Abstract:
A motor-vehicle gear arrangement for a power-assist gearing in a motor vehicle, that includes a gear, a flange arrangement including at least one flange, wherein the gear is located adjacent to the flange in the flange arrangement so as to rotate about a common axis, and at least one connecting element to connect the gear to the at least one flange. This gear arrangement, or a flange for this gear arrangement, is advantageous due to the fact that the ribs are formed on the flange laterally within a plane perpendicularly to the rotational axis so as to reinforce the flange.

Description:
PRIORITY INFORMATION 
   This application claims priority from German patent application 10 2004 002 847.8 filed Jan. 19, 2004. 
   BACKGROUND OF THE INVENTION 
   The invention relates to a motor-vehicle gear arrangement for a power-assist gearing in a motor vehicle. 
   U.S. Patent Application Publication No. 2004/0060379A1 discloses a steering device for motor vehicles with a gearing system. The gearing system has a gear arrangement with a gear which is employed in the form of a worm gear between a first and a second flange. Driver elements in the form of connecting elements project in a spaced configuration from the central rotational axis that extends between the first flange and the second flange. The driver elements pass through corresponding take-up openings formed in the gear. In the gearing system, a worm of a steering linkage engages teeth of a gear ring on the outer circumference of the gear. 
   Individual components made of metal are generally preferred when constructing a gear arrangement of this type in order to provide sufficient stability. Gears made of plastic are also generally known—however, these exhibit limited stability. 
   What is needed is an improved motor vehicle gear arrangement for a power assist gearing in a motor vehicle. 
   SUMMARY OF THE INVENTION 
   A goal of the invention is to simplify a motor-vehicle gear arrangement for a power-assist gearing in a motor vehicle in regard to fabrication and the material employed, while at the same time ensuring high stability and strength. 
   A motor-vehicle gear arrangement for a power-assist gearing in a motor vehicle may include a gear, a flange arrangement, and at least one connecting element to connect the gear to the at least one flange. Ribs are formed laterally in one plane of the flange. 
   A motor-vehicle gear arrangement for a power-assist gearing in a motor vehicle is advantageous, for example, for use in an electrical steering device to couple a steering assist apparatus when the gear arrangement has a gear, a flange arrangement with at least one flange. The gear is located within the flange arrangement adjacent to the flange so they rotate about a common rotational axis. At least one connecting element connects the gear to the at least one flange. In some embodiments, ribs are formed on the flange laterally within a plane that extends perpendicular to the rotational axis of the flange, to reinforce the flange. 
   An arrangement of this type having ribs on the face of the flange increases the stability of the flange relative to a flat flange with the same flange thickness. The stability provided by the ribs permits the use of a flange thinner than would be possible otherwise, thereby saving material. An additional advantage is provided when the flange has lateral ribs as reinforcement elements, and the flange together with the ribs is fabricated out of plastic. 
   A flange of this type is thus composed of a material with relatively less strength when compared to metal. In order to increase the strength of the actual flange body, this body has laterally arranged ribs acting as reinforcement elements. This arrangement in particular allows for the use of a plastice, rather than metal, flange. In addition to permitting simpler machining, the use of plastic also offers a weight advantage relative to a flange made of metal. 
   In addition, a method of fabricating a motor-vehicle gear arrangement of the type having a flange like that described above is provided. The flange is designed with ribs located on one side of the flange which act as reinforcement elements for the flange. In particular, the flange can be produced with plastic ribs by injection molding. 
   In addition, a gear arrangement is provided that has at least one pin-shaped connecting element to connect the flange arrangement, or the at least one flange within the arrangement, to the gear. The flange has a circumferential rib around the connecting element in one insertion region for this connecting element. For example, at least some of the ribs are designed specifically as ring-shaped ribs in one region in which the body of the flange has a passage for the insertion of a connecting element. A pin-shaped connecting element thus has a lateral support (i.e., a support perpendicular to its longitudinal axis) not only in the insertion region through the body of the flange but also in the adjacent widened insertion region which is formed by the circumferential rib. The circumferential rib forms a reinforcement node for the flange, whereby the pins, or metal pins or other connecting elements, are inserted into the gear arrangement through the reinforcement node. In some embodiments, the pin is coated by injection molding to ensure a strong bond between the plastic and the pin. 
   In addition, a gear arrangement is provided in which the connecting element has a hole which passes from one front surface axially into the connecting element. In some embodiments, the hole extends through the connecting element. This arrangement has several advantages. In the event the pin is inserted into an injection molding die and then coated by injection molding, only a short segment of the pin is immersed in the die, if the complete length is coated with plastic by injection molding. The long end of the pin with the head that is free-standing within the die is supported or centered so that the pin is not deformed or damaged by the injection forces as it is coated by injection molding. In addition, the pin is supported so that the position of the free end with the head is sufficiently precise. 
   A gear arrangement is provided in which one or more connecting elements connect the flange to an additional flange and pass through connecting openings located in the gear between the flanges. The gear is thus supported between the flanges and is carried along by the connecting elements when the gear arrangement rotates. 
   A gear arrangement is also provided in which the additional flange is fabricated out of metal. The additional flange essentially functions as an end plate, thereby providing high strength in the axial direction, even with a reduced dimensioning. Alternatively, it is also possible to fabricate the additional flange out of plastic. In particular, the additional flange can be formed with the same type of ribs as the first flange. 
   A gear arrangement is also provided in which the additional flange is formed from a flat disk having on one side concavities or depressions, for example, ones deeper than a disk thickness or the thickness of the flange, which concavities or depressions form corresponding protrusions acting as drivers on the other side facing the gear. The protrusions that are created fulfill a driver function for the gear. The gear advantageously has corresponding slots within its lateral surface which the thus formed drivers engage. 
   A lateral surface of the flanges and gear is understood to mean a surface that extends essentially perpendicularly to the rotational axis of the flanges or gear. 
   A gear arrangement is also provided in which a finished hub of metal, (e.g., steel), is inserted into an axial opening of the flange fabricated out of plastic so as to introduce a shaft or spindle in a rotationally fixed manner. The steel hub provides sufficient strength and support for a shaft or spindle, while additionally providing the advantage of not requiring any subsequent finishing as long as the initial work was done sufficiently well. 
   A gear arrangement or flange of this type is advantageous when the ribs are formed as a single piece with the flange. As a result of the single-piece design, the ribs are connected in an especially rigid manner to the flange and provide especially high stability. In addition, single-piece fabrication is especially simple when using, for example, a powder-metallurgical molding process or plastic injection-molding process. 
   Advantageously, the ribs maybe arranged relative to each other in a framework for stability. Advantageously, the ribs, or some of the ribs, are circumferentially adjacent to one edge of the flange. These ribs are thus located in the outer lateral circumferential region or in the inner lateral circumferential region which is adjacent to the hub. Circumferential ribs formed on a circumferential path may also, however, be formed between the edge regions of the flange to increase stability. In particular, a circumferential rib may be ring-shaped and run from one reinforcement node to the next to increase the reinforcement of the entire system with respect to the connecting elements when the connecting elements pass through the reinforcement nodes. 
   An embodiment is also provided in which the connecting element passes through a neck of the flange, where the flange neck passes in the direction of the gear into or through an opening in the gear. While the ribs are preferably formed on a side of the flange facing away from the gear, the flange neck is preferably in the form of a connecting piece in the direction of the gear. Ultimately, the flange neck can also be formed by a rib of this type. In the event the ribs are located on the side of the flange which faces the gear or the side of the gear, the flange neck can also be formed by a raised rib which passes into the opening in the gear, thereby performing an active function between the flange and the gear as a driver or stabilization element. 
   In one embodiment, at least one sprue segment for the injection molding of the flange is located on that side of the flange on which the ribs are located. 
   In another embodiment, at least one sprue segment for the injection molding of the flange is adjacent to an opening, where the opening is formed for the insertion of a connecting element. This has the advantage that any weak points during the injection molding process which normally occur at some distance from the sprue segment are created at a considerable distance from those regions in which the connecting elements are located. 
   Whereas in a preferred embodiment, the material used for the flange is plastic, the various advantages of the basic principle are also achieved when employing another material, in particular a metal such as light aluminum. 
   These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of preferred embodiments thereof, as illustrated in the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of a flange of a motor-vehicle gear arrangement for a power-assist gearing in a motor vehicle, the laterally oriented flange having ribs or struts acting as reinforcement elements; 
       FIG. 2  illustrates a lateral arrangement of the gear arrangement of  FIG. 1 , as seen from the opposite side; and 
       FIG. 3  is illustrates an example of such a gear arrangement in an exploded view. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  is a side view of an example of a preferred gear arrangement, wherein a side wall of a first flange of a flange arrangement is shown which extends in a plane perpendicular to the rotational axis of the gear arrangement  1 . In the region of the central rotational axis, an axial opening  2  passes through the entire gear arrangement I to accommodate a shaft or spindle which is connected by a hub  3  to the gear arrangement I in a rotationally fixed manner. In a preferred embodiment, the hub  3  is inserted in a rotationally fixed manner within an axial opening of a flange  16  which transmits the rotation to a gear  14 , preferably one fabricated out of plastic, of the gear arrangement  1 . When using a flange  16  composed of a plastic material, the hub  3  may be formed from a metal material (e.g., case-hardened steel) with the result that there is no need for subsequent finishing. In the conventional manner, the gear  14  has a circumferential gear ring  23  extending radially over its outer circumference. 
   The gear  14  is located in the gear arrangement  1  between the first flange  16  and a second flange  28  shown in  FIG. 2 . Connection of the two flanges  16 ,  28  is preferably effected by pin-shaped connecting elements or pins  4 , or metal pins which pass through passages  5  or holes in the flanges  16 ,  28  and through passages or slots  22 , illustrated in  FIG. 3 , within the intermediate gear  14 . Connecting elements  4  can interconnect the two flanges  16 ,  28  here by rivet or screw connections, or other suitable connectors. In some embodiments (e.g., a motor vehicle steering-effort assist device), a simple plug-in connection between the pins and the flanges may be used. In this plug-in connection, the outer circumference of the connecting elements  4  is matched to the inner circumference of the passages  5  in such a way that a frictional connection is created that provides sufficient support. The connection between the connecting elements  4  and the second flange  28  can be radially riveted, while the opposite end of the connecting elements  4  are each provided with a wider outer circumference end section and are recessed so as to be flush within the material of the first flange at its outer surface. For purposes of insertion and possibly further stabilization, a hole  4   a  passes into the widened region of the outside face of the connecting elements  4 . 
   The first flange  16  is fabricated out of a light material; e.g., plastic. In order to increase the stability or to reinforce the first flange  16 , the flange has struts or ribs  30 - 36  on its lateral surface. The ribs  30 - 36  are arranged in a manner analogous to a framework, such as one known from a housing construction application not according to the species. In some embodiments, the ribs  30 - 36  are formed as a single piece with the actual main body of the flange  16  to form a stable connection between the main body and the ribs. A further advantage of the single-piece design for the main body and the ribs is that the main body and ribs can be formed in a single operation through pressing or injection molding. 
   In the lateral region adjacent to the inside edge or circumference of the flange  16 , a ring-shaped rib  35  is formed as an inner ring to provide reinforcement of the inner side. The inside ring-shaped rib  35  projects further away from the surface of the main body of the flange  16  than the remaining ribs  30 - 34 ,  36 , and surrounds the hub  3 . The outer circumference of the hub  3  is thus connected to the ring-shaped inside rib  35  over a large circumferential surface such that the area for power transmission during a rotation is advantageously large. 
   The ring-shaped rib  35 , located or separately formed on the inside, also advantageously extends from the opposite lateral surface of the flange  16  in the form of a connecting piece  24 , illustrated in  FIG. 3 . The inner circumference of the connecting piece  24  in turn surrounds the outer circumference of the hub  3 , and at its outer circumference engages and passes through a central passage of the gear  14 . The gear  14  thus receives inside support by the outer circumference of the connecting piece  24  to the extent these components are not separated by a ring-shaped gap in another embodiment. 
   An outside rib  33  is also provided in the lateral adjacent region of the outer circumference of the flange  16 . The outside ring-shaped rib  33  of this type widens out the outer circumferential surface of the flange  16  axially, thereby increasing the stability of the outer circumferential region. 
   The ring-shaped ribs  34  are particularly advantageous which are formed on the lateral surface of the flange  16  around the passages in order to accommodate connecting the elements  4 . These circumferential ring-shaped ribs  34  form reinforcement nodes and provide increased support for the connecting elements  4 . In addition to increased stability and strength for the flange  16  in the region of the connecting elements  4 , the entire gear arrangement  1  is also stabilized by the stronger support of the connecting elements  4 . 
   Additional ribs may run along the lateral surface of the flange  16 , in particular, for example, an additional ring-shaped or circular rib  31 . Reinforcement is also enhanced by obliquely running ribs  32 ,  30 . Advantageously, all of these various ribs (i.e., the obliquely running ribs  32 ,  30  and the circular rib  31 ) run in each case through at least one reinforcement node or to one of the circumferential ribs  34 , each of which encircle a connecting element  4 . Radially running ribs  36  are also advantageous, these being especially preferred when each is located in the region between two respective ribs  34  which are designed as reinforcement nodes. 
   An injection molding process can be used to fabricate the flange out of plastic. Sprue segments  37  for injecting liquefied plastic can be formed adjacent to the ring-shaped ribs  34  or reinforcement nodes through which the passages for the insertion of the connecting elements  4  are formed. The sprue  38  is thus produced in a region of the flange  16  in which especially high stability is required. In addition, this arrangement of the sprue segments  37  allows for distribution of the injected plastic material into the regions with the ribs  30 - 36 . The sprue  38  is placed on the side of the flange  16  on which the ribs  30 - 36  protrude away from the lateral surface of the flange  16 . However, it is also possible to locate the sprue segments  37  on the opposite side of the flange. 
   Although it is disclosed above that the ribs  30 - 36  are located on the side of the flange  16  which faces away from the gear  14 , the ribs can alternatively be formed on the side of the flange  16  which faces the gear  14  exclusively, or in addition to ribs on the side facing away from the gear  14 . 
   Referring to  FIG. 3 , structural elements  21 ,  24  are formed on the side of the flange  16  facing the gear  14 . The structural elements  21 ,  24  may be formed as a single piece with the flange  16 . The structural elements  21 ,  24  connect the gear  14  to the second flange  28 . 
   Referring to  FIG. 2 , the second flange  28  is also designed to be functionally structured. Depressions  39  in the outside surface lead to protrusions on the inside lateral surface of the second flange  28  facing the gear  14 . These protrusions engage, for example, correspondingly formed depressions having contact surfaces  19   e ,  19   f  in the opposite lateral surface of the gear  14 , thereby functioning as drivers and/or guide elements. Advantageously depressions and protrusions in the second flange  28  are located in segments which are adjacent to the connecting elements  4  leading through the passages  5 . Forces acting on protrusions are thus directly transmittable through the pins  4  to the first flange  16 , or in the opposite direction. 
   While the second flange  28  can be made of metal, it is also possible to make the second flange out of plastic. In addition, ribs for reinforcement can also be formed on the lateral walls of the second flange  28 . In the embodiment shown, the inner circumference of the second flange, as well as the outer circumferential segment of the first flange passing through the second, have an interlocking structure with concavities and protrusions, or a toothing which also has the function of force transmission. 
     FIG. 3  is an exploded view of an elastic compensation coupling of which the gear  14  of  FIGS. 1 and 2  forming a worm gear is a part. A motor-vehicle gear arrangement for a power-assist gearing of a motor vehicle is thus formed, wherein the power-assist gearing of a motor vehicle functions, for example to couple an electromotive auxiliary force for power steering to a steering linkage system. 
   The gear  14  has a gear ring  23 , the teeth not being shown, which a worm engages. The other coupling component of the elastic compensation coupling, the first flange  16 , is connected in a rotationally fixed manner to an input shaft, not shown, specifically through a connecting piece, along with a front surface  16   a  and a peripheral surface  24   d , and the hub  3 . 
   In addition to the two components of the compensation coupling, the gear  14  and the flange  16 , there is a ring-shaped elastic spacer  17  with extensions  20 . In the assembled state, an inner surface  24   b  of the spacer  17  rests on the peripheral surface  24   d  of the connecting piece of the flange  16 . Two of the extensions  20  each surround a respective one of a plurality of studs or pins  25  on the flange  16 . 
   The gear  14  exhibits mirror symmetry in other words, it has the same appearance on the nonvisible rear side as it does on the front side. After assembly, the gear  14  is supported by the spacer  17 , which in turn is supported by the connecting piece of the flange  16 . An inner surface  24   c  of the gear  14  thus rests on an outer ring surface  18   d  of the spacer  17 . Concavities  26  of slots  22  are provided in the gear  14 . The extensions  20  fit within the concavities  26 . 
   Although it is possible that the gear  14 , flange  16 , and spacer  17  would be sufficient to fulfill the function of an elastic compensation coupling, the front side of the gear  14  is augmented by a second spacer  27  and the second flange  28  forming another compensation coupling. In the assembled state, the flanges  16  and  28  are interconnected by driver elements or lugs  21 , and the pin-shaped connecting elements  4 . In addition, an inner toothing  40  of the second flange  28  engages a toothing  41  of the connecting piece on the first flange  16 . In the assembled state, the second elastic spacer  27  is also seated on the connecting piece of flange  16 . The rear side of the second flange  28  has these same studs  25  as the first flange  16 . These studs of the second flange  28  each project into the intermediate space between two closely adjacent extensions  20  of the spacer  27 . The studs are preferably formed as protrusions which are formed opposite the depressions  39 . 
   In this case, for example, a front-side contact surface  18   a  of the second spacer  27  contacts the rear side of the second flange  28 . A rear-side contact surface  18   b  of the second spacer  27  contacts a contact surface  18   e  of the concavity  26  in the gear  14 . Lateral contact surfaces  19   a ,  19   b  of the spacers  17  or  27  contact the lateral contact surfaces  19   c ,  19   d  of the stud  25 , or contact the lateral contact surfaces l 9   e ,  19   f  of the concavities  26  in the gear  14 . 
   The extensions  20  thus prevent the studs  25  from directly touching the lateral surfaces  19   e ,  19   f  of the concavities  26  when torque is transmitted in one or the other direction. The spacers  17 ,  27  are designed to be sufficiently wide that they prevent direct contact axially between the gear  14  and the flange  16 , or between the gear  14  and the second flange  28 . Since the ring-shaped parts of the spacers  17 ,  27  are located between the peripheral surface  24   d  of the flange  16  and the inner surface  24   c  of the gear  14 , the design also ensures that in a radial direction direct contact between the connecting piece of the flange  16  and the gear  14  is avoided. In other words, the spacers  17 ,  27  thus form a buffer, both axially and radially, and ultimately even tangentially, between the flange  16 , and thus the input shaft on the one hand, and the gear  14  on the other. 
   In the tangential direction, however, the elastic buffering is not unlimited, since the slots  22  in the gear  14  through which the lugs  21  of the flange  16  engage are tangentially only slightly larger than lugs  21 . The result is that the lugs  21  and the slots  22  form mutual stops which come into effect if the extensions  20  of the spacers  17 ,  27  are squeezed together by a certain amount whenever an excessively large torque is transmitted. 
     FIGS. 1 and 2  show the gear arrangement  1  which may be employed as the gear  14 , as shown in  FIG. 3 , for example, in a power-assist gearing in a motor vehicle. It is of course also possible to employ the gear  14  in other gearing systems as well. 
   Although the present invention has been illustrated and described with respect to several preferred embodiments thereof, various changes, omissions and additions to the form and detail thereof, may be made therein, without departing from the spirit and scope of the invention.