Honda’s 2014 Accord Hybrid Drivetrain Topology Breakout

Discussion in 'In the News' started by xcel, Oct 18, 2013.

  1. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    [​IMG] A combination of an almost diesel like compression ratio (think SKYACTIV) and ingenious serial hybrid action during light load cruise provide the spectacular fuel economy results.

    [​IMG]Wayne Gerdes - CleanMPG - Oct. 18, 2013

    2014 Honda Accord Hybrid - $29,945 to start with an incredible 50/45/47 mpgUS city/highway/combined rating for a well appointed and true midsize sedan.

    Honda details the 2014 Accord Hybrid Powertrain

    The ninth-generation Accord Hybrid offers an all-out Earth Dreams Technology effort consisting of an all-new heavily atkinsonized 2.0L I4 with a two-motor hybrid system.

    The Accord PHEV-11 and the Accord Hybrid have a completely new hybrid system that is in no way associated with their previous and aging Integrated Motor Assist (IMA) system.

    The Accord Hybrid incorporates an all-new new system called Intelligent Multi-Mode Drive (i-MMD). Here is the cool part. Under most conditions the gas engine powers a generator, which in turn provides energy to charge the hybrid battery and/or for the electric motor to drive the wheels. In past automobile serial hybrid efforts, the conversion efficiency losses have been so high as to make a parallel system almost mandatory. It appears that is no longer the case? At mid to high speed cruising, the i-MMD can operate on gasoline engine power only. I would love to see some of the computer models for this but unfortunately I have not found one. Yet. ;)

    Honda's i-MMD uses a new two-motor hybrid approach that continuously cycles between three different modes - EV drive, hybrid drive and engine drive - to maximize fuel efficiency. The Accord Hybrid uses a compact 1.3 kWh Li-Ion battery that is charged via the vehicle's 2.0L engine, regenerative braking, or a combination of the two. The result of the Accord Hybrid's cutting-edge powertrain is a new found fun-to-drive character, coupled with an unmatched city and yes, highway fuel-economy rating given the Fusion’s 47 mpgUS rating is made up.

    [​IMG]

    Atkinsonized 2.0L I4 Hybrid Features
    • 2.0L DOHC, i-VTEC I4
    • Maintenance-free 124-kW electric motor
    • 1.3 kWh Li-Ion battery
    • Electric-servo braking system
    • i-VTEC® (Variable Valve Timing and Lift Electronic Control) + Electric VTC
    • Regular unleaded fuel
    • Drive-by-Wire Throttle System
    • Electric Continuously Variable Transmission (E-CVT)
    • Close-coupled catalytic converter plus under-floor catalytic converter
    • 100,000+/- miles engine tune-up interval
    • Eight-year/100,000-mile or ten-year/150,000 mile Li-Ion battery limited warranty, depending on the state of purchase/registration.
    • 24-hour roadside assistance (during initial warranty period)
    • High-efficiency Earth Dreams Technology Two-Motor Hybrid System
    The Accord Hybrid's i-MMD system is a highly efficient powertrain that selects the optimal drive mode under a wide range of driving conditions. Detailed energy management for each component enables this system to make the best use of both the electric propulsion motor and the gasoline engine to seamlessly provide smooth and responsive performance and a best-in-class (four door sedan) city fuel-economy rating.

    To help maximize efficiency on the road, the Accord Hybrid seamlessly shifts between three distinct drive modes: EV Drive (100 percent electric motor), Hybrid Drive (electric motor and gasoline engine [driving the generator motor]) and Engine Drive (gasoline engine). The Accord Hybrid's powertrain shifts seamlessly and smoothly among the three driving modes, utilizing power from the i-VTEC I4 and the electric motor to suit the driving conditions moment to moment.

    EV Drive Mode - All-electric drive EV Drive Mode is active when starting from a stop, during light cruising and acceleration, and when braking. The gasoline engine is off in this mode and is decoupled from the drivetrain to reduce friction.

    Hybrid Drive Mode - The electric motor and gasoline engine work together when accelerating and at higher speeds. The electric propulsion motor alone powers the front wheels, as the gasoline engine (decoupled from the drive wheels) powers the electric-generator motor, which in turn provides power to the battery pack. This allows the gas engine-generator motor combo to supplement the battery by providing added electrical power to the propulsion motor or, alternatively, to charge the battery. The electric propulsion motor offers crisp acceleration, and can reach maximum torque almost instantaneously, thanks to electrical power that can be supplied from both the gas engine-powered motor/generator and the battery.

    Engine Drive Mode - When cruising at medium to high speeds, the high-efficiency Atkinson-cycle i-VTEC gasoline engine provides propulsion via the E-CVT with lock-up clutch, which connects the generator motor (always linked to the engine) and the electric drive motor, effectively sending motive power directly from the engine to the drive wheels.

    [​IMG]

    Thermodynamic efficiency is through the roof!

    The Atkinsonized 2.0L I4 is an all-new DOHC i-VTEC engine that develops a peak 141 hp and 122 lb-ft. of torque. It is the world’s most thermodynamically efficient gasoline fueled powerplants in the world. At 214 g/kWh on 87-octane gasoline fuel, this equates to approximately 38.4% which is even higher than the third gen Prius’ 37.0% efficient 1.8L!

    The engines excellent fuel efficiency comes about with an exceptionally low exhaust emission level. This clean-running engine meets the upcoming LEV3- AT-PZEV (SULEV30)/BIN3 emission standard.

    The Accord Hybrid’s total system output (peak horsepower of both the gas engine and the two-motor hybrid-drive system) is 196 hp.

    Since the gasoline engine can be decoupled from the rest of the hybrid powertrain, it only operates as needed. Depending on the state of battery charge and other parameters, it will automatically shut off during deceleration and when the vehicle is at a stop or operating under battery power. When needed, the gasoline engine restarts automatically, without action from the driver.

    Engine Block, Crankshaft and Pistons

    The engine has a displacement of 1993cc and cast-in iron cylinder liners provide long-lasting durability. Each journal on the forged-steel crankshaft is micro-polished to reduce internal friction. To improve smoothness throughout the rpm range and help lower noise levels, the Accord Hybrid is fitted with an internal balancer unit. Consisting of a pair of chain-driven counter-rotating shafts located in the oil pan, the balancing system helps quell the inherent second-order harmonic vibrations that are normally associated with inline 4-cylinder engines.

    The 2.0L has cylinder bores offset by 8.0 mm from the crankshaft to help reduce piston-sliding friction. This gives the connecting rods a more favorable angle during each power stroke, which reduces side loading on the pistons and, in turn, improves efficiency.

    The lightweight pistons have a carefully optimized skirt design to minimize reciprocating weight, and reduced weight minimizes vibration and increases operating efficiency.

    Cylinder Head and Valvetrain

    The Accord Hybrid I4 has a lightweight cylinder head that is made of pressure-cast aluminum alloy. A silent chain drives dual overhead cams and four valves per cylinder. The cam drive is maintenance free throughout the life of the engine.

    To help boost fuel efficiency and power, the engine has a 3.4-degree included angle between the intake and exhaust valves. The narrow valve angle decreases the surface-to-volume ratio and helps create a flatter, more compact combustion chamber that reduces unburned hydrocarbon emissions. This combustion chamber shape and the precise control allows the compression ratio to be a high 13.0:1 (up from 11.0:1 on the direct injected 2.4L non-hybrid Accord engine), yet the engine still operates on regular unleaded fuel.

    i-VTEC Valve Control System

    The Accord Hybrid's 2.0L DOHC 16-valve i-VTEC engine uses an advanced valve-control system to combine high power output with high fuel efficiency and low emissions. The system combines E-VTC (Electronic Variable Timing Control), which continuously adjusts the intake camshaft phase, with Variable Valve Timing and Lift Electronic Control (VTEC), which changes the lift profile, timing and duration of the intake valves' operation.

    High-Efficiency Catalytic Converter(s)

    Key contributors to the Accord I4 engine's excellent emissions performance are its dual high-efficiency catalytic converters. One converter mounts directly to the front of the cylinder head, close-coupled for fast activation after the engine is started. A second converter is positioned slightly downstream, beneath the passenger compartment floor. Both converters use a thin-wall design that increases internal reaction area and improves efficiency.

    Electric Motors

    The Accord Hybrid uses two electric motors. The 124 kW AC synchronous permanent-magnet propulsion motor, linked to the drive wheels, provides primary motive power for the vehicle. When in regenerative mode, the propulsion motor converts the kinetic energy of the decelerating vehicle into electrical energy to recharge the battery. Its operation is seamlessly coordinated with the Accord Hybrid's electric-servo braking system. A separate generator motor is driven by the gasoline engine to generate electric energy to drive the propulsion motor when the vehicle is operating in Hybrid Drive Mode. This generator motor can also restart the gasoline engine when the vehicle is in idle-stop mode.

    [​IMG]

    Li-Ion Hybrid Battery

    The Accord Hybrid's integrated Power unit (IPU), located behind the rear seat, and consists of a 1.3 kWh Li-Ion battery and a DC-DC converter. The Li-Ion battery type offers high energy density, allowing the compact and lightweight battery to be positioned behind the Accord Hybrid's fixed rear seatback. Meaning once again split fold down rear seats.

    Battery temperature is controlled by a fan system that pulls air from the interior of the vehicle via vents on the driver's side of the rear seatback. The battery powers the Accord Hybrid's electric propulsion motor. It is recharged by the propulsion motor operating in regenerative braking mode, and by the generator motor, which is powered by the gasoline engine. The battery pack is covered by a special warranty that covers defects in material and workmanship for eight-years/100,000-miles or ten-year/150,000 miles depending on the state of purchase/registration.

    Electric Continuously Variable Transmission (E-CVT)

    The Accord Hybrid is not equipped with a conventional physical transmission. Instead, the Electric Continuously Variable Transmission (E-CVT) consists of the interaction of the Accord Hybrid's gasoline engine and two electric motors. Coordinated by the IPU, the E-CVT offers smooth and predictable acceleration matched with efficient low-rpm highway cruising when the gasoline engine is in operation. Gasoline engine shutdown is seamlessly integrated into the operation of the Accord Hybrid when appropriate.

    The E-CVT system, unlike other full hybrid systems, operates without the need for a torque converter, mechanical pulley or belt. It instead uses two motors for driving and generating power. Unlike a conventional CVT, E-CVT is optimally and rapidly able to control both engine and electric motor rotation in order to deliver higher fuel efficiency and quicker engine response in each driving mode.

    [​IMG]

    When cruising at mid- or high-speeds in the high-efficiency range of the engine, the lock-up clutch built into the E-CVT is engaged, connecting the drive motor to the generator motor to transmit engine torque directly to the drive wheels as efficiently as possible. In EV Drive mode, when the battery-powered drive motor is used for either acceleration or regenerative braking, a clutch disengages the stopped gasoline engine from the drivetrain to eliminate efficiency loss from mechanical friction in the engine.

    E-CVT Automatic Modes

    The transmission, with its console-mounted straight-gate shifter, can be operated in two different fully automatic modes. The D mode is ideal for most driving situations, and combines fuel efficiency with smooth operation and responsive power when needed. The B (Brake) mode offers substantially increased regenerative braking.

    EV Button

    Immediately behind the shifter is an EV button that lets the driver select purely electric operation. A green EV icon lights on the instrument panel in this mode. When the battery charge is sufficiently depleted, EV Mode is automatically cancelled and the gasoline engine will automatically restart to recharge the battery in Hybrid Drive Mode or Engine Mode.

    Electric Engine Accessories - The Accord Hybrid's engine accessories operate electrically, both for maximum efficiency and to allow their operation whether the gasoline engine is running or not. The air conditioning compressor and water pump are both powered by the electrical system. In addition, the Accord Hybrid has Electric Power Steering (EPS).

    [​IMG]

    The 2014 Honda Accord Hybrid e-CVT Deep Dive - This detail was pulled from the Honda patent that Carcus linked in a follow up post.

    One "possible" configuration?

    [​IMG]
    The 2014 Honda Accord Hybrid’s e-CVT Transmission Layout.​

    The Components

    • 13 Main shaft (input shaft)
    • 14 Second intermediate shaft (intermediate shaft)
    • 15 Sun gear (second element of planetary gear mechanism)
    • 16 Ring gear (first element of planetary gear mechanism)
    • 17 Carrier (third element of planetary gear mechanism)
    • 19 Countershaft (output shaft)
    • 20 First intermediate shaft
    • 21 Speed-increasing drive gear (speed-increasing mechanism, first gear)
    • 22 Speed-increasing driven gear (speed-increasing mechanism, second gear)
    • 23 Speed-increasing output gear (third gear)
    • 23′ Speed-increasing/speed-decreasing output gear (third gear)
    • 30 Casing
    • B1 Brake
    • C1 First clutch (equal-speed clutch)
    • C2 Second clutch (speed-increasing clutch)
    • C3 Third clutch
    • E Engine
    • P Planetary gear mechanism (main speed-changing part)
    • MG1 First motor/generator
    • MG2 Second motor/generator
    • T Transmission

    When the first clutch C1 is engaged, the main shaft 13 is directly coupled to the second intermediate shaft 14, the second intermediate shaft 14 rotates at the same rotational speed as that of the main shaft 13. When the second clutch C2 is engaged, rotation of the main shaft 13 is transmitted to the ring gear 16 of the planetary gear mechanism P via the speed-increasing drive gear 21, the speed-increasing driven gear 22, the second clutch C2, the first intermediate shaft 20, the speed-increasing output gear 23, and the speed-changing input gear 24. In this process, since the number of teeth of the speed-increasing drive gear 21 is larger than the number of teeth of the speed-increasing driven gear 22, rotation of the ring gear 16 is increased in speed relative to rotation of the main shaft 13.

    Although it is always necessary to set the gear ratio of the speed-increasing drive gear 21 and the speed-increasing driven gear 22 for a speed increase, the gear ratio of the speed-increasing output gear 23 and the speed-changing input gear 24 may be set for equal speed or for a speed increase or may be set for a speed decrease to a degree that does not offset the speed increase by the speed-increasing drive gear 21 and the speed-increasing driven gear 22.

    When the brake B1 is engaged, since the ring gear 16 of the planetary gear mechanism P is fixed to the casing 30, rotation inputted from the second intermediate shaft 14 into the sun gear 15 is decreased in speed and outputted to the carrier 17, that is, the first speed-changing output gear 25. When the third clutch C3 is engaged, the ring gear 16 is coupled to the sun gear 15 via the second intermediate shaft 14, thus putting the planetary gear mechanism P into a locked state, and rotation of the second intermediate shaft 14 is outputted as it is to the carrier 17, that is, the first speed-changing output gear 25.

    The Outcome

    By combining engagement and disengagement of the first to third clutches C1, C2, C3 and the brake B1 enables rotation of the main shaft 13 to be changed in speed in 4 specific gear ratios whose output is transmitted to the countershaft 19.

    Effective First Gear

    [​IMG]
    The e-CVT Transmission in an effective 1st gear configuration​

    The figure above shows the first clutch C1 and the brake B1 engaged establishing first gear.

    Rotation of the engine E is transmitted to the driven wheels W and W via the path: crankshaft 11→damper 12→main shaft 13→first clutch C1→second intermediate shaft 14→sun gear 15, pinions 18, and carrier 17 of planetary gear mechanism P→first speed-changing output gear 25→second speed-changing output gear 26→countershaft 19→final drive gear 27→final driven gear 28→differential gear D→drive shafts 29 and 29.

    The planetary gear mechanism P carries out speed reduction and establishes first gear.

    Effective Second Gear

    [​IMG]
    The e-CVT Transmission in an effective 2nd gear configuration​

    The figure above shows the first clutch C1 and the third clutch C3 engaged establishing second gear.

    Since the planetary gear mechanism P attains a locked state due to the sun gear 15 and the ring gear 16 being coupled by engagement of the third clutch C3, rotation of the engine E is transmitted to the driven wheels W and W via the path: crankshaft 11→damper 12→main shaft 13→first clutch C1→second intermediate shaft 14→planetary gear mechanism P in locked state→first speed-changing output gear 25→second speed-changing output gear 26→countershaft 19→final drive gear 27→final driven gear 28→differential gear D→drive shafts 29 and 29.

    The planetary gear mechanism P does not carry out speed increase or speed decrease, enabling second gear, which has a smaller ratio than first.

    Effective Third Gear

    [​IMG]
    The e-CVT Transmission in an effective 3rd gear configuration​

    The figure above shows the first clutch C1 and the second clutch C2 engaged establishing third gear.

    Due to engagement of the second clutch C2, rotation of the main shaft 13 is transmitted to the ring gear 16 of the planetary gear mechanism P via a speed increase path that includes the speed-increasing drive gear 21, the speed-increasing driven gear 21, the second clutch C2, the first intermediate shaft 20, the speed-increasing output gear 23, and the speed-changing input gear 24, rotation of the ring gear 16 is increased in speed relative to rotation of the main shaft 13, and due to engagement of the first clutch C 1 the main shaft 13 is directly coupled to the sun gear 15 of the planetary gear mechanism P via the second intermediate shaft 14. As a result, rotation of the engine E is transmitted to the driven wheels W and W via the path: crankshaft 11→damper 12→main shaft 13→first clutch C1→second intermediate shaft 14→sun gear 15, pinions 18, and carrier 17 of planetary gear mechanism P→first speed-changing output gear 25→second speed-changing output gear 26→countershaft 19→final drive gear 27→final driven gear 28→differential gear D→drive shafts 29 and 29.

    The planetary gear mechanism P carries out speed increase, enabling third gear position, which has a smaller ratio than second.

    Effective Fourth Gear

    [​IMG]
    The e-CVT Transmission in an effective 4th gear configuration​

    The Figure above shows the second clutch C2 and the third clutch C3 engaged establishing fourth gear.

    Since the planetary gear mechanism P attains a locked state due to the sun gear 15 and the ring gear 16 being coupled by engagement of the third clutch C3, rotation of the engine E is transmitted to the driven wheels W and W via the path: crankshaft 11→damper 12→main shaft 13→speed-increasing drive gear 21→speed-increasing driven gear 22→second clutch C2→first intermediate shaft 20→speed-increasing output gear 23→speed-changing input gear 24→planetary gear mechanism P in locked state→first speed-changing output gear 25→second speed-changing output gear 26→countershaft 19→final drive gear 27→final driven gear 28→differential gear D→drive shafts 29 and 29.

    The planetary gear mechanism P does not carry out speed reduction or speed increase, and the speed-increasing drive gear 21 and the speed-increasing driven gear 22 carry out speed increase, enabling fourth gear which has a smaller gear ratio than third.

    [​IMG]
    The e-CVT Transmission Speed and Ratio Topology​

    Which of the three Clutches and Brake are open or closed to create the 4 effective gears

    [​IMG]
    The e-CVT Transmission - Effective Gears with the Brake and (3) Clutches either open (white circle) or closed (black circle)​

    The Deep Dive Overview

    The main shaft 13, the speed-increasing drive gear 21, the speed-increasing driven gear 22, the first intermediate shaft 20, and the speed-increasing output gear 23 form speed-increasing means with parallel shafts, rotation of the main shaft 13 is increased in speed and transmitted to the planetary gear mechanism P, and the power generation efficiency can be enhanced by driving the first motor/generator MG1, which is integral with the speed-increasing driven gear 22 of the speed-increasing means, at an increased rotational speed. In this process, since rotation of the main shaft 13 is increased in speed by the speed-increasing drive gear 21 and the speed-increasing driven gear 22 and transmitted to the first motor/generator MG1, compared with a case in which it is increased in speed by a planetary gear mechanism exclusively used and transmitted to the first motor/generator MG1, it is possible to decrease the number of gears meshing, thus enhancing the transmission efficiency.

    In addition, if the first motor/generator MG1 is made to function as a motor, the crankshaft 11 is cranked by the driving force of the first motor/generator MG1, thus starting the engine E. In this process, since rotation of the first motor/generator MG1 is decreased in speed by the speed-increasing driven gear 22 and the speed-increasing drive gear 21 and transmitted to the crankshaft 11 of the engine E, it is possible to crank the crankshaft 11 with a large torque, thus enhancing the ease of starting.

    Since rotation of the main shaft 13 is inputted into the planetary gear mechanism P for speed change at an equal speed due to engagement of the first clutch C1 and rotation of the main shaft 13 is inputted at an increased speed via the speed-increasing means due to engagement of the second clutch C2, selectively engaging the first clutch C1 and the second clutch C2 enables a plurality of gear positions to be established. In this process, since the speed-increasing drive gear 21, the speed-increasing driven gear 22, the second clutch C2, the first intermediate shaft 20, and the speed-increasing output gear 23 forming the speed-increasing means for speed change are disposed coaxially with the countershaft 19, the size of the transmission T can be reduced.

    The speed-increasing means for speed change is utilized for overdriving the first motor/generator MG1, not only is it possible to reduce the cost, but it is also possible to enhance the power generation efficiency by overdriving the first motor/generator MG1 even if the second clutch C2 is disengaged when an increase in speed is not required for speed change since the second clutch C2 can couple the speed-increasing driven gear 22 to the first intermediate shaft 20.

    Two gear positions can be achieved by coupling the ring gear 16 of the planetary gear mechanism P for speed change to the second intermediate shaft 14 via the third clutch C3 or coupling the ring gear 16 to the casing 30 via the brake B1, combining engagement and disengagement of the third clutch C3 and the brake B1 and combining engagement and disengagement of the first clutch C1 and the second clutch C2 enables a total of four gear positions.

    In addition, if it is assumed that only rotation at an increased speed can be inputted into the planetary gear mechanism P of the transmission T, in order to reduce the increased speed rotation to a required gear ratio, a very large reduction ratio is necessary, and there is a possibility that transmission efficiency will be degraded or the transmission T will increase in size, but in accordance with the present embodiment, since it is unnecessary to employ a very large reduction ratio, it becomes possible to improve the transmission efficiency and reduce the size of the transmission T.

    Since the second motor/generator MG2 that can be rotated integrally with the second intermediate shaft 14 is provided, it is possible by a simple structure to make a vehicle travel by means of the driving force of the second motor/generator MG2, assist the driving force of the engine E by means of the driving force of the second motor/generator MG2, and recover the kinetic energy of the vehicle as electrical energy by regenerative braking the second motor/generator MG2.

    The speed-increasing driven gear 22 and the speed-increasing output gear 23 are disposed in a divided manner on opposite sides in the axial direction of the first motor/generator MG1 disposed on the outer peripheral side of the first intermediate shaft 20, and the second clutch C2 is disposed at a position that is coaxial with and on the inner peripheral side of the first motor/generator MG1 and at which it is superimposed thereon in the axial direction, it is possible to shorten the length of the transmission T in the axial direction.

    The first clutch C1 is disposed at a position that is coaxial with and on the inner peripheral side of the second motor/generator MG2 and at which it is superimposed thereon in the axial direction, it is possible to shorten the length of the transmission T in the axial direction.

    So it is a simpler powersplit power transmission layout with a main clutch providing the ability to remove the ICE from the equation. Or is it something else altogether?
     
  2. smart-za

    smart-za Well-Known Member

    Erm, let me get this straight. Does this mean that the Accord Hybrid has no mechanical transmission, except for the lockup clutch?

    Is this a one-gear car?
     
  3. Bruce

    Bruce cheapskate

    The powertrain sounds like de-PHEV'd version of the Volt. But for the smaller battery, it's pretty amazing that they'd come up with substantially better numbers when running on gasoline, since the CdA, engine size and passenger seating should all be substantially larger as well.
     
  4. Prozac

    Prozac Well-Known Member

    Sounds great, except for the price. Ouch! I understand the rest of the category is priced just as high, it just still hurts to look at a Honda Accord that starts at almost $30k.
     
  5. PaleMelanesian

    PaleMelanesian Beat the System Staff Member

    It doesn't look so bad when you compare against the new Cadillac ELR... $75,000!
     
  6. volton

    volton Well-Known Member

    A very impressive technical tour de force indeed. Now Honda has something to compete with against Toyota. The Accord is just the beginning, I see this system coming later in the CR-V and a perhaps Fit/Civic.
     
  7. bestmapman

    bestmapman Fighting untruth and misinformation

    It sounds very similar to the Toyota HSD system with an added clutch to couple the engine at high speeds.
     
  8. jbart

    jbart Well-Known Member

    this would be awesome in a CRV package. We can only dream here in Canada :(
     
  9. Carcus

    Carcus Well-Known Member

    E-cvt = Hysteresis-powered clutch?

    I have a hard time believing honda can get 50 mpg city efficiency out of a (mostly) series hybrid. .... So I'm wondering if there's a hysteresis clutch on the shaft (along with miles and miles of computer code) that links the 2 electric motors and the ICE?

    /add .. I've seen other journo reports of 70+ mpg city loops without a whole lot of effort -- this appears to be a very different type of hybrid drive that is raising the bar.
     
    Last edited: Oct 18, 2013
  10. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi All:

    A friend who was at one of the short leads provided this detail which sounds just like the description I posted early this morning.
    Wayne
     
  11. Carcus

    Carcus Well-Known Member

    I think we all agree that this is a series/parallel hybrid.

    But it seems to me that Honda is not revealing (yet) everything about its parallel operation. Doesn't there have to be some type of 'transmission' to link ICE to drivetrain in parallel mode? I can't believe it's just a "1 ratio and that's it" connection.


    The only way I could see that (1 ratio) is if the parallel mode was high speed highway only, and that does not appear to be the case. That plus the high efficiency makes me think Honda has a "sophisticated parallel tranny" somehow in the mix.
     
    Last edited: Oct 18, 2013
  12. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi Carcus:

    The ability to control RPM and speed lead me to believe there is an HSD series parallel hybrid solution at work. The low load driving mode with the engine filling the battery and the battery supplying the traction motor for essentially ever if the condition exists is pure serial action which is new.

    Wayne
     
    Last edited: Oct 18, 2013
  13. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi All:

    The latest and it comes from someone who also knows a little about engines and tranny’s.
    Wayne
     
  14. Carcus

    Carcus Well-Known Member

    ... and Honda does seem to converse that there are no belts, gears, torque converters etc... the ususal suspects. By process of elimination (and internetual deduction) we kind of get down to hysteresis clutch or similar .. some type of electro-magnetic connection that allows changeable ratios.

    So I'm willing to risk it all and bet a chocolate glazed donut that's what Honda is using.
     
  15. priusCpilot

    priusCpilot George

    I wounder how many cycles that clutch goes through on a typical drive? 1000s I would imagine? Is there a warning light ("Hybrid Clutch Failure") for that on the dash? I wounder if the warranty for that is 10 years 150k here in CA?

    The thermo efficiency is higher then the 3rd Gen but how about the Prius C? It has a more advanced system then the 3rd Gen?
     
  16. Carcus

    Carcus Well-Known Member

    IF it's a hysteresis type clutch thingy then there's gonna be hardly any moving parts to wear out. (Although heat might be an issue)

    Vs the Prius C, ..... it's a substantially bigger, heavier (1,000 lbs +) car and will probably meet or beat the C on a mpg drive compo.
     
  17. xcel

    xcel PZEV, there's nothing like it :) Staff Member

    Hi All:

    It does not sound like Pop Mechanics knew what it was driving either???
    Wayne
     
  18. brick

    brick Answers to "that guy."

    I think I might have an inkling of what's going on. It almost sounds like they took the HSD (single planetary set) concept but made it a two-way split instead of three-way. If you put the engine and one MG on the input and the wheels and the other MG on the output, that basically gives you a 1-speed box with electric assist unless the carrier is on that hysteresis clutch that you guys have been talking about. If you lock the clutch, the carrier stops and it's in "high" gear. Varying degrees of slip give you varying degrees of "reduction" all the way to neutral if it is completely unlocked and allowed to spin free.

    It's almost 5, so I better go have a beer and see if that still makes sense.
     
  19. brick

    brick Answers to "that guy."

    Here's a schematic of what I visualized. (It would make more sense as an isometric view but the best I have is Inkscape.)

    [​IMG]

    **EDIT**
    I should have drawn an electrical energy path between the two motors. The more I think about it, the more I think that's a really big deal. I can't imagine this working efficiently without a bunch of current going from the starter/generator to the assist motor at low speeds. The control gurus probably minimize energy losses to clutch slip by maximizing electricity flow across the MG set.
     
    Last edited: Oct 18, 2013
    xcel likes this.
  20. 300kmileprius

    300kmileprius Well-Known Member

    Really hope the numbers are real. Can't wait to do a 65 mph round trip to find out.
     
    xcel likes this.

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