SUSPENSION FOR A SADDLE TYPE VEHICLE

FIELD OF THE INVENTION

[0001] The present subject matter is related, in general to a suspension, and in particular, but not exclusively to a rear suspension for a saddle type vehicle.

BACKGROUND OF THE INVENTION

[0002] Conventionally, a saddle type vehicle includes a suspension system connecting a vehicle wheel to a body frame of the vehicle, in order to provide a smoother ride to the occupants of the vehicle. Usually, at least one suspension system (also known as shock absorber) is disposed respectively at a front and a rear portion of the vehicle, and comprises of a spring and a damper which collectively control the vertical movement of the vehicle body frame relative to the wheel. The front and rear suspension systems function jointly to absorb all the road shocks while also bearing the weight of the vehicle and its occupants.

[0003] A typical rear suspension is shown in Figure 1. It includes a spring damper arrangement wherein a spring 401 surrounds a damper 402, both being coaxial. The spring 401 is loaded upon relative movement of the body frame with respect to wheel, while the damper 402 damps the relative movement. Generally, a single helical coil spring is used in the spring damper arrangement to absorb energy from the road input and a damper with a viscous medium inside to dissipate that energy. However a plurality of such springs arranged in series or in parallel with each other may also be used.

[0004] A lot of variations in the aforementioned arrangement are known in terms of number of springs, spring load ratings and the type of damping medium used. A notable variation is the arrangement of a plurality of helical coil springs of similar or dissimilar ratings in series, which are placed coaxially with the damper. Such helical coil springs exhibit a phenomenon called 'buckling' by which either or both springs in series tend to bend or curve on compression loading and the spring coils move out of the axis. The extent of buckling is determined by spring design parameters like coil diameter of spring, length of spring, outer diameter of spring and majorly by the length to depth ratio of the spring.

[0005] Another problem associated with the aforementioned suspension arrangement is the unfavourable interaction between the spring and damper surfaces caused due to buckling of series springs and subsequent friction between the spring and damper surfaces. This undesirable interaction called scouring (or rubbing) occurs, between an outer surface of the damper tube and an inner surface of the spring facing the damper, when the springs move axially while in operation thus creating visible scouring marks on the outer surface of the damper and inner surface of the spring. The scouring marks cause removal of surface coating of the springs and damper, and accelerate their corrosion while producing undesirable and troublesome noise. The phenomenon of scouring also results in the wear and tear of the suspension components thereby diminishing its durability. Additionally scouring causes frictional resistance to motion thus inhibiting the performance of the suspension.

[0006] Consequently, to avoid buckling and scouring, the series arrangement of springs requires the springs to be constrained with respect to each other and avoid any form of undesirable physical contact between the springs and the damper tube. The prior art, as illustrated in Figure 2, further reveals a spring separator 403 used to ensure that the coaxial springs remain in series and at the same time they do not enter into physical contact with the damper tube, either in static or dynamic condition.

[0007] The spring separator 403 is located between the spring 401 and the damper tube 402. The spring separator 403 guides the inner surface of the upper and lower spring coils, respectively above and below the separator. The location of the spring separator 403 in between spring and the damper tube ideally prevents the physical contact between springs' and the damper tube surfaces. But it creates a new problem of its own i.e. the scouring of the spring separator 403 with the damper tube, owing to the reduction in clearance between the damper tube and the spring due to the consumption of space by the spring separator itself. This renders the use of spring separator as an incomplete solution to avoid physical contact between the spring and the damper tube.

[0008] An alternate way of achieving the desired clearance between the spring and the spring separator is to increase the outer diameter of the spring as well as that of spring separator. But it is not an optimal solution to the existing problem as it would affect the packaging and aesthetic appearance of the suspension. Besides, an increase in dimension of any of the components adds to unwanted cost.

[0009] In order to overcome the problem caused by the introduction of spring separator, a spring seat 404 employed between the damper tube 402 and spring separator 403 is revealed in the prior art as shown in Figure 3 but its use further aggravates the issue of lack of clearance. Moreover, any damper, by virtue of its construction and function, is required to dissipate heat. The dissipation of heat occurs through the walls of the damper tube. When the spring seat 404 is employed in the suspension assembly, it sits between the spring and the damper and rests on a spring retainer. The spring seat 404, primarily made of plastic, guides the spring along a considerable length of the damper tube and ends up covering a substantial portion of the outer surface of the damper to avoid scouring. Unfortunately, the spring seat falls within the stroking range of the damper thereby inhibiting the dissipation of heat and hampering the performance of the rear suspension.

[0010] Therefore the use of spring separator and spring seat, as per the prior art, to achieve incomplete solution to the problem of spring unfavourably contacting with the damper tube, resulting in the additional
problem of inadequate heat dissipation, adds to unwanted costs to begin with and then making its way into assembly, storage, service and warranty costs.

[0011] The present invention is directed to overcoming all or any of the problems as set forth above. Hence it is a principal object of the present subject matter to provide a suspension for a rear wheel of a saddle type vehicle including a spring locator cum guide which ensures clearance between the springs and the damper, has minimum parts and is of low cost. It is another object of the present invention to disclose a spring-damper system comprising a means for aligning a spring system along one axis and also locating the springs on its surface. It is yet another object of the present invention to increase the durability of the suspension components by minimizing or preventing scouring between the spring and the damper as well as ensuring heat dissipation from the damper while separating the spring from the damper.

SUMMARY OF THE INVENTION

[0012] To this end, a suspension for a rear wheel of a saddle type vehicle is disclosed comprising a damper; a spring system surrounding the damper and having a plurality of springs coaxially arranged in series, the said spring system receiving the said damper from one of its ends, the said springs having an inner surface facing toward the damper and an outer surface not facing toward the damper; at least one spring locator cum guide disposed between the said springs of the spring system, locating the said springs on its surface, circumferencing the interface of the springs on their outer surface and guiding the outer surface of springs to keep them axially aligned; and a damper cap extended axially and partially along the length of the said damper, the damper cap separating an inner surface of the said springs forming the spring system from an outer surface of the said damper so as to prevent an outer surface of the damper from scouring by the said springs of the spring system. Further, according to an aspect of the present subject matter, the spring locator cum guide has an outer annular surface and an inner surface, the inner surface having a horizontal wall perpendicular to the inner surface and extending radially inwards, thereby forming a flanged portion, so as to maintain a radial clearance with the said damper, the spring locator cum guide disposed between the springs in such a way the said flanged portion is sandwiched between the springs.

[0013] According to an aspect of the present subject matter, a means disposed between at least two springs arranged in series forming a spring system, the said spring system receiving a damper from one of its ends, the said means guiding an outer surface of the said springs to align them along a vertical axis, the said means maintaining a radial clearance of springs arranged in series with the damper in a coaxial and overlapping arrangement of the said springs and the damper is disclosed.

[0014] The foregoing objectives and summary provide only a brief introduction to the present subject matter. To fully appreciate these and other objects of the present subject matter as well as the subject matter itself, all of which will become apparent to those skilled in the art, the ensuing detailed description of the invntion and the claims should be read in conjunction with the accompanying drawings. The summary is not intended to identify essential features of the claimed subject matter nor is it intended for use in determining or limiting the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The above and other features, aspects, and advantages of the present subject matter will be better understood with regard to the following description, appended claims and accompanying drawings where:

Figure 1 shows a typical sectional view of a suspension of a saddle type vehicle according to the prior art.

Figure 2 shows a sectional view of the rear suspension including a spring separator according to prior art.

Figure 3 shows a sectional view of the rear suspension including a spring seat and the spring separator according to prior art.

Figure 4 shows a side view of a saddle type vehicle including a rear suspension, in accordance with an implementation of the present subject matter.

Figure 5 shows a side view of the rear suspension including a spring locator cum guide, in accordance with an implementation of the present subject matter.

Figure 6 shows a sectional view of the rear suspension including the spring locator cum guide.

Figure 7 shows a sectional view of the rear suspension with spring and damper arrangement, in accordance with an implementation of the present subject matter.

Figure 8 shows a side view of the spring locator cum guide according to the present subject matter.

Figure 9 shows a top view of the spring locator cum guide according to the present subject matter.

[0016] In the figures, the same reference numerals are given to members and parts performing the same functions.

DETAILED DESCRIPTION OF THE INVENTION

[0017] The subject matter described herein relates to suspension for a rear wheel of a saddle type vehicle. Various other features and embodiments of the suspension system according to the present invention here will be discernible from the following further description thereof, set out hereunder. In the ensuing exemplary embodiments, the vehicle is a saddle ride type vehicle. However it is contemplated that the concepts of the present invention may be applied to other types of vehicles within the spirit and scope of this invention. For example, the vehicle may be any saddle ride type vehicle that may use a suspension such as a scooter, moped or a motorcycle. It is to be noted that the detailed explanation of the constitution of parts other than the subject matter which constitutes an essential part has been omitted at suitable places.

[0018] As shown in Figure 4, a typical saddle type vehicle M comprises a body frame assembly made up of a number of tubes welded together. The vehicle M has a steerable front wheel 11 and a driven rear wheel 12. The body frame primarily includes a head pipe 1 disposed at a front end of the body frame, a main tube running across the longitudinal axis of the vehicle M and enclosed by several vehicle components, and a down tube 2. A front fork 3 may be connected to the head pipe 1 through any known type of suspension system for the front wheel and rotatably carries the front wheel 11. The head pipe 1 supports a steering shaft (not shown) disposed inside the head pipe 1. The upper and lower ends of the steering shaft are fixed on an upper bracket and the under bracket. The front end of the main tube and an upper end of the down tube 2 are connected to the head pipe 1. The down tube 2 extends obliquely downward in front of an engine 15 from the head pipe 1 whereas the main tube extends rearward from the front end thereof.

[0019] A front fender 4 is provided below the under bracket to avoid the vehicle and its occupants from being splashed with mud. A fuel tank 5 is disposed above the main tube for storing the fuel for propelling the vehicle M. A seat 6 for a driver and a pillion is further provided, with the said seat 6 being placed behind the fuel tank 5 and rearwardly of the main tube.

[0020] The anterior portion of the vehicle placed forward to the fuel tank 5 comprises of a headlamp assembly, the headlamp assembly further comprising a headlamp 8 and a visor 7 placed forward to a handlebar assembly. The handle bar assembly further comprises of a handle bar 9 extending transversely to the vehicle and several control switches for various vehicle operations.

[0021] The said vehicle M is powered by the internal combustion engine 15 disposed below the main tube and supported by the down tube 2. The engine may be liquid-cooled or air-cooled. Drive force output from the engine 15 is transmitted to the rear wheel 12 through a transmission system. The transmission system includes a clutch actuated by a clutch lever placed forwardly to one side of the handle bar 9, a gear box and a chain drive.

[0022] Further, the rear wheel 12 revolves about a sprocket splined shaft (or central axle) 13. The axle 13
is supported at each end by a swing arm 14, the swing arm in turn pivotally connected to the body frame of the vehicle M by a suspension 300. Generally a saddle type vehicle may use any of the two arrangements for rear suspensions, namely dual suspension and mono suspension. However the present vehicle is exemplified through a dual suspension system. In the description, the suspension present only on one side of the rear wheel is described. The other side would incorporate an identical suspension in the dual suspension system. Both suspensions in the suspension system are fixed at their upper ends to the vehicle frame and at their lower ends to the swing arm 14.

[0023] Figure 5 shows a side view of the rear suspension 300. According to an aspect of the present subject matter, the suspension 300 utilizes a spring damper arrangement where a plurality of springs is connected in series thus forming a spring system. The springs may be of different diameters and different load ratings. For the sake of simplicity of description and according to a preferred embodiment of the present invention, the spring system has two springs arranged in series. The said spring system receives a damper 303 from any of its end such that the damper is engulfed on all sides by the spring system. The damper 303 is a cylindrical structure filled with hydraulic oil. A piston is slidably fitted into the damper. A piston rod 304 is fitted at the lower end thereof in the piston and projected at the upper end thereof from the damper 303.

[0024] Further, the suspension 300 is provided with a means for guiding an outer surface of the said springs to align them along a vertical axis, the said means maintaining a radial clearance of springs arranged in series with the damper in a coaxial and overlapping arrangement in the spring damper system. In accordance with one embodiment thereof, the aforementioned means provided with the suspension 300 is a spring locator cum guide 501 substantially circumferencing the said springs at their interface. At least one spring is located above the said spring locator cum guide 501, namely the upper spring 301 whereas at least one spring is located below it, namely the lower spring 302. The structure of the spring locator cum guide 501 is now described according to a preferred embodiment of the present invention.

[0025] Figure 8 shows a side view of the spring locator cum guide according to the present invention. The H-H axis represents a horizontal axis whereas V-V axis represents a vertical axis. The spring locator cum guide 501 is located at the interface of the two springs 301, 302 of the spring system along the V-V axis and a portion of it is sandwiched between them.

[0026] According to an aspect of the present subject matter, the basic shape of the spring locator cum guide 501 is that of an annular tube having an outer surface and an inner surface, the inner surface facing directly towards the spring system. The spring locator cum guide 501 is profiled in such a way that it locates a lower portion of the upper spring 301 and an upper portion of the lower spring 302 respectively on its radial surface along the V-V axis. The outer surface of the said spring locator cum guide prevents the springs from going out of their vertical axis on dynamic loading. It also guides the said springs respectively on their outer surface with sufficient clearance between inner surface of the springs, and damper.

[0027] Figure 9 shows a top view of the spring locator cum guide 501 according to the present invention. A flanged portion 502 originates from the inner surface, at a midsection of the said guide 501, projecting radially inwards towards the damper 303 along the H-H axis. It forms a horizontal wall projecting from the midsection of the inner surface of the spring locator cum guide 501 towards the damper and maintains sufficient clearance from the damper 303. The sectional view of the said spring locator cum guide 501 illustrates that it forms a lateral T shape, the base of the said T being the said flanged portion 502. Further, the flanged portion 502 is wide enough to accommodate the squared and ground ends of the springs in the spring system. It holds up the spring locator cum guide 501 between the springs of the spring system. The lowermost coil of the upper spring 301 and the topmost coil of the lower spring 302 are ensconced on the two surfaces of the said flanged portion 502 inside of the outer surface of the spring locator cum guide 501. Thus the present subject matter ascertains that the outer surface of the end coil of either spring, upper and lower, is radially constrained within the walls of the spring locator cum guide 501.

[0028] It is evident that the spring locator cum guide 501 does not consume the space between the springs of the spring system and the damper tube owing to its location on the outer surface of the springs. It prevents the springs in series from going out of the V-V axis by constraining them within its walls, on dynamic loading of the suspension. This arrangement further ensures that the radial clearance between the springs and the damper is left intact as in a typical suspension because the said spring locator cum guide 501 is present on the outer surface of the springs arranged in series unlike the prior art.

[0029] Further, the spring system in the shock absorber 300 in the present invention may use springs with different diameter, different lengths, different load ratings and different spring coil diameter. In the preferred embodiment of the present invention, the shock absorber uses the upper spring 301 with larger spring diameter and the lower spring 302 with smaller spring diameter. Additionally the use of a small spring in combination with a long spring, where the ratio of free length or assembled lengths of the springs varies from 0.1 to 1, coupled with the spring locator cum guide 501, nullifies the effect of the buckling and also prevents radial movement of the spring locator cum guide 501 towards the damper 303. Thus elimination of the problem of unfavourable physical contact of the spring separator with the damper tube, as found in the prior art, is achieved by the use of the proposed spring locator cum guide 501.

[0030] Furthermore, in an embodiment, the spring locator cum guide 501 can be made as a single component or in two parts which can be cast, machined, fabricated or bonded together. The said spring locator cum guide can be made from any material of ferrous, nonferrous, composite or organic nature including plastic resin.

[0031] The top surface of the damper 303 is provided with a damper cap 305 to isolate the spun area of the damper tube from air and moisture, two measure pre-requisites for initiating corrosion. The damper cap 305 is press fitted at the top surface of the damper tube 303. According to an aspect of the present invention, the damper cap 305 overlaps with the damper tube 303 and is extended along the length of the damper tube 303 such that it prevents physical contact of the spring system with the damper tube 303, and also ensures that the damper tube 303 is exposed at its lower portion to atmospheric air to ensure adequate heat dissipation. The damper cap 305 is illustrated in Figure 7. In an embodiment, an upper spring of a larger diameter is used in the suspension which ensures that the damper cap itself does not rub with the springs. This arrangement forms a barrier between the spring system and the damper tube 303. Further, the damper cap 305 due to its proximity to the damper tube provides strength to the damper thereby resisting any deformation or bending. The extended damper cap 305 may be made of any polymer, elastomer or organic substance and may be bonded or constrained otherwise to the damper tube 303.

[0032] The present subject matter and its equivalent thereof offer many advantages, including those which have been described henceforth. The above suspension arrangement, along with the spring locator cum guide and an extended damper cap, simplifies the method of locating two springs in series with ease and at the same time ensures that sufficient radial clearance between the spring system and the damper tube is maintained with minimum number of parts and low cost. Due to its positioning and profile, the spring locator cum guide does not consume space between the springs of the spring system and the damper tube thus enabling compact packaging. The suspension prevents buckling of the springs in the spring system on compression loading and ensures proper heat dissipation from the damper by way of extended damper cap.

[0033] The present subject matter is thus described. It is to be noted that the inner surface of springs refers to the surface of springs in the spring system facing towards the damper whereas the outer surface of the springs refers to the surface of the springs not facing towards the damper. The description is not intended to be exhaustive nor is it intended to limit the invention to the precise form disclosed. It will be apparent to those skilled in the art that the disclosed embodiments may be modified in light of the above description. The embodiments described are chosen to provide an illustration of principles of the invention and its practical application to enable thereby one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore the forgoing description is to be considered exemplary, rather than limiting, and the true scope of the invention is that described in the appended claims.

We claim:

A suspension for a rear wheel of a saddle type vehicle comprising: a damper;

at least two springs coaxially arranged in series forming a spring system, the said spring system receiving the said damper from one of its ends, the said springs having an inner surface facing toward the damper and an outer surface not facing toward the damper; at least one spring locator cum guide disposed between the said springs of the spring system, locating the said springs on its surface, circumferencing the interface of the springs on their outer surface and guiding the outer surface of springs to keep them axially aligned; and

a damper cap extended axially and partially along the length of the said damper, the damper cap separating an inner surface of the said springs forming the spring system from an outer surface of the said damper so as to prevent an outer surface of the damper from scouring by the said springs of the spring system.

2. The suspension as claimed in claim 1 wherein the said spring locator cum guide has an outer annular surface and an inner surface, the inner surface having a horizontal wall perpendicular to the inner surface and extending radially inwards along a horizontal axis, thereby forming a flanged portion, so as to maintain a radial clearance with the said damper, the spring locator cum guide disposed between the said springs in such a way the said flanged portion is sandwiched between the said springs.

3. The suspension as claimed in claim 1 wherein the said spring locator cum guide is annular in shape and the outer surface of the said spring locator cum guide partially covers the outer surface of some coils of the said springs on each side of the said spring locator cum guide.

4. The suspension as claimed in claim 1 wherein the said springs of the spring system are preferably helical coil springs.

5. The suspension as claimed in any of the preceding claims wherein the said spring locator cum guide may be made of any material including plastic resin.

6. A means disposed between at least two springs arranged in series forming a spring system, the said spring system receiving a damper from one of its ends, the said means guiding an outer surface of the said springs to align them along a vertical axis, the said means maintaining a radial clearance of springs arranged in series with the damper in a coaxial and overlapping arrangement of the said springs and the damper.

7. The said means as claimed in claim 6 where the said means may be made of any material including plastic resin and attached with a saddle type vehicle.


8. A suspension wherein the suspension incorporates the said means as claimed in claim 5 and claim 6.

9. A suspension substantially as herein described and illustrated with reference to the accompanying drawings.