Toyota introduces 2012 Prius Plug-in Hybrid

2012 Prius Plug-in hybrid. Click to enlarge.

Toyota introduced the production Prius Plug-in Hybrid at the Green Drive Expo in Richmond, CA, as the newest member of the expanding Prius Family. With a starting base price of $32,000 (before rebates), the production Prius Plug-in features a 4.4 kWh Li-ion pack enabling an electric range of up to 15 miles (24 km) at speeds of up to 62 mph (100 km/h), according to Toyota. (The advanced grade plug-in Prius carries a base price of $39,525.)

With seating for five, the 2012 Prius Plug-in hybrid is expected to achieve a manufacturer-estimated 87 mpge (miles per gallon equivalent) in combined driving and 49 mpg in hybrid mode, or 2.7 L/100km equivalent and 4.8 L/100km, respectively. The production plug-in hybrid has a number of key changes from the 125 prototype demo units that were deployed in the field for testing and customer feedback. Toyota applied experience from that test phase, along with input from participants, to finalize engineering and improve features for the production model. Changes include:

• Completely new battery design. Toyota’s goal was to reduce the cost, weight and volume of the pack from the NiMH system used earlier. The Li-ion pack is almost half the weight of the earlier pack, and so much more compact that the dimensions of the plug-in Prius are the same as those of the iconic liftback—i.e., there is no cargo penalty for plug-in capability.

  Although the gross energy capacity of the pack is reduced (4.4 kWh), the EV range is increased. At a media preview of the introduction Toyota declined to be more specific as to the enabling mechanisms, citing some final issues that needed to be worked through by the battery supplier.

• EV mode is now user-selectable. The demo units defaulted to EV mode.

• Maximum EV speed is up to 62 mph.

• Maximum electric range is 15 miles

• A charge timer allows you to set charge start and finish time. (According to Toyota, one of the things they discovered during the demo program was that the battery packs responded better if they were allowed to rest prior to recharging.)

• The charge port is moved from the front driver-side fender to the rear passenger-side fender, while the charger is now moved back with the smaller battery pack. The result is a shorter distance from the charge port to the charger/battery, reducing weight.

• The charging cable is redesigned to be more flexible and lighter.

• Entune with plug-in hybrid applications.

• Other cosmetic and convenience features.

The 2012 Prius Plug-in Hybrid retains the Hybrid Synergy Drive of the standard Prius model and will seamlessly switch into hybrid operation at a pre-determined state of battery charge. The hybrid system includes the 1.8-liter engine, third-generation hybrid transaxle, and power control unit (PCU), now supplemented by the new Li-ion battery and on-board charging system. Net hybrid system output is 134 hp, and the plug-in achieves a California SULEV (with Enhanced AT-PZEV) rating, or Tier 2 Bin 3 Federal.

Engine. The 2ZR-FXE 1.8-liter DOHC 16-valve VVT-i engine develops 98 hp (732 kW) @ 5200 rpm, and 105 lb-ft (142 N·m) @ 4000 rpm. Key features of the engine include the Atkinson combustion cycle; Electronic Throttle Control System with intelligence (ETCS-i); exhaust heat recirculation to heat engine coolant to reduce time to reach operating temperature (shortening the time until the gasoline engine can stop); and cooled exhaust gas recirculation to reduce cooling loss and pumping loss. With lower exhaust heat, heat efficiency was enhanced, and consequently, fuel efficiency was enhanced as well.

The engine also uses an electrically driven air conditioning compressor and water pump to reduce mechanical losses. The electrically driven water pump allows coolant flow rate to be controlled with greater precision based on vehicle conditions for better fuel efficiency. Cabin heating and air conditioning can also continue operating with the engine stopped.

Hybrid transaxle. MG1 (motor-generator 1) is an air-cooled permanent magnet motor rated at 56 hp (42 kW). MG2 is an air-cooled permanent magnet motor rated at 80 hp (60 kW), and develops 153 lb-ft (207 N·m) of torque. MG2 runs at 13500 rpm maximum.

The multifunction gear combines a power split planetary gear set ring with a speed reduction planetary gear set ring, and incorporates parking gear and counter drive gear. The differential ratio is 3.267.

The power split planetary gear set comprises two sets of planetary gears; there are no clutches, bands, valves or hydraulics. The sun gear is connected to MG1 (acting as the generator); the planet carrier is connected directly to the engine, and the ring gear is connected to the counter gear.

The speed reduction planetary gear set’s sun gear is connected to MG2 (acting as the motor), the carrier is grounded and the ring gear is connected to the counter gear.

Power Control Unit. The PCU features a compact inverter design with direct cooling of IGBT transistors, and converts DC to 3-phase AC to drive MG1 and MG2. Controlled by the hybrid ECU, the PCU boost converter raises 201.6 VDC up to 650 volts DC. (The MG ECU is packaged within the inverter assembly.)

Charger. The on-board charging system accommodates single pulse DC 110/220 volt input, and is compliant to SAE J1772 standards. Maximum input current is 12A, and maximum output is 2 kW. Charging time at 110V is about 3 hours; charging at 220V cuts that in half.

Even with the addition of the new onboard battery charging system and larger 176-lb Li-ion battery pack, the 2012 Prius Plug-in Hybrid weighs just 123 lbs more than the standard Prius Liftback, due to weight-savings techniques applied elsewhere. As a result, driving performance for the 2012 Prius Plug-in Hybrid will be similar to the standard Prius.

Leviton, an approved provider of Level 2 (240V) home charging stations, has developed a residential program exclusively tailored for Prius Plug-in customers. The program will include a one-stop solution for home charging stations, installation services for 120V and 240V applications, and dedicated support for Toyota customers. The program will also offer Level 2 (240V) 16-amp and 30-amp home charging stations designed exclusively for the Prius Plug-in (UL-certified). Pricing starts at $999 for Level 2 (240V). Prius Plug-in customers will be able take advantage of Leviton’s special pricing starting early October.

Driving modes. The Prius Plug-in offers a user-selectable EV mode and two hybrid modes: Eco and Power. In EV mode, the hybrid ECU operates the vehicle using only MG2 if required conditions—such as sufficient battery state of charge and vehicle speed within ECV mode range—are satisfied.

Eco mode maximizes fuel savings across all driving conditions. It modifies or smoothes out the electronic throttle control program to reduce throttle response (throttle opening reduced to a maximum of 11.6%) and modifies air conditioning operation. As an ancillary benefit, it improves performance in low-traction conditions such as ice and snow because the reduced output helps to minimize wheel slippage. EPA label calculations do not include Eco mode.

Power mode increases throttle response in the middle range more than normal.

Displays and information. New multi-information display additions have been included in the Prius Plug-in. A new EV Drive Ratio display records the ratio of driving distance covered by EV power, and the Hybrid System Indicator shows possible EV driving range when in EV mode. An Eco Savings Record screen, new to both the 2012 updated Prius and the Prius Plug-in, allows drivers to measure their savings over a customizable pre-set comparison vehicle. The pre-set areas include fuel cost for a gallon of gas and miles-per-gallon average.

In addition to offering Entune, Toyota’s new multimedia system, available smartphone applications developed for the Prius Plug-in Hybrid include Charge Management, Remote Air Conditioning System, Charging Station Map, Vehicle Finder and Eco Dashboard.

Packaging and weight optimization. A key goal for development of the Prius Plug-in was to deliver the optimal balance of performance, range, economy, packaging and affordable price. The new model delivers extended EV range without sacrificing roominess for passengers or for luggage.

The compact Li-ion battery pack is installed under the rear luggage area. Width, height and length of the luggage space remain the same as the standard Prius. There is no reduction in rear seat passenger room from the standard Prius model, with seating for three and 36.0 inches of legroom that is on par with midsize sedans. Significantly, the biggest change in packaging from the Prius Plug-in Hybrid test-fleet model is the smaller, more efficient battery pack in the production model. The new battery pack is approximately one-half the weight of the demonstration-phase vehicle, yet provides about 15% more range.

The 2012 Toyota Prius Plug-in has a weight of 3,165 lbs (1,436 kg) versus 3,042 lbs (1,380 kg) for the standard Prius and 3,373 lbs (1,530 kg) for the Plug-in test-fleet model. Suspension tuning has been altered in accordance with the change in weight distribution from the standard Prius model.

The Prius Plug-in reduced vehicle weight in other areas as well. In place of a spare tire, the Prius Plug-in carries a tire-sealing kit and inflator. The trunk floor panel features a reinforced honeycomb design and is about half the weight of the standard model’s floor panel, while the charging cable stores in a compartment at the rear edge of the trunk floor. As on the standard Prius model, weight was saved through use of aluminum in the hood, rear hatch, front stabilizer bar and brake calipers and by using super high-tensile strength steel in the inner rocker panel, center pillar and roof reinforcement.

Externally, the Prius Plug-in inherits the standard model’s low coefficient of drag at 0.25 Cd. The current Prius had received more wind tunnel hours of testing than any other Toyota in history.

The new Prius Plug-in will be offered in two trim levels, standard and Advanced. The standard trim level provides all of the features of the standard Prius Two grade, plus some features from the upscale Prius Three and Prius Four grades. The Prius Plug-in Hybrid also makes standard a new touch-screen Display Audio and navigation system with rear backup camera and Toyota’s new Entune multimedia services.

Toyota’s 36-month/36,000 mile basic new-vehicle warranty applies to all components other than normal wear and maintenance items. Additional 60-month warranties cover the powertrain for 60,000 miles and against corrosion with no mileage limitation. The hybrid-related components, including the HV battery, battery control module, hybrid control module and inverter with converter, and the battery-charging system and cable/connector, are covered for eight years/100,000 miles (10 years/150,000 miles for CARB states).

The Prius Plug-in Hybrid will also come standard with Toyota Care, a complimentary plan covering normal factory-scheduled maintenance and 24-hour roadside assistance for three years or 25,000 miles, whichever comes first.

The Prius Plug-in Hybrid will be on sale in 14 launch states beginning this October through Toyota’s Online Order System at www.toyota.com. Vehicle deliveries begin in Spring 2012. The launch states include California, Oregon, Washington, Arizona, Maine, Massachusetts, Vermont, New Hampshire, Rhode Island, Connecticut, New York, New Jersey, Maryland, and Virginia. A national rollout is planned for 2013.

Source: Green Car Congress