TWO-WHEELED AUTOMOTIVE VEHICLE FIELD OF THE INVENTION

The present invention relates to a 'two-wheeled automotive vehicle' and more particularly to a two-wheeled automotive vehicle having a single suspension system.

BACKGROUND OF THE INVENTION

Suspension system in a vehicle refers to the system of springs, shock absorbers and linkages that connects a vehicle to its wheels. Suspension systems serve multiple purposes including contributing to the vehicle's road handling and braking. Suspension system also enhances ride quality and keeps the vehicle's occupants comfortable and reasonably well isolated from road noise, bumps, vibrations, etc.

A conventional two-wheeled automotive vehicle comprises a front suspension system and a rear suspension system. Rear suspension system used in the art comprises either one or two rear shock absorbers connected to a rear swing arm, which in turn mounts the rear wheel. The rear swing arm allows the rear wheel to move when it encounters any load and is pivoted to the vehicle frame at its front end. Front suspension in a conventional two-wheeled vehicle consists of a pair of telescopic fork tubes to which the front wheel is mounted.

The fork tubes contain internal spring and shock-absorbing elements, which absorbs loads, vibrations etc on the front wheel. The fork tubes are typically connected to a steering head assembly, which is connected to the steering column, which in turn is connected to the handlebar. The telescopic fork tube suspension used in typical vehicle arrangement has numerous inherent disadvantages. Since the steering function and the suspension function are combined in the same fork tube suspension system, all weight and shock loads on the front wheel is bome by the fork tubes, the associated steering head assembly and the steering column. This results in the steering system having considerably greater weight than would be necessary to steer the vehicle. Moreover, this excess weight is located high on the vehicle and is spaced significantly from the center of gravity and therefore has an adverse effect on weight distribution and performance of the vehicle.

SUMMARY OF THE INVENTION

The telescopic fork arrangement causes the vehicle to have a tendency to nosedive on hard braking especially while negotiating curves. Still further, there is a possibility for uneven displacement of the fork tubes, for example on uneven roads. This causes wobbling leading to vehicle instability. Therefore to obviate defects in the prior art, it would be very convenient to have a two-wheeled automotive vehicle with an alternate suspension system, which provides safer riding conditions and significantly reduces weight and manufacturing costs. Hence, a single suspension system for an entire vehicle is proposed. The proposed vehicle as per the present invention has a frame which comprises of a head tube , a down tube which extends slantingly downward from the head tube and a main tube which extends rearward from the head tube . A handlebar is mounted on the head tube by way of a revolute joint and a front wheel is secured to the head tube through a rigid fork. The down tube has an engine mounting bracket mounted at its rear end. The present invention is characterized by a single suspension system for front wheel and rear wheel, a front swing arm and a double link steering arrangement. The single suspension system further consists of a spring damper arrangement, and a connecting member. The single suspension system has its front end secured to the engine mounting bracket and rear end secured to the main tube. The double link steering arrangement welded to the head tube transfers torque from the handlebar to the front wheel. The double link steering arrangement also insulates the frame and the handlebar from jerks from the front wheel. A front swing arm has its one end connected to the rigid fork by way of a revolving joint, and the other end pivoted to the front end of the single suspension system. A rear swing arm rotatably supports the rear wheel through the rear axle. The other end of the rear swing arm is pivoted to the rear end of the single suspension system. The front swing arm and the rear swing arm are pivoted to the single suspension system in such a manner that the horizontal distance between the pivoting points always remains constant.

BRIEF DESCRIPTION OF THE DRAWINGS:

Figure 1 Shows a typical motorcycle with twin suspension system.

Figure 2 Shows a motorcycle with proposed mono suspension system.

Figure 3 Shows essential elements of the proposed mono suspension system.

Figure 4 Shows the longitudinal and transverse displacement of the wheel centre points during motion of the proposed mono suspension system.

DETAILED DESCRIPTION OF THE INVENTION

A conventional two wheeled automotive vehicle as illustrated in Figure, 1 includes a power unit 41, a front wheel 25, a rear wheel 27, a body frame 19 and a fuel tank 56. Body frame 19 includes a head pipe 12, a main tube 17, a down tube 22, and seat rails 18. The head pipe 12 is provided at the front end of body frame 19 to support a steering shaft 11 disposed within the head pipe 12. The upper and lower ends of the steering shaft 11 are fixed to an upper bracket 13 and a lower bracket 14 respectively. Upper bracket 13 and lower bracket 14 retain front suspensions 16 that supports front wheel 25. The front wheel 25 is connected at the lower end of the front fork 16, and the upper portion of the front wheel 25 is covered by a front fender 54 mounted to the lower portion of the front fork 16. A handlebar 15 is fixed to upper bracket 13 and can rotate to both sides. A head light 36 is arranged on an upper portion of the front fork 16. Down tube 22 is located in front of the power unit 41 and stretches slantingly downward from head pipe 12. A bracket 55 is provided at the lower end of down tube 22 for supporting the power unit 41. Main tube 17 is located above the power unit 41 and stretches rearward from head pipe 12 and connects the rear of the power unit 41. A vertical pipe 28 is joined to the rear end of main tube 17 and stretches downward from the point where the main tube 17 joins the seat rails 18. Seat rails 18 are joined to main tube 17 and stretch rearward to support a seat 57 disposed above seat rails 18. A side stand 58 is arranged towards the lower portion of the power unit 41. Left and right rear arm bracket portions support a rear swing arm 26 to swing vertically, and a rear wheel 27 is connected to rear end of the rear swing arm 26. A rear wheel suspension 34 is arranged between rear swing arms 26. A tail light unit 64 is disposed on the rear cover 61. A pillion footrest 31 is connected to the vertical pipe 28. A grab rail 62 is also provided on the rear portion of the seat rails 18. Rear wheel 27 is arranged below seat and rotates by the driving force of the power unit 41.

As illustrated in Figure 2 and Figure 3, the two-wheeled automotive vehicle 99 as per the present invention has a frame which comprises of a head tube 111, a down tube 109 which extends slantingly downward from the head tube 111 and a main tube 110 which extends rearward from the head tube 111. A handlebar 108 is mounted on the head tube 111 by way of a revolute joint and a front wheel 105 is secured to the head tube 111 through a rigid fork 107. The down tube 109 has an engine mounting bracket 112 mounted at its rear end. The present invention is characterized by a single suspension system 100 for front wheel 105 and rear wheel 106, a front swing arm 101 and a double link steering arrangement 102.

The single suspension system 100 further consists of a spring damper arrangement 100a and a connecting member 100b. The single suspension system 100 has its front end secured to the engine mounting bracket 112 and rear end secured to the main tube 110. The double link steering arrangement 102 welded to the head tube 111 transfers torque from the handlebar 108 to the front wheel 105. The double link steering arrangement 102 also insulates the frame and the handlebar 108 from jerks from the front wheel 105. A front swing arm 101 has its one end connected to the rigid fork 107 by way of a revolving joint 104, and the other end pivoted to the front end of the single suspension system 100. A rear swing arm 103 rotatably supports the rear wheel 106 through the rear axle. The other end of the rear swing arm 103 is pivoted to the rear end of the single suspension system 100. The front swing arm 101 and the rear swing arm 103 are pivoted to the single suspension system 100 in such a manner that the horizontal distance between the pivoting points always remains constant.

By virtue of the above arrangement and as illustrated in Figure 4, any vertical motion of the front wheel 105 and the rear wheel 106 results in angular motion of the front swing arm 101 and rear swing arm 103 respectively which further leads to compression of the single suspension system 100 from its front end and rear end. In Figure 4, dotted lines indicate the position of the wheels and the swing arms when there is no load on the wheels and solid lines represent the position of wheels and swing arms when there is load (bumps on road etc.) on the wheels which further causes vertical motion as mentioned above. Hence the displacements between these two dotted lines represent the displacements 113 and 114 of the centre line of the front wheel and the rear wheel respectively in two cases. In the present invention, the single suspension system 100 is preferably mounted below the power unit and is arranged inclined to the vertical plane of the vehicle. The spring damper arrangement 100a consists of atleast one spring element.

The two-wheeled automotive vehicle as per the present invention thus provides an alternative suspension system and avoids all the aforementioned drawbacks inherent in the telescopic fork tube front suspension arrangement used in conventional two wheeled automotive vehicles. There is much improvement in vehicle stability and very significant reduction in part count and weight of the suspension system, which further leads to lessened manufacturing costs and assembly time.

WE CLAIM:

1. A two-wheeled automotive vehicle 99 comprising of:

a frame which further comprises a head tube 111, a down tube 109 and a main tube 110; an engine mounting bracket 112 mounted on the rear end of the down tube 109;

a handlebar 108 mounted on the head tube 111;

a front wheel 105 secured to the head tube 111 by way of a rigid fork 107;

a double link steering arrangement 102 welded to the head tube 111, the said double link steering arrangement 102 transfers torque from the handlebar 108 to the front wheel 105;

a single suspension system 100 consisting a spring damper arrangement 100a and a connecting member 100b, the said single suspension system 100 having a front end and a rear end such that the front end is secured to the engine mounting bracket 112 and the rear end is secured to the main tube 110;

a front swing arm 101 whose one end is connected to the rigid fork 107 through a revolving joint 104 and other end pivoted to the front end of the single suspension system 100; and
a rear swing arm 103 whose one end is connected to a rear wheel 106 through a rear axle and the other end pivoted to the rear end of the single suspension system 100 wherein vertical motion of the front wheel 105 and the rear wheel 106 is converted to angular motion of the front swing arm 101 and the rear swing arm 103 respectively, which consequently compresses the single suspension arrangement 100 from its front end and rear end.

2. The two-wheeled automotive vehicle as claimed in claim 1 wherein the horizontal distance between the pivoting points of the front swing arm 101 and the rear swing 103 is always constant.

3. The two-wheeled automotive vehicle as claimed in claim 1 wherein the down tube 109 extends slantingly downward from the head tube 111 and the main tube 110 extends rearward from the head tube 111.

4. The two-wheeled automotive vehicle as claimed in claim 1 wherein the single suspension system 100 is preferably mounted below the power unit.

5. The two-wheeled automotive vehicle as claimed in claim 1 wherein the spring damper arrangement comprises of atleast one spring element.

6. The two-wheeled automotive vehicle as claimed in claim 1 wherein the single suspension system 100 is preferably arranged inclined to its vertical plane.

7. The two-wheeled automotive vehicle as hereinabove described in the specification with the accompanying drawings.