Portable vehicle-mounted dynamometer

Abstract

A portable vehicle dynamometer comprises a containment frame (2), a drum (3) rotatably housed in said containment frame (2) to rotate about a load shaft (4), mechanical transmission means (5) adapted to connect said load shaft (4) to the hub of a wheel of the vehicle being measured to transfer the motion of the vehicle's engine to said drum (3), wherein said mechanical transmission means (5) comprises a connecting flange (6) provided with a central axis of rotation and suitable for stably but removably attachment to the hub of the vehicle's wheel, wherein said mechanical transmission means (5) further comprises a constant velocity joint (7) adapted to connect said flange (6) to one end of said load shaft (4) and designed to permit mutual angular adjustment between said load shaft (4) and the central axis of rotation of said flange (6) with respect to at least one plane of inclination.

Description

Portable vehicle-mounted dynamometer Technical Field

[0001] The present invention finds application in the field of measuring instruments for vehicles and, in particular, relates to a Portable Vehicle Mounted Dynamometer (POD) suitable for attaching to a vehicle wheel output shaft to measure the power transmitted by the engine. State of the Art

[0002] In general, engine performance tests are important for the development of engine and fuel technologies.

[0003] An engine is a machine designed to convert one form of energy into mechanical energy. Heat engines convert heat into work through various thermodynamic processes. Electric motors convert electrical energy into mechanical motion, pneumatic motors use compressed air, and so on. Numerous parameters influence an engine's performance: the engine's basic design, speed, torque and power, compression ratio, valve timing, ignition timing, and fuel (in the case of internal combustion engines). Proper engine tuning requires precise measurements of torque, speed, temperature, and fuel consumption as a function of throttle position.

[0004] The use of dynamometers to measure the performance of an engine is known in the automotive sector.

[0005] In summary, a dynamometer is an instrument suitable for simultaneously measuring the torque and rotational speed (RPM) of a motor, so that its instantaneous power can be calculated and usually displayed in kW (kilowatt) or HP (Horsepower).

[0006] In addition to simple HP and torque measurements, dynamometers can be used as part of a test bench for various engine development tasks, such as calibrating engine management controllers, detailed investigations of combustion behavior and the interaction of surfaces in relative motion (friction, lubrication, etc.).

[0007] Typically, a dynamometer is provided with a support frame or dynamometer bench suitable for supporting the entire vehicle and which has one or more rotating drums on which the vehicle's wheels are placed.

[0008] In this way, the engine power is transferred to the vehicle's wheels and, therefore, to the rotating drum of the dynamometer frame.

[0009] The drum is connected to measuring instruments that indirectly measure the power supplied by the motor.

[0010] A first drawback of these solutions lies in their large dimensions, which complicate the placement of the instrument, also because adequate stabilization of the entire structure is required.

[0011] Secondly, the fact that the connection between the motor and the drum is made through the vehicle wheel, simply resting on the drum, does not guarantee the reliability of the measurement due to the inevitable slippage of the wheel, with the need to make consequent corrections in the measurement itself.

[0012] To overcome, at least partially, these drawbacks, solutions have been proposed characterized by smaller dimensions and greater reliability in measurement.

[0013] In particular, the so-called PODs (Portable Vehicle-Mounted Dynamometers) have been developed, i.e., small portable instruments also characterized by the possibility of directly connecting the drum's rotation axis to the wheel hub, in order to avoid measurement errors caused by the wheel sliding on the drum itself.

[0014] In patent US8505374 an example of a POD is disclosed, where the instrument comprises a compact housing that houses the drum and is provided with rollers for its movement.

[0015] However, these instruments have been shown to be susceptible to improvement in several aspects, particularly regarding their ability to be moved and their connection to the wheel hub, to compensate for possible axle tilts and camber angles. US2018 / 0095007 discloses a fixed dynamometer that connects to the wheel hub via a constant velocity joint.

[0016] However, this joint, while allowing minimal adaptation between the dynamometer drum's rotation axis and the vehicle's wheel hub, has several limitations.

[0017] In particular, the constant velocity joint used has an axial rigidity that does not allow sufficiently high tilt angles to be reached or guarantee a correct, safe and simple attachment to the hub.

[0018] Last but not least, there are no systems that guarantee safety in the presence of faults that may cause an angle greater than the maximum design angle.

[0019] Document D1: Patent Publication No. US 8,505,374 B1 (Paul N. ARSENAU, August 13, 2013) (“VEHICLE-MOUNTED PORTABLE DYNAMOMETER”) discloses a vehicle-mounted portable dynamometer comprising a containment frame, a drum rotatably housed in the containment frame to rotate about a load shaft; a mechanical transmission adapted to connect the load shaft to the hub of a wheel of the vehicle being measured, to transfer motion from the vehicle's engine to the drum. The mechanical transmission comprises a connecting flange provided with a central rotation shaft and suitable for stably but detachably attachment to the hub of the vehicle's wheel.

[0020] However, document D1 discloses a dynamometer that includes a dual-arm stabilization system, which increases complexity, alignment time, and user effort.

[0021] Document D2: Publication of patent application No. US 2018 / 0095007 A1 (Masao MIZUTA, April 5, 2018) ("VEHICLE TEST SYSTEM, METHOD FOR MOVING A TEST VEHICLE AND SIMULATED WHEEL") discloses the use of a constant velocity joint to improve the adaptability of the mechanical transmission to different output shafts.

[0022] However, document D2 refers to standard constant velocity joints that do not include axial travel limiting mechanisms, nor are they structurally designed to withstand extreme elongation or compression cycles. Scope of the invention

[0023] The object of the present invention is to overcome the aforementioned drawbacks by providing a vehicle-mounted portable dynamometer characterized by high efficiency, relative cost-effectiveness, and reduced overall dimensions.

[0024] A particular object is to provide a vehicle-mounted portable dynamometer that allows compensation for any tilt of the rotation axis of the wheel hub of the vehicle to which the instrument is connected in each assembly.

[0025] In particular, the vehicle-mounted portable dynamometer is intended to allow a relatively wide range of mutual tilt angle between the rotation axis of the vehicle wheel hub and the rotation axis of the dynamometer drum, always ensuring a correct and simple attachment of the dynamometer to the hub and safety in the presence of faults that may cause a tilt angle higher than the maximum value of the design range.

[0026] Another object is to provide a vehicle-mounted portable dynamometer that is easy to transport and characterized by high stability during use.

[0027] These objects, as well as others that will become more evident below, are achieved by means of a vehicle-mounted portable dynamometer which, according to claim 1, comprises a containment frame, a drum rotatably housed in said frame to rotate about a load shaft fixed to said frame, and mechanical transmission means adapted to connect said load shaft to a wheel hub of the vehicle being measured, to transfer motion from the vehicle's engine to said drum.

[0028] The mechanical transmission means comprise a connecting flange provided with a central axis of rotation and suitable for stable but detachable attachment to the vehicle wheel hub, and a constant velocity joint adapted to connect said flange to one end of the load axle. The constant velocity joint is designed to permit reciprocal angulation between said load axle and the central axis of rotation of said flange with respect to one or, preferably, two mutually orthogonal planes of inclination, so as to restore axial alignment between the load and the wheel hub in the presence of any camber and toe angles of the vehicle or any other type of wheel inclination with respect to the supporting surface.

[0029] Furthermore, the constant velocity joint features a structure that can extend along its axis to allow the flange to be fixed without losing its tilting properties, enabling the constant velocity joint to maintain constant speed transmission throughout its range of motion. Particularly advantageous embodiments of the invention are obtained according to the dependent claims. Brief description of the drawings

[0030] Other features and advantages of the invention will become more apparent in light of the detailed description of a preferred, but not exclusive, embodiment of a vehicle-mounted portable dynamometer, which is shown by way of non-limiting example with the aid of the accompanying drawings, in which: Figure 1 is a front perspective view of the dynamometer; Figure 2 is a rear perspective view of the dynamometer; Figure 3 is a side view of the dynamometer; Figure 4 is a front view of the dynamometer; Figure 5 is a cross-sectional side view of a possible configuration of a constant velocity joint detail belonging to the dynamometer under two different operating conditions; Figure 6 is a cross-sectional side view of the dynamometer along line AA of Figure 4 in a first operating condition; Figure 7 is a cross-sectional side view of the dynamometer in a second operating condition; Figure 8 is an enlarged view of a detail from Figure 7; Figure 9 is a schematic view of a measuring system that includes the dynamometer. Preferred embodiments of the invention

[0031] As shown in Figure 1, a portable vehicle-mounted dynamometer, hereinafter also referred to in short as POD (Portable Vehicle-Mounted Dynamometer) and generally designated by number 1, comprises a transportable containment frame 2 that houses a drum 3 (shown in Figure 6) capable of rotating within the frame 2 to rotate a load shaft 4.

[0032] The latter is provided with mechanical transmission means 5 adapted to connect one end of the load shaft 4 to the hub of a wheel of the vehicle being measured, not shown, since it is a known type in itself and to transfer the motion of the vehicle's engine to the drum 3 and, from this, to the suitable measuring means, which are also not shown, since they are not limiting to the present invention.

[0033] Without going into too much technical detail of the measuring means, according to a preferred, but not exclusive, embodiment, POD 1 will be provided with a high torque and power on-board eddy current brake, with a load sensor to measure retarder torque and an incremental optical encoder to measure hub revolutions.

[0034] The mechanical transmission means 5 comprise, in turn, a connecting flange 6 provided with a central rotating shaft and adapted to be fixed stably but detachably to the hub of the vehicle wheel, for example by means of forged steel adapters, which will effectively eliminate the variables related to the specific type of wheels and tires from the test and setup equation, in order to guarantee absolute accuracy and maximum repeatability of the test data from one power test to another.

[0035] Again, the mechanical transmission means 5 will comprise a constant velocity joint 7 adapted to connect the flange 6 to one end of the load shaft 4.

[0036] The constant velocity joint 7 is designed to allow reciprocal angulation between the load axis 4 and the central rotation axis of the flange 6 with respect to at least one tilt plane.

[0037] Even more preferably, the constant velocity joint 7 is designed to allow mutual angular adjustment between the load shaft 4 and the central axis of rotation of the flange 6 with respect to at least one inclination plane perpendicular to each other.

[0038] In addition, the constant velocity joint 7 is connected at one end to a articulated bearing 8 suitable for connecting the constant velocity joint 7 to the flange 6, to allow the latter to adapt to the natural camber and toe of the vehicle's wheels.

[0039] Particularly advantageously, the constant velocity joint 7 has a structure that can extend along its own axis.

[0040] In particular, the constant velocity joint 7 comprises a first end joint 20 located at the end of the load shaft 4 and a second end joint 21 located at the flange 6 and connected to the first end joint 20 by means of a connecting rod 22 that defines the aforementioned axis A of the constant velocity joint 7. Conveniently, at least one of the end joints 20, 21 is an axial freedom or plunge joint, the possible configuration of which is illustrated in Figure 5, where a plunge joint is illustrated under two conditions that differ in that the end of the joint is translated with respect to the connecting rod 22.

[0041] More preferably, the constant velocity joint 7 shall be a double "offset" joint, i.e., provided with immersion joints 20, 21 at both ends.

[0042] The constant velocity joint 7 is also fixed to a connecting shaft 9 with a variable diameter suitable for connecting one end to the flange 6.

[0043] In addition, the constant velocity joint 7 is connected at one end to an articulated bearing 10 adapted to connect it to the flange 6 in an adjustable manner.

[0044] In particular, the articulated bearing 10 constitutes a restriction, preferably, but not necessarily, of +-10° on said inclination planes, for the adjustment of the constant velocity joint 7 with respect to the flange 6.

[0045] Conveniently, the articulated bearing 10 will be keyed over the aforementioned connecting shaft 9 and will be a double-row angular contact ball bearing 10 provided with two rows of balls 11 defining respective raceways, staggered from each other along the axial direction.

[0046] In this way, this bearing 10 will be adapted to support combined loads, i.e., radial and axial loads acting simultaneously.

[0047] The elongation capacity of the constant velocity joint 7 allows the flange 6 to be firmly mounted on the bearing 10 without losing the tilting properties, by locking it with a nut 23.

[0048] The combination of bearing 10 and constant velocity joint 7, together with the locking by means of nut 23, allows for a safe tilting system that allows a vehicle with a tilt angle of up to 10° to be attached comfortably.

[0049] The presence of the double displacement homokinetic joint 7 will allow the homokinetic power transmission to be maintained throughout the range of motion.

[0050] In fact, the constant velocity joint 7 is designed to expand and contract, thus allowing the correct operation of the flange tilt 6 connected to the wheel hub.

[0051] The axial load properties of angular contact ball bearings 10 increase as the contact angle increases. The contact angle is defined as the angle between the line joining the contact points of the balls and the raceway in the radial plane, along which the combined load is transmitted from one raceway to the other, and a line perpendicular to the bearing axis.

[0052] This type of bearing is mounted on the end of the constant velocity joint 7, in front of the outer flange 6, which in turn will be mounted on another ball bearing 12 located at the end of the connecting shaft 9.

[0053] The bearing 10 will have a safety function to prevent, in the event of an excessive joint angle above a maximum value, for example above 10°, the joint flange 7 from colliding with the tubular element 13 fixed externally to the frame 2 and housing the constant velocity joint 7.

[0054] The entire load will be supported by the outer cage of bearing 12.

[0055] In particular, the stiffening tubular element 13 has a front support plate 24 for the articulated bearing 10 and has a passage 25 for the connecting shaft 9.

[0056] Therefore, the articulated bearing 10 shall be designed to interfere with the front support plate 24 at an angle of the connecting shaft 9 at least equal to the maximum tilt angle.

[0057] The tubular element 13, which extends frontally from the frame 2 in a horizontal direction, will also have the function of stiffening the structure and will house the constant velocity joint 7 inside.

[0058] To facilitate the handling and lifting of POD 1, the frame 2 shall be provided with four wheels and, in particular, with two directional side wheels 14 located inside the frame, a directional center wheel 15 also located inside the frame 2 and larger in size than the side wheels 14, and a non-directional front wheel 16 located outside the frame 2 and connected by a support arm 17 to the stiffening tubular element 13.

[0059] Operationally, the wheels represent the contact point between POD 1 and the ground and, preferably, will be wheels with high mechanical strength to support the weight of the POD and the vehicle. In addition to this structural function, they also serve to help the user move POD 1 and thus assist in aligning the tool with the wheel hub or repositioning it in storage after use.

[0060] According to an additional aspect, the frame 2 will also be provided with a single anti-torsion reinforcement arm 18 with the aim of preventing POD 1 from vibrating or moving in any way due to the engine torque exerted by vehicles with a particularly high torque at the wheels.

[0061] The above represents the mechanical part of the POD, which can be implemented with additional elements, even of a known type, such as one or more handles 19 to facilitate the transport of the POD, or internal mechanical and / or electromechanical components necessary for the operation of the POD, but which do not represent a limitation for the scope of the present invention.

[0062] Next, the POD will be provided with an electrical / electronic subsystem, which is shown schematically in Figure 9 and comprises the following components: Master Control Unit (MCU): This is a bridge between one or more Brake Control Units and the client software backend (servers and databases). It provides interoperability between different devices and adapters, as well as control and message routing between adapters.

[0063] Brake Control Unit (BCU): This is the real-time control system of the POD; it is an electronic unit capable of controlling the load on the dynamometer (i.e., it controls the voltage and electrical current in the resistance coils of the eddy current dynamometer) and can measure or detect load and speed.

[0064] Electrical panel: receives the external three-phase and single-phase power supply and supplies it to the boards and other subsystems.

[0065] Power supply: transforms the 220V voltage to the 24V required by the MCU.

[0066] Wiring system: comprises all power and signal cables of the electrical subsystem.

[0067] The POD will be completed with a software subsystem and, in particular, with its own firmware, for the management and regulation of the measurement phases, according to schemes that may vary depending on the needs and that are not part of the scope of the present invention.

Claims

1. A portable vehicle-mounted dynamometer comprising: - a containment frame (2); - a drum (3) rotatably housed in said containment frame (2) to rotate about a load axle (4); - mechanical transmission means (5) adapted to connect said load axle (4) to the hub of a wheel of the vehicle being measured, to transfer the motion of the vehicle's engine to said drum (3); wherein said mechanical transmission means (5) comprises a connecting flange (6) provided with a central axis of rotation and suitable for stably but detachably attachment to the hub of the vehicle's wheel; characterized in that said mechanical transmission means (5) comprises a constant velocity joint (7) having an axially extensible structure and adapted to connect said flange (6) to an end of said load axle (4),1. Portable dynamometer according to claim 1, characterized in that the homokinetic joint (7) is designed to permit mutual angular adjustment between the load shaft (4) and the central rotation axis of the flange (6).

2. Portable dynamometer according to claim 1, characterized in that the homokinetic joint (7) is designed to permit reciprocal angulation between the load shaft (4) and the central rotation axis of the flange (6) with respect to at least two mutually perpendicular planes of inclination.

3. Portable dynamometer according to claim 1 or 2, characterized in that the homokinetic joint (7) comprises an axially free end plunge joint (20) on both the flange (6) and the end of the load shaft (4).

4. Portable dynamometer according to claim 1 or 2, characterized in that the homokinetic joint (7) is provided with axially free end plunge joints (20,21) both on said flange (6) and on said end of said load shaft (4).

5. Portable dynamometer according to any of the preceding claims, characterized in that said constant velocity joint (7) is connected at one end to a articulated bearing (10) adapted to connect said constant velocity joint (7) to said flange (6) in an adjustable manner.

6. Portable dynamometer according to claim 4, characterized in that said constant velocity joint (7) is fixed to a connecting shaft of variable diameter (9), adapted to connect one of its ends to said flange (6) and on which said articulated bearing (10) is keyed.

7. Portable dynamometer according to claim 5, characterized in that said articulated bearing (10) is a double-row angular contact ball bearing (10) provided with two rows of balls (11) offset from each other in the axial direction.

8. Portable dynamometer according to any of the preceding claims,characterized in that said containment frame (2) comprises a stiffening tubular element (13) extending frontally from it and housing said constant velocity joint (7).

9. Portable dynamometer according to claim 8, characterized in that said stiffening tubular element (13) has a front support plate (24) for said articulated bearing (10) and has a passage (25) for said connecting shaft (9).

10. Portable dynamometer according to claim 2 and any of claims 5 to 9, characterized in that said articulated bearing (10) constitutes a limit for the inclination of said constant velocity joint (7) with respect to said flange (6) in said inclination planes, to determine a maximum inclination angle ().

11. Portable dynamometer according to claim 10,characterized in that said maximum tilt angle () is equal to ± 10° on said tilt planes.

12. Portable dynamometer according to claim 10 or 11, characterized in that said articulated bearing (10) is designed to interfere against said front support plate (24) when said connecting shaft (9) reaches a tilt angle at least equal to said maximum tilt angle ().

13. Portable dynamometer according to any of the preceding claims, characterized in that said containment frame (2) is provided with wheels for its movement on a plane.

14. Portable dynamometer according to claim 13,characterized in that said containment frame (2) comprises two steerable side wheels (14) and a steerable central wheel (15) adapted to facilitate the movement of said containment frame (2) and a non-steerable front wheel (16) arranged externally to said containment frame (2).

15. Portable dynamometer according to claims 8 and 14, characterized in that said front wheel (16) is attached to said tubular stiffening element (13).

16. Portable dynamometer according to any of the preceding claims, characterized in that said containment frame (2) is provided with an anti-torsion reinforcement arm (18).

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