EP1831552B1 - Dry-running swash plate compressor with a piston-rod mounting - Google Patents

Abstract

The invention relates to a dry-running swash-plate compressor, particularly for generating compressed air in goods-carrying vehicles, comprising a swash-plate (2), which is coaxially fastened to a drive shaft (1) and which, via a bearing arrangement (3), converts the driving rotational motion into a reciprocating motion that displaces at least one piston rod (4), which is mounted on the bearing arrangement (3) and which is mounted on a piston (5) running inside an associated cylinder (6), in order to generate the compressed air. The axially displaceable piston rod (4) is guided via a bearing bore (11) whose position is fixed with regard to the compressor housing (10). This bearing bore (11), in the vicinity of the end facing the swash-plate (2), is provided with a first lubricatable plain bearing bush (12), which is connected to means for supplying oil, and the bearing bore (11), in the vicinity of the end facing the piston (5), is provided with a second plain bearing bush (15) that is capable of dry-running.

Description

The present invention relates to a dry-running swash plate compressor, with at least one axially movable driving piston rod, which transmits the driving force to running in an associated cylinder piston for generating the compressed air, wherein the axially movable piston rod is guided over a stationary to the compressor housing arranged bearing bore.

The field of application of such a compressor, which is driven as a linear compressor via an axially movable piston rod, extends primarily to the commercial vehicle technology. Other linear compressors include crankcase compressors, crosshead compressors and, in particular, swash plate compressors.

In commercial vehicles come compressors are used, which are usually driven directly by the engine of the commercial vehicle and supply compressed air to feed the compressed air electrical system. In commercial vehicles, the compressed air thus generated is used for example for operating a compressed air brake system.

In a generally known manner, primarily oil-lubricated reciprocating compressors are used for the production of compressed air in commercial vehicles. The lubrication of these compressors usually takes place from the oil circuit of the engine. In this case, however, inevitably oil passes through the pistons of the compressor in the generated compressed air. Depending on the age and maintenance condition of the compressor, significant quantities of oil can enter the environment via the compressed air, namely via various vents in the compressed air system. Another problem of oil-lubricated reciprocating compressors in the commercial vehicle sector is that ever higher operating pressures demanded from the compressor, which is accompanied by quite high thermal stresses, which leads to coking of a part of the oil got into the compressed air. This carbon builds up inside the cylinder inside the cylinder Compressors and downstream compressed air devices from and influenced there very sustainable their life.

From the EP 0 859 151 A2 is a compressor for generating compressed air in commercial vehicles, which solves this problem in that the compressor is constructed here largely dry running The compressor is constructed in the manner of a swash plate compressor and has only a conventional oil-lubricated engine, which essentially arranged on a drive shaft Swash plate with hemispheres in bearing cups, which form a bearing assembly for transmitting the rotational movement in an oscillating stroke. From the bearing assembly extend piston rods to various pistons, which generate by a reciprocating motion in associated cylinders in a conventional manner, the compressed air. Usually several pistons are arranged on a circumferential circle adjacent to each other in order to realize the highest possible delivery of the swash plate compressor.

The bearing of the piston rods stationary to the compressor housing via bearing bores on the oil-lubricated engine side. The bearing bores extend on a circumferential circle at an angular distance from each other parallel to the longitudinal axis of the compressor through a central housing portion, on which the piston facing individual ölabstreifende sealing elements are provided. At the rear of the pistons are suction chambers, which are connected by an annular space to a common suction space, in which a suction port opens to the atmosphere.

A problem of this prior art results from the fact that particularly high demands are placed on the region of the guidance of the piston rod due to the different forces acting thereon. Thus, for example, in the course of the lifetime of the swash plate compressor at this point come to a deflection of the bearing bore, since this has to absorb resulting from the rotation of the swash plate radial forces. These forces occur in particular on the end of the bearing bore assigned to the swashplate. Wear of the bearing bore was previously counteracted by the bearing bore was dimensioned with a large length and low tolerances. However, these measures lead to an undesirable increase in the geometric dimensions of the entire compressor or to increased manufacturing costs for the production of the long, tight toleranced fit. The mating piston rod to bearing bore must reliably prevent oil from entering the engine inside the cylinder. At the same time, the sliding friction between the two relative to each other moving components had to have low, so as not to adversely affect the efficiency of the swash plate compressor. Furthermore, it should be prevented that compressed air from the interior of the cylinder does not reach the areas of the engine.

From the DE 198 47 159 A1 is a generic swash plate compressor known. The subject-matter of claim 1 is delimited from this document. Since the swash plate runs in an oil bath, this is an oil-lubricated swash plate compressor. The above problems associated with the bearing bore of the piston rod are hereby solved by each piston rod is mounted on the oil-lubricated engine side in a bearing bush. The bearing bushes extend on a pitch circle at an angular distance from each other parallel to the longitudinal axis of the swash plate compressor through a central housing portion, on which the piston facing oil-repellent sealing elements are provided. In the absence of the oil bath, so when designing this Taumetscheibenverdichters to a dry-running swash plate compressor, sufficient lubrication of the bearing could not be made sure.

It is therefore an object of the present invention to further improve a generic swash plate compressor to the effect that a reliable piston rod storage is ensured over the longest possible operating time.

The object is achieved on the basis of a swash plate compressor according to the preamble of claim 1 in conjunction with its characterizing features. The following dependent claims reflect advantageous developments of the invention.

The invention includes the technical teaching that the bearing bore in the region of the swash plate end facing is equipped with a first lubricious plain bearing bush, which is in communication with means for oil supply, and the bearing bore in the region of the piston end facing with a second dry-running - plain bearing bush is equipped.

The advantage of the solution according to the invention is, in particular, that the highly stressed bearing point can be reliably cooled and lubricated by the lubricious plain bearing bush with external oil supply. For this it is then no longer necessary to use oil from the engine area. By the separate Oil supply to the bearing, which is reinforced by a plain bearing bush, contributes to the dry running of the entire area of the engine, ie by local permanent lubrication measures, in order to obtain a completely dry-running swash plate compressor. By using the first lubricious plain bearing bush according to the invention, mixed friction states in this area are also largely excluded. Since the point at which the second plain bearing bush is arranged anyway has oil supply problems due to the longitudinal movement of the piston rod, this is another, namely dry-running plain bearing bush, provided. The dry-running plain bearing bush simultaneously acts as a scraper before downstream sealing elements to the interior of the cylinder. The combination of the special plain bearing bushes within the bearing bore enables a long-lasting rod bearing.

Preferably, the means for own oil supply of the first lubricious plain bearing bushing a stationary to the compressor housing extending oil passage. The oil channel leads, starting from a refillable oil reservoir in the compressor housing, the oil to the first plain bearing bushing. The advantage here is that oil escaping from the lubricious plain bearing bush in the direction of the engine, is converted by rotation of the drive shaft in spray oil, which contributes to a lubrication of the bearing assembly between the swash plate and the piston rod. The oil reservoir for feeding the oil channel can be closed to a lubricant circuit of the swash plate compressor or a commercial vehicle. This is done by refilling the oil reservoir then automatically.

As a lubricious plain bearing bush is particularly suitable in the context of the invention, a multi-component bushing made of a steel-aluminum alloy. The second, dry-running plain bearing bushing can be made of PTFE (Teflon). This material ensures the storage properties specifically required at the storage location.

According to a further improvement of the invention measure is provided for sealing the boundary point between the cylinder containing compressed air and the swashplate comprising the engine either a single sealing ring or advantageously a acting between the second dry-run plain bearing bush and the interior of the cylinder on the piston rod seal assembly. A requirement of this bar seal is that it must seal compressed air to the sides of the engine oil and to the sides of the cylinder, and to separate the two areas of the swash plate compressor so far reliable. At the point indicated above, a sealing arrangement provides the desired result.

Particularly suitable for this purpose is a sealing arrangement, which consists of a first sealing element for oil seal, which is adjacent to the second dry-run plain bearing bush, and which cooperates with a second axially spaced apart sealing element for compressed air sealing, which is disposed adjacent to the interior of the cylinder, wherein the Region between the two sealing elements via a vent channel communicates with the atmosphere.

As a result of the atmosphere connection, both sealing elements can function properly and a reliable separation of the adjacent regions of the swash plate compressor can be implemented in a simple manner. A mutual influence of the sealing elements by oil or compressed air is thus excluded.

Preferably, the venting channel arranged between the two sealing elements should extend from the region of the sealing arrangement into a suction chamber arranged below the piston and communicating with the atmosphere. This measure requires that a suction of the compressed air in the swash plate compressor is performed by a check valve integrated in the piston. This results in the position of the suction chamber below the piston in a region of the swash plate compressor so that allows a short channel guide the vent channel. Because the seal assembly is in close proximity to the suction chamber placed. Such a short venting channel can be produced in a simple manner by drilling.

According to a further measure improving the invention, optimum sealing results are achieved in that the first sealing element for oil sealing and also the second sealing element are formed as a profiled sealing ring with an inner radial sealing lip. Of course, comparable sealing elements can be used as long as they ensure a reliable sealing of the axially mutually movable components.

Another measure improving the sealing effect is that the piston rod made of steel is provided with a surface which has a similar surface quality as piston rods of pneumatic cylinders, preferably a maximum of 4 μm.

Figur 1

einen Längsschnitt durch einen trockenlaufenden Taumelscheibenverdichter, und

Figur 2

eine Detailvergrößerung aus Figur 1 im Bereich einer der Kolbenstangen.

Further measures improving the invention will be described in more detail below together with the description of a preferred embodiment of the invention with reference to FIGS. It shows:

FIG. 1

a longitudinal section through a dry-running swash plate compressor, and

FIG. 2

an enlarged detail FIG. 1 in the area of one of the piston rods.

The in FIG. 1 shown dry-running swash plate compressor has on the part of the engine to a drive shaft 1, which is offset by a - not shown here - engine in rotary motion. On the drive shaft 1, a swash plate 2 is fixed in a conventional manner. The swash plate 2 is about a bearing assembly 3, the rotational movement of the drive shaft 1 in an oscillating stroke movement. The lifting movement is transmitted to a mounted on the bearing assembly 3 piston rod 4. In addition to the piston rod 4 are still more piston rods associated with Bearing arrangements available; The following description is thus to be understood as an example. The piston rod 4 forwards the reciprocating motion generated due to the rotation of the swash plate 2 to a piston 5 which is fixed coaxially to the end of the piston rod 4 opposite the bearing assembly 3. The piston 5 runs within an associated cylinder 6, in which the compressed air is generated due to the movement of the piston 5. A suction of air from the atmosphere takes place through the piston, which has a check valve device 7 for this purpose. The compressed compressed air leaves the cylinder 6 via a further correspondingly switched non-return valve device 8 on the cylinder head 9, which is attached to the valve housing 10.

The axial guidance of the piston rod 4 via a stationary to the compressor housing 10 arranged bearing bore eleventh

As in detail FIG. 2 it can be seen, the bearing bore 11 is provided in the region of the swash plate 2 facing the end with a first plain bearing bush 12. The plain bearing bush 12 is lubricated by oil supply means. The means for supplying oil to the lubricious plain bearing bush 12 consist of an oil channel 13 for supplying oil to the lubricious plain bearing bush 12, starting from an oil reservoir 14, which is arranged in the region of the valve housing 10 and can be refilled via the lubricating circuit of the swash plate compressor 12 consists of a copper-lead alloy.

In addition, the bearing bore 11 is provided in the region of the end facing the piston 5 with a second, dry-running plain bearing bush 15. The dry-running plain bearing bush 15 here has a sliding bearing layer made of PTFE.

The compressed air-containing cylinder 6 is sealed with respect to the swash plate 2 comprising the engine with a sealing arrangement which between the second dry-running plain bearing bush 15 and the interior of the cylinder 2 sealingly acts on the piston rod 4.

The sealing arrangement here consists of a first sealing element 16 for sealing oil, which is so far adjacent to the second dry-running plain bearing bush 15 and prevents penetration of the first plain bearing bush 12 supplied oil due to the reciprocating motion of the piston rod 4 in the region of the cylinder 2 , Adjacent to the first sealing element 16 is a second, this axially spaced-apart sealing element 17 is provided. The second sealing element 17 has the task of avoiding an outflow of compressed air from the interior of the cylinder 2. For reliable media separation, the area between the two sealing elements 16 and 17 is connected via a venting channel 18 to the atmosphere. The vent channel 18 runs concretely starting from the region of the seal arrangement in a provided below the piston 5 and communicating with the atmosphere suction chamber 19 to improve the sealing effect between the profiled sealing ring formed as sealing elements 16 and 17 and the piston rod 4, the latter made of steel with a polished Surface, which corresponds in its surface quality of the surface of a pneumatic cylinder.

The present invention is not limited to the preferred embodiment described above. On the contrary, modifications are also conceivable which are encompassed by the scope of protection of the following claims. So it is also possible, if necessary, to accommodate further plain bearing bushes in the bearing bore for the piston rod or to provide them with a continuous plain bearing bush with different functional areas according to this invention.

LIST OF REFERENCE NUMBERS

1

drive shaft

2

swash plate

3

bearing arrangement

4

piston rod

5

piston

6

cylinder

7

Check valve means

8th

Check valve means

9

cylinder head

10

compressor housing

11

bearing bore

12

plain bearing bush

13

oil passage

14

oil reservoir

15

plain bearing bush

16

sealing element

17

sealing element

18

vent channel

19

suction

Claims (12)

1. Dry-running swash plate compressor, with at least one axially movable driving piston rod (4) which passes on the driving force to a piston (5) running in an associated cylinder (6) to produce compressed air, the axially movable piston rod (4) being guided through a bearing bore (11) whose position it fixed relative to the compressor housing (10), the said bearing bore (11) being fitted in the area of its end facing towards the swash plate (2) with a first slide bearing bush (12) that can be lubricated, which is connected to oil supply means,
   characterised in that in the area of its end facing the piston (5) the bearing bore (11) is fitted with a second slide bearing bush (15) made as a slide bearing bush capable or dry running.
2. Dry-running swash plate compressor according to Claim 1,
   characterised in that the oil supply means comprise an oil duct (13) for the supply of oil from a refillable oil reservoir (14) in the compressor housing (10) to the first slide bearing bush (12).
3. Dry-running swash plate compressor according to Claim 1,
   characterised in that the first slide bearing bush (12) is made as a multi-material bush.
4. Dry-running swash plate compressor according to Claim 1,
   characterised in that the slide bearing lining of the second slide bearing bush (15) capable of dry running consists of a PTFE lining.
5. Dry-running swash plate compressor according to Claim 1,
   characterised in that at least one sealing ring is provided on the piston rod (4), on the side of the dry-running slide bearing bush (15) facing towards the inside space on the cylinder (6).
6. Dry-running swash plate compressor according to Claim 1,
   characterised in that to seal the boundary between the cylinder (6) containing compressed air and the drive mechanism comprising the swash plate (2), a seal arrangement that acts upon the piston rod (4) is provided between the second, dry-running slide bearing bush (15) and the inside space of the cylinder (6).
7. Dry-running swash plate compressor according to Claim 6,
   characterised in that the sealing arrangement consists of a first seal element (16) made for oil sealing, arranged close to the second, dry-running slide bearing bush (15) and cooperating with a second seal element (17) an axial distance away from it, made as a compressed-air seal, arranged close to the inside space of the cylinder (6), the area between the two said seal elements (16, 17) being connected to the atmosphere by a venting duct (18).
8. Dry-running swash plate compressor according to Claim 7,
   characterised in that starting from the area of the seal arrangement, the venting duct (18) opens into a suction chamber (19) located under the piston, which communicates with the atmosphere.
9. Dry-running swash plate compressor according to Claim 7,
   characterised in that the first, oil-seal element (16) is in the form of a profiled sealing ring with an inner radial sealing lip.
10. Dry-running swash plate compressor according to Claim 7,
    characterised in that the second, compressed-air seal element (17) is also in the form of a profiled sealing ring with an inner radial sealing lip.
11. Dry-running swash plate compressor according to any of the preceding claims,
    characterised in that the piston rod (4) is made of steel and has a mean surface roughness of at most 4 µm.
12. Dry-running swash plate compressor according to any of the preceding claims,
    characterised in that it is made as a swash plate compressor and converts the driving rotary movement into an oscillating stroke movement of the piston rod (4) by means of a swash plate (2) fixed on a driveshaft (1) and by means of a bearing arrangement (3).

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