Abstract:
A valve unit for internal combustion engines with a drive unit, a gear mechanism, a valve rod and a valve disk, the gear mehanicm being provided with an eccentrically disposed coupling part which is connected coactingly with the valve rod, the coupling part being a bearing element which serves as a connection means with the valve rod. A combustion-air intake-channel portion and an exhaust-gas return unit are integrally combined with the valve unit.

Description:
This application claims the benefit of U.S. provisional application No. 60/223,046, filed Aug. 4, 2000. 
    
    
     FIELD OF THE INVENTION 
     The invention related to an assembly of a valve unit, a combustion air intake and an exhaust gas recirculation unit for an internal combustion engine. 
     BACKGROUND AND PRIOR ART 
     A valve unit for use in an exhaust-gas return unit is known, for example, from European Patent A2 900930. The valve unit therein is provided with a drive unit, a gear mechanism, a valve rod and at least one valve disk, the gear mechanism being provided with an eccentrically disposed coupling which is connected coactingly with the valve rod. Rotary movements of the motor and of the gear mechanism connected thereto can be transformed in simple manner to linear movements of the valve rod with large positioning force by such an eccentric arrangement of the coupling. Because the valve rod is fixed on the coupling in this case, however, relatively large friction forces must be overcome, thus making it difficult, because of the slewing movement of the valve rod, to achieve positioning of the valve element. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide a valve unit of the above type for internal combustion engines, which avoids the aforesaid disadvantages and in addition can be manufactured inexpensively with simple construction. 
     This object is achieved in that the coupling comprises a bearing element which serves as a connection means with the valve rod. 
     In this way, it is ensured that straight, linear movement of the valve rod takes place despite the eccentricity of the coupling. Moreover, frictional losses are limited to a minimum. A particularly simple and robust embodiment of the valve unit can be achieved by constructing the bearing element as a roller bearing. The gear mechanism can then be provided with a guide member which has cam elements acting on the roller bearing, one in the vertical direction and the other in the horizontal direction, the guide member being fixed to the valve rod, whereby the valve rod and thus also the valve disk attached thereto, by virtue of the horizontal cam element, can also be moved in closing direction in response to reversal of the direction of rotation of the drive unit. In this respect, the vertical cam element functions as an end stop for the roller bearing if it were to exceed the maximum stroke (or angle of rotation). In this way, it is possible to achieve motor-assisted closing and retaining forces, which can prevent unwanted opening of the valve when it is used, for example, as an exhaust-gas return valve. Moreover, critical operating conditions such as seizing or sticking of the valve disk can be overcome. For automatic restoration of the valve disk to closed position, a spring element is provided which applies tension on the valve rod in the direction of the roller bearing. 
     A gear mehanicm comprising a planetary gear mechanism or planetary stationary gear mechanism is particularly advantageous for compact construction of the valve unit. In particular, the planetary stationary gear mechanism allows a short overall length of the gear mehanicm, with the accompanying result that reduced inertia as well as low friction result in higher efficiency of the gear mehanicm. 
     A valve unit which is simple to assembly is obtained in that there is provided a cover element, which is equipped with a connection plug for establishing electrical contact and which has plug contact elements which engage complementary plug contact elements of the drive unit when the cover element is mounted in place, thus establishing an electrical connection to the drive unit. In a particularly advantageous embodiment, there is provided a sensor for sensing the position of the valve stroke, the sensor being designed such that it can be electrically connected to the connection plug. The sensor can be comprised of a diametral annular magnet and a Hall-effect sensor element. Thus, a ring gear of the planetary or planetary stationary gear mechanism can be disposed in the annular magnet. There can also be provided an on-board electronic module for system control. 
     From the viewpoint of assembly, it is particularly advantageous to dispose the drive unit and the gear mechanism unit in a tunnel housing. 
     The valve unit of the invention is suitable in particular for use in the exhaust-gas return line of an internal combustion engine. In a valve unit for exhaust-gas return as disclosed, for example, in German Patent A1 4338192, the valve rod projects directly into the air intake tube, and extreme fouling can occur because of the contact of the cold fresh air with the hot exhaust gas. This disadvantage is avoided in a combustion-air intake-channel portion in which the exhaust-gas inlet portion is provided with a discharge portion, which is disposed coaxially relative to the intake-channel portion and which, via a connecting channel disposed transversely relative to the discharge portion, is connected to a valve-channel portion, which is intersected by the connecting channel, the connecting channel being provided with an outwardly projecting channel attachment, which is closed by a plug type insert. This valve-channel portion can form a connecting nozzle for an exhaust-gas return line, and this connecting nozzle can also be provided with the valve seat. 
     Also provided in accordance with the invention, is an exhaust-gas return unit with a valve unit and a combustion-air channel portion, in which the valve rod extends into a valve guide bushing, which at one end projects into the valve-channel portion and at the other end into a valve spring chamber. In this case it is advantageous for the valve rod, on the portion which projects into the valve spring chamber, to support the guide member, which bears on one end of the spring element whose other end is braced against the wall of the valve-spring chamber. The valve-spring chamber can be closed off from the outside by the housing for the gear mechanism and drive unit. The valve guide bushing can be provided with a dirt chamber, which is formed, for example, by a bore in the housing. In order to achieve an advantageous exhaust gas return, the valve disk can be provided with a cylindrical portion extending downstream from the valve seat. In order to be able to use a smaller valve disk, which in turn permits smaller positioning forces, the valve disk can be provided with a tapered edge, which cooperates with a taper portion of the valve seat and located downstream from the line of contact to form a diffusor portion. A throttle valve can be disposed in the intake-channel portion, upstream from the discharge portion. To achieve a construction which saves as much space as possible, the combustion-air intake-channel portion can be integrated with the housing of the gear mechanism and drive unit. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a valve unit according to the invention in which a cover has been removed. 
     FIG. 2 is a longitudinal sectional view of the valve unit. 
     FIG. 3 is a transverse sectional view through a drive unit of the valve unit, the cover being in place. 
     FIG. 4 is a longitudinal sectional view showing an exhaust-gas return unit integrated with the valve unit. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 shows a valve unit  1  provided with a drive motor  2  and a gear mechanism  3 , (illustrated in detail in FIG. 2) and with a bearing  5  disposed eccentrically on a journal  4  as a coupling, which is connected coactingly with a valve rod  6 , for moving a valve disk  7  to an open position. Valve unit  1  is further provided with an outlet port  8  and an inlet port  9  constructed as the valve seat. 
     For return of the valve disk to its closed position when the drive motor  2  is deactivated, a spring element  10 , engages a guide member  11  fixed securely on valve rod  6  to urge valve rod  6  in the direction of bearing  5 . The guide member  11  ensures that valve rod  6  can also be moved in the closing direction in response to reversal of the direction of rotation of the drive unit. In this way, valve disk  7  can be freed from a jammed or stuck position. For this purpose, guide member  11  is provided with cam elements  12  acting on the bearing, one in vertical direction and the other in horizontal direction. A housing plate  13  is disposed above drive unit  2 , for mounting an operational on-board electronic module thereon. 
     FIG. 2 shows in greater detail gear mechanism  3  with bearing  5  disposed eccentrically above a bearing journal  4 . Gear mechanism  3  is in the form of a planetary stationary gear mechanism, in which there are driven, by an input shaft  15 , which is connected to drive motor  2 , three non-revolving planetary gears  16 , which in turn drive a ring gear  17 , on the side of which remote from drive motor  2  there is disposed bearing journal  4  with bearing  5 . 
     A particular compact construction is achieved when ring gear  17  carries a co-rotating diametral annular magnet, which cooperates in known manner with a Hall-effect sensor, so that the valve stroke can be determined in simple manner from the rotary movement of the ring gear. 
     Further illustrated is a cover  18 , which, as an alternative to the aforesaid Hall-effect sensor, can be provided with a sensor  19 , which in known manner senses the linear position of the valve stroke. Also provided is a connection plug  20 , to establish electrical contact between sensor  19  and motor  2 . The connecting plug  20  includes plug contact elements which are connected with drive motor  2 , so that electrical control of valve unit  1  is obtained. 
     For simplicity of assembly, a housing  21  of valve unit  1  is constructed in the region of drive motor  2  as a tunnel housing. 
     FIG. 3 shows a sectional view of drive unit  2  with cover  18  in place. As already discussed hereinabove, cover  18  is provided with plug contact elements  22 , which cooperate with cover contact elements  23  of drive motor  2 . In this way, electrical contact can be established in simple manner by the mounting of cover  18 . 
     FIG. 4 shows a sectional view including an exhaust-gas return unit  24  according to the invention. The exhaust-gas return unit is integrated with valve unit  1  and is provided with a combustion-air intake-channel  25  and with an exhaust-gas inlet portion  26 . 
     According to the invention, the exhaust-gas inlet  26  is equipped with a discharge portion  27 , which is disposed coaxially relative to combustion-air intake-channel  25  and which is connected via a connecting channel  28 , disposed transversely relative to discharge portion  27 , to a channel  29  in valve  1 . Connecting channel  28  is provided with an outwardly projecting channel attachment  30 , which is closed by a plug insert  31 . This construction provides a space-saving arrangement as well as manufacture in one piece. 
     It is advantageous if the valve-channel portion  29  forms a connecting nozzle  32  for an exhaust-gas return line (not illustrated), the connecting nozzle  32  being provided with a valve seat  33 , which cooperates with valve disk  7  fastened to valve rod  6  and disposed coaxially relative to valve-channel portion  29 . 
     It is further provided that valve rod  6  is guided in a valve guide bushing  34 , which projects at one end into valve-channel portion  29  and at the other end into a valve spring chamber  35 , valve rod  6  being provided on the portion which projects into valve spring chamber  35  with guide member  11 , on which engages spring element  10 , whose other end is braced against wall  36  of the valve spring chamber  35 . 
     In a particular space-saving construction, valve spring chamber  35  is sealed off from the outside by housing  21  which simultaneously forms the housing of the gear mechanism and drive unit. The valve spring chamber  35  can be connected to the atmosphere by a vent hole (not illustrated). 
     Advantageously the valve guide bushing  36  is equipped with a dirt chamber  37 . Because valve disk  7  can be provided with a cylindrical portion (not shown) downstream from valve seat  33 , an advantageous characteristic of exhaust gas flow in the exhaust gas return line can be achieved and, because valve disk  7  is provided with a taper edge  38 , which cooperates with a taper portion  39  of valve seat  33  to form a diffusor portion  40 , a smaller size valve-disk can be employed, which needs smaller size positioning forces, since delivery pressure recovery is achieved in the diffusor. 
     Although the invention is disclosed with reference to particular embodiments thereof, it will become apparent to those skilled in the art that numerous modifications and variations can be made which will fall within the scope and spirit of the invention as defined by the attached claims.