Abstract:
In an adjusting device with a transmission, high gear ratios are frequently required. In the transmission, powerful lateral forces are frequently generated, which must be absorbed by correspondingly dimensioned bearings. The present invention proposes an adjusting device having a transmission in which at least one gear is supported on an axle with a diameter that varies in the longitudinal direction. This achieves a uniform material loading of the axle supporting the gear and permits the diameter of the axle as a whole to be significantly reduced. The adjusting device is particularly intended for motor vehicles with an internal combustion engine.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application is based on German Patent Application 10 2005 042 201.2 filed Sep. 6, 2005, upon which priority is claimed. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention is directed to an improved adjusting device for adjusting the position of a final control element using a transmission. 
   2. Description of the Prior Art 
   There are known adjusting devices for internal combustion engines in which a servomotor must move a final control element via a transmission. For example, the final control element is a throttle valve flap. Because there is frequently very little room available for the adjusting device in a motor vehicle, it is necessary to keep its size to a minimum. In order for a relatively small servomotor to be able to move the final control element quickly and precisely, a transmission is provided between the servomotor and the final control element. Due to the limited amount of available space, the transmission must be as small as possible. 
   DE 195 25 510 A1 and U.S. Pat. No. 5,672,818 have disclosed an adjusting device provided in the intake manifold of an internal combustion engine. The adjusting device disclosed therein has a throttle valve shaft that is supported in a throttle valve housing in pivoting fashion and has a throttle valve flap attached to it. The throttle valve housing has a gas duct passing through it. The throttle valve flap opens or closes the gas duct in response to the pivoting of the throttle valve shaft. A servomotor can move the throttle valve flap via a transmission. The transmission is situated in a transmission housing and has a number of gears. A middle gear is supported in rotary fashion on an axle that is attached to the main body of the throttle valve housing. The transmission housing is covered by a cover. Because the cover has, among other things, parts of a position sensor attached to it, the cover must be positioned very precisely in the region of the position sensor. For this reason and due to production tolerances that can never be entirely avoided, there is necessarily play, particularly in the radial direction, in the region between the cover and the end of the axle oriented toward the cover. For this reason, the axle can only be secured in the region of the main body, whereas in the region of the cover, it is only possible for it to be supported loosely, with a large amount of play. This has the disadvantage that the axle, particularly at the point at which the axle comes out of the main body, is loaded with a large amount of bending stresses and shearing stresses and that a particularly high-strength material must therefore be used for the axle or else the axle would have to be so thick that it would require the entire device to be unnecessarily large. 
   OBJECT AND SUMMARY OF THE INVENTION 
   The adjusting device according to the invention has the advantage over the prior art that due to the varying diameter of the axle supporting the gear, the material used for the axle can be put to optimum use because a relatively uniform flow of stress is produced in the entire axle. 
   Advantageous modifications and improvements of the adjusting device are disclosed. If the axle becomes smaller in diameter as the distance from the main body increases, then this has the advantage that the gear can be attached to the axle very easily. 
   If the change in the axle diameter is achieved by means of steps, then this can yield cylindrical regions of the axle, which is good for supporting the gear in order to avoid forces in the axial direction. 
   If a sleeve is provided in at least subregions of the support of the gear, then this offers advantages with regard to the support, particularly with regard to reduced wear. 
   If the sleeve is provided in the smaller diameter region of the axle, then this has the advantage of an improved support, particularly in places where powerful surface pressures occur. 
   The at least one raised area on the axle offers the advantage that the sleeve can very easily be press-fitted onto the axle without requiring much material to be deformed, which is advantageous when selecting which material to use. Another advantage is that the raised area causes an elastic deformation to occur in the sleeve, which assures a long-lasting, advantageous initial stress between the sleeve and the axle. Another advantage is that this does not require such strict tolerances to be kept. 
   The molding device between the axle and the cover offers the advantage that the axle is optimally secured at the cover end as well. This offers the advantage that the axle as a whole can be embodied as thinner. 
   The relatively hard stamping body of the molding device offers the advantage that the molding can be very easily produced while the cover is being attached to the main body for mounting the axle to the side of the cover. 
   If the stamping body is comprised of the sleeve, which can also be used to mount the gear, then this offers the advantage of not requiring an additional component for the molding device. 

   
     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 preferred embodiments, taken in conjunction with the drawings, in which: 
       FIG. 1  is a top view of an adjusting device embodying the invention, 
       FIG. 2  is a side view of the adjusting device of  FIG. 1 , 
       FIG. 3  shows a section through the adjusting device, 
       FIG. 4  shows a detail from  FIG. 3 , 
       FIG. 5  shows a second section through the adjusting device, 
       FIG. 6  shows a detail from  FIG. 5 , 
       FIG. 7  shows another section through the adjusting device, 
       FIG. 8  shows a detail from  FIG. 7 , 
       FIG. 9  shows a section through the gear, transversely in relation to the axle, and 
       FIG. 10  shows a detail from  FIG. 9 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The adjusting device according to the present invention can be used at various locations in internal combustion engines, in particular for controlling a passage through a gas duct. The gas duct is provided, for example, for a flow of air or a fuel/air mixture or for controlling exhaust, etc. The flow of the gas is throttled to a greater or lesser degree as a function of the pivot position of the throttle valve flap. Normally, the throttle valve flap can be pivoted by up to 90°. There are, however, also embodiments in which the throttle valve flap can be pivoted by less than 90° or more than 90°, for example up to 180°. The throttle valve shaft with the throttle valve flap can be pivoted, for example, with the aid of a servomotor. For example, the servomotor engages the throttle valve shaft via at least one gear. 
   In all of the drawing figures, parts that are the same or function in the same manner are provided with the same reference numerals. Provided that nothing to the contrary is mentioned or is depicted in the drawings, that which is mentioned and depicted in conjunction with one of the figures also applies to the other figures. Provided that nothing to the contrary is stated in the explanations, the various details can be combined with one another. 
     FIG. 1  shows an adjusting device  2  with a main body  4 , a throttle valve shaft  6 , a throttle valve flap  8 , and a cover  10 . The adjusting device  2  contains a transmission housing  12 . The transmission housing  12  is encompassed by the main body  4 , the side walls of the main body  4 , and the cover  10 . The main body  4  also contains a servomotor  14 . Because the transmission housing  12  and the servomotor  14  are obscured by the main body  4  and the cover  10  in  FIG. 1  and are therefore not directly visible, the reference lines of the reference numerals  12  and  14  are depicted in dashed form. 
   The transmission housing  12  contains a transmission  16  ( FIG. 2 ) with a motor pinion  18 , a drive gear  20 , and a driven gear  22 . Because the motor pinion  18  and the driven gear  22  are obscured by the cover  10  in the viewing direction selected for  FIG. 2 , these parts are depicted with dashed lines in  FIG. 2 . 
   During the manufacture of the adjusting device  2 , after the servomotor  14  and the transmission  16  have been installed, the cover  10  is attached to the main body  4 . When fully assembled, the circumference of the cover  10  is welded, glued, or clamped to the main body  4 . 
   The cover  10  is provided with a first rib  24   a  and a second rib  24   b  ( FIG. 2 ). Because the ribs  24   a  and  24   b  are situated on the side of the cover  10  oriented away from the viewer, the ribs  24   a  and  24   b  are depicted with dashed lines in  FIG. 2 . 
   An axle  28  is formed onto the main body  4  ( FIGS. 3 ,  5 ,  7 ). In the preferably selected, particularly advantageous exemplary embodiment, the main body  4  and the axle  28  are molded from the same plastic, for example by means of injection molding. The axle  28 , however, can also be made of a separate material that is attached to the main body  4 , for example by means of a press fit. Thanks to the invention proposed here, in which the load on the axle  28  is significantly reduced in comparison to known adjusting devices, it is easily possible to manufacture the axle  28  and the main body  4  out of the same plastic. 
   The axle  28  has a diameter that varies along its axial direction. Starting from the main body  4 , the axle  28  first has a larger outer diameter  28   a  and, as the distance from the main body  4  increases, the axle  28  has a smaller diameter  28   c . In a transition region  28   b , the larger outer diameter  28   a  transitions into the smaller outer diameter  28   c . At the end oriented away from the main body  4 , the axle  28  has an end  28   d  oriented toward the cover. 
   The drive gear  20  is supported on the axle  28  in rotary fashion. The gear  20  has a region with a larger inner diameter  20   a  and a region with a smaller inner diameter  20   c  ( FIGS. 3 ,  5 , and  7 ). 
   The gear  20  is supported in rotary fashion with the larger inner diameter  20   a  on the larger axle diameter  28   a  and with the smaller inner diameter  20   c  on the smaller axle diameter  28   c . It is also possible to provide more than two different diameter steps so that starting from the main body  4 , the axle  28  becomes thinner in more or less finely graduated steps, the inner diameters of the gear  20  being correspondingly adapted to at least selected diameters of the axle  28 . 
   The axle  28  has a sleeve  30  mounted on it and enclosing the smaller axle diameter  28   c . The sleeve  30  is press-fitted onto the axle  28  and protrudes in the axial direction beyond the cover end  28   d  of the axle  28 . The sleeve  30  has a first region  30   c  which is press-fitted onto the smaller axle diameter  28   c  of the axle  28 . At the point at which the sleeve  30  protrudes beyond the end  28   d  oriented toward the cover, the sleeve  30  has a diameter step  30   d  ( FIG. 8 ). This is adjoined by a second region  30   e  with a reduced diameter. Starting from the diameter step  30   d , the second region  30   e  of the sleeve  30  extends axially toward the cover  10 . The sleeve  30  or at least the second region  30   e  of the sleeve  30  or at least the axially protruding edge of the second region  30   e  of the sleeve  30  is comprised of a relatively hard or hardened material and the second region  30   e  is relatively thin-walled and preferably tapers off to a point or blade shape at the end. When the cover  10  is being attached to the main body  4 , the second region  30   e  of the sleeve  30  presses into the ribs  24   a  and  24   b  provided on the cover  10 . As a result, the sleeve  30 , together with the cover  10 , constitutes a molding device  33 . The second region  30   e  of the sleeve  30  functions as the stamping body  33   e  of the molding device  33  and the ribs  24   a  and  24   b  of the cover  10  function as a receiving region  33   b  for the stamping body  33   e  of the molding device  33 . 
   The molding device  33  is embodied so that the relatively hard stamping body  33   e  pushes into the receptacle  33   b  as the cover  10  is being attached to the main body  4 . Because the receptacle  33   b  is molded only as the cover  10  is being attached to the main body  4 , an exact positioning occurs between the axle  28  and the cover  10 , independent of dimensional tolerances of the cover  10  and/or main body  4 . 
   The gear  20  has a larger gear rim  20   g  and a smaller gear rim  20   k  ( FIGS. 2 and 7 ). The larger gear rim  20   g  meshes with the motor pinion  18  ( FIG. 2 ) and the smaller gear rim  20   k  meshes with the driven gear  22 . Depending on the torque to be transmitted, the gear  20  loads the axle  28  with a lateral force  35  transverse to the rotation axis  26 . The direction of this lateral force  35  on the axle  28  is essentially perpendicular to the connecting line between the rotation axis  26  of the gear  20  and the rotation axis of the driven gear  22 . The direction of the lateral force  35  also depends somewhat on the rotation axis of the motor pinion  18 ; this influence is relatively slight.  FIG. 2  contains an arrow labeled with the reference numeral  35 , which is intended to roughly indicate the direction of the lateral force  35 . Depending on the rotation direction of the torque, the lateral force  35  can also be oriented in the direction opposite from that indicated by the arrow. The lateral force  35  is particularly powerful when the throttle valve flap  8  ( FIG. 1 ) is being moved quickly and strikes against an end stop. 
   The ribs  24   a  and  24   b  on the cover  10  offer the advantage that the stamping body  33   e  of the molding device  33  does not have to dig into the cover  10  over the entire circumference of the second region  30   e  of the sleeve  30 , but only over parts of the circumference of the second region  30   e  of the sleeve  30 . 
   In lieu of the two ribs  24   a  and  24   b , it is also possible for only one rib  24   a  to be provided. It is also possible, however, to provide three or more ribs. It is furthermore possible to make the cover  10  without ribs and to embody it so that the stamping body  33   e  on the axle  28  presses directly into the inside of the cover  10  oriented toward the transmission housing  12  and for the receptacle  33   b  of the molding device  33  to be embodied directly on the cover  10 . 
   The at least one rib  24   a  or the ribs  24   a  and  24   b  are oriented so that they extend parallel to the direction of the lateral force  35  exerted on the axle  28  by the gear  20  ( FIG. 2 ). The lengths of the ribs  24   a  and  24   b  are dimensioned so that the stamping body  33   e  comprised of the second region  30   e  of the sleeve  30  penetrates into two different places spaced apart from each other in each of the ribs  24   a ,  24   b . As a result, the receptacle  33   b  in the ribs  24   a  and  24   b  extends transversely in relation to the lateral force  35  so that when the lateral force  35  occurs, this lateral force  35  can be optimally absorbed by the cover  10 . A favorable hold between the cover  10  and the axle  28  is thus achieved with a relatively short receptacle  33   b . The short receptacle  33   b  has the advantage that the stamping body  33   e  of the molding device  33  can push into the receptacle  33   b  with a relatively small amount of force. 
   At the point at which the sleeve  30  is press-fitted onto it, the axle  28  in the exemplary embodiment shown, i.e. with the smaller axle diameter  28   c , has a main diameter  28   g  ( FIGS. 8 and 10 ). At the circumference of the main diameter  28   g , it has a raised area  28   h  or has several raised areas  28   h  distributed more or less uniformly over the circumference. Before the sleeve  30  is mounted onto it, the main diameter  28   g  with the raised areas  28   h  has a circumcircle. The circumcircle is the smallest possible circle into which the main diameter  28   g  with the raised areas  28   h  would fit without being pressed into it. It is recommended that the circumcircle of the main diameter  28   g  with the raised areas  28   h  be selected to be larger than the inner diameter of the region  30   c  of sleeve  30 , but for the main diameter  28   g  without considering the raised areas  28   h  to be smaller than the inner diameter of the region  30   c  of the sleeve  30 . As a result, the region  30   c  of the sleeve  30  can be press-fitted onto the axle  28  with a relatively small amount of force and with relatively little deformation to the material of the axle  28 . When the sleeve  30  is being press-fitted onto the axle  28 , only the tips in the region of the raised areas  28   h  must be slightly deformed. This offers the advantage that the axle  28  can be made of a material that has a relatively low subsequent deformability. Another advantage is that because of the raised areas  28   h , the sleeve  30  is slightly deformed elastically so that an initial stress is generated that reliably secures the sleeve  30  to the axle  28 . 
   In the region of the large gear rim  20   g , the gear  20  rests with the larger inner diameter  20   a  against the larger axle diameter  28   e  of the axle  28  ( FIGS. 5 and 7 ). The large gear rim  20   g  is quite large so that the larger axle diameter  28   a  can also be of relatively large dimensions. This offers the advantage that it is relatively easily for the axle  28  to absorb the load exerted on it by the lateral force  35 . 
   In the region of the small gear rim  20   k , the gear  20  rests with the smaller inner diameter  20   c  against the first region  30   c  of the sleeve  30  and thus indirectly against the smaller axle diameter  28   c  of the axle  28 . The reduction of the diameter of the axle  28  in the transition region  28   b  advantageously permits the small gear rim  20   k  to be selected as quite small, thus permitting a high gear ratio to be achieved between the gear  20  and the driven gear  22  ( FIG. 2 ). 
   In order to attain the highest possible gear ratio between the gear  20  and the driven gear  22 , the small gear rim  20   k  of the gear  20  must be relatively small. Because the axle  28  has the smaller axle diameter  28   c  at a greater distance from the main body  4 , the small gear rim  20   k  of the gear  20  can be kept quite small, which is desirable. 
   The molding device  33  between the axle  28  and the cover  10  achieves the advantage that the axle  28  is secured at one end directly by the main body  4  and is secured in an excellent fashion at the other end by the cover  10 . The fact that the cover  10  is nondetachably fastened by the main body  4  results in a good support of the gear  20  on both sides on the axle  28  and therefore on the main body  4 . 
   If the sleeve  30  only encompasses the small axle diameter  28   c  of the axle  28 , then this offers the advantages of reduced tolerance problems and reduced forces required for press fitting the sleeve and also distributes the surface load on the axle  28  in the place where the load between the gear  20  and the axle  28  is particularly high, i.e. at the smaller axle diameter  28   c.    
   The foregoing relates to preferred exemplary embodiments 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.