EP2005002B1 - Screw compressor comprising a relief valve - Google Patents

Description

The present invention relates to a compressor assembly, in particular a screw compressor for compressed air generation, comprising a compressor housing having a suction region and further comprising a feed pressure port for supplying the compressed pressure medium, wherein a means for venting the feed pressure port is provided.

From the DE 29 44 053 C2 An intake control device for a compressor is known, in particular for a screw compressor with an oil injection. Here, in the closed position in the closed position with the operating pressure line leading bore in the closure piece after switching off the compressor built the operating pressure, and it can be omitted in a screw compressor with oil injection usually present check valve that after switching off the compressor leakage Oil from the oil tank prevented. By the spring force opposing pressure surface on the control piston and its connection with this operating pressure line leading in cooperation with the application of the opposite piston surface with the pressure of the suction side via a hole of small cross section, the closure piece when starting the compressor, after which interruption Vent line already a lower operating pressure is sufficient to bring the closure piece in the full open position. By acting on the control piston with the network pressure in the closing direction, a proportional control is finally achieved, wherein the network pressure counteracts the operating pressure on the opposite pressure surface on the piston.

Furthermore, relief valves are known, in particular in screw compressors with a small delivery quantity, which however have the disadvantage that no complete relief takes place up to ambient pressure, but only according to the pressure relief takes place, which is sufficient for the function of the valve, in particular for the required spring pressure in Valve.

The problem arises that further relief takes place only via a nozzle, which has the massive disadvantage that it causes a permanent loss of compressed air during operation of the compressor, and thus the available delivery quantity is reduced. Furthermore, the nozzle tends to clog as it is made as small as possible to limit the above-mentioned delivery quantity loss. The latter in turn leads to relatively long discharge sides to ambient pressure. Another disadvantage of the known relief valves is the fact that, especially when used in rail vehicles and other mobile applications such as buses temperatures of - 25 ° C can not be exceeded. With regard to the mentioned area of application, however, operating temperatures of up to - 40 ° C are sometimes required. It should be noted that, unlike a vent valve on a tank with screw compressors, the discharge takes place only in the case of shutdown and then only on the already freed from the oil compressed air side. The latter is necessary for reasons of environmental protection, but in particular in order to obtain the oil charge which is absolutely necessary for operation for as long as possible. A simple, spring-loaded check valve or overflow valve can not be used for this reason. In addition show the known systems have a complicated structure, since these are spring-loaded and often require an external control of the valve position.

The EP 0 684 385 A1 discloses a compressor assembly whose intake region is formed by a suction valve. After switching off the compressor assembly, a venting of the system-side pressure accumulator by a spring-reset monostable relief valve is transferred by a withdrawn from the suction overpressure from a blocking position to a passage position to connect the pressure accumulator via a conduit system with the atmosphere. Due to the multi-membered pressure line system used and the valve technology, this technical solution seems quite expensive.

It is therefore the object of the present invention to provide a device for venting in a compressor assembly, which allows complete venting of the feed pressure port after switching off the compressor assembly, has a simple structure and performs the necessary switching operation automatically.

This object is achieved on the basis of a compressor arrangement according to the preamble of claim 1 in conjunction with its characterizing features. Advantageous developments of the invention are specified in the dependent claims.

The invention includes the technical teaching that the device comprises a springless relief valve having a control piston, which occupies a first switching position during operation of the compressor assembly and closes the feed pressure port against at least one sealing element and the control piston in the off state of the compressor assembly via a with the Intake area communicating control pressure port can be acted upon by an increase in the pressure in the intake and thereby assumes a second switching position in which vented the feed pressure port via a vent port.

The relief valve according to the invention is characterized in that it requires neither a return spring nor an external control. In addition, no nozzle is required, and the venting of the feed pressure side takes place in a short time exclusively via the relief valve. From the proposed means for venting the feed pressure port it is apparent that the valve causes only small delivery losses during the short switching operation of the closing, but not during operation. This means that, especially with smaller compressors, at the benefit of each additional delivery loss is particularly noticeable, the advantage is that the complete delivery volume of the compressor without restriction to the at least one consumer is available.

Furthermore, there is the advantage of an extremely small number of parts and a simple embodiment of the relief valve with appropriately arranged sealing elements, which reduces the effort in terms of production, storage and assembly times. The latter is also achieved by a simple installation of the valve, which only has to be inserted and fastened. In addition, especially in applications in the mobile area impurities and a water attack are critical factors. By the axial sealing seat of the valve function, the possibility of deposition of dirt or the accumulation of water is significantly reduced, in particular, as well as the counter surface is completely overflowed with each switching operation of air. The reduction of the water attack plays an important role, especially at low temperatures, and represents a decisive protection against freezing, in particular of the sealing points.

The elimination of a return spring for movement of the control piston increases the reliability of the relief valve, since a fatigue or a direct failure of the spring does not need to be considered further. Furthermore, the absence of the spring has the advantage that no spring force has to be overcome which would result in corresponding switching delays, pressure losses or incomplete relief.

The control piston has two switching positions, wherein the first switching position is present in the operation of the compressor assembly and the second switching position in the off state. In normal operation of the compressor, the air presses with overpressure from the compressor housing from the clean side of the air de-oiling element through the feed pressure port on an annular feed pressure surface, so that the control piston closes the feed pressure port against the sealing element. As long as the operation of the compressor is maintained, the control piston remains in the first switching position, while in the intake region, and thus with this in fluidly communicating control pressure port, a considerably lower pressure of the corresponding pressure medium than in the feed pressure port is present.

Advantageously, an annular control pressure surface is formed opposite to the feed pressure surface on the control piston, which is acted upon via the control pressure port, wherein the control piston occupies the second switching position via the pressurization of the control pressure surface. This is achieved as soon as the compressor is switched off. The compressed, mixed with oil air strikes back into the intake, so that equally the control pressure port is pressurized. A check valve ensures a maintenance of the pressure in the intake, so that the control piston is pressurized via the control pressure surface, and this occupies the second switching position. As a result, the sealing element is released, so that the air from the clean side, i. from the supply pressure port via the relief valve can flow.

In this case, the control piston is formed so advantageous that the control pressure surface is greater than the feed pressure surface, so that the control piston assumes the second switching position at approximately the same pressure of the feed pressure in the feed pressure port and the control pressure in the control pressure port. Thus, the switching movement of the control piston is only possible because the effective areas are different in size, since applied to both the feed pressure port and the control pressure port housing pressure. After switching the compressor vented on the side of the feed pressure port to ambient pressure.

When the compressor is put back into operation, air continues to flow through the relief valve for a short time. However, since the pressure in the feed pressure port is built up faster than it can flow through the relief valve, and at the same time after opening the Check valve in the intake a slight negative pressure is generated, the control piston moves after a short time back to the first switching position so that it rests again on the sealing element and the valve closes.

For design reasons, it is of particular advantage that the relief valve is received directly from the housing of the compressor assembly, wherein the housing forms the valve seat. The control piston is annular, and a guide element extends coaxially through the control piston, wherein the guide element can be screwed via a thread in the housing and receives the sealing element. Advantageously, the relief valve is not formed as a single part, but integrated directly into the housing of the compressor assembly. The geometric design of the valve seat comprises a plurality of concentric bores, which are arranged coaxially with each other such that they can be manufactured from a machining direction, preferably by drilling.

The guide element is helically designed, which comprises a cylindrical guide portion and a screw shank portion, so that it can be screwed into a thread, and thus either firmly defined screwed to the stop or can be varied in the depth of engagement. The part of the guide element forming the valve component has correspondingly machined outer circumferential surfaces, wherein the latter further receives the sealing element against which the control piston seals in the first switching position. At the same time, the guide element via an outer cylindrical surface for guiding the annular piston, wherein the annular piston moves axially over the guide element on its stroke length. The control piston is provided with radially extending bores, which form venting channels between the annular gap and the venting connection. The annular gap is designed as a ventilation cross section between the control piston and the guide element. In the second switching position, in which the annular piston releases an annular flow cross-section for venting relative to the sealing element, the pressure medium can now be removed from the feed pressure port via the annular gap between the piston Bleed the guide element and the ring piston through the radial bores into a vent connection. The vent connection preferably leads into the suction filter of the compressor, since the pressure medium may be contaminated with oil and thus does not reach the atmosphere.

For structural reasons, it is particularly advantageous that the valve seat forming bores are closed to the outside with a closure element, wherein the closure element is detachably arranged in the housing. The closure element further comprises a seal to seal against the outside of the housing of the compressor pressure-tight. The closure element may be formed as a lid-shaped plate, which is arranged with a snap ring in a corresponding bore or a groove, whereas the closure element may also be designed as a screw-in lid or as a closure element which is pressure-tight with a plurality of individual connection elements on the housing is attached. The necessity of the closure element results in particular from the manufacture of the valve seat, since the individual contours have to be generated in the housing from a machining direction supplied from the outside of the housing, so that subsequently a pressure-tight closure is required.

Fig. 1

einen Ausschnitt aus einer Verdichteranordnung mit einer Schnittansicht eines Entlastungsventils, wobei sich der Steuerkolben in einer ersten Schaltstellung befindet; und

Fig. 2

einen Ausschnitt aus einer Verdichteranordnung mit einer Schnittansicht eines Entlastungsventils, wobei sich der Steuerkolben in einer zweiten Schaltstellung befindet.

Further, the invention improving measures are specified in the subclaims or are presented below together with the description of a preferred embodiment of the invention with reference to the figures. It shows:

Fig. 1

a detail of a compressor assembly with a sectional view of a relief valve, wherein the control piston is in a first switching position; and

Fig. 2

a section of a compressor assembly with a sectional view of a relief valve, wherein the control piston is in a second switching position.

In the Fig.1 shown compressor assembly 1 initially comprises a compressor housing 2, which has a suction region 3, from which the air to be compressed is sucked. This is supplied as feed pressure air to the corresponding consumers, wherein the feed pressure is also present in the feed pressure port 4.

In the sectional plane, a relief valve 5 is shown, wherein the relief valve is present in a first switching position. The relief valve is used to vent the feed pressure port 4 when the compressor assembly 1 is put out of operation. The feed pressure port 4 is connected to the clean side of the Luftentölelements, and has a housing overpressure during operation, said overpressure is lowered when switching off the compressor assembly 1 by means of the relief valve to ambient pressure.

The illustrated relief valve 5 further comprises a control piston 6, which is located in the first switching position. In this case, the control piston 6 seals the feed pressure connection 4 against a sealing element 7. The feed pressure in the feed pressure port 4 has in operation at a pressure which is higher than the ambient pressure. With the feed pressure, a feed pressure surface 8 is acted upon, so that the control piston 6 - in the image plane - moves upward. The control piston 6 is annular, wherein a sealing surface is arranged so that it moves in a movement of the control piston 6 up against the sealing element 7 and thereby seals. The feed pressure port 4 is thus sealed pressure-tight, since this is sealed in the lower region of the control piston 6 on the outside against the valve seat in the compressor housing 2 also with a sealing element.

A guide element 9 extends coaxially through the annular control piston 6. This is screwed into a threaded bore in the lower region of the valve seat in the housing 2, so that the guide element 9 in the vertical position either firmly defined screwed to the stop or be variably arranged depending on the depth of engagement can. The deeper the guide element 9 is screwed into the compressor housing 2, the smaller is the possible stroke movement of the control piston 6. In the case of a large stroke movement, the possible flow cross-section for venting the feed pressure port 4 is correspondingly greater. The sealing element 7 is received in the guide member 9 and is formed as an O-ring seal. Between the control piston 6 and the guide member 9 and between the control piston 6 and the valve seat in the compressor housing 2 more sealing element are arranged, which are also designed as O-ring seals. The intake area 3 is connected via a control pressure port 10 with the relief valve 5, wherein above the control piston 6, a control pressure chamber 11 is formed. Since during operation of the compressor assembly 1, the pressure in the intake 3 and thus in the control pressure chamber 11 is low and approximately equal to the ambient pressure, the control piston 6 remains in the first position, and seals the feed pressure port 4 against the sealing element 7. Two arrows drawn next to the shank portion of the guide element 9 indicate the direction of movement or the holding direction of the control piston 6 in the first switching position.

The relief valve 5 is incorporated in the compressor housing 2, wherein the compressor housing 2 itself forms the valve seat. The relief valve 5 is essentially composed of two components which correspond only to the control piston 6 and the guide element 9. These components are accommodated in the valve seat, wherein it is formed of concentrically arranged bore sections, so that the machining of the bore sections can take place from a machining direction.

Above the components control piston 6 and guide element 9 of the relief valve 5, a closure element 13 is inserted, which closes the control pressure chamber 11 pressure-tight. The closure element 13 is formed according to the present embodiment as a circular lid, which seals by means of an O-ring against the housing 2 of the compressor assembly 1. To secure the closure element 13, this is fixed by means of a retaining ring axially in the receiving bore. To remove the closure element 13, this has a central bore into which a thread can be screwed in order to pull the closure element 13 out of the bore during disassembly.

Fig. 2 shows the compressor assembly 1 with a sectional view of a relief valve 5, wherein the control piston 6 is in a second switching position. This switching position corresponds to the switched-off state of the compressor, so that there is a need to vent the feed pressure port 4 to ambient pressure. If the compressor 1 is switched off, the pressure in the feed pressure connection 4 drops slightly, since the compressed air strikes back into the intake region 3. Thus, the pressure in the control pressure chamber 11 is increased via the control pressure port 10, so that the control pressure surface 12 is subjected to a higher pressure. Since the control pressure surface 12 is formed larger than the feed pressure surface 8, this results in a vertical movement of the control piston 6 down, so that the sealing element 7 is released from the sealing surface of the control piston 6, and the feed pressure port 4 is vented. With an assumed pressure equality in the feed pressure port 4 and in the control pressure port 10 in the off state, the control piston 6 remains in the second position, since the control pressure surface 12 is greater than the feed pressure surface 8, so that the force acting on the control piston 6 axial force in the vertical direction directed downward is greater than the force which is directed over the feed pressure surface 8 upwards. Two arrows drawn next to the shank portion of the guide element 9 indicate the direction of movement or the holding direction of the control piston 6 in the second switching position.

The venting of the feed pressure port 4 initially takes place via an annular gap 14, which extends vertically between the guide element 9 and the control piston 6. The bore through which the guide member 9 passes is formed larger in diameter than the shank of the guide member 9. Since now the sealing element 7 is not applied to the sealing surface of the control piston 6, escapes the pressure from the feed pressure port 4 initially through the annular gap 14 through radial bores 15, which are applied within the control piston 6 to fluidly connect the inside of the control piston 6 with a vent port 16. The vent port 16 may be connected to the intake filter of the compressor assembly to vent in this. In this case, the possibly still easily contaminated with oil air can be cleaned, so that the oil from the lubrication of the screw compressor can not get into the environment.

The switching movement of the control piston is possible in pressure equality between the feed pressure port 4 and the intake 3, characterized in that the effective areas are different sizes, so that the venting position according to Fig. 2 is maintained even when the compressor is vented to ambient pressure after the circuit is switched. If the compressor is put back into operation, briefly air continues to flow via the feed pressure port 4, the annular gap 14 and the radial bores 15 in the vent port 16. However, since faster air is nachgefördert than can flow, and at the same time after opening of the check valve in the intake 3 a slight negative pressure is generated, the control piston 6 moves after a short time back up and seals again against the sealing element 7. Thus, the valve is closed again and the compressor can be operated without a valve-related pressure loss.

LIST OF REFERENCE NUMBERS

1

compressor assembly

2

compressor housing

3

suction

4

Feed pressure connection

5

relief valve

6

spool

7

sealing element

8th

Supply pressure area

9

guide element

10

Control pressure connection

11

Control pressure chamber

12

Control pressure face

13

closure element

14

annular gap

15

radial bore

16

exhaust port

Claims (11)

1. Compressor arrangement (1), in particular screw compressor for compressed air generation, comprising a compressor housing (2) which has an intake region (3) and, furthermore, comprises a feed pressure port (4) for delivering the compressed pressure medium, a device for venting the feed pressure (4) being provided, which device comprises a relief valve (5) having a control piston (6) which, when the compressor arrangement (1) is in operation, assumes a first switching position in order to close the feed pressure port (4) against at least one sealing element (7) and which, in a second switching position, when the compressor arrangement (1) is in the switched-off state, acts upon the control piston (6) by means of a rise in pressure in the intake region (3) via a control pressure port (10) communicating with the intake region (3), so that the feed pressure (4) is vented via a venting port (16) characterised in that the control piston (6) of the springless relief valve (5) comprises an annular feed pressure face (8) which can be acted upon via the feed pressure port (4) in order to assume the first switching position under the action of pressure.
2. Compressor arrangement (1) according to claim 1,
   characterised in that the control piston (6) comprises an annular control pressure face (12) which can be acted upon via the control pressure port (10) in order to assume the second switching position.
3. Compressor arrangement (1) according to any of the preceding claims,
   characterised in that the control pressure face (12) is larger than the feed pressure face (8), so that, in the case of an approximately equal pressure of the feed pressure in the feed pressure port (4) and of the control pressure in the control pressure port (10), the control piston (6) assumes the second switching position.
4. Compressor arrangement (1) according to any of the preceding claims,
   characterised in that the relief valve (5) is accommodated in the housing (2) of the compressor arrangement (1) in such a way that the housing (2) forms the valve seat.
5. Compressor arrangement (1) according to any of the preceding claims,
   characterised in that a guide element (9) extends coaxially through the annular control piston (6), the guide element (9) being capable of being screwed in via a thread in the housing (2) and accommodating the sealing element (7).
6. Compressor arrangement (1) according to any of the preceding claims,
   characterised in that the bores forming the valve seat and introduced in the housing (2) are designed concentrically to one another.
7. Compressor arrangement (1) according to any of the preceding claims,
   characterised in that the bores forming the valve seat are closed by means of a closing element (13), the closing element (13) being arranged releasably in the housing (2).
8. Compressor arrangement (1) according to any of the preceding claims,
   characterised in that the venting cross section is designed as an annular gap (14) between the control piston (6) and the guide element (9).
9. Compressor arrangement (1) according to any of the preceding claims,
   characterised in that the control piston (6) has radial bores (15) which form venting ducts between the annular gap (14) and the venting port (16) located in the housing (2).
10. Compressor arrangement (1) according to any of the preceding claims,
    characterised in that the venting port (16) is connected to an intake filter of the compressor arrangement (1).
11. Compressor arrangement (1) according to any of the preceding claims,
    characterised in that the compressed medium is compressed air, and the feed pressure port (10) is connected to the clean side of an air-deoiling element.

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