Adjustable shock absorber

A shock absorber assembly includes a damping adjustment mechanism that can easily be incorporated into a twin cylinder design. The shock absorber includes an outer cylinder and an inner cylinder mounted within the outer cylinder. The inner cylinder is spaced apart from the outer cylinder to define a gap. A piston is mounted within a fluid filled chamber formed within the inner cylinder to dampen vibrations. Holes are drilled into the wall of the inner cylinder to provide fluid ports that can communicate with the gap to form a bi-directional fluid path as the piston moves back and forth within the chamber to dampen vibrations. To provide variable damping, the outer cylinder includes an eccentric inner diameter to outer diameter profile that allows damping adjustment between high and low damping forces. The damping force is adjusted by rotating the outer cylinder relative to the inner cylinder to vary the size of the gap with respect to the ports.

BACKGROUND OF THE INVENTION

This invention relates to a device and method for adjusting damping in a vehicle shock absorber.

Vehicles utilize shock absorbers to dampen vibrations and shocks experienced by a vehicle. Variations in payload and ground conditions can affect vehicle control and handling. Having the ability to selectively adjust the damping force in a shock absorber is desirable to improve vehicle control and handling in response to these variables. Some shock absorbers include position sensing technology and damping adjustment that permit a vehicle operator to selectively change damping to a desired level.

Current adjustment systems rely on external components or adjuster modules to provide adjustment. Utilizing additional components significantly increases cost and assembly time. Thus, the adjustment feature is not typically incorporated on most vehicles.

It is desirable to provide a shock absorber with an adjustment mechanism that utilizes components already found within the shock absorber, and which can be easily adjusted by a vehicle operator to control damping levels. The adjustment mechanism should also be cost effective in addition to overcoming the above referenced deficiencies with prior art systems

SUMMARY OF THE INVENTION

The subject invention provides a shock absorber that includes damping adjustment for a twin cylinder configuration having an inner cylinder mounted within an outer cylinder in a spaced relationship to form a flow gap. Simultaneous and/or independent compression and rebound damping adjustment is achieved by moving the outer cylinder with respect to the inner cylinder to adjust flow gap size around flow ports formed within the inner cylinder. The outer cylinder can be rotated or axially translated relative to the inner cylinder to adjust gap size.

In the preferred embodiment, this is accomplished by the outer cylinder having an eccentric inner diameter to outer diameter profile to control the width of the flow gap is in relation to the ports. The outer cylinder forms an outer wall of the shock absorber and the inner cylinder forms an inner wall of the shock absorber. The outer wall is defined by an outer diameter that has a first center and an inner diameter that has a second center that is different than the first center to form the eccentric profile. The eccentricity of the outer wall adjusts flow gap size as the outer cylinder is rotated or translated to adjust damping. The eccentricity is formed by varying the wall thickness or profile of the outer cylinder. Multiple eccentricities to provide multiple gap size variations are achieved by forming the outer wall with several different thicknesses about the circumference.

In one embodiment, the eccentricity is uniform such that the gap is uniform in cross-section along the length of the cylinders. The shock absorber is adjustable between a low damping force where the gap size is defined by a first width in relation to the ports and a high damping force where the gap size is defined by a second width in relation to the ports that is less than the first width.

In an alternate embodiment, the eccentricity is variable such that the gap is nonuniform in cross-section along the length of the cylinders. The variable eccentricity results from an inner surface of the outer wall having a stepped or tapered profile. The steps or taper provide variable gap widths for each of the ports.

DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

Referring to FIG. 1 , a shock absorber assembly is shown generally at 10 . The shock absorber 10 includes an outer cylinder 12 and an inner cylinder 14 mounted within the outer cylinder 12 in a spaced relationship to form a flow gap 16 . The outer cylinder 12 forms an outer wall 18 of the shock absorber 10 and the inner cylinder 14 forms the inner wall 20 of the shock absorber 10 .

The inner wall 20 defines a chamber 22 in which a plunger or piston member 24 is mounted. Fluid is sealed within the chamber 22 , as is known in the art, and is compressed by the piston 24 to dampen vibrations. Any type of known fluid can be used, including hydraulic fluid or gas either of which could be compressible or incompressible, for example.

Multiple ports 26 are formed within the inner wall 20 . The ports 26 are preferably formed on only one side of the inner cylinder 14 to define a ported side 28 and non-ported side 30 of the inner cylinder 14 . The ports 26 allow fluid communication with the gap 16 as the piston 24 moves within the chamber 22 .

The piston 24 separates the chamber 22 into a compression side 22 a and a rebound side 22 b . There are ports 26 positioned on both the compression 22 a and rebound 22 b sides. As vibrations are dampened, fluid flows from the rebound side 22 b to the compression side 22 a and/or vice versa via the ports 26 and gap 16 . Thus, fluid flow can be bi-directional between the rebound 22 b and compression 22 a sides or check valves can be used to allow fluid to flow in one direction while preventing fluid flow in an opposite direction. Fluid also flows back and forth between the rebound 22 b and compression 22 a sides via disc valves (not shown) through the piston 24 as known in the art. The operation of disc and check valves is well known and will not be discussed in further detail.

The subject invention provides an adjustment mechanism for varying the damping force of the shock absorber 10 that can be selectively actuated by a vehicle operator. It is desirable to control damping force to provide improved vehicle control and handling to accommodate vehicle payload changes or ground condition changes. For example, one vehicle application in which shock absorber damping adjustment is desirable is for snowmobiles. Aggressive drivers may desire high damping forces while non-aggressive drivers desire lower damping forces. Or, if more than one passenger is riding on the snowmobile it may be desirable to change the damping force to accommodate the additional weight.

Damping force adjustment is accomplished by selectively rotating or axially translating the outer cylinder 12 with respect to the inner cylinder 14 to vary the size of the gap 16 in relation to the ports 26 . The rotation or translation of the outer cylinder 12 is accomplished by any of various types of actuation methods. For example, the outer cylinder 12 can be manually moved by the operator or can be electrically moved upon selection of a desired damping position by the operator.

For manual rotation or translation, a grip portion 32 can be formed on the outer surface of the outer cylinder 12 and a label or markings 34 can be made on the outer cylinder 12 to indicate various adjustment positions. The grip portion 32 can be positioned anywhere along the length of the outer cylinder 12 and can be a separate member attached to or formed within the cylinder 12 , as shown in FIG. 1 , or can simply be defined as any exterior surface presented by the outer cylinder 12 .

For electrical rotation or translation, a controller and motor 36 can be selectively actuated by the operator to move the outer cylinder 12 . A push-button, switch, dial, or toggle (not shown) can be selected to power the system.

As discussed above, the damping adjustment occurs as a result of variation in flow gap size. One way to vary the flow gap size is by varying the thickness or profile of the outer wall 18 . In prior art systems, shown in FIG. 2 , the outer cylinder 12 was defined by a wall 40 having equal thickness about the circumference of the cylinder 12 . With this configuration the flow gap 16 has a constant and uniform width between the inner 14 and outer 12 cylinders. As the piston 24 moves back and forth in the chamber 22 , fluid flows back and forth between the compression 22 a and rebound 22 b sides via the ports 26 and gap 16 and there is a constant damping force.

As indicated above, in one embodiment the subject invention varies flow gap size by eccentrically forming the outer wall 18 , as shown in FIGS. 3-5 . The outer wall 18 is defined by an outer diameter and an inner diameter that have different centers creating an eccentric inner diameter to outer diameter profile. This is accomplished by forming one portion of the outer cylindrical wall 18 with greater thickness than another portion of the wall 18 , i.e. the wall thickness for the outer wall is non-uniform. A cross-section of the outer wall 18 is shown in FIG. 6 A. In this embodiment, one side of the wall 18 is significantly thicker than the other side. The wall is formed with multiple eccentricities by varying the wall thickness between a maximum thickness and a minimum thickness. Thus, the gap size can be infinitely varied as the outer cylinder 12 is rotated anywhere between 0 to 180 .

An alternate embodiment for a cross-section of the outer cylinder 12 is shown in FIG. 6 B. In this embodiment, the outer cylinder 12 is defined by an inner diameter that presents a variable profile. An example of this is shown in FIG. 6 b in which the wall 18 includes multiple waves or steps 38 formed on the inner surface to vary gap size between multiple widths as the outer cylinder 12 is rotated between 0 to 180 .

Thus, the eccentric inner diameter to outer diameter profile changes the flow gap width in relation to the ports 26 to vary damping. It should be understood that while only two (2) ports 26 are shown in FIGS. 3-5 , additional ports could also be formed within the inner wall 20 .

In one embodiment, shown in FIGS. 3A and 3B , the gap size is uniform and constant in cross-section along the longitudinal direction (length) of the cylinders 12 , 14 . Due to the eccentric formation of the outer cylinder 12 , the ported side 28 of the inner cylinder 14 defines a first gap width in relation to the ports 26 and the non-ported side 30 of the inner cylinder 14 defines a second gap width between the inner 14 and outer 12 cylinders. In the low damping force configuration, shown in FIG. 3A , the first gap width is greater than the second gap width. In the high damping force configuration, shown in FIG. 3B , the outer cylinder 12 is rotated such that the first gap width is less than the second gap width. Due to the decrease in gap width in relation to the ports 26 , less fluid can flow back and forth between the compression 22 a and rebound 22 b sides of the piston 24 as compared to the amount of fluid flowing in the low damping configuration.

In an alternate embodiment, shown in FIGS. 4A and 4B , the outer cylinder 12 includes a stepped surface to provide variable gap widths for different ports 26 . In this embodiment, the outer cylinder 12 is defined by a wall 50 having a stepped inner surface 52 . In this embodiment, the gap 16 is non-uniform and variable along the longitudinal direction of the cylinders 12 , 14 . The gap widths for each port 26 in relation to the stepped inner surface are different with respect to each other. For example, a first gap width 54 a is defined between one of the ports 26 a and the outer cylinder 12 and a second gap width 54 b is defined between another of the ports 26 b and the outer cylinder 12 . A step 56 decreases the size of the first gap width 54 a . A third gap width 54 c is defined between the non-ported side 30 of the inner cylinder 14 and the outer cylinder 12 .

In the low damping force configuration, shown in FIG. 4A , the first gap width 54 a is less than the second gap width 54 b and both the first 54 a and second 54 b gap widths are greater than the third gap width 54 c . In the high damping force configuration, shown in FIG. 4B , the outer cylinder 12 is rotated or translated such that the first gap width 54 a and the second gap widths 54 b are both less than the third gap width 54 c . Due to the decrease in gap width in relation to the ports 26 in the high damping force position, less fluid can flow back and forth between the compression 22 a and rebound 22 b sides of the piston 24 as compared to the amount of fluid flowing in the low damping configuration. But, in the low damping configuration, damping force is further adjusted by providing different gap widths between each of the ports 26 and the outer cylinder 12 . It should be understood that while two ports 26 are shown in FIGS. 4A and 4B , additional ports 26 and additional steps 56 could be formed to provide further damping adjustment.

In an alternate embodiment, shown in FIGS. 5A and 5B , the outer cylinder 12 includes a tapered surface to provide variable gap widths for different ports 26 . In this embodiment, the outer cylinder 12 is defined by a wall 60 having a tapered inner surface 62 providing multiple diameter changes along the length of the wall 60 . In this embodiment, the gap 16 is non-uniform and variable along the longitudinal direction of the cylinders 12 , 14 . The gap widths for each port 26 in relation to the tapered inner surface 62 are different with respect to each other. For example, a first gap width 64 a is defined between one of the ports 26 a and the outer cylinder 12 and a second gap width 64 b is defined between another of the ports 26 b and the outer cylinder 12 . The tapered surface 62 decreases the size of the first gap width 64 a in comparison to the second gap width 64 b . A third gap width 64 c is defined between the non-ported side 30 of the inner cylinder 14 and the outer cylinder 12 .

In the low damping force configuration, shown in FIG. 5A , the first gap width 64 a is less than the second gap width 64 b and both the first 64 a and second 64 b gap widths are greater than the third gap width 64 c . In the high damping force configuration, shown in FIG. 5B , the outer cylinder 12 is rotated or translated such that the first gap width 64 a and the second gap width 64 b are both less than the third gap width 64 c . Due to the decrease in gap width in relation to the ports 26 in the high damping force position, less fluid can flow back and forth between the compression 22 a and rebound 22 b sides of the piston 24 as compared to the amount of fluid flowing in the low damping configuration. But, in the low damping configuration, damping force is further adjusted by providing different gap widths between each of the ports 26 and the outer cylinder 12 . It should be understood that while two ports 26 are shown in FIGS. 5A and 5B , additional ports 26 could be formed to provide further damping adjustment.

The aforementioned description is exemplary rather that limiting. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed. However, one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. Hence, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For this reason the following claims should be studied to determine the true scope and content of this invention.