It has reference and guidance significance for the structural improvement of rubber suspension device in our country. In general, the car is mainly stimulated by two aspects, one is caused by the unevenness of the road surface, and the other is the unbalanced force and moment generated during the operation of the engine itself. With the improvement of the level of modern highways and the optimization of various suspensions, powertrains have gradually become the main source of vibration affecting vehicle vibration. On the other hand, Hyundai Motors is developing toward the goal of miniaturization, light weight, and high comfort. The powertrain suspension device plays an important role in improving the comfort of the car and reducing the noise in the car. Domestic and foreign scholars have conducted extensive research on various powertrain suspension devices. As early as 1920, rubber components were used to connect the powertrain assembly and the frame. After 1930, the rubber suspension device was used to isolate the engine from the frame. The vibration, after decades of research, has been a great development of the suspension device components, resulting in a hydraulic resistance hydraulic suspension device, semi-active control and active control suspension device. At present, due to limitations in manufacturing cost, structure size, and manufacturing processes, foreign liquid suspension suspension devices on medium- and heavy-duty trucks have barely been used, and traditional rubber materials are also used as vibration-isolating elements. Most of our passenger cars and trucks also use rubber suspension devices. Because the traditional rubber suspension device has the disadvantages of large rigidity, insufficient damping, and high-frequency dynamic hardening, it is difficult to meet the requirements of the powertrain. However, the rubber suspension device can design suitable stiffness characteristics for vibration isolation in all directions. It is small in size, low in price, hardly maintenance-free, and the rubber suspension device bonded together can have better performance and longer life. . Therefore, the application of nonlinear stiffness and damping characteristics to improve the performance of passive rubber suspension devices, the application of high internal damping materials and materials with amplitude dependent stiffness and damping are very valuable. Due to the instability of the current large damping rubber material, the application is still very difficult. This article uses a rubber suspension device made of natural rubber as the object, through a relatively simple transformation of the principle, it has a good nonlinear characteristics, get the ideal dynamic characteristics . In this paper, the mechanical model of the modified rubber suspension device is established. Through theoretical analysis and simulation calculation, it is proved that it has better dynamic characteristics. Comparison of a conventional rubber suspension device and an ideal suspension device A vehicle powertrain is mounted on a vehicle frame or a vehicle body through a suspension device system, and the suspension device system is subjected to the powertrain mass and is subject to various interference forces. For example, under braking, acceleration, cornering, etc., the suspension device system should be able to effectively limit the maximum displacement of the powertrain to avoid collisions with adjacent components.
At the same time, it should have a good vibration isolation, reducing the two-way vibration transmission between the powertrain and the car frame or body as much as possible. It is known from vibration analysis that in order to make the powertrain suspension device capable of vibrating at low frequency and large amplitude, the maximum displacement of the engine powertrain is effectively limited, and the suspension device should have large dynamic stiffness and large damping. On the other hand, in order to reduce the force transmission rate of the engine powertrain to the vehicle frame or the vehicle body when oscillating at high frequency and small amplitude, it is required that the suspension device should have less rigidity and damping. Thus, an ideal suspension device characteristic diagram was obtained through research and compared with a conventional rubber suspension device, as shown.
It can be known that the damping of the traditional rubber suspension device hardly changes with the change of frequency and amplitude, and is a constant, and the dynamic stiffness characteristics also run counter to the ideal suspension device, with low stiffness at low frequencies and high stiffness at high frequencies. Large, and basically linear changes; and a large value when the dynamic stiffness is small, a small value of the dynamic stiffness of the traditional rubber suspension device characteristics and the ideal contrast of the suspension device characteristics. Therefore, the traditional rubber suspension device is difficult to meet the high frequency small amplitude and low frequency large amplitude requirements of the powertrain suspension device at the same time. It must be structurally modified to make it have non-linear characteristics, to better meet the total power Paired suspension device system requirements. The structure of the traditional rubber suspension device damping block is usually a compression type, a shear type, and a composite type, and its structural diagram is as shown.
The structure of the conventional rubber suspension device is structurally modified as shown in the compression type rubber damping block. Rubber is a kind of macromolecule material, which is a kind of non-linear material. Rubber has elastic hysteresis, that is, it will produce final deformation after loading for a certain period of time. Similarly, after uninstalling, it will take some time to recover. The illustrated modified rubber suspension devices each include five unequal rubber blocks, which are separated by a metal skeleton and do not affect each other. According to the layout of the different orientation can be divided into high and low side of the middle and high side of the low-type. Under different working conditions, they have different working conditions. When the powertrain works under low-frequency and large-amplitude vibration conditions, the five rubber blocks of the two rubber suspension devices are arranged to work at the same time, so that the stiffness of the suspension device is greatly increased, and the damping is also increased accordingly, thereby satisfying When the powertrain has a large amplitude at low frequencies, it requires a large stiffness and large damping of the suspension device. When the powertrain is in the vibration of high frequency and small amplitude, the working conditions of the two types of rubber suspension devices are different. For the mid-to-high low rubber suspension device shown in a, only one piece of the schematic diagram of the most improved rubber suspension device is in working condition, so the stiffness and damping of this device are minimal. For the b-side high, medium and low type, the two highest rubber blocks are in working condition, so they also have less rigidity and damping at this time. Both types of rubber suspension devices can effectively improve the working conditions of the traditional rubber suspension device at high frequencies and small amplitudes, and better meet the requirements of low stiffness and small stiffness when the powertrain is used for rubber suspension devices at high frequencies and small amplitudes. . Of course, in order to match the rubber suspension device with the powertrain, it is necessary to reasonably set the height difference of the five rubber blocks. Because the traditional rubber suspension device is often studied using the mechanical model shown in a. Therefore, the middle-high-side and low-profile rubber suspension device of a can establish the mechanical model shown in b.
k Suspension device stiffness c Suspension device damping k1 Rigidity of rubber block 1 k2 Rigidity of rubber block 2, 5 k3 Rigidity of rubber block 3, 4 c1 Damping of rubber block 1 c2 Damping of rubber block 2, 5 c3 Rubber Mechanical model of the damping rubber suspension device of blocks 3, 4 Since the suspension device is designed to be symmetrical, the right and left rubber blocks are simplified so that they have the same stiffness and damping. Since the quality of the rubber itself is much smaller than that of the powertrain, the mass of the rubber block is neglected. Assuming that the amplitude increases, the amplitude is consumed by attenuation and collision, and has an equation corresponding to large-amplitude vibration. Solving the equation yields the time response history for various amplitudes, and then the magnitude and phase difference of each steady-state response. The stimuli are sinusoidal. The dynamic characteristics of the improved rubber suspension device are calculated and analyzed. The dynamic characteristics of the small amplitude vibration model are established in the simulation model. The frequency response of the amplitude is obtained by the transfer function programming procedure. The frequency response under small amplitude is shown in a. . As can be seen in the figure, when the amplitude is smaller, the main working area of ​​the system is concentrated in the frequency, especially when the high-frequency area is present, the amplitude is smaller than that of the system, which has a very good damping effect and can effectively improve the high powertrain. Frequency characteristics. In the resonance region, the amplitude will increase. When it is larger, the displacement will be too large. At this time, the rubber block will play a role in time to increase the stiffness and damping of the suspension device, which will reduce the amplitude. In other words, if the vibration of the system is large, the amplitude will be hardly generated and it will be replaced. Due to the intervention of the rubber block, the natural frequency of the vibration system is instantaneously increased, and the amplitude is rapidly reduced. In addition, the increase in damping also causes the amplitude to decrease rapidly. The effect can be seen more clearly by comparing the amplitude-frequency characteristics of a conventional rubber suspension device (as shown in c). The frequency domain response under small amplitude can be calculated and analyzed through the above calculations. It can be known that this improved rubber suspension device has ideal amplitude-frequency characteristics when the vibration amplitude is small, especially in the high frequency region.
When the dynamic characteristics of a large-amplitude vibration powertrain work in starting, idle, acceleration, deceleration, braking and sharp turn and other working conditions, often cause the engine to jump significantly. Therefore, it is necessary to study its dynamic characteristics at large amplitude. Usually in these conditions, the excitation frequency is low, so only work at low frequencies is studied. At this point, the block rubber blocks are all in working condition. The suspension device system has large rigidity and damping and can effectively limit the maximum displacement of the powertrain. The amplitude-frequency characteristics are as shown. The amplitude-frequency characteristic diagram of large-amplitude and low-frequency vibration concluded that the characteristics of the traditional rubber suspension device were compared with the ideal suspension device, and a structural improvement program was proposed. Aiming at the improved structure of the suspension device, a corresponding mechanical model was established. Based on this, the mathematical model of the system was obtained. The program was programmed to simulate the model. The results showed that the new structure of the rubber suspension device can be ideal. The dynamic characteristics (only the amplitude-frequency characteristics are discussed in this article) have a good reference for the improvement of our country's rubber suspension device. However, it should be pointed out that the improved structure proposed in this paper can not completely solve the problem of dynamic hardening of the rubber suspension device at high frequencies and can only effectively reduce the problem of dynamic hardening. In addition, the pre-tightening force of the suspension device is reasonably designed, and the dynamic characteristics of this type of suspension device also have a great influence.
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