SCROLL COMPRESSOR

Abstract: A scroll compressor has a fixed scroll member (20) and an orbiting scroll member (21), the latter being arranged in a juxtaposed relation with the former so that wraps thereof are fitted closely together, an electric motor (13) having a driving shaft (6), and a swing link (33) between the orbiting scroll member and the electric motor for delivering a rotational force of the electric motor to the orbiting scroll member. The swing link has an opening (34) for receiving a boss (32) of the orbiting scroll member and an eccentric opening to receive a driving pin of the driving shaft so that the orbiting scroll member orbits relative to the fixed scroll member. The swing link, admitting a positional relation between the eccentric opening and the boss opening of the swing link, has a first member which is a main portion of the swing link and a second member which is a balance weight movably attached to the first member. The balance weight is limited in its movement in a radius direction of the rotary shaft.

Description: BACKGROUND OF THE INVENTION The present invention relates in general to a gas compressor for, for example, a refrigerating apparatus and an air conditioning system, and more particularly to a scroll compressor in which air or other gas is compressed to increase its pressure. Generally, the scroll compressor has an orbiting scroll member which includes an end plate and a spiral member or a wrap formed sbustantially in an involute curve and attached to one surface of the end plate in an upstanding position, and a fixed scroll member which is formed as similar as the orbiting scroll member and is arranged is a juxtaposed relation with the wraps of both members being fitted closely together. The orbiting scroll member is moved in an orbiting motion while the rotation of it on its own axis is inhibited by an Oldham's ring disposed between, for example, the orbiting scroll member and a main frame or a housing. The orbiting movement of the orbiting scroll member reduces a sealed space or a fluid pocket defined by the two scroll members and thus compresses a gas therein to increase its pressure. A structure and operational mechanism of the scroll compressor as described above are old and have advantages comparing to an old piston-type compressor but, on the other hand, have disadvantages and problems in unsatisfactory sealing of a fluid pocket of the wraps, wear of the wraps, and pumping in and out of the used fluid. Attempts have been made to overcome these disadvantages as disclosed in U.S. Patents 3884599 and 3924977. However, these attempts have not yet satisfactorily solved other problems of prevention of damage in case of the liquid compression and an increase of a pushing force of the two wraps in case that a rotational speed of an electric motor is changed. In a scroll compressor fluid pockets are formed between connected portions of the two cooperative wraps and the connected portions are moved toward the center along the surface of the wraps by a relative movement of the two scroll members. By this movement the fluid pocket moves toward the center to compress a fluid and, accordingly, a sealing force of the moving connected portions must be fully insured. In order to try to obtain a desired sealing force, an attempt may be made to increase the connecting force of the wraps which, however, produces an undesired wear to the wraps. Thus, the connecting force of the wraps must be determined to produce a suitable sealing force. However, the connecting force of the wraps is not always maintained constant when the orbiting scroll member is driven at a fixed crank radius, due to a production measurement error of the wraps and reduction of the measurement error of production will undoubtedly causes difficulty in production. Further, in case that a liquid compression, that is produced when a liquid refrigerant is introduced into a compression chamber, and an orbiting movement of one of the scroll members for the fluid compression are given, there is a disadvantage that the compressor body is vibrated by the orbiting movement of the scroll member and, particularly, when a rotational speed of an electric motor for the orbiting movement is changed by, for example, inverter driving, a centrifugal force becomes increased by the orbiting scroll member which is in an orbiting movement and the connecting force of the wraps of the two scroll members is tremendously increased to result in problematic wear of the wraps. These problems are not fully solved by the above-described U.S. Patents. SUMMARY OF THE INVENTION An object of the present invention is to provide a new scroll compressor which permits to maintain a substantial dynamic balance when a rotational speed of an electric motor for driving a scroll member is rapidly and/or largely changed, so that a vibration of the compressor itself is minimized. Another object of the present invention is to provide a scroll compressor which, when a liquid compression occurs by a liquid refrigerant coming into the fluid, permits to disconnect an orbiting scroll member from a fixed scroll member to release the fluid to thereby immediately recover the dynamic balance of the compressor. A further object of the present invention is to provide an improved scroll compressor which has a swing link and a balancing weight movably adapted to the swing link so that the compressor may meet with various requirements and conditions of gas pressure increasing systems such as a freezing apparatus, a refrigerating apparatus and an air conditioning apparatus. Briefly, a scroll compressor according to the present invention has a fixed scroll member and an orbiting scroll member, the latter being arranged in a juxtaposed relation with the former so that wraps thereof are fitted closely together, an electric motor having a driving shaft, and a swing link between the orbiting scroll member and the electric motor for delivering a rotational force of the electric motor to the orbiting scroll member. The swing link has an opening for receiving a boss of the orbiting scroll member and an eccentric opening to receive an eccentric driving pin of the driving shaft so that the orbiting scroll member orbits but does not rotate relative to the fixed scroll member. In the present invention, the swing link has a first member which is a main portion of the swing link and a second member which is a balance weight movably attached to the first member. The swing link has a center of mass so that said swing link generates a centrifugal force smaller than that of the orbiting scroll member in a diametrically opposite direction relative to the centrifugal force of the orbiting scroll member, in such a manner that a sealing force between the wraps of the above-described two scroll members is formed by both a difference between a centrifugal force of the orbiting scroll member and a centrifugal force of the swing link and a component of force by a gas pressure. The balance weight is limited in its movement in a radius direction of the rotary shaft. In the present invention, an eccentric distance of the driving pin (distance between a center of the driving shaft and a center of the driving pin) is determined that it is larger than a radius of the orbiting movement of the orbiting scroll member so that a center of the boss opening of the first member is spaced from a center of the driving shaft by a radius of the orbiting movement; and that a center of the eccentric opening is located at the same side as the center of the driving shaft relative to a first line extending at a right angle to a second line connecting the center of the boss opening to the center of the driving shaft and extending through the center of the boss opening; and that the center of the driving pin is located in a deviated position in a counter-clockwise direction of the driving shaft relative to a third line which extends at a right angle to the above-described second line which extends from the center of the boss and the center of the driving shaft and which extends through the center of the driving shaft. As described above, the swing link has a movable balance weight so that an eccentricity of the orbiting scroll member relative to the fixed scroll member can be adjusted automatically by the balance weight, and a sealing effect between the wraps of the two scroll members can be improved and a liquid compression does not occur at the time of an unusually high pressure operation by disconnecting the wraps of the two scroll members. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a longitudinally sectional view of a scroll compressor in accordance with the present invention, Figure 2 is an illustration showing a part of the scroll compressor according to the present invention, Figure 3A, 3B and 3C are plan views of a swing link which has a balance weight movable relative to a swing link and a driving shaft, showing an operation of the balance weight, Figure 4 is a sectional view of the swing link and a driving shaft shown in Figures 3A-3C, Figures 5A, 5B and 5C are plan views of a swing link and a driving shaft according to another embodiment of the invention, Figure 6 is a sectional view of the swing link and the driving shaft shown in Figures 5A-5C, Figures 7 and 8 are a plan view and a sectional view, respectively, of a swing link according to a further embodiment of the present invention, and Figure 9 is an illustration explaining an operation and effect of the swing link according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring first to Figures 1 and 2, a scroll compressor 1 of the invention has a cup-like cylindrical casing 2 having a closed bottom end and an open upper end and an upper closure member 3 to constitute a housing 4. The upper closure member 3 has an exhaust pipe 5 for discharging therethrough a fluid out of the apparatus. The upper closure member 3 is press-fitted to the cylindrical casing 2 of a steel and the press-fitted portion is welded by a known suitable method. A driving shaft 6 has at its upper end a large-diameter portion 7, which has an eccentric driving pin 8 projecting axially from a portion spaced from a center thereof. The driving shaft 6 is rotatably secured by a ball bearing 12 in the bearing portion 10 of the frame 9. The electric motor 13 has a rotor 17 and a stator 14 having a winding 16, and the rotor 17 is rotated by supplying electric current to the winding 16 to deliver a rotational force to the driving shaft 6. In the cylindrical casing 2 a fixed scroll member 20, an orbiting scroll member 21, a driving mechanism for the orbiting scroll member and Oldham ring 22 are provided. The fixed scroll member 20 has in general an end plate 23, a wrap 24 attached to one surface of the end plate 23 in an upstanding posture and substantially formed in an involute curve, and an annular wall 26. The fixed scroll member 20 is fixed to the frame 9 by means of bolts or any other suitable fixing means. An exhaust muffler 27 is disposed on the other surface of the end plate 23 to form an exhaust port 25 therebetween. The exhaust muffler 27 has the exhaust pipe 5 and the exhaust port 25 is connected to an exhaust opening 28 which is formed in a center of the end plate of the fixed scroll member 20. The orbiting scroll member 21 has an end plate 29, and a wrap 30 attached to one surface of the end plate 29 in an upstanding posture and substantially formed in an involute curve. The wrap 30 of the orbiting scroll member 21 is associated with the wrap 24 of the fixed scroll member 20 in a deviated relation at 180° so that the wraps of the two scroll members 20, 21 are fitted closely together to form a fluid pocket 31 therebetween. The orbiting scroll member 21 is connected to driving mechanism, which will be described presently, and is driven to provide an orbiting movement on a circle of a radius OP (Figs. 3A - 3C and Fig. 9) to compress the refrigerant gas within the wraps of the two scroll members 20, 21. At this moment, Oldham ring 22 prevents the orbiting scroll member 21 from its rotating relative to the fixed scroll member 20. An radius OP of the circle is given as the formula Next, the driving mechanism for the orbiting scroll member 21 will be explained. As described above, the driving shaft 6 which is rotatably supported by the ball bearing 12 at the bearing portion 10 of the frame 9 has a large-diameter portion 7 which has the driving pin 8 at a spaced or deviated position from the center of the driving shaft 6. The orbiting scroll member 21 has a boss 32 at a lower surface of the end plate 29 which has the wrap 30 on the upper surface thereof, and a center of the boss 32 in the illustrated embodiment is axially aligned with a center of the spirally shaped wrap 30 of the orbiting scroll member 21. The boss 32 is inserted into a boss opening 34 of a swing link 33 and rotatably supported thereto through a needle bearing 35. The swing link 33 has a semi-circular portion 47 and an opening 36 in the portion 34 for movably receiving therein a balance weight 35. The swing link 33 has also an eccentric hole 37 which is formed at a spaced or deviated position from a center of the driving shaft 6 and the driving pin 8 is rotatably fitted to the eccentric hole 37. The balance weight 35 in the embodiment of Figures 3A-3C and 4 has two oval openings 40 for freely receiving guide pins 39 which extend in the same direction as the driving pin 8 of the large-diameter portion 7 of the driving shaft 6. By the oval openings 40, when the swing link 33 is pivoted about the driving pin 8 in the eccentric hole 37, a movement of the balance weight 35 is limited by the guide pins 39 and the balance weight 35 does not follow the movement of the swing link 33. A positional relation among a center O of the driving shaft 6, a center P of the boss opening 34 of the wing link 33, the eccentric hole 37, namely, a center Q of the driving pin 8 is shown in Figures 3A and 9. The distance between the center O of the driving shaft 6 and the center P is selected to be the radius OP of the aforementioned orbiting circle, and the center Q of the driving pin 8 is located at the same side as the center O of the driving shaft 6 relative to a first line Y′ extending at a right angle to a second line X between the center P of the boss opening 34 and the center O of the driving shaft 6 and extending through the center P of the boss opening 34, and the center Q of the driving pin 8 is located in a shifted position in a counterclockwise direction of the driving shaft 6 relative to a third line which extends at a right angle to the second line X which extends from the center P of the boss and the center O of the driving shaft 6 and which extends through the center O of the driving shaft 6. In the structure of the driving mechanism described above, the center P of the swing link 33 can move on a circle having a center Q and a radius QP. In other words, when the driving shaft 6 is rotated in the counterclockwise, the swing link 33 is driven by the driving pin 8 so that the center P of the swing link 33 is isolated from the center O of the driving shaft 6, and the wrap 30 of the orbiting scroll member 21 abuts against a side wall of the wrap 24 of the fixed scroll member 20. Consequently, the center P of the orbiting scroll member moves in the predetermined orbiting movement around the center O of the driving shaft 6 with a radius of a distance OP. At this moment, rotation of the orbiting scroll member 21 is prevented by the Oldham ring 22 and, accordingly, the orbiting scroll member 21 provides an orbiting movement and not a rotation thereof. By contrast, the swing link 33 is rotated at the same speed as the driving shaft 6. By the orbiting movement of the orbiting scroll member 21, the fluid pocket constituted by cooperative arrangement of the two wraps is moved to establish compression of the fluid. The gas to be compressed is supplied into a hermetically sealed compressor structure 1 through a fluid inlet port 42 of the cylindrical casing 2. The compressed gas is discharged into the exhaust muffler 27 from the exhaust opening 28 of the end plate 23 of the fixed scroll member 20 and exhausted out of the exhaust muffler 27 through exhaust pipe 4 of the upper closure member 3. A contact portion of the wraps 24, 30 of the two scroll members 20, 21 is always located on the same plane as the above-described centers O and P . When the orbiting scroll member 21 is driven by using the swing link 33 having the eccentric hole 37, a mutual pressing force at the contact portion of the wraps 24, 30 is automatically obtained by a reaction of the fluid (gas) compression and, consequently, a sealing effect of the fluid pocket is established. Further, the center P of the swing link 33 is rotatable around the center Q of the driving pin 8 and, accordingly, the distance between the center P of the boss opening 34 of the orbiting scroll member 21 and the center O of the driving shaft 6 may be changed in accordance with the centrifugal force and the reactionof the fluid. The balance weight 35 according to the present invention functions to reduce a centrifugal force F c by an orbiting operation of the orbiting scroll member 21 as well as the swing link 33 and the ball bearing 12, and a centrifugal force F s of the swing link 38 including the balance weight 35 is determined to be slightly less than the centrifugal force F c . As illustrated in Figures 3A-3C and 4, the balance weight 35 is formed separate from the swing link 33 and movably disposed in the opening 36 formed in the semi-circular portion of the swing link 33, and the movement of the balance weight 35 is guided and limited by the guide pins 39 formed on the large-diameter portion 7 of the driving shaft 6. By the structure described above, when the swing link 33 is pivoted about the driving pin 8 (Fig. 3C), the balacne weight 35 which has been contacted with the inner wall of the opening 36 of the semi-circular portion 56 illustrated in Figures 3A and 3B is separated from the inner wall while same is guided by the guide pins 39 so that a centrifugal force F s of the balance weight 35 is not effected on the swing link 33. In other words, when the swing link 33 is driven so that the wrap 30 of the orbiting scroll member 21 is moved away from the wrap 24 of the fixed scroll member 20 by a liquid compression in the fluid pocket 31, the centrifugal force F c effected to the orbiting scroll member 21 becomes larger as much as reduction of the centrifugal force F s of the balance weight which acts in the opposite direction of the centrifugal force F c of the orbiting scroll member 21, and when the liquid compression is ceased the swing link returns to its original condition. Now, with reference to Figure 9, a lateral force F is given as follows: F = (F c - F s ) + (F T tanα - F B ) wherein: F c : a centrifugal force of the orbiting scroll member F s : a centrifugal force of the balance weight (F T tanα - F B ) : a force of the gas pressure F B : a load of gas in a radius direction of an orbiting circle F T : a load of gas in a tangential direction of the orbiting circle In the conditions of F c >F s , F T tanα < F B and a condition of pressure, all conditional components are determined so that the unequity F>O is satisfied. Similarly all conditional components are determined to satisfy the unequity F<O when F T becomes abnormally large. Thus, when the value of F T becomes larger than a certain value, the contact portions of the scroll wraps 24, 30 are separated from each other to open the gas pocket to prevent the liquid compression. Referring next to Figures 5A-5C and 6 which show another embodiment of the present invention, the swing link 33 does not have a semi-circular portion 56 of the embodiment of Figures 3A-3C and 4, but has a pin 43. In this embodiment, a balance weight 35 has a guide opening for laterally movably receiving the pin 43 of the swing link 33. The large-diameter portion 7 of the driving shaft 6 has a stopper pin 45 while the balance weight 35 has a notch 46 which will contact the stopper pin 45 to prevent a further rotational movement of the balance weight 35. Namely, the swing link 33 in this embodiment is contacted with the balance weight 35, a pivotal movement of which is limited by the pin 45 of the large-diameter portion of the driving shaft 6. Thus, the orbiting scroll member 21 and the swing link 33 do not contact any portions of the frame 9 when these elements 21, 33 are driven or swivelled about the driving pin 8 of the driving shaft 6. By the swivelling movement of the swing link 33 about the driving pin 8, a degree of the eccentricity of the orbiting scroll member 21 is changed so that the contacting portions of the wraps 24, 30 of the two scroll members 20, 21 are moved closer to each other in case of a normal operation and, on the other hand, moved away from each other in case of a liquid compression. A force effected onto the center P of the swing link 33 will be understood from Figure 9. In case of a normal operation, the following formula (1) is satisfied by the force onto the center of the swing link 33. F B - F T tanα < F c - F s ...... (1) By contrast, in case of an abnormal, high pressure operation, the following formula (2) is satisfied. F B - F T tanα > F c - F s ...... (2) To be more specifically, the angle α can be determined in connection with the boss opening 34 and the center O of the driving shaft 6 at the time when the eccentric hole 37 (or Q in Fig. 9) is formed in the swing link 33 and, if dimensional values such as height, thickness and turning degree of the wrap of the scroll members have been determined, a ratio of F B to F T can be obtained as a specific value for the scroll compressor. Accordingly, the dimensional values are determined , the value of the F B - F T tan α in the above formulas (1) and (2) is in a proportional relation to a gas pressure of the fluid pocket 31 (Fig. 1) fomed by the two wraps 24, 30. By contrast, the value of the centrifugal forces F c - F s , if a rotational speed of the driving shaft 6 is constant, is prescribed by the design or dimension of the orbiting scroll member 21 and the swing link 33. Therefore, either the formula (1) or (2) is satisfied by a gas pressure in the fluid pocket 31. In the present invention, in a normal operation in which a gas pressure of the fluid pocket 31 does not increase above a prescribed value, a contact force of the two wraps is produced by the centrifugal force to satisfy the above formula (1) and, on the other hand, if the gas pressure exceeds the prescribed value, a force which is larger than the contacting force (i.e., F c - F s ) of the two wraps produced by the difference of the centrifugal forces is produced by the gas in the fluid pocket. By this larger force the contacting force of the two wraps is released to avoid an abnormal increase of the gas pressure within the fluid pocket. Therefore, the swing link 33 functions to produce a contacting force between the two wraps 24, 30 of the scroll members 20, 21 in a normal operation and also to release the thus produced contacting force so that the wrap 30 of the orbiting scroll member 21 is moved away from the wrap 24 of the fixed scroll member 20. Figures 7 and 8 show a further embodiment of the invention in which a balance weight holder 50 is provided to resiliently holding a balance weight 35 so as to reduce the difference between a centrifugal force F c of the orbiting scroll member 21 and a centrifugal force F s of the balance weight 35 when such difference becomes large, by increasing automatically a centrifugal force of the balance weight 35. In the embodiment of Figures 7 and 8, the swing link 33 has a recess 55 on a semi-circular portion 34 to secure therein the balance weight 35. The swing link 33 has an eccentric hole 37 at a position deviated from the center of the driving shaft 6 so that the driving pin 8 is rotatably secured in the eccentric hole 37. Further, the swing link 33 has an oval opening 49 to freely receiving a pin 48 which is fixed to, and projecting from, the large-diameter portion 7 of the driving shaft 6. The oval opening 49 functions to limit a swivelling angle of the swing link 28 when same is rotated about the driving pin 8 in the eccentric hole 37. The balance weight holder 50 which resiliently holds the balance weight in the recess 55 of the swing link 33 has a bolt 52, which extends through a through-hole 53 of the balance weight 35 and threadedly engages a threaded hole formed in the swing link 33, a ring 54 fitted to the bolt 52 at its head portion, and a coil spring 51 between the ring 54 and the balance weight 35 and around the bolt 52. The coil spring 51 resiliently urges the balance weight 35 toward the swing link 33. The through-hole 53 of the balance weight 35 has a diameter larger than a diameter of the bolt 52. Thus, the balance weight 35 is outwardly movable against a resilient force of the coil spring 51. According to the present invention, a degree of eccentricity of the orbiting scroll member is changed by the swing link to improve the sealing effect between the wraps of the two scroll members, and to separate the wraps from each other when an abnormally high pressure such as a liquid compression occurs in the wraps to thereby prevent a wear or damage of the wraps. Further, when the swing link having a unique balance weight is swivelled in case of an abnormally high pressure, the balance weight which is separated from the swing link provides a larger centrifugal force to the orbiting scroll member than a centrifugal force of the swing link. Consequently the swing link is returned to its original position by the centrifugal force of the orbiting scroll member to return the compression mechanism to compress the fluid in the fluid pocket of the wraps. Although the present invention has been described with reference to the preferred embodiments, many modifications and alterations can be made within the spirit of the invention.

Claims: 1. A scroll compressor comprising: a fixed scroll member having an end plate and a wrap attached to one surface of said end plate in an involute curve, an orbiting scroll member having an end plate and a wrap attached to one surface of said end plate of the orbiting scroll member in a juxtaposed relation with said fixed scroll member so that the wraps of the two scroll members are fitted closely together, and a boss on the other surface of said end plate, an electric motor having a driving shaft rotating in a counter-clockwise direction, with an eccentric driving pin, a swing link between said orbiting scroll member and said electric motor for delivering a rotational force of said electric motor to said orbiting scroll member through said driving shaft, said swing link having a bass opening for receiving said boss of the orbiting scroll member and an eccentric opening to receive said driving pin, said swing link having a center of mass so that said swing link generates a centrifugal force smaller than that of said orbiting scroll member in a diametrically opposite direction relative to the centrifugal force of said orbiting scroll member, in such a manner that a sealing force between said wraps of the above-described two scroll members is generated by both a difference between a centrifugal force of said orbiting scroll member and a centrifugal force of said swing link and a component of force by a gas pressure wherein a distance (OQ) between a center (P) of said boss opening and a center (Q) of said eccentric opening is determined that: said distance (OQ) is larger than a radius of an orbiting circle of said orbiting scroll member so that the center (P) of said boss opening is spaced from a center (O) of said driving shaft as long as a radius of the orbiting circle; the center (Q) of said eccentric opening is located at the same side as the center (O) of said driving shaft relative to a first straight line (Y′) extending at a right angle to a second line (X;OP) connecting the center (P) of said boss opening to the center (O) of said driving shaft and extending through the center (P) of said boss opening; and the center (Q) of said driving pin is located in a deviated position in a counterclockwise direction of said driving shaft relative to a third straight line (Y) which extends at a right angle to said second line (OP;X) and extends through the center (O) of said driving shaft. 2. A scroll compressor according to claim 1, wherein said swing link has a first member which is a main portion of said swing link and a second member which is a balance weight movably attached to said first member. 3. A scroll compressor according to claim 2, wherein said swing link has a semi-circular portion and an opening in said semi-circular portion, and said balance weight is movably secured in said opening by guide pin means. 4. A scroll compressor according to claim 2, wherein said swing link has a pin and said balance weight has an opening for movably secured by said pin and a notch, and wherein said driving shaft has a stopper pin for engaging with said notch to thereby limit a pivotal movement of said balance weight about said driving pin. 5. A scroll compressor according to claim 2, wherein said swing link has a recess, and said balance weight is resiliently movably secured in said recess by means of a spring.

Inventors: NOBORU, YOSHINORI
Applicants: SANYO ELECTRIC CO., LTD.
Application year: 1987
Main classification: F04C18
IPC codes: F04C18, F16F15, F04C29