The main types and characteristics of automobile automatic transmission
The specific category and current application status of automobile automatic transmission (AT)
AT has the following methods:
(1) Hydraulic machinery AT-HMT (Hydrodynamic Mechanical Transmission) is widely used in cars, buses, super-heavy vehicles, commercial vehicles and construction machinery, and it is the popularity of AT at this stage.
(2) Pedal AT-AMT (Automated Mechanical Transmission) is basically composed of a general pedal gearbox plus a microcomputer operating a hydraulic servo motor to operate a fully automatic gear shift. At this stage, it is used in some low-speed cars. and some trucks and commercial vehicles.
(3) The stepless AT-CVT (Continuously Variable Transmission) has the following methods: Pedal type: There are many methods, the key at this stage is the V-type continuous transmission system of push block metal material, which has gradually been used in cars. Used in large quantities. ●Hydraulic transmission system (HST hydrostatic transmission): It has been used in construction machinery and agricultural machinery. Although Guangzhou Honda has recently developed and designed an AT with a hydraulic system and a double-flow transmission system of mechanical equipment that integrates the pump and motor, it is used in small multi-purpose vehicles, but there are limitations on speed ratio, high efficiency, noise, net weight and specifications. problem, almost no use in the car. ●Electrical engineering type: for electric vehicles (EV electric vehicle).
Analysis of the structure and performance characteristics of AMT
AMT is based on the general manual shifting pedal gearbox, which is basically composed of an electronic device that replaces manual shifting.
AMT is made by upgrading and transforming the gearbox of general mechanical equipment. Only part of the manual shift operation is changed. The transferability of production and manufacturing is good, the capital investment for upgrading and transformation is low, and the technical level does not seem to be large. Partially automated technology. For example: fully automatic operation of the clutch, complete automatic operation between some gears, etc., and then complete the all-round automation technology. This has a certain temptation for the production in my country's automobile industry, which lacks assets, low production and manufacturing capabilities, and lacks technical skills. Several Chinese companies have already carried out scientific research, development and design, and obtained exciting test results.
AMT retains the previous mechanical equipment gearbox, so its transmission system performance is mostly the same as the mechanical equipment gearbox. In addition to the transmission gear, the main feature is that it has the following two organizations: development equipment, the main clutch with torque shock absorber;
This kind of pure gear transmission has the advantages of high transmission efficiency and simple structure, but it is difficult to avoid the interruption of driving force in the whole process of shifting. The defect is that only after one fusion component is released, the other fusion component can be fused, and the steel bar overlap operation during the transformation of the fusion component during the whole shifting process cannot be completed. Therefore, the development and shifting must not be stable and the impact is great. At the same time, the gear transmission is difficult to isolate the vibration caused by the uneven torque of the engine. AMT cars have relatively large vibration and noise, and poor ride comfort, so they are not suitable for high-end luxury cars.
In fact, it is technically not easy to develop a high-quality microcomputer-controlled automatic gearshift organization. In addition to the technicality of high-quality hydraulic control algorithms, it is also necessary to achieve the driver's desire for driving and satisfy various driving tasks. In addition, the whole process of shifting is an intricate and comprehensive operation process. In addition to operating the main clutch and gearbox, it also involves the operation of the accelerator pedal and braking system of the automobile engine. From the current stage, it seems that AMT is still very difficult to achieve this level, and the manufacturing cost of this shift robotic arm system software is not low, and there is no price advantage between AMT and HMT. In addition, the AMT fully automatic shifting mechanism must drive the power, so it must reduce the transmission efficiency more or less.
According to the above analysis, everyone thinks that AMT is suitable for commercial vehicles and trucks. This kind of vehicle has many gears, and it is difficult to choose HMT. It must be fully automated to ease the driver's work, and the disconnection of the driving force during the whole shifting process is not harmful. There are no high requirements for ride comfort. AMT can also be used in low-speed cars, and it is not necessarily automatic. It is also possible to engage in partial automatic control and gear shifting. It can deal with the problems of complicated shifting manipulation and high labor efficiency in the development of manual shifting mechanical equipment gearboxes. Practical technical measures to simplify safe driving maneuvers.
Analysis of the structure and performance characteristics of HMT
HMT is composed of a torque converter and a hydraulic press-operated shift gearbox.
The key differences between HMT and AMT are:
1. The development equipment replaces the main clutch torque converter with a torque converter. The transmission torque is related to the speed of the pump wheel. The transmission torque is small when the automobile engine has a low speed ratio. It solves the problem that the gas turbine cannot run on load. No need to manipulate, just give the throttle to be able to develop fully automatically. A torque converter has been proven to be a reasonable component for a vehicle based on long-term use, with the following advantages:
●Fully automatic torque change, the torque is automatically increased when starting, to improve the development performance, and the change of external friction resistance should be fully integrated into the driving. Torque and driving force are very easy to manipulate and adjust with the change of the throttle, especially when starting in low gears or going uphill, making it very easy and convenient to drive safely.
● Development is accelerated and gear shifting is stable, reducing the load on the transmission and increasing the service life of the transmission.
●Isolate the vibration caused by the uneven torque of the engine, reduce noise, and improve the ride comfort, giving people a feeling of safe driving, stable and advanced.
●Avoid the sudden break of fire of the car engine due to the load, and improve the usability of the car.
The key defect of the torque converter is the high efficiency and low efficiency of the transmission system, which increases the fuel consumption. In the early stage of the application of the torque converter, there is a common misconception that the torque converter can open the automatic torque conversion function, so the flutter ratio of the first HMT torque converter is very high. Large, the key to torque change is to complete the torque converter, and the gearbox is assisted, so there are very few gears. There are only two kinds of gears at first, and then it is gradually understood that it is necessary to use the torque converter. Increasing the torque ratio will inevitably increase the fuel consumption of the torque converter, which is difficult to achieve. The key to the transformation of HMT into external friction resistance is to rely on the gearbox. Therefore, the ten-digit transmission gear of HMT continues to increase, from 2nd gear to 3rd and 4th gear. At this stage, high-end cars use 5th gear, and it may develop to 6th gear. The flutter torque conversion ratio of the torque converter is reduced to below 2 to enhance its maximum efficiency.
At the same time, the effect of the torque converter has also been further established. It only plays an effective role in the whole process of acceleration and shifting, but it does not play any role in smooth driving, but instead increases fuel consumption. Therefore, the locking clutch is selected to lock the torque converter into a gear transmission to improve work efficiency. At the beginning, the lock-up clutch was selected, and its lock-up area was limited to areas with high-end, high-speed and low-speed accelerator pedals. After the torque converter is locked in the low gear area, the vibration caused by the unbalanced torque of the car engine is not sent to the gear train immediately after the hydraulic transmission damping, which will cause vibration and noise, which will endanger the comfort of riding. In order to better deal with the differences between the rationality of gasoline and diesel and safe driving stability, the locked area is promoted to expand to the industry of low gear, low speed and large accelerator pedal opening. Recently, most of the cars have adopted the lock-up clutch and slight deviation control, which has led to a slight increase in fuel consumption, but the safe driving stability has been greatly improved.
From the above analysis, it can be seen that the application of torque converters in automobiles has already become more and more perfect, and the defects of high transmission efficiency and low transmission efficiency should be resolved as much as possible, and the advantages of stable transmission system and automatic torque increase of all sunshine auto parts manufacturers should be fully exerted. In the formulation of the torque converter, the excellent basic theory of three-dimensional cascade is adopted, and the reliability design is carried out on the circular shape of the circulation system, the leaves and patterns of each centrifugal impeller, and the torque index of the torque converter is effectively clarified, so that the hydraulic The torque converter and the car engine are paired up to improve the rationality and driving force of their working together.
From the perspective of production and manufacturing, the production of torque converters is not complicated, and the cost is not high. From the perspective of application, the torque converters are safe to work and have a long service life.
The gear shifting mechanism adopts hydraulic press to operate friction fusion components. Compared with gear shifting with synchronous controller, there is no significant driving force interruption in the whole shifting process, and the steam pressure of the separated fusion components can be released and the steam pressure of the fused fusion components can be increased. , to accurately control the lap of the shifting steel bars, and complete the quick, stable and shock-free shifting.
2 From the perspective of the overall automatic control system:
●AMT: The gear shift of the mechanical equipment is a synchronous controller lever dial * hydraulic control organization. The whole process of manipulation consists of electronic signal → hydraulic press data signal → reusing mechanical equipment organization (lever and synchronous controller) to shift gears
●HMT: The entire shifting process of the driving force shift transmission consists of electronic signal → hydraulic machine data signal, and the fusion and separation of the shifting fusion components are immediately manipulated.
3 From the perspective of AMT and HMT shift manipulation methods:
(1) The HMT shift operation method is very simple and immediate. The electronic signal is converted to the hydraulic machine data signal to immediately manipulate the fusion components to shift, and after the AMT is converted to the hydraulic machine data signal, the shift must be manipulated according to the organization of the mechanical equipment. Obviously, it is more inconvenient.
(2) AMT is a power switch type operation (separation and fusion); HMT is a proportional type operation, which can control the gradual separation of one fusion component and the gradual fusion of another fusion component. In this way, the steel bar overlap and orderly advance in the whole process of shifting can be controlled.
If both AMT and HMT use fixed tooth inlay gearbox (Guangzhou Honda HMT uses fixed tooth inlay), HMT is no worse than AMT in terms of structural complexity and manufacturing difficulty.
It should be said that HMT uses steam pressure control fusion components to shift gears better than AMT uses hydraulic press to organize synchronous controllers, and the structure is not complicated.
At this stage, many HMTs have a manual mode. In the manual mode, the HMT is equivalent to a driving force shift gearbox, that is, a manual and fully automatic gearbox. It has the characteristics of high efficiency and manual selection of gear shifting of general mechanical equipment gearboxes, but the shifting operation is greatly simplified.
From the above analysis, it is known that HMT is better than AMT in performance, which also shows why HMT is the popularity of AT.
Everyone thinks that HMT can choose a variety of working modes, it is very easy and convenient to operate safe driving, develop shift without shock, safe driving and stable, low vibration and noise, giving people a feeling of comfort and high-end, it is especially suitable for high-end cars. With the continuous innovation and perfection of HMT, for the average driver, its driving force performance and economic development performance are not worse than AMT.
Analysis of the structure and performance characteristics of CVT:
There are various forms of CVT, and here only the symbolic push-block V-shaped metal material continuous type is analyzed.
1 The structure of CVT consists of:
(1) There are three ways to develop equipment:
●Electromagnetic brake: large net weight specifications, low heat consumption and working capacity, generally only used in small cars;
●Electronic device-operated wet-test friction clutch: small in structure, fast in response, and low in kinetic energy loss, it is used in some cars;
●Torque converter: The development torque is large, the half-slope starting performance is good, the safe driving is very easy and convenient, the axle body performance is good (in and out of the parking space), and it can isolate the vibration and impact caused by the unbalanced engine torque. Therefore, at this stage, CVT is also more inclined to use a torque converter.
(2) Push block type metal material V-belt stepless speed change equipment.
(3) The forward and backward commutation organization has two types: large planet type and fixed tooth type.
2 Comparison of CVT and HMT
(1) From the performance point of view, CVT is a stepless transmission system, which can maximize the use of the characteristics of the automobile engine, improve the driving force and rationality, and at the same time, the speed regulation is stable, and the driving performance and safe driving feel good. HMT It is a stepped transmission system. In order to better improve the performance, it is necessary to increase the gear by ten digits. At this stage, it has been upgraded to 5th gear, which is closer to the performance of the CVT, but there is still a slight difference.
(2) From the point of view of structure and production, the hydraulic torque converter is still used on the CVT, and it must also be turned forward and backward to control the friction and fusion components of the mechanism and the hydraulic press. From the perspective of the complexity of structure and production, the difference between the two is not large. At this stage, it seems that the CVT manufacturing cost is slightly higher.
(3) As a new product, CVT must go through sufficient time to challenge and be confirmed by Rizhao auto parts manufacturers from its introduction, development trend to perfection; for users, there must be a whole process of understanding, trust and acceptance. At this stage, CVT commodities are still immature and need to be improved.
●The structural style and main parameters of the steel belt are still being perfected and perfected, and its function of transmitting torque is further improved.
●During the whole process of speed regulation, the radial deviation of the belt will lead to the situation that the axis of the belt plan view of the master-slave relationship driving pulley is not on the same level. This condition can cause the belt to distort during its running process, cause shock at the incoming and outgoing ends of the pulley, increase noise, make the drive system unstable, and drastically reduce the service life of the belt. In order to solve this problem, at this stage, the spherical shape of the pulley in contact with the steel belt is used to carry out the adjustment design scheme. However, try to make the center of both sides of the master-slave relationship pulley move symmetrically, so that the axis of the two-pulley belt plan view is not deviated.
●In areas where the application has been unsatisfactory, such as when developing and driving at a slow speed, there will be a wet and unrounded feeling that is different from the CVT. the state of legal development.
●From the point of view of the automatic control system, including speed control, gripping force control and development control are all areas with insufficient soundness. From the current stage, CVT has not replaced the large-scale application of HMT. The key is that compared with HMT, there is no obvious excellent performance area, and there are still immature areas, and HMT has been produced for more than 60 years. The application history time, the performance is very sound, and the goods are very perfect. Therefore, although many manufacturers are conducting scientific research, experiments, using CVT, and completing mass production, they still take a cautious attitude towards CVT. From the current stage, the core influence of HMT has not swayed.