★モーターと組み合わされるトランスミッションたち【EV】
Summary
TLDRこのビデオでは、電気自動車(EV)におけるトランスミッションの可能性を探求します。エンジンからモーターへの主な力の移り変わりにより、トランスミッションの役割は減少しつつありますが、EVにはトランスミッションが不要とは限りません。モーターはゼロRPMから最大トルクをすぐに得られるため、多段ギアは不要とされていますが、効率やパフォーマンスの向上を目的に、2段ギアやCVTなどのトランスミッションが提案されています。これにより、走行距離の延長や運転パフォーマンスの向上が期待されます。
Takeaways
- 🔌 エレクトロモーバーの電気モーターは、エンジンからモーターへの主な力の移行により、トランスミッションの役割が減少していますが、必ずしもトランスミッションが不要とは限りません。
- 🚗 トランスミッションはエンジンからタイヤにトルクとスピードを変速して伝達し、運転条件に応じてスピードを増減させる役割を果たします。
- ⚙️ ギアボックスの原則は、サイズの異なるギアの組み合わせに基づいており、大きなギアが小さなギアを回すと回転速度が増加し、小さなギアが大きなギアを回すとトルクが増します。
- 🏞️ 車両は発進や坂を上がる際にトルクが必要なため、トランスミッションはエンジンから車両のニーズに最も適したトルク、スピード、回転方向を変更するために使用されます。
- 🚀 電気モーターはゼロrpmから最大トルクをすぐに引き出すことができ、エンジンと比較して高いギアが発進のための必要はありません。
- 🚦 日本では都市部で60km/h、高速道路で120km/hの速度制限があるため、実用的な使用では更に高い速度を引き出す必要はありません。
- 🔧 エンジンを動力とする車は、エンジンの回転速度トルク特性と車両に必要な運転力特性の「ギャップ」を埋めるためにトランスミッションを必要とします。
- 🛠️ 現在市場に存在するEVはトランスミッションを必要とせずに運転できますが、モーターとドライブホイールの回転は同じ速度ではありません。
- 🔄 減速ギアは、ギアやその他のデバイスで回転速度を減速させてトルクを出力を調整するデバイスであり、減速比に反比例してトルクを出力できます。
- 🚗 EVはトランスミッションを必要とすることにより、モーターをより効率的な範囲で運転できるようにし、走行距離を延長し、ドライブトルクを増加して運転性能を向上させることができます。
- 🏎️ スポーツカー向けの2速トランスミッションは、ドイツの自動車バッハでの高速運転や起動時の強力な加速力を組み合わせるために使用されます。
Q & A
電気自動車(EV)にはなぜトランスミッションが必要ないと言われるのですか?
-電気モーターはゼロrpmから最大トルクをすぐに得ることができます。そのため、スタートや加速に必要な高トルクを生み出すためには、エンジンと比べて広い速度帯で運転できるため、トランスミッションは不要です。
トランスミッションが車に必要な理由は何ですか?
-エンジンのトルク、速度、回転方向は任意に変更できませんが、トランスミッションを用いることで、エンジンから車に最適なトルク、速度、回転方向を提供することができます。
電気モーターの特徴とは何ですか?
-電気モーターはゼロrpmから最大トルクを引き出せることが特徴で、エンジンと比べて広い回転速度帯で運転でき、トランスミッションを必要としないことが多いです。
現在市場に販売されているEVはどのようにしてモーターの回転をドライブホイールに伝えますか?
-多くの商業EVは減速ギアセットを使用して、モーターの出力シャフトの回転速度を低下させ、タイヤに伝えています。これは実用的な速度範囲外であり、効率的ではありません。
減速ギアとは何ですか?
-減速ギアはギアやその他のデバイスを用いて回転速度を低下させ、トルクを出力を調整するデバイスです。逆に回転速度を低下させると、出力されるトルクはその分だけ増加します。
EVがトランスミッションを必要とする理由は何ですか?
-モーターはrpmが上昇すると効率が低下するため、マルチステージギアシフトを用いることで効率を高め、巡航距離を延ばすことができます。また、ドライブトルクを増やして運転性能を向上させます。
トランスミッションを装備することの利点は何ですか?
-トランスミッションを装備することで、モーターをダウンサイジングでき、補助機器もダウンサイジング可能でコストを削減できます。また、バッテリーのスペースを増やすこともできます。
トランスミッションを装備するEVの欠点は何ですか?
-トランスミッションを組み込むと、EVのシームレスでスムーズな加速の魅力が低下し、トランスミッション全体のドライブトレインの効率が低下し、重量やサイズ、コストが増加します。
EVトランスミッションの例として挙げられる製品は何ですか?
-Audi e-tron GTやPorsche Taikan、ZFの2速トランスミッション、BoschのCVT4EV、AisinとDensoのBlueE Nexus、NSKのインホイールモーター(IWM)に組み込まれたトランスミッションなどが挙げられます。
EVのトランスミッションはどのようにして効率を高めますか?
-トランスミッションを用いることで、モーターの効率の良い範囲をよりよく利用し、巡航距離を延ばすことができます。また、変速によってモーターのrpmを一定の範囲内に抑えることで、熱発生を減らす効果もあります。
EVのトランスミッションは将来どのように発展する見込みですか?
-トランスミッションは将来的には大型車両に導入されることが予想されますが、市内運転向きの小型EVへの導入の利点はそれほど大きくないかもしれません。モーターの高効率を実現するように引き続き発展が期待されます。
Outlines
🚗 EVトランスミッションの可能性
このビデオでは、エンジンからモーターへの主な推進力のシフトにより、トランスミッションの役割が減少しているが、EVにはトランスミッションが不要とは限らないと説明しています。トランスミッションはエンジンからタイヤにトルクと速度を伝達し、運転条件に応じて速度を増減させる役割を果たします。エンジンとモーターの特性の違いにより、エンジン車のトランスミッションはエンジンのトルク、速度、回転方向を車のニーズに合わせるために使用されますが、モーターはゼロRPMから最大トルクをすぐに得ることができます。しかし、日本の都市部では60km/h、高速では120km/hの速度制限があるため、実用的な使用においては多段ギアの必要性が低いとされています。
🔧 モーターとエンジン車の特性
エンジン車のトランスミッションはエンジンの回転速度とトルク特性を車の運転特性に合わせるために必要な精密な制御を提供します。一方で、モーターは静止から最大トルクを維持し、一定の回転速度まで達するとトルクは減少します。そのため、EVはモーターに固定減速ギアを付けることで、多様な運転条件下で運転することができます。現在市場に存在するEVは、モーターとドライブホイールの回転が同じ速度でないことを意味し、多くの商用EVはモーターの出力をタイヤに伝えるために減速ギアセットを使用しています。
🚀 EVにトランスミッションが必要になる理由
モーターは回転開始直後に最大トルクを生成し、効率は徐々に低下します。したがって、EVの主流のパワートレインは、減速ギアを使用してトルクを増幅し、トランスミッションを備えないことです。しかし、モーターも高い効率を必要とし、広い範囲と高性能を結合する電気パワートレインが登場しています。トランスミッションを用いることで、モーターをより効率的な範囲で運転し、走行距離を延長し、ドライブトルクを増やして運転性能を向上させることができます。
🔩 EVトランスミッションの例
モーターは低またはゼロRPMから最大トルクを生成し、エンジンよりも高い回転数まで回転できます。そのため、1つのギアのみが必要ですが、トランスミッション効率と重量の面で利点があります。市場に存在するすべての乗用車EVは、e-tron GTやPorsche Taikanを除いて1つのギアしか備えていません。スポーツカーの場合、ドイツのAutobahnで高速運転するため2段ギアに変更することで、素晴らしいスタートアップ加速と非常に高い速度での性能を組み合わせることができます。
🌐 EVトランスミッションの進化と選択
AisinグループとDensoの提携であるBlueE Nexus電気パワートレインラインナップも、2段トランスミッションを持つユニットを含んでいます。これは、通常のATと同様のクラッチメカニズムとプラネットギアメカニズム、そして差動ギアへの出力ギアを備えています。2段ギアシフトメカニズムを採用することで、車両に搭載する電池の量を減らすことでコストと電気消費量を改善することを目指しています。NSKは2016年12月に、トランスミッションを備えたホイールモーター(IWM)システムを開発したと発表しました。ZFは、2段シフトメカニズムを使用する2段トランスミッションを開発しています。トランスミッションを組み込むことで、同じ電池サイズで走行距離を5%増加させることができます。
Mindmap
Keywords
💡電気自動車(EV)
💡トランスミッション
💡トルク
💡回転数(rpm)
💡減速ギア
💡バックEMF
💡最大速度
💡ダウンサイジング
💡CVT(無段変速)
💡プラネットギア
Highlights
电动车传动系统的主题探讨,传统传动系统在电动车中的作用正在减少。
电动车不需要传统意义上的变速器,因为电机可以直接提供动力。
尽管如此,电动车的传动系统仍有其可能性和必要性。
传动系统的定义及其在传统汽车中的作用。
电机的特性允许电动车在没有变速器的情况下也能良好运行。
日本城市和高速公路的速度限制意味着电动车不需要多速变速器。
电动车目前市场上的传动系统现状,多数使用固定减速齿轮而非变速器。
减速齿轮的作用和工作原理,以及它在电动车中的应用。
电动车为何需要变速器,以及变速器如何提高电动车的效率和性能。
电动车在高速行驶时的效率问题,以及变速器如何帮助解决这一问题。
使用变速器的电动车可以缩小电机尺寸,从而降低成本和重量。
电动车传动系统的未来发展,包括多速变速器的潜在应用。
特定电动车模型如e-tron GT和Porsche Taikan采用两速变速器的例子。
德国ZF公司开发的两速电动车传动系统,以及其对续航里程的影响。
Aisin和Denso合作开发的BlueE Nexus电动动力传动系统,包括两速变速器。
NSK开发的带变速器的轮内电机系统,以及其对体积和效率的影响。
电动车传动系统的多样性和未来可能的发展趋势。
Formula E赛车中使用的多速变速器,以及其对性能的影响。
对于城市驾驶的小型电动车而言,采用变速器的效益可能并不显著。
Transcripts
Hello everyone.
The theme this time is about EV transmissions.
Today, the electrification of powertrains
is changing the environment surrounding transmissions.
This is because the role of the transmission is decreasing
as the main driving force is shifting from the engine to the motor.
However, just because it is an EV does not necessarily mean
that a transmission is unnecessary.
This video will show you the possibilities of transmissions in EVs.
What is transmission?
The transmission is often mounted behind the engine
and transmits the turning power (torque) and speed
from the engine to the tires by increasing or decreasing
and reversing the speed according to the driving conditions.
The principle of the gearbox uses a combination of gears of different sizes.
When a large gear turns a small gear in an intermeshing pair of gears,
the rotation speed of the small gear increases.
Conversely, when a small gear turns a large gear,
the large gear has more turning force (torque).
Transmissions are based on this principle.
A vehicle requires turning power (torque) when starting off or going up and down hills,
and conversely, when traveling at high speeds,
it is necessary to increase the number of revolutions in order to speed up the vehicle.
Also, when moving backward, the rotation is required to be reversed.
Why do we need transmissions in automobiles in the first place?
The torque, speed, and direction of rotation of an engine cannot be changed at will,
but can only fluctuate within a certain range.
Outside of that certain rpm range, operation may stop, efficiency may drop,
or in the worst case, damage may result.
Therefore, the transmission is used to change the torque, speed,
and direction of rotation from the engine
to what is best suited to the vehicle's needs by combining gears.
In addition, the torque generated by the engine is poor
for moving a car weighing thousands of kilograms,
and deceleration is required to increase torque.
Multiple gear sets are also intended to reduce rpm, i.e., amplify torque.
Characteristics of motors
Most EVs currently in mass production do not employ transmissions.
In EVs, anyone can easily start driving by setting the selector for driving
to D range and stepping on the accelerator pedal.
Driving force and speed can be controlled
only by the number of motor revolutions and the gas pedal opening.
It can be said that the lack of any difficulty and the beginner-friendly ease of use are
the beauty of EVs without transmission.
This is due to the characteristics of electric motors.
As is widely known,
electric motors are able to extract maximum torque immediately from zero rpm.
The motor can immediately extract a large amount of torque
that a gasoline engine would need to rev up to 3-4000 rpm and apply a load,
eliminating the need for high gears for starting.
And if the motor speed is increased as it is, the vehicle speed will also increase
with the maximum torque, so it is said that a transmission is not necessary.
In Japan, there is a speed limit of 60 km/h in urban areas and 120 km/h on highways,
so there is no need to extract higher speeds for practical use.
Except for a very few areas with unlimited maximum speed,
it is considered globally acceptable to support a maximum speed of about 140 km/h.
Therefore, the characteristic of electric motors is that
they can handle this without having a multi-speed transmission.
However, a transmission is essential for an engine-powered car.
The reason why a transmission is installed in a car in the first place is
to bridge the "gap" between the "rotational speed-torque characteristics" of the engine
and the "driving force characteristics" required of the car.
The engine reaches its maximum torque at a particular rpm,
and torque drops off sharply at other times.
On the other hand, a car requires a large driving force when starting and accelerating,
and can run with a small driving force without slowing down
when it reaches a certain speed.
To achieve these driving force characteristics required of a car,
engine cars need a transmission.
Engine cars require precise control using a multi-stage transmission
so that the engine can operate near the eyeballs of fuel economy
even as vehicle speed, torque requirements,
and other factors vary with driving conditions.
In contrast, a motor maintains its maximum torque
from a standstill up to a certain rotational speed, and then drops off above that speed.
Since these rotational speed-torque characteristics are similar
to the driving force characteristics required of a car,
EVs can be driven in a variety of driving conditions simply
by attaching a fixed-stage reduction gear to the motor.
Current EV transmission system
EVs do not necessarily need a transmission,
but EVs currently on the market do not transmit
the rotation of the motor directly to the drive wheels.
This means that
the motor and the tires of the drive wheels do not rotate at the same speed.
Unlike an engine, a motor has no reciprocating parts,
so it can increase its rpm compared to an engine.
Take, for example, the Nissan LEAF, a domestically produced EV,
with an EM57 AC synchronous motor
with specifications of maximum output of 150 hp at 3283-9795 rpm (normal grade).
If this motor speed is transmitted directly to the drive wheels,
the speed is converted to about 400 to 1200 km/h.
This is far from the practical range and inefficient.
Therefore, many commercial EVs use a set of reduction gears
to decelerate the speed of the motor output shaft and transmit it to the tires.
No matter how much torque a motor can produce,
more power is needed to move a vehicle weighing 1 to 2 tons.
To achieve this, torque is increased by a combination of large and small gears.
The reduction gear plays this role.
EVs can be driven in a variety of driving conditions simply
by attaching a fixed-stage reduction gear to the motor.
So many EVs today are equipped with a reduction gearbox
even if they do not have a transmission.
What is a reduction gear?
A reduction gear is a device
that outputs torque by decelerating the rotational speed with gears or other devices.
It can output torque inversely proportional to the deceleration.
Reduction gears are devices that spread along with the development of motors.
It is no exaggeration to say that
unless the mechanism utilizes the rotation of the motor as it is,
some kind of reduction device is necessary,
and where there is a motor, there is a reduction gear.
By installing a reduction gear between the motor and the device it drives,
the required torque and rotational speed can be obtained.
They are widely used in industrial machinery such as robots and factory conveyor lines,
as well as ship's screws and airplane propellers.
The reduction gear mechanism uses the principle of leverage.
In the principle of leverage, the greater the distance
between the point of application of force and the point of support,
the greater the force generated with less force.
The force point for the gears is "where the gears engage"
and the fulcrum is "the center point of the gear on the tire side.
A makes one turn, B makes only 1/2 turn, but less force is required to turn B.
Therefore, if the rotational speed is 1/2, its rotational force (torque) is doubled.
The reduction ratio at this time is expressed as "2.
Incidentally, a reduction gearbox is a device with one fixed reduction ratio,
while a transmission is a device with variable speed ratio.
By using a reduction gear, low-speed rotation can be efficiently obtained
and high torque can be obtained as a so-called doubling device.
Why EVs need transmissions
The engine produces more torque as the rpm increases,
while the motor produces its maximum torque immediately after rotation
and gradually decreases in efficiency.
Therefore, the mainstream powertrain for EVs
has been to use a reduction gear to amplify torque and not to have a transmission.
However, even motors need to be highly efficient.
Electric powertrains that combine wide range and high performance are emerging,
based on the concept that if efficiency declines as rpm rises,
a multi-stage gearshift should be used.
As some say, "EVs lose battery power faster at high speeds,"
the efficiency of motors differs by more than 10%
between ordinary roads and highways.
In the case of permanent magnet synchronous motors, when running at high speeds,
the back EMF generated by rotation creates rotational resistance,
which reduces efficiency. If the speed is shifted according to the rotation speed,
the efficiency can be improved by up to 4% in the case of a D-segment car.
The role of the transmission for EVs is to allow the motor to be driven
in a more efficient range, thereby extending the cruising range,
and also to improve driving performance by increasing the drive torque.
1 High speed and maximum speed
The energy conversion efficiency of electric motors is much higher
than that of internal combustion engines.
While the highest value for mass-produced gasoline engines is about 41%,
electric motors achieve more than 90%.
However, not all ranges exceed 90%. In the low RPM, high torque range,
the resistance due to the electrical resistance of the copper wire increases,
and in the higher RPM, lower torque range, the more loss occurs
when switching the magnetic field of the iron core.
Also, even a motor heats up because a large current continues to flow
if it continues to run at high RPM.
Therefore, in order to lower the motor speed at high speeds,
shifting to a combination with a small gear ratio difference allows
efficient use of the motor speed and reduces heat generation.
And if the car is designed to run at 200 km/h or more,
as in a GT or sports car, a transmission is required.
Many mass-produced EVs without transmissions have
a maximum speed of 160 km/h or less.
While this is sufficient for mainly city driving,
the current electric powertrains fall a little short
when seeking performance equivalent to that of an engine-powered vehicle.
EVs have a fixed 3rd gear that covers the entire range from start to high speed,
and the technology of combining a transmission
with a gear ratio range equivalent to 1st to 6th gears makes it possible
to raise the starting, hill climbing, or towing performance.
At the same time, the maximum speed can be increased.
However, since the motor has a wider speed range than the engine,
it is said that a two-speed gear shift is sufficient.
2 Downsizing of motors
One of the benefits of using a transmission for EVs is
that the motor can be downsized;
EVs require large motors in situations where high torque is required,
such as starting and rapid acceleration.
If large torque is required at startup, the motor must necessarily be larger.
This will involve issues of cost and size.
The advantage of electric vehicles equipped with a transmission mechanism is that
by combining the transmission mechanism with the motor,
not only can the motor be downsized, but also auxiliary equipment
such as inverters can be downsized.
The smaller the motor can be made, the more space it takes up for the battery.
This is directly related to extending the cruising range of EVs.
And it not only reduces weight, but also reduces
the amount of expensive rare earth and electromagnetic copper plates used in motors.
So, downsizing can also reduce costs.
Adding a multistage transmission to a smaller motor
rather than a larger motor that covers 0-140 km/h
would cover the starting torque and reduce the burden at the highest speed,
which would reduce the cost of the motor.
However, there are also disadvantages to having a transmission.
EVs have problems such as back EMF of the motor,
which makes it difficult to increase the maximum speed without a transmission.
However, since it is sufficient for EVs used
in daily life to be able to reach speeds of around 100 km/h or more,
there is no need to go to the trouble and expense of installing a heavy transmission.
The appeal of EVs is their seamless and smooth acceleration.
The appeal of EVs would be diminished
if the combination of a gearbox and a transmission caused shifting shocks.
It is inevitable that the transmission efficiency of the entire drivetrain will be reduced
when a transmission is combined.
Weight and volume will increase, and so will cost.
A prerequisite for adoption is that
the positive factors resulting from the transmission combination outweigh
the negative factors associated with the adoption of the transmission.
Electric motors have a thermal efficiency of over 90%,
and they can do so over a wide range of speeds.
So while it certainly only needs one gear,
there is still room to improve efficiency by using a transmission.
The total cost of EVs may become more advantageous if the weak points of EVs,
such as improved power consumption at high speeds, smaller motors,
and reduced battery capacity due to improved power consumption,
are taken into account.
Examples of EV Transmission
Electric motors can generate maximum torque from low or zero RPM
and can rev higher than engines.
Therefore, they require only one gear,
which has advantages in terms of transmission efficiency and weight.
Therefore, all passenger car EVs on the market today have one gear
except for the e-tron GT and the Porsche Taikan,
which shares hardware with the e-tron GT.
If a sports-type car is converted
to a two-speed for the purpose of speeding down the German Autobahn,
it can combine tremendous start-up acceleration with performance at very high speeds.
In fact, first gear is used when using launch control
and when the Audi Drive Select is set to dynamic for stronger acceleration,
and second gear is used during normal driving.
Structurally, a planetary gear system is used.
It is not the case that two-speed EVs are only for models
that require super performance.
Major suppliers such as ZF and Bosch in Germany
and Aisin and NSK in Japan are developing transmissions for EVs,
including 2-speed transmissions.
They are not only for sports and premium cars,
but also for general passenger and commercial vehicles.
Bosch is developing the CVT4EV, a continuously variable transmission (CVT) for EVs,
utilizing the technology it has cultivated in the development of CVTs.
They are currently developing the technology using a demo car
and aim to put it to practical use in 2025.
The CVT4EV, by its special design, allows for increased efficiency,
more torque in towing mode, good acceleration and top speed, etc.
The smoothness characteristic of EV driving is maintained
through stepless gear shifting without torque steps.
The LOW ratio improves acceleration and hill climbing performance at low speeds,
while the TOP ratio improves efficiency and top speed at high speeds;
the LOW ratio can also be used for towing and off-road driving
by increasing torque more than efficiency.
Efficiency can be improved by making better use of the motor's efficient range.
If fluctuations in vehicle speed are absorbed by the CVT gearshift,
the motor's rpm can be kept within a certain range.
Compared to planetary gear systems, the ideal range of gear ratios is easier to achieve,
and CVTs have an advantage over stepless systems
in that they do not cause gearshift shocks.
The greatest advantage is
the ability to use the motor's highly efficient range without waste.
The CVT4EV is expected to improve energy consumption by up to 5%
and at the same time improve acceleration performance by up to 50%.
The BlueE Nexus electric powertrain lineup, a partnership
between the Aisin Group and Denso,
also includes a unit with a two-speed transmission.
This type has a mechanism called a planetary gear type 2-stage transmission.
Like a standard AT, it has a clutch mechanism for gear shifting,
a planetary gear mechanism for the first and second rows,
and an output gear to the differential gear.
By adopting a two-stage gear shift mechanism,
the amount of batteries installed in the vehicle can be reduced,
with the aim of improving cost and electric power consumption.
NSK (NSK) announced in December 2016 that it has developed
a system of in-wheel motors (IWM) equipped with a transmission.
By combining a gearbox with two small motors,
the IWM system enables a smaller overall volume
than using only one large conventional motor.
The NSK system has three planetary gears.
Two of these act as transmissions and one as a reduction gear
that amplifies the combined power of the two motors.
There are two transmission gears: a low gear used primarily
for starting and a high gear used for driving.
In high gear, the two motors rotate in the same direction,
while in low gear and when traveling backward, they rotate in opposite directions.
The two-speed electric drive unit developed by ZF,
a well-known transmission manufacturer,
has a two-speed shifting mechanism using a planetary gear set.
Starting in first gear provides higher torque for powerful starting and acceleration.
On the other hand, shifting to 2nd gear at 70 km/h allows for higher speeds.
2nd gear also greatly improves acceleration performance.
By incorporating a two-speed transmission,
ZF engineers say they can increase the range by 5% if the battery size is the same.
A 2-speed transmission should be heavier and larger than a 1-speed,
but ZF has succeeded in integrating a 2-speed transmission
into the same size as the 1-speed electric drive unit.
By the way, Formula E, the premier EV race, currently uses regulations
that allow the use of gearboxes with up to six speeds.
It is expected that transmissions for EVs will be introduced starting
with large vehicles in the future.
However, the benefits of adopting transmissions for small EVs
for city driving may not be significant.
Many people consider "C-segment cars to be the borderline for mounting.
Motors are not all-powerful, either; they have their strengths and weaknesses.
We look forward to the continued evolution of motors to achieve high efficiency.
What kind of EV transmissions do you like?
All right, that's all for this time. Thanks for watching!
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