Air dryer cartridge for a compressed air treatment system of a vehicle

An air dryer cartridge for a compressed air treatment system of a vehicle, in particular for a commercial vehicle, has a spring cover and a support element, which together define a volume of the air dryer cartridge in the assembled state of the air dryer cartridge. A desiccant box arranged inside the volume and filled with a desiccant is provided. The spring cover and the carrier element can be coupled via a snap connection.

BACKGROUND AND SUMMARY OF THE INVENTION

The invention relates to an air dryer cartridge for a compressed air treatment system of a vehicle, in particular of a commercial vehicle, having a spring cover and a support element which together, in the assembled state of the air dryer cartridge, define a volume of the air dryer cartridge. A drying agent (desiccant) box is provided, which is arranged within the volume and which is filled with a drying agent. The spring cover and the support element are designed as cylinders substantially closed off on one side, at the open ends of which the spring cover and the support element can be coupled.

The invention also relates to a method for producing an air dryer cartridge for a compressed air treatment system of a vehicle, in particular of a commercial vehicle, wherein the air dryer cartridge includes a spring cover and a support element which together, in the assembled state of the air dryer cartridge, define a volume of the air dryer cartridge, and wherein a drying agent box which is filled with a drying agent is arranged within the volume.

The invention still further relates to a compressed air treatment system for a vehicle, in particular a commercial vehicle, having an air dryer cartridge according to the invention.

Air dryer cartridges are required within the context of the provision and treatment of compressed air for compressed air treatment systems, EAC for short, in particular in the commercial vehicle field. There, the air dryer cartridges are used for removing oil and dirt particles from the generated compressed air, and for drying the compressed air. Such air dryer cartridges are considered “wear parts” since they must be occasionally replaced.

An air dryer cartridge known from the prior art is illustrated inFIG. 1. The air dryer cartridge10shown is composed substantially of a drying agent box (also called a “desiccant box”)20, which is filled with a drying agent (also called a “desiccant”)38and which is arranged in a spring cover16. The spring cover16is closed off in the lower region by a base plate42with an air inlet50and an air outlet52. The base plate42and the spring cover16are fixedly connected to one another by way of a flanged seam56. An O-ring44and a sealing ring40with a rubber lip48provide sealing between the base plate42and the drying agent box20, wherein the rubber lip48operates as a check valve.

The sealing ring40is mechanically or chemically connected to the drying agent box20, wherein the rubber lip48has a defined opening and closing characteristic. In particular, the rubber lip48opens in the event of an excess pressure in the air dryer cartridge10, and thus acts as a safety valve. The drying agent box20is delimited in its axial direction of extent by a first air filter30and a second air filter32, which retain the drying agent38in the interior of the drying agent box20.

Furthermore, in the upper region of the air dryer cartridge10, there is arranged a compression spring34and a granulate cover36, by which the drying agent38in the interior of the drying agent box20is compressed. The granulate cover36is, in particular, designed to be air permeable.

A combination filter, for example in the form of a coalescence filter26, extends in the axial direction around the lower half of the drying agent box20and is fixed in the radial direction to a supporting structure54of the drying agent box20by a sleeve28. The coalescence filter26divides the air dryer cartridge10into a pre-filter region and a post-filter region. It is the object of the coalescence filter26during a compressed air delivery phase to retain oil and dirt particles and also emulsion droplets on an incident-flow surface, to store liquid oil, and by means of a coalescence effect to convert extremely fine oil droplets and aerosols into liquid oil and separate out said oil. Here, the design of the outflow surface and the filter construction yield a defined ratio of air outflow speed and oil droplet size. This ratio ensures that no oil droplets pass via the post-filter region into the drying agent box20and thus shorten the service life of the air dryer cartridge10and downstream consumers.

Air guiding elements46project in the radial direction from the drying agent box20into the coalescence filter26and prevent the inflowing air from bypassing the coalescence filter26. The sealing between the pre-filter region and the post-filter region during a compressed air delivery phase is thus realized by way of a special sealing geometry composed of air guiding elements46in conjunction with the sleeve28at the outside.

The coalescence filter26is wound in the azimuthal direction around the drying agent box20, in particular on the supporting structure54which is permeable to air and which is part of the drying agent box20. Here, the filter material of the coalescence filter26forms at least one filter layer in the radial direction. The sleeve28, which may be formed for example as an elastic rubber sleeve, fixes the filter material of the coalescence filter26in the radial direction. At the same time, the sleeve28allows the coalescence filter26to breathe during the accumulation of oil and dirt particles within the filter material, and protects the coalescence filter26against destruction. The filter material of the coalescence filter26directly adjoins the drying agent box20.

Furthermore, EP 0 230 991 A2 discloses an air dryer cartridge in which the housing parts of the air dryer cartridge are connected to one another by means of a snap-action connection which comprises a circlip.

Furthermore, U.S. Pat. No. 4,838,901 A and DE 198 27 566 A1 each disclose an air filter, the housings of which are, respectively, closed off by at least one flexible pair of “shoulders and posts” and joined together by means of a snap-action connection.

It is an object of the present invention to simplify the construction of an air dryer cartridge.

This and other objects are achieved by an air dryer cartridge for a compressed air treatment system of a vehicle, in particular of a commercial vehicle, having a spring cover and a support element which together, in the assembled state of the air dryer cartridge, define a volume of the air dryer cartridge. A drying agent box is provided which is arranged within the volume and which is filled with a drying agent. The spring cover and the support element are designed as cylinders substantially closed off on one side, at the open ends of which are arranged a snap-action connection by which the spring cover and the support element can be coupled. The snap-action connection element on the spring is encompassed on both sides perpendicular to an axial direction by the snap-action connection element on the support element.

As a result of the encompassment at both sides, the snap-action connection provides an adequate sealing action, such that an additional seal between the spring cover and the support element for sealing off the housing of the air dryer cartridge can be dispensed with. All the parts of the air dryer cartridge, in particular the necessary parts, are clamped between the spring cover and the support element. The parts of the air dryer cartridge include, for example, a granulate cover, a compression spring, a drying agent box, an air filter in the form of a nonwoven filter, drying agent, a check valve and a small O-ring. The compact cartridge unit can be easily removed from the compressed air treatment system, and exchanged, as a unit. The releasable snap-action connection allows the spring cover, the support element and further parts of the air dryer cartridge to be re-used, while worn parts, in particular the drying agent and filter nonwovens, can be exchanged.

It may preferably be provided that a coalescence filter is wound on the drying agent box and is fixed by a sleeve. The winding of the coalescence filter on the drying agent box makes it possible to dispense with a support device, which is separate from the drying agent box and which positions the coalescence filter within the air dryer cartridge at the side remote from the drying agent box.

It is particularly preferable for air filters to be arranged on an upper end and on a lower end of the drying agent box. The drying agent present in the interior of the drying agent box can be prevented from exiting the drying agent box by means of the air filters.

It may be provided that a granulate cover which is braced with respect to the spring cover by a compression spring fixes the drying agent in the drying agent box. In this way, the drying agent, which is usually present as granulate in the drying agent box, can be kept as densely packed as possible, wherein drying agent losses which occur through natural wear can be compensated by a reduction in size of the provided volume, in order to maintain the dense packing.

It may also be provided that the support element and the drying agent box are produced in one piece. This permits a “direct” coupling of the spring cover to the drying agent box without further components, such that the construction of the air dryer cartridge as a whole is simplified.

In the described method, it may be provided that the spring cover and the support element are coupled by a snap-action connection.

This also applies to the particularly preferred embodiments of the described method.

The method may in particular be refined in that a coalescence filter is wound on the drying agent box and fixed by a sleeve.

It may advantageously be provided that, before the filling of the drying agent box with drying agent, a first air filter is arranged at a lower end of the drying agent box, and that after the filling of the drying agent box with drying agent, a second air filter is arranged at the top end of the drying agent box.

It may also be provided that the drying agent is fixed in the drying agent box by a granulate cover, which is braced with respect to the spring cover by a compression spring.

It may also be provided that the support element and the drying agent box are produced in one piece.

DETAILED DESCRIPTION OF THE DRAWINGS

In the following drawings, the same reference numerals are used to denote identical or similar parts.

FIG. 1shows an air dryer cartridge10according to the prior art, the construction of which has already been described.

FIG. 2is a schematic illustration of a vehicle14having an air treatment system12, which includes an air dryer58with an air dryer cartridge10. The compressed air treatment system12receives compressed air from a compressor64, and distributes the treated compressed air to individual consumers via compressed air lines66. For this purpose, a valve device60comprising numerous valves and having a vent62is provided, which valve device60can be actuated by a control unit (not illustrated). The valve device60may, for example, include a pressure regulator and a multi-circuit protection valve. Illustrated in schematically simplified form inFIG. 2as consumers are brake cylinders of a compressed-air-operated brake system, without the necessary actuation means being indicated.

FIG. 3is a cross-sectional illustration of an air dryer cartridge according to an embodiment of the invention. The mode of operation of the air dryer cartridge10illustrated inFIG. 3corresponds to that of the air dryer cartridge10known fromFIG. 1. In the illustrated embodiment, the base plate42, which is fixedly connected by a flanged seam56to the spring cover16inFIG. 1, is replaced by a support element18, which is coupled by snap-action connectors22,24to the spring cover16. The snap-action connectors22,24form a positively locking connection between the spring cover16and the support element18, wherein the individual elements of the snap-action connectors22,24may be formed as hooks, studs or beads on the spring cover16and/or on the support element18and, after assembly, latch into corresponding depressions or cutouts on the other part18,16in each case.

Here, the spring cover16and the support element18constitute joining partners, which are to be coupled by the snap-action connectors22,24and which, during the assembly of the air dryer cartridge10, are pushed into or onto one another in an axial direction74until the latching of the snap-action connectors22,24takes place, wherein the hooks, studs or beads which are guided past the associated depressions or recesses by way of elastic deformation of one or both joining partners and/or the hooks, studs and beads themselves.

Here, the spring cover16and support element18are clipped together by the snap-action connectors22,24. On the support element18there is arranged a projection72surrounded by a first seal68, which provides sealing between the support element18and the cartridge housing (not illustrated), and a second seal70, which provides sealing between the support element18and a housing (not illustrated) of the compressed air treatment system (EAC).

The arrangement may be provided, for example, for the mounting of the air dryer cartridge10on the compressed air treatment system12by way of a bayonet ring connection (not illustrated). The two seals68,70therefore constitute seals which seal off the interior of the compressed air supply system, which during operation is generally at an elevated pressure in relation to the environment, from the environment. The spring cover16and the support element18may be formed in particular by cylindrical structures which are substantially open on one side, wherein the air inlet50and the air outlet52are provided in the support element18.

It is, however, also contemplated in a way which is not illustrated, for the support element18to take more the form of a circular ring, by which the drying agent box20is pressed against the spring cover16. In this case, the air inlet50and the air outlet52may be formed directly by the drying agent box20.

It is likewise possible for the support element18to be formed in one piece with the drying agent box20. In this case, the spring cover16would be coupled “directly” to the drying agent box20, because a separate support element18would be dispensed with, or would be regarded as a constituent part of the drying agent box20. The diameter of the spring cover16perpendicular to the axial direction74may be greater than or smaller than the diameter of the support element18, or may be selected to allow the spring cover16and support element18to be at least partially pushed one into the other until the “latching”, that is to say closure, of the snap-action connectors22,24occurs. It is also contemplated for the diameter of the spring cover16to correspond to that of the support element18, wherein then, during the joining process, the snap-action connectors22,24on those edges of the cylinder walls which come into contact with one another engage one into the other in order to produce the connection. The structural height of the support element18in the axial direction74may be varied in a simple manner.

The production of the air dryer cartridge10according to the invention will be briefly described below.

The coalescence filter26is wound on the drying agent box20and fixed by way of the sleeve28. The O-ring44is mounted on the base side of the drying agent box20. The first air filter30is subsequently placed into the open drying agent box20from above, and the drying agent box is filled with granular drying agent38. The second air filter32is placed onto the drying agent38from above, and is covered on its top side by the granulate cover36in order that the drying agent38cannot trickle out of the drying agent box20. To prevent relative movements within the drying agent38, the granulate cover36is braced with respect to the spring cover16(to be placed on), and in the process is pressed into the drying agent38, by way of the pressure spring34. This prevents mechanical disintegration of the granulate as a result of vibrations, and at the same time permits automatic fixing of the drying agent38, by the lowering of the granulate cover36, as the “fill level” within the drying box20falls as a result of wear. The support element18is subsequently equipped with the sealing ring40, the first seal68and the second seal70. The filled, preassembled container unit composed of the spring cover16and the filled drying agent box20is inserted into the support element18equipped with the seals68,70and the sealing ring40, and the drying agent box20is braced between the spring cover16and the support element18by the snap-action connectors22,24. It is alternatively also contemplated for the sealing ring40to be fastened to the drying agent box20. The functionality of the sealing lip48as a safety valve is important in both possible arrangements. The safety valve opens when an excess pressure prevails in the air dryer cartridge10. In this way, it is also possible for deposited oil and dirt particles to be flushed out, bypassing the coalescence filter26, during a regeneration phase of the air dryer cartridge10.

By way of the snap-action connectors22,24, the air dryer cartridge10can be temporarily stored or transported within the assembly facility without the entire unit falling apart, and without drying agent38trickling out. By means of corresponding outer packaging (not illustrated), it is also possible for this unit to be placed in storage and used for easy exchange of the filter cartridge during servicing. Here, the outer packaging serves substantially to protect the drying agent38against moisture.

A particular advantage of the construction according to the invention is that assembly can be realized by simply placing the spring cover16and support element18together, wherein no additional working steps or tools are required. Depending on requirements, the provision of the coalescence filter26in the air dryer cartridge10may be dispensed with.

LIST OF REFERENCE NUMERALS