Four-wheel drive vehicle

A four-wheel drive vehicle having straddle-type seating. A power train is located beneath the seat and between the footpegs of the vehicle, the engine employs parallel output shafts located on either side of the crankshaft to drive power transmission means to the front and rear axles. A speed change mechanism is contained within the engine case along with the output shafts and includes a first transmission shaft between the crankshaft and one of the output shafts. The arrangement of the frame is such that the upper portion of the frame is narrower than the lower portion of the frame for appropriate rider comfort and footpeg location. The wheels are located such that the front and rear tracks are substantially the same and diagonals between the wheel centers cross close to the center of gravity of the vehicle. The cushion assemblies of the vehicle are inclined to increase cushion stroke and the steering assembly is arranged with crossing tie bars for maximum steering control with minimum mechanical complexity.

BACKGROUND OF THE INVENTION 
The field of the present invention is four wheel drive vehicles of the type 
wherein the rider straddles the vehicle and more specifically the 
configuration and layout of such vehicles. 
Small cross-country vehicles generally of the type where the rider 
straddles the vehicle advantageously are designed with a substantial 
degree of stability as a means for improving the off-road capability of 
the vehicle. To this end, it is preferable that each of the driven wheels 
be in contact with the ground as much as possible to obtain a stable ride. 
This is especially true in swampy or watery conditions. 
Naturally, the rider may take an active part in establishing stability by 
shifting weight. Footpegs have been provided on many vehicles for allowing 
the rider greater control over the rider's position versus the vehicle's 
center of gravity. To further enhance the vehicle's stability beyond the 
capability of the rider, the location of components and the center of 
gravity should be considered. 
SUMMARY OF THE INVENTION 
The present invention is directed to a four wheel drive vehicle of the type 
wherein the rider straddles the vehicle and employs laterally extending 
footpegs to help control vehicle stability. To enhance stability, the 
front and rear tracks of the vehicle are contemplated as being 
substantially equal with the center of gravity of the vehicle located 
generally at the intersection of diagonals extending from the centers of 
the wheels. By placing the center of gravity at the foregoing location, 
distance from the center of gravity to the wheels is maximized. Through 
the location of the power train generally at the mid-position of the 
vehicle, this result is readily effected. 
Additionally, stability is enhanced by the action of the rider who is 
capable of moving the rider's center of gravity responsive to terrain 
conditions. To aid in this movement, footpegs extend laterally from the 
vehicle. To accommodate the appropriate location of such footpegs, the 
frame may be arranged wherein the lower frame elements are more widely 
spaced than the upper frame elements. This arrangement allows the rider to 
be comfortable astride the vehicle while providing well-supported footpegs 
appropriately placed. 
Thus, it is an object of the present invention to provide an improved 
four-wheel drive vehicle of the type wherein the rider straddles the 
vehicle. Other and further objects and advantages will appear hereinafter.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Turning in detail to the drawings, a four wheel vehicle is illustrated in 
FIG. 1 as including four high flotation tires 10 and 11, a body 12 and a 
frame 14. Positioned centrally on the vehicle is a seat 16 and a fuel tank 
18. The vehicle is shown to have a handlebar-type steering mechanism 20. 
Footpegs 22 extend laterally from either side of the vehicle and are fixed 
to the frame 14. A bumper 24 extends forwardly of the front tires 10. 
The front tires 10 have a track which is substantially equal to the track 
of the rear tires 11. Diagonals extending from the centers of the wheels 
25 associated with each tire 10 and 11 defines a point G located centrally 
on the vehicle as best seen in FIG. 3. Because of the similarity of 
components fore and aft on the vehicle and because of the location of the 
engine centrally on the vehicle, this point G is approximately at the 
center of gravity of the vehicle. 
Looking in greater detail to the frame 14, FIGS. 2, 3 and 4 illustrate the 
frame structure of the first embodiment. A head pipe 26 is located 
forwardly of the main frame structure. The frame structure 14 includes 
main frame pipes 28 of which there are two. Down tubes 30 of which there 
are also two extend downwardly from the head pipe 26 and include rearward 
extensions 32. Center tubes 34 extend downwardly from the main frame pipes 
28 to meet the rearward extensions 32 of the down tubes 30. The 
configuration of the frame is such that the rearward extensions 32 of the 
down tubes 30 are spaced wider than the main frame pipes 28 as can best be 
seen in FIG. 3. Extending rearwardly from the main frame body are seat 
rails 36 supported by rear stays 38. As noted above, the footpegs 22 are 
fixed to the frame 14 at two brackets 40 which are fixed to the rearward 
extensions 32 of the down tubes 30. 
The brackets 40 are preferably adjustable to accommodate the rider. 
However, the brackets 40 remain located laterally adjacent the center of 
gravity of the vehicle. The location of the footpegs as determined by the 
brackets 40 places the weight of the rider when cornering near the center 
of gravity of the vehicle. Thus, shifting of the rider's weight does not 
unbalance the central position of the center of gravity of both rider and 
vehicle which might otherwise excessively unload either the front or rear 
tires. 
Associated with the frame 14 are front and rear suspension systems. A front 
swing arm 42 is pinned to two front brackets 44 located on the down tubes 
30 by means of a front pivot shaft 46 extending between the brackets 44. 
The front swing arm 42 is shown to be symmetrical, extending in two swing 
arm elements with a cross member 43 all of unitary construction. Two 
supporting journals 48 and 50 are arranged at the forward end of the front 
swing arm 42 to receive a drive axle shaft 52 for driving the front wheels 
10. The two swing arm elements are preferably curved to accommodate the 
steering action of the front wheels 10. The bumper 24 is illustrated in 
FIG. 2 as being fixed to the front swing arm 42. 
The rear suspension includes a rear swing arm 54 pivotally pinned to pivot 
brackets 56 by a rear pivot shaft 58. The rear swing arm 54 extends 
rearwardly to a supporting journal 60 which receives a rear drive axle 
shaft 62. Inboard front and rear brakes 64 and 66 include elements fixed 
to the swing arms 42 and 54, respectively, and drive axle shafts 52 and 
62, respectively, employed in a conventional manner. 
The front swing arm 42 is associated with a cushion assembly 68 extending 
from a pivot bracket 70 to the cross member 43. The axis of the cushion 
assembly 68 is conveniently displaced from the center line of the vehicle 
in order to accommodate the steering mechanism and to locate the upper 
bracket 70 at an appropriate location. The cross member 43 is arranged 
such that the lower end of the cushion assembly 68 is specifically located 
outside of the angle defined by the tie rods 84 discussed below. 
A rear cushion assembly 72 is similarly associated with the rear swing arm 
54. The rear cushion assembly 72 is conveniently oriented on the axis of 
the vehicle and extends between a cross member 74 of the frame 14 and a 
cross member 76 of the rear swing arm 54. 
The steering linkage associated with the handlebar steering mechanism 20 
extends through the head pipe 26 including a steering stem 78. The 
steering stem 78 is pivotally associated with a connecting rod 80 to 
transmit rotational position to a steering link 82 pivotally mounted to 
the front swing arm 42. The steering stem 78 and the connecting rod 80 are 
shown to be inclined in opposite directions. The association of the 
connecting rod 80 with the steering link 82 and with the steering stem 78 
are illustrated in greatest detail in FIG. 4 as including universal 
couplings. 
Because the steering link 82 is pivotally mounted to the front swing arm 
42, the steering link 82 moves relative to the rod 80. By placing the 
steering link 82 close to the pivot axis of the front swing arm 42, this 
motion is kept to a minimum. To accommodate the limited motion, the rod 80 
may be arranged in two pieces allowed to slide axially relative to one 
another and splined to prevent relative rotation therebetween. A dust 
cover 87 covers the joint. 
The steering link 82 is pivotally coupled with tie rods 84 which cross and 
extend to steering hubs 86 at the ends of the front axle shaft 52. The 
front ends of the tie rods 84 are associated with the steering hubs 86 at 
the forward end of the steering hubs. This location of the connection 
between the steering hubs 86 and the tie rods 84 provides more control of 
the wheels with less steering movement. There is additionally more freedom 
in layout of the front wheels. The wheels are located and arranged such 
that minimum interference with the air flow to the engine is experienced. 
The orientation of the front cushion assembly 68, as best seen in FIG. 4, 
is designed for a larger cushion stroke. To this end, the attachment of 
the cushion assembly 68 to the cross member 43 is forwardly of the 
brackets 70. With the increase in angle, the cushion stroke is increased. 
This results in more freedom in the cushion mechanism design and adds to 
the capacity of the cushion assembly. Likewise, the rear cushion assembly 
72 is also inclined as can best be seen in FIG. 4. With the rear cushion 
assembly 72, the cross member 74 is located well ahead of cross member 76 
on the vehicle. This results in the inclination of the cushion assembly 
72. 
Located centrally within the frame 14 and supported thereby is an engine 
and power output assembly, generally designated 88. The engine 88 may be 
assembled with the frame 14 by inserting the engine from underneath and 
fixing it to the mounts 89 provided. The engine and power output assembly 
88 generally includes an engine case 90, a cylinder block 92, a head 94 
and a head cover 96. The engine intake system includes an air cleaner 98 
and a carburetor 100. The exhaust system includes exhaust pipes 102, a 
manifold 104, a tail pipe 106 and a muffler 108. The exhaust pipes extend 
around one side of the engine inside of the frame 14 and the tail pipe 106 
is attached to one of the seat rails 36. 
The engine 88 includes the crankcase and transmission case as one 
structural unit. The cylinder block 92 extends from the upper portion of 
the engine case 90. The engine includes a crankshaft 114 which, in the 
embodiment of FIG. 2, extends transversely of the vehicle. Associated with 
the crankshaft 114 is a crankpin 116. A connecting rod extends from the 
crankpin 116 into the cylinder block 92 and is connected by means of a 
wrist pin to a piston in a conventional manner. 
Associated with a first end of the crankshaft 114 is an alternating current 
generator 132. A generator housing 134 extends over the generator 132. 
From the other end of the crankshaft 114, a first reduction gear 142 
drives a second reduction gear 144 which in turn drives a clutch assembly 
146. The clutch assembly 146 may be manually actuated in a conventional 
manner. Surrounding the end of the crankshaft and the clutch assembly 146 
is a clutch cover 148. 
Driven by the clutch assembly 146 when engaged is a first transmission 
shaft 150. The first transmission shaft 150 is associated with a speed 
change transmission 152 which cooperates to provide varying output ratios 
to a second transmission shaft 154. The second transmission shaft 154 also 
is an output shaft. The output shaft 154, the first transmission shaft 150 
and the crankshaft 114 are aligned in parallel in a plane. Conveniently 
for fabrication of the bearing seats, the plane of the shafts is also the 
part line for the upper and lower portions of the engine case 90. 
The output shaft 154 extends outwardly from the engine case 90 to one side 
of the generator cover 134. At this external location, a drive sprocket 
156 engages a drive chain 158 as part of a power transmission means to the 
rear axle shaft 62. Thus, power is directed from the engine through the 
crankshaft 114, the clutch assembly 146, the first transmission shaft 150, 
the speed change transmission 152, the output shaft 154, the drive 
sprocket 156 and the drive chain 158 to the rear wheels. 
To provide power to the front wheels, the output shaft 154 includes a power 
transmission sprocket 160. A driven sprocket 162 located at the opposite 
side of the engine from the power transmission sprocket 160 is coupled 
thereto by means of a power transmission chain 164. An output shaft 166 
extends outwardly from the engine case 90 on the opposite side of the 
engine from the drive sprocket 156. This output shaft 166 may be manually 
coupled by means of an engagement mechanism 168 to a drive sprocket 170. A 
cover 172 surrounds the engagement mechanism 168. The drive sprocket 170 
is located to one side of the clutch cover 148 and extends no further out 
than the clutch cover 148. The drive sprocket provides power to a drive 
chain 174 providing a power transmission means to the front drive axle 
shaft 52. 
The power transmission means including the drive sprockets 156 and 170, the 
drive chains 158 and 174 and driven sprockets 176 and 178 associated with 
the drive axle shafts 62 and 52, respectively, are displaced on the drive 
axle shafts 62 and 52 from the inboard rear brake 66 and inboard front 
brake 64, respectively. By locating the driven sprockets and brakes, there 
is no concentration of power and braking control. The chains may be 
independently covered as well. Also for convenience, the front and rear 
swing arms may be the same shape. 
The embodiment of FIG. 2 may be modified slightly as illustrated in FIG. 6. 
In FIG. 6, the cross member 43 is located in the angle formed by the 
crossing tie rods 84. This location allows the lower end of the cushion 
assembly 68 to be positioned more centrally on the vehicle and located 
forwardly as well. 
Turning next to the embodiment of FIGS. 8 through 10, identical reference 
numerals are employed where identical or equivalent components are 
illustrated. The emobidment of FIG. 8 is chiefly distinguished from that 
of FIG. 2 by the employment of shaft drives, the orientation of the engine 
with the crankshaft extending longitudinally of the vehicle and the 
orientation of the cylinder block relative to the engine case. Features 
having substantial similarity to the foregoing embodiment of FIG. 2 are 
not specifically discussed with reference to the embodiment of FIG. 8. 
Thus, the foregoing discussion is incorporated with reference to this 
second embodiment. 
As stated above, a first distinction over the first embodiment is the 
orientation of the engine and power output assembly 88 with the crankshaft 
114 extending longitudinally of the vehicle. The output shafts 154 and 156 
similarly extend fore and aft parallel to the crankshaft 114. This 
orientation of the engine 88 is preferable for coupling with a power 
transmission means incorporating drive shafts. The output shafts 154 and 
166 remain accessible from opposite sides of the engine. The location of 
the output shafts 154 and 166 allow the engine to be of minimum dimension 
and avoid complication associated with gearing necessary to circumvent the 
clutch assembly. 
The power transmission means deriving power from the output shafts 154 and 
166 include enclosed drive shafts of substantially identical design. The 
drive shafts 200 are contained within housings 202 forming part of the 
swing arms. A gear box 204 is positioned about each axle 52 and 62 and 
includes beveled gearing. At the other end of each drive shaft 200 is a 
universal joint 206 to allow flexure of the drive line. 
The front and rear swing arms include the housings 202 and a spaced member 
208 as can best be seen in FIG. 9. A cross member 210 adds rigidity to the 
system and provides for attachment of the cushion assemblies 68 and 72. 
The swing arms thus formed are pivotally mounted about pivot shafts 212 
and 214. The universal joint 206 associated with each drive shaft 200 is 
located on the axis of the pivot shafts 212 and 214 for optimized 
performance. 
The location of the output shafts 154 and 166 are generally oriented at the 
same level of the pivot shafts 212 and 214. This arrangement along with 
the orientation of the output shafts parallel to the centerline of the 
vehicle reduces the number of gears, universal joints and the like which 
may be necessary to convey power to the axles. Consequently, power output 
loss is minimized. Additionally, greater compactness is obtained. 
Similarly, the location of the entire power system, the air cleaner and 
the exhaust system inside of the frame 14 also enables the overall system 
to be very compact. The location of the starter motor above the engine 
case further aids in that regard. 
As stated above, the cylinder block of the second embodiment is oriented 
relative to the engine case in a manner not described with the first 
embodiment. The cylinder block 92 is shown to be at an angle relative to 
the center line of the engine case 90. The cylinder block 92 extends 
outwardly from the engine case 90 as can best be seen in FIG. 10 and is 
angled or inclined toward the portion of the engine case 90 containing the 
speed change transmission. Normally, engines having an integral crank case 
and transmission case are oriented with the cylinder blocks inclined away 
from the speed change transmission. However, by the present orientation, 
the cylinder block 92, the cylinder head 94 and the head cover 96 do not 
extend laterally beyond the extension case 90. Additionally, the 
carburetor 100 and exhaust pipes 102 similarly do not extend laterally 
beyond the engine case 90. 
Thus, a plurality of embodiments for power train arrangements have been 
illustrated which employ a minimum of space to properly accommodate 
additional features of a vehicle having front and rear wheel drive. While 
embodiments and applications of this invention have been shown and 
described, it would be apparent to those skilled in the art that many more 
modifications are possible without departing from the inventive concepts 
herein. The invention, therefore, is not to be restricted except in the 
spirit of the appended claims.