New transmission and emission control systems

New transmission and emission control systems


The development of engines with very high tensile force and torque levels-which are due, in diesel mechanics, to pump-fying technology-represents an important challenge for transmissions engineering.




Volkswagen has begun to reorient and expedite its transmissions program to achieve greater progress in designs, although always taking into account basic objectives such as the reduction of costs that an economy of scale implies. The elements that are currently used as fundamental pillars are a consequence of the principle of modular design, in which the well -known \ "common platform \" is framed and that allows identical sets to be used in a varied range of models within the Volkswagen group. The objectives are as follows:

· All manual exchange boxes will be six marches.
· Development of six -speed automatic gearboxes.
· Integral traction systems available for transverse or longitudinal assembly engines and with manual or automatic change boxes.

New six -speed manual exchange boxes
The new change boxes called MQ (acronym in which M means manual and Q transversal assembly of mechanics) have::

· A precise change action, which includes a minimum level of movement of the lever and precise gear points, identical for all VW manual exchange boxes.
or carefully defined relationships for the characteristics of the engine in which they are used.
· Manufacture with exceptional precision standards, so that they offer absolutely silent operation and a prolonged useful life.
The new exchange boxes with cable mechanism have six or, if sufficient, of five relationships, and meet the following criteria:
· Minimum friction losses to supply maximum efficiency.
· Compact design, through the use of high strength materials and minimum dimensions.
· Reduced weight, through use, for example, of magnesium housings.

The MQ 200, 250, 350 and 500 change boxes (the figures indicate the maximum pair in NM that the box has the ability to transmit) are already used or will be used in a short term in the new Volkswagen models. Special emphasis has been placed on ensuring that change boxes are not only suitable for use with different engines but also in models of various segments.
Volkswagen's trend towards the use of six marches forward in the new models ensures that change relations can be adequate with much greater precision depending on the characteristics of the various mechanics; This represents more vigorous responses to the accelerator and, at the same time, a reduction in consumption.

New automatic transmissions with torque converter
As in the case of manual change, a new range of automatic boxes with hydraulic pair converters will imminently replace the current ones. If the V10 TDI engine is marked as an example, with its maximum torque figure of 750 nm and a power of 313 hp, the important power and torque flows that will have to withstand automatic transmissions in the future are seen. Also, the six marches will be used in the transmissions for the same reasons as in the manual change.
Volkswagen is currently developing three automatic exchange boxes for torque ranges from 250 to 800 Nm, some of which will be usable with longitudinal or transverse installation engines. Through the continuous progress that occurs in software development, fuel savings programs can be used without any loss of refinement in driving through, for example, the installation of a torque converter \ "armored \", to eliminate the current hydraulic transmission losses that occur between the two parts of the converter.

Smart Transmission Technology
The advances offered by the latest generation of mechanics, which develop powers and torque figures superior to the usual ones is, from every point of view, the confirmation of the validity of Volkswagen's policy to adopt integral traction as the only practical way of transmitting these notable increases in the traction force reliably to the road. The research and development carried out are already giving their fruits, and the integral traction systems of the Volkswagen Group - be it by means of the Haldex clutch for the engines mounted in a transverse way or through the integral traction system with central differential torsen for the longitudinal installation engines - are capable of satisfying, in practice, all the mechanical demands.
The development of the new SUV, which will use a longitudinal assembly engine with automatic transmission, has required the design of an integral traction system capable of supporting the most severe loads both in driving on the road and outside it. For this, a classical configuration was chosen, with a transfer box by planetary gears that, coupled to automatic transmission, acts as an additional lower gear and allows, therefore, circular at a very slow speed on very difficult terrain.
Up to 50% of the torque that is normally applied to the rear wheels can be directed without problems to the front wheels by means of a dentated chain and an external transmission axis. An electronic control block in the central differential ensures the best torque distribution between the two axes, while driver controlled electrical control blocks on the controlled front and rear axle guarantee progress even in the most difficult terrain.
In pavement driving, all blockages are released, so that the transmission reaches the rear wheels without stored tensions. This whole -wheel drive system will also be available for light commercial vehicles, and will also be used in other models.

EMISSION CONTROL STRATEGY
Throughout the twenty -five years that passed since Volkswagen marketed their first diesel engine in tourism vehicles, R&D engineers have made constant efforts to maximize the environment. The reduction of the volume of pollutant exhaust gas emissions is always a priority during the development of each new motor or optimization of existing ones. At present, R&D work focuses on bringing emissions at a level clearly below the \ "Euro 4 \" regulations, which will enter into force as of 2005.
Volkswagen mechanical engineers trust the developments they are currently working to continue reducing pollution levels:

New improvements in the internal combustion process.
Even more efficient catalysts
Use of an additional particle filter.
Additional exhaust treatment to reduce nitrogen oxide (NOX).

Injection optimization and combustion techniques
The most ecological Volkswagen engine, that of Lupo TDI \ "3l \" is, since 1999, the only one that exceeds the D4 standard on emissions, although in a very short period, another VW tourism will also achieve this goal: the 1.9 TDI golf of 100 hp with front -wheel drive will meet this standard of emission control, starting next June.
It will maintain its intact benefits, with a power of 100 hp available at 4,800 rpm and a maximum torque of 240 Nm at 1,800 rpm. The fuel injection system and other interior operating processes have experienced new developments.
The initial step to achieve this is a new design of the injectors's nozzles - with an even more precise mechanization of the holes, which causes a better fuel spray - and a more effective combustion, to which the use of flat piston heads contributes, for which the valves were also modified. The new system eliminates the usual concavities for the heads of the valves that, to some extent, interfere with the spread of the flame during the combustion process.
An innovative concept of recirculation of exhaust gases that helps reduce NOX emissions has also been incorporated. Gases that return to combustion chambers are cooled depending on the temperature and motor operation point. This additional cooling system allows the exhaust gases that return to combustion chambers to do it at the optimal temperature to keep NX emissions contained, without major carbon monoxide emissions (CO), hydrocarbons (HC) and particles containing.
An especially thin wall oxidation catalyst makes it easier for gas conversion to start faster after cold engine. The insulation with an intermediate air layer of the exhaust tube that reaches the catalyst also contributes to minimizing the loss of temperature.
Both factors reduce the components that the catalyst has to convert during the engine heating phase. Through this, the 100 hp TDI engine has the capacity to comply with the future Euro 4 standard, even with two valve technology per cylinder. Greater progress will be achieved with the commercialization of the second generation of pump-fybody, with a higher degree of pressure.
It is increasingly evident that the development rate on all gas emission control processes will allow to exceed the Euro 4 standard with reliability in the case of vehicles with engines of a certain power.
However, larger and more heavy cars, such as luxury berlina or the future SUV with V10 TDI engine, work frequently in operational points in which there is a risk of exceeding the limits of the future standard. For that reason, an additional treatment of escape gases is essential. The objective is to reduce the level of gaseous nitrogen oxides (NOX) and solid particles. To do this, Volkswagen Development Engineers have developed an active system for treatment of exhaust gases.

Volkswagen CRT active system
Unlike the traditional discontinuous regeneration system due to particle filter, the new CRT system (continuous regeneration storage) operates with a filter load that does not exceed 20 or 30% of its capacity, which prevents extreme setback pressures in the exhaust system, which usually causes a very high consumption.
The regeneration of the continuous system uses nitrogen dioxide (NO2) produced in the oxidation catalyst near the engine instead of oxygen (O2), as with the current system. In order for the CRT to operate continuously, a working temperature of more than 300 degrees is necessary, which is reached with a gentle level of the position.
In the range of low loads, at speeds of up to 100 km/h, the system accumulates filtered soot particles until the limit of 30% filter capacity is reached. At this point the active function of the CRT begins. The oxidation catalyst eliminates carbon monoxide (CO) and hydrocarbons (HC) from the exhaust and provides nitrogen dioxide (NO2) necessary for oxidation (combustion) of the soot particles in carbon dioxide (CO2) in the second catalyst.
If the load in the filter falls below 20% of its capacity, the CRT active function stops. The control values ​​are the temperature and pressure differences in the anterior and posterior area of ​​the filter; These can be determined with great accuracy and reliability, to guarantee the efficient operation of the CRT.
The diesel that is currently marketed contains a high proportion of sulfur, which is contaminating the catalysts gradually. This situation would adversely affect the CRT - with a rapid elevation in filter contamination by soot particles - unless an external action is caused to correct it. To maintain reliability in these conditions, an \ "emergency brake \" has been incorporated into the CRT system.
This \ "brake \" causes a fuel post-fiction to raise the temperature of the exhaust gas to more than 500 degrees; At this temperature, the soot particles in the filter burn with the presence of atmospheric oxygen (O2). At the same time, this \ "fire injection \" cleanses catalysts by stirring sulfur deposits.
As a consequence of the next introduction of super-gloss free gasoline to the market, the controlled changes in the composition of the fuels will be established in a relatively short time. It is very likely, therefore, that an average term also marketed diesel fuel without sulfur presence, which will unnecessary the use of this additional function in the CRT active system, with the severe increase in the temperature it implies.

Storage catalyst for nitrogen oxides (NOX)
In order to reach a composition of adequate exhaust gases to comply with the Euro 4 regulations in all the marching phases of a large power, not even the almost total elimination of the soot particles is sufficient. Nitrogen oxides (NOX) remaining gaseous should also be minimized. The most appropriate way to achieve this is the storage catalyst for nitrogen oxides, an element that is already known for its use in direct gas injection engines. Catalytic coating absorbs nitrogen oxides in exhaust as if it were a sponge.
However, its limited absorption capacity implies that it must be cleaned at intervals through the enrichment of the mixture. To do so, the admission air of a diesel engine, which normally operates with more air than fuel (that is, with a very soft mixture), is temporarily accelerated and the engine operates by means of post-injection. This procedure is maintained for five or ten kilometers, although it is generally not noticeable for the driver. The process ensures that the storage catalyst can eliminate 60 or 70% of escape nitrogen oxides under normal operating conditions.



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