Tour Engine’s Split-Cycle Technology Improves Internal Combustion

Tour Engine is a San Diego company that has developed a more fuel efficient internal combustion engine (ICE) based on standard piston/cylinder engine architecture.

The company’s TourEngine builds on a “split-cycle” design. While conventional ICEs use the same cylinder for all four strokes, the TourEngine splits the 4-stroke cycle between two opposing cylinders. The elegant innovation of the engine – and what differentiates it from previous split-cycle engines – is the direct coupling of the two cylinders by a special crossover valve.

In the TourEngine design, the two cold strokes – intake and compression – occur in one relatively cold cylinder while the hot strokes – combustion and exhaust – occur in the other relatively hot cylinder. Thus, the hot and cold strokes occur in parallel, and this configuration allows flexibility in thermal management, minimizing energy losses and boosting efficiency.

I recently met Dr. Oded Tour, the company’s Co-founder and CEO, at the New Energy New York Symposium. Tour Engine was a semifinalist at the startup competition, and I was able to catch up with Dr. Tour after his presentation to discuss the company’s technology and intellectual property.

He told me the company has patented the basic core innovation, which is the direct coupling of the two cylinders by a special crossover valve that regulates the precisely timed transfer of the compressed charge from the cold cylinder to the hot cylinder.

Tour said the special valve is designed to be wide enough to eliminate any bottleneck between the two cylinders yet narrow enough so it does not become a separate compartment. In this way, any energy input and compression by the engine is transferred completely between cylinders without losing energy. The direct coupling of the cylinders via the valve also eliminates the need for a connecting tube.

Tour Engine owns at least three U.S. Patents and several international patent applications covering its technology.

Two related patents – U.S. Patent Nos. 7,383,797 and 7,516,723 – are entitled “Double piston cycle engine” and directed to a dual piston apparatus including an interstage valve (collectively “Valve Patents”).

The Valve Patents describe and claim a dual piston apparatus comprising a compression cylinder (01) housing a compression piston (03), a power cylinder (02) housing a power piston (04), two piston connection rods (05, 06) connecting their respective pistons to their respective compression crankshaft (07) or power crankshaft (08), a crankshaft connecting rod (09), an intake valve (10), an exhaust valve (11), and an interstage valve (12).

The compression piston (03) moves relative to the compression cylinder (01) in the direction indicated by the illustrated arrows, and the power piston (04) moves similarly relative to the power cylinder (02).

The interstage valve (12), which may be formed as a shaft having a conic shaped sealing surface, governs the compressed carbureted air/fuel charge flow from a volume B in the compression cylinder (01) as it is pushed into a volume C in the power cylinder (02). In addition, the interstage valve (12) prevents reverse flow of fuel from volume C back into volume B.

In an open position, the interstage valve (12) allows compressed fuel to flow from compression cylinder (01) into the power cylinder (02). The valve remains closed during combustion and along the power stroke, and typically opens around the time the exhaust valve (11) closes.

U.S. Patent No. 7,273,023 is entitled “Steam enhanced double piston cycle engine” and directed to a dual piston apparatus for a combustion engine in which the piston in the first cylinder performs only intake and compression strokes and the piston in the second cylinder performs only power and exhaust strokes. A third piston utilizes heat energy generated by the second piston to perform additional power strokes.

According to Dr. Tour, the company’s patented core innovation is important for a few reasons. First, the simplicity of the patented technology makes it a very cost-effective solution. Second, the TourEngine is a platform technology that can be utilized in multiple verticals. Finally, the patented innovation is just the beginning and sets the stage for additional IP protection. Dr. Tour told me with confidence, “there will be hundreds of patents around this technology.”

With the recent passage of new federal automobile mileage mandates, electric vehicles alone probably can’t carry us to 54.5 miles per gallon, and improved ICE technology like the TourEngine could play a major role.

Eric Lane is a patent attorney at McKenna Long & Aldridge LLP in San Diego and the author of Green Patent Blog. Mr. Lane can be reached at elane@mckennalong.com