The engine is an important part of the vehicle, the same bus chassis can match different types and different displacement engines. In the matching of the engine and the vehicle, the selection should be made according to the specific use requirements and the characteristics of the engine, and further necessary adjustments should be made during the matching. There should be an overall and systematic concept in the matching, and the change of the engine operating point should be analyzed, so that the common operating conditions of the engine should be located in an economical operating area as much as possible.
The emission, power, and torque of the engine will meet the requirements of relevant standards and vehicle grades, considering the model, type, bore, stroke, displacement, maximum power, rough torque, and minimum fuel consumption,Emissions and dimensions etc.
The main accessories of the engine are fuel filter, turbocharger, air pump, steering pump and generator. The configurations of air conditioner and fan pulleys, flywheels, clutches and clutch housings, front and rear suspension brackets and cushions are optional.
Engine peripheral parts such as the matching of engine intake, exhaust, cooling, fuel, after-treatment, electrical appliances and other systems, interface dimensions, supporting specifications, installation requirements, etc.
Clutch selection: The transmission torque meets the requirements of the engine and vehicle weight, and the connection with the engine and transmission adopts SAE standard interface.
The layout of the engine on the general layout drawing: the front and rear positions of the engine are arranged together with the upper and lower positions, which not only ensures the passability but also ensures the minimum space in the engine compartment to increase the space in the car. The engine oil pan of the chassis in front of the engine and the I-beam of the front axle ensure the interference margin of up and down jumping. It is 45°,and it is necessary to ensure that the center line of the crankshaft and the center line of the driving gear of the rear axle tend to be straight, so that the equivalent angle of the transmission shaft under the two working conditions of full load and no load is the smallest. The left and right directions of the crankshaft centerline of the engine are generally consistent with the centerline of the frame, and the crankshaft centerline of the rear engine can be properly close to the centerline of the driving gear of the rear axle; 30mm, to ensure that there is no interference between the upper parts of the engine and the frame after the deformation and vibration of the engine mount.
When considering the matching of the transmission system, the engine and transmission should be integrated according to the specific use and requirements of the vehicle, and designed and optimized as a whole. The transmission ratio range of the transmission should be determined according to the operating conditions and requirements of the bus, the maximum power, maximum torque and speed of the engine, and the maximum vehicle speed proposed by the overall design of the chassis, that is, the ratio of the transmission ratio of the lowest gear to the highest gear; the highest gear The determination of , mainly considers the relationship between the maximum vehicle speed and the rotational speed corresponding to the maximum power condition of the engine. At the same time, considering that the time of driving in the highest gear is the most, from the perspective of improving fuel economy, it is more beneficial to make the engine work at a lower speed, and the speed ratio of the highest gear can be appropriately reduced. The determination of the lowest gear should take into account the requirements of the maximum gradient, adhesion rate and the minimum stable speed of the vehicle. When the selected engine power is relatively small, the speed ratio of the gearbox should be increased appropriately to ensure the dynamic performance of the vehicle. The determination of the number of gears is theoretically the more gears the better, the most ideal is the continuously variable transmission to adapt to complex conditions of use, so that the auto has good power and economy, but in fact it is limited by the complexity of the structure, Manufacturing costs and other constraints, the basic bus are mostly used five-speed and six-speed gearbox. In addition, it is necessary to consider that the maximum input torque should be greater than 10% of the maximum torque of the engine and the shape and installation dimensions.
