Abstract:
Actuator having at least three coupling elements connected with stabilizers ( 3, 5 ) and coupling splines ( 4, 16, 17 ), wherein one axially movable coupling element ( 10 ) is prestressed by a spring ( 11 ) while the other coupling elements are firmly connected with said stabilizers, and a pressure chamber ( 12 ) whose internal pressure regulates the disengagement operation.

Description:
BACKGROUND OF THE INVENTION 
     In EP 344 183 B1 has been described an actuator in the form of a positive-fit shaft coupling in which a quick engagement and disengagement of two shaft parts is made possible by the fact that at least one of the two coupling halves is equipped with drivers which engage in recesses of the other coupling half or of a part connected therewith and the relative position of the drivers can be changed to two shift positions so that different rotational angles can be adjusted between the shaft parts to be coupled. The coupling halves have distributed on the periphery drivers in the form of driver bolts which carry rollers. The latter engage in recesses designed as guide grooves of a coupling sleeve. 
     Disadvantageous in the prior art such as described in EP 344 183 B1 is the fact that due to the design principle with the drivers distributed on the periphery, a larger radial installation space is needed which, in the first place, limits the ground clearance in off-road vehicles and that, due to the multiplicity of small structural parts, the resulting high sensitivity to soiling can impair operation. 
     The problem on which this invention is based is to show an actuator which, because of its small radial extension, does not limit the ground clearance of motor vehicles and yet can transmit strong torques and allow firm teeth settings. 
     SUMMARY OF THE INVENTION 
     This problem is solved by a generic actuator incorporating the present invention. 
     Because of the compact design mainly in radial direction and reduced number of structural parts susceptible to failure and sensitive to soiling, the actuator, according to the invention, is particularly adequate for installation in vehicles used in difficult grounds. By integrating the driver and prestressed springs in a housing, it is possible to reduce installation space and the multiplicity of structural parts. 
     An annular coupling element with an internal driver preferably designed as internal tooth forms a housing bottom and is connected with a stabilizer. A second annular coupling element has an external driver connected with one other stabilizer. A third coupling element is preferably designed as an axially displaceable piston with teeth contours adapted to the two other coupling elements. By the interaction of the three coupling parts, a very stable construction can be shown on small installation space. The coupling splines of the individual coupling elements can be adapted to the particular utilization. They can be designed, e.g. as teeth or shaft/hub connections. Besides, the effective torsional length of the actuator is not limited by the compact design. This is made possible primarily by a stabilizer that passes through the actuator. To avoid an expensive surface machining of the stabilizer and makes an optimum service life of the structural part possible, a housing cover can be connected with the stabilizer by a low-friction bearing bush. The low-friction bearing bush is secured on rods. An expensive machining of the stabilizer can thus be eliminated. In the coupling element designed as piston, an end cutoff can be integrated which can work mechanically, electrically, or hydraulically. Besides, a valve function can be integrated in the coupling element designed as piston. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Different embodiments of this invention are described in principle with reference to the drawings wherein: 
     FIG. 1 is a constructional embodiment of an inventive actuator; and 
     FIGS. 2 and 3 are examples of utilization of an inventive actuator. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In FIG. 1 is shown a constructional design of an inventive actuator  1 . A housing  2  is firmly connected with a stabilizer  3 . The housing  2  has a coupling spline  4  which can be adapted to the particular utilization for which it is required. A second stabilizer  5  is displaceably supported in a housing cover  6  and provided with a seal  7 , which encloses in a pressure chamber  9 , the actuation pressure introduced through a connection  8 . A coupling element  10  designed as a piston is loaded by a spring  11  against the pressure acting in a pressure chamber  12 , i.e. when there is high pressure force in the pressure chamber  12 , a disengagement occurs. Under low pressure, high spring force engagement occurs. The coupling element  10 , designed as a piston, has seals  13  and  14  which separate from each other the pressure chambers  9  and  12 . The coupling element  10  has a prolongation  15  with a coupling spline  16  which interacts with the coupling spline  4 . Upon the stabilizer  5  is situated one other coupling spline  17  which is in an operative connection with the coupling splines  4  and  16 . The pressure chamber  12  can be loaded with pressure via a connection  18  so that the coupling splines  4 ,  16  and  17  allow an adjustable slewing range in which stabilizers  3  and  5  can be rotated relative to each other. 
     By reducing the diameter of the connections  8  and  18 , a hydraulic damping can additionally be shown by the inventive actuator  1 . The coupling splines  4 ,  16  and  17  always overlap axially in the disengaged state so that the stabilizers  3  and  5  automatically engage during a pressure breakdown. 
     FIG. 2 show a utilization of inventive actuators  19  and  20  with appertaining energy supply and control system. 
     According to the invention, on the bottom (not shown) of a multi-axle vehicle, actuators  19  and  20  are supported on swivel bearings  21 ,  22 ,  23  and  24 . On the external ends of the stabilizes  3  and  5  of similar construction, additional swivel bearings  25 ,  26 ,  27  and  28  are mounted which also axially fix the stabilizers  3  and  5 , respectively, on the vehicle axles  29  and  30 . 
     The pressure required for the disengagement of the actuators  19  and  20  is produced by an electromagnetically actuatable control valve  33  installed in a return pipe  31  of a steering system  32 . The control valve  33  is actuated at the low speed range for the cases when in difficult ground the vehicle would effect great shaking movements over stiff stabilizers. The disengagement can be activated automatically by an electronic control unit  34  via a speed signal delivered by a tachometer  35  or manually via a switch (not shown). But for reasons of safety, the engagement must be automatic when high transverse accelerations occur and according to a limiting speed. 
     The control valve  33  is advantageously shifted so that the power coupling on the actuators  19  and  20 , i.e. the engagement of the coupling splines  4 ,  16  and  17 , are automatic in case of failure of the electric system. This is required in order to limit the angle of shaking during high speeds and transverse accelerations. Since the driving on difficult ground at low speeds and disengaged actuators  19  and  20  makes up only a very small portion of the utilization time of the vehicle, it is especially advantageous for energy supply to use the oil hydraulic system of the steering system  32 . 
     The example of utilization shown in FIG. 3 stands out by an alternative control of the inventive actuators  19  and  20 . By virtue of a control valve  36  the hydraulics of the steering system  32  at very high actuator forces can be used to assist the spring  11  in the engagement operation. 
     REFERENCE NUMERALS 
       1  actuator 
       2  housing 
       3  stabilizer 
       4  coupling spline 
       5  stabilizer 
       6  housing cover 
       7  seal 
       8  connection 
       9  pressure chamber 
       10  coupling element 
       11  spring 
       12  pressure chamber 
       13  seal 
       14  seal 
       15  prolongation 
       16  coupling spline 
       17  coupling spline 
       18  connection 
       19  actuator 
       20  actuator 
       21  swivel bearing 
       22  swivel bearing 
       23  swivel bearing 
       24  swivel bearing 
       25  swivel bearing 
       26  swivel bearing 
       27  swivel bearing 
       28  swivel bearing 
       29  vehicle axle 
       30  vehicle axle 
       31  recoil pipe 
       32  steering system 
       33  control valve 
       34  control unit 
       35  tachometer 
       36  control valve