Abstract:
A burner system, especially for a vehicle heater, includes a fuel atomizer arrangement ( 20 ) for feeding fuel into a combustion chamber, a fuel pump arrangement ( 16 ) for feeding fuel, which is under pressure, to the fuel atomizer arrangement ( 20 ), as well as a pressure regulator arrangement ( 26 ) for setting the fuel pressure in a fuel line area ( 18 ) leading from the fuel pump arrangement ( 16 ) to the fuel atomizer arrangement ( 20 ). The pressure regulator arrangement ( 26 ) has a plurality of pressure regulator units ( 28, 30 ), and wherein at least some ( 28 ) of the pressure regulator units ( 28, 30 ) can be activated and deactivated to change the pressure regulation characteristic of the pressure regulator arrangement ( 26 ).

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention pertains to a burner system, especially for a vehicle heater, comprising a fuel atomization arrangement for feeding fuel into a combustion chamber, a fuel pump arrangement for feeding fuel that is under pressure to the fuel atomization arrangement, as well as a pressure regulating arrangement for setting the fuel pressure in a fuel line area leading from the fuel pump arrangement to the fuel atomization arrangement.  
         BACKGROUND OF THE INVENTION  
         [0002]    Such systems, which are generally also called atomization burner systems, are used, e.g., in vehicles as parking heaters or as auxiliary heaters. The fuel, which is under pressure, is fed into the combustion space by the fuel atomization arrangement in the atomized form, i.e., in a form divided into very fine particles, and is burned there together with the combustion air, which is likewise fed into the combustion space. The amount of the fuel fed in, which is to be burned, and the amount of the combustion air to be burned therewith are set as a function of the required heat output. If, e.g., comparatively low outside temperatures prevail and a vehicle is to be started under these conditions, both the air present in the interior space of the vehicle and the drive unit and the cooling medium for same are comparatively cold. To heat up these two areas of the system as rapidly as possible, a heating means must consequently be operated in this state with a comparatively high heat output. Such a high heat output is no longer necessary at higher outside temperatures or after sufficient heating of various areas of the system.  
           [0003]    It is known that the pressure regulator arrangement is set in such burner systems such that the fuel pressure set by the pressure regulator arrangement forms a certain compromise for the required heat output range. The heat output can then be set per se more or less accurately by the cyclic operation of the burner system. At low heat requirement, i.e., e.g., at higher outside temperatures or after sufficient heating of a system to be heated, this causes that the burner system is switched off and on again comparatively frequently, with the associated drawback of comparatively high pollutant emissions. A longer uninterrupted burner operation is desired at least during the start-up phase of the combustion to reduce the pollutant emission.  
         SUMMARY OF THE INVENTION  
         [0004]    The object of the present invention is to provide a burner system, especially for a vehicle heater, in which the heat output can be adapted to the actually required heat output in a simple manner without generating the risk for a high pollutant emission.  
           [0005]    This object is accomplished according to the present invention by a burner system, especially for a vehicle heater, comprising a fuel atomization arrangement for feeding fuel into a combustion chamber, a fuel pump arrangement for feeding fuel, which is under pressure, to the fuel atomization arrangement, as well as a pressure regulator arrangement for setting the fuel pressure in a fuel line area leading from the fuel pump arrangement to the fuel atomization arrangement, wherein the pressure regulating arrangement has a plurality of pressure regulator units and wherein at least some of the pressure regulator units can be activated and deactivated to change the pressure regulation characteristic of the pressure regulator arrangement.  
           [0006]    It is elementary in the present invention that the change in the heat output of a burner system can be brought about not by changing the cyclic operation or not only by changing the cyclic operation, but by the fact that a change can be brought about in the pressure of the fuel being fed to the fuel atomization arrangement actively and, e.g., as a function of the required heat output. A lower fuel pressure leads to a correspondingly small amount of feed, as a result of which the heat output made available is reduced at the same time while the burner operation proceeds continuously. An increased fuel pressure correspondingly leads to a larger amount of fuel fed in and consequently to a higher heat output made available. It is apparent that the amount of the combustion air fed into the combustion chamber can also be adapted for adaptation to a change in the pressure or for adaption to the change in the amount of fuel fed in, in order, to make it possible to keep the fuel emission as low as possible during the combustion taking place in the combustion chamber.  
           [0007]    For example, the change in the pressure conditions and consequently the change in the amount of fuel fed in can be varied in the burner system according to the present invention by at least two pressure regulator units having different pressure regulation characteristics in relation to one another. Furthermore, it is possible, e.g., for at least two pressure regulator units to be connected in parallel to one another in terms of function and for a pressure connection between at least one of the pressure regulator units and the fuel line area to be able to be interrupted.  
           [0008]    To make it possible to adjust the fuel pressure to certain values by means of the pressure regulator units, it is proposed that at least one of the pressure regulator units be designed to change a connection between the fuel line area and the fuel drain area as a function of the pressure prevailing in the fuel line area. According to an advantageous embodiment of the present invention, provisions may be made in the burner system for at least one of the pressure regulator units to have a pressure regulator member that can be displaced against the action of a resetting arrangement corresponding to the fuel pressure in the fuel line area, wherein a fuel drain throttling action of the pressure regulator unit can be varied by displacing the pressure regulator member. This may be achieved, e.g., such that an effective flow cross section of a fuel drain opening arrangement of the pressure regulator unit can be varied by displacing the pressure regulator member.  
           [0009]    A pressure regulator unit that can be used in a burner system according to the present invention may be designed, e.g., such that the pressure regulator member comprises a piston element, by the resetting arrangement comprising a pretensioning spring, against the action, of the force of which the piston element can be displaced in a working space formed in a cylinder element, wherein the working space is in connection or can be brought into connection with the fuel line area via a fuel inlet opening arrangement by admitting fuel pressure, and a fuel drain opening arrangement, which can be closed at least partially by the piston element as a function of the positioning of the piston in the cylinder element, is in connection or can be brought into connection with a fuel drain area.  
           [0010]    To make it possible, e.g., to set or preset a certain pressure regulation characteristic at the time of or before putting in operation of the system initially, it is proposed that the resetting characteristic of the resetting arrangement be able to be changed by at least one of the pressure regulator units.  
           [0011]    The activation or deactivation of the various pressure regulator units provided in the arrangement according to the present invention may be brought about, e.g., by correspondingly actuating a valve arrangement.  
           [0012]    The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawing and descriptive matter in which a preferred embodiment of the invention is illustrated.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0013]    The only FIGURE is a schematic view of a burner system according to the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0014]    Referring to the drawing in particular, the attached FIGURE shows a schematic view of a burner system according to the present invention with two pressure regulator units.  
         [0015]    The burner system  10 , as is schematically shown in the FIGURE, comprises a line section  12 , which leads from a fuel reservoir  14  to a fuel pump  16 . A fuel line area  18  leads from the fuel pump  16  to an atomizing nozzle  20 , via which the fuel is fed into a combustion chamber, not shown, in the form of a fuel mist  22  indicated. The amount of fuel fed in depends, among other things, on the fuel pressure prevailing in the line area  18 , so that, as will be described below, the amount of fuel fed into the combustion chamber can be influenced by varying the fuel pressure prevailing in the line area  18  in a simple manner. For example, fuel feed to the atomizing nozzle  20  can be interrupted by a valve arrangement  24 , which can be actuated, e.g., magnetically. The fuel feed may, of course, be brought about via a plurality of atomizing nozzles  20  connected in parallel.  
         [0016]    The burner system  10  shown in the FIGURE comprises, furthermore, a pressure regulator arrangement, which is generally designated by  26 . This in turn has two pressure regulator units  28 ,  30 , which are identical, in principle, but do not necessarily have the same design. The pressure regulator unit  30  is in connection with the line area  18  via a branch line  32 . Another branch line  34  leads from the branch line  32  to the pressure regulator unit  28 , so that this pressure regulator unit  28  is also in connection or can be brought into connection with the line area  18  via the branch lines  34 ,  32 . A valve arrangement  36 , which can, e.g., likewise be actuated magnetically, is provided in the branch line  34 , so that the connection of the pressure regulator unit  28  with the branch line  32  and consequently with the line area  18  can be interrupted or established as described by actuating this valve arrangement  36 . It shall be pointed out here that, e.g., the branch line  34  could also open directly into the line area  18 .  
         [0017]    The general design of the pressure regulator units  28 ,  30  and the general mode of action of these pressure regulator units will be described below. Since, as was mentioned, these two pressure regulator units  28 ,  30  may have the same design, reference will hereinafter be made to the pressure regulator unit  30 . This will, of course, also apply to the pressure regulator unit  28 .  
         [0018]    The pressure regulator unit  30  comprises a cylinder housing  38 , in which a cylindrical work space  40  is formed. A piston element  42  forming a pressure regulator member is displaceably accommodated in the working space  40 . The piston element  42  may be sealed with respect to the cylinder housing  38  by an O ring-like sealing element or the like.  
         [0019]    A pretensioning spring  46 , which is designed, e.g., as a compression coil spring, is supported at an abutment element  44 , and the other end of the said pretensioning spring is supported at the piston element  42 . The piston element  42  is pretensioned by the pretensioning spring  46  in the direction of a bottom area  48  of the working space  40 . The branch line  32  opens into this bottom area  48  in the area of a fuel inlet opening  50 . Consequently, the working space  40  is in pressure connection with the line area  18 , as a consequence of which the pressure prevailing in the branch line  32 , which essentially also corresponds to the pressure prevailing in the line area  18 , is admitted to the piston element  42  against the pretensioning action of the pretensioning spring  46 . Thus, due to the two forces acting on the piston element  42 , an equilibrium position of the piston element  42  will become established in the cylinder housing  38  depending on the fuel pressure prevailing in the line area  18 .  
         [0020]    A fuel drain area  54  is in connection with the working space  40  via a drain opening  52 . The fuel drain line area  54  leads to the fuel reservoir  14 . Since the fuel inlet opening  50  and the fuel drain opening  52  or the branch line  32  and the fuel drain area  54  thus are or can be in connection via the working space  40 , part of the fuel fed by the fuel pump  16  into the line area  18  will return to the fuel reservoir  14  via this line connection.  
         [0021]    Consequently, fuel is fed into the line area  18  by the fuel pump  16 , which is operated, e.g., such that it feeds fuel into the line area  18  with a preset, e.g., maximum delivery capacity. Since the atomizing nozzle  20  generates a considerable throttling action, a certain fuel pressure will become established in the line area  18  and consequently also in the branch line  32 . This fuel is admitted via the above-described line connection to the piston element  42  against the pretensioning action of the pretensioning spring  46 . The action of the pretensioning spring  46  is set, e.g., such that the piston element  42  closes the drain opening  52 , doing so, e.g., completely, when the fuel pressure in the line area  18  is below a certain threshold value. The line connection between the branch line  32  and the fuel drain line area  34  is now interrupted, except for a possibly present bypass line  56 , which makes possible a permanent draining. When the fuel pump  16  is put into operation, a fuel pressure will consequently build up in the line area  18 , so that the piston element  42  is displaced against the pretensioning force of the pretensioning spring  46  by the fuel pressure building up and it gradually opens the fuel drain opening  52 . The throttling action prevailing in the area of this opening is changed or reduced by this gradual opening of the fuel drain opening  52 , so that an increasing percentage of fuel can flow back into the fuel reservoir with increasing fuel pressure. A pressure-dependent state of equilibrium will become established, so that variations in pressure in the line area  18 , which may possibly also be caused by variations in the operation of the fuel pump  16 , can be essentially suppressed. This state of equilibrium can be influenced by the pretensioning action of the pretensioning spring  46 . For example, a screw-like adjusting element  58  is associated with this pretensioning spring, so that the pretensioning action of the pretensioning spring  46  and consequently the pressure regulation characteristic of the pressure regulator unit can be affected by displacing the abutment element  44 . This pretensioning action or the pressure regulation characteristic resulting therefrom is set once at the time of or before the putting into operation of the burner system  10  and is then left essentially unchanged in the example being shown.  
         [0022]    To nevertheless achieve a change in the pressure in the line area  18  and consequently a change in the amount of fuel fed in with pressure regulation characteristics that are essentially preset in the individual pressure regulator units  28 ,  30 , the pressure regulator unit  28  can be connected in parallel with the pressure regulator unit  30  by the corresponding switching of the valve arrangement  36 , depending on the required heat output or depending on the required fuel pressure. Provisions may, furthermore, be made for the two pressure regulator units  28 ,  30  to have different pressure regulation characteristics. For example, provisions may be made for the pretensioning spring  46  of the pressure regulator unit  28  to provide a weaker pretensioning force, so that a lower fuel pressure is sufficient to displace the piston element  42  of the pressure regulator unit  28  such that fuel can flow back into the fuel reservoir  14  via the fuel drain opening  52  of the pressure regulator unit  28 . This results in such an operating characteristic that if the required heat output is at first high, the valve arrangement  36  is set such that the pressure connection between the pressure regulator arrangement  28  and the line area  18  is interrupted. The fuel pressure will therefore become established at a higher level according to the pressure regulation characteristic of the pressure regulator unit  30 . If such a high burner output is not necessary any longer, a connection is established between the working space  40  of the pressure regulator unit  28  and the line area  18  by actuating the valve arrangement  36 . The two working spaces  40  of the pressure regulator units  28 ,  30  are thus connected in parallel in terms of function. However, since the pretensioning spring  46  of the pressure regulator unit  28  offers a weaker opposing force than the pretensioning spring  46  of the pressure regulator unit  30 , the piston element  46  of the pressure regulator unit  28  is displaced farther by the now prevailing fuel pressure, so that the pressure regulator unit  28  generates a weaker throttling action, and a larger amount of fuel will flow back to the fuel reservoir  14  via the pressure regulator unit  28 . This leads to a pressure drop in the line area  18  and also in the branch line  32 , so that, e.g., the piston element  42  of the pressure regulator unit  30  is again displaced such that it will cover the corresponding fuel drain opening  52  essentially completely. The fuel draining or the setting of the pressure in the line area  18  is then set essentially on the basis of the pressure regulation characteristic of the pressure regulator unit  28 . This will then result, corresponding to the pretensioning action of the pretensioning spring  46  of the pressure regulator unit  28 , in a lower pressure in the line area  18 , so that a smaller amount of the liquid fuel being fed by the fuel pump  16  will also be fed into the combustion chamber via the atomizing nozzle  20 . To ensure in the process that the combustion takes place in the combustion chamber at the correct fuel-to-air ratio, the feed of the combustion air to the combustion chamber can also be influenced for adaptation to the changed pressure conditions in the line area  18 . Provisions may be made for this purpose, e.g., for operating a combustion air fan at a higher or lower speed, depending on the state of switching of the valve arrangement  36 , when more or less fuel is being atomized. The combustion air fan is driven in this embodiment by the same drive motor as the fuel pump  16 . Since, as was already described above, the fuel pump  16  is operated, in principle, such that it operates at the maximum delivery capacity, an increase in the speed of the drive motor to increase the speed of the combustion air fan will not bring about essentially any change in the delivery capacity and consequently any change in the pressure conditions.  
         [0023]    The valve unit  36  and optionally also the motor for the combustion air fan may be controlled via a control device, in which temperature values are stored as threshold values for switching the pressure regulator unit  28  on and off, and these threshold values are then compared with temperature values that are supplied by temperature sensors. These sensors may in turn detect, e.g., the temperature of the medium to be heated, e.g., in a water circuit.  
         [0024]    It shall be pointed out that various variations may be made in the burner system shown in the FIGURE. For example, more than two pressure regulator units may be provided for setting the pressure conditions more accurately, and these pressure regulator units may have different regulation characteristics in relation to one another. Furthermore, the pressure regulation characteristics of the various pressure regulator units may be coordinated with one another such that depending on the activation or deactivation of such a pressure regulator unit or of a plurality of such pressure regulator units, fuel draining will take place not only via the pressure regulator unit whose regulation characteristic presets the fuel pressure, but at least small amounts of fuel can also drain off via other pressure regulator units. Furthermore, it is, of course, possible for a valve arrangement to be assigned to each pressure regulator unit, so that one pressure regulator unit can be switched on and another one can be switched off in a defined manner by correspondingly actuating the different valve arrangements.  
         [0025]    While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.