Handle lever steering device of three-wheel and four-wheel automotive vehicles

A handle lever steering device including a handle lever and a pair of knuckle arms pivotally supported by a frame and constituting the Ackermann mechanism has a rod end secured to a rotary shaft for supporting the handle lever and having a first support shaft and a second support shaft. The first support shaft is connected to a support shaft connected to an arm of one of the left and right knuckle arms, and the second support shaft is connected to a support shaft connected to an arm of the other knuckle arm. The first and second support shafts and the rotary shaft for supporting the handle lever are located on an imaginary straight line. The ratio of the distance Y.sub.l between the center of the rotary shaft for supporting the handle lever and the center of the first support shaft to the distance X.sub.l between the center of the support shaft connected to the arm of one knuckle arm connected to the first support shaft and the center of a rotary shaft for supporting the one knuckle arm is substantially equal to the ratio of the distance Y.sub.r between the center of the rotary shaft for supporting the handle lever and the center of the second support shaft to the distance X.sub.r between the center of the support shaft connected to the arm of the other knuckle arm connected to the second support shaft and the center of a rotary shaft for supporting the other knuckle arm.

FIELD OF THE INVENTION 
This invention relates to a handle lever steering device suitable for use 
with a three-wheel automotive vehicle and a four-wheel automotive vehicle 
having left and right front wheels.

DESCRIPTION OF THE PRIOR ART 
FIG. 1 shows one type of handle lever steering device of the prior art 
suitable for use with a three-wheel automotive vehicle and a four-wheel 
automotive vehicle. A handle lever 11 is pivotally supported by a rotary 
shaft 12 of a frame, not shown, which has secured thereto a vertex 13a of 
a rod end 13 in the form of a triangle having a first support shaft 14a 
and a second support shaft 14b located symmetrically at a left lower 
corner 13b and a right lower corner 13c, respectively. Meanwhile, disposed 
leftwardly and rightwardly of the rotary shaft 12 are rotary shafts 15a 
and 16a for supporting knuckle arms 15 and 16, respectively, which are 
rotatably supported by the frame, not shown. The left and right knuckle 
arms 15 and 16 include a left arm 15b and a right arm 16b which have a 
support shaft 17a and a support shaft 17b, respectively. The support 
shafts 17a and 17b are connected to the first support shaft 14a and the 
second support shaft 14b of the rod end 13 of the triangular shape through 
tie rods 18 and 19, respectively, while axles 15c and 16c are connected to 
outer sides of the left arm 15b and right arm 16b for supporting wheels 
20a and 20b, respectively. The parts described hereinabove constitute the 
Ackermann machanism. 
In this type of steering device, when the angle of pivotal movement of the 
handle lever 11 reaches the uppermost limit, a great difference is 
produced in the angle of pivotal movement of the left and right knuckle 
arms 15 and 16. For example, when the handle lever 11 is turned to the 
right to increase the angle of pivotal movement .theta..sub.6 of the 
handle lever 11 from 6.degree. to about 42.degree., the angle of pivotal 
movement .theta..sub.l of the left knuckle arm 15 is about 23.degree. but 
the angle of pivotal movement .theta.r of the right knuckle 16 is about 
36.degree.. This phenomenon gives rise to the problem that, since this 
difference represents the difference in the angle of revolution of the 
left and right wheels, not shown, it is impossible to swerve the vehicle 
body stably when the handle lever 11 is turned greatly. The same 
phenomenon occurs when the handle lever 11 is turned greatly to the left. 
SUMMARY OF THE INVENTION 
This invention has been developed for the purpose of obviating the 
aforesaid problem of the prior art. Accordingly, the invention has as its 
object the provision of a handle lever steering device of three-wheel and 
four-wheel automotive vehicles having improved maneuverability in steering 
a handle lever capable of preventing the difference in the pivotal angle 
between the left and right knuckle arms from becoming too great even if 
the handle lever is turned through a great pivotal angle. 
According to the invention, there is provided a handle lever steering 
device of three-wheel and four-wheel automotive vehicles comprising a 
handle lever supported by a rotary shaft connected to a frame, a left 
knuckle arm supported by a rotary shaft connected to the frame and 
disposed on the left side of said rotary shaft for supporting the handle 
lever and a right knuckle arm supported by a rotary shaft connected to the 
frame and disposed on the right side of said rotary shaft for supporting 
the handle lever, the aforesaid parts constituting the Ackermann 
mechanism, a support shaft connected to a left arm of said left knuckle 
arm and another support shaft connected to a right arm of said right 
knuckle arm, a rod end connected to said rotary shaft for supporting the 
handle lever and having a first support shaft and a second support shaft 
connected thereto, and a tie rod connecting the support shaft connected to 
said left arm to the first support shaft of the rod end and another tie 
rod connecting the support shaft connected to said right arm to the second 
support shaft of the rod end, wherein the improvement resides in that said 
first support shaft and said second support shaft of said rod end are 
located on an imaginary straight line extending through the center of said 
rotary shaft for supporting the handle lever in a front-to-rear direction, 
and the ratio of the distance Y.sub.l between the center of the rotary 
shaft for supporting the handle lever and the center of the first support 
shaft of the rod end to the distance X.sub.l between the center of the 
rotary shaft for supporting the left knuckle arm and the center of the 
support shaft connected to the left arm is substantially equal to the 
ratio of the distance Y.sub. r between the center of the rotary shaft for 
supporting the handle lever and the center of the second support shaft of 
the rod end to the distance X.sub.r between the center of the rotary shaft 
for supporting the right knuckle arm and the center of the support shaft 
connected to the right arm. 
By virtue of the aforesaid constituent features of the invention that the 
first support shaft and second support shaft of the rod end are located on 
the imaginary straight line extending through center of the rotary shaft 
for supporting the handle lever and that the ratio Y.sub.l /X.sub.l is 
substantially equal to the ratio Y.sub.r /X.sub.r, the angle of pivotal 
movement of the left and right knuckle arms can be kept in an optimum 
range even if the handle lever is turned rightwardly or leftwardly through 
an angle of a maximum value. This is conducive to stable steering of the 
handle lever when the vehicle body is swerved. Thus, the handle lever 
steering device according to the invention is suitable for use with 
threewheel and four-wheel automotive vehicles for travelling off-road (in 
the rough country). 
DESCRIPTION OF THE PREFERRED EMBODIMENT 
A preferred embodiment of the invention will now be described by referring 
to the accompanying drawings. 
FIG. 2 shows a handle lever steering device according to the invention 
suitable for use with three-wheel and four-wheel automotive vehicles, 
comprising a handle lever 1 supported for pivotal movement by a rotary 
shaft 2 supported by a frame, not shown, and a rod end 3 of an elliptic 
form secured to the rotary shaft 2. The rod end 3 has connected thereto a 
first support shaft 4a and a second support shaft 4b located on an 
imaginary straight line A extending in a front-to-rear direction through 
the center of the rotary shaft 2, the first support shaft 4a being 
disposed in a position remote from the center of the rotary shaft 2 and 
the second support shaft 4b being disposed in a position near the center 
of the rotary shaft 2. Left and right knuckle arms 5 and 6 are pivotally 
supported by rotary shafts 5a and 6a, respectively, which are supported by 
the frame, not shown, and the left and right knuckle arms 5 and 6 include 
a left arm 5b and a right arm 6b having a support shaft 7a and a support 
shaft 7b, respectively. Axles 5c and 6c are located on the outer sides of 
the left arm 5b and right arm 6b, respectively. A left tie rod 8a connects 
the support shaft 7a of the left arm 5b to the first support shaft 4a of 
the rod end 3, and a right tie rod 8b connects the support shaft 7b of the 
right arm 6b to the second support shaft 4b of the rod end 3. In the 
handle lever steering device of the aforesaid construction, the parts 
constitute the Ackermann mechanism in which the left arm 5b of the left 
knuckle arm 5 and the right arm 6b of the left knuckle arm are oriented 
toward the center of the axis of rear wheels, not shown, when a vehicle 
body, not shown, is travelling straight-forwardly. The center of the 
rotary shaft 2 supporting the handle lever 1 and the center of the first 
support shaft 4a of the rod end 3 are spaced apart from each other by a 
distance Y.sub.l, and the center of the rotary shaft 5a supporting the 
left knuckle arm 5 and the center of the support shaft 7a of the left arm 
5b are spaced apart from each other by a distance X.sub.l. The center of 
the rotary shaft 2 and the center of the second support shaft 4b of the 
rod end 3 are spaced apart from each other by a distance Y.sub.r, and the 
center of the rotary shaft 6a supporting the right knuckle arm 6 and the 
center of the support shaft 7b of the right arm 6b are spaced apart from 
each other by a distance X.sub.r. The ratio Y.sub.l /Y.sub.l is 
substantially equal to the ratio Y.sub.r /X.sub.r. 
Operation of the handle lever steering device of the aforesaid construction 
will be described by setting the dimensions as follows: 
The distance Y.sub.l =71 (from the center of the rotary shaft 2 supporting 
the handle lever 1 to the center of the first support shaft 4a of the end 
rod 3); 
The distance Y.sub.r =41 (from the center of the rotary shaft 2 to the 
center of the second support shaft 4b of the rod end 3); 
The distance X.sub.l =90 (from the center of the rotary shaft 5a supporting 
the left knuckle arm 5 to the center of the support shaft 7a of the left 
arm 5b); 
The distance X.sub.r =52 (from the center of the rotary shaft 6a supporting 
the right knuckle arm 6 to the center of the support shaft 7b of the right 
arm 6b); and 
The distance Z=280 (from the center of the rotary shaft 2 to the centers of 
the rotary shaft 5a supporting the left knuckle arm 5 and the rotary shaft 
6a supporting the right knuckle arm 6). 
Thus, these values are set as follows: Y.sub.l /X.sub.l .apprxeq.Y.sub.r 
/X.sub.r .apprxeq.0.788. 
In the handle lever steering device of the aforesaid dimensions, when the 
handle lever 1 is turned rightwardly so that the handle lever pivoting 
angle .theta..sub.1 becomes 42.degree. which is near the uppermost limit 
of the pivoting angle of the handle lever 1, the pivoting angle 
.theta..sub.z of the left knuckle arm 5 which is disposed on the outer 
wheel side and the pivoting angle .theta..sub.3 of the right knuckle arm 6 
which is disposed on the inner wheel side are 30.degree. and 34.degree., 
respectively. Thus, the difference (.theta..sub.3 -.theta..sub.2) between 
the right and left knuckle arms 6 and 5 is 4.degree.. This difference 
represents a difference in angle substantially corresponding to the 
difference in radius between an arc drawn by an inner wheel, not shown, of 
the vehicle body, not shown, and an arc drawn by an outer wheel, not 
shown, of the vehicle body. Also, when the handle lever 1 is turned 
leftwardly so that the handle lever pivoting angle .theta..sub.1 becomes 
42.degree., the pivoting angle .theta..sub.4 of the right knuckle arm 6 
which is disposed on the outer wheel side and the pivoting angle 
.theta..sub.5 of the left knuckle arm 5 which is disposed on the inner 
wheel side are 30.degree. and 34.degree., respectively, so that the 
difference in the pivoting angle between the left and right knuckle arms 5 
and 6 (.theta..sub.5 -.theta..sub.4) is 4.degree.. 
It will be seen that when the handle lever 1 is turned rightwardly and 
leftwardly through a pivoting angle which is near the upper limit of the 
range of handle lever pivoting angles, no great difference is produced 
between the left and right knuckle arms 5 and 6 in pivoting angle. This is 
achieved by the constituent features of the invention that the first 
support shaft 4a and second support shaft 4b of the rod end 3 are located 
on the imaginary straight line A extending through the center of the 
rotary shaft 2 for supporting the handle lever 1 in a front-to-rear 
direction, and that the ratio Y.sub.l /X.sub.l is substantially equal to 
the ratio Y.sub.r /X.sub.r.