Joint structure for axle housing ball-end

In a joint structure for an axle, the outer race of a constant-velocity joint is formed at the end of an axle shaft disposed inside a hollow spherical portion of a tubular axle, a seal fitted to a knuckle is disposed in such a manner as to cross the axes of a pair of king-pins disposed in a vertical direction, the fitting position of the seal is substantially the largest diameter position of the hollow spherical portion of the tubular axle, the knuckle consists of a knuckle portion supported rotatably by the king-pin on the upper side and a knuckle portion supported rotatably by the king-pin on the lower side, and the seal is clamped between the knuckle portion on the upper side and the knuckle portion on the lower side. Accordingly, the annular seal is slidable substantially to the part of the hollow spherical portion with the swinging movement of the knuckle, which part is the connection of the hollow spherical portion with the end of the tubular axle, and a steering angle can thus be increased.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to a joint structure for an axle, 
and more particularly to a joint structure for an axle in a driving axle 
structure with a steering device. 
2. Description of the Prior Art 
According to a conventional arrangement, a driving axle structure equipped 
with a steering device includes generally a hollow spherical portion 
formed at the end portion of a non-rotatable tubular axle extending in the 
transverse direction of the car, a non-rotatable hollow axle casing 
disposed on the wheel side and a knuckle mounted rotatably on the 
spherical surface of the hollow spherical portion by a pair of king pins 
fitted to the end surface of the axle casing and positioned on the 
diameter substantially in the vertical direction relative to the hollow 
spherical portion and a king pin bearing supporting pivotally each of the 
king pins. A constant-velocity joint is disposed inside the space defined 
by the hollow spherical portion, the axle casing and the knuckle. 
Moreover, the outer race of the constant-velocity joint is coupled to a 
drive shaft disposed rotatably inside the axle casing on the wheel side 
while its inner race is coupled to an axle shaft supported rotatably 
inside the tubular axle on the car body side. In the driving axle 
structure having this conventional arrangement, a dust-tight annular seal 
is mounted to the knuckle in such a manner as to come into sliding contact 
with the spherical surface of the hollow spherical portion and to prevent 
any dust from entering the constant-velocity joint. According to this 
conventional arrangement, there is a limitation to the annular seal in 
that the seal can hardly be disposed ideally to the hollows spherical 
portion of the tubular axle because the tip of the knuckle, or in other 
words, the dust-tight seal, becomes an obstacle. The hollow spherical 
portion in the driving axle structure is a member which bears the load as 
part of the axle. For this reason, the conventional configuration of a 
rotary body housing an axle shaft which is worked by means of a lathe does 
not allow for any reduction in the diameter of the neck i.e. from the 
viewpoints of strength, so that a seal sliding surface necessary for 
satisfactory steering cannot be ensured and the maximum steering angle 
possible is therefore restrained up to about 30.degree.. 
A limitation imposed on the disposition of the constant-velocity joint is 
as follows: The tip of the hollow spherical portion formed at the end of 
the tubular axles butts against or interferes with the spherical surface 
of the outer race of the constant-velocity joint having an increased 
diameter so that the angle of rotation of the drive shaft disposed inside 
the axle casing and hence the angle of rotation of the knuckle relative to 
the hollow spherical portion, that is, the steering angle, is limited to 
approximately 30.degree.. In practice, however, the internal structure of 
the constant-velocity joint can permit the steering angle of up to about 
40.degree., and an improvement is therefore desired in the disposition of 
the annular seal and the constant-velocity joint so as to proportionally 
increase the steering angle. 
For the above-described reason, the prior art discloses an ellipitic-seal 
structure in which a surface of each knuckle on which a seal is mounted is 
inclined with respect to the hollow spherical portion of an associated 
tubular axle. This type of structure is disclosed, for example, in the 
specifications of Japanese Utility Model Publication No. 37386/1984 and 
37387/1984. 
First of all, a diagrammatic description will be made with respect to a 
front-wheel support device for a front drive vehicle described in Japanese 
Utility Model Publication No. 37386/1984. Either an oil seal member or an 
oil seal protection member is so formed as to have an axial length greater 
on the rear side than on the front side in the direction of movement of 
the vehicle when a knuckle housing is mounted. The seal of this prior art 
is disposed around a king-pin for pivoting the knuckle housing and a 
trunnion socket in an inclined manner at a predetermined angle, so that, 
when a vehicle is moved straight, a flat surface including the seal edge 
of either the oil seal member or the oil seal protection member is 
disposed closer to the shaft of the trunnion socket on the front side than 
on the rear side. In this front-wheel support device for a front drive 
vehicle, the seal is formed in a special shape so as to increase the 
steering angle. However, even if the seal is formed in such a special 
shape, it is not necessarily satisfactory in respect of its strength, 
sealing characteristics and durability. In addition, this type of seal is 
difficult to produce and of no practical use, thus leading to various 
problems. 
In the second place, a diagrammatic description will be made with respect 
to an oil seal device for a front-wheel support of a front drive vehicle 
described in the specification of Japanese Utility Model Publication No. 
37387/1984. Referring to an oil seal member in this prior art, a 
rubber-made seal body has an equal width along its entire circumference in 
a natural state, and a circumferential groove of a L-shaped in section is 
formed from a mounting flange of the seal body to an arm portion 
perpendicular to the mounting flange. A reinforced flange member of a 
metal-made cylindrical flange body has a cut surface on the cylindrical 
side, such cut surface being inclined with respect to a flange surface, 
and is adherently engaged with the circumferential groove in a state 
wherein this groove is under an elastic tension. The reinforced flange 
member is also disposed around a king-pin for pivoting the knuckle housing 
and the trunnion socket in an inclined manner at a predetermined angle, so 
that, when a vehicle is moved straight, a flat surface including the edge 
of the annual seal is positioned nearer the trunnion socket on the front 
side than on the rear side. As in the case of the above-described example, 
this oil seal device for the front-wheel support of a front drive vehicle 
needs a seal with a special shape, and thus there is a problem in that the 
seal provided may not necessarily be satisfactory from the viewpoint of 
strength, sealing characteristics and durability, nor with respect to 
considerations regarding the production of the seal. 
Heretofore known drive axles equipped with a steering device include the 
arrangement which is opposite to the conventional arrangement described 
above or in other words, the arrangement wherein the disposition of the 
constant-velocity joint is reversed. This constant-velocity joint is 
disposed inside the space defined by the hollow spherical portion at the 
end of the tubular axle, the axle casing and the knuckle fixed to the axle 
casing. However, the inner race of the constant-velocity joint is coupled 
to the drive shaft disposed rotatably inside the axle casing on the wheel 
side while the outer race of the constant-velocity joint is coupled to the 
axle shaft supported rotatably inside the tubular axle on the car body 
side. This type of joint structure for an axle housing ballend is 
disclosed, for example, in the specification of Japanese Patent Laid-open 
No. 24226/1981. A follower steering shaft of the type disclosed in the 
above-mentioned specification will hereinafter be described with reference 
to FIG. 6. 
Referring to FIG. 6, the follower steering shaft is essentially constituted 
by three components which can be separated from one another: a shank 71 
coupled to a differential unit; a constant-velocity joint 72; and a 
steering shaft 74 for driving a boss or a sun gear (not shown) within a 
planetary unit. The constant-velocity joint 72 includes a spherical 
external coupling member 75 as an outer race mounted on one end of the 
shank 71 and an internal coupling member 77 as an inner race mounted on a 
corresponding end of the steering shaft 74. A bellows 73 hermetically 
seals the inner chamber of the constant-velocity joint 72, the bellows 
being detachably mounted on the external coupling member 75 of the 
constant-velocity joint 72, and a neck 76 of the bellows 73 being 
maintained in airtight contact with the steering shaft 74 for free 
movement along the axis thereof. The bellows 73 has an axial residual 
stress, and is therefore formed strongly enough to be extended to its 
maximum axial length. The constant-velocity joint 72 equipped with the 
bellows 73 can be removed without the need to release it. In such driving 
axles equipped with a steering device, however, bellows 73 as the 
dust-tight seal are interposed between a spherical external joint member 
75 as the outer race of the constant-velocity joint 72 and a drive shaft 
74, though the drive shaft 74 of the constant-velocity joint 72 having a 
reduced diameter is positioned on the wheel side, in order to prevent 
instrusion of dust and the like into the constant-velocity joint 72. 
Therefore, since the tip of the tubular axle 78 butts against or 
interferes with the outer peripheral surface of the bellows 73 having an 
increased diameter, the angle of ratation of the drive shaft disposed 
inside the axle casing and hence the angle of ratation of the knuckle to 
the tubular axle 78, that is, the steering angle, is limited in the same 
way as described above. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a joint structure for 
an axle, which solves the above-described problems and improve the 
structure relating to knuckles, a tubular axle and king-pins, increaseing 
the inflective angle of each joint with respect to the hollow spherical 
portion of the respective tubular axle, that is, the steering angle, and 
yet of ensuring the strength of the axle. 
It is another object of the present invention to provide a joint structure 
for an axle, in which the annular seal mounted on each knuckle is disposed 
to obliquely cross the axis connecting king-pin bearings which rotatably 
support the respective upper and lower king-pins, the position of the 
annular dust-guard seal with respect to a steering angle is set to the 
middle position of the slide surface of the hollow spherical portion of 
the tubular axle, thereby ensuring response to a steering angle needed 
when large wheels are used. 
It is another object of the present invention to provide a joint structure 
for an axle capable of reducing the interference produced between the 
hollow spherical portion at the end of the axle shaft and the tubular axle 
during a steering operation, and yet increasing the steering angle of the 
wheels, thereby reducing the turning radius of a vehicle and improving the 
steerability of the vehicle when making sharp turns. 
It is another object of the present invention to provide a joint structure 
for an axle, in which an annular seal mounting position is set to a 
position corresponding to the substantial largest diameter of the hollow 
spherical portion of the tubular axle, and in which, during assembly, the 
annular seal can be removed from the hollow spherical portion by virtue of 
its own flexibility, and thus assembly is enabled without the need to 
partially cut annular seal rubber or its retainer. 
It is another object of the present invention to provide a joint structure 
for an axle, in which a knuckle is obliquely divided into a knuckle member 
including an upper king-pin bearing hole and a knuckle member including a 
lower king-pin bearing hole, the annular seal being firmly clamped between 
the knuckle member on the upper side and the knuckle member on the lower 
side, and the respective knuckle members being easily dissasembled without 
the need to pull the king-pins out of the tubular axle. 
It is another object of the present invention to provide a joint structure 
for an axle, in which a king-pin seal is disposed around at least one of 
the king-pin bearings. 
It is a further object of the present invention to provide a joint 
structure for an axle, in which, when the annular dust guard seal removes 
dried mud from the spherical portion, physical resistance can be reduced 
because the seal is arranged to obliquely scrape against the mud, and in 
which the annular seal need not be formed into a special shape, and yet 
the annular seal suffers no problems from the viewpoint of strength, 
sealing characteristics and durability, nor with respect to considerations 
regarding the production of the annular seal, the knuckle being capable of 
moving freely on the spherical portion since the annular seal is not 
hindered by the tubular axle. 
It is a still further object of the present invention to provide a joint 
structure for an axle, which is capable of preventing the breakage and 
damage of large or expensive devices or components by utilizing a 
particular small member of a drive shaft connected to a constant-velocity 
joint as a mechanical safety device with respect to torque. 
It is an additional object of the present invention to provide a joint 
structure for an axle, in which each end of the axle shaft disposed in the 
hollow spherical portion of the tubular axle constitutes an outer race of 
a constant-velocity joint.

DETAILED DESCRIPTION OF THE EMBODIMENT 
An embodiment of a driving axle structure with a steering device in 
accordance with the present invention will be described below in detail 
with reference to the accompanying drawings. 
FIG. 1 shows a preferred embodiment of a joint structure for an axle in 
accordance with the present invention. Referring to the illustrated joint 
structure, a hollow spherical portion 1 is formed at the end of a tubular 
axle 9, and an annular seal 3 made of rubber, felt or the like mounted on 
a knuckle 2 is maintained in contact with the hollow spherical portion 1, 
thereby preventing foreign matter from entering the interior of the joint 
structure. This annular seal 3 is disposed to obliquely cross the vertical 
axis connecting king-pin bearings 19 for ratatably supporting upper and 
lower king-pins 4, thereby to keep the annular seal 3 at an ideal 
location. When the knuckle 2 swings about the king-pins 4, the annual seal 
3 may perform its sealing function while it is hermetically sliding over 
the hollow spherical portion 1. 
This constant-velocity joint 12 is disposed inside the space defined by the 
hollow spherical portion 1 at the end of the tubular axle 9, the axle 
casing 20 and the knuckle 2 fixed to the axle casing 20. However, the 
inner race of the constant-velocity joint 12 is coupled to the drive shaft 
25 disposed rotatably inside the axle casing 20 on the wheel 24 side while 
the outer race 11 of the constant-velocity 12 joint is coupled to the axle 
shaft 5 supported rotatably inside the tubular axle 9 on the car body 
side. 
An axle shaft 5 is supported by a bearing 7. An oil seal 8 which is 
radially tightened by a lip is capable of hermetically sealing a rotating 
or reciprocally movable portion, and prevents differential-gear 
lubricating oil from entering the inner chamber of the constant-velocity 
joint. Since the interference produced between the root portion of the 
hollow spherical portion to the tubular axle 9 and the portion of the 
knuckle 2 provides limitations with respect to the length of a portion of 
the knuckle extending from the respective king-pins 4 to the exterior, the 
portion of the shaft connected to the constant-velocity joint 12 which 
portion interfer with the terminal end of the hollow spherical portion 1 
formed at the end of the tubular axle 9 preferably has a structure as thin 
as possible in order to ensure a sufficient area in which the annular seal 
3 can be moved. Since the constant-velocity joint 12 is arranged so as to 
dispose the thinnest portion of the shaft at an interference portion, it 
is effective from the viewpoint of the arrangement structure of the 
constant-velocity joint 12 that the constant-velocity joint 12 is arranged 
in a direction opposite to a normal structure, that is, the outer race 11 
of the constant-velocity joint 12 is mounted on each end of the axle shaft 
5. In addition to this, if the thinnest portion of the shaft of the 
constant-velocity joint 12 is formed in such a manner that it is twisted 
off at the time of application of an excessive power input, it is possible 
effectively to protect other expensive components. 
In addition, in order to effectively utilize the area of the slide surface 
of the hollow spherical portion 1 on which the annular seal 3 is slided, 
it is preferable that the annular seal 3 is located at the middle position 
of the slide surface while a vehicle is moving straight forward. For this 
reason, in order to ideally dispose the annular seal 3 while it has a 
shape easy to produce and a true circle enabling positive performance of 
its function are maintained, it is preferable that the annular seal 3 is 
disposed at an ideal position corresponding to upper and lower substantial 
middle portions by taking notice of the fact that the upper and lower 
portions of the annular seal 3 is not substantially moved while the 
knuckle 2 is swinging. For example, as shown in FIG. 1, the annular seal 3 
may be arranged to obliquely cross the axis connecting the upper and lower 
king-pins 4. 
The structure of the embodiment in which the annular seal 3 is interposed 
between the two-piece knuckle 2 will be described below with reference to 
FIGS. 1, 2A, 2B, 3A and 3B. 
Referring to FIG. 1 showing a structure in which the annular seal 3 is 
secured at the location, the knuckle 2 is constituted by upper and lower 
divisions: knuckle members 2a and 2b. The annular seal 3 is sandwiched 
between the knuckle members 2a and 2b, whereby the annular seal 3 may be 
firmly mounted. 
FIGS. 2A, 2B, 3A and 3B shows the details of the structure in which the 
knuckle 2 is divided into the knuckle member 2a and 2b. 
FIG. 2A is a perspective view of the knuckle member 2a, that is, the 
knuckle member including an upper king-pin hole 13, with FIG. 2B being a 
cross-sectional view of the member 2a shown in FIG. 2A. FIG. 3A is a 
perspective view of the knuckle member 2b, that is, the lower knuckle 
member, with FIG. 3B being a cross-sectional view of the member 2b shown 
in FIG. 3A. The upper king-pin hole 13 in the knuckle member 2a may be 
machined together with a king-pin hole 14 in the knuckle member 2b. An 
cutout step 15 of the knuckle member 2a is engaged with a projection 18 of 
the knuckle member 2b while a projection 17 of the knuckle member 2a is 
engaged with a cutout step 16 of the knuckle member 2b. An cutout step 15 
of the knuckle differs from the height of the projection 18, and thus a 
clearance is formed therebetween for firmly clamping the annular seal 3. 
By mounting the annular seal 3 on the knuckle 2 in this manner, the 
annular seal 3 is disposed obliquely to cross the axis connecting king-pin 
bearings 19 mounted around the king-pins 4. Therefore, since either of the 
upper and lower king-pins 4 is exposed to the outside of the annular seal 
3, a king-pin seal 6 is disposed around the exposed king-pin bearings 19. 
Referring to FIGS. 5A and 5B, description will be made in connection with 
an arrangement wherein the annular seal 3 is inclined with respect to the 
hollow spherical portion 1, that is, a mounting structure in which the 
annular seal 3 is inclined with respect to the hollow spherical portion 1. 
As shown in FIGS. 5A and 5B, the hollow spherical portion 1 is integral 
with the tubular axle 9. 
In FIG. 5B, there is shown the relation between the annular seal 3 fitted 
to the knuckle and the hollow spherical portion 1 formed at the end of the 
tubular axle 9 in the conventional joint structure of the axle. In this 
case, an embodiment in which an angle at which the annular seal 3 is 
mounted is not inclined as in the case of the prior art, that is, the 
predetermined angle .theta. is 0.degree., with the annular seal 3 
corresponding to positions N, O and P. The position N of the annular seal 
3 corresponds to a steering angle of 0.degree., the position O of the 
annular seal 3 corresponding to the maximum steering angle of a wheel on 
the inner side of a curve, that is, a case wherein the maximum steering 
angle of the wheel on the inner side is 34.degree., and the position P of 
the annular seal 3 coresponding to the maximum steering angle of a wheel 
on the outer side of the curve, that is, a case where the maximum steering 
angle of the wheel on the outer side is 27.degree. . If the seal mounting 
angle is 0.degree. in this manner, when the annular seal 3 is mounted, the 
spherical surface of the hollow spherical portion 1 cannot be utilized 
from end to end, that is, it is impossible completely to utilize the 
entire range continuing to a position at which the annular seal 3 comes 
into contact with the tubular axle 9. Accordingly, although there is a 
margin equivalent to a length indicated by symbol L on the hollow 
spherical portion 1, the marging cannot be covered. In other words, the N 
position of the annular seal 3 is up to the O position in terms of a 
steering angle of the wheel on the inner side but generally, there is 
still the allowance of the steering angle capacity of the 
constant-velocity joint. Therefore, the steering angle can be increased by 
inclining the annular seal 3 by a predetermined angle in such a manner as 
to let the annular seal 3 come closer to the P position from the N 
position and to increase the moving distance of the annular seal 3 from 
the N position to the O position. In terms of the steering angle of the 
wheel on the outer side in this case, however, since the N position of the 
annular seal 3 comes closer to the P position, there is no sliding surface 
(corresponding to the upper portion of FIG. 3B) on the spherical surface 
of the hollow spherical portion 1 formed at the end of the tubular axle 9 
and the annular seal 3 protrudes out from the slide surface. Moreover, 
according to the conventional disposition, since the tip of the hollow 
spherical portion 1 butts against the outer race of the constant-velocity 
joint, the slide surface of the annular seal of the hollow spherical 
portion 1 cannot be extended so that the annular seal 3 cannot be brought 
closer to the P position from the N position. Therefore, a structure 
wherein the constant-velocity joint does not interfere even when the slide 
surface for the steering angle of the wheel on the outer side is increased 
has been desired. 
Next, in FIG. 5A, there is shown the relation between the annular seal 3 
and the hollow spherical portion 1 in the joint structure of the axle in 
accordance with the present invention. The annular seal 3 is clamped 
between the knuckle members 2a and 2b of the knuckle 2, the annular seal 3 
being located at positions J, K and M. 
FIG. 5A shows an embodiment in which the mounting angle of the annular seal 
3, that is, the predetermined angle .theta. is, for example, about 
4.degree.. The position J of the annular seal 3 corresponds to a steering 
angle of 0.degree., the position K of the annular seal 3 corresponding to 
the maximum steering angle of the wheel on the inner side, that is, a 
steering angle of 38.degree., and the position M of the annular seal 3 
corresponding to the maximum steering angle of the wheel on the outer 
side, that is, a steering angle of 30.degree.. When the annular seal 3 is 
mounted, if the seal mounting angle is inclined at about 4.degree., the 
slide distance of the annnular seal 3 on the side of the steered wheel on 
the inner side can be enlarged effectively to utilize the whole spherical 
surface of the hollow spherical portion 1. In other words, as shown in 
FIG. 1, the disposition of the constant-velocity joint 12 is reverse to 
the conventional disposition. The outer race of the constant-velocity 
joint 12 is coupled to the axle shaft 5 and since the drive shaft 25 
having a reduced diameter is positioned on the side of the wheel 24, the 
tip of the hollow spherical portion 1 which is formed at the end of the 
tubular axle 5 can extend on the annular seal slide surface (the portion 
corresponding to the upper portion of FIG. 5A) of the hollow spherical 
portion 1 on the steering angle side of the wheel on the outer side 
without interferring with the outer face of the constant-velocity joint 
12, and the slide surface of the annular seal 3 on the steering angle side 
of the wheel on the outer side can be thus secured. Therefore, as 
described above, it is possible to increase the maximum steering angle of 
the wheel on the inner side by inclining the N position of the annular 
seal 3 towards the P position and setting the position of the annular seal 
3 to the J position so as to increase the moving distance of the annular 
seal 3 from the J position to the K position, and at the same time, to 
increase the maximum steering angle of the wheel on the outer side by 
increasing the moving distance of the annular seal 3 from the J position 
to the M position. Moreover, even when the annular seal 3 is slid from the 
J position to the M position, the annular seal 3 does not protrude from 
the slide surface of the hollow spherical portion 1. 
One embodiment of the joint structure for an axle in accordance with the 
present invention is constructed as described above. However, it will be 
readily understood by those skilled in the art that this invention is not 
confined solely to the structure described above in detail. For example, 
the following structure may be applied. 
Another example of the inclined annular seal 3 mounted on the knuckle 2 
will be described below with reference to FIGS. 4A, 4B and 4C. Although 
the knuckle 2 is not divided in the accompanying drawings, it will be 
appreciated that the technical concept on which the knuckle 2 is inclined 
at a predetermined angle can be applied to the two-piece knuckle 2. 
Referring to FIGS. 4A, 4B and 4C respectively showing a first preferred 
embodiment of a joint structure for an axle in accordance with the present 
invention, a knuckle 2 mounted on an axle casing 20 is schematically 
illustrated. FIG. 4A is a top plan view of the knuckle 2, in which a 
mounting surface 21 of the knuckle 2 mounted on the hollow axle casing 20 
is inclined at a predetermined angle .theta., for example, about 4.degree. 
with respect to the axis of an axle, that is, the horizontal axis of the 
hollow axle casing 20. FIG. 4B shows the abutting surface 21 of the 
knuckle 2 which is inclined at the predetermined angle .theta., for 
example, about 4.degree. with respect to the axis of the hollow axle 
casing 20, and therefore is biased a distance l, for example, a distance 
of about 2 mm. FIG. 4C, shows for abutting surface 21 of the knuckle 2 
which is inclined at the predetermined angle .theta.. 
For example, it will be appreciated that it is possible to adopt a 
structure in which the annular seal is disposed on a knuckle per se, 
instead of the arrangement in which the annular seal is clamped between a 
pair of knuckle members of the two-piece knuckle. As an example, the seal 
may be disposed in a groove formed in the inner circumference of the 
knuckle. 
Even in a conventional structure, if the arrangement of the 
constant-velocity joint is reversed such that the front side of the seal 
mounting surface is inclined inwardly of a vehicle with the rear side 
outwardly of the same, the difference between the steering angles of the 
wheels on the inner and outer sides in the Ackerman steering mechanism is 
suitably distributed between the areas of the seal slide surfaces 
corresponding to the respective wheels, thereby increasing the steering 
angle of the wheel on the inner side, so that the turning radius of the 
vehicle can be reduced. 
Referring to a method of inclining the seal mounting surface, the 
inclination of the surface of a knuckle to be worked provides the 
advantage that it is unnecessary to prepare a seal of a special shape. The 
structure of this invention has the potential of achieving the steering 
angles 40.degree., 40.degree. of wheels by disposing the seal in an 
obliquely crossed manner with respect to the axis connecting the 
king-pins. Therefore, where a difference is to be formed between the 
steering angles of the wheels on the inner and outer sides in the Ackerman 
steering mechanism, a caster angle equivalent to half the difference is 
formed, and in addition each terminal end of the follow spherical portion 
of the tubular axle is inclined by half of the angle difference in order 
to prevent the occurence of unwanted interference. By these measures, as 
an example, it is possible to obtain large steering angles such as 
45.degree. and 35.degree.. As a matter of course, although the built-in 
constant-velocity joints need ability responsive to these steering angles, 
constant-velocity joints generally have such ability as a part of their 
own functions.