Air spring suspension technology for bogies of modern rail transit vehicles
Release time：2017/1/18 Author：Xinyi spring
1 Overview
Modern rail transit vehicles are developing towards high speed, light weight and low noise. Air spring suspension system has many advantages that steel spiral spring does not have. Therefore, air spring is widely used as secondary suspension device in trunk high-speed railway vehicle Bogies and urban rail transit vehicle bogies. Compared with air spring, steel spring has linear stiffness characteristics, which limits its application in rail transit vehicles
1、 In the field of high-speed rail transit, the rigid spring can not greatly improve the static deflection of vehicle suspension system to reduce the natural vibration frequency of the vehicle body, especially when the vehicle carrying capacity is large;
2、 The passenger capacity of urban rail transit vehicles is large, and the floor height is required to be basically unchanged under different passenger capacity. The steel spring does not have this characteristic.
In a word, the application of air spring suspension can significantly improve the running stability of the vehicle system, greatly simplify the structure of the bogie, and make the bogie lightweight and easy to maintain. Generally speaking, the adoption of air spring in rail transit vehicles can be divided into three stages
(1) make use of the vertical characteristics of the air spring to improve the vertical running stability of the vehicle system;
(2) the vertical and lateral characteristics of the air spring are used together, the shaking table in the secondary suspension device of the bogie is cancelled, and the bogie structure is simplified;
(3) make full use of the three-dimensional characteristics of large displacement (including torsion) and low lateral stiffness air spring (figure-1, figure-2), cancel the bolster, completely realize the lightweight of bogie secondary suspension device, and make it possible to adopt anti hunting damper, which can better coordinate the contradiction between hunting stability and good curving performance of bogie.
2 composition of air spring suspension system
1. Air spring 2. Height control valve 3. Height adjusting link 4. Height adjusting lever
5. Train air source 6. Exhaust port 7. Throttle (valve) 8. Additional air chamber 9. Differential pressure valve
The whole system of air spring suspension is shown in figure-3, which is mainly composed of air spring body, additional air chamber, height control device, differential pressure valve and orifice (valve). The working principle of the system is as follows: when the static load of the vehicle increases, the air spring 1 is compressed to reduce the working height of the air spring, so that the height control valve 2 drops with the vehicle body. Because the length of the height adjustment link 3 is fixed, the height adjustment lever 4 rotates to open the air inlet mechanism of the height control valve, The pressure air enters the air spring 1 and the additional air chamber 8 from the train air source 5 through the air intake mechanism of the height control valve until the height adjustment lever returns to the horizontal position, that is, the air spring returns to its original working height; When the static load of the vehicle is reduced, the working height of the air spring is increased by the elongation of the air spring 1, and the height control valve 2 rises with the vehicle body. Similarly, because the length of the height adjustment link 3 is fixed, the height adjustment lever 4 reverses and opens the exhaust mechanism of the height control valve, The pressure air is discharged into the atmosphere by the air spring 1 and the additional air chamber 8 through the exhaust mechanism of the height control valve through the exhaust port 6 until the height adjustment lever returns to the horizontal position.
2.1 air spring and additional air chamber
2.1.1 air spring
The air spring suspension system has ideal anti-s-shape nonlinear stiffness characteristics, and its stiffness is very low in the normal working range. When the amplitude is large, its stiffness has the characteristics of sharp increase, which can limit the excessive displacement of the car body. The air spring can also effectively absorb high-frequency vibration and isolate noise, and because of the use of automatic height control valve, the air spring suspension can keep the floor height from changing with the change of vehicle static load (except the primary suspension and wheel wear), that is, the air spring has a constant working height. In addition, more importantly, with the continuous progress of air spring technology, especially the practical application of air spring with low lateral stiffness and large torsional deformation, the development of Bolsterless bogies becomes possible. In Bolsterless bogies, due to the characteristics of high flexibility air spring, low lateral stiffness and large torsional deformation, the shaking table and bolster device in the traditional secondary suspension structure of bogies are eliminated, and the air spring is used to support the car body directly, which greatly simplifies the structure of bogies, reduces the weight of bogies by 800-1000kg and realizes lightweight, At the same time, it improves the maintainability, safety and reliability of the bogie. Under the same conditions, the main factors that determine the stiffness characteristics of the air spring are the shape, material, cord angle of the rubber capsule and the geometric parameters of the upper cover and lower seat. In addition, the form of metal laminated rubber auxiliary spring also has an important influence on the performance of the air spring system. Generally, for vehicles with air spring suspension, the vertical and horizontal low frequency natural frequency of the vehicle is required to be no more than 1 Hz. The main parameters to evaluate the performance of air spring are as follows
(1) the effective diameter is about 450-640mm.
(2) vertical static / dynamic stiffness, which is generally 0.3-0.4mn/m.
(3) horizontal static / dynamic stiffness, which is generally 0.15-0.2mn/m.
(4) maximum allowable vertical displacement, ± 30mm。
(5) maximum allowable lateral displacement, ± 60～120mm。
(6) working height, about 200-300 mm.
2.1.2 additional air chamber
The function of the additional air chamber is to significantly reduce the vertical stiffness of the air spring, but when the volume of the additional air chamber reaches a certain value (generally 60-70l), the stiffness change is no longer obvious. For bogies with bolsters, the inner cavity of the bolsters is generally used as the additional air chamber of the air spring. There are two types of Bolsterless bogies: one is to use the inner cavity of the side beam and (or) cross beam of the bogie frame; The other is to set a separate air spring additional air chamber on the car body. These two situations have their own advantages and disadvantages, which should be selected according to different design conditions.
2.2 height control valve and differential pressure valve
2.2.1 height control valve
It is because of the use of automatic height control valve that the air spring has many advantages. The car body height control is realized by controlling the air spring charging and discharging through the height control valve. In general, when the load of urban rail transit vehicles changes, the time for adjusting the vehicle floor height shall not exceed the stop time of the station, and the variation range of the floor height is ± 10mm。 The height valve can only be used to compensate for the change of passenger weight, but not for the wear of wheels and bogie parts. The height valve shall not be affected by vehicle vibration and rail impact. The main technical performance indexes of height control valve are as follows (lever length 140mm, temperature 20 ℃, main air cylinder pressure 5kg / cm2)
(1) cut off frequency, generally 1 Hz;
(2) non sensitive zone, 9-11mm;
(3) action delay time, 3 ± 1s；
(4) air flow: below 40s (40L air cylinder, pressure drops from 5kg / cm2 to 2kg / cm2).
2.2.2 differential pressure valve
The differential pressure valve is installed in the middle of the connecting pipeline between the left and right air springs of the same bogie. When the air spring on any side is abnormal, it acts as a safety device to connect the left and right air springs to prevent the car body from tilting too much. The operating pressure of differential pressure valve is generally 1kg / cm2, 1.2kg/cm2 and 1.5kg/cm2. In order to reduce the diagonal pressure difference on the transition curve of the vehicle and improve the anti derailment safety of the vehicle, various factors should be taken into account in the selection of the action pressure of the differential pressure valve.
2.3 anti roll torsion bar
On the one hand, the adoption of air spring greatly improves the static deflection of vehicle suspension system, reduces the vertical and horizontal natural vibration frequency of vehicle, and improves the running stability; At the same time, the increase of vertical static deflection reduces the anti roll stiffness of the vehicle system, resulting in the increase of roll angle when the vehicle passes through the turnout and curve, and the decrease of ride comfort. The function of anti roll torsion bar is to improve the anti roll stiffness of the vehicle without increasing the vertical and lateral suspension stiffness of the vehicle, so as to limit the roll angle of the vehicle when the large line is uneven, ensure that the vehicle does not exceed the allowable vehicle limit under dynamic conditions, and improve the riding comfort. It can be seen that the essence of anti rolling torsion bar is a torsion spring, which does not restrict the heave and yaw movement of the car body, but can produce a larger restoring moment when the car body rolls, so as to improve the anti overturning stability of the car. The stiffness of anti rolling torsion bar is generally 2 ~ 3MN · M / rad. The anti roll torsion bar device must have reasonable design and installation structure, otherwise it will have adverse effects on the running stability of the vehicle in a straight line.
Another way to improve the anti overturning stability of the vehicle is to increase the transverse span of the air spring and the height of the upper bearing surface of the air spring, but it is limited by the width of the vehicle and the height of the floor, and the influence on the curving performance of the vehicle should be considered. This method is widely used in Japan.
2.4 orifice and throttle valve
Another advantage of using air spring is that a fixed orifice or a variable damping throttle valve with appropriate size can be set between the air spring body and the additional air chamber to replace the secondary vertical oil damper. The structure of the fixed orifice is simple, almost does not increase the cost of the air spring, but the damping effect is not good, so it is generally used for low speed vehicles. The diameter of fixed orifice is about 13mm. The variable damping throttle valve can change the opening of the orifice according to the change of vibration speed, so it has good damping effect in both low-frequency vibration range and high-frequency vibration range. The air spring with variable damping throttle valve can not only damp the high and low frequency vertical vibration of vehicle, but also attenuate the low frequency rolling vibration of vehicle. Of course, whether throttle valve or oil damper is used to provide vertical damping is related to the structure and working characteristics of air spring. In Europe, vertical oil damper is used, while in Japan, throttle valve is used.
The lateral damping of the air spring suspension system is provided by the lateral oil damper. In the bogie with bolster, the slewing damping is usually provided by the side bearing of the support to increase the critical speed of the vehicle hunting motion; In Bolsterless bogies, when the running speed of the vehicle reaches 120km / h, the critical speed of hunting motion is ensured by installing anti hunting oil damper between the car body and the bogie frame.
3 requirements of secondary suspension device of bogie for air spring performance
It can be said that the progress of air spring technology promotes the progress of Bogie Technology. It can also be said that the development requirements of high speed and lightweight of bogie promote the continuous improvement of the performance of air spring. Taking a comprehensive view of typical bogies at home and abroad, there are three basic forms of air spring secondary suspension structure: shaking table type, bolster type and non bolster type. These three forms are not only progressive in turn, but also co-exist, and their requirements for the performance of air spring are very different.
3.1 bogies with shaking table and bolster
The secondary suspension device of this kind of bogie (figure-4) is mainly composed of bolster suspender 1, spring joist 2, air spring 3, bolster 4, anti roll torsion bar 5, height control valve 6, differential pressure valve 7, variable throttle valve 8, transverse oil damper 9, supporting side bearing 10, transverse stop 11, traction rod 12 and center pin 13. In this structure, the low vertical stiffness of the air spring is mainly used, while the low lateral stiffness of the secondary suspension is mainly provided by the bolster hanger device, and there is no requirement for the longitudinal stiffness of the air spring. The lateral displacement of the air spring is very small, and there is no longitudinal and torsional displacement. Typical bogies include 209PK, 209HS, bt10 and CW-2.
1. Bolster hanger 2. Spring joist 3. Air spring 4. Bolster 5. Anti roll torsion bar 6. Height control valve 7. Differential pressure valve
8. Variable throttle valve 9. Transverse oil damper 10. Supporting side bearing 11. Transverse stop 12. Traction rod 13. Center pin
209PK bogie is a long suspender with pin hole structure. There is abrasion in the structure, but it is safe and reliable. 209HS bogie is a long suspender with elastic contact, which has no abrasion. At the same time, due to the use of bowl shaped laminated rubber pile, the transverse stiffness of shaking table is further reduced, that is, the effective length of suspender is increased. CW-2 bogie adopts rigid concave convex swing block type long suspender, which is different from 209 series bogies in that transverse tie rod is set between bolster and spring joist, so the transverse rigidity of secondary suspension is completely provided by shaking table.
In addition to supporting the weight of the car body, the side bearing can also provide the turning friction moment of the bogie relative to the car body, so as to improve the hunting stability of the vehicle. The lateral stop acts as an elastic buffer to limit the excessive lateral displacement of the car body. The function of the traction rod is to transfer the longitudinal force between the car body and the bogie. The center pin transmits the longitudinal force and provides the turning center for the bogie.
3.2 bogies without shaking table and with bolster device
The secondary suspension device of bogie (figure-5) is mainly composed of air spring 1, bolster 2, anti roll torsion bar 3, height control valve 4, differential pressure valve 5, variable throttle valve 6, lateral oil damper 7, side bearing 8, lateral stop 9, traction rod 10 and center pin 11. In this structure, not only the low vertical stiffness of the air spring but also the low lateral stiffness of the air spring is used to cancel the shaking table device, and there is no requirement for the longitudinal stiffness of the air spring. The maximum lateral displacement of air spring is not more than 60mm, and there is no longitudinal and torsional displacement. This kind of bogies are y36p, dt200, 206KP, SW-160 and dk3 Type Metro car bogies.
The air spring is directly installed on the bogie frame or bolster. By using the low lateral stiffness of the air spring, the bolster suspender, spring joist and other parts are eliminated, the bogie structure is simplified, and the weight is reduced by about 300kg.
1. Air spring 2. Bolster 3. Anti roll torsion bar 4. Height control valve 5. Differential pressure valve 6. Variable throttle valve
7. Lateral oil damper 8. Side bearing of support 9. Lateral stop 10. Traction rod 11. Center pin
3.3 Bolsterless Bogies
The secondary suspension device of Bolsterless bogie (figure-6) is mainly composed of air spring 1, anti roll torsion bar 2, height control valve 3, differential pressure valve 4, variable throttle valve 5, transverse oil damper 6, anti hunting damper 7, transverse stop 8, traction rod 9, traction seat 10, etc. In this structure, not only the low vertical and lateral stiffness of the air spring, but also the large lateral displacement and torsional deformation of the air spring are used to cancel the bolster. Generally, the maximum lateral displacement of air spring is not more than 60mm, and the maximum longitudinal displacement (including torsion) is 110-120mm. This kind of bogies include y237 of TGV in France, sgp400 of ice2, Shinkansen series bogies in Japan, various types of metro passenger car bogies imported from Shanghai and Guangzhou in China, domestic cw-200 trunk railway passenger car bogies, ccdz11 metro passenger car bogies, etc.
1. Air spring 2. Anti roll torsion bar 3. Height control valve 4. Differential pressure valve 5. Variable throttle valve
6. Lateral oil damper 7. Anti hunting damper 8. Lateral stop 9. Traction rod 10. Traction seat
The bogie with "three no" structure (no center plate, no side bearing and no bolster) adopts the structure of high flexibility air spring directly supporting the car body. When passing the curve, the horizontal movement and torsional deformation of air spring are used to replace the rotation function of center pin and side bearing friction pair of bogie with bolster, which greatly simplifies the bogie structure and further reduces the weight by about 500-700kg. In addition to the high flexible air spring, the anti hunting shock absorber with good performance and the traction device with small additional stiffness are also the key technologies of high-speed Bolsterless bogies. The anti hunting damper has nonlinear damping characteristics, which can not only improve the motion stability of the vehicle, but also facilitate the curve passing of the vehicle. At present, the traction devices of Bolsterless bogies mainly include single pull rod type, Z-type pull rod type and laminated rubber pile type. The single pull rod traction device with simple structure, light weight and small space occupation is widely used in Japan, while the Z-type pull rod traction device is widely used in Europe. Due to its large vertical and lateral additional stiffness, the laminated rubber pile traction device is usually used in the bogies of urban rail transit vehicles. In addition, in order to further improve the lateral performance of high-speed Bolsterless bogies, the secondary suspension of 700 series bogies of Shinkansen vehicles is equipped with adjustable damping lateral oil damper (semi-active control) and anisotropic air spring. Sgp400 bogie in ice2 is equipped with DES rotary damping device and active lateral elastic system.
4 high flexibility air spring for Bolsterless Bogies
At present, there are mainly two types of high flexibility free membrane air spring commonly used in Bolsterless bogies at home and abroad, one is large curved bladder type (figure-7); The other is the small curved pouch type (fig-8). The structural characteristics of the large curved bladder type high flexibility air spring are large radius rubber capsule and cone
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