EP1395754B1 - Multi-step piston compressor - Google Patents

Abstract

The invention relates to a novel piston compressor whose return valves have a very good closure force and are extremely tight. The inlet return valve (15) is provided with a first sealing membrane (17) and the outlet return valve (30) is provided with a third sealing membrane. The two sealing membranes (17,32) are produced from an elastic polymer which has high disruptive strength, high temperature compatibility and memory properties.

Description

The invention relates to a reciprocating compressor according to the preamble of claim 1.
Such reciprocating compressors are used in all technical areas where there is a need for compressed air. First and foremost, such piston compressors are used in the automotive industry for air suspension and / or air damping.

Such a reciprocating compressor in a two-stage design, for example, in DE 197 15 291 A1 described. This reciprocating compressor consists of a compressor housing, in which a cylinic low-pressure chamber with a larger low-pressure piston and a cylindrical high-pressure chamber with a smaller high-pressure piston are formed. In this case, the low-pressure chamber and the high-pressure chamber are located on a common axis and the low-pressure piston and the high-pressure piston are formed into a one-piece pressure piston with a common piston rod. The low-pressure chamber has an inlet with an inlet check valve, the high-pressure chamber has an outlet with an outlet check valve, and both pressure chambers are connected by an overflow channel in which an overflow check valve is arranged. In the common piston rod of the low-pressure piston and the high-pressure piston engages in a rectangular orientation, a crank pin of a crankshaft, which is driven for example by a Elekt-romotor and their rotating movement in a linear movement on the one-piece pressure piston converts. This linear movement results in an oscillating movement on the pressure piston.
The inlet check valve, the outlet check valve, and the spill check valve have spring steel gaskets which, as in the case of the inlet check and overflow check valves, are fastened by a central screw and which sealingly cover a plurality of flow channels arranged on a pitch circle or, as in the case of Outlet check valve is held by a laterally offset screw and seal an adjacent flow channel.
These check valves do not perform their task adequately. Thus, it should be noted that the metallic sealing washers do not adequately seal. This is due to the fact that the closing force of the sealing washers is applied exclusively by the residual stresses of the spring steel. This closing force often counteracts even a clamping force, which starts from the fastening screw and prevents the pressure-balanced state, a smooth support of the gasket. Leaks also occur due to the fact that, over time, fatigue phenomena occur on the sealing disk and that the sealing disks do not fit perfectly against the sealing surface for this reason. To compensate for these adverse effects, the sealing discs are usually made stronger. However, this in turn increases the installation space of such a sealing disc and reduces the volume of the corresponding pressure chamber. Such reciprocating compressors are then not very powerful. However, the higher closing force achieved by the reinforcement of the sealing disc also increases the required opening force for the free flow, which must be applied by the system pressure. This also reduces the efficiency of the reciprocating compressor considerably.
It has also been shown that the material of the sealing discs fatigues quite quickly because of the high frequencies of the reciprocating compressor and therefore only a short service life of the sealing discs is recorded.

Ultimately, the production of sealing washers made of spring steel is very expensive, since on the one hand, the material is difficult to work and on the other hand, high demands are placed on the quality of the sealing surface on the gasket.

From the US 6,234,774 B1 now a double piston pump for a rubber dinghy is described in which a pressure chamber is equipped with an input check valve and an outlet check valve. In this case, the inlet check valve has a closure element in the form of a thin-walled membrane made of a rubber material and the closure element of the outlet check valve consists of a molded body made of rubber. Very disadvantageous is the inlet closure membrane. Due to its thinness and due to the nature of the material, the membrane has a very low residual stress, which leads to a low closing capacity. Therefore, this membrane is intended only for low pressures. A use in multi-stage air compressors eliminates this. It is also disadvantageous that the inlet check valve and the outlet check valve have different closure elements, which leads to an increase in the cost of production, and that the inlet closure membrane and the corpulent outlet closure element require a large installation space. However, this required installation space is at the expense of the pressure chamber volume and thus at the expense of the performance of the air compressor.

The invention is therefore based on the object to develop a generic reciprocating compressor whose check valves have a very low closing force and at the same time ensure a high density.

This object is solved by the characterizing features of claim 1. Further refinements result from the dependent claims 2 to 7. The new piston compressor eliminates the disadvantages of the prior art.

Fig. 1:

einen zweistufigen Kolbenverdichter in einer schematischen Schnittdarstellung,

Fig. 2:

eine Einzelheit des Kolbenverdichters mit der Darstellung des Einlass- rückschlagventiles,

Fig. 3:

eine Einzelheit des Kolbenverdichters mit der Darstellung des Ü- berströmrückschlagventiles und des Auslassrückschlagventiles und

Fig. 4:

eine Draufsicht zum Überströmrückschlagventil gehörenden Ventil- einsatzes.

The invention will be explained in more detail with reference to an embodiment. To show:

Fig. 1:

a two-stage reciprocating compressor in a schematic sectional view,

Fig. 2:

a detail of the reciprocating compressor with the representation of the inlet check valve,

3:

a detail of the reciprocating compressor with the representation of Ü overflow check valve and the outlet check valve and

4:

a plan view of the overflow check valve belonging valve insert.

After Fig. 1 a two-stage reciprocating compressor consists in its main components of the actual reciprocating compressor 1, a drive motor 2 and an air dryer unit. 3
For piston compressor 1 includes a valve housing 4 with a cylindrical, stepped in diameter interior, which is in a low-pressure chamber 5 with a larger diameter and divides into a high-pressure chamber 6 with a smaller diameter. The low pressure chamber 5 is closed with a valve housing bottom 7 and the high pressure chamber 6 with a valve housing cover 8 sealingly outwards. In this case, the valve housing cover 8 is connected to the housing of the air dryer unit 3 or made in one piece. In the interior of the valve housing 4, a one-piece compressor piston 9 is fitted, which accordingly consists of a low-pressure piston 10 with a larger diameter, a high-pressure piston 11 with a smaller diameter and a common piston rod 12. In the outer region of the piston rod 12, a crankcase is formed, in which engages in a rectangular orientation, the connecting rod 13 of the crankshaft 14 of the drive motor 2.

The low pressure chamber 5 and the high pressure chamber 6 have connections to each other and to the outside.

So is in accordance with the Fig. 2 In the valve housing bottom 7 of the reciprocating compressor 1, an inlet check valve 15 which connects the low pressure chamber 5 to the atmosphere. To this inlet check valve 15 includes a plurality of, arranged on a common circular path inlet openings 16 and, all inlet openings 16 covering, inlet closure membrane 17. Here, the inlet closure membrane 17 is fitted in an inner counterbore, which has a crowned or angled bottom hole. A centered and mushroom-type fastener 18 secures the inlet closure membrane 17 and holds the inlet closure membrane 17 under a slight tension on the bottom of the counterbore. In this case, this introduced by the fastening element 18 voltage is chosen so that the inlet closure membrane 17 is rotatable in position and not lifted in the pressure-balanced state from the inlet openings 16. In addition, the inlet closure membrane 17 and the fastening element 18 are flush in the counterbore so that no volume of the low-pressure chamber 5 is lost.

Thus, a continuous overflow channel 19, which connects the low-pressure chamber 5 and the high-pressure chamber 6 to one another, is furthermore located in the compressor piston 9. According to the Fig. 3 is arranged in the high-pressure side mouth region of this overflow 19, a Überströmrückschlagventil 20, the function of the low pressure chamber 5 and the high-pressure chamber 6 connects or disconnects due to function. For this purpose, the mouth of the overflow channel 19 is expanded to a kidney-shaped in cross-section chamber 21, wherein the kidney shape follows a circular path.
The overflow check valve 20 consists of a cup sleeve 22 made of plastic, which rests with its bottom on the end face of the high pressure piston 11 and sealingly abuts the inner wall of the high pressure chamber 6. In the region of the overflow channel 19, the cup sleeve 22 is broken.
For overflow check valve 20 further includes a specially designed valve holder 23 which is fittingly inserted into the interior of the cup sleeve 22 and in the Fig. 4 is shown in more detail. This valve holder 23 therefore has an outer shape, which is aligned with the interior of the cup 22. From the side of the high-pressure chamber 6, a cylindrical recess 24 is introduced, the axis of which is arranged at a certain amount of eccentricity away from the axis of the high-pressure piston 11. This amount of eccentricity as well as the size and the radial position of the cylindrical recess 24 ensure that the cylindrical recess 24 is in register with the kidney-shaped chamber 21 of the overflow channel 19. The valve holder 23 is equipped outside the cylindrical recess 24 with distributed arranged fastening elements 25 for position-determining anchoring with the high pressure piston 11.
In the outer radial region of the cylindrical recess 24 are a first through hole 26 having a smaller diameter and a second through hole 27 having a larger diameter, which have an equal or different distance from the axis of the cylindrical recess 24 and in their position and in their extension are designed so that they communicate with the kidney-shaped chamber 21st the overflow 19 are in overlap. In addition to the first through hole 26 and the second through hole 27 further through holes can be used in the same way. In the cylindrical recess 24 a freely overflow Überströmverschlussmembran 28 is fitted with such a game that it is freely movable in the direction of rotation and in the axial direction and the annular space between the Überströmverschlussmembran 28 and the inner wall of the cylindrical recess 24 is suitable as an air passage. To reduce the frictional resistance, the adjacent edges of the cylindrical recess 24 and the Überströmverschlussmembran 28 are rounded or broken executed. The cylindrical recess 24 is further covered with a stop grid 29, on the one hand limits the axial stroke of the Überströmverschlussmembran 28 and on the other hand grants the released compressed air flow a largely free passage. The structure of the lattice struts is chosen freely, wherein the openings in the stop grid 29 are made so small that the Überströmverschlussmembran 28 can not jam. The breakthroughs can also be different sizes.

Furthermore, the high-pressure chamber 6 has an outlet check valve 30 for connecting the high-pressure chamber 6 to a consumer line. This outlet check valve 30 is after Fig. 3 The valve plate 31 is embodied sealed relative to the valve housing 4 and relative to the valve housing cover 8 and has a plurality of outlet openings 33 arranged on a common graduated circle. The valve plate 31 is arranged between the valve housing 4 and the valve housing cover 8 and consists of a circumferentially clamped valve plate 31 and a Auslassverschlussmembran Outlet closure membrane 32 is designed as a ring and thus has a central flow bore 34. With its periphery, the outlet closure membrane 32 is held between the valve plate 31 and the valve housing cover 8, while the flow bore 34 is sufficiently smaller in diameter than the pitch circle diameter the diameter of the outlet openings is designed such that the outlet openings 33 are completely covered by the outlet closure membrane 32. The Auslassverschlussmembran 32 is installed without constructive bias, so that the closing force results only from the material-specific residual stress. The inlet closure membrane 17 of the inlet check valve 15, the overflow closure membrane 28 of the overflow check valve 28 and the outlet closure membrane 32 of the outlet check valve 30 are made of plastic, in particular of an elastic polymer, which has a high dielectric strength in the main, is highly temperature resistant and has elastic properties with memory effect ,

During operation, the rotating movement of the driven by the drive motor 2 crankshaft 14 is converted via the connecting rod 13 in an oscillating linear motion and transmitted to the valve piston 9. Thus, both the low-pressure piston 10 and the high-pressure piston 11 move between two opposing reversal points and thus form two alternately changing low-pressure chamber 5 and high-pressure chamber 6. This results in a magnifying low-pressure chamber 5 such a negative pressure, the first inlet closure membrane 17 at its outer Raise the circumference and allow outside air to flow through the inlet openings 16. This opening pressure results from the sum of the material tension of the inlet closure membrane 17 and the installation-related prestress at the inlet closure membrane 17. At the same time, the negative pressure closes the overflow closure membrane 28 of the overflow check valve 20.

At the upper reversal point of the movement of the valve piston 9, a balanced pressure between the low-pressure chamber 5 and the atmosphere is established at the inlet closure membrane 17, whereby the inlet closure membrane 17 is pressed onto the inlet openings 16 by the said forces of prestressing and closes them. Due to the optimal selection of the material and installation voltages occur on the one hand during suction least flow resistance and on the other hand closes the inlet closure membrane 17 in the shortest possible time after reaching the upper reversal point. This considerably improves the efficiency of the reciprocating compressor.

With the reverse movement of the valve piston 9, the low pressure chamber 5 is reduced, so that the air clamped there is conveyed under pressure through the overflow 19 to the high pressure chamber 6. In this case, the air first flows into the kidney-shaped chamber 21 of the overflow 19 and loads from there the Überströmverschlussmembran 28 in the area and in the circumference of the first through hole 26 and the second through hole 27. Thus acts on the first through hole 26, a first opening force and the second through hole 27, a second opening force on the spill over membrane 28, both of which act in parallel. These two forces are as different as the cross sections of the two through holes 26 and 27. Thus, the exposed Überströmverschlussmembran 28 comes into an imbalance and by radial force components in a radial rotational movement, which is directed from the smaller flow bore 26 to the larger flow bore 27 and the Position of Überströmverschlussmembran 28 to the two through holes 26, 27 changed steadily. This prolongs the service life of the overflow closure membrane 28, since the load on the material of the overflow closure membrane 28 is distributed circumferentially, thus avoiding premature overloading of only a specific point of the overflow closure membrane 28. Such an overload quickly leads to strike through and failure of the overflow check valve 20. The exposed Überströmverschlussmembran 28 opposes the flow of compressed air flow only a slight resistance.

At the lower reversal point of the movement of the valve piston 9 is again a balanced pressure between the low-pressure chamber 5 and the high-pressure chamber 6, which can close the overflow check valve 20. Due to the free and low-friction guidance of Überströmverschlussmembran 28, the closure is extremely responsive.

With the movement of the valve piston 9, which reduces the high-pressure chamber 6, the compressed air enclosed in the high-pressure chamber 6 is displaced via the outlet check valve 30. The compressed air passes from the inlet closure membrane 32 released outlet openings 33. At the upper reversal point of the movement of the valve piston 9, the outlet check valve 30 in turn closes extremely fast reaction.

List of reference numbers

1

Kolbenveidichler

2

drive motor

3

Lufilrocknereinheit

4

valve housing

5

Low-pressure chamber

6

High-pressure chamber

7

Valve housing bottom

8th

Ventilgchäusedeckel

9

pistons compressor

10

Low-pressure piston

11

High pressure piston

12

piston rod

13

pleuel

14

crankshaft

15

Inlet check valve

16

Einlassölfnungen

17

Inlet closure membrane

18

fastener

19

overflow

20

Überströmrückschlagventil

21

Kidney shaped chamber

22

cup seal

23

valve holder

24

Cylindrical recess

25

fastener

26

First through hole

27

Second through-hole

28

Übetström sealing membrane

29

stop grid

30

outlet check valve

31

valve plate

32

Inlet closure membrane

33

outlet

34

Flow bore

Claims (7)

1. Multi-stage piston compressor, consisting of a valve housing (4) and of a displaceable valve piston (9) driven in linear oscillation by a drive motor (2) and produced in one piece, the multi-stage piston compressor having at least one variable-volume low-pressure chamber (5) having an inlet non-return valve (15) and at least one variable-volume high-pressure chamber (6) having an outlet non-return valve (30), the valve piston (9) consisting of a low-pressure piston (10) and of a high-pressure piston (11) and the low-pressure chamber (5) and the high-pressure chamber (6) being connected to one another via an overflow duct (19) in which an overflow non-return valve (20) opening in the direction of the high-pressure chamber (6) is inserted, characterized in that the inlet non-return valve (15) is equipped with an inlet closing diaphragm (17) and the outlet non-return valve (30) is equipped with an outlet closing diaphragm (32), and the two closing diaphragms (17, 32) consist of an elastic polymer with a high puncture strength, with high temperature compatibility and with memory properties.
2. Multi-stage piston compressor according to Claim 1, in which the inlet non-return valve (15) is equipped with a plurality of inlet ports (16) arranged on a reference circle, characterized in that the inlet closing diaphragm (17) of the inlet non-return valve (15) is fitted into a countersunk bore of the valve-housing bottom (7), with a cambered or angled bore base, and is fixed under tension by means of a centrally attached mushroom-like fastening element (18), the fastening element (18) penetrating into the countersunk bore only to an extent such that it is flush with the inner face of the valve-housing bottom (7) and pretensions the inlet closing diaphragm (17) only to an extent such that the inlet closing diaphragm (17) still remains rotatable.
3. Multi-stage piston compressor according to Claim 1, in which the outlet non-return valve (30) possesses a plurality of outlet ports (33) arranged on a common reference circle, characterized in that the outlet ports (33) are introduced into a valve plate (31) which is tension-mounted between the valve housing (4) and a valve-housing cover (8), and the outlet closing diaphragm (32) is designed as a ring and is held with its outer circumference, without tension, between the valve plate (31) and the valve-housing cover (8), the outlet closing diaphragm (32) covering the outlet ports (33) with its inner circumference.
4. Multi-stage piston compressor according to Claims 2 and 3, the overflow non-return valve (20) being equipped with a sealing disc, characterized in that the overflow duct (19) issues into at least two passage bores (26, 27), and the sealing disc of the overflow non-return valve (20) is designed as a loosely guided and stroke-limited overflow closing diaphragm (28), the passage bores (26, 27) of the overflow duct (19) having different diameters and being arranged on a common reference circle at a radial distance from the axis of the overflow closing diaphragm (28) and being covered completely by the overflow closing diaphragm (28).
5. Multi-stage piston compressor according to Claim 4, characterized in that the overflow closing diaphragm (28) consists of an elastic polymer with a high puncture strength, with high temperature compatibility and with memory properties.
6. Multi-stage piston compressor according to Claim 5, characterized in that the overflow closing diaphragm (28) is fitted into a recess (24) of a valve holder (23) and is covered by an abutment grid (29).
7. Multi-stage piston compressor according to Claim 6, characterized in that the two throughflow bores (26, 27) of different diameter are introduced into the cylindrical recess (24) of the valve holder (23) and possess a connection to the overflow duct (19), the overflow duct (19) being designed in the region of issue as a kidney-shaped chamber (21).

Images