Measuring device on air cushion

Abstract

Measuring device (3) for a motor vehicle (1), comprising a chassis (9) and a fixing device (10) for fixing to a hub (4A, 4B) of the motor vehicle, the fixing device being supported by the chassis, characterized in that the measuring device comprises at least one air cushion (13), the at least one air cushion is fixed on a bottom surface (14) of the chassis and is used for cooperating with a horizontal surface (S) so as to enable the measuring device to move on the horizontal surface.

Description

Field of the Invention

[0001] The present invention relates to a measuring device for attachment to a wheel hub of a motor vehicle. The present invention also relates to a test bench comprising such a measuring device. The present invention also relates to a method of installing and a method of removing such a measuring device. Background Art

[0002] To characterize the performance of a motor vehicle, test benches equipped with measuring devices for attachment to vehicle wheel hubs are known. These test benches allow measurements to be made in a highly reproducible manner without using the vehicle in an external environment. Each measuring device generally includes a chassis that rests on the ground and supports a fixing device for attachment to the vehicle wheel hub. Each measuring device may also include torque generating means such as an electric motor for generating a driving torque or a resistance torque, and sensors such as torque sensors. The rotational connection about the wheel hub axis of rotation of the fixing device is generally supported by the chassis. The torque sensor is configured to measure the torque transmitted between the wheel hub and the driving or resistance torque generating means. To characterize the vehicle performance, one such measuring device is coupled to each wheel hub of the vehicle.

[0003] To mount the vehicle on such a test bench, it is generally done in the following manner. First, the vehicle equipped with its wheels is brought into the laboratory. Then the vehicle is lifted by a lifting device so that it no longer rests on the ground by its wheels. Then, the wheels of the vehicle are removed in order to access the wheel hubs. Next, the fixing device of the measuring device is coupled to each wheel hub. For this purpose, the fixing holes provided for fixing the vehicle wheels of the wheel hub are generally used. The fastening bolts are passed through each fixing hole of the wheel hub and the fixing holes provided in the fixing device for this purpose. Then the fastening bolts are tightened in order to firmly fix each wheel hub to the fixing device of the measuring device. Once the wheel hub is fixed to the fixing device, the lifting device is gradually removed so that the weight of the vehicle or at least the weight of the vehicle axle falls on the measuring device. Thus, the vehicle is supported by its wheel hubs, which allows test conditions to be obtained that are highly representative of the vehicle's actual use conditions.

[0004] The operation of coupling the wheel hub to the fixing device is a long and complex operation. In fact, if the fixing holes of the wheel hub and the corresponding fixing device are not properly aligned, it is not possible to insert the fastening bolts and / or there is a risk of damaging the wheel hub and / or the fixing device. In addition, when this operation is performed improperly, the assembly formed by the vehicle and the measuring device may have residual stresses and / or geometric alignment defects, which may cause the measurements taken to be incorrect. Therefore, the coupling operation requires the combination of a horizontal displacement of the measuring device and a vertical displacement of the vehicle. Therefore, it is necessary to move a large mass very precisely.

[0005] For a vehicle positioning measurement device, it is known to mount the measurement device on a guide rail. The guide rail is configured to horizontally move the measurement device either along the longitudinal axis of the vehicle or along the transverse axis of the vehicle. However, the use of the guide rail requires a large infrastructure. In addition, the measurement device mounted on the guide rail has limited mobility. In particular, the measurement device cannot be moved between different laboratories. The published document EP3325937A1 discloses such a measurement device, for example.

[0006] Measurement devices mounted on casters are also known. Such a measurement device can be manually moved on a flat ground and then stabilized with detachable stabilizing feet. The published document US 8505374B1 discloses such a measurement device, for example.

[0007] However, the measurement devices known in the prior art are not satisfactory and cannot achieve connection to a vehicle wheel hub in a simple and precise manner.

[0008] After characterizing the vehicle performance, the measurement device is disassembled, especially separating the fixing device and the wheel hub. The separation operation is also a particularly tricky operation. In fact, during this operation, a vehicle lifting device is used again, and the load applied by the vehicle is gradually transferred from the measurement device to the lifting device. If the vehicle is not lifted sufficiently or is lifted excessively, there will still be stress at the interface between the wheel hub and the fixing device. Loosening the fastening bolts connecting the wheel hub and the fixing device then causes a sudden release of the residual stress, resulting in damage to the fixing device and / or the wheel hub. Summary of the Invention

[0009] The object of the present invention is to provide a measurement device, an installation method and a disassembly method of such a measurement device, so as to overcome the above-mentioned drawbacks and improve the measurement device and its installation method known in the prior art.

[0010] More precisely, the primary object of the present invention is a measurement device that can be simply and precisely connected to a vehicle wheel hub. Overview of the Invention

[0012] The present invention relates to a measurement device for a motor vehicle, the measurement device including a chassis, a fixing device for fixing to a wheel hub of the motor vehicle, a torque generating device for generating a driving torque or a resistance torque, in particular a motor, a transmission device connecting the torque generating device to the fixing device, and a torque sensor configured to measure the torque transmitted between the torque generating device and the fixing device. The fixing device and the torque generating device are supported by the chassis. The measurement device includes at least one air cushion, and the at least one air cushion is fixed to the bottom surface of the chassis and is used to cooperate with a horizontal surface to move the measurement device on the horizontal surface.

[0013] The at least one air cushion may include at least three air cushions. The at least one air cushion may be configured such that the measuring device is supported on the ground only by the at least one air cushion when the at least one air cushion is operating.

[0014] The measuring device may include a pneumatic pressure changing device for changing the air pressure in the at least one air cushion to change the position of the fixing device relative to the vertical axis.

[0015] The measuring device may include a compressed air source fixed to the chassis and at least one pneumatic conduit connecting the compressed air source to the at least one air cushion.

[0016] The at least one air cushion may include at least two air cushions, and the measuring device may include an automatic pressure distributor configured to adjust the pneumatic pressure between the at least two air cushions so as to keep the measuring device in a suspended state when transferring a load from a lifting device for lifting a motor vehicle to the measuring device.

[0017] The fixing device may be rotationally hinged relative to the chassis about a transverse axis perpendicular to the rotational axis of the wheel hub.

[0018] The transmission device may include a constant velocity member.

[0019] The measuring device may include at least one support leg fixed to the chassis, the at least one support leg being separate from the at least one air cushion. When the at least one air cushion is not operating, the at least one support leg is used to support on a horizontal surface and support the chassis, and when the at least one air cushion is operating, the at least one support leg is used to be in a position above the ground.

[0020] The present invention also relates to a test bench including two measuring devices as defined above, the two measuring devices being independent of each other. The fixing device of the first measuring device is for fixing to the first wheel hub of a motor vehicle, and the fixing device of the second measuring device is for fixing to the second wheel hub of the motor vehicle.

[0021] The present invention also relates to an installation method for installing a measuring device as defined above, the installation method including:

[0022] - lifting the measuring device off the ground by activating the at least one air cushion, and then

[0023] - moving the measuring device by horizontal translation and / or by rotation about the vertical axis so that the fixing device is aligned with the wheel hub of the motor vehicle or with an adapter fixed to the wheel hub of the motor vehicle, and then

[0024] - fixing the fixing device of the measuring device to the wheel hub of the motor vehicle or to an adapter fixed to the wheel hub of the motor vehicle.

[0025] The installation method may include:

[0026] - After fixing the fixing device of the measuring device to the wheel hub of the motor vehicle or to an adapter fixed to the wheel hub of the motor vehicle, deactivate the at least one air cushion, and then

[0027] - Perform a torque measurement, during which a driving torque or a resistance torque is applied to the wheel hub by a torque generating device.

[0028] The installation method may include:

[0029] - Lift the motor vehicle with a lifting device so that at least one wheel of the motor vehicle leaves the ground, and then

[0030] - Remove the at least one wheel of the motor vehicle to access at least one wheel hub, and then

[0031] - Lift the measuring device off the ground by activating the at least one air cushion, and then

[0032] - Move the measuring device by horizontal translation and / or by rotation about a vertical axis so that the fixing device is aligned with the wheel hub of the motor vehicle or with an adapter fixed to the wheel hub of the motor vehicle, and then

[0033] - Fix the fixing device of the measuring device to the wheel hub of the motor vehicle or to an adapter fixed to the wheel hub of the motor vehicle, and then

[0034] - Transfer the load applied by the weight of the motor vehicle from the lifting device to the measuring device, and then

[0035] - Deactivate the at least one air cushion, and then

[0036] - Perform a torque measurement, during which a driving torque or a resistance torque is applied to the wheel hub by a torque generating device.

[0037] The present invention also relates to a disassembly method for disassembling the measuring device as defined above, the disassembly method including:

[0038] - Transfer the weight of the motor vehicle from the measuring device to the lifting device for lifting the motor vehicle, and then

[0039] - Adjust the position of the fixing device along the vertical axis by changing the air pressure in the at least one air cushion, and then

[0040] - Detect that there is no stress at the interface between the fixing device and the wheel hub or between the fixing device and an adapter fixed to the wheel hub, and then

[0041] - Separate the fixing device of the measuring device from the wheel hub of the motor vehicle or from an adapter fixed to the wheel hub of the motor vehicle. Description of the Drawings

[0042] These objects, features and advantages of the present invention will be described in detail in the following description of specific embodiments in conjunction with the accompanying drawings in a non - restrictive manner, wherein:

[0043] Figure 1 is a schematic front view of a motor vehicle mounted on a test bench, the test bench being equipped with two measuring devices according to an embodiment of the present invention.

[0044] Figure 2 is a top perspective view of the measuring device according to an embodiment of the present invention.

[0045] Figure 3 is Figure 2 a bottom perspective view of the measuring device of

[0046] Figure 4 is a schematic cross - sectional view of the air cushion of the measuring device. Detailed Description of the Invention

[0047] Figure 1 A motor vehicle 1 mounted on a test bench 2 according to an embodiment of the present invention is schematically shown in a front view. The vehicle 1 can be of any type. For example, it can be a passenger car, a commercial vehicle, a truck or even a bus. The test bench 2 supporting the vehicle 1 is rested on a horizontal surface S, in particular on the ground.

[0048] An orthogonal coordinate system XYZ is defined in the following way: The Y - axis represents the longitudinal axis of the vehicle. In forward straight - line travel, the vehicle moves from the rear to the front in a direction parallel to the longitudinal Y - axis of it. The X - axis is a horizontal axis perpendicular to the Y - axis. The X - axis is oriented from right to left, where left and right are defined according to the viewpoint of the vehicle driver. The Z - axis is parallel to the vertical axis and is oriented from bottom to top.

[0049] According to the illustrated embodiment, the test bench 2 is equipped with two measuring devices 3, which are respectively connected to the right wheel hub 4A and the left wheel hub 4B of the two driving wheels of the vehicle. Each measuring device 3 includes a fixing device 10, and after the wheels fixed to the wheel hubs 4A, 4B are removed, the measuring device is fixed to the wheel hubs 4A and 4B of the vehicle through the fixing device 10.

[0050] The vehicle weight is at least partially supported by the measuring devices 3. More precisely, for a vehicle with four wheels, if four measuring devices 3 fixed to the four wheel hubs of the vehicle are used, the weight of the vehicle 1 is completely supported by the measuring devices 3. If only two measuring devices 3 fixed to the two wheel hubs of two wheels of the vehicle are used, only the weight of the first axle (front axle or rear axle) of the vehicle 1 is supported by the measuring devices, while the weight of the second axle of the vehicle can be supported by the wheels of it resting on the horizontal surface S.

[0051] The two measuring devices 3 fixed to the hubs 4A and 4B may be substantially identical. Therefore, a specific measuring device 3 will now be described.

[0052] The measuring device 3 includes torque generating means for generating a driving torque or a resistance torque, such as an electric motor 6. As a variant, the torque generating means may also include an eddy current brake and / or a hydraulic motor. The torque generating means generates a resistance torque when it tends to resist the rotation of the hub to which it is coupled. The torque generating means generates a driving torque when it tends to drive the rotation of the hub to which it is coupled. The fixing means 10 is connected to the electric motor 6 by a transmission means 7. The measuring device 3 also includes a measuring member 8 or a torque sensor (capteur dynamométrique) 8 for measuring the rotational torque. The torque sensor 8 is arranged to measure the torque transmitted between the electric motor 6 and the fixing means 10. This torque is also equal to the torque transmitted by the hubs 4A, 4B to the fixing means 10. The torque sensor 8 may include, for example, at least one strain gauge that can convert the deformation of the member into a change in resistance. A computer connected to the measuring device may be configured to record the electrical signal from the torque sensor 8. In addition, the measuring device 3 also includes a chassis 9 for supporting the fixing means 10, the electric motor 6, the transmission means 7 and the torque sensor 8. As will be seen in more detail later, the measuring device is configured to move on a horizontal surface S and then stabilize at a selected position.

[0053] In addition, the measuring device 3 can be used to measure other characteristics of the vehicle 1, such as the characteristics of the steering system, the suspension system or the braking system.

[0054] The fixing means 10 (more clearly visible in Figure 2 ) may be in the form of a substantially circular flange. The fixing means 10 is used to be fixed to the vehicle hub, in particular through an adapter. The fixing means 10 may include holes 11 and may also include fastening bolts 12 pre-set in the holes 11 for fixing the hub or the adapter. The adapter allows the fixing means 10 to be fixed to any form of hub 4A. On the one hand, it includes holes for cooperating with the fastening bolts 12, and the positions of these holes correspond to the positions of the holes 11 of the fixing means 10. On the other hand, it includes a fixing interface specifically adapted to the hub 4A of the vehicle to be tested, such as holes that can be positioned opposite the hub holes provided for fixing the wheel.

[0055] The vehicle 1 has a camber angle A1, which is shown in an exaggerated manner in Figure 1 . The camber angle A1 represents the angle formed by the wheel rotation plane and the Z-axis. For some vehicles, the camber angle can typically be between 0° and 3°, or even exceed 3°. The camber angle can be either negative (as shown in Figure 1 ) or positive without distinction. As shown in Figure 1As schematically shown, the fixing device 10 of each measuring device 3 can be tilted relative to the chassis 9 about a transverse axis Y1 parallel to the Y axis.

[0056] The transmission device 7 includes a first shaft and a second shaft, and the second shaft is connected to the first shaft through a constant velocity joint. The first shaft is coupled to the motor 6, in particular to the rotor of the motor 6, and the first shaft can rotate relative to the chassis 9 about a first axis X1 parallel to the X axis. The second shaft is fixed to the fixing device 10, and the second shaft can rotate relative to the chassis 9 about a second axis X2. Therefore, the fixing device 10 can rotate relative to the chassis 9 about the second axis X2. The axis X2 coincides with the rotation axis of the hubs 4A, 4B to which the fixing device is connected. The angle formed between the two axes X1 and X2 is approximately equal to the camber angle A1. The axes X1 and X2 are perpendicular to the transverse axis Y1. When the camber angle A1 is zero, the two axes X1 and X2 can coincide and be parallel to the X axis. When the camber angle A1 is not zero, the two axes X1 and X2 extend in a plane parallel to the X axis and the Z axis.

[0057] The constant velocity joint, also known as a constant velocity coupling or a drive coupling, is a ball and socket joint type connecting member that ensures the connection between the first shaft and the second shaft such that even if the two axes X1 and X2 are misaligned, the speed of the first shaft and the speed of the second shaft are the same at each moment. The constant velocity joint can be, for example, a finger ball and socket joint type. The constant velocity joint can include a single rotation center or a ball and socket joint center located on the axis Y1. This positioning of the rotation center allows for a more compact and lighter measuring device that also has a smaller resistance torque when the fixing device 10 is tilted. Alternatively, the constant velocity joint can include two different rotation centers or ball and socket joint centers. As a variant, the measuring device 3 can be simplified and can not include any constant velocity joint.

[0058] The chassis 9 forms a rigid structure for supporting different components of the measuring device. For example, it can include a metal frame. Also as Figure 2 shown, the chassis 9 can include a substantially rectangular base. The chassis 9 can also be equipped with a handle, which enables the operator to manually move the measuring device 3 on the horizontal surface S by pulling and / or by pushing.

[0059] The measuring device 3 includes a set of air cushions 13 arranged on the bottom surface 14 of the chassis 9. The bottom surface 14 represents the surface of the chassis 9 facing the horizontal surface S. When the air cushions are activated, the air cushions 13 are configured to lift the measuring device 3 above the horizontal surface S. In particular, the air cushions 13 are supplied by a compressed air source 15, which generates an air flow such that the measuring device 3 can be slightly lifted off the horizontal surface S. Advantageously, the compressed air source 15 is mounted on the measuring device 3, in particular fixed to the chassis 9, and is connected to the air cushions 13 through a pneumatic conduit 16. The compressed air source 15 can, for example, include a pump and an air inlet for sucking in ambient air, and can be supplied with electrical energy from a power distribution network. Advantageously, the compressed air source 15 includes a pneumatic pressure changing device for changing the air pressure and a control box for adjusting the air pressure in at least one or each of the air cushions. As a variant, the measuring device 3 may not include the compressed air source 15, and the air cushions 13 can be supplied by a compressed air distribution network separate from the measuring device 3. However, the distribution network can include a pneumatic pressure changing device for changing the air pressure and a control box for allowing the adjustment of the air pressure in at least one or each of the air cushions.

[0060] Figure 4 An embodiment of the air cushion 13 is schematically shown. The air cushion 13 includes a base 17, on which a skirt 18 is fixed. The skirt 18 is, for example, annular and / or made of leather, for example. The base 17 is fixed to the bottom surface 14 of the chassis 9. The skirt 18 is provided with an air inlet 19 and an air outlet 20 connected to the compressed air source 15. The air outlet 20 is arranged approximately towards the center of the skirt 18 and is directed towards the horizontal surface S. When the air cushion 13 is supplied with an air flow, the pressurized air enters the skirt 18 through its air inlet 19 and exits through the air outlet 20. Thus, an air gap 21 is formed between the skirt 18 and the horizontal surface S, resulting in the lifting of the air cushion. The skirt is preferably flexible, but as a variant, the skirt can also be rigid.

[0061] Advantageously, the dimensions of the skirt 18 and / or the air gap 21 along the Z-axis can vary according to the air pressure in the air cushion 13. Thus, by changing the air pressure circulating in the air cushion 13, the position of the fixing device 10 along the Z-axis can be adjusted within a range of several millimeters or even several centimeters. Advantageously, the air cushion 13 is configured such that the position of the fixing device 10 along the vertical Z-axis can vary by at least 5 mm, preferably at least 10 mm, and even at least 20 mm according to the air pressure in the air cushion. The control box for allowing the adjustment of the air pressure in the air cushion can be used for this purpose.

[0062] The horizontal surface must be smooth and clean enough to allow the normal operation of the air cushion 13. Preferably, the horizontal surface has no cracks or holes through which the pressurized air may escape.

[0063] From Figure 3It can be seen quite clearly that the measuring device 3 includes three air cushions 13 fixed to the bottom surface 14 of the chassis 9. In particular, the measuring device 3 includes two air cushions arranged on the chassis side below the fixing device 10 and one air cushion located on the side of the chassis 9 opposite to the fixing device 10. The center of gravity of the triangle formed by the centers of these three air cushions can be approximately aligned with the center of gravity of the measuring device 3.

[0064] As a variant, the number of air cushions 13 can be different, for example, one, two, four or even more air cushions. By using at least three air cushions, the entire chassis can be supported only by these air cushions 13. According to an implementation variant, the measuring device 3 can include one or more casters that rest on the ground and cooperate with at least one air cushion 13 to support the measuring device. The number of air cushions 13 included in the measuring device can be adjusted according to the mass of the measuring device.

[0065] In addition, the measuring device 3 also includes a set of feet 22 fixed to the bottom surface 14 of the chassis 9. The feet 22 are separated from the air cushions 13. These feet can be, for example, studs made of rubber or flexible material and are suitable for filtering vibrations. As Figure 1 shown, when the air cushions are not working, that is, when the air cushions are not supplied with pressurized air, the feet 22 are used to support on the horizontal surface S to support and stabilize the chassis 9. When the air cushions are working, that is, when the air cushions are supplied with pressurized air, the feet 22 are used to be in a position above the ground and thus do not contact the ground.

[0066] To install the vehicle 1 on the test bench 2, it can be done as follows. First, bring the vehicle 1 into the laboratory. Then, use a lifting device to lift the vehicle so that the wheels leave the ground, and then remove the wheels to access the hubs 4A and 4B. Then an adapter can be fixed to the hubs 4A and 4B instead of the wheels.

[0067] At the same time, two independent measuring devices 3 are also brought into the laboratory. For this purpose, the air cushion 13 is activated by supplying pressurized air to the air cushion. Each measuring device 3 is then lifted above the horizontal surface 3. Each measuring device 3 can thus be easily moved on the horizontal surface S. In particular, each measuring device can be freely translated along the X-axis and the Y-axis and pivoted about the Z-axis. The easy movement not only reduces the burden on the person operating the measuring device, but also enables the measuring device to be positioned with high precision. In fact, there is no friction between the measuring device and the horizontal surface, which allows for the assumption that the measuring device 3 can perform very small displacements, such as displacements on the order of centimeters or millimeters. It is very difficult to obtain such movement with measuring devices mounted on casters because their movement requires overcoming the adhesion force. The adhesion force is usually greater than the force required to roll these measuring devices. Therefore, to move a measuring device mounted on casters over a short distance, a relatively large force must be applied in one direction and then a holding force in the opposite direction once the measuring device starts to move. In addition, the initial orientation of the casters tends to make the direction of movement of the applied measuring device not necessarily correspond to the desired direction of movement. This operation requires a great deal of force and is very cumbersome. In contrast, with the aid of the present invention, each measuring device 3 can be easily moved so that the fixing device 10 is aligned with the hubs 4A, 4B or with the adapter fixed to the hub.

[0068] Advantageously, the air cushion also allows the measuring device to be moved along the vertical Z-axis. For this purpose, it is only necessary to change the air pressure in each air cushion. It is also possible to obtain a certain inclination with respect to the ground by individually adjusting the air pressure level of each air cushion.

[0069] Then, it is only necessary to bring the fixing device 10 into contact with the adapter fixed to the hubs 4A, 4B so that the fixing device 10 automatically adapts to the vehicle camber. The fixing device pivots freely about the transverse axis Y1. An angle is then established between the first axis X1 and the second axis X2, the value of which is equal to the vehicle camber A1. The first axis X1 remains parallel to the X-axis, while the second axis X2 is inclined in the plane containing the X-axis and the Z-axis. When the fixing device 10 is in contact with the adapter fixed to the corresponding hubs 4A, 4B, the position or orientation of the measuring device 3 can be easily adjusted by moving on the air cushion 13. When the fixing device 10 is completely aligned with the adapter fixed to the hub 4A or 4B, the two elements can be fixed with the fastening bolts 12.

[0070] The two measuring devices 3 can be assembled to the two hubs 4A, 4B successively or simultaneously.

[0071] Then, when the two measuring devices 3 are respectively fixed to the two wheel hubs 4A and 4B, the lifting device can be deactivated, so that the vehicle weight or at least the weight of one vehicle axle gradually falls onto the measuring devices 3. Therefore, when the lifting device is deactivated, a load transfer from the lifting device to the measuring devices occurs. During this load transfer, the air cushions remain operational so as to be able to adjust the position and orientation of each measuring device. Advantageously, the size of the air cushions is determined to support the weight of the measuring device 3 itself plus the weight exerted by the vehicle 1 on the fixing device 10. Since the adhesion of the measuring device to the horizontal surface is very small, during this load transfer, each measuring device naturally positions itself in a position with less stress.

[0072] Advantageously, the measuring device 3 includes an automatic pressure distributor configured to adjust the pneumatic pressure between the air cushions so as to keep the measuring device in a lifted state when transferring the load from the lifting device to the measuring device. In fact, fixing the wheel hub to the fixing device 10 causes the center of gravity of the measuring device 3 to move in the direction of the fixing device 10. In Figure 1 , the force exerted by the measuring device not connected to the vehicle is represented by a first arrow F1. The second arrow F2 represents the force exerted by the measuring device after being connected to the vehicle wheel hub and transferring the load. In the absence of a pressure distributor, the movement of the center of gravity may cause the air cushion 13 arranged on the side of the fixing device 10 to be more squeezed. This greater squeezing may cause some feet 22 of the measuring device to come into contact with the horizontal surface S, thus resulting in the loss of mobility of the measuring device. Due to the pressure distributor, the measuring device remains horizontal or substantially horizontal during the load transfer. Therefore, the measuring device does not rest on the ground before the vehicle load is completely transferred to the measuring device. Since the measuring device remains in a lifted state throughout the load transfer process, it can naturally be positioned in a position with less stress.

[0073] When the load transfer from the lifting device to the measuring device is completed, the air cushions can be deactivated so that each measuring device is supported on the ground by its feet 22. Then, torque measurement (mesure dynamométrique) can be carried out, during which a resistance torque or a driving torque is applied to the wheel hub of the vehicle wheel.

[0074] With the present invention, there is no need to accurately position the vehicle to connect each measuring device. The present invention allows for the consideration of designing smaller-sized experimental centers without the need for a laboratory dedicated to the measurements performed using the measuring device 3. Each measuring device can be easily moved between different laboratories. Regardless of the position of the vehicle in the laboratory, the measuring device allows alignment with the vehicle under test without increasing stress.

[0075] In addition, the measuring device can be easily moved on a horizontal ground. The measuring device can be easily moved with at least three degrees of freedom, namely translation along the X-axis, translation along the Y-axis, and rotation about the Z-axis. This facilitates the operation of connecting the test device to the vehicle wheel hub. In particular, the free rotation of the measuring device about the Z-axis allows the test device to be coupled to a wheel hub whose axis of rotation is inclined with respect to the X-axis. This occurs, for example, when the steering wheel hub has a non-zero clamping angle, especially when attempting to couple the test device to a deflected steering wheel hub. The measuring device allows torque measurement of the vehicle in different states of the vehicle steering system. Therefore, the test device can envisage a greater number of test configurations.

[0076] The movement of the measuring device is also particularly ergonomic. Therefore, the present invention allows for the envisagement of larger measuring devices that can still be manually moved.

[0077] To separate the test device 3 from the vehicle, the lifting device can be activated to gradually transfer the vehicle weight from the measuring device to the lifting device. Advantageously, the air pressure in each air cushion can be changed so as to more finely adjust the position of each fixing device 10 along the vertical Z-axis until no stress is observed at the interface between the fixing device 10 and the wheel hubs 4A, 4B or between the fixing device 10 and the adapter fixed to the wheel hubs 4A and 4B. This no stress can be detected by visually observing the interface between the fixing device 10 and the wheel hubs 4A, 4B or between the fixing device 10 and the adapter fixed to the wheel hubs 4A, 4B. When no stress is achieved, slight movement may occur at this interface. This movement can be more easily detected if the fastening bolts 12 are partially loosened during this operation. Advantageously, the pressure changing device for changing the air pressure in the said air cushions is positioned such that it can be controlled by the operator while visually observing the interface between the fixing device 10 and the wheel hubs 4A, 4B or between the fixing device 10 and the adapter fixed to the wheel hubs 4A, 4B. Thus, the fixing device 10 can be positioned at a location where the wheel hub no longer exerts any stress or the minimum stress on the fixing device 10. At this position, the fastening bolts 12 can be completely removed without the risk of damaging the vehicle and / or the measuring device.

Claims

1. A measuring device (3) for a motor vehicle (1), the measuring device comprising a chassis (9), fixing means (10) for fixing to the vehicle wheels (4A, 4B) of the motor vehicle, torque generating means in particular an electric motor (6) for generating a driving torque or a resistance torque, a transmission means (7) connecting the torque generating means to the fixing means (10), and a torque sensor (8) configured to measure the torque transmitted between the torque generating means and the fixing means (10), the fixing means and the torque generating means being supported by the chassis, characterized in that, The measuring device includes at least one air cushion (13) which is fixed to the bottom surface (14) of the chassis and is used to cooperate with a horizontal surface (S) to enable the measuring device to move on the horizontal surface.

2. The measuring device (3) according to claim 1, characterized in that, The at least one air cushion (13) includes at least three air cushions; and / or the at least one air cushion is configured such that when the at least one air cushion is operating, the measuring device is supported on the ground only by the at least one air cushion.

3. The measuring device (3) according to any one of the preceding claims, characterized in that, The measuring device includes a pneumatic pressure changing device which is used to change the air pressure in the at least one air cushion so as to change the position of the fixing device (10) relative to the vertical axis (Z).

4. The measuring device (3) according to any one of the preceding claims, characterized in that, The measuring device includes a compressed air source (15) fixed to the chassis (9) and at least one pneumatic conduit (16) connecting the compressed air source to the at least one air cushion (13).

5. The measuring device (3) according to any one of the preceding claims, characterized in that, The at least one air cushion (13) includes at least two air cushions; and the measuring device includes an automatic pressure distributor which is configured to adjust the pneumatic pressure between the at least two air cushions so as to keep the measuring device in a suspended state when transferring a load from a lifting device of a motor vehicle (1) to the measuring device.

6. The measuring device (3) according to any one of the preceding claims, characterized in that, The fixing device (10) is rotationally hinged relative to the chassis (9) about a transverse axis (Y1) which is perpendicular to the rotational axis (X1) of the wheels (4A, 4B).

7. The measuring device (3) according to claim 6, characterized in that, The transmission device (7) includes constant velocity components.

8. The measuring device (3) according to any one of the preceding claims, characterized in that, The measuring device includes at least one support leg (22) fixed to the chassis (9), the at least one support leg being separate from the at least one air cushion (13). When the at least one air cushion is not operating, the at least one support leg is used to support on the horizontal surface (S) and support the chassis, and when the at least one air cushion is operating, the at least one support leg is used to be in a position above the ground.

9. A test bench (2) which includes two measuring devices (3) according to any one of the preceding claims, the two measuring devices being independent of each other. The fixing device (10) of the first measuring device is used to be fixed to the first wheel (4A) of a motor vehicle, and the fixing device (10) of the second measuring device is used to be fixed to the second wheel (4B) of the motor vehicle.

10. An installation method for installing the measuring device (3) according to any one of claims 1 to 8, characterized in that, The installation method includes: - lifting the measuring device off the ground by activating the at least one air cushion (13), and then - moving the measuring device by horizontal translation and / or by rotation about the vertical axis so that the fixing device (10) is aligned with the wheel (4A, 4B) of the motor vehicle or with an adapter fixed to the wheel of the motor vehicle, and then - fixing the fixing device (10) of the measuring device to the wheel of the motor vehicle or to an adapter fixed to the wheel of the motor vehicle.

11. The installation method of the measuring device (3) according to claim 10, characterized in that, The installation method includes: - after fixing the fixing device (10) of the measuring device to the wheel of the motor vehicle or to an adapter fixed to the wheel of the motor vehicle, deactivating the at least one air cushion (13), and then - performing a torque measurement, during which a driving torque or a resistance torque is applied to the wheel by a torque generating device.

12. The installation method of the measuring device (3) according to claim 11, characterized in that, The installation method includes: - Lift the motor vehicle (1) using a lifting device so that at least one wheel of the motor vehicle is lifted off the ground, and then - Remove the at least one wheel of the motor vehicle to access at least one wheel hub, and then - Lift the measuring device off the ground by activating the at least one air cushion (13), and then - Move the measuring device by horizontal translation and / or by rotation about a vertical axis so that the fixing device (10) is aligned with the wheel hub (4A, 4B) of the motor vehicle or with an adapter fixed to the wheel hub of the motor vehicle, and then - Fix the fixing device (10) of the measuring device to the wheel hub of the motor vehicle or to an adapter fixed to the wheel hub of the motor vehicle, and then - Transfer the load exerted by the weight of the motor vehicle from the lifting device to the measuring device (3), and then - Deactivate the at least one air cushion, and then - Perform a torque measurement, during which a driving torque or a resistance torque is applied to the wheel hub by a torque generating device.

13. A disassembly method for disassembling the measuring device (3) according to any one of claims 1 to 8, characterized in that, The removal method comprises: - Transfer the weight of the motor vehicle from the measuring device to the lifting device for lifting the motor vehicle, and then - Adjust the position of the fixing device (10) along the vertical axis (Z) by changing the air pressure in the at least one air cushion, and then - Detect that there is no stress at the interface between the fixing device and the wheel hub or between the fixing device and the adapter fixed to the wheel hub, and then - Separate the fixing device of the measuring device from the wheel hub of the motor vehicle or from the adapter fixed to the wheel hub of the motor vehicle.

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