Mitsubishi Heavy Industries Technical Review Vol. 46 No. 1 (Mar. 2009)
37Expansion of Products Equipped withSmall, Highly Efficient 3D Scroll Compressors
HAJIME SATO

HIROYUKI KOBAYASHIHISAO MIZUNOTETSUZO UKAI

MAKOTO TAKEUCHIYOSHIYUKI KIMATA|1. Introduction
Global efforts toward conserving energy have grown due to rising concerns about globalwarming. Because most energy consumed by refrigeration and air-conditioning appliances goes tothe compressor, its efficiency must be improved to save energy.
Meanwhile, the installation space of refrigeration and air-conditioning appliances is often
restricted. Reduction in the size and weight of each component, including the compressors, istherefore required to enhance installation flexibility.
Mitsubishi Heavy Industries, Ltd. (MHI) uses scroll compressors featuring high efficiency
and low vibration in its major refrigeration and air-conditioning products to meet the demand forenergy conservation. To improve efficiency even further while reducing size and weight, MHI hasnotedeveloped its innovative three-dimensional (3D) compression mechanism (3D scroll) that adds
axial compression to conventional radial compression. 3D scroll compressors are now in
production for a variety of refrigeration and air-conditioning products.
This paper describes the features of the 3D scroll and the application of the 3D scroll
compressor to refrigeration and air-conditioning products.
Note: “3D scroll” is a registered trademark of MHI.

|2. Features of the 3D scroll
Figure 1 shows a cross-sectional view of the 3D scroll compressor for a commercial
air-conditioner. The scroll compressor compresses the refrigerant using the mutual eccentricity of
one fixed and one orbiting scroll, each composed of end plates and wrapped scroll blades. Figure 2
shows cross-sectional views of conventional and 3D scrolls.

Figure 1 3D scroll compressor

Figure 2 Cross-sectional view of conventional
and the 3D scrolls

Mitsubishi Heavy Industries Technical Review Vol. 46 No. 1 (Mar. 2009)38

In conventional scrolls, the wrap height is constant throughout the compression process, andthe refrigerant is compressed two-dimensionally from the outer to the inner sides. For the 3D scroll,the outer wrap is made higher than the inner wrap by installing steps in the scroll tips and the endplates. The 3D scroll is thus able to compress the refrigerant three-dimensionally in the axial aswell as the radial directions. The 3D scroll has the following features.
･ A high compression ratio is possible by radial and axial compression.
･ The scroll is stronger and more reliable because of the reduced height of the inner wrap, which
receives a heavy load.
･ The scroll has a large capacity because the height of the outer wrap is greater, while the outer
diameter of the scroll remains unchanged. The 3D scroll is therefore smaller and lighter.

|3. Application of the 3D scroll to refrigeration and air-conditioningproducts
As described above, the 3D scroll is a high-performance compression mechanism with higher
efficiency, greater reliability, smaller size, and lighter weight than conventional scrolls. This makes
it suitable for specific applications such as refrigerators that require a high compression ratio andautomotive air-conditioners in which miniaturization is essential. As shown in Figure 3, MHI has
achieved significant improvement in efficiency and miniaturization in its current use of the 3D
12
scroll in commercial air-conditioners , gas heat pump (GHP) air-conditioners , reefer truck
34
refrigeration units , and automotive air-conditioners . We discuss some examples of these
improvements below.

Figure 3 Compressor products equipped with the 3D scroll

3.1.

Efficiency improvement

Figure 4 compares the efficiency of the conventional compressors with that of developed
compressors equipped with the 3D scroll. The increase in compression ratio using the 3D scroll
reduces the loss due to an insufficient compression ratio, and improves the efficiency under highcompression ratio conditions. Creating a mechanism to bypass the gas in the compression process
makes it possible to maintain high efficiency under low compression ratio conditions, resulting inhigh compression performance throughout the operating range1. Thus, use of the 3D scroll resulted
in a 6% improvement in efficiency compared to conventional scroll compressors and a 15%
improvement compared to conventional reciprocating compressors.

Figure 4 Comparison of efficiency with conventional compressors

Mitsubishi Heavy Industries Technical Review Vol. 46 No. 1 (Mar. 2009)
39

3.2.

Size and weight reduction

Figure 5 compares the outside dimensions of conventional compressors with those of thenewly developed 3D scroll compressors. The capacity of the scroll compressor is determined
mainly by the diameter of the scroll and the wrap height. In a conventional scroll compressor, any
increase in the wrap height decreases the strength of the inner side of the scroll, so scroll diametermust be increased to increase the capacity. However, the introduction of the 3D scroll made it
possible to increase the outside wrap height without increasing the inner wrap height. Thus, thecapacity of the 3D scroll compressor was increased without enlarging the diameter of the scroll.
Using this technology, the compressor size and weight are significantly reduced compared toconventional compressors, resulting in improved installation flexibility.

Figure 5 Outlines of conventional and the 3D scroll compressors|4. Conclusion
The development of MHI’s new 3D scroll compression mechanism has resulted in a
substantial improvement in efficiency, as well as a reduction in size and weight compared to theconventional scroll. The introduction of the 3D scroll to a wide variety of products has been amajor step for energy conservation in the refrigeration and air-conditioning industry. Theseactivities have been internationally recognized, and MHI was awarded the “2007 Climate
noteProtection Award”
by the Environmental Protection Agency and the “Japan Society ofRefrigerating and Air Conditioning Engineers Technology Prize” in 2007 and 2008. MHI isexpanding its scope of development to contribute to the preservation of the global environment
through eco-friendly refrigeration and air-conditioning products.
Note: Joint prize with Mitsubishi Motor Corporation

Mitsubishi Heavy Industries Technical Review Vol. 46 No. 1 (Mar. 2009)40

References
1.
2.
3.
4.

Sato, H. et al., Development of 3D Scroll Compressor, Proc. of 2007 International Conference onCompressors and Their Systems （2007） C658-009-07
Miyamoto et al., Development of R410A Scroll Compressor for Gas Engine Heat Pumps, Proc. of 2004
JSRAE Annual Conf., C308 (2004)
Fujitani et al., Development of Environment-Friendly Scroll Compressor for Truck Refrigerator, Proc. of2007 JSRAE Annual Conf. E315 (2007)
Takeuchi, M. et al., Development of Scroll Compressor QS90 for Automotive Air-Conditioning Systems,
Proc. of The International Symposium on New Refrigerants and Environmental Technology 2008 （2008）
p.189-195

Authors
Hajime Sato
Machinery Laboratory
Nagoya Research & Development
Center, Technical Headquarters

Hiroyuki Kobayashi
General Manager,
Air-Conditioner Designing andEngineering Department
Air-Conditioning & RefrigerationSystems Headquarters

Hisao Mizuno
Manager,
Air-Conditioner Designing andEngineering Department
Air-Conditioning & Refrigeration
Systems Headquarters

Tetsuzo Ukai
Manager, Automotive Thermal
Systems Designing & Engineering
Department
Air-Conditioning & Refrigeration
Systems Headquarters

Makoto Takeuchi
Manager,
Machinery Laboratory
Nagoya Research & Development
Center, Technical Headquarters

Yoshiyuki Kimata
Air-Conditioner Designing andEngineering Department
Air-Conditioning & Refrigeration
Systems Headquarters