Abstract:
A valve device for an internal combustion engine includes a housing with an inlet and an outlet, a passage opening which fluidically connects the inlet with the outlet, a first valve-closing member which controls the passage opening, an actuator, a valve rod on which the first valve-closing member is arranged, a stop element, a spring surrounding the valve rod, and an element. A first end of the spring is supported against the first valve-closing member, and a second end of the spring is supported against the stop element. The element substantially surrounds the spring. The element comprises a first lateral surface and a second lateral surface in mutual engagement with each other. The first lateral surface abuts against the first valve-closing member and is movable therewith. The second lateral surface abuts against the stop element. The first valve closing member moves relative to the stop element.

Description:
CROSS REFERENCE TO PRIOR APPLICATIONS 
     This application is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/EP2012/057777, filed on Apr. 27, 2012 and which claims benefit to German Patent Application No. 10 2011 050 263.7, filed on May 11, 2011. The International Application was published in German on Nov. 15, 2012 as WO 2012/152601 A1 under PCT Article 21(2). 
     FIELD 
     The present invention relates to a valve device for internal combustion engines which comprises a housing with at least one inlet and one outlet formed therein, at least one passage opening via which the at least one inlet can be fluidically connected to the at least one outlet, at least one valve-closing member by means of which the passage opening can be controlled, a valve rod which can be translationally moved by means of an actuator and on which the at least one valve-closing member is arranged, a spring that surrounds the valve rod and is supported with its first end against the at least one valve-closing member and with its opposite end against a stop element, and a protective element that substantially surrounds said spring. 
     BACKGROUND 
     Such valve devices are used, for example, for controlling a recirculated exhaust gas flow in an internal combustion engine for the purpose of reducing pollutants in the exhaust gas. The spring element provides that the valve-closing member is pressed on the corresponding valve seat. Depending on the installation site of the exhaust gas recirculation valve immediately behind the exhaust gas outlet of the cylinder or in the region of the intake pipe, in the low-pressure line or the high-pressure line, upstream or downstream of an exhaust gas cooler, the exhaust gas recirculation valve is exposed to different loads. A high thermal load, for example, exists in the immediate vicinity of the exhaust gas outlet of the cylinder, whereas a rather strong sooting tendency can be expected downstream of an exhaust gas cooler. 
     Two-way valves are also known via which a controlled exhaust gas flow can be directed selectively through an exhaust gas cooler or a bypass duct so that a valve situated downstream of the exhaust gas cooler is sometimes exposed to hot exhaust gas and sometimes to cold exhaust gas, depending on the exhaust gas recirculation line used. 
     A valve of this type is described, for example, in DE 197 33 964 A1. This valve is arranged downstream of an exhaust gas cooler or a bypass duct and comprises an actuator by which a valve rod can be displaced on which two valve-closing members are slidably arranged. A spring is disposed between the valve-closing members, by which the valve-closing members are biased against stops formed on the valve rod. Both valve-closing members are conical in shape and, in the non-actuated state, are caused by the spring pressure to contact corresponding valve seats. When the actuator is actuated, one of the valve-closing members, depending on the direction, is lifted from the valve seat by the stop against the spring force, whereas the other valve-closing member is still pressed against the valve seat by the spring force. It is thus possible to selectively control the flow-through section of the bypass duct or of the exhaust gas cooler outlet, depending on the direction of actuation. However, the spring disposed centrally in the flow-through region is exposed to high thermal loads and to occurring soiling. 
     EP 1 859 156 B1 describes a valve device wherein the spring of a correspondingly designed valve is surrounded by a compensation element in the form of a bellows, the axial ends of which are connected with the valve plates. This element is intended to generate a vacuum in the space enclosed thereby so that both valve plates can be lifted from their valve seats at the same time. The bellows may protect the spring and the valve rod area against soiling, however, it no longer functions under high thermal loads. 
     SUMMARY 
     An aspect of the present invention is to provide a valve device which operates without malfunction both under high thermal loads and in a sooty environment. Depositions on the valve rod, for example, in regions serving for slidable guiding, are to be avoided as are excessive thermal loads on the spring. 
     In an embodiment, the present invention provides a valve device for an internal combustion engine which includes a housing comprising at least one inlet and an outlet, at least one passage opening configured to fluidically connect the at least one inlet with the at least one outlet, a first valve-closing member configured to control the at least one passage opening, an actuator, a valve rod on which the first valve-closing member is arranged, a stop element, a spring surrounding the valve rod, and an element. The valve rod is configured so as to be translationally movable by the actuator. A first end of the spring is supported against the first valve-closing member, and a second end of the spring is supported against the stop element. The element is configured to substantially surround the spring. The element comprises a first lateral surface and a second lateral surface which are configured to be in mutual engagement with each other. The first lateral surface is arranged to abut against the first valve-closing member and is configured to be movable therewith. The second lateral surface is arranged to abut against the stop element. The first valve closing member is configured to move relative to the stop element. Owing to the fact that the element is substantially formed by two radially closed lateral surfaces in mutual engagement, the valve rod and the spring are shielded from the exhaust gas flow, with the first surface contacting the at least one valve-closing member and being movable together with the same, and the second surface contacting the stop element, while the valve-closing member is movable with respect to the stop element. A direct flow is omitted, resulting in thermal relief and reduced soiling. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is described in greater detail below on the basis of embodiments and of the drawing in which: 
         FIG. 1  shows a side elevational view of a valve device of the present invention illustrated in section. 
     
    
    
     DETAILED DESCRIPTION 
     In an embodiment of the present invention, one of the interengaging radially closed lateral surfaces can, for example, be arranged in the other lateral surface, with the inner diameter of the one lateral surface being larger than the outer diameter of the other lateral surface. In this manner, a jamming of the two lateral surfaces is avoided. A good sealing effect is nevertheless achieved between the two protective elements, whereby the intrusion of dirt particles is significantly reduced. 
     In an embodiment of the present invention, the interengaging radially closed lateral surfaces can, for example, be formed by pot-shape components, the valve rod extending through the bottoms thereof. This facilitates the fastening of the protective elements. 
     In an embodiment of the present invention, the pot-shaped components are deep-drawn parts. These can be produced in a particularly economic manner. 
     In an embodiment of the present invention, the spring can, for example, press the bottoms of the pot-shaped components against the stop element on the first side and, on the opposite side, against the valve-closing member. The pot-shaped components can thus be maintained in their positions without establishing a material connection with the valve-closing element or having to use additional fastening means. 
     In an embodiment of the present invention, the valve-closing member can, for example, be disposed on the valve rod for translational movement and can, for example, be biased by the spring towards a stop connected with the valve rod. A secure seating of the valve-closing member on the valve seat can thereby be provided in the closed state. 
     In an embodiment of the present invention, the valve rod can, for example, have an end provided with an outer thread onto which a nut is threaded that serves as a stop. This screw allows the position of the valve-closing member on the valve rod to change so that the stop can be positioned in an optimal manner relative to the position of the valve seat. 
     In an embodiment of the present invention, a second valve-closing member can, for example, be arranged on the valve rod at a distance from the first valve-closing member, the second valve-closing member serving as a stop element for the spring and enabling the control of a second passage opening that leads to a second inlet or outlet. In this manner, a combined exhaust gas recirculation and bypass valve can be provided, whose passages can be controlled selectively. 
     Both valve-closing members can have recesses of a shape corresponding to that of the bottoms of the pot-shaped components and into which the pot-shaped components extend. A simple positioning and pre-fixation of the protective elements on the valve-closing members is thereby achieved during assembly. A tilting of the protective elements is reliably avoided. 
     Both valve-closing members can further be provided with annular protrusions extending into the interior of the spring, whereby a kinking of the spring is avoided. These protrusions form an elongated guiding portion. 
     In an embodiment of the present invention, both valve-closing members are arranged on the valve rod for translational movement and are biased by the spring between the two valve-closing members in respectively opposite directions towards stops formed on the valve rod on the side of the two valve-closing members opposite the spring. A selective control of the flow-through sections is thus achieved, with the respective closed duct being closed tightly. A relatively high tightness between the interior of the protective elements and the outer space is further provided. The valve-closing members are moreover biased towards their associated valve seats by the spring. 
     Such a valve device can be subjected to high thermal loads and can therefore be arranged just behind the exhaust gas outlet, since the heat is dissipated via the lateral surfaces. A particle-loaded environment does not limit functionality, since the valve rod, on which the valve-closing members have to slide, does not contact the loaded environment. A valve device is thus provided that has a long service life under adverse environmental influences. 
     An embodiment of the present invention is illustrated in the FIGURE and will be described hereinafter. 
     The present valve device comprises a housing  2  in which are formed two inlets  4 ,  6  and an outlet  8  arranged centrally between the inlets  4 ,  6 . Two passage openings  10 ,  12  are formed in the housing  2  between the inlets  4 ,  6  and the outlet  8 , via which passage openings  10 ,  12  a fluidic connection can be established from the inlets  4 ,  6  to the outlet  8 . 
     These passage openings  10 ,  12  are delimited radially by a first valve seat  14  and a second valve seat  16  that cooperate with a first valve-closing member  18  and a second valve-closing member  20  to control the free flow-through section of the passage openings  10 ,  12 . 
     The two valve closing-members  18 ,  20  are arranged on a valve rod  22  on which they can slide translationally. The distance of the possible sliding movement is limited by a first stop  24  for the first valve-closing member  18  and a second stop  26  for the second valve-closing member  20 . The first stop  24  is formed in an adjustable manner by a nut  28  threaded onto an outer thread  30  at the end of the valve rod  22 . Depending on how far the nut  28  is threaded onto the valve rod  22 , the distance to the second stop  26  fixedly formed on the valve rod  22  can thereby be decreased or increased during assembly. 
     A spring  32  is mounted between the two valve-closing members  18 ,  20 , the first end of the spring  32  pressing the first valve-closing member  18  against the nut  28  and the opposite second end of the spring  32  pressing the second valve-closing member  20  against the second stop  26 . For the purpose of receiving the spring  32 , the valve-closing members  18 ,  20  are each formed with a recess  34 ,  36  facing to the spring  32 , the outer diameter of the recesses  34 ,  36  being slightly larger than the outer diameter of the spring  32 . The valve-closing members  18 ,  20  are each further formed with an annular protrusion  38 ,  40  that surrounds the valve rod  22  and extends into the interior of the spring  32  and whose outer diameter is, correspondingly, slightly smaller than the inner diameter of the spring  32 . 
     The valve-closing members  18 ,  20  comprise a section flaring towards the spring  32 , by which they abut on the valve seat  14 ,  16  of a corresponding complementary shape. The distance between the two stops  24 ,  26  is then matched to the distance between the two valve seats  14 ,  16  such that, when the valve rod  22  is in its rest position, the spring  32  presses the valve-closing members  18 ,  20  against the valve seats  14 ,  16 , with a small distance existing to the stops  24 ,  26 . 
     According to the present invention, the spring  32  is surrounded by two pot-shaped parts  42 ,  44  manufactured as deep-drawn parts that serve as protective elements and whose lateral surfaces  46 ,  48  fully enclose the spring  32  in the radial direction. The bottoms  50 ,  52  of the pot-shaped parts  42 ,  44  have a hole at the center through which the valve rod  22  and the annular protrusions  38 ,  40  extend. The bottoms  50 ,  52  are seated in the respective associated recess  34 ,  36  of the valve-closing members  18 ,  20  so that the spring  32  does not rest directly on the respective valve-closing member  18 ,  20 , but biases the respective bottom  50 ,  52  of the pot-shaped parts  42 ,  44  towards the valve-closing member  18 ,  20 . 
     In the present embodiment, the recesses  34 ,  36  of the two valve-closing members  18 ,  20  have the same size. Immediately above the position at which the first pot-shaped part  42  protrudes from the recess  34 , the same has an enlargement  54  from where the lateral surface  46  again extends in a hollow cylindrical shape towards the second pot-shaped part  44 , but with a slightly larger diameter. The diameter of this end is selected such that its inner diameter is slightly larger than the outer diameter of the second pot-shaped part  44 . This means the second pot-shaped  44  can be pushed into the first pot-shaped part  42 . Care should be taken that, on the one hand, jamming is also avoided in case of axial misalignment and, on the other hand, a sealing effect is achieved. 
     The valve rod  22  is driven in a manner known per se by an electromotive actuator  56  having its output shaft  58  provided with an eccentric  60  whose output journal  62  has a ball bearing  64  fixed thereto that moves in a link plate  66  of a coupling element  68  to which the valve rod  22  is fastened. 
     The valve rod  22  extends through a bore  70  in the housing  2 , wherein sealing rings  72 ,  74  arranged one above the other are disposed in the bore  70  in a manner surrounding the valve rod  22 , the sealing rings resting on a shield element  76  that extends from the bore  70 , which takes the shape of a stepped bore, into the region of the first inlet  4  in a manner surrounding the valve rod  22 . This shield element  76  serves to guide the valve rod  22  and also has a constriction  78  at its end by which the flow resistance along the valve rod is increased so that a flow along the valve rod is significantly reduced. The inner diameter of this constriction  78  is, for example, about 0.5 mm larger than the outer diameter of the valve rod  22 . 
     When the actuator  56  is rotated clockwise from the position illustrated in  FIG. 1 , the ball bearing  64  presses the coupling element  68  and thereby the valve rod  22  downward. As a consequence, the second stop  26  presses against the second valve-closing member  20  and the same is lifted from the valve seat  16  against the spring force. Cooled exhaust gas can thus, for example, flow from the inlet  4  into the outlet  8 . 
     As the valve-closing member  20  is lifted, the second valve-closing member  18  remains on the valve seat  14 , since it cannot escape downward, so that the size of the passage opening  10  that can be flown through can be controlled freely. For the valve-closing member  18  to remain in this position, it is arranged in a slidably movable manner on the valve rod  22 , i.e., the valve rod  22  slides through the hole in the valve-closing member  18  as it moves. 
     Lifting the valve-closing ember  20  further causes a reduction of the mutual distance between the two valve-closing members  18 ,  20  so that the spring  32  is compressed. During this compression, the second pot-shaped part  44  slides into the first pot-shaped part  42  so that the spring  32  remains fully enclosed in any position. The hot exhaust gas flow thus does not make direct contact with the spring  32 . Instead, the heat can at least partly be dissipated to the housing  2  via the protective elements  42 ,  44  and the valve-closing members  18 ,  20 . Further, dirt particles do not reach the vicinity of the spring or the region, where the valve-closing members  18 ,  20  slide on the valve rod  22 . 
     When the actuator  56  is rotated in the opposite direction again, the valve-closing member  20  returns to its valve seat  16 , with the spring  32  being relaxed and the overlap between the two pot-shaped parts  42 ,  44  being reduced again, until the initial position is finally reached. 
     By rotating the actuator  56  further, the valve rod is moved upward towards the actuator  56 , whereby the nut  28  lifts the valve-closing member  18  from the first valve seat  14 , while the spring  32  still presses the second valve-closing member  20  on its valve seat  16  and the valve rod  22  slides upward through the hole in the second valve-closing member. In the same manner as described before, the spring  32  is compressed again. The first passage opening  10  is thus controlled, via which, for example, a fluidic connection is established from a bypass duct, bypassing the exhaust gas cooler, via the first inlet  4  to the outlet  8 . 
     The spring  32  and the sliding region of the valve rod  22  are again shielded against the thermal load and the dirt particle load caused by the exhaust gas flow. Less expensive spring raw materials can therefore be used. It is further avoided that the valve-closing members become stuck on the valve rod  22 . A valve device is thus provided that can be manufactured at low cost, has a long service life, and high functionality. 
     It should be clear that the scope of protection of the application is not limited to the embodiment described above. For example, the arrangement of the two protective elements is also useful in valve devices having only one valve-closing member. In this case, the upper element is moved firmly against a stop element which in the present embodiment is the second valve-closing member. The function would then be restricted to the above-described function of the first valve-closing member, the spring serving as a return element. Other structural modifications are also conceivable. Reference should also be had to the appended claims.