Abstract:
An actuator for a valve in an internal combustion engine includes a housing, an electric drive unit arranged in an interior of the housing, an aeration opening arranged in the housing, a plug configured to electrically connect the electric drive unit to a voltage source, and a membrane comprising pores. The membrane is configured to close the aeration opening in the housing.

Description:
CROSS REFERENCE TO PRIOR APPLICATIONS 
       [0001]    This application is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/EP2014/070008, filed on Sep. 19, 2014 and which claims benefit to German Patent Application No. 10 2013 111 722.8, filed on Oct. 24, 2013. The International Application was published in German on Apr. 30, 2015 as WO 2015/058914 A1 under PCT Article 21(2). 
     
    
     FIELD 
       [0002]    The present invention relates to an actuator for valves in an internal combustion engine. The actuator having an electric drive unit, a housing in the interior of which the drive unit is arranged, at least one aeration opening in the housing, and a plug via which the drive unit is adapted to be electrically connected with a voltage source. 
       BACKGROUND 
       [0003]    Such actuators serve to operate exhaust gas return valves to control the amount of exhaust gas returned to the combustion chamber or secondary air valves to control the amount of secondary air introduced into the exhaust gas piping, which are used to reduce pollutants in internal combustion engines. These actuators are frequently operated electromagnetically, but can also be operated by an electric motor. 
         [0004]    An electromagnetically operated secondary air valve is described, for example, in DE 10 2009 058 930 A1. This valve controls, via a globe valve whose valve rod is connected with the armature of the electromagnet, an amount of air to be supplied to the exhaust gas pipe and pumped by a secondary air pump by adjusting, via operation of the electromagnet, a flow cross-section between a fluid inlet duct and a fluid outlet duct connected with the exhaust gas pipe. The valve comprises a non-return flap which, when the valve is closed, is pressed against the valve seat to prevent air from flowing back when exhaust gas pulsations occur. However, air pulsations also act upon the interior of the actuator. Pressure differences also occur in the armature space due to the movement of the armature. 
         [0005]    Exhaust gas pulsations occurring in exhaust gas return valves act directly upon the interior of the actuator so that malfunctioning must be expected. 
         [0006]    To provide aeration of the armature space and at the same time prevent dirt, in particular spray water, from entering the interior of the electromagnet from outside, DE 10 2008 004 531 B3 describes connecting the armature space with the exterior of the valve via a de-aeration bore. A mushroom valve having an elastic edge bears upon and closes the deaeration bore when the pressure in the armature space is lower than that of the exterior. The valve opens upon reversal of the pressure difference. This means, however, that aeration is not possible if a vacuum occurs in the armature space. Opening and closing noises are also produced by the movement of the mushroom valve. 
       SUMMARY 
       [0007]    An aspect of the present invention is to provide an actuator for valves in internal combustion engines which provide both de-aeration and aeration of the actuator and, in particular, the armature space of electromagnets, and which at the same time reliably protects against penetration of dust particles or spray water into the interior of the actuator. An additional aspect of the present invention is to provide an actuator with a simple and inexpensive manufacture and installation. 
         [0008]    In an embodiment, the present invention provides an actuator for a valve in an internal combustion engine which includes a housing, an electric drive unit arranged in an interior of the housing, an aeration opening arranged in the housing, a plug configured to electrically connect the electric drive unit to a voltage source, and a membrane comprising pores. The membrane is configured to close the aeration opening in the housing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The present invention is described in greater detail below on the basis of embodiments and of the drawing in which: 
           [0010]      FIG. 1  shows a cross-sectional side view of an actuator according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    Because the aeration opening in the housing is closed by a fine-pored membrane, gas can escape either into the interior or to the exterior depending on the prevailing pressure difference. Penetration of solids or spray water into the interior of the actuator is also prevented by the membrane since the molecules of these substances are larger than the pores of the membrane. 
         [0012]    In an embodiment of the present invention, the membrane can, for example, be arranged at a surface of the housing facing the interior. Possible damage to the fastening surface of the membrane is thereby prevented since no outer force application surface exists. 
         [0013]    It has turned out to be particularly advantageous when the membrane is a PTFE membrane since the pore size of such a membrane provides aeration and de-aeration and prevents penetration of water and solids. This membrane also has a very long service life. 
         [0014]    In an embodiment of the present invention, the membrane can, for example, be welded to the housing. This fastening process provides a high stability of the fastening at low costs. 
         [0015]    In an embodiment of the present invention, the edges of the membrane can, for example, be overmolded by the plastic material of the housing. 
         [0016]    In an embodiment of the present invention, the aeration opening at the housing can, for example, be formed in the area of the plug which, in such an arrangement, serves as an additional shield against spray water. 
         [0017]    In an embodiment of the present invention, the plug can, for example, comprise a portion which extends essentially in parallel to a surface of the housing. The aeration opening is thereby arranged in the housing opposite to the portion of the plug extending in parallel. In this embodiment, the plug serves as a cap or a shielding plate, whereby even less spray water can flow to the aeration bore without an additional component parts being required or the aeration function being restricted. 
         [0018]    A particularly simple manufacture of the actuator is realized when the plug extends from a cover portion of the electric drive unit, wherein the housing surrounding the drive unit is injection-molded to the cover portion. The membrane can thus first be fastened and/or welded to the side of the cover facing the interior, whereby good accessibility is offered. 
         [0019]    In an embodiment of the present invention, the electric drive unit can, for example, be an electromagnet whose armature is operatively connected with a valve rod. This provides a rapid and reliable operation of the valve at low current consumption as well as a simple connection between the actuator and the valve. 
         [0020]    In an embodiment of the present invention, the aeration opening at the housing can, for example, lead into an armature space of the electromagnet so that pressure pulsations produced by displacement of the armature in the interior of the electromagnet can be rapidly and reliably dissipated. 
         [0021]    An actuator for valves in internal combustion engines is thus provided via which both the aeration and the de-aeration of the housing of the actuator are provided and which shows a high insensitivity to liquid or solid dirt. This actuator is easy and inexpensive to manufacture and install, has a long service life, and a very good functionality since faults caused by dirt or pressure are avoided. 
         [0022]    An exemplary embodiment of the present invention is illustrated in the drawing and is described below. 
         [0023]    The actuator  10  shown in  FIG. 1  comprises an electric drive unit  12  which is surrounded by a housing  14  that separates an interior  16 , where the electric drive unit  12  is arranged, from an exterior  18 . The housing  14  comprises a housing portion  20 , which essentially radially surrounds the drive unit  12 , as well as a cover portion  22 , via which the housing  14  is closed at a first axial end. 
         [0024]    The electric drive unit  12  is configured as an electromagnet and is composed of a coil  24  wound around a coil carrier  26 , a core  28  fastened in the coil carrier  26 , a yoke  30 , as well as a reflux metal sheet  32  arranged at the end of the housing  14  opposite to the first axial end, which reflux metal sheet  32  closes the first axial end to a large extent and at the same time can serve as a flange surface to fasten a flow housing. The reflux metal sheet  32  surrounds an axial end portion of the core  28  and is of an essentially plate-shaped configuration. The core  28  comprises a central through-going opening  34  through which extends a valve rod  36  of a valve to be operated, which valve rod  36  is connected with a movable armature  38  that, when the coil  24  is energized, is pulled towards the core  28  and loaded towards the core  28  via a spring  40  which radially surrounds a projection  41  defined at the cover portion  22  and which is guided thereby. Another spring (not shown) presses the armature  38 , in the non-energized state of the coil  24 , from the core  28  into its initial position. The armature  38  is supported in a sliding bushing  42  which is fastened in the interior of the coil carrier  26 . 
         [0025]    Lead frames  44  are inserted or injection-molded in the housing  14  to supply the coil  24  with current and also to contact any integrated circuit boards, position sensors, and pressure sensors. The lead frames  44  lead to a plug  46  that is defined at the cover portion  22 . The contact tabs  48  of the lead frame  44  extend from plug  46 , via which the actuator  10  is connected in a conventional manner with a voltage source and/or a motor control unit via continuing lines. 
         [0026]    The plug  46  first extends orthogonally away from a surface  50  of the cover portion  22  and comprises a bend  52  in its further course from which it extends orthogonally again so that this portion  54  of the plug  46  extends essentially in parallel to the surface  50  of the cover portion  22 . 
         [0027]    An aeration opening  56  is defined in the area of the cover portion  22  covered by the portion  54  of the plug  46  via which a connection between the interior  16  and the exterior  18  of the housing  14  is established. An armature space  58  is aerated and de-aerated in this manner in the shown embodiment. A fine-pored membrane  62  which completely covers the aeration bore is welded to the surface  60  facing the armature space  58 . In the shown embodiment, this membrane  62  is a PTFE membrane through the pores of which gases can flow to the inside or the outside, but no liquids or solids, such as soot particles, can enter the interior  16 . The size of these pores is approximately 0.2 to 1 μm. 
         [0028]    During manufacture of the housing  14  of the actuator  10 , the cover portion  22  is first injection-molded, and the membrane  62  is then welded to the aeration opening  56  from the inside. The housing portion  20  radially surrounding the electric drive unit  12  is subsequently injection-molded to the cover portion  22 . The connecting plane between the membrane  62  and the cover portion  22  is accordingly located in the area of the interior  16  so that an unintentional detachment of the membrane  62  due to the application of a force from outside can be prevented to a large extent. 
         [0029]    A negative pressure may be produced in the armature space  58  of the actuator  10  if, due to energizing, the armature  38  is pulled towards the core  28  to open a connected valve. This is prevented by taking in air from the exterior  18  via the aeration opening  56  and the membrane  62 . A buildup of a positive pressure in the armature space  58  can likewise be prevented in the case of a reverse movement of the armature  38 . Other pressure differences due to pressure pulsations in the lines or simply due to temperature changes can, for example, also be compensated for. 
         [0030]    If this actuator  10  is used in a vehicle, it is usually subjected to spray water or solid contaminants. A large amount of these contaminants and of the spray water is shielded off by the plug  46  projecting above the aeration opening  56 , which plug serves as a kind of spray water cap. Liquids or solids which nevertheless reach the aeration opening  56  are prevented from entering the interior  16  by the membrane  62  since the pores thereof are too small for these substances to pass through. 
         [0031]    An actuator is thus provided which is not subject to any restrictions of functionality due to pressure differences in the interior and which has a long service life since the interior is shielded against contaminants from outside. These functions are realized without any major installation or manufacturing costs being involved. A long service life of the membrane is also provided. 
         [0032]    It should be appreciated that various design changes of the actuator are conceivable without departing from the scope of protection of the main claim. Thus, depending on the plastic material used, the membrane  62  may also be injection-molded for fastening purposes, during the manufacture of the cover. Various electric drive units  12 , such as electric motors, can also be used. Other advantageous materials can also be used for the membrane  62 . The plug  46  can further have a straight configuration or can be defined at the radially delimiting housing portion  20 . Reference should also be had to the appended claims.