Automatic/Automated transmissions trend
- Nov. 24, 2014
- Marcel Romijn
While automatic transmissions have been popular for decades this popularity was very regional dependent. With the roll-out of more automatic and automated transmissions concepts and a stronger push for fuel economy and vehicle comfort the traditional situation has changed.
We asked BRACE Automotive Engineer Ruud Bogers to shine some light on the topic.
What is your position at BRACE Automotive and how long have you been working in Automotive Engineering?
Ruud: “I am a Project engineer, specialized in mechanical engineering of gearboxes. I have been working in automotive engineering for about seven years, with a background in mechanical engineering.”
What types of automatic and automated concepts exist?
Ruud: “You can divide automatic transmissions in 4 major concepts:
Automated Manual Transmissions (AMT): this is basically is a manual gearbox where the clutch is operated and shifting is done automatically by electronics/hydraulics.
Dual Clutch Transmissions (DCT): are basically two AMT gearboxes in one. However with a complex clutch systems which allows smooth gear changes between either of the two. Actually you should sort the DCT’s in wet and dry clutch based transmissions.
Automatic Transmissions (AT): is the most traditionally well-known type of automatic transmission. In this type of transmission a (large) number of clutches are used to select a gear. AT’s are almost always equipped with a torque converter, improving the launch performance.
Continuous Variable Transmissions (CVT): has unlike the other types no fixed ‘gears’ but allows for continuously step less shifting without torque interruption.
What distinguish is there in customer preference per regions?
Ruud: “There is a surprisingly large difference in customer preference around the world.
The European customer still prefers manual instead of automatic transmissions. In the luxury brands however there is still a market for AT’s. But especially the DCT has nowadays a growing market share.
The North-American market is traditionally a good market for Automatic transmissions. Especially AT’s are popular.
Japanese manufacturers on the other hand have embraced the CVT. Notably in the Kei-cars (small city cars) this transmission is hugely popular.
These differences are caused by differences in how the end customers are using the car, size of the cars, and the different infrastructure in the countries. The desired comfort, but also factors like additional cost and fuel economy each play important roles.
Traditionally automatic transmissions are associated with higher fuel consumption. However many “ECO” models on the market today are not available with manual gearbox. What has changed?
Ruud: “Before the main focus for fuel improvement was on the engine, think about the down-sizing. Today, although the real down-sizing has just began, that is just not sufficient by itself anymore, so companies are also more and more interested in finding improvements elsewhere in the driveline.
One of the most significant changes has been the number of gears. With more gears manufactures have a greater flexibility in choosing the right ratio. Even more important than the number of gears is the distance between lowest (1st) and highest gear, the so-called ratio coverage. This helps increasing fuel economy by reducing the steps between the gears allowing the engine to keep running under optimal working conditions. And to give you a better example creating the ability to reduce engine speeds to around 2000 rpm at cruising speeds of 120 km/h.
On the other hand an automatic transmission still has a lower efficiency than manual transmissions by design. A lot of these losses, that affect the efficiency, come from the fact that an automatic transmission often has complex control systems and multiple clutches. So it may be no surprise that exactly on these components there has been a lot of innovation over the last decade.
Most challenging: all improvements have been made without making the transmissions bigger and heavier. So you have more gears, larger ratio coverage and more efficiency in a lighter and smaller package.”
For the traditional European customer who has always been used to a manual gearbox the automatic and automated transmissions require some adjustment. Sound, shifting smoothness, shifting speed are examples. The most modern transmissions in European applications have made the transition easier. What improvements were made to achieve this?
Ruud: “Shift quality is a very important factor in the acceptance of automatic transmissions. Shift times have been reduced, and also the engagement of clutches have been made smoother. As earlier mentioned higher number of gears also allows for smaller steps between the ratios with also contributes to a higher driveability, but also increases the launch performance.
All these improvements also had benefits to the sportiness of cars with automatic transmissions, something that definitely helps in the acceptance on the European market.”
What are the capabilities of BRACE in this field?
Ruud: “BRACE engineers have worked on projects from concept, to concept realization, to bringing transmissions into production.
We support our customers with the design of their gears (systems) for higher durability, efficiency and better NVH performance, but also in project management, to give two examples.
Within the powertrain domain we work closely with experts from competence clusters like controls, software and Functional Safety. This allows us to complete the full picture of transmission development at BRACE”