TECHNICAL FIELD
[0001] The present subject matter described herein in general relates to a suspension assembly for a vehicle and in particular relates to a telescopic front fork assembly for a two-wheeled vehicle.
BACKGROUND [0002] A telescopic front fork assembly is employed in a two-wheeled vehicle to act as a shock absorbing means or suspension means, and to facilitate effective braking and handling of the vehicle. Shock absorbers are necessary to keep a rider isolated from the road jerks and vibrations, thereby making the ride comfortable. In addition, effective braking and handling of the vehicle is important for safety reasons. Typically, the telescopic front fork assembly connects the front wheel of the two-wheeled vehicle with the handlebar and in this way shares the load of the vehicle. [0003] The telescopic front fork assembly includes two parallel placed fork tubes, each of which has an identical construction. The telescopic front fork assembly including two fork tubes with non-identical construction is also possible. These tubes, in particular, dampen the vibrations felt by a rider. The telescopic front fork assembly facilitates upward and downward displacements of the front wheel to absorb jerks and vibrations caused due to a rough and uneven road while the vehicle is in motion. In addition, the telescopic front fork assembly ensures a firm ground contact of the front wheel for belter control and steerabilily. However, the front forks may include a brake lug disposed in. any one fork of the front forks.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] The above and other features, aspects and advantages of the subject matter will be better understood with regard to the following description, appended claims, and accompanying drawings, where:

[0005] Fig. 1 illustrates a right side view of a saddle-ride type vehicle, in
accordance with an embodiment of present subject matter.
[0006] Fig. 2 illustrates a sectional view of one of the forks of a pair of forks of a
typical front suspension assembly.
[0007] FIG. 3 depicts a detailed view of a sectional view of one of the forks of a
typical front suspension assembly.
[0008] Fig. 4 illustrates a comparative study of the graphical representation of
damping response of the suspension assembly.
[0009] Fig. 5a illustrates a detailed view of an end portion of the inner tube
comprising various parts there within.
[00010] Fig. 5b illustrates an exploded view of the check-valve assembly.
[00011] Fig. 6(a), 6(b), 6(c), and 6(d) illustrate a top view of the restrictor member
according to different embodiments of the present invention.
DETAILED DESCRIPTION [00012] Typically, the suspension assembly for a two-wheeled motorcycle comprises of an outer lube, an inner tube slidably connected to the outer tube, a piston including a piston head and a piston rod disposed within the inner lube. The piston facilitates the flow of damping fluid across during an extension stroke and a compression stroke of the suspension assembly. The inner tube includes an extension chamber and a compression chamber. The damping fluid flows from the extension chamber to the compression chamber during the extension stroke of the suspension assembly and the damping fluid flows from the compression chamber to the extension chamber during the compression stroke of the suspension assembly. The suspension assembly further includes an elastic member disposed inside the inner tube and the elastic member is capable of undergoing compression and extension during the compression stroke and the extension stroke respectively. [00013] Typically, damping in a pair of front forks in the front suspension assembly during the extension stroke and the compression stroke is achieved by optimally

controlling (he flow of damping fluid inlo and through the piston orifices in the piston. However, the required damping cannot be achieved after an extent, that is, after a limited resistance provided to the flow of damping fluid, further damping cannot be achieved by further optimally controlling the flow of damping fluid inside the suspension assembly.
[00014] Owing to vehicle turning demand, the damping in the extension stroke of the pair of front forks is generally higher than damping in the compression stroke. To meet the demand of high extension damping, an additional pressure for flow of damping fluid is built up by using a guide spring, a check valve mechanism, and the like. This additional pressure is attributed as a cause for sudden loss of damping at high operating speeds, known as 'damping lag'.
[00015] Further, due to the phenomenon of 'damping lag', the pair of front forks of the suspension assembly tends to emanate hissing noise. The emanated hissing noise is audible to the users of the vehicle and the user might perceive the hissing noise as some irregularity in the normal working condition of the vehicle, the user might be, -put to discomfort and makes the vehicle to be undesirable.
[00016] The typical construction of a front suspension assembly including a pair of front forks are such that they have to achieve a soft ride to provide good ride comfort and nimble handling. The pair of front forks has to possess enough resistance force to be offered to the flow of damping fluid there within. Else, the pair of front forks is subjected to abrupt compression on sharp and large undulations on the road surface. Optimal compression damping and extension damping as desired cannot be achieved if enough resistance as desired is not been able to provide to the pair of front forks. [00017] The failure to achieve optimum compression damping and extension damping in response to sharp inputs from the ground in the pair of front forks, results in poor dampened motion and results in ineffective handling and very poor ride comfort, which is not desirable by the user.

[00018] Further, it is also known in the art wherein in order to achieve good riding comfort, the size and number of extension damping orifice and compression damping orifice on the piston is optimized to achieve the right pressure balance and adequate dampening effect for the elastic member. Further, since the damping occurring during the extension stroke is higher as compared to the damping occurring during the compression stroke, the area available for flow of the damping fluid through the extension damping orifice is less. The resistance offered to the flow of damping fluid is high since the area for flow of damping fluid is less. Though a more resistance to the flow of damping fluid is offered, it also attributes to other side effects like lag in damping and poor reliability. Further, in order to achieve smooth dampening, sharp edges on the extension damping orifice and the compression damping orifice is avoided and instead are provided with sloping edges, like, chamfer. But, designing and manufacturing of chamfer demands high precision control and has high cost impact. Further, with usage, the damping fluid often loses its viscosity and is contaminated with wear and tear of particles from sliding movement of various parts inside the front fork assembly. These particles occurred due to wear and tear that is now freely movable get trapped in the orifices and leads to poor durability of the front fork assembly. Therefore, there is a need to provide an improved front fork assembly overcoming the above explained drawbacks.
[00019] Therefore, according to an embodiment of the present invention, the flow of damping fluid is further optimally controlled to increase the amount of damping provided by the suspension assembly during the extension stroke and the compression stroke.
[00020] According to an embodiment of the present invention, an end portion of the inner tube includes a check valve and a spacer member. The check valve allows the flow of damping fluid there within only during the extension stroke. In order to optimally control the flow of damping fluid into the piston, at least one restrictor

member is sandwiched between an upper surface of the spacer member and a lower ' surface of Ihe spacer member.
[00021] According to an embodiment of the present invention, the at least one restrictor member includes one or more damping orifices disposed on any one of an outer diametrical surface, an inner diametrical surface and, between the inner diametrical surface and the outer diametrical surface. The one or more damping orifices optimally control the flow of the damping fluid between different chambers inside the front suspension assembly. The at least one restrictor member, in other words, creates an additional path for the flow of damping fluid during extension damping mechanism as well as during compression damping mechanism of the front suspension assembly.
[00022] Therefore, according to an embodiinent of the present invention, an additionaJ path of damping fluid flow is created during the extension stroke and during the compression stroke of the front fork. The additional path of damping fluid flow is achieved by creating additional one or more damping orifices between the spacer and the check valve surface. The additional one or more damping orifices are created through the at least one restrictor member of certain thickness with one or more damping orifices to allow passage of damping fluid.
[00023] The one or more damping orifices is configured to allow the damping fluid to flow from a high pressure region to a low pressure region during the compression damping stroke and the extension damping stroke. Therefore, the additional flow path created now enables the flow of damping fluid between the extension chamber and the compression chamber of the pair of front forks.
[00024] Therefore,-the damping control of the pair of front forks is enabled by altering the extent of area of the flow path of the damping fluid. [00025] According to an embodiment of the present invention, the flow paths through the one or more damping orifices are in different forms depending upon the positioning of the one or more damping orifices on the at least one restrictor member.

The one or more damping orifices is disposed in any of the inner diametrical surface, an outer diametrical surface and in between the inner diametrical surface and the outer diametrical surface of the at least one restrictor member. [00026] According to another embodiment of the present invention, since, additional path for the flow of the damping fluid is created, the extension damping orifice on the outer diametrical surface of the piston can be eliminated. Therefore, the machining cost in manufacturing of the piston is saved by eliminating the operation of drilling holes on the piston. This further also helps in ease of manufacturing of the piston. [00027] Therefore, by eliminating the extension dampening hole on the outer diametrical surface of the piston, the accuracy of the damping in terms of product performance is now improved since the damping is controlled by an additional path through the at least one restrictor member.
[00028] According to another embodiment of the present invention, the damping created inside the pair of front forks is sensitive to the accuracy of the netiarea and shape of the one or more damping orifices with or without chamfer. [00029] According'to yet another embodiment of the present invention, the inner tube may include a second check valve disposed below the spacer member. [00030] Thus the synergistic effect of an additional flow path created for providing the controlled flow to the damping fluid from the high pressure chamber to the tow pressure chamber along with the elimination of the extension dampening orifice on the piston provides an improved functionality, that is, improved damping. This further results in smooth riding and provides good ride comfort to the user. [00031] Fig. 1 illustrates a right side view of a saddle-ride type vehicle, in accordance with an embodiment of present subject matter. The figure depicts a front portion F of a vehicle and the rear portion R along the longitudinal direction of the vehicle 100 from right to left. The vehicle 100 has a frame assembly 105, which acts as a skeleton for the vehicle 100. The frame assembly 105 includes a head tube 105A, a main tube (not shown) and may have a down tube (not shown). A swing arm 110 is

swingably connected to a pivotal point of the frame assembly 105. A swing arm HO rotatably supports a rear wheel 115. One or more rear suspension(s) 120 connect the swing arm 110 to the frame assembly 105. A seat assembly 125 is mounted to the frame assembly 105. A fuel tank assembly 130 is disposed in an anterior portion of the seat assembly 125. An engine assembly 135 is mounted in the anterior portion of the frame assembly 105. The engine assembly 135 includes an internal combustion, a kick-start mechanism, a transmission mechanism for transferring the power to the rear wheel 115, an air-fuel supply mechanism for the engine assembly 135 includes a carburetor or the like, and an exhaust mechanism. The vehicle 100 includes a front suspension assembly 145 and a front wheel 150 is rotatably connected to the front suspension assembly 145. The vehicle 100 has various electrical loads including a headlamp 151, a tail lamp 155, and a starter motor (not shown). A front fender 160 covers at least a portion of the front wheel 150. A rear fender 165 covers at least a portion of the rear wheel 115. The frame assembly 105 is covered by plurality of panels 170.
[00032] Fig. 2 illustrates a sectional view of one of the forks of a pair of forks of a typical front suspension assembly. The different parts present in the typical suspension assembly 145 include an outer tube 202, and an inner lube 201 slidably connected to the outer tube 202. The suspension assembly 145 also includes a piston 203 including a piston rod having a piston head at one end along with an elastic member 204. One or more compression damping orifices 209, a compression chamber, an extension chamber, and a fluid reservoir are also provided in the suspension assembly 145 described in accordance with an embodiment of the present subject matter. The inner lube 201 includes an inner tube upper end 201b and a lower end 202a of the outer tube 202 capable of facilitating movemenl of the damping fluid there between. Typically, the suspension assembly 145 works under the two strokes, namely, the compression stroke and the extension stroke. The working of Ihe suspension assembly 145 employing the present invention accounting lo improved

performance of the vehicle 100 can be understood in detail by the following description.
[00033] FIG. 3 depicts a detailed view of a sectional view of one of the forks of a typical front suspension assembly. In one embodiment, the inner tube 201 is slidably inserted into and connected to the outer tube 202. The piston 203 is connected to an end of the outer tube 202. The elastic member 204 is seated above a piston head 203a, and the elastic member 204 is disposed concentrically inside the inner tube 201. The inner tube 201 includes a lower end portion 201a comprising a check-valve assembly 201 aa including a first check valve 206, a second check valve 208, and a spacer member 207 and at least one restriclor member 205 disposed between the first check valve 206 and the second check valve 208. As depicted from the figure, the piston 203 does not include an extension damping orifice. According to an embodiment of (he present invention, the check-valve assembly 201aa is press-fitted into an inner surface of the lower end portion 201a of the inner tube 201. [00034] Fig. 4 illustrates a comparative study of the graphical representation of damping response of the suspension assembly. The graphical representation as shown in the figure is a comparative study of the damping response of the suspension assembly with at least one restriclor member and a conventional suspension assembly without the at least one restriclor member. The curve 302 indicates the damping response of the suspension assembly with the at least one restriclor member. Whereas, the dotted curve 301 indicates the damping response of the suspension assembly without the at least one member.
[00035] Typically the area enclosed by the curve in the graphical representation indicates the damping response of the suspension assembly. Therefore, bigger area enclosed by the curve indicates a good damping response and a smaller area enclosed by the curve indicates a poor damping response of the suspension assembly. The area enclosed by the various points of the curve PQRS indicate the damping response of the suspension assembly. It is inferred from the figure that the curve PQRS is

obtained by the damping response of the suspension assembly incorporating the at least one restrictor member. The curve PQRS encloses a larger area compared to the curve ABCD representing the dotted curve 220. Therefore, the suspension assembly including the at least one restrictor member gives better damping response. [00036] A smooth curve is formed by an area enclosed by a plurality of points P, Q, R, and S. The point 'P' is the beginning of the extension stroke. The highest point 'Q' is obtained in the graph when the front fork is just extended and not fully extended. Jt can be observed from the figure that from point 'P' to point 'Q' a smooth curve is obtained. The smooth curve indicates that the compressed elastic member is not suddenly released during the extension stroke. The front fork employing the present invention prevents the sudden release of the elastic member. Hence, a belter damping response is obtained through the present invention. In addition, the hissing noise emanating out of the pair of front forks is eliminated. A similar smooth curve achieving better damping response is obtained from point 'Q' to point 'R'. [00037] The understanding of the damping response indicated by the curve can be better understood with working of the suspension assembly in different working strokes including compression stroke and extension stroke. Point P is the beginning of the extension stroke of the suspension assembly including the at least one restrictor member. The point 'Q' is the highest point obtained in the graph when the suspension assembly is just extended and not fully extended. According to the present invention, the additional path provided by the restrictor member 205 for the flow of the damping fluid provides enough resistance to the flow of damping fluid even during the extension stroke. Hence, required desired damping is achieved in the extension stroke and the compression stroke of the suspension assembly.
[00038] Further, a sufficient amount of resistance to the damping fluid is available making elastic member release slowly by preventing sudden release of the compressed elastic member from the compression stroke. Therefore, a smooth release of the elastic member is ensured and a corresponding smooth curve is obtained from

point P and point Q. Whereas, referring to the clotted curve 220, during compression stroke, from point A to point B, a smooth curve is not obtained, instead, a sudden fall in the energy dissipation is observed. Therefore, a better damping is not obtained in conventional suspension assembly.
[00039] Furthermore, when the suspension assembly is fully extended, as indicated by a curve from point Q to point R, again a smooth curve is obtained, indicating smooth extension of the suspension assembly. Again from point R to point S, the suspension assembly undergoes compression stroke and the elastic member is compressed, but not fully compressed. Again during the compression stroke, the damping fluid enters into the additional path created by the at least one restrictor member to facilitate effective compression of the suspension assembly in the corresponding compression stroke. Finally, from point S to point P, the suspension assembly is fully compressed and the damping response obtained is lesser than that of the damping response obtained when the suspension assembly is extended as seen ^ from point P to point Q. Even when the suspension assembly is fully compressed, a minimum amount of damping response is observed as depicted by (he point R, S and, P in the graph. Therefore, the suspension assembly employing the proposed invention prevents sudden jerks or sudden shocks from reaching the rider by preventing rapid return of the compressed elastic member during the extension stroke and the compression stroke.
[00040] Fig. 5a illustrates a detailed view of an end portion of the inner tube comprising various parts there within. The figure depicts a detailed view of the check-valve assembly comprising the first check valve 206 disposed above the spacer member 207. At least one restrictor member 205 is disposed in between the first check valve 206 and the spacer member 207. The restrictor member 205 provides an additional controlled and optimized path for the flow of the damping fluid during the extension stroke and during the compression stroke of the front suspension assembly. The restrictor member provides resistance to the flow of the damping fluid. Referring

to Fig. 5b, the reslrictor member 205 includes a one or more damping orifices 205a that enable an additional path for the How of the damping fluid. Fig. 5b is an exploded view of the check-valve assembly.
[00041] According to an embodiment of the present invention, the piston (not shown) does not include the extension damping orifice, therefore, an easy to manufacture piston is obtained. However, the additional path provided by the reslrictor member 205 for the flow of the damping fluid provides enough resistance to the flow of damping fluid even during the extension stroke. Hence, required desired damping is achieved in the extension stroke and the compression stroke of the suspension assembly.
[00042] Fig. 6(a), 6(b), 6(c), and 6(d) illustrate a top view of the reslrictor member according.to different embodiments of the present invention. Fig. 6(a) includes one or more damping orifices 205a disposed on a surface between an outer diametrical surface 205b and an inner diametrical surface 205c. Fig. 6(b) includes portions of the one or more damping orifices 205a disposed on an inner diametrical surface 205c. The portions of one or more damping orifices 205a have sloping edges. The sloping edges of the one or more damping orifices 205a do not include any sharp edges; instead include smooth curving edges, like a chamfer. Fig. 6(c) includes portions of the one or more damping orifices 205a disposed on an inner diametrical surface 205c. The one or more damping orifices 205a have sharp edges. Fig. 6(d) includes portions of one or more damping orifices 205a disposed on an outer diametrical surface 205b. [00043] The present invention is applicable to vehicles powered by other power sources as well, for examples, the vehicles include, electric powered vehicles, hybrid vehicles and the like.
[00044J According to an embodiment of the present invention, the thickness of the reslrictor member varies from 0.01 mm- 5mm.

[00045] According to the damping desired, Ihe net area of the one or more damping
orifices can be altered. The net area of the one or more damping orifices is
approximately in the range of 2.0mm" - 14.5 mm"'
[00046] According to an embodiment of the present invention, the one or more
damping orifices are any one of the shape including square, circular, elliptical and
rectangular.
[00047] According to an embodiment of the present invention, the reslrictor member
is made of sheet metal.
[00048] Although the subject matter has been described with reference to specific
embodiments, this description is not meant to be construed in a limiting, sense.
Various modifications of the disclosed embodiments, as well as alternate
embodiments of the subject matter, will become apparent to persons skilled in the art
upon reference to the description of the subject matter. It is therefore contemplated
that such modifications can be made without departing from the spirit or scope of the
present subject matter as defined.