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Drive shaft

Drive shaft

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This article is about the mechanical device. For the fictional music group from the American television series 'Lost', see Charlie Pace.
Not to be confused with Axle.

Drive shaft with universal joints at each end and a spline in the center
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A drive shaft, driving shaft, propeller shaft, or Cardan shaft is a mechanical component for transmitting torque and rotation, usually used to connect other components of a drive train that cannot be connected directly because of distance or the need to allow for relative movement between them.
Drive shafts are carriers of torque: they are subject to torsion and shear stress, equivalent to the difference between the input torque and the load. They must therefore be strong enough to bear the stress, whilst avoiding too much additional weight as that would in turn increase their inertia.
Drive shafts frequently incorporate one or more universal joints or jaw couplings, and sometimes a splined joint or prismatic joint to allow for variations in the alignment and distance between the driving and driven components.

History

The term drive shaft first appeared during the mid 19th century. In Storer's 1861 patent reissue for a planing and matching machine, the term is used to refer to the belt-driven shaft by which the machine is driven.[1] The term is not used in his original patent.[2] Another early use of the term occurs in the 1861 patent reissue for the Watkins and Bryson horse-drawn mowing machine.[3] Here, the term refers to the shaft transmitting power from the machine's wheels to the gear train that works the cutting mechanism.
In the 1890s, the term began to be used in a manner closer to the modern sense. In 1891, for example, Battles referred to the shaft between the transmission and driving trucks of his Climax locomotive as the drive shaft,[4] and Stillman referred to the shaft linking the crankshaft to the rear axle of his shaft-driven bicycle as a drive shaft.[5] In 1899, Bukey used the term to describe the shaft transmitting power from the wheel to the driven machinery by a universal joint in his Horse-Power.[6] In the same year, Clark described his Marine Velocipede using the term to refer to the gear-driven shaft transmitting power through a universal joint to the propeller shaft.[7] Crompton used the term to refer to the shaft between the transmission of his steam-powered Motor Vehicle of 1903 and the driven axle.[8]

Automotive drive shafts

Vehicles

An automobile may use a longitudinal shaft to deliver power from an engine/transmission to the other end of the vehicle before it goes to the wheels. A pair of short drive shafts is commonly used to send power from a central differential, transmission, or transaxle to the wheels.

A truck double propeller shaft

Front-engine, rear-wheel drive

Main article: Front-engine, rear-wheel drive layout
In front-engined, rear-drive vehicles, a longer drive shaft is also required to send power the length of the vehicle. Two forms dominate: The torque tube with a single universal joint and the more common Hotchkiss drive with two or more joints. This system became known as Système Panhard after the automobile company Panhard et Levassor patented it.
Most of these vehicles have a clutch and gearbox (or transmission) mounted directly on the engine with a drive shaft leading to a final drive in the rear axle. When the vehicle is stationary, the drive shaft does not rotate. A few, mostly sports, cars seeking improved weight balance between front and rear, and most commonly Alfa Romeos or Porsche 924s, have instead used a rear-mounted transaxle. This places the clutch and transmission at the rear of the car and the drive shaft between them and the engine. In this case the drive shaft rotates continuously as long as the engine does, even when the car is stationary and out of gear.
Early automobiles often used chain drive or belt drive mechanisms rather than a drive shaft. Some used electrical generators and motors to transmit power to the wheels.

Front-wheel drive

In British English, the term "drive shaft" is restricted to a transverse shaft that transmits power to the wheels, especially the front wheels. A drive shaft connecting the gearbox to a rear differential is called a propeller shaft, or prop-shaft. A prop-shaft assembly consists of a propeller shaft, a slip joint and one or more universal joints. Where the engine and axles are separated from each other, as on four-wheel drive and rear-wheel drive vehicles, it is the propeller shaft that serves to transmit the drive force generated by the engine to the axles.
A drive shaft connecting a rear differential to a rear wheel may be called a half shaft. The name derives from the fact that two such shafts are required to form one rear axle.
Several different types of drive shaft are used in the automotive industry:
  • One-piece drive shaft
  • Two-piece drive shaft
  • Slip-in-tube drive shaft
The slip-in-tube drive shaft is a new type that also helps in crash energy management. It can be compressed in the event of a crash, so is also known as a collapsible drive shaft.

Four wheel and all-wheel drive

These evolved from the front-engine rear-wheel drive layout. A new form of transmission called the transfer case was placed between transmission and final drives in both axles. This split the drive to the two axles and may also have included reduction gears, a dog clutch or differential. At least two drive shafts were used, one from the transfer case to each axle. In some larger vehicles, the transfer box was centrally mounted and was itself driven by a short drive shaft. In vehicles the size of a Land Rover, the drive shaft to the front axle is noticeably shorter and more steeply articulated than the rear shaft, making it a more difficult engineering problem to build a reliable drive shaft, and which may involve a more sophisticated form of universal joint.
Modern light cars with all-wheel drive (notably Audi or the Fiat Panda) may use a system that more closely resembles a front-wheel drive layout. The transmission and final drive for the front axle are combined into one housing alongside the engine, and a single drive shaft runs the length of the car to the rear axle. This is a favoured design where the torque is biased to the front wheels to give car-like handling, or where the maker wishes to produce both four-wheel drive and front-wheel drive cars with many shared components.

Drive shaft for Research and Development (R&D)

The automotive industry also uses drive shafts at testing plants. At an engine test stand a drive shaft is used to transfer a certain speed / torque from the Internal combustion engine to a dynamometer. A "shaft guard" is used at a shaft connection to protect against contact with the drive shaft and for detection of a shaft failure. At a transmission test stand a drive shaft connects the prime mover with the transmission.

Motorcycle drive shafts


A 1913 FN (Fabrique Nationale), Belgium, 4cylinders and shaft drive

A 1923 BMW R32, with a shaft-drive, boxer twin engine
Drive shafts have been used on motorcycles almost as long as there have been motorcycles. As an alternative to chain and belt drives, drive shafts offer relatively maintenance-free operation and long life. A disadvantage of shaft drive on a motorcycle is that gearing or a Hobson's joint or similar is needed to turn the power 90° from the shaft to the rear wheel, losing some power in the process. On the other hand, it is easier to protect the shaft linkages and drive gears from dust, sand and mud.
The best known motorcycle manufacturer to use shaft drive for a long time—since 1923—is BMW. Among contemporary manufacturers, Moto Guzzi is also well-known for its shaft drive motorcycles. The British company, Triumph and all four Japanese brands, Honda, Suzuki, Kawasaki and Yamaha, have produced shaft drive motorcycles. All geared models of the Vespa scooter produced to date have been shaft-driven. The automatic models, however, use a belt.
Motorcycle engines positioned such that the crankshaft is longitudinal and parallel to the frame are often used for shaft driven motorcycles. This requires only one 90° turn in power transmission, rather than two. Bikes from Moto Guzzi and BMW, plus the Triumph Rocket III and Honda ST series all use this engine layout.
Motorcycles with shaft drive are subject to shaft effect where the chassis climbs when power is applied. This is counteracted with systems such as BMW's Paralever, Moto Guzzi's CARC and Kawasaki's Tetra Lever.

Marine drive shafts

On a power-driven ship, the drive shaft, or propeller shaft, usually connects the transmission inside the vessel directly to the propeller, passing through a stuffing box or other seal at the point it exits the hull. There is also a thrust block, a bearing to resist the axial force of the propeller. As the rotating propeller pushes the vessel forward, any length of drive shaft between propeller and thrust block is subject to compression, and when going astern to tension. Except for the very smallest of boats, this force isn't taken on the gearbox or engine directly.
Cardan shafts are also often used in marine applications between the transmission and either a propeller gearbox or waterjet.

Locomotive drive shafts


The rear drive shaft, crankshaft and front drive shaft of a Shay locomotive.
The Shay, Climax and Heisler locomotives, all introduced in the late 19th century, used quill drives to couple power from a centrally mounted multi-cylinder engine to each of the trucks supporting the engine. On each of these geared steam locomotives, one end of each drive shaft was coupled to the driven truck through a universal joint while the other end was powered by the crankshaft, transmission or another truck through a second universal joint. A quill drive also has the ability to slide lengthways, effectively varying its length. This is required to allow the bogies to rotate when passing a curve.
Cardan shafts are used in some diesel locomotives (mainly diesel-hydraulics, such as British Rail Class 52) and some electric locomotives (e.g. British Rail Class 91). They are also widely used in diesel multiple units.

Drive shafts in Bicycles


A shaft-driven bicycle.
The drive shaft has served as an alternative to a chain-drive in bicycles for the past century, although never becoming very popular. A shaft-driven bicycle is described as an "Acatane", from one of their early makers. When used on a bicycle, a drive shaft has several advantages and disadvantages:

Advantages

  • Drive system is less likely to become jammed or broken, a common problem with chain-driven bicycles
  • The use of a gear system creates a smoother and more consistent pedaling motion
  • The rider cannot become dirtied from chain grease or injured by the chain from "Chain bite", which occurs when clothing or even a body part catches between the chain and a sprocket
  • Lower maintenance than a chain system when the drive shaft is enclosed in a tube, the common convention
  • More consistent performance. Dynamic Bicycles claims that a drive shaft bicycle consistently delivers 94% efficiency, whereas a chain-driven bike can deliver anywhere from 75-97% efficiency based on condition.
  • Greater clearance: with the absence of a derailleur or other low-hanging machinery, the bicycle has nearly twice the ground clearance
  • For bicycle rental companies, a drive-shaft bicycle is less prone to be stolen, since the shaft is non-standard, and both noticeable and non-maintainable. This type of bicycle is in use in several major cities of Europe, where there have been large municipal funded, public (and automatic) bicycle rental projects.[citation needed]

Disadvantages

  • A drive shaft system weighs more than a chain system, usually 1-2 pounds heavier
  • At optimum upkeep, a chain delivers greater efficiency
  • Many of the advantages claimed by drive shaft's proponents can be achieved on a chain-driven bicycle, such as covering the chain and gears with a metal or plastic cover
  • Use of lightweight derailleur gears with a high number of ratios is impossible, although hub gears can be used
  • Wheel removal can be complicated in some designs (as it is for some chain-driven bicycles with hub gears).

References

  1. ^ Henry D. Stover, Improvement in Wood-Planing Machines, U.S. Patent Reissue 1,190, May 21, 1861.
  2. ^ Henry D. Stover, Planing Machine, U.S. Patent 30,993, Dec. 18, 1860, 1861.
  3. ^ John DeLancy Watkins and Robert Bryson, Mowing Machines, U.S. Patent Reissue 1,904, July 23, 1861.
  4. ^ Rush S. Battles, Locomotive, U.S. Patent 455,154, June 30, 1891.
  5. ^ Walter Stillman, Bicycle, U.S. Patent 456,387, July 21, 1891.
  6. ^ Dudley D. Bukey, Horse-Power, U.S. Patent 631,198, Aug. 15, 1899.
  7. ^ Charles Clark, Marine Velocipede, [U.S. Patent 637,547], Nov. 21, 1899.
  8. ^ Charles Crompton, Motor-Vehicle U.S. Patent 718,097, Jan. 1903.

See also

Retrieved from "http://en.wikipedia.org/wiki/Drive_shaft"
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Direct-Shift Gearbox

Direct-Shift Gearbox

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Transmission types
Manual
Automatic
Semi-automatic
Continuously variable
Bicycle gearing
 v • d • e 
Part-cutaway view of the Volkswagen Group 6-speed Direct-Shift Gearbox. The concentric multi-plate clutches have been sectioned, along with the mechatronics module. This also shows the additional power take-off for distributing torque to the rear axle for four-wheel drive applications. - View this image with annotations
Schematic diagram of a dual clutch transmission
Dual-clutch gearbox:
M: Motor
A: Primary drive
B: Double Clutch
C: shaft
D: main shaft speeds equal
E: main shaft speeds disparities
F: Output
The Direct-Shift Gearbox (German: Direkt-Schalt-Getriebe[1]), commonly abbreviated to DSG,[2][3] is an electronically controlled dual clutch[2] multiple-shaft manual gearbox, in a transaxle design - without a conventional clutch pedal,[4] and with full automatic,[2] or semi-manual control. The first actual Dual Clutch transmissions arrived from Porsche in-house development for 962 racing cars in the 80's.
In simple terms, it is two separate manual gearboxes (and clutches), contained within one housing, and working as one unit.[2][3][5] It was designed by BorgWarner,[4] 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), with support by IAV GmbH.[citation needed] By using two independent clutches,[2][5] a DSG can achieve faster shift times,[2][5] and eliminates the torque converter of a conventional epicyclic automatic transmission.[2]

Overview

Transverse DSG

At the time of launch in 2003[2][6] - it became the world's first dual clutch transmission in a series production car,[2][6] in the German-market Volkswagen Golf Mk4 R32[2][6] and shortly afterwards, worldwide in the original Audi TT 3.2;[7] and for the first few years of production, this original DSG transmission was only available in transversely-orientated[2] 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),[6][7] and used wet/submerged multi-plate clutch packs[2][4] (Volkswagen Group internal code: DQ250, parts code prefix: 02E).[7][8] It has been paired to engines with up to 350 N·m (260 lb·ft) of torque,[6][7] and the two-wheel drive version weighs 93 kg (210 lb). It is manufactured at Volkswagen Groups Kassel plant,[2] with a daily production output of 1,500 units.[6]
At the start of 2008, another world first,[6] an additional 70 kg (150 lb) seven-speed DSG transaxle[6] (Volkswagen Group internal code: DQ200, parts code prefix: 0AM)[8][9][10] became available. It differs from the six-speed DSG, in that uses two single-plate dry clutches (of similar diameter).[10] This clutch pack was designed by LuK Clutch Systems, LLC.[11] This seven-speed DSG is used in smaller front-wheel drive cars with smaller displacement engines with lower torque outputs,[6][7][10] such as the latest Volkswagen Golf,[6][10] Volkswagen Polo Mk5,[10] and the new SEAT Ibiza,[7] due to it having a maximum torque handling capacity of 250 N·m (180 lb·ft).[6] It uses considerably less oil than the six-speed DQ250; this new DQ200 uses just 1.7 litres (0.37 imp gal; 0.45 US gal) of transmission fluid.[6]

Audi longitudinal DSG

In late 2008, an all-new seven speed longitudinal[7][12] S tronic[12] version of the DSG transaxle went into series production (Volkswagen Group internal code: DL501, parts code prefix: 0B5),[8] lead by Audi transmission design engineer Mario Schenker.[12] Initially, from early 2009, it is only used in certain Audi cars, and only with longitudinally-mounted engines. Like the original six-speed DSG, it features a concentric dual wet multi-plate clutch.[12] However, this particular variant uses notably more plates — the larger outer clutch (for the odd-numbered gears) uses 10 plates, whereas the smaller inner clutch (driving even-numbered gears and reverse) uses 12 plates.[12] Another notable change over the original transverse DSGs is the lubrication system[13] — Audi now utilise two totally separate oil circuits.[12] One oil circuit, consisting of 7.5 litres (1.65 imp gal; 1.98 US gal), lubricates the hydraulic clutches and mechatronics with fully synthetic specialist automatic transmission fluid (ATF),[12] whilst the other oil circuit lubricates the gear trains and front and centre differentials with 4.3 litres (0.95 imp gal; 1.14 US gal) of conventional hypoid gear oil.[12] This dual circuit lubrication is aimed at increasing overall reliability, due to eliminating cross-contamination of debris and wear particles.[12] It has a torque handling limit of up to 600 N·m (440 lb·ft),[7] and engine power outputs of up to 330 kW (450 PS; 440 bhp).[7] It has a total mass, including all lubricants and the dual-mass flywheel of 141.5 kg (312 lb).[7]
This was initially available in their quattro four-wheel drive variants,[8] and is very similar to the new ZF Friedrichshafen-supplied[14] Porsche Doppel-Kupplung (PDK).[15][16]

Operational introduction

The internal combustion engine drives two clutch packs.[2][4][5] The outer clutch pack drives gears 1, 3, 5[2][4] (and 7 when fitted), and reverse[2] — 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.[2][4] 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.[5] Because the alternate clutch pack's gear-sets can be pre-selected[2][4][5] (predictive shifts enabled via the 'unused' section of the gearbox), un-powered time while shifting is avoided[2][5] because the transmission of torque is simply switched from one clutch-pack to the other.[2] This means that the DSG takes only about 8 milliseconds to upshift.[3][4] In comparison, the sequential manual transmission (SMT) in the Ferrari F430 Scuderia takes 60 milliseconds to shift,[17] or 150 milliseconds in the Ferrari Enzo.[3] The quoted time for upshifts is the time the wheels are completely non-powered.

DSG controls

The Direct-Shift Gearbox utilises a floor-mounted transmission shift lever, very similar to that of a conventional automatic transmission.[10] The lever is operated in a straight 'fore and aft' plane (without any 'dog-leg' offset movements), and utilises an additional button to help prevent an inadvertent selection of an inappropriate shift lever position.

"P"

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.

"N"

N position of the floor-mounted shift lever means that the transmission is in "neutral". Similar to P above, both clutch packs and all gear-sets are fully disengaged, however the parking lock is disengaged. This position should be used when the motor vehicle is stationary for a period of time, such as at red traffic lights, or waiting in a queue of stationary traffic.[18] The DSG should not be held in any of the active gear modes while stationary using the footbrake for other than brief periods — due to the clutches being held on the bite point, as this can overheat the clutches and transmission fluid. This position also allows the engine to be restarted (in some cars needing the key to be partially disengaged) which cannot be done in any of the active modes.[18]

"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 first gear is selected on the first shaft,[3] and the outer clutch engages at the start of the 'bite point'. At the same time, on the alternate gear shaft, the second gear is also selected[2][3] (pre-selected), but the clutch pack for second gear remains fully disengaged. When the driver releases the foot brake pedal, the outer clutch pack increases the clamping force, allowing the first 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. 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),[4] the DSG then upshifts. During this sequence, the DSG disengages the first outer clutch whilst simultaneously engaging the second inner clutch[2][3][4] (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),[3][4] and can happen even with full throttle opening, and as a result, there is virtually no power loss.[2][4]
Once the vehicle has completed the shift to second gear, the first gear is immediately de-selected, and third gear (being on the same shaft as 1st and 5th) is pre-selected,[2][3][4] and is pending. Once the time comes to shift into 3rd, the second clutch disengages and the first clutch re-engages.[2] This method of operation continues in the same manner up to 6th (or top) gear.
Downshifting is similar to upshifting but in reverse order, and is slower, at 600 milliseconds, due to the engine ECU needing to 'blip' the throttle, so that the engine crankshaft speed can match the appropriate gear shaft speed.[2][4] The car's computer senses the car slowing down, or more power required (during acceleration), and thus engages a lower gear on the shaft not in use, and then completes the downshift.
The actual shift points are determined by the DSG's transmission Electronic Control Unit, or ECU, which commands a hydro-mechanical unit.[2] The transmission ECU, combined with the hydro-mechanical unit, are collectively called a "mechatronics"[2] unit or module. Because the DSGs ECU uses "fuzzy logic", the operation of the DSG is said to be "adaptive"; that is, the DSG will "learn" how the user drives the car, and will progressively tailor the shift points accordingly to suit the habits of the driver.
In the vehicle instrument display, between the speedometer and tachometer, the available shift-lever positions are shown, the current position of the shift-lever is highlighted (emboldend), and the current gear ratio in use is also displayed as a number.
Under "normal", progressive and linear acceleration and deceleration, the DSG shifts in a "sequential" manner, i.e. under acceleration: 1st > 2nd > 3rd > 4th > 5th > 6th; and the same sequence reversed for deceleration. However, the DSG can also skip the normal sequential method, by 'missing out' adjacent gears, and shift two or more gears.[3] This is most apparent if the car is being driven at sedate speeds in one of the higher gears with a light throttle opening, and the accelerator pedal is then pressed fully to the floor against a further additional 'resistance'; this activates the "kick-down" function. During kick-down, the DSG can skip gears,[10] going from 6th gear straight down to 2nd gear (conditions permitting).
When the floor-mounted gear selector lever is in position D, the DSG works in fully automatic mode,[3][5] with emphasis placed on gear shifts programmed to deliver maximum fuel economy.[3][10] That means that shifts will change up and down very early in the rev-range. As an example, on the Volkswagen Golf Mk5 GTI, sixth gear will be engaged around 52 km/h (32 mph), when initially using the DSG transmission with the 'default' ECU adaptation - although with an "aggressive" or "sporty" driving style, the adaptive shift pattern will increase the vehicle speed at which 6th gear engages.

"S" mode

The floor selector lever also has an S position.[2] When S is selected, "sport" mode[2] is activated in the DSG. Sport mode still functions as a fully-automatic mode,[3] identical in operation to "D" mode, but upshifts and downshifts are made much higher up the engine rev-range.[2][3][10] This aids a more sporty driving manner,[2] 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. On the six-speed unit in the 2010 Volkswagen GTI, "S" mode will not automatically shift to 6th gear... maxing out at 5th to keep power available at high RPM while cruising.
S is highlighted in the instrument display, and like D mode, the currently used gear ratio is also displayed as a number.

"R"

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[3][5] 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.
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. 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".[2] 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.[3]
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[2] — steering wheel-mounted paddle shifters[3][5] 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.[10]
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,[10] and gain instant manual control of the DSG transmission[10] (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[10] for at least two seconds.

Advantages and disadvantages

Advantages
  • Better fuel economy[2][6] (up to 15% improvement) than conventional planetary geared automatic transmission (due to lower parasitic losses from oil churning)[5] and for some models with manual transmissions;[2]
  • No loss of torque transmission from the engine to the driving wheels during gear shifts;[2][4][5]
  • Extremely fast up-shift time of 8 milliseconds when shifting to a gear the alternate gear shaft has preselected;[3][4]
  • Very smooth gear-shift operations;[4][5]
  • Consistent shift time of 600 milliseconds, regardless of throttle or operational mode;[4]
Disadvantages
  • Marginally worse overall mechanical efficiency compared to a conventional manual transmission, especially on wet-clutch variants (due to electronics and hydraulic systems);[5]
  • Expensive specialist transmission fluids/lubricants with dedicated additives are required, which need changing on a regular basis;[13]
  • Relatively lengthy shift time when shifting to a gear ratio which the transmission ECU did not anticipate (around 1100 ms, depending on the situation);[4][19]
  • Heavier than a comparable Getrag conventional manual transmission (75 kg (170 lb) vs. 47.5 kg (105 lb));

Applications

For applications of similar transmissions in other vehicles beyond Volkswagen Groups DSG and S tronic, see dual clutch transmission.
Volkswagen Group vehicles with the DSG gearbox include:[8]

Audi

After originally using the 'DSG' moniker, Audi subsequently renamed the Direct-Shift Gearbox to "S tronic".

Bugatti

SEAT

Škoda

Volkswagen Passenger Cars

Volkswagen Commercial Vehicles

Recall of DSG-equipped vehicles

In August 2009, Volkswagen of America issued two recalls of DSG-equipped vehicles. The first involved 13,500 vehicles,[22] and was to address rare unplanned shifts to the neutral gear,[22] while the second involved similar problems (by then attributed to faulty temperature sensors) and applied to 53,300 vehicles.[22][23][24] These recalls arose as a result of investigations carried out by the US National Highway Traffic Safety Administration (NHTSA),[25] where owners reported to the NHTSA a loss of power whilst driving.[22] This investigation preliminary found only 2008 and 2009 model year vehicles as being affected.[22][25]

See also

References

  1. ^ Volkswagen Service Training Manual 308 - 02E 6-speed DSG 
  2. ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al Volkswagen Group / Volkswagen AG (22 November 2002). "Volkswagen DSG - World's first dual-clutch gearbox in a production car". Press release. https://www.volkswagen-media-services.com/medias_publish/ms/content/en/pressemitteilungen/2002/11/22/volkswagen_dsg_-_world.standard.gid-oeffentlichkeit.html. Retrieved 30 October 2009. 
  3. ^ a b c d e f g h i j k l m n o p q r "Twin Clutch / Direct Shift Gearbox (DSG) - What it is, how it works". Cars.About.com. http://cars.about.com/od/thingsyouneedtoknow/a/ag_howDSGworks.htm. Retrieved 27 October 2009. 
  4. ^ a b c d e f g h i j k l m n o p q r s Mark Wan. Gearbox "Transmission - Twin-Clutch Gearbox". AutoZine.org. AutoZine Technical School. http://www.autozine.org/technical_school/gearbox/tech_gear_manual.htm#Twin-Clutch Gearbox. Retrieved 27 October 2009. 
  5. ^ a b c d e f g h i j k l m n "How the Dual Clutch Transmission Works". DCTfacts.com. The Lubrizol Corporation. 2009. http://www.dctfacts.com/widc_pg3a.asp. Retrieved 27 October 2009. 
  6. ^ a b c d e f g h i j k l m n o p "The 7-speed DSG - the intelligent automatic gearbox from Volkswagen". VolkswagenAG.com. Volkswagen Group / Volkswagen AG. 21 January 2008. http://www.volkswagenag.com/vwag/vwcorp/info_center/en/themes/2008/01/the_7speed_dsg.html. Retrieved 3 November 2009. 
  7. ^ a b c d e f g h i j k l m "Volkswagen Group extends reach of dual clutch transmissions". DCTfacts.com. The Lubrizol Corporation. 8 May 2009. http://www.dctfacts.com/hmStory6a.asp. Retrieved 27 October 2009. 
  8. ^ a b c d e ETKA[clarification needed]
  9. ^ Volkswagen Service Training Manual 390 - 0AM 7-speed DSG 
  10. ^ a b c d e f g h i j k l m "Golf Plus on the Road". DCTfacts.com. The Lubrizol Corporation. 2009. http://www.dctfacts.com/otr_pg1.asp. Retrieved 28 October 2009. 
  11. ^ "LuK Dual Dry Clutch 7-Speed DSG Gearbox in volume production at Volkswagen". LuKclutch.com. Schaeffler Group USA Inc., BÜHL, GERMANY. 13 February 2008. http://www.lukclutch.com/content.schaeffler_as.us/us/press/press-releases/press-details.jsp?id=2877676. Retrieved 27 October 2009. 
  12. ^ a b c d e f g h i j k l "Inside Audi’s premium DCT". DCTfacts.com. The Lubrizol Corporation. 8 May 2009. http://www.dctfacts.com/indusIn_pg3.asp. Retrieved 27 October 2009. 
  13. ^ a b "Special Transmissions Need Special Lubricants". DCTfacts.com. The Lubrizol Corporation. 2009. http://www.dctfacts.com/hmStory2a.asp. Retrieved 28 October 2009. 
  14. ^ "ZF 7-speed dual clutch transmission". ZF.com. ZF Friedrichshafen AG. http://www.zf.com/corporate/en/products/innovations/7_speed_dualclutch/7_speed_dualclutch.html. Retrieved 28 October 2009. 
  15. ^ "Top 911 moves to industry-standard shift controls". DCTfacts.com. The Lubrizol Corporation. 24 September 2009. http://www.dctfacts.com/lnws_pg12a.asp. Retrieved 27 October 2009. 
  16. ^ "Porsche Joins the DCT Set". DCTfacts.com. The Lubrizol Corporation. http://www.dctfacts.com/hmStory3.asp. Retrieved 28 October 2009. 
  17. ^ Mark Wan (17 October 2007). "Ferrari F430 Scuderia". AutoZine.org. http://www.autozine.org/html/Ferrari/F430.html#Scuderia. Retrieved 27 October 2009. 
  18. ^ a b "Mitsubishi Evo X - Precautions". DCTfacts.com. The Lubrizol Corporation. 9 March 2009. http://www.dctfacts.com/otr_pg2.asp#Precautions. Retrieved 28 October 2009. "engage neutral while waiting at lights or in a traffic queue, rather than holding the car on the footbrake – a practice which could lead to overheating" 
  19. ^ "How Dual-Clutch Transmissions Work". AutoEvolution.com. SoftNews NET. 31 March 2009. http://www.autoevolution.com/news/how-dual-clutch-transmissions-work-5458.html. Retrieved 30 October 2009. 
  20. ^ "Ricardo Extends DCT Production for Open-top Bugatti". DCTfacts.com. The Lubrizol Corporation. 16 January 2009. http://www.dctfacts.com/hmStory2b.asp. Retrieved 28 October 2009. 
  21. ^ "Volkswagen (Commercial Vehicles) medium van is first with DCT". DCTfacts.com. The Lubrizol Corporation. 24 September 2009. http://www.dctfacts.com/dcmarket_pg4.asp. Retrieved 27 October 2009. 
  22. ^ a b c d e Jensen, Christopher (21 August 2009). "VW DSG Transmission Problem Leads to Recall". wheels.blogs.nytimes.com (The New York Times Company). http://wheels.blogs.nytimes.com/2009/08/21/vw-dsg-transmission-problem-leads-to-recall/. Retrieved 30 November 2009. 
  23. ^ Chang, Richard S. (28 August 2009). "VW Has More Problems With Its DSG Transmission". wheels.blogs.nytimes.com (The New York Times Company). http://wheels.blogs.nytimes.com/2009/08/28/vw-has-more-problems-with-its-dsg-transmission/. Retrieved 30 November 2009. 
  24. ^ "Volkswagen will repair DSG transmissions on 53,300 vehicles". Blog.CarAndDriver.com. Hachette Filipacchi Media U.S., Inc.,. 28 August 2009. http://blog.caranddriver.com/volkswagen-will-repair-dsg-transmissions-on-53300-vehicles/. Retrieved 27 October 2009. 
  25. ^ a b ODI Resume - Volkswagen of America, Inc., 2008-2009 Volkswagen EOS, GTI, Jetta and R32 with DSG transmissionPDF, NHTSA, Retrieved 30 November 2009. The direct shift gearbox can malfunction at any speed and cause the vehicle to loose motive power suddenly and without warning

External links

Official links

Independent links

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