MOTOR VEHICLE CONSTRAINING APPARATUS, PARTICULARLY SUITABLE FOR VEHICLE RUNNING SIMULATION BENCHES

Abstract: The apparatus comprises three rigid elements (1, 2, 3) joined articulatedly together by constraint means such as to allow a first articulated element (1) to oscillate with respect to a second element (2) about a first substantially fixed axis of virtual oscillation (X), and to allow a second articulated element (2) to oscillate with respect to the third element (3) about a second substantially fixed axis of virtual oscillation (Y) perpendicular to the first axis; the first articulated element (1) is arranged to be fixed rigidly to the vehicle body (4) and the third element (3) is arranged to be fixed to a support structure (5) interposed between the apparatus and the apparatus base.

Description: This invention relates to a motor vehicle constraining apparatus for use on vehicle running simulation benches, according to the preamble of claim 1- Simulation benches enable the vehicle running conditions to be reproduced in an environment of small dimensions comparable with the dimensions of the vehicle itself and allows the value certain physical quantities to be measured during running. A bench of this type therefore comprises a runway on which the wheels of the vehicle rest and an apparatus to constrain this latter in such a manner as to prevent it moving forwards. For the running simulation provided by the bench to be valid, the constraining apparatus must allow some degrees of freedom of movement and manoeuvre, which although being of subsidiary order compared with the forward movement, are of fundamental importance in obtaining proper reproduction of the running behaviour. The movements which such an apparatus must allow are substantially the suspension movements (roll, pitch and translation in a direction substantially normal to the ground) and the attitude movements (lateral translation and yaw). Currently used constraining apparatus normally comprises assemblies of flexible elements anchored in various ways to the vehicle body and passing about pulleys fixed to points somewhat distant for the body, so as to keep the direction of the constraints imposed by said elements constant even when the body moves. In other case such constraining apparatus comprises lattice structures formed to generate a virtual constraint through the vehicle barycentre, these structures being positioned substantially laterally to the sides of the vehicle. The constraining apparatus of the aforesaid type has numerous drawbacks. Firstly, such apparatus involves rather large masses and moments of inertia which cannot be totally ignored compared with those of the vehicle itself, thus altering the running conditions simulated by the bench and negatively influencing the measurements taken during the test. In addition, such apparatus is rather bulky and considerably reduces access to the vehicle under test. Furthermore, the operations involved in connecting the vehicle to such constraining apparatus are long and complicated and require particular care and caution. Finally, such apparatus is not always able to provide rigorous virtual constraint of the barycentre of the vehicle and preserve all the degrees of freedom which this possesses under real operating conditions. A constraining apparatus of the type defined in the preamble of claim 1 is disclosed in US-A-3 837 221, wherein the third element is defined by a bracket. The object of the present invention is to provide a constraining apparatus of the type defined in the preamble of claim 1 which is free of the stated drawbacks in that it has low masses and moments of inertia compared with those of the vehicle, it allows the same access to the vehicle as under normal running conditions, it enables the vehicle to be fixed to the apparatus by simple and rapid operations, and it rigorously constrains only the barycentre of the vehicle while allowing it the same degrees of freedom of movement which it possesses when under real running conditions. This object is attained by a motor vehicle constraining apparatus particularly suitable for vehicle running simulation benches, having the features of claim 1- The apparatus of the present invention will be more apparent from the detailed description thereof given by way of example with reference to the accompanying drawings in which: Figure 1 is a diagrammatic representation of the elements and basic parts of the apparatus of the invention; Figure 2 is a perspective representation of one embodiment of the invention, with some parts shown in section; Figure 3 is a perspective representation of some parts of the apparatus corresponding to a slightly different embodiment from the preceding. The constraining apparatus of the invention is for use on a motor vehicle running simulation bench, not shown in the figures, which comprises substantially a runway on which the vehicle is rested and formed for example from belts, rollers or crawler tracks. The purpose of the constraining apparatus according to the invention, shown in Figures 1 and 2 in which corresponding members and parts are indicated by the same reference numeral, is to prevent the vehicle moving forward on the runway while allowing it those degrees of movement and manoeuvring freedom which pertain during vehicle running. The apparatus comprises three rigid elements indicated by 1, 2 and 3 (Figure 1), joined articulatedly together by constraint means such as to allow a first element 1 to oscillate with respect to a second element 2 about a first substantially fixed axis of oscillation (indicated by X), and to simultaneously allow the second element 2 to oscillate with respect to the third element 3 about a second substantially fixed axis of oscillation (indicated by Y) perpendicular to the first axis. The X and Y axes can be coplanar and intersect at the barycentre G₁ of the assembly formed from the vehicle and those parts of the apparatus rigid with it, or alternatively said axes can pass through the barycentres G₁, G₂ of said assembly with respect to its movement about the axes X and Y respectively. The first element 1 is arranged to be fixed rigidly to the vehicle body in any convenient manner, for example to important structural elements such as the longitudinal (side) members 4 (Figure 2). The third element 3 is arranged to be fixed to a support structure, indicated overall by 5 (Figure 1), which is interposed between the apparatus itself and the apparatus base. In one non-illustrated embodiment of the structure according to the invention, the support structure 5 can comprise simply a rigid connection member 6 (Figure 1) arranged to rigidly connect element 3 directly to the base. Said constraint means which connect together the three said elements conveniently comprise a first and a second series of guides 7 and 8 lying along a cylindrical surface having an axis which coincides with the respective oscillation axis, the guides 7 and 8 being interposed between element 1 and element 2 and between this latter and element 3 respectively. These guides are arranged to allow relative oscillation movements about said X and Y ares respectively. The third element 3 comprises a pair of mutually facing plates 3a, 3b between which there is disposed an assembly of dynamometer cells 9 arranged to measure the components of the forces transferred between the plates. Said assembly conveniently comprises four cells disposed such that the relative axes lie along the lateral sides of a pyramid, as is clearly visible in Figure 2. As can be clearly seen from Figure 2 element 1 comprises substantially a beam of rectilinear axis to which the longitudinal members 4 of the vehicle body and part of the guides 7 of the first series are fixed. The second element 2 is substantially cross-shaped and comprises a first pair of substantially colinear arms 2a to which are parallel to axis Y and which parts of the guides 7 of the first series are fixed, and a second pair of substantially colinear arms 2b perpendicular to the preceding, which are parallel to axis X and to which parts of the guides 8 of the other series are fixed. Conveniently, said guides comprise shoes with rolling body circulation (not shown). The connection element 6 of the support structure 5, the former being fixed to the third element 3, is mobile axially in the direction of a third axis Z perpendicular to said X and Y axes. In addition, said connection member can rotate about the Z axis. For this purpose the connection member 6 is housed in a sleeve 12 rigid with a slide 13 mobile in the direction of the Y axis. Conveniently, a bush (not shown) comprising rolling body circulation is interposed between the member 6 and sleeve 12. The slide 13 is supported by a pair of rectilinear guides 14 (Figure 2) having their axis parallel to the Y axis, and is provided with two pairs of tracks 15, 16 arranged to cooperate with corresponding tracks 17 and 18 on said guides, as can be clearly seen in Figure 2. Conveniently, bearings 19 comprising rolling body circulation are interposed between said tracks. An actuator 22 arranged to apply a predetermined force to the slide 13 in the direction of the Y axis conveniently comprises a hydraulic cylinder the rod 23 of which is connected to the slide. The apparatus also comprises a rod 24 rigidly connected to the plate 3a of element 3, said plate rotating about the Z axis under the action of an actuator 25 which applies a torque of predetermined value to said rod. Consequently, as can be clearly seen in Figure 2, said rod is housed within an axial bore in the connection member 6, its lower end projecting from said member. The actuator 25 (Figure 2) consists conveniently of a hydraulic cylinder fixed to the slide 13 and provided with an axially mobile rod 26 to which there is connected a rack 27 engaging with a toothed sector 28 rigid with a rotatable ring 29. This latter is fixed onto a seat on the slide 13 by way of a ring of rolling bodies 30. A coupling indicated overall by 31 is arranged to transmit rotation from the ring 29 to the lower end of the rod 24 to enable the rod to translate axially in the direction of the Z axis. This coupling comprises at least one pair of connecting links 32 hinged together. One of them is hinged to the rotatable ring 29 and the other to an arm 33 rigid with the rod 24 in such a manner as to form a compass. The coupling conveniently comprises two pairs of such connecting links. In the embodiment shown in Figure 3, the sleeve 12 oscillates about the slide 13, being hinged to this by a ball joint 34. In addition, two actuators 35 and 36 with mutually orthogonal axes are arranged to apply predetermined forces to the sleeve 12 to cause it to oscillate about axes passing through the centre of the joint 34. Said actuators are conveniently in the form of hydraulic cylinders the casing and rod of which are hinged to the slide 13 and sleeve 12 respectively. It is apparent that although the apparatus of the invention prevents the vehicle undergoing forward movement, it preserves all the degrees of freedom of movement necessary to reproduce real vehicle running conditions. In this respect all suspension movements (roll, pitch and translation in a direction orthogonal to the support plane) are preserved. Roll motion (virtual rotation about the X axis) is allowed as a consequence of the relative oscillation of the articulated element 1 about said axis, enabled by the cylindrical guides 7. The pitch motion (oscillation about the Y axis) is obtained by the oscillation of element 2 about said axis, enabled by the presence of the cylindrical guides 8. The vertical translational motion in the direction of the Z axis is enabled by the coupling between the connection member 6 and the sleeve 12. The apparatus also preserves the degrees of freedom of movement necessary to reproduce the attitude motion (transverse movement and yaw). Motion in the transverse direction (in the direction of the Y axis) is enabled by the slide 13 which moves transversely on the guides 14, and yaw motion is enabled by the rotation of the connection member 6 about the Z axis by virtue of the type of coupling between said member and the sleeve 12. The apparatus of the invention also enables certain actions which the vehicle undergoes under certain running conditions to be simulated, such as centrifugal force action, lateral wind action, and the action of a wind oblique to the running direction which tends to rotate the vehicle about a vertical axis. In this respect, by means of the actuator 22 it is possible to apply to the slide 13 a force of predetermined value in the direction of the Y axis and thus in a direction normal to the running direction, which can simulate the action of the centrifugal force on the vehicle along a curve or the action of the wind on the vehicle. In addition, by means of the actuator 25 it is possible to apply a torque of predetermined value to the rod 24 to generate a yaw moment which could simulate the effect of a wind oblique to the running direction. By means of the coupling formed by the rack 27 (Figure 2) and toothed sector 28 the actuator 25 is able to rotate the ring 29, which by way of the coupling 31 transmits rotation to the rod 24. The coupling 31 allows correct transmission of this moment, even if the vehicle undergoes movement in the direction of the Z axis. The two pairs of connecting links 32 which connect the ring 29 to the arm 33 allow the rod 24 and slide 13 to undergo relative axial movements. Finally, with the embodiment of Figure 3 it is also possible to induce by means of the actuator 35 a rotation about an axis parallel to the X axis, and by means of the actuator 36 a rotation about an axis parallel to the Y axis, thus tending to cause the sleeve 12 to oscillate about axes passing through the centre of the coupling 34. The assembly of dynamometer cells 9 allows the components of the forces transferred between the plates 3a and 3b forming part of the third element 3 to be measured. It is apparent that because of the small dimensions, the shape and arrangement of the members and parts of the apparatus, there is no generation of forces or moments of inertia during its operation which are of such as extent as to negatively influence the measurements or the vehicle motion. In addition, as the apparatus is positioned totally below the vehicle, this latter remains completely accessible from all sides. Again, the operations required to connect the vehicle to the apparatus are simple and rapid, it being necessary only to fix the end of element 1 to the longitudinal members 4. It is apparent that modifications can be made to the invention in terms of both the shape and arrangement of the various parts, but without leaving the scope of the inventive idea.

Claims: A motor vehicle constraining apparatus particularly suitable for vehicle running simulation benches, comprising three rigid elements (1, 2, 3) joined articulately together by constraint means such as to allow a first element (1) to oscillate with respect to a second element (2) about a first substantially fixed oscillation axis (X), and to allow a second element (2) to oscillate with respect to the third element (3) about a second substantially fixed articulation axis (Y) perpendicular to the first axis, said first element (1) being arranged to be fixed rigidly to the vehicle body (4) and the third element being arranged to be fixed to a support structure (5) interposed between said apparatus and a base, characterized in that said third element (3) comprises a pair of mutually facing plates (3a, 3b) between which there is disposed an assembly of dynamometer cells (9) arranged to measure the components of the forces transferred between said plates. An apparatus as claimed in claim 1, characterized in that said constraint means comprise a first (7) and a second (8) series of guides lying along a respective cylindrical surface having an axis which coincides with the respective oscillation axis (X, Y), said first and second series (7, 8) of guides being interposed respectively between said first (1) and second (2) element and between said second (2) and third (3) element and arranged to allow relative oscillation movements about said first (X) and second (Y) axis respectively. An apparatus as claimed in claim 1 or 2, characterized in that said assembly of dynamometer cells comprises four cells (9) disposed such that their axes lie along the lateral sides of a pyramid. An apparatus as claimed in one of the preceding claims, characterised in that said support structure (5) comprises a rigid connection member (6) arranged to rigidly connect said third element (3) to the floor. An apparatus as claimed in one of claims 1 to 3, characterised in that said support structure (5) comprises a connection member (6) fixed to said third element (3) and mobile axially in the direction of a third axis (Z) perpendicular to said first (X) and second (Y) axes. An apparatus as claimed in one of claims 1 to 3, characterised in that said support structure (5) comprises a connection member (6) fixed to said third element (3) and rotatable about a third axis (Z) perpendicular to said first (X) and second (Y) axes. An apparatus as claimed in one of claims 1 to 3, characterised in that said support structure (5) comprises a connection member (6) fixed to said third element (3), and mobile in the direction of a third axis (Z) perpendicular to said first (X) and second (Y) axes and rotatable about said axis within a sleeve (12) rigid with a slide (13) mobile in the direction of said second axis (Y). An apparatus as claimed in claim 7, characterised by comprising a first actuator (22) arranged to apply a predetermined force to said slide (13) in the direction of said second axis (Y). An apparatus as claimed in one of claims 5 to 8, characterised by comprising a rod (24) rotationally rigidly connected to one of said two plates (3a, 3b) of said third element (3) and rotatable about said third axis (Z) under the action of a second actuator (25) arranged to apply a torque of predetermined value to said rod. An apparatus as claimed in one of claims 2 to 9, characterised in that said second element (2) is in the form of a cross and comprises a first pair of substantially colinear arms (2a) which are parallel to said second axis (Y) and to which parts of said guides (7) of said first series are fixed, and a second pair of substantially colinear arms (2b) perpendicular to said first arms, which are parallel to said first axis (X) and to which parts of said guides (8) of said second series are fixes, said first element (1) comprising a beam of rectilinear axis to which said vehicle body (4) and parts of said guides (7) of said first series are fixed to allow roll and pitch movement of the vehicle. An apparatus as claimed in claim 10, characterised in that said guides (7, 8) comprise shoes with rolling body circulation. An apparatus as claimed in one of claims 7 or 8 characterised by comprising a pair of guides (14) arranged to support said mobile slide (13), this latter being provided with two first tracks (15) arranged to cooperate with corresponding traks (17) of a first of said guides (14) and with two second tracks (16) arranged to cooperate with corresponding tracks (18) of said guides (14), bearings with rolling body circulation (19) being interposed between said guide tracks and slide tracks. An apparatus according to claims 7 or 8 and claim 9 characterised in that said second actuator (25) comprises a hyrdaulic cylinder provided with an axially mobile rod (26) to which there is fixed a rack (27) engaging with a toothed sector (28) rigid with a ring (29) rotatable on said slide (13) and a coupling (31) arranged to transmit rotation from said ring (29) to said rod (24) to allow axial translation of said rod. An apparatus as claimed in claim 13, characterised in that said coupling (31) comprises at least one pair of connecting links (32) hinged together, one of said connecting links being hinged to said ring (29) and the other beig hinged to an arm (33) rigid with said rod (24). An apparatus as claimed in one of claims 7 to 14, characterised by comprising a third and fourth actuator (35, 36) which have their axes subtantially perpendicular and are arranged to apply predetermined forces to said sleeve (12) to cause it to oscillate about axes parallel to said axes (X, Y), said sleeve being mounted to oscillate on said slide by means of a ball joint (34) the centre of which lies on the sleeve axis.

Inventors: MORELLI, ALBERTO
Applicants: FIAT AUTO S.P.A.
Application year: 1989
Main classification: G01M17
IPC codes: G01M17