Rotary shafts – gudgeons – housings – and flexible couplings for ro – Coupling accommodates drive between members having... – Coupling transmits torque via radially spaced ball
Reexamination Certificate
1999-02-19
2001-05-01
Browne, Lynne H. (Department: 3629)
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Coupling accommodates drive between members having...
Coupling transmits torque via radially spaced ball
C464S143000, C464S141000, C464S139000
Reexamination Certificate
active
06224490
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a constant velocity joint which may be mainly used in association with an automobile shaft, and also to a method of making an outer race used in the constant velocity joint.
2. Description of the Prior Art
A constant velocity joint has been well known in the art which comprises an outer race having a spherical inner surface formed with track grooves, an inner race having a spherical outer surface formed with track grooves, a plurality of torque transmitting balls sandwiched accommodated in between the inner race and the outer race, and a cage for retaining the torque transmitting balls. The outer race has an open edge formed with an entry chamfer to provide an outwardly flaring surface so that at the time of inclination of one of the inner and outer races relative to the other, a shaft mounted with the inner race will not collide against the open edge of the outer edge.
In making the outer race for this type of the constant velocity joint, the use of the working process in which a milling or grinding technique is used, tends to take a relatively long time to make, renders it to be difficult to achieve an increase in preciseness and tends to reduce the yield.
For this reason, it has hitherto been suggested in which (
1
) an entry chamfer of the outer race is worked on by the use of a plastic working process and the track grooves are formed by a milling process, and (
2
) the track grooves and the spherical inner surfaces are worked on by the use of the plastic working process and the entry chamfer is finished by the use of a mechanical process.
However, in the case where the track grooves are formed by the use of the milling process as described under item (
1
) above, difficulty has been encountered in that the precision of the track grooves cannot easily be increased and, accordingly, a grinding process is necessary to be performed after the milling process, resulting in increase of the number of manufacturing steps and, also, reduction in yield.
Also, in the case where the entry chamfer is finished by the use of the mechanical process as described under item (
2
) above, difficulty has similarly been encountered in that precision of the entry chamfer cannot easily be increased, accompanied by increase of the number of manufacturing steps and, also, reduction in yield. Since the entry chamfer is an element operable to regulate the maximum angle of inclination of the constant velocity joint, the entry chamfer is required to have a high precision.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been devised with a view to substantially eliminating the above discussed problems and is intended to provide a method of making the constant velocity joint and the outer race used therein, which are effective to increase the precision of the track grooves and the entry chamfer, to reduce the number of the manufacturing steps, to increase the yield and to reduce the manufacturing cost.
Another important object of the present invention is to increase the precision of the spherical inner surface of the outer race, to further reduce the number of the manufacturing steps and to increase the yield.
To accomplish these objects, the present invention provides a constant velocity joint which comprises an outer race having a spherical inner surface formed with track grooves each extending in an axial direction thereof, an inner race having a spherical outer surface formed with track grooves equal in number to the number of the track grooves in the outer race, a plurality of torque transmitting balls sandwiched between the inner race and the outer race and accommodated in part in the track grooves in the inner race and in part in the track grooves in the outer race, and a cage for retaining the torque transmitting balls while being guided by and between the spherical inner surface of the outer race and the spherical outer surface of the inner race. This constant velocity joint of the structure described above is featured in that at least the track grooves in the outer race and an entry chamfer of the outer race are formed by a plastic working process.
According to the present invention, since the track grooves and the entry chamfer of the outer race are finished by the use of the plastic working process, the precision of the track grooves and the entry chamfer can advantageously be increased. Also, formation of the track grooves and the entry chamfer in the outer race requires no post-working process such as a grinding process and, therefore, not only can the number of manufacturing steps be reduced, but the yield can be increased. In addition, the precision of the track grooves and the entry chamfer can also be increased.
In the constant velocity joint of the present invention, the spherical inner surface of the outer race may also be formed by the plastic working process. In this case, not only can the precision of the spherical inner surface be increased, but the number of the manufacturing steps can also be further reduced, accompanied by increase of the yield.
Preferably, each of the track grooves formed on the outer race may have each of opposite sides defined in a deep region thereof, which is formed with an escapement which is recessed radially outwardly from the spherical inner surface. The presence of the escapements in the track grooves is effective to retain a grease with which the track grooves, serving as ball rolling surfaces for the torque transmitting balls, can be lubricated positively and effectively.
The present invention also provides a method of making the outer race for the constant velocity joint of the type referred to above. This outer race making method of the present invention comprises preparing a drawing die and a combination punch which comprises a plurality of split punches arranged in a circular row each punch having a track groove shaping portion defined therein and a ring-shaped chamfer forming die having a chamfer forming portion disposed adjacently in a direction axially of the circular row of the split punches, inserting the combination punch inside a cup-shaped outer race material flaring outwardly towards an open end thereof; drawing an outer diameter of the outer race material by means of a drawing die while track forming portions of the split punches are inserted in track grooves formed in an inner peripheral surface of the outer race material, to thereby press inner surfaces of the track grooves of the outer race material against the track forming portions, and pressing the chamfer forming die against an end face of a peripheral entry edge of the outer race material incident to insertion of the combination punch. The plastic working of the outer race material may be carried out by means of a cold process, a hot process or a heated process.
According to the present invention, using the split punches each having the track groove forming portion, and the combination punch provided with the ring-shaped chamfer forming die, and by forming with this combination punch and the drawing die, the track grooves and the entry chamfer can advantageously be formed in the outer race material all at a time by the plastic working process during a single process step.
In the practice of the outer race making method of the present invention, each of the split punches may have a spherical surface forming portion with the track groove forming portion protruding outwardly from the spherical surface forming portion and, in such case, during a process in which the outer diameter of the outer race material is drawn inwardly by the drawing die and the inner surface of the track grooves of the outer race material is pressed against the track groove forming portions, the inner surface of the outer race material may be pressed against the spherical surface forming portion of each of the split punches.
Thus, using the split punches each having the spherical surface forming portion and the track groove forming portion, in combination with the combination punch provided with the ring-s
Iihara Michio
Takahara Yasushi
Yamaguchi Masami
Browne Lynne H.
Dunwoody Aaron
NTN Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
LandOfFree
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