All terrain vehicle with semi-independent rear suspension

• US 5,845,918 A
• Filed: 10/29/1996
• Issued: 12/08/1998
• Est. Priority Date: 10/29/1996
• Status: Expired due to Fees

• Current Assignee: Arctic Cat Incorporated (Textron Inc)
• Original Assignee: Arctic Cat Incorporated (Textron Inc)
• Inventors: Leiphart, Troy, Grinde, James E., Solberg, Ronald
• Primary Examiner(s): Rice, Kenneth R.
• Application Number:
  US08/739,449
• Time in Patent Office: 770 Days
• Field of Search: 280/680, 280/788, 280/124.1, 280/124.103, 180/215
• US Class Current: 280/124.1
• CPC Class Codes: B60G 7/02 Attaching arms to sprung part of vehicle B60G7/006 takes precedence
• CPC Class Codes: B60G 9/00 Resilient suspensions of a rigid axle or axle housing for two or more wheels the axle being a part of a set of tandem axles B60G5/00-B60G5/065; with leaf springs B60G11/02-B60G11/08

Abstract

An all terrain vehicle having its chassis, its front suspension, its rear axle, its rear suspension, and its power transmission shaft interconnected in a manner that allows the rear axle to rotate about both the longitudinal and a transverse axis of the all-terrain vehicle to provide increased flexibility in its rear end so that the vehicle'"'"'s rear tires remain on the ground at least as long as its front tires remain on the ground when traversing relatively even terrain so that the vehicle will not transition from understeer to oversteer.

Claims

1. An all terrain vehicle for operation on varying terrain comprising a chassis, an engine, two front wheels and tires, a front suspension interconnecting the front wheels and tires to the chassis, two rear wheels and tires, a rear axle interconnecting the rear wheels to each other, and semi-independent rear suspension means interconnecting the rear axle to the chassis so that, in travel over relatively even terrain, roll moment loading on the all terrain vehicle will cause a front tire to lose contact with the terrain before any rear tire loses contact with the terrain, thereby maintaining understeer in the all terrain vehicle.

2. An all terrain vehicle for operation on varying terrain comprising a chassis, an engine, two front wheels and tires, a front suspension interconnecting the front wheels and tires to the chassis, two rear wheels and tires, a rear axle interconnecting the rear wheels to each other, and semi-independent rear suspension means interconnecting the rear axle to the chassis so that centrifugal force loading on the all terrain vehicle traveling over relatively even terrain will cause a front tire to lose contact with the terrain before any rear tire loses contact with the terrain, thereby maintaining understeer in the all terrain vehicle.

3. An all terrain vehicle for operation on varying terrain comprising a chassis, an engine, front wheels and tires, a front suspension interconnecting the front wheels and tires to the chassis, two rear wheels and tires, a rear axle interconnecting the rear wheels to each other, and semi-independent rear suspension means interconnecting the rear axle to the chassis so that, if the all terrain vehicle is able to maintain all of its tires on a given terrain when negotiating a curve of given radius at one speed, negotiating said curve at a higher speed will not cause any rear tire of the all terrain vehicle to lose contact with said terrain prior to a front tire losing contact with said terrain, thereby maintaining understeer in the all terrain vehicle.

4. An all terrain vehicle for operation on varying terrain comprising a chassis, an engine, two front wheels and tires, a front suspension interconnecting the front wheels and tires to the chassis, two rear wheels and tires, a rear axle interconnecting the rear wheels to each other, and semi-independent rear suspension means interconnecting the rear axle to the chassis, the semi-independent rear suspension allowing the rear axle to rotate in both roll and pitch modes, so that both rear tires are kept in contact with relatively even terrain whenever the front tires are in contact with relatively even terrain, thereby maintaining understeer in the all terrain vehicle.

5. An all terrain vehicle for operation on varying terrain comprising a chassis, an engine, two front wheels and tires, a front suspension interconnecting the front wheels and tires to the chassis, two rear wheels and tires, a rear axle interconnecting the rear wheels to each other, and a semi-independent rear suspension interconnecting the rear axle to the chassis, the semi-independent rear suspension allowing the rear axle to rotate in both roll and pitch modes, thereby keeping both rear tires in contact with relatively even terrain whenever the front tires are in contact with relatively even terrain, and thereby maintaining understeer in the all terrain vehicle;

in said all terrain vehicle, the chassis has a left side and a right side, left and right being defined as a seated operator would view them;

the rear axle is generally horizontal and comprises a left end, a middle, and a right end, and has at least one rear wheel and one tire at each of its ends;

the left and right rear wheels and tires are spaced from each other at a rear tread width (track);

the engine is located longitudinally between the front wheels and the rear axle, and the engine is connected to the chassis and has a rear power outlet;

the all terrain vehicle has a vertical longitudinal plane passing through its center and passing through the rear axle;

the rear power outlet of the engine is located within ten percent of the rear tread width (track) to either side of the vertical longitudinal plane;

the all terrain vehicle has a horizontal transverse axis which is perpendicular to the vertical longitudinal plane and passes through the rear power outlet of the engine; and

the all terrain vehicle has a semi-independent rear suspension which has more angularity of roll than the front suspension, comprising;

a. a power transmission shaft having a longitudinal centerline which is generally parallel to, and located within ten percent of the rear tread width to either side of, the vertical longitudinal plane and interconnected between the rear power outlet of the engine and the rear axle, said power transmission shaft

(1) connected to the rear power outlet of the engine through a joint with high angular compliance in a manner that (a) permits drive rotation of the power transmission shaft about its longitudinal centerline, (b) permits pitch rotation of the rear axle about the transverse axis of the all terrain vehicle, (c) restricts lateral and vertical movement of the power transmission shaft at said joint, (d) permits roll rotation of the rear axle about the longitudinal centerline of the power transmission shaft, and (e) restricts lateral movement of the rear axle;

(2) connected to the rear axle in a manner that permits transmission of drive torque from the power transmission shaft to the rear axle; and

b. a rear suspension linkage interconnected between the rear axle and the chassis, said rear suspension linkage comprising

(1) one or more first springs and shock absorbers on the left side of the all terrain vehicle, and one or more second springs and shock absorbers on the right side of the all terrain vehicle, each of said springs and shock absorbers having a base end and a rod end,

(a) the first of the ends, either the base end or the rod end, pivotally connected to the chassis at a point on the left side of the center of the chassis for the first springs and shock absorbers and on the right side of the center of the chassis for the second springs and shock absorbers, and

(b) the second of the ends, either the rod end or the base end, oriented substantially perpendicular to the first end connection and pivotally connected to the rear axle at a point between the left end of the rear axle and the connection of the power transmission shaft to the rear axle for the first springs and shock absorbers and between the right end of the rear axle and the connection of the power transmission shaft to the rear axle for the second springs and shock absorbers;

(c) each of the ends being connected to the chassis or to the rear axle in a manner that permits the springs and shock absorbers to maintain their connections as the rear axle rotates in roll about the longitudinal centerline of the power transmission shaft and in pitch about the transverse axis of the all terrain vehicle; and

(d) the first and second springs and shock absorbers being symmetrical to each other about the vertical longitudinal plane of the all terrain vehicle;

(2) one or more left link arms on the left side of the all terrain vehicle and one or more right link arms on the right side of the all terrain vehicle, each of said link arms comprising an axle end and a chassis end,

(a) the axle end of each of the one or more left and right link arms pivotally connected to the rear axle at a point between the left end of the rear axle and the connection of the power transmission shaft to the rear axle for the left link arms and between the right end of the rear axle and the connection of the power transmission shaft to the rear axle for the right link arms;

(b) the chassis end of each of the one or more left and right link arms pivotally connected to the left side of the chassis for the left link arms and the right side of the chassis for the right link arms;

(c) each of the ends connected to the rear axle or the chassis in a manner that permits said link arms to maintain their connections as the rear axle rotates in roll about the longitudinal centerline of the power transmission shaft and in pitch about the transverse axis of the all terrain vehicle;

(d) the one or more left link arms functioning to create an effective left link arm, and the one or more right link arms functioning to create an effective right link arm, of sufficient size, length, and orientation to transmit drive thrust from the rear axle to the chassis;

(e) the relationship between the left and right link arms being symmetrical about the vertical longitudinal plane of the all terrain vehicle.

6. An all terrain vehicle having a chassis, an engine, two front wheels and tires, a front suspension interconnecting the front wheels and tires to the chassis, two rear wheels and tires, a rear axle interconnecting the rear wheels to each other, a semi-independent rear suspension means interconnecting the rear axle to the chassis, the said rear suspension means comprising two or more link arms, two or more springs and shock absorbers, and a power transmission shaft between the rear axle and the engine, said power transmission shaft having a longitudinal axis, so that the rear axle can rotate approximately twenty-two degrees in roll about the longitudinal axis of the power transmission shaft and can rotate approximately twenty-one degrees in pitch about a transverse axis of the ATV, thereby providing continuous and consistent understeer.

7. In an all terrain vehicle having a vertical longitudinal plane through its center and having a transverse axis perpendicular to said vertical longitudinal plane, having a chassis, having front wheels and tires, having a front suspension connecting the front wheels and tires to the chassis, having an engine, having two rear wheels and tires, and having a rear axle connecting the two rear wheels to each other, a semi-independent rear suspension to give improved control and handling of the all terrain vehicle, comprising:

a. a power transmission shaft having a longitudinal centerline, said longitudinal centerline lying within the vertical longitudinal plane, to (1) transmit rotational drive torque to the rear axle and (2) provide lateral stability to the rear axle;

b. a connection between the engine and the power transmission shaft which (1) permits transmission of drive torque from the engine to the power transmission shaft;

(2) permits pitch rotation of the rear axle about the transverse axis of the ATV;

(3) restricts lateral and vertical movement of the power transmission shaft at said connection;

(4) permits roll rotation of the rear axle about the longitudinal centerline of the power transmission shaft; and

(5) restricts lateral movement of the rear axle;

c. a connection between the power transmission shaft and the rear axle which permits transmission of drive torque from the power transmission shaft to the rear axle;

d. one or more springs and shock absorbers interconnected between the rear axle and the chassis in a manner to accommodate pitch and roll rotation of the rear axle; and

e. one or more substantially horizontal link arms (1) interconnected between the rear axle and the chassis in a manner to accommodate the pitch and roll rotation of the rear axle and (2) of a size, length, and orientation to transmit drive force from the rear axle to the chassis while minimizing jacking and lowering effect on the chassis in acceleration and deceleration.

8. An all terrain vehicle for operation on varying terrain, including a chassis, an engine attached to the chassis, two front wheels and tires, a front suspension interconnecting the front wheels and tires to the chassis, two rear wheels and tires, a rear axle interconnecting the rear wheels to each other, a rear axle housing surrounding and connected to the rear axle, a vertical longitudinal plane through its center, and a semi-independent rear suspension interconnecting the rear axle and rear axle housing to the chassis, said semi-independent rear suspension including

(1) a transverse axis forward of the rear wheels and tires and perpendicular to the vertical longitudinal plane,

(2) an effective left link arm on the left rear of the vehicle and outward of the vertical longitudinal plane, pivotally connected to the chassis on the transverse axis, and extending rearwardly and pivotally connected to the rear axle housing,

(3) an effective right link arm on the right rear of the vehicle and outward of the vertical longitudinal plane, pivotally connected to the chassis on the transverse axis, and extending rearwardly and pivotally connected to the rear axle housing,

(4) a power transmission shaft extending rearwardly from said engine to said rear axle and having a longitudinal axis, and shock absorbers pivotally connected to said chassis and said rear axle housing, wherein the improvement comprises:

a. said left and right effective link arms are pivotally connected to said chassis and said axle housing; and

b. said shock absorbers are pivotally connected to said chassis and said axle housing;

to allow said rear axle to rotate about the longitudinal axis of the power transmission shaft, wherein, in travel over relatively even terrain, roll moment loading on the all terrain vehicle will cause a front tire to lose contact with the terrain before any rear tire loses contact with the terrain, thereby maintaining understeer in the all terrain vehicle.

9. The all terrain vehicle of claim 8, wherein

(a) the effective left link arm comprising (1) a first link arm, on the left rear of the vehicle and outward of the vertical longitudinal plane, and (2) a second link arm, on the left rear of the vehicle and inward of said first link arm, and

(b) the effective right link arm comprising (1) a fourth link arm, on the right rear of the vehicle and outward of the vertical longitudinal plane, and (2) a third link arm, on the right rear of the vehicle and inward of said fourth link arm.

10. The all terrain vehicle of claim 8, wherein each of the shock absorbers has a top and a bottom end connection and the top end connection is substantially perpendicular to the bottom end connection.

11. The all terrain vehicle of claim 8, comprising springs interconnected between the chassis and the rear axle.

12. The all terrain vehicle of claim 11, wherein the springs are interconnected with the shock absorbers.