Patent Application
20170152842
The invention relates to a cylinder head for a compressor, including at least one coolant-conducting region and at least two air-conducting regions, wherein the at least one coolant-conducting region is at least partially arranged around the at least two air-conducting regions. Furthermore, the at least two air-conducting regions have at least one air-supplying duct for feeding the air to be compressed into the compressor and at least one air-discharging duct for outputting compressed air compressed by the compressor.
Modern commercial vehicles which are used in rail or road traffic are equipped with a large number of subsystems using compressed air. These subsystems include, for example, a service brake operated with compressed air, and a pneumatic suspension system. The compressed air consumers are supplied with compressed air with the aid of a compressed air supply device which includes a compressor. Ambient air is sucked up by the compressor, compressed and cleared of foreign components, such as oil and water, in further parts of the compressed air supply device prior to use in the consumers.
As a consequence of the continuously increasing power parameters, such as efficiency and defined compressed air outlet temperatures, modern compressors impose exacting requirements on its components, such as the valve plate, cooling unit and cylinder head. These components are greatly stressed by the thermal and mechanical loads arising from the compression. To ensure the defined requirements in respect of the compressed air outlet temperature at the connections of the compressor, effective cooling by a coolant is necessary. On the other hand, however, the compressor also requires a rigid structure with corresponding wall thicknesses. The dimensioning of the walls and the efficiency of the cooling contradict each other because of the heat-directing paths. Added to this are restrictions in the casting of the cylinder heads, making it difficult for narrow cooling cross sections to be formed by correspondingly delicate casting cores.
The current prior art for meeting the defined requirements, in particular for reducing the air outlet temperature of the compressed air on the pressure side, is distinguished by the integration of cooling ribs and/or an extension of the air-conducting regions. Both procedures are aimed at increasing the heat input areas.
During the compression of the air in the compressor, the air is greatly heated. This heating increases as the conveying pressure rises and as the speed of the compressor increases. This is disadvantageous in respect of the further processing of the compressed air, in particular for drying of the air. The air moisture is customarily extracted from the air in an air filter cartridge connected downstream of the compressor. The air filter cartridge contains a drying means which can extract moisture from the air only up to at maximum 80° C. Therefore, a lower maximally permissible temperature of 60° C. is normally stated in order to permit effective drying. However, during the compression in the compressor, the compressed air at the outlet opening of the piston chamber reaches temperatures of up to 320° C. It should still at maximum be 220° C. at the outlet of the compressor itself. This results in the necessity of having to cool the air between the compressor and the air filter cartridge. For this purpose, a pressure line of several meters in length is used in the prior art, wherein the heated compressed air can cool without further cooling measures as it flows through the pressure line from the compressor to the air filter cartridge. Disadvantages here include the pressure loss because of the long line and the structural outlay which the pressure line itself causes.
In order to be able to shorten the long pressure line between the compressor and the filter cartridge, the compressed air has to be cooled by active cooling. For this purpose, a “supercooling plate” through which a coolant flows and which acts as a heat exchanger is fitted into the cylinder head of the compressor above the valve plate. The supercooling plate makes it possible to reduce the outlet temperature of the compressed air to 140 to 150° C. at the compressor outlet and to shorten the adjoining pressure line by 5 to 30%. An example of such a supercooling plate can be found in DE 195 35 079 C2.
Disadvantages here include in particular the complicated construction which arises because of the integration of the supercooling plate as a separate component in the cylinder head of the compressor since additional seals are thereby necessary.
Furthermore, DE 10 2008 018 467 A1 discloses a valve plate with a coolant duct for a compressor. The coolant duct runs in a meandering manner, as seen from a piston chamber of the compressor, between the piston chamber and an air outlet valve arranged in the valve plate. The valve plate without a supercooling plate produces an at least identical cooling power in comparison to a combination of a conventional valve plate and a supercooling plate.
It is the object of the present invention to provide a cylinder head for a compressor that has an improved cooling power of the compressed air.
The object is achieved on the basis of a cylinder head according to embodiments of the invention.
According to the invention, the at least one air-discharging duct comprises an open-pore metallic cell structure. The open-pore metallic cell structure is at least partially adjacent to the at least one coolant-conducting region. In other words, the open-pore metallic cell structure is arranged on a wall of the at least one coolant-conducting region outside the at least one coolant-conducting region.
The open-pore metallic cell structure provides very good heat dissipation which is realized in the narrowest space by means of a surface involved in the heat transfer. Highly efficient cooling arises in particular by increasing the heat input areas of the air-conducting regions of the cylinder head. Furthermore, the open-pore metallic cell structure additionally produces a supporting structure which correspondingly improves the mechanical strength of the cylinder head, as a result of which a low wall thickness of a wall of the cylinder head with short heat-directing paths is realized. By means of the efficient cooling of the compressed air, the surface temperatures are lowered on the pressure side and the tendency to carbonization is thereby reduced. Furthermore, the open-core metallic cell structure equally produces the basis for catalytic reactions in order to optimize the quality of the compressed air. The metallic cell structure also has a damping inflow on the acoustic behavior.
The at least one air-discharging duct is preferably at least partially designed as an open-pore metallic cell structure. In other words, the at least one air-discharging duct can be partially, but also completely, designed as an open-pore metallic cell structure. The throughflow of the compressed air is made possible by means of the open pores. A dimension of the open-pore metallic cell structure should be set in accordance with the required throughflow rate and cooling rate of the compressed air.
The position, shape, orientation and size of the cells of the open-pore metallic cell structure are as desired and may be both regular and also random or irregular. For example, it is contemplated for the cells of the open-pore metallic cell structure to be of spherical, cylindrical or honeycomb-shaped design.
It is furthermore preferred that the open-pore metallic cell structure is produced by using inserts. The open-pore metallic cell structure is advantageously placed as a preshaped semi-finished product into a casting mold and insert molded to form the cylinder head. For example, a metal foam with closed pores can be used so that the insert-molding molten metal cannot penetrate. It is also possible to use a metal foam with unclosed pores, wherein then a certain infiltration of the cell structure by the cylinder head material arises.
A negative mold of the open-pore metallic cell structure is preferably placed into the casting mold in order to completely infiltrate the latter during the casting operation to form the open-pore cell structure and, at the same time, to cast the surrounding walls of the cylinder head. The pores should subsequently be exposed.
The invention includes the technical teaching that the open-pore metallic cell structure is produced by mechanical manufacturing. In other words, the open-pore metallic cell structure can be produced in particular by machining methods.
It is proposed that the open-pore metallic cell structure is produced by a lost foam method. In the lost foam method, subsequently removable, contacting cell bodies are placed into a mold, embedded and infiltrated. The cell bodies are then removed, for example, by gasifying.
Alternatively, during the production by the lost foam method, the walls of the cylinder head and the cellular structure can be produced in the lost foam method. The cellular structure is gasified here at the flow front of the molten metal during the casting. The remaining cell intermediate spaces, which were filled with sand prior to the casting, are exposed to form the open-pore structure.
The open-pore metallic cell structure is preferably produced by foaming. Aluminum alloys are in particular suitable for this purpose. Furthermore, aluminum has better heat conductivity and a lower density in comparison to steel. The use of the aluminum alloy can therefore both improve the cooling rate and reduce the weight of the cylinder head.
In terms of method, it is proposed that the cylinder head is cast as a thin wall casting, wherein, subsequently, an expandable metallic material is cast therein, said material being expanded to form the open-pore metallic cell structure.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.
According to
According to
The two air-conducting regions 4a, 4b comprise an air-supplying duct 5 for feeding the air to be compressed into the compressor 2 and an air-discharging duct 6 for letting out compressed air that has been compressed by the compressor 2. The air to be compressed is supplied by connections (not illustrated here) on the cylinder head 1 to the piston chamber 11. After the compression of the air in the piston chamber 11, the compressed air escapes via an outlet valve (not illustrated here) and is conducted via the air-discharging duct 6 to the connections on the cylinder head 1.
The air-discharging duct 6 includes an open-pore metallic cell structure 7 which is divided into six subsections 7a-7f. The open-pore metallic cell structure provides very good heat dissipation which is realized in the narrowest space by a surface involved in the heat transfer. Furthermore, the open-pore metallic cell structure 7 additionally results in a supporting structure which improves the mechanical strength of the cylinder head 1, as a result of which a low wall thickness of a wall of the cylinder head with short heat-directing paths is realized. In order to produce the cylinder head 1 with the open-pore metallic cell structure 7, the cylinder head 1 is cast as a thin wall casting, wherein, subsequently, an expandable metallic material is cast therein, said material being expanded to form the open-pore metallic cell structure 7.
Furthermore, the cylinder head 1 is suitable for a compressor 2 with an ESS (Energy Saving System). For this purpose, the cylinder head 1 has two openings 13a, 13b for an ESS piston (not illustrated here), and also a dead space volume 14 and a bore 15 for ESS activation. Furthermore, the cylinder head 1 has eight openings 12a-12h for cylinder head screws (not illustrated here).
The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2014 111 527.9 | Aug 2014 | DE | national |
This application is a continuation of PCT International Application No. PCT/EP2015/066375, filed Jul. 17, 2015, which claims priority under 35 U.S.C. §119 from German Patent Application No. 10 2014 111 527.9, filed Aug. 13, 2014, the entire disclosures of which are herein expressly incorporated by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2015/066375 | Jul 2015 | US |
| Child | 15431327 | US |
