except that an engaging portion 15 at 
the other end of the shaft 5, is slightly larger in diameter than the hole 
4. The engaging portion 15 is provided with a flange 16 at its extreme end 
that prevents separation of the shaft and the outer ring. The hole 4 of 
the outer ring 1 has a polygonal surface 8 or serrated surface 10 similar 
to those shown in FIGS. 2 and 3 and is subjected to hardening. 
The shaft 5 is inserted into the hole 4 from inside the outer ring 1 as 
shown by the arrow in FIG. 4A, until the engaging portion 15 abuts a die 
17. In this state, the shaft 5 is struck with a caulking tool 9 as shown 
in FIG. 4B to form a caulked portion 18 thereby constituting a flange 
member. The portion of the engaging portion 15 fitted in the hole 4 is 
deformed into the polygonal or serrated shape conforming to the shape of 
the polygonal surface 8 or serrated surface 10. 
Industrial Application 
According to this invention, as fully described above, the outer ring and 
the shaft are mechanically joined together by pressing. Thus, the 
manufacturing steps of press-forming the outer ring and joining the outer 
ring to the shaft can be carried out continuously, so that homokinetic 
joints can be manufactured with high efficiency. 
Since the outer ring and the shaft are prevented from rotating relative to 
each other by the flat surfaces or serrated grooves formed on the inner 
periphery of the hole of the outer ring in which the shaft is 
press-fitted, the outer ring and the shaft can be coupled together with 
high reliability. The homokinetic joint thus formed will operate stably. 
Since the surface of the hole formed in the outer ring is harder than the 
portion of the shaft inserted into the hole, the shaft can be held stably 
in position once it is press-fitted and deformed into the shape of the 
hole. The outer ring and the shaft can thus be strongly joined.