Grease consists of three major components: base oil, additives, and thickener. Thickener forms entangled fiber network which can be observed using an electron microscope. Due to the network structure of thickener, thickener holds base oil like a sponge. In order to develop energy-saving grease, optimization of the formulation of these three components is necessary.

The design of energy-saving grease is as follows.
Energy-saving can be achieved by reducing friction. The Stribeck curve shows the relationship between the lubrication states and friction coefficient. In the hydrodynamic lubrication region where the oil film prevents metal contacts, it is important to reduce stirring resistance by selecting low viscosity and low friction base oil. In the boundary and the mixed lubrication regions, where the oil film is broken and metal contact occurs, it is important to reduce friction and wear by optimization of thickener and additives.

It is necessary to consider difference in rotational resistance of bearings due to the state of grease distribution. As shown in the figure, when balls pass through grease inside the bearing, grease is pushed away. In the churning state, the grease adheres to the bearing balls after the balls pass through, therefore the resistance that balls receive from the grease increases. On the other hand, in the channeling state, the grease hardly adheres to the balls, so the resistance becomes small. For energy-saving grease, a proper transition to the channeling state is desired, and to achieve this, the grease must have the property that stays in appropriate places.

Concept based on flow characteristics specific to grease (flow in rolling bearings)

In general, lithium complex grease has stronger fibers than lithium soap grease, and has flow characteristics that allow it to stay in place, so it is likely to get into a channeling state.
We have succeeded in observing this phenomenon in three dimensions by using neutrons.
Since neutrons easily penetrate metals and are absorbed by grease, it is possible to visualize the flow state of the grease in metal bearings. In the case of lithium soap grease, it can be seen that there is a large amount of adhesion to the balls in the bearing, resulting in a churning state, and therefore, stirring resistance is high (top figure). On the other hand, in the case of lithium complex grease, there is little adhesion to the balls and the grease is in a channeling state, indicating that the stirring resistance remains at a low level (bottom figure).
In recognition of this achievement, our company received the award, Hamon President Choice, from the Japanese Society for Neutron Science.

• "Hamon President Choice" -Neutron Imaging for Observation of Grease Fluidity in Ball Bearings-