Abstract:
A combustion chamber subassembly for a vehicle heating device, includes a housing with a housing wall and a fuel feed through the housing wall, a fuel distribution element covering the housing wall on the side facing toward a combustion chamber and together with the housing wall bounding a fuel distribution channel arrangement, a plurality of fuel inlet apertures being formed in the fuel distribution element for conducting fuel from the fuel distribution channel arrangement toward the combustion chamber.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
         [0001]    Not applicable.  
         STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
         [0002]    Not applicable.  
         BACKGROUND OF THE INVENTION  
         [0003]    The present invention relates to a combustion chamber subassembly for a heating device, particularly a vehicle heating device, including a housing with a housing wall and a fuel supply through the housing wall.  
         PRIOR ART  
         [0004]    In fuel-operated vehicle heating devices, which are to be built in as auxiliary heating or as supplementary heaters in vehicles or trailers, the mounting position generally depends on the specific vehicle type. The heating performance should however remain constant, independent of the mounting position. In evaporative burners, in which the fuel is delivered into a combustion chamber via a porous medium, the problem exists that the introduction of the fuel into this porous evaporator medium can be impaired by changing the mounting position, since the fuel is generally distributed by gravity before introduction and after introduction into this porous medium. A very non-uniform distribution leads to a correspondingly non-uniform evaporation of fuel in the combustion chamber, which can have the consequences that the combustion taking place in the combustion chamber leads to an increased exhaust gas emission, that the starting process of such a combustion chamber is impaired, and that excessive accumulation of combustion residues in the combustion chamber occurs, which in extreme cases can lead to failure of the combustion chamber.  
         BRIEF SUMMARY OF THE INVENTION  
         [0005]    The present invention has as its object to provide a combustion chamber subassembly for a heating device, in particular for a vehicle, in which a fuel distribution substantially independent of the mounting position is provided for.  
           [0006]    According to the present invention, this object is attained by a combustion chamber subassembly for a heating device, in particular a vehicle heating device, including a housing with a housing wall and a fuel supply through the housing wall, a fuel distribution element covering the housing wall at the side toward the combustion chamber and, together with the housing wall, limiting a fuel distribution channel arrangement, a plurality of fuel inlet apertures being formed in the fuel distribution element for conducting fuel from the fuel distribution channel arrangement toward the combustion chamber.  
           [0007]    The fuel is thus not delivered directly from the fuel supply toward the combustion chamber, but instead there is a pre-distribution, which results in an evening out of the fuel introduction into the combustion chamber and thus a markedly improved independence on the mounting position. For example, it can be provided that a groove-like recess is formed for forming the fuel distribution channel arrangement in the housing wall.  
           [0008]    In order to ensure that the fuel forwarded by the fuel feed cannot directly then enter the combustion chamber through at least one of the fuel inlet apertures, it is proposed that the fuel feed includes at least one fuel feed aperture opening into the fuel distribution channel arrangement, and that the at least one fuel feed aperture is offset with respect to the fuel inlet apertures. Here at least one fuel feed aperture opens into the fuel distribution channel arrangement in the region between the fuel inlet apertures.  
           [0009]    As already mentioned hereinabove, in the arrangement according to the invention an evaporator medium is provided, receiving fuel from the fuel inlet aperture, on the side of the fuel distribution element facing toward the combustion chamber. This evaporator medium, in general thus a porous evaporator medium, can for example include nonwoven material, woven material, spun yarn, braided material, foamed ceramic material, or any material which because of its structural composition or its porosity can provide for the forwarding or distribution of fuel introduced into it.  
           [0010]    It can be provided that the housing is formed in a pot shape, with a floor and an annular peripheral wall, the fuel distribution element being annular and at least regionally covering the peripheral wall of the housing.  
           [0011]    To provide for a good mixing with combustion air of the evaporated fuel delivered into the combustion chamber, at least one combustion air inlet aperture is formed at a region of the peripheral wall not covered by the fuel distribution element.  
           [0012]    To further the evaporation of the fuel, which in particular improves the starting behavior at low environmental temperatures, the fuel distribution element forms or contains at least a portion of a heating arrangement.  
           [0013]    The invention furthermore relates to a vehicle heating device with a combustion chamber subassembly according to the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]    The present invention is described in detail hereinafter with reference to the accompanying drawings.  
         [0015]    [0015]FIG. 1 shows a longitudinal section of a combustion chamber subassembly according to the invention;  
         [0016]    [0016]FIG. 2 shows a sectional view of the combustion chamber subassembly of FIG. 1, sectioned along a line II-II in FIG. 1. 
     
    
     DETAILED DESCRIPTION OF INVENTION  
       [0017]    In the Figures, a combustion chamber subassembly according to the invention is denoted with the reference numeral  10 . The combustion chamber subassembly  10  comprises a housing  12 , which in general forms a wall  14  with a pot-like structure. This wall  14  includes a floor  16  and adjoining this a substantially cylindrical or else annular peripheral wall  18 . A likewise cylindrical or annular fuel distribution element  24  is arranged on an inner side  22  of the peripheral wall surrounding the combustion chamber  20 , abuts flush on the inner side  22  of the peripheral wall  18 , and in the example shown is positioned adjoining the floor  16 . An annular recess  26  is provided, for example by milling out, on the inner side  22  of the peripheral wall  18 , and forms a fuel distribution channel  18 . Fuel can be introduced into this annular recess  26  through a fuel feed aperture  28  in the peripheral wall  18  via a fuel feed duct (not shown). This recess  26  is closed radially inward with respect to a longitudinal axis L by the fuel distribution element  24 . However, fuel inlet apertures  30  are provided at plural peripheral positions in the fuel distribution element  24 . The fuel introduced into the recess  26  or into the fuel distribution channel can flow further through these fuel inlet apertures  30  toward the combustion chamber  20  after it has been distributed, with relatively low flow resistance, in the peripheral direction in this recess  26  around the longitudinal axis L. The fuel flowing through the fuel inlet apertures  30  then enters a porous evaporator medium  34  provided on the inner side  32  of the fuel distribution element  24 . This preferably covers the inner side  32  of the fuel distribution element  24  over the whole surface, i.e., it is likewise substantially of annular form and has the same axial extension length as the fuel distribution element  24 . By the prior evening out of the fuel introduction provided by the recess  26 , and furthermore by the distribution of the liquid fuel in the evaporator medium  34  by capillary action, a very uniform delivery of the fuel to the inner side  26  of the evaporator medium  34  in the direction toward the combustion chamber  20  is obtained.  
         [0018]    It can be seen in FIG. 2 that the fuel feed aperture  28  opens in the peripheral direction at a position in the recess  26  which is offset relative to the fuel inlet apertures  30 . Fuel is thereby prevented from entering directly from the fuel feed aperture  28  into one of the fuel inlet apertures  30  and then intensified there into the porous evaporator medium  34 .  
         [0019]    The combustion air is introduced in the example shown at two regions in the combustion chamber  20 . On the one hand, a combustion air inlet aperture  38  is provided in the central region of the floor  16 ; on the other hand, a plurality of combustion air inlet apertures  42  is provided, distributed in the peripheral direction in the region  40  of the peripheral wall  18  not covered by the fuel distribution element  24 , so that likewise a very uniform distribution of the combustion air into the combustion chamber  20  results. It should be mentioned that of course the combustion air can also be introduced into the combustion chamber  20  only in the region of the floor  16 , or else only in the region of the peripheral wall  18 .  
         [0020]    Furthermore an ignition member  44 , for example in the form of a glow ignition pin, is provided on the floor  16  and can provide the high temperatures required to start the combustion. This also can of course be provided at another position, for example, also on the peripheral wall  18  and projecting through the fuel distribution element  24  or the evaporator medium  34 .  
         [0021]    In order to be able to accelerate the evaporation of the fuel, particularly in the cold start phase in which the combustion chamber subassembly  10  is not yet preheated by the ongoing combustion, it is possible to keep a heating arrangement in readiness in the fuel distribution element  24 , for example in the form of a heating coil or the like, or to form the fuel distribution element  24  as a portion of such a heating device, so that by excitation of this electrically operable heating device, the porous evaporator medium  34  and thus also the liquid fuel contained therein are heated and thus the evaporation rate can be increased.  
         [0022]    It goes without saying that various modifications are possible to the combustion chamber subassembly  10  described hereinabove without departing from the principle of the present invention. Thus the recess  26 , instead of or additionally to being provided in the peripheral wall  18 , can also be provided on the outer peripheral side of the fuel distribution element  24 . Furthermore, it is possible that the recess  26  can have plural recess sections, in order to conduct the fuel into different peripheral regions or also axial regions in a defined manner. It is also possible to provide plural such annular recesses in axial succession and to supply these through a single or through respectively separate fuel feed apertures.  
         [0023]    The combustion chamber subassembly  10  shown in the Figures, or respectively a heating device having the same, is for example built in so that basically the fuel feed aperture is situated on the upper side. Even if such a mounting position is deviated for example in an angular range of 90° to one or other side, a very uniform distribution of the fuel is furthermore provided for by the provision of the recess  26  or the fuel inlet apertures  30 . This means that there is a great deal of freedom when installing such a device in a vehicle, without the mixture formation and thus the combustion being substantially impaired thereby. All of this can be attained by a very simple and thus also cost-effective construction.