A HYDRAULIC ARRANGEMENT TO BE LOCATED BETWEEN A BODY AND AN AXLE OF A COMMERCIAL VEHICLE

Abstract: The invention relates to a hydraulic arrangement to be located between a body (23) and an axle (18) of a commercial vehicle. For the adjustment of the springing characteristics of the vehicle the arrangement comprises a first (15) and a second (16) hydraulic cylinder on the different sides of the body (23); a cross-connection of fluid spaces above and below the pistons of the cylinders (15, 16); a first (10) and a second (9) pressure accumulator arranged in the first (26) and the second (27) cross-connection, respectively; a first (12) and a second (11) directional valve arranged in the first (26) and the second (27) cross-connection, respectively; and a first (14) and a second (13) throttle valve arranged parallel with the first (12) and the second (11) directional valve, respectively.

Description: A hydraulic arrangement to be located between a body and an axle of a commercial vehicle The present invention relates to a hydraulic arrangement to be located between a body and an axle of a commercial vehicle and to be used for the ad¬ justment of the springing characteristics of the ve¬ hicle, as of the stabilization of shock absorption and sway, and if desired, also for the realization of lifting and lowering the body as well as for the de¬ finition of the axle weight. This arrangement com¬ prises - a first and a second hydraulic cylinder on different sides of the body, the cylinders being at one end fastened to the vehicle body and at the other end to the axle of the vehicle; - a cross-connection of fluid spaces above and below the pistons of the cylinders in such a way that from the fluid space above the piston of the first cylinder there is a first connection into the fluid space below the piston of the second cylinder, and respectively, from the fluid space above the piston of the second cylinder there is a second connection into the space below the piston of the first cylin- der; and - a first and a second pressure accumulator ar¬ ranged in the first and the second cross-connection, respectively, to receive or to deliver an amount of fluid corresponding to the change of the total volume of the fluid spaces of the cylinders, the fluid spaces communicating with each other. Operations of the kind described above have ge¬ nerally been realized by means of separate struc¬ tures, e.g. shock absorption by means of hydraulic or hydropneumatic or pneumatic dampers and sway stabili- zation by means of different spring 5 solutions. Lift¬ ing and lowering the body of an air spring suspended car succeeds typically by adjusting the amount of air. For the definition of axle weights, methods of various kinds have been used, most of them carried out by means of sensors measuring the elongation of loaded parts. The object of the present invention is to pro¬ vide a hydraulic arrangement by means of which the operations mentioned above can be carried out even by means of one and the same arrangement. This arrange¬ ment of the invention suitable for the adjustment of the springing characteristics of a vehicle is charac¬ terized in that it comprises - a first and a second directional valve ar¬ ranged in the first and the second cross-connection, respectively, to allow a one-way flow from the fluid space above the piston of the second cylinder into the fluid space below the piston of the second cylin- der in each particular case; and - a first and a second throttle valve arranged parallel with the first and the second directional control valve, respectively. To complement this arrangement to include also the realization of lifting and lowering the body, the arrangement further preferably comprises a first and a second magnetic valve opening and closing a two-way connection and arranged in the first and the second cross-connection, respectively. In this invention, the structure based on hyd¬ raulics gives good possibilities of adjusting the springing characteristics of a commercial vehicle. In commercial vehicles, a great load variation between an empty and a loaded vehicle causes problems, be- cause the springing characteristics of a vehicle tra- ditionally provided with leaf springs must in the first place be planned for a situation when the ve¬ hicle is loaded, which leads to a strong spring sus¬ pension in case of a partially loaded or an empty car. In this invention, the shock absorption can be influenced by adjusting the throttle valve, which makes it possible to decrease throttling and thus to adjust the shock absorption smaller when the car is empty. Further, the possibility of adjusting the level of the vehicle body known from the air spring suspen¬ sion can also be utilized at the traditional leaf spring suspension by means of the structure of the invention. Level adjustment is of importance when a vehicle is loaded from loading bridges, in which case the height of a load space can be adjusted accurately to the level of the bridge. By means of the arrange¬ ment of the invention, the level adjustment can be locked in place to the extent that an increased load- ing does not change the level. The level adjustment makes it possible to use also separate load spaces standing on their legs in such a way that for in¬ stance when a car is loaded with a load space it is driven under the load space with the body level low- ered, after which the level is lifted until the legs of the load space rise into the air and the legs can be bent into a driving position. The arrangement of the invention does not re¬ strict the solution of the spring suspension, and consequently, the actual spring suspension can be carried out e.g. by means of leaf springs or air springs. When defining the axle weight in connection with air spring suspension, it is possible to release the pressure from suspension air bags, if desired. The invention preferably unites shock absorp- tion, sway stabilization, lifting and lowering the body as well as definition of the axle weight of a commercial vehicle into the same hydraulic circuit. In the following, the arrangement of the inven- tion for the realization of various operations will be described in detail referring to the drawing en¬ closed, in which the hydraulic arrangement of the in¬ vention is described partly schematically and partly as a hydraulic diagram. A hydraulic arrangement of the invention com¬ prises a first 15 and a second 16 hydraulic cylinder on different sides of a body 23, the cylinders being at one end fastened to the vehicle body 23 and at the other end to an axle 18 of the vehicle; a cross-con- nection of fluid spaces above and below the pistons of the cylinders 15, 16 in such a way that from the fluid space above the piston of the first cylinder 15 there is a first connection 26 to the fluid space be¬ low the piston of the second cylinder 16, and respec- tively, from the fluid space above the piston of the second cylinder 16 there is a second connection 27 to the space below the piston of the first cylinder 15; a first 3 and a second 4 magnetic valve opening and closing a two-way connection and arranged in the first 26 and the second 27 cross-connection, respec¬ tively; a first 10 and a second 9 pressure accumula¬ tor arranged in the first 26 and second 27 cross-con¬ nection, respectively, to receive or to deliver an amount of fluid corresponding to the change of the total volume of the fluid spaces of the cylinders 15, 16, the fluid spaces communicating with each other; a first 12 and a second 11 directional valve arranged in the first 26 and the second 27 cross-connection, respectively, to allow a one-way flow from the fluid space above the piston of the second cylinder into the fluid space below the piston of the second cylin¬ der in each particular case; and a first 14 and a second 13 throttle valve advantageously adjustable and arranged parallel with the first 12 and the sec- ond 11 directional valve, respectively. Moreover, the arrangement comprises a fluid reservoir 17 to be connected through connections 29, 28 provided with magnetic valves 6, 5 with the first 26 and the second 27 cross-connection, respectively, to equalize the pressure of the pressure accumulators 9, 10 connected therewith to the atmospheric pres¬ sure, and a hydraulic pump 8 to be connected through connections 30, 31 provided with magnetic valves 1, 2 with the fluid space above the piston of the first 15 and the second 16 hydraulic cylinder, respectively, to pressurize the first 26 and the second 27 cross- connection and the pressure accumulators 10, 9 at¬ tached to them. The arrangement includes further a first 24 and a second 25 pressure sensor arranged to measure the pressure of the fluid space above the piston of the first 15 and the second 16 hydraulic cylinder, re¬ spectively. Shock absorption and sway damping can be real- ized by means of a circuit of the invention when the magnetic valves 1, 2, 5 and 6 are closed and the mag¬ netic valves 3 and 4 are open. At simultaneous bump travel of wheels 19 and 20 of the vehicle, the fluid then flows from above the piston of the cylinder 15 below the piston of the cylinder 16 through the di¬ rectional valve 12 in the first place, and respec¬ tively, the same amount of fluid flows also from the cylinder 16 into the cylinder 15 through the direc¬ tional valve 11, whereby the damping at bump travel is caused by flow resistances of the pipe system only. At rebound travel the flow takes place in the opposite direction through the throttle valves 13 and 14 only with the directional valves in the closing direction, whereby the damping is greater than at bump travel and it can be adjusted by adjusting the throttling. If the springiness is one-sided, i.e. if the vehicle is swaying, a fluid volume corresponding to the bump travel flows from the cylinder 15 on the side of a bump travel wheel, e.g. 19, through the magnetic valve 3 into the pressure accumulator 10, and a fluid volume corresponding to the rebound trav¬ el flows from the cylinder 16 on the side of the re- bound travel wheel 20 through the throttle valve 14 also into the pressure accumulator 10, whereby the pressure of the pressure accumulator 10 increases. In the case described, fluid flows from the pressure ac¬ cumulator 9 into the cylinders and the pressure of the pressure accumulator 9 decreases. The pressure difference between the accumulators 10 and 9 creates a pair of opposing forces preventing the cylinders from swaying, i.e. a stabilization of the sway. The body 23 can be lifted with respect to the axle 18 by opening the magnetic valves 1, 2, 5 and 6 and by closing the magnetic valves 3 and 4. The at¬ mospheric pressure prevails then in the pressure ac¬ cumulators and the fluid spaces below the pistons of the cylinders 15 and 16 are communicating with the reservoir 17. When the hydraulic pump 8 pumps more fluid through the magnetic valves 1 and 2 into the fluid space above the pistons of the cylinders 15 and 16, the pistons push downwards and the body rises with respect to the axle. The body can be lowered with respect to the axle by closing the valves 1 and 2 and by opening the valves 3 and 4 with the valves 5 and 6 still open. The lowering is only restricted by the stroke of the cylinders or by the force caused by springs 21 and 22. The definition of the axle weight can be car¬ ried out by measuring the pressure prevailing above the piston of the cylinders 15 and 16. The measuring is begun by opening the magnetic valves 5 and 6 and by closing the magnetic valves 3 and 4 after that, while the magnetic valves 1 and 2 are closed and the vehicle is unloaded. The circuit gets the atmospheric pressure again when the magnetic valves 5 and 6 are opened. At this stage, only the springs 21 and 22 bear the load of the body, i.e. the axle weight of the axle in question. By closing the valves 3 and 4 the situation is locked, whereby the pistons of the hydraulic cylinders 15 and 16 cannot move in the up¬ per or lower direction, i.e. in bump travel or re¬ bound travel direction, and thus, the spring force cannot change, which means that the load increased when loading the vehicle is borne only by the pres¬ sure increased above the piston in the cylinders, which pressure can be measured by means of pressure sensors 24 and 25 of any conventional type, e.g. electrical or mechanical sensors. The arrangement of the invention has been de¬ scribed above in connection with one exemplifying arrangement only and it is to be understood that the invention can be modified rather extensively, without departing from the scope defined by the claims en¬ closed, however.

Claims: Claims : 1. A hydraulic arrangement to be located be¬ tween a body (23) and an axle (18) of a commercial vehicle, which arrangement comprises - a first (15) and a second (16) hydraulic cy¬ linder on different sides of the body (23), the cy¬ linders being at one end fastened to the vehicle body (23) and at the other end to the axle (18) of the vehicle; - a cross-connection of fluid spaces above and below the pistons of the cylinders (15, 16) in such a way that from the fluid space above the piston of the first cylinder (15) there is a first connection (26) into the fluid space below the piston of the second cylinder (16), and respectively, from the fluid space above the piston of the second cylinder (16) there is a second connection (27) into the space below the piston of the first cylinder (15); and - a first (10) and a second (9) pressure accu¬ mulator arranged in the first (26) and the second (27) cross-connection, respectively, to receive or to deliver an amount of fluid corresponding to the change of the total volume of the fluid spaces of the cylinders (15, 16), the fluid spaces communicating with each other; c h a r a c t e r i z e d in that it further com¬ prises - a first (12) and a second (11) directional valve arranged in the first (26) and the second (27) cross-connection, respectively, to allow a one-way flow from the fluid space above the piston of the second cylinder into the fluid space below the piston of the second cylinder in each particular case; and - a first (14) and a second (13) throttle valve arranged parallel with the first (12) and the second (11) directional valve, respectively. 2. An arrangement according to claim 1, c h a r a c t e r i z e d in that it further com¬ prises a first (3) and a second (4) magnetic valve opening and closing a two-way connection arranged in the first (26) and the second (27) cross-connection, respectively.

Inventors: LEHTOVUO TARMO, LUOSTARINEN HEIKKI, OESTRING ESA, LEHTOVUO, TARMO, LUOSTARINEN, HEIKKI, OESTRING, ESA
Applicants: SISU AUTO OY AB, OY SISU-AUTO AB
Application year: 1990
Main classification: B60G21
IPC codes: B60G21