Powertrain

Tribology has been an essential part of the development of improved powertrains for decades and - even with a growing shift to electrical vehicles - this continues to be the case today.

piston and chain

The powertrain of a vehicle encompasses every component that is involved in the conversion of power to movement. This is true for any sort of vehicle, from boats to planes and cars to bikes, although each of these will have very different requirements placed on powertrain components. However, one thing all will have in common is that they will consist of many moving parts that are in near-constant contact with other components. It is in these contacts – found in any powertrain – where tribological research has been focused to continually improve and optimise designs.

PCS’ range of instruments are used extensively by industry and academia to achieve this continual improvement. The MTM and ETM are key tools used for this work. Both have independently driven specimens which enable a wide range of contact conditions to be replicated, and together cover an impressive range of contact pressures from close to 0 to 3.5 GPa with standard specimens, and even more with non-standard specimens. This versatility means that researchers can use these instruments to investigate all the different contacts you would find in a whole host of powertrain applications, investigating wear, friction and film build up. The EHD is also extensively used in this area for investigating film thicknesses and traction coefficients of lubricants found in these systems; and the MPR is used to investigate how parts and lubricants will stand up to prolonged use over the years.

As an area of significant power wastage in vehicles, powertrains have always been of interest to tribologists. This interest will only continue to grow, as the frictional losses in the powertrains of electric vehicles are a larger portion of total losses than in internal combustion engines. As such, powertrain research and developments that tribology can bring are only going to become more important in the future.

Powertrain industry research areas include:

  • CV Joints
  • Gearboxes
  • Marine specific lubricants
  • Engine systems
  • Wind turbines
  • Bearings and gears

Powertrain Industry includes the following:

Agriculture

Agriculture

The powertrains in agricultural vehicles must regularly deal with high-stress forces, and be very reliable to prevent down-time. One way this reliability is improved is through the optimisation of tribological contacts.

Automotive

Automotive

Automotive powertrains are an area ripe for continual improvement through tribological study, and this study is important now more than ever as the industry adapts to more complicated systems incorporating electric power.

Aviation

Aviation

With reliability forming the cornerstone of the aviation industry, knowing how components in your powertrain will wear and fail is fundamentally important for knowing when they need to be inspected and replaced.

Machinery

Machinery

The requirements on powertrains in machinery are as varied as the jobs performed by the machines. Every one of them will need lubricating, and choosing the right lubricant comes down to knowing the tribology of the contacts involved.

Marine

Marine

Marine powertrains can be large or small, and some have to deal with as much as 80MW of power and 7.6MNm of torque. These conditions mean lubrication and part protection are critical to the longevity of an engine.

Mining

Mining

Facing constant high loads, harsh and dirty environments, and huge costs associated with downtime, the powertrains in mining vehicles have to be reliable even in the most adverse conditions. Tribological studies helps ensure this is the case.

Trains

Trains

Trains often now work by using a diesel engine to generate power, which is then converted to electrical power, which runs the motors to drive the train. These myriad components and processes are designed with tribology and lubrication in mind.

Wind Turbines

Wind Turbines

Wind power remains one of the most rapidly growing renewable power sources, so the tribological problems found in the powertrain - from the blades to the generator - are the focus of significant research.

Instruments for the Powertrain Industry

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Powertrain Industry Articles & Papers

Paper

Coefficient of Friction Behavior of Gear Oils and Significance for the Meshing Process of Spur Gears

The mechanical properties of oils are determined using test methods. There are standardized test methods for determining viscosity and density. …

The mechanical properties of oils are determined using test methods. There are standardized test methods for determining viscosity and density. The characterization of transmission oil based on its dynamic viscosity alone is not sufficient for the physical explanation of different levels of noise emissions in vehicle transmissions. For this reason, the test procedure for determining the coefficient of friction is used in the following to enable a further differentiation between the oils according to mechanical properties.
In gear transmissions with involute gear teeth, rolling friction occurs in the gear pair meshing along the line of action due to the variation in the equivalent curvature radii throughout the meshing cycle. This is rolling friction on which a sliding friction component, so-called slip, is superimposed. Pure rolling friction only occurs in the pitch point. From the pitch point to the start and end of the meshing, there is a superimposed sliding friction component that increases with increasing distance from the pitch point. Slip values occur in the range of 5–50% depending on tooth geometry.
These friction conditions during tooth flank lubrication can be assessed using the Stribeck curve. The Stribeck curve represents the coefficient of friction as a function of the speed. A mini traction machine from PCS Instruments with a ball/plate measurement setup was used to determine the coefficient of friction behavior of gear oils. This allows the coefficient of friction of an oil to be assessed at low speeds in the range from boundary and mixed friction to elastohydrodynamic fluid friction at high speeds.
The investigations show that the coefficient of friction behavior of a gear oil depends on the oil viscosity and above all on the chemical composition. The lower the coefficient of friction, the less energy is required to shear the lubricating film and the lower the power transmission through the fluid. The coefficient of friction is a property that is dominated by the type of base oil and the type of VI improver in the area of mixed and fluid friction, especially with additional sliding in contact.
It will be shown in the paper that the use of a gear oil that has been optimized with regard to the coefficient of friction curve can reduce the entry impacts of meshing gear pairs under vibration excitation and the gear transmission thus generates lower noise emissions.


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Paper

Rheological Properties of Lubricants and Their Correlation With Fuel Economy Performance

One of the least expensive pathways to achieving improvements in vehicle fuel economy is through changes to engine lubricant viscosity …

One of the least expensive pathways to achieving improvements in vehicle fuel economy is through changes to engine lubricant viscosity and composition. Driven by ever more stringent emissions regulations, OEMs are therefore requiring engine oils to continue protecting engines at lower viscosities and reduced friction.
Different engine operating conditions represent a range of lubrication conditions, and to better understand the full impact of engine lubrication process, one must understand how oils perform in these conditions. In general, additives in lubricants help to provide the right balance of fuel economy while maintaining durability protection. The focus of the present study is on the hydrodynamic lubrication regime, and the rheological properties of oils were investigated and correlated to their fuel economy performance in different engines, Mercedes Benz OM 501 LA and Detroit Diesel DD13, and driving cycles, WHTC (World-Harmonized Transient Cycle) and modal.

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