What Is Fluid Coupling and How Does It Work?

The principles of fluid dynamics are present in nearly all modern inventions. From modern toilets to rocket propulsion, it’s hard to find any revolutionary technology that doesn’t use it. Fluid dynamics is one of the most important products in engineering.

Like most engineering concepts, the fluid coupling can be a bit of a puzzle. Luckily, we’re here to make things simple. Read on for a simple and intuitive way to understand fluid coupling.

What Is Fluid Coupling?

Fluid coupling, also called hydraulic coupling, is a hydrodynamic device that uses transmission fluid to transfer mechanical power. 

German scientist Dr. Hermann Fottinger invented fluid couplings. His invention was patented posthumously in 1950 and has been used for various industrial applications since then. 

How Does It Work?

The principles of fluid coupling are based on hydrokinetics and fluid dynamics. This makes it distinctly different from hydrostatic systems like hydraulic pumps. 

A fluid coupling consists of a pair of bladed wheels that face each other but make no physical contact. One wheel, called the impeller, gets connected to a power source. The other, called the turbine, receives power from the impeller that transfers directly to the transmission.

The impeller, also known as the input, spins faster than the turbine, which is the output. Fluid flowing from the input causes the output to spin and transfers energy throughout the system. Both wheels are housed in an oil-filled casing that keeps them in place.

Fluid Coupling Applications

Fluid couplings get used in several different industries. However, its most important contribution is to the automotive industry. Let’s take a look at how.

Automatic Transmissions

Before the invention of fluid coupling, all cars had a manual transmission. Manual transmission requires the driver to operate a clutch, which is the link between the engine and the transmission. Without its clutch, a manual transmission car would stall whenever it stops.

The invention of fluid coupling removed the need for a clutch. It became the source of torque conversion needed to make cars shift gears automatically. Every automatic car on the road today has been partly built using fluid coupling.

Semi-Automatic Transmissions

The use of fluid coupling extends beyond just motor vehicles. Fluid couplings also have an important benefit in rail transportation.

In Britain, diesel locomotives have a power transmission system that is semi-automatic. This power transmission employs fluid couplings to make the locomotives shift gears automatically while in motion.

Additional Resources

Despite being less than 100 years old, fluid couplings have revolutionized how automobiles and locomotives run. The automotive industry relies on its principles and wouldn’t be the same without them. 

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Posted in Couplings.