HYDRAULIC ACTUATOR FOR ACTIVE RIDE SUSPENSION

Abstract: An oil pressurized telescoping actuator (11) for active ride vehicle suspension having a folded dual piston (18,20) design with an inner piston (32) stroking within the rod (34) of an outer piston (40) to foreshorten overall length. A special universal joint (28) provided for a larger tolerance so that three bearing surfaces (36,49,54) will not encounter binding. The upper mount (146) accommodates the upper end cap (26) of the actuator which extends therethrough to further foreshorten the assembly. The entire assembly is jacketed (102) to provide a reservoir (108) connected to a drain line (110,112) so that leakage oil can be pressurized by a pump into the system for pressurized feed into the actuator for powered expansion and contraction of the actuator for level ride for all vehicle manoeuvres.

Description: This invention relates to active ride suspension and more particularly to hydraulically powered actuators used to adjustably mount the vehicle road wheels to the vehicle body and to control the plane of the vehicle through all handling manoeuvres. In order to actively control the attitude of the body of a vehicle with respect to the roadway, special dual acting hydraulic actuators have been proposed to control the plane of the vehicle body through a wide range of handling manoeuvres including cornering, acceleration and braking without impairing the basic ride of the vehicle. These actuators are high pressure oil adjustable units operatively disposed between the road wheels and support structure in the vehicle body. An example of such an actuator is disclosed in DE-B-1286278 and US-A-3186305. The present invention is of the general category of the active suspension actuator of the publications referenced above and provides a new and improved actuator which will control the vehicle body attitude in any selected plane and preferably a substantially level plane through vehicle handling manoeuvres including high G load cornering without impairing the basic ride desired for the particular vehicle such as for sports car operation. FR-A-2372708 shows a hydraulic actuator mounted in a support structure opening. DE-B-1057891 discloses a hydraulic actuator having an outer reservoir tube and compliant joint. GB-A-2199618 discloses a hydraulic actuator having bore means extending through an end cap, but was published after the priority date of the present application. A hydraulically powered actuator in accordance with the present invention is characterised over DE-B-1 286 278 by the features specified in the characterising portion of claim 1. The present invention features a new and improved hydraulic actuator with equal area pistons for the road wheels that provides for a shortened overall length which length is further minimized by mounting the upper end of the actuator through the upper mount. In addition to the effective shortened length provided by the "through-mount" feature of the present invention, there is improved environment routing of hydraulic lines and electrical wiring used in the controls for power adjusting actuator length and vehicle body attitude. This routing is accordingly through protected areas such as the engine compartment or covered beams instead of wheel well routings. This invention further features a compliant joint to compensate for dimensional tolerances in at least three primary bearing surfaces to eliminate the high cost to quantity produce actuators with precisely aligned telescopic tubing and pistons. An additional feature of the present invention is the provision of new and improved sump tubing enveloping the powered telescopic components so that oil leakage from sealed high pressure extension and contraction chambers as well as other areas in the actuator is trapped for delivery to sump. This not only conserves oil and increases efficiency, but also prevents contamination and oiling of roadways and parking areas. The present invention will now be described, by way of example, with reference to the accompanying drawings, in which:- Figure 1 is a pictorial view of a portion of a vehicle illustrating a hydraulically powered actuator of this invention operatively disposed between a road wheel assembly and support structure in the vehicle body; Figure 2 is a cross-sectional view taken along lines 2-2 of Figure 1; and Figure 3 is a view taken along lines 3-3 of Figure 2. Turning now in greater detail to the drawings, there is shown in Figures 1 and 2, an active ride suspension strut 10 operatively connected between the steering knuckle and hub assembly 12 of a road wheel 14 and a mounting tower 16 or other support structure in the body work of a vehicle. The active ride suspension strut 10 comprises a hydraulically powered actuator 11 which is a high pressure oil adjustable unit having inverted or folded piston assemblies (one piston assembly within the other) to, in effect, foreshorten overall length so that it may be readily used in a wide range of vehicular applications including those that employ MacPherson type struts. The internal arrangement of the hydraulically powered actuated 11, shown in Figure 2, comprises a pair of telescopic piston assemblies formed by a (downwardly extending) expansion piston assembly 18 and an (upwardly extending) contraction piston assembly 20. The expansion piston assembly 18 is telescopically mounted within the contraction piston assembly 20 and has a (hollow tubular) piston rod 24 which is connected at its upper to a (cylindrical) end cap 26 by a ball and socket compliant joint 28. This compliant joint 28 is effective to allow limited pivotal movement of the piston rod 24 relative to end cap 26 during actuator 11 operation to compensate for any misalignment of the bearing surfaces or components of the actuator including elements of the piston assemblies 18,20. From a ball 30 of the compliant joint 28, the piston rod 24 extends downwardly and coaxial with the axis of actuator 11 into threaded connection with an expansion piston 32 which strokes in a hollow rod 34 of the contraction piston assembly 20 and cooperates with piston rod 24 to form expansion chamber 35. A (band type) annular seal 36 carried on the periphery of expansion piston 32 slidably and sealingly engages the inner wall of hollow rod 34 to form the first of the above-mentioned bearing components. As shown, the hollow rod 34 extends upwardly from a threaded connection 37 with a lower connector rod 38 into threaded connection at 39 with a contraction piston 40. The contraction piston 40 is slidably mounted in an (elongated) cylinder tube 42 that is connected to a shouldered inner end 44 of the end cap 26 and cooperates therewith to form a contraction chamber 48. The contraction piston 40 also has a (band type) annular seal 49 slidably and sealingly contacting the inner wall of the cylinder tube 42 to define a second of the bearing components. The hydraulically powered actuator 11 also has an outer pressure tube 50 connected with a shouldered end portion of the end cap 26 and extends downwardly therefrom to a lower bearing and closure assembly 53. The hollow rod 34 slides through the inner cylindrical wall of a sleeve bearing 54 of closure assembly 53 which defines a third of the bearings referenced above. The closure assembly 53 is secured to a washer-like plate 55 that fits in a shouldered recess of a (lower cup-like) end plate 56. This end plate 56 has a shouldered inner recess in which a seal assembly 57 is operatively mounted to provide sealing engagement with the outer periphery of the hollow rod 34. A cylindrical space 58 between the outer pressure tube 50 and the cylinder tube 42 provides a fluid passage connected at its lower end to contraction chamber 48 by radial openings 59 in the lower end of the cylinder tube 42. At its upper end the fluid passage provided by cylindrical space 58 is connected to a first bore 60 in the end cap 26 that in turn is hydraulically connected to controls through a valve and adapter assembly 62 and external line 63. The valve and adapter assembly 62 is mounted to the top of the end cap 26 by screws 65 as shown in Figure 3. The socket 67 for the ball and socket compliant joint 28 is formed in a (downwardly extending) neck 64 of the end cap 26 and is retained in the neck by a nut 66 which threads into the interior wall of the neck. An annular O-ring seal 68 is positioned in the neck 64 between the underside of ball 30 and nut 66 to block the passage of fluid therethrough. An axial passage 70 extending through ball 30, the piston rod 24 and expansion piston 32 connects expansion chamber 35 to a second bore 72 in the end cap 26. Second bore 72 is operatively connected by the valve and adapter assembly 62 and external line 73 to the hydraulic controls by which the hydraulically powered actuator 11 is pressurized for expansion or contraction. To control height, this hydraulically powered actuator 11 incorporates a height sensor assembly 76 comprising an (elongated rod-like) shutter 78 having a lower head 80 mounted in a recess 82 in the upper end of lower connector rod 38 by a suitable retainer 84. The shutter 78 being fixed to the lower connector rod 38 can stroke within a (cylindrical and elongated) linear variable inductance transducer 86 of the height sensor assembly 76 which has its upper end a (cylindrical) terminal block 88 fixed in a third and centralized bore 90 in the end cap 26. The terminal block 88 has projecting terminals 92 which fit within the receptor terminals of a socket 94 and connect to controls 96 by leads 98 (Figure 3). The controls 96 correspond to those in GB-A-2199618 referenced above and respond to the position of the shutter 78 in the linear variable inductance transducer 86 to provide appropriate pressures to the extension and contraction chambers 35 and 48 of the hydraulically powered actuator 11. These actuators 11 are preferably positioned at the corners of the vehicle to adjustably support the road wheels 14 with respect to the vehicle body. During vehicle operation when pressure oil is supplied to or oil is exhausted from appropriate extension and contraction chambers 35, 48 in accordance with signals fed to the controls 96, the vehicle is maintained level through cornering manoeuvres, braking, acceleration and basically unchanged from straight ahead driving. To prevent leaking, this hydraulically powered actuator 11 incorporates an outer cylindrical jacket or reservoir tube 102 that encompasses the outer pressure tube 50 of this actuator. The upper end of reservoir tube 102 is threaded at 104 to the end cap 26 and the lower end thereof is threadably connected at 106 to the outer periphery of the end plate 56. A reservoir space 108 between the reservoir tube 102 and the outer pressure tube 50 communicates with drain lines 110, 112 and to outlet port 114, and from outlet port 114 and by a hydraulic line (not shown) to a pump sump (not shown) connected to the controls 96. A (variable volume) inner chamber 118 formed by the cylindrical space between the upper end of the expansion and contraction pistons 32 and 40 is connected to the drain line 110 by a line (not shown). With this construction, any leakage past the various sealed components will flow into the drain system to avoid contamination of parking areas and roadways and to ensure that oil is effectively utilized. Operatively mounted in a retainer cup 124 at the lower end of the hydraulically powered actuator 11 is a generally torrodial spring 126 of rubber or rubber like material to provide for damping the ride motions of the vehicle. Retainer cup 124 is mounted on a washer-like seat 128 fitted on shoulder 130 of lower connector rod 38. An elastomer convoluted boot 140 which is attached to the retainer cup 124 by retainer ring 142 and from this retainer cup the convoluted boot 140 extends upwardly along the outer periphery of the reservoir tube 102 where the upper end is secured by a constricted band 144. As pointed above, the overall wheel mounting length of the hydraulically powered actuator 11 is in effect reduced by the mounting arrangement of the upper end of the actuator to the support structure within the vehicle. This is accomplished through a (multi-part) upper mount 146 that comprises primary and secondary rubber annuli 148, 150. An (annular shouldered) metallic retainer 151 is bonded or otherwise secured to the outer periphery of the primary rubber annulus 148 and fits within an opening 152 of mounting tower 16. Screws 154 thread through the bodywork into the annular shoulder of metallic retainer 151 to secure the upper mount to the vehicle. The primary rubber annulus 148 has a central opening 156 through which the reservoir tube 102 and end cap 26 extend. The secondary rubber annulus 150 fits on top of the primary rubber annulus 148 as shown and defines a dished conical upper surface 158 on which a conical retainer 160 is fitted. This conical retainer 160 and the upper mount are secured in place by washer 162 and by a nut 164 which threads onto the end cap 26. The lower part of the primary rubber annulus 148 receives an annular seat 166 for an upper end of a helical suspension spring 168 which coils around the outside of the actuator 11 to a lower seat 170 (Figure 1) that is fastened to the lower connector rod 38 or other suitable support which is secured to the hub assembly 12 to provide for the spring suspension of the vehicle. The vehicle is primarily supported by the suspension springs 168 at the four corners of the vehicle. In the event that the vehicle beings to lean, such as when cornering, the height sensor assembly 76 will trigger the active ride controls to appropriately exhaust and pressurize the expansion and contraction chambers 35, 48 in the four corners of the vehicle to quickly and actively extend and contract the actuator 11 to keep the vehicle operating in a level plane. In the same manner, the vehicle will be kept level during positive and negative vehicle accelerating such as might occur on fast starts or braking. Accordingly, with this invention, the ride is active and the vehicle will operate in a substantially level plane for all manoeuvres. With the present invention, the compliant joint 28 allows for a wide range of production tolerances between the linearly spaced, bearing surfaces of the contraction piston 40 and the cylinder tube 42, the expansion piston 32 and the inner wall of the hollow rod 34, and between the sleeve bearing 54 and the hollow rod 34. The compliant joint 28 compensates for any misalignment of the three bearing surfaces and compensates for dimensional tolerances eliminating the need for precision alignment between bearing surfaces. With the new enveloping outer reservoir tube 102, high pressure oil is leak trapped and any leakage past the seals is to the sump for reuse in the system.

Claims: A hydraulically powered actuator (11) for adjustably mounting a road wheel assembly (12) to support structure (16) in a vehicle that has an opening (152) therethrough, comprising an expansion piston assembly (18) having a piston rod (24) connected at an upper end thereof to an upper end cap (26) and extending downwardly from the end cap to a terminal end; an expansion piston (32) secured to the terminal end; a cylinder tube (42) connected at one end to the end cap (26) and extending downwardly therefrom to a lower bearing and closure assembly (53); a contraction piston assembly (20) operatively mounted in the cylinder tube (42) and having a hollow rod (34) extending through the lower bearing and closure assembly (53) receiving the expansion piston (32) and forming an expansion chamber (35) therewith, the expansion chamber (35) being positioned below the expansion piston (32); the hollow rod (34) of the contraction piston assembly (20) extending in telescopic relationship with the piston rod (24) of the expansion piston assembly (18) into connection with a contraction piston (40); a contraction chamber (48) formed by the contraction piston (40) and between the hollow rod (34) of the contraction piston assembly (20) and the cylinder tube (42); and first and second passage means (70,58) to selectively supply high pressure fluid to the expansion and contraction chambers (35,48) respectively, the first passage means comprising a passage (70) extending from the end cap to the expansion chamber; characterised by an upper mount (146) extending through the opening (152) and operatively secured to the support structure; in that the upper end cap (26) is mounted within the upper mount (146) and extends through the opening (152) in the support structure (16); in that the second passage means comprises a passage (58) extending from the end cap (26) to the contraction chamber (48); and by first and second bore means (72,60) extending through the end cap and connected to the first and second passage means respectively for the supply of the high pressure fluid thereto. A hydraulically powered actuator as claimed in claim 1, comprising an outer reservoir tube (102) to form a reservoir space (108) to collect leakage oil from the expansion and contraction chambers (35,48). A hydraulically powered actuator as claimed in claim 1 or claim 2, wherein an annular seal (36) is carried on the expansion piston (32) to slidably and sealingly engage the hollow rod (34) to form a first bearing component. A hydraulically powered actuator as claimed in any one of claims 1 to 3, wherein an annular seal (49) is carried on the contraction piston (40) to slidably and sealingly engage the cylinder tube (42) to form a second bearing component. A hydraulically powered actuator as claimed in any one of claims 1 to 4, wherein a sleeve bearing (54) on the lower bearing and closure member (53) slidably engages the hollow rod (34) to form a third bearing component. A hydraulically powered actuator as claimed in any one of claims 1 to 5, wherein said connection between the piston rod (24) and the end cap (26) is provided by a compliant joint (28) which can compensate for bearing misalignments formed between the contraction piston (40) and the cylinder tube (42), between the expansion piston (32) and the hollow rod (34) of the contraction piston (40) and between the hollow rod (34) of the contraction piston (40) and the lower bearing and closure assembly (53). A hydraulically powered actuator as claimed in any one of claims 1 to 6, wherein the end cap (26) extends through the upper mount (146) and is secured thereto by an annular connector member (148, 150, 151) securely fastened to the support structure (16).

Inventors: FANNIN, WAYNE VINCENT, KLOESS, SCOTT R., KRUCKEMEYER, WILLIAM C.
Applicants: GENERAL MOTORS CORPORATION
Application year: 1988
Main classification: B60G17
IPC codes: B60G17, B60G23