NL1039939C2 - Motorcycle rear suspension hydraulic link system with controllable shock absorber displacement. - Google Patents

Description

V

-1-

Motorcycle rear suspension hydraulic link system with controllable shock absorber displacement.

Field of the invention 5 The present invention relates to a motorcycle, and more particularly to a rear suspension system for a motorcycle

Background of the invention

Most motorcycles in use today use a swing arm to locate the rear wheel relative to 10 the motorcycle frame. The swing arm is typically attached to the main frame of the motorcycle by a suspension system, this suspension system permits independent vertical movement of the swing arm relative to the main frame. This independent movement allows the rear wheel to respond to height puctuations in the road and variances in terrain. The suspension system also prevents or decreases forces caused by bumps in the road 15 from being transmitted to the main frame and the rider.

Rear suspension systems come in a variety of designs and configurations, they typically include many components such as arms, links, shock absorbers, spring and/or torsion bars. In most designs, a single shock absorber is located forward of the wheel and extends from the area of the swing arm upward to an area under the forward portion of the 20 seat. These single shock absorber designs often make use of a mechanical linkage to connect the shock absorber to the swing arm and control its response to vertical movement of the rear wheel. Such linkage systems can be designed to create any desired ratio between wheel travel and shock absorber travel, and offer the possibility to create a progressive damping rate curve.

25 A major drawback of mechanical linkage is that it is usually very complex and has a large impact on the design of the motorcycle, it uses up a lot of space that otherwise could be used for other purposes. And consequently in practice the damping ratio possibilities will not be unlimited but determined by the available space. The links need very strong attachment points on the frame and swingarm and their positioning is 30 determined by the desired ratio, thus the designer may be forced to place links and attachment points at positions in the design that are undesirable with regard to appearance and or other design requirements.

Another limiting characteristic of mechanical linkage is the interdependence of the ratio and progressiveness. The progressive damping curve is determined by the chosen 35 ratio, both depend on the position of the swivel points and the length of the links. Once the 1 03 9939 -2- links are in place both are fixed, changing the progressiveness will change the ratio and vice versa. Furthermore with the damping rate curve being defined by the geometry of the installed linkage system, changing this curve involves changing links and moving swivel points which naturally can't be done while riding. Especially in racing motorcycles the 5 progressiveness issue is very important, for optimal racing conditions the progressiveness should be adjustable during the race. Each track has different demands, every corner asks for a different approach, but because with mechanical linkage it is impossible to change the design while riding, the damping rate curve will always have to be a compromise that is optimal for the average track. An active system that allows the rider to 10 control the compression of the shock absorber at any time during a race would be an important improvement in racing motorcycles.

Further drawbacks of a mechanical linkage system are that it adds undesirable unsprung weight and reduces accessibility of other items for service and maintenance. Thus even for normal driving conditions that may not ask for a real-time adjustable 15 linkage, a need remains for a more compact, lightweight system which is simple to manufacture and install and breaks the interdependency between ratio and progressiveness.

In terms of lifespan there is a lot to win as well, the mechanical linkage parts suffer a great deal from being loaded under large angles, combined with the lack of protection from dirt 20 and water etc, the lifespan of a linkage system in a off-roader is often no more than a year.

Summary of the invention

It is an object of the invention to provide a motorcycle suspension that solves the 25 above-mentioned disadvantages.

In order to eliminate the above-stated disadvantages of the use of mechanical linkage the present invention provides a hydraulically linked rear suspension system for a motorcycle comprising a shock absorber and a hydraulic link between the shock absorber and the swing arm to replace the mechanical linkage to control the shock absorbers 30 response to vertical movement of the swing arm.

To this end in a first preferred embodiment a hydraulic linkage is integrated in the swing arm and the relationship between the magnitude of compression of the shock absorber and the stroke of the rocking motion of the swing arm will be defined by the ratio of the effective piston areas of the communicating hydraulic cylinders it comprises of.

35 The present design provides several advantages over conventional 1-shock -3- absorber designs using mechanical linkage. The hydraulic linkage can be integrated in the swing arm, and therefore as opposed to a mechanical one doesn't occupy limited space in the upper rear frame area, thereby allowing more freedom in the size and location of air filter boxes, batteries etc.

5 Another advantage is that due to the small dimensions of the linkage system, available space is no longer a limiting factor in suspension design. Any desired ratio between wheel travel and shock absorber travel can easily be achieved by varying the corresponding ratio of piston areas.

A further advantage of using hydraulics to create that desired ratio is that any 10 progressiveness damping curve can be achieved independent of the chosen ratio. The ratio is determined by the ratio of the effective piston areas of the communicating hydraulic cylinders.

In a second preferred embodiment the progressiveness can be brought in at any desired position along the stroke by building a design wherein the effective piston area is 15 increased at that position along the stroke in the cylinder.

In a further preferred embodiment the hydraulic linkage apparatus can be extended to become an real-time adjustable system that controls the compression of the shock absorber at any point during a race by adjusting the amount of fluid that is present in the different chambers of the hydraulic cylinders.

20 Another advantage is that by integrating the hydraulic linkage in the swing arm it is shielded from dirt and water and by designing the system in a way that the shock-absorber is positioned nearly in line with the hydraulic cylinders, the parts won't be loaded under large angles, combined with them being constantly oiled the lifespan of an hydraulic link system can be expected to be significantly longer.

25 A further advantage is that the subject suspension design is simple light weight and has less impact on the design. The mechanical suspension linkage often reduces accessibility of other items for service and maintenance. The present design allows such items to be more accessible.

The above and other configurations, features and advantages of the invention will 30 be, or will become, apparent to one with skill in the art upon examination of the following figures and detailed description. It is intended that all such additional systems, methods, features and advantages be included within this description, be within the scope of the invention, and be protected by the following claims.

The various aspects and features described and shown in the specification can be 35 applied, individually, wherever possible. These individual aspects, in particular the aspects -4- and features described in the attached dependent claims, can be made subject of divisional patent applications.

Brief description of the drawings 5 Three preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which; FIG. 1 is a schematic side view of the first preferred embodiment of a motorcycle in accordance with the present invention.

FIG. 2 is a cross-section, in an enlarged scale, of the swing arm and the 10 suspension system of the motorcycle shown in fig 1 with the position of the rear wheel as under normal driving conditions.

FIG. 3 is an enlarged view of the cross-section of the suspension system showing only the hydraulic link apparatus.

FIG. 4 is an enlarged cross-section of the swing arm and the suspension system 15 similar to FIG. 2 but with the rear wheel raised to illustrate a “load condition” FIG. 5 is an schematic view of one of the hydraulic cylinders from the hydraulic link apparatus of FIG. 3 but in this further preferred embodiment a system to design a progressive damping rate curve is added.

FIG. 6 & FIG. 7 demonstrate how in the third preferred embodiment the hydraulic 20 system can be extended to become an real time adjustable linkage system by creating a means to add and remove fluid from the communicating cylinders.

The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like reference numerals designate corresponding parts throughout the different views.

25

Detailed description of the invention in the described preferred embodiment the hydraulically linked suspension system is embedded in the swing arm of the motorcycle. FIG.1 shows a schematic side view of a motorcycle in accordance with the preferred embodiment of the invention.

30 The swing arm (17) has a forward end thereof pivotally mounted on the main frame (18) by means of a pivot shaft (26) and thus comprises a rear wheel supporting member which is rocked up and down around the pivot shaft (26) to allow the rear wheel (27) to move up and down in following undulations of a road surface.

A shock absorber (20) for damping movement of the rear wheel includes a spring and a 35 pneumatic, hydraulic or hydro-pneumatic damper, and has one end thereof pivotally ! -5- mounted, by means of pin (21) on bracket (19), that is attached to the main frame (18) A link .(23) in the form of a rod extends downwardly parallel to shock absorber (20). In this embodiment link (23) is connected to the shock absorber (20) by means of a pin (22), but it will be appreciated that said link (23) could be directly connected to bracket (19) as well. 5 The other ends of the shock absorber (20) and link (23) are connected to the hydraulic link system that is integrated in the swing arm (17) and therefore not visible in Fig 1.

FIG. 2 is a schematic cross-section of the swing arm and the suspension system, that shows how the other ends of shock absorber (20) and link (23) are connected to the hydraulic link system. The lower end of the shock absorber (20) is connected to piston rod 10 (7), by means of hinge (25) and the lower end of link (23) is connected to piston rod (5) by means of hinge (24).

FIG. 3 is an enlarged view of the cross-section showing only the hydraulic link apparatus of the embodiment considered. Within a housing (1), two cylinder barrels (2) and (3) are provided. Cylinder barrel (2) includes a piston (4) and a connecting piston rod 15 (5), cylinder barrel (3) includes a piston (6) and a connecting piston rod (7).

Barrel (2) is closed on each end by cylinder head (8) and cylinder bottom (9). Cylinder head (8) and cylinder bottom (9) both contain openings allowing the piston rod (5) to move through the cylinders head (8) as well as its bottom (9).

Barrel (3) is closed on each end by cylinder head (10) and cylinder bottom (11). Cylinder 20 head (10) and cylinder bottom (11) both contain openings allowing the piston rod (7) to move through the cylinders head (10) as well as its bottom (11). Naturally fluid sealing means (14) are provided in each of the cylinder heads and bottoms to prevent fluid leakage from the barrels (2) and (3).

Piston (4) divides the inside of barrel (2) into two chambers, resp. (12a) and (13a) and 25 piston (6) divides the inside of barrel (3) into two chambers resp. (12b) and (13b).

Naturally fluid sealing means are provided around the pistons to prevent fluid leakage from chamber (12a) to (13a) and to prevent fluid leakage from chamber (12b) to (13b). Underneath the cylinder heads (8) and (10) of barrels (2) and (3) a fluid communication path is established by means of a chamber (12c), consequently the volumes of upper 30 chambers (12a) and (12b) and the connecting chamber (12c) are combined and together form one upper volume (12).

Just above the cylinder bottoms (9) and (11) of barrels (2) and (3) a fluid communication path is established by means of a chamber (13c), consequently the volumes of lower chambers (13a) and (13b) and the connecting chamber 13c are combined and together 35 form one lower volume (13).

-6-

Upper and lower volumes (12) and (13) are filled with a fluid which can be selected from any number of non-compressible fluids suitable for use in hydraulic applications.

Due to the non-compressible character of hydraulic fluids, total volumes (12) and (13) will have to remain the same under movement of the pistons (4) or (6). Consequently 5 movement of one of the pistons will result in movement of the other piston in the opposite direction. The ratio of the magnitude of their displacements will be determined by the ratio of their diameters squared. Thus while volumes of the chambers (12a), (12b), (13a) and (13b) change by movement of the pistons (4) and (6) trough barrels (2) and (3), the total upper and lower volumes (12) and (13) remain the same.

10 Holes (15) and (16) in the top ends of piston rods (5) and (7) are used to connect them to the lower ends of the shock-absorber (20) and link (23) as was shown in FIG 2.

FIG. 4 is similar to FIG. 2 but with the swing arm raised as a result of a vertical movement of the rear wheel and together with FIG. 2 it demonstrates the function of the suspension system.

15 With housing (1) integrated in the swing arm (17), movement of the swing arm (17), due to a vertical movement of wheel (27), results in a movement of housing (1). With piston (4) and piston rod (5) able to move freely through barrel (2) and with piston rod (5) connected to the rigid link (21), a movement of housing (1) causing volumes (12a), (12b), (13a) and (13b) to change, must result in a movement of piston (6) and piston rod (7), through barrel 20 (3) to compensate for those changes in order for total volumes (12) and (13) to remain the same. Consequently with piston rod (7) being connected to the shock-absorber (20) the relationship between movement of the swing arm (17) and the magnitude of compression of the shock-absorber (20) will be determined by the ratio between the diameters of pistons (4) and (6) moving through barrels (2) and (3).

25 Thus with the entire housing being integrated in the swing arm any desired ratio between wheel travel and shock absorber travel can be achieved, by choosing the right diameters for the hydraulic cylinders, without taking up more space in the upper rear frame. In the first preferred embodiment the housing (1) preferably has a cylindrical shape with a 80mm diameter and a height of 58mm. The diameters of piston (4) is preferably 24 mm and the 30 diameter of piston (6) is preferably 23 mm. These dimensions are stated by way of example, to indicate how compact the system can be designed but the invention is expressly not limited to these dimensions or shapes. Furthermore the hydraulic linkage system is not limited to comprise of two hydraulic cylinders, it can also be designed to comprise of three or more communicating hydraulic cylinders to achieve the desired ratio, 35 nor is it necessary for the two or more communicating hydraulic cylinders that are used to % -7- be embedded in a housing.

In a second embodiment, a system to design a non-linear damping rate curve is added. FIG. 5 shows how the effective piston area of a hydraulic cylinder can be increased at a certain position along its stroke. With a progressive curve the compression 5 of the shock absorber increases at the end of its stroke, to achieve that more fluid must be moved in the last part of the stroke. A second barrel (28) is placed inside of cylinder barrel (2) of FIG.3. Barrel (28) comprises piston (4), is not closed by a cylinder bottom or cylinder head and naturally has a smaller diameter than barrel (2). At the top and bottom end of barrel (28) a narrowed portion is provided, prohibiting piston (4) to exit barrel (28). Under 10 pressure of the fluid piston (4) can slide freely through barrel (28), the pressure of the surrounding fluid will prevent barrel (28) from moving along, but when piston (4) encounters the narrowed top or bottom end of barrel (28), piston (4) will slide further through barrel (2) taking barrel (28) along, thereby creating an increased effective piston area at the end of it's stroke. The choice for the length of barrel (28) determines the 15 moment where the progressiveness comes in and the thickness of the wall of barrel (28) determines the increase in effective area.

In a further embodiment a control device is added to the hydraulic link apparatus of FIG. 3 through which the amount of fluid in volumes (12) and (13) can be controlled at any time while riding. In FIG. 6 & FIG. 7, volumes (12) and (13) of the hydraulic link apparatus 20 of FIG. 3 are equipped with valves that can be opened and closed to let hydraulic fluid flow in and out. In FIG.6 fluid is added to volume (12) and released from volume (13). With piston rods (5) and (7) being connected to the shock absorber and the frame as demonstrated in FIG. 3 adding fluid to volume (12) and releasing fluid from volume (13) will cause the swing arm of the motorcycle to move downwards. To make the swing arm 25 move upwards fluid must be added to volume (13) and released form volume(12) as illustrated in FIG.7.

A preferred system to create and control these flows comprises of a control unit, an accumulator to provide hydraulic fluid under pressure, a reservoir to store hydraulic fluid, control valves and channels to transport the hydraulic fluid from the accumulator to the 30 volumes (12) and (13) and to transport the hydraulic fluid from volumes (12) and (13) to the storage reservoir.

The control unit calculates the flow demand by the input from different sensors, for instance : g-force, speed, acceleration, pressure, position on the track (gps)/ the bike/ front and rear suspension, rpm of the wheels and engine, position off the throttle , brakes 35 etc . On the output it controls the timing off the valves and thereby the flow which controls * -8- the displacement off the shock absorber.

An other system to control the displacement of the shock-absorber comprises of the hydraulic link apparatus of FIG. 3 and a system that can vary the length off connecter rod (23). By varying the length of connector rod (23) the flow and thereby the 5 displacement of the shock absorber can be controlled.

This could be done directly by an Stack actuator, piezo translator or by using an actuator who turns an eccentric pivot placed on (22), or by screw & nut turning by hand . This system could have a control unit and sensors as described above to calculate the desired flow and thereby the displacement off the shock absorber. This system could be 10 installed in a very simple form to have adjustable ride height.

It is to be understood that the above description is included to illustrate the operation of the preferred embodiments and is not meant to limit the scope of the invention. From the above discussion, many variations will be apparent to one skilled in the art that would yet be encompassed by the spirit and scope of the present invention.

15 20 25 30 1 03 9 9 39

Claims (8)

A device for transferring the vertical movement of the rear wheel of a motorcycle to the movement of a shock absorber in which the device is provided with a closed fluid system for transferring this movement in a determined ratio, comprising: - a first hydraulic cylinder comprising a piston and a first and a second liquid reservoir, - a second hydraulic cylinder comprising a piston and a third and a fourth liquid reservoir, - wherein the first, second, third and fourth reservoir are filled with a hydraulic liquid, the fluid system further comprising, - a first fluid communication channel connecting the first and third fluid reservoirs, 15. a second fluid communication channel connecting the second and fourth fluid reservoirs, the hydraulic cylinders being provided with continuous piston rods which exit openings in the cylinder heads and the cylinder bottoms are movably received and of which one piston rod is rotatably connected at one end to the bottom of a shock absorber and one piston rod is rotatably connected at one end to the frame, and wherein in the device the ratio between the vertical movement of the wheel and the impact of the shock absorber is determined by the ratio between the piston surfaces of the hydraulic cylinders. 25 Device as claimed in claim 1, wherein the hydraulic cylinders are included in a housing. 3. Device as claimed in claim 2, wherein the housing is integrated in the rear fork of the motorcycle. (FIG 2) Device as claimed in claim 2, wherein the housing is attached to the rear fork of the motorcycle. Device as claimed in any of the foregoing claims, wherein one piston rod (5,7) is rotatably connected to the bottom of the shock absorber and one piston rod (5,7) is rotatably connected to a rigid element ( 23) connected to the top of the shock absorber. (FIG 2) Device according to any one of the preceding claims, wherein the closed fluid system for transferring the vertical movement of the rear wheel to the movement of the shock absorber comprises three or more communicating hydraulic cylinders. Device as claimed in any of the foregoing claims, wherein the at least one communicating hydraulic cylinder is provided with a system for varying the effective area of one of the pistons in the hydraulic cylinders comprising: - an elongate guide (28) arranged in one of the communicating hydraulic cylinders and which extends along a part of this cylinder, comprising the piston, and wherein a narrowing (29,30) is arranged at both ends, the length of the inserted guide determining at which moment during the stroke the effective surface of the cylinder changed and the thickness of the conductor wall determined the extent of this change. Device as claimed in any of the foregoing claims, wherein the device is provided with a system with which the amount of liquid in the liquid reservoirs can be continuously controlled comprising: - reservoir and the communication channel that interconnects the second and fourth liquid reservoir. 25. an accumulator - a valve in the chamber formed by the first and third fluid reservoirs and the communication channel that interconnects the first and third fluid reservoirs. - a valve in the chamber formed by the second and fourth fluid pressure and return lines through which the fluid can be fed to and from the chambers 30. a control valve - a control unit - a fifth reservoir for collecting hydraulic fluid and a pump to pressurize the accumulator. 35