Computer Controlled DSG Transmission

Figure 1 Demonstration model DSG transmission with programmable control.

 

 

The Volkswagen/Audi DSG Transmission

Early in 2003, Volkswagen introduced a new kind of automatic gearbox as fitted to the Golf RS32. This DCT (Dual Clutch Transmission), known as DSG (Direct Shift Gearbox), was also made available in the Audi 3.2 TT Quattro, who named the DSG "S-Tronic".Since then, the DSG has become optional equipment on most VW cars and is manufactured in the Kassal transmission plant which is capable of producing 1000 transmissions per day.

The DSG is a kind of automated manual gearbox in that it uses the Borg Warner DualTronic wet-clutch and control system technology in conjunction with a new configuration of VW standard gear and synchromesh mechanisms.It is a six-speed and reverse arrangement, effectively two gearboxes in one. It uses two clutches, one (C1) serving the odd numbered gear ratios, driving an input shaft to the 1st, 3rd, 5th and reverse synchronizers, and the other (C2) serving the even numbered gear ratios, driving the input shaft to the 2nd, 4th and 6th speed synchronizers. The odd and even geared shafts then drive a common differential gear. Figure 2 is a cut-away of the whole transmission.

Figure 2 DSG Transmission as fitted to the Audi TT 3.2 V6 Quattro, 4WD version.
Viewed from the front of car.

 

 

Drive to the rear axle is taken from the output at the left hand side, to a rear axle mounted Haldex clutch

The principle of operation is that whilst an odd numbered gear ratio is being driven by one clutch (C1), an even numbered gear ratio can be pre-selected, ready for engagement by switching to the second clutch (C2). This action repeats for even to odd gear changes and hence for all upshifts and downshifts.

The result is virtually continuous power flow during gearshifts that are quicker than a manual gearbox and smoother than a conventional automatic transmission.

 Typical shift times are 0.3 to 0.4 seconds; during upshifts engine power is interrupted for only 8 milliseconds. Shift quality is ensured by the modulated transfer of torque from clutch to clutch, since in multi-plate wet clutches, better control of friction and wear is possible, and heat energy is dissipated by the circulating cooling fluid. This is unlike dry clutches, which consume their friction material and require eventual replacement.

The DSG arrangement is also more efficient than the conventional hydrodynamic torque converter equipped automatic transmission (a torque converter has a peak efficiency of 86-90% at a pre-determined speed ratio, at all other speed ratios the efficiency falls to zero at stall and run-out).

 

Figure 3 DSG gear/clutch schematic and 1st and 2nd gear drive-paths.

 

 

 

 

 History

The beauty and simplicity of the DSG principle is not new, however. The invention of the double clutch gearbox is attributed to a French engineer, Andolphe Kegresse, around 1939 (figure 5). He intended to use it in the Citroen "Traction" vehicle, but business and war circumstances prevented further development.

Figure 4 Kegresse dual clutch gearbox proposal.

Years later, Automotive Products (AP) proposed a double clutch/gearbox of different design (figure 6). In 1985 Porsche raced a similar gearbox to Kegresse known as PDK (Porsche Dual Klutch), a 5-speed unit with dry plate clutches (figures 7 and 8), whilst Luk/Devotek proposed the PSG (Parallel Shift Gearbox) using wet or dry clutches (figure 9).

Figure 5 AP schematic for 4 and 6 speed designs

 Figure 6  Porsche-Audi PDKcaption.

Figure 7 Porche-Audi PDK schematic.

Figure 8 Luk/Devotek PSG twin dry plate clutch.

 

 

 

 

 

 

 

 

DSG - The Future Of The Gearbox.

The VAG Direct Shift Gearbox - sometimes called the S-Tronic in the Audi range - is the world's first production dual clutch semi automatic gearbox. The system was developed for Audi by BorgWarner for use in the companies Audi TT 3.2V6, and was so well received it is now used in much of the Volkswagen Audi Group range.The DSG is often compared to F1 style automated or robotic manual gearboxes, but differs in some very important ways.

The DSG gearbox is, however, not a new invention. The system was first designed by Andolphe Kégresse just before the second world war but because of the lack of technology, not to mention the war, he never produced a working version of the Dual Clutch Gearbox (DCG). The system was used by another German car company in the 80's though: Porsche used the PDK (Porsche Doppelkupplungs) system in their 956 and 962 Le Mans race cars, and Audi used the same system in the Sport Quatro S1. Porsche and Audi have a long history of technology sharing.

 Both of these uses eventually faded, primarily because the computing technology that allows the system to work so effectively did not prove to be reliable enough in the tough and demanding world of the race car.To understand how revolutionary the DSG gearbox is, first we  will explain the F1 style systems. These differ in name depending on the manufacturer; Ferrari call theirs the F1 system, and BMW call theirs the SMG system.

These gearboxes all have one thing in common: they are just manual gearboxes, with a manual clutch that is operated by pneumatics. This method has many of the benefits the DSG box does. The gearbox itself weighs less: as the gear change is accurate, and no human mistakes can be made, the materials can be less hardy. They are also far more performance than the manual equivalent, both the BMW SMG II and the Ferrari F1 systems change cogs in around 80 milliseconds. This means that, while the gear is being shifted, all the power from the engine is waisted and a feeling of on-off-on is felt in the car as the pneumatics shift from in gear, to clutched, and then back into gear. The smoothness of this in the car depends on the software controlling it: for the fastest changes it can feel quite 'bumpy', similar to a bad gear change in a manual car. The only way of releaving this issue in the past was to fit a torque converter, this is the way that a standard auto box does it, and why it feels far smoother than any of the manual gearboxes produced. A torque converter, however, is very wasteful in terms of power, and usually very heavy.

 Reference:  http://blogcritics.org/scitech/article/dsg-the-future-of-the-gearbox/#ixzz1ouUvbLAt

Volkswagen Group vehicles with the DSG gearbox.

Volkswagen Passenger Cars

Volkswagen Cross Touran

Volkswagen Polo

Volkswagen Golf

Volkwagen Golf GTI

Volkswagen EOS

Volkswagen Jetta

Volkswagen Tiguan

Volkswagen Passat CC

Volkswagen Touareg

Reference: http://www.volkswagen.com.my/

Description of the DSG System.

Picture 1.1 : DSG Gearbox Overview

The Direct-Shift Gearbox , commonly abbreviated to DSG is an electronically controlled dual clutch multiple-shaft manual gearbox, in a transaxle design  without a conventional clutch pedal, and with full automatic, or semi-manual control. The first actual Dual Clutch transmissions derived from Porsche in-house development for 962 racing cars in the 1980s.

In simple terms, it is two separate manual gearboxes (and clutches), contained within one housing, and working as one unit. It was designed by BorgWarner,  and was initially licensed to the German automotive industry concern Volkswagen Group (which includes the Volkswagen Passenger Cars, Audi, SEAT, Škoda, Lamborghini, Bentley, Bugatti, Porsche, and Volkswagen Commercial Vehicles automotive marques),by using two independent clutches,  a DSG can achieve faster shift times,  and eliminates the torque converter of a conventional epicyclic automatic transmission. 

Transverse DSG. 

At the time of launch in 2003  - it became the world's first dual clutch transmission in a series production car,  in the German-market Volkswagen Golf Mk4 R32  and shortly afterwards, worldwide in the original Audi TT 3.2; and for the first few years of production, this original DSG transmission was only available in transversely orientated  front-engine, front-wheel-drive — or Haldex Traction-based four-wheel-drive vehicle layouts.

The first DSG transaxle that went into production for the Volkswagen Group mainstream marques had six forward speeds (and one reverse),  and used wet/submerged multi-plate clutch packs  (Volkswagen Group internal code: DQ250, parts code prefix: 02E).  It has been paired to engines with up to 350 N•m (260 lb•ft) of torque,  and the two-wheel-drive version weighs 93 kg (210 lb). It is manufactured at Volkswagen Group's Kassel plant,  with a daily production output of 1,500 units.

Operational Introduction.

The internal combustion engine drives two clutch packs. The outer clutch pack drives gears 1, 3, 5  (and 7 when fitted), and reverse  — the outer clutch pack has a larger diameter compared to the inner clutch, and can therefore handle greater torque loadings. The inner clutch pack drives gears 2, 4, and 6.  Instead of a standard large dry single-plate clutch, each clutch pack for the six-speed DSG is a collection of four small wet interleaved clutch plates (similar to a motorcycle wet multi-plate clutch).

 Due to space constraints, the two clutch assemblies are concentric, and the shafts within the gearbox are hollow and also concentric.   Because the alternate clutch pack's gear-sets can be pre-selected  (predictive shifts enabled via the 'unused' section of the gearbox), un-powered time while shifting is avoided  because the transmission of torque is simply switched from one clutch-pack to the other.  

This means that the DSG takes only about 8 milliseconds to upshift.  In comparison, the sequential manual transmission (SMT) in the Ferrari F430 Scuderia takes 60 milliseconds to shift,  or 150 milliseconds in the Ferrari Enzo.  The quoted time for upshifts is the time the wheels are completely non-powered.  

DSG controls

The Direct-Shift Gearbox utilizes a floor-mounted transmission shift lever, very similar to that of a conventional automatic transmission.  The lever is operated in a straight 'fore and aft' plane (without any 'dog-leg' offset movements), and utilizes an additional button to help prevent an inadvertent selection of an inappropriate shift lever position.

"P'' Mode

P position of the floor-mounted gear shift lever means that the transmission is set in "Park". Both clutch packs are fully disengaged, all gear-sets are disengaged, and a solid mechanical transmission 'lock' is applied to the crown wheel of the DSG's internal differential. This position must only be used when the motor vehicle is stationary. Furthermore, this is the position which must be set on the shift lever before the vehicle ignition key can be removed. 

"D'' Mode

 Whilst the motor vehicle is stationary and in neutral (N), the driver can select D for "drive" (after first pressing the foot brake pedal). The transmission's reverse gear is selected on the first shaft k1 ,  and the outer clutch K2 engages at the start of the 'bite point'. At the same time, on the alternate gear shaft, the reverse gear clutch K1 is also selected  (pre-selected),gearbox still doesn't know whether the customer wants to go forward or reverse (could still change even though its in d) but the clutch pack for second gear (k2) get ready to engage . When the driver releases the foot brake pedal, the k2 clutch pack increases the clamping force, allowing the second gear to take up the drive through an increase of the 'bite point', and therefore transferring the torque from the engine through the transmission to the driveshafts and roadwheels — and the vehicle moves forward. Pressing the throttle / accelerator pedal will fully engage the clutch, and causes an increase of forward vehicle speed, pressing the throttle pedal to the floor (hard acceleration) will cause the gear box to kick down to first gear to provide the acceleration associate with first although there will be a slight hesitation while the mechatronics deselects second gear and selects first gear As the vehicle accelerates, the transmission's computer determines when the second gear (which is connected to the second clutch) should be fully utilised. Depending on the vehicle speed, and amount of engine power being requested by the driver (full throttle, or part-throttle normal driving), the DSG then upshifts. During this sequence, the DSG disengages the first outer clutch whilst simultaneously engaging the second inner clutch  (all power from the engine is now going through the second shaft), thus completing the shift sequence. This sequence happens in 8 milliseconds (aided by pre-selection),  and can happen even with full throttle opening, and as a result, there is virtually no power loss.  

"S'' Mode.

The floor selector lever also has an S position.  When S is selected, "sport" mode  is activated in the DSG. Sport mode still functions as a fully automatic mode,  identical in operation to "D" mode, but upshifts and downshifts are made much higher up the engine rev-range.  This aids a more sporty driving manner,  by utilising considerably more of the available engine power, and also maximising engine braking. However, this mode does have a detrimental effect on the vehicle fuel consumption, when compared to D mode. This mode may not be ideal to use when wanting to drive in a 'sedate' manner; nor when road conditions are very slippery, due to ice, snow or torrential rain — because loss of tyre traction may be experienced (wheel spin during acceleration, and may also result in roadwheel locking during downshifts at high engine rpms under closed throttle). On 4motion or quattro-equipped vehicles this may be partially offset by the drivetrain maintaining full-time engagement of the rear differential in 'S' mode, so power distribution under loss of front-wheel traction may be marginally improved.
S is highlighted in the instrument display, and like D mode, the currently used gear ratio is also displayed as a number.

''R'' Mode

R position of the floor-mounted shift lever means that the transmission is in "reverse". This functions in a similar way to D, but there is just one 'reverse gear'. When selected, R is highlighted in the instrument display.

Manual Mode

Additionally, the floor shift lever also has another plane of operation, for manual  mode, with spring-loaded "+" and "−" positions. This plane is selected by moving the stick away from the driver (in vehicles with the driver's seat on the right, the lever is pushed to the left, and in left-hand drive cars, the stick is pushed to the right) when in "D" mode only. When this plane is selected, the DSG can now be controlled like a manual gearbox, albeit only under a sequential shift pattern.
In most (VW) applications, the readout in the instrument display changes to 6 5 4 3 2 1, and just like the automatic modes, the currently used gear ratio is highlighted or emboldened. In other versions (e.g. on the Audi TT) the display shows just M followed by the gear currently selected, e.g. M1, M2 etc.
To change up a gear, the lever is pushed forward (against a spring pressure) towards the "+", and to change down, the lever is pulled rearward towards the "−". The DSG transmission can now be operated with the gear changes being (primarily) determined by the driver. This method of operation is commonly called "tiptronic".  In the interests of engine preservation, when accelerating in Manual/tiptronic mode, the DSG will still automatically change up just before the redline, and when decelerating, it will change down automatically at very low revs, just before the engine idle speed (tickover). Furthermore, if the driver calls for a gear when it is not appropriate (e.g.: requesting a downshift when engine speed is near the redline) the DSG will not change to the driver's requested gear.
Current variants of the DSG will still downshift to the lowest possible gear ratio when the kick-down button is activated during full throttle whilst in manual mode. In Manual mode this kick-down is only activated by an additional button at the bottom of the accelerator pedal travel; unless this is pressed the DSG will not downshift, and will simply perform a full-throttle acceleration in whatever gear was previously being utilised.

Paddle shifters
Initially available on certain high-powered cars, and those with a "sporty" trim level — such as those using the 2.0 TFSI and 3.2/3.6 VR6 engines  — steering wheel-mounted paddle shifters  were available. However, these are now being offered (either as a standard inclusive fitment, or as a factory optional extra) on virtually all DSG-equipped cars, throughout all model ranges, including lesser power output applications, such as the 105 PS Volkswagen Golf Plus.
These operate in an identical manner as the floor mounted shift lever when it is placed across the gate in manual mode. The paddle shifters have two distinct advantages: the driver can safely keep both hands on the steering wheel when using the Manual/tiptronic mode; and the driver can immediately manually override either of the automatic programmes (D or S) on a temporary basis,  and gain instant manual control of the DSG transmission  (within the above described constraints).
If the paddle-shift activated manual override of one of the automatic modes (D or S) is utilised intermittently, the DSG transmission will "default" back to the previously selected automatic mode after a predetermined duration of inactivity of the paddles, or when the vehicle becomes stationary. Alternatively, should the driver wish to immediately revert to fully automatic control, this can be done by activating and holding the "+" paddle  for at least two seconds.

Advantages and disadvantages

Advantages 

•  Better fuel economy  (up to 15% improvement) than conventional planetary geared automatic transmission (due to lower parasitic losses from oil churning)  and for some models with manual transmissions.

• No loss of torque transmission from the engine to the driving wheels during gear shifts;  Short up-shift time of 8 milliseconds when shifting to a gear the alternate gear shaft has preselected.

•  Smooth gear-shift operations. Consistent shift time of 600 milliseconds, regardless of throttle or operational mode.   
 

Disadvantages

• Achieving maximum acceleration or hill climbing, while avoiding engine speeds higher than a certain limit (e.g. 3000 or 4000 RPM), is difficult since it requires avoiding triggering the kick-down-switch. Avoiding triggering the kick-down-switch requires a good feel of the throttle pedal, but use of full throttle can still be achieved with a little sensitivity as the kick-down button is only activated beyond the normal full opening of the accelerator pedal.  
• Marginally worse overall mechanical efficiency compared to a conventional manual transmission, especially on wet-clutch variants (due to electronics and hydraulic systems).
• Expensive specialist transmission fluids/lubricants with dedicated additives are required, which need regular changes.
• Relatively expensive to manufacture,  and therefore increases new vehicle purchase price.
• Relatively lengthy shift time when shifting to a gear ratio which the transmission ECU did not anticipate (around 1100 ms, depending on the situation).
• Torque handling capability constraints perceive a limit on after-market engine tuning modifications (though many tuners and users have now greatly exceeded the official torque limits  Later variants have been fitted to more powerful cars, such as the 300bhp/350Nm VW R36 and the 272 bp/350 Nm Audi TTS. 

Reference : http://en.wikipedia.org/wiki/Direct-Shift_Gearbox

Volkwagen Transmission Technology.

Diagram 1.0: DSG Cuteaway Engines

 Transmission Technology 

 
Direct Shift Gearbox (DSG) The twin-clutch transmission, also known as the Direct Shift Gearbox (DSG) or dual-clutch transmission, is an automated transmission that can change gears faster than any other gear transmission. Twin-clutch transmissions deliver more power and better control than a traditional automatic transmission and faster performance than a manual transmission.

Volkswagen Component Identification

The twin-clutch transmission is essentially two separate transmissions with a pair of clutches between them. One transmission (or gearbox) provides odd-numbered speeds (ie first, third and fifth gear), the other provides even-numbered speeds (second, fourth and sixth). When the car starts out, the "odd" gearbox is in first gear and the "even" gearbox is in second gear. The clutch engages the odd gearbox and the car starts out in first gear. When it's time to change gears, the transmission simply uses the clutches to switch from the odd gearbox to the even gearbox, for a near-instant change to second gear. The odd gearbox immediately pre-selects third gear. At the next change the transmission swaps gearboxes again, engaging third gear, and the even gearbox pre-selects fourth gear. The twin-clutch transmission's computerized controller calculates the next likely gearchange based on speed and driver behavior and has the "idle" gearbox pre-select that gear.

Benefits of Technology

Twin-clutch/DSG transmissions is the ability to perform matched-rev downshifts. When a driver selects a lower gear, both types of transmission disengage the clutch(es) and rev the engine to the exact speed required by the selected gear. Not only does this make for a smoother downshift, but in the case of the twin-clutch transmission, it allows plenty of time for the proper gear to be pre-selected. Most (though not all) twin-clutch transmissions can skip gears when downshifting, i.e. shifting from 6th gear directly down to 3rd gear -- and because of their ability to match revs, they can do so without the lurching or surging typical of traditional automatic and manual transmissions.


Reference : http://cars.about.com/od/thingsyouneedtoknow/a/ag_howDSGworks.htm

See the Video in Youtube 
http://www.youtube.com/watch?v=WVWP7TYhP0c

Volkswagen Malaysia

The Volkswagen brand is no stranger to Malaysians. Generations of Malaysians have grown up with their own or someone else's Volkswagen Beetle occupying a place of affection in their hearts and life stories. Till today, this hallmark of the Volkswagen brand's lasting quality and distinct character continues to enjoy a faithful following even as newer models from Volkswagen have started to spark off their own groups of fans in the country.
It is for these people, and for the love of cars, that Volkswagen has established an official presence on Malaysian shores.Volkswagen Group Malaysia was officially launched in Malaysia on 16 February 2006, with the Corporate Headquarters situated in Wisma Volkswagen, Bangsar. From here, it will control marketing, sales and after sales to cater and fulfil the Malaysian customer's wishes for individual mobility in all situations of life.