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1 CVT system
CVT system – development survey
CVT technology development, has been a hundred years of history. Benz originator CVT is employed in the automotive art, as early as 1886 will be V-shaped rubber belt CVT attached to the car company’s gasoline. In 1958, Dr. H.VanDoorne Dutch DAF company successfully developed a double V-shaped rubber belt CVT, called Variomatic and equipment on the DAF Daffodil sedan manufactured, which sold more than 1 million. However, due to a series of defects in the rubber belt type CVT: power limited (limited torque 135Nm less), unstable energy clutch, a hydraulic pump, the belt and the clamping means greater losses, and therefore is not generally accepted automotive industry.
However, studies to improve the performance and belt CVT transmission power limit has been engaged, the torque converter integrated into the CVT system, the main clamping force of the driven wheels to achieve electronic control employed in the CVT efficient pumps, with a belt with a metal instead of the traditional rubber band. New advances in technology to overcome the technical defects of the original CVT system, results in a larger transfer torque capacity, better performance of second-generation CVT is available.
into the 1990s, the automobile industry for research and development of CVT technology growing importance, especially in the mini-car, CVT is considered a key technology. The rapid development of global science and technology, making the new electronic technology and automatic control technology has been used to a CVT.
in the first half of 1997, Japan’s Nissan has developed for use on the car 2.0L CVT. On this basis, in 1998, Nissan has developed includes a manual shift mode CVT Design for mid-size sedan. New CVT using a newly developed high strength and a high width strip hydraulic control system. Be obtained by the use of these advanced technologies largeTorque capacity, Nissan CVT research and development of electronic control technology, change the transmission ratio of the full implementation of the electronic control gear, the car may have been downhill engine brake control according to the vehicle speed, but also on slippery surfaces able to smoothly increase ratio prevent slipping. Nissan plans to its scope of application of CVT 3.0L from 1.0L to expand into the car.
Mitsubishi CVT has selected the smooth power transfer without loss of energy of the direct injection engine to drive the car. V-belt / gear transmission mechanism may ensure that the engine power is transmitted smoothly without interruption at all rates. Fight tooth CVT eradication of the phenomenon by a conventional automatic transmission gear shift, so as to obtain more satisfactory response and control. Preparation Mitsubishi direct injection engine (1.5 L of or less) in combination with a CVT.
Japan’s Fuji Heavy Industries also has 15 years of experience in the development of the CVT. In May 1997, it is Vistro FHI miniature car equipped with computer-controlled all-E-CVT (containing six-speed manual shift mode CVT). The driver can be performed without operating the clutch six-speed transmission. FHI employed Pleo miniature electric car is a kind of lock-up torque converter type? Type the CVT, the slide can be kept to a minimum torque converter, a planetary gear for switching the lockup forward by small / reverse gear. Ratio ranging from 1: 10-5.5: 1.
in the first half of 1999, Ford’s US and German ZF companies as Ford cars and light truck production CVT. In 2001 production of Ford’s design in Batavia, Ohio, and the new joint venture will, CFT23 type CVT with electronic management functions. ZF designed for a torque converter type transmission is a CVT, the use of steel for automobile production laterally mounted engine front-drive. ZF companies can drive vehicles and rear wheel drive automobile production CVT series of wheels that are mounted in the longitudinal direction of the engine. ZF company said: Compared with the four-speed automatic transmission, CVT system can be increased by 10 percentage acceleration performance, fuel economy improved by 10 percentage -15 percentage. Compared with A locking torque converter, CVT system more efficient without leakage. Ford is designing a light-duty trucks and all company-matched traction drive CVT, including rear-wheel drive and all-wheel drive trucks. In the synovial fluid using the special traction driveA movable slide instead of the belt and the drive wheel. The relative position of the sliding portion of the gear ratio determined, power is transmitted between the very thin layer of liquid oil components.
German ZF company from mid-1999 to provide steel for CVT VT1 drive for Rover216 cars. Such transmission CVT includes a helical gear or a suitable hydraulic system, wet clutch. The integrated ECU in the system may allow the mechanical, hydraulic and electronic systems further combinations, which make better use of the unique advantages of the various systems.
Bosch type CVT electronic control system is based on the sensor and actuator control electronics unit / module on the basis of the torque. Bosch has an independent member, actuators, sensors and ECU transmission shift comprise a single module, the transmission manufacturer simply add an integrated control unit.
Continuously Variable Transmission System – works
the CVT system mainly includes a driving wheel set, driven wheel set, with a metal basic member and a hydraulic pump. The metal strip is made of metal rings and two beams hundreds metal sheet. Driving wheel and the driven wheel set set by the movable and stationary discs, and the elements close to the cylinder side of the pulley the shaft can slide, the other side is fixed. The movable plate and the fixed plate are tapered structure, the tapered surface thereof to form a V-groove engaged with V-belt metal. Output power of the engine output shaft is transmitted to the first drive wheel of the CVT, and then transmitted through the V-belt to the driven wheels, the final reduction gear, a differential transmitted to the wheel to drive the car. Work driving wheel and the driven wheel disc movable axially movable to change the working radius of the driving wheel, the driven wheel tapered surface engaged with the V-belt, thus changing the transmission ratio through. Amount of axial movement of the movable plate is adjusted to achieve the driving wheel, the driven wheel cylinder pressure of the hydraulic pump by the control system as required by the driver. Since the radius of the driving wheel and the driven working wheel can be implemented continuously adjusted to achieve a continuously variable transmission.
In the hydraulic system of the metal belt type continuously variable transmission, the role of the slave cylinder is to control the tension of the metal strip, power from the engine to ensure efficient, reliable delivery. Active cylinder control bevel wheel axially movable position, with movement along the V-groove in the driving wheel set of metal, unchanged since the length of the metal strip, the driven wheel set along with the change of the metal V-groove in the opposite direction. Metal stripRadius of gyration on the driving wheel and the driven wheel set groups undergo a change in speed ratio is continuously changed.
When the automobile started, the working radius of the driving wheel is small, the transmission can obtain a large gear ratio, which then drives the axle to have sufficient torque to ensure that cars have great acceleration. As vehicle speed increases, the working radius of the driving wheel is gradually reduced, the working radius of the driven wheel increases correspondingly, the CVT transmission ratio decreased, so that the car can travel at a higher speed.
Continuously Variable Transmission System – Characteristics
1 economy
the CVT continuously variable transmission may be implemented within a relatively wide range, to thereby obtain the drive train and the best match engine operating conditions, to improve the fuel economy of the vehicle.
2 dynamic
determines the back-up power car cars climbing ability and acceleration. The greater the power back-up car, the car’s dynamics better. Since the characteristics of the continuously variable transmission CVT, it is possible to obtain the maximum power reserve ratio, the CVT dynamic performance was superior mechanical transmission (MT) and an automatic transmission (AT).
Emission 3
wide operating range of the CVT speed ratio, the engine can work in optimum operating conditions, thus improving the combustion process and reduce exhaust emissions. ZF will own production of CVT loading test, its emissions in cars installed 4-AT is reduced by about 10 percentage.
4 Cost
Simple
the CVT system configuration, the number of parts is less than the AT (about 500) (about 300), once the car manufacturers began mass production, the cost of the CVT will smaller than AT. As a result the system can save fuel, as well as large-scale production systems, materials innovation, the CVT components (such as belt or chain driving wheel, a driven wheel and a hydraulic pump) production costs, reduced by 20 -30 Percentage Percentage .
CVT system – trends
future development
CVT technology can be analyzed from the following four aspects.
the CVT member
push belt and the drive chain torque transmission capacity and expertiseFurther strengthen the usability. Given the rapidly increasing number of products, along with product into the process?-Step automation, the cost will be greatly reduced.
CVT dedicated hydraulic pump will be extended. For emergency brake and kickdown small electronic driven pump, and for the normal operating conditions of the engine driven pump to work together, to further improve the efficiency of the entire transmission.
Optimal Design pulley reduction system will not only reduce the cost and quality, but also to ensure the maximum transmitted torque between the driving and driven wheels and the drive belt. Different components, and an electronic microprocessor control for differences in test equipment, resulting in a very high research and manufacturing costs, which will be reduced by electrically controlling the liquid modular design and mass production, so that the flexible organic functionality and low cost combination.
as more and more CVT enter the market, manufacturers have begun to research and development of special CVT transmission fluid, which will further optimize the CVT performance.
the CVT transmission
a number of different arrangements may occur, since not only the required vehicle drive and the difference (FWD, RWD, AWD), but also due to the continuous increase in transmission ratio coverage requirements.
The electronic lead to faster, more precise control of the gear ratio, velocity, pressure, and torque, ensure better regulation engine and transmission, a different driving modes, e.g. sports, comfort and cruise control, thus allowing users access to a full range of ldquo; rdquo ;. driving fun
with the CVT of the engine integrated control
is more accurate, faster CVT control, the integration into the overall driveline management system with an engine control, such that further reduce fuel consumption and emissions. The first prototype CVT drive train integrated with the engine management unit has a driving cycle test.
The hybrid CVT drive train
CVT will assume an important role in the hybrid powertrain design with a flywheel energy storage device. By CVT drive train of a hybrid vehicle fuel consumption it is possible to reduce the percentage of 30, 50 discharge may be decreased percentage.
Continuously Variable Transmission System – Application
In 1987, the Japanese Subaru CV equipmentT transmission car on the market, to be successful. European Ford and Fiat will VDT-CVT equipped cars in the displacement of 1.1L to 1.6L. As technology advances, the energy crisis and increasing global energy-saving awareness of environmental protection, the basis of summing up the experience of the first generation CVT, developed a better performance, greater torque capacity CVT. Currently, the world’s major car manufacturers in order to improve the competitiveness of their products, are vigorously CVT research and development. Now NISSAN, TOYOTA, FORD, GM, AUDI and other famous car brands, are equipped with CVT transmission car sales, the annual output of CVT cars worldwide has reached nearly 500,000. It is worth noting that, equipped with the CVT auto market, from the original Japanese, European, have infiltrated the North American market, so the CVT auto is the main trend of car development.
Our country has a huge auto market, auto industry is one of China’s national industry. However, the automatic transmission (AT) needed for China’s auto industry all rely on imports, which makes domestic cars equipped with the AT, costs a lot, and equipment development and production of its own CVT transmission, which costs less, indicating that the market outlook is very CVT optimism.
At present, China is considering the development of car automatic transmission problems. Since ldquo; ninety-five rdquo; research and development of the car during the metal belt continuously variable automatic transmission has been included in major national research programs to track the world’s technology development and the development of China’s national conditions of the car.
CVT systems – use matters
for the proper use of CVT should note the following:
1, when traveling, do not move the shift lever pulled ldquo; Nrdquo; file.
2, changed back from the forward, backward from the time varying forward speed, to completely stop the car, the operation of the shift lever while the brake pedal is stepped on, or has the potential to damage the transmission.
3, downhill, use ldquo; Srdquo; manual mode or low speed, using the engine braking effect, to avoid a long time the brake sheet degenerative heat generated by braking, the brake poor performance.
4, since the CVT structure and working principle, all the controls are carried out by internal hydraulic pressure to complete. Therefore, you should check the CVT oil, oil in accordance with the deadline specified by the manufacturer, and regular replacement of oil in line with the provisions of the manufacturers.
5, in order to maximize fuel economy, is preferably used in an automatic mode with CVT gearbox. This allows to maintain throughout the engine and the transmission to achieve the best matching state, to maximize the use of torque and power output of the engine, vehicle speed reaches the economy, thereby improving fuel economy.
6, since the structure of the CVT, after overhaul or off if its associated parts or circuits, must be of a special internal program to make the CVT is set to play a normal state. So, with respect to the maintenance CVT gearbox should go to a professional repair unit for maintenance.