Technology: What is HMIVT

The Kinetics Drive Solutions Inc. (KDS) Hydro-Mechanical IVT technology combines a hydrostatic transmission with a planetary gearset in a hybrid configuration. Such a device provides a dual power path through the transmission that is parallel in nature, permitting it to transfer power in any of three modes - purely hydraulic, combined hydraulic and mechanical, or purely mechanical.

At low output speeds, most power is transmitted hydraulically and a small amount mechanically. At high output speeds, all power is transmitted mechanically as the transmission “locks up” in an overdrive ratio allowing cruising speeds with low engine rpm. Between these two extremes, power is transmitted as a mixture of hydraulic and mechanical with the ratio continually favoring mechanical power as it progresses upward through the range. Additionally, a 2 speed planetary with a speed matching shift transition is used to expand the operating range of the transmission.

The resultant powerpath is one where the engine rpm and torque are “decoupled” from the vehicle speed allowing freedom in powertrain management. This enables the vehicle powertrain to be optimized so that the combined efficiency of the engine and transmission as a package is significantly greater.

The technology also offers significant other advantages including, but not limited to:

Hydraulic energy recovery and launch assist using the vehicle’s braking energy. Since one of the key driving elements of the transmission is a variable displacement motor, the key components to hydraulic launch assist already exist within the transmission core. Therefore, by adding an energy storage device called an accumulator, braking energy from the vehicle can be recovered, stored and reused in the acceleration cycle of the vehicle. This provides further significant gains in economy, especially for vocational truck driving cycles such as refuse vehicles.

Power take-off functions are also enhanced with the HMIVT. Since the transmission behaves very similar to a conventional hydrostatic transmission at low speeds, it is possible to run the vehicle engine at rated power/rpm while driving slowly without any sacrifice in efficiency. The advantage is seen in vehicles such as road sweepers where the current convention is to use a second engine to power the implement requirements. In this case, the second engine would be eliminated and replaced with a PTO output on the transmission.

Extended powertrain life is a result of the HMIVT. The smooth power flow and constant engine speed operation enabled by the HMIVT will provide vehicle owners with lower life cycle costs thru better fuel economy and reduced wear and tear on all major components. The engine, drive shafts and differentials will all last longer due to the constant speed of the engine and constant power output from the transmission thru the driveline. Brake wear is also reduced due to the regenerative engine braking that is inherent in the HMIVT with or without the Energy Recovery System.

KDS has existing HMIVT designs in the torque range of 800-2600 Nm (see the UDT Product range here). KDS has considerable experience in heavy vehicle transmissions; therefore, no “scaling up” of a design is required. Additionally, KDS has also demonstrated that increasing the torque capacity of the transmission is within the design capacity of existing technologies without requiring ground-up component design.

The HMIVT technology is fully transferable to EMIVT architecture (Electro-Mechanical IVT). KDS has patented technology that enables the Hydraulic Variators to be replaced with Electric Variators. All the benefits and more of the HMIVT are realized in the EMIVT system. The additional benefits of the EMIVT include additional flexibility of power management when used in a hybrid application. Just as with the HMIVT, the EMIVT can operate with or without the energy storage devices (Batteries or Capacitors).