Adjustable height dual rate vehicle suspension system

Abstract

A spring configuration comprises a cylindrical damper (5), a primary coil spring (9) having a first predetermined spring rate K1 and a secondary coil spring (11) having a second predetermined spring rate K2, the coil springs being arranged in series around the cylindrical damper (5) to provide a total combined spring rate KT, an actuator (20) configured to compress and decompress the coil springs (9, 11), a stop (12) configured to deactivate the secondary coil spring in a stop position such that: when the system is in a first comfort mode, the total 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 total vehicle suspension spring rate is defined by the series equation KT = K1, thereby selectively and switchably providing a low stiffness, best-in-class ride comfort setting and a high stiffness, best-in-class handling, lower ride height setting.

Description

Technical Field

[0001] This invention relates to a suspension system for wheeled vehicles, and more particularly to a suspension system that provides two different operating modes. To overcome the inherent trade-off between optimal ride comfort and optimal on-road vehicle handling, this invention provides a dual-mode suspension system in which the stiffness of the main spring can be switched between an optimal handling setting and an optimal ride setting. Background Technology

[0002] The fundamental premise of motor vehicle suspension is to allow the vehicle's wheels to move independently over road disturbances (such as bumps), rather than allowing the entire vehicle and its occupants to move in this way. When passengers are not directly affected by road disturbances, passenger comfort is significantly improved. Significant fuel economy can also be achieved by moving only the wheels, rather than the entire vehicle, to overcome road disturbances. Furthermore, because the overall vehicle mass does not tilt when overcoming road disturbances, vehicle steering control is significantly enhanced at increased speeds.

[0003] While vehicle suspensions can be constructed in various ways, they typically use an energy storage medium (usually some type of spring) to isolate the main body (called "sprung mass") from the wheel system (called "unsprung mass"). When a road disturbance causes the wheel system, including the wheel hubs, brakes, and motion control linkages, to move relative to the main body, the spring stores energy. Once the disturbance has passed, the spring releases its stored energy, allowing the wheel system to return to its undisturbed state. To avoid uncontrolled vibrational responses in a simple spring-mass system, some form of damping is employed. Typically, hydraulically based components generate a force proportional to velocity to provide resistance in both directions of spring movement, helping the spring return to zero velocity from its undisturbed position. This damper is an auxiliary component and does not support the weight of the vehicle.

[0004] As a vehicle approaches its dynamic response limits, the suspension system (including motion control linkages and energy storage and damping components) becomes a limiting factor in achieving optimal performance. If the springs and dampers are made relatively soft to provide a high degree of isolation between the occupants and road disturbances, the sprung mass tends to over-move in response to the lateral and longitudinal forces generated by the driver's steering, acceleration, and braking demands. These demands result in what is commonly referred to as "handling response," while the mass responsible for occupant isolation is known as "riding response."

[0005] By altering the stiffness and damping coefficient at each of the four wheel corners, a vehicle's ride and handling performance can be optimized. Generally, a stiffer stiffness (measured as force per unit displacement) results in a firmer ride and better body control, while a softer stiffness provides a smoother ride but less control. The damping coefficient typically translates directly to its associated stiffness. Unfortunately, lower stiffness produces better ride response, while higher stiffness produces better handling response. Historically, this has led to vehicles becoming compromises between ride and handling responses.

[0006] Many adaptive and manual dual-stiffness suspension systems have been described in this field. However, until recently, no system has been able to provide the characteristics required for performance vehicles using metal energy storage devices such as coil springs, leaf springs, or torsion springs.

[0007] Holt et al. describe a selectively switchable dual-stiffness suspension system in PCT / US2017 / 012588. The pushrod-activated inner spring configuration comprises a torsion bar and a coil spring in series, each with its own elastic stiffness. A locking actuator is arranged parallel to the coil spring. In a first mode, the coil spring is allowed free movement, such that the total elastic stiffness is contributed by both the torsion bar and coil spring elastic stiffness. In a second locking mode, the movement of the coil spring is restricted, thereby changing the total elastic stiffness to the elastic stiffness of the torsion bar. This selectively provides an optimal ride height comfort setting with low stiffness and an optimal handling setting with lower ride height with high stiffness. While this selectively switchable dual-stiffness suspension system is very effective, the use of its pushrod configuration limits its use in general high-performance vehicles. Therefore, there is a need for a selectively switchable dual-stiffness suspension system that can be used in a wider range of autonomous vehicles.

[0008] Numerous attempts have been made to design more universally applicable dual-stiffness suspension systems. However, none of them provide an active, selective switching of ride height in the optimal handling mode at high elastic stiffness. For example, Doerfel's US 2009 / 0302559 describes a non-manually adjustable configuration with two coil springs arranged around a strut. The spring assembly has a primary spring, a slider, a stop, and at least one auxiliary spring connected in series with the primary 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. Alternative arrangements with the springs connected in parallel are also described. Similar configurations are described in Wakeman's US 9162548 and Mason's US 9821621. Neither involves complete locking of a single spring. Mason generally seeks to maintain ride height, while Wakeman allows the ride height to rise from unloaded or neutral, but not to lower it. Neither provides a method for lowering the ride height in the optimal handling mode at high elastic stiffness. Summary of the Invention

[0009] In one key aspect of the invention, a selectively switchable dual-stiffness vehicle suspension system includes: a spring configuration typically oriented between the unsprung mass and sprung mass at a corner of the vehicle, comprising a cylindrical damper, a primary coil spring having a first predetermined elastic stiffness K1, and a secondary coil spring having a second predetermined elastic stiffness K2, the coil springs being arranged in series around the cylindrical damper to provide a total combined elastic stiffness KT; an actuator configured to compress and decompress the coil springs; and a stop configured to deactivate the secondary coil springs in a stop position, such that when the system is in a first comfort mode, the total suspension elastic stiffness is defined by the series equation 1 / KT = 1 / K1 + 1 / K2, and when the system is in a second handling mode, the total vehicle suspension elastic stiffness is defined by the series equation KT = K1, thereby selectively and switchably providing both an optimal ride comfort setting with low stiffness and an optimal handling lower ride height setting with high stiffness.

[0010] In a further aspect of the invention, both the main helical spring and the auxiliary helical spring are connected to the intermediate spring support.

[0011] In a further aspect of the invention, the actuator acts on the secondary helical spring via a lower spring support.

[0012] In a further aspect of the invention, the actuator includes a hydraulic cylinder and a hydraulic piston.

[0013] In a further aspect of the invention, the secondary helical spring is deactivated during decompression.

[0014] In a further aspect of the invention, the intermediate spring support includes a hydraulic cylinder with a hydraulic piston.

[0015] In a further aspect of the invention, the secondary helical spring is deactivated during compression.

[0016] In a further aspect of the invention, the hydraulic cylinder is mounted on the outer wall of the cylindrical damper.

[0017] In a further aspect of the invention, the stop member includes a stop portion of the outer wall of a cylindrical damper, and a contact portion of the hydraulic cylinder abuts against the stop portion.

[0018] In a further aspect of the invention, the suspension system also includes a locking device configured to hold the sub-coil spring in the actuated position.

[0019] In a further aspect of the invention, the suspension system also includes a third operating mode in which the secondary coil spring is depressurized while the primary coil spring is raised to increase the ride height above the optimal ride comfort setting.

[0020] In a further aspect of the invention, the cylindrical damper provides adjustable damping to match variations in elastic stiffness, thereby achieving optimal vehicle comfort and handling. Attached Figure Description

[0021] Figure 1A A perspective view of a front component single-acting cylinder system installed in a conventional double wishbone suspension system is shown. This system is used at one corner of the vehicle, typically at the front corner.

[0022] Figure 1B , 1C The diagram shows a three-dimensional isolated view of the front component single-acting cylinder system viewed from multiple angles.

[0023] Figure 2A A cross-sectional view of a portion of a single-acting cylinder system is shown.

[0024] Figure 2B A perspective view of a portion of a single-acting cylinder system and certain damper components is shown.

[0025] Figure 3A , 3B The images and 3C respectively show, in multiple front views, the front component single-acting cylinder system mounted on a conventional double wishbone suspension system in vehicle height configurations that are lowered, adjusted, and raised.

[0026] Figure 4A and 4B The front assembly single-acting cylinder system in a lowered vehicle height configuration is shown in paired cross-sectional views and standard diagrams of the system.

[0027] Figure 4C and 4D The front assembly single-acting cylinder system in the vehicle height adjustment configuration is shown in paired cross-sectional views and standard views.

[0028] Figure 4E and 4F The front assembly single-acting cylinder system in an elevated vehicle height configuration is shown in paired cross-sectional views and standard views.

[0029] Figure 5A The alternative front-component dual-acting cylinder system is shown in a 3D isolated diagram.

[0030] Figure 5B A three-dimensional isolation diagram is shown. Figure 5A The partial unfolded portion of the replacement front component double-acting cylinder system.

[0031] Figure 5C This shows from another perspective Figure 5A The replacement for the front component double-acting cylinder system.

[0032] Figure 6 A cross-sectional view of a portion of this double-acting cylinder system is shown.

[0033] Figure 7A A front view of an alternative front component dual-acting cylinder system installed in a conventional double wishbone suspension system is shown.

[0034] Figure 7B A three-dimensional isolation diagram of the alternative front-component double-acting cylinder system is shown.

[0035] The embodiments, examples, and alternatives (including their various aspects or individual features) described in the foregoing paragraphs, claims, or the following description and drawings may be carried out independently or in any combination. Features described in conjunction with one embodiment may be applied to all embodiments unless those features are incompatible. Detailed Implementation

[0036] In a first embodiment, the suspension system 1 includes a front assembly and a single-acting cylinder assembly 3. A cylindrical damper 5 or strut provides damping in a conventional double wishbone 7 suspension system. Unlike a conventional strut arrangement with a single coil spring mounted coaxially around the strut, two coil springs (typically with different elastic stiffnesses) are mounted in series coaxially around the cylindrical damper or strut 5. These are a primary coil spring 9 with elastic stiffness K1 and a secondary coil spring 11 with elastic stiffness K2. A common spring support 13 connects the two coil springs 9 and 11. The primary coil spring 9 is connected to or abuts against a top mount 15 at the free end 16 of the strut 5. A lower spring support 17 is connected to or abuts against the secondary coil spring 11 located away from the common spring support 13.

[0037] In a spring system comprising two springs connected in series, the combined elastic stiffness KT is defined by the equation 1 / KT = 1 / K1 + 1 / K2.

[0038] The hydraulic cylinder actuator 20 is mounted around the cylindrical damper 5 between the lower spring support 17 and the non-free end 21 of the cylindrical damper 5. Although a preferred hydraulic cylinder actuator has been described, the actuator may include any suitable mechanism, including electric, pneumatic, or other types.

[0039] When the secondary coil spring 11 is fully extended, causing the lower spring support 17 to rest against the lower suspension component 23 and the actuator 20 to retract, the secondary spring 11 does not contribute to the total elastic stiffness KT. In this case, the secondary elastic stiffness K2 deviates from the equation, making the elastic stiffness defined as 1 / KT = 1 / K1. This corresponds to a stiffer suspension because the combined elastic stiffness of the two springs in series is always lower than the individual elastic stiffness of either spring alone. It also corresponds to a lower ride height for optimal handling on road conditions such as flat roads or racetracks. Figure 3A , 4A The 4B illustrates this lower chassis height configuration.

[0040] When actuator 20 extends under hydraulic pressure, it compresses sub-coil spring 11 until, at a certain point, spring support 13 lifts off spring stop 12, and sub-coil spring 11 begins to contribute to the total elastic stiffness again according to formula 1 / KT = 1 / K1 + 1 / K2. This corresponds to a softer suspension for optimal ride comfort, typically best on bumpy roads. In this mode, ride height also increases, which is preferable for the vehicle's ground clearance from potentially bumpy road conditions. Figure 3B , 4C The 4D diagram illustrates the construction of this comfortable ride height or adjustment mode.

[0041] For driving under normal varying road conditions, the optimal ride comfort setting and height or adjustment mode can be selected by locking the actuator 20 in a specific position associated with the cylindrical shock absorber 5. In the illustrated hydraulic actuator 20, this is achieved by closing the valve 25 to prevent the flow of hydraulic fluid 27 into and out of the actuator 20.

[0042] Actuator 20 may include a hydraulic cylinder 19 slidably sealed to a hydraulic piston 29, which in turn is slidably sealed to the outer wall of a 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 a lower spring support 17, such that the hydraulic piston 29 and the lower spring support 7 reciprocate back and forth relative to the cylindrical damper 5. As previously described, seal 39 prevents hydraulic fluid from escaping between these components while allowing relatively low-friction reciprocating motion. Valve 25 may be closed to fix the volume of hydraulic fluid in the hydraulic chamber 33 to lock actuator 20 in a position for suspension system adjustment mode.

[0043] For certain vehicle handling purposes, further increasing the vehicle height is advantageous. For example, if a vehicle must descend a steep lane to enter the road, the additional vehicle height helps prevent parts of the vehicle from contacting the lane or road surface. In this case, actuator 20 can extend further to raise the front of the vehicle. Figure 3C , 4E As shown in 4F, the system in this additional elevated position can be called the handling mode. In handling mode, there is no intention to drive the vehicle at any significant speed, but it is a useful option in certain situations.

[0044] In the second embodiment, such as Figures 5A-5C As shown in Figures 6 and 7A-7B, the system includes a front assembly and a double-acting cylinder assembly. Similar to the single-acting cylinder arrangement in the first embodiment, the suspension system of the second embodiment includes a cylindrical damper 5 and has a main coil spring 9 and a secondary coil spring 11 connected in series and coaxially mounted around the cylindrical damper 5. However, in this embodiment, the spring support 13 connecting the coil springs 9 and 11 also includes a reciprocating hydraulic cylinder 41 that moves along the cylindrical damper 5. Furthermore, the secondary coil spring 11 is fixed relative to the suspension component 23 attached to the cylindrical damper 5 at its distal end away from the spring support 13. Therefore, compression or decompression of the springs 9 and 11 is generated from the position between the springs by the hydraulic cylinder 41.

[0045] Hydraulic cylinder 41 is mounted to reciprocate along a portion of the outer wall 37 of cylindrical damper 5. Hydraulic chambers are located on either side of the piston between hydraulic cylinder 41 and the outer wall 37 of cylindrical damper 5. By supplying hydraulic fluid to one of the hydraulic chambers 43 and 45, hydraulic cylinder 41 is forced to move along cylindrical damper 5 in one direction. In the illustrated embodiment, the increased hydraulic fluid pressure in the first hydraulic chamber 43 forces hydraulic cylinder 41 to compress the main helical spring 9, thereby raising the vehicle height. Conversely, the increased hydraulic fluid pressure in the second hydraulic chamber 43 forces hydraulic cylinder 41 to compress the auxiliary helical spring 11, thereby lowering the vehicle height. When the vehicle has fully lowered, valve 25 can be closed to stop further flow of hydraulic fluid in hydraulic chambers 43 and 45. This locks hydraulic cylinder 41 relative to cylindrical damper 5, and because hydraulic cylinder 41 is restricted from movement, the auxiliary helical spring 11 is also locked and cannot contribute to the total elastic stiffness KT. In this optimal control mode, the total elastic stiffness KT is equal to the elastic stiffness K1 of the main helix, and the elastic stiffness is controlled by the equation 1 / KT = 1 / K1.

[0046] When valve 25 opens, allowing the secondary helical spring 11 to contribute to the total elastic stiffness again, the elastic stiffness is once again controlled by the formula 1 / KT = 1 / K1 + 1 / K2. In this adjustment mode, which is the optimal comfort mode, the hydraulic cylinder 41 moves freely longitudinally under the compression of the main helical spring 9 and the secondary helical spring 11, the hydraulic fluid flows freely between the first hydraulic chamber 43 and the second hydraulic chamber 45, and the riding height remains higher than the optimal operating mode.

[0047] A wall stop 47, a contact portion 49 abutting against the hydraulic cylinder 41, can be provided on the outer wall 37 of the cylindrical damper 5. When sufficient hydraulic fluid is forced into the first hydraulic chamber 43, the contact portion 49 abuts against the wall stop 47, which further increases the vehicle height. This height-increasing operating mode can be maintained by closing the valve 25 to stop the flow of hydraulic fluid between the first hydraulic chamber 43 and the second hydraulic chamber 45 again.

[0048] It should be noted that the adjustable damping system is highly advantageous for use with the described suspension system to compensate for variations in elastic stiffness and ride height.

[0049] It should also be understood that although a particular arrangement of components is disclosed in the illustrated embodiment, other arrangements will benefit therefrom. Although a particular sequence of steps has been shown, described, and claimed, it should be understood that these steps may be performed, separated, or combined in any order, unless otherwise indicated, and will still benefit from the invention.

[0050] Although the different examples have the specific components shown in the illustrations, the implementation of the invention is not limited to those specific combinations. Some components or features of one example can be combined with features or components of another example.

[0051] Although exemplary embodiments have been disclosed, those skilled in the art will recognize that certain modifications will fall within the scope of the claims. Therefore, the following claims should be examined to determine their true scope and content.

Claims

1. A selectively switchable dual-stiffness vehicle suspension system, the dual-stiffness vehicle suspension system being configured to be oriented between the unsprung mass and sprung mass at one corner of the vehicle, comprising: Cylindrical damper; A main helical spring having a first predetermined elastic stiffness K1 and a secondary helical spring having a second predetermined elastic stiffness K2 are both connected to a common spring support and are arranged in series around the cylindrical damper to provide a total combined elastic stiffness KT. An actuator, which is mounted to the cylindrical damper and configured to compress and depress the main helical spring and the secondary helical spring based on the position of the actuator relative to the cylindrical damper, wherein the actuator includes the common spring support; and A stop device configured to deactivate the secondary helical spring in at least one stop position; When the dual-stiffness vehicle suspension system is in a first mode, the actuator is positioned to compress the primary coil spring and the secondary coil spring, and the total suspension stiffness is defined by the series equation 1 / KT = 1 / K1 + 1 / K2. When the dual-stiffness vehicle suspension system is in a second mode, the actuator is positioned to depress and deactivate the secondary coil spring, and the total suspension stiffness is defined by the series equation 1 / KT = 1 / K1. This allows for selective and switchable provision of low stiffness, optimal ride comfort, and increased ride height in the first mode, and high stiffness, optimal handling, and lower ride height in the second mode.

2. The dual-stiffness vehicle suspension system according to claim 1, wherein, The actuator includes a hydraulic cylinder and a hydraulic piston.

3. The dual-stiffness vehicle suspension system according to claim 2, wherein, The hydraulic cylinder is mounted on the outer wall of the cylindrical damper.

4. The dual-stiffness vehicle suspension system according to any one of claims 1 to 3, wherein, The secondary helical spring is deactivated during decompression.

5. The dual-stiffness vehicle suspension system according to claim 2, wherein, The stop device includes a locking device configured to hold the secondary helical spring in a plurality of selectable stop positions.

6. The dual-stiffness vehicle suspension system according to claim 5, wherein, The locking device includes a valve that prevents the flow of hydraulic fluid in the hydraulic cylinder.

7. The dual-stiffness vehicle suspension system according to claim 1 further includes a third control mode, wherein, The secondary coil spring is depressurized and the primary coil spring is raised to increase the vehicle's ride height above the optimal ride comfort setting in the first mode.

8. The dual-stiffness vehicle suspension system according to claim 1, wherein, The cylindrical damper provides adjustable damping to match variations in elastic stiffness in order to achieve optimal vehicle comfort and handling.

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