Has anyone caught wind of the nuts and bolts of Honda's latest hybrid system?
They threw virtually everything about IMA out the window and adopted a hybrid system very similar to that of a diesel-electric locomotive; the serial hybrid design. However, it has one main difference, the ability to mechanically connect the engine to the wheels via ONE overdrive gear ratio.
Quote:
Ferdinand Porsche used this arrangement in the early 20th century in racing cars, effectively inventing the series-hybrid arrangement.
Basically, for most lower speed operation the engine acts as a prime mover- it spins a generator. From here electrical energy is converted to chemical energy into the Li-Ion battery pack. From there, it is converted back to electrical energy and distributed to the "traction motor" as needed. There is zero mechanical connection to the wheels. However the process of converting electric - chemical - electric is inefficient- losses remain (also why this type of hybrid is not normally desirable).
Honda's solution? Take advantage of the ICE disconnect. They can tune the engine to be efficient in a narrow RPM range, and then operate it in that range to compensate for energy-conversion losses. The net result is more stable (not better but more stable) efficiency during various operating regimes than say a gearbox. They've accepted energy transformation losses and offset it by using efficiency logics, losing gearbox frictional losses and using a narrowly tuned engine netting overall gains.
So they've got the city operation covered, but how about steady-state cruising?
Using a serial-hybrid operation for this would not be efficient, as there would be too much loss from energy transformation. A direct mechanical connection is still more efficient, therefore the Honda Accord hybrid system has ONE gear, an overdrive. This gear is engaged via clutch during steady state cruising over 44MPH for maximum efficiency. So in essence there is no transmission, apart from one OD. With the clutch engaged, the system operates like IMA- the motor supplements the narrowly-tuned ICE's dead spots for a seamless powerband at higher speeds. Below 44MPH, the engine cannot engage due to the OD ratio being so tall.
http://www.technologyreview.com/view/520...-to-hit-50-mpg/
While I don't like Alex Dykes as a writer or pseudo-auto journalist (really, I can't stand him- no concept of objectivity at all) he sure is creaming his shorts over the Accord Hybrid.
http://www.thetruthaboutcars.com/2013/10...eo/#more-612689
The drawbacks? @$35,700MSRP it ain't cheap, and at 3700lbs, it's pretty massive.
They threw virtually everything about IMA out the window and adopted a hybrid system very similar to that of a diesel-electric locomotive; the serial hybrid design. However, it has one main difference, the ability to mechanically connect the engine to the wheels via ONE overdrive gear ratio.
Quote:
Ferdinand Porsche used this arrangement in the early 20th century in racing cars, effectively inventing the series-hybrid arrangement.
Basically, for most lower speed operation the engine acts as a prime mover- it spins a generator. From here electrical energy is converted to chemical energy into the Li-Ion battery pack. From there, it is converted back to electrical energy and distributed to the "traction motor" as needed. There is zero mechanical connection to the wheels. However the process of converting electric - chemical - electric is inefficient- losses remain (also why this type of hybrid is not normally desirable).
Honda's solution? Take advantage of the ICE disconnect. They can tune the engine to be efficient in a narrow RPM range, and then operate it in that range to compensate for energy-conversion losses. The net result is more stable (not better but more stable) efficiency during various operating regimes than say a gearbox. They've accepted energy transformation losses and offset it by using efficiency logics, losing gearbox frictional losses and using a narrowly tuned engine netting overall gains.
So they've got the city operation covered, but how about steady-state cruising?
Using a serial-hybrid operation for this would not be efficient, as there would be too much loss from energy transformation. A direct mechanical connection is still more efficient, therefore the Honda Accord hybrid system has ONE gear, an overdrive. This gear is engaged via clutch during steady state cruising over 44MPH for maximum efficiency. So in essence there is no transmission, apart from one OD. With the clutch engaged, the system operates like IMA- the motor supplements the narrowly-tuned ICE's dead spots for a seamless powerband at higher speeds. Below 44MPH, the engine cannot engage due to the OD ratio being so tall.
http://www.technologyreview.com/view/520...-to-hit-50-mpg/
While I don't like Alex Dykes as a writer or pseudo-auto journalist (really, I can't stand him- no concept of objectivity at all) he sure is creaming his shorts over the Accord Hybrid.
http://www.thetruthaboutcars.com/2013/10...eo/#more-612689
The drawbacks? @$35,700MSRP it ain't cheap, and at 3700lbs, it's pretty massive.
