Scroll compressor with direct return of oil from an oil separator into a compression portion

Abstract

The invention relates to a scroll compressor for compressing a fluid, comprising a compression section with an inlet for sucking the fluid into the compression section, an outlet for discharging the compressed fluid out of the compression section, a stationary disk having a stationary spiral, and an orbiting disk having an orbiting spiral. The orbiting disk is orbitable relative to the stationary disk to move the fluid from the inlet to the outlet and to compress it thereby. The scroll compressor comprises an oil separator for separating oil from the compressed fluid and a direct oil return for directly returning oil from the oil separator to the compression section, the direct oil return comprising at least one orifice opening. For enabling efficient operation, the direct oil return comprises an outgassing chamber arranged between the first flow valve and the orifice opening and a fluid return for returning fluid from the outgassing chamber to the compression section.

Claims

1. Scroll compressor for compressing a fluid, comprising: a compression section with an inlet of the compression section for sucking the fluid into the compression section, an outlet of the compression section for discharging the compressed fluid out of the compression section, a stationary disk having a stationary spiral, and an orbiting disk having an orbiting spiral, the orbiting disk being orbitable relative to the stationary disk along a compression direction to move the fluid from the inlet of the compression section to the outlet of the compression section, thereby compressing the fluid; and an oil separator for separating oil from the compressed fluid; wherein the scroll compressor additionally comprises a direct oil return for directly returning oil from the oil separator to the compression section, the direct oil return comprising at least one orifice opening, wherein the direct oil return comprises a first flow valve, characterized in that the direct oil return comprises an outgassing chamber arranged between the first flow valve and the orifice opening of the direct oil return, and in that the scroll compressor has a fluid return for returning fluid from the outgassing chamber to the compression section.

2. Scroll compressor according to claim 1, characterized in that the orifice opening of the direct oil return is arranged in the stationary disk.

3. Scroll compressor according to claim 2, wherein the stationary disk comprises the stationary spiral arranged on a stationary base of the stationary disk and forming a spiral compressor channel of the stationary disk, characterized in that the orifice opening of the direct oil return is arranged in an intake portion of the compressor channel which, in operation, is at least temporarily in direct fluid communication with the inlet of the compression section or is arranged outside the compressor channel.

4. Scroll compressor according to claim 3, wherein the stationary disk comprises the stationary spiral, which is arranged on the stationary base of the stationary disk and forms the spiral-shaped compressor channel, characterized in that the orifice opening of the direct oil return either is disposed at a position angle in a range of 30 and +30, where is a position angle of an outer end of the compressor channel, and is disposed at a radial distance R.sub.M,1 from a center of the stationary disk, where R.sub.M,1 is in a range between (R.sub.I()B.sub.K) and R.sub.I(), where R.sub.I() is a radial distance of an inner side of the stationary spiral at an outer end of the compressor channel, and B.sub.K is a width of the compressor channel along the radial direction at the outer end of the compressor channel, or outside the stationary spiral and at a position angle in the range of 30 to +30, and at a radial distance R.sub.M,2 from the center of the stationary disk (20), where =+180, and R.sub.M,2 is in a range of R.sub.A(360) to R.sub.A(360)+B.sub.K, where R.sub.A(360) is a radial distance of an outer side of the stationary spiral at the position angle 360.

5. Scroll compressor according to claim 3, wherein during compression operation at least one compression chamber is formed between the orbiting spiral and the stationary spiral, characterized in that the at least one orifice opening is not swept by any compression chamber at any time.

6. Scroll compressor according to claim 2, wherein the stationary disk comprises the stationary spiral, which is arranged on a stationary base of the stationary disk and forms a spiral-shaped compressor channel, characterized in that the orifice opening of the direct oil return either is disposed at a position angle in a range of 30 and +30, where is a position angle of an outer end of the compressor channel, and is disposed at a radial distance R.sub.M,1 from a center of the stationary disk, where R.sub.M,1 is in a range between (R.sub.I()B.sub.K) and R.sub.I(), where R.sub.I() is a radial distance of an inner side of the stationary spiral at an outer end of the compressor channel, and B.sub.K is a width of the compressor channel along the radial direction at the outer end of the compressor channel, or outside the stationary spiral and at a position angle in the range of 30 to +30, and at a radial distance R.sub.M,2 from the center of the stationary disk (20), where =+180, and R.sub.M,2 is in a range of R.sub.A(360) to R.sub.A(360)+B.sub.K, where R.sub.A(360) is a radial distance of an outer side of the stationary spiral at the position angle 360.

7. Scroll compressor according to claim 2, wherein during compression operation at least one compression chamber is formed between the orbiting spiral and the stationary spiral, characterized in that the at least one orifice opening is not swept by any compression chamber at any time.

8. Scroll compressor according to claim 1, wherein the stationary disk comprises the stationary spiral, which is arranged on a stationary base of the stationary disk and forms a spiral-shaped compressor channel, characterized in that the orifice opening of the direct oil return either is disposed at a position angle in a range of 30 and +30, where is a position angle of an outer end of the compressor channel, and is disposed at a radial distance R.sub.M,1 from a center of the stationary disk, where R.sub.M,1 is in a range between (R.sub.I()B.sub.K) and R.sub.I(), where R.sub.I() is a radial distance of an inner side of the stationary spiral at an outer end of the compressor channel, and B.sub.K is a width of the compressor channel along the radial direction at the outer end of the compressor channel, or outside the stationary spiral and at a position angle in the range of 30 to +30, and at a radial distance R.sub.M,2 from the center of the stationary disk (20), where =+180, and R.sub.M,2 is in a range of R.sub.A(360) to R.sub.A(360)+B.sub.K, where R.sub.A(360) is a radial distance of an outer side of the stationary spiral at the position angle 360.

9. Scroll compressor according to claim 4, wherein during compression operation at least one compression chamber is formed between the orbiting spiral and the stationary spiral, characterized in that the at least one orifice opening is not swept by any compression chamber at any time.

10. Scroll compressor according to claim 1, wherein during compression operation at least one compression chamber is formed between the orbiting spiral and the stationary spiral, characterized in that the at least one orifice opening is not swept by any compression chamber at any time.

11. Scroll compressor according to claim 1, characterized in that the direct oil return comprises a second flow valve arranged after of the outgassing chamber.

12. Scroll compressor according to claim 1, characterized in that the scroll compressor is configured such that, during compression operation, an intermediate pressure in the outgassing chamber is in a range from 0.2 bar to 6 bar above an intake pressure of the compression section.

13. Scroll compressor according to claim 1, characterized in that the scroll compressor has an outlet pressure chamber, the oil separator being in direct fluid communication with the outlet of the compression section via the outlet pressure chamber.

14. Scroll compressor according to claim 13, characterized in that the outgassing chamber is formed radially outside the outlet pressure chamber and surrounds the outlet pressure chamber.

15. Scroll compressor according to claim 1, characterized in that the scroll compressor further comprises: a contact pressure chamber to which a contact pressure is applied during compression operation, wherein the orbiting disk is pressed against the stationary disk by the contact pressure; and a second oil return for returning oil from the oil separator to the contact pressure chamber.

16. Scroll compressor according to claim 15, characterized in that the second oil return has priority over the direct oil return in case of oil shortage.

17. Scroll compressor according to claim 10, characterized in that the direct oil return has a first oil inlet opening into the oil separator, and that the second oil return has a second oil inlet opening into the oil separator, the first oil inlet being arranged above the second oil inlet.

18. Scroll compressor according to claim 15, characterized in that the scroll compressor comprises a reference opening, arranged in the compression section, and a reference connection forming a fluid connection between the contact pressure chamber and the reference opening for influencing the contact pressure by means of a reference pressure applied to the reference opening during operation.

19. Scroll compressor according to claim 1, characterized in that the outgassing chamber has a volume in the range from 30 cm.sup.3 to 150 cm.sup.3.

20. Scroll compressor according to claim 1, characterized in that an orifice opening of the fluid return is arranged in a central portion of a compressor channel of the stationary disk, the central portion of the compressor channel being composed of all portions of the compressor channel that cannot be in direct fluid communication either with the inlet of the compression section or with the outlet of the compression section.

Description

SCHEMATICALLY IT IS SHOWN

(1) FIG. 1 a longitudinal section of a first embodiment of a scroll compressor according to the invention;

(2) FIG. 2 a compression section, an oil separator and a direct oil return for direct return of oil from the oil separator to the compression section of the scroll compressor of FIG. 1;

(3) FIG. 3 a cross-section of the compression section of FIG. 1 with two orifice openings of the direct oil return and one orifice opening of a fluid return for returning refrigerant from an outgassing chamber of the direct oil return, wherein all these orifice openings are arranged in a stationary disk of a stationary spiral of the compression section and wherein only an orbiting spiral is visible from an orbiting disk of the compression section;

(4) FIG. 4 a top view of a modification of the stationary disk of the scroll compressor of FIG. 3 for a detailed explanation of a preferred arrangement of the orifice openings of the direct oil return;

(5) FIG. 5 a longitudinal section of a compression section, an outlet pressure chamber, an oil separator and a direct oil return system for direct return of oil from the oil separator to the compression section according to a second embodiment of a scroll compressor according to the invention;

(6) FIG. 6 a cross-section at section line A in FIG. 5; and

(7) FIG. 7 a top view of the stationary disk in FIG. 3 FIG. 7 to explain advantageous positions for orifice openings of the fluid return system.

(8) In FIG. 1, a first embodiment of a scroll compressor 1 according to the invention for compressing a fluid is shown schematically in a longitudinal section. The fluid is, for example, a refrigerant or a refrigerant mixture of a refrigerant circuit.

(9) The scroll compressor 1 comprises a compression section 10 with an inlet 11, a stationary disk 20, an orbiting disk 30 and an outlet 12. An outlet pressure chamber 40 is directly connected to the outlet 12. In this embodiment, the outlet 12 includes a non-return device 13 that prevents compressed refrigerant from flowing back from the outlet pressure chamber 40 into the compression section 10. The non-return device 13 is exemplified here as a check valve and forms a downstream end of the compression section 10.

(10) Seen along a flow direction of the refrigerant (in operation), an oil separator 45 directly adjoins the outlet pressure chamber 40. The oil separator 45 is thus in direct fluid communication with the outlet pressure chamber 40 andvia the outlet pressure chamber 40in direct fluid communication with the outlet 12 of the compression section 10.

(11) The scroll compressor 1 comprises a housing 90 having an intake connection 91 and an outlet connection 92.

(12) The intake connection 91 is in direct fluid communication with the inlet 11 of the compression section 10 via an intake pressure chamber 93. In operation, refrigerant is drawn in from an external refrigerant circuit via the intake connection 91.

(13) The outlet connection 92 is in direct fluid communication with an oil separator outlet opening 46 of the oil separator 45. Compressed refrigerant is discharged into the external refrigerant circuit via the outlet connection 92 during operation.

(14) An intake pressure is present in the intake pressure chamber 93 and the inlet 11 of the compression section during operation. The intake pressure can be in the range of 0.7 bar to 9 bar, for example. In operation, there is an outlet pressure in the outlet pressure chamber 40, the oil separator 45 and the outlet connection 92 which is greater than the intake pressure. For example, the outlet pressure may be in the range of 6 bar to 32 bar. The intake pressure and the outlet pressure depend, among other things, on the refrigerant used and on an operating condition of the external refrigerant circuit.

(15) The intake pressure chamber 93 is shown only schematically in FIG. 1. Preferably, the intake pressure chamber 93 encloses at least the contact pressure chamber 80 in a circumventing manner. That is, the intake pressure chamber 93 extends completely around the contact pressure chamber 80 along a circumferential direction (relative to the center axis). Alternatively or additionally, the intake pressure chamber 93 can enclose at least part of the compression section 10 in a circumventing manner. That is, the intake pressure chamber 93 extends along the circumferential direction (with respect to the central axis) completely around said part of the compression section 10. Said part of the compression section 10 may, in particular, face the contact pressure chamber 80 when viewed along the central axis.

(16) For example, the intake pressure chamber 93 may be formed at least substantially in the shape of a cylinder barrel around the contact pressure chamber 80 and/or at least a part of the compression section 10 on the side of the contact pressure chamber 80.

(17) The stationary disk 20 faces the outlet pressure chamber 40, while the orbiting disk 30 faces a contact pressure chamber 80.

(18) A cut surface for FIG. 3 lies between the orbiting disk 30 and the stationary disk 20 in FIG. 1 and FIG. 2, respectively, and extends parallel to a stationary base 22 of the stationary disk 20. A stationary spiral 21 having 2.25 turns is arranged on the stationary base 22. Accordingly, an outer end 25 of the stationary spiral 21 is arranged at a spiral angle of 810 from an inner end 24 of the stationary spiral 21.

(19) FIG. 4 is a simplified view of a top view of the stationary disk 20.

(20) For simplicity, the orbiting spiral 31 in FIG. 4 is shown in a modification with two turns. Accordingly, the outer end 25 of the stationary spiral 21 is disposed at a spiral angle of 720 from the inner end 24 of the stationary spiral 21. Otherwise, the structure and function of the stationary disk 20 in FIG. 3 and FIG. 4 are the same, and the same reference signs are used for the same elements.

(21) Returning to FIG. 3, only an orbiting spiral 31 is visible from the orbiting disk 30 due to the cross-section, which is arranged on an orbiting base 32 (not shown in FIG. 3; see FIG. 5) of the orbiting disk 30. The orbiting spiral 31 has (like the stationary spiral 21 design in FIG. 3) 2.25 turns.

(22) The stationary disk 20 and the orbiting disk 30 are arranged nested within each other. In (compression) operation, the orbiting disk 30 is pressed onto the stationary disk 20 by a contact pressure in the contact pressure chamber 80 (see FIG. 1). As a result, on the one hand, an end face of the orbiting spiral 31 facing away from the orbiting base 32 is in sealing contact with the stationary base 22 and, on the other hand, an end face of the stationary spiral 21 facing away from the stationary base 22 is in sealing contact with the orbiting base 32.

(23) The stationary base 22, the stationary spiral 21, the orbiting base 32 and the orbiting spiral 31 thus delimit a plurality of compression chambers 14a, 14b, 14c.

(24) In the position of the orbiting disk 30 or the orbiting spiral 31 shown in FIG. 3, a compression chamber 14c of the last stage and two compression chambers 14a, 14b of the penultimate stage are defined in a compressor channel 26 formed between the turns of the stationary spiral 21, the compression chamber 14c of the last stage comprising two sub-sections which are in fluid communication with each other via narrow gaps (not visible in FIG. 3) between the stationary spiral 21 and the orbiting spiral 31.

(25) On the left side of FIG. 3 is shown a pointer diagram depicting a revolution position 103 of the orbiting disk 30 (and thus the orbiting spiral 31) and its orbiting direction or a compression direction 100. The orbiting disk 30 starts a new revolution when its revolution position 103 in the pointer diagram is just at a revolution angle 101 of 0. Then, an outer side of the orbiting spiral 31 just touches the outer end 25 of the stationary spiral 21, thereby closing the outer-side-guided compression chamber of penultimate stage 14b. At the same time, an outer end 34 of the orbiting spiral 31 contacts an outer side of an outermost turn of the stationary spiral 21, thereby closing the inner-side-guided compression chamber of penultimate stage 14a. In FIG. 3, starting from the revolution angle 101 of 0, the orbiting disk 30 has already moved along the compression direction 100 to the revolution position 103 at a revolution angle 102 of 90. Starting from FIG. 3, the orbiting disk 30 orbits further along the compression direction 100 around a center of the stationary spiral 21.

(26) Starting from FIG. 3, when the orbiting disk 30 orbits another 270 along the compression direction 100 relative to the stationary disk 20, it reaches a revolution position at the revolution angle 101 of 0 and its current revolution ends. The refrigerant, which in FIG. 3 had been in the compression chamber of last stage 14c, has been led to a large extent into an outlet opening 28 in the stationary base 22 and thus to the outlet 12 of the compression section 10. The outlet opening 28 is located at a center of the stationary disk 20 or stationary spiral 21.

(27) The scroll compressor 1 has a direct oil return 50 for returning oil from oil separator 45 to the compression section 10.

(28) More specifically, the direct oil return 50 extends from a first oil inlet 51 in the oil separator 45 to two orifice openings 59a, 59b in the stationary base 22 of the stationary disk 20. In operation, the direct oil return 50 injects oil from the oil separator 45 from the orifice openings 59a, 59b directly between the stationary disk 20 and the orbiting disk 30.

(29) In the embodiment shown in FIG. 1, the direct oil return 50, viewed along the direction of flow of the oil, comprises the first oil inlet 51, a first fluid connection 52 with a first throttle valve 53, an outgassing chamber 54, a second fluid connection 56 with a second throttle valve 57 and a branching 58, and further two orifice openings 59a, 59b.

(30) In operation, the outlet pressure prevails in the interior of the oil separator 45. In the oil separator 45, the refrigerant rises while liquid oil accumulates in a lower half of the oil separator 45. Thus, the refrigerant and the oil are separated from each other. There is increased solubility for the refrigerant in the liquid oil due to the high outlet pressure, and the liquid oil contains a portion of dissolved refrigerant.

(31) The first oil inlet 51 is disposed in a lower half of an interior of the oil separator 45, while the oil separator outlet opening is disposed at an upper end of the interior of the oil separator 45. The outlet pressure forces liquid oil from the oil separator 45 through the first oil inlet 51 into the first fluid connection 52.

(32) In the first fluid connection 52 of the direct oil return 50, this oil flows through the first throttle valve 53. The first throttle valve 53 may be configured as an unregulated throttle valve. For example, the first throttle valve 53 may be designed as an orifice or nozzle. The first throttle valve 53 reduces the mass flow of the oil. The oil then continues to flow into the outgassing chamber 54. By influencing the mass flow of the oil, an intermediate pressure in the outgassing chamber 54 can be influenced. Due to the pressure drop, the solubility for the refrigerant in the oil decreases. The oil may be oversaturated with refrigerant after the first throttle valve 53. An oversaturation fraction of the refrigerant may evaporate in the outgassing chamber 54. Liquid oil collects in a lower portion of the outgassing chamber 54 and refrigerant collects in an upper portion of the outgassing chamber 54. The outgassing chamber 54 acts, so to speak, as an additional oil separator of the direct oil return 50 and a fluid return 70.

(33) In the lower region of the outgassing chamber 54, for example at a bottom region of the outgassing chamber 54, an oil inlet 55 of the second fluid connection 56 of the direct oil return 50 is arranged. Due to the intermediate pressure prevailing in the exhaust chamber 54, liquid oil is forced from the exhaust chamber 54 through the oil inlet 55 into the second fluid connection 56.

(34) The second fluid connection 56 has a second throttle valve 57, which limits a mass flow rate of the oil exiting the outgassing chamber. Incidentally, this can also prevent an undesirably large drop in the intermediate pressure in the outgassing chamber 54. The second throttle valve 57 may also be designed as an unregulated throttle valve, for example as an orifice or nozzle.

(35) Downstream of the second throttle valve 57, the second fluid connection 56 branches into two arms at a branching 58. Both arms pass at least partially through the stationary disk 20, each terminating in one of the orifice openings 59a, 59b disposed in the stationary base 22.

(36) Each of the orifice openings 59a, 59b is thereby arranged in an inlet region of the compression section 10, which in operation is at least temporarily in direct fluid communication with the inlet 11 of the compression section 10. As a result, oil escaping from the orifice openings 59a, 59b is entrained by the sucked-in refrigerant and then enclosed together with the refrigerant in newly formed compression chambers. Because the orifice openings 59a, 59b are each positioned in the inlet area of the compression section 10, the radially outer engagement areas of the stationary spiral 21 and the orbiting spiral 31 are also excellently lubricated.

(37) In addition, all orifice openings 59a, 59b are each swept at least once by the orbiting spiral 31 during each revolution of the orbiting disk 30. This ensures good distribution of the oil supplied. The oil coming out of the orifice openings 59a, 59b is smeared by the orbiting spiral 31. For example, it can be seen from FIG. 4 that the orifice opening 59a is swept by an outer end 34 of the orbiting spiral 31 in each revolution.

(38) Particularly preferred positioning of the orifice openings 59a, 59b will be discussed in more detail below with reference to FIG. 4.

(39) In the compression chambers 14a, 14b 14c (see FIG. 3) formed in the compression section 10 between the stationary disk 20 and the orbiting disk 30, the refrigerant is transported to the center of the stationary spiral 21 and thereby compressed by reducing the volumes of the compression chambers 14a, 14b, 14c until it reaches outlet pressure. It is then moved through the outlet 12, which in this example includes an outlet opening 28 at the center of stationary disk 20 and the non-return device 13, and outlet pressure chamber 40 into oil separator 45.

(40) Oil is transported together with the refrigerant and finally returns to the oil separator 45, where it is separated from the refrigerant and is available for a new cycle of direct oil return 50. The refrigerant, freed from the oil, compressed and under outlet pressure, is discharged from the scroll compressor 1 through the oil separator outlet opening 46 and outlet connection 92.

(41) With reference to FIG. 4, it will now be explained where the orifice openings 59a, 59b of the direct oil return may preferably be arranged.

(42) A position angle of 0 is determined by the inner end 24 of the stationary spiral 21. It should be noted that a terminal bead 24a of the inner end 24 is irrelevant to the determination of the position angle of 0. Since the stationary spiral 21 in FIG. 4 has two turns, its outer end 25 is arranged at a position angle or spiral angle of 720. Correspondingly, an inlet opening of a compressor channel 26, extending between the outer end 25 and a beginning of an outer turn of the stationary spiral 21 at a position angle of 360, is located at the position angle 720.

(43) FIG. 4 shows a preferred first area A.sub.M,1 for the arrangement of orifice openings of the direct oil return 50.

(44) In FIG. 4, is a position angle of the outer end 25 of the stationary spiral 21. Accordingly, is also a position angle of an outer end of the compressor channel 26. At the position angle , the inner side of the stationary spiral 21 has a distance R.sub.I() from the center of the stationary spiral 21 in a radial direction. At the same time, an inlet opening of the compressor channel 26 of the stationary disk 20 has a width B.sub.K at the position angle in the radial direction. Here, the width B.sub.K is obtained as B.sub.K=R.sub.I()R.sub.A(360), where R.sub.A(360) is a distance of the outer side of the stationary spiral 21 at a position angle corresponding to 360.

(45) The first area A.sub.M,1 extends in the circumferential direction from a position angle 30 to a position angle of +30 and in the radial direction from R.sub.I()B.sub.K/2 to R.sub.I(). This means that the first area A.sub.M,1 is arranged at the inlet opening of the compressor channel 26, namely on a radially outer half of the compressor channel 26 in this position angle area or its imaginary continuation.

(46) In FIG. 4, the orifice opening 59a is positioned in the first area A.sub.M,1 exactly at the position angle =720 and close to the outer side of the compressor channel 26, for example with a radial distance R.sub.I()B.sub.K/10 from the center of the stationary spiral 21. The orifice opening 59a is closed only once per revolution by the orbiting spiral 31. In the embodiment shown, it does not directly communicate with inner-side-guided compression chambers 14b. The orifice opening 59a ensures lubrication of the outer-side-guided compression chambers in a particularly advantageous manner. In FIG. 3, the compression chamber 14b is outer-side-guided.

(47) FIG. 4 further shows a preferred second area A.sub.M,2 for the arrangement of orifice openings of the direct oil return 50. In this example, the orifice opening 59b is positioned in the second area A.sub.M,2.

(48) The second regions A.sub.M,2 extends radially outwardly of the stationary spiral 21 about a position angle , where =+180. The second area A.sub.M,2 extends circumferentially from a position angle 30 to a position angle of +30 and radially from R.sub.A( 360) to R.sub.A( 360)+B.sub.K/2. A second area A.sub.M,2 therefore lies outside the compressor channel 26 of the stationary disk 20, more specifically on a side opposite to the inlet opening of the compressor channel 26. Here, R.sub.A( 360) is a radial distance of the outer side of the stationary spiral 21 at the position angle 360=180.

(49) In FIG. 4, the orifice opening 59b is positioned in the second area A.sub.M,2 exactly at the position angle =900 and close to the outer side of the outermost turn of the stationary spiral 21, for example, at a radial distance R.sub.A()+B.sub.K/10 from the center of the stationary spiral 21. The orifice opening 59b provides lubrication of inner-side-guided compression chambers in a particularly advantageous manner. In FIG. 3, the compression chamber 14b is inner-side-guided.

(50) In FIG. 3, the orifice openings 59a, 59b of the direct oil return 50 are also positioned as described with reference to FIG. 4.

(51) The scroll compressor 1 further comprises a fluid return 70 for returning refrigerant from the outgassing chamber 54 to the compression unit. A fluid inlet 71 of the fluid return 70 is arranged in an upper portion of the outgassing chamber 54. Thus, no liquid oil flows from the outgassing chamber 54 into the fluid return 70.

(52) The fluid return 70 extends through the stationary disk 20. An orifice opening 72a of the fluid return 70 is arranged in the compressor channel 26 of the stationary disk 20 (see FIG. 3 and FIG. 5). Here, the orifice opening 72a is located in an inlet region of the compressor channel 26, but is also swept by closed compression chambers at times. In FIG. 3, the compression chamber 14b of penultimate stage is presently sweeping over the orifice opening 72a. Consequently, a time average of the pressure of the refrigerant in the compressor channel 26 at the orifice opening 72a is higher than the intake pressure. In the present embodiment, the intermediate pressure in the outgassing chamber 54 in proper operation is higher than the time-average pressure of the refrigerant in the compressor channel 26 at the position of the orifice opening 72a, in the range of 0.2 bar to 1.5 bar, depending on the exact operating condition. The pressure difference with respect to the outlet pressure forces liquid oil out of the outgassing chamber into the second fluid connection 56 and out of the orifice openings 59a, 59b of the direct oil return 50.

(53) The intermediate pressure in the outgassing chamber 54 is influenced in particular by: The outlet pressure and the mass flow of the oil together with the co-transported refrigerant, which flow through the first fluid connection 52 into the outgassing chamber 54, the time-average pressures at the orifice openings 59a and 59b and the corresponding mass flow of oil leaving the outgassing chamber 54 through the second fluid connection 56, and the time average of the pressure of the refrigerant in the compressor chamber 26 at the orifice opening 72a and the corresponding mass flow of the refrigerant leaving the outgassing chamber 54 through the fluid return 70.

(54) The driving force is the outlet pressure in the oil separator 45.

(55) In this embodiment, the intermediate pressure (or a time-average value of the intermediate pressure under unchanged operating conditions) is in the range of 0.3 bar to 5 bar above the intake pressure during operation. At an intake pressure of 1 bar, the intermediate pressure in operation is a minimum of 0.3 bar above the intake pressure, i.e. 1.3 bar in absolute terms, and a maximum of 1.9 bar, i.e. 2.9 bar in absolute terms. At an intake pressure of 7 bar, the intermediate pressure in operation is a maximum of 4.2 bar above the intake pressure, i.e. 11.2 bar. Of course, even then the intermediate pressure remains well below the outlet pressure, which in this case is 32 bar. At an intake pressure of 5 bar, the intermediate pressure is in the range of 0.6 bar to 3.5 bar above the intake pressure. These values are examples. The exact intermediate pressure depends on the exact operating condition, for example also on the outlet pressure. The exact pressure ratios may also depend on the refrigerant used.

(56) In other words, the intermediate pressure in operation ranges from 1.3 bar (minimum intermediate pressure) to 11.2 bar (maximum intermediate pressure).

(57) With reference to FIG. 7, advantageous positions for orifice openings 72a, 72b of the fluid return 70 are explained below.

(58) In general, the orifice opening 72a, 72b of the fluid return 70 in the compressor channel 26 is preferably arranged at a position angle (of the compressor channel 26) which is in a range of .sub.min=300 and .sub.max=, where is the position angle of the outer end of the compressor channel.

(59) FIG. 7 shows two particularly preferred areas A.sub.M,3 and A.sub.M,4 for the arrangement of orifice openings 72a, 72b of the fluid return 70 in the compressor channel 26.

(60) The one area A.sub.M,3 for the arrangement of orifice openings 72a is defined in that an orifice opening 72a of the fluid return 70 located therein is arranged at a position angle .sub.1 which is in a range from .sub.min=300 to .sub.max, 1=180, the orifice opening 72a being further arranged such that it is swept only by outer-side-guided compression chambers 14b and is swept exactly once per revolution by the orbiting spiral 31. For example, in FIG. 3, FIG. 4 and FIG. 7, the orifice opening 72a of the fluid return 70 is located in the compressor channel 26 at a position angle .sub.1=248. Furthermore, the orifice opening 72a is arranged on the outer side of the compressor channel 26 at this position angle. As a result, the orifice opening 72a in this embodiment is swept only by outer-side-guided compression chambers 14b. The orifice opening 72a here at no time is in direct fluid communication with any of the inner-side-guided compression chambers 14a.

(61) More precisely, the orifice opening 72a of the fluid return 70 in this embodiment is closed by the orbiting spiral 31 in the range of the revolution angle from 0 to 20. When the revolution angle reaches 20, the outer-side-guided compression chamber 14b begins to sweep over the orifice opening 72a. In a range of the revolution angle from 20 to 270, the orifice opening 72a and the outer-side-guided compression chamber 14b are in fluid communication. For example, at the revolution angle of 90 shown in FIG. 3, the orifice opening 72a of the fluid return 70 is in direct fluid communication with the outer-side-guided compression chamber 14b over its full area. In a range of the revolution angle of 270 to 360, the orbiting spiral 31 closes the orifice opening 72a again.

(62) At the revolution angle of 20, the pressure of the refrigerant in the outer-side-guided compression chamber 14b, which just enters into fluid communication with the orifice opening 72a, is already slightly above the intake pressure. This is due to the fact that this compression chamber 14b has already been closed shortly before at the revolution angle of 0 (reference sign 101) and has already been reduced somewhat up to the revolution angle of 20.

(63) For the following example, assume an intake pressure of 3 bar. Then the pressure of the refrigerant in this compression chamber 14b at the revolution angle of 20 is, for example, 3.08 bar. Up to the revolution angle of 270, the pressure of the refrigerant in this compression chamber 14b increases continuously to 4.76 bar in this example. The time average value of the pressure of the refrigerant in the compressor channel 26 at the orifice opening 72a is thereby 3.76 bar, it is therefore 0.76 bar above the intake pressure of 3 bar. This is a non-limiting example for a certain operating condition.

(64) For example, in the embodiment according to FIG. 3, the time-average value of the pressure of the refrigerant in the compressor channel 26 at the position of the orifice opening 72a of the fluid return 70 is at an intake pressure of 1 bar at 126% of this intake pressure, at an intake pressure of 3 bar at 125% of this intake pressure, at an intake pressure of 5 bar at 124% of this intake pressure and at an intake pressure of 7 bar at 123% of this intake pressure.

(65) If the orifice opening 72a of the fluid return 70 is displaced in a modification of the embodiment not shown in the range A.sub.M,3 to a position angle of .sub.1=295, then the time average value of the pressure of the refrigerant in the compressor channel 26 at the position of the orifice opening 72a of the fluid return 70 is in the range of 138% to 142% of the respective intake pressure, for example, depending on the operating state.

(66) If the orifice opening 72a of the fluid return 70 in a modification of the embodiment not shown is shifted in the range A.sub.M,3 to a position angle of .sub.1=190, then the time average value of the pressure of the refrigerant in the compressor channel 26 at the position of the orifice opening 72a of the fluid return 70 is in the range of 107% to 109% of the respective intake pressure, for example, depending on the operating state.

(67) The other range A.sub.M,4 for the arrangement of orifice openings 72b is defined in that an orifice opening 72b of the fluid return 70 located therein is arranged at a position angle .sub.2 which is in a range from .sub.min,2=120 to .sub.max=, wherein the orifice opening 72b is further arranged such that it is swept only by inner-side-guided compression chambers 14a and is swept exactly once per revolution by the orbiting spiral 31.

(68) In FIG. 7, the position for an orifice opening 72b in the region A.sub.M,4 with a position angle .sub.2=68 is drawn as an example. Furthermore, the orifice opening 72b is arranged on the inner side of the compressor channel 26 at this position angle .sub.2. As a result, this orifice opening 72b is swept only by inner-side-guided compression chambers 14a. The orifice opening 72b is therefore at no time in direct fluid communication with any of the outer-side-guided compression chambers 14b. This orifice opening 72b can be formed alternatively or in addition to the other orifice opening 72a of the fluid return 70 shown in FIG. 7.

(69) When the compression chambers 14a, 14b are closed, the position angle of the inner-side-guided compression chambers 14a is offset by +180 with respect to the position angle of the outer-side-guided compression chambers 14b. Since the position angle of the orifice opening 72b is also offset by +180 relative to that of the orifice opening 72a, the pressure conditions at the orifice opening 72b develop similarly to those at the orifice opening 72a during a revolution.

(70) In an embodiment not shown, an orifice opening of the fluid return 70 may be disposed, for example, at a position angle in the range of max,1 to min,2. Such an orifice opening may be arranged in a central portion of the compressor channel 26 at this position angle, so that it is completely closed by the orbiting spiral 31 twice in each revolution and alternately enters into fluid communication with inner-side-guided compression chambers 14a and with outer-side-guided compression chambers 14b. As a result, the average pressure of the refrigerant at this orifice opening is between the average pressure of the refrigerant in outer-side-guided compression chambers 14b on the outer side of compressor channel 26 at this position angle and the average pressure of the refrigerant in inner-side-guided compression chambers 14a on the inner side of compressor channel 26 this position angle. As mentioned elsewhere, the time periods during which the orifice opening is completely closed by the orbiting spiral 31 can be left out for calculating the average pressure of the refrigerant at the orifice opening.

(71) The scroll compressor 1 also includes a second oil return 82. The second oil return 82 returns oil from the oil separator 45 to the contact pressure chamber 80. It comprises a second oil inlet 81 in the oil separator 45 and a throttle valve 83 arranged between the second oil inlet and the contact pressure chamber 80 in the second oil return 82.

(72) In operation, the outlet pressure prevailing in the oil separator 45 forces oil through the second oil inlet 81 into the second oil return 82. The pressure of the oil is reduced by the throttle valve 83. The pressure drop in the throttle valve 83 affects the contact pressure.

(73) The oil in the contact pressure chamber 80 contributes to the lubrication of the orbiting disk 30. In addition, a small amount of the oil can creep past the orbiting disk 30 and into the interior of the compression section 10.

(74) The scroll compressor 1 shown in FIG. 1 also includes a reference connection 84 between an interior of the contact pressure chamber 80 to a reference opening 86. The reference opening 86 is disposed in the orbiting base 32 of the orbiting disk 30, specifically in a compressor channel of the orbiting disk 30. The reference connection 84 influences the contact pressure in the contact pressure chamber 80 depending on the operating condition of the scroll compressor 1. The reference connection 84 leads from the contact pressure chamber 80 through the orbiting disk 30 to the reference opening 86 in the orbiting base 32.

(75) The reference opening 86 of the reference connection 84 is positioned further inward, as viewed in the radial direction, than the orifice openings 59a, 59b of the direct oil return 50. In FIG. 3, a position of the reference opening 86 of the reference connection 84 in an outlet region of the compressor channel of the orbiting disk 30 is indicated. Therefore, the reference connection 84 cannot contribute much, if at all, to the lubrication of the radially outer portions of the stationary spiral 21 and the orbiting spiral 31. The reference opening 86 is not located in the inlet region of the compressor channel of the orbiting disk 30. Therefore, in operation of the scroll compressor 1, there is no direct fluid connection between the inlet 11 of the compression section 10 and the reference opening 86.

(76) Optionally, the reference connection 84 comprises a throttle valve 85. The throttle valve 85 contributes to the regulation of the contact pressure.

(77) The second oil inlet 81 of the second oil return 82 is arranged in a bottom region of the oil separator 45. In particular, it is arranged below the first oil inlet 51 of the direct oil return 50. In operation, when an oil level in the oil separator 45 drops to a level below the first oil inlet 51, the first oil inlet 51 falls dry and is no longer supplied with oil. However, the second oil inlet 81 continues to be supplied with oil. The oil supply to the second oil return thus has priority over the oil supply to the direct oil return 50. This ensures that the contact pressure is maintained even in the event of an oil shortage. Some lubrication of the compression section 10 is maintained by oil creeping past the outside of the orbiting disk 30, as well as by oil returning to the inlet 11 of the compression section 10 from the external refrigerant circuit. In addition, oil from the contact pressure chamber 80 may enter the compression section 10 through the reference connection 84, especially when an oil level in the contact pressure chamber is very high.

(78) The scroll compressor 1 further includes an electric motor and an inverter for the electric motor (not shown). The scroll compressor 1 is capable of being integrated into a refrigerant circuit of a vehicle. For example, the scroll compressor 1 may be incorporated into an electric vehicle or a hybrid vehicle.

(79) FIG. 5 shows a longitudinal section of a compression section 10, an outlet pressure chamber 40, an oil separator 45 and a direct oil return 50 for direct return of oil from the oil separator 45 to the compression section 10 according to a second embodiment of a scroll compressor according to the invention. The remaining elements of this scroll compressor are not shown. The scroll compressor and its components correspond to the structure and operation of the scroll compressor 1 of FIG. 1, unless otherwise indicated. The same reference signs are used for the same elements.

(80) FIG. 6 shows a cross-section at section line A in FIG. 5.

(81) In FIG. 5 and FIG. 6, it is shown that the outgassing chamber 54 is formed outside the outlet pressure chamber 40 in the radial direction (perpendicular to the center axis of the stationary disk 20) and surrounds the outlet pressure chamber 40. The outgassing chamber 54 has a (at least substantially) hollow cylindrical shape. The outlet pressure chamber 40 has an (at least substantially) cylindrical shape. The outlet pressure chamber 40 and the outgassing chamber 54 are coaxially arranged. A hollow cylindrical jacketing wall 41 of the outlet pressure chamber 40 separates the outlet pressure chamber 40 and the outgassing chamber 54 from each other. In this way, the otherwise unused space around the jacketing wall 41 is used in an advantageous manner.

(82) The outlet pressure chamber 40 is in direct fluid communication with the oil separator 45 via an opening 42. Similar to FIG. 1, a non-return device can optionally be formed at the outlet 12 of the compression section 10 (not shown).

(83) The described embodiments with the direct oil return 50 allow a particularly efficient operation and exhibit a high reliability.

LIST OF REFERENCE SIGNS

(84) 1 scroll compressor 10 compression section 11 inlet (of the compression section) 12 outlet (of the compression section) 13 non-return device 14a, 14b, 14c compression chamber 20 stationary disk 21 stationary spiral 22 stationary base 24 inner end (of the stationary spiral) 25 outer end (of the stationary spiral) 26 compressor channel (of the stationary disk) 28 outlet opening (of the stationary disk) 30 orbiting disk 31 orbiting spiral 32 orbiting base 34 outer end (of the orbiting spiral) 40 outlet pressure chamber 41 jacketing wall 42 opening 45 oil separator 46 oil separator outlet opening 50 direct oil return 51 first oil inlet 52 first fluid connection 53 first flow valve (throttle valve) 54 outgassing chamber 55 oil inlet 56 second fluid connection 57 second flow valve (throttle valve) 58 branching 59a, 59b orifice opening (of the direct oil return) 70 fluid return 71 fluid inlet 72a, 72b orifice opening (of the fluid return) 80 contact pressure chamber 81 second oil inlet 83 flow valve (throttle valve) 84 reference connection 85 flow valve (throttle valve) 86 reference opening 90 housing 91 intake connection 92 outlet connection 93 intake pressure chamber A.sub.M,1, A.sub.M,2, A.sub.M,3, A.sub.M,4 Range .sub.1, .sub.2, .sub.min, .sub.max position angle .sub.1,max, .sub.2,min position angle position angle of the outer compressor channel position angle R.sub.I() radial distance of the inner side of the stationary spiral at the outer end of the compressor channel. B.sub.K width of the compressor channel in the radial direction at the outer end of the compressor channel R.sub.A(360) radial distance of the outer side of the stationary spiral at the position angle 360