Patent Application
20100116233
The invention is in the technical field of internal combustion engines and generally relates to a rotary piston adjuster for an internal combustion engine.
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
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
Finally,
It is an object of the present invention to provide a rotary piston adjuster for which the disadvantages (explained above in conjunction with
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.
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:
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
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 A1 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 A2 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
In order to avoid unnecessary repetitions, only the differences from the first exemplary embodiment shown in
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
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102008056796.5 | Nov 2008 | DE | national |
