Energy Conservation: Why a Hybrid is more Efficient The physics of energy conservation. Gasoline when burned in an internal combustion engine produces heat and noise and of course pressure created during the expansion cycle creates the usable energy for the drive system. Even with a clean tailpipe the engine efficiency is less than 40%. The hybrid gasoline engines that are typically of a lower displacement four cylinder or smaller. Toyota uses a unique design that includes variable valve timing and incorporates an offset crankshaft to maximize the expansion stroke. Most hybrid engines designs and calibrations are configured to run at a constant speed for electrical energy production. Reducing throttle changes improves engine efficiency. more... |
Hybrid Types There are a few different hybrid naming conventions to understand
Mild Hybrid or (Hybrid Lite) like beer... Any vehicle that can't be driven by either method independent of each other is a mild hybrid. These are not really hybrids they are just gimmicks vehicles to say look at us... For example if you look at the GM trucks that are mild hybrids they have a power outlet for contractor use... hmm net but a very expensive power source when a portable generator is less than $1000. And the generator does nothing other than start the car and charge the batteries, providing no additional power to the drive wheels. Volkswagen Jetta ,Dodge Ram Contractor,Chev Malibu, Saturn Vue are all versions on the mild variety...more |
What About Honda? By strict interpretation the Honda hybrids are also mild hybrid designs, the electric motor is not able to drive the wheels independently because the engine is directly coupled to the electric motor. When the electric motor is powering the vehicle the engine crankshaft is along for the ride. Honda uses their proven VTEC engines combined with a very efficient brush less three phase AC motor.
Honda Insight
The Insight was the first modern Hybrid that was not built from and existing model. The Insight is a small and light 2 seater vehicle that gets exceptional mileage, but was eliminated due to low sales volumes less than 2000 vehicles sold in the last year of production.
The Insight used a very efficient 12 valve 1.0 liter 3 cylinder engine that produces 67 hp, 10kW @144 volts and is rated as a SULEV vehicle. Testing has produced repeatable fuel economy numbers of 65+ mpg ,or 3.9 / 3.3 Liters/100 Km.
Honda Civic
The Civic hybrid was introduced in 2003 and looks like a regular Civic. All of the Civic models use a 1.3L 4 cylinder engine direct coupled to an IMA electric motor. more...
Honda Accord
The Accord was the first of the performance hybrids, only available with the 3.0L V6 VTEC engine. Many have wondered why they did not consider the smaller 2.4L engine for greater economy, but they wanted to have performance that compared to the Toyota and Lexus models. The Insight Civic and Accord get great gas mileage mainly because of the use of a small engine. This produces a problem for acceleration. The gasoline engine is almost always running at cruising speeds and the electric motor supplies supplemental power for acceleration or power when required. The Honda hybrids do not have a conventional starter motor, relying on the electric motor to start the engine. The Honda iTEC engines have the ability to shut off individual cylinders during light loads cruise. more... |
Toyota Prius Certified SULEV, AT-PZEV, AT-ZEV, Tier 2 Bin 3 The latin word for "Prius "to go before"
Toyota's are proudly full hybrid designs, able to provide drive to the wheels using either engine or battery to electric power independently. Toyota has been working on their hybrid technology since 1994 called project G21. Taskshi Uchiyamada was given the role of Lead Engineer in charge of advanced component development and was given a free hand to enhance his four engineer teams creativity. There were many challenges that they were aware of and .a few surprises. For example the prototype vehicle that was presented at the Japanese auto show in November 1995 was not able to power itself, due to computer communication problems. This problem persisted until March of 1996, with the vehicle able to run under limited power. The engineering team target launch was for the end of 1999, but management had other wishes wanting a delivery by 1998. The push was for a exhibition of the vehicle at the Kyoto conference in 1997. The generation 1 Prius launched in October 1997 in Japan only. North America did not see the 1st generation vehicles, but in 2001 the 2nd generation Prius was launched and was selected as the best engineered car for 2001. The 3rd generation Prius was delivered in 2004 and was also awarded with the distinction of being the best engineered vehicle for 2004. Engine selection was probably the easiest choice for the team since Taskshi Uchiyamada was involved with engine designs using fuel optimization at the Fuji center. The choice was an high expansion ratio Atkinson cycle derivative engine that retards the closing of the intake valves to increase the effective compression ratio to 13.5 : 1 since the engine runs at a constant speed it made sense to take advantage of a cycle that had reduced pumping losses. Every droplet of fuel counts in this ultra high fuel economy engine, the fuel injectors are a 12 hole design( 0.006" or 0.15mm) The NZ series engines are all chain driven double overhead cam engines with inverted bucket tappets. The valves are inclined at an included angel of 33.5° degrees, with a slanted squish area combustion chamber. Each piston has a shallow oval indentation. Even the top compression ring thickness was reduced from 1.2 mm to 0.8 mm (.050 to .030") the thinnest in the world. The crankshaft centerline is offset by 12 mm or 0.5" from the bore centerline to counter the effect of side thrust. more ... |
P111, P112, P310 Hybrid Transaxles Toyota transaxle's are very complex. The propulsion motor/generator, generator /starter, planetary gear-type torque splitter and continuously variable transmission, transaxle dampener, and final drive unit in a lightweight die cast aluminum case.
The components: Propulsion motor/generator is an synchronous AC design containing the uses Neodymium permanent magnets within the rotor.
Continuously Variable Transmissions have a low gear ratio and a high gear ratio with infinitely many ratios in-between. The advantage of a CVT is the ability to keep the engine RPM in it's optimum power output range for all operating conditions. A vehicle with a CVT transmission can be diagnosed with this software. Most Daimler Chrysler, Ford, GM, Honda, and Nissan CVT's use a drive belt and two variable size pulleys, as shown below, to deliver power to the transaxle final drive planetary gear set. The Toyota Prius, Ford Escape Hybrid, and Mercury Mariner Hybrid use a gasoline engine and two electric motor-generators (MG1 and MG2) connected to a planetary gear set called the "Power Split Device" to deliver power to the transaxle final drive planetary gear set. more... |
Cooling System The Prius contains two cooling systems, one for the engine heating system and the other for the electrical inverter / converter.
The system does share some similarities to a conventional gasoline engine. A mechanical water pump to circulate coolant through the engine, radiator to release the stored heat to the passing air, thermostat to regulate engine core temperature and coolant transport hoses. So far no differences, but when the gasoline engine is shut off it no longer generates heat for the passenger compartment. Also the engine cools off which leads to fuel wasting cold restarts. To solve this problem 2004 and new Prius vehicles use a coolant storage tank, a three way water valve and two electric water pumps to circulate coolant. more...
Coolant Storage
The North American Version of the Prius has a very unique feature to assist the warm-up phase of the vehicle. Toyota calls it a thermo-jar, this component is installed within the left front fender, constructed using a stainless steel thermos manufactured for Denso by Tiger Corp a well known japanese thermos manufacturer. The thermo-jar holds 2.5L of engine coolant and is capable of retaining waste engine heat for over one full day. The purpose of adding this component was to attain the emission certification as AT-ZEV Advanced Technology Zero Emissions Vehicle. more...
Hybrid Cooling System
Heat comes from motor magnetic induction and from current flow through the inverter/converter. Converting the generated power from AC to DC, DC to AC an DC to DC current is only necessary for battery / drive motor interactions. The coolant used in this system is the same as the engine but they do not intermix, containing a separate reservoir, coolant pump, temperature sensors, radiator and hoses.
Efficiency losses are further reduced by increasing system voltage while keeping current flow constant. more...
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Panasonic EV Energy (Batteries) Panasonic EV Energy has been building batteries since 1996 with partner Matsushita Electric and Toyota. Ninety percent of the EV R&D is carried out by Matsushita Electric , who specializes in Ni/MH battery and sub technologies. They supply battery technology for most of the production EV's available on the market. Battery density has been improving steadily this includes mass reduction, storage capacity, design and life expectancy. The first generation battery packs weighed 75 Kg (165lbs) and a volume of 75L, this pack contains 40 cylindrical cell modules containing 240 cells. This was called an upright design that took up significant trunk space. The second generation battery is a totally different design, a rectangular prismatic structure. This design change allowed a mass reduction of 25% and a volume reduction of 15%. The battery contained 38 modules compared to the previous 40 cell modules. This change allowed the interior space to include a rear split seat . The third generation battery pack... more... |
IGBT High Voltage Controllers Insulated gate bi-polar transistor. IGBT
Toyota develops and uses their own design of semiconductor switching elements.
The IGBT is a recent invention. The "first-generation" devices of the 1980s and early '90s were relatively slow in switching, and prone to failure through such modes as latchup and secondary breakdown. Second-generation devices were much improved, and the current third-generation ones are even better, with speed rivaling MOSFETs, and excellent ruggedness and tolerance of overloads.Availability of affordable, reliable IGBTs is a key enabler for electrc vehicles and hybrid cars. Toyota's second generation hybrid Prius has a 50 kW IGBT inverter controlling two AC motor/generators connected to the DC battery pack. more... |
Propulsion / Motor / Generator / Starter
The propulsion motor/generator is an ac synchronous design with eight sets of rare earth Neodymium calssification (NZ50) integrated in the rotor. THS-I or Generation one output was 33kW (45 ) hp @ 1040-5600 Rpm THS-II or Generation two output was increased by more than 50% to 50kW (68) hp @ 1200-1540, there was also a corresponding torque yield increase of 50 N.m (33 ft.lb) The motor now operates at voltages up to 500 volts this is almost double previous generation one units.
Increasing the voltage was made possible with the integration of new high voltage power control unit circuits. The new control unit allowed the voltage to be increased from 202 volts to 500 while keeping current flows constant. Voltage is increased from the base voltage to the higher voltages with the aid of computer control strategies that measure the present work load. It was found that by increasing the voltage and reducing the current flow reduced the heat significantly and reduced energy loss.
Motor generator unit
revolutions are monitored very accurately using a "resolver" a 48 tooth /sensor wheel that creates a digital signal that is used by the control unit and is a PID on the vehicle serial data line.
The generator / starter is also an ac synchronous motor. Generator speed range for generation on THS-1 is 6500 Rpm, generation THS-2 has increased the speeds to 10,000 rpm. The higher Rpm allows more power to be available to the motor improving vehicle start up and acceleration.
Regenerative Braking
Brakes produce kinetic energy, the result is heat. A hybrid design incorporates vehicle standard vehicle braking with the electric motors. By loading the generator the drive wheels are forced to slow down and the mass of the vehicle in turn drives the generator. This allows the system to top up the battery state of charge. A separate brake ECU uses data from the PCM and HV ECU to perform the deceleration calculations that determine the available energy recovery rate. more... |
Powertrain Evolution |
| Engine (1NZ-FXE) |
Gasoline, Atkinson cycle, DOHC, In Line 4 Valve per Cyl.Intake VVT-i electronic fuel injection, liquid cooled |
| Generation |
1st Gen1998 |
1st 2001 |
2nd Gen 2004 |
| Bore & Stroke & Displacement |
75.0 mm |
84.7mm |
1496cc |
| Maximum power kW, (HP), RPM |
43(58)@4000 |
543(71)@4500 |
57(76)@5000 |
| Maximum Torque N.m(lb.ft) RPM |
102(75)@4000 |
115(85)@4200 |
115(85)@4200 |
| Expansion Ratio |
13.5:1 |
13.0:1 |
13.0:1 |
| Intake Valve Timing
|
| Opening BTDC° |
10° to -30° |
18° to -25° |
18° to -15° |
| Closing ATDC° |
80° to 120° |
72° to 115° |
72°to 105° |
| Exhaust Valve Timing
|
| Opening BTDC° |
32 |
34 |
34 |
| Closing ATDC° |
2 |
2 |
2 |
| Fuel System |
Electronic Fuel Injection (MAF) |
| Drive or Propulsion Motor |
AC Permenant Magnet synchronous, liquid cooled |
| Max Power, kW (PS) @ RPM |
30,(41)
@
940-2000 |
33 (45)
@ 1040- 5600
|
50,(68)
@1200-1540 |
| Max Torque N.m(lb.ft) RPM |
305 (225)
@ 0-940
|
350(258)
@ 0-400 |
400(295)
@ 0-1200 |
| System Maximum Voltage |
275 Volts |
275 Volts |
500 Volts |
| Combined Powertrain Output
|
| Maximum Output kW (PS) |
------ |
74(101) |
82(113) |
| Maximum Torque N.m (lb.ft) |
------ |
421(311) |
478(353) |
|
