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Prius Primer L. David Roper Professor Emeritus of Physics Virginia Polytechnic Inst. & St. Univ.

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Presentation on theme: "Prius Primer L. David Roper Professor Emeritus of Physics Virginia Polytechnic Inst. & St. Univ."— Presentation transcript:

1 Prius Primer L. David Roper Professor Emeritus of Physics Virginia Polytechnic Inst. & St. Univ.

2 Toyota Prius II ($21,000 to $30,000) A serial-parallel (full) hybrid (gasoline + electric) car

3 Prius Under the Hood EngineGenerator/motor Motor/generator Inverter Unit Fuse box with jump-start terminals 4 cylinder engine + electric motors = 6 cylinder engine performance. Hood brace Aluminum hood

4 Toyota Prius Motion selector Power button 8-feet ladder (not included) 2005 Fastest selling car in the U.S. Energy-Use 7” Display generator/motor Motor/generator VoltsTraction battery 12-Volts system-start/accessories battery “Key” fob slot

5 Prius Cargo Areas Small-items storage Back seats down Pull up extra space cover to make room for large suitcases. False spare tire & tools are under storage bin. Remove storage bin to get to 12V system-start/accessories battery on right side. Cargo cover 3’ 3” by 5’ 9” long

6 Prius Cargo Area Split back seat False spare tire & jack Cargo box & tire tools Front tow hook. Maps & bottle holder (both sides) Traction Battery Battery safety plug Small storage bin 12-Volts system-start/accessories battery

7 Toyota Prius Motion selector To start hybrid system, depress brake pedal before pressing Power once. Smart Start option: fob can be anywhere in the car. Smart Entry Also, audio.

8 7” Multi-Display Can be turned off (Display/Screen off) Has daytime and nighttime settings (dark background). Nighttime settings are in effect when lights are on, except when panel dimmer wheel is set to maximum. Can save settings for different users. Outside temperature is shown when energy display is active. Several display controls are on the steering wheel. Holding a button done turns on and off. Audio and air conditioning controls can be displayed, but some are also available on the dash and steering wheel.

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10 Rear tie down hooks; can be replaced by tow bar for rear bicycle rack. Emissions controls Oil filter Oil drain Note the flat plates to cut down on drag at high speeds. Front of vehicle Whats Underneath.

11 Toyota Prius Specifications Engine: cc, 4 cyl, 16 valves, VVT-i, ETCS-i, 76 hp ( rpm, compression ratio 13.0/1 Motor/generator: 500-Volts Permanent Magnet rotor AC Sync, 67 hp ( rpm Generator/motor: 500-Volts PM AC Sync, 34 hp (25 kW). Starts engine at 1000 rpm when needed. Can turn up to 10,000 rpm. A crucial part of the Electronic Continuous Variable Transmission (ECVT). Power Split Device: fixed gears that connect engine, motor/generator & generator/motor to provide the ECVT by electronic control. Traction Battery: Volts NiMH, 38 kW (51 hp) 5 networked hybrid system computers. Net Hybrid System power: 110 hp (82 kW) Heated coolant when starting Regenerative coasting and braking Realistic Mileage: mpg ( EPA: 60 city/51 not so ) 1 hp = kW 1 kW = 1.34 hp

12 Toyota Prius Specifications Weight: 2890 lb (~$10/lb with all options.) People and cargo capacity: 825 lbs (374 kg) Turning radius: 17 feet (Turns around within most streets.) Coefficient of drag: 0.26 (Only Honda Insight is lower.) Ground clearance: 4.9 inches (Not an SUV!) Height/width/length: 58.1/67.9/175 inches Electric: reverse motion, initial motion, climate control, steering, braking Interior: size of Toyota Camry Exterior: size of Toyota Corolla 12-Volts battery to start system & for accessories Tires: P185/65R15 Goodyear Integrity (low snow traction) 11.9 gal = miles per tank Uses 87 octane gasoline with up to 10% ethanol 0-60 mph in 10.1 seconds Top speed: 103 mph

13 Toyota Prius Specifications Air bags: 2 standard; 4 more as extras Energy-use, climate control and audio 7” display Tilt steering wheel Warranty: Basic: 3 yrs/36 kmi; Hybrid system: 8 yrs/100 kmi; Power train: 5 yrs/60 kmi; Rust-through: 5 yrs/unlimited mi; Accessories purchased with car: 3 yrs/36 kmi. Road side assistance and hazard insurance: 3 yrs/36 kmi Excellent navigation system and wireless Bluetooth phone connection as an option Seats are cloth or leather. Toyota has seat covers that are easy to install, with 2 map pockets for each front seat. (2006 model offers leather seats.) Classified as a mid-sized car.

14 Standard Features ($23,000) Micron-filter 201V electric air conditioner Power windows and door locks Heated outside mirrors and rear window Remote keyless entry Cruise control 6-speaker AM/FM/CD stereo Anti-lock brakes with electronic assist Traction control Multi-stage dual front air bags Illuminated sun-visor mirrors Self-leveling headlights Much storage space for small items.

15 Optional Features ($30,000) Front side and roll-sensing curtain air bags (front & back) Intermittent rear window wiper Key-less entry & start system (Smart Key) Vehicle stability control (Automatically controls brakes and hybrid system to prevent skidding when cornering on a slippery road or turning steering wheel abruptly. There is a slip-indicator icon in dash display.) High-intensity discharge headlamps Integrated fog lamps Homelink remote transmitter on auto-dimming mirror 9-speaker AM/FM/Cassette/6-CD stereo Immobilizing security alarm Floor and cargo mats; cargo net DVD Navigation system with voice activation Bluetooth wireless telephone connection

16 How Does It Achieve Fuel Efficiency? Because of electric motor assistance, the engine can run at peak efficiency more often. Electric motors are more efficient than gasoline engines over a larger range of rpm. The high voltage (500 V) for the motors/generators cuts down resistance loss. Deceleration and braking recharge the battery. The engine shuts off when not needed; for example, at stops and down hill. It then instantly restarts when needed. The engine receives hot coolant before starting, which enhances efficiency. Starts at 1000 rpm. The body is aerodynamically designed for low drag (0.26 drag coefficient).

17 Aerodynamics Underneath

18 Air Flow Around a Prius II

19 Location: Minnesota. Mix of city, suburban & highway driving Prius mpg Versus Month of Year 12 mpg difference between January and June driving in Minnesota. I guess 6 in Virginia.

20 Total Cost of a Prius The Prius hybrid system has no clutches or friction bands to wear out, contrary to the case for a gasoline car. There is nothing in the hybrid system to wear out except gears and bearings. The hybrid system should last for at least 500,000 miles if properly maintained. The engine is not stressed nearly as much as one is in a gasoline car. So, the engine should last for over 200,000 miles if properly maintained. The electric motors are brushless designs, so they should last for 500,000 miles if properly maintained. Regenerative braking greatly delays brake pad and rotor wear. So, the brakes should last for more than 100,000 miles. So, cost effectiveness of driving a Prius is as much due to the longevity of the hybrid system, the gasoline engine, the electric motors and the brakes as it is due to higher mpg. As important as high mpg is the low emissions of a Prius compared to any gasoline car. High mpg for a gasoline car does not equate to low emissions. A gasoline car optimized for low emissions usually has high mpg, but it sacrifices performance. Performance is not sacrificed in a Prius.

21 How Does the Prius Achieve Low Emissions? Since it uses less fuel, it produces less emissions. Because of electric motor assistance, the engine can run at peak efficiency more often, which makes emissions lower. The engine design (Atkinson cycle, cylinder shape, fuel injection and variable firing timing) is aimed at low NO x emissions. The engine shuts off when not needed; at stops and going down hills. It then instantly restarts when needed. This reduces emissions. The engine receives hot coolant before starting, which reduces NO x emissions. Has bladder-lined gasoline tank to eliminate escaping fumes. (Makes it difficult to manually calculate mpg.) Has lowest emissions rating of any gasoline vehicle.

22 Bladder-Lined Gasoline Tank Gasoline tank has a plastic bladder liner, which expands and contracts as gasoline is added and used. This minimized evaporative losses into the environment. The bladder can become less flexible in cooler weather, which will keep you from putting a full 11.9 gallons in the tank. The bladder makes the fuel gauge (“guess” gauge) not very accurate. Always refuel when or before the last marker shows on the fuel gauge. Filling a nearly empty tank with less than 3 gallons will not register on the fuel gauge.

23 Drive it another 100,000 kms and watch these differences grow. Based on 10- years use and 100,000 km (62,000 miles).

24 Prius Life-Cycle Carbon Dioxide Emissions 1 km = 0.62 mi: 20,000 km = 12,400 mi; 100,000 km = 62,000 mi

25 Toyota Prius A series-parallel full hybrid (gasoline + electric) car The power split device (PSD) can be regarded as an asymmetrical differential, for which the two motor/generators are analogous to the two wheels that connect to a conventional differential and the engine is analogous to the crank shaft (reduction gears in the Prius) going into a conventional differential. DC AC AC AC->DCDC->ACAC->DCDC->AC Engine shaft goes through MG1 shaft to the planetary carrier of the PSD.

26 Toyota Prius Power System Power-split device

27 Prius Power System Large motor/ generator Power Split Device Small generator/ motor

28 Toyota Prius Power Split Device Power Split Device: 78 teeth in ring gear, 30 teeth in sun gear, 23 teeth in each planet/pinion gear. (Also called planetary gears, epicycle gears and trans-axle.)

29 Prius Power Split Device (PSD) Sun gear: MG1 Ring gear: MG2 & Wheels Planet/pinion gears Planetary carrier: Engine Notice how small it is! Effectively, this and the electronics comprise the continuously variable “transmission” of the Hybrid Synergy Drive.

30 Toyota Prius Hybrid Synergy Drive Control This contains the DC/AC inverters. Notice the orange power cables to the traction battery and to the motor/generator and the generator/motor. The 5 computers are located at different places in the car. It is a “drive by wire” system similar to modern airplanes.

31 Effective Hybrid Transmission The Prius does not have a "true" transmission, instead the gear ratios are fixed. One can accelerate from zero to the maximum speed in one gear; however engine torque is not multiplied by a transmission. This lack of low-end engine torque is replaced by a large electric motor/generator and a smaller generator/motor, which are connected to the engine in a planetary gear arrangement (Power Split Device). The onboard computer shifts power from the engine and to and from (using the traction battery’s power) the motor/generators, determining the most efficient use of the engine and/or the electric motor/generators based on driving conditions, accessories in use and when to charge the battery.

32 Movement of Power-Split Device Gears Moving in ReverseStarting Engine at Rest Accelerating & Hill ClimbingCruisingCoasting & braking Two cases when the engine is not running.

33 Toyota Prius Volts Battery Under the backseat with cooling vent beside the seat. 28 sealed modules of six NiMH 1.2-Volts cells per module. 6.5 Amp-hours. 28 sealed modules of six NiMH 1.2-Volts cells per module. 6.5 Amp-hours. Weighs 86 lb (39 kg). Highest output per weight in the world (1300 W/kg). Weighs 86 lb (39 kg). Highest output per weight in the world (1300 W/kg). Charge ranges from 40% to 80% of maximum, usually 50% to 70%. Charge ranges from 40% to 80% of maximum, usually 50% to 70%. Alkaline electrolyte is a gel that will not leak, even in a collision. Alkaline electrolyte is a gel that will not leak, even in a collision. Sealed in a steel case electrically isolated from battery terminals. Sealed in a steel case electrically isolated from battery terminals. Each module is vented underneath in case of overcharge gas release. Each module is vented underneath in case of overcharge gas release. All components are recyclable. All components are recyclable. Incentive of $200 for each battery returned for recycling. Incentive of $200 for each battery returned for recycling. Guaranteed for 8 years or 100,000 miles (10 years/150,000 in California). Guaranteed for 8 years or 100,000 miles (10 years/150,000 in California). Battery safety plug/fuse 1.31 kWh

34 Prius Battery Module & Safety Plug/Fuse Note the six NiMH 1.2 Volts cells. Note the six NiMH 1.2 Volts cells. Note the electrical connectors on the ends. Note the electrical connectors on the ends. Note the overcharge gas vent at the bottom left. Note the overcharge gas vent at the bottom left. Battery safety plug and fuse

35 Charging the Battery at Rest Stop the car and set the parking brake firmly. Firmly press the brake pedal. Set the motion selector to “D”. Press the accelerator pedal most or all of the way down. (Only the small generator/motor is charging the battery, since the large motor/generator is at rest with the wheels. This is the reverse of starting the engine at rest.)This is the reverse of starting the engine at rest. The battery will be fully charged in about 5 minutes or less. You might want to do this before climbing or at a rest stop on a long, steep hill for which the battery eventually will run out of charge and, thus, does not supply power to the motor.

36 Prius 12-Volts Battery Turns the hybrid system on by actuating contact relays. Turns the hybrid system on by actuating contact relays. Provides power for the five computers and the networks in the car. Provides power for the five computers and the networks in the car. Provides power for the accessories. Provides power for the accessories. Charged by the traction battery. Can be jump-started by other 12-Volts batteries by using terminals in the fuse box under left side of hood. (When jump-starting other vehicles, best to charge the other battery from the Prius battery, disconnect the jump and then start the other vehicle.) If the 12-Volts battery becomes discharged, you cannot move the Prius with its front wheels on the ground, because it is in PARK. Charged by the traction battery. Can be jump-started by other 12-Volts batteries by using terminals in the fuse box under left side of hood. (When jump-starting other vehicles, best to charge the other battery from the Prius battery, disconnect the jump and then start the other vehicle.) If the 12-Volts battery becomes discharged, you cannot move the Prius with its front wheels on the ground, because it is in PARK. Will gradually discharge when car is dormant. Decrease the discharge by turning off the smart-key switch under the steering wheel. For longer dormancy periods use a BatteryMINDer (https://www.batteryweb.com/batteryminder.cfm) or disconnect the cable from the positive jump-start terminal in the fuse box on the right under the hood (and lose memory settings). You can buy a VW solar battery charger on eBay for parking the Prius outside for long periods. Will gradually discharge when car is dormant. Decrease the discharge by turning off the smart-key switch under the steering wheel. For longer dormancy periods use a BatteryMINDer (https://www.batteryweb.com/batteryminder.cfm) or disconnect the cable from the positive jump-start terminal in the fuse box on the right under the hood (and lose memory settings). You can buy a VW solar battery charger on eBay for parking the Prius outside for long periods.https://www.batteryweb.com/batteryminder.cfm Batteries maintenance: Batteries maintenance:

37 Locations of Prius Batteries This is a wrecked Prius that will be shown in more detail later. Notice the orange power cable on the left side and the small 12-V battery at the right rear. There are connections for the 12-V battery under the hood for jump starting. Traction battery Battery cooler

38 Prius Gasoline Engine cc, 76 hp ( rpm, 82 lb-ft ( rpm, 4 cyl, 16 valves, VVT-i=Variable Valve Timing- intelligent, ETCS-i=Electronic Throttle Control-intelligent, compression ratio 13.0/1 Aluminum alloy Atkinson/Miller cycle: short compression stroke (Valves do not close until after the end of expansion stroke.) Offset crank shaft allows straight down power stroke. 3 liters of Heated coolant stored near boiling point for 3 days used to preheat the engine before starting. Engine stopped at precise point in cycle to minimize stress when restarted. Engine is cranked to 1000 rpm and oil pressure established before spark is applied first to 2 of the 4 cylinders. This takes about ½ second. Variable valve timing to optimize efficiency. Unique air intake system to reduce manifold friction.

39 2004/6 Prius Gasoline Engine

40 Prius Power vs rpm Small motor extends to 10,000 rpm. One can see why the electric motor is important for power at all, but especially low, rpm.

41 Prius Power Train Performance

42 When Does The Engine Run? To move the vehicle. To charge the traction battery. To warm up for lowest emissions. To provide heat for passengers if needed. To power the air-conditioner compressor if needed. To run hybrid-system diagnostics. Prius misconceptions:

43 Smooth Acceleration

44 Regenerative Braking ECB = Electronically Controlled Braking System which controls the coordination between friction braking and regenerative braking, which preferentially uses regenerative braking. Recovers up to 90%? of the possible recoverable energy down to 7 mph. Each wheel’s brake is independently controlled electronically. Hydraulic backup brake control is on the front wheels.

45 To “B” or not to “B” The “B” selection on the motion selector causes the engine to turn without firing, using air compression and engine friction to turn some of the vehicle’s motion energy into heat. Some of the motion energy still goes into charging the battery, but not as much as when “B” is not selected. (After using “B” you will need to reset the cruise control.) When might one use “B”?: Be sure to move the motion selector back to “D” after using “B”, or you will decrease the mpg for normal driving. When the battery is fully charged: all battery bars are green and you want to slow down. When the battery is fully charged: all battery bars are green and you want to slow down. When a sign says “Trucks use low gear”. When a sign says “Trucks use low gear”. When going down a steep hill and the cruise control cannot hold the car to less than 5 mph above the speed setting. When going down a steep hill and the cruise control cannot hold the car to less than 5 mph above the speed setting. B = engine braking.

46 Constant Driving in B Some owners of Prii drove all the time in B. I know of two examples of this. They complained that the mpg was low. The reason is that the engine spins at high rpm, without firing, going down hills and when braking, instead of turning off. It is an easy mistake to make, since the B position is straight down from the rest position of the movement selector. One has to move it to the left and then down for D.

47 Towing a Prius Do not leave the front wheels on the ground when towing if hybrid system is not on and in neutral. Doing so could damage the hybrid system. Towing hook for front is in cargo storage box; screw it into covered hole in front bumper. Best to use a flat-bed tow truck and raise the front wheels before pulling the Prius onto the truck. Two tie-down hooks are under the back, do not use them to tow the Prius from the back. Can be replaced by a tow bar for a bicycle rack. Do not allow towing or tie-down chain attachments to car frame; always use the front tow hook and the back tie-down hooks! If it must be towed with front wheels on ground, turn on hybrid system and put hybrid system in “N” and have someone guide it and work the brakes. Towing by Prius: should not be done! (Some have towed small trailers with a tow bar.)

48 Towing a Prius Best way to put a Prius in Neutral to tow it with all wheels on the road: Press the power button twice without pressing the brake (IG ON mode). Put foot on brake and shift into Neutral. Hold the motion selector in Neutral for 3 seconds. Then it can be towed with the wheels on the road.

49 Prius as a Powerful Computer Network There are many Local Area Networks (LANs) connecting 5 computers in the vehicle. (All new vehicles have powerful computers and networks; hybrids take that one giant step further.) The LANs communicate through super networks. E.g., the climate-control network and the braking network communicate with the power-train network. For the keyless entry & start option, the vehicle’s main computer powers up using the 12-Volts battery when you approach the vehicle. When you press the Power button the other computers and LANs are turned on, powered by the 500-Volts traction battery. Pressing on the accelerator activates the motive networks according to the movement selection.

50 Prius as a Powerful Computer ECU = Electronic Control Unit = 32-bit computer See and SOC = State of Charge of traction battery

51 What Happens When Your Press on the Accelerator? 1.The motive power demand from depression of the accelerator pedal (not the "throttle") goes to the Hybrid-ECU. 2.The Hybrid-ECU also gets power demand from the battery-ECU ("charge me" or "discharge me"), the air conditioner, etc. 3.The Hybrid-ECU decides where to get this power from, the ICE or the battery. If it wants power from the ICE, it sends a power demand to the Engine-ECU. 4.The Engine-ECU figures out how to get that much power from the ICE at the best efficiency and tells the Hybrid-ECU its choice of spin (torque) so that MG1 can be controlled appropriately. 5.The Hybrid-ECU controls MG2 to add or subtract power at the final drive as necessary. 6.Electrical power generated or consumed by MG1 and MG2 will result in a net surplus or deficiency that is provided or absorbed by the battery. In theory, this will correspond to the battery- ECU’s charge demand (see 2 above) but in practice there is much lee-way for things to come out differently and other power demands still to be met exactly. In a sense, the battery makes up the error.

52 15 Computers in a “Loaded” Prius

53 Prius Safe Computer “Hacks” Turn off the backup beeper: – Cycle ODO/TRIP, stopping on ODO. – Power off. – Power on, within 6 seconds, hold ODO for at least 10 seconds. – While still holding ODO shift into Reverse and back into Park. – "b-on" shows on display, press ODO to cycle to "b-off". Allow navigation destination parameters to be set while moving:navigation destination parameters – Press the "Menu" button (hardware button). – Press the "Voice" icon on the display. – Press the upper left corner of the display, where the speaker icon is. – Press the lower left corner. – Press the upper left corner again. – Press the lower left corner again. – The screen should change to a diagnostic screen. – Hold the "Override" button for several seconds until it changes to black and a beep is heard. – Press the “Back” button. – This will be in effect only until the Power is turned off. – Warning: do not play with things on this screen that you don't know about!

54 Prius Electric Safety Battery is placed between the frame rails and in front of the axle where it is least likely to be damaged in an accident. High-voltage cables are metal shielded, orange colored and placed away from possible damage in collisions. Battery power is cut off when an air bag deploys and other collision sensors activate. Vehicle does an electric system check when powered up. Toyota provides special pamphlets for emergency personnel: See See prius/message/8834 for information about the difficulty of getting shocked by a Toyota Prius.http://autos.groups.yahoo.com/group/toyota- prius/message/8834

55 Prius Electric Safety A ground-fault monitor keeps the car frame from being accidentally charged. Battery shut-off relays. Fused safety plug: Pulling it out turns off the high voltage.

56 Hybrid Reliability Consumer Reports listed Toyota Prius and Honda Civic hybrid among the most reliable vehicles for 2005 models. Toyota Prius traction batteries regularly last for over 200,000 miles driving. Should last 15 years. The Toyota Synergy Hybrid System is much simpler mechanically than gasoline vehicles (no transmission). The complexity is in the electronics, which is highly reliable. Engine does not always run, standard brakes are not always used for stopping and there is no starter or alternator to wear out. Brakes should last 100,000 miles. Early Toyota Prii had a software problem that caused the engine to stop. (EV still worked to move vehicle.) A software download fixed the problem after 68 known incidents of engine stalling. The modular design of the Toyota Prius allows defective modules to be quickly diagnosed and replaced. Prius Maintenance: Car Talk Prius excellent review: I have had one 2005 Prius recall to replace the steering column.

57 Prius I Engine Efficiency Peak efficiency is at about half power. The “sweet spot” rpm 2200 rpm 3000 rpm Better to floorboard than to creep! Worst efficiency is at low power.

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59 Differences in Driving a Prius Power button starts the hybrid system, rather than a key. The “key” fob must be somewhere in the car for “smart start” option; in the fob slot otherwise. Engine does not start immediately after system power is turned on; it starts about 7 seconds later to warm up the engine, then shuts off a few seconds later if not needed. Engine turns off at stops and when going down hills; also it does not provide power for backing up. Creep is built in at stops, provided by the electric motor. It is increased on an upward and downward slope to hold car in place. It can be turned off by pressing the brake pedal or putting the movement selector in the Neutral position. Slight sounds occur after stopping the car as hot coolant is pumped into the thermos container. Electric whine during slows starts and braking. Special Brake position of movement selector to cause engine braking.

60 How to Drive a Prius Efficiency Use “Pulse Driving”: – Accelerate rapidly at about half power, because a brief medium engine load uses less fuel than a prolonged low engine load. Best is when only the engine is moving the vehicle. – Decelerate slowly well ahead of the stopping point to maximize brake regeneration. Best is when neither engine nor motor is moving the vehicle and the battery is not charging (gliding). Keep the vehicle in a garage during cold weather because a cold vehicle reduces brake regeneration. Keep tire pressure at recommended levels or higher to reduce tire friction losses. I up them by 2 psi. Steady 55 mph (55-60 mpg) is the point of peak efficiency. 75 mph: mpg. For every mph faster than 55 mph, fuel economy drops by about 1 percent.

61 Driving for Lowest Emissions and Highest MPG MPG is much lower for the first 5-10 minutes of driving, because the engine is run until it reaches the best temperature for the lowest emissions. So, combine short-trips to save gasoline. MPG, as for all new cars, increases as the miles are driven up to about 10,000 miles. Higher tire pressure=higher MPG. Maximum pressure for the tires=44 psi. (Standard=35 front/33 back) Should be 2 psi greater in front than in back. I use 38/36; many use 42/40. Use cruise control when possible to get best MPG.

62 MPG versus MPH for Prius Note the big decrease in mpg above 70 mph!


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