The automotive chassis dynamometer is a testing device used to test the power performance, emission performance, and other related performance of automobiles. With the help of other test benches and instrument equipment, it can simulate various road driving conditions of automobiles, measure the output power of the driving wheels, and measure multi condition emission indicators and fuel consumption. It has good guiding significance for environmental protection departments to monitor vehicle exhaust emissions. Compared with outdoor road tests, conducting vehicle tests on a chassis dynamometer has the advantages of safety, efficiency, and good repeatability. The following introduces the basic structure and working principle of several conventional automotive chassis dynamometers.
Basic structure of chassis dynamometer
In response to different needs, JT/T 445-2008 "Automotive Chassis Dynamometer" stipulates that chassis dynamometers are divided into 3t, 10t, and 13t according to their rated load capacity, with 3t and 10t being dual axis and 13t being three-axis. The dual axis chassis dynamometer is mainly used to detect light and medium-sized single axis drive vehicles, while the three-axis chassis dynamometer is mainly used to detect heavy-duty single axis drive vehicles and dual axis drive vehicles.
As shown, the structure of a standard dual axis chassis dynamometer generally consists of a dynamometer main body, a power absorption device (eddy current machine), an inertia simulation device (flywheel group), a lifting device, a safety device (limit guide roller), and related sensors. It can be used for speedometer detection, odometer detection, chassis power detection (constant speed control, multi-point continuous power testing), acceleration time detection, coasting distance detection, constant speed fuel consumption detection, etc. It can comprehensively meet the needs of automotive testing and automotive fault diagnosis, and is widely used in the automotive repair, automotive manufacturing, and automotive comprehensive performance testing industries.
With the increasingly severe atmospheric environment and the sharp increase in the number of motor vehicles, the environmental protection department's efforts to monitor vehicle exhaust emissions have become increasingly prominent. Therefore, chassis dynamometers have become an important equipment for environmental testing stations and M-class maintenance enterprises. Compared to the standard chassis dynamometer, the working condition method chassis dynamometer with exhaust pollutant testing function (Figure 2) requires a reverse drag device in addition to the basic structure mentioned above, and the reverse drag device and inertia simulation device must meet the relevant provisions of H J/T 291 "Technical Requirements for Exhaust Pollutant Measurement Equipment of Gasoline Vehicle Steady State Working Condition Method" and HJ/T 292 "Technical Requirements for Exhaust Smoke Measurement Equipment of Diesel Vehicle Loading and Deceleration Working Condition Method".
As shown, the three-axis chassis dynamometer is equipped with a dynamometer double platform body, a power absorption device (dual eddy current machine), 151, a measurement simulation device (flywheel group, multiple groups can be configured according to demand), a lifting device, a safety device (limit guide roller), and related sensors. During measurement, the drive shaft (dual axis front wheel) lands on the rollers of the first two axes, the dual axis rear wheel lands on the roller of the third axis, and the rollers of the three axes rotate synchronously through a synchronous belt.
Working principle of chassis dynamometer
Cars have kinetic energy and driving resistance during motion. The so-called simulation of the working conditions of cars on various roads is to simulate the inertia or kinetic energy of the car's motion through the inertia simulation device of the chassis dynamometer, simulate the driving resistance through the power absorption device, and use the adhesive roller to simulate the road surface on which the car is driving.
Before testing, all necessary preparations must be made, including site and power supply. When the equipment is in normal operation, the lift is in a lifting state, and the inspected vehicle is driven onto the dynamometer platform, with the drive shaft stopped on the lift and the wheels stopped in the center of the drum. Lower the lift and place the wheels on the drum. Run the vehicle slowly and check for any deviation. If there is any deviation, raise the lifting beam and adjust the vehicle position until there is no deviation. When the inspected vehicle travels on the drum, the surface linear velocity of the drum is equal to the vehicle's traveling speed, and drives the inertia simulation device flywheel group to rotate, generating rotational inertia. The speed of the drum is detected by the speed sensor installed on the rolling shaft and converted into the vehicle speed. The main drum group is connected to the eddy current power absorber, which generates a resistance equal in magnitude and opposite in direction to the driving force of the vehicle by applying excitation current to the eddy current machine. This resistance is balanced by a force sensor installed on the arm of the eddy current machine, and converted into an electrical signal by the force sensor for output to the computer for processing and control.