The present invention relates to a sealed type compressor, more particularly, an improvement in the structure of a sealed type compressor.
<Overall Arrangement of Rotary Compressor>
An overall arrangement of a rotary compressor will be described with reference to
<Compression Element 7>
Compression element 7 is configured having a cylinder chamber at an upper stage and at a lower stage, i.e. two cylinder chambers. Compression element 7 includes an upper cylinder 12a with a cylinder chamber 11a having a circular transverse cross section, a lower cylinder 12b with a cylinder chamber 11b having a circular transverse cross section, and a middle plate 18 therebetween. On both upper and lower surfaces of upper cylinder 12a and lower cylinder 12b are provided an upper bearing 13 having a boss-shaped bearing portion 13a at its center and a lower bearing 14 also having a boss-shaped bearing portion 14a at its center, fastened by a plurality of bolts 15 to set cylinder chambers 11a and 11b at a sealed state.
Upper cylinder 12a and lower cylinder 12b are supported at a horizontal state in casing 1. An outlet 13c is provided at upper bearing 13. A front muffler 16 is secured to upper bearing 13 around bearing portion 13a so as to form an annular gap with respect to bearing portion 13a of upper bearing 13. Furthermore, an outlet 14c is provided at lower bearing 14. In addition, a rear muffler 17 that partitions oil reservoir 9 from the discharge space is secured to lower bearing 14 around bearing portion 14a of lower bearing 14.
An upper piston 19a and a lower piston 19b are arranged at cylinder chambers 11a and 11b of upper cylinder 12a and lower cylinder 12b, respectively. Upper and lower pistons 19a and 19b are arranged at the outer circumference of eccentric portions 20a and 20b of a crankshaft 26.
<Drive Element 8>
Drive element 8 includes an electric motor constituted of a stator 24 and a rotor 25. Stator 24 is fixedly-supported to an inner wall of a middle cylindrical body 2 in a casing 1. A rotor 25 is disposed concentrically with and at the inner side of stator 24 with a predetermined circumferential gap therebetween. The upper half portion of crankshaft 26 is mounted at the inner side of rotor 25 to rotate integrally about the shaft center. The lower half portion of crankshaft 26 is fit-supported rotatably by both bearing portions 13a and 14a of upper bearing 13 and lower bearing 14.
An oil channel 26a extending along the shaft center direction is formed at crankshaft 26. A centrifugal oil pump 27 is attached at the lower end of crankshaft 26. Oil pump 27 is constantly immersed in lubricant O of oil reservoir 9 to draw up lubricant O into oil channel 26a according to the rotation of crankshaft 26. The lubricant is supplied through a plurality of lubricant supply holes 26b provided at crankshaft 26 to each slidable site of compression element 7 and drive element 8.
The supply of lubricant towards bearing portion 14a of lower bearing 14 will be described hereinafter with reference to
Since communicating groove 14c has both the upper and lower ends open as shown in
It is to be noted that oil pump 27 draws up an amount of lubricant, a portion that will discharged to oil reservoir 9 without being used for lubrication, in addition to the amount required for lubrication towards respective sliding sites, causing futile pump loss. Patent Document 1 set forth below can be cited as a document disclosing a rotary compressor such as that shown in
Patent Document 1: Japanese Patent Laying-Open No. 2004-324652
Non-Patent Document 1: Takahide Ito et al. “Study On Oil Supply System for Rotary Compressors”, Mitsubishi Juko Giho, Mitsubishi Heavy Industries Ltd. September 1992, Vol. 29, No. 5, pp. 458-462
The problem to be solved by the invention arises from the fact that the oil supply groove provided at the lower bearing employed in a sealed type compressor is a communicating groove with both the upper and lower ends open. Futile pump loss occurs since the oil pump must draw up the lubricant that is merely to be output to the oil reservoir without being supplied to the lower bearing even though there is sufficient lubricant to be discharged to the oil reservoir. Thus, the present invention is directed to solving the above-described problem, and provides a sealed type compressor allowing improvement in the oil supply capability of the oil pump to suppress occurrence of pump loss by reducing futile induction of lubricant at the oil pump.
A sealed type compressor according to the present invention has a compression element and a drive element accommodated in a sealed vessel, and includes a crankshaft, a piston disposed at an outer circumference of an eccentric portion of the crankshaft, a cylinder defining a cylinder chamber where the piston is disposed, and an upper bearing and a lower bearing having a bearing portion to support the crankshaft axially, and sandwiching the cylinder and the piston from respective axial sides of the crankshaft.
The sealed type compressor includes an oil pump provided at a lower end of the crankshaft to draw up a lubricant stored in an oil reservoir at the lower end portion of the sealed vessel into an oil channel provided extending along a shaft center direction of the crankshaft to provide lubrication to each sliding site of the compression element and drive element, and an oil supply groove provided at a sliding face of the bearing portion of the lower bearing, extending along an axial direction of the crankshaft to supply the lubricant to the outer surface of the crankshaft.
The oil supply groove has one end side open at an end face of the cylinder side, and the other end side closed at a lower end side of the crankshaft.
According to the sealed type compressor of the present invention, the oil supply groove provided at the lower bearing is not a communicating groove open at the upper and lower ends, and is closed at the lower end side of the crankshaft. As a result, the lubricant supplied to the lower bearing is entirely applied to the lower bearing without a portion being discharged to the oil reservoir.
Thus, by reducing futile induction of lubricant at the oil pump, the oil supply capability of the oil pump can be improved to suppress occurrence of pump loss.
1 casing; 4 lower lid; 5a, 5b induction pipe; 7 compressor element; 8 drive element; 9 oil reservoir; 10 storage space; 11a, 11b cylinder chamber; 12a upper cylinder; 12b lower cylinder; 13 upper bearing; 13a bearing portion; 13c, 14c outlet; 14A lower bearing; 14a bearing portion; 14b oil supply groove; 14c communicating groove; 15 bolt; 16 front muffler; 17 rear muffler; 18 middle plate; 19a upper piston; 19b lower piston; 24 stator; 25 rotor; 26a oil channel; 26b lubricant supply hole; 27 oil pump; O lubricant.
Each of the embodiments of a sealed type compressor according to the present invention will be described hereinafter with reference to the drawings. As an example of a sealed type compressor of the present embodiment, an application of the present invention to the rotary compressor set forth above in the background art will be described.
The rotary compressor of the present embodiment has the same basic arrangement as the rotary compressor with a cylinder chamber at an upper stage and at a lower stage, i.e. two cylinder chambers, described with reference to
There are further provided an upper bearing 13 and a lower bearing 14 sandwiching upper cylinder 12a, upper piston 19a, lower cylinder 12b and lower piston 19b from respective axial sides of crankshaft 26.
In addition, at the lower end of crankshaft 26 is provided an oil pump 27 to draw up a lubricant O stored in an oil reservoir 9 at the lower end portion of casing 1 into an oil channel 26a provided so as to extend along the shaft center direction of crankshaft 26 to, provide lubrication to each sliding site of compression element 7 and drive element 8, according to the rotation of crankshaft 26.
In the following description, elements identical to or corresponding to those of the rotary compressor described with reference to
Referring to
As shown in
The lubricant (F1) discharged from lubricant supply opening 26b provided at crankshaft 26 (refer to
As shown in
However the oil supply rate (cc/min) of lubricant to the lower bearing (A4) is greatly reduced in the present embodiment, as compared to that of the background art. This is because the lubricant supplied to lower bearing 14A of the present embodiment is entirely applied to lower bearing 14 without being partially discharged to oil reservoir 9 (refer to
The effect on the bearing performance when oil supply groove 14b is closed at the lower end side of bearing portion 14a will be studied from the standpoint of <bearing friction loss> and <cooling performance of bearing>.
<Bearing Friction Loss>
The most critical factor in the issue of the oil supply rate involved in the reliability of a bearing is the cooling performance. It is possible to appraise the cooling performance by estimating how much the oil temperature rises by the generated bearing friction loss. The bearing friction loss W can be expressed by equation 1 set forth below, where L is the overall bearing length, r the bearing radius, μ the oil viscosity, u the sliding rate, C the clearance, and δ the oil film clearance. Assuming that overall bearing length L, bearing radius r, oil viscosity μ and sliding rate u are constants in equation 1, bearing friction loss W will rapidly increase when the oil film clearance δ approaches zero.
W=[2πLrμu2]÷[C(1−δ2)1/2] (1)
(where λ=1−(δ/C))
<Cooling Performance of Bearing>
In the case where it is assumed that the oil supply rate to the bearing varies linearly when the length of the oil supply groove is shortened, and that the oil film clearance in such a case also varies linearly in proportion to the oil supply rate, a shorter length of the oil supply groove causes reduction in the oil supply rate, which in turn reduces the oil film clearance to increase the bearing friction loss. It is to be noted that the bearing friction loss tends to increase suddenly when the oil film clearance becomes small, as indicated by equation 1 set forth above. Therefore, when the oil film clearance becomes small, the temperature of the bearing rises significantly since cooling is effected with a smaller amount of lubricant corresponding to the greater bearing friction loss.
The relationship between the ratio (X/L) of the length of the oil supply groove (X) to the entire length of the bearing (L) and the bearing temperature increase will be described with reference to
Although the embodiment has been described based on the case where the present invention is applied to a rotary compressor having a cylinder at an upper stage and at a lower stage, i.e. two cylinders, the present invention is also applicable to a rotary compressor having a cylinder at one stage. Moreover, the structure based on the present invention is widely applicable, not only to rotary compressors, but to other sealed type compressors having a similar compression element structure.
It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the appended claims, and all changes that fall within the limits and bounds of the claims, or equivalence thereof are intended to be embraced by the claims.
Number | Date | Country | Kind |
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2007-295657 | Nov 2007 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/JP2008/069493 | 10/28/2008 | WO | 00 | 5/11/2010 |