DUAL RATE VEHICLE SUSPENSION SYSTEM WITH ADJUSTABLE TRAVEL HEIGHT

Abstract

A spring configuration comprises a cylindrical damper, a primary coil spring with a first predetermined spring rate K1, and a secondary coil spring with a second predetermined spring rate K2, the coil springs accommodated around the cylindrical damper in series to provide a total combined spring rate KT, an actuator configured to compress and decompress the coil springs, a stop configured to deactivate the secondary coil spring in a stop position, such that, when the system is in a first comfort mode, the overall suspension spring rate is defined by the series equation 1 / KT = 1 / K1 + 1 / K2, and when the system is in a second handling mode, the overall vehicle suspension spring rate is defined by the series equation KT = K1, thereby selectively and switchably providing both a low,The optimal travel comfort configuration, such as a high rate and the optimal handling lower travel height configuration.

Description

DUAL RATE VEHICLE SUSPENSION SYSTEM WITH ADJUSTABLE TRAVEL HEIGHT rz Lznn / eznz / E / YiAi BACKGROUND OF THE INVENTION This invention relates to a suspension system for wheeled vehicles and, specifically, to a suspension system that offers two distinct modes of operation. To overcome the inherent compromise that must be made between optimizing ride comfort and optimizing the handling capabilities of a road vehicle, this invention provides a dual-mode suspension system in which the primary road spring rate can be switched between an optimal handling configuration and an optimal ride configuration. The basic premise of a motor vehicle's suspension is to allow the wheels of a vehicle to independently experience road disturbances such as potholes, rather than the entire vehicle and its occupants experiencing them. When passengers are not directly exposed to the effects of road disturbances, passenger comfort is significantly improved. Substantial energy savings are also achieved by simply moving one wheel instead of the entire vehicle over a road disturbance. Furthermore, vehicle steering control is significantly improved at increasing speed because not all of the vehicle's mass is oriented around the road disturbances. Although a vehicle's suspension can be configured in many ways, it is generally arranged to isolate the main vehicle body, referred to as the "spring mass," from the wheel system, also referred to as the "unspring mass," using an energy storage medium, typically a spring of some type. The spring stores energy as the wheel system, which includes a hub, brake, and motion control linkage, is allowed to move relative to the main vehicle body in response to road disturbances. Once a disturbance has passed, the spring then releases its stored energy to return the wheel system to its undisturbed state. To prevent an uncontrolled oscillatory response in a simple spring mass system, some form of damping device is employed.Typically, a hydraulically based component generates a force proportional to the velocity to produce a resistive force in both directions of spring movement, helping the spring return to its undisturbed position at zero velocity. This damper is a secondary component that does not support the weight of the vehicle. As a vehicle's dynamic response reaches its limits, the suspension system, including motion control links and damper and energy storage components, becomes a limiting factor in achieving optimal performance levels. If the springs and dampers are tuned relatively softly to provide a high level of occupant isolation from road disturbances, the sprung mass tends to move excessively in response to the lateral and longitudinal forces generated by the driver's steering, acceleration, and braking demands. These demands result in what is generally referred to as "handling response," while the quality of occupant isolation is called "ride response." By changing the spring rates and damping coefficients at each of the four wheel corners, the vehicle's ride and handling performance can be optimized. Generally, a stiffer spring rate, measured in force per unit of displacement, results in a firmer ride and superior vehicle body control, while a softer spring rate provides a smoother ride but less control. Damping coefficients are typically directly tuned to their corresponding spring rates. Unfortunately, optimal ride response occurs with lower spring rates, and optimal handling response occurs with higher spring rates. This has historically resulted in vehicles being tuned to a compromise between ride and handling responses. Numerous manual and adaptive dual-rate suspension systems are described in the art. Until recently, however, none were able to provide the required performance characteristics of a vehicle using metallic energy storage devices such as coil, leaf, or torsion springs. A selectively switchable, dual-rate suspension system is described in PCT / US2017 / 012588 by Holt et al. A push-rod-activated onboard spring configuration comprises a torsion bar and a coil spring in series, each with its own spring rate. A locking actuator is accommodated in parallel with the coil spring. In a first mode, the coil spring can move freely so that the overall spring rate has contributions from both the torsion bar and coil spring rates. In a second, locked mode, movement of the coil spring is prevented, thereby changing the overall spring rate to that of the torsion bar. This selectively provides a low-rate, optimal ride height comfort setting and a high-rate, optimal handling, lower ride height setting.Although this selectively switchable dual-rate suspension system is extremely effective, its use of a pushrod configuration limits its application to generally very high-performance vehicles. Therefore, there is a need for a selectively switchable dual-rate suspension system that can be used on a wider range of motor vehicles. Several attempts have been made to design a more general-purpose dual-rate suspension system. None of them, however, is a selectively switchable, active system that provides lower ride height in a high spring rate, optimal handling mode. For example, US 2009 / 0302559 to Doerfel describes a non-manually adjustable structure with two coil springs accommodated around a strut. The spring assembly has a master spring, a slider, a stop, and at least one auxiliary spring connected in series with the master spring. During compression of the spring assembly, when the auxiliary spring is compressed to a predetermined point, the stop contacts the slider to prevent further compression of the auxiliary spring. An alternative arrangement with the springs connected in parallel is also described. US 9,162,548 to V.Fakeman and US 9,821,621 to Mason describe similar structures.Neither involves a complete locking of a spring. Mason generally seeks to maintain the height of travel, while Wakeman allows the height of travel to be raised from an unloaded or neutral state, but does not allow it to be lowered. Neither provides a means of reducing the height of travel at a high spring rate, the optimal handling mode. BRIEF DESCRIPTION OF THE INVENTION In a principal aspect of the invention, a selectively switchable dual-rate vehicle suspension system comprises a conventionally oriented spring configuration between the unspringed mass and the springed mass of another corner of the vehicle, comprising a cylindrical damper, a primary coil spring with a first predetermined spring rate K1, and a secondary coil spring with a second predetermined spring rate K2, the coil springs accommodated around the cylindrical damper in series to provide a total combined spring rate KT, an actuator configured to compress and decompress the coil springs, a stop configured to deactivate the secondary coil spring in a stop position, such that, when the system is in a first comfort mode, the overall suspension spring rate is defined by the series equation 1 / KT = 1 / K1 + 1 / K2,And when the system is in a second handling mode, the general vehicle suspension spring rate is defined by the series equation KT = K1, thus selectively and switchably providing both a low rate, optimal ride comfort setting and a high rate, optimal handling lower ride height setting. In a further aspect of the invention, the primary coil spring and the secondary coil spring are connected to an intermediate spring stop. In a further aspect of the invention, the actuator acts on the secondary coil spring through a lower spring stop. In a further aspect of the invention, the actuator comprises a hydraulic cylinder and a hydraulic piston. In a further aspect of the invention, the secondary coil spring is deactivated when it is decompressed. In a further aspect of the invention, the intermediate spring stop comprises a hydraulic cylinder with a hydraulic piston. In a further aspect of the invention, the secondary coil spring is deactivated when it is compressed. In a further aspect of the invention, the hydraulic cylinder moves on an outer wall of the cylindrical damper. In a further aspect of the invention, the stop comprises a stopping portion of the outer wall of the cylindrical damper against which a contact portion of the hydraulic cylinder presses. In a further aspect of the invention, the suspension system further comprises a locking means configured to hold the secondary coil spring in the stopped position. In a further aspect of the invention, the suspension system further comprises a third maneuvering mode, wherein the secondary coil spring is decompressed and the primary coil spring is raised to increase the ride height above the optimum ride comfort setting. In a further aspect of the invention, the cylindrical damper provides adjustable damping to match changes in spring rate for optimal comfort and vehicle handling. BRIEF DESCRIPTION OF THE FIGURES FIGURE 1A illustrates a perspective view of a front-mounted, single-acting cylinder system mounted on a conventional double-wishbone suspension system for use on a vehicle corner, typically a front corner. FIGURES 1B, 1C and 1D illustrate isolated perspective views of a front-mounted single-acting cylinder system from various angles. FIGURE 2A illustrates an elevation cross-sectional view of a portion of the single-acting cylinder system. FIGURE 2B illustrates a perspective view of a portion of the single-acting cylinder system and certain damper components. FIGURES 3A, 3B and 30 illustrate the front-mounted single-acting cylinder system in multiple elevation views mounted on a conventional twin-wishbone suspension system in lowered, trimmed and raised vehicle height configurations respectively. FIGURES 4A and 4B illustrate the front-mounted single-acting cylinder system in standard and paired elevation cross-section views of the system in a lowered vehicle height configuration. FIGURES 40 and 4D illustrate the front-mounted single-acting cylinder system in standard and paired elevation cross-section views of the system in a trimmed vehicle height configuration. FIGURES 4E and 4F illustrate the front-mounted single-acting cylinder system in standard and paired elevation cross-section views of the system in a raised vehicle height configuration. FIGURE 5A illustrates an alternative front-mounted dual-acting cylinder system 15 in an isolated perspective view. FIGURE 5B illustrates a partial expanded portion of the alternative front-assembly dual-acting cylinder system of FIGURE 5A in an isolated perspective view. FIGURE 50 illustrates the alternative front-mounted dual-acting cylinder system of FIGURE 5A from another angle. FIGURE 6 illustrates an elevation cross-sectional view of a portion of the dual-acting cylinder system. FIGURE 7A illustrates an elevation view of the alternative front-mounted dual-acting cylinder system mounted on a conventional twin-wishbone suspension system. FIGURE 7B illustrates an isolated perspective view of the alternate front assembly's dual-acting cylinder system. The embodiments, examples, and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible. DETAILED DESCRIPTION OF THE INVENTION In a first embodiment, the suspension system 1 comprises a single-acting, front-mounted 35-cylinder arrangement. A cylindrical damper 5, or strut, provides shock absorption in a conventional double-wishbone suspension system 7. A Unlike a conventional strut arrangement with a single coil spring mounted coaxially around the strut, two coil springs, typically with different spring rates, are mounted coaxially in series around the cylindrical damper or strut 5. These are a primary coil spring 9 with a spring rate K1 and a secondary coil spring 11 with a spring rate K2. A common spring stop 13 connects the two coil springs 9 and 11. The primary coil spring 9 is connected to, or abuts, an upper mounting 15 at the free end 16 of the strut 5. A lower spring stop 17 is connected to, or abuts, the secondary coil spring 11 distal to the common spring stop 13. In a spring system comprising two springs connected in series, the combined spring rate KT is defined by the equation 1 / KT = 1 / K1 + 1 / K2. A hydraulic cylinder actuator 20 is mounted around the cylindrical damper 5 between the lower spring stop 17 and the non-free end 21 of the cylindrical damper 5. Although a preferred hydraulic cylinder actuator is described, the actuator may comprise any convenient mechanism, including electric, pneumatic, or otherwise. When the secondary coil spring 11 is fully extended so that the lower spring stop 17 rests on the suspension components 23 below, and the actuator 20 is retracted, the secondary spring 11 does not contribute to the overall spring rate KT. In this condition, the secondary spring rate K2 is removed from the equation so that the spring rate is defined as 1 / KT = 1 / K1. This corresponds to a stiffer suspension because the combined spring rate of the two springs in series is always lower than the single spring rate of any one spring. This also corresponds to a lower ride height for optimal handling under road conditions such as a smooth highway or racetrack. This lower ride height configuration is illustrated in Figures 3A, 4A, and 4B. As actuator 20 extends under hydraulic pressure, it compresses the secondary coil spring 11 until, at a certain point, the spring stop 13 disengages from a spring stop 12, and the secondary coil spring 11 begins to contribute again to the overall spring rate according to the formula 1 / KT = 1 / K1 + 1 / K2. This corresponds to a softer suspension for optimal ride comfort, typically better under rougher road conditions. Ride height is also increased in this mode, which is preferable for vehicle clearance from potentially rougher road conditions. This comfort ride height setting, or trim mode, is illustrated in FIGURES 3B, 4C, and 4D. For driving under normal variable road conditions, the optimal ride comfort setting and height, or trim mode, can be selected by locking actuator 20 in a certain position relative to the cylindrical damper 5. On the actuator Rz Lznn / eznz / E / YiAi hydraulic illustrated 20, this is achieved by closing a valve 25 to stop the flow of hydraulic fluid 27 into and out of the actuator 20. The actuator 20 may comprise the hydraulic cylinder 19 slidably sealed to a hydraulic piston 29, which in turn is slidably sealed to the outer wall of the cylindrical damper 5. The position of the hydraulic piston 29 is determined by the volume of hydraulic fluid in a hydraulic chamber 33 defined by the inner wall 35 of the hydraulic cylinder 19, the outer wall 31 of the cylindrical damper 5, and the piston 29. The piston 29 may contact the lower spring stop 17 such that the hydraulic piston 29 and the lower spring stop 17 oscillate together relative to the cylindrical damper 5. As previously stated, seals 39 prevent the escape of hydraulic fluid between these components while allowing relatively low-friction reciprocating motion.Valve 25 can be closed to fix the volume of hydraulic fluid in hydraulic chamber 33 to secure actuator 20 in position for suspension system trim mode. For certain vehicle maneuvering purposes, it is advantageous to further increase the vehicle's height. For example, if a vehicle must descend a steep incline to enter a highway, additional vehicle height can be beneficial to prevent portions of the vehicle from contacting the road surface. In this situation, actuator 20 can be extended further to raise the front of the vehicle. The system in this extra raised position can be referred to as maneuvering mode, as illustrated in Figures 3C, 4E, and 4F. The vehicle is not intended to be driven at any significant speed in maneuvering mode, but it is a useful option under certain conditions. In a second embodiment, as illustrated in FIGURES 5A-5C, 6, and 7A-7B, the system comprises a front-mounted, dual-acting cylinder arrangement. As in the first embodiment, the single-acting cylinder arrangement, the suspension system of the second embodiment comprises a cylindrical damper 5 with primary and secondary coil springs 9, 11 connected in series and mounted coaxially around the cylindrical damper 5. In this embodiment, however, the spring stop 13 connecting the coil springs 9, 11 also comprises a reciprocating hydraulic cylinder 41 which moves along the cylindrical damper 5. Furthermore, the secondary coil spring 11 is fixed at its distal end from the spring stop 13, relative to the suspension components 23 to which the cylindrical damper 5 is attached.Therefore, the compression or decompression of springs 9, 11 is generated from a position between the springs by the hydraulic cylinder 41. Rz Lznn / eznz / E / YiAi The hydraulic cylinder 41 is mounted to reciprocate along a portion of the outer wall 37 of the cylindrical damper 5. Hydraulic chambers lie on either side of a piston between the hydraulic cylinder 41 and the outer wall 37 of the cylindrical damper 5. By supplying hydraulic fluid to one of the hydraulic chambers 43, 45, the hydraulic cylinder 41 is pushed to move in one direction along the cylindrical damper 5. In the illustrated embodiment, increased hydraulic fluid pressure in the first hydraulic chamber 43 pushes the hydraulic cylinder 41 to compress the primary coil spring 9 and raises the vehicle height. Conversely, increased hydraulic fluid pressure in the second hydraulic chamber 43 pushes the hydraulic cylinder 41 to compress the secondary coil spring 11 and lower the vehicle height.When the vehicle is lowered sufficiently, a valve 25 can be closed to further stop the flow of hydraulic fluid in hydraulic chambers 43, 45. This locks the hydraulic cylinder 41 relative to the cylindrical damper 5 and, because it cannot move, also prevents the secondary coil spring 11 from contributing to the overall spring rate KT. In this optimal handling mode, the overall spring rate KT equals the primary coil spring rate K1, and the spring rate is regulated by the equation 1 / KT = 1 / K1. When valve 25 is opened and the secondary coil spring 11 is allowed to contribute again to the overall spring rate, the spring rate is again regulated by the formula 1 / KT = 1 / K1 + 1 / K2. In this trim mode, which is an optimal comfort mode, the hydraulic cylinder 41 moves freely, regulated longitudinally by the compression of the primary and secondary coil springs 9, 11, hydraulic fluid flows freely between the first and second hydraulic chambers 43, 45, and the stroke height remains higher than in the optimal handling mode. A wall stop 47 may be provided on the outer wall 37 of the cylindrical damper 5 to abut a contact portion 49 of the hydraulic cylinder 41. The contact portion 49 abuts the wall stop 47 when sufficient hydraulic fluid is pushed into the first hydraulic chamber 43, which further raises the vehicle's height. This raised-height maneuvering mode may be maintained by closing valve 25 to again stop the flow of hydraulic fluid between the first and second hydraulic chambers 43, 45. It should be noted that an adjustable damping system is very beneficial for use in conjunction with the suspension system described to compensate for changes in spring rate and ride height. It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit from it. Although particular sequences of steps are shown, described, and claimed, it should be understood that the steps may be executed in any order, separately or in combination, unless otherwise indicated, and will still benefit from the present invention. Although the different examples have specific components shown in the illustrations, embodiments of this invention will not be limited to those combinations. Rz Lznn / eznz / E / YiAi particulars. It is possible to use some of the components or features of one of the examples in combination with features or components of another of the examples. Although an exemplary embodiment has been disclosed, a person skilled in the art would recognize that some modifications would fall within the scope of the claims. For this reason, the following claims should be examined to determine their true scope and content.

Claims

1. A selectively switchable dual-rate vehicle suspension system configured to be oriented between the unspringed mass and the springed mass of a corner of a vehicle, characterized in that it comprises: 5 a cylindrical damper; a primary coil spring having a first predetermined spring rate K1, and a secondary coil spring having a second predetermined spring rate K2, the coil springs being connected to a common spring stop and arranged around the cylindrical damper in series to provide a total combined spring rate KT; 10 an actuator mounted to the damper and configured to compress and decompress the coil springs; stop means configured to deactivate the secondary coil spring in at least one stop position;so that, when the system is in a first mode, the overall suspension spring rate is defined by the series equation 1 / KT = 1 / K1 + 1 / K2, and when the system is in a second mode, the overall vehicle suspension spring rate is defined by the series equation 1 / KT = 1 / K1, thereby selectively and switchably providing both an optimal low-rate ride comfort setting in the first mode and an optimal high-rate ride height setting in the second mode.

2. The suspension system according to claim 1, characterized in that the actuator comprises a hydraulic cylinder and a hydraulic piston.

3. The suspension system according to claim 2, characterized in that the hydraulic cylinder slides on an outer wall of the cylindrical shock absorber. 25 4. The suspension system according to claim 3, characterized in that the stopping means comprises a stopping portion of the outer wall of the cylindrical damper against which a contact portion of the hydraulic cylinder abuts.

5. The suspension system according to any of claims 1 to 4, characterized in that the actuator acts on the secondary coil spring through a lower spring stop 30.

6. The suspension system according to any of claims 1 to 5, characterized in that the secondary coil spring is deactivated when decompressed.

7. The suspension system according to any of claims 1 to 35, characterized in that it further comprises a third maneuvering mode in which both the secondary coil spring and the primary coil spring are compressed beyond the first mode to increase the vehicle ride height above that in the first mode, the optimum ride comfort configuration.

8. The suspension system according to any of claims 1 to 3, characterized in that the actuator comprises the common spring stop.

9. The suspension system according to claim 8, characterized in that the stopping means comprises a locking means configured to hold the secondary coil spring in multiple selected stopping positions.

10. The suspension system according to claim 9, characterized in that the locking means comprises a valve means for inhibiting the flow of a hydraulic fluid in the hydraulic cylinder.

11. The suspension system according to any of claims 8 to 10, characterized in that it further comprises a third maneuvering mode in which the secondary coil spring is decompressed and the primary coil spring is raised to increase a vehicle ride height above that in the first mode, the optimum ride comfort configuration.

12. The suspension system according to any of claims 1 to 11, characterized in that the cylindrical damper provides adjustable damping to match changes in spring rate for optimum comfort and vehicle handling.

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