Abstract:
A thermostatic valve in a cooling system in an internal combustion engine, with a common short-circuit element ( 21 ), comprising a section serving as a short circuit valve gate ( 26 ) and a short circuit valve disc ( 25 ), arranged upstream in the extending direction of the thermostatic working element ( 16 ), between which a common valve seat is provided, wherein an overpressure valve ( 32 ) opening into the mixing chamber ( 15 ) is provided in the common valve seat.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of German patent application 10 2006 025 065.6, filed May 23, 2006, herein incorporated by reference. 
       FIELD OF THE INVENTION 
       [0002]    The invention relates to a thermostatic valve for a cooling system of an internal combustion engine, having a thermostatic work element to be disposed in a mixing chamber, which work element acts as a drive element for a main valve element to be disposed between the mixing chamber and a connection from a coolant radiator and as a drive element for two short-circuit valve elements which are to be disposed upstream of the mixing chamber and are disposed relative to a valve seat such that upon an extension motion of the thermostatic work element, the initially closed first short-circuit valve element opens and the other closes upon a further extension motion. 
       BACKGROUND OF THE INVENTION 
       [0003]    A known thermostatic valve of the above type (German Patent Disclosure De 2755462 B1,  FIGS. 5-8 ) is used for engine inlet regulation. As short-circuit valve elements, it has two short-circuit valve plates, between which a valve seat is disposed. The two short-circuit valve plates are displaceable on a bolt and are loaded by compensation springs. In the cold state, one short-circuit valve plate closes the communication between the mixing chamber and the engine outlet, so that the engine warms up faster. When the thermostatic work element is extended because of the warming of the coolant, this valve plate opens, while the other short-circuit valve plate gradually closes in accordance with the extension motion of the short-circuit valve. 
       SUMMARY OF THE INVENTION 
       [0004]    It is the object of the invention to structurally simplify the thermostatic valve of the type defined at the outset and moreover to enhance its functional reliability. 
         [0005]    This object is attained in that a common short-circuit valve element is provided which has a portion acting as a short-circuit valve slide and a short-circuit valve plate located upstream in the extension direction, of the thermostatic work element, between which a common valve seat is provided; and that in the common valve seat, an overpressure valve that opens toward the mixing chamber is provided. 
         [0006]    By means of the common short-circuit valve element, the number of components can be reduced. Since one of the valve elements is embodied as a short-circuit valve slide, one spring can be dispensed with. It is moreover assured that whenever the engine rpm is elevated in the cold state, the thermal and/or mechanical damage to the internal combustion engine or its components ensues. It is for this purpose that the overpressure valve is provided, which at an elevated pressure opens the flow of the coolant from the engine outlet to the engine inlet. 
         [0007]    In one feature of the invention, it is provided that the common valve seat is formed by an annular component, which has a portion that is insertable in sealing fashion into an engine block or a cylinder head, and a radially inward-protruding annular rib, the inner edge of which acts as a valve seat for the short-circuit valve slide and as a valve seat for the short-circuit valve plate. It is thereby possible to embody the thermostatic valve as a prefabricated component, without having to contemplate machining operations on the internal combustion engine especially for the short-circuit valve, for instance for a support face for a spring. In a further feature of the invention, it is provided that the annular rib of the component is provided with openings, which are covered on the side of the mixing chamber with an overpressure valve ring that is loaded by an overpressure valve spring. 
         [0008]    In a further feature of the invention, it is provided that the overpressure valve spring is braced on the common short-circuit valve element. It is thereby possible to assign the overpressure valve an additional function, namely the function of a supplementary restoring spring, which is required when an idle distance is provided between the thermostatic work element and the main valve element. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    Further characteristics and advantages of the invention will become apparent from the ensuing description of the exemplary embodiment shown in the drawings. 
           [0010]      FIG. 1  shows an axial section through a thermostatic valve of the invention in the “cold” state; 
           [0011]      FIG. 2  shows the axial section through the thermostatic valve when the overpressure valve has responded; 
           [0012]      FIG. 3  shows the axial section through the thermostatic valve during the extension motion of the thermostatic work element; and 
           [0013]      FIG. 4  shows the axial section through the thermostatic valve when the thermostatic work element is extended. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0014]    The thermostatic valve shown in  FIGS. 1-4  has a lidlike upper valve part  10 , which is mounted on an engine block  11  or cylinder head indicated by dot-dash lines. The upper valve part  10  has a connection  12 , which leads to a coolant radiator, not shown. The engine block  11  or cylinder head has an opening  13 , which acts as an engine inlet, and an opening  14 , which communicates with the engine outlet (short-circuit circulation). 
         [0015]    Between the opening  14  for the engine outlet and the opening  13  for the engine inlet, a mixing chamber  15  is provided, into which a thermostatic work element  16  protrudes. The housing  17  of the thermostatic work element  16  is braced by the interposition of a plastic cap  18  in the upper valve part  10 . If the upper valve part  10  is made from plastic, then the plastic cap  18  can be integrated with the upper valve part. An expandable material, in particular a wax mixture, which changes its volume as a function of temperature is disposed in the housing  17  of the thermostatic work element  16 . Upon an increase in its volume, a work piston  19  is driven out of the housing  17  of the thermostatic work element  16 . Upon its extension motion, via a hat-shaped transmission part  20 , the work piston  19  slaves first a short-circuit valve element  21  and then a main valve plate  22  to its own motion. A valve seat of the upper valve part  10  is associated with the main valve plate  22 . The main valve plate  22  has a cagelike middle part  23 , which embraces the thermostatic work element  16  and whose bottom is associated with the transmission part  20 . A restoring spring or closing spring  24  is associated with the main valve plate  22 . 
         [0016]    The short-circuit valve element  21  has a short-circuit valve plate  25  and a portion that acts as a short-circuit valve slide  26 . The short-circuit valve plate  25  and the short-circuit valve slide  26  are spaced apart from one another in the extension direction of the thermostatic work element  16 . Between them is an annular groovelike recess  27 , in the region of which the short-circuit valve element  21  is provided with reinforcing ribs, which also serve the purpose of axial guidance when the short-circuit valve element  21  is in an open position ( FIG. 3 ). 
         [0017]    Between the short-circuit valve plate  25  and the short-circuit valve slide  26  is an annular component  28 , which is inserted in sealing fashion by a cylindrical portion into the engine block or cylinder head  11 . The annular component  28  further has an inward-protruding annular rib  29 , which acts as a valve seat for the short-circuit valve plate  26  and also as a valve slide seat for the short-circuit valve slide  26  of the short-circuit valve element  21 . The restoring spring or closing spring  24  is braced on the annular component  28 . The annular component  28  is retained on the upper valve part  10 . The upper valve part  10  is equipped with a plurality of prongs  30 , preferably three of them, from which the annular component  28  is suspended by similar prongs  31 . 
         [0018]    An overpressure valve  32  is integrated with the annular component  28 . To that end, the annular rib  29  of the annular component  28  is provided with a plurality of openings  36 , which are covered by means of an overpressure valve ring  33 . The overpressure valve ring  33  is provided with a plurality of pawls  34 , which protrude into the openings  36  in the annular rib  29  and serve to guide the overpressure valve ring  33 . The overpressure valve ring  33  is loaded by an overpressure valve spring  35 . This overpressure valve ring  35  is braced on the short-circuit valve element  21 . In the exemplary embodiment, it has latched into an annular groove of the short-circuit valve element  21 . 
         [0019]    The hat-shaped transmission part  20 , which is slipped onto the work piston  19 , penetrates the bottom of the middle part  23  of the main valve plate  22  and engages an internal recess in the short-circuit valve element  21 . Between the flangelike part of the transmission part  20  and the bottom of the middle part  23  of the main valve plate  22 , a spacing is provided, which dictates an idle distance over which the thermostatic work element  16  in an extension motion slaves initially only the short-circuit valve element  21  to its motion and then, only after the idle distance has been traversed, the main valve plate  22  as well. The overpressure valve spring  35  is embodied such that it also acts as a restoring spring, which causes the work piston  19  to be restored by the short-circuit valve element  21  to its outset position, or in other words, to the position in  FIG. 1 . 
         [0020]    When the internal combustion engine is cold, the communication from the radiator to the mixing chamber  15  via the connection  12  is closed by the main valve plate  22 . The communication from the connection  14  of the engine outlet to the mixing chamber  15  is closed as well. Thus a flow of coolant is largely suppressed, except for leakage flows, so that a rapid warmup of the engine and coolant ensues. 
         [0021]    If when the engine is cold and hence the radiator is cold as well, the engine is operated at elevated rpm, an overpressure occurs in the region of the connection  14  of the engine outlet. This overpressure causes the overpressure valve  32  to open; that is, the overpressure valve ring  33  lifts from the annular rib  29 , counter to the action of the overpressure valve spring  35 , and uncovers the openings  36 . The result is a flow of coolant from the connection  14  of the engine outlet to the connection  13  of the engine inlet, so that thermal and/or mechanical overloads on the engine, or components connected to it, are avoided. When the coolant temperature matches the response temperature of the thermostatic work element  16 , the latter&#39;s work piston  16  is extended. This work piston  19  initially slaves only the short-circuit valve element  21 , as is shown in  FIG. 3 . In the process, the short-circuit valve element  21  moves relative to the middle part  23  of the main valve plate  22 . Once the transmission part  20  has moved far enough that the idle distance to the bottom of the middle part  23  has been spanned, then in addition to the short-circuit valve, the main valve is opened as well; that is, the main valve plate  22  is lifted from the valve seat of the upper valve part  10 , as is shown in  FIG. 4 . After a certain distance, the short-circuit valve slide  26  of the short-circuit valve element  21  then closes the short-circuit valve, i.e., when it reaches the region of the valve seat formed by the annular rib  29 . 
         [0022]    In the exemplary embodiment shown, an electrically heatable thermostatic work element  16  is provided. In the interior of the stationary housing  17 , there is an electric heating element, to which electrical energy is supplied, in a manner not shown in further detail, through the bottom of the housing  17 . In a modified embodiment, it is provided that the thermostatic work element  16  is not electrically heatable. 
         [0023]    In another modified embodiment, it is provided that the thermostatic work element  16  is disposed rotated by 180°; that is, the work piston  19  is braced in stationary fashion, for instance on the upper valve part  10 , so that upon warming with an ensuing extension motion of the work piston  19 , the housing  17  is slaved. In that case, the main valve plate  22  and the short-circuit valve element  21  are mounted on the housing  17  of the thermostatic work element  16 . 
         [0024]    When the short-circuit valve slide  26  of the short-circuit valve element  21  is closed and the main valve plate  22  is open, it is possible, if the differential pressure between the connection  14  and the mixing chamber  15  is too high, for the overpressure valve ring  33  to be opened counter to the overpressure spring  35  and for the overpressure to be reduced. 
         [0025]    It is readily possible for the thermostatic valve shown in  FIGS. 1-4  to be used for engine outlet regulation as well. In that case, the connection  13  would be provided for the engine outlet, the connection  14  would be provided for the engine inlet, and the connection  12  would be provided for a communication with a coolant radiator. In that case, the overpressure valve  32  is nonfunctional, since at an elevated engine rpm with a cold engine, an overpressure would arise inside the mixing chamber  15  acting as a distributor chamber. However, then the short-circuit valve plate  25  of the short-circuit valve element  21  can cooperate with the short-circuit valve spring  35  as an overpressure valve. If the thermostatic valve is used for engine outlet regulation and there is an overpressure in the mixing chamber  15  acting as a distributor chamber, the position shown in  FIG. 3  would result. Since in the use for engine outlet regulation the overpressure valve ring  33  is superfluous, it is expedient to omit the overpressure valve ring  33  and to provide an annular component  28  that has a closed annular rib  29 . The overpressure spring  35  is then braced directly on the annular component  28 . 
         [0026]    In a modified embodiment, the thermostatic valve is embodied as a so-called housing thermostat. This thermostat has a two-part or multi-part housing, in which all the elements are accommodated and which is provided with hose connections for the engine outlet, the coolant radiator, and the engine inlet.