Cost, Effectiveness, and Deployment of Fuel Economy Technologies for Light-Duty Vehicles (2015) / Chapter Skim
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5 Transmissions
5 Transmissions
Pages 167-206
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From page 167... ...
Automatic transtribute is not realized because the parasitic losses can exceed missions include conventional planetary automatic transmisthose of a conventional automatic transmission. sions and DCTs.
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From page 168... ...
168 COST, EFFECTIVENESS, AND DEPLOYMENT OF FUEL ECONOMY TECHNOLOGIES FOR LIGHT-DUTY VEHICLES FIGURE 5.1 Wheel force, which is proportional to wheel torque, versus vehicle speed, which illustrates multiplication of engine torque and reduction in engine speed provided by a six-speed transmission. CAFEII 5.1.eps line determines maximum vehicle speed.
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From page 169... ...
This provides four Conventional automatic transmissions generally use forward gears plus neutral and reverse. planetary gear sets to transfer power and multiply engine • Lapelletier gear set connects a simple planetary gear torque to the drive axle.
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From page 170... ...
A typical six-speed planetary transmission is shown in Figure 5.5 and includes the torque converter, Ten-Speed Automatic Transmissions the planetary gear set, clutches, the gerotor oil pump, and the Ford Motor Company and General Motors announced in valve body. A transmission control unit (TCU)
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From page 171... ...
The As an additional benefit, torque multiplication of the torque CVT also benefits from the lack of discrete shift events of converter will improve acceleration from idle. conventional automatic transmissions, preventing customer Another method OEMs are using to increase the market issues with possible shift harshness.
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From page 172... ...
matic transmissions require. These factors contribute to a manual transmission's ability to transfer torque with only about 4 percent energy loss of the engine's gross output, compared to 13 percent loss for conventional automatic transmissions.
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From page 173... ...
Figure 5.10, which is a plot of vibration dose value (VDV) , a common metric used to measure shift comfort, shows that AMTs are significantly worse than conventional automatic transmissions and dual clutch transmissions.
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From page 174... ...
. FIGURE 5.12 Fuel consumption benefits of an eight-speed compared to a six-speed automatic transmission, shown as an overlay on a BSFC island map.
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From page 175... ...
Similar results have been reported from other modeling As automatic transmissions and dual clutch transmissions studies. As the engine efficiency map improves, the penalty trend toward higher numbers of ratios and ratio spreads, of having a larger ratio step between gears is significantly diminishing benefits for fuel consumption reduction are reduced compared to the example shown in Figure 5.12 for anticipated.
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From page 176... ...
Conventional automatic transmissions are not expected to require the large ratio spreads of DCTs to achieve acceptable launch feel because torque converters provide torque multiplication during launch. The Honda DCT that utilizes a torque converter will also not require a higher number of example transmission, and the categories of loss are identispeeds for customer satisfaction.
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From page 177... ...
for both conventional automatic transmissions and CVTs. The dominant loss in the oil supply category results from Studies have shown that utilizing a small vane pump that is the oil pump.
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From page 178... ...
pump system for conventional automatic transmissions, as High efficiency gearbox -- level 3 -- involves removing shown in Figure 5.20. The smaller, more frequently operating a full-time oil pump from the automatic transmission and pump of the dual pump system can be better optimized for using an on-demand electric pump for lubrication/cooling its operating conditions than the larger, single variable dis- and electromechanical shifting.
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From page 179... ...
The clutch automatic transmission with this technology was developed packs are used in automatic transmissions to change ratio by by FEV; the shifting element is shown in Figure 5.21. The locking elements of planetary gear sets.
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From page 180... ...
indicating that a 90 percent turbocharged, downsized engines, clutch slip is increasreduction in clutch drag loss can be achieved from a baseline ingly being used for the lockup torque converter clutch of of flat friction plates. While not shown in Figure 5.23, other conventional automatic transmissions and in DCTs to reduce components that should be considered are dual-rate clutch the transmission of these torsionals to the wheels.
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From page 181... ...
In manual transmissions and DCTs, Newly developed low-friction seals for transmission some amount of churning is required, as those transmis- bearings can reduce seal friction by 50 percent to provide an sions typically depend on splash lubrication for their internal overall reduction in bearing friction loss of approximately components. Automatic transmissions and CVTs typically 10 percent (NSK 2014)
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From page 182... ...
Further investigation of the fuel consumption reductions and associ- Automatic Transmissions ated durability are required. The committee has assumed • Constant pump operation for clutch pressure and a conservative 0.5 percent benefit from lower viscosity cooling, oil at a 2017 direct manufacturing cost of $50, which is • Forced lubrication, included in the high efficiency gearbox (level 2)
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From page 183... ...
These losses continue to increase input speed in Figure 5.26 and as a function of input torque for high torque loads, so that a degradation in customer fuel in Figure 5.27. Conventional automatic transmissions have economy would be anticipated for driving conditions beyond parasitic losses from clutches, the torque converter, and the CAFE test cycles.
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From page 184... ...
. R02853 CAFEII 5.27.eps FIGURE 5.28 Torque losses as a function of input torque for a dual clutch transmission.
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From page 185... ...
FUEL CONSUMPTION REDUCTION TECHNOLOGIES Improved Automatic Transmission Controls/Externals CONSIDERED IN THE FINAL CAFE RULE ANALYSIS Improved automatic transmission controls (IATCs) are This section discusses the committee's fuel consump- defined in the NHTSA RIA (NHTSA 2012)
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From page 186... ...
Because of this consistent feedback, the committee rec- Extrapolating the Autonomie results to a six-speed from a ommends that shift optimization is not available to provide four-speed transmission is estimated to provide more than TABLE 5.4 Estimated Fuel Consumption Reductions and 2025 MY Direct Manufacturing Costs (2010 dollars) for Improved Automatic Transmission Controls/Externals Improved Automatic NRC Estimated Most NHTSA Estimated Fuel NRC Estimated Most Transmission Controls/Externals Likely Fuel Consumption Consumption Reduction Likely MY2025 DMC NHTSA Estimated MY 2025 (IATC)
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From page 187... ...
developed a cost of $101 for direct manufacturing cost of −$13 (savings) for a six-speed a six-speed automatic transmission relative to a four-speed automatic transmission relative to a four-speed automatic TABLE 5.6 Derivation of Direct Manufacturing Costs for Automatic Transmission (2007 dollars)
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From page 188... ...
transmission, which appears to have resulted from using Eight-Speed Automatic Transmissions only the case with the Lepelletier gear set. Applying the approach used by NHTSA in Table 5.6, which considers Effectiveness both Lepelletier and non-Lepelletier gear sets rather than NHTSA estimated that an eight-speed automatic transthe epelletier gear set alone, the committee developed L mission can provide a 4.6 percent reduction in fuel consumpincremental direct manufacturing costs for both gear sets, tion relative to a six-speed automatic transmission, which as shown in Table 5.7.
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From page 189... ...
TABLE 5.9 Other Available Direct Manufacturing Cost Estimates for Transmission Technologies Relative to 2007 FourSpeed Automatic Transmissions (dollars) Transmission Type EEA 2007($)
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From page 190... ...
analysis shows that the costs could range from $61.84 up BOX 5.2 Teardown Cost Study Issues: Eight-Speed Automatic Transmission and Dual-Clutch Transmission Teardown cost studies have been used by the Agencies to significantly improve cost estimates of new technologies that may be applied to meet future CAFE targets. The teardown process involves selecting an example of the new technology that has been implemented in production and an example of the outgoing technology.
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From page 191... ...
Losses in automatic transmissions vary significantly, but the Ricardo (2011) analysis showed that a 2010 MY auto- Six- and Eight-Speed Dual-Clutch Transmissions matic transmission was approximately 90 percent effi ient, c so that the energy losses through the transmission were Effectiveness approximately 10 percent of the input energy.
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From page 192... ...
49 6.5 TABLE 5.12 Estimated Fuel Consumption Reductions and 2025 MY Direct Manufacturing Costs for High-Efficiency Gearboxes (2010 dollars) NRC Estimated Most Likely NHTSA Estimated Fuel NRC Estimated Most NHTSA Estimated High-Efficiency Fuel Consumption Reduction Consumption Reduction Likely 2025 MY DMC 2025 MY DMC Costs Gearbox (HEG)
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From page 193... ...
2.49 3.04 2.78 TABLE 5.14 Estimated Fuel Consumption Reductions and 2025 MY Direct Manufacturing Costs for Six- and Eight-Speed Dual-Clutch Transmissions (DCTs) NRC Estimated Most Likely NHTSA Estimated Fuel NRC Estimated Most Likely NHTSA Estimated Dual Clutch Transmissions Fuel Consumption Reduction Consumption Reduction 2025 MY DMC Costs 2025 MY DMC Costs (DCT)
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From page 194... ...
Relative to a Six-Speed Conventional Automatic Transmission 6-Speed DCT versus 6-Speed Automatic Transmission Possible Incremental Cost over EPA/FEV Teardown Cost Estimate of −$97 for 2012 MY (2007 dollars) Technology DMC ($)
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From page 195... ...
be especially difficult without the smooth performance of a torque converter. This lack of smooth launch performance Turbine torsional dampers are generally included in has prompted Honda to announce the development of an automatic transmissions with lockup torque converters.
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From page 196... ...
However, EPA and NHTSA considered them in the the coefficient of friction between the pulley and belt, and TABLE 5.18 Estimated Fuel Consumption Reductions and 2025 MY Direct Manufacturing Costs for Secondary Axle Disconnect System NRC Estimated Most Likely NHTSA Estimated Fuel NRC Estimated Most Likely NHTSA Estimated 2025 Fuel Consumption Reduction Consumption Reduction 2025 MY DMC Costs MY (2010$s) DMC Secondary Axle Disconnect (%)
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From page 197... ...
Shift scheduling controls are also influenced by engine and vehicle conditions TABLE 5.19 Estimated Fuel Consumption Reductions and 2025 MY Direct Manufacturing Costs for Continuously Variable Transmission and High Efficiency Gearbox NRC Estimated Most Likely NHTSA Estimated Fuel NRC Estimated Most Likely NHTSA Estimated Continuously Variable Fuel Consumption Reduction Consumption Reduction 2025 MY DMC Costs 2025 MY DMC Costs Transmission (CVT)
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From page 198... ...
ing to a nine-speed transmission incurs a nonlinear increase As the number of gears or ratios increased in transmis- to 3.5 megabytes of ROM. sions, the complexity of the electronic controller, the number Migrating from conventional automatic transmissions to of sensor inputs and controller outputs, the software algo- dual clutch transmissions has been shown in this chapter Engine limitations FIGURE 5.30 Schematic of signal flow and coordination between engine controller and driveline controller for gear ratio selection and clutch control.
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From page 199... ...
. Although transmission control methodologies have been Finding 5.1 New eight-, nine-, and ten-speed automatic successfully developed and implemented to address quan- transmissions are being introduced to replace six-speed tifiable metrics such as reduction in fuel consumption or automatic transmissions, which are currently dominant in undesirable driveline oscillations, drivability metrics that light-duty vehicles.
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From page 200... ...
If secondrelative to conventional automatic transmissions, they are ary axle disconnect systems could reduce the losses of the not likely to reach the high penetration rates predicted by AWD system by 50 percent, fuel consumption reductions of EPA/NHTSA in the U.S. market.
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From page 201... ...
2013. The ZF automatic transmission 9HP48 Replacement of Aluminum Cast Components in a Production V6 Engine transmission system, design and mechanical parts.
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From page 202... ...
HEG2 2.6 - 2.7 2.6 - 2.7 2.6 - 2.7 Previous Tech Shift Optimizer (ASL-2) SHFTOPT 0.5 - 1.0 0.5 - 1.0 0.5 - 1.0 Previous Tech Secondary Axle Disconnect SAX 1.4 - 3.0 1.4 - 3.0 1.4 - 3.0 Baseline Other Technologies Continuously Variable Transmission with Improved internals (Rel to 6 sp AT)
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From page 203... ...
HEG2 194 194 194 Previous Tech Shift Optimizer (ASL-2) SHFTOPT 26 26 26 Previous Tech Secondary Axle Disconnect SAX 100 100 100 Baseline Other Technologies Continuously Variable Transmission with Improved internals (Rel to 6 sp AT)
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From page 204... ...
HEG2 183 183 183 Previous Tech Shift Optimizer (ASL-2) SHFTOPT 24 24 24 Previous Tech Secondary Axle Disconnect SAX 94 94 94 Baseline Other Technologies Continuously Variable Transmission with Improved internals (Rel to 6 sp AT)
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From page 205... ...
HEG2 165 165 165 Previous Tech Shift Optimizer (ASL-2) SHFTOPT 22 22 22 Previous Tech Secondary Axle Disconnect SAX 86 86 86 Baseline Other Technologies Continuously Variable Transmission with Improved internals (Rel to 6 sp AT)
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