Internal Combustion Engine Vibration Isolation System

1.2. General arrangement of vibration counters on cars

The buffers have the same functions as above, the general arrangement of the types of buffers on cars is shown in Figure 1.1 and the buffer system on internal combustion engines is shown in Figure 1.2. Engine buffers receive both low and high frequency excitation forces transmitted by road surface and engine bumps.

Figure 1.1. Anti-vibration cushioning system on cars

Figure 1.2. Internal combustion engine vibration isolation system

The history of the development of internal combustion engine vibration isolators is shown in Figure 1.3.

Figure 1.3. History of development of internal combustion engine vibration isolation system

1.3. Analysis of motor vibration isolation structures

The structural characteristics and advantages and disadvantages of internal combustion engine vibration isolation buffer systems are analyzed below:

a) Rubber vibration isolation cushion system

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Figure 1.4. Rubber vibration isolation system of internal combustion engine

* Advantage:

+ Simple structure and easy to manufacture;

+ Effectively reduces noise and vibration at high excitation frequencies;

* Disadvantage: the system's drag coefficient is small, so it is difficult to reduce vibration under the impact of low excitation frequencies. Because of this disadvantage, researchers have proposed a system of internal combustion engine vibration isolation buffers combining rubber and hydraulics, which will continue to be presented below.

b). Suspension system (vibration isolation cushion) combines hydraulics and rubber

To increase the efficiency of the motor vibration isolation system when the excitation frequency is low, researchers and designers have used hydraulic oil, the structure of the rubber vibration isolation system combined with hydraulics. The structure of the rubber vibration isolation system combined with hydraulics is shown in Figure 1.5 and the vibration model of the rubber vibration isolation system combined with hydraulics is shown in Figure 1.6.

Figure 1.5. Hydraulic rubber vibration isolation system of internal combustion engine[22]

Figure 1.6. Vibration model of the combined hydraulic and rubber vibration isolating cushion system

* Advantages: Effectively reduces noise and vibration at low excitation frequencies by increasing the damping coefficient value of the suspension system.

* Disadvantages:

+ Complex structure;

+ Although the system's resistance characteristics have been significantly improved compared to the pure rubber system using friction to generate the coefficient of resistance, this is still a passive system. Therefore, due to this disadvantage, researchers have proposed a suspension isolation system (oscillation isolation system) for internal combustion engines combining rubber and hydraulics with a controlled coefficient of resistance, which will continue to be presented below.

c. Semi-active oscillating wing cushion system

The development trend of semi-active hydraulic high-vibration damper system of internal combustion engine is shown in figure 1.7. In order to intelligently control the drag coefficient of the engine's vibration damper system, researchers and designers have proposed many different control theories to control the drag coefficient in accordance with the engine's working conditions. The modeling of semi-active hydraulic rubber vibration damper system is shown in figure 1.8.

Figure 1.7. Semi-active hydraulic rubber engine cushion system[21]

Figure 1.8. Modeling of semi-automatic hydraulic rubber vibration isolation buffer system[21]

* Advantages: Reduces vibrations under all different working conditions by conveniently controlling the suspension system's damping coefficient (vibration buffer).

* Disadvantages:

+ Complex structure and expensive price;

+ Although the vibration and noise caused by the internal combustion engine are significantly reduced, the stiffness of the system has not been controlled. Therefore, the electromagnetic vibration buffer system was born and will be presented below.

c. Active oscillating wing cushion system

The development and improvement trend of the active vibration isolation system of internal combustion engines is shown in Figure 1.9. In order to intelligently control both the stiffness and drag coefficient parameters of the engine's vibration isolation system with the engine's working conditions. The structure of the electromagnetic vibration isolation system was born, a model of the active electromagnetic vibration isolation system is shown in Figure 1.10.

Figure 1.9. Active electromagnetic oscillation buffer system[23]

Figure 1.10. Modeling of active electromagnetic high-frequency oscillation buffer system [23]

* Advantages: Reduces vibrations under all different working conditions by conveniently controlling both the stiffness and damping coefficient values of the system. Therefore, it has the advantage of a semi-active hydraulic high vibration buffer system.

* Disadvantages:

+ Complex structure and expensive price;

+ Although the reduction of vibration and noise caused by the internal combustion engine is better than the semi-active vibration isolation system, in this thesis the author only considers the semi-active hydraulic rubber vibration isolation system.

1.3. Domestic and international research situation

a. Domestic research

In the trend of integration, the Vietnamese automobile industry has made significant progress in many research areas such as assembly lines, body manufacturing technology, etc. 2018 marked the launch of the Vinfast automobile brand and in June 2019, the Vinfast automobile factory began operating. Through statistics of published articles, topics, and theses, the field of automobile vibration has also been studied by Vietnamese scientists early on and vibration models often underestimate the impact of engine vibration.

In 2003, the study of the influence of engine torque on the hydromechanical transmission system was mentioned by author Nguyen Khac Tuan[7] in his Master's thesis, the results of which evaluated the influence of different loads on the oscillation of the transmission system.

In 2006, the author Khieu Huu Hung[8] presented a survey on the torsional vibration of the engine crankshaft and its influence on the transmission system of an automobile in his Master's thesis. The research results showed the resonance frequency of the mechanical system.

In 2009, the author Nguyen Tan Chinh[9] presented the simulation of internal combustion engine vibration and its impact on the smoothness of passenger cars in his Master's thesis. The research results analyzed the engine suspension system parameters such as stiffness and drag coefficient of the engine affecting the smoothness of passenger cars. However, the above authors have not yet evaluated the impact of engine excitation forces on the smoothness of the car.

In 2010, a study on the model and simulation of vertical oscillation from the combination of two excitations from the engine torque and the road surface was published by Nguyen Khac Tuan and Le Van Quynh[12] in the proceedings of the International Conference. The research results evaluated the influence of the presence or absence of torque excitation from the internal combustion engine on the smoothness of the movement of a passenger car and when the car moves on a conditioned road surface with road surface parameters such as q=0.015m, s=6m, v a =11.1m/s 2 and when the car is in 5th gear, the average square acceleration of the car body increases by 9.7% when not considering the excitation from the engine torque.

In 2015, a study on the influence of suspension system design parameters on the smoothness of car movement was conducted by Le Van Quynh, Hoang Anh Tan, Nguyen Khac Minh[13]. The research results on the stiffness parameters and drag coefficient of the engine vibration buffer system considered their influence on the smoothness of the car based on the spatial vibration model of the whole car under the excitation of the national highway surface and did not consider the influence of engine excitation.

In 2015, the author Hoang Anh Tan [10] presented in his Master's thesis the study on the influence of engine vibration on the smoothness of passenger cars, the research results analyzed the influence of engine excitation on the smoothness based on the spatial model. However, in this study, the author only considered passive rubber vibration damping pads.

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