DE10255680A1 - Axial piston compressors, especially CO2 compressors for vehicle air conditioning systems with split cylinder heads - Google Patents

Abstract

Axial piston compressors, in particular CO¶2¶ compressors for vehicle air conditioning systems, comprising a housing (38) delimiting an engine room, a cylinder block and a cavities (40, 41) for cylinder heads (39) with suction and compressed gas. The cylinder head (39) is constructed in at least two parts, one part (21) comprising the cavities (40, 41) for suction and pressure gas and made of a high-strength material, in particular steel, while the other part (22) a lighter and in particular easily editable material, in particular aluminum or temperature-resistant plastic.

Description

• – einem einen Triebwerksraum begrenzenden Gehäuse,
• – einem Zylinderblock, und
• – einem Kavitäten für Saug- und Druckgas aufweisenden Zylinderkopf.

The invention relates to an axial piston compressor, in particular a CO ₂ compressor, for vehicle air conditioning systems, consisting of

• A housing delimiting an engine room,
• - a cylinder block, and
• - A cylinder head with suction and compressed gas cavities.

Such axial piston compressors are generally known. They consist either of light metal, in particular aluminum, or of steel. An example of the latter embodiment is shown in FIG DE 198 33 604 A1 , from the in 5 a longitudinal section is shown. Accordingly, the known axial piston compressor consists of a cylinder head 4 with suction gas and compressed gas connections, a cylinder block 14 with several evenly over the circumference of a compressor longitudinal axis 8th arranged cylinders 16 in which pistons 9 are axially movable back and forth, and a housing 3 , which - because made of steel - is relatively thin-walled. At the the cylinder head 4 facing end of the housing 3 this is through a lid 17 closed, through which there is a drive shaft 7 extends. The drive shaft 7 is via an electromagnetic clutch with a drive pulley 6 coupled. Furthermore, the drive shaft 7 inside the case 3 connected to a swash plate mechanism. This consists of one with the drive shaft 7 rotating swashplate 10 , Relative to the swash plate 10 is a swashplate 12 rotatably supported, namely via axial bearings 11 on the one hand and radial bearing 18 on the other hand. The swashplate 12 is about piston rods 13 with the pistons 9 connected. The housing 3 delimits an engine room 5 , within which the aforementioned swash plate mechanism is arranged. The swash plate is dependent on the operation of the compressor 10 more or less strong compared to the drive shaft 7 inclined.

Since this is a mechanism known per se, no further explanation is required here. Between the cylinder head 4 and cylinder block 14 is still a valve plate 15 arranged. cylinder block 14 and valve plate 15 are inside the housing 3 , cover 17 , Casing 3 and cylinder head 4 are created by several connecting screws that are evenly distributed over the circumference 19 held together. The cohesion of the cylinder block 14 , Valve plate 15 and cylinder head 4 is done by separate connecting screws 20 ,

Because the housing and cylinder head are made of steel, the compressor described is particularly suitable for CO ₂ refrigerant applications. CO ₂ sealers are characterized by high operating temperatures and operating pressures. The compressor made of steel can withstand these CO ₂ specific parameters in the long term. Above all, with such CO ₂ compressors there are high differential pressures between the suction and the pressure side on the one hand and also the engine room on the other. The compressor made of steel can withstand these high differential pressures well.

R134a compressors are preferred made of aluminum materials, which have a lower strength and can only withstand lower temperatures. For R134a as a refrigerant the stability of aluminum is sufficient. But there is to consider that from 100 ° C assumed a significantly reduced strength of aluminum must become. Accordingly, aluminum compressors should not exceed 100 ° C be charged. The strength of aluminum at temperatures decrease 150 ° C reached only values from about 20 to a maximum of 60% of the strength at room temperature. Since it is for compressors Vehicle air conditioners very common to relatively high pressure and temperature fluctuations must itself high quality aluminum can be used in R134a compressors to be able to withstand the above-mentioned fluctuations. For this reason increasingly steel as a material for Axial piston compressor of the type in question used here.

• – (A) ein (oder zwei) Regelventile mit korrespondierenden Gasführungskanälen
• – (B) eine Ölabscheidevorrichtung
• – (C) Sauggasanschluß und Druckgasanschluß
• – (D) Sicherheitsvorkehrungen, wie z.B. Berstscheiben oder Abblasventile
• – (E) (differenz)druckabhängiges Absperrventil (check valve) auf der Saug- und/oder Hochdruckseite für das Anfahren des Verdichters
• – (F) Überströmventil zwischen Saug- und Druckseite, etc.
• – (G) Befestigung/Halter

It should also be borne in mind that the cylinder head of a CO ₂ compressor has a large number of channels and built-in parts, which make the production of the cylinder head correspondingly more expensive. The following components / functions generally have to be integrated in a cylinder block:

• - (A) one (or two) control valves with corresponding gas routing channels
• - (B) an oil separator
• - (C) Suction gas connection and compressed gas connection
• - (D) Safety precautions, such as rupture disks or blow-off valves
• - (E) (difference) pressure-dependent shut-off valve (check valve) on the suction and / or high pressure side for starting the compressor
• - (F) overflow valve between suction and pressure side, etc.
• - (G) mounting / bracket

From the DE 100 37 659 A1 is also known an axial piston compressor, the cylinder head is made of steel. The cylinder head is fitted into the cylindrical or cup-shaped housing and screwed in using a ring nut. It is also conceivable to screw the cylinder head as a whole into the housing. For this purpose, the housing and the cylinder head must have corresponding internal and external threads.

It should also be pointed out that insulation is provided between the suction gas and compressed gas side, particularly in the case of CO ₂ compressors, in order to avoid excessive heat exchange between these two sides. Above all, the suction gas should not be preheated unnecessarily by the compressed gas; because this would not negatively affect the efficiency of the compressor. The aforementioned insulation takes the form of a wall coating. Steel has proven to be very advantageous as a base for such a coating. Aluminum materials are less suitable for this.

The known embodiments, where steel is used are characterized by being practical all Parts, especially the entire cylinder head made of steel is the consequence of a relatively high compressor weight.

Due to the large number of channels and components in the cylinder head, it must be machined accordingly (drilling, milling, thread cutting, etc.). Since steel is more difficult to machine than aluminum, it would be desirable to use aluminum that is easier to machine for the cylinder head even with a CO ₂ compressor.

To simplify manufacturing would it be Moreover desirable, if the cylinder head in a so-called master molding process, such as Forging, pressing or casting could be made. To a higher one To achieve strength, it is advantageous if the cylinder head is produced by forging or pressing. Only then is again machining post-processing required, the corresponding processing costs has the consequence.

Finally, the aim is for the cylinder head to use a material that has a low thermal conductivity. Steel alloys, that have such a property are usually difficult to edit.

The present invention lies So the task to avoid the aforementioned disadvantages conventional cylinder heads to propose a compromise that is both easy to edit on the one hand and sufficiently high strength on the other hand and the one above is also weight-saving.

This object is achieved according to the invention solved the characterizing features of claim 1, wherein advantageous details are described in the subclaims.

The essence of the present invention So it consists of a cylinder head made of at least two parts to be provided, the part comprising cavities with large volume, such as suction gas and compressed gas chamber, made of steel or a steel alloy, while the other part of the cylinder head, in which only small cavities are provided are like gas routing channels for regulation, Fasteners and connections as well as thread for Control valves, safety devices or the like, from one Material is made that is less firm but easier to work with is. This other part is preferably made of aluminum or an aluminum alloy.

Steel represents a high material Strength that is ensured even at high temperatures. Aluminum, on the other hand, enables primarily good machinability, especially machining Processing. The strength of the cylinder head part made of aluminum is natural less than that of the part made of steel. Because of aluminum or the like light metal or temperature-resistant plastic manufactured part of the cylinder head has only small cavities, the strength of this part is less important. In particular must the encompassing the larger cavities Part be permanently solid, even at higher temperatures of up to at 200 to 250 ° C.

A steel-aluminum combination is preferred. However, it is also conceivable to combine steel / steel or aluminum / aluminum, then appropriate alloys of these two materials are to be selected such that one material is easier to work with while the other material is characterized by a higher strength.

In a particularly simple construction, the two parts forming the cylinder head are screwed together, either directly or indirectly by means of separate connecting screws, similar to the embodiment according to 5 , Alternatively, it is also conceivable for the two parts of the cylinder head to be welded to one another, in particular friction welded. It is also possible to glue the two aforementioned parts.

When using a screw connection this is preferably carried out with the interposition of a separate one Fluid seal, especially elastomer-coated metal bead seal.

The made of high-strength material, such as e.g. Steel or a steel alloy made part of the cylinder head is preferably designed as a forged part, while the other part is a cast or Press part can be. The forged part can be manufactured that post-processing, especially machining post-processing eliminated.

In an embodiment in which the part of the cylinder head with the high-strength material casing is screw-connected, it is possible without washers; because both the aforementioned part of the cylinder head and the connecting screws are made of same high-strength material, so that even with high tightening torques a material deformation is eliminated.

Below is a preferred one embodiment a compressor according to the invention, in particular one designed according to the invention Cylinder head based on the attached Drawing closer explained. Show it:

1a an exploded view of a cylinder head designed according to the invention, seen from the engine chamber side;

1b the cylinder head according to 1a also in an exploded view, but seen from the top of the cylinder head;

2 the high-strength part of a cylinder head according to the 1a . 1b in perspective view;

3 an axial piston compressor with a cylinder head according to the invention in a perspective view;

4a the cylinder head accordingly 1b with additional representation of the housing connecting screws; and

4b the cylinder head according to the illustration 1a , also showing the housing connecting screws.

The one in the 1a and 1b The cylinder head shown consists of two parts, namely a part facing the engine chamber 21 and an outer part 22 , these two parts by connecting screws 44 are interconnectable, with the interposition of an elastomer-coated metal bead seal 23 , The part 21 of the cylinder head, which is a compressed gas chamber 41 and Sauggaskam mer 40 comprises, consists of steel or a steel alloy, ie high-strength material. Preferably the part 21 Provided as a forged part, which only needs to be processed slightly, and preferably only in the axial direction with the formation of

• - Several, here 14 holes arranged around the circumference 37 for housing mounting screws,
• - an oval hole 30 for the tangential flow of a centrifugal oil separator for the separation of oil and compressed gas (for the compressed gas connection of the compressor),
• - one kidney-shaped opening 31 for suction gas to enter a central chamber,
• - three small holes 32 (with a diameter of about 2 mm) for the application of control valves with the three pressure levels "high pressure", "suction pressure" and "engine room pressure",
• - a hole 33 for returning separated oil (including seat for oil restriction, filter etc.),
• - holes 34 for pinning in the flange area, and
• - Threaded holes, here four threaded holes 36 for the fastening screws 44 , by means of which the two cylinder head parts 21 . 22 be connected to each other.

The metal bead seal 23 has three large openings 24 . 25 and 26 which, in addition to saving material and adjusting the pressure on the webs, have no other function, in particular do not include any volumes to be sealed. Otherwise, only relatively small openings and openings between the two cylinder head parts have to be sealed, specifically the following bores and openings of the cylinder head part 21 :

• - threaded holes 36 .
• - Pressurizing holes 32 .
• - kidney-shaped opening 31 .
• - oval hole 30 ,

The corresponding bores and openings are also on the cylinder head part 21 facing side of the outer cylinder head part 22 , which consists of easily machinable material, in particular aluminum or an aluminum alloy. This cylinder head part 22 comprises a plurality of smaller cavities for the formation of gas guide channels or for the installation of valves or the like. Since the processing of the material used for this is relatively easy and simple, the formation of even more complicated, merging cavities does not pose any particular difficulty Cylinder head 21 is designed as a relatively thin disk, the axial passages and bores formed in this component are relatively short, with the consequence of correspondingly short work processes. The bores and passages mentioned can be produced very easily on a machining center.

Again 1a can still be removed, the cavities defining or delimiting the suction gas chamber on the one hand and the pressure gas chamber on the other are each annular. They are in particular through an annular web 27 separated from each other.

As already explained above, only small openings and passages between the two cylinder head components need to be sealed off from the outside environment. The overall length of the required sealing edges or beads is correspondingly small, with the consequence of a correspondingly low risk of leakages. Instead of an elastomer-coated metal bead seal 23 other seals can also be used, such as elastomer or PTFE coated metal rings, especially C or O rings.

As already stated above, the arrangement of a seal 23 between the two cylinder head parts can be completely dispensed with if they are directly connected to one another in a fluid-tight manner, for example by friction or magnetic pulse welding or by gluing.

In principle, it is also conceivable to manufacture both cylinder head parts from the same base material, whereby Naturally the alloys are different, so that the outer cylinder head part is easier to machine than the one closer to the engine room Part. The material of the cylinder head part closer to the engine compartment must Naturally are just as strong as steel.

The engine head closer to the cylinder head will - how already mentioned - preferably also forged high strength steel, while the outer cylinder head part is preferred is cast, namely from aluminum or a similar Light alloy. in principle it is natural also conceivable the outer part to forge or press the cylinder head.

It is conceivable the flange area of the cylinder head or the part of the cylinder chamber closer to it axially to extend further such that a valve plate is at least partially is enclosed by this part. It is provided that the corresponding cylinder head component flanged directly to the cylinder block and only between the cylinder head and the cylinder block a seal to the outside is necessary. In this context, the following three variants are conceivable:

• - the The valve plate assembly lies in a "pocket" of the cylinder block,
• - the The valve plate assembly lies in a "pocket" of the cylinder head, or
• - the The valve plate assembly lies in two "pockets" of both components.

In an outside view of the compressor 28 corresponding 3 there is only one sealing point in each of these three cases 29 outward like 3 clearly shows. Another sealing point is the metal bead seal 23 between the two cylinder head parts 21 . 22 Are defined.

For the rest, the aim is that the parts 21 . 22 lie against each other with minimized contact areas, for example only locally at certain points, so to speak "on stilts". The corresponding points are then, for example, sealing points and the areas of the screw connections; in between can be left out.

3 leaves the screw heads of the housing mounting screws 35 recognize very well, by means of which the engine chamber closer part 21 of the cylinder head directly with the housing 38 of the compressor 28 connected is. The assignment of the housing connection screws 35 to the cylinder head part 21 show the other very clearly 4a and 4b ,

In principle, it would also be conceivable to use the housing fastening screws 35 also the two cylinder head parts 21 . 22 connect with each other. However, this is not the case in the illustrated embodiment. Rather, there is the outer cylinder head part 22 using separate screws 44 on the cylinder head part closer to the engine room 21 attached.

Because both the housing mounting screws 35 as well as the cylinder head 21 made of the same high-strength material, in particular steel, can be on washers between the screw heads on the one hand and the cylinder head part 21 on the other hand, can be dispensed with, which reduces the overall weight of the compressor accordingly.

In addition, it should be pointed out that by screwing the cylinder head part 21 with the housing 38 of the compressor 28 the housing mounting screws 35 can be made somewhat shorter than in a conventional compressor, such as that shown in FIG 5 is shown. This also results in additional weight savings.

The fact that the cylinder head part comprising the larger cavities 21 preferably made of steel, the suction side can be relatively easily isolated from the pressure side by appropriate insulation coating of the boundary wall between these two cavities. Steel is particularly suitable for a corresponding coating, as already mentioned at the beginning. Otherwise, the two-part embodiment of the cylinder head is distinguished from a one-piece embodiment by an enlarged overall surface, with the advantage of a higher degree of heat exchange with the external environment. Accordingly, the heat dissipation is better, which increases the overall efficiency of the compressor is promoted.

As already mentioned, it is important to keep the heat exchange between the suction side and the pressure side as low as possible. This goal can also be achieved, among other things, by using a suitable steel material for the cylinder head part 21 is used, ie a material with particularly low thermal conductivity. For example, the 18 CrNi8 steel alloy has a thermal conductivity of 40 W / mK (in contrast, structural steel approx. 50 W / mK). The thermal conductivity of the steel alloy X40CrMoV-1 has a thermal conductivity of only about 20 W / mK. The alloy X5CrNi18 10 (V2A) has a thermal conductivity of only about 16 W / mK. So these materials are for the cylinder head part 21 Particularly well suited, whereby these materials are also characterized by high tensile strength. The tendency to corrosion is also very low. These advantages outweigh the disadvantage of poorer machinability. On the other hand, the cylinder head part 21 be manufactured in such a way that machining is avoided as far as possible. Only the axial passages and bores mentioned are required or have to be reworked. Since the length of these passages and bores is relatively short, the disadvantage of more difficult machining can be accepted.

Incidentally, as isolation between the suction and pressure side preferably a polytetrafluoroethylene coating (PTFE coating) proposed. This coating holds on to steel or a steel alloy particularly well.

In connection with the component masses, the following can be said in comparison to the prior art for the inventive design: Weight State-of-the-art cylinder head according to Figure 5 made of steel approx. 1380 g State-of-the-art cylinder head made of aluminum approx. 480 g Cylinder head part 22 made of aluminum approx. 250 g Cylinder head part 21 made of steel approx. 440 g Elastomer coated metal bead seal 23 approx. 10 g Fastening screws 44 between parts 21 and 22 approx. 25 g Weight saving by shortening the housing mounting screws 35 approx. - 65 g No washers (weight reduction) approx. - 35 g Two-part cylinder head aluminum / steel (total weight) approx. 625 g.

The above illustration shows that all the advantages of a steel cylinder head on the one hand and all the advantages of an aluminum cylinder head on the other hand can only be achieved with a slightly increased weight compared to an aluminum cylinder head. Compared to a pure steel cylinder head, weight savings of at least 50% can be achieved. The two parts 21 . 22 existing cylinder head according to the invention is in the 1a and 1b with the reference number 39 characterized.

With reference to the components / functions that conventionally comprise a cylinder head, in particular the components / functions (A) to (G) mentioned in the introduction to the description, it should be pointed out that these relate to the parts 21 . 22 of the present invention are preferably divided as follows:

Alternative 1: Part 21: (F) with respect to the suction and pressure chambers 40 and 41, respectively Part 22: (A) to (E) and (G) Note: illustrated embodiment

Alternative 2: Part 21: (B) to (G) Part 22: only (A) Note: Part 22 is practically only a "control block".

Alternative 3: Part 21: (B), (D) to (G) Part 22: (A) and (C) - Suction gas connection Note: Suction gas-filled "control block".

Alternative 4:

like alternative 1, but attachment / holder (G) integrated in part 21 because it is relevant to strength.

All Features disclosed in the application documents are essential to the invention claimed, insofar as they are used individually or in combination with the State of the art are new.

1

Swash plate mechanism

2

compressor

3

casing

4

cylinder head

5

Machine Room

6

sheave

7

drive shaft

8th

longitudinal axis

9

piston

10

swash plate

11

thrust

12

swash plate

13

piston rod

14

cylinder block

15

valve plate

16

cylinder

17

housing cover

18

radial bearings

19

connecting screw

20

connecting screw

21

Engine room closer part of the cylinder head

22

outer part of the cylinder head

23

Metalisickendichtung

24

opening

25

opening

26

opening

27

web

28

compressor

29

sealing point

30

oval Hole or slot hole

31

kidney-shaped or also teardrop-shaped opening

32

drilling

33

drilling

34

drilling for pinning

35

Case screw

36

threaded hole

37

drilling

38a

cylinder block

38b

casing

39

cylinder head

40

Sauggaskammer

41

Pressure gas chamber

44

connecting screw

Claims (6)

Axial piston compressors, in particular CO ₂ compressors for vehicle air conditioning systems, consisting of - a housing delimiting an engine room ( 38a ), - a cylinder block ( 38b ), and - one cavities ( 40 . 41 ) for cylinder head with suction and compressed gas ( 39 ), characterized in that the cylinder head ( 39 ) is formed at least in two parts, one part ( 21 ) the cavities ( 40 . 41 ) for suction and compressed gas and is made of a high-strength material, in particular steel or a steel alloy, while the other part ( 22 ) consists of a lighter and in particular easily workable material, such as aluminum, light metal or temperature-resistant plastic. Compressor according to claim 1, characterized in that the two the cylinder head ( 39 ) forming parts ( 21 . 22 ) are screwed together, either directly or indirectly using separate connecting screws ( 44 ). Compressor according to claim 1 or 2, characterized in that the two parts ( 21 . 22 ) of the cylinder head ( 39 ) either lie directly against one another in a fluid-tight manner, in particular are glued or welded to one another (eg friction welding), or alternatively with the interposition of a separate fluid seal, in particular an elastomer-coated metal bead seal ( 23 ) are connected. Compressor according to one of claims 1 to 3, characterized in that the part made of high-strength material ( 21 ) of the cylinder head ( 39 ) is designed as a hot or cold deformed part, in particular a forged part, while the other part ( 22 ) is a cast or pressed part. Compressor according to one of claims 1 to 4, characterized in that the part made of high-strength material ( 21 ) of the cylinder head ( 39 ) with the housing ( 38 ) is screw-connected, either with the interposition of the cylinder block and a valve plate or with the inclusion of one or both parts such that between the cylinder head ( 39 ) and housing ( 38 ) only one sealing surface ( 29 ) is available. Compressor according to one of claims 1 to 5, characterized in that the part made of high-strength material ( 21 ) of the cylinder head ( 39 ) made of steel with a thermal conductivity λ <40 W / mK, in particular a chromium-molybdenum or chromium-nickel steel alloy.