Ishii, N.

Kawahara, S.

Kojima, Y.

Sakai, M.

Sawai, K.

Tsubokawa, M.

Yamamoto, S.

Yamamura, M.

English

Purdue E-Pubs

Purdue UniversityPurdue e-PubsInternational Compressor Engineering Conference School of Mechanical Engineering1992A Compact Horizontal Scroll Type Compressor forRoom Air ConditionersK. SawaiMatsushita Electric Industrial CompanyM. YamamuraMatsushita Electric Industrial CompanyY. KojimaMatsushita Electric Industrial CompanyS. YamamotoMatsushita Electric Industrial CompanyS. KawaharaMatsushita Electric Industrial CompanySee next page for additional authorsFollow this and additional works at: https://docs.lib.purdue.edu/icecThis document has been made available through Purdue e-Pubs, a service of the Purdue University Libraries. Please contact epubs@purdue.edu foradditional information.Complete proceedings may be acquired in print and on CD-ROM directly from the Ray W. Herrick Laboratories at https://engineering.purdue.edu/Herrick/Events/orderlit.htmlSawai, K.; Yamamura, M.; Kojima, Y.; Yamamoto, S.; Kawahara, S.; Sakai, M.; Tsubokawa, M.; and Ishii, N., "A Compact HorizontalScroll Type Compressor for Room Air Conditioners" (1992). International Compressor Engineering Conference. Paper 848.https://docs.lib.purdue.edu/icec/848AuthorsK. Sawai, M. Yamamura, Y. Kojima, S. Yamamoto, S. Kawahara, M. Sakai, M. Tsubokawa, and N. IshiiThis article is available at Purdue e-Pubs: https://docs.lib.purdue.edu/icec/848A Compact Horizontal Scroll-Type Compressor for Room Air Condi~ioners by Kiyoahi Sawai 1 , Miehio Yamamura2 , Yoshioori Kojima 1 , Shuiehi Yamamoto 1 , Sadao Kawahara•, Maoabu Sakal 3 , Masahiro Tsubokawa4 and N oriaki Is bii 5 Chief Engineer, Air Conditioning Research Laboratory, Director, Air Conditioning Research Laboratory, Engineer, Air Conditioning Research Laboratory, Engineer, Compressor Division, Matsushita Electric Industrial Co., Ltd. (PANASONIC), Noji-cho, Kusatsu 525, Japan Professor, Faculty of Engineering, Osaka Electro-Communication Universiry, Neyagawa, Osaka 572, Japan. ABSTRACT This paper presents the construcrion, newly developed design technologies and performance characteristics of a compact horizontal scroll-type compressor for room air conditione~:s. The authors were able lo develop a compacl variable speed horizontal scroll-type compressor with a cooling capacity of I. 8 kW, which necessitated the devel-opment of new mechanisms, namely, an alCial compliance mechanism for compensating liquid compression, an oil pump mechanism for Iubricalion and a suppression mecha-nism for oil discharge. Use of the new compressor in room air conditioners made it possible to reduce rhe elCternal unil of the air conditioner by about 25%. The new com-pressor possesses a high efficiency: about I 0% higher especially al low speed opera-tion. !.INTRODUCTION In recent years, in the field of room air conditioners, I here has been an increasing demand for reduced equipment energy consumption as well as for lower vibration and noise. The attention of the authors was drawn to the outstanding low vibration and low noise characteristics of scroll compressors, and the authors have already developed the world's first compact vertical scroll compressor with a cooling capacity of 2.4 kW, which is used in room air conditioners that were put on the market in 1990. This paper describes efforts to develop a smaller horizontal scroll compressor, with the goal of re-ducing the size of lhe external unit of split-type room air conditioners. The cooling ca-pacity of the new compressor is 1. 8 kW, which is the most frequently used capacity for household applications in Japan. Because horizontal compressors have up to now presented problems such as diffi-culty in supplying lubricating oil to the mechanisms and discharging large amounts of oil from the compressor to the refrigeration cycle, achieving this goal was considered difficult. However, by developing a new trochoid-type oil pump mechanism for lubri-cation and a suppression mechanism for oil discharge, completely horizontal installation was made possible. In addition, by using a radial compliance device developed by our company, high efficiency was assured when the cooling capacity· was reduced. Furthermore, greater reliability was achieved by developing and adopting an uial compliance device that limits the effects of liquid compression. In this paper, the structure of the newly developed scroll compressor, as well as its features and perfor-mance characterisrics, are presented. 2. OVERVIEW OF THE NEWLY DEVELOPED SCROLL COMPRESSOR The design of the newly developed scroll compressor is shown in Figure I, and its specifications are given in Table 1. 2.1 Internal High-Pressure Structure gf the Shell In development, emphasis was placed on compression efficiency, and rhus a high-pressure shell was adopted with the aim of minimizing the degree of superheat of the intake gas and suppressing the amount of oil discharged from the discharge conduit. 569 Table I Specifications of Horizontal scroll compressor Description Specification Compressor type --- Hermetic & motor-drive I111peller for111 - - Involute scro 11 Variable rotating speed rpm 600-7800 Displacement volume cc/rev 10.3 Built-in volume ratio --- 2.3 * Refri srati ng capacity k\'1 1 . 85 Outer dimension I Diameter mm 110 I Height mm 280 Weight . kg 1 0. 6 * JIS-A reQuir.ements; Pd=2.18 MPa , Ps=0.62 MPa , Ts=291 K N=3450 rpm (60 Hz) Oi 1 snpressor I Oi I pump Mo I or Ax i il Matn1 shaft I 0 i l I up pI J dnue ...;- Gas flow Fig. I Construction of horizontal scroll-type compressor Orb Ill oc -1<.41" Slide bub force Fig. 2 Slide bushing mechanism 2.2 Compressjon Mechanism The refrigerant gas is compressed in the crescent-shaped chambers bounded by the wraps of both the fixed scroll and the orbiting scroll, Bnd their end plates. The fixed scroll has an inlet on its periphery and an ou1let in the center of the end plate, and is secured to the main bearing frame at the periphery. A shaft is located in the center of the orbiting scroll end plate, and is driven by the main shaft (drive shaft). As shown in Figure 2, on the one end of the drive shaft, there is a rectangular hole in the vertical cross section, which is fitted with an eccentric bearing, namely a sliding bushing, con-nected to the shaft of the orbiling scroll in such a way as to rotate freely. This is a MBtsusbita original radial compliance device, name.ly a sliding bushing mechanism. The eccentric bearing is pressed against the inner side wall of the rectangular hole by a spring, which is attac:hed to the main shaft, so that the clearance between the scroll wraps in the radial direction can be maintained at a minimum value. The gas pressure in the compression chambers acts on the orbiting scroll end plate to pU5h it in the axial direction, away from the fixed scroll. In the new compres-sor, the discharge pressure is brought to the rear surface near the orbiting scroll cod 570 Oil discharge suppressor (011cbu(e pipe COfer) (Eucoooter plate) Fig.) Oil pump mechanism and oil discharge suppressor plate center, thereby suppressing an irregular orbiting scroll vibration in the axial di-rection. An Oldham ring is positioned in the space between the orbiting scroll end plate and the main bearing, preventing the orbiting scroll from rotating frec:ly. Additionally, an axial compliance device composed of a thrust ring and a wavy spring is positioned inside the: Oldham ring, prevc:nting liquid compression from occurring in the compres-sion chambers. The: ends of the orbiting scroll wrap are also equippc:d with a tip seal, sealing the compression chamber in the axial direction. The: main shaft is supported by a sliding bearing on its end on the orbiting scroll side, and by a ball bearing on the other end, thus giving a design that providc:s double end support. 3. MAIN TECHNOLOGIES USED IN DEVELOPMENT 3. I Oil Pump Mechanism With horizontal compressors, the comprc:ssion mechanism is generally isolated from the accumulated?? oil level, and for this rc:ason some mechanism is required to pump up the oil and supply it to the: compression mechanism. The new compressor is equipped with an oil pump, the cross-sectional view of which is shown in Figure 3. The oil pump has a trochoid volumetric rotor at one end of the main shaft, which pumps the oil and supplies it to the compression mc:chanism through a hole in the center of the main shaft. This provides a constant supply of lubrication for the sliding bushing, the main bearing and each sliding pair around the orbiting scroll. A portion of the oil used for lubrication is supplied to the compression chamber, but the major portion is returned to the inside of the shell. This oil pump makes it possible for the new room air conditioner to achieve a wide operating range, ranging from a low speed of 600 rpm to a high speed of 7,800 rpm. 3. 2 Oil Discharge Suppressor With horizontal compressors, oil pooled at the bottom of the shell is agitated by the motor's rotor and dispersed. Additionally, because of the short distance between the discharge pipe and the oil surface, the dispersed oil mist is discharged from the dis-charge pipe to the refrigeration cycle. When the oil discharge from the comprenor in-creases, the amount of oil within the shell decreases, and reliability-related problems such as insufficient lubrication occur. Furthermore, if there is an increase in the amount of oil mixed in with the refrigerant circulating in the refrige-ration cycle, the pressure losses especially in the low pressure conduit increase, thus decreasing the cooling or heating capacity. For these reasons, the new compressor is equipped with dual oil discharge sup-pressors, as shown in Figure 3. Using one method, several circular paths for refriger-ant gas were made on the plate supporting the ball bearing, as well as on the fan-shaped plates at positions corresponding to these gas paths. The refrigerant gas then strikes the fan-shaped plates at high speed, and the oil mist is separated from the gas. Using another method, the discharge piping is fitted with a cover, and because the refrigerant gas is in contact with the covc:r until it reaches the discharge piping, the oil mist in the gas adheres to the cover and is separated. These two methods made it possible to reduce the oil discharged from the dis-charge pipe to the refrigeration cycle to less than 0. 5%, in terms of the mass ratio of the discharged oil to the recirculating refrigerant. When used in conjunction with the re· 571 JIS-A r e q u i r em en 1 , 60Hz I .02~--~--~------~~ , Cap~city n:: I . 0 ·---------+---··:::--.. ·--Ell--...:.· c..: 0. 96 ·-.. :--t-·-----:---------:------- ' ________ :T=,,·-~t:·: .. ! j j ; D:: 0 • 9 4 :------'-----'---'-----' 0 0. I 0 i 1 /R e f r i g i r a n t 0.2 Ratio I. I 0::: "' I .0 ~ H Fig.4 Effect of the amount of oil on performance Orbit1ng scroll Mun shaft Fig.5 Axial compliance device frigeration cycle, the oil discharge suppression mechanism made it possible to maintain cooling and heating performance equivalent to that of vertical compressors. 3.3 Sealing Technologjes for Cnmpressjon Chambers In making the scroll compressor more compact, the most important issue. is to de· velop sealing technologies to reduce gas leakage and boost compression efficiency. The gas in the compression chamber leaks throagh the axial and radial clearances between the orbiting and fixed scroll wraps. For the axial clearance, tip seals were moanted on the tips of the wraps to prevent refrigerant gas leakage, while a sliding bushing mecha· nism was used to minimize the radial clearance, and thus prevent gas leakage there. In addition, a portion of the lubricating oil was supplied to the compression chamber via a pressure reducer embedded in the end plate of the orbiting scroll, helping to improve the seal of the compression chamber. The relationship between the amount of oil supplied to the compreuion ~:hamber and the performan<:e is shown in Figure 4. The pressure-reducing resistance was determined so as to maximize the performan~:c co-efficient within the normal range of operation. 3.4 Axial Compliance Mechanjsm An axial colliplian~:e device was newly developed and adopted for this compressor to protect the compressor from excessive loads resulting from liquid compression, and to improve reliability. Figure 5 shows the structure of this. device. The axial compli-ance device is composed of a thrust ring mounted on the rear surface of the orbiting scroll end plate, and a wavy spring sup-porting this ring. Ibis wavy spring has a pre· load. When an excessive load devo:olops within the compression chamber because of liquid compression or similar reasons, the thrust force acting on the orbiting scroll end plate overcomes the pre·load of the spring, and the orbiting scroll moves axially. This enlarges tbc axial clearance of the wraps, and tbe refrigerant liquid at high pressure Si2 3.0 N=3450 rpm (60 Hz) '; LIQUID PHASE RATIO a. :::;: 2,4 at SUCT!ON:X=0.9 <ll 1-6 I.. :J 1.2 00 00 aJ 0.6 I.. c.. 0 0 27! 47! 6rr Crank Angle Fig. 6 Calculated effect of axial compliance device moves from this space to another compression chamber, withoutincreasing the pressure of the compression chamber above a fixed value. Figure 6 shows the resulls of the calculations for evaluating the effectiveness of the new axial compliance device to limit the pressure changes within the compression chamber when liquid compression occurs .. In the c:alculations, it was assumed that a gas-liquid mixture is compressed. The leakage flow velocity of refrigerant from the high-pressure compression chamber, v , was calculated using the following expression: _K_ p { (!.L_)21< !.L_(<•Il/•j K-1 2 Pz Pz For the fluid phase, the leakage flow velocity of the refrigerant liquid, v1, was determined using Bernoulli's equation: 02RL.:..!2 v - g 1 Yt (1) (2) where I( represents the specific heat ratio of the refrigerant gas, Pt the compression chamber pressure (high pressure), p2 the pressure of the neighboring compression chamber (low pressure), y g the specific gravity of the refrigerant gas, y 1 the specific gravity of the refrigerant fluid, and g the gravitational acceleration. Through this simu-lation, it was determined that even when the percentage of the fluid phase is high during intake, use of the axial compliance device makes it possible to limit the compression chamber pressure to a low value, effectively protecting the compressor. 4. COMPRESSOR PERFORMANCE CHARACTERISTICS 4. 1 Performance Coefficient In Figure 7, the performance coefficient for cooling capacity of the new compres-sor is compared to that of a scroll compressor previously developed by Matsushita. The performance coefficient of the newly developed compressor is equivalent to that of the I . I JIS-A r e qui r em e 11 t "' 0::: I .0 0.9 E 0.8 0.... 0.7 I .0 2.0 3-0 4.0 Ref. Capac ty ( k w) Fig. 7 Comparison of performance coefficients 573 Pd=2. 18 MPa , Ps=0.62 HPa , Ts•291 ~ Measurement position:30cm """70r--..-------.-....... ----,--..---, "' >"' "' ..."' "' "' "' '-.p._ ..., c "' " 1/3 OCTAV I N=5250 rpm (90 Hz) I DEVELOPED 5k Frequency (Hz) 20k Fig. 8 Comparison of sound pressure spectra ~@~ ·-,-1ll1~~ -....::: ;::.-lJ~ I Compressor I 5 4 0 '\ 7 8 0 compressor Fig. 9 New smaller external unit of split-type room air conditioner existing compressor when the cooling capacity is in the 3 kW range, and is 10% higher than that of the previous compressor in the I kW range. Thus, the lower the cooling capacity, the higher the performance coefricient in comparison with the existing scroll compressor. This is due to the success, in practice, of a compressor with a smaller stroke volume (reduced 30%) through the usc o"f more sophisticated compression cham-ber sealing technologies, which make it possible to achieve higher operating speeds with identical cooling capacity. Because air conditioners are frequently used at low cooling capacities during constant operation for cooling or heating, the seasonal energy consumption efficiency ratio (SEER) is directly proportional to the rate of increase of the performance coeffi-cient at tow speed. 4.2 Noise Charaqeristjqs The noise characteristics of the newly developed compressor are shown in Figure 8. Compared with the previous scroll compressor, the newly developed compressor displays virtually the same noise level and noise spectrum. In comparison with Matsushita's rotary compressor, the noise levels of the new com-pressor are much lower at nearly all frequencies. However, there is a need to further reduce the level of noise below 1 kHz, because at these Jow frequencies, it is difficult to provide noise insulation in the air conditioner. 5. EFFECT OF COMPRESSOR ON SIZE OF THE AIR CONDITIONER Figure 9 is a schematic diagram of the externally mounted portion of a room air conditioner in which the newly developed compressor is installed. In contrast to com-574 pressors in the external units of existing air conditioners, the new compressor is posi-tioned horizontally, and its external diameter has been reduced from I I 8 mm to II 0 mm, enabling the space occupied by the external unit to be reduced by 25%. This has changed the appearance of the external unit as well as its image. 6. CONCLUSIONS By developing a lubricating oil pump and an oil discharge suppressor, the authors were able to make a horizontal compressor that can be mounted completely horizontally. Furthermore, by using a sliding bushing mechanism and optimizing the amount of seal-ing oil, the sealing technologies were significantly improved, making it possible to pro-duce the world's smallest capacity scroll compressor. When this compressor is in-stalled in an air cooditioner, the size of the external unit can be reduced by 25%, thus improving its appearance as well as its image. Matsushita has been marketing air conditioners equipped with this compressor since December 1991, and market response has been extremely favorable. Further ef-forts will be made to improve the efficiency of this compressor and reduce noise, boosting air conditioner energy efficiency and comfort. REFERENCES I. Ishii, N., Fukushima, M., Sano, K. & Sawai, K., A Study on Dynamic Behavior of a Scroll Compressor, Proc. International Compressor Engineering Conference at Purdue, Vol.3, Aug., 1986, pp.90l-916. 2.Ishii, N., Yamamura, M., Morokoshi, H., Fukushima, M., Yamamoto, S. & Sakai, M., On the Superior Dynamic Behavior of a Variable Rotating Speed Scroll Compressor, Proc.International Compressor Engineering Conference at Purdue, Vol. I, July, 1988, pp. 75-82; Transactions of the Japan Society of Mechanical Engineers (in Japanese), Series C, Vol. 55, No.517, 1989, pp.2436-2445. 3. Ishii, N., M., Yamamura, M., Muramatsu, S., Yamamoto, S. & Sakai, M., Mechanical Efficiency of a Vatiable Speed Scroll Compressor, Proc. International Compressor Engineering Conference at Purdue, Vol. 1, July, 1990, pp.l92- I 99. 4. Yamamura, M., Muramatsu, S., Kojima, Y., Yamamoto, S., Kawahara, S. & Ishii, N., Compact type Scroll Compressor for Air Conditioners, Proc. of Purdue Int. Compressor Engineering Conference, 1990, pp.l40-146. 5. Shibamoto, Y., Fujimoto, S., Takano, S., Higuchi, M. & Matoba, Y., The Characteristics of Small Capacity Scroll Compressors for Residential Air Conditioners, Proc. of Purdue Int. Compressor Engineering Conference, 1990, pp.l73-182. 575 

A Compact Horizontal Scroll Type Compressor for Room Air Conditioners

https://docs.lib.purdue.edu/cgi/viewcontent.cgi?article=1847&amp;context=icec

A Compact Horizontal Scroll Type Compressor for Room Air Conditioners

Abstract

Similar works

Full text

Available Versions

Purdue E-Pubs