Dual rate vehicle suspension system with adjustable ride height - Patents.com

Abstract

The spring structure includes a cylindrical damper (5), a primary coil spring (9) having a first predetermined spring rate Kl, and a secondary coil spring (11) having a second predetermined spring rate K2, the coil springs arranged in series around the cylindrical damper to provide an overall resultant spring rate KT, an actuator (20) configured to compress and decompress the coil springs (9, 11), and a stop (12) configured to deactivate the secondary coil spring at a stop position, wherein when the system is in a first comfort mode, the overall suspension spring rate is defined by the series equation 1 / KT = 1 / Kl + 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 = Kl, thereby selectively and switchably providing both a low rate, optimum ride comfort setting and a high rate, optimum handling, low ride height setting.

Description

[Technical field]

[0001] The present invention relates to suspension systems for vehicles, and more particularly to suspension systems that provide 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, the present invention provides a dual mode suspension system in which the rate of the primary load coil spring can be switched between an optimum handling setting and an optimum ride comfort setting. [Background technology]

[0002] The basic premise of automotive suspension is to allow the wheels of a vehicle to independently ride up and over road disturbances such as bumps, without causing the entire vehicle and its occupants to do so. Passenger comfort is greatly improved when the passengers are not directly affected by the road disturbances. Also, significant energy savings are realized by only allowing the wheels, rather than the entire vehicle, to move over road disturbances. Additionally, because the entire mass of the vehicle does not pitch over road disturbances, steering control of the vehicle is greatly improved with increasing speed.

[0003] Vehicle suspensions can be configured in a variety of ways, but are generally arranged to separate the vehicle body, called the "sprung mass," from the wheel system, called the "unsprung mass," using an energy storage medium, usually some type of spring. The spring stores energy so that the wheel system, including the hub, brakes, and motion control linkages, can move relative to the vehicle body in response to road disturbances. Once the disturbance has passed, the spring releases its stored energy to return the wheel system to an undisturbed condition. To avoid uncontrolled oscillatory response in a simple spring-mass system, some form of damping device is used. Typically, a hydraulic-based component generates a force proportional to velocity to provide resistance in both directions of spring motion and assist the spring in returning to zero velocity at the undisturbed position. This damper is a secondary component that does not support the weight of the vehicle.

[0004] As the limits of a vehicle's dynamic response are approached, the suspension system, including the motion control linkages and the energy storage and damping components, becomes the limiting factor in reaching optimal performance levels. Tuning the springs and dampers relatively softly to provide a high degree of occupant isolation from road disturbances tends to cause the sprung mass 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 commonly referred to as "handling response," while the quality of occupant isolation is referred to as "ride response."

[0005] By varying the spring rate (spring constant) and damping coefficient at each of the four wheel corners, the ride and handling performance of the vehicle can be optimized. Generally, a stiffer spring rate, measured in force per unit displacement, results in a stiffer ride and better body control, while a softer spring rate provides a softer ride but less control. The damping coefficient is usually matched directly to the associated spring rate. Unfortunately, optimal ride response occurs with low spring rates and optimal handling response occurs with high spring rates. This has historically led to vehicles being tuned for a compromise between ride response and handling response.

[0006] There are many adaptive and manual dual rate suspension systems described in the art, however, until recently, none have been able to provide the required performance vehicle characteristics using metallic energy storage devices such as coil, leaf, or torsion springs.

[0007] A selectively switchable dual rate suspension system is described in US Patent No. 5,399,323 to Holt et al. A pushrod actuated inner spring structure includes a torsion bar and a coil spring in series, each with its own spring rate. A lockout actuator is positioned in parallel with the coil spring. In a first mode, the coil spring is free to move, so that the overall spring rate is contributed by both the torsion bar spring rate and the coil spring rate. In a second, locked out mode, the coil spring is prevented from moving, and the overall spring rate is changed to the torsion bar spring rate. This selectively provides both a low rate, optimum ride height, comfort setting, and a high rate, low ride height, optimum handling setting. While this selectively switchable dual rate suspension system is highly effective, its pushrod configuration generally limits its use to very high performance vehicles. Thus, there is a need for a selectively switchable dual rate suspension system that can be used on a wider range of automobiles. Several attempts have been made to design a more generally applicable dual-rate suspension system. However, none of them are actively and selectively switchable systems that provide a lower ride height in the optimum handling mode with a higher spring rate. For example, US Pat. No. 5,399,433 to Doerfel describes a non-manually adjustable structure with two coil springs arranged around a strut. The spring assembly has a master spring, a slide, 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 slide and prevents further compression of the auxiliary spring. Alternative configurations with parallel connected springs are also described. US Pat. No. 5,399,433 to Wakeman and US Pat. No. 5,399,433 to Mason describe similar structures. Neither involves a complete lockout of one spring. Mason attempts to maintain ride height overall, while Wakeman can raise but not lower the ride height from an unloaded or neutral condition. Neither provides a means to lower the ride height in the optimum handling mode with a higher spring rate. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2017 / 120509 (PCT / US2017 / 012588) [Patent Document 2] US Patent Application Publication No. 2009 / 0302559 [Patent Document 3] U.S. Pat. No. 9,162,548 [Patent Document 4] U.S. Pat. No. 9,821,621 Summary of the Invention [Means for solving the problem]

[0009] In a main aspect of the present invention, a selectively switchable dual-rate vehicle suspension system is conventionally oriented between the unsprung mass and the sprung mass at one corner of the vehicle and includes a cylindrical damper, a primary coil spring having a predetermined first spring rate K1, and a secondary coil spring having a predetermined second spring rate K2. The primary coil spring and the secondary coil spring are arranged in series around the cylindrical damper to provide a spring structure for the overall combined spring rate KT, an actuator configured to compress and decompress the primary coil spring and the secondary coil spring, and a stopper configured to deactivate the secondary coil spring in a stop position. When the suspension system is in a first comfort mode, the overall suspension spring rate is defined by the series equation 1 / KT = 1 / K1 + 1 / K2. When the suspension 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 an optimal ride comfort setting at a low rate and an optimal handling low ride height setting at a high rate.

[0010] In a further aspect of the present invention, both the primary coil spring and the secondary coil spring are connected to an intermediate spring abutment.

[0011] In a further aspect of the present invention, the actuator acts on the secondary coil spring via a lower spring abutment.

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

[0013] In a further aspect of the present invention, the secondary coil spring is deactivated when decompressed.

[0014] In a further aspect of the present invention, the intermediate spring abutment includes a hydraulic cylinder having a hydraulic piston.

[0015] In a further aspect of the present invention, the secondary coil spring is deactivated when compressed.

[0016] In a further aspect of the invention, the hydraulic cylinder rests against the outer wall of the cylindrical damper.

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

[0018] In a further aspect of the invention, the suspension system further includes a lockout means configured to hold the secondary coil spring in a parked position.

[0019] In a further aspect of the invention, the suspension system further includes a third steering mode that decompresses the secondary coil spring and raises the primary coil spring to increase ride height above an optimum ride comfort setting.

[0020] In a further aspect of the present invention, the cylindrical damper provides adjustable damping to accommodate changes in spring rates for optimum vehicle comfort and handling. [Brief description of the drawings]

[0021] [Figure 1A] FIG. 1 shows a perspective view of a front assembly single acting cylinder system mounted on a conventional double wishbone suspension system for use at one corner of a vehicle, typically the front corner.

[0022] [Figure 1B] 1 shows perspective isolated views of the front assembly single acting cylinder system from various angles. [Figure 1C] 1 shows perspective isolated views of the front assembly single acting cylinder system from various angles. [Figure 1D] 1 shows perspective isolated views of the front assembly single acting cylinder system from various angles.

[0023] [Figure 2A] FIG. 1 shows an elevational cross-sectional view of a portion of a single-acting cylinder system.

[0024] [Figure 2B] FIG. 1 illustrates a perspective view of a portion of a single-acting cylinder system and certain damper components.

[0025] [Diagram 3] 3A, 3B and 3C show multiple elevation views of a front assembly single acting cylinder system mounted on a conventional double wishbone suspension system in lowered, trimmed and raised ride height configurations, respectively.

[0026] [Figure 4A-4B] 4A and 4B show the front assembly single acting cylinder system in a pair of elevational sectional and standard views of the system in a lowered ride height configuration.

[0027] [Fig. 4C-4D] 4C and 4D show the front assembly single acting cylinder system in a pair of elevational sectional and standard views of the system in a trimmed ride height configuration.

[0028] [Fig. 4E-4F] 4E and 4F show the front assembly single acting cylinder system in a pair of elevational sectional and standard views of the system in an elevated ride height configuration.

[0029] [Diagram 5] FIG. 5A illustrates an alternative front assembly double acting cylinder system in a perspective isolated view.

[0030] FIG. 5B illustrates a partially enlarged perspective isolated view of the alternative front assembly double acting cylinder system of FIG. 5A.

[0031] FIG. 5C shows the alternative front assembly double acting cylinder system of FIG. 5A from another angle.

[0032] [Figure 6] FIG. 1 shows an elevational cross-sectional view of a portion of a double-acting cylinder system.

[0033] [Figure 7] FIG. 7A shows an elevation view of an alternative front assembly double acting cylinder system mounted on a conventional double wishbone suspension system.

[0034] FIG. 7B shows a perspective isolated view of an alternative front assembly double acting cylinder system.

[0035] The embodiments, examples and alternatives of the previous paragraphs, claims or the following description and drawings, including any of their various aspects or their respective individual features, can be taken independently or in any combination. Features described in relation to one embodiment are applicable to all embodiments, unless such features are incompatible. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] In a first embodiment, the suspension system 1 includes a front assembly single acting cylinder arrangement 3. A cylindrical damper 5, or strut, provides shock absorption in a conventional double wishbone 7 suspension system. Unlike a conventional strut arrangement where a single coil spring is 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 abutment 13 serves to connect the two coil springs 9, 11. The primary coil spring 9 is connected or abuts a top mount 15 at a free end 16 of the strut 5. A lower spring abutment 17 is connected or abuts the secondary coil spring 11 distal from the common spring abutment 13.

[0037] For a spring system containing two springs connected in series, the resultant spring rate KT is defined by the equation 1 / KT=1 / K1+1 / K2.

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

[0039] When the secondary coil spring 11 is fully extended so that the lower spring abutment 17 rests on the lower suspension component 23, 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 drops out of the equation and the spring rate is defined as 1 / KT = 1 / K1. This corresponds to a stiffer suspension since the combined spring rate of two springs in series is always lower than the single spring rate of either spring alone. This also corresponds to a lower ride height for optimal handling on road conditions such as smooth highways or race tracks. This lower ride height configuration is shown in Figures 3A, 4A and 4B.

[0040] As the actuator 20 hydraulically extends, it compresses the secondary coil spring 11 until at a certain point the spring abutment 13 lifts off the spring stop 12 and the secondary coil spring 11 begins to contribute to the overall spring rate again according to the formula 1 / KT=1 / K1+1 / K2. This corresponds to a softer suspension for optimal ride comfort, typically best suited for rougher road conditions. This mode also results in a higher ride height, which is favorable for vehicle clearance from potentially rougher road conditions. This comfortable ride height or trim mode configuration is shown in Figures 3B, 4C and 4D.

[0041] For driving in normal and variable road conditions, the optimum ride setting and height, or trim mode, can be selected by locking the actuator 20 in a particular position relative to the cylindrical damper 5. In the illustrated hydraulic actuator 20, this is accomplished by closing valve 25 to stop the flow of hydraulic fluid 27 to and from the actuator 20.

[0042] The actuator 20 may include a hydraulic cylinder 19 slidably sealed to a hydraulic piston 29, which in turn is slidably sealed to an 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 an inner wall 35 of the hydraulic cylinder 19, an outer wall 31 of the cylindrical damper 5, and the piston 29. The piston 29 may contact the lower spring abutment 17 such that the hydraulic piston 29 and the lower spring abutment 17 reciprocate in tandem relative to the cylindrical damper 5. As previously indicated, the seal 39 prevents leakage of hydraulic fluid between these components while allowing for relatively low friction reciprocating motion. The valve 25 may be closed to define the volume of hydraulic fluid in the hydraulic chamber 33 and lock the actuator 20 in position for the trim mode of the suspension system.

[0043] For certain vehicle maneuvering purposes, it is advantageous to have an even higher ride height. For example, if the vehicle must go down a steep driveway to enter the roadway, a higher ride height may be beneficial to prevent any part of the vehicle from contacting the driveway or road surface. In this situation, the actuator 20 can be extended further to raise the front of the vehicle. The system in this special raised position can be referred to as a steering mode as shown in Figures 3C, 4E and 4F. Although the steering mode does not intend to drive the vehicle at any significant speed, it is a useful option in certain conditions.

[0044] In a second embodiment, as shown in Figures 5A-5C, 6 and 7A-7B, the system includes a front assembly double-acting cylinder device. Similar to the first embodiment, the single-acting cylinder device, the suspension system of the second embodiment includes a cylindrical damper 5 with primary and secondary coil springs 9, 11 connected in series and mounted coaxially around the cylindrical damper 5. However, in this embodiment, the spring abutment 13 connecting the coil springs 9, 11 also includes a reciprocating hydraulic cylinder 41 that moves along the cylindrical damper 5. Also, the secondary coil spring 11 is fixed at an end distal to the spring abutment 13 relative to the suspension component 23 to which the cylindrical damper 5 is mounted. In this manner, compression or decompression of the springs 9, 11 occurs from a position between the springs by the hydraulic cylinder 41.

[0045] The hydraulic cylinder 41 is mounted for reciprocating movement along a portion of the outer wall 37 of the cylindrical damper 5. Hydraulic chambers are on either side of the piston between the hydraulic cylinder 41 and the outer wall 37 of the cylindrical damper 5. The hydraulic cylinder 41 is biased to move in one direction along the cylindrical damper 5 by supplying hydraulic fluid to one of the hydraulic chambers 43, 45. In the illustrated embodiment, when hydraulic fluid pressure in the first hydraulic chamber 43 increases, the hydraulic cylinder 41 compresses the primary coil spring 9, raising the vehicle height. In contrast, when hydraulic fluid pressure in the second hydraulic chamber 43 increases, the hydraulic cylinder 41 compresses the secondary coil spring 11, lowering the vehicle height. When the vehicle has been sufficiently lowered, the valve 25 can be closed to stop further flow of hydraulic fluid in the hydraulic chambers 43, 45. This locks the hydraulic cylinder 41 against the cylindrical damper 5 and restricts its movement, so that the secondary coil spring 11 is also locked out from contributing to the overall spring rate KT. In this optimum handling mode, the total spring rate KT is equal to the primary coil spring rate K1, and the spring rates are determined by the equation 1 / KT=1 / K1.

[0046] By opening valve 25 and allowing the secondary coil spring 11 to again contribute to the overall spring rate, the spring rate is again determined by the equation 1 / KT=1 / K1+1 / K2. In this trim mode, which is the optimum comfort mode, the hydraulic cylinder 41 is free to move longitudinally as controlled by the compression of the primary and secondary coil springs 9, 11, hydraulic fluid flows freely between the first hydraulic chamber 43 and the second hydraulic chamber 45, and the ride height remains higher than in the optimum handling mode.

[0047] The outer wall 37 of the cylindrical damper 5 may be provided with a wall stop 47 which abuts against a contact portion 49 of the hydraulic cylinder 41. The contact portion 49 abuts against the wall stop 47 when sufficient hydraulic fluid is forced into the first hydraulic chamber 43, thereby further increasing the vehicle height. This increased height mode of operation may be maintained by closing the valve 25 to again stop the flow of hydraulic fluid between the first hydraulic chamber 43 and the second hydraulic chamber 45.

[0048] It should be noted that an adjustable damping system, when used with the described suspension system, is highly beneficial in compensating for changes in spring rate and ride height.

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

[0050] Although different examples have specific components shown in the figures, the embodiments of the present invention are not limited to those specific combinations. Some of the components or features of one example can be used in combination with the features or components of another example.

[0051] While exemplary embodiments have been disclosed, those of ordinary skill in the art will recognize that certain modifications would come within the scope of the following claims, and therefore the following claims should be studied to determine their true scope and content.

Claims

1. 1. A selectively switchable dual rate vehicle suspension system configured to be disposed between an unsprung mass and a sprung mass at one corner of a vehicle, the system comprising: 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 primary coil spring (9) and the secondary coil spring (11) both connected to a common spring abutment (13) and arranged in series around the cylindrical damper (5) to provide an overall resultant spring rate KT; an actuator (20) attached to the cylindrical damper (5) and configured to compress and decompress the primary coil spring (9) and the secondary coil spring (11); a stop means (12) configured to deactivate said secondary coil spring (11) in at least one stop position; Including, when said suspension system is in a first mode, an overall suspension spring rate is defined by the series equation 1 / KT=1 / K1+1 / K2, and when said suspension system is in a second mode, an overall vehicle suspension spring rate is defined by the series equation 1 / KT=1 / K1, thereby selectively and switchably providing both a low rate, optimum ride comfort setting in said first mode and a high rate, optimum handling, low ride height setting in said second mode; The actuator (20) includes the common spring abutment (13).

2. 2. The suspension system of claim 1, wherein the actuator (20) comprises a hydraulic cylinder (19, 41) and a hydraulic piston (29).

3. 3. The suspension system according to claim 2, wherein the hydraulic piston (29) or hydraulic cylinder (41) moves against an outer wall of the cylindrical damper (5).

4. 4. A suspension system according to claim 2 or 3, wherein the stop means (12) comprises lockout means configured to hold the secondary coil spring (11) in a number of selected stop positions.

5. 5. The suspension system of claim 4, wherein said lockout means includes valve means (25) for preventing the flow of hydraulic fluid in said hydraulic cylinder (41).

6. 6. The suspension system of claim 1, further comprising a third steering mode, wherein in said third steering mode, said secondary coil springs (11) are decompressed and said primary coil springs (9) are raised to increase the ride height of the vehicle above the ride height at an optimum ride comfort setting of said first mode.

7. 7. A suspension system as claimed in any one of claims 1 to 6, wherein the cylindrical damper (5) provides adjustable damping to accommodate changes in spring rate for optimum vehicle comfort and handling.

Images