# Patent

## Title
Suspension with hydraulic preload adjust

## Abstract

A shock absorber for a vehicle having a damper and a first and second springs mounted coaxially around the damper and a preload adjuster for partially compressing at least one of the springs independently of the compression stroke. In one embodiment the preload adjuster is remotely controllable. In another embodiment the shock absorber includes an additional mechanism for preloading at least one of the springs.

## Background
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation application of and claims priority to and benefit of co-pending U.S. patent application Ser. No. 13/758,330, filed on Feb. 4, 2013, which claims benefit of U.S. provisional patent application Ser. No. 61/594,886, filed Feb. 3, 2012. All of these applications are herein incorporated herein, by reference, in their entireties.


BACKGROUND OF THE INVENTION
1. Field of the Invention
Embodiments of the invention generally relate to a damper assembly for a vehicle. More specifically, certain embodiments relate to spring preload adjustment used in conjunction with a vehicle suspension.
2. Description of the Related Art
Vehicle suspension systems typically include a spring component or components and a damping component or components. Typically, mechanical springs, like helical springs, are used with some type of viscous fluid-based damping mechanism and the two are mounted functionally in parallel. In some instances, features of the damper or spring are user-adjustable. What is needed is an improved method and apparatus for varying spring preload characteristics.
SUMMARY OF THE INVENTION
The present invention generally includes a shock absorber for a vehicle having a damper and a first and second springs mounted coaxially around the damper and a preload adjuster for partially compressing at least one of the springs independently of the compression stroke. In one embodiment the preload adjuster is remotely controllable. In another embodiment the shock absorber includes an additional mechanism for preloading at least one of the springs.



BRIEF DESCRIPTION OF THE DRAWINGS
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
FIG. 1 is a section view of a shock absorber having two coaxial springs, both of which are pre-loadable.
FIG. 2 is a section view of the shock absorber of FIG. 1 in which the spring members are pre-loaded.
FIG. 3 is a section view of the shock absorber illustrating an independent way of pre-loading one of the springs relative to the other spring.
FIG. 4 is a schematic diagram showing a control arrangement for a remotely operated bypass.
FIG. 5 is a schematic diagram showing another control arrangement for a remotely operated bypass.



DETAILED DESCRIPTION
As used herein, the terms “down,” “up,” “downward,” “upward,” “lower,” “upper” and other directional references are relative and are used for reference only.
FIGS. 1-3 illustrate a shock absorber 100 having damper and spring functions. In the Figures the shock is shown in its most extended (rebound) position. The damper 100 includes a cylinder 102 with a rod 107 and a piston 105 which is sealed in the cylinder with a seal 108. In one embodiment, as the piston 105 moves in a compression or rebound stroke, fluid meters from one side of the piston 105 to the other side by passing through flow paths (not shown) formed in the piston 105. Typically, shims are used to partially obstruct flow paths through the piston 105 in each direction. By selecting shims having certain desired stiffness characteristics, the dampening effects caused by the piston 105 as it travels through the fluid can be increased or decreased, and dampening rates can be different between the compression and rebound strokes of the piston 105.
A reservoir (not shown) is typically in fluid communication with the damper cylinder 102 for receiving and supplying damping fluid as the piston rod 107 moves in and out of the cylinder. The reservoir includes a cylinder portion 128 in fluid communication with the damper cylinder 102. Certain features of reservoir type dampers are shown and described in U.S. Pat. No. 7,374,028, which is incorporated herein, in its entirety, by reference. One end of the piston rod 107 is supplied with an eyelet 109 for connecting to a portion of a vehicle wheel suspension linkage. An opposite end (opposite the piston), is supplied with an eyelet 111 to be mounted to another portion of the vehicle, such as the frame, that moves independently of the first part.
In one embodiment, as shown in all of the figures, a closure 110, is constructed and arranged to thread onto an end of cylinder 102 and engage telescopically with a preload piston 120. The preload piston is slidable relative to and sealed against (by seal 131) an exterior surface of cylinder 102 and is also slidably sealed against an exterior of the closure 110 by seal 132.
The preload piston includes two separate spring axial abutment structures. Shown are large diameter abutment 115 and a small diameter abutment 130. A spring abutment 125 is attached at an opposite end of rod 107, adjacent a lower connecting eye. As shown in the figures, abutment 125 may be stepped with two surfaces 126, 127 and of sufficient diameter to support either the lower end of a large diameter spring 150 or a small diameter spring 155 or both simultaneously (as shown).
In one embodiment, a preload adjuster assembly includes a hydraulic fluid flow path comprising fill fitting 160, flow path 161, 162 and piston chamber 163 (visible in FIG. 2). In practice, one or more springs are mounted to abut surfaces 125 and one or both of 115 and 130. FIG. 1 shows the shock absorber in the “minimum extension” position (no hydraulic fluid in chamber 163) as it is shown in FIG. 1. The springs 150, 155 so mounted will be in their most compliant state due to minimum preload (i.e. pre-compression). When greater preload and hence more rigid vehicle ride are desired, fluid is introduced manually or via onboard hydraulic reservoir and pump, into port 160. The fluid then flows through paths 161, 162 and begins to expand chamber 163. As chamber 163 expands due to fluid fill (see FIG. 2), the piston 120 moves axially, compressing spring 150, 155 against abutment 125 (between the abutment 130 and/or 115). The result is a stiffer spring.
In the embodiment shown in the Figures, both springs 150, 155 are acted upon by the preload piston 120 causing both to become more or less compressed as the preload piston 120 moves in relation to the fluid in chamber 163. However, it will be understood that either of the springs could be independently mounted wherein it is not affected at all by the expansion and contraction of the chamber 163.
While the embodiment described presumes chamber 163 of the preload adjuster is operated with relatively non-compressible fluid, compressible fluid such as gas may be used in the chamber to create a composite spring rate comprising compressible gas and mechanical spring.
While the embodiment described includes springs coaxially arranged around a fluid damper, the spring could be used in conjunction with an air spring, especially one that is combined in a central cylinder member with a damper. An example of a combination air spring/damper is taught in U.S. Patent Application Publication No. 2009/0236807 A1 and that publication is incorporated herein in its entirety.
In the embodiment shown, large diameter abutment 115 holding larger diameter spring 150 at one end is independently adjustable relative to the other spring 155 and the chamber. Independent adjustment is provided by a threaded relationship 156 between the abutment 115 and the outer diameter of the chamber. For example, in FIGS. 1, 2 the abutment is located near an end of the chamber wall. In FIG. 3, however, abutment 115 has been threadedly moved axially along the cylinder to a location closer to an opposite end of the chamber. In this manner, additional preload is placed upon the larger diameter spring 150 separate and apart from preload supplied by the preload piston 120. While the independent adjustment feature is shown in relation to the larger diameter spring 150, it will be understood that such a feature could be associated with either or both springs. Additionally, any number of springs (including a single spring) can be used with their ends mounted at various locations along a length of the cylinder 102.
The preload adjuster may be automated such that onboard load sensing associated with a vehicle adjusts the spring rate based on sensed operational conditions and microprocessor-controlled fluid introduction into one or more preload adjusters on the vehicle (e.g. 4 on a 4 wheeler),
FIG. 4 is a schematic diagram illustrating a sample circuit 400 used to provide remote control of a preload adjuster using a vehicle's power steering fluid (although any suitable fluid pressure source may be substituted for reservoir 410 as could an electrical current source in the case of an electrically actuated valve member 175). As illustrated, a fluid pathway 405 having a switch-operated valve 402 therein runs from a fluid (or current) reservoir 410 that is kept pressurized by, in one embodiment, a power steering pump (not shown) to a preload adjuster that is operable, for example, by a user selectable dash board switch 415. The valve 402 permits fluid to travel to the adjuster, thereby urging it to an expanded position. When the switch 415 is in the “off” position, the adjuster is in its compressed position and no additional preload is placed on the springs. Hydraulically actuated valving for use with additional components is shown and described in U.S. Pat. No. 6,073,536 and that patent is incorporated by reference herein in its entirety. While FIG. 4 is simplified and involves control of a single preload adjuster, it will be understood that the valve 402 could be plumbed to simultaneously provide a signal to two or more adjusters, one related to each wheel of a vehicle, for instance.
A remotely operable preload adjuster like the one described above is particularly useful with on/off road vehicles. These vehicles can have as much as 20′′ of shock absorber travel to permit them to negotiate rough, uneven terrain at speed with usable shock absorbing function. In off-road applications, compliant shock absorbing is necessary as the vehicle relies on its long travel suspension when encountering off-road obstacles. However, operating a vehicle with very compliant, long travel suspension on a smooth road at higher speeds can be problematic due to the springiness/sponginess of the suspension. Such compliance can cause reduced handling characteristics and even loss of control. Such control issues can be pronounced when cornering at high speed as a compliant, long travel vehicle may tend to roll excessively. Similarly, such a vehicle may pitch and yaw excessively during braking and acceleration. With the remotely operated preload adjuster described herein, spring characteristics of a shock absorber can be completely changed from a compliantly dampened “springy” arrangement to a “stiffer” system ideal for higher speeds on a smooth road.
In addition to, or in lieu of, the simple, switch operated preload adjuster arrangement of FIG. 4, the preload adjuster can be operated automatically based upon one or more driving conditions. FIG. 5 shows a schematic diagram of a remote control system 500 based upon any or all of vehicle speed, damper rod speed, and damper rod position. One embodiment of FIG. 5 is designed to automatically increase spring compression in a shock absorber in the event a damper rod reaches a certain velocity in its travel towards the bottom end of travel at a predetermined speed of the vehicle. In one embodiment, the system adds stiffness (and control) in the event of rapid operation (e.g. high rod velocity) to avoid a bottoming out of the rod as well as a loss of control that can accompany rapid compression of a shock absorber with a relative long amount of travel. In one embodiment, the system adds stiffness (e.g. expands the chamber 163) in the event that the rod velocity in compression is relatively low, but the rod progresses past a certain point in the travel. Such configuration aids in stabilizing the vehicle against excessive low rare suspension movement events such as cornering roll, braking and acceleration yaw and pitch and “g-out.”
FIG. 5 illustrates, for example, a system including three variables: rod speed, rod position and vehicle speed. Any or all of the variables shown may be considered by processor 502 in controlling the valve 175. Any other suitable vehicle operation variable may be used in addition to or in lieu of the variables 515, 505, 510 such as, for example, piston rod compression strain, eyelet strain, vehicle mounted accelerometer data or any other suitable vehicle or component performance data. In one embodiment, a suitable proximity sensor or linear coil transducer or other electro-magnetic transducer is incorporated in the dampening cylinder to provide a sensor to monitor the position and/or speed of the piston (and suitable magnetic tag) with respect to the cylinder.
In one embodiment, the magnetic transducer includes a waveguide and a magnet, such as a doughnut (toroidal) magnet that is joined to the cylinder and oriented such that the magnetic field generated by the magnet passes through the piston rod and the waveguide. Electric pulses are applied to the waveguide from a pulse generator that provides a stream of electric pulses, each of which is also provided to a signal processing circuit for timing purposes. When the electric pulse is applied to the waveguide a magnetic field is formed surrounding the waveguide. Interaction of this field with the magnetic field from the magnet causes a torsional strain wave pulse to be launched in the waveguide in both directions away from the magnet. A coil assembly and sensing tape is joined to the waveguide. The strain wave causes a dynamic effect in the permeability of the sensing tape which is biased with a permanent magnetic field by the magnet. The dynamic effect in the magnetic field of the coil assembly due to the strain wave pulse, results in an output signal from the coil assembly that is provided to the signal processing circuit along signal lines. By comparing the time of application of a particular electric pulse and a time of return of a sonic torsional strain wave pulse back along the waveguide, the signal processing circuit can calculate a distance of the magnet from the coil assembly or the relative velocity between the waveguide and the magnet. The signal processing circuit provides an output signal, digital or analog, proportional to the calculated distance and/or velocity. Such a transducer-operated arrangement for measuring rod speed and velocity is described in U.S. Pat. No. 5,952,823 and that patent is incorporated by reference herein in its entirety.
While a transducer assembly measures rod speed and location, a separate wheel speed transducer for sensing the rotational speed of a wheel about an axle includes housing fixed to the axle and containing therein, for example, two permanent magnets. In one embodiment the magnets are arranged such that an elongated pole piece commonly abuts first surfaces of each of the magnets, such surfaces being of like polarity. Two inductive cons having flux-conductive cores axially passing therethrough abut each of the magnets on second surfaces thereof, the second surfaces of the magnets again being of like polarity with respect to each other and of opposite polarity with respect to the first surfaces. Wheel speed transducers are described in U.S. Pat. No. 3,986,118 which is incorporated herein by reference in its entirety.
In one embodiment, as illustrated in FIG. 5, a logic unit 502 with user-definable settings receives inputs from the rod speed 510 and location 505 transducers as well as the wheel speed transducer 515. The logic unit is user-programmable and depending on the needs of the operator, the unit records the variables, and then if certain criteria are met, the logic circuit sends its own signal to the preload adjuster to either expand or contract. Thereafter, the condition of the preload adjuster 175 is relayed back to the logic unit 502.
In one embodiment, the logic shown in FIG. 5 assumes a single shock absorber but the logic circuit is usable with any number of shocks or groups of shocks. For instance, the shock absorbers on one side of the vehicle can be acted upon while the vehicle's other shocks remain unaffected.
While the examples illustrated relate to manual operation and automated operation based upon specific parameters, the remotely operated preload adjuster can be used in a variety of ways with many different driving and road variables. In one example, the preload adjuster is controlled based upon vehicle speed in conjunction with the angular location of the vehicle's steering wheel. In this manner, by sensing the steering wheel turn severity (angle of rotation), additional stiffness can be applied to one shock or one set of shocks on one side of the vehicle (suitable, for example, to mitigate cornering roll) in the event of a sharp turn at a relatively high speed. In another example, a transducer, such as an accelerometer, measures other aspects of the vehicle's suspension system, like axle force and/or moments applied to various parts of the vehicle, like steering tie rods, and directs change to the preload adjuster positioning in response thereto. In another example, the preload adjuster can be controlled at least in part by a pressure transducer measuring pressure in a vehicle tire and adding or subtracting stiffness characteristics to some or all of the wheels in the event of, for example, an increased or decreased pressure reading. In still another example, a parameter might include a gyroscopic mechanism that monitors vehicle trajectory and identifies a “spin-out” or other loss of control condition and adds and/or reduces spring stiffness to some or all of the vehicle's shock absorbers in the event of a loss of control to help the operator of the vehicle to regain control.
While the foregoing is directed to embodiments of the invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

## Claims

1. A shock absorber for a vehicle, comprising
a fluid-filled damper having a piston and rod for movement therein;
a first and second springs mounted coaxially around the damper, the springs constructed and arranged to become compressed during a compression stroke of the damper; and
a preload adjuster for partially compressing both of the springs independently of the compression stroke.

2. The shock absorber of claim 1, wherein the shock absorber further comprises a preload piston that includes at least two separate spring axial abutment structures.

3. The shock absorber of claim 2, wherein the at least two separate spring axial abutment structures includes a first abutment structure, wherein the shock absorber further comprises a piston chamber and a threaded relationship between the first abutment structure and an outer diameter of the piston chamber, and wherein the first spring that is proximate to the first abutment structure is independently adjustable relative to the second spring using the threaded relationship.

4. The shock absorber of claim 2, wherein one of the springs is a large diameter spring and wherein one of the spring axial abutment structures is a large diameter abutment that supports one end of the large diameter spring.

5. The shock absorber of claim 2, wherein one of the springs is a small diameter spring and wherein one of the spring axial abutment structures is a small diameter abutment that supports one end of the small diameter spring.

6. The shock absorber of claim 2, wherein the at least two separate spring axial abutment structures are in a stair step relationship with each other.

7. A shock absorber for a vehicle, comprising:
a fluid-filled damper having a damper chamber, a piston and rod, wherein the piston and rod move inside a central cylinder member formed by the damper chamber;
a first spring and a second spring both mounted coaxially with respect to the damper, the springs constructed and arranged to become compressed during a compression stroke of the damper;
a preload adjuster for partially compressing at least one of the springs independently of the compression stroke, the preload adjuster comprising a piston chamber, the piston chamber having a volume that remains constant throughout a compression stroke of the damper; and
an air spring located in a central cylinder member.

8. The shock absorber of claim 7, wherein the shock absorber further comprises a preload piston that includes at least two separate spring axial abutment structures.

9. The shock absorber of claim 8, wherein the at least two separate spring axial abutment structures includes a first abutment structure, wherein the shock absorber further comprises a threaded relationship between the first abutment structure and an outer diameter of the piston chamber, and wherein the first spring that is proximate to the first abutment structure is independently adjustable relative to the second spring using the threaded relationship.

10. The shock absorber of claim 8, wherein the fluid filled damper has a shape of a cylinder, wherein the shock absorber further comprises a closure with threads, wherein the threads are arranged onto an end of the cylinder, and wherein the threads engage with the preload piston.

11. The shock absorber of claim 8, wherein one of the springs is a large diameter spring and wherein one of the spring axial abutment structures is a large diameter abutment that supports one end of the large diameter spring.

12. The shock absorber of claim 8, wherein one of the springs is a small diameter spring and wherein one of the spring axial abutment structures is a small diameter abutment that supports one end of the small diameter spring.

13. The shock absorber of claim 8, wherein the at least two separate spring axial abutment structures are in a stair step relationship with each other.

14. The shock absorber of claim 7, wherein the shock absorber further includes a preload adjuster assembly that includes a hydraulic fluid flow path, wherein the hydraulic fluid flow path includes a fill fitting, at least two flow paths and the piston chamber.

15. The shock absorber of claim 14, wherein fluid is introduced into the fill fitting using a technique selected from a group consisting of manual pumping and a pump coupled with an onboard hydraulic reservoir.

16. The shock absorber of claim 14, wherein fluid introduced into the fill fitting expands the piston chamber and compresses the first spring and the second spring against respective abutments.

17. The shock absorber of claim 7, wherein the preload adjuster is controlled using a valve selected from a group consisting of a hydraulically actuated valve and an electrically actuated valve.

18. A shock absorber system for a vehicle, the shock absorber system comprising:
a first shock absorber and a second shock absorber, wherein each of the shock absorbers include:
a fluid-filled damper having a piston and rod for movement therein;
a first spring and a second spring both mounted coaxially with respect to the damper, the springs constructed and arranged to become compressed during a compression stroke of the damper; and
a preload adjuster for partially compressing at least one of the springs independently of the compression stroke, the preload adjuster comprising an expandable piston chamber, the piston chamber having a volume that remains constant throughout the compression stroke of the damper;

a first control circuit that controls the first shock absorber; and
a second control circuit that controls the second shock absorber,
wherein the first control circuit adjusts the first shock absorber without requiring the second control circuit to adjust the second shock absorber.

19. The shock absorber system of claim 18, wherein the first control circuit and the second control circuit adjust the respective first and second shock absorbers in a different manner based on at least one characteristic of the vehicle.

20. The shock absorber system of claim 19, wherein the characteristic is at least two of vehicle speed, vehicle trajectory angular acceleration, damper rod velocity, and rod location in a damper cylinder.