EP1228314B1 - Axial piston compressor - Google Patents

Description

The invention relates to an axial piston compressor for a Refrigerant, especially for a vehicle air conditioning system the features of the preamble of claim 1.

Such an axial piston compressor is e.g. from DE 199 07 492 A1 known.

Another axial piston compressor is from, for example DE 196 21 174 A1 known. It is used as a compressor for that Refrigerant used and used in a vehicle air conditioning system to the refrigerant from a heat exchanger in which it evaporated while absorbing heat at low pressure and compress to a higher pressure at which the Refrigerant in another heat exchanger, giving off heat is liquefied and / or cooled.

Such compressors come in a wide variety of designs known; have different reasons Axial piston compressors with a swash plate work. With this design, the axial movement of the pistons generated by a swashplate, the tilt angle relative to Drive shaft can be controlled. With the swashplate the pistons are connected in a tensile and compressive manner; because the cylinders, in which the pistons are slidable are stationary while the swashplate is driven as a coupling mechanism between the swash plate and the pistons either sliding blocks with plain bearings attached to the pistons, or a swashplate with piston rods that are in plain bearings are attached to the piston. If the pistons directly with the Swashplate are connected, there are two on each piston hemispherical bearing formed in which the two Sliding blocks are arranged so that they on one and the attack the other side of the swash plate on a tread. On the other hand, if a swashplate is used, it is rotatably mounted relative to the swash plate, so that on the Swashplate only the inclined position of the swashplate is transmitted, but not their rotational movement. The Piston rods are on the swash plate as well as on the Piston supported by a ball joint.

An oil circuit with a pump for lubricating the component of the Axial piston compressor is for axial piston compressors that are in Motor vehicles is not possible. For one thing, would the axial piston compressor by the lubricant pump may considerably more expensive. Furthermore, it leads to performance losses, with an axial piston compressor for vehicle air conditioning, that have a rather low performance are more important than a high performance axial piston compressor. After all, a pump that would take the lubricant out of a Oil sump would have to suck in, together with this oil sump lead to significantly larger construction volumes. For all of these reasons is the lubrication inside the housing instead of through an oil circuit with a pump through an oil mist generated there achieved. From European patent application 0 738 832 also known to use an oil sump that is used to to collect oil drops occurring in the interior of the housing. This oil sump is through a lubricating oil channel with one of the Bearing connected inside the case. Because the oil sump is higher lies as the corresponding bearing, the oil flows due to the Gravity to the camp.

The situation is very similar with the axial piston compressor according to DE 198 21 265 A1. Oil also drips there due to the Gravity on moving parts within one Swash plate chamber. Accordingly, this too Design the lubrication of the bearings without pressure.

The same applies to the construction according to US 4,283,997 oil is separated on the high pressure side and to the Support the moving parts of the axial piston compressor promoted. However, since there is an oil separator behind the high-pressure side Throttle is located and also the oil channel in one Oil collection chamber opens out via a drive shaft radial bearing communicates with the engine chamber, that is what it learns Lube oil reduces pressure to near engine chamber pressure with the result that the lubricating oil supply to the bearings is significantly reduced. This construction also stands out through an almost pressure-free supply of lubricant out.

The previously planned lubrication through a lubricating oil mist or by supplying lubricant without pressure not satisfactory under all operating conditions. Especially with plain bearings, where only a minor there is an oscillating relative movement, it can lead to a Lack of lubrication come because the lubricant mist does not can supply enough lubricant.

The object of the invention is therefore in one Axial piston compressor of the type mentioned at the beginning the simplest means of reliable pressure oil lubrication To ensure bearings without a separate oil pump is required, but lubrication is still achieved that is supposed to be qualitative through the lubrication of the bearings the lubricant mist inside the housing goes.

Advantages of the invention

The object of the invention is achieved with an axial piston compressor of the type mentioned Features of the characterizing part of patent claim 1.

When using both plain and roller bearings, especially needle bearings, are preferably the first Plain bearings with "narrow gaps" supplied with oil, since plain bearings design-related efficient throttling points for Represent the low pressure side. If design-related Rolling or needle bearings must first be supplied be sealed to the low pressure side. In aforementioned sense is the essence of the present invention understand that the lubricant is due solely to the Pressure difference between the compression pressure of the refrigerant and the internal pressure of the housing from the lubricant separator conveyed to and through the lubricant channel is fed to the bearings under appropriate pressure. This means that all bearings are under high pressure with lubricant can be supplied without the need for a separate oil pump is.

The lubricant separator is on the pressure side of the Circuit arranged, either between the Compressor and a pressure side heat exchanger or between the pressure side heat exchanger and an expansion valve.

According to a preferred embodiment of the invention provided that the supply line with a controllable valve is provided. With this valve, the supply line can when the axial piston compressor is at a standstill, so that the existing high pressure on the compressor Lubricant present in the collecting chamber is not in the housing Axial piston compressor can push in, causing the Eventually the collecting room would be emptied. In this case none when starting up the axial piston compressor Lubricant available. If, however, the valve with Commissioning of the axial piston compressor is opened Sufficient lubrication immediately by the in Lubricant collection containers available.

If the lubricant drains from the reservoir due to the internal resistances and throttling points of the system a sufficient resistance could be opposed the controllable valve can also be dispensed with. If the The compressor only comes to a standstill for a short time no pressure equalization between the pressure side of the compressor and the low pressure side. Thus, the compressor must Restarting against high pressure; it stands but also immediately available lubricants. Against that the compressor after a long standstill leading to a Pressure equalization has resulted, so that not immediately below Lubricant under pressure is supplied, only pressure build up; so he doesn’t work under heavy loads at first, so that not even a complete lubrication is required. With increasing load of the compressor then the lubrication also improves.

Alternatively, the controllable valve could be replaced by a Throttle point to be replaced if it is ensured that the Pressure equalization when the compressor stops first Line happens over other points of the cycle for example through a separate valve.

Instead of a separate choke point, one could Throttle line can be used by the various pressure drops in the lubricant supply, especially through channels in the compressor, the required Throttling is brought about.

An overflow line is preferably provided, which runs from Lubricant separator leads to the interior of the housing. On this way excess lubricant that is in the Collecting room accumulates, if necessary, removed. Therefor a controllable valve can be provided in the overflow line be depending on, for example, a Level sensor in the collecting room is opened.

According to one embodiment of the invention, that the lubricant separator is integrated in the housing. This leads to a particularly compact design.

Alternatively, it can be provided that the lubricant separator is separated from the housing and the supply line acts as a lubricant cooler. This ensures that that too Lubricant returned to the bearings, from the Refrigerant was warmed up during the compression stroke is returned to its initial temperature.

According to a preferred embodiment is a drive shaft provided that is provided with an axial distribution bore. An axial distribution hole in the drive shaft enables almost all important ones with particularly little effort Bearing points inside the housing of the axial piston compressor to reach. The effort is significantly less than with a solution in which in the housing of the compressor appropriate lubricant channels to all bearings are trained.

The distribution bore preferably opens into one in the interior of the housing arranged end face of the drive shaft, that is the end face, which is the drive end of the drive shaft opposite. With an axial supply of the lubricant can be axially due to the low peripheral speeds use a small sealing element so that it is compact Design results.

According to a preferred embodiment is a swash plate provided by means of a plain bearing on the drive shaft is arranged displaceably, in the region of the plain bearing a branch hole is provided in the drive shaft, the connects the plain bearing to the distribution hole. The plain bearing is due to the existing in the interior of the housing Lubricant mist is very difficult to lubricate; the Branch hole allows the slide bearing to the required Amount of lubricant. The amount supplied can be determined by the cross section of the branch hole.

There is preferably a supply hole in the swash plate trained with the through the slide bearing Lubricant is supplied, being on the swash plate Attack sliding blocks, which use the supply hole of the Swashplate be supplied with lubricant. To this Ways are also the sliding blocks, which are only a minor execute oscillating movement and therefore by the Lubricant mist is also difficult to lubricate, specifically supplied with lubricant under pressure.

According to a preferred embodiment, the drive shaft by at least one assembly consisting of a radial bearing and a thrust bearing stored, this assembly through a branch hole from the drive shaft is supplied with lubricant and the Lubricant first through the radial bearing and then through that Thrust bearing flows. The series connection of the bearings used allows both bearings in terms of lubricant flow to lubricate with comparatively little effort. There due to the available space and the resulting bearing size the radial bearing in terms of Life is most at risk, this bearing is included first Lubricant supplies; the one leaving the radial bearing Lubricant flow is then led to the thrust bearing. The Supply of the bearings can be done as this is preferred is intended to be adjusted by sealing washers form a defined leakage gap. By suitable Dimensioning of the passage points for the lubricant can realize the function of a non-controllable valve be prevented that with the compressor stopped a lot of lubricant from the separator to the compressor is shifted.

According to a preferred embodiment of the invention, CO _{2 is} used as the refrigerant. Apart from the various technical advantages that CO ₂ offers compared to the currently common refrigerants such as R134a, an air conditioning system with the refrigerant CO _{2 works} at a much higher pressure level than an air conditioning system with a conventional refrigerant. When using CO ₂ , there is a suction pressure of about 50 bar and a compression pressure of about 120 bar. In contrast, the suction pressure for the refrigerant R134a is approximately 5 bar and the compression pressure is approximately 20 bar. It follows from this that when CO _{2 is used} as the refrigerant there is a much higher pressure difference between the lubricant separator and the interior of the housing of the axial piston compressor than with conventional axial piston compressors, namely approximately 70 bar compared to 15 bar with conventional axial piston compressors. This higher pressure difference provided according to the invention leads to an improved supply of lubricant to the bearings.

Advantageous embodiments of the invention result from the Dependent claims.

drawings

Fig. 1

in einer schematischen Schnittansicht einen Axialkolbenverdichter gemäß einer ersten Ausführungsform der Erfindung;

Fig. 2

in einem schematischen Schnitt einen Axialkolbenverdichter gemäß einer zweiten Ausführungsform der Erfindung; und

Fig. 3

in einem schematischen Schnitt einen Axialkolbenverdichter gemäß einer dritten Ausführungsform der Erfindung.

The invention is described below with reference to various embodiments which are illustrated in the accompanying drawings. In these show:

Fig. 1

in a schematic sectional view of an axial piston compressor according to a first embodiment of the invention;

Fig. 2

in a schematic section an axial piston compressor according to a second embodiment of the invention; and

Fig. 3

in a schematic section an axial piston compressor according to a third embodiment of the invention.

Description of the embodiments

In Figure 1 is an axial piston compressor according to a first embodiment shown. It contains one Drive shaft 10, which is mounted in a housing 12. With the Drive shaft 10 is non-rotatably connected to a swash plate 14, between a position in which they are approximately perpendicular to the Longitudinal axis of the drive shaft 10 extends, and a maximum tilted position can be pivoted in Figure 1 is shown. The position of the swash plate 14 in operation takes place depending on the difference between the suction pressure of the compressor and the pressure in the Interior of the housing 12 and the bias of a spring 16, which the swash plate on the drive shaft 10 can move, the swashplate on a holder 18 supports, so that it is in a shift on the Drive shaft is pivoted.

A swash plate 20 can be rotated on the swash plate by means of radial and axial roller bearings 22, 24 mounted. At the Swash plate 20 attack several ball joints 26 by means of which each have a piston 28 tensile and pressure resistant with the Swash plate 20 is connected. Each piston 28 is in one Cylinder 30 slidable, the central axis parallel to Longitudinal axis of the drive shaft 10 runs. In the drawing are only two pistons shown; actually the compressor can be up to seven pistons included.

When the drive shaft 10 is rotated and the swash plate is in a position oblique to the drive shaft, each piston 28 reciprocates in the corresponding cylinder 30. This movement can be used to compress a refrigerant, for example CO ₂ . The refrigerant is sucked up from an inlet line 32 under evaporation pressure or suction pressure and conveyed into an outlet line 34 while standing under condensation pressure or evaporation pressure. During compression, the refrigerant takes up small amounts of a lubricant that is present in the interior of the housing and is also present on the inner wall of the cylinders 30.

The outlet line 34 opens into a lubricant separator 36. This has a separation space 38, in which the Lubricants at a reduction in Flow rate of the present as compressed gas Refrigerant is separated by gravity, as well as a Collection space 40 for the separated lubricant. That in Collection space 40 existing lubricant is under pressure of the refrigerant. One leads from the separation chamber 38 Compressor line 39 for the compressed refrigerant to one Heat exchanger.

In principle, an alternative to a gravity separator every common separation principle for the realization of the Lubricant circuit can be used.

At the collecting space 40 there is one at the lowest point Supply line 42 connected to a controllable Valve 44 is provided. The feed line 42 leads to one Supply channel 46 in the housing 12, which is connected to a radial bearing 48 for the drive shaft 10 opens. At the separation room 38 is an overflow line 43 connected to a valve 45 is provided. By opening the valve 45, it is possible to excess volume of the contained in the collecting space 40, deposited lubricant in the housing.

The drive shaft 10 is axially extending Distribution bore 50 provided which is radial extending supply bore 52 with the radial bearing 48 connected is. The drive shaft 10 is also with two radially extending branch holes 54 are provided, of which one is assigned to a plain bearing 56, by means of which the Swash plate is mounted on the drive shaft 10, and the another is assigned to a radial bearing 58, which together with an axial bearing 60 in the interior of the housing 12 arranged to the drive side of the drive shaft 10 opposite end camps.

If the operation of the axial piston compressor described Valve 44 of the supply line 42 is open, the flows in Collection space 40 contained lubricant due to the difference between the pressure in the separation space 38 and the interior of the housing 12 through the supply line 42 to the supply channel 46. From this it flows over the radial bearing 48 and Supply bore 52 in the distribution bore 50 of the Drive shaft 10. From this it can over the Branch holes 54 to the various bearings in the Enter the interior of the housing. That way it will Slide bearing 56 as well as the assembly from the radial bearing 58 and the thrust bearing 60 lubricated. The radial bearing 58 is included designed so that the lubricant provided after Flow through the radial bearing is guided to the thrust bearing. To For this purpose, the radial bearing can be integrated into the housing be that a paragraph of the housing together with the rotating Drive shaft forms a narrow gap that only so much Lubricant can escape that for the "series connection" an acceptable lubricant pressure throughout the bearings can be guaranteed.

The return of the fed to the interior of the housing Lubricant to the lubricant separator is thereby ensures that due to the rotating components of the Axial piston compressor in the interior of the housing always on Lubricant mist is present. This also beats on the Inner wall of the cylinder 30 from where it through the compressed refrigerant back into the lubricant separator arrives.

In Figure 2 is an axial piston compressor according to shown a second embodiment. For those from the first Embodiment known components are the same here Reference numerals are used, so that on the above explanations can be referred.

In contrast to the first embodiment, the second Embodiment the lubricant of the distribution bore 50 in the Drive shaft 10 axially fed, namely on the Figure 2 right end of the drive shaft. For this purpose is on a sealing element 62 on the end face of the drive shaft 10 provided that due to the low there Circumferential speed can be carried out with small dimensions can.

In this embodiment is in the area of the drive side radial bearing 48 assigned to the drive shaft is now one Branch bore 54 is provided so that this bearing is reliable is supplied with lubricant. That flows from this camp Lubricant to a thrust bearing 64, the holder 18th supported.

An axial piston compressor according to FIG a third embodiment shown. Again, for known components used the same reference numerals as in the first embodiment, so that on the above explanations is referred.

This is comparable to the first embodiment Lubricant supplied here again radially, but this time in Area of the radial bearing 58. From there it can over the Distribution bore 50 to the slide bearing 56 and the radial bearing 48 flow.

The third embodiment differs from the first Embodiment a supply bore 66 in both the Swash plate 14 and the swash plate 20 are provided.

Thus, the lubricant provided can over the Branch bore 54 through the slide bearing 56 through which Radial bearing 22 and the swash plate 20 to the ball joints 26 get and this, especially those in the ball joints arranged articulated stones, with lubricant.

It is also possible to have the pistons 28 in the cylinders 30 To supply pressure oil in the area of the friction pairing there, which can be seen as a plain bearing, a better one Ensure lubricating film. For this purpose, the Cylinder career formed a lubricant pocket that with Lubricant is supplied through a suitable channel. The narrow gap between cylinder and piston ensures that required throttling of the lubricant throughput.

LIST OF REFERENCE NUMBERS

10

drive shaft

12

casing

14

swash plate

16

feather

18

holder

20

swash plate

22

roller bearing

24

roller bearing

26

ball joint

28

piston

30

cylinder

32

input line

34

output line

36

Lubricant separator

38

separating chamber

39

compressor line

40

plenum

42

supply line

43

Overflow pipe

44

Valve

45

Valve

46

supply channel

48

radial bearings

50

distribution bore

52

supply hole

54

branch bore

56

bearings

58

radial bearings

60

thrust

62

sealing element

64

thrust

66

supply hole

Claims (13)

1. An axial piston compressor for a refrigerant, especially intended for a vehicle climate control system, comprising

   a housing (12), in the inner space of which a plurality of bearings (22, 24, 26, 28, 30, 48, 56, 58, 60, 64) is arranged,

   an output line (34) for the compressed refrigerant,

   a lubricant present in the inner space of the housing (12),

   at least one lubricant channel (46) provided in the housing for feeding the bearings with lubricant,

   a lubricant separator (36) connected to the output line (34) for the refrigerant, and including a collecting space (40) for the lubricant separated from the compressed refrigerant, and

   a feed line (42) connecting the collecting space and the lubricant channel (46), with the lubricant being conveyed from the lubricant separator to the lubricant channel solely by the pressure difference between the compression pressure of the refrigerant and the inner pressure of the housing,

   characterized in that said plurality of bearings comprise roller bearings as well as plain bearings, with the roller bearings being first supplied with lubricant, and being sealed towards the low pressure side, i.e. towards the inner space of the housing (12) so that the entirety of bearings may be supplied with lubricant at essentially the same high pressure.
2. The axial piston compressor according to claim 1,
   characterized in that the feed line (42) is provided with a controllable valve (44).
3. The axial piston compressor according to any one of claims 1 and 2,
   characterized in that an overflow line (43) is provided, leading from the lubricant separator (36) to the inner space of the housing.
4. The axial piston compressor according to claim 3,
   characterized in that the overflow line (43) is provided with a controllable valve (45).
5. The axial piston compressor according to any one of the preceding claims,
   characterized in that the lubricant separator (36) is integrated in the housing (12).
6. The axial piston compressor according to any one of claims 1 through 4,
   characterized in that the lubricant separator (36) is separated from the housing (12), and the feed line (42) acts as a lubricant cooler.
7. The axial piston compressor according to any one of the preceding claims,
   characterized in that a drive shaft (10) is provided having an axial distribution bore (50).
8. The axial piston compressor according to claim 7,
   characterized in that the distribution bore (50) runs out in a drive shaft front side disposed in the inner space of the housing.
9. The axial piston compressor according to any one of claims 7 and 8,
   characterized in that a swash plate (14) is provided which is mounted shiftable on the drive shaft by means of a plain bearing (56), and that in the zone of the plain bearing (56), a branch bore (54) is provided in the drive shaft, connecting the plain bearing with the distribution bore (50).
10. The axial piston compressor according to claim 9,
    characterized in that in the swash plate, a supply bore (66) is realized, which is supplied with lubricant through the plain bearing, and that slide blocks engage at the swash plate, which are supplied with lubricant by means of the supply bore (66) of the swash plate.
11. The axial piston compressor according to any one of claims 7 through 10,
    characterized in that the drive shaft is mounted by means of at least one assembly of a radial bearing (58) and an axial bearing (60), and that said assembly is supplied with lubricant by a branch bore (54) through the drive shaft, the lubricant flowing first through the radial bearing and then through the axial bearing.
12. The axial piston compressor according to claim 11,
    characterized in that the bearings of the assembly are provided with sealing disks forming a defined leakage gap (10).
13. The axial piston compressor according to any one of the preceding claims,
    characterized in that CO₂ is used as the refrigerant.

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