Abstract:
One-part stabilizers are designed for road traffic only or for off-road travel only. Two-part stabilizers with a shiftable clutch have drawbacks in terms of quality and safety. A clutch is therefore presented, whose radial carriers ( 14, 16 ) are located on the same plane and which are fixed without clearance via a shiftable and axially displaceable locking piston ( 17 ) with locking elements ( 23 ) or are released over a predetermined pivot angle.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a United States National Phase application of International Application PCT/DE 2004/002693 and claims the benefit of priority under 35 U.S.C. § 119 of German Patent Application DE 103 58 762.4 filed Dec. 12, 2003, the entire contents of which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention pertains to a stabilizer with stabilizer parts, which are connected to the wheel suspension of a wheel, on the one hand, and with the vehicle body via a mounting point, on the other hand, and both the stabilizer parts can be connected to one another via a shiftable and positive-locking clutch. 
       BACKGROUND OF THE INVENTION 
       [0003]    Such stabilizers are used in automotive engineering. 
         [0004]    In principle, a stabilizer, which operates according to the principle of the torsion bar, extends in parallel to the axle and is fastened at both ends of a wheel suspension, is associated with each axle of a motor vehicle. These stabilizers have the task of preventing or weakening the transmission of the rolling motions that are caused by the road conditions and originate from the wheels to the vehicle. Such rolling motions are generated mainly in road curves or in case of unevenness of the road, for example, potholes or ruts. There are one-part stabilizers adapted to certain fields of use, but they respond either too softly or too harshly to different loads and lack a sufficient range of torsion for some applications. This has a disadvantageous effect on driving comfort. 
         [0005]    Two-part stabilizers, which are connected to one another by a clutch, are therefore increasingly used for special applications. The two parts of the stabilizer are connected to one another directly in the coupled state in such a way that they rotate in unison, so that the action of a one-part stabilizer is thus achieved. In the uncoupled state, an additional free angle of rotation is set between a mechanical stop for one direction of rotation and a stop for the other direction of rotation. A vehicle equipped with such a stabilizer that can be coupled can be used under normal road conditions and abnormal road conditions alike. 
         [0006]    Such a two-part stabilizer with a clutch is described in DE 199 23 100 C1. The corresponding clutch comprises a cylindrical housing, which is connected to one of the two stabilizer halves in such a way that they rotate in unison. A shaft, which projects from the housing and is connected to the second stabilizer half in such a way that they rotate in unison, is mounted rotatably in the cylindrical housing. The housing has a stationary and inwardly directed carrier, and the shaft located inside carries, in the same radial plane, an outwardly directed, second carrier, which rotates in unison. Corresponding free spaces, with which two claws of a locking piston mesh, are located between the two carriers. This locking piston is axially displaceable and is loaded by a compression spring in the closing direction and by a hydraulic force in the opposite direction. Both the carriers and the claws are mutually fitting force transmission surfaces, which are axially conical and radially flat. 
         [0007]    It has now been found that the carriers of the two stabilizer parts and the claws of the locking piston are jammed with one another under the loads of the compression spring and the torsional forces, so that unusually strong hydraulic adjusting forces are necessary for uncoupling. This can be attributed to the fact that force components that load the two stabilizer halves, on the one hand, and the claws of the locking piston, on the other hand, radially in opposite directions, occur in the areas of the force transmission surfaces. This leads to widening or narrowing of the carriers and the locking claws, as a result of which the position of the conical surfaces located opposite each other will change as well. After elimination of the external loads, the carriers and the claws seek, due to their internal stresses, to assume their original shapes, and the carriers and the claws are wedged in one another because the conical surfaces no longer fit each other. 
       SUMMARY OF THE INVENTION 
       [0008]    The basic object of the present invention is therefore to develop a stabilizer of this type, in which the positions of the mutually corresponding and force-transmitting conical surfaces of the clutch in relation to one another remain unchanged. 
         [0009]    According to the invention, a stabilizer for a motor vehicle is provided comprising two stabilizer parts, which are connected to the wheel suspension of a wheel, on the one hand, and with the vehicle body via a mounting point, on the other hand. Both of the stabilizer parts can be connected to one another via a shiftable and positive-locking clutch. The clutch comprises at least one radial carrier of one stabilizer part, at least one radial carrier of the other stabilizer part and an axially displaceable locking piston with locking claws. The locking claws and the carriers have conical surfaces, which fit each other and are designed as force transmission surfaces. The conical surfaces of the radial carriers and the conical surfaces of the locking claws have an arched cross section over the entire force transmission area. The arch is designed as a concave arch, on the one hand, and as a convex arch, on the other hand. 
         [0010]    Jamming of the torque-transmitting elements is ruled out in the new clutch. This has an advantageous effect on the shifting function of the clutch and also requires only very weak adjusting forces. It is advantageous in this connection if the arches of the conical surfaces of the radial carriers and of the locking claws have an equal radius, because the load-bearing capacity and the slidability of the mutually corresponding conical surfaces improve. 
         [0011]    The new clutch with its arched contour has special technical effects. Thus, the arch of the force-transmitting conical surfaces causes the circumferential forces prevailing in the contact area of the conical surfaces located opposite each other to develop different force components along the arched conical surface. Thus, the radial force components are greater at the inner and outer ends of the arch than in the area located in between. However, since these radial force components are directed opposite each other, they largely offset each other, so that there are, in toto, only small radial force components, which bend the free ends of the radial carriers and of the locking claws either to the outside or to the inside. This considerably reduces the risk of jamming. 
         [0012]    If radial force components still act on the radial carriers and the locking claws and change their positions in relation to one another, the mutually corresponding conical surfaces act like the sliding surfaces of a ball bearing. Jamming of the corresponding carriers and locking claws is therefore also ruled out. The present invention shall be explained in greater detail below on the basis of an exemplary embodiment. 
         [0013]    The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    In the drawings: 
           [0015]      FIG. 1  is a simplified view of a stabilizer that can be coupled; 
           [0016]      FIG. 2  is a simplified sectional view of the clutch; 
           [0017]      FIG. 3  is the clutch in the locked state; 
           [0018]      FIG. 4  is the locking piston; 
           [0019]      FIG. 5  is the radial carrier of one stabilizer part; 
           [0020]      FIG. 6  is the radial carrier of the other stabilizer part; and 
           [0021]      FIG. 7  is a partial view of the engaged clutch. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0022]    Referring to the drawings in particular, each axle of a motor vehicle comprises, in principle, the two wheels  1  and an axle  2  carrying the two wheels  1 . A divided stabilizer  3  with its two stabilizer parts  4  and  5  is located in parallel to the axle  2 , each stabilizer part  4 ,  5  being connected to a wheel suspension, not shown, of the corresponding wheel  1  and, on the other hand, via a mounting point  6 , with the vehicle chassis. A clutch  7 , which connects the two stabilizer parts  4 ,  5  to one another into a continuous stabilizer  3  or separates them from one another, is arranged between the two stabilizer parts  4  and  5 . The dimensioning and the properties of the material of the connected stabilizer  3  are selected such as to absorb the torsional forces introduced via the wheels  1  and to build up corresponding opposing forces. Thus, these forces are not transmitted to the vehicle body or are at least attenuated. 
         [0023]    The clutch  7  can be shifted axially and has a positive-locking design. The clutch  7  comprises for this purpose, according to  FIG. 2 , a cylindrical housing  8  with a closed bottom  9 , which is joined by a connection pin  10  for one of the two stabilizer parts  4 ,  5 . A mounting point  11  for a hinge is located on the inner side of the bottom  9 . Opposite the bottom  9 , the housing  8  is closed, rotating in unison, with a cover  12 , which is equipped with a continuous bearing bore  13  for another hinge, and with a radial carrier  14 , which protrudes into the interior of the cylindrical housing  8 . The radial carrier  14  is located in the radial space between the continuous bearing bore  13  and the inner wall of the cylindrical housing  8 . 
         [0024]    Furthermore, a shaft  15 , which passes through the interior of the cylindrical housing  8  and is mounted rotatably in the mounting point  11  in the bottom  9  of the housing  8 , on the one hand, and in the bearing bore  13  in the cover  12  of the housing  8 , on the other hand, is fitted into the housing  8 . The shaft  15  is connected to the other stabilizer part  4 ,  5  in such a way that they rotate in unison. 
         [0025]    Another radial carrier  16 , which is arranged in the housing  8  and designed in the same manner as the radial carrier  14 , is located on the shaft  15 . The radial carrier  14  at the cylindrical housing  8  and the radial carrier  16  on the shaft  15  are thus located on a common radial plane, as a result of which both radial carriers  14  and  16  are pivotable in relation to one another to a limited extent only. 
         [0026]    Furthermore, a locking piston  17 , to which hydraulic pressure can be admitted, is axially displaceable on the shaft  15  and is guided in a radially rotatable manner and which divides the interior space of the cylindrical housing  8  into a compression spring space  18  on the bottom side and into a pressure space  19  on the cover side, is located in the interior of the cylindrical housing  8 . A compression spring  20 , which is supported at the bottom  9  of the housing  8  and loads the locking piston  17 , is inserted into the compression spring space  18 . The compression spring space  18  is connected to a hydraulic tank via an overflow oil connection  21 . By contrast, the pressure space  19  is connected to a hydraulic compressed oil supply unit via a compressed oil connection, not shown. 
         [0027]    As is shown in  FIGS. 3 and 4 , two locking claws  22 , which are located, in the same manner as the two radial carriers  14  and  16 , in the radial free space between the shaft  15  and the inner wall of the housing  8  and which are both arranged opposite each other, i.e., offset by 180° in relation to one another, are formed on the cover side of the locking piston  17 . The shape and the dimensions of the two locking claws  22  are coordinated in a special manner with the shapes and dimensions of the two radial carriers  14  and  16 . Thus, the two gaps between the two radial carriers  14  and  16  are thus filled out without a clearance. Furthermore, the locking piston  17  is equipped with a stroke limitation means, which prevents the two radial carriers  14 ,  16  and the two locking claws  22  from becoming disengaged in the other end position of the locking piston  17 . Consequently, a positive length coverage of the radial carriers  14 ,  16  and the locking claws  22  of the locking piston  17  continues to be present in this end position. 
         [0028]    The contact surfaces of the two carriers  14 ,  16  and of the two locking claws  22 , which said surfaces are located opposite each other and communicate with one another, are designed as force transmission surfaces. The two carriers  14 ,  16  and the two locking claws  22  have for this purpose a conical surface  23  each with a smaller angle, which are in contact with one another without a clearance in the coupled state. The conicity of the conical surfaces  23  with the smaller angle is selected to be so small that the axial force component of a radial force introduced to the stabilizer  3  from the outside does not exceed the spring force of the compression spring  22 . In addition, the two carriers  14 ,  16  have a conical surface  24  with a larger angle at their free end and the two locking claws  22  have a conical surface  25  with a larger angle at their free ends, which conical surfaces form a radial clearance with one another in the uncoupled state. The two stabilizer halves  4 ,  5  are freely rotatable in relation to one another within this free space. 
         [0029]    The force transmission surfaces composed of the conical surfaces  23 ,  24 ,  25  at the two carriers  14 ,  16  and at the two locking claws  22  have an arched contour in their cross section. Thus,  FIG. 4  shows conical surfaces  23 ,  25  at the locking claws  22  with a concave arch that extends over the entire force transmission area and has a uniform design. By contrast, the conical surfaces  23 ,  24  of the two radial carriers  14 ,  16  according to  FIGS. 5 and 6  are provided with a convex arch over their entire force transmission area. The dimensions and the geometries of the concave arch of the force transmission surfaces of the two locking claws  22  and of the convex arch of the force transmission surfaces of the two carriers  14 ,  16  are adapted to one another. 
         [0030]    Under normal road conditions, for example, during road traffic, the pressure space  19  in the cylindrical housing  8  is kept pressureless, so that the compression spring  20  loads the locking piston  17  and displaces it in the direction of the radial carriers  14 ,  16 . Lateral contact develops between the radial carriers  14 ,  16  and the two locking claws  22 . As a result, the radial carriers  14 ,  16  and the rotatable locking piston  17  are centered, so that the two locking claws  22  penetrate into the intermediate spaces between the two radial carriers  14 ,  16  to the extent that the conical surfaces  23  with smaller angle will mutually come into contact with one another. The locking piston  17  is held in this position by the force of the compression spring  20  over the entire loading area. The stabilizer parts  4 ,  5  thus coupled behave now as a one-part stabilizer. 
         [0031]    Under poor road conditions, which occur, for example, off the road, the torsion range of the coupled stabilizer  3  is no longer sufficient to compensate the rolling motions of the wheels. By actuating a preferably hydraulic pressure supply unit, the pressure space  19  of the clutch is pressurized in such cases, so that the locking piston  17  separates from the contact area of the conical surfaces  23  with the smaller angle against the force of the compression spring  20  and is displaced into its end position defined by the stroke limitation means. By maintaining the hydraulic pressure in the pressure space  19 , the locking piston  17  is held in this position. The two stabilizer parts  4 ,  5  are thus separated, but they remain in axial overlap in the area of the conical surfaces  24 ,  25  with a larger angle. In case of different loads on the two wheels of one axle, one of the two radial carriers  14 ,  16  in the area of the conical surfaces  24  with the larger angle comes into contact in the area of the conical surface  25  with a larger angle of one of the locking claws  22  and rotates until it is supported on the conical surface  24  with the larger angle of the other of the two carriers  14 ,  16 . The two stabilizer parts  4 ,  5  are again connected to one another in this coupled state, so that they are capable of absorbing torsional forces in the same direction of rotation. 
         [0032]    While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.