Abstract:
A throttle device for controlling an internal combustion engine, in which the throttle valve is supported precisely employs a bearing recess serving to support the throttle valve shaft which is surrounded by a clamping element. As a result, there is excellent, durable stabilization of the bearing recess. The throttle device is especially well suited to vehicles that have a throttle-type internal combustion engine.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is based on German Patent Application 10 2004 043 125.6 filed Sep. 7, 2004, upon which priority is claimed. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention is directed to an improved throttle device for an internal combustion engine. 
   2. Description of the Prior Art 
   Throttle devices for internal combustion engines typically have a throttle valve shaft, which is pivotably supported in a throttle valve housing and onto which a throttle valve is integrally formed or secured. A gas duct extends through the throttle valve housing. Through the gas duct, air or a fuel-air mixture, for instance, can flow to an engine. The throttle valve opens and closes the gas duct by pivoting of the throttle valve shaft. 
   To keep the throttle valve from hitting the wall of the gas duct, it is known to set close tolerances for the mobility of the throttle valve shaft in its axial direction. 
   In the throttle device shown in German Patent Disclosure DE 39 24 611 A1, the throttle valve shaft is fixed in the axial direction, that is, the longitudinal direction of the throttle valve shaft, by a pin extending transversely through the throttle valve shaft. 
   In the throttle device shown in German Patent Disclosure DE 30 48 995 A1, the axial force transmission between the throttle valve shaft and the throttle valve housing is effected via a ball bearing built into the throttle valve housing. 
   In German Patent Disclosure DE 195 10 622 A1, a bearing means is press-fitted into the throttle valve housing, and a spring tenses the throttle valve shaft against this bearing means for the sake of exact axial positioning of the throttle valve shaft. 
   Depending on the material used, and particularly depending on the material used for the throttle valve housing, it can happen in the prior art that the axial support of the throttle valve shaft shifts, so that the unimpeded mobility of the throttle valve in the throttle valve housing at every temperature is no longer assured. 
   OBJECT AND SUMMARY OF THE INVENTION 
   The throttle device of the invention, for an internal combustion engine has the advantage over the prior art that the throttle valve housing is so stable in the region of the bearing recess that forces that occur between the throttle valve shaft and the throttle valve housing can be securely intercepted in both the radial and the axial direction. This is true even whenever, for the sake of simple manufacture and/or inexpensive material and/or other demands, such as resistance to chemical attacks from outside, a material for the throttle valve housing is chosen that is relatively soft and/or relatively yielding and/or a that yields over the course of time because of forces acting on it. 
   Because of the clamping element, the throttle valve housing, even in the region of the bearing recess, can for instance be a plastic. 
   The clamping element can also serve very well as a guard against friction or impact, in order to protect the throttle valve housing against damage from mechanical abrasion, indentations, or blows. The clamping element can protect the throttle valve housing against damage from a spring, for instance, that might come to vibrate. 
   When the throttle valve housing for the bearing recess is formed onto or built onto an extension as well, the advantage is attained with a clamping element that even in this design of the throttle valve housing, secure support of the throttle valve is assured. 
   The clamping element can preferably be embodied in the form of a sleeve, which has the advantage that the clamping element can be produced at little effort or expense. 
   If the throttle valve housing is entirely, or at least in the region of the bearing recess, of plastic, this then has the advantage that the throttle valve housing can be produced rather simply and nevertheless, with the aid of the clamping element, a secure support of the throttle valve shaft is obtained. 
   The clamping element may for instance comprise metal, which has the advantage that even with a small clamping element, made for instance from a thin metal sheet, a good stabilizing action is attained. 
   Because of the clamping element, good stability is attained in the region of the bearing recess, which has the advantage that a bearing can be built into the bearing recess without problems; the bearing may for instance be a slide bearing or a roller bearing, in particular a roller bearing or a ball bearing. 
   Because of the stabilizing action of the clamping element, a bearing can be built or press-fitted into the bearing recess with rather great radial prestressing. 
   If a material is selected for the clamping element that has a coefficient of thermal expansion which is approximately equivalent to that of the bearing built into the bearing recess, then this has the advantage that at both a very high and a very low temperature, the pressure between the bearing and the bearing recess remains essentially unchanged. This is even true if the throttle valve housing or the extension, in the region of the bearing recess, is of a material having a different coefficient of thermal expansion. For the throttle valve housing and for the extension, plastic can then easily also be used. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood and further objects and advantages thereof will become more apparent from the ensuing detailed description of a preferred embodiment taken in conjunction with the drawings, in which: 
       FIG. 1  shows a plan view on the selected exemplary embodiment of the throttle device; 
       FIG. 2  shows a section through the throttle device along the plane marked II-II in  FIG. 1 ; and 
       FIG. 3  shows an enlarged detail of a circular area marked III in  FIG. 2 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The throttle device according to the invention can be employed in various internal combustion engines in which a passage through a gas duct is to be controlled with the aid of a throttle valve. The gas duct is intended for instance for a flow of air, a fuel-air mixture, and so forth. Depending on the pivoted position of the throttle valve, the flow of gas is more or less throttled. Normally, the throttle valve can be pivoted to an angle of up to 90°. However, versions also exist in which the throttle valve can be pivoted by less than 90° or more than 90°, for instance up to 180°. The throttle valve shaft with the throttle valve can be pivoted with the aid of an adjusting device that engages the throttle valve shaft. The adjusting device is for instance a control motor, which engages the throttle valve shaft and adjusts the throttle valve shaft, for instance directly or via a gear. 
   In all the drawing figures, parts that are the same or function the same are identified by the same reference numerals. 
     FIGS. 1 through 3  show the throttle device with a throttle valve housing  2 . A gas duct  4  shown end-on in  FIG. 1  extends through the throttle valve housing  2 . The gas duct  4  is for instance part of an intake tube leading to combustion chambers of an internal combustion engine. Extending transversely through the gas duct  4  is a throttle valve shaft  6 , which is pivotably supported in the throttle valve housing  2 . A throttle valve  8  is secured to the throttle valve shaft  6 . The throttle valve  8  may for instance also be manufactured in one piece from plastic together with the throttle valve shaft  6 . 
   A bearing recess  10  and a further bearing recess  12  are provided on the throttle valve housing  2 . The throttle valve shaft  6  is pivotably supported in the bearing recesses  10 ,  12 . 
   An articulation means  14  is solidly joined to the throttle valve shaft  6 . In the exemplary embodiment shown, the articulation means  14  is embodied in the form of a gear wheel injection-molded or welded onto the throttle valve shaft  6 . Since the throttle valve  8  is not supposed to be pivoted by more than  1100 , for instance, it suffices if the injection-molded-on gear wheel has outer teeth in a region of only 110°, which teeth mesh with a drive pinion or a control motor via a further gear wheel. The control motor together with the gear wheel and the articulation means  14  form an adjusting device  18  for adjusting the throttle valve  8  supported on the throttle valve shaft  6 . 
   One end of an adjusting spring  20  is pivotably connected on one end directly or indirectly to the throttle valve housing  2 , and on the other end the adjusting spring  20  is pivotably connected directly or indirectly to the throttle valve shaft  6  or the throttle valve  8 . In the exemplary embodiment shown, the right-hand end of the adjusting spring  20  acts on the throttle valve shaft  6  via the articulation means  14 . The left-hand end of the adjusting spring  20  is supported on the throttle valve housing  2 . The adjusting spring  20  serves the purpose of restoring the throttle valve shaft  6  or the throttle valve  8  to an unactuated position of repose. 
   An extension  22  protrudes laterally onto the throttle valve housing  2 . The extension  22  is preferably formed integrally together with the throttle valve housing  2 . The extension  22  is preferably of the same material as the throttle valve housing  2 . The extension  22  is preferably, like the rest of the throttle valve housing  2 , made of a plastic. Thus the throttle valve housing  2  can be produced together with the extension  2  very simply, for instance by injection molding. 
   The bearing recess  10  is formed for instance by a stepped bore extending from the outside into the extension  22  of the throttle valve housing  2 . A bearing  24  with oversize is press-fitted into the bearing recess  10 . The diameter of the outer cylindrical surface  24   a  of the bearing  24  is greater than the diameter of the bearing recess  10  in the region of the bearing  24 . As a result, the bearing  24  presses in the radial direction against the throttle valve housing  2 , but the bearing  24  is not displaced, by the forces that occur during the operation of the throttle device. 
   The bearing  24  is for instance a roller bearing  24   b . In the preferred selected exemplary embodiment, the roller bearing  24   b  has an outer ring  24   d  and a plurality of rollers  24   c  or bearing needles, which are received in the outer ring  24   d.    
   The outer circumference  24   a  of the outer ring  24   d  is dimensioned such that the outer ring  24   d  is retained with prestressing in the bearing recess  10 . 
   A plunge cut  6   b  extending all the way around is provided on the throttle valve shaft  6 . A disk  26  is installed in the plunge cut  6   b . A wave washer  28  that is resilient in the axial direction tenses the disk  26  against the outer ring  24   d  of the bearing  24 . In the process, the wave washer  28  is braced on the throttle valve housing  2 ; more precisely, it is braced on its face end on the stepped bore that forms the bearing recess  10 . It is thus assured that during the operation of the throttle device, no relative motion in the longitudinal direction of the throttle valve shaft  6  occurs between the disk  26  and the bearing  24 , or between the disk  26  and the throttle valve housing  2 . 
   The plunge cut  6   b  in the throttle valve shaft  6  is minimally wider than the thickness of the disk  26 , so that when the disk  26  is stopped the throttle valve shaft  6  can easily be rotated. 
   A clamping element  30  surrounds the bearing recess  10 . In the preferred selected exemplary embodiment, the clamping element  30  is provided on the outer circumference of the extension  22  of the throttle valve housing  2 . The clamping element  30  surrounds the extension  22  completely in the region of the bearing recess  10 . In the preferred selected exemplary embodiment, the outer ring  24   d  of the bearing  24  presses from the inside outward against the extension  22 , and the clamping element  30  presses from the outside inward against the extension  22 . Since the clamping element  30  presses radially against the extension  22  from the outside inward, the extension  22  cannot expand, despite the radial force of the press-fitted bearing  24  that acts on the extension  22 . This is true even if the extension  22  or the entire throttle valve housing  2  is of a plastic that would yield, without the proposed fastening by the clamping element  30 , or if the plastic would creep over the course of time, if there were not the stabilizing clamping element  30 . 
   The clamping element  30  is preferably cylindrical or sleevelike and has approximately the shape of a stepped, hat-shaped cylinder, open at the face end, with a cylindrical region  30   a  and a radial region  30   b.    
   The clamping element  30  is preferably closed, viewed in the circumferential direction. However, the clamping element  30  may also be slit along a center line, for instance. 
   The clamping element  30  is preferably of metal, for instance, preferably a hardened metal, and in particular spring steel. 
   The adjusting spring  20  can be braced by one end at the transition between the cylindrical region  30   a  and the radial region  30   b . This prevents the end of the adjusting spring  20  from being able to dig into the relatively soft material comprising the throttle valve housing  2 . 
   The cylindrical region  30   a  of the clamping element  30  is located between the extension  22  of the throttle valve housing  2  and the adjusting spring  20 . It is thus assured that even under severe vibrational stress of the throttle device, the windings of the adjusting spring  20  cannot directly strike the extension  22  of the throttle valve housing  2 . As a result, it can be assured, even if a relatively soft material is used for the extension  22 , that the adjusting spring  20  can damage neither the extension  22  nor any other region of the throttle valve housing  2 . 
   The material of the clamping element  30  is preferably selected such that it has largely the same coefficient of thermal expansion as the bearing  24 , or at least the outer ring  24   d  of the bearing  24 . This can be achieved very simply by providing that the bearing  24 , or at least the outer ring  24   d  of the bearing  24 , is of metal and the clamping element  30  is likewise of metal, so that both the clamping element  30  and the bearing  24 , or the outer ring  24   d , have practically the same coefficient of thermal expansion. Because the bearing  24  and the clamping element  30  have the same coefficient of thermal expansion, it is assured that at both a very high incident operating temperature and a very low temperature, the press fit of the material comprising the extension  22  or the throttle valve housing  2  remains practically unchanged between the bearing  24  and the clamping element  30 . 
   The foregoing relates to a preferred exemplary embodiment of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims.