Preassembly Of A Camshaft Phaser

Abstract

A camshaft phasing system (10) for an internal combustion engine (6) includes a camshaft (16) and a camshaft phaser (15) that is axially slid onto the camshaft (16) and that has stator (34) and a rotor (36) driven by the stator (34), whereby the rotor (36) is mounted rotatably relative to the stator (34). A bushing (26) that is secured on the camshaft (16) is provided, whereby the camshaft phaser (15) is tightened on the camshaft (16) against the bushing (26). Moreover, a drive has an internal combustion engine and such a camshaft phasing system.

Description

[0001] The invention relates to a camshaft phasing system and it also relates to a drive with the camshaft phasing system.

BACKGROUND OF THE INVENTION

[0002] German patent application DE 10 2009 041 873 A1 discloses a camshaft phasing system in which a camshaft is rotatably connected via its end face to a camshaft phaser. The camshaft phaser can influence the timing of the transmission of drive power to the camshaft, for example, in order to change the valve timing in an internal combustion engine.

SUMMARY OF THE INVENTION

[0003] It is an object of the present invention to improve upon a prior-art camshaft phasing system.

[0004] In a prior-art camshaft phasing system, the camshaft phaser has to be mounted concentrically on the camshaft in order to avoid unbalances that can lead to noisy vibrations and to greater wear and tear of the prior-art camshaft phasing system.

[0005] In the prior-art camshaft phasing system, a concentric mounting of the camshaft phaser on the camshaft is labor-intensive. In addition, narrow manufacturing tolerances have to be observed. The camshaft phasing system should only be assembled when it is being installed in the internal combustion engine. However, this not only leads to undesired higher costs for the manufacturer of the internal combustion engine but there is also fundamentally the risk of improper assembly of the camshaft phasing system in the internal combustion engine.

[0006] The present invention provides sliding the camshaft phaser axially onto the camshaft and tightening it on the camshaft against a bushing. The partial axial placement of the camshaft in the camshaft phaser simplifies the assembly of the camshaft phaser on the camshaft. In the assembled state, a sturdy concentric connection is created between the camshaft phaser and the camshaft. Through the tightening of the camshaft phaser on the camshaft, the camshaft phaser is mounted radially and non-rotatably on the camshaft, whereby a torque is transmitted from the camshaft phaser to the camshaft via the bushing. The radial mounting of the camshaft phaser onto the camshaft translates into an easy-to-assemble camshaft phasing system with a secure concentric connection of the camshaft phaser to the camshaft. Such a camshaft phasing system can be prefabricated by its manufacturer, whereas its final assembly as a system is carried out by the manufacturer of the internal combustion engine. Since the camshaft phaser is radially mounted on the camshaft and axially slid into place, the invention creates additional ways to simplify the assembly such as, for example, by using axial guide mechanisms such as teeth or the like.

[0007] The invention also simplifies the installation of the camshaft phasing system since, in order to install the camshaft phasing system, it is merely necessary to assemble the entire system without the risk that parts which might be forgotten during the installation would then still have to be delivered, entailing considerable costs.

[0008] The bushing can be configured in any desired manner. For example, the bushing can be ring-shaped or else it can form just a partial ring. It is also possible for the bushing to have steps or the like. The bushing provides a ring-shaped or partially ring-shaped stop surface on the camshaft for the camshaft phaser and, via this stop surface, the camshaft phaser can be joined to the bushing and thus mounted axially and non-rotatably on the camshaft. The size of the stop surface can be specified as desired as a function of the wall thickness of the bushing. Consequently, the non-rotatable mounting of the camshaft phaser on the camshaft can be ensured as a function of the wall thickness of the bushing so that the anticipated torques can be reliably transmitted. A separate bushing offers the additional advantage that a material that is optimized for the non-rotatable, frictional connection of the camshaft phaser can be selected independently of the material of the camshaft.

[0009] Therefore, the invention puts forward a camshaft phasing system for an internal combustion engine that comprises a camshaft as well as a camshaft phaser that is slid axially onto the camshaft and that has stator and a rotor driven by the stator, whereby the rotor is mounted rotatably relative to the stator. According to the invention, the camshaft phasing system has a bushing that is secured on the camshaft, whereby the camshaft phaser is tightened on the camshaft against the bushing.

[0010] The separate bushing can fundamentally be secured in any desired manner. A positive connection such as, for instance, a screwed connection or a sliding block connection, is likewise possible, and so is a frictional connection with which a friction-increasing means is inserted between the camshaft and the bushing.

[0011] In a special refinement, the bushing is held on the camshaft via a press fit. The press fit is especially advantageous since it acts along the circumference of the camshaft and thus distributes the mechanical loads while the torque is being transmitted from the camshaft phaser onto the camshaft uniformly along the circumference of the camshaft. The assembly of the bushing is also quite simple.

[0012] In one refinement, the rotor is tightened on the camshaft against the bushing. In this manner, the stator can take up the drive power for the camshaft and transmit it via the rotor to the camshaft in a phase-shifted manner.

[0013] In another refinement, the camshaft has an axial stop for the bushing on which the bushing can be mounted on a counter-bearing in order to tighten the camshaft phaser. In this manner, it is not only possible to increase the tightening effect of the bushing, but also, the axial stop simultaneously serves as a positioning element that prescribes the position of the bushing on the camshaft.

[0014] In a preferred refinement, the camshaft phasing system has a nut for tightening the camshaft phaser, especially the rotor, against the bushing. Owing to the torque while the nut is being screwed in, the tightening forces can be set, on the one hand, in order to protect the camshaft phasing system against an excessive tightening stress and, on the other hand, to ensure sufficient tightening so that the camshaft phaser is mounted non-rotatably and radially on the camshaft.

[0015] In another preferred embodiment, the camshaft phaser, especially the rotor, is frictionally connected to the bushing. A friction coupling between the bushing and the camshaft phaser, especially the bushing, allows a simple assembly, since the friction partners are pressed flat against each other. By means of suitable material pairing, the normal force can optionally be reduced, so that smaller tightening forces are needed. Especially preferably, a diamond perforated disk is placed between the camshaft phaser or the rotor and the bushing, whereby this diamond perforated disk creates an adequate frictional connection, even when the normal force is reduced. As a result, the torques that can be transmitted via the bushing from the camshaft phaser to the camshaft can be increased. As an alternative or additionally, a non-rotatable connection can also be achieved by means of a positive or adhesive connection.

[0016] In another embodiment of the invention, the camshaft phasing system has an outer tubular camshaft in which the camshaft is held concentrically, whereby the outer camshaft is connected to the stator of the camshaft phaser. Owing to the outer camshaft, a double camshaft phasing system having only a single camshaft phaser can be put forward that is able to actuate the inlet valves and the outlet valves of an internal combustion engine independently of each other.

[0017] In a special embodiment, the outer camshaft and the stator of the camshaft phaser are positively connected, especially by teeth. Thanks to a tangential positive connection of the type achieved, for instance, by teeth, the stator can rotate the outer camshaft relative to the inner camshaft, but it can move axially on the outer camshaft. This axial movement capability achieves a further simplification of the assembly since the camshaft phaser can be slid over the stator axially onto the outer camshaft, whereby especially the teeth serve as a guiding aid. The teeth or the tangential positive connection also function as a non-rotatable radial bearing.

[0018] In an especially preferred embodiment, the stator is additionally mounted radially on the bushing. This, too, translates into a simplified assembly. The camshaft phaser is additionally positioned opposite to the camshaft.

[0019] The invention also puts forward a drive comprising an internal combustion engine having a driven shaft, and a camshaft phasing system as described above for actuating a valve of the internal combustion engine based on a rotation of the driven shaft.

BRIEF DESCRIPTION OF THE DRAWING

[0020] An embodiment of the invention will be described in greater detail below with reference to a drawing.

[0021] The FIGURE shows a drive system according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE DRAWING

[0022] The single FIGURE shows a drive system 2 in which valves 4 of a schematically depicted internal combustion engine 6 are actuated by a double camshaft 8 of a camshaft phasing system 10. The internal combustion engine 6 drives a driven shaft 12 that drives a camshaft phaser 15 via an endless drive 14 in a manner still to be described. The FIGURE shows the endless drive 14 in the open position.

[0023] The double camshaft 8 has an inner camshaft 16 that is held concentrically in an outer camshaft 18. On each of the camshafts 16, 18, there are corresponding cams 20, 22 that, for the sake of clarity, are shown in a synchronous position in the FIGURE. During actual use, the cam 20 of the inner camshaft 16 is angle-offset relative to the cam 22 of the outer camshaft 18.

[0024] The inner camshaft 16 runs concentrically and rotatably in the outer camshaft 18. Via an axial seal 24, it is axially secured in the outer camshaft 18. The axial seal 24 can be formed, for example, by a groove that extends around the inner camshaft 16 and by a groove (without a reference numeral) into which a projection (without a reference numeral) protruding from the inside of the outer camshaft 18 enters.

[0025] The camshaft phaser 15 is slid concentrically onto the inner camshaft 16 and onto the outer camshaft 18, and it is tightened against the inner camshaft 16 between a bushing 26 and a nut 28. Here, the bushing 26 is axially mounted on a counter-bearing at an axial stop 30 on the inner camshaft 16. The nut 28 is screwed onto an axial end section 32 of the camshaft 16. In this embodiment, the tightening force needed to hold the camshaft phaser 15 is generated by screwing the nut 28 onto the axial end section 32 and by the axial mounting of the bushing 26 on a counter-bearing against the axial stop 30.

[0026] The camshaft phaser 15 has a stator 34 and a rotor 36 whose phase shifts can be adjusted relative to each other in a manner known to the person skilled in the art. Whereas the stator 34 is rotatably connected to the outer camshaft 18, the rotor 36 is non-rotatably connected to the inner camshaft 16.

[0027] The non-rotatable connection between the stator 34 and the outer camshaft 16 is established by teeth. 38. In addition, the stator 34 is mounted radially on the bushing 26. Both of these measures permit a simple and less error-prone assembly of the camshaft phaser 15 on the camshaft 16, 18.

[0028] The non-rotatable connection between the rotor 36 and the inner camshaft 16 is created by means of tightening with the nut 38 and the bushing 26, whereby the bushing 26 is non-rotatably connected to the inner camshaft 16 via a press fit. A diamond ring 40 between the rotor 36 and the bushing 26 further improves the frictional and thus non-rotatable connection.

[0029] The stator 34 has a hub 42 that is connected via the teeth 38 to the outer camshaft 18. A drive wheel is formed in one piece with the hub 42, and the endless drive 14 is wrapped around this drive wheel so that the stator 34 can drive the outer camshaft 18 via the driven shaft 12, and the rotor 36 can drive the inner camshaft 16 via the stator 34. On the side of the hub 42 opposite from the outer camshaft 18, there is an adjoining stator housing 44 in which the rotor 36 is accommodated. The stator housing 44 is closed by a cover 46 that is affixed to the housing 44 by means of pins 48 that have been screwed into the hub 42.

LIST OF REFERENCE NUMERALS

[0030] 2 drive means [0031] 4 valves [0032] 6 internal combustion engine [0033] 8 double camshaft [0034] 10 camshaft phasing system [0035] 12 driven shaft [0036] 14 endless drive [0037] 15 camshaft phaser [0038] 16 inner camshaft [0039] 18 outer camshaft [0040] 20 cam [0041] 22 cam [0042] 24 axial seal [0043] 26 ushing [0044] 28 nut [0045] 30 axial stop [0046] 32 axial end section [0047] 34 stator [0048] 36 rotor [0049] 38 teeth [0050] 40 diamond disk [0051] 42 hub [0052] 44 stator housing [0053] 46 cover [0054] 48 pins

Claims

1-10. (canceled)

11. A camshaft phasing system for an internal combustion engine, the camshaft phasing system comprising: a camshaft; a camshaft phaser axially slid onto the camshaft and having stator and a rotor driven by the stator, the rotor being mounted rotatably relative to the stator; and a bushing secured on the camshaft, the camshaft phaser tightened on the camshaft against the bushing.

12. The camshaft phasing system as recited in claim 11 wherein the rotor is tightened on the camshaft against the bushing.

13. The camshaft phasing system as recited in claim 11 wherein the bushing is held on the camshaft via a press fit.

14. The camshaft phasing system as recited in claim 11 wherein the camshaft has an axial stop for the bushing.

15. The camshaft phasing system as recited in claim 11 further comprising a nut for tightening the camshaft phaser against the bushing.

16. The camshaft phasing system as recited in claim 15 wherein the nut tightens the rotor.

17. The camshaft phasing system as recited in claim 11 wherein the stator is mounted radially on the bushing.

18. The camshaft phasing system as recited in claim 11 wherein the camshaft phaser is frictionally connected to the bushing.

19. The camshaft phasing system as recited in claim 18 wherein the rotor is frictionally connected to the bushing.

20. The camshaft phasing system as recited in claim 11 further comprising an outer tubular camshaft, the camshaft being held concentrically in the outer tubular camshaft, the outer tubular camshaft being connected to the stator of the camshaft phaser.

21. The camshaft phasing system as recited in claim 20 wherein the outer tubular camshaft and the stator of the camshaft phaser are positively connected.

22. The camshaft phasing system as recited in claim 21 wherein teeth positively connect the outer tubular camshaft and the stator.

23. A drive comprising: an internal combustion engine having a driven shaft; and