Patent Publication Number: US-2010116233-A1

Title: Rotary piston adjuster having a torsion spring

Description:
TECHNICAL FIELD 
     The invention is in the technical field of internal combustion engines and generally relates to a rotary piston adjuster for an internal combustion engine. 
     BACKGROUND OF THE INVENTION 
     In internal combustion engines with a mechanical valve actuating mechanism, gas exchange valves are actuated by the cams of a camshaft which is driven by a crankshaft, it being possible to use the arrangement and the shape of the cams to fix the control times of the valves for a defined phase relation between the crankshaft and the camshaft. The control times of the valves can be influenced via a change in the phase relation between the crankshaft and the camshaft as a function of the instantaneous operating state of the internal combustion engine, as a result of which advantageous effects can be achieved, such as a reduction in fuel consumption and pollutant generation. The use of special apparatuses for optionally adjusting the phase relation between the crankshaft and the camshaft is sufficiently well known, which special apparatuses are usually called “camshaft adjusters”. 
     In general, camshaft adjusters comprise a drive part which is drive-connected to the crankshaft via a drive wheel, an output part which is fixed to the camshaft, and an actuating mechanism which is connected between the drive part and the output part, which activating mechanism transmits the torque from the drive part to the output part and makes it possible to adjust and fix the phase relation between the two. 
     In a conventional design as a hydraulic rotary piston adjuster, the drive part is configured as an outer rotor and the output part is configured as an inner rotor, the outer and inner rotors being arranged concentrically with regard to a common rotational axis and such that they can be adjusted rotationally with respect to one another. In the radial intermediate space between the outer and inner rotors, at least one pressure space is formed by one of the two rotors, into which pressure space a vane which is connected to the respectively other rotor extends, as a result of which the pressure space is divided into a pair of pressure chambers which act counter to one another. The outer and inner rotors can be rotated relative to one another by targeted pressure loading of the pressure chambers, in order to bring about a change in the phase relation between the crankshaft and the camshaft as a result. Similarly, a phase relation can be maintained by hydraulic stressing. 
     Alternating torques then occur on the camshaft during the operation of the internal combustion engine, which alternating torques, in the case of insufficient pressure medium supply, as is the case, for example, during the starting phase or when idling, lead to the inner and outer rotors being moved with respect to one another in an uncontrolled manner. This can have the result that the vanes strike to and fro within the pressure spaces, as a result of which wear is increased and unpleasant noise is caused. In addition, the phase relation between the crankshaft and the camshaft varies to a pronounced extent in this case, with the result that the internal combustion engine does not start or runs uneasily. 
     In order to avoid this, hydraulic rotary piston adjusters are equipped with a locking device for the rotationally fixed locking of the outer and inner rotors, locking taking place in a phase relation which is denoted as a basic position and is favorable thermodynamically for starting the internal combustion engine. The selection of the basic position depends on the concrete design of the internal combustion engine and can be an early, late or intermediate position, the late position corresponding to maximum adjustment of the inner rotor in the trailing direction, the early position corresponding to maximum adjustment of the inner rotor in the leading direction and the intermediate position corresponding to a rotary angle position between said two end rotary positions, in relation to the rotational direction of the camshaft. A rotary angle position of the inner rotor relative to the outer rotor which is situated at least approximately in the middle between the early and the late position is denoted as middle position. In a corresponding way, adjustment of the inner rotor in the direction of the early position is called early adjustment, and adjustment in the opposite direction is called late adjustment. 
     The locking device for locking the outer and inner rotors in the basic position in a rotationally fixed manner typically comprises one or more bolts which are received in one of the two rotors, can be moved, in the basic position, into positively locking engagement with the respectively other rotor and can be unlocked hydraulically in order to release the rotational adjustability of the outer and inner rotors. 
     Hydraulic rotary piston adjusters having a locking device for locking the outer and inner rotors in the basic position in a rotationally fixed manner are described in detail, for example, in documents DE 202005008264 U1, EP 1596040 A2, DE 102005013141 A1, DE 19908934 A1 and WO 2006/039966 from the applicant. 
     If the basic position is not reached during switching off of the internal combustion engine, for example by “stalling” of the engine, the inner rotor is adjusted automatically into the late position on account of the frictional moments of the camshaft, with the result that special precautionary measures are to be made for locking in a basic position which is different than the late position, by which precautionary measures the inner rotor is adjusted in the early direction relative to the outer rotor, in the direction of the basic position. In addition, the adjusting speed in the two adjusting directions differs on account of the frictional moments which act in the “late” direction, with the result that matching of the adjusting speeds is desirable. 
     For this purpose, restoring or compensation springs are installed which prestress the inner rotor with respect to the outer rotor in the “early” direction. For example, German laid-open specifications DE 10007200 A1 and DE 10215879 A1 describe in each case rotary piston adjusters having restoring springs, by which the inner rotor is prestressed with respect to the outer rotor in an adjusting direction in order to reach the basic position. 
     Different variants which are used by the applicant in industrial series production for the arrangement of restoring springs in a rotary piston adjuster will now be described with reference to  FIGS. 3A-3C . 
       FIG. 3A  is to be considered first of all, in which a first variant for the arrangement of a helical spring  105  in a rotary piston adjuster  101  is shown in a diagrammatic axial section illustration. Accordingly, the rotary piston adjuster  101  which is attached on the end side of a camshaft  104  comprises an outer rotor  102  which is drive-connected to a crankshaft (not shown) and an inner rotor  103  which is connected in a rotationally fixed manner to the camshaft  104 , the outer and inner rotors being arranged concentrically with respect to a common rotational axis  114  and such that they can be adjusted rotationally with respect to one another. A relative rotary angle position of the outer and inner rotors can be changed or fixed by a hydraulic actuating mechanism (not shown in greater detail). In addition, rotationally fixed locking of the outer and inner rotors in a basic position which is different than the late position is possible by way of a locking device (likewise not shown in greater detail). 
     The helical spring  105  which comprises a plurality of radial windings is connected by way of an inner hook  106  to a first connecting pin  108  which projects axially from the inner rotor  103 , the inner hook  106  being bent away at a bending angle of approximately 180° with regard to a tangential extent direction of the end of an inner winding  113 . Furthermore, said helical spring  105  is connected by way of an outer hook  107  to a second connecting pin  109  which projects axially from the outer rotor  102 , the outer hook  107  being bent away at a bending angle of approximately 90° with regard to an extent direction of an outer winding  112 , with a curvature direction which changes with regard to the helical spring  105 . 
     Via a first supporting pin  110  which projects axially from the inner rotor  103  and is at approximately the same radial spacing from the rotational axis  114  of the camshaft  104  as the first connecting pin  108 , and by way of a second supporting pin  111  which protrudes axially from the outer rotor  102  and is at approximately the same radial spacing from the rotational axis  114  of the camshaft  104  as the second connecting pin  109 , the inner winding  113  and the outer winding  112  of the helical spring  105  are fixed in their respective position, in order to prevent the hooked action of the inner hook  106  with the first connecting pin  108  and that of the outer hook  107  with the second connecting pin  109  becoming released. In relation to the common rotational axis  114 , both the first connecting pin  108  and the first supporting pin  110  and also the second connecting pin  109  and the second supporting pin  111  are at in each case an angular spacing measured in the circumferential direction of less than 90°. 
     A disadvantage of the arrangement which is shown in  FIG. 3A  is, in particular, the fact that, in the case of a wraparound angle of approximately 180° of the inner hook  106 , the radial installation space requirement is increased on account of the doubly placed inner winding  113 . In addition, a rotational center (not denoted in greater detail) of the helical spring  105  lies outside the common rotational axis  114  of the arrangement, with the result that an unbalance occurs in an undesirable way on account of the eccentricity of the helical spring  105  caused by this. 
       FIG. 3B  shows a second variant for the arrangement of the helical spring  105 . In order to avoid unnecessary repetitions, only the differences from the first variant of  FIG. 3A  will be explained, reference otherwise being made to the above comments with respect to  FIG. 3A . Accordingly, an at least approximately symmetrical four-cornered shaft  115  is provided which is connected in a rotationally fixed manner to the inner rotor  103 , an inner winding  113  of the helical spring  105  surrounding an outer face of the four-cornered shaft  115  on three sides, as a result of which a positively locking, rotationally fixed connection is formed between the helical spring  105  and the four-cornered shaft  115 . The four-cornered shaft  115  is arranged in a manner which is centered with respect to the rotational axis  114  of the camshaft  104 , with the result that the generation of an unbalance is avoided. However, the four-cornered shaft  115  increases the radial installation space requirement of the arrangement in an undesirable manner, and the manufacturing costs for the camshaft adjuster  101  increase as a result of the greater material requirement for the helical spring  105 . 
     Finally,  FIG. 3C  shows a third variant for the arrangement of the helical spring  105 . In order to avoid unnecessary repetitions, once again only the differences from the first variant of  FIG. 3A  will be explained, reference being made otherwise to the above comments on  FIG. 3A . Accordingly, a cylindrical journal  116  is provided which is connected in a rotationally fixed manner to the inner rotor  103  and is provided with an axial connecting groove  117 , to which the inner hook  106  is connected. The inner winding  113  of the helical spring  105  bears largely against the journal  116 , as a result of which a positively locking connection is produced between the inner winding  113  and the journal  116 . The journal  116  is arranged coaxially with respect to the camshaft  104 , as a result of which an unbalance is avoided. However, in industrial serial production, the shaping of the journal  116  requires an additional manufacturing step for turning and/or milling of the inner rotor  103  and/or for the attachment of an additional component on the inner rotor  103 , as a result of which the manufacturing costs for the rotary piston adjuster  101  are increased. In addition, the component weight for the inner rotor  103  is increased. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a rotary piston adjuster for which the disadvantages (explained above in conjunction with  FIGS. 3A-3C ) of conventional rotary piston adjusters can be avoided. 
     According to one aspect of the invention, there is provided a rotary piston adjuster for adjusting the phase relation of the crankshaft and the camshaft of an internal combustion engine. The rotary piston adjuster comprises an outer rotor which can be drive-connected to a crankshaft (or is fixed to the crankshaft) and an inner rotor which can be connected in a rotationally fixed manner to a camshaft (or is fixed to the camshaft). The rotors are mounted in a concentric arrangement about a common rotational axis such that they can be adjusted rotationally about the common axis. The rotary angular position of the inner rotor with respect to the outer rotor can be adjusted by means of a hydraulic actuating mechanism which comprises at least one pair of pressure chambers which act counter to one another. 
     Furthermore, the rotary piston adjuster comprises a torsion spring which is rotationally coupled to the outer and inner rotors in such a way that the inner rotor is prestressed in an adjusting direction with respect to the outer rotor. The torsion spring is connected by way of a hook-shaped, first end section to a first connecting element which is connected in a rotationally fixed manner to the inner rotor. In one embodiment, the torsion spring can be advantageously configured in the form of a helical spring with a plurality of radial spring windings, the spring plane being directed perpendicularly with respect to the common rotational axis of the outer and inner rotors. 
     The rotary piston adjuster includes at least two first supporting elements which are connected in a rotationally fixed manner to the inner rotor for supporting the torsion spring, which first supporting elements are arranged at an angular spacing in the angular range of from 90° inclusive to 270° inclusive with respect to the first connecting element. In the context of the present invention, the expression “angular spacing” relates to an angular difference in the circumferential direction between radial connecting lines which connect respective elements (connecting and/or supporting elements) to the common rotational axis. 
     Release of the hook-shaped, first end section from its hooked connection with the first connecting element can be prevented by the first supporting elements, with the result that a radial dimension of the rotary piston adjuster can advantageously be reduced by the material thickness of the torsion spring. 
     According to one preferred embodiment of the rotary piston adjuster according to the invention, a first supporting element for supporting the torsion spring is arranged at least approximately at an angular spacing of 180° from the first connecting element, as a result of which release of the hook-shaped, first end section from its hooked connection with the first connecting element can be prevented in a particularly effective way. 
     According to a further embodiment of the rotary piston adjuster according to the invention, which embodiment is preferred, in particular, with regard to the manufacturing costs, two first supporting elements are provided for supporting the torsion spring, which is to be preferred, in particular, when a first supporting element is at an angular spacing of more than 180° from the first connecting element, in order in this way to ensure sufficient support of the torsion spring with relatively low manufacturing costs, even in the case of high torques. In this case, it can be advantageous if a first supporting element is at least approximately half as great an angular spacing from the first connecting element as the other first supporting element, as a result of which symmetrical support of the torsion spring can be achieved. 
     According to a further preferred embodiment of the rotary piston adjuster according to the invention, the first supporting elements are at an at least approximately identical radial spacing from the common rotational axis as the first connecting element, with the result that the torsion spring can be arranged in a centered manner with respect to the common rotational axis of the outer and inner rotors, in order to avoid an unbalance in this way. In this case, it can be advantageous if the rotary piston adjuster is provided with at least one second supporting element which is connected in a rotationally fixed manner to the outer rotor, for supporting the torsion spring, in order, as a result, to prevent release of the hook-shaped, second end section from its hooked connection with the second connecting element. It can be particularly preferred here if the at least one second supporting element is at an at least approximately identical radial spacing from the common rotational axis as the second connecting element, in order to achieve an orientation of the torsion spring in a simple way, which orientation is centered with respect to the common rotational axis of the outer and inner rotors. 
     According to a further preferred embodiment of the rotary piston adjuster according to the invention, the hook-shaped, first end section of the torsion spring is bent away at a bending angle of at most 90° in relation to a (tangential) extent direction of a spring section which is immediately adjacent to the first end section. 
     In a further advantageous embodiment of the rotary piston adjuster according to the invention, the torsion spring is arranged on a side of a side plate which faces away from the inner rotor, in order to close the at least one pair of pressure chambers in an axially pressure-tight manner. In this case, in particular, it can be advantageous if the connecting elements and/or supporting elements are configured in each case in pin form, for example as axial extensions of fastening screws for fastening the side plate to a part of the outer rotor which forms the at least one pressure space. 
     Furthermore, the invention can include an internal combustion engine which is provided with at least one rotary piston adjuster as described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will now be described in greater detail using exemplary embodiments, reference being made to the appended drawings. Elements which are identical and/or have the identical action are denoted by the same designations in the drawings, in which: 
         FIG. 1  shows a diagrammatic perspective axial view of a first exemplary embodiment of the rotary piston adjuster according to the invention, in order to illustrate the arrangement of a restoring spring; 
         FIG. 2  shows a diagrammatic perspective axial view of a second exemplary embodiment of the rotary piston adjuster according to the invention, in order to illustrate the arrangement of a restoring spring; and 
         FIGS. 3A-3C  show diagrammatic perspective axial views of conventional rotary piston adjusters, in order to illustrate the arrangement of a restoring spring. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  diagrammatically shows, in a perspective axial view, a first exemplary embodiment of the rotary piston adjuster  1  according to the invention with early locking (locking in the early position or leading direction as basic position). 
     The rotary piston adjuster  1  comprises an outer rotor  2  which is drive-connected to a crankshaft (not shown) via a chain sprocket  16  and a chain drive (not shown), and an inner rotor  3  which is connected in a rotationally fixed manner to a camshaft  4 , the outer and inner rotors being arranged concentrically with regard to a common rotational axis  15  of the camshaft  4  and such that they can be adjusted rotationally with respect to one another. The rotary piston adjuster  1  is fastened to the end side of the camshaft  4 , for example by means of a central screw. 
     A plurality of pressure spaces (not shown) are formed by the outer rotor  2  in the radial intermediate space between the outer and inner rotors, into which pressure spaces in each case a vane extends which is connected to the inner rotor  3 , as a result of which each pressure space is divided into a pair of pressure chambers which act counter to one another. By targeted pressure loading of the pressure chambers which act counter to one another, a rotary angular position of the inner rotor  3  with respect to the outer rotor  4  can be changed or fixed by hydraulic clamping. Here, the outer rotor  2  forms a pressure-tight housing for the rotary piston adjuster  1 , the pressure chambers being closed in an axially pressure-tight manner by two side plates which are arranged on the end side and of which only one side plate  17  can be seen in  FIG. 1 . The side plate  17  is attached to a housing part  20  which forms the pressure spaces and supports the chain sprocket  16 , by a plurality of axial fastening screws  18  which are distributed uniformly in the circumferential direction. Furthermore, the side plate  17  is provided with a circular aperture  19  which is centered with respect to the rotational axis  15  of the camshaft  4  and releases the inner rotor  3  or an attachment component which is connected in a rotationally fixed manner to the inner rotor  3 . 
     For locking the outer and inner rotors in the middle position in a rotationally fixed manner, at least one axial or radial locking pin (not shown) is provided in a conventional way which is received, for example, in the inner rotor  3 , is displaced out of its receptacle in the axial or radial direction by a compression coil spring, and can engage positively into a locking guide which is formed by the outer rotor  2 . In order to unlock the locking pin, it can be loaded on the end side with pressure medium and displaced back into its receptacle. 
     The precise construction of a rotary piston adjuster of this type is sufficiently well known to a person skilled in the art, for example from the documents which are cited in the introduction, with the result that it does not have to be explained in greater detail here. 
     Furthermore, the rotary piston adjuster  1  is provided with a flat helical spring  5  which is arranged with its spring plane perpendicular with respect to the axial direction, on that side of the side plate  17  which faces away from the inner rotor  3 . The helical spring  5  is provided with a plurality of radial windings which surround an imaginary axial extension of the camshaft  4 . A hook-shaped, first end section is formed as outer hook  6  on the helical spring  5  and a hook-shaped, second end section is formed as inner hook  7 . 
     The inner hook  7  is connected to a first connecting pin  8  which projects from the inner rotor  3 , the inner hook  7  being formed in such a way that it surrounds the first connecting pin  8  partly positively. Here, the inner hook is bent at a bending angle of approximately 90° in the curvature direction of the helical spring  5  (corner angle) with regard to a tangential extent direction of a first spring section  21  of the inner winding  14 , which first spring section  21  immediately adjoins the inner hook  7 , which results in a wraparound angle of approximately 90° which describes the positive connection between the inner hook  7  and the first connecting pin  8 . 
     Via a first supporting pin  10  which projects from the inner rotor  3  and via a second supporting pin  11  which projects from the inner rotor  3 , which supporting pins  10 ,  11  are both in each case at approximately the same radial spacing from the rotational axis  15  of the camshaft  4  as the first connecting pin  8 , an inner wall  14  is fixed in such a way that release of the hooked connection of the inner hook  7  with the first connecting pin  8  is prevented. 
     In relation to the common rotational axis  15 , the first connecting pin  8 , the first supporting pin  10  and the second supporting pin  11  (or their radial connecting lines to the rotational axis  15 ) are arranged in an angular range of approximately 270°, viewed in the counterclockwise direction, however, beginning at the first connecting pin  8 . In particular, the first supporting pin  10  is arranged at least approximately in the opposite position to the first connecting pin  8 , according to an angular spacing A 1  of approximately 180° between the first connecting pin  8  and the first supporting pin  10 . The second supporting pin  11  is arranged at an angular spacing A 2  of approximately 270° from the first connecting pin  8 . 
     The outer hook  6  is connected to a second connecting pin  9  which projects from the outer rotor  2  and is formed as an axial extension of a fastening screw  18 , the outer hook  6  being formed in such a way that it surrounds the second connecting pin  9  partly positively. Here, the outer hook  6  is bent away at a bending angle of approximately 170° counter to the curvature direction of the helical spring  5 , with regard to a tangential extent direction of a second spring section  22  of the outer winding  13 , which second spring section  22  immediately adjoins the outer hook  6 . Via a third supporting pin  12  which projects from the outer rotor  2 , is formed as an axial extension of a fastening screw  18  and is at approximately the same radial spacing from the rotational axis  15  of the camshaft  4  as the second connecting pin  9 , the outer winding  13  is fixed in such a way that release of the hooked connection of the outer hook  6  with the second connecting pin  9  is prevented. In relation to the rotational axis  15  of the camshaft  4 , the second connecting pin  9  and the third supporting pin  12  (or their radial connecting lines to the rotational axis  15 ) are arranged in an angular range of approximately 90°, as viewed in the clockwise direction, beginning at the second connecting pin  9 . 
     The helical spring  5  which is shown in  FIG. 1  prestresses the inner rotor  3  with respect to the outer rotor  2  in the “early” direction, in order firstly to match the adjusting speeds in the two adjusting directions and secondly to adjust the inner rotor  3  correspondingly in the “early” direction in order to reach the basic position. As a result of the inner hook  7  which is bent away at a bending angle of approximately 90° with respect to the extent direction of the helical spring  5 , the radial dimension of the rotary piston adjuster  1  can be reduced by the amount of the material thickness of the helical spring  5  with respect to the conventional connection (shown in  FIG. 3A ) of the helical spring  5 . The helical spring  5  is held centered with respect to the common rotational axis  15  by the uniform support in the circumferential direction of the helical spring  5  by means of three inner supporting points, described by the first connecting pin  8 , the first supporting pin  10  and the second supporting pin  11 , with the result that an eccentric position of the helical spring  5  can be avoided. In particular, this can reduce spring hysteresis and ensure the freedom of movement with respect to the camshaft  4 . 
       FIG. 2  shows, diagrammatically in an axial view, a second exemplary embodiment of the rotary piston adjuster  1  according to the invention with early locking (locking in the leading direction as basic position). 
     In order to avoid unnecessary repetitions, only the differences from the first exemplary embodiment shown in  FIG. 1  will be explained, reference otherwise being made to the comments made there. 
     Accordingly, the rotary piston adjuster  1  is provided with a helical spring  5  which has an opposed winding direction of its windings corresponding to a rotational direction of the camshaft  4  which is different than  FIG. 1 . Here, the first connecting pin  8 , the first supporting pin  10  and the second supporting pin  11  (or radial connecting lines of them with the rotational axis  15 ) are arranged within an angular range of approximately 270°. In the exemplary embodiment which is shown, the angular range begins at the first connecting pin  8  and is measured in the clockwise direction, in a corresponding manner to the radially increasing course of the helical spring  5 . In particular, the first supporting pin  10  is arranged at least approximately in the opposite position to the first connecting pin  8 , according to a rotary angular spacing A 1  of approximately 180° from the first connecting pin  8 . The second supporting pin  11  is arranged at least approximately in the region of the bisector between the first connecting pin  8  and the first supporting pin  10 , corresponding to a rotary angular spacing A 2  of approximately 90° from the first connecting pin  8 , as a result of which support of the helical spring  5  is achieved which is particularly reliable with regard to a hooked connection of the inner hook  7  with the first connecting pin  8  and is suitable in equal measure for low and high torques. 
     Although an inner support of the inner winding  14  of the helical spring  5  by means of three supporting points is illustrated in the exemplary embodiments, it is conceivable to provide only two supporting points which lie at least approximately opposite one another (that is to say, a hooked connection of the inner hook  7  on the first connecting pin  8 , and a first supporting pin  10  which is arranged at a rotary angular spacing of approximately 180° from the first connecting pin  8 ) or more than three inner supporting points, three inner supporting points being preferred from the aspect of manufacturing costs. Instead of a helical spring  5 , another torsion spring which is suitable for the rotational adjustment of the outer and inner rotors, for example a torsion coil spring, can likewise be provided.