Abstract:
A temperature-controlled fuel valve, especially for a fuel-operated heating burner of a vehicle heating system has at least one valve member ( 40 ) that is adjustable as a function of a temperature in the area of a heating burner ( 30 ).

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention pertains to a temperature-controlled fuel valve, which can be used especially in a fuel-operated heating burner of a vehicle heater.  
         BACKGROUND OF THE INVENTION  
         [0002]    In heaters used in vehicles, which may be operated, e.g., as parking heaters or auxiliary heaters, the fuel is taken up, in general, in a metering pump from a fuel tank via a suction line and is introduced by the metering pump under pressure into the combustion chamber of the heating burner via a pressure pipe. To ignite the fuel introduced into the combustion chamber, e.g., by evaporation or atomization together with the combustion air, which is likewise introduced, at the beginning of a phase of operation, e.g., an igniting member designed as a glow-type ignition pin is provided.  
           [0003]    The problem arises during the operation of such systems that fuel is still present in the line section between the metering pump and the combustion chamber on switching off, and this fuel still evaporates at least in the area of the pressure pipe close to the combustion chamber with the ignition stopped and thus leads to emissions that are potentially hazardous as to ones health. A generally asymmetric feed of the fuel into the combustion chamber during the operation leads to a combustion that is not distributed uniformly over the combustion chamber, as a consequence of which the combustion does not take place in the optimal lambda range in all areas of the combustion chamber, which may lead to the formation of deposits.  
         SUMMARY OF THE INVENTION  
         [0004]    The object of the present invention is to provide measures with which undesired emissions can be reduced and the quality of the combustion in a heating burner can be improved.  
           [0005]    This object is accomplished according to the present invention by a temperature-controlled fuel valve, especially for a fuel-operated heating burner of a vehicle heating system, comprising at least one valve member adjustable as a function of the temperature in the area of a heating burner.  
           [0006]    It can be ensured by the use of a temperature-controlled fuel valve that the introduction of fuel into a combustion chamber can take place as a function of the temperature and consequently also as a function of the combustion conditions. Due to the information feedback that is thus present, it is ensured that fuel can be sent into the correct area of a heater at a suitable time and in a suitable amount.  
           [0007]    Provisions may be made for this, e.g., for the fuel valve to have one feed area and two drain areas, and for the valve member to interrupt a connection between the feed area and the two drain areas at a temperature located in a first temperature range, for the valve member not to interrupt the connection between the feed area and the two drain areas at a temperature in a second temperature range that is higher than the first temperature range, and for the valve member not to interrupt the connection between the feed area and one of the drain areas and to interrupt the connection between the feed area and the other of the drain areas at a temperature in a third temperature range that is higher than the second temperature range.  
           [0008]    To make it possible to bring about the temperature-controlled switchover between different flow paths in a simple manner in the fuel valve according to the present invention, it is proposed that a first flow path area, which can be brought into connection with a feed area and which leads to a first drain area and to a second flow path area, be provided in a valve body, wherein the second flow path area leads to a second drain area. Furthermore, provisions may be preferably made for the valve member to close the first flow path area at a temperature in the first temperature range, to close the second flow path area at a temperature in the third temperature range, and not to close the first and second flow path areas at a temperature in the second temperature range.  
           [0009]    The defined switchover between different flow paths by the fuel valve according to the present invention may be achieved, e.g., by the valve member having a first valve member surface and a second valve member surface directed opposite the first valve member surface and by providing a first valve seat surface and a second valve seat surface in the valve body for the first valve member surface and for the second valve member surface, respectively, wherein the first flow path area opens into the first valve seat surface and the second flow path area opens into the second valve seat surface, wherein provisions may, furthermore, be preferably made for the second valve member surface not to be seated on the second valve seat surface when the first valve member surface is seated on the first valve seat surface.  
           [0010]    To detect the temperature and to actuate the valve member correspondingly, the fuel valve according to the present invention may have, furthermore, a temperature sensor arrangement with a temperature sensor medium with temperature-dependent volume as well as a transmission arrangement which can be displaced by a change in the temperature of the temperature sensor medium and which admits pressure to the valve member.  
           [0011]    The conversion of a change in the volume of the temperature sensor medium into a pressing movement for the valve member may be achieved, e.g., in a very simple manner by the transmission arrangement comprising a closing element that can be deformed by the change in the volume of the temperature sensor medium and a plunger that can be displaced by a deformation of the closing element.  
           [0012]    The present invention pertains, furthermore, to a heating system, especially for a vehicle, comprising a heating burner with a combustion chamber, a pump arrangement for delivering fuel to the combustion chamber, as well as a temperature-controlled fuel valve according to the present invention in the flow path between the pump arrangement and the combustion chamber.  
           [0013]    By integrating the fuel valve according to the present invention in the area between the metering pump and the heating burner, preferably as close to the heating burner as possible, it is ensured that the line path that cannot be closed any longer is kept as short as possible. The amount of the fuel that is not burned any more when the combustion is stopped and then tends to evaporate because of the still comparatively high temperatures can be markedly reduced in this manner.  
           [0014]    Furthermore, provisions may be made for arranging a temperature sensor arrangement of the fuel valve for detecting a temperature in the area of an igniting member of the heating burner or in the area of a waste gas stream.  
           [0015]    To ensure in the heating system according to the present invention that the fuel is introduced into the area that is optimal for different operating states and for the states of combustion occurring as a function of the temperature, it is proposed, furthermore, that fuel be able to be introduced into the combustion chamber in the area of the igniting member via a first drain area of the fuel valve and that fuel be able to be introduced into the combustion chamber in an area located farther away from the igniting member via a second drain area of the fuel valve.  
           [0016]    A further improvement in the quality of the combustion can be achieved by the second drain area providing a smaller flow resistance than the first drain area.  
           [0017]    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 drawings and descriptive matter in which a preferred embodiment of the invention is illustrated. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    In the drawings:  
         [0019]    [0019]FIG. 1 is a schematic view of a heating system according to the present invention with a temperature-controlled fuel valve;  
         [0020]    [0020]FIG. 2 is a longitudinal sectional view of the fuel valve;  
         [0021]    [0021]FIG. 3 is a cross-sectional view of the fuel valve shown in FIG. 2, cut along a line III-III in FIG. 2, wherein the fuel valve is in an operating state associated with a lower temperature;  
         [0022]    [0022]FIG. 4 is a view of the temperature-controlled fuel valve corresponding to FIG. 2 in a state that is associated with a higher temperature occurring during the phase of ignition; and  
         [0023]    [0023]FIG. 5 is another view of the temperature-controlled fuel valve corresponding to FIG. 2 in a state that is associated with a medium temperature occurring during the normal combustion. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0024]    Referring to the drawings in particular, a heating system according to the present invention is designated in general by  10  in FIG. 1. A fuel line  14  leads from a fuel tank  12  to a metering pump  16 , which may be of the conventional design. Another fuel line  18  leads from the metering pump  16  to a feed area  20  of a temperature-controlled fuel valve  22 . The fuel introduced under increased pressure into the fuel valve  22  via the line  18  can be introduced via a first drain area  24  and another fuel line  26  into a combustion chamber  28  of a heating burner  30  in an area that is located close to a glow-type ignition pin or another igniting member  31 . Furthermore, fuel can be introduced via a second drain area  32  and another line  34  from the fuel valve  22  into an area of the combustion chamber  28  that is located farther away from the glow-type ignition pin  31 . It shall be pointed out here that the heating burner  30  may be an atomization burner or a vaporizing burner. The fuel is released into the combustion chamber  28  accordingly by atomization or evaporation from a porous medium to form an ignitable mixture there with the combustion air that is likewise introduced into the combustion chamber  28 .  
         [0025]    Furthermore, a temperature sensor arrangement of the fuel valve  22 , which is designated generally by  36  and which detects a temperature in the combustion chamber  28  in the area of the glow-type ignition pin  31 , can be recognized in FIG. 1. Depending on the temperature, the fuel is released via the fuel valve  22  via both drain areas  24 ,  32 , via only one of the drain areas  24 ,  32  or via neither of the drain areas  24 ,  32 . This will be described in detail below with reference to FIGS. 2 through 5.  
         [0026]    The internal structure of the fuel valve  22  can be first recognized in FIG. 2. This fuel valve comprises a valve body  38 , in which a valve member or valve slide  40  is accommodated slidingly in the direction of a valve slide longitudinal axis L. An inlet opening  42  of the feed area  20  leads into a first valve chamber  44 . An outlet opening  48  of the first drain area  24  opens into a second valve chamber  46 , which follows the first valve chamber  44  in the direction of the longitudinal axis L. An outlet opening  52  of the second drain area  32  opens into a third valve chamber  50 , which follows the first valve chamber  44  in the direction of the longitudinal axis L and follows the second valve chamber  46 . A first flow path area  54  comprises a plurality of hole-like channels  56 , which extend essentially in the direction of the longitudinal axis L and establish a connection between the first valve chamber  44  and the second valve chamber  46 . It can be recognized in FIG. 3 that the channels  56  are arranged in a ring-like pattern around the valve slide  40 . A second flow path area  58  comprises a plurality of channels  60 , which, just like the channels  56  of the first flow path area  54 , are arranged in a ring-like pattern around the valve slide  40  and establish a connection between the second valve chamber  46  and the third valve chamber  50 .  
         [0027]    The channels  56  of the first flow path area open into the first valve chamber  44  in the area of a first valve seat surface  62 . This first valve seat surface  62  has an approximately truncated cone-like shape. In association with this first valve seat surface  62 , the valve slide  40  has a first valve slide surface  64  with a corresponding truncated cone shape.  
         [0028]    The channels  60  of the second flow path area  58  open into the third valve chamber  50  in the area of a second valve seat surface  66 , which likewise has an essentially truncated cone shape. In association with this second valve seat surface  66 , the valve slide  40  has a second valve slide surface  68 , which has a shape corresponding to that of the second valve seat surface  66  and therefore also has a truncated cone shape in the example being shown. It can be recognized that the first valve seat surface  64  and the second valve seat surface  68  are directed or oriented opposite each other.  
         [0029]    The valve slide  40  is pretensioned by a pretensioning spring  70  supported at the valve body  38  into a first operating position, in which the valve slide surface  64  is seated on the valve seat surface  62 , as can be recognized from FIG. 2, and thus closes the channels  56  of the first flow path area  54 . Because of the length of the valve slide  40 , the second valve slide surface  68  is lifted off from the second valve seat surface  66  in this first operating position.  
         [0030]    The temperature sensor arrangement already mentioned in reference to FIG. 1 has a chamber  72 . A medium with temperature-depending volume is accommodated in this chamber  72 . This may be, e.g., a gas-like medium. The chamber  72  is closed off at one end area by an elastic closing element  74  toward a channel area  76 . The closing element  74 , which is, e.g., a membrane, may be made of a rubber material or the like, so that an essentially tight closure of the chamber  72  is achieved at the same time by inserting this closing element  74  in a corresponding depression  78 . A plunger  80 , which forms essentially a transmission arrangement  82  together with the closing element  74 , is provided in the channel area  76 . As will be described below, temperature-determined volume changes of the medium contained in the chamber  72  are transmitted by this transmission arrangement  82  as adjusting movements to the valve slide  40 . The assembly group comprising the valve slide  40 , the plunger  80  and the elastic closing element  74  is held in an essentially rigid mutual contact during all phases of operation by the pressing action of the spring  70 , on the one hand, and, on the other hand, by the medium in the chamber  72 , which is, in general, under pressure.  
         [0031]    It shall be assumed at first that the heating system  10  is not in operation and that the medium contained in the chamber  72  and positioned in the area of the glow-type ignition pin  31  requires a relatively small volume. The valve slide  40  is moved by the pretensioning action of the spring  70  into its first operating position already described above, in which the feed area  20  has no connection with the two drain areas  24 ,  32  because of the closure of the first flow path area  54 . Thus, fuel cannot flow into the combustion chamber  28  via any of the feed areas. The line area in which fuel may still be present for a possible evaporation after the stopping of a combustion operation is limited essentially to the length of the two lines  26 ,  34 .  
         [0032]    If the heating system  10  is now put into operation, the glow-type ignition pin  31  is first heated. The temperature then rises sharply in the environment of the glow-type ignition pin  31 , as a consequence of which the medium contained in the chamber  72  seeks to enlarge its volume. The pressure in the chamber  72  will rise, and the elastic closing element  74  will undergo such a deformation under the effect of this pressure that it will protrude farther into the channel area  76 . As a consequence, the plunger  80  will be displaced as well. The plunger  80  now applies pressure on the valve slide  40 , which will now come to be seated with its second valve slide surface  68  at this comparatively high temperature on the second valve seat surface  66  in the area of the temperature sensor arrangement  36 , i.e., in the area of the glow-type ignition pin  31 . The first valve slide surface  64  is no longer seated on the first valve seat surface  62  in this second operating position of the fuel valve  22 , which is assumed during the ignition operation. The first flow path area  54  is thus released and there is now a connection between the first valve chamber  44  and the second valve chamber  46 . Since the second valve slide surface  68  is seated on the second valve seat surface  66 , the second flow path area  58  is now blocked, so that there is no connection between the second valve chamber  46  and the third valve chamber  50 . The fuel sent by the metering pump  16  to the fuel valve  22  will now flow into the second valve chamber  46  through the inlet opening  42  of the feed area  20 , the first valve chamber  44  and the channels  56  of the first flow path area  54  and it will be released herefrom via the outlet opening  48  of the first drain area  24  and the line  26  that can be recognized in FIG. 1 into the combustion chamber  28 . In this state, in which the ignition shall begin, the fuel is consequently introduced into the combustion chamber  28  into an area close to the glow-type ignition pin  31 , so that the combustion can start very rapidly.  
         [0033]    After the rated output has been essentially reached and the combustion has spread over a larger volume area or the entire volume area of the combustion chamber  28 , the power supply to the glow-type ignition pin  31  is stopped. The temperature in the area of this glow-type ignition pin  31  decreases again, but it remains higher because of the combustion taking place in the combustion chamber  28  than in a state in which the heating system  10  is fully out of operation. Because of the decrease in temperature in the area of the glow-type ignition pin  31 , the temperature of the medium enclosed in the chamber  72  will again decrease as well, which will lead to a corresponding decrease in the inner pressure in the chamber  72 . Due to the pretensioning action of the spring  70 , the valve slide  40  will now move because of the reduced pressure in the chamber  72 , together with the plunger  80 , from the second operating position shown in FIG. 4 into an operating position shown in FIG.  5 , in which there is a balance of forces between the force of the spring  70  and the pressing force of the medium enclosed in the chamber  72 . It can be recognized that due to the decrease in the pressure, the elastic closing element  74  has again moved farther out of the channel area  76 . In this third operating position, both valve slide surfaces  64 ,  68  are positioned at a spaced location from the respective associated valve seat surfaces  62 ,  66 . Both flow path areas  54 ,  58  are therefore released. The first valve chamber  44  is therefore in connection through the first flow path area  54  with the second valve chamber  46 , which is in turn in connection through the second flow path area  58  with the third valve chamber  50 . The fuel fed in under pressure through the inlet opening  42  of the feed area  20  will enter the second valve chamber  46  through the channels  56  of the first flow path area  54  after flowing through the first valve chamber  44 . The fuel will then flow off from there through the outlet opening  48  of the first drain area  24 , on the one hand, and, on the other hand, it will enter the third valve chamber  50  through the channels  60  of the second flow path area  58 , and it will flow off from the third valve chamber  50  through the outlet opening  52  of the second drain area  32 . Consequently, the fuel is introduced into the combustion chamber  28  in this normal state of combustion via both drain areas  24 ,  32  and consequently the two lines  26 ,  34  recognizable in FIG. 1. Better distribution of the fuel made available for the combustion is therefore already achieved due to the two introduction points. Furthermore, provisions may be made for the line  34  that is additionally used to introduce fuel in the normal combustion operation to lead into an area that is optimal for this normal combustion. It can also be recognized in the figures that the second drain area  32  has a larger flow cross section than the first drain area  24 . Due to the fact that the flow resistance is thus lower in the second drain area  32 , the larger portion of the fuel is introduced via the line  34  into the combustion chamber  28  during the normal combustion operation, which leads to a further improvement in combustion together with the selection of the area of introduction. It shall be pointed out here that the splitting of the two fuel streams may, of course, also be brought about by means of throttling points located in other areas. For example, the selection of the overall cross-sectional area of the channels  60  of the second flow path area  58  already has a certain throttling function. Throttling elements may also be provided in the lines  26 ,  34 , and these throttling elements, just as the throttling points provided in the valve body, are functionally to be associated with the respective drain areas  24  and  52  in the sense of the present invention, because they cause essentially that, depending on the setting of the throttling ratios, a larger amount of fuel will be discharged via one of the drain areas than via the other of the drain areas.  
         [0034]    It is consequently achieved by the use of the temperature-controlled fuel valve according to the present invention that the undesired evaporation of fuel that is no longer burned will decrease markedly when the combustion operation is stopped because of the reduction of the volume of the fuel available for the evaporation. Furthermore, the temperature-controlled fuel valve designed according to the present invention ensures that a temperature-adapted distribution of the fuel introduction can take place in all operating states, and it can be recognized in this connection, in particular, that a correspondingly continuous transition in the amounts of fuel introduced, which flow via both drain areas  24 ,  32 , is achieved at the time of the transition from the second operating position shown in FIG. 4, which is associated with the ignition operating, into the third operating position shown in FIG. 5, which is associated with the normal combustion operation, due to the gradual and non-abrupt displacement of the valve slide  40 , along with a correspondingly gradual change in temperature in the area of the glow-type ignition pin  31 .  
         [0035]    It shall finally also be pointed out that the fuel valve shown in the figures is represented in a simplified form. It is obviously possible for the valve body and the temperature sensor arrangement to be composed of more components. It is equally possible that, e.g., sealing members, e.g., fuel-resistant rubber seals, are present, e.g., at the valve slide in its surfaces that assume a sealing function. The positioning of the temperature sensor arrangement in association with the valve body is also only an example. It is obvious that another association of the positions, depending on the design of the heating burner, may also be provided, and it would also be possible to design the plunger  80  in the form of a bowden cable core. It would also be possible to transmit the pressure change of the medium present in the temperature sensor arrangement to the valve slide directly, i.e., without the intermediary of any mechanical components, and the valve slide would have a piston-like design in one end area in this case.  
         [0036]    While specific embodiments of the invention have 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.