WO2002060564A1

WO2002060564A1 - Arrangement and method for compressed air systems in vehicles

Info

Publication number: WO2002060564A1
Application number: PCT/SE2002/000160
Authority: WO
Inventors: Mats SABELSTRÖM; Lucas Megas
Original assignee: Volvo Lastvagnar Ab
Priority date: 2001-02-02
Filing date: 2002-01-30
Publication date: 2002-08-08
Also published as: SE0100312D0; JP2004522893A; US6880327B2; US20040103644A1; BR0206743A; EP1363721A1; SE520559C2; JP4067406B2; SE0100312L

Abstract

The invention relates to an arrangement for a compressed air system in a vehicle, comprising a compressor (2) for generating compressed air and a connection (11) for feeding compressed air generated by the compressor (2) to the remaining compressed air system (1) in the vehicle. the invention is characterized in that it comprises an oxidation catalyst (10) which is adapted for purifying said generated compressed air in direct connection with an outlet of said compressor (2), and that said oxidation catalyst (10) is connected to said remaining compressed air system (1). The invention lso relates to a method for a compressed air system in a vehicle, and to a compressor (2) for generating compressed air. By means of the invention, an improved arrangement for purifying generated compressed air in a compressed air system in a vehicle is provided.

Description

TITLE:

Arrangement and method for compressed air systems in vehicles.

TECHNICAL FIELD:

The present invention relates to an arrangement for a compressed air system in a vehicle, comprising a compressor for generating compressed air and a connection for feeding compressed air generated by the compressor to the remaining compressed air system in the vehicle. The invention is particularly intended to be used for compressed air systems in heavy goods vehicles.

The invention also relates to a method for a compressed air system in a vehicle, comprising generating compressed air by means of a compressor, and feeding compressed air generated by said compressor to the remaining compressed air system in the vehicle.

The invention also relates to a device for generating and purifying compressed air, comprising a compressor and an oxidation catalyst.

BACKGROUND OF THE INVENTION: In the field of vehicles provided with a compressed air system for generating, storing and distributing compressed air to, for example, air suspension system and brake system, which in a known manner comprises pressure tanks, compressed air lines and various types of valves, said system is supplied with compressed air from a compressed air compressor. Said compressor is in a known manner operated by the vehicle's combustion engine. For lubricating the compressor, lubricating oil from the lubricating oil system of the combustion engine is utilized according to the prior art.

In accordance with the prior art, the compressed air can- be fed from the compressor to the vehicle's compressed air system. One problem which occur in connection with previously known compressed air systems of the above-mentioned type, is related to the fact that the compressed air which is generated in the compressor often is contaminated with lubricating oil in the form of aerosol and gas. When the compressor is in operation, a very high temperature occurs, which can result in oxidation of the lubricating oil which is mixed into the compressed air, which can result in polymerisation of the oil and in the formation of aggressive oxidation products. If these pollutants should be allowed to be supplied to the vehicle's remaining compressed air system, coatings could be formed in said system's components. These coatings can cause choking and material dissolution of said components, which in turn can result in functional incapability of the components.

In accordance with the prior art, the compressed air generated in the compressed air compressor can be purified by means of a mechanical filter, combined with cooling. One drawback as regards this technique, however, is that is has low efficiency.

Another previously known system for purifying compressed air is shown in the SE patent application 9901355-9. This document discloses a system with a compressor and a separate oxidation catalyst which is connected with the compressor via a special line. By means of the oxidation catalyst, the compressed air generated in the compressor can be purified, which reduces the risk of accumulation of pollutants in the vehicle's compressed air system.

One drawback as regards this known system is that it requires a comparatively large space, which is a problem since the available space in an engine house of a heavy goods vehicle is considerably limited. Another factor which must be taken into consideration is that the oxidation catalyst requires a comparatively high temperature in order to obtain normal purification effect.

SUMMARY OF THE INVENTION:

The object of the present invention is to provide an arrangement for an efficient purification of compressed air in a compressed air system for a vehicle, in particular a compressed air system where the compressed air is generated by a compressor which is lubricated with lubricating oil from a combustion engine.

The above-mentioned object is achieved by means of an arrangement of the above-mentioned type, the characterizing features of which will be apparent from appended claim 1 and which comprises an oxidation catalyst which is adapted for purifying said generated compressed air in direct connection with an outlet of said compressor, and that said oxidation catalyst is connected to said remaining compressed air system.

An additional object of the invention is to provide an improved method for a compressed air system in a vehicle. This is achieved by means of a method of the above-mentioned type, the characterizing features of which will be apparent from appended claim 9 and which comprises purifying said generated compressed air in an oxidation catalyst in direct connection with an outlet of said compressor, and feeding the compressed air being purified by the oxidation catalyst to said remaining compressed air system.

An additional object of the invention is to provide an improved device for generating and purifying compressed air. This is achieved by means of a device of the above-mentioned type, the characterizing features of which will be apparent from appended claim 10 and where said oxidation catalyst is adapted for purifying said generated compressed air in direct connection with an outlet of said compressor.

By means of the invention, several advantages are achieved. Primarily, it can be noted that the arrangement according to the invention requires a considerably smaller available space than previously known arrangements. This implies that the oxidation catalyst which is utilized according to the invention can be formed with a volume which is sufficiently large for providing a satisfactory purification effect for the compressed air from the compressor. This is in turn based on the understanding that the purification effect of the oxidation catalyst in principle is proportional to its volume.

Another advantage as regards the invention is that the oxidation catalyst according to the invention can be positioned in direct connection with the compressor, which implies that the operating temperature which is required for the oxidation catalyst (normally at least 200° C) can be obtained in a reliable manner without the need of having to use any particular heat aggregates. Nor is it in that way necessary to utilize any particular heat insulation or the like for maintaining the required high operating temperature of the compressed air being fed from the compressor.

According to a preferred embodiment of the invention, the oxidation catalyst is provided in the cylinder head of the compressor, which thus implies that the arrangement according to the invention can be said to constitute an integrated compressor and catalyst device which constitutes a compact and space-saving unit which comprises functions both of a compressor and a catalyst.

Advantageous embodiments of the invention will be apparent from the appended dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS:

The invention will be further described in the following with reference to a preferred embodiment and to the annexed drawings, in which

Fig. 1 shows a principal view of an arrangement in accordance with the present invention, and

Fig. 2 shows a cross-sectional view of a compressor which is to be utilized in accordance with the invention. PREFERRED EMBODIMENTS:

Fig. 1 shows a principal view of an arrangement according to the present invention. According to a preferred embodiment, the arrangement is utilized in connection with a compressed air system 1 of a per se previously known type, which preferably but not exclusively can be constituted by a compressed air system for a heavy goods vehicle. The compressed air system 1 , which comprises for example an air dryer, a pressure tank and the vehicle's air suspension system and brake system, is only schematically shown in Fig. 1.

The compressed air which is intended for the compressed air system 1 is generated in a compressor 2 which is mechanically connected with a combustion engine 3 via a transmission 4. In this manner, the air which flows from the atmosphere, according to what is indicated by means of an arrow in the drawing, and to the compressor 2 via an incoming air channel 5, can be compressed and fed out from the compressor 2. The compressor 2 is provided with lubricating oil from the lubricating oil system 7 of the combustion engine 3, wherein the lubricating oil is fed into the compressor 2 via an oil feed line 8 and fed out from the compressor 2 via an oil exhaust line 9.

When the compressor 2 is in operation, a very high temperature is generated in the compressed air which is generated in the compressor. This in turn results in oxidation of the lubricating oil which is mixed into the compressed air. The aggressive oxidation products which in that connection are formed, e.g. esters, resin-like substances and aerosol, may contaminate the compressed air being generated in the compressor 2. If this contaminated air should be fed further to the compressed air system 1 , coatings on pressure tanks and the like could be formed. Furthermore, it could cause for example choking of valves and material dissolution of components forming part of the system. To this end, the contaminated compressed air is guided from the compressor 2 to an oxidation catalyst 10 which is provided in connection with the compressor 2. In the oxidation catalyst 10, the pollutants forming part of the compressed air will be transformed into carbon dioxide and water. Next, the purified compressed air will be fed further to the compressed air system 1 by means of an additional line 11.

According to what will be described in detail below, the invention is based on the fact that the oxidation catalyst 10 is provided in direct connection with the compressor 2. Preferably, the oxidation catalyst 10 is positioned in connection with an outlet for compressed air at the compressor 2, which implies that the compressor 2 together with the oxidation catalyst 10 can be said to constitute a combined compressor and catalyst device, which device is indicated by means of dashed lines and with the reference numeral 12 in Fig. 1.

The oxidation catalyst 10 is constructed in such manner that it has a certain minimum limit temperature at which it is capable of operating with a satisfactory purification capacity. This limit temperature is normally of the order of approximately 200° C. In a normal application, the temperature of the air flowing out from the compressor 2 will obtain this temperature. However, in order to secure the desired limit temperature, the invention - according to an alternative embodiment - can be arranged with special means for heating. This can in turn be realized by providing the oxidation catalyst 10 with an electric heating device, by means of which it can be secured that the desired temperature of the oxidation catalyst 10 always can be obtained. In order to secure that the temperature of the oxidation catalyst 10 will not become too high, the invention can alternatively also be provided with a cooling system, e.g. based on cooling water, which is utilized for cooling the oxidation catalyst 10 during those operating conditions where its temperature runs the risk of becoming too high. To this end, the line 11 can also be adapted so that the air which flows through the line 11 is cooled. However, it shall be noted that for most applications, a correct operating temperature can be obtained in the oxidation catalyst 10 without the need of having to use any particular device for temperature control.

Fig. 2 shows a slightly simplified cross-sectional view of a combined compressor and catalyst device 12 according to the present invention. This device 12 comprises a compressor 2 (cf. Fig. 1) of an essentially known type, the main parts and function of which will now be described.

The compressor 2 comprises a case 13 with a cylinder head 14. Inside the case, there is a cylinder 15 in which an upwardly and downwardly moving piston 16 is provided. The piston 16 is in a known manner connected with a connecting rod 17 which in turn is provided on a crankshaft 18. This crankshaft 18 is rotatably mounted in the case 13 and is connected with the combustion engine (cf. Fig. 1 ) via a mechanical transmission.

Incoming air is fed to the compressor 2 via the incoming air channel 5. During a downward movement of the piston 16, air is fed into the cylinder 15 via an admission 19. This admission 19 is normally covered by a lamella-based admission valve 20. However, the admission valve 20 is opened in a known manner due to a decrease of pressure in the cylinder 15, which is obtained during the downward movement of the piston 16. The opened condition of^" the admission valve 20 is indicated by means of dashed lines in Fig. 2.

When the piston 16 has reached its lowest position and begins its upward motion, the admission valve 20 is first closed. When the piston 16 is pressed upwards, the air in the cylinder 15, which is now compressed, will be pressed out via a lamella-based exhaust valve 21 , which in Fig. 2 is shown in the opened condition which it adapts automatically due to an increased pressure which prevails in the cylinder 15. Thus, in this opened condition, the compressed air can flow out through an outlet 22. The above-mentioned oil feed line 8 is connected to the compressor 2 for supplying lubricating oil, whereas the above-mentioned oil exhaust line 9 also is connected to the compressor 2, for removing lubricating oil.

In the cylinder head 14 of the compressor 2, a space 23 is defined through which the outgoing air from the compressor 2 flows before it reaches the outgoing line 11 which leads to the vehicle's remaining compressed air system 1 (cf. Fig. 1 ). According to what has been mentioned above, a basic principle of the present invention is that an oxidation catalyst is provided in direct connection with the compressor 2, more precisely in connection with its air outlet 22. This oxidation catalyst is indicated in Fig. 2 in the form of a catalyst unit 10 being provided downstream of the air outlet 22. The oxidation catalyst can in turn be constituted by one single catalyst unit or several smaller catalyst units which together correspond to the oxidation catalyst which is indicated schematically in Figs. 1 and 2 with the reference numeral 10.

The catalyst unit 10 is formed in such manner that it fits into the space 23 which is defined in the cylinder head 14. The catalyst unit 10 can for example be constituted by several smaller units which are essentially cylindrical and tube-like.

The invention is, however, not limited to this design, but the catalyst unit 10 is formed depending on available space, flow characteristics of the compressed air in the compressor's cylinder head 14 and the possibility of service. Preferably, the oxidation catalyst is formed so that it completely utilizes the space 23 which is defined in cylinder head 14 and so that the compressed air will flow evenly through it.

All in all, the catalyst unit thus constitutes an oxidation catalyst which is utilized for purifying the air flowing out from the cylinder 15, before it is fed further through the line 11 to the compressed air system 1. In this manner, there will be a reduced risk of harmful coatings causing choking or damages on components in the compressed air system.

The basic principle of the invention is that an oxidation catalyst is provided in direct connection with the outlet 22 of the compressor 2 so that a combined compressor and catalyst device is formed. This combined device comprises an oxidation catalyst which in turn is constituted by at least one, but alternatively also several catalyst units which each one in a catalytic manner is capable of purifying a certain amount of compressed air generated in the compressor 2. Preferably, the catalyst unit (alternatively the catalyst units) can be constituted by short tube-like units which each one is formed with a folded plate being coated with a catalytically active material. These catalyst units are positioned in the cylinder head 14 so that the air from the cylinder 15 is guided through the catalyst units. The direction of flow for the compressed air through the catalyst unit 10 and the space 23 in the cylinder head 14 is indicated schematically by means of arrows in Fig. 2.

For mounting the catalyst unit 10 (alternatively the catalyst units), the cylinder head 14 preferably comprises (not shown) guiding means, which e.g. can be constituted by suitably formed recessions in which a catalyst unit can be pushed into place during manufacture or during service of the compressor 2. In this manner, the catalyst unit 10 can be mounted in the cylinder head 14 in a simple manner. In case of several units being utilized, they can suitably be formed as small short tubes, which results in that they form easily exchangeable units which can be pushed into place in corresponding recessions or similar spaces in the cylinder head 14. In this manner, an advantage is obtained as regards the invention since for example a defect catalyst unit can be exchanged in a simple manner.

By means of the invention, an improved purification capacity is obtained by means of the fact that the oxidation catalyst 10 is arranged in direct connection with the compressor 2, which results in that separate, long connection lines between theses components can be completely eliminated. In this manner, the oxidation catalyst will also obtain its required operating temperature without any unnecessary heat losses along the way between the compressor and the oxidation catalyst. By means of the arrangement according to the invention, a smaller volume compared with previously known devices is also obtained.

The invention is not limited to comprise a certain number of catalyst units, but this number can be varied depending on the present application and depending on the present dimensions of catalyst units, cylinder head and other components. In principle, the invention can be realized with one single catalyst body which fills out the interior of the cylinder head 14 in a suitable manner. Alternatively, the invention can be realized with several catalyst units which in that case can be mounted individually in the cylinder head.

The invention is not limited to the oxidation catalyst being provided in connection with the cylinder head 14 of the compressor 2. According to an alternative embodiment, the exhaust valve 21 , particularly its under side, can be coated with a material which provides the function of an oxidation catalyst. This has a certain purifying effect on the air flowing past the exhaust valve 21. The upper side of the piston 16 may also be coated with a catalytic material, by means of which the catalytic surface can be increased without the need of having to increase the size of the compressor.

Depending on the present application, the invention can alternatively be formed with means for cooling the purified compressed air, wherein said means in that case are provided along the connection 11 between the oxidation catalyst and the remaining compressed air system 1 (cf. Fig. 1). In this manner, the temperature of the compressed air can be reduced to a value which is adjusted to the compressed air system 1 being arranged downstream. The invention is not limited to the embodiments described above, but may be varied within the scope of the appended claims. For example, the invention can be utilized in various types of vehicles, e.g. passenger cars, lorries, loaders and buses, which comprise a compressor for generating compressed air to a compressed air system.

Furthermore, for example the outlet port 22 and the exhaust valve 21 can suitably be formed in such manner that the flow of air through the space 23 is distributed to the respective catalyst unit in a manner which is suitable as regards the flow.

The invention can be implemented with various types of compressors, e.g. a compressor of the type which comprises two pistons with two sets of admission valves and exhaust valves.

Claims

CLAIMS:

1. Arrangement for a compressed air system in a vehicle, comprising a compressor (2) for generating compressed air and a connection (11) for feeding compressed air generated by the compressor (2) to the remaining compressed air system (1) in the vehicle, cha racte rized i n that said arrangement comprises an oxidation catalyst (10) which is adapted for purifying said generated compressed air in direct connection with an outlet of said compressor (2), and that said oxidation catalyst (10) is connected to said remaining compressed air system (1).

2. Arrangement according to claim 1 , c h a r a ct e r i z e d i n that said oxidation catalyst (10) is integrally arranged within said compressor (2) and together with the compressor (2) constitutes a combined compressor and catalyst device (12).

3. Arrangement according to claim 2, characterized in that said oxidation catalyst (10) is arranged so that it fits into a space (23) which is defined in a cylinder head (14) at an outlet of said compressor (2).

4. Arrangement according to any of the preceding claims, characterized in that said oxidation catalyst (10) is constituted by several separate catalyst units with catalytically active material.

5. Arrangement according to any of the preceding claims, c h a r a c t e r i z e d i n that it comprises means for controlling the temperature of the compressed air generated by the compressor (2).

6. Arrangement according to claim 5, ch a ra ct e ri ze d i n that said means comprise an electric heating device.

7. Arrangement according to claim 5, characterized in that said means comprise a cooling device.

8. Arrangement according to any of the preceding claims, ch a ra ct e r ize d i n that the engine (3) is constituted by a diesel engine.

9. Method for a compressed air system in a vehicle, comprising: generating compressed air by means of a compressor (2), and feeding compressed air generated by said compressor (2) to the remaining compressed air system (1 ) in the vehicle, characterized i n that said method also comprises: purifying said generated compressed air in an oxidation catalyst (10) in direct connection with an outlet of said compressor (2), and feeding the compressed air being purified by the oxidation catalyst (10) to said remaining compressed air system (1).

10. Device for generating and purifying compressed air, comprising a compressor (2) and an oxidation catalyst (10), characterized in that said oxidation catalyst (10) is adapted for purifying said generated compressed air in direct connection with an outlet of said compressor (2).