Patent Application
20060185348
The present application claims priority under 35 U.S.C. §119 of Austrian Patent Application No. A 169/2005, filed on Feb. 2, 2005, the disclosure of which is expressly incorporated by reference herein in its entirety.
1. Field of the Invention
The invention relates to a device for purifying motor vehicle exhaust gases. The device includes a housing with an intake opening and an outlet opening, and at least one module for purifying exhaust gas arranged in the housing and connecting an exhaust gas inflow area and an exhaust gas outflow area.
2. Discussion of Background Information
Motor vehicle exhaust gases that are emitted unpurified or little purified from automobiles and commercial vehicles during their operation are considered to be one of the main causes of environmental pollution. Therefore, in many nations and regions, attempts are being made to combat this adverse pollution load on the environment that is on the rise. This is being accomplished statutory measures, for example by imposing maximum permissible pollutant levels for exhaust gases from motor vehicles.
Since the maximum pollutant levels for exhaust gases are regularly further lowered with new statutory measures or standards, there is a constant requirement on the part of automobile manufacturers to purify exhaust gases from motor vehicles better or more effectively. Intensive efforts are therefore being made to increase the efficiency of purification modules for motor vehicle exhaust gases.
The efforts have hitherto been directed at increasing an efficiency or purification effect of modules for purifying motor vehicle exhaust gases by improving a quality of the modules. This is accomplished, for example, by applying more effective catalysts for converting nitrogen oxides or by more effective particulate filters.
Modules for purifying motor vehicle exhaust gases are provided in the exhaust trains of motor vehicles. Particulate filters can be installed in the housings of rear mufflers that are easily accessible, providing a simple retrofit of motor vehicles supplied without particulate filters. Two problems are associated with such retrofits, however. First, installation space is limited for modules to be retrofitted. Second, it is not possible to install any desired number of modules one behind the other, because then such a high pressure is built up at the modules arranged between the exhaust gas inflow area and the exhaust gas outflow area that a motor performance decreases. To put it differently: an installation space and a reliable pressure difference between exhaust gas inflow area and exhaust gas outflow area are predetermined.
Recognizing these problems, the present invention relates to a device for purifying exhaust gasses from motor vehicles that provides a great volume of modules for purifying while taking into account installation space and reliable pressure difference.
This is attained with a device where the module(s) is/are arranged tilted towards a longitudinal axis of the housing. Advantageous embodiments of a device according to the invention are described.
An advantage achieved with the invention is that, even taking into consideration a reliable pressure difference between a tilted arrangement of the module(s) relative to a longitudinal axis of the housing, larger modules can be accommodated in the housing than with an arrangement perpendicular to the longitudinal axis. Module volume, or a catalytically effective or filter-active module surface, is thus maximized and utilization of a predetermined volume of the installation space is improved. The length of a flow path from exhaust gas inflow area to exhaust gas outflow area can be kept constant compared to an arrangement of the module(s) perpendicular to the longitudinal axis. Flow cross section is increased despite increased module volume. A reduction of pressure difference between an exhaust gas inflow area and outflow area occurs.
In a preferred embodiment, the module is tilted at a tilt angle of 15° to 75° relative to the longitudinal axis of the housing. In this range of tilt angle, an advantageously effective increase in the module surface can be achieved with good flow over the module front sides by exhaust gas.
In a preferred embodiment, the housing is essentially cylindrical. If the cylindrical housing has an intake opening on the front and an outlet opening on the end (for example, if the device is a muffler), then the module(s) can be arranged essentially over an entire length of the housing.
According to the invention, the module is made at least partially of metal foam. When exhaust gas flows through metal foam, due to a labyrinthine pore structure of the metal foam, a homogenization of the exhaust gas flow occurs over its cross section and any inhomogeneities can be offset. The invention provides modules with several connected lamellar filter and catalyst elements, with an element of a pure metal foam facing towards the exhaust gas inflow area. The metal foam preferably has a porosity of 80 to 98% and a pore size of 4 to 30 ppi (pores per inch). Downstream catalyst and/or filter elements of the module may include metal foam, or at least have such as a substrate for catalytically active substances. In this case, a well-balanced flow distribution and flow speed result in the module, and pressure and temperature inhomogeneities are effectively counteracted.
The module may comprise several filter elements and/or catalyst elements in order to purify as completely as possible the exhaust gas guided through the module.
One or several modules spaced apart from one another can be arranged in a device according to the invention in order to optimize an exhaust gas flow within the housing.
An advantageously large inflow surface for exhaust gas is given if, in a cross-sectional view, the module covers the entire cross section of the housing.
In an embodiment of the invention, the module is connected to the housing. For example, with corresponding sizing, the module can be clamped in the housing. This approach is suitable in particular for a retrofit of motor vehicles, because expenditure for retrofitting modules for purifying exhaust gases can be kept low. However, it is also possible to connect the module to the housing in another way, e.g., by metallic connection such as welding or soldering or indirectly by a swelling mat.
In another embodiment, the module is kept spaced apart from the housing by a gas-tight support element connected to the housing. The module penetrates the support element in order to provide a gas flow between exhaust gas inflow area and exhaust gas outflow area. In particular, when several modules are provided, a support element allows individual modules to be adjusted as needed and adapted in their alignment to the flow conditions within the housing or the device.
The support element is preferably a metal plate due to thermal and mechanical loadability of the support element and in order to keep the space necessary for the support element small.
The module(s) can be of any geometric shape. A cylindrical embodiment is preferable in terms of flow technology. An arrangement in the support element is then made such that the module penetrates the support element with a module longitudinal axis. Accordingly, the modules are encased in a gas-tight manner in some areas so that exhaust gas must flow through the module completely after entering the exhaust gas inflow area.
According to the invention, the support element is installed in the housing such that the exhaust gas inflow area is conically tapering in the direction from the inlet opening to the outlet opening. Through this geometric design, the flow conditions in a cylindrical housing are such that the exhaust gas inflow area has a large cross section area near the inlet opening where there are large exhaust gas volumes. Due to this tapering, the exhaust gas inflow area has a small cross section at a point where a small exhaust gas volume is given, because a large amount of the exhaust gas has already flowed into the module(s). The local volume conditions of the exhaust gas inflow area are thus adjusted in a targeted manner to the locally given exhaust gas volumes. As a result, all module areas or all modules are flowed over or loaded approximately equally and virtually the same pressure and temperature conditions are achieved in the entire module or the individual modules.
At least one flow guidance device (e.g., a baffle plate) can be provided in order to provide a uniform flow of exhaust gas over the module(s).
Further advantages and effects of the invention result from the context of the specification and the exemplary embodiments.
The present invention is directed to a device for purifying exhaust gases from motor vehicles that includes a housing including an intake opening, an outlet opening, an exhaust gas inflow area, an exhaust gas outflow area, and a longitudinal axis. At least one module for purifying exhaust gas is arranged in the housing and has a module axis. The at least one module connects the exhaust gas inflow area and the exhaust gas outflow area, and the module axis is tilted relative to the longitudinal axis of the housing.
According to a feature of the invention, the module axis can be tilted at an angle of 15° to 75° relative to the longitudinal axis of the housing.
In accordance with another feature of the present invention, the housing may be substantially cylindrical.
According to still another feature of the instant invention, the device can be a muffler.
Moreover, the at least one module can be at least partially made of metal foam.
Further, the at least one module may include at least one of: at least one filter element and at least one catalyst element.
According to another feature of the invention, the at least one module may include several modules that are spaced apart from one another.
In accordance with a feature of the invention, the at least one module can cover an entire cross section of the housing.
According to still another feature, the at least one module may be connected to the housing.
Further, a gas-tight support element may be connected to the housing to maintain the at least one module in a spaced apart relationship from the housing. The at least one module may penetrate the support element to allow the exhaust gas to flow between the exhaust gas inflow area and the exhaust gas outflow area. The support element may be a metal plate. Further, the at least one module can be substantially cylindrical and penetrate the support element with the module axis. The at least one module can include plural modules encased in a gas-tight manner in some areas. The support element may be connected to the housing such that the exhaust gas inflow area is substantially conically tapered in a direction from the intake opening to the outlet opening.
In accordance with still another feature, the device comprises at least one flow guidance device. The flow guidance device can include a baffle plate.
The present invention is directed to a method of purifying exhaust gases of motor vehicles. The method includes directing exhaust gas through an inlet opening of a housing, purifying the exhaust gas in at least one module arranged in the housing, in which the at least one module has a module axis tilted with respect to a longitudinal axis of the housing, and directing the exhaust gas through an outlet opening of the housing.
According to a feature of the invention, the module axis can be tilted at an angle of 15° to 75° relative to the longitudinal axis of the housing.
In accordance with still yet another feature of the present invention, a gas-tight support element can be connected to the housing to maintain the at least one module in a spaced apart relationship from the housing, and the at least one module can be supported to allow the exhaust gas to flow between the exhaust gas inflow area and the exhaust gas outflow area. The support element may be arranged in the housing to form a conically tapered exhaust gas inflow area.
Other exemplary embodiments and advantages of the present invention may be ascertained by reviewing the present disclosure and the accompanying drawings.
The present invention is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein:
The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the present invention. In this regard, no attempt is made to show structural details of the present invention in more detail than is necessary for the fundamental understanding of the present invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the present invention may be embodied in practice.
Exhaust gas enters through the inlet opening 3 into an exhaust gas inflow area 5 within the housing 2. The exhaust gas first flows over metal foam body 8 and then over the downstream elements of the module 7. The exhaust gas then reaches the exhaust gas outflow area 6 and subsequently exits, purified, through the outlet opening 4.
A pressure difference between exhaust gas inflow area 5 and exhaust gas outflow area 6 is determined by the length of a minimal flow path L for the exhaust gas through the connected elements of the module 7. Compared to a conventional arrangement where modules are arranged with a module axis that is parallel to the housing axis, the tilted arrangement of the invention provides that the length of a minimal flow path L can be kept the same with simultaneous enlargement of a gas entry surface 14 and with an increase of a module volume. That is why both an improved purification effect and a low pressure difference between exhaust gas inflow area 5 and exhaust gas outflow area 6 can be achieved with a device 1 according to the invention.
The exhaust gas flow is shown in more detail in
Still referring to
According to another exemplary embodiment of the invention, the support element 11 and the modules 7 installed therein can be arranged to form a centrosymmetrical formation, which eliminates the danger of an incorrect or inverted installation of a prefabricated combination of support element 11 and modules 7.
The catalyst or filter elements shown in
It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to an exemplary embodiment, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| A 169/2005 | Feb 2005 | AT | national |
