SCROLL COMPRESSOR

Abstract: A scroll compressor provided with first and second scrolls rotating in the same direction, wherein a discharge valve for blocking an opening of a discharge hole provided in one of the first and the second scrolls is formed so as to be acted on by a centrifugal force at the opening portion of the discharge hole, a centrifugal force is caused to act on a check valve at the opening portion of the discharge hole during the operation to normally open the check valve, the check valve is prevented from opening or closing due to the difference in pressure between the interior of the discharge hole and the interior of a high pressure chamber, and the scroll compressor is prevented from rotating in the reverse direction during the stop of operation.

Description: The present invention relates to a scroll compressor having a driving scroll member and a driven (idling) scroll member directly rotated by the driving scroll member wherein the two scroll member are rotated in the same direction. BACKGROUND OF THE INVENTION A conventional scroll compressor is shown in, for example, Japanese Patent Publication No. 1-35196/1989 (examined) in which the first and second scroll members in an excentric relation with each other are rotated in the same direction to compress a refrigerant in a compression space to thereby reduce vibration at the time of compression, so that the scroll compressor can be used for high-speed and/or large scaled applications. However, in the conventional scroll compressor, the refrigerant in a central compression space is discharged directly to a discharge chamber from a discharge port of a rotary shaft and, accordingly, it is difficult to affix a check valve directly to the rotary shaft. Besides, when the compressor is stopped, it is likely that the refrigerant in the discharge chamber flows back into the compression space through the discharge port to cause reversal rotation of the first and second scrolls. US-A-4842499 discloses a scroll compressor having the features set out in the preamble to claim 1. SUMMARY OF THE INVENTION An object of the present invention is to provide an improved scroll compressor which permits the discharge port to be normally open during operation and closed at the stop of the operation, wherein the discharge port is disposed on at least one of the first and second scrolls. According to the present invention, there is provided a scroll compressor incorporating a scroll compressor unit in a sealed container, wherein said scroll compressor unit comprises: a first scroll member having an end plate, a wrap of an involute curve projecting from one side of said end plate, a rotary shaft projecting from the other side of said end plate and connected to an electric motor unit, a second scroll member having an end plate, a wrap of an involute curve projecting from one side of said end plate, a rotary shaft projecting from the other side of said end plate of said second scroll member, a main frame rotatably supporting said shaft of said first scroll member, a subsidiary frame rotatably supporting said shaft of said second scroll member, said wrap of said first scroll member being in a juxtaposed engagement relation with said wrap of said second scroll member, said shaft of said second scroll member being eccentrically spaced from said shaft of said first scroll member so that the wraps of the first and second scroll members are fitted closely together to form a plurality of compression spaces, and a driving device for rotating said second scroll member in the same direction as said first scroll member to continuously compress said compression spaces radially inwardly from an outer position to an inner position, wherein at least one of said first scroll member and said second scroll member has a discharge port connected to the inner position for said compression spaces, an opening for flowing a refrigerant, discharged into said discharge port, into said sealed container, and a check valve means for closing an opening of said discharge port, characterised by said check valve means having a valve body, said valve body being configured to effectively receive a centrifugal force of said shaft having said discharge port so that said opening of said discharge port is normally opened by the effect of the centrifugal force, and by the scroll compressor also incorporating the electric motor unit in the sealed container. By the construction described above, the check valve is disposed to the opening of the discharge port of the first or second scroll member in such a manner that the check valve is so configured that it is effected by a centrifugal force of the shaft of the scroll member, thereby normally opening the check valve by the centrifugal force. Thus, the check valve is prevented from being actuated by a pressure difference between the discharge port and a high pressure chamber in the sealed container, and thus a reversal rotation of the scroll members can be prevented. In one embodiment of the present invention, at least one of the first and second scroll members is provided with, at its rotary shaft, a discharge port connected to the compression space, and an opening connected to the discharge port is disposed on an outer surface of the rotary shaft. Further, the rotary shaft is provided with an arc-shaped spring-like discharge valve for closing the opening and a holding means for holding the discharge valve in such a manner that the holding means is disposed at an outer position of the discharge valve. In the embodiment described, the discharge valve for closing the discharge port is of spring-like arc-shaped structure for effectively receiving a centrifugal force, so that the discharge valve is normally opened by the centrifugal force. Thus, the discharge valve is not accidentally activated by a pressure difference between the discharge port and the high pressure chamber of the compressor unit and, at the same time, a reversal rotation of the scroll members at the time of stop of operation can be prevented. BRIEF DESCRIPTION OF THE DRAWING Fig. 1 is a sectional elevation of the scroll compressor embodying the present invention, Fig. 2 is an enlarged sectional view of a part of a check valve employed in the scroll compressor shown in Fig. 1, Fig. 3 is a sectional elevation of the scroll compressor according to another embodiment of the invention, Fig. 4 is an enlarged sectional view of a part of a check valve employed in the scroll compressor shown in Fig. 3, Fig. 5 is a sectional view showing a further embodiment of the invention, Fig. 6 is a sectional view showing a still further embodiment of the invention, Fig. 7 is a front view showing another embodiment of the invention, and Fig. 8 is a front view showing still another embodiment of the invention. PREFERRED EMBODIMENT OF THE INVENTION A first preferred embodiment of the present invention will be described with reference to Figs. 1 and 2. An electric motor unit 2 and a scroll compressor unit 3 are disposed at a lower portion and an upper portion, respectively, in a sealed container 1. The electric motor unit 2 has a stator 4 and a rotor 5 inside the stator with an air gap 6 therebetween. A passage 7 is formed on the outer surface of the stator 4 by partly cutting out the outer surface of the stator. A main frame 8 is press-fitted to an inner surface of the sealed container 1 and is provided with a main bearing 9 at a center thereof and, similarly, a subsidiary frame 10 is press-fitted to the inner surface of the sealed container 1. The subsidiary frame 10 has a subsidiary bearing 11 at a center thereof but spaced from the main bearing 9 of the main frame 8 by a distance "ε", and the main frame 8 and the subsidiary frame 10 are connected together by bolts 13 to form a chamber 12. The scroll compressor unit 3 has a first scroll 14 (i.e., driving scroll) and a second scroll 15 (i.e., idler or driven scroll) rotated in the same direction as the driving scroll 14. The driving scroll 14 has a disc end plate 16, a spiral wrap 17 extending from an upper surface of the end plate 16 in an involute curve configuration, and a driving shaft 18 projecting from a center of the lower surface of the end plate 16 to be fitted fixedly into a bore of the rotor 5. The driven scroll 15 has a sisc end plate 19, an annular wall 20 projecting from an outer circumference of the end plate 19 to slidably contact the end plate 16 of the driving scroll 14, a spiral wrap 21 extending from a lower surface of the end plate 19 in an angle-corrected involute curve configuration inside the annular wall 20, and an idler shaft 22. The spiral wrap 17 of the driving scroll 14 has coordinates which are obtained by: X = R (cos ϑ + ϑ sin ϑ) Y = R (sin ϑ - ϑ cos ϑ) and the spiral wrap 21 in an angle-corrected involute curve of the driven scroll 15 has coordinates which are obtained by: X = -R [cos ϑ + (ϑ + β) sin (ϑ + β)] Y = -R [sin ϑ - (ϑ + β) cos (ϑ + β)] β = tan ⁻¹ {P sin ϑ / (P cos ϑ + ε)} wherein: R : a radius of a basic circle P : a radius of a circle orbit of a driving pin The driving shaft 18 of the driving scroll 14 is journalled on the main beraring 9 of the main frame 8, and the idler shaft 22 of the driven scroll 15 is journalled on the subsidiary bearing 11. The driving scroll 14 and the driven scroll 15 are placed in a confronting engagement relation in the chamber 12 so that the wraps 17, 21 of the two scrolls 14, 15 are contacted with each other at a plurality of points to form a plurality of compression sapces 23. The interior of the sealed container 1 is divided into a low pressure chamber 24 and a high pressure chamber 25 by the main frame 8 and the subsidiary frame 10. A driving device 26 has a driving pin 27 projecting from an outer circumference of the end plate 16 of the driving scroll 14, and a guide groove 28 extending in a radial direction on the annular wall 20 of the driven scroll 15 for receiving therein the driving pin 27. The guide groove 28 is formed in a U-shape by cutting an outer portion of the driven scroll 15 so that a circle orbit of the outer circumferential end of the guide groove 28 is positioned outside a circle orbit of the center of the driving pin 27. The driving shaft 18 has a discharge port 29 for discharging therethrough a compressed refrigerant in the compression space 23 into the high pressure chamber 25. The discharge port 29 has an upper opening 30 and a lower opening 31, the both openings 30, 31 being connected to the high pressure chamber 25. The idler shaft 22 has a suction port 32 for directing the refrigerant in the low pressure chamber 24 to the compression space 23. The end plate 19 has a channel 33 which is connected to the suction port 32 for directing the refrigerant inwardly into the compression space 23. The end plate 16 of the first scroll 14 has a small through-hole 34 which connects the compression space 23 in a mid-compression with the chamber 12. The chamber 12 and the low pressure chamber 24 are hermetically sealed and shielded with each other by the sealing member 35 disposed on a sliding surface of the subsidiary bearing 11 of the subsidiary frame 10 relative to the idler shaft 22 of the driven scroll 15. Similarly, the chamber 12 and the high pressure chamber 25 are hermetically sealed by a sealing member 36 disposed on a sliding surface of the main bearing of the main frame 8 relative to the driving shaft 18 of the driving scroll 14. The structure which has been described so far is common to the other embodiments shown in Figs. 3 - 8. Referring again to Figs. 1 and 2, a check valve 37 has a valve body 39 for closing and opening a discharge opening 30, a spring 41 for biasing the check valve 37 toward the driving shaft 18 and a holder 43 fitted to the driving shaft 18 for fixing one end of the spring 41. Similarly, a check valve 38 has a valve body 40 for colsing and opening a discharge opening 31, a spring 42 for biasing the check valve 38 toward the driving shaft 18 and a holder 44 fitted to the driving shaft 18 for fixing one end of the spring 42. The valve bodies 39, 40 are made of materials having a large mass. A suction pipe 45 is disposed at an upper portion of the sealed container 1 so that it is connected with the low pressure chamber 24, and a discharge pipe 46 is disposed adjacent the lower portion of the main frame 8 so that it is connected with the high pressure chamber 25. In the scroll compressor shown in Figs. 1 and 2, when the electric motor unit 2 is driven, the first or driving scroll 14 is rotated through the main driving shaft 18 and then a rotational force of the driving scroll 14 is delivered to the second or driven scroll 15 through the driving device 26. Thus, the driven scroll 15 is rotated in the same direction as the driving scroll 14. The idler shaft 22 of the driven scroll 15 is eccentrically spaced from the driving shaft 18 of the driving scroll 14 by a distance "ε" and accordinly the driven scroll 15 is eccentrically rotated relative to the driving scroll 14. Thus, the compression space 23 is gradually reduced in its volume as it is moved inwardly from an outer position to an inner position of the spiral wraps, and the refrigerant flown from the suction pipe 45 into the low pressure chamber 24 is directed into the compression space 23 for the compression purposes through the suction port 32 of the shaft 22 and the channel 33 of the end plate 19. The thus compressed refrigerant is fed to the dicharge port 29 of the main driving shaft 18 of the driving scroll 14 and then to the high pressure chamber 25 through the discharge openings 30, 31, and after that discharged out of the sealed cantainer 1 through the discharge pipe 46. If the refrigerant is in a mid- compression stage and is of a middle pressure, it is discharged into the chamber 12 from the small through-hole 34 so that it serves as a back pressure to the two scrolls 14, 15, and the ends of the two spiral wraps 17, 21 of the driving and driven scroll members 14, 15 are slidably moved along the surfaces of the end plates 16, 19 with a constant clearance maintained between the two ends of the wraps. As described, the second or driven scroll 15 is rotated in the same direction as the first or driving scroll 14 by means of the driving device 26 and the driving device 26 is constructed in such a manner that a circle orbit of the outer circumference of the guide groove 28 is located outside a circle orbit of a center of the driving pin 27. By this construction, the driving pin 27 is snugly and reliably received in the guide groove 28 without removal therefrom, and only a single driving pin 27 can rotate the two scrolls in the same direction to gradually reduce the volume of the compression space 23 for the predetermined compression purposes. Further, the center of the driving scroll 14 is deviated or spaced from the center of the driven scroll 15 by a distance "ε" and the spiral wrap 17 of the driving scroll 14 is formed in an involute curve configuration whereas the spiral wrap 21 of the driven scroll 15 is formed in an angle-corrected involute curve configuration. This construction permits a suitable contact between the two wraps 17, 21 and prevents one wrap from releasing from, and abnormally press-fitting against, the other wrap so that a preferable compression is attained by the compression space 23, even when the rotational speed of the scroll members is changed. Since the low pressure chamber 24 and the high pressure chamber 25 are hermetically sealed by the sealing members 35, 36, a refrigerant of low pressure or high pressure is prohibited from flowing into the chamber 12 within the main and subsidiary frames 8 and 10 so that the predetermined middle pressure can be maintained in the chamber 12. Thus, a suitable sealing force in the axial direction of the two scrolls 14, 15 can be maintained. The compressed refrigerant in the compression space 23 is discharged from the upper opening 30 and the lower opening 31 into the high pressure chamber 25 through the discharge port 29 and, therefore, pressure reduction of the refrigerant discharged into the high pressure chamber 25 can be prevented. In addition, the refrigerant from the lower dicharge opening 31 is directed to the discharge pipe 46 through the air gap 6 and the passage 7 of the electric motor unit 2 and efficiently cool the electric motor unit 2 and, at the same time, the heat of the electric motor unit 2 is effectively utilized. The check valves 37, 38 receives a centrifugal force to their massive valve bodies 39, 40 by rotation of the main driving shaft 18 to thereby normally open the discharge openings 30, 31 against a resilient biasing force of the springs 41, 42, so that it does not serve as a resistance to the refrigerant flowing from the compression space 23 to the high pressure chamber 25 through the discharge port 29. Thus, at the time of a high compression ratio in a refrigeration operation in which less refrigerant is flown from the compression space 23 into the discharge port 29, the check valves 37, 38 are not actuated by a pressure difference occurred between the discharge port 29 and the high pressure chamber 25. In addition, the valve bodies 39, 40 of the check valves 37, 38, respectively, are pressed toward the main driving shaft 18 by the resilient force of the springs 41, 42 at the time of stop of operation and, accordingly, the discharge openings 30, 31 are closed to cut out the communication between the high pressure chamber 25 and the compression space 23. Thus, the refrigerant in the high pressure chamber 25 is prevented from flowing back into the compression space 23. In the embodiment discribed above, the check valves 37, 38 are fitted to the main driving shaft 18, and if desired, the check valves can be fittd to the subsidiary shaft by providing suitable discharge openings thereto. According to the first embodiment of the invention explained with reference to Figs. 1 and 2, check valves are provided to either the driving shaft of the first scroll member or the shaft of the second scroll member to selectively open and close the openings of the discharge port, and the check valves are so formed that they effectively receive a centrifugal force of the shaft. Therefore, when the scroll compresor is driven, the check valves are effected by a centrifugal force to thereby normally open the openings of the discharge port so that an increase in resistance at the passage or channel thereof can be prevented and, in addition, a noise due to the valve actuation can be reduced substantially at the high compression ratio operation since the valves are normally opened. Further, the openings of the discharge port are closed at the time of stop of operation and, accordingly, the refrigerant in the high pressure chamber is prevented from flowing back into the compression space. Figs. 3 and 4 show a second embodiment of the present invention. In Figs. 3 and 4 of the drawing, like reference numerals represent like parts of the previous embodiment of Figs. 1 and 2, and a general structure is as similar as the previous embodiment and, accordingly, the explanation of the same or similar structural features will be omitted for simplification only. In the embodiment of Figs. 3 and 4, the suction pipe 45 is connected to the low pressure chamber 24 and the discharge pipe 46 is connected to the high pressure chamber 25. A discharge opening 49, similar to the discharge opening 30 in Fig. 1 embodiment, is provided on the driving shaft 18, and a circular or arc-shaped spring valve 50 is provided to close the discharge opening 49. The spring valve 50 is held to the driving shaft 18 by a circular or arc-shaped valve holder 51. As shown in Fig. 4, the discharge valve 50 and its valve holder 51 are commonly fixed to the driving shaft 18 by means of a screw 54 at their ends 52, 53, respectively, and the other ends 55, 56 are located outside the discharge opening 49. The ends 52, 53 of the discharge valve 50 and its holder 51 are located at a preceding position of a rotational direction of the driving shaft 18, shown by arrow, relative to the other ends 55, 56, and the discharge valve 50 is resiliently pressed against the outer surface of the driving shaft 18. In the structure described above, the discharge valve 50 is press-fitted around the driving shaft 18 by its spring force to close the discharge opening 49 at the time of stop of operation. Accordingly, this prevents back-flow of the refrigirant and also prevents reversal rotation of the scroll compression unit 3 and resultant generation of noise and damages. In operation of the scroll compressor, the driving shaft 18 is rotated to permit the discharge valve 50 to be opened by a centrifugal force, so that the compressed refrigerant is readily discharged out of the dischare opening 49 without obstruction. In Fig. 5 which shows a modification, a discharge valve 57 is resiliently contacted by its spring force to an inner surface of the arc-shaped spring holder 51 so that the discharge valve 52 is held opened. In this modification, since the discharge valve 52 is opened by the effect of its own spring force and the centrifugal force, unnecessary activation of the valve 52 due to a pulsating flow of the refrigerant can by prevented and, therefore a noise produced generally by such pulsating flow of the refrigerant can be prevented. Further, since the resistance to the flow of refigerant at the discharge valve can be reduced, an efficient operation of the scroll compressor can be obtained. Besides, the discharge valve 57 closes the discharge opening 49 by a pressure of back-flowing refrigerant only immediately after the stop of the scroll compressor, so that the refrigerant does not flow back through the discharge opening 49. Fig. 6 shows another modification in which the circular or arc-shaped valve holder 58 is commonly secured at its opposite ends to the driving shaft together with one end of the arc-shaped valve 50 by the screw 54. This structure provide improvement in mechanical strength of the assembly. Fig. 7 shows a further modification in which a discharge valve 59 is wound around the driving shaft 18 so that a stress generated at the discharge valve 59 can be reduced. In Fig. 8 showing still another embodiment of the invention, a discharge valve 60 is divided at its one end into a plurality of portions such as two portions as in the illustrated embodiment, and similarly the discharge opening 49 is divided into two hole portions. These hole portions (49, 49) are closed by the divided end 55 of the discharge valve 60. In the embodiments shown in Figs. 5 to 8, the other structural and operational features can be considered to be similar to those of the embodiment of Figs. 3 and 4, and a detailed description will be omitted. In each of the embodiments, the discharge port can be provided to the ilder or subsidiary shaft 22 instead of the driving shaft 18 and in that case a discharge valve and its holder can be disposed in an appropriate way. In the embodiment shown in Figs. 3 and 4 and its modifications shown in Figs. 5 to 8, the arc-shaped spring valve has a long span to thereby decrease its bending stress, so that it can sufficiently and immediately respeond to the refrigerant flow to open and close the discharge opening. During the operation of the scroll compressor, the discharge opening can be held opened by a centrifugal force and, therefore, unnecessary activation, or open/close movement, of the valve body can be prevented. Thus, a noise due to unnecessary activation of the valve body can be limited. An application of the arc-shaped spring value having a long span may provide a problem of reduction of a mechanical strength but this problem can be solved completely by the use of the valve holder. Thus, the improved, noiseless scroll compressor is achieved without back-flow of the refrigerant, and reversal rotation of the scroll members.

Claims: A scroll compressor incorporating a scroll compressor unit (3) in a sealed container (1), wherein said scroll compressor unit (3) comprises: a first scroll member (14) having an end plate (16), a wrap (17) of an involute curve projecting from one side of said end plate (16), a rotary shaft (18) projecting from the other side of said end plate (16) and connected to an electric motor unit (2), a second scroll member (15) having an end plate (19), a wrap (21) of an involute curve projecting from one side of said end plate (19), a rotary shaft (22) projecting from the other side of said end plate (19) of said second scroll member (15), a main frame (8) rotatably supporting said shaft (18) of said first scroll member (14), a subsidiary frame (10) rotatably supporting said shaft (22) of said second scroll member (15), said wrap (17) of said first scroll member (14) being in a juxtaposed engagement relation with said wrap (21) of said second scroll member (15), said shaft (22) of said second scroll member (15) being eccentrically spaced from said shaft (18) of said first scroll member (14) so that the wraps (17,21) of the first and second scroll members are fitted closely together to form a plurality of compression spaces (23), and a driving device (26) for rotating said second scroll member (15) in the same direction as said first scroll member (14) to continuously compress said compression spaces (23) radially inwardly from an outer position to an inner position, wherein at least one of said first scroll member (14)and said second scroll member (15) has a discharge port (29) connected to the inner position for said compression spaces (23), an opening (30,31;49) for flowing a refrigerant, discharged into said discharge port (29), into said sealed container(1), and a check valve means (37,38;50;57;59;60) for closing an opening of said discharge port, characterised by said check valve means (37,38;50;57;59;60) having a valve body (39,40;50;57;59;60), said valve body being configured to effectively receive a centrifugal force of said shaft (18) having said discharge port (29) so that said opening (30,31;49) of said discharge port (29) is normally opened by the effect of the centrifugal force, and by the scroll compressor also incorporating the electric motor unit (2) in the sealed container (1). The scroll compressor according to claim 1, wherein said check valve means (37,38) has a valve body (39,40), a spring (41,42) for holding said valve body (39,40) and a valve holder (43,44) for securing one end of said spring (41,42) to said shaft (18) having said discharge port (29), said valve body (39,40) being formed of a massive material. The scroll compressor according to claim 1, wherein said check valve means (59;57) has an arc-shaped spring discharge valve (50;57) and an arc-shaped valve holder (51;58) for holding thereinside said arc-shaped spring discharge valve (50;57), said arc-shaped spring discharge valve (50;57) and said arc-shaped valve holder (51;58) being fitted together to said shaft (18) having said discharge port (29). The scroll compressor according to claim 3, wherein said discharge valve (50;57) and said valve holder (51;58) are fixed together at one end thereof to said shaft (18) by a common screw (54), and the other end of each said discharge valve (50;57) and said valve holder (51;58) is located outside said discharge opening of said discharge port. The scroll compressor according to claim 4, wherein one end of each said discharge valve (50;57) and said valve holder (51) is located at a preceding position in a rotational direction of said shaft (18) relative to said other end thereof. The scroll compressor according to claim 3, wherein said discharge valve (50) is resiliently pressed against an outer surface of said shaft (18) by a spring force thereof. The scroll compressor according to claim 3, wherein said discharge valve (57) is resiliently contacted with an inner surface of said arc-shaped valve holder (51) by a spring force thereof. The scroll compressor according to claim 3, wherein said discharge valve (59) is wound at least one turning around said shaft (18). The scroll compressor according to claim 3, wherein said opening (49) of said discharge port (29) consists of a plurality of discharge opening portions, and said discharge valve (60) is divided at its one end into a plurality of end portions (55) to thereby close said discharge opening portions (49).

Inventors: MITSUNAGA TOSHIHIKO, NOBORU YOSHINORI, SUGIMOTO KAZUYOSHI, MITSUNAGA, TOSHIHIKO, 5-16-18, ASAHI, NOBORU, YOSHINORI, 4-19-13, NISHIKOIZUMI, SUGIMOTO, KAZUYOSHI, 611, YORIKIDO
Applicants: SANYO ELECTRIC CO, SANYO ELECTRIC CO., LTD.
Application year: 1991
Main classification: F04C18
IPC codes: F04C18, F04C29, F04C28, F04C23