Positive-displacement machine according to the spiral principle, method for operating a positive-displacement machine, positive-displacement spiral, vehicle air-conditioning system and vehicle

Abstract

The invention relates to a positive-displacement machine according to the spiral principle, particularly a scroll compressor, having a high-pressure region, which comprises a high-pressure chamber, furthermore having a low-pressure chamber and an orbiting positive-displacement spiral, which engages into a counterpart spiral in such a manner that compression chambers are formed between the positive-displacement spiral and the counterpart spiral, in order to accommodate a working medium, wherein a counterpart-pressure chamber is constructed between the low-pressure chamber and the positive-displacement spiral. According to the invention, the positive-displacement spiral has at least two passages, which at least temporarily produce a fluid connection between the counterpart-pressure chamber and at least one of the compression chambers, wherein a first passage is essentially constructed in a central section of the positive-displacement spiral and at least one second passage is constructed in the initial region of the positive-displacement spiral.

Claims

1. A scroll compressor comprising: a high-pressure chamber, a low-pressure chamber, an orbiting positive-displacement spiral, which engages into a counterpart spiral so that compression chambers are formed between the orbiting positive-displacement spiral and the counterpart spiral, in order to accommodate a working medium, and a counterpart-pressure chamber being constructed between the low-pressure chamber and the orbiting positive-displacement spiral, wherein the orbiting positive-displacement spiral has at least two passages, which at least temporarily produce a fluid connection between the counterpart-pressure chamber and at least one of the compression chambers, the at least two passages including a first passage and a second passage, wherein the first passage is essentially constructed in a central section of the orbiting positive-displacement spiral and at least one second passage is constructed in the initial region of the orbiting positive-displacement spiral, wherein the first passage is constructed in a section of the orbiting positive-displacement spiral, in which the first passage in the activated state of the scroll compressor is open when 85% of the relative compression chamber volume is reached, and remains open during a rotation of the orbiting positive-displacement spiral, subsequent to opening, by an angle of rotation of 180, and wherein a gas-connection line is formed from the high-pressure chamber of the scroll compressor to the counterpart-pressure chamber.

2. The scroll compressor according to claim 1, wherein the first passage and/or the at least second passage is constructed in a section of the base of the orbiting positive-displacement spiral.

3. The scroll compressor according to claim 1, wherein the second passage is constructed in a section of the orbiting positive-displacement spiral, in which the second passage is closed when the maximum compression chamber volume Vmax is reached, and is open during a rotation, prior to the closure, of the orbiting positive-displacement spiral by an angle of rotation of 180.

4. The scroll compressor according to claim 3, wherein the maximum compression chamber volume Vmax is assigned to an angle of rotation Vmax, wherein the second passage is closed when the angle of rotation Vmax+/30 is reached.

5. The positive displacement machine scroll compressor according to claim 1, wherein the first passage is closed at least at an angle of rotation of 30, before the discharge angle is reached.

6. The scroll compressor according to claim 1, wherein the gas-connection line is constructed in the housing and connects the high-pressure chamber to the counterpart-pressure chamber.

7. The scroll compressor according to claim 1, wherein an oil return channel is formed from the high-pressure chamber of the scroll compressor to the low-pressure chamber.

8. A method for operating a scroll compressor according to claim 1, comprising opening the first passage when 85% of the relative compression chamber volume is reached, and remains open during a rotation of the orbiting positive-displacement spiral, subsequent to opening, by an angle of rotation of 180.

9. The method according to claim 8, comprising closing the second passage when the maximum relative compression chamber volume Vmax is reached, and is open during a rotation, prior to the closure, of the orbiting positive-displacement spiral by an angle of rotation of 180.

10. A vehicle air-conditioning system having a scroll compressor according to claim 1.

11. A vehicle having a scroll compressor according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the following, the invention is explained in more detail on the basis of exemplary embodiments with reference to the accompanying, schematic drawings.

(2) In the figures

(3) FIG. 1 shows a positive-displacement spiral according to the invention in a perspective plan view;

(4) FIG. 2 shows a longitudinal section of a positive-displacement machine according to the invention, particularly of a scroll compressor;

(5) FIGS. 3a+3b show various positionings and method states of a positive-displacement machine according to the invention, with a plan view onto the positive-displacement spiral, which carries out orbiting movements in the counterpart spiral, wherein the base of the counterpart spiral is not illustrated;

(6) FIG. 4 shows a schematic illustration of the operating principle of the positive-displacement machine according to the invention;

(7) FIG. 5 shows an illustration of the opening time periods of the passages as a function of the angle of rotation;

(8) FIG. 6 shows an illustration of the pressure in the compression chamber as a function of the angle of rotation and of the chosen suction pressure in connection with the coolant R134a used;

(9) FIG. 7 shows an illustration of expulsion cycles from the compression chamber into the high-pressure chamber and an illustration of the opening phases of the first passage in connection with the coolant R134a;

(10) FIG. 8 shows an illustration of the closing force in relation to the suction pressure and the final pressure to be achieved;

(11) FIG. 9 shows an illustration of the pressure behaviour during the intake phase; and

(12) FIG. 10 shows the back-pressure curve whilst additionally displaying the compression pressure for the coolant R134a.

DETAILED DESCRIPTION

(13) In the following, the same reference numbers are used for the same parts and parts with the same effect.

(14) A positive-displacement spiral 31 according to the invention is illustrated in FIG. 1. This is used in particular for installation into a positive-displacement machine, particularly into a scroll compressor 10, according to the exemplary embodiment of FIG. 2.

(15) As illustrated in FIG. 1, the positive-displacement spiral 31 comprises a base 34. The base 34 can also be termed the rear wall of the positive-displacement spiral 31. The base 34 is constructed in a circular manner and has the shape of a round plate. A spiral 35 with spiral flank sections 36a, 36b and 36c are constructed on the base 34.

(16) The spiral element 35 extends starting from the centre point M up to an initial region 37.

(17) Two passages, namely a first passage 60 and a second passage 61, are constructed in the base 34. The passages 60 and 61 are through holes, which essentially run perpendicularly to the surface of the base 34. The first passage 60 in this case is constructed in a central section 38 of the positive-displacement spiral 31. By contrast, the second passage 61 is constructed in the initial region 37 of the positive-displacement spiral 31.

(18) The first passage 60 is constructed in a section of the base 34, wherein the first passage 60 is constructed eccentrically between the spiral flank sections 36a and 36b. By contrast, the second passage 61 is constructed eccentrically between the spiral flank sections 36b and 36c. The section of the duct 39 constructed between the spiral flank sections 36c and 36b are to be understood as the initial region 37, which section, starting from the opening 37a, corresponds approximately to a region of at most 10% of the total length of the spiral duct 39. The total length of the spiral duct 39 is defined starting from the opening 37a up to the end section 39a of the spiral duct 39. The end section 39a is the last section of the spiral duct 39 in the flow direction of the coolant. In the illustrated example, the end section 39a is constructed in a curved manner.

(19) The positive-displacement spiral 31 illustrated in FIG. 1 is installed in a scroll compressor 10 according to the exemplary embodiment of FIG. 2. This scroll compressor 10 can for example act as a compressor of a vehicle air-conditioning system. A vehicle air-conditioning system, such as e.g. a CO.sub.2 vehicle air-conditioning system, typically has a gas cooler, an inner heat exchanger, a throttle, an evaporator and a compressor. The compressor can consequently be the depicted scroll compressor 10. The scroll compressor 10 in other words is a positive-displacement machine according to the spiral principle.

(20) The illustrated scroll compressor 10 has a mechanical drive 11 in the form of a belt pulley. During use, the belt pulley 11 is connected to an electric motor or an internal combustion engine. Alternatively, it is possible that the scroll compressor is driven electrically or electromotively.

(21) The scroll compressor 10 additionally comprises a housing 20 with an upper housing part 21, which closes the high-pressure region 47 of the scroll compressor 10. A housing partition wall 22 is constructed in the housing 20, which delimits a low-pressure chamber 30. The low-pressure chamber 30 can also be termed a suction space. A through opening is constructed in the housing base 23, through which a drive shaft 12 extends. The shaft end 13 arranged outside the housing 20 is connected in a rotationally fixed manner to the driver 14, which engages into the belt pulley mounted on the housing 20 in a rotatable manner, i.e. into the mechanical drive 11, so that a torque can be transmitted from the belt pulley to the drive shaft 12.

(22) The drive shaft 12 is mounted in a rotatable manner in the housing base 23 on the one hand and in the housing partition wall 22 on the other hand. The sealing of the drive shaft 12 against the housing base 23 takes place by means of a first shaft seal 24 and against the housing partition wall 22 by means of a second shaft seal 25.

(23) The scroll compressor 10 furthermore comprises the positive-displacement spiral 31 and a counterpart spiral 32. The positive-displacement spiral 31 and the counterpart spiral 32 engage into one another. The counterpart spiral 32 is preferably fixed both in the circumferential direction and in the radial direction. The movable positive-displacement spiral 31 coupled to the drive shaft 12 describes a circular path, so that a plurality of gas pockets or sealing chambers 65a, 65b, 65c and 65d are generated in a manner known per se by means of this movement, which migrate radially inwards between the positive-displacement spiral 31 and the counterpart spiral 32.

(24) By means of this orbiting movement, working medium, particularly a coolant, is sucked in and, with the further spiral movement and the associated reduction in size of the sealing chamber 65a, 65b, 65c and 65d, sealed. The working medium, particularly the coolant, is compressed increasingly from radially outside to radially inside, for example linearly, and expelled in the centre of the counterpart spiral 32 into the high-pressure chamber 40.

(25) In order to create an orbiting movement of the positive-displacement spiral 31, an eccentric bearing 26 is constructed, which is connected to the drive shaft 12 by means of an eccentric pin 27. The eccentric bearing 26 and the positive-displacement spiral 31 are arranged eccentrically with respect to the counterpart spiral 32. The compression chambers 65a, 65b and 65c are separated from one another in a pressure-tight manner by means of the bearing of the positive-displacement spiral 31 against the counterpart spiral 32.

(26) The high-pressure chamber 40 is arranged downstream of the counterpart spiral 32 in the flow direction and is in fluid connection with the counterpart spiral 32 by means of an outlet 48. The outlet 48 is preferably not arranged exactly in the centre point of the counterpart spiral 32, but rather is located eccentrically in the region of an innermost compression chamber 65a, which is formed between the positive-displacement spiral 31 and the counterpart spiral 32. This means that the outlet 48 is not covered by the bearing bushing 28 of the eccentric bearing 26 and the fully compressed working medium can be expelled into the high-pressure chamber 40.

(27) The base 33 of the counterpart spiral 32 forms the base of the high-pressure chamber 40 in certain sections. The base 33 is wider than the high-pressure chamber 40. The high-pressure chamber 40 is delimited at the side by the side wall 41. A recess 42 is formed in an end of the side wall 41 facing the base 33 of the counterpart spiral 32, in which recess a sealing ring 43 is arranged. The side wall 41 is a circumferential wall, which forms a stop of the counterpart spiral 32. The high-pressure chamber 40 is constructed in the upper housing part 21. This has a rotationally symmetrical cross section.

(28) The compressed working medium collected in the high-pressure chamber 40, namely the cooling gas, flows through an outlet 44 out of the high-pressure chamber 40 into an oil separator 45, which in the present case is constructed as a cyclone separator. The compressed working medium, namely the compressed cooling gas, flows through the oil separator 45 and the opening 46 into the circuit of the exemplary air-conditioning system.

(29) The control of the contact pressure of the positive-displacement spiral 31 against the counterpart spiral 32 is effected in that a base 34 of the positive-displacement spiral 31 is loaded with a corresponding pressure. A counterpart-pressure chamber 50, which can also be termed the back-pressure space, is also constructed. The eccentric bearing 26 is located in the counterpart-pressure chamber 50. The counterpart-pressure chamber 50 is delimited by the base 34 of the positive-displacement spiral 31 and by means of the housing partition wall 22.

(30) The counterpart-pressure chamber 50 is separated from the low-pressure chamber 30 in a fluid-tight manner by means of the previously described second shaft seal 25. A sealing and sliding ring 29 sits in an annular groove in the housing partition wall 22. The positive-displacement spiral 31 is therefore supported in the axial direction on the sealing and sliding ring 29 and slides on the same.

(31) As can likewise be seen in FIG. 2, the passages 60 and 61 of the positive-displacement spiral 31 can at least temporarily produce a fluid connection between the counterpart-pressure chamber 50 and the illustrated compression chambers 65a and 65c. In the cross section, it can clearly be seen that the first passage 60 is essentially constructed in a central section 38, and the second passage is constructed in the initial region 37 of the positive-displacement spiral 31.

(32) The spiral element 66 of the counterpart spiral 32, particularly the spiral flank sections 67a and 67b can temporarily close the passages 60 and 61. In other words, the passages 60 and 61 are for example cleared in a simultaneous and/or temporally offset manner by means of corresponding displacement in relation to the spiral flank sections 67a and 67b, so that a working medium can flow from the compression chambers 65a and/or 65b and/or 65c and/or 65d in the direction of the counterpart-pressure chamber 50.

(33) As is furthermore illustrated in FIG. 2, a gas-connection line 70 is constructed from the high-pressure region 47 of the positive-displacement machine or the scroll compressor 10 to the counterpart-pressure chamber 50. The gas-connection line 70 is constructed downstream of the oil separator 45, so that actually only gas and no oil is transported through the gas-connection line 70. A throttle 71 is constructed in the gas-connection line 70.

(34) In an alternative design of the invention (not illustrated), a gas-connection line can be constructed in the counterpart spiral 32. A gas-connection line of this type can produce a connection from the high-pressure chamber 40 to the counterpart-pressure chamber 50.

(35) It is to be mentioned that the second passage 61 does not produce a connection into the low-pressure chamber 30, as the mass flow of a coolant is sucked up in this region and is only transported in the direction of the compression process, i.e. in the direction of the compression chambers 65a, 65b, 65c and 65d between the two spirals 31 and 32. The mass flow cannot pass from the counterpart-pressure chamber 50 into the low-pressure chamber 30.

(36) As is furthermore indicated in FIG. 2, an oil return channel 75 with a throttle 76 is constructed starting from the high-pressure region 47. An oil return channel 75 of this type produces a connection from the high-pressure region 47 to the low-pressure region 30, in order to ensure oil return. Thus, a separate oil return and a separate gas return can be realized.

(37) With the aid of the scroll compressor according to the invention or with the aid of the use of a positive-displacement spiral 31 according to the invention, a variable back-pressure system, i.e. a variable counterpart-pressure system can be constructed, wherein the pressure in the counterpart-pressure chamber 50 is set by means of a balance between the high pressure prevailing in the high-pressure region 47 and the suction pressure or low pressure prevailing in the low-pressure chamber 30.

(38) This is based inter alia on the arrangement of the passages 60 and 61.

(39) Various positions of the spirals 31 and 32 with respect to one another result, depending on the time of the compression process, so that, as is illustrated in FIGS. 3a-3b, one or none of the two passages 60 and 61 is free, and a fluid connection from the respective compression chamber to the counterpart-pressure chamber 50 can be produced.

(40) A view onto the positive-displacement spiral 31 from above is illustrated in FIGS. 3a and 3b, wherein the spiral element 66 or the spiral flank sections 67a, 67b of the counterpart spiral 32 can be seen. By contrast, the base 33 of the counterpart spiral 32 cannot be seen.

(41) In FIG. 3a, the two passages 60 and 61 are closed, i.e. the spiral element 66 of the counterpart spiral 32 or the spiral flank sections 67a and 67b cover the passages 60 and 61. In other words, in FIG. 3a, the 0 position of the compression process is illustrated. In this case, the coolant was already sucked in and the corresponding compression chambers 65a-65e were formed. The compression chamber 65e is the compression chamber, which is first closed in the flow direction.

(42) By contrast, in FIG. 3b, an 80 position is illustrated. In this position, the first passage 60 is just opened. This corresponds to a 90% point of the relative volume, as is explained in detail in FIG. 5.

(43) In FIG. 3a, no fluid connection from the compression chambers 65a-65e to the counterpart-pressure chamber 50 is possible. By contrast, in FIG. 3b, owing to the opening of the first passage 60, a fluid connection can be produced between the compression chamber 65c and the counterpart-pressure chamber 50.

(44) In FIG. 4, the basic principle of the positive-displacement machine according to the invention is illustrated schematically. The low-pressure chamber or suction chamber 30, the high-pressure chamber 40 and the counterpart-pressure chamber and the back-pressure space 50 can be seen. An oil return channel 75 is constructed between the high-pressure chamber 40 and the low-pressure chamber 30. The oil return consequently takes place exclusively between the high-pressure chamber 40 and the low-pressure chamber 30. Separately, the gas connection line 70 is constructed between the high-pressure chamber 40 and the counterpart-pressure chamber 50. The first passage 60 and the second passage 61 in the positive-displacement spiral 31 can likewise be seen. Owing to the passages 60 and 61 constructed, connections from the compression chambers 65a-65e to the counterpart-pressure chamber 50 are possible.

(45) A volumetric change curve of a scroll compressor is illustrated in FIG. 5. This volumetric change curve is in principle approximately identical for all scroll compressors and independent of the coolant used. The angle of rotation (rotational angle) 0 in this case shows the start of the compression process in a scroll compressor. The graphs THS-1 and THS-2 can likewise be seen. In this case, THS-1 illustrates the times in the compression process at which the first passage 60 is open as a function of the relative volume in the compression chamber. It can be seen that the first passage 60 is constructed in a section of this type, particularly in a central section 38 of the positive-displacement spiral 31 of this type, in which the first passage 60 is open in the activated state of the positive-displacement machine when 90% of the relative compression chamber volume is reached and subsequently remains open, after the opening, during a subsequent rotation of the positive-displacement spiral 31 by an angle of rotation of 270. The first passage 60 is opened in the present case at an angle of rotation of 80. By contrast, the closure of the first passage takes place at an angle of rotation of 350.

(46) Furthermore, the closing time of the second passage 61 (THS-2) is illustrated in FIG. 5. Consequently, the second passage 61, which is constructed in the initial region 37 of the positive-displacement spiral 31, is to be closed at the time at which the maximum relative compression chamber volume (Vmax) is present. The closure consequently takes place at an angle of rotation of 50, wherein the negative angle of rotation is to be interpreted in relation to 0 angle of the scroll compressor 10, at which the compression process starts. Consequently, the second passage 61 is open prior to the closure for approx. 270.

(47) In other words, the second passage 61 is constructed in a section of the positive-displacement spiral 31 of this type, in which the second passage 61 is closed when the maximum relative compression chamber volume and is open during a rotation, prior to the closure, of the positive-displacement spiral 31 by an angle of rotation of 270.

(48) The opening time periods of the passages 60 and 61 are likewise illustrated in FIG. 6. The illustration corresponds to a scroll compressor 10, wherein R134a is used as coolant. The graphs illustrated are coolant-dependent. The graphs are furthermore illustrated for different suction pressures (pS) of 3 bar, 1 bar and 6 bar. As can be seen, the behaviour of the pressure in the compression chamber (chamber pressure) is illustrated as a function of the angle of rotation (rotational angle). For a suction pressure or low pressure of 1 bar, the compression curve runs relatively flat, whereas the compression curve runs relatively steeply at a suction pressure of 6 bar. The suction pressures 3 bar, 1 bar and 6 bar represent the respective saturation temperatures/evaporation temperatures u 25 C., 0 C. and 25 C. A standard scroll compressor must provide corresponding temperatures in vehicle air-conditioning systems in a temperature range of 25 C. to +25 C., so that the suction pressure (pS) varies in a range from 1 bar-6 bar.

(49) In FIG. 7, graphs are in turn depicted, which illustrate pressures in the compression chamber (chamber pressure) as a function of the angle of rotation (rotational angle). In this case, the current compression cycle is illustrated with a thick solid line. The previous cycle and the next cycle are indicated with thinner lines. With respect to the current compression cycle, the opening duration of the first passage 60 (THS-1) and the second passage 61 (THS-2) is additionally illustrated.

(50) It can be seen that a compression pressure of 20 bar is achieved, wherein the flattened upper part of the graph describes the expulsion limit 80. At this limit 80, the compressed gas is expelled into the high-pressure chamber 40. The expulsion takes place at an angle of rotation of approx. 180 to 360. The graph furthermore indicates the so-called discharge angle 81. This discharge angle 81 relates to the time at which the last compressed gas was expelled into the high-pressure chamber and subsequently the pressure in the compression chamber falls suddenly. The gas compressed in the compression chamber is not expelled completely. Residual gas remains in the compression chamber. This must not be expelled into the counterpart-pressure chamber 50 however, so that the first opening 60 must be closed before the discharge angle 81 is reached. According to FIG. 7, the first passage 60 is to be closed at least 30 before the discharge angle 81 is reached. The area 82, which is formed between the graph of the current compression cycle and a dashed line located thereabove, represents the residual gas of the previous compression cycle, which was not expelled into the high-pressure chamber.

(51) In FIG. 8, an area is illustrated, which illustrates the relative closing force relating to the positive-displacement spiral 31 and the counterpart spiral 32. This is illustrated as a function of the suction pressure and the final pressure (discharge pressure) to be achieved. It becomes clear that with increasing final pressure, the closing force must also be increased. The illustration of FIG. 8 relates in turn to a scroll compressor, which is operated with the working medium R134a. Actually, for safety, higher closing forces are created than is illustrated in FIG. 8.

(52) By contrast, the dynamic effects in the intake phase of a compression process are illustrated in FIG. 9. This illustration also relates in turn to a compression with the coolant R134a. An underpressure can accordingly arise in the intake phase or in the intake region of the positive-displacement spiral. In the case of an underpressure, no increased pressure must be present in the counterpart-pressure chamber, the underpressure already presses the two spirals 31 and 32 against one another. The area 83, which runs between the horizontal, which runs through the intersection point 3.0 bar, and the graph, which describes the pressure in the compression chamber in the intake phase, is detected by means of a corresponding opening of the second passage 62 during the angle of rotation (rotational angle) of 360-50.

(53) Overall, it is true that a technical advantage results, owing to the positive-displacement machine according to the invention or owing to the scroll compressor according to the invention, that by means of the detection of a plurality of pressures in various phases of the compression and in various sections of the compression chambers, the pressure in the counterpart chamber can be set in a more optimal manner, particularly lower.

(54) In FIG. 10, as a function of the angle of rotation (rotational angle), on the one hand, the curve of the counterpart-chamber pressure (back pressure) and on the other hand, the curve of the compression chamber pressure (chamber pressure) is illustrated. In the lower illustration, the opening sections of the first passage 60 and the second passage 61 are also illustrated. These graphs have also been created in connection with the coolant R134a. It is very clearly illustrated that with increasing pressure in the compression chamber (chamber pressure), the pressure in the counterpart-pressure chamber falls accordingly, so that it is accordingly necessary to implement countermeasures in this regard.

REFERENCE LIST

(55) 10 Scroll compressor

(56) 11 Mechanical drive

(57) 12 Drive shaft

(58) 13 Shaft end

(59) 14 Driver

(60) 15 Circumferential wall

(61) 20 Housing

(62) 21 Upper housing part

(63) 22 Housing partition wall

(64) 23 Housing base

(65) 24 First shaft seal

(66) 25 Second shaft seal

(67) 26 Eccentric bearing

(68) 27 Eccentric pin

(69) 28 Bearing bushing

(70) 29 Sliding ring

(71) 30 Low-pressure chamber

(72) 31 Positive-displacement spiral

(73) 32 Counterpart spiral

(74) 33 Base, counterpart spiral

(75) 34 Base, positive-displacement spiral

(76) 35 Spiral element

(77) 36a, 36b, 36c Spiral flank section

(78) 37 Initial region

(79) 37a Opening

(80) 38 Central section

(81) 39 Spiral duct

(82) 39a End section

(83) 40 High-pressure chamber

(84) 41 Side wall

(85) 42 Recess

(86) 43 Sealing ring

(87) 44 Outlet

(88) 45 Oil separator

(89) 46 Opening

(90) 47 High-pressure region

(91) 48 Outlet

(92) 50 Counterpart-pressure chamber

(93) 60 First passage

(94) 61 Second passage

(95) 65a, 65b, 65c, 65d, 65e Compression chamber

(96) 66 Spiral element

(97) 67a, 67b Spiral flank section

(98) 70 Gas-connection line

(99) 71 Throttle

(100) 75 Oil return channel

(101) 76 Throttle

(102) 80 Expulsion limit

(103) 81 Discharge angle

(104) 82 Area

(105) 83 Area

(106) M Centre point, positive displacement spiral