VEHICLE WITH AXLE SUSPENSION DEVICE WITH GAS SPRING SUSPENSION, AND CONTROL SYSTEM THEREFOR

Abstract: In an axle suspension device for a vehicle with gas spring suspension (6) and roll stabilisation an essentially rigid stabilizer body (15) is used which is hingedly connected in two points (14, 16) to the axle (2) to be stabilized, each near one end thereof, and in two points (17, 18) to the vehicle frame (1), which latter connections are formed by substantially vertical hydraulic cylinders (31) with piston rods (30), having a sliding bearing (34) in the cylinders, which can absorb transverse forces, the cylinders (31) or piston rods (30) thereof being connected to the frame (1) by rigid connections (35). A control system for such cylinders has a pressure transformer (40) with a larger surface (41), which is directly or indirectly under the pressure of the gas in the gas spring system (6), and has a smaller surface (42), on which the hydraulic pressure in said cylinders (31)acts in the opposite direction, said surfaces (41, 42) being connected for common movement, a control pressure (through 47) exerted by a fluid acting on the other side of said larger surface (41) in the same direction as said hydraulic pressure being variable to control this system depending on one or more parameters on the basis of driving or road conditions. All this allows a simple and reliable design, safety and adaptation of roll stabilizing to different conditions for maximum comfort.

Description: The invention relates to an axle suspension device according to the preamble of claim 1. Such a device is known from FR-A-2196921. Therein, the roll stabilizer element is formed as a closed rectangular body with rounded corners, which is deformed, mainly by torsion, when roll occurs. The substantially vertical connections to the vehicle frame are rigid brackets, extending downwardly from the frame and terminating in bearings for hingedly taking up this stabilizer element in two points, one near each side of the vehicle. Although this is a device of simple design and allows for a roll centre in a low position, advantageous as to transverse movements and accelerations when following uneven road surfaces, this known device does not allow a variation in the amount of roll stabilizing, as the roll resistance only depends on the deformation of the rectangular stabilizer body. It is an object of the present invention to provide an axle suspension device according to the preamble of claim 1, which allows for easy variation of the roll stability, so that it can be ideal as it can be adapted to all kinds of desired parameters and give maximum driving comfort, with freedom to maintain sufficient spring facility by the spring system in all conditions of roll suppression, while maintaining a simple design and the minimum number of four pivoted joints. In view thereof, an axle suspension device according to the preamble of claim 1 is, according to the invention, characterized by the characterizing part of claim 1. Thereby, the said object is obtained without vertical reactions to braking and propulsion forces influencing the system. Also with the invention the roll center can be low down, which is advantageous as regards transverse movement and accelerations when following uneven road surfaces. To this end, the rigid stabilizer element is preferably fitted below the central axis of the axle to be stabilized, while above said axis a reaction rod running in the lengthwise direction of the vehicle is hingedly connected to frame and axle, as in said FR-A. A vehicle according to the invention is preferably characterized in that the rigid connections to the frame of said cylinders or their piston rods are fitted against vertical side walls of runners (beams or bars) of the frame. It is remarked that from EP-A-152914 a suspension device for two opposite vehicle wheels in the same axis, but not connected to a common axle, is known, in which a U-shaped roll stabilizer bar connects the wheel suspensions at the end of each leg of the U, the U-part between these legs being connected in two points, one at each side of the vehicle frame, to this frame by vertical hydraulic cylinders, pivotably connected to this frame and to the stabilizer bar. By influencing the hydraulic pressure in the cylinders, these are elongated or shortened to vary the stabilizer action. The main stabilizing action is due to deformation (twisting) of the stabilizer bar to counteract rolling mainly by torsional resistance of its U-part connected to the hydraulic cylinders. This gives less freedom in varying the roll resistance and requires 6 pivot connections instead of the 4 pivots of the present invention, while requiring additional means to keep the wheels horizontally in the correct position with respect to the frame of the vehicle. The invention also relates, in dependent claims, to preferred embodiments of this device as will be clear from the following description. The invention will now be explained in greater detail with reference to the appended drawings. Fig. 1 shows a side view, partially cross-section, of an axle suspension device in a preferred embodiment of the invention, partially in cross-section. Fig. 2 shows a top view of the stabilizer element used therein. Fig. 3 shows a cross-section along the line III-III in Fig. 2. Fig. 4 shows a schematic view of the main parts of the pneumatic/hydraulic system for use in an axle suspension device according to the invention. A vehicle with an axle suspension device according to the invention has two longitudinal frame bars 1 and a tubular axle 2 bearing two or more wheels 3. At each side a yoke 4 with straps 5 is clamped firmly underneath against the axle. Each yoke 4 bears at each end a pneumatic spring bellows 6, which at the other side is supported and fixed underneath against the frame bar 1 (see mounting plates 7). Fitted hingedly at 10 on an elevation 8 on the axle 2, in this case on the housing 9 of a differential gear, is a guide rod 11 which at the other side is hingedly connected at 12 to a transverse bar 13 between the longitudinal bars 1 of the frame. The rod 11 runs in the lengthwise direction of the vehicle in the longitudinal centre plane thereof and, through the design of its pivot points 10 and/or 12, permits sufficient roll between axle and frame. A hinge bearing 14 is fitted inside each yoke 4 to the side of the axle. An essentially rigid stabilizer body 15, made of sheet material and in the form of a hollow tubular element, extends approximately horizontally at the level of the yokes 4 and has at the bearings 14 a bearing pin 16 with which it engages in said bearings, so that it can pivot therein only about the central axis of said bearings 14. Near the other side, said element 15 has two bearing forks 17, each bearing a bearing pin 18 of a bearing 19 (Fig. 3). A shock absorber 20 is fitted between each yoke 4 and the frame, in such a way that at 21 and 22 it is fixed firmly but to some extent swivellably, on the top of the yoke 4 and at the side to a longitudinal bar 1 of the frame respectively. Said shock absorbers 20 are controllable depending on load, for which purpose it is possible to use commercially available, variably adjustable shock absorbers which influence, for example, the passage resistance of the narrow passages for damping the oil flow through the fact that a flowing medium, for example the air from the pneumatic spring bellows, is admitted through a conduit 23 below a piston 24, connected to a rod 25, which at its other end bears a head 26, pressing on a spring 27 which influences a non-return (check-) valve system with narrow passages in a piston 28 in such a way that at higher pressure below piston 24 the narrow openings in said piston 28 are more closed. All this is shown only partially and schematically in Fig. 1, since these are shock absorbers which are known per se. Such shock absorbers are variable in one or both directions. Such shock absorbers can also be controlled electronically. Each bearing 19 is fixed with its external bearing bush 29 on the hollow piston rod 30 of a hydraulic cylinder 31. Inside this bush 29 is a rubber bush 50 around bearing pin 18, which bush 50 bears a broad rubber flange 51 at each end in order to permit some lateral movement and tilting between bush 29 and element 15, as is necessary during rolling. A ball hinge with some lateral mobility could also be used here. The piston 32 on the top of this piston rod 30 cooperates with an annular abutment 33 in the top of said cylinder 31 and the piston rod 30 is guided in the bottom of the cylinder by a sealing bearing 34 which can absorb transverse forces. The cylinder 31 is fixed on a mounting plate 35 which supports it firmly up to the bottom end and is fixed firmly against the outside of the adjacent frame bar 1. A duct connection 36 can supply hydraulic control medium to the cylinder 31 below piston 32. In order to prevent the piston 32 from bumping against parts of the cylinder 31 on reaching one or the other end position, a throttling device which is known per se in shock absorbers can become active at each stroke end of said piston (so-called hydraulic buffering). A hydraulic/pneumatic control system for such a device is shown schematically by way of example in Fig. 4. Air is fed into the four bellows 6 from a source for air under pressure (not shown). These bellows are connected, by means of a bilaterally operating non-return valve 37, possibly via a throttling constriction 8, to the space 39 in a pressure transformer 40 in which a piston 41 (or diaphragm) is movable. Said piston 41 is fixed to a much smaller piston 42 (or diaphragm) by means of a rod 43. Oil from the hydraulic system of the cylinders 31 presses on the piston 42, against the pressure of the air from the bellows on piston 41. Throttling constrictions 44 can be provided in the oil pipe 45 to each cylinder 31. An air duct 47 is connected to the space 46 between the pistons 41 and 42, by means of which controllable quantities of air can be admitted from a source 48 of air under pressure through an electrically operated valve 49, the short variable opening time of which determines the quantity of air which is fed to the space 46. This valve 49 is operated depending on desired parameters which one wishes to apply in order to influence the roll rigidity, for example the driving speed, roll accelerations, steering wheel movement and road surface condition. Since the volume of the space 39 below piston 41 is much greater than that of space 46, relatively small quantities of air fed into space 46 will have a relatively great influence on pressure changes therein. All kinds of parts, ducts, valves etc. used in practice are omitted in Fig. 4, since every expert knows them and knows that they are likely to be used in such a system. For example, a relay valve can be fitted in line 47, which valve very rapidly controls opening and closing thereof for accurately determined, for example also very short time intervals, valve 49 being kept in a certain position for longer periods. This system works as follows. Air under pressure, for example at a normal working pressure of 8 to 9 bar, is fed to the air bellows through a duct which is not shown. This fairly high air pressure makes small bellows 6 possible, which gives space for other adjacent parts. The air pressure in the bellows can be changed in the known manner depending on load by means of a height regulator, so that the frame is always at the same height relative to the axle, despite differences in load. The air pressure in the bellows 6 is conveyed by means of the double-acting non-return valve 37 and the constriction 38 to the space 39 in transformer 40, and thus presses on piston 41. By means of the valve 37, pressure changes can be passed on selectively between transformer 40 and bellows 6. The pressure increase in the transformer can be utilized to supply a counter-moment to those bellows which have the highest pressure, which is advantageous for an additional roll suppression. The valve 37 then will automatically take up the correct position. Pressure increases through constriction 38 are also passed on to said space only in throttled condition. The duct 23 to the shock absorbers 20, if the latter are controlled depending on load, can branch off from the duct in which said constriction 38 is provided, and this as desired from a point either upstream (as shown) or downstream of said constriction. In the former case the shock absorbers react more quickly to pressure increases in the bellows. It can be advantageous to provide two ducts instead of the duct 23, one from the air system of the two lefthand spring bellows 6, and one from that of the righthand spring bellows, each leading to a shock absorber at the same side of the vehicle. The piston 41 transmits the air pressure in space 39 via the rod 43 to the piston 42, which due to its much smaller surface exerts a much higher pressure on the oil in the pipe system 45, 36 to the hydraulic cylinders 31 of the stabilizer system. A throttling constriction 44 can be provided in duct 45 in every branch thereof. The roll rigidity is, of course, reduced if the pressure in the intermediary space 46 is increased. Through the control described with pressure change in said intermediary space, a very universal influencing of the roll rigidity can be achieved with a very simple transformer 40 and, for example, ideal driving comfort can be achieved even during straight driving over poor roads; in the case of transverse accelerations the roll rigidity can be increased easily and rapidly by making the pressure in intermediary space 46 drop, and during tipping or far extension of parts such as crane arms and ladders the system can easily be made rigid. In the arrangement shown, even with heavy rolling, sufficient spring travel always remains in all bellows to maintain full spring comfort in the process. The further parts of the control system, such as those with a central electronic control unit, are not shown in detail here, since they are universally known per se, and for understanding the invention do not require any further explanation here. The stabilizer element 15 can project forwards or backwards relative to the axle, as desired depending on all kinds of circumstances such as the vicinity of another axle set, the course of the drive between tandem axles etc. If there are several axles close together, the stabilizer element can extend forwards for one axle and backwards for the other one. If there is a monocoque body or "space frame", as is often the case in buses, but also in other circumstances, then it can be advisable to fit the stabilizer element 15 above the axle and the rod 11 below it.

Claims: Axle suspension device for a vehicle with spring suspension (6) and with a roll stabilizer element (15) which in four points (14,16; 17,19), situated on the corner points of a rectangle or isosceles trapezium, is hingedly connected to other parts, in two points (14,16) to the axle (2) to be stabilized, each near one end thereof, and in two points (17,19) each with a substantially vertical connection (31) to the vehicle frame (1), characterized in that the roll stabilizer element (15) is an essentially rigid body and that said substantially vertical connections (31) are hydraulic cylinders, variable in length under the influence of roll loads, of which cylinders (31) the piston rods (30) near the place where they come out of the cylinders (31) run through a sliding bearing (34) in the cylinders, which bearing can absorb transverse forces, and in which the connections (35) to the frame (1) of said cylinders (31) or their piston rods (30) are rigid. Axle suspension device according to Claim 1, in which the stabilizer element (15) lies approximately horizontally essentially below the central axis of the axle (2) to be stabilized, and a reaction rod (11) running in the lengthwise direction of the vehicle is fitted above said central axis, pivoting at one side (at 12) on the vehicle frame (1) and at the other side (at 10) on the axle (2). Axle suspension device according to Claim 1 or 2, in which the hinge connections (17,19) between the stabilizer element (15) and said hydraulic cylinders (31) have rubber cushions (50) or the like to permit some movement in all directions. Axle suspension device according to any of the preceding claims, in which a yoke (4) projecting forwards and backwards is fitted on the axle (2) at each side, while a gas spring bellows (6) is fitted near each end of each yoke (4) between said yoke and the vehicle frame (1), and the pivot points (14,16) of the stabilizer element (15) with the axle (2) are fitted on said yokes (4) at some distance from a vertical plane through the central axis of the axle (2), towards the hydraulic cylinders (31). Axle suspension device according to Claim 4, in which a shock absorber (20) acts on such a yoke (4) at each side of the vehicle, at the other side of the axle (2) from that at which said pivot points (14,16) with the stabilizer element (15) are provided. Axle suspension device according to any of the preceding claims, in which the rigid connections (35) to the frame (1) of said cylinders (31) or their piston rods (30) are fitted against upstanding side walls of beams of the frame (1). Axle suspension device according to Claim 6, in which the cylinders (31) are fixed to the frame (1) at such a height that the working stroke of the pistons (32) therein lies essentially at the side of and at the same height as said upstanding side walls. Axle suspension device according to any of the preceding claims 4 to 7, in which the gas pressure in the gas spring bellows (6) acting on an active surface of a pressure transformer (40) together with a fluid pressure acting on another active surface (41) thereof and depending on another parameter of running conditions of the vehicle determines the pressure in the hydraulic system to which the above-mentioned hydraulic cylinders (31) are connected.

Inventors: AALDERINK, DERK GEERT, ZANTINGE, JOHAN MICHIEL
Applicants: WEWELER N.V.
Application year: 1990
Main classification: B60G21
IPC codes: B60G9, B60G21, B60G17, B60G5