Abstract:
An easy-to-assemble motor-adjustable throttle valve for fluid channels, especially in motor vehicle air conditioning systems, which can be obtained when a geared motor is integrated in the setting stem without causing an unacceptable reduction of the remaining clear channel cross-section. A built-in housing fitted with a high-speed small servomotor and provided with a strongly reducing shaft gear disposed inn the axial extension of the housing is radially inserted through a side wall of the channel and coaxially inserted into a pot-shaped tapered section of one end of the setting stem, the output wheel of the shaft gear being formed on the inner covering surface of such section.

Description:
BACKGROUND 
   The invention relates to a valve, in particular for influencing the cross section of a fluid duct. 
   A valve of this type is known from DE 42 23 933 A1 as a throttle device of an internal combustion engine, an electric servomotor for the throttle valve no longer lying outside the throttle duct, but instead, for cooling purposes, in this case in the intake-airstream, determined by the instantaneous valve position, through the throttle duct itself. However, because the cooling action is consequently dependent on the valve position, the motor still has to be designed again for minimum convection cooling and therefore with bulky heat exchanger surfaces, thus appreciably restricting the useful maximum cross section of the throttle duct. 
   Considerable torques often have to be applied for valve adjustment and then for holding the valve in its desired angular position under the load of the medium flowing up in the duct, whereas an installation of a correspondingly large-dimensioned servomotor into the interior of the duct would again reduce the useful cross section of the latter unacceptably. Consequently, an actuating shaft connected in a rotationally rigid manner to the valve and mounted in duct side walls located opposite one another transversely to the longitudinal extent usually projects out of one of the side walls to a servomotor for valve movement which is mounted outside the duct. On the other hand, an externally arranged valve drive markedly projecting beyond the outer cross section of the duct may be disturbing for the operational surroundings, particularly in the case of systems with narrow dimensioning. The space for a valve drive located outside the duct is even often not readily available particularly for the subsequent installation of such a throttle valve at an operationally predetermined point of a complex pipeline system, such as in the engine space of a motor vehicle, for regulating the air-conditioning of the passenger cell. This may then mean that a complicated, but otherwise functionally disturbing lever mechanism has to bridge the distance from the motor to the valve mounting. 
   Motor-moveable valves, depending on their dimensions, are used particularly in supply-air and waste-air ducts, for example for the throttling of fresh air in the air-conditioning of stationary or mobile spaces, but also, in general, for influencing the throughflow during the flow transport of flowable materials. For this purpose, the respective valve is mounted in the inner cross section of the duct about a pivot axis and can be set into different angular positions with respect to the direction of flow. When it is oriented parallel to the direction of flow, the throttle action is minimal, being forwarded only by the installation dimensions of the valve. By contrast, when the latter is oriented transversely to the direction of flow, the smallest free residual cross section remains. The geometry of the valve usually has exactly the cross-sectional form of the duct and, if necessary, depending on the flow medium, sealing lips along its circumference, so that, when the valve is oriented transversely to the longitudinal extent of the duct, the entire inner cross section of the said duct is shut off hermetically. The valve drive conventionally takes place via an electric servomotor, but, in surroundings where there is an explosion hazard, also by means of a hydraulic or pneumatic fluid motor. 
   SUMMARY OF THE INVENTION 
   The object on which the invention is based is, to design a motor-operated valve of the generic type, particularly for fluid conduction systems, such as are encountered in motor vehicle air-conditioning systems, to the effect that it, together with its drive, can be used without difficulty, to be precise, in particular, without an unacceptable impairment of cross section, and even subsequently. 
   This object is achieved, according to the invention, in that the generic valve also includes a reducing geared motor inserted into the interior of the hollow shaft of the valve. The high geared reduction makes it possible to use a very high-speed and therefore small-build motor, such as is available as a highly cost-effective mass product, for example, in the form of a low-voltage direct-current servomotor. In spite of the unusually high reduction, the gear can be designed with an extremely small build when it is conceived as what may be referred to as a wave gear, such as is described in functional terms, for example, in the contribution “Genial einfach” (“Ingeniously simple”) by H. Hirn in ANTRIEBSTECHNIK 11/1996 pages 48–51, to the full content of which reference is made here in order to supplement the disclosure of the present invention. 
   Preferably, the commercially available micromotor is embedded axially into an installation housing in the form of a thin-walled bowl, which has engaged over it in turn, on the opposite side, the hollow shaft of the valve. The coaxial gear arranged in the axial extension of the motor in the hollow shaft utilizes a wall part, projecting axially above the bottom of the installation housing, as a supporting wheel and a part of the hollow shaft itself, which is axially adjacent thereto, as an output wheel for the tappet wheel of the wave gear and consequently has a particularly compact construction. 
   The diameter of such a small-build motor/gear combination is at most one third of the diameter of ventilation ducts normally to be encountered in motor vehicle air-conditioning, and the axial length of the motor/gear combination is of the order of magnitude of typically half the duct diameter, so that the reduction in cross section occurring when the actuating drive is installed into the very interior of a duct of comparatively small diameter is justifiable. The thinner the duct to be shut off is, the further the geared motor of standardized constructional length engages radially into the duct; in the case of a very small duct, the geared motor is then arranged in a continuous hollow shaft as the valve actuating shaft, without the reduction in cross section becoming unacceptable—in the case of larger ducts, such as those with customary inner dimensions of 120×120 mm, the valve shaft, then widened in a tulip-shaped manner only over a correspondingly short part of its axial length, no longer has any bearing in any case. 
   The motor may be designed as a bar-armature direct-current motor, but also as a stepping motor. The small-volume installation housing with its integrated functions as a bearing journal for the actuating shaft end widened in the form of a bowl, as a housing with a supporting wheel, fixed with respect to the apparatus, for the wave gear and, if appropriate, also as a substrate for electrical conductors, such as potentiometer slide tracks and their connecting conductor tracks, is advantageously a plastic injection molding, for example manufactured from a duroplastic. 
   A motor-adjustable throttle valve, mountable in a simple way, for fluid ducts, such as have to be encountered particularly in motor vehicle air-conditioning, is thus obtained, in the case of a geared motor integrated according to the invention into the valve actuating shaft, without any unjustifiable weakening of the remaining thin duct cross section, when an installation housing equipped with a high-speed small servomotor is equipped in the axial extension of the motor space with a very highly reducing wave gear and is inserted into a hollow valve actuating shaft, on the inner-surface area of which is formed the output wheel of the wave gear. 

   
     DESCRIPTION OF THE DRAWING 
     With regards to further properties and advantages and also features and developments of the invention, reference is made to the following description of the preferred exemplary embodiment of the solution according to the invention, said exemplary embodiment being sketched, not entirely true to scale, in the drawing and with restriction to what is functionally essential. The single FIGURE of the drawing shows, in a truncated longitudinal section through a ventilation duct of rectangular inner cross section, the installation of the servomotor into the partially hollow shaft of the throttle valve oriented exactly in the passage position. 
   

   DESCRIPTION OF THE INVENTION 
   A fluid duct  11  of rectangular cross section here has installed in it a throttle valve  12 , the contour of which has the same geometry as the duct cross section and therefore shuts off the duct through-flow is oriented transversely to the drawing plane. By contrast, in the depicted position parallel to the longitudinal axis of the duct  11 , the cross section of the latter is reduced only by the comparatively very small installation dimensions of the valve  12 , together with its servomotor  14 , integrated in the hollow shaft  13  of said valve, with the reduction gear  15 . 
   In the preferred example illustrated, the valve  12  has, on both sides of its shaft  13 , in each case a wing in a common plane. The two wings of the valve  12  are formed in one piece with its common shaft  13 , preferably produced in one part by plastic injection molding. To the extent that the axial length of the geared motor  14 - 15  is smaller than the diameter of the duct  11  in the direction of the valve actuating shaft  13 , the shaft  13  does not need to occupy over its entire length the volume of a hollow shaft. For the example illustrated, to reduce the installation dimensions, the shaft  13  has a tulip-shaped configuration in the longitudinal section, with a stem of greater or lesser length as a continuation of its hollow-cylindrical orifice, that is to say, only over a part of the shaft length as is evident from the sectional illustration of the drawing, hollow so as to open in a bowl-shaped manner toward the adjacent side wall  16  and otherwise compact, here restricted to the minimum cross section necessitated by the bending moment requirements. 
   This stepped or continuously hollow pivoting shaft  13  for the angular position of the valve  12  inside the duct  11  is mounted, on the one hand, in a side wall  18  of the duct  11  by means of a journal  17 . A long bowl-shaped installation housing  22  for the geared motor  14 - 15  projects from the opposite side wall  16  radially into the interior of the duct  11  and serves as a bearing journal, fixed with respect to the duct, for the adjacent end of the shaft  13 , said end surrounding said geared motor and being hollow-cylindrical here or widened radially in a bowl-shaped manner. To reduce the friction, the shaft bowl  19  does not rest against the in each case radially opposite cylindrical surface area over the full surface, but only with at least one rib  20  running around on its inner surface area or on the outer surface area of the housing  22 . Thus, the valve  11  is mounted pivotably with its hollow shaft  13  on the installation housing  22  for the geared motor  14 - 15  about the axis  23  of the latter. The motor  14  itself is simply inserted axially, secured nonpositively or positively against rotation, into the end face of the installation housing  22 , said end face being opened toward the adjacent side wall  16 . When the installation housing  22  equipped with the geared motor  14 - 15  is being installed, a collar  24  running radially around the installation orifice  34  on the outside is fastened in an orifice  25  in the duct side wall  16 , through which, during assembly, the valve  12  thus equipped with its drive can be introduced radially into the duct  11 . Expediently, as outlined, the collar  24  is enlarged in the radial direction so far beyond the cross section of the installation housing  22  that, together with the installation mounting of the geared motor  14 - 15 , said collar at the same time also serves as a cover for closing the assembly orifice  25  which does not necessarily have to be circular and the largest diameter of which is somewhat larger than the overall dimension, radial to the shaft  13 , of the valve  12  to be introduced here. 
   For the particularly high, but compact-build reduction of the rotational movement of the motor output shaft  27 , a wave gear  15  is formed in front of that end face of the installation housing  22  which is remote from the mounting wall  16  for the geared motor  14 - 15 . Its wave generator  26 , as it may be referred to, which is nonround (preferably elliptic in axial cross section or, as assumed here for the drawing, triangular) and which is connected rotationally to the output shaft  27  of the motor  14 , has the effect, in a way known as such, that a spoked tappet wheel  28  is peripherally deformed radially, so that only an azimuthally short region (on the left in the drawing) of its toothed outer ring, which may be referred to as the flexible band  29 , is in engagement both with the toothing of a supporting wheel  30  fixed with respect to the apparatus and also with the toothing of an output wheel  31  fixed with respect to the valve. These toothings are preferably oriented radially, as outlined; in principle, however, they may also be oriented axially, for example, in the manner of contrate wheels. 
   Preferably, as outlined, the supporting wheel  30  lies in the direct axial extension of the hollow cylindrical wall of the motor installation housing  22  on the inner surface area of a gear housing  32  integrally formed coaxially here, the output wheel  31  lying on that region of the inner surface area of the hollow shaft  13  which is adjacent to the bottom of the valve shaft bowl  19 . As a result, the tappet wheel  28  rolls within the supporting wheel  30  at the angular speed of the motor shaft  27 , but takes along the output wheel  31  and therefore the valve shaft  13  only at the very greatly reduced angular speed according to the slight difference in the number of teeth, for example, between the supporting wheel  30  and the output wheel  31 . High-speed motor rotation is thus converted into the high torque of a slow valve adjustment. 
   For a feedback of the current angular position of the valve  12  in the duct  11 , a rotary angle encoder  33  is installed in a radially widened region between the outer surface area  21  of the motor housing  22  and the shaft bowl  19  near the end face orifice of the latter. Said encoder may be an incremental or coded digital counting system; or simply, as outlined, an analog potentio metric system with at least one contact brush on at least one circulating resistance track. The latter, including its conductor track to externally accessible connecting plugs on the collar  24  of the installation housing  22  can then be integrated (not indicated in the drawing) into the plastic surface area  21  of the housing  22  or of the shaft bowl  19  mounted on said surface area, by the technology of what is known as the Molded Interconnected Device (MID). However, it is more expedient, since, for example, it is accessible in a simpler way for an exchange which may possibly be necessary, to have a conventional solution with a separately produced and here mounted substrate plate for the count marking or for the resistance tracks. This substrate may be designed as an annular disk oriented radially to the axis  23  or as a flexible sleeve bent concentrically to the axis  23  and be secured in a stationary manner on the outer surface area  21  of the installation housing  22  or peripherally in the end-face widening of the hollow-shaft bowl  19 , with contact brushes held opposite and radially or axially oriented correspondingly. 
   For assembly, the throttle valve  12  is only to be introduced, with its integrated shaft  13  widened at least over part of its axial length to form a bowl, radially through the orifice  25  in a duct side wall  16  into the duct cross section and be plugged with its bearing journal  17  into the opposite wall  18 , whereupon the installation housing  22  prefitted with the geared motor  14 - 15  can be introduced axially as a second bearing journal into the shaft bowl  19 , as a result of which the assembly orifice  25  is at the same time closed by the housing collar  24  of the motor  14 . Even more expediently, the valve  21 , together with its at least partially hollow shaft  13 , and the geared motor  14 - 15  in its installation housing  22  are preassembled externally to form a single manageable subassembly, as illustrated in the drawing, by way of example, by the engagement of the radial bearing rib  20  into a snap-in groove on the outer surface area of the housing  22 , which may then serve at the same time for securing the shaft  13  axially in the opposite direction to the mounting of the journal  17 . 
   The contact lugs  35 , projecting from the bearing plate of the motor  14 , for the electrical feed of the motor  14  are easily accessible there for the connecting cabling in the housing installation orifice  34 . The latter may be closed by means of a cover  36  in the form of a plug or of a shallow bowl, preferably simply to be inserted nonpositively, preferably with an integrated plug cage. For matching to different motors  14  in terms of the position of contact lugs  35 , the cover  36  then needs only to be equipped with a different plug cage. This is expediently designed at the same time for electrical access to the rotary angle encoder  33 , so that no separate contact means have to be attached for connecting the latter to the control periphery.