ROTARY COMPRESSOR

Abstract: A known rotary compressor is improved in that besides a top clearance volume (33a) formed between a cylinder chamber and at least one delivery valve, another top clearance volume (33b) producing a reverse flow of compressed fluid which generates pulsations adapted to offset a high frequency component of pulsations generated in the cylinder chamber by compressed fluid reversely flowing from the first-referred top clearance volume to the cylinder cham­ ber, is provided in communication with the cylinder chamber. Thereby a high frequency component of pulsations generated in the cylinder chamber can be eliminated, and a low-noise rotary compresser can be provided.

Description: BACKGROUND OF THE INVENTION: Field of the Invention: The present invention relates to improvements in a rotary compressor that is available as a refrigerant compressor for use in refrigeration or air-conditioning or the like, and more particularly to reduction of noises in such rotary compressor. Description of the Prior Art: At first, description will be made on a rotary compressor in the prior art, by way of example, in connec­ tion to a refrigerant compressor for use in refrigeration or air-conditioning with reference to Figs. 9 to 15. In these figures, reference numeral 1 designates a tightly closed housing, and at the top of this housing is provided a delivery pipe 2 for leading compressed refrigerant gas within the housing to the outside. To this delivery pipe 2 are successively connected a condenser 4, a throttling mechanism 5, an evaporator 6 and an accumulator 7 via refrigerant pipings 3, and the accumulator 7 is communi­ cated with a cylinder chamber 20 within the tightly closed housing 1 via a suction pipe 8. Reference numeral 9 designates an inlet portion of the suction pipe 8 within the accumulator 7. A gaseous refrigerant sucked from the inlet portion 9 through the suction pipe 8 into the cylinder chamber 20 is compressed, then it is delivered into a delivery cavity 13 through a delivery port 34 and a delivery valve 42, and thereafter it is led out to a space portion 14 within the tightly closed housing 1, passed around a motor 11 and delivered to the outside of the tightly closed housing 1 through the delivery pipe 2. Reference numeral 12 designates a crank shaft and numeral 15 designates a lubricating oil kept at the bottom of the tightly closed housing. Reference numeral 30 designates a cylinder main body fixedly secured to the lower portion of the tightly closed housing 1, at the upper and lower ends of the cylinder main body 30 are fixedly secured by bolts an upper bearing 40 and a lower bearing 41, respectively, which rotatably support the crank shaft 12, and thereby a tightly closed cylinder chamber 20 is formed. Within the cylinder chamber 20 is disposed a rotor 31 as loosely fitted in an eccentric portion of the crank shaft 12, and this cylinder chamber 20 is partitioned into a suction side space 20a communicat­ ing with the suction pipe 8 and a compression side space 20b by means of a partition plate 32 which is slidably fitted in a groove provided in the cylinder main body 30 so that the tip end of the partition plate 32 on the side of the cylinder chamber 20 may be pressed against the outer circumferential surface of the rotor 31. The above-mentioned delivery port 34 is provided in the upper bearing 40 contiguously to the partition plate 32 so as to communicate with the compression side space 20b, and to this delivery port 34 is mounted a delivery valve 42 via a retainer 43 and a bolt 44. Reference numeral 33 designates a notched groove provided on the cylinder 30 for the purpose of ensuring a cross-section area of the passageway between the delivery port 34 and the cylinder chamber 20, and compressed gas is adapted to be delivered from this notched groove 33 through the delivery port 34. In the rotary compressor having the above-­ mentioned construction, while refrigerant gas at a low pressure is being sucked through the suction pipe 8 into the suction side space 20a, the gas sucked during the preceding rotation is compressed in the compression side space 20b whose volume is being reduced as the rotor 31 rotates, and thereafter it is passed through the notched groove 33 and the delivery port 34 and delivered from the delivery port 42. However, the notched groove 33 and the delivery port 34 form the so-called to clearance volume, and the delivery gas existing in this space portion would not be delivered through the delivery valve 42, but after the rotor 31 has passed the top clearance volume portion, it would flow reversely into the suction side space 20a which is in a suction stroke. Accordingly, if the pres­ sure within this cylinder chamber 20 is measured, it shows the behavior as shown in Fig. 12. In Fig. 12, a rotational angle of a rotor is taken along an abscissa, while a pressure within a cylinder chamber is taken along an ordinate, and since the gas in the top clearance volume portion would abruptly flow in the reverse direction into the suction side space 20a at a low pressure, a pressure waveform measured in the suction side space 20a would contain pulsations having a high frequency component as shown at A. Therefore, there was a problem in the prior art that due to influence of these pulsations, noises of a compressor became large. Hence, in order to prevent these pulsations having a high frequency component, improved structures were invented in the prior art such that a buffer 35 making use of a sound effect as shown in Figs. 13 and 14 was provided at the top clearance volume portion, or that a scraped portion 36 of about several hundreds microns in depth was provided from the notched groove 33 up to the suction side space 20a so as to leak gas gradually for the purpose of preventing the gas in the top clearance volume from leaking abruptly to the suction side space 20a as shown in Fig. 15. However, the structure shown in Figs. 13 and 14 involved the problem that if a part of lubricating oil sucked into the cylinder during operation should enter the buffer 35 and the volume of the buffer should be fill­ ed with the lubricating oil, a sufficient noise reduction effect could not be revealed. On the other hand, the structure shown in Fig. 15 involved the problem that de­ terioration of a performance due to leakage of gas generat­ ed when the rotor 31 came to the scraped portion 36 that is larger than that generated in the case where the scraped portion 36 is not present, was observed, and also depending upon an operating pressure condition the effect was reduced due to a constant cross-section area of the leakage path. Moreover, since the depth of scraping was several hundred microns, the structure was associated with difficulties in machining, and in order to maintain the effect for a wide range of operating pressure condition it was necessary to decrease the depth of the scraped portion 36 and elongate its length, but this would quicken the timing of leakage and would increase deterioration of a performance. In essence, the heretofore known rotary com­ pressors involved the problems that due to abrupt leakage of gas in a top clearance volume into a cylinder space at a low pressure, pulsations having a high frequency com­ ponent were generated in the cylinder space and noises caused by these pulsations were produced, or that even with improved structures proposed for resolving the above-­ mentioned problem, the effect of improvement was not suf­ ficiently revealed, and deterioration of a performance caused by leakage of gas or difficulties in machining were associated. SUMMARY OF THE INVENTION: It is therefore one subject of the present inven­ tion to provide an improved rotary compressor that is free from the above-described disadvantages in the prior art. A more specific object of the present invention is to provide a low noise rotary compressor in which noises caused by pulsations having a high frequency com­ ponent generated by compressed fluid flowing reversely from a top clearance volume to a cylinder chamber are eliminated or at least largely reduced. According to one feature of the present inven­ tion, there is provided a rotary compressor of the type that the compressor includes a rotor performing rotary motion within a cylinder, and a cylinder chamber formed between the cylinder and the rotor and partitioned by a partition plate into a suction side space and a compres­ sion side space, and in which fluid sucked into the suction side space is compressed and delivered from the compression side space through a delivery valve, improved in that besides a top clearance volume formed between the cylinder chamber and at least one delivery valve, another top clearance volume producing a reverse flow of compressed fluid which generates pulsations adapted to offset a high frequency component of pulsations generated in the cylinder chamber by compressed fluid reversely flowing from the first-referred top clearance volume to the cylinder chamber, is provided in communication with the cylinder chamber. According to another feature of the present invention, there is provided the above-featured rotary compressor, in which the above-mentioned another top clearance volume is provided at such position that a reverse flow of compressed fluid which generates pulsa­ tions phase-shifted by one-half cycle with respect to the high frequency component of the pulsations generated by the reverse flow of compressed fluid from the first-­ referred top clearance volume may be produced. According to the present invention, owing to the improved structure of the rotary compressor as de­ scribed above, an inversed flow of compressed fluid from the additional top clearance volume into the cylinder chamber is produced, a high frequency component of pulsa­ tions generated by this inverse flow serves to offset the high frequency component of the pulsations generated by the compressed fluid flowing reversely from the top clearance volume formed between the cylinder chamber and the delivery valve, and thereby the high frequency com­ ponent of the pulsations generated in the cylinder chamber can be eliminated. Therefore, reduction of noises of a rotary compressor caused by a high frequency component of the above-described pulsations, can be achieved. Moreover, since the additional top clearance volume could be provided at a displaced position, lubricat­ ing oil would not fill the additional top clearance volume, nor there is no difficulty in machining, and so, the effect of the improved structure can be fully revealed without deteriorating a performance of the rotary compressor. The above-mentioned and other objects, features and advantages of the present invention will become more apparent by reference to the following description of preferred embodiments of the invention taken in conjunc­ tion with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS: In the accompanying drawings: Figs. 1 to 6 are partial perspective views, respectively, showing structures of essential parts of different preferred embodiments of the present invention; Fig. 7 is a diagram showing a variation of a pressure within a cylinder as a function of a rotational angle of a rotor; Fig. 8 is a diagram showing results of experi­ ments conducted for reducing noises of a rotary compressor; Fig. 9 is a longitudinal cross-section view showing a structure of a conventional rotary compressor; Fig. 10 is a transverse cross-section view taken along line I-I in Fig. 9; Fig. 11 is a transverse cross-section view taken along line II-II in Fig. 9; Fig. 12 is a diagram showing a variation of a pressure within a cylinder as a function of a rotational angle of a rotor; Fig. 13 is an enlarged partial cross-section view showing a structure of a portion in the proximity of a delivery valve in a different example of a rotary com­ pressor in the prior art; Fig. 14 is a partial perspective view of the portion shown in Fig. 13; and Fig. 15 is a partial perspective view similar to Fig. 14 showing a structure of a corresponding portion in a further different example of a rotary compressor in the prior art. DESCRIPTION OF THE PREFERRED EMBODIMENTS: In the following, one preferred embodiment of the present invention will be described with reference to Figs. 1 to 8. It is to be noted that in the following descrip­ tion only an essential part of the preferred embodiment will be explained and the remaining part of the embodiment is assumed to be identical to the corresponding part of the rotary compressor in the prior art as described previously. The embodiment shown in Fig. 1 is of such type that delivery valves are provided at two locations on the upper side and the lower side of a cylinder 30, in which two notched grooves 33a and 33b provided respectively on the opposite sides of the cylinder (that is, in the upper side portion and in the lower side portion) and communi­ cated with the upper and lower delivery valves, respec­ tively, are disposed as displaced from each other in the circumferential direction of the cylinder 30, an angle of displacement between these respective notched grooves 33a and 33b as viewed from a center axis of the cylinder represented by Δϑ [rad] is chosen so as to fulfil the following relation: Δϑ ≒ π × Δt × N/60 where Δt represents a time period [sec] from a crest to the next crest of a high frequency component of pulsa­ tions in a cylinder chamber generated in the beginning of a compression stroke, and N represents a rotational speed [rpm] in operation of a compressor, and the con­ struction is such that the notched groove 33b and a delivery port communicating therewith may function as another top clearance volume with respect to a top clear­ ance volume formed by the notched groove 33a and a delivery port communicating therewith. While the embodiment shown in Fig. 1 is of such type that the positions of the upper and lower delivery ports are also displaced by Δϑ from each other, modification could be made such that the positions of the upper and lower delivery ports are selected at the same position and the angle of displacement Δϑ is realized by broadening the width in the circumferential direction of one notched groove 33b as shown in Fig. 2. In other words, with regard to the notched grooves serv­ ing as means for shifting a timing of leakage by Δϑ, though it is preferable to dispose notched grooves having the same configuration as displaced by Δϑ as shown in Fig. 1, a notched groove of different shape such as the notched groove 33a shown in Fig. 2 or 3 could be employed. It is to be noted that in the case where the configurations of the two notched grooves are different from each other as is the case with the embodiments shown in Figs. 2 and 3, though the leakage timing is always shifted by Δϑ due to their geometrical configurations, cross-section areas of the leakage paths are not identical because of the different shapes of notched grooves. Especially, in the case of the embodiment shown in Fig. 3, the leakage path cross-section area in the beginning of leakage of the notched groove 33a is small as compared to the leakage path cross-section area in the beginning of leakage of the notched groove 33b. According to the present invention it is desired to shift a substantial leakage by Δϑ, that is, by one-half cycle of a high fre­ quency component of the pulsations, hence in the case where the configurations of two notched grooves are not identical to each other, in order to shift a substantial leakage by Δϑ it is necessary to determine the displace­ ment angle between the two notched grooves as taking into account the difference in the leakage path cross-section area, and for instance in the embodiment shown in Fig. 3, the displacement angle ϑ between the notched grooves would fall in the following range: Δϑ ≒ (1.0 - 2.0) × π × Δt × N/60 Next, description will be made on preferred embodiments in which a delivery valve is provided at one location on one side of a cylinder. Fig. 4 shows one preferred embodiment of the present invention in which a notched groove 33b is provided on the same end side of a cylinder as a notched groove 33a as shifted in position by Δϑ in the circum­ ferential direction with respect to the latter notched groove 33a and a delivery port is provided in communica­ tion with the notched groove 33a. The notched groove 33b is provided independently as an additional top clearance volume. In the embodiment shown in Fig. 4, the top clearance volume formed on the side of the notched groove 33a is the sum of the volume of this notched groove 33a plus the volume of the delivery port communicated with the notched groove 33a. However, if the notched groove 33b is provided so as to have the same volume as this sum, then the top clearance volume would be increased and would result in deterioration of a performance. Therefore, modification could be made such that the volume of the notched groove 33b is made nearly equal to the volume of the notched groove 33a, a communication groove 33 is provided to communicate the respective notched grooves 33a and 33b with each other as shown in Fig. 5 and there­ by the amount of compressed fluid flowing reversely may be divided equally. At this instance, the communication groove 33c could be provided on an end surface of the cylinder main body 30 apart from the cylinder chamber as shown in Fig. 6. Furthermore, as will be apparent from the above-­ described embodiments, in essense it is only necessary to make the compressed fluid in the top clearance volume flow reversely as divided into two occurrences at timings shifted by Δϑ, and hence it will understood that in the embodiments having delivery port at one location, another top clearance volume, that is a a top clearance volume corresponding to the notched groove 33b shown in Figs. 4, 5 and 6 could be provided in the upper bearing 40 or in the lower bearing 41 without being restricted to only the cylinder main body 30. As described above, owing to the fact that with respect to at least one top clearance volume formed be­ tween a cylinder chamber and a delivery valve, another top clearance volume is provided as displaced by Δϑ to make the compressed fluid in the top clearance volumes flow reversely into the cylinder chamber as divided into two occurrences at timings shifted by Δϑ, the phases of the high frequency components of the pulsations generated within the cylinder by the reverse flow would act so as to offset each other and would be eliminated because with respect to a high frequency component A of the pulsations generated by the initial reverse flow, a high frequency component B of the pulsations generated by the subsequent reverse flow is shifted by one-half cycle, that is, by 180 degrees. Accordingly, noises caused by the above-­ mentioned pulsations can be reduced. Fig. 8 shows results of experiments conducted by means of a refrigerant com­ pressor having a displacement of 28 cc/rev. and a capacity of 20000 BTU/H. As will be apparent from this diagram, in a high frequency range of 1 KHz or higher, noise reduc­ tion of several decibels was observed. It is a matter of course that the present inven­ tion is not limited to a roller type of rotary compressors employed in the above-described embodiments but it is equally applicable to a vane type and other types of rotary compressors. As described in detail above, according to the present invention, a high frequency component of pulsa­ tions generated in a cylinder chamber by a reverse flow of compressed fluid from a top clearance volume into the cylinder chamber can be eliminated by providing another top clearance volume, producing a reverse flow of the compressed fluid from this additional top clearance volume at a shifted timing, and offsetting the first-referred high frequency component with a high frequency of pulsa­ tions generated by the additional reverse flow of the compressed fluid, and therefore, reduction of noises caused by high frequency components of the above-mentioned pulsations can be realized. Moreover, since the additional top clearance volume may be provided at a displaced position, lubricat­ ing oil would not fill the top clearance volume, no dif­ ficulty in machining is associated, deterioration of a performance would not be resulted, and the effect of the additional top clearance volume can be fully revealed. Since many changes and modifications in design can be made to the above-described construction without departing from the spirit of the present invention, all matter contained in the above description and illustrated in the accompanying drawings shall be interpreted to be illustrative and not as a limitation to the scope of the invention.

Claims: 1. A rotary compressor of the type that the compressor includes a rotor performing rotary motion within a cylinder, and a cylinder chamber formed between said cylinder and said rotor and partitioned by a partition plate into a suction side space and a compression side space, and in which fluid sucked into the suction side space is compressed and delivered from the compression side space through a delivery valve; characterized in that besides a top clearance volume formed between said cylinder chamber and at least one delivery valve, another top clearance volume producing a reverse flow of compressed fluid which generates pulsations adapted to offset a high frequency component of pulsations generated in the cyl­ inder chamber by compressed fluid reversely flowing from first said top clearance volume to the cylinder chamber, is provided in communication with said cylinder chamber. 2. A rotary compressor as claimed in Claim 1, characterized in that said another top clearance volume is provided at such position that a reverse flow of com­ pressed fluid which generates pulsations phase-shifted by one-half cycle with respect to the high frequency compo­ nent of the pulsations generated by the reverse flow of compressed fluid from first said top clearance volume may be produced. 3. A rotary compressor as claimed in Claim 1 or 2, characterized in that said another to clearance volume is formed between first said top clearance volume and another delivery valve provided on the opposite side of the cylinder chamber with respect to first said top clearance volume. 4. A rotary compressor as claimed in Claim 1 or 2, characterized in that said another top clearance volume is provided as an independent top clearance volume on the same cylinder chamber end side as first said top clearance volume. 5. A rotary compressor as claimed in Claim 4, characterized in that said another top clearance volume and first said top clearance volume are communicated with each other. 6. A rotary compressor as claimed in Claim 1, characterized in that said another top clearance volume is formed as a notched groove provided in said cylinder or at least one of members closing the opposite ends of said cylinder.

Inventors: FUJITANI, MAKOTO NAGOYA TECHNICAL INSTITUTE, HIRABAYASHI, MASASHI NAGOYA TECHNICAL INSTITUTE, HONDA, HIDEO NAGOYA AIR-COND. &RMW, KONDO, MASAMI C/O CHURYO ENGINEERING K.K., MACHIDA, HIROSHI NAGOYA AIR-COND. &RMW, ONODA, SACHIO C/O CHURYO ENGINEERING K.K., Honda, Hideo Nagoya Air-Cond. &amp;RMW, Machida, Hiroshi Nagoya Air-Cond. &amp;RMW
Applicants: CHURYO ENGINEERING KABUSHIKI KAISHA, MITSUBISHI JUKOGYO KABUSHIKI KAISHA
Application year: 1988
Main classification: F04C29
IPC codes: F04C29, F04C18