Prise winners list

Mass production of eco-friendly next-generation refrigerator, 'Free Piston Stirling Cooler (FPSC)'

Tsubame-City, Niigata Prefecture
Twinbird Corporation
Other award winners
Satoshi Kobayashi, Kiyoko Saito, Takeshi Sano, Yoshiyuki Shiobara, Soji Suzuki, Kazuya Sone
Recommended by
Twinbord Corporation, SC Business Dept.

Yamagiri, Tsuneo  (65)
Development and Production Headquarters, Executive Director in charge of SC


This company succeeded in mass production of "Stirling cooler" for the first time in the world. It was said to be impossible to commercialize a Stirling cooler though people knew it had a superior cooling capacity. The cooler uses a helium gas as refrigerant, which is harmless and not a greenhouse gas. Adiabatic expansion (phenomenon that temperature lowers when gas expands) of the gas is used to perform quick cooling. The cooler, which is light-weighted, compact and portable, can perform cooling of 100C or lower and consumes less electric power. This cooler is used for an outdoor cooler box, medical purpose and semiconductor production.


If we were not supported by others, we could not do it. We could mass-produce it because we were supported by the metalworking technology in the local area

"When we put this refrigerator on sale, people acknowledged this old little-known technology like it was new."
"This refrigerator" Mr. Yamagiri talked about is formally called "free piston stirling cooler (FPSC)". In an ordinary refrigerator, a refrigerant (gas) is circulated in the order of gas  liquid  gas. The interior of refrigerator is chilled by making use of the phenomenon that when a liquid is turned into a gas, heat of surrounding area is removed just like sprinkling water in mid summer (heat of evaporation). On the other hand, the RPSC makes use of the property of gas that temperature rises when it is compressed and that temperature lowers when it is expanded.
A cylinder filled with a refrigerant helium gas is installed in the interior of refrigerator, and two pistons are set in series vertically. The lower piston is operated by a linear motor, and the lower one is operated indirectly by the pressure fluctuation caused when the upper one is operated. These two pistons repeat their reciprocating motion while keeping their phase difference (difference in cycle) and then the gas is expanded at the upper part of cylinder and the surrounding is cooled. This is a simple explanation of the mechanism. The basic principle was invented by Doctor Stirling in Scotland in 1816. Many companies tried to manufacture a refrigerator that used this "Stirling cycle" but failed. Almost all the experts thought, "We know that the theory and idea are excellent, but it is next to impossible to mass-produce that refrigerator."
This company challenged this problem 1998. The company was manufacturing an outdoor portable refrigerator at that time but its cooling capacity was not good enough.  The company looked for a new technology alternative to the Peltier element used for that refrigerator, and finally decided to manufacture a FPSC. However, it was unexpectedly difficult to develop it, and the company produced many prototypes but they were all failures. The company invited Mr. Yamagiri, who was retiring from a major electric-appliance maker, in 2002 when it was still struggling to develop a FPSC. 

"I also knew a little bit about what the Stirling theory was, but honestly thought that it was difficult to commercialize a FPSC. However, I was invited to develop it and so I had to do something. I reviewed the structure comprehensively and revised the drawings. 
Mass-production of it was difficult because high and precise technologies for metallic working and assembly were required. For example, the clearance between the cylinder and the piston was required to be only 0.01mm, ten times higher accuracy than that for a car engine. This company developed a dedicated working machine and succeeded in assuring that clearance. "However, it was impossible to do all the works for ourselves. We asked about fifteen companies including a stainless steel working company in our region to develop parts." 
Their basic research began to bear fruit because Mr. Yamagiri, who was a specialist in the manufacturing technology, joined the company. Finally they enabled mass-production of a FPSC and commercialized it in 2003, five years after they started development. Needless to say, this is the first mass-produced FPSC in the world, a remarkable accomplishment.

This innovative refrigerator also contributes greatly to the cut-edging industries including the manufacturing of semiconductors and the medical field

The greatest feature of this product is that it can "produce" an ultra-low temperature of -100C or lower easily, which the conventional compressor refrigerator could not produce.
Furthermore, it takes only five minutes to produce such an ultra-low temperature after its switch is turned on. The 40W refrigerator weighs only 1.7kg, less than half the conventional one, because its structure is simple. The power consumption is small and helium gas, non-greenhouse gas, is used as refrigerant. Thus this refrigerator is very eco-friendly.
People began to use this product for many purposes. Needless to say, they use it as an outdoor cooler box, and it is sometimes used for transportation of blood and vaccine. In the U.S., medical staff uses it to cool a surgical knife to remove a wart and mole in cryoablation.
"In many cases, for example, some parts of machine and device such as a magnetic resonance imaging scanner (MRI) are cooled selectively to increase the accuracy, and in production process of semiconductors and liquid crystal, ultra-low temperature is needed to increase the degree of vacuum. The FPSC can satisfy users' needs most effectively to 'cool a limited space like a cooler box within a short time to an ultra-cold temperature'. When we consider the cooling capability and cost, the FPSC is much better than the conventional refrigerator and can be used for various industries."
The technology, which materialized two centuries after its theory was invented, improves our daily life.

Twinbird Corporation

Apr. 1962
1,742.4 million yen
284 (as of Dec. 2009)
Brief information:
Established as a manufacturer of plated ware and started production of home electric appliances in the 1980s. The motto of the company is "development of amazing and pleasant products"

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The company developed a dedicated working machine for itself.


The compact product is best suited for a cooler box.


The tip of cylinder is chilled quickly by "adiabatic expansion" and frost is formed on it within several minutes after the switch is turned on.


The demonstration model displayed in the meeting room