Pressure relief valve

Abstract

Pressure relief valve (1) of a gas line carrying aerosols, comprising a valve body (2) which is movable between a closed position adjacent to a valve seat (8) and an open position spaced apart from the valve seat (8), and which is held in its closed position by force and is movable against the force acting from the closed position to the open position, wherein the valve body (2) is provided with openings (15) and the valve seat (8) with nozzle openings (9) such that the valve body (2) is also permeable to gas flowing in the gas line in the closed position, and the valve seat (8) has several nozzle openings (9) collectively referred to as a nozzle arrangement (10), and wherein a compressible coalescing medium (7) is arranged between the valve body (2) and the valve seat (8) such that it is compressed against the valve seat (8) when the valve body (2) is in the closed position, and that itwhen the valve body (2) is in the open position, is spaced away from the valve seat (8) and by means of this space creates a gap (12) which is in flow communication with the nozzle openings (9), characterized in that the mutually facing surfaces of the coalescing medium (7) and the valve seat (8) are designed differently from each other such that, during movement into the open position, with increasing distance of the valve body (2) and the coalescing medium (7) from the valve seat (8), the gap (12) present between the coalescing medium (7) and the valve seat (8) becomes increasingly larger, and successively an increasing number of nozzle openings (9) of the nozzle arrangement (10) are in flow communication with this gap (12).

Description

The invention relates to a pressure limiting valve according to the preamble of claim 1.A pressure limiting valve of the generic type is known from DE 10 2010 029 322 A1. In the case of low volume flows, the valve body maintains its closed position in which it bears against the valve seat. In this case, the gas is conducted through the apertures provided in the valve seat and in the valve body. The gas is thereby conducted through the coalescing medium, which is located between the valve seat and the valve body. Aerosols contained in the gas stream are thereby collected in the coalescence medium, coagulate into larger droplets and can then be discharged from the gas stream as correspondingly large droplets.In the case of larger volume flows, the valve body is moved into its open position counter to the force action which normally holds it in its closed position and bears against the valve seat, for example counter to the action of a spring acting on the valve body. In this open position, a gap is formed between the coalescing medium and the valve seat, so that the gas flow is guided through the pressure limiting valve, such as through an impactor. Due to a direction deflection, the comparatively heavier aerosol particles still pass into the coalescing medium, while the gas stream otherwise flows along the surface of the coalescing medium through the gap created between the coalescing medium and the valve seat when the valve body is in its open position.Such pressure limiting valves take account of the fact that, in the case of low volume flows, a good separation effect is achieved by the gas flow with the aerosols passing through the coalescing medium, while, in the case of larger volume flows and correspondingly higher flow speeds, the impactor effect additionally acts with a good separation performance, which cannot be achieved in the case of the low volume flows. In this way, the pressure limiting valves of the generic type first make it possible to adapt to the prevailing flow conditions in the gas line and prevent an impermissible increase in pressure, and second, they always ensure a good separation effect of the pressure limiting valve even in the case of the different flow conditions.The invention is based on the object of improving a pressure limiting valve of the generic type to the effect that it is adapted in a particularly sensitive manner to different flow conditions which prevail in the gas line and thus always enables an optimum separation performance.This object is achieved by a pressure limiting valve having the features of claim 1. Advantageous embodiments are described in the dependent claims. A particularly advantageous embodiment of an oil mist separator is achieved in that it is equipped with a pressure limiting valve according to the proposal.In other words, the invention proposes to enable a plurality of different operating states of the pressure limiting valve, namely either the pure separator operation or the switched-on impactor operation, wherein intermediate states are also enabled in which a part of the coalescing medium is operated in the usual separator operation and through which the gas stream flows, while another part of the coalescing medium is operated in the impactor operation and a part of the gas stream is guided along the surface of the coalescing medium. According to the proposal, the division between separator and impactor operation can be effected in a plurality of different weights. In this way, an adaptation to different volume flows is made possible: when a specific pressure difference-usually correlating with a specific volume flow-is exceeded in the gas line, the pressure limiting valve opens, wherein the valve plate is however not yet guided into its final open position, but rather into an intermediate position which corresponds, for example, only to a portion of the overall possible valve stroke. In the case of two surfaces of the valve seat on the one hand and of the coalescing medium on the other hand which are designed completely complementarily to one another, a gap over the entire surface would already result in this intermediate position, and during the further movement of the valve body into its open position, only the gap width would be increased.According to the proposal, however, the mutually facing surfaces of the coalescing medium and of the valve seat are intentionally not designed exactly complementary to one another, but rather differ from one another in such a way that, although a gap is formed between the coalescing medium and the valve seat in the intermediate position of the valve body, this gap does not extend over the entire surface of the coalescing medium. This so-called "gap size" is distinguished from the gap width in the context of the present proposal, wherein the gap width denotes the distance between coalescing medium and valve seat, while the gap size denotes the area over which the gap extends at the valve seat or at the coalescing medium.Since the coalescing medium is compressible, it rests against the valve seat without any gaps in the closed position of the valve disk. As the distance of the valve disk from the valve seat increases, the coalescing medium located therebetween is increasingly decompressed, and because of the surface configuration which differs from one another, the mentioned gap between the coalescing medium and the valve seat results in certain regions, while the coalescing medium still rests against the valve seat in other regions, still compressed. The nozzle openings of the nozzle arrangement, which are covered by these regions of the coalescing medium that are in contact with the valve seat, consequently direct those portions of the gas stream through the pressure limiting valve that flow through the coalescing medium. The other nozzle openings of the nozzle arrangement, which open out into the gap formed, guide that portion of the gas stream which then experiences a reversal of direction between the valve seat and the coalescing medium and flows over the coalescing medium, so that the pressure limiting valve acts as an impactor for this portion of the gas stream.As the distance of the valve body from the valve seat increases, the coalescing medium is gradually decompressed further and further until it possibly no longer abuts the valve seat at all when the valve disk is in its open position. In this operating state, which is achieved at high pressure differences or volume flows flowing through the gas line, the pressure limiting valve acts in particular as an impactor, wherein in connection with the impactor effect it is to be noted that a small proportion of the gas also penetrates into the coalescing material during the impactor effect and here a separation effect is still effected to a certain extent by flow. At low pressure differences or volume flows, we have a more centrally compressed coalescing medium, thereby having lower fiber spacings and also better separation at the low flow rates. At higher volume flows, the coalescing medium decompresses, the fiber spacings become larger, but, due to the higher flow rate, such high fiber spacings are also no longer required. Due to the decompression, the coalescing medium can be "flushed" as a rule right from any particles which have been fixed. This may possibly extend the useful life during the separation via the coalescing medium.Consequently, as the distance of the valve body from the valve seat increases, the gap surface increases, so that an increasingly large-area gap is created between the coalescing medium and the valve seat. The nozzle openings of the nozzle arrangement are arranged in such a way that as the gap size increases, more nozzle openings gradually open into this gap, i.e. are in flow communication with the gap.Advantageously, it can be provided that the surface of the valve seat facing the coalescing medium reaches closer to the coalescing medium or to the valve disk in the central region than to the edge. This embodiment enables the use of a coalescing medium which can be produced, for example, as a flat disk from a web material and is therefore particularly economically available. Since such a coalescing medium has a planar surface, the described course of the valve seat brings about the desired surface configuration which differs from one another. In addition, in this embodiment, the first gap surface is initially formed on the outer circumferential edge of the valve seat, which is then gradually enlarged the further the valve plate with the coalescing medium is removed from the valve seat.Starting from this described, basically conical configuration, a first variant of the pressure limiting valve can provide that the surface of the valve seat extends concavely arched from the central region to the edge. In this way, in the case of small changes in the distance of the valve disk from the valve seat, a large increase in the gap size is already made possible.In a second variant, it can be provided that the surface of the valve seat extends convexly arched from the central region to the edge. In this case, as the distance of the valve disk from the valve seat increases, the coalescing medium is kept in contact with the valve seat over a comparatively long distance.In a third variant, it can be provided that the surface of the valve seat extends conically in a straight line from the center to the edge, so that a linear relationship is brought about between the gap size and the movement of the valve disk into its open position.The three variants described can be chosen, for example, depending on the composition of the gas guided through the gas line or how the nozzle openings in the valve seat and the apertures in the valve disk are configured.A fourth variant of this basically conical configuration of the valve seat consists in that a surface facing the coalescing medium runs spirally from the central region to the edge, so that a step-like switching of individual nozzle openings of the nozzle arrangement into impactor operation can be prevented particularly effectively and instead a gradual increase of the gap surface is effected, which can be adapted particularly well to the likewise not stepped but continuously increasing size of the gas stream.As an alternative to the described configuration of the coalescing medium as a flat disk, it can be provided that the surface of the coalescing medium facing the valve seat runs three-dimensionally. For example, this surface can, similar to the description for the valve seat, run essentially conically, for example, run concavely, convexly or rectilinearly conically. Alternatively, it can be provided that this surface of the coalescing medium has radially extending ribs and valleys.However, it can advantageously be provided that the coalescing medium is not configured as shaped bodies which are difficult to produce, but rather that the three-dimensional surface configuration is effected in that the coalescing medium consists of a plurality of concentrically arranged flat disks which have different diameters. In this way, a basically conical, but stepped course of the surface of the coalescing medium can be effected, wherein, in order to create such a three-dimensionally shaped body, a plurality of flat disks of different sizes, which have been produced from a web material, for example, can be placed one on top of the other and connected to one another. In this basically conical configuration of the surface of the coalescing medium, it is provided that the coalescing medium extends in its central region closer to the valve seat than to the edge. In this way, it is ensured that the gap between the coalescing medium and the valve seat is formed in the radially outer region of the pressure limiting valve, so that the gas can flow unimpeded through this gap.The coalescing medium can advantageously contain a multiplicity of fibers, so that overall a large surface area is available on which the aerosol particles can precipitate. For example, the coalescing medium may contain fibers of paper, plastic or metal.In particular, it can be advantageously provided that the coalescing medium is configured as a nonwoven fabric. Nonwoven fabrics are commercially available from the most varied materials and with the most varied space weights as web material, so that the coalescence medium used according to the proposal can be produced economically.The pressure limiting valve according to the invention can be used in particular advantageously in an oil mist separator, as is provided, for example, in compressors or in the region of the crankcase ventilation of an internal combustion engine, and in principle in all ventilation situations in which a mist, in particular oil mist, is produced.Exemplary embodiments of the invention are explained in more detail below with reference to the purely schematic representations. This shows FIG. 1 shows a cross section through a first exemplary embodiment of a pressure limiting valve in its closed position, FIGS. 2-4 show the pressure limiting valve of FIG. 1 in different positions up to its open position, FIG. 5 is a perspective view of the interior of the valve seat of the pressure limiting valve of FIGS. 1 to 4; FIGS. 6 to 9 are side views of further exemplary embodiments of valve seats; and FIG. 10 is a view similar to FIG. 4 of a further exemplary embodiment of a pressure limiting valve in its open position.In the drawings, reference numeral 1 designates a pressure limiting valve in total, which has a valve body 2 which forms a valve plate 3 and a valve stem 4. A valve spring 5 supports the valve body 2 on a member referred to as a seat member 6. The valve spring 5 acts on the valve stem 4 in the upper region and is designed as a compression spring, so that it tends to raise the valve body 2 upwards with respect to the seat component 6.A coalescing medium 7 is arranged on the valve disk 3, which is designed as a flat, round, centrally perforated disk, through the central opening of which the valve stem 4 extends. The coalescing medium 7 consists of a nonwoven fabric and is designed to be compressible with respect to the force of the valve spring 5, so that it is pressed against the seat component 6 by means of the spring force of the valve spring 5 and is thereby compressed. In FIG. 1, the coalescing medium 7 is shown in the decompressed state, and the penetrations with the seat component 6 show that, in contrast to the idealised representation of FIG. 1, the coalescing medium 7 is actually compressed in the region of these penetrations.In this case, the coalescing medium 7 bears against the seat component 6 along a surface which is designated as valve seat 8. In the radially outer region, the coalescing medium 7 bears in an uncompressed manner against the valve seat 8, while the remaining surfaces of the valve seat 8, corresponding to the penetration which can be seen in FIG. 1, compress the coalescing medium 7 which bears against them to different extents.In the seat component 6, a plurality of separate passages in the form of nozzle openings 9 are provided, which are collectively referred to as a nozzle arrangement 10 and are separated or bounded from one another by webs 11 of the seat component 6.Passages are also provided in the valve disk 3, which are designated as apertures 15, so that a gas stream which flows through the nozzle arrangement 10 into the coalescing medium 7 can leave the coalescing medium 7 through the apertures 15 of the valve actuator 3.FIG. 1 shows the pressure limiting valve 1 or its valve body 2 in its closed position, in which all nozzle openings 9 of the nozzle arrangement 10 are covered by the coalescing medium 7. The separation of aerosols carried along in the gas stream takes place in pure separator operation, in which the gas stream is completely guided through the coalescence medium 7.The gas flow acts on the valve body 2 in a direction which is opposite to the action of the valve spring 5, so that the gas flow tends to open the pressure limiting valve 1 against the action of the valve spring 5. However, in the case of small volume flows, the valve body 2 remains in its closed position illustrated in FIG. 1. Because the coalescing medium 7 is compressed by the valve seat 8 in the region of the nozzle arrangement 10, a very dense arrangement of the fibers within the fiber fleece, which forms the coalescing medium 7, results for these low volume flows.FIG. 2 shows the pressure limiting valve 1 of FIG. 1 in an operating state in which a greater volume flow has led to the valve body 2 having been guided partially from its closed position in the direction of an open position of the valve counter to the action of the valve spring 5. The valve body 2 has been moved away from the valve seat 8 to such an extent that the coalescing medium 7 no longer abuts the valve seat 8 in its radially outer region, but a gap 12 has formed here, while the coalescing medium 7 still abuts the regions of the valve seat 8 there in the radially further inner regions and is also partially compressed by the valve seat 8, as the penetrations shown illustrate.FIG. 3 shows a further operating state of the pressure limiting valve 1 in the event of a further increase in the volume flow which flows through the pressure limiting valve 1. The valve disk 3 is still further away from the valve seat 8, the gap width of the gap 12 has thereby increased, but the gap size has also been increased overall, and as a result only the radially inner nozzle openings 9 of the nozzle arrangement 10 open into the coalescing medium 7, while the nozzle openings 9 arranged radially further outward open into the gap 12 and accordingly bring about a reversal of the direction of the gas flowing through these nozzle openings 9, so that the pressure limiting valve is operated as an impactor in this radially outer region.FIG. 4 finally shows the pressure limiting valve 1 in its open position, in which the valve disk 3 and thus the coalescing medium 7 are so far away from the valve seat 8 that all nozzle openings 9 of the nozzle arrangement 10 open into the gap 12. Only in the radially innermost region does the coalescing medium 7 still lie against the valve seat 8, which however has no effect on the flowability of the nozzle arrangement 10.FIG. 5 shows a perspective view of the interior of the seat component 6 with the annular, stepwise arranged individual sections of the valve seat 8 and the webs 11 which run between the nozzle openings 9 of the nozzle arrangement 10.FIG. 6 shows a side view of the central region of a seat component 6, without the outer collar of the seat component 6 that can be seen from FIGS. 1 to 5; in the exemplary embodiment of FIG. 6, this central region of the seat component 6 runs concave, that is to say in a curved curve in a retracted manner, wherein the central region of the valve seat 8 extends, as in the exemplary embodiment of FIGS. 1 to 5, closer to the valve disk 3 or to the coalescing medium 7 than the region of the valve seat 8 that is located radially further outward.FIG. 7 shows, in a representation similar to FIG. 6, a further exemplary embodiment of a seat component 6, in which the valve seat 8 does not run concave, but convexly curved, that is to say with a bulge running outwardly in a bulge.FIG. 8 shows a view similar to FIGS. 6 and 7, wherein the valve seat 8 basically extends in the same conical manner as in the exemplary embodiments of FIGS. 6 and 7, but does not extend in a convex or concave manner in its radial course, but rather extends in a rectilinear conical manner.FIG. 9 shows a view similar to FIGS. 6 to 8 of a valve seat 8 which extends in a spiral shape, the nozzle openings 9 being provided between the turns of the spiral.FIG. 10 shows a further exemplary embodiment of a pressure limiting valve 1 in a view similar to FIG. 4, i.e. in its open position.In contrast to the exemplary embodiment of FIGS. 1 to 4, it is provided in FIG. 10 that the coalescing medium 7 has a surface which is directed toward the valve seat 8 and is of three-dimensional configuration. This is achieved in that disks 14 of different sizes, each flat, made of the material of the coalescing medium 7 are arranged one above the other. Purely by way of example, it is provided that wafers of different thicknesses have been processed. In contrast to this, it can be provided in particular advantageously that all the discs 14 have the same material thickness, so that they can be produced from the same material web, for example.In the exemplary embodiment of FIG. 10 and also in the other exemplary embodiments, it holds true that the fiber spacing within the coalescing medium 7 is greater in the decompressed state than in the compressed state of the coalescing medium 7. however, this is not disadvantageous for the separation performance of the coalescing medium 7 insofar as, in the case of the high volume flows, those portions of the gas stream which are not deflected into the gap 12 but rather enter the coalescing medium 7 enter at a flow speed which is so high that a good separation efficiency of the coalescing medium 7 is achieved under these conditions.Reference Number:1 Pressure limiting valve 2 Valve body 3 Valve disk 4 Valve shaft 5 Valve spring 6 Seat component 7 Coalescing medium 8 Valve seat 9 Nozzle opening 10 Nozzle arrangement 11 Web 12 Gap 14 Disk 15 Aperture

Claims

Pressure limiting valve (1) of a gas line conducting aerosols, having a valve body (2) which is movable between a closed position lying against a valve seat (8) and an open position spaced apart from the valve seat (8), and which is held in its closed position under force load and is movable against the force effect from the closed position into the open position, wherein the valve body (2) is provided with apertures (15) and the valve seat (8) is provided with nozzle openings (9) in such a way that the valve body (2) is also permeable to gas flowing in the gas line in the closed position, and the valve seat (8) has a plurality of nozzle openings (9), collectively referred to as a nozzle arrangement (10), and wherein a compressible coalescing medium (7) is arranged between the valve body (2) and the valve seat (8) in such a way that it lies in compressed contact with the valve seat (8) when the valve body (2) is in the closed position, and in such a way that it acts as a pressure limiting valve, when the valve body (2) is in the closed position, when the valve body (2) is in the open position, is spaced apart from the valve seat (8) and creates by means of this spacing a gap (12) which is in flow connection with the nozzle openings (9), characterized in that the mutually facing surfaces of the coalescing medium (7) and of the valve seat (8) are configured differently from one another in such a way that, during the movement into the open position, with increasing distance of the valve body (2) and of the coalescing medium (7) from the valve seat (8) • the gap (12) present between the coalescing medium (7) and the valve seat (8) becomes increasingly large-area • and an increasing number of nozzle openings (9) of the nozzle arrangement (10) is successively in flow connection with this gap (12).Pressure limiting valve according to Claim 1, characterized in that the surface of the valve seat (8) facing the coalescence medium (7) extends closer to the coalescence medium (7) in the central region than to the edge.Pressure limiting valve according to Claim 2, characterized in that the surface of the valve seat (8) facing the coalescence medium (7) runs concavely arched from the central region to the edge.Pressure limiting valve according to Claim 2, characterized in that the surface of the valve seat (8) facing the coalescence medium (7) runs convexly curved from the central region to the edge.Pressure limiting valve according to Claim 2, characterized in that the surface of the valve seat (8) facing the coalescence medium (7) extends conically in a straight line from the central region to the edge.Pressure limiting valve according to Claim 2, characterized in that the surface of the valve seat (8) facing the coalescence medium (7) runs spirally from the central region to the edge.Pressure limiting valve according to one of the preceding claims, characterized in that the coalescence medium (7) is designed as a flat disc.Pressure limiting valve according to one of Claims 1 to 6, characterized in that the surface of the coalescing medium (7) facing the valve seat (8) runs three-dimensionally.Pressure limiting valve according to Claim 8, characterized in that the coalescing medium (7) is constructed from a plurality of concentrically arranged, flat disks of different diameters and extends closer to the valve seat (8) in the central region than to the edge.Pressure limiting valve according to one of the preceding claims, characterized in that the coalescing medium (7) contains a multiplicity of fibres.Pressure limiting valve according to one of the preceding claims, characterized in that the coalescing medium (7) is designed as a fibre fleece.Oil mist separator, having a pressure limiting valve (1) designed according to one of the preceding claims.

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