there is a older related article posted on AudiZine here:
- Details of the Clutch Release Systems of Audi (Manual Gearboxes)
Click here:
http://www.audizine.com/forum/showth...ystems-of-Audi
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This is the new 7 Speed S-Tronic Double clutch gearbox found in the A4 B8 and Q5 series. It is also found in the S5 Cabriolet/S4.
The information presented here is for the high torque DL501 model. The gearbox code for this box in Audi is called "OB5". The general principals of operation and many other details are covered
Enjoy the contents and hopefully gives drivers a better understanding on how this S-tronic gearbox actually works.
Seven-speed dual-clutch gearbox 0B5/S tronic
Following the great success of the six-speed S tronic on the Audi A3 and Audi TT models, a seven-speed dual-clutch gearbox, combined with the quattro powertrain, is now used for the first time, in a longitudinal configuration, on the Audi Q5/A4/A5.
In combining the plus-points of the automatic gearbox (ride comfort and gear shifting without any interruption in tractive power) and the manual gearbox (sportiness and efficiency) in combination with extremely short shift times and "direct power transmission", the dual-clutch gearbox 0B5 provides a special driving experience.
Specifications of Gearbox
**The 7th gear is configured as an overdrive (6 + E). Top speed is in 6th gear. At present, the petrol engines have a ratio spread of approx. 6 : 1 and the diesel engines approx. 8 : 1.
Exterior View of the Gearbox
Partial Cut Away View of the Gearbox
**The 7th gear is configured as an overdrive (6 + E). Top speed is in 6th gear. At present, the petrol engines have a ratio spread of approx. 6 : 1 and the diesel engines approx. 8 : 1.
Exterior View of the Gearbox
Partial Cut Away View of the Gearbox
The advantages of having seven gear ratios
Seven gear ratios enable a wide ratio spread to be realised, resulting in highly dynamic starting performance and allowing 7th gear to be used as an overdrive (E-gear). Low fuel consumption figures are thus achievable.
In addition to the many other innovative detail solutions, which have been incorporated into the 0B5 gearbox, the seven gear ratios are a key factor enabling the Audi vehicle to combine sportiness and efficiency.
Sectional view of gearbox – overview of the component parts
Gearbox mechanism design – function
Drive is transmitted to the dual-mass flywheel through the transmission plate. From here, torque is transmitted to the electro-hydraulically controlled dual clutch, which selectively operates the even or odd numbered gears.
The gearbox is thus subdivided into two sub-gearboxes.
Sub-gearbox 1
The odd numbered gears (1, 3, 5, 7) can be driven
through the central input shaft 1 by clutch K1.
Sub-gearbox 2
The even numbered gears (2, 4, 6) and the reverse gear can be driven through input shaft 2 (a hollow shaft) by clutch K2.
Power is output through the common output shaft, from where the torque is transmitted directly to the centre differential. Torque is distributed approx. 60 % to the flange shaft connecting to the rear axle and approx. 40 % to the spur pinion and through the side shaft connecting to the front axle drive.
Design features of the dual clutch
The dual clutch serves two tasks:
– To engage the engine at driveaway and to disengage the engine when stopping
– To shift the gears (= changeover to sub-gearbox)
The dual clutch was designed in such a way that clutch K1 is located on the outside, and therefore has the larger diameter. This meets the higher demands placed on K1 as the starting clutch (in first gear).
Small pressure cylinders and coil spring assemblies on both clutches provide good controllability at driveaway and when changing gear. Hydraulic pressure equalisation is no longer required. The clutch control corrects the dynamic pressure build-up caused by centrifugal forces at high engine speeds. A pressure characteristic allows the dynamic pressure build-up to be compensated for in any situation.
Gearshift sequence
Driveaway:
In selector lever position P or N, only 1st gear and reverse are engaged. This allows immediate driveaway from a standing stop. Depending on whether the driver decides to drive in reverse or forwards, the correct gears are already preselected.
Shifting:
To drive forwards, the driver shifts the selector lever into D and drives away in 1st gear. When a defined speed threshold of approx. 15 kph is exceeded, 2nd gear is engaged in sub-gearbox 2 (reverse was previously engaged).
When the shift point for upshifting from 1st to 2nd gear is reached, the gearshift is made by lightningfast opening of clutch K1 and simultaneous rapid closing of clutch K2 without any interruption in tractive power. To enhance shift comfort and preserve the clutch, engine torque is reduced during the gearshift (overlap).
The gear shifting process is completed within a few hundredths of a second. 3rd gear is now preselected in sub-gearbox 1. The process described
above repeats itself alternately during the subsequent gearshifts from 2-3 up to 6-7.
Synchromesh
To achieve extremely short shift times, all synchromesh gearboxes have carbon-coated synchroniser rings.
Gears one to three and reverse are also configured as triple-cone synchronisers, due to the high stresses to which the y are subjected.
Gears four to seven use single-cone synchronisers.
Gearbox oil system
ATF oil system
The 0B5 gearbox has two separate oil systems. The first oil system accommodates the dual clutch, the mechatronic syste m and the oil supply.
These components use an ATF developed specially for the B5 gearbox.
This ATF provides rapid response of the shift and clutch control mechanisms even at low temperatures, and serves to lubricate and cool the dual clutch.
A basic requirement for the ATF is that it allows the dual clutch to be controlled in a precise fashion.
Gear oil system
The second oil system incorporates the manual gearbox, the transfer case (centre differential) and the front axle drive.
Lubrication is by means of a hypoid gear oil with a special oil additive for the centre differential. By separating these oil chambers, it has been
possible to design the individual component parts of the gearbox optimally. Thus, it was not necessary to make any compromises due to conflicting demands on the lubricant.
** compare this to the transverse mount 6 speed where a single ATF was used to lubricate the clutches and the gears.
Sealing the oil systems
The oil chambers must be reliably sealed off from one another at the transitions between the two oil systems. For instance, the ingress of gear oil into the ATF oil chamber (the ATF mixes with the gear oil) would adversely affect the performance of the dual clutch. To prevent this from occurring, special sealing elements are fitted in the relevant places.
Input shafts 1 and 2 are sealed by a double oil seal ring (in total, four radial sealing rings are used). If a radial seal is leaking, the oil drain port allows the leaking oil to drain off and prevents it from entering the other oil chamber. The transverse bore in input shaft 2 establishes a connection between input shaft 1 and the oil drain port.
ATF supply – lubrication
A sufficient supply of ATF is essential for the operation of the gearbox. An external gear pump driven by the dual clutch through a gear step provides the necessary oil flow and oil pressure.
The ATF pump supplies the mechatronic system with the oil pressure it requires to perform the following functions:
– Control of the multi-plate clutch (engagement and disengagement)
– Cooling and lubrication of the multi-plate clutch
– Control of the gearbox hydraulics
Gearbox control - Mechatronics
The gearbox is controlled by a recently developed mechatronic system. Its control concept allows precision control of gear engagement speed and force when changing gear. Thus, depending on the driving situation, it is possible to achieve rapid gearshifting without compromising on comfort, e.g. while coasting.
The mechatronic system acts as the central gearbox control unit. It combines the electro-hydraulic control unit (actuators), the electronic control unit and some of the sensors into a single unit. On account of the longitudinal configuration, the rpm sensors of both gearbox input shafts and the gear sensor are located on a separate mounting bracket.
The mechatronic system controls, regulates and performs the following functions:
– Adaptation of oil pressure in the hydraulic system to requirements
– Dual clutch regulation
– Clutch cooling regulation
– Shift point selection
– Gearbox control and regulation
– Communication with other control units
– Limp-home programs
– Self-diagnostics
Gearbox protection functions
Control unit temperature monitoring
High temperatures have a negative impact on the useful life and performance of electronic components. Due to the integration of the gearbox control unit into the gearbox (lubricated by ATF), it is very important to monitor the temperature of the electronics and, accordingly, the ATF.
When the temperature reaches approx. 135 °C ( measured by one of the two temperature sensors in the gearbox control unit), the gearbox electronics must be protected against a further rise in temperature.
When this threshold value is exceeded, the gearbox control unit initiates a reduction in engine torque in order to reduce heat input. Up to a temperature of approx. 145 °C, engine torque can be reduced gradually until the engine is at idle.
When the engine is at idle, the clutches are open and there is no power transmission from the engine to the drive wheels.
When the protective function is activated, an entry is made in the fault memory and the following text message is displayed in the dash panel insert: "You can continue driving to a limited extent".
Clutch protection
If the clutch cooling oil temperature exceeds a value of approx. 160 °C , the clutch is within a critical temperature range which can damage it. These temperatures occur, for example, when driving away on extreme gradients (possibly when towing a trailer) or when the vehicle is held stationary on an uphill slope using the accelerator and the clutch (without using the brake).
As a safety precaution, en gine torque is reduced when the cooling oil temperature exceeds 160 °C. If the cooling oil temperature continues to rise, engine torque is gradually reduced; this can be to the extent that the engine is only idling. When the engine is at idle, the clutches are open and there is no power transmission from the engine to the drive wheels.
When the protective function is initiated, an entry is made in the fault memory and the following text message is displayed in the dash panel insert: "You can continue driving to a limited extent".
As an additional safety precaution, the clutch temperature is determined using a computer model.
If the computed temperature exceeds a pre-defined value, the above-mentioned precautions are taken.
All you need to know about the …
… gearbox control unit
In the B8 series, a new data and diagnostic log is used for the engine control units, the gearbox control units and the airbag control unit.
The previous data blocks and numberings are no longer used. In return, individual measured data is now available and listed as full text in alphabetical order. The required measured data can then be specifically
selected.
… Clearing the fault memory
The fault memories of the engine and gearbox control unit are always cleared jointly. If the fault memory of the gearbox control unit is cleared, then the fault memory in the engine control unit will automatically be cleared as well. The converse also applies if the event memory in the engine control unit is cleared.
… towing
If a vehicle with S tronic needs towing, the conventional restrictions on automatic gearboxes apply:
– Selector lever in position "N"
– A max. towing speed of 50 kph must not be exceeded.
– A max. towing dis tance of 50 km must not be exceeded.
Explanation:
When the engine is at standstill, the oil pump is not driven and certain parts of the gearbox are no longer lubricated. Exceeding a speed of 50 kph results in unacceptably high rotational speeds within the gearbox and dual clutch, because one gear is always engaged in both sub-gearboxes.
If the towing conditions are not observed, serious gearbox damage can occur.
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Originally Posted by NWS4Guy
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