AU690084B2 - Stabilization apparatus - Google Patents

Description

"STABILIZATION APPARATUS" This invention relates to stabilization apparatus.

This invention has particular but not exclusive application to the stabilization or damping of vibrations in heavy-haulage vehicles, and for illustrative purposes reference will be made to such application. However, it is to be understood that this invention could be used in other applications, such as stabilising travelling caravans.

Many articulated vehicles suffer from a vibration problem known as "loping", in which a pitching motion is induced in the prime mover about a transverse axis located near its rear end and resulting in rapid cyclical changes of the relative longitudinal inclinations of the prime mover relative to the trailer about the transverse axis. As the driver's cab is located in the vicinity of the front axle of the vehicle, the driver is subjected to a S vertical shaking motion. It is known that loping is generally ~induced by imbalance or out-of-round in the front tires of the vehicle, and by undulations in the road. It is also known that g. high friction in the front suspension springs causes bumps to be S 20 absorbed primarily by the lightly-damped tires rather than the damped suspension springs, so that oscillations are not damped out rapidly. Vehicles using tires of radial construction are particularly susceptible because of the low stiffness and light damping offered by such tire construction.

The problem can be particularly severe in the case of

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large off-road semi-trailers used for the haulage of minerals such as coal at mine sites. The prime movers of these vehicles,

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I which typically have payloads in said order of two hundred tonnes, have very short wheelbases relative to their height, width and trailer length and loping vibrations can be particularly severe on the driver. Efforts have been made to eliminate loping by stricter controls on tire characteristics and reduced-friction springs, but the problem still occurs.

The present invention aims to alleviate the above disadvantages and to provide stabilization apparatus which will be reliable and efficient in use.

For the purposes of this specification a reference to "viscous damping" is to be a reference to a force or moment applied to a vibrating element in an orientation which tends to 0*e* reduce the amplitude of the vibration, and with a magnitude or moment which increases according to the instantaneous velocity of 15 the vibration. A reference to "Coulomb damping" is to be a reference to a force or moment applied to a vibrating element in r an orientation which tends to reduce the amplitude of the vibration, with the magnitude of the force or moment being Ssubstantially constant.

With the foregoing objects in view, this invention in one Saspect resides broadly in an articulated vehicle including a prime mover joined to a trailer by a hitch assembly, said assembly including a trensverse load equalizing pivot assembly, a longitudinal ,oll pivot assembly, and a vertical articulating pivot assembly, said transverse load equalizing pivot assembly connected to said prime mover, said vertical articulating pivot assembly connected to said trailer, and said longitudinal roll pivot assembly interconnecting said transverse load equalizing pivot assembly to said vertical articulating pivot assembly, said longitudinal pivot assembly providing a pivotal movemerit about a longitudinal roll point, and including a stabilization apparatus including: a first cylinder pivot located on said longitudinal roll pivot assembly and spaced from said transverse load equalizing pivot assembly; .a second cylinder pivot located on said prime mover and B~b~-r~as~ spaced from said transverse load equalizing pivot assembly; a double acting hydraulic cylinder assembly extending between said first and second cylinder pivots, said double acting hydraulic cylinder assembly having a ram shaft assembly including a cylinder containing a ram piston supported by a ram shaft, said ram shaft extending to and connected with one of said cylinder pivots and said cylinder body extending to and connecting with the other of said cylinder pivots; opposed fluid chambers formed within said cylinder body and defined at opposite sides of said ram piston; fluid flow control means for controlling flow of fluid to and from said fluid chambers, including a ram piston bypass e passage and a pressure relief valve each communicating with said opposed fluid chambers, said pressure relief valve permitting 15 flow between chambers when fluid pressure in one of said chambers reaches a predetermined pressure.

The hitch assembly may be a fifth wheel type hitch assembly but preferably the hitch assembly includes a longitudinal roll pivot having its axis aligned with the 20 longitudinal axis of the vehicle and adapted for accommodating Sdifferential roll motion between the prime mover and the trailer.

The damping means may be utilised for the attenuation of pitching motion of the prime mover by inducing vibration-damping torques about the transverse pivot as the prime mover pitches. A pair of hydraulic dampers may be used if required.

Suitably, the or each damper includes a pair of fluid chambers charged with fluid and interconnected by connection means which includes restrictor means for dissipating energy in order to provide viscous damping and/or pressure relief means for limiting the maximum force applied by the linear damper in order

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0~n/-ll 9- I Bls pF to provide coulomb damping. The restrictor means may include an aperture formed in a piston, or an external restrictor valve, flow-control valve o- the like.

In the case where the transverse pivot is attached to a longitudinal and/or vertical pin assembly (as is the case for heavy-haul trailers), the damping means may include a pair of hydraulic dampers which may be disposed, if desired, on either side of the longitudinal or vertical pivot such that the damping forces may be balanced about the centerline of the vehicle. A single damper disposed about the centerline of the vehicle may be used if desired.

The damping means may include clamping means which may be adapted for selectively holding the prime mover and the trailer in a selected orientation, or restrain relative pivotal movement therebetween about a selected axis, unless a pre-determined load Slimit is reached and then releasing the prime mover to permit free or controlled pivoting relative to the trailer about the pivot as desired. Suitably, the clamping means includes a hydraulic cylinder or the like extending between the prime mover and the trailer across the transverse pivot, the cylinder including control means such as a pressure relief valve whereby So.o the cylinder may maintain a relatively rigid connection across the transverse pivot up to a load at which the pressure relief valve may operate, permitting movement of the prime mover 0* 25 relative to the trailer for following irregular road profiles.

While the clamping means is in operation, the trailer and the prime mover may operate functionally as a rigid vehicle having il M I natural frequencies of pitch and bounce which are less susceptible to excitation than an equivalent articulated vehicle.

The damping means may further include spring means or restoring means for generating restoring torques about the connecting pivot as a result of rotation thereabout, such that relatively small motions of the prime mover relative to the trailer may occur. The spring means may include mechanical springs such as coil or leaf springs, and be either linear or non-linear as desired. Where the damping means includes hydraulic cylinders, the spring means may include hydra,,ic accumulators attached to the hydraulic system.

In another aspect of this invention, stabilization apparatus is disclosed for an articulated vehicle of the type comprising a prime mover joined to a trailer by a vertical steering pivot, a longitudinal roll pivot, and a transverse pitch pivot, including a pair of double-acting hydraulic cylinders disposed on either side of the longitudinal pivot and connected to the prime mover and the trailer such that pitching movement of the prime mover relative to the trailer about said pitch pivot extends or retracts said double-acting hydraulic cylinders.

:The stabilization apparatus may include fluid control means for controlling the flow of fluid to and from the hydraulic Schambers of said double-acting hydraulic cylinders, the fluid control means including a connection between the respective oo 25 hydraulic chambers and/or between the hydraulic chambers and an external fluid source.

In yet another embodiment, this invention resides broadly

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Li S\V suO' I -r 6 in stabilization apparatus for an articulated vehicle of the type having a prime mover supported by front and rear axle assemblies and joined to a trailer by a hitch assembly in the form of an articulated connection having a vertical steering pivot which enables the prime mover to pivot relative to the trailer about a vertical axis whereby the trailer can follow the steered course of the prime mover, a longitudinal roll pivot which enables the prime mover and the trailer to roll about a longitudinal axis independent of one another, and a transverse pitch pivot which enables the prime mover and the trailer to pivot relative to one another about a transverse axis, the stabilization apparatus comprising:a double acting hydraulic cylinder assembly attached to the hitch assembly so that pitching movement of the prime mover, resulting in rapid cyclical changes of the relative longitudinal inclinations of the prime mover relative to the trailer about the transverse pitch pivot, causes extension and retraction of the hydraulic cylinder assembly, the double acting hydraulic cylinder ao sembly having a piston and opposed fluid chambers at opposite sides of the piston, and fluid flow control means associated with the hydraulic cylinder assembly for controlling the flow of fluid to the a a S opposed fluid chambers upon extension or retraction of the double acting hydraulic cylinder assembly for damping purposes 25 only.

In order that this invention may be more readily understood and put into practical effect, reference will now be i 0 "I u LLla b 111 7 made to the accompanying drawings which illustrate a preferred embodiment of the invention, wherein:- FIG. 1 is a pictorial side view of a prime mover/trailer combination including pitch damping apparatus according to the invention; FIG. 2 is a cross-sectional side view of the pitch damping apparatus shown in FIG. 1; FIG. 3 is a pictorial view of a further embodiment of pitch damping apparatus; FIG. 4 is a schematic diagram of the hydraulic system for the pitch damping apparatus shown in FIG. 3; FIG. 5 is a part-sectional elevation of an articulated vehicle hitch including an alternate form of stabilization apparatus according to the invention, and FIG. 6 is 2 crross-sectional view through the stabilization :apparatus illustrated in FIG. p The prime mover/trailer combination 10 shown in FIG. 1 includes a prime mover 11 connected to a trailer 12 through a hitch assembly 13. The latter comprises a transverse pivot assembly 14 attached between the prime mover 11 and a i 1 longitudinal pivot assembly 15, and the latter is in turn attached to the trailer 12 through a vertical pivot assembly 16.

A damper assembly 17 comprises a pair of double-acting hydraulic cylinders 20 mounted between the longitudinal pivot 25 assembly 15 and the prime mover 11 on cylinder pivots 21, as well as damping control apparatus 22 connected between the two hydraulic chambers 23 and 24 of each of the cylinders 20. The r I II r 11 111 JI 8~59~~ IL L~I~ _LL~s I pi I raap 8 damping control apparatus 22 includes restrictors 25 and pressure relief valves 26. Accumulators 27 introduce springing into the damping assembly 17, permitting a controlled degree of rotation about the pivot 14 without the interchange of fluid between the chambers 23 and 24.

If desired, one of the cylinders 20 may be mounted to the prime mover 11 behind the hitch assembly 13 such that rotation of the trailer 12 relative to the prime mover 11 about the transverse pivot assembly 14 will extend one cylinder and retract the other. The rod-side chambers of both cylinders 20 may then be coupled by damper control apparatus 22, and the piston-side chambers of both cylinders 20 may also be coupled by further damper control apparatus 22. This arrangement permits the use of standard hydraulic cylinders without problems in respect of the difference in cross-sectional areas between rod-side and pistonside chambers.

If the prime mover 11 develops a loping or pitching motion during operation, the hitch assembly 13 rotates in oscillatory motion about the transverse pivot assembly 14. This oscillatory motion causes extension and retraction of the hydraulic cylinders 20, forcing fluid between the chambers 23 and 24 through the restrictors 25. The forces produced by this action act to dampen out the pitching vibrations. If these forces reach an undesirably high level, the pressure reliaf valves 26 act to i 25 bypass the restrictors If desired, the restrictors 25 may be deleted, whereby the hydraulic cylinders 20 may effectively lock the transverse pivot Ls M ~9P~ I 9 assembly up to a torque level at which the pressure relief valves 26 function. This permits the articulated vehicle to function as a rigid vehicle with fewer modes of vibration while minimising excessive forces at the pivot 14 due to road irregularities.

Referring now to FIGS. 3 and 4, it will be seen that the double-acting hydraulic cylinders 30 are connected between chassis lugs 31 attached to the prime mover chassis rails 32 and coupling lugs 33 attached to the sides of the longitudinal pivnt assembly 34, the latter pivoting on a transverse pivot attached between the prime mover chassis rails 32. The longitudinal pivot assembly 34 is surmounted by a longitudinal pivot 36, and a vertical pivot assembly 37, to which a trailer (not shown) may be coupled, pivots about the latter.

The piston-side chambers 40 of both cylinders 30 are connected together, as are the rod-side chambers 41. Each pair of chambers 40 and 41 are connected to a hydraulic fluid source 42 hrough a pressure-regulating valve 43 and a check-valve 44, and to a fluid drain tank 45 through a restrictor 4& and a pressure-relief valve 47. Hydraulic accumulators 50 permit a controlled degree of springing to be provided by the damping apparatus.

S Pitching movement of the prime mover relative to the trailer ab.ut the transverse pivot 35 tends to extend or contract the cylinders 30, extension causing a rise in fluid pressure in 25 the piston-side chambers 40, and contraction causing a rise in .4 fluid pressure in the rod-side chambers 41. If the fluid pressure remains below the relief setting of the appropriate "ZOVT I pressure-relief valve 47, the cylinders 30 will not extend or retract, and pitching of the prime mover about the transverse pivot 35 will be inhibited. If the fluid pressure in the chambers 40 does rise above the relief setting of the appropriate pressure-relief valve, fluid will flow from the chambers through the restrictor 46 and the pressure-relief valve 47 to the drain tank 45, dissipating energy and damping out the movement.

The consequent increase in volume of the chambers 41 will be filled from the fluid source 42 through the pressure-regulating valve 43. A complementary effect applies if the pressure in the rod-side chambers 41 increases above the relief-valve setting.

The ritch damping apparatus of FIGS. 3 and 4 is particularly useful in applications where it is desirable to utilise standard hydraulic cylinders, in which the piston-side and rod-side chambers have different piston areas and it is thus not practicable to transfer fluid between such chambers. It has oe the disadvantage that it requires constant pressurization from a source of hydraulic fluid, but such a source is normally available on such a vehicle, and the circulation of the damping fluid through the vehicle's hydraulic system allows heat generated within the stabilization apparatus to be dissipated by the vehicle's hydraulic cooling system.

As illustrated in FIGS. 5 and 6, the chassis 51 of a prime mover is connected to the leading end 60 of a trailer through a 25 hitch assembly 53 and a single centrally mounted damper assembly 62 is attached to a chassis cross-member 63 via a gimbal ring 64 attached to the body 61. It will be seen that the damper

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I I II R IIC~RO 9~ IICl~l~~~r~-- 11 assembly 62 comprises a unitary upper, double-acting hydraulic cylinder 65, and a lower, single-acting preload cylinder 66, the pistons within the cylinders 65 and 66 sharing a common piston rod 67, the exposed end of which is connected to the transverse pivot assembly 54 behind the longitudinal pivot assembly 56.

The double-acting hydraulic cylinder 65 is divided into an upper chamber 70 and a lower chamber 71 by a piston 72. As the piston rod 67 passes out of the double-acting hydraulic cylinder at both of its ends, the chambers 70 and 71 are of equal annular cross-sectional area. The piston rod 67 is penetrated by a damping passage 73 which connects the chambers 70 and 71 and the piston 72 contains a series of relief valves 74 which allow fluid to pass in either direction between the chambers 70 and 71 when a preset pressure differential exists between them.

The outer end of the preload cylinder 66 is closed by a vented cylinder head 75. The chamber 76 of the preload cylinder 3 66 and the lower chamber 71 are connected to a supply of pressurized hydraulic oil 77. The upper chamber 70 is connected to a fluid drain 80 through a bleed orifice 81, the latter having a very low flow rate relative to the damping passage 73. This arrangement has several advantages. Circulating oil assists 4@ cooling and thus efficient operation. The upwardly directed flow of fluid tends to purge entrapped air from the chambers and the pressure reduces the volume of any remaining air and thus 25 increases the efficiency of damping and the effective stiffness of the damping.

The tensile preload induced in the damper assembly 62 by i) 'I I I-h 12 the preload cylinder 66 minimises all mechanical clearances within the mounting pivots of the damper assembly 62 and the hitch assembly 53, as in use these are fully taken up by the preload. Thus for pitch vibrations of small magnitude, there is no lost motion in the damping mechanism due to such mechanical clearances, ensuring that effective damping can occur, even for pitching vibrations of an amplitude of the same order as the clearances within the mounting pivots.

Alternatively the double acting cylinder assembly may be in the form of a conventional cylinder assembly with the piston side of the chamber having a greater area than the rod side of the chamber such that equal pressure applied to both sides will result in a preload tending to maintain the piston rod preloaded in compression. The viscous damping aperture may pass directly through the piston, it be formed between a longitudinal bypass groove in the cylinder wall and the piston or it may be formed as an external passage which may have accessible flow adjustment means if desired.

In use, the pressurized oil supply is energised, filling the lower chamber 71 directly and the upper chamber 70 through :e the damping passage 73. The pressurized oil supply also applies a tensile preload to the damper assembly 62 through the preload C C cylinder 66. When pitching motion develops for the prime mover 51 relative to the trailer 52 about the transverse pivot assembly 25 54, the piston rod 67 is forced to slide relative to the hydraulic cylinder 65. Such movement can only occur if fluid flows between the upper chamber 70 and the lower chamber 71.

Y i 1 -7 1~83 II~PIC~b~P~-ss 13 When the pitching forces applied to the piston rod 67 are relatively low, the fluid passes between the chambers 70 and 71 through the damping passage 73, dissipating energy and damping out the vibration. If the pitching forces become larger, or if the vehicle is obliged to pivot about the transverse pivot assembly 54 to conform to changing road profiles, the relief valves 74 will open, allowing rapid movement of the damper assembly 62 without developing excessive pressures within the chambers 70 and 71.

While the above has been given by way of illustrative examples of this invention it will of course be realised that all such modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of this invention as is defined in the appended claims.

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Claims (6)

1. 2. Stabilization apparatus as claimed in claim 1, wherein said double acting hydraulic cylinder assembly includes a preload means for maintaining said double acting hydraulic cylinder assembly in either a state of tension or a state of compression between said cylinder pivots. ,e
2. 3. Stabilization apparatus as claimed in claim 2, wherein said preload means has a pair of ends and includes a single- acting preload cylinder attached at one said end to said cylinder body of said double acting hydraulic cylinder assembly and at its other said end to said ram shaft assembly of said double acting hydraulic cylinder.
3. 4. Stabilization apparatus as claimed in claim 3, wherein said single-acting preload cylinder includes a piston mounted on said same ram shaft of said double acting cylinder assembly and 10 is located remote from said ram piston wherein said single-acting .eo..i preload cylinder communicates with a pressurized fluid supply so as to maintain said ram shaft in tension. Stabilization apparatus as claimed in claim 4, and S: including a common pressurized fluid supply said common supply supplying both said single-acting preload cylinder and said double acting hydraulic cylinder assembly and wherein said common pressurized supply enters said double acting hydraulic cylinder assembly at a lower location and exits at an upper location.
4. 6. Stabilization apparatus as claimed in any one of claims 2 20 to 5, wherein said double acting hydraulic cylinder assembly extends between an upper mounting on said hitch assembly and a lower mounting on said prime mover.
5. 7. Stabilization apparatus as claimed in any one of claims 2 to 6, wherein said cylinder pivot on said prime mover is a gimbal mounting. ~,rdC, la~ i 16
6. 8. An articulated vehicle including a prime mover joined to a trailer by a hitch assembly, said assembly including stabilization apparatus as claimed in any one of claims 1 to 7. DATED THIS eleventh DAY OF February 1998. HASTINGS DEERING (AUSTRALIA) LTD ACN 054 094 647 and VIPAC ENGINEERS AND SCIENTISTS LTD ACN 005 453 627 BY PIZZEYS PATENT TRADE MARK ATTORNEYS a. -o 0'. rs~l~-nm~~ ABSTRACT Stabilization apparatus is provided for stabilizing articulated vehicles. The stabilization apparatus includes damping means (17) connected between a prime mover (11) and its trailer (12) and arranged about the articulation pivot assembly The damping means provides resistance to movement of the trailer relative to the prime mover about the pivot assembly so as to reduce or substantially eliminate undesirable loping motion of the prime mover. *sees: o 0 *0 **SO S *a 0 S o0 so *0 5 0 e g"o -M