The invention relates to a camshaft adjuster according to the preamble of claim 1. Furthermore, the invention relates to a method for adjusting the angle-of-rotation position of a camshaft relative to a crankshaft for an internal combustion engine, in particular according to the preamble of claim 12.
DE 100 84 408 B4 discloses a camshaft adjuster of vane cell design, the driving clement of which, in the form of a driving toothed wheel, is driven by a crankshaft via a traction element, such as a chain or a belt. A “stator,” in which a rotor is arranged rotatably in order to produce an actuating angle, is connected to the driving wheel for rotation therewith. The rotor is connected to a camshaft for rotation therewith. A relative angular position between the camshaft and driving wheel, and therefore the crankshaft, can be influenced according to the actuating angle, this being associated with a change in the engine timings. In an embodiment of vane cell design, the rotor has vanes which are displaceable in the circumferential direction, depending on a hydraulic pressure in control chambers of the stator, in order to produce an actuating angle. On the side facing away from the camshaft, the stator is formed by a disk which delimits the control chambers in the axial direction. The ratios of force between the rotor and stator can influenced, in addition to the hydraulic ratios in the region of the vanes, by a torsion spring, the base points of which are supported on the stator and on the rotor. The torsion spring is arranged on that side of the disk which faces away from the rotor, with a plurality of turns about the longitudinal axis. The radially outer base point is supported in relation to the stator via screws which serve at the same time to fasten the disk in the stator. The radially inner base point of the torsion spring is bent in a U-shaped manner and engages in a form-fitting manner around a rectangular partial cross-section of a supporting element. The supporting element furthermore has a cylindrical extension with which said supporting element extends through a central bore in the disk so as to permit relative rotation. The extension is connected in the stator to the camshaft for rotation therewith, in particular via an end side of the rotor.
A pin which is referred to in the document as a locking pin is guided displaceably in a bore of the rotor parallel to the longitudinal axis of the camshaft adjuster, wherein the axial position of the pin can be influenced by the ratios of force of a compression spring and/or the hydraulic ratios in the region of end surfaces of the pin. The disk of the stator has a corresponding recess which is oriented in the axial direction and is in the form of a blind hole. For an activated position of the pin, in particular a starting position, intermediate position, central position, advanced or retarded position, the pin emerges with an end region out of the rotor and enters the recess of the disk of the stator such that the degree of freedom of rotation between the rotor and stator is limited.
The present invention is based on the object of providing a camshaft adjuster which requires particularly little oil. It is a further object of the invention to provide a corresponding method for adjusting the angle-of-rotation position of a camshaft relative to a crankshaft.
According to the invention, the object directed towards a camshaft adjuster is achieved by the provision of a camshaft adjuster for adjusting the angle-of-rotation position of a camshaft relative to a crankshaft, with at least two working chambers to which pressure oil can be supplied to change the angle-of-rotation position, wherein at least one of the working chambers can be cut off depending on an operating parameter by the supply of pressure oil being blocked.
The invention is based on the finding that the pressure transmission ratio, which is at the basis of the torque, which is imparted by the pressure oil, for rotating the camshaft, is decisively determined by ratios at a low pressure. The pressure transmission ratio of a camshaft adjuster is selected in such a manner that reliable adjustment is still possible even at a low engine oil pressure. The pressure transmission ratio follows here from the size and number of the working chambers and the size of the operative surfaces of the actuating elements, i.e. the vane surfaces in the case of a vane cell adjuster. As the engine oil pressure rises, a higher actuating torque therefore occurs. In this case, the actuating torque exceeds a value which would actually be sufficient for reliable and sufficiently rapid adjustment. Therefore, by definition of the requirement at low oil pressure, resources are given away at a higher oil pressure. In particular, it is endeavored to configure the oil pump of an internal combustion engine to be as small as possible, this being limited by the requirement of the oil consumers. A lower oil requirement in the adjustment of a camshaft would therefore be advantageous.
The invention now achieves this by at least one of the working chambers of the camshaft adjuster being configured so as to be able to be cut off. That is to say, depending on an operating parameter, in particular the oil pressure, the supply of oil to one of the working chambers is prevented and, as a result, the oil requirement is reduced. In an operating state in which the torque provided for adjusting the camshaft is sufficient even without said working chamber, the reduction of the quantity of oil does not result in any impairment of the operation.
The camshaft adjuster is advantageously of vane cell design, each working chamber being divided by a respective vane into two sub chambers, and the pressure oil being supplied to one of the two chambers, depending on the desired direction of the change in the angle-of-rotation position, in such a manner that said sub chamber is increased and the second sub chamber is reduced. Owing to the fact that a vane cell adjuster is in any case divided into a plurality of working chambers, this construction is particularly suitable for being adapted to an operating state because of the possibility of cutting off a working chamber.
The supply of pressure oil can preferably be blocked by an actuating body, the actuating position of which is determined by the pressure of the pressure oil. The actuating body furthermore preferably has a resetting spring, the spring force of which is directed counter to the actuating effect of the pressure oil. This configuration results in a particularly simple mechanism for cutting off the working chamber. The rising pressure of the pressure oil acts here directly on the actuating body in such a manner that, from a certain pressure, said actuating body prevents the supply of pressure oil to the working chamber. The resetting force of a spring serves to set the cut-off value for the pressure.
Preferably, when the working chamber is cut off, a short-circuiting pressure oil connection is produced at the same time between the two sub chambers of said working chamber. This ensures that the cut-off working chamber does not cause any impermissible delay in the adjusting operation because of the oil which continues to remain therein. The short-circuiting pressure oil connection permits the movement of the actuating element, driven by the other working chambers which remain active, within the cut-off working chamber. In this case, the actuating element displaces oil via the short-circuit between the two sub chambers of the working chamber without being impermissibly severely braked as a result. The cutting off of the working chamber and the short-circuit of the pressure oil are furthermore preferably brought about simultaneously by an actuating body.
Preferably, at least two working chambers can be cut off, the first working chamber being able to be cut off at a first value of the operating parameter, and the second working chamber being able to be cut off at a second value of the operating parameter, which value is greater than the first value. By means of this configuration, it is possible to even more finely adapt the oil required to the particular operating state. As the pressure rises and therefore the torque available for the adjustment operation also rises, first of all a first working chamber and then a second chamber or even further chambers can be cut off. When the cut-off mechanism is configured as described above with the actuating body and resetting spring, this gradual adaptation can be realized in a simple manner by a dedicated cut-off mechanism having a resetting spring of respectively differing strength being provided for each working chamber.
The actuating body is preferably of double-action design in such a manner that, depending on the direction of the change in the angle-of-rotation position, the working chamber can be cut off by the supply of pressure oil either to the first or second sub chamber being blocked. A mechanism is therefore provided by means of which both the first and the second sub chamber can be cut off. It is therefore possible to use a single cut-off mechanism for both possible actuating directions to cut off the working chamber.
A locking mechanism is preferably provided, by means of which an adjustment of the angle-of-rotation position can be blocked, wherein the blocking of the supply of pressure oil can also be set by the locking mechanism. Furthermore preferably, at a first oil pressure, the locking mechanism releases the supply of pressure oil counter to the force of a first spring and, at a second, higher oil pressure, blocks the supply of pressure oil counter to the force of a second spring. Therefore, both locking of the adjuster and cutting off of the working chamber are brought about by a single mechanism.
According to the invention, the object directed towards a method is achieved by provision of a method for adjusting the angle-of-rotation position of a camshaft relative to a crankshaft, in which pressure oil can be supplied into the working chambers of a camshaft adjuster having at least two working chambers to change the angle-of-rotation position, wherein the supply of pressure oil to at least one of the working chambers is blocked if a predetermined pressure of the pressure oil is exceeded, while the supply of pressure oil to at least one of the remaining working chambers remains open.
The advantages of a method of this type correspond to the advantages of the camshaft adjuster described above.
The invention is explained in more detail by way of example with reference to the drawing, in which:
The camshaft adjuster 1 has a driving wheel 2 via which said camshaft adjuster is connected in terms of drive to a crankshaft. The driving wheel 2 is connected to a stator 3 for rotation therewith, the stator being formed with a pot-shaped housing 4 and a housing cover 5. The interior, which is delimited by the housing 4 and housing cover 5, is divided into two sub spaces located axially next to each other via a circular-ring-shaped disk 6 which is oriented transversely with respect to a longitudinal axis 7-7 of the camshaft adjuster 1. The sub space facing the camshaft accommodates, in a manner not illustrated and with the formation of control chambers, the rotor 8 which has vanes and which is connected or braced to a threaded bore on the end side of the camshaft with the use of a central screw (not illustrated). A torsion spring 16 which extends with multiple turns about the longitudinal axis 7-7 is connected in between the stator 3 and rotor 8. The sub space arranged on that side of the disk 6 which faces away from the camshaft forms an annular space 10 encircling around the longitudinal axis 7-7. The annular space 10 is sealed in the contact region between the housing 4 of the stator 3 and housing cover 5 by the interconnection of a sealing plate 11 which can be braced between the housing 4 and housing cover 5 by fastening screws 12 being tightened.
It becomes clear in
It can be seen in
The cut-off mechanism in
Finally,
1 Camshaft Adjuster
2 Driving Wheel
3 Stator
4 Housing
5 Housing Cover
6 Disk
7 Longitudinal Axis
8 Rotor
10 Annular Space
11 Sealing Plate
12 Fastening Screw
21 Vane
25 Cut-Off Mechanism
26 Spring Support
27 Cut-Off Mechanism
29 Oil Duct
31 Oil Duct
33 Spring
35 Actuating Body
37 Bypass Duct
39 Recess
41 Working Chamber
41A Sub Chamber
41B Sub Chamber
51, 53 Inflow/Outflow
61, 63 Chamber Inflow/Outflow
67 Annular Groove
67A Annular Groove
67B Annular Groove
65 Short-Circuit Duct
71 Locking Spring
73 Locking Pin
75 Slotted Locking Link
77 Side Cover
Number | Date | Country | Kind |
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10 2009 015 882.0 | Apr 2009 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2010/053343 | 3/16/2010 | WO | 00 | 12/16/2011 |