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      06-05-2012, 12:55 PM   #1
southlight
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Exclamation Patent Reveals BMW 7 Speed Manual Transmission Design!

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Patent Reveals BMW 7 Speed Manual Transmission Design!
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Many of our members know that I love manual transmissions. Yes, DCT is faster and technically superior, but everytime BMW hints at a future with fewer manual offerings (due to low take rates), it makes me cringe.

For manual BMW fans, there may be hope yet! A knock against manual transmissions now is fuel consumption (compared to the latest autos). With 7, 8 or even 9 gears, automatic and automated transmissions have an efficiency advantage as the extra gears allow for more economical gear ratios (think of really long 7th and 8th gears to improve MPG figures). A manual transmission cannot match this as the spacing of the gears for the shifter become too close to each other. But, we've now discovered a patent filed by BMW last year which shows that the company is exploring a manual transmission with 7 or more gears which solves these issues. Porsche by the way, also recently released a 7 speed manual in the new 911 (991).

Here's what BMW's patent entails. BMW first describes a problem with adding more gears above the current six speeds: "an 8 speed manual transmission would need four shift gates for the 8 gears alone" - meaning that's more gears than a normal driver can safely or practically handle (think of the higher probability of a mechanical over-rev from having so many gears, for example). BMW's solution is: A manual gear shifter that only allows the driver to shift into proper gears.

How is this achieved? According to the design, the shift gates are surrounded by a magnetorheologic or electrorheologic fluid. Relying on various sensors, a computerized shifting module calculates which gears are proper and which gears are wrong to select, given the driving situation (e.g. system will not allow shifting to 5th gear at 10mph or -- way worse -- shifting to 1st gear at 100mph). To prevent an improper shift, a magnetic field or electric voltage is applied to change the viscosity of the fluid, which will physically block the engaging of certain gears. This process is illustrated in the first diagram below.

The patent mentions two specific ways of implementing this technology:

Traditional Manual Transmission (With Clutch Pedal)

The technology can be used on a traditional manual transmission with up to 8 gears. The driver rows his own gears as usual (and uses a clutch pedal), but the computerized shifting module described above allows the driver to shift into proper gears while blocking dangerous gears, thus avoiding mechanical over-revs (the "money shift") for a manual transmission with so many gears.

Shift by Wire (Without Clutch Pedal)

BMW also sees a potential second application for this technology in the form of shift by wire. Think of it as a manual transmission without a clutch pedal - a mix of the traditional manual gear shift lever with the automated SMG transmission. When a driver attempts to move the shifter into a gear, the system first calculates if it's a good idea to go into that gear. If it is not, the shift gate for that gear is blocked as described above. If however, the system deems the desired shift OK, the clutch is disengaged automatically, the desired gear engaged, and then (and only then) can the shifter be maneuvered into the particular shift gate by the driver. All this is performed in less than a second. Additionally, the engaged gear number will be illuminated on the shifter's shift pattern (diagram below).

Please keep in mind that patents can take years to see actual implementation, if ever. But, we're happy to have discovered that BMW still sees a potential future for the manual shifting experience, albeit possibly with more gears, better fuel efficiency, and maybe even sans clutch pedal. Bring it on, BMW!


BMW Patent Drawings


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